Showing papers by "University of Victoria published in 1996"

The influence on climate forcing of mineral aerosols from disturbed soils

Abstract: AEROSOLS influence the global radiation budget1, and so changes in the atmospheric aerosol load due to either natural causes or human activity will contribute to climate change2. A large fraction of the mass of tropospheric aerosol is wind-blown mineral dust, and its contribution to radiative forcing can be locally significant3,22. Model calculations indicate that 50 ± 20% of the total atmospheric dust mass originates from disturbed soils4 (those affected by cultivation, deforestation, erosion, and frequent shifts in vegetation due to droughts and rains). Here, using a radiative transfer model embedded in a general circulation model, we find that dust from disturbed soils causes a decrease of the net surface radiation forcing of about lWm-2, accompanied by increased atmospheric heating that may be a significant forcing of atmospheric dynamics. These findings suggest that mineral dust from disturbed soils needs to be included among the climate forcing factors that are influenced by human activities.

Intraseasonal oscillations in 15 atmospheric general circulation models: results from an AMIP diagnostic subproject

Abstract: The ability of 15 atmospheric general circulation models (AGCM) to simulate the tropical intraseasonal oscillation has been studied as part of the Atmospheric Model Intercomparison Project (AMIP). Time series of the daily upper tropospheric velocity poential and zonal wind, averaged over the equatorial belt, were provided from each AGCM simulation. These data were analyzed using a variety of techniques such as time filtering and space-time spectral analysis to identify eastward and westward moving waves. The results have been compared with an identical assessment of the European Centre for Medium-range Weather Forecasts (ECMWF) analyses for the period 1982–1991. The models display a wide range of skill in simulating the intraseasonal oscillation. Most models show evidence of an eastward propagating anomaly in the velocity potential field, although in some models there is a greater tendency for a standing oscillation, and in one or two the field is rather chaotic with no preferred direction of propagation. Where a model has a clear eastward propagating signal, typical periodicities seem quite reasonable although there is a tendency for the models to simulate shorter periods than in the ECMWF analyses, where it is near 50 days. The results of the space-time spectral analysis have shown that no model has captured the dominance of the intraseasonal oscillation found in the analyses. Several models have peaks at intraseasonal time scales, but nearly all have relatively more power at higher frequencies (< 30 days) than the analyses. Most models underestimate the strength of the intraseasonal variability. The observed intraseasonal oscillation shows a marked seasonality in its occurrence with greatest activity during northern winter and spring. Most models failed to capture this seasonality. The interannual variability in the activity of the intraseasonal oscillation has also been assessed, although the AMIP decade is too short to provide any conclusive results. There is a suggestion that the observed oscillation was suppressed during the strong El Nino of 1982/83, and this relationship has also been reproduced by some models. The relationship between a model's intraseasonal activity, its seasonal cycle and characteristics of its basic climate has been examined. It is clear that those models with weak intraseasonal activity tend also to have a weak seasonal cycle. It is becoming increasingly evident that an accurate description of the basic climate may be a prerequisite for producing a realistic intraseasonal oscillation. In particular, models with the most realistic intraseasonal oscillations appear to have precipitation distributions which are better correlated with warm sea surface temperatures. These models predominantly employ convective parameterizations which are closed on buoyancy rather than moisture convergence.

Comparison of radiative and physiological effects of doubled atmospheric CO2 on climate

Abstract: The physiological response of terrestrial vegetation when directly exposed to an increase in atmospheric carbon dioxide (CO 2 ) concentration could result in warming over the continents in addition to that due to the conventional CO 2 “greenhouse effect.” Results from a coupled biosphere-atmosphere model (SiB2-GCM) indicate that, for doubled CO 2 conditions, evapotranspiration will drop and air temperature will increase over the tropical continents, amplifying the changes resulting from atmospheric radiative effects. The range of responses in surface air temperature and terrestrial carbon uptake due to increased CO 2 are projected to be inversely related in the tropics year-round and inversely related during the growing season elsewhere.

The Complete 685-Kilobase DNA Sequence of the Human β T Cell Receptor Locus

Abstract: The human beta T cell receptor (TCR) locus, comprising a complex family of genes, has been sequenced. The locus contains two types of coding elements--TCR elements (65 variable gene segments and two clusters of diversity, joining, and constant segments) and eight trypsinogen genes --that constitute 4.6 percent of the DNA. Genome-wide interspersed repeats and locus-specific repeats span 30 and 47 percent, respectively, of the 685-kilobase sequence. A comparison of the germline variable elements with their approximately 300 complementary DNA counterparts reveals marked differential patterns of variable gene expression, the importance of exonuclease activity in generating TCR diversity, and the predominant tendency for only functional variable elements to be present in complementary DNA libraries.

