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Iowa State University

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2004

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Articles 1 - 30 of 30

Full-Text Articles in Physics

Anisotropy Of The Magnetoresistance In Gd5si2ge2, H. Tang, Vitalij K. Pecharsky, G. D. Samolyuk, Min Zou, Karl A. Gschneidner Jr., Vladimir P. Antropov, Deborah L. Schlagel, Thomas A. Lograsso Nov 2004

Anisotropy Of The Magnetoresistance In Gd5si2ge2, H. Tang, Vitalij K. Pecharsky, G. D. Samolyuk, Min Zou, Karl A. Gschneidner Jr., Vladimir P. Antropov, Deborah L. Schlagel, Thomas A. Lograsso

Ames Laboratory Publications

The observed magnetoresistance of single crystalline Gd5Si2Ge2 is negative and strongly anisotropic. The absolute values measured along the [100] and [010] directions exceed those parallel to the [001] direction by more than 60%. First principles calculations demonstrate that a structural modification is responsible for the anisotropy of the magnetoresistance, and that the latter is due to a significant reduction of electronic velocity in the [100] direction and the anisotropy of electrical conductivity.


Double Helicity Asymmetry In Inclusive Midrapidity Pi(0) Production For Polarized P+P Collisions At Root S=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration Nov 2004

Double Helicity Asymmetry In Inclusive Midrapidity Pi(0) Production For Polarized P+P Collisions At Root S=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration

Physics and Astronomy Publications

We present a measurement of the double longitudinal spin asymmetry in inclusive pi(0) production in polarized proton-proton collisions at roots=200 GeV. The data were taken at the Relativistic Heavy Ion Collider with average beam polarizations of 0.27. The measurements are the first in a program to study the longitudinal spin structure of the proton, using strongly interacting probes, at collider energies. The asymmetry is presented for transverse momenta 1-5 GeV/c at midrapidity, where next-to-leading-order perturbative quantum chromodynamic (NLO pQCD) calculations well describe the unpolarized cross section. The observed asymmetry is small and is compared to a ...


From Atomic Scale Reactant Ordering To Mesoscale Reaction Front Propagation: Co Oxidation On Pd(100), Da-Jiang Liu, James W. Evans Nov 2004

From Atomic Scale Reactant Ordering To Mesoscale Reaction Front Propagation: Co Oxidation On Pd(100), Da-Jiang Liu, James W. Evans

Mathematics Publications

We utilize a heterogeneous coupled lattice-gas (HCLG) approach to connect the length scales from a realistic atomistic description of surface reactions to the associated mesoscale spatiotemporal behavior. This method is applied to describe reaction front structure in a model for CO oxidation on Pd(100) which incorporates complex ordering of CO and O adlayers, and a precise treatment of the chemical diffusion for interacting CO adlayers in an environment of coadsorbed O.


Phase Relationships And Structural, Magnetic, And Thermodynamic Properties Of Alloys In The Pseudobinary Er5si4-Er5ge4 System, A. O. Pecharsky, Karl A. Gschneidner Jr., Vitalij K. Pecharsky, Deborah L. Schlagel, Thomas A. Lograsso Oct 2004

Phase Relationships And Structural, Magnetic, And Thermodynamic Properties Of Alloys In The Pseudobinary Er5si4-Er5ge4 System, A. O. Pecharsky, Karl A. Gschneidner Jr., Vitalij K. Pecharsky, Deborah L. Schlagel, Thomas A. Lograsso

Ames Laboratory Publications

The room temperature crystal structures of Er5SixGe4−x alloys change systematically with the concentration of Ge from the orthorhombic Gd5Si4-type when x=4, to the monoclinic Gd5Si2Ge2 type when 3.5⩽x⩽3.9 and to the orthorhombic Sm5Ge4 type forx⩽3. The Curie-Weiss behavior of Er5SixGe4−x materials is consistent with the Er3+ state. The compounds order magnetically below 30 K, apparently adopting complex noncollinear magnetic structures with magnetization not reaching saturation in 50 kOe magnetic fields ...


