Articoli di riviste: "Non linear reactivity"

1

Grimm, K. N., e D. Meneghetti. "Reactivity-induced time-dependencies of EBR-II linear and non-linear feedbacks". Annals of Nuclear Energy 15, n. 4 (gennaio 1988): 167–74. http://dx.doi.org/10.1016/0306-4549(88)90010-2.

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Mohammed, Mohammed S. G., James Lawrence, Fátima García, Pedro Brandimarte, Alejandro Berdonces-Layunta, Dolores Pérez, Daniel Sánchez-Portal, Diego Peña e Dimas G. de Oteyza. "From starphenes to non-benzenoid linear conjugated polymers by substrate templating". Nanoscale Advances 3, n. 8 (2021): 2351–58. http://dx.doi.org/10.1039/d1na00126d.

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We reveal the templating effect of substrates with two-fold or three-fold symmetry on the reactivity of acene-based reactants. This allows us to choose whether to form and characterize non-benzenoid conjugated polymers or starphene-derivatives.

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Joshi, Bhawani Datta. "Chemical Reactivity, Dipole Moment and First Hyperpolarizability of Aristolochic Acid I". Journal of Institute of Science and Technology 21, n. 1 (24 novembre 2016): 1–9. http://dx.doi.org/10.3126/jist.v21i1.16030.

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Aristolochic acids (AAs) have been used in the treatment of oedema in Chinese herb medicine since long ago. In this paper, molecular electrostatic potential, chemical reactivity and non linear optical properties of aristolochic acid I (AA I) have been analyzed using density functional theory employing 6-311++G(d,p) basis set. The chemical reactivity of the molecule has been explained with the help of chemical reactivity descriptors, molar refractivity and the molecular electrostatic potential surface (ESP). The calculated dipole moment and first order hyperpolarizability show that the molecule possesses non-linear optical property.Journal of Institute of Science and TechnologyVolume 21, Issue 1, August 2016, page: 1-9

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Rieke, Peter C., Sebastien Kerisit, Joseph V. Ryan e James J. Neeway. "Adaptation of the GRAAL model of Glass Reactivity to accommodate non-linear diffusivity". Journal of Nuclear Materials 512 (dicembre 2018): 79–93. http://dx.doi.org/10.1016/j.jnucmat.2018.09.058.

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Bučys, K., e D. Švitra. "MODELLING OF NUCLEAR REACTORS DYNAMICS". Mathematical Modelling and Analysis 4, n. 1 (15 dicembre 1999): 26–32. http://dx.doi.org/10.3846/13926292.1999.9637107.

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The point model of a nuclear reactor with delay in feedback line “power ‐ reactivity” estimating the influence of six groups of delayed neutrons is investigated. A linear and non‐linear analysis of the model is made.

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AlSalem, Huda S., Soha T. Al-Goul, Alejandro García-Miranda Ferrari, Dale A. C. Brownson, Luis Velarde e Sven P. K. Koehler. "Imaging the reactivity and width of graphene's boundary region". Chemical Communications 56, n. 67 (2020): 9612–15. http://dx.doi.org/10.1039/d0cc02675a.

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Yamane, Yuichi. "Improvement in estimation of first peak power based on non-linear temperature feedback reactivity in criticality accident with instantaneous reactivity insertion". Journal of Nuclear Science and Technology 52, n. 11 (4 febbraio 2015): 1425–35. http://dx.doi.org/10.1080/00223131.2015.1005718.

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Patra, A., e S. Saha Ray. "Solution of non-linear neutron point kinetics equations with feedback reactivity in nuclear reactor dynamics". International Journal of Nuclear Energy Science and Technology 9, n. 1 (2015): 23. http://dx.doi.org/10.1504/ijnest.2015.067803.

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9

Škvareninová, Katarína, Štefan Baláž, Ernest Šturdík, Miroslav Veverka, Jana Adamcová e Jana Olexová. "Biologically Important Physicochemical Properties of Some Cephalosporins". Collection of Czechoslovak Chemical Communications 57, n. 8 (1992): 1739–46. http://dx.doi.org/10.1135/cccc19921739.

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In the series of cephalosporin derivatives, consisting of eight 7-(R1-CH2-CO-NH)cephalosporanic acids and of seven analogical compounds with 3-acetoxymethyl replaced by 3-CH3, physicochemical properties, which are expected to play a role in their antibacterial effects (the transport rate parameters and partition coefficients in the systems 1-octanol-water and 1-octanol-buffer, dissociation constants of the 4-carboxyl group, reactivity towards L-glutathione imitating the nucleophilic groups of the cell components and hydrolysis rate parameters), were determined. Linear dependences were observed between the partition coefficients and the π-constants of the varying substituents as well as between reactivity towards SH-groups of L-glutathione and OH-groups. The relationship between the transport rate parameters and partition coefficients, both measured in buffered as well as non-buffered system, was described by a common non-linear equation.

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Wang, Chih-Hsien, Yu-Hsien Lai, Chiu-Huang Kuo, Yu-Li Lin, Jen-Pi Tsai e Bang-Gee Hsu. "Association between Serum Indoxyl Sulfate Levels and Endothelial Function in Non-Dialysis Chronic Kidney Disease". Toxins 11, n. 10 (11 ottobre 2019): 589. http://dx.doi.org/10.3390/toxins11100589.

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Indoxyl sulfate (IS), a product metabolized from tryptophan, is negatively correlated with renal function and cardiovascular diseases in patients with chronic kidney disease (CKD). We investigated the association between serum IS levels and endothelial function in patients with CKD. Fasting blood samples were obtained from 110 patients with stages 3–5 CKD. The endothelial function, represented by vascular reactivity index (VRI), was measured non-invasively using digital thermal monitoring. Serum IS levels were determined using liquid chromatography–mass spectrometry. Twenty-one (19.1%), 36 (32.7%), and 53 (48.2%) patients had poor (VRI < 1.0), intermediate (1.0 ≤ VRI < 2.0), and good (VRI ≥ 2.0) vascular reactivity. By univariate linear regression analysis, a higher prevalence of smoking, advanced age, higher systolic, and diastolic blood pressure (DBP), elevated levels of serum phosphorus, blood urea nitrogen, creatinine, and IS were negatively correlated with VRI values, but estimated glomerular filtration rate negatively associated with VRI values. After being adjusted by using multivariate stepwise linear regression analysis, DBP and IS levels were significantly negatively associated with VRI values in CKD patients. We concluded that IS level associated inversely with VRI values and had a modulating role in endothelial function in patients with stages 3–5 CKD.

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Liu, Xiao Jing, Xin Sun e Jing Hua Guo. "Non Linear Optical, Thermodynamic Analysis and Spectroscopic Investigation of GPA Optical Materials". Key Engineering Materials 730 (febbraio 2017): 106–11. http://dx.doi.org/10.4028/www.scientific.net/kem.730.106.

