La economía norteamericana en la segunda Administración Reagan

La economía norteamericana se ha introducido en un proceso de auge cíclico en los años ochenta, al menos al inicio de esta década, sin embargo, este proceso es aún incapaz de resolver el deterioro económico del país. El déficit total acumulado por la Administración Reagan en el periodo fiscal 1981-1984 fue de cerca de 530 mil mdd, casi rtres veces el déficti total acumulado por la administración anterior

Influence of the organic matter on the specific surface of a Typic argiudoll

El contenido de materia orgánica (MO) del suelo se relaciona positivamente, en algunos casos, con la superficie específica (SE) del mismo, pero grandes cantidades de MO pueden resultar en una SE menor, cuando se la determina a través de la adsorción de nitrógeno a bajas temperaturas. Tradicionalmente se asocia a la MO una elevada SE, del orden de los 500 a 800 m2 g-1. Estos valores, obtenidos mediante técnicas que emplean solventes polares, por ejemplo, etilenglicol, hicieron suponer que la misma contribuye en gran medida a la SE del suelo. No obstante, hay referencias que señalan una sobrestimación de los resultados obtenidos, atribuida a la utilización de estos solventes. Mediciones que emplean el método con adsorción de N2 a 77 K, cuya interpretación se basa en el modelo de Brunauer, Emmett y Teller (BET), considerado internacionalmente como método patrón, arrojan valores de SE para la MO que son menores que los primeros, en dos órdenes de magnitud. Con el objetivo de aportar conocimiento que contribuyera a una mejor comprensión del papel de la MO en procesos edáficos, se realizaron determinaciones de SE en muestras de un Argiudol típico, con diferentes contenidos de MO y contenido de arcilla constante (20%). Las medidas se llevaron a cabo interpretando las isotermas de adsorción de N2 a 77 K, mediante el modelo BET. Los resultados obtenidos mostraron una relación no lineal negativa entre la SE y el contenido de MO. La eliminación de la MO mediante H2O2 incrementó la SE de las muestras en todos los casos. La variación de SE por unidad de MO eliminada sugiere que la misma no se adsorbe de manera uniforme y continua sobre la superficie de la fase mineral.The organic matter (OM) of soil is positively related to the specific surface area (SSA), but large amounts of OM result in reduced SSA when determined by the Brunauer-Emmett- Teller (BET) method with N2 adsorption at low temperature. It is common to assign a large SSA to OM, ranging from 500 to 800 m2 g-1. These values, obtained with methods using polar adsorbates, e.g. ethylene glycol, imply a high contribution of OM to soil SSA. However, some works claimed an overestimation of the effect of OM on SSA when polar solvents are used. Measurements with the BET method (using N2 at 77 K), considered internationally as a standard method, resulted in values of SSA for OM two order of magnitude smaller than the former ones. With the objective to contribute to a better knowledge about the OM role in edaphological processes, determinations of SSA in samples from a Typic argiudoll with different OM contents were made. Measurements of SSA were carried out with N2 at 77 K, and the isotherms were interpreted with the BET model. Results showed a negative non linear relationship between SSA and the OM content of the samples. Destruction of OM with H2O2 increased SSA in all cases. The increments in SSA, normalized by the content of removed OM, suggested that the adsorption of OM on the mineral surface is not uniform.Fil: Gelati, Pablo R..Fil: Sarli, Guillermo O..Fil: Soracco, Carlos Germán.Fil: Lozano, Luis A..Fil: Filgueira, Roberto R.