Bose-Einstein Correlations Of Charged Pion Pairs In Au+Au Collisions At Root(Nn)-N-S = 200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Oct 2004

Bose-Einstein Correlations Of Charged Pion Pairs In Au+Au Collisions At Root(Nn)-N-S = 200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

Bose-Einstein correlations of identically charged pion pairs were measured by the PHENIX experiment at midrapidity in Au+Au collisions at roots(NN)=200 GeV. The Bertsch-Pratt radius parameters were determined as a function of the transverse momentum of the pair and as a function of the centrality of the collision. Using the standard core-halo partial Coulomb fits, and a new parametrization which constrains the Coulomb fraction as determined from the unlike-sign pion correlation, the ratio R-out/R-side is within 0.8-1.1 for 0.25 < < k(T) > < 1.2 GeV/c. The centrality dependence of all radii is well described by a linear scaling in N-part(1/3), and R-out/R-side for < k(T) > similar to 0.45 GeV/c is approximately constant at unity as a function of ...


Bridgman-Grown I-Al68.9pd21.6mn9.5 Quasicrystal: Comparison Of Α, Cp, Σ, And Χ With Those For Flux-Grown Samples, Clayton A. Swenson, Thomas A. Lograsso, N. E. Anderson Jr., A. R. Ross Sep 2004

Bridgman-Grown I-Al68.9pd21.6mn9.5 Quasicrystal: Comparison Of Α, Cp, Σ, And Χ With Those For Flux-Grown Samples, Clayton A. Swenson, Thomas A. Lograsso, N. E. Anderson Jr., A. R. Ross

Ames Laboratory Publications

Thermal expansivity (α, 1–300 K), heat capacity (CP, 1–108 K), electrical conductivity (σ, 1–300 K) and magnetic susceptibility (χ, 1–300 K) data have been obtained for a Bridgman-grown single grain i-Al68.9Pd21.6Mn9.5 quasicrystal (BR) for direct comparison with data previously published for a flux-grown single grain sample [ Phys. Rev. B 65 184206 (2002)], and present σ, χ and CP data for a second flux-grown sample described in an earlier publication [ Philos. Mag. B 79 1673 (1999)]. Fortuitously, comparative analyses show these samples to have essentially the same ...


Elastic Constants Of Ni-Mn-Ga Magnetic Shape Memory Alloys, Marcelo Stipcich, Lluís Mañosa, Antoni Planes, Michel Morin, Jerel L. Zarestky, Thomas A. Lograsso, C. Stassis Aug 2004

Elastic Constants Of Ni-Mn-Ga Magnetic Shape Memory Alloys, Marcelo Stipcich, Lluís Mañosa, Antoni Planes, Michel Morin, Jerel L. Zarestky, Thomas A. Lograsso, C. Stassis

Ames Laboratory Publications

We have measured the adiabatic second order elastic constants of two Ni-Mn-Ga magnetic shape memory crystals with different martensitic transition temperatures, using ultrasonic methods. The temperature dependence of the elastic constants has been followed across the ferromagnetic transition and down to the martensitic transition temperature. Within experimental errors no noticeable change in any of the elastic constants has been observed at the Curie point. The temperature dependence of the shear elastic constant C′ has been found to be very different for the two alloys. Such a different behavior is in agreement with recent theoretical predictions for systems undergoing multi-stage structural ...


Electrical Transport In Amorphous Semiconducting Almgb14 Films, Y. Tian, G. Li, Joseph Shinar, N. L. Wang, Bruce A. Cook, James W. Anderegg, Alan P. Constant, Alan Mark Russell, J. E. Snyder Aug 2004

Electrical Transport In Amorphous Semiconducting Almgb14 Films, Y. Tian, G. Li, Joseph Shinar, N. L. Wang, Bruce A. Cook, James W. Anderegg, Alan P. Constant, Alan Mark Russell, J. E. Snyder

Materials Science and Engineering Publications

The electrical transport properties of semiconducting AlMgB14films deposited at room temperature and 573K are reported in this letter. The as-deposited films are amorphous, and they exhibit high n-type electrical conductivity, which is believed to stem from the conduction electrons donated by Al, Mg, and/or Fe impurities in these films. The film deposited at 573K is less conductive than the room-temperature-deposited film. This is attributed to the nature of donor or trap states in the band gap related to the different deposition temperatures.


