Single-Ion Anisotropy and Intramolecular Interactions in CeIIIand NdIIIDimers

[Image: see text] This article reports the syntheses, characterization, structural description, together with magnetic and spectroscopic properties of two isostructural molecular magnets based on the chiral ligand N,N′-bis((1,2-diphenyl-(pyridine-2-yl)methylene)-(R,R/S,S)-ethane-1,2-diamine), L1, of general formula [Ln(2)(RR-L1)(2)(Cl(6))]·MeOH·1.5H(2)O, (Ln = Ce (1) or Nd (2)). Multifrequency electron paramagnetic resonance (EPR), cantilever torque magnetometry (CTM) measurements, and ab initio calculations allowed us to determine single-ion magnetic anisotropy and intramolecular magnetic interactions in both compounds, evidencing a more important role of the anisotropic exchange for the Nd(III) derivative. The comparison of experimental and theoretical data indicates that, in the case of largely rhombic lanthanide ions, ab initio calculations can fail in determining the orientation of the weakest components, while being reliable in determining their principal values. However, they remain of paramount importance to set the analysis of EPR and CTM on sound basis, thus obtaining a very precise picture of the magnetic interactions in these systems. Finally, the electronic structure of the two complexes, as obtained by this approach, is consistent with the absence of zero-field slow relaxation observed in ac susceptibility

Long-term monitoring of habitats and reef fish found inside and outside the U.S. Virgin Islands Coral Reef National Monument: a comparative assessment

The primary objective of this study was to assess the efficacy of the Virgin Islands Coral Reef National Monument (VICR), a marine protected area in St John, US Virgin Islands. Surveys of habitat and fishes inside and outside of VICR were conducted in 2003-2008. Areas outside the VICR had significantly more scleractinian corals, greater habitat complexity, and greater species richness and density of reef fishes than areas inside., Areas inside and outside the VICR exhibited significant decreases in percent scleractinian coral coverage over the study period. A contrasting trend of increasing macroalgal cover was also observed. No clear effect of the severe 2005 coral bleaching event was observed suggesting other causal factors. No obvious trends in the fish community were observed across the study period. The significant decline in habitat condition, coupled with the initial incorporation of some of the more degraded reefs into the marine protected area may result in a longer time period necessary to detect positive changes in the St. John coral reef ecosystem and associated reef fish abundance and community structure

Modélisation constitutive du comportement cyclique des sables en condition drainée

Dans cette étude, une modélisation numérique simple du comportement des sables sous chargement cyclique est proposée ; la démarche proposée consiste, en condition drainée, à déterminer les paramètres caractérisant le chemin cyclique moyen du sol sous l’'effet de N cycles dûment caractérisés, et à traduire l'’effet cyclique par une déformation volumique cumulée ainsi que par une variation de module du sol. Dans cette étude on s’'intéresse à des essais triaxiaux cycliques simulés au moyen d’'un calcul en éléments finis utilisant le programme Plaxis. On détermine les paramètres d’'identification du premier cycle (charge-décharge) réalisé pas à pas en prenant, comme modèle de comportement du sol le modèle HSM. Puis le comportement après N cycles (N>1000) est simulé par la formulation proposée comme un pseudo-fluage. La comparaison de la méthode proposée à plusieurs essais triaxiaux cycliques confirme la bonne adaptation du modèle proposé à ce type de problème

An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR-Through-UV Curve Morphology