Silo Clogging Reduction by the Presence of an Obstacle

We present experimental results on the effect that inserting an obstacle just above the outlet of a silo has on the clogging process. We find that, if the obstacle position is properly selected, the probability that the granular flow is arrested can be reduced by a factor of 100. This dramatic effect occurs without any remarkable modification of the flow rate or the packing fraction above the outlet, which are discarded as the cause of the change in the clogging probability. Hence, inspired by previous results of pedestrian crowd dynamics, we propose that the physical mechanism behind the clogging reduction is a pressure decrease in the region of arch formation

Neutron-induced fission cross section of 234 U measured at the CERN n_TOF facility

The neutron-induced fission cross section of 234U has been measured at the CERN n-TOF facility relative to the standard fission cross section of 235U from 20 keV to 1.4 MeV and of 238U from 1.4 to 200 MeV. A fast ionization chamber (FIC) was used as a fission fragment detector with a detection efficiency of no less than 97%. The high instantaneous flux and the low background characterizing the n-TOF facility resulted in wide-energy-range data (0.02 to 200 MeV), with high energy resolution, high statistics, and systematic uncertainties bellow 3%. Previous investigations around the energy of the fission threshold revealed structures attributed to β-vibrational levels, which have been confirmed by the present measurements. Theoretical calculations have been performed, employing the talys code with model parameters tuned to fairly reproduce the experimental data

The 139 La(n ,γ) cross section: Key for the onset of the s -process

The nuclear resonance parameters and the capture cross section of the neutron magic isotope La139 have been measured relative to Au197 in the energy range of 0.6 eV to 9 keV at the neutron time-of-flight (n_TOF) facility at CERN. We describe the experimental apparatus and the data analysis procedures, which concerned mainly the efficiency correction by means of the pulse height weighting function technique and the determination of different background components. We extracted the resonance parameters and the main nuclear quantities such as the resonance integral RI=10.8±1.0b, the average widths for s and p waves a 1=0=50.7 5.4 meV and l=1=33. 6±6.9 meV, the nuclear level densities l=0=252A 22 eV and l=1<250 eV, and the neutron strength functions S0=(0.82±0.05) Ö10-4 and S1=(0.55±0.04)Ö10-4. These results represent a significant improvement over previous data. The deduced Maxwellian-averaged capture cross sections are important for the interpretation of the most recent spectroscopic observations in low-metallicity stars.EC FIKW-CT-2000-0010

Comportamiento de novillos bajo dos sistemas de alimentación melaza/urea vs grano de sorgo con la utilización de dos fuentes de proteína y forraje restringido

Se llevó a cabo un experimento para evaluar el efecto de la suplementación con dos fuentes proteicas (harinolina y pasta de girasol) al utilizar dietas altas en melaza/urea o grano de sorgo con forraje restringido en la alimentación de novillos en crecim

Influence of the organic matter on the specific surface of a Typic argiudoll

El contenido de materia orgánica (MO) del suelo se relaciona positivamente, en algunos casos, con la superficie específica (SE) del mismo, pero grandes cantidades de MO pue­den resultar en una SE menor, cuando se la determina a través de la adsorción de nitrógeno a bajas temperaturas. Tradicionalmente se asocia a la MO una elevada SE, del orden de los 500 a 800 m2 g-1. Estos valores, obtenidos mediante técnicas que emplean solventes po­lares, por ejemplo, etilenglicol, hicieron suponer que la misma contribuye en gran medida a la SE del suelo. No obstante, hay referencias que señalan una sobrestimación de los resultados obtenidos, atribuida a la utilización de estos solventes. Mediciones que emplean el método con adsorción de N2 a 77 K, cuya interpretación se basa en el modelo de Brunauer, Emmett y Teller (BET), considerado internacionalmente como método patrón, arrojan valores de SE para la MO que son menores que los primeros, en dos órdenes de magnitud. Con el objetivo de aportar conocimiento que contribuyera a una mejor comprensión del papel de la MO en procesos edáficos, se realizaron determinacio­nes de SE en muestras de un Argiudol típico, con diferentes contenidos de MO y contenido de arcilla constante (20%). Las medidas se llevaron a cabo interpretando las isotermas de adsorción de N2 a 77 K, mediante el modelo BET. Los resultados obtenidos mostraron una relación no lineal negativa entre la SE y el contenido de MO. La eliminación de la MO mediante H2O2 incrementó la SE de las muestras en todos los casos. La variación de SE por unidad de MO eliminada sugiere que la misma no se adsorbe de manera uniforme y continua sobre la superficie de la fase mineral.The organic matter (OM) of soil is posi­tively related to the specific surface area (SSA), but large amounts of OM result in reduced SSA when determined by the Brunauer-Emmett-Teller (BET) method with N2 adsorption at low temperature. It is common to assign a large SSA to OM, ranging from 500 to 800 m2 g-1. These values, obtained with methods using polar adsorbates, e.g. ethylene glycol, imply a high contribution of OM to soil SSA. However, some works claimed an overestimation of the effect of OM on SSA when polar solvents are used. Measurements with the BET method (using N2 at 77 K), considered internationally as a standard method, resulted in values of SSA for OM two order of magnitude smaller than the former ones. With the objective to contribute to a better knowledge about the OM role in edaphological processes, determinations of SSA in samples from a Typic argiudoll with different OM contents were made. Measure­ments of SSAwere carried out with N2 at77 K, and the isotherms were interpreted with the BET model. Results showed a negative non linear relationship between SSA and the OM content of the samples. Destruction of OM with H2O2 increased SSA in all cases. The increments in SSA, normalized by the content of removed OM, suggested that the adsorption of OM on the mineral surface is not uniform.Facultad de Ciencias Agrarias y Forestale

