Interaction of near-IR laser radiation with plasma of a continuous optical discharge

The interaction of 1.07-μm laser radiation with plasma of a continuous optical discharge (COD) in xenon and argon at a pressure of p = 3–25 bar and temperature of T = 15 kK has been studied. The threshold power required to sustain COD is found to decrease with increasing gas pressure to P _t < 30 W in xenon at p > 20 bar and to P _t < 350 W in argon at p > 15 bar. This effect is explained by an increase in the coefficient of laser radiation absorption to 20?25 cm^–1 in Xe and 1?2 cm^–1 in Ar due to electronic transitions between the broadened excited atomic levels. The COD characteristics also depend on the laser beam refraction in plasma. This effect can be partially compensated by a tighter focusing of the laser beam. COD is applied as a broadband light source with a high spectral brightness.     

New data on the Pteromalid wasps (Hymenoptera,Chalcidoidea: Pteromalidae) of the Russian Far East

Fourteen genera (Ardilea Graham, Glyphognathus Graham, Rhicnocoelia Graham, Eulonchetron Graham, Habritys Thomson, Heteroprymna Graham, Janssoniella Kerrich, Lyubana Bou?ek, Muscidifurax Girault et Sanders, Nazgulia Hedqvist, Notoglyptus Masi, Oxysychus Delucchi, Platygerrhus Thomson, and Stenetra Masi) and 81 species are recorded for the first time for the fauna of Russia; in addition, 13 species are new to the fauna of the Russian Far East.     

Study of Implosion of Combined Nested Arrays

New experimental data on the implosion of plasma of nested kapron?tungsten arrays are obtained at the Angara-5-1 facility. The mode of plasma implosion is implemented in which a shock wave region forms in the space between the inner and outer arrays where a transition from the super-Alfvénic (V _r > V _A ) to sub-Alfvénic (V _r < V _A ) plasma flow takes place. Specific features of the formation and decay of the shock region are studied using laser shadow imaging and X-ray frame photography. The plasma density in the transition region is estimated. By comparing the experimental data with the results of simulations of quasi-steady implosion of a nested array with allowance for extended plasma production, the physical conditions are determined at which the implosion mode with the formation the shock region takes place. Stable compression of the plasma of the inner array was observed during the implosion of combined nested arrays with a fiber outer array and tungsten inner array. Suppression of magnetic Rayleigh-Taylor instability during the compression of the inner array plasma results in the formation of a compact radiating Z-pinch and generation of a soft X-ray pulse with a peak power of 4 TW and duration of about 5 ns.     

Lambda Red-mediated recombinogenic engineering of enterohemorrhagic and enteropathogenic <Emphasis Type="Italic">E. coli</Emphasis>

Background

The λ Red recombineering technology has been used extensively in Escherichia coli and Salmonella typhimurium for easy PCR-mediated generation of deletion mutants, but less so in pathogenic species of E. coli such as EHEC and EPEC. Our early experiments with the use of λ Red in EHEC and EPEC have led to sporadic results, leading to the present study to identify factors that might improve the efficiency of Red recombineering in these pathogenic strains of E. coli.

Results

In this report, we have identified conditions that optimize the use of λ Red for recombineering in EHEC and EPEC. Using plasmids that contain a P_tac-red-gam operon and a temperature-sensitive origin of replication, we have generated multiple mutations (both marked and unmarked) in known virulence genes. In addition, we have easily deleted five O157-specific islands (O-islands) of EHEC suspected of containing virulence factors. We have examined the use of both PCR-generated substrates (40 bp of flanking homology) and plasmid-derived substrates (~1 kb of flanking homology); both work well and each have their own advantages. The establishment of the hyper-rec phenotype requires only a 20 minute IPTG induction period of red and gam. This recombinogenic window is important as constitutive expression of red and gam induces a 10-fold increase in spontaneous resistance to rifampicin. Other factors such as the orientation of the drug marker in recombination substrates and heat shock effects also play roles in the success of Red-mediated recombination in EHEC and EPEC.

Conclusions

The λ Red recombineering technology has been optimized for use in pathogenic species of E. coli, namely EHEC and EPEC. As demonstration of this technology, five O-islands of EHEC were easily and precisely deleted from the chromosome by electroporation with PCR-generated substrates containing drug markers flanked with 40 bp of target DNA. These results should encourage the use of λ Red recombineering in these and other strains of pathogenic bacteria for faster identification of virulence factors and the speedy generation of bacterial mutants for vaccine development.