We study the IR-through-UV interstellar extinction curves towards 328 Galactic B and late-O stars. We use a new technique which employs stellar atmosphere models in lieu of unreddened "standard" stars. This technique is capable of virtually eliminating spectral mismatch errors in the curves. It also allows a quantitative assessment of the errors and enables a rigorous testing of the significance of relationships between various curve parameters, regardless of whether their uncertainties are correlated. Analysis of the curves gives the following results: (1) In accord with our previous findings, the central position of the 2175 A extinction bump is mildly variable, its width is highly variable, and the two variations are unrelated. (2) Strong correlations are found among some extinction properties within the UV region, and within the IR region. (3) With the exception of a few curves with extreme (i.e., large) values of R(V), the UV and IR portions of Galactic extinction curves are not correlated with each other. (4) The large sightline-to-sightline variation seen in our sample implies that any average Galactic extinction curve will always reflect the biases of its parent sample. (5) The use of an average curve to deredden a spectral energy distribution (SED) will result in significant errors, and a realistic error budget for the dereddened SED must include the observed variance of Galactic curves. While the observed large sightline-to-sightline variations, and the lack of correlation among the various features of the curves, make it difficult to meaningfully characterize average extinction properties, they demonstrate that extinction curves respond sensitively to local conditions. Thus, each curve contains potentially unique information about the grains along its sightline.Comment: To appear in the Astrophysical Journal, Part 1, July 1, 2007. Figures and Tables which will appear only in the electronic version of the Journal can be obtained via anonymous ftp from ftp://ftp.astronomy.villanova.edu . After logging in, change directories to "fitz/FMV_EXTINCTION". A README file describes the various files present in the director

Mineralization of chitosan membrane using a double diffusion system for bone related applications

Chitosan membranes were subjected to a pre-treatment in a double diffusion system, with a calcium solution in one chamber and a phosphate solution in the other chamber. Both chambers were separated by the chitosan membrane and subject to three mineralization periods (5, 10 and 15 minutes). After this pre-treatment the bioactivity of the different calcium phosphate coatings formed was tested for different periods of immersion time, 7, 14 and 21 days at room temperature and 37ºC, in acellular simulated body fluid (1.0x). The results obtained demonstrated that the calcium phosphate coatings formed during the pre-treatment process are bioactive. It was found that the calcification is effective just in the side of the membrane exposed to the calcium solution chamber. This enabled to develop membranes with asymmetric osteoinductive properties that can be useful in different orthopedic applications

Seasonal variations in aerosol particle composition at the puy-de-Dôme research station in France

Detailed investigations of the chemical and microphysical properties of atmospheric aerosol particles were performed at the puy-de-Dôme (pdD) research station (1465 m) in autumn (September and October 2008), winter (February and March 2009), and summer (June 2010) using a compact Time-of-Flight Aerosol Mass Spectrometer (cToF-AMS). Over the three campaigns, the average mass concentrations of the non-refractory submicron particles ranged from 10 μg m<sup>−3</sup> up to 27 μg m<sup>−3</sup>. Highest nitrate and ammonium mass concentrations were measured during the winter and during periods when marine modified airmasses were arriving at the site, whereas highest concentrations of organic particles were measured during the summer and during periods when continental airmasses arrived at the site. The measurements reported in this paper show that atmospheric particle composition is strongly influenced by both the season and the origin of the airmass. The total organic mass spectra were analysed using positive matrix factorisation to separate individual organic components contributing to the overall organic particle mass concentrations. These organic components include a low volatility oxygenated organic aerosol particle (LV-OOA) and a semi-volatile organic aerosol particle (SV-OOA). Correlations of the LV-OOA components with fragments of <i>m/z</i> 60 and <i>m/z</i> 73 (mass spectral markers of wood burning) during the winter campaign suggest that wintertime LV-OOA are related to aged biomass burning emissions, whereas organic aerosol particles measured during the summer are likely linked to biogenic sources. Equivalent potential temperature calculations, gas-phase, and LIDAR measurements define whether the research site is in the planetary boundary layer (PBL) or in the free troposphere (FT)/residual layer (RL). We observe that SV-OOA and nitrate particles are associated with air masses arriving from the PBL where as particle composition measured from RL/FT airmasses contain high mass fractions of sulphate and LV-OOA. This study provides unique insights into the effects of season and airmass variability on regional aerosol particles measured at an elevated site

Same Not the Same: Thermally Driven Transformation of Nickel Phosphinate-Bipyridine One-Dimensional Chains into Three-Dimensional Coordination Polymers

