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.

Parametric attosecond pulse amplification far from the ionization threshold from high order harmonic generation in He.

Parametric amplification of attosecond coherent pulses around 100 eV at the single-atom level is demonstrated for the first time by using the 3D time-dependent Schrödinger equation in high-harmonic generation processes from excited states of He+. We present the attosecond dynamics of the amplification process far from the ionization threshold and resolve the physics behind it. The amplification of a particular central photon energy requires the seed XUV pulses to be perfectly synchronized in time with the driving laser field for stimulated recombination to the He+ ground state and is only produced in a few specific laser cycles in agreement with the experimental measurements. Our simulations show that the amplified photon energy region can be controlled by varying the peak intensity of the laser field. Our results pave the way to the realization of compact attosecond pulse intense XUV lasers with broad applications.

Burst intensification by singularity emitting radiation in multi-stream flows.

Burst Intensification by Singularity Emitting Radiation (BISER) is proposed. Singularities in multi-stream flows of emitting media cause constructive interference of emitted travelling waves, forming extremely localized sources of bright coherent emission. Here we for the first time demonstrate this extreme localization of BISER by direct observation of nano-scale coherent x-ray sources in a laser plasma. The energy emitted into the spectral range from 60 to 100 eV is up to ~100 nJ, corresponding to ~1010 photons. Simulations reveal that these sources emit trains of attosecond x-ray pulses. Our findings establish a new class of bright laboratory sources of electromagnetic radiation. Furthermore, being applicable to travelling waves of any nature (e.g. electromagnetic, gravitational or acoustic), BISER provides a novel framework for creating new emitters and for interpreting observations in many fields of science.

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.

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.

Quantitative measurement of hard x-ray spectra for high intensity laser produced plasma.

X-ray line spectra ranging from 17 to 77 keV were quantitatively measured with a Laue spectrometer, composed of a cylindrically curved crystal and a detector. Either a visible CCD detector coupled with a CsI phosphor screen or an imaging plate can be chosen, depending on the signal intensities and exposure times. The absolute sensitivity of the spectrometer system was calibrated using pre-characterized laser-produced x-ray sources and radioisotopes. The integrated reflectivity for the crystal is in good agreement with predictions by an open code for x-ray diffraction. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer agency for specific x-ray line emissions, is derived as a consequence of this work.

Efficient multi-keV x-ray generation from a high-Z target irradiated with a clean ultra-short laser pulse.

Kα line emissions from Mo and Ag plates were experimentally studied using clean, ultrahigh-intensity femtosecond laser pulses. The absolute yields of Kα x-rays at 17 keV from Mo and 22 keV from Ag were measured as a function of the laser pulse contrast ratio and irradiation intensity. Significantly enhanced Kα yields were obtained for both Mo and Ag by employing high contrast ratios and irradiances. Conversion efficiencies of 4.28×10⁻5/sr for Mo and 4.84×10⁻5/sr for Ag, the highest values obtained to date, were demonstrated with contrast ratios in the range 10⁻¹° to 10⁻¹¹.

Validity of mid-arm muscular area measured by anthropometry in nonobese patients with increased muscle atrophy and variation of subcutaneous fat thickness.

BACKGROUND: The anthropometric measurement of mid-arm muscular area (MAMA) involves overestimation because of various assumptions, this overestimation being progressive with increasing adiposity. However, the effects of muscle atrophy and variation of the subcutaneous fat thickness have remained uncertain. OBJECTIVES: The validity of MAMA estimated by anthropometry was examined by comparing with MAMA measured by computed tomography (CT) in a nonobese population. The effects of muscle atrophy and variation of the subcutaneous fat thickness on the validity of MAMA were examined by new indices. SUBJECTS/METHODS: The relative MAMA was compared between the anthropometric and CT methods in 45 patients. New indices were introduced for assessing muscle deformity (muscle deformity index, MDI) and subcutaneous fat variation (SFVI). The effects of MDI, SFVI and age on the difference of MAMA between the anthropometric and CT methods were investigated. RESULTS: MDIs were positively correlated with age in males (r=0.47, P<0.05) and females (r=0.66, P<0.001). SFVI was positively correlated with age only in females (r=0.54, P<0.01). Even in these patients, the relative MAMA estimated by anthropometry was significantly associated with that measured by CT (r=0.85, P<0.0001 in males and r=0.90, P<0.0001 in females). A Bland-Altman plot indicated that the difference between both methods was relatively small, although increased adiposity might be a source of overestimation for anthropometric MAMA measurement. CONCLUSIONS: MAMA estimated by anthropometry was a reliable indicator of muscle mass in patients with muscle atrophy and varying thickness of subcutaneous fat in lean patients.

Submicrometer-resolution in situ imaging of the focus pattern of a soft x-ray laser by color center formation in LiF crystal.

We demonstrate high quality, single-shot in situ imaging of the focused Ag x-ray laser (XRL) at 13.9 nm with 700 nm spatial resolution by color center formation in LiF. The flux and intensity for the color center formation in LiF are evaluated from the experimental data. Comparisons with previous reports show that the threshold x-ray flux for the color center formation in LiF for the 13.9 nm, 7 ps Ag XRL is 3 orders of magnitude less than that with the 46.9 nm, 2 ns capillary discharge Ar XRL.

Direct observation of the critical relaxation of polarization clusters in BaTiO3 using a pulsed x-ray laser technique.

We have developed a new method to investigate the relaxation time of the dipole moment in polarization clusters in BaTiO3. Time correlation of speckle intensities was measured by the use of a double pulsed soft x-ray laser. The evolution of the relaxation time of the dipole moment near the Curie temperature (T(C)) was investigated. The maximum relaxation time (approximately 90 ps) is shown to appear at a temperature of 4.5 K above the T(C), being coincident with the one where the maximum polarization takes place. This method is widely applicable to any other critical decay processes at phase transitions.

