Showing papers by "University of Minnesota published in 1982"

Phytoplankton Community Ecology: The Role of Limiting Nutrients

Abstract: This paper is a summary and synthesis of the role of nutrients and spatial and temporal fluctuations in controlling the species composition, diversity, and seasonal succession of planktonic algal communities. We do not review the full breadth and depth of the literature that has appeared since the seminal papers by Hutchinson (34) and Dugdale (19). Rather, we focus on some of the major questions and hypotheses, and evaluate these in light of their consistency with observation and experimentation. Because the combined net effect of limiting nutrients, major ions, pH, and other physical factors ultimately determines the reproductive rate of a local algal population, we first briefly review the data on the role of these factors in phytoplankton ecology. We then review the theory of resource competition and apply it to the questions of equilibrium versus nonequilibrium approaches, seasonal succession, and multitrophic level effects in phytoplankton com-

The local regularity of solutions of degenerate elliptic equations

Abstract: (1982). The local regularity of solutions of degenerate elliptic equations. Communications in Partial Differential Equations: Vol. 7, No. 1, pp. 77-116.

Strategies for information requirements determination

Abstract: Correct and complete information requirements are key ingredients in planning organizational information systems and in implementing information systems applications. Yet, there has been relatively little research on information requirements determination, and there are relatively few practical, well-formulated procedures for obtaining complete, correct information requirements. Methods for obtaining and documenting information requirements are proposed, but they tend to be presented as general solutions rather than alternative methods for implementing a chosen strategy of requirements determination. This paper identifies two major levels of requirements: the organizational information requirements reflected in a planned portfolio of applications and the detailed information requirements to be implemented in a specific application. The constraints on humans as information processors are described in order to explain why "asking" users for information requirements may not yield a complete, correct set. Various strategies for obtaining information requirements are explained. Examples are given of methods that fit each strategy. A contingency approach is then presented for selecting an information requirements determination strategy. The contingency approach is explained both for defining organizational information requirements and for defining specific, detailed requirements in the development of an application.

Conditions for the definition of a strictly diabatic electronic basis for molecular systems

Abstract: A strictly diabatic electronic basis is defined as one for which all components of the nuclear momentum coupling vanish. We examine the possibility that such a basis may exist, and we find that, in general, it does not. The only important exception is for diatomic states of the same symmetry. We also consider some conditions for the definition of an approximately diabatic electronic basis. For molecular systems with three or more nuclei, one can obtain useful approximate diabatic basis sets if the transverse (solenoidal) part of the coupling is negligible; this may occur, for example, if the part of the coupling due to the internuclear‐distance dependence of the configurational wave functions is negligible as compared to that due to the internuclear‐distance dependence of the configurational coefficients. We derive a criterion showing that such approximations may be useful and accurate if the role of the coupling is important over regions of sufficiently small linear dimensions.

Developmental Stages of the Coming Out Process

Abstract: Five developmental stages which describe the patterns seen in individuals with predominantly same-sex sexual orientation are described in the paper. The stages are: pre-coming out, coming out, exploration, first relationship, and identity integration.

Distinctive Chromosomal Abnormalities in Histologic Subtypes of Non-Hodgkin's Lymphoma

Abstract: Using a new high-resolution technique for chromosomal analysis, we have successfully studied biopsy specimens of lymph nodes from 42 of 44 patients with non-Hodgkin's lymphoma and have categorized them using the new international histologic formulation and immunologic markers. Abnormalities of the clonal chromosomes were detected in all 42 patients. Three recurrent chromosomal aberrations were found to correlate with certain histologic types: a translocation between chromosomes 18 and 14 in 16 of 19 patients with follicular lymphomas (small cleaved cell, mixed cell, and large cell); a translocation between chromosomes 8 and 14 in 5 of 6 patients with small noncleaved-cell (non-Burkitt's) or large-cell immunoblastic lymphoma; and a trisomy 12 in 4 of 11 patients with small-cell lymphocytic lymphoma. Our findings suggest that characteristic chromosomal defects occur in certain lymphoma subtypes and that high-resolution chromosomal analysis promises to become an important tool in improving our basic understanding of lymphoid cancers.

