Systematic investigations of fatigue crack growth behavior of a PE‐HD pipe grade in through‐thickness direction

Fatigue crack growth (FCG) experiments were performed on a commercial high‐density polyethylene (PE‐HD) pipe grade. To investigate the influence of different specimen types on FCG results, tests were conducted using compact tension (CT) specimens and cracked round bars (CRB). The effects of frequency and R‐ratio on FCG behavior were also studied. Furthermore, FCG tests were interrupted in the region of stable crack propagation. The crack front and the front of the process zone ahead of the crack were systematically characterized via microscopic methods in the thickness direction of the specimen. The experimental data are employed to study the mechanisms of process zone development and to determine the effective crack length by compliance relationships. This detailed information allows modeling FCG in PE‐HD at various positions in the thickness direction of the specimen. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:1745–1758, 2007     

浅析混凝土的施工温度与裂缝

在大体积混凝土中,温度应力及温度控制具有重要意义,通过现场观察及查阅有关混凝土内部应力方面的专著,对混凝土度裂缝产生的原因、现场混凝土温度的控制和预防裂缝的措施进行等进行阐述。     

Optimization in risk management

Our purpose is to indicate how optimization concepts and techniques can be combined with probabilistic risk analysis to structure and solve risk management problems. Cost-optimal and risk-minimizing models are formulated in both deterministic and stochastic settings: the approach proposed is illustrated by several examples.     

Two fluid compartments in the renal inner medulla: a view through the keyhole of the concentrating process

Approximately four decades ago, the countercurrent theory became influential in studies on the concentrating process in the mammalian kidney. The theory successfully represented the concentrating process in the outer medulla, but the problem of the concentrating mechanism in the inner medulla, as defined by Homer Smith has remained essentially intractable.In a recent comprehensive review by Knepper and coworkers of various theories and models, attention was refocused on the possible role of hyaluronate (HA) in the inner medullary concentrating process. The authors proposed a hypothesis that HA can convert hydrostatic pressure to concentrating work.Here, we briefly survey the earlier ideas on the role imputed to HA and present a new hypothesis which is different from that of Knepper and coworkers. We estimate that the hydrostatic pressures available in the inner medulla can account only for a very small fraction of the concentrating work. We hypothesize that the role of HA is tied up with extravasated plasma albumin and suggest that owing to the property of HA solutions to exclude other macromolecules, extravasated plasma albumin and HA constitute two fluid compartments in the interstitium in the inner medulla. In this proposed two-compartment model, the Gibbs-Donnan distribution influences the movement of ions and water between the HA and the extravasated albumin compartment.To relate the hypothetical role of HA to the concentrating process, we briefly describe new results obtained by other investigators on the accumulation of urea in the inner medulla. This subject has been critically reviewed recently by Yang & Bankir.Many processes have been identified as contributing to the concentrating process in the mammalian inner medulla. We speculate that among these many processes, the primary responsibility for the final concentration of the excreted urine may be portioned out differently in different mammalian species.     

大板块大体积防水防渗混凝土无缝施工技术

通过对大板块、大体积混凝土在不同环境温度下产生裂缝原因的分析,选取合理的施工材料及施工措施,并掺加一种合适的外加剂,有效的解决了大板块无缝施工及大体积混凝土水化热、塑性收缩、干燥收缩、温度收缩和混凝土自防水。     

Transient increase of pancreatic enzymes evoked by apomorphine in Parkinson's disease

In one of our first patients with severely disabling and fluctuating Parkinson's disease (PD) we observed a transient pancreatic enzymes increase 6 months after continuous apomorphine therapy. Since this adverse effect had not been previously reported, we systematically investigated the course of pancreas and liver functions in response to apomorphine: laboratory and neurological assessments were conducted before initiation of apomorphine therapy, during the increment phase up to the optimal motor effective level and at all follow-up visits. We found in five out of 29PD patients a transient increase of pancreatic enzymes during the initial phase of continuous subcutaneous apomorphine application. Peaks of pathological plasma levels were apparent from the first day up to the fifth day after apomorphine initiation, and returned to normal levels within 10 days in all 5 patients. Otherwise, this pancreatic enzymes increase was not accompanied by any raising in plasma levels of corresponding liver enzymes. No pathological signs in the endoscopic-retrograde cholangiopancreatography, the abdominal ultrasonography and the computed tomography of the abdomen were found in any of the affected PD patients. Furthermore, there was no evidence of pancreato-hepatal risk factors in the previous history in any of the PD patients studied. With respect to the course of PD, no differences were obtained upon comparison of affected and non-affected PD patients. Considering the patients' history, clinical course and current knowledge about the effect of apomorphine on pancreato-hepatal function, we conclude that a possible cumulative pathomechanism between transient pancreato-hepatal enzymes and continuous applied apomorpine, especially in the titrating phase, might cause this adverse event in about 20% of PD patients treated with apomorphine continuously.     

