Physics Commons^™

Demonstration Of Ultra-High Recyclable Energy Densities In Domain-Engineered Ferroelectric Films, Hongbo Cheng, Jun Ouyang, Yun-Xiang Zhang, David J. Ascienzo, Yao Li, Yu-Yao Zhao, Yuhang Ren

Publications and Research

Dielectric capacitors have the highest charge/discharge speed among all electrical energy devices, but lag behind in energy density. Here we report dielectric ultracapacitors based on ferroelectric films of Ba(Zr0.2,Ti0.8)O3 which display high-energy densities (up to 166 J cm–3) and efficiencies (up to 96%). Different from a typical ferroelectric whose electric polarization is easily saturated, these Ba(Zr0.2,Ti0.8)O3 films display a much delayed saturation of the electric polarization, which increases continuously from nearly zero at remnant in a multipolar state, to a large value under the maximum electric field, leading to drastically improved recyclable energy densities. This is achieved by the creation …

Dynamic Self-Assembly And Self-Organized Transport Of Magnetic Micro-Swimmers, Gašper Kokot, German Kolmakov V, Igor S. Aranson, Alexey Snezhko

Publications and Research

We demonstrate experimentally and in computer simulations that magnetic microfloaters can self-organize into various functional structures while energized by an external alternating (ac) magnetic field. The structures exhibit self-propelled motion and an ability to carry a cargo along a pre-defined path. The morphology of the self-assembled swimmers is controlled by the frequency and amplitude of the magnetic field.

Experiential Learning Opportunity (Elo) And Utilization Of Field-And-Data- Based Information Obtained Through The Infusion Of Technology: Highlights On Nasa Stem And Earth Science Curricula, Nazrul I. Khandaker, Matthew Khargie, Shuayb Siddiqu, Sol De Leon, Katina Singh, Newrence Wills, Krishna Mahibar

Publications and Research

There is a greater emphasis on hands-on involvement and critical thinking skills in the geosciences and other STEM fields to inspire and engage K- 16 students to value scientific content and enable them to discover the well-documented nature of the fundamental scientific principles needed to explain various earth science and other STEM-related core phenomena. NASA MAA curricula are ideal for engaging K1-16 students in this context, since grade-specific lesson plans open-up a plethora of pedagogically sound and relevant earth science activities. These include earth’s materials and properties, meteorites, robotics, hot air balloon, flight simulation, star gazing, material science, crystal growth, …

Detecting Majorana Fermion Induced Crossed Andreev Reflection, Lei Fang

Dissertations, Theses, and Capstone Projects

This dissertation is devoted to a study of detecting the Majorana fermion induced crossed Andreev reflection.

Majorana fermions are particles that constitute their own antiparticles. In condensed matter physics, Majorana fermions are zero energy modes that reside at edges or around vortices of topological superconductors. The special properties of Majorana fermions result in their potential to conduct topological quantum computation, which has been attracting a lot of current research. One of the most important issues in the field of the Majorana fermion physics now is to detect their existence in realistic systems. Among many classes of detecting methods, a transport …

Stochastic Resonance In A Proton Pumping Complex I Of Mitochondria Membranes, Davneet Kaur, Ilan Filonenko, Lev Mourokh, Cornelius Fendler, Robert H. Blick

Publications and Research

We make use of the physical mechanism of proton pumping in the so-called Complex I within mitochondria membranes. Our model is based on sequential charge transfer assisted by conformational changes which facilitate the indirect electron-proton coupling. The equations of motion for the proton operators are derived and solved numerically in combination with the phenomenological Langevin equation describing the periodic conformational changes. We show that with an appropriate set of parameters, protons can be transferred against an applied voltage. In addition, we demonstrate that only the joint action of the periodic energy modulation and thermal noise leads to efficient uphill proton …

Continuum Electrostatics Analysis Of The Kok Cycle Of Photosystem Ii, Witold Szejgis

