The incompatibility of knowledge regimes: consequences of the material world for cross-domain work

In this paper, we argue that successful integration of knowledge across work domains in the short-term can mask the generation of long-term consequences. We explore a setting, the introduction of environmental considerations into semiconductor manufacturing, where the eventual adoption of common measurement artifacts and associated practices enabled knowledge integration, but failed to address significant underlying consequences. Drawing from observational, interview, and archival data we develop an understanding of the work practices of the Tech and EnviroTech groups as structured by the material world and broader collective conventions. We introduce the concept of knowledge regime to outline the differences in knowledge across these work domains. More specifically, we find that differences in the causal specificity and developmental time horizon of knowledge and the measurement artifacts that result contribute to the relative power of one knowledge regime over another. Understanding these sources of incompatibility provides insight into the design requirements of information systems as boundary objects for knowledge integration, but also specifies the potential limits to any design effort.     

Superconducting control for surge currents

Systems designed to use superconductors to limit fault currents in power grids are undergoing testing. The authors describe superconducting fault current limiters (SCFCL) which may be categorised into resistive or shielded core types. The features and operation of each type of device are outlined. Both the shielded-core and resistive types of SCFCL use the same amount of superconductor material to achieve a given limitation behavior. This is because the rated power per volume of conductor is determined by the product of fault-induced field and critical current, which is the same for both devices, assuming the same type of superconducting material is employed. The shielded-core limiter works only with AC currents and is much larger and heavier than the resistive SCFCL. While there is only one large program left in the low-temperature type of SCFCL, more than 10 major projects are under way worldwide on the high-temperature type of device. The main reason is the lower HTS cooling cost     

Virus load as a marker of disease progression in HIV-infected children

The relationship of virus load to clinical disease progression in HIV-infected children remains to be elucidated. In this study, HIV-1 proviral DNA load was determined in peripheral blood mononuclear cells (PBMCs) by the quantitative competitive DNA polymerase chain reaction assay (QC-PCR) in 47 HIV-infected children subdivided by age (group I, < or = 2 years; group II, > or = 5 years), who were further categorized to include 12 rapid progressors (RP, age < or = 2 years, Centers for Disease Control [CDC] defined clinical category C and/or immune category 3, or death before age 2 years) and slow progressors (SP, age > or = 5 years, excluding CDC categories C and/or immune category 3). Significantly higher mean proviral copies/10(3) PBMCs were detected in group I versus group II (75.4 +/- 104.3 and 13.0 +/- 17.8 respectively, p < 0.0001) and in RP (158.0 +/- 118.2) as compared to either SP (11.8 +/- 18.8, p < 0.0001) or other age-matched infected children (20.3 +/- 38.8, p < 0.0001). Thus HIV-infected children appear to have a higher cell-associated virus load early in life, especially in association with rapid disease progression.     

Allergy and depression: A neurochemical threshold model of the relation between the illnesses.

Empirical studies suggest a very high prevalence of atopic disorder in people with depression. Research indicates that individuals with allergy have cholinergic hyperresponsiveness and beta-adrenergic hyporesponsiveness in the autonomic nervous system. Evidence is reviewed that similar imbalances in CNS cholinergic–adrenergic activity play a causal role in depression behaviors. It is hypothesized that the allergic state or allergic reactions can accentuate cholinergic–adrenergic activity imbalances in the CNS of a small subgroup of people at risk for endogenous depression thereby producing depression symptomatology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of leaf-spring with aircushion trailer suspensions in the transport environment

Packaging engineers need to be able to accurately determine the forces present in the shipping environment in order to protect packaged goods. The purpose of this study was to determine the vertical vibration levels measured in three separate truck-trailer suspension systems; conventional leaf-spring, conventional air-ride and damaged air-ride. The main conclusion reached in this study is that the air-ride suspension when maintained gives lower power density (PD) levels on all road surfaces studied. A damaged air-ride suspension and leaf-spring suspension are very similar in response frequencies, although the damaged air-ride produces higher vibration levels at lower frequencies.     

β-Si3N4Whiskers Embedded in Oxynitride Glasses: Interfacial Microstructure

Interfacial microstructures in βP-Si₃N₄( w )-Si-Al-Y-O-N-glass systems were investigated by systematically varying the nitrogen content and the Al:Y ratio of the glass matrix. High-resolution and analytical transmission electron microscopy (HREM and AEM) studies revealed that the interfacial microstructure is a function of the glass composition. No interfacial phases were formed in glasses with low Al:Y ratios and in glasses with high Al:Y ratios and low nitrogen content, whereas epitaxial growth of an interfacial layer (100–200 μm thick) on the βP-Si₃N₄( w ) occurred in a glass matrix with high Al:Y ratio and high nitrogen content. The interfacial layer was identified to be a β'-SiAION phase. Interfaces containing the SiAION layer exhibited high debonding energy compared to Si₃N₄( w )–glass interfaces. HREM studies indicated that the lattice-mismatch strain in the SiAION layer was relieved by dislocation formation at the SiAION–Si₃N₄( w ) interface. The difference in interfacial debonding energy was, hence, attributed to the local atomic structure and bonding between the glass-β-Si₃N₄ and the glass–β'-SiAION phases. This observation was clear evidence of the strong influence of glass chemistry on the interfacial debonding behavior by altering the interfacial microstructure.     

Reaction of zirconium fluoride glass with water: kinetics of dissolution

When liquid water contacts a zirconium-barium-lanthanum fluoride glass, at least three different processes occur. Barium and zirconium fluoride dissolve into the water, water penetrates into the glass, and zirconium fluoride crystals grow on the glass surface, in static solution. The rate of dissolution, as measured by solution analysis, is possibly controlled by diffusion in the solid surface; surface blockage and surface reactions are other possible kinetic steps involved. Diffusion in solution is not the controlling mechanism. Hydrogen profiles in the glass surface suggest that the penetration rate of water into the glass is controlled by diffusion and a surface reaction.