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Mierzejewska, Sylwia, Jarosław Diakun, Mariusz Seńcio, and Joanna Piepiórka-Stepuk. "Effect of Tumbling Conditions on the Tendinous and Tenderness Index of Chicken Leg Meat." Sustainability 15, no. 1 (2022): 273. http://dx.doi.org/10.3390/su15010273.
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This article presents the results of the effect of chicken leg meat tumbling parameters on its texture, as assessed by the tendinous-tenderness index KZ-S, where the value of KZ-S = 1 index means maximum tendinous—no tenderness and the value of KZ-S = 0 means no tendinous—maximum tenderness. The tumbling of the meat was performed in an agitator-tilt tumbler. The variable factors of the tumbling process were temperature (T), time (τ), rotational speed (ω) and angle of the tumbler drum inclination (α). The meat texture was tested using the universal testing machine TMS-Pro with a Warner–Bratzler knife. The results of the study were described using second-degree polynomial correlation functions with couplings and presented in the form of diagrams. The effect of the favorable reduction of the tendinous in favor of the tenderness of meat is most significantly influenced by the angle of the inclination of the drum of the tumbler and the time of massage. The optimal results for the tendinous-tenderness index KZ-S were obtained for the angle of the inclination of the drum of the tumbler α = 45° and tumbling duration τ = 50 min. For such tumbling parameters, the index KZ-S = 0.25 (reduced meat tendons). It is unfavorable, whereas massage tumbling at T = 0 °C, compared to higher and lower temperatures of massaging. The effect of the agitator speed ω depends on the time and temperature. The research results showed that the most favorable effects of the tendinous loss in favor of the tenderness, determined by the tendinous-tenderness index KZ-S, are obtained by the tumbling condition with high a high angle of inclination of the tank (α > 45°), a low value of the rotational speed (ω < 12 [1/min]), a longer time (τ > 50 min) and a temperature different from 0 °C.
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Jeevanandham, P., S. Kumar, P. Periyasamy, and A. C. Kumbharkhane. "Dielectric Relaxation Studies of 2-Butoxyethanol with Aniline and Substituted Anilines Using Time Domain Reflectometry." Advances in Physical Chemistry 2014 (February 18, 2014): 1–9. http://dx.doi.org/10.1155/2014/659531.
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The complex dielectric spectra of 2-butoxyethanol with aniline and substituted anilines like aniline, o-chloroaniline, m-chloroaniline, o-anisidine and m-anisidine binary mixtures in the composition of different volumes of percent (0%, 25%, 50%, 75%, and 100%) have been measured as a function of frequency between 10 MHz and 30 GHz at 298.15 K. The dielectric parameters like static dielectric constant ε0 and relaxation time τ have been obtained by using least square fit method. By using these parameters ε0,τ, effective Kirkwood correlation factor geff, corrective Kirkwood correlation factor gf, Bruggeman factor fB, excess dielectric constant εE, and excess inverse relaxation time 1/τE values are calculated and discussed to yield information on the dipolar alignment and molecular rotation of the binary liquid mixtures. From all the derived dielectric parameters, molecular interactions are interpreted through hydrogen bonding.
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Bezuglaya, Elena, Hanna Ivashchenko, Nikolay Lyapunov, et al. "Study of factors affecting the in vitro release of diclofenac sodium from hypromelose-based gels." ScienceRise: Pharmaceutical Science, no. 5(33) (October 29, 2021): 12–31. http://dx.doi.org/10.15587/2519-4852.2021.243040.
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The aim of our study was to identify factors affecting the in vitro release of diclofenac sodium (DS) from hypromellose-based gels (HPMC).
 Materials and methods. Gels with HPMC and liquids without HPMC were studied by viscosity-rotating viscometer method and spin probe electron paramagnetic resonance spectroscopy. Rheograms were used to determine the flow behavior and the apparent viscosity, and the EPR spectra were used to determine the rotational correlation time (τ–1) of the dissolved spin probes. The in vitro release tests were performed using vertical diffusion cells according to a validated procedure. The assay of DS and isopropyl alcohol (IPA) in the receptor medium was performed by high performance liquid chromatography (HPLC) and gas chromatography (GC) according to validated procedures, and the water content was determined using semi-micro method.
 Results. The apparent viscosity of the gels increased with increasing HPMC content and depended on the HPMC grade. The high apparent viscosity of the gels did not affect the values of τ–1 of the dissolved spin probes. In viscous gels and Newtonian fluids, the composition of which corresponded to the dispersion medium of gels, the values of τ–1 were identical and were in the range of rapid rotation, which is a prerequisite for similar and rapid release of the dissolved substances from gels and liquids. It was shown that the HPMC-based gel and Newtonian liquid without HPMC in terms of in vitro release parameters DS and IPA were equivalent. During in vitro testing the release of dissolved DS increased with increasing its concentration in the gel and depended on the dispersed state of DS. When the content of IPA was changed from 45.0 % to 22.5 %, the water absorption by the gel and the release of IPA decreased, and the release of DS increased, which was due to the decrease in the solubility of DS in the gel.
 Conclusions. HPMC, which provided high apparent viscosity of the gels, did not affect the value of τ–1 of the dissolved spin probes and the in vitro release of DS from the gels. The gel and Newtonian liquid were equivalent in terms of in vitro release of DS and IPA. The release of DS altered proportionally with the concentration of DS and depended on its dispersed state. As the content of IPA decreased, the release of IPA decreased, but the release of DS increased because of the decrease in the solubility of the DS in the gel
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Matam, Santhosh K., C. Richard A. Catlow, Ian P. Silverwood, and Alexander J. O’Malley. "Methanol dynamics in H-ZSM-5 with Si/Al ratio of 25: a quasi-elastic neutron scattering (QENS) study." Topics in Catalysis 64, no. 9-12 (2021): 699–706. http://dx.doi.org/10.1007/s11244-021-01450-z.
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AbstractMethanol dynamics in zeolite H-ZSM-5 (Si/Al of 25) with a methanol loading of ~ 30 molecules per unit cell has been studied at 298, 323, 348 and 373 K by incoherent quasi-elastic neutron scattering (QENS). The elastic incoherent structure factor (EISF) reveals that the majority of methanol is immobile, in the range between 70 and 80%, depending on the measurement temperature. At 298 K, ≈ 20% methanol is mobile on the instrumental timescale, exhibiting isotropic rotational dynamics with a rotational diffusion coefficient (DR) of 4.75 × 1010 s−1. Upon increasing the measurement temperature from 298 to 323 K, the nature of the methanol dynamics changes from rotational to translational diffusion dynamics. Similar translational diffusion rates are measured at 348 and 373 K, though with a larger mobile fraction as temperature increases. The translational diffusion is characterised as jump diffusion confined to a sphere with a radius close to that of a ZSM-5 channel. The diffusion coefficients may be calculated using either the Volino–Dianoux (VD) model of diffusion confined to a sphere, or the Chudley–Elliot (CE) jump diffusion model. The VD model gives rise to a self-diffusion co-efficient (Ds) of methanol in the range of 7.8–8.4 × 10–10 m2 s−1. The CE model gives a Ds of around 1.2 (± 0.1) × 10–9 m2 s−1 with a jump distance of 2.8 (either + 0.15 or − 0.1) Å and a residence time (τ) of ~ 10.8 (either + 0.1 or − 0.2) ps. A correlation between the present and earlier studies that report methanol dynamics in H-ZSM-5 with Si/Al of 36 is made, suggesting that with increasing Si/Al ratio, the mobile fraction of methanol increases while DR decreases.
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Elena, Bezuglaya, Ivashchenko Hanna, Lyapunov Nikolay, et al. "Study of factors affecting the in vitro release of diclofenac sodium from hypromelose-based gels." ScienceRise: Pharmaceutical Science, no. 5(33) (October 29, 2021): 12–31. https://doi.org/10.15587/2519-4852.2021.243040.
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<strong>The aim </strong>of our study was to identify factors affecting the in vitro release of diclofenac sodium (DS) from hypromellose-based gels (HPMC). <strong>Materials and methods.</strong> Gels with HPMC and liquids without HPMC were studied by viscosity-rotating viscometer method and spin probe electron paramagnetic resonance spectroscopy. Rheograms were used to determine the flow behavior and the apparent viscosity, and the EPR spectra were used to determine the rotational correlation time (τ<sub>–1</sub>) of the dissolved spin probes. The in vitro release tests were performed using vertical diffusion cells according to a validated procedure. The assay of DS and isopropyl alcohol (IPA) in the receptor medium was performed by high performance liquid chromatography (HPLC) and gas chromatography (GC) according to validated procedures, and the water content was determined using semi-micro method. <strong>Results.</strong> The apparent viscosity of the gels increased with increasing HPMC content and depended on the HPMC grade. The high apparent viscosity of the gels did not affect the values of τ<sub>–1</sub> of the dissolved spin probes. In viscous gels and Newtonian fluids, the composition of which corresponded to the dispersion medium of gels, the values of τ<sub>–1</sub> were identical and were in the range of rapid rotation, which is a prerequisite for similar and rapid release of the dissolved substances from gels and liquids. It was shown that the HPMC-based gel and Newtonian liquid without HPMC in terms of in vitro release parameters DS and IPA were equivalent. During in vitro testing the release of dissolved DS increased with increasing its concentration in the gel and depended on the dispersed state of DS. When the content of IPA was changed from 45.0 % to 22.5 %, the water absorption by the gel and the release of IPA decreased, and the release of DS increased, which was due to the decrease in the solubility of DS in the gel. <strong>Conclusions</strong><strong>.</strong> HPMC, which provided high apparent viscosity of the gels, did not affect the value of τ<sub>–1</sub> of the dissolved spin probes and the in vitro release of DS from the gels. The gel and Newtonian liquid were equivalent in terms of in vitro release of DS and IPA. The release of DS altered proportionally with the concentration of DS and depended on its dispersed state. As the content of IPA decreased, the release of IPA decreased, but the release of DS increased because of the decrease in the solubility of the DS in the gel
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Arosio, Paolo, Davide Cicolari, Amedea Manfredi, et al. "Nanosized T1 MRI Contrast Agent Based on a Polyamidoamine as Multidentate Gd Ligand." Molecules 27, no. 1 (2021): 174. http://dx.doi.org/10.3390/molecules27010174.
