Effect of Small Focus on Electron Heating and Proton Acceleration in Ultrarelativistic Laser-Solid Interactions.

Acceleration of particles from the interaction of ultraintense laser pulses up to 5×10^{21} W cm^{-2} with thin foils is investigated experimentally. The electron beam parameters varied with decreasing spot size, not just laser intensity, resulting in reduced temperatures and divergence. In particular, the temperature saturated due to insufficient acceleration length in the tightly focused spot. These dependencies affected the sheath-accelerated protons, which showed poorer spot-size scaling than widely used scaling laws. It is therefore shown that maximizing laser intensity by using very small foci has reducing returns for some applications.

Laser-Particle Collider for Multi-GeV Photon Production.

As an alternative to Compton backscattering and bremsstrahlung, the process of colliding high-energy electron beams with strong laser fields can more efficiently provide both a cleaner and brighter source of photons in the multi-GeV range for fundamental studies in nuclear and quark-gluon physics. In order to favor the emission of high-energy quanta and minimize their decay into electron-positron pairs, the fields must not only be sufficiently strong, but also well localized. We here examine these aspects and develop the concept of a laser-particle collider tailored for high-energy photon generation. We show that the use of multiple colliding laser pulses with 0.4 PW of total power is capable of converting more than 18% of multi-GeV electrons passing through the high-field region into photons, each of which carries more than half of the electron initial energy.

Soft-x-ray harmonic comb from relativistic electron spikes.

We demonstrate a new high-order harmonic generation mechanism reaching the "water window" spectral region in experiments with multiterawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving µJ/sr pulses. Harmonics are collectively emitted by an oscillating electron spike formed at the joint of the boundaries of a cavity and bow wave created by a relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by particle-in-cell simulations.

Polarity reversal of wakefields driven by ultrashort pulse laser.

Using an analytical model and computer simulation, we show that the wakefield driven by an ultrashort laser pulse in high-density plasma periodically reverses its polarity due to the carrier-envelope phase shift of the driver. The wakefield polarity reversal occurs on spatial scales shorter than the typical length considered for electron acceleration with the laser-wakefield mechanism. Consequently, the energies of accelerated electrons are significantly affected. The results obtained are important for the laser-wakefield acceleration under the conditions relevant to present-day high-repetition-rate laser systems.

Characteristics of light reflected from a dense ionization wave with a tunable velocity.

An optically dense ionization wave (IW) produced by two femtosecond (approximately 10/30 fs) laser pulses focused cylindrically and crossing each other may become an efficient coherent x-ray converter in accordance with the Semenova-Lampe theory. The resulting velocity of a quasiplane IW in the vicinity of pulse intersection changes with the angle between the pulses from the group velocity of ionizing pulses to infinity allowing a tuning of the wavelength of x rays and their bunching. The x-ray spectra after scattering of a lower frequency and long coherent light pulse change from the monochromatic to high order harmoniclike with the duration of the ionizing pulses.

Enhancement of photon number reflected by the relativistic flying mirror.

Laser light reflection by a relativistically moving electron density modulation (flying mirror) in a wake wave generated in a plasma by a high intensity laser pulse is investigated experimentally. A counterpropagating laser pulse is reflected and upshifted in frequency with a multiplication factor of 37-66, corresponding to the extreme ultraviolet wavelength. The demonstrated flying mirror reflectivity (from 3 x 10(-6) to 2 x 10(-5), and from 1.3 x 10(-4) to 0.6 x 10(-3), for the photon number and pulse energy, respectively) is close to the theoretical estimate for the parameters of the experiment.

Electron optical injection with head-on and countercrossing colliding laser pulses.

A high stability electron bunch is generated by laser wakefield acceleration with the help of a colliding laser pulse. The wakefield is generated by a laser pulse; the second laser pulse collides with the first pulse at 180 degrees and at 135 degrees realizing optical injection of an electron bunch. The electron bunch has high stability and high reproducibility compared with single pulse electron generation. In the case of 180 degrees collision, special measures have been taken to prevent damage. In the case of 135 degrees collision, since the second pulse is countercrossing, it cannot damage the laser system.

