The first lithium-drifted silicon (Si(Li)) detectors to satisfy the unique geometric, performance, and cost requirements of the General Antiparticle Spectrometer (GAPS) experiment have been produced ...by Shimadzu Corporation. The GAPS Si(Li) detectors will form the first large-area, relatively high-temperature Si(Li) detector system with sensitivity to X-rays to operate at high altitude. These 10 cm-diameter, 2.5 mm-thick, 4- or 8-strip detectors provide the active area, X-ray absorption efficiency, energy resolution, and particle tracking capability necessary for the GAPS exotic-atom particle identification technique. In this paper, the detector performance is validated on the bases of X-ray energy resolution and reconstruction of cosmic minimum ionizing particle (MIP) signals. We use the established noise model for semiconductor detectors to distinguish sources of noise due to the detector from those due to signal processing electronics. We demonstrate that detectors with either 4 strips or 8 strips can provide the required ≲4 keV (FWHM) X-ray energy resolution at flight temperatures of −35 to −45ˆC, given the proper choice of signal processing electronics. Approximately 1000 8-strip detectors will be used for the first GAPS Antarctic balloon flight, scheduled for late 2021.
The aim of this study was to determine whether an arm ergometry exercise test can successfully predict a clinician's decision for prosthetic fitting, and to define what other factors are also ...important predictors of a patient's ability to walk with a prosthesis.
The study included 63 patients who had undergone transfemoral amputation due to peripheral vascular disease and who had been admitted for primary inpatient rehabilitation. Participating patients went through standard admission procedures and performed an intermittent sub maximal arm ergometry exercise test in the first week after admission consisting of a two-minute exercise routine with a one-minute pause in-between by means of the Angio V2. The work loads started at 10 W and were increased by 10 W at each level. The cranking rate was 50 to 55 rpm.
The patients reached an output level of 20 W on average. Those patients selected for fitting with a prosthesis achieved higher levels on the exercise stress test (26 versus 12 W, P<0.000). The results of the exercise stress test, the 6-minute walking test and the functional independence measures (FIM) at admission, as well as their age and gender, allowed for successful discrimination between patients who were fitted with a prosthesis and those who were not (P<0.000). The best discriminator was that of the results achieved on the exercise stress test. Using the five previously mentioned variables, 83.6% of the patients were successfully classified as to whether or not they were fitted for a prosthesis on the basis of our clinical decision.
The exercise stress test is a good predictor of prosthetic fitting. It also anticipates the possibility of cardiovascular complications during rehabilitation programmes. Combined with the 6-minute walk, the FIM, and age, it may be an important criteria to consider in making the decision about the appropriateness of prosthetic fitting.
This study presents a fabrication process for lithium-drifted silicon (Si(Li)) detectors that, compared to previous methods, allows for mass production at a higher yield, while providing a large ...sensitive area and low leakage currents at relatively high temperatures. This design, developed for the unique requirements of the General Antiparticle Spectrometer (GAPS) experiment, has an overall diameter of 10 cm, with ∼9 cm of active area segmented into 8 readout strips, and an overall thickness of 2.5 mm, with ≳2.2 mm (≳90%) sensitive thickness. An energy resolution ≲4 keV full-width at half-maximum (FWHM) for 20−100 keV X-rays is required at the operating temperature ∼−40°C, which is far above the liquid nitrogen temperatures conventionally used to achieve fine energy resolution. High-yield production is also required for GAPS, which consists of ≳1000 detectors. Our specially-developed Si crystal and custom methods of Li evaporation, diffusion and drifting allow for a thick, large-area and uniform sensitive layer. We find that retaining a thin undrifted layer on the p-side of the detector drastically reduces the leakage current, which is a dominant component of the energy resolution at these temperatures. A guard-ring structure and optimal etching of the detector surface are also confirmed to suppress the leakage current. We report on the mass production of these detectors that is ongoing now, and demonstrate it is capable of delivering a high yield of ∼90%.
