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Search Results: 1 - 10 of 148276 matches for " Charles K. Syengo "
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Local Polynomial Regression Estimator of the Finite Population Total under Stratified Random Sampling: A Model-Based Approach  [PDF]
Charles K. Syengo, Sarah Pyeye, George O. Orwa, Romanus O. Odhiambo
Open Journal of Statistics (OJS) , 2016, DOI: 10.4236/ojs.2016.66088
Abstract: In this paper, auxiliary information is used to determine an estimator of finite population total using nonparametric regression under stratified random sampling. To achieve this, a model-based approach is adopted by making use of the local polynomial regression estimation to predict the nonsampled values of the survey variable y. The performance of the proposed estimator is investigated against some design-based and model-based regression estimators. The simulation experiments show that the resulting estimator exhibits good properties. Generally, good confidence intervals are seen for the nonparametric regression estimators, and use of the proposed estimator leads to relatively smaller values of RE compared to other estimators.
Longitudinal Survey, Nonmonotone, Nonresponse, Imputation, Nonparametric Regression  [PDF]
Sarah Pyeye, Charles K. Syengo, Leo Odongo, George O. Orwa, Romanus O. Odhiambo
Open Journal of Statistics (OJS) , 2016, DOI: 10.4236/ojs.2016.66092
Abstract: The study focuses on the imputation for the longitudinal survey data which often has nonignorable nonrespondents. Local linear regression is used to impute the missing values and then the estimation of the time-dependent finite populations means. The asymptotic properties (unbiasedness and consistency) of the proposed estimator are investigated. Comparisons between different parametric and nonparametric estimators are performed based on the bootstrap standard deviation, mean square error and percentage relative bias. A simulation study is carried out to determine the best performing estimator of the time-dependent finite population means. The simulation results show that local linear regression estimator yields good properties.
Sensitivity Evaluation of Two Human Breast Cancer Cell Lines to Tamoxifen through Apoptosis Induction  [PDF]
Spencer Keene, Charles Azuelos, Shyamal K. Majumdar
Open Journal of Apoptosis (OJApo) , 2014, DOI: 10.4236/ojapo.2014.34008
Abstract: Tamoxifen citrate (TAM) has been used to treat breast cancer in women for many years. The com-parative effects of TAM in inducing apoptosis were evaluated in estrogen receptor-positive (ER- positive MCF-7) and estrogen receptor-negative (ER-negative MDA-MB-231) human breast cancer cell lines in vitro in order to determine if these two cell lines differ in their sensitivity to TAM. Mi-tochondrial membrane permeability potential disruption was assessed in both cell lines by a lip-ophilic cationic dye (DePsipher assay, Trevigen, Inc.) utilizing fluorescence microscopy. Using this specific fluorochrome, we were able to associate mitochondrial membrane disruption to early, mid-, and late apoptotic cells. TAM induced cell death via apoptosis in both ER-positive and ER- negative cells, however, apoptosis induction was more pronounced in ER-positive MCF-7 compared to ER-negative MDA-MB-231 breast cancer cells. These findings may have some therapeutic use in the treatment of estrogen dependent and estrogen independent breast cancer.
The Prospects of E-Commerce Implementation in Nigeria
Ayo Charles. K.
Journal of Internet Banking and Commerce , 2006,
Abstract: The Internet has brought about the emergence of virtual markets with four primary distinct characteristics, which are real-time, shared, open and global (Mohammad, 2003). The growing rate of ICT utilization particularly the Internet has influenced at an exponential rate, online interaction and communication among the generality of the populace. The shortcomings notwithstanding, most people are connected through their cell phones, home PCs and others through corporate access and public kiosks. The patronage of the Internet allover the world is monumental and has remained on the increase from inception. However, with the enormity of businesses on the Internet, Nigeria is yet to harness the opportunities for optimal financial gains.This study is exploratory in nature as it attempts to unveil the prospects of e-commerce participation based on the ability-motivation-opportunity (AMO) framework. The paper proposes to investigate the ability of consumers to purchase online, the available motivation to do so, and the opportunities for Internet access.Findings revealed that Nigerians have the ability to participate in e-commerce, but there is need for improved national image to bring in the element of trust and discipline within, and before the international communities. Furthermore, there is need to encourage public and private initiatives in the provision of the basic infrastructures for improved motivation and opportunities for e-commerce implementation. Currently, consumers source for information online but make purchases the traditional way.
