405 research outputs found
A statistical mechanical description of metastable states and hysteresis in the 3D soft-spin random-field model at T=0
We present a formalism for computing the complexity of metastable states and
the zero-temperature magnetic hysteresis loop in the soft-spin random-field
model in finite dimensions. The complexity is obtained as the Legendre
transform of the free-energy associated to a certain action in replica space
and the hysteresis loop above the critical disorder is defined as the curve in
the field-magnetization plane where the complexity vanishes; the nonequilibrium
magnetization is therefore obtained without having to follow the dynamical
evolution. We use approximations borrowed from condensed-matter theory and
based on assumptions on the structure of the direct correlation functions (or
proper vertices), such as a local approximation for the self-energies, to
calculate the hysteresis loop in three dimensions, the correlation functions
along the loop, and the second moment of the avalanche-size distribution.Comment: 28 pages, 12 figure
Dietary influences over proliferating cell nuclear antigen expression in the locust midgut
We have studied the influence of variations in dietary protein (P) and digestible carbohydrate (C), the quantity of food eaten, and insect age during the fifth instar on the expression of the proliferating cell nuclear antigen (PCNA) in the epithelial cells of the midgut (with special reference to the midgut caeca) in the African migratory locust, Locusta migratoria. Densitometric analysis of PCNA-immunostained cells was used as an indirect measure of the levels of expression of PCNA, and a PCNA cellular index (PCNA-I) was obtained. Measurements of the DNA content of the cells have also been carried out by means of microdensitometry of Feulgen-stained, thick sections of midgut. A comparison between the PCNA nuclear level and the DNA content was performed. The PCNA levels were significantly different among the cells of the five regions studied: caeca, anterior ventricle, medial ventricle, posterior ventricle and ampullae of the Malpighian tubules. We have studied in more detail the region with highest PCNA-I, i.e. the caeca. The quality and the quantity of food eaten under ad libitum conditions were highly correlated with both the PCNA and DNA levels in the caeca cells. Locusts fed a diet with a close to optimal P:C content (P 21%, C 21%) showed the highest PCNA and DNA content. In locusts fed a food that also contained a 1:1 ratio of P to C but was diluted three-fold by addition of indigestible cellulose (P 7%, C 7%), a compensatory increase in consumption was critical to maintaining PCNA levels. Our measurements also showed that the nuclear DNA content of the mature and differentiated epithelial cells was several-fold higher than the levels in the undifferentiated stem cells of the regenerative nests. These results, combined with the low number of mitotic figures found in the regenerative nests of the caeca and the marked variation in PCNA levels among groups, suggest that some type of DNA endoreduplication process may be taking place. Our data also indicate that the DNA synthetic activity in the midgut is related to feeding in locusts. The possible dietary and nutritional regulatory mechanisms and the significance of the differences found are discussed
Preparations for Quantum Simulations of Quantum Chromodynamics in 1+1 Dimensions: (II) Single-Baryon -Decay in Real Time
A framework for quantum simulations of real-time weak decays of hadrons and
nuclei in a 2-flavor lattice theory in one spatial dimension is presented. A
single generation of the Standard Model is found to require 16 qubits per
spatial lattice site after mapping to spin operators via the Jordan-Wigner
transformation. Both quantum chromodynamics and flavor-changing weak
interactions are included in the dynamics, the latter through four-Fermi
effective operators. Quantum circuits which implement time evolution in this
lattice theory are developed and run on Quantinuum's H1-1 20-qubit trapped ion
system to simulate the -decay of a single baryon on one lattice site.
These simulations include the initial state preparation and are performed for
both one and two Trotter time steps. The potential intrinsic error-correction
properties of this type of lattice theory are discussed and the leading lattice
Hamiltonian required to simulate -decay of nuclei induced by a
neutrino Majorana mass term is provided.Comment: 26 pages, 11 figure
The effect of thresholding on temporal avalanche statistics
We discuss intermittent time series consisting of discrete bursts or
avalanches separated by waiting or silent times. The short time correlations
can be understood to follow from the properties of individual avalanches, while
longer time correlations often present in such signals reflect correlations
between triggerings of different avalanches. As one possible source of the
latter kind of correlations in experimental time series, we consider the effect
of a finite detection threshold, due to e.g. experimental noise that needs to
be removed. To this end, we study a simple toy model of an avalanche, a random
walk returning to the origin or a Brownian bridge, in the presence and absence
of superimposed delta-correlated noise. We discuss the properties after
thresholding of artificial timeseries obtained by mixing toy avalanches and
waiting times from a Poisson process. Most of the resulting scalings for
individual avalanches and the composite timeseries can be understood via random
walk theory, except for the waiting time distributions when strong additional
noise is added. Then, to compare with a more complicated case we study the
Manna sandpile model of self-organized criticality, where some further
complications appear.Comment: 15 pages, 12 figures, submitted to J. Stat. Mech., special issue of
the UPoN2008 conferenc
A Multi-APD readout for EL detectors
Detectors with an electroluminesence readout show an excellence performance
in respect of energy resolution making them interesting for various
applications as X-ray detection, double beta and dark matter experiments,
Compton and gamma cameras, etc. In the following the study of a readout based
on avalanche photo diodes to detect directly the VUV photons is presented.
