Effect of the structure on luminescent characteristics of SRO-based light emitting capacitors.

In this paper, we study the structural, optical and electro-optical properties of silicon rich oxide (SRO) films, with 6.2 (SRO30) and 7.3 at.% (SRO20) of silicon excess thermally annealed at different temperatures and used as an active layer in light emitting capacitors (LECs). A typical photoluminescence (PL) red-shift is observed as the silicon content and annealing temperature are increased. Nevertheless, when SRO30 films are used in LECs, a resistance switching (RS) behavior from a high current state (HCS) to a low conduction state (LCS) is observed, enhancing the intense blue electroluminescence (EL). This RS produces a long spectral blue-shift (∼227 nm) between the EL and PL band, and it is related to structural defects created by a high current flow through preferential conductive paths breaking off Si-Si bonds from very small silicon nanoparticles (Si-nps) (Eδ (Si ↑ Si ≡ Si) centers). LECs with SRO20 films do not present the RS behavior and only exhibit a slight shift between PL and EL, both in red spectra. The carrier transport in these LEC devices is analyzed as being trap assisted tunnelling and Poole-Frenkel through a quasi 'continuum' of defect traps and quantum dots for the conduction mechanism in SRO30 and SRO20 films, respectively. The results prove the feasibility of obtaining light emitting devices by using simple panel structures with Si-nps embedded in the dielectric layer.

A path-integral Monte Carlo study of a small cluster: The Ar trimer.

The Ar(3) system has been studied between T=0 K and T=40 K by means of a path-integral Monte Carlo (PIMC) method. The behavior of the average energy in terms of the temperature has been explained by comparison with results obtained with the thermal averaged rovibrational spectra estimated via: (i) a quantum mechanical method based on distributed Gaussian functions for the interparticle distances and (ii) an analytical model which precisely accounts for the participation of the dissociative continua Ar(2)+Ar and Ar+Ar+Ar. Beyond T approximately 20 K, the system explores floppier configurations than the rigid equilateral geometry, as linear and Ar-Ar(2)-like arrangements, and fragmentates around T approximately 40 K. A careful investigation of the specific heat in terms of a confining radius in the PIMC calculation seems to discard a proper phase transition as in larger clusters, in apparent contradiction with previous reports of precise values for a liquid-gas transition. The onset of this noticeable change in the dynamics of the trimer occurs, however, at a remarkably low value of the temperature in comparison with Ar(n) systems formed with more Ar atoms. Quantum mechanical effects are found of relevance at T

DC and AC electroluminescence in silicon nanoparticles embedded in silicon-rich oxide films.

Electroluminescent properties of silicon-rich oxide (SRO) films were studied using metal oxide semiconductor-(MOS)-like devices. Thin SRO films with 4 at.% of silicon excess were deposited by low pressure chemical vapour deposition followed by a thermal annealing at 1100 degrees C. Intense continuous visible and infrared luminescence has been observed when devices are reversely and forwardly bias, respectively. After an electrical stress, the continuous electroluminescence (EL) is quenched but devices show strong field-effect EL with pulsed polarization. A model based on conductive paths--across the SRO film--has been proposed to explain the EL behaviour in these devices.

A theoretical investigation on the spectrum of the Ar trimer for high rotational excitations.

A detailed study of the rovibrational spectrum of the Ar trimer is performed by means of an exact hyperspherical coordinate (HC) method and a variational approach based on distributed Gaussian functions (DGFs) to describe the interparticle distances. The good agreement observed between the energy levels obtained with both procedures for high values of the total angular momentum (J=15 and 20) reveals the quality of the DGF method to describe the rotation of the title system. Rotational constants for the lowest bound states, obtained as averages for each vibrational state, have been obtained and compared to previous results. A detailed analysis of density probability functions obtained by means of the HC approach for rovibrational states at J=0 and 20 shows close similitudes thus supporting the vibration-rotation separation adopted within the DGF scheme for the Ar(3) system.

Divertículo de Zenker. Presentación de un caso

En este trabajo se presentan las características clínicas y la conducta seguida en un caso estudiado en el servicio de Geriatría y Gerontología del Hospital Provincial Universitario Camilo Cienfuegos de Sancti Spíritus, que por su escasa frecuencia y mostrarse exclusivamente en el anciano se consideró importante su conocimiento. Paciente geriátrico que ingresa por disfagia, dificultad para el habla y sepsis respiratoria, se estudiaron las afecciones que pudieron causar este cuadro, llegándose a la conclusión de que se trataba de un divertículo de Zenker. Luego de valorar con cirugía se procedió a la diverticulectomía con miotomía del músculo cricofaríngeo, siendo un éxito la operación y desapareciendo todos los síntomas que presentaba el paciente.

Plasma fibrinogen level and the risk of major cardiovascular diseases and nonvascular mortality: an individual participant meta-analysis.

