Physical Sciences and Mathematics Commons^™

Analytical And Numerical Studies Of Photo-Injected Charge Transport In Molecularly-Doped Polymers, Amrita Roy Chowdhury

Doctoral Dissertations

"The mobility of photo-injected charge carriers in molecularly-doped polymers (MDPs) exhibits a commonly observed, and nearly universal Poole-Frenkel field dependence, µ ~ exp [square root (ß₀E)], that has been shown to arise from the correlated Gaussian energy distribution of transport sites encountered by charges undergoing hopping transport through the material. Analytical and numerical studies of photo-injected charge transport in these materials are presented here with an attempt to understand how specific features of the various models developed to describe these systems depend on the microscopic parameters that define them. Specifically, previously published time-of-flight mobility data for the molecularly …

Essays On Unit Root Testing In Time Series, Xiao Zhong

Doctoral Dissertations

"Unit root tests are frequently employed by applied time series analysts to determine if the underlying model that generates an empirical process has a component that can be well-described by a random walk. More specifically, when the time series can be modeled using an autoregressive moving average (ARMA) process, such tests aim to determine if the autoregressive (AR) polynomial has one or more unit roots. The effect of economic shocks do not diminish with time when there is one or more unit roots in the AR polynomial, whereas the contribution of shocks decay geometrically when all the roots are outside …

Long-Term Litter Decomposition Controlled By Manganese Redox Cycling, Marco Keiluweit, Peter Nico, Mark E. Harmon, Jingdong Mao, Jennifer Pett-Ridge, Markus Kleber

Chemistry & Biochemistry Faculty Publications

Litter decomposition is a keystone ecosystem process impacting nutrient cycling and productivity, soil properties, and the terrestrial carbon (C) balance, but the factors regulating decomposition rate are still poorly understood. Traditional models assume that the rate is controlled by litter quality, relying on parameters such as lignin content as predictors. However, a strong correlation has been observed between the manganese (Mn) content of litter and decomposition rates across a variety of forest ecosystems. Here, we show that long-term litter decomposition in forest ecosystems is tightly coupled to Mn redox cycling. Over 7 years of litter decomposition, microbial transformation of litter …

On Testing Common Indices For Several Multi-Index Models: A Link-Free Approach, Xuejing Liu

Doctoral Dissertations

"To avoid the curse of dimensionality, and to help us better understand the structure of the high dimensional data, methods for dimension reduction are clearly called for. The common linear dimension reduction techniques for single population include principal component analysis (PCA) which is unsupervised in regression and supervised Partial Least Squares (PLS). Modern sufficient dimension reduction techniques, like the ones we consider, constitute a form of supervised linear dimension reduction which outperform PCA and PLS without the underlying model assumptions.

In practice, we often deal with situations where the same variables are being measured on objects from different groups, and …

Occurrence, Monitoring And Removal Of Drinking Water Contaminants By Advanced Technologies, Danielle Marie West

Doctoral Dissertations

"In order to maintain drinking water primary standards compliance under the USEPA Stage 2 Disinfectant Disinfection Byproducts Rule, drinking water treatment plants (DWTPs) are switching from free chlorine (FC) to chloramines (MCA). Concerns are raised as MCA disinfection has been linked N-nitrosamine formation. N-nitrosamines are a group of nitrogenous DBPs (N-DBPs) which are highly carcinogenic in comparison to regulated DBPs (THMs and HAAs, generated by FC disinfection). Also in the forefront of drinking water concerns are other emerging drinking water contaminants such as perchlorate. Perchlorate is a contaminant which can enter drinking water from natural deposits or through introduction by …

Nano-Structured Materials For Energy Storage Applications, Dongxue Zhao

Doctoral Dissertations

"Hydrogen is a non-polluting and efficient energy carrier. One barrier to utilizing hydrogen is a reliable storage method. NaAlH₄ is the prototypical example of a complex metal hydride with high hydrogen storage capacities (~ 5.5 wt.%) and acceptable reaction temperatures of around 100⁰ when using catalyst. On decomposition of these complex hydrides, such as NaAlH₄, one is left with monohydride NaH. The kinetics of diffusion in the monohydrides is important because reversibility hinges on mass transport and the formation of [AlH₄]^- anions that must structurally coordinate with the alkali metal cation on hydrogen absorption. …

Discrete Analogues Of Some Classical Special Functions, Thomas Joseph Cuchta

Doctoral Dissertations

"Analogues of special functions on time scales are studied with special focus on the time scale 𝕋 = hℤ. Functions investigated in particular include complex monomials, new trigonometric functions, Gaussian bell, Hermite and Laguerre polynomials, Bessel functions, and hypergeometric series"--Abstract, page iii.

