Measurement of 1323 and 1487 keV resonances in 15N({\alpha}, {\gamma})19F with the recoil separator ERNA

The origin of fluorine is a widely debated issue. Nevertheless, the ^{15}N({\alpha},{\gamma})^{19}F reaction is a common feature among the various production channels so far proposed. Its reaction rate at relevant temperatures is determined by a number of narrow resonances together with the DC component and the tails of the two broad resonances at E_{c.m.} = 1323 and 1487 keV. Measurement through the direct detection of the 19F recoil ions with the European Recoil separator for Nuclear Astrophysics (ERNA) were performed. The reaction was initiated by a 15N beam impinging onto a 4He windowless gas target. The observed yield of the resonances at Ec.m. = 1323 and 1487 keV is used to determine their widths in the {\alpha} and {\gamma} channels. We show that a direct measurement of the cross section of the ^{15}N({\alpha},{\gamma})^{19}F reaction can be successfully obtained with the Recoil Separator ERNA, and the widths {\Gamma}_{\gamma} and {\Gamma}_{\alpha} of the two broad resonances have been determined. While a fair agreement is found with earlier determination of the widths of the 1487 keV resonance, a significant difference is found for the 1323 keV resonance {\Gamma}_{\alpha} . The revision of the widths of the two more relevant broad resonances in the 15N({\alpha},{\gamma})19F reaction presented in this work is the first step toward a more firm determination of the reaction rate. At present, the residual uncertainty at the temperatures of the ^{19}F stellar nucleosynthesis is dominated by the uncertainties affecting the Direct Capture component and the 364 keV narrow resonance, both so far investigated only through indirect experiments.Comment: 8 pages, 11 figures. Accepted for publication in PR

Rendimiento y características agronómicas de frijol de temporal en generaciones tempranas

En el programa de mejoramiento genético de frijol de la región semiárida de México la selección por rendimiento se realiza en generaciones avanzadas. El presente estudio se realizó con el objetivo de determinar en poblaciones segregantes de frijol de temporal el nivel de heterosis, heterobeltiosis y depresión endogámica de diversas caracter ísticas agronómicas. Se evaluaron cuatro poblaciones de frijol de grano negro en las generaciones F2 y F3, y siete de diferentes colores en las generaciones F3 y F4. Además, se incluyeron los progenitores de cada población. En las poblaciones de grano negro, la derivada de la cruza BAT 76 x Negro Qro. presentó en ambas generaciones los más altos rendimientos, la mayor producción de materia seca total y los más altos valores de heterosis para esas caracter ísticas, así como el mayor valor de heterobeltiosis en la generación F3. En el grupo de colores, la población derivada de la cruza 102- M x Bayo Victoria fue de las más rendidoras en las dos generaciones, presentó los más altos valores de heterosis y fue la única que mostró heterobeltiosis en ambas generaciones. Las poblaciones con alto rendimiento y heterosis en las generaciones tempranas, conservaron ambas caracter ísticas en la generacion posterior y los mejores progenitores produjeron las mejores poblaciones. Lo anterior sugiere que en frijol, es posible predecir las mejores cruzas e identificar poblaciones con alto potencial de rendimiento en generaciones tempranas

The normalisation of Food Aid: What happened to feeding people well?

In the UK, food poverty has increased in the last 15 years and the food aid supply chain that has emerged to tackle it is now roughly 10 years old. In this time, we have seen the food aid supply chain grow at a rate that has astounded many.  Recently that growth has been aided by a grant of £20m from a large supermarket chain. It appears institutionalisation is just around the corner, if not already here. It also appears that there is far greater emphasis on dealing with  the symptoms as opposed to solving the root causes of the problem. As an opinion piece, this paper reflects on some of the prevalent issues, and suggests some ways forward

AB 1007 Full Fuel Cycle Analysis (FFCA) Peer Review

LLNL is a participant of California's Advanced Energy Pathways (AEP) team funded by DOE (NETL). At the AEP technical review meeting on November 9, 2006. The AB 1007 FFCA team (Appendix A) requested LLNL participate in a peer review of the FFCA reports. The primary contact at the CEC was McKinley Addy. The following reports/presentations were received by LLNL: (1) Full Fuel Cycle Energy and Emissions Assumptions dated September 2006, TIAX; (2) Full Fuel cycle Assessment-Well to Tank Energy Inputs, Emissions, and Water Impacts dated December 2006, TIAX; and (3) Full Fuel Cycle Analysis Assessment dated October 12, 2006, TIAX

Soft X-ray harmonic comb from relativistic electron spikes

We demonstrate a new high-order harmonic generation mechanism reaching the `water window' spectral region in experiments with multi-terawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving uJ/sr pulses. Harmonics are collectively emitted by an oscillating electron spike formed at the joint of the boundaries of a cavity and bow wave created by a relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by particle-in-cell simulations

Effect of self-generated magnetic fields on fast-electron beam divergence in solid targets

The collimating effect of self-generated magnetic fields on fast-electron transport in solid aluminium targets irradiated by ultra-intense, picosecond laser pulses is investigated in this study. As the target thickness is varied in the range of 25 mu m to 1.4 mm, the maximum energies of protons accelerated from the rear surface are measured to infer changes in the fast-electron density and therefore the divergence of the fast-electron beam transported through the target. Purely ballistic spreading of the fast-electrons would result in a much faster decrease in the maximum proton energy with increasing target thickness than that measured. This implies that some degree of 'global' magnetic pinching of the fast-electrons occurs, particularly for thick (>400 mu m) targets. Numerical simulations of electron transport are in good agreement with the experimental data and show that the pinching effect of the magnetic field in thin targets is significantly reduced due to disruption of the field growth by refluxing fast-electrons

A strategy to characterize the LISA-Pathfinder cold gas thruster system

The cold gas micro-propulsion system that will be used during the LISA-Pathfinder mission will be one of the most important component used to ensure the "free-fall" of the enclosed test masses. In this paper we present a possible strategy to characterize the effective direction and amplitude gain of each of the 6 thrusters of this system