Sum-Frequency Generation of Femtosecond Pulses in CsLiB(6)O(10) Down to 175 nm

Using a 150-mum-thick CsLiB(6)O(10) crystal, we produced 100-fs, >200-nJ light pulses tunable between 175 and 180 nm by sum-frequency generation at a 1-kHz repetition rate with an all-solid-state laser system mixing the fourth harmonic of a femtosecond Ti:sapphire regenerative amplifier and the idler pulse from a traveling-wave optical parametric amplifier.     

Modular visions: Referents, context and strategies for database open media works

The processes of constructing meaning in digital database environments entail a paradigm shift from previous models of audio-visual communication. Media emerging from the Electro-mechanical era (film/TV/video) present fixed spatio-temporal linearity and material conditions which objectify and render passive viewer and process. The problematic aspects of cinematic communication were addressed by Latin American filmmakers of the Third Cinema movement. Their concerns and approach presaged and assisted an understanding of the radical redefinition of audio-visual communication possible with digital databases. The conceptual and aesthetic aspirations of Third Cinema artists such as Julio Garcia Espinosa and Fernando Solanas were ultimately contradictory to linear media and find their fitting medium in digital modular construction. The materiality of database expression lacks an intrinsic temporal or spatial state and permits a more dynamic and multidirectional set of power relationships between author/s, piece, viewer/s. Other important referents for contextualising database art are modern art practitioners that rejected linear representational space and fractured the centrality of authorship. The author's own work, ...two, three, many Guevaras, an exploratory database environment, embraces the redefinition of process as artistic expression, the empowerment of interacting generative forces, and serves to illustrate the revolutionary potential of the new media.     

Syndiospecific polymerization of propene under different processes with different bridged [(RPh)2C(Cp)(2,7-BuFlu)]ZrCl2 metallocene catalysts

The synthesis of syndiotactic polypropene was achieved by using new C_S-symmetric ansa-metallocene catalysts of the type [Ph′₂C(Cp)(2,7-^tertBu₂Flu)]ZrCl₂ (Ph′₂=Ph₂, (4-MePh)₂, 3,4′-Me₂Ph₂, (4-OCH₃Ph)₂). Applying these catalysts, the influence of the substitution pattern of the bridge on the polymerization performance can be studied and highly syndiotactic polypropene (rrrr>99%) with high molar masses and high melting temperatures (up to 153 °C) was obtained.Propene was polymerized at different temperatures under four sets of conditions: in toluene solution, bulk, toluene slurry, and gas phase with NaCl as stirred bed material. Methylaluminoxane (MAO) and methylaluminoxane supported on silicagel (MAO/SiO₂) were used as cocatalyst, respectively. In order to estimate the influence of the process on the single site properties of the catalysts, comparisons were made between polymer properties, i.e. microstructure, melting temperature, molar mass, and polymer morphology, thus allowing the effect of the support on the catalyst to be observed.     

Biomechanical assessment of new hand-powered pruning shears

The aim of the study was to assess the biomechanical strains on the hand-wrist system during grapevine pruning with newly designed pruning shears. Surface electromyography of the finger flexor muscle and wrist postures were analyzed in four vineyard workers during actual work with the new and reference hand-powered pruning shears. Due to the large inter-individual differences in biomechanical data observed with both pruning shears, no systematic effect of the new pruning shears on "extreme" flexion/extension (F/E) and ulnar/radial (U/R) wrist deviations was demonstrated. However, the use of the new pruning shears was associated with a higher frequency of "neutral and moderate" U/R deviations (U/R < 20%(max)) and, to a lesser extent, of "neutral and moderate" F/E deviations (F/E < 20%(max)). Due to the small sample of workers, this result must be confirmed in a larger population of vineyard workers.     

Some aspects of the biology of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), a pest of stored groundnuts in Nigeria

The biology of Plodia interpunctella (Hübner) was studied at various combinations of temperature and relative humidity. The incubation period of eggs ranged from 4 to 7 days. Development from laying of egg to adult lasted an average of 50.9 days at 25°C and 60% r.h. and 34.6 days at 30°C and 80% r.h. At 70 and 80% relative humidity, development was faster, more progeny were produced and the moths were heavier than at 60% r.h. Relative humidity had little effect on egg and pupal development.The larvae were negatively phototactic. However, the rate of development of the strain studied was similar in constant darkness, constant light or in a 12 hr-light: 12 hr-dark light system. The adult moths were immobile in diffused daylight. Locomotory activity was markedly high at dusk and was accompanied by an increase in the rate of pairing. Temperatures between 27 and 31°C did not appear to influence locomotory activity.Cracked groundnuts were more favourable for development than whole nuts which were in turn better than groundnut meal. The weight losses inflicted on infested groundnuts were directly correlated with the total weights of emerged moths and differed according to the treatment given to the medium. Losses in weight of about 8.7 and 8.6% were observed when 13 larvae completed development in 30 g of whole nuts and cracked nuts, respectively. Females consumed more food and were heavier than the males. Each larva ate an average of 140 mg of whole nuts and 190 mg of cracked groundnuts to complete development. The increases in free fatty acid values were not appreciably higher in infested media than in the control. Increases of 17.5 and 18.2 m-equiv of peroxides were observed in infested whole and cracked nuts, respectively.     

