Preparation of Ni/Al2O3 catalysts from vapor phase by atomic layer epitaxy

Ni/Al₂O₃ catalysts were prepared by saturating gas-solid reactions as an atomic layer epitaxy (ALE) process. Vaporized Ni(acac)₂ was chemisorbed on a porous alumina support, and the produced surface complex was then air treated to remove the ligand residues. The nickel content could be precisely controlled by repeating this reactor cycle. On alumina preheated at 800°C, the nickel content varied from 3 to 21 wt%, when the number of reaction cycles was increased from one to ten. The performance of the Ni-catalysts was evaluated in the gas-phase hydrogenation of toluene. The preheat temperature of alumina influenced the activity of the catalyst, and a maximum in the activity was observed for catalysts prepared from alumina preheated at 875°C. Catalysts prepared by four reaction cycles, containing about 10 wt% nickel, gave the highest utilization of nickel.     

Glucokinase gene polymorphisms: a genetic marker for glucose intolerance in a cohort of elderly Finnish men

Although mutations in the glucokinase gene are implicated in the pathogenesis of glucose intolerance in pedigrees with maturity-onset diabetes of the young, the role of such mutations in typical Type 2 diabetes is poorly characterized. We studied a cohort of elderly men born (between 1900 and 1919) in two Finnish communities and exhibiting a continuous spectrum of glucose tolerance at assessments made in 1984 and 1989. Individuals were typed at two polymorphic microsatellites straddling the glucokinase gene, GCK(3') (n = 169) and GCK(5') (n = 166): these two markers were in linkage equilibrium in this cohort. Significant associations between alleles at the GCK(3') marker and glucose tolerance were evident (p = 0.002), the frequency of the (z + 2) allele rising from zero in control subjects (n = 88 chromosomes) to 6.5% (n = 62) in subjects with impaired tolerance and 12.2% (n = 188) in subjects with diabetes. Mean 2-h glucose levels were 10.5 (9.6-11.4, 95% confidence interval) mmol l-1 in individuals with the (z + 2) allele and 8.1 (7.6-8.7) mmol l-1 in those without (p = 0.01, corrected for multiple comparisons). No association was evident between GCK(5') alleles and glucose tolerance. The GCK(3') microsatellite is a marker for abnormal glucose tolerance in this cohort of elderly Finnish men.     

The structure of E.coli soluble inorganic pyrophosphatase at 2.7 A resolution

Due to retyping the authors' names when transferring correctionsat the first proof stage, a typographical error was introduced.The correct spelling of the authors' names appears above.     

The structure of E.coli soluble inorganic pyrophosphatase at 2.7 A resolution

Hie structure of E.coli soluble inorganic pyrophosphatase hasbeen refined at 2.7 resolution to an R-factor of 20.9. Theoverall fold of the molecule is essentially the same as yeastpyrophosphatase, except that yeast pyrophosphatase is longerat both the N- and C-termini. Escherichia coli pyrophosphataseis a mixed +ß protein with a complicated topology.The active site cavity, which is also very similar to the yeastenzyme, is formed by seven ß-strands and an -helixand has a rather asymmetric distribution of charged residues.Our structure-based alignment extends and improves upon earliersequence alignment studies; it shows that probably no more than14, not 15–17 charged and polar residues are part of theconserved enzyme mechanism of pyrophosphatases. Six of theseconserved residues, at the bottom of the active site cavity,form a tight group centred on Asp70 and probably bind the twoessential Mg⁺ ions. The others, more spreadout and more positivelycharged, presumably bind substrate. Escherichia coli pyrophosphatasehas an extra aspartate residue in the active site cavity, whichmay explain why the two enzymes bind divalent cation differently.Based on the structure, we have identified a sequence motifthat seems to occur only in soluble inorganic pyrophosphatases.     

Rapid synthesis of nanostructured porous silicon carbide from biogenic silica

Nanostructured silicon carbide (SiC) is an exceptional material with numerous applications, for example, in catalysis, biomedicine, high-performance composites, and sensing. In this study, a fast and scalable method of producing nanostructured SiC from plant materials by magnesiothermic reduction via self-propagating high-temperature synthesis (SHS) route was developed. The produced biogenic material possessed a high surface area above 200 m²/g with a SiC crystallite size below 10 nm, which has not been done previously by SHS. This method enables affordable synthesis of the material plant-based precursors in a reaction that only takes a few seconds, thereby paving a way for nanostructured SiC production in high volumes using renewable resources. The material was also functionalized with carboxylic acid and bisphosphonate moieties, and its use as metal adsorbent in applications such as wastewater remediation was demonstrated.     

