The Outer Edges of Dwarf Irregular Galaxies: Stars and Gas

We have in recent years come to view dwarf galaxy evolution in the broader context of the cosmic evolution of large-scale structure. Dwarf galaxies, as the putative building blocks of hierarchical galaxy formation, and also as the most numerous galaxies in the Universe, play a central role in cosmic evolution. In particular, the interplay of galactic and intergalactic material around dwarf irregulars must be more extensive than in more massive disk galaxies because of their lower gravitational potential and lower interstellar pressures. The outer regions of dwarf irregular galaxies therefore yield vital clues to the dominant processes in this interaction zone. The Workshop addressed a number of questions related to the role of the outer regions in the evolution of dwarf galaxies and broader consequences. On-line Workshop Proceedings are at http://www.lowell.edu/Workshops/Lowell02/Comment: Summary of the 2002 Lowell Observatory Workshop, to appear in PASP Conference Highlights; 6 pp, uses aaspp4.sty. On-line Proceedings at http://www.lowell.edu/Workshops/Lowell02

Impact of Argument Type and Concerns in Argumentation with a Chatbot

Conversational agents, also known as chatbots, are versatile tools that have the potential of being used in dialogical argumentation. They could possibly be deployed in tasks such as persuasion for behaviour change (e.g. persuading people to eat more fruit, to take regular exercise, etc.) However, to achieve this, there is a need to develop methods for acquiring appropriate arguments and counterargument that reflect both sides of the discussion. For instance, to persuade someone to do regular exercise, the chatbot needs to know counterarguments that the user might have for not doing exercise. To address this need, we present methods for acquiring arguments and counterarguments, and importantly, meta-level information that can be useful for deciding when arguments can be used during an argumentation dialogue. We evaluate these methods in studies with participants and show how harnessing these methods in a chatbot can make it more persuasive

Unconstrained video monitoring of breathing behavior and application to diagnosis of sleep apnea

This paper presents a new real-time automated infrared video monitoring technique for detection of breathing anomalies, and its application in the diagnosis of obstructive sleep apnea. We introduce a novel motion model to detect subtle, cyclical breathing signals from video, a new 3-D unsupervised self-adaptive breathing template to learn individuals' normal breathing patterns online, and a robust action classification method to recognize abnormal breathing activities and limb movements. This technique avoids imposing positional constraints on the patient, allowing patients to sleep on their back or side, with or without facing the camera, fully or partially occluded by the bed clothes. Moreover, shallow and abdominal breathing patterns do not adversely affect the performance of the method, and it is insensitive to environmental settings such as infrared lighting levels and camera view angles. The experimental results show that the technique achieves high accuracy (94% for the clinical data) in recognizing apnea episodes and body movements and is robust to various occlusion levels, body poses, body movements (i.e., minor head movement, limb movement, body rotation, and slight torso movement), and breathing behavior (e.g., shallow versus heavy breathing, mouth breathing, chest breathing, and abdominal breathing). © 2013 IEEE

Length control of microtubules by depolymerizing motor proteins

In many intracellular processes, the length distribution of microtubules is controlled by depolymerizing motor proteins. Experiments have shown that, following non-specific binding to the surface of a microtubule, depolymerizers are transported to the microtubule tip(s) by diffusion or directed walk and, then, depolymerize the microtubule from the tip(s) after accumulating there. We develop a quantitative model to study the depolymerizing action of such a generic motor protein, and its possible effects on the length distribution of microtubules. We show that, when the motor protein concentration in solution exceeds a critical value, a steady state is reached where the length distribution is, in general, non-monotonic with a single peak. However, for highly processive motors and large motor densities, this distribution effectively becomes an exponential decay. Our findings suggest that such motor proteins may be selectively used by the cell to ensure precise control of MT lengths. The model is also used to analyze experimental observations of motor-induced depolymerization.Comment: Added section with figures and significantly expanded text, current version to appear in Europhys. Let

Is There a Sex Difference in the Age of Elite Marathon Runners?

