Precipitation in the system Al-0.05 wt pct Fe

The precipitation reaction in an aluminum alloy containing 0.05 wt pct Fe (enriched in Fe⁵⁷) was studied using Mössbauer spectroscopy. It was found that in addition to the equilibrium precipitate, Fe Al₃, the metastable phase FeAl₆ occurs as well. Formation of FeAl₆ is favored when the rate of precipitation is accelerated by cold working the supersaturated alloy. Step anneal experiments were performed in an effort to determine an activation energy for growth of precipitate particles. The results of these experiments are not entirely consistent with simple models of the nucleation and growth process.     

Asymptotic analysis of laminar flame propagation: Review and extension

The structure of a steady 1-dimensional isobaric deflagration is analysed in the physical plane for the case of a direct first-order one-step irreversible exothermic unimolecular decomposition under Arrhenius kinetics. In particular, the eigenvalue giving the speed of propagation of the laminar flame into the unburned gas is sought for Lewis-Semenov number unity. Limit-process expansion techniques are applied for the physically interesting limit of activation temperature large relative to the adiabatic flame temperature. Through consideration of the higher-order contributions to the asymptotic solutions for the downstream reactive-diffusive zone and the upstream convective-diffusive zone of the laminar flame, the physical-plane anslysis brings out details of the flame structure, including the two-region character of the downstream zone, not brought out in the conventional phase-plane analysis. Applications of the results of this analysis to more general deflagration problems are discussed.     

Mobile ATM buffer capacity analysis

This paper extends a stochastic theory for buffer fill distribution for multiple on and off sources to a mobile environment. Queue fill distribution is described by a set of differential equations assuming sources alternate asynchronously between exponentially distributed periods in on and off states. This paper includes the probabilities that mobile sources have links to a given queue. The sources represent mobile user nodes, and the queue represents the capacity of a switch. This paper presents a method of analysis which uses mobile parameters such as speed, call rates per unit area, cell area, and call duration and determines queue fill distribution at the ATM cell level. The analytic results are compared with simulation results.This paper is partially funded by ARPA contract number J-FBI-94-223.The Mathematica code for this paper can be found on http://www.tisl.ukans.edu/sbush.     

Symbiosis and Software Evolvability

Software systems need to evolve to adapt to either a new environment or a new requirement. This position paper discusses the evolution of a software system from the viewpoint of an ecosystem and asserts that the evolution of a software system is not a standalone process but an aggregate process of other related software systems that forms a software ecosystem. This paper describes several of our ongoing projects in studying different types of symbiotic relationships between software systems and their effects on software evolvability.     

Differences among sibling speciesRhagoletis mendax andR. pomonella (diptera: ephritidae) in their antennal sensitivity to host fruit compounds

Prior electrophoretic and morphological studies have identified two closely related, economically important tephritid flies,R. mendax (Curran) andR. pomonella (Walsh), which infest the fruits of ericaceous and rosaceous plants, respectively. Further studies also have shown consistent differences among these species in their ovipositional preferences for apples and highbush blueberries and have determined that their ovipositional behavior is elicited by extracts obtained from these fruits. In this paper we report the results of an experiment that tested whether these species show distinct electroantennogram (EAG) responses to a large array of compounds present in gas chromatograph-fractionated pentane extracts of apples and highbush blueberries.R. mendax andR. pomonella flies were found to have significant differences in their antennal sensitivity to 11 blueberry and nine apple extract peaks, which correspond to 24.4% of all blueberry and 25.0% of all apple peaks that elicited a measurable EAG response from either species. Interspecific differences in peripheral sensitivity were more pronounced for blueberry than apple extract;R. pomonella flies were most sensitive to blueberry compounds with low retention times, whereasR. mendax flies responded to blueberry compounds with a broader range of retention times. Both species were most sensitive to apple peaks with high retention times. The retention times of most apple and blueberry peaks that elicited EAG responses fromR. mendax andR. pomonella flies were different from the retention times of seven attractant fruit esters that were previously identified by Fein et al. (1982). The identification of these unknown apple and blueberry compounds could lead to the discovery of new chemical cues that mediate the host-plant preferences of these sibling species.     