Energy increase in multi-MeV ion acceleration in the interaction of a short pulse laser with a cluster-gas target.

An approach for accelerating ions, with the use of a cluster-gas target and an ultrashort pulse laser of 150-mJ energy and 40-fs duration, is presented. Ions with energy 10-20 MeV per nucleon having a small divergence (full angle) of 3.4 degrees are generated in the forward direction, corresponding to approximately tenfold increase in the ion energies compared to previous experiments using solid targets. It is inferred from a particle-in-cell simulation that the high energy ions are generated at the rear side of the target due to the formation of a strong dipole vortex structure in subcritical density plasmas.

Electro-optic spatial decoding on the spherical-wavefront Coulomb fields of plasma electron sources.

Detections of the pulse durations and arrival timings of relativistic electron beams are important issues in accelerator physics. Electro-optic diagnostics on the Coulomb fields of electron beams have the advantages of single shot and non-destructive characteristics. We present a study of introducing the electro-optic spatial decoding technique to laser wakefield acceleration. By placing an electro-optic crystal very close to a gas target, we discovered that the Coulomb field of the electron beam possessed a spherical wavefront and was inconsistent with the previously widely used model. The field structure was demonstrated by experimental measurement, analytic calculations and simulations. A temporal mapping relationship with generality was derived in a geometry where the signals had spherical wavefronts. This study could be helpful for the applications of electro-optic diagnostics in laser plasma acceleration experiments.

Exon skipping during splicing of dystrophin mRNA precursor due to an intraexon deletion in the dystrophin gene of Duchenne muscular dystrophy kobe.

Recent molecular studies have shown that in a patient with Duchenne muscular dystrophy (DMD) Kobe, the size of exon 19 of the dystrophin gene was reduced to 36 bp due to the deletion of 52 bp out of 88 bp of the exon. The consensus sequences at the 5' and 3' splice sites of exon 19 were unaltered (Matsuo, M., et al. 1990. Biochem. Biophys. Res. Commun. 170:963-967). To further elucidate the molecular nature of the defect, we examined the primary structure of cytoplasmic dystrophin mRNA of the DMD Kobe patient across the junctions of exons 18, 19, and 20 by gel electrophoresis and sequencing of polymerase chain reaction-amplified cDNA. The mRNA coding for dystrophin was reverse transcribed using random primers, and the cDNA was then enzymatically amplified in vitro. The targeted fragment was smaller than expected from the genomic DNA analysis. By sequencing of the amplified product, we found that exon 18 was joined directly to exon 20, so that exon 19 was completely absent, suggesting that this exon was skipped during processing of the dystrophin mRNA precursor. All other bases in the amplified product were unaltered. Therefore, the data strongly suggest that the internal exon deletion generates an abnormally spliced mRNA in which the sequence of exon 18 is joined to the sequence of exon 20. We propose that the deletion is responsible for abnormal processing of the DMD Kobe allele. This finding has important implications regarding the determinants of a functional splice site.

Biologically inactive growth hormone caused by an amino acid substitution.

Short stature caused by biologically inactive growth hormone (GH) is characterized by lack of GH action despite high immunoassayable GH levels in serum and marked catch-up growth to exogenous GH administration. We found a heterozygous single-base substitution (A-->G) in exon 4 of the GH-1 gene of a girl with short stature, clinically suspected to indicate the presence of bioinactive GH and resulting in the substitution of glycine for aspartic acid at codon 112. We confirmed the presence of mutant GH in the serum using isoelectric focusing analysis. The locus of mutation D112G was found within site 2 of the GH molecule in binding with GH receptor (GHR)/GH binding protein (GHBP). The expressed recombinant mutant GH tended to form a 1:1 instead of the 1:2 GH-GHBP complex normally produced by wild-type GH. The formation of a 1:2 GH-GHBP complex is compatible with the dimerization of GHRs by GH, a crucial step in GH signal transduction. Mutant GH was less potent than wild-type GH not only in phosphorylation of tyrosine residues in GHR, janus kinase 2 (JAK2), and signal transducers and activators of transcription 5 (STAT5) in IM-9 cells, but also in metabolic responses of BaF/GM cells, a stable clone transfected with cDNA of the chimera of the extracellular domain of human GHR, the transmembrane and the cytoplasmic domain of the human thrombopoietin receptor. These results indicate that the D112G mutation in the GH-1 gene causes production of bioinactive GH, which prevents dimerization of GHR and is therefore responsible for the patient's short stature.

