Academic literature on the topic 'LF S-parameter'

1. The spinal pathways for tonic and stimulation-produced descending inhibition of spinal nociceptive neurons were investigated in anesthetized paralyzed cats. Reversible circumscribed blocks were produced at various depths in the lateral funiculi (LF) at L1-L2 using the microinjection of the local anesthetic lidocaine. The total amount of tonic descending inhibition in the absence of LF blocks was evaluated by monitoring the spinal neuronal activity during reversible spinalization by cold block and compared with the activity of the same neuron during LF blocks. Stimulation-induced descending inhibition of neuronal responses to noxious skin heating was produced by bipolar focal electrical stimulation in the periaqueductal gray (PAG) or nucleus raphe magnus (NRM) and compared with the inhibition of the same neurons during LF blocks. The relative significance of ipsi- and contralateral pathways in the dorsal, medial, or ventral aspects of the lateral funiculi for these types of descending inhibition are quantitatively described. 2. All 35 lumbar spinal dorsal horn neurons studied responded to noxious and innocuous mechanical and noxious thermal stimuli applied within the receptive fields on the glabrous skin of the hindlimb. Responses to noxious skin stimuli (50 degrees C, 10 s at 3-min intervals) were constant over time and served as a parameter to evaluate tonic and stimulation-produced descending inhibition. All neurons also responded to electrical stimulation of hindlimb cutaneous nerves supramaximal for the activation of A-beta-, delta-, and C-fibers. Neurons were located in laminae I-VI of the dorsal horn at L5-L7 levels. LF blocks were produced by the microinjection of 1 microliter lidocaine at each of one to six sites in the ipsilateral and/or contralateral LF 500, 1,500, and/or 2,500 microns below cord surface. 3. LF blocks ipsilateral to the recording sites in the cord significantly reduced tonic inhibition, with blocks in the dorsal part of the LF [i.e., the dorsolateral funiculus (DLF)] being equally effective to complete LF blocks. Stimulation-produced inhibition from PAG or NRM was, however, not significantly affected by ipsilateral LF blocks. 4. Contralateral LF blocks significantly reduced stimulation-produced descending inhibition and failed to affect tonic descending inhibition. Ventral LF blocks attenuated inhibition from the PAG but not from NRM, whereas DLF blocks were more effective on inhibition from the NRM. 5. Bilateral LF blocks significantly reduced tonic as well as stimulation-produced descending inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

Context. The OSIRIS Tunable Filter Emission Line Object (OTELO) survey is a very deep, blind exploration of a selected region of the Extended Groth Strip and is designed for finding emission-line sources (ELSs). The survey design, observations, data reduction, astrometry, and photometry, as well as the correlation with ancillary data used to obtain a final catalogue, including photo-z estimates and a preliminary selection of ELS, were described in a previous contribution. Aims. Here, we aim to determine the main properties and luminosity function (LF) of the [O III] ELS sample of OTELO as a scientific demonstration of its capabilities, advantages, and complementarity with respect to other surveys. Methods. The selection and analysis procedures of ELS candidates obtained using tunable filter pseudo-spectra are described. We performed simulations in the parameter space of the survey to obtain emission-line detection probabilities. Relevant characteristics of [O III] emitters and the LF ([O III]), including the main selection biases and uncertainties, are presented. Results. From 541 preliminary emission-line source candidates selected around z = 0.8, a total of 184 sources were confirmed as [O III] emitters. Consistent with simulations, the minimum detectable line flux and equivalent width in this ELS sample are ∼5 × 10−19 erg s−1 cm2 and ∼6 Å, respectively. We are able to constrain the faint-end slope (α = −1.03 ± 0.08) of the observed LF ([O III]) at a mean redshift of z = 0.83. This LF reaches values that are approximately ten times lower than those from other surveys. The vast majority (84%) of the morphologically classified [O III] ELSs are disc-like sources, and 87% of this sample is comprised of galaxies with stellar masses of M⋆ < 1010 M⊙.

