Prediction of the superimposed laser shot number for copper using a deep convolutional neural network

Image-based deep learning (IBDL) is an advanced technique for predicting the surface irradiation conditions of laser surface processing technology. In pulsed-laser surface processing techniques, the number of superimposed laser shots is one of the fundamental and essential parameters that should be optimized for each material. Our primary research aims to build an adequate dataset using laser-irradiated surface images and to successfully predict the number of superimposed shots using the pre-trained deep convolutional neural network (CNN) models. First, the laser shot experiments were performed on copper targets using a nanosecond YAG laser with a wavelength of 532 nm. Then, the training data were obtained with the different superimposed shots of 1 to 1024 in powers of 2. After that, we used several pre-trained deep CNN models to predict the number of superimposed laser shots. Based on the dataset with 1936 images, VGG16 shows a high validation accuracy, higher sensitivity, and more than 99% precision than other deep CNN models. Utilizing the VGG16 model with high sensitivity could positively impact the industries' time, efficiency, and overall production.

Direct observations of pure electron outflow in magnetic reconnection

Magnetic reconnection is a universal process in space, astrophysical, and laboratory plasmas. It alters magnetic field topology and results in energy release to the plasma. Here we report the experimental results of a pure electron outflow in magnetic reconnection, which is not accompanied with ion flows. By controlling an applied magnetic field in a laser produced plasma, we have constructed an experiment that magnetizes the electrons but not the ions. This allows us to isolate the electron dynamics from the ions. Collective Thomson scattering measurements reveal the electron Alfvénic outflow without ion outflow. The resultant plasmoid and whistler waves are observed with the magnetic induction probe measurements. We observe the unique features of electron-scale magnetic reconnection simultaneously in laser produced plasmas, including global structures, local plasma parameters, magnetic field, and waves.

Development of an experimental platform for the investigation of laser-plasma interaction in conditions relevant to shock ignition regime

The shock ignition (SI) approach to inertial confinement fusion is a promising scheme for achieving energy production by nuclear fusion. SI relies on using a high intensity laser pulse (≈10¹⁶ W/cm², with a duration of several hundred ps) at the end of the fuel compression stage. However, during laser-plasma interaction (LPI), several parametric instabilities, such as stimulated Raman scattering and two plasmon decay, nonlinearly generate hot electrons (HEs). The whole behavior of HE under SI conditions, including their generation, transport, and final absorption, is still unclear and needs further experimental investigation. This paper focuses on the development of an experimental platform for SI-related experiments, which simultaneously makes use of multiple diagnostics to characterize LPI and HE generation, transport, and energy deposition. Such diagnostics include optical spectrometers, streaked optical shadowgraph, an x-ray pinhole camera, a two-dimensional x-ray imager, a Cu Kα line spectrometer, two hot-electron spectrometers, a hard x-ray (bremsstrahlung) detector, and a streaked optical pyrometer. Diagnostics successfully operated simultaneously in single-shot mode, revealing the features of HEs under SI-relevant conditions.

Super-strong magnetic field-dominated ion beam dynamics in focusing plasma devices

High energy density physics is the field of physics dedicated to the study of matter and plasmas in extreme conditions of temperature, densities and pressures. It encompasses multiple disciplines such as material science, planetary science, laboratory and astrophysical plasma science. For the latter, high energy density states can be accompanied by extreme radiation environments and super-strong magnetic fields. The creation of high energy density states in the laboratory consists in concentrating/depositing large amounts of energy in a reduced mass, typically solid material sample or dense plasma, over a time shorter than the typical timescales of heat conduction and hydrodynamic expansion. Laser-generated, high current–density ion beams constitute an important tool for the creation of high energy density states in the laboratory. Focusing plasma devices, such as cone-targets are necessary in order to focus and direct these intense beams towards the heating sample or dense plasma, while protecting the proton generation foil from the harsh environments typical of an integrated high-power laser experiment. A full understanding of the ion beam dynamics in focusing devices is therefore necessary in order to properly design and interpret the numerous experiments in the field. In this work, we report a detailed investigation of large-scale, kilojoule-class laser-generated ion beam dynamics in focusing devices and we demonstrate that high-brilliance ion beams compress magnetic fields to amplitudes exceeding tens of kilo-Tesla, which in turn play a dominant role in the focusing process, resulting either in a worsening or enhancement of focusing capabilities depending on the target geometry.

Erratum: Using Diffuse Scattering to Observe X-Ray-Driven Nonthermal Melting [Phys. Rev. Lett. 126, 015703 (2021)]

This corrects the article DOI: 10.1103/PhysRevLett.126.015703.

Micron-scale phenomena observed in a turbulent laser-produced plasma

Turbulence is ubiquitous in the universe and in fluid dynamics. It influences a wide range of high energy density systems, from inertial confinement fusion to astrophysical-object evolution. Understanding this phenomenon is crucial, however, due to limitations in experimental and numerical methods in plasma systems, a complete description of the turbulent spectrum is still lacking. Here, we present the measurement of a turbulent spectrum down to micron scale in a laser-plasma experiment. We use an experimental platform, which couples a high power optical laser, an x-ray free-electron laser and a lithium fluoride crystal, to study the dynamics of a plasma flow with micrometric resolution (~1μm) over a large field of view (>1 mm²). After the evolution of a Rayleigh–Taylor unstable system, we obtain spectra, which are overall consistent with existing turbulent theory, but present unexpected features. This work paves the way towards a better understanding of numerous systems, as it allows the direct comparison of experimental results, theory and numerical simulations.