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In this work, density functional theory (DFT) calculations with B3LYP/6-311++G(d,p) basis sets was used to explore the electronic, structural, nonlinear optical and thermal properties aspects of glycine-phthalic acid (GPA) optical materials. Dipole moment, static polarizability and first hyperpolarizability analysis of the molecule have been performed. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. MEP study confirms GPA as an electron rich species and explains its electrophilic nature. MEP shows that this molecule has several possible sites for electrophilic/nucleophilic attack in which V(r) calculations provide insights into the order of preference. The low value of HOMO-LUMO energy gap reflects the high chemical reactivity, low chemical stability and hardness of GPA molecule. Thermodynamic properties of the title compound have been calculated at different temperatures and the results reveal that the standard heat capacities (Cp), standard entropies (S) and standard enthalpy (H) increase with rise in temperature. These results discussed in this study will upsurge the knowledge to design and synthesize new type nonlinear optical materials with exceptional chemical and physical properties.

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Joshi, Bhawani Dutt. "NBO, chemical reactivity, thermodynamic properties and hyperpolarizability analysis of aristolochic acid II". BIBECHANA 14 (28 novembre 2016): 86–97. http://dx.doi.org/10.3126/bibechana.v14i0.15892.

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Alkaloids are a group of naturally occurring chemical compounds and show immense potential of medicinal uses in traditional systems. In this work, a computational study on an alkaloid aristolochc acidid II (AA II) is presented using density functional theory, B3LYP functional employing 6-311G (d,p) basis set. Natural bond orbital analysis has been carried out to investigate the various conjugative and hyperconjugative interactions within the molecule and their second-order stabilisation energy (E(2)). The local nucleophilic reactivity descriptors such as Fukui functions (f+k, f-k), local softness (s+k, s-k) and electrophilicity indices (ω+k,ω-k) analyses have been carried out to determine the reactive sites within the molecule. The non-linear optical properties have been calculated using the same basis set. The calculated value of the first order hyperpolarisability (β0), suggests that the investigated molecule is an attractive object in future for non-linear optical properties.

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Journal, Baghdad Science. "Study of Reactivity Effect on Reactor Power by Using the Neutronic- Thermohydrolic Coupling". Baghdad Science Journal 9, n. 3 (2 settembre 2012): 459–65. http://dx.doi.org/10.21123/bsj.9.3.459-465.

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The study deals with reactivity insertion linear and non linear and/or Ramp reactivity expressed as a polynomial in time in the presence of two Feedback mechanisms, using the neutronic-thermohydraulic coupling in order to predict the neutron behavior as a function of time in terms of reactor power. Also, a comparative study has been achieved in the case of the presence of the feedback mechanisms. Insertion of Ramp reactivities in terms of polynomial in time to study the behavior of power and reactivity as a function of time in the presence of two feedback mechanisms (fuel and coolant) has been carried out and the results are displayed as plots, and showed this results corresponding with international results. The present study shows that the simulation of neutron time behavior is a vital tool to predict the behavior of reactivity and/or power as a function of time in case of insertion of negative or positive and/or Ramp reactivities in power reactor core for the case including feedback mechanism. Also, the simulation may be considered a unique technique to predict unexpected incident and/or accident that may occur in reactor power core in case of the availability of accurated input data.

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Manassir, Mohammad, e Ali H. Pakiari. "Total non-lewis structures: An application to predict the stability and reactivity of linear and angular polyacenes". Journal of Molecular Graphics and Modelling 99 (settembre 2020): 107643. http://dx.doi.org/10.1016/j.jmgm.2020.107643.

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15

Rawat, Poonam, R. N. Singh, Sangeeta Sahu, Priydarshni Niranjan, Himanshu Rani, Rajat Saxena e Sartaj Ahmad. "Assessment of Antimicrobial Activity, Reactivity and Non-Linear Optical Properties of New Pyrazoline Derivatives having Pyrrole moiety". ChemistrySelect 1, n. 13 (16 agosto 2016): 4008–15. http://dx.doi.org/10.1002/slct.201600826.

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Dias, A. R., M. Helena Garcia, M. Paula Robalo, M. L. H. Green, K. K. Lai, Andrew J. Pulham, Stephen M. Klueber e G. Balavoine. "Organometallic compounds for non-linear optics: Synthesis, reactivity and electrochemistry of chiral η5-monocyclopentadienyl(nitrile)iron complexes". Journal of Organometallic Chemistry 453, n. 2 (luglio 1993): 241–47. http://dx.doi.org/10.1016/0022-328x(93)83117-e.

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Beddingfield, Brandon J., Jessica N. Hartnett, Russell B. Wilson, Peter C. Kulakosky, Kristian G. Andersen, Refugio Robles-Sikisaka, Nathan D. Grubaugh et al. "Zika Virus Non-Structural Protein 1 Antigen-Capture Immunoassay". Viruses 13, n. 9 (5 settembre 2021): 1771. http://dx.doi.org/10.3390/v13091771.

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Infection with Zika virus (ZIKV), a member of the Flavivirus genus of the Flaviviridae family, typically results in mild self-limited illness, but severe neurological disease occurs in a limited subset of patients. In contrast, serious outcomes commonly occur in pregnancy that affect the developing fetus, including microcephaly and other major birth defects. The genetic similarity of ZIKV to other widespread flaviviruses, such as dengue virus (DENV), presents a challenge to the development of specific ZIKV diagnostic assays. Nonstructural protein 1 (NS1) is established for use in immunodiagnostic assays for flaviviruses. To address the cross-reactivity of ZIKV NS1 with proteins from other flaviviruses we used site-directed mutagenesis to modify putative epitopes. Goat polyclonal antibodies to variant ZIKV NS1 were affinity-purified to remove antibodies binding to the closely related NS1 protein of DENV. An antigen-capture ELISA configured with the affinity-purified polyclonal antibody showed a linear dynamic range between approximately 500 and 30 ng/mL, with a limit of detection of between 1.95 and 7.8 ng/mL. NS1 proteins from DENV, yellow fever virus, St. Louis encephalitis virus and West Nile virus showed significantly reduced reactivity in the ZIKV antigen-capture ELISA. Refinement of approaches similar to those employed here could lead to development of ZIKV-specific immunoassays suitable for use in areas where infections with related flaviviruses are common.

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Lamare, R., L. Ruhlmann, R. Ruppert e J. Weiss. "Case studies of the radical cation reactivity in meso-aryl and octaethyl porphyrins". Journal of Porphyrins and Phthalocyanines 24, n. 05n07 (maggio 2020): 860–68. http://dx.doi.org/10.1142/s1088424619501980.

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The reactivity of porphyrin radical cationic species derived from octaethyl porphyrin (OEP) or meso-aryl porphyrins with nucleophiles, envisioned as an access route to elaborate porphyrin dimers, has been studied and optimized in the case of OEP. Standardized conditions have been applied to various spacers to show that the success of the reaction is mostly nucleophile dependent and that the method has little chances to yield non-linear bis-porphyrins.

