41,435 research outputs found
An experimental study on a motion sensing system for sports training
In sports science, motion data collected from athletes is
used to derive key performance characteristics, such as stride length
and stride frequency, that are vital coaching support information. The
sensors for use must be more accurate, must capture more vigorous
events, and have strict weight and size requirements, since they must
not themselves affect performance. These requirements mean each
wireless sensor device is necessarily resource poor and yet must be
capable of communicating a considerable amount of data, contending
for the bandwidth with other sensors on the body. This paper analyses
the results of a set of network traffic experiments that were designed
to investigate the suitability of conventional wireless motion sensing
system design � which generally assumes in-network processing - as
an efficient and scalable design for use in sports training
Compressing Inertial Motion Data in Wireless Sensing Systems – An Initial Experiment
The use of wireless inertial motion sensors, such as accelerometers, for supporting medical care and sport’s training, has been under investigation in recent years. As the number of sensors (or their sampling rates) increases, compressing data at source(s) (i.e. at the sensors), i.e. reducing the quantity of data that needs to be transmitted between the on-body sensors and the remote repository, would be essential especially in a bandwidth-limited wireless environment. This paper presents a set of compression experiment results on a set of inertial motion data collected during running exercises. As a starting point, we selected a set of common compression algorithms to experiment with. Our results show that, conventional lossy compression algorithms would achieve a desirable compression ratio with an acceptable time delay. The results also show that the quality of the decompressed data is within acceptable range
Combining Genome Wide Association Studies and Differential Gene Expression Data Analyses Identifies Candidate Genes Affecting Mastitis Caused by Two Different Pathogens in the Dairy Cow
Mastitis is a costly disease which hampers the dairy industry. Inflammation of the mammary gland is commonly caused by bacterial infection, mainly Escherichia coli, Streptococcus uberis and Staphylococcus aureus. As more bacteria become multi-drug resistant, one potential approach to reduce the disease incidence rate is to breed selectively for the most appropriate and potentially protective innate immune response. The genetic contribution to effective disease resistance is, however, difficult to identify due to the complex interactions that occur. In the present study two published datasets were searched for common differentially expressed genes (DEGs) with similar changes in expression in mammary tissue following intra-mammary challenge with either E. coli or S. uberis. Additionally, the results of seven published genome-wide association studies (GWAS) on different dairy cow populations were used to compile a list of SNPs associated with somatic cell count. All genes located within 2 Mbp of significant SNPs were retrieved from the Ensembl database, based on the UMD3.1 assembly. A final list of 48 candidate genes with a role in the innate immune response identified from both the DEG and GWAS studies was further analyzed using Ingenuity Pathway Analysis. The main signalling pathways highlighted in the response of the bovine mammary gland to both bacterial infections were 1) granulocyte adhesion and diapedesis, 2) ephrin receptor signalling, 3) RhoA signalling and 4) LPS/IL1 mediated inhibition of RXR function. These pathways comprised a network regulating the activity of leukocytes, especially neutrophils, during mammary gland inflammation. The timely and properly controlled movement of leukocytes to infection loci seems particularly important in achieving a good balance between pathogen elimination and excessive tissue damage. These results suggest that polymorphisms in key genes in these pathways such as SELP, SELL, BCAR1, ACTR3, CXCL2, CXCL6, CXCL8 and FABP may influence the ability of dairy cows to resist mastitis
Is GRO J1744-28 a Strange Star?