Turbulence effects explored use macroscale systems in general. Here the authors generate a turbulent plasma using laser irradiation of a solid target and study the dynamics of the plasma flow at the micron-scale by using scattering of an XFEL beam.

Liquid Structure of Tantalum under Internal Negative Pressure

In situ femtosecond x-ray diffraction measurements and ab initio molecular dynamics simulations were performed to study the liquid structure of tantalum shock released from several hundred gigapascals (GPa) on the nanosecond timescale. The results show that the internal negative pressure applied to the liquid tantalum reached -5.6 (0.8)  GPa, suggesting the existence of a liquid-gas mixing state due to cavitation. This is the first direct evidence to prove the classical nucleation theory which predicts that liquids with high surface tension can support GPa regime tensile stress.

Using Diffuse Scattering to Observe X-Ray-Driven Nonthermal Melting

We present results from the SPring-8 Angstrom Compact free electron LAser facility, where we used a high intensity (∼10^{20}  W/cm^{2}) x-ray pump x-ray probe scheme to observe changes in the ionic structure of silicon induced by x-ray heating of the electrons. By avoiding Laue spots in the scattering signal from a single crystalline sample, we observe a rapid rise in diffuse scattering and a transition to a disordered, liquidlike state with a structure significantly different from liquid silicon. The disordering occurs within 100 fs of irradiation, a timescale that agrees well with first principles simulations, and is faster than that predicted by purely inertial behavior, suggesting that both the phase change and disordered state reached are dominated by Coulomb forces. This method is capable of observing liquid scattering without masking signal from the ambient solid, allowing the liquid structure to be measured throughout and beyond the phase change.

Effect of plastic coating on the density of plasma formed in Si foil targets irradiated by ultra-high-contrast relativistic laser pulses

The formation of high energy density matter occurs in inertial confinement fusion, astrophysical, and geophysical systems. In this context, it is important to couple as much energy as possible into a target while maintaining high density. A recent experimental campaign, using buried layer (or "sandwich" type) targets and the ultrahigh laser contrast Vulcan petawatt laser facility, resulted in 500 Mbar pressures in solid density plasmas (which corresponds to about 4.6×10^{7}J/cm^{3} energy density). The densities and temperatures of the generated plasma were measured based on the analysis of x-ray spectral line profiles and relative intensities.

Laser-driven shock compression of "synthetic planetary mixtures" of water, ethanol, and ammonia

Water, methane, and ammonia are commonly considered to be the key components of the interiors of Uranus and Neptune. Modelling the planets' internal structure, evolution, and dynamo heavily relies on the properties of the complex mixtures with uncertain exact composition in their deep interiors. Therefore, characterising icy mixtures with varying composition at planetary conditions of several hundred gigapascal and a few thousand Kelvin is crucial to improve our understanding of the ice giants. In this work, pure water, a water-ethanol mixture, and a water-ethanol-ammonia "synthetic planetary mixture" (SPM) have been compressed through laser-driven decaying shocks along their principal Hugoniot curves up to 270, 280, and 260 GPa, respectively. Measured temperatures spanned from 4000 to 25000 K, just above the coldest predicted adiabatic Uranus and Neptune profiles (3000-4000 K) but more similar to those predicted by more recent models including a thermal boundary layer (7000-14000 K). The experiments were performed at the GEKKO XII and LULI2000 laser facilities using standard optical diagnostics (Doppler velocimetry and optical pyrometry) to measure the thermodynamic state and the shock-front reflectivity at two different wavelengths. The results show that water and the mixtures undergo a similar compression path under single shock loading in agreement with Density Functional Theory Molecular Dynamics (DFT-MD) calculations using the Linear Mixing Approximation (LMA). On the contrary, their shock-front reflectivities behave differently by what concerns both the onset pressures and the saturation values, with possible impact on planetary dynamos.

Enhancing laser beam performance by interfering intense laser beamlets

Increasing the laser energy absorption into energetic particle beams represents a longstanding quest in intense laser-plasma physics. During the interaction with matter, part of the laser energy is converted into relativistic electron beams, which are the origin of secondary sources of energetic ions, γ-rays and neutrons. Here we experimentally demonstrate that using multiple coherent laser beamlets spatially and temporally overlapped, thus producing an interference pattern in the laser focus, significantly improves the laser energy conversion efficiency into hot electrons, compared to one beam with the same energy and nominal intensity as the four beamlets combined. Two-dimensional particle-in-cell simulations support the experimental results, suggesting that beamlet interference pattern induces a periodical shaping of the critical density, ultimately playing a key-role in enhancing the laser-to-electron energy conversion efficiency. This method is rather insensitive to laser pulse contrast and duration, making this approach robust and suitable to many existing facilities.

