Physical Sciences and Mathematics Commons^™

Almost Split Morphisms, Preprojective Algebras And Multiplication Maps Of Maximal Rank, Steven P. Diaz, Mark Kleiner

Mathematics - All Scholarship

With a grading previously introduced by the second-named author, the multiplication maps in the preprojective algebra satisfy a maximal rank property that is similar to the maximal rank property proven by Hochster and Laksov for the multiplication maps in the commutative polynomial ring. The result follows from a more general theorem about the maximal rank property of a minimal almost split morphism, which also yields a quadratic inequality for the dimensions of indecomposable modules involved.

Finite-Dimensional Algebras With Smallest Resolutions Of Simple Modules, Shashidhar Jagadeeshan, Mark Kleiner

Mathematics - All Scholarship

Let lamda be an associative ring with identity and with the Jacobson radical r, let mod lamda be the category of finitely generated left lamda-modules, and let lamda^op be the opposite ring of lamda. All modules are left unital modules, and if X is a module then pd X is the projective dimension of X. If lamda is left artinian and M in mod labmda, we denote by P(M) a projective cover of M.

Performance Of A C4f8o Gas Radiator Ring Imaging Cherenkov Detector Using Multi-Anode Photomultiplier Tubes, Raymond Mountain, Marina Artuso, Chaouki Boulahouache, S. Blusk

Physics - All Scholarship

We report on test results of a novel ring imaging Cherenkov (RICH) detection system consisting of a 3 meter long gaseous C4F8O radiator, a focusing mirror, and a photon detector array based on Hamamatsu multi-anode photomultiplier tubes. This system was developed to identify charged particles in the momentum range from 3-70 GeV/c for the BTeV experiment.

Inhibition Of Cellular Respiration By Doxorubicin, Zhimin Tao, Henry G. Withers, Harvey S. Penefsky, Jerry Goodisman, Abdul Kader Souid

Chemistry - All Scholarship

Doxorubicin executes apoptosis, a process known to produce leakage of cytochrome c and opening of the mitochondrial permeability transition pores. To define the loss of mitochondrial function by apoptosis, we monitored cellular respiration during continuous exposure to doxorubicin. A phosphorescence analyzer capable of stable measurements over at least 5 h was used to measure [O(2)]. In solutions containing glucose and cells, [O(2)] declined linearly with time, showing that the kinetics of oxygen consumption was zero order. Complete inhibition of oxygen consumption by cyanide indicated that oxidations occurred in the respiratory chain. A decline in the rate of respiration was evident …

Effects Of Disorder On Electron Transport In Arrays Of Quantum Dots, Alan Middleton, Shantenu Jha

Physics - All Scholarship

We investigate the zero-temperature transport of electrons in a model of quantum dot arrays with a disordered background potential. One effect of the disorder is that conduction through the array is possible only for voltages across the array that exceed a critical voltage $V_T$. We investigate the behavior of arrays in three voltage regimes: below, at and above the critical voltage. For voltages less than $V_T$, we find that the features of the invasion of charge onto the array depend on whether the dots have uniform or varying capacitances. We compute the first conduction path at voltages just above $V_T$ …

Notes On (Twisted) Lattice Supersymmetry, Simon Catterall

Physics - All Scholarship

We describe a new approach to the problem of putting supersymmetric theories on the lattice. The basic idea is to discretize a {\it twisted} formulation of the supersymmetric theory. For certain theories with extended supersymmetry these twisted formulations contain only integer spin fields. The twisting exposes a scalar nilpotent supercharge which generates an exact lattice symmetry. We gives examples from quantum mechanics, sigma models and Yang-Mills theories.