The unusal hard x-ray burster GRO J1744-28 recently discovered by the Compton
Gamma-ray Observatory (GRO) can be modeled as a strange star with a dipolar
magnetic field Gauss. When the accreted mass of the star exceeds
some critical mass, its crust may break, resulting in conversion of the
accreted matter into strange matter and release of energy. Subsequently, a
fireball may form and expand relativistically outward. The expanding fireball
may interact with the surrounding interstellar medium, causing its kinetic
energy to be radiated in shock waves, producing a burst of x-ray radiation. The
burst energy, duration, interval and spectrum derived from such a model are
consistent with the observations of GRO J1744-28.Comment: Latex, has been published in SCIENCE, Vol. 280, 40
Formation and kinetics of transient metastable states in mixtures under coupled phase ordering and chemical demixing
We present theory and simulation of simultaneous chemical demixing and phase
ordering in a polymer-liquid crystal mixture in conditions where isotropic-
isotropic phase separation is metastable with respect to isotropic-nematic
phase transition. It is found that mesophase formation proceeds by a transient
metastable phase that surround the ordered phase, and whose lifetime is a
function of the ratio of diffusional to orientational mobilities. It is shown
that kinetic phase ordering in polymer-mesogen mixtures is analogous to kinetic
crystallization in polymer solutions.Comment: 17 pages, 5 figures accepted for publication in EP
Modeling the Optical Afterglow of GRB 030329
The best-sampled afterglow light curves are available for GRB 030329. A
distinguishing feature of this event is the obvious rebrightening at around 1.6
days after the burst. Proposed explanations for the rebrightening mainly
include the two-component jet model and the refreshed shock model, although a
sudden density-jump in the circumburst environment is also a potential choice.
Here we re-examine the optical afterglow of GRB 030329 numerically in light of
the three models. In the density-jump model, no obvious rebrightening can be
produced at the jump moment. Additionally, after the density jump, the
predicted flux density decreases rapidly to a level that is significantly below
observations. A simple density-jump model thus can be excluded. In the
two-component jet model, although the observed late afterglow (after 1.6 days)
can potentially be explained as emission from the wide-component, the emergence
of this emission actually is too slow and it does not manifest as a
rebrightening as previously expected. The energy-injection model seems to be
the most preferred choice. By engaging a sequence of energy-injection events,
it provides an acceptable fit to the rebrightening at d, as well as
the whole observed light curve that extends to d. Further studies on
these multiple energy-injection processes may provide a valuable insight into
the nature of the central engines of gamma-ray bursts.Comment: 18 pages, 3 figures; a few references added and minor word changes;
now accepted for publication in Ap
A classification of 2D fermionic and bosonic topological orders
The string-net approach by Levin and Wen, and the local unitary
transformation approach by Chen, Gu, and Wen, provide ways to classify
topological orders with gappable edge in 2D bosonic systems. The two approaches
reveal that the mathematical framework for 2+1D bosonic topological order with
gappable edge is closely related to unitary fusion category theory. In this
paper, we generalize these systematic descriptions of topological orders to 2D
fermion systems. We find a classification of 2+1D fermionic topological orders
with gappable edge in terms of the following set of data , that satisfy a set of non-linear
algebraic equations. The exactly soluble Hamiltonians can be constructed from
the above data on any lattices to realize the corresponding topological orders.
When , our result recovers the previous classification of 2+1D
bosonic topological orders with gappable edge.Comment: 19 page 5 figures, RevTeX
Probabilistic Fragmentation and Effective Power Law
A simple fragmentation model is introduced and analysed. We show that, under
very general conditions, an effective power law for the mass distribution
arises with realistic exponent. This exponent has a universal limit, but in
practice the effective exponent depends on the detailed breaking mechanism and
the initial conditions. This dependence is in good agreement with experimental
results of fragmentation.Comment: 4 pages Revtex, 2 figures, zipped and uuencode
Monte Carlo modeling of spin injection through a Schottky barrier and spin transport in a semiconductor quantum well
We develop a Monte Carlo model to study injection of spin-polarized electrons
through a Schottky barrier from a ferromagnetic metal contact into a
non-magnetic low-dimensional semiconductor structure. Both mechanisms of
thermionic emission and tunneling injection are included in the model. Due to
the barrier shape, the injected electrons are non-thermalized. Spin dynamics in
the semiconductor heterostructure is controlled by the Rashba and Dresselhaus
spin-orbit interactions and described by a single electron spin density matrix
formalism. In addition to the linear term, the third order term in momentum for
the Dresselhaus interaction is included. Effect of the Schottky potential on
the spin dynamics in a 2 dimensional semiconductor device channel is studied.
It is found that the injected current can maintain substantial spin
polarization to a length scale in the order of 1 micrometer at room temperature
without external magnetic fields.Comment: 18 pages, 4 figures, J. Appl. Phys., accepted for publicatio
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