Showing papers by "Dalhousie University published in 1997"

Electrochemical and In Situ X‐Ray Diffraction Studies of the Reaction of Lithium with Tin Oxide Composites

Abstract: We report our electrochemical and in situ x‐ray diffraction experiments on a variety of tin oxide based compounds; SnO, , , and glass, as cathodes opposite lithium metal in a rechargeable Li‐ion coin cell. These materials demonstrate discharge capacities on the order of 1000 mAh/(g Sn), which is consistent with the alloying capacity limit of 4.4 Li atoms per Sn atom, or 991 mAh/(g Sn). These materials also demonstrate significant irreversible capacities ranging from 200 mAh/(g active) to 700 mAh/(g active). In situ x‐ray diffraction experiments on these materials show that by introducing lithium, lithium oxide and tin form first, which is then followed by the formation of the various Li‐Sn alloy phases. When lithium is removed the original material does not reform. The ending composition is metallic tin, presumably mixed with amorphous lithium oxide. The oxygen from the tin oxide in the starting material bonds irreversibly with lithium to form an amorphous matrix. The Li‐Sn alloying process is quite reversible; perhaps due to the formation of this lithia "matrix" which helps to keep the electrode particles mechanically connected together.

Strategic Management of the Family Business: Past Research and Future Challenges

Abstract: This article reviews the literature on family business from a strategic management perspective. In general, this literature is dominated by descriptive articles that typically focus on family relationships. However, the literature does not usually address how these relationships affect the performance of a family business. Taking a strategic management perspective, we outline a new set of objectives for family-business research. We also identify some of the key issues and gaps that should be explored in future studies if research is to contribute to improving the management practices and performance of family firms.

The role of nitrogen fixation in biogeochemical cycling in the subtropical North Pacific Ocean

Abstract: Seven years of time-series observations of biogeochemical processes in the subtropical North Pacific Ocean gyre have revealed dramatic changes in the microbial community structure and in the mechanisms of nutrient cycling in response to large-scale ocean–atmosphere interactions. Several independent lines of evidence show that the fixation of atmospheric nitrogen by cyanobacteria can fuel up to half of the new production. These and other observations demand a reassessment of present views of nutrient and carbon cycling in one of the Earth′s largest biomes.

Distinct sites of intracellular production for Alzheimer's disease A beta40/42 amyloid peptides.

Abstract: The Alzheimer amyloid precursor protein (APP) is cleaved by several proteases, the most studied, but still unidentified ones, are those involved in the release of a fragment of APP, the amyloidogenic beta-protein A beta. Proteolysis by gamma-secretase is the last processing step resulting in release of A beta. Cleavage occurs after residue 40 of A beta [A beta(1-40)], occasionally after residue 42 [A beta(1-42)]. Even slightly increased amounts of this A beta(1-42) might be sufficient to cause Alzheimer's disease (AD) (reviewed in ref. 1, 2). It is thus generally believed that inhibition of this enzyme could aid in prevention of AD. Unexpectedly we have identified in neurons the endoplasmic reticulum (ER) as the site for generation of A beta(1-42) and the trans-Golgi network (TGN) as the site for A beta(1-40) generation. It is interesting that intracellular generation of A beta seemed to be unique to neurons, because we found that nonneuronal cells produced significant amounts of A beta(1-40) and A beta(1-42) only at the cell surface. The specific production of the critical A beta isoform in the ER of neurons links this compartment with the generation of A beta and explains why primarily ER localized (mutant) proteins such as the presenilins could induce AD. We suggest that the earliest event taking place in AD might be the generation of A beta(1-42) in the ER.

World-Wide Web survey research: Benefits, potential problems, and solutions

Abstract: The World-Wide Web presents survey researchers with an unprecedented tool for the collection of data. The costs in terms of both time and money for publishing a survey on the Web are low compared with costs associated with conventional surveying methods. The data entry stage is eliminated for the survey administrator, and software can ensure that the data acquired from participants is free from common entry errors. Importantly, Web surveys can interactively provide participants with customized feedback. These features come at a price—ensuring that appropriately written software manages the data collection process. Although the potential for missing data, unacceptable responses, duplicate submissions, and Web abuse exist, one can take measures when creating the survey software to minimize the frequency and negative consequences of such incidents.

The reliability of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index in patients with systemic lupus erythematosus.

