DArKSIDE-50: A view of the first atmospheric argon run

The DArKside (DS) program aims to detect the so-called WIMPs (Weakly Interactive Massive Particle) which are considered the best candidates for Dark Matter. WIMPs elastically scattering would be detected by using a twophase Time Projection Chamber (TPC) based on argon nuclei target. Thanks to the properties of the scintillation and ionization signals detected by the TPC it is possible to discriminate a WIMP-induced signal from one induced by background. DS-50 started its data taking on November 2013 with atmospheric argon (later with underground argon depleted in 39Ar.

Pore evolution in interstellar ice analogues: simulating the effects of temperature increase

Context. The level of porosity of interstellar ices - largely comprised of amorphous solid water (ASW) - contains clues on the trapping capacity of other volatile species and determines the surface accessibility that is needed for solid state reactions to take place. Aims. Our goal is to simulate the growth of amorphous water ice at low temperature (10 K) and to characterize the evolution of the porosity (and the specific surface area) as a function of temperature (from 10 to 120 K). Methods. Kinetic Monte Carlo simulations are used to mimic the formation and the thermal evolution of pores in amorphous water ice. We follow the accretion of gas-phase water molecules as well as their migration on surfaces with different grid sizes, both at the top growing layer and within the bulk. Results. We show that the porosity characteristics change substantially in water ice as the temperature increases. The total surface of the pores decreases strongly while the total volume decreases only slightly for higher temperatures. This will decrease the overall reaction efficiency, but in parallel, small pores connect and merge, allowing trapped molecules to meet and react within the pores network, providing a pathway to increase the reaction efficiency. We introduce pore coalescence as a new solid state process that may boost the solid state formation of new molecules in space and has not been considered so far.Comment: 9 pages, 8 figures Accepted for publication in A&

Porosity measurements of interstellar ice mixtures using optical laser interference and extended effective medium approximations

Aims. This article aims to provide an alternative method of measuring the porosity of multi-phase composite ices from their refractive indices and of characterising how the abundance of a premixed contaminant (e.g., CO2) affects the porosity of water-rich ice mixtures during omni-directional deposition. Methods. We combine optical laser interference and extended effective medium approximations (EMAs) to measure the porosity of three astrophysically relevant ice mixtures: H2O:CO2=10:1, 4:1, and 2:1. Infrared spectroscopy is used as a benchmarking test of this new laboratory-based method. Results. By independently monitoring the O-H dangling modes of the different water-rich ice mixtures, we confirm the porosities predicted by the extended EMAs. We also demonstrate that CO2 premixed with water in the gas phase does not significantly affect the ice morphology during omni-directional deposition, as long as the physical conditions favourable to segregation are not reached. We propose a mechanism in which CO2 molecules diffuse on the surface of the growing ice sample prior to being incorporated into the bulk and then fill the pores partly or completely, depending on the relative abundance and the growth temperature.Comment: 9 pages, 6 figures, 1 table. Accepted for publication in A&

Primary structure of a protease isoinhibitor from bovine spleen. A possible intermediate in the processing of the primary gene product.

Sequence studies on the protease isoinhibitor I isolated from bovine spleen have revealed that it consists of two molecular variants which differ only in the presence of an additional COOH-terminal residue, asparagine, in the less abundant form. The complete amino acid sequence shows that they are composed of 65 or 66 residues and predicts Mr of 7223 or 7338, respectively. The sequences correspond exactly to the 58-residue polypeptide chain of spleen isoinhibitor II plus NH2- and COOH-terminal extensions of 2 and 5 or 6 amino acid residues, respectively. Moreover the entire sequences are located within the 100-residue structure deduced from the mRNA and DNA sequences of the putative precursor. These data support the idea that the molecular variants of isoinhibitor I are either mature proteins with distinct functional roles, or intermediates in the multistage processing of the primary product of gene expression, which eventually leads to the mature protein, i.e. inhibitor II

Comparative Impact of SiO2 and TiO2 Nanofillers on the Performance of Thin Film Nanocomposite Membranes

Nanoparticle (NP) additions can substantially improve the performance of reverse osmosis and nanofiltration polyamide (PA) membranes. However, the relative impacts of leading additives are poorly understood. In this study, we compare the effects of TiO2 and SiO2 NPs as nanofillers in PA membranes with respect to permeate flux and the rejection of organic matter (OM) and salts. Thin‐film nanocomposite (TFN) PA membranes were fabricated using similarly sized TiO2 15 nm and SiO2 (10 – 20 nm) NPs, introduced at four different NP concentrations (0.01, 0.05, 0.2, and 0.5% w/v). Compared with PA membranes fabricated without NPs, membranes fabricated with nanofillers improved membranes hydrophilicity, membrane porosity, and consequently the permeability. Permeability was increased by 24 and 58% with the addition of TiO2 and SiO2, respectively. Rejection performance and fouling behavior of the membranes were examined with salt (MgSO4 and NaCl) and OM (humic acid [HA] and tannic acid [TA]). The addition of TiO2 and SiO2 nanofillers to the PA membranes improved the permeability of these membranes and also increased the rejection of MgSO4, especially for TiO2 membranes. The addition of TiO2 and SiO2 to the membranes exhibited a higher flux and lower flux decline ratio than the control membrane in OM solution filtration. TFN membranes\u27 HA and TA rejections were at least 77 and 71%, respectively. The surface change properties of NPs appear to play a dominant role in determining their effects as nanofillers in the composite membrane matrix through a balance of changes produced in membrane pore size and membrane hydrophilicity