Dissertations, Theses, and Capstone Projects

The Kok cycle is catalytic process by which the oxygen-evolving complex (OEC) of photosystem II (PSII) oxidizes two water molecules forming oxygen. Four OEC oxidation states (S₀ to S₃) in the Kok cycle precede the final product formation in the S₄ state. Here a semi-empirical classical electrostatics analysis is applied to S₀ to S₃ states of the OEC is used to estimate the electrochemical midpoints for each S-state transition and the proton loss coupled to oxidation. To account for geometrical rearrangement within the cluster during Kok cycle optimized QM/MM geometries are used for each …

Nonlinear Optical Studies Of Defects And Domain Structures In Perovskite-Type Dielectric Ceramics, David J. Ascienzo

Dissertations, Theses, and Capstone Projects

In order to improve future generations of dielectric capacitors a deeper understanding of voltage-induced dielectric breakdown and electrical energy storage limitations is required. This dissertation presents the use of far-field optical second harmonic generation (SHG) polarimetry for probing structural defects and polar domains in linear and nonlinear perovskite dielectric ceramics. We investigated the formation of electric field-induced structural distortions at pristine Fe-doped SrTiO₃ (Fe:STO) electrode interfaces, structural defect and strain formation due to oxygen vacancy migration in electrodegraded Fe:STO single crystals, and mixed tetragonal and rhombohedral phase domains in ferroelectric Zr-doped BaTiO₃ (BZT) films exhibiting excellent …

Characterization Of Hydrophobic Interactions Of Polymers With Water And Phospholipid Membranes Using Molecular Dynamics Simulations, Mihaela Drenscko

Dissertations, Theses, and Capstone Projects

Polymers and lipid membranes are both essential soft materials. The structure and hydrophobicity/hydrophilicity of polymers, as well as the solvent they are embedded in, ultimately determines their size and shape. Understating the variation of shape of the polymer as well as its interactions with model biological membranes can assist in understanding the biocompatibility of the polymer itself. Computer simulations, in particular molecular dynamics, can aid in characterization of the interaction of polymers with solvent, as well as polymers with model membranes. In this thesis, molecular dynamics serve to describe polymer interactions with a solvent (water) and with a lipid membrane. …

Control Of Light-Matter Interaction In 2d Semiconductors, Zheng Sun

Dissertations, Theses, and Capstone Projects

In this thesis we discuss the control of light matter interaction in low dimensional nanostructure cavity light confining structures. These structures have controllable dispersion properties through design which can be exploited to modify the interaction of light and matter. We will discuss two different types of light confining microcavities: a dielectric cavity and a metal cavity. The specific design of the cavity gives rise to the confinement of the electric field in the center where the nano-materials are placed. In this work, the main material was on the new class of two- dimensional semiconductors of transition metal dichalcogenides (TMDs). Due …

A Realization Of Modernity: Case Studies In Connectivity And Time, Mari Gorman

Dissertations, Theses, and Capstone Projects

My stated goal in applying to The Graduate Center was to explore my previous research in diverse fields of study. This research, the result of a formal investigation of acting, was and still is centrally focused on the subject of relationship itself, relationships being what actors create. In pursuit of a greater understanding of the essential nature of relationship in practical terms, a self-organizing complex system that constitutes universal relationship was unexpectedly discovered. As such, this system has been shown to offer solutions to many outstanding problems in diverse areas of study. The Liberal Studies program track, Approaches to Modernity …

Nuclear Magnetic Resonance Studies Of Electrode And Electrolyte Materials For Li-Ion Batteries, Lisa Cirrincione

Dissertations, Theses, and Capstone Projects

In this thesis, Nuclear Magnetic Resonance (NMR) spectroscopic techniques are used to study lithium electrode and electrolyte materials for advanced rechargeable lithium ion batteries. Three projects are described in this thesis. The first involves ²³Na and ³⁷Al static and magic angle spinning NMR studies of NaAlH₄/C anode materials for advanced rechargeable batteries. The second project is a study of paramagnetic lithium transition-metal phosphate cathode materials for Li-ion batteries, where ⁷Li, and ³¹P single crystal NMR was used in order to obtain detailed information on the local electronic and magnetic environments. The third project investigates …

Elliptic Genera Of 2d (0,2) Gauge Theories From Brane Brick Models, Sebastian Franco, Dongwook Ghim, Sangmin Lee, Rak-Kyeong Seong

