Physics Seminar

 physics seminar1

Physics Seminars will nominally be scheduled for Tuesdays at 2:30 pm in Optics Building Room 234. Coffee and cookies will be available 15 minutes prior to the start of each seminar.

Schedule

Upcoming Seminars

 

Schedule for Spring 2015

Tuesday, January 13, 2015

Optics Building 234, 2:30PM

Dr. Henry Everitt (AMRDEC)

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Tuesday, January 20, 2015

Optics Building 234, 2:30PM

Dr. Norbert Werner (KIPAC/Stanford)

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Tuesday, January 27, 2015

Optics Building 234, 2:30PM

Dr. Andrea Morandi (Physics/UAH)

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Tuesday, February 3, 2015

Optics Building 234, 2:30PM

Prof. David Weinberg (Astronomy/OhioState)

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Tuesday, February 10, 2015

Optics Building 234, 2:30PM

Open

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Tuesday, February 17, 2015

Optics Building 234, 2:30PM

Prof. Seyed  Sadeghi (UAH/Physics)

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Tuesday, February 24, 2015

Optics Building 234, 2:30PM

Dr. Michael Briggs (CSPAR/UAH)

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Tuesday, March 3, 2015

Optics Building 234, 2:30PM

Prof. Dawn Williams (Physics&Astronomy/University of Alabama)

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Tuesday, March 10, 2015

Optics Building 234, 2:30PM

Dr. Thomas Kohlgraf-Owens (Kord Technology)

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Tuesday, March 17, 2015

Optics Building 234, 2:30PM

Dr. Athina Meli (Univ. of Gent/Phyiscs & Astronomy)

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Tuesday, March 31, 2015

Optics Building 234, 2:30PM

Prof. Rick Trebino (Gergia Tech/Phyiscs)   

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Tuesday, April 7, 2015

Optics Building 234, 2:30PM

Prof. Anup Sharma (Alababa A&M/Phyiscs)

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Tuesday, April 14, 2015

Optics Building 234, 2:30PM

Dr. Grant Tremblay (Yale)

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Past Seminars

 

Tuesday, January 14, 2014

Optics Building 234, 2:30PM

Some Physical Properties of Cosmic Rays

Dr. Richard Lieu, Department of Physics, UAH

 

Abstract:  The population of cosmic rays with energy beneath the spectral `knee' is widely believed to be of Galactic origin, with diffusive shock acceleration at supernova remnants being the most favored acceleration mechanism.  The basics of this mechanism in the context of parallel and oblique shocks and the direct evidence supporting its existence from shell supernova remnants will be presented, along with the relativistic extension to include jet termination and superluminally oblique geometries.  Beyond the spectral `knee', the challenge is to find a mechanism that preserves the spectral `normalization' while steepening the slope by an index of 0.4.  Such attractive possibilities as the re-acceleration of `pre-knee' population by colliding shock fronts, and large scale shocks including those associated with merging clusters of galaxies and cluster wind accelerated by dark energy, will be addressed.  Lastly, I will discuss the GZK cutoff of the highest energy cosmic rays and its relevance to the question of Lorentz invariance violation, by explaining how the evidence gathered in the last decade against such a violation from stellar interferometry and Fermi gamma-ray observations reinstated the validity of the cutoff prediction.  

 

Full Presentation

 


Tuesday, January 21, 2014

Optics Building 234, 2:30PM

Particle acceleration and associated radiation in relativistic jets with shocks and shear-flow

Ken Nishikawa (UAH/Physics)
 

Abstract:  We investigated particle acceleration and shock structure associated with an unmagnetized relativistic jet propagating into an unmagnetized plasma. The Weibel (filamentation) instability is excited in the jet and shocks are formed. Strong magnetic fields generated in the trailing shock contribute to the electron’s transverse deflection and acceleration. Kinetic Kelvin-Helmholtz instability (KKHI) is also responsible to create strong magnetic fields. The velocity shears in core-sheath jets create strong magnetic field perpendicular to the jet. We examine how the Lorentz factors of jets affect the growth rates of KKHI. We have calculated, self-consistently, the radiation from electrons accelerated in these turbulent magnetic fields in the shocks. We found that the synthetic spectra depend on the bulk Lorentz factor of the jet, its temperature and strength of the generated magnetic fields. The calculated properties of the emerging radiation provide our understanding of the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants.