Perceptions of Organizational Politics: Prediction, Stress-Related Implications, and Outcomes

Abstract: The perceptions of organizational politics model proposed by Ferris, Russ, and Fandt (1989) was tested in this study, and reasonably strong support was found for most of the linkages in the model, including the moderating effects of control and understanding, and the mediating effects of politics between predictors and outcomes. Furthermore, politics was characterized as a potential source of stress in the work environment, contributing to our understanding of the dynamics of politics in organizations. The results of the present study are discussed in light of the implications and directions for future research.

Analysis of an SEIRS epidemic model with two delays

Abstract: A disease transmission model of SEIRS type with exponential demographic structure is formulated. All newborns are assumed susceptible, there is a natural death rate constant, and an excess death rate constant for infective individuals. Latent and immune periods are assumed to be constants, and the force of infection is assumed to be of the standard form, namely proportional to I(t)/N(t) where N(t) is the total (variable) population size and I(t) is the size of the infective population. The model consists of a set of integro-differential equations. Stability of the disease free proportion equilibrium, and existence, uniqueness, and stability of an endemic proportion equilibrium, are investigated. The stability results are stated in terms of a key threshold parameter. More detailed analyses are given for two cases, the SEIS model (with no immune period), and the SIRS model (with no latent period). Several threshold parameters quantify the two ways that the disease can be controlled, by forcing the number or the proportion of infectives to zero.

Diatom resting stages

Abstract: Resting cells and spores are common to many groups of algae (J. S. Davis 1972) and, particularly in the diatoms, they appear to have many roles. This review discusses the morphology and physiology of diatom resting stages as well as the classical and more recent hypotheses about the functions of these cells. Most of the literature suggests that resting stages are a means of longor short-term survival. However, the timing of formation and germination of these cells may also be important for species succession, dispersal, and cycling of nutrients through the water column.

A normal mode model for acousto‐elastic ocean environments

Abstract: A normal mode method for propagation modeling in acousto‐elastic ocean waveguides is described. The compressional (p‐) and shear (s‐) wave propagation speeds in the multilayer environment may be constant or have a gradient (1/c2 linear) in each layer. Mode eigenvalues are found by analytically computing the downward‐ and upward‐looking plane wave reflection coefficients R1 and R2 at a reference depth in the fluid and searching the complex k plane for points where the product R1R2=1. The complex k‐plane search is greatly simplified by following the path along which |R1R2|=1. Modes are found as points on the path where the phase of R1R2 is a multiple of 2π. The direction of the path is found by computing the derivatives d(R1R2)/dk analytically. Leaky modes are found, allowing the mode solution to be accurate at short ranges. Seismic interface modes such as the Scholte and Stonely modes are also found. Multiple ducts in the sound speed profile are handled by employing multiple reference depths. Use of Airy function solutions to the wave equation in each layer when computing R1 and R2 results in computation times that increase only linearly with frequency.

Master Framing and Cross-Movement Networking in Contemporary Social Movements

Abstract: This article maps the network of cross-movement activism in Greater Vancouver, British Columbia, and explores the relationship between position in the network and cognitive use of different injusti...

Two new forms of gonadotropin-releasing hormone in a protochordate and the evolutionary implications.

Abstract: The neuropeptide gonadotropin-releasing hormone (GnRH) is the major regulator of reproduction in vertebrates. Our goal was to determine whether GnRH could be isolated and identified by primary structure in a protochordate and to examine its location by immunocytochemistry. The primary structure of two novel decapeptides from the tunicate Chelyosoma productum (class Ascidiacea) was determined. Both show significant identity with vertebrate GnRH. Tunicate GnRH-I (pGlu-His-Trp-Ser-Asp-Tyr-Phe-Lys-Pro-Gly-NH2) has 60% of its residues conserved, compared with mammalian GnRH, whereas tunicate GnRH-II (pGlu-His-Trp-Ser-Leu-Cys-His-Ala-Pro-Gly-NH2) is unusual in that it was isolated as a disulfide-linked dimer. Numerous immunoreactive GnRH neurons lie within blood sinuses close to the gonoducts and gonads in both juveniles and adults, implying that the neuropeptide is released into the bloodstream. It is suggested that in ancestral chordates, before the evolution of the pituitary, the hormone was released into the bloodstream and acted directly on the gonads.

