1,794 research outputs found
Intra-day Variability of Sagittarius A* at 3 Millimeters
We report observations and analysis of flux monitoring of Sagittarius A* at
3-mm wavelength using the OVRO millimeter interferometer over a period of eight
days (2002 May 23-30). Frequent phase and flux referencing (every 5 minutes)
with the nearby calibrator source J1744-312 was employed to control for
instrumental and atmospheric effects. Time variations are sought by computing
and subtracting, from each visibility in the database, an average visibility
obtained from all the data acquired in our monitoring program having similar uv
spacings. This removes the confusing effects of baseline-dependent, correlated
flux interference caused by the static, thermal emission from the extended
source Sgr A West. Few-day variations up to ~20% and intra-day variability of
\~20% and in some cases up to ~40% on few-hour time scales emerge from the
differenced data on SgrA*. Power spectra of the residuals indicate the presence
of hourly variations on all but two of the eight days. Monte Carlo simulation
of red-noise light curves indicates that the hourly variations are well
described by a red-noise power spectrum with P(f) ~ f^(-1). Of particular
interest is a ~2.5 hour variation seen prominently on two consecutive days. An
average power spectrum from all eight days of data reveals noteworthy power on
this time scale. There is some indication that few-hour variations are more
pronounced on days when the average daily flux is highest. We briefly discuss
the possibility that these few-hour variations are due to the dynamical
modulation of accreting gas around the central supermassive black hole, as well
as the implications for the structure of the SgrA* photosphere at 3 mm.
Finally, these data have enabled us to produce a high sensitivity 3-mm map of
the extended thermal emission surrounding SgrA*.Comment: Accepted for publication in The Astrophysical Journal Letters, 8
pages, 4 figure
A cross-linguistic investigation of the onset effect in reading aloud : No need to mope about the MOPE
There are around 7,000 different languages. The unique orthographic characteristics of different languages can help us to gain insight into the seemingly simple process of transforming written script to spoken words (i.e., reading aloud). In this thesis, using behavioral and electroencephalography (EEG) measures the time course of reading (aloud) was investigated in first, second, and cross-language situations. Overall, target words (e.g., CARPET) were read aloud faster when preceded by phonologically (e.g., kettle) but not orthographically onset-related primes (e.g., circus). However, this pattern was absent during silent reading and reading in Persian where words are printed without vowels. EEG data revealed both orthographic and phonological activation about 150 milliseconds after target presentation for all situations and languages. These results suggest that reading starts with same processes __ whether silent or aloud or in different scripts. Additionally, even if we have an accent in a second language, the phonological code is activated similarly as for a native speaker. To conclude, this thesis favors computational models assuming early conversion of orthography-to-phonology. However, with approximately half of the world__s population being bilingual and the results presented in this thesis, it is important that computational models of reading processes extend their horizon.Theoretical and Experimental Linguistic
Is pitch accent necessary for comprehension by native Japanese speakers? - An ERP investigation
Not unlike the tonal system in Chinese, Japanese habitually attaches pitch accents to the production of words. However, in contrast to Chinese, few homophonic word-pairs are really distinguished by pitch accents (Shibata & Shibata, 1990). This predicts that pitch accent plays a small role in lexical selection for Japanese language comprehension. The present study investigated whether native Japanese speakers necessarily use pitch accent in the processing of accent-contrasted homophonic pairs (e.g., ame [LH] for 'candy' and ame [HI] for 'rain') measuring electroencephalographic (EEG) potentials. Electrophysiological evidence (i.e., N400) was obtained when a word was semantically incorrect for a given context but not for incorrectly accented homophones. This suggests that pitch accent indeed plays a minor role when understanding Japanese. (C) 2013 Elsevier Ltd. All rights reserved
Correlated X-ray and Optical Variability in Mkn 509
We present results of a 3 year monitoring campaign of the Seyfert 1 galaxy
Markarian 509, using X-ray data from the Rossi X-ray Timing Explorer (RXTE) and
optical data taken by the SMARTS consortium. Both light curves show significant
variations, and are strongly correlated with the optical flux leading the X-ray
flux by 15 days. The X-ray power spectrum shows a steep high-frequency slope of
-2.0, breaking to a slope of -1.0 at at timescale of 34 days. The lag from
optical to X-ray emission is most likely caused by variations in the accretion
disk propagating inward.Comment: 13 pages, 3 figures. Accepted for publication in the Astrophysical
Journa
Clinical Appraisals of Individual Differences in Treatment Responsivity Among Patients With Psychopathy: A Consensual Qualitative Research Study
