60 research outputs found
Elastic Instability Triggered Pattern Formation
Recent experiments have exploited elastic instabilities in membranes to
create complex patterns. However, the rational design of such structures poses
many challenges, as they are products of nonlinear elastic behavior. We pose a
simple model for determining the orientational order of such patterns using
only linear elasticity theory which correctly predicts the outcomes of several
experiments. Each element of the pattern is modeled by a "dislocation dipole"
located at a point on a lattice, which then interacts elastically with all
other dipoles in the system. We explicitly consider a membrane with a square
lattice of circular holes under uniform compression and examine the changes in
morphology as it is allowed to relax in a specified direction.Comment: 15 pages, 7 figures, the full catastroph
Competition-based model of pheromone component ratio detection in the moth
For some moth species, especially those closely interrelated and sympatric, recognizing a specific pheromone component concentration ratio is essential for males to successfully locate conspecific females. We propose and determine the properties of a minimalist competition-based feed-forward neuronal model capable of detecting a certain ratio of pheromone components independently of overall concentration. This model represents an elementary recognition unit for the ratio of binary mixtures which we propose is entirely contained in the macroglomerular complex (MGC) of the male moth. A set of such units, along with projection neurons (PNs), can provide the input to higher brain centres. We found that (1) accuracy is mainly achieved by maintaining a certain ratio of connection strengths between olfactory receptor neurons (ORN) and local neurons (LN), much less by properties of the interconnections between the competing LNs proper. An exception to this rule is that it is beneficial if connections between generalist LNs (i.e. excited by either pheromone component) and specialist LNs (i.e. excited by one component only) have the same strength as the reciprocal specialist to generalist connections. (2) successful ratio recognition is achieved using latency-to-first-spike in the LN populations which, in contrast to expectations with a population rate code, leads to a broadening of responses for higher overall concentrations consistent with experimental observations. (3) when longer durations of the competition between LNs were observed it did not lead to higher recognition accuracy
Developing a platform for Fresnel diffractive radiography with 1 μm spatial resolution at the National Ignition Facility
Mechanisms explaining transitions between tonic and phasic firing in neuronal populations as predicted by a low dimensional firing rate model
Several firing patterns experimentally observed in neural populations have
been successfully correlated to animal behavior. Population bursting, hereby
regarded as a period of high firing rate followed by a period of quiescence, is
typically observed in groups of neurons during behavior. Biophysical
membrane-potential models of single cell bursting involve at least three
equations. Extending such models to study the collective behavior of neural
populations involves thousands of equations and can be very expensive
computationally. For this reason, low dimensional population models that
capture biophysical aspects of networks are needed.
\noindent The present paper uses a firing-rate model to study mechanisms that
trigger and stop transitions between tonic and phasic population firing. These
mechanisms are captured through a two-dimensional system, which can potentially
be extended to include interactions between different areas of the nervous
system with a small number of equations. The typical behavior of midbrain
dopaminergic neurons in the rodent is used as an example to illustrate and
interpret our results.
\noindent The model presented here can be used as a building block to study
interactions between networks of neurons. This theoretical approach may help
contextualize and understand the factors involved in regulating burst firing in
populations and how it may modulate distinct aspects of behavior.Comment: 25 pages (including references and appendices); 12 figures uploaded
as separate file
The synthetic antimicrobial peptide 19-2.5 attenuates septic cardiomyopathy and prevents down-regulation of SERCA2 in polymicrobial sepsis
LM has received grants by the Faculty of Medicine at the RWTH Aachen University (START 15/14 and
START 46/16) and the Deutsche Forschungsgemeinschaft (DFG, MA 7082/1–1). This work was supported by
the Immunohistochemistry and Confocal Microscopy Unit, a core facility of the Interdisciplinary Centre for
Clinical Research (IZKF) Aachen, within the Faculty of Medicine at the RWTH Aachen University and the
RWTH centralized Biomaterial Database (RWTH cBMB) of the University Hospital RWTH Aachen. We are
very grateful to Antons Martincuks M.Sc. and Professor Gerhard Müller-Newen for live-cell imaging. This work
was supported, in part, by the University of Turin (ex-60% 2015A and B) and by the William Harvey Research
Foundation and forms part of the research themes contributing to the translational research portfolio of Barts
and the London Cardiovascular Biomedical Research Unit that is supported and funded by the National Institute
for Health Research. This work also contributes to the Organ Protection research theme of the Barts Centre for
Trauma Sciences supported by the Barts and The London Charity (Award 753/1722)
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Time-Efficient Inspiratory Muscle Strength Training Lowers Blood Pressure and Improves Endothelial Function, NO Bioavailability, and Oxidative Stress in Midlife/Older Adults With Above-Normal Blood Pressure
Background
High‐resistance inspiratory muscle strength training (IMST) is a novel, time‐efficient physical training modality.
Methods and Results
We performed a double‐blind, randomized, sham‐controlled trial to investigate whether 6 weeks of IMST (30 breaths/day, 6 days/week) improves blood pressure, endothelial function, and arterial stiffness in midlife/older adults (aged 50–79 years) with systolic blood pressure ≥120 mm Hg, while also investigating potential mechanisms and long‐lasting effects. Thirty‐six participants completed high‐resistance IMST (75% maximal inspiratory pressure, n=18) or low‐resistance sham training (15% maximal inspiratory pressure, n=18). IMST was safe, well tolerated, and had excellent adherence (≈95% of training sessions completed). Casual systolic blood pressure decreased from 135±2 mm Hg to 126±3 mm Hg (P<0.01) with IMST, which was ≈75% sustained 6 weeks after IMST (P<0.01), whereas IMST modestly decreased casual diastolic blood pressure (79±2 mm Hg to 77±2 mm Hg, P=0.03); blood pressure was unaffected by sham training (all P>0.05). Twenty‐four hour systolic blood pressure was lower after IMST versus sham training (P=0.01). Brachial artery flow‐mediated dilation improved ≈45% with IMST (P<0.01) but was unchanged with sham training (P=0.73). Human umbilical vein endothelial cells cultured with subject serum sampled after versus before IMST exhibited increased NO bioavailability, greater endothelial NO synthase activation, and lower reactive oxygen species bioactivity (P<0.05). IMST decreased C‐reactive protein (P=0.05) and altered select circulating metabolites (targeted plasma metabolomics) associated with cardiovascular function. Neither IMST nor sham training influenced arterial stiffness (P>0.05).
Conclusions
High‐resistance IMST is a safe, highly adherable lifestyle intervention for improving blood pressure and endothelial function in midlife/older adults with above‐normal initial systolic blood pressure.
Registration
URL: https://www.clinicaltrials.gov; Unique identifier: NCT03266510.
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Is there a space–time continuum in olfaction?
The coding of olfactory stimuli across a wide range of organisms may rely on fundamentally similar mechanisms in which a complement of specific odorant receptors on olfactory sensory neurons respond differentially to airborne chemicals to initiate the process by which specific odors are perceived. The question that we address in this review is the role of specific neurons in mediating this sensory system—an identity code—relative to the role that temporally specific responses across many neurons play in producing an olfactory perception—a temporal code. While information coded in specific neurons may be converted into a temporal code, it is also possible that temporal codes exist in the absence of response specificity for any particular neuron or subset of neurons. We review the data supporting these ideas, and we discuss the research perspectives that could help to reveal the mechanisms by which odorants become perceptions
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