The room temperature phosphine-free synthesis of near-infrared emitting HgSe quantum dots

Luminescent mercury selenide (HgSe) quantum dots have been synthesised by a phosphine-free method using oleic acid as a capping agent. The modification of experimental conditions such as temperature resulted in particles of various sizes (15–100 nm) and morphologies not previously seen in HgSe, with emission tuneable between 1000 nm and 1350 nm

CELLULAR AND HUMORAL RESPONSE TO TRANSPLANTATION ANTIGENS : I. DEVELOPMENT OF ALLOANTIBODY-FORMING CELLS AND CYTOTOXIC LYMPHOCYTES IN THE GRAFT-VERSUS-HOST REACTION

After transfer into heavily-irradiated allogeneic mice, spleen cells were found to produce two types of effector cells directed against the recipient alloantigens, namely alloantibody plaque-forming cells (PFC) and cytotoxic lymphocytes (CL). Both types of effector cells were detectable in vitro by virtue of their lytic effect on target cells carrying the recipient alloantigens. Alloantibody PFC activity was dependent on the presence of an exogenous source of complement and could be inhibited by the addition of heterologous antisera to mouse µ-chain or Fab fragment in the assay system. CL activity was independent of added complement, was not affected by anti-immunoglobulin antisera, but was inhibited by the addition of antibody against target cell alloantigens. Treatment of the transferred spleen cells with anti-θ-serum and complement before in vitro assays for PFC and CL completely abolished the CL activity but had no effect on alloantibody-plaque formation. These results indicate that the two types of effector cells can be differentiated in vitro by virtue of their susceptibility to anti-θ-serum and the mechanisms by which they cause cell lysis

Application of econometric procedures to the demands for agricultural products

The objective of this study is to get for several food products the kind of demand information that is relevant when a price support administrator selects a support price. The specific problems dealt with are those of estimating the retail demand conditions for (1) pork, beef and poultry products and (2) eggs. In connection with each problem, demand equations have been set up. In each case demand relations have been estimated by the least squares method, which treats demand equations in isolation from supply equations. Demand equations have also been estimated by simultaneous equations methods, which deal with a demand equation as part of a system of equations including a supply equation and perhaps others

The universe dynamics in the tachyon cosmology with non-minimal coupling to matter

Recently, the tachyon cosmology has been represented as dark energy model to support the current acceleration of the universe without phantom crossing. In this paper, we study the dynamics of the tachyon cosmology in which the field plays the role of tachyon field and also non--minimally coupled to the matter lagrangian. The model shows current universe acceleration and also phantom crossing in the future. Two cosmological tests are also performed to validate the model; the difference in the distance modulus and the model independent Cosmological Redshift Drift (CRD) test.Comment: 14 pages, 11 figure

NTT and NOT spectroscopy of SDSS-II supernovae

Context. The SDSS-II Supernova Survey, conducted between 2005 and 2007, was designed to detect a large number of Type Ia supernovae (SNe Ia) around z~0.2, the redshift "gap" between low-z and high-z SN searches. The survey has provided multi-band photometric lightcurves for variable targets, and SN candidates were scheduled for spectroscopic observations, primarily to provide SN classification and accurate redshifts. We present SN spectra obtained in 2006 and 2007 using the NTT and the NOT. Aims. We provide an atlas of SN spectra in the range z =0.03-0.32 that complements the well-sampled lightcurves from SDSS-II in the forthcoming three-year SDSS SN cosmology analysis. The sample can, for example, be used for spectral studies of SNe Ia, which are critical for understanding potential systematic effects when SNe are used to determine cosmological distances. Methods. The spectra were reduced in a uniform manner, and special care was taken in estimating the uncertainties for the different processing steps. Host-galaxy light was subtracted when possible and the SN type fitted using the SuperNova IDentification code (SNID). We also present comparisons between spectral and photometric dating using SALT lightcurve fits to the photometry from SDSS-II, as well as the global distribution of our sample in terms of the lightcurve parameters: stretch and colour. Results. We report new spectroscopic data from 141 SNe Ia, mainly between -9 and +15 days from lightcurve maximum, including a few cases of multi-epoch observations. This homogeneous, host-galaxy subtracted, SN Ia spectroscopic sample is among the largest such data sets and unique in its redshift interval. The sample includes two potential SN 1991T-like SNe (SN 2006on and SN 2007ni) and one potential SN 2002cx-like SN (SN 2007ie). In addition, the new compilation includes spectra from 23 confirmed Type II and 8 Type Ib/c SNe.Comment: Accepted for publication in A&

