Physical Sciences and Mathematics Commons^™

Topics Over Time: A Nonmarkov Continuoustime Model Of Topical Trends, Xuerui Wang, Andrew Mccallum

Andrew McCallum

This paper presents an LDA-style topic model that captures not only the low-dimensional structure of data, but also how the structure changes over time. Unlike other recent work that relies on Markov assumptions or discretization of time, here each topic is associated with a continuous distribution over timestamps, and for each generated document, the mixture distribution over topics is influenced by both word co-occurrences and the document's timestamp. Thus, the meaning of a particular topic can be relied upon as constant, but the topics' occurrence and correlations change significantly over time. We present results on nine months of personal email, …

Corrective Feedback And Persistent Learning For Information Extraction, Aron Culotta, Trausti Kristjansson, Andrew Mccallum, Paul Viola

Andrew McCallum

To successfully embed statistical machine learning models in real world applications, two post-deployment capabilities must be provided: (1) the ability to solicit user corrections and (2) the ability to update the model from these corrections. We refer to the former capability as corrective feedback and the latter as persistent learning. While these capabilities have a natural implementation for simple classification tasks such as spam filtering, we argue that a more careful design is required for structured classification tasks. One example of a structured classification task is information extraction, in which raw text is analyzed to automatically populate a database. In …

Practical Markov Logic Containing First-Order Quantifiers With Application To Identity Uncertainty, Aron Culotta, Andrew Mccallum

Andrew McCallum

Markov logic is a highly expressive language recently introduced to specify the connectivity of a Markov network using first-order logic. While Markov logic is capable of constructing arbitrary first-order formulae over the data, the complexity of these formulae is often limited in practice because of the size and connectivity of the resulting network. In this paper, we present approximate inference and estimation methods that incrementally instantiate portions of the network as needed to enable first-order existential and universal quantifiers in Markov logic networks. When applied to the problem of identity uncertainty, this approach results in a conditional probabilistic model that …

Nmr Investigations Of Natural Organic Matter In Forest Ecosystems, Chris E. Johnson

Chris E Johnson

No abstract provided.

First-Order Probabilistic Models For Coreference Resolution, Aron Culotta, Michael Wick, Robert Hall, Andrew Mccallum

Andrew McCallum

Traditional noun phrase coreference resolution systems represent features only of pairs of noun phrases. In this paper, we propose a machine learning method that enables features over sets of noun phrases, resulting in a first-order probabilistic model for coreference. We outline a set of approximations that make this approach practical, and apply our method to the ACE coreference dataset, achieving an 11% error reduction over a comparable method that only considers features of pairs of noun phrases. This result demonstrates an example of how a powerful representation language can be incorporated into a probabilistic model and be scaled efficiently.

Bibliometric Impact Measures Leveraging Topic Analysis, Gideon S. Mann, David Mimno, Andrew Mccallum

Andrew McCallum

Measurements of the impact and history of research literature provide a useful complement to scientific digital library collections. Bibliometric indicators have been extensively studied, mostly in the context of journals. However, journal-based metrics poorly capture topical distinctions in fast-moving fields, and are increasingly problematic in the context of open-access publishing. Recent developments in latent topic models have produced promising results for automatic sub-field discovery. The fine-grained, faceted topics produced by such models provide a more clear view of the topical divisions of a body of research literature and the interactions between those divisions. We demonstrate the usefulness of topic models …

Enumerations Of The Kolmogorov Function, Richard Beigel, Harry Buhrman, Peter Fejer, Lance Fortnow, Piotr Grabowski, Luc Longpré, Andrej Muchnik, Frank Stephan, Leen Torenvliet

Peter Fejer

A recursive enumerator for a function h is an algorithm f which enumerates for an input x finitely many elements including h(x). f is a k(n)-enumerator if for every input x of length n, h(x) is among the first k(n) elements enumerated by f. If there is a k(n)-enumerator for h then h is called k(n)-enumerable. We also consider enumerators which are only A-recursive for some oracle A.

