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The atomic dynamics of the Al0.550Si0.070Cu0.255Fe0.125 alloy with the structure that approximates the structure of an icosahedral quasicrystal with a similar chemical composition has been investigated using inelastic neutron scattering. The partial vibrational spectra of copper, iron, and aluminum atoms and the total spectrum of thermal vibrations of the compound have been directly reconstructed from the experimental data for the first time. A combined analysis of the results obtained and the data on the atomic dynamics of the i-AlCuFe icosahedral quasicrystal has been performed.

Maintenance and repair of corneal stromal extracellular matrix (ECM) requires a tightly coordinated balance of ECM synthesis, degradation and remodeling in which proteolytic enzymes (proteinases) perform important functions. There are natural proteinase inhibitors present in preocular tear film (PTF) and cornea simultaneously with proteinases that prevent excessive degradation of normal healthy tissue. Disorders occur when there is an imbalance between proteinases and proteinase inhibitors in favor of the proteinases, causing pathologic degradation of stromal collagen and proteoglycans in the cornea. Two matrix metalloproteinases (MMPs), MMP-2 and MMP-9, are of major importance in terms of remodeling and degradation of the corneal stromal collagen. Immunohistochemical studies have shown different origins of MMP-2 and -9. MMP-2 is synthesized by corneal keratocytes and performs a surveillance function in the normal cornea, becoming locally activated to degrade collagen molecules that occasionally become damaged. Alternatively, MMP-9 may be produced by epithelial cells and polymorphonuclear neutrophils following corneal wounding. Because the cornea is in close contact with the preocular tear film (PTF), proteinases have been evaluated in the PTF. In damaged corneas, total proteolytic activity in the tear fluid was found to be significantly increased compared to normal eyes and contralateral eyes. Studies analyzing the proteolytic activity in serial PTF samples during corneal healing led to the following conclusions: ulcerative keratitis in animals is associated with initially high levels of tear film proteolytic activity, which decrease as ulcers heal; proteinase levels in melting ulcers remain elevated leading to rapid progression of the ulcers. The success of medical and surgical treatment of the corneal ulcers is reflected by the proteolytic activity in tears. In animals, successful treatment leads to a rapid reduction in tear film proteolytic activity that corresponds with the improvement in the clinical signs of corneal ulceration. The in vitro effects of various compounds on proteolytic activity in the tear fluid of animals with ulcerative keratitis have been evaluated and their important inhibitory effects have been confirmed. Because these various compounds utilize different mechanisms to inhibit various families of proteinases, a combination of these proteinase inhibitors may be beneficial.

Objective—To examine in vitro effects of various antiproteolytic compounds on activity of matrix metalloproteinase (MMP)-2 and -9 in the tear film of horses with active corneal ulcers. Sample Population—Samples of tear film obtained from the eyes of 34 horses with active ulcerative keratitis. Procedure—Horses were sedated, and tear samples were collected from the lower fornix of 34 ulcerated eyes by use of capillary tubes. The protease inhibitors 0.2% EDTA, 0.1% doxycycline, 10% N-acetylcysteine (NAC), 0.1% solution of a modified dipeptide that contains hydroxamic acid (ie, ilomostat), 0.1% α1-proteinase inhibitor (PI), 0.5% α1-PI, and 100% fresh equine serum (ES) were used to treat pooled samples. Amount of latent and active MMP-2 and -9 was measured by optical density scanning of gelatin zymograms of treated and untreated tear samples. Results—Pooled tear samples obtained from ulcerated eyes contained the latent and active forms of MMP-2 and -9. Compared with MMP activity in untreated samples, total MMP activity (sum of all bands detected) observed on the gelatin zymogram gels was reduced by 99.4% by EDTA, 96.3% by doxycycline, 98.8% by NAC, 98.9% by ilomostat, 52.4% by 0.1% α1-PI, 93.6% by 0.5% α1-PI, and 90.0% by ES. Conclusions and Clinical Relevance—We documented that EDTA, doxycycline, NAC, ilomostat, α1- PI, and ES inhibited MMP activity in vitro. Because these compounds use different mechanisms to inhibit various families of proteases in the tear film of horses, a combination of these protease inhibitors may be beneficial for treatment of corneal ulcers in horses. (Am J Vet Res 2003;64:1081–1087)

In nanoporous organic intergrowth crystals, guest molecules are confined to narrow channels created by the host sublattice. Such crystals present coherent diffuse scattering, well localised in the reciprocal space, which reflects the translational and rotational disorder of the guest molecules inside the channels. Combining thermal neutron triple axis and high energy resolution cold neutron time-of-flight spectrometers, we report geometrical and dynamical information on the rotational motions of the alkane molecules in the urea sublattice.