Angle-Resolved Photoemission Study Of The Rare-Earth Intermetallic Compounds: Rni2ge2(R=Eu,Gd), Joong Mok Park, D. P. Brammeier, C. G. Olson, Paul C. Canfield, David W. Lynch Aug 2004

Angle-Resolved Photoemission Study Of The Rare-Earth Intermetallic Compounds: Rni2ge2(R=Eu,Gd), Joong Mok Park, D. P. Brammeier, C. G. Olson, Paul C. Canfield, David W. Lynch

Physics and Astronomy Publications

Experimental energy bands mapped from normal-emission photoelectron spectra of EuNi2Ge2 and GdNi2Ge2(001)surfaces show four photoemission features that disperse in both materials in good agreement with band calculations. Segments of the Fermi surfaces mapped by angle-resolved photoemission spectroscopy in the ΓXPZ plane of the Brillouin zones for both EuNi2Ge2 and GdNi2Ge2 are in good agreement with band calculations. This Fermi surface segment changes when one electron is added to EuNi2Ge2, corresponding to GdNi2Ge2, based on the rigid-band approximation.


Measurement Of Nonrandom Event-By-Event Fluctuations Of Average Transverse Momentum In Root S-Nn=200 Gev Au+Au And P+P Collisions, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Aug 2004

Measurement Of Nonrandom Event-By-Event Fluctuations Of Average Transverse Momentum In Root S-Nn=200 Gev Au+Au And P+P Collisions, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

Event-by-event fluctuations of the average transverse momentum of produced particles near midrapidity have been measured by the PHENIX Collaboration in roots(NN)=200 GeV Au+Au, and p+p collisions at the Relativistic Heavy Ion Collider. The fluctuations are observed to be in excess of the expectation for statistically independent particle emission for all centralities. The excess fluctuations exhibit a dependence on both the centrality of the collision and on the p(T) range over which the average is calculated. Both the centrality and p(T) dependence can be well reproduced by a simulation of random particle production with the ...


Effect Of Gas Distributor On Gas Holdup In Fiber Suspensions, Xufeng Su, Theodore J. Heindel Jul 2004

Effect Of Gas Distributor On Gas Holdup In Fiber Suspensions, Xufeng Su, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Two different aeration plates are used to study their effect on gas holdup and flow regime transition in fiber suspensions. Two gas distributors with different open areas (A = 0.57% and 2.14%) and the same orifice diameter (do = 1 mm) are used, and experiments are performed using three different Rayon fiber lengths (L = 3, 6, and 12 mm) over a range of superficial gas velocities (Ug ≤ 18 cm/s) and a range of fiber mass fractions (0 ≤ C ≤ 1.8%) in a 15.24 cm diameter semi-batch bubble column. Experimental results show that the distributor with A = 2.14 ...


Gas Holdup In A Cocurrent Air-Water-Fiber Bubble Column, Chengzhi Tang, Theodore J. Heindel Jul 2004

Gas Holdup In A Cocurrent Air-Water-Fiber Bubble Column, Chengzhi Tang, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Effects of superficial liquid velocity (Ul ), superficial gas velocity (Ug ), and fiber mass fraction (C) on gas holdup (ε) and flow regime transition are studied experimentally in well-mixed water-cellulose fiber suspensions in a cocurrent bubble column. Experimental results show that the gas holdup decreases with increasing Ul when C and Ug are constant. The gas holdup is not significantly affected by C in the range of C < 0.4%, but decreases with increasing C in the range of 0.4% ≤ C ≤ 1.5%. When C > 1.5%, a significant amount of gas is trapped in the fiber network and recirculates with the ...


