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Search Results: 1 - 10 of 236446 matches for " Thomas L. Toth "
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Optimization of Contrast Material Dose for Abdominal Multi-Detector Row CT: Predicting Patient Lean Body Weight by Using Preliminary Transverse CT Images  [PDF]
Antonino Guerrisi, Daniele Marin, Huiman Barnhart, Lisa Ho, Thomas L. Toth, Carlo Catalano, Rendon C. Nelson
Advances in Computed Tomography (ACT) , 2014, DOI: 10.4236/act.2014.31001
Abstract:

Estimated LBW could be used to determine the contrast material dose and rate during MDCT. The aim of this study is to test the accuracy of a technique for estimation of lean body weight (LBW) from a single multi-detector row computed tomographic (MDCT) abdominal image, using a bioelectrical body composition analyzer scale as the reference standard. CT images of 21 patients with previously measured LBW (mLBW) were processed using computer-assisted, vendor-specific software (Advantage Windows 4.2; GE Healthcare, Inc). For each transverse image, a fat-fraction was automatically measured as the number of fat pixels (-200 to -50 HU) divided by the total number of pixels having an attenuation value ≥-200 HU. Estimated LBW (eLBW) of five single contiguous sections was calculated in each of three abdominal regions (upper abdomen, mid abdomen and pelvis) by multiplying TBW by (1 – fat-fraction). Bland-Altman plot with limits of agreement was used to assess agreement between mLBW and eLBW. The mean mLBW for all patients was 56 kg (range, 39 - 75 kg). Mean differences and limits of agreement between mLBW and eLBW measurements for the upper abdomen, mid abdomen and pelvis reported were -8.9 kg (-25.6 kg, +7.5 kg), -10.6 kg (-27.7 kg, +6.4 kg), and +0.5 kg (-12.8 kg, +13.8 kg) respectively. eLBW deriving directly from a transverse CT image of the pelvis can accurately predict mLBW.

Differential Gene Expression and Protein Abundance Evince Ontogenetic Bias toward Castes in a Primitively Eusocial Wasp
James H. Hunt,Florian Wolschin,Michael T. Henshaw,Thomas C. Newman,Amy L. Toth,Gro V. Amdam
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0010674
Abstract: Polistes paper wasps are models for understanding conditions that may have characterized the origin of worker and queen castes and, therefore, the origin of paper wasp sociality. Polistes is “primitively eusocial” by virtue of having context-dependent caste determination and no morphological differences between castes. Even so, Polistes colonies have a temporal pattern in which most female larvae reared by the foundress become workers, and most reared by workers become future-reproductive gynes. This pattern is hypothesized to reflect development onto two pathways, which may utilize mechanisms that regulate diapause in other insects. Using expressed sequence tags (ESTs) for Polistes metricus we selected candidate genes differentially expressed in other insects in three categories: 1) diapause vs. non-diapause phenotypes and/or worker vs. queen differentiation, 2) behavioral subcastes of worker honey bees, and 3) no a priori expectation of a role in worker/gyne development. We also used a non-targeted proteomics screen to test for peptide/protein abundance differences that could reflect larval developmental divergence. We found that foundress-reared larvae (putative worker-destined) and worker-reared larvae (putative gyne-destined) differed in quantitative expression of sixteen genes, twelve of which were associated with caste and/or diapause in other insects, and they also differed in abundance of nine peptides/proteins. Some differentially-expressed genes are involved in diapause regulation in other insects, and other differentially-expressed genes and proteins are involved in the insulin signaling pathway, nutrient metabolism, and caste determination in highly social bees. Differential expression of a gene and a peptide encoding hexameric storage proteins is especially noteworthy. Although not conclusive, our results support hypotheses of 1) larval developmental pathway divergence that can lead to caste bias in adults and 2) nutritional differences as the foundation of the pathway divergence. Finally, the differential expression in Polistes larvae of genes and proteins also differentially expressed during queen vs. worker caste development in honey bees may indicate that regulatory mechanisms of caste outcomes share similarities between primitively eusocial and advanced eusocial Hymenoptera.
