Session D1: Poster Session (4:30 pm - 6:30 pm)

X-ray and Optical observations of CXOU J005509.2+262714

During a 2002 Chandra X-ray observation of the super cluster Abell 115, a strong and previously unknown X-ray source (CXOU J005509.2+262714) was discovered close to the edge of the field of view, prompting investigations to determine if counterparts to this object existed in other energy bands. An optical counterpart was subsequently discovered in the STScl DSS, prompting an optical observation of this counterpart in 2008. This poster will present the X-ray analysis of this object along with preliminary analysis of the optical counterpart.   

Driving the 5D$_{5/2}$ to 6P$_{1/2}$ transition of Barium 138 ions

We present our efforts to drive the 5D$_{5/2}$ to 6P$_{1/2}$ transition of Barium-138 ions. Ytterbium is the only element in which a similarly forbidden transition has been observed: an electric octupole transition with a subhertz linewidth connects the ground state to a metastable state [1]. In Barium, the transition connects the metastable 5D$_{5/2}$ state to the short-lived 6P$_{1/2}$ state, so the natural linewidth is much broader. Measurements were performed on a single Doppler-cooled ion in a linear Paul trap. We drive the transition with a frequency stabilized external cavity diode laser of nominal wavelength 686nm, with accuracy better than 20MHz. Detection is facilitated by a laser at 1762nm which takes the ion from the ground state to the 5D$_{5/2}$ level. To date, we have not found significant evidence of a driven transition, suggesting that it is too weak to be excited by laser intensities on the order of 10W/cm$^{2}$ over an integration times of 10s. \\[4pt] [1] M. Roberts \textit{et al}., Phys. Rev. Lett. \textbf{78,} 1876 (1997).   

Control of coherent nonlinear optical processes in turbid media

Nonlinear optical signals such as sum-frequency mixing or coherent anti-Stokes Raman scattering (CARS) require laser beams with high spatiotemporal power density for their efficient generation. Random light scattering in turbid optical media reduces the intensity and peak power of laser pulses by lowering their degree of spatial and temporal coherence. We investigate the use of wavefront shaping to increase the sum frequency mixing (SFM) of two ultrashort laser pulses which have passed through an optically diffusive material. Using the spectrally filtered SFM intensity as feedback, we apply a simple search algorithm to find the optimal two-dimensional phase mask for enhancing the nonlinear signal behind the diffuser. Our preliminary results show that increasing the total SFM intensity is possible. This technique should improve the utility of nonlinear optical methods for chemical analysis in turbid environments.   

Control of Molecular Rotation with a Chiral Pulse Train

Trains of ultrashort laser pulses separated by the time of rotational revival (typically, tens of picoseconds) have been exploited for creating ensembles of aligned molecules. In this work we introduce a chiral pulse train -- a sequence of linearly polarized pulses with the polarization direction rotating from pulse to pulse by a controllable angle. The chirality of such a train, expressed through the period and direction of its polarization rotation, is used as a new control parameter for achieving selectivity and directionality of laser-induced rotational excitation. The method employs chiral trains with a large number of pulses separated on the time scale much shorter than the rotational revival (a few hundred femtoseconds), enabling the use of conventional pulse shapers.   

Isochronal chaos synchronization of delay-coupled optoelectronic oscillators

We study experimentally chaos synchronization of nonlinear optoelectronic oscillators with time-delayed mutual coupling and self-feedback. Coupling three oscillators in a chain, we find that the outer two oscillators always synchronize. In contrast, isochronal synchronization of the mediating middle oscillator is found only when sufficient self-feedback is added to the middle oscillator. We show how the stability of the isochronal solution of any network, including the case of three coupled oscillators, can be determined by measuring the synchronization threshold of two unidirectionally coupled systems. In addition, we provide a sufficient condition that guarantees global asymptotic stability of the synchronized solution.   

