Partitioning Optimization for Massively Parallel Transport Sweeps on Unstructured Grids

The field of radiation transport studies the distribution of radiation throughout a seven-dimensional phase-space consisting of time, space, energy, and direction. Radiation transport is described by the Boltzmann equation that can be solved stochastically or deterministically. The work presented in this dissertation utilizes the deterministic method known as the transport sweep, a popular technique that has been the subject of a large amount of research. We specifically focus on the parallel implementations of the transport sweep, and predicting the time it takes to sweep across a structured or unstructured mesh given a set of partitioning parameters, achieved through a time-to-solution estimator, written in Python. The time-to-solution estimator is tested against PDT, Texas A&M’s massively deterministic transport code. The time-to-solution estimator’s sweep time is within 10% of PDT’s sweep time for the majority of problems tested. We use the time-to-solution estimator as the objective function in an optimization scheme to attempt to get the partitions that lead to the fastest sweep time for a given problem and partitioning scheme. Two optimization methods are discussed: using a black box tool (scipy’s optimize library) and an intuitive method that prioritizes placing partitions in mesh locations that does not increase the number of cells (which we chose to name the CDF method). The time-to-solution estimator proved to not be smooth enough for a black box tool to work, so the CDF optimization method became the primary method. The CDF method proved effective for the majority of problems run, improving the time to solution over previously used partitioning scheme

Load Balancing Unstructured Meshes for Massively Parallel Transport Sweeps

When running any massively parallel code, load balancing is a priority in order to achieve the best possible parallel efficiency. A load balanced problem has an equal num-ber of degrees of freedom per processor. Load balancing is important in order to minimize idle time for all processors by equally distributing (as much as possible) the work each processor has to do. An unstructured meshing capability was implemented in PDT, Texas A&M University’s massively parallel deterministic transport code, utilizing the Triangle mesh generator, hence allowing the user to define more realistic problem geometries and to define 3D problems through the extrusion of 2D meshes. However, unstructured grids are significantly harder to load balance than Cartesian rectangular meshes. A load balancing algorithm was implemented in PDT to minimize a metric that determines how unbalanced a mesh is based on the number of mesh cells per processor. Three test cases were con-structed, and a series of 162 inputs were created for each case. A maximum improvement of 89.0% was seen in Test Case 1, 89.1% was seen in Test Case 2, and 55.2% was seen in Test Case 3

Fabrication of one-dimensional organic nanostructures using anodic aluminum oxide templates

Organic nanostructures are new comers to the fields of nanoscience and nanotechnology. In recent years novel methods for controlling the growth and uniformity of one-dimensional (1D) organic nanostructures (nanowires and nanotubes) have been developing. The use of hard templates as molds for the formation of organic nanowires or nanotubes seems to be a reliable and convenient method. In this review we will discuss the use of anodic aluminum oxide (AAO) templates as the inorganic hard template of choice. We will briefly survey advances in the fabrication of 1D polymer nanostructures using AAO templates, while the bulk of the review will focus on the synthesis of small molecule nanowires, nanotubes, and nanorods. We will also discuss unique properties of some highly crystalline small molecule nanorods fabricated using AAO templates

Therapeutic potential of flavonoids in cancer: ROS-mediated mechanisms

Cancer is a leading cause of morbidity and mortality around the globe. Reactive oxygen species (ROS) play contradicting roles in cancer incidence and progression. Antioxidants have attracted attention as emerging therapeutic agents. Among these are flavonoids, which are natural polyphenols with established anticancer and antioxidant capacities. Increasing evidence shows that flavonoids can inhibit carcinogenesis via suppressing ROS levels. Surprisingly, flavonoids can also trigger excessive oxidative stress, but this can also induce death of malignant cells. In this review, we explore the inherent characteristics that contribute to the antioxidant capacity of flavonoids, and we dissect the scenarios in which they play the contrasting role as pro-oxidants. Furthermore, we elaborate on the pathways that link flavonoid-mediated modulation of ROS to the prevention and treatment of cancer. Special attention is given to the ROS-mediated anticancer functions that (-)-epigallocatechin gallate (EGCG), hesperetin, naringenin, quercetin, luteolin, and apigenin evoke in various cancers. We also delve into the structure-function relations that make flavonoids potent antioxidants. This review provides a detailed perspective that can be utilized in future experiments or trials that aim at utilizing flavonoids or verifying their efficacy for developing new pharmacologic agents. We support the argument that flavonoids are attractive candidates for cancer therapy

Do Counter Electrodes on Metal Substrates Work with Cobalt Complex Based Electrolyte in Dye Sensitized Solar Cells?

