Position-sensitive detector for the 6-meter optical telescope

The Position-Sensitive Detector (PSD) for photometrical and spectral observation on the 6-meter optical telescope of the Special Astrophysical Observatory (Russia) is described. The PSD consists of a position-sensitive tube, amplifiers of output signals, analog-to-digital converters (ADC) and a digital logic plate, which produces a signal for ADC start and an external strob pulse for reading information by registration system. If necessary, the thermoelectric cooler can be used. The position-sensitive tube has the following main elements: a photocathode, electrodes of inverting optics, a block of microchannel plates (MCP) and a position-sensitive collector of quadrant type. The main parameters of the PSD are the diameter of the sensitive surface is 25 mm, the spatial resolution is better than 100 (\mu)m in the centre and a little worse on the periphery; the dead time is near 0.5 (\mu)s; the detection quantum efficiency is defined by the photocathode and it is not less than 0.1, as a rule; dark current is about hundreds of cps, or less, when cooling. PSD spectral sensitivity depends on the type of photocathode and input window material. We use a multialkali photocathode and a fiber or UV-glass, which gives the short- wave cut of 360 nm or 250 nm, respectively.Comment: 4 pages, 7 figures, to be published in Nuclear Instruments & Methods in Physics Researc

Extraordinary Magnetoresistance in Hybrid Semiconductor-Metal Systems

We show that extraordinary magnetoresistance (EMR) arises in systems consisting of two components; a semiconducting ring with a metallic inclusion embedded. The im- portant aspect of this discovery is that the system must have a quasi-two-dimensional character. Using the same materials and geometries for the samples as in experiments by Solin et al.[1;2], we show that such systems indeed exhibit a huge magnetoresistance. The magnetoresistance arises due to the switching of electrical current paths passing through the metallic inclusion. Diagrams illustrating the flow of the current density within the samples are utilised in discussion of the mechanism responsible for the magnetoresistance effect. Extensions are then suggested which may be applicable to the silver chalcogenides. Our theory offers an excellent description and explanation of experiments where a huge magnetoresistance has been discovered[2;3].Comment: 12 Pages, 5 Figure

Multifunctional semiconductor micro-Hall devices for magnetic, electric, and photo-detection

We report the real-space voltage response of InSb/AlInSb micro-Hall devices to local photo-excitation, electric, and magnetic fields at room temperature using scanning probe microscopy. We show that the ultrafast generation of localised photocarriers results in conductance perturbations analogous to those produced by local electric fields. Experimental results are in good agreement with tight-binding transport calculations in the diffusive regime. The magnetic, photo, and charge sensitivity of a 2 μm wide probe are evaluated at a 10 μA bias current in the Johnson noise limit (valid at measurement frequencies > 10 kHz) to be, respectively, 500 nT/√Hz; 20 pW/√Hz (λ = 635 nm) comparable to commercial photoconductive detectors; and 0.05 e/√Hz comparable to that of single electron transistors. These results demonstrate the remarkably versatile sensing attributes of simple semiconductor micro-Hall devices that can be applied to a host of imaging and sensing applications

Pancreatic metabolism, blood flow, and β-cell function in obese humans.

Context: Glucolipotoxicity is believed to induce pancreatic &beta;-cell dysfunction in obesity. Previously, it has not been possible to study pancreatic metabolism and blood flow in humans. Objective: The objective of the study was to investigate whether pancreatic metabolism and blood flow are altered in obesity using positron emission tomography (PET). In the preclinical part, the method was validated in animals. Design: This was a cross-sectional study. Setting: The study was conducted in a clinical research center. Participants: Human studies consisted of 52 morbidly obese and 25 healthy age-matched control subjects. Validation experiments were done with rodents and pigs. Interventions: PET and magnetic resonance imaging studies using a glucose analog ([18F]fluoro-2-deoxy-d-glucose), a palmitate analog [14(R,S)-[18F]fluoro-6-thia-heptadecanoic acid], and radiowater ([15O]H2O) were performed. In animals, a comparison between ex vivo and in vivo data was performed. Main Outcome Measures: Pancreatic glucose/fatty acid (FA) uptake, fat accumulation, and blood flow parameters of &beta;-cell function were measured. Results: PET proved to be a feasible method to measure pancreatic metabolism. Compared with healthy participants, obese participants had elevated pancreatic FA uptake (P &lt; .0001), more fat accumulation (P = .0001), lowered glucose uptake both during fasting and euglycemic hyperinsulinemia, and blunted blood flow (P &lt; .01) in the pancreas. Blood flow, FA uptake, and fat accumulation were negatively associated with multiple markers of &beta;-cell function. Conclusions: Obesity leads to changes in pancreatic energy metabolism with a substrate shift from glucose to FAs. In morbidly obese humans, impaired pancreatic blood flow may contribute to &beta;-cell dysfunction and in the pathogenesis of type 2 diabetes. &nbsp;</div

The effect of dalargin on growth factors content in experimental ulcerative colitis

