Showing papers by "Dalhousie University published in 1999"

Defining the Family Business by Behavior

Abstract: It is generally accepted that a family's involvement in the business makes the family business unique; but the literature continues to have difficulty defining the family business. We argue for a d...

The American College of Rheumatology nomenclature and case definitions for neuropsychiatric lupus syndromes

Abstract: OBJECTIVE To develop a standardized nomenclature system for the neuropsychiatric syndromes of systemic lupus erythematosus (NPSLE). METHODS An international, multidisciplinary committee representing rheumatology, neurology, psychiatry, neuropsychology, and hematology developed case definitions, reporting standards, and diagnostic testing recommendations. Before and after the meeting, clinician committee members assigned diagnoses to sets of vignettes randomly generated from a pool of 108 NPSLE patients. To assess whether the nomenclature system improved diagnostic agreement, a consensus index was developed and pre- and postmeeting scores were compared by t-tests. RESULTS Case definitions including diagnostic criteria, important exclusions, and methods of ascertainment were developed for 19 NPSLE syndromes. Recommendations for standard reporting requirements, minimum laboratory evaluation, and imaging techniques were formulated. A short neuropsychological test battery for the diagnosis of cognitive deficits was proposed. In the postmeeting exercise, a statistically significant improvement in diagnostic agreement was observed. CONCLUSION The American College of Rheumatology (ACR) Nomenclature for NPSLE provides case definitions for 19 neuropsychiatric syndromes seen in SLE, with reporting standards and recommendations for laboratory and imaging tests. It is intended to facilitate and enhance clinical research, particularly multicenter studies, and reporting. In clinical settings, consultation with other specialists may be required. It should be useful for didactic purposes but should not be used uncritically or as a substitute for a clinical diagnosis. The complete case definitions are available on the ACR World Wide Web site: http://www.rheumatology .org/ar/ar.html.

Toward a Reconciliation of the Definitional Issues in the Field of Corporate Entrepreneurship

Abstract: Although authors generally agree on the nature of entrepreneurial activities within existing firms, differences in the terminology used to describe those activities have created confusion. This article discusses existing definitions in the field of corporate entrepreneurship, reconciles these definitions, and provides criteria for classifying and understanding the activities associated with corporate venturing.

Extinction rates of North American freshwater fauna

Abstract: Since 1900, 123 freshwater animal species have been recorded as extinct in North America. Hun- dreds of additional species of fishes, mollusks, crayfishes, and amphibians are considered imperiled. Using an exponential decay model, we derived recent and future extinction rates for North American freshwater fauna that are five times higher than those for terrestrial fauna. Assuming that imperiled freshwater species will not survive throughout the next century, our model projects a future extinction rate of 4% per decade, which sug- gests that North America's temperate freshwater ecosystems are being depleted of species as rapidly as tropi- cal forests.

A comparison of three months of anticoagulation with extended anticoagulation for a first episode of idiopathic venous thromboembolism.

Abstract: Background Patients who have a first episode of venous thromboembolism in the absence of known risk factors for thrombosis (idiopathic thrombosis) are often treated with anticoagulant therapy for three months. Such patients may benefit from longer treatment, however, because they appear to have an increased risk of recurrence after anticoagulant therapy is stopped. Methods In this double-blind study, we randomly assigned patients who had completed 3 months of anticoagulant therapy for a first episode of idiopathic venous thromboembolism to continue receiving warfarin, with the dose adjusted to achieve an international normalized ratio of 2.0 to 3.0, or to receive placebo for a further 24 months. Our goal was to determine the effects of extended anticoagulant therapy on rates of recurrent symptomatic venous thromboembolism and bleeding. Results A prespecified interim analysis of efficacy led to the early termination of the trial after 162 patients had been enrolled and followed for an average of 10 months....

Inhibition of Return is a Foraging Facilitator in Visual Search

Abstract: Using overt orienting, participants searched a complex visual scene for a camouflaged target (Waldo from the “Where's Waldo?™” books). After several saccades, we presented an uncamouflaged probe (black disk) while removing or maintaining the scene, and participants were required to locate this probe by foveating it. Inhibition of return was observed as a relative increase in the time required to locate these probes when they were in the general region of a previous fixation, but only when the search array remained present. Perhaps also reflecting inhibition of return, preprobe saccades showed a strong directional bias away from a previously fixated region. Together with recent studies that replicate the finding of inhibition at distractor locations following serial but not parallel visual search—so long as the search array remains visible—these data strongly support the proposal that inhibition of return functions to facilitate visual search by inhibiting orienting to previously examined locations.

Projections of the median raphe nucleus in the rat.

Abstract: No previous report in any species has examined comprehensively the projections of the median raphe (MR) nucleus with modern tracing techniques. The present report represents an in depth analysis of the projections of MR by use of the anterograde anatomical tracer Phaseolus vulgaris-leucoagglutinin. MR fibers descend along the midline within the brainstem and mainly ascend within the medial forebrain bundle in the forebrain. MR fibers distribute densely to the following brainstem/forebrain sites: caudal raphe nuclei, laterodorsal tegmental nucleus, dorsal raphe nucleus, interpeduncular nucleus, medial mammillary body, supramammillary nucleus, posterior nucleus and perifornical region of the hypothalamus, midline and intralaminar nuclei of thalamus, dopamine-containing cell region of medial zona incerta, lateral habenula, horizontal and vertical limbs of the diagonal band nuclei, medial septum, and hippocampal formation. Virtually all of these structures lie on or close to the midline, indicating that the MR represents a midline/para-midline system of projections. Overall, MR projections to the cortex are light. MR projects moderately to the perirhinal, entorhinal and frontal cortices, but sparingly to remaining regions of cortex. A comparison of MR with dorsal raphe (DR) projections (Vertes RP. 1991. J Comp Neurol 313:643-668) shows that these two major serotonin-containing cell groups of the midbrain distribute to essentially nonoverlapping regions of the forebrain; that is, the MR and DR project to complementary sites in the forebrain. A direct role for the MR in the desynchronization of the electroencephalographic activity of the hippocampus and its possible consequences for memory-associated functions of the hippocampus is discussed.

Accelerating Rate Calorimetry Study on the Thermal Stability of Lithium Intercalated Graphite in Electrolyte. I. Experimental

Abstract: An accelerating rate calorimeter (ARC) was used to measure the thermal stability of a lithiated mesocarbon microbead (MCMB) material in electrolyte under adiabatic conditions. Measurements were carried out to determine the effects of the lithium content and surface area of the electrode as well as the effects of the electrolyte type and the initial heating temperature on thermal stability. MCMB electrodes with both high and low surface area were reacted electrochemically to three compositions: , , and in ethylene carbonate/diethyl carbonate (EC:DEC) (33:67) electrolyte. The low‐surface‐area MCMB samples were also lithiated in EC:DEC (50:50) and EC:DEC (50:50) electrolytes The results showed that self‐heating of the MCMB samples depends on (i) the initial lithium content of the material; (ii) the electrolyte used; (iii) the surface area, and (iv) the initial heating temperature of the sample. Measurable self‐heating in the EC:DEC (33:67) samples was detected at 80°C, at 70°C for MCMB in EC:DEC (1:1), and at 50°C for MCMB in EC:DEC (1:1). The initial self‐heating rate for samples containing EC:DEC (33:67) electrolyte could be fit by an Arrhenius relation with an activation energy of 1.4 eV. The initial form of the self‐heating rate profile was a result of the conversion of metastable solid electrolyte interface (SEI) components to stable SEI components. © 1999 The Electrochemical Society. All rights reserved.

On the possibility of constructive neutral evolution.

Abstract: The neutral theory often is presented as a theory of "noise" or silent changes at an isolated "mo- lecular level," relevant to marking the steady pace of divergence, but not to the origin of biological structure, function, or complexity. Nevertheless, precisely these is- sues can be addressed in neutral models, such as those elaborated here with regard to scrambled ciliate genes, gRNA-mediated RNA editing, the transition from self- splicing to spliceosomal splicing, and the retention of duplicate genes. All of these are instances of a more general scheme of "constructive neutral evolution" that invokes biased variation, epistatic interactions, and ex- cess capacities to account for a complex series of steps giving rise to novel structures or operations. The direc- tional and constructive outcomes of these models are due not to neutral allele fixations per se, but to these other factors. Neutral models of this type may help to clarify the poorly understood role of nonselective factors in evo- lutionary innovation and directionality.

Role of primate superior colliculus in preparation and execution of anti-saccades and pro-saccades

Abstract: We investigated how the brain switches between the preparation of a movement where a stimulus is the target of the movement, and a movement where a stimulus serves as a landmark for an instructed movement elsewhere. Monkeys were trained on a pro-/anti-saccade paradigm in which they either had to generate a pro-saccade toward a visual stimulus or an anti-saccade away from the stimulus to its mirror position, depending on the color of an initial fixation point. Neural activity was recorded in the superior colliculus (SC), a structure that is known to be involved in the generation of fast saccades, to determine whether it was also involved in the generation of anti-saccades. On anti-saccade trials, fixation during the instruction period was associated with an increased activity of collicular fixation-related neurons and a decreased activity of saccade-related neurons. Stimulus-related and saccade-related activity was reduced on anti-saccade trials. Our results demonstrate that the anti-saccade task involves (and may require) the attenuation of preparatory and stimulus-related activity in the SC to avoid unwanted pro-saccades. Because the attenuated pre-saccade activity that we found in the SC may be insufficient by itself to elicit correct anti-saccades, additional movement signals from other brain areas are presumably required.

Mechanically Alloyed Sn‐Fe(‐C) Powders as Anode Materials for Li‐Ion Batteries: I. The Sn2Fe ‐ C System

Abstract: The authors have prepared intermetallic phases and mixtures of such phases in the Sn-Fe-C Gibbs triangle by mechanical alloying methods or by direct melting. This second paper in a three-part series focuses on the intermetallic phases in the binary Sn-Fe system, Sn{sub 2}Fe, SnFe, Sn{sub 2}Fe{sub 3}, and Sn{sub 3}Fe{sub 5}. Using in situ X-ray diffraction and electrochemical methods, the authors study the reversible reaction of Li with these materials. Li/Sn-Fe cells made from annealed powders have reversible capacities of 600, 50, 20 mAh/g, respectively, for Sn{sub 2}Fe, SnFe, Sn{sub 2}Fe{sub 3}, and Sn{sub 3}Fe{sub 5}. Li/Sn-Fe cells made from the same materials, but after high-impact ballmilling, show reversible capacities of 650, 320, 200, and 150 mAh/g. Specific capacities of 804, 676, 582, and 557 mAh/g are expected for Sn{sub 2}Fe, SnFe, Sn{sub 2}Fe{sub 3}, and Sn{sub 3}Fe{sub 5} if all compounds react fully with Li to form Li{sub 4.4}Sn and Fe. In situ X-ray diffraction experiments on the ballmilled materials confirm the formation of /Li{sub 4}Sn during discharge but also show that in the cases of SnFe, Sn{sub 2}Fe{sub 3}, and Sn{sub 3}Fe{sub 5} at least 50% of the starting phase remains unreacted. Structural considerations suggest that as themore » Fe:Sn ratio increases, Fe atoms may form a impenetrable skin on the surface of particles or grains, as Li reacts with the Sn-Fe compounds. This skin prevents the full reaction of the intermetallic with Li, leading to an observed capacity which is lower than expected. High-impact ballmilling reduces particle and grain size, so the effect of the skin is less than for the annealed powders and higher capacities are obtained. As the Fe content in the Sn-Fe intermetallics increases, the cycle life of the materials improves, presumably because there is more Fe per Sn and because the formed Fe and residual starting material act as a matrix to hold the Sn and Li-Sn alloys together during cycling. The authors give an example of a material with a volumetric capacity of 1200 mAh/cm{sup 3} showing stable cycling for over 80 cycles.« less

A finite-difference time-domain method without the Courant stability conditions

Abstract: In this paper, a finite-difference time-domain method that is free of the constraint of the Courant stability condition is presented for solving electromagnetic problems. In it, the alternating direction implicit (ADI) technique is applied in formulating the finite-difference time-domain (FDTD) algorithm. Although the resulting formulations are computationally more complicated than the conventional FDTD, the proposed FDTD is very appealing since the time step used in the simulation is no longer restricted by stability but by accuracy. As a result, computation speed can be improved. It is found that the number of iterations with the proposed FDTD can be at least three times less than that with the conventional FDTD with the same numerical accuracy.

The risk of dementia and death after delirium.

Abstract: Background delirium is common and is associated with many adverse short-term consequences. Objectives to examine the relationship between an episode of delirium and subsequent dementia and death over 3 years. Design prospective cohort study. Setting patients (n = 203) were aged 65 years or older at baseline and survivors of the index admission. Methods Using a standard assessment of cognitive function, we followed 38 inpatients diagnosed with delirium (22 with delirium and dementia, 16 with delirium only) and 148 patients with no delirium or dementia, for a median of 32.5 months. Follow-up was by personal interviews, supplemented by standardized clinical examinations. We calculated the incidence and odds of dementia and the incidence and hazard ratio for death, with adjustment for potential confounders. Results The incidence of dementia was 5.6% per year over 3 years for those without delirium and 18.1% per year for those with delirium. The unadjusted relative risk of dementia for those with delirium was 3.23 (95% confidence interval 1.86-5.63). The adjusted relative risk of death also increased (1.80; 1.11-2.92), while the median survival time was significantly shorter in those with (510 days; 433-587) than in those without delirium (1122 days; 922-1322). Conclusion delirium appears to be an important marker of risk for dementia and death, even in older people without prior cognitive or functional impairment.

Proteus syndrome: diagnostic criteria, differential diagnosis, and patient evaluation.

Abstract: Proteus syndrome is a complex disorder comprising malformations and overgrowth of multiple tissues. The disorder is highly variable and appears to affect patients in a mosaic manner. This intrinsic variability has led to diagnostic confusion associated with a dearth of longitudinal data on the natural history of Proteus syndrome. To clarify some of these issues, a workshop on Proteus syndrome was held in March 1998 at the National Institutes of Health, and participants developed recommendations for diagnostic criteria, differential diagnosis, and guidelines for the evaluation of patients. This is a review of those recommendations.

Molecular evolution of the metaplasia-dysplasia-adenocarcinoma sequence in the esophagus.

Abstract: The incidence of adenocarcinoma of the esophagus has been increasing in developing countries over the last three decades and probably reflects a genuine increase in the incidence of its recognized precursor lesion, Barrett's metaplasia. Despite advances in multimodality therapy, the prognosis for invasive esophageal adenocarcinoma is poor. An improved understanding of the molecular biology of this disease may allow improved diagnosis, therapy, and prognosis. We focus on recent developments in the molecular and cell biology of Barrett's metaplasia, a heterogeneous lesion affecting the transitional zone of the gastro-esophageal junction whose associated molecular alterations may vary both in nature and temporally. Early premalignant clones produce biological and genetic heterogeneity as seen by multiple p53 mutations, p16 mutations, aneuploidy, and abnormal methylation resulting in stepwise changes in differentiation, proliferation, and apoptosis, allowing disease progression under selective pressure. Abnormalities in expression of growth factors of the epidermal growth factor family and cell adhesion molecules, especially cadherin/catenin complexes, may occur early in invasion. Exploitation of these molecular events may lead to a more appropriate diagnosis and understanding of these lesions in the future.

