Synthesis and photovoltaic properties of mono-substituted quaterthiophenes bearing strong electron-withdrawing group

We report here on the synthesis and properties of a monosubstituted quaterthiophene derivative asymmetrically functionalized by an electron-withdrawing group using the palladium-catalyzed Stille's coupling reaction. The UV–vis absorption spectrum evidences a strong intramolecular charge transfer transition. Thus oligothiophenes act as electron donors and substituent group as acceptor. The diodes in which monosubstituted quaterthiophenes behave as organic semiconductors, exhibit a rectifying behavior. Photovoltaic measurements show moderate power conversion efficiency.     

Computer support for learning in collaborative contexts: prompted hypothesis testing in physics

An enormous amount of work has been carried out into the ways in which computers can support collaboration in the service of learning. Less attention has been paid to computer support for learning when collaboration is non-problematic, yet this is arguably of equal significance. Recognizing this, the present paper reports software which was developed to help collaborating pupils test hypotheses, an activity thought by many to be relevant to conceptual learning. The software addressed hypotheses relating to: (a) the factors which influence the pressure of water; and (b) the factors which influence the formation of shadows. It required collaborating pupils to formulate hypotheses about such factors, decide which factors must be manipulated to check correctness, formulate predictions about outcomes prior to testing, observe the results of tests, and draw conclusions across test series. Pupils were asked to input their decisions at key points as they used the software, and they received prompts to the extent that their decisions were inappropriate. The prompts became increasingly explicit as inappropriate decisions persisted. The paper describes the use of the software by 9–14-year-old pupils, comparing their activity with that of similarly aged pupils who worked with otherwise equivalent software which lacked any prompts. Evidence is presented for the value of prompting, with implications not simply for the use of hypothesis testing as an instructional strategy but also for the design of computer-based support for other complex and co-ordinated activities.     

Orientation and Feeding Responses of the Pollen Beetle, Meligethes aeneus, to Candytuft, Iberis amara

The pollen beetle, Meligethes aeneus, which is an important pest of oilseed rape, Brassica napus, and turnip rape, B. rapa var. campestris, does not oviposit in all species of the Brassicaceae. The relationship between M. aeneus and candytuft, Iberis amara (Brassicacae), was investigated as part of chemical ecological studies into the development of control methods employing non-host-derived repellents. In choice and nonchoice feeding tests, M. aeneus completely rejected I. amara. However, in a field experiment using traps baited with flowering racemes of I. amara and B. napus, M. aeneus was attracted to both species. Gas chromatographic (GC) and GC-electroantennogram (GC-EAG) analyses indicated that the profiles of the floral volatiles of the two species are different. At least 12 compounds among the I. amara floral volatiles were detected by the M. aeneus antenna, and, of these, hexanoic acid, (E)-4,8-dimethyl-1,3,7-nonatriene and alpha-cedrene were not found among B. napus flower volatiles. Since M. aeneus is stimulated by floral volatiles to approach I. amara, but rejects it near, or at, the plant surface, I. amara does not produce repellents that could be used to manipulate M. aeneus. However, it may contain feeding deterrent(s) that could be used in "push-pull" control techniques or in the development of resistant brassicaceous crops.     

Benzoic Acid Derivatives in a Hypogastrurid Collembolan: Temperature-Dependent Formation and Biological Significance as Deterrents

Two phenolic acids were identified in the collembolan Ceratophysella denticulata: 3-hydroxy-4,5 dimethoxy benzoic acid and 4-hydroxy-3,5-dimethoxybenzoic acid (syringic acid). These are localized on or in the integument of the springtail, in field-collected animals, in a ratio of 47:100 (v/v). Springtails kept under different temperature regimes showed differences in production and ratio of the benzoic acid derivatives. At 20 degrees C, C. denticulata produced only syringic acid, whereas at 10 degrees C both isomers in a ratio of 100:61 (v/v) were detected. Bioassays with C. denticulata as well as with the specialized collembolan predator Stenus comma (Staphylinidae) were carried out. Staphylinid beetles topically treated with the acids try to clean their mouthparts by rubbing them on the ground significantly more often than do control beetles. Both compounds individually and as a natural mixture have deterrent effects towards the predator S. comma.     

