An ultra-high gain and efficient amplifier based on Raman amplification in plasma.

Raman amplification arising from the excitation of a density echelon in plasma could lead to amplifiers that significantly exceed current power limits of conventional laser media. Here we show that 1-100 J pump pulses can amplify picojoule seed pulses to nearly joule level. The extremely high gain also leads to significant amplification of backscattered radiation from "noise", arising from stochastic plasma fluctuations that competes with externally injected seed pulses, which are amplified to similar levels at the highest pump energies. The pump energy is scattered into the seed at an oblique angle with 14 J sr-1, and net gains of more than eight orders of magnitude. The maximum gain coefficient, of 180 cm-1, exceeds high-power solid-state amplifying media by orders of magnitude. The observation of a minimum of 640 J sr-1 directly backscattered from noise, corresponding to ≈10% of the pump energy in the observation solid angle, implies potential overall efficiencies greater than 10%.

Three electron beams from a laser-plasma wakefield accelerator and the energy apportioning question.

Laser-wakefield accelerators are compact devices capable of delivering ultra-short electron bunches with pC-level charge and MeV-GeV energy by exploiting the ultra-high electric fields arising from the interaction of intense laser pulses with plasma. We show experimentally and through numerical simulations that a high-energy electron beam is produced simultaneously with two stable lower-energy beams that are ejected in oblique and counter-propagating directions, typically carrying off 5-10% of the initial laser energy. A MeV, 10s nC oblique beam is ejected in a 30°-60° hollow cone, which is filled with more energetic electrons determined by the injection dynamics. A nC-level, 100s keV backward-directed beam is mainly produced at the leading edge of the plasma column. We discuss the apportioning of absorbed laser energy amongst the three beams. Knowledge of the distribution of laser energy and electron beam charge, which determine the overall efficiency, is important for various applications of laser-wakefield accelerators, including the development of staged high-energy accelerators.

Possible side reactions due to water in emulsion polymerization by late transition metal complexes. 1. Water complexation and hydrolysis of the growing chain.

The transition metal catalyzed ethylene polymerization in aqueous emulsion has been increasingly successful in the last couple of years. Water however adversely affects the polymerization process by (a) competing with ethylene for the binding site at the metal and (b) hydrolyzing the growing chain. Neutral salicylaldiminato and cationic diimine complexes of Ni and Pd with different substituent patterns are studied here by density functional theory to determine their propensity toward water complexation and hydrolysis of the growing chain. Experimental NMR studies have also been carried out on the protonolysis of the Ni(II)-based Grubbs catalyst. It is found that in general that (a) ethylene coordination is preferred over water coordination for both Ni and Pd catalysts and (b) hydrolysis of the metal alkyl bond is competitive to ethylene insertion.

Should the tradition of right cerebral hemisphere shunting still prevail?

A review of the literature suggests that the right hemisphere compared with the left may be more sensitive to, and take longer to recover from, cerebral trauma. As there are also grounds for suggesting that shunting may be associated with limited cerebral insult, it is possible to conclude that, theoretically, left hemisphere shunting may be a preferable policy.

Right-hemisphere function in hydrocephalic children.

Right-hemisphere function was assessed in 28 hydrocephalic children by a colour-naming divided visual field task and a matching-to-sample manipulo-spatial task. A complementary word-naming divided visual field task was also administered. Comparisons with non-handicapped children revealed a visual processing deficit only. An interpretation of perceptual asymmetries in terms of differential hemispheric sensitivity and regional cortical thinning is advanced.

Germination of Rhizopus oligosporus Sporangiospores.

The morphology of Rhizopus oligosporus (NRRL 2710) sporangiospores and their physiological requirements for germination were studied. Germination proceeded in two separable phases: phase I (swelling) and phase II (germ tube protrusion). The optimal conditions for germination were 42 degrees C and pH 4.0. Sporangiospores contained insufficient endogenous carbon for swelling or germination to occur in distilled water. Initial swelling during phase I occurred only in the presence of a suitable carbohydrate. Subsequent production of germ tubes during phase II required exogenous sources of both carbon and nitrogen. Spores germinated most rapidly in mixtures of amino acids; l-proline and l-alanine were the most effective. These amino acids, at concentrations as low as 10 M, supported germination when combined with glucose and McIlvaine (citric acid-phosphate) buffer. d-Glucose, d-xylose, and d-mannose were the most effective carbohydrates tested for promotion of germination.

Visual asymmetry on a color-naming task: a longitudinal study with primary school children.

Visual half-field asymmetries on a unilateral, monocularly presented tachistoscopic color-naming task for a 5- and a 7-year-old cohort were were remeasured after a 2-year interval and after a 1-year interval for a 10-year-old cohort. The curvilinear developmental trend observed on the first occasion of testing was fitted to a second-order polynomial equation, and this was used to predict mean laterality indices for each cohort on retesting. Null hypotheses were advanced that the mean values observed on retesting would not depart significantly from predicted means. These null hypotheses were upheld and an explanation of the curvilinear developmental trend in terms of changes in information-processing strategies is advanced.

An immunoanalysis for kojic acid.

An enzyme-linked immunosorbent assay (ELISA) was developed for the analysis of kojic acid in aqueous solutions and biological fluids. As little as 100 pg kojic acid ml-1 was detected in standard buffer. Analysis of biological fluids containing 1 mg kojic acid ml-1 showed that ELISA could detect the toxin at dilutions of 10(-4) in urine, deporteinated plasma, or serum. Urine and plasma samples collected form rabbits dosed intravenously with 56 mg kojic acid kg-1 body weight gave positive tests at dilutions of 10(-4). The immunoassay described may be used for detection of kojic acid produced during experimental or clinical aspergillosis.

Visual asymmetry on a color-naming task: a developmental perspective.

5-, 7-, and 10-yr.-old children were tested on a lateralized color-naming task, the colors being presented unilaterally and monocularly. Each age group was composed of 20 boys and 20 girls. A significant effect of age was found, with the greatest perceptual asymmetry (a significant left visual-field effect) being observed for the 5-yr.-old group, and the smallest perceptual asymmetry for the 7-yr.-old group.

Aflatoxin localization by the enzyme-linked immunocytochemical technique.

Visualization of aflatoxin deposits within Aspergillus parasiticus ATCC 15517 hyphae was made possible by using an enzyme-linked immunocytochemical technique.

Enzyme-linked immunosorbent analysis for aflatoxin B1.

An enzyme-linked immunosorbent analysis (ELISA) permitted the detection of less than 10 pg of aflatoxin B1 per ml. The antitoxin was most specific for aflatoxins B1 and B2alpha, and least specific for aflatoxin G1.