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Tsud N.,Charles University | Bercha S.,Charles University | Acres R.G.,Elettra - Sincrotrone Trieste | Vorokhta M.,Charles University | And 5 more authors.
Physical Chemistry Chemical Physics | Year: 2015

The surfaces of polycrystalline cerium oxide films were modified by histidine adsorption under vacuum and characterized by the synchrotron based techniques of core and valence level photoemission, resonant photoemission and near edge X-ray absorption spectroscopy, as well as atomic force microscopy. Histidine is strongly bound to the oxide surface in the anionic form through the deprotonated carboxylate group, and forms a disordered molecular adlayer. The imidazole ring and the amino side group do not form bonds with the substrate but are involved in the intermolecular hydrogen bonding which stabilizes the molecular adlayer. The surface reaction with histidine results in water desorption accompanied by oxide reduction, which is propagated into the bulk of the film. Previously studied, well-characterized surfaces are a guide to the chemistry of the present polycrystalline surface and histidine bonds via the carboxylate group in both cases. In contrast, bonding via the imidazole group occurs on the well-ordered surface but not in the present case. The morphology and structure of the cerium oxide are decisive factors which define the adsorption geometry of the histidine adlayer. © the Owner Societies 2015.


Ould-Chikh S.,King Abdullah University of Science and Technology | Proux O.,European Synchrotron Radiation Facility | Afanasiev P.,CNRS Research on Catalysis and Environment in Lyon | Khrouz L.,Chemistry Laboratory | And 6 more authors.
ChemSusChem | Year: 2014

The photocatalytic properties of TiO2 modified by chromium are usually found to depend strongly on the preparation method. To clarify this problem, two series of chromium-doped titania with a chromium content of up to 1.56 wt % have been prepared under hydrothermal conditions: the first series (Cr:TiO2) is intended to dope the bulk of TiO2, whereas the second series (Cr/TiO2) is intended to load the surface of TiO2 with Cr. The catalytic properties have been compared in the photocatalytic oxidation of formic acid. Characterization data provides evidence that in the Cr/TiO2 catalysts chromium is located on the surface of TiO2 as amorphous CrOOH clusters. In contrast, in the Cr:TiO 2 series, chromium is mostly dissolved in the titania lattice, although a minor part is still present on the surface. Photocatalytic tests show that both series of chromium-doped titania demonstrate visible-light-driven photo-oxidation activity. Surface-doped Cr/TiO2 solids appear to be more efficient photocatalysts than the bulk-doped Cr:TiO2 counterparts. It's classified! The photocatalytic properties of TiO2 modified by chromium depend strongly on the preparation method. To clarify this problem, two types of modified titania are discussed: one with CrIII doped in the bulk and one with CrOOH clusters on the TiO2 surface (see picture). Both series show visible-light-driven photo-oxidation activity. However, surface modification appears to be a more efficient strategy. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


News Article | February 29, 2016
Site: www.techtimes.com

In an effort to learn more about Mars, NASA scientists explore Atacama Desert in Chile, known as the "driest place on Earth." Atacama offers a Mars-like environment that could offer researchers opportunities for conducting field tests of new life-detecting instruments that may be brought into future missions to the Red Planet. Because of its harsh environment characterized by intense ultraviolet radiation and very little water, life in Atacama exists as microbial colonies that thrive inside rocks or undergrounds. While the region is considerably warmer compared with Mars, its soil chemistry and extreme dryness are remarkably similar to that of the Red Planet, which makes the region an excellent Mars-like laboratory where researchers can study the limits of their life-detection and test drilling technologies. With Mars having cold and dry condition, there is high possibility that life in the planet may be found below its surface where the unwanted effects of radiation are reduced. Evidence for alien life in the extraterrestrial world may come in the form of organic molecules called biomarkers. "Putting life-detection instruments in a difficult, Mars-analog environment will help us figure out the best ways of looking for past or current life on Mars, if it existed," said NASA's Brian Glass. "Having both subsurface reach and surface mobility should greatly increase the number of biomarker and life-target sites we can sample in the Atacama." Brian Glass and colleagues spent a month running experiments in the arid region testing a Mars-prototype drill, Signs of Life Detector (SOLID), which was developed by the Centro de Astrobiologia (CAB) of Spain, and a prototype of Wet Chemistry Laboratory (WCL), which accompanied the Phoenix lander to Mars in 2007. Researchers also collected samples of extreme microorganisms that live in the Atacama's salt habitats for laboratory investigations. These habitats could serve as host for life in the extremely dry region known to be devoid of animals, plants and most types of microorganisms. NASA Ames researcher Mary Beth Wilhelm said that they are excited about the distinctive and resilient microorganisms and are optimistic that their studies will help improve the life-detection technology and strategies that will be adopted for the Red Planet.


