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  • 1
    ISSN: 0300-9629
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0300-9629
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-601X
    Keywords: 23.20.Ck ; 2320.Lv ; 27.60.+j
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The β− decay of101Zr has been investigated at the fission-product separators JOSEF and LOHENGRIN. The half-life of101Zr has been determined to 2.5(1) s and a level scheme for101Nb has been established fromγ ray singles as well as X/3-γ and γ—γ coincidence measurements. Conversion coefficients for transitions in101Nb and level half-lives between 10 ps and 2 ns have been determined. Three rotational bands are identified among the low-lying levels with band heads at 0 keV, 206 keV and 208 keV. The bands are probably based on the Nilsson configurations [422 5/2+], [301 3/2−] and [303 5/2−], respectively. The deformation has been determined to βq=0.40(4) and 0.41(8) for the ground state band and the band based on the 206 keV level from the half-lives of the first and second excited members of these bands. This shows that the rapid onset of deformation at N=60 which is typical for the A=100 region of neutron-rich nuclei, takes also place in the Nb isotopes. Nilsson model calculations describe the experimental data well, especially the several determined transition probabilities including those for E1 transitions from the 206 and 208 keV band heads to the ground state.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 344 (1992), S. 357-358 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Tie half-lives of 8 low lying levels of103Nb have been determined at the fission-product separator JOSEF. A B-γ-γ triple-coincidence method was used which consists in a measurement of the time delay between the feeding of the levels through the B− decay of103Zr and their γ decay, in coincidence with a tagging γ ray, with plastic, BaF2 and Ge detectors, respectively. Most of the investigated levels are members of the three known rotational bands based on the ground state and the 164 and 248 keV levels. The deformation Bq=0.31(3) of103Nb could be deduced from the half-life data. The half-lives are well reproduced through calculations in the frame of the Nilsson model.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The half-lives of low-lying levels of the neutron-rich isotopes102Mo and104Mo have been measured at the fission product separator Josef with the ß-γ-γ triple coincidence technique. Values of t1/2= 126(4)ps and 0.72(4)ns have been obtained for the 21 + levels at 296 keV and 192 keV in102Mo and104Mo, respectively. Deformation parameters of ßq=0.28(1) and 0.31(1), respectively, are deduced, which are smaller than those of the isotones of Sr and Zr. The interacting boson model accounts well for the trend of 2+ energies in the Mo isotopes but slightly overpredicts the B(E2) values at saturation. A smooth dependence of τ 21 + vs. E 21 + is found for the A ∼ 100 region in agreement with the hydrodynamical model.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In euthermic and hibernating marmots (Marmota flaviventris), the pancreatic A and B cells respond in the appropriate secretory manner to glucose or arginine injection. Although reduced, this response, is clearly present in hibernating marmots. When glucose is administered to euthermic or hibernating marmots, plasma insulin concentrations rise and glucagon levels fall. While similar results are obtained in hibernation, the time period of the response is much longer due to the slowing of temperature dependent metabolic processes. Injection ofl-arginine stimulates an increase in plasma glucose, insulin, and glucagon as expected. Measurements of plasma glucose, insulin, and glucagon under basal conditions, suggest that there are no significant differences between any phase of hibernation (eg. entrance, deep hibernation, arousal) and euthermia. These results provide indirect evidence that the pancreatic A and B cells of hibernating marmots continue to function in order to help regulate plasma glucose concentration.
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  • 7
    Publication Date: 2018-06-11
    Description: The Genesis spacecraft, launched in 2001, traveled to a Lagrangian point between the Earth and Sun to collect particles from the solar wind and return them to Earth. However, during the return of the spacecraft in 2004, the parachute failed to open during descent, and the Genesis spacecraft crashed into the Utah desert. Many of the solar wind collectors were broken into smaller pieces, and the field team rapidly collected the capsule and collector pieces for later assessment. On each of the next few days, the team discovered that various collectors had survived intact, including three of four concentrator targets. Within a month, the team had imaged more than 10,000 fragments and packed them for transport to the Astromaterials Acquisition and Curation Office within the ARES Directorate at JSC. Currently, the Genesis samples are curated along with the other extraterrestrial sample collections within ARES. Although they were broken and dirty, the Genesis solar wind collectors still offered the science community the opportunity to better understand our Sun and the solar system as a whole. One of the more highly prized concentrator collectors survived the crash almost completely intact. The Genesis Concentrator was designed to concentrate the solar wind by a factor of at least 20 so that solar oxygen and nitrogen isotopes could be measured. One of these materials was the Diamond-on-Silicon (DoS) concentrator target. Unfortunately, the DoS concentrator broke on impact. Nevertheless, the scientific value of the DoS concentrator target was high. The Genesis Allocation Committee received a request for approximately 1 cm(sup 2) of the DoS specimen taken near the focal point of the concentrator for the analysis of solar wind nitrogen isotopes. The largest fragment, Genesis sample 60000, was designated for this allocation and needed to be precisely cut. The requirement was to subdivide the designated sample in a manner that prevented contamination of the sample and minimized the risk of losing or breaking the precious requested sample fragment. The Genesis curator determined that the use of laser scribing techniques to "cut" a precise line and subsequently cleave the sample (in a controlled break of the sample along that line) was the best method for accomplishing the