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A linear polyamidoamine (PAA) named BAC-EDDS, containing metal chelating repeat units composed of two tert-amines and four carboxylic groups, has been prepared by the aza-Michael polyaddition of ethylendiaminodisuccinic (EDDS) with 2,2-bis(acrylamido)acetic acid (BAC). It was characterized by size exclusion chromatography (SEC), FTIR, UV–Vis and NMR spectroscopies. The pKa values of the ionizable groups of the repeat unit were estimated by potentiometric titration, using a purposely synthesized molecular ligand (Agly-EDDS) mimicking the structure of the BAC-EDDS repeat unit. Dynamic light scattering (DLS) and ζ-potential analyses revealed the propensity of BAC-EDDS to form stable nanoaggregates with a diameter of approximately 150 nm at pH 5 and a net negative charge at physiological pH, in line with an isoelectric point <2. BAC-EDDS stably chelated Gd (III) ions with a molar ratio of 0.5:1 Gd (III)/repeat unit. The stability constant of the molecular model Gd-Agly-EDDS (log K = 17.43) was determined as well, by simulating the potentiometric titration through the use of Hyperquad software. In order to comprehend the efficiency of Gd-BAC-EDDS in contrasting magnetic resonance images, the nuclear longitudinal (r1) and transverse (r2) relaxivities as a function of the externally applied static magnetic field were investigated and compared to the ones of commercial contrast agents. Furthermore, a model derived from the Solomon–Bloembergen–Morgan theory for the field dependence of the NMR relaxivity curves was applied and allowed us to evaluate the rotational correlation time of the complex (τ = 0.66 ns). This relatively high value is due to the dimensions of Gd-BAC-EDDS, and the associated rotational motion causes a peak in the longitudinal relaxivity at ca. 75 MHz, which is close to the frequencies used in clinics. The good performances of Gd-BAC-EDDS as a contrast agent were also confirmed through in vitro magnetic resonance imaging experiments with a 0.2 T magnetic field.
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Man, Dariusz, Rudolf Słota, Giuseppe Mele, and Jun Li. "Fluidity of Liposome Membranes Doped with Metalloporphyrins: An ESR Study." Zeitschrift für Naturforschung C 63, no. 5-6 (2008): 440–44. http://dx.doi.org/10.1515/znc-2008-5-621.
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Changes in membrane fluidity of porphyrin-doped liposomes have been investigated to assess the kinetics of the fluidization process. Metal complexes of tert-butylphenyl mesosubstituted porphyrin, containing ions of Mg, Mn, Fe, Co, Ni and Cu, were used as dopants. Liposomes were obtained by sonication of hen egg yolk lecithin (EYL). Electron paramagnetic resonance (ESR) was applied using two spin probes, TEMPO (2,2,6,6-tetramethylpiperidine- 1-oxyl) and 16-DOXYL-stearic acid [2-ethyl-2-(15-methoxy-15-oxopentadecyl)-4,4- dimethyl-3-oxazolidinyloxyl], localized at different sites within the membrane to determine the spectroscopic parameters: partition (F) and rotation correlation time (τ), related to the membrane’s fluidity. It was found, that porphyrins considerably fluidize the membranes, and the dynamics of this process depends on the kind of the compound used and the membrane’s area surveyed by the probes. The Cu complex proved to be the most effective one within the surface layer, whereas the Mn complex most strongly fluidized the deeper parts of the lipid double-layer. Variations in fluidity observed after the porphyrins had been introduced into the liposome were found to stabilize inside the double-layer and within the surface layer after ca. 25 and 50 h, most probably due to hydration of the hydrophilic part of the membrane.
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Jakeš, Jaromír. "Plots of the Spin-Lattice Relaxation Time and Nuclear Overhauser Enhancement NMR Values Yielding a Spread Distribution of the Rotational Correlation Time." Collection of Czechoslovak Chemical Communications 65, no. 10 (2000): 1537–58. http://dx.doi.org/10.1135/cccc20001537.
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It is shown, that the plots of ω/T1 and NOE × ω/T1 versus -log ω give the distribution of rotational correlation time τ plotted versus log τ and spread by (rather wide) "slit" functions the form and shape of which are independent of the position on the log τ axis. When plotting data at various temperatures, temperature shift factors aT and the plots versus -log (ωaT) should be used. The plots permit to check the data compatibility and are helpful in studying molecular dynamics. Examples of the plots are given. One example stimulated a consideration of the segmental motion dynamics, which showed that the Hall-Helfand distribution is inappropriate for a description of the orientational relaxation of the non-backbone (C-H) bonds in a polymer chain.
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Fang, Angbo. "Dynamical effective field model for interacting ferrofluids: II. The proper relaxation time and effects of dynamic correlations." Journal of Physics: Condensed Matter 34, no. 11 (2021): 115103. http://dx.doi.org/10.1088/1361-648x/ac4346.
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Abstract The recently proposed dynamical effective field model (DEFM) is quantitatively accurate for ferrofluid dynamics. It is derived in paper I within the framework of dynamical density functional theory (DDFT) along with a phenomenological description of nonadiabatic effects. However, it remains to clarify how the characteristic rotational relaxation time of a dressed particle, denoted by τ r , is quantitatively related to that of a bare particle, denoted by τ r 0 . By building macro-micro connections via two different routes, I reveal that under some gentle assumptions τ r can be identified with the mean time characterizing long-time rotational self-diffusion. I further introduce two simple but useful integrated correlation factors, describing the effects of quasi-static (adiabatic) and dynamic (nonadiabatic) inter-particle correlations, respectively. In terms of both the dynamic magnetic susceptibility is expressed in an illuminating and elegant form. Remarkably, it shows that the macro-micro connection is established via two successive steps: a dynamical coarse-graining with nonadiabatic effects accounted for by the dynamic factor, followed by equilibrium ensemble averaging captured by the static factor. By analyzing data from Brownian dynamics simulations on monodisperse interacting ferrofluids, I find τ r / τ r 0 is, somehow unexpectedly, insensitive to changes of particle volume fraction. A physical picture is proposed to explain it. Furthermore, an empirical formula is proposed to characterize the dependence of τ r / τ r 0 on dipole-dipole interaction strength. The DEFM supplemented with this formula leads to parameter-free predictions in good agreement with results from Brownian dynamics simulations. The theoretical developments presented in this paper may have important consequences to studies of ferrofluid dynamics in particular and other systems modeled by DDFTs in general.
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Karppa, Matti, Petteri Kaski, Jukka Kohonen, and Padraig Ó Catháin. "Explicit Correlation Amplifiers for Finding Outlier Correlations in Deterministic Subquadratic Time." Algorithmica 82, no. 11 (2020): 3306–37. http://dx.doi.org/10.1007/s00453-020-00727-1.
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Abstract We derandomize Valiant’s (J ACM 62, Article 13, 2015) subquadratic-time algorithm for finding outlier correlations in binary data. This demonstrates that it is possible to perform a deterministic subquadratic-time similarity join of high dimensionality. Our derandomized algorithm gives deterministic subquadratic scaling essentially for the same parameter range as Valiant’s randomized algorithm, but the precise constants we save over quadratic scaling are more modest. Our main technical tool for derandomization is an explicit family of correlation amplifiers built via a family of zigzag-product expanders by Reingold et al. (Ann Math 155(1):157–187, 2002). We say that a function $$f:\{-1,1\}^d\rightarrow \{-1,1\}^D$$ f : { - 1 , 1 } d → { - 1 , 1 } D is a correlation amplifier with threshold $$0\le \tau \le 1$$ 0 ≤ τ ≤ 1 , error $$\gamma \ge 1$$ γ ≥ 1 , and strength p an even positive integer if for all pairs of vectors $$x,y\in \{-1,1\}^d$$ x , y ∈ { - 1 , 1 } d it holds that (i) $$|\langle x,y\rangle |<\tau d$$ | ⟨ x , y ⟩ | < τ d implies $$|\langle f(x),f(y)\rangle |\le (\tau \gamma )^pD$$ | ⟨ f ( x ) , f ( y ) ⟩ | ≤ ( τ γ ) p D ; and (ii) $$|\langle x,y\rangle |\ge \tau d$$ | ⟨ x , y ⟩ | ≥ τ d implies $$\left (\frac{\langle x,y\rangle }{\gamma d}\right )^pD \le \langle f(x),f(y)\rangle \le \left (\frac{\gamma \langle x,y\rangle }{d}\right )^pD$$ ⟨ x , y ⟩ γ d p D ≤ ⟨ f ( x ) , f ( y ) ⟩ ≤ γ ⟨ x , y ⟩ d p D .
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Fan, Naixin, Sujan Koirala, Markus Reichstein, et al. "Apparent ecosystem carbon turnover time: uncertainties and robust features." Earth System Science Data 12, no. 4 (2020): 2517–36. http://dx.doi.org/10.5194/essd-12-2517-2020.
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Abstract. The turnover time of terrestrial ecosystem carbon is an emergent ecosystem property that quantifies the strength of land surface on the global carbon cycle–climate feedback. However, observation- and modeling-based estimates of carbon turnover and its response to climate are still characterized by large uncertainties. In this study, by assessing the apparent whole ecosystem carbon turnover times (τ) as the ratio between carbon stocks and fluxes, we provide an update of this ecosystem level diagnostic and its associated uncertainties in high spatial resolution (0.083∘) using multiple, state-of-the-art, observation-based datasets of soil organic carbon stock (Csoil), vegetation biomass (Cveg) and gross primary productivity (GPP). Using this new ensemble of data, we estimated the global median τ to be 43-7+7 yr (median-difference to percentile 25+difference to percentile 75) when the full soil is considered, in contrast to limiting it to 1 m depth. Only considering the top 1 m of soil carbon in circumpolar regions (assuming maximum active layer depth is up to 1 m) yields a global median τ of 37-6+3 yr, which is longer than the previous estimates of 23-4+7 yr (Carvalhais et al., 2014). We show that the difference is mostly attributed to changes in global Csoil estimates. Csoil accounts for approximately 84 % of the total uncertainty in global τ estimates; GPP also contributes significantly (15 %), whereas Cveg contributes only marginally (less than 1 %) to the total uncertainty. The high uncertainty in Csoil is reflected in the large range across state-of-the-art data products, in which full-depth Csoil spans between 3362 and 4792 PgC. The uncertainty is especially high in circumpolar regions with an uncertainty of 50 % and a low spatial correlation between the different datasets (0.2<r<0.5) when compared to other regions (0.6<r<0.8). These uncertainties cast a shadow on current global estimates of τ in circumpolar regions, for which further geographical representativeness and clarification on variations in Csoil with soil depth are needed. Different GPP estimates contribute significantly to the uncertainties of τ mainly in semiarid and arid regions, whereas Cveg causes the uncertainties of τ in the subtropics and tropics. In spite of the large uncertainties, our findings reveal that the latitudinal gradients of τ are consistent across different datasets and soil depths. The current results show a strong ensemble agreement on the negative correlation between τ and temperature along latitude that is stronger in temperate zones (30–60∘ N) than in the subtropical and tropical zones (30∘ S–30∘ N). Additionally, while the strength of the τ–precipitation correlation was dependent on the Csoil data source, the latitudinal gradients also agree among different ensemble members. Overall, and despite the large variation in τ, we identified robust features in the spatial patterns of τ that emerge beyond the differences stemming from the data-driven estimates of Csoil, Cveg and GPP. These robust patterns, and associated uncertainties, can be used to infer τ–climate relationships and for constraining contemporaneous behavior of Earth system models (ESMs), which could contribute to uncertainty reductions in future projections of the carbon cycle–climate feedback. The dataset of τ is openly available at https://doi.org/10.17871/bgitau.201911 (Fan et al., 2019).