Results of measurements with 5 APDs in xenon at pressures between 1 and 1.65
bar are shown indicating that such a readout can provide excellent energy and a
moderate position resolution.Comment: Talk given at the 5th Symposium on Large TPCs for Low Energy Rare
Events. Submitted to JPCS (Journal of Physics: Conference Series) for
publication. 8 pages, 17 figure
Metastable Random Field Ising model with exchange enhancement: a simple model for Exchange Bias
We present a simple model that allows hysteresis loops with exchange bias to
be reproduced. The model is a modification of the T=0 random field Ising model
driven by an external field and with synchronous local relaxation dynamics. The
main novelty of the model is that a certain fraction f of the exchange
constants between neighbouring spins is enhanced to a very large value J_E. The
model allows the dependence of the exchange bias and other properties of the
hysteresis loops to be analyzed as a function of the parameters of the model:
the fraction f of enhanced bonds, the amount of the enhancement J_E and the
amount of disorder which is controlled by the width sigma of the Gaussian
distribution of the random fields.Comment: 8 pages, 11 figure
Efecto del momento de arrancado y la permanencia del cultivo en andana sobre el rendimiento, calidad lipídica y sanidad del grano de maní
The indeterminate growth habit of peanut and characteristic underground fruiting make it difficult to identify the harvesting practices to achieve the highest yield and kernel quality. The objective of this work was to evaluate the effect of the digging dates and the subsequent stay in the field on the yield, lipid quality and health of the peanut kernels. The tests were carried out with cv. Granoleic during four seasons. The experimental design was completely randomized with three repetitions, with two digging moments (150 and 165 days from sowing) and in each of them four harvesting dates (7, 15, 21 and 28 days). According to the results, the delay in the digging dates increased the yield without kernel size and lipid fraction changes. On the other hand, increasing the number of days in the windrow did not improve these variables, but it did decrease the sanitary quality. Extending the crop cycle and the permanence of the pods in the field under the evaluated conditions did not improve the quality of the peanut kernel destined for human consumption.En el cultivo de maní su crecimiento indeterminado y la fructificación subterránea característica dificulta la identificación de las prácticas de cosecha para alcanzar el mayor rendimiento y calidad de grano. El objetivo de este trabajo fue evaluar el efecto del momento de arrancado y la posterior permanencia en andana sobre el rendimiento, calidad lipídica y sanidad del grano de maní. Los ensayos se realizaron con el cv. Granoleico durante cuatro campañas. El diseño experimental fue completamente aleatorizado con tres repeticiones, con dos momentos de arrancado (150 y 165 días desde la siembra) y en cada uno de ellos, cuatro momentos de recolección (7, 15, 21 y 28 días desde arrancado). De acuerdo a los resultados, el retraso en el momento de arrancado aumentó el rendimiento sin cambios en la granometría, ni en la fracción lipídica. Por otra parte, aumentar la cantidad de días en la andana no mejoró estas variables, pero sí disminuyó la calidad sanitaria. Extender el ciclo del cultivo y la permanencia de las vainas en el campo en las condiciones evaluadas, no mejoró la calidad del grano de maní destinado a consumo humano.
Caveats and pitfalls of SOX1 autoantibody testing with a commercial line blot assay in paraneoplastic neurological investigations
SOX1 autoantibodies are considered markers of small cell lung cancer (SCLC) and paraneoplastic neurological syndromes (PNS) and are usually determined by commercial line blot in many clinical services. Recent studies suggested that SOX1 autoantibodies also occur in patients with neuropathies unrelated to SCLC, questioning the value of SOX1 autoantibodies as paraneoplastic biomarkers. Here, we compared the specificity and sensitivity of a commercial line blot (Euroimmun, Lübeck, Germany) with those of an in house cell-based assay (CBA) with HEK293 cells transfected with SOX1. Overall, 210 patients were included in the study, 139 patients with polyneuropathies without SCLC, and 71 with disorders associated with SOX1 autoantibodies detected with the in-house CBA. Forty one of these 71 cases had been referred to our laboratory for onconeuronal antibody assessment and 30/71 were patients with known PNS and SCLC. None of the patients with polyneuropathies had SOX1 autoantibodies by either line blot or CBA (specificity of the immunoblot: 100%; 95%C.I.: 97.8-100). Among the 71 patients with CBA SOX1 autoantibodies, only 53 were positive by line blot (sensitivity: 74.6%; 95%C.I.: 62.9-84.2). Lung cancer was detected in 37/41 (90%; 34 with SCLC) patients referred for onconeuronal antibody assessment and 34 of them also had a PNS. Our study confirms the association of SOX1 autoantibodies with SCLC and PNS. The line blot test misses 25% of the cases; therefore, to minimize the frequency of false negative results we recommend the use of a confirmatory test, such as CBA, in patients suspected to have a SCLC-related PNS
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