 

Full Presentation

 


Tuesday, January 28, 2014

Optics Building 234, 2:30PM

Quantum nanosensors: Towards optical detection and recognition of single biological molecules using the rules of quantum mechanics and plasmonics

Seyed Sadeghi, UAH Department of Physics (seyed.sadeghi@uah.edu)
 

Abstract:  Conventional nanosensors are based on intrinsic resonances of metallic nanoparticles (localized surface plasmon resonances) and/or semiconductor quantum dots (excitons). In this talk I discuss the results of our recent theoretical investigation that have shown how one can use the rules  of quantum mechanics in a system consisting of one metallic nanorod and one semiconductor quantum dot to design plasmonic nanosensors capable of digital optical detection and recognition of single biological molecules. In such sensors the adsorption of a specific molecule to the nanorod turns off the emission of the system when it interacts with an optical pulse having a certain intensity and temporal width. The proposed quantum sensors can count the number of molecules of the same type or differentiate between molecule types with digital optical signals that can be measured with high certainty. I discuss the physics behind such nanosensors and highlight how, despite the ultrafast quantum decoherence processes in quantum dots, we expect such sensors to perform at room temperature.

 

Full Presentation

 


Tuesday, February 4, 2014

Optics Building 234, 2:30PM

Funding Opportunities for Graduate and Undergraduate students at The University of Alabama in Huntsville

Ms. Kenya Cole, Contract Specialist, Office of Sponsored Programs; Ms. Susan Phelan, Grant Writer, Office of Proposal Development; Ms. Laurie Collins, Contracts & Grants Coordinator, Office of Sponsored Programs


Abstract:
 UAH is a major research university with over $225million in research proposals submitted in FY13 and almost $100million in research expenditures.  The Office of Sponsored Programs is committed to providing support to Graduate and Undergraduate students who wish to submit proposals for funding that would enhance their education and broaden their research experience.

Ms. Phelan will discuss her role as Grant Writer and provide resources for finding funding opportunities.

Ms. Cole will provide information about specific upcoming graduate student funding and what to expect when applying.

Ms. Collins will conclude with final instructions for students about who to contact if interested and other practical issues.

 


  

Tuesday, February 11, 2014 

Optics Building 234, 2:30PM

Silicon Photonics: a Scientific and Technological Platform

Dr. Jaime Cardenas (Cornell University/Nanophotonics)
 

Abstract: Silicon photonics is a versatile optical platform on which we can gain scientific insight and achieve technological breakthroughs: from invisibility cloaks to radio frequency and on-chip digital communications. In this talk, I will present my research on several silicon photonics topics. We will delve into the basic properties of silicon that make it a nearly ideal material for photonics, and I will present the techniques that we developed to achieve efficient coupling of light into a silicon chip, ultimately leading to applications such as the realization of linear RF modulators, and how we demonstrated the carpet cloak at optical frequencies. 

  


 

Tuesday, February 18, 2014

Optics Building 234, 2:30PM

Chaotic Systems with Analytic Solutions

Dr. Jon Blakely (AMRDEC)

 

Abstract: 'Chaos' is complex, non-repeating behavior displayed by nonlinear dynamical systems. Well known physical examples include atmospheric convection and oscillating chemical reactions. Mathematically, these phenomena are typically described by nonlinear differential equations, for which there are no general methods for finding analytic solutions. Thus, it is common practice to resort to numerical methods to study chaos. Nonetheless, there are a few chaotic systems for which analytic solutions are known. In this talk, I will describe one such example of 'solvable chaos'. I will show how a complicated, non-repeating chaotic solution can be derived and written in a concise form. Then I will show experimental data from some physical implementations of this dynamical system including a chaotic electronic circuit, and a spring-mass-type mechanical chaotic oscillator.

