Physical Sciences and Mathematics Commons^™

Modeling The Incubation Period Of Anthrax, Ron Brookmeyer, Elizabeth Johnson, Sarah Barry

Ron Brookmeyer

Models of the incubation period of anthrax are important to public health planners because they can be used to predict the delay before outbreaks are detected, the size of an outbreak and the duration of time that persons should remain on antibiotics to prevent disease. The difficulty is that there is little direct data about the incubation period in humans. The objective of this paper is to develop and apply models for the incubation period of anthrax. Mechanistic models that account for the biology of spore clearance and germination are developed based on a competing risks formulation. The models predict …

Fractional-Period Excitations In Continuum Periodic Systems, H E. Nistazakis, Mason A. Porter, Pg Kevrekidis, Dj Frantzeskakis, N Nicolin, Jk Chin

Panos Kevrekidis

We investigate the generation of fractional-period states in continuum periodic systems. As an example, we consider a Bose-Einstein condensate confined in an optical-lattice potential. We show that when the potential is turned on nonadiabatically, the system explores a number of transient states whose periodicity is a fraction of that of the lattice. We illustrate the origin of fractional-period states analytically by treating them as resonant states of a parametrically forced Duffing oscillator and discuss their transient nature and potential observability.

Coefficient Of Bohm Diffusion In Fully Ionized Plasma And Its Theoretical Proof, Ahmad Talaei, Reza Amrollahi

Ahmad Talaei

A Note On Empirical Likelihood Inference Of Residual Life Regression, Ying Qing Chen, Yichuan Zhao

Yichuan Zhao

Mean residual life function, or life expectancy, is an important function to characterize distribution of residual life. The proportional mean residual life model by Oakes and Dasu (1990) is a regression tool to study the association between life expectancy and its associated covariates. Although semiparametric inference procedures have been proposed in the literature, the accuracy of such procedures may be low when the censoring proportion is relatively large. In this paper, the semiparametric inference procedures are studied with an empirical likelihood ratio method. An empirical likelihood confidence region is constructed for the regression parameters. The proposed method is further compared …

Sigma Exchange In The Nuclear Force And Effective Field Theory, John Donoghue

John Donoghue

In the phenomenological description of the nuclear interaction a crucial role is traditionally played by the exchange of a scalar I=0 meson, the sigma, of mass 500-600 MeV, which however is not seen clearly in the particle spectrum and which has a very ambiguous status in QCD. I show that a remarkably simple and reasonably controlled combination of ingredients can reproduce the features of this part of the nuclear force. The use of chiral perturbation theory calculations for two pion exchange supplemented by the Omnes function for pion rescattering suffices to reproduce the magnitude and shape of the exchange of …

High-Resolution, Real-Time Three-Dimensional Shape Measurement, Song Zhang, Peisen S. Huang

Song Zhang

We describe a high-resolution, real-time 3-D shape measurement system based on a digital fringe projection and phase-shifting technique. It utilizes a single-chip digital light processing projector to project computer-generated fringe patterns onto the object, and a high-speed CCD camera synchronized with the projector to acquire the fringe images at a frame rate of 120frames∕s. A color CCD camera is also used to capture images for texture mapping. Based on a three-step phase-shifting technique, each frame of the 3-D shape is reconstructed using three consecutive fringe images. Therefore the 3-D data acquisition speed of the system is 40frames∕s. With this system, …

Stability Of Discrete Solitons In The Presence Of Parametric Driving, H. Susanto, Q. E. Hoq, Panos Kevrekidis

Panos Kevrekidis

In this Brief Report, we consider parametrically driven bright solitons in the vicinity of the anticontinuum limit. We illustrate the mechanism through which these solitons become unstable due to the collision of the phase mode with the continuous spectrum, or eigenvalues bifurcating thereof. We show how this mechanism typically leads to complete destruction of the bright solitary wave.

Simple Braids For Surface Homeomorphisms, Kamlesh Parwani

Kamlesh Parwani

Let S be a compact, oriented surface with negative Euler characteristic and f:S→S be a homeomorphism isotopic to the identity. If there exists a periodic orbit with a non-zero rotation vector (p→,q), then there exists a simple braid with the same rotation vector.

