Predictive capability of material screening by fast neutron activation analysis using laser-driven neutron sources.

Bright, short-pulsed neutron beams from laser-driven neutron sources (LANSs) provide a new perspective on material screening via fast neutron activation analysis (FNAA). FNAA is a nondestructive technique for determining material elemental composition based on nuclear excitation by fast neutron bombardment and subsequent spectral analysis of prompt γ-rays emitted by the active nuclei. Our recent experiments and simulations have shown that activation analysis can be used in practice with modest neutron fluences on the order of 105 n/cm2, which is available with current laser technology. In addition, time-resolved γ-ray measurements combined with picosecond neutron probes from LANSs are effective in mitigating the issue of spectral interference between elements, enabling highly accurate screening of complex samples containing many elements. This paper describes the predictive capability of LANS-based activation analysis based on experimental demonstrations and spectral calculations with Monte Carlo simulations.

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.

Direct observation of imploded core heating via fast electrons with super-penetration scheme.

Fast ignition (FI) is a promising approach for high-energy-gain inertial confinement fusion in the laboratory. To achieve ignition, the energy of a short-pulse laser is required to be delivered efficiently to the pre-compressed fuel core via a high-energy electron beam. Therefore, understanding the transport and energy deposition of this electron beam inside the pre-compressed core is the key for FI. Here we report on the direct observation of the electron beam transport and deposition in a compressed core through the stimulated Cu Kα emission in the super-penetration scheme. Simulations reproducing the experimental measurements indicate that, at the time of peak compression, about 1% of the short-pulse energy is coupled to a relatively low-density core with a radius of 70 µm. Analysis with the support of 2D particle-in-cell simulations uncovers the key factors improving this coupling efficiency. Our findings are of critical importance for optimizing FI experiments in a super-penetration scheme.

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.

A multichannel gated neutron detector with reduced afterpulse for low-yield neutron measurements in intense hard X-ray backgrounds.

A design of multichannel gated photomultiplier tube (PMT) is presented for the 960-channel neutron time-of-flight detector at the Institute of Laser Engineering of Osaka University. This is important for the fusion science and the nuclear photonics where intense hard X-rays are generated from the interaction of ultra-short laser pulse of petawatt power density with matter. The hard X-rays often overload PMTs and cause signal-induced background noises called afterpulses, making the detection of subsequent neutrons impossible. For this reason, the PMTs are coupled with an electrical time-gating (ETG) system to avoid overloading. The ETG system disables the PMT by modulating the dynode potential during the primary X-ray flash. An after-pulsing suppression technique is demonstrated by applying a reverse bias voltage between the photocathode and the first dynode. The presented multichannel scheme provides a gate response time of 80 ns, a signal cutoff ratio of 2.5 × 102, and requires reasonably low power consumption.

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.

"Intact nephrons" as the primary origin of proteinuria in chronic renal disease. Study in the rat model of subtotal nephrectomy.

Single nephron filtration rate of albumin (SNGFRAlb) was measured in remnant nephrons of Munich-Wistar rats 4-6 wk after subtotal nephrectomy (NPX). Serial thin-section histological analysis was then conducted on the same glomeruli by light microscopy. SNGFRAlb ranged from 1 to 15 times normal. However, a direct relationship between abnormalities of structure and function was not seen, e.g. the glomeruli with the fewest structural abnormalities and marked hyperfiltration often had the highest SNGFRAlb. Moreover, the majority of glomeruli had minimal structural abnormalities. Normalization of the markedly elevated glomerular capillary pressure (PGC) in these glomeruli was accomplished by acute intravenous infusion of verapamil, which decreased SNGFRAlb by 9-83% without affecting the single nephron filtration rate of water (SNGFRH2O). 1-2 wk after subtotal NPX, all glomeruli were hyperfiltering and had elevated PGC. The fractional clearance of larger (greater than 36 A) dextrans was selectively increased in these glomeruli that lacked discernible damage by light microscopy. Verapamil normalized PGC, reduced proteinuria to 48 +/- 4% of baseline, and improved glomerular size selectivity without altering SNGFRH2O. Proteinuria after subtotal NPX thus originates largely from glomeruli with minimal structural abnormalities. The defect in size selectivity is largely attributed to the prevailing high PGC, producing large, nonselective channels on the glomerular capillary wall. The observations raise the possibility that in chronic renal diseases, the reduction in proteinuria often seen after therapeutic measures, including antihypertensive medication, may reflect their functional effect on the relatively intact glomeruli rather than their structure-sparing effect on severely damaged glomeruli, which contribute little to the proteinuria.