Full Presentation 

 


 

Tuesday, February 25, 2014

Optics Building 234, 2:30PM

Macroscopic and Microscopic Instabilities in Relativistic Jets

Dr. Philip E. Hardee, Professor Emeritus (The University of Alabama, Tuscaloosa) 


Abstract: Relativistic jets be they Poynting flux or kinetic flux dominated are current driven (CD) and/or Kelvin-Helmholtz (KH) velocity shear driven unstable. These macroscopic MHD instabilities may be responsible for some observed larger scale twisted jet structures and typically do not disrupt jets on less than kiloparsec scales.  Here I review our understanding of the jet properties that will lead to the observed relative stability of astrophysical jets. In addition, I review the progress made on the microscopic scale plasma instabilities in shocks and velocity shears that may lead to magnetic field generation and that does lead to the particle acceleration required to produce the observed emission from radio wavelengths to TeV energies.  Finally, I discuss these instabilities in the context of the jet in M 87.

Full Presentation

 


 

Wednesday, February 26, 2014

Optics Building 234, 2:30PM

Origin of galactic cosmic rays - are supernova remnants particle PeVatrons?

Dr. Jacek Niemiec (IPN, Krokow)


Abstract: 
Diffusive shock acceleration process at supernova remnant shocks is widely believed to be the major source of Galactic cosmic rays of energies up and possibly beyond 10^15 eV (1 PeV). I will present current theoretical and observational evidence supporting this paradigm and point outstanding problems awaiting further investigation. I will also discuss the expected contribution of the planned Cherenkov Telescope Array (CTA) in resolving the question whether supernova remnants operate as PeVatrons.

Full Presentation

 


 

Thursday, February 27, 2014

Optics Building 234, 1:30PM

Measurement of cluster masses via Sunyaev-Zel’dovich Effect observations of a complete sample of X-ray selected galaxy clusters 

Ashley Lindley (Dissertation talk)
 
 

Abstract: A powerful method for investigating cosmology is to observe the evolution of clusters over time, accomplished through analysis of cluster properties over a range of redshifts.  One important property to examine is the cluster mass function, i.e., the number density of clusters of a given mass at a given redshift range.  Studies of the evolution of the cluster mass function over redshift ranges are used for obtaining cosmological constraints.  To expand our mass knowledge to higher redshifts, a robust method for determining cluster masses utilizing radio data is desired.

Presented are measurements of the Sunyaev-Zel'dovich Effect of a sample of 32 galaxy clusters observed with the Sunyaev-Zel'dovich Array, an interferometric array at the Combined Array for Research in Millimeter-wave Astronomy observatory.  The sample is selected from the most luminous galaxy clusters in the ROSAT Bright Cluster Sample in the redshift range 0.15  z  0.3. The data are analyzed using a method that makes use of the virial theorem to measure masses directly from the SZE observations.  It is shown that masses can be accurately estimated from the SZE data alone, provided the availability of an average gas mass fraction that can be calibrated separately from X-ray observations. This method is therefore an alternative to mass-observable scaling relations to measure dynamical masses directly from SZE observations.

 


 

Tuesday, March 4, 2014

Optics Building 234, 2:30PM

Understanding the physics of galaxy clusters

Dr. Andrea Morandi, Department of Physics, UAH
 

Abstract: In this talk, I will review the physics of galaxy clusters, focusing on what can be learned from Xray, Sunyaev Zel'dovich and lensing observations, hydrodynamical numerical simulations and on the recent development on the modeling of both dark matter and intracluster medium. I will discuss temperature and entropy profiles, scaling properties, in order to constrain the non-gravitational processes which affect the thermal history of the gas, as well as how we can use galaxy clusters as cosmological probes. Then I will discuss the first determination of the intrinsic shape and the physical parameters of both dark matter and intracluster medium in triaxial galaxy clusters via mutliwavelenght analysis. Finally, I will overview recent development in the virialization region of clusters.

