Vesicle shape, molecular tilt, and the suppression of necks

Can the presence of molecular-tilt order significantly affect the shapes of lipid bilayer membranes, particularly membrane shapes with narrow necks? Motivated by the propensity for tilt order and the common occurrence of narrow necks in the intermediate stages of biological processes such as endocytosis and vesicle trafficking, we examine how tilt order inhibits the formation of necks in the equilibrium shapes of vesicles. For vesicles with a spherical topology, point defects in the molecular order with a total strength of $+2$ are required. We study axisymmetric shapes and suppose that there is a unit-strength defect at each pole of the vesicle. The model is further simplified by the assumption of tilt isotropy: invariance of the energy with respect to rotations of the molecules about the local membrane normal. This isotropy condition leads to a minimal coupling of tilt order and curvature, giving a high energetic cost to regions with Gaussian curvature and tilt order. Minimizing the elastic free energy with constraints of fixed area and fixed enclosed volume determines the allowed shapes. Using numerical calculations, we find several branches of solutions and identify them with the branches previously known for fluid membranes. We find that tilt order changes the relative energy of the branches, suppressing thin necks by making them costly, leading to elongated prolate vesicles as a generic family of tilt-ordered membrane shapes.Comment: 10 pages, 7 figures, submitted to Phy. Rew.

Assessment of emergency medical services in the Ashanti region of Ghana

Background: We aimed to assess the structure, function and performance of Ashanti Region’s emergency medical services system in the context of the regional need for prehospital emergency care.Design: A mixed-methods approach was employed, using retrospective collection of quantitative data and prospectively gathered qualitative data. Setting – pertinent data were collected from Ghanaian and international sources; interviews and technical assessments were performed primarily in the Ashanti Region of Ghana.Participants: All stakeholders relevant to emergency medical services in the Ashanti Region of Ghana were assessed; there was a special focus on National Ambulance Service (NAS) and Ashanti Region healthcare personnel.Intervention: This was an observational study using qualitative and quantitative assessment techniques.Main outcome measures: The structure, function and performance of the Ashanti emergency medical services system, guided by a relevant technical assessment framework.Results: NAS is the premier and only true prehospital agency in the Ashanti Region. NAS has developed almost every essential aspect of an EMS system necessary to achieve its mission within a low-resource setting. NAS continues to increase its number of response units to address the overwhelming Ashanti region demand, especially primary calls. Deficient areas in need of development are governance, reliable revenue, public access, community integration, clinical care guidelines, research and quality assurance processes.Conclusions: The Ashanti Region has a growing and thriving emergency medical services system. Although many essential areas for development were identified, NAS is well poised to meet the regional demand for prehospital emergency care and transport.Keywords: EMS, prehospital, ambulance, emergency, Ghana, Afric

The compensation of Gaussian curvature in developable cones is local

In this paper we use the angular deficit scheme [V. Borrelli, F. Cazals, and J.-M. Morvan, {\sl Computer Aided Geometric Design} {\bf 20}, 319 (2003)] to determine the distribution of Gaussian curvature in developable cones (d-cones) [E. Cerda, S. Chaieb, F. Melo, and L. Mahadevan, {\sl Nature} {\bf 401}, 46 (1999)] numerically. These d-cones are formed by pushing a thin elastic sheet into a circular container. Negative Gaussian curvatures are identified at the rim where the sheet touches the container. Around the rim there are two narrow bands with positive Gaussian curvatures. The integral of the (negative) Gaussian curvature near the rim is almost completely compensated by that of the two adjacent bands. This suggests that the Gauss-Bonnet theorem which constrains the integral of Gaussian curvature globally does not explain the spontaneous curvature cancellation phenomenon [T. Liang and T. A. Witten, {\sl Phys. Rev. E} {\bf 73}, 046604 (2006)]. The locality of the compensation seems to increase for decreasing d-cone thickness. The angular deficit scheme also provides a new way to confirm the curvature cancellation phenomenon.Comment: 12 pages; 5 figure

