Multiwavelength sources using laser diodes frequency-locked toatomic resonances

It is shown that low-cost compact disk AlGaAs laser diodes make it possible to realize manifold optical sources with precise and stable wavelengths when locked to rubidium vapor resonances. Many optical frequency references can be obtained with the use of absorption cells containing a foreign gas or by placing cells in static magnetic fields. The same approach can be used with other wavelengths required by optical fiber communications     

Solution-processed PbS quantum dot infrared photodetectors and photovoltaics

In contrast to traditional semiconductors, conjugated polymers provide ease of processing, low cost, physical flexibility and large area coverage. These active optoelectronic materials produce and harvest light efficiently in the visible spectrum. The same functions are required in the infrared for telecommunications (1,300-1,600 nm), thermal imaging (1,500 nm and beyond), biological imaging (transparent tissue windows at 800 nm and 1,100 nm), thermal photovoltaics (>1,900 nm), and solar cells (800-2,000 nm). Photoconductive polymer devices have yet to demonstrate sensitivity beyond approximately 800 nm (refs 2,3). Sensitizing conjugated polymers with infrared-active nanocrystal quantum dots provides a spectrally tunable means of accessing the infrared while maintaining the advantageous properties of polymers. Here we use such a nanocomposite approach in which PbS nanocrystals tuned by the quantum size effect sensitize the conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) into the infrared. We achieve, in a solution-processed device and with sensitivity far beyond 800 nm, harvesting of infrared-photogenerated carriers and the demonstration of an infrared photovoltaic effect. We also make use of the wavelength tunability afforded by the nanocrystals to show photocurrent spectra tailored to three different regions of the infrared spectrum.     

Website design in an international context: The role of gender in masculine versus feminine oriented countries

Previous research confirms there are differences between men and women concerning website design preferences. A few researchers have further suggested website preferences based on gender (i.e. whether one is a man or a woman) differ in countries that are typically considered higher in masculinity versus higher in femininity. As such, this supposes fewer differences exist between men and women in more feminine societies, while more significant differences occur in more masculine societies. To test this assumption, we survey a total of 955 participants located in six countries. More particularly, we examine design constructs of Information Content, Navigation Design, Visual Design modeled to Website Trust and Website Satisfaction. We are interested to determine if gender differences are strong in higher masculinity countries and weak in lower masculinity countries. We also investigate if gender moderates the various relationships in our model. As predicted, in higher masculinity countries there are more differences between men and women, and gender is more likely to moderate the relationships in the model. This research has implications for the complexity of website design preferences, and extends earlier work on website design in a multiple country sample where masculinity–femininity differs. Theoretical contributions and design issues are elaborated.     

AI-SIMCOG: a simulator for spiking neurons and multiple animats’ behaviours

Designing a biologically inspired neural architecture as a controller for a complete animat or physical robot environment, to test the hypotheses on intelligence or cognition is non-trivial, particularly, if the controller is a network of spiking neurons. As a result, simulators that integrate spike coding and artificial or real-world platforms are scarce. In this paper, we present artificial intelligence simulator of cognition, a software simulator designed to explore the computational power of pulsed coding at the level of small cognitive systems. Our focus is on convivial graphical user interface, real-time operation and multilevel Hebbian synaptic adaptation, accomplished through a set of non-linear dynamic weights and on-line, life-long modulation. Inclusions of transducer and hormone components, intrinsic oscillator and several learning functions in a discrete spiking neural algorithm are distinctive features of the software. Additional features are the easy link between the production of specific neural architectures and an artificial 2D-world simulator, where one or more animats implement an input–output transfer function in real-time, as do robots in the real world. As a result, the simulator code is exportable to a robot’s microprocessor. This realistic neural model is thus amenable to investigate several time related cognitive problems.

Self-administered questionnaire and direct observation by checklist: comparing two methods for physical exposure surveillance in a highly repetitive tasks plant

Background

We evaluated the agreement between a questionnaire and an observational checklist for exposure assessment in the setting of an upper-limb work-related musculoskeletal disorders (UWMSD) surveillance program in a population with a high level of physical exposures.

Methods

A surveillance program was implemented in a large shoe factory. Physical exposures were assessed in 1996 by a self-administered questionnaire and by the direct observation of work tasks assessed using a checklist filled out by trained assessors. Items were summed into a “questionnaire” score and an “observational” score. These scores were compared by Pearson's correlation. The association between exposure assessment by each method and UWMSD incidence between 1996 and 1997, defined by a standardized examination, was also studied.

Results

Correlation between the “questionnaire” score and the “observational” score was low among the 196 workers (77%) who received both evaluations (rho=0.06, p>0.05). Only exposure assessed by the questionnaire method was significantly associated with high incidence of UWMSD between 1996 and 1997, with good sensitivity (97%) and poor specificity (27%).

Conclusion

In this surveillance program, self-reported physical exposures assessed by questionnaire and by direct observation did not evaluate same dimensions of high physical exposures. In this sample, exposures assessed by questionnaire identified workers at high risk of incident UWMSD more precisely than exposures identified by direct observation.     

