Nano Vacancy Clusters and Trap Limited Diffusion of Si Interstitials in Silicon

The objective of this project is to develop a method to characterize nano vacancy clusters and the dynamics of their formation in ion-irradiated silicon. It will impact (1) semiconductor device processing involving ion implantation, and (2) device design concerning irradiation hardness in harsh environments. It also aims to enhance minority participation in research and curricula on emerging materials and ion beam science. Vacancy defects are of scientific and technological importance since they are ubiquitous when the host materials are exposed to particle irradiation. Studies on vacancy clustering in the past decades were mainly theoretical and the approach heavily relied on the total-energy calculation methods. The lack of experimental data is mainly due to the formidable task in measuring the cluster size and density using modern metrological techniques, including transmission electron microscopy and positron annihilation spectroscopy. To surmount these challenges, we proposed a novel approach to tackle the metrological problems on the nano vacancy clusters, especially in determining densities and sizes of the nano vacancies based on the premise that the vacancy-clusters act as diffusion-trapping centers. For a silicon substrate containing vacancyclusters, the diffusion of interstitials (from the surface) can be classified into three phases: (1) an ultrafast phase-I in which the trapping centers have little effect on the diffusion of interstitials; (2) a prolonged phase-II in which the loss rate of interstitials by trapping balances the influx of interstitials from the surface; and (3) a phase-III diffusion in which surface influx of interstitials depletes the trapping centers and interstitials consequently propagate deeper into the bulk. By measuring diffusion profiles of Si interstitials as a function of diffusion time, void sizes and void densities can be obtained through fitting. Experimentally, our approach to characterize voids is realized through three consecutive steps. (a) First, high energy self ion irradiation is used to create a wide vacancy-rich region, and to form voids by post implantation annealing. (b) In an additional annealing step in oxygen ambient, Si interstitials are injected in by surface oxidation. (c) Analyzing trap-limited diffusion of Si interstitials, which is experimentally detectable by studying the diffusion of multiple boron superlattices grown in Si, and enables us to characterize the nano voids, e.g. their sizes and densities

Advanced technology lunar telescope

A new type of telescope pointing system designed specifically for space and lunar applications will be discussed, based upon a prototype advanced technology telescope under investigation. The focus here will be the system of hybrid superconductor magnetic bearings (HSMB) used to provide isolation support and steering functions. HSMB's are combinations of high temperature superconductors, permanent magnets, and coils, being passive (requiring no power), noncontact, and essentially frictionless. These also are well suited to long-term unattended operation in the space environment. The characteristics of these subsystems, their expected behavior under space vacuum, and thermal and radiation environments are discussed

A Natural Application for High Temperature Superconductors: a Bearing for the Azimuth Mount of a Lunar Telescope

A bearing for telescope mounts on the moon has to function in a cold dusty vacuum environment that impairs the operation of almost all traditional bearings, but it is a natural environment for bearings constructed out of magnets and high temperature superconductors. The challenge lies not so much in the weight of the telescope that has to be supported, but in the smoothness of forces required for precision positioning control over a long stretch of time without human intervention. In this paper, we present a design of hybrid superconductor magnet bearings intended for use on the azimuth mount of an altitude-azimuth telescope mount system. In addition to the general features of hybrid super conducting magnet bearings, we will address particular issues connected with the application of these bearings on a telescope mount

Benzodiazepines Associated With Acute Respiratory Failure in Patients With Obstructive Sleep Apnea

