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Full-Text Articles in Physics

Enhancement Of The Superconducting Gap By Nesting In Cakfe4as4: A New High Temperature Superconductor, Daixiang Mou, Tai Kong, William R. Meier, Felix Lochner, Lin-Lin Wang, Qisheng Lin, Yun Wu, S. L. Bud’Ko, Ilya Eremin, Duane D. Johnson, Paul C. Canfield, Adam Kaminski Dec 2016

Enhancement Of The Superconducting Gap By Nesting In Cakfe4as4: A New High Temperature Superconductor, Daixiang Mou, Tai Kong, William R. Meier, Felix Lochner, Lin-Lin Wang, Qisheng Lin, Yun Wu, S. L. Bud’Ko, Ilya Eremin, Duane D. Johnson, Paul C. Canfield, Adam Kaminski

Chemistry Publications

We use high resolution angle resolved photoemission spectroscopy and density functional theory with measured crystal structure parameters to study the electronic properties of CaKFe4As4. In contrast to the related CaFe2As2 compounds, CaKFe4As4 has a high Tc of 35 K at stochiometric composition. This presents a unique opportunity to study the properties of high temperature superconductivity in the iron arsenides in the absence of doping or substitution. The Fermi surface consists of several hole and electron pockets that have a range of diameters. We find that the values of the superconducting gap are nearly isotropic (within the explored portions of the ...


Epilogue: Superconducting Materials Past, Present And Future, C. W. Chu, Paul C. Canfield, R. C. Dynes, Z. Fisk, B. Batlogg, G. Deutscher, T. H. Geballe, Z. X. Zhao, R. L. Greene, H. Hosono, M. B. Maple Jul 2015

Epilogue: Superconducting Materials Past, Present And Future, C. W. Chu, Paul C. Canfield, R. C. Dynes, Z. Fisk, B. Batlogg, G. Deutscher, T. H. Geballe, Z. X. Zhao, R. L. Greene, H. Hosono, M. B. Maple

Physics and Astronomy Publications

Experimental contributors to the field of superconducting materials share their informal views on the subject.


Commentary: The Hash House Harriers And The Winding Path To Materials Discovery, Paul C. Canfield Apr 2015

Commentary: The Hash House Harriers And The Winding Path To Materials Discovery, Paul C. Canfield

Physics and Astronomy Publications

Materials science research can be both very demanding and extremely rewarding. In this Commentary, in my own research of new electronic and magnetic materials, I give numerous exemplars of the path followed to materials discovery. I also highlight the parallels between my research experiences with the pastime of running. I hope that my thoughts will help guide junior researchers along the often tortuous and exciting path to new materials and that I can teach them to be open minded and persistent about following new lines of discovery. “No-pain, no-gain” applies to many things in life, running and scientific research being ...


Structure And Function Of Neisseria Gonorrhoeae Mtrf Illuminates A Class Of Antimetabolite Efflux Pumps, Chih-Chia Su, Jani Reddy Bolla, Nitin Kumar, Pattathil Radhakrishnan, Feng Long, Jared A. Delmar, Tsung-Han Chou, Kanagalaghatta R. Rajashankar, William M. Shafer, Edward Yu Jan 2015

Structure And Function Of Neisseria Gonorrhoeae Mtrf Illuminates A Class Of Antimetabolite Efflux Pumps, Chih-Chia Su, Jani Reddy Bolla, Nitin Kumar, Pattathil Radhakrishnan, Feng Long, Jared A. Delmar, Tsung-Han Chou, Kanagalaghatta R. Rajashankar, William M. Shafer, Edward Yu

Physics and Astronomy Publications

Neisseria gonorrhoeae is an obligate human pathogen and the causative agent of the sexually transmitted disease gonorrhea. The control of this disease has been compromised by the increasing proportion of infections due to antibiotic-resistant strains, which are growing at an alarming rate. N. gonorrhoeae MtrF is an integral membrane protein that belongs to the AbgT family of transporters for which no structural information is available. Here, we describe the crystal structure of MtrF, revealing a dimeric molecule with architecture distinct from all other families of transporters. MtrF is a bowl-shaped dimer with a solvent-filled basin extending from the cytoplasm to ...


