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Bulk high-temperature superconducting materials can trap magnetic fields up to an order of magnitude larger than conventional permanent magnets. Recent advances in pulsed field magnetization (PFM) techniques now provide a fast and cost-effective method to magnetize bulk superconductors to fields of up to 5 T. We have developed a portable, desktop bulk high-temperature superconducting magnet system by combining advanced PFM techniques with state-of-the-art cryocooler technology and single-grain, REâ€"Baâ€"Cuâ€"O [(RE)BCO, where RE is a rare-earth element or yttrium] bulk superconducting materials. The base temperature of the system is 41 K and it takes about 1 h for the system to cool down to 50 K from room temperature. A capacitor bank, combined with easily-interchangeable, solenoid- or split-type copper magnetizing coils and an insulated bipolar gate transistor acting as a high-speed switch, allows magnetic pulses to be generated with different pulse profiles. The system is capable of trapping magnetic fields of up to ∼3 T. In this work, we report the results of the magnetization of a range of single-grain Yâ€"Baâ€"Cuâ€"O, Euâ€"Baâ€"Cuâ€"O and Gdâ€"Baâ€"Cuâ€"O (GdBCO), bulk superconducting discs using this system. A higher trapped field was recorded using a split coil incorporating iron yokes at temperatures of 65 K and above, whereas at lower temperatures, a higher trapped field was obtained using the solenoid coil. The GdBCO sample achieved the highest trapped field for both single-pulse (SP) and two-stage-multi-pulse (TSMP) methods using the solenoid coil. Maximum trapped fields of 2.26 T at 55 K and 2.85 T at 49 K were recorded at the centre of the top surface of the GdBCO sample for the SP and TSMP methods, respectively. The PFM process is substantially an adiabatic process so, therefore, the thermal contact between the sample and sample holder is of critical importance for cooling the bulk sample during application of the pulse. The design of the sample holder can be modified easily to enhance the thermal stability of the sample in order to achieve a higher trapped field. [ABSTRACT FROM AUTHOR]

Bulk superconductors can act as trapped-field magnets with the potential to be used for many applications such as portable medical magnet systems and rotating machines. Maximising the trapped field, particularly for practical magnetisation techniques such as pulsed field magnetisation (PFM), still remains a challenge. PFM is a dynamic process in which the magnetic field is driven into a superconducting bulk over milliseconds. This flux motion causes heating and a complex interplay between the magnetic and thermal properties. In this work, the local flux density during PFM in a MgB2 bulk superconductor has been studied. We find that improving the cooling architecture increases the flux trapping capabilities and alters the flux motion during PFM. These improvements lead to the largest trapped field (0.95 T) for a single MgB2 bulk sample magnetised by a solenoidal pulsed field magnet. The findings illustrate the fundamental role bulk cooling plays during PFM. [ABSTRACT FROM AUTHOR]

Here, we extend flatbed scanner calibrations of GafChromic EBT3, MD-V3, and HD-V2 radiochromic films using high-precision x-ray irradiation and monoenergetic proton bombardment. By computing a visibility parameter based on fractional errors, optimal dose ranges and transitions between film types are identified. The visibility analysis is used to design an ideal radiochromic film stack for the proton energy spectrum expected from the interaction of a petawatt laser with a cryogenic hydrogen jet target. [ABSTRACT FROM AUTHOR]

The effect of ambient air pressure on the redeposition of debris, ablated from the zinc borosilicate glass target using 6 ns, 266 nm laser pulses, has been studied for incident fluences of 3–18 J/cm2. Measurements were carried out in air at pressures ranging from 10–750 Torr. Scanning electron microscopy and optical microscope observations of the target surface were made to analyze the morphology of the redeposited debris. It was found that for higher values of the laser fluence and ambient pressure, the target surface is extremely rough, with large pieces of molten glass and debris fragments deposited near and around the ablation site. The profile of the redeposited debris also shows signs of a strong shock-wave-cleaning effect and possibly a Rayleigh-Taylor instability at higher pressures. Contrary to this, under low-pressure environment the surface of the redeposited debris is cleaner and smoother, with minimal damage around the ablated crater. The measured radius of the debris field was found to be proportional to the inverse cube root of the ambient pressure, consistent with the stagnation distance of the expansion plume when energy balance with the displaced air is considered. In addition to this, the mass of the redeposited debris was estimated from the measured optical thickness of the film and compared to the ablated mass. In the range below 100 Torr, both the mass of the redeposited debris and the percentage of the ablated mass which was redeposited were found to increase with the increasing fluence and the ambient air pressure. [ABSTRACT FROM AUTHOR]

Presents information on a study which measured the thermal properties of gadolinium-gallium garnet. Sample characteristics and experimental details; Results and discussion.