Magnetostriction And Elasticity Of Body Centered Cubic Fe100−Xbex Alloys, A. E. Clark, M. Wun-Fogle, J. B. Restorff, Thomas A. Lograsso, G. Petculescu Jun 2004

Magnetostriction And Elasticity Of Body Centered Cubic Fe100−Xbex Alloys, A. E. Clark, M. Wun-Fogle, J. B. Restorff, Thomas A. Lograsso, G. Petculescu

Ames Laboratory Conference Papers, Posters, and Presentations

Magnetostriction measurements from 77 K to room temperature on oriented (100) and (110) disk samples of Fe93.9Be6.1 and Fe88.7Be11.3 reveal substantial increases in λ100compared to iron. For the 11.3% alloy, λ100=110 ppm, a sixfold increase above that of α-Fe. For the 6.1% alloy, λ100=81 ppm, ∼40% and ∼170% greater than λ100 of comparable Fe–Ga and Fe–Al alloys, respectively, for H=15 kOe. Large differences exist between the values of λ100 and λ111 (λ100>0, λ111 ...


Neutron Scattering Study Of Tbptin Intermetallic Compound, O. Garlea, Emilia Morosan, Sergey L. Bud'ko, Jerel L. Zarestky, Paul C. Canfield, C. Stassis Jun 2004

Neutron Scattering Study Of Tbptin Intermetallic Compound, O. Garlea, Emilia Morosan, Sergey L. Bud'ko, Jerel L. Zarestky, Paul C. Canfield, C. Stassis

Ames Laboratory Publications

Neutron diffraction techniques have been used to study the magnetic properties of a TbPtIn single-crystal as a function of temperature and magnetic field. In the absence of an externally applied magnetic field, the compound orders, below approximately 47 K, in an antiferromagnetic structure with propagation vector k=(12,0,12); the magnetic moments were found to be parallel to the [12̄0] direction. Measurements at 4.2 K, with a magnetic field applied along the [12̄0] direction, revealed metamagnetic transitions at approximately 20 kG and 40 kG.


Dynamics Of The Magnetic Field-Induced First Order Magnetic-Structural Phase Transformation Of Gd5(Si0.5ge0.5)4, J. Leib, J. E. Snyder, Thomas A. Lograsso, Deborah L. Schlagel, David C. Jiles Jun 2004

Dynamics Of The Magnetic Field-Induced First Order Magnetic-Structural Phase Transformation Of Gd5(Si0.5ge0.5)4, J. Leib, J. E. Snyder, Thomas A. Lograsso, Deborah L. Schlagel, David C. Jiles

Ames Laboratory Conference Papers, Posters, and Presentations

The system Gd5(SixGe1−x)4 for 0.4⩽x⩽0.5 has been shown to have an unusual first order, coupled magnetic-structural phase transformation at the Curie temperature. Above the transformation temperature Tc, the material is paramagnetic with a monoclinic structure; below Tc, it is ferromagnetic with an orthorhombic structure. Another unusual feature of this phase transformation is that an applied magnetic field can increase Tc by 5 K per tesla. In this study, the magnetic-structural transformation in single crystalGd5Si2Ge2 was triggered by holding the sample at ...


Giant Magnetostriction Behavior At The Curie Temperature Of Single Crystal Gd5(Si0.5ge0.5)4, M. Han, David C. Jiles, J. E. Snyder, Thomas A. Lograsso, Deborah L. Schlagel Jun 2004

Giant Magnetostriction Behavior At The Curie Temperature Of Single Crystal Gd5(Si0.5ge0.5)4, M. Han, David C. Jiles, J. E. Snyder, Thomas A. Lograsso, Deborah L. Schlagel

Ames Laboratory Conference Papers, Posters, and Presentations

We report results of thermal expansion (TE) and magnetostriction (MS) measurements on a single crystal sample of Gd5(Si0.5Ge0.5)4 prepared by the Bridgman method. TE and MS were measured along the c axis by the strain gauge method and the temperature was controlled using a closed cycle helium refrigerator. From the TE measurements the magnetic structural phase transition temperature was found to be 259.5 K on cooling and 261.5 K on heating. The abrupt change in strain and the temperature hysteresis indicate that it is a first order transition. MS measurements ...


