On the rescaled Riemannian metric of Cheeger Gromoll type on the cotangent bundle

Let $(M,g)$ be an n-dimensional Riemannian manifold and $T^{*}M$ be its cotangent bundle equipped with a Riemannian metric of Cheeger Gromoll type which rescale the horizontal part by a nonzero differentiable function. The main purpose of the present paper is to discuss curvature properties of $T^{*}M$ and construct almost paracomplex Norden structures on $T^{*}M$. We investigate conditions for these structures to be para-K\"ahler (paraholomorphic) and quasi-K\"ahler. Also, some properties of almost paracomplex Norden structures in context of almost product Riemannian manifolds are presented

Some electrical and structural properties of Pr-Ce alloys

The electrical resistivity of praseodymium-cerium (Pr-Ce) and lanthanum-cerium (La-Ce) alloys has been studied in the temperature range 1.3 - 1100 K and 0 - 900 C respectively. The present data have confirmed the existence of a conventional Kendo divergence at T = 0 K in double-hexagonal close packed Pr-Ce alloys. In addition to this, evidence has been found of structure at about 20 K and 90 K. This is tentatively ascribed to the presence of Kondo sidebands of the type discussed by Maranzana. These Kondo sidebands are related to the cerium crystalline electric field levels expected in the Pr-Ce alloys on the basis of Rainford's (1971) crystalline electric field parameters for pure praseodymium. Evidence has also been obtained, under certain conditions, for the existence of antiferromagnetic ordering in the alloys at around 26 K. In connection with the structural properties, the dhcp →← fee phase transition in the Pr-Ce alloys and the absence of this transition in pure praseodymium have been discussed on the basis of electrical resistivity and X-ray powder diffraetion data. At high temperatures, a hysteresis loop for the dhcp →← fcc transition in the Pr-Ce alloys has been observed which decreased in size with increasing praseodymium content and vanished in the Ce Pr alloy .(_10)Pr(_.90) alloy. No hysteresis was observed with alloys of higher praseodymium content. The similarity between the atomic volumes of the dhcp - Pr and the hypothetical fce-Pr phases and the disappearance of the dhcp →← fee transition in the Pr-Ce alloys containing more than 90 at.% Pr have indicated the possibility that there is a delicate relationship in favour of the dhcp phase towards the praseodymium end. The observed positive deviation from the line connecting the atomic volumes of the dhcp-Pr and dhcp-Ce has been attributed to the change of the effective valency of cerium from 3.1 to 3. A tentative phase diagram for the Pr-Ce system has been presented which is similar to the La-Nd phase diagram proposed by Gschneidner (1961)

Structural, optical and magnetic properties of Cr doped ZnO microrods prepared by spray pyrolysis

A series of Cr-doped ZnO micro-rod arrays were fabricated by a spray pyrolysis method. X-ray diffraction patterns of the samples showed that the undoped and Cr-doped ZnO microrods exhibit hexagonal crystal structure. Surface morphology analysis of the samples has revealed that pure ZnO sample has a hexagonal microrod morphology. From X-ray photoelectron spectroscopy studies, the Cr 2p3/2 binding energy is found to be 577.34 eV indicating that the electron binding energy of the Cr in ZnO is almost the same as the binding energy of Cr3+ states in Cr2O3. The optical band gap Eg decreases slightly from 3.26 to 3.15 eV with the increase of actual Cr content from x = 0.00 to 4.63 at % in ZnO. Photoluminescence studies at 10 K show that the incorporation of chromium leads to a relative increase of deep level band intensity. It was also observed that Cr doped samples clearly showed ferromagnetic behavior; however, 2.49 % Cr doped ZnO showed remnant magnetization higher than that of 1.07 % and 4.63 % Cr doped samples, while 4.63 % Cr doped ZnO samples had a coercive field higher than the other dopings

Beam Performance of Tracking Detectors with Industrially Produced GEM Foils

Three Gas-Electron-Multiplier tracking detectors with an active area of 10 cm x 10 cm and a two-dimensional, laser-etched orthogonal strip readout have been tested extensively in particle beams at the Meson Test Beam Facility at Fermilab. These detectors used GEM foils produced by Tech-Etch, Inc. They showed an efficiency in excess of 95% and spatial resolution better than 70 um. The influence of the angle of incidence of particles on efficiency and spatial resolution was studied in detail.Comment: 8 pages, 9 figures, accepted by Nuclear Instruments and Methods in Physics Research

Aging measurements with the gas electron multiplier (GEM)

