Showing papers by "University of Ottawa published in 1991"

Transition from “Supercapacitor” to “Battery” Behavior in Electrochemical Energy Storage

Abstract: The storage of electrochemical energy in battery, "supercapacitor," and double‐layer capacitor devices is considered. A comparison of the mechanisms and performance of such systems enables their essential features to be recognized and distinguished, and the conditions for transition between supercapacitor and "battery" behavior to be characterized. Supercapacitor systems based on two‐dimensional underpotential deposition reactions are highly reversible and their behavior arises from the pseudocapacitance associated with potential‐dependence of two‐dimensional coverage of electroactive adatoms on an electrode substrate surface. Such capacitance can be 10–100 times the double‐layer capacitance of the same electrode area. An essential fundamental difference from battery behavior arises because, in such systems, the chemical and associated electrode potentials are a continuous function of degree of charge, unlike the thermodynamic behavior of single‐phase battery reactants. Quasi‐two‐dimensional systems, such as hyperextended hydrous , also exhibit large pseudocapacitance which, in this case, is associated with a sequence of redox processes that are highly reversible. Such oxide redox systems give rise to the best supercapacitor behavior and capacitances of farads per gram can be achieved. Other examples are the conducting polymer electrodes and Li intercalate systems. These systems provide examples of the transition between battery and supercapacitor behavior arising from a range of degrees of oxidation/ reduction that arise over an appreciable range of potentials. The impedance behavior of an supercapacitor is illustrated but is far from that expected for an electrostatic capacitor.

Comparison of plasma exchange with plasma infusion in the treatment of thrombotic thrombocytopenic purpura.

Abstract: Background. Thrombotic thrombocytopenic purpura is an uncommon disease with a high mortality rate even with current treatment. The cause of the syndrome and its optimal treatment are unknown. Although both plasma exchange and plasma infusion have been useful treatments, it is not clear which is superior. In this report we describe a prospective randomized trial comparing plasma exchange with plasma infusion for the treatment of thrombotic thrombocytopenic purpura. Methods. One hundred two patients with thrombotic thrombocytopenic purpura were randomly assigned to receive either plasma exchange or plasma infusion with fresh-frozen plasma on seven of the first nine days after entry into the trial. The total volume of plasma received by patients undergoing plasma exchange was three times that received by patients undergoing plasma infusion. All the patients also received aspirin and dipyridamole. The outcomes in the two groups were compared at the end of the first treatment cycle (day 9) and after s...

Voigt-based methods for arbitrary-shape static hyperfine parameter distributions in Mössbauer spectroscopy

Abstract: We introduce a powerful approach for obtaining arbitrary-shape static hyperfine parameter distributions from thickness corrected Mossbauer spectra. The distributions are taken to be sums of Gaussian components and the corresponding spectra are shown analytically to be sums of Voigt lines. Three cases are worked out in detail for distributions of: i) center shifts, ii) quadrupole splittings with linear coupling to center shifts, and iii) hyperfine fields with linear couplings to center shifts and quadrupole splittings. The domain of validity of our method is described, with particular attention given to recognizing the presence of dynamic effects. An application of hyperfine field distributions to the spectra of FeNi alloys is given. In all cases, convergence is rapid and unambiguous with only two or three Gaussian components being needed for ideal fits. Adding more components does not destabilize the solution but only results in the same distribution and the same values of all the parameters being obtained. Problems occurring with other methods are eliminated by design — given the intrinsic suitability of an expansion in terms of Gaussians.

Survival and Vehicular Spread of Human Rotaviruses: Possible Relation to Seasonality of Outbreaks

Abstract: In developing countries rotavirus infections account for nearly 6% of all diarrheal episodes and for 20% of diarrhea-associated deaths of young children. Even in industrialized countries rotavirus diarrhea in the young is among the leading causes of hospitalization. In temperate regions institutional outbreaks of the disease occur mainly in cold dry weather, whereas in tropical settings the seasonality is less well defined. Waterborne outbreaks of rotavirus gastroenteritis have been recorded; air, hands, fomities, and food may also act as vehicles for this infection. Rotaviruses can survive for weeks in potable and recreational waters and for at least 4 hours on human hands. In air and on nonporous inanimate surfaces, the survival of rotaviruses is favored by a relative humidity of less than or equal to 50% and viral infectivity can be retained for several days. Rotaviruses are relatively resistant to commonly used hard-surface disinfectants and hygienic hand-wash agents.