The activation of materials due to exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k, currently under construction at ...the Laboratori Nazionali del Gran Sasso, is a direct detection experiment for galactic dark matter particles, using a two-phase liquid-argon Time Projection Chamber (TPC) filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Despite the outstanding capability of discriminating γ/β background in argon TPCs, this background must be considered because of induced dead time or accidental coincidences mimicking dark-matter signals and it is relevant for low-threshold electron-counting measurements. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the experiment has been estimated to set requirements and procedures during preparation of the experiment and to check that it is not dominant over primordial radioactivity; particular attention has been paid to the activation of the 120 t of UAr used in DarkSide-20k. Expected exposures above ground and production rates, either measured or calculated, have been considered in detail. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. The activity of 39Ar induced during extraction, purification and transport on surface is evaluated to be 2.8% of the activity measured in UAr by DarkSide-50 experiment, which used the same underground source, and thus considered acceptable. Other isotopes in the UAr such as 37Ar and 3H are shown not to be relevant due to short half-life and assumed purification methods.
New-type lithium-drifted silicon (Si(Li)) detectors have been developed and mass-produced to construct a large-volume silicon tracker for the General Antiparticle Spectrometer (GAPS). It is the first ...success of the mass production of large-area Si(Li) detectors. The mass production of over 1000 detectors provided valuable datasets related to detector fabrication, such as detector performance and manufacturing parameters. This study analyzes the datasets using data-mining methods. We report on the preliminary results and their interpretations, which provide valuable insights into the production methods for such large-area Si(Li) detectors.
We have developed large-area lithium-drifted silicon (Si(Li)) detectors to meet the unique requirements of the General Antiparticle Spectrometer (GAPS) experiment. GAPS is an Antarctic balloon-borne ...mission scheduled for the first flight in late 2020. The GAPS experiment aims to survey low-energy cosmic-ray antinuclei, particularly antideuterons, which are recognized as essentially background-free signals from dark matter annihilation or decay. The GAPS Si(Li) detector design is a thickness of 2.5 mm, diameter of 10 cm and 8 readout strips. The energy resolution of <4 keV (FWHM) for 20 to 100 keV X-rays at temperature of -35 to -45 C, far above the liquid nitrogen temperatures frequently used to achieve fine energy resolution, is required. We developed a high-quality Si crystal and Li-evaporation, diffusion and drift methods to form a uniform Li-drifted layer. Guard ring structure and optimal etching of the surface are confirmed to suppress the leakage current, which is a main source of noise. We found a thin un-drifted layer retained on the p-side effectively suppresses the leakage current. By these developments, we succeeded in developing the GAPS Si(Li) detector. As the ultimate GAPS instrument will require >1000 10-cm diameter Si(Li) detectors to achieve high sensitivity to rare antideuteron events, high-yield production is also a key factor for the success of the GAPS mission.
Thirteen tetraplegic patients were included in the study of the effects of respiratory muscle training and of electrical stimulation of the abdominal muscles on their respiratory capabilities. Each ...patient was subjected for three 1 month lasting periods of the study: for inspiratory muscle training, expiratory muscle training and for a period without training. The sequence of these three periods was random for each patient. Respiratory tests (RT) measuring forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were conducted before and following each monthly period. Measurements were taken under four sets of conditions: the patients' unassisted efforts, their efforts combined with pressure manually applied by a therapist to the upper part of their abdomen, and their efforts accompanied by electrical stimulation (ES) of the abdominal muscles during the early phase of expirium, once triggered by the therapist and once by the patients themselves. RT values were increasing following respiratory muscle training and inspiratory training apparently had a slightly greater effect than its expiratory counterpart. The increments of values of RT were statistically significant (P < 0.05) after the inspiratory muscle training. RT measurements were greater when the patient's voluntary effort was combined with ES of abdominal muscles than when it was not. This study concludes that respiratory muscle training is a potentially effective approach and that ES of the abdominal muscles has potentials to improve coughing in tetraplegic patients.
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