14,764 research outputs found
Domino-type progressive collapse analysis of a multi-span simply-supported bridge: A case study
Hongqi Viaduct, a multi-span simply-supported bridge in Zhuzhou city, Hunan Province, China, collapsed progressively during the mechanical demolishing of the bridge on May 17, 2009. Totally nine spans collapsed in the accident and it is a typical domino-type progressive collapse. The accident resulted in the loss of 9 lives and 16 injuries. Investigations were conducted after the accident to determine the cause of the unexpected progressive collapse. This paper is aimed at presenting a summary of the bridge before and after the incident, the demolishing plans and field investigations after the accident. To better understand the cause and mechanism of the progressive collapse, a numerical simulation is carried out. A detail 3D finite element (FE) model is developed by using the explicit FE code LS-DYNA. The bridge components including the bridge slabs, wall-type piers, longitudinal and transverse reinforcement bars are included in the model. The non-linear material behaviour including the strain rate effects of the concrete and steel rebar are considered. The model is used to simulate the bridge collapse induced by demolishing, and the domino-type progressive collapse of the bridge is clearly captured. Based on the numerical results, the reason for the failure is discussed and better understood. Finally, the possible mitigation methods of such progressive collapses of multi-span viaducts are suggested
Entanglement control in one-dimensional random XY spin chain
The entanglement in one-dimensional random XY spin systems where the
impurities of exchange couplings and the external magnetic fields are
considered as random variables is investigated by solving the different
spin-spin correlation functions and the average magnetization per spin. The
entanglement dynamics near particular locations of the system is also studied
when the exchange couplings (or the external magnetic fields) satisfy three
different distributions(the Gaussian distribution, double-Gaussian
distribution, and bimodal distribution). We find that the entanglement can be
controlled by varying the strength of external magnetic field and the different
distributions of impurities. Moreover, the entanglement of some
nearest-neighboring qubits can be increased for certain parameter values of the
three different distributions.Comment: 13 pages, 4 figure
Production of squeezed state of single mode cavity field by the coupling of squeezed vacuum field reservoir in nonautonomous case
The dissipative and decoherence properties as well as the asymptotic behavior
of the single mode electromagnetic field interacting with the time-dependent
squeezed vacuum field reservoir are investigated in detail by using the
algebraic dynamical method. With the help of the left and right representations
of the relevant algebra, the dynamical symmetry of the nonautonomous
master equation of the system is found to be . The unique equilibrium
steady solution is found to be the squeezed state and any initial state of the
system is proved to approach the unique squeezed state asymptotically. Thus the
squeezed vacuum field reservoir is found to play the role of a squeezing mold
of the cavity field.Comment: 5 pages, no figure, Revtex
Continuous extremal optimization for Lennard-Jones Clusters
In this paper, we explore a general-purpose heuristic algorithm for finding
high-quality solutions to continuous optimization problems. The method, called
continuous extremal optimization(CEO), can be considered as an extension of
extremal optimization(EO) and is consisted of two components, one is with
responsibility for global searching and the other is with responsibility for
local searching. With only one adjustable parameter, the CEO's performance
proves competitive with more elaborate stochastic optimization procedures. We
demonstrate it on a well known continuous optimization problem: the
Lennerd-Jones clusters optimization problem.Comment: 5 pages and 3 figure
Transcriptional regulation of the grape cytochrome P450 monooxygenase gene CYP736B expression in response to Xylella fastidiosa infection
<p>Abstract</p> <p>Background</p> <p>Plant cytochrome P450 monooxygenases (CYP) mediate synthesis and metabolism of many physiologically important primary and secondary compounds that are related to plant defense against a range of pathogenic microbes and insects. To determine if cytochrome P450 monooxygenases are involved in defense response to <it>Xylella fastidiosa </it>(<it>Xf</it>) infection, we investigated expression and regulatory mechanisms of the cytochrome P450 monooxygenase <it>CYP736B </it>gene in both disease resistant and susceptible grapevines.</p> <p>Results</p> <p>Cloning of genomic DNA and cDNA revealed that the <it>CYP736B </it>gene was composed of two exons and one intron with GT as a donor site and AG as an acceptor site. <it>CYP736B </it>transcript was up-regulated in PD-resistant plants and down-regulated in PD-susceptible plants 6 weeks after <it>Xf </it>inoculation. However, <it>CYP736B </it>expression was very low in stem tissues at all evaluated time points. 