Noncompact Manifolds With Nonnegative Ricci Curvature, William Wylie

Mathematics - All Scholarship

Let (M,d) be a metric space. For 0

Dirac-Kähler Fermions And Exact Lattice Supersymmetry, Simon Catterall

Physics - All Scholarship

We discuss a new approach to putting supersymmetric theories on the lattice. The basic idea is to start from a {\it twisted} formulation of the underlying supersymmetric theory in which the fermions are represented as grassmann valued antisymmetric tensor fields. The original supersymmetry algebra is replaced by a twisted algebra which contains a scalar nilpotent supercharge Q. Furthermore the action of the theory can then be written as the Q-variation of some function. The case of {\cal N}=2 super Yang-Mills theory in two dimensions is discussed in some detail. We then present our proposal for discretizing this theory and derive …

Lattice Formulation Of {\Cal N}=4 Super Yang-Mills Theory, Simon Catterall

Physics - All Scholarship

We construct a lattice action for {\cal N}=4 super Yang-Mills theory in four dimensions which is local, gauge invariant, free of spectrum doubling and possesses a single exact supersymmetry. Our construction starts from the observation that the fermions of the continuum theory can be mapped into the component fields of a single real anticommuting Kahler-Dirac field. The original supersymmetry algebra then implies the existence of a nilpotent scalar supercharge Q and a corresponding set of bosonic superpartners. Using this field content we write down a Q-exact action and show that, with an appropriate change of variables, it reduces to a …

Grain Boundary Scars On Spherical Crystals, Mark Bowick, Thomas Einert, Peter Lipowsky, Jorg Schilling, Andreas R. Bausch

Physics - All Scholarship

We present an experimental system suitable for producing spherical crystals and for observing the distribution of lattice defects (disclinations and dislocations) on a significant fraction (50%) of the sphere. The introduction of fluorescently labeled particles enables us to determine the location and orientation of grain boundary scars. We find that the total number of scars and the number of excess dislocations per scar agree with theoretical predictions and that the geometrical centers of the scars are roughly positioned at the vertices of an icosahedron.

Crystalline Particle Packings On A Sphere With Long Range Power Law Potentials, Mark Bowick, Angelo Cacciuto, David R. Nelson, Alex Travesset

Physics - All Scholarship

The original Thomson problem of "spherical crystallography" seeks the ground state of electron shells interacting via the Coulomb potential; however one can also study crystalline ground states of particles interacting with other potentials. We focus here on long range power law interactions of the form 1/r^gamma (0 < \gamma < 2), with the classic Thomson problem given by gamma=1. At large R/a, where R is the sphere radius and a is the particle spacing, the problem can be reformulated as a continuum elastic model that depends on the Young's modulus of particles packed in the plane and the universal (independent of the pair potential) geometrical interactions between disclination defects. The energy of the continuum model can be expressed as an expansion in powers of the total number of particles, M sim (R/a)^2, with coefficients explicitly related to both geometric and potential-dependent terms. For icosahedral configurations of twelve 5-fold disclinations, the first non-trivial coefficient of the expansion agrees with explicit numerical evaluation for discrete particle arrangements to 4 significant digits; the discrepancy in the 5th digit arises from a contribution to the energy that is sensitive to the particular icosadeltahedral configuration and that is neglected in the continuum calculation. In the limit of a very large number of particles, an instability toward grain boundaries can be understood in terms of a "Debye{--}Huckel" solution, where dislocations have continuous Burgers' vector "charges". Discrete dislocations in grain boundaries for intermediate particle numbers are discussed as well.

