Development of a qualification standard for adhesives used in hybrid microcircuits

Improved qualification standards and test procedures for adhesives used in microelectronic packaging are developed. The test methods in specification for the Selection and Use of Organic Adhesives in Hybrid Microcircuits are reevaluated versus industry and government requirements. Four electrically insulative and four electrically conductive adhesives used in the assembly of hybrid microcircuits are selected to evaluate the proposed revised test methods. An estimate of the cost to perform qualification testing of an adhesive to the requirements of the revised specification is also prepared

Potential biomedical applications of ion beam technology

Electron bombardment ion thrusters used as ion sources have demonstrated a unique capability to vary the surface morphology of surgical implant materials. The microscopically rough surface texture produced by ion beam sputtering of these materials may result in improvements in the biological response and/or performance of implanted devices. Control of surface roughness may result in improved attachment of the implant to soft tissue, hard tissue, bone cement, or components deposited from blood. Potential biomedical applications of ion beam texturing discussed include: vascular prostheses, artificial heart pump diaphragms, pacemaker fixation, percutaneous connectors, orthopedic pros-thesis fixtion, and dental implants

Strong Enhancement of the Critical Current at the Antiferromagnetic Transition in ErNi2B2C Single Crystals

We report on transport and magnetization measurements of the critical current density Jc in ErNi2B2C single crystals that show strongly enhanced vortex pinning at the Neel temperature TN and low applied fields. The height of the observed Jc peak decreases with increasing magnetic field in clear contrast with that of the peak effect found at the upper critical field. We also performed the first angular transport measurements of Jc ever conducted on this compound. They reveal the correlated nature of this pinning enhancement, which we attribute to the formation of antiphase boundaries at TN.Comment: 3 figure

Chiral symmetry breaking of magnetic vortices by sample roughness

Finite-element micromagnetic simulations are employed to study the chiral symmetry breaking of magnetic vortices, caused by the surface roughness of thin-film magnetic structures. An asymmetry between vortices with different core polarizations has been experimentally observed for square-shaped platelets. E.g., the threshold fields for vortex core switching were found to differ for core up and down. This asymmetry was however not expected for these symmetrically-shaped structures, where both core polarizations should behave symmetrically. Three-dimensional finite element simulations are employed to show that a small surface roughness can break the symmetry between vortex cores pointing up and down. A relatively small sample roughness is found sufficient to reproduce the experimentally observed asymmetries. It arises from the lack of mirror-symmetry of the rough thin-film structures, which causes vortices with different handedness to exhibit asymmetric dynamics

Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean

In the Southern Ocean, the nitrogen (N) isotopes of organic matter and the N and oxygen (O) isotopes of nitrate (NO_3^−) have been used to investigate NO_3^− assimilation and N cycling in the summertime period of phytoplankton growth, both today and in the past. However, recent studies indicate the significance of processes in other seasons for producing the annual cycle of N isotope changes. This study explores the impact of fall conditions on the ^(15)N/^(14)N (δ^(15)N) and ^(18)O/^(16)O (δ^(18)O) of NO_3^− and nitrite (NO_2^−) in the Pacific Antarctic Zone using depth profiles from late summer/fall of 2014. In the mixed layer, the δ^(15)N and δ^(18)O of NO_3^− + NO_2^− increase roughly equally, as expected for NO_3^− assimilation; however, the δ^(15)N of NO_3^−-only (measured after NO_2− removal) increases more than does NO_3^− -only δ^(18)O. Differencing indicates that NO_2^− has an extremely low δ^(15)N, often < −70‰ versus air. These observations are consistent with the expression of an equilibrium N isotope effect between NO_3^− and NO_2^−, likely due to enzymatic NO_3^- - NO_2^− interconversion. Specifically, we propose reversibility of the nitrite oxidoreductase (NXR) enzyme of nitrite oxidizers that, having been entrained from the subsurface during late summer mixed layer deepening, are inhibited by light. Our interpretation suggests a role for NO_3^- - NO_2^− interconversion where nitrifiers are transported into environments that discourage NO_2^− oxidation. This may apply to surface regions with upwelling, such as the summertime Antarctic. It may also apply to oxygen-deficient zones, where NXR-catalyzed interconversion may explain previously reported evidence of NO_2^− oxidation

Stellar 36,38^{36,38}Ar(n,γ)37,39(n,\gamma)^{37,39}Ar reactions and their effect on light neutron-rich nuclide synthesis

