Improving flexural ductility of high-strength concrete beams

With the advent of advanced mineral and chemical admixtures, the strength level of concrete has been raised dramatically and high-strength concrete (HSC) is becoming more and more commonly used. However, HSC is generally more brittle than normal strength concrete. In fact, it has been shown that the use of HSC, if not properly controlled, could significantly reduce the flexural ductility of reinforced concrete beams. Herein, it is proposed to compensate for the reduction in flexural ductility owing to the use of HSC by adding compression and confining reinforcements. A parametric study based on complete moment-curvature analysis of beam sections made of different grades of concrete and provided with different amounts of tension, compression and confining reinforcements has been carried out to evaluate the increases in flexural ductility achievable by adding compression and confining reinforcements. From the numerical results, the compression and/or confining reinforcements needed to maintain a consistent level of minimum flexural ductility at all concrete strength levels have been determined and correlated to the concrete strength for direct evaluation in the design of HSC beams.published_or_final_versio

Theoretical study on effect of confinement on flexural ductility of normal and high-strength concrete beams

Compared with normal concrete, high-strength concrete has higher strength but is generally more brittle. Its use in a reinforced concrete structure, if not properly controlled, could lead to an unsustainable reduction in ductility. However, confinement could be provided to improve the ductility of the structure. In this study, the effects of concrete strength and confinement on the flexural ductility of reinforced concrete beams have been evaluated by means of complete moment-curvature analysis of beam sections cast in different concretes and provided with different confinements. The results reveal that the use of high-strength concrete at a constant tension steel ratio would increase the flexural ductility, but at a constant tension to balanced steel ratio would decrease the flexural ductility. In contrast, the provision of confinement would always increase the flexural ductility. It does this in two ways: first, it increases the balanced steel ratio so that, at the same tension steel ratio, the tension to balanced steel ratio is decreased; and second, it increases the residual strength and ductility of the concrete so that, at the same tension to balanced steel ratio, the flexural ductility of the beam section is increased.published_or_final_versio

Design of high-strength concrete beams subjected to small axial loads

In the design of reinforced concrete beams, the effects of small axial loads (axial load ≤ 0% of axial capacity of concrete section) are often ignored or at most only nominally allowed for. Moreover, the existing guidelines given in the various design codes are applicable only to beams cast of normal-strength concrete and designers are left to themselves to decide what to do when high-strength concrete is used. In this study, the effects of small axial loads on the flexural strength and ductility of normal- and high-strength concrete beams have been investigated by complete moment–curvature analysis of beam sections cast of different grades of concrete and subjected to different levels of axial load. The results revealed that the application of a small axial load has the beneficial effect of increasing the flexural strength but also the adverse effect of decreasing the flexural ductility. Based on the numerical results, simple formulae for estimating the effects of small axial loads and guidelines for the design of normal- and high-strength concrete beams subjected to small axial loads have been developed.published_or_final_versio

Enucleation of painful blind eye for refractory intraocular lymphoma after dose-limiting chemotherapy and radiotherapy

published_or_final_versionSpringer Open Choice, 25 May 201

Evaluation of moderate alcohol use and cognitive function among men using a mendelian randomization design in the guangzhou biobank cohort study

Observational studies usually show that moderate alcohol use is associated with better cognitive function. Such studies are vulnerable to residual confounding arising from systematic differences between moderate alcohol users and others. A Mendelian randomization study carried out in a suitable population, such as southern Chinese men, in which alcohol use is low to moderate and is influenced by genotype, offers an alternative and superior approach for clarifying the causal effect of moderate alcohol use on cognitive function. The authors used aldehyde dehydrogenase 2 (ALDH2) genotype (AA, GA, or GG) as an instrumental variable in 2-stage least squares analysis to obtain unbiased estimates of the relation of alcohol consumption (measured in alcohol units (10 g ethanol) per day) with cognitive function, assessed from delayed 10-word recall score (n = 4,707) and Mini-Mental State Examination (MMSE) score (n = 2,284), among men from the Guangzhou Biobank Cohort Study (2003-2008). ALHD2 genotype was strongly associated with alcohol consumption, with an F statistic of 71.0 in 2-stage least squares analysis. Alcohol consumption was not associated with delayed 10-word recall score (-0.03 words per alcohol unit, 95% confidence interval:-0.18, 0.13) or MMSE score (0.06 points per alcohol unit, 95% confidence interval:-0.22, 0.34). Moderate alcohol use is unlikely to be cognitively protective. © The Author 2012. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved.postprin

Estimated birth weight and adult cardiovascular risk factors in a developing southern Chinese population: a cross sectional study

