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Scale Analysis (scale + analysis)
Selected AbstractsSimple methods for convection in porous media: scale analysis and the intersection of asymptotesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2003Adrian Bejan Abstract This article outlines the basic rules and promise of two of the simplest methods for solving problems of convection in porous media. First, scale analysis is the method that produces order-of-magnitude results and trends (scaling laws) for concrete and applicable results such as heat transfer rates, flow rates, and time intervals. Scale analysis also reveals the correct dimensionless form in which to present more exact results produced by more complicated methods. Second, the intersection of asymptotes method identifies the correct flow configuration (e.g. Bénard convection in a porous medium) by intersecting the two extremes in which the flow may exist: the many cells limit, and the few plumes limit. Every important feature of the flow and its transport characteristics is found at the intersection, i.e. at the point where the two extremes compete and find themselves in balance. The intersection is also the flow configuration that minimizes the global resistance to heat transfer through the system. This is an example of the constructal principle of deducing flow patterns by optimizing the flow geometry for minimal global resistance. The article stresses the importance of trying the simplest method first, and the researcher's freedom to choose the appropriate problem solving method. Copyright © 2003 John Wiley & Sons, Ltd. [source] Relative influence of variables at multiple spatial scales on stream macroinvertebrates in the Northern Lakes and Forest ecoregion, U.S.A.FRESHWATER BIOLOGY, Issue 8 2003Brian M. Weigel Summary 1We used 94 sites within the Northern Lakes and Forests ecoregion spanning Minnesota, Wisconsin and Michigan to identify environmental variables at the catchment, reach and riparian scales that influence stream macroinvertebrates. Redundancy analyses (RDA) found significantly influential variables within each scale and compared their relative importance in structuring macroinvertebrate assemblages. 2Environmental variables included landcover, geology and groundwater delivery estimates at the catchment scale, water chemistry, channel morphology and stream habitat at the reach scale, and landcover influences at three distances perpendicular to the stream at the riparian scale. Macroinvertebrate responses were characterised with 22 assemblage attributes, and the relative abundance and presence/absence of 66 taxa. 3Each scale defined macroinvertebrates along an erosional to depositional gradient. Wisconsin's macroinvertebrate index of biotic integrity, Ephemeroptera,Plecoptera,Trichoptera taxa and erosional taxa corresponded with forest streams, whereas organic pollution tolerant, Chironomidae and depositional taxa corresponded with wetland streams. Reach scale analyses defined the gradient similarly as dissolved oxygen and wide, shallow channels (erosional) opposed instream macrophytes and pool habitats (depositional). Riparian forests within 30 m of the stream coincided with an erosional assemblage and biotic integrity. 4Next, we combined all significant environmental variables across scales to compare the relative influence of each spatial scale on macroinvertebrates. Partial RDA procedures described how much of the explained variance was attributable to each spatial scale and each interrelated scale combination. 5Our results appeared consistent with the concept of hierarchical functioning of scale in which large-scale variables restrict the potential for macroinvertebrate traits or taxa at smaller spatial scales. Catchment and reach variables were equally influential in defining assemblage attributes, whereas the reach scale was more influential in determining relative abundance and presence/absence. 6Ultimately, comprehending the relative influence of catchment and reach scale properties in structuring stream biota will assist prioritising the scale at which to rehabilitate, manage and derive policies for stream ecosystem integrity. [source] Retrospective growth analysis of Atlantic salmon Salmo salar and implications for abundance trendsJOURNAL OF FISH BIOLOGY, Issue 10 2010F. Hogan Scale archives of Atlantic salmon Salmo salar from Maine, U.S.A., were examined to determine whether ocean conditions affected the long-term trends in S. salar populations in the southern tier of the species' range in North America. To date, scale analyses of southern tier populations have been limited to hatchery fish; previous studies suggest that post-smolt growth does not influence recruitment, with the exception that winter growth may play a role in stock maturation rate. A time series of scales from the Machias and Narraguagus Rivers spanning the years 1946 to 1999 was analysed. Image analysis was used to measure intercirculi spacing, which provided proxy variables of growth rate. Post-smolt growth increment has increased since the early 1990s, as returns have decreased, suggesting that survival factors act on post-smolts independent of growth. The data support the hypothesis of a decoupling between freshwater size and early marine growth. Growth during the second sea winter was independent of post-smolt growth, suggesting that individuals are capable of significant compensatory growth. Southern tier North American stocks exhibit a similar pattern of independence between growth and survival as observed for northern tier North American stocks. These data support the inference that the recruitment