5,517 research outputs found
Relationship of Latitude-of-Origin to Winter Survival and to Forage and Seed Yields of Wheatgrass (Agropyron species) in Subarctic Alaska
Five field experiments evaluating and comparing
numerous grasses were conducted over seven years at
the Matanuska Research Farm (61.6°N) near Palmer in
southcentral Alaska. Grasses were 34 strains within 14
species of wheatgrass (Agropyron) derived from various
geographic areas spanning 32 degrees of latitude;
also included were the intergeneric hybrid Agroelymus
palmerensis Lepage, Siberian wildrye (Elymus sibiricus
L.), two bromegrass (Bromus) cultivars, and one timothy
(Phleum pratense L.) cultivar. They were grown in
broadcast-seeded plots for forage (two cuts per year),
in drilled rows for seed production, and as individual
plants in rows for winter-survival determinations
Microscopic theory of the coupling of intrinsic Josephson oscillations and phonons
A microscopic theory for the coupling of intrinsic Josephson oscillations and
dispersive phonon branches in layered superconductors is developed. Thereby the
effect of phonons on the electronic c-axis transport enters through an
effective longitudinal dielectric function. This coupling provides an
explanation of recently observed subgap resonances in the --
curve of anisotropic cuprate superconductors forming a stack of short Josephson
junctions. Due to the finite dispersion these resonances can appear at
van-Hove-singularities of both optical and acoustical phonon branches,
explaining low-voltage structures in the I-V-characteristic, which are not
understood in phonon models without dispersion. In long junctions the
dispersion of collective electron-phonon modes parallel to the layers is
investigated.Comment: 4 pages, 3 figures, 1 table, espcrc2.sty, invited contribution to
"Materials and Mechanisms of Superconductivity and High Temperature
Superconductors VI - M2S-HTSC-VI", Houston, Texas, 20-25 Feb 2000, to appear
in Physica
Quantum oscillations in from an incommensurate -density wave order
We consider quantum oscillation experiments in
from the perspective of an incommensurate
Fermi surface reconstruction using an exact transfer matrix method and the
Pichard-Landauer formula for the conductivity. The specific density wave order
considered is a period-8 -density wave in which the current density is
unidirectionally modulated. The current modulation is also naturally
accompanied by a period-4 site charge modulation in the same direction, which
is consistent with recent magnetic resonance measurements. In principle Landau
theory also allows for a period-4 bond charge modulation, which is not
discussed, but should be simple to incorporate in the future. This scenario
leads to a natural, but not a unique, explanation of why only oscillations from
a single electron pocket is observed, and a hole pocket of roughly twice the
frequency as dictated by two-fold commensurate order, and the corresponding
Luttinger sum rule, is not observed. However, it is possible that even higher
magnetic fields will reveal a hole pocket of half the frequency of the electron
pocket or smaller. This may be at the borderline of achievable high field
measurements because at least a few complete oscillations have to be clearly
resolved.Comment: 8 pages, 7 figure
Electronic compressibility and charge imbalance relaxation in cuprate superconductors
In the material SmLaSrCuO with alternating intrinsic
Josephson junctions we explain theoretically the relative amplitude of the two
plasma peaks in transmission by taking into account the spatial dispersion of
the Josephson Plasma Resonance in direction due to charge coupling. From
this and the magnetic field dependence of the plasma peaks in the vortex solid
and liquid states it is shown that the electronic compressibility of the
CuO layers is consistent with a free electron value. Also the London
penetration depth near can be
determined. The voltage response in the -curve of a
BiSrCaCuO mesa due to microwave irradiation or current
injection in a second mesa is related to the nonequilibrium charge imbalance of
quasiparticles and Cooper pairs and from our experimental data the relaxation
time is obtained.Comment: 2 pages, 2 figures, phc-proc4-auth.cls, to be published in Physica C
as a proceeding of M2S-HTSC Rio 200
Urban-like night illumination reduces melatonin release in European blackbirds (Turdus merula): implications of city life for biological time-keeping of songbirds
<p>Introduction:
Artificial light-at-night is known to affect a broad array of behaviours and physiological processes. In urbanized bird species, light-at-night advances important biological rhythms such as daily cycles of activity/rest and timing of reproduction, but our knowledge of the underlying physiological mechanisms is limited. Given its role as chronobiological signal, melatonin is a strong candidate for mediating the effects of light-at-night.</p>
<p>Results:
