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Results for “BASIC INTERACTIONS”
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Investigation of the chemical interface in the soybean–aphid and rice–bacteria interactions using MALDI-mass spectrometry imaging
Mass spectrometry imaging (MSI) is an emerging technology for high-resolution plant biology. It has been utilized to study plant–pest interactions, but limited to the surface interfaces. Here we expand the technology to explore the chemical interactions occurring inside the plant tissues. Two sample preparation methods, imprinting and fracturing, were developed and applied, for the first time, to visualize internal metabolites of leaves in matrix-assisted laser desorption ionization (MALDI)-MSI. This is also the first time nanoparticle-based ionization was implemented to ionize diterpenoid phytochemicals that were difficult to analyze with traditional organic matrices. The interactions between rice–bacterium and soybean–aphid were investigated as two model systems to demonstrate the capability of high-resolution MSI based on MALDI. Localized molecular information on various plant- or pest-derived chemicals provided valuable insight for the molecular processes occurring during the plant–pest interactions. Basically, salicylic acid and isoflavone based resistance was visualized in the soybean–aphid system and antibiotic diterpenoids in rice–bacterium interactions.
Examining Interactions of Uranyl(VI) Ions with Amino Acids in the Gas Phase
Gas-phase experiments, using electrospray ionization quadrupole ion trap mass spectrometry (ESI-QIT/MS), were conducted to probe basic interactions of the uranyl(VI) ion, UO 2 2+ , with selected natural amino acids, namely, L-cysteine (Cys), L-histidine (His), and L-aspartic acid (Asp), which strongly bind to metal ions. The simplest amino acid, glycine (Gly), was also studied for comparison. Cys, His, and Asp have additional potentially coordinating groups beyond the amino and carboxylic acid functional groups, specifically thiol in Cys, imidazole in His, and a second carboxylate in Asp. Gas-phase experiments comprised collision-induced dissociation (CID) of uranyl–amino acid complexes and competitive CID to assess the relative binding strength of different amino acids in the same uranyl complex. Reactivity of selected uranyl–amino acid complexes with water provided further insights into relative stabilities. In positive ion mode, CID and ensuing reactions with water suggested that uranyl–neutral AA binding strength decreased in the order His > Asp > Cys > Gly, which is similar to amino acid proton affinities. In negative ion mode, CID revealed a decreasing dissociation tendency in the order Gly >> His ≈ Cys > Asp, presumably reflecting a reverse enhanced binding to uranyl of the doubly deprotonated amino acids formed in CID.
Probing Induced Structural Changes in Biomimetic Bacterial Cell Membrane Interactions with Divalent Cations
Biological membranes, formed primarily by the self-assembly of complex mixtures of phospholipids, provide a structured scaffold for compartmentalization and structural processes in living cells. The specific physical properties of phospholipid species present in a given membrane play a key role in mediating these processes. Phosphatidylethanolamine (PE), a zwitterionic lipid present in bacterial, yeast, and mammalian cell membranes, is exceptional. In addition to undergoing the standard lipid polymorphic transition between the gel and liquid-crystalline phase, it can also assume an unusual polymorphic state, the inverse hexagonal phase (HII). Divalent cations are among the factors that drive the formation of the HII phase, wherein the lipid molecules form stacked tubular structures by burying the hydrophilic head groups and exposing the hydrophobic tails to the bulk solvent. Most biological membranes contain a lipid species capable of forming the HII state suggesting that such lipid polymorphic structural states play an important role in structural biological processes such as membrane fusion. In this study, the interactions between Mg2+ and biomimetic bacterial cell membranes composed of PE and phosphatidylglycerol (PG) were probed using differential scanning calorimetry (DSC), small-angle x-ray scattering (SAXS), and fluorescence spectroscopy. The lipid phase transitions were examined at varying ratios of PE to PG and upon exposure to physiologically relevant concentrations of Mg2+. An understanding of these basic interactions enhances our understanding of membrane dynamics and how membrane-mediated structural changes may occur in vivo.
A search for resonant production of tt pairs in 4.8 fb -1 of integrated luminosity of pp collisions at √s=1.96 TeV
We search for resonant production of tt pairs in 4.8 fb -1 integrated luminosity of pp collision data at √s = 1.96 TeV in the lepton+jets decay channel, where one top quark decays leptonically and the other hadronically. A matrix element reconstruction technique is used; for each event a probability density function (pdf) of the tt candidate invariant mass is sampled. These pdfs are used to construct a likelihood function, whereby the cross section for resonant tt production is estimated, given a hypothetical resonance mass and width. The data indicate no evidence of resonant production of tt pairs. A benchmark model of leptophobic Z' → tt is excluded with m Z' < 900 GeV at 95% confidence level.
