CO2-laser induced X-ray emission from high density gaseous targets

A theory for the emission of X-rays from a high density gaseous plasma interacting with CO2 laser is given. It predicts a sharp increase in the X-ray intensity for densities close to the critical.

Pathogen-Induced Defense Signaling and Signal Crosstalk in Arabidopsis

Erwinia carotovora subsp. carotovora is a bacterial phytopathogen that causes soft rot in various agronomically important crop plants. A genetically specified resistance to E. carotovora has not been defined, and plant resistance to this pathogen is established through nonspecific activation of basal defense responses. This, together with the broad host range, makes this pathogen a good model for studying the activation of plant defenses. Production and secretion of plant cell wall-degrading enzymes (PCWDE) are central to the virulence of E. carotovora. It also possesses the type III secretion system (TTSS) utilized by many Gram-negative bacteria to secrete virulence- promoting effector proteins to plant cells. This study elucidated the role of E. carotovora HrpN (HrpNEcc), an effector protein secreted through TTSS, and the contribution of this protein in the virulence of E. carotovora. Treatment of plants with HrpNEcc was demonstrated to induce a hypersensitive response (HR) as well as resistance to E. carotovora. Resistance induced by HrpNEcc required both salicylic acid (SA)- and jasmonate/ethylene (JA/ET)-dependent defense signaling in Arabidopsis. Simultaneous treatment of Arabidopsis with HrpNEcc and PCWDE polygalacturonase PehA elicited accelerated and enhanced induction of defense genes but also increased production of superoxide and lesion formation. This demonstrates mutual amplification of defense signaling by these two virulence factors of E. carotovora. Identification of genes that are rapidly induced in response to a pathogen can provide novel information about the early events occurring in the plant defense response. CHLOROPHYLLASE 1 (AtCLH1) and EARLY RESPONSIVE TO DEHYDRATION 15 (ERD15) are both rapidly triggered by E. carotovora in Arabidopsis. Characterization of AtCLH1 encoding chlorophyll-degrading enzyme chlorophyllase indicated that it might have a role in chlorophyll degradation during plant tissue damage. Silencing of this gene resulted in increased accumulation of reactive oxygen species (ROS) in response to pathogen infection in a light-dependent manner. This led to enhanced SA-dependent defenses and resistance to E. carotovora. Moreover, crosstalk between different defense signaling pathways was observed; JA-dependent defenses and resistance to fungal pathogen Alternaria brassicicola were impaired, indicating antagonism between SA- and JA-dependent signaling. Characterization of ERD15 suggested that it is a novel, negative regulator of abscisic acid (ABA) signaling in Arabidopsis. Overexpression of ERD15 resulted in insensitivity to ABA and reduced tolerance of the plants to dehydration stress. However, simultaneously, the resistance of the plants to E. carotovora was enhanced. Silencing of ERD15 improved freezing and drought tolerance of transgenic plants. This, together with the reducing effect of ABA on seed germination, indicated hypersensitivity to this phytohormone. ERD15 was hypothesized to act as a capacitor that controls the appropriate activation of ABA responses in Arabidopsis.

Theory of CO2-laser induced x-ray emission from high density gaseous targets

Abstract is not available.

SOCS3 expression induced by PIM2 requires PKC and PI3K signaling

Initiation of proinflammatory host immunity in response to infection represents as a key event in effective control and containment of the pathogen at the site of infection as well as in elicitation of robust immune memory responses. In the current investigation, we demonstrate that an integral cell wall antigen of the mycobacterial envelope, Phosphatidyl-myo-inositol dimannosides (PIM2) triggers Suppressor of cytokine signaling (SOCS) 3 expression in macrophages in a Toll-like receptor 2 (TLR2)-MyD88 dependent manner. Data derived from signaling perturbations suggest the involvement of phosphoinositide-3 kinase (PI3K) and protein kinase C (PKC) signaling pathways during PIM2 induced SOCS3 expression. Further, pharmacological inhibition of ERK1/2, but not of p38 MAP kinase or JNK abrogated the induced expression of SOCS3. The PIM2 induced activation of ERK1/2 was dependent on the activation of PI3K or PKC signaling which in turn regulated p65 nuclear factor -kappa B (NF-kappa B) nuclear translocation. Overall, current study delineates the role for PI3K-PKC axis and ERK1/2 signaling as key signaling events during PIM2 induced SOCS3 expression in macrophages.

