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Search Results: 1 - 10 of 168688 matches for " Dawn E. Henderson "
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Nutrient Use Efficiency of Three Fast Growing Hardwood Species across a Resource Gradient  [PDF]
Dawn E. Henderson, Shibu Jose
Open Journal of Forestry (OJF) , 2012, DOI: 10.4236/ojf.2012.24023
Abstract: Attitudes regarding traditional energy sources have shifted toward renewable resources. Specifically, short-rotation woody crop supply systems have become more prevalent for biomass and biofuel production. However, a number of factors such as environmental and inherent resource availability can limit tree production. Given the intensified demand for wood biomass production, forest and plantation management practices are focusing on increasing productivity. Fertilizer application, while generally one of the least expensive silvicultural tools, can become costly if application rates exceed nutrient uptake or demand of the trees especially if it does not result in additional biomass production. We investigated the effect of water and varying levels of nitrogen application (56, 112, and 224 kg·N·ha-1·yr-1) on nutrient content, resorption efficiency and proficiency, N:P and the relationship with ANPP, as well as leaf- and canopy-level nutrient use efficiency of nitrogen, phosphorus, and potassium for Populus deltoides, Quercus pagoda, and Platanus occidentalis. P. deltoides and P. occidentalis reached their maximum nitrogen budget with the application of water suggesting old agricultural fields may have sufficient nutrient levels to sustain short-rotation woody crops negating the application of additional nitrogen for these two species. Additionally, for P. deltoides and Q. pagoda application of nitrogen appeared to increase the uptake of phosphorus however, resorption efficiency for these two species were more similar to studies conducted on nutrient poor sites. Nutrient resorption proficiency for all three nutrients and all three species were at levels below the highest rates of nitrogen application. These findings suggest maximum biomass production may not necessarily be tied to maximum nutrient application.
Toward An Understanding of Developmental Coordination Disorder: Terminological and Diagnostic Issues
Sheila E. Henderson,Leslie Henderson
Neural Plasticity , 2003, DOI: 10.1155/np.2003.1
Abstract: Awareness of children who experience unexpected difficulty in the acquisition of motor skills has increased dramatically over the last twenty years. Although the positing of a distinct syndrome has proven seminal in provoking further questions, several basic terminological problems remain unresolved. In this paper, we conduct a component analysis of the three, principal competing labels for this disorder, two of them being elements derived from systematic diagnostic frameworks. Our preference for the DSM IV term Developmental Coordination Disorder (DCD) is stated find justified. Problems in diagnosis are discussed, especially in relation to the etiology-dominated medical model. We argue that an attempt should be made to identify (pathological) positive signs that can reliably be detected rather than relying entirely on normative evidence of a lack of skills exhibited by other children of the same age. The high degree of overlap between DCD and other developmental disorders suggests that DCD might not constitute a distinct syndrome. In this context, we emphasize the need to determine whether incoordination takes a different form when it occurs alone or whether it is combined with general developmental delay or with other specific disorders in children of normal intelligence.
Physical and Behavioral Markers Help Identify Written Language Disability (WLD) Related to Attention Deficit Hyperactivity Disorder (ADHD)  [PDF]
Rowe A. Young, Benson E. Ginsburg, Dawn Bradway
Psychology (PSYCH) , 2012, DOI: 10.4236/psych.2012.31006
Abstract: Rotation, its physiological processing, as well as how this lateralized direction of movement is sensed, is regularly taken for granted and little appreciated when studying how learning develops. Preference for direction of rotational movement and how one processes this information has been found to differ greatly from one individual to another. This report discusses how bimanual rotational hand use preference and reversed direction of body part and movement sensation detection may be utilized to help identify certain currently unrecognized classroom learning difficulties. What we label Reversed Positioning Sensation (RPS) is evidenced in our research and is found in many children and adults presently identified as ‘learning disabled’ and/or ‘hyperactive’ or just those considered “bright underachievers”. Easily administered tests to help identify individuals who may be at risk are discussed. When RPS occurs without the necessary sensory-motor accommodation or compensation, we theorize that written language disability (WLD), as well as compromised organizational skills often identified as ADHD, result. In addition, this paper discusses a summary of our findings examining families with biologically related family members reporting primary difficulties related to organization and written language skills. Case studies from four of the many families we have studied demonstrate how to determine if an individual is able to sense his/her own body extremities in correctly functioning or maladaptive directional orientation. In some cases, just changing a writing hand position has been shown to help overcome many of the problems of RPS. This change is meant is to redirect the writing hand movement to sense a top/down orientation.
The exotic Robinson-Schensted correspondence
Anthony Henderson,Peter E. Trapa
Mathematics , 2011, DOI: 10.1016/j.jalgebra.2012.06.029
Abstract: We study the action of the symplectic group on pairs of a vector and a flag. Considering the irreducible components of the conormal variety, we obtain an exotic analogue of the Robinson-Schensted correspondence. Conjecturally, the resulting cells are related to exotic character sheaves.
