Observation of the Askaryan Effect: Coherent Microwave Cherenkov Emission from Charge Asymmetry in High Energy Particle Cascades

We present the first direct experimental evidence for the charge excess in high energy particle showers predicted nearly 40 years ago by Askaryan. We directed bremsstrahlung photons from picosecond pulses of 28.5 GeV electrons at the SLAC Final Focus Test Beam facility into a 3.5 ton silica sand target, producing electromagnetic showers several meters long. A series of antennas spanning 0.3 to 6 GHz were used to detect strong, sub-nanosecond radio frequency pulses produced whenever a shower was present. The measured electric field strengths are consistent with a completely coherent radiation process. The pulses show 100% linear polarization, consistent with the expectations of Cherenkov radiation. The field strength versus depth closely follows the expected particle number density profile of the cascade, consistent with emission from excess charge distributed along the shower. These measurements therefore provide strong support for experiments designed to detect high energy cosmic rays and neutrinos via coherent radio emission from their cascades.Comment: 10 pages, 4 figures. Submitted to Phys. Rev. Let

Addendum to "Coherent radio pulses from GEANT generated electromagnetic showers in ice"

We reevaluate our published calculations of electromagnetic showers generated by GEANT 3.21 and the radio frequency pulses they produce in ice. We are prompted by a recent report showing that GEANT 3.21-modeled showers are sensitive to internal settings in the electron tracking subroutine. We report the shower and pulse characteristics obtained with different settings of GEANT 3.21 and with GEANT 4. The default setting of electron tracking in GEANT 3.21 we used in previous work speeds up the shower simulation at the cost of information near the end of the tracks. We find that settings tracking electron and positron to lower energy yield a more accurate calculation, a more intense shower, and proportionately stronger radio pulses at low frequencies. At high frequencies the relation between shower tracking algorithm and pulse spectrum is more complex. We obtain radial distributions of shower particles and phase distributions of pulses from 100 GeV showers that are consistent with our published results.Comment: 4 pages, 3 figure

Effects of the plant growth stimulant SBPI on Bemisia tabaci Genn. (Homoptera: Aleyrodidae)

The environmentally friendly plant growth stimulant and pesticide SB Plant Invigorator (SBPI, Stan Brouard Group)helps the plant to produce quality fruit. Three days after tomato plants were sprayed for the first time with SBPI (2 ml*L-1 solution), this product seemed to be ineffective against Bemisia tabaci adults, as the numbers of dead females were practically equal on control and treated plants. After 3 days oviposition values on control plants did not differ significantly from those on treated plants. However, 31 days after the first treatment with weekly repeated treatments, new adult whiteflies started to emerge from pupae on control plants, but no L3, L4 or new adults were found on SBPI-treated plants. However, differences in the number of 1st+2nd instar larvae were not statistically significant. From these findings it can be concluded that, under these conditions, SBPI is an effective alternative product for the control of B. tabaci on tomato plants, as foliar application inhibits larval development decreasing the risk of a new whitefly generation.Peer reviewe

