The competitive inhibition of of the urease-catalyzed hydrolysis of urea by phosphate

The urease-catalyzed hydrolysis of urea has been found to be competitively inhibited by phosphate at pH 7.0 and 25°. The Michaelis constant of the urea-urease system has been found to be approximately 0.003 M urea and the comparable constant defining the phosphate-urease system 0.035 M phosphate

The hydrolysis of N-benzoyl-L-argininamide by crystalline trypsin

A reinvestigation of the kinetics of hydrolysis of N-benzoyl-n-argininamide by crystalline trypsin has led to the conclusion that the hydrolysis products enter into the over-all reaction as inhibitors

A procedure for the determination of proteolytic activity

The difficulties introduced by the desire to maintain a constant pH during an enzyme-catalyzed hydrolysis of peptide-like substrates and at the same time to determine the extent of hydrolysis by an acid-base titration have been pointed out (1), but to date no completely satisfactory solution of the problem has been given. With those enzymes whose pH optima lie in the region between pH 7.5 to 8.5, e.g. trypsin and chymotrypsin, the poor buffering capacity of phosphate in this region prompted us, as it has others (2-5), to consider the use of organic amines whose pK’alpha values were near to or identical with the pH optimum of the enzyme being used. In the course of such studies it soon became evident that coincidental use of a suitable primary or secondary amine buffer system and a formol titration (1) would insure adequate buffering capacity with low buffer concentration during the hydrolysis and at the same time permit the final acid-base titration to be conducted under nearly ideal conditions. In this communication we shall limit the discussion to results obtained with chymotrypsin and specific acylated-a-amino acid amide substrates, since the application of the general method to other proteolytic enzymes and other types of substrates will be obvious

The dependence of the specific activity of urease upon the apparent absolute enzyme concentration

If the activity of an enzyme preparation is determined under conditions in which a further increase in substrate concentration is without demonstrable effect, all other factors being held constant, it is ordinarily assumed that the specific activity of the enzyme, expressed in terms of arbitrary units per unit weight of the enzyme, is independent of the absolute enzyme concentration (1, 2). However, with urease solutions stabilized with hydrogen sulfide or cysteine (1) we have observed that the specific activity of a given urease preparation, when determined under the above conditions, increases with decreasing apparent enzyme concentration over a wide range of concentrations and that this increase in specific activity proceeds with a measurable velocity at temperatures above 15°. This phenomenon was observed with crude urease preparations, such as jack bean meal, and with two, three, and seven times recrystallized urease. Since little or no difference was observed in the behavior of three and seven times recrystallized urease, the data presented in this paper are limited to those obtained with thrice recrystallized preparations. Urease activity was determined by a modification of the procedure described by Van Slyke and Cullen (3). The precision of the modified procedure was ±2 to 3 per cent

Towards Understanding Spontaneous Speech: Word Accuracy vs. Concept Accuracy

In this paper we describe an approach to automatic evaluation of both the speech recognition and understanding capabilities of a spoken dialogue system for train time table information. We use word accuracy for recognition and concept accuracy for understanding performance judgement. Both measures are calculated by comparing these modules' output with a correct reference answer. We report evaluation results for a spontaneous speech corpus with about 10000 utterances. We observed a nearly linear relationship between word accuracy and concept accuracy.Comment: 4 pages PS, Latex2e source importing 2 eps figures, uses icslp.cls, caption.sty, psfig.sty; to appear in the Proceedings of the Fourth International Conference on Spoken Language Processing (ICSLP 96

Journal writing for the academic and psychosocial development of student teachers : an action research project

Published ArticleThis study explored reflective journals as a means to enable students to take a more active role in their learning to understand their own psychosocial growth towards maturity. This article presents the author's living journey to explore the value of journal writing in the identity formation of third year student teachers. In this article, the researcher makes a case that her own values of involvement in the personal lives of students may have contributed to facilitating the emotional growth of her students. In the process, they learnt to write about their emotions and feelings and to come to grips with unpleasant experiences in their lives. They also learnt that reflection could support their professional growth as teachers

Inflation, Investment Composition and Total Factor Productivity

This paper employs a dynamic stochastic general equilibrium model with a financial market friction to rationalize the empirically observed negative relationship between inflation and total factor productivity (TFP). Specifically, an empirical analysis of US macroeconomic time series establishes that there is a negative causal effect of inflation on aggregate productivity. Rather than taking the productivity process as exogenous, the model is therefore set up to feature an endogenous component of TFP. This is achieved by allowing physical investment to be channelled into two distinct technologies: a safe, but return-dominated technology and a superior technology which is subject to idiosyncratic liquidity risk. An agency problem prevents complete insurance against liquidity risk, and the scope for insurance is endogenously determined via the relevant liquidity premium. Since the liquidity premium is positively related to the rate of inflation, the model demonstrates how nominal fluctuations have an influence not only on the overall amount, but also on the qualitative composition of aggregate investment and hence on TFP. The quantitative relevance of the underlying transmission mechanism which links nominal fluctuations to TFP via corporate liquidity holdings and the composition of aggregate investment is corroborated by means of the quantitative analysis of the calibrated model economy as well as a detailed analysis of industry-level and firm-level panel data. Notably, the empirical findings are consistent with both the properties of the agency problem postulated in the theoretical model and its implications for corporate liquidity holdings and physical investment portfolios

Interdisciplinary research on the application of ERTS-1 data to the regional land use planning process

The author has identified the following significant results. Although the degree to which ERTS-1 imagery can satisfy regional land use planning data needs is not yet known, it appears to offer means by which the data acquisition process can be immeasurably improved. The initial experiences of an interdisciplinary group attempting to formulate ways of analyzing the effectiveness of ERTS-1 imagery as a base for environmental monitoring and the resolution of regional land allocation problems are documented. Application of imagery to the regional planning process consists of utilizing representative geographical regions within the state of Wisconsin. Because of the need to describe and depict regional resource complexity in an interrelatable state, certain resources within the geographical regions have been inventoried and stored in a two-dimensional computer-based map form. Computer oriented processes were developed to provide for the economical storage, analysis, and spatial display of natural and cultural data for regional land use planning purposes. The authors are optimistic that the imagery will provide revelant data for land use decision making at regional levels

The use of ERTS-1 data for the inventory of critical land resources for regional land use planning

Computer-generated spatial and statistical comparisons of critical land resource data derived from conventional sources, RB-57 photographs, and ERTS images, for an eastern Wisconsin test site, suggest that certain critical land resource data can be mapped from ERTS images on a statewide basis. This paper presents one of the biotic resources, wetlands, as an example of the use of ERTS imagery to inventory land resources