Multiplexed fluorescence spectroscopy with holographic optical tweezers

We present a multiplexed spectroscopy technique using holographic optical tweezers to trap and excite multiple sensor particles. Our goal is to develop a lab-on-a-chip measurement platform for monitoring pH and other ion concentrations with high spatial resolution in a microfluidic device or within biological cells. We have developed a variety of polymeric pH/ion sensitive nanoparticles with fluorescence spectra that change with the pH/ion concentration of the surrounding environment. We optically trap and manipulate multiple nanosensors using holographic optical tweezers. The trapped particles are irradiated with a separate excitation laser and the fluorescence from all the particles is detected simultaneously with an imaging spectrometer. Electronic separation of the parallel, discrete spectra allows for concurrent determination of multiple spectra.   

Acyl chain composition and coexisting fluid phases in lipid bilayers

At room temperature phospholipid bilayers enriched in sphingolipids and cholesterol may form a solid phase as well as two coexisting fluid phases. These are the standard fluid phase, or the liquid-disordered phase, ld, and the liquid-ordered phase, lo, which is commonly associated with lipid rafts. Ternary mixtures of palmitoyl-oleoyl-phosphocholine (POPC; 16:0,18:1 PC), sphingomyelin (SPM), and cholesterol (Chol) form coexisting lo, ld and solid phases over a wide range of molar ratios. We are examining the ability of two fluorescent probes to detect these 2 phases: NBD linked to di-16:0 PE which partitions strongly into the lo phase and NBD linked to di-18:1 PE which partitions strongly into the ld phase.~ We are also examining the effect of the highly polyunsaturated phospholipid stearoyl-docosahexanoyl-phosphocholine (SDPC; 18:0, 22:6 PC) on the ternary phase diagram of POPC/SPM/Chol with particular focus on the functionally important lo/ld coexistence region. We report on the fluorescence lifetime and anisotropy decay dynamics of these two fluorescent probes.   

Dynamic light scattering can determine platelet function

Platelet transfusions are life-saving procedures for patients who are bleeding or undergoing chemotherapy. The effectiveness of transfusions depends on the number of platelets transfused and the platelet function. Platelet function correlates with proportion of discoid to activated platelets, morphology response to temperature stress, and inversely correlates with microparticle content. ThromboLUX is a novel device that determines platelet function by measuring all of these characteristics using dynamic light scattering (DLS). During periods of stress, such as decreased temperature, cytoskeletal rearrangements will cause normal, discoid platelets to activate and become spiny spheres. The formation of pseudopods of various lengths facilitates the clotting cascade and also increases the apparent size of platelets. ThromboLUX uses a 37-20-37\r{ }C temperature cycle that mimics the bleeding, storage, and transfusion process. As the temperature fluctuates, DLS will measure the changing platelet hydrodynamic radius and the size of any microparticles present. ThromboLUX analysis of platelet concentrates \textit{in vitro} would allow determination of high platelet function units before transfusion and would therefore improve transfusion outcomes and patient safety. This study examined how DLS is able to distinguish between discoid and activated platelets as well as measure the parameters that contribute to high platelet function.   

Conceptual understanding, reasoning and attitudes in intro physics -- the continuing saga

Previous evidence that student reasoning ability and conceptual understanding were correlated led us to look for better ways to support the development of student reasoning in introductory physics. Additional data now seems to show that activities designed to promote not just interactivity but reasoning also help with conceptual understanding.   

Item Response Theory in the context of Improving Student Reasoning

We are interested to see if Item Response Theory can help to better inform the development of reasoning ability in introductory physics. A first pass through our latest batch of data from the Heat and Temperature Conceptual Evaluation, the Lawson Classroom Test of Scientific Reasoning, and the Epistemological Beliefs About Physics Survey may help in this effort.   