Enhanced coupling of laser energy to the target particles is a fundamental issue in laser-plasma interactions. Here the authors demonstrate increased photon absorption leading into higher laser to electron and proton energy transfer through the interference of multiple coherent beamlets.

Do sarcopenia and/or osteoporosis increase the risk of frailty? A 4-year observation of the second and third ROAD study surveys

In this 4-year follow-up study including 1083 subjects (≥ 60 years), the prevalence of frailty was estimated to be 5.6%; osteoporosis was found to be significantly associated with frailty. Moreover, the presence of both osteoporosis and sarcopenia increased the risk of frailty compared to the presence of osteoporosis or sarcopenia alone.

INTRODUCTION

This study aims to examine the contribution of sarcopenia and osteoporosis to the occurrence of frailty using 4-year follow-up information of a population-based cohort study.

METHODS

The second survey of the Research on Osteoarthritis/Osteoporosis Against Disability (ROAD) study was conducted between 2008 and 2010; 1083 subjects (aged ≥ 60 years, 372 men, 711 women) completed all examinations on frailty, sarcopenia, and osteoporosis, which were defined using Fried's definition, Asian Working Group for Sarcopenia criteria, and WHO criteria, respectively. The third survey was conducted between 2012 and 2013; 749 of 1083 individuals enrolled from the second survey (69.2%, 248 men, 501 women) completed assessments identical to those in the second survey.

RESULTS

The prevalence of frailty in the second survey was 5.6% (men, 3.8%; women, 6.6%). The cumulative incidence of frailty was 1.2%/year (men, 0.8%/year; women, 1.3%/year). After adjustment for confounding factors, logistic regression analysis indicated that osteoporosis was significantly associated with the occurrence of frailty (odds ratio, 3.07; 95% confidence interval, 1.26-7.36; p = 0.012). Moreover, the occurrence of frailty significantly increased according to the presence of osteoporosis and sarcopenia (odds ratio vs. neither osteoporosis nor sarcopenia: osteoporosis alone, 2.50; osteoporosis and sarcopenia, 5.80).

CONCLUSIONS

Preventing osteoporosis and coexistence of osteoporosis and sarcopenia may help reduce the risk of frailty.

A large-aperture high-sensitivity avalanche image intensifier panel

A large-aperture high-sensitivity image intensifier panel that consists of an avalanche photodiode array and a light-emitting diode array is presented. The device has 40% quantum efficiency, over 10⁴ optical gain, and 80-ns time resolution. The aperture size of the device is 20 cm, and with the current manufacturing process, it can be scaled to arbitrarily larger sizes. The device can intensify the light from a single particle scintillation emission to an eye-visible bright flash. The image resolution of the device is currently limited by the size of the avalanche photodiode that is 2 mm, although it can be scaled to smaller sizes in the near future. The image intensifier is operated at a small voltage, typically +57 V. The device can be applied to various applications, such as scintillation imaging, night vision cameras, and an image converter from non-visible light (such as infrared or ultraviolet) to visible light.

Self-generated surface magnetic fields inhibit laser-driven sheath acceleration of high-energy protons

High-intensity lasers interacting with solid foils produce copious numbers of relativistic electrons, which in turn create strong sheath electric fields around the target. The proton beams accelerated in such fields have remarkable properties, enabling ultrafast radiography of plasma phenomena or isochoric heating of dense materials. In view of longer-term multidisciplinary purposes (e.g., spallation neutron sources or cancer therapy), the current challenge is to achieve proton energies well in excess of 100 MeV, which is commonly thought to be possible by raising the on-target laser intensity. Here we present experimental and numerical results demonstrating that magnetostatic fields self-generated on the target surface may pose a fundamental limit to sheath-driven ion acceleration for high enough laser intensities. Those fields can be strong enough (~10⁵ T at laser intensities ~10²¹ W cm^–2) to magnetize the sheath electrons and deflect protons off the accelerating region, hence degrading the maximum energy the latter can acquire.

Laser-generated ion acceleration has received increasing attention due to recent progress in super-intense lasers. Here the authors demonstrate the role of the self-generated magnetic field on the ion acceleration and limitations on the energy scaling with laser intensity.

Radiographic measurements of the hip joint and their associations with hip pain in Japanese men and women: the Research on Osteoarthritis/osteoporosis Against Disability (ROAD) study

OBJECTIVE

To investigate radiographic measurements of the hip joint and their associations with hip pain, and the prevalence of acetabular dysplasia defined by radiographic measurements of the hip joint in Japanese men and women using the large-scale population-based cohort of the Research on Osteoarthritis/osteoporosis Against Disability (ROAD) study.

METHODS

From the baseline survey of the ROAD study (cross-sectional study), 2963 participants (1040 men, 1923 women; mean age, 70.2 years) were analyzed. All participants underwent radiographic examinations of both hips using an anteroposterior view under weight-bearing. Minimum joint space width (mJSW), central-edge (CE) angle, acetabular depth-to-width ratio (ADR), and acetabular head index (AHI) were measured. Associations between these radiographic measurements and hip pain were assessed by calculating odds ratios (ORs) using multivariable logistic-regression analysis. Acetabular dysplasia was defined as a CE angle <20°.