sample subdivision. However, there were risks, including excess heating of the sample, that could cause some of the implanted solar wind to be lost via thermal diffusion. Accidentally breaking the sample during the handling and cleaving process was an additional risk. Early in fiscal year 2013, to address this delicate, complicated task, the ARES Directorate assembled its top scientists to develop a cutting plan that would ensure success when applied to the actual concentrator target wafer; i.e., to produce an approximately 1 cm(sup 2) piece from the requested area of the wafer. The team, subsequently referred to as the JSC Genesis Tiger Team, spent months researching and testing parameters and techniques related to scribing, cleaving, transporting, handling, and holding (i.e., mounting) the specimen. The investigation required considerable "thinking outside the box," and many, many trials using nonflight wafer analogs. After all preliminary testing, the following method was adopted as the final cutting plan. It was used in two final end-to-end practice runs before being used on the actual flight target wafer. The wafer was oriented on the laser cutting stage with the 100 and 010 directions of the wafer parallel to the corresponding X and Y directions of the cutting stage. The laser was programed to scribe 31 lines of the appropriate length along the Y stage direction. The programed scribe lines were separated by 5 micron in the X direction. The laser parameters were set as follows: (1) The laser power was 0.5 watts; (2) each line consisted of 50 passes, with the Z position being advanced 5 micron per pass; and (3) 30 s would elapse before the next line was scribed to allow for wafer cool down from any possible heating via the laser. The ablated material that "stuck" in the "scribe-cut" was removed from the "cut" using an ultrasonic micro-tool. After all the ablated silicon was removed from the wafer, the wafer was repositioned in exactly the same orientation on the laser stage. The laser was focused using the bottom of the wafer channel, and the 31-line scribing pattern described above was reprogrammed using the Z position of the groove bottom as the starting Z value instead of the top wafer surface, which was used previously. Upon completion of the second set of scribes, the ultrasonic micro-tool was again used to clean out the cut. The wafer was remounted on the stage in exactly the same orientation as before. The laser was again focused on the bottom of the groove. This time, however, the laser was.programed to scribe only one line down the exact center of the channel. The final scribe line consisted of 100 passes with a Z advance of 5 micron per pass and with the laser power set at 0.5 watts. As mentioned above, the final cutting plan was practiced in two end-to-end trials using non-flight, triangular-shaped silicon wafers similar in size and orientation to the actual DOS 60000 target sample. The actual scribing of the triangular-shaped wafers required scribing two lines and cleaving (i.e. scribe-cleave, then scribe-cleave) to obtain the piece requested for allocation. Early in December 2012, after many months of experiments and practicing and perfecting the techniques and procedures, the team successfully subdivided the Genesis DoS 60000 target sample, one of the most scientifically important samples from the Genesis mission (figure 2). On December 17, 2012, the allocated piece of concentrator target sample was delivered to the requesting principal investigator.The cutting plan developed for the subdivision of this sample will be used as the model for subdividing future requested Genesis flight wafers (appropriately modified for different wafer types).
    Keywords: Lasers and Masers
    Type: ARES Biennial Report 2012 Final; 44-46; JSC-CN-30442
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  • 8
    Publication Date: 2018-06-11
    Description: Studies of Martian surface geomorphology and detection of near-surface water ice by the Mars Odyssey gamma ray spectrometer suggest that Mars may have had a water-rich past. While 2 to 5 wt.% of carbonate has been detected in the Martian dust [1,2], no spectral evidence for significant deposits of carbonates or sulfates has been found to date. Most investigations into Mars aqueous mineralogy have been global in scope with only a few regional studies (e.g., [3]). We are searching for localized deposits in putative lacustrine basins utilizing a basin flow model to identify basins with large drainage areas. Such basins are more likely to accumulate high concentrations of aqueous minerals than deep basins which drain only small regions.
    Keywords: Geophysics
    Type: Lunar and Planetary Science XXXV: Mars Mineralogy: Weathered and Dry; LPI-Contrib-1197
    Format: text
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  • 9
    ISSN: 0011-2240
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 10
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    In:  CASI
    Publication Date: 2017-10-02
    Description: Precipitation as snow is an emerging paradigm for understanding water flow on Mars, which gracefully resolves many outstanding uncertainties in climatic and geomorphic interpretation. Snowfall does not require a powerful global greenhouse to effect global precipitation. It has long been assumed that global average temperatures greater than 273K are required to sustain liquid water at the surface via rainfall and runoff. Unfortunately, the best greenhouse models to date predict global mean surface temperatures early in Mars' history that differ little from today's, unless exceptional conditions are invoked. Snowfall however, can occur at temperatures less than 273K; all that is required is saturation of the atmosphere. At global temperatures lower than 273K, H2O would have been injected into the atmosphere by impacts and volcanic eruptions during the Noachian, and by obliquity-driven climate oscillations more recently. Snow cover can accumulate for a considerable period, and be available for melting during local spring and summer, unless sublimation rates are sufficient to remove the entire snowpack. We decided to explore the physics that controls the melting of snow in the high-latitude regions of Mars to understand the frequency and drainage of snowmelt in the high martian latitudes.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXVI, Part 22; LPI-Contrib-1234-Pt-22
    Format: application/pdf
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