Wavelet-Based Functional Mixed Models To Characterize Population Heterogeneity In Accelerometer Profiles: A Case Study. , Jeffrey S. Morris, Cassandra Arroyo, Brent A. Coull, Louise M. Ryan, Steven L. Gortmaker

Jeffrey S. Morris

We present a case study illustrating the challenges of analyzing accelerometer data taken from a sample of children participating in an intervention study designed to increase physical activity. An accelerometer is a small device worn on the hip that records the minute-by-minute activity levels of the child throughout the day for each day it is worn. The resulting data are irregular functions characterized by many peaks representing short bursts of intense activity. We model these data using the wavelet-based functional mixed model. This approach incorporates multiple fixed effects and random effect functions of arbitrary form, the estimates of which are …

Alternative Probeset Definitions For Combining Microarray Data Across Studies Using Different Versions Of Affymetrix Oligonucleotide Arrays, Jeffrey S. Morris, Chunlei Wu, Kevin R. Coombes, Keith A. Baggerly, Jing Wang, Li Zhang

Jeffrey S. Morris

Many published microarray studies have small to moderate sample sizes, and thus have low statistical power to detect significant relationships between gene expression levels and outcomes of interest. By pooling data across multiple studies, however, we can gain power, enabling us to detect new relationships. This type of pooling is complicated by the fact that gene expression measurements from different microarray platforms are not directly comparable. In this chapter, we discuss two methods for combining information across different versions of Affymetrix oligonucleotide arrays. Each involves a new approach for combining probes on the array into probesets. The first approach involves …

An Econometric Method Of Correcting For Unit Nonresponse Bias In Surveys, Martin Ravallion, Anton Korinek, Johan Mistiaen

Martin Ravallion

Past approaches to correcting for unit nonresponse in sample surveys by re-weighting the data assume that the problem is ignorable within arbitrary subgroups of the population. Theory and evidence suggest that this assumption is unlikely to hold, and that household characteristics such as income systematically affect survey compliance. We show that this leaves a bias in the re-weighted data and we propose a method of correcting for this bias. The geographic structure of nonresponse rates allows us to identify a micro compliance function, which is then used to re-weight the unit-record data. An example is given for the US Current …

Identifying Important Explanatory Variables For Time-Varying Outcomes., Oliver Bembom, Maya L. Petersen, Mark J. Van Der Laan

Maya Petersen

This chapter describes a systematic and targeted approach for estimating the impact of each of a large number of baseline covariates on an outcome that is measured repeatedly over time. These variable importance estimates can be adjusted for a user-specified set of confounders and lend themselves in a straightforward way to obtaining confidence intervals and p-values. Hence, they can in particular be used to identify a subset of baseline covariates that are the most important explanatory variables for the time-varying outcome of interest. We illustrate the methodology in a data analysis aimed at finding mutations of the human immunodeficiency virus …

Identifying Important Explanatory Variables For Time-Varying Outcomes., Oliver Bembom, Maya L. Petersen, Mark J. Van Der Laan

Oliver Bembom

This chapter describes a systematic and targeted approach for estimating the impact of each of a large number of baseline covariates on an outcome that is measured repeatedly over time. These variable importance estimates can be adjusted for a user-specified set of confounders and lend themselves in a straightforward way to obtaining confidence intervals and p-values. Hence, they can in particular be used to identify a subset of baseline covariates that are the most important explanatory variables for the time-varying outcome of interest. We illustrate the methodology in a data analysis aimed at finding mutations of the human immunodeficiency virus …

Guiding Of Laser Beams In Plasmas By Radiation Cascade Compression, Serguei Y. Kalmykov, Gennady Shvets

Serge Youri Kalmykov

The near-resonant beatwave excitation of an electron plasma wave (EPW) can be employed for generating trains of few-fs electromagnetic pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the beat frequency. Consequently, the cascade of sidebands red- and blue-shifted from the fundamental by integer multiples of the beat frequency is generated in the laser spectrum. When the beat frequency is lower than the electron plasma frequency, the phase chirp enables laser beatnote compression by the group velocity dispersion [S. Kalmykov and G. Shvets, Phys. Rev. E 73, 46403 (2006)]. In the …

Modeling An Outbreak Of Anthrax, Ron Brookmeyer

Ron Brookmeyer

Introduction

On October 2, 2001 a sixty-three-year-old Florida man who worked as a photo editor at a media publishing company was admitted to an emergency department complaining of nausea, vomiting, and fever. His symptoms began four days earlier on a recreational trip to North Carolina. The man died shortly thereafter. An astute clinician quickly made the surprising diagnosis of inhalational anthrax, which is a serious and deadly disease. The diagnosis was surprising because inhalational anthrax is extremely rare; only 18 cases were reported in the United States between 1900 and 1978. Public health officials at first believed that the Florida …

Optimizing The Expected Overlap Of Survey Samples Via The Northwest Corner Rule, Lenka Mach, Philip T. Reiss, Ioana Schiopu-Kratina

Philip T. Reiss

In survey sampling there is often a need to coordinate the selection of pairs of samples drawn from two overlapping populations so as to maximize or minimize their expected overlap, subject to constraints on the marginal probabilities determined by the respective designs. For instance, maximizing the expected overlap between repeated samples can stabilize the resulting estimates of change and reduce the costs of first contacts; minimizing the expected overlap can avoid overburdening respondents with multiple surveys. We focus on the important special case in which both samples are selected by simple random sampling without replacement (SRSWOR) conducted independently within each …

