This paper reports on large field-of-regard, high-efficiency, and large aperture active optical phased arrays (OPAs) for optical beam steering in LIDAR systems. The fabricated 5 mm-long silicon ...photonic OPA with a 1.3 μm waveguide pitch achieved adjacent waveguide crosstalk below -12dB. A relatively large and uniform emission aperture has been achieved with a low-contrast silicon nitride assisted grating (~20 dB/cm) whose emission profile can be further optimized using an apodized design. The fabricated silicon-photonic OPA demonstrated > 40° lateral beam steering with no sidelobes in a ± 33° field-of-regard and 3.3° longitudinal beam steering via wavelength tuning by 20 nm centered at 1550 nm. We have fully integrated the silicon photonic OPA device with electronic controls and successfully demonstrated 2-dimensional coherent optical beam steering of pre-planned far-field patterns. Future improvements include placement of a distributed Bragg reflector (DBR) underneath the grating emitter in order to achieve nearly a factor of two improvement in emission efficiency.
Laser Powder Bed Fusion is a leading additive manufacturing technology, whose use has been recently extended to refractory metals such as tungsten. This work was carried out to manufacture a pure ...tungsten pinhole collimator that would otherwise be difficult to produce using conventional methods such as machining. The laser powder bed fusion process was used to produce an ultra-fine 0.5 mm diameter hole running along a 40 mm long beam stop component. A laser powder bed fusion scanning strategy (laser energy density of 348 J/mm3) was selected with the aim of fabricating a high density tungsten component. The manufactured collimator was then used for gamma-ray detector characterisation. A collimated gamma-ray using a 241Am source mounted on an automated scanning table was used to study the gamma-ray interaction with respect to position in a semiconductor detector, so that the position-dependent charge collection process could be characterized. The 0.5 mm diameter fine tungsten collimator yielded a relatively narrower beam spot, leading to more accurate scan results. However that was at the expense of number of gamma rays detected per second. Overall, the 0.5 mm collimator allowed for higher resolution scans giving better detector characterisation results in comparison to a 1 mm diameter collimator.
•LPBF was used to produce a tungsten collimator that would be difficult to produce using conventional methods•Collimated gamma-ray sources were used to study the gamma-ray interaction wrt position in a semiconductor detector•Position-dependent charge collection was characterized and the fine LPBF tungsten collimator yielded a narrower beam spot•The more accurate scan results came at the expense of gamma rays per second•It is envisaged that the 0.5 mm LPBF collimator would be used to scan specific regions of interest on a detector.
Mitochondrial dysfunction is implicated in many human diseases and occurs in normal aging. Mitochondrial health is maintained through organelle biogenesis and repair or turnover of existing ...mitochondria. Mitochondrial turnover is principally mediated by mitophagy, the trafficking of damaged mitochondria to lysosomes via macroautophagy (autophagy). Mitophagy requires autophagy, but is itself a selective process that relies on specific autophagy-targeting mechanisms, and thus can be dissociated from autophagy under certain circumstances. Therefore, it is important to assess autophagy and mitophagy together and separately. We sought to develop a robust, high-throughput, quantitative method for monitoring both processes in parallel. Here we report a flow cytometry-based assay capable of rapid parallel measurements of mitophagy and autophagy in mammalian cells using a single fluorescent protein biosensor. We demonstrate the ability of the assay to quantify Parkin-dependent selective mitophagy in CCCP-treated HeLa cells. In addition, we show the utility of the assay for measuring mitophagy in other cell lines, as well as for Parkin-independent mitophagy stimulated by deferiprone. The assay makes rapid measurements (10,000 cells per 6 seconds) and can be combined with other fluorescent indicators to monitor distinct cell populations, enabling design of high-throughput screening experiments to identify novel regulators of mitophagy in mammalian cells.
An experimental characterisation of a Broad Energy Germanium detector Harkness-Brennan, L.J.; Judson, D.S.; Boston, A.J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2014, Letnik:
760
Journal Article
Recenzirano
The spectroscopic and charge collection performance of a BE2825 Broad Energy Germanium (BEGe) detector has been experimentally investigated. The efficiency and energy resolution of the detector have ...been measured as a function of energy and the noise contributions to the preamplifier signal have been determined. Collimated gamma-ray sources mounted on an automated 3-axis scanning table have been used to study the variation in preamplifier signal shape with gamma-ray interaction position in the detector, so that the position-dependent charge collection process could be characterised. A suite of experimental measurements have also been undertaken to investigate the performance of the detector as a function of bias voltage and we report on anomalous behaviour observed when the detector was operating close to the depletion voltage.
