Substituted Mo–V(Ti)–Te(Ce)-oxide M2 Catalysts for Propene Ammoxidation

One of the most effective propane to acrylonitrile ammoxidation catalyst is comprised of the two phases M1 (orthorhombic) Mo_7.5V_1.5NbTeO₂₉ and M2 (pseudo-hexagonal) Mo₄V₂Te₂O₂₀. Under reaction conditions, the two phases work in symbiosis with each other where M1 is the paraffin activating component and M2 is the olefin activating component. Since the catalytic improvement of either phase should result in an enhancement of the overall acrylonitrile yield, controlled substitution of certain elements in either or both phases might result in the desired improvement. Our current study concentrates on the partial substitutions of V with Ti and Te with Ce in the M2 phase. Ti substitution results in a considerable propene activity improvement, whereas the selectivity to acrylonitrile is unaffected. Substitution with Ce, on the contrary, substantially improves the selectivity to acrylonitrile. Also, a minor improvement of the activity is notable. The acrylonitrile selectivity improvement is a result of better NH₃ utilization and comes at the expense of reduced acrolein make. XRD reveals that all of the substituted compositions retain the M2 structure and essentially are monophasic. XANES recordings show for the bulk that the Mo is 6+, the V is 4+, or 4+ and 5+ when Ce is present, the Ti is 4+, the Ce is 3+, and the Te 4+ with some 6+ also present. According to the ESR data, in the M2 with Ce (7Te/3Ce) only 21% of the V is 4+, the remainder being 5+, which tentatively can be explained by the existence of some cation vacancies in the hexagonal channels. HRTEM imaging reveals little if any differences between the materials, all have the typical pseudo-hexagonal habit of the M2 phase and expose a 1–2 nm thick surface layer without any apparent long-range ordering. XPS data show that all catalysts, including the base, are highly enriched at the surface with Te at the expense of other metals. The 7Te/3Ce composition exhibits also substantial Ce surface enrichment. Moreover, the valences of the cations at the surface differ from the bulk in that for all fresh catalysts V is 5+ and Te is 6+ on the surface. Characterization by XPS of catalysts used in propene ammoxidation, reveals reduction of Te and, except when Ce is present, also Mo. Therefore, it might be inferred that the surfaces of the catalysts studied here are comprised essentially of one or a few monolayers of TeMoO or TeCeMoO on an interacting M2 crystalline base.     

Type IIB von Willebrand''s disease: gene mutations and clinical presentation in nine families from Denmark, Germany and Sweden

Type IIB of von Willebrand's disease (vWD) is a variant in which the structurally abnormal von Willebrand factor (vWF) shows an increased affinity for the platelet vWF receptor, glycoprotein Ib (GPIb). This may sometimes give rise to platelet aggregation and thrombocytopenia in vivo. In 20 patients from nine unrelated families with type IIB vWD from Denmark, Germany and Sweden we studied the molecular defect by amplification and direct sequencing of parts of exon 28 which encode for the vWF domain that interacts with platelet GPIb. Three different point mutations were identified one of which has not previously been reported. Fifteen patients from five families were heterozygous for the Arg543-->Trp substitution. The mutation had occurred independently in all five families and in two of them represented a de novo mutation. In one of these families the father, though asymptomatic and with normal laboratory test results, carried the mutation in heterozygous form. In three families, four affected members were found to be heterozygous for the Arg543-->Cys substitution. The mutations were of different origin at least in two of the families. The third substitution, Val551-->Leu, which has not previously been described, was found in one patient and was due to a de novo mutation. In most of the patients spontaneous thrombocytopenia had been recorded on at least one occasion. Five of the patients with the Arg543-->Trp substitution and the one with the Val555-->Leu substitution had all had bleeding associated with thrombocytopenia in the neonatal period of early infancy.     

Postparturient metabolic and production responses in cows previously exposed to long-term treatment with somatotropin.

Postparturient metabolic and production responses were studied for 85 multiparous cows consisting of controls and animals that had been previously exposed to long-term treatment with bST. Older cows previously exposed to bST at high doses (51.6 mg/d) had lower milk yields than controls. However, there were no significant differences compared with controls in milk yield for lower dose (17.2 mg/d) older cows or parity 2 cow groups. The bST-treated groups had higher postpartum DMI, lower serum FFA, lower serum beta-hydroxybutyrate levels, and higher serum glucose than controls. Some bST-exposed groups had lower milk fat but higher milk protein levels. All bST-treated groups had significantly lower ratios of C18 to C4 to 10 milk fatty acids. Control cows of both parity groups were in higher body condition and weighed more than bST-treated cows prior to calving. The differences in postpartum metabolism may be attributed to differences in body composition resulting from bST treatment in the prior lactation, because use of body condition score prior to calving as a covariate did not substantially alter responses. The control cows probably had greater reserves of mobilizable lipid. These contentions are supported by changes in milk composition for bST-treated cows, which were consistent with animals of greater appetite, mobilizing less lipid. The bST-treated cows were probably more energetically efficient milk producers because they produced milk from feed rather than from mobilization of tissue stores. These data suggest that bST use in a prior lactation may have potential benefit in reducing risk of metabolic disorders associated with lipid mobilization in the postparturient period.     