Final Report: Searches for New Physics Phenomena in Hadronic Jet Production in the early ATLAS data
The project is using the data taken during the early running period of the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland to explore the fundamental properties and the basic interactions of matter in a yet unexplored energy regime. The central goal is to search for unexpected “new physics” phenomena using the data taken with the ATLAS detector in proton proton collisions at a center of mass energy of 8 TeV. For this purpose the production rates and the angular distributions of hadronic jets are studiess which have, of all high energy processes at a hadron collider, the largest production rates. Measurements of multi-jet quantities provide unique access to the kinematic region at highest energies and, thus, unique potential to discover new physics phenomena, not explained by the Standard Model of particle physics. The project is performed in collaboration with Dr. Michael Begel from Brookhaven National Laboratory (BNL).
Final Report: Magnetotransport studies of low dimensional electron systems based on GaAs/AlGaAs heterostructures and graphene
Emergence is the process of complex behaviors arising out of a multiplicity of basic interactions. Emergent phenomena often exhibit remarkable, useful, and collective aspects - features which have helped to make emergent behavior a topic of current research. A high quality GaAs/AlGaAs two-dimensional electron system subjected to modest microwave/terahertz photo-excitation at low temperature exhibits radiation-induced zero-resistance states at small magnetic fields, and this phenomenon has been cited as evidence for emergence in a driven, steady state non-equilibrium context. Since the initial observations, photo-excited electronic systems have become a popular arena to search for new physical phenomena.
Lepton event rates in neutrino-nucleus DIS
In this work we have studied the nuclear effect in F{sub 2}{sup A}(x) and F{sub 3}{sup A}(x) weak structure functions and calculated {nu}-nucleus cross section using them by taking into account Fermi motion, binding energy, pion and rho meson cloud contributions and shadowing and anti-shadowing effects. The numerical calculations have been performed in a local density approximation using relativistic nuclear spectral functions which include nucleon correlations for nuclear matter. The results have been compared with the experimental results of NuTeV and CDHSW collaborations.
pp{yields}p{Lambda}K{sup +} reaction in search for the K{sup -}pp state - quest for a kaonic nuclei
The dibaryonic kaonic nuclear bound state, K{sup -}pp is searched by studying an exclusive p+p{yields}p+{Lambda}+K{sup +} process at several beam energies. A signature of the K{sup -}pp is explored in a p+p{yields}X({identical_to}K{sup -}pp)+K{sup +} reaction that follows a decay of the X into p+{Lambda}. We found in a missing-mass {Delta}M(K{sup +}) spectrum and a {Lambda}p invariant-mass M({Lambda}p) spectrum of DISTO data at 2.85 GeV a resonance with M = 2267 MeV/c{sup 2} and {Gamma} = 118 MeV. Those events are found to be associated with a mono energetic kaon. We investigate this resonance as a candidate of the K{sup -}pp further also with a different beam energies.
N-{Delta} weak transition
A short review of the Rein-Sehgal and isobar models is presented. The attention is focused on the nucleon-{Delta}(1232) weak transition form-factors. The results of the recent re-analyses of the ANL and BNL bubble chamber neutrino-deuteron scattering data are discussed.
Determination of the Basic Parameters of Impact Interaction of Abrasive Particles Against the Blades of the Rotor Accelerator of a Centrifugal Mill
Ways to improve the efficiency with which materials are pulverized in impact centrifugal mills as well as ways of preventing wear of the blades are proposed. The problem is solved using equations that describe the motion of particles on the surface of the rotor in a polar coordinate system. It is discovered that the rate of impact of the particles against a blade increases linearly with increasing angular velocity. The angle of attack and radius of contact of a particle with the blade are independent of this velocity, though they are substantially affected by the initial position of the particles. The nature of the variation of the rate of impact and the angle of attack is determined, based on which possible wear of the blades may be predicted and measures taken to reduce wear.
Structure of Sesquisabinene Synthase 1, a Terpenoid Cyclase That Generates a Strained [3.1.0] Bridged-Bicyclic Product
The natural product sesquisabinene is a key component of the fragrant essential oil of the sandalwood tree, currently valued at $5,000/L. Sesquisabinene contains a highly strained [3.1.0] bicyclic ring system and is generated from farnesyl diphosphate in a reaction catalyzed by a class I terpenoid cyclase. To understand how the enzyme directs the formation of a strained hydrocarbon ring system, in this study we report the X-ray crystal structure of sesquisabinene synthase 1 (SQS1) from the Indian sandalwood tree ( Santalum album ). Specifically, we report the structure of unliganded SQS1 at 1.90 Å resolution and the structure of its complex with three Mg 2+ ions and the inhibitor ibandronate at 2.10 Å resolution. The bisphosphonate group of ibandronate coordinates to all three metal ions and makes hydrogen bond interactions with basic residues at the mouth of the active site. These interactions are similarly required for activation of the substrate diphosphate group to initiate catalysis, although partial occupancy binding of the Mg 2+ B ion suggests that this structure represents the penultimate metal coordination complex just prior to substrate activation. The structure of the liganded enzyme enables a precise definition of the enclosed active site contour that serves as a template for the cyclization reaction. This contour is very product-like in shape and readily fits an extended conformation of sesquisabinene and its precursor, the homobisabolyl cation. Structural comparisons of SQS1 with epi -isozizaene synthase mutants that also generate sesquisabinene suggest that [3.1.0] ring formation is not dependent on the isoprenoid tail conformation of the homobisabolyl cation.
Erratum to: 'Potential of the Neutron Lloyd's Mirror Interferometer for the Search for New Interactions'
No abstract prepared.
Physics Prospects with GlueX
The new experiment GlueX is currently being constructed at Jefferson Lab. The experiment was designed to search for hybrid mesons with exotic-quantum-numbers using a beam of linearly polarized photons incident on a liquid hydrogen target. We will discuss the discovery potential of the GlueX experiment and briefly overview its physics program.
Kinetic instabilities and turbulence in photonic plasma
The purpose of this proposal was to study the statistical dynamics of plasma and demonstrate it experimentally in all-optical systems. That this was possible followed from (1) a direct mapping between the equations of plasma kinetics and the nonlinear propagation of statistical light and (2) advances in photonic technology, which enabled versatile control of the input conditions and direct imaging of the output fields. At the start of the proposal, theory exploiting the optics plasma relationship was minimal, and few experiments had been performed. By the end, the field of photonic plasma had been firmly established. There were two main themes in the proposal. The first was optical confirmation of existing plasma theory, particularly where competing theories or numerical codes needed to be distinguished. The second was the genesis of new research directions for plasma, both fundamentally and for applications. These arose naturally from the proposed projects, as experiment raises different questions than theory, while optics gives a much different perspective than material science. The photonic analogues also provide a unified language for many issues that are difficult (and expensive) to study directly, such as high-energy laser-plasma interactions. Moreover, basic imaging techniques enable measurements that are difficult, if not impossible, in material plasma. For example, Debye shielding hides internal dynamics from outside detectors while nonlinear interactions must often be inferred by deviations from linear expectations. In contrast, optics allows the creation of a wide range of spatial and spectral distributions, along with high-resolution measurements in the full position-momentum phase space.
The energy dependence of the pp {yields} K{sup +}n{Sigma}{sup +} reaction
The energy dependence of the total cross section for the pp {yields} K{sup +}n{Sigma}{sup +} reaction has been investigated at the magnetic spectrometer COSY-ANKE. Signals from the production of the {Sigma}{sup +} hyperon were searched for in three simultaneously measured spectra. The values obtained for the total production cross section {sigma}({Sigma}{sup +}) are slightly below those of {sigma}({Sigma}{sup 0}) at the same excess energies. They follow a phase space dependence and do not show any evidence for strong threshold effects or a significant n{Sigma}{sup +} final state interaction.
Photoproduction of {pi}{pi} Pairs off {sup 7}Li
This paper reports on the quasi-free photoproduction of {pi}{sup 0}{pi}{sup 0} and {pi}{sup 0}{pi}{sup +/-} pairs from {sup 7}Li in view of the in-medium properties of hadrons. Measurements have been done using the CB/TAPS detector setup and the Glasgow photon tagging spectrometer for incident photon energies up to 820 MeV. At small invariant masses, an enhancement of the neutral invariant mass distributions is seen compared to the mixed charged channel and could be explained either by an in-medium modification of the {pi}{pi} interaction in the I = J = 0 channel or by effects related to the final state interactions.
Influence of amine-grafted multi-walled carbon nanotubes on physical and rheological properties of PMMA-based nanocomposites
In this work, poly(methyl methacrylate) (PMMA) was grafted onto amine treated multi-walled carbon nanotubes (NH-MWNTs) and the physical and rheological properties of the NH-MWNTs-g-PMMA nanocomposites were investigated. The graft reaction of NH-MWNTs and the PMMA matrix was confirmed from the change of the N{sub 1S} peaks, including those of amine oxygen and amide oxygen, by X-ray photoelectron spectroscopy (XPS). The thermal and mechanical properties of the NH-MWNT-g-PMMA nanocomposites were enhanced by the graft reaction between NH-MWNTs and PMMA matrix. In addition, the viscosity of the nanocomposites was increased with the addition of NH-MWNTs. Storage (G') and loss modulus (G'') were significantly increased by increase in the NH-MWNT content compared to acid-treated MWNTs/PMMA nanocomposites. This increase was attributed to the strong interaction by the grafting reaction between NH-MWNTs and the PMMA matrix. - Graphical abstract: This describes the increase of mechanical properties in NH-MWNTs-g-PMMA hybrid composites with different NH-MWNT contents. Highlights: > Aminized carbon nanotubes are used as reinforcement for poly(methylmethacrylate). > Poly(methylmethacrylate) is grafted on aminized carbon nanotubes by thermal reaction. > Grafting of carbon nanotubes and polymer provide enhanced physical properties. > It was due to the strong interaction between carbon nanotubes and polymer matrix.