Dependence of the neodymium random laser threshold on the diameter of the pumped spot

We experimentally studied the dependence of the threshold energy density E/sub th//S in Nd/sub 0.5/La/sub 0.5/Al/sub 3/(BO/sub 3/)/sub 4/ random laser on the diameter of the pumped spot d and found that at d/spl ges/130/spl mu/m, E/sub th//S is proportional to 1/d+const. This functional dependence is different from the one commonly expected in the case of diffusion, /spl prop/1/d/sup 2/+const. However, the obtained experimental dependence does not mean the failure of the diffusion model. Calculating the mean photon's residence time /spl tau//sub res//sup p/ (which photons, making their diffusion-like random walks, spend inside the gain volume) as the function of d and further assuming that E/sub th//S/spl prop/(/spl tau//sup p//sub res/)/sup -1/, we predicted the experimentally obtained functional dependence, /spl prop/1/d+const. The major difference between our model and that of and was in the boundary conditions.     

Gender and age differences in employee decisions about new technology: an extension to the theory of planned behavior

This research extends the theory of planned behavior by incorporating gender and age as moderators of user perceptions and individual adoption and sustained use of technology in the workplace. Individual reactions and technology use behavior were studied over a six-month period among 342 workers being introduced to a new software technology application. While previous studies in the literature have reported gender or age differences separately, the pattern of results from the study reported here indicated that gender effects in individual adoption and use of technology differed based on age. Specifically, gender differences in technology perceptions became more pronounced among older workers, but a unisex pattern of results emerged among younger workers. The theory and empirical results are also discussed in relation to the widely employed technology acceptance model. The results from this study suggest that old stereotypes that portray "technology" as a male-oriented domain may be disappearing; particularly among younger workers. In light of these findings, theoretical implications for researchers and practical suggestions for managers are discussed.     

Effects of cooling rate on mechanical properties of near-eutectic tin-lead solder joints

This paper reports the results of a study on the effect of the cooling rate during solidification on the shear creep and low cycle shear fatigue behavior of 60 Sn/40 Pb solder joints, and on bulk solder tensile properties. Solder joints were made with three different initial microstructures by quenching, air-cooling and furnace-cooling. They have similar steady-state strain rates under creep at relatively high shear stresses (i.e. in the matrix creep region) but creep at quite different strain rates at lower shear stresses (i.e. in the grain boundary creep region). These results are ascribed to the refined grain size and less lamellar phase morphology that results on increasing the cooling rate. Tensile tests on bulk solders that were cold-worked, quenched and furnace-cooled show that a faster cooling rate decreases the ultimate strength and increases the ductility at low strain rates. The fatigue life of quenched solder joints is shown to be longer than that of the furnace-cooled joints.     

Toughening Mechanisms in Cemented Carbides

Plastic zones much larger than previously expected have been observed around cracks in several cemented carbide materials. A preliminary estimate of the crack tip shielding due to the plastic zone in one material suggests that a substantial fraction of the fracture toughness may be due to the zone. Moreover, reduced zone sizes were observed in regions of rapid crack growth, implying that the dynamic fracture toughness may be smaller than the quasi-static value.     

A Modular Vaccine Platform Combining Self‐Assembled Peptide Cages and Immunogenic Peptides

Subunit vaccines use delivery platforms to present minimal antigenic components for immunization. The benefits of such systems include multivalency, self‐adjuvanting properties, and more specific immune responses. Previously, the design, synthesis, and characterization of self‐assembling peptide cages (SAGEs) have been reported. In these, de novo peptides are combined to make hubs that assemble into nanoparticles when mixed in aqueous solution. Here it is shown that SAGEs are nontoxic particles with potential as accessible synthetic peptide scaffolds for the delivery of immunogenic components. To this end, SAGEs functionalized with the model antigenic peptides tetanus toxoid_632‐651 and ovalbumin_323‐339 drive antigen‐specific responses both in vitro and in vivo, eliciting both CD4⁺ T cell and B cell responses. Additionally, SAGEs functionalized with the antigenic peptide hemagglutinin_518‐526 from the influenza virus are also able to drive a CD8⁺ T cell response in vivo. This work demonstrates the potential of SAGEs to act as a modular scaffold for antigen delivery, capable of inducing and boosting specific and tailored immune responses.     

Satellites for communications and broadcasting: The evolving european market

The paper traces the development of the market for communications and direct broadcasting satellites in Europe, since the original specification of the European Communications Satellite (ECS) in 1977. It reviews the experiments undertaken on the Orbital Test Satellite (OTS) and the way in which demonstrations with this satellite have influenced the way in which ECS is being developed. It continues by considering the impact of television on the market, first cable television and its distribution requirements, then direct broadcasting by satellite, where the introduction of homes into the customer configuration will bring with it programme content as a salient feature in market development. Finally it speculates on the possibilities for the future, both in terms of the effect of new and higher frequencies on satellite communications systems, and the possible effects that interaction from small earth-stations could have on satellite design.     

UNICORE 6 — Recent and Future Advancements

UNICORE is a European Grid Technology with more than 10 years of history. Originating from the Supercomputing domain, the latest version UNICORE 6 has turned into a general-purpose Grid technology that follows established standards and offers a rich set of features to its users. The paper starts with an architectural insight into UNICORE 6, highlighting the workflow features, standards and the different clients. Next, the current state of advancement is presented by describing recent developments. The paper closes with an outlook on future planned developments.     

A formal approach to specifying assembly operations

Experience has proved that exploiting robots for assembly tasks is much more difficult than manufacturing engineers had expected and many attempts at implementing robotic assembly have failed. Our research has led us to believe that a formal approach to specifying the steps required for assembly would be of great benefit in developing the required software for a specific task, and in adaptively controlling and monitoring the execution of robotic assembly steps. The US National Bureau of Standards has developed a formal system, called ABC (for Assembly By Constraints) for specifying the steps required for assembly. The system is based on the reduction in the degrees of freedom of objects as they are assembled. Using this basic concept, we have developed 14 primitive operations which can be used to completely specify assembly steps for a large class of problems. This paper initially outlines the historical development of the system, then describes two pieces of software developed to allow easy definition of assembly tasks using the ABC system, and finally presents two practical examples.     

Optical receiver array in silicon bipolar technology with selfaligned, low parasitic III/V detectors for DC-1 Gbit/s parallel links

A 1*8 element III-V photodetector/silicon bipolar circuit receiver array has been fabricated using a selfaligning, low parasitic, flipchip solder bond hybridisation process. Receiver elements operate at data rates up to 1 Gbit/s with an input sensitivity of -23 dBm at 1.3 mu m wavelength, and with negligible interchannel crosstalk. An overall delay of 1.5 ns was measured between optical input and digital output.<>     

High efficiency organic photovoltaic cells based on inverted SubPc/C60/ITO cascade junctions

Conventional heterojunction organic photovoltaic cells typically involve the deposition of the electron donor layer (or donor–acceptor blend) on top of a transparent anode, with the cathode deposited last. Inverting the structure and deposition sequence usually worsens the performance characteristics, except device lifetime. We compare conventional (SubPc/C₆₀) and inverted (C₆₀/SubPc) junctions, the latter exhibiting a power conversion efficiency of 3.5%. We also find a significant trade-off between the open circuit voltage and short circuit photocurrent, potentially attributable to the formation of a C₆₀/ITO Schottky junction, and a change from exciton-quenching to exciton-blocking behavior of the SubPc:MoO_X interface in inverted devices.