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.

Involvement of L-tryptophan aminotransferase in indole-3-acetic acid biosynthesis in Enterobacter cloacae.

L-Tryptophan aminotransferase (L-tryptophan:2-oxoglutarate aminotransferase; EC 2.6.1.27) from Enterobacter cloacae was purified 62-fold and characterized to determine its role in indole-3-acetic acid biosynthesis. The enzyme reversibly catalyzed the transamination of L-tryptophan with 2-oxoglutarate as the amino acceptor to yield indole-3-pyruvic acid and L-glutamate, and the Km values for L-tryptophan and indole-3-pyruvic acid were 3.3 mM and 24 microM, respectively. In the indole-3-acetaldehyde synthesis experiments in vitro, 94% of L-tryptophan was efficiently converted to indole-3-acetaldehyde by the purified L-tryptophan aminotransferase plus indolepyruvate decarboxylase. Furthermore, the amounts of L-tryptophan decreased with increases in the indolepyruvate decarboxylase activity, while the amounts of indole-3-acetaldehyde increased with increases in this activity. In genetic experiments, the amounts of L-tryptophan produced by Enterobacter and Pseudomonas strains harboring the gene for indolepyruvate decarboxylase were lower than those produced by these same strains without the gene, while the amounts of indole-3-acetic acid produced by Enterobacter and Pseudomonas strains harboring the gene for indolepyruvate decarboxylase were higher than those produced by these same strains without the gene. These results clearly show that L-tryptophan aminotransferase is involved in the indole-3-acetic acid biosynthesis and that indolepyruvate decarboxylase is the rate-limiting step in this pathway.

Difference in interaction of fibronectin with type I collagen and type IV collagen.

In our studies on fibronectin, difference in binding to type I collagen and type IV collagen was observed and analysed. Four different fragments, which consist of I6-II1-II2-I7-I8-I9, I6-II1-II2-I7, I6-II1-II2, and I8-I9 within the collagen binding domain, have been isolated from proteolytic digests of fibronectin. The N-terminal fragments of the collagen binding domain showed the binding affinity to both of type I and type IV collagens. On the other hand, the C-terminal portion of the domain, I8-I9, only bound to type I collagen. The newly developed monoclonal antibody FN 40, which recognizes type I9 homology repeat of the collagen binding domain, inhibited the binding of fibronectin to type I collagen in a dose-dependent manner. Three overlapping fragments, I6-II1-II2-I7, I6-II1-II2-I7-I8, and I7-I8-I9, which have been expressed in Escherichia coli, showed the similar binding affinity to type IV collagen, whereas the fragment containing type I9 repeat (I7-I8-I9) showed the significantly stronger binding activity to type I collagen. In addition, the expressed fragment lacking I9 competitively inhibited the binding of fibronectin to type IV collagen. In contrast, the interference of this fragment to type I collagen binding activity of fibronectin was not significant. These data indicate that the collagen binding domain contains at least 2 sites for interaction with each type of collagen and that type I9 repeat is important for type I collagen binding, whereas I7 is for type IV collagen binding. Chemical modification studies revealed that the three-dimensional structure of fibronectin is more important for type I collagen binding.

Electron acceleration by a nonlinear wakefield generated by ultrashort (23-fs) high-peak-power laser pulses in plasma.

We study experimentally the interaction of the shortest at present (23-fs) , relativistically intense (20-TW), tightly focused laser pulses with underdense plasma. MeV electrons constitute a two-temperature distribution due to different plasma wave-breaking processes at a plasma density of 10(20) cm(-3). These two groups of electrons are shown numerically to constitute bunches with very distinctive time durations.

