Multimodal Non-Contact Luminescence Thermometry with Cr-Doped Oxides.

Luminescence methods for non-contact temperature monitoring have evolved through improvements of hardware and sensor materials. Future advances in this field rely on the development of multimodal sensing capabilities of temperature probes and extend the temperature range across which they operate. The family of Cr-doped oxides appears particularly promising and we review their luminescence characteristics in light of their application in non-contact measurements of temperature over the 5-300 K range. Multimodal sensing utilizes the intensity ratio of emission lines, their wavelength shift, and the scintillation decay time constant. We carried out systematic studies of the temperature-induced changes in the luminescence of the Cr3+-doped oxides Al2O3, Ga2O3, Y3Al5O12, and YAlO3. The mechanism responsible for the temperature-dependent luminescence characteristic is discussed in terms of relevant models. It is shown that the thermally-induced processes of particle exchange, governing the dynamics of Cr3+ ion excited state populations, require low activation energy. This then translates into tangible changes of a luminescence parameter with temperature. We compare different schemes of temperature sensing and demonstrate that Ga2O3-Cr is a promising material for non-contact measurements at cryogenic temperatures. A temperature resolution better than ±1 K can be achieved by monitoring the luminescence intensity ratio (40-140 K) and decay time constant (80-300 K range).

Three-Dimensional Proton Beam Writing of Optically Active Coherent Vacancy Spins in Silicon Carbide.

Constructing quantum devices comprises various challenging tasks, especially when concerning their nanoscale geometry. For quantum color centers, the traditional approach is to fabricate the device structure after the nondeterministic placement of the centers. Reversing this approach, we present the controlled generation of quantum centers in silicon carbide (SiC) by focused proton beam in a noncomplex manner without need for pre- or postirradiation treatment. The generation depth and resolution can be predicted by matching the proton energy to the material's stopping power, and the amount of quantum centers at one specific sample volume is tunable from ensembles of millions to discernible single photon emitters. We identify the generated centers as silicon vacancies through their characteristic magnetic resonance signatures and demonstrate that they possess a long spin-echo coherence time of 42 ± 20 µs at room temperature. Our approach hence enables the fabrication of quantum hybrid nanodevices based on SiC platform, where spin centers are integrated into p-i-n diodes, photonic cavities, and mechanical resonators.

Non-contact luminescence lifetime cryothermometry for macromolecular crystallography.

Temperature is a very important parameter when aiming to minimize radiation damage to biological samples during experiments that utilize intense ionizing radiation. A novel technique for remote, non-contact, in situ monitoring of the protein crystal temperature has been developed for the new I23 beamline at the Diamond Light Source, a facility dedicated to macromolecular crystallography (MX) with long-wavelength X-rays. The temperature is derived from the temperature-dependent decay time constant of luminescence from a minuscule scintillation sensor (<0.05 mm3) located in very close proximity to the sample under test. In this work the underlying principle of cryogenic luminescence lifetime thermometry is presented, the features of the detection method and the choice of temperature sensor are discussed, and it is demonstrated how the temperature monitoring system was integrated within the viewing system of the endstation used for the visualization of protein crystals. The thermometry system was characterized using a Bi4Ge3O12 crystal scintillator that exhibits good responsivity of the decay time constant as a function of temperature over a wide range (8-270 K). The scintillation sensor was calibrated and the uncertainty of the temperature measurements over the primary operation temperature range of the beamline (30-150 K) was assessed to be ±1.6 K. It has been shown that the temperature of the sample holder, measured using the luminescence sensor, agrees well with the expected value. The technique was applied to characterize the thermal performance of different sample mounts that have been used in MX experiments at the I23 beamline. The thickness of the mount is shown to have the greatest impact upon the temperature distribution across the sample mount. Altogether, these tests and findings demonstrate the usefulness of the thermometry system in highlighting the challenges that remain to be addressed for the in-vacuum MX experiment to become a reliable and indispensable tool for structural biology.

Limits on Momentum-Dependent Asymmetric Dark Matter with CRESST-II.

