Structure and Magnetic Properties of the Radical Cation Salt of a TTF-based NiII Complex

Chemical oxidation of a TTF-based NiII complex with I2 produces the corresponding radical cation salt 1, [Ni2Cl2(L)2](I3)2(I5)2(I2)(H2O)2(C4H8O)3, (L=4,5-bis(2-pyridylmethylsulfanyl)-4',5'-ethylenedithiotetrathiafulvalene). The results of magnetic susceptibility measurements show the occurrence of intramolecular magnetic exchange interactions in 1. The lack of close S···S contacts, confirmed by crystal structure analysis, results in an insulating behavio

Dithiinmaleimide Functionalized ET Derivatives: Syntheses, Characterization and X-ray Structure

Dithiinmaleimide (ethylenedithio)tetrathiafulvalene (1) and N-phenyldithiinmaleimide (ethylenedithio)tetrathiafulvalene (2) have been synthesized from bis(tetraethylammonium)bis(ethylenedithiotetrathiafulvalenyldithiolato)-zincate (3) in high yields. Their electrochemical properties were investigated by cyclic voltammetry (CV) measurements which show two reversible redox potentials of the tetrathiafulvalene (TTF) moiety and an irreversible reduction potential of the maleimide ring. The X-ray structure of 1 shows close S···S contacts in the range of the van der Waals radii (3.6 Å) and hydrogen bonds between the maleimide unite

Применение методов ядерной физики и ускорителей ННЦ ХФТИ для изучения состава, структуры и свойств твердых тел

Излагается применение методов ядерной физики и ускорителей ННЦ ХФТИ для решения научных и технологических задач в области физики металлов, сплавов, полупроводников, металлоксидных и магнитных материалов. Представляются результаты экспериментов по определению концентрации и распределения элементов, выполненных с помощью пучков ионов водорода и гелия, ускоренных в электростатическом ускорителе до энергии 0,5…4,0 МэВ. Для идентификации элементов и изотопов использовались резонансные ядерные реакции, кулоновское и резонансное ядерное рассеяние и возбуждаемое ускоренными частицами характеристическое рентгеновское излучение. Излагаются результаты и возможности применения каналированных частиц и ориентационных эффектов для изучения локализации, структуры, ориентации, образования, распада и аннигиляции простейших дефектов, определения концентрации и распределения дефектов в радиационно нарушенных кристаллах.Викладається застосування методів ядерної фізики і прискорювачів ННЦ ХФТИ для рішення наукових і технологічних задач в області фізики металів, сплавів, напівпровідників, металооксидних та магнітних матеріалів. Приведені результати експерементів з визначення концентрації та розподілу елементів, виконаних за допомогою пучків іонів водню та гелію, що прискорюються в електростатичному прискорювачю до енергії 0,5 - 4,0 МеВ. Для ідентифікації елементів і ізотопів використовувалися резонансні ядерні реакції, кулонівське і резонансне ядерне розсіювання та збуджуване прискореними частками характеристичне рентгенівське випромінюваня. Викладаються результати і можливості застосування часток що каналюють та орієнтаційных ефектів для вивчення локалізації, структури, орієнтації, утворення, розпаду й анігіляції найпростіших дефектів, визначення концентрації і розподілу дефектів у радіаційно порушених кристалах.Nuclear physics methods and use of the NSC KIPT accelerators as applied to scientific and technological problems in the field of physics of metals, alloys, semiconductors, metal oxide and magnetic materials are surveyed. The results of the experiments relevant to determination of element concentration and distribution using 0,5 - 4,0 MeV hydrogen and helium ions of electrostatic accelerator are presented. Resonance nuclear reactions, coulomb and nuclear resonance scattering as well as X-ray radiation were used for element and isotope identification. The possibilities of application of channeling particles and oriented effects for study of localization, structure, orientation, formation, disintegration and annihilation of elementary defects, determination of defect concentration and distribution in radiation disturbed crystals

Bond energy/eond order relationships for N-O linkages and a quantitative measure of ionicity: the rôle of nitro groups in hydrogen bonding

