990 research outputs found
Detection of eight different tospovirus species by a monoclonal antibody against the common epitope of NSs protein
Rabbit antisera against the nucleocapsid protein (NP) have been commonly used for detection of tospoviruses and classification into serogroups or serotypes. Mouse monoclonal antibodies (MAbs) with high specificity to the NPs have also been widely used to identify tospovirus species. Recently, a serogroup-specific MAb against the NSs protein of Watermelon silver mottle virus (WSMoV) was produced by our laboratory to react with five members of WSMoV serogroup, i.e., WSMoV, Capsicum chlorosis virus (CaCV), Calla lily chlorotic spot virus (CCSV), Peanut bud necrosis virus (PBNV) and Watermelon bud necrosis virus (WBNV). The epitope recognized by the NSs MAb was determined and the comparison with the reported sequences of tospoviral NSs proteins revealed that the epitope is highly conserved at the N-terminal region of NSs proteins among members of WSMoV and Iris yellow spot virus (IYSV) serogroups, and Melon yellow spot virus (MYSV) serotype. When the NSs MAb was further used to react with the crude antigens of MYSV serotype, IYSV and Tomato yellow ring virus (TYRV) of IYSV serogroup, strong serological reactions, both in ELISA and western blotting, were observed. Thus, our results indicated that the NSs MAb is a useful and convenient tool for detection of the eight tospovirus species. It is also suggested that these eight Asian-type tospoviruses, i.e., WSMoV, CaCV, CCSV, PBNV, WBNV, MYSV, IYSV and TYRV, may share a common evolutionary ancesto
Universal scaling of the Hall resistivity in MgB2 superconductors
The mixed-state Hall resistivity and the longitudinal resistivity in
superconducting MgB2 thin films have been investigated as a function of the
magnetic field over a wide range of current densities from 100 to 10000 A/cm^2.
We observe a universal Hall scaling behavior with a constant exponent of 2.0,
which is independent of the magnetic field, the temperature, and the current
density. This result can be interpreted well within the context of recent
theories.Comment: 4 page
A hybrid neuro--wavelet predictor for QoS control and stability
For distributed systems to properly react to peaks of requests, their
adaptation activities would benefit from the estimation of the amount of
requests. This paper proposes a solution to produce a short-term forecast based
on data characterising user behaviour of online services. We use \emph{wavelet
analysis}, providing compression and denoising on the observed time series of
the amount of past user requests; and a \emph{recurrent neural network} trained
with observed data and designed so as to provide well-timed estimations of
future requests. The said ensemble has the ability to predict the amount of
future user requests with a root mean squared error below 0.06\%. Thanks to
prediction, advance resource provision can be performed for the duration of a
request peak and for just the right amount of resources, hence avoiding
over-provisioning and associated costs. Moreover, reliable provision lets users
enjoy a level of availability of services unaffected by load variations
The Applications and Challenges of the Development of In Vitro Tumor Microenvironment Chips
The tumor microenvironment (TME) plays a critical, yet mechanistically elusive role in tumor development and progression, as well as drug resistance. To better understand the pathophysiology of the complex TME, a reductionist approach has been employed to create in vitro microfluidic models called “tumor chips”. Herein, we review the fabrication processes, applications, and limitations of the tumor chips currently under development for use in cancer research. Tumor chips afford capabilities for real-time observation, precise control of microenvironment factors (e.g. stromal and cellular components), and application of physiologically relevant fluid shear stresses and perturbations. Applications for tumor chips include drug screening and toxicity testing, assessment of drug delivery modalities, and studies of transport and interactions of immune cells and circulating tumor cells with primary tumor sites. The utility of tumor chips is currently limited by the ability to recapitulate the nuances of tumor physiology, including extracellular matrix composition and stiffness, heterogeneity of cellular components, hypoxic gradients, and inclusion of blood cells and the coagulome in the blood microenvironment. Overcoming these challenges and improving the physiological relevance of in vitro tumor models could provide powerful testing platforms in cancer research and decrease the need for animal and clinical studies
Charge Density Wave-Assisted Tunneling Between Hall Edge States
We study the intra-planar tunneling between quantum Hall samples separated by
a quasi one-dimensional barrier, induced through the interaction of edge
degrees of freedom with the charge density waves of a Hall crystal defined in a
parallel layer. A field theory formulation is set up in terms of bosonic
(2+1)-dimensional excitations coupled to (1+1)-dimensional fermions. Parity
symmetry is broken at the quantum level by the confinement of
soliton-antisoliton pairs near the tunneling region. The usual Peierls argument
allows to estimate the critical temperature , so that for mass
corrections due to longitudinal density fluctuations disappear from the edge
spectrum. We compute the gap dependence upon the random global phase of the
pinned charge density wave, as well as the effects of a voltage bias applied
across the tunneling junction.Comment: Additional references + 1 figure + more detailed discussions. To be
published in Phys. Rev.