Abstract Zischke, M. T., Griffiths, S. P., and Tibbetts, I. R. 2013. Rapid growth of wahoo (Acanthocybium solandri) in the Coral Sea, based on length-at-age estimates using annual and daily increments on sagittal otoliths. – ICES Journal of Marine Science, 70: 1128–1139. The wahoo (Acanthocybium solandri) is an economically important species incidentally caught in oceanic fisheries targeting tuna and coastal fisheries targeting mackerels. The age and growth of wahoo was examined using whole and sectioned otoliths from 395 fish (790–1770 mm LF) sampled from the Coral Sea. Growth increments were more reliably assigned on whole otoliths than sectioned otoliths. Edge analyses revealed that growth increments were deposited annually, primarily between October and February. Furthermore, analysis of presumed daily microincrements showed that ∼90% of fish had deposited the first “annual” growth increment by the 365th day, thereby indirectly validating annual increment formation. Wahoo were aged at between 108 d and 7 years, with 76% of fish being <2-year old. The specialized von Bertalanffy growth function provided the best fit to length-at-age data, with parameter estimates (sexes combined) of L∞ = 1499 mm LF, K = 1.58 year−1, and t0 = −0.17 years. The growth performance index for wahoo in the Coral Sea (φ′ = 4.55) was one of the highest of all pelagic fish, with their growth and maximum size most similar to dolphinfish. This study suggests that wahoo are one of the fastest growing teleosts and provides growth parameter estimates that may facilitate future stock assessments and guide fisheries management.

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. This study aimed to evaluate the performance of four ultrasound-based techniques for the non-invasive multiparametric (MPUS) assessment of liver fibrosis (LF), steatosis (HS), and inflammation in patients with NAFLD. We included 215 consecutive adult patients with NAFLD (mean age: 54.9 ± 11.7; 54.5% were male), in whom LF, HS, and viscosity were evaluated in the same session using four new ultrasound-based techniques embedded on the Aixplorer MACH 30 system: ShearWave Elastography (2D-SWE.PLUS), Sound Speed Plane-wave UltraSound (SSp.PLUS), Attenuation Plane-wave UltraSound (Att.PLUS), and Viscosity Plane-wave UltraSound (Vi.PLUS). Transient Elastography (TE) with Controlled Attenuation Parameter (CAP) (FibroScan) were considered as control. All elastographic measurements were performed according to guidelines. Valid liver stiffness measurements (LSM) were obtained in 98.6% of patients by TE, in 95.8% of patients by 2D-SWE.PLUS/Vi.PLUS, and in 98.1% of patients by Att.PLUS/SSp.PLUS, respectively. Therefore, 204 subjects were included in the final analysis. A strong correlation between LSMs by 2D-SWE.PLUS and TE (r = 0.89) was found. The best 2D-SWE.PLUS cut-off value for the presence of significant fibrosis (F ≥ 2) was 7 kPa. Regarding steatosis, SSp.PLUS correlated better than Att.PLUS with CAP values: (r = −0.74) vs. (r = 0.45). The best SSp.PLUS cut-off value for predicting the presence of significant steatosis was 1524 m/s. The multivariate regression analysis showed that Vi.PLUS values were associated with BMI and LSM by 2D-SWE.PLUS. In conclusion, MPUS was useful for assessing fibrosis, steatosis, and inflammation in a single examination in patients with NAFLD.

Abstract Griffiths, S. P., Fry, G. C., Manson, F. J., and Lou, D. C. 2010. Age and growth of longtail tuna (Thunnus tonggol) in tropical and temperate waters of the central Indo-Pacific. – ICES Journal of Marine Science, 67: 125–134. Age and growth of longtail tuna (Thunnus tonggol) were assessed by examination of annual growth increments in sectioned sagittal otoliths from 461 fish (238–1250 mm fork length, LF) sampled from tropical and temperate waters in the central Indo-Pacific between February 2003 and April 2005. Edge and microincrement analyses (presumed daily increments) suggest that longtail tuna deposit a single annual growth increment mainly between August and October. Age was, therefore, estimated for all fish by counting assumed annual growth increments. Ages ranged from 154 d to 18.7 years, with most fish being 3–9 years. Five growth models were fitted to length-at-age data, all of which indicated that the species is relatively slow-growing and long-lived. Recaptures of two tagged fish at liberty for 6.2 and 10.5 years support this notion. A bias-corrected form of Akaike's Information Criterion determined that the Schnute–Richards model provided the best fit to length-at-age data, with model parameter estimates (sexes combined) of L∞ = 135.4 cm LF, K = 22.3 year−1, t0 = 0.120 years, δ = 150.0, v = 0.019, and γ = 2.7 × 10−8. There was no significant difference in growth between sexes. The results suggest that longtail tuna grow more slowly and live longer than other tuna species of similar size. Coupled with their restricted neritic distribution, longtail tuna may be vulnerable to overexploitation by fisheries, and caution needs to be exercised in managing the species until more reliable biological and catch data are collected to assess the status of the population.

