465 research outputs found
Structure-stiffness relation of live mouse brain tissue determined by depth-controlled indentation mapping
The mechanical properties of brain tissue play a pivotal role in
neurodevelopment and neurological disorders. Yet, at present, there is no
consensus on how the different structural parts of the tissue contribute to its
stiffness variations. Here, we have gathered depth-controlled indentation
viscoelasticity maps of the hippocampus of isolated horizontal live mouse brain
sections. Our results confirm the highly viscoelestic nature of the material
and clearly show that the mechanical properties correlate with the different
morphological layers of the samples investigated. Interestingly, the relative
cell nuclei area seems to negatively correlate with the stiffness observed
On the torque on birefringent plates induced by quantum fluctuations
We present detailed numerical calculations of the mechanical torque induced
by quantum fluctuations on two parallel birefringent plates with in plane
optical anisotropy, separated by either vacuum or a liquid (ethanol). The
torque is found to vary as , where represents the angle
between the two optical axes, and its magnitude rapidly increases with
decreasing plate separation . For a 40 m diameter disk, made out of
either quartz or calcite, kept parallel to a Barium Titanate plate at nm, the maximum torque (at ) is of the order of
Nm. We propose an experiment to observe this torque
when the Barium Titanate plate is immersed in ethanol and the other
birefringent disk is placed on top of it. In this case the retarded van der
Waals (or Casimir-Lifshitz) force between the two birefringent slabs is
repulsive. The disk would float parallel to the plate at a distance where its
net weight is counterbalanced by the retarded van der Waals repulsion, free to
rotate in response to very small driving torques.Comment: 7 figures, submitted to Phys. Rev.
Isolated Pulmonary Valve Endocarditis.
Infective endocarditis involving the right side of the heart is typically associated with IV drug abuse and chronic indwelling catheters which commonly involve the tricuspid valve. Isolated pulmonary valve endocarditis (PVE) is a rare clinical entity. We report a rare case of a young woman with a history of end-stage renal disease (ESRD) on hemodialysis through tunneled catheter presenting with persistent coagulase-negative staphylococcus (CoNS) epidermidis bacteremia despite being on appropriate treatment with IV vancomycin for two weeks. Because of the persistent bacteremia, a transesophageal echocardiogram was performed and it revealed a thickened pulmonary valve with 1.8 cm vegetation in the left posterior cusp. She was successfully treated with IV daptomycin course for a total of six weeks. The recommended management for PVE is usually medical treatment with IV antibiotics gauged according to sensitivities of the cultures. Our article highlights the fact that the decision to manage it medically versus surgically can propose a challenge as the guidelines are not very robust
Precision measurement of the Casimir-Lifshitz force in a fluid
The Casimir force, which results from the confinement of the quantum
mechanical zero-point fluctuations of the electromagnetic fields, has received
significant attention in recent years for its effect on micro- and nano-scale
mechanical systems. With few exceptions, experimental observations have been
limited to conductive bodies interacting separated by vacuum or air. However,
interesting phenomena including repulsive forces are expected to exist in
certain circumstances between metals and dielectrics when the intervening
medium is not vacuum. In order to better understand the effect of the Casimir
force in such situations and to test the robustness of the generalized
Casimir-Lifshitz theory, we have performed the first precision measurements of
the Casimir force between two metals immersed in a fluid. For this situation,
the measured force is attractive and is approximately 80% smaller than the
force predicted by Casimir for ideal metals in vacuum. We present experimental
results and find them to be consistent with Lifshitz's theory.Comment: 6 pages, 3 figures. (version before final publication
Investigating Mitonuclear Genetic Interactions Through Machine Learning: A Case Study on Cold Adaptation Genes in Human Populations From Different European Climate Regions