News Article | November 28, 2016
Site: www.eurekalert.org

A team led by researchers at the RIKEN Biofunctional Synthetic Chemistry Laboratory in Japan has developed a way to engineer glycan complexes--clusters of sugar chains attached to proteins or lipids--in a way that allows the molecules to be transported preferentially to specific organs of the body, depending on the sugar chains contained in the cluster. According to Katsunori Tanaka, the leader of the team, this work, which was published in Advanced Science, could lead to the development of glycocluster-based diagnostic tools with better selectivity and precision than current tracers based on peptides and antibodies. Chains of sugar molecules--called glycans--are found on the surfaces of cells, where they play important roles in controlling cell-to-cell communications and the recognition of foreign pathogens. It has long been known that these glycans form heterogenous clusters of different sugars, and that they form patterns that allow them to fit with certain proteins. However, researchers did not understand whether these pattern variations were simply random or played a purpose, influencing the movement of proteins and cells through the body. To investigate this, the researchers used a method they developed, the RIKEN click method, to selectively attach two different glycans to a common protein--albumin--in specific patterns, where the sugars were ordered randomly or in a specific sequence. They then injected the resulting molecules, called heterogeneous glycoclusters, into mice. Following the administration, they used noninvasive imaging techniques to determine where in the body the conjugates traveled and how they were excreted. They then compared the results of their studies with these well-engineered glycans to homogenous glycoclusters--which only contain one type of glycan. They found that the heterogeneous glycoclusters exhibited special properties entirely different from homogeneous ones, such as being rapidly transported from the gallbladder to the intestine for excretion or accumulating selectively in the liver. According to Tanaka, "This work shows that the heterogeneity of clusters does indeed play an important role in creating strong and selective binding in vivo. In the same way that burrs--and Velcro, which was developed based on the idea--attach powerfully even though each individual bond is weak, biological molecules often attach together using weak covalent bonds that together form a strong connection. In addition, using multiple glycan molecules--or in other words, heterogeneity--allows us to promote selective interactions with target molecules through pattern recognition. Hence, precisely controlling the configuration of the glycans may allow us to design new glycoconjugates that can be used to target certain tumors, for example." The work was done by the RIKEN Biofunctional Synthetic Chemistry Laboratory in collaboration with researchers at Kazan Federal University in Russia and the RIKEN Center for Life Science Technologies in Japan.