Abstract: Objective. To test the reliability of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) Damage Index and the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) in the assessment of patients with SLE. Methods. Ten patients with SLE, representing a spectrum of damage and activity, were included. Each patient was examined by 6 of 10 physicians from 5 countries, representing 10 lupus clinics. The SLICC/ACR Damage Index was used to assess accumulated damage, and the SLEDAI was used to assess disease activity. The order of the patients and physicians was randomized according to a Youden square design. Results. The SLICC/ACR Damage Index detected differences among patients (P < 0.001). There was no detectable observer difference (P = 0.933), and there was no order effect (P = 0.261). Similar results were obtained with the SLEDAI. There was concordance in the SLICC/ACR Damage Index among observers, despite a wide spectrum of disease activity detected by the SLEDAI. Conclusion. Physicians from different centers are able to assess patients with SLE in a reproducible way, using the SLEDAI to assess disease activity and the SLICC/ACR Damage Index to assess accumulated damage.

Gross and microscopic anatomy of the human intrinsic cardiac nervous system

Abstract: Background The extent and locations of intrinsic cardiac ganglia on the human heart were investigated to facilitate studying their function. Methods The locations and number of major intrinsic cardiac ganglia were determined in six human hearts by means of microdissection following methylene blue staining. Light and electron microscopic analyses were performed on right atrial and cranial medial ventricular ganglia obtained from 12 other human hearts. Results Gross anatomy: Collections of ganglia associated with nerves, i.e., ganglionated plexuses, were observed consistently in five atrial and five ventricular regions. Occasional ganglia were located in other atrial and ventricular regions. Atrial ganglionated plexuses were identified on 1) the superior surface of the right atrium, 2) the superior surface of the left atrium, 3) the posterior surface of the right atrium, 4) the posterior medial surface of the left atrium (the latter two fuse medially where they extend anteriorly into the interatrial septum), and 5) the inferior and lateral aspect of the posterior left atrium. Ventricular ganglionated plexuses were located in fat 1) surrounding the aortic root, 2) at the origins of the right and left coronary arteries (the latter extending to the origins of the left anterior descending and circumflex coronary arteries), 3) at the origin of the posterior descending coronary artery, 4) adjacent to the origin of the right acute marginal coronary artery, and 5) at the origin of the left obtuse marginal coronary artery. Microscopic anatomy: Ganglia ranged in size from those containing a few neurons to large ganglia measuring up to 0.5 × 1 mm. The human heart is estimated to contain more than 14,000 neurons. Neuronal somata varied in size and shape. Many axon terminals in intrinsic cardiac ganglia contained large numbers of small, clear, round vesicles that formed asymmetrical axodendritic synapses, whereas a few axons contained large, dense-cored vesicles. Conclusions The human intrinsic cardiac nervous system is distributed more extensively than was considered previously, most of its ganglia being located on the posterior surfaces of the atria and superior aspect of the ventricles. Each ganglion therein contains a variety of neurons that are associated with complex synaptology. Anat. Rec. 247:289-298, 1997. © 1997 Wiley-Liss, Inc.

An ancestral mitochondrial DNA resembling a eubacterial genome in miniature

Abstract: Mitochondria, organelles specialized in energy conservation reactions in eukaryotic cells, have evolved from eubacteria-like endo-symbionts 1–3 whose closest known relatives are the rickettsial group of α-proteobacteria 4,5. Because characterized mitochondrial genomes vary markedly in structure3, it has been impossible to infer from them the initial form of the proto-mitochondrial genome. This would require the identification of minimally derived mitochondrial DNAs that better reflect the ancestral state. Here we describe such a primitive mitochondrial genome, in the freshwater protozoon Reclinomonas americana6. This protist displays ultrastructural characteristics that ally it with the retortamonads7,8, a protozoan group that lacks mitochondria8,9. R. americana mtDNA (69,034 base pairs) contains the largest collection of genes (97) so far identified in any mtDNA, including genes for 5S ribosomal RNA, the RNA component of RNase P, and at least 18 proteins not previously known to be encoded in mitochondria. Most surprising are four genes specifying a multisubunit, eubacterial-type RNA polymerase. Features of gene content together with eubacterial characteristics of genome organization and expression not found before in mitochondrial genomes indicate that R. americana mtDNA more closely resembles the ancestral proto-mitochondrial genome than any other mtDNA investigated to date.

Key Factors Controlling the Reversibility of the Reaction of Lithium with SnO2 and Sn2 BPO 6 Glass

Abstract: Tin oxide composite glasses represent a new class of material for the anode of Li-ion cells. Using results of experiments on Li/Sn{sub 2}BPO{sub 6} and Li/SnO{sub 2} cells, the authors identify those factors which are responsible for good charge-discharge capacity retention. First, the grains (those regions which diffract coherently) which make up the particles of the material should be as small as possible. Then, regions of tin which form are kept small and two-phase coexistence regions between bulk Li-Sn alloys of different composition do not occur. The Sn{sub 2}BPO{sub 6} glass represents the smallest grains possible. Second, the particles themselves should be small so that they can each be well contacted by carbon black during electrode manufacture. Third, the voltage range of cycling must be selected so that the tin atoms do not aggregate into large regions which grow in size. This aggregation is evidenced by the growth of peaks in the differential capacity vs. voltage as a function of cycle number. The peaks represent the coexistence between bulk Li-Sn alloy phases which have substantially different volumes. The coexistence is thought to cause fracturing and loss of contact between the grains. Therefore, materials with small particles, small grains, and smoothmore » sloping voltage profiles which do not change with cycle number (as indicated by a stable differential capacity) give the best cycling performance. The selection of the voltage limits for cycling strongly influences the stability of the voltage profile (as illustrated here), so this must be done with much care.« less

Why do fish stocks collapse? the example of cod in atlantic canada

Abstract: In 1993, six Canadian populations of Atlantic cod (Gadus morhua) had collapsed to the point where a moratorium was declared on fishing. It has been argued that the collapses were caused by poor recruitment of cod to the fishery. Yet we are unable to detect a difference between the recruitment of year classes that should have contributed most to the spawning stock at the time of the collapse and recruitment levels in earlier years. A power analysis shows that we would have almost certainly detected an overall reduction of recruitment of 20%. There are considerable differences in the abundance trends as determined by research surveys and reconstructed from the commercial catch at age data (called “virtual population analysis” [VPA]) for each stock. VPA-based abundances consistently depict lower recruitment levels than do survey-based estimates in recent years. More important is the observation that from the early 1980s the VPA-based trend shows a decline where none is apparent in the survey-based trend. One...

Molecular chaperones and the cytoskeleton

Abstract: Heat shock proteins, first observed because they are preferentially synthesized by organisms exposed to heat or other physiological stress, are also synthesized constitutively. These proteins are divided into several families, namely, HSP100, 90, 70, 60 (chaperonin), and the small heat shock/alpha-crystallin proteins. They enjoy a wide phylogenetic distribution and are important because they function as molecular chaperones, able to mediate many cellular processes through an influence on higher order protein structure. For example, molecular chaperones assist in the transport of proteins into mitochondria and chloroplasts, as well as influencing clathrin lattice dynamics, viral replication and transcriptional activation. Under conditions of stress, some molecular chaperones prevent denaturation of proteins while others may dissociate protein aggregates, refolding monomers derived therefrom or directing their proteolytic destruction. We present in this review an analysis of the emerging literature on the relationship between molecular chaperones and the cytoskeleton, a collection of polymeric structures consisting of microtubules, microfilaments and intermediate filaments. A recent development in this field is identification of the TCP-1 complex as the eukaryotic cytoplasmic chaperonin which directs folding of cytoskeletal proteins such as alpha/beta/gamma-tubulin, actin and centractin. Moreover, the TCP-1 complex is a centrosomal component, apparently involved in the nucleation of microtubules. Other molecular chaperones recognize one or more cytoskeletal elements and in most cases they modulate the assembly of and/or provide protection for their constituent proteins. For example, HSP70 protects the centrosome and perhaps intermediate filaments during heat shock, and like HSP90, it binds to microtubules. Small heat shock proteins interact with microfilaments and intermediate filaments, affect their polymerization and guard them from heat shock by a phosphorylation-dependent mechanism. We conclude that molecular chaperones have different but cooperative roles in the formation and function of the eukaryotic cell cytoskeleton.

Iron and grazing constraints on primary production in the central equatorial Pacific: An EqPac synthesis

Abstract: Recent studies in the central equatorial Pacific allow a comprehensive assessment of phytoplankton regulation in a high-nutrient, low-chlorophyll (HNLC) ecosystem. Elemental iron enters the euphotic zone principally via upwelling and is present at concentrations (530 PM) well below the estimated half-saturation constant (120 PM) for the large cells that bloom with iron enrichment. In addition, the meridional trend in quantum yield of photosynthesis suggests that even the dominant small phytoplankton are held below their physiological potential by iron deficiency. Grazing by microzooplankton dominates phytoplankton losses, accounting for virtually all of the measured phytoplankton production during El Nina conditions and -66% during normal upwelling conditions, with mesozooplankton grazing and lateral advection closing the balance. Nitrate uptake is strongly correlated with the pigment biomass of diatoms, which increase in relative abundance during normal upwelling conditions. Nonetheless, the f-ratio remains low (0.07-0.12) under all conditions. Iron budgets are consistent with the notions that new production is determined by the rate of new iron input to the system while total production depends on efficient iron recycling by grazers. Although the limiting substrates differ, the interactions of resource limitation and grazing in HNLC regions are conceptually similar to the generally accepted view for oligotrophic subtropical regions. In both systems, small dominant phytoplankton grow at rapid, but usually less than physiologically maximal, rates; they are cropped to low stable abundances by microzooplankton; and their sustained high rates of growth depend on the remineralized by-products of grazing.

The Extracellular Fluid of Solid Carcinomas Contains Immunosuppressive Concentrations of Adenosine

Abstract: The purine nucleoside adenosine (9-beta-D-ribofuranosyladenine) inhibits a number of lymphocyte functions in vitro, including the ability of activated T lymphocytes and natural killer cells to adhere to and kill tumor targets. Solid tumors, such as adenocarcinomas of the lung and colon, are frequently hypoxic and are, therefore, likely to exhibit increased adenine nucleotide breakdown through the 5'-nucleotidase pathway, yielding adenosine. We examined whether the concentration of adenosine in the extracellular fluid of such tumors is adequate to cause immunosuppression. Murine tumors grown in syngeneic hosts or human tumors grown in immunodeficient nu/nu mice were subjected to microdialysis, and adenosine levels in the microdialysate were measured by high-performance liquid chromatography. Treatment of the tumor microdialysates with adenosine deaminase eliminated the adenosine peak. Recovery of adenosine ranged from 15 to 29%, depending on the microdialysis probe, and concentrations of adenosine in tumors ranged from 0.2 to 2.4 microM with a mean of 0.5 microM. In contrast, the adenosine concentration measured s.c. at the same location was 30 +/- 5 nM (mean +/- SE). Inclusion of the adenosine deaminase inhibitor coformycin (10 microM) and the adenosine kinase inhibitor 5'-iodotubercidin (0.1 microM) in the microdialysis perfusion buffer increased extracellular adenosine concentration in tumors to as high as 13 microM. These data show that extracellular adenosine levels in solid tumors are sufficient to suppress the local antitumor immune response and that interference with pathways of adenosine metabolism causes marked increases in tumor extracellular adenosine concentration.

Shortening the CES-D to improve its ability to detect cases of depression

Abstract: Psychometric analyses evaluated how primary care patients with and without major depressive disorder endorsed individual response options on the Center for Epidemiologic Studies-Depression Scale (CES-D; L. S. Radloff, 1977). The analyses were then used to identify a subset of items that when appropriately weighted improved the efficiency with which depressed individuals were identified. Efficiency of the revised measure was evaluated relative to standard cutpoints used with the full scale. Results showed that some improvement in most indices of efficiency could be achieved with half as many items and a simplified scoring scheme, but great improvement in one measure was usually achieved only at the expense of other measures of efficiency. The efficiency of the CES-D can be improved with appropriate analytic techniques, but its limitations as a self-report screening measure persist.

Microsatellite DNA in fishes

Abstract: For the last 30 years, attempts have been made to discriminate among fish populations by using molecular markers. Although some techniques have proved successful in certain circumstances, the consistent trend to newer markers among fishery geneticists highlights the general lack of resolving power observed with older technologies. The last decade has seen the increasing use of satellite DNA in investigations of genetic variability and divergence. Applications to fish and fisheries-related issues initially concentrated on minisatellite single-locus probes. Although minisatellites have successfully addressed a number of fishery-related questions, this class of satellite DNA has not been widely adopted by fishery geneticists. Most of the current research effort is concentrated on another class of satellite DNA called microsatellites. The large interest in microsatellite loci is largely due to the very high levels of variability that have been observed and the ability to investigate this variation using PCR technology. The isolation and application of microsatellites to research fields as diverse as population genetics, parentage analyses and genome mapping are reviewed. Despite the undisputed advantages that the marker possesses, there are a number of potential problems associated with investigating variation at microsatellite loci. Statistical considerations (e.g. appropriate sample sizes, number of loci and the mutation model assumptions on which the estimate is based) have not been considered in detail yet and the problems are often exacerbated in fish species, as some species show very large numbers of alleles at microsatellite loci. These issues and others, e.g. null alleles, are reviewed and possible solutions are proposed

The systemic inflammatory response to cardiopulmonary bypass: pathophysiological, therapeutic, and pharmacological considerations.

