H‐adaptive finite element solution of high Rayleigh number thermally driven cavity problem

An h‐adaptive finite element code for solving coupled Navier‐Stokes and energy equations is used to solve the thermally driven cavity problem. The buoyancy forces are represented using the Boussinesq approximation. The problem is characterised by very thin boundary layers at high values of Rayleigh number (>106). However, steady state solutions are achievable with adequate discretisation. This is where the auto‐adaptive finite element method provides a powerful means of achieving optimal solutions without having to pre‐define a mesh, which may be either inadequate or too expensive. Steady state and transient results are given for six different Rayleigh numbers in the range 103 to 108 for a Prandtl number of 0.71. The use of h‐adaptivity, based on a posteriori error estimation, is found to ensure a very accurate problem solution at a reasonable computational cost

Analysis of Restrained Composite Perforated Beams during Fire Using a Hybrid Simulation Approach

This paper is concerned with the behavior of restrained perforated beams acting compositely with a profiled slab during a fire. These members are increasingly popular in the construction of long-span floor systems because they provide a structurally and materially efficient design solution and provide space for placement of building services. However, their response during a fire has received little attention from the research community until recently. In the current work, a hybrid simulation-type numerical approach is adopted using a combination of the OpenSEES, ABAQUS, and OpenFresco software. The accuracy of the model is validated using available fire test data whereby the temperatures measured during the experiments are directly applied in the numerical model at various locations. The effect of axial and rotational restraint due to the connections between the beams and columns is also investigated following validation of the model. Furthermore, the hybrid simulation approach is employed to study a number of salient parameters, including load ratios, material grade, and the location of the openings. The variation in axial force during the fire is also examined. Various failure modes were observed during the analysis, including flexural and shear failure, failure of the web-post, concrete crushing, and also a Vierendeel mechanism. The fire resistance of the analyzed beams is compared with the values obtained from the most common design codes. Because of the consideration of restraint forces, which are not included in the design codes, the resistances predicted by the finite-element simulations were more favorable. It was found that the location of the openings along the span and also the boundary conditions had a considerable effect on the time-displacement behavior, axial reactions, and web-post buckling behavior, as well as the fire performance of the perforated beam

H‐adaptive finite element solution of unsteady thermally driven cavity problem

An h‐adaptive finite element code for solving coupled Navier‐Stokes and energy equations is used to solve the thermally driven cavity problem for Rayleigh numbers at which no steady state exists (greater than 1.9 × 108). This problem is characterised by sharp thermal and flow boundary layers and highly advection dominated transport, which normally requires special algorithms, such as streamline upwinding, to achieve stable and smooth solutions. It will be shown that h‐adaptivity provides a suitable solution to both of these problems (sharp gradients and advection dominated transport). Adaptivity is also very effective in resolving the flow physics, characterised by unsteady internal waves, are calculated for three Rayleigh numbers; 2 × 108, 3 × 108 and 4 × 108 using a Prandtl number of 0.71 and results are compared with other published results.EPSRC research studentshi

The world trade center 9/11 disaster and progressive collapse of tall buildings

The collapse of the World Trade Center buildings on September 11, 2001 posed questions on the stability of tall buildings in fire. Understanding the collapse of the WTC Towers offers the opportunity to learn useful engineering lessons in order to improve the design of future tall buildings against fire induced collapse. This paper extends previous research on the modelling of the collapse of the WTC Towers on September 11, 2001 using a newly developed ‘‘structures in fire’’ simulation capability in the open source software framework OpenSees. The simulations carried out are validated by comparisons with previous work and against the findings from the NIST investigation, albeit not in the forensic sense. The column ‘‘pull in’’ that triggers the instability of the structure and leads to collapse is explained. The collapse mechanisms of generic composite tall buildings are also examined. This is achieved through carrying out a detailed parametric study varying the relative stiffness of the column and the floors. The two main mechanisms identified in previous research (weak and strong floor) are reproduced and criteria are established on their occurrence. The analyses performed revealed that the collapse mechanism type depended on the bending stiffness ratio and the number of floors subjected to fire and that the most probable type of failure is the strong floor collapse. The knowledge of these mechanisms is of practical use if stakeholders wish to extend the tenability of a tall building structure in a major fire.Professor Jose Torero and the Open-Sees team at PEER, UC Berkele

Glauber theory of initial- and final-state interactions in (p,2p) scattering

We develop the Glauber theory description of initial- and final-state interactions (IFSI) in quasielastic A(p,2p) scattering. We study the IFSI-distortion effects both for the inclusive and exclusive conditions. In inclusive reaction the important new effect is an interaction between the two sets of the trajectories which enter the calculation of IFSI-distorted one-body density matrix for inclusive (p,2p) scattering and are connected with incoherent elastic rescatterings of the initial and final protons on spectator nucleons. We demonstrate that IFSI-distortions of the missing momentum distribution are large over the whole range of missing momentum both for inclusive and exclusive reactions and affect in a crucial way the interpretation of the BNL data on (p,2p) scattering. Our numerical results show that in the region of missing momentum p_{m}\lsim 100-150 MeV/c the incoherent IFSI increase nuclear transparency by 5-10\%. The incoherent IFSI become dominant at p_{m}\gsim 200 MeV/c.Comment: Accepted in Z. Phys.A, Latex, 26 pages, uuencoded 9 figure

