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Search Results: 1 - 10 of 20569 matches for " Kim Patten "
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The Impacts of Nonnative Japanese Eelgrass (Zostera japonica) on Commercial Shellfish Production in Willapa Bay, WA  [PDF]
Kim Patten
Agricultural Sciences (AS) , 2014, DOI: 10.4236/as.2014.57066
Abstract:

Eelgrass species worldwide are valued for the ecosystem service they provide to estuarine and marine habitats. One species, Zostera japonica, however, has some negative impacts outside its native range and is considered invasive. In Willapa Bay WA, USA, the nonnative eelgrass has expanded to the level where the shellfish industry is concerned about its potential impacts on its livelihood. Studies were conducted using paired plots, Z. japonica controlled with the herbicide imazamox vs. untreated controls, to assess the effects of Z. japonica on Manila clams (Ruditapes philippinarum) and Pacific oysters (Crassostrea gigas). Recruitment of new Manila clams was not affected by Z. japonica. The growth of young clams, total commercial clam harvests, clam quality and clam harvest efficiency, however, were greater on plots where Z. japonica was chemically controlled than where it was not treated. The response of oysters to Z. japonica control varied by site; there was no effect at one site, while the other sites had a 15% increase in shucked meat with Z. japonica control. The potential economic impact of a

Suprafibrillar structures of collagen, evidence for local organization and auxetic behaviour in architectures  [PDF]
Kate Patten, Tim Wess
Journal of Biophysical Chemistry (JBPC) , 2013, DOI: 10.4236/jbpc.2013.43014
Abstract: The suprafibrillar organisation of collagen rich tissues is the keystone to the diversity of resultant structures made from relatively similar materials. The local organisation between fibrils may be essential to suprafibril structures that are critical to functionality such as transparency in cornea, where specific lateral relationships between fibrils dictate optical properties. Here we show that corneal X-ray diffraction combined with mechanical strains to disrupt a specific suprafibrillar relationship between fibrils evidence and a coherent staggered axial relationship between collagen fibrils. The data also shows evidence for auxetic behavior of the collagen fibrils and reveals a 120 nm diffraction feature previously unreported in collagen tissues. The results show that suprafibrillar organisation can be an essential component in tissue architecture that has hitherto been ignored, but now must be considered in mechanical and structural models.
Biotech Stock Selection Using Peer Group Analysis and Relative Valuation
Stephan Patten
University of Toronto Medical Journal , 2002, DOI: 10.5015/utmj.v79i2.911
Abstract:
An animated depiction of major depression epidemiology
Scott B Patten
BMC Psychiatry , 2007, DOI: 10.1186/1471-244x-7-23
Abstract: In this study, up-to-date data on major depression epidemiology were integrated using a discrete event simulation model. The mathematical model was animated in Virtual Reality Modeling Language (VRML) to create a visual, rather than mathematical, depiction of the epidemiology.Consistent with existing literature, the model highlights potential advantages of population health strategies that emphasize access to effective long-term treatment. The paper contains a web-link to the animation.Visual animation of epidemiological results may be an effective knowledge translation tool. In clinical practice, such animations could potentially assist with patient education and enhanced long-term compliance.A comprehensive picture of the epidemiology of an episodic condition cannot be embodied in a single parameter such as an estimate of incidence or prevalence. The incidence of major depressive disorder conveys information about the risk of onset of an initial episode, but this is of limited value for clinical practice (where presentations occur after onset) or for public policy (since the rate of onset of new episodes does not adequately reflect the burden of disease). Prevalence is in some respects an even more obscure parameter. Prevalence is the number or proportion ("prevalence proportion") of population members who have a disorder at a point ("point prevalence") in time or during a period ("period prevalence") in time. This parameter is salient to the problem of quantifying disease burden but ultimately reflects a balance between entry into the prevalence pool (incidence or recurrence) and a other factors such as episode duration and mortality.Attempts to integrate epidemiological estimates into a comprehensive "picture" of the epidemiology of major depression have used Markov models [1,2] and micro-simulation approaches [3]. The complexity of major depression epidemiology has required the development of fairly complex models, the mathematics of which may not be of great i
Major depression epidemiology from a diathesis-stress conceptualization
Scott B Patten
BMC Psychiatry , 2013, DOI: 10.1186/1471-244x-13-19
Abstract: Simulation provides an opportunity to explore these issues. In this study, a simulation model based on an intuitive representation of diathesis-stress interaction was developed. Both diathesis and stress were represented using continuous distributions, without categorization. A diagnostic threshold was then applied to the simulation output to create nominal categories and to explore their consistency with available information.An apparently complex epidemiologic pattern emerged from the diathesis-stress interaction when thresholds were applied: incidence was time dependent, recurrence depended on the number of past episodes, baseline symptoms were associated with an increased risk of subsequent episodes and the remission rate declined with increasing episode duration.A diathesis-stress conceptualization coupled with application of a threshold-based diagnostic definition may explain several of the apparent complexities of major depression epidemiology. Some of these complexities may be artifacts of the nominal diagnostic approach. These observations should encourage an empirical exploration of whether diathesis-stress interactions provide a more parsimonious framework for understanding depression than current approaches.Depressive symptoms can be measured using rating scales, which provide an assessment of symptom severity on an ordinal or continuous scale. However, such ratings do not capture important aspects of the concept of a depressive disorder, as this is currently understood. Disorder definitions, and hence most available epidemiologic data, derive from nominal classifications (e.g. major depression (MD) as a named category rather than a scaled rating) that incorporate symptom severity but also thresholds for duration and severity of symptoms and require features such as dysfunction, distress or danger [1]. Diagnostic categories typically play a larger role than symptom ratings in medical practice because they align more closely with clinical decision-making.
