Photoelectrochemical Cells With Single-Crystal Cadmium Telluride and Alkaline Telluride, Ditelluride Redox Couple

In the photoelectrochemical cell Ga -In /n- CdTe (single crystal) 0.1 M Te2- , Te22-, OH- /Pt the efficiency of energy conversion of solar radiation (AM2 spectral distribution, 58 mW cm-2 was increased from the previously reported 5% to 9.0%, by etching the polished crystal surface, by making [Te2-] as large as practicable by using KOH as the supporting electrolyte, and by optimizing [Te22- At reduced irradiances the energy conversion efficiency was higher. At AM2, an efficiency of 14% is predicted to be attainable. Etching with chromic acid (Na2Cr2O7 in 3M HNO3) increased the open-circuit voltage in 0.1 M partly oxidized Na2Te, 5 M KOH, to 0.74 V from 0.48 V as observed on the polished but unetched crystal, and increased the short-circuit photocurrent density Jsc from 4 mA cm-2 to 13 mA cm-2 (AM2 spectral distribution, 58 mW cm-2. Etching reduced the surface defect concentration as recorded by two-beam photocurrent spectroscopy. For redox potentials Eredox more negative than - 1.12 V v . s.c.e . the crystal potential at open circuit Ec,oc was independent of the value of Eradox which was varied by changing [Te22-]; a change in Eredox therefore produced a quantitatively similar change in the open-circuit photovoltage Uoc (both at 1 mWcm-2 of 633 nm radiation and at AM2 solar radiation) and so Fermi-level pinning did not occur. Uoc was proportional to In Jsc . The very negative value of - 1.86 V v . s.c.e . observed for Ec,oc was attributed to adsorbed anionic charge, estimated as c.1013 elementary charges cm-2, which gave rise to a potential drop of 1.5 V across the Helmholtz layer.

School performance characteristics preceding onset of smoking in high school students

The cigarette smoking status of 1,442 high school students was determined by questionnaire. Of the respondents (smoking and nonsmoking), 60% had been enrolled in the same school system during elementary school. Thus, records were available of school absence, grades, achievement tests, and IQ tests during elementary school, prior to the time when the smokers had commenced the practice. Smoking in high school was significantly related to high absence rates, low achievement test scores, and low grade point averages during elementary school years, prior to the onset of smoking. The IQ was not significantly different in the third grade among pupils who became smokers in high school and those who did not, but sixth-grade IQ scores were significantly lower in students who later identified themselves as smokers. Although smokers demonstrated these characteristics prior to beginning smoking, the differences were not large enough to predict which elementary school students would become high school smokers. The findings support the view that smoking and these school-related characteristics may both be part of a "smoker life-style."

Alkaline Selenide, Polyselenide Electrolytes: Concentrations, Absorption-Spectra and Formal Potentials

Spectrophotometric, titrimetric, electron spin resonance and 77Se nuclear magnetic resonance studies made on the alkaline selenide, selenium electrolyte showed that soluble selenium species existed in four oxidation states, none of the species was a radical, and the mean state of oxidation of the Se-saturated solution was equivalent to Se3.82. It was concluded that the species were Sen2- with n = 1, 2, 3 and 4, or their protonated forms. On the basis of the Nernst equation, we analysed independently (A) the titration Eredox against the mean state of oxidation of the solution and (B) the absorption spectra of solutions with different mean states of oxidation. Thus formal redox potentials E′ were determined as E′12 = -0.935, E′13 = -0.931 and E′14 = -0.914 V against s.c.e. for the couples Se2-, Se22-; Se2-, Se32-; and Se2-, Se42- respectively in 1 mol dm-3 KOH supporting electrolyte at 304 K. It followed that E′23 = -0.919 for Se32-,Se32- and E′34 = -0.778 for Se32-,Se42-. The concentration of each species at each redox potential and the absorption spectrum of each distinct oxidation state were found. Excellent fits and agreement between the two analyses were observed. Ultraviolet absorption spectra showed that the reduced ion was approximately 50% protonated in 1 mol dm-3 KOH supporting electrolyte.

On the Flat-Band Potential and the Frequency Dispersion of Capacitance and Its Removal in an Normal-Cadmium Telluride in Alkaline Selenide, Polyselenide Photoelectrochemical Cell

When seepage of the electrolyte between the semiconductor crystal and its insulation was prevented, the equivalent series capacitance CS of an n-CdTe|Se2-, Sen2-,OH-|Pt cell was almost independent of frequency (<2% increase of CS per decade decrease of frequency) in the range 104-2 Hz. Attributing CS wholly to the space-charge capacitance resulted in a linear Mott- Schottky plot and this yielded a flat-band potential of -2.0�0.1 V v . s.c.e . and a built-in potential of 1.08�0.06 V. This was consistent with the observed current-voltage curves in both dark and light. Two conditions under which frequency dispersion was observed were (a) electrolyte seepage and (b) surface damage. The insulating techniques which allowed seepage were similar to those of other workers. The effects of these imperfections on the Mott- Schottky plot are considered. Attempts to extract useful information from frequency dispersion data showed that it is difficult or impossible to obtain a unambiguous equivalent circuit solely on the basis of goodness-of-fit of calculated to observed impedances. The ambiguity can be removed only when sufficient information beyond impedance-frequency data is available. For electrodes with seepage, a model due to Tomkiewicz led to the correct value of the built-in potential.

Blastomycosis in a Papanicolaou Smear. Report of a case with possible venereal transmission

An incidental case of cervical blastomycosis discovered by examination of a Papanicolaou smear is reported. Examinations revealed no other focus of blastomycosis in the patient. Since her husband was undergoing treatment for disseminated blastomycosis involving the lungs and prostate at the time the fungus was found, this case may represent venereally transmitted blastomycosis.

Uptake of Lipids by the Entomophilic Nematode Romanomermis culicivorax

Romanomermis culicivorax juveniles were dissected out of Aedes aegypti larvae 7 days after infection and incubated under controlled conditions in isotonic saline containing a (1)C-labeled fatty acid (palmitic acid), monoacylglycerol (glycerol monoolein), or triacylglycerol (glycerol tripalmate) nutrient source. The mermithid absorbed each of these lipids from the incubation medium, the rate of uptake being greatest for glycerol monoolein. No lipase activity was detected in whole nematode homogenates or in the media in which the nematodes were incubated. It is suggested that the nematode transports complex lipid molecules across its outer cuticle intact.