RESULTS

Mean radiographic measurements of the hip joint for men were: mJSW, 3.8 mm; CE angle, 30.6°; ADR, 262.1 per 1000; and AHI, 81.4%. For women, these values were: mJSW, 3.4 mm; CE angle, 29.9°; ADR, 262.7 per 1000; and AHI, 81.2%. Associations were seen between hip pain and each of mJSW, CE angle, ADR, and AHI (OR 4.52, 95% confidence interval 3.45-5.97; 1.14, 1.11-1.18; 1.31, 1.24-1.40; and 1.15, 1.12-1.18, respectively). Acetabular dysplasia showed an overall prevalence of 13.9%, and was significantly more prevalent in women than in men (P = 0.012).

CONCLUSION

The present study of radiographic measurements of the hip joint showed that mJSW, CE angle, ADR, and AHI were associated with hip pain.

Optical coherence tomography detection of characteristic retinal nerve fiber layer thinning in nasal hypoplasia of the optic disc

PurposeTo determine the clinical usefulness of optical coherence tomography (OCT) for detecting thinning of the retinal nerve fiber layer (RNFL) in eyes with nasal hypoplasia of the optic discs (NHOD).Patients and methodsThe medical records of five patients (eight eyes) with NHOD were reviewed. The ratio of the disc-macula distance to the disc diameter (DM/DD) and the disc ovality ratio of the minimal to maximal DD were assessed using fundus photographs. The RNFL thicknesses of the temporal, superior, nasal, and inferior quadrants were evaluated using OCT quadrant maps.ResultsAll eight eyes had temporal visual field defects that respected the vertical meridians that needed to be differentiated from those related to chiasmal compression. The mean DM/DD ratio was 3.1 and the mean disc ovality ratio was 0.81. The mean RNFL thicknesses of the temporal, superior, nasal, and inferior quadrants were 90.3, 103.1, 34.8, and 112.8 microns, respectively.ConclusionSmall optic discs and tilted discs might be associated with NHOD. Measurement of the RNFL thickness around the optic disc using OCT scans clearly visualized the characteristic RNFL thinning of the nasal quadrants corresponding to the temporal sector visual field defects in eyes with NHOD. OCT confirmed the presence of NHOD and might differentiate eyes with NHOD from those with chiasmal compression.

Using X-ray spectroscopy of relativistic laser plasma interaction to reveal parametric decay instabilities: a modeling tool for astrophysics

By analyzing profiles of experimental x-ray spectral lines of Si XIV and Al XIII, we found that both Langmuir and ion acoustic waves developed in plasmas produced via irradiation of thin Si foils by relativistic laser pulses (intensities ~10²¹ W/cm²). We prove that these waves are due to the parametric decay instability (PDI). This is the first time that the PDI-induced ion acoustic turbulence was discovered by the x-ray spectroscopy in laser-produced plasmas. These conclusions are also supported by PIC simulations. Our results can be used for laboratory modeling of physical processes in astrophysical objects and a better understanding of intense laser-plasma interactions.

Coherent X-ray beam metrology using 2D high-resolution Fresnel-diffraction analysis

Direct metrology of coherent short-wavelength beamlines is important for obtaining operational beam characteristics at the experimental site. However, since beam-time limitation imposes fast metrology procedures, a multi-parametric metrology from as low as a single shot is desirable. Here a two-dimensional (2D) procedure based on high-resolution Fresnel diffraction analysis is discussed and applied, which allowed an efficient and detailed beamline characterization at the SACLA XFEL. So far, the potential of Fresnel diffraction for beamline metrology has not been fully exploited because its high-frequency fringes could be only partly resolved with ordinary pixel-limited detectors. Using the high-spatial-frequency imaging capability of an irradiated LiF crystal, 2D information of the coherence degree, beam divergence and beam quality factor M² were retrieved from simple diffraction patterns. The developed beam metrology was validated with a laboratory reference laser, and then successfully applied at a beamline facility, in agreement with the source specifications.

Is osteoporosis a predictor for future sarcopenia or vice versa? Four-year observations between the second and third ROAD study surveys

In a 4-year follow-up study that enrolled 1099 subjects aged ≥60 years, sarcopenia prevalence was estimated at 8.2%. Moreover, the presence of osteoporosis was significantly associated with short-term sarcopenia occurrence, but the reciprocal relationship was not observed, suggesting that osteoporosis would increase the risk of osteoporotic fracture and sarcopenia occurrence.

INTRODUCTION

The present 4-year follow-up study was performed to clarify the prevalence, incidence, and relationships between sarcopenia (SP) and osteoporosis (OP) in older Japanese men and women.

METHODS

We enrolled 1099 participants (aged, ≥60 years; 377 men) from the second survey of the Research on Osteoarthritis/Osteoporosis against Disability (ROAD) study (2008-2010) and followed them up for 4 years. Handgrip strength, gait speed, skeletal muscle mass, and bone mineral density were assessed. SP was defined according to the Asian Working Group for Sarcopenia. OP was defined based on the World Health Organization criteria.

