Physical Sciences and Mathematics Commons^™

Probing The Cob(Ii)Alamin Cond Uctorhhypothesis With Glutamate Mutase From Clostridium Cochlearium, Fe Lyatuu, A Parthasarathy, K Zhou, K Zelenka, Fh Zelder, W Buckel

Tanzania Journal of Science

It had been proposed that during reversible coenzyme B12 dependent rearrangements, cob(II)alamin is not merely present as a spectator but also acts as a conductor by stabilizing the methylene radical intermediates. Density functional theory (DFT) calculations suggested a hydrogen bond between C19-H of the corrin ring and the 3'-OH moiety (O3RL) of the 5'- deoxyadenosyl radical resulting in a decrease of the activation energy by about 30 kJ mol-1. We tested this hypothesis with glutamate mutase and artificial coenzyme B12 derivatives. The assembly of coenzyme B12 (adenosylcobalamin) with recombinant components GlmS and GlmE of glutamate mutase from Clostridium cochlearium reconstitutes …

Biorecognition Ability Of Polysaccharides As Piezo Quartz Biosensors, En Kalmykova, Ca Mgina

Tanzania Journal of Science

Piezoquartz biosensors (PQB) which are analytical devices for recognition of biochemical interactions have recently attracted increasing interest from different researchers such as analysts, immune-chemists, medical doctors, environmentalists, etc. This is due to the advantages of PQB for having high detection sensitivity (at ng and mg level depending on the mass of sorbates or micro-organisms) and the ability to monitor biochemical reactions in turbid or highly coloured liquids (including in biological fluids) in real time. The use of additional markers and preliminary sample preparation are not required in this biorecognition process. This paper reports on the principle of the PQB and …

Development Of Information And Communication Technology In Education In Tanzania: How Is Duce Playing Its Role?, Josta L. Nzilano, Ayoub C. Kafyulilo

Journal of Humanities and Social Sciences

This paper presents the ICT integration situation in Tanzania, and the efforts that are being made by the Dar es Salaam University College of Education (DUCE), as a teacher training institution, to have ICT integrated in the education system at the college and country at large. Over 60 articles and reports were gathered and read in the process of writing the paper. However, through rigorous review of each article only 35 were found to match best with the goal of this study. Results from literature indicate that technology integration in the country was still at an infant stage. Most educational …

Adsorption And Electrooxidation Of Carbon Monoxide On Platinum Surfaces Modified With Sulfur, A. Mattox Mathew, W. Henney Matthew, Johnson Adam, Zou Shouzhong

Journal of Electrochemistry

Adsorbed sulfur is commonly considered as a reaction poison. However, small amounts of sulfur on platinum significantly increase the surface reactivity toward carbon monoxide (CO) electrooxidation. For the solution CO oxidation, the onset potential was shifted up to over 300 mV negative to that on S-free surface, and the extent of the negative potential shift increases with the sulfur coverage (X_s) up to about 0.6. The enhanced CO oxidation also depends on the solution pH. For the adsorbed CO, at low sulfur coverages (X_s < 0.3), the oxidation peak potential is about 40 mV negative to that of the corresponding clean Pt. However, at higher coverages, the peak potential is about 30 mV more positive. Surface-enhanced Raman spectra show that the adsorption of sulfur significantly redshifts the Pt-CO stretching frequency. These observations are explained by the weakening of the Pt-CO bond and the hindrance of CO diffusion by Sads.

Kinetic Study Of Photoelectrochemical Oxidation Of Lignin Model Compounds On Tio2 Nanotubes, Min Tian, Daniel Liba, Aicheng Chen

Journal of Electrochemistry

In this study, TiO₂ nanotubes were prepared via the electrochemical oxidation of titanium substrates in a non-aqueous electrolyte and their morphology and microstructures were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photoelectrochemical oxidation of two lignin model compounds, 1-(3,4-dimethoxyphenoxy)-2-(2-methoxyphenoxy)-1,3-propanediol (DMP) and 3-hydroxy-1-(3,4-dimethoxyphenoxy)-2-(2-methoxyphenoxy)-1,3-propanone (HDM), was investigated. A new band appeared at ~304 nm during the photoelectrochemical oxidation of DMP. The rate of DMP intermediate formation was amplified with the increase of initial concentrations, while it was diminished with increased temperature. Despite the similarity in structure between HDM and DMP, there are only small increases in absorbance …

Electrochemical Performance Of Screen-Printed Composite Coatings Of Conducting Polymers And Carbon Nanotubes On Titanium Bipolar Plates In Aqueous Asymmetrical Supercapacitors, Xiaohang Zhou, George Z. Chen