Criticality For The Gehring Link Problem, Jason Cantarella, Joseph H.G. Fu, Robert Kusner, John M. Sullivan, Nancy C. Wrinkle

Robert Kusner

In 1974, Gehring posed the problem of minimizing the length of two linked curves separated by unit distance. This constraint can be viewed as a measure of thickness for links, and the ratio of length over thickness as the ropelength. In this paper we refine Gehring’s problem to deal with links in a fixed link-homotopy class: we prove ropelength minimizers exist and introduce a theory of ropelength criticality.

Our balance criterion is a set of necessary and sufficient conditions for criticality, based on a strengthened, infinite-dimensional version of the Kuhn–Tucker theorem. We use this to prove that every critical link …

Prepms: Tof Ms Data Graphical Preprocessing Tool, Yuliya V. Karpievitch, Elizabeth G. Hill, Adam J. Smolka, Jeffrey S. Morris, Kevin R. Coombes, Keith A. Baggerly, Jonas S. Almeida

Jeffrey S. Morris

We introduce a simple-to-use graphical tool that enables researchers to easily prepare time-of-flight mass spectrometry data for analysis. For ease of use, the graphical executable provides default parameter settings experimentally determined to work well in most situations. These values can be changed by the user if desired. PrepMS is a stand-alone application made freely available (open source), and is under the General Public License (GPL). Its graphical user interface, default parameter settings, and display plots allow PrepMS to be used effectively for data preprocessing, peak detection, and visual data quality assessment.

Grundlagen Der Kognition Und Perzeption Für Die Software-Ergonomie, Philipp Schaer, Holger Heuser

Philipp Schaer

Der folgende Arbeitsbericht soll eine kurze Zusammenfassung über die perzeptorischen und kognitiven Fähigkeiten des Menschen geben. Diese Zusammenfassung ist weit davon entfernt, umfassend zu sein. Jedoch bietet sie die Möglichkeit für Informatiker und Computervisualisten, einen kurzen Einblick in kognitionspsychologische Modelle zu gewinnen.

Towards A New Taxation System For Motor Vehicles, Theodoros Zachariadis

Theodoros Zachariadis

No abstract provided.

Energy In Vectorial Relativity: E ≈ M.C2, Jorge A. Franco

Jorge A Franco

In previous work it was shown that assumptions, y = y' and z = z’, within Lorentz Transformations were needless, and therefore groundless. Because of such assumptions, Lorentz Transformations (LT) depend on the body’s spatial orientation, i.e. the well-known transverse and longitudinal transformations of magnitudes, characterized by different scaling factors. On the contrary, the development of LT without assumptions, brought about new transformations that do not depend on spatial orientation and a unique mass definition, m = °m /[1 –(v/c)^2]^(3/2). As it is known, Einstein arrived at two definitions: transverse mass mT = °m /[1 –(v/c)^2]^ (1/2) and longitudinal mass …

Gravitation In Vectorial Relativity, Jorge A. Franco

Jorge A Franco

It is known that Kepler’s Laws can be derived from the Newton’s Law of Universal Gravitation. For doing this, mass is considered as an invariable parameter. Although this consideration works wonderfully to solve most of problems in astronomy calculations, as in all physics, when body’s speeds are so high and very precise measurements are required, the referred Kepler Laws do not cope enough what is expected. That’s why the General Theory of Relativity materialized. As it was indirectly pointed out by Einstein in 1905, Newton and Kepler Laws do not consider the relativistic variation of mass with its velocity. In …

Local Lorentz Transformations And Vectorial Relativity, Jorge A. Franco, Jose G. Quintero

Jorge A Franco

In previous work it was shown that instead of the known Lorentz Transformations (LT) the new obtained Vectorial Lorentz Transformations (VLT) were the transformations that truly respected the postulates of the Principle of Relativity and the consideration of the speed of light as a universal constant. In this review is presented the way how it is possible to obtain practical consequences of the VLT, and its applications to our real life.

Posterminaries: After Nabarro, Alexander H. King

Alexander H. King

With the passing of Frank Nabarro in July of this year, we have lost one of the founding fathers of materials science. His name appears in many of the textbooks from which we train our students today, and also on the spines of several volumes on dislocation theory, including his classic monograph on the subject. He rightly stands among the gods of our field. Ninety years old at his death, he was a sprightly dancer at the frontiers of knowledge, right up to the end.