Studies on transport phenomena during solidification of an aluminum alloy in the presence of linear electromagnetic stirring

Numerical and experimental studies on transport phenomena during solidification of an aluminum alloy in the presence of linear electromagnetic stirring are performed. The alloy is electromagnetically stirred to produce semisolid slurry in a cylindrical graphite mould placed in the annulus of a linear electromagnetic stirrer. The mould is cooled at the bottom, such that solidification progresses from the bottom to the top of the cylindrical mould. A numerical model is developed for simulating the transport phenomena associated with the solidification process using a set of single-phase governing equations of mass. momentum, energy. and species conservation. The viscosity variation of the slurry, used in the model, is determined experimentally using a rotary viscometer. The set of governing equations is solved using a pressure-based finite volume technique, along with an enthalpy based phase change algorithm. The numerical study involves prediction of temperature, velocity, species and solid fraction distribution in the mould. Corresponding solidification experiments are performed, with time-temperature history recorded at key locations. The microstructures at various temperature measurement locations in the solidified billet are analyzed. The numerical predictions of temperature variations are in good agreement with experiments, and the predicted flow field evolution correlates well with the microstructures observed at various locations.

Modeling of Convection and Macrosegregation through Appropriate Consideration of Multiphase/Multiscale Phenomena during Alloy Solidification

Solidification processes are complex in nature, involving multiple phases and several length scales. The properties of solidified products are dictated by the microstructure, the mactostructure, and various defects present in the casting. These, in turn, are governed by the multiphase transport phenomena Occurring at different length scales. In order to control and improve the quality of cast products, it is important to have a thorough understanding of various physical and physicochemical phenomena Occurring at various length scales. preferably through predictive models and controlled experiments. In this context, the modeling of transport phenomena during alloy solidification has evolved over the last few decades due to the complex multiscale nature of the problem. Despite this, a model accounting for all the important length scales directly is computationally prohibitive. Thus, in the past, single-phase continuum models have often been employed with respect to a single length scale to model solidification processing. However, continuous development in understanding the physics of solidification at various length scales oil one hand and the phenomenal growth of computational power oil the other have allowed researchers to use increasingly complex multiphase/multiscale models in recent. times. These models have allowed greater understanding of the coupled micro/macro nature of the process and have made it possible to predict solute segregation and microstructure evolution at different length scales. In this paper, a brief overview of the current status of modeling of convection and macrosegregation in alloy solidification processing is presented.

Time to rest : Signals in shoot apex developmental transitions underlying dormancy

Vuodenajat rytmittävät monivuotisten kasvien elämää pohjoisella pallonpuoliskolla, jolla varmin merkki lähestyvästä talvikaudesta on asteittain lyhenevä päivänpituus. Kun päivänpituus on lyhentynyt tiettyyn raja-arvoon saakka, kasvu hiipuu ja kasvin kehityksessä tapahtuu suuria muutoksia. Väitöskirjatyössäni tutkittiin mekanismeja, jotka liittyvät pituuskasvun päättymiseen, silmujen lepotilan kehittymiseen ja kärkisilmun muodostumiseen hybridihaavan ja koivuntaimilla lyhyen päivänpituuden seurauksena kasvihuoneolosuhteissa. Vain lepotilaiset silmut selviytyvät luonnossa ankaran talvikauden yli, joten etenkin lepotilan kehittymisen tutkiminen on keskeistä pyrittäessä selvittämään monivuotisille kasveille tyypillisen kasvutavan mekanismeja. Jo pitkään on tiedetty, että täysikasvuiset lehdet vastaanottavat tiedon päivänpituudesta ja lähettävät signaaleja varren johtojänteissä ylöspäin kohti kasvin kärkiosaa. Sen sijaan varren kärjen ja kärkikasvupisteen roolia lepotilan kehittymisessä on selvitetty vain vähän. Kuitenkin juuri kärkikasvupisteen selviytyminen vuodesta toiseen on tärkeää, koska sen jakautumiskykyiset solukot tuottavat kasvin maanpäälliset osat. Tässä työssä tehdyissä varttamiskokeissa osoitettiin, että varren kärki ei ainoastaan vastaanota signaaleja lehdistä ja ajoita toimintaansa niiden mukaan, vaan myös kärjellä itsellään on aktiivinen rooli lepotilan kehittymisessä. Erityisesti kiinnitettiin huomiota kärkikasvupisteen eri alueiden, ns. apikaalimeristeemin ja rib-meristeemin erilaisiin tehtäviin ja pääteltiin, että molemmat vaikuttavat lepotilan kehittymiseen. Kokeissa käytettiin normaalien hybridihaapojen lisäksi siirtogeenisiä hybridihaapoja, jotka eivät lopeta kasvuaan lyhyt päivä –olosuhteissa. Siirtogeeniset hybridihaavat ilmensivät voimakkaasti fytokromi A -nimistä valon vastaanottajamolekyyliä rib-meristeemin alueella, mikä saattoi osaltaan vaikuttaa poikkeavaan pituuskasvukäyttäytymiseen. Myös useiden lepotilan kehittymiseen liittyvien geenien ilmenemisessä havaittiin poikkeavuuksia verrattuna ei-siirtogeenisiin kontrolleihin, joiden silmuissa kehittyi lepotila lyhyt päivä –altistuksen seurauksena. Väitöskirjatyössäni havaittiin, että myös kaasumainen kasvihormoni etyleeni toimii viestinvälittäjänä silmujen lepotilan kehittymisessä ja vaikuttaa etenkin lepotilan oikeaan ajoittumiseen. Etyleenillä huomattiin olevan määräävä rooli päätesilmun muodostumisessa: siirtogeeniset koivut, jotka eivät aisti etyleeniä, eivät muodostaneet päätesilmua. Silti siirtogeeniset koivut vaipuivat lepotilaan, joskin myöhemmin kuin ei-siirtogeeniset kontrollit. Tämän perusteella todettiin, että lepotilan ja päätesilmun kehittyminen ovat erillisiä kehitystapahtumia, vaikka ne saattavatkin ajoittua osaksi päällekkäin.

