203 research outputs found
That Mild-Mannered Bruce Lee
The article focuses on various studies related to the link between martial arts training and its various outcomes like aggressiveness. An inverse relationship between aggressiveness and length of martial arts training, was found by T. A. Nosanchuk of Carleton University. Another study found that problem teenagers changed after some months of practice in Tae Kwon Do. It is stated that the ability to defend one\u27s self and physical fitness are two other benefits of martial arts
Electromagnetic Energy, Momentum, and Angular Momentum in an Inhomogeneous Linear Dielectric
In a previous work, Optics Communications 284 (2011) 2460--2465, we
considered a dielectric medium with an anti-reflection coating and a spatially
uniform index of refraction illuminated at normal incidence by a
quasimonochromatic field. Using the continuity equations for the
electromagnetic energy density and the Gordon momentum density, we constructed
a traceless, symmetric energy--momentum tensor for the closed system. In this
work, we relax the condition of a uniform index of refraction and consider a
dielectric medium with a spatially varying index of refraction that is
independent of time, which essentially represents a mechanically rigid
dielectric medium due to external constraints. Using continuity equations for
energy density and for Gordon momentum density, we construct a symmetric
energy--momentum matrix, whose four-divergence is equal to a generalized
Helmholtz force density four-vector. Assuming that the energy-momentum matrix
has tensor transformation properties under a symmetry group of space-time
coordinate transformations, we derive the global conservation laws for the
total energy, momentum, and angular momentum.Comment: added publication informatio
The First Ultra-cool Brown Dwarf Discovered by the Wide-field Infrared Survey Explorer
We report the discovery of the first new ultra-cool brown dwarf (BDs) found with the Wide-field Infrared Survey
Explorer (WISE). The object’s preliminary designation is WISEPC J045853.90+643451.9. Follow-up spectroscopy
with the LUCIFER instrument on the Large Binocular Telescope indicates that it is a very late-type T dwarf with a
spectral type approximately equal to T9. Fits to an IRTF/SpeX 0.8–2.5 μm spectrum to the model atmospheres of
Marley and Saumon indicate an effective temperature of approximately 600 K as well as the presence of vertical
mixing in its atmosphere. The new BD is easily detected by WISE, with a signal-to-noise ratio of ~36 at 4.6 μm.
Current estimates place it at a distance of 6–10 pc. This object represents the first in what will likely be hundreds of
nearby BDs found by WISE that will be suitable for follow-up observations, including those with the James Webb
Space Telescope. One of the two primary scientific goals of the WISE mission is to find the coolest, closest stars to
our Sun; the discovery of this new BD proves that WISE is capable of fulfilling this objective
The Spitzer c2d survey of Large, Nearby, Interstellar Clouds. V. Chamaeleon II Observed with IRAC
We present IRAC (3.6, 4.5, 5.8, and 8.0 micron) observations of the
Chamaeleon II molecular cloud. The observed area covers about 1 square degree
defined by . Analysis of the data in the 2005 c2d catalogs reveals a
small number of sources (40) with properties similar to those of young
stellaror substellar objects (YSOs). The surface density of these YSO
candidates is low, and contamination by background galaxies appears to be
substantial, especially for sources classified as Class I or flat SED. We
discuss this problem in some detail and conclude that very few of the candidate
YSOs in early evolutionary stages are actually in the Cha II cloud. Using a
refined set of criteria, we define a smaller, but more reliable, set of 24 YSO
candidates.Comment: 19 pages, 10 figures, in press Ap
Formation and Evolution of Planetary Systems: Cold Outer Disks Associated with Sun-like stars
We present the discovery of debris systems around three solar mass stars
based upon observations performed with the Spitzer Space Telescope as part of a
Legacy Science Program, ``the Formation and Evolution of Planetary Systems''
(FEPS). We also confirm the presence of debris around two other stars. All the
stars exhibit infrared emission in excess of the expected photospheres in the
70 micron band, but are consistent with photospheric emission at <= 33 micron.
This restricts the maximum temperature of debris in equilibrium with the
stellar radiation to T < 70 K. We find that these sources are relatively old in
the FEPS sample, in the age range 0.7 - 3 Gyr. Based on models of the spectral
energy distributions, we suggest that these debris systems represent materials
generated by collisions of planetesimal belts. We speculate on the nature of
these systems through comparisons to our own Kuiper Belt, and on the likely
planet(s) responsible for stirring the system and ultimately releasing dust
through collisions. We further report observations of a nearby star HD 13974 (d
=11 pc) that is indistinguishable from a bare photosphere at both 24 micron and
70 micron. The observations place strong upper limits on the presence of any
cold dust in this nearby system (L_IR/L_* < 10^{-5.2}).Comment: 31 pages, 9 figures, accepted for publication in Ap
Emergence of good conduct, scaling and Zipf laws in human behavioral sequences in an online world
We study behavioral action sequences of players in a massive multiplayer
online game. In their virtual life players use eight basic actions which allow
them to interact with each other. These actions are communication, trade,
establishing or breaking friendships and enmities, attack, and punishment. We
measure the probabilities for these actions conditional on previous taken and
received actions and find a dramatic increase of negative behavior immediately
after receiving negative actions. Similarly, positive behavior is intensified
by receiving positive actions. We observe a tendency towards anti-persistence
in communication sequences. Classifying actions as positive (good) and negative
(bad) allows us to define binary 'world lines' of lives of individuals.
