Making use of electron spin in semiconductors, or spintronics has attracted much interest in recent year. Intense research has been focused on narrow gap semiconductors (NGSs) because of its large spin-orbit interaction, and large Rashba effect. InSb based semiconductors have been recognized as one of the most attractive narrow gap semicon- ductors. Amongst all semiconductors, InSb has the smallest effective mass, largest g- factor, highest intrinsic mobility, and largest spin orbit coupling. In this talk, I will discuss the time resolved measurement of spin and charge relaxation using generated (one-color) and non-degenerated (two-color) pump-probe and magneto-optical Kerr effect (MOKE) spectroscopy of near infrared radiation of InSb QWs and InMnSb ferromagnetic semiconductor. The measurements will provide new information on the carrier and spin dynamics in these structures with strong spin-orbit interaction.

Antireflection coatings have been fabricated by self-assembly using silica nanoparticles. The ionic self-assembled multilayer (ISAM) films are tightly packed and homogeneous. While the geometric properties of a matrix of spherical particles with corresponding void interstices are highly suitable to meet the conditions for minimal reflectivity, it is also a cause for the lack of cohesion within the constituent body, as well as to the substrate surface. This study investigates methods for improving the interconnectivity of the nanoparticle structure. One such method involves UV curing of diazo-resin (DAR)/silica nanoparticle films, thereby converting the ionic interaction into a stronger covalent bond. Factorial analysis and response surface methods are incorporated to determine factors that affect film properties, and to optimize their optical and adhesive capabilities. The second study looks at the adhesive strength of composite multilayer films. Films are fabricated with silica nanoparticles and poly(allylamine hydrochloride) (PAH), and dipped into aqueous solutions of PAH and poly(methacrylic acid, sodium salt) (PMA) to improve cohesion of silica nanoparticles in the matrix, as well as binding strength to the substrate surface.

Borexino is a liquid detector featuring 300 tonnes of well shielded ultrapure scintillator viewed by 2200 photomultipliers. Now that Borexino has made the first real-time measurement of sub-MeV solar neutrinos, the task at hand is to decrease the systematic error via energy and position calibrations. These calibrations will be led by the group here at Virginia Tech. Such calibrations require that a radioactive source of a known energy and position be placed in the detector. I will explain the techniques that will be used to have a successful calibration campaign while minimizing the possibility of introducing contaminants to a detector with such stringent purity requirements.

I will review the latest development on the WARP direct search for WIMP dark matter at Gran Sasso. I will also review some recent results on the program for exploration of underground sources of argon depleted from 39Ar, and the prospects for use of this material in large WIMP detectors.

I will talk about an unique measurement that I have performed at the e⁺e^- energy asymmetric collider in the famed KEKB accelerator located in Tsukuba, Japan. This measurement is based on a proposal by phenomenologists that there may exist an asymmetry in the decay rates of the neutral charmed meson D⁰ into its two final states of K_L⁰ π⁰ and K_S⁰ π⁰, up to the order of 5%. Given the experimental situation involved in the measurement of the K_L⁰ mesons this offers a formidable task to extract this asymmetry. I am using noble experimental techniques and several innovative concepts to extract the true signal present in Nature for such an asymmetry. The quality of the measurement is on the most positive side for such measurements. The measurement is going through its final phases of review and calculations and will lead to my Ph.D. thesis. The successful determination of such an asymmetry is of very important consequences in the related Physical studies namely in determination of the strong phase δ_Kπ.

A large nonlinearity in any nonlinear fiber device, such as Raman or parametric amplifiers, can be achieved by having a large nonlinear coefficient, a small effective area, or both. However, having a small effective area requires efficient coupling to very small core fibers. A novel technique for splicing standard fibers to small core fibers is proposed. This technique uses a highly tapered splice in which the field leaves the core and propagates as a fundamental cladding mode in the taper region then couples back to the fundamental core mode of the small core fiber. Theoretical analysis of coupling and fabrication issues will be addressed.

Several of the most important astronomical topics today that involve UV and optical astronomical spectroscopy require detailed understanding of neutral and singly and doubly ionized iron-peak species (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu). Some of these topics are: determination the kinetic luminosity and chemical abundances of observed quasar winds; modeling of light curves Type I and II supernovae; investigating the effects of non-Local Thermodynamic equilibrium (hereafter NLTE) on the total opacities in the chromosphere of the SUN and late type stars; interpretation of the afterglows of gamma-rays bursters; study of gas phase abundances and dust formation of supermassive stars such as ? Carinae. For this reason, understanding NLTE synthetic opacities and spectra of these species can be considered as an objective of 21st century astronomy.