The centenary of Annals of Applied Biology in 2014

Annals of Applied Biology (Annals)  has  published the results of original research in applied biology for 100 years. The journal was established because of the need for a more efficient distribution of scientific information of applied importance, especially in agriculture and horticulture. Over the years, most papers in Annals have reported on crop science, horticulture, pests and diseases of field crops and horticultural plants, and plant breeding. The scope of the journal has remained consistent, although currently the research fields covered in Annals can also be described using the terms agriculture and the environment, crop improvement, pest and invertebrate biology, and plant–pathogen interactions. Maintaining high standards of statistical analysis in the papers published has always been emphasised in Annals. The Centenary of Annals in 2014 will be celebrated by highlighting some of the most influential papers published in the journal over the 100 years. These papers have been selected by the Senior Editors (the authors of this editorial), following consultation of the Editorial Board of Annals, which consists of scientists from all parts of the world. Each issue of Annals in 2014 will contain at least one Centenary editorial that introduces an influential paper. Furthermore, the same issue will contain a solicited review article related to the influential paper. The first influential paper introduced in this issue is the study by Chester I. Bliss (1935) on the calculation of the dosage‐mortality curve, which has been cited over 850 times and is still regularly referred to today. The editorial has been written by David Finney, who knew Bliss personally and who acted as an unofficial statistical editor of the journal during the period 1942–54. It is noteworthy that this editorial marks 76 years since David Finney's first publication in 1938 (Finney, 1938). The review article has been written by Roger Payne, who was the Senior Statistical Editor of Annals from 1980 to 1989. The editorials, influential papers and review articles will be made available for free access on the home page of Annals (http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1744‐7348). The Association of Applied Biologists (Association) will organise a Centenary conference under the title ‘Sustainable Intensification’ in December 2014. For details of the programme and other details, please refer to the home page of the Association in the near future (http://www.aab.org.uk/). In the following sections we provide some perspectives as to the development of Annals as a scientific journal and statistical data on its impact in the field of applied biology

Dynamics of filaments and membranes in a viscous fluid

Motivated by the motion of biopolymers and membranes in solution, this article presents a formulation of the equations of motion for curves and surfaces in a viscous fluid. We focus on geometrical aspects and simple variational methods for calculating internal stresses and forces, and we derive the full nonlinear equations of motion. In the case of membranes, we pay particular attention to the formulation of the equations of hydrodynamics on a curved, deforming surface. The formalism is illustrated by two simple case studies: (1) the twirling instability of straight elastic rod rotating in a viscous fluid, and (2) the pearling and buckling instabilities of a tubular liposome or polymersome.Comment: 26 pages, 12 figures, to be published in Reviews of Modern Physic

Modeling of droplet generation in a top blowing steelmaking process

Quantification of metal droplets ejected due to impinging gas jet on the surface of liquid metal is an important parameter for the understanding and for the modeling of the refining kinetics of reactions in slag-metal emulsion zone. In the present work, a numerical study has been carried out to critically examine the applicability of droplet generation rate correlation previously proposed by Subagyo et al. on the basis of dimensionless blowing number (N B). The blowing number was re-evaluated at the impingement point of jet with taking into account the temperature effect of change in density and velocity of the gas jet. The result obtained from the work shows that the modified blowing number N B,T at the furnace temperature of 1873 K (1600 °C) is approximately double in magnitude compared to N B calculated by Subagyo and co-workers. When N B,T has been employed to the Subagyo’s empirical correlation for droplet generation, a wide mismatch is observed between the experimental data obtained from cold model and hot model experiments. The reason for this large deviation has been investigated in the current study, and a theoretical approach to estimate the droplet generation rate has been proposed. The suitability of the proposed model has been tested by numerically calculating the amount of metals in slag. The study shows that the weight of metals in emulsion falls in the range of 0 to 21 wt pct of hot metal weight when droplet generation rate has been calculated at ambient furnace temperature of 1873 K (1600 °C)

Novel sampling method for assessing human-pathogen interactions in the natural environment using boot socks and citizen scientists, with application to Campylobacter seasonality