Maximum Caliber Analysis of Ion-Channel Gating

The principle of maximum caliber, MaxCal, is a generalization to nonequilibrium statistical mechanics of the principle of maximum entropy, MaxEnt. E. T. Jaynes introduced the MaxEnt approach to equilibrium statistical mechanics in 1957 and its MaxCal generalization in 1980. MaxCal has recently been used to derive dynamical laws of transport, analyze single particle two-state dynamics, and study few state models of non-equilibrium processes. We use MaxCal to analyze hidden Markov models of ion-channel gating and make logical inferences concerning the underlying dynamics. MaxCal is used to determine model parameters; test the adequacy of a model; and predict unmeasured quantities from the trajectory probability distribution. Results will be given for a MaxCal analysis of inositol trisphosphate receptor patch clamp data.   

Non-controlled impurities and their recharge in LiNbO$_{3}$:Rh

Rapid developments in material science and nanotechnology have made it necessary to develop advanced materials for optical applications. Rhodium doped lithium niobate is a candidate for use in photorefractive applications and holographic data storage. Basic knowledge about the defects and their structures within this material are necessary to improve crystals for these applications. Magnetic resonance techniques combined with optical spectroscopy are powerful tools to investigate paramagnetic impurities and determine their characteristics. EPR provides information on charge states, symmetries and positions of the defects in the crystal lattice. Optical absorption spectroscopy allows us to establish optical absorption bands within the visible region of the electromagnetic spectrum. It was found that rhodium doping facilitates an entering of additional non-controlled impurities: Fe$^{3+}$, Mn$^{2+}$, Cu$^{2+}$ and Co$^{3+}$. Several Rh$^{4+}$ centers have also identified. The recharge of Rh$^{4+}$ to Rh$^{5+}$ and accompanying recharge of Fe$^{3+}$ to Fe$^{2+}$ were confirmed with measurements of optical absorption changes under pump light illumination.   

Deconfinement of gauge theories

It is known that the large N gauge theories with SU(N) symmetry on the sphere undergo the phase transition, and color singlets are deconfined at high temperature. The ordinary ungauged partition function is represented by the singlet gauged partition function, $Z_{singlet}$. We examine whether the singlet constraint at the deconfinement phase was a physical consequence. A model of multiple matrices harmonic oscillators is considered as a toy model of the large N, 4D SU(N) gauge theory. We compare $Z_{singlet}$ to the known partition function of a group of non- interacting harmonic oscillators, which represent the model without imposing the singlet constraint. To calculate $Z_{singlet}$, we change the integration variables of group elements to eigenvalues, and the integral becomes a 1D many body system of particles with pairwise interaction. We compute the equilibrium distribution and the free energy. We assure that the eigenvalues are frozen at the saddle point at high temperature. However $Z_{singlet}$ has the free energy converging to $(m-1)N^2\ln (1-q)$ while the free energy of harmonic oscillators is $mN^2\ln (1-q)$. Changing the integration variables from group elements to eigenvalues explains the discrepancy of the free energy between imposing and relaxing the single constraint. Gauge theory cannot simply relax the singlet constraint at high temperature without adding a normalization factor.   

Investigation of the Sr2Ir1-xTixO4 Solid Solution

Motivated by a number of unique physical properties and a spirited search for superconducting oxides with structures analogous to La2CuO4, there have been a number of detailed investigations on the physical properties of Sr2IrO4. The effect of Ti substitution for Ir in Sr2IrO4 is investigated. A complete solid solution Sr2Ir1-xTixO4 is obtained. Structural, magnetic and electronic properties are discussed.   

