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  • MacPherson Wulff posted an update 1 year, 6 months ago

    An extension of the online implantation chamber used for emission Mössbauer Spectroscopy (eMS) at ISOLDE/CERN that allows for quick removal of samples for offline low temperature studies is briefly described. We demonstrate how online eMS data obtained during implantation at temperatures between 300 K and 650 K of short-lived parent isotopes combined with rapid cooling and offline eMS measurements during the decay of the parent isotope can give detailed information on the binding properties of the Mössbauer probe in the lattice. This approach has been applied to study the properties of Sn impurities in ZnO following implantation of 119In (T½ = 2.4 min). Sn in the 4+ and 2+ charge states is observed. Above T > 600 K, Sn2+ is observed and is ascribed to Sn on regular Zn sites, while Sn2+ detected at T less then 600 K is due to Sn in local amorphous regions. A new annealing stage is reported at T ≈ 550 K, characterized by changes in the Sn4+ emission profile, and is attributed to the annihilation of close Frenkel pairs.This paper presents a hybrid interferometric system designed to measure the surface velocity of tested specimens in shock-wave experiments. The system integrates the All-Fiber Velocity Interferometer System for Any Reflector (AFVISAR) and the Photonic Doppler Velocimeter (PDV) interferometric channels using a single probing system to measure the velocity of one surface point of specimens under study. This design allows the same optical signal containing the Doppler frequency shift to be processed by the AFVISAR and PDV independent interferometric devices. The interferometric system has been tested in dynamic experiments and provides the velocity measurement accuracy of at least 1.5 m/s with a nanosecond time resolution.In order to realize the miniaturization and leadless function of the electric field probe working from 10 MHz to 1000 MHz, a small stand-alone probe based on the dipole and Schottky detector diode is developed in this paper. First, a 20 mm dipole printed on the circuit board is adopted as the receiving antenna, and the Schottky detector diode is connected across the two arms of the dipole. Then, the signal output by the detector diode is amplified by a chopper amplifier circuit, which also isolates the alternating component. Finally, a microprogrammed control unit is set inside the metal shield to realize data acquisition and storage. The size of the probe developed is not exceeding 20 × 20 × 30 mm3, and the characteristics of the probe are temperature dependent. The field strength from 1.4 V/m to 1627 V/m can be measured within 10 MHz-1000 MHz, achieving a dynamic range over 61 dB at 21 °C. It has the advantages of small size, large dynamic range, and integrated data collection and storage.The photoabsorption spectroscopic studies (PASS) beamline (PASS-BL07), installed at a bending magnet 450 MeV, 100 mA Indus-1 synchrotron source (India), is capable of performing photoabsorption studies in the vacuum ultraviolet to soft x-ray range of thin films and solid samples. selleck kinase inhibitor The beamline covers an energy range of 55 eV-840 eV by an in-house developed SX-700 type plane grating monochromator. This energy range will cover the absorption spectra of low Z-elements like C, N, and O as well as the L and M threshold of 3d elements such as Ti, V, S, etc. The beamline will be significantly used for studying organic semiconductors, graphene, etc. In this article, the design details of the beamline and some of the recent scientific results have been presented.This study investigated the abnormal pupillary light reflex in patients with early diabetes mellitus (DM) without retinopathy by using a custom-made noninvasive portable pupilometer. The pupilometer recorded and analyzed the pupillary light reflex. Two light intensities, 0.2 cd and 1.2 cd, and four wavelengths of stimulus light-white (400 nm-800 nm), red (640 ± 5 nm), green (534 ± 5 nm), and blue (470 ± 5 nm)-were used to stimulate the pupil for 10 ms. The pupillary response was recorded for 15 s. A total of 40 healthy people and 40 people with DM without retinopathy participated in the experiment at the National Taiwan University Hospital. The mean and standard deviation of DM duration were 4.5 years and 3.9 years. Of the 16 indices, the duration that pupil restores from its minimum size to half of its resting size (DRP), maximum pupil restoration velocity (MRV), and average restoration velocity (ARV) exhibited the most significant differences between the healthy people and those with DM. Compared with healthy participants, DRP was 16.33% higher, and MRV and ARV were 17.45% and 4.58% lower, respectively, in those with DM. This might be attributable to the sympathetic nervous system (SNS) controlling the dilator muscle during the dark-adapted period and relaxing the pupil; the SNS had few degenerated nerve endings in people with DM. The three aforementioned indices might be used to evaluate the severity of autonomic neuropathy in early DM.Broadband seismometers and gravitational wave detectors make use of mechanical resonators with a high quality factor to reduce Brownian noise. At low frequency, Brownian noise is ultimately dominated by internal friction in the suspension, which has a 1/f noise compared with the white noise arising from viscous dissipation. Internal friction is typically modeled as a frequency-dependent loss and can be challenging to measure reliably through experiment. In this work, we present the physics and experimental implementation of electrostatic frequency reduction (EFR) in a mechanical oscillator-a method to measure dissipation as a function of frequency. By applying a high voltage to two parallel capacitor plates, with the center plate being a suspended mass, an electrostatic force is created that acts as a negative stiffness mechanism to reduce the system’s resonance frequency. Through EFR, the loss angle can be measured as a function of frequency by measuring amplitude decay response curves for a range of applied voltages. We present experimental measurements of the loss angle for three metal helical extension springs in the nominal frequency range 0.7-2.9 Hz at 0.2 Hz intervals, demonstrating the possibility for fine adjustment of the resonance frequency for loss angle measurements. A quality factor proportional to the resonance frequency squared was measured, an indication that internal friction and other non-viscous dissipation elements, such as electrostatic damping, were the prominent loss mechanisms in our experiments. Finally, we consider the implications of Brownian noise arising from internal friction on a low 1/f noise seismometer.