of the North American and European subspecies is governed by fundamentally different mechanisms. [source] Re-Examining Whether and Why Acculturation Relates to Drinking Outcomes in a Rigorous, National Survey of LatinosALCOHOLISM, Issue 12 2005Sarah E. Zemore Abstract: Background: Fundamental limitations have hampered conclusions surrounding acculturation's effects among Latinos. This research re-examines associations between acculturation and alcohol use, addressing the most troubling of these limitations. The research also explores mediators of the association, and the dimensional structure of acculturation. Methods: Linear regressions and scale analyses were used to analyze data from Latino adults in the U.S. (825 women, 761 men) sampled in the 1995 National Alcohol Survey. Analyses used a standard, reliable acculturation scale and well-validated drinking measures; systematically accounted for demographic covariates; and analyzed men and women separately. Results: As expected, higher acculturation was positively associated with a higher probability of drinking (vs. abstinence) among women, and higher average volumes and more frequent drunkenness among female drinkers. Acculturation was unrelated to alcohol use among men. Also as expected, mediational analyses of average volume supported expectations that gender-specific drinking norms would mediate acculturation's effects (though norms did not explain acculturation's associations with either drinking status or frequency of drunkenness). Analyses investigating depressive symptoms showed no support for the acculturation-stress model. Factor analyses of the acculturation scale supported the hypothesized distinctions between linguistic acculturation, attitudinal acculturation, and the social environment of acculturation. Further, items implying more intimate exposure to Anglo culture (i.e., language use) were most strongly related to drinking outcomes among women, supporting the normative interpretation of acculturation's effects on drinking. Conclusions: Results underline acculturation's influence on alcohol consumption among Latina women, and highlight the role of drinking norms in mediating this association. Results also suggest a multidimensional view of acculturation. The article recommends further research on drinking norms and other potential mediators of acculturation's effects among Latina women. [source] A ChemoSensory Questionnaire for Patients Treated for Cancer of the Head and Neck,THE LARYNGOSCOPE, Issue 12 2005Andrew N. Goldberg MD, MSCE Abstract Objectives: To investigate primary chemosensory issues experienced by patients who undergo treatment for cancer of the head and neck and to develop and assess a ChemoSensory Questionnaire (CSQ). Design: Cross sectional survey for questionnaire development and testing. Methods: Literature, expert opinion, and focus group methodology were used to identify aspects of smell and taste affecting patients before, during, and after therapy for cancer of the head and neck. A draft instrument was compiled, reviewed, and revised. The revised instrument was administered along with a demographic and clinical form, the SF-12, the Performance Status Survey, and the University of Michigan Head and Neck Quality of Life Questionnaire (HRQOL) to a sample of patients. After item and scale analyses and reductions, a final instrument was assembled. Construct validity and test-retest reliability were assessed. Results: Two hundred six patients were included in the study. The final survey instrument consisted of eight items, four on smell and four on taste. Cronbach's alpha was 0.89 for the smell scale and 0.78 for the taste scale. Correlations with other HRQOL scales ranged from 0.20 to 0.64 for the taste scale and from 0.10 to 0.33 for the smell scale. Good construct validity of the CSQ scores was demonstrated. Conclusions: Treatment for head and neck cancer negatively impacts smell and taste. A survey instrument was developed to evaluate chemosensory function that is simple to administer and is brief. This instrument will be of value in identifying factors that contribute to chemosensory disturbance and may serve as a guide for planning treatment regimens that minimize such disturbance. [source] Detection of trends in hydrological extremes for Canadian watershedsHYDROLOGICAL PROCESSES, Issue 13 2010Donald H. Burn Abstract The potential impacts of climate change can alter the risk to critical infrastructure resulting from changes to the frequency and magnitude of extreme events. As well, the natural environment is affected by the hydrologic regime, and changes in high flows or low flows can have negative impacts on ecosystems. This article examines the detection of trends in extreme hydrological events, both high and low flow events, for streamflow gauging stations in Canada. The trend analysis involves the application of the Mann,Kendall non-parametric test. A bootstrap resampling process has been used to determine the field significance of the trend results. A total of 68 gauging stations having a nominal record length of at least 50 years are analysed for two analysis periods of 50 and 40 years. The database of Canadian rivers investigated represents a diversity of hydrological conditions encompassing different extreme flow generating processes and reflects a national scale analysis of trends. The results reveal more trends than would be expected to occur by chance for most of the measures of extreme flow characteristics. Annual and spring maximum flows show decreasing trends in flow magnitude and decreasing trends in event timing (earlier events). Low flow magnitudes exhibit both decreasing