Objective To describe the demographic characteristics, clinical features, functional status and quality of life of elderly-onset ( EORA) and young-onset ( YORA) rheumatoid arthritis ( RA) patients in an Asian cohort. Methods We studied all RA patients in our prospective disease registry, utilizing baseline data. EORA was defined as disease onset at 60 years or older. We collected data from January 2001 to December 2012. Results There were 1206 patients in our cohort, of which 178 (14.8%) had EORA, with a mean age of onset of 66.7 ± 5.6 years. There were more males in the EORA than YORA group (23.0% vs. 14.7%, P = 0.005). EORA patients were diagnosed sooner after symptom onset and had a higher number of comorbidities (median 2 [inter-quartile range 1-3] vs. 1 (0-2), P < 0.001). They were less likely to be rheumatoid factor positive, had higher erythrocyte sedimentation rate values and lower hemoglobin concentrations. There was no significant difference in joint counts, Disease Activity Score of 28 joints activity score and prevalence of radiographic erosions. Though EORA patients had worse Health Assessment Questionnaire scores and poorer functional status than YORA ones, they had lower pain scores and higher scores in the general health and mental component summary of the Short Form-36. EORA patients received significantly lower numbers of disease-modifying anti-rheumatic drugs. Conclusions EORA and YORA patients had different demographic characteristics. Although they had similar disease activities, EORA patients received less intensive treatment. EORA patients had a higher number of RA-related co-morbidities and poorer physical functioning but they coped better emotionally and mentally. [ABSTRACT FROM AUTHOR]

Describes a model heterostructure composed of several different manganites of different compositions in which the colossal magnetoresistance is extended over a broad range in temperatures. Evidences presented in the effectiveness of the model; Implications of the temperature variation of the sharp peak in magnetoresistance.

An optical damage threshold for crystalline silicon from single femtosecond laser pulses was determined by detecting a permanent change in the refractive index of the material. This index change could be detected with unprecedented sensitivity by measuring the resonant wavelength shift of silicon integrated optics microring resonators irradiated with femtosecond laser pulses at 400 nm and 800 nm wavelengths. The threshold for permanent index change at 400 nm wavelength was determined to be 0.05360.007 J/cm2, which agrees with previously reported threshold values for femtosecond laser modification of crystalline silicon. However, the threshold for index change at 800 nm wavelength was found to be 0.04460.005 J/cm2, which is five times lower than the previously reported threshold values for visual change on the silicon surface. The discrepancy is attributed to possible modification of the crystallinity of silicon below the melting temperature that has not been detected before. [ABSTRACT FROM AUTHOR]

Using both experiment and 2D3V particle-in-cell (PIC) simulations, we describe the use of specular reflectivity measurements to study relativistic (Iλ² > 1018 W/cm²·μm²) laser-plasma interactions for both high and low-contrast 527 nm laser pulses on initially solid density aluminum targets. In the context of hot-electron generation, studies typically rely on diagnostics which, moreoften-than-not, represent indirect processes driven by fast electrons transiting through solid density materials. Specular reflectivity measurements, however, can provide a direct measure of the interaction that is highly sensitive to how the EM fields and plasma profiles, critical input parameters for modeling of hot-electron generation, evolve near the interaction region. While the fields of interest occur near the relativistic critical electron density, experimental reflectivity measurements are obtained centimeters away from the interaction region, well after diffraction has fully manifested itself. Using a combination of PIC simulations with experimentally inspired conditions and an analytic, non-paraxial, pulse propagation algorithm, we calculate reflected pulse properties, both near and far from the interaction region, and compare with specular reflectivity measurements. The experiment results and PIC simulations demonstrate that specular reflectivity measurements are an extremely sensitive qualitative, and partially quantitative, indicator of initial laser/target conditions, ionization effects, and other details of intense laser-matter interactions. The techniques described can provide strong constraints on many systems of importance in ultra-intense laser interactions with matter. [ABSTRACT FROM AUTHOR]