Sediment desorption of PCB congeners and their bio-uptake by dipteran larvae

Sediment desorption of PCB congeners and their bio-uptake by Chironomus tentans Fabricus were investigated in a continuous flow system. The desorption of 71 congeners (in Aroclors 1221, 1016, 1254 and 1260) determined by glass capillary gas chromatography could be described by a first order function. The release rate of the individual congeners was inversely related to their octanol/water partition coefficients (K_ow). The depth of mobilization generally decreased with the number of chlorine substitutions and was inversely related to K_ow.Bio-uptake of the congeners by Chironomus tentans Fabricus was selective with the bio-uptake factor being highest for those with 2–4 chlorines. There was no correlation between the factor and either K_ow or desorption rate from the sediments.     

Randomized controlled trial of an intervention to prevent adherence failure among HIV-infected patients initiating antiretroviral therapy.

Objective: Compare the efficacy of a multicomponent social support intervention to standard-of-care counseling on medication adherence among HIV-infected patients initiating antiretroviral therapy. Design: Randomized controlled trial. Generalized estimating equations tested for differences in the percentage of participants achieving 90% adherence. Main Outcome Measures: Pill-taking, electronically monitored over 6 consecutive months; plasma viral load (VL), assessed at 3 and 6 months following initiation of therapy. Results: Of 226 participants who were randomized and began the trial, 87 (38%) were lost to the study by 6 months. The proportion of adherent participants declined steadily over time, with no time by group interaction. Sustained adherence was associated with increased odds of achieving an undetectable VL (OR = 1.78; 95% CI = 1.01, 3.13). In intention-to-treat analyses, a larger proportion of the intervention group than the control group was adherent (40.15% vs. 27.59%, p = .02) and achieved an undetectable VL p = .04). However, the majority of participants who remained on study experienced some reduction in VL (≥ 1-log drop or undetectable), regardless of experimental condition. Conclusion: The multicomponent social support intervention significantly improved medication adherence over standard-of-care counseling; evidence for improved virologic outcomes was inconsistent. Early discontinuation of care and treatment may be a greater threat to the health of HIV patients than imperfect medication-taking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relationship-contingent self-esteem and the ups and downs of romantic relationships.

Relationship-contingent self-esteem (RCSE) emerges from perspectives on authenticity, need fulfillment, and relationship functioning and is an unhealthy form of self-esteem that depends on one's relationship. Four studies provided evidence of convergent, discriminant, incremental, and predictive validity for RCSE. Study 1 tested associations between RCSE and several conceptually related and unrelated constructs in multiple samples. In Study 2, the authors employed an event-contingent diary procedure to examine reports of self-esteem as a function of everyday relationship events. The association between event valence and changes in self-esteem became stronger with RCSE, and this interaction remained controlling for several parallel interactions by other constructs. Study 3 employed an interval-contingent diary procedure and found support for a mediation model in which the moderating role of RCSE largely occurred through momentary emotions, which in turn predicted momentary self-esteem. Study 4 sampled couples and found that partners who were both higher in RCSE felt more committed but not more satisfied or close. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electromagnetically-coupled plane waves in linear multiferroics

This paper presents the analytical development of a wave equation for real, rapidly altering fields in linear, electromagnetically-coupled materials. Giving consideration to phenomenology, crystal color symmetry and the laws of Ampere and Faraday, the analysis is applied to an orthorhombic single-crystal, linear ferroelectromagnet. The results of the analysis are discussed with an emphasis on the influence of the magnetoelectric coupling coefficient on the velocity expression obtained for electromagnetic plane waves. The implications of the expressions to modulated optical properties and the use of electromagnetically-coupled materials are discussed.