Vaccination and the population structure of antigenically diverse pathogens that exchange genetic material

Populations of antigenically diverse pathogens undergoing genetic exchange may be categorized into strains on the basis of a set of principal protective antigens. The extent to which polyvalent vaccines based on these protective antigens can alter the population structure of the pathogen is determined by the degree of cross-protection between strains. In the case where there is no cross-protection, vaccinating against a particular strain will have no effect on the others. As cross-protection increases, the strains containing the antigenic variants included in the vaccine will be diminished in prevalence, and those that do not will increase in prevalence. The rise in prevalence of the latter will become more and more exaggerated as cross-protection increases. However, beyond a critical level of cross-protection, in the absence of vaccination, the steady state of the system is asymmetric in that a certain subset of strains (with non-overlapping repertoires of antigenic variants) will dominate over the others in terms of prevalence. Under these circumstances, a vaccine consisting of the most immunogenic combinations of antigenic variants can cause a dramatic increase in frequency of a subset of rare strains.     

Load Bearing Capacity of Reinforced Concrete Beams Subjected to Dynamic Cyclic Loads

A kinematic method is developed to determine the shakedown limits of elastic-perfectly plastic steel-reinforced concrete beams under quasi-static and dynamic cyclic loads. This procedure, like the respective kinematic approach of plastic limit analysis, is visual and easy to use in engineering applications. The load parameters (amplitudes, frequency) versus yield moment diagrams, constructed from possible collapse modes, should assist in choosing the reinforcement scheme and amounts of reinforcement to meet the load bearing requirements for the structures.     

Mechanisms underlying the effects of membrane fouling on the nanofiltration of trace organic contaminants

The influence of membrane fouling on the retention of four trace organic contaminants - namely sulfamethoxazole, ibuprofen, carbamazepine, and triclosan - by nanofiltration membranes was investigated in this study. Humic acid, alginate, bovine serum albumin, and silica colloids were selected as model foulants to simulate various organic fractions and colloidal matter that are found in secondary treated effluent and surface water. The effects of membrane fouling on the separation process was delineated by comparing retention values of clean and fouled membranes and relate them to the membrane properties (under both clean and fouled conditions) as well as physicochemical characteristics of the trace organic contaminants. Membrane fouling was dependent on the physicochemical properties of the model foulants. Initial foulant-membrane interaction could probably be a major factor governing the process of membrane fouling particularly by the organic foulants. Such membrane-foulant interaction was also a dominating factor governing the effects of membrane fouling on the membrane separation efficacy. In good agreement with our previous study (Nghiem and Hawkes, 2007 [1]), the effects of fouling on retention were found to be membrane pore size dependent. In addition, results reported here suggest that these effects could also be foulant dependent. It was probable that the influence of membrane fouling on trace organic retention could be governed by four distinctive mechanisms: modification of the membrane charge surface, pore blocking, cake enhanced concentration polarisation, and modification of the membrane hydrophobicity. The presence of the fouling layer could affect the retention behavior of charged solutes by altering the membrane surface charge density. While the effect of surface charge modification was clear for inorganic salts, it was less obvious for the negatively charged pharmaceutical species (sulfamethoxazole and ibuprofen) examined in this investigation, possibly due to the interference of the pore blocking mechanism. Evidence of the cake enhanced concentration polarisation effect was quite clear, particularly under colloidal fouling conditions. In addition, organic fouling could also interfere with the solute-membrane interaction, and therefore, exerted considerable influence on the separation process of the hydrophobic trace organic contaminant triclosan.     

天然裂缝性储层的特征

天然裂缝性储层给开采带来了一个矛盾难题。这类储层包括低油气采收率储层,这些储层最初可能表现出高产,但产能下降得非常快。此外,这类储层还经常出现早期见气或见水等问题。而另一方面,一些天然裂缝性储层也是全球最大、产量最高的储层。这类储层的这种矛盾特性激发业界尽力去深入了解其特征,以便更有把握地对其进行模拟分析。     

Agreement and clinical utility of 2 techniques for measuring cardiac output in patients with low cardiac output

BACKGROUND: The reliability of cardiac output obtained with the bolus technique is a problem. OBJECTIVES: To compare measurements of cardiac output measured with bolus and continuous techniques in patients with low cardiac output and to determine if measurements obtained with the continuous technique increased the number of subsequent clinical decisions. METHODS: In 60 intensive care patients, a nurse recorded a single continuous cardiac output measurement and then obtained the mean of 3 consecutive bolus determinations. The medical records of these 60 patients (experimental group) for the next 48 hours and of 60 other patients with regular or mixed venous oximetry catheters (control group) were reviewed to assess the occurrence of cardiac output events and the frequency of clinical decisions based on the events. RESULTS: Mean cardiac output was 4.46 L/min by the continuous technique and 5.20 L/min by the bolus technique (P = .011) for the experimental group. Median bias between the 2 types of measurements was -0.10 L/min (P = .79). Twenty-three of the pairs (38%) had an absolute percent difference greater than 15%. Of these, 18 (78%) had a higher bolus reading. Treatment decisions per 48 hours were 9.9 for the experimental group and 8.6 for the control group (P = .014). Median length of stay was 2 days less in the experimental group (P = .02), and mean highest cardiac output was 0.81 L/min higher (P = .009). CONCLUSIONS: Measurements of cardiac output determined with the continuous technique may be more precise than measurements determined with the bolus technique. Continuous cardiac output information increases the number of treatment decisions and actions that may shorten hospital length of stay.     

Towards the detection of human papillomavirus infection by a reagentless electrochemical peptide biosensor

In the present work, we report first results about a technology using a conjugated copolymer poly(5-hydroxy-1,4-naphthoquinone-co-5-hydroxy-2-carboxyethyl-1,4-naphthoquinone) acting both as immobilizing and transducing element for reagentless immunosensor, and its application for the detection of HPV infection. It was shown that the reagentless immunosensor was able to detect the interaction between antigenic peptide L1 from HPV-16 major capsid protein, a dominant epitope involved in viral infection as well as in prophylactic vaccine, and the relevant antibody.