Epigenetics in Social Insects: A New Direction for Understanding the Evolution of Castes
Susan A. Weiner,Amy L. Toth
Genetics Research International , 2012, DOI: 10.1155/2012/609810
Abstract: Epigenetic modifications to DNA, such as DNA methylation, can expand a genome’s regulatory flexibility, and thus may contribute to the evolution of phenotypic plasticity. Recent work has demonstrated the importance of DNA methylation in alternative queen and worker “castes” in social insects, particularly honeybees. Social insects are an excellent system for addressing questions about epigenetics and evolution because: (1) they have dramatic caste polyphenisms that appear to be tied to differential methylation, (2) DNA methylation is widespread in various groups of social insects, and (3) there are intriguing connections between the social environment and DNA methylation in many species, from insects to mammals. In this article, we review research on honeybees, and, when available, other social insects, on DNA methylation and queen and worker caste differences. We outline a conceptual framework for the effects of methylation on caste determination in honeybees that may help guide studies of epigenetic regulation in other polyphenic taxa. Finally, we suggest future paths of study for social insect epigenetic research, including the importance of comparative studies of DNA methylation on a broader range of species, and highlight some key unanswered mechanistic questions about how DNA methylation affects gene regulation. 1. Introduction Phenotypic plasticity is an important biological phenomenon that allows organisms with same genotype to respond adaptively to variable biotic and abiotic environments. There are several molecular mechanisms that can contribute to genomic flexibility and thus phenotypic plasticity, including transcriptional regulation, posttranscriptional modification, alternative splicing, and epigenetic modifications of DNA (reviewed in [1]). In this paper, we explore the potential role of epigenetic modifications in phenotypic plasticity in social insects in the order Hymenoptera (bees, ants, and wasps), a group of animals that exhibit many remarkable forms of morphological and behavioral plasticity [2]. Phenotypic polymorphism has arisen many times in different insect lineages [3] and not always among eusocial insects. Other well-studied examples of extreme phenotypic plasticity in insects include pea aphids with winged and wingless morphs, as well as sexual and asexual generations (reviewed in [4]), horned and hornless morphs in dung beetles [5], and phase differences in migratory locusts [6]. Studies of insects, and especially social insects, are providing intriguing new insights into the relevance of epigenetic modifications of DNA to
Interplay of diffraction and nonlinear effects in propagation of ultrashort pulses
C. L. Korpa,Gy. Toth,J. Hebling
Physics , 2015,
Abstract: We investigate the interplay of diffraction and nonlinear effects during propagation of very short light pulses. Adapting the factorization approach to the problem at hand by keeping the transverse-derivative terms apart from the residual nonlinear contributions we derive an unidirectional propagation equation valid for weak dispersion and reducing to the slowly-evolving-wave-approximation for the case of paraxial rays. Comparison of numerical simulation results for the two equations shows pronounced differences when self-focusing plays important role. We devote special attention to modelling propagation of ultrashort terahertz pulses taking into account diffraction as well as Kerr type and second order nonlinearities. Comparing measured and simulated wave forms we deduce the value of the nonlinear refractive index of lithium niobate in the terahertz region to be three orders of magnitude larger than in the visible.
Merkel Cell Carcinoma Metastatic to the Head of the Pancreas
Ouellette JR,Woodyard L,Toth L,Termuhlen PM
JOP Journal of the Pancreas , 2004,
Abstract: CONTEXT: Merkel cell carcinoma is an aggressive cutaneous tumor without clearly defined treatment and high propensity for metastasis. CASE REPORT: This case describes a sixty four year old presenting with obstructive jaundice approximately two years after having a Merkel cell carcinoma resected from his finger. He underwent a successful pancreaticoduodenectomy with pathology confirming metastatic Merkel cell carcinoma. This report reviews the history, presentation, and current treatment recommendations for Merkel cell carcinoma. CONCLUSIONS: We propose that resection of metastases from Merkel cell carcinoma may confer a survival advantage and should be strongly considered, particularly if isolated.
A New Strategy for Solving Two Cosmological Constant Problems in Hadron Physics  [PDF]
Thomas L. Wilson
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.45096
Abstract:

A new approach to solving two of the cosmological constant problems (CCPs) is proposed by introducing the Abbott-Deser (AD) method for defining Killing charges in asymptotic de Sitter space as the only consistent means for defining the ground-state vacuum for the CCP. That granted, Einstein gravity will also need to be modified at short-distance nuclear scales, using instead a nonminimally coupled scalar-tensor theory of gravitation that provides for the existence of QCD’s two-phase vacuum having two different zero-point energy states as a function of temperature. Einstein gravity alone cannot accomplish this. The scalar field will be taken from bag theory in hadron physics, and the origin of the bag constant B is accounted for by gravity’s CC as \"\" B—noting that the Higgs mechanism does not account for either the curved-space origin of λ or the mass of composite hadrons. A small Hubble-scale graviton mass mg10-33eV naturally appears external to the hadron bag, induced by λ≠0. This mass is unobservable and gravitationally gauge-dependent. It is shown to be related to the cosmological event horizon in asymptotic de Sitter space.