Random Time-Dependent Quantum Walks
We consider the discrete time unitary dynamics given by a quantum walk on the
lattice performed by a quantum particle with internal degree of freedom,
called coin state, according to the following iterated rule: a unitary update
of the coin state takes place, followed by a shift on the lattice, conditioned
on the coin state of the particle. We study the large time behavior of the
quantum mechanical probability distribution of the position observable in
when the sequence of unitary updates is given by an i.i.d. sequence of
random matrices. When averaged over the randomness, this distribution is shown
to display a drift proportional to the time and its centered counterpart is
shown to display a diffusive behavior with a diffusion matrix we compute. A
moderate deviation principle is also proven to hold for the averaged
distribution and the limit of the suitably rescaled corresponding
characteristic function is shown to satisfy a diffusion equation. A
generalization to unitary updates distributed according to a Markov process is
also provided. An example of i.i.d. random updates for which the analysis of
the distribution can be performed without averaging is worked out. The
distribution also displays a deterministic drift proportional to time and its
centered counterpart gives rise to a random diffusion matrix whose law we
compute. A large deviation principle is shown to hold for this example. We
finally show that, in general, the expectation of the random diffusion matrix
equals the diffusion matrix of the averaged distribution.Comment: Typos and minor errors corrected. To appear In Communications in
Mathematical Physic
Correlated Markov Quantum Walks
We consider the discrete time unitary dynamics given by a quantum walk on
performed by a particle with internal degree of freedom, called coin
state, according to the following iterated rule: a unitary update of the coin
state takes place, followed by a shift on the lattice, conditioned on the coin
state of the particle. We study the large time behavior of the quantum
mechanical probability distribution of the position observable in for
random updates of the coin states of the following form. The random sequences
of unitary updates are given by a site dependent function of a Markov chain in
time, with the following properties: on each site, they share the same
stationnary Markovian distribution and, for each fixed time, they form a
deterministic periodic pattern on the lattice.
We prove a Feynman-Kac formula to express the characteristic function of the
averaged distribution over the randomness at time in terms of the nth power
of an operator . By analyzing the spectrum of , we show that this
distribution posesses a drift proportional to the time and its centered
counterpart displays a diffusive behavior with a diffusion matrix we compute.
Moderate and large deviations principles are also proven to hold for the
averaged distribution and the limit of the suitably rescaled corresponding
characteristic function is shown to satisfy a diffusion equation.
An example of random updates for which the analysis of the distribution can
be performed without averaging is worked out. The random distribution displays
a deterministic drift proportional to time and its centered counterpart gives
rise to a random diffusion matrix whose law we compute. We complete the picture
by presenting an uncorrelated example.Comment: 37 pages. arXiv admin note: substantial text overlap with
arXiv:1010.400
In-plane Hall effect in c-axis-oriented MgB2 thin films
We have measured the longitudinal resistivity and the Hall resistivity in the
ab-plane of highly c-axis-oriented MgB2 thin films. In the normal state, the
Hall coefficient (R_H) behaves as R_H ~ T with increasing temperature (T) up to
130 K and then deviates from that linear T-dependence at higher temperatures.
The T^2 dependence of the cotangent of the Hall angle is only observed above
130 K. The mixed-state Hall effect reveals no sign anomaly over a wide range of
current densities from 10^2 to 10^4 A/cm^2 and for magnetic fields up to 5 T.Comment: 5 pages including 5 figure
Processing of ultrafine-size particulate metal matrix composites by advanced shear technology
Copyright @ 2009 ASM International. This paper was published in Metallurgical & Materials Transactions A 40A(3) and is made available as an electronic reprint with the permission of ASM International. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplications of any material in this paper for a fee or for commercial purposes, or modification of the content of this paper are prohibited.Lack of efficient mixing technology to achieve a uniform distribution of fine-size reinforcement within the matrix and the high cost of producing components have hindered the widespread adaptation of particulate metal matrix composites (PMMCs) for engineering applications. A new rheo-processing method, the melt-conditioning high-pressure die-cast (MC-HPDC) process, has been developed for manufacturing near-net-shape components of high integrity. The MC-HPDC process adapts the well-established high shear dispersive mixing action of a twin-screw mechanism to the task of overcoming the cohesive force of the agglomerates under a high shear rate and high intensity of turbulence. This is followed by direct shaping of the slurry into near-net-shape components using an existing cold-chamber die-casting process. The results indicate that the MC-HPDC samples have a uniform distribution of ultrafine-sized SiC particles throughout the entire sample in the as-cast condition. Compared to those produced by conventional high-pressure die casting (HPDC), MC-HPDC samples have a much improved tensile strength and ductility.EP-SR
Magnetic Flux of EUV Arcade and Dimming Regions as a Relevant Parameter for Early Diagnostics of Solar Eruptions - Sources of Non-Recurrent Geomagnetic Storms and Forbush Decreases
This study aims at the early diagnostics of geoeffectiveness of coronal mass
ejections (CMEs) from quantitative parameters of the accompanying EUV dimming
and arcade events. We study events of the 23th solar cycle, in which major
non-recurrent geomagnetic storms (GMS) with Dst <-100 nT are sufficiently
reliably identified with their solar sources in the central part of the disk.
Using the SOHO/EIT 195 A images and MDI magnetograms, we select significant
dimming and arcade areas and calculate summarized unsigned magnetic fluxes in
these regions at the photospheric level. The high relevance of this eruption
parameter is displayed by its pronounced correlation with the Forbush decrease
(FD) magnitude, which, unlike GMSs, does not depend on the sign of the Bz
component but is determined by global characteristics of ICMEs. Correlations
with the same magnetic flux in the solar source region are found for the GMS
intensity (at the first step, without taking into account factors determining
the Bz component near the Earth), as well as for the temporal intervals between
the solar eruptions and the GMS onset and peak times. The larger the magnetic
flux, the stronger the FD and GMS intensities are and the shorter the ICME
transit time is. The revealed correlations indicate that the main quantitative
characteristics of major non-recurrent space weather disturbances are largely
determined by measurable parameters of solar eruptions, in particular, by the
magnetic flux in dimming areas and arcades, and can be tentatively estimated in
advance with a lead time from 1 to 4 days. For GMS intensity, the revealed
dependencies allow one to estimate a possible value, which can be expected if
the Bz component is negative.Comment: 27 pages, 5 figures. Accepted for publication in Solar Physic
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