AMANDA Observations Constrain the Ultra-High Energy Neutrino Flux

A number of experimental techniques are currently being deployed in an effort to make the first detection of ultra-high energy cosmic neutrinos. To accomplish this goal, techniques using radio and acoustic detectors are being developed, which are optimally designed for studying neutrinos with energies in the PeV-EeV range and above. Data from the AMANDA experiment, in contrast, has been used to place limits on the cosmic neutrino flux at less extreme energies (up to ~10 PeV). In this letter, we show that by adopting a different analysis strategy, optimized for much higher energy neutrinos, the same AMANDA data can be used to place a limit competitive with radio techniques at EeV energies. We also discuss the sensitivity of the IceCube experiment, in various stages of deployment, to ultra-high energy neutrinos.Comment: 4 pages, 3 figure

What Can Gamma Ray Bursts Teach Us About Dark Energy?

It has been suggested that Gamma Ray Bursts (GRB) may enable the expansion rate of our Universe to be measured out to very high redshifts (z \gsim 5) just as type Ia supernovae have done at $z \sim$1--1.5. We explore this possibility here, and find that GRB have the potential to detect dark energy at high statistical significance, but they are unlikely to be competitive with future supernovae missions, such as SNAP, in measuring the properties of the dark energy. The exception to this conclusion is if there is appreciable dark energy at early times, in which case the information from GRB's will provide an excellent complement to the $z\sim 1$ information from supernovae.Comment: 5 pages, 9 figure

Light Neutralino Dark Matter in the NMSSM

Neutralino dark matter is generally assumed to be relatively heavy, with a mass near the electroweak scale. This does not necessarily need to be the case, however. In the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and other supersymmetric models with an extended Higgs sector, a very light CP-odd Higgs boson can naturally arise making it possible for a very light neutralino to annihilate efficiently enough to avoid being overproduced in the early Universe. In this article, we explore the characteristics of a supersymmetric model needed to include a very light neutralino, 100 MeV < \mcnone < 20 GeV, using the NMSSM as a prototype. We discuss the most important constraints from Upsilon decays, $b \to s \gamma$, $B_s \to \mu^+ \mu^-$ and the magnetic moment of the muon, and find that a light bino or singlino neutralino is allowed, and can be generated with the appropriate relic density. It has previously been shown that the positive detection of dark matter claimed by the DAMA collaboration can be reconciled with other direct dark matter experiments such as CDMS II if the dark matter particle is rather light, between about 6 and 9 GeV. A singlino or bino-like neutralino could easily fall within this range of masses within the NMSSM. Additionally, models with sub-GeV neutralinos may be capable of generating the 511 keV gamma-ray emission observed from the galactic bulge by the INTEGRAL/SPI experiment. We also point out measurements which can be performed immediately at CLEO, BaBar and Belle using existing data to discover or significantly constrain this scenario.Comment: References updated, accepted for publication in PR

Some new results concerning the vacuum in Dirac Hole Theory

In Dirac's hole theory the vacuum state is generally believed to be the state of minimum energy. It will be shown that this is not, in fact, the case and that there must exist states in hole theory with less energy than the vacuum state. It will be shown that energy can be extracted from the hole theory vacuum state through the application of an electric field.Comment: Accepted by Physica Scripta, 19 page

Constraints on Light Dark Matter From Core-Collapse Supernovae

We show that light ($\simeq$ 1 -- 30 MeV) dark matter particles can play a significant role in core-collapse supernovae, if they have relatively large annihilation and scattering cross sections, as compared to neutrinos. We find that if such particles are lighter than $\simeq$ 10 MeV and reproduce the observed dark matter relic density, supernovae would cool on a much longer time scale and would emit neutrinos with significantly smaller energies than in the standard scenario, in disagreement with observations. This constraint may be avoided, however, in certain situations for which the neutrino--dark matter scattering cross sections remain comparatively small.Comment: 4 pages, 1 figur

Diagnostic methods of frequency response analysis for power transformer winding a review

Abstract: Monitoring and diagnosis of power transformers in power systems have been investigated and discussed for the past decades. Earlier detect power transformer winding failures is recommended for both manufacturing process and also for power system operators. One of the most powerful and accurate tool for sufficient winding deformation detection is considered Frequency Response Analysis (FRA) among other diagnostic methods. In this paper a review of diagnostic methods of FRA for power transformer winding are presented. Different methods of transformer winding diagnosis, with their benefits and drawbacks where investigated. Moreover, possible windings failures, diagnostic methods of FRA in Off-line and On-line power transformers, detailed advantages and disadvantages of two major types of FRA are presented. The paper was able to show that some uncertainties have not been eliminated completely

Lateral diffusion of a protein on a fluctuating membrane

Measurements of lateral diffusion of proteins in a membrane typically assume that the movement of the protein occurs in a flat plane. Real membranes, however, are subject to thermal fluctuations, leading to movement of an inclusion into the third dimension. We calculate the magnitude of this effect by projecting real three-dimensional diffusion onto an effective one on a flat plane. We consider both a protein that is free to diffuse in the membrane and one that also couples to the local curvature. For a freely diffusing inclusion the measured projected diffusion constant is up to 15% smaller than the actual value. Coupling to the curvature enhances diffusion significantly up to a factor of two.Comment: 6 pages, 4 figure

Potensi Abu Sekam Padi untuk Meningkatkan Ketahanan Oksidatif Non-enzimatik dan Produksi Padi Merah pada Cekaman Kekeringan

Drought inhibits several physiological process and induces oxidative stress due to the enhanced production of reactive oxygen species (ROS) mainly in photosynthetic apparatus. Silicon (Si) is known to increase tolerance of rice against drought stress. However, long period of intensive crop cultivation depleted the available soil Si by approximately 11-20%. Rice husk ash (RHA) is potential Si source. The objective of this research was to analyze the potency of RHA through pot experiment to observe: 1) internal water balanced; 2) integrity of cell membrane and antioxidant content; and 3) production of tolerant cultivar ‘Segreng' and sensitive one ‘Cempo merah'. Application of RHA was at level of 0, 4, and 8 tons ha-1. Drought stress was imposed by with holding water until soil water content reached 50% of field capacity (moderate stress) and 25% of field capacity (severe stress). Application of RHA significantly increased leaf relative water content and membrane stability index of rice ‘Segreng' and ‘Cempo merah'. Tolerant cultivar ‘Segreng' had better response than ‘Cempo merah' as shown by greater leaf relative water content under moderate and severe stress. RHA application at level of 8 tons ha-1 increased index of membrane stability and level of antioxidant (AAred and α-tocopherol) which determine production of both rice ‘Segreng' and ‘Cempo merah' during drought