Influence of the organic matter on the specific surface of a Typic argiudoll

El contenido de materia orgánica (MO) del suelo se relaciona positivamente, en algunos casos, con la superficie específica (SE) del mismo, pero grandes cantidades de MO pue­den resultar en una SE menor, cuando se la determina a través de la adsorción de nitrógeno a bajas temperaturas. Tradicionalmente se asocia a la MO una elevada SE, del orden de los 500 a 800 m2 g-1. Estos valores, obtenidos mediante técnicas que emplean solventes po­lares, por ejemplo, etilenglicol, hicieron suponer que la misma contribuye en gran medida a la SE del suelo. No obstante, hay referencias que señalan una sobrestimación de los resultados obtenidos, atribuida a la utilización de estos solventes. Mediciones que emplean el método con adsorción de N2 a 77 K, cuya interpretación se basa en el modelo de Brunauer, Emmett y Teller (BET), considerado internacionalmente como método patrón, arrojan valores de SE para la MO que son menores que los primeros, en dos órdenes de magnitud. Con el objetivo de aportar conocimiento que contribuyera a una mejor comprensión del papel de la MO en procesos edáficos, se realizaron determinacio­nes de SE en muestras de un Argiudol típico, con diferentes contenidos de MO y contenido de arcilla constante (20%). Las medidas se llevaron a cabo interpretando las isotermas de adsorción de N2 a 77 K, mediante el modelo BET. Los resultados obtenidos mostraron una relación no lineal negativa entre la SE y el contenido de MO. La eliminación de la MO mediante H2O2 incrementó la SE de las muestras en todos los casos. La variación de SE por unidad de MO eliminada sugiere que la misma no se adsorbe de manera uniforme y continua sobre la superficie de la fase mineral.The organic matter (OM) of soil is posi­tively related to the specific surface area (SSA), but large amounts of OM result in reduced SSA when determined by the Brunauer-Emmett-Teller (BET) method with N2 adsorption at low temperature. It is common to assign a large SSA to OM, ranging from 500 to 800 m2 g-1. These values, obtained with methods using polar adsorbates, e.g. ethylene glycol, imply a high contribution of OM to soil SSA. However, some works claimed an overestimation of the effect of OM on SSA when polar solvents are used. Measurements with the BET method (using N2 at 77 K), considered internationally as a standard method, resulted in values of SSA for OM two order of magnitude smaller than the former ones. With the objective to contribute to a better knowledge about the OM role in edaphological processes, determinations of SSA in samples from a Typic argiudoll with different OM contents were made. Measure­ments of SSAwere carried out with N2 at77 K, and the isotherms were interpreted with the BET model. Results showed a negative non linear relationship between SSA and the OM content of the samples. Destruction of OM with H2O2 increased SSA in all cases. The increments in SSA, normalized by the content of removed OM, suggested that the adsorption of OM on the mineral surface is not uniform.Facultad de Ciencias Agrarias y Forestale

