5,315 research outputs found
Daytime lidar measurements of tidal winds in the mesospheric sodium layer at Urbana, Illinois
For more than 15 years lidar systems have been used to study the chemistry and dynamics of the mesospheric sodium layer. Because the layer is an excellent tracer of atmospheric wave motions, sodium lidar has proven to be particularly useful for studying the influence of gravity waves and tides on mesospheric dynamics. These waves, which originate in the troposphere and stratosphere, propagate through the mesosphere and dissipate their energy near the mesopause making important contributions to the momentum and turbulence budget in this region of the atmosphere. Recently, the sodium lidar was modified for daytime operation so that wave phenomena and chemical effects could be monitored throughout the complete diurnal cycle. The results of continuous 24 hour lidar observations of the sodium layer structure are presented alond with measurement of the semidiurnal tidal winds
Scanning Electron Microscopy of Kidney Cells in Culture: Surface Features of Polarized Epithelia
We have used scanning electron microscopy (SEM) to examine the surface morphology of the renal epithelial cell lines MDCK and LLC-PK1 to determine the influence of alternative culture substrate conditions on cell polarity. We observed that regardless of physical culture conditions, cells establishes and maintained polarity, expressed by the characteristics of apical and basal surfaces. culture conditions did, however, influence the orientation of cell polarity in vitro. MDCK cells were grown within collagen gel, in which individual cells exhibited clonal growth to form fluid-filled epithelial cysts. The cells of MDCK-cysts were polarized with apical surface facing the lumen and basal surface against the surrounding collagen gel. This configuration made it possible to gain direct visual access, by SEM, to the basal surface by removing the supportive collagen lattice. The apical surface of MDCK-cysts was lined by short microvilli. Each cell possessed a solitary cilium. In comparison, the basal surface had few appendages, although cell boundaries were marked by interdigitating short processes. LLC-PK1 cells in monolayer culture bore solitary cilia and long microvilli at their apical surface. The basal surface of cells involved in dome formation was observed to possess only a sparse population of short, blunt processes. When LLC-PK1 cells were raised in stationary suspension culture or in monolayer atop non-culture grade plastic, they formed cysts with the cell apex facing the surrounding medium. These cells showed variable apical morphology. The cells of large, highly expanded cysts were often attenuated and had a relatively smooth apical surface. The basal surface of cells of fractured LLC-PK1 cysts commonly was also smooth, without prominent appendages
Polarized Epithelial Cysts in vitro: A Review of Cell and Explant Culture Systems that Exhibit Epithelial Cyst Formation
The purpose of this paper is to review in vitro cell and explant culture systems that exhibit epithelial cyst formation and that are used as models of polarized epithelial function. We examine a number of culture systems derived from a variety of cell and organ types, briefly describe the methodology and conditions used to establish these cultures and discuss aspects of the experimental application of each system. We conclude that the characteristics of epithelial cyst-forming cultures are dependent upon the origin and identity of the cell population, as well as the multiple factors that define the culture environment. Culture systems in which epithelial cyst development occurs provide tools to study fundamental problems in epithelial biology, such as the establishment and maintenance of cell polarity, cell recognition and cell sorting, also cell-specific functions involving solute and water transport and the production and modification of secreted products. In addition, epithelial cyst culture systems offer useful models to better understand cellular behavior in various pathologic conditions of cyst formation in man
A canonical ensemble approach to graded-response perceptrons
Perceptrons with graded input-output relations and a limited output precision
are studied within the Gardner-Derrida canonical ensemble approach. Soft non-
negative error measures are introduced allowing for extended retrieval
properties. In particular, the performance of these systems for a linear and
quadratic error measure, corresponding to the perceptron respectively the
adaline learning algorithm, is compared with the performance for a rigid error
measure, simply counting the number of errors. Replica-symmetry-breaking
effects are evaluated.Comment: 26 pages, 10 ps figure
Thermal noise limitations to force measurements with torsion pendulums: Applications to the measurement of the Casimir force and its thermal correction
A general analysis of thermal noise in torsion pendulums is presented. The
specific case where the torsion angle is kept fixed by electronic feedback is
