Physics Commons^™

Zno Nanoparticles Modulate The Ionic Transport And Voltage Regulation Of Lysenin Nanochannels, Sheenah L. Bryant, Josh E. Eixenberger, Steven Rossland, Holly Apsley, Connor Hoffman, Nisha Shrestha, Michael Mchugh, Alex Punnoose, Daniel Fologea

Physics Faculty Publications and Presentations

Background: The insufficient understanding of unintended biological impacts from nanomaterials (NMs) represents a serious impediment to their use for scientific, technological, and medical applications. While previous studies have focused on understanding nanotoxicity effects mostly resulting from cellular internalization, recent work indicates that NMs may interfere with transmembrane transport mechanisms, hence enabling contributions to nanotoxicity by affecting key biological activities dependent on transmembrane transport. In this line of inquiry, we investigated the effects of charged nanoparticles (NPs) on the transport properties of lysenin, a pore-forming toxin that shares fundamental features with ion channels such as regulation and high transport rate.

Results: …

Confined Photonic Mode Propagation Observed In Photoemission Electron Microscopy, Theodore Stenmark, Robert Campbell Word, Rolf Konenkamp

Physics Faculty Publications and Presentations

Using photoemission electron microscopy (PEEM) we present a comparative analysis of the wavelength dependence of propagating fields in a simple optical slab waveguide and a thin film photonic crystal W1-type waveguide. We utilize an interferometric imaging approach for light in the near-ultraviolet regime where a 2-photon process is required to produce photoelectron emission. The typical spatial resolution in these experiments is < 30 nm. Electromagnetic theory and finite element simulations are shown to be in good agreement with the experimental observations. Our results indicate that multiphoton PEEM is a useful sub-wavelength characterization technique in thin film optics.

Entropy Production And Volume Contraction In Thermostated Hamiltonian Dynamics, John D. Ramshaw

Physics Faculty Publications and Presentations

Patra et al. [Int. J. Bifurcat. Chaos 26, 1650089 (2016)] recently showed that the time-averaged rates of entropy production and phase-space volume contraction are equal for several different molecular dynamics methods used to simulate nonequilibrium steady states in Hamiltonian systems with thermostated temperature gradients. This equality is a plausible statistical analog of the second law of thermodynamics. Here we show that those two rates are identically equal in a wide class of methods in which the thermostat variables z are determined by ordinary differential equations of motion (i.e., methods of the Nosé-Hoover or integral feedback control type). This …

Mixing Times Of Organic Molecules Within Secondary Organic Aerosol Particles: A Global Planetary Boundary Layer Perspective, Adrian M. Maclean, Christopher L. Butenhoff, James W. Grayson, Kelley Barsanti, Jose L. Jimenez, Allan K. Bertram

Physics Faculty Publications and Presentations

When simulating the formation and life cycle of secondary organic aerosol (SOA) with chemical transport models, it is often assumed that organic molecules are well mixed within SOA particles on the timescale of 1 h. While this assumption has been debated vigorously in the literature, the issue remains unresolved in part due to a lack of information on the mixing times within SOA particles as a function of both temperature and relative humidity. Using laboratory data, meteorological fields, and a chemical transport model, we estimated how often mixing times are < 1 h within SOA in the planetary boundary layer (PBL), the region of the atmosphere where SOA concentrations are on average the highest. First, a parameterization for viscosity as a function of temperature and RH was developed for α-pinene SOA using room-temperature and low-temperature viscosity data for α-pinene SOA generated in the laboratory using mass concentrations of ∼ 1000 µg m−3. Based on this parameterization, the mixing times within α-pinene SOA are < 1 h for 98.5 % and 99.9 % of the occurrences in the PBL during January and July, respectively, when concentrations are significant (total organic aerosol concentrations are > 0.5 µg m−3 at the surface). Next, as a starting …

Ion Transport Across Biological Membranes By Carborane-Capped Gold Nanoparticles, Marcin P. Grzelczak, Stephen P. Danks, Robert C. Klipp, Domagoj Belic, Adnana Zaulet, Casper Kunstmann-Olsen, Dan F. Bradley, Tatsuya Tsukuda, Clara ViñAs, Francesc Teixidor, Jonathan J. Abramson, Mathias Brust

