Phase stability of chromium based compensated ferrimagnets with inverse Heusler structure

Chromium based inverse Heusler compounds of the type Cr2YZ (Y=Co, Fe; Z=Al, Ga, In, Si, Ge, Sn) have been proposed as fully compensated half-metallic ferrimagnets. Such materials are of large interest for spintronics because they combine small magnetic moment with high spin polarization over a wide temperature range. We assess their thermodynamic stability by their formation enthalpies obtained from density functional theory calculations. All compounds under investigation are unstable. Cr2FeSi and Cr2CoAl are stable with respect to the elemental constituents, but decompose into binary phases. Cr2FeGe, Cr2CoGa, Cr2FeSn and Cr2CoIn are found to be unstable with respect to their elemental constituents. We identify possible binary decompositions.Comment: 3 pages, 1 figure, 2 table

Experimental realization of a semiconducting full Heusler compound: Fe2TiSi

Single-phase films of the full Heusler compound Fe2TiSi have been prepared by magnetron sputtering. The compound is found to be a semiconductor with a gap of 0.4eV. The electrical resistivity has a logarithmic temperature dependence up to room temperature due to Kondo scattering of a dilute free electron gas off superparamagnetic impurities. The origin of the electron gas is extrinsic due to disorder or off-stoichiometry. Density functional theory calculations of the electronic structure are in excellent agreement with electron energy loss, optical, and x-ray absorption experiments. Fe2TiSi may find applications as a thermoelectric material.Comment: 6 pages, 6 figure

Improving Searches for Dark Matter Using Missing Transverse Momentum and Jets: An Analysis with the ATLAS Detector at √s = 13 TeV

This thesis presents a novel strategy for searches for Dark Matter at particle colliders using variables that are corrected for detector effects. Dark Matter is experimentally motivated by cosmological evidence and is one of the great contemporary puzzles of physics. This thesis describes the conventional approach of searches for Dark Matter using final states with missing transverse momentum, \ptm, and hadronic jets and discusses its shortcomings. Several techniques for improvements are put forward. An analysis is presented that implements these improvements. It is performed on 3.2 fb⁻¹ of data collected by the ATLAS experiment in 2015 at √s = 13 TeV and measures an unfolded fiducial cross-section ratio in two kinematic regions and in total four differential distributions. The numerator of the ratio is defined as σ(\ptm + jets) and the denominator as σ(Z →l^+l^- + jets). The ratio leads to the cancellation of many systematic uncertainties and detector-induced effects. Limits on three Dark Matter scenarios are set using the distributions. An improved performance with respect to the conventional \ptm + jets Dark Matter search is observed. These distributions can be used to set limits on models containing new physics without using an ATLAS detector simulation. Additional studies are presented investigating further performance enhancements for a future iteration of this analysis

BVRI Light Curves for 29 Type Ia Supernovae

BVRI light curves are presented for 27 Type Ia supernovae discovered during the course of the Calan/Tololo Survey and for two other SNe Ia observed during the same period. Estimates of the maximum light magnitudes in the B, V, and I bands and the initial decline rate parameter m15(B) are also given.Comment: 17 pages, figures and tables are not included (contact first author if needed), to appear in the Astronomical Journa

Origin of Aging of a P2-Nax_xMn3/4_{3/4}Ni1/4_{1/4}O2_2 Cathode Active Material for Sodium-Ion Batteries

Sodium-ion batteries (SIB) are currently being developed and commercialized as a promising new technology for cost-effective and powerful electrical energy storage. In this study, we investigate the origin of capacity fading in P2-type layered sodium cathode materials for SIBs using a micron-sized single-crystalline P2-Na$_x$Mn$_{3/4}$Ni$_{1/4}$O$_2$ model cathode active material. Using various electrochemical techniques, we identify the following aging effects upon cycling: (i) a state of charge (SOC)-independent increase in polarization, (ii) a SOC-dependent increase in polarization at high voltage, and (iii) a loss of active material due to electronic disconnection after prolonged cycling. With high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray (EDX) spectroscopy, we identify surface densification, resulting in 5–10 nm thick surface layers on cycled cathode active materials as the origin for SOC-independent increase of polarization. The corresponding oxygen loss is in accordance with gas evolution in differential electrochemical mass spectrometry (DEMS) measurements. Furthermore, with scanning electron microscopy (SEM) electrode cross sections, we identify (partly) reversible cracking at a high SOC as the cause for increased polarization depending on SOC. Operando X-ray diffraction (XRD) identifies significant anisotropic volume change, which suggests mechanical stress as the cause for cracking at a high SOC and loss of active material after prolonged cycling. We believe that the herein provided understanding on the aging of this highly attractive class of cathode active materials for SIBs will enable the development of future powerful and stable layered oxide cathode materials for SIBs