We report on a high resolution neutron study of the dynamical response of bis (4-chlorophenyl) sulfon near its displacive structural phase transition. On the basis of previous estimations of the soft mode characteristics [1], we show that for this molecular compound the narrow central peak arising at the transition can be partially energy resolved. The central line can be described as composed of, at least, two contributions with different energy scales: a weak relaxation in the 10 GHz frequency range and a main component, elastic within the neutron energy window. These results are analyzed in the light of existing microscopic models.

The aim of this paper is to determinate the total organic matter content of grinding sludges by a simple and fast methodology based on a solvent extraction followed by a UV spectrophotometry analysis. Several UV spectra exploitation methods are used. The multiwavelength deconvolution procedure provides quantitative results in good accordance with those obtained by a gravimetric method, possibly underestimated and enables a separate quantification of the cuttings fluids and the lubricants in the sludges. The normalisation procedure and the search of isobestic points provide important qualitative information on the evolution and on the composition of the oils used in metal processing. Therefore, this study is a first step for the development of a tool for the characterisation of organic matter in grinding sludges

We investigated molecular motions in the 0.3–350 ps time range of D2O-hydrated bilayers of 1-palmitoyl-oleoyl-sn-glycero-phosphocholine and 1,2-dimyristoyl-sn-glycero-phosphocholine in the liquid phase by quasielastic neutron scattering. Model analysis of sets of spectra covering scale lengths from 4.8 to 30 A revealed the presence of three types of motion taking place on well-separated time scales: (i) slow diffusion of the whole phospholipid molecules in a confined cylindrical region; (ii) conformational motion of the phospholipid chains; and (iii) fast uniaxial rotation of the hydrogen atoms around their carbon atoms. Based on theoretical models for the hydrogen dynamics in phospholipids, the spatial extent of these motions was analysed in detail and the results were compared with existing literature data. The complex dynamics of protons was described in terms of elemental dynamical processes involving different parts of the phospholipid chain on whose motions the hydrogen atoms ride.

Unilamellar colloids of graphite oxide (GO) were prepared from natural graphite and were grown as monolayer and multilayer thin films on cationic surfaces by electrostatic self-assembly. The multilayer films were grown by alternate adsorption of anionic GO sheets and cationic poly(allylamine hydrochloride) (PAH). The monolayer films consisted of 11−14 A thick GO sheets, with lateral dimensions between 150 nm and 9 μm. Silicon substrates primed with amine monolayers gave partial GO monolayers, but surfaces primed with Al13O4(OH)24(H2O)127+ ions gave densely tiled films that covered approximately 90% of the surface. When alkaline GO colloids were used, the monolayer assembly process selected the largest sheets (from 900 nm to 9 μm) from the suspension. In this case, many of the flexible sheets appeared folded in AFM images. Multilayer (GO/PAH)n films were invariably thicker than expected from the individual thicknesses of the sheets and the polymer monolayers, and this behavior is also attributed to folding...

A wet layer-by-layer self-assembly of composite TiO 2 /polymer films on Si and Al 2 O 3 /Al, substrates has been studied by AFM, STM, and ellipsometry techniques. The quality of the first adsorbed TiO 2 layer has been found to be the governing factor in multilayer film growth. The first layer consists of single particles and particle agglomerates 30–120 nm wide The surface coverage in the layer is determined by the chemical composition of the substrate surface and water pH in post-adsorption rinsing procedure. Well-packed TiO 2 /polymer film completely covering the surface has been prepared in five adsorption cycle on Al 2 O 3 /Al substrate. The film remained crack-free after heat treatment at 300°C. I–V curves measurement reveals high resistivity ( R ∼10 10 O in the voltage range from −2 to +3 V) of TiO 2 /polymer films prepared in ten adsorption cycles.