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Keilson, Julian. "Covariance and relaxation time in finite Markov chains." Journal of Applied Mathematics and Stochastic Analysis 11, no. 3 (1998): 391–96. http://dx.doi.org/10.1155/s104895339800032x.
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The relaxation time TREL of a finite ergodic Markov chain in continuous time, i.e., the time to reach ergodicity from some initial state distribution, is loosely given in the literature in terms of the eigenvalues λj of the infinitesimal generator Q¯¯. One uses TREL=θ−1 where θ=minλj≠0{Reλj[−Q¯¯]}. This paper establishes for the relaxation time θ−1 the theoretical solidity of the time reversible case. It does so by examining the structure of the quadratic distance d(t) to ergodicity. It is shown that, for any function f(j) defined for states j, the correlation function ρf(τ) has the bound |ρf(τ)|≤exp[−π|τ|] and that this inequality is tight. The argument is almost entirely in the real domain.
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VESPIGNANI, A., A. PETRI, A. ALIPPI, G. PAPARO, and M. COSTANTINI. "LONG RANGE CORRELATION PROPERTIES OF AFTERSHOCK RELAXATION SIGNALS." Fractals 03, no. 04 (1995): 839–47. http://dx.doi.org/10.1142/s0218348x95000746.
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Relaxation processes taking place after microfracturing of laboratory samples give rise to ultrasonic acoustic emission signals. Statistical analysis of the resulting time series has revealed many features which are characteristic of critical phenomena. In particular, the autocorrelation functions obey a power-law behavior, implying a power spectrum of the kind 1/f. Also the amplitude distribution N(V) of such signals follows a power law, and the obtained exponents are consistent with those found in other experiments: N(V) dV≃V–γ dV, with γ=1.7±0.2. We also analyzed the distribution N(τ) of the delay time τ between two consecutive acoustic emission events. We found that a N(τ) distribution rather close to a power law constitutes a common feature of all the recorded signals. These experimental results can be considered as a striking evidence for a critical dynamics underlying the microfracturing processes.
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WANG, CAN-JUN, and DONG-CHENG MEI. "THE RELAXATION TIME AND THE CORRELATION FUNCTION FOR A LOGISTIC GROWTH SYSTEM DRIVEN BY COLORED CROSS-CORRELATION NOISES." Fluctuation and Noise Letters 08, no. 02 (2008): L213—L228. http://dx.doi.org/10.1142/s0219477508004398.
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The associated relaxation time Tc and the normalized correlation function C(s) are investigated in the logistic growth system, which is used to describe a tumor cell growth process, driven by two Gaussian white noise sources and the correlation between the additive and multiplicative noise. The expression of Tc and C(s), which is the function of noise parameters (additive noise intensity α, multiplicative noise intensity D, correlation intensity λ and correlation time τ), is obtained by using the projection operator method. After introducing noise intensity ratio, a dimensionless parameter R = α/D, and performing the numerical computations, the two case are analyzed: (1) In the growth case, λ and τ play opposite roles on the Tc and the C(s). It must emphasize that there is a minimal evolution velocity to appear and the tumor cell numbers is hard to evolve from an arbitrary initial condition to the maximum. (2) In the decay case, λ and τ play same roles on the Tc and the C(s). There is a maximal evolution velocity to appear. The noises induce different responses of tumor cells between the growth and decay case.
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van Dinther, Daniëlle, and Oscar K. Hartogensis. "Using the Time-Lag Correlation Function of Dual-Aperture Scintillometer Measurements to Obtain the Crosswind." Journal of Atmospheric and Oceanic Technology 31, no. 1 (2014): 62–78. http://dx.doi.org/10.1175/jtech-d-13-00118.1.
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Abstract In this study the crosswind (U⊥) is determined from the time-lag correlation function [r12(τ)] measured by a dual large-aperture scintillometer; U⊥ is defined as the wind component perpendicular to a path—in this case, the scintillometer path. A scintillometer obtains a path-averaged U⊥, which for some applications is an advantage compared to other wind measurement devices. Four methods were used to obtain U⊥: the peak method, the Briggs method, the zero-slope method, and the lookup table method. This last method is a new method introduced in this paper, which obtains U⊥ by comparing r12(τ) of a measurement to r12(τ) of a theoretical model. The U⊥ values obtained from the scintillometer were validated with sonic anemometer measurements. The best results were obtained by the zero-slope method for U⊥ &lt; 2 m s−1 and by the lookup table method for U⊥ &gt; 2 m s−1. The Briggs method also showed promising results, but it is not always able to obtain U⊥. The results showed that a high parallel wind component (&gt;2.5 m s−1) on the scintillometer path can cause an overestimation of U⊥ mainly for low U⊥ values (&lt;2 m s−1).
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Chung, Charles S., David M. Ajo, and Sándor J. Kovács. "Isovolumic pressure-to-early rapid filling decay rate relation: model-based derivation and validation via simultaneous catheterization echocardiography." Journal of Applied Physiology 100, no. 2 (2006): 528–34. http://dx.doi.org/10.1152/japplphysiol.00617.2005.
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Transmitral Doppler echocardiography is the preferred method of noninvasive diastolic function assessment. Correlations between catheterization-based measures of isovolumic relaxation (IVR) and transmitral, early rapid filling (Doppler E-wave)-derived parameters have been observed, but no model-based, causal explanation has been offered. IVR has also been characterized in terms of its duration as IVR time (IVRT) and by τ, the time-constant of IVR, by approximating the terminal left ventricular IVR pressure contour as P( t) = P∞ + Po e− t/τ, where P( t) is the continuity of pressure, P∞ and Po are constants, t is time, and τ is the time constant of IVR. To characterize the relation between IVR and early rapid filling more fully, simultaneous (micromanometric) left ventricular pressure and transmitral Doppler E-wave data from 25 subjects undergoing elective cardiac catheterization and having normal physiology were analyzed. The time constant τ was determined from the dP /d t vs. P (phase) plane and, simultaneous Doppler E-waves provided global indexes of chamber viscosity/relaxation ( c), chamber stiffness ( k), and load ( xo). We hypothesize that temporal continuity of pressure decay at mitral valve opening and physiological constraints permit the algebraic derivation of linear relations relating 1/τ to both peak atrioventricular pressure gradient ( kxo) and E-wave-derived viscosity/relaxation ( c) but does not support a similar, causal (linear) relation between deceleration time and τ or IVRT. Both predicted linear relations were observed: kxo to 1/τ ( r = 0.71) and viscosity/relaxation to 1/τ ( r = 0.71). Similarly, as anticipated, only a weak linear correlation between deceleration time and IVRT or τ was observed ( r = 0.41). The observed in vivo relationship provides insight into the isovolumic mechanism of relaxation and the changing-volume mechanism of early rapid filling via a link of the respective relaxation properties.
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Chung, Charles S., and Sándor J. Kovács. "Physical determinants of left ventricular isovolumic pressure decline: model prediction with in vivo validation." American Journal of Physiology-Heart and Circulatory Physiology 294, no. 4 (2008): H1589—H1596. http://dx.doi.org/10.1152/ajpheart.00990.2007.
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The rapid decline in pressure during isovolumic relaxation (IVR) is traditionally fit algebraically via two empiric indexes: τ, the time constant of IVR, or τL, a logistic time constant. Although these indexes are used for in vivo diastolic function characterization of the same physiological process, their characterization of IVR in the pressure phase plane is strikingly different, and no smooth and continuous transformation between them exists. To avoid the parametric discontinuity between τ and τL and more fully characterize isovolumic relaxation in mechanistic terms, we modeled ventricular IVR kinematically, employing a traditional, lumped relaxation (resistive) and a novel elastic parameter. The model predicts IVR pressure as a function of time as the solution of d2P/d t2 + (1/μ)dP/d t + EkP = 0, where μ (ms) is a relaxation rate (resistance) similar to τ or τL and Ek (1/s2) is an elastic (stiffness) parameter (per unit mass). Validation involved analysis of 310 beats (10 consecutive beats for 31 subjects). This model fit the IVR data as well as or better than τ or τL in all cases (average root mean squared error for dP/d t vs. t: 29 mmHg/s for model and 35 and 65 mmHg/s for τ and τL, respectively). The solution naturally encompasses τ and τL as parametric limits, and good correlation between τ and 1/μ Ek (τ = 1.15/μ Ek − 11.85; r2 = 0.96) indicates that isovolumic pressure decline is determined jointly by elastic ( Ek) and resistive (1/μ) parameters. We conclude that pressure decline during IVR is incompletely characterized by resistance (i.e., τ and τL) alone but is determined jointly by elastic ( Ek) and resistive (1/μ) mechanisms.
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CAVALLERI, GIANCARLO, ERNESTO TONNI, LEONARDO BOSI, and GIANFRANCO SPAVIERI. "VERY LONG DECAY TIME FOR ELECTRON VELOCITY DISTRIBUTION IN SEMICONDUCTORS, AND CONSEQUENT 1/f NOISE." Fluctuation and Noise Letters 07, no. 03 (2007): L193—L207. http://dx.doi.org/10.1142/s0219477507003842.