Nonminimal coupling of the scalar field and inflation

Abstract: We study the prescriptions for the coupling constant of a scalar field to the Ricci curvature of spacetime in specific gravity and scalar field theories. The results are applied to the most popular inflationary scenarios of the universe; their theoretical consistency and certain observational constraints are discussed. \textcopyright{} 1996 The American Physical Society.

Area-efficient multipliers for digital signal processing applications

Abstract: An area-efficient parallel sign-magnitude multiplier that receives two N-bit numbers and produces an N-bit product, referred to as a truncated multiplier, is described. The quantization of the product to N bits is achieved by omitting about half the adder cells needed to add the partial products but in order to keep the quantization error to a minimum, probabilistic biases are obtained and are then fed to the inputs of the retained adder cells. The truncated multiplier requires approximately 50% of the area of a standard parallel multiplier. The paper then shows that this design strategy can also be applied for the design of two's-complement multipliers. The paper concludes with the application of the truncated multiplier for the implementation of a digital filter and it is shown that the signal-to-noise ratio of the digital filter using a truncated multiplier is better than that using a standard multiplier.

Characterization of a post-translational modification of Campylobacter flagellin: identification of a sero-specific glycosyl moiety.

Abstract: The flagellins of Campylobacter spp. differ antigenically. In variants of C. coli strain VC167, two antigenic flagellin types determined by sero-specific antibodies have been described (termed T1 and T2). Post-translational modification has been suggested to be responsible for T1 and T2 epitopes, and, using mild periodate treatment and biotin hydrazide labelling, flagellin from both VC167-T1 and T2 were shown to be glycosylated. Glycosylation was also shown to be present on other Campylobacter flagellins. The ability to label all Campylobacter flagellins examined with the lectin LFA demonstrated the presence of a terminal sialic acid moiety. Furthermore, mild periodate treatment of the flagellins of VC167 eliminated reactivity with T1 and T2 specific antibodies LAH1 and LAH2, respectively, and LFA could also compete with LAH1 and LAH2 antibodies for binding to their respective flagellins. These data implicate terminal sialic acid as part of the LAH strain-specific epitopes. However, using mutants in genes affecting LAH serorecognition of flagellin it was demonstrated that sialic acid alone is not the LAH epitope. Rather, the epitope(s) is complex, probably involving multiple glycosyl and/or amino acid residues.

Victoria symptom validity test: Efficiency for detecting feigned memory impairment and relationship to neuropsychological tests and MMPI-2 validity scales

Abstract: Error scores and response times from a computer-administered, forced-choice recognition test of symptom validity were evaluated for efficiency in detecting feigned memory deficits. Participants included controls (n = 95), experimental malingerers (n = 43), compensation-seeking patients (n = 206), and patients not seeking financial compensation (n = 32). Adopting a three-level cut-score system that classified participant performance as malingered, questionable, or valid greatly improved sensitivity with relatively little impact on specificity. For error scores, convergent validity was found to be adequate and divergent validity was found to be excellent. Although response times showed promise for assisting in the detection of feigned impairment, divergent and convergent validity were weaker, suggesting somewhat less utility than error scores.

The Experiences of Families of Children with Learning Disabilities: Parental Stress, Family Functioning, and Sibling Self-Concept

Abstract: Quantitative and qualitative measures of 19 parents and 19 siblings of school-age children with learning disabilities (a parent-sibling pair for each child) showed that the functioning of the families and the self-concept of the siblings were comparable to that in families of nondisabled children, but the parents in the former group experienced greater stress than did parents of nondisabled children. Furthermore, despite few problems in sibling relationships, the families experienced adaptational difficulties, especially with regard to the school. Family intervention and future research are suggested.