A New Approach To Modeling The Magnetomechanical Effect, David C. Jiles, L. Li Jun 2004

A New Approach To Modeling The Magnetomechanical Effect, David C. Jiles, L. Li

Materials Science and Engineering Publications

This paper reports on results taken to validate the extension to the theory of the magnetomechanical effect reported recently. This theory is based on a “law of approach” but the underlying equations have been generalized to include linear and nonlinear terms which are analogous to those in the well-known Rayleigh law of magnetization. It is shown that the generalized theory can be applied to materials with negative magnetostriction, such as nickel, and that the stress dependent model parameters can be determined from experimental measurements. It has been found that the results show improved agreement with experimental observation compared with the ...


Reversible Spin-Flop And Irreversible Metamagneticlike Transitions Induced By A Magnetic Field In The Layered Gd5ge4 Antiferromagnet, Evgenii M. Levin, Karl A. Gschneidner Jr., Thomas A. Lograsso, Deborah L. Schlagel, Vitalij K. Pecharsky Apr 2004

Reversible Spin-Flop And Irreversible Metamagneticlike Transitions Induced By A Magnetic Field In The Layered Gd5ge4 Antiferromagnet, Evgenii M. Levin, Karl A. Gschneidner Jr., Thomas A. Lograsso, Deborah L. Schlagel, Vitalij K. Pecharsky

Ames Laboratory Publications

Temperature and magnetic field dependencies of the magnetization of single crystal Gd5Ge4 indicate antiferromagnetic coupling along the c direction below 130 K. Both a reversible spin-flop transition when a magnetic field of ∼8.4kOe is applied along the cdirection, and irreversible metamagneticlike transitions when a 20 kOe or greater magnetic field is applied at 4.3 K along any of the three crystallographic axes are observed. Although Gd3+ ions have negligible single ion anisotropy, the metamagnetic transitions and magnetization of Gd5Ge4 in the ferromagnetic state depend on the crystallographic direction reflecting the anisotropy of ...


Reflectance Anisotropy Of Gd5si2ge2 And Tb5si2.2ge1.8, S. J. Lee, Joong Mok Park, J. E. Snyder, David C. Jiles, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Pecharsky, David W. Lynch Mar 2004

Reflectance Anisotropy Of Gd5si2ge2 And Tb5si2.2ge1.8, S. J. Lee, Joong Mok Park, J. E. Snyder, David C. Jiles, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Pecharsky, David W. Lynch

Ames Laboratory Publications

Reflectance difference (RD) spectra for the ab plane of the single crystals of Gd5Si2Ge2and bc planes of Gd5Si2Ge2 and Tb5Si2.2Ge1.8 were obtained in the photon energy range of 1.5–5.5 eV. Several peaks were observed for these crystals in the measured spectrum range. Similar features were observed in the RD spectra for the bc planes ofGd5Si2Ge2 and Tb5Si2.2Ge1.8, while different features were observed for the ...


Identified Charged Particle Spectra And Yields In Au Plus Au Collisions At Root(Snn)=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Mar 2004

Identified Charged Particle Spectra And Yields In Au Plus Au Collisions At Root(Snn)=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

The centrality dependence of transverse momentum distributions and yields for pi(+/-),K+/-,p, and (p) over bar in Au+Au collisions at roots(NN)=200 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider. We observe a clear particle mass dependence of the shapes of transverse momentum spectra in central collisions below similar to2 GeV/c in p(T). Both mean transverse momenta and particle yields per participant pair increase from peripheral to midcentral and saturate at the most central collisions for all particle species. We also measure particle ratios of pi(-)/pi(+), K- ...


High-P(T) Charged Hadron Suppression In Au+Au Collisions At Root(Snn)=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Mar 2004

High-P(T) Charged Hadron Suppression In Au+Au Collisions At Root(Snn)=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured charged hadron yields at midrapidity over a wide range of transverse momenta (0.5 < p(T) < 10 GeV/c) in Au+Au collisions at roots(NN)=200 GeV. The data are compared to pi(0) measurements from the same experiment. For both charged hadrons and neutral pions, the yields per nucleon-nucleon collision are significantly suppressed in central compared to peripheral and nucleon-nucleon collisions. The suppression sets in gradually and increases with increasing centrality of the collisions. Above 4-5 GeV/c in p(T), a constant and almost identical suppression of charged hadrons and pi(0)'s is observed. The p(T) spectra are compared to published spectra from Au+Au at roots(NN)=130 in terms of x(T) scaling. Central and peripheral pi(0) as well as peripheral charged spectra exhibit the same x(T) scaling as observed in p+p data.


