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Search Results: 1 - 10 of 150452 matches for " H. Lester Kirchner "
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Transfusion, erythropoiesis-stimulating agent therapy, and kidney transplant wait time  [PDF]
Robert M. Perkins, H. Lester Kirchner, Rajesh Govindasamy
Open Journal of Internal Medicine (OJIM) , 2012, DOI: 10.4236/ojim.2012.21001
Abstract: Aim: Anemia is highly prevalent among patients wait-listed for renal transplant, and management with blood transfusion or erythropoietin stimulating agents may impact transplant wait time. The purpose of this study was to examine the impact of blood transfusion and erythropoiesis stimulating agent therapy on renal transplant wait time. Methods: We retrospectively analyzed all adult patients listed for first deceased donor kidney transplantation at two transplant centers in Central Pennsylvania between 2004 and 2008. The exposures of interest were blood transfusion and erythropoietin stimulating agent therapy. Cox proportional hazards were used to model time to deceased donor kidney transplant. Results: Among 407 patients listed for transplant, 84 received a deceased donor kidney during a median follow-up of 26.3 months. In an adjusted Cox proportional hazards model, with erythropoiesis stimulating agent and transfusion both treated as time-dependent exposures, UNOS inactive status at listing date (hazard ratio [HR] 0.81; 95% CI 0.73 - 0.89; P < 0.001) and transfusion during the wait list period (HR 0.27; 95% CI 0.11 - 0.69; P = 0.01) independently predicted longer transplant wait time. Erythropoiesis stimulating agent use prior to or after transplant wait listing date did not independently predict wait time. Conclusion: Blood transfusion while waitlisted for kidney transplant is strongly associated with prolonged wait time.
The Impact of Nutritional Status and Longitudinal Recovery of Motor and Cognitive Milestones in Internationally Adopted Children
Hyun Park,Denise Bothe,Eva Holsinger,H. Lester Kirchner,Karen Olness,Anna Mandalakas
International Journal of Environmental Research and Public Health , 2011, DOI: 10.3390/ijerph8010105
Abstract: Internationally adopted children often arrive from institutional settings where they have experienced medical, nutritional and psychosocial deprivation. This study uses a validated research assessment tool to prospectively assess the impact of baseline (immediately post adoption) nutritional status on fifty-eight children as measured by weight-for-age, height-for-age, weight-for-height and head circumference-for-age z scores, as a determinant of cognitive (MDI) and psychomotor development (PDI) scores longitudinally. A statistical model was developed to allow for different ages at time of initial assessment as well as variable intervals between follow up visits. The study results show that both acute and chronic measures of malnutrition significantly affect baseline developmental status as well as the rate of improvement in both MDI and PDI scores. This study contributes to the body of literature with its prospective nature, unique statistical model for longitudinal evaluation, and use of a validated assessment tool to assess outcomes.
A rewriting point of view on strategies
Hélène Kirchner
Electronic Proceedings in Theoretical Computer Science , 2013, DOI: 10.4204/eptcs.112.15
Abstract: This paper is an expository contribution reporting on published work. It focusses on an approach followed in the rewriting community to formalize the concept of strategy. Based on rewriting concepts, several definitions of strategy are reviewed and connected: in order to catch the higher-order nature of strategies, a strategy is defined as a proof term expressed in the rewriting logic or in the rewriting calculus; to address in a coherent way deduction and computation, a strategy is seen as a subset of derivations; and to recover the definition of strategy in sequential path-building games or in functional programs, a strategy is considered as a partial function that associates to a reduction-in-progress, the possible next steps in the reduction sequence.