The mathematical analysis and the assessment of heart rate variability (HRV) based on computer systems can assist the diagnostic process with determining the cardiac status of patients. The new cardio-diagnostic assisting computer system created uses the classic Time-Domain, Frequency-Domain, and Time-Frequency analysis indices, as well as the nonlinear methods (Poincaré plot, Recurrence plot, Hurst R/S method, Detrended Fluctuation Analysis (DFA), Multi-Fractal DFA, Approximate Entropy and Sample Entropy). To test the feasibility of the software developed, 24-hour Holter recordings of four groups of people were analysed: healthy subjects and patients with arrhythmia, heart failure and syncope. Time-Domain (SDNN < 50 ms, SDANN < 100 ms, RMSSD < 17 ms) and Frequency-Domain (the spectrum of HRV in the LF < 550 ms2, and HF < 540 ms2) parameter values decreased in the cardiovascular disease groups compared to the control group as a result of lower HRV due to decreased parasympathetic and increased sympathetic activity. The results of the nonlinear analysis showed low values of (SD1 < 56 ms, SD2 < 110 ms) at Poincaré plot (Alpha < 90 ms) at DFA in patients with diseases. Significantly reducing these parameters are markers of cardiac dysfunction. The examined groups of patients showed an increase in the parameters (DET% > 95, REC% > 38, ENTR > 3.2) at the Recurrence plot. This is evidence of a pathological change in the regulation of heart rhythm. The system created can be useful in making the diagnosis by the cardiologist and in bringing greater accuracy and objectivity to the treatment.

Articulatory speech synthesis has long been based on one-dimensional (1D) approaches. They assume plane wave propagation within the vocal tract and disregard higher order modes that typically appear above 5 kHz. However, such modes may be relevant in obtaining a more natural voice, especially for phonation types with significant high frequency energy (HFE) content. This work studies the contribution of the glottal source at high frequencies in the 3D numerical synthesis of vowels. The spoken vocal range is explored using an LF (Liljencrants–Fant) model enhanced with aspiration noise and controlled by the R d glottal shape parameter. The vowels [ɑ], [i], and [u] are generated with a finite element method (FEM) using realistic 3D vocal tract geometries obtained from magnetic resonance imaging (MRI), as well as simplified straight vocal tracts of a circular cross-sectional area. The symmetry of the latter prevents the onset of higher order modes. Thus, the comparison between realistic and simplified geometries enables us to analyse the influence of such modes. The simulations indicate that higher order modes may be perceptually relevant, particularly for tense phonations (lower R d values) and/or high fundamental frequency values, F 0 s. Conversely, vowels with a lax phonation and/or low F0s may result in inaudible HFE levels, especially if aspiration noise is not considered in the glottal source model.

ResumoO estudo da Variabilidade da Frequência Cardíaca (VFC) tem permitido, de forma não invasiva, avaliar o Sistema Nervoso autônomo e o risco cardíaco, sendo um importante indicador prognóstico de doenças cardíacas e sistêmicas. O objetivo foi avaliar e comparar a VFC no domínio da frequência e do tempo de idosos com hipertensão arterial e de idosos saudáveis frente à mudança postural de repouso para sentado. Foram estudados 18 indivíduos hipertensos e 18 indivíduos saudáveis na faixa etária de 60 a 85 anos. A frequência cardíaca e os intervalos R-R foram coletados pelo instrumento Polar S810i durante 1200 s nas posturas supina e sentada. A VFC foi analisada no domínio do tempo - DT pelas variáveis: Índice raiz quadrada da média dos quadrados das diferenças entre intervalos R-R (iR-R) sucessivos (RMSSD), desvio padrão da média dos iR-R normais em ms - SDNN e PNN50%, que traduz a diferença de duração superior a 50 milissegundos, e no domínio da frequência, pelas bandas de alta (AF) e baixa frequência (BF), e da razão BF/AF. Ocorreu alteração na VFC dos idosos tanto no grupo controle e hipertenso, no entanto não houve mudanças significativas na VFC entre os grupos estudados. Ao analisar a VFC no domínio do tempo, o estudo mostrou que a amostragem estudada apresenta alto risco cardíaco ao analisar o parâmetro SDNN. Conclui-se que a mudança postural alterou a VFC desses idosos, tanto no grupo controle e hipertenso, no entanto não houve mudanças significativas na VFC entre as fases dos grupos estudados e obteve-se como resultado alto risco cardíaco ao avaliar o parâmetro SDNN em ambos os grupos.Palavras-chave: Hipertensão. Idoso. Frequência Cardíaca.AbstractThe study of heart rate variability (HRV) allows noninvasive way to evaluate the autonomic nervous system and cardiac risk, and an important prognostic indicator of heart and systemic diseases disease. The objective was to evaluate and compare the HRV in the frequency and duration of elderly patients with hypertension and healthy elderly versus postural change in the condition of rest. The study comprised 18 hypertensive individuals and 18 healthy subjects aged 60 to 85 years, both sexes. Heart rate and RR intervals were collected by the instrument Polar S810i during 1200 s in supine and sitting postures. HRV was analyzed in time domain indices SDNN, RMSSD and PNN50% and the frequency domain, by bands of high (AF) and low frequency (LF), and the ratio LF / HF. Intergroup intra-analyes were used as well as the tests of normality D’Augustine as a criterion for parametric groups. There was change in heart rate variability of both the elderly and hypertensive patients in the control group, however there were no significant changes in studied HRV intergroups . In the area of the time it was found that the sampling shows high-risk cardiac parsing the parameter SDNN. The results showed that the change posture changed the variability of heart rate in the control group and hypertension, however there were no significant changes in HRV among the phases of the groups and a high risk was obtained as a result of the parameter SDNN for both heart the groups.Keywords: Hypertension. Aged. Heart Rate.