Flexibility analysis of a surface mount technology electronic assembly plant: An integrated model using simulation

This paper focuses on developing an integrated model using simulation to evaluate the effect of several independent variables on the performance of a surface mount technology (SMT) production line. Real data and an existing SMT line from a high product mix/low volume electronics manufacturer are used to conduct the analysis. The independent variables used are set-up formation policies (group technology based family grouping methods), machine feeder types, similarity factor in set-up formation, parts reduction at design step of products, and inter-families and intra-family scheduling rules. In addition, a new method of grouping products is proposed. The measures of performance evaluated by the model are average lead time, average work-in-process (WIP) inventory and average set-up time. Data analysis shows that the proposed method of grouping products will reduce set-up time and lead time while slightly increasing WIP. The proposed simulation model helps assess the effects of some of the independent variables on line performance. Recommendations are made in order to help the user choose the best alternative to improve production line productivity and flexibility.     

13C-NMR OF SOLID ORGANIC DEPOSITS ON SPENT HYDROPROCESSING CATALYSTS

Carbonaceous deposits on four spent hydroprocessing catalysts were studied using carbon-13 NMR spectroscopy with cross polarization/magic angle spinning (CP/MAS) and dipolar-dephasing technique. The spent catalysts were extracted with methylene chloride and methanol before analysis of insoluble organic material. These deposits, which are generally referred to as “coke”, were found to contain a significant proportion of aliphatic and hydroaromatic structures in addition to aromatic compounds. Different feedstocks and operating conditions formed carbonaceous deposits with different aliphatic carbon contents, ranging from a gas oil catalyst with 62% aliphatic carbon to a bitumen catalyst with only 9% aliphatic carbon. Qualitative dipolar-dephasing experiments showed that the amount of methyl carbon on gas oil catalysts was much greater than on catalysts used to treat naphtha or bitumen. This study shows that solid-state NMR spectroscopy can be used to quantitatively investigate the nature of catalyst residues formed under different conditions.     

Correlates of Attachment at Age 3: Construct Validity of the Preschool Attachment Classification System.

This study examined correlates of attachment at age 3 to further validate preschool separation-reunion measures. Three-year-olds (N = 150) and their mothers participated in a separation-reunion protocol, the Preschool Attachment Classification System (PACS: J. Cassidy & R. S. Marvin with the MacArthur Working Group on Attachment, 1992), and a mother-child interaction session during a laboratory visit. Mothers also completed psychosocial measures and, along with teachers, evaluated child behavior problems. The secure and disorganized groups received, respectively, the highest and lowest interaction scores. Disorganized children showed a higher level of teacher-reported externalizing and internalizing problems than did secure children. Mothers of insecure children reported higher child externalizing (all insecure groups) and internalizing (avoidant group) scores, more personal distress related to emotional bonding (disorganized group), childrearing control (ambivalent group), and child hyperactivity (avoidant group). Results strongly support the validity of the PACS as a measure of attachment in 3-year-olds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attachment at Early School Age and Developmental Risk: Examining Family Contexts and Behavior Problems of Controlling-Caregiving, Controlling-Punitive, and Behaviorally Disorganized Children.

Preschool to school-age trajectories of 242 children, including 37 with insecure-disorganized and 66 with insecure-organized attachment patterns, were examined. Child attachment and stressful life events (the latter retrospectively) were measured at ages 5-7, and mother-child interactive quality, parenting stress, marital satisfaction, and teacher-reported behavior problems were evaluated concurrently and 2 years earlier. Results indicated that all three disorganized subgroups had poorer mother-child interactive patterns and more difficult family climates than secure or insecure-organized children. The controlling-punitive group showed significant increases in maternal reports of child-related stress between preschool and school age. The controlling-caregiving group showed greater likelihood of loss of a close family member, and mothers of the insecure-other group reported lower marital satisfaction and greater likelihood of their own or a spouse's hospitalization. Controlling-punitive children had higher externalizing scores, and controlling-caregiving children higher internalizing scores, than secure children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fiber optic Raman sensor to monitor the concentration ratio of nitrogen and oxygen in a cryogenic mixture

A spontaneous Raman scattering optical fiber sensor was developed for a specific need of the National Aeronautics and Space Administration (NASA) for long-term detection and monitoring of the purity of liquid oxygen (LO(2)) in the oxidizer feed line during ground testing of rocket engines. The Raman peak intensity ratios for liquid nitrogen (LN(2)) and LO(2) with varied weight ratios (LN(2)/LO(2)) were analyzed for their applicability to impurity sensing. The study of the sensor performance with different excitation light sources has helped to design a miniaturized, cost-effective system for this application. The optimal system response time of this miniaturized sensor for LN(2)/LO(2) measurement was found to be in the range of a few seconds. It will need to be further reduced to the millisecond range for real-time, quantitative monitoring of the quality of cryogenic fluids in a harsh environment.