Amplification of ten deletion-rich exons of the dystrophin gene by polymerase chain reaction shows deletions in 36 of 90 Japanese families with Duchenne muscular dystrophy.

We analyzed DNA samples taken from 95 Duchenne muscular dystrophy (DMD) patients belonging to 90 different families in Japan using the polymerase chain reaction. Ten different regions at the 5' end or in the central region of the dystrophin cDNA gene that were previously shown to be prone to deletion were selected for amplification and analysis. Patients in 36 of the 90 families (40%) had deletions in at least one of these segments of the gene. Identical deletions were detected in the dystrophin gene of patients from the same family. The deletions were heterogeneous in size and location. One patient had deletions in 7 of the 10 amplified regions, while 19 patients from 18 families had a deletion in only one of the regions studied. Deletions at the 5' end were generally larger and more heterogeneous than those in the central region of the gene. One third of deletions had their proximal end breakpoints between exons 44 and 45. This region seems to be particularly vulnerable to gene breakage in DMD patients.

Antiviral effect of the extract of culture medium of Lentinus edodes mycelia on the replication of herpes simplex virus type 1.

An extract of culture medium of Lentinus edodes mycelia, JLS-S001, significantly blocked the release of infectious herpes simplex virus type 1 (HSV-1) from African green monkey kidney cells. The block in replication was not due to the effect of JLS-S001 on the adsorption and penetration of HSV-1 to the monkey kidney cells. This observation was supported by the fact that JLS-S001 had no significant effect on the expression of virus-specific nucleocapsid proteins in the treated cells. Furthermore, electron microscopy demonstrated the presence of nucleocapsids within the nuclei of the infected and JLS-S001-treated cells. However, the expression of glycoproteins B, C, D, E and I was reduced in the JLS-S001-treated cells. These results suggested that JLS-S001 blocked HSV-1 replication at a late stage in virus replication cycle probably in the assembly and budding of nucleocapsids and subsequent egress from the treated cells.

Studies on subtype composition in natural leukocyte interferon preparations.

Antisera raised against partially purified human leukocyte interferon in goat and horse were exhaustively adsorbed and purified. Affinity chromatography using these antibodies gave 10,000-fold purification in one step without losing interferon activity. Then enzyme immunoassay was established with these antibodies and utilized for subtype analysis. Crude and affinity purified leukocyte interferons showed identical profiles of antiviral activity and immunoreactivity when fractionated by means of reversed phase high performance liquid chromatography. These results suggested the possibility of providing mixture of subtypes of leukocyte interferon occurring in natural host response, with comparable purity of recombinant ones.

Screening of gene deletions by polymerase chain reaction in Japanese patients with Duchenne muscular dystrophy.

Gene deletions were screened in 49 Japanese Duchenne muscular dystrophy patients from 43 families, using the polymerase chain reaction. Enzymatic amplification was carried out on six regions prone to deletion. Fifteen of 43 families (33%) had gene deletions in at least one of the six regions. This frequency was almost the same as that previously reported in Caucasians. The mid-part of the dystrophin gene was the location most frequently deleted. The frequency of deletion of the region encompassing exon 45 was higher in Japanese families (18.4%) than in Caucasians.

The trimannosyl cores of N-glycans are important for the procoagulant protease-inhibitory activity of urinary protein C inhibitor.

We investigated the relationship between the procoagulant protease-inhibitory activity and the N-glycan structures in urinary protein C inhibitor (uPCI) by sequential exoglycosidase digestions based on the N-glycan structures elucidated in this report. uPCI was glycosylated on the three potential N-glycosylation sites, asparagines 230, 243 and 319 (N230, N243 and N319) in the molecule and had four biantennary complex type sugar chains. The inhibitory activities of uPCI toward thrombin and plasma kallikrein were little changed by the sequential removal of N-acetylneuraminic acid and galactose residues from the termini and N-acetylglucosamine residues from the branches of the N-glycans. However, the inhibitory activities were markedly decreased by further removing alpha-mannose residues from the trimannosyl cores of the N-glycans. These results suggest that the trimannosyl cores of N-glycans are important for uPCI to inhibit the procoagulant protease.