Compromising Power:Development, Culture, and Rule in Indonesia

Abstract: accomplishment of rule owes as much to the understandings and practices worked out in the contingent and compromised space of cultural intimacy as it does to the imposition of development schemes and related forms of disciplinary power.3 My study is grounded ethnographically in an analysis of Indonesia's official program for the resettlement of isolated people. Resettlement programs are familiar enough as objects of anthropological study and critique, and there are many important accounts of the damage done to indigenous folk by inept bureaucrats and bullying regimes. My focus is rather different, for I seek less to expose the all-too-predictable havoc wreaked by state power in the periphery than to highlight the significance of that periphery, and the activities that go on there, in the constitution of the self-proclaimed center. Just as others have shown that colonialism was critical to the self-fashioning of the West (Cooper and Stoler 1997), "development" is here explored as a modern state's attempt at self-fashioning and rule, considered always as fragile and contingent accomplishments.4

Leptin gene expression in the brain and pituitary gland.

Abstract: The adipocyte-derived hormone, leptin, and its receptor, are now known to be integral components of a physiological signalling system that regulates fuel stores and energy balance. Constitutive leptin expression has been demonstrated only in adipose tissue, placenta and stomach. We have used RT-PCR to show that leptin mRNA is selectively transcribed in specific areas of rat brain and pituitary, and in a rat glioblastoma cell line. Using immunocytochemistry we have also shown leptin protein immunoreactivity in the corresponding tissues and cells, and confirmed this by Western blot using two epitope-specific antisera. Leptin mRNA expression in the hypothalamus is suppressed by fasting (48hr), suggesting a role for brain leptin in the central regulation of appetite. These data support the hypothesis that central nervous system derived leptin is a likely ligand for central leptin receptors.

Transcription factors and their genes in higher plants functional domains, evolution and regulation.

Abstract: A typical plant transcription factor contains, with few exceptions, a DNA-binding region, an oligomerization site, a transcription-regulation domain, and a nuclear localization signal Most transcription factors exhibit only one type of DNA-binding and oligomerization domain, occasionally in multiple copies, but some contain two distinct types DNA-binding regions are normally adjacent to or overlap with oligomerization sites, and their combined tertiary structure determines critical aspects of transcription factor activity Pairs of nuclear localization signals exist in several transcription factors, and basic amino acid residues play essential roles in their function, a property also true for DNA-binding domains Multigene families encode transcription factors, with members either dispersed in the genome or clustered on the same chromosome Distribution and sequence analyses suggest that transcription factor families evolved via gene duplication, exon capture, translocation, and mutation The expression of transcription factor genes in plants is regulated at transcriptional and post-transcriptional levels, while the activity of their protein products is modulated post-translationally The purpose of this review is to describe the domain structure of plant transcription factors, and to relate this information to processes that control the synthesis and action of these proteins

Thickness and Elasticity of Gram-Negative Murein Sacculi Measured by Atomic Force Microscopy

Abstract: Atomic force microscopy was used to measure the thickness of air-dried, collapsed murein sacculi from Escherichia coli K-12 and Pseudomonas aeruginosa PAO1. Air-dried sacculi from E. coli had a thickness of 3.0 nm, whereas those from P. aeruginosa were 1.5 nm thick. When rehydrated, the sacculi of both bacteria swelled to double their anhydrous thickness. Computer simulation of a section of a model single-layer peptidoglycan network in an aqueous solution with a Debye shielding length of 0.3 nm gave a mass distribution full width at half height of 2.4 nm, in essential agreement with these results. When E. coli sacculi were suspended over a narrow groove that had been etched into a silicon surface and the tip of the atomic force microscope used to depress and stretch the peptidoglycan, an elastic modulus of 2.5 x 10(7) N/m(2) was determined for hydrated sacculi; they were perfectly elastic, springing back to their original position when the tip was removed. Dried sacculi were more rigid with a modulus of 3 x 10(8) to 4 x 10(8) N/m(2) and at times could be broken by the atomic force microscope tip. Sacculi aligned over the groove with their long axis at right angles to the channel axis were more deformable than those with their long axis parallel to the groove axis, as would be expected if the peptidoglycan strands in the sacculus were oriented at right angles to the long cell axis of this gram-negative rod. Polar caps were not found to be more rigid structures but collapsed to the same thickness as the cylindrical portions of the sacculi. The elasticity of intact E. coli sacculi is such that, if the peptidoglycan strands are aligned in unison, the interstrand spacing should increase by 12% with every 1 atm increase in (turgor) pressure. Assuming an unstressed hydrated interstrand spacing of 1.3 nm (R. E. Burge, A. G. Fowler, and D. A. Reaveley, J. Mol. Biol. 117:927-953, 1977) and an internal turgor pressure of 3 to 5 atm (or 304 to 507 kPa) (A. L. Koch, Adv. Microbial Physiol. 24:301-366, 1983), the natural interstrand spacing in cells would be 1.6 to 2.0 nm. Clearly, if large macromolecules of a diameter greater than these spacings are secreted through this layer, the local ordering of the peptidoglycan must somehow be disrupted.

