DSMC investigation of rarefied gas flow through diverging micro- and nanochannels

Direct simulation Monte Carlo (DSMC) method with simplified Bernoulli-trials (SBT) collision scheme has been used to study the rarefied pressure-driven nitrogen flow through diverging microchannels. The fluid behaviours flowing between two plates with different divergence angles ranging between 0$^{\circ}$ to 17$^{\circ}$ are described at different pressure ratios (1.5${\le}{\prod}{\le}$2.5) and Knudsen numbers (0.03${\le}$Kn${\le}$12.7). The primary flow field properties, including pressure, velocity, and temperature, are presented for divergent microchannels and are compared with those of a microchannel with a uniform cross-section. The variations of the flow field properties in divergent microchannels, which are influenced by the area change, the channel pressure ratio and the rarefication are discussed. The results show no flow separation in divergent microchannels for all the range of simulation parameters studied in the present work. It has been found that a divergent channel can carry higher amounts of mass in comparison with an equivalent straight channel geometry. A correlation between the mass flow rate through microchannels, the divergence angle, the pressure ratio, and the Knudsen number has been suggested. The present numerical findings prove the occurrence of Knudsen minimum phenomenon in micro- and Nano- channels with non-uniform cross-sections.Comment: Accepted manuscript; 25 Pages and 11 Figures; "Microfluidics and Nanofluidics

Knudsen pump inspired by Crookes radiometer with a specular wall

A rarefied gas is considered in a channel consisting of two infinite parallel plates between which an evenly spaced array of smaller plates is arranged normal to the channel direction. Each of these smaller plates is assumed to possess one ideally specularly reflective and one ideally diffusively reflective side. When the temperature of the small plates differs from the temperature of the sidewalls of the channel, these boundary conditions result in a temperature profile around the edges of each small plate which breaks the reflection symmetry along the channel direction. This in turn results in a force on each plate and a net gas flow along the channel. The situation is analysed numerically using the direct simulation Monte Carlo (DSMC) method and compared with analytical results where available. The influence of the ideally specularly reflective wall is assessed by comparing with simulations using a finite accommodation coefficient at the corresponding wall. The configuration bears some similarity with a Crookes radiometer, where a non-symmetric temperature profile at the radiometer vanes is generated by different temperatures on each side of the vane, resulting in a motion of the rotor. The described principle may find applications in pumping gas on small scales driven by temperature gradients

A Form-Critical Analysis of the al-Rajīʿ and Biʾr Maʿūna Stories

Due to their heavy reliance on late, contradictory, and tendentious literary sources, scholars of formative Islam have always been in danger of taking as authentic evidence what is mere literary topos. Adopting a form-critical methodology that includes both classic and “new” approaches to the accounts of the al-Rajīʿ and Biʾr Maʿūna expeditions, this article strives to reveal the literary devices deployed in the sources and to demonstrate the motivations behind their utilization. It will argue, using the classic form-critical method, that reports about the al-Rajīʿ and Biʾr Maʿūna raids reflect far more about the circumstances of their composition and redaction than about first/seventh-century Arabia. Motivated by second/eighth-century tribal feuds, many components of these narratives owe their existence to later modifications and adornments that were retrojected to the time of the Prophet Muḥammad. We shall, furthermore, see that by the third/ninth century, when tribal motivations ceased to be amongst the prime socio-political exigencies of the time, new incentives emerged for the transmission of these narratives, which can be uncovered through implementation of “new” form criticism

Częstość występowania incydentaloma tarczycy w Isfahanie, Iran - badanie populacyjne

Introduction: Thyroid nodules not detected in palpation but diagnosed following a radiological procedure or during surgery are called thyroid incidentalomas. We designed this study to investigate the prevalence of sonographic thyroid incidentaloma in Isfahan, Iran, for the first time. Material and methods: By a multistage cluster sampling method, 2523 adults were selected randomly. From this group, 2045 had normal thyroid examination. 234 out of the 2045 were selected randomly for thyroid sonography. Thyroid stimulating hormone (TSH), urinary iodine concentrations (UIC) and antithyroid antibodies were measured. Results: The prevalence of thyroid incidentaloma was 13.2% [Confidence interval (CI) 95% = 8–18]. The average age of subjects with and without incidentaloma was 46.1 (12.4) and 38.4 (12.1), respectively (P = 0.002). It was more prevalent in females than in males (19% vs. 10%) [Odds ratio (OR) = 2.59, CI 95% = 1.17–5.76, P value (P) = 0.01]. Median UIC in the incidentaloma group (14 μg/dl) was significantly lower than in the group of subjects without nodules (20 μg/dl) (OR = 0.9, CI 95% = 0.91–0.99, P = 0.02). There was no difference in the levels of TSH and antithyroid antibodies between the two groups (P > 0.05). Mean diameter of nodules was 8.14 (3.43) mm. Conclusions: The prevalence of thyroid incidentaloma was 13.2% in Isfahan. It was higher in females than males and increased with age.Wstęp: Incidentalona to guzki tarczycy niewykrywalne palpacyjnie, lecz zdiagnozowane przypadkowo podczas badania obrazowego lub zabiegu chirurgicznego. Celem badania było określenie po raz pierwszy częstości incidentaloma wykrywanych w badaniu sonograficznym w populacji irackiego miasta Isfahan. Materiał i metody: Metodą wielostopniowego losowania zespołowego wybrano grupę 2523 dorosłych osób. Spośród 2045 osób, u których nie stwierdzono zmian w badaniu palpacyjnym, wytypowano losowo 234 osoby do badania sonograficznego tarczycy. Oznaczono u nich również stężenie hormonu tyreotropowego (TSH, thyroid stimulating hormone), stężenie jodu w moczu (UIC, urinary iodine concentration) oraz przeciwciała przeciwtarczycowe. Wyniki: Incidentaloma tarczycy wykryto u 13,2% badanych (95% przedział ufności [CI] = 8–11). Średni wiek osób, u których wykazano obecność guzków wynosił 46,1 (± 12,4) lat, natomiast osób bez guzków - 38,4 (± 12,1) lat (p = 0,002). Incidentaloma występowały częściej u kobiet niż u mężczyzn (19 vs. 10%; iloraz szans [OR] = 2,59; 95% CI = 1,17–5,76; p = 0,01). Obie grupy nie różniły się pod względem stężeń TSH i przeciwciał przeciwtarczycowych (p > 0,05). Średnica guzków wynosiła średnio 8,14 (± 3,43) mm. Wnioski: Częstość incidentaloma tarczycy w populacji Isfahanu wynosiła 13,2%; była większa u kobiet niż u mężczyzn i wzrastała z wiekiem

