Broadband directional coupling in aluminum nitride nanophotonic circuits

Aluminum nitride (AlN)-on-insulator has emerged as a promising platform for the realization of linear and non-linear integrated photonic circuits. In order to efficiently route optical signals on-chip, precise control over the interaction and polarization of evanescently coupled waveguide modes is required. Here we employ nanophotonic AlN waveguides to realize directional couplers with a broad coupling bandwidth and low insertion loss. We achieve uniform splitting of incoming modes, confirmed by high extinction-ratio exceeding 33dB in integrated Mach-Zehnder Interferometers. Optimized three-waveguide couplers furthermore allow for extending the coupling bandwidth over traditional side-coupled devices by almost an order of magnitude, with variable splitting ratio. Our work illustrates the potential of AlN circuits for coupled waveguide optics, DWDM applications and integrated polarization diversity schemes

Nonvolatile All-Optical 1 × 2 Switch for Chipscale Photonic Networks

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.Integrated chip-level photonics has the potential to revolutionize future computer systems by eliminating the “von-Neumann information bottleneck” and the power losses resulting from the use of electrical interconnects. Yet, the need for optical-to-electrical conversion has so far hindered the implementation of chip-level all-optical routing schemes, which remain operational without continuous power consumption. Here, a crucial component to successful implementation of such all-photonic networks is demonstrated – an effective, practicable all-optical nonvolatile switch. Current integrated all-optical switches require constant bias power to operate, and lose their state when it is removed. By contrast, our switch is entirely nonvolatile, with the direction of light flow altered by switching the phase state of an embedded phase-change cell using 1 ps optical pulses. High on/off switching contrast devices are achieved that are fully integrated and compatible with existing photonic circuits. It is shown that individual switching events occur with transition times below 200 ps and thus hold promise for ultrafast light routing on chip. The approach offers a reliable and simple route toward hybrid reconfigurable photonic devices without the need for electrical contacting.Funded by: DFG. Grant Numbers: PE 1832/1-1, PE 1832/2-1; EPSRC. Grant Numbers: EP/J018783/1, EP/M015173/1, EP/M015130/1; Clarendon Fun

The sequential trauma score - a new instrument for the sequential mortality prediction in major trauma*

<p>Abstract</p> <p>Background</p> <p>There are several well established scores for the assessment of the prognosis of major trauma patients that all have in common that they can be calculated at the earliest during intensive care unit stay. We intended to develop a sequential trauma score (STS) that allows prognosis at several early stages based on the information that is available at a particular time.</p> <p>Study design</p> <p>In a retrospective, multicenter study using data derived from the Trauma Registry of the German Trauma Society (2002-2006), we identified the most relevant prognostic factors from the patients basic data (P), prehospital phase (A), early (B1), and late (B2) trauma room phase. Univariate and logistic regression models as well as score quality criteria and the explanatory power have been calculated.</p> <p>Results</p> <p>A total of 2,354 patients with complete data were identified. From the patients basic data (P), logistic regression showed that age was a significant predictor of survival (AUC_{model p}, area under the curve = 0.63). Logistic regression of the prehospital data (A) showed that blood pressure, pulse rate, Glasgow coma scale (GCS), and anisocoria were significant predictors (AUC_{model A}= 0.76; AUC_{model P + A}= 0.82). Logistic regression of the early trauma room phase (B1) showed that peripheral oxygen saturation, GCS, anisocoria, base excess, and thromboplastin time to be significant predictors of survival (AUC_{model B1}= 0.78; AUC_{model P +A + B1}= 0.85). Multivariate analysis of the late trauma room phase (B2) detected cardiac massage, abbreviated injury score (AIS) of the head ≥ 3, the maximum AIS, the need for transfusion or massive blood transfusion, to be the most important predictors (AUCmodel B2 = 0.84; AUCfinal model P + A + B1 + B2 = 0.90). The explanatory power - a tool for the assessment of the relative impact of each segment to mortality - is 25% for P, 7% for A, 17% for B1 and 51% for B2. A spreadsheet for the easy calculation of the sequential trauma score is available at: <url>http://www.sequential-trauma-score.com</url></p> <p>Conclusions</p> <p>This score is the first sequential, dynamic score to provide a prognosis for patients with blunt major trauma at several points in time. With every additional piece of information the precision increases. The medical team has a simple, useful tool to identify patients at high risk and to predict the prognosis of an individual patient with major trauma very early, quickly and precisely.</p

Results of the QUENCH-20 experiment with BWR test bundle [in press]

