Numerical simulation of electrophoresis separation processes

A new Petrov-Galerkin finite element formulation has been proposed for transient convection-diffusion problems. Most Petrov-Galerkin formulations take into account the spatial discretization, and the weighting functions so developed give satisfactory solutions for steady state problems. Though these schemes can be used for transient problems, there is scope for improvement. The schemes proposed here, which consider temporal as well as spatial discretization, provide improved solutions. Electrophoresis, which involves the motion of charged entities under the influence of an applied electric field, is governed by equations similiar to those encountered in fluid flow problems, i.e., transient convection-diffusion equations. Test problems are solved in electrophoresis and fluid flow. The results obtained are satisfactory. It is also expected that these schemes, suitably adapted, will improve the numerical solutions of the compressible Euler and the Navier-Stokes equations

Photo-induced volume changes in selenium. Tight-binding molecular dynamics study

Tight-binding molecular dynamics simulations of photo-excitations in small Se clusters (isolated Se$_8$ ring and helical Se chain) and glassy Se networks (containing 162 atoms) were carried out in order to analyse the photo induced instability inside the amorphous selenium. In the cluster systems after taking an electron from the highest occupied molecular orbital to the lowest unoccupied molecular orbital a bond breaking occurs. In the glassy networks photoinduced volume expansion was observed and at the same time the number of coordination defects changed significantly due to illumination

Intermediate Phases, structural variance and network demixing in chalcogenides: the unusual case of group V sulfides

We review Intermediate Phases (IPs) in chalcogenide glasses and provide a structural interpretation of these phases. In binary group IV selenides, IPs reside in the 2.40 < r < 2.54 range, and in binary group V selenides they shift to a lower r, in the 2.29< r < 2.40 range. Here r represents the mean coordination number of glasses. In ternary alloys containing equal proportions of group IV and V selenides, IPs are wider and encompass ranges of respective binary glasses. These data suggest that the local structural variance contributing to IP widths largely derives from four isostatic local structures of varying connectivity r; two include group V based quasi-tetrahedral (r = 2.29) and pyramidal (r = 2.40) units, and the other two are group IV based corner-sharing (r = 2.40) and edge-sharing (r = 2.67) tetrahedral units. Remarkably, binary group V (P, As) sulfides exhibit IPs that are shifted to even a lower r than their selenide counterparts; a result that we trace to excess Sn chains either partially (As-S) or completely (P-S) demixing from network backbone, in contrast to excess Sen chains forming part of the backbone in corresponding selenide glasses. In ternary chalcogenides of Ge with the group V elements (As, P), IPs of the sulfides are similar to their selenide counterparts, suggesting that presence of Ge serves to reign in the excess Sn chain fragments back in the backbone as in their selenide counterparts

Effect of Replacement of As by Ge and Sb on the Photo-Response under Near Infrared Femtosecond Laser Irradiation in As-based Sulfide Glasses

Bulk glasses having the compositions As42S58, As36Sb6S58, and As36Ge6S58 have been irradiated at 800 nm using a femtosecond-pulsed laser to determine the relationship between composition and photo-response. Localized variation in the glass volume (photo-expansion) has been determined through interferometric measurements of surface exposures, whereas induced refractive index change (photo-darkening) was determined from the diffraction efficiency of subsurface direct-written phase gratings. To understand the compositional dependence of the photo-response, the linear and nonlinear optical properties and structure of the unexposed glasses have been compared. The ablation threshold is shown to be controlled by variation of the nonlinear absorption, related to shifts of the absorption band gap with exchange of As by Ge or Sb. Changes in the unexposed network structure show that partial replacement of As by Ge or Sb induces an increased number of As–As bonding defects in the glass, particularly in the form of As4S4 molecular units which become polymerized into the network, impacting the photo-modification process. The Ge was found to induce an increase in the ablation threshold, and enhance both photo-darkening and photo-expansion effects, whereas Sb was shown to decrease ablation threshold and inhibit photo-darkening while enhancing photo-expansion

Nuclear medicine procedures and the evaluation of male sexual organs: a short review

