High-Spin Molecules: Synthesis, X-ray Characterization, and Magnetic Behavior of Two New Cyano-Bridged Ni II 9 Mo V 6 and Ni II 9 W V 6 Clusters with a S = 12 Ground State

The preparations, X-ray structures, and magnetic characterizations are presented for two new pentadecanuclear cluster compounds:  [NiII{NiII(MeOH)3}8(μ-CN)30{MV(CN)3}6]·xMeOH·yH2O (MV = MoV (1) with x = 17, y = 1; MV = WV (2) with x = 15, y = 0). Both compounds crystallize in the monoclinic space group C2/c, with cell dimensions of a = 28.4957(18) Å, b = 19.2583(10) Å, c = 32.4279(17) Å, β = 113.155(6)°, and Z = 4 for 1 and a = 28.5278(16) Å, b = 19.2008(18) Å, c = 32.4072(17) Å, β = 113.727(6)°, and Z = 4 for 2. The structures of 1 and 2 consist of neutral cluster complexes comprising 15 metal ions, 9 NiII and 6 MV, all linked by μ-cyano ligands. Magnetic susceptibilities and magnetization measurements of compounds 1 and 2 in the crystalline and dissolved state indicate that these clusters have a S = 12 ground state, originating from intracluster ferromagnetic exchange interactions between the μ-cyano-bridged metal ions of the type NiII−NC−MV. Indeed, these data show clearly that the cluster molecules stay intact in solution. Ac magnetic susceptibility measurements reveal that the cluster compounds exhibit magnetic susceptibility relaxation phenomena at low temperatures since, with nonzero dc fields, χ‘ ‘M has a nonzero value that is frequency dependent. However, there appears no out-of-phase (χ‘ ‘M) signal in zero dc field down to 1.8 K, which excludes the expected signature for a single molecule magnet. This finding is confirmed with the small uniaxial magnetic anisotropy value for D of 0.015 cm-1, deduced from the high-field, high-frequency EPR measurement, which distinctly reveals a positive sign in D. Obviously, the overall magnetic anisotropy of the compounds is too low, and this may be a consequence of a small single ion magnetic anisotropy combined with the highly symmetric arrangement of the metal ions in the cluster molecule.

Synthesis and Thermodynamic and Biophysical Properties of Tricyclo-DNA

The DNA analogue tricyclo-DNA, built from conformationally rigid nucleoside analogues that were linked via tertiary phosphodiester functions, can efficiently be synthesized from the corresponding phosphoramidites by conventional solid-phase cyanoethyl phosphoramidite chemistry. 5'-End phosphorylated tricyclo-DNA sequences are chemically stable in aqueous, pH-neutral media at temperatures from 0 to 90 C. Tricyclo-DNA sequences resist enzymatic hydrolysis by the 3'-exonuclease snake venom phosphodiesterase. Homobasic adenine- and thymine-containing tricyclo-DNA octa- and nonamers are extraordinarily stable A-T base-pairing systems, not only in their own series but also with complementary DNA and RNA. Base mismatch formation is strongly destabilized. As in bicyclo-DNA, the tricyclo-DNA purine sequences preferentially accept a complementary strand on the Hoogsteen face of the base. A thermodynamic analysis reveals entropic benefits in the case of hetero-backbone duplex formation (tricyclo-DNA/DNA duplexes) and both an enthalpic and entropic benefit for duplex formation in the pure tricyclo-DNA series compared to natural DNA. Stability of tricyclo-DNA duplex formation depends more strongly on monovalent salt concentration compared to natural DNA. Homopyrimidine DNA sequences containing tricyclothymidine residues form triplexes with complementary double-stranded DNA. Triple-helix stability depends on the sequence composition and can be higher when compared to that of natural DNA. The use of one tricyclothymidine residue in the center of the self-complementary dodecamer duplex (d(CGCGAAT t CGCG), t = tricyclothymidine) strongly stabilizes its monomolecular hairpin loop structure relative to that of the corresponding pure DNA dodecamer ( T m = +20 C), indicating (tetra)loop-stabilizing properties of this rigid nucleoside analogue.