The experiment QUENCH-20 with BWR geometry simulation bundle was successfully conducted at KIT on 9th October 2019 in the framework of the international SAFEST project. The test bundle mock-up represented one quarter of a BWR fuel assembly with 24 electrically heated fuel rod simulators and two B4C control blades. The rod simulators were filled with Kr to an inner pressure of 5.5 bar. The pre-oxidation stage in a flowing gas mixture of steam and argon (each 3 g/s) and system pressure of 2 bar lasted 4 hours at the peak cladding temperature of 1250 K. The Zry-4 corner rod, withdrawn at the end of this stage, showed the maximal oxidation at elevations between 930 and 1020 mm with signs of breakaway. During the transient stage, the bundle was heated to a maximum temperature of 2000 K. The coolability of the bundle was decreased by its squeezing due to the shroud ductile deformation caused by an overpressure outside the shroud. The cladding radial strain and failures due to inner overpressure (about 4 bar) were observed at temperature about 1700 K and lasted about 200 s. During the period of rod failures also the first absorber melt relocation accompanied by shroud failure were registered. The interaction of B4C with the steel blade and the ZIRLO channel box were observed at elevations 650…950 mm with the formation of eutectic melt. The typical components of this melt are (Fe, Cr) borides and ZrB2 precipitated in steel or in Zr-steel eutectic melt. Massive absorber melt relocation was observed 50 s before the end of transition stage. Small fragments of the absorber melt moved down to the elevation of 50 mm. The melting point of Inconel spacer grids at 500 and 1050 mm was also reached at the end of the transition stage. The Inconel melt from the elevation 1050 mm relocated downwards through hot bundle regions to the Inconel grid spacer at 550 mm and later (during the escalation caused by quench) to 450 mm. This melt penetrated also under the damaged cladding oxide layer and formed molten eutectic mixtures between elevations 450 and 550 mm. The test was terminated by quench water injection with a flow rate of 50 g/s from the bundle bottom. Fast temperature escalation from 2000 to 2300 K during 20 s was observed due to the strongly exothermic oxidation reactions. As result, the metal part (prior β-Zr) of the claddings between 550 and 950 mm was melted, partially released into space between rods and partially relocated in the gap between pellet and outer oxide layer to 450 mm. In this case, the positive role of the oxide layer should be noted, which does not allow the melt to completely escape into the inter-rod space. It is thereby limiting the possibility of interactions of a large amount of melt with steam, which could significantly increase the exothermic oxidation processes and the escalation of temperatures. The distribution of the oxidation rate within each bundle cross section is very inhomogeneous: whereas the average outer ZrO2 layer thickness for the central rod (#1) at the elevation of 750 mm is 465 µm, the same parameter for the peripheral rod #24 is only 108 µm. The average oxidation rate of the inner cladding surface (due to interaction with steam and with ZrO2 pellets) is about 20% in comparison to the outer cladding oxidation. The bundle elevations 850 and 750 mm are mostly oxidized with average cladding ECR 33%. The oxidation of the melt relocated inside the rods was observed at elevations 550…950 mm. The mass spectrometer measured release of CO (12.6 g), CO2 (9.7 g) and CH4 (0.4 g) during the reflood as products of absorber oxidation; the corresponding B4C reacted mass was 41 g or 4.6% of the total B4C inventory. It is significantly lower than in the PWR bundle tests QUENCH-07 and QUENCH-09 containing central absorber rod with B4C pellets inserted into a thin stainless steel cladding and Zry-4 guide tubes (20% and 50% reacted B4C correspondingly). Hydrogen production during the reflood amounted to 32 g during the reflood (57.4 g during the whole test) including 10 g from B4C oxidation

Charge carrier injection into insulating media: single-particle versus mean-field approach

Self-consistent, mean-field description of charge injection into a dielectric medium is modified to account for discreteness of charge carriers. The improved scheme includes both the Schottky barrier lowering due to the individual image charge and the barrier change due to the field penetration into the injecting electrode that ensures validity of the model at both high and low injection rates including the barrier dominated and the space-charge dominated regimes. Comparison of the theory with experiment on an unipolar ITO/PPV/Au-device is presented.Comment: 32 pages, 9 figures; revised version accepted to PR

Duration and predictors of emergency surgical operations - basis for medical management of mass casualty incidents

<p>Abstract</p> <p>Background</p> <p>Hospitals have a critically important role in the management of mass causality incidents (MCI), yet there is little information to assist emergency planners. A significantly limiting factor of a hospital's capability to treat those affected is its surgical capacity. We therefore intended to provide data about the duration and predictors of life saving operations.</p> <p>Methods</p> <p>The data of 20,815 predominantly blunt trauma patients recorded in the Trauma Registry of the German-Trauma-Society was retrospectively analyzed to calculate the duration of life-saving operations as well as their predictors. Inclusion criteria were an ISS ≥ 16 and the performance of relevant ICPM-coded procedures within 6 h of admission.</p> <p>Results</p> <p>From 1,228 patients fulfilling the inclusion criteria 1,793 operations could be identified as life-saving operations. Acute injuries to the abdomen accounted for 54.1% followed by head injuries (26.3%), pelvic injuries (11.5%), thoracic injuries (5.0%) and major amputations (3.1%). The mean cut to suture time was 130 min (IQR 65-165 min). Logistic regression revealed 8 variables associated with an emergency operation: AIS of abdomen ≥ 3 (OR 4,00), ISS ≥ 35 (OR 2,94), hemoglobin level ≤ 8 mg/dL (OR 1,40), pulse rate on hospital admission < 40 or > 120/min (OR 1,39), blood pressure on hospital admission < 90 mmHg (OR 1,35), prehospital infusion volume ≥ 2000 ml (OR 1,34), GCS ≤ 8 (OR 1,32) and anisocoria (OR 1,28) on-scene.</p> <p>Conclusions</p> <p>The mean operation time of 130 min calculated for emergency life-saving surgical operations provides a realistic guideline for the prospective treatment capacity which can be estimated and projected into an actual incident admission capacity. Knowledge of predictive factors for life-saving emergency operations helps to identify those patients that need most urgent operative treatment in case of blunt MCI.</p

The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory

The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submillimetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16x25 pixels, each, and two filled silicon bolometer arrays with 16x32 and 32x64 pixels, respectively, to perform integral-field spectroscopy and imaging photometry in the 60-210\mu\ m wavelength regime. In photometry mode, it simultaneously images two bands, 60-85\mu\ m or 85-125\mu\m and 125-210\mu\ m, over a field of view of ~1.75'x3.5', with close to Nyquist beam sampling in each band. In spectroscopy mode, it images a field of 47"x47", resolved into 5x5 pixels, with an instantaneous spectral coverage of ~1500km/s and a spectral resolution of ~175km/s. We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the Performance Verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions