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Showing papers by "Carleton University published in 1996"


Journal ArticleDOI
Claude Amsler1, Michael Doser2, Mario Antonelli, D. M. Asner3  +173 moreInstitutions (86)
TL;DR: This biennial Review summarizes much of particle physics, using data from previous editions.

12,798 citations


Journal ArticleDOI
TL;DR: This review addresses the technical, statistical, and theoretical issues related to the use of the PR schedule in self-administration studies in rats to examine psychostimulant and opiate reinforcement.

1,242 citations


Journal ArticleDOI
KF Rust1, Jnk Rao2
TL;DR: The use of the jackknife, balanced repeated replication, and the bootstrap techniques for estimating sampling variances and the use of such variance estimates in drawing inferences from survey data is discussed.
Abstract: The analysis of survey data requires the application of special methods to deal appropriately with the effects of the sample design on the properties of estimators and test statistics. The class of replication techniques represents one approach to handling this problem. This paper discusses the use of these techniques for estimating sampling variances, and the use of such variance estimates in drawing inferences from survey data. The techniques of the jackknife, balanced repeated replication (balanced half-samples), and the bootstrap are described, and the properties of these methods are summarized. Several examples from the literature of the use of replication in analysing large complex surveys are outlined.

687 citations


Journal Article
TL;DR: The key to successful transitions in several systems is the induction, during the oxygen-limited state, of elevated activities of antioxidant and associated enzymes, so that damage during the reintroduction of oxygen is minimized.
Abstract: As a consequence of aerobic life, an organism must deal with the continuous generation of reactive oxygen species (O2-, H202, OH) as byproducts of metabolism and defend itself against the harm that these can do to cellular macromolecules Organisms protect themselves from such damage with both enzymatic and nonenzymatic antioxidant defenses However, the reperfusion injuries noted after ischemic insult in mammalian organs and ascribed to a burst of reactive oxygen species produced when oxygenated blood is reintroduced demonstrate that the antioxidant defenses of many organisms can be overwhelmed, Although unusual among most mammals, many organisms routinely experience wide variation in oxygen availability to their tissues due to factors such as environmental oxygen lack, breath-hold diving, extracellular freezing, or apnoeic breathing patterns in arrested metabolic states In recent studies using various animal models (anoxia-tolerant turtles, freeze-tolerant snakes and frogs, estivating snails) our laboratory has explored the adaptations of antioxidant defenses that allow such organisms to deal with rapid changes in tissue oxygenation with little or no accumulation of damage products The key to successful transitions in several systems is the induction, during the oxygen-limited state, of elevated activities of antioxidant and associated enzymes, such as catalase, superoxide dismutase, glutathione-S-transferase, and glutathione peroxidase, so that damage during the reintroduction of oxygen (such as lipid peroxidation) is minimized However, animals that are excellent facultative anaerobes, such as freshwater turtles, appear to deal with potential of oxidative stress during the anoxic-aerobic transition by maintaining constitutively high antioxidant defenses (eg enzyme activities similar to those of mammals and much higher than those of anoxia-intolerant lower vertebrates) that can readily accommodate the burst of reactive oxygen species generation when breathing is renewed

680 citations


Journal ArticleDOI
TL;DR: This paper examined whether variations in knowledge of storybooks (assumed to index factors such as frequency of shared reading) were related to vocabulary scores for 3- to 6-year-olds.
Abstract: Shared book reading provides a rich source of linguistic stimulation for young children. The authors examined whether variations in knowledge of storybooks (assumed to index factors such as frequency of shared reading) were related to vocabulary scores for 3- to 6-year-olds. In Experiment 1, parents' knowledge of storybooks explained unique variance in children's receptive vocabulary scores after controlling for children's analytic intelligence, parents' exposure to adult reading material, and parents' education. In Experiment 2, children's knowledge of storybooks explained unique variance in their receptive and expressive vocabulary scores after controlling for parents' exposure to print and socioeconomic status level. Children's knowledge of storybooks indexed cognitive factors as well as exposure. The findings obtained in the 2 experiments suggest that storybook experiences during the preschool years may be an important influence on the development of children's language skills.

