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Search Results: 1 - 10 of 146200 matches for " Clement F. Kent "
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The Drosophila foraging Gene Mediates Adult Plasticity and Gene–Environment Interactions in Behaviour, Metabolites, and Gene Expression in Response to Food Deprivation
Clement F. Kent,Tim Daskalchuk,Lisa Cook,Marla B. Sokolowski ,Ralph J. Greenspan
PLOS Genetics , 2009, DOI: 10.1371/journal.pgen.1000609
Abstract: Nutrition is known to interact with genotype in human metabolic syndromes, obesity, and diabetes, and also in Drosophila metabolism. Plasticity in metabolic responses, such as changes in body fat or blood sugar in response to changes in dietary alterations, may also be affected by genotype. Here we show that variants of the foraging (for) gene in Drosophila melanogaster affect the response to food deprivation in a large suite of adult phenotypes by measuring gene by environment interactions (GEI) in a suite of food-related traits. for affects body fat, carbohydrates, food-leaving behavior, metabolite, and gene expression levels in response to food deprivation. This results in broad patterns of metabolic, genomic, and behavioral gene by environment interactions (GEI), in part by interaction with the insulin signaling pathway. Our results show that a single gene that varies in nature can have far reaching effects on behavior and metabolism by acting through multiple other genes and pathways.
A Model-Based Analysis of Chemical and Temporal Patterns of Cuticular Hydrocarbons in Male Drosophila melanogaster
Clement Kent, Reza Azanchi, Ben Smith, Adrienne Chu, Joel Levine
PLOS ONE , 2007, DOI: 10.1371/journal.pone.0000962
Abstract: Drosophila Cuticular Hydrocarbons (CH) influence courtship behaviour, mating, aggregation, oviposition, and resistance to desiccation. We measured levels of 24 different CH compounds of individual male D. melanogaster hourly under a variety of environmental (LD/DD) conditions. Using a model-based analysis of CH variation, we developed an improved normalization method for CH data, and show that CH compounds have reproducible cyclic within-day temporal patterns of expression which differ between LD and DD conditions. Multivariate clustering of expression patterns identified 5 clusters of co-expressed compounds with common chemical characteristics. Turnover rate estimates suggest CH production may be a significant metabolic cost. Male cuticular hydrocarbon expression is a dynamic trait influenced by light and time of day; since abundant hydrocarbons affect male sexual behavior, males may present different pheromonal profiles at different times and under different conditions.
Juntas en edificios de acero Joints in steel buildings
Valencia Clement Gabriel F.
Ingeniería e Investigación , 2006,
Abstract: Los elementos de mampostería y los miembros de acero usados en la construcción de edificios se mantienen en constante movimiento. Los cambios volumétricos son producto de las variaciones de temperatura y las deformaciones producidas por las cargas estáticas o dinámicas, y en algunos materiales, por los cambios en el contenido de humedad dentro de los mismos, tal el caso de la mampostería. El presente articulo está dirigido a la determinación de cuándo se requieren juntas de expansión o sísmicas, y como proporcionarlas y dise arlas con propiedad, específicamente en edificios de acero. No se incluye el estudio de las juntas en estructuras de concreto, en muros, ni otros elementos arquitectónicos. Masonry and steel components used in constructing buildings are in a constant state of motion. Volumetric changes are produced by temperature variation and deformation resulting from static or dynamic loading and in some materials, such as masonry, due to moisture content. This article addresses means of determining when expansion and seismic joints are required and how to proportion and design appropriate joints, specifically in steel buildings. It does not cover the study of expansion joints in concrete structures, in masonry construction or in non-structural (architectural) elements.
Natural Variation in the Thermotolerance of Neural Function and Behavior due to a cGMP-Dependent Protein Kinase
Ken Dawson-Scully, Gary A. B. Armstrong, Clement Kent, R. Meldrum Robertson, Marla B. Sokolowski
PLOS ONE , 2007, DOI: 10.1371/journal.pone.0000773
Abstract: Although it is acknowledged that genetic variation contributes to individual differences in thermotolerance, the specific genes and pathways involved and how they are modulated by the environment remain poorly understood. We link natural variation in the thermotolerance of neural function and behavior in Drosophila melanogaster to the foraging gene (for, which encodes a cGMP-dependent protein kinase (PKG)) as well as to its downstream target, protein phosphatase 2A (PP2A). Genetic and pharmacological manipulations revealed that reduced PKG (or PP2A) activity caused increased thermotolerance of synaptic transmission at the larval neuromuscular junction. Like synaptic transmission, feeding movements were preserved at higher temperatures in larvae with lower PKG levels. In a comparative assay, pharmacological manipulations altering thermotolerance in a central circuit of Locusta migratoria demonstrated conservation of this neuroprotective pathway. In this circuit, either the inhibition of PKG or PP2A induced robust thermotolerance of neural function. We suggest that PKG and therefore the polymorphism associated with the allelic variation in for may provide populations with natural variation in heat stress tolerance. for's function in behavior is conserved across most organisms, including ants, bees, nematodes, and mammals. PKG's role in thermotolerance may also apply to these and other species. Natural variation in thermotolerance arising from genes involved in the PKG pathway could impact the evolution of thermotolerance in natural populations.
