6,976 research outputs found
Effects of random localizing events on matter waves: formalism and examples
A formalism is introduced to describe a number of physical processes that may
break down the coherence of a matter wave over a characteristic length scale l.
In a second-quantized description, an appropriate master equation for a set of
bosonic "modes" (such as atoms in a lattice, in a tight-binding approximation)
is derived. Two kinds of "localizing processes" are discussed in some detail
and shown to lead to master equations of this general form: spontaneous
emission (more precisely, light scattering), and modulation by external random
potentials. Some of the dynamical consequences of these processes are
considered: in particular, it is shown that they generically lead to a damping
of the motion of the matter-wave currents, and may also cause a "flattening" of
the density distribution of a trapped condensate at rest.Comment: v3; a few corrections, especially in Sections IV and
Towards an -theorem for granular gases
The -theorem, originally derived at the level of Boltzmann non-linear
kinetic equation for a dilute gas undergoing elastic collisions, strongly
constrains the velocity distribution of the gas to evolve irreversibly towards
equilibrium. As such, the theorem could not be generalized to account for
dissipative systems: the conservative nature of collisions is an essential
ingredient in the standard derivation. For a dissipative gas of grains, we
construct here a simple functional related to the original ,
that can be qualified as a Lyapunov functional. It is positive, and results
backed by three independent simulation approaches (a deterministic spectral
method, the stochastic Direct Simulation Monte Carlo technique, and Molecular
Dynamics) indicate that it is also non-increasing. Both driven and unforced
cases are investigated
Production of Polyclonal Antibodies Against a Yam Isolate of Cucumber Mosaic Virus (Cmv).
Cucumber mosaic virus (CMV) genus Cucumovirus was recently detected in yam in Ghana, Togo and Benin bringing to six the total number of countries reporting CMV infection in yam worldwide. Two serotypes of CMV are distinguished and a specific antibody against the yam isolate of CMV is currently not available. Rabbit polyclonal antibodies were produced against purified preparations of a yam isolate of CMV from Nigeria. The antibody titre was determined by Protein-A sandwich (PAS) enzymelinked immunosorbent assay (ELISA) and antigen-coated plate (ACP) ELISA. Antigen detection limit of the antibody was determined by PAS-ELISA using serial dilutions of infected sap. The CMV antiserum produced had a titre of 1:25,600 and 1:64,000 by PAS- and ACP-ELISA, respectively and a sap dilution end point of 1:160. The antibody detected homologous antigen in infected yam leaves from Ghana, Togo, Benin and Nigeria. The CMV polyclonal antibody produced in this study will enhance CMV monitoring and contribute to prevention of the spread of CMV infection which is spreading in yamCucumber mosaic virus (CMV) genus Cucumovirus was recently detected in yam in Ghana, Togo and Benin bringing to six the total number of countries reporting CMV infection in yam worldwide. Two serotypes of CMV are distinguished and a specific antibody against the yam isolate of CMV is currently not available. Rabbit polyclonal antibodies were produced against purified preparations of a yam isolate of CMV from Nigeria. The antibody titre was determined by Protein-A sandwich (PAS) enzymelinked immunosorbent assay (ELISA) and antigen-coated plate (ACP) ELISA. Antigen detection limit of the antibody was determined by PAS-ELISA using serial dilutions of infected sap. The CMV antiserum produced had a titre of 1:25,600 and 1:64,000 by PAS- and ACP-ELISA, respectively and a sap dilution end point of 1:160. The antibody detected homologous antigen in infected yam leaves from Ghana, Togo, Benin and Nigeria. The CMV polyclonal antibody produced in this study will enhance CMV monitoring and contribute to prevention of the spread of CMV infection which is spreading in ya
Children's construction task performance and spatial ability: controlling task complexity and predicting mathematics performance.
This paper presents a methodology to control construction task complexity and examined the relationships between construction performance and spatial and mathematical abilities in children. The study included three groups of children (N = 96); ages 7-8, 10-11, and 13-14 years. Each group constructed seven pre-specified objects. The study replicated and extended previous findings that indicated that the extent of component symmetry and variety, and the number of components for each object and available for selection, significantly predicted construction task difficulty. Results showed that this methodology is a valid and reliable technique for assessing and predicting construction play task difficulty. Furthermore, construction play performance predicted mathematical attainment independently of spatial ability
Production of Polyclonal Antibody Against an Isolate of Yam-infecting Badnavirus from Nigeria
Integrated viral sequences and high sequence variability among badnaviruses complicates the
development of specific reliable molecular detection tests for yam-infecting badnaviruses. Thus
Serological techniques are of notable importance for routine testing and monitoring of these viruses.
The major limiting factor to the use of serological techniques is the limited availability of antibodies.