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Terrier, François, Patricio MacCormack, Elyane Kizilian, Jean-Claude Hallé, Pierre Demerseman, Frédéric Guir e Claude Lion. "Non-linear Brønsted correlations: evidence for a levelling off in the reactivity of oximate ions in aqueous solution". J. Chem. Soc., Perkin Trans. 2, n. 1 (1991): 153–58. http://dx.doi.org/10.1039/p29910000153.

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Ramakrishnan, Venkatesh, e Karunakaran Kulandaivelu. "Kinetic investigation of oxidation of aromatic anils by magnesium monoperoxyphthalate in aqueous acidic medium". Polish Journal of Chemical Technology 15, n. 3 (1 settembre 2013): 55–60. http://dx.doi.org/10.2478/pjct-2013-0044.

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Abstract The kinetics of oxidation of aromatic anils to benzaldehyde and azobenzene by magnesium monoperoxyphthalate (MMPP) has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. It has been found that ionic strength of the reaction has no significant effect on rate. The added acrylonitrile has no effect on the reaction rate indicating the absence of free radical mechanism. The added Mn(II) decreases the rate of the reaction, which indicates the involvement of two-electron transfer. Highly negative ΔS# values indicate a structured transition state. The deviation of Hammett plot is noted and a non-linear concave downward curve is obtained for the anils with substituents in the aniline moiety. The observed break in the log kobs versus σ is attributed to the transition state whereas the non-linear concave upward curve is observed for the substituents in the benzaldehyde moiety and a non-linear concacve upward curve is observed for the substituents in the combination of aniline and benzaldehyde moiety and a suitable mechanism is proposed

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Sun, En-Cheng, Jing Zhao, Ni-Hong Liu, Tao Yang, Jian-Nan Ma, Hong-Wei Geng, Ling-Feng Wang et al. "Comprehensive mapping of West Nile virus (WNV)- and Japanese encephalitis virus serocomplex-specific linear B-cell epitopes from WNV non-structural protein 1". Journal of General Virology 93, n. 1 (1 gennaio 2012): 50–60. http://dx.doi.org/10.1099/vir.0.034900-0.

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West Nile virus (WNV) non-structural protein 1 (NS1) elicits protective immune responses during infection of animals. WNV NS1-specific antibody responses can provide the basis for serological diagnostic reagents, so the antigenic sites in NS1 that are targeted by host immune responses need to be identified and the conservation of these sites among the Japanese encephalitis virus (JEV) serocomplex members also needs to be defined. The present study describes the mapping of linear B-cell epitopes in WNV NS1. We screened eight NS1-specific mAbs and antisera (polyclonal antibodies; pAbs) from mice immunized with recombinant NS1 for reactivity against 35 partially overlapping peptides covering the entire WNV NS1. The screen using mAbs identified four WNV-specific (including Kunjin virus) epitopes, located at aa 21–36, 101–116, 191–206 and 261–276 in WNV NS1. However, using pAbs, only three WNV-specific epitopes were identified, located at positions 101–116, 191–206 and 231–246. Two of these epitopes (aa 21–36 and 261–276) had different reactivity with mAbs and pAbs. The knowledge and reagents generated in this study have potential applications in differential diagnostics and epitope-based marker vaccine development for WNV and viruses of the JEV serocomplex.

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Kumar, M. Dinesh, P. Rajesh, R. Priya Dharsini e M. Ezhil Inban. "Molecular Geometry, NLO, MEP, HOMO-LUMO and Mulliken Charges of Substituted Piperidine Phenyl Hydrazines by Using Density Functional Theory". Asian Journal of Chemistry 32, n. 2 (30 dicembre 2019): 401–7. http://dx.doi.org/10.14233/ajchem.2020.22444.

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The quantum chemical calculations of organic compounds viz. (E)-1-(2,6-bis(4-chlorophenyl)-3-ethylpiperidine-4-ylidene)-2-phenyl-hydrazine (3ECl), (E)-1-(2,6-bis(4-chlorophenyl)-3-methylpiperidine-4-ylidene)-2-phenylhydrazine (3MCl) and (E)-1-(2,6-bis(4-chloro-phenyl)-3,5-dimethylpiperidine-4-ylidene)-2-phenylhydrazine (3,5-DMCl) have been performed by density functional theory (DFT) using B3LYP method with 6-311G (d,p) basis set. The electronic properties such as Frontier orbital and band gap energies have been calculated using DFT. Global reactivity descriptor has been computed to predict chemical stability and reactivity of the molecule. The chemical reactivity sites of compounds were predicted by mapping molecular electrostatic potential (MEP) surface over optimized geometries and comparing these with MEP map generated over crystal structures. The charge distribution of molecules predict by using Mulliken atomic charges. The non-linear optical property was predicted and interpreted the dipole moment (μ), polarizability (α) and hyperpolarizability (β) by using density functional theory.

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Šturdík, Ernest, Štefan Baláž, Marián Antalík e Pavol Sulo. "Lipophilic-hydrophilic properties and retention of phenylhydrazonopropanedinitriles by biological systems". Collection of Czechoslovak Chemical Communications 50, n. 2 (1985): 538–50. http://dx.doi.org/10.1135/cccc19850538.

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Apparent partition coefficients in n-octanol-buffer system, solubility in the buffers, and retention by mitochondria from rat liver, by Mycobacterium phlei and by Saccharomyces cerevisiae (after 10 min incubation) have been characterized for 13 arylsubstituted phenylhydrazonopropanedinitrile derivatives. Regression analysis has shown linear dependence of logarithms of the apparent partition coefficients on the published π parameters characterizing lipophilicity of the substituents. The apparent partition coefficients are inversely proportional to the solubility of the phenylhydrazonopropanedinitriles. The retention by the biosystems studied increases linearly with increasing lipophilicity, being independent of reactivity of the phenylhydrazonopropanedinitriles. The non-linear dependence of concentration of the phenylhydrazonopropanedinitriles remaining in the medium on the lipophilicity indicates that a lipophilic-hydrophilic equilibrium is established in the given time. The retained amount of the derivatives tested decreases with increasing pH values. The dependences are Z-shaped and have been described by the equations derived from the model presented by application of non-linear regression analysis.

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Meenakshisundaram, Subbiah, e M. Amutha. "Studies on the Oxidation of some Sulfides with Pyridinium Dichromate in Acetonitrile medium". Journal of Chemical Research 23, n. 1 (gennaio 1999): 2–3. http://dx.doi.org/10.1177/174751989902300107.

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The kinetic behaviours of oxidation of dialkyl, alkyl aryl and diphenyl sulfides are quite different with pyridinium dichromate in acetonitrile medium; studies indicate the involvement of a sulfur cation free radical intermediate in diphenyl sulfide oxidation; electron releasing and withdrawing groups retard the reactivity of aryl methyl sulfides; the observed non-linear concave downwards type Hammett plot is well explained by assuming shifts in the rate-limiting step within the same overall reaction pathway.