Full Presentation

 


 

Tuesday, March 11, 2014

Optics Building 234, 2:30PM

Femtosecond Frequency Combs and Their Applications

Dr. Lingze Duan, Department of Physics, UAH
 

Abstract: Femtosecond frequency combs combine broad spectral width with high spectral precision and offer unprecedented frequency stability. These features make them versatile tools. Over the last few years, we have explored a number of novel applications that can take advantage of the excellent performance of frequency combs. In this talk, I will first give a brief review of the concept and the main characteristics of femtosecond frequency combs, and then I will describe our recent work on frequency comb-based remote clock transfer, target tracking, tomographic imaging and refractive index measurement.

Full Presentation

 


 

Tuesday, March 18, 2014

Optics Building 234, 2:30PM

Studying baryon physics with galaxy groups and clusters

Prof. Ming Sun, Department of Physics, UAH
 

Abstract: Most of the cosmic baryons are not locked in stars. Understanding the properties and underlying cause of baryons that are not locked into stars will shed light on the formation of galaxies, which only account for ~ 10% of baryons. Galaxy groups and clusters are the only systems where the bulk of the baryons have been detected. This makes them great objects to study baryon physics, such as cooling, star formation, heating from supermassive black holes and galactic winds. Moreover, a better understanding of these baryon processes is also important for cluster cosmology. In this talk, I will discuss several topics related to the study of baryon physics in groups and clusters, including AGN heating, ram pressure stripping, star formation and radio relics/halos.

Full Presentation

 


 

Tuesday, April 1, 2014

Optics Building 234, 2:30PM

Timing noise of radio pulsars and implications to neutron star's interior structure and gravitational wave detection

Dr. Shuang-Nan Zhang, Department of Physics, UAH

 

Abstract: Radio pulsars are the most stable natural clocks in the universe, yet timing noises can still be substantial when the times of arrivals of their pulses are fitted with some well accepted spin-down models or templates of pulsars. In this talk, I will review our recent work on modeling the timing noises of radio pulsars. Our model includes a long-term power-law decay modulated by periodic oscillations of the surface magnetic fields of neutron stars, which can explain the statistical properties of their timing noises. We find that the spin-down evolutions of young and old pulsars are dominated by the power-law decay and periodic oscillations, respectively. By applying our model to the individual spin-down evolutions of many well-measured radio pulsars, we find evidence for Hall drifts and Hall waves in the crusts of neutron stars. Finally we also attempt to improve the sensitivity of detecting gravitational waves with pulsars by applying our model to reduce the timing residuals of millisecond radio pulsars. The main publications related to this talk can be found at this ads link: http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?library&;;libname=pulsar+timing&libid=44cf02882f

Full Presentation

 

 


 

 

Special Seminar - Thursday, April 3, 2014

Optics Building 234, 10:30AM

Future Missions of Space High Energy Astrophysics of China

Dr. Shuang-Nan Zhang


Abstract
: I will first review several missions of China on space high energy astrophysics approved and to be launched in the next several years: (1) The Hard X-ray Modulation Telescope (HXMT) to be launched in 2015, which has three sets of collimated detectors with broad band (1-250 keV) and large effective area (400-5000 cm^2); (2) The dedicated gamma-ray (50-350 keV) polarization experiment POLAR onboard China’s Tiang-Gong-2 spacelab, jointly developed between China and Switzerland and to be launched in 2015; (3) The dark matter particle and cosmic ray detection satellite (DAMPE) to be launched in 2016-2017, jointly developed between China, Switzerland and Italy; (4) The multi-wavelength Space Viable Object Monitor (SVOM) mission, jointly developed between China and France and to be launched in around 2020.