A Revised Land Surface Parameterization (SiB2) for GCMS. Part III: The Greening of the Colorado State University General Circulation Model

Abstract: SiB2, the second-generation land-surface parameterization developed by Sellers et al., has been incorporated into the Colorado State University general circulation model and tested in multidecade simulation. The control run uses a “bucket” hydrology but employs the same surface albedo and surface roughness distributions as the SiB2 run. Results show that SiB2 leads to a general warming of the continents, as evidenced in the ground temperature, surface air temperature, and boundary-layer-mean potential temperature. The surface sensible heat flux increases and the latent heat flux decreases. This warming occurs virtually everywhere but is most spectacular over Siberia in winter. Precipitation generally decreases over land but increases in the monsoon regions, especially the Amazon basin in January and equatorial Africa and Southeast Asia in July. Evaporation decreases considerably, especially in dry regions such as the Sahara. The excess of precipitation over evaporation increases in the monsoon re...

DNA repair by oocytes.

Abstract: Experimental evidence in a number of different in vivo and in vitro systems indicates clearly that the vertebrate oocyte is capable of repairing endogenous and exogenous DNA damaged as a result of meiotic recombination, the action of UV and X-irradiation or the effects of mutagenic chemicals. It would appear that both before and after the dictyate stage of meiosis the oocyte has less repair capacity and/or is more sensitive to DNA damaging agents. Epigenetic factors associated with the expression of genetic faults arising in oocytes have been largely ignored in the past. It is probable that attention to such factors, will in the future, lead to a better appreciation of the capacity of oocytes to repair genetic damage. Non-disjunctional events are particularly prone to occur in dictyate oocytes. Oxygen deprivation, perturbations of microtubular structure by temperature and other factors appear to have disastrous cytogenetic consequences at this otherwise resistant resting stage.

Health within illness: experiences of chronically ill/disabled people

Abstract: The concept of health within illness is beginning to gain recognition in nursing. However, there has been little research to explore and describe this phenomenon. The results of a recent study investigating the meaning of the experience of feeling healthy for people living with a chronic illness and/or disability are presented. An interpretive phenomenological study was undertaken with eight participants living with a variety of different chronic conditions. The results provide a rich mosaic of themes describing the participants' health experiences. These themes include: (a) honouring the self; (b) seeking and connecting with others; (c) creating opportunities; (d) celebrating life; (e) transcending the self; and (f) acquiring a state of grace. The significance of these results is that they provide for a reconceptualization of health and illness. Such a reconceptualization calls for a transformation in nursing care, from a problem focus and a deficit perspective, to one which focuses on the client's capacity and the promotion of health and healing.

Salmonella enteritidis agfBAC operon encoding thin, aggregative fimbriae.

Abstract: Salmonella enteritidis produces thin, aggregative fimbriae, named SEF17, which are composed of polymerized AgfA fimbrin proteins. DNA sequence analysis of a 2-kb region of S. enteritidis DNA revealed three contiguous genes, agfBAC. The 453-bp agfA gene encodes the AgfA fimbrin, which was predicted to be 74% identical and 86% similar in primary sequence to the Escherichia coli curli structural protein, CsgA. pHAG, a pUC18 derivative containing a 3.0-kb HindIII fragment encoding agfBAC, directed the in vitro expression of the major AgfA fimbrin, with an M(r) of 17,000, and a minor AgfB protein, with an M(r) of 16,000, encoded by the 453-bp agfB gene. AgfA was not expressed from pDAG, a pUC18 derivative containing a 3.1-kb DraI DNA fragment encoding agfA but not agfB. Primer extension analysis identified two adjacent transcription start sites located immediately upstream of agfB in positions analogous to those of the E. coli curlin csgBA operon. No transcription start sites were located immediately upstream of agfA or agfC. Northern (RNA) blot analysis confirmed that transcription of agfA was initiated from the agfB promoter region. Secondary-structure analysis of the putative mRNA transcript for agfBAC predicted the formation of a stem-loop structure (delta Gzero, -22 kcal/mol [-91 kJ/mol]) in the intercistronic region between agfA and agfC, which may be involved in stabilization of the agfBA portion of the agfBAC transcript. agfBAC and flanking regions had a high degree of sequence similarity with those counterparts of the E. coli curlin csgBA region for which sequence data are available. These data are demonstrative of the high degree of similarity between S. enteritidis SEF17 fimbriae and E. coli curli with respect to fimbrin amino acid sequence and genetic organization and, therefore, are indicative of a common and relatively recent ancestry.