Cortical filamentous actin disassembly and scinderin redistribution during chromaffin cell stimulation precede exocytosis, a phenomenon not exhibited by gelsolin.

Abstract: Immunofluorescence and cytochemical studies have demonstrated that filamentous actin is mainly localized in the cortical surface of the chromaffin cell. It has been suggested that these actin filament networks act as a barrier to the secretory granules, impeding their contact with the plasma membrane. Stimulation of chromaffin cells produces a disassembly of actin filament networks, implying the removal of the barrier. The presence of gelsolin and scinderin, two Ca(2+)-dependent actin filament severing proteins, in the cortical surface of the chromaffin cells, suggests the possibility that cell stimulation brings about activation of one or more actin filament severing proteins with the consequent disruption of actin networks. Therefore, biochemical studies and fluorescence microscopy experiments with scinderin and gelsolin antibodies and rhodamine-phalloidin, a probe for filamentous actin, were performed in cultured chromaffin cells to study the distribution of scinderin, gelsolin, and filamentous actin during cell stimulation and to correlate the possible changes with catecholamine secretion. Here we report that during nicotinic stimulation or K(+)-evoked depolarization, subcortical scinderin but not gelsolin is redistributed and that this redistribution precedes catecholamine secretion. The rearrangement of scinderin in patches is mediated by nicotinic receptors. Cell stimulation produces similar patterns of distribution of scinderin and filamentous actin. However, after the removal of the stimulus, the recovery of scinderin cortical pattern of distribution is faster than F-actin reassembly, suggesting that scinderin is bound in the cortical region of the cell to a component other than F-actin. We also demonstrate that peripheral actin filament disassembly and subplasmalemmal scinderin redistribution are calcium-dependent events. Moreover, experiments with an antibody against dopamine-beta-hydroxylase suggest that exocytosis sites are preferentially localized to areas of F-actin disassembly.

Effect of relative humidity and air temperature on survival of hepatitis A virus on environmental surfaces.

Abstract: Stainless steel disks (diameter, 1 cm) were contaminated with fecally suspended hepatitis A virus (HAV; strain HM-175) and held at low (25% +/- 5%), medium (55% +/- 5%), high (80% +/- 5%), or ultrahigh (95% +/- 5%) relative humidity (RH) at an air temperature of 5,20, or 35 degrees C. HAV survival was inversely proportional to the level of RH and temperature, and the half-lives of the virus ranged from greater than 7 days at the low RH and 5 degrees C to about 2 h at the ultrahigh RH and 35 degrees C. In parallel tests with fecally suspended Sabin poliovirus (PV) type 1 at the low and ultrahigh RH, all PV activity was lost within 4 h at the low RH whereas at the ultrahigh RH it remained detectable up to 12 h. HAV could therefore survive much better than PV on nonporous environmental surfaces. Moreover, the ability of HAV to survive better at low levels of RH is in direct contrast to the behavior of other enteroviruses. These findings should help in understanding the genesis of HAV outbreaks more clearly and in designing better measures for their control and prevention.

Potential role of hands in the spread of respiratory viral infections: studies with human parainfluenza virus 3 and rhinovirus 14.

Abstract: Hands often become contaminated with respiratory viruses, either directly or through contact with contaminated surfaces. Spread of such viruses could then occur by touching the nasal mucosa or the conjunctivae. In this quantitative study, we compared the survival of mucin-suspended human parainfluenza virus 3 (HPIV-3) and rhinovirus 14 (RV-14) and the transfer of the viruses to and from the fingers of adult volunteers. When each finger pad was contaminated with 10 microliters of either HPIV-3 (1.3 x 10(5) to 5.5 x 10(5) PFU) or RV-14 (2.1 x 10(4) to 1.1 x 10(5) PFU), less than 1.0% of HPIV-3 and 37.8% of RV-14 remained viable after 1 h; after 3 h, nearly 16% of RV-14 could still be detected, whereas HPIV-3 became undetectable. Tests on the potential spread of viruses from contaminated hands or surfaces were conducted 20 min after contamination of the donor surface by pressing together donor and recipient surfaces for 5 s. Transfer of HPIV-3 from finger to finger or finger to metal disk could not be detected, but 1.5% of infectious HPIV-3 was transferred from disk to finger. Irrespective of the type of donor or recipient surface, 0.7 to 0.9% of RV-14 was transferred. The relatively rapid loss of HPIV-3 infectivity on hands suggests that their role in the direct spread of parainfluenza viruses is limited. However, the findings of this study further reinforce the view that hands can be vehicles for rhinovirus colds. These results also suggest a role for nonporous environmental surfaces in the contamination of hands with respiratory viruses.