Single Identified Hadron Spectra From Root S(Nn)=130 Gev Au+Au Collisions, K. Adcox, Sergey Belikov, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Athanasios N. Petridis, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Feb 2004

Single Identified Hadron Spectra From Root S(Nn)=130 Gev Au+Au Collisions, K. Adcox, Sergey Belikov, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Athanasios N. Petridis, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

Transverse momentum spectra and yields of hadrons are measured by the PHENIX collaboration in Au+Au collisions at roots(NN)=130 GeV at the Relativistic Heavy Ion Collider. The time-of-flight resolution allows identification of pions to transverse momenta of 2 GeV/c and protons and antiprotons to 4 GeV/c. The yield of pions rises approximately linearly with the number of nucleons participating in the collision, while the number of kaons, protons, and antiprotons increases more rapidly. The shape of the momentum distribution changes between peripheral and central collisions. Simultaneous analysis of all the p(T) spectra indicates radial collective ...


J/Psi Production From Proton-Proton Collisions At Root S=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Feb 2004

J/Psi Production From Proton-Proton Collisions At Root S=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

J/psi production has been measured in proton-proton collisions at roots=200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at the Relativistic Heavy Ion Collider. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 4.0+/-0.6(stat)+/-0.6(syst)+/-0.4(abs) mu b. The mean transverse momentum is 1.80+/-0.23(stat)+/-0.16(syst) GeV/c.


J/Psi Production In Au-Au Collisions At Root S(Nn)=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Jan 2004

J/Psi Production In Au-Au Collisions At Root S(Nn)=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

First results on charm quarkonia production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The yield of J/psi's measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au-Au reactions at roots(NN) = 200 GeV is analyzed as a function of collision centrality. For this analysis we have studied 49.3x10(6) minimum bias Au-Au reactions. We present the J/psi invariant yield dN/dy for peripheral and midcentral reactions. For the most central collisions where we observe no signal above background, we quote 90% confidence level upper limits. We compare ...


Crossover Between Mean-Field And Ising Critical Behavior In A Lattice-Gas Reaction-Diffusion Model, Da-Jiang Liu, N. Pavlenko, James W. Evans Jan 2004

Crossover Between Mean-Field And Ising Critical Behavior In A Lattice-Gas Reaction-Diffusion Model, Da-Jiang Liu, N. Pavlenko, James W. Evans

Physics and Astronomy Publications

Lattice-gas models for CO oxidation can exhibit a discontinuous nonequilibrium transition between reactive and inactive states, which disappears above a critical CO-desorption rate. Using finite-size-scaling analysis, we demonstrate a crossover from Ising to mean-field behavior at the critical point, with increasing surface mobility of adsorbed CO or with decreasing system size. This behavior is elucidated by analogy with that of equilibrium Ising-type systems with long-range interactions.


Growth Coalescence Shapes For Islands During Metal (100) Homoepitaxy, Maozhi Li, James W. Evans Jan 2004

Growth Coalescence Shapes For Islands During Metal (100) Homoepitaxy, Maozhi Li, James W. Evans

Mathematics Publications

During submonolayer homoepitaxy, instability in the shapes of growing two-dimensional islands can develop due to the diffusion-limited aggregation of deposited adatoms at their edges. However, in metal (100) systems, periphery diffusion is typically efficient, quenching this shape instability, and resulting in simple near-square or near-rectangular shapes of isolated islands. Despite this feature, growth coalescence shapes resulting from collision of two or more growing islands are nontrivial. These coalescence shapes are elucidated here by developing three complementary formulations: (i) suitable atomistic lattice-gas models analyzed by kinetic Monte Carlo simulation; (ii) deterministic rate equations for the dynamics of kinks along island step ...