and increasing trends. Copyright © 2010 John Wiley & Sons, Ltd. [source] Simple methods for convection in porous media: scale analysis and the intersection of asymptotesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2003Adrian Bejan Abstract This article outlines the basic rules and promise of two of the simplest methods for solving problems of convection in porous media. First, scale analysis is the method that produces order-of-magnitude results and trends (scaling laws) for concrete and applicable results such as heat transfer rates, flow rates, and time intervals. Scale analysis also reveals the correct dimensionless form in which to present more exact results produced by more complicated methods. Second, the intersection of asymptotes method identifies the correct flow configuration (e.g. Bénard convection in a porous medium) by intersecting the two extremes in which the flow may exist: the many cells limit, and the few plumes limit. Every important feature of the flow and its transport characteristics is found at the intersection, i.e. at the point where the two extremes compete and find themselves in balance. The intersection is also the flow configuration that minimizes the global resistance to heat transfer through the system. This is an example of the constructal principle of deducing flow patterns by optimizing the flow geometry for minimal global resistance. The article stresses the importance of trying the simplest method first, and the researcher's freedom to choose the appropriate problem solving method. Copyright © 2003 John Wiley & Sons, Ltd. [source] The assessment of communities of practiceKNOWLEDGE AND PROCESS MANAGEMENT: THE JOURNAL OF CORPORATE TRANSFORMATION, Issue 1 2006Robert M. Verburg This paper introduces the Community Assessment Toolkit (CAT) as a method for the assessment of Communities of Practice (CoPs) and provides an overview of its construction and applicability. It shows that the methodology is based on current theories with regard to CoPs and group dynamics. The method was also tested in practice through a pilot and a study among members of 7 communities of practice (N=271) in order to enable reliability tests and scale analysis. The method is unique in the sense that it provides feedback on the overall performance of CoPs on the individual, group and organizational level. The systematic nature of the CAT questionnaire enables comparisons between communities both within and between organizations. The CAT may be used for further scientific research into CoPs as well as for the analysis of community effectiveness for companies. Copyright © 2006 John Wiley & Sons, Ltd. [source] ENVIRONMENTAL FACTORS INFLUENCING THE DISTRIBUTION OF SOUTHERN RIGHT WHALES (EUBALAENA AUSTRALIS) ON THE SOUTH COAST OF SOUTH AFRICA I: BROAD SCALE PATTERNSMARINE MAMMAL SCIENCE, Issue 3 2004Simon H. Elwen Abstract Aerial surveys over the last 32 yr have shown that the distribution of southern right whales Eubalaena australis along the south coast of South Africa is markedly discontinuous, but highly predictable. A GIS was used at a variety of scales to investigate whether this pattern was related to environmental characteristics. Whale distribution was analyzed as density per 20-min bin of longitude over two temporal and spatial scales, namely 15 bins for 32 yr, and a wider scale but shorter time period, 23 bins for 19 yr, as well as using three years of GPS accuracy data (15 bins) for finer scale analysis. Environmental factors tested were depth, distance from shore, sea floor slope, protection from swell, protection from wind, and shore type. The majority of whales were concentrated in areas that provided reasonable protection from open ocean swell and seasonal winds, and had sedimentary floors with gentle slopes. They generally avoided exposed rocky shorelines. Cow-calf pairs were found significantly closer to shore and in shallower water than unaccompanied whales, particularly off sandy beaches. Habitat choice at this time of year may be related both to energy conservation for calves and lactating females (calm sea conditions) and to protection of the new-born. [source] Expression and chromosomal organization of mouse meiotic genesMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 3 2010Hiba Waldman Ben-Asher Microarray technology which enables large scale analysis of gene expression and thus comparison between transcriptomes of different cell types, cells undergoing different treatments or cells at different developmental stages has also been used to study the transcriptome involved with spermatogenesis. Many new germ cell-specific genes were determined, and the resulting genes were classified according to different criteria. However, the biological significance of these classifications and their clustering according to developmental transcriptional patterns during spermatogenesis have not yet been addressed. In this study we utilized mouse testicular transcriptome analysis at five distinct post-natal ages (Days 7, 10, 12, 14, and 17), representing distinct meiotic stages, in an attempt to better understand the biological significance of genes clustered into similar expression patterns during this process. Among 790 sequences that showed an expression level change of twofold or more in any of the five key stages that were monitored, relative to the geometric average of all stages, about 40% peaked and about 30% were specifically suppressed at post-natal day 14 (representing the early pachytene stage of spermatocytes), reflecting tight transcriptional regulation at this stage. We also found that each of the six main transcription clusters that were