Journal of Electrochemistry

Composites of conducting polymers (polypyrrole and polyaniline) with acid treated multi-walled carbon nanotubes were formulated into printable aqueous inks, with the aid of functional additives (benzethonium chloride as a surfactant with or without polyvinyl alcohol as a binder). The inks were screen-printed as fairly uniform coatings of various mass loading densities and areas (up to 75 mg cm^-2 and 100 cm²) on thin titanium plates (0.1 mm in thickness). These screen-printed plates were used to fabricate both unit cell and multi-cell stack of asymmetrical supercapacitors with screen-printed negative electrodes of activated carbon (pigment black) in aqueous electrolytes …

Advances And Challenges Of Intermediate Temperature Solid Oxide Fuel Cells: A Concise Review, Sanping Jiang

Journal of Electrochemistry

Fuel cell is an electrochemical energy conversion device to directly convert the chemical energy of fuels to electricity. Among all types of fuel cells, solid oxide fuel cells (SOFCs) operating at intermediate temperatures of 600~800 ^oC offer an attractive option that is much more fuel flexible than low temperature fuel cells such as proton exchange membrane fuel cells, and is suitable for a wide range of applications. However, two main challenges remain towards the commercial viability and acceptance of the SOFC technologies: the cost and durability. Both are critically dependent on the process, fabrication, performance, chemical and microstructural stability …

Ternary Alloy Electrocatalysts For Oxygen Reduction Reaction, Jin Luo, Lefu Yang, Binghui Chen, Chuanjian Zhong

Journal of Electrochemistry

Proton exchange membrane fuel cell represents an important electrochemical energy conversion device with many attractive features in terms of efficiency of energy conversion and minimization of environmental pollution. However, the large overpotential for oxygen reduction reaction at the cathode and the low activity, poor durability and high cost of platinum-based catalysts in the fuel cells constitute a focal point of major barriers to the commercialization of fuel cells. The development of nanostructured catalysts shows promises to addresses some of the challenging problems. The ability to engineer the composition and nanostructure of nanoalloy catalysts is important for developing active, robust and …

Electrocatalytic Activity Of Palladium Nanocatalysts Supported On Carbon Nanoparticles In Formic Acid Oxidation, Jie Huang, Zhiyou Zhou, Yang Song, Xiongwu Kang, Ke Liu, Wancheng Zhou, Shaowei Chen

Journal of Electrochemistry

Palladium nanostructures were deposited onto carbon nanoparticle surface by a chemical reduction method. Transmission electron microscopic studies showed that whereas the resulting metal-carbon (Pd-CNP) nanocomposites exhibited a diameter of 20 to 30 nm, the metal components actually showed a cauliflower-like surface morphology that consisted of numerous smaller Pd nanoparticles (3 to 8 nm). Electrochemical studies showed that the effective surface area of the Pd-CNP nanoparticles was about 40% less than that of Pd black, possibly because the Pd nanoparticles were coated with a layer of carbon nanoparticles; yet, the Pd-CNP nanocomposites exhibited marked enhancement of the electrocatalytic activity in formic …

Electrocatalytic Oxidation Of Formic Acid On Pd/Ni Heterostructured Catalyst, Mingjun Ren, Liangliang Zou, Ju Chen, Ting Yuan, Qinghong Huang, Haifeng Zhang, Hui Yang, Songlin Feng

Journal of Electrochemistry

A Pd/Ni bimetallic nanostructured electrocatalyst was fabricated via a two-step reduction route. Owing to an epitaxial growth of Pd atoms on the surface of Ni nanoparticles, heterostructured Pd/Ni nanocomposites were formed and verified by high resolution transmission electron microscopy combined with energy-dispersion X-ray spectroscopy. X-ray diffraction confirmed that the as-prepared Pd/Ni nanocomposites possessed a single face-centered-cubic (fcc) Pd structure, probably due to a weaker diffraction intensity of metallic Ni and/or overlapping by that of Pd. The intrinsic catalytic activity on the Pd/Ni is higher than that on the Pd. Moreover, the durability of formic acid oxidation on the Pd/Ni was …

Testing Diagnostics Of Nuclear Activity And Star Formation In Galaxies At Z > 1, Jonathan R. Trump, Nicholas P. Konidaris, Guillermo Barro, David C. Koo, Dale D. Kocevski, Stéphanie Juneau, Benjamin J. Weiner, S. M. Faber, Ian S. Mclean, Renbin Yan, Pablo G. Pérez-González, Victor Villar

