Symbolic computer language for multibody systems

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76245/1/AIAA-20770-590.pd

Establishing SARS-CoV-2 membrane protein-specific antibodies as a valuable serological target via high-content microscopy

The prevalence and strength of serological responses mounted toward SARS-CoV-2 proteins other than nucleocapsid (N) and spike (S), which may be of use as additional serological markers, remains underexplored. Using high-content microscopy to assess antibody responses against full-length StrepTagged SARS-CoV-2 proteins, we found that 85% (166/196) of unvaccinated individuals with RT-PCR confirmed SARS-CoV-2 infections and 74% (31/42) of individuals infected after being vaccinated developed detectable IgG against the structural protein M, which is higher than previous estimates. Compared with N antibodies, M IgG displayed a shallower time-dependent decay and greater specificity. Sensitivity for SARS-CoV-2 seroprevalence was enhanced when N and M IgG detection was combined. These findings indicate that screening for M seroconversion may be a good approach for detecting additional vaccine breakthrough infections and highlight the potential to use HCM as a rapidly deployable method to identify the most immunogenic targets of newly emergent pathogens

X-RAY ABSORPTION STUDIES OF AMORPHOUS SEMICONDUCTORS

Two families of amorphous (a-) semiconductors are chosen to demonstrate current state-of-the-art techniques in x-ray absorption spectros copy (XAS). We first briefly review recent developments in XAS methods before limiting the discussion to tetrahedrally co-ordinated films (a-Si, a-Ge, and a-SixGe1-x:H with 0 < x < 1) and arsenic trisulfide (a-As2S3). The phenomenon of crystallization of a-Si and a-Ge as well as the ordering of these elemental a-semiconductors prior to the nucleation of microcrystallites is discussed in terms of XAS experiments. We review XAS studies of the role of H in determining the structure of a-SixGe1-x:H. Investigations of XAS on a-As2S3 are shown to result in : (1) an ability to use XAS to measure bond strengths ; (2) a better understanding of reversible photodarkening ; and, (3) development of a technique for crystallizing pure bulk As2S3 glass

THE DEFECT STRUCTURE OF CALCIA STABILISED ZIRCONIA

EXAFS data comparing the local structural environments of the calcium and zirconium ions in calcia-stabilised zirconia are presented. The Zr data resembles that observed previously for yttria-stabilised zirconia with the zirconium ions tending to be displaced from their centrosymmetric sites and a Zr-O distance of 2.12 Å. These similarities suggest that anion vacancies in this material are also to be found adjacent to Zr4+. The calcium ions are not displaced from their lattice sites but their immediate anion neighbours are highly disordered resulting in at least two Ca-O distances in the radial distribution of the nearest neighbour shell

ANALYSIS OF BOND STRENGTHS OF ARSENIC AND ARSENIC CHALCOGEN COMPOUNDS USING THE TEMPERATURE DEPENDENCE OF THE EXAFS

We present a study of the temperature dependence of the EXAFS of crystalline (c-) As. As2S3 and As4S4, amorphous (a-) As and glassy (g-) As2S3. Based on an Einstein mode, we find that for the first shell of these materials, the mean square relative displacement (MSRD) is related to the bond-stretching force constant. Our result indicates that As-As bonds in c- As are about 17% softer than those in a- As. The stretching forces of the As-S bonds in c- and g- As2S3 are quite similar. The calculation of bond strengths in c- As4S4 shows that As-S bonds are about 30% stronger than As-As bonds. This work underscores the fact that temperature dependent EXAFS data may be used to provide information about the nature and, in particular, the strength of local bonding

Characterization of Carbon Supported Pt/Ru Alloy Particles Using EXAFS Spectroscopy

Pt/Ru alloys are used for electrooxidation of methanol in direct methanol fuel cells. Their catalytic activity strongly depends upon the structure and composition of the alloy particles. We have investigated the structure of Pt/Ru alloy particles supported on high surface area carbon for three different compositions, namely Pt:Ru,8.5:1.5,1:1 and 1.5:8.5. The samples were prepared by impregnating the carbon with salt solutions of the two metals followed by reduction to the alloy. The total metal loading was 10 wt%. The PtL3 and Ru K EXAFS experiments were carried out at LN2 temperature on beamline X11A of NSLS. The data were analyzed to get consistent structural parameters from both the Pt and Ru EXAFS. The results show that the metals are completely alloyed and the average Pt-Ru distance is 2.70 Å. Difficulties which arose in the data analysis will be discussed

EXAFS STUDIES OF THERMOSTRUCTURAL AND PHOTOSTRUCTURAL CHANGES OF VAPOR-DEPOSITED AMORPHOUS As2S3 FILMS

We report the effects of thermal-annealing and light-soaking on the structure of amorphous (a-) As2S3 films. The EXAFS of near-stochiometric films were examined for as-deposited, thermally-annealed and light-soaked samples. The principle As-S feature increases slowly for spectra of all films, while a weak homopolar As-As feature decreases with both thermal-annealing and subsequent light-soaking. Slight changes are also seen in the higher shells. Our results imply that structural changes in a- As2S3 brought about by thermal-annealing and by light-soaking involve breaking, rearranging and remaking a significant fraction of the material's bonds