We have developed a laser wakefield generated X-ray probe to directly measure the temporal evolution of the ionization states in warm dense aluminum by means of absorption spectroscopy. As a promising alternative to the free electron excited X-ray sources, Betatron X-ray radiation, with femtosecond pulse duration, provides a new technique to diagnose femtosecond to picosecond transitions in the atomic structure. The X-ray probe system consists of an adjustable Kirkpatrick-Baez (KB) microscope for focusing the Betatron emission to a small probe spot on the sample being measured, and a flat Potassium Acid Phthalate Bragg crystal spectrometer to measure the transmitted X-ray spectrum in the region of the aluminum K-edge absorption lines. An X-ray focal spot size of around 50 μm was achieved after reflection from the platinum-coated 10-cm-long KB microscope mirrors. Shot to shot positioning stability of the Betatron radiation was measured resulting in an rms shot to shot variation in spatial pointing on the sample of 16 μm. The entire probe setup had a spectral resolution of ∼1.5 eV, a detection bandwidth of ∼24 eV, and an overall photon throughput efficiency of the order of 10-5. Approximately 10 photons were detected by the X-ray CCD per laser shot within the spectrally resolved detection band. Thus, it is expected that hundreds of shots will be required per absorption spectrum to clearly observe the K-shell absorption features expected from the ionization states of the warm dense aluminum. [ABSTRACT FROM AUTHOR]

Aus dem Gehirn lebender Tiere können Stamm ‐ /Vorläuferzellen mithilfe von Antikörperkonjugaten magnetischer Nanopartikel (Ab ‐ MNPs) extrahiert werden. Wenn Ab ‐ MNPs in Rattengehirn injiziert werden, lagern sich die Stammzellen an diese an und können auf magnetischem Weg isoliert werden. Außerhalb des Körpers können sie sich zu Neurosphären entwickeln und zu verschiedenen Zellarten differenzieren, während die Ratten gesund weiterleben. [ABSTRACT FROM AUTHOR]

It stems from the magnetism: The extraction of stem/progenitor cells from the brain of live animals is possible using antibodies conjugated to magnetic nanoparticles (Ab‐MNPs). The Ab‐MNPs are introduced to a rat's brain with a superfine micro‐syringe. The stem cells attach to the Ab‐MNPs and are magnetically isolated and removed. They can develop into neurospheres and differentiate into different types of cells outside the subject body. The rat remains alive and healthy. [ABSTRACT FROM AUTHOR]

We provide evidence that a single mechanism--flux flow along channels--can explain the functional form of the critical current density (Jc) in the low-temperature superconductor Nb3Sn and in the high-temperature superconductors (HTS) YBa2Cu3O7-δ (YBCO) and (Bi,Pb)2Sr2Can-1CunOx (BiSCCO) in low and high magnetic fields. In this paper, we show that standard flux pinning theories, used for the past four decades to describe Jc in low-temperature superconductors (LTS), cannot explain the strain dependence of Jc in YBCO because Jc is a function of strain but the average superconducting properties are not. We conclude that in the polycrystalline samples presented here, the channels are grain boundaries that are narrow and metallic in Nb3 Sn and YBCO but wide and semiconducting in BiSCCO. In Nb3Sn, strain alters Jc by changing the superconducting properties of the grains, whereas in YBCO, strain alters Jc by changing the properties of the grain boundaries. [ABSTRACT FROM AUTHOR]

The resolution enhancement of laser-induced forward transfer (LIFT) is investigated through the pre-patterning of Cr on the donor substrate. 85 nm dots are first patterned on a microscope slide, and an 800 nm wavelength and 130 fs pulse laser with a beam waist of ∼9 μm is used to transfer the Cr dots to an acceptor substrate. The threshold fluence is found to be ∼0.15 the threshold fluence of a similar continuous film, which is thought to be due to the fact that no force is needed to tear away Cr from the film itself, unlike in a continuous film experiment. Since the volume of the material limits the transfer feature sizes instead of the laser parameters, as in a continuous film system, minimum transferable feature diameters are significantly lower compared to the continuous film case. Also, the transferred feature diameters are not dependent on the laser parameters, so the diameters are consistent across a wide range of fluences. The force per unit area generated by the laser at threshold fluence is estimated to be ∼3 GPa, which is consistent with previous results in the literature. The simplified model that our pre-patterned Cr LIFT experiment represents would make it an ideal case for benchmarking molecular dynamics simulations of femtosecond laser ablation. [ABSTRACT FROM AUTHOR]