CONTEXT: Plasma fibrinogen levels may be associated with the risk of coronary heart disease (CHD) and stroke. OBJECTIVE: To assess the relationships of fibrinogen levels with risk of major vascular and with risk of nonvascular outcomes based on individual participant data. DATA SOURCES: Relevant studies were identified by computer-assisted searches, hand searches of reference lists, and personal communication with relevant investigators. STUDY SELECTION: All identified prospective studies were included with information available on baseline fibrinogen levels and details of subsequent major vascular morbidity and/or cause-specific mortality during at least 1 year of follow-up. Studies were excluded if they recruited participants on the basis of having had a previous history of cardiovascular disease; participants with known preexisting CHD or stroke were excluded. DATA EXTRACTION: Individual records were provided on each of 154,211 participants in 31 prospective studies. During 1.38 million person-years of follow-up, there were 6944 first nonfatal myocardial infarctions or stroke events and 13,210 deaths. Cause-specific mortality was generally available. Analyses involved proportional hazards modeling with adjustment for confounding by known cardiovascular risk factors and for regression dilution bias. DATA SYNTHESIS: Within each age group considered (40-59, 60-69, and > or =70 years), there was an approximately log-linear association with usual fibrinogen level for the risk of any CHD, any stroke, other vascular (eg, non-CHD, nonstroke) mortality, and nonvascular mortality. There was no evidence of a threshold within the range of usual fibrinogen level studied at any age. The age- and sex- adjusted hazard ratio per 1-g/L increase in usual fibrinogen level for CHD was 2.42 (95% confidence interval [CI], 2.24-2.60); stroke, 2.06 (95% CI, 1.83-2.33); other vascular mortality, 2.76 (95% CI, 2.28-3.35); and nonvascular mortality, 2.03 (95% CI, 1.90-2.18). The hazard ratios for CHD and stroke were reduced to about 1.8 after further adjustment for measured values of several established vascular risk factors. In a subset of 7011 participants with available C-reactive protein values, the findings for CHD were essentially unchanged following additional adjustment for C-reactive protein. The associations of fibrinogen level with CHD or stroke did not differ substantially according to sex, smoking, blood pressure, blood lipid levels, or several features of study design. CONCLUSIONS: In this large individual participant meta-analysis, moderately strong associations were found between usual plasma fibrinogen level and the risks of CHD, stroke, other vascular mortality, and nonvascular mortality in a wide range of circumstances in healthy middle-aged adults. Assessment of any causal relevance of elevated fibrinogen levels to disease requires additional research.

Fencamfamine-induced changes in the parameters of the matching law and the effect of previous exposure to the drug.

The purpose of this study was to assess the effects of the psychomotor stimulant fencamfamine (FCF) on the operant response rate and on the parameters k and R(e) of Herrnstein's hyperbola. In the first experiment, rats were trained on a multiple variable interval (VI) schedule. Each rat was then given two i.p. injections of a randomly assigned FCF dose (0.0, 0.88, 1.75 and 3.5 mg/kg) at 48 h intervals. The overall response rate, the individual VI response rate, and the k and R(e) parameters of the hyperbola equation were calculated. In the second experiment, two groups of animals were trained drug-free on the same schedule. Afterwards, the animals in one group received six i.p. injections of 1.75 mg/kg FCF at 48 h intervals while subjects in the other group received vehicle injections, 15 min before each experimental session. Seven days after the last injection, a challenge dose (0.88 mg/kg) of FCF was administered and performance was measured. FCF increased overall response rate and decreased R(e) without changing k. Previous exposure to FCF did not induce sensitization of these measures. These results indicate that FCF has similar effects on k and R(e) as those produced by other indirect dopaminergic agents, and supports previous findings suggesting FCF as a potential drug of abuse.

[Vitamin K: biochemistry, function, and deficiency. Review]. / La vitamina K: bioquímica, función y deficiencias. Revisión.

Vitamin K is a cofactor for the synthesis of blood coagulation Factors II, VII, IX and X, and inhibitors such as Protein C and S and bone matrix protein. Its active form is a coenzyme in the glutamic acid carboxylation. Vitamin K-dependent factors form enzymatic complexes with calcium and membrane phospholipids. The insufficiency of gamma glutamic carboxylation impairs the hemostatic function. Hereditary deficiencies, antibiotics and oral anticoagulants, decrease the capacity of complex formation giving way to hemorrhage or thrombosis, or bone mass disturbances which are easily treated with administration of Vitamin K. The main causes of Vitamin K deficiency are lack of hepatic storage in newborns, liver insufficiency, malabsorption, dietetic deficiency, therapy with the antibiotics and coumarin administration. For the study of Vitamin K there are methods to measure the Vit K dependent proteins and as well methods to measure specifically the quinonas.

