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Tricalcium phosphate (TCP) is a biomaterial produced in several biomedical applications, in addition to having biocompatibility and osteoconductive capacity. Biodegradable polymers of natural or synthetic origin such as chitosan and polyvinyl alcohol (PVA) have been used for tissue engineering applications because they have the properties of the native organic phase of bone tissue. Thus, the objective of this study was to obtain ceramic tapes based on TCP, chitosan, and PVA through the tape casting method. The viscosity data for all suspensions were ideal for the chosen processing. The thermogravimetric curves showed similar profiles, and it was possible to observe that a greater total mass loss occurred with the increase in the chitosan content. XRD reflections related to the β-TCP phase of the orthorhombic structure were found, showing no phase transformation. SEM analysis showed degrees of roughness on the film surfaces with little influence from the increase in chitosan content. Resumo O fosfato tricálcico (TCP) é um biomaterial que está sendo produzido em diversas aplicações biomédicas, além de sua biocompatibilidade e capacidade osteocondutora. Polímeros biodegradáveis de origem natural ou sintética, como quitosana e poli(álcool vinílico) (PVA), vêm sendo utilizados para aplicações de engenharia de tecidos por apresentarem as propriedades da fase orgânica nativa do tecido ósseo. Desse modo, o objetivo deste trabalho foi a obtenção de filmes finos cerâmicos baseados em TCP, quitosana e PVA através do método de tape casting. Dados de viscosidade para todas as suspensões mostraram-se ideais para o processamento escolhido. As curvas termogravimétricas demonstraram perfis semelhantes e foi possível observar que com o aumento do teor de quitosana ocorreu maior perda de massa total. Reflexões de DRX relacionadas à fase β-TCP de estrutura ortorrômbica foram encontradas, evidenciando que não houve transformação de fases. A análise de MEV revelou graus de rugosidade nas superfícies dos filmes com pouca influência do aumento do conteúdo de quitosana.

A comparison between the Zn-Ni, Zn-Ni-Fe and Zn-Ni-Co coatings was performed in this study. The co-deposition process was obtained by electrodeposition on ASTM A624 steel using sulphate baths in acid media and low current density. The characterization of the coatings by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP OES), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD) and Anodic Linear Sweep Voltammetry (ALSV) allowed a detailed analysis of the phases formed and its amounts in the coatings, which enabled to verify the influence of the Fe and Co co-deposited separately with Zn/Ni. The co-deposits showed different characteristics in relation to the deposition efficiency and film thickness, in addition of the topography and surface roughness, which were measured by a confocal optical microscope and of the hardness determined by an ultra-microhardness tester. Finally, the corrosion tests analyzed by open circuit potential, potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) determined the corrosion characteristics of each co-deposit in saline solution. Results showed that Zn-Ni-Co was superior to the others co-deposits in relation to the deposit efficiency and corrosion protection, in contrast, the Zn-Ni-Fe coating showed uniformity and the greater compaction of the surface grains, resulting in lower roughness and higher hardness between the co-deposits studied.

In this work we report a first principles study of benzonitrile (BZN) interaction with pristine and Fe-doped single-walled carbon nanotubes (SWNTs), graphene, and C60. The results show that the BZN molecule weakly adsorbs on SWNTs, graphene, and C60 through π−π aromatic ring stacking. This interaction can be considerably strengthened by the inclusion of Fe atoms, which leads to a strong π−3d−π covalent bond linking the BZN to the carbon nanostructure. The calculated binding energy values suggest that the BZN molecule adsorption with Fe atoms is much stronger than those for Fe−SWNT, Fe−C60, or Fe−graphene interaction. Indeed, the BZN−Fe stability on each carbon nanostructure surface was studied and the SWNTs complexes are more stable than those of C60 and graphene.

