The generation of longshore currents on a plane beach

The generation of longshore currents on a beach is investigated theoretically, using the concept of radiation stress to describe the flux of momentum associated with the incoming waves. Outside the surf zone, the longshore gradient of the radiation stress is always zero, and the flow is therefore driven only inside the surf zone...

Evaluation of a Web-Based Research Course

A web-based research course for graduate nursing students was developed, implemented, and evaluated for academic and satisfactions outcomes. A collaborative paradigm was utilized in designing the course to increase successful attainment of the graduate nursing program’s goal of a complete online graduate nursing MSN program. This web-based research course with 24 enrolled students was compared to an identical classroom based research course with 20 enrolled students. Areas of evaluation were academic outcomes of overall numerical course grades, satisfaction with course scores, and qualitative data on satisfaction of course. Results of this descriptive exploratory study demonstrated no statistically significant differences between the academic outcomes of these two groups of students. Both groups were satisfied with the course, however there was a statistically significant difference in mean satisfaction scores for the research courses. Further investigation of environmental factors will need to be done to determine the significance of differences in satisfaction outcomes

Wind characteristics over complex terrain: laboratory simulation and field measurements at Rakaia Gorge, New Zealand: final report, part II

CER77-78RNM29.Prepared for the United States Department of Energy, Division of Solar Technology, Federal Wind Energy Program.DOE contract no. EY-76-S06-2438, A001.Includes bibliographical references (pages 93-102).May 1978

Mechanical characterization of torsional micro-paddles using atomic force microscopy

The reference cantilever method is shown to act as a direct and simple method for determination of torsional spring constant. It has been applied to the characterization of micropaddle structures similar to those proposed for resonant functionalized chemical sensors and resonant thermal detectors. It is shown that this method can be used as an effective procedure to characterize a key parameter of these devices and would be applicable to characterization of other similar MEMS/NEMS devices such as micromirrors. In this study, two sets of micropaddles are manufactured (beams at centre and offset by 2.5 μm) by using LPCVD silicon nitride as a substrate. The patterning is made by direct milling using focused ion beam. The torsional spring constant is achieved through micromechanical analysis via atomic force microscopy. To obtain the gradient of force curve, the area of the micropaddle is scanned and the behaviour of each pixel is investigated through an automated developed code. The experimental results are in a good agreement with theoretical results

Vertical structure of surface gravity waves propagating over a sloping sea bed: theory and field measurements

[1] Theoretical predictions of the vertical structure of wave motion over a sloping seabed are compared with field observations close to the bed in the nearshore zone. Of particular interest is the effect of the local slope on the magnitude and phase of the vertical velocity. Field measurements of near-bed velocity profiles on a 2°bed slope were obtained using a coherent Doppler profiler. The surface elevation was measured by a colocated, upward looking, acoustic sounder. Results are presented from two intervals of different wave energy levels during a storm event: for wave height/water depth ratios smaller than 0.3 and for Ursell numbers smaller than 0.6. The local comparisons of magnitude and phase between the vertical velocity and surface elevation measurements are in good agreement with linear theory for a sloping bed, but differ greatly from that for a horizontal bottom, especially in the lower water column. The sloping bottom, however, has little effect on the horizontal velocity. Linear theory appears to adequately describe the transfer function between the surface elevation and the near-bed velocities, not only at the peak frequencies but also at their harmonics. However, in relatively shallow water the local transformations of free and forced waves at the harmonic frequencies are indistinguishable in the lower water column. Therefore, given surface elevation measurements at a particular location (which reflect the integrated effects of nonlinearities associated with wave shoaling), the vertical structure of the third moments of velocity fields estimated from linear theory is in reasonable agreement with the observations. Both theory and observations show that the skewness and asymmetry of the vertical velocity are subject to significant bottom slope effects, whereas those of horizontal velocity are not. Citation: Zou, Q., A. E. Hay, and A. J. Bowen, Vertical structure of surface gravity waves propagating over a sloping seabed: Theory and field measurements

Edge waves in the presence of strong longshore currents

A form of the linear, inviscid shallow water wave equation which includes alongshore uniform, but cross-shore variable, longshore currents and bathymetry is presented. This formulation provides a continuum between gravity waves (either leaky or edge waves) on a longshore current, and the recently discovered shear waves. In this paper we will concentrate on gravity wave solutions for which V(x)/c < 1, where V(x) is the longshore current, and c is the edge wave celerity. The effects of the current can be uniquely accounted for in terms of a modification to the true beach profile, h'(x) = h(x) [I - V(x)/c]¯², where h(x) is the true profile and h'(x) is the effective profile. This is particularly useful in conceptualizing the combined effects of longshore currents and variable bottom topography. We have solved numerically for the dispersion relationship and the cross-shore shapes of edge waves on a plane beach under a range of current conditions. Changes to the edge wave alongshore wavenumber, K, of over 50% are found for reasonable current profiles, showing that the departure from plane beach dispersion due to longshore currents can be of the same order as the effect of introducing nonplanar topography. These changes are not symmetric as they are for profile changes; IKI increases for edge waves opposing the current flow (a shallower effective profile), but decreases for those coincident with the flow (a deeper effective profile). The cross-shore structure of the edge waves is also strongly modified. As lkl increases (decreases), the nodal structure shifts landward (seaward) from the positions found on the test beach in the absence of a current. In addition, the predicted variances away from the nodes, particularly for the alongshore component of edge wave orbital velocity, may change dramatically from the no-current case. Many of the edge wave responses are related to the ratio V max/c, where V max is the maximum current, and to the dimensionless cross-shore scale of the current, lkl x(V max), where x(V max) is the cross-shore distance to V max. This is most easily understood in terms of the effective profile and the strong dependence of the edge waves on the details of the inner part of the beach profile. Inclusion of the longshore current also has implications regarding the role of edge waves in the generation of nearshore morphology. For example, in the absence of a current, two phase-locked edge waves of equal frequency and mode progressing in opposite directions are expected to produce a crescentic bar. However, in the presence of a current, the wavenumbers would differ, stretching the expected crescentic bar into a welded bar. A more interesting effect is the possibility that modifications to the edge waves due to the presence of a virtual bar in the effective profile could lead to the development of a real sand bar on the true profile. These modifications appear to be only weakly sensitive to frequency, in contrast to the relatively strong dependence of the traditional model of sand bar generation at infragravity wave nodes