Enfermedad hemolítica del recien nacido por isoinmunización por grupos sanguíneos / Hemolitic disease of the newborns

Se estudiaron 251 recién nacidos a término y sus respectivas madres en la Maternidad Concepción Palacios, Caracas-Venezuela, con el fin de establecer la frecuencia de Enfermedad Hemolítica (EH) y tratar de terminar parámetros útiles para la predicción de la severidad de al EH-ABO. Hubo 23 casos de incompatibilidad ABO con los siguientes hallazgos serológicos: 9 (39) por ciento presentaron la prueba de atoaglutinación positiva, 5(21 por ciento) el Coombs directo positivo, 20(36 por ciento) el eludio positivo. De cuatro (2 por ciento) casos co EH-ABO, dos (50 por ciento) tuvieron Coombs directo positivo y tres (75 por ciento) la prueba de autoaglutinación y el eluido positivos. El título de anticuerpos maternos varió entre 1:12 y 1:4096. La determinación semicuantitativa de las subclases IgG en 3 casos de EH-ABO demostró en forma constante la presencia de IgG1 e IgG4 y en 2 casos se asoció la IgG2. Se determinó la presencia de sustancia A en el suero de 14 niños con incompatibilidad ABO, no observándose aparentemente el efecto protector del carácter secretor. Se presentaron 2 casos de EH-Rh, los cuales tuvieron un comportamiento diferente, lo cual podría atribuirse a las subclases de IgG presentes en el suero materno. debido a los resultados obtenidos en nuestro estudio consideramos que ninguna de las pruebas realizadas puede ser tomada como factor de predicción de presentación y evolución de EH-ABO

Immunochemical demonstration of tropomyosin in the neurofibrillary pathology of Alzheimer's disease.

The focus of research on the neurofibrillary pathology (NFP) of Alzheimer disease has been not only to determine the component forming the paired helical filaments but also to determine whether they result from abnormal processes affecting a single protein. Therefore, although these studies have lead to controversy concerning the respective contribution of components of microtubules and neurofilaments, there has been essentially no consideration of whether other cytoskeletal systems might also be involved and of what are the common features for the incorporated components. Particularly relevant to this issue is our finding that several antisera raised to either skeletal or smooth muscle tropomyosin, a microfilament component, intensely recognize NFP. These antibodies continue to recognize NFP after affinity purification to tropomyosin or paired helical filament fractions. We show that the antibodies do not recognize NFP due to cross-reactivity with the previously identified NFP components related to neurofilaments and microtubules, tau, and MAP2, or neurofilament proteins because the antisera did not recognize these proteins on immunoblots or were not adsorbable by the proteins. Ultrastructural analysis of the immunoreaction showed that tropomyosin-related epitopes were clustered rather than uniformly distributed along paired helical and straight filaments. Although the distribution suggests that tropomyosin is an NFP-associated protein, its retention by paired helical and straight filaments after detergent extraction indicates that it is an integral component strongly and specifically associated with the filaments characteristic of NFP. These findings indicate that NFP involves the three primary neuronal cytoskeletal filament systems, microtubules, neurofilaments, as well as microfilaments, and therefore that NFP probably results from the reorganization of these normal filaments that interact to comprise the cytomatrix and may continue this interaction under the pathologic condition of Alzheimer's disease to generate novel, abnormal polymers.

Immunolocalization of the amyloid precursor protein within the senile plaque.

The isolation and sequencing of three transcripts for the precursor of the cerebral amyloid of Alzheimer disease have greatly facilitated understanding the relationship of the amyloid precursor protein (APP) to its 42 amino acid residue fragment (beta-protein or A4) which composes amyloid fibrils. In this study, we have used the 695 amino acid residue sequence described by Kang and co-workers to prepare antisera to synthetic peptides corresponding to various regions of APP in order to identify localized concentrations of this protein in cerebral cortex in cases of Alzheimer disease. We found that antisera to APP regions outside those of the amyloidogenic beta protein recognize diffuse non-congophilic plaques. While these antisera did not recognize the congophilic senile plaque core, they did recognize a halo surrounding them. Interestingly, cell processes were often identified in this halo region. In contrast, those antisera raised to sequences contained within beta-protein recognized both congophilic amyloid cores as well as non-congophilic diffuse plaques. Our findings suggest that accumulation of APP precedes development of and probably defines the senile plaque and the site of APP processing.

[Strongyloidiasic hyperinfestation]. / Hiperinfestación strongyloidiásica.

A study was made of twelve cases of fatal Strongylodiasis with Hyperinfestation which presented a severe picture of the small intestine and colon, some with localization in the lungs, bronchus, and other organs. Preliminary results are given of a prospective study related to the bacterial flora and its role in the pictures of larvarial aggression, which could lead to greater knowledge about the biology of the parasite, and therefore to interesting findings of a therapeutic nature.