The effect of HgI2 crystal encapsulation using different polymer resins, with the intent of avoiding the oxidation of the crystal surface, was evaluated in this work. The crystal was purified and grown by the physical vapor transport (PVT) technique modified. Systematic measurements were carried out for evaluating the stoichiometry, structure orientation, surface morphology and impurity of the crystal grown. The purer region of the crystal grown was selected to be prepared as a radiation detector, applying water-based conductive ink contacts and copper wire on the crystal surfaces. After that, the crystal was encapsulated with a polymeric resin which insulates atmospheric gases, aiming to improve the stability of the HgI2 detector. Four resins were used for crystal encapslation and the performance of the detector depended on the composition of the resins used. Among the four resins studied to evaluate the influence of encapsulation on the performance of crystals, as a radiation detector, the best result of resistivity and energy spectrum was obtained for the resin #3 (50% - 100% of Methylacetate and 5% - 10% of n-butylacetate). The encapsulation of crystals with polymer resins, performed with the intent of avoiding the oxidation of the crystal surface, did not compromise the measurements and were fully capable of detecting the presence of gamma radiation. The stability of the encapsulated HgI2 crystal detector was of up to 78 hs, while the stability found for HgI2 detector no encapsulated was in order 3 ~4 hs.

In this work, a systematic study of SO2 molecules interacting with pristine and transition metal (TM) covered C60 is presented by means of first principles calculations. It is observed that the SO2 molecule interacts weakly with the pristine C60 fullerene, although the resulting interaction is largely increased when the C60 structure is covered with Fe, Mn, or Ti atoms and the SO2 molecules are bounded through the TM atoms. The number of bounded SO2 molecules per TM atoms, in addition to the elevated binding energies per molecules, allows us to conclude that such composites can be used as a template for efficient devices to remove SO2 molecules or, alternatively, as SO2 gas sensor.

Laser-driven shocks have broken new ground in providing data on strongly coupled systems. One example is the measurements of the Hugoniot of hydrogen isotopes to over 300 GPa and the clear signature of metallic behavior at pressures of 60 GPa. The resulting fluid is strongly coupled (Γ > 10) and probably composed of ions, atoms, and molecules - a very difficult system to understand. The latest interpretation of these measurements is discussed. In addition, recent shock measurements on the hydrogen-bonded compound water - both EOS and reflectivity - are shown. The metallic signature for water is very different than that of hydrogen.

We report on measurements of the equation of state and optical reflectivity at 1064 nm wavelength of a high pressure shock front propagating through a sample of liquid deuterium. We find that the shock front reflectivity increases from a low value (< 3.5%) to a saturation level of 65% in the pressure range of 0.22 - 0.55 Mbar. The pressure range where this metallization transformation takes place coincides with the pressure range where high compressibilities were observed on the principal Hugoniot.

A preliminary single-animal study of in vivo argon laser vascular welding was conducted using a canine model. The effects of temperature feedback control and saline drip cooling on patency and collagen cross-linking were investigated. The surface temperature at the centre of the laser spot was monitored using a two-colour infrared thermometer. The surface temperature was limited by either a saline drip or feedback control of the laser. Acute patency was evaluated and collagen cross-link assays were performed. Though both protocols yielded successful tissue fusion, welds maintained at a surface temperature of 50°C using feedback control had an elevated cross-link count compared to controls, whereas tissues irradiated without feedback control experienced a cross-link decrease. Simulations using the LATIS (LAser-TISsue) computer code suggest that drip-cooled procedures achieve significantly higher temperatures beneath the tissue surface than temperature feedback-controlled procedures. Differences between the volumetric heating associated with drip-cooled and feedback-controlled protocols may account for the different effects on collagen cross-links. Covalent mechanisms may play a role in argon laser vascular fusion.

Ultrashort laser pulse ablation removes material with low-energy fluence required and minimal collateral damage. The ultimate usefulness of this technology for biomedical application depends, in part, on characterization of the physical conditions attained, and determination of the zone of shockwave and heat-affected material in particular tissues. Detailed numerical modeling of the relevant physics (deposition, plasma formation, shockwave generation and propagation, thermal conduction) are providing this information. A wide range of time scales is involved, ranging from picosecond for energy deposition and peak pressure and temperature, to nanosecond for development of shockwave, to microsecond for macroscopic thermophysical response.