Abstract: C ardiac surgery and cardiopulmonary bypass (CPB) activate a systemic inflammatory response characterized clinically by alterations in cardiovascular and pulmonary function. Significant morbidity is rare (approximately l%-2% of cases), but when severe acute lung injury occurs, mortality is high (50%-70%) (1). H owever, most patients undergoing CPB experience some degree of organ dysfunction as a result of activation of the inflammatory response. The purpose of this review is to examine the recent developments in our understanding of the pathophysiological mechanisms responsible for this response, the treatment modalities that have been used to ameliorate it, and the possible implications of these findings for the conduct of anesthesia for cardiac surgery.

Deriving weights from pairwise comparison matrices

Abstract: We study the problem of deriving weights from pairwise comparisons. Properties of acceptable solutions are analysed, including immunity to rank reversals, independence of description of the problem, independence of scale inversion, left-right eigenvector asymmetry, uniqueness, independence of order of operations and inter-level consistency, preservation of the algebraic structure of the problem, extensibility to the additive case, related optimization models and related error measures. We derive the geometric mean from two simple axioms and establish that it is the only acceptable solution to this problem.

A unique point mutation in the fibroblast growth factor receptor 3 gene (FGFR3) defines a new craniosynostosis syndrome.

Abstract: The underlying basis of many forms of syndromic craniosynostosis has been defined on a molecular level However, many patients with familial or sporadic craniosynostosis do not have the classical findings of those craniosynostosis syndromes Here we present 61 individuals from 20 unrelated families where coronal synostosis is due to an amino acid substitution (Pro250Arg) that results from a single point mutation in the fibroblast growth factor receptor 3 gene on chromosome 4p In this instance, a new clinical syndrome is being defined on the basis of the molecular finding In addition to the skull findings, some patients had abnormalities on radiographs of hands and feet, including thimble-like middle phalanges, coned epiphyses, and carpal and tarsal fusions Brachydactyly was seen in some cases; none had clinically significant syndactyly or deviation of the great toe Sensorineural hearing loss was present in some, and developmental delay was seen in a minority While the radiological findings of hands and feet can be very helpful in diagnosing this syndrome, it is not in all cases clearly distinguishable on a clinical basis from other craniosynostosis syndromes Therefore, this mutation should be tested for in patients with coronal synostosis

Interaction of photochemical and microbial processes in the degradation of refractory dissolved organic matter from a coastal marine environment

Abstract: The interaction between photochemical and biological processes in the degradation of marine dissolved organic matter (DOM) was investigated with seawater from a coastal southeastern U.S. salt marsh. Seawater supplemented with humic substances was exposed to alternating cycles of sunlight (equivalent to 8 h of midday sun) and dark incubations with natural bacterial populations (l-2 weeks in length). Photochemical degradation of the DOM was monitored during sunlight exposure by direct measurements of dissolved inorganic carbon (DIC) and carbon monoxide (CO) formation in 0.2-Frn filtered seawater. Bacterial degradation was monitored during dark incubations by tritiated leucine uptake and changes in bacterial numbers in bacterivore-free incubations and by direct measurements of DOM loss. The alternating cycles of sunlight and microbial activity resulted in more complete degradation of bulk DOM and marine humic substances than was found for nonirradiated controls (i.e. with microbial activity alone) by a factor of up to 3-fold. Increased decomposition was due both to direct losses of carbon gas photoproducts (DIC and CO in a 15 : 1 ratio) and to enhanced microbial degradation of photodegraded DOM, with approximately equal contributions from each pathway. Mass balance calculations indicated that low-molecular-weight carbon photoproducts, currently considered to be the compounds responsible for stimulating bacterial activity following photodegradation of DOM, were insufficient to account for the enhanced bacterial production observed. Thus, higher molecular weight, chemically uncharacterized fractions of DOM may also be modified to more biologically available forms during exposure to natural sunlight. Photochemical processes play a number of important roles in the biogeochemical cycling of dissolved organic matter (DOM) in natural waters. Water optical properties, biological processes, and trace element distributions have all been demonstrated to be affected, either directly or indirectly, by