Background Acoustic radiation force impulse (ARFI) is a non-invasive alternative to a liver biopsy for the evaluation of liver fibrosis (LF). Purpose To investigate the potential usefulness of acoustic radiation force impulse ARFI for detecting LF in overweight and obese children Material and Methods A cross-sectional study was conducted in 148 schoolchildren. A diagnosis of non-alcoholic fatty liver disease (NAFLD) and LF was based on ultrasound (US) and ARFI shear wave velocity (SWV). Results The laboratory parameters were normal in all the children. NAFLD was observed in 50 children (33.8%). The median SWV was 1.18 ± 0.28 m/s. Differences between ARFI categories and hepatic steatosis grades were observed (χ2 = 43.38, P = 0.0005). No fibrosis or insignificant fibrosis (SWV ≤ 1.60 m/s) was detected in 137 children (92.5%), and significant fibrosis (SWV > 1.60 m/s) in 11 children (7.5%), nine of whom had normal US or mild steatosis. Conclusion The present study is the first to evaluate the utility of the ARFI technique for detecting LF in overweight and obese children. The results of the study suggest that children with normal laboratory parameters such as normal liver ultrasound or mild steatosis may present with significant LF.

The aim of this study was to test whether the heart rate (HR) control in infants at risk differs in comparison with healthy infants. Twelve former preterm infants suffering from bronchopulmonary dysplasia and 18 control infants, matched for their postconceptional age, were examined polygraphically during quiet and active sleep. HR, low-frequency (LF) power, high-frequency (HF) power, total power, and the ratio of LF to HF power (LF/HF) of the instantaneous HR spectra were calculated for linear analysis. The largest Lyapunov exponent (LLE) of the R-R interval time series was calculated to determine a nonlinear property of HR. Infants at risk had significantly lower LF power (median: 0.51 x 10(-3) vs. 1.16 x 10(-3) Hz2) and lower LF/HF (median: 1.05 vs. 1.94) during quiet sleep. LLE was positive, revealing low-dimensional chaotic behavior of HR control, and did not differ between both groups (median: quiet sleep, 0.05 bit/s vs. 0.06 bit/s; active sleep, 0.16 bit/s vs. 0.15 bit/s). Sleep state-related changes in spectral parameters and LLE were similar in both groups. In infants at risk, the lower LF/HF during quiet sleep can be interpreted in terms of changes in the rhythmic components of the sympathovagal balance of the autonomic system, which is an expression of linear properties of HR control. Conversely, the lack of differences in LLE between both groups indicates similar nonlinear properties of the control system.

