Ionic Shock Research Articles

The feasibility study of ion driven shock ignition of reactor-size targets in inertial confinement fusion

In this paper, we are intending to investigate the shock ignition approach to inertial confinement fusion (ICF) by using an ion beam driver to examine energy gain performance in reactor-size targets filled by cryogenic deuterium-tritium hydrogen isotopes. Here, pressure dynamics across the fuel layer affected by ignition beam parameters have been analyzed by using the DEIRA-4 simulation code, for the two targets that we chose for the case study. By choosing the proper pulse shaping and evaluation of finding the appropriate time and position of the inter-collision time between two compression and ignition pulses, it has been found that shock ignition can create the pressure more than 104 Gbar at the fuel center and therefore increase gain by 18% and 25% for Case 1 and Case 2, respectively. Ionic shock ignition can also decrease the ignition threshold; hence, it causes 19% reduction for Case 1 and 39% reduction for Case 2 of the internal beam energy. It has been shown that besides the lower implosion velocities relative to traditional central ignition, which are now maintained, the fuel pressure at stagnation becomes much higher than it is. In addition, the stable stagnation stage, ignition condition, and high-energy gain are achieved when the optimum configuration of the ignition beam has been derived. Our results show that we can attain pressures level of 200 Gbar < P < 500 Gbar and implosion velocities of 170 km s−1 < Uimp < 291 km s−1 which are in agreement with laser-driven shock ignition alternatives. The pressure range is more than the Standard ICF, laser-driven shock ignition, and impact fast ignition (IFI), and the implosion velocity range is less than Standard ICF and IFI.

Negative regulation of the vacuole-mediated resistance to K(+) stress by a novel C2H2 zinc finger transcription factor encoded by aslA in Aspergillus nidulans.

In fungi and plants, vacuoles function as a storage and sequestration vessel for a wide variety of ions and are responsible for cytosolic ion homeostasis and responses to ionic shock. In the filamentous fungus Aspergillus nidulans, however, little is known about the molecular genetic mechanisms of vacuolar biogenesis and function. In the present study, we analyzed the function of the aslA gene (AN5583) encoding a novel C2H2-type zinc finger transcription factor (TF) in relation to K(+) stress resistance, vacuolar morphology, and vacuolar transporters. The mutant lacking aslA showed increased mycelial growth and decreased branching at high K(+) concentrations. Deletion of aslA also caused elevated K(+) stress-inducible expression of the genes, nhxA (AN2288), vnxA (AN6986), and vcxA (AN0471), encoding putative endosomal and vacuolar cation/H(+) exchangers, as well as cpyA and vpsA genes encoding the proteins involved in vacuolar biogenesis. Interestingly, vacuolar fragmentation induced by K(+) stress was alleviated by aslA deletion, resulting in persistence of unfragmented vacuoles. In the presence of bafilomycin, an inhibitor of vacuolar H(+)-ATPase, the mutant phenotype was suppressed in terms of growth rates and vacuolar morphology. These results together suggest that the C2H2-type zinc finger TF AslA attenuates the K(+) stress-inducible expression of the genes encoding the ion pumps involved in vacuolar sequestration of K(+) ions powered by vacuolar H(+)-ATPase, as well as the proteins that function in vacuolar biogenesis.

Ionic Control of Crack Propagation in Biopolymer Hydrogels

Alginate hydrogels stabilized by ionic interactions, fracture via crosslink unzipping and chain pull-out. It is found that, allowing non-binding ions to diffuse from a drop of brine into the crack tip region, leads to a strong acceleration of the crack. This is ascribed to the exchange between binding (Ca2+) cations and non-binding ones, which facilitates the opening of unit chelating cages. The resulting lowering of the effective energy barrier is found merely entropic. The ion-exchange can be modelled as a rate-limited kinetic process, the order of which is fixed by the electroneutrality requirement, as checked by comparing the effect of monovalent and divalent cations. Although the embrittlement induced by a ionic shock could hinder the use of alginate gels in physiological environments where structural integrity and load-bearing capacity are required, it however can be thought as a powerful analytic tool for studying the nature and spatial extent of the dissipative mechanism at work when fracturing ultra-tough double network (including a ionic one) gels.