The usual assumption in direct dark matter searches is to consider only the spin-dependent or spin-independent scattering of dark matter particles. However, especially in models with light dark matter particles O(GeV/c^{2}), operators which carry additional powers of the momentum transfer q^{2} can become dominant. One such model based on asymmetric dark matter has been invoked to overcome discrepancies in helioseismology and an indication was found for a particle with a preferred mass of 3 GeV/c^{2} and a cross section of 10^{-37} cm^{2}. Recent data from the CRESST-II experiment, which uses cryogenic detectors based on CaWO_{4} to search for nuclear recoils induced by dark matter particles, are used to constrain these momentum-dependent models. The low energy threshold of 307 eV for nuclear recoils of the detector used, allows us to rule out the proposed best fit value above.

Towards an automated data cleaning with deep learning in CRESST.

The CRESST experiment employs cryogenic calorimeters for the sensitive measurement of nuclear recoils induced by dark matter particles. The recorded signals need to undergo a careful cleaning process to avoid wrongly reconstructed recoil energies caused by pile-up and read-out artefacts. We frame this process as a time series classification task and propose to automate it with neural networks. With a data set of over one million labeled records from 68 detectors, recorded between 2013 and 2019 by CRESST, we test the capability of four commonly used neural network architectures to learn the data cleaning task. Our best performing model achieves a balanced accuracy of 0.932 on our test set. We show on an exemplary detector that about half of the wrongly predicted events are in fact wrongly labeled events, and a large share of the remaining ones have a context-dependent ground truth. We furthermore evaluate the recall and selectivity of our classifiers with simulated data. The results confirm that the trained classifiers are well suited for the data cleaning task.

Secular equilibrium assessment in a CaWO4 target crystal from the dark matter experiment CRESST using Bayesian likelihood normalisation.

CRESST is a leading direct detection sub-GeVc-2 dark matter experiment. During its second phase, cryogenic bolometers were used to detect nuclear recoils off the CaWO4 target crystal nuclei. The previously established electromagnetic background model relies on Secular Equilibrium (SE) assumptions. In this work, a validation of SE is attempted by comparing two likelihood-based normalisation results using a recently developed spectral template normalisation method based on Bayesian likelihood. Albeit we find deviations from SE in some cases we conclude that these deviations are artefacts of the fit and that the assumptions of SE is physically meaningful.

Resonant addressing and manipulation of silicon vacancy qubits in silicon carbide.

Several systems in the solid state have been suggested as promising candidates for spin-based quantum information processing. In spite of significant progress during the last decade, there is a search for new systems with higher potential [D. DiVincenzo, Nat. Mater. 9, 468 (2010)]. We report that silicon vacancy defects in silicon carbide comprise the technological advantages of semiconductor quantum dots and the unique spin properties of the nitrogen-vacancy defects in diamond. Similar to atoms, the silicon vacancy qubits can be controlled under the double radio-optical resonance conditions, allowing for their selective addressing and manipulation. Furthermore, we reveal their long spin memory using pulsed magnetic resonance technique. All these results make silicon vacancy defects in silicon carbide very attractive for quantum applications.

Al2O3 co-doped with Cr3+ and Mn4+, a dual-emitter probe for multimodal non-contact luminescence thermometry.

Luminescence probes that facilitate multimodal non-contact measurements of temperature are of particular interest due to the possibility of cross-referencing results across different readout techniques. This intrinsic referencing is an essential addition that enhances accuracy and reliability of the technique. A further enhancement of sensor performance can be achieved by using two luminescent ions acting as independent emitters, thereby adding in-built redundancy to non-contact temperature sensing, using a single readout technique. In this study we combine both approaches by engineering a material with two luminescent ions that can be independently probed through different readout modes of non-contact temperature sensing. The approach was tested using Al2O3 co-doped with Cr3+ and Mn4+, exhibiting sharp emission lines due to 2E → 4A2 transitions. The temperature sensing performance was examined by measuring three characteristics: temperature-induced changes of the intensity ratio of the emission lines, their spectral position, and the luminescence decay time constant. The processes responsible for the changes with temperature of the measured luminescence characteristics are discussed in terms of relevant models. By comparing temperature resolutions achievable by different modes of temperature sensing it is established that in Al2O3-Cr,Mn spectroscopic methods provide the best measurement accuracy over a broad temperature range. A temperature resolution better than ±2.8 K can be achieved by monitoring the luminescence intensity ratio (40-145 K) and the spectral shift of the R-line of Mn4+ (145-300 K range).