Erbium ions in congruent and stoichiometric lithium niobate. Searching for a clue

Lithium Niobate (LN) doped with Er$^{3+}$ ions is of great interest for both fundamental science and advanced applications: lasers with frequency conversion, elements of all-optical telecommunication network and quantum cryptography. According to the EXAFS and RBS data, trivalent ions substitute for Li$^{+}$ and should create similar centers with charge compensation by lithium vacancies. The EPR studies confirmed this conclusion for Cr, Fe, Nd, and Yb Their most intense lines belong to axial centers with C$_{3}$ symmetry. Distant lithium vacancies cause a line broadening, but do not change the C$_{3}$ symmetry of observed spectra. Our EPR study of Er$^{3+}$ in stoichiometric LN has unexpectedly shown that all observed Er$^{3+}$ centers have C$_{1}$ symmetry. Therefore, models with cation vacancies cannot describe our experimental data for LN:Er, and we have to consider complexes which excludes the existence of axial centers: erbium substituted for lithium or incorporated in octahedral or tetrahedral structural vacancy plus interstitial oxygen ion as a charge compensator, erbium substituted for niobium and oxygen vacancy as compensator of excessive negative charges. Re-investigating congruent samples of LN:Er, we did not find undisputable evidences of the existence of axial Er$^{3+}$ centers.   

Collective excitations in thin $^{3}$He films

The spectra for (longitudinal) collective excitations in thin polarized $^{3}$\textrm{He} films are calculated from Fermi liquid theory. The calculation uses state-dependent Landau parameters that have been computed to quadratic order in \textit{s}-wave and \textit{p}-wave effective interaction components. The interaction components have been determined from existing spin susceptibility and specific heat measurements for $^{3}$\textrm{He} adsorbed on graphite substrates and also in thin $^{3}$\textrm{He} - superfluid $^{4}$\textrm{He} films. The zero sound and spin-zero sound spectra as a function of density and polarization are obtained by solving Landau's kinetic equation. The matrix elements are computed exactly and analytically. The solutions contain partial wave contributions up to the $\ell = 3$ angular momentum components. In particular, we study features in the oscillation amplitudes of the two Fermi surfaces at finite polarization. We note that at this time there have been no direct measurements of sound speeds in $^{3}$\textrm{He} films and so all of these results constitute predictions.   

Spin Valves and Magnetic Tunnel Junctions

This is a presentation of research conducted through the National Institute of Standards and Technology's Summer Undergraduate Research Fellowship program. A spintronic device is one that uses the electron's magnetic moment (its spin) as well as its charge to perform operations, such as data storage or logic. Many of today's spintronic devices are based on the ``tunneling magnetoresistance'' effect of CoFeB/MgO/CoFeB tunnel junctions. The MgO barrier in devices must be highly uniform and only 1-2 nm thick. Relevant background, including electron spin and tunneling, is supplied. The fabrication, operation, and behavior of spin-valves and magnetic tunnel junctions are described, and applications in Hard Disk Drives, Magnetic Random Access Memory, Magnetic Field Sensors, and Spin-Torque Oscillators are discussed.   

Thermal conductivity measurements of amorphous HafSO$_x$ and AlPO thin films

The novel insulators HafSO$_x$ and AlPO are useful as gate dielectrics in field effect transistors as high quality, atomically flat, dense films with low current leakage can be deposited at low temperatures. Since these materials are expected to be used in microelectronics, it is important to understand their thermal transport properties. The room temperature thermal conductivity of thin HafSO$_x$ and AlPO films is determined by a differential 3-omega method, which uses an alternating current signal to heat a sample and a resistance temperature detector (RTD) to measure the frequency- dependent magnitude and phase of the resulting temperature oscillations. The method is modified by using two heater/RTDs of different widths deposited on a single sample to eliminate the need for a reference substrate.   

EPR of Cr$^{3+}$ and Fe$^{3+}$ centers in congruent and stoichiometric lithium niobate crystals doped with Mg

