A Notation and Logic for Mobile Computing

We define a concurrent mobile system as one where independently executing components may migrate through some space during the course of the computation, and where the pattern of connectivity among the components changes as they move in and out of proximity. The definition is general enough to encompass a system of mobile hosts moving in physical space as well as a system of migrating software agents implemented on a set of possibly non-mobile hosts. In this paper, we present Mobile UNITY, a notation for expressing mobile computations and a logic for reasoning about their temporal properties. Our goal is to find a minimalist model of mobile computation that will allow us to express mobile components in a modular fashion and to reason formally about the possible behaviors of a system composed from mobile components. A simplified serial communication protocol among components which can move in space serves as an illustration for the notation.     

Effects of Nutrient Source and Supply on Crude Oil Biodegradation in Continuous-Flow Beach Microcosms

Ammonium and nitrate were used as nitrogen sources to support microbial biodegradation of crude oil in continuous-flow beach microcosms to determine whether either nutrient was more effective in open systems, such as intertidal shorelines. No differences in the rate or extent of oil biodegradation were observed, regardless of whether these nutrients were provided continuously or intermittently. Nutrients were provided once every two weeks to intermittent-input microcosms and washed out within four to five days. In continuous-input microcosms, ammonium and nitrate were assimilated as quickly as they were provided during the first week, but both accumulated to greater than 10?mg?N/L thereafter. The sensitivity of the oil mineralization rate to nutrient input decreased rapidly as the extent of oil degradation increased, and after about two weeks the rate of oil-mineralization appeared to be independent of nutrient input. Therefore, there may be little value in maintaining a long-term supply of nutrients in contact with oil-contaminated sediments. The rates of microbial assimilation of ammonium and nitrate followed similar trends. Both compounds were assimilated more slowly as the extent of oil biodegradation increased, and the nitrate uptake rates approached zero after about two weeks. Ammonium assimilation continued at a low rate throughout the six-week experiment, but this did not appear to affect the rate of oil mineralization. Assimilation of ammonium resulted in a sharp decrease in the pH of the synthetic seawater that was pumped continuously through the microcosms, but nitrate had a much smaller effect on pH. The magnitude of the ammonium-associated pH change was never as large as was observed in previous studies involving oil biodegradation in batch reactors, however, and did not affect the oil-biodegradation rate.     

Cancer risk assessment of extremely low frequency electric and magnetic fields: a critical review of methodology

This review provides a discussion of cancer risk assessment methodology pertinent to developing a strategy for extremely low frequency electric and magnetic fields (EMF). Approaches taken for chemical agents or ionizing radiation in six key topic areas are briefly reviewed, and then those areas are examined from the perspective of EMF, identifying issues to be addressed in developing a risk assessment strategy. The following recommendations are offered: 1) risk assessment should be viewed as an iterative process that informs an overall judgment as to health risk and consists of a complex of related activities incorporating both positive and negative data, tumor and nontumor end points, and human and nonhuman sources of information; 2) a hazard identification resulting in a conclusion of weak or null effects, such as may be associated with EMF, will need to assign significant weight to animal cancer bioassays conducted under defined exposure conditions as well as to human epidemiologic studies; 3) a default factor to account for possible age differences in sensitivity to carcinogenesis should be included in an EMF risk assessment; 4) lack of evidence of dose response and the apparent lack of DNA reactivity of EMF suggest that a safety (or uncertainty) factor or margin of exposure type of risk characterization may be most appropriate; and 5) an EMF risk assessment should permit at least tentative conclusions to be reached as to the limits of carcinogenic risk from exposure to EMF, and should also define an efficient research agenda aimed at clarifying uncertainties appropriate to a more complete assessment.     

A high-risk method for studying psychosocial antecedents of chronic pain: The prospective investigation of herpes zoster.

Although patients with chronic pain (CP) are often psychologically distressed, it has been difficult to determine whether this distress is an antecedent of CP or whether it is caused by the experience of living with CP. This investigation aimed to develop a method that would allow individuals who are at risk for the development of CP to be studied before the pain has become chronic. Patients with acute herpes zoster (HZ) were assessed with demographic, medical, pain, and psychosocial measures. Pain was assessed in follow-up interviews at 6 wks and 3, 5, 8, and 12 mo after these initial assessments. There were no significant differences between Ss who developed short-term HZ pain and Ss who did not develop short-term pain for any of the measures at the initial assessment, except for 1 measure of pain intensity. Ss who developed HZ CP, however, had significantly greater pain intensity, higher state and trait anxiety, greater depression, lower life satisfaction, and greater disease conviction at the initial assessment than Ss who did not develop CP. In discriminant analyses, disease conviction, pain intensity, and state anxiety each made a unique contribution to discriminating Ss who did and did not develop CP. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mean-value analysis of multi-facility blocking models with state-dependent arrivals

A new mean-value type of algorithm is developed for analyzing multi-facility blocking models with state-dependent arrival rates. It can be applied to a broad class of blocking systems with simultaneous resource possession including, for example, circuit-switched networks. The underlying recursion is cast in terms of blocking probabilities and marginal state probabilities. The developments made here generalize previous results that were restricted to the case of constant arrival rates.     

ECOWARM: News and information

ECOWARM: News and information     

A Comparison of Spawning,Harvested, and Die-Off Rainbow Smelt, Osmerus Mordax, in Eastern Lake Erie

Rainbow smelt were collected in the area of Long Point, Lake Erie from 1) a commercial trawler, 2) spawning runs in streams, and 3) die-offs along beaches. The parasite Glugea hertwigi was found to have no effects on the fecundity or condition of smelt. However, infested smelt grew more slowly than uninfested ones. The percentage of infested smelt in die-offs was not significantly higher than in the spawning stock, suggesting that the parasite was not the primary cause of the mortality. Growth, maximum age, and fecundity of smelt in the samples were lower than in most other smelt populations for which data are available. Since there are no data available for Lake Erie smelt prior to or during the development of the fishery, it is not possible to assess if the observed population structure is the result of exploitation. Sex ratio changes suggest that spawning smelt may remix with the harvested stock gradually throughout the summer.     

A technique for measuring the impurity concentration of silicon-on-sapphire films using C-V plots

The problem of calculating the impurity concentration of lightly doped silicon-on-sapphire (SOS) films using a C-V curve is addressed. The existing techniques for calculating impurity concentration and their limitations are briefly discussed. One of these limitations is the low Q of lightly doped SOS capacitors. A technique based on the inflection point slope (maximum slope) is presented. This technique is not only simple and accurate but also avoids the problem of low Q. The accuracy limitations of this technique caused by interface states and Q_ss fluctuations are examined. A simple test is also presented to determine if a given C-V curve grossly departs from ideal C-V theory about the inflection point.     

Use of the slave emulator

In-circuit emulation is the ability to imitate electrically a target microprocessor, responding to system inputs or instructions, and producing accurately the expected outputs or responses to the instructions. A modular building block approach to microprocessor-based design is given, the Slave Emulator Control Unit (SECU) is described and its flexibility shown.