A Spatio-Temporal Point Process Model for Ambulance Demand
Zhengyi Zhou,David S. Matteson,Dawn B. Woodard,Shane G. Henderson,Athanasios C. Micheas
Statistics , 2014,
Abstract: Ambulance demand estimation at fine time and location scales is critical for fleet management and dynamic deployment. We are motivated by the problem of estimating the spatial distribution of ambulance demand in Toronto, Canada, as it changes over discrete 2-hour intervals. This large-scale dataset is sparse at the desired temporal resolutions and exhibits location-specific serial dependence, daily and weekly seasonality. We address these challenges by introducing a novel characterization of time-varying Gaussian mixture models. We fix the mixture component distributions across all time periods to overcome data sparsity and accurately describe Toronto's spatial structure, while representing the complex spatio-temporal dynamics through time-varying mixture weights. We constrain the mixture weights to capture weekly seasonality, and apply a conditionally autoregressive prior on the mixture weights of each component to represent location-specific short-term serial dependence and daily seasonality. While estimation may be performed using a fixed number of mixture components, we also extend to estimate the number of components using birth-and-death Markov chain Monte Carlo. The proposed model is shown to give higher statistical predictive accuracy and to reduce the error in predicting EMS operational performance by as much as two-thirds compared to a typical industry practice.
Travel time estimation for ambulances using Bayesian data augmentation
Bradford S. Westgate,Dawn B. Woodard,David S. Matteson,Shane G. Henderson
Statistics , 2013, DOI: 10.1214/13-AOAS626
Abstract: We introduce a Bayesian model for estimating the distribution of ambulance travel times on each road segment in a city, using Global Positioning System (GPS) data. Due to sparseness and error in the GPS data, the exact ambulance paths and travel times on each road segment are unknown. We simultaneously estimate the paths, travel times, and parameters of each road segment travel time distribution using Bayesian data augmentation. To draw ambulance path samples, we use a novel reversible jump Metropolis-Hastings step. We also introduce two simpler estimation methods based on GPS speed data. We compare these methods to a recently published travel time estimation method, using simulated data and data from Toronto EMS. In both cases, out-of-sample point and interval estimates of ambulance trip times from the Bayesian method outperform estimates from the alternative methods. We also construct probability-of-coverage maps for ambulances. The Bayesian method gives more realistic maps than the recently published method. Finally, path estimates from the Bayesian method interpolate well between sparsely recorded GPS readings and are robust to GPS location errors.
Forecasting emergency medical service call arrival rates
David S. Matteson,Mathew W. McLean,Dawn B. Woodard,Shane G. Henderson
Statistics , 2011, DOI: 10.1214/10-AOAS442
Abstract: We introduce a new method for forecasting emergency call arrival rates that combines integer-valued time series models with a dynamic latent factor structure. Covariate information is captured via simple constraints on the factor loadings. We directly model the count-valued arrivals per hour, rather than using an artificial assumption of normality. This is crucial for the emergency medical service context, in which the volume of calls may be very low. Smoothing splines are used in estimating the factor levels and loadings to improve long-term forecasts. We impose time series structure at the hourly level, rather than at the daily level, capturing the fine-scale dependence in addition to the long-term structure. Our analysis considers all emergency priority calls received by Toronto EMS between January 2007 and December 2008 for which an ambulance was dispatched. Empirical results demonstrate significantly reduced error in forecasting call arrival volume. To quantify the impact of reduced forecast errors, we design a queueing model simulation that approximates the dynamics of an ambulance system. The results show better performance as the forecasting method improves. This notion of quantifying the operational impact of improved statistical procedures may be of independent interest.
