[en] The effect of 12 weeks of treadmill exercise on the mineralization of trabecular and cortical bone was studied in rats 7, 14, and 19 months of age. Bone mineralization was evaluated by measuring concentrations of Ca, Mg, and hydroxyproline as well as uptake of 45Ca concentration in the femur, humerus, rib and calvaria. The 7- and 14-month-old rats increased mineralization in those cortical bones directly involved in exercise. The 19-month animal responded to exercise by increasing mineralization in all bones examined, including the nonweight bearing trabecular calvaria and cortical rib. From these data, it is apparent that the older animals undergo a total skeletal mineralization in response to exercise compared with local adaptation in the younger animal. Further, we provide evidence to support the use of the rat as a model in which to study mammalian bone physiology during the aging process

[en] The chemical preparation of a novel uranium dimethylpyrazolyl borato complex has been described. X-ray crystallography reveals a unique capped-octahedral molecular structure. H¹ spectra for the complex were reported as well

[en] Our first successful Low Energy Beam Line (LEBL) experiment was during the first 2 weeks of October. While this is outside the period covered by this report, such a large part of last year's efforts were devoted to this program that some mention is appropriate. Two detectors at small angles inside the scattering chamber proper were of the GASP design and were capable of detecting all possible reaction products from damped La to 120 MeV protons. The larger-angle detectors were designed primarily for lower energy light charged particles and consisted of 1.5 mm position-sensitive silicon detectors backed by 2'' thick plastic scintillators. The pie-shaped extension to the scattering chamber allowed measurement to very small angles. The product charge distributions measured with GASP centered at 7⁰ are given for the La and Au targets. The remnants of the La elastic peak are visible. Since the grazing angle for the Au reaction (Theta/sub g/ = 5.9⁰) is greater than that for the La reaction (Theta/sub g/ = 3.6⁰) the elastic contribution is more pronounced with the Au target. Both reactions show a broad range of product charges. However, unlike lower energy heavy-ion reactions, there are very few damped products with charges greater than half that of the beam Z=57. 2 references, 4 figures

[en] The syntheses of bis-hydrotris (3-^tBu-5-Mepyrazolyl)borate lanthanide (II) complexes, Ln(Tp^tBu,Me)₂ (Ln =3D Sm, 1; Yb, 2), are reported. The X-ray crystal structure of the Sm complex (1) has been determined and shows two different Tp^tBu,Me ligands; one is bonded via classical η³ -bonding mode, the other is coordinated via two pyrazolyl nitrogens and an agostic B-H - Sm interaction. The spectroscopic data are consistent with a solution structure which is identical with the solid state form. In particular, the observation of ¹⁷¹Yb-HB coupling of 85 Hz confirms the persistence of the agostic interaction in solution. Variable temperature NMR studies show that the molecules are fluxional in solution and execute two distinct and specific rearrangement processes. The low temperature process involves exchange of the pyrazolyl rings within individual Tp^tBu,Me ligands without exchanging the bonding modes of the ligands, it is also suggested that the process preserves the B-H - Ln interaction. Above room temperature the two different Tp^tBu,Me ligands also begin to slowly exchange their bonding modes. Estimates of the activation barriers for the exchange processes are 8.5 and 16.5 kcal/mol, respectively. (authors). 37 refs., 6 figs., 2 tabs., 2 schemes

[en] Downstream migrating salmon and steelhead (Oncoryhnchus spp.) smolts were monitored at the Rock Island Dam bypass trap from April 1--August 31, 1996. This was the twelfth consecutive year that the bypass trap was monitored. Data collected included: (1) number of fish collected by species, (2) number of fin clipped and/or Passive Integrated Transponder (PIT) tagged fish caught by species, (3) total number of fish showing signs of gas bubble trauma (GBT), (4) percent of descaled fish, and (5) daily average river flow, powerhouse number-sign 1 flow, powerhouse number-sign 2 flow and daily average spill. These data were transmitted to the Fish Passage Center (FPC), which manages the Smolt Monitoring Program throughout the Columbia River Basin. The Smolt Monitoring Program is used to manage the water budget, releasing upstream reservoir water storage allocated to supplement river flows during the downstream migration of juvenile salmonids

