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Search Results: 1 - 10 of 21688 matches for " Gregory Su "
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Direct Colorimetric Detection of Hydrogen Peroxide Using 4-Nitrophenyl Boronic Acid or Its Pinacol Ester  [PDF]
Gregory Su, Yibin Wei, Maolin Guo
American Journal of Analytical Chemistry (AJAC) , 2011, DOI: 10.4236/ajac.2011.28101
Abstract: A colorimetric method for the direct determination of hydrogen peroxide in aqueous solution is described. H2O2 stoichiometrically converts 4-nitrophenyl boronic acid or 4-nitrophenyl boronic acid pinacol ester into 4-nitrophenol, which can be quantified by measuring the absorption at 400 nm in neutral or basic media. The reactions proceed fast under basic conditions and complete in 2 minutes to at pH 11 and 80?C. The linear range for the colorimetric method extends beyond 1.0 to 40 µM H2O2, and the limit of detection is ~1.0 µM H2O2. This method offers a convenient and practical process for rapid determination of hydrogen peroxide in aqueous media. Compared to many other techniques in H2O2 detection, this process is a direct measurement of H2O2, and is relatively unaffected by the presence of various salts, metal ions and the chelator EDTA.
Computing Similarity Distances Between Rankings
Farzad Farnoud,Lili Su,Gregory J. Puleo,Olgica Milenkovic
Computer Science , 2013,
Abstract: We address the problem of computing distances between rankings that take into account similarities between candidates. The need for evaluating such distances is governed by applications as diverse as rank aggregation, bioinformatics, social sciences and data storage. The problem may be summarized as follows: Given two rankings and a positive cost function on transpositions that depends on the similarity of the candidates involved, find a smallest cost sequence of transpositions that converts one ranking into another. Our focus is on costs that may be described via special metric-tree structures and on complete rankings modeled as permutations. The presented results include a quadratic-time algorithm for finding a minimum cost decomposition for simple cycles, and a quadratic-time, $4/3$-approximation algorithm for permutations that contain multiple cycles. The proposed methods rely on investigating a newly introduced balancing property of cycles embedded in trees, cycle-merging methods, and shortest path optimization techniques.
Unique Measure for the Time-Periodic Navier-Stokes on the Sphere Navier-Stokes on the Sphere  [PDF]
Gregory Varner
Applied Mathematics (AM) , 2015, DOI: 10.4236/am.2015.611160
Abstract:

This paper proves the existence and uniqueness of a time-invariant measure for the 2D Navier-Stokes equations on the sphere under a random kick-force and a time-periodic deterministic force. Several examples of deterministic force satisfying the necessary conditions for a unique invariant measure to exist are given. The support of the measure is examined and given explicitly for several cases.

