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Colloquia









Upcoming Colloquia
Wednesday, Nov. 19, 2014, 2:30
Freeman hall room 105


Christopher Aubin
Assistant Professor of Physics
Fordham University

Magnetic dipole moments: Looking for physics beyond the Standard Model

The current standard model of particle physics is the prevailing theory of fundamental interactions in the universe. There is currently near-perfect agreement between experiment and theory for all physical observables. However, for the magnetic dipole moment of the muon, there is a possible 3-σ discrepancy between the theoretical calculation and the experimental measurement. I will discuss the current status of these two numbers, specifically updating the method used for the theoretical determination. Currently the theoretical calculation uses a significant input from experiment, while a method using Lattice QCD (numerical simulations) is currently being advanced. I will discuss how this could be the best hope for breaking the standard model.



Wednesday, Jan. 21, 2015, 2:30
Freeman hall room 105


Sam Walker
Bobby Wurtz
FCRH

TBA


Previous Colloquia
Wednesday, Nov. 5, 2014, 2:30
Freeman hall room 105


Jon Gustafson
FCRH

Characterization of Fast Camera with Twenty-Nanosecond Resolution

A fast camera is an imaging sensor with a time resolution typically on the nanoscale. The main advantage of having a nanosecond resolution camera is the ability to detect multiple events that occur on a nanosecond or greater time scale without having to time gate the detector. This project’s objective was to study and characterize fast cameras, more particularly the XRI-UNO fast camera detector developed by X-Ray Imatex. To do this, we used the XRI-UNO detector to image oxygen ions at Brookhaven National Laboratory’s Chemistry Department. The Medipix2/Timepix complementary metal-oxide-semiconductor (CMOS) application-specific integrated circuit (ASIC) located on the detector was the chip that specifically detected these oxygen ions. We analyzed the time-stamped data collected by this Medipix2/ Timepix chip by plotting different distributions of the data using python and the LSST Application Framework in the integrated development environment Eclipse. Using these distributions, we were ultimately able to characterize the sensitivity of the detector, as well as characterize the occurrence of charge sharing in the detector.

Chris Guerrero
FCRH

Motion Control System Using EPICS and ND280

This past summer, I created a motion control system for the NSLS-II Controls Group using the Heidenhain ND280 measuring gauge and Delta Tau GeoBrick LV via EPICS communication. This motion control system tracks how much the motor moves with feedback values from the ND280 sensor and position output values from the Delta Tau. These values are then compared and calculated for repeatabilty. This system contains a display to access motor values and compare them to sensor values so that users have easy access using CS Studio software. Measuring the change in position of the linear stepper motor is essential for precision on the sample stages of x-ray beamlines in the new multi-million dollar facility at Brookhaven National Lab.

Wednesday, Oct. 29, 2014, 2:30
Freeman hall room 105


A Brief Study of Microtubule Persistence Length
Juin Zhou
FCRH

Microtubules, which consist of α-β tubulin heterodimers, are the most rigid of the cytoskeletal filaments. They are both structurally and functionally important in the cell: providing shape and support, forming the highway by which intracellular cargo is transported, and are essential in mitotic processes. To be this versatile, the rigidity of microtubules has to play an important role in cellular mechanics. Persistence length (Lp) is a measure that quantifies microtubule stiffness. It determines how microtubules move and can affect how well they function. Mutated microtubule associated proteins (MAPs) cause various degenerative diseases, such as Alzheimer's and Lou Gehrig's. MAPs have been shown to have the ability to tune microtubule stiffness. Our study focuses on the mechanics of microtubules by imaging fluorescently labeled, freely fluctuating filaments within a thin (< 3 µm) chamber. Fourier analysis and bootstrapping statistics were then applied to extract the persistence length.

Chiral Liquid Crystalline Nanocomposites as Environmental Sensors
John Murray
FCRH

Droplets and films of liquid crystalline mixtures were studied as detectors of volatile organic gaseous compounds. Relatively low concentrations of these vapors were observed to have a noticeable effect on the structure of the liquid crystalline composites, proving their worth as detectors of volatile organic compounds in the air. Under microscope observation, we observed these structural changes in the films/droplets to be manifested as changes to their optical properties (wavelength of reflected light, interference patterns, etc.), We tested multiple composites and combinations, as well as various spatial arrangements and confinements to determine the most effective means of detecting low concentrations of environmental agents.