Type Ia supernova Hubble diagram with near-infrared and optical observations

We main goal of this paper is to test whether the NIR peak magnitudes of SNe Ia could be accurately estimated with only a single observation obtained close to maximum light, provided the time of B band maximum and the optical stretch parameter are known. We obtained multi-epoch UBVRI and single-epoch J and H photometric observations of 16 SNe Ia in the redshift range z=0.037-0.183, doubling the leverage of the current SN Ia NIR Hubble diagram and the number of SNe beyond redshift 0.04. This sample was analyzed together with 102 NIR and 458 optical light curves (LCs) of normal SNe Ia from the literature. The analysis of 45 well-sampled NIR LCs shows that a single template accurately describes them if its time axis is stretched with the optical stretch parameter. This allows us to estimate the NIR peak magnitudes even with one observation obtained within 10 days from B-band maximum. We find that the NIR Hubble residuals show weak correlation with DM_15 and E(B-V), and for the first time we report a possible dependence on the J_max-H_max color. The intrinsic NIR luminosity scatter of SNe Ia is estimated to be around 0.10 mag, which is smaller than what can be derived for a similarly heterogeneous sample at optical wavelengths. In conclusion, we find that SNe Ia are at least as good standard candles in the NIR as in the optical. We showed that it is feasible to extended the NIR SN Ia Hubble diagram to z=0.2 with very modest sampling of the NIR LCs, if complemented by well-sampled optical LCs. Our results suggest that the most efficient way to extend the NIR Hubble diagram to high redshift would be to obtain a single observation close to the NIR maximum. (abridged)Comment: 39 pages, 15 figures, accepted by A&

Global assessment of nitrogen deposition effects on terrestrial plant diversity : a synthesis

Atmospheric nitrogen (N) deposition is it recognized threat to plant diversity ill temperate and northern parts of Europe and North America. This paper assesses evidence from field experiments for N deposition effects and thresholds for terrestrial plant diversity protection across a latitudinal range of main categories of ecosystems. from arctic and boreal systems to tropical forests. Current thinking on the mechanisms of N deposition effects on plant diversity, the global distribution of G200 ecoregions, and current and future (2030) estimates of atmospheric N-deposition rates are then used to identify the risks to plant diversity in all major ecosystem types now and in the future. This synthesis paper clearly shows that N accumulation is the main driver of changes to species composition across the whole range of different ecosystem types by driving the competitive interactions that lead to composition change and/or making conditions unfavorable for some species. Other effects such its direct toxicity of nitrogen gases and aerosols long-term negative effects of increased ammonium and ammonia availability, soil-mediated effects of acidification, and secondary stress and disturbance are more ecosystem, and site-specific and often play a supporting role. N deposition effects in mediterranean ecosystems have now been identified, leading to a first estimate of an effect threshold. Importantly, ecosystems thought of as not N limited, such as tropical and subtropical systems, may be more vulnerable in the regeneration phase. in situations where heterogeneity in N availability is reduced by atmospheric N deposition, on sandy soils, or in montane areas. Critical loads are effect thresholds for N deposition. and the critical load concept has helped European governments make progress toward reducing N loads on sensitive ecosystems. More needs to be done in Europe and North America. especially for the more sensitive ecosystem types. including several ecosystems of high conservation importance. The results of this assessment Show that the Vulnerable regions outside Europe and North America which have not received enough attention are ecoregions in eastern and Southern Asia (China, India), an important part of the mediterranean ecoregion (California, southern Europe). and in the coming decades several subtropical and tropical parts of Latin America and Africa. Reductions in plant diversity by increased atmospheric N deposition may be more widespread than first thought, and more targeted Studies are required in low background areas, especially in the G200 ecoregions

Cosmic Dynamics in the Chameleon Cosmology

We study in this paper chameleon cosmology applied to Friedmann-Robertson-Walker space, which gives rise to the equation of state (EoS) parameter larger than -1 in the past and less than -1 today, satisfying current observations. We also study cosmological constraints on the model using the time evolution of the cosmological redshift of distant sources which directly probes the expansion history of the universe. Due to the evolution of the universe's expansion rate, the model independent Cosmological Redshift Drift (CRD)test is expected to experience a small, systematic drift as a function of time. The model is supported by the observational data obtained from the test.Comment: 16 pages, 9 figure