Production of ultracollimated bunches of multi-MeV electrons by 35 fs laser pulses propagating in exploding-foil plasmas

Very collimated bunches of high energy electrons have been produced by focusing super-intense femtosecond laser pulses in submillimeter under-dense plasmas. The density of the plasma, preformed with the laser exploding-foil technique, was mapped using Nomarski interferometry. The electron beam was fully characterized: up to 10(9) electrons per shot were accelerated, most of which in a beam of aperture below 10(-3) sterad, with energies up to 40 MeV. These measurements, which are well modeled by three-dimensional numerical simulations, validate a reliable method to generate ultrashort and ultracollimated electron bunches. (C) 2002 American Institute of Physics.

Acetaldehyde Production in the Direct Ethanol Fuel Cell: Mechanistic Elucidation by Density Functional Theory

This study employs density functional theory (DFT) calculations to examine the mechanism by which acetaldehyde is formed on platinum in a typical direct ethanol fuel cell (DEFC). A pathway is found involving the formation of a strongly hydrogen-bonded complex between adsorbed ethanol and the surface hydroxyl (OH) species, followed by the facile alpha-dehydrogenation of ethanol, with spontaneous weakening of the hydrogen bond in favor of adsorbed acetaldehyde and water. This mechanism is found to be comparably viable on both the close-packed surface and the monatomic steps. Comparison of further reactions on these two sites strongly indicates that the steps act as net removers of acetaldehyde from the product stream, while the flat surface acts as a net producer.

Food intake, milk production, and tissue changes of Holstein-Friesian and Jersey x Holstein-Friesian dairy cows within a medium-input grazing system and a high-input total confinement system

Although interest in crossbreeding within dairy systems has increased, the role of Jersey crossbred cows within high concentrate input systems has received little attention. This experiment was designed to examine the performance of Holstein-Friesian (HF) and Jersey x Holstein-Friesian (J x HF) cows within a high concentrate input total confinement system (CON) and a medium concentrate input grazing system (GRZ). Eighty spring-calving dairy cows were used in a 2 (cow genotype) x 2 (milk production system) factorial design experiment. The experiment commenced when cows calved and encompassed a full lactation. With GRZ, cows were offered diets containing grass silage and concentrates [70:30 dry matter (DM) ratio] until turnout, grazed grass plus 1.0 kg of concentrate/day during a 199-d grazing period, and grass silage and concentrates (75:25 DM ratio) following rehousing and until drying-off. With CON, cows were confined throughout the lactation and offered diets containing grass silage and concentrates (DM ratio; 40:60, 50:50, 40:40, and 75:25 during d 1 to 100, 101 to 200, 201 to 250, and 251 until drying-off, respectively). Full-lactation concentrate DM intakes were 791 and 2,905 kg/cow for systems GRZ and CON, respectively. Although HF cows had a higher lactation milk yield than J x HF cows, the latter produced milk with a higher fat and protein content, so that solids-corrected milk yield (SCM) was unaffected by genotype. Somatic cell score was higher with the J x HF cows. Throughout lactation, HF cows were on average 37 kg heavier than J x HF cows, whereas the J x HF cows had a higher body condition score. Within each system, food intake did not differ between genotypes, whereas full-lactation yields of milk, fat plus protein, and SCM were higher with CON than with GRZ. A significant genotype x environment interaction was observed for milk yield, and a trend was found for an interaction with SCM. Crossbred cows on CON gained more body condition than HF cows, and overall pregnancy rate was unaffected by either genotype or management system. In summary, milk and SCM yields were higher with CON than with GRZ, whereas genotype had no effect on SCM. However, HF cows exhibited a greater milk yield response and a trend toward a greater SCM yield response with increasing concentrate levels compared with the crossbred cows.

High power laser production of short-lived isotopes for positron emission tomography

Positron emission tomography (PET) is a powerful diagnostic/imaging technique requiring the production of the short-lived positron emitting isotopes C-11, N-13, O-15 and F-18 by proton irradiation of natural/enriched targets using cyclotrons. The development of PET has been hampered due to the size and shielding requirements of nuclear installations. Recent results show that when an intense laser beam interacts with solid targets, megaelectronvolt (MeV) protons capable of producing PET isotopes are generated. This report describes how to generate intense PET sources of C-11 and F-18 using a petawatt laser beam. The work describing the laser production of F-18 through a (p,n) O-18 reaction, and the subsequent synthesis of 2-[F-18] is reported for the first time. The potential for developing compact laser technology for this purpose is discussed.

Laser generation of proton beams for the production of short-lived positron emitting radioisotopes

Protons of energies up to 37 MeV have been generated when ultra-intense lasers (up to 10(20) W cm(-2)) interact with hydrogen containing solid targets. These protons can be used to induce nuclear reactions in secondary targets to produce P-emitting nuclei of relevance to the nuclear medicine community, namely C-11 and N-13 via (p, n) and (p, alpha) reactions. Activities of the order of 200 kBq have been measured from a single laser pulse interacting with a thin solid target. The possibility of using ultra-intense lasers to produce commercial amounts of short-lived positron emitting sources for positron emission tomography (PET) is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

Production of radioactive nuclides by energetic protons generated from intense laser-plasma interactions

Nuclear activation has been observed in materials exposed to the ablated plasma generated from high intensity laser-solid interactions (at focused intensities up to 2x10(19) W/cm(2)) and is produced by protons having energies up to 30 MeV. The energy spectrum of the protons is determined from these activation measurements and is found to be consistent with other ion diagnostics. The possible development of this technique for

Biorefining of perennial ryegrass for the production of nano-fibrillated cellulose

This study has demonstrated biorefining steps for ryegrass and silage at a pilot scale to extrude fibre cake for the production of nanofibrillated cellulose (NFC), a potentially green biomaterial for replacing conventional fillers in the manufacture of polymer composites. Further treatments of processed ryegrass fibres with mechanical shearing, microfluidising, hydrochloric acid (HCl)/ sulphuric acid and a four stage {ethylenediaminetetra-acetic acid, sodium hydroxide, sodium hypochlorite and HCl} hydrolysis yielded 43.8, 36.1, 25.6 and 39.8 kg t21 DM of NFCs respectively. The NFCs were characterised using microscopy, X-ray diffraction, dynamic light scattering, spectroscopy and thermogravimetry. The NFC had diameters from 3.0–9.1 nm and length 308 nm– 4.6 mm. NFC-polyvinyl alcohol composites containing NFC (5 wt%) exhibited enhanced Young’s modulus and thermal stability by factors of 2.5 and 2 respectively compared with control. The mass, energy, water and chemical balances of the four process steps were assessed to evaluate technical feasibility and also to provide baseline production data for scaling up. The microfluidised product has been identified as the best NFC product, but production cost needs to be reduced.

Production, characterisation and applications of monoclonal antibodies to two novel porcine bocaviruses from swine in Northern Ireland

The production, preliminary characterisation and applications of monoclonal antibodies (mAbs) against two novel swine bocaviruses isolated in cell culture from swine in Northern Ireland are described. Of the 17 stable final clones produced, four were characterised. All were of the IgG2a isotype and showed no cross-reactivity with either bocavirus strain. Partial neutralisation was observed with PBoV4 mAbs and homologous virus. The two mAbs selected for use in antigen-detecting ELISAs were successful in highlighting those fractions containing infectious virus within sucrose gradients. This is the first report of the production of specific reagents that will prove useful in the study of the biology of these viruses and swine bocavirus-associated diseases.