Manifestations of Broken Symmetry: The Surfaces Phases of Ca\u3csub\u3e2−x\u3c/sub\u3eSr\u3csub\u3ex\u3c/sub\u3eRuO\u3csub\u3e4\u3c/sub\u3e

The discovery of superconductivity in Sr2RuO4 has renewed vigor in the study of correlated electron systems. The evolution of a p-wave superconducting state from a para- magnetic 2-dimensional Fermi liquid shows the ruthenate superconductivity is anything but conventional. Sr2RuO4 is isostructural with La2CuO4, the parent compound for the high temperature superconducting family La2−xSrxRuO4. The substitution of Ca2+ for Sr2+ generates a different structure involving a static rotation and tilt of the RuO6 octahedral, however, the antiferromagnetic insulating ground state of Ca2RuO4 is more akin to the cuprate parent. The generation of Ca2−xSrxRuO4 has offered a new family of com- pounds where the evolution from an antiferromagnetic insulator to a superconductor can be studied. Bulk studies have demonstrated how the intricate couplings between structural, orbital, electronic, and magnetic degrees of freedom are responsible for the exotic phases of the system. The layered perovskite structure which plays a key role in the properties observed also makes the crystals amenable to cleaving. Breaking symmetry by the creation of a surface on a quasi 2-dimensional system offers an opportunity to gain insight into the role of structure and symmetry on the properties of the system and offers a new avenue to discover new physics. Inelastic neutron scattering has been utilized to reveal the structural instability against the RuO6 tilt. While the Σ4 phonon mode involving the octahedral tilt shows classic soft phonon mode behavior across a tetragonal to orthorhombic phase transition, a new anomalous mode is discovered and its origin is explored. Surface phonon dynamics have been investigated across a Mott metal-to-insulator transition utilizing High Resolution Electron Energy Loss Spectroscopy where it is revealed the surface electronic transition temperature is significantly lower than the bulk. Low Energy Electron Diffraction has been employed to investigate the surface structure and structural transitions on the surface. Results show surface relaxations inhibit the RuO6 tilt dramatically altering the ensuing orthorhombic phase transition near a quantum critical point at xc = 0.5. It is also revealed that structural distortions accompanying the bulk metal-to-insulator transition are simply nonexistent on the surface. Physical manifestations from breaking symmetry in a correlated electron system are revealed

Atmospheric forcing during active convection in the Labrador Sea and its impact on mixed-layer depth

Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 6978–6992, doi:10.1002/2015JC011607.Hydrographic data from the Labrador Sea collected in February–March 1997, together with atmospheric reanalysis fields, are used to explore relationships between the air-sea fluxes and the observed mixed-layer depths. The strongest winds and highest heat fluxes occurred in February, due to the nature and tracks of the storms. While greater numbers of storms occurred earlier and later in the winter, the storms in February followed a more organized track extending from the Gulf Stream region to the Irminger Sea where they slowed and deepened. The canonical low-pressure system that drives convection is located east of the southern tip of Greenland, with strong westerly winds advecting cold air off the ice edge over the warm ocean. The deepest mixed layers were observed in the western interior basin, although the variability in mixed-layer depth was greater in the eastern interior basin. The overall trend in mixed-layer depth through the winter in both regions of the basin was consistent with that predicted by a 1-D mixed-layer model. We argue that the deeper mixed layers in the west were due to the enhanced heat fluxes on that side of the basin as opposed to oceanic preconditioning.National Science Foundation (RP); Natural Science and Engineering Research Council of Canada Grant Number: OCE-12596182017-03-2

Launch and Landing Infrastructure on the Moon

To explore the solar system effectively, we need to develop outposts on the Moon, Mars, and other surfaces so that we can make use of their in situ resources, stage equipment for further exploration, and perform more in-depth scientific investigations in those chosen locales. This strategy will differ from our previous sortie missions to the Moon in that it will require engineers to develop infrastructure on planetary surfaces and thus export features of human civilization into space. One example of the need for engineering is the development of launch and landing pads on the Moon. Without these pads, the high velocity rocket exhaust would eject regolith as an intense sandblasting spray onto the outpost and surrounding hardware, ruining coated surfaces, jamming mechanisms, pitting windows and optics, and possibly causing damage through gravel and rock impacts. Our analysis indicates that landing pads should consist of a stabilized surface, blast barriers (such as berms or fences), navigation beacons, lighting, video cameras (to monitor spacecraft health and debris transport), roads to move spacecraft off the pads, and infrastructure to access the spacecraft (for servicing, safing, and loading/unloading). This paper describes the methods and technologies necessary for lunar landing pad construction and describes our progress in developing them

EBV-Associated Smooth Muscle Neoplasms: Solid Tumors Arising in the Presence of Immunosuppression and Autoimmune Diseases

