9,620 research outputs found
Parameters influencing potency of Bacillus thuringiensis var. israelensis products
Bioassays of products based on #Bacillus thuringiensis var. #israelensis have been carried out according to standard protocols. Theses analyses revealed that the slopes of the log-probit transformed concentration mortality curves of various products were different from that of the international standards (IPS82 for #Bacillus thuringiensis israelensis). For statistical reasons, this invalidates the tests. Products giving various slopes of the concentration mortality curves will obtain different potencies when estimated at a LC90 level than when estimated at LC50 level, as normally done. The LC90 level is probably pore relevant for the field effect. Changing the median particle size of a product in a non destructive way results in change of slope and LC50 and thereby potency. Therefore, potency of a product as measured in these bioassays is not just a measure of the quantity of #B. thuringiensis israelensis crystal protein present, but a function of product parameters like median particle size. Biochemical methods for quantification of toxin can therefore not relate simply to potency of the products obtained with this method. It is suggested that standard protocols for bioassay may be changed to assure equal particle size of products and samples to obtain parallel close response. (Résumé d'auteur
The [Y/Mg] clock works for evolved solar metallicity stars
Previously [Y/Mg] has been proven to be an age indicator for solar twins.
Here, we investigate if this relation also holds for helium-core-burning stars
of solar metallicity. High resolution and high signal-to-noise ratio (S/N)
spectroscopic data of stars in the helium-core-burning phase have been obtained
with the FIES spectrograph on the NOT 2.56m telescope and the HIRES
spectrograph on the Keck I 10 m telescope. They have been analyzed to determine
the chemical abundances of four open clusters with close to solar metallicity;
NGC 6811, NGC 6819, M67 and NGC 188. The abundances are derived from equivalent
widths of spectral lines using ATLAS9 model atmospheres with parameters
determined from the excitation and ionization balance of Fe lines. Results from
asteroseismology and binary studies were used as priors on the atmospheric
parameters, where especially the is determined to much higher
precision than what is possible with spectroscopy. It is confirmed that the
four open clusters are close to solar metallicity and they follow the [Y/Mg]
vs. age trend previously found for solar twins. The [Y/Mg] vs. age clock also
works for giant stars in the helium-core burning phase, which vastly increases
the possibilities to estimate the age of stars not only in the solar
neighborhood, but in large parts of the Galaxy, due to the brighter nature of
evolved stars compared to dwarfs.Comment: 5 pages, 3 figures, accepted for publication as a Letter to A&
Extraction of Airways with Probabilistic State-space Models and Bayesian Smoothing
Segmenting tree structures is common in several image processing
applications. In medical image analysis, reliable segmentations of airways,
vessels, neurons and other tree structures can enable important clinical
applications. We present a framework for tracking tree structures comprising of
elongated branches using probabilistic state-space models and Bayesian
smoothing. Unlike most existing methods that proceed with sequential tracking
of branches, we present an exploratory method, that is less sensitive to local
anomalies in the data due to acquisition noise and/or interfering structures.
The evolution of individual branches is modelled using a process model and the
observed data is incorporated into the update step of the Bayesian smoother
using a measurement model that is based on a multi-scale blob detector.
Bayesian smoothing is performed using the RTS (Rauch-Tung-Striebel) smoother,
which provides Gaussian density estimates of branch states at each tracking
step. We select likely branch seed points automatically based on the response
of the blob detection and track from all such seed points using the RTS
smoother. We use covariance of the marginal posterior density estimated for
each branch to discriminate false positive and true positive branches. The
method is evaluated on 3D chest CT scans to track airways. We show that the
presented method results in additional branches compared to a baseline method
based on region growing on probability images.Comment: 10 pages. Pre-print of the paper accepted at Workshop on Graphs in
Biomedical Image Analysis. MICCAI 2017. Quebec Cit
Risk of schizophrenia in relation to parental origin and genome-wide divergence
Background. Second-generation immigrants have an increased risk of schizophrenia, a finding that still lacks a satisfactory explanation. Various operational definitions of second-generation immigrants have been used, including foreign parental country of birth. However, with increasing global migration, it is not clear that parental country of birth necessarily is informative with regard to ethnicity. We compare two independently collected measures of parental foreign ethnicity, parental foreign country of birth versus genetic divergence, based on genome-wide genotypic data, to access which measure most efficiently captures the increased risk of schizophrenia among second-generation immigrants residing in Denmark. Method. A case-control study covering all children born in Denmark since 1981 included 892 cases of schizophrenia and 883 matched controls. Genetic divergence was assessed using principal component analyses of the genotypic data. Independently, parental foreign country of birth was assessed using information recorded prospectively in the Danish Civil Registration System. We compared incidence rate ratios of schizophrenia associated with these two independently collected measures of parental foreign ethnicity. Results. People with foreign-born parents had a significantly increased risk of schizophrenia [relative risk (RR) 1.94 (95% confidence intervals (CI) 1.41-2.65)]. Genetically divergent persons also had a significant increased risk [RR 2.43 ( 95% CI 1.55-3.82)]. Mutual adjustment of parental foreign country of birth and genetic divergence showed no difference between these measures with regard to their potential impact on the results. Conclusions. In terms of RR of schizophrenia, genetic divergence and parental foreign country of birth are interchangeable entities, and both entities have validity with regard to identifying second-generation immigrants