The Scaling Constant D in Item Response Theory  [PDF]
Gregory Camilli
Open Journal of Statistics (OJS) , 2017, DOI: 10.4236/ojs.2017.75055
Abstract: In item response theory (IRT), the scaling constant D = 1.7 is used to scale a discrimination coefficient a estimated with the logistic model to the normal metric. Empirical verification is provided that Savalei’s[1] proposed a scaling constant of D = 1.749 based on Kullback-Leibler divergence appears to give the best empirical approximation. However, the understanding of this issue as one of the accuracy of the approximation is incorrect for two reasons. First, scaling does not affect the fit of the logistic model to the data. Second, the best scaling constant to the normal metric varies with item difficulty, and the constant D = 1.749 is best thought of as the average of scaling transformations across items. The reason why the traditional scaling with D = 1.7 is used is simply because it preserves historical interpretation of the metric of item discrimination parameters.
An Exploratory Survey of Sound Levels in New York City Restaurants and Bars  [PDF]
Gregory Scott
Open Journal of Social Sciences (JSS) , 2018, DOI: 10.4236/jss.2018.68005
Abstract: For several decades, there has been a significant need to better educate the public about noise pollution. A small number of small-scale studies have focused on the sound levels of restaurants and their impact on health and hearing. There have also been an increasing number of media articles stating that eating and drinking venues are getting increasingly loud making it more difficult for people to connect with others in conversation. This study reports on an exploratory large-scale noise survey of sound levels of 2376 restaurants and bars in New York City using a novel smart-phone application and categorized them based on how quiet or loud they were. The results suggest that: 1) A significant number of venues have high sound levels that are not conducive to conversation and may be endangering the health of patrons and employees, 2) that the reported sound levels by the venue managers on their online public business pages generally underestimated actual sound levels, and 3) the average sound levels in restaurants and bars are correlated by neighborhood and type of cuisine.
Cellular dynamical mean-field theory study of an interacting topological honeycomb lattice model at finite temperature
Yao-Hua Chen,Hsiang-Hsuan Hung,Guoxiong Su,Gregory A. Fiete,C. S. Ting
Physics , 2014, DOI: 10.1103/PhysRevB.91.045122
Abstract: Topological phases originating from spin-orbit coupling have attracted great attention recently. In this work, we use cellular dynamical mean field theory with the continuous-time quantum Monte Carlo solver to study the Kane-Mele-Hubbard model supplemented with an additional third-neighbor hopping term. For weak interactions, the third-neighbor hopping term drives a topological phase transition between a topological insulator and a trivial insulator, consistent with previous fermion sign-free quantum Monte Carlo results [H.-Hung et al., Phys. Rev. B 89, 235104 (2014)]. At finite temperatures, the Dirac cones of the zero temperature topological phase boundary give rise to a metallic regime of finite width in the third-neighbor hopping. Furthermore, we extend the range of interactions into the strong coupling regime and find an easy-plane anti-ferromagnetic insulating state across a wide range of third-neighbor hopping. In contrast to the weak coupling regime, no topological phase transition occurs at strong coupling, and the ground state is a trivial anti-ferromagnetic insulating state. A comprehensive finite temperature phase diagram in the interaction-third-neighbor hopping plane is provided.
Algebras of Hamieh and Abbas Used in the Dirac Equation  [PDF]
Gregory Peter Wene
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.39120
Abstract: Hamieh and Abbas [1] propose using a 3-dimensional real algebra in a solution of the Dirac equation. We show that this algebra, denoted by , belongs to a large class of quadratic Jordan algebras with subalgebras isomorphic to the complex numbers and that the spinor matrices associated with the solution of the Dirac equation generate a six-dimensional real noncommutative Jordan algebra.
High Performance Liquid Chromatographic Identification and Estimation of Phthalates in Sewer Waste and a Receiving River in Ibadan City, Southwestern Nigeria  [PDF]
Gregory O. Adewuyi
Journal of Water Resource and Protection (JWARP) , 2012, DOI: 10.4236/jwarp.2012.410099
Abstract: Medical wastes have been implicated in river pollution in developing countries and most often people depend on water from such rivers for sources of livelihood. Phthalates (endocrine disruptors) are major components in medical wastes and are commonly found contaminants in aquatic environment. Most sewage treatment facilities handling medical waste are inefficient due to overuse and poor maintenance and discharge directly into rivers. This study aimed to investigate the identity and estimates the concentration of phthalates in supposed treated medical wastes from a hospital sewer and water from a receiving river. Samples were randomly collected before and after treatment by the sewer plants, while samples were randomly collected along the course of the river starting from point of discharge. Control samples were taken from upstream about 500 m along the river course. The samples were extracted by liquid-liquid chroma- tographic process using dichloromethane, after which they were cleaned up in a column of silica gel using hexane as the mobile solvent. The cleaned extracts were analyzed by HPLC. The concentrations (μg/L) of dimethyl-, diethyl-, diphenyl-, dibutyl- and di-(2-ethyl)hexyl phthalates ranged from 62.81 ± 18.53; 4.74 ± 3.57; 2.05 ± 1.80; 11.40 ± 5.58 to 141.92 ± 35.8 respectively in the sewer waste. The receiving river had a concentration (μg/L) of 9.17 ± 14.02; 0.18 ± 0.31; 0.48 ± 0.84; 2.84 ± 1.21; 61.72 ± 38.35 respectively for dimethyl-, diethyl-, diphenyl-, dibutyl- and di-(2-ethyl) hexyl phthalates. These concentrations were higher than control and far exceeded the USEPA limits of 3 μg/l recom- mended for phthalates in water. Contaminants of aquatic environment by untreated wastes from hospitals has serious implications on public health and environment as human risks for phthalate esters downstream are high and this calls for urgent need to develop strategy to build incentives for compliance in treatment and discharge of wastes into river waters.
Implications of apoptosis in cancer immunotherapy  [PDF]
Gregory Lee, Bixia Ge
Advances in Bioscience and Biotechnology (ABB) , 2012, DOI: 10.4236/abb.2012.326088
Abstract: Inhibitions or blockages of ligand-receptor interactions on cancer cell surfaces by exogenous competetors or antibodies often result in apoptosis or “programmed cell death.” The underlying mechanisms of action for cellular apoptosis depend greatly on the molecular nature of specific ligand-receptor interactions and the signal transduction pathways involved. Two such unrelated systems which are potentially involved in apoptosis of cancer cells are described in this review. They are, respectively, gonadotropinreleasing hormone (GnRH) receptor and cancerous immunoglobulins, or CA215, both of which are widely expressed on the surface of cancer cells from diversified tissue origins. Bindings of GnRH or its decapeptide analogs as ligands to GnRH receptor were known to induce apoptosis of several extrapituitary cell types in gonadal tissues, as well as different cancer cells. Monoclonal antibodies against the GnRH receptor of cancer cells were shown to induce apoptosis, similar to the action of GnRH analogs. In contrast, RP215 monoclonal antibody reacts specifically with the carbohydrate-associated epitope of cancerous immunoglobulins and is known to induce apoptosis of cancer cells in vitro. It also causes growth inhibition of tumor cells in nude mouse experimental models. Elucidations of the specific mechanisms of apoptosis in cancer cells of these two molecular interaction systems will not only lead to a better understanding of cancer biology but also benefit patients in cancer monitoring and therapy.
Tylor vs. Westermarck: Explaining the Incest Taboo  [PDF]
Gregory C. Leavitt
Sociology Mind (SM) , 2013, DOI: 10.4236/sm.2013.31008
Abstract:

In the late 19th century arguments explaining incest avoidance were framed separately by Edward Tylor and Edward Westermarck. Tylor offered an environmental theory asserting that people have to marry outside of their own kin and communities or die out from the detrimental effects of isolation. Westermarck turned to Darwin’s theory to explain that harmful inbreeding had been selected against in the human genome. By the late 20th and early 21st centuries explanations of human behaviors have become increasingly encompassed by natural selection theory. The debate concerning the productiveness of evolutionary biology for explaining complex human behaviors is highly contentious and continues unabated. Although human evolutionists repeatedly say that environment is important for understanding human behavior they often do not develop this part of the equation. Behind the prestige of evolutionary biology selection models of human behavior have passed into popular science and the public psyche. Often heard today from a wide range of highly visible media sources is an assortment of topics on human behaviors which are framed by Darwinian assumptions. Contemplations about incest and inbreeding avoidance fall into this category and are presented by Darwinian social science as the best case example demonstrating evolutionary suppositions about human behavior. In the article that follows these issues are framed and examined. The argument is offered that evolutionary approaches are not always the most compelling and that convincing environmental explanations are overlooked.

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