438 citations


Journal ArticleDOI
TL;DR: Ashcraft et al. as mentioned in this paper found that the problem size effect in simple addition is mainly due to participants' selection of non-retrieval procedures on larger problems (i.e., problems with sums greater than 10).
Abstract: Adults' solution times to simple addition problems typically increase with the sum of the problems (the problem size effect). Models of the solution process are based on the assumption that adults always directly retrieve answers to problems from an associative network. Accordingly, attempts to explain the problem size effect have focused either on structural explanations that relate latencies to numerical indices (e.g., the area of a tabular representation) or on explanations that are based on frequency of presentation or amount of practice. In this study, the authors have shown that the problem size effect in simple addition is mainly due to participants' selection of nonretrieval procedures on larger problems (i.e., problems with sums greater than 10). The implications of these results for extant models of addition performance are discussed. Twenty years of research on mental arithmetic has shown that problems involving larger numbers (e.g., 9 + 6) are solved more slowly than problems involving smaller numbers (e.g., 3 + 4). Surprisingly, in spite of the wealth of empirical data and the extensive theoretical development on mental arithmetic, the problem size effect has eluded satisfactory explanation (Ashcraft, 1992; McCloskey, Harley, & Sokol, 1991; Widaman & Little, 1992). The goal of the present research was to test an explanation of the problem size effect in adults that has been used to account for the arithmetic performance of children (Ashcraft, 1992; Siegler, 1987). We hypothesized that variability in the selection of procedures to solve simple addition problems has a major impact on solution latencies and may account for a substantial portion of the problem size effect.

402 citations


Journal ArticleDOI
TL;DR: This paper found that participants were slower to retrieve problems that were most likely to be solved by non-retrieval procedures and faster to retrieve problem that were usually solved by retrieval, indicating that direct retrieval models are incomplete accounts of adults' performance and support a continuing influence of learning and experience on the mental representation of simple multiplication problems.
Abstract: Researchers have assumed that adults solve simple arithmetic problems by retrieving answers from a network of stored facts. In 2 studies, undergraduates described their solutions of single-digit multiplication problems. They reported direct retrieval on approximately 80% of trials, but also reported rules (e.g., anything times 0 is 0), repeated addition (e.g., 2 × 4 = 4 + 4), number series (e.g., 3 × 5 = 5, 10, 15), and derived facts (e.g., 6 × 7 = [6 × 6] + 6). Participants were slower to retrieve problems that were most likely to be solved by nonretrieval procedures and faster to retrieve problems that were usually solved by retrieval. These results indicate that direct-retrieval models are incomplete accounts of adults' performance and support a continuing influence of learning and experience on the mental representation of simple multiplication problems.

290 citations


Journal ArticleDOI
TL;DR: In this article, the Modified Mini-Mental State Examination (3MS) has been extended with four additional subtests (date and place of birth, word fluency, similarities, and delayed recall of words).
Abstract: study, 525 community-dwelling participants, aged 65-89, were divided into 2 groups: no cognitive impairment (NCI; n - 406) and Alzheimer's disease (n = 119). Both tests yielded comparable reliability estimates. Fewer years of education decreased specificity and increased sensitivity, whereas increasing age primarily decreased specificity. It is concluded that although the 2 tests produce comparable effects, the inclusion of a verbal fluency test would increase the sensitivity of the MMSE. Normative data for the NCI group, stratified for 2 age levels (65-79 and 80-89) and 2 educational levels (0-8 and 9+ years), are presented. Folstein, Folstein, and McHugh (1975) introduced the MiniMental State Examination (MMSE) as a brief, objective assessment of cognitive functioning and as a measure of changes in cognitive status. The MMSE usually can be administered in 510 min and has been employed extensively in clinical settings, community surveys, and epidemiological studies. In a recent review of the literature, Tombaugh and Mclntyre (1992) concluded that the MMSE possessed moderate to high reliability coefficients, demonstrated high levels of sensitivity for cognitive deficits in patients suffering from moderate to severe Alzheimer's disease, and reflected the cognitive decline typical of dementia patients. Criticisms of the MMSE included (a) its failure to discriminate between people with mild dementia and those who are not demented, (b) a limited ability to detect impairment caused by focal lesions, particularly those in the right hemisphere, (c) overly simple language items that reduce sensitivity to mild linguistic deficits, and (d) a large number of false-positive errors because of its bias against individuals with low education. In response to these problems, several attempts have been made to improve the MMSE. Of these, the Modified Mini-Mental State Examination (3MS; Teng & Chui, 1987) represents the most extensive revision. Teng and Chui (1987) added four additional subtests (date and place of birth, word fluency, similarities, and delayed recall of words). The maximum score was

277 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examined the reliability and validity of the psychopathy checklist-Revised: Screening Version (PCL-R:SV) in a sample of 75 male and 75 female university students.