The effect of annealing atmosphere on microstructural and photoluminescence characteristics of multiferroic BiFeO (BFO) thin films deposited by pulsed laser deposition (PLD) technique is reported. The films annealed in oxygen environment showed improved microstructure and photoluminescence (PL) characteristics. The PL spectra of oxygen-annealed BFO thin films at room temperature show a strong emission in the blue region. A plot of ( αE) vs. photon energy ( E) ( α-absorption coefficient) and the linear extrapolation to ( αE)=0 indicates a direct gap at 2.69±0.02 eV, which is in agreement with the previous reports. The results obtained in this study are accordingly expected to facilitate the understanding and optimization of BFO thin films for photovoltaic applications. [ABSTRACT FROM AUTHOR]

Detailed measurements are provided of the engineering critical current density (Jc) and the index of transition (n-value) of two different types of advanced ITER Nb3Sn superconducting strand for fusion applications. The samples consist of one internal-tin strand (OST) and two bronze-route strands (BEAS I and BEAS II--reacted using different heat treatments). Tests on different sections of these wires show that prior to applying strain, Jc is homogeneous to better than 2% along the length of each strand. Jc data have been characterized as a function of magnetic field (B ≤ 14:5 T), temperature (4:2 K ≤ T ≤ 12 K) and applied axial strain (-1% ≤ &egr;A ≤ 0:8%). Strain-cycling tests demonstrate that the variable strain Jc data are reversible to better than 2% when the applied axial strain is in the range of -1% ≤ &egr;A ≤ 0:5%. The wires are damaged when the intrinsic strain (&egr;I) is &egr;I ≥ 0:55% and &egr;I ≥ 0:23% for the OST and BEAS strands, respectively. The strain dependences of the normalized Jc for each type of strand are similar to those of prototype strands of similar design measured in 2005 and 2008 to about 2% which makes them candidate strands for a round-robin interlaboratory comparison. The Jc data are described by Durham, ITER and Josephson-junction parameterizations to an accuracy of about 4%. For all of these scaling laws, the percentage difference between the data and the parameterization is larger when Jc is small, caused by high B, T or &egr;I. The n-values can be described by a modified power law of the form n = 1 + rIsc, where r and s are approximately constant and Ic is the critical current. It has long been known that pivot-points (or cross-overs) in Jc occur at high magnetic field and temperature. Changing the magnetic field or temperature from one side of the pivot-point to the other changes the highest Jc sample to the lowest Jc sample and vice versa. The pivot-point follows the B-T phase boundary associated with the upper critical field and is usually attributed to the different tin content profiles and pinning properties of internal-tin and bronze-route strands. We report that the strain dependence of the pivot-point in these strands is quite different from that of the upper critical field and suggest that its origin in optimized high tin content strands is the proximity of the tetragonal Nb3Sn phase, which has low superconducting critical parameters. [ABSTRACT FROM AUTHOR]

Development of a microfluidic device is generally based on fabrication-design-fabrication loop, as, unlike the microelectronics design, there is no rigorous simulation-based verification of the chip before fabrication. This usually results in extremely long, and hence expensive, product development cycle if micro/nano fabrication facilities are used from the beginning of the cycle. Here, we illustrate a novel approach of device prototyping that is fast, cheap, reliable, and most importantly, this technique can be adopted even if no state-of-the-art microfabrication facility is available. A water-jet machine is used to cut the desired microfluidic channels into a thin steel plate which is then used as a template to cut the channels into a thin sheet of a transparent and cheap polymer material named Surlyn® by using a Hot Knife™. The feature-inscribed Surlyn sheet is bonded in between two microscope glass slides by utilizing the techniques which has been being used in curing polymer film between dual layer automotive glasses for years. Optical fibers are inserted from the sides of chip and are bonded by UV epoxy. To study the applicability of this prototyping approach, we made a basic microfluidic sorter and tested its functionalities. Sample containing microparticles is injected into the chip. Light from a 532-nm diode laser is coupled into the optical fiber that delivers light to the interrogation region in the channel. The emitted light from the particle is collected by a photodiode (PD) placed over the detection window. The device sorts the particles into the sorted or waste outlets depending on the level of the PD signal. We used fluorescent latex beads to test the detection and sorting functionalities of the device. We found that the system could detect all the beads that passed through its geometric observation region and could sort almost all the beads it detected. © 2011 International Society for Advancement of Cytometry [ABSTRACT FROM AUTHOR]