News Article | November 28, 2016
Site: phys.org

A team led by researchers at the RIKEN Biofunctional Synthetic Chemistry Laboratory in Japan has developed a way to engineer glycan complexes—clusters of sugar chains attached to proteins or lipids—in a way that allows the molecules to be transported preferentially to specific organs of the body, depending on the sugar chains contained in the cluster. According to Katsunori Tanaka, the leader of the team, this work, which was published in Advanced Science, could lead to the development of glycocluster-based diagnostic tools with better selectivity and precision than current tracers based on peptides and antibodies. Chains of sugar molecules—called glycans—are found on the surfaces of cells, where they play important roles in controlling cell-to-cell communications and the recognition of foreign pathogens. It has long been known that these glycans form heterogenous clusters of different sugars, and that they form patterns that allow them to fit with certain proteins. However, researchers did not understand whether these pattern variations were simply random or played a purpose, influencing the movement of proteins and cells through the body. To investigate this, the researchers used a method they developed, the RIKEN click method, to selectively attach two different glycans to a common protein—albumin—in specific patterns, where the sugars were ordered randomly or in a specific sequence. They then injected the resulting molecules, called heterogeneous glycoclusters, into mice. Following the administration, they used noninvasive imaging techniques to determine where in the body the conjugates traveled and how they were excreted. They then compared the results of their studies with these well-engineered glycans to homogenous glycoclusters—which only contain one type of glycan. They found that the heterogeneous glycoclusters exhibited special properties entirely different from homogeneous ones, such as being rapidly transported from the gallbladder to the intestine for excretion or accumulating selectively in the liver. According to Tanaka, "This work shows that the heterogeneity of clusters does indeed play an important role in creating strong and selective binding in vivo. In the same way that burrs—and Velcro, which was developed based on the idea—attach powerfully even though each individual bond is weak, biological molecules often attach together using weak covalent bonds that together form a strong connection. In addition, using multiple glycan molecules—or in other words, heterogeneity—allows us to promote selective interactions with target molecules through pattern recognition. Hence, precisely controlling the configuration of the glycans may allow us to design new glycoconjugates that can be used to target certain tumors, for example." The work was done by the RIKEN Biofunctional Synthetic Chemistry Laboratory in collaboration with researchers at Kazan Federal University in Russia and the RIKEN Center for Life Science Technologies in Japan. Explore further: Large tree-like sugar clusters provide potential in vivo probes for cancer cells More information: Sequential double "clicks" toward structurally well-defined heterogeneous N-glycoclusters: The importance of cluster heterogeneity on pattern recognition in vivo, Advanced Science


Zhilei C.,Chemistry Laboratory | Maobing S.,Chemistry Laboratory | Lida W.,Dalian University of Technology
Journal of Solid State Electrochemistry | Year: 2013

A facile method for fabricating super-hydrophobic surfaces on the magnetron sputtering aluminum film by cathodic electrochemical etching followed by the modification of myristic acid was presented in this article. The morphologies and the compositions of the films were characterized by means of scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), respectively. The corrosion behavior of the super-hydrophobic film was evaluated by potentiodynamic polarization measurement, linear polarization measurement, and electrochemical impedance spectroscopy. After the treatment with cathodic electrochemical etching, the thin aluminum film remained unbroken and the bulk structure of the aluminum coating maintained a microcrystalline morphology while the surface of the coating presented a petal-shaped microstructure dotted with nano-sized floccules. Aluminum myristate was formed on the nano/microstructural surface of the coating when the sample was modified in melting myristic acid. The static water contact angle on the surface was larger than 165, which demonstrated that a super-hydrophobic film was prepared on the magnetron sputtering aluminum coating. The corrosion resistance of the aluminum coating was enhanced remarkably because of the super-hydrophobic modification. © 2013 Springer-Verlag Berlin Heidelberg.


Li C.,University of Hawaii at Manoa | Yang B.,University of Hawaii at Manoa | Fenstemacher R.,Chemistry Laboratory | Turkson J.,University of Hawaii at Manoa | Cao S.,University of Hawaii at Manoa
Tetrahedron Letters | Year: 2015

An endophytic fungus Paraphaeosphaeria neglecta FT462 from the Hawaiian plant Lycopodiella cernua (L.) Pic. Serm produced an unusual δ-lactone-isochromanone with a methylene bridge (1). The structure of 1 was determined by NMR and MS spectroscopic analysis. © 2015 Elsevier Ltd.


