8,966 research outputs found
Wetland vegetation monitoring, 1999/2000 (Salinity Action Plan)
This report represents the vegetation component of a project designed to provide on-going monitoring of wetland salinity and biological resources in wetlands of the agricultural zone of south-west Western Australia. Maintenance of wetland biological diversity in the agricultural zone is one of the major objectives of the Salinity Action Plan. Due to their low position in the landscape, wetlands are the habitat most affected by salinisation
Mid-term report for the CORE Organic II funded project. “Innovative cropping Practices to increase soil health of organic fruit tree orchards” BIO-INCROP
Activities performed in the first part of BIO-INCROP project concern five of the eight main objectives fixed in the project proposal. They are:
Evaluation of soil borne pest and pathogens involved in replant disease
Role of rhizospheric bacterial and fungal communities in plant health
Selection of naturally available resources to increase microbial diversity and biomass
Compost and organic amendments
Evaluation of biologically active formulates
The document reports main research results and shows main items of dissemination activity performed in the first part of the project
Comparison of quantum field perturbation theory for the light front with the theory in lorentz coordinates
The relationship between the perturbation theory in light-front coordinates
and Lorentz-covariant perturbation theory is investigated. A method for finding
the difference between separate terms of the corresponding series without their
explicit evaluation is proposed. A procedure of constructing additional
counter-terms to the canonical Hamiltonian that compensate this difference at
any finite order is proposed. For the Yukawa model, the light-front Hamiltonian
with all of these counter-terms is obtained in a closed form. Possible
application of this approach to gauge theories is discussed.Comment: LaTex 2.09, 20 pages, 5 figure
Unoccupied states of individual silver clusters and chains on Ag(111)
Size-selected silver clusters on Ag(111) were fabricated with the tip of a
scanning tunneling microscope. Unoccupied electron resonances give rise to
image contrast and spectral features which shift toward the Fermi level with
increasing cluster size. Linear assemblies exhibit higher resonance energies
than equally sized compact assemblies. Density functional theory calculations
reproduce the observed energies and enable an assignment of the resonances to
hybridized atomic 5s and 5p orbitals with silver substrate states.Comment: 9 pages, 8 figure
Wide Band Gap Devices and Their Application in Power Electronics
Power electronic systems have a great impact on modern society. Their applications target a more sustainable future by minimizing the negative impacts of industrialization on the environment, such as global warming effects and greenhouse gas emission. Power devices based on wide band gap (WBG) material have the potential to deliver a paradigm shift in regard to energy efficiency and working with respect to the devices based on mature silicon (Si). Gallium nitride (GaN) and silicon carbide (SiC) have been treated as one of the most promising WBG materials that allow the performance limits of matured Si switching devices to be significantly exceeded. WBG-based power devices enable fast switching with lower power losses at higher switching frequency and hence, allow the development of high power density and high efficiency power converters. This paper reviews popular SiC and GaN power devices, discusses the associated merits and challenges, and finally their applications in power electronics
About direct Dark Matter detection in Next-to-Minimal Supersymmetric Standard Model
Direct dark matter detection is considered in the Next-to-Minimal
Supersymmetric Standard Model (NMSSM). The effective neutralino-quark
Lagrangian is obtained and event rates are calculated for the Ge-73 isotope.
Accelerator and cosmological constraints on the NMSSM parameter space are
included. By means of scanning the parameter space at the Fermi scale we show
that the lightest neutralino could be detected in dark matter experiments with
sizable event rate.Comment: latex, 12 pages, 2 ps-figures; extra LEP constraint is included,
extra figure is added, recorrected version, resubmitted to Phys.Rev.
Noninvasiveness and time symmetry of weak measurements
Measurements in classical and quantum physics are described in fundamentally
different ways. Nevertheless, one can formally define similar measurement
procedures with respect to the disturbance they cause. Obviously, strong
measurements, both classical and quantum, are invasive -- they disturb the
measured system. We show that it is possible to define general weak
measurements, which are noninvasive: the disturbance becomes negligible as the
measurement strength goes to zero. Classical intuition suggests that
noninvasive measurements should be time symmetric (if the system dynamics is
reversible) and we confirm that correlations are time-reversal symmetric in the
classical case. However, quantum weak measurements -- defined analogously to
their classical counterparts -- can be noninvasive but not time symmetric. We
present a simple example of measurements on a two-level system which violates
time symmetry and propose an experiment with quantum dots to measure the
time-symmetry violation in a third-order current correlation function.Comment: 19 pages, 5 figures, more information at
http://www.fuw.edu.pl/~abednorz/tasym
- …