Background. Epstein-Barr virus (EBV)-related smooth muscle neoplasms (SMNs) have been associated with immune dysregulation, most notably in patients who have undergone solid organ transplantation or in patients with HIV/AIDS. Objective. to report our experience with EBV-related neoplasms as well as describing the first EBV-related SMN in the setting of administration of glucocorticoids and the tumor necrosis factor inhibitor etanercept. Design. We have case reports, of minimum 3-year follow-up, 2002–2005. Setting. It was held in an academic and tertiary referral cancer center. Patients. Patients are with dysregulated immunity after solid organ transplantation, HIV/AIDS, or with psoriasis after treatment with etanercept. Interventions. There were discontinuation of etanercept, right hepatic trisegmentectomy, and chemotherapy. Measurements. We use survival as a measurement here. Results. Patients who were able to withstand reduction in immunosuppression survived. Surgical resection or chemotherapy was successful in delaying progression of disease. Limitations. There was a relatively short follow-up for these slow-growing neoplasms. Conclusion. EBV-related SMNs have variable aggressiveness. While chemotherapy may slow disease progression, resection and improving the host immune status provide the best opportunity for primary tumor control

Structural role of the tyrosine residues of cytochrome c

The tertiary structures of horse, tuna, Neurospora crassa, horse [Hse65,Leu67]- and horse [Hse65,Leu74]-cytochromes c were studied with high-resolution 1H n.m.r. spectroscopy. The amino acid sequences of these proteins differ at position 46, which is occupied by phenylalanine in the horse proteins but by tyrosine in the remaining two, and at positions 67, 74 and 97, which are all occupied by tyrosine residues in horse and tuna cytochrome c but in the other proteins are substituted by phenylalanine or leucine, though there is only one such substitution per protein. The various aromatic-amino-acid substitutions do not seriously affect the protein structure

High Performance Direct Gravitational N-body Simulations on Graphics Processing Units -- II: An implementation in CUDA

We present the results of gravitational direct $N$-body simulations using the Graphics Processing Unit (GPU) on a commercial NVIDIA GeForce 8800GTX designed for gaming computers. The force evaluation of the $N$-body problem is implemented in ``Compute Unified Device Architecture'' (CUDA) using the GPU to speed-up the calculations. We tested the implementation on three different $N$-body codes: two direct $N$-body integration codes, using the 4th order predictor-corrector Hermite integrator with block time-steps, and one Barnes-Hut treecode, which uses a 2nd order leapfrog integration scheme. The integration of the equations of motions for all codes is performed on the host CPU. We find that for $N > 512$ particles the GPU outperforms the GRAPE-6Af, if some softening in the force calculation is accepted. Without softening and for very small integration time steps the GRAPE still outperforms the GPU. We conclude that modern GPUs offer an attractive alternative to GRAPE-6Af special purpose hardware. Using the same time-step criterion, the total energy of the $N$-body system was conserved better than to one in $10^6$ on the GPU, only about an order of magnitude worse than obtained with GRAPE-6Af. For N \apgt 10^5 the 8800GTX outperforms the host CPU by a factor of about 100 and runs at about the same speed as the GRAPE-6Af.Comment: Accepted for publication in New Astronom

High-Temperature Monitoring of Refractory Wall Recession Using Frequency-modulated Continuous-wave (FM-CW) Radar Techniques

Furnaces are among the most crucial components in the glass and metallurgical industry. Nowadays, furnaces are being operated at higher temperatures and for longer periods of time thus increasing the rate of wear on the furnace refractory lining. Consequently, there is a great need for a nondestructive tool that can accurately measure refractory wall thickness at high temperatures. In this paper the utility of a frequency-modulated continuous-wave (FM-CW) radar is investigated for this purpose

Efficient Photometric Selection of Quasars from the Sloan Digital Sky Survey: 100,000 z<3 Quasars from Data Release One

We present a catalog of 100,563 unresolved, UV-excess (UVX) quasar candidates to g=21 from 2099 deg^2 of the Sloan Digital Sky Survey (SDSS) Data Release One (DR1) imaging data. Existing spectra of 22,737 sources reveals that 22,191 (97.6%) are quasars; accounting for the magnitude dependence of this efficiency, we estimate that 95,502 (95.0%) of the objects in the catalog are quasars. Such a high efficiency is unprecedented in broad-band surveys of quasars. This ``proof-of-concept'' sample is designed to be maximally efficient, but still has 94.7% completeness to unresolved, g<~19.5, UVX quasars from the DR1 quasar catalog. This efficient and complete selection is the result of our application of a probability density type analysis to training sets that describe the 4-D color distribution of stars and spectroscopically confirmed quasars in the SDSS. Specifically, we use a non-parametric Bayesian classification, based on kernel density estimation, to parameterize the color distribution of astronomical sources -- allowing for fast and robust classification. We further supplement the catalog by providing photometric redshifts and matches to FIRST/VLA, ROSAT, and USNO-B sources. Future work needed to extend the this selection algorithm to larger redshifts, fainter magnitudes, and resolved sources is discussed. Finally, we examine some science applications of the catalog, particularly a tentative quasar number counts distribution covering the largest range in magnitude (14.2<g<21.0) ever made within the framework of a single quasar survey.Comment: 35 pages, 11 figures (3 color), 2 tables, accepted by ApJS; higher resolution paper and ASCII version of catalog available at http://sdss.ncsa.uiuc.edu/qso/nbckde