Two-dimensional Vortex Behavior in Highly Underdoped YBa_2Cu_3O_{6+x} Observed byScanning Hall Probe Microscopy (open access)

Two-dimensional Vortex Behavior in Highly Underdoped YBa_2Cu_3O_{6+x} Observed byScanning Hall Probe Microscopy

We report scanning Hall probe microscopy of highly underdoped superconducting YBa{sub 2}Cu{sub 3}O{sub 6+z} with T{sub c} ranging from 5 to 15 K which showed distinct flux bundles with less than one superconducting flux quantum ({Phi}{sub 0}) through the sample surface. The sub-{Phi}{sub 0} features occurred more frequently for lower T{sub c}, were more mobile than conventional vortices, and occurred more readily when the sample was cooled with an in-plane field component. We show that these features are consistent with kinked stacks of pancake vortices.
Date: April 22, 2008
Creator: Guikema, J.W.; Bluhm, Hendrik; /Stanford U., Appl. Phys. Dept.; Bonn, D.A.; Liang, Ruixing; Hardy, W.N. et al.
System: The UNT Digital Library
MCF-10A-NeoST: A New Cell System for Studying Cell-ECM and Cell-Cell Interactions in Breast Cancer (open access)

MCF-10A-NeoST: A New Cell System for Studying Cell-ECM and Cell-Cell Interactions in Breast Cancer

There is a continuing need for genetically matched cell systems to model cellular behaviors that are frequently observed in aggressive breast cancers. We report here the isolation and initial characterization of a spontaneously arising variant of MCF-10A cells, NeoST, which provides a new model to study cell adhesion and signal transduction in breast cancer. NeoST cells recapitulate important biological and biochemical features of metastatic breast cancer, including anchorage-independent growth, invasiveness in threedimensional reconstituted membranes, loss of E-cadherin expression, and increased tyrosine kinase activity. A comprehensive analysis of tyrosine kinase expression revealed overexpression or functional activation of the Axl, FAK, and EphA2 tyrosine kinases in transformed MCF-10A cells. MCF-10A and these new derivatives provide a genetically matched model to study defects in cell adhesion and signaling that are relevant to cellular behaviors that often typify aggressive breast cancer cells.
Date: August 22, 2001
Creator: Zantek, N. D.; Walker-Daniels, J.; Stewart, J.; Hansen, R. K.; Robinson, D.; Miao, H. et al.
System: The UNT Digital Library
Observation of B^+\to\eta\rho^+ and Search for B^0 Decays to\eta^\prime\eta, \eta\pi^0, \eta^\prime\pi^0, and \omega\pi^0 (open access)

Observation of B^+\to\eta\rho^+ and Search for B^0 Decays to\eta^\prime\eta, \eta\pi^0, \eta^\prime\pi^0, and \omega\pi^0

The authors present measurements of branching fractions for five B-meson decays to two-body charmless final states. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 459 million B{bar B} pairs. The results for branching fractions are, in units of 10{sup -6} (upper limits at 90% C.L.): {Beta}(B{sup +} {yields} {eta}{rho}{sup +}) = 9.9 {+-} 1.2 {+-} 0.8, {Beta}(B{sup 0} {yields} {eta}{prime}{eta}) = 0.5 {+-} 0.4 {+-} 0.1 (< 1.2), {Beta}(B{sup 0} {yields} {eta}{pi}{sup 0}) = 0.9 {+-} 0.4 {+-} 0.1 (< 1.5), {Beta}(B{sup 0} {yields} {eta}{prime}{pi}{sup 0}) = 0.9 {+-} 0.4 {+-} 0.1 (< 1.5), and {Beta}(B{sup 0}{sup 0} {yields} {omega}{pi}{sup 0}) = {eta}{rho}{sup +} mode, they measure the charge asymmetry {Alpha}{sub ch} (B{sup +} {yields} {eta}{rho}{sup +}) = 0.13 {+-} 0.11 {+-} 0.02.
Date: April 22, 2008
Creator: Aubert, Bernard; Bona, Marcella; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
System: The UNT Digital Library
Molecular architecture of axonemal microtubule doublets revealedby cryo-electron tomography (open access)

Molecular architecture of axonemal microtubule doublets revealedby cryo-electron tomography