To study the rapid evolution of AC conductivity from ultrafast laser excited warm dense matter (WDM), a spatial chirp single-shot method is developed utilizing a crossing angle pump-probe configuration. The pump beam is shaped individually in two spatial dimensions so that it can provide both sufficient laser intensity to excite the material to warm dense matter state and a uniform time window of up to 1 ps with sub-100 fs FWHM temporal resolution. Temporal evolution of AC conductivity in laser excited warm dense gold was also measured. [ABSTRACT FROM AUTHOR]

The conversion efficiency from laser energy into proton kinetic energy is measured with the 0.6 ps, 9×1019 W/cm2 Titan laser at the Jupiter Laser Facility as a function of target thickness in Au foils. For targets thicker than 20 μm, the conversion efficiency scales approximately as 1/L, where L is the target thickness. This is explained by the domination of hot electron collisional losses over adiabatic cooling. In thinner targets, the two effects become comparable, causing the conversion efficiency to scale weaker than 1/L; the measured conversion efficiency is constant within the scatter in the data for targets between 5 and 15 μm, with a peak conversion efficiency of 4% into protons with energy greater than 3 MeV. Depletion of the hydrocarbon contaminant layer is eliminated as an explanation for this plateau by using targets coated with 200 nm of ErH3 on the rear surface. The proton acceleration is modeled with the hybrid-particle in cell code LSP, which reproduced the conversion efficiency scaling observed in the data. [ABSTRACT FROM AUTHOR]

Zinc oxide films with different microstructures have been produced using pulsed-laser deposition. Photoluminescence efficiency and angular emission patterns are characterized and reported in absolute radiometric units. Efficiencies between 0.6×10-6 and 7×10-6 were observed. In most cases, the angular emission pattern was lambertian, though the film microstructure produced an isotropic emission pattern in one case. A secondary peak, red-shifted 180 meV from the main ultraviolet ZnO emission peak, was observed for some films. The origin of the 180-meV red shift is tentatively attributed to zinc vacancies. [ABSTRACT FROM AUTHOR]

An InAs/GaAs quantum dot saturable absorber mirror was used to mode lock a Nd:YVO4 solid-state laser at the operation wavelength of 1064.6 nm. Multi-watt average power was obtained during stable cw mode locking with pulses as short as 24 ps, and with a repetition rate of 65 MHz. [ABSTRACT FROM AUTHOR]

The single-shot ablation threshold and incubation coefficient of copper were investigated using an amplified near-infrared, femtosecond Ti:sapphire laser. To date, the near-infrared femtosecond ablation threshold of copper has been reported in the range of several hundred millijoules per cm2 based primarily on multiple shot ablation studies. A careful study of the single shot ablation threshold for copper was carried out yielding an incident single-shot ablation threshold of (1.06±0.12) J/cm2 for a clean copper foil surface. This was determined by measuring the diameters of the ablation spots as a function of the laser pulse energy using scanning electron microscopy for spatially Gaussian laser spots. When multiple shots were taken on the same spot, a reduction in ablation threshold was observed, consistent with a multiple shot incubation coefficient of 0.76±0.02. Similar experiments on 250 nm and 500 nm copper thin films sputtered on a silicon substrate demonstrated that scaling the threshold values with the absorbance of energy at the surface yields a consistent absorbed fluence threshold for copper of (59±10) mJ/cm2. This absorbed threshold value is consistent with the expected value from a two-temperature model for the heating of copper with an electron-lattice coupling constant of g=1017 Wm-3 K-1. Single-shot rippling of the surface in the threshold ablation intensity regime was also observed for the foil target but not for the smooth thin film target. [ABSTRACT FROM AUTHOR]