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The Boltzmann equation with electron-electron (e − e) interactions has been reduced to a Fokker-Planck equation (e − e FP ) in a previuos paper. In steady-state conditions, its solution q0(v) (where v is the electron speed) depends on the square of the acceleration a = eE/m. If we introduce the nonrenormalized zero-point field (ZPF) of QED, i.e., the one considered in stochastic electrodynamics, so that [Formula: see text], then q0(v) becomes similar to the Fermi-Dirac equation, and the two collision frequencies ν1(v) and ν2(v) appearing in the e − e FP become both proportional to 1/v in a small δv interval. The condition ν1(v) ∝ ν2(v) ∝ 1/v is at the threshold of the runaways. In the same δv range, the time-dependent solution q0(v,τ) of the e − e FP decays no longer exponentially but according to a power law ∝ τ− ɛ where 0.004 < ɛ < 0.006, until τ → ∞. That extremely long memory of a fluctuation implies the same dependence τ − ɛ for the conductance correlation function, hence a corresponding power-spectral noise S(f) ∝ fɛ−1 where f is the frequency. That behaviour is maintained even for a small sample because the back diffusion velocity of the electrons in the effective range δv, where they are in runaway conditions, is much larger than the drift velocity.
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GONG, YUBING, XIU LIN, YINGHANG HAO, YANHANG XIE, and XIAOGUANG MA. "NON-GAUSSIAN NOISE-INDUCED FIRING TRANSITIONS AND ORDERED BURSTING IN A THERMO-SENSITIVE NEURON." Fluctuation and Noise Letters 09, no. 03 (2010): 289–99. http://dx.doi.org/10.1142/s0219477510000216.
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In this letter, we investigate how a particular kind of non-Gaussian colored noise (NGN), especially the correlation time τ and the departure q from Gaussian noise, affects the chaotic firing behavior in a thermo-sensitive neuron. It is found that transitions between spiking and bursting occur with changing τ or q, and ordered bursting appears when τ is optimal. As τ is increased, the neuron alternately exhibits spiking and bursting when q < 1, but always bursts when q > 1, and chaotic bursts may become ordered at an optimal τ. As q is increased, the neuron also exhibits transitions between spiking and bursting. These findings provide a new mechanism for the firing transitions in the neuron and present the constructive role of the NGN in the firing activity in the neuron. This reveals that the NGN would play subtle roles in the communication and information processing in the neurons.
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Mishra, M. K., G. Rastogi, and P. Chauhan. "Operational Retrieval of aerosol optical depth over Indian subcontinent and Indian Ocean using INSAT-3D/Imager product validation." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-8 (November 28, 2014): 277–82. http://dx.doi.org/10.5194/isprsarchives-xl-8-277-2014.
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Aerosol optical depth (AOD) over Indian subcontinent and Indian Ocean region is derived operationally for the first time from the geostationary earth orbit (GEO) satellite INSAT-3D Imager data at 0.65 μm wavelength. Single visible channel algorithm based on clear sky composites gives larger retrieval error in AOD than other multiple channel algorithms due to errors in estimating surface reflectance and atmospheric property. However, since MIR channel signal is insensitive to the presence of most aerosols, therefore in present study, AOD retrieval algorithm employs both visible (centred at 0.65 μm) and mid-infrared (MIR) band (centred at 3.9 μm) measurements, and allows us to monitor transport of aerosols at higher temporal resolution. Comparisons made between INSAT-3D derived AOD (τ<sub>I</sub>) and MODIS derived AOD (τ<sub>M</sub>) co-located in space (at 1&deg; resolution) and time during January, February and March (JFM) 2014 encompasses 1165, 1052 and 900 pixels, respectively. Good agreement found between τ<sub>I</sub> and τ<sub>M</sub> during JFM 2014 with linear correlation coefficients (R) of 0.87, 0.81 and 0.76, respectively. The extensive validation made during JFM 2014 encompasses 215 co-located AOD in space and time derived by INSAT 3D (τ<sub>I</sub>) and 10 sun-photometers (τ<sub>A</sub>) that includes 9 AERONET (Aerosol Robotic Network) and 1 handheld sun-photometer site. INSAT-3D derived AOD i.e. τ<sub>I</sub>, is found within the retrieval errors of τ<sub>I</sub> = ±0.07 ±0.15τ<sub>A</sub> with linear correlation coefficient (R) of 0.90 and root mean square error equal (RMSE) to 0.06. Present work shows that INSAT-3D aerosol products can be used quantitatively in many applications with caution for possible residual clouds, snow/ice, and water contamination.
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Zhao, Siqi, Huirong Yan, and Terry Z. Liu. "Observations of Turbulence and Particle Transport at Interplanetary Shocks: Transition of Transport Regimes." Astrophysical Journal 985, no. 1 (2025): 37. https://doi.org/10.3847/1538-4357/adc378.
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Abstract The transport of energetic particles is intimately related to the properties of plasma turbulence, a ubiquitous dynamic process that transfers energy across a broad range of spatial and temporal scales. However, the mechanisms governing the interactions between plasma turbulence and energetic particles are not completely understood. Here we present comprehensive observations from the upstream region of a quasi-perpendicular interplanetary (IP) shock on 2004 January 22, using data from four Cluster spacecraft to investigate the interplay between turbulence dynamics and energetic particle transport. Our observations reveal a transition in energetic proton fluxes from exponential to power-law decay with increasing distance from the IP shock. This result provides possible observational evidence of a shift in transport behavior from normal diffusion to superdiffusion. This transition correlates with an increase in the time ratio from τ s /τ c < 1 to τ s /τ c ≫ 1, where τ s is the proton isotropization time, and τ c is the turbulence correlation time. Additionally, the frequency–wavenumber distributions of magnetic energy in the power-law decay zone indicate that energetic particles excite linear Alfvén-like harmonic waves through gyroresonance, thereby modulating the original turbulence structure. These findings provide valuable insights for future studies on the propagation and acceleration of energetic particles in turbulent astrophysical and space plasma systems.
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G, TAMIZHARASI, and C.V.R.Mury. "Method to identify if torsional mode of a building is its first mode." Bulletin of the New Zealand Society for Earthquake Engineering 57, no. 2 (2024): 69–84. http://dx.doi.org/10.5459/bnzsee.1645.
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Torsionally flexible buildings (that have torsional mode as fundamental mode) twist during earthquake shaking, and may collapse partially or completely depending upon the direction and level of shaking. The problem is aggravated when the building is torsionally unsymmetrical. Some design codes (like Eurocode, Indian Code) explicitly prohibit the design of such buildings. This paper presents a simple approximate method to identify torsionally flexible RC Moment Frame and RC Structural Wall buildings at the initial proportioning stage itself without carrying out a detailed structural analysis. It is possible to identify whether or not the first mode is torsional mode of a building (i.e., torsionally flexible building) if Natural Period Ratio τ>1 by modelling the building with rigid diaphragm and distribution of mass & stiffness along the height of building, and estimating: (1) radius of gyration of rotational mass rm of each floor plan geometry by lumping the masses of slabs, beams and all vertical elements at each nodes, (2) radius of gyration of twisting stiffness rKθ of all vertical elements using their translational and torsional stiffnesses (considering flexibility of adjoining beams and vertical elements accounting for both flexural and shear deformations), and (iv) τ (=rm/rKθ). The method is validated with 3D Modal Analysis (using τ =Tθ/T, where Tθ is Uncoupled Torsional Natural Period and T Uncoupled Translational Natural Period) of hypothetical buildings using a commercial structural analysis software. Also, parameters are identified that lead to τ>1, and solutions suggested to avoid torsional flexibility in buildings. Further, the method helps identify vertical stiffness irregularity in buildings. Draft provisions are suggested for inclusion in seismic codes. Also, poor performance of multi-storey building (with τ>1) is demonstrated using nonlinear static and nonlinear time history analyses.
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Matilla-García, Mariano, Isidro Morales, Jose Miguel Rodríguez, and Manuel Ruiz Marín. "Selection of Embedding Dimension and Delay Time in Phase Space Reconstruction via Symbolic Dynamics." Entropy 23, no. 2 (2021): 221. http://dx.doi.org/10.3390/e23020221.
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The modeling and prediction of chaotic time series require proper reconstruction of the state space from the available data in order to successfully estimate invariant properties of the embedded attractor. Thus, one must choose appropriate time delay τ∗ and embedding dimension p for phase space reconstruction. The value of τ∗ can be estimated from the Mutual Information, but this method is rather cumbersome computationally. Additionally, some researchers have recommended that τ∗ should be chosen to be dependent on the embedding dimension p by means of an appropriate value for the time delay τw=(p−1)τ∗, which is the optimal time delay for independence of the time series. The C-C method, based on Correlation Integral, is a method simpler than Mutual Information and has been proposed to select optimally τw and τ∗. In this paper, we suggest a simple method for estimating τ∗ and τw based on symbolic analysis and symbolic entropy. As in the C-C method, τ∗ is estimated as the first local optimal time delay and τw as the time delay for independence of the time series. The method is applied to several chaotic time series that are the base of comparison for several techniques. The numerical simulations for these systems verify that the proposed symbolic-based method is useful for practitioners and, according to the studied models, has a better performance than the C-C method for the choice of the time delay and embedding dimension. In addition, the method is applied to EEG data in order to study and compare some dynamic characteristics of brain activity under epileptic episodes
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Kolhe, S. B., and S. G. Badhe. "Microwave Dielectric Study of Binary Mixture of Ethyl Acetate with Propylene Glycol using Time Domain Reflectometry Technique." Asian Journal of Chemistry 36, no. 11 (2024): 2635–39. http://dx.doi.org/10.14233/ajchem.2024.32624.
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Microwave dielectric study for the binary mixtures of ethyl acetate with propylene glycol was performed over the frequency range of 10 MHz –20 GHz and in the temperature range of 288 K to 318 K using time domain reflectometry technique. Dielectric parameters such as static dielectric constant (εs), relaxation time (τ), excess dielectric constant (εs)E, excess inverse relaxation time (1/τ)E, Kirkwood correlation factor (geff), Bruggeman factor (fB) and thermodynamic parameters viz. molar enthalpy of activation, molar entropy of activation were also determined. Variation of measured dielectric and thermodynamic parameters have been used to explain the intermolecular interactions between the ethyl acetate and propylene glycol.