Sexuality consists of three aspects that are interrelated and inseparable, biological, physiological and social. The biological aspect considers the individual's capability to give and to receive pleasure. In consequence, it covers the functionality of the sexual organs and the physiology of human sexual response cycle. Diagnostic imaging modalities, such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) have been used to evaluate clinical disorders of the male reproductive system. PET and SPECT procedures basically involve the administration of a radiopharmaceutical that has a higher uptake in a specific tumor or tissue. The aim of this brief review is to present some radiopharmaceuticals that have been used in the clinical evaluation of the male sexual organs (testes, prostate, seminal vesicles, penis) related with male sexuality. This information could be useful in better understanding the male sexual response cycle, as well as the sexual disorders, when considering the male sexual organs and the pelvic floor. Moreover, the findings obtained with PET and SPECT imaging could help to evaluate the efficacy of clinical results of therapeutic procedures. In conclusion, the knowledge from these images could aid in better understanding the physiology of the different organs related with sexuality. Furthermore, they could be important tools to evaluate the physiological integrity of the involved organs, to improve clinical strategies and to accompany the patients under treatment

Simulations of Gravitational Heating Due to Early Matter Domination

In cosmologies with an early matter-dominated era (EMDE) prior to Big Bang nucleosynthesis, the boosted growth of small-scale matter perturbations during the EMDE leads to microhalo formation long before halos would otherwise begin to form. For a range of models, halos can even form during the EMDE itself. These halos would dissipate at the end of the EMDE, releasing their gravitationally heated dark matter and thereby imprinting a free-streaming cut-off on the matter power spectrum. We conduct the first cosmological $N$-body simulations of the formation and evaporation of halos during and after an EMDE. We show that in these scenarios, the free-streaming cut-off after the EMDE can be predicted accurately from the linear matter power spectrum. Although the free streaming can erase much of the EMDE-driven boost to density perturbations, we use our findings to show that the (re-)formation of halos after the EMDE nevertheless proceeds before redshift $\sim 1000$. Early-forming microhalos are a key observational signature of an EMDE, and our prescription for the impact of gravitational heating will allow studies of the observational status and prospects of EMDE scenarios to cover a much wider range of parameters.Comment: 33 pages, 16 figures. Comments welcom

Limits on Early Matter Domination from the Isotropic Gamma-Ray Background

In cosmologies with hidden sector dark matter, the lightest hidden sector species can come to dominate the energy budget of the universe and cause an early matter-dominated era (EMDE). EMDEs amplify the matter power spectrum on small scales, leading to dense, early-forming microhalos which massively boost the dark matter annihilation signal. We use the Fermi-LAT measurement of the isotropic gamma-ray background to place limits on the parameter space of hidden sector models with EMDEs. We calculate the amplified annihilation signal by sampling the properties of prompt cusps, which reside at the centers of these microhalos and dominate the signal on account of their steep $\rho\propto r^{-3/2}$ density profiles. We also include the portions of the parameter space affected by the gravitational heating that arises from the formation and subsequent destruction of nonlinear structure during the EMDE. We are able to rule out significant portions of the parameter space, particularly at high reheat temperatures. Long EMDEs remain poorly constrained despite large structure-induced boosts to the annihilation signal.Comment: 32 pages, 17 figures. Comments welcom

Second trimester placental thickness: its’ correlation with gestational age, femur length and biparietal diameter

Background: Placental thickness (PT) is the easiest placental dimension to measure, yet little is known about the normal PT. The aim of this study was to determine the normal, sonographically measured PT in millimetre (mm) in the second trimester and to determine if this measurement can be adjusted for gestational age for that time and evaluate its relationship with femur length and biparietal diameter of the fetus.Methods: The study was a cross sectional observational study, recruiting 100 consecutive, singleton pregnancies, reporting for ultrasonography (USG) between 14 weeks and 24 weeks of gestation, having undergone at least one ultrasonogram in the first trimester, with known last menstrual period (LMP). The placental thickness was measured perpendicular to the uterine wall, through the placenta at the site of cord insertion.Results: The average age of study population was 24.96 with a standard deviation (SD) of 2.70 years with the minimum age being 18 years and maximum age being 32 years. Regression analysis yielded the following mathematical relationships between PT, Gestational age (GA), Biparietal diameter (BPD) and Femur length (FL) in the second trimester. Y(PT)= 0.9366x (Gestation age)+1.655, R2 = 0.7332; Y(PT)= 0.2872x(BPD)+6.9578, R2= 0.7314; Y(PT)=0.2995x(FL)+ 10.03, R2 = 0.6186Conclusions: PT in present study showed a positive linear correlation with gestational age, FL and BPD in second trimester. Also, it can be concluded that PT may be used as a predictor of GA in women with unknown LMP

