5,158 research outputs found
Collapsed 2-Dimensional Polymers on a Cylinder
Single partially confined collapsed polymers are studied in two dimensions.
They are described by self-avoiding random walks with nearest-neighbour
attractions below the -point, on the surface of an infinitely long
cylinder. For the simulations we employ the pruned-enriched-Rosenbluth method
(PERM). The same model had previously been studied for free polymers (infinite
lattice, no boundaries) and for polymers on finite lattices with periodic
boundary conditions. We verify the previous estimates of bulk densities, bulk
free energies, and surface tensions. We find that the free energy of a polymer
with fixed length has, for , a minimum at a finite cylinder
radius which diverges as . Furthermore, the surface
tension vanishes roughly as for with
. The density in the interior of a globule scales as
with .Comment: 4 pages, 8 figure
Maternal immune activation alters nonspatial information processing in the hippocampus of the adult offspring
The observation that maternal infection increases the risk for schizophrenia in the offspring suggests that the maternal immune system plays a key role in the etiology of schizophrenia. In a mouse model, maternal immune activation (MIA) by injection of poly(I:C) yields adult offspring that display abnormalities in a variety of behaviors relevant to schizophrenia. As abnormalities in the hippocampus are a consistent observation in schizophrenia patients, we examined synaptic properties in hippocampal slices prepared from the offspring of poly(I:C)- and saline-treated mothers. Compared to controls, CA1 pyramidal neurons from adult offspring of MIA mothers display reduced frequency and increased amplitude of miniature excitatory postsynaptic currents. In addition, the specific component of the temporoammonic pathway that mediates object-related information displays increased sensitivity to dopamine. To assess hippocampal network function in vivo, we used expression of the immediate-early gene, c-Fos, as a surrogate measure of neuronal activity. Compared to controls, the offspring of poly(I:C)-treated mothers display a distinct c-Fos expression pattern in area CA1 following novel object, but not novel location, exposure. Thus, the offspring of MIA mothers may have an abnormality in modality-specific information processing. Indeed, the MIA offspring display enhanced discrimination in a novel object recognition, but not in an object location, task. Thus, analysis of object and spatial information processing at both synaptic and behavioral levels reveals a largely selective abnormality in object information processing in this mouse model. Our results suggest that altered processing of object-related information may be part of the pathogenesis of schizophrenia-like cognitive behaviors
Stretched Polymers in a Poor Solvent
Stretched polymers with attractive interaction are studied in two and three
dimensions. They are described by biased self-avoiding random walks with
nearest neighbour attraction. The bias corresponds to opposite forces applied
to the first and last monomers. We show that both in and a phase
transition occurs as this force is increased beyond a critical value, where the
polymer changes from a collapsed globule to a stretched configuration. This
transition is second order in and first order in . For we
predict the transition point quantitatively from properties of the unstretched
polymer. This is not possible in , but even there we can estimate the
transition point precisely, and we can study the scaling at temperatures
slightly below the collapse temperature of the unstretched polymer. We find
very large finite size corrections which would make very difficult the estimate
of the transition point from straightforward simulations.Comment: 10 pages, 16 figure
Polymers grafted to porous membranes
We study a single flexible chain molecule grafted to a membrane which has
pores of size slightly larger than the monomer size. On both sides of the
membrane there is the same solvent. When this solvent is good, i.e. when the
polymer is described by a self avoiding walk, it can fairly easily penetrate
the membrane, so that the average number of membrane crossings tends, for chain
length , to a positive constant. The average numbers of monomers on
either side of the membrane diverges in this limit, although their ratio
becomes infinite. For a poor solvent, in contrast, the entire polymer is
located, for large , on one side of the membrane. For good and for theta
solvents (ideal polymers) we find scaling laws, whose exponents can in the
latter case be easily understood from the behaviour of random walks.Comment: 4 pages, 6 figure
Rapid and sensitive insulated isothermal PCR for point-of-need feline leukaemia virus detection
Objectives: Feline leukaemia virus (FeLV), a gamma retrovirus, causes diseases of the feline haematopoietic system that are invariably fatal. Rapid and accurate testing at the point-of-need (PON) supports prevention of virus spread and management of clinical disease. This study evaluated the performance of an insulated isothermal PCR (iiPCR) that detects proviral DNA, and a reverse transcription (RT)-iiPCR that detects both viral RNA and proviral DNA, for FeLV detection at the PON. Methods: Mycoplasma haemofelis, feline coronavirus, feline herpesvirus, feline calicivirus and feline immunodeficiency virus were used to test analytical specificity. In vitro transcribed RNA, artificial plasmid, FeLV strain American Type Culture Collection VR-719 and a clinical FeLV isolate were used in the analytical sensitivity assays. A retrospective study including 116 clinical plasma and serum samples that had been tested with virus isolation, real-time PCR and ELISA, and a prospective study including 150 clinical plasma and serum samples were implemented to evaluate the clinical performances of the iiPCR-based methods for FeLV detection. Results: Ninety-five percent assay limit of detection was calculated to be 16 RNA and five DNA copies for the RT-iiPCR, and six DNA copies for the iiPCR. Both reactions had analytical sensitivity comparable to a reference real-time PCR (qPCR) and did not detect five non-target feline pathogens. The clinical performance of the RT-iiPCR and iiPCR had 98.82% agreement (kappa[κ] = 0.97) and 100% agreement (κ = 1.0), respectively, with the qPCR (n = 85). The agreement between an automatic nucleic extraction/RT-iiPCR system and virus isolation to detect FeLV in plasma or serum was 95.69% (κ = 0.95) and 98.67% (κ = 0.85) in a retrospective (n = 116) and a prospective (n = 150) study, respectively. Conclusions and relevance: These results suggested that both RT-iiPCR and iiPCR assays can serve as reliable tools for PON FeLV detection
Szeg\"o kernel asymptotics and Morse inequalities on CR manifolds
We consider an abstract compact orientable Cauchy-Riemann manifold endowed
with a Cauchy-Riemann complex line bundle. We assume that the manifold
satisfies condition Y(q) everywhere. In this paper we obtain a scaling
upper-bound for the Szeg\"o kernel on (0, q)-forms with values in the high
tensor powers of the line bundle. This gives after integration weak Morse
inequalities, analogues of the holomorphic Morse inequalities of Demailly. By a
refined spectral analysis we obtain also strong Morse inequalities which we
apply to the embedding of some convex-concave manifolds.Comment: 40 pages, the constants in Theorems 1.1-1.8 have been modified by a
multiplicative constant 1/2 ; v.2 is a final updat
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Characterization of string cavitation in large-scale Diesel nozzles with tapered holes
The cavitation structures formed inside enlarged transparent replicas of tapered Diesel valve covered orifice nozzles have been characterized using high speed imaging visualization. Cavitation images obtained at fixed needle lift and flow rate conditions have revealed that although the conical shape of the converging tapered holes suppresses the formation of geometric cavitation, forming at the entry to the cylindrical injection hole, string cavitation has been found to prevail, particularly at low needle lifts. Computational fluid dynamics simulations have shown that cavitation strings appear in areas where large-scale vortices develop. The vortical structures are mainly formed upstream of the injection holes due to the nonuniform flow distribution and persist also inside them. Cavitation strings have been frequently observed to link adjacent holes while inspection of identical real-size injectors has revealed cavitation erosion sites in the area of string cavitation development. Image postprocessing has allowed estimation of their frequency of appearance, lifetime, and size along the injection hole length, as function of cavitation and Reynolds numbers and needle lif
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