On the Aggregation of Tin in SnO Composite Glasses Caused by the Reversible Reaction with Lithium

Abstract: We show that the reaction mechanism in Li/[SnO:(B 2 O 3 ) x :(P 2 O 5 ) y glass (0.1≤x,y≤0.5)], Li/[SnO: B 2 O 3 ) 0.5 :(P 2 O 5 ) 0.5 :(K 2 CO 3 ) 0.04 glass] and Li/SnO cells is common. During the first discharge, the oxygen bonded to tin (as SnO) reacts with lithium to give metallic tin (which can be present as clusters of a few atoms) and lithia. The tin reacts with further lithium to the composition limit of Li 4.4 Sn. During charge the Li is removed from the lithium-tin alloy. The other components of the glass (e.g., B 2 O 3 . P 2 O 5 , Li 2 O, etc, ) are inert with respect to lithium, and we call the atoms which make up these phases spectator atoms, Using X-ray diffraction (XRD) and electrochemical methods, we show that size of the initial tin regions which form is inversely proportional to the spectator:Sn atom ratio. However, during cycling, all of these materials show the subsequent aggregation of the tin atoms into clusters which grow with cycle number until they reach a saturated size. The final cluster size is larger for materials with smaller X:Sn ratio. We propose a speculative model, which predicts the saturated Sn cluster size, as a function of the spectator:Sn ratio.

Development of the Quality of Life in Epilepsy Inventory for Adolescents: the QOLIE-AD-48.

Abstract: Summary: Purpose: We report the development of an instrument to assess health-related quality of life (HRQOL) in adolescents with epilepsy. Methods: A sample of 197 English-speaking adolescents (aged 11–17 years) with epilepsy completed a test questionnaire of 88 items. Also included were mastery and self-esteem scales to assess external validity. A parent simultaneously completed an 11-item questionnaire to evaluate the child's HRQOL. Both adolescent and parent questionnaires were repeated in 2–4 weeks. Demographic information and information pertaining to seizures were collected at baseline along with assessment of systemic and neurologic toxicity. Results: The QOLIE-AD-48 contains 48 items in eight subscales: epilepsy impact (12 items), memory/concentration (10), attitudes toward epilepsy (four), physical functioning (five), stigma (six), social support (four), school behavior (four), health perceptions (three), and a total summary score, with higher scores indicating better HRQOL. Internal construct validity was demonstrated in a single-factor solution for the eight dimensions. All correlations were statistically significant at p < 0.05 level. Internal consistency reliability estimated by Cronbach's alpha coefficient was 0.74 for the summary score and ranged from a low of 0.52 (three-item Health Perceptions Scale) to 0.73–0.94 for the other individual scales. Good testretest reliability was found for the overall measure (0.83). Summary score correlations with the two external validity scales, self-efficacy and self-esteem were 0.65 and 0.54, respectively. Statistically significant differences in summary scores indicating that HRQOL was increasingly better for adolescents as seizure severity decreases (no seizures = 77 ± 13, low = 70 ± 17, high = 63 ± 17) were found among seizure-severity groups. Conclusions: These data describe the development of a robust instrument to evaluate HRQOL in adolescents with epilepsy. Empiric analyses provide strong evidence that the QOLIE-AD-48 is both a reliable and valid measure for adolescents with epilepsy.