Poly(3-hexylthiophene)/C60 heterojunction solar cells: Implication of morphology on performance and ambipolar charge collection

The performance of heterojunction organic solar cells is critically dependent on the morphology of the donor and acceptor components in the active film. We report results of photovoltaic devices consisting of bilayers and bulk heterojunctions using poly(3-hexylthiophene) (P3HT) and Buckminsterfullerene C₆₀. White light power efficiencies of η2.2% (bulk heterojunction) and 2.6% (bilayer) were measured after a thermal annealing step on completed devices. Optical and structural investigations on non-annealed bilayer thin films indicated a distinct porosity of the spin-coated polymer, which allows C₆₀ to penetrate the P3HT layer and to touch the anode. This resulted for these bilayer solar cells in the experimental observation that electrons were collected predominantly at the cathode after photo-excitation of P3HT, but predominantly at the anode after C₆₀ excitation. A morphological model to explain the ambipolar charge collection phenomenon is proposed.     

High-precision high-yield laser source using DFB array

We present high-yield efficient distributed-feedback lasers with excellent wavelength control. An array of 12 lasers with highly reflecting/antireflecting facets is fabricated on a single chip with precisely controlled variations in the grating period or phase relative to the facets. The stripe that best meets requirements is selected for bonding. From 200 unscreened chips, 93% contained lasers that achieved the specified power of 25 mW at 175 mA, 55/spl deg/C, and 41% achieved a /spl plusmn/0.1-nm wavelength tolerance at 25 mW, 55/spl deg/C. This low-cost high-precision device requires little thermal tuning for wavelength-division-multiplexed applications and reduces the power consumption of the transmitter.     

Long-range mapping and construction of a YAC contig within the cat eye syndrome critical region

Cat eye syndrome (CES) is typically associated with a supernumerary bisatellited marker chromosome derived from human chromosome 22pter to 22q11.2. The region of 22q duplicated in the typical CES marker chromosome extends between the centromere and locus D22S36. We have constructed a long-range restriction map of this region using pulsed-field gel electrophoresis and probes to 10 loci (11 probes). The map covers -3.6 Mb. We have also used 15 loci to construct a yeast artificial chromosome contig, which encompasses about half of the region critical to the production of the CES phenotype (centromere to D22S57). Thus, the CES critical region has been mapped and a substantial portion of it cloned in preparation for the isolation of genes in this region.     

Guides d’ondes enfouis dans des superréseaux GaAs-AIGaAs créés par interdiffusion induite par des impuretés

Heterostructures comprised of Al_xGa_1?xAs-Al_yGa_1?yAs As superlattices or quantum wells are compositionally stable up to very high temperatures but may become unstable with the introduction of particular impurities. The resulting layer interdiffusion leads to a compositionally averaged material. Since the introduction of impurities can be controlled by standard photolithographic masking techniques, the material properties can be modified in unmasked region. The disordered region has a wider bandgap and a lower index of refraction. This property has been used to fabricate delineated buried waveguides which exhibit very low propagation losses. Experimental results show that the index step between the layered and disordered region is at least 2.3 %. While not large in magnitude, this index difference is sufficient to allow complex waveguide structures to be made in the same materials used for other high performances opto-electronic devices.     

Birthweight and blood pressure among children in Harare, Zimbabwe

AIM: To determine whether poor uterine growth may be associated with increased blood pressure and subsequent hypertension in adulthood. METHODS: A retrospective cohort study of 756 schoolchildren (mean age 6.5 years) was carried out in six low income areas in Harare city, Zimbabwe. Indices of intrauterine growth and blood pressure were assessed. RESULTS: Adjusted for current weight, the children's systolic blood pressure was inversely related to their birthweight; for each decreasing kg of birthweight, systolic blood pressure rose by 1.73 mm Hg (95% CI; 0.181 to 3.28). After adjustment for current weight, systolic blood pressure was also inversely associated with occipito-frontal circumference, but not with birth length or gestational age. Diastolic blood pressure was not associated with any of the intrauterine indices. CONCLUSION: Fetal size may be inversely related to systolic blood pressure in childhood in an African population.     

Pre- and poststimulus activation of response channels: A psychophysiological analysis.

