The Web Can Be Suitable for Learning

The authors discuss the advantages and difficulties of Web-based online distance learning. Web-based ODL can and does work for most learners when designed with high levels of interactivity and when cost and access issues can be adequately addressed. However, Web-based ODL requires a fundamental paradigm shift in how we define concepts like education and the classroom

The Web Can Be Suitable for Learning

The authors discuss the advantages and difficulties of Web-based online distance learning. Web-based ODL can and does work for most learners when designed with high levels of interactivity and when cost and access issues can be adequately addressed. However, Web-based ODL requires a fundamental paradigm shift in how we define concepts like education and the classroom

Shorter length dialysis sessions are associated with increased mortality, independent of body weight

Hemodialysis patients have high rates of mortality that may be related to aspects of the dialytic procedure. In prior studies, shorter length dialysis sessions have been associated with decreased survival, but these studies may have been confounded by body size differences. Here we tested whether in-center thrice-weekly hemodialysis patients with adequate urea clearances but shorter dialysis session length is associated with mortality independent of body size. Data were taken from a large national cohort of patients from a large dialysis organization undergoing thrice-weekly, in-center hemodialysis. In the primary analysis, patients with prescribed dialysis sessions greater and less than 240 minutes were pair-matched on post-dialysis weight as well as on age, gender, and vascular access type. Compared to prescribed longer dialysis sessions, session lengths less than 240 minutes were significantly associated with increased all-cause mortality (adjusted hazard ratio 1.26). The association was consistent across strata of age, gender, and dialysis post-weight. Secondary analyses found a dose-response between prescribed session length and survival. Thus, among patients with adequate urea clearance, shorter dialysis session lengths are associated with increased mortality independent of body weight

Feral Goats and Sheep

Sheep and goats are among the earliest animals domesticated by mankind (Zeder 2009). Both goats and sheep may have made better candidates for domestication than other animals like deer because they follow a single dominant leader, the herdsman (Geist 1971). They now have a nearly ubiquitous worldwide distribution, and they are among the most abundant of all commensal animals. However, they have also become some of the most widespread invasive feral mammals, particularly on the 100 or more islands throughout the world where they have been introduced, causing severe damage to island ecosystems, in some cases for hundreds of years (Rudge 1984; Chynoweth 2013). Problems caused by feral goats and sheep are a subset of the larger problem of domestic livestock and natural systems. Feral goats are perhaps more widespread than feral sheep because goats have not been as highly modified by the process of domestication (Francis 2015). The Bezoar ibex (Capra aegagrus) is the most likely ancestor of domestic goats (C. hircus) from both genetic and paleontological evidence (Pidancier et al. 2006). The domestication process started at least 10,000 years ago in highlands of western Iran, beginning with the selective harvesting of subadult males and the transition from hunting to herding of the species (Zeder and Hesse 2000). Multiple independent domestication events may have occurred or domestication may have incorporated multiple ancestral lineages (Pidancier et al. 2006). Traits selected during domestication include behavior, dairy, meat, skins, pelage color, mohair, cashmere, horns, pathogen resistance, and even intestines for catgut. Selection for reduced body size may have been related to the ability to better survive in hot and arid environments (Zeder 2009). A profound reduction in horn size occurred after humans began to control breeding, particularly in males, possibly associated with the absence of selective pressures for large horns used in mate competition (Zeder 2009)

Evaporation of Lennard-Jones Fluids

Evaporation and condensation at a liquid/vapor interface are ubiquitous interphase mass and energy transfer phenomena that are still not well understood. We have carried out large scale molecular dynamics simulations of Lennard-Jones (LJ) fluids composed of monomers, dimers, or trimers to investigate these processes with molecular detail. For LJ monomers in contact with a vacuum, the evaporation rate is found to be very high with significant evaporative cooling and an accompanying density gradient in the liquid domain near the liquid/vapor interface. Increasing the chain length to just dimers significantly reduces the evaporation rate. We confirm that mechanical equilibrium plays a key role in determining the evaporation rate and the density and temperature profiles across the liquid/vapor interface. The velocity distributions of evaporated molecules and the evaporation and condensation coefficients are measured and compared to the predictions of an existing model based on kinetic theory of gases. Our results indicate that for both monatomic and polyatomic molecules, the evaporation and condensation coefficients are equal when systems are not far from equilibrium and smaller than one, and decrease with increasing temperature. For the same reduced temperature $T/T_c$, where $T_c$ is the critical temperature, these two coefficients are higher for LJ dimers and trimers than for monomers, in contrast to the traditional viewpoint that they are close to unity for monatomic molecules and decrease for polyatomic molecules. Furthermore, data for the two coefficients collapse onto a master curve when plotted against a translational length ratio between the liquid and vapor phase.Comment: revised version, 15 pages, 15 figures, to appear in J. Chem. Phy

