A method of synthesis of silicious inorganic ordered materials (MCM-41-SBA-1) employing polyacrylic acid-C(n)TAB-TEOS nanoassemblies

In this work we describe the synthesis of a variety of MCM-41 type hexagonal and SBA-1 type cubic mesostructures and mesoporous silicious materials employing a novel synthesis concept based on polyacrylic acid (Pac)-C(n)TAB complexes as backbones of the developing structures. The ordered porosity of the solids was established by XRD and TEM techniques. The synthesis concept makes use of Pac-C(n)TAB nanoassemblies as a preformed scaffold, formed by the gradual increase of pH. On this starting matrix the inorganic precursor species SiO2 precipitate via hydrolysis of TEOS under the influence of increasing pH. The molecular weight (MW) of Pac, as well as the length of carbon chain in C,TAB, determine the physical and structural characteristics of the obtained materials. Longer chain surfactants (C(16)TAB) lead to the formation of hexagonal phase, while shorter chain surfactants (C(14)TAB, C(12)TAB) favor the SBA-1 phase. Lower MW of Pac (approximate to2000) leads to better-organized structures compared to higher MW ( 450,000), which leads to worm-like mesostructures. Cell parameters and pore size increase with increasing polyelectrolyte and/or surfactant chain, while at the same time SEM photography reveals that the particle size decreases. Conductivity experiments provide some insight into the proposed self-assembling pathway. (C) 2003 Elsevier Inc. All rights reserved.

Effect of internal partitioning on indoor air quality of rooms with mixing ventilation - basic study

The internal partitioning, which is frequently introduced in open-space planning due to its flexibility, was tested to study its effects on the room air quality as well as ventilation performance. For the study, physical tests using a small model room and numerical modeling using CFD computation were utilized to evaluate different test conditions employing mixing ventilation from the ceiling. The partition parameters, such as its location, height, and the gap underneath, as well as contaminant source location were tested under isothermal conditions. This paper summarizes the results from the study.

Degradation products of clavulanic acid promote clavulanic acid production in cultures of Streptomyces clavuligerus

The role of clavulanic acid, an unstable antibiotic produced by Streptomyces clavuligerus, in biomass accumulation and production of clavulanic acid in batch cultures of the organism was examined. The organism was grown in a medium containing either 20 g/l lysine, 1 g/l lysine or 1 g/l lysine supplemented with degraded clavulanic acid as nitrogen sources. Biomass accumulation was highest in cultures grown with supplemented degraded clavulanic acid and reached a maximum of 2.2 g/l, compared with 1.5 g/l when lysine only was used. The yield coefficient for clavulanic acid production was again highest in cultures grown with supplemented degraded clavulanic acid, with a Y-p/x, value of 2 mg/g compared with Y-p/x value of 1.5 mg/g in 20 g/l lysine. No clavulanic acid was produced in cultures containing non-supplemented 1 g/l lysine. Non-degraded clavulanic, acid was added at 60 h to non-producing cultures of the organism containing 1 g/l lysine only. Clavulanic acid concentration immediately decreased on addition from 0.04 g/l over a period of 20 h, then remained constant at 0.02 g/l for a further 30 h until the end of the cultivation. This suggests that the rate of degradation was equivalent to the rate of production of clavulanic acid following a period of initial additive degradation. These results indicate that clavulanic acid is both produced and degraded in cultures of S. clavuligerus and that the products of degradation are used by the organism, resulting in further production of the antibiotic. (C) 2003 Elsevier Inc. All rights reserved.

Glutathione and related thiol compounds II: the importance of protein bound glutathione and related protein-bound compounds in gluten proteins

Protein-bound glutathione (PSSG) and protein-bound related thiol compounds, i.e. cysteine (PSSCys), glutamyl-cysteine (PSSGlu-Cys) and cysteinyl-glycine (PSSCys-Gly), were analysed in proteins of Osborne fractions, i.e. gliadin, glutenin and gliadin-, glutenin-subfractions separated by gel filtration chromatography, gel protein and the total gluten proteins separated from wheat varieties with varying breadmaking performances. The results showed that PSSG and some protein-bound related thiol compounds were found in monomeric gliadins, indicating that glutathione and some related thiol compounds are able to form disulphide bonds (SS) with sulphydryl group (SH) of those proteins and the formation of those disulphide bonds may prevent those monomeric proteins from binding to other proteins. It was also observed that a larger amount of PSSG in glutenin proteins was negatively correlated with the molecular weight (M-w) distribution of glutenin polymers, suggesting that PSSG and protein-bound related thiol compounds may play an important role in controlling polymerisation of glutenin. Furthermore, it was found that the level of PSSG in gel protein from flours with poor breadmaking performances was constantly higher and significantly different (p < 0.05) from that of flours with good breadmaking performance. The same trend was observed with gluten samples from breadmaking and biscuitmaking flours. (C) 2003 Elsevier Ltd. All rights reserved.

Low-temperature partial dissociation of water on Cu(110)

The low-temperature reactivity of water (D2O) adsorbed on clean and oxygen pre-covered Cu(1 1 0) was studied using high resolution X-ray photoelectron spectroscopy (HRXPS) and low energy electron diffraction (LEED). On the clean surface partial dissociation to hydroxyl was observed already at 95 K. Upon annealing to 220 K hydrogen bonded water-hydroxyl chains are formed. Upon further annealing water desorbs leaving behind a layer of hydroxyl, most of which desorbs recombinatively eventually. With pre-adsorbed oxygen water reacts to hydroxyl lifting the added-row reconstruction even below 225 K. Upon annealing this adsorbate layer passes through essentially the same stages as without pre-adsorbed oxygen.

Robust non-orthogonal space-time block codes over highly correlated channels: a generalisation

Little has so far been reported on the robustness of non-orthogonal space-time block codes (NO-STBCs) over highly correlated channels (HCC). Some of the existing NO-STBCs are indeed weak in robustness against HCC. With a view to overcoming such a limitation, a generalisation of the existing robust NO-STBCs based on a 'matrix Alamouti (MA)' structure is presented.

Implementation of robust hybrid feedback FxLMS active noise cancellation headset

Instability is a serious problem for acoustic Active Noise Cancellation (ANC) headsets as a result of large errors in estimating the transfer function of the plant. Typically this occurs when, for example, a wearer adjusts the headset. In this paper, the instability problem of adaptive ANC headset is addressed. To ensure stability of the whole system, we propose a hybrid solution consisting of an analog feedback loop parallel to the digital loop, and the role of the analog loop in stabilizing the headset is analyzed theoretically. Finally the methodology of implementing such a hybrid ANC headset is described in detail. The experiments carried out on the headset prototype show that the headset is robust under considerable fluctuations of the plant transfer characteristics, and has very good noise cancellation performance both for narrow-band and wide-band disturbances.