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Potapov, Alexei. "Characteristic Scales of Reconstruction Distortions." International Journal of Bifurcation and Chaos 08, no. 04 (1998): 835–41. http://dx.doi.org/10.1142/s0218127498000632.
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We consider the distortions of reconstructed chaotic attractors related with the choice of reconstruction parameters (embedding dimension m and delay τ) and characteristic scales of these distortions. The "spatial" scale may be interpreted as the upper bound for neighborhood size, which is used in many algorithms such as the calculation of Lyapunov exponents. The corresponding "temporal scale" gives the upper bound for the window length spanned by reconstructed vector w=(m-1)τ — the so-called "irrelevance time" [Casdagli et al., 1991]. The analysis enabled us to propose the new algorithm of time series processing for the direct estimation of generalized entropy from time series without calculating the correlation integral.
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Schinkel, Jeffrey E., and Gordon G. Hammes. "Chloroplast coupling factor 1: dependence of rotational correlation time on polypeptide composition." Biochemistry 25, no. 14 (1986): 4066–71. http://dx.doi.org/10.1021/bi00362a012.
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Yamada, Yoshitsugu, and Hong-Lin Du. "Analysis of the mechanisms of expiratory asynchrony in pressure support ventilation: a mathematical approach." Journal of Applied Physiology 88, no. 6 (2000): 2143–50. http://dx.doi.org/10.1152/jappl.2000.88.6.2143.
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A mathematical model was developed to analyze the mechanisms of expiratory asynchrony during pressure support ventilation (PSV). Solving the model revealed several results. 1) Ratio of the flow at the end of patient neural inspiration to peak inspiratory flow (V˙ti/V˙peak) during PSV is determined by the ratio of time constant of the respiratory system (τ) to patient neural inspiratory time (Ti) and the ratio of the set pressure support (Pps) level to maximal inspiratory muscle pressure (Pmus max). 2)V˙ti/V˙peakis affected more by τ/Ti than by Pps/Pmus max.V˙ti/V˙peakincreases in a sigmoidal relationship to τ/Ti. An increase in Pps/Pmus max slightly shifts theV˙ti/V˙peak-τ/Ticurve to the right, i.e.,V˙ti/V˙peakbecomes lower as Pps/Pmus max increases at the same τ/Ti. 3) Under the selected adult respiratory mechanics,V˙ti/V˙peakranges from 1 to 85% and has an excellent linear correlation with τ/Ti. 4) In mechanical ventilators, single fixed levels of the flow termination criterion will always have chances of both synchronized termination and asynchronized termination, depending on patient mechanics. An increase in τ/Ti causes more delayed and less premature termination opportunities. An increase in Pps/Pmus max narrows the synchronized zone, making inspiratory termination predisposed to be in asynchrony. Increasing the expiratory trigger sensitivity of a ventilator shifts the synchronized zone to the right, causing less delayed and more premature termination. Automation of expiratory trigger sensitivity in future mechanical ventilators may also be possible. In conclusion, our model provides a useful tool to analyze the mechanisms of expiratory asynchrony in PSV.
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Chen, Sizhe, Qingyun Yan, Shuanggen Jin, et al. "Soil Moisture Retrieval from the CyGNSS Data Based on a Bilinear Regression." Remote Sensing 14, no. 9 (2022): 1961. http://dx.doi.org/10.3390/rs14091961.
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Soil moisture (SM) has normally been estimated based on a linear relationship between SM and the surface reflectivity (Γ) from the spaceborne Global Navigation Satellite System (GNSS)-Reflectometry, while it usually relies on inputs of SM data without considering vegetation optical depth (VOD/τ) effects. In this study, a new scheme is proposed for retrieving soil moisture from the Cyclone GNSS (CyGNSS) data. The variation of CyGNSS-derived ΔΓ is modeled as a function of both variations in SM and VOD (ΔSM and Δτ). For retrieving SM, ancillary τ data can be obtained from the Soil Moisture Active Passive (SMAP) mission. In addition to this option, a model for simulating Δτ is suggested as an alternative. Experimental evaluation is performed for the time span from August 2019 to July 2021. Excellent agreements between the final retrievals and referenced SMAP SM products are achieved for both training (1-year period) and test (1-year duration) sets. On the whole, overall correlation coefficients (r) of 0.97 and 0.95 and root-mean-square errors (RMSEs) of 0.024 and 0.028 cm3/cm3 are obtained based on models using the SMAP and simulated Δτ, respectively. The model without τ generates an r of 0.95 and an RMSE of 0.031 cm3/cm3. The efficiency and necessity of considering τ are thus confirmed by its enhancement based on correlation and RMSE against the one without τ, and the usefulness of approximating Δτ by sinusoidal functions is also validated. Influences of SM statistics in terms of mean and variance on the retrieval accuracy are evaluated. This work unveils the interaction between CyGNSS data, SM, and τ and demonstrates the feasibility of integrating the Δτ approximation function into a bilinear regression model to obtain SM results.
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Yano, Masafumi, Michihiro Kohno, Shigeki Kobayashi, et al. "Influence of timing and magnitude of arterial wave reflection on left ventricular relaxation." American Journal of Physiology-Heart and Circulatory Physiology 280, no. 4 (2001): H1846—H1852. http://dx.doi.org/10.1152/ajpheart.2001.280.4.h1846.
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The influence of timing and magnitude of arterial wave reflection (WR) on afterload-dependent relaxation was evaluated in patients with a variety of heart diseases ( group 1, age < 30 yr; group 2, age > 40 yr) and in dogs. While both femoral arteries were compressed (FC), WR returned just after the dicrotic notch (early diastole) in group 1but before the dicrotic notch (late systole) in group 2. The time constant of the left ventricular pressure decay (τ) was shortened during FC in group 1, whereas it was prolonged in group 2. In dogs, a constriction of the thoracic aorta induced a late systolic augmentation of WR with a prolongation of τ (cf. group 2), whereas constriction of the lower abdominal aorta induced an early diastolic augmentation of WR with a shortening of τ (cf. group 1). With aortic constriction, coronary flow increased, and there was a close correlation between the peak change in backward aortic pressure and that in coronary flow regardless of the timing of WR. Thus the time at which WR returns during the cardiac cycle may have an important effect on left ventricular relaxation and coronary flow.
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Borisevich, Igor S., Anastasia K. Vinogradova, Eugeny N. Ofitserov, and Viktor M. Pojidaev. "The connection of inertia rotary moment with the chromatographic retention time in alkanes series. New retention indices." Butlerov Communications 57, no. 1 (2019): 15–20. http://dx.doi.org/10.37952/roi-jbc-01/19-57-1-15.
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Earlier it was shown that cause of physicochemical properties oscillation and splitting into even and odd groups in the organic compounds homologous series is the rotational motion energy, determined by the molecule structure. In turn, the organic compound structure can be numerically described or expressed in terms of rotational motion inertia moment. It was logical to assume the correlation between the retention time and rotational motion inertia moment. In order to establish the connection of molecule rotational inertia moment with the chromatographic retention time, a mixture of normal structure alkanes (C6-C17) was experimentally analyzed and corresponding graphs were constructed confirming the assumptions made. A new chromatographic index IJ was proposed, which has advantages over the Kovats index (IK).
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Huang, Bo, and Xuguang Wang. "On the Use of Cost-Effective Valid-Time-Shifting (VTS) Method to Increase Ensemble Size in the GFS Hybrid 4DEnVar System." Monthly Weather Review 146, no. 9 (2018): 2973–98. http://dx.doi.org/10.1175/mwr-d-18-0009.1.
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Abstract Valid-time-shifting (VTS) ensembles, either in the form of full ensemble members (VTSM) or ensemble perturbations (VTSP), were investigated as inexpensive means to increase ensemble size in the NCEP Global Forecast System (GFS) hybrid four-dimensional ensemble–variational (4DEnVar) data assimilation system. VTSM is designed to sample timing and/or phase errors, while VTSP can eliminate spurious covariances through temporal smoothing. When applying a shifting time interval (τ = 1, 2, or 3 h), VTSM and VTSP triple the baseline background ensemble size from 80 (ENS80) to 240 (ENS240) in the EnVar variational update, where the overall cost is only increased by 23%–27%, depending on the selected τ. Experiments during a 10-week summer period show the best-performing VTSP with τ = 2 h improves global temperature and wind forecasts out to 5 days over ENS80. This could be attributed to the improved background ensemble distribution, ensemble correlation accuracy, and increased effective rank in the populated background ensemble. VTSM generally degrades global forecasts in the troposphere. Improved global forecasts above 100 hPa by VTSM may benefit from the increased spread that alleviates the underdispersiveness of the original background ensemble at such levels. Both VTSM and VTSP improve tropical cyclone track forecasts over ENS80. Although VTSM and VTSP are much less expensive than directly running a 240-member background ensemble, owing to the improved ensemble covariances, the best-performing VTSP with τ = 1 h performs comparably or only slightly worse than ENS240. The best-performing VTSM with τ = 3 h even shows more accurate track forecasts than ENS240, likely contributed to by its better sampling of timing and/or phase errors for cases with small ensemble track spread.
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Pichugina, Yelena L., Sara C. Tucker, Robert M. Banta, et al. "Horizontal-Velocity and Variance Measurements in the Stable Boundary Layer Using Doppler Lidar: Sensitivity to Averaging Procedures." Journal of Atmospheric and Oceanic Technology 25, no. 8 (2008): 1307–27. http://dx.doi.org/10.1175/2008jtecha988.1.