The nitro group is active in metabolic systems and can be found as an integral part of a number of useful curative drugs and many toxic substances. The basis for much of this activity is not fully understood. It is not necessarily caused directly by through-bond electronic effects but may also be due to direct H-bonding to nitro or to indirect interference by the nitro group with existing H-bonding. An unusual effect of a nitro substituent on kinetic results from urethane addition/elimination reactions (Scheme 1) has been ascribed to some form of self-association, which was neither specified nor quantified. To investigate self-association phenomena caused by a nitro group, a bond energy/bond order formula for N–O bonds has been developed and then used to interpret relative amounts of covalent and ionic contributions to total N–O bond energy. Calculated bond energies were then used to obtain enthalpies of formation for H-bonds to nitro groups in crystals and in solution. Similar results from solution data reveal that direct H-bonding to nitro is much weaker than in crystals, unless intramolecular H-bonding can occur. The results revealed that the 'self-association' effects observed for nitro substituents in urethanes (Scheme 1) were not caused by nitro participating directly in intermolecular bonding to NH of another urethane but by an indirect intramolecular action of the nitro group on pre-existing normal NH–O amide/amide type H-bonding

Stability and Electronic Properties of TiO2 Nanostructures With and Without B and N Doping

We address one of the main challenges to TiO2-photocatalysis, namely band gap narrowing, by combining nanostructural changes with doping. With this aim we compare TiO2's electronic properties for small 0D clusters, 1D nanorods and nanotubes, 2D layers, and 3D surface and bulk phases using different approximations within density functional theory and GW calculations. In particular, we propose very small (R < 0.5 nm) but surprisingly stable nanotubes with promising properties. The nanotubes are initially formed from TiO2 layers with the PtO2 structure, with the smallest (2,2) nanotube relaxing to a rutile nanorod structure. We find that quantum confinement effects - as expected - generally lead to a widening of the energy gap. However, substitutional doping with boron or nitrogen is found to give rise to (meta-)stable structures and the introduction of dopant and mid-gap states which effectively reduce the band gap. Boron is seen to always give rise to n-type doping while depending on the local bonding geometry, nitrogen may give rise to n-type or p-type doping. For under coordinated TiO2 surface structures found in clusters, nanorods, nanotubes, layers and surfaces nitrogen gives rise to acceptor states while for larger clusters and bulk structures donor states are introduced

Toward a new hybrid proton conductor: lanthanum niobate layered perovskites as a source of tailorable surfaces

The modification of metal oxide surfaces with organic moieties has been widely studied as a method of preparing organic-inorganic hybrid materials for various applications. Among inorganic oxides, the ion-exchangeable layered perovskites [1], materials composed by perovskite-like slabs and intercalated cations, stimulated authors\u2019 interest in reason of some encouraging electronic and reactive properties. In particular it is well known that the interlayer surface of such materials in their protonated form can be easily functionalized with organic groups (such as alcohols [2-3] or organophosphonic acids [4]) thus allowing the production of stable hybrid materials with new electronic and reactive features. As a first step to design a new inorganic-organic hybrid proton conductor, a comprehensive theoretical investigation of the MLaNb2O7 (M=H, Li, Na, K, Rb and Cs) series of ion-exchangeable layered perovskite is presented. In particular, their structural and electronic properties have been investigated by periodic calculations in the framework of DFT. A general very good agreement with the available experimental data has been found. The protonated compound (HLaNb2O7) has been then functionalized with imidazole trying two different settings: in the first arrangement the molecule is adsorbed on the layered oxide exposing the interlayer surface, in the second the organic moiety is just put between two perovskites slabs. This latter model, including the effect of the confinement, allowed to better reproduce the experimental structural XRD data and 13C-NMR measurements of the hybrid system. [1] Schaak, R. E. and Mallouk T. E., Chem. Mat. 2002, 14, 1455-1471. [2] Takahashi S. et al., Inorg. Chem. 1995, 34, 5065-5069. [3] Suzuki H. et al., Chem. Mater. 2003, 15, 636-641. [4] Shimada, A. et al., Chem. Mat. 2009, 21, 4155-4162

Alternatives to penoxsulam to control Echinochloa spp. and cyperaceous weeds in rice crop in NE Spain

