Adhesion studies of GaAs-based ohmic contact and bond pad metallization

Adhesion strength and surface morphology of commonly used n- and p-type ohmic contacts and pad metallization schemes for GaAs were investigated. GeNiAu, GePdAu, BeAu, and TiPtAu (being studied as potential ohmic contacts for internal optoelectronic devices) had quantitiative measurements made using wire bond pull testing to determine adhesion. Bond pad metals deposited as evaporated TiAu, TiPtAu, and 2-5 micron thick electroplated Au deposited on both semi-insulating GaAs and on Si{sub 3}N{sub 4}/GaAs were evaluated independently from the ohmic contact metals. In all samples was observed a strong correlation between surface treatment, surface morphology, wire bondability, and bond strength. Very high bond strengths (pull test average values above 6.5 grams force with 25 micron dia Au wire) wereobtained for n-type, p-type, and bond pad metals. Average values of 8.0 gram force were achieved with two-step GeAu/NiAu/TiPtAu metallization, while one-step deposition yielded poorer values. Adhesion was also monitored after aging at 250 C in air for four different times up to 60 hr by wire bond pull testing, with little degradation occurring

Staff Perspectives of Service User Involvement on Two Clinical Psychology Training Courses

This study investigated both negative and positive staff perspectives of service user involvement on two clinical psychology training courses as part of an ongoing process of service evaluation. Ten clinical psychology staff from two training courses were interviewed over the telephone by a current trainee clinical psychologist using a semi-structured interview method. Data were coded into textual units of meaning and then analysed using content analysis. The categories most cited by participants regarding the positives of service user involvement were that it 'develops trainees' learning' and 'challenges power differences'. For opportunities of service user involvement to provide benefits to the training courses, most participants cited 'meaningful versus tokenistic involvement', followed by 'strategic involvement'. Regarding negatives and barriers, those most cited were 'differences of opinion or agendas' and 'lack of resources'. Whilst the findings suggested that the service user involvement initiatives on both courses have been well received, research is needed into how service users also experience the process. Interventions that facilitate staff reflection and processing of multiple perspectives was also recommended, particularly with regards to negative experiences of service user involvement

A blood atlas of COVID-19 defines hallmarks of disease severity and specificity.

Treatment of severe COVID-19 is currently limited by clinical heterogeneity and incomplete description of specific immune biomarkers. We present here a comprehensive multi-omic blood atlas for patients with varying COVID-19 severity in an integrated comparison with influenza and sepsis patients versus healthy volunteers. We identify immune signatures and correlates of host response. Hallmarks of disease severity involved cells, their inflammatory mediators and networks, including progenitor cells and specific myeloid and lymphocyte subsets, features of the immune repertoire, acute phase response, metabolism, and coagulation. Persisting immune activation involving AP-1/p38MAPK was a specific feature of COVID-19. The plasma proteome enabled sub-phenotyping into patient clusters, predictive of severity and outcome. Systems-based integrative analyses including tensor and matrix decomposition of all modalities revealed feature groupings linked with severity and specificity compared to influenza and sepsis. Our approach and blood atlas will support future drug development, clinical trial design, and personalized medicine approaches for COVID-19

Mixtures and products in two graphical models

We compare two statistical models of three binary random variables. One is a mixture model and the other is a product of mixtures model called a restricted Boltzmann machine. Although the two models we study look different from their parametrizations, we show that they represent the same set of distributions on the interior of the probability simplex, and are equal up to closure. We give a semi-algebraic description of the model in terms of six binomial inequalities and obtain closed form expressions for the maximum likelihood estimates. We briefly discuss extensions to larger models

CLASP (Capture and Locking alignment Spring Positioner): A micromachined fiber auto-positioning device

This work provides a method of mechanical alignment of an array of single mode fibers to an array of optical devices. The technique uses a micromachined metal spring, which captures a vertical, pre- positioned fiber, moves it into accurate alignment, and holds it for attachment. The spring is fabricated from electroplated mickel, using photodefined polyimide as a plating mask. The nickel is plated about 80 {mu}m thick, so that a large fiber depth is captured. In one application, the nickel springs can be aligned to optics on the back side of the substrate. This entire concept is referred to as CLASP (Capture and Locking Alignment Spring Positioner). These springs can be used for general alignment and capture of any fiber to any optical input or output device. Passive alignment of fiber arrays to {plus}/{minus} 2{mu}m accuracy has been demonstrated, with a clear path to improved accuracy

Optimal Transport to a Variety

We study the problem of minimizing the Wasserstein distance between a probability distribution and an algebraic variety. We consider the setting of finite state spaces and describe the solution depending on the choice of the ground metric and the given distribution. The Wasserstein distance between the distribution and the variety is the minimum of a linear functional over a union of transportation polytopes. We obtain a description in terms of the solutions of a finite number of systems of polynomial equations. The case analysis is based on the ground metric. A detailed analysis is given for the two bit independence model