Abstract
The Cherenkov Telescope Array (CTA) is the next-generation ground-based very-high-energy gamma-ray observatory. By using three types of telescopes CTA can cover a wide energy range (20 ...GeV–300 TeV) with an order of magnitude higher sensitivity than the current telescopes. The Large-Sized Telescope (LST) is designed to detect 20 GeV–1 TeV gamma rays thanks to the large light collection area, sensitive photosensors, a fast trigger system, and readout electronics. The camera readout system must have a high signal-to-noise ratio and a linear signal sampling with a large dynamic range in order to efficiently detect dim and low-energy atmospheric showers. To meet this requirement we use the Domino Ring Sampler version 4 (DRS4), which also enables ultra-fast sampling with low power consumption. Some of the intrinsic characteristics of DRS4 chips require software corrections. These procedures lower the effect of non-Gaussian noise contribution and improve the timing resolution of the system. In this contribution we discuss the calibration algorithms and the resulting performance.
In order to optimize external-beam conformal radiotherapy, patient movement during treatment must be minimized. For treatment on the upper torso, the target organs are known to move substantially due ...to patient respiration. This paper deals with the technical aspects of gating the radiotherapy beam synchronously with respiration: the optimal respiration monitoring system, measurements of organ displacement and linear accelerator gating. Several respiration sensors including a thermistor, a thermocouple, a strain gauge and a pneumotachograph were examined to find the optimal sensor. The magnitude of breast, chest wall and lung motion were determined using playback of fluoroscopic x-ray images recorded on a VCR during routine radiotherapy simulation. Total dose, beam symmetry and beam uniformity were examined to determine any effects on the Varian 2100C linear accelerator due to gating.
Left ventricular (LV) remodeling is related to adverse outcomes in heart failure. The CorCap Cardiac Support Device (CSD; Acorn Cardiovascular, Inc, St. Paul, MN) is an implantable device that ...attenuates LV remodeling.
The Acorn trial assessed the safety and efficacy of the CSD in 300 heart failure patients. Patients needing mitral surgery (n = 193) were randomized to mitral surgery alone or mitral surgery plus CSD. Patients who did not need mitral surgery (n = 107) were randomized to medical therapy or medical therapy plus CSD. The primary endpoint was a clinical composite based on changes in patient vital status, the need for major cardiac procedures for worsening heart failure, and a change in New York Heart Association (NYHA) class.
The proportional odds ratio for the primary endpoint favored treatment with the CSD (1.73 confidence interval CI: 1.07 to 2.79; p = 0.024). The CSD-treated patients received significantly (p = 0.01) fewer cardiac procedures indicative of worsening heart failure and had an improvement in New York Heart Association class (p = 0.049). There was no significant difference in survival between groups (p = 0.85). Treatment with the CSD led to a decrease in LV end-diastolic (p = 0.009) and end-systolic volumes (p = 0.017), an increase in the LV sphericity index (p = 0.026), an improvement in the Minnesota Living with Heart Failure score (p = 0.04), and the Short Form-36 Questionnaire (p = 0.015). There was no evidence for a significant difference (p = 0.43) in serious adverse events between the treatment and control groups.
The results of the Acorn trial support the hypothesis that preventing LV remodeling with a CSD favorably impacts the untoward natural history of heart failure.
For MeV gamma-ray astronomy, we have developed an electron-tracking Compton camera (ETCC) as a MeV gamma-ray telescope capable of rejecting the radiation background and attaining the high sensitivity ...of near 1mCrab in space. Our ETCC comprises a gaseous time-projection chamber (TPC) with a micro pattern gas detector for tracking recoil electrons and a position-sensitive scintillation camera for detecting scattered gamma rays. After the success of a first balloon experiment in 2006 with a small ETCC (using a 10×10×15cm3 TPC) for measuring diffuse cosmic and atmospheric sub-MeV gamma rays (Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment I; SMILE-I), a (30cm)3 medium-sized ETCC was developed to measure MeV gamma-ray spectra from celestial sources, such as the Crab Nebula, with single-day balloon flights (SMILE-II). To achieve this goal, a 100-times-larger detection area compared with that of SMILE-I is required without changing the weight or power consumption of the detector system. In addition, the event rate is also expected to dramatically increase during observation. Here, we describe both the concept and the performance of the new data-acquisition system with this (30cm)3 ETCC to manage 100 times more data while satisfying the severe restrictions regarding the weight and power consumption imposed by a balloon-borne observation. In particular, to improve the detection efficiency of the fine tracks in the TPC from ~10% to ~100%, we introduce a new data-handling algorithm in the TPC. Therefore, for efficient management of such large amounts of data, we developed a data-acquisition system with parallel data flow.