This study addressed which factors expert clinicians consider crucial in successful completion versus dropout in the mandatory forensic psychiatric treatment of psychopathic patients in the Netherlands. Eleven clinicians were interviewed about patient characteristics, treatment (provider) characteristics, and other factors they deemed associated with failure (transfer to another facility) or completion. The interviews were coded using the guidelines of Consensual Qualitative Research (CQR). Overall, extremely high scores on Psychopathy ChecklistāRevised (PCL-R) Facets 1 (Deceitful Interpersonal Style) and 2 (Defective Affective Experience) were thought to impede treatment retention, particularly by its negative impact on motivation and therapeutic relationship. Older patients, those with a prosocial network, and/or patients with comorbid borderline traits appeared to fare better. Treatment success was deemed more likely when treatment goals and expectations are stipulated in a concrete fashion, when an extended and gradual resocialization trajectory is offered, and the treatment team is expert, cohesive, and stable.</p
Disorder-Induced Shift of Condensation Temperature for Dilute Trapped Bose Gases
We determine the leading shift of the Bose-Einstein condensation temperature
for an ultracold dilute atomic gas in a harmonic trap due to weak disorder by
treating both a Gaussian and a Lorentzian spatial correlation for the quenched
disorder potential. Increasing the correlation length from values much smaller
than the geometric mean of the trap scale and the mean particle distance to
much larger values leads first to an increase of the positive shift to a
maximum at this critical length scale and then to a decrease.Comment: Author information under
http://www.theo-phys.uni-essen.de/tp/ags/pelster_di
Phase synchronization from noisy univariate signals
We present methods for detecting phase synchronization of two
unidirectionally coupled, self-sustained noisy oscillators from a signal of the
driven oscillator alone. One method detects soft, another hard phase locking.
Both are applied to the problem of detecting phase synchronization in von
Karman vortex flow meters.Comment: 4 pages, 4 figure
Artifacts with uneven sampling of red noise
The vast majority of sampling systems operate in a standard way: at each tick
of a fixed-frequency master clock a digitizer reads out a voltage that
corresponds to the value of some physical quantity and translates it into a bit
pattern that is either transmitted, stored, or processed right away. Thus
signal sampling at evenly spaced time intervals is the rule: however this is
not always the case, and uneven sampling is sometimes unavoidable.
While periodic or quasi-periodic uneven sampling of a deterministic signal
can reasonably be expected to produce artifacts, it is much less obvious that
the same happens with noise: here I show that this is indeed the case only for
long-memory noise processes, i.e., power-law noises with . The resulting artifacts are usually a nuisance although they can be
eliminated with a proper processing of the signal samples, but they could also
be turned to advantage and used to encode information.Comment: 5 figure
Inzicht en toezicht: controle in de kennissamenleving
Nieuwe technieken maken het opslaan en verwerken van informatie eenvoudiger. Sterker\ud
nog: ze maken de weg vrij om gegevens vast te leggen voordat duidelijk is welk inzicht\ud
we eigenlijk nastreven. Toezicht wint zo terrein ten opzichte van de kennisverwerving.\ud
\ud
Voorbeelden van toenemend toezicht zijn elektronische dossiers over burgers,\ud
informatievergaring door de politie en in private initiatieven zoals Google Earth. Deze\ud
systemen maken het mogelijk om op grote schaal verbanden te ontdekken en afwijkingen op\ud
te sporen, zonder dat er duidelijke kennisvragen aan vooraf gaan.\ud
\ud
De relatie tussen inzicht en toezicht is bepalend voor hoe we met de verzamelde kennis\ud
omgaan. Ligt de nadruk daarbij op inzicht, overzicht, toezicht, of nog iets anders? Dit\ud
Jaarboek Kennissamenleving 2010 stelt kritische vragen bij de alomtegenwoordige blik van\ud
toezicht. Het draagt ideeƫn aan om deze in de toekomst anders te richten, zodat inzicht en\ud
toezicht in balans kunnen blijven
Talking quiescence: a rigorous theory that supports parallel composition, action hiding and determinisation
The notion of quiescence - the absence of outputs - is vital in both
behavioural modelling and testing theory. Although the need for quiescence was
already recognised in the 90s, it has only been treated as a second-class
citizen thus far. This paper moves quiescence into the foreground and
introduces the notion of quiescent transition systems (QTSs): an extension of
regular input-output transition systems (IOTSs) in which quiescence is
represented explicitly, via quiescent transitions. Four carefully crafted rules
on the use of quiescent transitions ensure that our QTSs naturally capture
quiescent behaviour.
We present the building blocks for a comprehensive theory on QTSs supporting
parallel composition, action hiding and determinisation. In particular, we
prove that these operations preserve all the aforementioned rules.
Additionally, we provide a way to transform existing IOTSs into QTSs, allowing
even IOTSs as input that already contain some quiescent transitions. As an
important application, we show how our QTS framework simplifies the fundamental
model-based testing theory formalised around ioco.Comment: In Proceedings MBT 2012, arXiv:1202.582
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