Penoxsulam es un herbicida que se aplica de forma generalizada en los arrozales del nordeste peninsular al resultar eficaz frente a Echinochloa spp. y tener cierto control frente a ciperáceas, pero tiene el inconveniente de pertenecer a un grupo de herbicidas vulnerable a la aparición de resistencias. El objetivo del trabajo fue buscar programas de herbicidas alternativos al penoxsulam para preservar el máximo de tiempo posible las escasas materias activas disponibles. El trabajo constó de 6 ensayos, distribuidos en 3 localidades (Huesca y Zaragoza) durante tres años de cultivo (2011-2013). En cada ensayo se aplicaron 8 programas herbicidas repetidos dos veces y distribuidos al azar. Los resultados mostraron que, efectivamente, penoxsulam aplicado en estado de 1-3 hojas de arroz controla satisfactoriamente Echinochloa spp., con aplicación previa de oxadiazon en presiembra. Los dos mejores programas alternativos fueron: (1) Aplicación en presiembra de oxadiazon, en 1-3 hojas de arroz, profoxidim, y hasta ahijado del arroz, bentazona+ MCPA, o halosulfuron-metil (2) aplicación en 1-3 hojas del arroz: propanil+bispiribac-Na, y hasta ahijado, bentazona+MCPA, controlando además ciperáceas, teniendo como inconveniente este último programa que bispiribac-Na es del mismo modo de acción que penoxsulam (aunque pertenece a otra familia química). Los resultados muestran, por tanto, que existen varias combinaciones eficaces sobre las malas hierbas objetivo para prevenir la aparición de resistencias a los herbicidas.Penoxsulam is commonly-used in rice crop in North eastern Spain with excellent control against Echi - nochloa ssp. and with some effect on Cyperaceae, but it belongs to an herbicide group prone to develop resistant biotypes. The aim of this work was to test herbicide programmes alternative to penoxsulam to preserve the efficacy of the few available active ingredients. The work consisted of 6 trials. Located in three locations during three years (2011-2013). In each trial eight herbicide programmes were applied, in two replicates distributed randomly in the field. The results showed that, effectively, penoxsulam had a good control on Echinochloa spp. after applying oxadiazon presowing. The best two alternative programmes to control Echinochloa ssp. and cyperaceous weeds were: (1) oxadiazon presowing followed by an application of profoxydim at 1-3 leaves stages of the rice and a third treatment until rice tillering of bentazone + MCPA or halosulfuron-metil and (2) propanil + bispyribac-Na at 1-3 leaves stage of the rice, a second treatment until rice tillering of bentazone + MCPA controlling both Echinochloa spp. and cyperaceous weeds. The drawback of this second programme is that bispyribac-Na belongs to the same mode of action group as penoxsulam although to different chemical families. However, the results show that it is possible to control the target weeds with several herbicide combinations to prevent herbicide-resistance appearance.Publishe

An open source massively parallel solver for Richards equation: Mechanistic modelling of water fluxes at the watershed scale

In this paper we present a massively parallel open source solver for Richards equation, named the RichardsFOAM solver. This solver has been developed in the framework of the open source generalist computational fluid dynamics tool box OpenFOAM® and is capable to deal with large scale problems in both space and time. The source code for RichardsFOAM may be downloaded from the CPC program library website. It exhibits good parallel performances (up to ∼90% parallel efficiency with 1024 processors both in strong and weak scaling), and the conditions required for obtaining such performances are analysed and discussed. These performances enable the mechanistic modelling of water fluxes at the scale of experimental watersheds (up to few square kilometres of surface area), and on time scales of decades to a century. Such a solver can be useful in various applications, such as environmental engineering for long term transport of pollutants in soils, water engineering for assessing the impact of land settlement on water resources, or in the study of weathering processes on the watersheds

Presentation of the Smith-Purcell Experiment at SOLEIL

TUPC37 - Work supported by seed funding from Université Paris-Sud, program "Attractivité" and by the ANR under contract ANR-12-JS05-0003-01International audienceThe potential of Coherent Smith-Purcell radiation as a longitudinal bunch profile monitor has already been demonstrated and has recently been extended to the sub-picosecond range. As a critical step toward the construction of a single shot bunch profile monitor using Coherent Smith-Purcell radiation it is important to measure very accurately the distribution of such radiation. Optimum background suppression techniques need to be found and relatively cheap detectors suitable for the far infra-red need to be qualified. To performthese tasks a test stand has been installed at the end of the linac of the synchrotron SOLEIL. This test stand and the first results from its commissioning will be presented here