Effects of SB Plant Invigorator on Bemisia tabaci Development in Tomato Plants

Whitefly control programmes are mostly based on the application of insecticides. However, Bemisia tabaci is able to develop resistance to many of these chemical substances, and high levels of resistance have been reported for many insecticides in different agricultural systems worldwide. Moreover, many of these chemical products are toxic to the environment if they are not used properly. These disadvantages make necessary to search for alternative strategies of pest control for its implementation in IPM programmes. Utilization of new products which fight physically but not chemically against pest is one of the alternative methods investigated nowadays. The Stan Brouard Group has developed an environmentally respectful stimulant of plant growth called SB Plant Invigorator (SBPI) which helps the plant to produce quality fruits. It presents a physical mode of action that makes the product respectful with the environment. Due to its formulation, SBPI is not a pesticide but a plant stimulant, and it is proved not to be a toxic but an environmentally safe product. No harvest interval is therefore required after use, special health and safety measures for users are not necessary, and the product does not cause problems with residuals in food. As its activity against insects is achieved by physical means, insects do not develop resistance to SBPI and it continues being useful after a long time application. The objective of the present study was to test whether SBPI is effective to control B. tabaci in commercial tomato plants (cv. Marmande) which lack the Mi-1 gene of resistance to whiteflies. Three days after the first foliar spraying (2ml/l solution), the product seemed to be ineffective against the adult insects, as the numbers of died females were practically equal for both, control and treated plants. No statistically significant differences were found for the oviposition values, although the mean number of eggs laid on SBPI-treated leaves was slightly greater than that observed on control plants. Treatment was repeated weekly during the next 4 weeks. At 31 days, new adult whiteflies started to emerge from pupae in control plants, with significant differences with the SBPI-treated plants where any L3, L4 or new adults were not found. Differences in the number of L1+L2 were not statistically significant, although the mean number of individuals in these larval stages on SBPI-treated plants was twice as much on control plants. In conclusion, SBPI is an effective alternative product to control B. tabaci in tomato as foliar application under these conditions inhibits or delays larval development avoiding the risk of a new whitefly generation.Peer reviewe

Bending behavior analysis of geogrid reinforced adobe walls

La tierra cruda constituye el material de construcción más importante en muchas regiones del planeta. Dado el riesgo sísmico existente en la mayor parte de estas regiones, es necesario el desarrollo de técnicas de refuerzo eficaces y adecuadas desde un punto de vista tecnológico y socioeconómico. Este artículo analiza desde un punto experimental y analítico el comportamiento a flexión de muros de adobe reforzados con geomallas. Las leyes momento-curvatura de los muros ensayados son aproximadas mediante una serie de modelos analíticos que permiten analizar el comportamiento del material compuesto adobe-geomalla. Los resultados obtenidos muestran como la geomalla mejora el comportamiento de la mampostería de adobe en términos de resistencia y ductilidad, mejorando así su comportamiento en caso de movimiento sísmico.Rammed earth is a widely used building material in many regions of the world. Due to the high seismic risk in those areas, earthen constructions require suitable and efficient reinforcement techniques from a technological and socioeconomic point of view. This paper analyzes the bending behavior of geogrid reinforced adobe walls from an experimental and analytical point of view. The experimental bending moment-curvature relationships are analytically approached. The results show how geogrid reinforcement improves the performance of adobe masonry in terms of strength and ductility. Thus, a better seismic performance is achieve

Neutrino Induced Upward Going Muons from a Gamma Ray Burst in a Neutrino Telescope of Km^2 Area

The number of neutrino induced upward going muons from a single Gamma Ray Burst (GRB) expected to be detected by the proposed kilometer scale IceCube detector at the South Pole location has been calculated. The effects of the Lorentz factor, total energy of the GRB emitted in neutrinos and its distance from the observer (red shift) on the number of neutrino events from the GRB have been examined. The present investigation reveals that there is possibility of exploring the early Universe with the proposed kilometer scale IceCube neutrino telescope.Comment: 18pages, 5 figures. Physical Review D in pres

Energy and Flux Measurements of Ultra-High Energy Cosmic Rays Observed During the First ANITA Flight

The first flight of the Antarctic Impulsive Transient Antenna (ANITA) experiment recorded 16 radio signals that were emitted by cosmic-ray induced air showers. For 14 of these events, this radiation was reflected from the ice. The dominant contribution to the radiation from the deflection of positrons and electrons in the geomagnetic field, which is beamed in the direction of motion of the air shower. This radiation is reflected from the ice and subsequently detected by the ANITA experiment at a flight altitude of 36km. In this paper, we estimate the energy of the 14 individual events and find that the mean energy of the cosmic-ray sample is 2.9 EeV. By simulating the ANITA flight, we calculate its exposure for ultra-high energy cosmic rays. We estimate for the first time the cosmic-ray flux derived only from radio observations. In addition, we find that the Monte Carlo simulation of the ANITA data set is in agreement with the total number of observed events and with the properties of those events.Comment: Added more explanation of the experimental setup and textual improvement