The Intermetallic Compound Gd6ta4al43, Cathie L. Condron, Joel D. Strand, Paul C. Canfield, Gordon J. Miller Jan 2003

The Intermetallic Compound Gd6ta4al43, Cathie L. Condron, Joel D. Strand, Paul C. Canfield, Gordon J. Miller

Chemistry Publications

The elements Gd (99.999%; Ames Laboratory), Ta (99.999%; Ames Laboratory), and Al (99.98%; Alfa) were combined in the atomic ratio Gd6Ta4Al100 in a 2 ml alumina crucible. The crucible was placed into a fused silica tube and a second crucible, filled with SiO2 wool, was placed inverted on top of the first. The tube was sealed under 1/5 atm Ar and placed into a box furnace. The mixture was heated to 1463 K in 3 h, kept at 1463 K for 2 h, and then cooled to 1173 K over ...


A New Look At Bonding In Trialuminides:  Reinvestigation Of Taal3, C.L. Condron, Gordon J. Miller, Joel D. Strand, Sergey L. Bud'ko, Paul C. Canfield Jan 2003

A New Look At Bonding In Trialuminides:  Reinvestigation Of Taal3, C.L. Condron, Gordon J. Miller, Joel D. Strand, Sergey L. Bud'ko, Paul C. Canfield

Chemistry Publications

Single crystals of TaAl3 were grown at high temperatures from an Al-rich, binary solution. TaAl3 adopts the D022 structure type, space group I4/mmm with a = 3.8412(5) Å, c = 8.5402(17) Å, and Z = 2. The structure type, which is the preferred structure for all group 5 trialuminides and TiAl3 as well as the high-temperature form of HfAl3, is a binary coloring of the face-centered-cubic (fcc) arrangement. The distribution of Ta atoms creates a three-dimensional network of vertex and edge-sharing square pyramids of Al atoms. Temperature-dependent electrical resistivity and magnetic susceptibility ...


Electromagnetic Noise Studies Of Severe Convective Storms In Iowa: The 1970 Storm Season, S. L. Stanford, M. A. Lind, Eugene S. Takle Jan 1971

Electromagnetic Noise Studies Of Severe Convective Storms In Iowa: The 1970 Storm Season, S. L. Stanford, M. A. Lind, Eugene S. Takle

Geological and Atmospheric Sciences Publications

Electromagnetic noise from six convective storms in Iowa has been studied at a variety of frequencies from 0.67 to 144 MHz, with the majority of the data being recorded at 53 MHz. The quasi-static atmospheric electric field was also studied. Twelve tornadoes, numerous funnel clouds and several hailstorms occurred during these storms. Eleven of the tornadoes appear to correlate with some type of enhancement of the recorded electromagnetic pulse rate. A spectacular peak in pulse rate during Storm No. 5 is attributed to a brief but destructive tornado at 38 km; the event is discussed in detail. One tornado ...


Electrical Properties Of Thin Metallic Films, D. B. Barker, W. C. Caldwell Mar 1952

Electrical Properties Of Thin Metallic Films, D. B. Barker, W. C. Caldwell

Ames Laboratory ISC Technical Reports

The Hall coefficient and conductivity of silver films were measured by a DC method and comparisons with the theoretical calculations of Fuchs and Sondheimer were made. Films from 150 A. to 1500 A. in thickness were deposited by evaporation at pressures below 10^-2 microns. The electrical properties were studied at liquid nitrogen, dry ice and acetone, and room temperatures. Film thickness measurements were made by the interferometer method. Electron diffraction and electron micrograph pictures were taken to study agregation and to check on the purity of the films. The electron micrographs show aggregation in films less than 300 A ...