Two new vanadium oxide compounds, which contain interlamellar transition metal complexes bound to vanadium oxide sheets, were synthesized hydrothermally. The crystal structure of each reveals unusual coordination geometries and interlayer bonding. [Ni(2,2′-bipyridine)]2[V12O32] (1) was prepared from the reaction of V2O5, NiO, H2O and 2,2′-bipyridyl in the molar ratio 4:8:3312:0.5. The isomorphous compounds [M(2,2′-bipy)]2[V12O32] (where M is Co (1a) and Cu (1b)) were prepared in a similar fashion. The Ni coordination compound 1 crystallizes as amber needles, and the structure was solved in the space group C2/m (#12) with unit cell parameters a =24.344(3) A , b =6.897(3) A , c =12.028(2) A , β=93.60(2)° (R(Rw)=0.039(0.038)). This compound is composed of vanadium(V) oxide layers with nickel atoms coordinated within a single layer via four Ni–O–V linkages. Bidentate bipyridine (bpy) ligands complete the coordination sphere of the nickel atoms and interdigitate via π–π stacking with bpy ligands from the adjacent layer. Cu(en)2[V6O14] (2) crystallizes as black plates in the space group P21/n (#14) with unit cell parameters a =8.934(2) A , b =6.558(1) A , c =15.694(2) A , β=99.93(2)° (R(Rw)=0.039(0.035)), from the reaction of CuCl2·2H2O, V2O5, H2O and ethylenediamine in the ratio 1:1:447:4. This structure consists of mixed-valent vanadium(IV,V) oxide sheets forming weak O–Cu bonds to intercalated copper bis(ethylenediamine) complexes.

High-resolution light scattering spectroscopy has been performed on a series of n-alkane CnH2n + 2/urea inclusion compounds with n = 12,14,17 − 19. The elastic constants of these incommensurate composite crystals have been determined and found to be independent of the chain length of the guest molecules. In addition, no extraneous acoustic-like mode appeared in all spectra. However, quasi-elastic components with different widths are observed for different polarizations. In one of them the characteristics of the scattered light suggest that the quasi-elastic broadening could be generated by a sliding mode, whereas the other detected component is assigned to the reorientational motions of the n-alkane chains about their long axis.

Zeolites were used as templates to prepare microporous polymer replicas. Phenol−formaldehyde polymers were synthesized and cured within the channel networks of zeolites Y, β, and L. Dissolution of the aluminosilicate framework in aqueous HF yields an organic replica that contains

Bis(4-chlorophenyl)sulfone is a molecular compound whose structure results from the Van der Waals forces and dipolar moment interactions. The region of diffuse scattering in the range 300 K to the transition temperature TI = 150 K and the location of the incommensurate satellites from TI to 0 K, are very weakly temperature dependent demonstrating the existence of some intrinsic structural character. Neutron scattering results combined with light scattering, 35Cl NQR and X-ray analysis reveal peculiar structural and dynamical features in the compound.

15 Jobic, H. Santander, J. E. Conner, W. C., Jr. Wittaker, G. Giriat, G. Harrison, A. Ollivier, J. Auerbach, Scott M.; We have performed in situ quasielastic neutron scattering (QENS) measurements on zeolite-guest systems under microwave irradiation, for comparison with corresponding simulations. Both experiment and simulation reveal selective heating of methanol in silicalite, but little to no heating of benzene in silicalite. Effective translational and rotational temperatures extracted from QENS data under microwave heating were found to depend on microwave power. In agreement with simulation, QENS rotational temperatures significantly exceed translational ones at high microwave power, thus providing the first microscopic proof for athermal effects in microwave-driven nanopores.

La dissolution des chromates metalliques purs par l'EDTA en milieu alcalin est rapide et totale. Appliquee aux dechets industriels, la methode devient lente, et surtout conduit a une modification du degre d'oxydation du chrome.Les possibilites de speciation du chrome VI contenu dans des dechets par l'extraction d'une paire d'ions chromate-MTCA en phase cetonique ont ete explorees. L'extraction est rapide, quantitative sur une large plage de charges en metal, et specifique vis a vis du chrome III.

