Silicon based tandem cells: novel photocathodes for hydrogen production.

A photovoltaic tandem cell made of amorphous silicon (a-Si) and microcrystalline silicon (µc-Si) was investigated as a photocathode for hydrogen evolution in a photoelectrochemical device. The electronic and electrochemical properties of the samples were characterized using X-ray photoemission spectroscopy (XPS) and cyclic voltammetry (CV), whereas the morphology of the surface in contact with the electrolyte was investigated by scanning electron microscopy (SEM). The electric efficiency of the tandem cell was determined to be 5.2% in a photoelectrochemical (PEC) setup in acidic solution which is only about half of the photovoltaic efficiency of the tandem cell. A significant improvement in efficiency was achieved with platinum as a catalyst which was deposited by physical vapour deposition (PVD) under ultra-high vacuum (UHV) conditions.

Insulin detemir causes increased symptom awareness during hypoglycaemia compared to human insulin.

AIM: The long-acting insulin analogue detemir (Levemir) has structural and physicochemical properties which differ from human insulin. The aim of the present study was to test whether this leads to altered hormone and symptom response during hypoglycaemia. METHODS: 12 healthy subjects [6f/6m, age 32 +/- 6 years (mean +/- s.d.), body mass index (BMI) 24.2 +/- 2.5 kg/m(2)] underwent a 200-min stepwise hypoglycaemic clamp (45 min steps of 4.4, 3.7, 3.0 and 2.3 mmol/l) with either detemir or human insulin in random order. A bolus of detemir (660 mU/kg) or human insulin (60 mU/kg) was given before insulin was infused at a rate of 5 (detemir) or 2 (human insulin) mU/kg/min. Blood was drawn and a semi-quantitative symptom questionnaire was administered before and after each plateau of the hypoglycaemic clamp. Cognitive function was assessed during each step. RESULTS: Blood glucose levels and glucose infusion rates were comparable with detemir and human insulin. The total symptom score was higher with detemir during the 3 and 2.3 mmol glucose step compared to human insulin (p = 0.048). Especially sweating was increased with detemir (p = 0.02) with an earlier and faster increase during the clamp (interaction insulin x time: p = 0.04). No significant differences between detemir and human insulin in cortisol, norepinephrine, epinephrine, glucagon, growth hormone, lactate or free fatty acid (FFA) levels during hypoglycaemia were observed, and there were no significant differences in cognitive function tests. CONCLUSIONS: Insulin detemir increased symptom awareness during hypoglycaemia compared to human insulin in healthy individuals, whereas counter-regulatory hormone response and cognitive function were unaltered.

A cooperative clinical study of methadyl acetate. II. Friday-only regimen.

We conducted an open clinical trial of the feasibility of maintaining heroin addicts by administering methadone hydrochloride on Monday through Thursday, methadyl acetate on Friday, and no drug at all on Saturday or Sunday. Sixty-five patients from four participating clinics were randomly assigned to this schedule and another 71 to a daily methadone comparison group. The patient sample consisted of heroin addicts previously stabilized on a maintenance regimen of methadone. The starting dose of methadyl acetate was identical to the previously established dose of methadone but was flexible within limites thereafter. A greater number of patients in the methadyl acetate group failed to complete the full 40 weeks of the study, particularly because they claimed the medication was not holding. Although this particular use of methadyl acetate on Friday to provide a drug-free weekend does not appear to be widely applicable clinically, the fact that at least some patients in the methadyl acetate group tolerated the schedule with little or no illicit drug use or obvious discomfort suggests that the strategy is viable and should not be discarded.

Pneumococcal phosphoglycerate kinase interacts with plasminogen and its tissue activator.

Streptococcus pneumoniae is not only a commensal of the nasopharyngeal epithelium, but may also cause life-threatening diseases. Immune-electron microscopy studies revealed that the bacterial glycolytic enzyme, phosphoglycerate kinase (PGK), is localised on the pneumococcal surface of both capsulated and non-capsulated strains and colocalises with plasminogen. Since pneumococci may concentrate host plasminogen (PLG) together with its activators on the bacterial cell surface to facilitate the formation of plasmin, the involvement of PGK in this process was studied. Specific binding of human or murine PLG to strain-independent PGK was documented, and surface plasmon resonance analyses indicated a high affinity interaction with the kringle domains 1-4 of PLG. Crystal structure determination of pneumococcal PGK together with peptide array analysis revealed localisation of PLG-binding site in the N-terminal region and provided structural motifs for the interaction with PLG. Based on structural analysis data, a potential interaction of PGK with tissue plasminogen activator (tPA) was proposed and experimentally confirmed by binding studies, plasmin activity assays and thrombus degradation analyses.

Single electron transfer (SET) activity of the dialkyl-amido sodium zincate [(TMEDA)·Na(µ-TMP)(µ-tBu)Zn(tBu)] towards TEMPO and chalcone.