Necrotizing Infiltrative Lipomatosis in a Miniature Zebu Bull (Bos primigenius indicus)
Scott D. Reed,Dawn E. Evans
Veterinary Medicine International , 2010, DOI: 10.4061/2010/810496
Abstract: Lipomatosis is described in a miniature Zebu, Bos primigenius indicus, bull that died of perianesthetic complications. This is the first pathologic description of lipomatosis that we are aware of in this species and breed of cattle. Infiltration of multiple visceral organs is described and depicted along with comparison to previously published cases of lipomatosis in other breeds of cattle. A 131?kg, three-year-old, miniature Zebu bull with a body condition score of five out of nine presented to the LSU SVM farm animal medicine service for repair of a tail fracture. During anesthetic induction the bull developed a ventricular tachyarrhythmia and subsequently succumbed. At necropsy, there were large amounts of hard nodular accumulations of fat surrounding and infiltrating many of the abdominal visceral organs and support structures. The mesentery surrounding the small intestines and colon was infiltrated with abundant firm fat that compressed intestines and filled greater than 40% of the peritoneal cavity. The retroperitoneal space was also distended with firm fat which was mottled white, tan, and golden-brown, and was often gritty when sectioned. Approximately 80% of the jejunum and 90% of the duodenum had diffuse transmural reddening, and the aborad half of the abomasum was edematous and reddened transmurally. Grossly, no other pathologically relevant lesions were detected. Microscopic examination of peritoneal fat confirmed necrosis of large areas of fat (Figure 1). The perirenal and mesenteric lymph nodes revealed infiltration and partial effacement by adipose tissue. Normal lymph node architecture was lost and the remaining tissue was composed of widely separated lymphoid aggregates with interposed fat (Figure 2). The pancreas also had marked amounts of adipose tissue expanding the interstitium causing wide separation of islands of acinar tissue (Figure 3). Within abdominal fat there were multifocal areas of fat necrosis with lightly basophilic intracellular debris (mineralization). Other large foci of extracellular mineralization were also seen throughout the omental fat as characterized by large aggregates of intensely basophilic material. Sections of small intestines had a wide band of mature adipose tissue within the tunica muscularis, splitting the muscle into a thick inner circumferential layer and a thin longitudinal outer layer (Figure 4). Mature adipose tissue also frequently infiltrated the intestinal submucosa. In sections of duodenum taken from an area with a large mass of serosal fat, the muscle layers appeared compressed and
The BMP Ligand Gdf6 Prevents Differentiation of Coronal Suture Mesenchyme in Early Cranial Development
Dawn E. Clendenning, Douglas P. Mortlock
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0036789
Abstract: Growth Differentiation Factor-6 (Gdf6) is a member of the Bone Morphogenetic Protein (BMP) family of secreted signaling molecules. Previous studies have shown that Gdf6 plays a role in formation of a diverse subset of skeletal joints. In mice, loss of Gdf6 results in fusion of the coronal suture, the intramembranous joint that separates the frontal and parietal bones. Although the role of GDFs in the development of cartilaginous limb joints has been studied, limb joints are developmentally quite distinct from cranial sutures and how Gdf6 controls suture formation has remained unclear. In this study we show that coronal suture fusion in the Gdf6?/? mouse is due to accelerated differentiation of suture mesenchyme, prior to the onset of calvarial ossification. Gdf6 is expressed in the mouse frontal bone primordia from embryonic day (E) 10.5 through 12.5. In the Gdf6?/? embryo, the coronal suture fuses prematurely and concurrently with the initiation of osteogenesis in the cranial bones. Alkaline phosphatase (ALP) activity and Runx2 expression assays both showed that the suture width is reduced in Gdf6+/? embryos and is completely absent in Gdf6?/? embryos by E12.5. ALP activity is also increased in the suture mesenchyme of Gdf6+/? embryos compared to wild-type. This suggests Gdf6 delays differentiation of the mesenchyme occupying the suture, prior to the onset of ossification. Therefore, although BMPs are known to promote bone formation, Gdf6 plays an inhibitory role to prevent the osteogenic differentiation of the coronal suture mesenchyme.
Following Ariadne's thread: a new perspective on RBR ubiquitin ligases
Dawn M Wenzel, Rachel E Klevit
BMC Biology , 2012, DOI: 10.1186/1741-7007-10-24
Abstract: Ubiquitination is the process by which proteins are selectively targeted for a variety of cellular fates. This post-translational modification is carried out by a trio of enzymes: an E1 ubiquitin-activating enzyme, an E2 ubiquitin-conjugating enzyme, and an E3 ubiquitin ligase. In most cases, E3 ubiquitin ligases assume the role of transferring activated ubiquitin from a restricted cohort of E2s to specific substrates. In a given genome, putative E3s greatly outnumber E2s, underscoring their role in substrate selection. For example, in humans, there are over 600 E3 ubiquitin ligases and fewer than 40 E2s [1]. On the basis of their mechanism and structure, E3 ligases have historically been classified into two families, the HECT- and RING/UBOX-type ligases (Figure 1). Recently we determined that Ariadne, the defining member of a subclass of RING-containing E3 ligases known as RING-between-RINGs (RBRs), blurs the line between RING and HECT-type E3s.Eukaryotic E3 ubiquitin ligases are generally identified by the presence of either a HECT or a RING domain. The features of each type of domain are well defined and are readily predictable by primary sequence analysis. RINGs are characterized by a regular spacing of conserved cysteines and histidines which bind two Zn2+ ions that stabilize the overall structure of this domain, allowing for recognition and activation of E2 Ub-conjugating enzymes [2]. HECT domains are identified on the basis of their similarity to the founding member of the family, E6AP. In contrast to RING domains, which can occur at any position within a given protein, all known HECT domains are found at the carboxy-terminal end of their respective proteins. The HECT domain has a bilobal structure: the lobe at the amino-terminal end of the domain (the N-lobe) serves as the E2-binding domain, and the lobe at the carboxyl terminus (the C-lobe) contains the catalytic cysteine.There are two general mechanisms by which the ultimate substrate-ubiquitin isopeptide
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