PMS—A program to make learning Pascal easier

One of the essential tasks in the teaching of a programming language is the introduction of the main constructs of the language—the syntax and semantics of statements, control, procedures, file handling, and so on. Most teachers present this topic by simulating the operation of the computer on the chalkboard by manual tracing of the execution of sample demonstration programs. Upon closer inspection it becomes clear that this task could be performed by the computer itself. A program implementing this idea would help the teacher in the class and the student (who could use the computer to repeat the instructor's performance at any time and on any problem of his choice) both in the class and in study. This article describes a collection of programs called PMS that performs exactly this function for the teaching of Pascal.PMS is organized as a collection of “mimlanguages” each of which demonstrates, and allows the user to experiment with, a certain category of Pascal features using a particular screen representation. Each of the subsystems contains a syntax-driven, screen-oriented translator associated with an interpreter that controls execution and the appropriate screen representation. This modular structure of PMS reflects the fact that programming is always taught by presenting certain essentially disjoint language features individually. In addition to their logical independence, these disjoint concepts also require different graphical approaches for their visual representation and this reinforces the need for modularization of the package.PMS is written in Pascal and runs on several computers including the IBM PC.     

Sensory effect of the sorption of some flavouring agents on blood plasma protein preparations

Presented investigations included the assessment of the sorption of selected flavouring agents on blood plasma preparations. The following aromatizing spices were used: marjoram, dried garlic, lovage, pepper, nutmeg and smoke flavour preparations. Thresholds of recognition of the spices mentioned above were determined at the temperatures of 10, 20 and 40 degrees C. For different quantities of protein a definite influence of temperature was determined. Similarly the quantity of protein exerted influence upon the intensity of the sorption of the odour of spices. The analysis of the results obtained in the investigations allows an interpretation of the character of binding between the flavouring agents and the protein preparations. It turned out that this process is the resultant of chemisorption and physical sorption.     

Mammalian 3-methyladenine DNA glycosylase protects against the toxicity and clastogenicity of certain chemotherapeutic DNA cross-linking agents

DNA repair status is recognized as an important determinant of the clinical efficacy of cancer chemotherapy. To assess the role that a mammalian DNA glycosylase plays in modulating the toxicity and clastogenicity of the chemotherapeutic DNA cross-linking alkylating agents, we compared the sensitivity of wild-type murine cells to that of isogenic cells bearing homozygous null mutations in the 3-methyladenine DNA glycosylase gene (Aag). We show that Aag protects against the toxic and clastogenic effects of 1,3-bis(2-chloroethyl)-1-nitrosourea and mitomycin C (MMC), as measured by cell killing, sister chromatid exchange, and chromosome aberrations. This protection is accompanied by suppression of apoptosis and a slightly reduced p53 response. Our results identify 3-methyladenine DNA glycosylase-initiated base excision repair as a potentially important determinant of the clinical efficacy and, possibly, the carcinogenicity of these widely used chemotherapeutic agents. However, Aag does not contribute significantly to protection against the toxic and clastogenic effects of several chemotherapeutic nitrogen mustards (namely, mechlorethamine, melphalan, and chlorambucil), at least in the mouse embryonic stem cells used here. We also compare the Aag null phenotype with the Fanconi anemia phenotype, a human disorder characterized by cellular hypersensitivity to DNA cross-linking agents, including MMC. Although Aag null cells are sensitive to MMC-induced growth delay and cell cycle arrest, their sensitivity is modest compared to that of Fanconi anemia cells.     

Gate oxide leakage due to temperature accelerated degradation under plasma charging conditions

Plasma-induced gate charging and resulting damage to the gate oxide during fabrication of submicron devices becomes a serious yield and reliability concern, especially when oxide thickness and device dimensions shrink to the nanoscale region. In this paper experimental results from plasma damaged submicron MOS transistors, namely low-level gate leakage and degraded charge-to-breakdown characteristics, are analyzed with respect to conditions of electrical stress. It is demonstrated that wafer temperature is a crucial parameter for charging-induced oxide degradation due to plasma processing. Laboratory experiments simulating plasma charging showed that low-level oxide leakage is the result of oxide breakdown after electrical wear-out under low-level injection conditions. High field stress, performed at 150°C, confirmed that elevated temperature during plasma processing strongly accelerates oxide degradation and even at low-level stress leads to the effects observed in plasma damaged devices.     

Effect of stirring on cellulose graft copolymerization. V. Influence of reaction parameters

Styrene was grafted onto dissolving pulp by the cellulose xanthate–Fe²⁺–H₂O₂ system. Reaction parameters were found to have strong influence on conversion to both copolymer and total polymer, as well as on the dependence of polymerization on stirring. The formation of polymer was almost completely inhibited by pure oxygen, while air only slowed down the reaction. Under inert atmosphere, the effect of agitator speed was found to be strongly dependent on monomer and substrate concentration as well as on the concentration of emulsifier. The location of the maximum on the conversion vs. agitator speed curve was strongly affected by the shape of the stirrer. The presence of emulsifier had a relatively small effect on copolymer formation in the case of acrylamide, a water-soluble monomer. Also the effect of stirring was less marked in the case of acrylamide. In all the systems investigated, the conversion to copolymer and total polymer was found to drop rapidly above a certain limiting agitator speed. The latter was different and characteristic for each system. No polymer formation was observed beyond 1000 rpm regardless of all other reaction conditions.     

Incomplete deductive databases

We investigate the complexity of query processing in databases which have both incompletely specified data and deductive rules. The paper is divided into two parts: in the first we consider databases in which incompletely specified data occurs only in the database intension; in the second we consider databases in which incomplete information is represented only in database extension. We prove that, in general, the query processing problem for databases with incomplete intensions is undecidable. A number of classes of rules for which all conjunctive queries can be processed in polynomial time is then characterized. For databases with incomplete extensions we prove a number of CoNP completeness results. For instance, we demonstrate that processing disjunctions which are restricted to individual columns of database predicates can, in general, be as bad as processing arbitrary disjunctions (i.e. CoNP-complete). This falsifies the conjecture that such limited disjunctions could be computationally beneficial. We also show two simple examples of situations in which query processing is guaranteed to be polynomial. These situations are linked to certain assumptions about database updates.Finally, we provide a summary of the data complexity of queries depending on the type of database extension, intension, query sublanguage and Open World vs Closed World assumption.Research supported by NSF grant DCR 85-04140.More precisely, we can say this only in the presence of the closed world assumption [18].