We determine exactly how hard it is to enumerate the Kolmogorov function, which assigns to each string x its Kolmogorov complexity:

• For every underlying universal machine U, there is a constant a …

Best Constants For Certain Multilinear Integral Operators, Árpád Bényi, Tadahiro Oh

Mathematics Faculty Publications

We provide explicit formulas in terms of the special function gamma for the best constants in nontensorial multilinear extensions of some classical integral inequalities due to Hilbert, Hardy, and Hardy-Littlewood-Polya.

Self-Assembly And Conformation Of Tetrapyridilporphyrin On The Ag(111) Surface, Willi Auwärter, Alexander Weber-Bargioni, Andreas Riemann, Agustin Schiffrin, R. Fasel, O. Gröning, Johannes V. Barth

Physics & Astronomy

We present a low-temperature scanning tunneling microscopy (STM) study on the supramolecular ordering of tetrapyridyl-porphyrin (TPyP) molecules on Ag(111). Vapor deposition in a wide substrate temperature range reveals that TPyP molecules easily diffuse and self-assemble into large, highly ordered chiral domains. We identify two mirror-symmetric unit cells, each containing two differently oriented molecules. From an analysis of the respective arrangement it is concluded that lateral intermolecular interactions control the packing of the layer, while its orientation is induced by the coupling to the substrate. This finding is corroborated by molecular mechanics calculations. High-resolution STM images recorded at 15 K allow …

Relating Damping To Soil Permeability, Paul Michaels

CGISS Publications and Presentations

Published comparisons of complex moduli in dry and saturated soils have shown that viscous behavior is only evident when a sufficiently massive viscous fluid (like water) is present. That is, the loss tangent is frequency dependent for water saturated specimens, but nearly frequency independent for dry samples. While the Kelvin-Voigt (KV) representation of a soil captures the general viscous behavior using a dashpot, it fails to account for the possibly separate motions of the fluid and frame (there is only a single mass element). An alternative representation which separates the two masses, water and frame, is presented here. This Kelvin-Voigt-Maxwell-Biot …

Comparison Of Viscous Damping In Unsaturated Soils, Compression And Shear, Paul Michaels

CGISS Publications and Presentations

Geophysical down-hole surveys can be used to measure the small strain dynamic properties of soils by the effects these properties have on wave propagation. The relevant effects include amplitude decay (corrected for beam divergence) and velocity dispersion. In this paper, down-hole data collected during the GeoInstitute's Denver 2000 field day are presented and analyzed as a Kelvin-Voigt solid. Findings for these unsaturated soils include viscous damping and stiffness which differ significantly for shear and compressional waves. A strong viscous damping is observed in compression, but weak damping is presented in shear. Lumped parameter constitutive models are discussed which mathematically represent …

Seeing Through The Noise: Seismic Reflection Profiling In Urban Areas, Lee M. Liberty, Thomas L. Pratt, Scott S. Hess

CGISS Publications and Presentations

Studies for urban hazard or resource assessment often take place in densely populated areas characterized by considerable cultural noise. These site conditions can severely compromise seismic reflection data quality. We have collected vibroseis and hammer (weight drop) seismic reflection data in a range of geologic conditions to image stratigraphy and structures in the upper one km along regional highways, city streets,and power line access roads. In addition to the challenges of safety and outreach, acquisition efforts along busy streets and highways often encounter poor receiver coupling and large-amplitude coherent noise from traffic and power lines. Although higher quality seismic reflection …

Crosshole Radar Tomography In An Alluvial Aquifer Nearboise, Idaho, William P. Clement, Warren Barrash

CGISS Publications and Presentations

To determine the distribution of heterogeneities in an unconfined aquifer in Boise, ID, we compute radar tomograms for three adjacent well pairs. The fluvial deposits consist of unconsolidated cobbles and sands. We used a curved‐ray, finite‐difference approximation to the eikonal equation to generate the forward model. The inversion uses a linearized, iterative scheme to determine the slowness distribution from the first arrival traveltimes. The tomograms consist of a sequence of layers representing the saturated aquifer. The velocities in this saturated zone range between 0.06 to 0.10 m/ns. We use a variety of methods to assess the reliability of our velocity …

