Influence of polydispersity on micromechanics of granular materials

We study the effect of polydispersity on the macroscopic physical properties of granular packings in two and three dimensions. A mean-field approach is developed to approximate the macroscale quantities as functions of the microscopic ones. We show that the trace of the fabric and stress tensors are proportional to the mean packing properties (e.g. packing fraction, average coordination number, and average normal force) and dimensionless correction factors, which depend only on the moments of the particle-size distribution. Similar results are obtained for the elements of the stiffness tensor of isotropic packings in the linear affine response regime. Our theoretical predictions are in good agreement with the simulation results.Comment: 13 pages, 13 figures, 2 table

Application of the Fokker-Planck molecular mixing model to turbulent scalar mixing using moment methods

An extended quadrature method of moments using the beta kernel density function (beta-EQMOM) is used to approximate solutions to the evolution equation for univariate and bivariate composition probability distribution functions (PDFs) of a passive scalar for binary and ternary mixing. The key element of interest is the molecular mixing term, which is described using the Fokker-Planck (FP) molecular mixing model. The direct numerical simulations (DNSs) of Eswaran and Pope [ Direct numerical simulations of the turbulent mixing of a passive scalar, Phys. Fluids 31, 506 (1988)] and the amplitude mapping closure (AMC) of Pope [ Mapping closures for turbulent mixing and reaction, Theor. Comput. Fluid Dyn. 2, 255 (1991)] are taken as reference solutions to establish the accuracy of the FP model in the case of binary mixing. The DNSs of Juneja and Pope [ A DNS study of turbulent mixing of two passive scalars, Phys. Fluids 8, 2161 (1996)] are used to validate the results obtained for ternary mixing. Simulations are performed with both the conditional scalar dissipation rate (CSDR) proposed by Fox [Computational Methods for Turbulent Reacting Flows (Cambridge University Press, 2003)] and the CSDR from AMC, with the scalar dissipation rate provided as input and obtained from the DNS. Using scalar moments up to fourth order, the ability of the FP model to capture the evolution of the shape of the PDF, important in turbulent mixing problems, is demonstrated. Compared to the widely used assumed beta-PDF model [S. S. Girimaji, Assumed beta-pdf model for turbulent mixing: Validation and extension to multiple scalar mixing, Combust. Sci. Technol. 78, 177 (1991)], the beta-EQMOM solution to the FP model more accurately describes the initial mixing process with a relatively small increase in computational cost

The Influence of the Degree of Heterogeneity on the Elastic Properties of Random Sphere Packings

The macroscopic mechanical properties of colloidal particle gels strongly depend on the local arrangement of the powder particles. Experiments have shown that more heterogeneous microstructures exhibit up to one order of magnitude higher elastic properties than their more homogeneous counterparts at equal volume fraction. In this paper, packings of spherical particles are used as model structures to computationally investigate the elastic properties of coagulated particle gels as a function of their degree of heterogeneity. The discrete element model comprises a linear elastic contact law, particle bonding and damping. The simulation parameters were calibrated using a homogeneous and a heterogeneous microstructure originating from earlier Brownian dynamics simulations. A systematic study of the elastic properties as a function of the degree of heterogeneity was performed using two sets of microstructures obtained from Brownian dynamics simulation and from the void expansion method. Both sets cover a broad and to a large extent overlapping range of degrees of heterogeneity. The simulations have shown that the elastic properties as a function of the degree of heterogeneity are independent of the structure generation algorithm and that the relation between the shear modulus and the degree of heterogeneity can be well described by a power law. This suggests the presence of a critical degree of heterogeneity and, therefore, a phase transition between a phase with finite and one with zero elastic properties.Comment: 8 pages, 6 figures; Granular Matter (published online: 11. February 2012

Studies on Dibenzylamines as Inhibitors of Venezuelan Equine Encephalitis Virus

Alphaviruses are arthropod-transmitted members of the Togaviridae family that can cause severe disease in humans, including debilitating arthralgia and severe neurological complications. Currently, there are no approved vaccines or antiviral therapies directed against the alphaviruses, and care is limited to treating disease symptoms. A phenotypic cell-based high-throughput screen was performed to identify small molecules that inhibit the replication of Venezuelan Equine Encephalitis Virus (VEEV). The compound, 1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-N-(3-fluoro-4-methoxybenzyl)ethan-1-amine (1), was identified as a highly active, potent inhibitor of VEEV with an effective concentration for 90% inhibition of virus (EC90) of 0.89 μM and 7.49 log reduction in virus titers at 10 μM concentration. These data suggest that further investigation of compound 1 as an antiviral therapeutic against VEEV, and perhaps other alphaviruses, is warranted. Experiments suggested that the antiviral activity of compound 1 is directed at an early step in the VEEV replication cycle by blocking viral RNA and protein synthesis