Transition metal doping in LiNbO$_{3}$ (LN) has been developed during the search for potential laser devices. Doping with Mg in a concentration above 6 at.{\%} reduces the material's susceptibility to optical damage. However, it causes EPR line broadening due to an even larger disorder in the lattice compared to single-doped congruent crystals, which have a significant amount of niobium anti-sites and lithium vacancies. This has made determining the structure of impurity centers more difficult than in single-doped crystals, and models of impurity centers in LN:Mg were not determined until now. Detailed measurements of angular dependencies of EPR lines in X- and Q-band has shown Cr$^{3+}$ pairs appearing in highly doped material. Unexpectedly, besides Cr$^{3+}$-Cr$^{3+}$ pairs substituting for both Li$^{+}$ and Nb$^{5+}$ (self-compensating pairs), pairs with chromium occupying two neighbor Li$^{+}$ sites were also found. Significant line narrowing in stoichiometric LN:Mg crystals allowed us to distinguish four different Fe$^{3+}$ centers. The obtained results provided the keys for understanding Cr and Fe centers in both congruent and stoichiometric materials. This is important for fundamental material science and tailoring material properties for applications. The work was supported by NSF grant DMR- 0805175.   

Iron Chalcogenide Thin Film Deposition for Solar Absorbers

Interest in the Fe$_{2}$-IV-VI$_{4}$ system stems from a desire to fundamentally change the approach to thin-film inorganic solar absorbers by synthesizing and studying new flat-band d-element chalcogenides. Impetus for the work is provided by the band gap (Eg = 0.9 eV), excellent optical absorption ($\alpha >$ 10$^{5 }$cm$^{- 1})$, and minority electron transport properties (300 cm$^{2}$/V-s) of FeS2 (pyrite). Fermi level pinning, however, results in a low open circuit voltage (Voc) limiting the absorber potential of FeS$_{2}$. The olivines Fe$_{2}$SiS$_{4}$ and Fe$_{2}$GeS$_{4}$ are promising candidates for realizing the desired properties. Fe$_{2}$GeS$_{4}$ thin films are fabricated via RF sputtering and demonstrate a band gap of 1.5 eV with an optical absorption $\alpha $ $>$ 10$^{5 }$cm$^{-1}$ at Eg +1 eV. These ternaries provide a new entry point for development of highly efficient thin-film solar absorbers.   

Infrared Spectroscopy of Metallic Nanoparticles

Research into metallic nanoparticles is a growing field in the sciences because of high value in catalysis and cancer treatment. Since it has increasing importance, it is valuable to have distinct characterization on wide ranges of particles. While metallic nanoparticles are synthesized with organic molecules encapsulating them, it is difficult to observe how the metallic particles are behaving without obstructive interference from the organics. Over the summer we characterized metallic nanoparticles using infrared spectroscopy. We developed methods of producing uniform thin films to enable accurate repetition of experiments, and explored methods of removing the organic capping agents surrounding the metallic particles in order to get an IR spectrum of the metallic particles themselves. We examined changes to the spectrum as a function of quantity of solution. Two methods of thin film deposition were studied on a silicon substrate, spin-casting and micro-contact printing with distinct results for both. We investigated how to remove the organics and a thermal method was utilized. Heating the samples with a hot plate using varied temperatures resulted in unique data that concluded that thermal activation did change the composition of the nanoparticle samples, and the resulting samples provide new information about the characterization of the original samples.   

Multispace and Multistructure as a Theory of Everything

In a general definition, a multispace (also spelt multi-space) is a finite or infinite (countable or uncountable) union of many spaces that have various structures. The spaces may overlap. A such multispace can be used in physics for the Unified Field Theory that tries to unite the gravitational, electromagnetic, weak and strong interactions. Or in the parallel quantum computing and in the mu-bit theory, in multi-entangled states or particles and up to multi-entangles objects. It is believed that the multispace with its multistructure is the best candidate for 21$^{st}$ century Theory of Everything in any domain. It connects many knowledge fields. The multispace is a qualitative notion, since it is too large and includes both metric and non-metric spaces. The notion of multispace was introduced by the author in 1969 under the idea of hybrid mathematics: combining different fields into a unifying field, which is closer to our real life, since we don't have a homogeneous space, but many heterogeneous ones. As applications we also mention: the algebraic multispaces (multi-groups, multi-rings, multi-vector spaces, multi-operation systems and multi-manifolds, also multi-voltage graphs, multi-embedding of a graph in an n-manifold, etc.), geometric multispaces (combinations of Euclidean and Non-Euclidean geometries into one space as in Smarandache geometries), theoretical physics, including the relativity theory, the M-theory and the cosmology, then multi-space models for p-branes and cosmology, etc.   

