1,001 research outputs found
Exact solutions of the (2+1) Dimensional Dirac equation in a constant magnetic field in the presence of a minimal length
We study the (2+1) dimensional Dirac equation in an homogeneous magnetic
field (relativistic Landau problem) within a minimal length, or generalized
uncertainty principle -GUP-, scenario. We derive exact solutions for a given
explicit representation of the GUP and provide expressions of the wave
functions in the momentum representation. We find that in the minimal length
case the degeneracy of the states is modified and that there are states that do
not exist in the ordinary quantum mechanics limit (\beta -->0). We also discuss
the mass-less case which may find application in describing the behavior of
charged fermions in new materials like Graphene.Comment: 9 pages, to appear in Physical Review
Hunting for heavy composite Majorana neutrinos at the LHC
We investigate the search for heavy Majorana neutrinos stemming from a
composite model scenario at the upcoming LHC Run II at a center of mass energy
of 13 TeV. While previous studies of the composite Majorana neutrino were
focussed on gauge interactions via magnetic type transition coupling between
ordinary and heavy fermions (with mass ) here we complement the composite
model with contact interactions at the energy scale and we find that
the production cross sections are dominated by such contact interactions by
roughly two/three orders of magnitude. This mechanism provides therefore very
interesting rates at the prospected luminosities. We study the same sign
di-lepton and di-jet signature () and perform a fast
detector simulation based on Delphes. We compute 3 and 5
contour plots of the statistical significance in the parameter space
(). We find that the potentially excluded regions at TeV are quite larger than those excluded so far at Run I considering
searches with other signatures.Comment: 14 pages, 9 figures, Minor comments and few references added. Version
accepted by the European Physical Journal C (EPJC
Two-Time Correlation Functions: Stochastic and Conventional Quantum Mechanics
An investigation of two-time correlation functions is reported within the
framework of (i) Stochastic Quantum Mechanics and (ii) conventional
Heisenberg-Schr\"odinger Quantum Mechanics. The spectral functions associated
with the two-time electric dipole correlation functions are worked out in
detail for the case of the hydrogen atom. While the single time averages are
identical for stochastic and conventional quantum mechanics, differences arise
in the two approaches for multiple time correlation functions.Comment: Version published by the Eur. Phys. J. B. Few references added. Minor
typos correcte
Cell proliferation and oncogene expression after bile duct ligation in the rat: Evidence of a specific growth effect on bile duct cells
The proliferative response of the rat liver was measured after temporary or permanent total biliary obstruction (BDO) and in different regions after selective ligation of the lobar ducts draining the right 60% of the hepatic mass. The results were compared with those after 70% partial hepatectomy (PH). Cell proliferation was assessed globally by measuring DNA synthesis and stratified to the separate cell populations with cytostaining techniques that allowed distinction of hepatocytes, duct cells, and nonparenchymal cells (NPCs). In selected experimental groups, gene expression was determined of transforming growth factor-β1 (TGFβ-1), prothrombin, c-erb-B2, transforming growth factor alpha (TGFα), human Cyclophilin (CyP), and 28S ribosomal RNA. The stimulation of a proliferative response to total BDO required obstruction for longer than 24 hours, but after this deligation did not switch off regeneration. In the first week after permanent BDO, there was progressive infiltration of NPCs, fibrous linkage of some portal areas, and a crescendo of DNA synthesis that was obvious at 24 hours, maximal at 48 hours, and back nearly to baseline at 6 days. At the 2-day mark, the bile duct cells had a 17-fold increase in proliferation, accompanied by a threefold to fourfold increase in hepatocyte renewal. Little or no increase in expression of TGFα or the hepatocyte-specific prothrombin gene was detectable in the first 48 hours, whereas levels of the oncogene c-erb-B2 that is associated with cholangiocarcinoma were expressed from 48 to 96 hours. Livers subjected to regional BDO with or without immunosuppressive treatment with FK 506 and cyclosporine had an inflammatory reaction only on the side with ligated ducts. DNA synthesis increased in both the obstructed and freely draining lobes to approximately half the level that occurred after total BDO. The proliferation of the obstructed side was similar to the mixed duct cell/hepatocyte response after total BDO, but this almost exclusively involved duct cells on the freely draining side. In contrast to the findings after BDO, livers after PH regenerated maximally at 24 hours rather than 48 hours, had a predominantly noninflammatory hepatocyte as opposed to duct cell response, and had marked expression of the prothrombin and TGFα genes but only weakly and late of c-erb-B2 messenger RNA. The results show that the liver responds as a whole and in a biologically intelligent way to the nature of the injury inflicted on any part of it. It further implies the presence of humoral communications and control networks that assure organ homeostasis and relate this to total body homeostasis. © 1995
