1,662 research outputs found
Distinct forms of synaptic inhibition and neuromodulation regulate calretinin positive neuron excitability in the spinal cord dorsal horn
The dorsal horn (DH) of the spinal cord contains a heterogenous population of neurons that process incoming sensory signals before information ascends to the brain. We have recently characterized calretinin-expressing (CR+) neurons in the DH and shown that they can be divided into excitatory and inhibitory subpopulations. The excitatory population receives high-frequency excitatory synaptic input and expresses delayed firing action potential discharge, whereas the inhibitory population receives weak excitatory drive and exhibits tonic or initial bursting discharge. Here, we characterize inhibitory synaptic input and neuromodulation in the two CR+ populations, in order to determine how each is regulated. We show that excitatory CR+ neurons receive mixed inhibition from GABAergic and glycinergic sources, whereas inhibitory CR+ neurons receive inhibition, which is dominated by glycine. Noradrenaline and serotonin produced robust outward currents in excitatory CR+ neurons, predicting an inhibitory action on these neurons, but neither neuromodulator produced a response in CR+ inhibitory neurons. In contrast, enkephalin (along with selective mu and delta opioid receptor agonists) produced outward currents in inhibitory CR+ neurons, consistent with an inhibitory action but did not affect the excitatory CR+ population. Our findings show that the pharmacology of inhibitory inputs and neuromodulator actions on CR+ cells, along with their excitatory inputs can define these two subpopulations further, and this could be exploited to modulate discrete aspects of sensory processing selectively in the DH
Gender differences in working at home and time use patterns: evidence from Australia
Despite a wealth of research on working at home, few studies have examined the effects of working at home in relation to its regularity and fewer still have used time use studies to do so. Using data from the 2006 Australian Time Use Survey this article investigates the association between working at home, gender and time use, in relation to amount of time spent in paid work, unpaid work and recreational labour, as well as multi-tasking, fragmentation of time and scheduling flexibility. It examines time use patterns according to whether employees do no work at home or whether they work at home rarely, occasionally or regularly. Results show there is an association between working at home and time in paid and unpaid work and that this differs by the regularity of working at home and gender. Working at home does not create more time for recreational labour, although it may help women juggle work and family. © 2015, © The Author(s) 2015
Inferring mixed-culture growth from total biomass data in a wavelet approach
It is shown that the presence of mixed-culture growth in batch fermentation
processes can be very accurately inferred from total biomass data by means of
the wavelet analysis for singularity detection. This is accomplished by
considering simple phenomenological models for the mixed growth and the more
complicated case of mixed growth on a mixture of substrates. The main quantity
provided by the wavelet analysis is the Holder exponent of the singularity that
we determine for our illustrative examples. The numerical results point to the
possibility that Holder exponents can be used to characterize the nature of the
mixed-culture growth in batch fermentation processes with potential industrial
applications. Moreover, the analysis of the same data affected by the common
additive Gaussian noise still lead to the wavelet detection of the
singularities although the Holder exponent is no longer a useful parameterComment: 17 pages and 10 (png) figure
Ischaemic bowel within the thoracic cavity—An unusual cause of a pleural effusion
SummaryDiaphragmatic defects are a rare complication following thoracic or upper gastro-intestinal surgery. We present a case of a 78-year-old man who presented with ischaemic bowel that had herniated through such a diaphragmatic defect, 7 years after an oesophagogastrectomy for carcinoma. The patient was taken for an immediate laparatomy for resection of the infarcted bowel, and thereafter made an uneventful recovery. Patients found to have diaphragmatic defects should be considered for surgical repair to prevent this potentially life-threatening complication
Plastic Deformation of 2D Crumpled Wires
When a single long piece of elastic wire is injected trough channels into a
confining two-dimensional cavity, a complex structure of hierarchical loops is
formed. In the limit of maximum packing density, these structures are described
by several scaling laws. In this paper it is investigated this packing process
but using plastic wires which give origin to completely irreversible structures
of different morphology. In particular, it is studied experimentally the
plastic deformation from circular to oblate configurations of crumpled wires,
obtained by the application of an axial strain. Among other things, it is shown
that in spite of plasticity, irreversibility, and very large deformations,
scaling is still observed.Comment: 5 pages, 6 figure
Deforming glassy polystyrene: Influence of pressure, thermal history, and deformation mode on yielding and hardening
The toughness of a polymer glass is determined by the interplay of yielding, strain softening, and strain hardening. Molecular-dynamics simulations of a typical polymer glass, atactic polystyrene, under the influence of active deformation have been carried out to enlighten these processes. It is observed that the dominant interaction for the yield peak is of interchain nature and for the strain