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Abstract Quantitative data on turbulence variables aloft—above the region of the atmosphere conveniently measured from towers—have been an important but difficult measurement need for advancing understanding and modeling of the stable boundary layer (SBL). Vertical profiles of streamwise velocity variances obtained from NOAA’s high-resolution Doppler lidar (HRDL), which have been shown to be approximately equal to turbulence kinetic energy (TKE) for stable conditions, are a measure of the turbulence in the SBL. In the present study, the mean horizontal wind component U and variance σ2u were computed from HRDL measurements of the line-of-sight (LOS) velocity using a method described by Banta et al., which uses an elevation (vertical slice) scanning technique. The method was tested on datasets obtained during the Lamar Low-Level Jet Project (LLLJP) carried out in early September 2003, near the town of Lamar in southeastern Colorado. This paper compares U with mean wind speed obtained from sodar and sonic anemometer measurements. The results for the mean U and mean wind speed measured by sodar and in situ instruments for all nights of LLLJP show high correlation (0.71–0.97), independent of sampling strategies and averaging procedures, and correlation coefficients consistently &gt;0.9 for four high-wind nights, when the low-level jet speeds exceeded 15 m s−1 at some time during the night. Comparison of estimates of variance, on the other hand, proved sensitive to both the spatial and temporal averaging parameters. Several series of averaging tests are described, to find the best correlation between TKE calculated from sonic anemometer data at several tower levels and lidar measurements of horizontal-velocity variance σ2u. Because of the nonstationarity of the SBL data, the best results were obtained when the velocity data were first averaged over intervals of 1 min, and then further averaged over 3–15 consecutive 1-min intervals, with best results for the 10- and 15-min averaging periods. For these cases, correlation coefficients exceeded 0.9. As a part of the analysis, Eulerian integral time scales (τ) were estimated for the four high-wind nights. Time series of τ through each night indicated erratic behavior consistent with the nonstationarity. Histograms of τ showed a mode at 4–5 s, but frequent occurrences of larger τ values, mostly between 10 and 100 s.
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Oppenheim, S. F., G. R. Buettner, and V. G. J. Rodgers. "Relationship of rotational correlation time from EPR spectroscopy and protein-membrane interaction." Journal of Membrane Science 118, no. 1 (1996): 133–39. http://dx.doi.org/10.1016/0376-7388(96)00070-1.
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Výprachtický, Drahomír, Veronika Pokorná, Jan Pecka, and František Mikeš. "Fluorescence Anisotropy and Mobility of Dansyl Fluorophore in Labelled Homologous Alkanes." Collection of Czechoslovak Chemical Communications 64, no. 9 (1999): 1369–84. http://dx.doi.org/10.1135/cccc19991369.
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Using the steady-state and time-resolved fluorescence anisotropy, the mobility of 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) fluorophore in homologous 1-[2-acetamido-3-(1H-indol-3-yl)propanamido]-n-[5-(dimethylamino)naphthalene-1-sulfonamido]alkanes 1 was studied in binary solvents glycerol-water. Steady-state fluorescence data were evaluated by the generalized Perrin equation and the micro-Brownian motion of dansyl fluorophore was described by means of average characteristics (rotational relaxation times) of the rotational relaxation spectrum. The rotational relaxation time of "fast" motions caused by torsional vibrations of single bonds within the rotational-isomeric states decreases with increasing number of methylene groups in homologous compounds. The rotational relaxation time of "slow" motions due to conformational changes of the chain between the tryptophane and dansyl fluorophore remains at first approximately constant with increasing number of methylene groups but increases considerably for long aliphatic chains. The observed decrease in the rate of conformational changes of a long aliphatic chain is probably due to intramolecular interaction of parts of the methylene chain in a medium with high water content. The values of activation enthalpy ∆H≠ and activation entropy ∆S≠ calculated from experimental data corroborate such interpretation. Time-resolved anisotropy of dansyl fluorophore at a particular binary solvent composition confirmed the shape of rotational relaxation spectrum and the measured rotational correlation times have been discussed. The time-dependent decays of anisotropy supported our previous interpretation in terms of intramolecular association of the long aliphatic chain in polar medium.
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Schneider, T., T. Siegemund, R. Siegemund, and S. Petros. "Thrombin generation and rotational thromboelastometry in the healthy adult population." Hämostaseologie 35, no. 02 (2015): 181–86. http://dx.doi.org/10.5482/hamo-14-08-0033.
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SummaryPublished data on thrombin generation variables and their correlation with thrombo - elastometry in the healthy population are scarce. This study aimed at assessing thrombin generation in adults and its correlation to classical rotational thromboelastometry (ROTEM).Thrombin generation was measured in platelet-poor plasma from healthy volunteers using the calibrated automated thrombogram (CAT) with 1 and 5 pmol/l tissue factor final concentration. Lag time, thrombin peak, time to thrombin peak and endogenous thrombin potential (ETP) were analyzed. ROTEM was performed without activator (NATEM) and data for clotting time, alpha angle, clot formation time and maximum clot firmness were correlated with those of thrombin generation.Altogether 132 persons (72 men, 60 women; median age: 48.0 years) were included. There was a positive non-linear correlation for age versus lag time (p < 0.001) and time to peak (p = 0.001), and almost linear correlation for age versus thrombin peak (p = 0.024) and ETP (p = 0.001), although with a moderate regression slope. Regarding ROTEM, there was a positive correlation between age and maximum clot firmness and alpha angle (p = 0.001), but a negative correlation between age and clotting time (p = 0.039). Comparing both assays, thrombin peak and ETP measured with a final tissue factor concentration of 5 pmol/l correlated significantly with alpha angle and maximum clot firmness.The age-related changes in CAT and ROTEM variables among adults are not linear. There is a significant correlation, although with a moderate slope, between data from CAT measured with 5 pmol/l tissue factor and ROTEM.
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Zhang, Yuqiang, Zhensen Wu, Jian Feng, et al. "Statistical Study of Ionospheric Equivalent Slab Thickness at Guam Magnetic Equatorial Location." Remote Sensing 13, no. 24 (2021): 5175. http://dx.doi.org/10.3390/rs13245175.
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The ionospheric equivalent slab thickness (τ) is defined as the ratio of the total electron content (TEC) to the F2-layer peak electron density (NmF2), and it is a significant parameter representative of the ionosphere. In this paper, a comprehensive statistical analysis of the diurnal, seasonal, solar, and magnetic activity variations in the τ at Guam (144.86°E, 13.62°N, 5.54°N dip lat), which is located near the magnetic equator, is presented using the GPS-TEC and ionosonde NmF2 data during the years 2012–2017. It is found that, for geomagnetically quiet days, the τ reaches its maximum value in the noontime, and the peak value in winter and at the equinox are larger than that in summer. Moreover, there is a post-sunset peak observed in the winter and equinox, and the τ during the post-midnight period is smallest in equinox. The mainly diurnal and seasonal variation of τ can be explained within the framework of relative variation of TEC and NmF2 during different seasonal local time. The dependence of τ on the solar activity shows positive correlation during the daytime, and the opposite situation applies for the nighttime. Specifically, the disturbance index (DI), which can visually assess the relationship between instantaneous τ values and the median, is introduced in the paper to quantitatively describe the overall pattern of the geomagnetic storm effect on the τ variation. The results show that the geomagnetic storm seems to have positive effect on the τ during most of the storm-time period at Guam. An example, on the 1 June 2013, is also presented to analyze the physical mechanism. During the positive storms, the penetration electric field, along with storm time equator-ward neutral wind, tends to increase upward drift and uplift F region, causing the large increase in TEC, accompanied by a relatively small increase in NmF2. On the other hand, an enhanced equatorward wind tends to push more plasma, at low latitudes, into the topside ionosphere in the equatorial region, resulting in the TEC not undergoing severe depletion, as with NmF2, during the negative storms. The results would complement the analysis of τ behavior during quiet and disturbed conditions at equatorial latitudes in East Asia.
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Cividjian, Andrei, Emil Toader, Karel H. Wesseling, John M. Karemaker, Robin McAllen, and Luc Quintin. "Effect of clonidine on cardiac baroreflex delay in humans and rats." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 300, no. 4 (2011): R949—R957. http://dx.doi.org/10.1152/ajpregu.00438.2010.
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The delay τ between rising systolic blood pressure (SBP) and baroreflex bradycardia has been found to increase when vagal tone is low. The α2-agonist clonidine increases cardiac vagal tone, and this study tested how it affects τ. In eight conscious supine human volunteers clonidine (6 μg/kg po) reduced τ, assessed both by cross correlation baroreflex sensitivity and sequence methods (both P < 0.05). Experiments on urethane-anaesthetized rats reproduced the phenomenon and investigated the underlying mechanism. Heart rate (HR) responses to increasing SBP produced with an arterial balloon catheter showed reduced τ ( P < 0.05) after clonidine (100 μg/kg iv). The central latency of the reflex was unaltered, however, as shown by the unchanged timing with which antidromically identified cardiac vagal motoneurons (CVM) responded to the arterial pulse. Testing the latency of the HR response to brief electrical stimuli to the right vagus showed that this was also unchanged by clonidine. Nevertheless, vagal stimuli delivered at a fixed time in the cardiac cycle (triggered from the ECG R-wave) slowed HR with a 1-beat delay in the baseline state but a 0-beat delay after clonidine ( n = 5, P < 0.05). This was because clonidine lengthened the diastolic period, allowing the vagal volleys to arrive at the heart just in time to postpone the next beat. Calculations indicate that naturally generated CVM volleys in both humans and rats arrive around this critical time. Clonidine thus reduces τ not by changing central or efferent latencies but simply by slowing the heart.
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Alias, Siti Nadiah, Nor Zila Abd Hamid, Siti Hidayah Muhad Saleh, and Biliana Bidin. "Predicting Carbon Monoxide Time Series Between Different Settlements Area in Malaysia Through Chaotic Approach." Journal of Science and Mathematics Letters 9, Special (2021): 45–54. http://dx.doi.org/10.37134/jsml.vol9.sp.6.2021.
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This research is designed to analysing and predicting the time series of Carbon Monoxide (CO) at two stations located in Petaling Jaya and Jerantut through chaotic approach. Both stations were selected to represent CO time series in the urban and rural settlements. Chaotic approach has two steps, which are to (i) detect the presence of chaotic dynamics through phase space plot and Cao method and (ii) predict the time series which is done using local linear approximation method (LLAM). Through step (i), the result from phase space plot and parameter of Cao method shown that the presence of chaotic dynamics has been detected. Therefore, the chaotic approach is used to predict the time series. While in step (ii), the results shown that the correlation coefficient value of LLAM are 0.7536 for Petaling Jaya (τ=1, =4) and 0.6946 for Jerantut (τ=1, =5) which are close to one. This shows a positive sign that chaotic approach is applicable in both types of urban and rural settlements areas. These finding are expected to help stakeholders such as Ministry of Education and Department of Environment to having a better air pollution management.
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Jakeš, Jaromír. "Spin-Echo Experiment with NMR Spectra only Partially Narrowed by an Insufficiently Fast Motion." Collection of Czechoslovak Chemical Communications 68, no. 7 (2003): 1193–205. http://dx.doi.org/10.1135/cccc20031193.