Crystallographic Orientation Control in PZT Thin Films for Microelectromechanical Applications

Pb(Zr1-xTix)O3 (PZT) is widely used in ferroelectric and piezoelectric applications both in bulk and thin film form. As the piezoelectric response is strongly anisotropic, it is highly desirable to control the crystallographic orientation in order to maximize the displacement (for actuation) or charge generated (for sensing). Control of crystallographic texture in PZT thin films has been shown to be dependent on a variety of processing conditions including deposition method, substrate choice, chemical doping, etc. This work is focused on systematically exploring how processing conditions and substrate choice affect orientation in chemical solution derived PZT films. It was found that sputtered Pt/TiOx/SiO2/Si substrates provided a significantly improved template over evaporated Pt/Ti/SiO2/Si substrates. Additionally, alternative adhesion layers to Ti and TiOx resulted in improved chemical homogeneity within the PZT itself, which should lead to enhanced piezoelectric properties. Ongoing work to demonstrate improved piezoelectric properties will be presented.   

Markov-Binary Visibility Graph: A New Method for Analyzing Time Series

We introduce a new and simple transformation from time series to complex networks based on markov-binary visibility graph(MBVG). Due to the simple structure of this transformation in comparison with other transformations be obtained more precise results. Moreover, several topological aspects of the constructed graph, such as degree distribution, clustering coefficient, and mean visibility length have been thoroughly investigated. Numerical simulations confirm the reliability of markov-binary visibility graph for time series analysis. This algorithm have the capability of distinguishing between uncorrelated and correlated systems.   

Physical Locality in Pure Mathematics

It has been suggested that the only proper way to express the laws of physics (specifically the laws of Quantum Mechanics) is using Geometric Algebra (Christian 2006, 2008, 2010). Thus far, physics has resisted most attempts at being recast in these terms. Here we show that the reason for this failure lies in the conflict between the peculiar relationship between position and direction in Geometric (or Clifford) Algebra (which is not part of standard algebraic representations), and classical mathematical physics. The implications of this conflict for Christian's Clifford Algebra based hidden variables theory are discussed.   

Aberration reduction in electrostatic lenses

Chromatic and spherical aberration strongly limit the resolution in electron microscopes. The objective lens is often the largest contributer to the overall aberration, so it is useful to find a minimum aberration design. The thin lens regime is a suitable approximation for objective lenses in focused-ion-beam and photoemission electron microscopes, greatly simplifying the formulas for the chromatic and spherical aberration coefficients of an electrostatic lens. The simplified expressions have explicit factors of magnification and object distance, which are typically constrained quantities. The remainder of the aberration expression can be minimized by adjusting the shape of the lens. Through this approach, we arrive at a lens geometry with the minimum spherical and chromatic aberration. We compare the results of the optimization to a numerical ray-tracing computation, and find good agreement.   

Transient electrophoretic current in a nonpolar solvent

The transient electric current of surfactants dissolved in a nonpolar solvent is investigated both experimentally and theoretically in the parallel-plate geometry. Due to a low concentration of free charges the cell can be completely polarized by an external voltage of several volts. In this state, all the charged micelles are compacted against the electrodes. After the voltage is set to zero the reverse current features a sharp discharge spike and a broad peak. The peak time is a useful measure of the micelle mobility. After complete polarization is achieved, the peak stops evolving with further increase of the compacting voltage. The peak time grows logarithmically with the charge content in the bulk. These features are reproduced in a one-dimensional drift-diffusion model. Time integration of the peak yields the total charge in the system. By measuring its variation with temperature, the activation energy of bulk charge generation has been found to be 0.126 eV. The results are relevant to the development of electrophoretic reflective displays.   