hardening of intrachain nature. A connection is made with the microscopic cage-to-cage motion. It is found that the deformation does not lead to complete erasure of the thermal history but that differences persist at large length scales. Also we find that the strain-hardening modulus increases with increasing external pressure. This new observation cannot be explained by current theories
such as the one based on the entanglement picture and the inclusion of this effect will lead to an improvement in constitutive modeling
Ceramic Substrates for High-temperature Electronic Integration
One of the most attractive ways to increase power handling capacity in power modules is to increase the operating temperature using wide-band-gap semiconductors. Ceramics are ideal candidates for use as substrates in high-power high-temperature electronic devices. The present article aims to determine the most suitable ceramic material for this application
Functional and molecular analysis of proprioceptive sensory neuron excitability in mice
Neurons located in dorsal root ganglia (DRG) are crucial for transmitting peripheral sensations such as proprioception, touch, temperature, and nociception to the spinal cord before propagating these signals to higher brain structures. To date, difficulty in identifying modality-specific DRG neurons has limited our ability to study specific populations in detail. As the calcium-binding protein parvalbumin (PV) is a neurochemical marker for proprioceptive DRG cells we used a transgenic mouse line expressing green fluorescent protein (GFP) in PV positive DRGs, to study the functional and molecular properties of putative proprioceptive neurons. Immunolabeled DRGs showed a 100% overlap between GFP positive (GFP+) and PV positive cells, confirming the PVeGFP mouse accurately labeled PV neurons. Targeted patch-clamp recording from isolated GFP+ and GFP negative (GFP−) neurons showed the passive membrane properties of the two groups were similar, however, their active properties differed markedly. All GFP+ neurons fired a single spike in response to sustained current injection and their action potentials (APs) had faster rise times, lower thresholds and shorter half widths. A hyperpolarization-activated current (Ih) was observed in all GFP+ neurons but was infrequently noted in the GFP− population (100% vs. 11%). For GFP+ neurons, Ih activation rates varied markedly, suggesting differences in the underlying hyperpolarization-activated cyclic nucleotide-gated channel (HCN) subunit expression responsible for the current kinetics. Furthermore, quantitative polymerase chain reaction (qPCR) showed the HCN subunits 2, 1, and 4 mRNA (in that order) was more abundant in GFP+ neurons, while HCN 3 was more highly expressed in GFP− neurons. Likewise, immunolabeling confirmed HCN 1, 2, and 4 protein expression in GFP+ neurons. In summary, certain functional properties of GFP+ and GFP− cells differ markedly, providing evidence for modality-specific signaling between the two groups. However, the GFP+ DRG population demonstrates considerable internal heterogeneity when hyperpolarization-activated cyclic nucleotide-gated channel (HCN channel) properties and subunit expression are considered. We propose this heterogeneity reflects the existence of different peripheral receptors such as tendon organs, muscle spindles or mechanoreceptors in the putative proprioceptive neuron population
Universal aspects of vacancy-mediated disordering dynamics: the effect of external fields
We investigate the disordering of an initially phase-segregated binary alloy,
due to a highly mobile defect which couples to an electric or gravitational
field. Using both mean-field and Monte Carlo methods, we show that the late
stages of this process exhibit dynamic scaling, characterized by a set of
exponents and scaling functions. A new scaling variable emerges, associated
with the field. While the scaling functions carry information about the field
and the boundary conditions, the exponents are universal. They can be computed
analytically, in excellent agreement with simulation results.Comment: 15 pages, 6 figure
Optimal Packings of Superballs
Dense hard-particle packings are intimately related to the structure of
low-temperature phases of matter and are useful models of heterogeneous
materials and granular media. Most studies of the densest packings in three
dimensions have considered spherical shapes, and it is only more recently that
nonspherical shapes (e.g., ellipsoids) have been investigated. Superballs
(whose shapes are defined by |x1|^2p + |x2|^2p + |x3|^2p <= 1) provide a
versatile family of convex particles (p >= 0.5) with both cubic- and
octahedral-like shapes as well as concave particles (0 < p < 0.5) with
octahedral-like shapes. In this paper, we provide analytical constructions for
the densest known superball packings for all convex and concave cases. The
candidate maximally dense packings are certain families of Bravais lattice
packings. The maximal packing density as a function of p is nonanalytic at the
sphere-point (p = 1) and increases dramatically as p moves away from unity. The
packing characteristics determined by the broken rotational symmetry of
superballs are similar to but richer than their two-dimensional "superdisk"
counterparts, and are distinctly different from that of ellipsoid packings. Our
candidate optimal superball packings provide a starting point to quantify the
equilibrium phase behavior of superball systems, which should deepen our
understanding of the statistical thermodynamics of nonspherical-particle
systems.Comment: 28 pages, 16 figure
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