Removing Unclassified Hand Tremor Motion from Computer Mouse Input with Neural Networks

An artificial neural network based filter to remove unwanted tremor-induced motion in computer mouse input is presented and tested. A method to efficiently capture appropriate training data is shown to be important in the operation and training of the neural network filter. The architecture of the neural network as well as the numerous design choices are presented and explained. A simulation study proves the artificial neural network is successful at removing a simulated Parkinson’s tremor from computer mouse movements even with minimal training data. Resulting tremor-free motion estimated by the artificial neural network is shown to be similar to normal tremor free computer mouse movements

Song of Ourselves: Walt Whitman and the Fight for Democracy AND Whitman in Washington: Becoming the National Poet in the Federal City

Two books with two different audiences, Mark Edmundson\u27s Songs of Ourselves: Walt Whitman and the Fight for Democracy and Kenneth M. Price\u27s Whitman in Washington: Becoming the National Poet in the Federal City look at Whitman\u27s poetry in relationship to democracy in the nineteenth century

A Cautionary Tale: MARVELS Brown Dwarf Candidate Reveals Itself to be a Very Long Period, Highly Eccentric Spectroscopic Stellar Binary

We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R ≾ 30,000), this particular stellar binary mimics a single-lined binary with an RV signal that would be induced by a brown dwarf companion (Msin i ~ 50 M _(Jup)) to a solar-type primary. At least three properties of this system allow it to masquerade as a single star with a very-low-mass companion: its large eccentricity (e ~ 0.8), its relatively long period (P ~ 238 days), and the approximately perpendicular orientation of the semi-major axis with respect to the line of sight (ω ~ 189°). As a result of these properties, for ~95% of the orbit the two sets of stellar spectral lines are completely blended, and the RV measurements based on centroiding on the apparently single-lined spectrum is very well fit by an orbit solution indicative of a brown dwarf companion on a more circular orbit (e ~ 0.3). Only during the ~5% of the orbit near periastron passage does the true, double-lined nature and large RV amplitude of ~15 km s^(–1) reveal itself. The discovery of this binary system is an important lesson for RV surveys searching for substellar companions; at a given resolution and observing cadence, a survey will be susceptible to these kinds of astrophysical false positives for a range of orbital parameters. Finally, for surveys like MARVELS that lack the resolution for a useful line bisector analysis, it is imperative to monitor the peak of the cross-correlation function for suspicious changes in width or shape, so that such false positives can be flagged during the candidate vetting process

Optimality and flexibility in utilizing predictive spatial cues during visual search

Visual search is a critical and pervasive part of our everyday lives. However, the ease of which we perform search can mask its remarkable computational complexity. Search targets are often difficult to detect and embedded in statistically complex backgrounds. To optimize search, human observers often exploit known statistical properties of the visual environment which provide information about target location. Regularities in the spatial organization of the visual environment (e.g. predictive cues) have shown to be one such type of statistical property which can be leveraged to increase search efficiency. Here, a series of three studies examines how well human observers can exploit spatially predictive cues during multi-fixation search. Further exploration focuses on highlighting human flexibility in altering search strategy to enhance perceptual performance, as well as delineating situations in which predictive information in the environment may actually hurt search performance. Predictive spatial cues have been shown to improve perceptual performance for a variety of tasks, including visual search, under conditions of forced fixation. However, the potential benefits of predictive cues during multi-fixation search are poorly understood. In the first study, we present a letter identification search task, done in the presence and absence of an array of spatial cues which framed potential target locations. We show that human observers direct their eye movements towards cued locations to improve their search performance compared to when the cues are absent. We also develop a foveated eye movement model, which takes into account the diminishing acuity of the human visual system in the periphery, for the task. Model predictions reveal substantial performance benefits via predictive cues, the size of which are much larger than what is seen in human data. In the second study, we investigate whether human observers will utilize peripheral predictive cues which reside in display regions which have no chance of containing the target (which we call remote cues). In doing so, observers must depart from a commonly used "saccadic targeting" strategy, where eyes are directed to likely target locations. When informed of the predictive nature of the remote cues, observers readily adopt an atypical eye movement strategy which favors non-target locations to enhance task performance. A foveated model which ignores the cues reveals that these performance benefits are a likely result of foveating peripheral predictive information. Interestingly, a version of the remote cue task in which observers were not informed of cue contingencies, reveals that while observers can adopt atypical saccadic strategies to improve performance, they do not readily engage in such behavior without explicit information. In the final study, we explore a situation in which predictive cues actually hinder search performance. In natural viewing environments and everyday search tasks, predictive cues often do not mark the only target locations, but merely likely ones. We return to the letter identification search task and modify the cues so that they are only partially predictive of target location. With this increased uncertainty, the presence of predictive cues actually leads to worse performance when the target is highly visible, compared to when cues are absent. A control task in which the spatial cues were not predictive rules out the possibility of the effect being driven by exogenous attentional capture, and a foveated eye movement model reveals that cues hindering search performance would not be predicted by a rational observer. Implications for real-life and vocational search are discussed. In all, we see that human observers are willing and able to utilize predictive elements via intelligent eye movement selection of the environment to enhance search performance. In addition, when cue information is made clear, observers are able to readily adopt even extremely atypical eye movement strategies to optimize performance. However, human efficiency in implementing these strategies often falls short of that predicted by a near-optimal observer, even leading to a decrement in performance in extreme cases. Understanding the interaction between human performance and predictive cues, then, is critical to assessing natural visual search and optimizing vocational and life-critical search displays