5'RACE and 3'RACE sequence analyses revealed that there were three candidate transcription start sites (TSS) in the upstream region and three candidate polyadenylation (PolyA) sites in the downstream region of <it>CYP736B</it>. Usage frequencies of each transcription initiation site and each polyadenylation site varied depending on plant genotype, developmental stage, tissue, and treatment. These results demonstrate that expression of <it>CYP736B </it>is regulated developmentally and in response to <it>Xf </it>infection at both transcriptional and post-transcriptional levels. Multiple transcription start and polyadenylation sites contribute to regulation of <it>CYP736B </it>expression.</p> <p>Conclusions</p> <p>This report provides evidence that the cytochrome P450 monooxygenase <it>CYP736B </it>gene is involved in defense response at a specific stage of <it>Xf </it>infection in grapevines; multiple transcription initiation and polyadenylation sites exist for <it>CYP736B </it>in grapevine; and coordinative and selective use of transcription initiation and polyadenylation sites play an important role in regulation of <it>CYP736B </it>expression during growth, development and response to <it>Xf </it>infection.</p
Antibiotic resistance mechanisms inform discovery: identification and characterization of a novel amycolatopsis strain producing ristocetin.
Discovering new antibiotics is a major scientific challenge, made increasingly urgent by the continued development of resistance in bacterial pathogens. A fundamental understanding of the mechanisms of bacterial antibiotic resistance will be vital for the future discovery or design of new, more effective antibiotics. We have exploited our intimate knowledge of the molecular mechanism of glycopeptide antibiotic resistance in the harmless bacterium Streptomyces coelicolor to develop a new two-step cell wall bioactivity screen, which efficiently identified a new actinomycete strain containing a previously uncharacterized glycopeptide biosynthetic gene cluster. The screen first identifies natural product extracts capable of triggering a generalized cell wall stress response and then specifically selects for glycopeptide antibacterials by assaying for the induction of glycopeptide resistance genes. In this study, we established a diverse natural product extract library from actinomycete strains isolated from locations with widely varying climates and ecologies, and we screened them using the novel two-step bioassay system. The bioassay ultimately identified a single strain harboring the previously unidentified biosynthetic gene cluster for the glycopeptide ristocetin, providing a proof of principle for the effectiveness of the screen. This is the first report of the ristocetin biosynthetic gene cluster, which is predicted to include some interesting and previously uncharacterized enzymes. By focusing on screening libraries of microbial extracts, this strategy provides the certainty that identified producer strains are competent for growth and biosynthesis of the detected glycopeptide under laboratory conditions.This work was supported by funding from the Royal Society, UK (516002.K5877/ROG), the Medical Research council, UK (G0700141) and St. John’s College, University of CambridgeThis the the author accepted manuscript. The final version is available from ASM at http://aac.asm.org/content/early/2014/07/09/AAC.03349-14.abstract
The entanglement in one-dimensional random XY spin chain with Dzyaloshinskii-Moriya interaction
The impurities of exchange couplings, external magnetic fields and
Dzyaloshinskii--Moriya (DM) interaction considered as Gaussian distribution,
the entanglement in one-dimensional random spin systems is investigated by
the method of solving the different spin-spin correlation functions and the
average magnetization per spin. The entanglement dynamics at central locations
of ferromagnetic and antiferromagnetic chains have been studied by varying the
three impurities and the strength of DM interaction. (i) For ferromagnetic spin
chain, the weak DM interaction can improve the amount of entanglement to a
large value, and the impurities have the opposite effect on the entanglement
below and above critical DM interaction. (ii) For antiferromagnetic spin chain,
DM interaction can enhance the entanglement to a steady value. Our results
imply that DM interaction strength, the impurity and exchange couplings (or
magnetic field) play competing roles in enhancing quantum entanglement.Comment: 12 pages, 3 figure
DOP17 Identification of biomarkers and mechanistic insight for upadacitinib in ulcerative colitis: Analysis of serum inflammatory mediators in the phase 2b U-ACHIEVE study
Abstract
Background
The U-ACHIEVE trial evaluated upadacitinib (UPA), an oral JAK1 selective inhibitor, in patients with moderately to severely active ulcerative colitis (UC). Patient-reported and endoscopic outcomes improved after UPA treatment. This analysis used pharmacodynamic profiling to link changes in serum biomarkers to changes in UC disease activity, and to assess the UPA mechanism of action in UC.
