Molecular Dynamics Studies on Nanoscale Gas Transport

Three-dimensional molecular dynamics (MD) simulations of nanoscale gas flows are studied to reveal surface effects. A smart wall model that drastically reduces the memory requirements of MD simulations for gas flows is introduced. The smart wall molecular dynamics (SWMD) represents three-dimensional FCC walls using only 74 wall Molecules. This structure is kept in the memory and utilized for each gas molecule surface collision. Using SWMD, fluid behavior within nano-scale confinements is studied for argon in dilute gas, dense gas, and liquid states. Equilibrium MD method is employed to resolve the density and stress variations within the static fluid. Normal stress calculations are based on the Irving-Kirkwood method, which divides the stress tensor into its kinetic and virial parts. The kinetic component recovers pressure based on the ideal gas law. The particle-particle virial increases with increased density, while the surface-particle virial develops due to the surface force field effects. Normal stresses within nano-scale confinements show anisotropy induced primarily by the surface force-field and local variations in the fluid density near the surfaces. For dilute and dense gas cases, surface-force field that extends typically 1nm from each wall induces anisotropic normal stress. For liquid case, this effect is further amplified by the density fluctuations that extend beyond the three field penetration region. Outside the wall force-field penetration and density fluctuation regions the normal stress becomes isotropic and recovers the thermodynamic pressure, provided that sufficiently large force cut-off distances are utilized in the computations. Next, non-equilibrium SWMD is utilized to investigate the surface-gas interaction effects on nanoscale shear-driven gas flows in the transition and free molecular flow regimes. For the specified surface properties and gas-surface pair interactions, density and stress profiles exhibit a universal behavior inside the wall force penetration region at different flow conditions. Shear stress results are utilized to calculate the tangential momentum accommodation coefficient (TMAC) between argon gas and FCC walls. The TMAC value is shown to he independent of the now properties and Knudsen number in all simulations. Velocity profiles show distinct deviations from the kinetic theory based solutions inside the wall force penetration depth, while they match the linearized Boltzmann equation solution outside these zones. Afterwards, surface effects are studied as a function of the surface-gas potential strength ratio (ϵ wf/ϵff) for the shear driven argon gas flows in the early transition and tree molecular flow regimes. Results show that increased ϵwf/ϵ ff results in increased gas density, leading towards monolayer adsorption on surfaces. The near wall velocity profile shows reduced gas slip, and eventually velocity stick with increased ϵwf/ϵ ff. Similarly, using MD predicted shear stress values and kinetic theory, TMAC are calculated as a function of ϵwf/ϵ ff and TMAC values are shown to be independent of the Knudsen number. Results indicate emergence of the wall force field penetration depth as an additional length scale for gas flows in nano-channels, breaking the dynamic similarity between rarefied and nano-scale gas flows solely based on the Knudsen and Mach numbers

Expression of antimicrobial peptides in recurrent adenotonsillitis

Kilic, Murat/0000-0002-1377-2021; aydin, sedat/0000-0003-4939-5026; demir, mehmet/0000-0002-0609-6782WOS: 000393197500008Background: Recurrent acute tonsillitis is one of the most frequent otorhinolaryngology clinic referrals, yet its pathogenesis remains poorly understood. Antimicrobial cationic peptides are components of the innate system. They are generally small, highly positively charged peptides with broad spectrum antimicrobial activity which function as the body's "natural antibiotics". Our aim is to investigate the role of antimicrobial cationic peptides in the susceptibility of patients to recurrent acute tonsillitis. Materials and methods: The study is done with 100 children who had a history of recurrent adenotonsillitis as subject group and 100 children with adenotonsillar hypertrophy as control group. Tonsillar and adenoid tissues are dissected into parts as deep and surface epithelium and investigated semiquantitatively with immunohistochemistry. Human beta defensin (hBD) 1-3 and cathelecidin (LL-37) levels are compared with microscopically. Results: Immunohistochemistry revealed a strong expression of hBD-1, hBD-2 and hBD-3 in tonsillar tissue. Quantification of hBD-1, hBD-2 and hBD-3 expressions are shown more in tonsillar tissue than in adenoids. LL-37 is one of the antimicrobial peptides found in human tonsillar tissue and adenoids, that participates in the innate immune system of these tissues. Statistically, hBD-1, hBD-3 and LL-37 expressions were different in recurrent tonsillitis tissue than control (p < 0.05). Moreover hBD-2 expression was different in adenoid tissue than control (p < 0.05). Conclusion: Antimicrobial peptides have key role in adenotonsillar infections and this defense mechanism increases susceptibility to recurrent infections in upper respiratory tract

Impacts of COVID-19 and lockdown on mental health: depression, anxiety, stress and fear among adult population in Turkey