Wednesday, Oct. 15, 2014, 2:30
Freeman hall room 105

Quamrul Haider
Professor of Physics
Fordham University

Cosmic Inflation and Gravity Waves: "Smoking Gun" for Universe's Big Bang Expansion!

The Big Bang model of the Universe has been the paradigm of cosmology for many years, primarily because of the impressive agreement of the model with two cosmological phenomena – the recession of the galaxies and Cosmic Microwave Background Radiation (CMBR). The model deals with the large-scale structure of the Universe. According to the model, the Universe came into being almost 14 billion years ago with a violent explosion from which all matter and energy originated. Immediately after the Big Bang, space expanded at a mind-boggling rate and the expansion is still continuing at an accelerated rate. At any stage in the expansion of the Universe there is an important length scale called Planck length whose value is of the order of 10-35 meter and a time scale known as Planck time which is of the order of 10-43 second. From the beginning of the Big Bang to the Planck time, all known laws of physics fail. Hence we do not know how space, time, and matter behaved in that brief but important interval. Between zero hour and Planck time, physicists believe that extreme gravitational conditions prevailed.
The Inflationary Model, a variant of the Big Bang Model, was developed to describe the Universe at the Planck scale. According to this model, the Universe expanded exponentially just after its explosive birth. The expansion was caused by a repulsive form of gravity and the rapid expansion filled the cosmos with gravitational waves.
Last month physicists of the BICEP2 experiment claimed to have detected the signature of primeordial gravitational waves in the CMBR.  If the discovery holds up to scrutiny, it will shed light on how the Universe rapidly expanded during the Planck epoch.
In this talk, I will discuss the Big Bang and the Inflationary models of the Universe. Within the context of the Big Bang model, I will discuss the missing mass of the Universe and how mass influences the shape, size, age and fate of the Universe. I will also discuss the shortcomings of the Big Bang model and how the recent discovery lends support to the Inflationary model.



Wednesday, April 23, 2014, 2:30
Freeman hall room 103

Steve Holler
Assistant Professor of Physics
Fordham University

Whispers of a photonic atom: A quest for single protein detection

The detection of trace quantities of toxic material, whether chemical or biological in nature, is vital for homeland security, quality control, and clinical diagnostics. Pathogens that reside within the body manifest within the blood and other bodily fluids. The ability to detect trace quantities of such pathogens means that treatment may be initiated earlier thereby enhancing the probability of a successful eradication of the causative agent and mitigating infection. This talk will highlight the achievements of the whispering gallery mode biosensor (WGB). In its native state, the WGB has been shown to be capable of label-free detection of single influenza virions (~100 nm); the incorporation of plasmonic enhancements has since pushed the detection limit into the realm of single protein molecules. This sensitivity has been demonstrated on thyroglobulin, a protein marker used in evaluating efficacy of thyroid cancer treatments. Based on recentexperiments, we project a limit of detection of 5 kDa (~8 zg). These advances mean that label-free detection of bio-nanoparticles such as biowarfare toxins (e.g., Ricin ~32 kDa, Anthrax ~90 kDa) and disease markers (e.g., melanoma 84 kDa, breast cancer 290 kDa) are well within reach.


Wednesday, April 30 2014, 2:30
Freeman hall room 103


Michael E. Mann
Distinguished Professor of Meteorology and
Director of the Earth System Science Center
Pennsylvania State University

The Physics of Climate Change

I will review the basic underlying science of climate and climate change, including physically-based models of Earth's climate. I will motivate the use of a simple, zero-dimensional "Energy Balance Model" of Earth's radiative balance that can be used to estimate the global mean surface temperature of Earth. I will show how this model successfully reproduces the observed historical changes in global temperature, and how it can be used to assess various questions about future human-caused climate change.

Wednesday, April 16 2014, 2:30
Freeman hall room 103

Oleg Berman
Associate Professor of Physics
NYC College of Technology

Graphene based photonics and nanophotonics

The recent results of our studies of photonics, nanophotonics and plasmonics in graphene will be presented. We analyzed the nanophotonics and nanoplasmonics in graphene nanoribbon and photonics in graphene based metamaterials. The spaser with the net amplification of surface plasmons (SPs) in doped graphene nanoribbon will be described. The plasmons in THz region can be generated in a dopped graphene nanoribbon due to pumping, nonradiative excitation by two level quantum dots located along a graphene nanoribbon. The results for the minimal population inversion per unit area, needed for the net amplification of SPs in a doped graphene nanoribbon will be reported. The dependence of the minimal population inversion on the surface plasmon wavevector, graphene nanoribbon width, doping and damping parameters necessary for the amplification of surface plasmons in the armchair grapheme nanoribbon will be described. Besides, we will present the photonic one-dimensional (1D) and two-dimensional (2D) crystals based on graphene and dielectric constituents. The frequency band structure of 1D and 2D graphene-based photonic crystal will be reported.  The possibility of tuning the graphene-based spaser and photonic crystals by the voltage gate doping will be discussed.

