Hierarchical Knowledge-Gradient for Sequential Sampling

We consider the problem of selecting the best of a finite but very large set of alternatives. Each alternative may be characterized by a multi-dimensional vector and has independent normal rewards. This problem arises in various settings such as (i) ranking and selection, (ii) simulation optimization where the unknown mean of each alternative is estimated with stochastic simulation output, and (iii) approximate dynamic programming where we need to estimate values based on Monte-Carlo simulation. We use a Bayesian probability model for the unknown reward of each alternative and follow a fully sequential sampling policy called the knowledge-gradient policy. This policy myopically optimizes the expected increment in the value of sampling information in each time period. Because the number of alternatives is large, we propose a hierarchical aggregation technique that uses the common features shared by alternatives to learn about many alternatives from even a single measurement, thus greatly reducing the measurement effort required. We demonstrate how this hierarchical knowledge-gradient policy can be applied to efficiently maximize a continuous function and prove that this policy finds a globally optimal alternative in the limit

A New Optimal Stepsize For Approximate Dynamic Programming

Approximate dynamic programming (ADP) has proven itself in a wide range of applications spanning large-scale transportation problems, health care, revenue management, and energy systems. The design of effective ADP algorithms has many dimensions, but one crucial factor is the stepsize rule used to update a value function approximation. Many operations research applications are computationally intensive, and it is important to obtain good results quickly. Furthermore, the most popular stepsize formulas use tunable parameters and can produce very poor results if tuned improperly. We derive a new stepsize rule that optimizes the prediction error in order to improve the short-term performance of an ADP algorithm. With only one, relatively insensitive tunable parameter, the new rule adapts to the level of noise in the problem and produces faster convergence in numerical experiments.Comment: Matlab files are included with the paper sourc

The Effects of Endothelin-1 on Cell Migration of Corneal Endothelial Cells

Wound healing occurs through the processes of cell proliferation (mitosis) and/or cell migration. The corneal endothelium in humans is known to be mostly non-proliferative. As a result, wounds in the corneal endothelium heal by migration. A 21-amino acid peptide called Endothelin-1 (ET-1) is studied in the Crawford research lab and is a known mitogen, i.e. increases cell proliferation. Data suggests that Endothelin-1 can stimulate cell proliferation in the corneal endothelium. This fact led to the first hypothesis that ET-1 stimulated wound closure in this cell layer. I explored this hypothesis using a bovine model of corneal endothelial cells isolated and grown in 10% calf-serum DMEM media. Half the cells were treated with ET-1 and the other half were left in media alone (control). The cells were wounded mechanically and allowed to heal for 72-hours with photo micrographs taken every 24-hour to record wound closure. The data suggested that ET-1 stimulated wound closure because the cells treated with ET-1 had a higher percent wound closure when compared to the control. This experiment was modified to test my second hypothesis, that inhibition of cell proliferation would inhibit wound closure. In this experiment, half the cells were treated with 5-Flurouracil, an inhibitor of cell proliferation. The data showed that the prescence of 5-FU decreased the percentage of wound closure, but did not eliminate it. ET-1 was still able to increase wound closure in the presence of 5-FU by 10.8% compared to the cells treated with 5-FU alone. My third hypothesis then became that ET-1 stimulates cell migration. I explored this hypothesis using a chemotaxis assay. The endothelial cells were loaded with Calcein-AM, a fluorescent dye, and migration was examined with a Chemotx chemotaxis system. The cells were treated with serum free media (control), 0.1 nM ET-1, 1 nM ET-1, 10 nM ET-1, or serum (positive control). They were allowed to incubate for 48-hours and fluorescence of migrated cells was recorded. The data suggests that ET-1 stimulates wound healing, promotes wound closure in the absence of proliferation, and that ET-1 stimulates cell migration

A review of melt and vapor growth techniques for polydiacetylene thin films for nonlinear optical applications