Background: Most of the documented literature to date has reported that the COVID-19 pandemic is associated with greater distress, anxiety, anger, stress, and agitation among the general public compared to before the onset of the pandemic. Method and study design: A review was done to now the evidence for the antiviral and immune-modulatory properties of micronutrients. A search was done in PubMed, Scopus, and Google Scholar for the nutrients with proven effect against viral infection. Experimental studies, clinical studies, reviews, and meta-analyses were studied descriptively. Aim: The aim of study was to examine the impact of COVID-19 and the national lockdown on mental health perception of depression, anxiety, stress and fear among the general population in Turkey. Subjects and methods: The present study comprised a cross-sectional survey of 1,792 male and female participants aged 20-65 years in Turkey (June to October 2020) who completed the 21-item Depression, Anxiety, Stress Scale (DASS-21) and Fear of COVID-19 Scale (FCV-19S). Bivariate and multivariate stepwise regression analyses were used for the demographic and mental health-related variables. Results: The majority of the respondents recognized the main COVID-19 symptoms (82.9%), knew that there is no drug and vaccine (85.4%), were afraid to travel and visit a shopping mall (86.9%), believed wearing medical masks helped prevent against COVID-19 (81.1%), and considered lockdown isolation reduced the risk of COVID-19 (86.5%). The mean score (and standard deviation) for depression was 13.57 (SD±8.48); for anxiety was 9.32 (SD±7.62); for stress was 16.45 (SD±6.89); and for fear of COVID-19 was 23.47 (SD±4.24). The study showed that there was a significant relationship between fear of COVID-19 and higher levels of depression (r=0.345), anxiety (r=0.253), and stress (r=0.369), (all p-values <0.001). The results of multivariate regression analysis showed that the age (p<0.001), depression (p<0.001), anxiety (p<0.001), sleeping problems due to worrying about being infected with COVID-19 (p<0.001), stress (p<0.001), and being afraid to travel because of COVID-19 (p=0.041) were all significantly associated with greater fear of COVID-19. Conclusions: The findings of this study confirmed that fear of COVID-19 was significantly associated with depression, anxiety, and stress

Expression and prognostic significance of cox-2 and p-53 in hodgkin lymphomas: a retrospective study

<p>Abstract</p> <p>Background</p> <p>Cyclooxygenase (cox) is the rate-limiting enzyme, which catalyzes the conversion of arachidonic acid into prostaglandins and contributes to the inflammatory process. Cyclooxygenase-2 (cox-2), which is one of the two isoforms, plays a role in tumor progression and carcinogenesis. p53 contributes to apoptosis, DNA renewal and cell cycle. Studies concerning the relationship of cox-2 and p53 expressions and carcinogenesis are available, but the association between cox-2 and p53 in Hodgkin lymphoma (HL) is not exactly known.</p> <p>In our study, we examined the association of cox-2 and p53 expression, with age, stage, histopathological subtype, and survival in HL. We also examined correlation between cox-2 and p53 expression.</p> <p>Methods</p> <p>Cox-2 and p53 expressions in Hodgkin-Reed Sternberg cells (HRS) were examined in 54 patients with HL depending on cox-2 expression, stained cases were classified as positive, and unstained cases as negative. Nuclear staining of HRS cells with p53 was evaluated as positive. The classifications of positivity were as follows: negative if<10%; (1+) if 10-25%; (2+) if 25-50%; (3+) if 50-75%, (4+) if >75%.</p> <p>Results</p> <p>Cox-2 and p53 expressions were found in 49 (80%) and 29 (46%) patients, respectively. There were differences between histological subtypes according to cox-2 expression (p = 0.012). Mixed cellular (MC) and nodular sclerosing (NS) subtypes were seen most of the patients and cox-2 expression was evaluated mostly in the mixed cellular subtype.</p> <p>There were no statistically significant relationships between p53 and the histopathological subtypes; or between p53, cox-2 and the factors including stage, age and survival; or between p53 and cox-2 expression (p > 0.05).</p> <p>Conclusion</p> <p>Considering the significant relationship between the cox-2 expression and the subtypes of HL, cox-2 expression is higher in MC and NS subtypes. However the difference between these two subtypes was not significant. This submission must be advocated by studies with large series</p

The calculation of drag on nano-cylinders

A novel formulation, based on the molecular dynamics approach, has been proposed to calculate localised drag forces over nano-cylinders. The computational evidence suggests that the existing methods underestimate drag coefficients at nano-scales at least by 20-40%. These coefficients are also up to seven times higher than the ones calculated by continuum based analytical solutions. The deviation increases at Reynolds number values less than one. The proposed formulation describes a new method for calculating localised values for both the kinetic and configurational parts of the Irwin-Kirkwood stress tensor at given fixed positions within the computational domain

MD Simulations of Nano-Scale Gas Flows: A Case Study of Couette Flow at Kn=10

Abstract. Utilizing a recently developed 3D smart wall molecular dynamics algorithm, we investigate argon flow in a 5.4 nm channel, which corresponds to the free molecular flow regime. Simulation results are compared with the linearized Boltzmann equation solutions. Significant deviations from the kinetic theory predictions are observed for the velocity, density and average normal stress profiles in the near wall region, where the wall force field effects are dominant. The results clearly show incomplete similitude between the rarefied and nano-scale gas flows, if solely based on the Knudsen number

The relationship of budget & current deficit as a macroeconomic variable: The case of emerging markets

WOS: 000281883100004The relationship of budget & current deficit as a macroeconomic variable: The case of emerging markets The simultaneous deficit of budget and current account is called "twin deficit". In economic literature there are two basic economic views that try to explain the evolution of twin deficit: Traditional Keynesian Hypothesis and Ricardian Equivalence Hypothesis. The traditional Keynesian Hypothesis suggests a positive relationship between these two deficits but the Ricardian Equivalance Hypothesis suggests no relation. In this study, the theoretical relation between budget and current deficits is tested by using the Holtz-Eakin, Newey and Rosen 's panel casuality test with the annual data of 12 emerging markets countries for 1991-2007 period. The findings support the Traditional Keynesian Hypothesis. According to the results of the panel casuality test, there is a two- way casuality relation between budget and current deficit in 12 emerging markets countries for 1991-2007 period