 

I will then describe three candidate missions selected for further study and technology development: (1) The X-ray Timing and Polarization (XTP) Observatory, which is made of a large array of X-ray telescopes with focal length of 4-5 meters; (2) The High Energy cosmic Radiation Detection (HERD) facility onboard China’s Space Station, which has large geometrical factors and broad energy ranges for cosmic rays, electrons and gamma-rays and is made of a large stack of cubic scintillators surrounded by silicon microstrip detectors from five sides; (3) The Einstein Probe (EP), which is essentially a large Lobster Eye wide-field all-sky-monitor working between 0.5-4 keV band and has a fast follow-up X-ray telescope. All these three future missions are planned for launch and operation in around 2020-2025.

Finally I will mention briefly several other candidate space astronomy missions currently in different development phases, e.g., on dark energy survey, exoplanets, 21 cm emission in the early universe, missing baryon, etc.

Full Presentation

 


 

Tuesday, April 8, 2014

Optics Building 234, 2:30PM

Muon Radiography as a Probe of the Interior Structure of Small Solar System Bodies

Prof. Richard S. Miller, Professor, Department of Physics, UAH

AbstractSmall Solar System Bodies (SSSBs) such as asteroids are remnants of the early solar system. Our understanding of these objects has changed significantly over the past few decades with studies of surface composition, crater morphologies, and other physical properties by flyby and rendezvous missions contributing to a deeper understand our solar system’s formation and evolution. However, in contrast to these surface studies there has been no direct measurement of their internal structure - critical information which remains largely unknown. We are developing a new approach to the study of SSSBs: cosmic-ray induced muon radiography. This technique will enable remote determination of the density and three-dimensional structure of SSSBs using muons generated naturally by cosmic-ray interactions in these planetary bodies. Once fully implemented this concept will: a) Remotely measure density and structure variations for meter- to kilometer-scale asteroids and/or comets, b) uniquely enhance our understanding of the early solar system by providing new measurements of density, macroporosity, and other structural features of SSSBs, c) provide critical inputs to computational models of Near Earth Objects (NEOs) for impact avoidance strategies, and d) support efforts related to asteroid retrieval, mining, and in situ resource utilization. I will report the developmental details, limitations of the approach, and describe how such an approach might be implemented near-term.


 

Tuesday, April 15, 2014

Optics Building 234, 2:30PM

The Solar Storm of the Century: Did we dodge the big one in 2012?

Dr. Alex Young (NASA Goddard Space Flight Center)


Abstract: On July 23, 2012, the sun erupted sending a billion plus tons of plasma and magnetic field at speeds upwards of 12 million km per hour hurdling through the inner solar system. This kind of event, called a coronal mass ejection (CME), is a main driver of space weather and can significantly impact our technology on Earth and in space. This CME is the largest ever observed in the space age. Fortunately for us, the eruption directly impacted the STEREO A spacecraft but was not Earth-directed. If the CME had impacted Earth instead of STEREO, computer modeling estimates that the event could have produced geomagnetic storming on Earth at levels greater than the famous “perfect storm” Carrington event of 1859. In this talk, I will provide an overview of space weather science and forecasting. Then will I discuss what the July 2012 event tells us about extreme space weather and what impact it could have had on our critical infrastructure.

Tuesday, August 26, 2014

Optics Building 234, 2:30PM

A Journey of Burst Adventures

Dr. Binbin Zhang (CSPAR/UAH)

Abstract: In this talk I will review our current understanding of Gamma-Ray Bursts (GRBs), including their prompt emission and  mulit-wavelength observations. The talk will take you to  several milestones in the history of GRB research, along which I will discuss several difficult but fun topics such as GRB  radius, compositions, dissipation, radiation mechanisms, diversities and classifications.