A disordered three-dimensional perovskite phase SrTa2-xNbxO6 (x = 0, 0.2, 0.4) is formed by topochemical dehydration of acid-exchanged Ruddelsden Popper compounds K2SrTa2-xNbxO7. The metastable per...

Objectives The phenomenon of ‘eye-shine’ is seen in a variety of animal species, and is generally thought to be related to the presence of an intraocular reflecting structure, the tapetum lucidum. The tapetum lucidum is a biologic reflector system that is a common feature in the eyes of vertebrates. It normally functions to provide the light-sensitive retinal cells with a second opportunity for photon-photoreceptor stimulation, thereby enhancing visual sensitivity at low light levels. The tapetum lucidum is presented here according to a classification based on the location, as well as the composition, of this reflective layer. Finally, the physical and chemical properties, as well as the origins of the different tapeta lucida, are discussed and compared. Methods The anatomic and biochemical aspects of the tapetum lucidum in various vertebrates are examined. Morphologic observations were made from paraffin and plastic embedded specimens. Specimens were treated with traditional stains and observed by light and transmission electron microscopy. Results Some species (primates, squirrels, birds, red kangaroo and pig) do not have this structure and they usually are diurnal animals. In vertebrates, the tapetum lucidum exhibits diverse structure, organization and composition. Therefore, the retinal tapetum (teleosts, crocodilians, marsupials, fruit bat), the choroidal guanine tapetum (elasmobranchs), the choroidal tapetum cellulosum (carnivores, rodents, cetacea), and the choroidal tapetum fibrosum (cow, sheep, goat, horse) are described. Conclusions The tapetum lucidum represents a remarkable example of neural cell and tissue specialization as an adaptation to a dim light environment and, despite these differences, all tapetal variants act to increase retinal sensitivity by reflecting light back through the photoreceptor layer. These variations regarding both its location and structure, as well as the choice of reflective material, may represent selective visual adaptations associated with their feeding behavior, in response to the use of specific wavelengths and amount of reflectance required.

We present first results from neutron studies of ns to ps relaxations in bovine collagen, comparing data for a minimally cross-linked sample (young calf) with those for a highly cross-linked one (old cow). Proton displacements derived from quasielastic scans (30 T T

Corneal diseases are very common in small animals. Corneal disease associated with bacterial agents is frequent in the dog and maybe less frequent in the cat. The medical history, important steps of the ophthalmic examination, and the ophthalmic diagnostic tests that are relevant in such corneal conditions are outlined. Bacterial corneal diseases in dogs and cats are most commonly considered in one of two categories--bacterial ulcerative keratitis and corneal abscesses. The clinical aspects of these two entities as well as the therapeutic strategies available for general practitioners and ophthalmologists are discussed. Ulcerative keratitis is frequent; it represents the most common ocular diseases in dogs and cats. Because some of these corneal ulcers can be very severe, progress rapidly, and therefore are sight threatening, the crucial steps of their diagnosis and management are stressed. The use of a magnification system, fluorescein dye, and corneal cytology and culture, if indicated, is necessary for diagnosis at an early stage of the disease. The treatment of bacterial ulcerative keratitis should eradicate the infection, reduce or stop the corneal destruction and support the corneal structures, control the uveal reaction and the pain associated with it, and minimize the scarring. The prognosis depends on the stage and the severity of the corneal ulceration, the etiology of the condition, and the therapeutic choice. A close follow-up of animals with corneal ulceration is highly recommended because corneal ulcers can progress rapidly.

International audience; Dynamics of the guest alkane sublattice of the urea-alkane incommensurate composite is studied via its coherent diffuse scattering.

The growing interest in developing techniques to prepare ultrathin semiconductor nanoparticle films is motivated by the size-dependent electronic and optical properties of semiconductors, which lead to a range of potential applications in electronic and optoelectronic devices, solar cells, photoelectrodes, photocatalysts, and sensors. The wet chemical synthesis of ultrathin semiconductor films represents, in principle, a simple and inexpensive alternative to more technologically demanding chemical vapor deposition (CVD) and physical techniques [1]. However, the realization of practical devices from wet chemical synthesis requires the development of film growth techniques that give similar or better quality films than vapor-phase methods. In particular, precise control of film thickness, crystallinity, and morphology are significant problems to be overcome in wet chemical synthesis.

