Spin susceptibility and the pi-excitation in underdoped cuprates

The dynamical spin susceptibility chi'' at wave vector (pi, pi) and the spectrum pi'' of the spin-triplet particle--particle excitation with center of mass momentum (pi, pi) (pi-excitation) are considered in the slave-boson formulation of the t--J-model. Propagators are calculated in a diagrammatic t-matrix approximation in the d-wave superconducting state for a wide doping range. The resulting spectra chi'' and pi'' both show a resonance at a doping dependent energy, in qualitative agreement with recent numerical cluster calculations. In underdoped systems, the peak position is comparable to that found in neutron scattering experiments. The peak in chi'' as well as pi'' is at low doping entirely caused by spin fluctuations, whereas the triplet particle--particle channel does not contribute as a collective mode.Comment: 3 pages, 4 eps-figures included, uses revtex, eps

Gz, a guanine nucleotide-binding protein with unique biochemical properties

Cloning of a complementary DNA (cDNA) for Gz alpha, a newly appreciated member of the family of guanine nucleotide-binding regulatory proteins (G proteins), has allowed preparation of specific antisera to identify the protein in tissues and to assay it during purification from bovine brain. Additionally, expression of the cDNA in Escherichia coli has resulted in the production and purification of the recombinant protein. Purification of Gz from bovine brain is tedious, and only small quantities of protein have been obtained. The protein copurifies with the beta gamma subunit complex common to other G proteins; another 26- kDa GTP-binding protein is also present in these preparations. The purified protein could not serve as a substrate for NAD-dependent ADP- ribosylation catalyzed by either pertussis toxin or cholera toxin. Purification of recombinant Gz alpha (rGz alpha) from E. coli is simple, and quantities of homogeneous protein sufficient for biochemical analysis are obtained. Purified rGz alpha has several properties that distinguish it from other G protein alpha subunit polypeptides. These include a very slow rate of guanine nucleotide exchange (k = 0.02 min^-1), which is reduced greater than 20-fold in the presence of mM concentrations of Mg2+. In addition, the rate of the intrinsic GTPase activity of Gz alpha is extremely slow. The hydrolysis rate (kcat) for rGz alpha at 30 degrees C is 0.05 min^-1, or 200-fold slower than that determined for other G protein alpha subunits. rGz alpha can interact with bovine brain beta gamma but does not serve as a substrate for ADP-ribosylation catalyzed by either pertussis toxin or cholera toxin. These studies suggest that Gz may play a role in signal transduction pathways that are mechanistically distinct from those controlled by the other members of the G protein family

Understanding Deep Networks via Extremal Perturbations and Smooth Masks

The problem of attribution is concerned with identifying the parts of an input that are responsible for a model's output. An important family of attribution methods is based on measuring the effect of perturbations applied to the input. In this paper, we discuss some of the shortcomings of existing approaches to perturbation analysis and address them by introducing the concept of extremal perturbations, which are theoretically grounded and interpretable. We also introduce a number of technical innovations to compute extremal perturbations, including a new area constraint and a parametric family of smooth perturbations, which allow us to remove all tunable hyper-parameters from the optimization problem. We analyze the effect of perturbations as a function of their area, demonstrating excellent sensitivity to the spatial properties of the deep neural network under stimulation. We also extend perturbation analysis to the intermediate layers of a network. This application allows us to identify the salient channels necessary for classification, which, when visualized using feature inversion, can be used to elucidate model behavior. Lastly, we introduce TorchRay, an interpretability library built on PyTorch.Comment: Accepted at ICCV 2019 as oral; supp mat at http://ruthcfong.github.io/files/fong19_extremal_supps.pd

ASSESSING LATERAL ANKLE SPRAIN RISK USING LOWER LIMB ANTHROPOMETRICS

The purpose of this study was to identify clinical measures, that could be used to recognise individuals at an increased risk of ankle sprain based upon lateral centre of pressure (COP) patterns during running gait. A convenience sample of young healthy males (n=32) were recruited and assessed using basic anthropometric measures and questionnaires. Treadmill running COP patterns were collected using Novel pressure insoles. This study identified a model based upon the Cumberland Ankle Instability Tool, external rotation at the knee, and height, could predict an individual‘s COP distribution with an 84.4% accuracy. The outcome from the study could be used as a quick measure to identify individuals at potential increased risk of lateral ankle sprain

