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Physics Colloquia    Fall 2014 (usually Fridays 2:00 PM in SE 319)

Titles link to the abstracts.

Date
Speaker
Title
Aug 29
Georgios Kalantzis, FAU
Sep 19
Paul M. Alsing, AFRL
Sep 26
Wei Zeng, FIU
Oct 10
Robert Alfano, CUNY
Oct 24
Sarah Du, FAU
Nov 7
Pablo Laguna, Georgia Tech
Nov 21
Ted Jacobson, UMD
  


Colloquium Abstracts

From synaptic plasticity to IMRT optimization
Georgios Kalantzis, Aug 29
In neuroscience, synaptic plasticity is the ability of synapses to strengthen or weaken over time, in response to increases or decreases in their activity. (Wikipedia) Radiotherapy is the main non-surgical treatment for head and neck cancer. In recent years, intensity-modulated radiotherapy (IMRT) has become widely adopted for radiotherapeutic management of head and neck cancer because of its ability to achieve a highly conformal dose distribution. (M. Kong et al., Radiat Oncol J. 2013 Mar;31(1):1-11.)
 
Advances in Biomedical Optics
Paul M. Alsing, Sep 19
In this talk, we extend the investigation of Adami and Ver Steeg [Class. Quantum Grav. 31, 075015 (2014)] to treat the process of black hole particle emission as an effective parametric down conversion (PDC) with a depleted (vs. un-depleted) pump. We investigate both the short time (non-depleted pump) and long time (depleted pump) regimes and its impact on the Holevo channel capacity for communicating information from the far past to the far future in the presence of Hawking radiation. The new feature introduced in this paper is the coupling of the emitted modes through the black hole ‘source pump’ which can be depleted. Within our analogous quantum optical model we examine the entanglement between two emitted particle/anti-particle and anti-particle/particle pairs coupled via the black hole (BH) depleted ‘pump.’ We also discuss the ’Page time’ for our model which refers to the conventionally held belief that the information in the BH radiation becomes significant after the black hole has evaporated half its initial state into the outgoing radiation. Lastly, we outline our results on the effect of BH particle production/evaporation on two modes in the exterior region of the BH event horizon that are initially maximally entangled, when one mode falls inward and interacts with the black hole and the other remains forever outside and non- interacting.
 
Surface Ricci Flow and Its Applications
Wei Zeng, Sep 26
Ricci flow has been successfully applied in the proof of Poincaré’s conjecture, which deforms the Riemannian metric proportionally to the curvature, such that the curvature evolves according to a heat diffusion process. Ricci flow offers a powerful tool for shape registration and geometric analysis and has been used to tackle the following fundamental problems in engineering and biomedicine: conformal brain mapping and virtual colonoscopy in medical imaging; 3D human face registration and deformable surface tracking in computer vision; global surface parameterization in computer graphics; homotopy detection in computational topology; delivery guaranteed greedy routing and load balancing in wireless sensor network, and so on. This talk focuses on the theory of discrete surface Ricci flow, the computational algorithms and their applications in practice.
 
Advances in Biomedical Optics
Robert Alfano, Oct 10
The underlying optical physics behind linear and nonlinear processes involved in optical biopsy will be presented. The recent salient advances in biomedical optics to be discussed are : the key fingerprint biomarker of tryptophan to detect aggressive cancer cells; the two new NIR spectral windows( about 1250 nm and 1660nm ) with less scattering of light in tissues to image deeper into tissue ; the use of the of upper singlet S2 for dyes to increase imaging depth using two photon fluorescence microscope techniques for brain; the use of spatial frequencies spectra to detect structure changes in cancerous tissues vs normal tissues ; and most of all describe the use of compact optical analyzers for cancer detection without removing tissue for biomedicine applications.
 
Microfluidics for the Study of Biorheology and Biomechanics of Red Blood Cells
Sarah Du, Oct 24
Studies of the mechanics of single biological cells and cell populations offer useful insights into the mechanistic origins of human diseases, and pave the way for novel disease diagnostics, drug efficacy assays, and therapeutics. Red blood cell (RBC) is unique among human cells in that its membrane is the only structural component to maintain mechanical stability. The remarkable deformability is a main rheological property of RBCs and is one of the most important factors of blood flow to ensure mechanical filtering process in the microcirculation. We are interested in development of various experimental microfluidic platforms (passive and active) to quantitatively characterize the rheology and mechanical properties of RBCs. We demonstrate the capabilities of these methods by determining the deformation, velocity, and morphology characteristics of human RBCs and exploring the relationships between these cellular characteristics and onset and progression of their disease states. We hope these methods can provide potentially helpful tools to characterize quickly and effectively the isolated biomechanical and rheological properties of cells in a large population, for probing the pathological states of cells, disease diagnostics, and drug efficacy assays.
 
Prompt Accretion in Tidal Stellar Disruptions by Massive Black Holes
Pablo Laguna, Nov 7
A bright flare followed at late times by a power-law decay in luminosity are expected to be the generic signatures of a tidal disruption event. They are produced when the stellar debris returns to the vicinity of the massive black hole, self-intersects and eventually forms an accretion disk. In the canonical scenario of a solar-type star disrupted by a million solar mass black hole, the time elapsing between the disruption of the star as it passes periapsis and the formation of the accretion disk could be years. I will present results from a new class of tidal disruption events of solar-type stars in which the flare and disk formation take place promptly after disruption, with the accretion remaining super-Eddington throughout this process. The new class involves ultra-close encounters with intermediate mass black holes. I will discuss how these events could potentially be used as the smoking gun for the identification of intermediate mass black holes.
 
Black hole thermodynamics, then and now
Ted Jacobson, Nov 21
The outlandish notion that a black hole has a huge entropy, proportional to the horizon area in Planck units, was proposed in 1972 by Jacob Bekenstein, then a graduate student. Though initially rejected by experts, this idea was quickly embraced after Hawking's astonishing 1974 discovery that black holes radiate like a hot body in thermal equilibrium. I will recount the story of the origin and development of Black Hole Thermodynamics, and will discuss where it has led us so far, and what are the current puzzles and prospects.
 
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