Positive and negative actions are persistent and occur in clusters, indicated
by large scaling exponents alpha~0.87 of the mean square displacement of the
world lines. For all eight action types we find strong signs for high levels of
repetitiveness, especially for negative actions. We partition behavioral
sequences into segments of length n (behavioral `words' and 'motifs') and study
their statistical properties. We find two approximate power laws in the word
ranking distribution, one with an exponent of kappa-1 for the ranks up to 100,
and another with a lower exponent for higher ranks. The Shannon n-tuple
redundancy yields large values and increases in terms of word length, further
underscoring the non-trivial statistical properties of behavioral sequences. On
the collective, societal level the timeseries of particular actions per day can
be understood by a simple mean-reverting log-normal model.Comment: 6 pages, 5 figure
Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Luminous Infrared Galaxy Candidates
We present Spitzer 3.6 and 4.5 m photometry and positions for a sample
of 1510 brown dwarf candidates identified by the WISE all-sky survey. Of these,
166 have been spectroscopically classified as objects with spectral types M(1),
L(7), T(146), and Y(12); Sixteen other objects are non-(sub)stellar in nature.
The remainder are most likely distant L and T dwarfs lacking spectroscopic
verification, other Y dwarf candidates still awaiting follow-up, and assorted
other objects whose Spitzer photometry reveals them to be background sources.
We present a catalog of Spitzer photometry for all astrophysical sources
identified in these fields and use this catalog to identify 7 fainter (4.5
m 17.0 mag) brown dwarf candidates, which are possibly wide-field
companions to the original WISE sources. To test this hypothesis, we use a
sample of 919 Spitzer observations around WISE-selected high-redshift
hyper-luminous infrared galaxy (HyLIRG) candidates. For this control sample we
find another 6 brown dwarf candidates, suggesting that the 7 companion
candidates are not physically associated. In fact, only one of these 7 Spitzer
brown dwarf candidates has a photometric distance estimate consistent with
being a companion to the WISE brown dwarf candidate. Other than this there is
no evidence for any widely separated ( 20 AU) ultra-cool binaries. As an
adjunct to this paper, we make available a source catalog of 7.33
objects detected in all of these Spitzer follow-up fields for use
by the astronomical community. The complete catalog includes the Spitzer 3.6
and 4.5 m photometry, along with positionally matched and
photometry from USNO-B; , , and photometry from 2MASS; and ,
, , and photometry from the WISE all-sky catalog
A functional triazine framework based on N-heterocyclic building blocks
Covalent organic frameworks constitute a subclass of polymeric materials offering enhanced porosity, functionality and stability. In this work a covalent triazine framework based on bipyridine building blocks is presented, along with a comprehensive elucidation of its local structure, porosity, and capacity for metal uptake. A typical synthesis was carried out under ionothermal conditions at 400-700 degrees C using ZnCl2 as a Lewis acidic trimerization catalyst. A high degree of local order and the presence of triazine and bipyridine moieties are ascertained at a synthesis temperature of 400 degrees C, along with micropores and specific surface areas of up to 1100 m(2) g(-1). Mesopores are increasingly formed at synthesis temperatures above 450 degrees C, yielding highly porous frameworks with hierarchical porosity and exceptionally large surface areas in excess of 3200 m(2) g(-1) at 700 degrees C. We demonstrate the capability of the bipyridine unit to provide specific and strong binding sites for a large variety of transition metal ions, including Co, Ni, Pt and Pd. The degree of metal loading (up to 38 wt%) can be tuned by the metal concentration in solution and is dependent on both the type of metal as well as the temperature at which the CTF was synthesized. Evidence for site-specific metal coordination bodes well for the use of metal-loaded CTFs as heterogeneous catalysts carrying homogeneous-type active sites
Feedback from the heart: emotional learning and memory is controlled by cardiac cycle, interoceptive accuracy and personality
Feedback processing is critical to trial-and-error learning. Here, we examined whether interoceptive signals concerning the state of cardiovascular arousal influence the processing of reinforcing feedback during the learning of ‘emotional’ face-name pairs, with subsequent effects on retrieval. Participants (N = 29) engaged in a learning task of face-name pairs (fearful, neutral, happy faces). Correct and incorrect learning decisions were reinforced by auditory feedback, which was delivered either at cardiac systole (on the heartbeat, when baroreceptors signal the contraction of the heart to the brain), or at diastole (between heartbeats during baroreceptor quiescence). We discovered a cardiac influence on feedback processing that enhanced the learning of fearful faces in people with heightened interoceptive ability. Individuals with enhanced accuracy on a heartbeat counting task learned fearful face-name pairs better when feedback was given at systole than at diastole. This effect was not present for neutral and happy faces. At retrieval, we also observed related effects of personality: First, individuals scoring higher for extraversion showed poorer retrieval accuracy. These individuals additionally manifested lower resting heart rate and lower state anxiety, suggesting that attenuated levels of cardiovascular arousal in extraverts underlies poorer performance. Second, higher extraversion scores predicted higher emotional intensity ratings of fearful faces reinforced at systole. Third, individuals scoring higher for neuroticism showed higher retrieval confidence for fearful faces reinforced at diastole. Our results show that cardiac signals shape feedback processing to influence learning of fearful faces, an effect underpinned by personality differences linked to psychophysiological arousal
- …