LARGE-AREA [Fe II] LINE MAPPING OF THE SUPERNOVA REMNANT IC 443 WITH THE IRSF/SIRIUS

We present the result of near-infrared (near-IR) [Fe II] line mapping of the supernova remnant IC443 with the IRSF/SIRIUS, using the two narrow-band filters tuned for the [Fe II] 1.257 micron and [Fe II] 1.644 micron lines. Covering a large area of 30' x 35', our observations reveal that [Fe II] filamentary structures exist all over the remnant, not only in an ionic shock shell, but also in a molecular shock shell and a central region inside the shells. With the two [Fe II] lines, we performed corrections for dust extinction to derive the intrinsic line intensities. We also obtained the intensities of thermal emission from the warm dust associated with IC443, using the far- and mid-IR images taken with AKARI and Spitzer, respectively. As a result, we find that the [Fe II] line emission relative to the dust emission notably enhances in the inner central region. We discuss causes of the enhanced [Fe II] line emission, estimating the Fe+ and dust masses.

Rapid Response of the Yeast Plasma Membrane Proteome to Salt Stress

The plasma membrane separates the cell from the external environment and plays an important role in the stress response of the cell. In this study, we compared plasma membrane proteome modifications of yeast cells exposed to mild (0.4 m NaCl) or high (1 m NaCl) salt stress for 10, 30, or 90 min. Plasma membrane-enriched fractions were isolated, purified, and subjected to iTRAQ labeling for quantitative analysis. In total, 88-109 plasma membrane proteins were identified and quantified. The quantitative analysis revealed significant changes in the abundance of several plasma membrane proteins. Mild salt stress caused an increase in abundance of 12 plasma membrane proteins, including known salt-responsive proteins, as well as new targets. Interestingly, 20 plasma membrane proteins, including the P-type H(+)-ATPase Pma1, ABC transporters, glucose and amino acid transporters, t-SNAREs, and proteins involved in cell wall biogenesis showed a significant and rapid decrease in abundance in response to both 0.4 m and 1 m NaCl. We propose that rapid protein internalization occurs as a response to hyper-osmotic and/or ionic shock, which might affect plasma membrane morphology and ionic homeostasis. This rapid response might help the cell to survive until the transcriptional response takes place.

New roles for CDC25 in growth control, galactose regulation and cellular differentiation in Saccharomyces cerevisiae.

Living organisms display large differences in stress resistance throughout their life cycles. To study the coordinated regulation of development and stress responses in exponentially growing yeast, mutants that displayed elevated heat-shock resistance at this stage were screened for. Here, two new mutant alleles of CDC25 in Saccharomyces cerevisiae, cdc25-21 and cdc25-22, are described. During exponential growth in glucose at 25 degrees C, these mutants are resistant to heat, oxidative, osmotic and ionic shock, accumulate stress-protein transcripts, show slow growth rates, thick cell walls and glycogen hyperaccumulation and lack cAMP signalling in response to glucose. Genetic and cellular analyses revealed that the stationary-phase phenotypes of cdc25-21 and cdc25-22 mutants are not due to entrance to a G(0) state during exponential growth, but are the result of a prolonged G(1) phase. It was found that, in the W303 background, CDC25 is dispensable for growth in glucose media. However, CDC25 is essential for growth in galactose, in non-fermentable carbon sources and under continuous incubation at 38 degrees C. In conclusion, the function of the catalytic, C-terminal domain of Cdc25p is not only important for fermentative growth, but also for growth in non-fermentable carbon sources and to trigger galactose derepression.

Multifluid numerical models of wind-swept clumps

ABSTRA C T We present 2D axisymmetric numerical models of the dynamics of a multifluid interaction between a high-velocity rarefied wind of ionization fraction 0:5 and dense clumps of varying ionization fraction. The difference in the relative ram pressure acting on the neutral and ionic components of the clump results in a separation between the ionic and neutral bow shocks, which is an order of magnitude larger than that which would be expected from the different pressure to density ratios of the ions and neutrals. This results in the neutral bow shock leading for a low-ionization clump, and the ionic shock leading for a high-ionization clump. Simulated long-slit Ha spectra are calculated for each of three clump ionization fractions. For higher levels of clump ionization a narrow component at the preshock speed is clearly seen in the emission profile. Such a component is typically seen in spectroscopic observations of the Balmer filaments of supernova remnants.