High Temperature Stability of Onion-Like Carbon vs Highly Oriented Pyrolytic Graphite

Abstract The thermodynamic stability of onion-like carbon (OLC) nanostructures with respect to highly oriented pyrolytic graphite (HOPG) was determined in the interval 765–1030 K by the electromotive force (emf) measurements of solid electrolyte galvanic cell: (Low) Pt|Cr3C2,CrF2,OLC|CaF2s.c.|Cr3C2,CrF2,HOPG|Pt (High). The free energy change of transformation HOPG = OLC was found positive below 920.6 K crossing the zero value at this temperature. Its trend with temperature was well described by a 3rd degree polynomial. The unexpected too high values of LDrHT LT P ~DcPðTÞ jointly to the HR-TEM, STEM and EELS evidences that showed OLC completely embedded in rigid cages made of a Cr3C2/CrF2 matrix, suggested that carbon in the electrodes experienced different internal pressures. This was confirmed by the evaluation under constant volume of dP dT by the a k ratio for OLC (0.5 MPa K21) and HOPG (8 Pa K21) where a and k are the isobaric thermal expansion and isothermal compressibility coefficients, respectively. The temperature dependency of the pressure was derived and utilized to calculate the enthalpy and entropy changes as function of temperature and pressure. The highest value of the internal pressure experienced by OLC was calculated to be about 7 GPa at the highest temperature. At 920.6 K, DrH and DrS values are 95.8 kJ mol21 and 104.1 JK21 mol21, respectively. The surface contributions to the energetic of the system were evaluated and they were found negligible compared with the bulk terms. As a consequence of the high internal pressure, the values of the enthalpy and entropy changes were mainly attributed to the formation of carbon defects in OLC considered as multishell fullerenes. The change of the carbon defect fraction is reported as a function of temperature

Decaying neutron propagation in the Galaxy and the Cosmic Ray anisotropy at 1 EeV

We study the cosmic ray arrival distribution expected from a source of neutrons in the galactic center at energies around 1 EeV and compare it with the anisotropy detected by AGASA and SUGAR. Besides the point-like signal in the source direction produced by the direct neutrons, an extended signal due to the protons produced in neutron decays is expected. This associated proton signal also leads to an excess in the direction of the spiral arm. For realistic models of the regular and random galactic magnetic fields, the resulting anisotropy as a function of the energy is obtained. We find that for the anisotropy to become sufficiently suppressed below E\sim 10^{17.9}eV, a significant random magnetic field component is required, while on the other hand, this also tends to increase the angular spread of the associated proton signal and to reduce the excess in the spiral arm direction. The source luminosity required in order that the right ascension anisotropy be 4% for the AGASA angular exposure corresponds to a prediction for the point-like flux from direct neutrons compatible with the flux detected by SUGAR. We also analyse the distinguishing features predicted for a large statistics southern observatory.Comment: 14 pages, 6 figures, minor changes to match published versio

Novel Sugar-incorporated N-heterocyclic Carbene (NHC) Gold(I) Complexes as Potential Anticancer Agents

New metal complexes containing anticancer drugs are one of the major interests in bioinorganic or bioorganometallic medicinal chemistry. The development of novel metallodrugs is shifting to the use of non platinum central atoms coordinating different organic ligands in order to overcome the drawbacks (e.g. resistance, side effects) of the platinum antitumor agents. [1]. Gold(I) complexes show a very promising antiproliferative effects, but they are remarkable oxidizing properties. In order to reduce this character, in the last years, several studies have been reported based on gold(I) N-heterocyclic carbenes (NHCs) in vitro and in a few cases also in vivo [2]. Within this frame we have designed new gold(I) complexes based on sugar incorporated N-heterocyclic carbene. The presence of the sugar moiety allows to tune the lipophilicity behavior of the complexes. The complexes have been synthesized according to the scheme reported below. After the preparation of the NHC ligand, in the first step the corresponding Ag-complex (1AgBr) was prepared from Ag2O, to act as starting materials for transmetalation. The reaction of 1AgBr with gold(I) precursor, THTAuCl (THT = tetrahydrothiophene), in dichloromethane at room temperature overnight afford to gold complex. The compound was identified by NMR and RX. Starting from 1Cl, the cationic gold derivatives were prepared adding phosphorous and sulphur based neutral ligands, in the presence of silver tetrafluoroborate, as a chloride abstractor. The ligands have been selected in order to modulate electronic and hydrophilic complexes properties. The compounds will be investigated in screening on human cell line