1,859 research outputs found
SUSY breaking based on Abelian gaugino kinetic term mixings
We present a SUSY breaking scenario based on Abelian gaugino kinetic term
mixings between hidden and observable sectors. If an extra U(1) gaugino in the
observable sector obtains a large mass through this mixing effect based on SUSY
breaking in the hidden sector, soft SUSY breaking parameters in the MSSM may be
affected by radiative effects due to this gaugino mass. New phenomenological
aspects are discussed in such a SUSY breaking scenario.Comment: latex, 12pages, 2figures, published versio
Optical spectroscopy of gan microcavities with thicknesses controlled using a plasma etch-back
The effect of an etch-back step to control the cavity length within GaN-based microcavities formed between two dielectric Bragg mirrors was investigated using photoluminescence and reflectivity. The structures are fabricated using a combination of a laser lift-off technique to separate epitaxial III-N layers from their sapphire substrates and electron-beam evaporation to deposit silica/zirconia multilayer mirrors. The photoluminescence measurements reveal cavity modes from both etched and nonetched microcavities. Similar cavity finesses are measured for 2.0 and 0.8 mm GaN cavities fabricated from the same wafer, indicating that the etchback has had little effect on the microcavity quality. For InGaN quantum well samples the etchback is shown to allow controllable reduction of the cavity length. Two etch steps of 100 nm are demonstrated with an accuracy of approximately 5%. The etchback, achieved using inductively coupled plasma and wet chemical etching, allows removal of the low-quality GaN nucleation layer, control of the cavity length, and modification of the surface resulting from lift-off
The Database Architectures Research Group at CWI
The Database research group at CWI was established in 1985. It has steadily grown from two PhD students to a group of 17 people ultimo 2011. The group is supported by a scientific programmer and a system engineer to keep our machines running. In this short note, we look back at our past and highlight the multitude of topics being addressed
Pair Excitations and Vertex Corrections in Fermi Fluids
Based on an equations--of--motion approach for time--dependent pair
correlations in strongly interacting Fermi liquids, we have developed a theory
for describing the excitation spectrum of these systems. Compared to the known
``correlated'' random--phase approximation (CRPA), our approach has the
following properties: i) The CRPA is reproduced when pair fluctuations are
neglected. ii) The first two energy--weighted sumrules are fulfilled implying a
correct static structure. iii) No ad--hoc assumptions for the effective mass
are needed to reproduce the experimental dispersion of the roton in 3He. iv)
The density response function displays a novel form, arising from vertex
corrections in the proper polarisation. Our theory is presented here with
special emphasis on this latter point. We have also extended the approach to
the single particle self-energy and included pair fluctuations in the same way.
The theory provides a diagrammatic superset of the familiar GW approximation.
It aims at a consistent calculation of single particle excitations with an
accuracy that has previously only been achieved for impurities in Bose liquids.Comment: to be published in: JLTP (2007) Proc. Int. Symp. QFS2006, 1-6 Aug.
2006, Kyoto, Japa
Implications of a Massless Neutralino for Neutrino Physics
We consider the phenomenological implications of a soft SUSY breaking term BN
at the TeV scale (here B is the U(1)_Y gaugino and N is the right-handed
neutrino field). In models with a massless (or nearly massless) neutralino,
such a term will give rise through the see-saw mechanism to new contributions
to the mass matrix of the light neutrinos.
We treat the massless neutralino as an (almost) sterile neutrino and find
that its mass depends on the square of the soft SUSY breaking scale, with
interesting consequences for neutrino physics. We also show that, although it
requires fine-tuning, a massless neutralino in the MSSM or NMSSM is not
experimentally excluded. The implications of this scenario for neutrino physics
are discussed.Comment: 14 pages, latex, no figure
Observable Neutron-Antineutron Oscillations in Seesaw Models of Neutrino Mass
We show that in a large class of supersymmetric models with spontaneously
broken B-L symmetry, neutron--antineutron oscillations occur at an observable
level even though the scale of B-L breaking is very high, v_{B-L} ~ 2 x 10^{16}
GeV, as suggested by gauge coupling unification and neutrino masses. We
illustrate this phenomenon in the context of a recently proposed class of
seesaw models that solves the strong CP problem and the SUSY phase problem
using parity symmetry. We obtain an upper limit on N-\bar{N} oscillation time
in these models, \tau_{N-\bar{N}} < 10^{9} -10^{10} sec. This suggests that a
modest improvement in the current limit on \tau_{N-\bar{N}} of 0.86 x 10^8 sec
will either lead to the discovery of N-\bar{N} oscillations, or will
considerably restrict the allowed parameter space of an interesting class of
neutrino mass models.Comment: 11 pages RevTeX, 1 figur
Mitochondrial Approaches to Protect Against Cardiac Ischemia and Reperfusion Injury
The mitochondrion is a vital component in cellular energy metabolism and intracellular signaling processes. Mitochondria are involved in a myriad of complex signaling cascades regulating cell death vs. survival. Importantly, mitochondrial dysfunction and the resulting oxidative and nitrosative stress are central in the pathogenesis of numerous human maladies including cardiovascular diseases, neurodegenerative diseases, diabetes, and retinal diseases, many of which are related. This review will examine the emerging understanding of the role of mitochondria in the etiology and progression of cardiovascular diseases and will explore potential therapeutic benefits of targeting the organelle in attenuating the disease process. Indeed, recent advances in mitochondrial biology have led to selective targeting of drugs designed to modulate or manipulate mitochondrial function, to the use of light therapy directed to the mitochondrial function, and to modification of the mitochondrial genome for potential therapeutic benefit. The approach to rationally treat mitochondrial dysfunction could lead to more effective interventions in cardiovascular diseases that to date have remained elusive. The central premise of this review is that if mitochondrial abnormalities contribute to the etiology of cardiovascular diseases (e.g., ischemic heart disease), alleviating the mitochondrial dysfunction will contribute to mitigating the severity or progression of the disease. To this end, this review will provide an overview of our current understanding of mitochondria function in cardiovascular diseases as well as the potential role for targeting mitochondria with potential drugs or other interventions that lead to protection against cell injury
A survey of the ichthyofauna in the Noetsie Estuary, Western Cape Province, South Africa
The fish assemblage in the Noetsie Estuary, a temporarily open and closed estuary on the southern coast of South Africa, was sampled using multiple gears. A total of 12 species from 8 families were recorded. Collectively, estuarine-dependent marine species dominated seine net catches numerically and in terms of biomass for both sampling seasons. Estuarine round herring (Gilchristella aestuaria) was numerically the dominant species in late summer, while juvenile Mugilidae dominated catches in winter. Size class distributions of various fish species indicate that the estuary both serves a nursery function for important euryhaline marine species and supports estuarine resident taxa. Application of the Estuarine Fish Community Index indicates the ecological condition of the estuary to be ‘good’. This study contributes to the species list for the estuary while also reporting the presence of an alien invasive freshwater species, Gambusia affinis. Recommendations include the development of a management plan and the formalisation of an estuarine management committee.
Conservation implications: The Noetsie Estuary serves a nursery function for important euryhaline marine species, while supporting healthy populations of estuarine resident taxa. The presence of one alien invasive fish species is documented with potential implications for the conservation of biodiversity in the estuary
External validation of the derived neutrophil-tolymphocyte ratio as a prognostic factor in breast cancer patients [Poster]
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