The Selection of Azeotropes at Ambient Pressure Drying of Aerogels

The representation of phase states in the multicomponent systems by graphical images is used for estimation of the LV (xL = xV) azeotrope influence on SLV and L = V equilibria. These theoretical investigations occurred from complications arising at an ambient pressure drying (APD) synthesis of transparent and crackfree bulk silica aerogels. During the empiric selection of azeotropic mixtures, the negative azeotropes advantage over positive ones for this goal is determined and substantiated in theory. As shown, the forecast must base not only on the critical points of components (L = V), in which liquid and vapour become indistinguishable, but also on the triple points of components (SLV–crystal—liquid—vapour). Using the P—T—x phase diagrams, the prediction of ways to reach a supercritical region at the ambient pressure is done. A good agreement between the theoretical results and experimental data is revealed.Представлення фазових рівноваг у багатокомпонентних системах методою графічного зображення використовувалося для оцінки впливу азеотропу LV (xL = xV) на рівноваги SLV та L = V. Дані теоретичні дослідження виконувалися через виникнення ускладнень при синтезі прозорих і бездефектних кремнійових аероґелів способом атмосферного сушіння (APD). При емпіричному відборі азеотропних сумішей було визначено і теоретично обґрунтовано перевагу використання неґативних азеотропів над позитивними задля зазначеної мети. Показано, що прогноза має бути основаною не лише на критичних точках компонентів L = V, в яких рідина і пар стають нерозрізненними, але й на потрійних точках компонентів SLV (кристал—рідина—пар). У даній роботі з використанням P—T—x-фазових діяграм показано можливість досягнення надкритичної области за атмосферного тиску. Виявлено хорошу відповідність між теоретичними та експериментальними результатами.Представление фазовых равновесий в многокомпонентных системах методом графического изображения использовано для оценки влияния азеотропа LV (xL = xV) на равновесия SLV и L = V. Данные теоретические исследования выполнялись по причине возникновения сложностей при синтезе прозрачных и бездефектных кремниевых аэрогелей способом атмосферной сушки (APD). При эмпирическом отборе азеотропных смесей определено и теоретически обосновано преимущество использования негативных азеотропов над позитивными для этой цели. Показано, что прогноз должен быть основан не только на критических точках компонентов L = V, в которых жидкость и пар становятся неразличимыми, но и на тройных точках компонентов SLV (кристалл—жидкость—пар). В данной работе с использованием P—T—x-фазовых диаграмм показана возможность достижения сверхкритической области при атмосферном давлении. Обнаружено хорошее соответствие между теоретическими и экспериментальными результатами

Structure and dynamics of the interface between a binary hard-sphere crystal of NaCl type and its coexisting binary fluid

Molecular dynamics simulations are performed to study the [100] and [111] orientations of the crystal-melt interface between an ordered two-component hard sphere with a NaCl structure and its coexisting binary hard-sphere fluid. The diameter ratio of the two types of hard spheres making up the mixture is taken to be 0.414. This work complements our earlier interface simulations [J. Chem. Phys.116, 3410] for the same diameter ratio at lower pressures where the smaller component is immiscible in the solid and the fluid mixture coexists with a pure FCC crystal of large particles. Density profiles and diffusion coefficient profiles are presented for the AB interfacial system. We find that for this system, the transition from crystal-like to fluid-like behavior of both the density and diffusion constant profiles occurs over a narrower region than that seen in our previous studies [J. Chem. Phys. 116, 3410] of the FCC/binary fluid system. But similar to what was found in the FCC/binary fluid interface the transition region for the large particle diffusion constant is shifted about the size of the large particles toward the fluid phase relative to that for the small particles.Comment: 8 page

Control of Rayleigh-Taylor instability by vertical vibration in large aspect ratio containers

We consider a horizontal heavy fluid layer supported by a light, immiscible one in a wide (as compared to depth) container, which is vertically vibrated intending to counterbalance the Rayleigh-Taylor instability of the flat, rigid-body vibrating state. In the simplest case when the density and viscosity of the lighter fluid are small compared to their counterparts in the heavier fluid, we apply a long wave, weakly nonlinear analysis that yields a generalized Cahn-Hilliard equation for the evolution of the fluid interface. This equation shows that the stabilizing effect of vibration is like that of surface tension, and is used to analyze the linear stability of the flat state, the local bifurcation at the instability threshold and some global existence and stability properties concerning the steady states without dry spots. The analysis is extended to two cases of practical interest. Namely, (a) the viscosity of one of the fluids is much smaller than that of the other one, and (b) the densities and viscosities of both fluids are quite close to each other

Measurements of the Q2Q^2-Dependence of the Proton and Neutron Spin Structure Functions g1p and g1n