Induction of neurite outgrowth in PC12 cells by the medium-chain fatty acid octanoic acid.

It has been shown that polyunsaturated fatty acids such as arachinonic and docosahexanoic acids but not monounsaturated and saturated long-chain fatty acids promote basal and nerve growth factor (NGF)-induced neurite extension of PC12 cells, a line derived from a rat pheochromocytoma. On the other hand, short-chain fatty acids and valproic acid (2-propylpentanoic acid) enhance the growth of neurite processes of the cells only in the presence of inducers. In this study, we demonstrated that straight medium-chain fatty acids (MCFAs) at millimolar concentrations alone potently induced neuronal differentiation of PC12 cells. Hexanoic, heptanoic and octanoic acids dose-dependently induced neurite outgrowth of the cells: their maximal effects determined 2 days after addition to the culture medium were more marked than the effect of NGF. PC12 cells exposed to octanoic acid expressed increased levels of the neuronal marker beta-tubulin isotype III. Nonanoic, decanoic, and dodecanoic acids also induced growth of neurite processes, but their maximal effects were less marked than that of octanoic acid. In contrast, the polyunsaturated fatty acid linoleic acid and short-chain fatty acids had only slight or almost no effects on neurite formation in the absence of NGF. The effect of octanoic acid was synergistic with or additive to the effects of NGF and dibutyryl cyclic AMP. Octanoic acid upregulated phosphorylation of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK), critical signaling molecules in neuronal differentiation, but not phosphorylation of Akt, a signaling molecule downstream of phosphatidylinositol 3-kinase (PI3K). Moreover, growth of neurites induced by octanoic acid was potently inhibited by treatment of cells with the p38 MAPK inhibitor SB203580 and the ERK kinase inhibitor PD98059 but not inhibited and only slightly inhibited by the JNK inhibitor SP600125 and the PI3K inhibitor wortmannin, respectively. Taken together, our results indicate that MCFAs, including octanoic acid, induced neurite outgrowth of PC12 cells in the absence of NGF and suggest that the activation of p38 MAPK and ERK pathways is involved in this process.

Gain depletion of X-ray framing camera.

X-ray imaging is very useful to investigate imploded core plasma in inertial fusion experiments. We can obtain information from X-ray images, such as shape, density, and temperature. An X-ray framing camera (XFC) capable of taking two-dimensional, time-resolved X-ray images is used to capture the images. In previous work, we developed a numerical model of an XFC to analyze its X-ray image. The calculated results agreed qualitatively with experimental results. However, it was not accurate enough to determine the absolute value of the signal. We thought this discrepancy was caused by gain depletion. In high energy laser experiments, high photon flux may cause gain depletion. This is a problem for accurate X-ray measurement. In this paper, we report our new model, including gain depletion. The new model is evaluated by tabletop laser experiments and high energy laser experiments. The results calculated using the new model agree quantitatively with our experimental results. Furthermore, we confirmed that gain depletion occurs in our high energy laser experiments. For quantitatively accurate X-ray intensity measurements, the XFC should be used with limited incident photon flux such that the gain linearity is guaranteed.

Boosting laser-ion acceleration with multi-picosecond pulses.

Using one of the world most powerful laser facility, we demonstrate for the first time that high-contrast multi-picosecond pulses are advantageous for proton acceleration. By extending the pulse duration from 1.5 to 6 ps with fixed laser intensity of 1018 W cm-2, the maximum proton energy is improved more than twice (from 13 to 33 MeV). At the same time, laser-energy conversion efficiency into the MeV protons is enhanced with an order of magnitude, achieving 5% for protons above 6 MeV with the 6 ps pulse duration. The proton energies observed are discussed using a plasma expansion model newly developed that takes the electron temperature evolution beyond the ponderomotive energy in the over picoseconds interaction into account. The present results are quite encouraging for realizing ion-driven fast ignition and novel ion beamlines.

Response measurement of single-crystal chemical vapor deposition diamond radiation detector for intense X-rays aiming at neutron bang-time and neutron burn-history measurement on an inertial confinement fusion with fast ignition.