Virological and clinical characteristics of hepatitis delta virus in South Asia

<p>Abstract</p> <p>Background & Aims</p> <p>There is a paucity of data on the impact of hepatitis D virus (HDV) in patients with hepatitis B virus (HBV) infection from South Asia. We studied the impact of HDV co-infection on virological and clinical characteristics.</p> <p>Methods</p> <p>We collected data of 480 patients with HBsAg positive and a detectable HBV DNA PCR, who presented to the Aga Khan University, Karachi and Isra University in Hyderabad, Pakistan in the last 5 years. HDV co-infection was diagnosed on the basis of anti-HDV. ALT, HBeAg, HBeAb and HBV DNA PCR quantitative levels were checked in all patients. We divided all patients into two groups based on anti-HDV, and compared their biochemical, serological & virological labs and clinical spectrum. Clinical spectrum of disease included asymptomatic carrier (AC), chronic active hepatitis (CAH), immuno-tolerant phase (IP), and compensated cirrhosis (CC).</p> <p>Results</p> <p>HDV co-infection was found in 169 (35.2%). There were 164 (34.6%) HBeAg positive and 316 (65.4%) HBeAg negative patients. Mean ALT level was 66 ± 73 IU. 233 (48.5%) had raised ALT. HBV DNA level was ≥ 10e5 in 103(21.5%) patients. Overall, among HBV/HDV co-infection, 146/169 (86.4%) had suppressed HBV DNA PCR as compared to 231/311 (74.3%) patients with HBV mono-infection; p-value = 0.002. Among HBeAg negative patients 71/128(55.5%) had raised ALT levels among HBV/HDV co-infection as compared to 71/188 (37.8%) with HBV mono-infection (p-value = 0.002); levels of HBV DNA were equal in two groups; there were 27/128 (21%) patients with CC among HBV/HDV co-infection as compared to 23 (12%) in HBV mono-infection (p-value = 0.009); there were less AC (p-value = 0.009) and more CAH (p-value = 0.009) among HBV/HDV co-infection patients. Among HBeAg positive patients, serum ALT, HBV DNA levels and the spectrum of HBV were similar in the two groups.</p> <p>Conclusions</p> <p>HBV/HDV co-infection results in the suppression of HBV DNA. A fair proportion of HBV/HDV co-infected patients with HBeAg negative have active hepatitis B infection and cirrhosis as compared to those with mono-infection.</p

Identification of Novel Susceptibility Loci and Genes for Prostate Cancer Risk: A Transcriptome-Wide Association Study in over 140,000 European Descendants

Genome-wide association study–identified prostate cancer risk variants explain only a relatively small fraction of its familial relative risk, and the genes responsible for many of these identified associations remain unknown. To discover novel prostate cancer genetic loci and possible causal genes at previously identified risk loci, we performed a transcriptome-wide association study in 79,194 cases and 61,112 controls of European ancestry. Using data from the Genotype-Tissue Expression Project, we established genetic models to predict gene expression across the transcriptome for both prostate models and cross-tissue models and evaluated model performance using two independent datasets. We identified significant associations for 137 genes at P < 2.61 × 10−6, a Bonferroni-corrected threshold, including nine genes that remained significant at P < 2.61 × 10−6 after adjusting for all known prostate cancer risk variants in nearby regions. Of the 128 remaining associated genes, 94 have not yet been reported as potential target genes at known loci. We silenced 14 genes and many showed a consistent effect on viability and colony-forming efficiency in three cell lines. Our study provides substantial new information to advance our understanding of prostate cancer genetics and biology. SIGNIFICANCE: This study identifies novel prostate cancer genetic loci and possible causal genes, advancing our understanding of the molecular mechanisms that drive prostate cancer

Genome-wide association study identifies susceptibility loci for B-cell childhood acute lymphoblastic leukemia.

Genome-wide association studies (GWAS) have advanced our understanding of susceptibility to B-cell precursor acute lymphoblastic leukemia (BCP-ALL); however, much of the heritable risk remains unidentified. Here, we perform a GWAS and conduct a meta-analysis with two existing GWAS, totaling 2442 cases and 14,609 controls. We identify risk loci for BCP-ALL at 8q24.21 (rs28665337, P = 3.86 × 10-9, odds ratio (OR) = 1.34) and for ETV6-RUNX1 fusion-positive BCP-ALL at 2q22.3 (rs17481869, P = 3.20 × 10-8, OR = 2.14). Our findings provide further insights into genetic susceptibility to ALL and its biology