Comparison of self-reported and measured height and weight

Abstract: Screening data from the Hypertension Detection and Follow-up Program in Minneapolis, MN, 1973-1974, provided an opportunity to evaluate the accuracy of self-report of height and weight. It was found that both were reported, on the average, with small but systematic errors. Large errors were found in certain population subgroups. Also, men and women differed somewhat in their pattern of misreporting. Weight was understated by 1.6% by men and 3.1% by women, whereas height was overstated by 1.3% by men and 0.6% by women. As in previous studies, it was found that the most important correlates of the amount of error were the actual measurements of height and weight. An interesting finding was that misreporting of both height and weight in men was correlated with both aspects of body size, whereas for women, it was related mainly to the characteristic in question. Certain other demographic variables, such as age and educational level, were also found to have some importance as factors influencing misreporting.

The origin of man: a chromosomal pictorial legacy

Abstract: Man, gorilla, and chimpanzee likely shared an ancestor in whom the fine genetic organization of chromosomes was similar to that of present man. A comparative analysis of high-resolution chromosomes from orangutan, gorilla, chimpanzee, and man suggests that 18 or 23 pairs of chromosomes of modern man are virtually identical to those of our "common hominoid ancestor", with the remaining pairs slightly different. From this lineage, gorilla separated fist, and three major chromosomal rearrangements presumably occurred in a progenitor of chimpanzee and man before the final divergence of these tow species. A precursor of the hominoid ancestor and orangutan is also assumed.

Bedload and Size Distribution in Paved Gravel-Bed Streams

Abstract: Field data are used to study the size distribution of bedload in paved gravel-bed streams Similarity analysis yields the results that all grain size ranges are of approximately equal transportability when the critical condition for breaking the pavement is exceeded This result is only approximately correct due to deviations from similarity However, it is adequate to justify development of a method for calculating total bedload, which requires only the subpavement median grain size rather than the size distribution A method for calculating bedload size distribution that accounts for deviation from similarity is also developed

Some Approaches to the Correction of Selectivity Bias

Abstract: This article addresses the issue of specification of econometric selectivity models and suggests approaches for the correction of selectivity bias Our approaches provide ways to specify selectivity models without the assumption of multinormal distribution Some flexible function forms for the correction of selectivity bias in the regression equation are derived All the models considered can be estimated by simple consistent two stage methods Our approaches provide simple procedures for the testing of selectivity bias without imposing restrictive distributional assumptions and also tests for the normality assumption

Survival of Influenza Viruses on Environmental Surfaces

Abstract: To investigate the transmission of influenza viruses via hands and environmental surfaces, the survival of laboratory-grown influenza A and influenza B viruses on various surfaces was studied. Both influenza A and B viruses survived for 24-48 hr on hard, nonporous surfaces such as stainless steel and plastic but survived for less than 8-12 hr on cloth, paper, and tissues. Measurable quantities of influenza A virus were transferred from stainless steel surfaces to hands for 24 hr and from tissues to hands for up to 15 min. Virus survived on hands for up to 5 min after transfer from the environmental surfaces. These observations suggest that the transmission of virus from donors who are shedding large amounts could occur for 2-8 hr via stainless steel surfaces and for a few minutes via paper tissues. Thus, under conditions of heavy environmental contamination, the transmission of influenza virus via fomites may be possible.