Bis(1,2-Dihydroxy­Benzene) Hexa­Methyl­Ene­Tetra­Mine, Philias Daka, Kraig A. Wheeler

Kraig A. Wheeler

The title binary complex, 2C6H6O2·C6H12N4, is constructed from hexa­methyl­ene­tetra­mine, positioned about a twofold symmetry operator, and 1,2-dihydroxy­benzene. Each of the four tertiary amine N atoms participates in O—H⋯N contacts that produce mol­ecular strands that propagate along the c axis.

(Acetonitrile-Κn){2-[Bis­(2-Pyridylethyl)­Amino]Ethanol-Κ4n,N′,N′′,O}Zinc(Ii) Bis­(Perchlorate) Monohydrate, Hong-Chang Liang, Marcel M. Hetu, Kraig A. Wheeler, Lev N. Zakharov, Arnold L. Rheingold

Kraig A. Wheeler

In the title compound, [Zn(C2H3N)(C16H21N3O)](ClO4)2·H2O, the ZnII ion is coordinated by two pyridyl N atoms, one amine N atom, and an ethanol O atom from the N,N′,N′′,O-tetra­dentate 2-[bis­(2-pyridylethyl)amino]­ethanol donor ligand. The fifth coordination site is filled by an acetonitrile N atom, and there is one solvent water mol­ecule in the asymmetric unit. The 2+ charge of the cationic portion of the complex is balanced by two perchlorate counter-anions.

Vortex Matter, Effective Magnetic Charges, And Generalizations Of Dipolar Superfluidity Concept In Layered Systems, Egor Babaev

Egor Babaev

In the first part of this letter we discuss electrodynamics of an excitonic condensate in a bilayer. We show that under certain conditions the system has a dominant energy scale and is described by the effective electrodynamics with "planar magnetic charges". In the second part of the paper we point out that a vortex liquid state in bilayer superconductors also possesses dipolar superfluid modes and establish equivalence mapping between this state and a dipolar excitonic condensate. We point out that a vortex liquid state in an N-layer superconductor possesses multiple topologically coupled dipolar superfluid modes and therefore represents a generalization …

Stratospheric Variability And Trends In Models Used For The Ipcc Ar4, P. M. De F. Forster, Eugene Cordero

Eugene C. Cordero

Atmosphere and ocean general circulation model (AOGCM) experiments for the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) are analyzed to better understand model variability and assess the importance of various forcing mechanisms on stratospheric trends during the 20th century. While models represent the climatology of the stratosphere reasonably well in comparison with NCEP reanalysis, there are biases and large variability among models. In general, AOGCMs are cooler than NCEP throughout the stratosphere, with the largest differences in the tropics. Around half the AOGCMs have a top level beneath ~2 hPa and show a significant cold bias in their …

Assessment Of Temperature, Trace Species, And Ozone In Chemistry-Climate Model Simulations Of The Recent Past, V. Eyring, N. Butchart, D. W. Waugh, H. Akiyoshi, J. Austin, S. Bekki, G. E. Bodeker, B. A. Boville, C. Brühl, M. P. Chipperfield, E. Cordero, M. Dameris, M. Deushi, V. E. Fioletov, S. M. Frith, R. R. Garcia, A. Gettelman, M. A. Giorgetta, V. Grewe, L. Jourdain, D. E. Kinnison, E. Mancini, E. Manzini, M. Marchand, D. R. Marsh, T. Nagashima, P. A. Newman, J. E. Nielsen, S. Pawson, G. Pitari, D. A. Plummer, E. Rozanov, M. Schraner, T. G. Shepherd, K. Shibata, R. S. Stolarski, H. Struthers, W. Tian, M. Yoshiki

Eugene C. Cordero

[1] Simulations of the stratosphere from thirteen coupled chemistry-climate models (CCMs) are evaluated to provide guidance for the interpretation of ozone predictions made by the same CCMs. The focus of the evaluation is on how well the fields and processes that are important for determining the ozone distribution are represented in the simulations of the recent past. The core period of the evaluation is from 1980 to 1999 but long-term trends are compared for an extended period (1960–2004). Comparisons of polar high-latitude temperatures show that most CCMs have only small biases in the Northern Hemisphere in winter and spring, but …

A Content-Driven Reputation System For The Wikipedia, B. Thomas Adler, Luca De Alfaro

Luca de Alfaro

On-line forums for the collaborative creation of bodies of information are a phenomenon of rising importance; the Wikipedia is one of the best-known examples. The open nature of such forums could benefit from a notion of reputation for its authors. Author reputation could be used to flag new contributions from low-reputation authors, and it could be used to allow only authors with good reputation to contribute to controversial or critical pages. A reputation system for the Wikipedia would also provide an incentive to give high-quality contributions.

We present in this paper a novel type of content-driven reputation system for Wikipedia …