Footprints Of Statistical Anisotropies, Christian Armendariz-Picon

Physics - All Scholarship

We propose and develop a formalism to describe and constrain statistically anisotropic primordial perturbations. Starting from a decomposition of the primordial power spectrum in spherical harmonics, we find how the temperature fluctuations observed in the CMB sky are directly related to the coefficients in this harmonic expansion. Although the angular power spectrum does not discriminate between statistically isotropic and anisotropic perturbations, it is possible to define analogous quadratic estimators that are direct measures of statistical anisotropy. As a simple illustration of our formalism we test for the existence of a preferred direction in the primordial perturbations using full-sky CMB maps. …

Discretisation For Odd Quadratic Twists, J. Brian Conrey, Michael O. Rubinstein, Nina C. Snaith, Mark Watkins

Mathematics - All Scholarship

The discretisation problem for even quadratic twists is almost understood, with the main question now being how the arithmetic Delaunay heuristic interacts with the analytic random matrix theory prediction. The situation for odd quadratic twists is much more mysterious, as the height of a point enters the picture, which does not necessarily take integral values (as does the order of the Shafarevich-Tate group). We discuss a couple of models and present data on this question.

Rank Distribution In A Family Of Cubic Twists, Mark Watkins

Mathematics - All Scholarship

In 1987, Zagier and Kramarz published a paper in which they presented evidence that a positive proportion of the even-signed cubic twists of the elliptic curve x³+y³=1 should have positive rank. We extend their data, showing that it is more likely that the proportion goes to zero.

Activation Of Carboplatin By Carbonate, Anthony J. Di Pasqua, Jerry Goodisman, Deborah J. Kerwood, Bonnie B. Toms, James C. Dabrowiak

Chemistry - All Scholarship

Carboplatin, [Pt(NH3)2(CBDCA-O,O')], 1, where CBDCA is cyclobutane-1,1-dicarboxylate, is in wide clinical use for the treatment of ovarian, lung, and other types of cancer. Because carboplatin is relatively unreactive toward nucleophiles, an important question concerning the drug is the mechanism by which it is activated in vivo. Using [1H,15N] heteronuclear single quantum coherance spectroscopy (HSQC) NMR and 15N-labeled carboplatin, we show that carboplatin reacts with carbonate ion in carbonate buffer to produce ring-opened products, the nature of which depends on the pH of the medium. The assignment of HSQC NMR resonances was facilitated by studying the reaction of carboplatin in strong …

The Clash Of Symmetries In A Randall-Sundrum-Like Spacetime, Gareth Dando, Aharon Davidson, Damien P. George, Raymond R. Volkas, Kameshwar C. Wali

Physics - All Scholarship

We present a toy model that exhibits clash-of-symmetries style Higgs field kink configurations in a Randall-Sundrum-like spacetime. The model has two complex scalar fields Phi_{1,2}, with a sextic potential obeying global U(1)xU(1) and discrete Phi_1Phi_2 interchange symmetries. The scalar fields are coupled to 4+1 dimensional gravity endowed with a bulk cosmological constant. We show that the coupled Einstein-Higgs field equations have an interesting analytic solution provided the sextic potential adopts a particular form. The 4+1 metric is shown to be that of a smoothed-out Randall-Sundrum type of spacetime. The thin-brane Randall-Sundrum limit, whereby the Higgs field kinks become step functions, …

Isobar Rescattering Model And Light Scalar Mesons, Joseph Schechter

Physics - All Scholarship

We use a toy model to discuss the problem of parameterizing the possible contribution of a light scalar meson, sigma, to the final state interactions in the non leptonic decays of heavy mesons.

The Cleo Rich Detector, Raymond Mountain, Marina Artuso, R. Ayad, Konstantin Vladimirovich Bukin

Physics - All Scholarship

We describe the design, construction and performance of a Ring Imaging Cherenkov Detector (RICH) constructed to identify charged particles in the CLEO experiment. Cherenkov radiation occurs in LiF crystals, both planar and ones with a novel ``sawtooth''-shaped exit surface. Photons in the wavelength interval 135--165 nm are detected using multi-wire chambers filled with a mixture of methane gas and triethylamine vapor. Excellent pion/kaon separation is demonstrated.