Bright and fast scintillations of an inorganic halide perovskite CsPbBr3 crystal at cryogenic temperatures.

Highly efficient scintillation crystals with short decay times are indispensable for improving the performance of numerous detection and imaging instruments that use- X-rays, gamma-quanta, ionising particles or neutrons. Halide perovskites emerged recently as very promising materials for detection of ionising radiation that motivated further exploration of the materials. In this work, we report on excellent scintillation properties of CsPbBr3 crystals when cooled to cryogenic temperatures. The temperature dependence of luminescence spectra, decay kinetics and light yield under excitation with X-rays and α-particles was investigated. It is shown that the observed changes of spectral and kinetic characteristics of the crystal with temperature can be consistently explained by radiative decay of free excitons, bound and trapped excitons as well as electron-hole pairs originating from their disintegration. It has been found that the crystal exhibits a fast decay time constant of 1 ns at 7 K. The scintillation light yield of CsPbBr3 at 7 K is assessed to be 50,000 ± 10,000 ph/MeV at excitation with 12 keV X-rays and 109,000 ± 22,000 ph/MeV at excitation with α-particles of 241Am. This finding places CsPbBr3 in an excellent position for the development of a new generation of cryogenic, efficient scintillation detectors with nanosecond response time, marking a step-change in opportunities for scintillator-based applications.

Megahertz non-contact luminescence decay time cryothermometry by means of ultrafast PbI2 scintillator.

Realtime in situ temperature monitoring in difficult experimental conditions or inaccessible environments is critical for many applications. Non-contact luminescence decay time thermometry is often the method of choice for such applications due to a favorable combination of sensitivity, accuracy and robustness. In this work, we demonstrate the feasibility of an ultrafast PbI2 scintillator for temperature determination, using the time structure of X-ray radiation, produced by a synchrotron. The decay kinetics of the scintillations was measured over the 8-107 K temperature range using monochromatic pulsed X-ray excitation. It is found that lead iodide exhibits a very fast and intense scintillation response due to excitons and donor-acceptor pairs, with the fast decay component varying between 0.08 and 0.5 ns - a feature that can be readily exploited for temperature monitoring. The observed temperature dependence of the decay time is discussed in terms of two possible mechanisms of thermal quenching - transition over activation barrier and phonon-assisted escape. It is concluded that the latter provides a better fit to the experimental results and is consistent with the model of luminescence processes in PbI2. We evaluated the sensitivity and estimated the accuracy of the temperature determination as ca. ±6 K at 107 K, improving to ±1.4 K at 8 K. The results of this study prove the feasibility of temperature monitoring, using ultrafast scintillation of PbI2 excited by X-ray pulses from a synchrotron, thus enabling non-contact in-situ cryothermometry with megahertz sampling rate.

Geant4-based electromagnetic background model for the CRESST dark matter experiment.

The CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) dark matter search experiment aims for the detection of dark matter particles via elastic scattering off nuclei in CaWO 4 crystals. To understand the CRESST electromagnetic background due to the bulk contamination in the employed materials, a model based on Monte Carlo simulations was developed using the Geant4 simulation toolkit. The results of the simulation are applied to the TUM40 detector module of CRESST-II phase 2. We are able to explain up to ( 68 ± 16 ) % of the electromagnetic background in the energy range between 1 and 40 keV .

Development of superconducting contacts for the CRESST II 66-channel superconducting quantum interference device readout system.

The CRESST experiment is designed to search for weakly interacting massive particle dark matter with cryogenic detectors. CRESST II will use up to 33 CaWO(4) crystals with a total mass of approximately 10 kg. These many detectors require a readout system based on 66-channel superconducting quantum interference devices (SQUIDs). In this article we report on the development of a modular superconducting connector for the 66-channel SQUID readout circuit. We show that the technique developed reliably produces superconducting contacts.

Technical note: gold marker implants and high-frequency jet ventilation for stereotactic, single-dose irradiation of liver tumors.

