| 1. |
- Albert, F, et al.
(författare)
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Laser produced X-ray source in the 10-60 keV range at 1 kHz. Modified irradiation schemes in order to reach medical imaging quality
- 2001
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339. ; 11:PR2, s. 429-432
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Tidskriftsartikel (refereegranskat)abstract
- By tightly focusing ultra-short pulses from a Ti:sapphire terawatt laser onto a high-Z metallic target, hard x-ray pulses of short duration are produced. In most of our previous work concerning x-rays, a 150 mJ laser pulse with a 110 A duration has been used. Using mostly tin and tantalum targets, hard x-rays in the 10-60 keV range have been produced and used in differential absorption imaging around the K-alpha absorption edge of a contrast agent and also in imaging employing gated viewing for suppression of scattered radiation. In order to increase the x-ray yield (shortening the acquisition time) an increase in the laser repetition rate is desirable while still staying in the K-alpha energy regime. We have used a I kHz repetition-rate laser delivering 35 fs pulses in order to work towards these goals. We have clear evidence of hard x-ray generation above 30 keV, even for low laser pulse energies. We also studied the effect of a fs prepulse. The medical imaging capability of the source was explored. The use of a prepulse has been optimized in order to improve the image quality as well as the overall x-ray generation yield.
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| 2. |
- ANDERSSON, CBM, et al.
(författare)
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CORE-LEVEL PHOTOEMISSION FROM (III)-TYPE INAS SURFACES
- 1994
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 4:C9, s. 209-212
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Tidskriftsartikel (refereegranskat)abstract
- The InAs(111)2x2 and InAs(($$$) over bar 111)1x1 surfaces have been studied with high resolution core level spectroscopy. For the InAs(($$$) over bar 111)1x1 surface both the In 4d and the As 3d core levels display strong surface core level shifts, while for the InAs(111)2x2 surface only the In 4d level shows a detectable surface shift. The results indicate that the InAs(($$$) over bar 111)1x1 surface is relaxed, with atom layer displacement extending to subsurface layers. Unexpectedly, we find no surface shifted anion core level for the InAs(111)2x2 surface.
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| 3. |
- Andersson, Magnus, et al.
(författare)
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Effect of Prestraining and Training on the γ→ε Transformation in Fe-Mn-Si Alloys
- 1995
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 5:C8, s. 457-462
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Tidskriftsartikel (refereegranskat)abstract
- The effect of training and predeformation on the martensitic transformation is investigated. It is concluded that MS as a function of predeformation strain must have a maximum at around 3% strain. Prestrains less than 5% will enhance the martensitic transformation whereas larger prestrains depress it due to strain hardening of the γ phase.
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| 4. |
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| 5. |
- Andersson, Magnus, et al.
(författare)
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The Influence of External Stresses on the Transformation Behaviour in a Fe-Mn-Si Alloy
- 1997
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 7:C5, s. 411-416
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Tidskriftsartikel (refereegranskat)abstract
- The influence of external stresses on the transformation behaviour has been studied for a polycrystalline Fe-3 IMn-SSi alloy exhibiting the y-+& martensitic transformation. Samples have been loaded at temperatures above the M, temperature, cooled with a constant external load to a temperature below the M, temperature and subsequently heated without load to a temperature above the A, temperature of the alloy. Stress, strain and temperature have been continuously measured and transformation temperatures and strains have been determined from the change in strain during the transformation. It has been found that the M, temperature during cooling with load is not influenced by 0.3-2 % plastic pre-deformation of the austenite whereas there is a substantial increase in the transformation strain, i.e. variants with a favourable orientation are enhanced by pre-strain of austenite.
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| 6. |
- Astrath, N. G. C., et al.
(författare)
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Thermal lens and photoacoustic spectroscopy to determine the thermo-optical properties of semiconductors
- 2005
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 125, s. 181-183
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Tidskriftsartikel (refereegranskat)abstract
- In this work we used photoacoustic and thermal lens spectroscopy to study four different semiconductor samples: PbI2, 4HSiC, NiCrO and NiO. The results showed that the combination of these two techniques provided the values of the band gap energies and the thermal diffusivities.
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| 7. |
- Bertolo, M, et al.