Ordered mesoporous polymers have been prepared by replication of colloidal crystals made from silica spheres 35 nanometers in diameter. The pores in the colloidal crystals were filled with divinylbenzene (DVB), ethyleneglycol dimethacrylate (EDMA), or a mixture of the two. Polymerization and subsequent dissolution of the silica template leaves a polycrystalline network of interconnected pores. When mixtures of DVB and EDMA are used, the pore size of the polymer replicas can be varied continuously between 35 and 15 nanometers because the polymer shrinks when the silica template is removed.

We report neutron inelastic scattering measurements on polycrystalline LaFePO and Sr2ScO3FeP, two members of the iron phosphide families of superconductors. No evidence is found for any magnetic fluctuations in the spectrum of either material in the energy and wavevector ranges probed. Special attention is paid to the wavevector at which spin-density-wave-like fluctuations are seen in other iron-based superconductors. We estimate that the magnetic signal, if present, is at least a factor of four (Sr2ScO3FeP) or seven (LaFePO) smaller than in the related iron arsenide and chalcogenide superconductors. These results suggest that magnetic fluctuations are not as influential on the electronic properties of the iron phosphide systems as they are in other iron-based superconductors.

The dynamics of silver-alkali halide mixed single crystals (Ag(x)Na(1-x)Br, x = 0.23, 0.35, 0.40 and 0.70) were studied by inelastic neutron scattering during the process of spinodal decomposition. Using the thermal three-axes spectrometer PUMA as well as the time-of-flight spectrometer IN5, the time evolution of phonons was observed in time-resolved, stroboscopic measurements. Complementary to the study of long wavelength acoustic phonons, as studied previously, we extended these investigations to Brillouin-zone boundary modes that are particularly sensitive to variations of the local structure. Starting from the homogeneous mixed phase the behaviour of these modes during demixing is observed in real-time. A simple dynamical model based on local structure variants helps to interpret the results. It is shown that the phonon lifetimes vary strongly during the phase separation and increase drastically during the coarsening process. Up to a critical size of precipitates of about 10 nm, zone-boundary modes are found to be strongly damped, while beyond the line widths are reduced to the experimental resolution. This finding leads to the conclusion that the typical mean free path of these modes is of the order of 10 nm, which corresponds to 20 unit cells.

The intercalation/exfoliation reactions of MoS2 and SnS2 yield lamellar colloids, which may be grown layer-by-layer on cationic surfaces by alternate adsorption of cationic clusters or polymers.

The modified CNDO-CI method is applied for an analysis of electronic properties of formamide in its ground and excited states. Results obtained from the total wave function are in complete agreement with available data. The unobserved first triplet of formamide is predicted to be of n0 → π* type, located at 4-2 eV; this result indicates that in the photoamidation of olefins, the only role of excited acetone is the abstraction of the formyl hydrogen of ground formamide.

Combining elastic incoherent neutron scattering experiments at different resolutions with molecular dynamics simulations, we report the observation of a protein-like dynamical transition in linear chains of Poly(N-isopropylacrylamide). We identify the onset of the transition at a temperature $T_d$ of about 225~K. Thanks to a novel global fit procedure, we find quantitative agreement between measured and calculated polymer mean-squared displacements at all temperatures and time resolutions. Our results confirm the generality of the dynamical transition in macromolecular systems in aqueous environments, independently of the internal polymer topology.

International audience; Aperiodic composite crystals belong to a new state of matter that possesses long-range order without translational symmetry. We report measurements of low-lying phonon branches in a n-alkane/urea compound that provide a new insight to the urea sub-lattice and the commensurate basal plane dynamics. Focusing on the thoroughly studied n-nonadecane/urea compound makes a comparison with other inelastic scattering results possible, allowing the observation of a new aperiodic elastic signature. Using three techniques, slight but reproducible difference in sound velocities is observed between the transverse mode propagating along the aperiodic direction and polarized in the commensurate basal plane, and the one polarized along the aperiodic direction propagating in the basal plane.