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Mayer, W.

Publications and source records attributed to Mayer, W..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Tailoring superconducting phases observed in hyperdoped Si:Ga for cryogenic circuit applications

Hyperdoping with gallium (Ga) has been established as a route to observe superconductivity in silicon (Si). The relatively large critical temperatures (T c ) and magnetic fields (B c ) make this phase attractive for cryogenic circuit applications, particularly for scalable hybrid superconductor-semiconductor platforms. However, the robustness of Si:Ga superconductivity at millikelvin temperatures is yet to be evaluated. Here, we report the presence of a reentrant resistive transition below T c for Si:Ga whose magnitude strongly depends on the distribution of the Ga clusters that precipitate in the implanted Si after annealing. By monitoring the reentrant resistance over a wide parameter space of implantation energies and fluences, we determine conditions that significantly improve the coherent coupling of Ga clusters, therefore, eliminating the reentrant transition at temperatures as low as 20 mK.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS2010

Particular Characterisation of an In-Vitro-DTH Test to Monitor Cellular Immunity - Applications for Patient Care and Space Flight

Goal:i) Characterization of the role of the main immune reactive cell types contributing to the cellular immune response in the in-vitro DTH and ii) Validation of the in-vitro DTH under different clinical and field conditions. Methods:As positive control whole blood was incubated in the in-vitro DTH, supernatants were gathered after 12, 24 and 48h. Readout parameters of this test are cytokines in the assay's supernatant. To determine the role of T-cells, monocytes and natural killer (NK), these cell populations were depleted using magnetic beads prior to in-vitro-DTH incubation. Validation of the test has occurred under clinical (HIV-patients, ICU) and field-conditions (parabolic/space-flights, confinement). Results:T-cell depletion abandoned almost any IL-2 production and reduced IFN-gamma production irrespective of the type of antigen, whereas CD56 depleted cultures tended to lower IL-2 secretion and IFN-gamma and to parallel a IL-10-increase after viral challenge. This IL-10-increase was seen also in CD14-depleted setups. DTH read-out was significantly different under acute stress (parabolic flight) or chronic stress (ISS), respectively. Preliminary data of HIV infected patients demonstrate that this test can display the contemporary immune status during an antiviral therapy. Conclusion:The in-vitro DTH mirrors adaptive and innate immune activation and may serve as tool also for longitudinal follow up of Th1/Th2 weighed immune response under adverse life conditions on earth and in space. It is planned to implement the assay in the on the ISS (MoCISS).

Feurecker, M.↗
NASA NTRS1987

Taking Impressions of Hidden Cavity Walls

Lightweight, portable internal-molding device makes it possible to measure radii of, or examine contours of, passageways in hidden or complicated cavities. With device, measurements made in field, without returning assemblies to shop or laboratory for inspection. Molding head expands when compressed air applied. Inflatable tubes around head perform dual sealing and aligning function.

Burley, D.↗
NASA NTRS1987

The MIT spectroscopy investigations on AXAF and the study of supernova remnants

The MIT High Resolution X-Ray Spectroscopy experiment on the AXAF, which will study physical conditions in celestial sources by means of detailed measurements of emission and absorption features in their spectra, involves two complementary dispersive instruments: Bragg Crystal Spectrometer (BCS) and High Energy Transmission Grating (HETG). This paper discusses the principles of operation of BCS and HETG and the results that will be obtained by these instruments. Measurements of individual line strengths obtained by the AXAF spectrometers will allow the application of plasma diagnostic techniques to a study of the detailed physical conditions in celestial objects, particularly in the optically thin plasma of supernova remnants, which is particularly well suited to the application of plasma diagnostics.