Presnetation


Tuesday, September 2, 2014

Optics Building 234, 2:30PM

Physical Random Number Generation Using Chaos

Dr. Ned Corron (U.S. Army RDECOM)

Abstract: Chaos is a type of dynamics generated by deterministic systems that exhibit random, unpredictable behavior. The capability to generate randomness from a deterministic process is, to say the least, counterintuitive.   However, in terms of Shannon's information theory, a chaotic oscillator is an information source characterized by positive entropy when observed with finite precision. As such, chaotic dynamics offers a physical source of randomness that can be exploited for technological application. In this talk, we will explore the nature of chaos as an information source, including how determinism can yield random behavior, and consider recent reports of very fast physical random number generation using laser chaos.

Presentation


Tuesday, September 9, 2014

Optics Building 234, 2:30PM

Detecting WHIM filaments with UV and X-ray spectroscopy - The sightline towards PKS2155-304

Prof. Max Bonamente (Physics/UAH)       

Abstract: Much of the universe's baryons are located in a diffuse warm-hot intergalactic medium (WHIM), and not in collapsed structures such as galaxies or stars. The diffuse nature and their temperature (T=10^5-10^7 K) make them challenging to observe. A useful probe of these baryons is absorption spectroscopy, which uses a bright background source to detect the WHIM in absorption. We use FUSE and HST spectroscopy to measure a number of absorption lines towards a bright quasar, PKS2155-304. These absorption lines match the prediction of WHIM structures based on the distribution of galaxies from the two-degree-field (2dF) galaxy redshift survey. We show that WHIM structures can be identified efficiently from optical galaxy surveys, and their hydrogen content estimated accurately using results from numerical simulations.                             

Presentation


Wednesday, September 17, 2014 (attention for the date)

Optics Building 234, 2:30PM

The Search for Black Holes in Globular Clusters

Prof. Jimmy Irwin (UA Tuscaloosa)

Abstract: The existence of both stellar- and intermediate-mass black holes within globular clusters has been the subject of intense debate for decades. The rich globular cluster populations of nearby elliptical galaxies provide much more fertile hunting grounds over the meager globular cluster population of the Milky Way to search for accreting black holes emitting near their Eddington limit. Extreme X-ray variability of >1e39 ergs/s sources provide the best means of identifying such black holes. I will present the current evidence for black hole existing within globular clusters, and discuss the possibility that intermediate-mass (100-10,000 dolar mass) black holes reside at the centers of globular clusters much like supermassive black holes reside at the centers of galaxies.

Presentation


Tuesday, September 23, 2014 (cancelled)

Optics Building 234, 2:30PM 

Magnetic Reconnection: Anomalous resistivity a myth or reality affecting reconnection!

Prof. Nagendra Singh (ECE/UAH)

Abstract: Anomalous resistivity has been a controversial topic for affecting magnetic reconnection in laboratory, space and astrophysical plasmas. If one takes the meaning of anomalous resistivity in a broad physical sense of the loss of momentum from the current carrying particles (electrons and/or ions) in the reconnection diffusion region, the effective resistivity is absolute reality. This effective resistivity supports the reconnection (inductive) electric field. On the other hand, if one defines anomalous resistivity in a limited sense as that arising from instabilities generated by current-driven instabilities, then the application of this resistivity is limited to reconnection in electron current sheets when they thin down to a half width of the order of a few electron skin depths. Such anomalous resistivity plays a role in the onset of the reconnection. Since onset requires a reduction in current at the location of the onset, anomalous resitivity helps reduce the current and thus breaks the magnetic field lines, which subsequently rejoin affecting the reconnection. Once the reconnection has occurred, then the anomalous resistivity has no role any more, it is the effective resistivity due to the transport of the current carriers out of the diffusion region takes the role of resistivity. This effective resitivity does not dissipate power locally into heat; it transports momentum/energy out of the diffusion region.

