Ultrafast time-resolved 2D imaging of laser-driven fast electron transport in solid density matter using an x-ray free electron laser.

High-power, short-pulse laser-driven fast electrons can rapidly heat and ionize a high-density target before it hydrodynamically expands. The transport of such electrons within a solid target has been studied using two-dimensional (2D) imaging of electron-induced Kα radiation. However, it is currently limited to no or picosecond scale temporal resolutions. Here, we demonstrate femtosecond time-resolved 2D imaging of fast electron transport in a solid copper foil using the SACLA x-ray free electron laser (XFEL). An unfocused collimated x-ray beam produced transmission images with sub-micron and ∼10 fs resolutions. The XFEL beam, tuned to its photon energy slightly above the Cu K-edge, enabled 2D imaging of transmission changes induced by electron isochoric heating. Time-resolved measurements obtained by varying the time delay between the x-ray probe and the optical laser show that the signature of the electron-heated region expands at ∼25% of the speed of light in a picosecond duration. Time-integrated Cu Kα images support the electron energy and propagation distance observed with the transmission imaging. The x-ray near-edge transmission imaging with a tunable XFEL beam could be broadly applicable for imaging isochorically heated targets by laser-driven relativistic electrons, energetic protons, or an intense x-ray beam.

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.

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.

Controlling the phase matching conditions of optical parametric chirped-pulse amplification using partially deuterated KDP.

Using a partially deuterated KDP crystal for an optical parametric amplifier, we demonstrated ultrabroadband optical parametric chirped-pulse amplification of more than 250 nm bandwidth at a center wavelength of 1050 nm. We numerically show how to control the broadband phase matching conditions at different wavelengths to match center wavelengths of suitable broadband seed sources by adjusting the deuteration level in partially deuterated KDP.

Multisegmented kinoform phase plate for spatial and temporal control of the focal-plane irradiance profile.

Kinoform phase plates (KPPs) are widely used in inertial confinement fusion to improve energy efficiency and to produce an optimum irradiance profile on the target plane. However KPPs are sensitive to beam aberrations and offer little flexibility in temporally tailoring the far-field pattern. To overcome these problems, we developed a multisegmented KPP and demonstrated temporal control of a focusing pattern and protection against phase distortions by numerical simulations.

Laguerre-Gaussian beam generated with a multilevel spiral phase plate for high intensity laser pulses.

We investigated an Laguerre-Gaussian (LG) beam that can carry an orbital angular momentum and has a doughnut-shaped intensity pattern. We developed a multilevel spiral phase plate (SPP) that generates an LG beam by applying the wave surface of a spiral structure directly to a Gaussian beam for application to microscopic laser material processing.We experimentally demonstrate, for the first time, that it is possible to generate an LG beam with the multilevel SPP that allows the use in high intensity laser pulses.

Effect of acid-base disturbances on aldosterone secretion in man.

The present study was carried out to elucidate whether changes in blood pH induced by administration of alkalinizing and acidifying agents influence aldosterone secretion in man. Since aldosterone secretion is known to be regulated by various factors such as the renin-angiotensin system, adrenocorticotropic hormone (ACTH), and serum potassium concentration, these indices were simultaneously measured during manipulation. Oral administration of tris hydroxymethyl aminomethane (THAM) resulted in a moderate but not significant decrease in serum aldosterone together with an increase in blood pH, whereas plasma renin activity (PRA) remained unchanged and serum potassium was elevated. ACTH and cortisol decreased significantly. Following CaCO3 ingestion, blood pH, serum potassium concentration, and hormones did not change significantly compared with before ingestion. NH4Cl ingestion showed a significant fall of blood pH and serum cortisol, on the other hand, aldosterone increased significantly compared with CaCO3 ingestion. Following NaHCO3 ingestion, serum aldosterone decreased with an increase in blood pH compared with before ingestion, while serum cortisol and PRA did not change significantly. The overall results of experiments using THAM, CaCO3, NaHCO3, and NH4Cl led to the conclusion that under acid-base disturbances a change in aldosterone can not be induced by either renin-angiotensin or ACTH. We suggest that under acid-base disturbances blood pH may be related, at least, in part to changes in aldosterone in humans.

Hormonal responses to head-out water immersion diminish after exposure to head-down tilt.