Koga N.,Chemistry Laboratory | Maruta S.,Chemistry Laboratory | Kimura T.,Chemistry Laboratory | Yamada S.,Kyushu University
Journal of Physical Chemistry A | Year: 2011

Aiming to find rigorous understanding and novel features for their potential applications, the physico-geometrical kinetics of the thermal decomposition of sodium hydrogencar-bonate (SHC) was investigated by focusing on the phenomen-ological events taking place on a single crystalline particle during the course of the reaction. The overall kinetics evaluated by systematic measurements of the kinetic rate data by thermo-gravimetry under carefully controlled conditions were interpreted in association with the morphological studies on the precursory reaction, mechanism of surface reaction, structure of the surface product layer, diffusion path of evolved gases, crystal growth of the solid product, and so on. The precursory reaction was identified as the decomposition of impurity, taking place at the boundary between the surface of the SHC crystal and the adhesive small SHC particles deposited on the surface. In flowing dry N 2, the thermal decomposition of SHC proceeds by two-dimensional shrinkage of the reaction interface controlled by chemical reaction with the apparent activation energy of about 100 kJ mol -1, after rapid completion of the surface reaction and formation of porous surface product layer. Atmospheric CO 2 and water vapor influence differently on the overall kinetics of the thermal decomposition of SHC. Added gas phase of CO 2 slightly inhibits the overall rate because of the increasing contribution of the surface reaction. Under higher water vapor pressure, the physico-geometrical mechanism of the surface reaction changes drastically, indicating the preliminary reformation of reactant surface and the formation of needle crystals of solid product on the surface. The mechanistic change and extended contribution of the surface reaction result in the deceleration of the surface reaction and acceleration of the established reaction. (Figure presented) © 2011 American Chemical Society.


Nabi S.A.,Analytical Research Laboratory | Naushad Mu.,Chemistry Laboratory
Chemical Engineering Journal | Year: 2010

A new inorganic cation exchange material Ti(IV) iodovanadate has been synthesized under a variety of conditions. The experimental parameters such as mixing volume ratio, order of mixing and pH established for the synthesis of the material. The most stable sample has been prepared by adding aqueous mixture of 0.1 M potassium iodate and 0.1 M sodium vanadate into 0.1 M solution (CCl4 medium) of titanium chloride at pH 1. The material is characterized using various analytical techniques like XRD, FTIR, TGA-DTA and SEM. A tentative structural formula has been proposed on the basis of chemical composition, pH titration, FTIR and thermogravimetric analysis. The ion exchange capacity and distribution coefficients of various metal ions have been determined to understand the cation exchange behavior of the material. On the basis of distribution studies, the material was found to be selective for Pb2+ ion. Its selectivity has been examined by achieving some important and analytically difficult binary separations, viz. Cr3+-Pb2+, Fe3+-Pb2+, Zn2+-Pb2+, Cd2+-Pb2+, etc. The material has bee also used as an electron exchange material. The oxidation of Fe(II) to Fe(III) has been achieved by batch-equilibrium technique successfully. The decomposition of hydrogen peroxide by the material has also been studied. The practical utility of Ti(IV) iodovanadate has been demonstrated by separating metal ions quantitatively from a synthetic mixture using the packed column of Ti(IV) iodovanadate. © 2009 Elsevier B.V. All rights reserved.


Wucherer E.J.,Chemistry Laboratory | Witty W.,Chemistry Laboratory | Chenevert B.,Chemistry Laboratory | Morgan O.,Chemistry Laboratory | Yarnot V.,Chemistry Laboratory
49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference | Year: 2013

Most monopropellant hydrazine thrusters use iridium on alumina catalyst (e.g. Shell-405 or S-405) to spontaneously decompose hydrazine propellant. Aerojet has been manufacturing S-405 catalyst since 2002. In 2009 unexpected performance anomalies in a specific rocket engine module were traced to subtle processing differences between Shell and Aerojet processing. A thorough investigation included exhumation of early (1960s) Shell documents and identification of areas for processing improvement. The process was improved and validation completed using the specific rocket engine model that originally showed the differences. Many other tests were performed that did not show differences between the Shell and S-405. This paper will discuss both the steps taken to improve the catalyst and some of the parallel tests that occurred at the rocket engine level.

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