An Fe-Mn-Si-Cr shape memory alloy is applied to make crane rail fishplates. The shape recovery of the reverse martensite transformation from hcp to fcc is utilised to connect finite lengths of rail. ...Rails connected by normal steel fishplates gradually become separated at the joint and can be damaged by broken flakes in the gap and dents during heavy duty operation of the crane. To eliminate such problems, a sufficient and controlled compressive stress is required at the joint to resist the stress responsible for creating the gap. A quantitative estimate of the load required to separate the joint has been made to calibrate the compressive stress yielded by the reverse martensite transformation of fishplates. An innovative joining technique that ensures adequate and controlled compressive stress at the joined parts has been developed using a Fe-Mn-Si-Cr shape memory alloy together with sophisticated materials design and installation techniques.
The effects of carbon ion fraction on deuterium retention in tungsten coating layers were investigated by irradiating the layers with mixed deuterium and carbon ion beams. The mixed ion beams had ...atomic carbon fractions of up to 3.2% and the sample temperature was either 500 or 700K. Graphite was formed in the tungsten coating layer at the both temperatures; however, tungsten carbide and ditungsten carbide were not formed at the both temperatures. At 500K, deuterium was trapped at intrinsic defects and carbon was accumulated in the tungsten coating layer. At 700K, although trapping deuterium at intrinsic defects was difficult, deuterium was trapped predominantly at carbon accumulated in the tungsten coating layer. Analysis of deuterium desorption spectrum by multipeak fitting suggests that deuterium was retained by C–D bonds in the tungsten coating layer at 700K.
Abstract
Muon beam monitoring is indispensable for indirectly monitoring accelerator-produced neutrino beams in real time. Though Si photodiodes and ionization chambers have been successfully used as ...muon monitors at the T2K experiment, sensors that are more radiation tolerant are desired for future operation. We have investigated the electron-multiplier tube (EMT) as a new sensor for muon monitoring. Secondary electrons produced by the passage of muons at dynodes are multiplied in the tube and produce signal. Two prototype detectors were installed at the T2K muon monitor location, and various EMT properties were studied based on in situ data taken with the T2K muon beam. The signal size is as expected based on calculation, and the EMTs show a sufficiently fast time response for bunch-by-bunch beam monitoring. The spill-by-spill intensity resolution is 0.4%, better than the required value (1%). Signal linearity within $\pm$1% is achieved at proton beam powers up to 460 kW (with +250 kA focusing horn operation). A gradual signal decrease was observed during the initial exposure, due to the stabilization of dynode materials, before the response became stable within $\pm$1%. This work demonstrates that EMTs are a good candidate for future muon monitoring at T2K, and may also have other more general applications.
Generally, cystic tumors are divided into two categories: neoplastic cystic tumors and non-neoplastic cystic (NNC) tumors. Neoplastic cystic tumors include mucinous cystic neoplasm (MCN), intraductal ...papillary-mucinous neoplasm (IPMN), and serous cystic neoplasm (SCN). MCNs and IPMNs have the potential to progress to a malignant state, whereas SCNs are known for their almost benign behavior. Thus, in order to make management decisions, it is important to distinguish between potentially malignant (MCN and IPMN), and benign (SCN and NNC) tumors. The aim of this study was to retrospectively investigate the value of endoscopic ultrasonography (EUS) for the differential diagnosis of cystic tumors of the pancreas.
A total of 76 patients with cystic tumors of the pancreas were preoperatively examined by EUS. Eight cases were MCNs, 45 were IPMNs, 13 were SCNs, and 10 were NNC tumors. The EUS findings relevant to distinguishing between potentially malignant and benign were analyzed statistically.
All patients with MCNs were female and all these tumors were located in the pancreatic body/tail. IPMN, however, occurred predominantly in men, and in the pancreatic head. Eight of 11 monolocular cystic tumors were NNC in nature. Eleven of 13 SCNs included microcystic areas within the tumors. All MCNs were round in appearance, whereas 93 % of IPMNs were not round in appearance. Mural nodules were present in 25 % of MCN and 38 % of IPMN cases. In univariate analysis, age, tumor size, locularity, the number of cystic formation, cystic component, and appearance were significant variables. In multivariate analysis, locularity and cystic component were important for differential diagnosis of potentially malignant cystic tumors.
The characteristics of cystic tumors of the pancreas revealed by EUS are useful for their differential diagnosis.
A new method to magnify a small polarization angle with brazed gratings has been developed. In the method, difference in diffraction efficiency for S and P polarization components is used. The ...magnification dependence on the incident angle can be small by arranging the grating in Littrow layout. A magnification with a factor ~2.7 has been demonstrated for a 10.6 μm CO2 laser beam as expected from a calculation. The method is applicable in many polarimetry fields.
Detection of low-intensity light relies on the conversion of photons to photoelectrons, which are then multiplied and detected as an electrical signal. To measure the actual intensity of the light, ...one must know the factor by which the photoelectrons have been multiplied. To obtain this amplification factor, we have developed a procedure for estimating precisely the signal caused by a single photoelectron. The method utilizes the fact that the photoelectrons conform to a Poisson distribution. The average signal produced by a single photoelectron can then be estimated from the number of noise events, without requiring analysis of the distribution of the signal produced by a single photoelectron. The signal produced by one or more photoelectrons can be estimated experimentally without any assumptions. This technique, and an example of the analysis of a signal from a photomultiplier tube, are described in this study.
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