This paper presents a new package design for multichip modules. The developed package has a flip-chip-on-chip structure. Four chips [simulating dynamic random access memory (DRAM) chips for demonstration purpose] are assembled on a silicon chip carrier with eutectic solder joints. The I/Os of the four chips are fanned-in on the silicon chip carrier to form an area array with larger solder balls. A through-silicon via (TSV) hole is made at the center of the silicon chip carrier for optional underfill dispensing. The whole multichip module is mounted on the printed circuit board by the standard surface mount reflow process. After the board level assembly and X-ray inspection, the underfill process is applied to some selected specimens for comparative study purpose. The underfill material is dispensed through the center TSV hole on the silicon chip carrier to encapsulate the solder joints and the four smaller chips. Subsequently, scanning acoustic microscopy (SAM) is performed to inspect the quality of underfill. After the board-level assembly, all specimens are subject to the accelerated temperature cycling (ATC) test. During the ATC test, the electrical resistance of all specimens is monitored. The experimental results show that the packages without underfill encapsulation may fail in less than 100 thermal cycles while those with underfill can last for more than 1200 cycles. From the dye ink analysis and the cross-section inspection, it is identified that the packages without underfill have failure in the silicon chip carrier, instead of solder joints. The features and merits of the present package design are discussed in details in this paper. [ABSTRACT FROM AUTHOR]

The initiation, development, and coalescence of cracks when a rock specimen is loaded have been studied by various researchers. The current consensus is that such complex process is however not yet fully understood. In the present study, the problem has been revisited by carrying out extensive testing on granite specimens. Each specimen was loaded under uniaxial loading condition to various load levels in both prepeak and postpeak ranges. After unloading, the crack patterns were printed onto the surface of a piece of resin. The images of the patterns were then captured using a digital camera through optical microscope or scanning electron microscope. Statistical analyses on these images were then carried out using an image analysis software. The study focuses on the cracking behavior of the various mineral components of the granite and their respective roles in the failure process. In addition, a numerical model was developed to simulate the test results and parametric study was carried out to investigate the effects of various factors (heterogeneity index, C/ T ratio, grain arrangement, and grain size, etc.) on the failure behavior of the granite. The study has provided insight on the development of cracks, especially in the postpeak range. A better understanding on the roles of the major minerals in failure process of the granite has been achieved. [ABSTRACT FROM AUTHOR]

Discrete fracture network models can be used to study groundwater flow in fractured rock masses. However, one may find that it is not easy to apply such models to practical projects as it is difficult to investigate every fracture and measure its hydraulic parameters. To overcome such difficulties, a dual fracture model is proposed. Taking into account the hydraulic characteristics of the various elements of the fracture system, a hydrogeological medium is assumed to consist of two components: the dominant fracture network and the fractured rock matrix. As the dominant fracture network consists of large fractures and faults, it controls the groundwater flow in rock masses. Depending on the permeabilities of the in-fill materials, these fractures and faults may serve as channels or barriers of the flow. The fractured rock matrix, which includes rock blocks and numerous small fractures, plays a secondary role in groundwater flow in such medium. Although the small fractures and rock blocks possess low permeability, their numbers and their total porosity are relatively large. Therefore, they provide large volume for groundwater storage. In this paper, the application of the proposed model to simulate the groundwater flow for a hydropower station before and after reservoir storage is reported. The implications of the results on the design of the station are also highlighted.Key words: seepage flow, dual fracture model, dominant fracture, fractured rock matrix, case studies, rock-filled dam.Des modèles de réseaux de fractures discrètes peuvent être utilisés pour étudier l'écoulement des eaux souterraines dans les massifs rocheux, mais on peut trouver qu'il n'est pas facile d'appliquer de tels modèles dans des projets pratiques parce qu'il est difficile d'étudier chaque fracture et de mesurer ses paramètres hydrauliques. Afin de surmonter ces difficultés, on propose un modèle à fracturation double. Prenant en compte les caractéristiques hydrauliques des divers éléments du système de fractures, on suppose que le milieu hydro-géologique comprend deux composantes: le réseau de fractures dominantes et la matrice de la roche fracturée. Comme le réseau de fractures dominantes consiste en de larges fractures, il contrôle l'écoulement de l'eau souterraine dans les massifs rocheux. Dépendant des perméabilités des matériaux de remplissage, ces fractures et failles peuvent servir comme des canaux ou des barrières pour l'écoulement. La matrice de roc fracturé qui inclut les blocs de roches et de nombreuses petites fissures joue un rôle secondaire dans l'écoulement de l'eau souterraine dans un tel milieu. Quoique les petites fractures et les blocs de roches possèdent une faible perméabilité, leurs nombres et leur porosité totale sont relativement importants. En conséquence, ils fournissent un grand volume pour l'entreposage de l'eau souterraine. Dans cet article, on fait rapport de l'application du modèle proposé pour simuler l'écoulement de l'eau souterraine pour les centrales hydroélectriques avant et après le remplissage du réservoir. On met aussi en lumière les implications des résultats sur la conception de la centrale.Mots clés : écoulement d'infiltration, modèle à fracturation double, fracture dominante, matrice de roche fracturée, études de cas, barrages en enrochement.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

