Effects of plastic hinges on partial interaction behaviour of bolted side-plated beams

Slips of mechanical connectors in steel plate reinforced concrete (RC) structures can significantly affect the load-carrying capacity of the structures. The difference in deformation between the steel plate and the reinforced concrete counterpart is known as partial interaction. In this study, the flexural behaviour of bolted side-plated (BSP) reinforced concrete beams was investigated experimentally. Two new deformation-based parameters, namely the strain factor and curvature factor, were introduced to quantify the degree of partial interaction between the RC beam and the steel plates. The experimental results revealed that the degree of partial interaction between RC beams and steel plates could be reduced by as much as 50% when the BSP beam proceeded from a linear to a non-linear stage in which plastic hinges have formed in critical sections. Consequently, the load-carrying capacity was reduced by up to 30% of the theoretical additional strength provided by the bolt-plate system, which is more than double the allowance proposed previously in the literature. The under-estimation of the effect of partial interaction in composite structures can result in unsafe design. © 2010 Elsevier Ltd. All rights reserved.postprin

Use of bolted steel plates for strengthening of reinforced concrete beams and columns

Reinforced concrete (RC) structures often need strengthening due to defective construction, having higher loads than those foreseen in the initial design of the structure, or as a result of material deterioration or accidental damage. The need for strengthening concrete structures has become a crucial problem not only in developed countries but also in China and other developing countries. The use of bolted steel plates to retrofit existing RC structural components has been proven experimentally and practically to be effective in solving the problem. In this article, experimental and numerical studies conducted at The University of Hong Kong on the strengthening of RCcoupling beams, floor beams, and columns using bolted external steel plates are summarised. Features and design principles of this strengthening method are discussed. © 2011 The Institution of Engineers, Singapore.postprin

Spontaneous creation of Kibble-Zurek solitons in a Bose-Einstein condensate

When a system crosses a second-order phase transition on a finite timescale, spontaneous symmetry breaking can cause the development of domains with independent order parameters, which then grow and approach each other creating boundary defects. This is known as Kibble-Zurek mechanism. Originally introduced in cosmology, it applies both to classical and quantum phase transitions, in a wide variety of physical systems. Here we report on the spontaneous creation of solitons in Bose-Einstein condensates via the Kibble-Zurek mechanism. We measure the power-law dependence of defects number with the quench time, and provide a check of the Kibble-Zurek scaling with the sonic horizon. These results provide a promising test bed for the determination of critical exponents in Bose-Einstein condensates.Comment: 7 pages, 4 figure

Cavitation of Electrons Bubbles in Liquid Helium Below saturation Pressure

We have used a Hartree-type electron-helium potential together with a density functional description of liquid $^4$He and $^3$He to study the explosion of electron bubbles submitted to a negative pressure. The critical pressure at which bubbles explode has been determined as a function of temperature. It has been found that this critical pressure is very close to the pressure at which liquid helium becomes globally unstable in the presence of electrons. It is shown that at high temperatures the capillary model overestimates the critical pressures. We have checked that a commonly used and rather simple electron-helium interaction yields results very similar to those obtained using the more accurate Hartree-type interaction. We have estimated that the crossover temperature for thermal to quantum nucleation of electron bubbles is very low, of the order of 6 mK for $^4$He.Comment: 22 pages, 9 figure

Correlation between promoter methylation of p14ARF, TMS1/ASC, and DAPK, and p53 mutation with prognosis in cholangiocarcinoma

<p>Abstract</p> <p>Background</p> <p>To study the methylation status of genes that play a role in the p53-Bax mitochondrial apoptosis pathway and its clinical significance in cholangiocarcinoma.</p> <p>Patients and Methods</p> <p>Out of 36 cases cholangiocarcinoma patients from April 2000 to May 2005 were collected.Promoter hypermethylation of <it>DAPK</it>, <it>p14^ARF</it>, and <it>ASC </it>were detected by methylation-specific PCR on cholangiocarcinoma and normal adjacent tissues samples. Mutation of the p53 gene was examined by automated sequencing. Correlation between methylation of these genes and/or <it>p53 </it>mutation status with clinical characteristics of patients was investigated by statistical analysis.</p> <p>Results</p> <p>We found 66.7% of 36 cholangiocarcinoma patients had methylation of at least one of the tumor suppressor genes analyzed. <it>p53 </it>gene mutation was found in 22 of 36 patients (61.1%). Combined <it>p53 </it>mutation and <it>DAPK, p14^ARF, and/or ASC </it>methylation was detected in 14 cases (38.9%). There were statistically significant differences in the extent of pathologic biology, differentiation, and invasion between patients with combined <it>p53 </it>mutation and <it>DAPK, p14^ARF, and/or ASC </it>methylation compared to those without (P < 0.05). The survival rate of patients with combined <it>DAPK, p14^ARF, and ASC </it>methylation and <it>p53 </it>mutation was poorer than other patients (<it>P </it>< 0.05).</p> <p>Conclusion</p> <p>Our study indicates that methylation of <it>DAPK, p14^ARF, and ASC </it>in cholangiocarcinoma is a common event. Furthermore, <it>p53 </it>mutation combined with <it>DAPK, p14^ARF, and/or ASC </it>methylation correlates with malignancy and poor prognosis.</p