RESULTS

SP prevalence was 8.2% (men, 8.5%; women, 8.0%) in the second survey. In those with SP, 57.8% (21.9%; 77.6%) had OP at the lumbar spine L2-4 and/or femoral neck. SP cumulative incidence was 2.0%/year (2.2%/year; 1.9%/year). Multivariate regression analysis revealed that OP was significantly associated with SP occurrence within 4 years (odds ratio, 2.99; 95% confidence interval, 1.46-6.12; p < 0.01), but the reciprocal relationship was not significantly observed (2.11; 0.59-7.59; p = 0.25).

CONCLUSIONS

OP might raise the short-term risk of SP incidence. Therefore, OP would not only increase the risk for osteoporotic fracture but may also increase the risk for SP occurrence.

Highly efficient terahertz radiation from a thin foil irradiated by a high-contrast laser pulse

Radially polarized intense terahertz (THz) radiation behind a thin foil irradiated by ultrahigh-contrast ultrashort relativistic laser pulse is recorded by a single-shot THz time-domain spectroscopy system. As the thickness of the target is reduced from 30 to 2 µm, the duration of the THz emission increases from 5 to over 20 ps and the radiation energy increases dramatically, reaching ∼10.5mJ per pulse, corresponding to a laser-to-THz radiation energy conversion efficiency of 1.7%. The efficient THz emission can be attributed to reflection (deceleration and acceleration) of the laser-driven hot electrons by the target-rear sheath electric field. The experimental results are consistent with that of a simple model as well as particle-in-cell simulation.

Note: Single-shot time-domain spectroscopy and spatial profiling of terahertz pulses from intense laser systems

Single-shot terahertz time-domain spectroscopy is presented with directly encoded spatial resolution. A single reflective echelon and multiple semi-cylindrical lenses are used to obtain both the temporal waveform and the spatial distribution of the terahertz field. This system can be used to rapidly characterize terahertz pulses generated by high power pulsed laser systems, which themselves suffer from large pulse energy and spectrum fluctuations.

Dynamic compression of dense oxide (Gd3Ga5O12) from 0.4 to 2.6 TPa: Universal Hugoniot of fluid metals

Materials at high pressures and temperatures are of great current interest for warm dense matter physics, planetary sciences, and inertial fusion energy research. Shock-compression equation-of-state data and optical reflectivities of the fluid dense oxide, Gd3Ga5O12 (GGG), were measured at extremely high pressures up to 2.6 TPa (26 Mbar) generated by high-power laser irradiation and magnetically-driven hypervelocity impacts. Above 0.75 TPa, the GGG Hugoniot data approach/reach a universal linear line of fluid metals, and the optical reflectivity most likely reaches a constant value indicating that GGG undergoes a crossover from fluid semiconductor to poor metal with minimum metallic conductivity (MMC). These results suggest that most fluid compounds, e.g., strong planetary oxides, reach a common state on the universal Hugoniot of fluid metals (UHFM) with MMC at sufficiently extreme pressures and temperatures. The systematic behaviors of warm dense fluid would be useful benchmarks for developing theoretical equation-of-state and transport models in the warm dense matter regime in determining computational predictions.

Prevalence of radiographic hip osteoarthritis and its association with hip pain in Japanese men and women: the ROAD study

OBJECTIVE

Although hip osteoarthritis (OA) is a major cause of hip pain and disability in elderly people, few epidemiologic studies have been performed. We investigated the prevalence of radiographic hip OA and its association with hip pain in Japanese men and women using a large-scale population of a nationwide cohort study, Research on Osteoarthritis/osteoporosis Against Disability (ROAD).

METHODS

From the baseline survey of the ROAD study, 2975 participants (1043 men and 1932 women), aged 23-94 years (mean 70.2 years), living in urban, mountainous, and coastal communities were analyzed. The radiographic severity at both hips was determined by the Kellgren/Lawrence (K/L) grading system. Radiographic hip OA was defined as K/L ≥ 2, and severe radiographic hip OA as K/L ≥ 3.

RESULTS

The crude prevalence of radiographic hip OA was 18.2% and 14.3% in men and women, respectively, that of severe radiographic hip OA was 1.34% and 2.54%, and that of symptomatic K/L ≥ 2 OA was 0.29% and 0.99%, respectively. The crude prevalence of hip OA, including severe OA, was not age-dependent in men or women. Male sex was a risk factor for radiographic hip OA, whereas female sex was a risk factor for severe radiographic hip OA and hip pain. Compared with K/L = 0/1, hip pain was significantly associated with K/L ≥ 3, but not with K/L = 2.

CONCLUSION

The present cross-sectional study revealed the prevalence of radiographic hip OA and severe hip OA in Japanese men and women. Hip pain was strongly associated with K/L ≥ 3.