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Barale, Cristina, Franco Cavalot, Chiara Frascaroli, Katia Bonomo, Alessandro Morotti, Angelo Guerrasio e Isabella Russo. "Association between High On-Aspirin Platelet Reactivity and Reduced Superoxide Dismutase Activity in Patients Affected by Type 2 Diabetes Mellitus or Primary Hypercholesterolemia". International Journal of Molecular Sciences 21, n. 14 (15 luglio 2020): 4983. http://dx.doi.org/10.3390/ijms21144983.

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Platelet hyperactivation is involved in the established prothrombotic condition of metabolic diseases such as Type 2 Diabetes Mellitus (T2DM) and familial hypercholesterolemia (HC), justifying the therapy with aspirin, a suppressor of thromboxane synthesis through the irreversible inhibition of cyclooxygenase-1 (COX-1), to prevent cardiovascular diseases. However, some patients on aspirin show a higher than expected platelet reactivity due, at least in part, to a pro-oxidant milieu. The aim of this study was to investigate platelet reactivity in T2DM (n = 103) or HC (n = 61) patients (aspirin, 100 mg/day) and its correlation with biomarkers of redox function including the superoxide anion scavenger superoxide dismutase (SOD) and the in vivo marker of oxidative stress urinary 8-iso-prostaglandin F2α. As results, in T2DM and HC subjects the prevalence of high on-aspirin platelet reactivity was comparable when both non-COX-1-dependent and COX-1-dependent assays were performed, and platelet reactivity is associated with a lower SOD activity that in a stepwise linear regression appears as the only predictor of platelet reactivity. To conclude, in T2DM and HC, similarly, the impairment of redox equilibrium associated with a decrease of SOD activity could contribute to a suboptimal response to aspirin.

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Sanjeeva Reddy, Ch, e E. V. Sundaram. "Mechanism of acid bromate oxidation of trans mono-substituted cinnamic acids: structure reactivity correlation - a non-linear hammett's plot". Tetrahedron 45, n. 7 (gennaio 1989): 2109–26. http://dx.doi.org/10.1016/s0040-4020(01)80072-7.

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Jeeva, P., D. Barathi, K. Prabakaran, M. Seenivasa Perumal, Ahmet Atac e Etem Kose. "Crystal Structure, Experimental and DFT of (Z)-4-((4-Fluorophenyl)amino)pent-3-en-2-one". Asian Journal of Chemistry 33, n. 7 (2021): 1638–44. http://dx.doi.org/10.14233/ajchem.2021.23259.

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Single crystals of a organic compound, (Z)-4-((4-fluorophenyl)amino)pent-3-en-2-one (4FPA) were grown by the slow evaporation technique and characterized by X-ray diffraction and FT-IR spectra. The normal mode frequencies, intensities and the corresponding vibrational assignments were calculated using the GAUSSIAN 09W set of quantum chemistry codes at the DFT/B3LYP levels of theory using the 6-31+G(d,p) basis set. The Fourier transform infrared spectrum was obtained for the title molecule at room temperature. Reactivity features were determined based on global descriptors, electron density mapping and Fukui analysis to reveal the electrophilic and nucleophilic coordination of them. The thermodynamic and intramolecular interactions were also investigated. The non-covalent interaction mapped by reduced density gradient method reveals possible methyl (CH3) influence on the ring and NH groups with their reactivity and non-linear optical properties of 4FPA were found by first-order hyperpolarizability.

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Kuzmin, Anton V., Mikhail Yu Moskalik e Bagrat A. Shainyan. "Trifluoromethanesulfonamide vs. Non-Fluorinated Sulfonamides in Oxidative Sulfamidation of the C=C Bond: An In Silico Study". Molecules 25, n. 21 (22 ottobre 2020): 4877. http://dx.doi.org/10.3390/molecules25214877.

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A theoretical analysis of the reaction of oxidative sulfamidation of several alkenes was performed in order to explain the various experimental observations and different reactivity of triflamide and non-fluorinated sulfonamides. Transformations occurring in the system alkene–sulfonamide in the presence of oxidative system (ButOCl + NaI) were analyzed at the MP2/DGDZVP//B3LYP/DGDZVP level of theory using the IEF-PCM method for taking into account the solvent acetonitrile (MeCN) effect. As the model substrates, styrene, trimethyl(vinyl)silane, dimethyl(divinyl)silane and diphenyl(divinyl)silane were chosen and mesylamide, triflamide, tosylamide and p-nosylamide were taken as the reagents. ButOI generated from ButOCl and NaI reacts with sulfonamides to give N-iodinated sulfonamides RSO2NHI and RSO2NI2 as active intermediates, the iodinating activity of the latter being notably higher. The analysis allowed to answer such challenging questions as different reactivity of nonfluorinated sulfonamides leading to aziridination and of triflamide resulting in the formation the main products of bis-triflamidation, or different regioselectivity of halogenation of styrene and trimethyl(vinyl)silane caused by a linear intermediate iodonium cation in the former case and a cyclic one in the latter.

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Zouganelis, Choinopoulos, Goulas e Pitsikalis. "Statistical Copolymers of n-Butyl Vinyl Ether and 2-Chloroethyl Vinyl Ether via Metallocene-Mediated Cationic Polymerization. A Scaffold for the Synthesis of Graft Copolymers". Polymers 11, n. 9 (16 settembre 2019): 1510. http://dx.doi.org/10.3390/polym11091510.

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The cationic statistical copolymerization of n-butyl (be) and 2-chloroethyl vinyl ether (CEVE), is efficiently conducted using bis(η5-cyclopentadienyl)dimethyl zirconium (Cp2ZrMe2) in combination with tetrakis(pentafluorophenyl)borate dimethylanilinum salt [B(C6F5)4]–[Me2NHPh]+, as an initiation system. The reactivity ratios are calculated using both linear graphical and non-linear methods. Structural parameters of the copolymers are obtained by calculating the dyad sequence fractions and the mean sequence length, which are derived using the monomer reactivity ratios. The glass transition temperatures (Tg) of the copolymers are measured by Differential Scanning Calorimetry (DSC), and the results are compared with predictions based on several theoretical models. The statistical copolymers are further employed as scaffolds for the synthesis of graft copolymers having poly(vinyl ether)s as a backbone and either poly(ε-caprolactone) (PCL) or poly(l-lactide) (PLLA) as side chains. Both the grafting “onto” and the grafting “from” methodologies are employed. The reaction sequence is monitored by Size Exclusion Chromatography (SEC), NMR and IR spectroscopies. The advantages and limitations of each approach are thoroughly examined.

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Dallocchio, F., M. Matteuzzi e T. Bellini. "Half-site reactivity in 6-phosphogluconate dehydrogenase from human erythrocytes". Biochemical Journal 227, n. 1 (1 aprile 1985): 305–10. http://dx.doi.org/10.1042/bj2270305.