Small Sample Saddlepoint Confidence Intervals In Epidemiology, Pasan Manuranga Edirisinghe

Doctoral Dissertations

"In section 1, we develop a novel method of confidence interval construction for directly standardized rates. These intervals involve saddlepoint approximations to the intractable distribution of a weighted sum of Poisson random variables and the determination of hypothetical Poisson mean values for each of the age groups. Simulation studies show that, in terms of coverage probability and length, the saddlepoint confidence interval (SP) outperforms four competing confidence intervals obtained from the moment matching (M8), gamma-based (G1,G4) and ABC bootstrap (ABC) methods.

In section 2, we first consider Brillinger's classical model for a vital rate estimate with a random denominator. We …

Characterization Of Terrestrial Dissolved Organic Matter Fractionated By Ph And Polarity And Their Biological Effects On Plant Growth, Rachel L. Sleighter, Paolo Caricasole, Kristen M. Richards, Terry Hanson, Patrick G. Hatcher

Chemistry & Biochemistry Faculty Publications

Background: Humic substances are ubiquitous in the environment, complex mixtures, and known to be beneficial to plant growth. To better understand and identify components responsible for plant growth stimulation, a terrestrial aquatic DOM sample was fractionated according to pH and polarity, obtaining acid-soluble and acid-insoluble portions, as well as acid-soluble hydrophobic and hydrophilic fractions using C18. The various fractions were characterized then evaluated for their biological effects on plant growth using bioassays with corn at two carbon rates.

Results: Approximately 43% and 57% of the carbon, and 31% and 69% of the iron, was found in the acid-insoluble and acid-soluble …

Small Sample Umpu Equivalence Testing Based On Saddlepoint Approximations, Renren Zhao

Doctoral Dissertations

"In the first section, we consider small sample equivalence tests for exponentiality. Statistical inference in this setting is particularly challenging since equivalence testing procedures typically require a much larger sample size, in comparison to classical "difference tests", to perform well. We make use of Butler's marginal likelihood for the shape parameter of a gamma distribution in our development of equivalence tests for exponentiality. We consider two procedures using the principle of confidence interval inclusion, four Bayesian methods, and the uniformly most powerful unbiased (UMPU) test where a saddlepoint approximation to the intractable distribution of a canonical sufficient statistic is used. …

Quantum Inspired Algorithms For Learning And Control Of Stochastic Systems, Karthikeyan Rajagopal

Doctoral Dissertations

"Motivated by the limitations of the current reinforcement learning and optimal control techniques, this dissertation proposes quantum theory inspired algorithms for learning and control of both single-agent and multi-agent stochastic systems.

A common problem encountered in traditional reinforcement learning techniques is the exploration-exploitation trade-off. To address the above issue an action selection procedure inspired by a quantum search algorithm called Grover's iteration is developed. This procedure does not require an explicit design parameter to specify the relative frequency of explorative/exploitative actions.

The second part of this dissertation extends the powerful adaptive critic design methodology to solve finite horizon stochastic optimal …

Efficient Cryptographic Primitives: Secure Comparison, Binary Decomposition And Proxy Re-Encryption, Feng Li

Doctoral Dissertations

”Data outsourcing becomes an essential paradigm for an organization to reduce operation costs on supporting and managing its IT infrastructure. When sensitive data are outsourced to a remote server, the data generally need to be encrypted before outsourcing. To preserve the confidentiality of the data, any computations performed by the server should only be on the encrypted data. In other words, the encrypted data should not be decrypted during any stage of the computation. This kind of task is commonly termed as query processing over encrypted data (QPED).