Rabbit polyclonal antibody was produced against a purified preparation of a yam-infecting badnavirus
from Nigeria. Antibody titre was determined by Protein-A sandwich (PAS) enzyme-linked
immunosorbent assay (ELISA). The antibody produced had a titre of 1:1280 in PAS-ELISA and
detected yam-infecting badnaviruses in infected yam leaves from Nigeria, Ghana, Benin and Togo. The
suitability of the antibody for use in immunocapture polymerase chain reaction (IC-PCR) was evaluated.
The antibody successfully trapped both Dioscorea alata bacilliform virus (DaBV) and Dioscorea
sansibarensis bacilliform virus (DsBV) for IC-PCR detection. The antibody produced in this study will
enhance certification of yam planting materials across West Africa and also facilitate the safe
international movement of yam germplasm
Production of yam mosaic virus monoclonal antibodies in mice peritoneum
Yam mosaic virus (YMV) is one of the most economically important virus infecting yams.
Immunoassays are routinely used for laboratory diagnosis of YMV and for certification of planting
materials. However, YMV antibodies, the key reagents, needed for these immunoassays are not readily
available. We describe in this paper, the production of YMV monoclonal antibodies for the detection of
YMV. The monoclonal antibody was produced by immunizing six weeks old BALB/c mice with YMV
hybridoma cells and tapping soft peritoneal tumor tissues for antibody. Antibody titre was determined
by triple antibody sandwich-enzyme-linked immunosorbent assay (TAS-ELISA) using YMV infected yam
leaves and non-infected tissue culture yam leaves. The antibody produced had a titre of 1:1,310,720 and
an optimal TAS-ELISA detection dilution of 1:80,000. This high-titre YMV monoclonal antibody is useful
for monitoring and certification purposes
Back Reaction and Graceful Exit in String Inflationary Cosmology
Classical string cosmology consists of two branches related to each other by
scale-factor duality: a super-inflation branch and a Friedmann-Robertson-Walker
(FRW) branch. Curvature and string coupling singularity separates the two
branches, hence posing `graceful exit problem' to super-inflationary string
cosmology. In an exactly soluble two-dimensional compactification model it is
shown that quantum back reaction retards curvature and string coupling growth
and connects the super-inflation branch to the FRW branch without encountering
a singularity. This may offer an attractive solution to the `graceful exit
problem' in string inflationary cosmology.Comment: 12 pages, ReVTe
Variable stars in the Open Cluster M11 (NGC 6705)
V-band time-series CCD photometric observations of the intermediate-age open
cluster M11 were performed to search for variable stars. Using these
time-series data, we carefully examined light variations of all stars in the
observing field. A total of 82 variable stars were discovered, of which 39
stars had been detected recently by Hargis et al. (2005). On the basis of
observational properties such as variable period, light curve shape, and
position on a color-magnitude diagram, we classified their variable types as 11
delta Scuti-type pulsating stars, 2 gamma Doradus-type pulsating stars, 40 W
UMa-type contact eclipsing binaries, 13 Algol-type detached eclipsing binaries,
and 16 eclipsing binaries with long period. Cluster membership for each
variable star was deduced from the previous proper motion results (McNamara et
al. 1977) and position on the color-magnitude diagram. Many pulsating stars and
eclipsing binaries in the region of M11 are probable members of the cluster.Comment: 23 pages, 9 figures, 3 tables, and accepted for publication in PAS
Re-Evaluation of Yam Mosaic Virus (YMV) Detection Methods
Accurate and timely detection is vital for mitigation of tuber yield losses resulting from yam mosaic
virus (YMV) infection on yam, a major food security crop in West Africa. The observation, from our previous
studies, that the triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA), the most
commonly used detection method for YMV, detected the virus in significantly less leaf samples than
immunocapture reverse transcription polymerase chain reaction (IC-RT-PCR) necessitated a re-evaluation of
YMV detection methods. In the present study, eighteen previously tested YMV positive leaf samples from
Benin and Ghana were re-tested using TAS-ELISA, Protein A-sandwich (PAS) ELISA and IC-RT-PCR. Three
sap dilutions, 1/10, 1/50 and 1/100, were tested for each sample. Both at 1/10 and 1/50 dilutions, PAS-ELISA
and IC-RT-PCR detected YMV in 11 (61.1%) and 12 (66.7%) of the leaves respectively. Virus detection by
PAS-ELISA reduced to 50% at 1/100 sap dilution and increased to 77.8% in IC-RT-PCR. YMV detection by
TAS-ELISA varied between 38.9% and 16.7% at 1/10 and 1/100 dilutions respectively. These results indicate
a deficiency in the use of TAS-ELISA as a sole YMV certification method since the detecting monoclonal
antibody used in this assay may be strain specific. The use of PAS-ELISA at a 1/10 sap dilution is suggested
for YMV detection where the facilities for molecular detection are unavailabl
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