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6-Phosphogluconate dehydrogenase from human erythrocytes was purified by an improved procedure. Binding studies showed that the dimeric enzyme binds 2 mol of NADP+/mol but only 1 mol of NADPH/mol, and that the bindings of oxidized and reduced coenzyme are mutually exclusive. From initial-rate kinetics and inhibition studies, a sequential random-order mechanism is proposed. Double-reciprocal plots with NADP+ as varied substrate show a downward curvature, indicating a negative co-operativity. We suggest that the negative co-operativity observed kinetically is a result of the half-site reactivity for the NADPH. The different binding stoichiometries for NADP+ and NADPH generate a non-linear relationship between the apparent dissociation constant for the NADPH and the concentrations of the NADP+, resulting in a regulatory mechanism highly sensitive to the changes in the NADP+/NADPH ratio.

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Nazeer, Usman, Nasir Rasool, Aqsa Mujahid, Asim Mansha, Muhammad Zubair, Naveen Kosar, Tariq Mahmood et al. "Selective Arylation of 2-Bromo-4-chlorophenyl-2-bromobutanoate via a Pd-Catalyzed Suzuki Cross-Coupling Reaction and Its Electronic and Non-Linear Optical (NLO) Properties via DFT Studies". Molecules 25, n. 15 (31 luglio 2020): 3521. http://dx.doi.org/10.3390/molecules25153521.

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In the present study, 2-bromo-4-chlorophenyl-2-bromobutanoate (3) was synthesized via the reaction of 2-bromo-4-chlorophenol with 2-bromobutanoyl bromide in the presence of pyridine. A variety of 2-bromo-4-chlorophenyl-2-bromobutanoate derivatives (5a–f) were synthesized with moderate to good yields via a Pd-catalyzed Suzuki cross-coupling reaction. To find out the reactivity and electronic properties of the compounds, Frontier molecular orbital analysis, non-linear optical properties, and molecular electrostatic potential studies were performed.

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TERRIER, F., P. MACCORMACK, E. KIZILIAN, J. C. HALLE, P. DEMERSEMAN, F. GUIR e C. LION. "ChemInform Abstract: Non-Linear Broensted Correlations: Evidence for a Levelling Off in the Reactivity of Oximate Ions in Aqueous Solution." ChemInform 22, n. 15 (23 agosto 2010): no. http://dx.doi.org/10.1002/chin.199115106.

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Mathew, Manoj, e Thomas Duever. "Reactivity Ratio Estimation in Non-Linear Polymerization Models using Markov Chain Monte Carlo Techniques and an Error-In-Variables Framework". Macromolecular Theory and Simulations 24, n. 6 (20 luglio 2015): 566–79. http://dx.doi.org/10.1002/mats.201500017.

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34

Meadows, Guy E., Helen M. A. Dunroy, Mary J. Morrell e Douglas R. Corfield. "Hypercapnic cerebral vascular reactivity is decreased, in humans, during sleep compared with wakefulness". Journal of Applied Physiology 94, n. 6 (1 giugno 2003): 2197–202. http://dx.doi.org/10.1152/japplphysiol.00606.2002.

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During wakefulness, increases in the partial pressure of arterial CO2 result in marked rises in cortical blood flow. However, during stage III–IV, non-rapid eye movement (NREM) sleep, and despite a relative state of hypercapnia, cortical blood flow is reduced compared with wakefulness. In the present study, we tested the hypothesis that, in normal subjects, hypercapnic cerebral vascular reactivity is decreased during stage III–IV NREM sleep compared with wakefulness. A 2-MHz pulsed Doppler ultrasound system was used to measure the left middle cerebral artery velocity (MCAV; cm/s) in 12 healthy individuals while awake and during stage III–IV NREM sleep. The end-tidal Pco 2(Pet CO2 ) was elevated during the awake and sleep states by regulating the inspired CO2 load. The cerebral vascular reactivity to CO2 was calculated from the relationship between Pet CO2 and MCAV by using linear regression. From wakefulness to sleep, the Pet CO2 increased by 3.4 Torr ( P < 0.001) and the MCAV fell by 11.7% ( P < 0.001). A marked decrease in cerebral vascular reactivity was noted in all subjects, with an average fall of 70.1% ( P = 0.001). This decrease in hypercapnic cerebral vascular reactivity may, at least in part, explain the stage III–IV NREM sleep-related reduction in cortical blood flow.

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Fan, Gen, e Wen Bin Liu. "An Integral Method for Solving the Point Reactor Neutron Kinetics Equations with Newtonian Temperature Feedback". Advanced Materials Research 732-733 (agosto 2013): 83–89. http://dx.doi.org/10.4028/www.scientific.net/amr.732-733.83.

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A numerical integral method to efficiently solve the point kinetics equations with Newtonian temperature feedback is described and investigated, which employs the better basis function (BBF) for the approximation of the neutron density in integral of one time step. The numerical evaluation is performed by the developed BBF code. The code can solve the general non-linear kinetics problems with six groups of delayed neutron. For the application purposes, the developed code and the method are tested by using a variety of problems, including ramp reactivity input with or without temperature feedback. The results are shown that the BBF method is clearly an effective and accurate numerical method for solving the point kinetics equations with Newtonian temperature feedback, and it can be used in real time power reactor forecasting in order to prevent the reactivity accidents.

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Dulla, S., e C. Nicolino. "Dynamics of Fluid Fuel Reactors in the Presence of Periodic Perturbations". Science and Technology of Nuclear Installations 2008 (2008): 1–11. http://dx.doi.org/10.1155/2008/816543.

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The appearance of perturbations characterized by a periodic time behavior in fluid fuel reactors is connected to the possible precipitation of fissile compounds which are moved within the primary circuit by the fuel motion. In this paper the time-dependent response of a critical fluid fuel system to periodic perturbations is analyzed, solving the full neutronic model and comparing the results with approximate methods, such as point kinetics. A fundamental eigenvalue of the problem is defined, characterizing the trend of divergence of the power. Parametric studies on the reactivity insertion, the fuel velocity and the recirculation time are performed, evidencing the sensitivity of the eigenvalue on typical design parameters. Non-linear calculations in the presence of a negative feedback term are then performed, in order to assess the possibility to control a fluid fuel system when periodic reactivity perturbations are involved.

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Sarah, Siti, Adisalamun Adisalamun, Darmadi Darmadi, Suraiya Kamaruzzaman, Abrar Muslim e Saiful Saiful. "Bentonite and Magnetite Filler-Modified Polyurethane Foam in Fixed Bed Column for the Adsorption of Mercury(II) Ions from Aqueous Solution". Aceh International Journal of Science and Technology 10, n. 1 (30 aprile 2021): 27–37. http://dx.doi.org/10.13170/aijst.10.1.18890.