One natural solution to solve the QPED problem is to utilize fully …

Transverse Momentum Dependent (Tmd) Parton Distribution Functions: Status And Prospects, R. Angeles-Martinez, A. Bacchetta, I. I. Balitsky, D. Boer, M. Boglione, R. Boussarie, F. A. Ceccopieri, I. O. Cherednikov, P. Connor, M. G. Echevarria, G. Ferrera, J. Grados Luyando, F. Hautmann, H. Jung, T. Kasemets, K. Kutak, J. P. Lansberg, A. Lelek, G. Lykasov, J. D. Madrigal Martinez, P. J. Mulders, E. R. Nocera, E. Petreska, C. Pisano, R. Plaċakyte, V. Radescu, M. Radici, G. Schnell, I. Scimemi, A. Signori, L. Szymanowski, S. Taheri Monfared, F.F. Van Der Veken, H. J. Van Haevermaet, P. Van Mechelen, A. A. Vladimirov, S. Wallon

Physics Faculty Publications

We review transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum q_T spectra of Higgs and vector bosons for low q_T, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present the application of a new tool, TMD_LIB, to parton density fits and parameterizations.

Development Of Srf Cavity Tuners For Cern, K. Artoos, R. Calaga, O. Capatina, T. Capelli, F. Carra, L. Dassa, N. Kuder, R. Leuxe, P. Minginette, W. Venturini Delsolaro, G. Villiger, C. Zanoni, P. Zhang, S. Verdu-Andrés, B. Xiao, G. Burt, J. Delayen, Hyekyoung Park, T. Jones, N. Templeton

Physics Faculty Publications

Superconducting RF cavity developments are currently on-going for new accelerator projects at CERN such as HIE ISOLDE and HL-LHC. Mechanical RF tuning systems are required to compensate cavity frequency shifts of the cavities due to temperature, mechanical, pressure and RF effects on the cavity geometry. A rich history and experience is available for such mechanical tuners developed for existing RF cavities. Design constraints in the context of HIE ISOLDE and HL-LHC such as required resolution, space limitation, reliability and maintainability have led to new concepts in the tuning mechanisms. This paper will discuss such new approaches, their performances and planned …

Control Of Synchrotron Radiation Effects During Recirculation With Bunch Compression, D. R. Douglas, S. V. Benson, R. Li, Y. Roblin, C. D. Tennant, Geoffrey A. Krafft, Balŝa Terzić, C. -Y. Tsai

Physics Faculty Publications

Studies of beam quality preservation during recirculation * have been extended to generate a design of a compact arc providing bunch compression with positive momentum compaction ** and control of both incoherent and coherent synchrotron radiation (ISR and CSR) effects using the optics balance methods of diMitri et al.***. In addition, the arc/compressor generates very little micro-bunching gain. We detail the beam dynamical basis for the design, discuss the design process, give an example solution, and provide simulations of ISR and CSR effects. Reference will be made to a complete analysis of micro-bunching effects ****.

Anisotropy Reversal Of The Upper Critical Field At Low Temperatures And Spin-Locked Superconductivity In K₂Cr₃As₃, F. F. Balakirev, T. Kong, M. Jaime, R. D. Mcdonald, C. H. Mielke, A. Gurevich, P. C. Canfield, S. L. Bud'ko

Physics Faculty Publications

We report measurements of the anisotropic upper critical field H_c2(T) for K₂Cr₃As₃ single crystals up to 60 T and T > 0.6K. Our results show that the upper critical field parallel to the Cr chains, H^∥_c2(T), exhibits a paramagnetically limited behavior, whereas the shape of the H^⊥_c2(T) curve (perpendicular to the Cr chains) has no evidence of paramagnetic effects. As a result, the curves H^⊥_c2(T) and H^∥_c2(T) cross at T ≈ 4K, so that the anisotropy parameter _H(T)=H …

Current-Induced Depairing In The Bi₂Te₃/Fete Interfacial Superconductor, M. N. Kunchur, C. L. Dean, N. Shayesteh Moghadam, J. M. Knight, Q. L. He, H. Liu, J. Wang, R. Lortz, I. K. Sou, Alex Gurevich

Physics Faculty Publications

We investigated current induced depairing in the Bi₂Te₃/FeTe topological insulator-chalcogenide interface superconductor. The measured depairing current density provides information on the magnetic penetration depth and superfluid density, which in turn shed light on the nature of the normal state that underlies the interfacial superconductivity.