The Decline of Electoral Participation in America

Abstract: Since 1960 turnout has declined in presidential elections, and since 1966 it has declined in off-year congressional elections. These declines occurred despite several major trends that could have increased electoral participation. An analysis of the eight SRC-CPS presidential election surveys conducted between 1952 and 1980 and of the six SRC-CPS congressional election surveys conducted between 1958 and 1978 suggests that these declines may result largely from the combined impact of two attitudinal trends: the weakening of party identification and declining beliefs about government responsiveness, that is, lowered feelings of “external” political efficacy. Between two-thirds and seven-tenths of the decline in presidential turnout between 1960 and 1980 appears to result from the combined impact of these trends. Data limitations hinder our efforts to study the decline of congressional turnout, but approximately two-fifths to one-half of the decline between 1966 and 1978 appears to result from the combined impact of these attitudinal trends.

Theoretical Study of Aerosol Filtration by Fibrous Filters

Abstract: A theoretical analysis of filtration mechanisms has been made for fibrous filters in the region of maximum penetration. The theory is based on a boundary layer approach using the Kuwabara flow field to account for the interference effects of neighboring fibers. An improved expression for the diffusion and interception filtration efficiencies has been derived that compares well with the existing theories. A comparison of the developed theory with experimental data also confirms the validity of the present work. *This paper is based on the thesis of K. W. Lee in partial fulfillment of the requirements for the Ph.D. degree at the University of Minnesota.

Identifying valid measures of reading.

Abstract: Three concurrent validity studies were conducted to determine the relationship between performances on formative measures of reading and standardized achievement measures of reading. Correlational ...

Adenocarcinoma of the stomach: areas of failure in a re-operation series (second or symptomatic look) clinicopathologic correlation and implications for adjuvant therapy.

Abstract: Following initial “curative” operative procedures for gastric carcinoma, 107 patients had planned single or multiple re-operations at the University of Minnesota. Later evidence of cancer was found in 86 patients at re-operation and/or other follow-up. Initial operative-pathologic extent of disease was correlated with incidence and patterns of failure. Distant metastasis (DM) alone was uncommon, but was found as a new component in 25.6 °k of the failure group. Nearly half of the peritoneal failures (PS) were localized, and when diffuse, were usually accompanied by a moderate sized local-regional failure. Local recurrence and/or regional lymph node metastasis (LF-RF) occurred as the only failure in 53.7% of the failure group if localized peritoneal failures were included, and as any component of failure in 87.8% (67.3% of the total 107 patients). Operation alone yields inadequate results for the majority of patients with gastric carcinoma. The rationale of adjuvant radiation and systemic therapy alone or in combination is discussed.

An outline of a theory of action systems.

Abstract: It is argued that the traditional psychological construal of the distinction between central ("open loop") and peripheral ("closed loop") neural processes is no longer tenable. A review of the relevant psychobiological research on the control of movement shows that both the central-peripheral dichotomy and the distinction between sensory and motor systems derived from that dichotomy are incompatible with what is known about the processes underlying action. Based on experimental and comparative data, a new theory of action is proposed. The basic concept of this new theory is the action system: Unlike motor systems, action systems involve sensory as well as motor processes; action systems are not organized into response hierarchies, but rather in coalitional structures of adjustable movements and postures. The phylogeny of action systems is discussed, and the eight most important action systems are distinguished in terms of their evolved distinctive functions. The difficulties of developing a taxonomy of actions for functionally specific types of behavior made up of that can be controlled is resolved by showing how kinds of action are differentiated by the kinds of affordances their components help to realize.

The nitrogen and phosphorus dependence of algal biomass in lakes: An empirical and theoretical analysis1

Abstract: An analysis of mean growing season concentrations of chlorophyll, total phosphorus (TP), and total nitrogen (TN) in 228 north latitude lakes confirms previous observations that chlorophyll yield is dependent both on the phosphorus concentration and on the TN:TP ratio. Of two modified chlorophyll models which depend explicitly on both nitrogen and phosphorus developed and tested, one, a multiple regression model, appears to greatly reduce the error of chlorophyll prediction in lakes. A theoretical framework is presented which provides an explanation for the observed effects of N:P ratios.

Spontaneous oxygen radical generation by sickle erythrocytes.