251 citations


Journal ArticleDOI
TL;DR: In this article, strong-motion deamplification, accompanied by changes in resonant frequencies, are found in the data from the 1985 Michoacan, Mexico, and the 1989 Loma Prieta, California, earthquakes, the events recorded by the vertical and surface accelerograph arrays in Taiwan, as well as a number of other events throughout the world.
Abstract: Geotechnical models consistently indicate that the stress-strain relationship of soils is nonlinear and hysteretic, especially at shear strains larger than ∼10−5 to 10−4. Nonlinear effects, such as an increase in damping and reduction in shear-wave velocity as excitation strength increases, are commonly recognized in the dynamic loading of soils. On the other hand, these effects are usually ignored in seismological models of ground-motion prediction because of the lack of compelling corroborative evidence from strong-motion observations. The situation is being changed by recently obtained data. Explicit evidence of strong-motion deamplification, accompanied by changes in resonant frequencies, are found in the data from the 1985 Michoacan, Mexico, and the 1989 Loma Prieta, California, earthquakes, the events recorded by the vertical and surface accelerograph arrays in Taiwan, as well as a number of other events throughout the world. Evidence of nonlinear behavior becomes apparent beyond a threshold acceleration of ∼100 to 200 gal. Nonlinearity is considerable in cohesionless soil but may be negligible in stiff soils. The findings of recent years indicate that nonlinear site effects are more common than previously recognized in strong-motion seismology.

246 citations


Journal ArticleDOI
TL;DR: In this paper, an empirical analysis of farmers' decisions in light of variations in climate and other forces is based on a survey of 120 farm operators in southwestern Ontario, and some farmers were affected by variable climatic conditions over a six-year-period.
Abstract: Assumptions underlying impact assessments of climatic change for agriculture are explored conceptually and empirically. Variability in climatic conditions, the relevance of human decision-making, and the role of non-climatic forces are reviewed and captured in a model of agricultural adaptation to climate. An empirical analysis of farmers' decisions in light of variations in climate and other forces is based on a survey of 120 farm operators in southwestern Ontario. Many farmers were affected by variable climatic conditions over a six-year-period, and some undertook strategic adaptations in their farm operations. Frequency of dry years was the key climatic stimulus to farming adaptations. However, only 20 percent of farmers were sufficiently influenced by climatic conditions to respond with conscious changes in their farm operations.

Journal ArticleDOI
TL;DR: Risk variables reflecting family relationship and parenting problems were associated with heightened rates of re-offending and lower overall adjustment, and the presence of protective factors relating to positive peer relations, good school achievement, positive response to authority and effective use of leisure time was associated with more positive outcomes with controls for the risk variables.
Abstract: The study explored a set of potential risk and protective factors in relation to criminal activity and adjustment with a group of delinquent youths. The results indicated, first, that risk variables reflecting family relationship and parenting problems were associated with heightened rates of re-offending and lower overall adjustment. Second, the presence of protective factors relating to positive peer relations, good school achievement, positive response to authority and effective use of leisure time was associated with more positive outcomes with controls for the risk variables. Third, there was no evidence of interaction between risk and protective factors; the latter operated similarly at low and high levels of risk. These results are discussed in terms of their theoretical and applied significance.

Journal ArticleDOI
TL;DR: In this article, the effects of temperature and intensity on the rate of sonochemical oxidation of aqueous potassium iodide with irradiation at two frequencies, 20 and 900 kHz, were investigated.

Book ChapterDOI
03 Nov 1996
TL;DR: This work examines key agreement protocols providing key authentication, key confirmation and forward secrecy and presents a protocol providing the properties listed above.
Abstract: We examine key agreement protocols providing (i) key authentication (ii) key confirmation and (iii) forward secrecy. Attacks are presented against previous two-party key agreement schemes and we subsequently present a protocol providing the properties listed above.

Journal ArticleDOI
TL;DR: Data suggest that baclofen may produce a specific attenuation of cocaine reinforcement and support a number of recent observations that rate of drug intake may be an insensitive measure of changes in the motivation to self-administer cocaine.