Virtuality Distributions And Pion Transition Form Factor, A. V. Radyushkin

Physics Faculty Publications

Using the example of hard exclusive transition process ᵞ*ᵞ → π⁰ at the handbag level, we outline basics of a new approach to transverse momentum dependence in hard processes. In coordinate representation, matrix elements of operators (in the simplest case, bilocal 𝒪(0, z)) describing a hadron with momentum p, are functions of (pz) and z² parametrized through virtuality distribution amplitudes (VDA) Φ(x, σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z2. For intervals with z⁺ = 0, we introduce the transverse momentum distribution amplitude (TMDA) Ψ(x, k_⊥), and write it in terms of VDA …

Question 1: Star Speeds; Question 2: Slurping Gasoline, Larry Weinstein

Physics Faculty Publications

One piece of evidence that the center of our galaxy contains a super-massive black hole came from measuring the speed of a star orbiting that black hole. What is the maximum speed of that star?

If instead of carrying their gas in fuel tanks, cars “slurped up” a stream of gas as they drove, how thick a stream of gas would each car need?

Question 1: "Up" — A Fermi Question About Buoyancy; Question 2: Traffic Jams, Larry Weinstein

Physics Faculty Publications

Is it possible for a house to fly by the uplift of balloons, like in the movie "Up"? (written by R. Allart, A. Cazenave, and A. Müller, University of Geneva)

How much total time do Americans spend waiting in traffic each year? What is the total cost of this time?

Question 1: Shaving Time; Question 2: Half-Filling The Gas Tank, Larry Weinstein

Physics Faculty Publications

How much total time does a typical American spend shaving during his or her life? How much total time per year do Americans spend shaving?

How much money can you save by only half-filling your car's gas tank to reduce weight?

Question 1: Kill The K-Cup; Question 2: Water Cooling, Larry Weinstein

Physics Faculty Publications

According to KillTheKCup.org, single-use non-recyclable Keurig K-cups “are killing our planet.” How large is the environmental impact of K-Cups?

How much more cooling do you get from drinking cold rather than room-temperature water on a hot day? How much do you sweat per day when the ambient temperature is about 35 °C (95 °F)?

Minimally Nonlocal Nucleon-Nucleon Potentials With Chiral Two-Pion Exchange Including Δ Resonances, M. Piarulli, L. Girlanda, Rocco Schiavilla, R. Navarro Pérez, J. E. Amaro, E. Ruiz Arriola

Physics Faculty Publications

We construct a coordinate-space chiral potential, including Δ -isobar intermediate states in its two-pion-exchange component up to order Q³ (Q denotes generically the low momentum scale). The contact interactions entering at next-to-leading and next-to-next-to-next-to-leading orders (Q² and Q⁴ , respectively) are rearranged by Fierz transformations to yield terms at most quadratic in the relative momentum operator of the two nucleons. The low-energy constants multiplying these contact interactions are fitted to the 2013 Granada database, consisting of 2309 pp and 2982 np data (including, respectively, 148 and 218 normalizations) in the laboratory-energy range 0–300 MeV. For the total …

Precision Measurement Of The Longitudinal Double-Spin Asymmetry For Inclusive Jet Production In Polarized Proton Collisions At √S= 200gev, L. Adamczyk, J.K. Adkins, G. Agakishiev, S. Bültmann, I. Koralt, Star Collaboration

Physics Faculty Publications

We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, A_LL, in polarized pp collisions at center-of-mass energy √s = 200 GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. The measured asymmetries provide evidence at the 3σ level for positive gluon polarization in the Bjorken-x region x > 0.05.