Abstract: Since the various membrane abnormalities of sickle erythrocytes might result from excessive accumulation of oxidant damage, we have measured the generation of superoxide, peroxide, and hydroxyl radical by normal and sickle erythrocytes using assays involving reduction of cytochrome c, aminotriazole inhibition of catalase, and methane evolution from dimethyl sulfoxide, respectively. Compared with normal erythrocytes, sickle erythrocytes spontaneously generate approximately twice as much superoxide, peroxide, and hydroxyl radical. One possible source of hydroxyl radical generation was identified as hemichrome, excessive amounts of which are bound to sickle erythrocyte membranes. Hemichrome did not generate hydroxyl radical when exposed to superoxide alone or peroxide alone. However, in the presence of both superoxide and peroxide, hemichrome greatly facilitated hydroxyl radical generation. Supporting this, normal erythrocyte membranes induced to acquire sickle hemichrome concomitantly acquired an enhanced ability to mediate hydroxyl radical generation. Finally, sickle erythrocyte membranes greatly enhanced superoxide/peroxide-driven hydroxyl radical generation as compared with normal erythrocyte membranes. These data suggest that an excessive accumulation of oxidant damage in sickle erythrocyte membranes might contribute to the accelerated membrane senescence of these cells. They further indicate that accumulation of oxidant damage could be a determinant of normal erythrocyte membrane senescence.

Phagocyte Impotence Caused by an Invasive Bacterial Adenylate Cyclase

Abstract: For unknown reasons, humans infected with the bacterium Bordetella pertussis are exceptionally vulnerable to secondary infections. Bordetella species elaborate a soluble, heat-stable, and highly active adenylate cyclase. This enzyme is internalized by phagocytic cells and catalyzes the unregulated formation of adenosine 3',5'-monophosphate (cyclic AMP), thereby disrupting normal cellular function. This unusual phenomenon may explain Bordetella-induced aphylaxis and may prove to be useful for investigating a variety of cyclic AMP-governed processes.

A cognitive-behavioral approach to anorexia nervosa

Abstract: The initial section of this paper presents a rationale for describing the development of anorexia nervosa in cognitive-behavioral terms. The limitations of conceptualizing the disorder simply as a behavioral pattern maintained by environmental contingencies or negative reinforcement are discussed. The remainder of the paper outlines a basic cognitive-behavioral model for intervention that is based on Beck's cognitive therapy. Recommendations particularly relevant to the management of anorexic clients are presented, including techniques for developing motivation for psychotherapy and for monitoring weight gain and food intake. Common irrational beliefs and systematic cognitive distortions are described. Assessment procedures and behavioral strategies that complement the cognitive approach are presented. Detailed examples are provided to illustrate the specific cognitive strategies that are recommended for evoking and modifying the irrational beliefs and assumptions of anorexic clients.

The third place

Abstract: This article examines the benefits that accrue from the utilization and personalization of places outside the workplace and the home. It is argued that participation in these third places provides people with a large measure of their sense of wholeness and distinctiveness. Third places are characterized in terms of sociability and nondiscursive symbolism. The benefits of third place involvement are discussed with reference to diversity and novelty, emotional expressiveness, color, and perspective.

Improving Measurement Quality and Efficiency with Adaptive Testing

Abstract: Approaches to adaptive (tailored) testing based on item response theory are described and research results summarized. Through appropriate combinations of item pool design and use of different test termination criteria, adaptive tests can be designed (1) to improve both measurement quality and measurement efficiency, resulting in measurements of equal precision at all trait levels; (2) to improve measurement efficiency for test batteries using item pools designed for conventional test administration; and (3) to improve the accuracy and efficiency of testing for classification (e.g., mastery testing). Research results show that tests based on item response theory (IRT) can achieve measurements of equal precision at all trait levels, given an adequately designed item pool; these results contrast with those of conventional tests which require a tradeoff of bandwidth for fidelity/precision of measurements. Data also show reductions in bias, inaccuracy, and root mean square error of ability estimates. Improvem...