Staged cardiovascular magnetic resonance for differential diagnosis of Troponin T positive patients with low likelihood for acute coronary syndrome

<p>Abstract</p> <p>Background</p> <p>Cardiac Troponin-T (cTnT) is a cardio-specific indicator of myocardial necrosis due to ischemic or non-ischemic events. Considering the multiple causes of myocardial injury and treatment consequences there is great clinical need to clarify the underlying reason for cTnT release. We sought to implement acute CMR as a non-invasive imaging method for differential diagnosis of elevated cTnT in chest-pain unit (CPU) patients with non-conclusive symptoms and ECG-changes and a low to intermediate probability for coronary artery disease (CAD).</p> <p>Results</p> <p>CPU patients (n = 29) who had positive cTnT were scanned at 1.5T with a new step-by-step CMR algorithm including cine-, perfusion-, T2-, angiography-and late gadolinium enhancement (LGE) imaging. For comparison patients also underwent echocardiography and coronary angiography if necessary. CMR was conducted successfully in all patients and detected 93% of cTnT releases of unknown cause, without adverse hemodynamic or arrhythmic events. Acute myocardial infarction was detected in 11, pulmonary embolism in 6, myocarditis in 5, renal disease and cardiomyopathy in 2, storage disorder in 1 patient. In 2 patients CMR was unable to reveal the cause of cTnT elevations. Mean CMR scan-time was 35 ± 8 min. In 4 patients, CMR led to immediate coronary angiography with correct prediction of the infarct related artery.</p> <p>Conclusions</p> <p>We implemented a novel CMR algorithm to show the clinical value and practical feasibility of acute CMR in a non-conclusive patient cohort with unclear cTnT elevation. Since this pilot study has shown the feasibility of CMR in CPU patients, further prospective studies are warranted to compare CMR with other imaging modalities.</p

Effect of second timed appointments for non-attenders of breast cancer screening in England : a randomised controlled trial

BACKGROUND: In England, participation in breast cancer screening has been decreasing in the past 10 years, approaching the national minimum standard of 70%. Interventions aimed at improving participation need to be investigated and put into practice to stop this downward trend. We assessed the effect on participation of sending invitations for breast screening with a timed appointment to women who did not attend their first offered appointment within the NHS Breast Screening Programme (NHSBSP). METHODS: In this open, randomised controlled trial, women in six centres in the NHSBSP in England who were invited for routine breast cancer screening were randomly assigned (1:1) to receive an invitation to a second appointment with fixed date and time (intervention) or an invitation letter with a telephone number to call to book their new screening appointment (control) in the event of non-attendance at the first offered appointment. Randomisation was by SX number, a sequential unique identifier of each woman within the NHSBSP, and at the beginning of the study a coin toss decided whether women with odd or even SX numbers would be allocated to the intervention group. Women aged 50-70 years who did not attend their first offered appointment were eligible for the analysis. The primary endpoint was participation (ie, attendance at breast cancer screening) within 90 days of the date of the first offered appointment; we used Poisson regression to compare the proportion of women who participated in screening in the study groups. All analyses were by intention to treat. This trial is registered with Barts Health, number 009304QM. FINDINGS: We obtained 33 146 records of women invited for breast cancer screening at the six centres between June 2, 2014, and Sept 30, 2015, who did not attend their first offered appointment. 26 054 women were eligible for this analysis (12 807 in the intervention group and 13 247 in the control group). Participation within 90 days of the first offered appointment was significantly higher in the intervention group (2861 [22%] of 12 807) than in the control group (1632 [12%] of 13 247); relative risk of participation 1·81 (95% CI 1·70-1·93; p<0·0001). INTERPRETATION: These findings show that a policy of second appointments with fixed date and time for non-attenders of breast screening is effective in improving participation. This strategy can be easily implemented by the screening sites and, if combined with simple interventions, could further increase participation and ensure an upward shift in the participation trend nationally. Whether the policy should vary by time since last attended screen will have to be considered. FUNDING: National Health Service Cancer Screening Programmes and Department of Health Policy Research Programme