Inconsistencies in Theoretical Physics, with Focus on the Higgs Mechanism  [PDF]
Thomas L. Wilson
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.63027
Abstract: In spite of tremendous progress in experimental high-energy physics such as the apparent discovery of the Higgs boson at CERN, there exist a number of inconsistencies in theoretical physics which continue to go either unnoticed or unstated. These include the Higgs mechanism itself as well as recent discussions of problems with inflationary cosmology. The subject will be addressed in the context of this author’s recent paper [1] on the requirement for compatible asymptotic states in the study of the cosmological constant problem (CCP). Inconsistency in the Higgs mechanism is eliminated by using scalar-tensor gravity where the scalar field is a gravitational field with zero spin that represents the spontaneous symmetry breaking potential.
Accelerating relativistic reference frames in Minkowski space-time
Slava G. Turyshev,Olivier L. Minazzoli,Viktor T. Toth
Physics , 2011, DOI: 10.1063/1.3692166
Abstract: We study accelerating relativistic reference frames in Minkowski space-time under the harmonic gauge. It is well-known that the harmonic gauge imposes constraints on the components of the metric tensor and also on the functional form of admissible coordinate transformations. These two sets of constraints are equivalent and represent the dual nature of the harmonic gauge. We explore this duality and show that the harmonic gauge allows presenting an accelerated metric in an elegant form that depends only on two harmonic potentials. It also allows reconstruction of the spatial structure of the post-Galilean coordinate transformation functions relating inertial and accelerating frames. The remaining temporal dependence of these functions together with corresponding equations of motion are determined from dynamical conditions, obtained by constructing the relativistic proper reference frame of an accelerated test particle. In this frame, the effect of external forces acting on the observer is balanced by the fictitious frame-reaction force that is needed to keep the test particle at rest with respect to the frame, conserving its relativistic linear momentum. We find that this approach is sufficient to determine all the terms of the coordinate transformation. The same method is then used to develop the inverse transformations. The resulting post-Galilean coordinate transformations extend the Poincar\'e group on the case of accelerating observers. We present and discuss the resulting coordinate transformations, relativistic equations of motion, and the structure of the metric tensors corresponding to the relativistic reference frames involved.
Spin squeezing and entanglement for arbitrary spin
Giuseppe Vitagliano,Iagoba Apellaniz,Inigo L. Egusquiza,Geza Toth
Physics , 2013, DOI: 10.1103/PhysRevA.89.032307
Abstract: A complete set of generalized spin-squeezing inequalities is derived for an ensemble of particles with an arbitrary spin. Our conditions are formulated with the first and second moments of the collective angular momentum coordinates. A method for mapping the spin-squeezing inequalities for spin-1/2 particles to entanglement conditions for spin-j particles is also presented. We apply our mapping to obtain a generalization of the original spin-squeezing inequality to higher spins. We show that, for large particle numbers, a spin-squeezing parameter for entanglement detection based on one of our inequalities is strictly stronger than the original spin-squeezing parameter defined in [A. Sorensen et al., Nature 409, 63 (2001)]. We present a coordinate system independent form of our inequalities that contains, besides the correlation and covariance tensors of the collective angular momentum operators, the nematic tensor appearing in the theory of spin nematics. Finally, we discuss how to measure the quantities appearing in our inequalities in experiments.
Modeling of Deformation and Texture Development of Copper in a 120° ECAE Die
Roxane Arruffat Massion,L. S. Toth,Jean-Philippe Mathieu
Physics , 2012, DOI: 10.1016/j.scriptamat.2006.01.004
Abstract: A flow line function is proposed to describe the material deformation in ECAE for a 120\degree die. This new analytical approach is incorporated into a viscoplastic self-consistent polycrystal code to simulate the texture evolution in Route A of copper and compared to experimental textures as well as to those corresponding to simple shear.
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