     

Experimental study of radiation in the wavelength range 12.2–15.8 nm from a pulsed high-current plasma diode

Results are presented from experimental studies of the temporal and integral characteristics of radiation in the 12.2-to 15.8-nm spectral range from the anode region of an extended high-current (I ～ 30 kA) pulsed discharge in Sn vapor. It is found that the radiation pulse consists of intense spikes with a duration much shorter than the half-period of the discharge current. The spikes are shown to correlate with the onset of instability in the plasma column. It is supposed that the radiation spikes in the given wavelength range can be generated by a long-lived dense plasma core optimally supplied with energy. A method for achieving a highly efficient quasi-steady radiation regime is proposed.     

Generation of plasma Eields in the interaction between two oppositely propagating short laser pulses in an underdense plasma

A study is made of the interaction (“collision”) between two identical laser pulses with lengths much shorter than the diffraction length, propagating in a plasma toward one another. It is shown that the plasma response to the pulses depends essentially on the value of the parameter ω_pτ, where ω_p is the plasma frequency and τ is the pulse duration. Short laser pulses (such that \(\omega _p \tau \leqslant \sqrt 2 \)) efficiently generate plasma waves on two characteristic scale lengths. Large-scale wake waves with a wavelength of about c/ω_p are generated over the entire path of the pulses and form a two-dimensional standing plasma wave in the region between the pulses after their interaction. In the interaction region, the pulses excite small-scale plasma oscillations with a wavelength equal to half the laser wavelength, which remain in the plasma after the interaction. Long laser pulses (such that \(\omega _p \tau \leqslant \sqrt 2 \)) also generate quasistatic plasma perturbations on two scale lengths. Perturbations generated on large scales of about the pulse length accompany the propagating pulses and are somewhat amplified in the interaction between them. Small-scale plasma fields are generated only during the interaction between the pulses, and they disappear after the interaction. The influence of the generation of plasma fields on the energy of the laser pulses and on their shape, as well as the possible applications of the effects under consideration, is discussed.     

Properties of Surface Plasmon Polaritons Excited by Radially Polarized Sinh Gaussian Beams

Properties of surface plasmon polaritons (SPPs) excited by radially polarized sinh Gaussian beams with high-numerical-aperture system is investigated theoretically based on vector diffraction theory. It is observed that by properly tuning the beam waist size (w ₀ ) and beam order (m) of the incident sinh Gaussian beam, one can achieve higher confinement in axial and lateral size of the generated plasmonic focal spot. We observed that sinh Gaussian beam of larger w ₀ and m results in generation of highly confined plasmonic focal spot.     

Galactose-Containing Polymer-DOX Conjugates for Targeting Drug Delivery

A novel multifunctional drug delivery system was fabricated by conjugating galactose-based polymer, methoxy-poly(ethylene glycol)-block-poly(6-O-methacryloyl-D-galactopyranose) (mPEG-b-PMAGP) with doxorubicin (DOX) via an acid-labile carbamate linkage. The mPEG-b-PMAGP-co-DOX nanoparticles were spherical in shape, and the diameter determined by dynamic light scattering (DLS) was 54.84?±?0.58 nm, larger than that characterized by transmission electron microscopy (TEM). The in vitro drug release profiles were studied, and the release of DOX from the nanoparticles was pH-responsive. The cellular uptake behavior of free-DOX and mPEG-b-PMAGP-co-DOX nanoparticles by asialoglycoprotein (ASGP) receptor-positive cancer cell line (HepG2) and ASGP receptor-negative cancer cell lines (MCF-7 and A549 cells) was evaluated by confocal laser scanning microscopy (CLSM) and flow cytometry (FCM), respectively. The mPEG-b-PMAGP-co-DOX nanoparticles which contain galactose functional groups exhibited higher cellular uptake behavior via ASGP receptor-mediated endocytosis in HepG2 cells than in other two cancer cells. The in vitro cytotoxicity assay manifested that the mPEG-b-PMAGP-co-DOX nanoparticles exhibited higher anticancer efficacy against HepG2 cells than MCF-7 cells. These results indicated that the multifunctional mPEG-b-PMAGP-co-DOX nanoparticles possessing pH-responsible and hepatoma-targeting function have great potential to be used as a targeting drug delivery system for hepatoma therapy.     