Training the next generation of clinical researchers: Evaluation of a graduate podiatrist research internship in rheumatology

Background: The aim of this study was to evaluate the effectiveness of the Arthritis Research UK funded graduate internship scheme for podiatrists and to explore the experiences of interns and mentors. Methods: Nine new graduates completed the internship programme (July 2006-June 2010); six interns and two mentors participated in this study. The study was conducted in three phases. Phase 1: quantitative survey of career and research outcomes for interns. Phase 2 and 3: qualitative asynchronous interviews through email to explore the experiences of interns and mentors. Interpretive phenomenological analysis (IPA) of coded transcripts identified recurring themes. Results: Research outputs included ten peer reviewed publications with authorial contributions from interns, 23 conference abstract presentations and one subsequent 'Jewel in the Crown' award at the British Society for Rheumatology Conference. Career progression includes two National Institute for Health research (NIHR) PhD fellowships, two Arthritis Research UK PhD fellowships, one NIHR Master of Research fellowship and one specialist rheumatology clinical post. Two interns are members of NIHR and professional body committees. Seven important themes arose from the qualitative phases: perceptions of the internship pre-application; internship values; maximising personal and professional development; psychosocial components of the internship; the role of mentoring and networking; access to research career pathways; perceptions of future developments for the internship programme. The role of mentorship and the peer support network have had benefits that have persisted beyond the formal period of the scheme. Conclusions: The internship model appears to have been perceived to have been valuable to the interns' careers and may have contributed significantly to the broader building of capacity in clinical research in foot and ankle rheumatology. We believe the model has potential to be transferable across health disciplines and on national and international scales

On flammability hazards from pressurised high-flashpoint liquid releases

Hazardous area classification is well established for dust and vapours, however this is not the case for high flashpoint liquid fuels. This study highlights the limitations of current guidance in relation to flammable mists, through demonstration of flammability of a representative high flashpoint fuel for releases in the range of representative industrial operating pressure, complemented by a phenomenological analysis and semi-quantification of the results observed. Flammability results are presented from low-pressure practical releases ( 61 °C), through a plain orifice, at temperatures well below its flashpoint. Based on a proposed two-phase flow-regime diagram, a semi-quantitate analysis of the results observed is offered via a simple 1-D phenomenological model, accommodating jet breakup length, spray quality, air entrainment and droplet dynamics. The complex scenario of liquid releases impinging onto an unheated flat surface is also considered. An impingement model is utilised to show the relative increase in volume of fine secondary spray induced post-impingement relative to the unobstructed case, resulting in a significant volume of flammable mist. This is demonstrated experimentally by showing flammability of a 5 barg release post impingement whereas the unobstructed 10 barg case would not ignite

Analysis of the role of 13 major fimbrial subunits in colonisation of the chicken intestines by Salmonella enterica serovar Enteritidis reveals a role for a novel locus

<p>Abstract</p> <p>Background</p> <p><it>Salmonella enterica </it>is a facultative intracellular pathogen of worldwide importance. Over 2,500 serovars exist and infections in humans and animals may produce a spectrum of symptoms from enteritis to typhoid depending on serovar- and host-specific factors. <it>S</it>. Enteritidis is the most prevalent non-typhoidal serovar isolated from humans with acute diarrhoeal illness in many countries. Human infections are frequently associated with direct or indirect contact with contaminated poultry meat or eggs owing to the ability of the organism to persist in the avian intestinal and reproductive tract. The molecular mechanisms underlying colonisation of poultry by <it>S</it>. Enteritidis are ill-defined. Targeted and genome-wide mutagenesis of <it>S</it>. Typhimurium has revealed conserved and host-specific roles for selected fimbriae in intestinal colonisation of different hosts. Here we report the first systematic analysis of each chromosomally-encoded major fimbrial subunit of <it>S</it>. Enteritidis in intestinal colonisation of chickens.</p> <p>Results</p> <p>The repertoire, organisation and sequence of the fimbrial operons within members of <it>S. enterica </it>were compared. No single fimbrial locus could be correlated with the differential virulence and host range of serovars by comparison of available genome sequences. Fimbrial operons were highly conserved among serovars in respect of gene number, order and sequence, with the exception of <it>safA</it>. Thirteen predicted major fimbrial subunit genes were separately inactivated by lambda Red recombinase-mediated linear recombination followed by P22/int transduction. The magnitude and duration of intestinal colonisation by mutant and parent strains was measured after oral inoculation of out-bred chickens. Whilst the majority of <it>S</it>. Enteritidis major fimbrial subunit genes played no significant role in colonisation of the avian intestines, mutations affecting <it>pegA </it>in two different <it>S</it>. Enteritidis strains produced statistically significant attenuation. Plasmid-mediated <it>trans</it>-complementation partially restored the colonisation phenotype.</p> <p>Conclusion</p> <p>We describe the fimbrial gene repertoire of the predominant non-typhoidal <it>S. enterica </it>serovar affecting humans and the role played by each predicted major fimbrial subunit in intestinal colonisation of the primary reservoir. Our data support a role for PegA in the colonisation of poultry by <it>S</it>. Enteritidis and aid the design of improved vaccines.</p