7,240 research outputs found
Segregation by thermal diffusion in granular shear flows
Segregation by thermal diffusion of an intruder immersed in a sheared
granular gas is analyzed from the (inelastic) Boltzmann equation. Segregation
is induced by the presence of a temperature gradient orthogonal to the shear
flow plane and parallel to gravity. We show that, like in analogous systems
without shear, the segregation criterion yields a transition between upwards
segregation and downwards segregation. The form of the phase diagrams is
illustrated in detail showing that they depend sensitively on the value of
gravity relative to the thermal gradient. Two specific situations are
considered: i) absence of gravity, and ii) homogeneous temperature. We find
that both mechanisms (upwards and downwards segregation) are stronger and more
clearly separated when compared with segregation criteria in systems without
shear.Comment: 8 figures. To appear in J. Stat. Mec
Data management study, volume 5. Appendix A - Contractor data package technical description and system engineering /SE/ Final report
Technical description and systems engineering contractor data package for Voyager spacecraf
Production Systems Involving Stocker Cattle and Soft Red Winter Wheat
A three year study at the Livestock and Forestry Research Station near Batesville, Arkansas evaluated production systems involving stocker cattle and soft red winter wheat. Grazing of soft red winter wheat forage from October through February followed by harvesting wheat grain or grazing through April with stocker cattle offers an alternative to conventional farming. Soft red winter wheat, when planted by September 15, produces an ample supply of high-quality forage that supports rapid growth of stocker cattle during October through April. Net income from stocker cattle averaged over 75,000,000 per year if 750,000 acres of wheat are grazed
Pharmacokinetics of Scopolamine Intranasal Gel Formulation (INSCOP) During Antiorthostatic Bedrest
Space Motion Sickness (SMS) is experienced during early flight days of space missions and on reduced gravity simulation flights which require treatment with medications. Oral administration of scopolamine tablets is still a common practice to prevent SMS symptoms. Bioavailability of medications taken by mouth for SMS is often low and variable. Intranasal (IN) administration of medications has been reported to achieve higher and more reliable bioavailability than from an equivalent oral dose. In this FDA reviewed phase II clinical trial, we evaluated pharmacokinetics of an investigative new drug formulation, INSCOP during ambulatory (AMB) and antiorthostatic bedrest (HBR), a ground-based microgravity analog. Twelve subjects including 6 males and 6 females received 0.2 and 0.4 mg doses of INSCOP on separate days during AMB and ABR in a randomized, double blind cross over experimental design. Blood samples were collected at regular time intervals for 24 h post dose and analyzed for free scopolamine concentrations by an LC-MS-MS method. Pharmacokinetic parameters were calculated using concentration versus time data and compared between AMB and ABR conditions. Results indicated that maximum concentration and relative bioavailability increased marginally during ABR compared to AMB; differences in PK parameters between AMB and ABR were greater with 0.2 mg than with 0.4 mg dose. Gender specific differences in PK parameters was observed both during AMB and ABR with differences higher in females between the two conditions than in males. A significant observation is that while gender differences in PK appear to exist, the differences in primary PK parameters between AMB and ABR after IN administration, unlike oral administration, are minimal and may not be clinically significant for both genders
From the Forest to the River: Citizens\u27 Views of Stakeholder Engagement
Since the early 1990s collaboration and consensus processes have become associated with success in the environmental policy and natural resource policy arenas. Interest in collaboration and consensus processes have emerged, in part, out of a frustration with more conventional efforts used to involve stakeholders, to work though conflicts, and to make decisions in the environmental and natural resource policy arenas. Collaboration and consensus processes, when designed well and applied appropriately, provide opportunities for meaningful stakeholder engagement. This essay features aspects of two government-led or agency-based (Koontz et al. 2004; Moore and Koontz 2003) planning efforts that consider collaboration and citizens/stakeholder engagement. Both projects, a forest management plan revision on the Allegheny National Forest in Pennsylvania, and a regional sediment management planning effort at the mouth of the Columbia River in the Pacific Northwest, have considered a Collaborative Learning (CL) approach (Daniels and Walker 2001) for stakeholder involvement. As part of these CL applications, citizens/stakeholders have been asked for their views of the kind of participation processes they value and how they prefer to be involved. This essay presents a summary of citizens\u27 ideas. In doing so, it addresses the question: How do stakeholders want to be engaged in agency-led planning efforts? Data reveal that stakeholders prefer active engagement, access to information and events, and clearly defined decision space. Prior to presenting the project data germane to this question, the paper highlights the trinity of voice and Collaborative Learning
Effects of seawater and deionized water at 0 to 80 deg C on the flexural properties of a glass/epoxy composite
The effect on the flexural properties of a glass/epoxy composite of immersion in deionized water or seawater at 0, 25, and 80 C for 451 hr was examined. The percent weight gain at 0 and 25 C was low (0.06 to 0.17 percent) and there was no significant change in the flexural properties for these environmental conditions. At 80 C there was a decrease in the flexural strength of 17 and 20 percent in seawater and deionized water, respectively. This is a comparison to control samples exposed to 80 C heat alone. These decreases were found to be nearly reversible once the samples were dried. Optical microscopy did not reveal cracking of the matrix. The flexural modulus was essentially unaffected by exposure to deionized water and seawater at 80 C
Electric-field-induced phase transformation at a lead-free morphotropic phase boundary: Case study in a 93%(Bi0.5Na0.5)TiO3-7% BaTiO3 piezoelectric ceramic
The electric-field-induced strain in 93%(Bi0.5Na0.5)TiO3-7%BaTiO3 polycrystalline ceramic is shown to be the result of an electric-field-induced phase transformation from a pseudocubic to tetragonal symmetry. High-energy x-ray diffraction is used to illustrate the microstructural nature of the transformation. A combination of induced unit cell volumetric changes, domain texture, and anisotropic lattice strains are responsible for the observed macroscopic strain. This strain mechanism is not analogous to the high electric-field-induced strains observed in lead-based morphotropic phase boundary systems. Thus, systems which appear cubic under zero field should not be excluded from the search for lead-free piezoelectric compositions.open1127
Probabilistic Approach to Time-Dependent Load-Transfer Models of Fracture
A probabilistic method for solving time-dependent load-transfer models of
fracture is developed. It is applicable to any rule of load redistribution,
i.e, local, hierarchical, etc. In the new method, the fluctuations are
generated during the breaking process (annealed randomness) while in the usual
method, the random lifetimes are fixed at the beginning (quenched disorder).
Both approaches are equivalent.Comment: 13 pages, 4 figures. To appear in Phys.Rev.
Phase transition in the modified fiber bundle model
We extend the standard fiber bundle model (FBM) with the local load sharing
in such a way that the conservation of the total load is relaxed when an
isolated fiber is broken. In this modified FBM in one dimension (1D), it is
revealed that the model exhibits a well-defined phase transition at a finite
nonzero value of the load, which is in contrast to the standard 1D FBM. The
modified FBM defined in the Watts-Strogatz network is also investigated, and
found is the existences of two distinct transitions: one discontinuous and the
other continuous. The effects of the long-range shortcuts are also discussed.Comment: 7 pages, to appear in Europhys. Let
- …