Comment on "Pseudoelasticity of Cu-Zr nanowires via stress-induced martensitic phase transformations"

Recently, a novel stress-induced phase transformation in an initial < 100 >/{100} B2-CuZr nanowire has been reported for the first time [Sutrakar and Mahapatra, Mater. Lett. 63, 1289 (2009)]. Following this, a martenisitic phase transformation in Cu-Zr nanowire was shown [Cheng et al., Appl. Phys. Lett. 95, 021911 (2009)] using the same idea (Sutrakar and Mahapatra, Mater. Lett. 63, 1289 (2009)]. The pseudoelastic recovery of the bct phase of Cu-Zr by unloading has also been shown [Cheng et al., Appl. Phys. Lett. 95, 021911 (2009)]. They also tested the epitaxial bain path [Alippi et al., Phys. Rev. Lett. 78, 3892 (1997)] and reported that the bct phase in the nanowire is metastable, whereas the bulk counterpart is unstable. This aspect is re-examined in this comment with corrected results.

Unusual structural stability and ligand induced alterations in oligomerization of a galectin

Abstract L-14, a 14-kDa S-type lectin shows the jelly roll tertiary structural fold akin to legume lectins yet, unlike them, it does not dissociate on thermal unfolding. In the absence of ligand L-14 displays denaturation transitions corresponding to tetrameric and octameric entities. The presence of complementary ligand reduces the association of L-14, which is in stark contrast with legume lectins where no alterations in quaternary structures are brought about by saccharides. From the magnitude of the increase in denaturation temperature induced by disaccharides the binding constants calculated from differential scanning calorimetry are comparable with those extrapolated from titration calorimetry indicating that L-14 interacts with ligands essentially in the folded state.

Anode Phenomena in Triggered Vacuum Gaps

Arc voltage - current characteristics and threshold current densities occuring during the formation of anode spots in triggered vacuum gaps are reported. Single pulses of 1.65 ms arcing time, which correspond to switching surge currents, are used in the study with copper and aluminum anodes. The threshold values are 1.75 times the values reported earlier using the longer, 8 mis, arcing time. They are found to depend upon the duration of arcing time as well as upon electrode material, surface conditions, electrode size and contact separation. Lateral inhomogenity in the electrode geometry appears to reduce the threshold value by promoting early formation of anode spots.

A phosphorylation-induced turn defines the Alzheimer's disease AT8 antibody epitope on the tau protein

Post mortem biochemical staging of Alzheimer’s disease is currently based on immunochemical analysis of brain slices with the AT8 antibody. The epitope of AT8 is described around the pSer202/pThr205 region of the hyperphosphorylated form of the neuronal protein tau. In this study, NMR spectroscopy was used to precisely map the AT8 epitope on phosphorylated tau, and derive its defining structural features by a combination of NMR analyses and molecular dynamics. A particular turn conformation is stabilized by a hydrogen bond of the phosphorylated Thr205 residue to the amide proton of Gly207, and is further stabilized by the two Arg residues opposing the pSer202/pThr205.