An optical feedback system for controlled precise tissue ablation is discussed. Our setup includes an ultrashort pulse laser (USPL), and a diagnostic system utilizing analysis of either tissue fluorescence or plasma emission luminescence. Current research is focused on discriminating hard and soft tissues such as bone and spinal cord during spinal surgery using either technique. Our experimental observations exhibit considerable spectroscopic contrast between hard and soft tissue, and both techniques offer promise for a practical diagnostic system.

A technique has been developed that allows the measurement of equations of state of low-atomic-number materials in regimes of extremely high pressure. Using this technique we have obtained absolute multimegabar measurements on the principal Hugoniots of low-Z solids, including data on polystyrene up to 40Mbar (60times the previous absolutely measured pressure) and beryllium at pressures up to 15Mbar. The polystyrene data were able to differentiate between existing theoretical models. The beryllium data confirm theoretical Hugoniots of several materials as high as 65Mbar. {copyright} {ital 1998} {ital The American Physical Society}

The objective is to find new materials for the fabrication of X-ray mirrors with high reflectance at 45 A wavelength, at normal incidence. We have examined multilayers of inconel and carbon, which have high theoretical reflectivities. Planar magnetron sputtering was used to fabricate mirror samples (period = 22.5 A) on silicon substrates. Our best 30-period inconel/carbon multilayers had a reflectivity of 0.3%, which was about a factor of 20 below the theoretical maximum (5.5%). Experimental details presented here include our use of an in situ ellipsometer to monitor the thickness of the layers and to provide information on the early stages of film growth and interdiffusion at the interfaces. Interdiffusion was found to occur at the carbon-on-inconel interface because of the rough underlying inconel layer, but not at the inconel-on-carbon interface because of the smooth underlying carbon layer. Interdiffusion at the carbon-on-inconel layer was also found to increase with the number of layers. The accuracy of ellipsometry for monitoring film thickness during deposition was limited by the theoretical model used for the optical constants of the film. As a result, we were not able to improve on the standard technique of ‘timing’ for control of layer thicknesses.

We present results of the first measurements of density, shock speed, and particle speed in liquid deuterium compressed by laser-generated shock waves to pressures from 25 to 210Gpa (0.25 to 2.1Mbar). The data show a significant increase in D{sub 2} compressibility above 50Gpa compared to a widely used equation of state model. The data strongly suggest a thermal molecular dissociation transition of the diatomic fluid into a monatomic phase. {copyright} {ital 1997} {ital The American Physical Society}

We measured the conversion efficiency of laser pulse energy into keV x rays from a variety of solid planar targets and a Xe gas puff target irradiated using a high average power Nd:glass slab laser capable of delivering 13 ns full width at half‐maximum pulses at up to 20 J at 1.053 μm and 12 J at 0.53 μm. Targets were chosen to optimize emission in the 10–15 A wavelength band, including L‐shell emission from materials with atomic numbers in the range Z=24–30 and M‐shell emission from Xe (Z=54). With 1.053 μm a maximum conversion of 11% into 2π sr was measured from solid Xe targets. At 0.527 μm efficiencies of 12%–18%/(2π sr) were measured for all of the solid targets in the same wavelength band. The x‐ray conversion efficiency from the Xe gas puff target was considerably lower, at about 3%/(2π sr) when irradiated with 1.053 μm.

To date, lasers have not succeeded in replacing mechanical tools in many hard tissue applications. Slow material removal rates and unacceptable collateral damage has prevented such a successful transition. Ultrashort pulses (

Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range of 1 ns-300 fs at 1053-nm wavelength. It was found that pulsed laser ablation of transparent and weakly absorbing gels is always mediated by plasma. On the other hand, ablation of strongly absorbing tissues is mediated by plasma in the ultrashort-pulse range only. Ablation threshold along with plasma optical breakdown threshold decreases with increasing tissue absorbance for subnanosecond pulses. In contrast, the ablation threshold was found to be practically independent of tissue linear absorption for femtosecond laser pulses. The mechanism of optical breakdown at the tissue surface was theoretically investigated. In the nanosecond range of laser pulse duration, optical breakdown proceeds via avalanche ionization initiated by heating of electrons contributed by strongly absorbing impurities at the tissue surface. In the ultrashortpulse range, optical breakdown is initiated by multiphoton ionization of the irradiated medium (six photons in case of tissue irradiated at 1053-nm wavelength), and is less sensitive to linear absorption. High-quality ablation craters with no thermal or mechanical damage to surrounding material were obtained with subpicosecond laser pulses. Experimental results suggest that subpicosecond plasma mediated ablation can be employed as a tool for precise laser microsurgery of various tissues.

