Automated formal analysis of temporal properties of Ladder programs

International Journal on Software Tools for Technology Transfer - Programmable Logic Controllers are industrial digital computers used as automation controllers in manufacturing processes. The...     

Personal problems related to illicit drug use in dropouts compared to students]

The pharmacokinetic disposition, urinary excretion and toxicity of tolonium chloride were determined after i.v. administration to sheep. Pretreatment with sodium nitrite significantly decreased the volume of the central compartment, apparent volume of distribution, area under the concentration-time curve, and total body clearance of tolonium chloride. Urinary excretion of tolonium chloride and its metabolite, leucotolonium chloride, together accounted for less than 15% of the administered dose in sheep receiving sodium nitrite and less than 10% of the administered dose in control sheep. The LD50 of tolonium chloride was 10 mg/kg with a 95% confidence interval of 7.35-13.60 mg/kg. Comparison with previously published data describing the pharmacokinetics and toxicity of a related compound, methylene blue, indicated that tolonium chloride has a higher volume of distribution and a narrower therapeutic index.     

The use of various buffers in the preparation of human lymphocytes for SEM observation

A study is presented of various buffers utilized in the preparation of human lymphocytes for scanning electron microscopy. Of nineteen different buffers tested, Hanks' balanced salt solution +0·04 mol sucrose appeared most adequate for satisfactory preservation of lymphocyte surface architecture.     

Chemical modification of bacterial luciferase with ethoxyformic anhydride: evidence for an essential histidyl residue

Bacterial luciferase is a heteropolymeric protein (alphabeta) that catalyses the conversion of chemical energy to light by oxidation of a reduced flavin mononucleotide and a long chain aliphatic aldehyde. Elucidation of the specific amino acid residues involved in the enzymatic reaction is essential for understanding the mechanisms of the bioluminescent reaction. Luciferase has been found to be inactivated by ethoxyformic anhydride with a second-order rate constant of 146 M-1 min-1 at pH 6.1 and 0 degrees C with a concomitant increase in absorbance at 240 nm due to formation of ethoxyformylhistidyl derivatives. Activity could be restored by hydroxylamine and the pH curve of inactivation indicated the involvement of a residue having a pKa of 6.8. Both substrates, FMNH2 and aldehyde, protected the enzyme against inactivation, suggesting that the modification occurred at or near the active site. Incorporation of [14C]ethoxyformyl groups in luciferase indicated that inactivation resulted from the modification of about three histidyl residues, one histidine being found on the alpha subunit and two on the beta subunit. Hybridization experiments, in which ethoxyformylluciferase, alphambetam, was complemented with native subunits, alpha or beta, showed that the hybrid alphambetam, has the same activity as alphambetam whereas the activity of the hybrid alphabetam, was close to that of the reconstituted luciferase alphabeta. The results indicate that modification of only one histidyl residue on the alpha subunit inactivates luciferase and suggest that this histidyl residue plays an essential role in the mechanism of the bacterial bioluminescent reaction.     

Redefining the rules: Providing race models with a connectionist learning rule

In this paper, we describe the Parallel Race Network (PRN), a race model with the ability to learn stimulus-response associations using a formal framework that is very similar to the one used by the traditional connectionist networks. The PRN assumes that the connections represent abstract units of time rather than strengths of association. Consequently, the connections in the network indicate how rapidly the information should be sent to an output unit. The decision is based on a race between the outputs. To make learning functional and autonomous, the Delta rule was modified to fit the time-based assumption of the PRN. Finally, the PRN is used to simulate an identification task and the implications of its mode of representation are discussed.     

Health status of and access to health services by residents of urban encampments in Los Angeles

This paper reports findings from a survey of 134 homeless people living in 42 urban encampments in central Los Angeles. These data, of concern to public health officials, include the physical conditions in the camps, the health status of residents, their use of drugs and alcohol, and their access to and use of health care services such as substance abuse treatment. Many encampment residents report poor health status; over 30 percent report chronic illnesses, and 40 percent report a substance abuse problem. Although outreach efforts have had success in bringing HIV and tuberculosis screening services to encampments, residents report significant barriers to using primary health care and drug and alcohol treatment services. Public hospitals and clinics remain the major source of primary medical care for homeless people living in encampments. Outreach and case management continue to be critical components of improved access to health care for homeless people.     

Using knowledge partitioning to investigate the psychological plausibility of mixtures of experts

Over the years, the presence of knowledge partitioning (KP) in human function learning data has been used to argue that mixture-of-experts models (MOE) constitute a psychologically plausible explanation of human performance, and that the experts used by humans are always linear. These claims recently led to the proposition of the population of linear experts model (POLE). In this paper, variations of the firefighting paradigm developed by Lewandowsky and his colleagues, which initiated research about KP, were used to explore the psychological plausibility of MOE in general and POLE in particular. In a first experiment, these statements were tested by modifying the test display of the firefighting paradigm. The results showed that adding irrelevant information to the display resulted in a smaller proportion of partitioning participants. Also, some participants used non-linear experts to partition the stimulus space. This new type of KP was further explored in a second study, which included more training sessions. The results suggest that linear KP disappears with practice and that non-linear partitioning reflects the incapacity to correctly estimate the position of the function’s vertex. It is concluded that MOE are adequate psychological models, but that the linearity and ubiquity claims of the POLE model need to be weakened.