It has been postulated that gravitational change from 1 g to microgravity may cause cephalad fluid shift, resulting in suppression of antidiuretic hormone (ADH) secretion and diuresis (Gauer-Henry's reflex). However, results obtained in space flights did not confirm this. Since astronauts are confined at supine position for hours before launch, this posture may abolish the reflex in space flight. To investigate this possibility, effects of head-out water immersion (WI) after 2-hour head-down tilt (HDT) on hormonal and metabolic responses were examined and compared with those after 1-hour upright posture (UP). Hematocrit decreased by WI after UP, indicating hemodilution, but it did not change by WI after HDT. Plasma ADH, renin activity and aldosterone fell and atrial natriuretic peptide (ANP) rose by WI after UP, resulting in increased urine flow. On the other hand, appreciable hormonal changes were not elicited by WI after HDT, and urine flow stayed unchanged. These results indicate that fluid shift and hormonal and metabolic responses to WI are strongly attenuated by the prior exposure to HDT. Pre-launch posture of astronauts may at least partly explain why either suppression of ADH or diuresis was not observed on arrival at space.

Studies on the role of glycosylation for human corticosteroid-binding globulin: comparison with that for thyroxine-binding globulin.

The role of glycosylation on the secretion and the stability of human corticosteroid binding globulin (CBG) was studied. Cells of the human hepatoma line were labeled by [35S]methionine in presence of or absence of tunicamycin (TM). Media or cells were harvested at 0, 3, 6, and 20 h after the addition of excess unlabeled methionine. Media and cell lysates were incubated with anti-CBG serum and immune complexes were precipitated with Staphylococcus aureus protein A (Pansorbin). Immunoprecipitates were analyzed by fluorography after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunoprecipitation of T4-binding globulin (TBG) was also carried out with anti-TBG serum. Fluorographic analysis revealed three forms of CBG: CBG1, a glycosylated, mature, and secretory form with apparent mol wt of 70 K; CBG2, a glycosylated precursor which due to incomplete carbohydrate processing has an apparent mol wt of 54 K; and CBG3, a nonglycosylated form consisting of the 40 K core protein. In absence of TM, CBG1 was observed in media and CBG2 was detected in cell lysates. The proportion of CBG1 increased during the chase, whereas that of CBG2 decreased, indicating that CBG was secreted after processing of the oligosaccharides on CBG2. In presence of TM, CBG3 was found both in media and cell lysates. The sum of CBG3 in the medium and the cell lysate decreased during the chase, whereas that of CBG1 and CBG2 remained unchanged. Similar to CBG, TBG1 (mature form, 60 K) and TBG2 (partially processed glycosylated form, 54 K) were observed in media and cell lysates, respectively, in absence of TM. However, TBG3 (nonglycosylated, 44 K) was not detected in medium. These results indicate that glycosylation is not a key factor for the secretion of CBG but is important for its stability. On the other hand the glycosylation is indispensable for the secretion of TBG.

Comparative study of primates' transcortin: immunoreactivity and steroid-binding activity.

To investigate the phylogenic aspect of transcortin (corticosteroid-binding globulin, CBG), the immunoreactivity of transcortin with anti-human transcortin antiserum was studied in primates. The anti-human transcortin antibody was recognized by plasma proteins obtained from Catarrhini, taxonomically the most evolved monkey group. The immunoreactivity was not observed in plasma obtained from Platyrrhini and Prosimiae, classified as less evolved monkey groups than Catarrhini. Though comparison of immunoreactivity among different classes of Catarrhini was difficult because of non-parallelism of their displacement curves, displacement of 125I-labelled human transcortin from the antiserum by 1:10 and 1:100 diluted plasma was highest in human followed by Pongidae, Cercopithecoidea. The immunoreactivity of thyroxine-binding globulin (TBG) with anti-human TBG antiserum was also examined. The anti-human TBG antibody was only recognized in plasma from Pan (anthropoid ape) among Pongidae, highly evolved monkeys among Catarrhini. The existence of immunoreactive transcortin and TBG to respective human protein antibody in the highly evolved ape agreed well with the cladogenetic division of primate species delineated by Goodman and Moore (1971). Cortisol-binding activity of transcortin was detected in all monkeys except three, tafted capuchin monkey, night monkey and cotton-headed tamarin, which belong to Platyrrhini. The absence of cortisol-binding activity in these animals might be attributed to high levels of endogenous cortisol and low cortisol-binding capacity of transcortin. It is speculated that the structure of the immunoreactive site in transcortin could be modified by evolution without affecting the biologically important site, the site for cortisol binding.