The structure functions g1p and g1n have been measured over the range 0.014 < x < 0.9 and 1 < Q2 < 40 GeV2 using deep-inelastic scattering of 48 GeV longitudinally polarized electrons from polarized protons and deuterons. We find that the Q2 dependence of g1p (g1n) at fixed x is very similar to that of the spin-averaged structure function F1p (F1n). From a NLO QCD fit to all available data we find $\Gamma_1^p - \Gamma_1^n =0.176 \pm 0.003 \pm 0.007$ at Q2=5 GeV2, in agreement with the Bjorken sum rule prediction of 0.182 \pm 0.005.Comment: 17 pages, 3 figures. Submitted to Physics Letters

Bedmap2: improved ice bed, surface and thickness datasets for Antarctica

We present Bedmap2, a new suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60° S. We derived these products using data from a variety of sources, including many substantial surveys completed since the original Bedmap compilation (Bedmap1) in 2001. In particular, the Bedmap2 ice thickness grid is made from 25 million measurements, over two orders of magnitude more than were used in Bedmap1. In most parts of Antarctica the subglacial landscape is visible in much greater detail than was previously available and the improved data-coverage has in many areas revealed the full scale of mountain ranges, valleys, basins and troughs, only fragments of which were previously indicated in local surveys. The derived statistics for Bedmap2 show that the volume of ice contained in the Antarctic ice sheet (27 million km3) and its potential contribution to sea-level rise (58 m) are similar to those of Bedmap1, but the mean thickness of the ice sheet is 4.6% greater, the mean depth of the bed beneath the grounded ice sheet is 72 m lower and the area of ice sheet grounded on bed below sea level is increased by 10%. The Bedmap2 compilation highlights several areas beneath the ice sheet where the bed elevation is substantially lower than the deepest bed indicated by Bedmap1. These products, along with grids of data coverage and uncertainty, provide new opportunities for detailed modelling of the past and future evolution of the Antarctic ice sheets

Precision measurement of the deuteron spin structure function g1dg^{d}_{1}

We report on a high-statistics measurement of the deuteron spin structure function g[sup d][sub 1] at a beam energy of 29 GeV in the kinematic range 0.029 < x < 0.8 and 1 < Q2 < 10 (GeV/c)2. The integral Gamma [sup d][sub 1] = (integral)[sup 1][sub 0]g[sup d][sub 1]dx evaluated at fixed Q2 = 3 (GeV/c)2 gives 0.042 ± 0.003(stat) ± 0.004(syst). Combining this result with our earlier measurement of g[sup p][sub 1], we find Gamma [sup p][sub 1]- Gamma [sup n][sub 1] = 0.163 ± 0.010(stat) ± 0.016(syst), which agrees with the prediction of the Bjorken sum rule with O( alpha [sup 3][sub s]) corrections, Gamma [sup p][sub 1]- Gamma [sup n][sub 1] = 0.171 ± 0.008. We find the quark contribution to the proton helicity to be Delta q = 0.30 ± 0.06

Epstein-Barr virus: clinical and epidemiological revisits and genetic basis of oncogenesis

Epstein-Barr virus (EBV) is classified as a member in the order herpesvirales, family herpesviridae, subfamily gammaherpesvirinae and the genus lymphocytovirus. The virus is an exclusively human pathogen and thus also termed as human herpesvirus 4 (HHV4). It was the first oncogenic virus recognized and has been incriminated in the causation of tumors of both lymphatic and epithelial nature. It was reported in some previous studies that 95% of the population worldwide are serologically positive to the virus. Clinically, EBV primary infection is almost silent, persisting as a life-long asymptomatic latent infection in B cells although it may be responsible for a transient clinical syndrome called infectious mononucleosis. Following reactivation of the virus from latency due to immunocompromised status, EBV was found to be associated with several tumors. EBV linked to oncogenesis as detected in lymphoid tumors such as Burkitt's lymphoma (BL), Hodgkin's disease (HD), post-transplant lymphoproliferative disorders (PTLD) and T-cell lymphomas (e.g. Peripheral T-cell lymphomas; PTCL and Anaplastic large cell lymphomas; ALCL). It is also linked to epithelial tumors such as nasopharyngeal carcinoma (NPC), gastric carcinomas and oral hairy leukoplakia (OHL). In vitro, EBV many studies have demonstrated its ability to transform B cells into lymphoblastoid cell lines (LCLs). Despite these malignancies showing different clinical and epidemiological patterns when studied, genetic studies have suggested that these EBV- associated transformations were characterized generally by low level of virus gene expression with only the latent virus proteins (LVPs) upregulated in both tumors and LCLs. In this review, we summarize some clinical and epidemiological features of EBV- associated tumors. We also discuss how EBV latent genes may lead to oncogenesis in the different clinical malignancie