A neon-like yttrium laboratory x-ray laser (XRL) at 155 A has been used to perform radiography, Moire deflectometry and interferometry of plasmas created in various laser-initiated experiments. A system consisting of the XRL, multilayer mirrors, and multilayer beam splitters was assembled to obtain high resolution images of the plasmas. Work is continuing to improve the XRL—higher brightness, shorter pulse length, and enhanced coherence—through a program of simulations and experiments.

Deformed single-wall carbon nanotubes (SWCNT) are investigated through ab initio simulations as sensors to detect the presence of chemical gases. Although the viability of using undeformed SWCNT devices has been demonstrated for many molecules, there are important exceptions of toxic gases, such as carbon monoxide, which are not detectable by these sensors. To overcome this problem, recent interesting propositions have been presented based on doping of impurity atoms into SWCNT. In this paper, an alternative method is proposed using radial deformation, which induces fundamental changes on the electronic properties of SWCNT, allowing functionalization of the tube surface to detect the presence of CO molecules.

We point out that existing Ne-like X-ray lasers have sufficient brightness to be used as pump sources in resonant pump-fluorescence experiments, and we discuss some of the potential benefits and limitations of such experiments. In preliminary experiments, we have measured the line overlap of the Ne-like yttrium X-ray laser near 155 A with 4f−3d transitions in H-like Na and He-like Mg. These experiments used a high-resolution grating spectrometer, and calibrated the wavelength of the yttrium laser by comparison against lines of known wavelength. The results indicate that the wavelength of the yttrium laser is 154.985 ± 0.025 A, a factor of 2–4 improvement in precision over previous calibrations. We find that the yttrium laser is ≈ 100 mA to the long-wavelength side of both the He-like Mg line and the H-like Na line, so that neither resonance is perfect; however, Stark broadening could improve the overlap in the latter scheme, and bulk Doppler shifting could improve both resonances. We also find a good resonance between the yttrium laser and an un-identified transition which we tentatively attribute to copper.

The experiments reported in this paper were undertaken to measure the rear x-ray flux of foils having different thicknesses. The targets were burnthrough foils, planar free-standing Au foils and CH supported Au foils, that were nearly entirely ablated during the laser pulse. The x-ray flux from the non-irradiated rear side is of sufficient intensity that it can serve as an x-ray heating source, backlight, or photon pump. The foils were irradiated with one smoothed beam of Nova which provided ∼ 3300 J of 2ω0 light in a 1 nsec square pulse. The primary diagnostics measured absolute flux and transmitted laser light. The time-dependent absolute flux measurements, the total-integrated energy of the x-ray spectrum, and the temporal evolution will be discussed.

The electronic and structural properties of an (8, 0) single-walled carbon nanotube (SWNT) with a single vacancy and interacting with a Si atom are studied using first principles calculations based on the density-functional theory. Initially, the Si atom is positioned in the site above the vacancy, with its position fixed until the nanotube geometry is fully relaxed. After that, the Si atom approaches the tube and it is shown that one C atom is displaced outwards forming a bump. The final configuration, as well as each step of the process, is studied in detail and the resulting band structures and the total charge densities are systematically analysed.

This paper presents the electronic charge density modifications due to the effects of the transverse uniform electric fields applied on the semiconductor and metallic single wall carbon nanotubes. The results obtained, by means of density functional calculations, show that semiconductor and metallic nanotubes have different behavior in the presence of the transverse electric field: the first present the electronic charge polarized due to the local orbital localization, while the metallic species are polarized due to charge dislocation throughout the surface.