The Transformation of Computing: Riding the Wave

Abstract

In an IS world characterized by high stress and low unemployment, IS executives must not only secure scarce talent but also ensure that staffing patterns optimally meet corporate and IT goals. the staffing model presented here offers a new way of looking at IS culture, bringing IS in tandem with the strategic direction of the organization, and fostering ongoing, global assessment of overall IS performance.     

Vertically Aligned Hybrid Core/Shell Semiconductor Nanowires for Photonics Applications

A family of 1D organic/inorganic core/shell materials formed by an inner organic nanowire (ONW) conformally covered with an inorganic wide band gap semiconductor (ZnO or TiO₂) layer is presented. The developed procedure is a two‐steps vacuum methodology involving the formation of supported single crystal small‐molecule nanowires by physical vapor deposition and plasma enhance chemical vapor deposition (PECVD) of the inorganic shell. Critical characteristics of the last technique are the possibilities of low temperature and remote configuration deposition. Additionally, an initial step has to be included in order to create nucleation centers for the growth of the ONWs. The procedure and its general character in terms of the variability in organic core and inorganic shells composition and the applicability of the technique to different substrates are presented. The formation of the inorganic shell with no damage of the organic core single‐crystalline structure is demonstrated by high resolution transmission electron microscopy. The vertical alignment of the hybrid nanostructure is achieved thanks to the interaction of the 1D organic nanostructured surfaces and the glow discharge during the deposition of the inorganic shell by PECVD. The optical properties of these core/shell NWs are studied by fluorescence spectroscopy and microscopy, and their application as nanoscale waveguides in the 550–750 nm range addressed.     

The Case of a Broken Plank

A construction worker was seriously injured after falling from a roof to a concrete floor. He was working on a plank while placing insulation material when the accident occurred. The plank broke into three pieces. Visual observation of the plank indicated a relatively new plank. Further investigation of the plank revealed a grade of structural plank no. 2. A common practice is for a construction worker to use scaffold grade plank, which has twice the capacity of a structural grade plank. This represents the most probable procedural cause of the plank's failure. The most probable enabling cause (internal cause) of the failure is a local split at the midspan, whereas the most probable triggering cause (external cause) is the impact loads produced by the weight of the worker and the insulation material he carried while walking on the plank. The study also concluded a failure mechanism that was initiated by a longitudinal split at the midspan of the plank. The split weakened the plank and led to a transverse break at the midspan.     

Analysis of Causes of Falsework Failures in Concrete Structures

A study of 85 major falsework collapses of bridges and buildings in the past 23 yrs has documented the types of collapsed falseworks and failed permanent structures, the construction stages at the time of collapse, and the causes of failures. Three causes of failure were identified: triggering; enabling; and procedural causes. Most failures occurred because of the interaction of the triggering and enabling events that were, in many cases, produced by inadequacies in the procedural methods. Impact forces resulting from concreting operations have repeatedly triggered falsework failures that were enabled by deficiencies in the falsework bracings, components, connections, foundations, and design. Inadequate review of falsework design and monitoring procedures were frequent problems that facilitated the occurrernce of these events. The findings emphasize the importance of proper delineation of responsibility of each party in the building process in order to reduce falsework failures in the future.     

Surface chemistry of phosphorus-containing carbons of lignocellulosic origin

Activated carbon adsorbents were prepared by phosphoric acid activation of fruit stones in an argon atmosphere at various temperatures in the 400-1000 °C range and at different acid/precursor impregnation ratios (0.63-1.02). The surface chemistry of the carbons was investigated by elemental analysis, cation exchange capacity (CEC, measured by neutralization of NaOH with acidic surface groups), infrared spectroscopy and potentiometric titration. Porous structure was derived from adsorption isotherms (N₂ at −196 °C and CO₂ at 0 °C). It was demonstrated that all carbons show considerable cation exchange capacity, the maximum (CEC = 2.2 mmol g⁻¹) being attained at 800 °C, which coincides with the maximum contents of phosphorus and oxygen. The cation exchange properties of phosphoric acid activated carbons from fruit stones are chemically stable in very acidic and basic solutions. Proton affinity distributions of all carbons show the presence of three types of surface groups with pK at 2.0-3.3, 4.6-5.9 and 7.6-9.1. These pK ranges were ascribed primarily to: (a) phosphorus-containing and carboxylic groups; (b) lactonic groups, and (c) phenolic groups, respectively. Phosphoric acid activated carbons are microporous with a relatively small contribution of mesopores. A maximum BET surface area of 1740 m² g⁻¹ was attained at 400 °C.