An Examination of the Flipped Classroom\u27s Efficacy on Post-Baccalaureate Pre-Medical Students

Existing flipped classroom (FC) research focuses on a typical, homogenous student population in terms of age. Research focuses on student satisfaction and perception of the FC to assess if student performance translates to actual perceived learning. Further, a growing number of studies show that outcomes of FC depend on student motivation. This study examines student performance, perception, and satisfaction in the FC in a novel demographic: Post-Baccalaureate Pre-Medical students. These students, who vary widely in age, experience, and prior knowledge of subject matter, are career changers who become full-time students to complete prerequisite coursework for medical school. Students enrolled in the undergraduate Biology course in GWU\u27s Post-Baccalaureate Pre-Medicine program were taught by the same instructor for this study. 17 students (Cohort 1), enrolled in 2017-2018, had a traditional classroom with a three hour didactic lecture. 30 students (Cohort 2), enrolled in 2018-2019, had the flipped classroom with 50% less didactic lecture time and more active and independent learning. End-of-course evaluations, pre and post quizzes, exam performance, and overall course grades were compared between cohorts. Course perceptions from evaluations were also compared, and Cohort 2 completed an additional survey on their perceptions of the FC. Results show that students were between ages 20 and 40 years of age for both cohorts. Student performance on exams and overall course grades did not vary significantly between the cohorts. FC components such as pre- and post- quizzes were perceived as significantly useful (p\u3c.01) and were often found to be engaging and most beneficial in promoting understanding. FC components viewed by students as really useful for exam preparation included pre-quizzes (68.96%), post-quizzes (82.75%), and jeopardy (51.72%). Components viewed by students as really useful for concept comprehension included pre-quizzes (42.85%), post-quizzes (57.14%), and questionnaire worksheets (58.62%). Group work was also viewed by 51.72% students as useful for concept comprehension. Student comments between cohorts indicated that students almost universally desired to maintain a lecture component to their learning. Surprisingly, course evaluation data further showed most students in both cohorts viewing lectures as contributing most to their learning over other class activities. This seems contrary to the majority of the current literature on student learning. These results suggest that student motivation and engagement are important factors in assessing student comprehension, and understanding the influence of these factors in learning methods could alter how instructors approach and effectively structure courses to increase student satisfaction

Carpal tunnel syndrome in females: pregnancy and lactation the major risk factors

Background: Carpal Tunnel Syndrome (CTS) is the most common entrapment neuropathy. CTS is more common in the age group of 45-65 years and more common in women than men.  Several factors cause CTS, including pregnancy and lactation.Methods: The study was conducted on 60 females with carpal tunnel syndrome. Each patient was subjected to detailed history and relevant clinical examination with emphasis on elaborate neurological examination. Informed consent regarding participation into the study was taken from the patients. Patients suspected of suffering from carpal tunnel syndrome were subjected to nerve conduction study. Patients were classified into mild- moderate and severe carpal tunnel syndrome according to clinical and nerve conduction grading.Results: Out of 60 females, 21 were pregnant (35%) and 19 were lactating (31.7%).  The mean age of presentation was 44.6±14.14 years with range from 22 to 63 years. Causes were attributed to Pregnancy (35%) lactation (31.7%), hypothyroidism (18.3%), occupational risk factors (15.85%) and gout (2.4%).Conclusions: Carpal tunnel syndrome has a high incidence in females. Sensory symptoms (paresthesia, numbness and nocturnal pain) were more common than symptoms of motor weakness. Dominant hand involvement was more common