Haloes Of K-Essence, Christian Armendariz-Picon, Eugene A. Lim

Physics - All Scholarship

We study gravitationally bound static and spherically symmetric configurations of k-essence fields. In particular, we investigate whether these configurations can reproduce the properties of dark matter haloes. The classes of Lagrangians we consider lead to non-isotropic fluids with barotropic and polytropic equations of state. The latter include microscopic realizations of the often-considered Chaplygin gases, which we find can cluster into dark matter halo-like objects with flat rotation curves, while exhibiting a dark energy-like negative pressure on cosmological scales. We complement our studies with a series of formal general results about the stability and initial value formulation of non-canonical scalar field …

Toy Model For Two Chiral Nonets, Joseph Schechter, Amir H. Fariborz, Renata Jora

Physics - All Scholarship

Motivated by the possibility that nonets of scalar mesons might be described as mixtures of "two quark" and "four quark" components, we further study a toy model in which corresponding chiral nonets (containing also the pseudoscalar partners) interact with each other. Although the "two quark" and "four quark" chiral fields transform identically under SU(3)_L \times SU(3)_R transformations they transform differently under the U(1)_A transformation which essentially counts total (quark + antiquark) content of the mesons. To implement this we formulate an effective Lagrangian which mocks up the U(1)_A behavior of the underlying QCD. We derive generating equations which yield Ward …

Cisplatin Carbonato Complexes. Implications For Uptake, Antitumor Properties, And Toxicity, Corey R. Centerwall, Jerry Goodisman, Deborah J. Kerwood, James C. Dabrowiak

Chemistry - All Scholarship

The reaction of aquated cisplatin with carbonate which is present in culture media and blood is described. The first formed complex is a monochloro monocarbonato species, which upon continued exposure to carbonate slowly forms a biscarbonato complex. The formation of carbonato species under conditions that simulate therapy may have important implications for uptake, antitumor properties, and toxicity of cisplatin.

Fine Structure Of Beta Decay Endpoint Spectrum, Joseph Schechter, Samina S. Masood, Salah Nasri

Physics - All Scholarship

We note that the fine structure at the endpoint region of the beta decay spectrum is now essentially known using neutrino oscillation data, if the mass of one neutrino is specified. This may help to identify the effects of nonzero neutrino masses in future experiments. An exact treatment of phase space kinematics is used. This work is independent of theoretical models. Additional restrictions due to the assumption of a so-called "complementary ansatz" for the neutrino mass matrix are also discussed.

Endomorphism Rings Of Finite Global Dimension, Graham J. Leuschke

Mathematics - All Scholarship

For a commutative local ring R, consider (noncommutative) R-algebras lamda of the form lamda = End R(M) where M is a reflexive R-module with nonzero free direct summand. Such algebras lamda of finite global dimension can be viewed as potential substitutes for, or analogues of, a resolution of singularities of Spec R. For example, Van den Bergh has shown that a three-dimensional Gorenstein normal C-algebra with isolated terminal singularities has a crepant resolution of singularities if and only if it has such an algebra lamda with finite global dimension and which is maximal Cohen–Macaulay over R (a “noncommutative crepant resolution …

Direct Visualization Of Dislocation Dynamics In Grain Boundary Scars, Mark Bowick, Peter Lipowsky, Jan H. Meinke, David R. Nelson, Andreas R. Bausch

Physics - All Scholarship

Mesoscale objects with unusual structural features may serve as the analogues of atoms in the design of larger-scale materials with novel optical, electronic or mechanical behaviour. In this paper we investigate the structural features and the equilibrium dynamics of micron-scale spherical crystals formed by polystyrene particles adsorbed on the surface of a spherical water droplet. The ground state of sufficiently large crystals possesses finite-length grain boundaries (scars). We determine the elastic response of the crystal by measuring single-particle diffusion and quantify the fluctuations of individual dislocations about their equilibrium positions within a scar determining the dislocation spring constants. We observe …

Synthesis Of Novel Alkaline Earth Metal Acetylides, Eva Baker

Honors Capstone Projects - All

Acetylide complexes of the heavy alkaline-earth metals were first introduced by our group. With our group being interested in how the ligand and donor affect the structural chemistry of the resulting complexes, my project was focused on the detailed analysis of past work and the extension towards new ligand and donor sets. The work required the analysis and development of synthetic procedures towards these highly reactive species.

