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Search Results: 1 - 10 of 298408 matches for " J Harvey "
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Photosynthesis and Yellow Vine Syndrome of American Cranberry
Harvey J. M. Hou
Agriculture , 2012, DOI: 10.3390/agriculture2020125
Abstract: The American cranberry ( Vaccinium macrocarpon Ait.) contains rich antioxidants and has significant health benefits in fighting a variety of human diseases. In the past ten years, cranberry growers have reported yellow vine syndrome, which is associated with reduced photosynthetic performance, in the cranberry bogs. It has been found that the yellow vine syndrome of cranberry is associated with nutritional imbalance; it might be an issue for cranberry quality and food security as well as the crop production. This review evaluates the present state of knowledge of yellow vine syndrome, together with recent advances that are resulting from an improved mechanistic understanding and a possible solution that will be of considerable value to cranberry growers. This review also includes results from the author’s own laboratory. Water stress, nutritional imbalance, and photoinhibition are the likely reasons for producing yellow vine of cranberry. Future endeavors should be placed on the combination of genetic, biochemical, and biophysical techniques at the molecular level and plant physiology at the field and greenhouse level. This may provide specific information in order to understand the molecular details of yellow vine of cranberry as well as a tool for guiding future breeding efforts and management practices.
Image Quality of SOLIS/VSM in Helium vs. Nitrogen
J. W. Harvey
Physics , 2014,
Abstract: The National Solar Observatory (NSO) Synoptic Optical Long-term Investigations of the Sun (SOLIS) Vector SpectroMagnetograph (VSM) is sealed and was designed to be filled with helium at slightly above ambient pressure. After 11 years of operation filled with helium, an acute shortage of helium prompted a test using nitrogen as the fill gas. Four months of nitrogen-filled observations in 2014 are compared the same months in 2013 with helium fill. On average, the image sharpness is slightly degraded when using nitrogen.
Generalized prime ideals of the rings C(X,Y) and the quasi-components of X
Harvey J. Charlton
Mathematics , 2014,
Abstract: In the set of continuous functions C(X,Y) where Y has a topology close to being discrete, there is an equivalence relation on X which characterizes the quasi-components of X. If Y satisfies weak algebraic conditions with a single binary operation then a stable set of functions forms an object generalizing an ideal of a ring. Calling such sets ideals there is a concept of a prime ideal. The ideal of functions vanishing on a quasi-component are prime ideals of C(X,Y). If Y has a zero set that is open then these prime ideals are min- max implying that when Y is a ring all of the prime ideals of C(X,Y) are of this form and min-max. However this is a study of C(X,Y) and its ideals beginning with a few algebraic hypothesis on Y and adding to them as needed. So there are conditions when a prime ideal is minimal, when the set of quasi-components is in bijective correspondence with the set of prime ideals of functions which vanish on them, when C(X,Y) can not be like a local ring, when the prime (nil) radical is trivial, and when the corresponding Spec(C(X,Y)) is a disconnected topological space. Example of results are; if a quasi-component of x is open then the prime ideal of functions vanishing on it is minimal independent of the zero set of Y being open; if the zero set of Y is open then the set of all ideals of functions vanishing on quasi-components is the set of minimal prime ideals irrespective of any quasi-component being open in X. These results imply the same for the ideals of the ring C(X,Y) when Y is a ring. The techniques developed give a method of generating unlimited number of rings with prescribed sets of prime ideals and minimal prime ideals.
A note on the discrepancy of matrices with bounded row and column sums
Nicholas J. A. Harvey
Mathematics , 2013,
Abstract: A folklore result uses the Lovasz local lemma to analyze the discrepancy of hypergraphs with bounded degree and edge size. We generalize this result to the context of real matrices with bounded row and column sums.
Algebraic Structures and Algorithms for Matching and Matroid Problems (Preliminary Version)
Nicholas J. A. Harvey
Computer Science , 2006,
Abstract: Basic path-matchings, introduced by Cunningham and Geelen (FOCS 1996), are a common generalization of matroid intersection and non-bipartite matching. The main results of this paper are a new algebraic characterization of basic path-matching problems and an algorithm for constructing basic path-matchings in O(n^w) time, where n is the number of vertices and w is the exponent for matrix multiplication. Our algorithms are randomized, and our approach assumes that the given matroids are linear and can be represented over the same field. Our main results have interesting consequences for several special cases of path-matching problems. For matroid intersection, we obtain an algorithm with running time O(nr^(w-1))=O(nr^1.38), where the matroids have n elements and rank r. This improves the long-standing bound of O(nr^1.62) due to Gabow and Xu (FOCS 1989). Also, we obtain a simple, purely algebraic algorithm for non-bipartite matching with running time O(n^w). This resolves the central open problem of Mucha and Sankowski (FOCS 2004).
Manganese-based Materials Inspired by Photosynthesis for Water-Splitting
Harvey J.M. Hou
Materials , 2011, DOI: 10.3390/ma4101693
Abstract: In nature, the water-splitting reaction via photosynthesis driven by sunlight in plants, algae, and cyanobacteria stores the vast solar energy and provides vital oxygen to life on earth. The recent advances in elucidating the structures and functions of natural photosynthesis has provided firm framework and solid foundation in applying the knowledge to transform the carbon-based energy to renewable solar energy into our energy systems. In this review, inspired by photosynthesis robust photo water-splitting systems using manganese-containing materials including Mn-terpy dimer/titanium oxide, Mn-oxo tetramer/Nafion, and Mn-terpy oligomer/tungsten oxide, in solar fuel production are summarized and evaluated. Potential problems and future endeavors are also discussed.
Unidirectional Photodamage of Pheophytin in Photosynthesis
Harvey J.M. Hou
Frontiers in Plant Science , 2013, DOI: 10.3389/fpls.2013.00554
The Heterotic String is a Soliton
J. A. Harvey,A. Strominger
Physics , 1995, DOI: 10.1016/0550-3213(95)00310-O
Abstract: It is shown that the Type IIA superstring compactified on $K3$ has a smooth string soliton with the same zero mode structure as the heterotic string compactified on a four torus, thus providing new evidence for a conjectured exact duality between the two six-dimensional string theories. The chiral worldsheet bosons arise as zero modes of Ramond-Ramond fields of the IIA string theory and live on a signature $(20,4)$ even, self-dual lattice. Stable, finite loops of soliton string provide the charged Ramond-Ramond states necessary for enhanced gauge symmetries at degeneration points of the $K3$ surface. It is also shown that Type IIB strings toroidally compactified to six dimensions have a multiplet of string solutions with Type II worldsheets.
Quantum Aspects of Black Holes
J. A. Harvey,A. Strominger
Physics , 1992,
Abstract: This review is based on lectures given at the 1992 Trieste Spring School on String Theory and Quantum Gravity and at the 1992 TASI Summer School in Boulder, Colorado.
Black Holes with a Massive Dilaton
R. Gregory,J. A. Harvey
Physics , 1992, DOI: 10.1103/PhysRevD.47.2411
Abstract: The modifications of dilaton black holes which result when the dilaton acquires a mass are investigated. We derive some general constraints on the number of horizons of the black hole and argue that if the product of the black hole charge $Q$ and the dilaton mass $m$ satisfies $Q m < O(1)$ then the black hole has only one horizon. We also argue that for $Q m > O(1)$ there may exist solutions with three horizons and we discuss the causal structure of such solutions. We also investigate the possible structures of extremal solutions and the related problem of two-dimensional dilaton gravity with a massive dilaton.
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