We demonstrate cross-sectional birefringence- and polarization-independent backscatter imaging of laser-induced thermal damage in porcine myocardium in vitro, using a polarization-sensitive optical coherence tomography system. We compare the generated images with histological sections of the tissue and demonstrate that birefringence is a more sensitive indicator of thermal damage than is backscattered light. Loss of birefringence in thermally damaged regions is quantified and shown to have significant contrast with undamaged sections of the tissue. A detailed theoretical analysis of the birefringence measurements is provided, including a calculation of the systematic errors associated with background noise, system imperfections, and tissue dichroism.

Spatial filters are essential components for maintaining high beam quality in high-energy pulsed laser systems. The long-duration (21 ns) high-energy pulses envisioned for future inertial-confinement fusion drive systems, such as the U.S. National Ignition Facility (NIF), are likely to lead to increased plasma generation and closure effects within the pinholes in the spatial filters. The design goal for the pinhole spatial filter for the NIF design is to remove small-angle scatter in the beam to as little as a ?100-murad divergence. It is uncertain whether this design requirement can be met with a conventional pinhole design. We propose a new pinhole architecture that addresses these issues by incorporating features intended to reduce the rate of plasma generation. Initial experiments with this design have verified its performance improvement relative to a conventional pinhole design.

We have developed a prototype optical coherence tomography (OCT) system for the imaging of hard and soft tissue in the oral cavity. High-resolution images of in vitro porcine periodontal tissues have been obtained with this system. The images clearly show the enamel-cementum and the gingiva-tooth interfaces, indicating OCT is a potentially useful technique for diagnosis of periodontal diseases. To our knowledge, this is the first application of OCT for imaging biologic hard tissue.

The use femtosecond pulses for materials processing results in very precise cutting and drilling with high efficiency. Energy deposited in the electrons is not coupled into the bulk during the pulse, resulting in negligible shock or thermal loading to adjacent areas.

Neon-like niobium X-ray lasers have been studied using both slab and thin-foil target geometries. Niobium foils of various lengths were irradiated from both sides with two beams of the frequency-doubled Nova laser system using a line focus. We looked for gain by measuring spectrally integrated line intensities at different plasma lengths. Gain was observed in four neon-like niobium lines corresponding to 3s−3p transitions. The line profile of theJ = 0−1 line (λ = 145.9 A) shows splitting due to the hyperfine effect. Improved contrast in the hyperfine structure is observed as the plasma length is increased. Hyperfine splitting may be relevant to other 3s−3p transitions in neon-like niobium as well as other neon-like X-ray laser systems.

Our studies of Ne-like X-ray lasers have focused on detailed measurements of the yttrium X-ray laser. This system is ideal for multilayer mirror applications because the spectrum is dominated by the short wavelength J=2-1 transition which operates at 154.98 /spl Aring/. At this wavelength multilayer mirrors with peak normal incidence reflectivities of 60 % can be produced. The high gain of this transition has allowed us to achieve saturated output with peak powers of 30 MW from a 3.8 cm long yttrium target irradiated by a 500 ps square 0.53 /spl mu/m optical laser pulse. >

Employing new advances in the technology of ultrashort pulse lasers, a laser parameter regime which could provide hard tissue interaction characteristics that are superior to conventional mechanical drill technology has now been identified. The major advantages of this tissue ablation method are: 1) efficient ablation; 2) minimization of collateral damage; 3) ablation thresholds and ablation rates which are relatively insensitive to tissue type; 4) high control over ablation depth is achievable because only a small amount of tissue is ablated per pulse; 5) low operation noise level; and finally, 6) precise spatial control due to the multiphoton nature of the interaction. In our experiments, laser pulses generated by a 1053 nm Ti:sapphire chirped pulse amplifier (CPA) system were used. Seed pulses of 100 fs from a Kerr-lens mode locked, Ti:sapphire oscillator were stretched to 1 ns in a four-pass, single-grating pulse stretcher. We have demonstrated negligible collateral damage and highly efficient ablation rates per pulse.

The second order nonlinear optical properties and orientation of collagen fibers were measured simultaneously using polarization modulation and phase sensitive detection.

