Physical Sciences and Mathematics Commons^™

Collapse Of Skyrmions In Two-Dimensional Ferromagnets And Antiferromagnets, Luifei Cai, Eugene M. Chudnovsky, Dmitry A. Garanin

Publications and Research

Collapse of a skyrmion due to the discreteness of a crystal lattice in isotropic two-dimensional ferro- and antiferromagnets has been studied analytically and by numerical solution of equations of motion for up to 2000 x 2000 classical spins on a square lattice coupled via Heisenberg exchange interaction. Excellent agreement between analytical and numerical results has been achieved. The lifetime of the skyrmion scales with its initial size, lambda_0, as(lambda_0/a)^5 in ferromagnets and as (lambda_0/a)^2.15 in antiferromagnets, with a being the lattice parameter. This makes antiferromagnetic skyrmions significantly shorter lived than ferromagnetic skyrmions.

Study Of The Gelling Process In The La-Co-Citric Acid System, Luminita Predoana, Andrei Jitianu, Barbara Malic, Maria Zaharescu

Publications and Research

The gelling process in the aqueous lanthanum-cobalt-citric acid system was studied using UV-VIS and IR spectroscopic methods, as well as viscosity measurements, to establish the gelling mechanism of transition metal ions (La3+ and Co2+) in the presence of chelating agent. Lanthanum and cobalt nitrates and lanthanum and cobalt acetates, respectively, were used as starting reagents, and the citric acid was used as chelating agent. The gelation process was investigated at room temperature and at 80°C. At elevated temperature, the gels were obtained after 30 h, whereas at room temperature, these were obtained in 1 month. Complex gels were formed for …

The Effect Of Dissolved Humic Acids On Aluminosilicate Formation And Associated Carbon Sequestration, Ashaki A. Rouff, Brian L. Phillips, Stacey G. Cochiara, Kathryn L. Nagy

Publications and Research

Allophane and imogolite neogenesis in soils may occur in the presence of organic matter. To understand this process under conditions relevant to soils, the influence of dissolved organic carbon (DOC) as humic acid (HA), on aluminosilicate formation was studied at 25◦C, pH 6, and low-DOC concentrations. For solutions with initial Al/Si ratios of 1–2.1, and 0–6mg/L DOC, precipitates recovered after 20h had Al/Si ratios of 2.2–2.7. The formation of allophane, imogolite-like material, and aluminosilicate gel was confirmed by XRD, FTIR, and NMR. The effect of DOC was to produce a small, but systematic increase in imogolite-like Si in the precipitate, …

Beefmoves: Dissemination, Diversity, And Dynamics Of English Borrowings In A German Hip Hop Forum, Matt Garley, Julia Hockenmaier

Publications and Research

We investigate how novel English-derived words (anglicisms) are used in a German-language Internet hip hop forum, and what factors contribute to their uptake.

Thermal Analysis Of Organically Modified Siloxane Melting Gels, Andrei Jitianu, Kristin Lammers, Georgia A. Arbuckle-Kiel, Lisa C. Klein

Publications and Research

Hybrid melting gels were prepared by a sol–gel process, starting with a mono-substituted siloxane and a disubstituted siloxane, methyltrimethoxysilane (MTES) together with dimethyldimethoxysilane (DMDES). Five gel compositions were prepared with concentrations between 50% MTES–50% DMDES and 75% MTES–25% DMDES (in mol.%).

Homogeneous Besov Spaces On Stratified Lie Groups And Their Wavelet Characterization, Hartmut Fuhr, Azita Mayeli

Publications and Research

We establish wavelet characterizations of homogeneous Besov spaces on stratified Lie groups, bothin terms of continuous and discrete wavelet systems. We first introduce a notion of homogeneous Besov space ̇Bsp,qin terms of a Littlewood-Paley-type decomposition, in analogy to the well-known characterization of the Euclidean case. Such decompositions can be defined via the spectral measure of a suitably chosen sub-Laplacian. We prove that the scale of Besov spaces is independent of the precise choice of Littlewood-Paley decomposition. In particular, different sub-Laplacians yield the same Besov spaces. We then turn to wavelet characterizations, first via continuous wavelet transforms which can be viewed …

Equivariant Degenerations Of Spherical Modules For Groups Of Type A, Stavros Argyrios Papadakis, Bart Van Steirteghem

