Quantum fluctuations in the spiral phase of the Hubbard model

We study the magnetic excitations in the spiral phase of the two--dimensional Hubbard model using a functional integral method. Spin waves are strongly renormalized and a line of near--zeros is observed in the spectrum around the spiral pitch $\pm{\bf Q}$. The possibility of disordered spiral states is examined by studying the one--loop corrections to the spiral order parameter. We also show that the spiral phase presents an intrinsic instability towards an inhomogeneous state (phase separation, CDW, ...) at weak doping. Though phase separation is suppressed by weak long--range Coulomb interactions, the CDW instability only disappears for sufficiently strong Coulomb interaction.Comment: Figures are NOW appended via uuencoded postscript fil

UREA/ammonium ion removal system for the orbiting frog otolith experiment

The feasibility of using free urease enzyme and ANGC-101 ion exchange resin to remove urea and ammonium ion for space system waste water applications was studied. Specifically examined is the prevention of urea and ammonia toxicity in a 30-day Orbiting Frog Otolith (OFO) flight experiment. It is shown that free urease enzyme used in conjunction with ANGC-101 ion-exchange resin and pH control can control urea and amonium ion concentration in unbuffered recirculating water. In addition, the resin does not adversely effect the bullfrogs by lowering the concentration of cations below critical minimum levels. Further investigations on bioburden control, frog waste excretion on an OFO diet, a trade-off analysis of methods of automating the urea/ammonium ion removal system and fabrication and test of a semiautomated breadboard were recommended as continuing efforts. Photographs of test equipment and test animals are shown

Cow-Calf Producer Perceptions Regarding Individual Animal Traceability

This study provides valuable insights into cow-calf producer voluntary participation in the National Animal Identification System and producers’ perceptions of several issues critically impacting the success of voluntary traceability systems. Cow-calf producers believe that the most important issues to the U.S. beef industry in designing a national, individual animal traceability system are monitoring/managing disease, maintaining current foreign markets, accessing foreign markets, and increasing consumer confidence. Furthermore, producers are concerned with cost, liability, reliability of technology, failure of system to meet stated goals, and confidentiality of information associated with these systems.animal traceability, cow-calf, National Animal Identification System, voluntary adoption, Agribusiness, Community/Rural/Urban Development, Crop Production/Industries, Farm Management, Labor and Human Capital, Land Economics/Use, Livestock Production/Industries, Production Economics, Research and Development/Tech Change/Emerging Technologies, Q12, Q18, R38,

Anderson localization in Hubbard ladders

The effect of a weak random potential on two-leg Hubbard ladders is investigated. The random potential is shown to induce Anderson localization except for attractive enough interactions, supressing completely d-wave superconductivity. These localization effects remain very strong even for many ladders coupled by Josephson coupling. Both dc and ac conductivities and localization lengths are obtained. Consequences for the superconducting ladder compound Sr$_x$Ca$_{14-x}$Cu$_{24}$O$_{41+\delta}$ are discussed.Comment: 2 Pages, 2 Figures, Uses espcrc2.sty (included); Proceedings of the SCES98 conference, July 1998 Paris, France; To be published in Physica

Immunohistochemische Untersuchung zur Expression von Mastzelltryptase an Beckenkammbiopsien bei Mastozytose

In der vorliegenden Studie wurden Knochenmarkpräparate von insgesamt 57 Patienten berücksichtigt, wobei 24 keine systemische Mastozytose, und 33 eine systemische Mastozytose in den konventionellen Färbungen aufwiesen. Durch die Mastzelltryptase, eine Serinprotease, die fast ausschließlich in menschlichen Mastzellen vorkommt und in allen Stadien der Mastzelle gebildet wird, ist ein sehr spezifischer Nachweis von Mastzellen und damit der systemischen Mastozytose möglich. Bei der Korrelation von konservativen Färbungen an Beckenkammbiopsien bei Patienten mit systemischer Mastozytose und ohne systemische Mastozytose aus dem Zeitraum zwischen 1993 und 2003, und den neu angefertigten, immunohistochemischen Färbungen der Mastzelltryptase, findet sich eine Übereinstimmung der Diagnosen in 97 Prozent bei Patienten mit systemischer Mastozytose, und in 95,8 Prozent bei Patienten ohne systemische Mastozytose

Dimension Reduction on Measures of Impulsivity

The main focus of this study was twofold: the first purpose being the assessment of convergent validity on six different measures of impulsivity, and the second being a comparison of dimension reduction techniques for quantitative data. Results from a Principal Components Analysis (PCA) were compared with results from a novel dimension technique known as Local Linear Embedding (LLE). LLE is an analysis of dimension reduction for nonlinear, high dimensional data. By computing neighborhood preserving embeddings, LLE aims to map newly constructed coordinates into a global coordinate structure of a lower dimension. Past research using LLE has solely been conducted on visual and auditory-oriented data. Thus, this is a novel approach, applying LLE to cognitive measures rather than visual or auditory data. This paper acts as a secondary analysis of data collected by a prior Masters student (Robles, 2016). The measures of impulsivity included in this study were: The Barratt Impulsiveness Scale (BIS), the Iowa Gambling Task (IGT), the UPPS-P Impulsive Behavior Scale, the Cued Go/No-Go Task, the Stroop Color-Word Interference Test, and the Delay and Probability Discounting Task (DPDT) – all tests performed in a Latin-square determined order by each of 151 students. Findings not only indicate that convergent validity was absent for certain measures of impulsivity, but that with future programming, LLE may be a suitable method of dimension reduction for quantitative data

The Legal Implications of United States Policy toward Nicaragua: A Machiavellian Dilemma

This Comment examines the impact on international law of the claims by Nicaragua that recent United States\u27 actions violate specific norms of international law and behavior and the claims by the United States that its actions are legal under international principles of collective self-defense. This Comment examines these claims under the relevant rules of international law and concludes that the methods employed by the United States were in violation of international standards of behavior

Renormalization of impurity scattering in one-dimensional interacting electron systems in magnetic field

We study the renormalization of a single impurity potential in one-dimensional interacting electron systems in the presence of magnetic field. Using the bosonization technique and Bethe ansatz solutions, we determine the renormalization group flow diagram for the amplitudes of scattering of up- and down-spin electrons by the impurity in a quantum wire at low electron density and in the Hubbard model at less than half filling. In the absence of magnetic field the repulsive interactions are known to enhance backscattering and make the impurity potential impenetrable in the low-energy limit. On the contrary, we show that in a strong magnetic field the interaction may suppress the backscattering of majority-spin electrons by the impurity potential in the vicinity of the weak-potential fixed point. This implies that in a certain temperature range the impurity becomes almost transparent for the majority-spin electrons while it is impenetrable for the minority-spin ones. The impurity potential can thus have a strong spin-filtering effect.Comment: 11 pages, 2 figures; v2: a typo corrected and a reference added; v3: published version, Sec.II revised with an additional explanatory subsection, comments on the case of more than half-filling added, typos corrected, a reference update

Auroral magnetosphere-ionosphere coupling: A brief topical review

Auroral arcs result from the acceleration and precipitation of magnetospheric plasma in narrow regions characterized by strong electric fields both perpendicular and parallel to the earth's magnetic field. The various mechanisms that were proposed for the origin of such strong electric fields are often complementary Such mechanisms include: (1) electrostatic double layers; (2) double reverse shock; (3) anomalous resistivity; (4) magnetic mirroring of hot plasma; and (5) mapping of the magnetospheric-convection electric field through an auroral discontinuity