727 research outputs found
Quasi-Exact Solvability and the direct approach to invariant subspaces
We propose a more direct approach to constructing differential operators that
preserve polynomial subspaces than the one based on considering elements of the
enveloping algebra of sl(2). This approach is used here to construct new
exactly solvable and quasi-exactly solvable quantum Hamiltonians on the line
which are not Lie-algebraic. It is also applied to generate potentials with
multiple algebraic sectors. We discuss two illustrative examples of these two
applications: an interesting generalization of the Lam\'e potential which
posses four algebraic sectors, and a quasi-exactly solvable deformation of the
Morse potential which is not Lie-algebraic.Comment: 17 pages, 3 figure
Cyclophilins in Ischemic Heart Disease: Differences Between Acute and Chronic Coronary Artery Disease Patients
Background: Cyclophilins (Cyps) are a family of peptidyl-prolyl cis/trans isomerases consistently involved in cardiovascular diseases through the inflammation pathway. This study aims to investigate the serum levels of Cyps (CypA, CypB, CypC and CypD) in patients with coronary artery disease (CAD) and the correlation with clinical characteristics and inflammation parameters. Methods: We developed an observational prospective study with a total of 125 subjects: 40 patients with acute CAD, 40 patients with chronic CAD and 45 control volunteers, in whom serum levels of Cyps (CypA, CypB, CypC and CypD), interleukins and metalloproteinases were measured. Results: CypA levels increased significantly in CAD patients compared with control subjects, but no differences were noted between acute CAD (7.80 +/- 1.30 ng/mL) and chronic CAD (5.52 +/- 0.76 ng/mL) patients (P = 0.13). No differences in CypB and CypD levels were showed between CAD patients and controls and between acute CAD and chronic CAD patients. In relation with CypC, the levels in CAD patients were significantly higher compared to controls (32.42 +/- 3.71 pg/mL vs. 9.38 +/- 1.51 pg/mL, P 17.5 pg/mL cut-off point, and it was significantly associated with older age, hypertension, dyslipidemia and more extensive CAD in acute and chronic CAD groups. Conclusions: CypA and CypC levels are increased in CAD patients. High CypC serum levels could be a novel biomarker in CAD patients correlating with a more severe disease
La gestión del mantenimiento una oportunidad de cambio
El articulo presenta una reflexión de los autores sobre la gestión del mantenimiento a nivel internacional nacional y local, utiliza fuentes de información como opiniones de diferentes expertos nacionales e internacionales, bases de datos bibliográficas internacionales especializadas como ProQuest, Scielo.  Este artÃÂculo se desarrolla en el marco del proyecto del grupo de investigación IDENTUS Estudio Sobre la Gestión de Mantenimiento de las PYMES Industriales de la Provincia Guanentá. Se emplean opiniones y publicaciones de diferentes expertos nacionales e internacionales del mismo modo que indicadores bibliométricos de producción. Se recoge la producción cientÃÂfica registrada en las bases de datos ProQuest y Scielo
Gamma Ray Bursts as Probes of Quantum Gravity
Gamma ray bursts (GRBs) are short and intense pulses of -rays
arriving from random directions in the sky. Several years ago Amelino-Camelia
et al. pointed out that a comparison of time of arrival of photons at different
energies from a GRB could be used to measure (or obtain a limit on) possible
deviations from a constant speed of light at high photons energies. I review
here our current understanding of GRBs and reconsider the possibility of
performing these observations.Comment: Lectures given at the 40th winter school of theretical physics:
Quantum Gravity and Phenomenology, Feb. 2004 Polan
Effects of alirocumab on types of myocardial infarction: insights from the ODYSSEY OUTCOMES trial
AIMS: The third Universal Definition of Myocardial Infarction (MI) Task Force classified MIs into five types: Type 1, spontaneous; Type 2, related to oxygen supply/demand imbalance; Type 3, fatal without ascertainment of cardiac biomarkers; Type 4, related to percutaneous coronary intervention; and Type 5, related to coronary artery bypass surgery. Low-density lipoprotein cholesterol (LDL-C) reduction with statins and proprotein convertase subtilisin-kexin Type 9 (PCSK9) inhibitors reduces risk of MI, but less is known about effects on types of MI. ODYSSEY OUTCOMES compared the PCSK9 inhibitor alirocumab with placebo in 18 924 patients with recent acute coronary syndrome (ACS) and elevated LDL-C (>/=1.8 mmol/L) despite intensive statin therapy. In a pre-specified analysis, we assessed the effects of alirocumab on types of MI. METHODS AND RESULTS: Median follow-up was 2.8 years. Myocardial infarction types were prospectively adjudicated and classified. Of 1860 total MIs, 1223 (65.8%) were adjudicated as Type 1, 386 (20.8%) as Type 2, and 244 (13.1%) as Type 4. Few events were Type 3 (n = 2) or Type 5 (n = 5). Alirocumab reduced first MIs [hazard ratio (HR) 0.85, 95% confidence interval (CI) 0.77-0.95; P = 0.003], with reductions in both Type 1 (HR 0.87, 95% CI 0.77-0.99; P = 0.032) and Type 2 (0.77, 0.61-0.97; P = 0.025), but not Type 4 MI. CONCLUSION: After ACS, alirocumab added to intensive statin therapy favourably impacted on Type 1 and 2 MIs. The data indicate for the first time that a lipid-lowering therapy can attenuate the risk of Type 2 MI. Low-density lipoprotein cholesterol reduction below levels achievable with statins is an effective preventive strategy for both MI types
On new gravitational instantons describing creation of brane-worlds