With reference to radiosurgery of the liver, we describe techniques designed to solve the methodological problem of striking targets subject to respiratory motion with the necessary precision. Implanting a gold marker in the vicinity of the liver tumor was the first step in ensuring the reproducibility of the isocenter's position. An 18-karat gold rod measuring 1.9 x 3 mm was implanted approximately 2 cm from the edge of the tumor as this was displayed in the spiral, thin-slice CT with contrast media. Both the implantation of the marker and the required, CT-controlled biopsy of the liver tumor can be achieved simultaneously with the same puncture needle. The efficiency of high-frequency jet ventilation (HFJV) in neutralizing the targeted organ's respiratory motion during stereotactic single-dose irradiation was evaluated. The procedure was carried out on ten patients without any complications. In the time between treatment planning and irradiation (3 days), no significant marker migration was observable. In all cases, the gold marker (volume: 7.5 mm(3)) was readily observable in the treatment beam using portal imaging. HFJV provided reliable immobilization. The liver motion in each anesthetized patient was limited to under 3.0 mm in all directions. Thus, the correct field settings and target reproducibility were able to be analyzed and documented during the irradiation. The combination of marker and HFJV enables the determination of stereotactic coordinates directly related to the liver itself and, in this way, stereotactic radiation treatment of liver tumors is freed from the uncertainties involved in orientation to bony landmarks, in respiratory motion, and in changes of position in the stereotactic body frame. The method is feasible and can improve the accuracy of stereotactic body radiation therapy.

Comparison of immunoglobulin G heavy-chain sequences in MS and SSPE brains reveals an antigen-driven response.

OBJECTIVE: To better understand B-cell activation in MS by analyzing the immunoglobulin (Ig)G heavy chain variable region (VH) repertoire found in MS brains and comparing it with brain VH sequences in individuals with subacute sclerosing panencephalitis (SSPE)--a chronic encephalitis produced by measles virus (MV)-and characterized by an antigen-driven oligoclonal IgG response to MV antigens. BACKGROUND: The specificity of oligoclonal IgG in MS CSF and plaques, and their relevance to the pathogenesis of MS is unknown. METHODS: Nested PCR was used to amplify and sequence the rearranged IgG heavy-chain VH repertoire in plaques of three acute MS brains and in three SSPE brains. A representative population of VH sequences from each tissue was aligned to the known 51 functional VH germline segments. From this the authors determined the closest VH family germline segment, and the degree and location of somatic mutations for each unique IgG. RESULTS: As expected for an antigen-driven response against MV antigens, most VH sequences from the SSPE brains were mutated extensively compared with their closest germline segments. Furthermore, SSPE VH sequences accumulated replacement mutations preferentially in the complementary-determining regions (CDRs) relative to framework regions-features normally observed during antigen-driven selection. A comparison of VH family and germline usage also demonstrated that each SSPE brain had its own unique IgG response. When the authors compared the VH response in MS plaques with SSPE, MS VH sequences were also mutated extensively, displayed a preferential accumulation of replacement mutations in CDRs, and were unique in each MS brain. CONCLUSION: The presence of an antigen-driven response in MS, rather than a nonconventional mechanism of B-cell activation, warrants additional analysis of the specificity of IgG in MS brain and CSF.

Effects of arginine infusion in infants: increased urea synthesis associated with unchanged ammonia blood levels.

Infusion of L-arginine hydrochloride in infants and children (ages ranging from 1 day to 12 yr) at a dosage of 0.5 g/kg body weight resulted in a dramatic increase in the arginine plasma concentration, with highest values of approximately 7 mmole/liter immediately after the end of the infusion; 120 min later the mean plasma level of the amino acid had decreased to mean values of 1 mmole/liter. These fluctuations were paralleled by increased ornithine concentrations, although the mean plasma levels of this amino acid remained far below those of arginine, i.e., 0.73 and 0.22 mmole/liter after 30 and 90 min, respectively. When expressed on a molar basis, arginine administration resulted in an almost stoichiometric rise in urinary urea excretion. These findings indicate that arginine is rapidly metabolized via urea and ornithine, the latter being transformed to glucose, as evidenced by a significant rise in the blood glucose concentration. Blood gas analyses and serum urea and blood ammonia concentrations determined after the load showed no significant deviations from preinfusion levels. Thus, in contrast to the effects to be expected form studies with tissue culture homogenates, even when administered to newborn infants, arginine does not impair the turnover of the urea cycle.

Optical triple sensor for measuring pH, oxygen and carbon dioxide.