Sorption-Desorption Of Imidacloprid And Its Metabolites In Soil And Vadose Zone Materials, Sharon V. Papiernik, William C. Koskinen, Lucia Cox, Pamela J. Rice, Sharon A. Clay, Nancy R. Werdin-Pfisterer, Kristen A. Norberg

Agronomy, Horticulture and Plant Science Faculty Publications

Sorption-desorption is one of the most important processes affecting the leaching of pesticides through soil because it controls the amount of pesticide available for transport. Subsurface soil properties can significantly affect pesticide transport and the potential for groundwater contamination. This research characterized the sorption-desorption of imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-Nnitro-2-imidazolidinimine) and three of its metabolites, 1-[(6-chloro-3-pyridinyl)methyl]-2-imidazolidinone (imidacloprid-urea), 1-[(6-chloro-3-pyridinyl)methyl]-4,5-dihydro-1H-imidazol-2-amine (imidaclopridguanidine), and 1-[(6-chloro-3-pyridinyl)methyl]-1H-imidazol-2-amine (imidacloprid-guanidine-olefin), as a function of changing soil properties with depth in two profiles extending from the surface to a depth of 1.8 or 8 m. Sorption of each compound was highly variable and hysteretic in all cases. Normalizing the sorption coefficients (Kf) …

A Systematic Review Of The Roles And Competencies Of Medical Information Professionals(Mips) In Evidence-Based Medicine In Thailand, Somrux Sahapong, Lampang Manmart, Dusadee Ayuvat, Somkiet Potisat

EDU-COM International Conference

The aim of this study was to systematically review the roles and competencies of Medical Information Professionals (MIPs: non-medical personnel who are information technology and medical library literacy) in supporting clinicians in the practice of evidence-based medicine (EBM) as reported in the published literature. It analysed and synthesized information from textbooks on EBM and research and review articles drawn from MEDLINE using the following keywords: ―evidence-based medicine‖, ―information seeking and physician‖, ―information need and physician‖, ―EBM librarian‖, ―clinical librarian‖, ―library service‖, ―informationist‖, and ―knowledge management‖. Information from research articles published in local journals and conference proceedings was also included evidence-based …

A Real-Time Virtual Classroom System With Two-Way Communication For Distance Learning At King Mongkut’S University Of Technology Thonburi, Thailand, Surachai Suksakulchai, Chalathip Chunkul

EDU-COM International Conference

Because of high demands for higher education in the provinces of Thailand, the school of Industrial Education and Technology at KMUTT has started off-campus courses since 2002. However, the major problem of operation is distance. To cope with the problem, a real-time virtual classroom system with two-way communication has been developed. The system has to overcome the bandwidth problem, which is the major struggle of web-based learning in Thailand, and to maintain the two-way communication between instructors and students. To cope with those problems, video streaming and live chat systems are used. The technique is the trade-off between two-way and …

Neutron Multiplicity Measurements Of Target/Blanket Materials, Denis Beller

Transmutation Sciences Physics (TRP)

The U.S. Advanced Fuel Cycle Initiative (AFCI) is a program to develop economic and environmental methods to reduce the impact of waste from commercial nuclear fuel cycles. One concept for near-complete destruction of waste isotopes from used nuclear fuel is accelerator-driven transmutation. High-power accelerators would be used to produce high-energy charged particles, which then collide with heavy metal targets to create a cascade of neutrons. These neutrons then cause nuclear reactions in subcritical systems.

To design these systems, complex reactor physics computer codes and highly detailed data libraries are used to compute the reactivity of systems, reaction rates, destruction rates, …

Corrosion Mechanisms And Kinetics Of Steels In Lead-Bismuth Eutectic: Quaterly Report, Allen L. Johnson, John Farley

Transmutation Sciences Materials (TRP)

A large number of studies of corroded samples were conducted using SEM, XPS, probe, and the TEM. Samples from the DELTA loop at LANL and from other sources were examined. Also, the investigation of 316 class stainless steel in LBE is continuing.

