The matching law

This article introduces the quantitative analysis of choice behavior by describing a number of equations developed over the years to describe the relation between the allocation of behavior under concurrent schedules of reinforcement and the consequences received for alternative responses. Direct proportionality between rate of responding and rate of reinforcement was observed in early studies, suggesting that behavioral output matched environmental input in a mathematical sense. This relation is termed "strict matching," and the equation that describes it is referred to as "the matching law." Later data showed systematic departures from strict matching, and a generalized version of the matching equation is now used to describe such data. This equation, referred to as "the generalized matching equation," also describes data that follow strict matching. It has become convention to refer to either of these equations as "the matching law." Empirical support for the matching law is briefly summarized, as is the applied and practical significance of matching analyses

Bacterial-epithelial contact is a key determinant of host innate immune responses to enteropathogenic and enteroaggregative escherichia coli

Background: Enteropathogenic (EPEC) and Enteroaggregative (EAEC) E. coli have similar, but distinct clinical symptoms and modes of pathogenesis. Nevertheless when they infect the gastrointestinal tract, it is thought that their flagellin causes IL-8 release leading to neutrophil recruitment and gastroenteritis. However, this may not be the whole story as the effect of bacterial adherence to IEC innate response(s) remains unclear. Therefore, we have characterized which bacterial motifs contribute to the innate epithelial response to EPEC and EAEC, using a range of EPEC and EAEC isogenic mutant strains. Methodology: Caco-2 and HEp-2 cell lines were exposed to prototypical EPEC strain E2348/69 or EAEC strain O42, in addition to a range of isogenic mutant strains. E69 [LPS, non-motile, non-adherent, type three secretion system (TTSS) negative, signalling negative] or O42 [non-motile, non-adherent]. IL-8 and CCL20 protein secretion was measured. Bacterial surface structures were assessed by negative staining Transmission Electron Microscopy. The Fluorescent-actin staining test was carried out to determine bacterial adherence. Results: Previous studies have reported a balance between the host pro-inflammatory response and microbial suppression of this response. In our system an overall balance towards the host pro-inflammatory response is seen with the E69 WT and to a greater extent O42 WT, which is in fit with clinical symptoms. On removal of the external EPEC structures flagella, LPS, BFP, EspA and EspC; and EAEC flagella and AAF, the host inflammatory response is reduced. However, removal of E69 lymphostatin increases the host inflammatory response suggesting involvement in the bacterial mediated anti-inflammatory response. Conclusion: Epithelial responses were due to combinations of bacterial agonists, with host-bacterial contact a key determinant of these innate responses. Host epithelial recognition was offset by the microbe's ability to down-regulate the inflammatory response. Understanding the complexity of this host-microbial balance will contribute to improved vaccine design for infectious gastroenteritis

Women's perceptions of their healthcare experience when they choose not to breastfeed

Research Question How do women who choose not to breastfeed perceive their healthcare experience? Method This qualitative research study used a phenomenographic approach to explore the healthcare experience of women who do not breastfeed. Seven women were interviewed about their healthcare experience relating to their choice of feeding, approximately four weeks after giving birth. Six conceptions were identified and an outcome space was developed to demonstrate the relationships and meaning of the conceptions in a visual format. Findings There were five unmet needs identified by the participants during this study. These needs included equity, self sufficiency, support, education and the need not to feel pressured. Conclusion Women in this study who chose not to breastfeed identified important areas where they felt that their needs were not met. In keeping with the Code of Ethics for Nurses and Midwives, the identified needs of women who do not breastfeed must be addressed in a caring, compassionate and just manner. The care and education of women who formula feed should be of the highest standard possible, even if the choice not to breastfeed is not the preferred choice of healthcare professionals

Sub-clinical left and right ventricular dysfunction in patients with COPD

SummaryBackgroundCardiovascular manifestations in COPD include increased arterial stiffness, ischaemic heart disease, chronic heart failure and cor pulmonale. We hypothesised that sub-clinical right (RV) and left ventricular (LV) dysfunction occurs in patients with COPD, related to the severity of airflow obstruction, arterial stiffness and systemic inflammation.MethodsThirty six patients and 14 controls, all free of overt cardiovascular disease underwent tissue Doppler echocardiography, spirometry, measurement of aortic pulse wave velocity (PWV) and venous sampling for inflammatory markers.ResultsMean LV myocardial strain and strain rate were less in patients than controls, p<0.05. LV isovolumic relaxation time (IVRT) was prolonged in patients (125±15.2ms) compared with controls (98.2±21.1ms), p<0.01, indicating LV diastolic dysfunction. The RV free wall strain and strain rate were less in patients than controls, both p<0.05, indicating RV systolic dysfunction. Patients had sub-clinical pulmonary arterial hypertension with a greater RV myocardial relaxation time and Tei index, both p<0.01. Patients with mild airways obstruction had LV and RV dysfunction and evidence of increased RV afterload compared with controls. In multivariate analyses aortic PWV predicted LV IVRT, p<0.01, while FEV1 predicted RV Tei index and myocardial relaxation time, both p<0.01.ConclusionsPatients with COPD have sub-clinical left ventricular dysfunction related to arterial stiffness, and right ventricular dysfunction related to airways obstruction. Both right and left ventricular dysfunction are present in patients with mild airways obstruction suggesting that cardiac co-morbidities commence early in the development of COPD