Role of CFTR expressed by neutrophils in modulating acute lung inflammation and injury in mice

Objective and designCystic fibrosis transmembrane conductance regulator (CFTR) regulates infection and inflammation. In this study, we investigated whether a lack of functional CFTR in neutrophils would promote lipopolysaccharide (LPS)-induced lung inflammation and injury.Materials and methodsCFTR-inhibited or F508del-CFTR-mutated neutrophils were stimulated with LPS and cultured to evaluate production of cytokines and NF-κB activation. Wild-type mice were reconstituted with F508del neutrophils or bone marrow and then intratracheally challenged with LPS to observe lung inflammatory response.ResultsPharmacologic inhibition and genetic mutation of CFTR in neutrophils activated NF-κB and facilitated macrophage inflammatory protein-2 (MIP-2) and tumor necrosis factor-α (TNF-α) production. Wild-type mice reconstituted with F508del neutrophils and bone marrow had more severe lung inflammation and injury after LPS challenge compared to wild-type mice receiving wild-type neutrophils or bone marrow reconstitution.ConclusionsLack of functional CFTR in neutrophils can promote LPS-induced acute lung inflammation and injury

Stochastic Gravity: Theory and Applications

Whereas semiclassical gravity is based on the semiclassical Einstein equation with sources given by the expectation value of the stress-energy tensor of quantum fields, stochastic semiclassical gravity is based on the Einstein-Langevin equation, which has in addition sources due to the noise kernel.In the first part, we describe the fundamentals of this new theory via two approaches: the axiomatic and the functional. In the second part, we describe three applications of stochastic gravity theory. First, we consider metric perturbations in a Minkowski spacetime: we compute the two-point correlation functions for the linearized Einstein tensor and for the metric perturbations. Second, we discuss structure formation from the stochastic gravity viewpoint. Third, we discuss the backreaction of Hawking radiation in the gravitational background of a quasi-static black hole.Comment: 75 pages, no figures, submitted to Living Reviews in Relativit

Stochastic Gravity: Theory and Applications

Whereas semiclassical gravity is based on the semiclassical Einstein equation with sources given by the expectation value of the stress-energy tensor of quantum fields, stochastic semiclassical gravity is based on the Einstein-Langevin equation, which has in addition sources due to the noise kernel. In the first part, we describe the fundamentals of this new theory via two approaches: the axiomatic and the functional. In the second part, we describe three applications of stochastic gravity theory. First, we consider metric perturbations in a Minkowski spacetime, compute the two-point correlation functions of these perturbations and prove that Minkowski spacetime is a stable solution of semiclassical gravity. Second, we discuss structure formation from the stochastic gravity viewpoint. Third, we discuss the backreaction of Hawking radiation in the gravitational background of a black hole and describe the metric fluctuations near the event horizon of an evaporating black holeComment: 100 pages, no figures; an update of the 2003 review in Living Reviews in Relativity gr-qc/0307032 ; it includes new sections on the Validity of Semiclassical Gravity, the Stability of Minkowski Spacetime, and the Metric Fluctuations of an Evaporating Black Hol

Lensfree Fluorescent On-Chip Imaging of Transgenic Caenorhabditis elegans Over an Ultra-Wide Field-of-View

We demonstrate lensfree on-chip fluorescent imaging of transgenic Caenorhabditis elegans (C. elegans) over an ultra-wide field-of-view (FOV) of e.g., >2–8 cm2 with a spatial resolution of ∼10µm. This is the first time that a lensfree on-chip platform has successfully imaged fluorescent C. elegans samples. In our wide-field lensfree imaging platform, the transgenic samples are excited using a prism interface from the side, where the pump light is rejected through total internal reflection occurring at the bottom facet of the substrate. The emitted fluorescent signal from C. elegans samples is then recorded on a large area opto-electronic sensor-array over an FOV of e.g., >2–8 cm2, without the use of any lenses, thin-film interference filters or mechanical scanners. Because fluorescent emission rapidly diverges, such lensfree fluorescent images recorded on a chip look blurred due to broad point-spread-function of our platform. To combat this resolution challenge, we use a compressive sampling algorithm to uniquely decode the recorded lensfree fluorescent patterns into higher resolution images, demonstrating ∼10 µm resolution. We tested the efficacy of this compressive decoding approach with different types of opto-electronic sensors to achieve a similar resolution level, independent of the imaging chip. We further demonstrate that this wide FOV lensfree fluorescent imaging platform can also perform sequential bright-field imaging of the same samples using partially-coherent lensfree digital in-line holography that is coupled from the top facet of the same prism used in fluorescent excitation. This unique combination permits ultra-wide field dual-mode imaging of C. elegans on a chip which could especially provide a useful tool for high-throughput screening applications in biomedical research