4,669 research outputs found
Brownian forces in sheared granular matter
We present results from a series of experiments on a granular medium sheared
in a Couette geometry and show that their statistical properties can be
computed in a quantitative way from the assumption that the resultant from the
set of forces acting in the system performs a Brownian motion. The same
assumption has been utilised, with success, to describe other phenomena, such
as the Barkhausen effect in ferromagnets, and so the scheme suggests itself as
a more general description of a wider class of driven instabilities.Comment: 4 pages, 5 figures and 1 tabl
One at a time, live tracking of NGF axonal transport using quantum dots
Retrograde axonal transport of nerve growth factor (NGF) signals is critical for the survival, differentiation, and maintenance of peripheral sympathetic and sensory neurons and basal forebrain cholinergic neurons. However, the mechanisms by which the NGF signal is propagated from the axon terminal to the cell body are yet to be fully elucidated. To gain insight into the mechanisms, we used quantum dot-labeled NGF (QD-NGF) to track the movement of NGF in real time in compartmentalized culture of rat dorsal root ganglion (DRG) neurons. Our studies showed that active transport of NGF within the axons was characterized by rapid, unidirectional movements interrupted by frequent pauses. Almost all movements were retrograde, but short-distance anterograde movements were occasionally observed. Surprisingly, quantitative analysis at the single molecule level demonstrated that the majority of NGF-containing endosomes contained only a single NGF dimer. Electron microscopic analysis of axonal vesicles carrying QD-NGF confirmed this finding. The majority of QD-NGF was found to localize in vesicles 50–150 nm in diameter with a single lumen and no visible intralumenal membranous components. Our findings point to the possibility that a single NGF dimer is sufficient to sustain signaling during retrograde axonal transport to the cell body
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Cx3cr1-deficient microglia exhibit a premature aging transcriptome.
CX3CR1, one of the highest expressed genes in microglia in mice and humans, is implicated in numerous microglial functions. However, the molecular mechanisms underlying Cx3cr1 signaling are not well understood. Here, we analyzed transcriptomes of Cx3cr1-deficient microglia under varying conditions by RNA-sequencing (RNA-seq). In 2-mo-old mice, Cx3cr1 deletion resulted in the down-regulation of a subset of immune-related genes, without substantial epigenetic changes in markers of active chromatin. Surprisingly, Cx3cr1-deficient microglia from young mice exhibited a transcriptome consistent with that of aged Cx3cr1-sufficient animals, suggesting a premature aging transcriptomic signature. Immunohistochemical analysis of microglia in young and aged mice revealed that loss of Cx3cr1 modulates microglial morphology in a comparable fashion. Our results suggest that CX3CR1 may regulate microglial function in part by modulating the expression levels of a subset of inflammatory genes during chronological aging, making Cx3cr1-deficient mice useful for studying aged microglia
On the spherical-axial transition in supernova remnants
A new law of motion for supernova remnant (SNR) which introduces the quantity
of swept matter in the thin layer approximation is introduced. This new law of
motion is tested on 10 years observations of SN1993J. The introduction of an
exponential gradient in the surrounding medium allows to model an aspherical
expansion. A weakly asymmetric SNR, SN1006, and a strongly asymmetric SNR,
SN1987a, are modeled. In the case of SN1987a the three observed rings are
simulated.Comment: 19 figures and 14 pages Accepted for publication in Astrophysics &
Space Science in the year 201
GS100-02-41: a new large HI shell in the outer part of the Galaxy
Massive stars have a profound effect on the surrounding interstellar medium.
They ionize and heat the neutral gas, and due to their strong winds, they swept
the gas up forming large HI shells. In this way, they generate a dense shell
where the physical conditions for the formation of new stars are given. The aim
of this study is to analyze the origin and evolution of the large HI shell
GS100-02-41 and its role in triggering star forming processes.To characterize
the shell and its environs, we carry out a multi-wavelength study. We analyze
he HI 21 cm line, the radio continuum, and infrared emission distributions. The
analysis of the HI data shows an expanding shell structure centred at (l, b) =
(100.6 deg, -2.04 deg) in the velocity range from -29 to -51.7 km/s.