Interface Fluctuations under Shear

Coarsening systems under uniform shear display a long time regime characterized by the presence of highly stretched and thin domains. The question then arises whether thermal fluctuations may actually destroy this layered structure. To address this problem in the case of non-conserved dynamics we study an anisotropic version of the Burgers equation, constructed to describe thermal fluctuations of an interface in the presence of a uniform shear flow. As a result, we find that stretched domains are only marginally stable against thermal fluctuations in $d=2$, whereas they are stable in $d=3$.Comment: 3 pages, shorter version, additional reference

Sample size calculations for cluster randomised controlled trials with a fixed number of clusters

Background\ud Cluster randomised controlled trials (CRCTs) are frequently used in health service evaluation. Assuming an average cluster size, required sample sizes are readily computed for both binary and continuous outcomes, by estimating a design effect or inflation factor. However, where the number of clusters are fixed in advance, but where it is possible to increase the number of individuals within each cluster, as is frequently the case in health service evaluation, sample size formulae have been less well studied. \ud \ud Methods\ud We systematically outline sample size formulae (including required number of randomisation units, detectable difference and power) for CRCTs with a fixed number of clusters, to provide a concise summary for both binary and continuous outcomes. Extensions to the case of unequal cluster sizes are provided. \ud \ud Results\ud For trials with a fixed number of equal sized clusters (k), the trial will be feasible provided the number of clusters is greater than the product of the number of individuals required under individual randomisation ($n_i$) and the estimated intra-cluster correlation ($\rho$). So, a simple rule is that the number of clusters ($\kappa$) will be sufficient provided: \ud \ud $\kappa$ > $n_i$ x $\rho$\ud \ud Where this is not the case, investigators can determine the maximum available power to detect the pre-specified difference, or the minimum detectable difference under the pre-specified value for power. \ud \ud Conclusions\ud Designing a CRCT with a fixed number of clusters might mean that the study will not be feasible, leading to the notion of a minimum detectable difference (or a maximum achievable power), irrespective of how many individuals are included within each cluster. \ud \u

The perceived barriers to the inclusion of rainwater harvesting systems by UK house building companies

This work investigates the barriers that exist to deter the implementation of rainwater harvesting into new UK housing. A postal questionnaire was sent to a selection of large, medium and small house-builders distributed across the UK. Questions were asked concerning potential barriers to the inclusion of rainwater harvesting in homes separated into five sections; (1) institutional and regulatory gaps, (2) economic and financial constraints, (3) absence of incentives, (4) lack of information and technical knowledge, and (5) house-builder attitudes. The study concludes that although the knowledge of rainwater systems has increased these barriers are deterring house-builders from installing rainwater harvesting systems in new homes. It is further acknowledged that the implementation of rainwater harvesting will continue to be limited whilst these barriers remain and unless resolved, rainwater harvesting's potential to reduce the consumption of potable water in houses will continue to be limited

Colonic Catabolism of Ellagitannins, Ellagic Acid, and Raspberry Anthocyanins: In Vivo and In Vitro Studies

ABSTRACT: Red raspberries contain principally anthocyanins and ellagitannins. After ingestion of raspberries by humans, trace levels of anthocyanins, absorbed in the upper gastrointestinal tract, are excreted in urine in amounts corresponding to &lt;0.1% of intake. Urine also contains urolithin-O-glucuronides derived from colonic metabolism of the ellagitannins. Raspberry feedings with ileostomists show that substantial amounts of the anthocyanin and ellagitannin intake are excreted in ileal fluid. In subjects with an intact functioning colon, these compounds would pass to the large intestine. The aim of this study was to identify raspberry-derived phenolic acid catabolites that form in the colon and those that are subsequently excreted in urine. In vitro anaerobic incubation of ellagitannins with fecal suspensions demonstrated conversion to ellagic acid and several urolithins. Fecal suspensions converted 80% of added ellagic acid to urolithins. In vivo, urolithins are excreted in urine as O-glucuronides, not aglycones, indicating that the colonic microflora convert ellagitannins to urolithins, whereas glucuronidation occurs in the wall of the large intestine and/or postabsorption in the liver. Unlike ellagitannins, raspberry anthocyanins were converted in vitro to phenolic acids by anaerobic fecal suspensions. Urinary excretion of phenolic acids after ingestion of raspberries indicates that after formation in the colon some phenolic acids undergo phase II metabolism, resulting in the formation of products that do not accumulate when anthocyanins are degraded in fecal suspensions. There is a growing realization that colonic catabolites such as phenolic acids and urolithins may have important roles in the protective effects of a fruit-and vegetablerich diet