Sonographic and functional characteristics of thyroid nodules in a population of adult people in Isfahan

Wstęp: Celem badania była ocena cech sonograficznych zmian ogniskowych tarczycy u mieszkańców Isfahanu, obszaru w cenralnym Iranie, który wcześniej charakteryzował się niedoborem jodu. Materiał i metody: W przekrojowym badaniu przeprowadzonym w 2006 roku wybrano próbę liczącą 2523 dorosłych osób (wiek > 20 lat) metodą wielostopniowego losowania grupowego. Spośród tej grupy, 263 ochotników poddano badaniom sonograficznym. Badanie tarczycy przeprowadzili doświadczeni specjaliści w zakresie ultrasonografii. Ponadto oznaczono stężenia T3, T4, T3RU, TSH, TPO Ab i Tg Ab w surowicy oraz wydalanie jodu z moczem. Wyniki: Kobiety stanowiły 46% grupy poddanej badaniom sonograficznym (n = 263). Średnia wieku wynosiła 35,5 lat (zakres 20-64 lat). Mediana stężenia jodu w moczu wynosiła 19.4 μg/dl. Obecność zmian ogniskowych tarczycy wykazano w badaniu sonograficznym u 22,4% osób z badanej grupy; u 30% kobiet i 16,3% mężczyzn (OR = 2,2; p = 0,01). Częstość występowania zmian ogniskowych tarczycy zwiększała się z wiekiem (p = 0,006). Zmiany ogniskowe tarczycy występowały częściej u osób z niedoczynnością tarczycy niż w grupie z eutyreozą (35,1% v. 20,5%, OR = 2,1; p = 0,04). Nie stwierdzono korelacji między stężeniem jodu w moczu ani stężeniem autoprzeciwciał a występowaniem zmian ogniskowych tarczycy w badaniu sonograficznym. Wnioski: Częstość występowania zmian ogniskowych tarczycy oceniana na podstawie wyników badania sonograficznego jest nadal duża w badanej populacji, mimo prawidłowego stężenia jodu w moczu. (Endokrynol Pol 2010; 61 (2): 188-191)Introduction: The aim of this study was to investigate the current status of sonographic characteristics of thyroid nodules in Isfahan, a previously iodine deficient area in central Iran. Material and methods: In a cross-sectional study conducted in 2006, 2523 adult people (age > 20 years) were selected by a multistage clustering sampling method. Of these people, 263 volunteered persons were underwent sonographic evaluation. Thyroid examination was done by two expert sonographers. Serum T3, T3, T3RU, TSH, TPO Ab and Tg Ab, and urinary iodine were measured. Results: Forty-six per cent of the 263 people were women. Their mean age was 35.5 years with a range of 20-64 years. Median urinary iodine was 19.4 μg/dL. The prevalence of thyroid nodules on sonography was 22.4% in the whole group; 30% in women and 16.3% in men (OR = 2.2, P = 0.01). The prevalence of thyroid nodules increased with age (P = 0.006). The prevalence of thyroid nodules was higher in hypothyroid people than in euthyroid people (35.1% v. 20.5%, OR = 2.1, P = 0.04). Neither urinary iodine nor autoantibody concentrations correlated with the prevalence of thyroid nodules in sonography. Conclusions: The prevalence of thyroid nodule by sonography is still high despite relatively normal urinary iodine in this population. (Pol J Endocrinol 2010; 61 (2): 188-191

On the Rarefied Thermally-Driven Flows in Cavities and Bends

This study examined rarefied thermally-driven flow in a square cavity (Case 1) and rectangular bend (Case 2), with various uniform wall temperatures in two dimensions. We employed the direct simulation Monte Carlo (DSMC) to solve problems with a wide range of Knudsen numbers Kn = 0.01 to 10, and the discrete unified gas kinetic scheme (DUGKS) solver was used at Kn = 0.01. The scenario was that, in case 1, the bottom side and its opposite were set hot, and the other sides were set cold. Diffuse reflector boundary conditions were set for all walls. The imposed temperature differences created four primary vortices. The results of the continuum set of equations of the slow non-isothermal flow (SNIT) solver proved that the primary vortices in the square cavity were caused by nonlinear thermal stress effects, and other smaller vortices appearing at Kn = 0.01, 0.1 were brought about by thermal creep processes. As the Kn increased, vortices generated by thermal creep disappeared, and eddies created by nonlinear thermal stress occupied the cavity. In case 2, i.e., a rectangular bend, two sides were set cold, and the others were hot. Two primary vortices were formed, which were caused by nonlinear thermal stress effects. The direction of streamlines in the two main vortices was opposite, from the warm to the cold zone, as some eddies on the left were counterclockwise, and others were clockwise