Molecular dynamics simulation of the phosphorylation-induced conformational changes of a tau peptide fragment

Aggregation of the microtubule associated protein tau (MAPT) within neurons of the brain is the leading cause of tauopathies such as Alzheimer's disease. MAPT is a phospho-protein that is selectively phosphorylated by a number of kinases in vivo to perform its biological function. However, it may become pathogenically hyperphosphorylated, causing aggregation into paired helical filaments and neurofibrillary tangles. The phosphorylation induced conformational change on a peptide of MAPT (htau225−250) was investigated by performing molecular dynamics simulations with different phosphorylation patterns of the peptide (pThr231 and/or pSer235) in different simulation conditions to determine the effect of ionic strength and phosphate charge. All phosphorylation patterns were found to disrupt a nascent terminal β-sheet pattern (226VAVVR230 and 244QTAPVP249), replacing it with a range of structures. The double pThr231/pSer235 phosphorylation pattern at experimental ionic strength resulted in the best agreement with NMR structural characterization, with the observation of a transient α-helix (239AKSRLQT245). PPII helical conformations were only found sporadically throughout the simulations. Proteins 2014; 82:1907–1923. © 2014 Wiley Periodicals, Inc.

Oestrogen-induced synthesis of thiamin-binding protein in immature chicks. Kinetics of induction, hormonal specificity and modulation

A specific radioimmunoassay procedure was developed to monitor the plasma concentrations of thiamin-binding protein, a minor yolk constituent of the chicken egg. By using this sensitive assay, the kinetics of oestrogen-induced elaboration of this specific protein in immature chicks was investigated. After a single injection of the steroid hormone, with an initial lag period of 4–5h the thiamin-binding protein rapidly accumulated in the plasma, attaining peak concentrations around 75h and declining thereafter. A 4-fold amplification of the response was noticed during the secondary stimulation, and this increased to 9-fold during the tertiary stimulation with the steroid hormone. The magnitude of the response was dependent on the hormone dose, and the initial latent period and the duration of the ascending phase of induction were unchanged for the hormonal doses tested during both the primary and secondary stimulations. The circulatory half-life of the protein was 6h as calculated from the measurement of the rate of disappearance of the exogenously administered 125I-labelled protein. Simultaneous administration of progesterone, dihydrotestosterone or corticosterone did not alter the pattern of induction. On the other hand, hyperthyroidism markedly decreased the oestrogenic response, whereas propylthiouracil-induced hypothyroidism had the opposite effect. The anti-oestrogen E- and Z-clomiphene citrates, administered 30min before oestrogen, effectively blocked the hormonal induction. α-Amanitin and cycloheximide administered along with or shortly after the sex steroid severely curtailed the protein elaboration. A comparison of the kinetics of induction of thiamin- and riboflavin-binding proteins by oestrogen revealed that, beneath an apparent similarity, a clear-cut difference exists between the two vitamin-binding proteins, particularly with regard to hormonal dose-dependent sensitivity of induction and the half-life in circulation. The steroid-mediated elaboration of the two yolk proteins thus appears to be not strictly co-ordinated, despite several common regulatory features underlying their induction.

Preservation of native conformation during aluminium-induced aggregation of tau protein

ALUMINIUM exposure has been shown to result in aggregation of microtubule-associated protein tau in vitro. In the light of recent observations that the native random structure of tau protein is maintained in its monomeric and dimeric states as well as in the paired helical filaments characteristic of Alzheimer's disease, it is likely that factors playing a causative role in neurofibrillary pathology would not drastically alter the native conformation of tau protein. We have studied the interaction of tau protein with aluminium using circular dichroism (CD) and 27(Al) NMR spectroscopy. The CD studies revealed a five-fold increase in the observed ellipticity of the tau-aluminium assembly. The increase in elipticity was not associated with a change in the general conformation of the protein and was most likely due to an aggregation of the tau protein induced by aluminium. Al-27 NMR spectroscopy confirmed the binding of aluminium to tau protein. Hyperphosphorylation of tau in Alzheimer's disease is known to be associated with defective microtubule assembly in this condition. Abnormally phosphorylated tau exists in a polymerized form in the paired helical filaments (PHF) which constitute the neurofibrillary tangles found in Alzheimer's disease. While it is hypothesized that its altered biophysical characteristics render abnormally phosphorylated tau resistant to proteolysis, causing the formation of stable deposits,the sequence of events resulting in the polymerization of tau are little understood, as are the additional factors or modifications required for tills process. Based on the results of our spectroscopic studies, a model for the sequence of events occurring in neurofibrillary pathology is proposed.