Publications and Research

Let G be a complex reductive algebraic group. Fix a Borel subgroup B of G and a maximal torus T in B. Call the monoid of dominant weights L+ and let S be a finitely generated submonoid of L+. V. Alexeev and M. Brion introduced a moduli scheme MS which classifies affine G-varieties X equipped with a T-equivariant isomorphism SpecC[X]U → SpecC[S], where U is the unipotent radical of B. Examples of MS have been obtained by S. Jansou, P. Bravi and S. Cupit-Foutou. In this paper, we prove that MS is isomorphic to an affine space when S is …

Cross-Talk: A Shared Parameter Space For Gesturally Extended Human/Machine Improvisation, William Brent, Adam James Wilson

Publications and Research

This paper describes Cross-talk, a piece of music and performance system for two instruments augmented with infrared motion-tracking capability, and an artificial software improviser. Cross-talk was commissioned by the Ammerman Center for Arts and Technology at Connecticut College, for the 13th Biennial Symposium on Arts and Technology. The work is part of an ongoing collaboration focused on developing integrated hardware and software performance systems to extend the timbral and expressive capabilities of traditional musical instruments and to generate musical structure in response to information retrieved from human performers in real-time. Artistic motivations and prior related work are presented here, along …

Ledzewicz Applies Math To Health Sciences, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

Hamad Studies, Teaches Properties Of Light, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

Minchin Studies, Teaches Conservation Issues, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

Ackad Uses Power Computers To Solve Problems, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

Jones Seeks To Engage Students In Chemistry, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

Hildebrandt Teaches Lessons About Tornadoes, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

Jennings Studies Environmental Pollutants, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

Diffuse Optical Imaging Using Decomposition Methods, Binlin Wu, M. Alrubaiee, W. Cai, M. Xu, S. K. Gayen

Publications and Research

Diffuse optical imaging (DOI) for detecting and locating targets in a highly scattering turbid medium is treated as a blind source separation (BSS) problem. Three matrix decomposition methods, independent component analysis (ICA), principal component analysis (PCA), and nonnegative matrix factorization (NMF) were used to study the DOI problem. The efficacy of resulting approaches was evaluated and compared using simulated and experimental data. Samples used in the experiments included Intralipid-10% or Intralipid-20% suspension in water as the medium with absorptive or scattering targets embedded.

Fluids, Anomalies And The Chiral Magnetic Effect: A Group-Theoretic Formulation, V. Parameswaran Nair, Rashmi Ray, Shubho Roy

Publications and Research

It is possible to formulate fluid dynamics in terms of group-valued variables. This is particularly suited to the cases where the fluid has nonabelian charges and is coupled to nonabelian gauge fields. We explore this formulation further in this paper. An action for a fluid of relativistic particles (with and without spin) is given in terms of the Lorentz and Poincare (or de Sitter) groups. Considering the case of particles with flavor symmetries, a general fluid action which also incorporates all flavor anomalies is given. The chiral magnetic and chiral vorticity effects as well as the consequences of the mixed …

Synthesis Of Melting Gels Using Mono-Substituted And Di-Substituted Alkoxysiloxanes, Lisa Klein, Andrei Jitianu

Publications and Research

Hybrid organic-inorganic sol-gel materials containing silica were first called “ORMOSILs” in 1984.¹ Since then, the number of hybrid organicinorganic combinations has increased rapidly.² Hybrid materials have remarkable features resulting from the synergistic combination of both inorganic and organic components that make them suitable for a wide range of applications such as electrochemical devices, biomedical applications including drug delivery, and electronic and optoelectronic applications including light-emitting diodes, photodiodes, solar cells, gas sensors and field effect transistors.

Generally, organic-inorganic materials are classified in two broad categories: Class I materials where the organic and inorganic components are embedded one within the …

Quantum Tunneling Of The Magnetic Moment In A Free Nanoparticle, Michael F. O'Keeffe, Eugene M. Chudnovsky, Dmitry A. Garanin

Publications and Research

We study tunneling of the magnetic moment in a particle that has full rotational freedom. Exact energy levels are obtained and the ground-state magnetic moment is computed for a symmetric rotor. The effect of the mechanical freedom on spin tunneling manifests itself in a strong dependence of the magnetic moment on the moments of inertia of the rotor. Energy of the particle exhibits quantum phase transitions between states with different values of the magnetic moment. Particles of various shapes are investigated and quantum phase diagram is obtained.