Aims: Obstructive sleep apnea (OSA) and insomnia commonly coexist; hypnotics are broadly prescribed for insomnia therapy. However, the safety of hypnotics use in OSA patients is unclear. We conducted a retrospective case-control study to investigate the risk of adverse respiratory events in hypnotics-using OSA patients.Methods: We obtained data from the Taiwan National Health Insurance Database from 1996 to 2013. The case group included 216 OSA patients with newly diagnosed adverse respiratory events, including pneumonia and acute respiratory failure. The control group included OSA patients without adverse respiratory events, which was randomly frequency-matched to the case group at a 1:1 ratio according to age, gender, and index year. Hypnotics exposure included benzodiazepines (BZD) and non-benzodiazepines (non-BZD). A recent user was defined as a patient who had taken hypnotics for 1–30 days, while a long-term user was one who had taken hypnotics for 31–365 days.Results: Multivariable adjusted analysis showed recent BZD use is an independent risk for adverse respiratory events (OR = 2.70; 95% CI = 1.15–6.33; P < 0.001). Subgroup analysis showed both recent and long-term BZD use increased the risk of acute respiratory failure compared to never BZD use (OR = 28.6; 95% CI = 5.24–156; P < 0.001, OR = 10.1; 95% CI = 1.51–67.7; P < 0.05, respectively). Neither BZD nor non-BZD use increased the risk of pneumonia in OSA patients.Conclusion: BZD use might increase the risk of acute respiratory failure in OSA patients

Microstructure and thermal stability of Fe, Ti and Ag implanted Yttria-stabilized zirconia

Yttria-stabilized zirconia (YSZ) was implanted with 15 keV Fe or Ti ions up to a dose of 8×1016 at cm−2. The resulting “dopant” concentrations exceeded the concentrations corresponding to the equilibrium solid solubility of Fe2O3 or TiO2 in YSZ. During oxidation in air at 400° C, the Fe and Ti concentration in the outermost surface layer increased even further until a surface layer was formed of mainly Fe2O3 and TiO2, as shown by XPS and ISS measurements. From the time dependence of the Fe and Ti depth profiles during anneal treatments, diffusion coefficients were calculated. From those values it was estimated that the maximum temperature at which the Fe- and Ti-implanted layers can be operated without changes in the dopant concentration profiles was 700 and 800° C, respectively. The high-dose implanted layer was completely amorphous even after annealing up to 1100° C, as shown by scanning transmission electron microscopy. Preliminary measurements on 50 keV Ag implanted YSZ indicate that in this case the amorphous layer recrystallizes into fine grained cubic YSZ at a temperature of about 1000° C. The average grain diameter was estimated at 20 nm, whereas the original grain size of YSZ before implantation was 400 nm. This result implies that the grain size in the surface of a ceramic material can be decreased by ion beam amorphisation and subsequent recrystallisation at elevated temperatures

The Quantitative Evaluation of Automatic Segmentation in Lumbar Magnetic Resonance Images

Objective This study aims to overcome challenges in lumbar spine imaging, particularly lumbar spinal stenosis, by developing an automated segmentation model using advanced techniques. Traditional manual measurement and lesion detection methods are limited by subjectivity and inefficiency. The objective is to create an accurate and automated segmentation model that identifies anatomical structures in lumbar spine magnetic resonance imaging scans. Methods Leveraging a dataset of 539 lumbar spinal stenosis patients, the study utilizes the residual U-Net for semantic segmentation in sagittal and axial lumbar spine magnetic resonance images. The model, trained to recognize specific tissue categories, employs a geometry algorithm for anatomical structure quantification. Validation metrics, like Intersection over Union (IOU) and Dice coefficients, validate the residual U-Net’s segmentation accuracy. A novel rotation matrix approach is introduced for detecting bulging discs, assessing dural sac compression, and measuring yellow ligament thickness. Results The residual U-Net achieves high precision in segmenting lumbar spine structures, with mean IOU values ranging from 0.82 to 0.93 across various tissue categories and views. The automated quantification system provides measurements for intervertebral disc dimensions, dural sac diameter, yellow ligament thickness, and disc hydration. Consistency between training and testing datasets assures the robustness of automated measurements. Conclusion Automated lumbar spine segmentation with residual U-Net and deep learning exhibits high precision in identifying anatomical structures, facilitating efficient quantification in lumbar spinal stenosis cases. The introduction of a rotation matrix enhances lesion detection, promising improved diagnostic accuracy, and supporting treatment decisions for lumbar spinal stenosis patients