Methods for the growth of polydiacetylene thin films by melt and vapor growth and their subsequent polymerization are summarized. Films with random orientations were obtained when glass or quartz were used as substrates in the vapor growth process. Oriented polydiacetylene films were fabricated by the vapor deposition of diacetylene monomer onto oriented polydiacetylene on a glass substrate and its subsequent polymerization by UV light. A method for the growth of oriented thin films by a melt-shear growth process as well as a method of film growth by seeded recrstallization from the melt between glass plates, that may be applied to the growth of polydiacetylene films, are described. Moreover, a method is presented for the fabrication of single crystal thin films of polyacetylenes by irradiation of the surface of diacetylene single crystals to a depth between 100 and 2000 angstroms

A preliminary review of organic materials single crystal growth by the Czochralski technique

The growth of single crystals of organic compounds by the Czochralski method is reviewed. From the literature it is found that single crystals of benzil, a nonlinear optical material with a d sub 11 value of 11.2 + or - 1.5 x d sub 11 value of alpha quartz, has fewer dislocations than generally contained in Bridgman crystals. More perfect crystals were grown by repeated Czochralski growth. This consists of etching away the defect-containing portion of a Czochralski grown crystal and using it as a seed for further growth. Other compounds used to grow single crystals are benzophenone, 12-tricosanone (laurone), and salol. The physical properties, growth apparatus, and processing conditions presented in the literature are discussed. Moreover, some of the possible advantages of growing single crystals of organic compounds in microgravity to obtain more perfect crystals than on Earth are reviewed

Finite Simple Graphs and Their Associated Graph Lattices

In his 2005 dissertation, Antoine Vella explored combinatorical aspects of finite graphs utilizing a topological space whose open sets are intimately tied to the structure of the graph. In this paper, we go a step further and examine some aspects of the open set lattices induced by these topological spaces. In particular, we will characterize all lattices that constitute the opens for finite simple graphs endowed with this topology, explore the structure of these lattices, and show that these lattices contain information necessary to reconstruct the graph and its complement in several ways

Spectral characteristics and the extent of paleosols of the Palouse formation

Three spectral models defining the spatial distribution of soil areas by levels of amorphous iron, organic carbon, and the ratio of amorphous iron to organic carbon were developed and field verification studies were conducted. The models used particular Thematic Mapper band ratios selected by statistical correlation with soil chemical data. The ability of the models to indicate erosion severity and to differentiate between iron enriched and carbonate paleosols is discussed. In addition, the effect of vegetation cover on paleosols is addressed

Bayesian optimization for materials design

We introduce Bayesian optimization, a technique developed for optimizing time-consuming engineering simulations and for fitting machine learning models on large datasets. Bayesian optimization guides the choice of experiments during materials design and discovery to find good material designs in as few experiments as possible. We focus on the case when materials designs are parameterized by a low-dimensional vector. Bayesian optimization is built on a statistical technique called Gaussian process regression, which allows predicting the performance of a new design based on previously tested designs. After providing a detailed introduction to Gaussian process regression, we introduce two Bayesian optimization methods: expected improvement, for design problems with noise-free evaluations; and the knowledge-gradient method, which generalizes expected improvement and may be used in design problems with noisy evaluations. Both methods are derived using a value-of-information analysis, and enjoy one-step Bayes-optimality

Risperidone-induced psychosis and depression in a child with a mitochondrial disorder

OBJECTIVE: To our knowledge, this is the first published case report of an adolescent girl with a mitochondrial disorder and depression who displayed both new-onset psychotic and increased mood symptoms during treatment with risperidone. DATA: A 16-year-old girl was treated with risperidone for mood lability and impulsivity at a community hospital. Within days, she developed paranoid ideation, profound psychomotor retardation, increased depression, and fatigue. She was transferred to an inpatient psychiatric hospital, where she was taken off risperidone. Within 48 hours after discontinuation of the medication, she had complete resolution of psychotic symptoms, fatigue, and psychomotor retardation, and her depression improved. CONCLUSIONS: This observation of on-off risperidone treatment suggests that risperidone may have worsened both psychiatric and physical manifestations of the mitochondrial disorder in this adolescent. These findings are consistent with recent in vitro literature, which implicate a series of neuroleptic medications with mitochondrial dysfunction. Furthermore, the authors provide diagnostic and treatment options that are available for mitochondrial disorders, which are of interest to child psychiatrists due to the central nervous system manifestations of these disorders