A distribution function calculation of the H profiles of high-velocity shocks -- III. Profiles from varying angles of observation

Steady-state Hα profiles from strong non-radiative shocks have been investigated in terms of the velocity distribution of the neutral gas by Lim & Raga. The authors' use of a one-dimensional distribution function, which describes only the neutral velocities in the direction normal to the plane of the shock front, limits the predicted line profiles to the line of sight in the direction of the flow. The steady-state model is here extended to a multidimensional distribution function which follows the thermalization of the atomic hydrogen in three dimensions. From this velocity structure it is possible to calculate the steady-state Hα emission profile seen by an observer with an arbitrary line-of-sight orientation to the shock velocity vector. The ionic shock structures used in the kinetic calculation are still of a plane-parallel nature. The predicted Hα profiles from the higher dimensional model follow the same trend of decreasing broad-to-narrow component ratio with increasing shock speed as those of the plane-parallel model. The effect of a variation of the line-of-sight angle from the normal is to reduce the velocity shift between the broad and narrow components in the line profile. Rotation around the shock normal has no effect upon the observed emission profile, as would be expected for a planar shock front.

Loss and recovery of zoospore motility in an isolate of Aphanomyces from a diseased fish

Zoospores of an Aphanomyces from a diseased fish ceased to be motile following physical shock, or ionic shock with 100 mg Ca l −1 , but motility was regained after 4·5 h, without an intervening encystment phase. This novel finding indicates that, in this fungus at least, zoospores might be transported, immobile, by water currents and encyst only in response to conducive surfaces.

Dissociation of immunocomplexes by ionic shock for the development of immunosensors: application to measurement of alpha 1-fetoprotein.

We report here our experimental results on the reaction rate of immunological complexes and on potential repeated use of membranes as a result of dissociation of the complexes between alpha 1-fetoprotein and catalase-labeled antibodies by different buffers with various ionic strengths. The measurement consists of an immunological process and an enzymatic reaction. The protein membrane activated by glutaraldehyde for the immobilization of antibodies is fixed over an oxygen electrode. After incubation with antibody/alpha 1-fetoprotein and antibody/alpha 1-fetoprotein antibodies coupled to catalase, the reaction medium is introduced into a continuous-flow cell. Oxygen production by the catalase is measured on-line, with the electrode in contact with hydrogen peroxide. This response is correlated to the alpha 1-fetoprotein concentration of the sample. We show a typical calibration curve between 0.5 and 120 micrograms/L. Replicate (n = 20) equilibrium measurement with the same membrane gave a CV of 2.2%. The reversible immunochemical sensor has been tested for 30 measurements without significant loss of activity.

The F 1-ATPase from Streptococcus cremoris: Isolation, purification and partial characterization

1. 1. The F 1-ATPase from the plasma membrane of Streptococcus cremoris HA was released by low ionic shock wash and purified by gel filtration and ion exchange chromatography. 2. 2. The specific activity of the purified F 1-ATPase was 25.8 μmol P i/mg protein/min. 3. 3. K m for ATP was 0.80 mM, and K i for ADP as a competetive inhibitor 0.40 mM. 4. 4. The purified F 1-ATPase consisted of five subunits, α, β, γ, δ and ϵ, with molecular masses of 47.0, 45.0, 29.5, 22.0 and 13.0 kDa, respectively. 5. 5. The isoelectric point of the enzyme complex was found to be 4.4.

The Effect of Sugars on the Binding of [203Hg]-p-Chloromercuribenzenesulfonic Acid to Leaf Tissues

Replacement of mannitol with sucrose decreases the binding of [(203)Hg]-p-chloromercuribenzenesulphonic acid (PCMBS) to Vicia faba leaf discs without epidermis. This decrease is optimal for 20 minutes on incubation, is concentration-dependent, and is also found with maltose and raffinose. In parallel experiments, the addition of sucrose, maltose, and raffinose during PCMBS pretreatment was shown to increase subsequent uptake of [U-(14)C]sucrose. In contrast, d- or l-glucose, 3-O-methylglucose, galactose, fructose, palatinose, turanose, or melibiose had no effect either on PCMBS binding or on [(14)C]sucrose uptake. The sucrose-induced decrease of PCMBS binding is retained after a cold and ionic shock. Measurements of specific activities of membrane fractions prepared from tissues incubated in labeled PCMBS show that the decrease concerns the 120,000 gravity pellet, but that very mild procedures must be chosen to prevent redistribution of label in the supernatant. Altogether, the data provide new support to the hypothesis that the active site of the sucrose carrier contains a group sensitive to PCMBS.

Study on the surface polypeptides isolated from human lymphoblastoid ce-ls by ionic shock.

Ionic shock treatment in the presence of 10% glycerol is an efficient and selective method for extracting cell surface components from Raji cells and effecting the solubilization of up to 22 polypeptides. The majority of these shock-released polypeptides are accessible to lactoperoxidase radioiodination. Sera from rabbits immunized against these soluble extracts are reactive against Raji cell surface as indicated by indirect membrane immunofluorescence and agglutination assays.