Relational observables in 2d quantum gravity

Local observation is an important problem both for the foundations of a quantum theory of gravity and for applications to quantum-cosmological problems such as eternal inflation. While gauge invariant local observables can't be defined, it has been argued that appropriate relational observables approximately reduce to local observables in certain states. However, quantum mechanics and gravity together imply limitations on the precision of their localization. Such a relational framework is studied in the context of two-dimensional gravity, where there is a high degree of analytic control. This example furnishes a concrete example of some of the essential features of relational observables.Comment: 15 pages, 1 figure, harvmac. v1: reference adde

Environmental risk factors for canine atopic dermatitis: a retrospective large‐scale study in Labrador and golden retrievers

Background - canine atopic dermatitis (cAD) is one the most common and distressing skin disorders seen in dogs. It is characterised by dysfunction in the skin barrier, with a complex pathogenesis combining both genetic and environmental factors.Objectives - to evaluate associations between environmental factors and case-control status in two closely related, at-risk breeds, the Labrador and Golden retriever.Animals - 2,445 pet dogs, of which 793 were classed as cases (575 Labradors and218 Golden retrievers) and 1,652 as controls (1,120 Labradors and 532 Golden retrievers). Methods – case-control status was assigned based upon owner response to a standardised validated questionnaire. Retrospective data on rearing environment was collected via additional questions. Univariate and multivariate logistic regressions were utilised to evaluate associations between environmental factors and case-control status.Results - risk factors included being reared in an urban environment (not living currently in an urban environment), being male, being neutered, receiving flea control, and being allowed on upholstered furniture. Protective factors included living with other dogs (not cats) and walking in woodlands, fields or beaches. Additionally, amongst Labradors, chocolate coated dogs were at greater risk of having cAD than black or yellow coated dogs.Conclusions and clinical importance - This study is the largest of its kind to date to investigate the role of the environment in canine atopic dermatitis. Although precise triggers are unclear, this study contributes to those of earlier studies to highlight the protective role of a rural environment and highlights some novel associations with disease development

Genome sequence of the Bacteroides fragilis phage ATCC 51477-B1

The genome of a fecal pollution indicator phage, Bacteroides fragilis ATCC 51477-B1, was sequenced and consisted of 44,929 bases with a G+C content of 38.7%. Forty-six putative open reading frames were identified and genes were organized into functional clusters for host specificity, lysis, replication and regulation, and packaging and structural proteins

Peak rates of diuresis in healthy humans during oral fluid overload

Objective. To determine whether rates of intestinal fluid absorption and renal diuresis can match high rates of fluid ingestion in healthy humans exposed to oral fluid overload, thereby preventing the development of hyponatraemia either by reverse sodium movement across the intestine (the Priestley-Haldane effect) or by expansion of the extracellular fluid volume.Methods. Changes in renal function and in plasma chemical measurements in response to an oral fluid overload (0.9 - 1.8 1/ h x 3 h) were investigated in 6 healthy control subjects at rest, and in a subject with a history of exercise induced symptomatic hyponatraemia, during both prolonged (160-minute) exercise and at rest.Findings. All control subjects gained weight (2.7 ± 0.2 kg, mean ± standard error of mean (SEM)) because the rate of oral fluid intake exceeded the peak rate of urine production (778 ± 39 rnl / h). Blood volume rose by 7.1 (± 0.5)% and plasma sodium concentrations fell progressively from 144 ± 2.6 to 136 ± 1.1 mmol/ 1 (P < 0.05) in the control subjects. Plasma potassium and angiotensin II concentrations were unchanged and creatinine clearance was normal ( -125 rnl/min). Free water clearance reached a maximum of 11.2 ± 0.9 rnl/min after 2 hours. The increase in body mass could be accounted for by calculated or measured changes in extra- and intracellular fluid volumes. Similar changes were measured in the subject with a previous history of symptomatic hyponatraernia.Conclusion. The rate of intestinal fluid absorption appeared to match the rate of oral fluid ingestion and there was no  evidence of fluid accumulation in the intestine with reverse sodium movement from the extracellular space into intestinal fluid. The results of this study are therefore at variance with the Priestley-Haldane hypothesis and suggest that reverse sodium movement did not contribute to the hyponatraernia induced by oral fluid overload in these subjects. Rather it appears that humans may have a limited capacity to excrete fluid at rates in excess of -900 rnl/ h in response to higher rates of oral fluid intake. When the rate of intestinal fluid absorption matches the rate of fluid ingestion and exceeds the kidneys' maximum capacity for fluid excretion, the excess fluid accumulates in the extra- and intracellular fluid compartments, inducing the dilutional hyponatraemia of water intoxication. These findings may have relevance to other clinical conditions in which hyponatraemia develops in response to high rates of oral or intravenous fluid provision