The axoneme, which forms the core of eukaryotic flagella and cilia, is one of the largest macromolecular machines with a structure that is largely conserved from protists to mammals. Microtubule doublets are structural components of axonemes containing a number of proteins besides tubulin, and are usually found in arrays of nine doublets arranged around two singlet microtubules. Coordinated sliding of adjacent doublets, which involves a host of other proteins in the axoneme, produces periodic beating movements of the axoneme. We have obtained a 3D density map of intact microtubule doublets using cryo-electron tomography and image averaging. Our map, with a resolution of about 3 nm, provides insights into locations of particular proteins within the doublets and the structural features of the doublets that define their mechanical properties. We identify likely candidates for several of these non-tubulin components of the doublets. This work offers novel insight on how tubulin protofilaments and accessory proteins attach together to form the doublets and provides a structural basis for understanding doublet function in axonemes.
Date: May 22, 2006
Creator: Sui, Haixin & Downing, Kenneth H.
System: The UNT Digital Library
VHE Gamma-ray Supernova Remnants (open access)

VHE Gamma-ray Supernova Remnants

Increasing observational evidence gathered especially in X-rays and {gamma}-rays during the course of the last few years support the notion that Supernova remnants (SNRs) are Galactic particle accelerators up to energies close to the ''knee'' in the energy spectrum of Cosmic rays. This review summarizes the current status of {gamma}-ray observations of SNRs. Shell-type as well as plerionic type SNRs are addressed and prospect for observations of these two source classes with the upcoming GLAST satellite in the energy regime above 100 MeV are given.
Date: January 22, 2007
Creator: Funk, Stefan
System: The UNT Digital Library
Improved Method for CKM Constraints in Charmless Three-body B and Bs Decays (open access)

Improved Method for CKM Constraints in Charmless Three-body B and Bs Decays

Recently Ciuchini, Pierini and Silvestrini proposed a method for constraining CKM parameters in B {yields} K{pi}{pi} and B{sub s} {yields} K{pi}{pi} through phase measurements of amplitudes involving I = 3/2 K*{pi} final states. We show that complementary information on CKM parameters may be obtained by studying the phases of {Delta}I = 1 B {yields} (K*{pi}){sub I = 1/2}, B{sub s} {yields} (K* {bar K}){sub l=1} and B{sub s} {yields} ({bar K}* K){sub I=1} amplitudes. Hadronic uncertainties in these constraints from electroweak penguin operators O{sub 9} and O{sub 10}, studied using flavor SU(3), are shown to be very small in B {yields} K{pi}{pi} and B{sub s} {yields} K{pi}{pi} and somewhat larger in B{sub s} {yields} K{bar K}{pi}. The first processes imply a precise linear relation between {bar {rho}} and {bar {eta}}, with a measurable slope and an intercept at {bar {eta}} = 0 involving a theoretical error of 0.03. The decays B{sub s} {yields} K{pi}{pi} permit a measurement of involving a theoretical error below a degree. We note that while time-dependence is required when studying B{sup 0} decays at the {Upsilon}(4S), it is not needed when studying B{sub s} decays at hadronic colliders.
Date: September 22, 2006
Creator: Gronau, Michael; /SLAC, /Technion; Pirjol, Dan; /MIT, LNS; Soni, Amarjit; /Brookhaven et al.
System: The UNT Digital Library
Dissipative Cryogenic Filters with Zero DC Resistance (open access)

Dissipative Cryogenic Filters with Zero DC Resistance

The authors designed, implemented and tested cryogenic RF filters with zero DC resistance, based on wires with a superconducting core inside a resistive sheath. The superconducting core allows low frequency currents to pass with negligible dissipation. Signals above the cutoff frequency are dissipated in the resistive part due to their small skin depth. The filters consist of twisted wire pairs shielded with copper tape. Above approximately 1 GHz, the attenuation is exponential in {radical}{omega}, as typical for skin depth based RF filters. By using additional capacitors of 10 nF per line, an attenuation of at least 45 dB above 10 MHz can be obtained. Thus, one single filter stage kept at mixing chamber temperature in a dilution refrigerator is sufficient to attenuate room temperature black body radiation to levels corresponding to 10 mK above about 10 MHz.
Date: April 22, 2008
Creator: Bluhm, Hendrik; Moler, Kathryn A. & /Stanford U., Appl. Phys. Dept
System: The UNT Digital Library