Production of Carbopol 974P and Carbopol 971P pellets by extrusion-spheronization: optimization of the processing parameters and water content

Pellets obtained by extrusion-spheronization represent multiparticulate dosage forms whose interest in intestinal drug delivery can be potentiated and targeted through bioadhesive properties. However, adhesion itself makes the process difficult or even impossible. The problem of tackiness encountered with bioadhesive wet masses was previously eliminated by the use of electrolytes such as CaCl₂. This approach is known to reduce the viscosity of polyacrylic acids by disturbing the interactions between carboxylate groups on adjacent polymer molecules, thereby decreasing their bioadhesive properties. The present study aimed at producing pellets containing carbomers without addition of electrolytes in order to maintain their bioadhesive potentiality at its maximum. Carbopol® 974P (10%, 15% and 20%) and Carbopol® 971P (10%) were used in combination with Avicel® PH101. The extrusion speed (30, 45, 60, 90, and 150 rpm), spheronizer speed (350, 700, 960, 1000, and 1300 rpm), spheronization time (5, 10, 15, and 20 minutes) and amount of water (45%, 50%, 54%, and 58%) were optimized in order to obtain the highest yield of spherical pellets ranging 710-1000 µm in diameter. For pellets containing 10%, 15% Carbopol® 974P or 10% Carbopol® 971P and 45% water content, 30 rpm extrusion speed, 960 rpm, and 10 minutes spheronization speed and time led to the highest yields and sphericities, respectively, 72% and 0.91, 67% and 0.78, and 76% and 0.80. Production of pellets with 20% Carbopol® 974P could be achieved through the increase of the water content up to 58% and implementation of 30 rpm extrusion speed, 1300 rpm, and 10 minutes spheronization speed and time. The yield and sphericity were 42% and 0.78 respectively.     

Equating student satisfaction measures

Colleges and universities conduct student satisfaction studies for many important policy making reasons. However the differences in instrumentation and the use of students' self-reported ratings of satisfaction makes such decisions sample-, instrument-, and institution-dependent. A common metric of student satisfaction would assist decision makers by providing a richness of information not typically obtained. The present study investigated the extent to which two nationally known instruments of student satisfaction could be scaled on the same quantitative metric. Pseudo-common item equating (Fisher, 1997) based on five link items of low and high endorsability enabled comparisons of "similar, but not identical items, from different instruments, calibrated on different samples" (p. 87). Results suggest that both instruments measured similar constructs and could be reasonably used to create a single, common metric. While samples used in the experiment were less than ideal, results clearly demonstrated the usefulness and reasonability of the pseudo-common item equating process.     

Multiple neural networks for a long term time series forecast

The artificial neural network (ANN) methodology has been used in various time series prediction applications. However, the accuracy of a neural network model may be seriously compromised when it is used recursively for making long-term multi-step predictions. This study presents a method using multiple ANNs to make a long term time series prediction. A multiple neural network (MNN) model is a group of neural networks that work together to solve a problem. In the proposed MNN approach, each component neural network makes forecasts at a different length of time ahead. The MNN method was applied to the problem of forecasting an hourly customer demand for gas at a compression station in Saskatchewan, Canada. The results showed that a MNN model performed better than a single ANN model for long term prediction.

Rapid Annealing Response of the Hardened 1802 Bulk CMOS Microprocessor

Rapid annealing test results show that the hardened RCA/Sandia 1802 Bulk CMOS Microprocessor will function immediately after application of intense ionizing radiation pulses. This result was established in LINAC tests using a comprehensive test procedure which exercised the ?P in logarithmic time intervals from 10 ?s to 1000 s. It was found that no loss of functionality occurs for doses up to about 280 KRads. At 790 KRads, the device initially loses functionality but anneals in 600 ms. At 1.6 MRads, the device loses functionality for 4 s, and at 2.4 MRads, the device loses functionality for at least 1000 s. A sample size of five devices was used. The 1802 ?P was tested using hardware and software especially designed for this purpose. The microprocessor was exercised using software routines of exponentially increasing length starting at 10 ?s after the pulse. A measure of ?P functionality was therefore provided at logarithmically increasing sample times, After 2 seconds was reached, the routines repeated every two seconds up to 1000 seconds when the test ended. The hardware and software are described in detail.     

Transfer of volatile substances from water to the atmosphere

Mass transfer coefficients and the degree of saturation of the exit gas are important parameters in transferring volatile organic substances from water to the atmosphere. Aeration systems in batch and continuous flow reactors are discussed based on theoretical analysis and experimental data. Three different ranges of the degree of saturation of the exit gas are introduced and their significance for model experiments and technical operations is evaluated. The effect of the aeration system and of surface active agents on the mass transfer coefficient of tetrachloroethylene is studied. Mass transfer coefficients for six nonpolar volatile organic compounds are presented. The stripping efficiencies of different types of gas-liquid contact devices used in water and waste water treatment are assessed.