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good

Severe early onset preeclampsia: short and long term clinical, psychosocial and biochemical aspects

Preeclampsia is a pregnancy specific disorder commonly defined as de novo hypertension and proteinuria after 20 weeks gestational age. It occurs in approximately 3-5% of pregnancies and it is still a major cause of both foetal and maternal morbidity and mortality worldwide1. As extensive research has not yet elucidated the aetiology of preeclampsia, there are no rational preventive or therapeutic interventions available. The only rational treatment is delivery, which benefits the mother but is not in the interest of the foetus, if remote from term. Early onset preeclampsia (<32 weeks’ gestational age) occurs in less than 1% of pregnancies. It is, however often associated with maternal morbidity as the risk of progression to severe maternal disease is inversely related with gestational age at onset2. Resulting prematurity is therefore the main cause of neonatal mortality and morbidity in patients with severe preeclampsia3. Although the discussion is ongoing, perinatal survival is suggested to be increased in patients with preterm preeclampsia by expectant, non-interventional management. This temporising treatment option to lengthen pregnancy includes the use of antihypertensive medication to control hypertension, magnesium sulphate to prevent eclampsia and corticosteroids to enhance foetal lung maturity4. With optimal maternal haemodynamic status and reassuring foetal condition this results on average in an extension of 2 weeks. Prolongation of these pregnancies is a great challenge for clinicians to balance between potential maternal risks on one the eve hand and possible foetal benefits on the other. Clinical controversies regarding prolongation of preterm preeclamptic pregnancies still exist – also taking into account that preeclampsia is the leading cause of maternal mortality in the Netherlands5 - a debate which is even more pronounced in very preterm pregnancies with questionable foetal viability6-9. Do maternal risks of prolongation of these very early pregnancies outweigh the chances of neonatal survival? Counselling of women with very early onset preeclampsia not only comprises of knowledge of the outcome of those particular pregnancies, but also knowledge of outcomes of future pregnancies of these women is of major clinical importance. This thesis opens with a review of the literature on identifiable risk factors of preeclampsia

Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon

The current consensus is that drought has developed in the Sahel during the second half of the twentieth century as a result of remote effects of oceanic anomalies amplified by local land–atmosphere interactions. This paper focuses on the impacts of oceanic anomalies upon West African climate and specifically aims to identify those from SST anomalies in the Pacific/Indian Oceans during spring and summer seasons, when they were significant. Idealized sensitivity experiments are performed with four atmospheric general circulation models (AGCMs). The prescribed SST patterns used in the AGCMs are based on the leading mode of covariability between SST anomalies over the Pacific/Indian Oceans and summer rainfall over West Africa. The results show that such oceanic anomalies in the Pacific/Indian Ocean lead to a northward shift of an anomalous dry belt from the Gulf of Guinea to the Sahel as the season advances. In the Sahel, the magnitude of rainfall anomalies is comparable to that obtained by other authors using SST anomalies confined to the proximity of the Atlantic Ocean. The mechanism connecting the Pacific/Indian SST anomalies with West African rainfall has a strong seasonal cycle. In spring (May and June), anomalous subsidence develops over both the Maritime Continent and the equatorial Atlantic in response to the enhanced equatorial heating. Precipitation increases over continental West Africa in association with stronger zonal convergence of moisture. In addition, precipitation decreases over the Gulf of Guinea. During the monsoon peak (July and August), the SST anomalies move westward over the equatorial Pacific and the two regions where subsidence occurred earlier in the seasons merge over West Africa. The monsoon weakens and rainfall decreases over the Sahel, especially in August.Peer reviewe