Emergence of Bloch oscillations in one-dimensional systems

Electrons in periodic potentials exhibit oscillatory motion in presence of an electric field. Such oscillations are known as Bloch oscillations. In this article we theoretically investigate the emergence of Bloch oscillations for systems where the electric field is confined to a finite region, like in typical electronic devices. We use a one-dimensional tight-binding model within the single-band approximation to numerically study the dynamics of electrons after a sudden switching-on of the electric field. We find a transition from a regime with direct current to Bloch oscillations when increasing the system size or decreasing the field strength. We propose a pump-probe scheme to observe the oscillations by measuring the accumulated charge as a function of the pulse-length

Novel Synchrotron-Based Analyses of Metal Pathology in Friedreich’s Ataxia

Friedreich’s ataxia (FRDA) is a progressive spinocerebellar ataxia (SCA) inherited as an autosomal recessive trait. The neurodegeneration, cardiomyopathy, diabetes mellitus and skeletal deformities characteristic to FRDA result from a deficiency in the mitochondrial protein frataxin. Frataxin chaperones iron to heme and iron-sulfur clusters and its deficiency causes mitochondrial iron accumulation and oxidative stress. To address the effect of frataxin deficiency on mitochondrial iron chemistry, mitochondria were isolated from FRDA and control fibroblasts. X-ray absorption spectroscopy showed that ferrihydrite was the predominant form of iron in both. Near edge analysis showed that the ferrihydrite in the FRDA mitochondria resembled the highly organized ferrihydrite of ferritin. Western blotting confirmed that FRDA mitochondria had 3-fold more holoferritin containing stainable iron. I conclude that mitochondria from FRDA fibroblasts mineralize excess iron as ferrihydrite within mitochondrial ferritin. To address how cellular iron dysregulation affected metal distribution in brain and spinal cord, a new synchrotron imaging technique, rapid-scanning x-ray fluorescence (RS-XRF) was employed and validated. Brain structures were readily identified by their unique metal content and distribution. This showed that RS-XRF could be used to reveal metal pathologies associated with diseases of metal metabolism such as FRDA. Since human FRDA tissues were not available for a detailed study, RS-XRF was employed to study the distribution of metals in normal cerebellum, a major site of FRDA-associated neurodegeneration, and to localize and quantify metals in the brain and spinal cord from a patient with a SCA of unknown aetiology. The motivation for this work is the prospect of future systematic studies on metal pathology in neurodegenerative diseases with direct application to FRDA. Novel findings arising from this work were the metal segmentation of the dentate nucleus, the high copper content of the olivary region and the different metal content of lesions at different stages of neurodegeneration. My results suggest that not only iron, but also copper and zinc may play a role in the physiopathology of neurodegeneration. Therefore, all three metals should be investigated in FRDA and other SCA of both known and unknown aetiologies to identify possible new therapeutic targets

End-stage head and neck cancer: coping mechanism

Coping mechanisms are patients’ means of adapting to stressful situations and involve psychological and physical changes in behavior. Patients adapt to head and neck cancer in a variety of ways. Head and neck cancers are extremely debilitating, especially in advanced stages of the disease or in end-of-life situations. While an oncology team needs to address the needs of all oncology patients, the advanced terminal patients require special attention. Most of these patients do not cope well with their situation and have a tendency to cease social interactions. Pain is the most frequentlyexperienced medical disability in patients having an end-stage illness experience, and thus an important medical endeavor is to afford dignity to the dying patient facingan incurable disease. In such cases, the medical community should never refuse therapy or to assist a dying patient.In some instances, the patient and family may derive benefit from their religious beliefs

Dust effects on the derived Sersic indexes of disks and bulges in spiral galaxies

We present a theoretical study that quantifies the effect of dust on the derived Sersic indexes of disks and bulges. The changes in the derived parameters from their intrinsic values (as seen in the absence of dust) were obtained by fitting Sersic distributions on simulated images of disks and bulges produced using radiative transfer calculations and the model of Popescu et al. 2011. We found that dust has the effect of lowering the measured Sersic index in most cases, with stronger effects for disks and bulges seen through more optically thick lines of sight.Comment: 3 pages, 2 figures, to appear in the Proceedings of the IAU Symposium No.284, "The Spectral Energy Distribution of Galaxies", 5-9 sept. 2011, editors Richard J. Tuffs and Cristina C. Popesc

STUDIES ON THE QUALITY AND AUTHENTICITY OF WHITE WINES FROM OLTENIA

For white wines, in addition to the level of the main chemical constituents defined for each category and type, the properties of fruitiness, aroma and expressiveness, typical of varieties and areas of origin, are fundamental quality criteria. In addition, these products must be offered to consumers in a perfect state of clarity and with lasting stability over time. The capitalization of the viticultural potential that Romania has, in order to obtain sustainable competitive advantages on foreign markets, requires the creation and promotion of an identity of Romanian wine, based on analytical investigations to certify the quality and natural chemical composition of wines. Determining the quality and authentication of wines involves several aspects, such as geographical origin, year of production, variety, producer and quality. It is important that the proof of the authenticity of the wine is based on those chemical parameters that do not change during vinification process or that are difficult to falsify.Â

A Comparative Analysis of the Immediate Post-Operative Complications Occurring After Subtotal Gastrectomy in Patients With Gastric Carcinoma

DergiPark: 379014tmsjAims: The aims of this study were to scrutinize the immediate post-operative complications encountered after different subtotal gastrectomy procedures and to identify the safest surgical variant.Methods: In this retrospective, observational study data of 54 patients, of whom 32 were male and 22 were female,with a mean age of 65.7 years diagnosed with gastric carcinoma underwent a variant of subtotal gastrectomy in the Surgery Department of the Bucharest Clinical Emergency Hospital between January 2010 and December 2012 were recorded. The categorical statistical data was obtained with Chi-square method using GraphPad Prism and statistical significance was set at a p-value lt;0.05.Results: A total of 73 immediate post-operative complications were encountered in 23 (41.8%) patients classifiedinto local in 14 (19.2%) patients and general in 59 (80.8%) patients. The most common complication classified as local was leakage found in 5 (6.9%) patients, while the most frequent ones in general complications were secondary anemia presented in 17 (23.3%) patients and pulmonary compromise: pleural effusion in 3 (4.1%) patients. Ten associated surgical procedures were necessary, the most common being omentectomy (30%). Re-operation was deemed imperative in 5 (9.1%) cases , 4 (80%) of which were after Billroth I and 1 (20%) case was subsequent to Roux-en-Y Side-End Esophagojejunostomy. Three (5.6%) deaths were reported, 2 (66.7%) of which occurred after Roux-en-Y Side-End Esophagojejunostomy and 1 (33.3%) after the Billroth I variant.Conclusion: Billroth I yielded the highest number of complications, both local and general, compared to Hofmeister-Finsterer which generated the lowest number. The same pattern was noted with respect to the length of hospital stay. The longest operative time was recorded in Hofmeister-Finsterer and the shortest in Billroth I. A statistically significant chi-square analysis between the type of subtotal gastrectomy procedure and anastomotic leakage was obtaine