A neutron bang time and burn history monitor in inertial confinement fusion with fast ignition are necessary for plasma diagnostics. In the FIREX project, however, no detector attained those capabilities because high-intensity X-rays accompanied fast electrons used for plasma heating. To solve this problem, single-crystal CVD diamond was grown and fabricated into a radiation detector. The detector, which had excellent charge transportation property, was tested to obtain a response function for intense X-rays. The applicability for neutron bang time and burn history monitor was verified experimentally. Charge collection efficiency of 99.5% ± 0.8% and 97.1% ± 1.4% for holes and electrons were obtained using 5.486 MeV alpha particles. The drift velocity at electric field which saturates charge collection efficiency was 1.1 ± 0.4 × 10(7) cm/s and 1.0 ± 0.3 × 10(7) cm/s for holes and electrons. Fast response of several ns pulse width for intense X-ray was obtained at the GEKKO XII experiment, which is sufficiently fast for ToF measurements to obtain a neutron signal separately from X-rays. Based on these results, we confirmed that the single-crystal CVD diamond detector obtained neutron signal with good S/N under ion temperature 0.5-1 keV and neutron yield of more than 10(9) neutrons/shot.

Effect of pre-and postoperative plasmapheresis on posttransplant recurrence of focal segmental glomerulosclerosis in children.

BACKGROUND: Posttransplant recurrence is frequent in patients who received renal transplantation for focal segmental glomerulosclerosis (FSGS). The recurrence has been ascribed to a circulating permeability factor or factors. We have used plasmapheresis (PP) to treat recurrent FSGS and also studied whether preoperative PP is effective in preventing recurrence of FSGS. METHODS: We retrospectively analyzed 21 allografts of 20 patients with nephrotic syndrome and biopsyproven FSGS. They were divided into two groups depending on whether they had prophylactic PP; a prophylactic (n=15) and a nonprophylactic group (n=6). PP was performed two to three times prophylactically and therapeutically until proteinuria was markedly reduced. In each session, 50-75 ml/kg of the patient's plasma was exchanged with 5-8% albumin. RESULTS: FSGS recurred in 9 of 21 allografts, 4 of 6 in the nonprophylactic group, and 5 of 15 in the prophylactic group. Therapeutic PP was performed in seven of nine recurrent patients without definite adverse effect, with satisfactory results except in one patient. Children lost proteinuria after 6 to > 100 sessions of PP and the number correlated with the pretreatment level of proteinuria. The mean follow-up periods were 62.7 and 41.6 months for the prophylactic and nonprophylactic groups, respectively. At the last follow-up, 66.7% of relapsing and 81.8% of nonrelapsing patients had a functioning graft. CONCLUSION: PP appears to be effective for the prevention and treatment of posttransplant recurrence of FSGS, although further consideration of cost/benefit and risks is required before a conclusive judgement can be made.

The effects of 6-hydroxydopamine and oxidative stress on the level of brain metallothionein.

Oxidative stress, resulting either from excess generation or reduced scavenging of free radicals, has been proposed to play a role in damaging striatal neurons in Parkinson's disease. Since metallothionein is able to regulate the intracellular redox potential, we have undertaken a group of experiments to see whether or not 6-hydroxydopamine, which generates free radicals and is toxic to dopaminergic neurons, could alter the level of zinc and metallothionein. 6-Hydroxydopamine (8 micrograms in 4 microliters 0.02% ascorbic acid) reduced the level of zinc and metallothionein in the striatum but not other brain regions tested. Dopamine plus selegiline increased the synthesis of metallothionein in Chang cells as judged by enhanced incorporation of [35S]cysteine into metallothionein. The effect of dopamine was selective, in that dopamine could not stimulate the synthesis of metallothionein in neuroblastoma IMR-32 cells, which are devoid of dopaminergic receptors. The effect of dopamine in stimulating the synthesis of metallothionein was similar to that of zinc, known to generate the synthesis of metallothionein, and to that of H2O2 and FeS04, known to generate free radicals. The results of these experiments provide additional evidence that zinc or zinc metallothionein are altered in conditions where oxidative stress has taken place.

Guanidino compound levels in the serum of healthy adults and epileptic patients.