Cold climates represent one of the major environmental challenges that anatomically modern humans faced during their dispersal out of Africa. The related adaptive traits have been achieved by modulation of thermogenesis and thermoregulation processes where nuclear (nuc) and mitochondrial (mt) genes play a major role. In human populations, mitonuclear genetic interactions are the result of both the peculiar genetic history of each human group and the different environments they have long occupied. This study aims to investigate mitonuclear genetic interactions by considering all the mitochondrial genes and 28 nuclear genes involved in brown adipose tissue metabolism, which have been previously hypothesized to be crucial for cold adaptation. For this purpose, we focused on three human populations (i.e., Finnish, British, and Central Italian people) of European ancestry from different biogeographical and climatic areas, and we used a machine learning approach to identify relevant nucDNAâmtDNA interactions that characterized each population. The obtained results are twofold: (i) at the methodological level, we demonstrated that a machine learning approach is able to detect patterns of genetic structure among human groups from different latitudes both at single genes and by considering combinations of mtDNA and nucDNA loci; (ii) at the biological level, the analysis identified population-specific nuclear genes and variants that likely play a relevant biological role in association with a mitochondrial gene (such as the âobesity geneâ FTO in Finnish people). Further studies are needed to fully elucidate the evolutionary dynamics (e.g., migration, admixture, and/or local adaptation) that shaped these nucDNAâmtDNA interactions and their functional role
Frequency-dependent Drude damping in Casimir force calculations
The Casimir force is calculated between Au thin films that are described by a
Drude model with a frequency dependent damping function. The model parameters
are obtained from available experimental data for Au thin films. Two cases are
considered; annealed and nonannealed films that have a different damping
function. Compared with the calculations using a Drude model with a constant
damping parameter, we observe changes in the Casimir force of a few percent.
This behavior is only observed in films of no more than 300 thick.Comment: Proceedings of the meeting "60 years of Casimir effect", Brasilia,
200
Comment on "On the temperature dependence of the Casimir effect"
Recently, Brevik et al. [Phys. Rev. E 71, 056101 (2005)] adduced arguments
against the traditional approach to the thermal Casimir force between real
metals and in favor of one of the alternative approaches. The latter assumes
zero contribution from the transverse electric mode at zero frequency in
qualitative disagreement with unity as given by the thermal quantum field
theory for ideal metals. Those authors claim that their approach is consistent
with experiments as well as with thermodynamics. We demonstrate that these
conclusions are incorrect. We show specifically that their results are
contradicted by four recent experiments and also violate the third law of
thermodynamics (the Nernst heat theorem).Comment: 11 pages, 3 figures, changed in accordance with the final published
versio
Impact of different types of physical activity in green urban space on adult health and behaviors: A systematic review
This systematic review aimed to investigate the type of physical activity carried out in green urban spaces by the adult population and to value its impact on the populationâs health. Additionally, another purpose was to examine if the presence of outdoor gyms in green urban spaces can promote participation in physical activity among adults. Searches of electronic databases, with no time restrictions and up to June 2020, resulted in 10 studies meeting the inclusion criteria. A quantitative assessment is reported as effect size. Many people practiced walking activity as a workout, which showed improvements in health. Walking is the most popular type of training due to its easy accessibility and it not requiring equipment or special skills. Outdoor fitness equipment has been installed in an increasing number of parks and has become very popular worldwide. Further, outdoor fitness equipment provides free access to fitness training and seems to promote physical activity in healthy adults. However, other studies about outdoor fitness equipment efficiency are needed. People living near to equipped areas are more likely to perform outdoor fitness than those who live further away. The most common training programs performed in green urban spaces included exercises with free and easy access, able to promote physical health and perception
Increased carotid intima-media thickness and stiffness in obese children
Summary (Abstract not available):Obesity in childhood increases the risk of atherosclerotic disease and death in adulthood. We studied 100 children with obesity and 47 healthy age-mathced control subjects, mean age 10 years of both groups. Biochemical parameters describing lipoprotein and glucose metabolism were measured. Quantitative B-mode ultrasound examination of common carotid arteries was performed. Carotid thickness and stiffness were significantly increased in obese children as compared to nonobese ones, independently of traditional cardiovascular risk factors. Obesity should be regarded as a disease with vascular implications even in young age
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