Publications and Research

We compute the elliptic genus of abelian 2d (0, 2) gauge theories corresponding to brane brick models. These theories are worldvolume theories on a single D1-brane probing a toric Calabi-Yau 4-fold singularity. We identify a match with the elliptic genus of the non-linear sigma model on the same Calabi-Yau background, which is computed using a new localization formula. The matching implies that the quantum effects do not drastically alter the correspondence between the geometry and the 2d (0, 2) gauge theory. In theories whose matter sector suffers from abelian gauge anomaly, we propose an ansatz for an anomaly …

Holography For Field Theory Solitons, Sophia K. Domokos, Andrew B. Royston

Publications and Research

We extend a well-known D-brane construction of the AdS/dCFT correspondence to non-abelian defects. We focus on the bulk side of the correspondence and show that there exists a regime of parameters in which the low-energy description consists of two approximately decoupled sectors. The two sectors are gravity in the ambient spacetime, and a six-dimensional supersymmetric Yang-Mills theory. The Yang-Mills theory is defined on a rigid AdS4 S2 background and admits sixteen supersymmetries. We also consider a one-parameter deformation that gives rise to a family of Yang-Mills theories on asymptotically AdS4 S2 spacetimes, which are invariant under eight supersymmetries. With future …

Quadrality For Supersymmetric Matrix Models, Sebastian Franco, Sangmin Lee, Rak-Kyeong Seong, Cumrun Vafa

Publications and Research

We introduce a new duality for N = 1 supersymmetric gauged matrix models. This 0d duality is an order 4 symmetry, namely an equivalence between four different theories, hence we call it Quadrality. Our proposal is motivated by mirror symmetry, but is not restricted to theories with a D-brane realization and holds for general N = 1 matrix models. We present various checks of the proposal, including the matching of: global symmetries, anomalies, deformations and the chiral ring. We also consider quivers and the corresponding quadrality networks. Finally, we initiate the study of matrix models that arise on the worldvolume …

Quantum Optical Interferometry And Quantum State Engineering, Richard J. Birrittella Jr

Dissertations, Theses, and Capstone Projects

We highlight some of our research done in the fields of quantum optical interferometry and quantum state engineering. We discuss the body of work for which our research is predicated, as well as discuss some of the fundamental tenants of the theory of phase estimation. We do this in the context of quantum optical interferometry where our primary interest lies in the calculation of the quantum Fisher information as it has been shown that the minimum phase uncertainty obtained, the quantum Cramer-Rao bound, is saturated by parity-based detection methods. We go on to show that the phase uncertainty one obtains …

Wave Propagation Inside Random Media, Xiaojun Cheng

Dissertations, Theses, and Capstone Projects

This thesis presents results of studies of wave scattering within and transmission through random and periodic systems. The main focus is on energy profiles inside quasi-1D and 1D random media.

The connection between transport and the states of the medium is manifested in the equivalence of the dimensionless conductance, g, and the Thouless number which is the ratio of the average linewidth and spacing of energy levels. This equivalence and theories regarding the energy profiles inside random media are based on the assumption that LDOS is uniform throughout the samples. We have conducted microwave measurements of the longitudinal energy profiles …

Light-Induced Electrohydrodynamic Instability In Plasmonically Absorbing Gold Nanofluids, Sujan Shrestha, Luat T. Vuong, Jorge Luis Dominguez-Juarez

Publications and Research

Plasmonically absorbing nanofluids exhibit light-induced electrokinetics. We measure an electrical response to the light-induced Rayleigh-Bénard-Marangoni convective instabilities in gold-polyvinylpyrrolidone (PVP) nanoparticles (NPs) suspended in isopropanol and water. Microampere current oscillations are measured and attributed to the presence of the Au-PVP NPs with negative zeta potential, in correspondence with the accompanying thermal lens oscillations and a nanofluid thermoelectric effect. The measured electrical oscillations represent an electrohydrodynamic stability driven by light, one among many that should be observed with plasmonic nanoparticles in liquids.