Hydrolysis and biodegradation studies of surface-active esters

Base-catalyzed hydrolysis, biodegradation, and enzyme-catalyzed hydrolysis of a series of four monoesters of tetra(ethylene glycol) have been investigated. The surfactants varied in substitution on the α-carbon of the acyl chain, from no substitution, to 2-methyl, to 2-ethyl, and on to 2,2-dimethyl. All surfactants were based on C₈-acids except the methyl-substituted, which was based on a C₇-acid. The hydrolysis was investigated using ¹H nuclear magnetic resonance. The surfactants showed a pronounced difference in stability with respect to type of substitution in the vicinity of the ester bond. In alka-line hydrolysis the most significant difference in reactivity lay between the surfactant with an ethyl group and the surfactant with a methyl group in the α-position of the acyl chain. However, in the biodegradation studies these surfactants broke down at almost exactly the same rate as the nonsubstituted surfactant. In the biodegradation test, the disubstituted surfactant deviated considerably. Two lipases, from Mucor miehei (MML) and Candida antarctica B (CALB), were used in the enzyme-catalyzed hydrolysis. The surfactant with no substitution was found to hydrolyze much faster than the other surfactants, and the hydrolytic activity of MML, but not CALB, increased in the presence of surfactant micelles.     

Surfactant inhibition of aluminium pigments for waterborne printing inks

Micrometre-sized aluminium particles are used as pigments in silver inks and for environmental reasons it is desirable to develop water-based formulations of such pigments. In waterborne coatings, however, aluminium is prone to react with water, with subsequent hydrogen gas evolution and loss of the silvery lustre. The protection against water of aluminium pigments by adsorption of either a nonionic or an anionic surfactant has been evaluated. Phosphate esters with different lengths of the hydrocarbon tail have been synthesised and tested, and were found to provide very effective protection of the pigments. Sodium dodecyl sulphate (SDS), on the other hand, was completely ineffective as inhibitor, even though the adsorption isotherm was about the same as for the structurally similar sodium dodecyl phosphate (SDP). This difference may be explained by formation of different types of complexes with the aluminium oxide surface. Outer-sphere complexes are suggested for SDS, whilst SDP can form more stable inner-sphere complexes. Tests with the non-surface active methyl phosphate as inhibiting agent gave insufficient protection, indicating that surface activity is crucial for the inhibition, and that the use of the phosphates as such is not enough to give proper protection. The work shows that amphiphilic compounds having phosphate as anchoring group are efficient in providing water resistance to aluminium pigments.     

Disciplinary differences in Twitter scholarly communication

This paper investigates disciplinary differences in how researchers use the microblogging site Twitter. Tweets from selected researchers in ten disciplines (astrophysics, biochemistry, digital humanities, economics, history of science, cheminformatics, cognitive science, drug discovery, social network analysis, and sociology) were collected and analyzed both statistically and qualitatively. The researchers tended to share more links and retweet more than the average Twitter users in earlier research and there were clear disciplinary differences in how they used Twitter. Biochemists retweeted substantially more than researchers in the other disciplines. Researchers in digital humanities and cognitive science used Twitter more for conversations, while researchers in economics shared the most links. Finally, whilst researchers in biochemistry, astrophysics, cheminformatics and digital humanities seemed to use Twitter for scholarly communication, scientific use of Twitter in economics, sociology and history of science appeared to be marginal.     

Real-time observation of impurity diffusion in silicon nanowires

Solid-state diffusion of the transition metal impurities, gold (Au), nickel (Ni), and copper (Cu), in silicon (Si) nanowires was studied by in situ transmission electron microscopy. Compared to diffusion in a bulk crystal, Au diffusion is extremely slow when the amount of metal is limited but significantly enhanced when an unlimited supply is available. Cu and Ni diffusion leads to rapid silicide formation but slows considerably with physical encapsulation by a volume-restricting carbon shell.     

Solution-liquid-solid synthesis of CuInSe₂ nanowires and their implementation in photovoltaic devices

CuInSe? (CIS) nanowires were synthesized by solution-liquid-solid (SLS) growth in a high boiling solvent using bismuth nanocrystals as seeds. The nanowires tended to be slightly deficient in In and exhibited either cubic or hexagonal crystal structure, depending on the synthesis conditions. The hexagonal structure, which is not observed in bulk crystals, appears to evolve from large concentrations of twin defects. The nanowires could be compressed into a free-standing fabric or paper-like material. Photovoltaic devices (PVs) were fabricated using the nanowires as the light-absorbing layer to test their viability as a solar cell material and were found to exhibit measurable PV response.