Roton Instability of the Spin Wave Excitation in the Fully Polarized Quatum Hall State and the Phase Diagram at ν=2\nu = 2

We consider the effect of interactions on electrons confined to two dimensions at Landau level filling $\nu=2$, with the specific aim to determine the range of parameters where the fully polarized state is stable. We calculate the charge and the spin density collective modes in random phase approximation (RPA) including vertex corrections (also known as time dependent Hartree Fock), and treating the Landau level mixing accurately within the subspace of a single particle hole pair. It is found that the spin wave excitation mode of the fully polarized state has a roton minimum which deepens as a result of the interaction induced Landau level mixing, and the energy of the roton vanishes at a critical Zeeman energy signaling an instability of the fully polarized state at still lower Zeeman energies. The feasibility of the experimental observation of the roton minimum in the spin wave mode and its softening will be discussed. The spin and charge density collective modes of the unpolarized state are also considered, and a phase diagram for the $\nu =2$ state as a function of $r_{S}$ and the Zeeman energy is obtained.Comment: 47 pages, 9 figure

Exchange Rate Fundamentals and Order Flow (July 2004)

This paper addresses the striking ability of transaction flows to explain exchange rate movements. Specifically, we examine whether this arises because transaction flows convey incremental information about fundamentals. If so, then these flows should affect price upon their realization and observation by price setters (marketmakers). Our model is a simple general equilibrium model of information aggregation that provides---in a setting of incomplete markets---a utility-based present-value representation for exchange rates. The model produces testable implications for the relationships between realized transaction flows, current and future exchange rate returns, and future fundamentals (e.g., money supplies). We then bring these implications to the data, making use of a new dataset covering over six years of transactions (which permits estimation at the monthly frequency). We find strong contemporanous effects of transaction flows on exchange rates, corroborating past findings. More importantly, we present four key findings that are both new to the literature and supportive of our model: (1) transaction flows forecast (Granger cause) future macroeconomic variables such as money growth, output growth, and inflation, (2) transaction flows forecast future exchange rates changes, and do so more effectively than forward discounts, (3) the future exchange rate components that current flows forecast are primarily the future non-flow-driven components, and (4) though flows convey new information about future fundamentals, much of this information is still not impounded in the exchange rate 9 months later. The slow pace of learning implies that abstracting from information aggregation---as is standard in exchange rate economics---is not innocuous.Exchange Rate Dynamics, Microstructure, Order Flow.

How is Macro News Transmitted to Exchange Rates? (December 2003)

This paper tests whether macroeconomic news is transmitted to exchange rates via the transactions process and if so, what share occurs via transactions versus the traditional direct channel. We identify the link between order flow and macro news using a heteroskedasticity-based approach, a la Rigobon and Sack (2002). In both daily and intra-daily data, order flow varies considerably with macro news flow. At least half of the effect of macro news on exchange rates is transmitted via order flow.

Meese-Rogoff Redux: Micro-Based Exchange Rate Forecasting

This paper compares the true, ex-ante forecasting performance of a micro-based model against both a standard macro model and a random walk. In contrast to existing literature, which is focused on longer horizon forecasting, we examine forecasting over horizons from one day to one month (the one-month horizon being where micro and macro analysis begin to overlap). Over our 3-year forecasting sample, we find that the micro-based model consistently out-performs both the random walk and the macro model. Micro-based forecasts account for almost 16 per cent of the sample variance in monthly spot rate changes. These results provide a level of empirical validation as yet unattained by other models. Though our micro-based model out-performs the macro model, this does not imply that past macro analysis has overlooked key fundamentals: our structural interpretation using a fundamentals-based model shows that our findings are consistent with exchange rates being driven by standard fundamentals.Exchange rates, forecasting, Meese and Rogoff, microstructure, order flow

Suppression of weak localization effects in low-density metallic 2D holes

We have measured the conductivity in a gated high-mobility GaAs two dimensional hole sample with densities in the range (7-17)x10^9 cm^-2 and at hole temperatures down to 5x10^-3 E_F. We measure the weak localization corrections to the conductivity g=G/(e^2/h) as a function of magnetic field (Delta g=0.019 +/- 0.006 at g=1.5 and T=9 mK) and temperature (d ln g/dT<0.0058 and 0.0084 at g=1.56 and 2.8). These values are less than a few percent of the value 1/pi predicted by standard weak localization theory for a disordered 2D Fermi liqui