More usually thought of as a base, the sodium zincate [(TMEDA)·Na(µ-TMP)(µ-(t)Bu)Zn((t)Bu)] 1 can undergo single electron transfer with TEMPO to give [(TMEDA)·Na(µ-TMP)(µ-TEMPO(-))Zn((t)Bu)] 2 and [(TMEDA)·Na(µ-TEMPO(-))(2)Zn((t)Bu)] 3; and with chalcone [PhCOCH=CHPh] gives [{(TMEDA)·Na(µ-TMP)Zn((t)Bu)}(2)(µ-OCPhCH=CHPhCHPhCH=CPh-µ-O)] which contains two chalcone units C-C coupled though their benzylic C atoms.

Stable analytical inversion solution for processing lidar returns.

A simple analytical method is presented that shows some potential for application to the problem of extracting attenuation and backscatter coefficients in an inhomogeneous atmosphere from the return signal of a monostatic single-wavelength lidar system. The method assumes the validity of the single-scattering lidar equation and a power law relationship between backscatter and attenuation. For optical depths greater than unity the inversion method can be applied in principle using only information contained in the signal itself. In contrast to a well-known related analytical inversion solution, the new solution form is shown to be stable with respect to perturbations in the signal, the postulated relationship between backscatter and attenuation, and the assumed or estimated boundary value of attenuation.

Lidar inversion with variable backscatter/extinction ratios.

The conventional approach to solving the single-scattering lidar equation makes use of the assumption of a power law relation between backscatter and extinction with a fixed exponent and constant of proportionality. An alternative formulation is given herein which assumes the proportionality factor in the power law relationship is itself a function of range or extinction. The resulting lidar equation is solvable as before, and examples are given to show how even an approximate description of deviations from the power law form can yield an improved inversion solution for the extinction. A further generalization is given which includes the effects of a background of Rayleigh scatterers.

Approximate methods for modeling the scattering properties of nonspherical particles: evaluation of the Wentzel-Kramers-Brillouin method.

Several approximate methods for modeling the electromagnetic (em) scattering properties of nonspherical particles are examined and evaluated. Although some of the approaches are applicable to arbitrary shapes we confine our attention here mainly to spheres and cylinders, for which exact solutions are available for comparisons. Evaluations include comparisons of the computed angular phase function, total extinction efficiency, and backscatter efficiency. Approximate methods investigated include the Rayleigh-Gans (RG) approximation, the Wentzel-Kramers-Brillouin or WKB approximation [and the closely related eikonal approximation (EA)], diffraction theory, and the second-order Shifrin iterative technique. Examples using spheres indicate that for weakly absorbing particles of moderate- to large-size parameters with a real refractive index near unity (i.e., the optically soft case), all models work well in representing the phase function over all scattering angles, with the Shifrin approximation showing the best agreement with the exact solutions. For larger refractive indices, however, the Shifrin approximation breaks down, whereas the WKB method continues to perform relatively well for all scattering angles over a wide range of particle sizes, including those appropriate in both the RG (small particle) and the diffraction (large particle) limits. The relationship between the WKB, eikonal, and anomalous diffraction descriptions of particle extinction is discussed briefly. Backscatter is also discussed in the context of the WKB model, and two modifications to improve the description are included: one to add an internal-reflected internal wave and the other to add a multiplicative scaling factor to preserve the correct backscatter result for strong absorption in the geometric optics limit. A major conclusion of the paper is that the WKB method offers a viable alternative to the more widely used RG and diffraction approximations and is a method that offers significant improvement in accuracy with only a slight increase in mathematical complexity.

Intraocular pressure more reduced during anesthesia with propofol than with sevoflurane: both combined with remifentanil.

BACKGROUND: Short-acting anesthetic agents are suitable and commonly used in ocular surgery. Propofol and remifentanil are known to reduce intraocular pressure (IOP), but no information is available regarding the effects of sevoflurane combined with remifentanil on IOP. METHODS: Therefore, a prospective, randomized study was conducted to compare the effects on IOP of two different anesthetic techniques: one based on a total intravenous anesthesia with propofol (Group P, bolus 1.5-2.0 mg/kg, maintenance 3.0-7.0 mg/kg/h); and the other based on sevoflurane (Group S, inhalational induction, end-tidal concentration 0.7-1.2 vol.%). An infusion of remifentanil (10 microg/kg/h) was used with both techniques. In ASA I-III patients with normal IOP undergoing elective cataract surgery, using an applanation tonometer, IOP was measured contralateral to the operated eye at nine predefined time points before, during and after anesthesia. RESULTS: The two groups (n=20 each) were comparable with regard to demographic data and hemodynamic variables. Baseline IOP was 14.2+/-2.8 mmHg (Group P) and 14.1+/-2.4 mmHg (Group S; NS). During and following the induction of anesthesia, IOP was reduced in both groups. Intraocular pressure was significantly lower in Group P (6.0+/-3.2 mmHg) than in Group S (8.9+/-3.4 mmHg) during the induction of anesthesia. CONCLUSION: In patients undergoing cataract surgery under general anesthesia with tracheal intubation, anesthetic regimens with propofol as well as with sevoflurane, both combined with remifentanil, decrease IOP significantly. The decrease in IOP was significantly more pronounced in the propofol group than in the sevoflurane group.