We exposed urban and rural European blackbirds (Turdus merula) to two light treatments equal in photoperiod but with different light intensities at night. The control group was exposed to 0.0001 lux (almost darkness), while the experimental group was exposed to 0.3 lux at night, simulating conditions recorded previously on free-living urban blackbirds. We obtained diel profiles of plasma melatonin for all birds in summer (July) and winter (January), while simultaneously recording locomotor activity. Daily patterns of melatonin concentrations were clearly affected by light-at-night in both seasons. In winter, melatonin concentrations of light-at-night birds were lower in the early and late night than in those of birds kept in darkness. In summer, melatonin concentrations of the light-at-night birds were lower through all night compared to birds kept in darkness. Locomotor activity in light-at-night birds was overall higher than in control individuals, both during the day and at night, and it increased sharply before dawn. In winter, the amount of activity before dawn in the light-at-night group correlated with changes in melatonin from midnight to late night: the greater the decrease in melatonin, the greater the amount of pre-dawn activity. Urban and rural birds responded similarly to light-at-night with respect to melatonin, but differed in their behaviour, with rural birds showing more locomotor activity than urban counterparts.</p>
<p>Conclusions:
This study points to reduced melatonin release at night as a potential physiological mechanism underlying the advanced onset of morning activity of urbanized birds. Based on the pattern of melatonin secretion, we suggest that birds responded to light-at-night as if they were exposed to a longer day than birds kept under dark nights.</p>
Wild clocks: preface and glossary
No abstract available
Large Wind Energy Converter: Growian 3 MW
The final report on the projected application of larger-scale wind turbine on the northern German coast is summarized. The designs of the tower, machinery housing, rotor, and rotor blades are described accompanied various construction materials are examined. Rotor blade adjustment devices auxiliary and accessory equipment are examined
Coupling of intrinsic Josephson oscillations in layered superconductors by charge fluctuations
The coupling of Josephson oscillations in layered superconductors is studied
with help of a tunneling Hamiltonian formalism. The general form of the current
density across the barriers between the superconducting layers is derived. The
induced charge fluctuations on the superconducting layers lead to a coupling of
the Josephson oscillations in different junctions. A simplified set of
equations is then used to study the non-linear dynamics of the system. In
particular the influence of the coupling on the current-voltage characteristics
is investigated and upper limits for the coupling strength are estimated from a
comparison with experiments on cuprate superconductors.Comment: To be published in proceedings of SPIE conference San Diego 199
Use of accelerometry to investigate physical activity in dogs receiving chemotherapy
Objectives:
To perform a preliminary study to assess whether single-agent palliative or adjuvant chemotherapy has an impact on objectively measured physical activity in dogs.
Methods:
Fifteen dogs with neoplasia (treatment group) wore ActiGraphâ„¢ accelerometers for 5-day periods before, during and after receiving single-agent adjuvant or palliative chemotherapy. Mean 5-day total physical activity and time spent in three different intensities of activity (sedentary, light-moderate and vigorous) before, during and after receiving chemotherapy were compared to a group of 15 healthy dogs (control group). Results were also compared within the treatment group across time.
Results:
Prior to chemotherapy, treated dogs tended to be less active than control dogs. Treatment group dogs were slightly more active at restaging than they were prior to treatment but had similar activity levels to control dogs. Marked effects of chemotherapy on physical activity were not detected. Physical activity was slightly lower in treated dogs during chemotherapy when compared to control dogs but there was a slight increase in physical activity of treated dogs during chemotherapy when compared with pretreatment recordings. There was little change in the mean 5-day total physical activity between treated dogs during chemotherapy and at restaging but a mild decrease in time spent sedentary and increase in time spent in light-moderate activity at this comparison of time points.
Clinical Significance:
Single-agent adjuvant or palliative chemotherapy had minimal impact on physical activity levels in dogs with neoplasia
Support for Drought Response and Community Preparedness: Filling the Gaps between Plans and Action
This chapter examines which levels of government handle various aspects of drought, as well as interactions between levels of government, providing examples from states across the western United States. It also takes a look at aspects of drought that fall outside traditional lines of authority and disciplinary boundaries. As part of a discussion on how states support local drought response, the chapter details and contrasts how California and Colorado track public water supply restrictions, and describes Colorado’s process for incorporating input from river basins across the state into its water plan. Case studies focus on drought planning in the Klamath River and Upper Colorado River basins through the lens of collaborative environmental planning. The chapter concludes that drought planning will be more effective as more states coordinate and align goals and policies at multiple levels of government
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