The mouse Pgk-1 gene promoter contains an upstream activator sequence.

Abstract: The Pgk-1 gene encodes the housekeeping enzyme, 3-phosphoglycerate kinase, and is ubiquitously expressed. This gene resides on the X chromosome in mammals and is always expressed except where it is silenced along with most other genes on the inactive X chromosome of female somatic cells or male germ cells. The Pgk-1 promoter is in a region rich in nucleotides G and C. This promoter can efficiently drive high levels of expression of reporter genes such as E. coli lacZ and neo. We have determined that the 120 bp upstream of the transcription start site functions as a core promoter. Upstream of this is a 320 bp region which enhances transcription from the core promoter in an orientation and position independent fashion. This 320 bp region does not enhance transcription from the core promoter of the SV40 early region. Nuclear proteins bind to this 320 bp fragment although the restricted regions to which binding can be demonstrated with gel mobility shift assays suggests that the activity of the enhancer may be mediated by factors which bind at multiple sites each with low affinity.

Aortic aneurysm in patients with functionally normal or minimally stenotic bicuspid aortic valve.

Abstract: Bicuspid aortic valve (BAV) is the most common form of congenital valvular disease, with a prevalence of approximately 1 to 2% in the general population.1 Aortic coarctation is often associated with BAV.1 A recent editorial by Lindsay2 has drawn attention once again to the concept that BAV and aortic coarctation may be manifestations of a single developmental anomaly—namely, aortic medial fragility. This idea was initially proposed by Abbot3 in 1928, revived by McKusick4 in 1972, and supported by circumstantial evidence referred to by Lindsay in his editorial. To prove that aortic medial fragility underlies BAV and aortic coarctation, one must demonstrate the presence of a pathologic or clinical correlate of aortic medial fragility in patients with the index conditions. The proposed pathologic correlate, cystic medial necrosis, is nonspecific. The clinical correlates of aortic medial fragility include aortic dilatation (aneurysm) or dissection. Although the data cited by Lindsay are suggestive of an increased prevalence of aortic dilatation/ dissection with BAV and coarctation, they could be expressions of the hemodynamic alterations accompanying the index conditions rather than manifestations of aortic medial fragility. To eliminate the confounding influence of hemodynamic disturbances, we studied the prevalence of aortic root dilatation (aneurysm) in patients with a functionally normal or minimally stenotic BAV. This study was to determine whether the aortic root at the sinus level is significantly dilated in patients with a functionally normal or minimally stenotic BAV, which we define as a resting mean aortic valve gradient <25 mm Hg, the absence of anything more than trivial aortic regurgitation and no coarctation as determined by Doppler echocardiography.

Failure to elicit neuronal macroscopic mechanosensitive currents anticipated by single-channel studies.

Abstract: Mechanosensitive channels can be observed in most cell types during single-channel recording and have been implicated in many cellular processes. Potassium-selective single-channel currents, both stretch-activated and stretch-inactivated, can be observed in growth cones and cell bodies of Lymnaea stagnalis neurons. Equivalent macroscopic mechanosensitive currents could not, however, be elicited while applying various mechanical stimuli. This discrepancy suggests that single-channel mechanosensitivity is an artifact of patch recording.