Comparison of preparation routes of spinel catalyst for alkaline fuel cells

MnCo₂O₄ has been used as a catalyst for oxygen reduction reaction (ORR) in alkaline fuel cells due to easier production and lower costs compared to noble metals. A novel method using a microwave-assisted route of synthesis in the presence of amorphous carbon was developed resulting in MnCo₂O₄ with particle sizes <30 nm. For comparison, spinel prepared in a conventional oven with or without carbon was also studied. The surface area, carbon content, and chemical and morphological properties of the catalyst materials were analyzed. The catalytic activity towards oxygen reduction reaction was measured in a half-cell in 6 M KOH and by microagglomerate method. Compared to the catalysts prepared in a conventional oven, microwave-assisted route resulted in higher specific surface areas, higher current densities and stability, as well as lower apparent activation energies and Tafel slopes.     

Narrow linewidth templates for nanoimprint lithography utilizing conformal deposition

Nanoimprint lithography has the potential to cost efficiently realize patterns with extremely narrow linewidth over a large area. A significant challenge to achieving this target is the fabrication of nanoimprint templates. The cost and writing time of conventional electron beam lithography for direct writing of the templates rapidly increases as the patterned area increases and the linewidth decreases. We have developed a novel process for creating narrow linewidth nanopatterns. This process is based on conformal deposition of thin films on seed nanopatterns. We have demonstrated the process by fabricating nanosized loops and lines. The linewidth of the structures can be tuned precisely, and in our experiments it could be reduced to 20?nm. The closed loop structures are interesting, since this geometry is crucially important in many leading edge research fields such as negative refractive index materials, ultrahigh density memory applications and quantum rings. The fabricated template was subsequently used as a template in soft-stamp UV nanoimprint lithography to successfully replicate the structures in UV-curable resist.     

Specific energy consumption of vacuum filtration: Experimental evaluation using a pilot-scale horizontal belt filter

Abstract

Horizontal vacuum belt filters are used for continuous solid–liquid separation in a wide variety of industrial processes. Despite the low pressure difference (usually Δp?<?0.8?bar), the high air pumping requirement to maintain the pressure difference results in considerable energy consumption. In this article, the specific energy consumption of vacuum filtration and air flow rates of a pilot-scale horizontal vacuum belt filter unit are investigated. The results show that a claw-type vacuum pump consumes only half the energy compared to a conventional liquid ring vacuum pump at corresponding operating points. A comparison between the specific energy consumption of vacuum filtration and thermal drying of the filter cake to zero moisture revealed that vacuum filtration accounted for less than half of the total energy consumption in the applied experimental conditions at Δp?=?0.2–0.5?bar. The majority of the total pumping requirement of the pilot-scale filter resulted from leaks, and only 2–25% of the air flow found its way through the cake and the filter medium. The results suggest that there is a combination of the pressure difference level and the mass of solids deposited per filtration area that together with thermal drying consumes the least amount of energy per solids mass.     

Microwave dielectric properties of low-temperature sinterable α-MoO3

The α-MoO₃ ceramics were prepared by uniaxial pressing and sintering of MoO₃ powder at 650 °C and their structure, microstructure, densification and sintering and microwave dielectric properties were investigated. The sintering temperature of α-MoO₃ was optimized based on the best densification and microwave dielectric properties. After sintering at 650 °C the relative permittivity was found to be 6.6 and the quality factor was 41,000 GHz at 11.3 GHz. The full-width half-maximum of the A_1g Raman mode of bulk α-MoO₃ at different sintering temperatures correlated well with the Qf values. Moreover, the sintered samples showed a temperature coefficient of the resonant frequency of ?25 ppm/°C in the temperature range from ?40 to 85 °C and they exhibited a very low coefficient of thermal expansion of ±4 ppm/°C. These microwave dielectric properties of α-MoO₃ will be of great benefit in future MoO₃ based materials and their applications.