Purpose: The purposes of this study were to determine i) if there is a sex difference in the age of the elite marathon runners and ii) if the sex difference in performance altered across the years that women have participated in the marathon. Methods: Age at time of competition and running times of the first five placed male and female runners who competed in the seven marathons of the World Marathon Majors Series were analyzed. Data from as many years as was available online were retrieved so that 410 men and 410 women were included in the analysis. The marathons and years included the Berlin (1999–2009), Boston (2000–2009), Chicago (1997–2009), London (2001–2009), New York City (1990–2009), International Athletic Association Federation World Championship (1983, 1987, and every 2 yr from 1991), and Olympic (every 4 yr since 1984) marathons. Results: Women were older than men (mean ± SD = 29.8 ± 4.2 vs 28.9 ± 3.8 yr), but for only two of the seven marathons, the Chicago and the London marathons (P \u3c 0.05): the sex difference in age was not consistent across the years. There was no sex difference in age for the Berlin, Boston, New York City, World Championship, and Olympic marathons. Men were faster than women (11.6% ± 1.8%). The sex difference in running velocity varied across marathons (least for the World Championships, 10.2%) and also across years, but not systematically. This sex difference in running velocity increased from first to fifth place across all marathons. Conclusions: These data indicate that men and women physiologically peak at a similar age in marathon running performance. The sex difference in performance of elite marathon runners varied across years but has not systemically decreased or varied since the 1980s

Bright Ultraviolet Regions and Star Formation Characteristics in Nearby Dwarf Galaxies

We compare star formation in the inner and outer disks of 11 dwarf Irregular galaxies (dIm) within 3.6 Mpc. The regions are identified on GALEX near-UV images, and modeled with UV, optical, and near-IR colors to determine masses and ages. A few galaxies have made 10^5-10^6 Msun complexes in a starburst phase, while others have not formed clusters in the last 50 Myrs. The maximum region mass correlates with the number of regions as expected from the size-of-sample effect. We find no radial gradients in region masses and ages, even beyond the realm of Halpha emission, although there is an exponential decrease in the luminosity density and number density of the regions with radius. Halpha is apparently lacking in the outer parts only because nebular emission around massive stars is too faint to see. The outermost regions for the 5 galaxies with HI data formed at average gas surface densities of 1.9-5.9 Msun/pc2. These low average densities imply either that local gas densities are high or sub-threshold star formation is possible. The distribution of regions on a log Mass - log age plot is is usually uniform along log age for equal intervals of log Mass. This uniformity results from either an individual region mass that varies as 1/age or a region disruption probability that varies as 1/age. A correlation between fading-corrected surface brightness and age suggests the former.Comment: Astronomical Journal, in press for November 2009. 34 pages, 18 figures, 5 table

A computerized method for calculating flutter characteristics of a system characterized by two degrees of freedom

A formulation is given for calculating flutter frequency and flutter speed for a problem with two degrees of freedom. Two different solutions for evaluating the flutter determinant are presented and the results for each method are compared. A program flow diagram, partial program listing, and a sample problem with input and output for the two different methods are included. Although the method was developed for computing flutter characteristics of a pylon installed in the NASA Langley VSTOL tunnel, it is sufficiently general to solve any flutter system that can be characterized by two degrees of freedom

Effects of Elevated H\u3csup\u3e+\u3c/sup\u3e And P\u3csub\u3ei\u3c/sub\u3e on The Contractile Mechanics of Skeletal Muscle Fibres From Young and Old Men: Implications for Muscle Fatigue in Humans

The present study aimed to identify the mechanisms responsible for the loss in muscle power and increased fatigability with ageing by integrating measures of whole‐muscle function with single fibre contractile mechanics. After adjusting for the 22% smaller muscle mass in old (73–89 years, n = 6) compared to young men (20–29 years, n = 6), isometric torque and power output of the knee extensors were, respectively, 38% and 53% lower with age. Fatigability was ∼2.7‐fold greater with age and strongly associated with reductions in the electrically‐evoked contractile properties. To test whether cross‐bridge mechanisms could explain age‐related decrements in knee extensor function, we exposed myofibres (n = 254) from the vastus lateralis to conditions mimicking quiescent muscle and fatiguing levels of acidosis (H+) (pH 6.2) and inorganic phosphate (Pi) (30 mm). The fatigue‐mimicking condition caused marked reductions in force, shortening velocity and power and inhibited the low‐ to high‐force state of the cross‐bridge cycle, confirming findings from non‐human studies that these ions act synergistically to impair cross‐bridge function. Other than severe age‐related atrophy of fast fibres (−55%), contractile function and the depressive effects of the fatigue‐mimicking condition did not differ in fibres from young and old men. The selective loss of fast myosin heavy chain II muscle was strongly associated with the age‐related decrease in isometric torque (r = 0.785) and power (r = 0.861). These data suggest that the age‐related loss in muscle strength and power are primarily determined by the atrophy of fast fibres, but the age‐related increased fatigability cannot be explained by an increased sensitivity of the cross‐bridge to H+ and Pi