determined was characterized by statistically significant representation of genes related to specific biological processes. Finally, our results indicated that genes important for meiosis are not randomly distributed along the mouse genome but rather preferentially located on specific chromosomes, suggesting for the first time that chromosomal location might be a regulating factor of meiotic gene expression. Mol. Reprod. Dev. 77: 241,248, 2010. © 2009 Wiley-Liss, Inc. [source] Genomic scale analysis of the human keratinocyte response to broad-band ultraviolet-B irradiationPHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 1 2002Joe Takao Ultraviolet B (UVB) radiation is an important inducer of many biologic changes in skin, of which keratinocytes are a key target. To gain better insight into changes in gene expression generated in the early phase after UVB exposure, we used complementary RNA (cRNA) microarray hybridization to compare differences in mRNA expression of UVB-irradiated (single dose of 100 J/m2 broad-band UVB) and sham-irradiated primary cultured human keratinocytes. Six hours after irradiation, total RNA was isolated from keratinocytes, and cRNA was synthesized and hybridized to a GeneChip expression array (Affymetrix) consisting of 6800 genes. Based on a threshold of >,twofold change, 187 genes (2.8%) were designated to be the most UVB-responsive. Surprisingly, none of these genes had been shown previously to be modulated by UVB. Conversely, several genes in the microarray that had been reported previously to be UVB- responsive by other methods showed less (< twofold) or no change. Northern blotting of seven differentially modulated genes produced results similar to those derived from microarray technology, thereby validating the accuracy of screening. Clustering based on known or likely functions indicated that among 88 upregulated genes, nine encode for cytochrome c subunits, six for ribosomal proteins, and two for regulators of apoptosis. By contrast, many of the 99 downregulated genes are involved in transcription, differentiation and transport. These findings indicate that keratinocytes respond to a single low dose of broad-band UVB irradiation by enhancing processes involved in energy production and translation, while suppressing those related to transcription, differentiation and transport. [source] The role of bioinformatics in two-dimensional gel electrophoresisPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 8 2003Andrew W. Dowsey Abstract Over the last two decades, two-dimensional electrophoresis (2-DE) gel has established itself as the de facto approach to separating proteins from cell and tissue samples. Due to the sheer volume of data and its experimental geometric and expression uncertainties, quantitative analysis of these data with image processing and modelling has become an actively pursued research topic. The results of these analyses include accurate protein quantification, isoelectric point and relative molecular mass estimation, and the detection of differential expression between samples run on different gels. Systematic errors such as current leakage and regional expression inhomogeneities are corrected for, followed by each protein spot in the gel being segmented and modelled for quantification. To assess differential expression of protein spots in different samples run on a series of two-dimensional gels, a number of image registration techniques for correcting geometric distortion have been proposed. This paper provides a comprehensive review of the computation techniques used in the analysis of 2-DE gels, together with a discussion of current and future trends in large scale analysis. We examine the pitfalls of existing techniques and highlight some of the key areas that need to be developed in the coming years, especially those related to statistical approaches based on multiple gel runs and image mining techniques through the use of parallel processing based on cluster computing and the grid technology. [source] Limitations of a linear model for the hurricane boundary layerTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 641 2009Stefanie Vogl Abstract The linear model for the steady boundary layer of a rapidly rotating axisymmetric vortex is derived from a detailed scale analysis of the full equations of motion. The previously known analytic solution is re-appraised for vortices of hurricane scale and strength. The internal consistency of the linear approximation is investigated for such a vortex by calculating from the solution the magnitude of the nonlinear terms that are neglected in the approximation compared with the terms retained. It is shown that the nonlinear terms are not negligibly small in a large region of the vortex, a feature that is consistent with the scale analysis. We argue that the boundary-layer problem is well-posed only at outer radii where there is subsidence into the layer. At inner radii, where there is ascent, only the radial pressure gradient may be prescribed and not the wind components at the top of the boundary layer, but the linear problem cannot be solved in these circumstances. We examine the radius at which the vertical flow at the top of the boundary layer changes sign for different tangential wind profiles relevant to hurricanes and show that this is several hundred kilometres from the vortex centre. This feature represents a further limitation of the linear model applied to hurricanes. While the present analysis assumes axial symmetry, the same limitations presumably apply to non-axisymmetric extensions to the linear model. 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