Corroded samples of D-9 steel have been in the process of being studies, which is a variant of 316 stainless steel that is optimized for resistance to swelling. The D-9 samples are notable for the process in which a localized failure of the protective oxide layer becomes widespread corrosion. The research group is examining the D-9 samples using …

Interaction Between Metal Fission Products And Triso Coating Materials, Clemens Heske

Fuels Campaign (TRP)

In this project the chemical bonding and interface formation of metal fission products with the coating materials used in TRISO fuel particles is investigated. The interface formation of Pd, Cs, and Ag with SiC and pyrolytic carbon is studied in detail. Using the SiC single crystals and TRISO coating materials as substrates, interfaces are prepared under controlled conditions in an ultra-high vacuum environment and are studied with a photoelectron spectroscopy, Auger electron spectroscopy, Inverse Photoemission, X-ray emission spectroscopy, and X-ray absorption spectroscopy. Recent additions to the experimental approach include microscopic techniques (Transmission Electron Microscopy, Scanning Tunneling Microscopy, Atomic Force Microscopy) …

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix, Kenneth Czerwinski

Fuels Campaign (TRP)

This project examines inert fuels containing ZrO₂ and MgO as the inert matrix, with the relative amount of MgO varied from 30% to 70% in ZrO₂. Reactor physics calculations are used to examine suitable quantities of burnable poisons from the candidate elements Gd, Er, or Hf with reactor grade Pu providing the fissile component, with up to 10% of ²³⁹Pu. Ceramics are synthesized and characterized based on the reactor physics results. The solubility of the fuel ceramics, in reactor conditions, reprocessing conditions, and repository conditions, are investigated in a manner to provide thermodynamic data necessary for …

Impact Of The Synthesis Process On Structure Properties For Afci Fuel Candidates, Thomas Hartmann

Fuels Campaign (TRP)

Advanced Fuel Cycle Initiative research on transmutation fuels includes mono-nitride ceramic fuel forms, and consists of closely coordinated “hot” actinide and “cold” inert and surrogate fuels work. Matrix and surrogate materials work involves three major components: (1) fuel matrix synthesis and fabrication, (2) fuel performance, and (3) fuel materials modeling. The synthesis and fabrication component supports basic material studies, as well as actinide fuel fabrication work through fuel fabrication process development. Fuel performance studies are examining the tolerance of nitride-type fuel to heavy irradiation damage. The fuel materials simulation work involves both atomistic and continuum scale modeling employing first principles, …

University Of Nevada, Las Vegas Transmutation Research Program Annual Report Academic Year 2005-2006, Anthony Hechanova, Rebecca Arbour

Transmutation Research Program Reports (TRP)

It is my pleasure to present the UNLV Transmutation Research Program’s fifth annual report that highlights the academic year 2005 – 2006. Supporting this document are the many technical reports and scientific papers that have been generated over the past five years.

In the fifth year of our program, we saw amazing growth in the Radiochemistry Ph.D. program with a total of 12 students in the second year of the program (twice the number we anticipated in the program proposal). In the back of this issue, under Infrastructure Augmentation, you will find some news about the new academic programs sponsored …

Oliver Ranch Science School Complex & Wild Horse And Burro Facility: Quarterly Progress Report, Period Ending September 30, 2006, Margaret N. Rees

Oliver Ranch Project

Assist in project coordination between numerous stakeholders such as the Clark County School System, Desert Research Institute, Community College of Southern Nevada, UNR Cooperative Extension, Nevada State College, local museums, state parks, non-profit organizations, federal agencies, and the public to ensure appropriate educational curricular activities and venues are provided for in the conceptual design of the School and the Wild Horse and Burro facility where appropriate as well as assist in the NEPA process as needed. The activities will be conducted at least in part by university faculty, staff and students as part of the university’s research, teaching, and service …

Red Rock Desert Learning Center Community Outreach Activities Plan, Red Rock Desert Learning Center

Oliver Ranch Project

The Red Rock Desert Learning Center is being designed to teach participants about the natural world through inquiry-based experiential and interdisciplinary methods in a residential outdoor setting in Red Rock Canyon National Conservation Area. The intent is for students, teachers, and researchers to gain an appreciation of desert ecosystems and to begin to apply and connect their knowledge to world ecological systems. The campus will incorporate many “green building” systems in its design and operation, and those systems will be an active part of the school’s curriculum.