Transcutaneous energy transfer device

Abstract: An improved transcutaneous energy transfer (TET) device comprises a primary winding for placement on or near a skin surface, and a secondary winding for implantation under said skin surface. A field effect transistor (FET) is arranged to switch said primary coil across an external DC power supply. A tuning capacitor is linked to said primary coil whereby said primary coil, when said FET is turned off, will resonate at its natural frequency thereby compensating for drift in component values and reducing power transfer sensitivity to component drift. In an alternative aspect of the invention, a bidirectional communications link is provided for the transfer of data across a boundary layer by infrared signals. A plurality of transmitters are arranged in a circular pattern on one side of the boundary layer, whereas a receiver is positioned within the circular pattern along the opposite side of the boundary layer.

Bolus administration of esmolol for controlling the haemodynamic response to tracheal intubation: the Canadian Multicentre Trial.

Abstract: A multicentre trial was designed to determine the dose-response and side-effects of esmolol when administered as a single iv bolus prior to induction of anaesthesia for controlling the haemodynamic response to tracheal intubation. Five hundred and forty-eight patients from 12 university-affiliated centres across Canada were randomized prospectively to receive either placebo (PLAC) or esmolol (E) in a dose of 100 mg (E100) or 200 mg (E200). Study medication was given immediately before induction of anaesthesia with thiopentone 3-5 mg.kg-1 and succinylcholine 1.5 mg.kg-1. Low-dose narcotic (fentanyl 2-3 micrograms.kg-1 or sufentanil 0.3 micrograms.kg-1) or moderate dose narcotic (fentanyl 4-7 micrograms.kg-1) was also given at five of the participating centres, whereas patients in the remaining seven centres received no narcotic. Patients who received PLAC and no narcotic had greater HR and SBP values after tracheal intubation than patients who received either E100 or E200 (P less than 0.005). The proportion of patients whose maximum HR exceeded 110 min-1 was also greater in the PLAC group (22/180) than in either the E100 (10/187) or E200 (9/181) groups (P less than 0.05), but was not different when comparing E100 with E200. Esmolol was less effective in controlling blood pressure, but, in combination with low-dose narcotic, esmolol suppressed the SBP response to tracheal intubation. In the presence of moderate-dose narcotic, however, a decrease in SBP occurred in all three groups following induction of anaesthesia (P less than 0.003), with the largest decrease (17 +/- 4%) occurring in patients who had received E200. The overall incidence of hypotension (SBP less than 90 mmHg) was greater in the E200 group (33%) than either the E100 (25%) or PLAC (16%) groups (P less than 0.05). Other side-effects, such as bradycardia, bronchospasm or pain on injection, occurred no more frequently in either esmolol group than with placebo. It is concluded that a 100 mg bolus of esmolol is safe and effective for controlling the haemodynamic response to tracheal intubation. This dose of esmolol combined with a low dose of narcotic (fentanyl 2-3 micrograms.kg-1 or equivalent) results in effective control of both heart rate and blood pressure, while avoiding important side-effects.

Stretch-activated channels in heart cells: relevance to cardiac hypertrophy.

Abstract: Stretch-activated channels have been proposed as the transduction mechanism between load and protein synthesis in cardiac hypertrophy. Under this hypothesis, cardiac deformation is linked to an increased sodium (Na) influx, which, in turn, increases protein synthesis. We have tested whether stretch actually increases Na influx by applying patch-clamp techniques to cultured chick embryo cardiac myocytes and to freshly isolated adult guinea pig cardiomyocytes. Our experiments, in excised and cell-attached patches, revealed the existence of ionic channels that opened, or increased their frequency of opening, upon the application of negative pressures to the lumen of the patch-clamp pipettes. These stretch-sensitive channels allowed the passage of the major monovalent physiological cations, Na and potassium (K), and, to a much lesser extent, the major divalent cations calcium (Ca) and magnesium (Mg). Under normal conditions, the channels had a high open channel noise that prevented the customary, straightforward statistical analysis of single channel data. However, when one of the major monovalent cations was iso-osmotically replaced by sucrose, the open channel noise decreased significantly and permitted a good delineation of the open and closed channel states and, therefore, application of standard patch-clamp, statistical analysis techniques. Under these "sucrose," "monoionic" conditions, the reversal potential was, as one should expect, close to the equilibrium potential for the major monovalent cation present. When high extracellular K solution was used to minimize the cell resting potential, the reversal potential for these stretch-activated currents was estimated to be around -40 mV. Therefore, under normal conditions, stretch should induce an inward, depolarizing current, carried mostly by Na ions.(ABSTRACT TRUNCATED AT 250 WORDS)