Data collection of depth and time integrated Calanus finmarchicus abundances, averaged temperatures, and integrated Chlorophyll concentration in the North Atlantic Ocean

Here we present a new, pan-North-Atlantic compilation of data on key mesozooplankton species, including the most important copepod, Calanus finmarchicus. Distributional data of eight representative zooplankton taxa, from recent (2000-2009) Continuous Plankton Recorder data, are presented, along with basin-scale data of the phytoplankton colour index. Then we present a compilation of data on C. finmarchicus, including observations of abundance, demography, egg production and female size, with accompanying data on temperature and chlorophyll. . This is a contribution by Canadian, European and US scientists and their institutions.

Soft solution fluorine-free synthesis of anatase nanoparticles with tailored morphology

TiO2 nanoparticles with tailored morphology have been synthesized under exceptionally soft conditions. The strategy is based on the use of a non-aqueous alcoholic reaction medium in which water traces, coming either from the air (atmospheric water) or from an ethanol–water azeotropic mixture (ethanol 96%), are incorporated in order to accelerate hydrolysis of the Ti–precursor. Moreover, organic surfactants have been used as capping agents so as to tailor crystal growth in certain preferential directions. Combinations of oleic acid and oleylamine, which lead to the formation of another surfactant, dioleamide, are employed instead of fluorine-based compounds, thus increasing the sustainability of the process. As a result, TiO2 nanostructured hierarchical microspheres and individual nanoparticles with exposed high-energy facets can be obtained at atmospheric pressure and temperatures as low as 78 °C.

Trigger factor is induced upon cold shock and enhances viability of Escherichia coli at low temperatures

Trigger factor (TF) in Escherichia coli is a molecular chaperone with remarkable properties: it has prolyl-isomerase activity, associates with nascent polypeptides on ribosomes, binds to GroEL, enhances GroEL’s affinity for unfolded proteins, and promotes degradation of certain polypeptides. Because the latter effects appeared larger at 20°C, we studied the influence of temperature on TF expression. Unlike most chaperones (e.g., GroEL), which are heat-shock proteins (hsps), TF levels increased progressively as growth temperature decreased from 42°C to 16°C and even rose in cells stored at 4°C. Upon temperature downshift from 37°C to 10°C or exposure to chloramphenicol, TF synthesis was induced, like that of many cold-shock proteins. We therefore tested if TF expression might be important for viability at low temperatures. When stored at 4°C, E. coli lose viability at exponential rates. Cells with reduced TF content die faster, while cells overexpressing TF showed greater viability. Although TF overproduction protected against cold, it reduced viability at 50°C, while TF deficiency enhanced viability at this temperature. By contrast, overproduction of GroEL/ES, or hsps generally, while protective against high temperatures, reduced viability at 4°C, which may explain why expression of hsps is suppressed in the cold. Thus, TF represents an example of an E. coli protein which protects cells against low temperatures. Moreover, the differential induction of TF at low temperatures and hsps at high temperatures appears to provide selective protection against these opposite thermal extremes.

High-Temperature Perturbation of Starch Synthesis Is Attributable to Inhibition of ADP-Glucose Pyrophosphorylase by Decreased Levels of Glycerate-3-Phosphate in Growing Potato Tubers1