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The spin-echo experiment on a spin system with only partial motional narrowing and an exponential field autocorrelation function is considered. The pattern of the intensity decrease in the echo spectra depends on the ratio τ/τc of the time delay τ in the echo experiment to the correlation time τc of the narrowing motion. With the large ratios (fast motion), the decrease is the same as in the case of extreme narrowing; to obtain undistorted T2 values, the ratio should be at least several units in the single-echo experiment and at least few decades in the multiple-echo experiment. With the small ratios (slow motion), the logarithmic decrease depends non-linearly on τ, and the T2 value found by the linear least-squares adjustment is much longer than that obtained from the extreme narrowing approximation. At very small ratios, the multiple echo yields about 3τc/(ωpτ)2 for T2 as compared with 1/(ωp2rc) obtained from the extreme narrowing approximation; ωp2 is the second moment of the Gaussian line being narrowed. The expression for T2 in the multiple spin echo is similar to that previously found for T2e in the solid multiple spin echo. The echo experiment changes the line shape, which at large τ/τc approaches the Lorentzian one. The case of a multiexponential field autocorrelation function is also briefly considered.
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Chamandy, Luke, and Anvar Shukurov. "Parameters of the Supernova-Driven Interstellar Turbulence." Galaxies 8, no. 3 (2020): 56. http://dx.doi.org/10.3390/galaxies8030056.
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Galactic dynamo models take as input certain parameters of the interstellar turbulence, most essentially the correlation time τ, root-mean-square turbulent speed u, and correlation scale l. However, these quantities are difficult, or, in the case of τ, impossible, to directly observe, and theorists have mostly relied on order of magnitude estimates. Here we present an analytic model to derive these quantities in terms of a small set of more accessible parameters. In our model, turbulence is assumed to be driven concurrently by isolated supernovae (SNe) and superbubbles (SBs), but clustering of SNe to form SBs can be turned off if desired, which reduces the number of model parameters by about half. In general, we find that isolated SNe and SBs can inject comparable amounts of turbulent energy into the interstellar medium, but SBs do so less efficiently. This results in rather low overall conversion rates of SN energy into turbulent energy of ∼1–3%. The results obtained for l, u and τ for model parameter values representative of the Solar neighbourhood are consistent with those determined from direct numerical simulations. Our analytic model can be combined with existing dynamo models to predict more directly the magnetic field properties for nearby galaxies or for statistical populations of galaxies in cosmological models.
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Kumar, N., and A. M. Jayannavar. "Statistics of Mesoscopic Fluctuations of Quantum Capacitance." Modern Physics Letters B 11, no. 02n03 (1997): 53–56. http://dx.doi.org/10.1142/s0217984997000086.
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The Thouless formula (G = (e2/h)(E c /Δ) for the two-probe dc conductance G of a d-dimensional mesoscopic cube is re-analysed to relate its quantum capacitance C Q to the reciprocal of the level spacing Δ. To this end, the escape time-scale τ occurring in the Thouless correlation energy (E c = ℏ/τ) is interpreted as the time constantτ = RC Q with RG ≡ 1, giving at once C Q = (e2/2π Δ). Thus, the statistics of the quantum capacitance is directly related to that of the level spacing, which is well known from the Random Matrix Theory for all the three universality classes of statistical ensembles. The basic questions of how intrinsic this quantum capacitance can arise purely quantum-resistively, and of its observability vis-à-vis the external geometric capacitance that combines with it in series, are discussed.
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Kmita, A., and A. Roczniak. "Nanocomposites Based on Water Glass Matrix as a Foundry Binder: Chosen Physicochemical Properties." Archives of Foundry Engineering 17, no. 1 (2017): 93–98. http://dx.doi.org/10.1515/afe-2017-0017.
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Abstract The nanocomposites based on water glass matrix were attempted in the study. Nanoparticles of ZnO, Al2O3 or MgO in organic solutions were applied into water glass matrix in the amounts of: 1.5; 3; 4 or 5 mas. %. Wettability of the quartz sad by the nanocomposites based on water glass matrix was determined by testing changes of the wetting angle θ in time τ for the system: quartz - binder in non-stationary state, by means of the device for measuring wetting angles. Wettability measurements were carried out under isothermal conditions at an ambient temperature (20 - 25°C). The modification improves wettability of quartz matrix by water glass, which is effective in improving strength properties of hardened moulding sands. Out of the considered modifiers in colloidal solution of propyl alcohol water glass modified by MgO nanoparticles indicated the smallest values of the equilibrium wetting angle θr. This value was equal app. 11 degrees and was smaller no less than 40 degrees than θr value determined for not modified water glass. Viscosity η of nanocomposites based on water glass matrix was determined from the flow curve, it means from the empirically determined dependence of the shearing stress τ on shear rate γ: τ = f (γ) (1), by means of the rotational rheometer. Measurements were carried out at a constant temperature of 20°C. The modification influences the binder viscosity. This influence is conditioned by: amount of the introduced modifier as well as dimensions and kinds of nanoparticles and organic solvents. The viscosity increase of the modified binder does not negatively influence its functional properties.
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Haas, Naomi B., Yan Song, Jaqueline Willemann Rogerio, et al. "Disease-free survival as a predictor of overall survival in localized renal cell carcinoma (RCC) following first nephrectomy." Journal of Clinical Oncology 39, no. 15_suppl (2021): 4581. http://dx.doi.org/10.1200/jco.2021.39.15_suppl.4581.
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4581 Background: Intermediate endpoints (e.g., disease free survival [DFS]) have gained traction lately as potential surrogates for OS in oncology as they require shorter follow up to show clinical benefit. Given the high post-nephrectomy survival in patients (pts) with localized RCC, evidence on if DFS can be used as a predictor of OS in the disease is warranted. We assessed the association between DFS and OS in pts with newly diagnosed, completely resected, intermediate-high (pT2N0 high grade, pT3N0) or high-risk (pT4N0, pTanyN1) RCC post-nephrectomy. Methods: This retrospective observational study used the SEER-Medicare database (2007–2016). DFS was defined as time from initial nephrectomy date to first recurrence (diagnosis of metastatic disease, additional surgery, starting systemic treatment for advanced RCC) or death, whichever occurred first. OS from time of recurrence in pts with recurrence were compared with OS from comparable time point in pts without, using Kaplan-Meier analyses and adjusted Cox models. OS was also compared between pts with and without recurrence by landmark time points at 1, 2, 3, 4 and 5 years (yrs) post-nephrectomy; hazard ratios (HRs) between the two cohorts were estimated using adjusted Cox models. Correlation between DFS and OS was assessed using the Kendall’s τ rank correlation. Monthly healthcare costs were compared between the two cohorts using generalized linear model. Results: 643 post-nephrectomy RCC pts (269 with recurrence vs 374 without) met the inclusion criteria (Median follow-up: 23 months). The mean age was 75.5 yrs, 61% male, and 86% white. The median post-nephrectomy OS and DFS was 8.61 and 4.44 yrs, respectively. Pts with and without recurrence had comparable baseline characteristics. Pts with recurrence had significantly shorter OS than those without [median: 2.53 yrs vs not reached; adjusted HR (95% confidence interval [CI]): 6.00 (4.24–8.48)]. Pts with recurrence by each landmark time point had significantly shorter OS than those without [1 yr post-nephrectomy median OS: 2.35 vs 9.66 yrs, and the OS 1, 3, and 5 after the 1 yr landmark was 69.9 vs 96.5%, 41.8 vs 83.8%, and 37.0 vs 70.1%, respectively; all Ps (log-rank test) < 0.001]. Cox models indicated that pts with recurrence by each landmark time point had 2.6–3.5 times increased risk of death compared with those without. Kendall’s τ rank correlation model demonstrated a statistically significant correlation between DFS and OS (Kendall’s τ = 0.70; 95% CI: 0.65–0.74; P < 0.001). Pts with recurrence had $4,924 and $1,387 higher adjusted all-cause medical costs and pharmacy costs per month (P < 0.001). Conclusions: Post-nephrectomy recurrence is associated with significantly shorter OS among pts with intermediate-high or high-risk RCC, resulting in a strong positive association between DFS and OS in the population. Higher healthcare cost was also seen among pts with recurrence.
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Gupta, Siddhant, Greg M. McFarquhar, Joseph R. O'Brien, et al. "In situ and satellite-based estimates of cloud properties and aerosol–cloud interactions over the southeast Atlantic Ocean." Atmospheric Chemistry and Physics 22, no. 19 (2022): 12923–43. http://dx.doi.org/10.5194/acp-22-12923-2022.
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Abstract. In situ cloud probe data from the NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) field campaign were used to estimate the effective radius (Re), cloud optical thickness (τ), and cloud droplet concentration (Nc) for marine stratocumulus over the southeast Atlantic Ocean. The in situ Re, τ, and Nc were compared with co-located Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals of Re and τ and MODIS-derived Nc. For 145 cloud profiles, a MODIS retrieval was co-located with in situ data with a time gap of less than 1 h. On average, the MODIS Re and τ (11.3 µm and 11.7) were 1.6 µm and 2.3 higher than the in situ Re and τ with Pearson's correlation coefficients (R) of 0.77 and 0.73, respectively. The average MODIS Nc (151.5 cm−3) was within 1 cm−3 of the average in situ Nc with an R of 0.90. The 145 cloud profiles were classified into 67 contact profiles where an aerosol concentration (Na) greater than 500 cm−3 was sampled within 100 m above cloud tops and 78 separated profiles where Na less than 500 cm−3 was sampled up to 100 m above cloud tops. Contact profiles had a higher in situ Nc (by 88 cm−3), higher τ (by 2.5), and lower in situ Re (by 2.2 µm) compared to separated profiles. These differences were associated with aerosol–cloud interactions (ACI), and MODIS estimates of the differences were within 5 cm−3, 0.5, and 0.2 µm of the in situ estimates when profiles with MODIS Re>15 µm or MODIS τ>25 were removed. The agreement between MODIS and in situ estimates of changes in Re, τ, and Nc associated with ACI was driven by small biases in MODIS retrievals of cloud properties relative to in situ measurements across different aerosol regimes. Thus, when combined with estimates of aerosol location and concentration, MODIS retrievals of marine stratocumulus cloud properties over the southeast Atlantic can be used to study ACI over larger domains and longer timescales than possible using in situ data.