An evaluation of the Islington community education provider network super hub

‘Super Hubs’ are novel initiatives which have arisen in order to aid various workforce developments and service improvements for promoting creative thinking and practice. The Islington Super Hub is a workstream of the Islington Community Education Provider Network (CEPN) which aids the learning and development of community nursing and new apprenticeships (Health Education North Central and East London 2015). In this paper we report on the findings from a realist evaluation of the Islington Super Hub (Pawson and Tilley 1997) using data from a range of provider organisations. The following areas of direct relevance to the Super Hub’s activity will be analysed: i) the factors enabling nursing staff to transfer between sectors; ii) the variety of current preceptorship and induction programmes supporting newly registered nurses moving into community roles; iii) the current links between primary/secondary care for strengthening inter-sectoral working and the core training needed for hospital-based nurses to support patient journeys; iv) the practice learning experiences of specialist practice community nurses, such as General Practice Nurses, District Nurses and Health Visitors as well as non-specialist practitioners and health care assistants; v) the current approaches for sustaining practice-based learning for enhanced learning/development; vi) the current approaches to multi-professional education across localities which contribute to establishing robust community focussed multi-professional collaborative educational approaches; vii) the availability of student nurse placements in community settings and the associated mentorship capacity. Our analysis concludes with critical reflection on the relative merits of the Super Hub’s programme of learning and development which aims to promote creative thought/practice and the contextual factors surrounding the newly emerging apprenticeship roles

The voice of experience: the unmet needs of older people in Barnet.

Between February and July 2008 six focus groups of older people were conducted in six locations across Barnet. The participants in the focus groups were either regular attendees at day centres or older people groups which met regularly. The aim of the study was to identify the unmet needs of older people across the Borough. The focus groups identified that need was felt across many domains of older peoples’ lives, including health and access to health care, exercise and responsibility for one’s own well-being, access to information, companionship, transport and the home environment

Crystal structures of 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium benzoate and 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium picrate

BKS thanks the UGC (India) for the award of Rajeev Gandhi Fellowship.In both 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3- benzothiazol-3-ium benzoate, C11H19N2S+·C7H5O2-, (I), and 2-amino-4,4,7,7-tetramethyl-4,5,6,7-tetrahydro-1,3-benzothiazol-3-ium picrate (2,4,6-trinitrophenolate), C11H19N2S+·C6H2N3O7-, (II), the cations are conformationally chiral as the six-membered rings adopt half-chair conformations, which are disordered over two sets of atomic sites giving approximately enantiomeric disorder. For both cations, the bond lengths indicate delocalization of the positive charge comparable to that in an amidinium cation. The bond lengths in the picrate anion in (II) are consistent with extensive delocalization of the negative charge into the ring and onto the nitro groups, in two of which the O atoms are disordered over two sets of sites. In (I), the ionic components are linked by N—H···O hydrogen bonds to form a chain of rings, and in (II), the N—H···O hydrogen bonds link the components into centrosymmetric four-ion aggregates containing seven hydrogen bonded rings of four different types.Publisher PDFPeer reviewe

Distribution and Kinematics of Molecular Gas in Barred Spiral Galaxies. I. NGC 3504

We present the results of the CO mapping observations of the barred spiral galaxy NGC3504 with the Nobeyama 45-m telescope. The distribution of the molecular gas shows offset ridges which correspond to the distribution of HII regions along the bar. The velocity perpendicular to the bar decreases abruptly at the ridge. The velocity change implies that the molecular gas changes the direction of its motion to parallel to the bar at the ridge. Since the position angle of the major axis of the bar and the line of nodes are almost the same in NGC 3504, an upper limit to the pattern speed of the bar can be derived directly from the radial velocity. The resultant upper limit is 41 km/s/kpc which is much smaller than that derived with an assumption that the corotation radius is located at the end of the bar (77 km/s/kpc). The corotaion radius derived from our upper limit is more than two times larger than the length of the semi-major axis of the bar in NGC 3504.Comment: 6 pages, 12 figures, To appear in PASJ(Publications of the Astronomical Society of Japan