Tunneling Of Hybridized Pairs Of Electrons Through A One-Dimensional Channel, Godfrey Gumbs, Danghong Huang, Julie Hon, M. Pepper, Sanjeev Kumar

Publications and Research

Recently, the electron transport through a quasi-one dimensional (quasi-1D) electron gas was investigated experimentally as a function of the confining potential. We present a physical model for quantum ballistic transport of electrons through a short conduction channel, and investigate the role played by the Coulomb interaction in modifying the energy levels of twoelectron states at low temperatures as the width of the channel is increased. In this regime, the effect of the Coulomb interaction on the two-electron states has been shown to lead to four split energy levels, including two anticrossings and two crossinglevel states. Due to the interplay between …

General Astronomy 110 Syllabus (Zero Textbook Cost), Carlos Chaparro

Open Educational Resources

The spring 2017 syllabus for the General Astronomy Course (AST 110), developed as part of the textbook free courseware initiative at Borough of Manhattan Community College.

Glass Polymorphism In Glycerol–Water Mixtures: I. A Computer Simulation Study, David A. Jahn, Jessina Wong, Johannes Bachler, Thomas Loerting, Nicolas Giovambattista

Publications and Research

We perform out-of-equilibrium molecular dynamics (MD) simulations of water–glycerol mixtures in the glass state. Specifically, we study the transformations between low-density (LDA) and high-density amorphous (HDA) forms of these mixtures induced by compression/decompression at constant temperature. Our MD simulations reproduce qualitatively the density changes observed in experiments. Specifically, the LDA–HDA transformation becomes (i) smoother and (ii) the hysteresis in a compression/ decompression cycle decreases as T and/or glycerol content increase. This is surprising given the fast compression/decompression rates (relative to experiments) accessible in MD simulations. We study mixtures with glycerol molar concentration wg = 0–13% and find that, for the …

Orbifold Reduction And 2d (0,2) Gauge Theories, Sebastian Franco, Sangmin Lee, Rak-Kyeong Seong

Publications and Research

We introduce Orbifold Reduction, a new method for generating 2d (0; 2) gauge theories associated to D1-branes probing singular toric Calabi-Yau 4-folds starting from 4d N = 1 gauge theories on D3-branes probing toric Calabi-Yau 3-folds. The new procedure generalizes dimensional reduction and orbifolding. In terms of T-dual configurations, it generates brane brick models starting from brane tilings. Orbifold reduction provides an agile approach for generating 2d (0; 2) theories with a brane realization. We present three practical applications of the new algorithm: the connection between 4d Seiberg duality and 2d triality, a combinatorial method for generating theories related by …

Nnll Resummation For The Associated Production Of A Top Pair And A Higgs Boson At The Lhc, Alessandro Broggio, Andrea Ferroglia, Ben D. Pecjak, Li Lin Yang

Publications and Research

We study the resummation of soft gluon emission corrections to the production of a top-antitop pair in association with a Higgs boson at the Large Hadron Collider. Starting from a soft-gluon resummation formula derived in previous work, we develop a bespoke parton-level Monte Carlo program which can be used to calculate the total cross section along with differential distributions. We use this tool to study the phenomenological impact of the resummation to next-to-next-to-leading logarithmic (NNLL) accuracy, finding that these corrections increase the total cross section and the differential distributions with respect to NLO calculations of the same observables.

Brane Brick Models In The Mirror, Sebastian Franco, Sangmin Lee, Rak-Kyeong Seong, Cumrun Vafa

Publications and Research

Brane brick models are Type IIA brane configurations that encode the 2d N = (0; 2) gauge theories on the worldvolume of D1-branes probing toric Calabi-Yau 4-folds. We use mirror symmetry to improve our understanding of this correspondence and to provide a systematic approach for constructing brane brick models starting from geometry. The mirror configuration consists of D5-branes wrapping 4-spheres and the gauge theory is determined by how they intersect. We also explain how 2d (0; 2) triality is realized in terms of geometric transitions in the mirror geometry. Mirror symmetry leads to a geometric unification of dualities in different …

The Effects Of Tilted Magnetic Fields On Quantum Transport In 2d Electron Systems, William A. Mayer

Dissertations, Theses, and Capstone Projects

There exists a myriad of quantum transport phenomena in highly mobile 2D electrons placed in a perpendicular magnetic field. We study the effects of tilted magnetic field on these transport properties to understand how the energy spectrum evolves. We observe significant changes of the electron transport in quantum wells of varying widths with high electron densities at high filling factors. In narrow quantum wells the spin splitting of Landau levels due to Zeeman effect is found to be the dominant mechanism reducing Quantum Positive Magnetoresistance. In wider quantum wells with two populated subbands Magnetointersubband oscillations appear to exhibit effects from …