Dimensions of perfectionism and irrational thinking

Abstract: Several authors have suggested that perfectionism is associated with irrational thinking. The purpose of the present research was to test the hypothesis that various dimensions of perfectionism are related significantly to core irrational beliefs. In Study 1, 102 subjects completed the Multidimensional Perfectionism Scale (MPS) and the Irrational Beliefs Test (IBT). The MPS provides assessments of self-oriented, other-oriented, and socially prescribed perfectionism. Analyses revealed that self-oriented perfectionism was correlated positively with the IBT high self-expectations and perfect solutions subscales. Socially prescribed perfectionism was correlated significantly with a variety of irrational beliefs including high self-expectations, demand for social approval, dependency, blame proneness, and anxious overconcern. Other-oriented perfectionism was correlated with few irrational beliefs. In Study 2, 130 subjects completed the MPS and the Survey of Personal Beliefs, a new measure of core irrational beliefs. Analyses confirmed that all three perfectionism dimensions were associated with core irrational beliefs. It is concluded that the results constitute general support for the hypothesis that cognitive aspects are important in both personal and social components of perfectionism and that perfectionists are characterized by increased levels of irrational beliefs that may contribute to maladjustment. The findings are discussed in terms of the associations among perfectionism, irrational beliefs, and maladjustment.

Professionalism, structures and systems: the impact of professional staff on voluntary sport organizations.

Abstract: The purpose of this study was to investigate the impact that the hiring of a professional staff person had on the structural and systemic arrangements of a voluntary sport organization. Six organizations were examined at critical decisions points following the hiring of a professional staff member. The introduction of these people was shown to result in an increase in both the levels of specialization and standardization within these organizations. The increases occurred differentially across organizational systems, with technical systems showing the greatest increases. Decision making was found to become more centralized immediately after the hiring of a professional, however it decentralized over time.

Psychopathology among substance abusing juvenile offenders.

Abstract: The prevalence of substance abuse and cocxisting DSM-III psychiatric disorders was evaluated in 111 juvenile offenders. As expected, a high rate of conduct disorder (91 %) was present in both substance abusing and nonsubstance abusing juvenile offenders. However, significantly higher rates of attention deficit disorder and aggressive subtype of conduct disorder were present in those offenders who abused drugs and alcohol (54%). Excluding all conduct and oppositional disorder diagnoses 39% of substance abusers versus 14% of the nonsubstance abusers demonstrated comorbid psychiatric diagnoses. These findings suggest that careful psychiatric evaluation of juvenile substance abusers may be necessary to optimize treatment planning.

A gene showing sequence similarity to pectin esterase is specifically expressed in developing pollen of Brassica napus. Sequences in its 5' flanking region are conserved in other pollen-specific promoters.

Abstract: Differential screening of a Brassica napus genomic library led to the isolation of the clone named Bp 19 containing a gene which is highly expressed during microspore development. The accumulation of Bp 19 mRNA starts in uninucleate microspores, increases during development reaching a peak in the late stages but declines considerably in mature pollen. The nucleotide sequence of the entire coding region and of extended portions of the 5′ and 3′ flanking regions was determined. Several homologous cDNA clones were also isolated and sequenced. The Bp 19 gene contains a single intron of 137 bp and gives origin to a mRNA of ca. 1.9 kb which codes for a polypeptide of 584 amino acids. Bp 19 protein has an estimated molecular weight of 63 kilodaltons and has a highly hydrophobic amino terminal region which shows features of a signal peptide. The carboxy half of the Bp 19 protein, starting at amino acid 269, has striking sequence similarity to the pectin esterases of tomato and of the plant pathogen Erwinia chrysanthemi. Four short domains are extremely well conserved in all the three proteins and therefore could represent catalytic sites responsible for enzyme activity. Comparison of the 5′ flanking region of the Bp 19 gene with the sequence of other pollen-specific promoters revealed the presence of several conserved regions. These short promoter sequences could correspond to regulatory elements responsible for pollen-specific gene expression.