This paper introduces a novel method for sampling pathogens in natural environments. It uses fabric boot socks worn over walkers' shoes to allow the collection of composite samples over large areas. Wide-area sampling is better suited to studies focusing on human exposure to pathogens (e.g., recreational walking). This sampling method is implemented using a citizen science approach: groups of three walkers wearing boot socks undertook one of six routes, 40 times over 16 months in the North West (NW) and East Anglian (EA) regions of England. To validate this methodology, we report the successful implementation of this citizen science approach, the observation that Campylobacter bacteria were detected on 47% of boot socks, and the observation that multiple boot socks from individual walks produced consistent results. The findings indicate higher Campylobacter levels in the livestock-dominated NW than in EA (55.8% versus 38.6%). Seasonal differences in the presence of Campylobacter bacteria were found between the regions, with indications of winter peaks in both regions but a spring peak in the NW. The presence of Campylobacter bacteria on boot socks was negatively associated with ambient temperature (P = 0.011) and positively associated with precipitation (P < 0.001), results consistent with our understanding of Campylobacter survival and the probability of material adhering to boot socks. Campylobacter jejuni was the predominant species found; Campylobacter coli was largely restricted to the livestock-dominated NW. Source attribution analysis indicated that the potential source of C. jejuni was predominantly sheep in the NW and wild birds in EA but did not differ between peak and nonpeak periods of human incidence

Opportunities for mesoscopics in thermometry and refrigeration: Physics and applications

This review presents an overview of the thermal properties of mesoscopic structures. The discussion is based on the concept of electron energy distribution, and, in particular, on controlling and probing it. The temperature of an electron gas is determined by this distribution: refrigeration is equivalent to narrowing it, and thermometry is probing its convolution with a function characterizing the measuring device. Temperature exists, strictly speaking, only in quasiequilibrium in which the distribution follows the Fermi-Dirac form. Interesting nonequilibrium deviations can occur due to slow relaxation rates of the electrons, e.g., among themselves or with lattice phonons. Observation and applications of nonequilibrium phenomena are also discussed. The focus in this paper is at low temperatures, primarily below 4 K, where physical phenomena on mesoscopic scales and hybrid combinations of various types of materials, e.g., superconductors, normal metals, insulators, and doped semiconductors, open up a rich variety of device concepts. This review starts with an introduction to theoretical concepts and experimental results on thermal properties of mesoscopic structures. Then thermometry and refrigeration are examined with an emphasis on experiments. An immediate application of solid-state refrigeration and thermometry is in ultrasensitive radiation detection, which is discussed in depth. This review concludes with a summary of pertinent fabrication methods of presented devices.Comment: Close to the version published in RMP; 59 pages, 35 figure

Combining Enzalutamide with Abiraterone, Prednisone, and Androgen Deprivation Therapy in the STAMPEDE Trial

There are compelling reasons to study the addition of both enzalutamide and abiraterone, in combination, to standard-of-care for hormone-naïve prostate cancer. Through a protocol amendment, this will be assessed in the STAMPEDE trial, with overall survival as primary outcome measure. © 2014 European Association of Urology

The retirement experiences of elite female gymnasts: Self identity and the physical self

This study explored experiences of retirement from elite sport among a sample of retired female gymnasts. Given the young age at which female gymnasts begin and end their sport careers, particular attention was afforded to the role of identity and the physical self in the process of adaptation. Retrospective, semi-structured interviews were conducted and interview transcripts analyzed using interpretative phenomenological analysis. Analysis indicated that retirement from gymnastics engendered adjustment difficulties for six of the seven participants. Identity loss was particularly salient, and for two gymnasts, physical changes associated with retirement were a further source of distress. The challenge of athletic retirement was intensified because the gymnasts had heavily invested in sport during adolescence, a period demarcated for the pursuit of an identity. Furthermore, their retirement coincided with a time when adolescents typically undergo profound changes physiologically. Practical suggestions to facilitate athletes' disengagement from sport are discussed