By considering 5--dimensional cosmological models with a bulk filled with a
pressureless scalar field; equivalently dust matter, and a negative
cosmological constant, we have found a regular instantonic solution which is
free from any singularity at the origin of the extra--coordinate. This
instanton describes 5--dimensional asymptotically anti de Sitter wormhole, when
the bulk has a topology R times S^4. Compactified brane-world instantons which
are built up from such instantonic solution describe either a single brane or a
string of branes. Their analytical continuation to the pseudo--Riemannian
metric can give rise to either 4-dimensional inflating branes or solutions with
the same dynamical behaviour for extra--dimension and branes, in addition to
multitemporal solutions. Dust brane-world models with arbitrary dimensions (D
>= 5) as well as other spatial topologies are also briefly discussed.Comment: 11 pages, 3 figures, LaTeX2e, accepted for publication in Classical
and Quantum Gravit
Total IgA and IgA reactivity to antigen I/II epitopes in HLA-DRB1*04 positive subjects
Bacterial adherence to the acquired dental pellicle, important in dental caries (caries), is mediated by receptor-adhesins such as salivary agglutinin binding to Streptococcus mutans antigen I/II (I/II). Ten selected I/II epitopes were chosen to determine their reactivity to human salivary IgA. Previous studies suggested that a specific HLA biomarker group (HLA-DRB1*04) may have differential influence of immune responses to I/II. However, it was not known whether secretory IgA (SIgA) responses to the selected epitopes from HLA-DRB1*04 positive subjects were different compared to controls, or across other caries-related factors such as total IgA (TIgA). Thirty-two total subjects were matched according to HLA type, gender, ethnicity and age. HLA genotyping, oral bacterial, immunoglobulin and antibody analyses were performed. A large observed difference emerged with regard to the natural immune reservoir of TIgA in HLA-DRB1*04 positive subjects, specifically, a 27.6% reduction compared to controls. In contrast to all other epitopes studied, HLA-DRB1*04 positive subjects also exhibited reduced reactivity to I/II epitope 834–853. HLA-DRB1*04 positive subjects exhibited lower specific SIgA activity/TIgA to 834–853 and also a lower specific reactivity to 834–853/whole cell S. mutans UA159. Furthermore, HLA-DRB1*04 positive subjects exhibited lower responses to I/II in its entirety. The large observed difference in TIgA and the 834–853 reactivity pattern across multiple measures suggest potentially important connections pertaining to the link between HLA-DRB1*04 and caries
Is there a caustic crossing in the lensed quasar Q2237+0305 observational data record?
We re-investigate the gravitationally lensed system Q2237+0305 data record to
quantify the probability of having a caustic crossing in the A component.
Several works assume that this is the case, but no quantitative analysis is
available in the literature. We combine the datasets from the OGLE and GLITP
collaborations to accurately trace the prominent event in the lightcurve for
the A component of the system. Then the observed event is compared with
synthetic light curves derived from trajectories in magnification maps. These
maps are generated using a ray-tracing technique. We take more than 10^9
trajectories and test a wide range of different physical properties of the
lensing galaxy and the source quasar (lens transverse velocity, microlens mass,
source intensity profile and source size). We found that around 75% of our good
trajectories (i.e. that are consistent with the observations) are caustic
crossings. In addition, a high transverse velocity exceeding 300 km/s, a
microlens mass of about 0.1 M_sun and a small standard accretion disk is the
best parameter combination. The results justify the interpretation of the
OGLE-GLITP event in Q2237+0305A as a caustic crossing. Moreover, the physical
properties of the lens and source are in very good agreement with previous
works. We also remark that a standard accretion disk is prefered to those
simpler approaches, and that the former should be used in subsequent
simulations.Comment: 5 pages, 3 figures, 3 tables, to appear in MNRA
Quantum Mechanics on the cylinder
A new approach to deformation quantization on the cylinder considered as
phase space is presented. The method is based on the standard Moyal formalism
for R^2 adapted to (S^1 x R) by the Weil--Brezin--Zak transformation. The
results are compared with other solutions of this problem presented by
Kasperkovitz and Peev (Ann. Phys. vol. 230, 21 (1994)0 and by Plebanski and
collaborators (Acta Phys. Pol. vol. B 31}, 561 (2000)). The equivalence of
these three methods is proved.Comment: 21 pages, LaTe
Variable G and : scalar-tensor versus RG-improved cosmology
We study the consequences due to time varying and in
scalar-tensor theories of gravity for cosmology, inspired by the modifications
introduced by the Renormalization Group (RG) equations in the Quantum Einstein
Gravity. We assume a power-law scale factor in presence contemporarily of both
the scalar field and the matter components of the cosmic fluid, and analyze a
special case and its generalization, also showing the possibility of a phantom
cosmology. In both such situations we find a negative kinetic term for the
scalar field and, possibly, an equation-of-state parameter . A
violation of dominant energy condition (DEC) for is also possible in both
of them; but, while in the first special case the -energy density then
remains positive, in the second one we find it negative.Comment: 25 pages, to be published in Gen. Rel. Grav. 200
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