Substrate limitations for heterotrophs: Implications for models that estimate the seasonal cycle of atmospheric CO2

Abstract: We examine the sensitivity of the seasonal cycle of heterotrophic respiration to model estimates of litterfall seasonality, herbivory, plant allocation, tissue chemistry, and land use. As a part of this analysis, we compare heterotrophic respiration models based solely on temperature and soil moisture controls (zero-order models) with models that depend on available substrate as well (first-order models). As indicators of regional and global CO2 exchange, we use maps of monthly global net ecosystem production, growing season net flux (GSNF), and simulated atmospheric CO2 concentrations from an atmospheric tracer transport model. In one first-order model, CASA, variations on the representation of the seasonal flow of organic matter from plants to heterotrophs can increase global GSNF as much as 60% (5.7 Pg C yr−1) above estimates obtained from a zero-order model. Under a new first-order scheme that includes separate seasonal dynamics for leaf litterfall, fine root mortality, coarse woody debris, and herbivory, we observe an increase in GSNF of 8% (0.7 Pg C yr−1) over that predicted by the zero-order model. The increase in seasonality of CO2 exchange in first-order models reflects the dynamics of labile litter fractions; specifically, the rapid decomposition of a pulse of labile leaf and fine root litter that enters the heterotrophic community primarily from the middle to the end of the growing season shifts respiration outside the growing season. From the perspective of a first-order model, we then explore the consequences of land use change and winter temperature anomalies on the amplitude of the seasonal cycle of atmospheric CO2. Agricultural practices that accelerate decomposition may drive a long-term increase in the amplitude, independent of human impacts on plant production. Consideration of first-order litter decomposition dynamics may also help explain year-to-year variation in the amplitude.

Influence of sea-floor spreading on the global hydrothermal vent fauna

Abstract: ONE remarkable discovery of recent decades is the presence of hundreds of unusual species, including fourteen new families, at hydrothermal vents. These animals, unknown from other habitats, live in extreme chemical and thermal conditions around vents on spreading centres of the mid-ocean ridges and back-arc basins. Chemosynthesis provides an in situ energy source for the thriving vent fauna. This habitat has existed through the Phanerozoic1,2 and probably since the Archaean, thus providing sites for long-term adaptation. We now test the hypothesis that animal distribution among hydrothermal vents is related to tectonic plate history3,4. The predominant migration pathway is most likely to occur along mid-ocean ridges rather than by shortest oceanic routes. Similarity analyses suggest that the distribution patterns of today's vent fauna display the strong imprint of the timing and geometry of ancient plate boundaries. Study of past ridge geometry provides a method to predict relationships among vent communities yet to be discovered.

Mapping nature: Territorialization of forest rights in Thailand

Abstract: In Thailand, as elsewhere, the administrative definition of forest has changed from one based on classification by species to one based on territory. This process was an important facet of the more general process by which the central government claimed a monopoly on the administration of property rights to natural resources. The process took place in three stages: First, the government declared that all territory not claimed by permanent cultivators or other government agencies was forest under the jurisdiction of the Royal Forestry Department. Second, it demarcated the forests into reserve and protected forests. Third, it mapped all forest land as well as nonforest land according to land use classifications, which became the basis for policies to control occupation and use. These strategies did not allow for local input into land use planning. As a result of this lack of state capacity, and interbureaucratic competition, the Thai government failed to control rural land use.

Stable carbon isotopes as indicators of increased water use efficiency and productivity in white spruce (Picea glauca (Moench) Voss) seedlings

Abstract: The relationship among water use efficiency (WUE), productivity and carbon isotopic composition (δ 13 C) in white spruce (Picea glauca (Moench) Voss) seedlings was investigated Sixteen hundred seedlings representing 10 controlled crosses were planted in the field in individual buried sand-filled cylinders The soil water content in the cylinders was measured using time domain reflectometry over two growing seasons and seedling water use determined by water balance Two watering treatments were imposed : irrigation and dry land There was significant (16-20‰) genetic variation in needle δ 13 C Ranking of crosses in terms of δ 13 C was generally maintained over watering treatments and there was not a significant genetic versus environmental interaction There was a positive correlation between δ 13 C and both intrinsic and long-term WUE (more positive δ 13 C with increased WUE) and between δ 13 C and productivity, suggesting a correlation due to variation in photosynthetic capacity Root to shoot ratios did not increase in water-stressed plants, indicating that responses to drought were primarily at the level of gas exchange, rather than through morphological changes Our results indicate that it should be possible to use δ 13 C as a surrogate for WUE and to select white spruce genotypes for high WUE without compromising yield