Canizares, C. R.↗
NASA NTRS1978

Discovery of 3.6-s X-ray pulsations from 4U0115+63

SAS 3 observations reveal a pulsation period of 3.61 sec for the transient X-ray source 4U0115+63. Positional measurement is accurate to approximately 30 arc s, and has led to the likely identification of an optical counterpart. The intensity of the pulses, as reported on 5.9 January 1978, is given as approximately 1.7 times that of the Crab Nebula (1-27 keV). Spectral information was also obtained from the ratios of counting rates in the first three energy channels of the center slat collimator detector (1-27 keV). Two classes of models are proposed to explain the transient nature of the X-ray sources: (1) episodic mass transfer in a binary system, and (2) eccentric binary orbits.

Cominsky, L.↗
NASA NTRS1977

On the optical identifications of five X-ray sources

The data from a recently completed survey of the galactic plane with the SAS-3 modulation collimators provide precise (20 to 60 arcsec) celestial positions of galactic X-ray sources. Preliminary positions of 60-arcsec precision are reported for five sources. One of these led to the identification of the star, Gamma Cas, as an X-ray source, and the others lend substantial confidence to previously proposed optical identifications: 3U 0352+30 = X Per, 3U 1145-61 = HEN 715, GX301-2 = WRA977, and GX304-1 = MMV star. These identifications seem to establish the existence of a previously suggested class of Be-star X-ray emitters.

Bradt, H. V.↗
NASA NTRS1976

Orbital elements and masses for the SMC X-1/Sanduleak 160 binary system

The binary X-ray source SMC X-1 was observed with the SAS-3 satellite for approximately four days (February 26-29, 1976). Sufficient timing data were obtained on the 0.71 s X-ray pulsations to measure the Doppler velocity curve of the X-ray source and thereby derive orbital and stellar parameters for the system. The projected velocity of the X-ray star is 301.5 plus or minus 2.0 (1 sigma) km/s, and the corresponding mass function is 11.05 plus or minus 0.22 (1 sigma) solar masses. Combining the X-ray timing data with constraints imposed by the X-ray eclipse duration and the available optical data on Sk 160, a range of allowable values of not less than 1.1 and not greater than 4.0 solar masses for the mass of the X-ray star is obtained.

Primini, F.↗
NASA NTRS1976

Recurrent brief X-ray bursts from the globular cluster NGC 6624

Observational data are presented on ten brief X-ray bursts, recurrent at nearly equal time intervals, recorded during a two-day observation of 3U 1820-30 in the globular cluster NGC 6624 with the wide-field modulation collimator detectors on the SAS-3 X-ray observatory. The occurrence times were fitted by least squares to a linear sequence with an rms deviation of 621 sec, corresponding to a phase jitter of 3.9%. The bursts were observed in two energy channels. For a sequence of five of the most clearly observed bursts, the 2-6 keV rate rose to its peak value in about 1 sec and then decayed to preburst level in about 10 sec. The 6-11 keV rate rose more slowly and decayed similarly. The smooth decay of their averaged light curve suggests the temporal evolution may have a geometrical origin, where Compton scattering in a surrounding cloud of hot plasma stretches the pulse out and causes a progressive hardening of the spectrum.

Clark, G. W.↗
NASA NTRS1976

The transient periodic X-ray source in Taurus, A0535+26

Eighteen X-ray light curves of the 104-sec periodicity in the Taurus X-ray nova A 0535+26 are analyzed which were obtained by SAS-3 in six energy intervals between 1 and 35 keV during the period from May 30 to June 2, 1975. It is shown that the pulse structure is relatively simple at energies above 19 keV, but develops a complex series of five irregularly spaced maxima at lower energies. The energy spectrum averaged over the 104-sec period is found to be extremely hard, with a best-fit temperature of about 30 keV for the exponential spectrum, an excess at about 15 keV, and a steepening above 20 keV. It is suggested that A 0535+26 may be a compact object in a binary system containing the peculiar Be star HDE 245770. The transient behavior could arise due to episodic mass loss by the primary or because the compact object is in a highly eccentric orbit about the companion, with appreciable mass transfer occurring only at periastron.

Bradt, H.↗