Better to Be a Renunciant: Buddhism, Happiness, and the Good Life
Charles K. Fink
Journal of Philosophy of Life , 2013,
Abstract: This essay seeks to understand the nature of happiness and the good life within the context of Buddhist philosophy. Buddhism is a pessimistic philosophy, but only in the sense that it insists that happiness, as we ordinarily conceive of it, is unattainable. It is optimistic insofar as it maintains that true happiness is humanly possible, but only if we see things as they really are and relinquish our desires. Yet, even if we would be happier as renunciants, would our lives be better? To answer this question, we must understand the relationship between happiness and the good life. I argue that happiness is a complex psychological state involving affective, cognitive, and motivational components. Buddhist practice seeks to cultivate these different dimensions of happiness and in this way lay the foundation for living a good life.
Variational Pseudolikelihood for Regularized Ising Inference
Charles K. Fisher
Computer Science , 2014,
Abstract: I propose a variational approach to maximum pseudolikelihood inference of the Ising model. The variational algorithm is more computationally efficient, and does a better job predicting out-of-sample correlations than $L_2$ regularized maximum pseudolikelihood inference as well as mean field and isolated spin pair approximations with pseudocount regularization. The key to the approach is a variational energy that regularizes the inference problem by shrinking the couplings towards zero, while still allowing some large couplings to explain strong correlations. The utility of the variational pseudolikelihood approach is illustrated by training an Ising model to represent the letters A-J using samples of letters from different computer fonts.
Antibacterial compounds from Rutaceae with activities against Flavobacterium columnare and Streptococcus iniae  [PDF]
Kumudini M. Meepagala, Kevin K. Schrader, Charles L. Burandt
Journal of Agricultural Chemistry and Environment (JACEN) , 2013, DOI: 10.4236/jacen.2013.24014
Abstract: From the ethyl acetate extract of Murraya koenegii (Rutaceae) leaves, isomahanine (1) and mahanine (2) were isolated that showed antibacterial activity towards Flavobacterium columnare and Streptococcus iniae which caused columnaris disease and streptococcosis respectively. Isomahanine was found to have the strongest activity against F. columnare (isolate ALM-00-173) and S. iniae (isolate LA94-426) based on 24-h 50% inhibition concentration (IC50) and minimum inhibition concentration (MIC). Although compound (7), a nicotinamide isolated from Amyris texana had the lowest MIC (2.8 ± 0 mg/L) of any of the test compounds against F. columnare, the 24-h IC50 of 14.8 ± 0.6 mg/L was higher than that of isomahanine and subsequently the 24-h IC50 RDC values for (7) were almost a magnitude of order higher than those obtained for isomahanine. Isomahanine also had the strongest activity against S. iniae, with a 24-h IC50 of 1.3 ± 0.1 mg/L and MIC of 3.5 ± 0 mg/L, respectively.
Late-Season Grass Weed Management with In-Crop and Post-Harvest Herbicides in Twin-Row Glyphosate-Resistant Soybean  [PDF]
Krishna N. Reddy, Charles T. Bryson, Vijay K. Nandula
American Journal of Plant Sciences (AJPS) , 2015, DOI: 10.4236/ajps.2015.61024
Abstract: Emergence of grasses late in the season has become a problem in glyphosate-resistant (GR) soybean production in the southern US. A 3-yr field study was conducted from 2011 to 2013 at Stoneville, MS to determine efficacy of post-harvest and pyroxasulfone-based in-crop herbicides on late-season grasses and yield in twin-row glyphosate-resistant soybean. Experiments were conducted in a split-plot arrangement of treatments in a randomized complete block design with fall herbicides (with and without pendimethalin at 1.12 kg ai ha-1 and paraquatat 0.84 kg ai ha-1) as main plots and in-crop herbicides as subplots with four replications. The six in-crop herbicide programs were: glyphosate applied early postemergence (EPOST) at 0.84 kg·aeha-1 followed by (fb) glyphosate late postemergence (LPOST) at 0.84 kg·ha-1 with and without pyroxasulfone preemergence (PRE) applied at 0.18 kg ai ha-1, pyroxasulfone PRE fb glyphosate at 0.84 kg·ha-1 LPOST or glyphosate at 0.84 kg·ha-1 + S-metolachlor at 1.68 kg ai ha-1 EPOST, pyroxasulfone PRE fb S-meto- lachlor at 1.12 kg·ha-1 + fomesafen at 0.27 kg ai ha-1 EPOST fb clethodim at 0.14 kg ai ha-1, and a no-herbicide control. Browntop millet, Digitaria spp., and junglerice densities at 2 weeks after LPOST, grass weed dry biomass at harvest, and soybean yield were similar regardless of post- harvest herbicides in all three years. At 2 weeks after LPOST, browntop millet, Digitaria spp. and junglerice densities were greatly reduced in all five in-crop herbicide treatments compared with no herbicide plot in all three years. Grass weed dry biomass in no-herbicide plots was 3346, 6136, and 6916 kg·ha-1 in 2011, 2012, and 2013, respectively and