Sex Hormone-Related Functions in Regenerating Male Rat Liver
Sex hormone receptors were quantitated in normal male rat liver and in regenerating liver at several different times after partial (70%) hepatectomy. Both estrogen and androgen receptor content were altered dramatically by partial hepatectomy. Total hepatic content and nuclear retention of estrogen receptors increased, with the zenith evident 2 days after partial hepatectomy, corresponding to the zenith of mitotic index. Serum estradiol increased after 1 day, and reached a maximum at 3 days after surgery. In contrast, total and nuclear androgen receptor content demonstrated a massive decline at 1, 2, and 3 days after resection. Serum testosterone displayed a parallel decline. In addition, hepatic content of two androgen-responsive proteins was reduced to 15% and 13% of normal values during this period. The activity of these various proteins during regeneration of male rat liver is comparable to that observed in the liver of normal female rats. Taken together, these results indicate that partial hepatectomy induces a feminization of certain sexually dimorphic aspects of liver function in male rats. Furthermore, these data provide evidence that estrogens, but not androgens, may have an important role in the process of liver regeneration. © 1986, American Gastroenterological Association. All rights reserved
Ultra Low Momentum Neutron Catalyzed Nuclear Reactions on Metallic Hydride Surfaces
Ultra low momentum neutron catalyzed nuclear reactions in metallic hydride
system surfaces are discussed. Weak interaction catalysis initially occurs when
neutrons (along with neutrinos) are produced from the protons which capture
``heavy'' electrons. Surface electron masses are shifted upwards by localized
condensed matter electromagnetic fields. Condensed matter quantum
electrodynamic processes may also shift the densities of final states allowing
an appreciable production of extremely low momentum neutrons which are thereby
efficiently absorbed by nearby nuclei. No Coulomb barriers exist for the weak
interaction neutron production or other resulting catalytic processes.Comment: 4 pages, ReVTeX forma
Is it possible to predict the success of non-invasive positive pressure ventilation in acute respiratory failure due to COPD?
AbstractThere is now sufficient evidence that non-invasive positive pressure ventilation (NIPPV) in selected patients with severe hypercapnic acute respiratory failure due to chronic obstructive pulmonary disease (COPD) is more effective than pharmacological therapy alone. The aim of this study was to identify prognostic factors to predict the success of this technique. Fifty-nine consecutive patients with COPD admitted to a respiratory ward for 75 episodes of acute respiratory failure treated with NIPPV were analysed: success (77%) or failure (23%) were evaluated by survival and the need for endotracheal intubation. There were no significant differences in age, sex, cause of relapse and lung function tests between the two groups. Patients in whom NIPPV was unsuccessful were significantly underweight, had an higher Acute Physiology and Chronic Health Evaluation (APACHE) II score, and a lower serum level of albumin in comparison with those in whom NIPPV was successful. They demonstrated significantly greater abnormalities in pH and P a CO2at baseline and after 2 h of NIPPV. The logistic regression analysis demonstrated that, when all the variables were tested together, a high APACHE II score and a low albumin level continued to have a significant predictive effect. This analysis could predict the outcome in 82% of patients. In conclusion, our study suggests that low albumin serum levels and a high APACHE II score may be important indices in predicting the success of NIPPV
Scattering of Woods-Saxon Potential in Schrodinger Equation
The scattering solutions of the one-dimensional Schrodinger equation for the
Woods-Saxon potential are obtained within the position-dependent mass
formalism. The wave functions, transmission and reflection coefficients are
calculated in terms of Heun's function. These results are also studied for the
constant mass case in detail.Comment: 14 page
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