Ionization, Transport and Non-Ideal Equations of State Models for the Pulsed Inductive Plasma Thruster

A computational model accounting for the internal thermodynamic state of the plasma sheet into an existing electro-mechanical model of pulsed inductive plasma acceleration is presented. The model includes the effects of electronic excitation, ionization, transport and non-ideal equation of state of the plasma and incorporates them into a set of circuit equations that are coupled to an equation of motion and energy equation for the plasma. Calculations showing the time-evolution of the various sources and sinks in the plasma-circuit system are presented to demonstrate the efficacy of the model. Comparisons with experimental data and with previous models show the utility of this model in aiding experimental research on inductive pulsed plasma accelerators.   

Evaluation of Low-Thrust Propulsion Options for Cargo Missions to Near-Earth Objects

A simple method developed to optimize low-thrust trajectories to near-Earth objects is presented. A computational tool developed using this method was tested for a round-trip cargo mission carrying a payload of 1000-2000 kg to the asteroid 1996XB27. Several existing electric thrusters (a Bi Hall thruster at two levels of operation, a Xe Hall thruster, an applied field Li Lorentz force accelerator, the HiPEP ion thruster and the VASIMR) were considered for this mission, at their demonstrated values of performance parameters, to examine the validity of this new computational tool. In the range of power levels considered (150 to 600 kW), increasing the power level had only a small effect on reducing the trip time. It was found that a Bi Hall thruster operating at a high thrust-to-power ratio allowed for the shortest trip time, and a Bi Hall thruster and the HiPEP ion thruster with very high values of exhaust velocity and efficiency required the least initial mass to transport the payload. It was found that this new tool yielded results that were realistic, and insights from the results for thruster development are discussed.   

Building and Testing a Photolithographic System

Photolithography is a technique used to deposit metals onto substrates in specific patterns. The process uses light to transfer geometric patterns onto a light sensitive photoresist on the surface of a substrate. We have built a low-cost, maskless photolithographic system assembled from a computer, a consumer projector, and a microscope. The photoresist is spun in a modified food processor and baked on a standard hot plate. Exposing the photoresist only takes a few minutes and allows for multiple runs on the same substrate in a short amount of time. Through multiple exposures, we can make features ranging from approximately 8 $\mu $m to 785 $\mu $m, which is especially useful when making contacts using the large features.   

Computational Studies of Protein Folding

Proteins are known to fold into tertiary structures that determine their functionality in living organisms. The goal of our research is to better understand the protein folding process. Using MATLAB, we created an algorithm that models the folding process via a Monte Carlo time step approach. Specifically, amino acids in the chain at each time step are allowed to fold to certain locations according to a set of rules. These rules are based on two main criteria: folds must maintain bond length and should be thermally and energetically favorable. One central goal of our research is to examine whether the folding process can be viewed through the lens of self-organized criticality. In particular we are interested in whether there are features of the folding process that are independent of the size of the protein.   

Particle Flow Calorimetry at the ILC

The Silicon Detector (SiD) concept is under development for the International Linear Collider (ILC). SiD is designed for high-precision measurements of electron-positron collisions at the ILC for center of mass energies up to 1 TeV, addressing fundamental questions of particle physics, including the mechanism responsible for electroweak symmetry breaking and the generation of mass, the unification of forces, the structure of space-time at short distances, and connections with cosmology. These studies require excellent jet energy resolution. SiD features a finely-segmented silicon-tungsten electromagnetic calorimeter (ECAL) and a multi-layer steel with resistive plate chambers (RPC) hadron calorimeter (HCAL), in a design optimized for Particle Flow Calorimetry. The Particle Flow Algorithm (PFA) uses energy measurements of charged particles in the tracker and separated calorimeter hits from neutral particles, in order to achieve the best possible jet energy resolution. We present studies of energy measurement and particle identification in the ECAL and HCAL investigating improvements in the SiD PFA.