Rice Hull Mulch Affects Germination of Bittercress and Creeping Woodsorrel in Container Plant Culture  [PDF]
James E. Altland, Jennifer K. Boldt, Charles C. Krause
American Journal of Plant Sciences (AJPS) , 2016, DOI: 10.4236/ajps.2016.716207
Abstract: Mulches are commonly used to control weeds in container nursery crops, especially in sites where preemergence herbicides are either not labeled or potentially phytotoxic to the crop. Parboiled rice hulls have been shown to provide effective weed control when applied 1.25 to 2.5 cm deep over the container substrate surface. The objective of this research was to determine if weed seed placement, above or below the mulch layer, affects flexuous bittercress or creeping woodsorrel establishment. Seeds of both species were placed either above or below rice hull mulch layers 0, 0.6, 1.3, or 2.5 cm deep in nursery containers with a 80 pine bark: 20 sphagnum peat moss substrate. Establishment of both weeds decreased with increasing mulch depth. Establishment of both species was generally greater from beneath the mulch compared to when seed were applied above the mulch. Light penetration through varying depths of rice hulls was determined with a spectroradiometer. Photosynthetically active radiation (PAR) decreased exponentially with increasing rice hull depth, and was less than 1 μmol·m-2·s-1 beneath depths greater than 1 cm. Germination of both species was determined in Petri dishes placed beneath varying densities of shade cloth. Flexuous bittercress germination responded quadratically to decreasing light level, but still germinated (13%) in complete darkness after 3 weeks. Creeping woodsorrel germination was not affected by light level and was high (92%) after 3 weeks. The role of light exclusion by rice hulls as a mechanism for controlling buried weed seed is discussed. Water retention immediately after irrigation, and for 24 hr following irrigation, was determined for a 2.5 cm layer of rice hulls, sphagnum peat moss, and pine bark. Rice hulls retained less water, and dried more quickly than peat moss or pine bark. The volumetric water content of the rice hull layer is less than 0.20 cm·cm-1 and what has been shown necessary for plant growth. Lack of water availability in the rice hull layer is discussed as the primary mechanism of control of weed seed above the mulch layer.
Mitochondria from cultured cells derived from normal and thiamine-responsive megaloblastic anemia individuals efficiently import thiamine diphosphate
Qilin Song, Charles K Singleton
BMC Biochemistry , 2002, DOI: 10.1186/1471-2091-3-8
Abstract: Here we examine ThDP uptake by mitochondria from several human cell types, including cells from patients with thiamine-responsive megaloblastic anemia (TRMA) that lack a functional thiamine transporter of the plasma membrane. Although mitochondria from normal lymphoblasts took up thiamine in the low micromolar range, surprisingly mitochondria from TRMA lymphoblasts lacked this uptake component. ThDP was taken up efficiently by mitochondria isolated from either normal or TRMA lymphoblasts. Uptake was saturable and biphasic with a high affinity component characterized by a Km of 0.4 to 0.6 μM. Mitochondria from other cell types possessed a similar high affinity uptake component with variation seen in uptake capacity as revealed by differences in Vmax values.The results suggest a shared thiamine transporter for mitochondria and the plasma membrane. Additionally, a high affinity component of ThDP uptake by mitochondria was identified with the apparent affinity constant less than the estimates of the cytosolic concentration of free ThDP. This finding indicates that the high affinity uptake is physiologically significant and may represent the main mechanism for supplying phosphorylated thiamine for mitochondrial enzymes.Thiamine is a water-soluble, B-complex vitamin that cannot be synthesized by mammals, and thus thiamine can be obtained only from dietary intake. This can lead to severe consequences in humans when thiamine is limiting; thiamine deficiency may result in beriberi and the Wernike-Korsakoff syndrome [1,2]. Being positively charged and present in relatively low plasma concentrations, thiamine movement across cellular membranes requires transporters. Upon being taken up by a cell, thiamine is rapidly diphosphorylated by thiamine diphosphokinase to give thiamine diphosphate (ThDP) [3]. Thus, thiamine represents only a few percent of the total cellular thiamine/thiamine phosphate derivatives. ThDP serves as a cofactor for several enzymes that are found both in th
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