Ito’s Formula for the Discrete-Time Quantum Walk in Two Dimensions  [PDF]
Clement Ampadu
Journal of Quantum Information Science (JQIS) , 2012, DOI: 10.4236/jqis.2012.22008
Abstract: Following Konno [1], it is natural to ask: What is the Ito’s formula for the discrete time quantum walk on a graph different than Z, the set of integers? In this paper we answer the question for the discrete time quantum walk on Z2, the square lattice.
On Some Questions of C. Ampadu Associated with the Quantum Random Walk  [PDF]
Clement Ampadu
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.519291
Abstract: We review (not exhaustively) the quantum random walk on the line in various settings, and propose some questions that we believe have not been tackled in the literature. In a sense, this article invites the readers (beginner, intermediate, or advanced), to explore the beautiful area of quantum random walks.
High and intermediate grade ductal carcinoma in-situ of the breast: a comparison of pathologic features in core biopsies and excisions and an evaluation of core biopsy features that may predict a close or positive margin in the excision
Oluwole Fadare, Nathan F Clement, Mohiedean Ghofrani
Diagnostic Pathology , 2009, DOI: 10.1186/1746-1596-4-26
Abstract: Ductal carcinoma in-situ (DCIS) of the breast is comprised of a heterogeneous spectrum of intraductal epithelial proliferations that are considered the probable precursor lesions to most invasive breast carcinomas [1,2]. The widespread implementation of screening mammography programs has resulted in a dramatic increase in the incidence of DCIS during the past few decades [3-8]. Whereas most DCIS in the pre-mammographic eras were of the comedo-type, screening-detected DCIS tend to be of a comparatively smaller size and lower grade [9]. Although low-grade and high-grade are unified by the fact that both are intraepithelial proliferations that are breast cancer precursors, they are considered to be substantially different processes. Low-grade DCIS is generally positive for the estrogen & progesterone receptors (ER & PR) and negative for HER2/neu, displays chromosomal losses at 16q, gains in 1q and near euploidy [10,11]. High-grade DCIS, in contrast, tends to display lack of expression of ER and PR, HER2/neu overexpression/amplification, a multitude of chromosomal changes, and aneuploidy [10,11]. Expectedly, intermediate grade DCIS displays changes that are intermediate between these two extremes [10]. Detailed evaluations of the protein expression patterns of DCIS of various grades and a comparison of such patterns with those of their synchronous invasive cancers, typically show strong correlations in a grade-dependent pattern [12]. Furthermore, progression from low-grade to high-grade DCIS is considered to be, at most, a very infrequent event [13]. Therefore, in one contemporary model of the evolution of invasive ductal breast carcinomas, well-differentiated ductal carcinomas evolve from low-grade DCIS whereas poorly differentiated invasive ductal carcinomas evolve from high-grade DCIS, with minimal, if any, overlap [11,13]. The present study focused on DCIS lesions that are not on the lower end of the spectrum to obtain a better understanding of this specific group.S
Activation of the control reporter plasmids pRL-TK and pRL-SV40 by multiple GATA transcription factors can lead to aberrant normalization of transfection efficiency
Clement KM Ho, Jerome F Strauss
BMC Biotechnology , 2004, DOI: 10.1186/1472-6750-4-10
Abstract: We report here that plasmids expressing GATA-4 or GATA-6 transcription factor increased Renilla luciferase gene expression by 2 to 8 fold when co-transfected with pRL-TK or pRL-SV40. This alteration of the control reporter gene activity was shown to cause erroneous normalization of transfection efficiency and thus misinterpretation of results in a transactivation assay. To circumvent the problem, we generated two mutant control plasmids from which putative GATA response elements were deleted. These deletions rendered pRL-SV40 unresponsive to GATA transcription factor stimulation and reduced the response of pRL-TK. A database search also indicates that consensus GATA binding sequences are present in other commercially available Renilla luciferase encoding plasmids; therefore, the latter can potentially be transactivated by GATA transcription factors.Taken together, these findings highlight the importance of the selection of an appropriate control reporter plasmid for the normalization of transfection efficiency.In transient transfection experiments, a promoter sequence of interest coupled to a reporter gene is often co-transfected with a control plasmid whose expression is constitutive in order to normalize for transfection efficiency or cell viability. Reporter plasmids which contain cDNA encoding the Renilla (Renilla reniformis) luciferase enzyme (Rluc) have become increasingly popular as controls for such a purpose. Rluc is not intrinsically expressed in mammalian cells and can function as an enzyme immediately following translation because post-translational modification is not required for its activity. Also, like firefly (Photinus pyralis) luciferase, Renilla luciferase activity can be assayed with high sensitivity and linearity over several orders of magnitude. In the widely used Dual Luciferase Reporter (DLR) assay system (Promega, Madison, WI), activities of firefly and Renilla luciferases are measured sequentially from a single sample based on the different