Quantum Deflagration And Supersonic Fronts Of Tunneling In Molecular Magnets, Dmitry A. Garanin, Saaber Shoyed

Publications and Research

Theory of magnetic deflagration taking into account dipolar-controlled spin tunneling has been applied to the realistic model of molecular magnet Mn_12 Ac. At small transverse field, the front speed v has tunneling maxima on the bias field B_z reflecting those of the molecular spin's relaxation rate calculated from the density-matrix equation. At high transverse field, spin tunneling directly out of the metastable ground state leads to front speeds that can exceed the speed of sound. Both for the weak and strong transverse field, the spatial profile of the deflagration front near tunneling resonances shows a front of tunneling that triggers …

Dipolar-Controlled Spin Tunneling And Relaxation In Molecular Magnets, Dmitry A. Garanin

Publications and Research

Spin tunneling in molecular magnets controlled by dipole-dipole interactions (DDI) in the disordered state has been considered numerically on the basis of the microscopic model using the quantum mean-field approximation. In the actual case of a strong DDI spin coherence is completely lost and there is a slow relaxation of magnetization, described by t^{3/4} at short times. Fast precessing nuclear spins, included in the model microscopically, only moderately speed up the relaxation.

Cosmic String Interactions Induced By Gauge And Scalar Fields, Daniel N. Kabat, Debajyoti Sarkar

Publications and Research

We study the interaction between two parallel cosmic strings induced by gauge fields and by scalar fields with non-minimal couplings to curvature. For small deficit angles the gauge field behaves like a collection of non-minimal scalars with a specific value for the non-minimal coupling. We check this equivalence by computing the interaction energy between strings at first order in the deficit angles. This result provides another physical context for the "contact terms" which play an important role in the renormalization of black hole entropy due to a spin-1 field.

Holographic Representation Of Bulk Fields With Spin In Ads/Cft, Daniel N. Kabat, Gilad Lifschytz, Shubho Roy, Debajyoti Sarkar

Publications and Research

We develop the representation of bulk fields with spin one and spin two in anti-de Sitter space, as non-local observables in the dual CFT. Working in holographic gauge in the bulk, at leading order in 1/N bulk gauge fields are obtained by smearing boundary currents over a sphere on the complexified boundary, while linearized metric fluctuations are obtained by smearing the boundary stress tensor over a ball. This representation respects AdS covariance up to a compensating gauge transformation. We also consider massive vector fields, where the bulk field is obtained by smearing a non-conserved current. We compute bulk two-point functions …

Casimir Effect: Edges And Diffraction, Dimitra Karabali

Publications and Research

The Casimir effect refers to the existence of a macroscopic force between conducting plates in vacuum due to quantum fluctuations of fields. These forces play an important role, among other things, in the design of nano-scale mechanical devices. Accurate experimental observations of this phenomenon have motivated the development of new theoretical approaches in dealing with the effects of different geometries, temperature etc. In this talk, I will focus on a new method we have developed in calculating the contribution to the Casimir effect due to diffraction from edges and holes in different geometries, at zero and at finite temperature.

The Minimum Of The Maximum Rectilinear Crossing Numbers Of Small Cubic Graphs, Matthew Alpert, Jens-P. Bode, Elie Feder, Heiko Harborth

Publications and Research

Here we consider the minimum of the maximum rectilin­ear crossing numbers for all d-regular graphs of order n. The case of connected graphs only is investigated also. For d = 3 exact values are determined for n are less than or equal to 12 and some estimations are given in general.