Human transcortin synthesis by a cell-free translation of hepatic mRNA.

To evaluate the site of synthesis and to characterize the translated transcortin, poly (A)-containing RNA (mRNA) from human liver was translated in a cell-free system derived from rabbit reticulocyte lysate. The in vitro synthesized product was identified as transcortin by immuno-precipitation with its specific antiserum. This translated transcortin could be displaced from the antibody by unlabeled purified transcortin obtained from plasma. Furthermore, when the translation mixture was applied to a cortisol-Sepharose column, the translated transcortin was bound to the matrix in a specific manner, indicating that this product binds to cortisol. The molecular weight of the translated transcortin was estimated to be 45,700 by its mobility in sodium dodecyl sulfate polyacrylamide gel electrophoresis, while that of plasma transcortin was 53,800. The difference in molecular weight between the translated transcortin and plasma transcortin was probably due to the presence of pre-sequence (signal peptide) in addition to the absence of carbohydrate moiety in the former. In conclusion, human liver mRNA directed the synthesis of transcortin, and the translated transcortin binds to cortisol in spite of the absence of carbohydrate moiety.

Radioimmunoassay of human transcortin.

A specific, sensitive and simple radioimmunoassay (RIA) system for human transcortin was developed. A highly purified transcortin was prepared from pooled human serum by the following four successive steps; ammonium sulfate fractionation, cortisol-Sepharose column chromatography, Ultragel AcAA column chromatography and hydroxylapatite column chromatography. Anti-transcortin antibody was raised by immunizing rabbits. The RIA employing 125I-labeled transcortin preparation and polyethylene glycol solution for separation of free and bound-form was sensitive to transcortin in concentrations as low as 10 ng/ml. This RIA was reliable in the tests of dilution, reproducibility and recovery. The presence of cortisol does not interfere with the assay. Also a test of cross reactivity revealed that the system was not influenced by human serum albumin in a concentration 10,000 times that of transcortin. The transcortin concentrations determined by the RIA (Y) and those by the conventional steroid-binding assay (X) revealed a good correlation (Y = 1.01 X + 6.25) in normal serum, and the immunoreactivity and steroid binding activity revealed a good correlation in heat and acid-inactivated transcortin. With some total cortisol concentrations given, the transcortin concentrations were inversely correlated with protein-unbound cortisol concentrations. The present assay is useful not only for biochemical research but also for clinical studies, in which the determination of transcortin makes it possible to evaluate the concentration of protein-unbound cortisol which is the physiologically active fraction in serum.

The effect of cortisol, progesterone, and transcortin on phytohemagglutinin-stimulated human blood mononuclear cells and their interplay.

The effect of transcortin on [3H]thymidine incorporation into phytohemagglutinin-stimulated human peripheral blood mononuclear cells and its influence on the well known suppressive effect of cortisol were investigated. Human transcortin by itself had no effect on thymidine incorporation between the concentrations of 0.25-1 X 10(-6) M. When transcortin was added to cortisol, the suppressive effect of cortisol decreased in proportion to the decrease in the protein-unbound cortisol concentration. We also investigated the influence of progesterone on transcortin-bound cortisol. When 0.5 and 1 X 10(-6) M transcortin, which contained 1 and 2 X 10(-7) M cortisol as a transcortin-bound form, were added to 5 X 10(-6) M progesterone, greater suppression of thymidine incorporation was observed that than produced by progesterone alone (86.1% and 81.3 for 0.5 and 1 X 10(-6) M transcortin, respectively). Moreover, when 5 X 10(-7) M transcortin containing the same amount of cortisol was added with 1, 2, and 5 X 10(-6) M progesterone, a greater suppression (92.6%, 74.1%, and 32.4% of control for 1, 2, and 5 x 10(-6) M progesterone) was demonstrated than that caused by progesterone alone (95.1%, 75.8%, and 49.5% of control for the corresponding concentrations of progesterone). This increased suppression was accompanied by an increase in the percentage of protein-unbound cortisol. These results indicate that unbound cortisol, whose concentration increases in the presence of progesterone, may be biologically active. The interaction between progesterone and cortisol may be modulated in part by the transcortin concentration.