Wafer-scale fabrication of target arrays for stable generation of proton beams by laser-plasma interaction

[EN] Large-scale fabrication of targets for laser-driven acceleration of ion beams is a prerequisite to establish suitable applications, and to keep up with the challenge of increasing repetition rate of currently available high-power lasers. Here we present manufacturing and test results of large arrays of solid targets for TNSA laser-driven ion acceleration. By applying micro-electro-mechanical-system (MEMS) based methods allowing for parallel processing of thousands of targets on a single Si wafer, sub-micrometric, thin-layer metallic membranes were fabricated by combining photolithography, physical and chemical vapor deposition, selective etching, and Si micromachining. These structures were characterized by using optical and atomic force microscopy. Their performance for the production of laser-driven proton beams was tested on a purpose-made table-top Ti:Sapphire laser system running at 3 TW peak power with a contrast over ASE of 108. We have performed several test series achieving maximum proton energy values around 2 MeV.This work has made use of the Spanish ICTS Network MICRONANOFABS partially supported by MEINCOM. This project has been financed by the Spanish Ministry for Economy and Competitiveness within the Retos- Colaboración 2015 initiative, ref. RTC-2015-3278-1. P. Mur has received a grant of the Garantía Juvenil 2015 program.Zaffino, R.; Seimetz, M.; Ruiz-De La Cruz, A.; Sánchez, I.; Mur, P.; Bellido-Millán, PJ.; Lera, R.... (2018). Wafer-scale fabrication of target arrays for stable generation of proton beams by laser-plasma interaction. Journal of Physics: Conference Series (Online). 1079. https://doi.org/10.1088/1742-6596/1079/1/012007S0120071079Abedi, S., Dorranian, D., Abari, M. E., & Shokri, B. (2011). Relativistic effects in the interaction of high intensity ultra-short laser pulse with collisional underdense plasma. Physics of Plasmas, 18(9), 093108. doi:10.1063/1.3633529Antici, P., Fuchs, J., d’ Humières, E., Lefebvre, E., Borghesi, M., Brambrink, E., … Pépin, H. (2007). Energetic protons generated by ultrahigh contrast laser pulses interacting with ultrathin targets. Physics of Plasmas, 14(3), 030701. doi:10.1063/1.2480610Ceccotti, T., Lévy, A., Popescu, H., Réau, F., D’Oliveira, P., Monot, P., … Martin, P. (2007). Proton Acceleration with High-Intensity Ultrahigh-Contrast Laser Pulses. Physical Review Letters, 99(18). doi:10.1103/physrevlett.99.18500

Efficient proton acceleration from a 3 TW table-top laser interacting with submicrometric mass-produced solid targets