Depuis plusieurs années, la technologie de transistors à effet de champ à haute mobilité (HEMT) sur Nitrure de Gallium (GaN) a démontré un potentiel très important pour la montée en puissance et en fréquence des dispositifs. Malheureusement, la présence des effets parasites dégrade les performances dynamiques des composants ainsi que leur fiabilité à long-terme. En outre, l'origine de ces pièges et leur emplacement physique restent incertains jusqu'à aujourd'hui. Une partie du travail de recherche menée dans cette thèse est axée sur la caractérisation des pièges existant dans les dispositifs HEMTs GaN à partir de mesures de paramètre S basse fréquence (BF), les mesures du bruit BF et les mesures I(V) impulsionnelles. Parallèlement, nous avons effectué des simulations physiques basées sur TCAD afin d'identifier la localisation des pièges dans le transistor. De plus, notre étude expérimentale de caractérisation et de simulation montre que les mesures BF pourraient constituer un outil efficace pour caractériser les pièges existant dans le buffer GaN, alors que la caractérisation de Gate-lag pourrait être plus utile pour identifier les pièges de barrière des dispositifs GaN HEMT. La deuxième partie de ce travail de recherche est axée sur la caractérisation des dispositifs AlN/GaN HEMT sur substrat Si et SiC. Une méthode d’extraction simple et efficace de la résistance canal et de la résistance de contact a été mise au point en utilisant conjointement la simulation physique et les techniques de caractérisation. Le principe de l’extraction de la résistance canal est basée sur la mesure de la résistance RON. Celle-ci est calculée à partir des mesures de courant de drain IDS et de la tension VDS pour différentes valeurs de températures En outre, nous avons procédé à une évaluation complète du comportement thermique de ces composants en utilisant conjointement les mesures et les simulations thermiques tridimensionnelles (3D) sur TCAD. La résistance thermique (RTH) a été extraite pour les transistors de différentes géométries à l'aide des mesures et ensuite validée par les simulations thermiques sur TCAD
GaN High Electron Mobility Transistors (HEMTs) have demonstrated their capabilities to be an excellent candidate for high power microwave and mm-wave applications. However, the presence of traps in the device structure significantly degrades the device performance and also detriments the device reliability. Moreover, the origin of these traps and their physical location remains unclear till today. A part of the research work carried out in this thesis is focused on characterizing the traps existing in the GaN/AlGaN/GaN HEMT devices using LF S-parameter measurements, LF noise measurements and drain-lag characterization. Furthermore, we have used TCAD-based physical device simulations in order to identify the physically confirm the location of traps in the device. Moreover, our experimental characterization and simulation study suggest that LF measurements could be an effective tool for characterizing the traps existing in the GaN buffer whereas gate-lag characterization could be more useful to characterize the AlGaN barrier traps of GaN HEMT devices. The second aspect of this research work is focused on characterizing the AlN/GaN/AlGaN HEMT devices grown on Si and SiC substrate. We attempt to characterize the temperature-dependent on-resistance (RON) extraction of these devices using on-wafer measurements and TCAD-based physical simulations. Furthermore, we have proposed a simplified methodology to extract the temperature and bias-dependent channel sheet resistance (Rsh) and parasitic series contact resistance (Rse) of AlN/GaN HEMT devices. Further, we have made a comprehensive evaluation of thermal behavior of these devices using on-wafer measurements and TCAD-based three-dimensional (3D) thermal simulations. The thermal resistance (RTH) has been extracted for various geometries of the device using measurements and validated using TCAD-thermal simulations

Les HEMT à base du GaN ont déjà démontré leur potentialité pour toutes les applications forte puissance et haute fréquence. Cependant, cette technologie souffre de limitations dues notamment à un mécanisme complexe de piégeage/dépiégeage de charges qui se produit dans le composant et reste encore aujourd’hui mal compris. Ce mécanisme de piégeage limite les performances RF et mais également la fiabilité du transistor. Dans ce travail, nous avons étudié les mécanismes issus de ce phénomène à l'aide de plusieurs méthodes de mesures approfondies (Paramètres S en basse fréquence, I-DLTS, densités spectrales de courant de bruit) qui nous ont permis d’extraire la signature des pièges. Grâce à de la simulation TCAD sur le logiciel de simulation Sentaurus, nous avons pu identifier l'emplacement physique de certains pièges dans le composant et comprendre les phénomènes physiques mis-en jeu. Cet apport fournira des informations efficaces pour les améliorations technologiques dans le futur
GaN-based HEMTs have already demonstrated their supreme potential for all high power and high frequency applications. However, this technology suffers from limitations due to complex trapping/de-trapping mechanisms that occurs in the device and that are still not well understood. This trapping mechanism limits the RF performances but also undermines the device reliability. In this work, we have investigated the trapping mechanisms using different advanced measurements techniques (LF S-parameter measurements, I-DLTS, noise current spectral density) to identify the signature of traps.Thanks to SentaurusTCAD simulation, we have identified and understood the physical location of several traps in the device. This contribution would provide an efficient feedback for future technological improvements