We will discuss these issues along with analytical calculations and/or 3D PIC numerical simulations of reconnection onset preceded by the generation of anomalous resistivity involving current-driven ion modes and their modulational collapse into filamentary structures of electric field and density cavities.

We will briefly visit the often used generalized Ohm’s low in explaining reconnection, mainly to point out that the various terms in the law do not ‘generate’ electric fields. Instead, they merely support the reconnection (induction) electric field. It is similar idea as in an electrical circuit driven by a voltage source; the source generates the voltage and the passive elements (resistor) merely support the part of the voltage drop.

 

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Tuesday, September 30, 2014

Optics Building 234, 2:30PM

Exciting physics with merging galaxy clusters

Dr. Reinout van Weeren (Harvard/CfA)

Abstract: Merging galaxy clusters are excellent laboratories to study particle acceleration in dilute cosmic plasmas, to explore the nature of dark matter, and to investigate galaxy cluster growth. In a few dozen merging galaxy clusters diffuse extended radio emission has been found, implying the presence of relativistic particles and magnetic fields in the intracluster medium. A major question is how these particles are accelerated up to such extreme energies. In this talk I will present X-ray and radio observations of merging clusters which provide new insights about the acceleration mechanism.  I will also show the latest results from the new revolutionary low-frequency telescope LOFAR, allowing observations of diffuse cluster emission with unprecedented resolution and sensitivity.  Finally, I will highlight ongoing work to constrain the properties of dark matter with merging clusters.

Presentation

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Tuesday, October 7, 2014

Optics Building 234, 2:30P

Optical/Digital Doomsday Navigation

Prof. Don Gregory and Mr. John Jasper (Physics/UAH)

In most EOTWAWKI (End Of The World As We Know It) event scenarios, it is assumed that access to the GPS satellite system will be limited or nonexistent. An updated “navigation by the stars” technique will be presented which is based on a classic Fourier optics idea covered in any course on the subject. The digital implementation of this analog optical technique utilizes a stand-alone (no internet) high-end PC equipped with a programmable gaming board and is capable of accurately aiding global navigation of any type, especially spacecraft. It has recently been used on a NASA/MSFC X-ray balloon flight to successfully monitor telescope alignment. The demonstration of this technology during the seminar will be interactive with attendees being allowed to convince themselves the technique really works.

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Tuesday, October 14, 2014

Optics Building 234, 2:30PM

Testing optical surfaces

Dr. Patrick Readon (Center for Applied Optics/UAH)

Testing optical surfaces for errors employs relatively straightforward instrumentation and methods.  However, for even the most simple surfaces, getting absolute measurements becomes quite complex.  This talk discusses optical testing methods, for simple rotationally symmetric spherical surfaces, and the modifications surfaces that must be employes to extract useful data on more complicated aspheres, off--axis aspheres, and general free-form surfaces.  Some specific examples will be given, include recent efforts in testing near-cylindrical surfaces.

Presentation

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Tuesday, October 21, 2014

Optics Building 234, 2:30PM

Cherenkov Telescope Array: Adventures in ground-based gamma-ray astronomy

Dr. Valerie Connaughton (CSPAR/UAH)

Ground-based Very High Energy (VHE) gamma-ray astronomy has moved from the fringes of the barely possible to become a vibrant field that explores the most energetic phenomena in the universe. VHE science is at the crossroads of physics and astronomy and draws from a diverse community of scientists interested in subjects from the origin of cosmic rays to the nature of dark matter through black hole formation and the invariance of the speed of light. I will review the history of ground-based gamma-ray astronomy from its lonely days in the wilderness of the Sonoran desert to the ambitious plan of a worldwide consortium dedicated to building the Cherenkov Telescope Array (CTA).