Calificación de una conexión rígida de una viga I y una columna tubular rellena de concreto bajo la acción de cargas dinámicas
Uribe Vallejo,Maritza; Valencia Clement,Gabriel F.;
Ingeniería e Investigación , 2009,
Abstract: using prequalified connections during the structural design stage becomes increasingly necessary when developing structural engineering projects which include steel elements; this is so that the steel elements? appropriate behavior can be ensured according to the structural system and seismic demand. unfortunately, the international entities providing this type of information (i.e. fema) only have a limit series of prequalified connections and such series do not include rigid connections between steel beams and concrete filled tubular (cft) columns having an extended end plate, which has become a very widespread building practice in colombia. this paper describes the most important aspects of a study at the universidad nacional de colombia concerning the behavior of a steel beam rigidly connected to a cft-column, using six physical models having different width-thickness ratio (b/t) columns. ansys v.10 software was used for studying theoretical models (finite elements analysis) for comparative analysis of cyclic test theoretical and experimental results for each specimen presented for the qualification phase. the six tested specimens? hysteretic curves are presented. several conclusions are drawn concerning finite element validation for this type of connection and the influence of width-thickness ratio (b/t) variation and design recommendations for suitable behavior under dynamic loads when this type of connection was used.
Evaluación del coeficiente de disipación de energía, R, para algunos tipos de estructuras de acero Evaluating response modification factor (R) for some types of steel structure
Valencia Restrepo Doralba,Valencia Clement Gabriel F.
Ingeniería e Investigación , 2008,
Abstract: En el presente artículo se cuestiona la validez del uso del coeficiente de disipación de energía tabulado en las Nor-mas Colombianas de Dise o y Construcción Sismorresistente, NSR-98, en la evaluación de las solicitaciones gene-radas por la acción del sismo de dise o en las estructuras de acero y las inconsistencias que se presentan al dimen-sionar la estructura para que cumpla derivas del 1%. Con tal fin se dise an 45 pórticos del sistema de resistencia sísmica de cinco edificios: 15 pórticos resistentes a momento (PRM), 15 pórticos arriostrados concéntricamente (PAC) y 15 pórticos arriostrados excéntricamente (PAE). El dise o se realiza de acuerdo con los requisitos de las NSR-98 en cuanto a solicitaciones (evaluación de cargas y combinaciones) y rigidez (1% de deriva) y a los requisitos de las provisiones sísmicas de AISC-2005 en cuanto a resistencia. Se evalúa el coeficiente de disipación de energía de los 45 pórticos para diferentes niveles de desempe o, por medio de plastificación progresiva modal, encontrán-dose que tal coeficiente no es constante para ninguno de los tres sistemas estructurales estudiados (PRM, PAC y PAE), tal como lo sugieren las NSR-98, y además los valores del coeficiente de disipación de energía hallados en la presente investigación son mucho menores a los tabulados en dichas normas, que rigen la práctica común del dise- o estructural, provocando graves errores en la evaluación de las solicitaciones de dise o, tanto de la estructura co-mo de los elementos de soporte (placas de base, fundaciones, pantallas) y estructuras adosadas a los pórticos del sistema de resistencia sísmico. Response modification factor (R), tabulated in the Colombian Design Code as NSR-98, is used in this paper for eva-luating internal member forces produced by design earthquake action on steel structures and the inconsistencies pre-sent when designing structures when 1% drift limits must be complied with. The article presents the design of 45 frames corresponding to the seismic resistance system of 5 buildings: 15 special moment frames (SMF), 15 special concentrically-braced frames (CBF) and 15 eccentrically-braced frames (EBF). External loads and their combination were used in estimating internal loads and rigidity demands (1% drift) were evaluated in line with NSR-98 requi-rements. Member strength requirements were evaluated by using the AISC-2005 seismic provisions for steel structu-red buildings. Modal pushover analysis was used for evaluating the response modification factor for the 45 given frames at different structural performance levels. It was
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