Bio-ecological study of river estuaries in Guilan province

The Caspian Sea with brackish water is known as typical environment due to geo position, precious biota and the largest land-enclosed drainage area in the world. Macrobenthos were performed the main group of the Caspian Sea fauna. While they use as environmental bio-assessment, they have not completely studied in the Caspian Sea especially in estuaries environments. In this survey were studied eighteen river estuaries in Guilan province off Caspian sea southwest including Asrara, Chelevand, Lemir, Havigh, Shirabad, Khotbesara, Lisar, Karganroud, Navroud, Nokandekeh, Sefidrud, Heshmatrud, Langerud, Polerud and Chabokrud. The macro-invertebrate sampling was conducted seasonally at eight stations during autumn 2008 to autumn 2009. The macrobenthos organisms were identified as possible level in genus or species. The Shannon Wiener diversity and the Hilsenhoff biotic indices were used for evaluation of environmental quality. In this study, 69 genus identified that belong to 36 families and 16 orders. The most presentation of genus belongs to Chironomidae family with twenty six genus while others families were included forty three genus. The most average of macro-invertebrate abundance belong to order of Diptera with 35 %, subsequently the abundance of Amphipoda and Bivalvia orders occupied the second rank with 8.2 %. Orders Polychaeta, Oligochaeta and Cumacea had a low abundance during the study, however the Polychaeta showed a high abundance in some seasons and stations (up to 25%). The Plecoptera was rarely observed in some stations with high abundance. The Stenogammarus genus had the normally distribution during study, while Chironomidae genera as Eukifferiella and Cricotopus were measured in the high abundance during autumn 2008 to spring 2009. While Streblospio and Limnodrilus had the high presentation during winter and spring 2009, Cerastoderma sp. showed a high percentage in spring and summer 2009. The result of Shannon Wiener index values showed a significantly difference among regions for most seasons. There was also observed significantly difference for diversity values among stations in different seasons. According to Hilsenhoff biotic index for water quality classification; the most stations had good quality in spring 2009, while they were slightly and moderately good condition in winter 2009. The water quality of the Caspian Sea stations was in good condition as compared with the rivers estuary stations

Study of Shovier and Mirzakhanlo dam reservoirs in Zanjan province in order to aquaculture activity

Inland water aquaculture activity have been known as an important approach for protein production while reservoir lakes recognized to have a significant potential for this purpose. Zanjan province in Iran with several dam reservoirs is suitable for aquaculture development. This study was conducted on biotic and abiotic factors of two lakes Shovir and Mirzakhanlo in order to determine aquaculture potentially of reservoirs. This two lakes located on different climatic region; Shovir located in region of semi arid area with very cold weather in winter, while Mirzakhanlo is in semi humid area and warm weather characteristic. In this study the plankton, benthos and fishes were assessed and the 15 hydrochemical factors were measured in order to determine the fisheries potential for fish introduction or release. The results showed that the phytoplankton abundance of Mirzakhanlo varied between 1.6 to 45.2 million cell/l. with 32 identified genus. The zooplankton abundance varied between 48 to 632 n/l. and 22 identified genus. The abundance plankton in shovir varied between 1.350 to 34.2 million cell/l. and 240 to 4500 n/l. for phyto and zooplankton respectively. Macrobenthos biomass were 21.4 and 0.34 g/m^2 in Shovir and Mirzakhanlo lakes respectively while Chironomidae and Tubificidae families were dominant groups. The lake sediment organic matter were 4.3 and 3.2 % respectively. In ichtiology survey identified 5 and 7 species in Mirzakhanlo and Shovir lakes respectively. The hydro-chemical results indicated no restriction for aquaculture activity and according to trophic model both lakes are recognized as meso-eutrophic and eutrophic. Despite of climatic restrictions, the potential for fish production was estimated about 321 and 151 kg/ha for Shovir and Mirzakhanlo lakes respectively that can be improved by using agricultural and the other native facilities

Conditional Gene Targeting in Mouse Pancreatic β-Cells: Analysis of Ectopic Cre Transgene Expression in the Brain

B. W. and M. B. Contributed equally to this manuscript Corresponding authors

Incidence of Isolated Biliary Atresia during the COVID Lockdown in Europe: Results from a Collaborative Project by RARE-Liver

Background: Biliary atresia (BA) is a rare cholangiopathy where one of the proposed aetiological mechanisms is an infectious viral trigger. Coronavirus disease-19 (COVID) lockdown restrictions were implemented to reduce the transmission of infections. Strictness of lockdown varied across European countries. This study aimed to investigate if there was an association between strictness of lockdown and change in isolated BA (IBA) incidence in Europe. Methods: We approached European centres involved in the European Reference Network RARE-LIVER. We included IBA patients born between 2015 and June 2020. We calculated the number of IBA patients born per centre per month. The Stringency Index (SI) was used as lockdown strictness indicator. The association between percentage change of mean number of IBA patients born per month and the SI was assessed. Results: We included 412 IBA patients from thirteen different centres. The median number of patients per month did not change: 6 (1–15) pre-lockdown and 7 (6–9) during lockdown (p = 0.34). There was an inverse association between SI and percentage change in IBA (B = -0.73, p = 0.03). Median age at Kasai portoenterostomy (days) did not differ between time periods (51 (9–179) vs. 53 (19–126), p = 0.73). Conclusion: In this European study, a stricter COVID-lockdown was seemingly accompanied by a simultaneous larger decrease in the number of IBA patients born per month in the lockdown. Results should be interpreted with caution due to the assumptions and limitations of the analysis