A triple sensor unit consisting of opto-chemical sensors for measurement of pH, oxygen and carbon dioxide in bioreactors is presented. The pH and the CO2 sensor are based on the color change of a pH-sensitive dye immobilized on a polymeric support. The resulting changes in absorption are monitored through optical fibers. The oxygen sensor is based on the quenching of the fluorescence of a metal-organic dye. All three sensors are fully LED compatible. The sensitive membranes consist of plastic films and can be stored and replaced conveniently. The sensors are sterilizable with hydrogen peroxide and ethanol. In addition, the pH sensor is steam sterilizable. Accuracy, resolution and reproducibility fulfill the requirements for use in biotechnological applications. Calibration procedures for each sensor are presented. The working principle and the performance of all three sensors are described, with particular emphasis given to their application in bioreactors.

Electrophysiological evaluation of visual loss in Müller cell sheen dystrophy.

AIMS: To describe the clinical picture and electrophysiological findings in Müller cell sheen dystrophy, a recently reported retinal dystrophy. METHOD: A basic ophthalmological evaluation as well as recording of standard electro-oculography and electroretinography were performed in one patient at the onset of visual loss and after 1 year of follow up. RESULTS: A 61 year old woman presented with visual loss in the right eye. Multiple folds at the level of the internal limiting membrane were seen at the posterior pole in both eyes. Macular oedema was present in the right eye. The visual acuity of the right eye was 6/30 and of the left 6/9. A paracentral scotoma was found in the right eye. Electro-oculographic examination of both eyes gave normal results. Electroretinography (ERG) revealed reduced b-wave and flicker amplitudes in the right eye; these potentials were normal for the left eye. The ON response in the right eye was reduced and delayed; it was normal in the left eye. A further loss of visual function was noted 1 year later in the right eye, but the ophthalmoscopic findings were unchanged. The ERG of the right eye had a negative waveform when dark adapted. Light adapted responses showed an unusual delayed b-wave, broad and delayed ON and OFF responses and a missing flicker response, suggesting a Müller cell dysfunction. Light adapted responses were slightly reduced in the left eye. CONCLUSIONS: Electrophysiological data indicate Müller cell dysfunction as a background of functional loss in Müller cell sheen dystrophy. This is in agreement with previously reported histological findings in this disorder.

Factors influencing manual muscle tests in physical therapy.

To determine whether it is the amount or the duration of the force applied manually by the tester, or both, that determines the tester's perception of the strength of the hip flexor or abductor muscles, an electromechanical device was designed which was placed between the tester's hand and the subject's limb. With the device we measured the force applied to the limb, the time interval during which it was applied, and the angular position of the limb during the entire test. In 240 such tests, the testers' ratings of the differences in strength between the right and left sides were correlated with seven variables involving force and time. It was found statistically that the impluse--that is, the duration of the tester's effort multiplied by the average applied force during each test--was the factor that most influenced the tester in the ratings.

Morphological changes in the cochlea of the mouse after the onset of hearing.

The cochleae of 5, 10, 12 and 15 day old mice and of adults (Mus musculus, strain NMRI) were studied by light and electron microscopy. In each case the same part of the organ of Corti (2.8-3.3 mm from the helicotrema) was examined. The results were correlated with the development of auditory thresholds (in mice of the same strain) obtained by Ehret (Ehret, G. (1971) J. Am. Audiol. Soc. 1, 179-184). It was demonstrated that morphological development of the organ of Corti is by no means complete at the onset of behavioural responses to acoustic stimuli. After this event the following morphological changes occur: (1) The basilar membrane filaments stain more intensely and the tympanic cover layer is greatly reduced in thickness and almost completely disappears. (2) The filaments of the pillar cells stain more intensely and apparently increase in number, and the angle between the outer and inner pillar cells increases so that the cross-sectional area of the tunnel of Corti expands. (3) Hook-shaped connections (marginal pillars) between the reticular membrane and the tectorial membrane disappear. The consequences of these morphological changes for the cochlear mechanics are discussed, especially in respect to the increase of sensitivity of hearing.

Diagnosis and treatment of myofascial pain.

The importance of muscle as a source of pain should not be underestimated. Proper diagnosis of the four types of muscle pain (tension, spasm, muscle deficiency, and trigger points) is essential to effective management. Pain-diagnostic instruments can quantify tenderness and spasm and help evaluate treatment results.