analyzed. This analysis is applied to a recent experiment that employed a
torsion pendulum to measure the Casimir force. The ultimate limit to the
distance at which the Casimir force can be measured to high accuracy is
discussed, and in particular the prospects for measuring the thermal correction
are elaborated upon.Comment: one figure, five pages, to be submitted to Phys Rev
Factors that impact on recruitment to randomised trials in health care: a qualitative evidence synthesis
BACKGROUND: Randomised trials (also referred to as 'randomised controlled trials' or 'trials') are the optimal way to minimise bias in evaluating the effects of competing treatments, therapies and innovations in health care. It is important to achieve the required sample size for a trial, otherwise trialists may not be able to draw conclusive results leading to research waste and raising ethical questions about trial participation. The reasons why potential participants may accept or decline participation are multifaceted. Yet, the evidence of effectiveness of interventions to improve recruitment to trials is not substantial and fails to recognise these individual decision-making processes. It is important to synthesise the experiences and perceptions of those invited to participate in randomised trials to better inform recruitment strategies. OBJECTIVES: To explore potential trial participants' views and experiences of the recruitment process for participation. The specific objectives are to describe potential participants' perceptions and experiences of accepting or declining to participate in trials, to explore barriers and facilitators to trial participation, and to explore to what extent barriers and facilitators identified are addressed by strategies to improve recruitment evaluated in previous reviews of the effects of interventions including a Cochrane Methodology Review. SEARCH METHODS: We searched the Cochrane Library, Medline, Embase, CINAHL, Epistemonikos, LILACS, PsycINFO, ORRCA, and grey literature sources. We ran the most recent set of searches for which the results were incorporated into the review in July 2017. SELECTION CRITERIA: We included qualitative and mixed-methods studies (with an identifiable qualitative component) that explored potential trial participants' experiences and perceptions of being invited to participate in a trial. We excluded studies that focused only on recruiters' perspectives, and trials solely involving children under 18 years, or adults who were assessed as having impaired mental capacity. DATA COLLECTION AND ANALYSIS: Five review authors independently assessed the titles, abstracts and full texts identified by the search. We used the CART (completeness, accuracy, relevance, timeliness) criteria to exclude studies that had limited focus on the phenomenon of interest. We used QSR NVivo to extract and manage the data. We assessed methodological limitations using the Critical Skills Appraisal Programme (CASP) tool. We used thematic synthesis to analyse and synthesise the evidence. This provided analytical themes and a conceptual model. We used the GRADE-CERQual (Confidence in the Evidence from Reviews of Qualitative research) approach to assess our confidence in each finding. Our findings were integrated with two previous intervention effectiveness reviews by juxtaposing the quantitative and qualitative findings in a matrix. MAIN RESULTS: We included 29 studies (published in 30 papers) in our synthesis. Twenty-two key findings were produced under three broad themes (with six subthemes) to capture the experience of being invited to participate in a trial and making the decision whether to participate. Most of these findings had moderate to high confidence. We identified factors from the trial itself that influenced participation. These included how trial information was communicated, and elements of the trial such as the time commitment that might be considered burdensome. The second theme related to personal factors such as how other people can influence the individual's decision; and how a personal understanding of potential harms and benefits could impact on the decision. Finally, the potential benefits of participation were found to be key to the decision to participate, namely personal benefits such as access to new treatments, but also the chance to make a difference and help others. The conceptual model we developed presents the decision-making process as a gauge and the factors that influence whether the person will, or will not, take part. AUTHORS' CONCLUSIONS: This qualitative evidence synthesis has provided comprehensive insight into the complexity of factors that influence a person's decision whether to participate in a trial. We developed key questions that trialists can ask when developing their recruitment strategy. In addition, our conceptual model emphasises the need for participant-centred approaches to recruitment. We demonstrated moderate to high level confidence in our findings, which in some way can be attributed to the large volume of highly relevant studies in this field. We recommend that these insights be used to direct or influence or underpin future recruitment strategies that are developed in a participant-driven way that ultimately improves trial conduct and reduces research waste