Methods
U-ACHIEVE (NCT02819635) was a randomised, double-blind, placebo (PBO)-controlled phase 2b clinical trial. Adults with an inadequate response, loss of response, or intolerance to corticosteroids, immunosuppressants, or biologic therapies were randomised to receive 7.5, 15, 30, or 45 mg UPA once daily or PBO for 8 weeks (weeks). Serum samples (baseline [BL], weeks 2, 4, and 8) were analysed by OLINK® inflammation panel (92 proteins) and by Singulex immunoassay for interleukin-1b (IL-1b), IL-17A, IL-17F, and IL-22. Protein-level changes were analysed by a mixed-effect model; BL protein level was adjusted as a covariate; treatment group, time point, and their interaction were included as fixed effects. Spearman rank-correlation coefficients were used to determine the relationship between changes of serum biomarker levels and improvements in adapted Mayo scores and endoscopic subscores. Multiplicity adjusted P values were calculated using 1000 runs of random permutations.
Results
Paired BL and week 8 serum samples were available from 114 patients (PBO, n = 17; UPA 7.5 mg, n = 21; UPA 15 mg, n = 21; UPA 30 mg, n = 29; UPA 45 mg, n = 26). UPA treatment reduced expression of pro-inflammatory mediators associated with immune cell migration, type I/II IFN responses, T-cell responses, macrophage and dendritic cell activity and increased expression of biomarkers associated with haematopoiesis, neuroprotection and mucosal repair in a dose-dependent manner. Improvements in adapted Mayo score, endoscopic subscore, and stool frequency correlated with increases in CX3CL1, DNER and FLt3L (p < 0.05 for all). Endoscopic improvements correlated with reductions in OSM, and improvements in fatigue correlated with increases in CCL25 and NT-3. There was a substantial overlap in biomarkers modulated by UPA in patients with UC and Crohn's disease (Figure).
Conclusion
UPA modulated expression of serum pro-inflammatory mediators found in pathways associated with the pathogenesis of UC, including immune cell migration, type I/II IFN responses, T-cell responses, macrophage and dendritic cell activity, haematopoiesis, neuroprotection, and mucosal repair. Consistent correlations were observed between changes in biomarker expression and improvements in disease activity and symptoms of UC
Vertex functions for d-wave mesons in the light-front approach
While the light-front quark model (LFQM) is employed to calculate hadronic
transition matrix elements, the vertex functions must be pre-determined. In
this work we derive the vertex functions for all d-wave states in this model.
Especially, since both of and are mesons, the Lorentz
structures of their vertex functions are the same. Thus when one needs to study
the processes where is involved, all the corresponding formulas for
states can be directly applied, only the coefficient of the vertex
function should be replaced by that for . The results would be useful
for studying the newly observed resonances which are supposed to be d-wave
mesons and furthermore the possible 2S-1D mixing in with the LFQM.Comment: 12 pages, 2 figures, some typos corrected and more discussions added.
Accepted by EPJ
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