The $^{36}$Ar$(n,\gamma)^{37}$Ar ($t_{1/2}$ = 35 d) and $^{38}$Ar$(n,\gamma)^{39}$Ar (269 y) reactions were studied for the first time with a quasi-Maxwellian ($kT \sim 47$ keV) neutron flux for Maxwellian Average Cross Section (MACS) measurements at stellar energies. Gas samples were irradiated at the high-intensity Soreq applied research accelerator facility-liquid-lithium target neutron source and the $^{37}$Ar/$^{36}$Ar and $^{39}$Ar/$^{38}$Ar ratios in the activated samples were determined by accelerator mass spectrometry at the ATLAS facility (Argonne National Laboratory). The $^{37}$Ar activity was also measured by low-level counting at the University of Bern. Experimental MACS of $^{36}$Ar and $^{38}$Ar, corrected to the standard 30 keV thermal energy, are 1.9(3) mb and 1.3(2) mb, respectively, differing from the theoretical and evaluated values published to date by up to an order of magnitude. The neutron capture cross sections of $^{36,38}$Ar are relevant to the stellar nucleosynthesis of light neutron-rich nuclides; the two experimental values are shown to affect the calculated mass fraction of nuclides in the region A=36-48 during the weak $s$-process. The new production cross sections have implications also for the use of $^{37}$Ar and $^{39}$Ar as environmental tracers in the atmosphere and hydrosphere.Comment: 18 pages + Supp. Mat. (13 pages) Accepted for publication in Phys. Rev. Let

On Flux Quantization in F-Theory

We study the problem of four-form flux quantization in F-theory compactifications. We prove that for smooth, elliptically fibered Calabi-Yau fourfolds with a Weierstrass representation, the flux is always integrally quantized. This implies that any possible half-integral quantization effects must come from 7-branes, i.e. from singularities of the fourfold. We subsequently analyze the quantization rule on explicit fourfolds with Sp(N) singularities, and connect our findings via Sen's limit to IIB string theory. Via direct computations we find that the four-form is half-integrally quantized whenever the corresponding 7-brane stacks wrap non-spin complex surfaces, in accordance with the perturbative Freed-Witten anomaly. Our calculations on the fourfolds are done via toric techniques, whereas in IIB we rely on Sen's tachyon condensation picture to treat bound states of branes. Finally, we give general formulae for the curvature- and flux-induced D3 tadpoles for general fourfolds with Sp(N) singularities.Comment: 46 page

Communication and patient safety in gynecology and obstetrics - study protocol of an intervention study.

BACKGROUND: Patient safety is a key target in public health, health services and medicine. Communication between all parties involved in gynecology and obstetrics (clinical staff/professionals, expectant mothers/patients and their partners, close relatives or friends providing social support) should be improved to ensure patient safety, including the avoidance of preventable adverse events (pAEs). Therefore, interventions including an app will be developed in this project through a participatory approach integrating two theoretical models. The interventions will be designed to support participants in their communication with each other and to overcome difficulties in everyday hospital life. The aim is to foster effective communication in order to reduce the frequency of pAEs. If communication is improved, clinical staff should show an increase in work satisfaction and patients should show an increase in patient satisfaction. METHODS: The study will take place in two maternity clinics in Germany. In line with previous studies of complex interventions, it is divided into three interdependent phases. Each phase provides its own methods and data. Phase 1: Needs assessment and a training for staff (n = 140) tested in a pre-experimental study with a pre/post-design. Phase 2: Assessment of communication training for patients and their social support providers (n = 423) in a randomized controlled study. Phase 3: Assessment of an app supporting the communication between staff, patients, and their social support providers (n = 423) in a case-control study. The primary outcome is improvement of communication competencies. A range of other implementation outcomes will also be assessed (i.e. pAEs, patient/treatment satisfaction, work satisfaction, safety culture, training-related outcomes). DISCUSSION: This is the first large intervention study on communication and patient safety in gynecology and obstetrics integrating two theoretical models that have not been applied to this setting. It is expected that the interventions, including the app, will improve communication practice which is linked to a lower probability of pAEs. The app will offer an effective and inexpensive way to promote effective communication independent of users' motivation. Insights gained from this study can inform other patient safety interventions and health policy developments. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03855735; date of registration: February 27, 2019

Approaching the Gamow Window with Stored Ions : Direct Measurement of Xe 124 (p,γ) in the ESR Storage Ring

© 2019 American Physical Society. All rights reserved.We report the first measurement of low-energy proton-capture cross sections of Xe124 in a heavy-ion storage ring. Xe12454+ ions of five different beam energies between 5.5 and 8 AMeV were stored to collide with a windowless hydrogen target. The Cs125 reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and x-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron and γ widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies.Peer reviewedFinal Published versio