Incremental learning of skill collections based on intrinsic motivation
Jan H. Metzen,Frank Kirchner
Frontiers in Neurorobotics , 2013, DOI: 10.3389/fnbot.2013.00011
Abstract: Life-long learning of reusable, versatile skills is a key prerequisite for embodied agents that act in a complex, dynamic environment and are faced with different tasks over their lifetime. We address the question of how an agent can learn useful skills efficiently during a developmental period, i.e., when no task is imposed on him and no external reward signal is provided. Learning of skills in a developmental period needs to be incremental and self-motivated. We propose a new incremental, task-independent skill discovery approach that is suited for continuous domains. Furthermore, the agent learns specific skills based on intrinsic motivation mechanisms that determine on which skills learning is focused at a given point in time. We evaluate the approach in a reinforcement learning setup in two continuous domains with complex dynamics. We show that an intrinsically motivated, skill learning agent outperforms an agent which learns task solutions from scratch. Furthermore, we compare different intrinsic motivation mechanisms and how efficiently they make use of the agent's developmental period.
Transplacental Passage of Interleukins 4 and 13?
Robert H. Lim, Lester Kobzik
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0004660
Abstract: The mechanisms by which prenatal events affect development of adult disease are incompletely characterized. Based on findings in a murine model of maternal transmission of asthma risk, we sought to test the role of the pro-asthmatic cytokines interleukin IL-4 and -13. To assess transplacental passage of functional cytokines, we assayed phosphorylation of STAT-6, a marker of IL-4 and -13 signaling via heterodimeric receptor complexes which require an IL-4 receptor alpha subunit. IL-4 receptor alpha?/? females were mated to wild-type males, and pregnant females were injected with supraphysiologic doses of IL-4 or 13. One hour after injection, the receptor heterozygotic embryos were harvested and tissue nuclear proteins extracts assayed for phosphorylation of STAT-6 by Western blot. While direct injection of embryos produced a robust positive control, no phosphorylation was seen after maternal injection with either IL-4 or -13, indicating that neither crossed the placenta in detectable amounts. The data demonstrate a useful approach to assay for transplacental passage of functional maternal molecules, and indicate that molecules other than IL-4 and IL-13 may mediate transplacental effects in maternal transmission of asthma risk.
Intra-aggregate CO2 enrichment: a modelling approach for aerobic soils
D. Schlotter ,H. Schack-Kirchner
Biogeosciences (BG) & Discussions (BGD) , 2013,
Abstract: CO2 concentration gradients inside soil aggregates, caused by the respiration of soil microorganisms and fungal hyphae, might lead to variations in the soil solution chemistry on a mm-scale, and to an underestimation of the CO2 storage. But, up to now, there seems to be no feasible method for measuring CO2 inside natural aggregates with sufficient spatial resolution. We combined a one-dimensional model for gas diffusion in the inter-aggregate pore space with a cylinder diffusion model, simulating the consumption/production and diffusion of O2 and CO2 inside soil aggregates with air- and water-filled pores. Our model predicts that for aerobic respiration (respiratory quotient = 1) the intra-aggregate increase in the CO2 partial pressure can never be higher than 0.9 kPa for siliceous, and 0.1 kPa for calcaric aggregates, independent of the level of water-saturation. This suggests that only for siliceous aggregates CO2 produced by aerobic respiration might cause a high small-scale spatial variability in the soil solution chemistry. In calcaric aggregates, however, the contribution of carbonate species to the CO2 transport should lead to secondary carbonates on the aggregate surfaces. As regards the total CO2 storage in aerobic soils, both siliceous and calcaric, the effect of intra-aggregate CO2 gradients seems to be negligible. To assess the effect of anaerobic respiration on the intra-aggregate CO2 gradients, the development of a device for measuring CO2 on a mm-scale in soils is indispensable.