Yes. Testing 7 different metals as a substrate for a counter electrode in dye sensitized solar cells (DSSC) showed that some metals can be a good option for use with cobalt electrolyte. It was found that Stainless steels 304 and 321 as well as Ni and Ti suit well to the counter electrodes in DSSCs with cobalt electrolyte. In these 4 cases both the efficiency and the lifetime were similar to the reference cells on conducting glass substrates. In contrast, the cells with Al, Cu and Zn substrates suffered from both a low efficiency and a poor stability. These three metals had clear marks of corrosion such as apparent corrosion products in the aged cells. Additionally, we also investigated how the different types of catalyst materials perform in the case of a metal counter electrode (stainless steel 304) with cobalt electrolyte in comparison to reference glass cells. Among the 5 different catalyst layers the best results for stainless steel electrode were achieved with low temperature platinization whereas polymer catalysts poly(3,4-ethylenedioxythiophene)-p-toluenesulfone and poly(3,4-ethylenedioxythiophene)-polystyrenesulfone that worked well on the glass worked very poorly on the metal.Peer reviewe

Partitioning Optimization for Massively Parallel Transport Sweeps on Unstructured Grids

The field of radiation transport studies the distribution of radiation throughout a seven-dimensional phase-space consisting of time, space, energy, and direction. Radiation transport is described by the Boltzmann equation that can be solved stochastically or deterministically. The work presented in this dissertation utilizes the deterministic method known as the transport sweep, a popular technique that has been the subject of a large amount of research. We specifically focus on the parallel implementations of the transport sweep, and predicting the time it takes to sweep across a structured or unstructured mesh given a set of partitioning parameters, achieved through a time-to-solution estimator, written in Python. The time-to-solution estimator is tested against PDT, Texas A&M’s massively deterministic transport code. The time-to-solution estimator’s sweep time is within 10% of PDT’s sweep time for the majority of problems tested. We use the time-to-solution estimator as the objective function in an optimization scheme to attempt to get the partitions that lead to the fastest sweep time for a given problem and partitioning scheme. Two optimization methods are discussed: using a black box tool (scipy’s optimize library) and an intuitive method that prioritizes placing partitions in mesh locations that does not increase the number of cells (which we chose to name the CDF method). The time-to-solution estimator proved to not be smooth enough for a black box tool to work, so the CDF optimization method became the primary method. The CDF method proved effective for the majority of problems run, improving the time to solution over previously used partitioning scheme

Fabrication of one-dimensional organic nanostructures using anodic aluminum oxide templates

Organic nanostructures are new comers to the fields of nanoscience and nanotechnology. In recent years novel methods for controlling the growth and uniformity of one-dimensional (1D) organic nanostructures (nanowires and nanotubes) have been developing. The use of hard templates as molds for the formation of organic nanowires or nanotubes seems to be a reliable and convenient method. In this review we will discuss the use of anodic aluminum oxide (AAO) templates as the inorganic hard template of choice. We will briefly survey advances in the fabrication of 1D polymer nanostructures using AAO templates, while the bulk of the review will focus on the synthesis of small molecule nanowires, nanotubes, and nanorods. We will also discuss unique properties of some highly crystalline small molecule nanorods fabricated using AAO templates

Universal Low-Temperature MWCNT-COOH-Based Counter Electrode and a New Thiolate/Disulfide Electrolyte System for Dye-Sensitized Solar Cells

A new thiolate/disulfide organic-based electrolyte system composed of the tetrabutylammonium salt of 2-methyl-5-trifluoromethyl-2<i>H</i>-[1,2,4]­triazole-3-thiol (S^–) and its oxidized form 3,3′-dithiobis­(2-methyl-5-trifluoromethyl-2<i>H</i>-[1,2,4]­triazole) (DS) has been formulated and used in dye-sensitized solar cells (DSSCs). The electrocatalytic activity of different counter electrodes (CEs) has been evaluated by means of measuring <i>J–V</i> curves, cyclic voltammetry, Tafel plots, and electrochemical impedance spectroscopy. A stable and low-temperature CE based on acid-functionalized multiwalled carbon nanotubes (MWCNT-COOH) was investigated with our S^–/DS, I^–/I₃^–, T^–/T₂, and Co^II/III-based electrolyte systems. The proposed CE showed superb electrocatalytic activity toward the regeneration of the different electrolytes. In addition, good stability of solar cell devices based on the reported electrolyte and CE was shown

Differential Growth Inhibitory Effects of Highly Oxygenated Guaianolides Isolated from the Middle Eastern Indigenous Plant Achillea falcata in HCT-116 Colorectal Cancer Cells

Medicinal plants play a crucial role in traditional medicine and in the maintenance of human health worldwide. Sesquiterpene lactones represent an interesting group of plant-derived compounds that are currently being tested as lead drugs in cancer clinical trials. Achillea falcata is a medicinal plant indigenous to the Middle Eastern region and belongs to the Asteraceae family, which is known to be rich in sesquiterpene lactones. We subjected Achillea falcata extracts to bioassay-guided fractionation against the growth of HCT-116 colorectal cancer cells and identified four secotanapartholides, namely 3-β-methoxy- isosecotanapartholide (1), isosecotanapartholide (2), tanaphallin (3), and 8-hydroxy-3-methoxyisosecotanapartholide (4). Three highly oxygenated guaianolides were isolated for the first time from Achillea falcata, namely rupin A (5), chrysartemin B (6), and 1β, 2β-epoxy- 3β,4α,10α-trihydroxyguaian- 6α,12-olide (7). These sesquiterpene lactones showed no or minor cytotoxicity while exhibiting promising anticancer effects against HCT-116 cells. Further structure-activity relationship studies related the bioactivity of the tested compounds to their skeleton, their lipophilicity, and to the type of functional groups neighboring the main alkylating center of the molecule