Accumulation of major depressive episodes over time in a prospective study indicates that retrospectively assessed lifetime prevalence estimates are too low
Scott B Patten
BMC Psychiatry , 2009, DOI: 10.1186/1471-244x-9-19
Abstract: The NPHS is a longitudinal study that has followed a community sample representative of household residents since 1994. Follow-up interviews have been completed every two years and have incorporated the Composite International Diagnostic Interview short form for major depression. Data are currently available for seven such interview cycles spanning the time frame 1994 to 2006. In this study, cumulative prevalence was calculated by determining the proportion of respondents who had one or more major depressive episodes during this follow-up interval.The annual prevalence of MDD ranged between 4% and 5% of the population during each assessment, consistent with existing literature. However, 19.7% of the population had at least one major depressive episode during follow-up. This included 24.2% of women and 14.2% of men. These estimates are nearly twice as high as the lifetime prevalence of major depressive episodes reported by cross-sectional studies during same time interval.In this study, prospectively observed cumulative prevalence over a relatively brief interval of time exceeded lifetime prevalence estimates by a considerable extent. This supports the idea that lifetime prevalence estimates are vulnerable to recall bias and that existing estimates are too low for this reason.Lifetime prevalence is one of the most frequently reported parameters in psychiatric epidemiology. Lifetime prevalence represents the proportion of the population who have experienced a disorder at some time in their life up to the time of interview. In the case of Major Depressive Disorder, this is the proportion of the population who have experienced a major depressive episode (MDE) but not a manic, hypomanic or mixed episode and who do not have a concurrent psychotic disorder. In Canada, the lifetime prevalence of MDE is 12.2% [1] as determined by a national survey called the Canadian Community Health Survey, Mental Health and Wellbeing (CCHS 1.2) conducted in 2002. Similar values have been r
Problems encountered with the use of simulation in an attempt to enhance interpretation of a secondary data source in epidemiologic mental health research
Scott B Patten
BMC Research Notes , 2010, DOI: 10.1186/1756-0500-3-231
Abstract: The data source was a Canadian longitudinal study called the National Population Health Survey (NPHS). A simulation model representing the course of depressive episodes was used to reshape estimates deriving from binary and ordinal logistic models (fit to the NPHS data) into equations more capable of informing clinical and public health decisions. Discrete event simulation was used for this purpose. Whereas the intention was to clarify a complex epidemiology, the models themselves needed to become excessively complex in order to provide an accurate description of the data.Simulation methods are useful in circumstances where a representation of a real-world system has practical value. In this particular scenario, the usefulness of simulation was limited both by problems with the data source and by inherent complexity of the underlying epidemiology.Major Depressive Disorder (MDD) is a mood disorder that is characterized by one or more major depressive episodes (MDE). Clinical practice guidelines for MDD have historically regarded the diagnosis as a de facto indication of treatment need (e.g.[1]). However, in community studies application of diagnostic criteria for MDD has been shown to identify some short lived episodes that may not be associated with a need for treatment [2]. This has led to more recent recommendations acknowledging the apparent heterogeneity of this condition. For example, in the strategy of "watchful waiting" treatment may be delayed for several weeks while there is ongoing monitoring in order to determine whether an episode will resolve without active treatment [3]. For mild episodes, guided self-management has also been proposed as a reasonable intervention [3,4].It would be helpful to make use of epidemiologic data in order to quantify the probability of various outcomes and ultimately to use this information as a means of supporting clinical decisions. Recently, the predictD study has reported predictive algorithms for the risk of MDE in genera
The impact of antidepressant treatment on population health: synthesis of data from two national data sources in Canada
Scott B Patten
Population Health Metrics , 2004, DOI: 10.1186/1478-7954-2-9