Journal ArticleDOI
TL;DR: In this article, a functional model of the permafrost-climate relationship is presented, which accommodates the geographical variations of climatic, surface and soil factors that control ground thermal regime.
Abstract: Ground temperature monitoring has been proposed as a means of detecting climate change in permafrost regions, although it is well known that the relationship is not simple. This paper presents a functional model of the permafrost-climate relationship, which accommodates the geographical variations of climatic, surface and soil factors that control ground thermal regime. The model is used to analyse the impacts of climate change on ground temperatures and to assess the design and interpretation of ground temperature monitoring programs. The model suggests that lithologic conditions form the primary local influence on permafrost temperatures, followed by snowcover and vegetation. Results using the model suggest that simple monitoring of active layer depth does not provide a reliable indicator of changes in permafrost temperature conditions, and that monitoring at exposed bedrock sites will produce the most direct signal of climate change on the ground thermal regime. © 1996 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the photosynthetic gas exchange characteristics of two common boreal forest mosses, Sphagnum (section acutifolia) and Pleurozium schreberi, and measured continuously during the time required for the moss to dry out from full hydration.
Abstract: Photosynthetic gas exchange characteristics of two common boreal forest mosses, Sphagnum (section acutifolia) and Pleurozium schreberi, were measured continuously during the time required for the moss to dry out from full hydration. Similar patterns of change in CO2 assimilation with variation in water content occurred for both species. The maximum rates of CO2 assimilation for Sphagnum (approx. 7 μmol m−2 s−1) occurred at a water content of approximately 7 (fresh weight/dry weight) while for Pleurozium the maximum rate (approx. 2 μmol m−2 s−1) occurred at a water content of approximately 6 (fresh weight/dry weight). Above and below these water contents CO2 assimilation declined. In both species total conductance to water vapour (expressed as a percentage of the maximum rates) remained nearly constant at a water content above 9 (fresh weight/dry weight), but below this level declined in a strong linear manner. Short-term, “on-line” 13CO2 and C18O16O discrimination varied substantially with changes in moss water content and associated changes in the ratio of chloroplast CO2 to ambient CO2 partial pressure. At full hydration (maximum water content) both Sphagnum and Pleurozium had similar values of 13CO2 discrimination (approx. 15). Discrimination against 13CO2 increased continuously with reductions in water content to a maximum of 27 in Sphagnum and 22 in Pleurozium. In a similar manner C18C16O discrimination increased from approximately 30 at full hydration in both species to a maximum of 150 in Sphagnum and 90 in Pleurozium, at low water content. The observed changes in C18O16O were strongly correlated to predictions of a mechanistic model of discrimination processes. Field measurements of moss water content suggested that photosynthetic gas exchange by moss in the understory of a black spruce forest was regularly limited by low water content.

Journal ArticleDOI
TL;DR: Using meta-analysis, it was found that FA-stress and FA-fitness relations were non-spurious, despite the large number of relations tested, and suggested that trait type was not predictive of the presence or strength of FA- stress or FA-Fitness relations and that relations were not stronger for poikilotherms, as one hypothesis suggested.
Abstract: :Recently, there has been much controversy over whether fluctuating asymmetry (FA) is related to stress during development, or to fitness of organisms following development. Many tests have found the predicted relations, whereas others have not. To account for these inconsistencies, some researchers have argued that FA of some traits (e.g., sexually selected traits) are more sensitive measures of stress, or are more strongly related to fitness, and that such relations will differ between poikilotherms and homeotherms. Using meta-analysis, we found that FA-stress and FA-fitness relations were non-spurious, despite the large number of relations tested. However, FA-stress and FA-fitness relations were fairly weak and highly heterogenous. Furthermore, our results suggested that trait type was not predictive of the presence or strength of FA-stress or FA-fitness relations and that relations were not stronger for poikilotherms, as one hypothesis suggested.

Journal ArticleDOI
TL;DR: This paper reviewed the literature on men who had been sexually abused in childhood and found that a significant number of men were sexually abused as children, and that very little empirically sound research has been undertaken to better the present situation of such individuals.