Second Harmonic Generation – A Novel Approach In Retinal Imaging, Denis Y. Sharoukhov

Dissertations, Theses, and Capstone Projects

Here we present the utilization of Second Harmonic Generation (SHG) for label-free imaging of microtubules (MTs) in the retinal nerve fiber layer (RNFL). MTs are an important part of axonal cytoskeleton, providing structural support and serving as a railroad in intracellular transport. We demonstrate the application of SHG microscopy to the following studies: 1) Can changes in MT conformation be detected when treated with a stabilizing drug (Taxol); 2) if disruption in MT precedes loss of axons in a mouse model of glaucoma (DBA/2J); and 3) if elevated levels of intraocular pressure affect MT integrity. Our results validate SHG imaging …

Optical Forces Generated By Plasmonic Nanostructures, Matthew A. Moocarme

Dissertations, Theses, and Capstone Projects

For millennia, scientists have sought to uncover the secrets of what holds the world together. Optical physicists are often at the forefront, unraveling material properties through investigations of light-matter interactions. As the field has progressed, the smallest unit at which matter can be probed and manipulated has subsequently decreased. The resulting sub-field nanophotonics- which reflects the processing of light at the nanoscale- has blossomed into a vast design space for both applied and theoretical researchers. Plasmonics, the phenomena by which the electron-density of a material oscillates in response to incident electromagnetic radiation, is a subject that has excited nanophotonics researchers …

Supergroups In Critical Dimensions And Division Algebras, Čestmir Burdik, Sultan Catto, Yasemin Gürcan, Amish Khalfan, Levent Kurt, V. Kato La

Publications and Research

We establish a link between classical heterotic strings and the groups of the magic square associated with Jordan algebras, allowing for a uniform treatment of the bosonic and superstring sectors of the heterotic string.

Schrödinger Theory Of Electrons In Electromagnetic Fields: New Perspectives, Viraht Sahni, Xiao-Yin Pan

Publications and Research

The Schrödinger theory of electrons in an external electromagnetic field is described from the new perspective of the individual electron. The perspective is arrived at via the time-dependent "Quantal Newtonian" law (or differential virial theorem). (The time-independent law, a special case, provides a similar description of stationary-state theory). These laws are in terms of "classical" fields whose sources are quantal expectations of Hermitian operators taken with respect to the wave function. The laws reveal the following physics: (a) in addition to the external field, each electron experiences an internal field whose components are representative of a specific property of the …

Rules And Mechanisms For Efficient Two-Stage Learning In Neural Circuits, Tiberiu Teşileanu, Bence Ölveczky, Vijay Balasubramanian

Publications and Research

Trial-and-error learning requires evaluating variable actions and reinforcing successful variants. In songbirds, vocal exploration is induced by LMAN, the output of a basal ganglia-related circuit that also contributes a corrective bias to the vocal output. This bias is gradually consolidated in RA, a motor cortex analogue downstream of LMAN. We develop a new model of such two-stage learning. Using stochastic gradient descent, we derive how the activity in ‘tutor’ circuits (e.g., LMAN) should match plasticity mechanisms in ‘student’ circuits (e.g., RA) to achieve efficient learning. We further describe a reinforcement learning framework through which the tutor can build its teaching …

Electron Correlations In An Excited State Of A Quantum Dot In A Uniform Magnetic Field, Marlina Slamet, Viraht Sahni

Publications and Research

Electron correlations in a two-electron two-dimensional ‘artificial atom’ or quantum dot (with harmonic confining potential) in the presence of a uniform magnetic field in an excited singlet state are studied via quantal density functional theory (QDFT). QDFT allows for the separation of the electron correlations due to the Pauli exclusion principle and Coulomb repulsion, as well as the determination of the contribution of these correlations to the kinetic energy. The QDFT mapping is from the excited state of the quantum dot to one of noninteracting fermions in their ground state possessing the same basic variables of the density and physical …