To examine mechanisms of response activation, we asked subjects to respond differentially to the central letter of one of four arrays—{hhhhh}, {sshss}, {sssss}, and {hhshh}—and measured event-related brain potentials (ERPs) and electromyographic activity (EMG). For very fast responses, accuracy was at chance level for all arrays, suggesting that subjects were guessing. For intermediate latency responses, accuracy was above chance if the noise was compatible with the targets and below chance if it was incompatible, suggesting that these responses were based on partial stimulus analysis. For slow responses, accuracy was above chance for all arrays, suggesting that these responses were based on complete stimulus analysis. The occurrence and accuracy of fast responses could be predicted by examining motor potentials preceding the presentation of the array. Measures of the motor potentials in the period following the presentation of the array suggested that partial analysis of stimulus information could activate responses and that the level of response activation at the time of the EMG response was constant for trials with different response latencies. The data are discussed in terms of a response channel conception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Complementary self-aligned laser by metalorganic chemical vapour deposition

A complementary two-step MOCVD growth technique for the self-aligned laser is described which eliminates any possible difficulty associated with regrowth on a high composition AlGaAs layer by placing the regrowth interface outside the stripe region. Single-longitudinal-mode operation with stable near and far-field patterns has been obtained to more than twice the laser threshold current.     

Soft-sensor models to estimate the efficiency of H2S removal from an oil refinery stream of nonphenolic sour water

A large set of results of concentration of hydrogen sulfide in the feed and bottom product streams of a sour water stripper found in a typical oil refinery was experimentally obtained. The readings of H₂S concentrations were at several different operating conditions in terms of the main process variables that classically have significant effects on the efficiency of H₂S removal (E). In particular, the considered factors were the mass flow rate, and temperature of sour water fed into the stripper, the mass flow rate of external steam injected into the reboiler, the difference between the temperature of the product stream leaving and entering the reboiler, and the difference of pressure at the two ends of the tower. Three different soft-sensor models were suggested to describe the observed variation in E from 63 to 97%, namely, an equilibrium, statistical and an artificial neural network model. The best of them was the neural network one with three input variables, four neurons in the one-hidden layer, and a hyperbolic tangent function for both the output and one-hidden layers. The mean absolute relative deviation between measured and calculated E by involving this model was only approximately 2.5% with negligible tendency for the residuals. It confirms the reliability of this approach as a tool to inferential estimation of the efficiency of removal of H₂S from the sour water by stripping.     

Euthanasia and physician-assisted suicide: attitudes and experiences of oncology patients, oncologists, and the public

BACKGROUND: Euthanasia and physician-assisted suicide are pressing public issues. We aimed to collect empirical data on these controversial interventions, particularly on the attitudes and experiences of oncology patients. METHODS: We interviewed, by telephone with vignette-style questions, 155 oncology patients, 355 oncologists, and 193 members of the public to assess their attitudes and experiences in relation to euthanasia and physician-assisted suicide. FINDINGS: About two thirds of oncology patients and the public found euthanasia and physician-assisted suicide acceptable for patients with unremitting pain. Oncology patients and the public found euthanasia and physician-assisted suicide least acceptable in vignettes involving "burden on the family" and "life viewed as meaningless". In no vignette--even for patients with unremitting pain--did a majority of oncologists find euthanasia or physician-assisted suicide ethically acceptable. Patients actually experiencing pain were more likely to find euthanasia or physician-assisted suicide unacceptable. More than a quarter of oncology patients had seriously thought about euthanasia or physician-assisted suicide and nearly 12 percent had seriously discussed these interventions with physicians or others. Patients with depression and psychological distress were significantly more likely to have seriously discussed euthanasia, hoarded drugs, or read Final Exit. More than half of oncologists had received requests for euthanasia or physician-assisted suicide. Nearly one in seven oncologists had carried out euthanasia or physician-assisted suicide. INTERPRETATION: Euthanasia and physician-assisted suicide are important issues in the care of terminally ill patients and while oncology patients experiencing pain are unlikely to desire these interventions patients with depression are more likely to request assistance in committing suicide. Patients who request such an intervention should be evaluated and, where appropriate, treated for depression before euthanasia can be discussed seriously.