Enhancement of double auger decay probability in xenon clusters irradiated with a soft-x-ray laser pulse.

The interaction of large Xe clusters with a soft x-ray laser pulse having a wavelength of 13.9 nm and an intensity of up to 2x10(10) W/cm2 was investigated using a time-of-flight ion mass spectrometer. The corresponding laser photon energy was sufficiently high to photoionize Xe 4d innershell electrons. It was found that Xe3+ ions (which result from double Auger decay of 4d vacancies) became the dominant final ionic product with increasing cluster size and x-ray intensity. This is in contrast to the results of synchrotron radiation experiments involving free Xe atoms, in which Xe2+ is the dominant resultant ion species. Possible mechanisms responsible for the enhancement of the double Auger transition probability in x-ray laser and cluster interaction are discussed.

Altered abdominal fat distribution and its association with the serum lipid profile in non-diabetic haemodialysis patients.

BACKGROUND: Disturbances of lipid and carbohydrate metabolism may be associated with the distribution of abdominal adiposity. However, little is known about the alteration of abdominal adiposity and its association with the serum lipid profile in haemodialysis patients. METHODS: We evaluated the distribution of abdominal adiposity by using computed tomography and examined its relationship with the serum lipid profile in 92 non-diabetic haemodialysis patients and 80 control subjects with normal renal function. Since the mean body mass index (BMI) and total body fat mass were significantly lower in the haemodialysis patients than in the control subjects, the subcutaneous abdominal fat area and the visceral fat area were standardized by body mass index and compared between the haemodialysis patients and the control subjects. RESULTS: Mean subcutaneous fat area/body mass index (SFA/BMI) was significantly lower, and mean visceral fat area/body mass index (VFA/BMI) was significantly higher in the haemodialysis patients (SFA/BMI, 2.40+/-0.12; VFA/BMI, 2.28+/-0.15) than in the control subjects (SFA/BMI, 3.75+/-0.21, P<0.01; VFA/BMI, 1.65+/-0.15, P<0.01). Consequently, visceral fat area/ subcutaneous fat area ratio was significantly higher in the haemodialysis patients (1.05+/-0.07) than in the control subjects (0.46+/-0.04, P<0.01). A scattered plot of visceral fat area relative to BMI revealed that visceral fat area was higher in the haemodialysis patients than in the control subjects at any BMI level. A simple regression analysis showed that BMI, total body fat mass, subcutaneous fat area and visceral fat area were all associated with serum triglycerides and the atherogenic index, (total cholesterol-HDL cholesterol)/HDL cholesterol. Furthermore, a multiple regression analysis indicated that the visceral fat area was the best predictor for either the atherogenic index or triglycerides among these fat components. CONCLUSIONS: These data indicate that haemodialysis patients exhibited a visceral fat accumulation irrespective of BMI, and this shift of abdominal adiposity might be associated with disturbance of the serum lipid profile in non-diabetic haemodialysis patients.

Association of the serum leptin concentration with weight loss in chronic hemodialysis patients.

Circulating leptin, which is partly cleared by the kidney, has been reported to increase with chronic renal failure and thus may play a role in the weight loss of patients with chronic renal failure. We investigated the association of body weight loss with the serum leptin concentration in Japanese hemodialysis patients. The relationship between serum leptin and the body mass index (BMI) or body fat mass was compared among 181 patients undergoing hemodialysis and 185 control subjects. There was no difference in the serum leptin concentration between the hemodialysis patients (HD) and controls (C) for either the men (3.9 +/- 0.2 ng/mL for HD, n=117; 3.9 +/- 0.3 ng/mL for C, n=89; NS) or women (8.9 +/- 1.2 ng/mL for HD, n=64; 7.4 +/- 0.5 ng/mL for C, n=96; NS), whereas BMI of the hemodialysis patients was significantly lower than that of the controls for both the men (20.1 +/- 0.2 kg/m2 for HD, 22.4 +/- 0.3 kg/m2 for C, P < 0.001) and women (19.2 +/- 0.3 kg/m2 for HD, 22.0 +/- 0.4 kg/m2 for C, P < 0.001). The serum leptin/body fat mass ratio was significantly correlated with the weight change of the patients during a follow-up evaluation period of 17 months (r = -0.37, P < 0.05 for men, n=27 and r = -0.53, P < 0.005 for women, n=28), indicating the possibility that a relatively high level of serum leptin had induced weight loss in the hemodialysis patients. The serum leptin/body fat mass ratio also showed a significant inverse correlation with the duration of hemodialysis (r = -0.31, P < 0.05 for men and r = -0.49, P < 0.05 for women). A multiple regression analysis indicated that the body fat mass was significantly correlated with serum leptin concentration, whereas the fat distribution did not have any relationship with leptin. These data indicate that a high level of serum leptin relative to the body fat mass might be associated with weight loss in long-term hemodialysis patients. The serum leptin level relative to the body fat mass also seems to have been affected by the duration of hemodialysis.

[A case of multiple colorectal cancers repeatedly resected 5 times].

A case of successive metachronous colorectal cancers repeatedly resected 5 times during an 8-year period is reported. The 1st cancer was found in the sigmoid colon when the patient (male) was 32 years old. The 2nd was a mucosal carcinoma of the rectum which was locally excised. The 3rd was found in the ascending colon, and there was detected yet another small cancer in the adenoma in the resected specimen. The 4th and 5th cancers were found in the transverse colon and rectum, respectively. This case is considered to be highly associated with genetic factors. Long-term and careful surveillance is mandatory for early detection of recurrent or additional tumors.