Three one-dimensional nickel coordination polymers (CPs) based on P,P′-diphenylethylenediphosphinic acid and three different bis-pyridine coligands, namely, 4,4′-bipyridine (bipy), 1,2-bis(4-pyridyl)ethane (bpy-ane), and 1,2-bis(4-pyridyl)ethylene (bpy-ene), were prepared in mild hydrothermal conditions from water solutions containing the dissolved reagents. The CPs have the formula [Ni(H2O)4(bipy)·pc2p]n (1), [Ni(H2O)4(bpy-ane)·pc2p]n (2), and [Ni(H2O)4(bpy-ene)·pc2p]n (3), and their structural features were investigated by single crystal X-ray diffraction, UV–vis, Fourier transform infrared spectroscopies, and magnetic measurements. They are constituted of infinite Ni(H2O)4(bis-pyridine) one-dimensional rows connected, through hydrogen bonds, with the phosphinic acids placed among adjacent rows. Although the formulas and the structural topologies of the three compounds are almost identical, they behave in different manners upon heating. Compound 1 yields an amorphous phase when water molecules are thermally removed, whereas compound 3 undergoes interesting phase transformations derived from the connection of Ni atoms with the phosphinates oxygen atoms, increasing the dimensionality to three-dimensional and maintaining crystallinity. The behavior of compound 2 has some analogies to that of 3, although a complete structural characterization was not performed because of a significant crystallinity loss of the heated phase. The structural features were studied by means of a combination of variable temperature single crystal and powder X-ray diffraction and thermogravimetric analysis. The reason for these different behaviors was ascribed to both the length and the flexibility degree of the nitrogenated coligands

Intercomparison of air ion spectrometers: An evaluation of results in varying conditions

We evaluated 11 air ion spectrometers from Airel Ltd. after they had spent one year in field measurements as a part of the EUCAARI project: 5 Air Ion Spectrometers (AIS), 5 Neutral cluster and Air Ion Spectrometers (NAIS) and one Airborne NAIS (ANAIS). This is the first time that an ANAIS is evaluated and compared so extensively. The ion spectrometers' mobility and concentration accuracy was evaluated. Their measurements of ambient air were compared between themselves and to reference instruments: a Differential Mobility Particle Sizer (DMPS), a Balanced Scanning Mobility Analyzer (BSMA), and an Ion-DMPS. We report on the simultaneous measurement of a new particle formation (NPF) event by all 11 instruments and the 3 reference instruments. To our knowledge, it is the first time that the size distribution of ions and particles is measured by so many ion spectrometers during a NPF event. The new particle formation rates (~0.2 cm−3 s−1 for ions and ~2 cm−3 s−1 for particles) and growth rates (~25 nm h−1 in the 3–7 nm size range) were calculated for all the instruments. The NAISs and the ANAIS gave higher concentrations and formation rates than the AISs. For example, the AISs agreed with the BSMA within 11 % and 28 % for negative and positive ion concentration respectively, whereas the NAISs agreed within 23 % and 29 %. Finally, based on the results presented here, we give guidelines for data evaluation, when data from different individual ion spectrometers are compared

Rtp1p Is a Karyopherin-Like Protein Required for RNA Polymerase II Biogenesis

The assembly and nuclear transport of RNA polymerase II (RNA pol II) are processes that require the participation of many auxiliary factors. In a yeast genetic screen, we identified a previously uncharacterized gene, YMR185w (renamed RTP1), which encodes a protein required for the nuclear import of RNA pol II. Using protein affinity purification coupled to mass spectrometry, we identified interactions between Rtp1p and members of the R2TP complex. Rtp1p also interacts, to a different extent, with several RNA pol II subunits. The pattern of interactions is compatible with a role for Rtp1p as an assembly factor that participates in the formation of the Rpb2/Rpb3 subassembly complex and its binding to the Rpb1p-containing subcomplex. Besides, Rtp1p has a molecular architecture characteristic of karyopherins, composed of HEAT repeats, and is able to interact with phenylalanine-glycine-containing nucleoporins. Our results define Rtp1p as a new component of the RNA pol II biogenesis machinery that plays roles in subunit assembly and likely in transport through the nuclear pore complex