514 research outputs found
Estimative for the size of the compactification radius of a one extra dimension Universe
In this work, we use the Casimir effect to probe the existence of one extra
dimension. We begin by evaluating the Casimir pressure between two plates in a
manifold, and then use an appropriate statistical analysis in
order to compare the theoretical expression with a recent experimental data and
set bounds for the compactification radius
Torsion and Inflammation of Meckel's Diverticulum: Rare Cause of Acute Abdominal Pain
Meckel's diverticulum is a remnant of the embryologic vitelline duct. It was named after its anatomical
and embryological description, in the early 19th century, by Johann Meckel. It is known as a true
diverticulum of the small bowel and is typically estimated to be present in 2% of the general population,
with only a very small percentage being symptomatic. In this report, we present a 14-year-old boy with
complaints of abdominal pain, fever, nausea, vomiting and diarrhea. During physical examination we
observed peritoneal irritation and raised inflammatory markers. Surgical exploration revealed torsion
and inflammation of a large Meckel's diverticulum with a gangrenous area. In order to ensure the
removal of etopic tissue, if present, segmental bowel resection with primary anastomosis was performed.
Histopathological analysis did not find ectopic tissue. The operative and postoperative courses were
uneventful. Meckel's diverticulum is an important differential diagnosis in acute abdominal pain in
children.info:eu-repo/semantics/publishedVersio
Development and application of 14 microsatellite markers in the burying beetle reveals population genetic differentiation at local spatial scales
Burying beetles (genus Nicrophorus) are relatively rare among insects in providing sophisticated parental care. Consequently, they have become model species in research analysing social evolution, the evolution of parental care and mating systems. We used the recently published N. vespilloides genome and transcriptome to develop microsatellite markers. Specifically, we developed 14 polymorphic markers with five to 13 alleles per locus and used them to investigate levels of genetic differentiation in four south Cambridgeshire (UK) populations of N. vespilloides, separated by 21 km at most. The markers revealed significant genetic structuring among populations (global FST = 0.023) with all but one of the pairwise comparisons among populations being significant. The single exception was the comparison between the two closest populations, which are approximately 2.5 km apart. In general, the microsatellite markers showed lower observed heterozygosity than expected. We infer that there is limited dispersal between populations and potentially also some inbreeding within them and suggest that this may be due to habitat fragmentation. We discuss these results in the context of recent laboratory experiments on inbreeding and beetle flight.This project was supported by a Consolidatorâs Grant from the European Research Council (310785 Baldwinian_Beetles) and a Royal Society Wolfson Merit Award, both to RMK. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Temperature inversion symmetry in the Casimir effect with an antiperiodic boundary condition
We present explicitly another example of a temperature inversion symmetry in
the Casimir effect for a nonsymmetric boundary condition. We also give an
interpretation for our result.Comment: 4 page
Dynamical Casimir effect for a massless scalar field between two concentric spherical shells
In this work we consider the dynamical Casimir effect for a massless scalar
field -- under Dirichlet boundary conditions -- between two concentric
spherical shells. We obtain a general expression for the average number of
particle creation, for an arbitrary law of radial motion of the spherical
shells, using two distinct methods: by computing the density operator of the
system and by calculating the Bogoliubov coefficients. We apply our general
expression to breathing modes: when only one of the shells oscillates and when
both shells oscillate in or out of phase. We also analyze the number of
particle production and compare it with the results for the case of plane
geometry.Comment: Final version. To apear in Physical Review
Numerical Thermal Analysis of a T Jump System Used for Studying Polymer Behaviour
Acknowledgements:
The authors would like to acknowledge the financial support from Fundação da CiĂȘncia e Tecnologia (Portugal) as part of the UC4EP (Understanding Crystallisation for Enhanced Polymer Properties) at CDRSP PTDC/CTM-POL/7133/2014, UID/Multi/04044/2013, PAMI NÂș 022158 and the Fundo Europeu de Desenvolvimento Regional (FEDER), Programa Portugal 2020, through the Programa Operacional Regional do Centro 2020 (CENTRO-01-0145-FEDER-022158). The neutron scattering measurement was performed at the STFC ISIS facilities (United Kingdom).The processing of polymers is highly complex. The study of their crystallisation assumes an important role and needs to be carefully detailed. Scattering experiments can be used to study polymer molecular organisation. However these procedures are still very multifaceted leading to the need for planning all the details in the experiments that are to be performed. This manuscript presents a finite element model developed to study the temperature variation of a T Jump System, which has been used for studying polymer behaviour with the NIMROD instrument at the ISIS Neutron and Muon Source, UK. Results show that the variation across the sample was 2ÂșC at a maximum temperature of 70ÂșC and 1ÂșC at a maximum temperature of 50ÂșC.info:eu-repo/semantics/publishedVersio
Traffic Vertical Signposting: Materials Characterization and Structural Numerical Simulation
Aknowlegements:
This work was supported by the project POCI-01-0247-FEDER-010797from the Agency for Competitiveness and Innovation (IAPMEI). In addition, the authors acknowledge the funding from the project UID/Multi/04044/2013 of the Portuguese Foundation for Science and Technology (FCT) and PAMI - ROTEIRO/0328/2013 (NÂș 022158).The existing metallic solutions used for vertical traffic signs are associated with higher
costs and environmental issues due to their manufacturing and degradation, when compared with polymeric solutions. Thus, the development of vertical signs considering the injection from polymeric materials in order to overcome problems related with sustainability, maintenance costs, and to achieve higher resistance to corrosion assumes nowadays an important role. The use of ecofriendly and innovative products considering the industrial waste combined with synthetic polymers performing the appropriate mechanical properties, can also be studied to find out new solutions that
allow to solve the aforementioned problems. Additionally, these innovative vertical signs can contribute to avoid vandalism events related with theft and graffiti activities. This work presents the prior materials investigation and the structural design of vertical signs that are intended to be produced through polymer injection. Three main steps were considered: i) materials research, ii) materials characterisation through the analysis of polycarbonate resin isolated and in different sets of mixtures with different concentrations through tensile testing and static water contact angle measurements to find the optimal material composition; and iii) structural numerical simulation considering polycarbonate resin and using the current standard EN 12899-1 [1] to compute wind resistance, temporary and permanent deflections. Both experimental and numerical results led to an optimized proposal of the vertical signposting structural design.info:eu-repo/semantics/publishedVersio
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