Assessment of efforts to reduce nonresponse bias: 1996 Survey of Income and Program Participation (SIPP)

Im Vorfeld der neuen Welle des SIPP 1996 tauchten Bedenken in Hinblick auf eine zunehmende Tendenz zur Antwortverweigerung in den Panelwellen der Jahre 1991 bis 1993 auf. Gleichzeitig wurde die Existenz eines Bias in den SIPP-Zeitreihenschätzungen zu Armut bekannt. Das US Census Bureau hat viel Zeit und Geld darauf verwandt, den Anteil der Antwortverweigerung zu reduzieren und die hierauf beruhende Fehlgewichtung zu korrigieren. Die Verfasser geben einen Überblick über diese Maßnahmen und diskutieren deren Wirksamkeit mit Blick auf das erste Jahr der Panelwelle 1996. Sie setzen sich mit dem Einsatz finanzieller Anreize, der Durchführung von Untersuchungen zur Antwortverweigerung sowie Veränderungen in der Durchführung der Feldforschung auseinander. (ICEÜbers)"Concern over increasing levels of nonresponse in the 1991-1993 SIPP Panels and new information about the existence of bias in time series estimates of poverty front the SIPP surfaced prior to fielding the newly redesigned SIPP 1996 sample. A tremendous amount of effort and expense has been dedicated by the U.S. Census Bureau to reducing nonresponse and adjusting for its bias. This paper will summarize these efforts and provide a preliminary assessment of the success of the efforts for the first year of the 1996 panel. The authors will discuss the use of monetary incentives, fielding nonresponse surveys, and changes in field staffing and procedures." (author's abstract

Propagule Pressure and Introduction Pathways of \u3cem\u3eBromus Tectorum\u3c/em\u3e (Cheatgrass; Poaceae) in the Central United States

An introduced species\u27 propagule pressure strongly influences the genetic diversity and evolutionary potential of its descendants and even the likelihood of biological invasion. We examined population genetic consequences arising from introduction of the invasive annual grass Bromus tectorum into the central United States (U.S.). The origin and frequency of introductions were investigated by assembling allozyme diversity data from 60 widely spaced populations. At least five introduction events contributed to the grass’s genetic diversity in the central U.S. Populations in this region have fewer alleles (30 vs. 43) and polymorphic loci (5 vs. 13) than native populations, evidence of a genetic bottleneck. However, the populations are, on average, more genetically diverse and less structured than native populations. Assembly within central U.S. populations of previously allopatric genotypes may have allowed the formation, via outcrossing, of a rare multilocus genotype. Genetic admixtures may have occurred through any combination of east-to-west spread coincident with nineteenth-century arrival of European settlers, dispersal from southern Ontario via Great Lakes shipping and commerce, and direct introduction from the native range. Our results illustrate the population genetic consequences of relatively high propagule pressure (i.e., repeated immigrations to a new range from multiple sources)

The Dimerization Domain in DapE Enzymes Is Required for Catalysis

The emergence of antibiotic-resistant bacterial strains underscores the importance of identifying new drug targets and developing new antimicrobial compounds. Lysine and meso-diaminopimelic acid are essential for protein production and bacterial peptidoglycan cell wall remodeling and are synthesized in bacteria by enzymes encoded within dap operon. Therefore dap enzymes may serve as excellent targets for developing a new class of antimicrobial agents. The dapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) converts N-succinyl-L,L-diaminopimelic acid to L,Ldiaminopimelic acid and succinate. The enzyme is composed of catalytic and dimerization domains, and belongs to the M20 peptidase family. To understand the specific role of each domain of the enzyme we engineered dimerization domain deletion mutants of DapEs from Haemophilus influenzae and Vibrio cholerae, and characterized these proteins structurally and biochemically. No activity was observed for all deletion mutants. Structural comparisons of wild-type, inactive monomeric DapE enzymes with other M20 peptidases suggest that the dimerization domain is essential for DapE enzymatic activity. Structural analysis and molecular dynamics simulations indicate that removal of the dimerization domain increased the flexibility of a conserved active site loop that may provide critical interactions with the substrate