Predicting Binding Sites Of Hydrolase-Inhibitor Complexes By Combining Several Methods, Taner Z. Sen, Andrzej Kloczkowski, Robert L. Jernigan, Changhui Yan, Vasant Honovar, Kai-Ming Ho, Cai-Zhuang Wang, Yungok Ihm, Haibo Cao, Xun Gu, Drena Dobbs Jan 2004

Predicting Binding Sites Of Hydrolase-Inhibitor Complexes By Combining Several Methods, Taner Z. Sen, Andrzej Kloczkowski, Robert L. Jernigan, Changhui Yan, Vasant Honovar, Kai-Ming Ho, Cai-Zhuang Wang, Yungok Ihm, Haibo Cao, Xun Gu, Drena Dobbs

Genetics, Development and Cell Biology Publications

Background

Protein-protein interactions play a critical role in protein function. Completion of many genomes is being followed rapidly by major efforts to identify interacting protein pairs experimentally in order to decipher the networks of interacting, coordinated-in-action proteins. Identification of protein-protein interaction sites and detection of specific amino acids that contribute to the specificity and the strength of protein interactions is an important problem with broad applications ranging from rational drug design to the analysis of metabolic and signal transduction networks.

Results

In order to increase the power of predictive methods for protein-protein interaction sites, we have developed a consensus methodology ...


Defect Detection In Correlated Noise, Aleksandar Dogandžić, Nawanat Eua-Anant Jan 2004

Defect Detection In Correlated Noise, Aleksandar Dogandžić, Nawanat Eua-Anant

Electrical and Computer Engineering Publications

We present methods for detecting NDE defect signals in correlated noise having unknown covariance. The proposed detectors are derived using the statistical theory of generalized likelihood ratio (GLR) tests and multivariate analysis of variance (MANOVA). We consider both real and complex data models. To allow accurate estimation of the noise covariance, we incorporate secondary data containing only noise into detector design. Probability distributions of the GLR test statistics are derived under the null hypothesis, i.e. assuming that the signal is absent, and used for detector design. We apply the proposed methods to simulated and experimental data and demonstrate their ...


Crystallographic, Electronic, And Magnetic Studies Of Ζ2-Gam (M = Cr, Mn Or Fe):  Trends In Itinerant Magnetism, Olivier Gourdon, Sergey L. Bud'ko, Darrick Williams, Gordon J. Miller Jan 2004

Crystallographic, Electronic, And Magnetic Studies Of Ζ2-Gam (M = Cr, Mn Or Fe):  Trends In Itinerant Magnetism, Olivier Gourdon, Sergey L. Bud'ko, Darrick Williams, Gordon J. Miller

Chemistry Publications

This study of the crystal structure, electronic structure, and magnetic properties of the ζ2-GaM (M = Cr, Mn or Fe) alloys is motivated by the recent reinvestigation of the crystallographic Al8Cr5 structure type of ζ2-GaMn. The isostructural compounds ζ2-GaFe and ζ2-GaCr have been refined using X-ray powder diffraction as well as neutron powder diffraction for ζ2-GaFe. Their structures have been refined using the space group Rm, with cell parameters a = 12.625(8) Å and c = 7.785(10) Å for ζ2-GaCr and a ...


Anomalous Temperature-Dependent Transport In Ybni2b2c And Its Correlation To Microstructural Features, M.A. Avila, Y.Q. Wu, C.L. Condron, Sergey L. Bud'ko, M. J. Kramer, Gordon J. Miller, Paul C. Canfield Jan 2004

Anomalous Temperature-Dependent Transport In Ybni2b2c And Its Correlation To Microstructural Features, M.A. Avila, Y.Q. Wu, C.L. Condron, Sergey L. Bud'ko, M. J. Kramer, Gordon J. Miller, Paul C. Canfield

Chemistry Publications

We address the nature of the ligandal disorder leading to local redistributions of Kondo temperatures, manifested as annealing-induced changes in the transport behavior of the heavy fermion system YbNi2B2C. The anomalous transport behavior was fully characterized by temperature dependent resistivity measurements in an extended range of 0.4