We infer for GS100-02-41, a kinematical distance of 2.8 +/- 0.6 kpc. Several
massive stars belonging to Cep OB1 are located in projection within the large
HI, shell boundaries. The analysis of the radio continuum and infrared data
reveal that there is no continuum counterpart of the HI shell. On the other
hand, three slightly extended radio continuum sources are observed in
projection onto the dense HI shell. From their flux density determinations we
infer that they are thermal in nature. An analysis of the HI emission
distribution in the environs of these sources shows, for each of them, a region
of low emissivity having a good morphological correlation with the ionized gas
in a velocity range similar to the one where GS100-02-41 is detected. The
origin of GS100-02-41 could have been mainly due to the action of the Cep OB1
massive stars located inside the HI shell. The obtained age difference between
the HI shell and the HII regions, together with their relative location, led us
to conclude that the ionizing stars could have been created as a consequence of
the shell evolution.Comment: Accepted for publication in A&
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“Tales and Adventures”: G.A. Henty’s Union Jack and the Competitive World of Publishing for Boys in the 1880s’
In the competitive publishing environment of the late nineteenth century, writers and magazines had to distinguish themselves carefully from potential rivals. This article examines how G.A. Henty’s quality boys’ weekly, Union Jack (1880-83), attempted to secure a niche in the juvenile publishing market by deliberately distinguishing itself from other papers as a literary, imperialist and “healthy” publication. The article explores the design and marketing techniques of the magazine, its status as a fiction paper, the high calibre of its contributors, and its aggressive rhetoric in targeting an exclusively masculine audience. It argues that while Union Jack was marketed as a niche publication, it eventually failed to distinguish itself sufficiently to survive in an extremely competitive environment
The GRA Beam-Splitter Experiments and Particle-Wave Duality of Light
Grangier, Roger and Aspect (GRA) performed a beam-splitter experiment to
demonstrate the particle behaviour of light and a Mach-Zehnder interferometer
experiment to demonstrate the wave behaviour of light. The distinguishing
feature of these experiments is the use of a gating system to produce near
ideal single photon states. With the demonstration of both wave and particle
behaviour (in two mutually exclusive experiments) they claim to have
demonstrated the dual particle-wave behaviour of light and hence to have
confirmed Bohr's principle of complementarity. The demonstration of the wave
behaviour of light is not in dispute. But we want to demonstrate, contrary to
the claims of GRA, that their beam-splitter experiment does not conclusively
confirm the particle behaviour of light, and hence does not confirm
particle-wave duality, nor, more generally, does it confirm complementarity.
Our demonstration consists of providing a detailed model based on the Causal
Interpretation of Quantum Fields (CIEM), which does not involve the particle
concept, of GRA's which-path experiment. We will also give a brief outline of a
CIEM model for the second, interference, GRA experiment.Comment: 24 pages, 4 figure
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The influence of the atmospheric boundary layer on nocturnal layers of noctuids and other moths migrating over southern Britain
Insects migrating at high altitude over southern Britain have been continuously monitored by automatically-operating, vertical-looking radars over a period of several years. During some occasions in the summer months, the migrants were observed to form well-defined layer concentrations, typically at heights of 200-400 m, in the stable night-time atmosphere. Under these conditions, insects are likely to have control over their vertical movements and are selecting flight heights which are favourable for long-range migration. We therefore investigated the factors influencing the formation of these insect layers by comparing radar measurements of the vertical distribution of insect density with meteorological profiles generated by the UK Met. Office’s Unified Model (UM). Radar-derived measurements of mass and displacement speed, along with data from Rothamsted Insect Survey light traps provided information on the identity of the migrants. We present here three case studies where noctuid and pyralid moths contributed substantially to the observed layers. The major meteorological factors influencing the layer concentrations appeared to be: (a) the altitude of the warmest air, (b) heights corresponding to temperature preferences or thresholds for sustained migration and (c), on nights when air temperatures are relatively high, wind-speed maxima associated with the nocturnal jet. Back-trajectories indicated that layer duration may have been determined by the distance to the coast. Overall, the unique combination of meteorological data from the UM and insect data from entomological radar described here show considerable promise for systematic studies of high-altitude insect layering
Improvement Initiative to Develop and Implement a Tool for Detecting Drug-Drug Interactions During Oncology Clinical Trial Enrollment Eligibility Screening
Objectives
Screening subjects for drug-drug interactions (DDIs) before enrollment in oncology clinical trials is integral to ensuring safety, but standard procedures or tools are not readily available to screen DDI in this setting. Our objectives were to develop a DDI screening tool for use during oncology clinical trial enrollment and to test usability in single-center and multicenter pilot studies. Methods
A multistage approach was used for this quality improvement intervention. Semistructured interviews with individuals responsible for DDI screening were conducted to develop a prototype tool. The tool was used for screening DDI in subjects enrolling in National Clinical Trials Network trials of commercially available agents during a single-center 3-month pilot. Improvements were made, and a 3-month multicenter pilot was conducted at volunteer SWOG Cancer Research Network sites. Participants were surveyed to determine tool usability and efficiency. Results
A tool was developed from semistructured interviews. A critical feature was reporting which medications had specific pharmacokinetic and pharmacodynamic characteristics including transporter and cytochrome P450 substrates, inhibitors, or inducers and QT prolongation. In the 12-site study, average (SD) DDI screening time for each patient decreased by 15.7 (10.2) minutes (range, 3–35 minutes; P \u3c 0.001). Users reported the tool highly usable, with \u3e90% agreeing with all positive usability characterizations and disagreeing with all negative complexity characterizations. Conclusions
A DDI screening tool for oncology clinical trial enrollment was created and its usability confirmed. Further testing with more diverse investigator sites and study drugs during eligibility screening is warranted to improve safety and data accuracy within clinical trials
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