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Raham, Tareef Fadhil. "Is Laps of Time Since Malaria Elimination a Factor in COVID-19 Mortality?" Biomedicine and Chemical Sciences 1, no. 2 (2022): 65–69. http://dx.doi.org/10.48112/bcs.v1i2.97.
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Malaria can elicit a non-specific immune response against viral, bacterial and other malarial and non-malarial infections. Early in this pandemic suggestions were raised for possible role of cross immunity induced by malaria or other agents against SARS-CoV-2 severity. A possible role of heterogeneous immunity generated by previous malaria infection was suggested to explain part of diversity in COVID-19 mortality among various countries. This study was designed to examine this hypothesis by looking for possible statistical relation between malaria elimination date and COVID-19 mortality. Sixty -nine malaria-free countries with a total population of 1 million or more were enrolled in this study using robust statistical tests which include: Mann-Whitney Test, Kendall's-τ coefficient test and receiver operation characteristic - (ROC) curve analyses. Results showed that there was a significant negative association among studied marker (COVID -19 deaths/million inhabitant , and date of elimination of malaria (using Kendall's-τ Correlation Coefficient test). There was a significant positive association between COVID-19 mortality and duration of time since the time of malaria elimination. With a cutoff point of 15, countries that eliminate malaria during the last 15 years had reduced median COVID-19 mortality, while countries that eliminate malaria more than 15 years ago there is high COVID-19 median mortality p value <0.05) . Receiver operation characteristic - (ROC) curve, was used to support these findings ( P value <0.05). The author of this article suggests that a correlation exists between malaria elimination duration and mortality due to COVID-19.
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Pasenkiewicz-Gierula, M., and T. Róg. "Conformations, orientations and time scales characterising dimyristoylphosphatidylcholine bilayer membrane. Molecular dynamics simulation studies." Acta Biochimica Polonica 44, no. 3 (1997): 607–24. http://dx.doi.org/10.18388/abp.1997_4409.
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The results of molecular dynamics simulation of fully hydrated dimyristoylphosphatidylcholine (DMPC) bilayer membrane in the liquid-crystalline phase are presented. They show that the probability of a gauche conformation varies periodically along the chain with only a slight increase towards the end of the chain. However, the frequency of transition between conformations increases, due to a decrease in the lifetime of the trans conformation, along the chain. The average lifetimes for trans conformations are in the range of 1-2 x 10(-10) s and for gauche conformations in the range of 4-7 x 10(-11) s. The alpha-chain of the DMPC head group has mainly an extended conformation, due to predominantly trans conformation of alpha5 torsion. The rotational correlation time for the P-N vector is 3.7 ns. The C2-C1-O11-P fragment of the DMPC head group (theta1, alpha1, alpha2 torsions) is rigid while the P-O12-C11-C12 fragment (alpha3, alpha4, alpha5 torsions) is flexible. The lateral diffusion coefficient for DMPC self-diffusion in the membrane is 2 x 10(-7) cm2/s; the rate of transverse diffusion is the same. Large differences in the calculated rotational correlation times for the alpha-, beta-, gamma-chains and for the O21-C1 vector indicate that in the liquid-crystalline bilayer each segment of the DMPC molecule exhibits its own rotational freedom, in addition to its internal flexibility resulting from rotational isomerism. The results obtained in these calculations, although in general agreement with some experimental data, shed new light on the dynamical behaviour of phosphatidylcholine molecules in the bilayer membrane in the liquid-crystalline phase.
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Fian, C., D. Chelouche, S. Kaspi, C. Sobrino Figaredo, S. Catalan, and T. Lewis. "Continuum reverberation mapping of the quasar PG 2130+099." Astronomy & Astrophysics 659 (February 25, 2022): A13. http://dx.doi.org/10.1051/0004-6361/202141509.
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Aims. We present the results of an intensive six-month optical continuum reverberation mapping campaign of the Seyfert 1 galaxy PG 2130+099 at redshift z = 0.063. The ground-based photometric monitoring was conducted on a daily basis with the robotic 46 cm telescope of the WISE observatory located in Israel. Specially designed narrowband filters were used to observe the central engine of the active galactic nucleus (AGN), avoiding line contamination from the broad-line region (BLR). We aim to measure inter-band continuum time lags across the optical range and determine the size-wavelength relation for this system. Methods. We used two methods, the traditional point-spread function photometry and the recently developed proper image subtraction technique, to independently perform the extraction of the continuum light curves. The inter-band time lags are measured with several methods, including the interpolated cross-correlation function, the z-transformed discrete correlation function, a von Neumann estimator, JAVELIN (in spectroscopic mode), and MICA. Results. PG 2130+099 displays correlated variability across the optical range, and we successfully detect significant time lags of up to ∼3 days between the multiband light curves. We find that the wavelength-dependent lags, τ(λ), generally follow the relation τ(λ)∝λ4/3, as expected for the temperature radial profile T ∝ R−3/4 of an optically thick, geometrically thin accretion disk. Despite that, the derived time lags can also be fitted by τ(λ)∝λ2, implying the possibility of a slim, rather than thin, accretion disk. Using the flux variation gradient method, we determined the AGN’s host-galaxy-subtracted rest frame 5100 Å luminosity at the time of our monitoring campaign with an uncertainty of ∼18% (λL5100 = (2.40 ± 0.42)×1044 erg s−1). While a continuum reprocessing model can fit the data reasonably well, our derived disk sizes are a factor of ∼2 − 6 larger than the theoretical disk sizes predicted from the AGN luminosity estimate of PG 2130+099. This result is in agreement with previous studies of AGN/quasars and suggests that the standard Shakura-Sunyaev disk theory has limitations in describing AGN accretion disks.
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Masuda, Kento. "On the Evolution of Rotational Modulation Amplitude in Solar-mass Main-sequence Stars." Astrophysical Journal 933, no. 2 (2022): 195. http://dx.doi.org/10.3847/1538-4357/ac7527.
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Abstract We investigate the relation between rotation periods P rot and photometric modulation amplitudes R per for ≈4000 Sun-like main-sequence stars observed by Kepler, using P rot and R per from McQuillan et al., effective temperature T eff from LAMOST DR6, and parallax data from Gaia EDR3. As has been suggested in previous works, we find that P rot scaled by the convective turnover time τ c, or the Rossby number Ro, serves as a good predictor of R per: R per plateaus at around 1% in relative flux for 0.2 ≲ Ro/Ro⊙ ≲ 0.4, and decays steeply with increasing Ro for 0.4 ≲ Ro/Ro⊙ ≲ 0.8, where Ro⊙ denotes Ro of the Sun. In the latter regime we find d ln R per / d ln Ro ∼ −4.5 to −2.5, although the value is sensitive to detection bias against weak modulation and may depend on other parameters including T eff and surface metallicity. The existing X-ray and Ca ii H and K flux data also show transitions at Ro/Ro⊙ ∼ 0.4, suggesting that all these transitions share the same physical origin. We also find that the rapid decrease of R per with increasing Ro causes rotational modulation of fainter Kepler stars with Ro/Ro⊙ ≳ 0.6 to be buried under the photometric noise. This effect sets the longest P rot detected in the McQuillan et al. sample as a function of T eff and obscures the signature of stalled spin down that has been proposed to set in around Ro/Ro⊙ ∼ 1.
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Livadiotis, G., D. J. McComas, and E. J. Zirnstein. "Temperature of the Polar Inner Heliosheath: Connection to Solar Activity." Astrophysical Journal 951, no. 1 (2023): 21. http://dx.doi.org/10.3847/1538-4357/acd1e1.
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Abstract We study the thermodynamics of the plasma protons in the polar regions of the inner heliosheath (IHS) and its connection with solar activity over solar cycle 24. First, we express the thermodynamic parameters of this plasma with respect to the year of energetic neutral atom (ENA) creation and perform a statistical analysis of temperatures, in order to provide a more precise characterization of the thermodynamics of IHS. Then, we perform an autocorrelation between the IHS temperature and the solar activity, using the proxies of sunspot number and fractional area of the polar coronal holes. We show that there is (i) high correlation between the time series of IHS proton temperatures and sunspot number, which is maximized for a time delay of τ ∼ 2.5 yr for both the north and south polar regions combined; (ii) high negative correlation between the temperature of the proton plasma in the north and south with the coronal hole fractional areas, where the time delay for the two poles combined is τ ∼ 2.71 ± 0.15 yr; and (iii) an asymmetry of a time-delay difference between the poles ∼0.22 yr, indicating that the southern polar ENA source region is ∼19 au closer than the northern one for a solar wind plasma protons of bulk speed of ∼400 km s−1. The findings demonstrate a connection between the IHS thermodynamics and solar activity through the solar wind, primarily manifested by the coronal holes expanding near solar minimum, which drives the expansion of fast solar wind over larger angles from high down to middle latitudes in the IHS.
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Villanueva, V., A. Bolatto, S. Vogel, et al. "The EDGE-CALIFA Survey: The Resolved Star Formation Efficiency and Local Physical Conditions." Astrophysical Journal 923, no. 1 (2021): 60. http://dx.doi.org/10.3847/1538-4357/ac2b29.
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Abstract We measure the star formation rate (SFR) per unit gas mass and the star formation efficiency (SFEgas for total gas, SFEmol for the molecular gas) in 81 nearby galaxies selected from the EDGE-CALIFA survey, using 12CO (J = 1–0) and optical IFU data. For this analysis we stack CO spectra coherently by using the velocities of Hα detections to detect fainter CO emission out to galactocentric radii r gal ∼ 1.2r 25 (∼3R e) and include the effects of metallicity and high surface densities in the CO-to-H2 conversion. We determine the scale lengths for the molecular and stellar components, finding a close to 1:1 relation between them. This result indicates that CO emission and star formation activity are closely related. We examine the radial dependence of SFEgas on physical parameters such as galactocentric radius, stellar surface density Σ⋆, dynamical equilibrium pressure P DE, orbital timescale τ orb, and the Toomre Q stability parameter (including star and gas Q star+gas). We observe a generally smooth, continuous exponential decline in the SFEgas with r gal. The SFEgas dependence on most of the physical quantities appears to be well described by a power law. Our results also show a flattening in the SFEgas–τ orb relation at log [ τ orb ] ∼ 7.9 – 8.1 and a morphological dependence of the SFEgas per orbital time, which may reflect star formation quenching due to the presence of a bulge component. We do not find a clear correlation between SFEgas and Q star+gas.