The aim of the study was to evaluate the dalargin effect on the content of transforming growth factor-β (TGF-β) and epidermal growth factor (EGF) in the colonic wall in mice with experimental ulcerative coliti

Molecular design of radiocopper-labelled Affibody molecules

The use of long-lived positron emitters Cu-64 or Cu-61 for labelling of Affibody molecules may improve breast cancer patients' stratification for HER-targeted therapy. Previous animal studies have shown that the use of triaza chelators for Cu-64 labelling of synthetic Affibody molecules is suboptimal. In this study, we tested a hypothesis that the use of cross-bridged chelator, CB-TE2A, in combination with Gly-Glu-Glu-Glu spacer for labelling of Affibody molecules with radiocopper would improve imaging contrast. CB-TE2A was coupled to the N-terminus of synthetic Affibody molecules extended either with a glycine (designation CB-TE2A-G-ZHER2:342) or Gly-Glu-Glu-Glu spacer (CB-TE2A-GEEE-ZHER2:342). Biodistribution and targeting properties of Cu-64-CB-TE2A-G-ZHER2:342 and Cu-64-CB-TE2A-GEEE-ZHER2:342 were compared in tumor-bearing mice with the properties of Cu-64-NODAGA-ZHER2:S1, which had the best targeting properties in the previous study. Cu-64-CB-TE2A-GEEE-ZHER2:342 provided appreciably lower uptake in normal tissues and higher tumor-to-organ ratios than Cu-64-CB-TE2A-GZHER2:342 and Cu-64-NODAGA-ZHER2:S1. The most pronounced was a several-fold difference in the hepatic uptake. At the optimal time point, 6 h after injection, the tumor uptake of Cu-64-CB-TE2A-GEEE-ZHER2: 342 was 16 +/- 6% ID/g and tumor-to-blood ratio was 181 +/- 52. In conclusion, a combination of the cross-bridged CB-TE2A chelator and Gly-Glu-Glu-Glu spacer is preferable for radiocopper labelling of Affibody molecules and, possibly, other scaffold proteins having high renal re-absorption

Increased Brain Fatty Acid Uptake in Metabolic Syndrome

OBJECTIVE: To test whether brain fatty acid uptake is enhanced in obese subjects with metabolic syndrome (MS) and whether weight reduction modifies it. RESEARCH DESIGN AND METHODS: We measured brain fatty acid uptake in a group of 23 patients with MS and 7 age-matched healthy control subjects during fasting conditions using positron emission tomography (PET) with [(11)C]-palmitate and [(18)F]fluoro-6-thia-heptadecanoic acid ([(18)F]-FTHA). Sixteen MS subjects were restudied after 6 weeks of very low calorie diet intervention. RESULTS: At baseline, brain global fatty acid uptake derived from [(18)F]-FTHA was 50% higher in patients with MS compared with control subjects. The mean percentage increment was 130% in the white matter, 47% in the gray matter, and uniform across brain regions. In the MS group, the nonoxidized fraction measured using [(11)C]-palmitate was 86% higher. Brain fatty acid uptake measured with [(18)F]-FTHA-PET was associated with age, fasting serum insulin, and homeostasis model assessment (HOMA) index. Both total and nonoxidized fractions of fatty acid uptake were associated with BMI. Rapid weight reduction decreased brain fatty acid uptake by 17%. CONCLUSIONS: To our knowledge, this is the first study on humans to observe enhanced brain fatty acid uptake in patients with MS. Both fatty acid uptake and accumulation appear to be increased in MS patients and reversed by weight reduction

Adaptive servoventilation improves cardiac function and respiratory stability

Cheyne–Stokes respiration (CSR) in patients with chronic heart failure (CHF) is of major prognostic impact and expresses respiratory instability. Other parameters are daytime pCO2, VE/VCO2-slope during exercise, exertional oscillatory ventilation (EOV), and increased sensitivity of central CO2 receptors. Adaptive servoventilation (ASV) was introduced to specifically treat CSR in CHF. Aim of this study was to investigate ASV effects on CSR, cardiac function, and respiratory stability. A total of 105 patients with CHF (NYHA ≥ II, left ventricular ejection fraction (EF) ≤ 40%) and CSR (apnoea–hypopnoea index ≥ 15/h) met inclusion criteria. According to adherence to ASV treatment (follow-up of 6.7 ± 3.2 months) this group was divided into controls (rejection of ASV treatment or usage <50% of nights possible and/or <4 h/night; n = 59) and ASV (n = 56) adhered patients. In the ASV group, ventilator therapy was able to effectively treat CSR. In contrast to controls, NYHA class, EF, oxygen uptake, 6-min walking distance, and NT-proBNP improved significantly. Moreover, exclusively in these patients pCO2, VE/VCO2-slope during exercise, EOV, and central CO2 receptor sensitivity improved. In CHF patients with CSR, ASV might be able to improve parameters of SDB, cardiac function, and respiratory stability

Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio