Large diameter graphite/carbon composite filament development Final report

Large diameter graphite/carbon composite monofilaments produced by pyrolysi

Discovering hidden sectors with mono-photon Z' searches

In many theories of physics beyond the Standard Model, from extra dimensions to Hidden Valleys and models of dark matter, Z' bosons mediate between Standard Model particles and hidden sector states. We study the feasibility of observing such hidden states through an invisibly decaying Z' at the LHC. We focus on the process pp -> \gamma Z' -> \gamma X X*, where X is any neutral, (quasi-) stable particle, whether a Standard Model (SM) neutrino or a new state. This complements a previous study using pp -> Z Z' -> l+ l- X X*. Only the Z' mass and two effective charges are needed to describe this process. If the Z' decays invisibly only to Standard Model neutrinos, then these charges are predicted by observation of the Z' through the Drell-Yan process, allowing discrimination between Z' decays to SM neutrinos and invisible decays to new states. We carefully discuss all backgrounds and systematic errors that affect this search. We find that hidden sector decays of a 1 TeV Z' can be observed at 5 sigma significance with 50 fb^{-1} at the LHC. Observation of a 1.5 TeV state requires super-LHC statistics of 1 ab^{-1}. Control of the systematic errors, in particular the parton distribution function uncertainty of the dominant Z \gamma background, is crucial to maximize the LHC searchComment: 13 pages, 4 figure

Measuring Z' couplings at the LHC

We study the properties of potential new Z' gauge bosons produced through the Drell-Yan mechanism at the LHC. Our analysis is performed using a fully differential next-to-leading order QCD calculation with spin correlations, interference effects, and experimental acceptances included. We examine the distinguishability of different models and the feasibility of extracting general coupling information with statistical, residual scale, and current parton distribution function error estimates included. We extend a previous parametrization of Z' couplings to include parity-violating coupling combinations, and introduce a convenient technique for simulating new gauge bosons on-peak using the concept of basis models. We illustrate our procedure using several example Z' models. We find that one can extract reliably four combinations of generation-independent quark and lepton couplings in our analysis. For a Z' mass of 1.5 TeV, one can determine coupling information very well assuming 100 fb^{-1} of integrated luminosity, and a precise measurement becomes possible with 1 ab^{-1} at the SLHC. For a 3 TeV mass, a reasonable determination requires the SLHC.Comment: 22 pgs., 6 figs; refs and discussion adde

Reconstructing a Z' Lagrangian using the LHC and low-energy data

We study the potential of the LHC and future low-energy experiments to precisely measure the underlying model parameters of a new Z' boson. We emphasize the complimentary information obtained from both on- and off-peak LHC dilepton data, from the future Q-weak measurement of the weak charge of the proton, and from a proposed measurement of parity violation in low-energy Moller scattering. We demonstrate the importance of off-peak LHC data and Q-weak for removing sign degeneracies between Z' couplings that occur if only on-peak LHC data is studied. A future precision measurement of low-energy Moller scattering can resolve a scaling degeneracy between quark and lepton couplings that remains after analyzing LHC dilepton data, permitting an extraction of the individual Z' couplings rather than combinations of them. We study how precisely Z' properties can be extracted for LHC integrated luminosities ranging from a few inverse femtobarns to super-LHC values of an inverse attobarn. For the several example cases studied with M_Z'=1.5 TeV, we find that coupling combinations can be determined with relative uncertainties reaching 30% with 30 fb^-1 of integrated luminosity, while 50% is possible with 10 fb^-1. With SLHC luminosities of 1 ab^-1, we find that products of quark and lepton couplings can be probed to 10%.Comment: 36 pages, 17 figure

New Directions in Subband Coding

Two very different subband coders are described. The first is a modified dynamic bit-allocation-subband coder (D-SBC) designed for variable rate coding situations and easily adaptable to noisy channel environments. It can operate at rates as low as 12 kb/s and still give good quality speech. The second coder is a 16-kb/s waveform coder, based on a combination of subband coding and vector quantization (VQ-SBC). The key feature of this coder is its short coding delay, which makes it suitable for real-time communication networks. The speech quality of both coders has been enhanced by adaptive postfiltering. The coders have been implemented on a single AT&T DSP32 signal processo

Mechanistic Studies of the Long Chain Acyl-CoA Synthetase Faa1p from \u3ci\u3eSaccharomyces cerevisiae\u3c/i\u3e

Long chain acyl-CoA synthetase (ACSL; fatty acid CoA ligase: AMP forming; EC 6.2.1.3) catalyzes the formation of acyl-CoA through a process, which requires fatty acid, ATP and coenzymeA as substrates. In the yeast Saccharomyces cerevisiae the principal ACSL is Faa1p (encoded by the FAA1 gene). The preferred substrates for this enzyme are cis-monounsaturated long chain fatty acids. Our previous work has shown Faa1p is a principal component of a fatty acid transport/activation complex that also includes the fatty acid transport protein Fat1p. In the present work hexameric histidine tagged Faa1p was purified to homogeneity through a two-step process in the presence of 0.1% η-dodecyl-β-maltoside following expression at 15°C in Escherichia coli. In order to further define the role of this enzyme in fatty acid transport-coupled activation (vectorial acylation), initial velocity kinetic studies were completed to define the kinetic parameters of Faa1p in response to the different substrates and to define mechanism. These studies showed Faa1p had a Vmax of 158.2 nmol/ min/mg protein and a Km of 71.1μM oleate. When the concentration of oleate was held constant at 50μM, the Km for CoA and ATP were 18.3μM and 51.6μM respectively. These initial velocity studies demonstrated the enzyme mechanism for Faa1p was Bi Uni Uni Bi Ping Pong

Stability of the M2 Phase of Vanadium Dioxide Induced by Coherent Epitaxial Strain

Tensile strain along the cR axis in epitaxial VO2 films raises the temperature of the metal insulator transition and is expected to stabilize the intermediate monoclinic M2 phase. We employ surface-sensitive x-ray spectroscopy to distinguish from the TiO2 substrate and identify the phases of VO2 as a function of temperature in epitaxial VO2/TiO2 thin films with well-defined biaxial strain. Although qualitatively similar to our Landau-Ginzburg theory predicted phase diagrams, the M2 phase is stabilized by nearly an order of magnitude more strain than expected for the measured temperature window. Our results reveal that the elongation of the cR axis is insufficient for describing the transition pathway of VO2 epitaxial films and that a strain induced increase of electron correlation effects must be considered