Molecular conformation and solvation of oligo(ethylene glycol)-terminated self-assembled monolayers and their resistance to protein adsorption

Abstract: We study the interaction of water with oligo(ethylene glycol) (OEG)-terminated alkane thiolate self-assembled monolayers (SAMs) in the helical and the planar “all-trans” form with ab initio methods to determine the stability and density distribution in water clusters as a function of molecular conformation. We find that the amphiphilic behavior of the OEG moieties depends on their molecular conformation and that the energetics of water adsorption is dominated by electrostatic interactions. The SAM surface of helical OEG provides a template for water nucleation, whereas water is not stable on a surface of planar OEG strands. These results suggest that protein resistance of OEG-terminated self-assembled monolayers is a consequence of the stability of the interfacial water layer, which prevents direct contact between the surface and the protein.

Tubulin post-translational modifications--enzymes and their mechanisms of action.

Abstract: This review describes the enzymes responsible for the post-translational modifications of tubulin, including detyrosination/tyrosination, acetylation/deacetylation, phosphorylation, polyglutamylation, polyglycylation and the generation of non-tyrosinatable alpha-tubulin. Tubulin tyrosine-ligase, which reattaches tyrosine to detyrosinated tubulin, has been extensively characterized and its gene sequenced. Enzymes such as tubulin-specific carboxypeptidase and alpha-tubulin acetyltransferase, required, respectively, for detyrosination and acetylation of tubulin, have yet to be purified to homogeneity and examined in defined systems. This has produced some conflicting results, especially for the carboxypeptidase. The phosphorylation of tubulin by several different types of kinases has been studied in detail but drawing conclusions is difficult because many of these enzymes modify proteins other than their actual substrates, an especially pertinent consideration for in vitro experiments. Tubulin phosphorylation in cultured neuronal cells has proven to be the best model for evaluation of kinase effects on tubulin/microtubule function. There is little information on the enzymes required for polyglutamylation, polyglycylation, and production of non-tyrosinatable tubulin, but the available data permit interesting speculation of a mechanistic nature. Clearly, to achieve a full appreciation of tubulin post-translational changes the responsible enzymes must be characterized. Knowing when the enzymes are active in cells, if soluble or polymerized tubulin is the preferred substrate and the amino acid residues modified by each enzyme are all important. Moreover, acquisition of purified enzymes will lead to cloning and sequencing of their genes. With this information, one can manipulate cell genomes in order to either modify key enzymes or change their relative amounts, and perhaps reveal the physiological significance of tubulin post-translational modifications.

Multiple Scattering Parameterization in Thermal Infrared Radiative Transfer

Abstract: A systematic formulation of various radiative transfer parameterizations is presented, including the absorption approximation (AA), δ-two-stream approximation (D2S), δ-four-stream approximation (D4S), and δ-two- and four-stream combination approximation (D2/4S), in a consistent manner for thermal infrared flux calculations. The D2/4S scheme uses a source function from the δ-two-stream approximation and evaluates intensities in the four-stream directions. A wide range of accuracy checks for monochromatic emissivity of a homogeneous layer and broadband heating rates and fluxes in nonhomogeneous atmospheres is performed with respect to the “exact” results computed from the δ-128-stream scheme for radiative transfer. The computer time required for the calculations using different radiative transfer parameterizations is compared. The results pertaining to the accuracy and efficiency of various radiative transfer approximations can be utilized to decide which approximate method is most appropriate for ...

Men in nursing: issues of gender segregation and hidden advantage

Abstract: The small but growing number of men in the nursing profession does not herald a progressive integration of masculine and feminine sex roles. The evidence presented in this paper suggests that even in female-dominated occupations such as nursing, patriarchal gender relations which reflect a high valuation of all that is male and masculine, play a significant role in situating a disproportionate number of men in administrative and elite specialty positions. At the heart of this gender dynamic is the need to separate the masculine from the lesser valued feminine. Male nurses do this by employing strategies that allow them to distance themselves from female colleagues and the quintessential feminine image of nursing itself, as a prerequisite to elevating their own prestige and power. They are aided in this task by patriarchal cultural institutions that create and perpetuate male advantage, as well as by women nurses themselves who, consciously or unconsciously, nurture the careers of men colleagues.