To investigate the short-term effect of elevated temperatures on carbon metabolism in growing potato (Solanum tuberosum L.) tubers, developing tubers were exposed to a range of temperatures between 19°C and 37°C. Incorporation of [14C]glucose (Glc) into starch showed a temperature optimum at 25°C. Increasing the temperature from 23°C or 25°C up to 37°C led to decreased labeling of starch, increased labeling of sucrose (Suc) and intermediates of the respiratory pathway, and increased respiration rates. At elevated temperatures, hexose-phosphate levels were increased, whereas the levels of glycerate-3-phosphate (3PGA) and phosphoenolpyruvate were decreased. There was an increase in pyruvate and malate, and a decrease in isocitrate. The amount of adenine diphosphoglucose (ADPGlc) decreased when tubers were exposed to elevated temperatures. There was a strong correlation between the in vivo levels of 3PGA and ADPGlc in tubers incubated at different temperatures, and the decrease in ADPGlc correlated very well with the decrease in the labeling of starch. In tubers incubated at temperatures above 30°C, the overall activities of Suc synthase and ADPGlc pyrophosphorylase declined slightly, whereas soluble starch synthase and pyruvate kinase remained unchanged. Elevated temperatures led to an activation of Suc phosphate synthase involving a change in its kinetic properties. There was a strong correlation between Suc phosphate synthase activation and the in vivo level of Glc-6-phosphate. It is proposed that elevated temperatures lead to increased rates of respiration, and the resulting decline of 3PGA then inhibits ADPGlc pyrophosphorylase and starch synthesis.

Synthesis of a thymidyl pentamer of deoxyribonucleic guanidine and binding studies with DNA homopolynucleotides.

Replacement of the phosphodiester linkages of the polyanion DNA with guanidine linkers provides the polycation deoxynucleic guanidine (DNG). The synthesis of pentameric thymidyl DNA is provided. This polycationic DNG species binds with unprecedented affinity and with base-pair specificity to negatively charged poly(dA) to provide both double and triple helices. The dramatic stability of these hybrid structures is shown by their denaturation temperatures (Tm). For example, the double helix of the pentameric thymidyl DNG and poly(dA) does not dissociate in boiling water (ionic strength = 0.12), whereas the Tm for pentameric thymidyl DNA associated with poly(dA) is approximately 13 degrees C (ionic strength = 0.12). The effect of ionic strength on Tm for DNG complexes with DNA shows an opposite correlation compared with double-stranded DNA and is much more dramatic than for double-stranded DNA.

Total oxidation of naphthalene at low temperatures using palladium nanoparticles supported on inorganic oxide-coated cordierite honeycomb monoliths

A study on the preparation of thin films of ZSM-5 and BETA zeolites, and a SAPO-5 silicoaluminophosphate, supported on cordierite honeycomb monoliths by in situ synthesis was carried out for their use as catalyst supports. Furthermore γ-Al2O3 was also coated onto a cordierite honeycomb monolith by a dip-coating method for use as a standard support. Structured monolithic catalysts were prepared by impregnation of the aforementioned coated monoliths with polymer-protected Pd nanoparticles. The monolithic catalysts have been tested for the total oxidation of naphthalene (100 ppm, GHSV 1220 h−1). From the combined use of the zeolite with polymer-protected nanoparticles, enhanced catalytic properties have been found for the total abatement of naphthalene. The Pd/MBETA and Pd/MZSM-5 catalytic monoliths have shown excellent activity with a high degree of stability, even after undergoing accelerated ageing experiments.

MINLP Optimization Algorithm for the Synthesis of Heat and Work Exchange Networks

This paper introduces a new optimization model for the simultaneous synthesis of heat and work exchange networks. The work integration is performed in the work exchange network (WEN), while the heat integration is carried out in the heat exchanger network (HEN). In the WEN synthesis, streams at high-pressure (HP) and low-pressure (LP) are subjected to pressure manipulation stages, via turbines and compressors running on common shafts and stand-alone equipment. The model allows the use of several units of single-shaft-turbine-compressor (SSTC), as well as helper motors and generators to respond to any shortage and/or excess of energy, respectively, in the SSTC axes. The heat integration of the streams occurs in the HEN between each WEN stage. Thus, as the inlet and outlet streams temperatures in the HEN are dependent of the WEN design, they must be considered as optimization variables. The proposed multi-stage superstructure is formulated in mixed-integer nonlinear programming (MINLP), in order to minimize the total annualized cost composed by capital and operational expenses. A case study is conducted to verify the accuracy of the proposed approach. The results indicate that the heat integration between the WEN stages is essential to enhance the work integration, and to reduce the total cost of process due the need of a smaller amount of hot and cold utilities.

