Physics Commons^™

Erratum: Experimental Study Of The Role Of Physicochemical Surface Processing On The In Ability Of Mineral Dust Particles (Atmospheric Chemistry And Physics (2011) 11 (11131-11144)), D. Niedermeier, S. Hartmann, T. Clauss, H. Wex, A. Kiselev, R. C. Sullivan, P. J. Demott, M. D. Petters, P. Reitz, J. Schneider, E. Mikhailov, B. Sierau, O. Stetzer, B. Reimann, U. Bundke, R. A. Shaw, A. Buchholz, T. F. Mentel, F. Stratmann

Michigan Tech Publications

No abstract provided.

Experimental Study Of The Role Of Physicochemical Surface Processing On The In Ability Of Mineral Dust Particles, D. Niedermeier, S. Hartmann, T. Clauss, H. Wex, A. Kiselev, R. C. Sullivan, P. J. Demott, M. D. Petters, P. Reitz, J. Schneider, E. Mikhailov, B. Sierau, O. Stetzer, B. Reimann, U. Bundke, R. A. Shaw, A. Buchholz, T. F. Mentel, F. Stratmann

Michigan Tech Publications

During the measurement campaign FROST 2 (FReezing Of duST 2), the Leipzig Aerosol Cloud Interaction Simulator (LACIS) was used to investigate the influence of various surface modifications on the ice nucleating ability of Arizona Test Dust (ATD) particles in the immersion freezing mode. The dust particles were exposed to sulfuric acid vapor, to water vapor with and without the addition of ammonia gas, and heat using a thermodenuder operating at 250 °C. Size selected, quasi monodisperse particles with a mobility diameter of 300 nm were fed into LACIS and droplets grew on these particles such that each droplet contained a …

Effect Of Coarse Marine Aerosols On Stratocumulus Clouds, Yoav Lehahn, Ilan Koren, Orit Altaratz, Alexander Kostinski

Department of Physics Publications

In contrast to fine anthropogenic aerosols (radii ∼μm), large aerosol particles are thought to enhance cloud droplet growth, promote precipitation formation and reduce cloud albedo. While shown in cloud simulation models, the impact of coarse aerosols on marine stratocumulus clouds lacks observational evidence. Here, by combining data from AMSR‐E and MODIS, both aboard NASA's satellite Aqua, we link the amount of coarse marine aerosols emitted to the atmosphere through wind‐driven processes with the size of cloud droplets, at the world's largest deck of marine stratocumulus clouds over the southeastern Pacific. For constrained meteorological conditions, approximately 1/2 of the change in …

Evolution And Distribution Of Record-Breaking High And Low Monthly Mean Temperatures, Amalia Anderson, Alexander Kostinski

Department of Physics Publications

The ratio of record highs to record lows is examined with respect to extent of time series for monthly mean temperatures within the continental United States for 1900–2006. In counting the number of records that occur in a single year, the authors find a ratio greater than unity in 2006, increasing nearly monotonically as the time series increases in length via a variable first year over 1900–76. For example, in 2006, the ratio of record highs to record lows ≈ 13:1 with 1950 as the first year and ≈ 25:1 with 1900 as the first year; both ratios are an …

Mechanism Behind The Switching Of Current Induced By A Gate Field In A Semiconducting Nanowire Junction, Subhasish Mandal, Ranjit Pati

Department of Physics Publications

We propose an orbital-controlled model to explain the gate field induced switching of current in a semiconducting PbS-nanowire junction. A single-particle scattering formalism in conjunction with a posteriori density-functional approach involving a hybrid functional is used to study the electronic current; both first- and higher-order Stark effects are explicitly treated in our model. Our calculation reveals that after a threshold gate voltage, orbital mixing produces p components at the S atoms in the participating orbitals. This results in an interlayer orbital interaction that allows electrons to delocalize along the channel axis. As a consequence, a higher conductance state is found. …

Heterogeneous Ice Nucleation: Exploring The Transition From Stochastic To Singular Freezing Behavior, D. Niedermeier, R. A. Shaw, S. Hartmann, H. Wex, T. Clauss, J. Voigtländer, F. Stratmann

Michigan Tech Publications

Heterogeneous ice nucleation, a primary pathway for ice formation in the atmosphere, has been described alternately as being stochastic, in direct analogy with homogeneous nucleation, or singular, with ice nuclei initiating freezing at deterministic temperatures. We present an idealized, conceptual model to explore the transition between stochastic and singular ice nucleation. This "soccer ball" model treats particles as being covered with surface sites (patches of finite area) characterized by different nucleation barriers, but with each surface site following the stochastic nature of ice embryo formation. The model provides a phenomenological explanation for seemingly contradictory experimental results obtained in our research …

Record Setting During Dispersive Transport In Porous Media, Yaniv Edery, Alexander Kostinski, Brian Berkowitz

Department of Physics Publications

How often does a contaminant ‘particle’ migrating in a porous medium set a distance record, i.e., advance farther from the origin than at all previous time steps? This question is of fundamental importance in characterizing the nature of the leading edge of a contaminant plume as it is transported through an aquifer. It was proven theoretically by Majumdar and Ziff (2008) that, in the 1d case for pure diffusion, record setting of a random walker scales with n^1/2, where n is the number of steps, regardless of the length and time distribution of steps. Here, we use numerical …