The AGATA spectrometer is an array of highly segmented high purity germanium detectors. The spectrometer uses pulse shape analysis in order to track Compton scattered γ-rays to increase the ...efficiency of nuclear spectroscopy studies. The characterisation of two high purity germanium detector capsules for AGATA of the same A-type has been performed at the University of Liverpool. This work will examine the uniformity of performance of the two capsules, including a comparison of the resolution and efficiency as well as a study of charge collection. The performance of the capsules shows good agreement, which is essential for the efficient operation of the γ-ray tracking array.
Dealing with contaminants in Coulomb excitation of radioactive beams Morrison, L; Hadyńska-Klęk, K; Podolyák, Zs ...
27th International Nuclear Physics Conference, INPC 2019,Glasgow, United Kingdom,2019-07-29 - 2019-08-02,
12/2020, Letnik:
1643, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Data analysis of the Coulomb excitation experiment of the exotic 206Hg nucleus, recently performed at CERN's HIE-ISOLDE facility, needs to account for the contribution to target excitation due to the ...strongly-present beam contaminant 130Xe. In this paper, the contamination subtraction procedure is presented.
The first low-energy Coulomb-excitation measurement of the radioactive, semi-magic, two proton-hole nucleus 206Hg, was performed at CERN's recently-commissioned HIE-ISOLDE facility. Two γ rays ...depopulating low-lying states in 206Hg were observed. From the data, a reduced transition strength B(E2;21+→01+)=4.4(6) W.u. was determined, the first such value for an N=126 nucleus south of 208Pb, which is found to be slightly lower than that predicted by shell-model calculations. In addition, a collective octupole state was identified at an excitation energy of 2705 keV, for which a reduced B(E3) transition probability of 30−13+10 W.u. was extracted. These results are crucial for understanding both quadrupole and octupole collectivity in the vicinity of the heaviest doubly-magic nucleus 208Pb, and for benchmarking a number of theoretical approaches in this key region. This is of particular importance given the paucity of data on transition strengths in this region, which could be used, in principle, to test calculations relevant to the astrophysical r-process.
Low-lying states in the isotope Xe130 were populated in a Coulomb-excitation experiment performed at CERN's HIE-ISOLDE facility. The magnitudes and relative signs of seven E2 matrix elements and one ...M1 matrix element coupling five low-lying states in Xe130 were determined using the semiclassical coupled-channel Coulomb-excitation least-squares search code gosia. The diagonal E2 matrix elements of both the 21+ and 41+ states were extracted for the first time. The reduced transition strengths are in line with those obtained from previous measurements. Experimental results were compared with the general Bohr Hamiltonian with the microscopic input from mean-field theory utilizing universal nuclear energy density functional (UNEDF0), shell-model calculations using the GCN50:82 and SN100PN interactions, and simple phenomenological models (Davydov-Filippov and γ-soft). The extracted shape parameters indicate triaxial-prolate deformation in the ground-state band. In general, good agreement between theoretical predictions and experimental values was found, while neither phenomenological model was found to provide an adequate description of Xe130.
There is an increased emphasis to identify clinically applicable methods that quantify gait deficits following anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to ...perform serial gait assessments in a clinical setting to determine whether and when clinical gait parameters normalize in patients following ACLR. The hypothesis was that a clinically available gait treadmill would quantify gait deficits measured at 4 weeks post‐reconstruction. The secondary hypothesis was that patients would demonstrate incremental improvements in these gait parameters measured at each interval up to 12 weeks post‐reconstruction, and that the objectively measured improvements would correlate to the patient's subjective rating of function. Fifteen subjects, five male and 10 female, who had initial unilateral anterior cruciate ligament injury were selected for this study on the basis of operative data. All subjects were evaluated in a physical therapy clinic within 3 days following ACLR and were enrolled in a standardized rehabilitation program. The dependent gait variables of step length, stance time and gait velocity were measured at 4, 6, 8 and 12 weeks post‐ACLR on a commercially available gait treadmill. A 2 × 4 multivariate analysis of variance (2 within factors) with measures for limb involvement (uninvolved and involved) and repeated measures for time (4, 6, 8 and 12 weeks) was used to assess the interactions and the main effects on the gait variables of stance time and step length. The results of this study supported the hypothesis that gait deficits and serial improvements can be objectively quantified in a clinical setting (P<0.001). Specifically, stance time, step length and gait velocity deficits evaluated at 4 weeks showed significant improvements at the measured intervals. Step length normalized at week 8. Stance time and gait velocity reached normal levels at the 12‐week time interval. Subjective activity of daily living scores (ADLS) also improved following the 12‐week rehabilitation, from 53±17% to a mean score of 88±11% (P<0.001). ADLS scores significantly correlated to step length (R=0.63) and stance time (R=0.53) in the involved limb. Self‐selected gait velocity also correlated to ADLS scores and significantly predicted 49% of the variance in the subjective outcome measure. A clinically available gait treadmill can be used to quantify gait deficits and improvements following ACLR. Serial assessments of walking gait may aid clinicians to identify and target deficits in their patients during rehabilitation.
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