Some guanidino compounds are known to be convulsants and to change in the brain during seizures. In this study, we examined the serum levels of guanidino compounds in healthy adults (controls), non-epileptic neurological patients (NENP) and epileptic neurological patients (ENP). In healthy adults, serum levels of guanidinoacetic acid (GAA), creatinine (CRN) and homoarginine (HArg) were significantly lower in women than in men. Serum levels of GAA in ENP and NENP were significantly lower than in controls, with the exception of female NENP. In the male patients, CRN levels were significantly lower in ENP and NENP compared to the controls. Significantly higher arginine (Arg) levels were observed in both male and female ENP and NENP. HArg levels in the male patients were significantly lower in ENP compared with both controls and NENP. With regard to serum levels of guanidino compounds in ENP with symptomatic generalized epilepsy and with symptomatic partial epilepsy, significantly lower levels of HArg were observed in male ENP with symptomatic generalized epilepsy than in NENP. Serum levels of GAA and HArg in uncontrolled female ENP were significantly lower than those in controlled ENP. Furthermore, Arg and HArg levels in uncontrolled male ENP were significantly lower than in controlled ENP. Serum levels of Arg in male ENP and HArg in both sexes of ENP taking valproic acid were significantly lower than those in ENP not taking valproic acid. These results suggest that some metabolic disorder of guanidino compounds may exist in ENP and NENP and that guanidino compounds may be affected by seizure types, seizure severity and anticonvulsants.

Delta-guanidinovaleric acid as an endogenous and specific GABA-receptor antagonist: electroencephalographic study.

Sporadic spike discharges recorded on EEGs from epidural electrodes appeared 5-10 min after topical application of 0.3 nmol delta-guanidinovaleric acid (DGVA) on the pia mater of the sensorimotor cortex, on the same side as the application. Spike discharges induced by DGVA were completely suppressed within 10 min of supplementary application of GABA (50 nmol), (3R)-(-)-4-amino-3-hydroxybutanoic acid (L-GABOB) (5 nmols) or muscimol (5 nmols) on the pia mater, but the discharges were not affected by supplementing with 500 nmol of alpha-amino-DGVA, i.e., arginine (Arg). Whereas spike discharges were not induced by DGVA together with L-GABOB or muscimol, DGVA applied together with Arg induced spike discharges. Neither phenobarbital (PB) (20 mg/kg, i.m.), diazepam (DZ) (10 mg/kg, i.p.), sodium valproate (200 mg/kg, i.p.) nor diphenylhydantoin (20 mg/kg, i.p.) showed any suppressive effects on spike discharges induced by DGVA. DGVA induced spike discharges 20 min after pre-injection of PB or DZ. These electroencephalographic findings suggest that DGVA, which has one more carbon in its chain than N-amidino-GABA, might act directly on the GABA-receptor to induce spike discharges and might be a specific GABA-receptor antagonist.

Acetyl-seryl-aspartyl-lysyl-proline is a novel natural cell cycle regulator of renal cells.

A natural tetrapeptide, acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) is a physiological negative regulator of hematopoiesis. The precursor of AcSDKP, thymocin beta 4, is expressed in many tissues including kidney. The present study examined the antiproliferative effect of AcSDKP in two renal cell lines, namely, renal interstitial fibloblasts cell line (NRK 49F) and renal proximal tubular epitherial cells (LLC-PK1). An addition of AcSDKP for 48 hours in theses cells resulted in a concentration-dependent attenuation in the proliferation rate (significant difference to non-treated cells was observed at 10(-9) to 10(-5) M AcSDKP) determined by a colorimetry of alamer blue oxidation. The cell cycle analysis of NRK 49F cells treated with AcSDKP showed that AcSDKP significantly reduced the ratio of S-phase to G2/M-phases. Thus, physiological concentrations of AcSDKP is capable of altering cell cycle to inhibit the proliferation of renal cells.

Transplantation of pediatric cadaveric kidneys into adult or pediatric recipients.

In Japan, nationwide cadaveric organ sharing for kidney transplantation by the Japan Organ Transplant Network (JOTN) has operated since April 1995. This study retrospectively analyzed the long-term results of single pediatric donor kidneys transplanted into adult or pediatric recipients at a single center. From March 1983 to December 2002, 281 cadaveric renal allografts were transplanted at our center, including, 17 recipients of cadaveric kidneys from donors aged less than 16 years. We divided these 17 recipients into two groups: 10 adult recipients (group 1; G1) and seven pediatric recipients (group 2; G2). HLA-AB, -DR mismatches were 1.3 +/- 1.3, 0.7 +/- 0.5 in G1 and 2.6 +/- 1.3, 1.4 +/- 0.8 in G2, respectively (P < .05 for both). The end of the observation of this study was March 2003. Among G1, two recipients died with functioning grafts and one died after graft loss. Among G2, no recipients died. Patient survival rates at 1 and 5 years were 90% and 80% in G1 and 100% and 100% in G2, respectively. At the end of the observation in this study, five recipients among G1 and six recipients among G2 had functioning grafts. Graft survival rates at 1 and 5 years were 90% and 80% in G1 and 85.7% and 85.7% in G2, respectively. Our results demonstrate that transplantation of pediatric cadaveric kidneys into pediatric recipients was excellent compared to adult recipients in terms of survival. Priority to pediatric patients should be given especially in cases of pediatric donors.

