Cosmology from MAXIMA-1, BOOMERANG, and COBE DMR cosmic microwave background observations

Recent results from BOOMERANG-98 and MAXIMA-1, taken together with COBE DMR, provide consistent and high signal-to-noise measurements of the cosmic microwave background power spectrum at spherical harmonic multipole bands over 2相似文献   

Thermal treatments and characterizations of pellets for SPES direct target

In this work targets of graphite-rich lanthanum dicarbide have been produced through carburization and sintering of suitable precursor pellets obtained by mixing and pressing lanthanum oxide and graphite powders. The results about the control of the production process and the investigation of the physical properties of the pellets, performed respectively through thermal analyses (TG/DTA) and X-ray diffraction (XRD), are reported and discussed.     

The SPES direct UCx target

A possible solution for a target system aimed at the production of exotic nuclei as a result of high energy fissions in ²³⁸U compounds has been analyzed. The proposed configuration is constituted by a primary proton beam (40 MeV, 0.2 mA) directly impinging on uranium carbide disks inserted within a cylindrical carbon box. This system has been conceived to obtain both a high number of neutron rich atoms (originated from about 10¹³ fissions/s) and a low power deposition in the target. In order to extract the fission fragments, the box has to be hold at 2000^○C. The thermal analysis shows the capability of the thermal radiation to cool the disks with a reasonable margin below the material melting point. Moreover, the analyses of the thermo-mechanical behaviour and of the effusion times confirm the promising features of this target configuration.     

Structural and EPR studies on single-crystal and polycrystalline samples of copper(II) and cobalt(II) complexes with N2S2-based macrocyclic ligands

The properties of Cu(II) and Co(II) complexes with oxygen- or nitrogen-containing macrocycles have been extensively studied; however, less attention has been paid to the study of complexes containing sulfur atoms in the first coordination sphere. Herein we present the interaction between these two metal ions and two macrocyclic ligands with N2S2 donor sets. Cu(II) and Co(II) complexes with the pyridine-containing 14-membered macrocycles 3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L) and 7-(9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L1) have been synthesized. The X-ray structural analysis of {[Co(ClO4)(H2O)(L)][Co(H2O)2(L)]}(ClO4)3 shows two different metal sites in octahedral coordination. The EPR spectra of powdered samples of this compound are typical of distorted six-coordinated Co(II) ions in a high-spin (S=3/2) configuration, with the ground state being S=1/2 (g1=5.20, g2=3.20, g3=1.95). The EPR spectrum of [Cu(ClO4)(L)](ClO4) was simulated assuming an axial g tensor (g1=g2=2.043, g3=2.145), while that of [Cu(ClO4)(L1)](ClO4) slightly differs from an axial symmetry (g1=2.025, g2=2.060, g3=2.155). These results are compatible with a Cu(II) ion in square-pyramidal coordination with N2S2 as basal ligands. Single-crystal EPR experiment performed on [Cu(ClO4)(L1)](ClO4) allowed determining the eigenvalues of the molecular g tensor associated with the copper site, as well as the two possible orientations for the tensor. On the basis of symmetry arguments, an assignment in which the eigenvectors are nearly along the Cu(II)-ligand bonds is chosen.     

Incorporation of chlorinated analogues of aliphatic amino acids during cell-free protein synthesis

3-Chloro-Abu and 4-chloro-Nva are biosynthetically incorporated into E. coli peptidyl-Pro cis-trans isomerase B, as substitutes for Val and Leu, respectively. The extent of incorporation is up to ~90%, and substituted protein is catalytically active. By contrast, 4-chloro-Val is not an effective replacement for Ile.     

Spectroscopic investigation and molecular modeling on porphyrin/PAMAM supramolecular adduct

Noncovalent adducts (TPPC@PAMAM) between meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and polyamidoamine PAMAM dendrimer (generation 2.0) have been obtained by simply mixing the two components at different stoichiometric amount. The resulting species are readily soluble and stable in aqueous solution up to millimolar concentration. Electrostatic interactions between the anionic carboxylate groups of TPPC and the protonated amino groups of the PAMAM dendrimer play an important role in the stabilization of these adducts. UV/Vis absorption, steady state and time-resolved fluorescence emission and anisotropy measurements suggest the presence of equilibria involving different species as function of the [PAMAM]/[TPPC] ratio. At low ratios the observed spectroscopic behavior evidence the presence of H-aggregates, while at higher ratios well-defined species containing monomeric TPPC strongly interacting with the charged dendrimer are formed. Docking of the binary supramolecular adduct further supports the experimental results showing a favorable interaction with the porphyrin being completely included in the dendrimer. The interaction of the binary TPPC@PAMAM adduct (1/1 ratio) with calf-thymus DNA has been investigated through spectroscopic and photophysical techniques. All the experimental results point to the formation of a ternary complex between the binary adduct and the DNA backbone.     

Evaporation and fission decay of 132Ce compound nuclei at Ex=122 MeV: some limitations of the statistical model

Light charged particle (LCP) emission in the evaporation residue (ER) and fusion fission (FF) channels have been studied for the 200 MeV ³²S + ¹⁰⁰Mo reaction, leading to ¹³²Ce composite nuclei at E _x =122 MeV. The main goal was to study the decay of ¹³² Ce on the basis of an extended set of observables, to get insights on the fission dynamics. The proton and alpha particle energy spectra, their multiplicities, ER-LCP angular correlations, ER and FF angular distributions, and ER and FF cross-sections were measured. The measured observables were compared with the Statistical Model (SM). Using standard parameters, the model was able to reproduce only the pre-scission multiplicities and the FF and ER cross-sections. The calculation was observed to strongly overestimate the proton and alpha particle multiplicities in the ER channel. Disagreements were also observed for the ER-LCP correlations, the LCP energy spectra and the ER angular distribution. By varying the SM input parameters over a wide range of values, it is shown that it is not possible to reproduce all the observables simultaneously with a unique set of parameters. The inadequacy of the model in reproducing the ER particle multiplicities is also observed analysing data from the literature for other systems in the A ≈ 150 and E _x ≈ 100?200 MeV region. These results indicate serious limitations about the use of the SM in extracting information on fission dynamics.     

Micropolar nematic model for polarized liquid crystals

A micromorphic electroelastic model for polarized liquid crystals is proposed on the basis of a representation of electric multipoles in terms of microdeformation. Nematic liquid crystals are modeled as micropolar continua endowed with intrinsic electric dipole and quadrupole. A nonlinear dimensionless problem for a homogeneous nematic layer is formulated and solved numerically. The existence of a threshold electric potential is discussed, and the corresponding linearized system is also obtained to compare results on small values of deformation and electric field. Differently from common results of the classical continuum approach, asymmetric deformations and electric potentials within the layer are obtained due to the occurrence of non-null intrinsic quadrupole.