At present, our knowledge of the atomic physics and spectra is lagging behind the avalanche of high quality spectra arising from these iron-peak species. We carry out systematic study of each of these species to remedy current deficiency in calculated NLTE opacities and spectra and to provide a comprehensive theory for the microphysics involved in the spectra of these species. We will calculate the necessary atomic data and construct models of ionization/excitation balance. The calculations will include atomic energy levels, radiative rates for dipole allowed and forbidden transitions, collision strengths for electron impact excitation, photoionization cross sections and recombination rate coefficients. The calculation are now possible thanks to he sum of various factors that include: (a) recent theoretical developments that allow for more accurate representations of the atomic species; (b) unprecedented computational power; (c) powerful modeling codes capable of solving for radiative transfer in 1D and 3D; (d) high quality spectra for detail comparisons with models.

The use of ultracold neutrons (UCN) to study fundamental parameters such as the angular correlations in polarized neutron beta decay and the neutron's lifetime are well underway. Many of these experiments require beam line components (UCN guides) with high critical velocity, low neutron absorption, high specularity, and minimal depolarization. To meet these constraints a thin film coating is usually applied to the bulk guide material. To this end, the UCN guide production facility at Virginia Tech employs electron beam and pulsed laser deposition techniques. What makes a "good" UCN coating will be discussed as well as the production process with a focus on our diamond like carbon coatings.

Recently, there has been much interest in developing and exploring spin based semiconductor devices and phenomena. One of the key challenges in developing spin based devices is to generate, control, and measure spin currents directly. In this talk, we report interband circular photogalvanic (CPG) effects using pulsed near-infrared radiations in an InSb film grown by the MOCVD technique. The film is n-type Te-doped with electron density of ~ 6.0 × 10¹⁵ cm^-3 and mobility of 58,500 cm²/Vs at 100 K. We observe a CPG current whose direction and magnitude depend on the helicity of the incident light, the angle of the incidence, and temperature. Our observation is important to understand zero-field spin splitting mechanisms in a system with strong-spin orbit interaction.

Computer simulations have proven to be an invaluable tool for investigating and understanding the behavior of bio-molecular systems. In many cases, computer simulations serve as a complement to conventional laboratory experiments. In other cases, they serve as an enabling tool to study and understand complex systems and natural phenomena that would otherwise be difficult or even impossible to study by direct measurements. By implementing this tool, insight into biochemical and biophysical processes is made possible.

The focus of the talk will be on two specific biological processes that are associated with biological membranes: membrane stabilization and fatty acids-induced membrane toxicity. In the first study, we aim to further investigate and to compare the interactions of model biological membranes with stabilizing agents (glucose or trehalose) under dehydrated conditions using molecular dynamics simulations. The results from our simulations are the first step toward a better understanding of the preservation of cellular systems. The second study integrates experimental and computational modelings to reveal the biophysical interactions of fatty acids with the cellular membrane and the role of trehalose in preventing changes to the membrane structure. Knowledge of the mechanism for fatty acid-induced toxicity is essential in the prevention and treatment of obesity-associated cirrhosis diseases.

Altshuler-Aronov-Spivak (AAS) oscillations are a spin-dependent non-local quantum interference effect. Studying AAS interference patterns informs our understanding of the role of spin-orbit interaction on spin phases. Our group is currently studying the effects of external electric fields on AAS patterns in InAs and InSb 2-dimensional electron systems. I will be presenting a brief background on AAS oscillations, then show recent data, and discuss our results.

We investigate the investment strategy of a myopic manager. A myopic manager should over invest in short term projects and under invest in long run projects. Given the difficulty in separating long term and short term investments and measuring optimal level of investment, it is difficult to test over investment in short term and under investment in long term projects. Further, looking at the total investments is not a viable way of measuring managerial myopia because of the invisibility of intangible investments. We look at the sensitivity of investment to growth opportunity and cash flow. We argue that looking at the change in the incremental investment in face of growth opportunity and cash flow can serve as a better measure of managerial myopia. We develop theoretical justification of lower investment sensitivity to cash flow and lower investment sensitivity to growth opportunities in case of myopic managers. We provide empirical evidence of managerial myopia by showing that the investment sensitivity to growth opportunities and investment sensitivity to cash flow is lower for myopic managers. CEO age is used as the main proxy for managerial myopia. Other proxies like managerial stock holding and managerial short term bonus are considered. This investment distortion is more prominent when the corporate governance is weak. Further, we show that overvaluation increases investment by the firm.