942 research outputs found
Ground state properties of ferromagnetic metal/conjugated polymer interfaces
We theoretically investigate the ground state properties of ferromagnetic
metal/conjugated polymer interfaces. The work is partially motivated by recent
experiments in which injection of spin polarized electrons from ferromagnetic
contacts into thin films of conjugated polymers was reported. We use a
one-dimensional nondegenerate Su-Schrieffer-Heeger (SSH) Hamiltonian to
describe the conjugated polymer and one-dimensional tight-binding models to
describe the ferromagnetic metal. We consider both a model for a conventional
ferromagnetic metal, in which there are no explicit structural degrees of
freedom, and a model for a half-metallic ferromagnetic colossal
magnetoresistance (CMR) oxide which has explicit structural degrees of freedom.
The Fermi energy of the magnetic metallic contact is adjusted to control the
degree of electron transfer into the polymer. We investigate electron charge
and spin transfer from the ferromagnetic metal to the organic polymer, and
structural relaxation near the interface. Bipolarons are the lowest energy
charge state in the bulk polymer for the nondegenerate SSH model Hamiltonian.
As a result electrons (or holes) transferred into the bulk of the polymer form
spinless bipolarons. However, there can be spin density in the polymer
localized near the interface.Comment: 7 figure
Structure and dynamics of Rh surfaces
Lattice relaxations, surface phonon spectra, surface energies, and work
functions are calculated for Rh(100) and Rh(110) surfaces using
density-functional theory and the full-potential linearized augmented plane
wave method. Both, the local-density approximation and the generalized gradient
approximation to the exchange-correlation functional are considered. The force
constants are obtained from the directly calculated atomic forces, and the
temperature dependence of the surface relaxation is evaluated by minimizing the
free energy of the system. The anharmonicity of the atomic vibrations is taken
into account within the quasiharmonic approximation. The importance of
contributions from different phonons to the surface relaxation is analyzed.Comment: 9 pages, 7 figures, scheduled to appear in Phys. Rev. B, Feb. 15
(1998). Other related publications can be found at
http://www.rz-berlin.mpg.de/th/paper.htm
Discovery and Development of Cyclic Peptide Inhibitors of CIB1
Calcium and integrin binding protein 1 (CIB1) is a small, intracellular protein recently implicated in survival and proliferation of triple-negative breast cancer (TNBC). Considering its interactions with PAK1 and downstream signaling, CIB1 has been suggested as a potential therapeutic target in TNBC. As such, CIB1 has been the focus of inhibitor discovery efforts. To overcome issues of potency and stability in previously reported CIB1 inhibitors, we deploy mRNA display to discover new cyclic peptide inhibitors with improved biophysical properties and cellular activity. We advance UNC10245131, a cyclic peptide with low nanomolar affinity and good selectivity for CIB1 over other EF-hand domain proteins and improved permeability and stability over previously identified linear peptide inhibitor UNC10245092. Unlike UNC10245092, UNC10245131 lacks cytotoxicity and does not affect downstream signaling. Despite this, UNC10245131 is a potent ligand that could aid in clarifying roles of CIB1 in TNBC survival and proliferation and other CIB1-associated biological phenotypes
Multi-spectral intravascular photoacoustic/ultrasound/optical coherence tomography tri-modality system with a fully-integrated 0.9-mm full field-of-view catheter for plaque vulnerability imaging
Myocardial infarctions are most often caused by the so-called vulnerable plaques, usually featured as non-obstructive lesions with a lipid-rich necrotic core, thin-cap fibroatheroma, and large plaque size. The identification and quantification of these characteristics are the keys to evaluate plaque vulnerability. However, single modality intravascular methods, such as intravascular ultrasound, optical coherence tomography and photoacoustic, can hardly achieve all the comprehensive information to satisfy clinical needs. In this paper, for the first time, we developed a novel multi-spectral intravascular tri-modality (MS-IVTM) imaging system, which can perform 360° continuous rotation and pull-backing with a 0.9-mm miniature catheter and achieve simultaneous acquisition of both morphological characteristics and pathological compositions. Intravascular tri-modality imaging demonstrates the ability of our MS-IVTM system to provide macroscopic and microscopic structural information of the vessel wall, with identity and quantification of lipids with multi-wavelength excitation. This study offers clinicians and researchers a novel imaging tool to facilitate the accurate diagnosis of vulnerable atherosclerotic plaques. It also has the potential of clinical translations to help better identify and evaluate high-risk plaques during coronary interventions
Heavy Quarks and Heavy Quarkonia as Tests of Thermalization
We present here a brief summary of new results on heavy quarks and heavy
quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma
Thermalization" Workshop in Vienna, Austria in August 2005, directly following
the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop
(Vienna August 2005) Proceeding
Proximity effect at superconducting Sn-Bi2Se3 interface
We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions
down to 250 mK and in different magnetic fields. A number of conductance