Theoretical Localized Electric Field Enhancement in Tip-Enhanced Spectroscopy Using Multi-Order Radially Polarized Modes

Multi-order radially polarized modes (RPMs), including Bessel-Gaussian, Gaussian, Super Gaussian, and multi-order hollow Gaussian are respectively utilized as the illumination laser to achieve tip-enhanced spectroscopy (TES). Based on the vector diffraction theory and finite difference time domain (FDTD) analysis, we achieve the optimization of RPM illuminated TES system, including the focal spot size, focal depth, and electric field enhancement factor, in which the focal spot size of 5th order hollow Gaussian RPM is smallest (0.54λ) and the focusing depth of super Gaussian RPM is longest (4.71λ). Specially, it is found that the multi-order hollow Gaussian RPM illuminated TES system with the tip cone angle of 45^° reveals better focusing ability and 40~60-fold electric field enhancement factor compared to the linearly polarized mode (LPM) illuminated TES system. These results will supply a useful reference for spectral signal enhancement of TES system.     

Calculation of the ion distribution function over transverse velocities under ICR heating conditions and separation parameters of a collector of heated ions

The ion distribution function over transverse velocities and the ion heating efficiency (which is defined as the fraction η of ions heated above a certain energy W_min) are calculated in the context of a plasma method for isotope separation on the basis of ion cyclotron resonance heating. The ion distribution function over longitudinal velocities is assumed to be linear in the range of low velocities. It is shown that, when the ions are heated to high energies, the averaged ion distribution function over transverse velocities becomes highly nonequilibrium and has two peaks. Results are presented from calculations of the ion heating efficiency η for W_min=40 eV and for different values of the parameter p that characterizes the ratio of the wavelength λ of the antenna electric field to the length L of the heating region. The relative roles of the time-of-flight and the Doppler broadening are analyzed, and the separation parameters of a collector of heated ions are estimated.     

Synthesis of Bacteriophage λ Proteins <Emphasis Type="Italic">in vitro</Emphasis>

λ DNA stimulates a low level of protein synthesis in extracts of E. coli supplemented with RNA polymerase. The synthesis is efficiently and specifically repressed by addition of purified λ repressor. About 90% of the protein product is from the rightwards, or tof, promoter (P _R ) and 10% from the leftwards, or N, promoter (P _L ). The main polypeptide product is a low molecular species from the tof operon.     

The Effects of Low Doses of Gamma-Radiation on Growth and Membrane Activity of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> GRP3 and <Emphasis Type="Italic">Escherichia coli</Emphasis> M17

Microorganisms are part of the natural environments and reflect the effects of different physical factors of surrounding environment, such as gamma (γ) radiation. This work was devoted to the study of the influence of low doses of γ radiation with the intensity of 2.56?μW (m²?s)^?1 (absorbed doses were 3.8 mGy for the radiation of 15?min and 7.2 mGy—for 30?min) on Escherichia coli M-17 and Pseudomonas aeruginosa GRP3 wild type cells. The changes of bacterial, growth, survival, morphology, and membrane activity had been studied after γ irradiation. Verified microbiological (specific growth rate, lag phase duration, colony-forming units (CFU) number, and light microscopy digital image analysis), biochemical (ATPase activity of bacterial membrane vesicles), and biophysical (H⁺ fluxes throughout cytoplasmic membrane of bacteria) methods were used for assessment of radiation implications on bacteria. It was shown that growth specific rate, lag phase duration and CFU number of these bacteria were lowered after irradiation, and average cell surface area was decreased too. Moreover ion fluxes of bacteria were changed: for P. aeruginosa they were decreased and for E. coli—increased. The N,N′-dicyclohexylcarbodiimide (DCCD) sensitive fluxes were also changed which were indicative for the membrane-associated F₀F₁-ATPase enzyme. ATPase activity of irradiated membrane vesicles was decreased for P. aeruginosa and stimulated for E. coli. Furthermore, DCCD sensitive ATPase activity was also changed. The results obtained suggest that these bacteria especially, P. aeruginosa are sensitive to γ radiation and might be used for developing new monitoring methods for estimating environmental changes after γ irradiation.     

A novel alphabaculovirus isolated from the cotton bollworm, <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> (Hubner) (Lepidoptera: Noctuidae): characterization and pathogenicity