[en] We propose a quantum oscillation experiment by which the rotation of an underdoped YBa₂Cu₃O_6+x sample about two different axes with respect to the orientation of the magnetic field can be used to infer the shape of the in-plane cross-section of corrugated Fermi surface cylinder(s). Deep corrugations in the Fermi surface are expected to give rise to nodes in the quantum oscillation amplitude that depend on the magnitude and orientation of the magnetic induction B. Because the symmetries of electron and hole cylinders within the Brillouin zone are expected to be very different, the topology can provide essential clues as to the broken symmetry responsible for the observed oscillations. The criterion for the applicability of this method to the cuprate superconductors (as well as other layered metals) is that the difference in quantum oscillation frequency 2ΔF between the maximum (belly) and minimum (neck) extremal cross-sections of the corrugated Fermi surface exceeds |B|. (fast track communication)

[en] This paper reports that characterization of Yucca Mountain for a potential repository requires construction of an underground Exploratory Studies Facility (ESF). Mechanical excavating methods have been proposed for construction of the ESF as they offer a number of advantages over drilling and blasting at the Yucca Mountain site, including; less ground disturbance and therefore a potential for less adverse effects on the integrity of the site, creation of a more stable excavation cross section requiring less ground support, and an inherently safer and cleaner working environment. The tunnel boring machine (TBM) provides a proven technology for excavating the welded and unwelded Yucca Mountain tuffs. The access ramps and main underground tunnels form the largest part of the ESF underground construction work, and have been designed for excavation by TBM

[en] We report quantum oscillation measurements on CaFe₂As₂ under strong magnetic fields-recently reported to become superconducting under pressures of as little as a kilobar. The largest observed carrier pocket occupies less than 0.05% of the paramagnetic Brillouin zone volume-consistent with Fermi surface reconstruction caused by antiferromagnetism. On comparing several alkaline earth AFe₂As₂ antiferromagnets (with A = Ca, Sr and Ba), the dependences of the Fermi surface cross-sectional area F_α and the effective mass m_α* of the primary observed pocket on the antiferromagnetic/structural transition temperature T_s are both found to be consistent with the case for quasiparticles in a conventional spin-density wave model. These findings suggest that the recently proposed strain-enhanced superconductivity in these materials occurs within a broadly conventional spin-density wave phase. (fast track communication)

[en] We report high-pressure skin-depth measurements on the heavy fermion material CeIn₃ in magnetic fields up to 64 T using a self-resonant tank circuit based on a tunnel diode oscillator. At ambient pressure, an anomaly in the skin depth is seen at 45 T. The field where this anomaly occurs decreases with applied pressure until approximately 1.0 GPa, where it begins to increase before merging with the antiferromagnetic phase boundary. Possible origins for this transport anomaly are explored in terms of a Fermi surface reconstruction. The critical magnetic field at which the Neel-ordered phase is suppressed, is also mapped as a function of pressure and extrapolates to the previous ambient-pressure measurements at high magnetic fields and high-pressure measurements at zero magnetic field.

[en] Thermo-mechanical behavior of oxide nuclear fuels is extremely important to overall fuel element performance. Critical to the understanding of Pellet-Cladding Mechanical Interactions (PCMI) are elasticity, plasticity and creep, as this interaction with the cladding can lead to fuel rod fracture and in turn affect its thermal performance significantly. In addition, sub-grain scale mechanical behavior, e.g. elastic anisotropy, as well as dislocation-driven plasticity and creep, can also play a significant role on microstructure evolution of the fuel elements and their cladding, failure of which would severely reduce the useful service life of the elements and allow the release of fission products out into the working fluid of the reactor. Therefore, careful measurements of mechanical properties are key to validate robust fuel performance codes able to predict this PCMI behavior from inputs at the micro-scale, e.g., MARMOT, and to quantify its effects on other aspects of fuel behavior. In uranium dioxide (UO₂), the thermomechanical response at the meso-scale depends strongly on crystallography of individual grains, and available datasets are far from complete in terms of temperature, stress, and stoichiometry in parameter space. Therefore, details of the fuel microstructure, such as porosity distribution and location, as well as grain boundary (GB) character, distribution, and location are needed to create accurate multiscale models to predict the fuel's evolution in-pile, and in turn aid in the design and development of more efficient fuels that can last longer cycles