Experimental and ab initio investigations of microscopic properties of laser-shocked Ge-doped ablator

Plastic materials (CH) doped with mid-Z elements are used as ablators in inertial confinement fusion (ICF) capsules and in their surrogates. Hugoniot equation of state (EOS) and electronic properties of CH doped with germanium (at 2.5% and 13% dopant fractions) are investigated experimentally up to 7 Mbar using velocity and reflectivity measurements of shock fronts on the GEKKO laser at Osaka University. Reflectivity and temperature measurements were updated using a quartz standard. Shocked quartz reflectivity was measured at 532 and 1064 nm. Theoretical investigation of shock pressure and reflectivity was then carried out by ab initio simulations using the quantum molecular dynamics (QMD) code abinit and compared with tabulated average atom EOS models. We find that shock states calculated by QMD are in better agreement with experimental data than EOS models because of a more accurate description of ionic structure. We finally discuss electronic properties by comparing reflectivity data to a semiconductor gap closure model and to QMD simulations.

Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 10(21)  W/cm(2) is efficiently converted to X-ray radiation, which is emitted by "hot" electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E(4-5) of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~10(17)  W/cm(2), there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.

P-ρ-T measurements of H2O up to 260 GPa under laser-driven shock loading

Pressure, density, and temperature data for H2O were obtained up to 260 GPa by using laser-driven shock compression technique. The shock compression technique combined with the diamond anvil cell was used to assess the equation of state models for the P-ρ-T conditions for both the principal Hugoniot and the off-Hugoniot states. The contrast between the models allowed for a clear assessment of the equation of state models. Our P-ρ-T data totally agree with those of the model based on quantum molecular dynamics calculations. These facts indicate that this model is adopted as the standard for modeling interior structures of Neptune, Uranus, and exoplanets in the liquid phase in the multi-Mbar range.

Laser-shock compression of magnesium oxide in the warm-dense-matter regime

Magnesium oxide has been experimentally and computationally investigated in the warm-dense solid and liquid ranges from 200 GPa to 1 TPa along the principal Hugoniot. The linear approximation between shock velocity and particle velocity is validated up to a shock velocity of 15 km/s from the experimental data, this suggesting that the MgO B1 structure is stable up to the corresponding shock pressure of ∼350 GPa. Moreover, our Hugoniot data, combined with ab initio simulations, show two crossovers between MgO Hugoniot and the extrapolation of the linear approximation line, occurring at a shock pressures of approximately 350 and 650 GPa, with shock temperatures of 8000 and 14,000 K, respectively. These crossover regions are consistent with the solid-solid (B1-B2) and the solid-liquid (B2-melt) phase boundaries predicted by the ab initio calculations.

Zidovudine, an anti-viral drug, resensitizes gemcitabine-resistant pancreatic cancer cells to gemcitabine by inhibition of the Akt-GSK3β-Snail pathway

Pancreatic cancer is one of the most difficult malignancies to treat owing to the rapid acquisition of resistance to chemotherapy. Gemcitabine, a first-line treatment for pancreatic cancer, prolongs patient survival by several months, and combination treatment with gemcitabine and other anti-cancer drugs in the clinic do not show any significant effects on overall survival. Thus, identification of a drug that resensitizes gemcitabine-resistant pancreatic cancer to gemcitabine and a better understanding of the molecular mechanisms of gemcitabine resistance are critical to develop new therapeutic options for pancreatic cancer. Here, we report that zidovudine resensitizes gemcitabine-resistant pancreatic cancer to gemcitabine as shown by screening a compound library, including clinical medicine, using gemcitabine-resistant cells. In analyzing the molecular mechanisms of zidovudine effects, we found that the epithelial-to-mesenchymal transition (EMT)-like phenotype and downregulation of human equilibrative nucleoside transporter 1 (hENT1) are essential for the acquisition of gemcitabine resistance, and zidovudine restored these changes. The chemical biology investigations also revealed that activation of the Akt-GSK3β-Snail1 pathway in resistant cells is a key signaling event for gemcitabine resistance, and zidovudine resensitized resistant cells to gemcitabine by inhibiting this activated pathway. Moreover, our in vivo study demonstrated that co-administration of zidovudine and gemcitabine strongly suppressed the formation of tumors by gemcitabine-resistant pancreatic cancer and prevented gemcitabine-sensitive pancreatic tumors from acquiring gemcitabine-resistant properties, inducing an EMT-like phenotype and downregulating hENT1 expression. These results suggested that co-treatment with zidovudine and gemcitabine may become a novel therapeutic strategy for pancreatic cancer by inhibiting chemoresistance-specific signaling.

Clinical features of a new disease concept, IgG4-related thyroiditis

OBJECTIVES

Immunoglobulin (Ig)G4-related disease is a recently proposed systemic disorder that includes autoimmune pancreatitis (AIP), Mikulicz's disease, and various other organ lesions. In the present retrospective study, we examined whether thyroid lesions should also be included in IgG4-related disease (Ig4-RD) under the new term IgG4-related thyroiditis.

METHOD

We enrolled 114 patients with Ig4-RD, including 92 patients with AIP, 15 patients with Mikulicz's disease, and seven patients with IgG4-related cholangitis, and analysed clinical findings, function, serum values of activity markers, computed tomography (CT) images, and histology of the thyroid gland.

