Microbial reduction of selenate and nitrate: common themes and variations.

A number of biochemically distinct systems have been characterized for the microbial reduction of the oxyanions, selenate (SeO(4)(2-)) and nitrate (NO(3)(-)). Two classes of molybdenum-dependent nitrate reductase catalyse the respiratory-linked reduction of nitrate (NO(3)(-)) to nitrite (NO(2)(-)). The main respiratory nitrate reductase (NAR) is membrane-anchored, with its active site facing the cytoplasmic compartment. The other enzyme (NAP) is water-soluble and located in the periplasm. In recent years, our understanding of each of these enzyme systems has increased significantly. The crystal structures of both NAR and NAP have now been solved and they provide new insight into the structure, function and evolution of these respiratory complexes. In contrast, our understanding of microbial selenate (SeO(4)(2-)) reduction and respiration is at an early stage; however, similarities to the nitrate reductase systems are emerging. This review will consider some of the common themes and variations between the different classes of nitrate and selenate reductases.

Supply chain management for small business--how to avoid being part of the food chain.

A supply chain is a series of customer and supplier relationships that extend throughout and beyond the company. It is an interwoven set of links that together form a chain supplying our customers in a seamless and integrated fashion delivering a high level of customer satisfaction. Supply chain management (SCM) integrates all activities so they are focused on customer satisfaction (both internally and externally). One of the things this article will attempt to accomplish is to provide a clear understanding of SCM's positive impact on customer service as well as on improving profitability, cash flow, product cycle times, and communication. Whether we go forward in the supply chain to the final end-user or backward in the supply chain to our supplier's suppliers, SCM will significantly improve our ability to serve our customers.

Demand for outpatient mental health services in a heavily insured population: the case of the Blue Cross and Blue Shield Association's Federal Employees Health Benefits Program.

This article presents the results of a study of the impact of an increase in coinsurance on the demand for outpatient mental health services. The study population was a set of fully employed subscribers enrolled in the Blue Cross and Blue Shield Association's Federal Employees Health Benefits Program at some time during the period 1979 through 1981. A two-part model was used to examine the determinants of both the probability of mental health service use and the level of use. Our results indicate little price sensitivity in either part of the model, but substantial and significant income elasticities. Our results concerning the role of various sociodemographic and environmental variables are also reported.

A long-term follow-up of schizophrenic patients: 1946-1983.

The clinical fate of 73 schizophrenic patients collected from a rural general practice in England was followed for 38 years. The incidence of schizophrenia appears to have fallen since the introduction of phenothiazine drugs, and a more liberal attitude has developed toward these patients. Of these patients, 35% were permanently scarred and disabled by the disease; 28% of those who were traced had made a complete recovery. The outlook for victims of schizophrenia is better than it was in 1946. Some of the reasons for this improvement are explained.

Depressive disorders in the community: the scene in Great Britain, 1965.

Clinical-epidemiologic data collected in a rural general practice in England over the course of 20 years revealed a lifetime risk for clinically significant depression of approximately 10 cases per thousand. The background and basic findings of this research (published as Depression in the Community in 1965) are reviewed. Difficulties in differential diagnosis are explained, with case vignettes as illustration. The importance of being alert to the possibility of depression in patients presenting to a general medical practitioner is stressed.

A current reappraisal of Berry's hospital typology.

In an earlier article, Berry published the results of a study that examined possible relationships among hospital facilities and services. In general, Berry found that hospitals behaved in a reasonably consistent fashion; that is, hospitals added facilities and services in a well-defined order, and these facilities and services were added in distinct groups. Berry defined five such groups and hypothesized that each group represents an increasing level of case-mix complexity. Given the current interest in using Berry's results to measure hospital case mix, this study attempted to replicate Berry's results using recent data from the American Hospital Association. Using a number of statistical methodologies (including cluster analysis and Guttman scale analysis), we found that hospitals continue to add facilities and services in a well-defined order (although this order contains some notable differences from the order found by Berry). However, our results indicate that hospitals no longer add facilities and services in well-defined groups but in a more continuous fashion. Thus, it would appear that hospitals have become more differentiated.

The determination of alternative hospital classifications.

The problem of determining alternative hospital classifications when explicit constraints are recognized in the classification process is discussed. It is argued that such constraints are an integral part of most hospital classification processes and should be handled directly. A methodology based on cluster analysis, which can directly accommodate any number of specific constraints that might be imposed on the classification process, is described. A number of these possible constraints are presented. To illustrate the process, the methodology is applied to a data set of 200 short-term general hospitals; empirical results are presented that demonstrate the potential effects of various constraints on the hospital classification process.

On the measurement of hospital case mix.

This article discusses a number of issues related to the measurement of hospital diagnostic case mix. We initially examine a number of previous attempts to measure case mix based on surrogate measures (e.g., facilities and services) and information from predetermined discharge-classification systems. Since a number of researchers have attempted to reduce diagnostic classification data into a single-valued (i.e., scalar) case mix index, we then discuss a number of concepts and assumptions implicit in the construction of such indices. Among these assumptions is the property of functional homogeneity; this property and a methodology baed on Q-type factor analysis for testing for the presence of this property are defined. In order to illustrate the use of the methodology, it is applied to data from 153 hospitals in downstate New York.

Cost effectiveness analysis: some problems of implementation.

Cost benefit analyses in the health sector frequently deal with situations in which the money value of the benefits is either difficult or impossible to measure. This paper asserts that the use of cost effectiveness analysis as a means of escaping the need to place a dollar value on benefits does not escape the need for appropriately discounting these benefits when they accrue in different periods over time. The choice of an appropriate discount rate is discussed, and the benefits of elective hysterectomy are used to demonstrate that a serious bias can result from ignoring the need for discounting.

Ascorbic Acid Stimulation of Diacetyl Production in Mixed-Strain Lactic Acid Cultures.

The effect of three levels of ascorbic acid on diacetyl and acid production by two mixed-strain cultures was investigated. Each culture was grown in nonfat dry milk reconstituted to 11% total solids with 0.1% added sodium citrate. Ascorbic acid concentrations in the milk were 0, 0.10, and 0.25%. Stimulation of diacetyl production was observed at both concentrations of ascorbic acid. The stimulatory effect of ascorbic acid at both concentrations was approximately the same for each culture. Diacetyl production was initiated earlier in samples containing ascorbic acid. Ascorbic acid did not stimulate acid production.