Among the many collagen-rich tissues, we studied rat-tail tendon in detail since it is composed of highly-organized type I collagen fibrils. We devised a confocal microscope that measures the second harmonic light generated from rat-tail tendon. Since SHG is sensitive to the linear polarization of the excitation pulse, a mathematical model was developed to investigate the relationship between linear polarization, the direction of the collagen fibrils, and the intensity of the generated second harmonic light. Also, the effect of collagen organization on the second harmonic intensity was studied.

The development of high brightness and short pulse width (200 picoseconds) x-ray lasers now offers biologists the possibility of high-resolution imaging of specimens in an aqueous environment without the blurring effects associated with natural motions and chemical erosion. As a step toward developing the capabilities of this type of x-ray microscopy, a tantalum x-ray laser at 44.83 angstrom wavelength was used together with an x-ray zone plate lens to image both unlabeled and selectively gold-labeled dried rat sperm nuclei. The observed images show approximately 500 angstrom features, illustrate the importance of x-ray microscopy in determining chemical composition, and provide information about the uniformity of sperm chromatin organization and the extent of sperm chromatin hydration.

The characteristics of the ultrashort pulse laser (USPL

The x‐ray laser is now being used at LLNL as a tool for measuring the behaviors of hot dense plasmas. In particular, we have used the 155A yttrium laser to study transient plasmas by both radiography and moire deflectometry. These techniques have been used to probe long scale length plasmas at electron densities exceeding 1022 cm−3. Recent advances in multilayer technology have made it possible to directly image ion densities in directly driven thin foils to an accuracy of 1–2 μm. In addition, we have constructed an x‐ray laser Mach‐Zehnder interferometer using multilayer beam‐splitters. This interferometer yields direct 2D projections of electron densities in plasmas with micron spatial resolution. In addition, this interferometer can be used to measure spectral line shapes to high accuracy. Among the subject plasmas under study are laser irradiated planar targets, gold hohlraums, and x‐ray lasers themselves.

The authors discuss the use of a prepulse technique to achieve lasing in low-Z neon-like ions on the 3p {r_arrow} 3s(J = 0 {r_arrow} 1) transition. Lasing has now been observed on this transitions for neon-like ions from chlorine to selenium with wavelengths ranging from 528 {angstrom} to 182 {angstrom}. For the germanium targets they present two dimensional space resolves images of the laser output with magnification of ten. Using a gas puff target as an alternative to the prepulse technique, they observe lasing at 469 {angstrom} in neon-like argon. Using a series of 100 ps pulses 400 ps apart to illuminate germanium and selenium plasmas they present results which now show the 3p {r_arrow} 3s(J = 0 {r_arrow} 1) transition to dominate the other laser lines even for selenium. Applying the multiple pulse technique to nickel-like ions they observed lasing at 79 {angstrom} on the 4d {r_arrow} 4p(J = 0 {r_arrow} 1) transition in nickel-like neodymium (Z = 60) when a series of 100--150 ps pulses which are 400--500 ps apart are used to illuminate slab targets of neodymium. To maximize the laser output for neodymium they combine the advantages of coupling two slab targets, using the traveling wavemore » geometry, and curving the target surface.« less

Summary form only given. Contact, transmission, and reflection X-ray laser microscopes have been constructed and are being used for biological microstructure studies. Two-dimensional images are being produced with sub-1000/spl Aring/ resolution. Efforts to improve the resolution and produce three-dimensional images are underway. X-ray lasers are also being used in moire deflectrometry experiments designed to measure electron density gradients in laser plasmas at densities near or above critical. An X-ray laser based interferometer is being designed for measuring two-dimensional electron density profiles in laser plasmas. In materials sciences, X-ray laser based experiments designed to study cluster formation are being developed. All of these applications exploit the unique short pulse, extremely high brightness output of the X-ray laser.

Summary form only given, as follows. A number of experiments have been performed using a high-resolution XUV (extreme ultraviolet) spectrometer to measure the spectral widths of X-ray laser lines from several elements. These experiments used yttrium, selenium, niobium, and zirconium targets, and included an investigation of the effects of gain and saturation on X-ray laser line widths and the measurement of hyperfine splitting effects on X-ray laser line shapes. The relevance of the data obtained to the understanding of the physics of X-ray laser plasmas and high-temperature laser-produced plasmas in general has been examined.