[EN] Thin layer membranes with controllable features and material arrangements are often used as target materials for laser driven particle accelerators. Reduced cost, large scale fabrication of such membranes with high reproducibility, and good stability are central for the efficient production of proton beams. These characteristics are of growing importance in the context of advanced laser light sources where increased repetition rates boost the need for consumable targets with design and properties adjusted to study the different phenomena arising in ultra-intense laser-plasma interaction. Wepresent the fabrication of sub-micrometric thin-layer gold or aluminum membranes in a silicon wafer frame by using nano/micro-electro-mechanical-system (N/MEMS) processing which are suitable for rapid patterning and machining of many samples at the same time and allowing for high-throughput production of targets for laser-driven acceleration. Obtained targets were tested for laserproton acceleration through the Target Normal Sheath Acceleration mechanism (TNSA) in a series of experiments carried out on a purpose-made table-top Ti:Sa running at 3 TW peak power and 10 Hz diode pump rate with a contrast over ASE of 10(8)The authors highly appreciate the collaboration of Radosys (Budapest) which provided CR-39 detector material, etching bath, and readout equipment. This project has been financed by the Spanish Ministry for Economy and Competitiveness within the Retos-Colaboracion 2015 initiative, ref. RTC-2015-3278-1. P Mur has received a grant of the Garantia Juvenil 2015 program. This work has made use of the Spanish ICTS Network MICRONANOFABS partially supported by MEINCOM.Zaffino, R.; Seimetz, M.; Ruiz-De La Cruz, A.; Sánchez, I.; Mur, P.; Quirión, D.; Bellido-Millán, PJ.... (2018). Efficient proton acceleration from a 3 TW table-top laser interacting with submicrometric mass-produced solid targets. Journal of Physics Communications. 2(4):1-6. https://doi.org/10.1088/2399-6528/aabc25S1624Borghesi, M., Campbell, D. H., Schiavi, A., Haines, M. G., Willi, O., MacKinnon, A. J., … Bulanov, S. (2002). Electric field detection in laser-plasma interaction experiments via the proton imaging technique. Physics of Plasmas, 9(5), 2214-2220. doi:10.1063/1.1459457Ledingham, K., Bolton, P., Shikazono, N., & Ma, C.-M. (2014). Towards Laser Driven Hadron Cancer Radiotherapy: A Review of Progress. Applied Sciences, 4(3), 402-443. doi:10.3390/app4030402Spindloe, C., Arthur, G., Hall, F., Tomlinson, S., Potter, R., Kar, S., … Tolley, M. K. (2016). High volume fabrication of laser targets using MEMS techniques. Journal of Physics: Conference Series, 713, 012002. doi:10.1088/1742-6596/713/1/012002Schomburg, W. K. (2011). Thin Films. RWTHedition, 9-20. doi:10.1007/978-3-642-19489-4_4Bellido, P., Lera, R., Seimetz, M., Cruz, A. R. la, Torres-Peirò, S., Galán, M., … Benlloch, J. M. (2017). Characterization of protons accelerated from a 3 TW table-top laser system. Journal of Instrumentation, 12(05), T05001-T05001. doi:10.1088/1748-0221/12/05/t05001Mayer, M. (1999). SIMNRA, a simulation program for the analysis of NRA, RBS and ERDA. AIP Conference Proceedings. doi:10.1063/1.59188Ceccotti, T., Lévy, A., Popescu, H., Réau, F., D’Oliveira, P., Monot, P., … Martin, P. (2007). Proton Acceleration with High-Intensity Ultrahigh-Contrast Laser Pulses. Physical Review Letters, 99(18). doi:10.1103/physrevlett.99.185002Dollar, F., Reed, S. A., Matsuoka, T., Bulanov, S. S., Chvykov, V., Kalintchenko, G., … Maksimchuk, A. (2013). High-intensity laser-driven proton acceleration enhancement from hydrogen containing ultrathin targets. Applied Physics Letters, 103(14), 141117. doi:10.1063/1.4824361Neely, D., Foster, P., Robinson, A., Lindau, F., Lundh, O., Persson, A., … McKenna, P. (2006). Enhanced proton beams from ultrathin targets driven by high contrast laser pulses. Applied Physics Letters, 89(2), 021502. doi:10.1063/1.2220011Green, J. S., Carroll, D. C., Brenner, C., Dromey, B., Foster, P. S., Kar, S., … Zepf, M. (2010). Enhanced proton flux in the MeV range by defocused laser irradiation. New Journal of Physics, 12(8), 085012. doi:10.1088/1367-2630/12/8/085012Giuffrida, L., Svensson, K., Psikal, J., Dalui, M., Ekerfelt, H., Gallardo Gonzalez, I., … Margarone, D. (2017). Manipulation of laser-accelerated proton beam profiles by nanostructured and microstructured targets. Physical Review Accelerators and Beams, 20(8). doi:10.1103/physrevaccelbeams.20.08130