Journal ArticleDOI
TL;DR: This article examined modified equa tions for the validity and reliability of difference scores that describe applied testing situations more realisti cally and reveal that simple gain scores can be more useful in research than commonly believed.
Abstract: It is widely believed that measures of gain, growth, or change, expressed as simple differences between pretest and posttest scores, are inherently unreliable It is also believed that gain scores lack predictive validity with respect to other criteria However, these conclu sions are based on misleading assumptions about the values of parameters in familiar equations in classical test theory The present paper examines modified equa tions for the validity and reliability of difference scores that describe applied testing situations more realisti cally and reveal that simple gain scores can be more useful in research than commonly believed

Patent
John R. Long1
01 Aug 1996
TL;DR: In this paper, a low voltage silicon bipolar RF (radio frequency) receiver front end includes a low noise preamplifier and double-balanced mixer, which can operate at supply voltages below 2 volts.
Abstract: A low voltage silicon bipolar RF (radio frequency) receiver front end includes a low noise preamplifier and double-balanced mixer. The receiver incorporates monolithic microstrip transformers for significant improvements in performance compared with silicon broadband designs. Reactive feedback and coupling elements are used in place of resistors to lower the front end noise figure through the reduction of resistor thermal noise, and this also allows both circuits to operate at supply voltages below 2 volts. Circuits fabricated using 0.8 μm Bipolar CMOS technology provide a peak npn transistor transit frequency fT of 11 GHz. At a supply voltage of 1.9 volts, the measured input third order intercept point is +2.3 dBm with a 10.9 dB single-sideband noise figure. Power dissipated is less than 5 mW. The low noise amplifier input intercept is -3 dBm with a 2.8 dB noise figure and 0.5 dB gain. Power dissipation of the preamplifier is less than 4 mW from a 1.9 V supply.

Journal ArticleDOI
TL;DR: It was demonstrated that early-life handling of mouse pups reduced the learning impairments seen when mice were tested in the Morris water-maze at 120 days of age and also prevented stress-induced disturbances in this task, consistent with the proposition that performance disturbances of BALB/cByJ mice tests in theMorris water- maze task are associated with excessive hypothalamic-pituitary-adrenal reactivity.
Abstract: Following stressor exposure BALB/cByJ mice exhibit hypersecretion of corticosterone and marked brain catecholamine alterations. In addition, mice of this strain exhibit impairments of performance in a Morris water-maze, which may be exacerbated by footshock application. In the present investigation it was demonstrated that early-life handling of mouse pups (coupled with brief separation periods from the dam over the course of 21 days postpartum) reduced the learning impairments seen when mice were tested in the Morris water-maze at 120 days of age and also prevented stress-induced disturbances in this task. Likewise, cross-fostering BALB/cByJ mice with a C57BL/6ByJ dam prevented the performance deficits. In contrast, C57BL/6ByJ mice cross-fostered to a BALB/cByJ dam exhibited proficient performance. Thus, maternal factors may be important in determining the Morris water-maze disturbances, provided that this was applied on the BALB/cByJ genetic background. Stressor exposure exacerbated the performance disturbances in BALB/cByJ mice, while diazepam treatment disrupted Morris water-maze performance in both BALB/cByJ and C57BL/6ByJ mice. Paralleling the behavioral changes associated with handling, the stress-induced hypercorticosterone secretion characteristic of the BALB/cByJ mouse was attenuated by the early handling procedure. Stressor exposure also produced strain-dependent variations of NE and 5-HT, but these effects were not appreciably influenced by the handling procedure. These data are consistent with the proposition that performance disturbances of BALB/cByJ mice tested in the Morris water-maze task are associated with excessive hypothalamic-pituitary-adrenal reactivity. Moreover, it appears that the influence of early-life stimulation may interact with genetic factors in determining endocrine and behavioral stress responses.

Journal ArticleDOI
TL;DR: In this article, the authors examined the practice of concurrent engineering in terms of process concurrency and the impact of concurrency on success of product development projects based on 50 cross-national projects from companies in Australia, Canada, Denmark, Finland, United Kingdom and the United States in the aerospace, automobile, chemical, computer, electronics, shipbuilding, and telecommunications industries.
Abstract: This study examines the practice of concurrent engineering (CE) in terms of process concurrency, and the impact of concurrency on success of product development projects. The study is based on 50 cross-national projects from companies in Australia, Canada, Denmark, Finland, United Kingdom, and the United States in the aerospace, automobile, chemical, computer, electronics, shipbuilding, and telecommunications industries. Four dimensions of process and behaviors of engineering/R&D and manufacturing members of cross-functional product development teams were reliably operationalized: (1) two-way communication, (2) overlapping problem solving, (3) readiness to make decisions on the basis of uncertain and ambiguous information, and (4) readiness to release uncertain and ambiguous information. These dimensions of process concurrency were found to be reliable predictors of development projects' success, as measured by product cost and quality, project schedule and budget performance, and project team satisfaction. The paper offers implications for theory and practice and models of CE management for future research.

