Importance and reduction of the sidewall-induced band-broadening effect in pressure-driven microfabricated columns

The influence of the detailed design of the sidewall region upon the over-all band-broadening in microfabricated packed-bed or collocated monolithic support structure (COMOSS) columns has been investigated using computational fluid dynamics (CFD) simulation techniques. It is shown that, under unretained solute conditions, very small structural variations of the order of only 5% of the particle diameter can give rise to a 4-fold increase of the band-broadening. A comprehensive study has been made to quantify this effect as a function of the fluid velocity, the particle diameter, the channel widths, and of course, the sidewall region design. Because the sidewall effect can be fully attributed to a mismatch between the flow rates in the column center and in the sidewall region, it is fortunately also quite straightforward to avoid it. A very simple design, yielding band-broadening values identical to that of a hypothetical sidewall-less column for all possible values of the flow velocity, the particle diameter, or the channel width is proposed.     

Class of majority-logic-decodable codes with a minimum distance of 4

We prove that the (n = 4a2 + 4a + l, k = 4a2) binary code generated by 1+X2a+X2a+1+X4a+1 has a minimum distance of 4 and is 1-step majority-Iogic-decodable.     

Stabilization of a chitinase from Serratia marcescens by Gly->Ala and Xxx->Pro mutations

This paper describes attempts to increase the kinetic stabilityof chitinase B from Serratia marcescens (ChiB) by the introductionof semi-automatically designed rigidifying mutations of theGlyAla and XxxPro type. Of 15 single mutants, several displayedsignificant increases in thermal stability, whereas most mutantsshowed minor effects. All mutations with non-marginal effectson stability clustered in a limited, surface-exposed regionof the enzyme, indicating that this region is involved in apartial unfolding process that triggers irreversible thermalinactivation (aggregation). A double mutant containing two stabilizingmutations in this region (G188A, A234P) displayed a 10-foldincrease in half-life at 57°C and a 4.2°C increase inapparent T_m. These results show that entropic stabilizationworks well for ChiB and they pinpoint a region whose unfoldingmay be crucial for the kinetic stability of this enzyme. Received June 18, 2003; revised September 3, 2003; accepted September 12, 2003.     

Using matrix peaks to map topography: increased mass resolution and enhanced sensitivity in chemical imaging

It is well known in secondary ion mass spectrometry (SIMS) that sample topography leads to decreased mass resolution. Specifically, the ion's time of flight is dependent on where it was generated. Here, using matrix-enhanced SIMS, it is demonstrated that, in addition to increasing the yield of intact pseudomolecular ions, the matrix allows the user to semiquantitatively record the topography of a sample. Through mapping the topography-related mass shifts of the matrix (which leads to decreased mass resolution), the analogous mass shifts of higher mass ions can be deconvoluted and higher resolution and greater sensitivity obtained. Furthermore, the semiquantitative topographical map obtained can be compared with any chemical images obtained, allowing the user to quickly ascertain whether local intensity maximums are due to topological features or represent genuine features of interest.     

Validity of fixed-interval observations for postural assessment in construction work

While observing six simulated construction tasks in the field, trained analysts recorded arm, trunk and leg postures categorically with two fixed-interval observational protocols. Observations were compared to measurements obtained with an electronic postural assessment system coupled with video analysis. The electronic postural assessment system consisted of electronic inclinometers to measure upper arm posture, knee flexion and trunk flexion, coveralls to house the inclinometer wiring, and an eletrogoniometric system to measure trunk lateral bending and twisting. Video analysis included frozen-frame analysis that corresponded to the moment of observation and simulated real-time analysis. Measurements were made on five male participants who each performed three tasks representative of construction laborers' work. Agreement among the observational and reference methods was generally high, although significant differences in measured frequency of exposure existed for knee flexion, trunk lateral bending and trunk twisting. The results suggest that, under appropriate conditions, discrete observations can be used to obtain reasonably accurate estimates of exposure frequency for broad categories of certain body postures.     

Youth crowds and substance use: The impact of perceived group norm and multiple group identification.

The impact of group identity on adolescent tobacco, alcohol, and marijuana use was examined through a postal survey. The study included adolescents who identified with 1 subgroup (n = 1425) as well as adolescents who identified with 2 (n = 895) or 3 (n = 339) subgroups. The results showed that identification with the pop, skate/hip-hop, techno, and hippie subgroups was associated with higher risks of substance use, whereas identification with the sporty, quiet, computer nerd, and religious subgroups was associated with lower risks. Perceived group norm mediated the group identity-substance use relationship. Furthermore, identification with multiple groups with corresponding norm increased norm-consistent substance use, whereas identification with multiple groups with opposing norms reduced normative behavior. Implications for health promotion are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bubble chamber for fixed-target experiments at multi-TeV accelerators

A tentative layout for a huge argon bubble chamber/calorimeter/scintillation detector, to be used for neutrino experiments at a multi-TeV accelerator, is described. Such a detector can be operated in beams with various spill duration and it combines the features of a bubble chamber with properties of counter detectors.     

Nuclear data sensitivity/uncertainty analysis for XT-ADS

The XT-ADS, an accelerator-driven system for an experimental demonstration, has been investigated in the framework of IP EUROTRANS FP6 project. In this study, the sensitivity and uncertainty analyses were performed to comprehend the reliability of the XT-ADS neutronic design.