718 research outputs found
Aglaia fellii W.E.Cooper & Joyce (Meliaceae), a new species for Cape York Peninsula
Aglaia fellii W.E.Cooper & Joyce (Meliaceae) is described from restricted areas of rainforest on Cape York Peninsula, Queensland, Australia. Given the unusual morphological features of the species, including solitary flowers and fruits, a molecular phylogenetic analysis was conducted to confirm its placement within Aglaia prior to formal description. All Australian Aglaia species and eight Australian representa- tives of closely allied Meliaceae genera were sampled, and 353 nuclear loci were sequenced. Maximum likelihood analysis of these loci retrieved A. fellii as nested within Aglaia, most closely related to A. cooper- ae and A. monticola. This validates its assignment to Aglaia, making it the only Aglaia species with mostly solitary flowers (rarely 3- or 4-flowered) and solitary fruits. A full taxonomic description of Aglaia fellii and notes on its habitat are provided
Managing Climatic Risks to Combat Land Degradation and Enhance Food security: Key Information Needs
This paper discusses the key information needs to reduce the negative impacts of weather variability and climate change on land degradation and food security, and identifies the opportunities and barriers between the information and services needed. It suggests that vulnerability assessments based on a livelihood concept that includes climate information and key socio-economic variables can overcome the narrow focus of common one-dimensional vulnerability studies. Both current and future climatic risks can be managed better if there is appropriate policy and institutional support together with technological interventions to address the complexities of multiple risks that agriculture has to face. This would require effective partnerships among agencies dealing with meteorological and hydrological services, agricultural research, land degradation and food security issues. In addition a state-of-the-art infrastructure to measure, record, store and disseminate data on weather variables, and access to weather and seasonal climate forecasts at desired spatial and temporal scales would be needed
О подборе материала профессиональной направленности на занятиях по немецкому языку в группах факультета искусств
Цель статьи показать ряд методических приемов профессиональной направленности для проведения
занятий по немецкому языку в группах факультета искусств
Anisotropic optical properties of single-crystal GdBa2Cu3O7-delta
The optical spectrum of reduced-T(c) GdBa2Cu3O7-delta has been measured for polarizations parallel and perpendicular to the ab plane. The sample was an oxygen-deficient single crystal with a large face containing the c axis. The polarized reflectance from this face was measured from 20-300 K in the spectral region from 30-3000 cm-1, with 300 K data to 30 000 cm-1. Kramers-Kronig analysis was used to determine the spectral dependence of the ab and the c components of the dielectric tensor. The optical properties are strongly anisotropic. The ab-plane response resembles that of other reduced-T(c) materials whereas the c axis, in contrast, shows only the presence of several phonons. There is a complete absence of charge carrier response along c above and below T(c). This observation allows us to set an upper limit to the free-carrier spectral weight for transport perpendicular to the CuO2 planes
Current-induced cooling phenomenon in a two-dimensional electron gas under a magnetic field
We investigate the spatial distribution of temperature induced by a dc
current in a two-dimensional electron gas (2DEG) subjected to a perpendicular
magnetic field. We numerically calculate the distributions of the electrostatic
potential phi and the temperature T in a 2DEG enclosed in a square area
surrounded by insulated-adiabatic (top and bottom) and isopotential-isothermal
(left and right) boundaries (with phi_{left} < phi_{right} and T_{left}
=T_{right}), using a pair of nonlinear Poisson equations (for phi and T) that
fully take into account thermoelectric and thermomagnetic phenomena, including
the Hall, Nernst, Ettingshausen, and Righi-Leduc effects. We find that, in the
vicinity of the left-bottom corner, the temperature becomes lower than the
fixed boundary temperature, contrary to the naive expectation that the
temperature is raised by the prevalent Joule heating effect. The cooling is
attributed to the Ettingshausen effect at the bottom adiabatic boundary, which
pumps up the heat away from the bottom boundary. In order to keep the adiabatic
condition, downward temperature gradient, hence the cooled area, is developed
near the boundary, with the resulting thermal diffusion compensating the upward
heat current due to the Ettingshausen effect.Comment: 25 pages, 7 figure
The framing of product ideas in the making: a case study of the development of an energy saving pump
Charged hydrogenic problem in a magnetic field: Non-commutative translations, unitary transformations, and coherent states
An operator formalism is developed for a description of charged electron-hole
complexes in magnetic fields. A novel unitary transformation of the Hamiltonian
that allows one to partially separate the center-of-mass and internal motions
is proposed. We study the operator algebra that leads to the appearance of new
effective particles, electrons and holes with modified interparticle
interactions, and their coherent states in magnetic fields. The developed
formalism is used for studying a two-dimensional negatively charged
magnetoexciton . It is shown that Fano-resonances are present in the
spectra of internal transitions, indicating the existence of
three-particle quasi-bound states embedded in the continuum of higher Landau
levels.Comment: 9 pages + 2 figures, accepted in PRB, a couple of typos correcte
The Layer 0 Inner Silicon Detector of the D0 Experiment
This paper describes the design, fabrication, installation and performance of
the new inner layer called Layer 0 (L0) that was inserted in the existing Run
IIa Silicon Micro-Strip Tracker (SMT) of the D0 experiment at the Fermilab
Tevatron collider. L0 provides tracking information from two layers of sensors,
which are mounted with center lines at a radial distance of 16.1 mm and 17.6 mm
respectively from the beam axis. The sensors and readout electronics are
mounted on a specially designed and fabricated carbon fiber structure that
includes cooling for sensor and readout electronics. The structure has a thin
polyimide circuit bonded to it so that the circuit couples electrically to the
carbon fiber allowing the support structure to be used both for detector
grounding and a low impedance connection between the remotely mounted hybrids
and the sensors.Comment: 28 pages, 9 figure
Cladoceran birth and death rates estimates
I. Birth and death rates of natural cladoceran populations cannot be measured directly. Estimates of these population parameters must be calculated using methods that make assumptions about the form of population growth. These methods generally assume that the population has a stable age distribution.
2. To assess the effect of variable age distributions, we tested six egg ratio methods for estimating birth and death rates with data from thirty-seven laboratory populations of Daphnia pulicaria. The populations were grown under constant conditions, but the initial age distributions and egg ratios of the populations varied. Actual death rates were virtually zero, so the difference between the estimated and actual death rates measured the error in both birth and death rate estimates.
3. The results demonstrate that unstable population structures may produce large errors in the birth and death rates estimated by any of these methods. Among the methods tested, Taylor and Slatkin's formula and Paloheimo's formula were most reliable for the experimental data.
4. Further analyses of three of the methods were made using computer simulations of growth of age-structured populations with initially unstable age distributions. These analyses show that the time interval between sampling strongly influences the reliability of birth and death rate estimates. At a sampling interval of 2.5 days (equal to the duration of the egg stage), Paloheimo's formula was most accurate. At longer intervals (7.5–10 days), Taylor and Slatkin's formula which includes information on population structure was most accurate
- …