Physics Faculty Publications and Presentations

Carborane-capped gold nanoparticles (Au/carborane NPs, 2–3 nm) can act as artificial ion transporters across biological membranes. The particles themselves are large hydrophobic anions that have the ability to disperse in aqueous media and to partition over both sides of a phospholipid bilayer membrane. Their presence therefore causes a membrane potential that is determined by the relative concentrations of particles on each side of the membrane according to the Nernst equation. The particles tend to adsorb to both sides of the membrane and can flip across if changes in membrane potential require their repartitioning. Such changes can be made either with …

Ribonucleoprotein Purification And Characterization Using Rna Mango, Shanker Shyam S. Panchapakesan, Matthew L. Ferguson, Eric J. Hayden, Xin Chen, Aaron A. Hoskins, Peter J. Unrau

Physics Faculty Publications and Presentations

The characterization of RNA–protein complexes (RNPs) is a difficult but increasingly important problem in modern biology. By combining the compact RNA Mango aptamer with a fluorogenic thiazole orange desthiobiotin (TO1-Dtb or TO3-Dtb) ligand, we have created an RNA tagging system that simplifies the purification and subsequent characterization of endogenous RNPs. Mango-tagged RNP complexes can be immobilized on a streptavidin solid support and recovered in their native state by the addition of free biotin. Furthermore, Mango-based RNP purification can be adapted to different scales of RNP isolation ranging from pull-down assays to the isolation of large amounts of biochemically defined cellular …

An Spm Stage Driven By 3 Stepper Motors, Jianghua Bai, Andres H. La Rosa

Physics Faculty Publications and Presentations

A Scanning Probe Microscope (SPM) stage controlled by 3 stepper motors is designed in this project. The SPM stage controlled by 3 steppers is more versatile than a stage controlled by one motor, but the control of the system is more complicated. In this project, we build the stage actions in an Arduino microcontroller. A finite state machine (FSM) is also built in Arduino to communicate with a PC and an RF controller. A special displaying scheme which has 5 states, is also employed to indicate the operation of the stage. Finally, the SPM stage is fully tested and has …

Low-Dose And In-Painting Methods For (Near) Atomic Resolution Stem Imaging Of Metal Organic Frameworks (Mofs), B. Layla Mehdi, A. J. Stevens, Peter Moeck, Alice Dohnalkova, A. Vjunov, John L. Fulton, Donald M. Camaioni, Omar K. Farha, Joseph T. Hupp, Bruce C. Gates, Johannes A. Lercher, Nigel D. Browning

Physics Faculty Publications and Presentations

Metal-organic Frameworks (MOFs) are a group of crystalline and highly porous materials consisting of inorganic metal ions/clusters (nodes) that are coordinated by organic linkers. The ability to create a wide range of porous structures, where the pore size can be easily changed in size and shape offers the potential for many applications in gas storage/separation and catalysis. The presence of the organic linkers or “struts” in the sample creates challenges for high resolution microscopy as the sample itself is very sensitive to beam damage. A key challenge for understanding the structures of MOFs and how the applications can be modified …

Essentials Of Building Virtual Instruments With Labview And Arduino For Lab Automation Applications, Jianghua Bai, Andres H. La Rosa

Physics Faculty Publications and Presentations

Four ways to improve the capabilities of a virtual instrument involving a microcontroller are covered in this paper. They are structural modeling and programming, real-time control, asynchronous communication between the microcontroller and the host PC, and system integration. This paper covers 4 common problems encountered by embedded developers and 5 solutions to the 4 problems. The solutions and examples demonstrated in this article will help readers build robust and reliable virtual instruments for crucial applications.

Estimates For The Number Of Visible Galaxy-Spanning Civilizations And The Cosmological Expansion Of Life, S. Jay Olson

Physics Faculty Publications and Presentations

If advanced civilizations appear in the universe with an ability and desire to expand, the entire universe can become saturated with life on a short timescale, even if such expanders appear rarely. Our presence in an apparently untouched Milky Way thus constrains the appearance rate of galaxyspanning Kardashev type III (K3) civilizations, if it is assumed that some fraction of K3 civilizations will continue their expansion at intergalactic distances. We use this constraint to estimate the appearance rate of K3 civilizations for 81 cosmological scenarios by specifying the extent to which humanity is a statistical outlier. We find that in …

