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X-ORIGINAL-URL:https://uwm.edu/physics
X-WR-CALDESC:Events for Physics & Astronomy
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DTSTART;TZID=America/Chicago:20170908T153000
DTEND;TZID=America/Chicago:20170908T163000
DTSTAMP:20170905T195621Z
CREATED:20170828T154001Z
LAST-MODIFIED:20170905T195621Z
UID:10376407-1504884600-1504888200@uwm.edu
SUMMARY:Physics Colloquium: Zhizhen (Jane) Zhao
DESCRIPTION:“2D Class Averaging of Cryo-Electron Microscopy Images”\nZhizhen (Jane) Zhao\, U of I – Urbana/Champaign\n \nCryo-electron microscopy (EM) single-particle reconstruction is the process by which 3D density maps are obtained from a set of low-dose cryo-EM images of individual macromolecules.  The low signal-to-noise ratio (SNR) of individual particle images makes it difficult to evaluate the images in a particle stack and reconstruct ab initio models.  2D class averaging is a crucial step to increase the SNR of raw projection images by clustering and averaging noisy images from similar viewing directions.  However\, without prior knowledge of the shape of the macromolecule\, it is challenging to accurately identify images with similar views at low SNR. \nIn this talk\, I introduce our 2D class averaging procedure and the computational methods within the pipeline.  We apply steerable principal component analysis to compress and denoise images.  We construct rotational invariant features of 2D images and use a fast approximate nearest neighbor search algorithm to achieve efficient initial classification.  The pairwise alignment of particle images are performed among the nearest neighbors.  The computational complexity of the initial classification scales linearly with the number of images.  At extremely low SNR\, the initial nearest neighbor list contains outliers.  Therefore\, we further improve the results by taking into account the geometry of the data manifold and the linear transformations between nearest neighbor pairs.  We show that our procedure succeeds at remarkably low SNRs.
URL:https://uwm.edu/physics/event/physics-colloquium-zhihen-zhao/
LOCATION:Lapham 160\, 3209 N. Maryland Ave.\, Milwaukee\, WI\, 53211\, United States
CATEGORIES:Physics Colloquia
X-TRIBE-STATUS:
GEO:43.0757204;-87.8840564
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=Lapham 160 3209 N. Maryland Ave. Milwaukee WI 53211 United States;X-APPLE-RADIUS=500;X-TITLE=3209 N. Maryland Ave.:geo:-87.8840564,43.0757204
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Chicago:20170915T153000
DTEND;TZID=America/Chicago:20170915T163000
DTSTAMP:20170918T134707Z
CREATED:20170912T133503Z
LAST-MODIFIED:20170918T134707Z
UID:10383472-1505489400-1505493000@uwm.edu
SUMMARY:Physics Colloquium: Mark A. Rizzo
DESCRIPTION:“Homotransfer FRET Sensors for Biological Exploration”\nMark A. Rizzo\, University of Maryland School of Medicine \nGenetically-encoded biosensors can reveal the dynamics of molecular regulation within living cells and tissues with unprecedented detail.  Conventionally\, these reagents incorporate Forster transfer pairs of different colors into their design to create a ratiometric readout. While this approach ought to be inherently quantitative\, the signal-to-noise of intensity-based measurements can limit the utility of the approach. To overcome these limitations for biological applications\, two strategies have been developed. First\, existing FRET biosensors were converted to homotransfer “Fluorescence Anisotropy Reporters (FLAREs).”  Measuring FRET via fluorescence polarizations improves the signal-to-noise of the sensors and enables multiplexing of different colors.  Second\, an improved red fluorescent protein was developed entirely in silico using statistics-guided engineering.  The new red fluorescent protein\, mVermilion\, is twice as bright as mCherry and shows improved fluorescence polarization properties for FLARE-type sensors.
URL:https://uwm.edu/physics/event/physics-colloquium-mark-a-rizzo/
LOCATION:Lapham 160\, 3209 N. Maryland Ave.\, Milwaukee\, WI\, 53211\, United States
CATEGORIES:Physics Colloquia
X-TRIBE-STATUS:
GEO:43.0757204;-87.8840564
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=Lapham 160 3209 N. Maryland Ave. Milwaukee WI 53211 United States;X-APPLE-RADIUS=500;X-TITLE=3209 N. Maryland Ave.:geo:-87.8840564,43.0757204
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Chicago:20170922T153000
DTEND;TZID=America/Chicago:20170922T163000
DTSTAMP:20170914T212931Z
CREATED:20170912T133054Z
LAST-MODIFIED:20170914T212931Z
UID:10376409-1506094200-1506097800@uwm.edu
SUMMARY:Physics Colloquium: Edward Snell
DESCRIPTION:“All That Glitters is Not Necessarily Gold: the accurate identification of metals in metalloproteins and post X-ray diffraction structural remediation”\nEdward Snell\, President & CEO\, Hauptman-Woodward Medical Research Institute\n \nAccurate metal identification in metalloprotein models deposited in the protein data bank is suspect in a significant number of cases.  By directly identifying and quantifying the metal through high-throughput particle induced emission of X-rays\, samples can be analyzed pre- or post-diffraction without concern for protein stability.  We show that this analysis can reveal new structural features\, leads to alternative ways of verifying the metal\, and can considerably improve the overall model\, and thereby mechanistic understanding.
URL:https://uwm.edu/physics/event/physics-colloquium-edward-snell/
LOCATION:Lapham 160\, 3209 N. Maryland Ave.\, Milwaukee\, WI\, 53211\, United States
CATEGORIES:Physics Colloquia
X-TRIBE-STATUS:
GEO:43.0757204;-87.8840564
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=Lapham 160 3209 N. Maryland Ave. Milwaukee WI 53211 United States;X-APPLE-RADIUS=500;X-TITLE=3209 N. Maryland Ave.:geo:-87.8840564,43.0757204
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Chicago:20170929T153000
DTEND;TZID=America/Chicago:20170929T163000
DTSTAMP:20170921T171201Z
CREATED:20170918T165254Z
LAST-MODIFIED:20170921T171201Z
UID:10384491-1506699000-1506702600@uwm.edu
SUMMARY:Physics Colloquium: Elena Gallo
DESCRIPTION:“The Local Black Hole Occupation Fraction”\nElena Gallo\, University of Michigan Department of Astronomy \nWhereas mergers and intermittently efficient accretion in larger black holes spur growth and remove observational signatures of their birth\, smaller black holes have more subdued histories and undergo mostly secular evolution. Consequently\, both the mass distribution and the very rate of occupance of massive black holes in lower-mass galaxies contain archaeological information on the initial “seeding” mechanism.  \nI will present recent results from a number of observational campaigns aimed at characterizing the AGN population in nearby low-mass galaxies down to the lowest measurable accretion-powered luminosities. Most notably\, I will discuss how\, making use of a novel Bayesian methodology\, a measurement of the local AGN fraction can be employed to yield the first\, quantitative constraints on the massive black hole occupation fraction (i.e.\, regardless of activity level).  As this measurement relies on Chandra X-ray Telescope data for hundreds of nearby galaxies\, it enables us to concurrently quantify the incidence and intensity of low-level black hole accretion as a function of host stellar mass as well as environment (such as living in isolation vs. belonging to a cluster or group)\, and characterize the relation between massive black holes and nuclear star clusters\, also as a function of environment and galactic morphology.
URL:https://uwm.edu/physics/event/physics-colloquium-elena-gallo/
LOCATION:Lapham 160\, 3209 N. Maryland Ave.\, Milwaukee\, WI\, 53211\, United States
CATEGORIES:Physics Colloquia
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