Successful management of CAPD in infants with cardiac failure.

Continuous ambulatory peritoneal dialysis (CAPD) was selected and introduced as a primary dialysis method in two infants with cardiac failure. CAPD was started at 14 days after birth with body weight of 2125 gm and at 7 months of age with body weight of 2325 gm. In both cases, cardiac failure was due to large ventricular septal defect (VSD) and renal failure was due to dysplastic kidneys. In the first case (case 1), direct closure of atrial septal defect and patch closure of VSD were successfully completed at 9.5 months of age with body weight of 4844 gm. CAPD has been managed well for 1 year and 8 months and the child reached a body weight of 8440 gm. In the second case (case 2), CAPD was managed well for 11 months with body weight increasing to 4920 gm at the age of 1 year and 7 months. This marked deterioration of this boy's physical growth was mainly caused by the delay in introducing CAPD and partly due to his cardiac dysfunction which has not been corrected surgically. Both cases show almost normal mental development and are managed well at home. Although CAPD introduction yielded water balance and physical growth in these infants, earlier introduction of CAPD may result in better clinical outcomes including management following open heart surgery. Selection of CAPD as a primary dialysis maneuver is strongly recommended for uremic infants with cardiac failure.

[Clinical study of 18 pediatric cadaveric renal transplantations: organ sharing in pediatric renal transplantation after enforcement of the organ transplant law in Japan].

Renal transplantation is considered to be the optimal replacement therapy for children with end-stage renal disease. However, the number of pediatric renal transplants in Japan is much lower than in the USA and/or Europe. Since October 1997, pediatric(< 15 years) recipients are given priority over adult recipients for organ sharing, only if one or two HLA-DR antigen(s) are matched between the recipient and pediatric(< 15 years) donor. However, the number of pediatric transplants is not increasing. One hundred and twenty-four pediatric renal transplantations were performed in Tokyo Women's Medical University between 1983 and 1999, of which 18(14.5%) were cadaveric transplants and the others (106, 85.5%) were living-related transplants. We examined 18 pediatric cadaveric renal transplantations. Seven patients received their graft from pediatric donors less than 15 years of age and 11 from adult donors. The mean age at transplantation was 13.2 years (range 4.5-18.7 years). Major etiologies of renal disease are hereditary renal disease(38.8%), chronic glomerulonephritis(33.3%), and focal segmental glomerulosclerosis[FSGS] (16.7%). Zero matches in HLA-DR locus were observed in 72.2%. Patient survival rate was 100%. Graft survival rates at 1 and 5 years after transplantation were 83% and 64% successively. There was no significant difference between the graft survival of cadaveric and living-related transplantation at 1 and 5 years. All 5 patients who received their graft between 1994 and 1998 have maintained normal graft function. Causes of their graft loss were chronic rejection in 3, recurrence of FSGS in 2, primary non-function in 1, and graft thrombosis in 1. Donor age and HLA-DR mismatching did not affect the outcome. We propose that pediatric renal grafts should be provided to children with priority, regardless of their HLA-A, B and HLA-DR matching.

[Advances in the treatment of hemolytic uremic syndrome (HUS)].

The hemolytic uremic syndrome (HUS) is the end result of a variety of etiologic agents that can induce endothelial cell injury and thrombotic microangiopathy (TMA) mostly within the kidney. The typical, post-diarrheal verocytotoxin associated HUS (D + HUS) is the major cause of acute renal failure in children worldwide. In the course of HUS treatment, fluid overload is usually the result of overhydration in the context of oliguria or anuria which cause edema, hypertension, worsening of neurologic signs and cardiac failure. Appropriate and timely use of dialysis has dramatically reduced complications of renal failure and extra-renal complications are now the main causes of mortality and morbidity in D + HUS. The reasons for treatment by infusion of fresh frozen plasma and/or plasmapheresis for D + HUS are theoretical and their therapeutic effects are inconclusive. We believe that plasma administration for regular D + HUS has no value and is potentially harmful. Until new strategies become available in clinical practice, the general consensus for the moment is that careful supportive management with patience is still the most appropriate form of D + HUS therapy.