RESULTS

Among the 22 patients (19%) in our cohort who were found to have hypothyroidism [thyroid stimulating hormone (TSH) > 4 mIU/L], 11 patients had clinical hypothyroidism [free thyroxine (FT4) < 1 ng/dL] and 11 patients had subclinical hypothyroidism (FT4 ≥ 1 ng/dL). Serum concentrations of IgG, IgG4, circulating immune complex (CIC), and β2-microglobulin (β2-MG) were significantly higher in the hypothyroidism group compared with the remaining 92 euthyroid patients, and serum C3 concentration was significantly lower. After prednisolone treatment, TSH values had decreased significantly (p = 0.005) in this group and FT4 values had increased significantly (p = 0.047). CT images showed that the thyroid glands of patients with clinical hypothyroidism had a significantly greater volume than those of the euthyroid and other groups. Pathological analysis of one resected thyroid gland disclosed a focused lesion with infiltration of lymphocytes and IgG4-bearing plasma cells and loss of thyroid follicles.

CONCLUSIONS

Thyroid lesions associated with hypothyroidism can be considered as a new disease termed IgG4-related thyroiditis. Awareness of this condition should lead to appropriate corticosteroid treatment that may prevent progression to a fibrous state.

A tapered parallel plate waveguide for frequency up-conversion of terahertz radiation

A tapered parallel plate waveguide was developed for frequency up-conversion experiments in the terahertz (THz) region by flash ionization. The element at the plasma-source-wave interaction area determines the conversion efficiency. It causes THz pulses to converge to a narrow plate separation, which is smaller than the wavelength. The waveguide exhibited good performance for transmitting p-polarized THz pulses in a 50 μm separation, making it suitable for flash ionization experiments.

50 EFFECTS OF VITAMINS ON THE QUALITY AND FERTILITY OF BOAR SEMEN AFTER LIQUID PRESERVATION AT 5°C

Liquid preservation can be used as an alternative to freeze-thawing for preserving semen for AI. The efficiency of some boar semen extenders has been studied over storage periods of 5 to 7 days. The objective of this study was to evaluate the viability and penetrability of boar spermatozoa preserved at 5°C in a modified Modena-based extender supplemented with either 100 μM vitamin C (Vc), 100 μM vitamin E (Ve), or 100 μM Vc + 100 μM Ve (Vc + e). The final sperm concentration was adjusted to cells mL–1 and the semen was then stored at 5°C for 4 weeks. In Experiment 1, the semen samples were assessed every week during the 4-week storage in each extender for the following factors: motility, by using computer-assisted semen analysis (CASA); viability, by using the Live/Dead fluorescence viability assay; plasma membrane integrity, by using the hypoosmotic swelling test (HOST); and acrosome integrity, by using fluorescein isothiocyanate (FITC)-labelled peanut agglutinin staining. In Experiment 2, we examined the penetrability of spermatozoa that had been stored in each extender for 4 weeks and the development of fertilized oocytes. Data were analysed using ANOVA. In Experiment 1, when the semen was stored for 2 weeks, the mean percentage values of total sperm motility and viability for semen stored with Ve were significantly higher than those for semen stored without Vc and Ve (control group) (84.3 vs 67.9% and 59.8 vs 51.2%, respectively; P < 0.05). Moreover, the percentage sperm motility for semen stored for 4 weeks tended to be higher in the Ve group than in the control group (44.2 vs 32.7%; P < 0.1). Storage with Vc or Vc + e did not improve sperm motility and viability of semen. The plasma membrane integrity and acrosome integrity of semen did not significantly differ among the groups during the 4-week storage. In Experiment 2, the rates of sperm penetration and of development to blastocysts of fertilized oocytes did not differ between the Ve and control groups (33.0 vs 28.5% and 14.9 vs 10.1%, respectively; P > 0.05). However, storage with Vc reduced the rate of oocyte development compared with the Ve and control groups (1.1%; P < 0.05). In conclusion, adding Ve to the semen extender may improve the motility and fertility of boar semen stored at 5°C. However, adding Vc has a harmful effect on the quality and fertility of stored boar semen.

Tunable radiation source by coupling laser-plasma-generated electrons to a periodic structure

Near-infrared radiation around 1000 nm generated from the interaction of a high-density MeV electron beam, obtained by impinging an intense ultrashort laser pulse on a solid target, with a metal grating is observed experimentally. Theoretical modeling and particle-in-cell simulation suggest that the radiation is caused by the Smith-Purcell mechanism. The results here indicate that tunable terahertz radiation with tens GV/m field strength can be achieved by using appropriate grating parameters.

Enhancement of laser interaction with vacuum for a large angular aperture

We study the nonlinear interaction of laser light with vacuum for a large angular aperture at electromagnetic field strengths far below the Schwinger limit. The polarization and magnetization in vacuum irradiated by a focused laser beam clearly differ from those in matter. This is due to the dependence on the Lorentz invariant, which results in a ring-shaped radiation distribution in vacuum. The number of the radiated photons increases nonlinearly with increasing angular aperture.