Background. Birth weight is negatively associated with cardiovascular diseases and diabetes, but the associations are less well-established in developing populations where birth weight is often unavailable. We studied the association of birth weight and cardiovascular risk, using birth rank as an instrumental variable, in Southern China. Methods. We used published data on birth weight by birth rank from an appropriate population and baseline data from the Guangzhou Biobank Cohort Study phases 2 & 3 (2005-8) to examine the adjusted associations, using instrumental variable analysis, of birth weight with clinically measured cardiovascular risk factors and the metabolic syndrome in older (≥ 50 years) men (n = 5,051) and women (n = 13,907). Results. Estimated birth weight was associated with lower blood pressure (systolic -0.25 mm Hg 95% confidence interval (CI), -0.53 to 0.03 and diastolic -0.33 mm Hg 95% CI -0.48 to -0.18 per standard deviation higher birth weight), but had little association with glucose, lipids, waist-hip ratio, body mass index or the metabolic syndrome, adjusted for age, sex, early environment and number of offspring. Conclusion. Birth weight may impact blood pressure; however associations of birth weight with other cardiovascular risk factors may not be related to foetal exposures, but speculatively could be an historical co-incidence, with corresponding implications for prevention. © 2010 Schooling et al; licensee BioMed Central Ltd.published_or_final_versio

The role of bacteria in the pathogenesis and progression of idiopathic pulmonary fibrosis

Rationale:Idiopathic pulmonaryfibrosis (IPF)isa progressivelung disease of unknown cause that leads to respiratory failure and death within 5 years of diagnosis. Overt respiratory infection and immunosuppression carry a high morbidity and mortality, and polymorphisms in genes related to epithelial integrity and host defense predispose to IPF. Objectives: To investigate the role of bacteria in the pathogenesis and progression of IPF. Methods: We prospectively enrolled patients diagnosed with IPF according to international criteria together with healthy smokers, nonsmokers, and subjectswithmoderate chronic obstructive pulmonary disease as control subjects. Subjects underwent bronchoalveolar lavage (BAL), from which genomic DNA was isolated. The V3–V5 region of the bacterial 16S rRNA gene was amplified, allowing quantification of bacterial load and identification of communities by 16S rRNA quantitative polymerase chain reaction and pyrosequencing. Measurements and Main Results: Sixty-five patients with IPF had double the burden of bacteria in BAL fluid compared with 44 control subjects. Baseline bacterial burden predicted the rate of decline in lung volume and risk of death and associated independently with the rs35705950 polymorphism of the MUC5B mucin gene, a proven host susceptibilityfactorfor IPF. Sequencing yielded912,883 high-quality reads from all subjects.WeidentifiedHaemophilus, Streptococcus,Neisseria, and Veillonella spp. to be more abundant in cases than control subjects. Regression analyses indicated that these specific operational taxonomic units as well as bacterial burden associated independently with IPF. Conclusions: IPF is characterized by an increased bacterial burden in BAL that predicts decline in lung function and death. Trials of antimicrobial therapy are needed to determine if microbial burden is pathogenic in the disease

Clusters of circulating tumor cells traverse capillary-sized vessels

Multicellular aggregates of circulating tumor cells (CTC clusters) are potent initiators of distant organ metastasis. However, it is currently assumed that CTC clusters are too large to pass through narrow vessels to reach these organs. Here, we present evidence that challenges this assumption through the use of microfluidic devices designed to mimic human capillary constrictions and CTC clusters obtained from patient and cancer cell origins. Over 90% of clusters containing up to 20 cells successfully traversed 5- to 10-μm constrictions even in whole blood. Clusters rapidly and reversibly reorganized into single-file chain-like geometries that substantially reduced their hydrodynamic resistances. Xenotransplantation of human CTC clusters into zebrafish showed similar reorganization and transit through capillary-sized vessels in vivo. Preliminary experiments demonstrated that clusters could be disrupted during transit using drugs that affected cellular interaction energies. These findings suggest that CTC clusters may contribute a greater role to tumor dissemination than previously believed and may point to strategies for combating CTC cluster-initiated metastasis

Diagnostic criteria for idiopathic pulmonary fibrosis: a Fleischner Society White Paper.

This Review provides an updated approach to the diagnosis of idiopathic pulmonary fibrosis (IPF), based on a systematic search of the medical literature and the expert opinion of members of the Fleischner Society. A checklist is provided for the clinical evaluation of patients with suspected usual interstitial pneumonia (UIP). The role of CT is expanded to permit diagnosis of IPF without surgical lung biopsy in select cases when CT shows a probable UIP pattern. Additional investigations, including surgical lung biopsy, should be considered in patients with either clinical or CT findings that are indeterminate for IPF. A multidisciplinary approach is particularly important when deciding to perform additional diagnostic assessments, integrating biopsy results with clinical and CT features, and establishing a working diagnosis of IPF if lung tissue is not available. A working diagnosis of IPF should be reviewed at regular intervals since the diagnosis might change. Criteria are presented to establish confident and working diagnoses of IPF