A study on the peak strength of brittle rock materials having random strength distributions was carried out using the re-normalization group theory approach. A major advantage of the approach is that it is scale invariant, and therefore, one can relate the micro-fractures with macro-fractures of rocks at the critical state. The stress transfer from the broken sub-sections to the unbroken sub-sections is defined by a conditional probability. The critical probability P and the relation between the peak strength and the mean strength of the elements have been obtained theoretically. On the other hand, the whole process of rock brittle fracture has also been simulated numerically from micro-fracture to macro-fracture by using the Rock Failure Process Analysis (RFPA) code. The peak strengths obtained by the numerical model agree fairly well with those obtained by the re-normalisation group theory. Due to the stress transfer from the broken subsections to the unbroken subsections, the peak strength is considerably less than the mean strength of the elements. [ABSTRACT FROM AUTHOR]

The male antifertility agent Gossypol did not affect the level of traditional chromosome breakage or number of micronuclei in 66-hour lymphocyte cultures at concentrations up to 40 micrograms/ml. It did increase the frequency of SCE slightly, although the inter-individual variation was greater than the increase resulting from Gossypol, and, even at the highest concentration (40 micrograms/ml), the SCE rate was still within the normal range. It also affected cell kinetics, reducing the mitotic index and the proportion of second and third metaphases after BUdR incorporation. [ABSTRACT FROM PUBLISHER]

Experimental measurements of ablation parameters in a KrF laser produced aluminum plasma are presented for the laser intensity range of 10[sup 11]-10[sup 13] W/cm². Plasma created from large focal spots shows single broad ion current pulses as compared to two groups of ions observed from small focal spots. Detailed analysis of the velocity distributions of emitted ions is carried out to understand this behavior and its effect on measurements of the ablation parameters. Scalings with laser intensity of the mass ablation rate (m ∼ I[sup 0.42, sub L]) and of the ablation pressure (P[sub a] ∼ I[sup 0.81, sub L) 8 - IL') giving m = 1.5 × 10[sup 5] g cm[sup -2] sec[sup -1] and P[sup a] = 5.5 Mbar at a laser intensity of 10[sup 13] W/cm² are obtained. The results are found to be in good agreement with the predictions of a plasma ablation model based on inverse bremsstrahlung dominated absorption. [ABSTRACT FROM AUTHOR]

A calculation of the charge state distribution of the asymptotic evolution of a plasma produced by an ultraviolet laser has been carried out by coupling the results of a detailed two-dimensional hydrodynamic simulation of the creation and heating of the plasma to a simpler one-dimensional hydrodynamic code. The latter incorporates time-dependent ionization and recombination physics and is used to model the subsequent expansion and cooling of the plasma. The simulation results are compared to experimental charge state distributions obtained by using a single shot electrodynamic charge analyzer. The sensitivity of the results to the rate coefficients used for the recombination calculations was tested and the calculated distributions were found to be most sensitive to the values of the three-body recombination rate and the amount of heat returned to the plasma. Reasonable agreement was found between the measured and calculated charge state distributions. [ABSTRACT FROM AUTHOR]

The detailed angular charge distributions of the asymptotic plasma produced from carbon and aluminum targets by UV and visible laser pulses in the intensity range of 1011–1013 W cm-2 and pulselength range of 1–20 nsec have been measured using a single shot electrodynamic charge analyzer. The observed variation of average charge state as a function of velocity was determined from measurement and has been found to be approximately linear with no apparent dependence on angle of observation. For similar irradiation conditions, shorter-wavelength radiation produces lower final charge states, as expected, from the higher interaction density in the initial laser produced plasma leading to enhanced recombination in the early stages of expansion of the plasma. The characteristics of the angular charge distribution can be qualitatively explained by considering the flow of the source plasma mapping different regions of the focal spot into different angles, relative to the target normal, in the expanding plasma. [ABSTRACT FROM AUTHOR]

The concentration of nitric oxide in the effluent of an air plasma (2350-2600 K) was studied as a function of the rate of quenching. Rapid quenching leads to concentrations higher than those predicted from stagnant equilibrium conditions. This observation may be attributed to a lack of chemical equilibrium under the conditions investigated. [ABSTRACT FROM AUTHOR]