One Dimensional Kondo Lattice Model Studied by the Density Matrix Renormalization Group Method
Recent developments of the theoretical investigations on the one-dimensional
Kondo lattice model by using the density matrix renormalization group (DMRG)
method are discussed in this review. Short summaries are given for the
zero-temperature DMRG, the finite-temperature DMRG, and also its application to
dynamic quantities. Away from half-filling, the paramagnetic metallic state is
shown to be a Tomonaga-Luttinger liquid with the large Fermi surface. For the
large Fermi surface its size is determined by the sum of the densities of the
conduction electrons and the localized spins. The correlation exponent K_rho of
this metallic phase is smaller than 1/2. At half-filling the ground state is
insulating. Excitation gaps are different depending on channels, the spin gap,
the charge gap and the quasiparticle gap. Temperature dependence of the spin
and charge susceptibilities and specific heat are discussed. Particularly
interesting is the temperature dependence of various excitation spectra, which
show unusual properties of the Kondo insulators.Comment: 18 pages, 23 Postscript figures, REVTe
Equine West Nile encephalitis, United States.
After the 1999 outbreak of West Nile (WN) encephalitis in New York horses, a case definition was developed that specified the clinical signs, coupled with laboratory test results, required to classify cases of WN encephalitis in equines as either probable or confirmed. In 2000, 60 horses from seven states met the criteria for a confirmed case. The cumulative experience from clinical observations and diagnostic testing during the 1999 and 2000 outbreaks of WN encephalitis in horses will contribute to further refinement of diagnostic criteria
Post-Prior discrepancies in CDW-EIS calculations for ion impact ionization fully differential cross sections
In this work we present fully differential cross sections (FDCSs)
calculations using post and prior version of CDW--EIS theory for helium single
ionization by 100 MeV C amu and 3.6 MeV amu Au and
Au ions. We performed our calculations for different momentum transfer
and ejected electron energies. The influence of internuclear potential on the
ejected electron spectra is taken into account in all cases. We compare our
calculations with absolute experimental measurements. It is shown that prior
version calculations give better agreement with experiments in almost all
studied cases.Comment: 9 pages, 7 figure
Switching between dynamic states in intermediate-length Josephson junctions
The appearance of zero-field steps (ZFS’s) in the current-voltage characteristics of intermediate-length overlap-geometry Josephson tunnel junctions described by a perturbed sine-Gordon equation (PSGE) is associated with the growth of parametrically excited instabilities of the McCumber background curve (MCB). A linear stability analysis of a McCumber solution of the PSGE in the asymptotic linear region of the MCB and in the absence of magnetic field yields a Hill’s equation which predicts how the number, locations, and widths of the instability regions depend on the junction parameters. A numerical integration of the PSGE in terms of truncated series of time-dependent Fourier spatial modes verifies that the parametrically excited instabilities of the MCB evolve into the fluxon oscillations characteristic of the ZFS’s. An approximate analysis of the Fourier mode equations in the presence of a small magnetic field yields a field-dependent Hill’s equation which predicts that the major effect of such a field is to reduce the widths of the instability regions. Experimental measurements on Nb-NbxOy-Pb junctions of intermediate length, performed at different operating temperatures in order to vary the junction parameters and for various magnetic field values, verify the physical existence of switching from the MCB to the ZFS’s. Good qualitative, and in many cases quantitative, agreement between analytic, numerical, and experimental results is obtained
Effects of Oral Glucose Load on Endothelial Function and on Insulin and Glucose Fluctuations in Healthy Individuals
Background/aims. Postprandial hyperglycemia, an independent risk factor for cardiovascular disease, is accompanied by endothelial dysfunction. We studied the effect of oral glucose load on insulin and glucose fluctuations, and on postprandial endothelial function in healthy individuals in order to better understand and cope with the postprandial state in insulin resistant individuals. Methods. We assessed post-oral glucose load endothelial function (flow mediated dilation), plasma insulin, and blood glucose in 9 healthy subjects. Results. The largest increases in delta FMD values (fasting FMD value subtracted from postprandial FMD value) occurred at 3 hours after both glucose or placebo load, respectively: 4.80 ± 1.41 (P = .009) and 2.34 ± 1.47 (P = .15). Glucose and insulin
concentrations achieved maximum peaks at one hour post-glucose load. Conclusion. Oral glucose load does not induce endothelial dysfunction in healthy individuals with mean insulin and glucose values of 5.6 mmol/L and 27.2 mmol/L, respectively, 2 hours after glucose load
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