Journal ArticleDOI
TL;DR: It is suggested that 2-VO causes neuronal dysfunction which can be exacerbated by stress and thereby manifested on aversively motivated tasks such as the water maze and reduced neuronal energy metabolism is associated with the progressive neurodegeneration that underlies disorders such as Alzheimer's.

Journal ArticleDOI
TL;DR: Comparing novices learning written genres in two different institutional settings within similar disciplines shows that when students move from the university to the workplace, they not only have to learn new genres but they need to learning new ways to learn these new genres.
Abstract: Drawing primarily on theories of situated learning, this study compares novices learning written genres in two different institutional settings within similar disciplines: university students in public administration courses and graduate student interns placed in government agencies. Observational and textual analyses of novices learning to write the genres necessary for these settings point to differences in writing goals, guide-learner roles, text evaluations, and learning sites. The results show that when students move from the university to the workplace, they not only have to learn new genres but they need to learn new ways to learn these new genres.

Book
01 Jan 1996
TL;DR: Chaves and Jones as discussed by the authors discussed the use of hypnosis as a therapeutic tool and the history of multiple personality disorder in other cultures and times, including cross-culture studies of spirit possession.
Abstract: Preface - John F. Chaves and Bill Jones About the Author Introduction I. The Use of Hypnosis as a Therapeutic Tool Hypnosis: Mythology Versus Reality High Hypnotizability and Dramatic Behaviors Hypnotic Amnesia, Posthypnotic Response, and "Brainwashing" II. Creating False Memories Distortions of Memory The Seduction Theory: Old and New Versions Child Sexual Abuse and the Fate of Abuse Memories Hypnosis, Age Regression, and Memory Complex False Memories, Body Memories, and Hypnosis UFO Abduction: An Example of Complex False Memory The Experimental Creation of Multiplicity III. Multiple Identities in Other Cultures and Times Cross-Cultural Studies of Spirit Possession Historical Manifestations of Demonic Possession The Social Functions of Possession From Possession to Dual Consciousness From Dual Consciousness to Multiple Personality The History of Dissociation IV. The Theory of Multiple Personality Disorder Multiple Personality Disorder and Social Learning Correlates of Multiple Personality Disorder Child Abuse and Multiple Personality Disorder Multiple Personality Disorder, Recovered Memories, and Sociopolitical Considerations V. Conclusion Final Thoughts References Author Index Subject Index

Journal ArticleDOI
TL;DR: In this paper, the authors measured the carbon isotope ratio of CO 2 released by respiration within forest canopies at different times during the growing season and used this information to estimate forest ecosystem CO 2 discrimination.
Abstract: Our objective was to measure the carbon isotope ratio of CO 2 released by respiration (δ r ) within forest canopies at different times during the growing season and to use this information to estimate forest ecosystem carbon isotope discrimination. We made measurements in the three major forest types (black spruce, jack pine, and aspen) at the southern and northern ends of the boreal forest in central Canada. This research was part of a larger study, the Boreal EcosystemAtmosphere Study (BOREAS). The δ r values, calculated from measurements of change in the concentration and carbon isotope ratio of atmospheric CO 2 in air samples collected at night, ranged from -28.1‰ to -25.9‰ with an average (± s.d.) of -26.8‰ ± 0.5‰. There was good correlation between calculated δ r values and measurements of (1) the carbon isotope ratio of CO 2 released directly from the soil and (2) the δ 13 C values of foliage collected from the dominant tree species at each site. Carbon isotope discrimination during photosynthetic gas exchange (Δ A ) by each forest ecosystem was estimated as the difference between the carbon isotope ratio of atmospheric CO 2 at the top of the canopy (δ a ) and the isotopic composition of respired CO 2 : Δ A = δ a - δ r . All three of the major forest types had similar values of Δ A , with an average (± s.d.) of 19.1‰ ± 0.5‰. However, a seasonal change in forest discrimination was observed for aspen forests in both the northern and southern study areas, with an increase in Δ A occurring between the middle and end of the growing season. In contrast, the evergreen conifer canopies exhibited relatively constant discrimination values throughout the active growing season.