Bomb-Pulse Chlorine-36 At The Proposed Yucca Mountain Repository Horizon: An Investigation Of Previous Conflicting Results And Collection Of New Data, James Cizdziel, Amy J. Smiecinski

Publications (YM)

Previous studies by scientists at Los Alamos National Laboratory (LANL) found elevated ratios of chlorine-36 to total chloride (36C1/C1) in samples of rock collected from the Exploratory Studies Facility (ESF) and the Enhanced Characterization of the Repository Block (ECRB) at Yucca Mountain as the tunnels were excavated. The data were interpreted as an indication that fluids containing "bomb-pulse" 36C1 reached the repository horizon in the -50 years since the peak period of above-ground nuclear testing. Moreover, the data support the concept that so-called fast pathways for infiltration not only exist but are active, possibly through a combination of porous media, …

Foreign-Born Population In Selected Ohio Cities, 1870 To 2000 A Brief Descriptive Report, Mark Salling, Ellen Cyran

All Maxine Goodman Levin School of Urban Affairs Publications

No abstract provided.

The Nonlinear Amplification Of Magnetic Fields By Cosmic Rays At Supernova Remnant Shocks, Brian Reville, Peter Duffy, Stephen O'Sullivan

Conference papers

A central problem in the theory of cosmic ray acceleration at supernova shock fronts is the generation of turbulent magnetic fields needed to scatter particles across a shock front. In this paper we build on previous studies [1], [2] into the effect of streaming cosmic rays produced by the outer shocks of supernova remnants on the stochastic component of the magnetic field. A three dimensional, MHD code has been constructed which demonstrates the nonlinear growth of the turbulent field.

Subpicosecond Time-Resolved Raman Studies Of Field-Induced Transient Transport In An Inxga1−Xas-Based P-I-N Semiconductor Nanostructure, K. T. Tsen, Juliann G. Kiang, D. K. Ferry, Hadis Morkoç

Physics Publications

Electron transient transport in an InxGa1−xAs-based (x=0.53) p-i-nnanostructure under the application of an electric field has been studied by time-resolvedRaman spectroscopy on a subpicosecond time scale and at T=300K. The experimental results reveal the time evolution of the electron distribution function and electron drift velocity with subpicosecond time resolution. These experimental results are compared with those of both InP-based and GaAs-based p-i-nnanostructures and provide a consistent understanding and better insight of electron transient transport phenomena in semiconductors.

Clustering Of Cr In Gan Nanotubes And The Onset Of Ferrimagnetic Order, Q. Wang, Q. Sun, Puru Jena, Y. Kawazoe

Physics Publications

A comprehensive theoretical study of the structure and magnetic properties of Cr-doped GaN nanotubes yields some interesting and unexpected results: (1) A single wall GaN nanotube constructed from the GaN wurtzite crystal relaxes to a carbon-like zigzag SWNT structure and remains stable at 300K, while a multiwall GaN nanotube retains its original wurtzite form. (2) Cr atoms prefer to form clusters and the underlying magnetism depends on the degree of clustering. (3) The coupling between two Cr atoms mediated by the neighboring N is ferromagnetic, but changes to ferrimagnetic as the cluster grows. These results are based on spin polarized …

Structural, Electronic, And Chemical Properties Of Multiply Iodized Aluminum Clusters, N. O. Jones, J. Ulises Reveles, S. N. Khanna, D. E. Bergeron, P. J. Roach, A. W. Castleman Jr.

Physics Publications

The electronic structure, stability, and reactivity of iodized aluminum clusters, which have been investigated via reactivity studies, are examined by first-principles gradient corrected density functional calculations. The observed behavior of Al13I−x and Al14I−x clusters is shown to indicate that for x⩽8, they consist of compact Al−13 and Al++14 cores, respectively, demonstrating that they behave as halogen- or alkaline earthlike superatoms. For x>8, the Al cores assume a cagelike structure associated with the charging of the cores. The observed mass spectra of the reacted clusters reveal that Al13I−x species are more stable for even x while Al14I−x exhibit enhanced stability …