Atomic Layer Growth Of Inse And Sb₂Se₃ Layered Semiconductors And Their Heterostructure, Robert Browning, Neal Kuperman, Bill Moon, Raj Solanki

Physics Faculty Publications and Presentations

Metal chalcogenides based on the C–M–M–C (C = chalcogen, M = metal) structure possess several attractive properties that can be utilized in both electrical and optical devices. We have shown that specular, large area films of ^_y-InSe and Sb₂Se₃ can be grown via atomic layer deposition (ALD) at relatively low temperatures. Optical (absorption, Raman), crystalline (X-ray diffraction), and composition (XPS) properties of these films have been measured and compared to those reported for exfoliated films and have been found to be similar. Heterostructures composed of a layer of y-InSe (intrinsically n-type) followed by a layer of …

Electrical Properties Of Covalently Functionalized Graphene, Paul Plachinda, David Evans, Raj Solanki

Physics Faculty Publications and Presentations

We have employed first-principle calculations to study transformation of graphene’s electronic structure under functionalization by covalent bonds with different atomic and molecular groups - epoxies, amines, PFPA. It is shown that this functionalization leads to an opening in the graphene’s band gap on order of tens meV, but also leads to reduction of electrical conductivity. We also discuss the influence of charge exchange between the functionalizing molecule and graphene’s conjugated electrons on electron transport properties.

A New Model Of Roche-Lobe Overflow For Short-Period Gaseous Planets And Binary Stars, Brian Jackson, Phil Arras, Kaloyan Penev, Sarah Peacock, Pablo Marchant

Physics Faculty Publications and Presentations

Some close-in gaseous exoplanets are nearly in Roche-lobe contact, and previous studies show tidal decay can drive hot Jupiters into contact during the main sequence of their host stars. Improving upon a previous model, we present a revised model for mass transfer in a semi-detached binary system that incorporates an extended atmosphere around the donor and allows for an arbitrary mass ratio. We apply this new formalism to hypothetical, confirmed, and candidate planetary systems to estimate mass loss rates and compare with models of evaporative mass loss. Overflow may be significant for hot Neptunes out to periods of ∼ 2 …

Ultra Short Period Planets In K2 With Companions: A Double Transiting System For Epic 220674823, Brian Jackson

Physics Faculty Publications and Presentations

Two transiting planets have been identified orbiting K2 target EPIC 220674823. One object is an ultra-short-period planet (USP) with a period of just 0.57 days (13.7 hours), while the other has a period of 13.3 days. Both planets are small, with the former having a radius of R_p1 = 1.5 R_⊕ and the latter R_p2 = 2.5 R_⊕. Follow-up observations, including radial velocity (with uncertainties of 110 ms⁻¹) and high-resolution adaptive optics imagery, show no signs of stellar companions. EPIC 220674823 is the 12th confirmed or validated planetary system in which an …

General Approach To Quantum Channel Impossibility By Local Operations And Classical Communication, Scott M. Cohen

Physics Faculty Publications and Presentations

We describe a general approach to proving the impossibility of implementing a quantum channel by local operations and classical communication (LOCC), even with an infinite number of rounds, and find that this can often be demonstrated by solving a set of linear equations. The method also allows one to design a LOCC protocol to implement the channel whenever such a protocol exists in any finite number of rounds. Perhaps surprisingly, the computational expense for analyzing LOCC channels is not much greater than that for LOCC measurements. We apply the method to several examples, two of which provide numerical evidence that …

Review Article: Molecular Beam Epitaxy Of Lattice-Matched Inalas And Ingaas Layers On Inp (111)A, (111)B, And (110), Christopher D. Yerino, Baolai Liang, Diana L. Huffaker, Paul J. Simmonds, Minjoo Larry Lee

Physics Faculty Publications and Presentations

For more than 50 years, research into III–V compound semiconductors has focused almost exclusively on materials grown on (001)-oriented substrates. In part, this is due to the relative ease with which III–Vs can be grown on (001) surfaces. However, in recent years, a number of key technologies have emerged that could be realized, or vastly improved, by the ability to also grow high-quality III–Vs on (111)- or (110)-oriented substrates These applications include: next-generation field-effect transistors, novel quantum dots, entangled photon emitters, spintronics, topological insulators, and transition metal dichalcogenides. The first purpose of this paper is to present a comprehensive review …