Cross Sections For The Exclusive Photon Electroproduction On The Proton And Generalized Parton Distributions, H. S. Jo, D. Adikaram, M. J. Amaryan, L. El Fassi, N. Guler, A. Klein, S E. Kuhn, Y. Prok, L. B. Weinstein, J. Zhang, Z. W. Zhao

Physics Faculty Publications

Unpolarized and beam-polarized fourfold cross sections (d⁴σ/dQ²dx_Bdtdϕ) for the ep → e'p'γ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 (Q²;x_B;t) bins over the widest phase space ever explored in the valence-quark region. Several models of generalized parton distributions (GPDs) describe the data well at most of our kinematics. This increases our confidence that we understand the GPD H, expected to be the dominant contributor to these observables. Through a leading-twist …

Longitudinal Target-Spin Asymmetries For Deeply Virtual Compton Scattering, E. Seder, A. Biselli, S. Bültmann, A. Klein, S. E. Kuhn, Y. Prok, Clas Collaboration

Physics Faculty Publications

A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6 GeV electron beam, a longitudinally polarized proton target, and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for e p → e'p'ɣ events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in Q², x_B, t, and ɸ, for 166 four-dimensional bins. In the framework of generalized parton distributions, at leading twist the t dependence of these asymmetries provides insight into …

Precise Determination Of The Deuteron Spin Structure At Low To Moderate Q² With Clas And Extraction Of The Neutron Contribution, The Clas Collaboration, N. Guler, S E. Kuhn, Y. Prok, K. P. Adhikari, D. Adikaram, M. J. Amaryan, L. El Fassi, C. E. Hyde, A. Klein, L. B. Weinstein, Z. W. Zhao

Physics Faculty Publications

We present the final results for the deuteron spin structure functions obtained from the full data set collected in 2000–2001 with Jefferson Lab's continuous electron beam accelerator facility (CEBAF) using the CEBAF large acceptance spectrometer (CLAS). Polarized electrons with energies of 1.6, 2.5, 4.2, and 5.8 GeV were scattered from deuteron (¹⁵ND₃ ) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double-spin asymmetry, the virtual photon absorption asymmetry A^d₁ and the polarized structure function g^d₁ were extracted over a wide kinematic range (0.05GeV² < Q2 < 5GeV² and 0.9 …

A Facility For Magnetic Field Penetration Measurements On Multilayer S-I-S Structures, Oleg B. Malyshev, Lewis Gurran, Shrikant Pattalwar, Ninad Pattalwar, Keith D. Dumbell, Reza Valizadeh, Alex Gurevich

Physics Faculty Publications

Superconducting RF cavities made of bulk Nb has reached a breakdown field of about 200 mT which is close to the superheating field for Nb. As it was theoretically shown a multilayer coating can be used to enhance the breakdown field of SRF cavities. The simple example is a superconductor-insulator-superconductor (S-I-S), for example bulk niobium (S) coated with a thin film of insulator (I) followed by a thin layer of a superconductor (S) which could be a dirty niobium. To verify such an enhancement in a presence of a DC magnetic field at 4.2 K a simple experimental facility was …

Recent Developments In Superconducting Deflecting-Mode Cavities, J. R. Delayen

Physics Faculty Publications

In the last few years there has been a growing interest in compact superconducting cavities operating in a deflecting mode to be used either in rf separators or crabbing systems. This talk will give an overview of recent progress in global activities towards SRF deflecting mode cavities.

Engineering Design And Prototype Fabrication Of Hom Couplers For Hl-Lhc Crab Cavities, C. Zanoni, S. Atieh, I. Aviles Santillana, S. Belomestnykh, G. Burt, R. Calaga, S. U. De Silva, J. R. Delayen, R. Olave, H. Park

Physics Faculty Publications

The High-Luminosity upgrade for the LHC relies on a set of RF Crab Cavities for reaching its goals. Two parallel concepts, the Double Quarter Wave (DQW) and the RF Dipole (RFD), are going through a comprehensive design process along with preparation of fabrication in view of extensive tests with beam in SPS. High Order Modes (HOM) couplers are critical in providing damping in RF cavities for operation in accelerators. HOM prototyping and fabrication have recently started at CERN. In this paper, an overview of the final shape is provided along with an insight in the mechanical and thermal analyses performed …