Journal ArticleDOI
TL;DR: Because convulsive seizures develop very rapidly from kindling sites in the anterior perirhinal cortex, the anterograde tracer Phaseolus vulgaris leucoagglutinin (PhAL) was studied to determine that layer V was the main source of the perirhinofrontal projection.
Abstract: Because convulsive seizures develop very rapidly from kindling sites in the anterior perirhinal cortex, we studied perirhinal efferents by using the anterograde tracer Phaseolus vulgaris leucoagglutinin (PhAL). PhAL injections into the anterior perirhinal cortex labelled a prominent network of fibers within the frontal cortex that was most dense within layers I and II and layer VI. As individual PhAL injection sites within the perirhinal cortex were restricted to one or two adjacent laminae, we were able to determine that layer V was the main source of the perirhinofrontal projection. This was confirmed by frontal cortex injections of the retrograde tracer Fluorogold (FG). Other cortical areas with densely labelled fibers following perirhinal PhAL injections included the agranular insular, infralimbic, orbital, parietal, and entorhinal cortices. Moderate to mild fiber labelling was also noted in the posterior piriform, temporal and occipital cortices, and the claustrum. Subcortical labelling was seen in the nucleus accumbens; fundus striati; basal and lateral amygdala nuclei; the "acoustic thalamus"; and the central grey. Several of these cortical and subcortical projections were bilateral. The different laminar origin of these perirhinal efferents is discussed. These results confirmed our prediction of extensive direct projections from the anterior perirhinal cortex to the frontal cortex in the rat. The significance of this projection is discussed with special reference to the anatomical basis of convulsive limbic seizures.

Journal ArticleDOI
TL;DR: Correlative data showing increased activities of some antioxidant enzymes during freezing, as well as constitutively higher activities of antioxidant enzymes and higher levels of glutathione in the freeze-tolerant species compared with Rana pipiens, suggest that antioxidant defenses play a key role in amphibian freeze tolerance.
Abstract: Freeze-tolerant wood frogs (Rana sylvatica) must endure prolonged ischemia on freezing. Reperfusion on thawing brings with it the potential or oxidative damage due to reactive oxygen species formation, a well-known consequence of mammalian ischemia-reperfusion. To determine whether oxidative damage occurs during thawing and how frogs deal with this, we examined oxidative damage and antioxidant and prooxidant systems in tissues of Rana sylvatica and a nonfreezing relative, Rana pipiens. Glutathione status indicated little oxidative stress in tissues during freezing or thawing; an increase of the glutathione pool in the oxidized form was observed during freezing only in Rana sylvatica kidney (by 85%) and brain (by 33%). Oxidative damage to tissue lipids, measured as the levels of thiobarbituric acid-reactive substances and/or by an Fe(III)-xylenol orange assay, did not increase above control values pver a freeze-thaw time course. Correlative data showing increased activities of some antioxidant enzymes during freezing, notably glutathione peroxidase (increasing 1.2- to 2.5-fold), as well as constitutively higher activities of antioxidant enzymes and higher levels of glutathione in the freeze-tolerant species compared with Rana pipiens, suggest that antioxidant defenses play a key role in amphibian freeze tolerance.

Journal ArticleDOI
J. N. K. Rao1
TL;DR: In this paper, the authors provide an account of some recent work on jackknife variance estimation based on adjusted imputed values, using only a single imputation and hence a single completed data set.
Abstract: Unit nonresponse and item nonresponse both occur frequently in surveys. Unit nonresponse is customarily handled by weighting adjustment, whereas item nonresponse is usually treated by some form of imputation. In particular, deterministic or stochastic imputation is often used to assign values for missing item responses. We provide an account of some recent work on jackknife variance estimation based on adjusted imputed values, using only a single imputation and hence a single completed data set. We also present linearized versions of the jackknife variance estimators. We study both stratified simple random sampling and stratified multistage sampling. Existing computer programs for jackknife and linearization variance estimation can be modified to implement the proposed variance estimators without requiring the creation and permanent retention of supplemental data sets. But for secondary analyses, the completed data set must include information on response status for each item as well as on the im...