Presentation

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Tuesday, October 28, 2014

Optics Building 234, 2:30PM

The Phase Rule and Chemical Equilibrium near the Critical Point of Solution

Prof. James Baird (Chemistry/UAH)

We will show how the principle of critical point universality, which is thought to apply to all critical phenomena, can be applied to understand chemical equilibria in binary liquid mixtures with a critical point of solution.

Presentation

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Tuesday, November 4, 2014

Optics Building 234, 2:30PM

Novel Stimuli-Responsive Shape Memory Polymers for Smart Nanooptics

Prof. Peng Jiang (Chemical Engineering/University of Florida)

Photonic crystals may hold the key to continued progress towards all-optical integrated circuits and quantum information processing. Shape memory polymers (SMPs), which can memorize and recover their permanent shapes upon application of an external stimulus (e.g., heat and light), provide a unique opportunity to achieve smart, reconfigurable photonic crystals with bistable states. Unfortunately, most of the currently available SMPs are thermoresponsive and they suffer from slow response speed and heat-demanding programming and recovery steps. Although pressure is an easily adjustable process variable like temperature, pressure-responsive SMPs are largely unexplored. By integrating scientific principles drawn from two disparate fields that do not typically intersect - the fast-growing photonic crystal and SMP technologies, we have recently developed a new type of SMP that enables unusual "cold" programming and instantaneous shape recovery triggered by applying an external pressure or exposing to an organic vapor (e.g., acetone) at ambient conditions. This unique integration has not only led to the discovery of the new pressure- and vapor-responsive SMPs, it also provides a simple and sensitive optical technique for investigating the intriguing shape memory effects at nanoscale. Simultaneously, stimuli-responsive SMPs can empower smart and reconfigurable nanooptical devices and thus can significantly broaden the fabrication and application scopes of current photonic crystal technology. The applications of these novel SMPs in a wide spectrum of fields ranging from smart nanooptical devices (e.g., tunable antireflection coatings) to chromogenic pressure and vapor sensors to new biometric and anti-counterfeiting materials will also be demonstrated. Improved fundamental understanding of capillary pressure-induced macropore collapse, as well as capillary condensation of vapors in complex hierarchical porous networks which is a topic that has received little examination, will also be presented.

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Tuesday, November 11, 2014

Optics Building 234, 2:30PM

Genus Topology of Large-Scale Structure in the Cosmic Microwave Background:  Overview and Recent Results from BICEP2

Dr. Wesley Colley (CMSA/UAH)

I will provide an overview of using genus topology to characterize large-scale structure in the Universe, and a brief overview of science  from the cosmic microwave background.  I will then discuss our group's  work on topology from the WMAP data, and our very recent work on the  BICEP2 data, the latter of which appears to confirm, at least partially,  the discovery of a gravity wave signature in the CMB.


Presentation

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Tuesday, November 18, 2014

Optics Building 234, 2:30PM

Microparticle Optics

Dr. Kirk A. Fuller (NSSTC/UAH)

The interaction of visible light with fine particles will be the focus of this presentation. Beginning with an overview of the exact theory of electromagnetic scattering and absorption by a sphere (Lorenz-Mie theory), the relevance of microparticle optics will be discussed as it pertains to atmospheric optics, remote sensing and photovoltaics. Issues involving nonspherical particles, polarimetry and recent findings at UAH related to chem/bio sensing will then be addressed.

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Tuesday, November 25, 2014 (cancelled)

Optics Building 234, 2:30PM

Prof. John Fix (Physics/UAH)

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Tuesday, December 2, 2014

Optics Building 234, 2.30PM

Supermassive black hole binaries

Prof. Tamara Bogdanovic (CRA/Georgia Tech)

Gravitationally bound supermassive black hole binaries are thought to be a natural product of galactic mergers and growth of the large scale structure in the universe. They however remain observationally elusive, thus raising a question about characteristic observational signatures associated with these systems. In my talk I will discuss current theoretical understanding and latest advances made in observational searches for supermassive black hole binaries.

Presentation

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