Wave-Function Functionals For The Density, Marlina Slamet, Xiao-Yin Pan, Viraht Sahni

Publications and Research

We extend the idea of the constrained-search variational method for the construction of wave-function functionals psi[chi] of functions chi. The search is constrained to those functions chi such that psi[chi] reproduces the density rho(r) while simultaneously leading to an upper bound to the energy. The functionals are thereby normalized and automatically satisfy the electron-nucleus coalescence condition. The functionals psi[chi] are also constructed to satisfy the electron-electron coalescence condition. The method is applied to the ground state of the helium atom to construct functionals psi[chi] that reproduce the density as given by the Kinoshita correlated wave function. The expectation of single-particle …

Fabrication Of Size-Tunable Metallic Nanoparticles Using Plasmid Dna As A Biomolecular Reactor, Jacopo Samson, Irene Piscopo, Alex Yampolski, Patrick Nahirney, Andrea Parpas, Amit Aggarwal, Raihan Saleh, Charles Michael Drain

Publications and Research

Plasmid DNA can be used as a template to yield gold, palladium, silver, and chromium nanoparticles of different sizes based on variations in incubation time at 70 °C with gold phosphine complexes, with the acetates of silver or palladium, or chromium acetylacetonate. The employment of mild synthetic conditions, minimal procedural steps, and aqueous solvents makes this method environmentally greener and ensures general feasibility. The use of plasmids exploits the capabilities of the biotechnology industry as a source of nanoreactor materials.

Dissemination Of Geological Information In Avoiding Geotechnical Risks Associated With Tunnel Construction: Lessons Learned From Deep Voids In Marble In Lower Manhattan, New York City, Nazrul I. Khandaker, Stanley Schleifer, Masud Ahmed, Leah Scott

Publications and Research

Test boring associated with the recently accomplished City Water Tunnel # 3 in Manhattan, New York City revealed moderately to highly weathered marble with insoluble silicate residues composed mostly of phlogopite, chlorite, and tremolite. Apparent control on the weatherability of the marble was in response to original mineral constituents dominating this lithology. Encountered marble samples ranged between pure calcitic to mixed dolomitic/siliceous types. Fresh marble samples collected from adjacent boring locations revealed characteristic geochemical data: Lime (25-45%), Silica (4-7%), Alumina (1-3%), MgO (5-20%), and LOI (35-42%); compressive strength of unweathered marble varied between 2000-3000 Kg/cm². Relict foliations with …

The Niddk Central Repository At 8 Years—Ambition, Revision, Use And Impact, Charles F. Turner, Huaqin Pan, Gregg W. Silk, Mary-Anne Ardini, Vesselina Bakalov, Stephanie Bryant, Susanna Cantor, Kung-Yen Chang, Michael Delatte, Paul Eggers, Laxminarayana Ganapathi, Sujatha Lakshmikanthan, Joshua Levy, Sheping Li, Joseph Pratt, Norma Pugh, Ying Qin, Rebekah Rasooly, Helen Ray, Jean E. Richardson, Amanda Flynn Riley, Susan M. Rogers, Charlotte Scheper, Sylvia Tan, Stacie White, Philip C. Cooley

Publications and Research

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Central Repository makes data and biospecimens from NIDDK-funded research available to the broader scientific community. It thereby facilitates: the testing of new hypotheses without new data or biospecimen collection; pooling data across several studies to increase statistical power; and informative genetic analyses using the Repository’s well-curated phenotypic data. This article describes the initial database plan for the Repository and its revision using a simpler model. Among the lessons learned were the trade-offs between the complexity of a database design and the costs in time and money of implementation; the …

Group 11 Metal Compounds With Tripodal Bis(Imidazole) Thioether Ligands. Applications As Catalysts In The Oxidation Of Alkenes And As Antimicrobial Agents, Fangwei Liu, Reema Anis, Eunmi Hwang, Rafael Ovalle, Armando Varela-Ramírez, Renato J. Aguilera, María Contel

Publications and Research

New group 11 metal complexes have been prepared using the previously described tripodal bis(imidazole) thioether ligand (N-methyl-4,5-diphenyl-2- imidazolyl)2C(OMe)C(CH3)2S(tert-Bu) ({BITOMe,StBu}, 2). The pincer ligand offers a N2S donor atom set that can be used to coordinate the group 11 metals in different oxidation states [AuI , AuIII, AgI , CuI and CuII]. Thus the new compounds [Au{BITOMe,StBu}Cl][AuCl4]2 (3), [Au{BITOMe,StBu}Cl] (4), [Ag{BITOMe,StBu}X] (X = OSO2CF3 - 5, PF6 - 6) and [Cu{BITOMe,StBu}Cl2] (7) have been synthesized from reaction of 2 with the appropriate metal precursors, and characterized in solution. While attempting characterization in the solid state of 3, single crystals of the …