A novel antibody-dependent cellular cytotoxicity epitope in gp120 is identified by two monoclonal antibodies isolated from a long-term survivor of human immunodeficiency virus type 1 infection

Two monoclonal antibodies (MAbs), 42F and 43F, were isolated some 14 months apart from a single long-term survivor of human immunodeficiency virus type 1 (HIV-1) infection. These MAbs were found to be indistinguishable in terms of their isotypes, specificities, affinities, and biological activities. Both 42F and 43F directed substantial antibody-dependent cellular cytotoxicity (ADCC) against cells infected with four divergent lab-adapted strains of HIV-1, but no neutralizing activity against these strains was detectable. The ability of MAbs 42F and 43F, as well as that of MAbs against two other gp120 epitopes, to direct ADCC against uninfected CD4+ cells to which recombinant gp120SF2 had been adsorbed (i.e., "innocent bystanders") was demonstrated to be less efficient by at least an order of magnitude than their ability to direct ADCC against HIV-1-infected cells. Flow cytometry analyses showed that 42F and 43F also bind to native primary isolate Envs from clades B and E expressed on cell surfaces. By direct binding and competition assays, it was demonstrated that the 42F/43F epitope lies in a domain of gp120 outside the previously described CD4-binding site and V3 loop ADCC epitope clusters. Immunoblot analysis revealed that the 42F/43F epitope is not dependent on disulfide bonds or N-linked glycans in gp120. Epitope mapping of 42F and 43F by binding to linear peptides demonstrated specificity of these MAbs for a sequence of 10 amino acids in the C5 domain comprising residues 491 to 500 (Los Alamos National Laboratory numbering for the HXB2 strain). Thus, 42F and 43F define a new ADCC epitope in gp120. Because of the relative conservation of this epitope and the fact that it appears to have been significantly immunogenic in the individual from which these MAbs were derived, it may prove to be a useful component of HIV vaccines. Furthermore, these MAbs may be used as tools to probe the potential importance of ADCC as an antiviral activity in HIV-1 infection.     

Cumulative impacts of river engineering,Mississippi and Lower Missouri rivers

The goal of this study was to construct a large, data‐rich model to test hydrological responses to engineering modifications on over 3200 km of the Mississippi and Lower Missouri Rivers. We compiled model explanatory variables from a geospatial database quantifying construction of all bridges, wing dikes, bendway weirs, levees, artificial meander cutoffs, channel constriction and navigational dams over the past 100–150 years. Response variables were derived from 68 rated and un‐rated hydrologic stations in the study area, with responses analysed across a range of discharges from within‐channel flows up to moderate floods. Correlation analysis, multiple linear regression and stepwise regression analyses document strong and consistent responses to construction history, both in individual reach‐scale models and systemwide. Meander cutoffs are associated with degradation and acceleration of flow that has reduced stages across the full discharge range. Navigational dams on the Upper Mississippi River increased low‐flow stages and flood levels to a lesser extent, with little or no post‐dam change. One of the strongest signals was the hydrologic response to wing‐dike construction, which resulted in large back‐water increases in stage upstream of wing dikes and mixed effects downstream, including the overlapping effects of incision and velocity losses. Levees were associated with local flow concentration, overbank storage loss and floodplain conveyance loss depending on reach‐scale conditions. The results presented here (1) quantify incremental and cumulative hydrologic responses to a range of engineering activities and (2) provide an empirical tool for verifying and assessing hydraulic and other models of river‐system change. Copyright © 2009 John Wiley & Sons, Ltd.     

Molecular dynamics simulation study on π-π stacking of Gemini surfactants in oil/water systems

Whereas the π-π stacking interactions at oil/water interfaces can affect interfacial structures hence the interfacial properties,the underlying microscopic mechanism remains largely unknown.We reported an all-atom molecular dynamics(MD) simulation study to demonstrate how the Gemini surfactants with pyrenyl groups affect the interracial properties,structural conformations,and the motion of molecules in the water/n-octane/surfactant ternary systems.It is found that the pyrenyl groups tend to be v...