Experimental evidence of nonthermal acceleration of relativistic electrons by an intensive laser pulse

Nonthermal acceleration of relativistic electrons is investigated with an intensive laser pulse. An energy distribution function of energetic particles in the universe or cosmic rays is well represented by a power-law spectrum, therefore, nonthermal acceleration is essential to understand the origin of cosmic rays. A possible candidate for the origin of cosmic rays is wakefield acceleration at relativistic astrophysical perpendicular shocks. The wakefield is considered to be excited by large-amplitude precursor light waves in the upstream of the shocks. Substituting an intensive laser pulse for the large amplitude light waves, we performed a model experiment of the shock environments in a laboratory plasma. An intensive laser pulse was propagated in a plasma tube created by imploding a hollow polystyrene cylinder, as the large amplitude light waves propagated in the upstream plasma at an astrophysical shock. Nonthermal electrons were generated, and the energy distribution functions of the electrons have a power-law component with an index of ~2. We described the detailed procedures to obtain the nonthermal components from data obtained by an electron spectrometer.

18 EFFECTS OF SKIM MILK ON THE QUALITY AND FERTILITY OF BOAR SEMEN FOLLOWING LIQUID PRESERVATION AT 5°C AND 15°C

Liquid preservation of semen can be an alternative to frozen–thawed semen for artificial insemination. The success of a selection of boar semen extenders has been studied over storage periods of 5 to 7 days. The objective of this study was to evaluate the effects of skim milk on the viability and in vitro fertility of boar spermatozoa preserved in Modena-based extenders at 5°C and 15°C for 2 weeks. A total of 7 ejaculates were collected from one boar. The sperm-rich fraction of each ejaculate was centrifuged and diluted in Modena extenders supplemented with 0 (control), 7.5, and 15 mg mL–1 of dry skim milk. The final sperm concentration was adjusted to 1 × 108 cells mL–1, and then the semen was stored at 5°C and 15°C for 2 weeks. In the first experiment, the motility, viability (live/dead fluorescence viability assay), plasma membrane integrity (hypoosmotic swelling test; HOST), and acrosome integrity (FITC-labelled peanut agglutinin staining) of semen stored for 2 weeks were assessed. In the second experiment, the fertilization of stored semen after 20 h of co-incubation with in vitro matured oocytes and their development were examined. Data were analysed using ANOVA. When the semen was stored at 5°C for 2 weeks, the mean total sperm motility of semen stored with 7.5 and 15 mg mL–1 of dry skim milk was significantly higher than that of semen in the control group (41.4% and 41.5% v. 17.4%; P < 0.05). However, the beneficial effects of skim milk on the sperm motility were not observed in the semen stored at 15°C. Moreover, there were no significant differences in the other parameters of semen quality among the groups in each storage temperature. Significantly higher penetration rates of semen stored with 7.5 and 15 mg mL–1 of dry skim milk were observed in the storage at 5°C (41.1% and 34.8% v. 19.8%; P < 0.05) but not at 15°C (38.9% and 26.0% v. 30.0%; P > 0.05) when compared with the control group. When the semen was stored at 5°C, the development rate to the blastocyst stage of oocytes fertilized with semen stored with 7.5 mg mL–1 of dry skim milk was significantly higher than that with control and 15 mg mL–1 of dry skim milk (15.4% v. 1.1% and 7.8%; P < 0.01). However, there were no significant differences in the development rates of oocytes fertilized with semen stored at 15°C among the groups (9.6–11.9%). In conclusion, our results indicate that the effect of skim milk on the viability and in vitro fertility of liquid-stored boar spermatozoa is dependent on the storage temperature. The addition of 7.5 mg mL–1 of dry skim milk may be effective for the improvement of viability and fertility of semen stored at 5°C but not at 15°C.

Quasimonoenergetic proton bunch generation by dual-peaked electrostatic-field acceleration in foils irradiated by an intense linearly polarized laser

It is found that stable proton acceleration from a thin foil irradiated by a linearly polarized ultraintense laser can be realized for appropriate foil thickness and laser intensity. A dual-peaked electrostatic field, originating from the oscillating and nonoscillating components of the laser ponderomotive force, is formed around the foil surfaces. This field combines radiation-pressure acceleration and target normal sheath acceleration to produce a single quasimonoenergetic ion bunch. A criterion for this mechanism to be operative is obtained and verified by two-dimensional particle-in-cell simulation. At a laser intensity of ∼5.5×10(22)  W/cm(2), quasimonoenergetic GeV proton bunches are obtained with ∼100  MeV energy spread, less than 4° spatial divergence, and ∼50% energy conversion efficiency from the laser.

Fast focusing of short-pulse lasers by innovative plasma optics toward extreme intensity

We developed a compact plasma-based focusing optic that, in one step, increases the peak intensity of ultrahigh-intensity lasers without modifying the laser system itself. By using a plasma-based focusing optic with extremely small f-number (f/0.4), we have experimentally demonstrated a fivefold reduction of the focal spot size (from 4.4 to 0.9 microm), thus producing an at least eightfold enhancement of the laser light intensity. This innovative plasma-based optic opens the way for the study of high-energy-density and high-field science at intensities greater than presently available.