Monolithically-integrated BiVO4/p+-n GaAs1-xPx tandem photoanodes capable of unassisted solar water splitting

Monolithically-integrated tandem photoanodes were fabricated on substrates consisting of epitaxial n-GaAs_1-xP_x (x ? 0.32) grown on n⁺-GaAs wafers. A p⁺-n junction photovoltaic (PV) cell was first formed by zinc diffusion into the n-GaAs_0.68P_0.32 from a deposited ZnO coating. After diffusion the ZnO serves as a transparent electrical contact to the resulting p⁺-GaAs_0.68P_0.32 surface layer. Transparent, conducting SnO₂:F provides chemical and mechanical protection for the ZnO and the underlying PV cell, and it electrically connects this cell to a top BiVO₄ photocatalyst layer. In some photoanodes, a WO₃ thin film was interposed between the SnO₂:F and BiVO₄. All oxide coatings were produced by ultrasonic spray pyrolysis except WO₃, which was spin coated. Unassisted (unbiased) solar water splitting was achieved, with a solar-to-hydrogen efficiency approaching 2%, without addition of any co-catalyst to the BiVO₄ surface. This work can provide insights to other researchers regarding scalable, low cost approaches for the planar monolithic integration of oxide photoanode materials with PV cells to create new tandem devices.     

The pharmacokinetics and protein-binding of fusidic acid in patients with severe renal failure requiring either haemodialysis or continuous ambulatory peritoneal dialysis

Antibiotic treatment options for Burkholderia cepacia infection are limited because of high intrinsic resistance. The problem is complicated by development of cross-resistance between antibiotics of different classes. We isolated antibiotic-resistant mutants by stepwise exposure to chloramphenicol (Chlor) and to trimethoprim/sulphamethoxazole (T/S) for four B. cepacia strains: ATCC13945, Per (clinical isolate), Cas and D4 (environmental isolates). Chlor(r) mutants did not produce chloramphenicol acetyl-transferase. Cross-resistance, defined as greater than four-fold increase in MIC by microtitre dilution method, was consistently seen in both types of mutants. For chloramphenicol-resistant (Chlor[r]) and trimethoprim/sulphamethoxazole-resistant (Tr/Sr) mutants of B. cepacia ATCC13945 and Cas, no MIC change was seen for piperacillin, ceftazidime, rifampicin, gentamicin, tobramycin, polymyxin B or azithromycin. B. cepacia-Per and -D4 mutants showed cross-resistance to ceftazidime and to piperacillin. Comparison of outer membrane protein (OMP) profiles of B. cepacia and their mutants by SDS-PAGE revealed Tr/Sr) mutants to be deficient in a major OMP (molecular weight 39-47 kDa). Tr/Sr mutants also expressed additional OMPs not found in wild type strains at 75-77 kDa for B. cepacia-ATCC13945 and -Cas, and 20-21 kDa in B. cepacia-D4 and -Per. No OMP changes occurred in Chlor(r) mutants. Lipopolysaccharide (LPS) profiles of each type of mutant showed new high and low molecular weight LPS bands. Cross-resistance seems to be mediated by alterations in porin and LPS for Tr/Sr mutants, but only by LPS in Chlor(r) mutants.     

Context-specific adaptation of vertical vergence to correlates of eye position

Vertical phoria (vertical vergence in the absence of binocular feedback) can be trained to vary with non-visual cues such as vertical conjugate eye position, horizontal conjugate eye position and horizontal vergence. These prior studies demonstrated a low-level association or coupling between vertical vergence and several oculomotor cues. As a test of the potential independence of multiple eye-position cues for vertical vergence, context-specific adaptation experiments were conducted in three orthogonal adapting planes (midsagittal, frontoparallel, and transverse). Four vertical disparities in each of these planes were associated with various combinations of two specific components of eye position. Vertical disparities in the plane were associated with horizontal vergence and vertical conjugate eye position; vertical disparities in the frontoparallel plane were associated with horizontal and vertical conjugate eye position; and vertical disparities in the transverse plane were associated with horizontal vergence and horizontal conjugate eye position. The results demonstrate that vertical vergence can be adapted to respond to specific combinations of two different sources of eye-position information. The results are modeled with an association matrix whose inputs are two classes of eye position and whose weighted output is vertical vergence.     

Determination of total non-sulphonated aromatic amines in tartrazine, sunset yellow FCF and allura red by reduction and derivatization followed by high-performance liquid chromatography.

Free and bound non-sulphonated aromatic amines (NSAA) are determined in the food colours tartrazine, sunset yellow FCF and allura red. After reduction of the bound amines with sodium dithionite, the NSAA are extracted into chloroform, then transferred to aqueous acid solution, diazotized with sodium nitrite and coupled with 2-naphthol-3,6-disulphonic acid, disodium salt (R-salt). Reversed-phase ion-pair liquid chromatography and an absorbance detector at 512 nm are used to analyse the coloured derivatives. Samples of dyes were spiked with known amounts of aniline, 1-naphthylamine, 2- and 4-aminobiphenyl, 4-aminoazobenzene, benzidine, p-cresidine or 4-nitro-p-cresidine bound to R-salt. Recoveries averaged 90% in tartrazine, 65% in sunset yellow FCF and 71% in allura red. Detection limits ranged between 2 and 32 ng/g. A survey of 24 commercial samples revealed levels up to 520 micrograms/g total NSAA. The majority of NSAA are bound to the coupling compound during the manufacturing process and less than 7% remain as free amines in the dye.     

Salt-water up-coning during extraction of fresh water from a tropical island

Rainwater can collect in a lens-shaped region within the rock of a tropical island, and may be separated from the underlying salt water by a sharp interface. This paper presents a nonlinear theory for determining the shape of this interface. The island is assumed to be saturated with rain, and provision is made for the outflow of rain-water through the sides of the island. The effect of a bore well on the shape of the interface is investigated, and the problem is solved using a spectral method. An integral-equation method is also presented for the case when the island has infinite width.