Physics and Astronomy Faculty Publications

We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z ~ 1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in 2 hr exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line ratio diagnostics and the alternative mass-excitation and color-excitation diagrams, combining new MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST survey) and multiwavelength photometry. We demonstrate that a high [O III]/Hβ ratio is insufficient as an active galactic nucleus (AGN) indicator …

Exploitation Of Rf-Dna For Device Classification And Verification Using Grlvqi Processing, Donald R. Reising

Theses and Dissertations

This dissertation introduces a GRLVQI classifier into an RF-DNA fingerprinting process and demonstrates applicability for device classification and ID verification. Unlike MDA/ML processing, GRLVQI provides a measure of feature relevance that enables Dimensional Reduction Analysis (DRA) to enhance the experimental-to-operational transition potential of RF-DNA fingerprinting. Using 2D Gabor Transform RF-DNA fingerprints extracted from experimentally collected OFDM-based 802.16 WiMAX and 802.11 WiFi device emissions, average GRLVQI classification accuracy of %C greater than or equal to 90% is achieved using full and reduced dimensional feature sets at SNR greater than or equal to 10.0 dB and SNR greater than or equal to …

Polymorphism And Polyamorphism In Bilayer Water Confined To Slit Nanopore Under High Pressure, Jaeil Bai, Xiao Cheng Zeng

Xiao Cheng Zeng Publications

A distinctive physical property of bulk water is its rich solid-state phase behavior, which includes 15 crystalline (ice I–ice XIV) and at least 3 glassy forms ofwater, namely, low-density amorphous, highdensity amorphous, and very-high-density amorphous (VHDA). Nanoscale confinement adds a new physical variable that can result in a wealth of new quasi-2D phases of ice and amorphous ice. Previous computer simulations have revealed that when water is confined between two flat hydrophobic plates about 7–9 Å apart, numerous bilayer (BL) ices (or polymorphs) can arise [e.g., BL-hexagonal ice (BL-ice I)]. Indeed, growth of the BL-ice I through vapor deposition on …

U.S. Drought Monitor, December 25, 2012, Richard R. Heim Jr.

United States Agricultural Commodities in Drought Archive

Drought map of the United States for December 25, 2012 (12/25/12) plus: United States crop areas experiencing drought (map), an approximate percentage of crop located in drought by state (bar graph), and the percentage of crop area located in drought during the past 52 weeks (line graph) for hay, cattle, and winter wheat.

A Novel Route To Organonitrites By Pd-Catalyzed Cross-Coupling Of Sodium Nitrite And Potassium Organotrifluoroborates, Mohammad Al-Masum, Nabil Saleh, Tasfia Islam

Chemistry Faculty Research

Microwave irradiated palladium-catalyzed cross-coupling reaction of potassium styryltrifluoroborates and sodium nitrite gives the corresponding styryl nitrites in high yields. Potassium aryltrifluoroborates also furnish aryl nitrites under same reaction condition. This unprecedented cross-coupling is an interesting development and has the potential to lead to new nitration protocols.

Public Expenditure, Environmental Pollution And Endogenous Economic Growth., Trishita Ray Barman Dr.

Doctoral Theses

Sources of Economic Growth and the Definition of Steady-State EquilibriumEconomic growth is defined as a continuous increase in national income taking place over a time horizon. According to the neoclassical theory of economic growth there are three sources of economic growth: (i) capital accumulation, (ii) growth of labour force and (iii) technological progress.The steady-state growth equilibrium is defined as a state where all major macro-economic variables grow at the same rate so that the ratios of these variables remain unchanged over time. For example, in the one sector aggregative model like that of Solow (1956), capital and labour grow at …

The Central Molecular Gas Structure In Liners With Low-Luminosity Active Galactic Nuclei: Evidence For Gradual Disappearance Of The Torus, F. Müller-Sánchez, M. A. Prieto, M. Mezcua, R. I. Davies, M. A. Malkan, Moshe Elitzur

Physics and Astronomy Faculty Publications

We present observations of the molecular gas in the nuclear environment of three prototypical low-luminosity active galactic nuclei (LLAGNs), based on VLT/SINFONI AO-assisted integral-field spectroscopy of H₂ 1-0 S(1) emission at angular resolutions of ~0.''17. On scales of 50-150 pc, the spatial distribution and kinematics of the molecular gas are consistent with a rotating thin disk, where the ratio of rotation (V) to dispersion (σ) exceeds unity. However, in the central 50 pc, the observations reveal a geometrically and optically thick structure of molecular gas (V/σ < 1 and N _H > 10²³ cm^{–2 …}

Multiple Subject Barycentric Discriminant Analysis (Musubada): How To Assign Scans To Categories Without Using Spatial Normalization, Hervé Abdi, Lynne J. Williams, Andrew C. Connolly, M. Ida Gobbini