CMS Connect
The CMS experiment collects and analyzes large amounts of data coming from high energy particle collisions produced by the Large Hadron Collider (LHC) at CERN. This involves a huge amount of real and simulated data processing that needs to be handled in batch-oriented platforms. The CMS Global Pool of computing resources provide +100K dedicated CPU cores and another 50K to 100K CPU cores from opportunistic resources for these kind of tasks and even though production and event processing analysis workflows are already managed by existing tools, there is still a lack of support to submit final stage condor-like analysis jobs familiar to Tier-3 or local Computing Facilities users into these distributed resources in an integrated (with other CMS services) and friendly way. CMS Connect is a set of computing tools and services designed to augment existing services in the CMS Physics community focusing on these kind of condor analysis jobs. It is based on the CI-Connect platform developed by the Open Science Grid and uses the CMS GlideInWMS infrastructure to transparently plug CMS global grid resources into a virtual pool accessed via a single submission machine. This paper describes the specific developments and deployment of CMS Connect beyond the CI-Connect platform in order to integrate the service with CMS specific needs, including specific Site submission, accounting of jobs and automated reporting to standard CMS monitoring resources in an effortless way to their users
Simulating complex social behaviour with the genetic action tree kernel
The concept of genetic action trees combines action trees with genetic algorithms. In this paper, we create a multi-agent simulation on the base of this concept and provide the interested reader with a software package to apply genetic action trees in a multi-agent simulation to simulate complex social behaviour. An example model is introduced to conduct a feasibility study with the described method. We find that our library can be used to simulate the behaviour of agents in a complex setting and observe a convergence to a global optimum in spite of the absence of stable states
The propensity to bargain while on a vacation
This article assesses how tourists' bargaining motivations and attitudes moderate their willingness to return to Italy, where bargaining is perceived as one of the best ways to deal with sellers. A non-probability quota sampling technique was used to survey domestic tourists in Italy through an online questionnaire which encompassed 26 bargaining values and one item to measure the likelihood that the tourists would bargain at the same destination in the future. The data comprised a total of 812 observations. An order probit model and marginal effects were estimated to measure the tourists' propensity to return to Italy for bargaining purposes. The study findings indicate that tourists' propensity to return for bargaining purposes is taken with the awareness that they will not obtain what they expected; as a matter of fact, they are unlikely to care about the final result but instead engage in this behaviour to have fun.FCT - National Funding Agency for Science, Research and Technology [UID/ECO/04007/2013 CEFAGE
Aboriginal young people’s perspectives and experiences of accessing sexual health services and sex education in Australia: A qualitative study
Aboriginal and Torres Strait Islander (Aboriginal) young people seek information and access health services for their sexual health needs. This study examined Aboriginal young people’s perspectives on sexual health services and sex education in Australia. Overall, 51 Aboriginal people aged 16–26 years were interviewed by peer researchers in Sydney, Australia in 2019–2020. The findings suggest that the internet was used to assess information quickly and confidentially, but Aboriginal young people questioned its reliability and accuracy. Family, Elders and peers were seen as sources of advice because they had real-life experience and highlighted intergenerational learning that occurs in Aboriginal communities. School-based sex education programmes had mixed reviews, with a preference for programmes delivered by external specialists providing anonymity, clear and accurate information about sex and relationships and positive approaches to sex education, including how to gain consent before sex. There was a need identified for school-based programmes to better consider the needs of Aboriginal young people, including those who identified as LGBTQI +. Aboriginal Medical Services were highly valued for providing culturally safe access to services, while sexual health clinics were valued for providing specialised confidential clinical services with low levels of judgement
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