Continuing previous aging measurements with detectors based on the Gas Electron Multiplier (GEM), a $31\times 31$cm$^2$ triple-GEM detector, as used in the small area tracking of the COMPASS experiment at CERN, was investigated. With a detector identical to those installed in the experiment, long-term, high-rate exposures to $8.9$keV X-ray radiation were performed to study its aging properties. In standard operation conditions, with Ar:CO$_2$ (70:30) filling and operated at an effective gain of $8.5\cdot 10^3$, no change in gain and energy resolution is observed after collecting a total charge of 7mC/mm$^2$, corresponding to seven years of normal operation. This observation confirms previous results demonstrating the relative insensitivity of GEM detectors to aging, even when manufactured with common materials

Readout of GEM Detectors Using the Medipix2 CMOS Pixel Chip

We have operated a Medipix2 CMOS readout chip, with amplifying, shaping and charge discriminating front-end electronics integrated on the pixel-level, as a highly segmented direct charge collecting anode in a three-stage gas electron multiplier (Triple-GEM) to detect the ionization from $^{55}$Fe X-rays and electrons from $^{106}$Ru. The device allows to perform moderate energy spectroscopy measurements (20 % FWHM at 5.9 keV $X$-rays) using only digital readout and two discriminator thresholds. Being a truly 2D-detector, it allows to observe individual clusters of minimum ionizing charged particles in $Ar/CO_2$ (70:30) and $He/CO_2$ (70:30) mixtures and to achieve excellent spatial resolution for position reconstruction of primary clusters down to $\sim 50 \mu m$, based on the binary centroid determination method.Comment: 18 pages, 14 pictures. submitted to Nuclear Instruments and Methods in Physics Research

THE COST STRUCTURE OF MICROFINANCE INSTITUTIONS IN EASTERN EUROPE AND CENTRAL ASIA

Microfinance institutions are important, particularly in developing countries, because they expand the frontier of financial intermediation by providing loans to those traditionally excluded from formal financial markets. This paper presents the first systematic statistical examination of the performance of MFIs operating in Eastern Europe and Central Asia. A cost function is estimated for MFIs in the region from 1999-2004. First, the presence of subsidies is found to be associated with higher MFI costs. When output is measured as the number of loans made, we find that MFIs become more efficient over time and that MFIs involved in the provision of group loans and loans to women have lower costs. However, when output is measured as volume of loans rather than their number, this last finding is reversed. This may be due to the fact that such loans are smaller in size; thus for a given volume more loans must be made.http://deepblue.lib.umich.edu/bitstream/2027.42/40195/3/wp809.pd

The risk‐taking channel in the United States : A GVAR approach

Using a panel of large U.S. banks, we examine banks' risk‐taking behaviour in response to monetary policy shocks. Our investigation provides support for the presence of a risk‐taking channel: banks' non‐performing loans increase in the medium to long‐run following an expansionary monetary policy shock. We also find that banks' capital structure plays an important role in explaining bank's risk‐taking appetite. Impulse response analysis shows that shocks emanating from larger banks spill over to the rest of the sector but no such effect is observed for smaller banks. These findings are confirmed for banks' Z‐score

Triple GEM tracking detectors for COMPASS

The small area tracker of COMPASS, a high-luminosity fixed target experiment at CERN's SPS, includes a set of 20 large-size (31\times 31\,\cm^2) Gas Electron Multiplier (GEM) detectors. Based on gas amplification in three cascaded GEM foils, these devices permit to obtain high gain and good spatial resolution even at very high particle fluxes. A two-coordinate projective readout yields, for each track, highly correlated signal amplitudes on both projections, allowing to resolve multiple hits in high occupancy regions close to the central deactivated area of 5\,\cm diameter. At the same time the material exposed to the beam is minimized. Splitting the amplification in three cascaded stages permits to achieve a gain of $\sim 8000$, necessary for efficient ($>98\%$) detection of minimum ionizing particles on both coordinates, already at relatively moderate voltages across individual GEM foils. As a consequence, the probability of a gas discharge to occur when a heavily ionizing particle enters the detector volume, is reduced by more than an order of magnitude at a given gain compared to the initially foreseen double GEM structure. In conjunction with other strategies resulting from extensive R\&D on discharge phenomena, we were able to further reduce both the triggered by heavily ionizing particles entering the detector volume, this helped to drastically reduce both the energy and the probability of such breakdowns. In order to completely exclude permanent damage to the front-end chip by the rare event of a discharge fully propagating to the readout strips, an external electronic protection circuit is used. The operational characteristics of these detectors were examined both in the laboratory and in the beam, where a spatial resolution for minimum ionizing particles of (46\pm 3)\,\mum and a time resolution of \sim 15\,\ns were achieved. For the 2001 run of COMPASS, a total of 14 triple GEM detectors have been installed. First results from the commissioning phase in the high-intensity $\mu$ beam are presented