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This paper proposed adsorbent development by synthesizing polyurethane foam (PUF) using a simple method, mixing polyol with isocyanate and adding fillers of bentonite and magnetite to the PUF matrix. The study's main objective was to produce a PUF-based adsorbent with high reactivity to remove Hg2+ in wastewater. This bentonite and magnetite filler-modified polyurethane foam (BMPUF) adsorbent was fixed in a bed column for the adsorption of mercury (II) ions from an aqueous solution. The effect of initial Hg2+ concentration on the removal rate and the effect of contact time on adsorption efficiency was investigated. Langmuir, Freundlich, and BET non-linear models were taken into account to determine the best adsorption isotherm fitting and obtain adsorption capacity, intensity, and pore volume. As a result, it followed the non-linear Freundlich model, and the average adsorption capacity and intensity were 0.466 mg/g and 0.923, respectively. The average BET-based pore volume obtained was 0.782 L/mg. The kinetics study showed that the non-linear pseudo-first-order kinetics model was more suitable for describing the Hg2+ adsorption kinetics. The maximum equilibrium adsorption capacity was 1.770 mg/g with the adsorption rate of 0.0013 min-1 based on the non-linear model. The effect of varying bentonite and magnetite ratio on adsorption isotherm and kinetics was also investigated. Overall, the potential application of BMPUF adsorbent in the adsorption of mercury (II) ions was demonstrated in the current study.

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Benedito, Adolfo, Eider Acarreta e Enrique Giménez. "Highly Efficient MOF Catalyst Systems for CO2 Conversion to Bis-Cyclic Carbonates as Building Blocks for NIPHUs (Non-Isocyanate Polyhydroxyurethanes) Synthesis". Catalysts 11, n. 5 (12 maggio 2021): 628. http://dx.doi.org/10.3390/catal11050628.

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The present paper describes a greener sustainable route toward the synthesis of NIPHUs. We report a highly efficient solvent-free process to produce [4,4′-bi(1,3-dioxolane)]-2,2′-dione (BDC), involving CO2, as renewable feedstock, and bis-epoxide (1,3-butadiendiepoxide) using only metal–organic frameworks (MOFs) as catalysts and cetyltrimethyl-ammonium bromide (CTAB) as a co-catalyst. This synthetic procedure is evaluated in the context of reducing global emissions of waste CO2 and converting CO2 into useful chemical feedstocks. The reaction was carried out in a pressurized reactor at pressures of 30 bars and controlled temperatures of around 120–130 °C. This study examines how reaction parameters such as catalyst used, temperature, or reaction time can influence the molar mass, yield, or reactivity of BDC. High BDC reactivity is essential for producing high molar mass linear non-isocyanate polyhydroxyurethane (NIPHU) via melt-phase polyaddition with aliphatic diamines. The optimized Al-OH-fumarate catalyst system described in this paper exhibited a 78% GC-MS conversion for the desired cyclic carbonates, in the absence of a solvent and a 50 wt % chemically fixed CO2. The cycloaddition reaction could also be carried out in the absence of CTAB, although lower cyclic carbonate yields were observed.

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Dolatkhani, Mohamad, Henri Cramail e Alain Deffieux. "Linear non-conjugated dienes from biomass as termonomers in EPDM synthesis, 1. Study of their reactivity in homo-, co- and terpolymerizations". Macromolecular Chemistry and Physics 196, n. 10 (ottobre 1995): 3091–105. http://dx.doi.org/10.1002/macp.1995.021961002.

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Corral-Frías, N. S., Y. S. Nikolova, L. J. Michalski, D. A. A. Baranger, A. R. Hariri e R. Bogdan. "Stress-related anhedonia is associated with ventral striatum reactivity to reward and transdiagnostic psychiatric symptomatology". Psychological Medicine 45, n. 12 (8 aprile 2015): 2605–17. http://dx.doi.org/10.1017/s0033291715000525.

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Abstract (sommario):

BackgroundEarly life stress (ELS) is consistently associated with increased risk for subsequent psychopathology. Individual differences in neural response to reward may confer vulnerability to stress-related psychopathology. Using data from the ongoing Duke Neurogenetics Study, the present study examined whether reward-related ventral striatum (VS) reactivity moderates the relationship between retrospectively reported ELS and anhedonic symptomatology. We further assessed whether individual differences in reward-related VS reactivity were associated with other depressive symptoms and problematic alcohol use via stress-related anhedonic symptoms and substance use-associated coping.MethodBlood oxygen level-dependent functional magnetic resonance imaging (fMRI) was collected while participants (n = 906) completed a card-guessing task, which robustly elicits VS reactivity. ELS, anhedonic symptoms, other depressive symptoms, coping behavior, and alcohol use behavior were assessed with self-report questionnaires. Linear regressions were run to examine whether VS reactivity moderated the relationship between ELS and anhedonic symptoms. Structural equation models examined whether this moderation was indirectly associated with other depression symptoms and problematic alcohol use through its association with anhedonia.ResultsAnalyses of data from 820 participants passing quality control procedures revealed that the VS × ELS interaction was associated with anhedonic symptoms (p = 0.011). Moreover, structural equation models indirectly linked this interaction to non-anhedonic depression symptoms and problematic alcohol use through anhedonic symptoms and substance-related coping.ConclusionsThese findings suggest that reduced VS reactivity to reward is associated with increased risk for anhedonia in individuals exposed to ELS. Such stress-related anhedonia is further associated with other depressive symptoms and problematic alcohol use through substance-related coping.

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Wang, Hong Juan, Jia Dao Zheng, Li Li Zhu, Feng Peng e Hao Yu. "Non-Metal Doped Pd/CNTs Catalysts for Oxygen Reduction Reaction in Alkaline Medium". Advanced Materials Research 550-553 (luglio 2012): 238–42. http://dx.doi.org/10.4028/www.scientific.net/amr.550-553.238.

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Phosphorus and boron-doped palladium nanoparticles supported on carbon nanotubes (P-Pd/CNTs and B-Pd/CNTs, respectively) were prepared and evaluated for oxygen reduction reactivity (ORR) in alkaline environments. The prepared catalysts were characterized by X-ray diffraction (XRD), electron probe microanalysis (EMPA), and X-ray photoelectron spectroscopy (XPS). The ORR activity, methanol tolerance, and durability of the prepared catalysts were evaluated in oxygen-saturated 0.1 M potassium hydroxide electrolytes via cyclic voltammetry (CV) and linear sweep voltammetry (LSV) on rotating disk electrodes. The mechanisms and kinetics of ORR were discussed. The results show that P-Pd/CNTs exhibit higher ORR activity than B-Pd/CNTs and Pd/CNTs, higher methanol tolerance than commercial Pt/C, and excellent durability with 90% of the original activity maintained after 1000 voltage cycles. The ORR on P-Pd/CNTs proceeds via a 4-electron reduction process with O2 reduced to H2O directly, during which the rate-determining step is charge transfer at low overpotential and then changes to mass transport at high overpotential.

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Drmanic, Sasa, Aleksandar Marinkovic e Bratislav Jovanovic. "Effects of solvent and structure on the reactivity of 6-substituted nicotinic acids with diazodiphenylmethane in aprotic solvents". Journal of the Serbian Chemical Society 74, n. 12 (2009): 1359–70. http://dx.doi.org/10.2298/jsc0912359d.