Dartmouth Scholarship

We present a new discriminant analysis (DA) method called Multiple Subject Barycentric Discriminant Analysis (MUSUBADA) suited for analyzing fMRI data because it handles datasets with multiple participants that each provides different number of variables (i.e., voxels) that are themselves grouped into regions of interest (ROIs). Like DA, MUSUBADA (1) assigns observations to predefined categories, (2) gives factorial maps displaying observations and categories, and (3) optimally assigns observations to categories. MUSUBADA handles cases with more variables than observations and can project portions of the data table (e.g., subtables, which can represent participants or ROIs) on the factorial maps. Therefore MUSUBADA can …

Transforming Fabry-Pérot Resonances Into A Tamm Mode, Maxim Durach, Anastasia Rusina

Physics & Astronomy: Faculty Publications

We propose an optical structure composed of two metal nanolayers enclosing a distributed Bragg reflector (DBR) mirror. The structure is an open photonic system whose bound modes are coupled to external radiation. We apply the special theoretical treatment based on inversion symmetry of the structure to classify its resonances. We show that the structure supports resonances transitional between Fabry-Pérot modes and Tamm plasmons. When the dielectric contrast of the DBR is removed these modes are a pair of conventional Fabry-Pérot resonances. They spectrally merge into a Tamm mode at high contrast. The optical properties of the structure in the frequency …

Facile Molten-Salt Synthesis Of Double Perovskite La2bmno 6 Nanoparticles, Yuanbing Mao

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

Crystalline double perovskite La2BMnO6 (B = Ni and Co) nanoparticles with an average grain size of ∼64 nm were successfully prepared using a facile, environmentally friendly, scalable molten-salt reaction at 700 °C in air. Their composition and structural and magnetic properties have been characterized.

Optimal Spatial Prediction Using Ensemble Machine Learning, Molly M. Davies, Mark J. Van Der Laan

U.C. Berkeley Division of Biostatistics Working Paper Series

Spatial prediction is an important problem in many scientific disciplines. Super Learner is an ensemble prediction approach related to stacked generalization that uses cross-validation to search for the optimal predictor amongst all convex combinations of a heterogeneous candidate set. It has been applied to non-spatial data, where theoretical results demonstrate it will perform asymptotically at least as well as the best candidate under consideration. We review these optimality properties and discuss the assumptions required in order for them to hold for spatial prediction problems. We present results of a simulation study confirming Super Learner works well in practice under a …

Kelt-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-Mass Companion Transiting A Mid-F Star, R. J. Siverd, T. G. Beatty, J. Pepper, J. D. Eastman, K. Collins, A. Bieryla, D. W. Latham, L. A. Buchhave, Eric L.N. Jensen, J. R. Crepp, R. Street, K. G. Stassun, B. S. Gaudi, P. Berlind, M. L. Calkins, D. L. Depoy, G. A. Esquerdo, B. J. Fulton, G. Fürész, J. C. Geary, A. Gould, L. Hebb, J. F. Kielkopf, J. L. Marshall, R. Pogge, K. Z. Stanek, R. P. Stefanik, A. H. Szentgyorgyi, M. Trueblood, P. Trueblood, A. M. Stutz, J. L. Van Saders

Physics & Astronomy Faculty Works

We present the discovery of KELT-1b, the first transiting low-mass companion from the wide-field Kilodegree Extremely Little Telescope-North (KELT-North) transit survey. A joint analysis of the spectroscopic, radial velocity, and photometric data indicates that the V = 10.7 primary is a mildly evolved mid-F star with T-eff = 6516 +/- 49 K, log g = 4.228(-0.021)(+0.014), and [Fe/H] = 0.052 +/- 0.079, with an inferred mass M* = 1.335 +/- 0.063M(circle dot) and radius R* = 1.471(-0.035)(+0.045) R-circle dot. The companion is a low-mass brown dwarf or a super-massive planet with mass M-P = 27.38 +/- 0.93 M-Jup and radius …

Measures Of Centrality Based On The Spectrum Of The Laplacian, Scott D. Pauls, Daniel Remondini

Dartmouth Scholarship

We introduce a family of new centralities, the k-spectral centralities. k-Spectral centrality is a measurement of importance with respect to the deformation of the graph Laplacian associated with the graph. Due to this connection, k-spectral centralities have various interpretations in terms of spectrally determined information.