The cotton bollworm, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) is a polyphagous pest that exist all over the world. It is also very destructive in Turkey on various agricultural products. In this study, we have detected an alphabaculovirus from Helicoverpa armigera larvae collected from cotton field. The virus isolate was named as Helicoverpa armigera nucleopolyhedrovirus (HearNPV-O1) based on morphological and molecular properties. This is the first record of baculovirus from H. armigera in Eurasia region. Scanning electron microscopy examinations of polyhedral inclusion bodies (PIBs) showed their irregular morphology with average diameter of 0.85 to 1.25 μm. Transmission electron microscopy studies revealed that the nucleocapsids were multiple enveloped and bacilliform shaped. The size of nucleocapsid was found as 279 nm with a width of 56 nm. Digestion of viral genome by PstI generated 8 fragments with total size of 130.9 kbp. According to the phylogenetic analysis of the partial polyhedrin (polh), late expression factor 8 (lef8) and late expression factor 9 (lef9) genes, HearNPV-O1 isolate is very close to H. armigera MNPV Indian isolate-443. Five different concentrations of HearNPV-O1 between 10³ and 10⁷ were used in dose-response test on neonate, 3rd and 5th instars larvae of H. armigera. The highest dose (10⁷) showed 92%, 88% and 57% mortality, respectively within 14 days. LC₅₀ values of HearNPV-O1 isolate were calculated as 6?×?10⁴, 7?×?10⁴ and 8?×?10⁶ PIBs/mL^?1 against neonate, 3rd and 5th instars larval stages, respectively. These results demonstrate that HearNPV-O1 isolate may be a potential biocontrol agent to be utilized against H. armigera.     

Mechanism for the Action of λ Exonuclease in Genetic Recombination

Lambda exonuclease degrades in vitro redundant single stranded regions which probably result in λ DNA from genetic recombination in vivo.     

Laser probing of the plasma in the S-300 facility

A method for the laser probing of an imploding plasma in the S-300 high-current generator (I=4 MA, Z=0.15 Ω, and τ=100 ns) with the use of a YAG: Nd laser is described. The first version of the method enables obtaining three-frame shadow and schlieren photographs of the plasma of the accelerator load with an exposure of 10 ns and an interval between frames of 25 ns. The second version enables the five-frame probing of the plasma with an exposure of 1 ns and an interval between frames of 10 ns. Stimulated Brillouin scattering in carbon tetrachloride is used to compress the probing laser pulse. A series of shadow and schlieren photographs of the plasma of different liners and Z-pinches are obtained. Mechanisms for the image formation are discussed. The magnitude and gradients of the plasma density are estimated.     

Effect of ionizing radiation on the DNA damage response in <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

The DNA damage response (DDR) is induced by various DNA damaging factors and maintains genome stability in all organisms. The Chlamydomonas reinhardtii genome contains putative homologous genes involved in DDR; however, little is known about the functions and responses of these genes to DNA damage. In this study, DDR by gamma radiation was determined in C. reinhardtii. Irradiation with 80, and 200 Gy gamma radiation caused death in approximately 47 and 97 % of C. reinhardtii cells, respectively. The absolute lethality of cells was at 300 Gy. The rate of DNA breaks was also determined using comet assays after exposure to different doses of gamma radiation. Irradiation with 80 and 400 Gy resulted in 17 and 34 % of nuclear degradation in C. reinhardtii cells, respectively. To identify the major DDR pathway of C. reinhardtii induced by gamma radiation, 24 putative DDR genes were selected from the Joint Genome Institute (JGI) database. Gamma radiation significantly affected expression of 15 genes among these. Therefore, these genes displaying expressional changes by gamma radiation are involved in DDR, which indicate that C. reinhardtii may possess a fundamental conserved DDR pathway with higher plants. Furthermore, radiation responsive proteins were identified by proteomic analysis, which are involved in metabolisms of carbohydrate, energy, and photosynthesis. This is the first report to describe the responses of DDR homologous genes to gamma radiation and to identify gamma radiation-responsive proteins in C. reinhardtii. Our data should provide molecular insights into gamma radiation responses including DNA damage in green algae.     

Mathematical models for cellular systems the von Foerster equation. Part I

P. B. M. Walker (1954) and H. C. Longuet-Higgins (quoted by Walker), as well as O. Scherbaum and G. Rasch (1957), made the first attempts towards a mathematical study of the age distribution in a cellular population. It was H. Von Foerster (1959), however, who derived the complete differential equation for the age density function,n(t, a). His equation is obtained from an analysis of the infinitesimal changes occurring during a time elementdt in a group of cells with ages betweena anda+da. The behavior of the population is determined by a quantity λ which we call the loss function. In this paper a rigorous discussion of the Von Foerster equation is presented, and a solution is given for the special case when λ depends, ont (time) anda (age) but not on other variables (such asn itself). It is also shown that the age density,n(t, a), is completely known only if the birth rate,α(t), and the initial age distribution, β(a), are given as boundary conditions. In Section II the steady state solution and some plausible forms of intrinsic loss functions (depending ona only) are discussed in view of later applications.