Past synthetic work in our group had established several synthetic routes towards the target compounds including transamination and toluene elimination. Using toluene elimination, I was able to reproduce the synthesis of M(C≡CSiPh_{3 …}

Studies On Novel Semiconductor Detectors And Front-End Electronics For Heavy Flavor Decay Studies, Gustavo Kertzscher

Honors Capstone Projects - All

I have studied novel semiconductor detectors designed to provide precise space point information of the trajectory of charged subatomic particles produced in high energy physics (HEP) collisions. The technological thrust aims toward maintaining good performance of these detectors in a hard radiation environment for an extended period of time. My studies approached two different types of silicon devices: a whole wafer comprised of test structures and pixel devices designed for the inner vertex detector of the BTeV experiment, and small test structures of a novel type of quasi-3D detectors developed in the context of the CERN RD50 collaboration. This collaboration …

Determining The Effects Of Psychosocial Interventions On Quality Of Life For Cancer Patients: Analysis Of Pilot Data And Recommendations For Full Experimental Design And Statistical Analysis, Sarah Julia Thomas

Honors Capstone Projects - All

The Hematology and Oncology Specialists Foundation plans to carry out a scientific study to assess the effects of several of its psychosocial interventions, or “wellness programs,” on the quality of life (QoL) experienced by cancer patients. Pilot data showed that participation in a meditation program significantly reduced the symptoms of stress experienced by the patients (t = 2.70, p = 0.011), and that participation in psychological counseling significantly reduced the anxiety and depression levels of the patients (t = 5.33, p = 0.002; t = 8.70, p < 0.001, respectively).

The full scale study has a 6×2 factorial design with six treatments (non-participation, …

Photo-Induced Current Measurements In Chlamydomonas Cell Suspensions, Collin D. Capano

Honors Capstone Projects - All

In order to fully understand the principles behind phototaxis in flagellate algae, it is necessary to measure the electric currents these cells create when processing light stimuli. Many different techniques have been developed to do this. One of these techniques, measuring from cell suspensions, has a number of advantages over the others that makes it highly desirable. However, the lab that first developed this method of recording did not describe the setup very well. The result is that in the thirteen years since it was first reported, only one other independent lab has been able to reproduce the results despite …

Formation Of Molecular Hydrogen On Analogues Of Interstellar Dust Grains: Experiments And Modelling, Gianfranco Vidali, Joe Roser

Physics - All Scholarship

Molecular hydrogen has an important role in the early stages of star formation as well as in the production of many other molecules that have been detected in the interstellar medium. In this review we show that it is now possible to study the formation of molecular hydrogen in simulated astrophysical environments. Since the formation of molecular hydrogen is believed to take place on dust grains, we show that surface science techniques such as thermal desorption and time-of-flight can be used to measure the recombination efficiency, the kinetics of reaction and the dynamics of desorption. The analysis of the experimental …

Weak Point Disorder In Strongly Fluctuating Flux-Line Liquids, Panayotis Benetatos, M. Cristina Marchetti

Physics - All Scholarship

We consider the effect of weak uncorrelated quenched disorder (point defects) on a strongly fluctuating flux-line liquid. We use a hydrodynamic model which is based on mapping the flux-line system onto a quantum liquid of relativistic charged bosons in 2+1 dimensions [P. Benetatos and M. C. Marchetti, Phys. Rev. B 64, 054518, (2001)]. In this model, flux lines are allowed to be arbitrarily curved and can even form closed loops. Point defects can be scalar or polar. In the latter case, the direction of their dipole moments can be random or correlated. Within the Gaussian approximation of our hydrodynamic model, …