(författare)
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Photoemission spectromicroscopy study of a Bi2Sr2CaCu2O8+delta single crystal
- 2003
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Ingår i: Journal de Physique IV - Proceedings. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 104, s. 487-490
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Konferensbidrag (refereegranskat)abstract
- Using photoemission spectromicroscopy at sub-micron lateral resolution we studied two superconductor systems of high fundamental and practical importance, such as Bi2Sr2CaCu2O8+delta and MgB2. Our findings demonstrate the importance of considering, for this class of systems, the possible presence of spatial inhomogeneities in interpreting the results of conventional photoemission experiments, which typically probe an area of the order of 1 mm(2). In particular, in the case of MgB2, we report a measured density of states directly comparable to the theoretical predictions, thus rejecting the claim for the existence of strong correlation effects proposed by previous spatially averaged measurements.
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| 8. |
- Bhand, Sunil, et al.
(författare)
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Coupled biosensor, biomimetic and chemometrics strategies for analysis of the metals in complex environmental matrices
- 2003
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Ingår i: Journal de Physique IV - Proceedings. - : EDP Sciences. - 1764-7177 .- 1155-4339. ; 107, s. 169-172
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Konferensbidrag (refereegranskat)abstract
- An analytical strategy to determine metals in environmental samples contaminated with both organophosphate pesticides and metals is presented. In the first step, parathion and arsenate were determined separately. Inhibition of the enzyme butyrylcholinesterase was quantified employing an enzyme thermistor and also with a CCD camera. Subsequently, parathion mixed with arsenate was measured. A molecularly imprinted polymer catalyst was then introduced as a pre-column to degrade OPs. The catalytic MIP enabled the measurement of metal from the mixture containing OPs. Hydrolysis of parathion, ethyl paraoxon, O-Ethyl-O-(4-nitrophenyl)-phenylphosphonothioate EPN and dichlorvos were monitored by using catalytic MIPs in the enzyme thermistor. Finally, inhibition patterns of parathion and arsenate were obtained employing multivariate analysis. The patterns generated after eliminating the OPs can be used for monitoring and mapping of metals in various environmental matrices.
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| 9. |
- Bhattacharya, Prosun, et al.
(författare)
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Geogenic arsenic in groundwaters from Terai Alluvial Plain of Nepal
- 2003
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 107, s. 173-176
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Tidskriftsartikel (refereegranskat)abstract
- The origin and mobility of arsenic (As) in the groundwater environment has received serious attention in recent years. Recent studies have reported naturally occurring As in groundwaters of the Terai Alluvial Plains (TAP) in southern Nepal, where groundwater exploitation has increased since the 1960s. The source of As in TAP is geogenic and leached primarily due to weathering of As bearing rocks and sediments in the Himalayas. In our present study, we have investigated the groundwater chemistry in the central part of the TAP in Nawalparasi district. TAP groundwaters are near-neutral to alkaline, with predominantly reducing character and high HCO3-, low SO4- and NO3- concentrations. Elevated HCO3 levels possibly result due to the oxidation of organic matter, low SO42- levels reflect sulfate reduction. Elevated NH4+ concentrations in these groundwaters suggest dissimilatory nitrate reduction in the aquifers. Total arsenic (As,.,) levels in groundwater varied from 1.7 mug/L to as high as 404 mug/L with dominance of As(III) species and elevated levels of dissolved Fe and Mn. Arsenic is mobilized in groundwaters as a result of desorption of As-oxyanions adsorbed onto Fe- and Mn-oxides as well as reductive dissolution of these surface reactive phases from the sediments along with release of As in anoxic groundwaters.
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| 10. |
- da Silva, A. F., et al.
(författare)
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Electronic properties of intrinsic and heavily doped AlN and GaN
- 2006
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 132, s. 105-110
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Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical study of the electronic structure, optical properties, and the effective masses of AlN and GaN based on the local density approximation (LDA) within the density functional theory (DFT), employing the first-principles, full-potential linearized augmented plane wave method. We also describe the effects on the electronic properties of the semiconductors due to heavily n- and p-type doping. The critical concentration N-c for the doping-induced metal-nonmetal (MNM) transition in both n- and p-type is calculated.
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