Intra-aggregate CO2 enrichment: a modelling approach for aerobic soils
D. Schlotter,H. Schack-Kirchner
Biogeosciences (BG) & Discussions (BGD) , 2013, DOI: 10.5194/bg-10-1209-2013
Abstract: CO2 concentration gradients inside soil aggregates, caused by the respiration of soil microorganisms and fungal hyphae, might lead to variations in the soil solution chemistry on a mm-scale, and to an underestimation of the CO2 storage. But, up to now, there seems to be no feasible method for measuring CO2 inside natural aggregates with sufficient spatial resolution. We combined a one-dimensional model for gas diffusion in the inter-aggregate pore space with a cylinder diffusion model, simulating the consumption/production and diffusion of O2 and CO2 inside soil aggregates with air- and water-filled pores. Our model predicts that for aerobic respiration (respiratory quotient = 1) the intra-aggregate increase in the CO2 partial pressure can never be higher than 0.9 kPa for siliceous, and 0.1 kPa for calcaric aggregates, independent of the level of water-saturation. This suggests that only for siliceous aggregates CO2 produced by aerobic respiration might cause a high small-scale spatial variability in the soil solution chemistry. In calcaric aggregates, however, the contribution of carbonate species to the CO2 transport should lead to secondary carbonates on the aggregate surfaces. As regards the total CO2 storage in aerobic soils, both siliceous and calcaric, the effect of intra-aggregate CO2 gradients seems to be negligible. To assess the effect of anaerobic respiration on the intra-aggregate CO2 gradients, the development of a device for measuring CO2 on a mm-scale in soils is indispensable.
Intra-aggregate CO2 enrichment: a modelling approach for aerobic soils
D. Schlotter,H. Schack-Kirchner
Biogeosciences Discussions , 2012, DOI: 10.5194/bgd-9-14795-2012
Abstract: CO2 concentration gradients inside soil aggregates, caused by the respiration of soil microorganisms and fungal hyphae, might lead to variations in the soil solution chemistry on a mm-scale, and to an underestimation of the CO2 storage. But, up to now, there seems to be no feasible method for measuring CO2 inside natural aggregates with sufficient spatial resolution. We combined a one-dimensional model for gas diffusion in the inter-aggregate pore-space with a cylinder diffusion model, simulating the consumption/production and diffusion of O2 and CO2 inside soil aggregates with air- and water-filled pores. Our model predicts that for aerobic respiration (respiratory quotient = 1) the intra-aggregate increase in the CO2 partial pressure can never be higher than 0.9 kPa for siliceous, and 0.08 kPa for calcaric aggregates, independent of the level of water-saturation. This suggests that only for siliceous aggregates CO2 produced by aerobic respiration might cause a high small-scale spatial variability in the soil solution chemistry. In calcaric aggregates, however, the contribution of carbonate species to the CO2 transport should lead to secondary carbonates on the aggregate surfaces. As regards the total CO2 storage in aerobic soils, both siliceous and calcaric, the effect of intra-aggregate CO2 gradients seems to be negligible. To assess the effect of anaerobic respiration on the intra-aggregate CO2 gradients, the development of a device for measuring CO2 on a mm-scale in soils is indispensable.
Transport Properties of One-Dimensional Hubbard Models
S. Kirchner,H. G. Evertz,W. Hanke
Physics , 1998, DOI: 10.1103/PhysRevB.59.1825
Abstract: We present results for the zero and finite temperature Drude weight D(T) and for the Meissner fraction of the attractive and the repulsive Hubbard model, as well as for the model with next nearest neighbor repulsion. They are based on Quantum Monte Carlo studies and on the Bethe ansatz. We show that the Drude weight is well defined as an extrapolation on the imaginary frequency axis, even for finite temperature. The temperature, filling, and system size dependence of D is obtained. We find counterexamples to a conjectured connection of dissipationless transport and integrability of lattice models.
Risk for Asthma in Offspring of Asthmatic Mothers versus Fathers: A Meta-Analysis
Robert H. Lim,Lester Kobzik,Morten Dahl
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0010134
Abstract: Many human epidemiologic studies demonstrate that maternal asthma confers greater risk of asthma to offspring than does paternal disease. However, a handful have shown the opposite. Given this disparity, a meta-analysis is necessary to determine the veracity and magnitude of the “maternal effect.”
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