Abstract: Data from two Canadian general health surveys were used in this analysis: the National Population Health Survey (NPHS) and the Canadian Community Health Survey (CCHS). The NPHS is a longitudinal study that collected data between 1994 and 2000. These longitudinal data allowed an approximation of episode incidence to be calculated. The cross-sectional CCHS allowed estimation of episode duration. The surveys used the same sampling frame and both incorporated a Short Form version of the Composite International Diagnostic Interview.Episodes occurring in antidepressant users lasted longer than those in non-users. The apparent incidence of major depressive episodes among those taking antidepressants was higher than that among respondents not taking antidepressants. Changes in duration and incidence over the data collection interval were not observed.The most probable explanation for these results is confounding by indication and/or severity: members of the general population who are taking antidepressants probably have more highly recurrent and more severe mood disorders. In part, this may have been due to the use of a brief predictive diagnostic interview, which may be prone to detection of sub-clinical cases. Whereas antidepressant use increased considerably over the data-collection period, differences in episode incidence and duration over time were not observed. This suggests that the impact of antidepressant medications on population health may have been less than expected.Depressive disorders are among the most important contributors to disease burden at the population level http://www.who.int/whr2001/2001/ webcite. While primary prevention for this condition has remained an elusive goal, provision of treatment has been viewed as having the capacity to reduce its impact on population health. Randomized, controlled clinical trials confirm that treatment with antidepressant medications can favorably impact the course of major depressive disorder. Clinical practice guid
The Two Faces of SLA: Mental Representation and Skill
Bill Van Patten
International Journal of English Studies (IJES) , 2010, DOI: 10.6018/ijes.10.1.113951
Abstract: In this essay, I argue for viewing mental representation and skill as distinct components of language acquisition. My claim is that language is not a monolithic entity—not a new concept, but one that is often overlooked by instructors and some scholars. I examine language as being (minimally) composed of mental representation and skill. Representation refers to the abstract and implicit knowledge that underlies all language. Skill refers to the use of language, especially fluency (the intersection of speed and accuracy). By thinking about language as at least the distinction between representation and skill, we might better sort out some of the issues related to adult SLA, namely the role that instruction has, and what instruction can actually impact. En este trabajo defiendo el supuesto de que tanto la representación mental como las destrezas (lingüísticas) deben ser tomadas como componentes diferenciados de la adquisición lingüística. Mi tesis es que el lenguaje no es una entidad monolítica –tesis no nueva, pero frecuentemente dejada de lado por profesores y estudiosos. Analizo el lenguaje como un compuesto de representación mental y destrezas. La representación se refiere al conocimiento abstracto e implícito que subyace en el lenguaje. Las destrezas hacen referencia al uso de la lengua, especialmente a la fluidez (intersección entre velocidad y precisión). Entendiendo el lenguaje de esta manera, distinguiendo entre representación y destrezas, será posible superar algunos de los problemas relativos al aprendizaje de lenguas por los adultos, y muy especialmente el cometido de la ense anza y lo que ésta puede producir.
A major depression prognosis calculator based on episode duration
Patten Scott B
Clinical Practice and Epidemiology in Mental Health , 2006, DOI: 10.1186/1745-0179-2-13
Abstract: Background Epidemiological data have shown that the probability of recovery from an episode declines with increasing episode duration, such that the duration of an episode may be an important factor in determining whether treatment is required. The objective of this study is to incorporate episode duration data into a calculator predicting the probability of recovery during a specified interval of time. Methods Data from two Canadian epidemiological studies were used, both studies were components of a program undertaken by the Canadian national statistical agency. One component was a cross-sectional psychiatric epidemiological survey (n = 36,984) and the other was a longitudinal study (n = 17,262). Results A Weibull distribution provided a good description of episode durations reported by subjects with major depression in the cross-sectional survey. This distribution was used to develop a discrete event simulation model for episode duration calibrated using the longitudinal data. The resulting estimates were then incorporated into a predictive calculator. During the early weeks of an episode, recovery probabilities are high. The model predicts that approximately 20% will recover in the first week after diagnostic criteria for major depression are met. However, after six months of illness, recovery during a subsequent week is less than 1%. Conclusion The duration of an episode is relevant to the probability of recovery. This epidemiological feature of depressive disorders can inform prognostic judgments. Watchful waiting may be an appropriate strategy for mild episodes of recent onset, but the risks and benefits of this strategy must be assessed in relation to time since onset of the episode.
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