In many applications, x-ray mulhilayer mirrors are exposed to high peak fluxes of x-rays with subsequent damage to the mirror. Mirror damage is a particularly severe problem with the use of multilayers as cavity optics for short wavelength x-ray lasers. Intense optical and x-ray radiation, from the x-ray laser plasma amplifier, often damages the multilayer mirror on time scales of hundreds of picoseconds. The phenomenon of multilayer mirror damage by pulsed xray emission has been studied using short duration (500 psec) bursts of soft x-rays from a laser produced gold plasma. The results of the experiments will be compared with some simple models and the possibility of increasing the damage thresholds of short wavelength multilayer mirrors will be discussed.

We introduce a novel method for determining analyte concentration as a function of depth in a highly scattering media by use of a dual-wavelength optical coherence tomography system. We account for the effect of scattering on the measured attenuation by using a second wavelength that is not absorbed by the sample. We assess the applicability of this technique by measuring the concentration of water in an Intralipid phantom, using a probe wavelength of 1.53 microm and a reference wavelength of 1.31 microm. The results of our study show a strong correlation between the measured absorption and the water content of the sample. The accuracy of the technique, however, was limited by the dominance of scattering over absorption in the turbid media. Thus, although the effects of scattering were minimized, significant errors remained in the calculated absorption values. More-accurate results could be obtained with the use of more powerful superluminescent diodes and a choice of wavelengths at which absorption effects are more significant relative to scattering.

An improved polarization-sensitive optical coherence tomography (OCT) system is developed and used to measure birefringence in porcine myocardium tissue and produce two-dimensional birefringence mapping of the tissue. Signal-to-noise issues that cause systematic measurement errors are analyzed to determine the regime in which such measurements are accurate. The advantage of polarization-sensitive OCT systems over standard OCT systems in avoiding image artifacts caused by birefringence is also demonstrated.

We measure the transverse spatial distribution of the gain region for the 19.6-nm neonlike germanium laser line by use of a short amplifier, which is backlit by a longer laser, both of which are created by illumination of a germanium slab target with a series of short 100-ps pulses from the Nova laser. The backlighting technique enables us to reduce greatly the refraction effects that dominated previous imaging experiments and made direct gain measurements impossible. Measurements are made with a two-dimensional high-resolution spatial-imaging diagnostic, and simulations of the gain are compared with experiments.

A review of recent laser-driven shock wave experiments at the University of British Columbia is presented. These include emissivity and reflectivity measurements on target rear surfaces when the shock wave emerges as well as measurements of the trajectories of shock propagation in initially transparent targets irradiated by temporally tailored laser pulses. The rear surface measurements allowed us to study the equation of state and electron conductivity of dense plasmas while coalescence of shock waves was evident in the trajectory of shock waves driven by a shaped pulse.

The authors have imaged laser-accelerated foils and exploding foils on the few-micron scale using an yttrium x-ray laser (155 {angstrom}, 80 eV, {approximately}200 ps duration) and a multilayer mirror imaging system. At the maximum magnification of 30, resolution was of order one micron. The images were side-on radiographs of the foils. Accelerated foils showed significant filamentation on the rear-side (away from the driving laser) of the foil, although the laser beam was smoothed. In addition to the narrow rear-side filamentation, some shots revealed larger-scale plume-like structures on the front (driven) side of the Al foil. These plumes seem to be little-affected by beam smoothing and are likely a consequence of Rayleigh-Taylor instability. The experiments were carried out at the Nova two-beam facility.

Pyrometric measurements of single-shock-compressed liquid deuterium reveal that shock front temperatures $T$ increase from 0.47 to 4.4 eV as the pressure $P$ increases from 31 to 230 GPa. Where deuterium becomes both conducting and highly compressible, $30\ensuremath{\le}P\ensuremath{\le}50\mathrm{GPa}$, $T$ is lower than most models predict and $T\ensuremath{\ll}{T}_{\mathrm{Fermi}}$, proving that deuterium is a degenerate Fermi-liquid metal. At $Pg50\mathrm{Gpa}$, where the optical reflectivity is saturated, there is an increase in the rate that $T$ increases with $P$.