Synthesis of Silver Nanoparticle Based Conductive Inks for Additively Manufactured Electronics

Thesis (Master's)--University of Washington, 2016-06

Synthesis and electrochemical properties of mesoporous nickel oxide

Mesoporous Ni(OH)(2) is synthesized using sodium dodecyl sulfate as a template and urea as a hydrolysis-controlling agent. Mesoporous NiO with a centralized pore-size distribution is obtained by calcining Ni(OH)(2) at different temperatures. The BET specific surface area reaches 477.7 m(2) g(-1) for NiO calcined at 250 degreesC. Structure characterizations indicate a good mesoporous structure for the nickel oxide samples. Cyclic voltammetry shows the NiO to have good capacitive behaviour due to its unique mesoporous structure when using a large amount of NiO to fabricate the electrode. Compared with NiO prepared by dip-coating and cathodic precipitation methods, mesoporous NiO with a controlled pore structure can be used in much larger amounts to fabricate electrodes and still maintain a high specific capacitance and good capacitive behaviour. (C) 2004 Elsevier B.V. All rights reserved.

Mesoporous bioactive glasses. I. Synthesis and structural characterization

Highly ordered mesoporous bioactive glasses (MBGs) with different compositions have been synthesized by a combination of surfactant templating, sol-gel method and evaporation-induced self-assembly (EISA) processes. The texture properties and compositional homogeneity of MBGs have been characterized and compared with conventional bioactive glasses (BGs) synthesized in the absence of surfactants by evaporation method. The formation mechanism (pore - composition dependence) and compositional homogeneity in the case of MBG materials are different from those in conventional BGs. Unlike conventional sol-gel-derived BGs that shows a direct correlation between their composition and pore architecture, MBGs with different compositions may possess similar pore volume and uniformly distributed pore size when the same structure-directing agent is utilized. The framework of MBG is homogeneously distributed in composition at the nanoscale and the inorganic species generally exists in the form of amorphous phase. MBGs calcined at temperatures

Synthesis and characterization of mesoporous nickel oxide and its application to electrochemical capacitor

Mesoporous Ni(OH)(2) was synthesized using cationic surfactant as template and urea as hydrolysis-controlling agent. Mesoporous NiO with centralized pore size distribution was obtained by calcining Ni(OH)(2) at different temperatures. The BET specific surface area reaches 477.7 m(2).g(-1) for NiO calcined at 523 K. Structure characterizations indicate the polycrystalline pore wall of mesoporous nickel oxide. The pore-formation mechanism is also deduced to be quasi-reverse micelle mechanism. Cyclic voltammetry shows the good capacitive behavior of these NiO samples due to its unique mesoporous structure when using large amount of NiO to fabricate electrode. Compared with NiO prepared by dip-coating and cathodic precipitation methods, this mesoporous NiO with controlled pore structure can be used in much larger amount to fabricate the electrode and still maintains high specific capacitance and good capacitive behavior.

Synthesis and characterization of silicalite-1 composite membrane

Silicalite-1/carbon-graphite composite membranes have been prepared using a standard hydrothermal synthesis method and characterized by XRD, SEM, TGA, BET and permeation experiments. Single gas permeation fluxes and binary mixtures separation and selectivity data are reported for methane, ethane and propane using the composite membranes. Carbon-graphite oxidized for 4 h prior to membrane preparation had the most promising separation properties. The permeation fluxes for the binary mixtures reflect that of the single component flux ratios. At 20 °C the membranes show high separation selectivity toward lighter component in binary mixtures. Single gas permeances for methane and ethane were found to decrease with increasing temperatures while that of propane fluctuates. © 2007 Elsevier Inc. All rights reserved.