anomalies were observed below the superconducting transition temperature of Sn,
including a small gap different from that of Sn, and a zero-bias conductance
peak growing up at lower temperatures. We discussed the possible origins of the
smaller gap and the zero-bias conductance peak. These phenomena support that a
proximity-effect-induced chiral superconducting phase is formed at the
interface between the superconducting Sn and the strong spin-orbit coupling
material Bi2Se3.Comment: 7 pages, 8 figure
Centrality Dependence of the High p_T Charged Hadron Suppression in Au+Au collisions at sqrt(s_NN) = 130 GeV
PHENIX has measured the centrality dependence of charged hadron p_T spectra
from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T
decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction
of the contribution from hard scattering to high p_T hadron production. For
central collisions the yield at high p_T is shown to be suppressed compared to
binary nucleon-nucleon collision scaling of p+p data. This suppression is
monotonically increasing with centrality, but most of the change occurs below
30% centrality, i.e. for collisions with less than about 140 participating
nucleons. The observed p_T and centrality dependence is consistent with the
particle production predicted by models including hard scattering and
subsequent energy loss of the scattered partons in the dense matter created in
the collisions.Comment: 7 pages text, LaTeX, 6 figures, 2 tables, 307 authors, resubmitted to
Phys. Lett. B. Revised to address referee concerns. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
Molecular and functional expression of anion exchangers in cultured normal human nasal epithelial cells
AIMS:
Anions have an important role in the regulation of airway surface liquid (ASL) volume, viscosity and pH. However, functional localization and regulation of anion exchangers (AEs) have not been clearly described. The aim of this study was to investigate the regulation of AE mRNA expression level in accordance with mucociliary differentiation and the functional expression of AEs cultured normal human nasal epithelial (NHNE) cells.
METHODS:
Nasal mucosal specimens from three patients are obtained and serially cultured cells are subjected to morphological examinations, RT-PCR, Western blot analysis and immunocytochemistry. AE activity is assessed by pHi measurements.
RESULTS:
Expression of ciliated cells on the apical membrane and expression of MUC5AC, a marker of mucous differentiation, increased with time. AE2 and SLC26A4 mRNA expression decreased as mucociliary differentiation progressed, and AE4, SLC26A7 and SLC26A8 mRNA expression increased on the 14th and 28th day after confluence. Accordingly, AE4 protein expression also progressively increased. AE activity in 100 mM K(+) buffer solutions was nearly twofold higher than that in 5 mM K(+) buffer solutions. Moreover, only luminal AE activity increased about fourfold over the control in the presence of 5 microM forskolin. In the presence of 100 microM adenosine-5'-triphosphate (ATP) which evokes intracellular calcium signalling through activation of purinergic receptors, only luminal AE activity was again significantly increased. On the other hand, 500 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), an inhibitor of most SLC4 and SLC26AE isoforms, nearly abolished AE activity in both luminal and basolateral membranes. We found that AE activity was affected by intracellular cAMP and calcium signalling in the luminal membrane and was DIDS-sensitive in both membranes of cultured NHNE cells.
CONCLUSION:
Our findings through molecular and functional studies using cultured NHNE cells suggest that AEs may have an important role in the regulation of ASL.ope
Single Electrons from Heavy Flavor Decays in p+p Collisions at sqrt(s) = 200 GeV
The invariant differential cross section for inclusive electron production in
p+p collisions at sqrt(s) = 200 GeV has been measured by the PHENIX experiment
at the Relativistic Heavy Ion Collider over the transverse momentum range $0.4
<= p_T <= 5.0 GeV/c at midrapidity (eta <= 0.35). The contribution to the
inclusive electron spectrum from semileptonic decays of hadrons carrying heavy
flavor, i.e. charm quarks or, at high p_T, bottom quarks, is determined via
three independent methods. The resulting electron spectrum from heavy flavor
decays is compared to recent leading and next-to-leading order perturbative QCD
calculations. The total cross section of charm quark-antiquark pair production
is determined as sigma_(c c^bar) = 0.92 +/- 0.15 (stat.) +- 0.54 (sys.) mb.Comment: 329 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Nuclear Modification of Electron Spectra and Implications for Heavy Quark Energy Loss in Au+Au Collisions at sqrt(s_NN)=200 GeV
The PHENIX experiment has measured mid-rapidity transverse momentum spectra
(0.4 < p_T < 5.0 GeV/c) of electrons as a function of centrality in Au+Au
collisions at sqrt(s_NN)=200 GeV. Contributions from photon conversions and
from light hadron decays, mainly Dalitz decays of pi^0 and eta mesons, were
removed. The resulting non-photonic electron spectra are primarily due to the
semi-leptonic decays of hadrons carrying heavy quarks. Nuclear modification
factors were determined by comparison to non-photonic electrons in p+p
collisions. A significant suppression of electrons at high p_T is observed in
central Au+Au collisions, indicating substantial energy loss of heavy quarks.Comment: 330 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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