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At least 559 records · Page 31Linked to original sources
PubMed2004

Ultralow emittance, multi-MeV proton beams from a laser virtual-cathode plasma accelerator.

The laminarity of high-current multi-MeV proton beams produced by irradiating thin metallic foils with ultraintense lasers has been measured. For proton energies >10 MeV, the transverse and longitudinal emittance are, respectively, <0.004 mm mrad and <10(-4) eV s, i.e., at least 100-fold and may be as much as 10(4)-fold better than conventional accelerator beams. The fast acceleration being electrostatic from an initially cold surface, only collisions with the accelerating fast electrons appear to limit the beam laminarity. The ion beam source size is measured to be <15 microm (FWHM) for proton energies >10 MeV.

Journal Article↗
PubMed2001

In situ XAFS study on cathode materials for lithium-ion batteries.

Ni and Co K-edge X-ray absorption spectra of LiNi0.8Co0.2O2 have been collected using in situ coin cells. To investigate the electronic and structural changes accompanied by the capacity fading during electrochemical cycling and keeping batteries at high temperatures, the cells with different cycling states and keeping conditions (temperature, time) were prepared. Upon charging the cell, the Ni and Co K absorption edge shifted towards higher energy, and the good correlation between the range of chemical shifts upon charging and the capacity of the cell was observed. From quantitative analysis of EXAFS data, it was revealed that the capacity fading is closely related to the Jahn-Teller distortion of the NiO6 octahedron.

Journal Article↗
PubMed2001

In situ XAS study of LixNi0.7Fe0.15Co0.15O2 cathode material.

We have examined the oxidation states and local atomic structures of Ni, Fe, and Co in Li(x)Ni0.7Fe0.15Co0.15O2 as a function of Li content during the first charge in a Li/Li(x)Ni0.7Fe0.15Co0.15O2 nonaqueous cell. We show that the composition of the material in the pristine state is more accurately described by Li0.95Ni(II)0.09Ni(III)0.66Fe(III)0.15Co(III)0.25O2 Half of the Ni(II) resides in Li-vacant sites. Both Fe and Co substitute for Ni within the NiO2 slabs with no significant amounts of Fe or Co that can be attributed to Li-vacant sites. The local structure parameters are consistent with oxidation states observed on the basis of the XANES data. The Ni K-edge energy continuously shifts to a higher energy with decrease in Li content due to oxidation of Ni(II) to Ni(II) and Ni(III) to Ni(IV). After the complete oxidation of Ni(III) to Ni(IV), the Fe K-edge energy begins to increase with further decrease in Li content indicating the oxidation of Fe(III) to Fe(IV). The Co K-edge energy at half-height, on the other hand, is unchanged during the whole range of Li deintercalation indicating that no significant change in the oxidation state of Co occurs upon the complete removal of Li.

Journal Article↗
PubMed2001

XAFS study of LiCo1-xFexO2 cathode for rechargeable lithium battery by laboratory XAFS spectrometer.

The change of local structure in layered-rock-salt-type iron doped lithium cobaltate LiCo(1-x)Fe(x)O2 under electrochemical Li de-intercalation (charge) /re-intercalation (discharge) was studied by a laboratory type XAFS spectrometer. In Co K-XANES and Fe K-XANES of LiCo0.85Fe0.15O2 the absorption peak shifted to higher energy by 1.5-2eV for Co K-edge and by 2-2.5eV for Fe K-edge, respectively, after the first charge. The spectra returned close to initial position and had almost original shape after the first discharge. In Co K- and Fe K-EXAFS of LiCo0.85Fe0.15O2 during the first charge and discharge the reversible change of the local structure was observed mainly around the Co atoms although the partly irreversible change of the local structure was found around the Fe atoms. The variation of local structure occurred in similar manner for the samples with x=0.05 and 0.25. This indicates that both Co3+/Co4+ and Fe3+/Fe4+ redox reactions occur reversibly during the first charge and discharge.

Journal Article↗
PubMed1995

Rabbit liver class III alcohol dehydrogenase: a cathodic isoform with formaldehyde dehydrogenase activity.

Electrophoresis of rabbit liver homogenate on starch gel followed by activity staining revealed multiple forms of alcohol dehydrogenase (ADH) which, based on their electrophoretic mobilities, had been tentatively labeled as class "I," class "II," and class "III" ADHs. The class II enzyme has now been purified to homogeneity by ion exchange and affinity chromatography and, except for an isoelectric point of 7.7, closely resembles human class III ADH. It is a homodimer of molecular weight near 80,000 with a similar amino acid composition and comparable kinetic parameters for the oxidation of primary alcohols. Like the rat, human, and Escherichia coli class III ADHs, the rabbit enzyme is a glutathione-dependent formaldehyde dehydrogenase, and catalyzes the oxidation of S-hydroxymethylglutathione and the hemithiolacetal of 8-thiooctanoic acid. Ethanol up to 3 M does not saturate the enzyme, whereas longer chain primary alcohols exhibit Michaelis-Menten kinetics.

Aldehyde Oxidoreductases↗
PubMed1984

Working with cathode-ray tube based visual display units.

Eye strain when working with visual display units might be due to bad ergonomics but also to eye functions not meeting the demands. If the symbol on the screen has a 4 mm height and the working distance is 60 cm, a visual acuity of 0.4 is required. However to read with ease in the long run a visual acuity of 0.7 is needed. Therefore the employee's visual acuity and refraction must be examined when newly employed, at the age of forty, then every fifth year and when having problems. Other eye dysfunctions could be revealed from questionnaires.

Asthenopia↗
PubMed1992

Human efficiency for visual detection of targets on cathode ray tube displays using a two-level multiple-channel time history format.

Human observers were tested for their ability to detect targets on visual displays. The displays simulated the multiple-channel time history format, using two levels of intensity encoding. A target was presented on 50% of the trials at a constant bearing. Observers indicated their judgment as to whether a target was present by using a four-category rating scale. Receiver-operating characteristics (ROCs) were generated from the rating data and compared to ROCs for an optimal detector. In experiment I, data were collected for two signal-to-noise ratios and for 32, 64, and 128 lines of data. Results indicated that observers were 3-5 dB less sensitive than an optimal detector. Performance improved as the number of lines increased but not to the extent predicted by optimal integration of information across lines of the display. In experiment II, the bearing at which subjects judged whether a target was present, was clearly delineated from the background by encoding information presented at this bearing in red. The purpose of experiment II was to determine the degree to which human inefficiency in detecting targets is due to the inability to focus on a single column of data. Subject performance improved when the red encoding was utilized, but subjects still performed 2 dB below ideal. This suggests that subjects use a suboptimal decision rule for judging the presence of the target.

Attention↗