First-Principles Study Of Strain-Induced Modulation Of Energy Gaps Of Graphene/Bn And Bn Bilayers, Xiaoliang Zhong, Yoke Khin Yap, Ravindra Pandey, Shashi P. Karna

Department of Physics Publications

First-principles calculations based on density functional theory are performed on graphene/BN and BN bilayers to investigate the effect of the strain on their energy gaps. For the graphene/BN bilayer, the bands have characteristic graphenelike features with a small band gap at K. Application of strain modulates the band gap, whose magnitude depends on the strength of interaction between constituent monolayers. For the BN bilayer, on the other hand, a large band gap is predicted, which remains nearly the same for small strains. The increased inhomogeneity in charge density of different carbon sublattices due to a stronger interplanar interaction is the …

Codoping In A Single Molecular Junction From First Principles, Subhasish Mandal, Ranjit Pati

Department of Physics Publications

Using a codoping model, where a cation and an anion are introduced simultaneously into the host to maintain charge neutrality, we probed the electron transport characteristics in a single molecular junction. We used the 1, 12-dicarba-closo-dodecaborane inorganic molecule as a precursor, replaced one of the vertex carbon atoms by a boron atom, and simultaneously decorated it with an endohedrally doped alkali atom (Li or Na) to look into the role of dopant atoms in the conductivity. The commonly used thiolate anchoring groups are used to attach the molecule between two gold electrodes, and a parameter-free, first-principles, single-particle Green’s …

Homogeneous And Heterogeneous Ice Nucleation At Lacis: Operating Principle And Theoretical Studies, S. Hartmann, D. Niedermeier, J. Voigtländer, T. Clauss, R. A. Shaw, H. Wex, A. Kiselev, F. Stratmann

Michigan Tech Publications

At the Leipzig Aerosol Cloud Interaction Simulator (LACIS) experiments investigating homogeneous and heterogeneous nucleation of ice (particularly immersion freezing in the latter case) have been carried out. Here both the physical LACIS setup and the numerical model developed to design experiments at LACIS and interpret their results are presented in detail. < br> < br> Combining results from the numerical model with experimental data, it was found that for the experimental parameter space considered, classical homogeneous ice nucleation theory is able to predict the freezing behavior of highly diluted ammonium sulfate solution droplets, while classical heterogeneous ice nucleation theory, together with the assumption of …

Quantum Transport In A Single Molecular Junction, Partha Pratim Pal

Dissertations, Master's Theses and Master's Reports - Open

The craze for faster and smaller electronic devices has never gone down and this has always kept researchers on their toes. Following Moore’s law, which states that the number of transistors in a single chip will double in every 18 months, today “30 million transistors can fit into the head of a 1.5 mm diameter pin”. But this miniaturization cannot continue indefinitely due to the ‘quantum leakage’ limit in the thickness of the insulating layer between the gate electrode and the current carrying channel. To bypass this limitation, scientists came up with the idea of using vastly available organic molecules …

Measuring Energy Spectra Of Tev Gamma-Ray Emission From The Cygnus Region Of Our Galaxy With Milagro, Jessica G. Galbraith-Frew

Dissertations, Master's Theses and Master's Reports - Open

High energy gamma rays can provide fundamental clues to the origins of cosmic rays. In this thesis, TeV gamma-ray emission from the Cygnus region is studied. Previously the Milagro experiment detected five TeV gamma-ray sources in this region and a significant excess of TeV gamma rays whose origin is still unclear. To better understand the diffuse excess the separation of sources and diffuse emission is studied using the latest and most sensitive data set of the Milagro experiment. In addition, a newly developed technique is applied that allows the energy spectrum of the TeV gamma rays to be reconstructed using …

Planar Magneto-Photonic And Gradient-Photonic Structures : Crystals And Metamaterials., Zhuoyuan Wu

Dissertations, Master's Theses and Master's Reports - Open

In the field of photonics, two new types of material structures, photonic crystals and metamaterials, are presently of great interest. Both are studied in the present work, which focus on planar magnetic materials in the former and planar gradient metamaterials in the latter. These planar periodic structures are easy to handle and integrate into optical systems. The applications are promising field for future optical telecommunication systems and give rise to new optical, microwave and radio technologies.

The photonic crystal part emphasizes the utilization of magnetic material based photonic crystals due to its remarkable magneto-optical characteristics. Bandgaps tuning by magnetic field …

Characterizing A Single Photon Detector, Paul N. Rojas

Dissertations, Master's Theses and Master's Reports - Open

I will present my work about constructing and characterizing a single photon detector. Using the 1550nm laser and second harmonic light generation, I am able to count single photons on a Multi‐Pixel Photon Counter (MPPC) silicon APD. My results show that upwards of 22% quantum efficiency is achievable with the MPPC. Future work will include coincidence detection of correlated photon‐pair.

Four-Window Technique For Measuring Optical-Phase-Space-Time-Frequency Tomography, Rachel A. Blaser

Dissertations, Master's Theses and Master's Reports - Open

A new approach, the four-window technique, was developed to measure optical phase-space-time-frequency tomography (OPSTFT). The four-window technique is based on balanced heterodyne detection with two local oscillator (LO) fields. This technique can provide independent control of position, momentum, time and frequency resolution. The OPSTFT is a Wigner distribution function of two independent Fourier transform pairs, phase-space and time-frequency. The OPSTFT can be applied for early disease detection.