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The rate constants for the reactions of diazodiphenylmethane (DDM) with 6-substituted nicotinic acids in aprotic solvents at 30?C were determined. The obtained second order rate constants in aprotic solvents, together with literature data for benzoic and nicotinic acids in protic solvents, were used for the calculation of solvent effects, employing the Kamlet-Taft solvatochromic equation (linear solvation energy relationship - LSER) in the form: log k = log k0 + + s?*+ a? + b?. The correlations of the kinetic data were performed by means of multiple linear regression analysis taking appropriate solvent parameters. The sign of the equation coefficients (s, a and b) were in agreement with the postulated reaction mechanism, and the mode of the solvent influences on the reaction rate is discussed based on the correlation results. A similar contribution of the non-specific solvent effect and electrophilic solvation was observed for all acids, while the highest contribution of nucleophilic solvation was influenced by their high acidity. Correlation analysis of the rate data with substituent ?p parameters in an appropriate solvent using the Hammett equation was also performed. The substituent effect on the acid reactivity was higher in aprotic solvents of higher dipolarity/polarizability. The mode of the transmission of the substituent effect is discussed in light of the contribution of solute-solvent interaction on the acid reactivity.

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Bello Robles, F. A., M. Chacon e R. B. Panerai. "Critical closing pressure as a proxy for PaCO2 in non-linear multivariate models for estimation of dynamic cerebral autoregulation and cerebrovascular reactivity". Journal of the Neurological Sciences 357 (ottobre 2015): e366. http://dx.doi.org/10.1016/j.jns.2015.08.1313.

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Belaya, Natalia I., e Alexander V. Belyi. "SEMI-EMPIRICAL MODEL FOR PREDICTING PHENOL CARBOXYLIC ACIDS ANTIRADICAL ACTIVITY". IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 62, n. 7 (21 luglio 2019): 80–84. http://dx.doi.org/10.6060/ivkkt.20196207.5952.

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Abstract (sommario):

Using the spectral method, the rate constants of natural phenolcarboxylic acids reaction with the radical 2,2'-diphenyl-1-picrylhydrazyl in benzene at a temperature of 293±2 K were determined. It is established that the reaction corresponds to the second-order kinetic equation and proceeds by the mechanism of the hydrogen atom transfer. This confirmed by the presence of the deuterium isotope effect. The parameter, affecting the proceed of this mechanism in a non-polar medium, is the energy of the homolytic rupture of the weakest phenolic O–H bond in the phenolcarboxylic acid molecule, calculated using the quantum-chemical methods. Changes in the strength of phenolic O–H bonds in an acid molecule lead to corresponding changes in their reactivity with respect to the hydrazyl radical. It is seen that the compounds with low bond strengths of functional groups – 3 pyrogallolcarboxylic and gallic acids, methyl- and ethyl- gallate – showed the most antiradical activity. According to the calculated and experimental data, a semiempirical linear single-factor equation is proposed. This equation describes the relationship between the antiradical activity of phenolic acids and the descriptor of their structure and allows to predict the reactivity of the antioxidant in lipid-like media. The applicability of the proposed model was proved by studying the control group of hydroxyacetophenones which belong to plant phenol compounds. According to the forecast, 3,4- and 2,5-hydroxyacetophenones can be recommended as potential effective antioxidants in non-polar environments. The unit relative deviations of the predicted rate constants from their experimental values vary from 2 to 9% with an average approximation error equals to 7.9%, which indicates a good selection of the linear model.

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Serdaroğlu, Goncagül, e Nesimi Uludağ. "The synthesis and spectroscopic characterization of (+)-demethoxyaspidospermine: Density functional theory calculations of the structural, electronic, and non-linear optic and spectroscopic properties". Journal of Chemical Research 43, n. 11-12 (17 settembre 2019): 531–41. http://dx.doi.org/10.1177/1747519819875859.

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(+)-Demethoxyaspidospermine was synthesized via the acylation of aspidospermidine with acetic anhydride, and the structure was determined by elemental analysis and Fourier-transform infrared and nuclear magnetic resonance spectroscopic tools and was supported by the simulated spectroscopic studies. Next, the stable geometries obtained by the conformational analysis performed at the B3LYP/6-31G(d, p) level were used for further investigations carried out in B3LYP and M06-2X functionals, and Hartree–Fock (HF) method, employed by the 6-311++G(d, p) basis set. Also, the natural bond orbital analysis revealed that the most contribution to the lowering of the stabilization energy came from n → π* and π → π* interactions. Moreover, the non-linear optic analysis has shown that the title compound can be a useful agent in the optoelectronic devices because of the optical properties. Also, the chemical reactivity tendency for nucleophilic or electrophilic attack reactions on the compound was evaluated by frontier molecular orbital analysis, and the reactive sites of the compound was shown by highest molecular orbital and lowest unoccupied orbital amplitudes and molecular electrostatic potential diagrams.

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Branca, Carmen, e Blasi di. "Parallel and series-reaction mechanisms of wood and char combustion". Thermal Science 8, n. 2 (2004): 51–64. http://dx.doi.org/10.2298/tsci0402051b.

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Thermo gravimetric curves in air of beech wood and char, obtained from conventional pyrolysis of beech wood at a laboratory scale, have been re-examined using different kinetic models. Multi-step reaction mechanisms consisting of either four (wood) or two (char) reactions are needed for accurate predictions of weight loss curves. In the case of wood, three reactions are linear in the reactant mass fraction whereas the fourth step presents a power-law dependence. A linear reaction for devolatilization and a non-linear reaction for combustion are used for the weight loss curves of char. It has been found that activation energies and pre-exponential factors are in variant with series or parallel reactions, providing changes in the stoichiometric coefficients. Further more, the activation energies of the two reactions occurring at higher temperatures in the four-step mechanism (wood) and those of the two-step mechanism (char) are the same. Thus pre-exponential factors and reaction order take into account variations in the char reactivity derived from different pyrolysis conditions.

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Pugliese, S. C., J. G. Murphy, J. A. Geddes e J. M. Wang. "The impacts of precursor reduction and meteorology on ground-level ozone in the Greater Toronto Area". Atmospheric Chemistry and Physics Discussions 14, n. 7 (22 aprile 2014): 10209–39. http://dx.doi.org/10.5194/acpd-14-10209-2014.

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Abstract. Tropospheric ozone (O3) is a major component of photochemical smog and is a known human health hazard as well as a damaging factor for vegetation. Its precursor compounds, nitrogen oxides (NOx) and volatile organic compounds (VOCs), have a variety of anthropogenic and biogenic sources and exhibit non-linear effects on ozone production. As an update to previous studies on ground-level ozone in the GTA, we present an analysis of NO2, VOC and O3 data from federal and provincial governmental monitoring sites in the GTA from 2000–2012. We show that over the study period, summertime 24 h VOC reactivity and NO2 midday (11:00–15:00) concentrations at all sites decreased significantly; since 2000, all sites experienced a decrease in NO2 of 28–62% and in measured VOC reactivity of at least 53–71%. Comparing 2002/2003 to 2011/2012, the summed reactivity of OH towards NO2 and a suite of measured VOCs decreased from 8.6 to 4.6 s−1. Ratios of reactive VOC pairs indicate that the effective OH concentration experienced by primary pollutants in the GTA has increased significantly over the study period. Despite the continuous decrease in precursor levels, ozone concentrations are not following the same pattern at all stations; it was found that the Canada-Wide Standard for ozone continues to be exceeded at all monitoring stations. Additionally, while the years 2008–2011 had consistently lower ozone levels than previous years, 2012 experienced one of the highest recorded summertime ozone concentrations and a large number of smog episodes. We demonstrate that these high ozone observations in 2012 may be a result of the number of days with high solar radiation, the number of stagnant periods and the transport of high ozone levels from upwind regions.