Wednesday, January 29, 2014, 2:30
Freeman hall room 103

Student Colloquium Series

Brigid Mulroe
Milan Paspaley-Grbavac

Drew Rotunno

 
Wednesday, december 4, 2013, 2:30
freeman hall room 103

Vinod Menon
CUNY: Queens College & Graduate Center
Hyperbolic Metamaterials: Towards Broadband Control of Light-Matter Interaction

The interaction of light with matter can be engineered by controlling the photonic density of states (PDOS). I will discuss our recent work on optical topological transition in strongly anisotropic metamaterials that can be used to engineer the PDOS [1]. The transition in the topology of the iso-frequency surface from a closed ellipsoid to an open hyperboloid resulting in hyperbolic dispersion manifests itself in increased rates of spontaneous emission of emitters positioned in the near-field of the metamaterial. Being a non-resonant effect, this enhancement is observed over wide spectral bandwidth. Approaches to enhance light extraction from such structures as well as anomalous cavity scaling observed in cavities fabricated using such metamaterials will be discussed. Finally, we will also discuss metal-free and tunable hyperbolic metamaterial structures.

[1] “Topological transitions in metamaterials,” H. Krishnamoorthy, Z. Jacob, E. Narimanov, I. Kretzschmar, and V. M. Menon, Science 336, 205 (2012).
Wednesday, november 13, 2013, 2:30
freeman hall room 103

Student Colloquium Series

Ariel Fragale
"Perturbative Quark Mass Renormalization for Anisotropic Lattices"

Kathryn Reddy
"Einstein's Sedimentation Equilibrium Revisited: Quantifying particle interaction through analysis of sedimentation equilibrium"

Wednesday, november 20, 2013, 2:30
freeman hall room 103

Maria Gherasimova
University of Bridgeport

Self-assembly and targeted distribution of nanoscale germanium island clusters on silicon surface

Persistent interest in the self-assembly of nanoscale semiconductor structures (quantum dots or nanowires, from several nanometers to about 100 nm in size) is partly sustained by the anticipation of reaching the fundamental limits of silicon-based device miniaturization. Precise nanoscale control of the quantum dot (QD) positioning on a substrate is desirable for many potential applications, such as the realization of quantum cellular automata (as an alternative paradigm for the logic circuits) or targeted incorporation of nanoscopic internal light sources in the photonic structures. Targeted nucleation of strained Ge islands on Si surface has been accomplished by modifying the surface with the low dose focused ion beam (FIB) patterning, enabling reliable placement of individual QDs in the closely spaced encoded locations (tens of nanometers apart) over relatively large area patterns (tens of microns in size). Ge islands are synthesized in an ultra-high vacuum environment inside a transmission electron microscope equipped with a video-rate data capture capability for in situ analysis, immediately after the FIB implantation in an adjacent chamber. Our findings indicate that the pattern assembly fidelity becomes limited by the competition between the target nucleation sites for the available Ge adatoms in the sub-100 nm site separation regime, while nearly 100 % registration rates are obtained at larger distances. To overcome this limitation, we investigate QD self-assembly on single topographical features to obtain clusters of QDs with smaller separations. Our recent work is focused on the formation of groups of Ge islands on the locations defined by the residual trenches on a footprint of a larger island that has been desorbed, as well as spontaneous cluster formation on FIB patterns.
Wednesday, october 30 2013, 2:30
freeman hall room 103

Student Colloquium Series


Katrina Colletti
"Measuring Underground Neutron Fluxes for Neutrinoless Double Beta Decay"

Joe Sweeney
"Using the Generalized Pencil-of-Function method for analyzing lattice two-point functions"


Wednesday, october 16, 2013, 2:30
freeman hall room 103

Student Colloquium Series


Jenna Kocsis
 
Rachel Sattler


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