UB Knightlines Winter 2010

The UB Knightlines newsletter for Winter 2010. This issue contains articles discussing UB alum Claire Ciscuolo and her business Claire's Corner Copia in New Haven, UB alum Art Landi's business of building product displays and his UB advocacy, UB alum Clodomiro Falcon creating a Hispanic phone directory in Fairfield County with UB, Fone's dental clinic to provide free checkups to local elementary school students, UB's First Year Achievement Floor, the Back-to-School Youth Education Summit, an exhibition on domestic violence, the Bridgeport/Shelton Big Read, alum Steve Ray's experience with UB Basketball in the late 80s, student David James story on marathon running, Sofia Hoflin and the UB women's Soccer team, the induction of alumni into UB's Athletic Hall of Fame, and other campus news

UB Knightlines Spring 2010

The UB Knightlines newsletter for Springer 2010. This issue contains articles discussing the gift of Mr. Shintaro Akatsu which renamed the School of Design, campus financial aid, Chinese language learning within the School of Education, the Engineering School working on next-gen unmanned projectiles for the U.S. Army, fashion merchandising students' visit to the New York city Garment District, student volunteerism on Martin Luther King Day, the addition of Olympian Monica Mesalles to the UB Gymnastics team, a highlight of UB Women's Basketball point guard Sidney Parsons, a recap of UB fall sports, and other campus news

A Model for Family Preservation Case Assessment

The outcomes of family preservation practice have been researched and debated. The effectiveness of family preservation is still inconclusive and many of the findings may only be inferred to specific situations. Few studies have addressed the assessment techniques or outcome factors from a qualitative perspective. This article synthesizes current literature, research and practice, and proposes a practice framework with questioning techniques to assist practitioners in assessing the strengths and characteristics of a family, and making decisions on whether or not familybased services are appropriate for the family. Two actual cases are presented to illustrate how the worker can benefit from having the assessment data derived from this model

Non Magnetic Impurities in the Spin-Gap Phase of the Cuprate

It is now well established that Zn doping of high-$T_C$ cuprates reduces their $T_C$ and triggers the appearence of a spin glass phase. In this context, we have solved exactly the problem of N non magnetic impurities in the staggered flux phase of the Heisenberg model which we assume to be a good mean-field approximation for the spin-gap phase of the cuprates. In this model, the quasiparticule spectrum has four nodes on the Fermi surface, and linearization of the spectrum in the neighbourhood of these nodes leads to a system of 2D Dirac fermions. In the presence of a macroscopic number of (non magnetic) impurities, the problem has a characteristic logarithmic structure that renders ineffective the usual perturbative expansions. We have used this logarithmic structure to calculate an exact solution. For a concentration ni of impurities in the unitary scattering limit, the additional density of states is found to be proportional to $ni/(w \ln^2 (|w|/D))$ (where D is the infrared cut-off of the linearized spectrum) in analogy with the 1D case of doped spin-Peierls and two-leg ladders compounds. We argue that the system exhibits a quasi long-range order at T=0 with instantaneous spin-spin correlations decreasing as $ni/ \ln^4 (ni/R_{ij})$ for large distances $R_{ij}$ between impurity sites. We predict enhanced low energy fluctuations and compare these results to NMR and inelastic neutron scattering experiments in the high-$T_C$ cuprates.Comment: proceeding of SCES98 conference in Paris, July '9

An epidemiological study of epilepsy in Hong Kong SAR, China

SummaryBackgroundSeveral specialist clinic-based epidemiology studies suggested low prevalence in Hong Kong Special Administrative Region (HKSAR) of China. Population-based epidemiological data for epilepsy is not available. We performed the first population-based epidemiological survey of epilepsy in this locality.MethodWe conducted a territory-wide survey. We randomly selected 9547 households from fixed-line telephone directory. We successfully surveyed 17,783 persons of 5178 households by telephone interview. All positive respondents 685 (3.85%) were invited for clinical validation. 127 subjects were validated by board-certified neurologists.ResultsSeizure disorders were confirmed in 28 subjects. The crude prevalence of active epilepsy and seizure disorder were estimated to be 3.94/1000 (95% confidence interval (CI): 2.10–6.74/1000) and 8.49/1000 (95% CI: 5.64–12.27/1000), respectively.ConclusionsThe prevalence of epilepsy in HKSAR is more common than previously thought. The data retrieved is useful for planning and allocation of health resources for patients with seizure disorders