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Pugliese, S. C., J. G. Murphy, J. A. Geddes e J. M. Wang. "The impacts of precursor reduction and meteorology on ground-level ozone in the Greater Toronto Area". Atmospheric Chemistry and Physics 14, n. 15 (15 agosto 2014): 8197–207. http://dx.doi.org/10.5194/acp-14-8197-2014.

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Abstract (sommario):

Abstract. Tropospheric ozone (O3) is a major component of photochemical smog and is a known human health hazard, as well as a damaging factor for vegetation. Its precursor compounds, nitrogen oxides (NOx) and volatile organic compounds (VOCs), have a variety of anthropogenic and biogenic sources and exhibit non-linear effects on ozone production. As an update to previous studies on ground-level ozone in the Greater Toronto Area (GTA), we present an analysis of NO2, VOC and O3 data from federal and provincial governmental monitoring sites in the GTA from 2000 to 2012. We show that, over the study period, summertime 24 h VOC reactivity and NO2 midday (11:00–15:00) concentrations at all sites decreased significantly; since 2000, all sites experienced a decrease in NO2 of 28–62% and in measured VOC reactivity of at least 53–71%. Comparing 2002–2003 to 2011–2012, the summed reactivity of OH towards NO2 and a suite of measured VOCs decreased from 8.6 to 4.6 s−1. Ratios of reactive VOC pairs indicate that the effective OH concentration experienced by primary pollutants in the GTA has increased significantly over the study period. Despite the continuous decrease in precursor levels, ozone concentrations are not following the same pattern at all stations; it was found that the Canada-wide Standard for ozone continues to be exceeded at all monitoring stations. Additionally, while the years 2008–2011 had consistently lower ozone levels than previous years, 2012 experienced one of the highest recorded summertime ozone concentrations and a large number of smog episodes. We demonstrate that these high ozone observations in 2012 may be a result of the number of days with high solar radiation, the number of stagnant periods and the transport of high ozone levels from upwind regions.

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Vlaminck, Johnny, Ole Lagatie, Daniel Dana, Zeleke Mekonnen, Peter Geldhof, Bruno Levecke e Lieven J. Stuyver. "Identification of antigenic linear peptides in the soil-transmitted helminth and Schistosoma mansoni proteome". PLOS Neglected Tropical Diseases 15, n. 4 (28 aprile 2021): e0009369. http://dx.doi.org/10.1371/journal.pntd.0009369.

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The scientific community identified non stool-based biomarkers as the way forward to support soil-transmitted helminth (STH; Ascaris lumbricoides, Trichuris trichiura and the hookworms Ancylostoma duodenale and Necator americanus) and schistosome (S. mansoni and S. haematobium) deworming programs. This support is needed in making the decision of whether or not to stop preventive chemotherapy intervention efforts and to ultimately transition towards a post-intervention surveillance phase. We applied a two-step micro-array approach to identify antigenic linear epitopes in the STH and S. mansoni proteomes. In a first experiment, we identified antigenic peptides by applying sera from 24 STH and/or S. mansoni infected Ethiopian children on a high-density peptide microarray containing 3.3 million peptides derived from the complete STH and S. mansoni proteomes. A second array experiment with 170,185 peptides that were recognized in the first array was designed to identify non-specific antibody reactivity by applying sera from 24 healthy individuals from Belgium (a non-endemic country). From this array testing cascade, several peptides were identified for STH but none of them appeared to be unique for one species. We therefore concluded that for STH, none of the peptides revealed to be sufficiently sensitive or species specific. For S. mansoni, some promising peptides were identified prompting future investigation. Based on these results, it is unlikely that linear epitopes would be highly useful in detecting species-specific antibody responses to STH in endemic communities. For S. mansoni, one particular peptide of the micro-exon gene 12 (MEG-12) protein deserves further research. In addition, this study emphasizes the need of well-characterized biobanks for biomarker discovery, particularly when the integration of multiple disease programs is envisioned.

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Mathieu, François, Frederick A. Zeiler, Daniel P. Whitehouse, Tilak Das, Ari Ercole, Peter Smielewski, Peter J. Hutchinson, Marek Czosnyka, Virginia F. J. Newcombe e David K. Menon. "Relationship Between Measures of Cerebrovascular Reactivity and Intracranial Lesion Progression in Acute TBI Patients: an Exploratory Analysis". Neurocritical Care 32, n. 2 (3 dicembre 2019): 373–82. http://dx.doi.org/10.1007/s12028-019-00885-3.

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Abstract Background Failure of cerebral autoregulation and progression of intracranial lesion have both been shown to contribute to poor outcome in patients with acute traumatic brain injury (TBI), but the interplay between the two phenomena has not been investigated. Preliminary evidence leads us to hypothesize that brain tissue adjacent to primary injury foci may be more vulnerable to large fluctuations in blood flow in the absence of intact autoregulatory mechanisms. The goal of this study was therefore to assess the influence of cerebrovascular reactivity measures on radiological lesion expansion in a cohort of patients with acute TBI. Methods We conducted a retrospective cohort analysis on 50 TBI patients who had undergone high-frequency multimodal intracranial monitoring and for which at least two brain computed tomography (CT) scans had been performed in the acute phase of injury. We first performed univariate analyses on the full cohort to identify non-neurophysiological factors (i.e., initial lesion volume, timing of scan, coagulopathy) associated with traumatic lesion growth in this population. In a subset analysis of 23 patients who had intracranial recording data covering the period between the initial and repeat CT scan, we then correlated changes in serial volumetric lesion measurements with cerebrovascular reactivity metrics derived from the pressure reactivity index (PRx), pulse amplitude index (PAx), and RAC (correlation coefficient between the pulse amplitude of intracranial pressure and cerebral perfusion pressure). Using multivariate methods, these results were subsequently adjusted for the non-neurophysiological confounders identified in the univariate analyses. Results We observed significant positive linear associations between the degree of cerebrovascular reactivity impairment and progression of pericontusional edema. The strongest correlations were observed between edema progression and the following indices of cerebrovascular reactivity between sequential scans: % time PRx > 0.25 (r = 0.69, p = 0.002) and % time PAx > 0.25 (r = 0.64, p = 0.006). These associations remained significant after adjusting for initial lesion volume and mean cerebral perfusion pressure. In contrast, progression of the hemorrhagic core and extra-axial hemorrhage volume did not appear to be strongly influenced by autoregulatory status. Conclusions Our preliminary findings suggest a possible link between autoregulatory failure and traumatic edema progression, which warrants re-evaluation in larger-scale prospective studies.

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