We explore this centrality in the context of several examples. While for sparse unweighted net- works 1-spectral centrality behaves similarly to other standard centralities, for dense weighted net- works they show different properties. In summary, the k-spectral centralities provide a novel and useful measurement of relevance (for single network elements as well as whole subnetworks) …

The Convergence Of Two Algorithms For Compressed Sensing Based Tomography, Xiezhang Li, Jiehua Zhu

Mathematical Sciences: Faculty Publications

The constrained total variation minimization has been developed successfully for image reconstruction in computed tomography. In this paper, the block component averaging and diagonally-relaxed orthogonal projection methods are proposed to incorporate with the total variation minimization in the compressed sensing framework. The convergence of the algorithms under a certain condition is derived. Examples are given to illustrate their convergence behavior and noise performance.

A Comparison Of Boltzmann And Gibbs Definitions Of Microcanonical Entropy For Small Systems, Randall B. Shirts

Faculty Publications

Two different definitions of entropy, S= klnW, in the microcanonical ensemble have been competing for over 100 years. The Boltzmann/Planck definition is that W is the number of states accessible to the system at its energy E (also called the surface entropy). The Gibbs/Hertz definition is that W is the number of states of the system up to the energy E (also called the volume entropy). These two definitions agree for large systems but differ by terms of order N^-1 for small systems, where N is the number of particles in the system. For three analytical …

A Modular Mind? A Test Using Individual Data From Seven Primate Species, Federica Amici, Bradley Barney, Valen E. Johnson, Josep Call, Filippo Aureli

Faculty Articles

It has long been debated whether the mind consists of specialized and independently evolving modules, or whether and to what extent a general factor accounts for the variance in performance across different cognitive domains. In this study, we used a hierarchical Bayesian model to re-analyse individual level data collected on seven primate species (chimpanzees, bonobos, orangutans, gorillas, spider monkeys, brown capuchin monkeys and long-tailed macaques) across 17 tasks within four domains (inhibition, memory, transposition and support). Our modelling approach evidenced the existence of both a domain-specific factor and a species factor, each accounting for the same amount (17%) of the …

Information Content Of Seasonal Forecasts In A Changing Climate, Nir Krakauer, Michael D. Grossberg, Irina Gladkova, Hannah Aizenman

Publications and Research

We study the potential value to stakeholders of probabilistic long-term forecasts, as quantified by the mean information gain of the forecast compared to climatology. We use as a case study the USA Climate Prediction Center (CPC) forecasts of 3-month temperature and precipitation anomalies made at 0.5-month lead time since 1995. Mean information gain was positive but low (about 2% and 0.5% of the maximum possible for temperature and precipitation forecasts, resp.) and has not increased over time. Information-based skill scores showed similar patterns to other, non-information-based, skill scores commonly used for evaluating seasonal forecasts but tended to be smaller, suggesting …

On The Peakon And Soliton Solutions Of An Integrable Pde With Cubic Nonlinearities, Rossen Ivanov, Tony Lyons

Conference papers

The interest in the singular solutions (peakons) has been inspired by the Camassa-Holm (CH) equation and its peakons. An integrable peakon equation with cubic nonlinearities was first discovered by Qiao. Another integrable equation with cubic nonlinearities was introduced by V. Novikov . We investigate the peakon and soliton solutions of the Qiao equation.

Use Of International Hydrographic Organization Tidal Data For Improved Tidal Prediction, Songwei Qi

Dissertations and Theses

Tides are the rise and fall of water level caused by gravitational forces exerted by the sun, moon and earth. Understanding sea level variation and its impact currents is very important especially in coastal regions. With knowledge of the tide-generating force and boundary conditions, hydrodynamic models can be used to predict or model tides in coastal regions. However, these models are not sufficiently accurate, and in-situ tide gauge data may be used to improve them in coastal regions. The International Hydrographic Organization (IHO) tidal data bank consists of over 4000 tide gauge stations scattered all around the globe, most of …

Tuning Of Alternative Splicing - Switch From Proto-Oncogene To Tumor Suppressor, Aleksandra Shchelkunova, Boris Ermolinsky, Meghan Boyle, Ivan Mendez, Michael Lehker, Karen S. Martirosyan, Alexander V. Kazansky

Physics & Astronomy Faculty Publications

STAT5B, a specific member of the ST AT family, is intimately associated with prostate tumor progression. While the full form of STAT5B is thought to promote tumor progression, a naturally occurring truncated isoform acts as a tumor suppressor. We previously demonstrated that truncated STAT5 is generated by insertion of an alternatively spliced exon and results in the introduction of an early termination codon. Present approaches targeting ST AT proteins based on inhibition of functional domains of STAT's, such as DNA-binding, cooperative binding (protein-protein interaction), dimerization and phosphorylation will halt the action of the entire gene, both the proto-oncogenic and tumor …