Properties of vitrinite concentrates of South African coals

Low-ash vitrinite concentrates of representative South African coals have been prepared and analysed. Various properties when plotted against carbon content show inflections at $\text{1}\text{1}\text{2}$ to 2% lower carbon content than normal British coals. These differences are ascribed to the heating effects of dolerite intrusions.     

Theoretical and numerical aspects of transmit SENSE

The ideas of parallel imaging techniques, designed to shorten the acquisition time by the simultaneous use of multiple receive coils, can be adapted for parallel transmission of a spatially selective multidimensional RF pulse. In analogy to data acquisition, a multidimensional RF pulse follows a certain trajectory in k-space. Shortening this trajectory shortens the pulse duration. The use of multiple transmit coils, each with its own time-dependent waveform and spatial sensitivity, compensates for the missing parts of k-space. This results in a maintained spatial definition of the pulse profile while its duration is reduced. This paper describes the basic equations of parallel transmission with arbitrarily shaped transmit coils ("Transmit SENSE") focusing on two-dimensional RF pulses. Results of numerical studies are presented demonstrating the theoretical feasibility of the approach.     

Computational Semantics in Discourse: Underspecification, Resolution, and Inference

In this paper I introduce a formalism for natural language understandingbased on a computational implementation of Discourse RepresentationTheory. The formalism covers a wide variety of semantic phenomena(including scope and lexical ambiguities, anaphora and presupposition),is computationally attractive, and has a genuine inference component. Itcombines a well-established linguistic formalism (DRT) with advancedtechniques to deal with ambiguity (underspecification), and isinnovative in the use of first-order theorem proving techniques.The architecture of the formalism for natural language understandingthat I advocate consists of three levels of processing:underspecification, resolution, andinference. Each of these levels has a distinct function andtherefore employs a different kind of semantic representation. Themappings between these different representations define the interfacesbetween the levels.I show how underspecified semantic representations can be built in acompositional way (for a fragment of English Grammar) using standardtechniques borrowed from the -calculus, how inferences can becarried out on discourse representations using a translation tofirst-order logic, and how existing research prototypes (discourseprocessing and spoken-dialogue systems) implement the formalism.     

Effect of spacer arm length on protein retention on a strong cation exchange adsorbent

The retention of five proteins was compared on a set of three strong cation exchange adsorbents that differed in spacer arm chemical structure and length. The adsorbents included a commercial product, Amersham Biosciences SP Sepharose Fast Flow, containing a six-carbon spacer between the agarose matrix and the anionic ligand, and two custom-prepared materials. One of the custom adsorbents contained a spacer of about half the length of the SP Sepharose Fast Flow, and the other contained no spacer arm. The adsorbent with no spacer arm was found to be significantly more retentive for all of the test proteins examined, in both isocratic and gradient elution tests. Reducing the spacer arm length by half resulted in increased retention for four of the five proteins, but this increase was less than what was observed when the spacer arm was eliminated. Retention increases were obtained without increasing the density of the anionic charge groups and appear to result from an enhancement of electrostatic or secondary nonelectrostatic interactions, or both. The results indicate that spacer arm length may be a useful variable in manipulating stationary-phase retention properties.     

Model selection and optimal sampling in high-throughput experimentation

The practical difficulties encountered in analyzing the kinetics of new reactions are considered from the viewpoint of the capabilities of state-of-the-art high-throughput systems. There are three problems. The first problem is that of model selection, i.e., choosing the correct reaction rate law. The second problem is how to obtain good estimates of the reaction parameters using only a small number of samples once a kinetic model is selected. The third problem is how to perform both functions using just one small set of measurements. To solve the first problem, we present an optimal sampling protocol to choose the correct kinetic model for a given reaction, based on T-optimal design. This protocol is then tested for the case of second-order and pseudo-first-order reactions using both experiments and computer simulations. To solve the second problem, we derive the information function for second-order reactions and use this function to find the optimal sampling points for estimating the kinetic constants. The third problem is further complicated by the fact that the optimal measurement times for determining the correct kinetic model differ from those needed to obtain good estimates of the kinetic constants. To solve this problem, we propose a Pareto optimal approach that can be tuned to give the set of best possible solutions for the two criteria. One important advantage of this approach is that it enables the integration of a priori knowledge into the workflow.     

Piroxicam benzoate--synthesis,HPLC determination,and hydrolysis

An improved method of piroxicam benzoate synthesis was described, and an isocratic reversed-phase high-performance liquid chromatography method for its determination was developed and fully validated. The method was found to be specific, precise (relative standard deviation 0.3%), accurate (mean recovery 99.9%), and robust. Limit of detection was estimated at 0.055 µg mL^-1 and limit of quantification at 0.185 µg mL^-1. The kinetics of piroxicam benzoate hydrolysis in aqueous buffer solutions (pH 1.1 and 10), simulated gastric and intestinal fluids was studied. The hydrolysis followed first-order kinetics. The following rate constants were obtained at pH 10: k = 1.8 × 10^-3 hr^-1 at 37°C and k = 3.4 × 10^-2 hr^-1 at 60°C. In acidic media, no significant hydrolysis was observed after 24 hr. During the 24-hr period in simulated intestinal fluid, only 10.9% of the starting ester was hydrolyzed.     

Coping with conflict at constitutional moments

The theme of this paper is the dynamics through which politicalorder and organized government is constituted and reconstitutedin democratic contexts. Key questions are how basic politicalrules evolve and change and the possible significance of reflection,deliberate design and explicit constitutional policy. In democraciesa focus on reflection and choice requires an understanding ofhow political support is mobilized and acquiescence, agreementand allegiance are achieved. It is important to analyze howconstitution making may turn a political system with enduringtensions and conflicts into an organized system of democraticgovernance, cooperation and problem solving.     

Accent Patterning on Domain-Related Information in Swedish Travel Dialogues

Investigation of travel-domain dialogues reveals travel-agent (System) utterances with intonational contours characterized by late-timed focal accents on given information. These accents occur on content words in utterance-initial position. The accentuation can be assumed to be related to the interactive nature of the dialogue in which the travel agent links back to a domain-related concept introduced by the client (User) and comments on it in an engaged manner. A perception test using constructed human-machine dialogues in which the machine (synthesized) responses vary as to the type of accent pattern on the initial words was developed to test listeners' preference for accent type. Results indicate that i) focal accents on domain-related utterance-initial given concepts are indeed preferred to nonfocal accents and that ii) late-timed focal accents are preferred to early-timed focal accents. These results have implications for the design of the prosody-generating component of human-machine dialogue systems.