10,435 research outputs found
Groups and semigroups with a one-counter word problem
We prove that a finitely generated semigroup whose word problem is a one-counter language has a linear growth function. This provides us with a very strong restriction on the structure of such a semigroup, which, in particular, yields an elementary proof of a result of Herbst, that a group with a one-counter word problem is virtually cyclic. We prove also that the word problem of a group is an intersection of finitely many one-counter languages if and only if the group is virtually abelian
Item response theory and validity of the NEO-FFI in adolescents
The present study applied item response theory (IRT) to the NEO five factor inventory (NEO-FFI) completed by a community based sample of adolescents. The results revealed that many of these personality items may not be discriminating well, with some traits demonstrating greater reliability than others. Furthermore, the threshold values highlighted that the majority of the items had skewed responses, suggesting a limited utility of some response categories. Generally, removing poorly discriminating items does not harm external validity, suggesting IRT reduces measurement error and increases reliability without compromising validity
Help-seeking in emerging adults with and without a history of mental health referral: a qualitative study
Background: Young people are generally reluctant to seek professional help when experiencing problems. However, past experience of services is often cited as increasing the intention to seek help, therefore those with a history of mental health referral may adopt more adaptive help seeking strategies. The current study investigated whether the pattern of different help seeking strategies and barriers to help seeking differed as a function of previous referral history.
Methods: Semi-structured interviews were conducted with 29 emerging adults (12 males, 17 females); 17 with a history of mental health referral and 12 without and analysed using thematic analysis.
Results: Overall, those with a referral to services were more likely than those without to rely on avoidant coping, especially techniques that depended upon suppression. This could help account for the increased use of strategies involving self-harm and substances in those with past referral. An exploration of barriers to help seeking showed those with a history of mental health referral were much more likely to self-stigmatise and this became attached to their sense of identity.
Conclusions: Emerging adults with a history of referral are more likely to adopt avoidant coping strategies when dealing with problems and self-stigmatise to a greater degree than those without a history of referral. This suggests that current approaches to mental health in emerging adults are not decreasing the sense of stigma with potentially far-reaching consequences for the developing sense of self and choice of help seeking strategie
A Multi-signal Variant for the GPU-based Parallelization of Growing Self-Organizing Networks
Among the many possible approaches for the parallelization of self-organizing
networks, and in particular of growing self-organizing networks, perhaps the
most common one is producing an optimized, parallel implementation of the
standard sequential algorithms reported in the literature. In this paper we
explore an alternative approach, based on a new algorithm variant specifically
designed to match the features of the large-scale, fine-grained parallelism of
GPUs, in which multiple input signals are processed at once. Comparative tests
have been performed, using both parallel and sequential implementations of the
new algorithm variant, in particular for a growing self-organizing network that
reconstructs surfaces from point clouds. The experimental results show that
this approach allows harnessing in a more effective way the intrinsic
parallelism that the self-organizing networks algorithms seem intuitively to
suggest, obtaining better performances even with networks of smaller size.Comment: 17 page
The Rapidly Fading Optical Afterglow of GRB 980519
GRB 980519 had the most rapidly fading of the well-documented GRB afterglows,
consistent with t^{-2.05 +/- 0.04} in BVRI as well as in X-rays during the two
days in which observations were made. We report VRI observations from the MDM
1.3m and WIYN 3.5m telescopes, and we synthesize an optical spectrum from all
of the available photometry. The optical spectrum alone is well fitted by a
power law of the form nu^{-1.20 +/- 0.25}, with some of the uncertainty due to
the significant Galactic reddening in this direction. The optical and X-ray
spectra together are adequately fitted by a single power law nu^{-1.05 +/-
0.10}. This combination of steep temporal decay and flat broad-band spectrum
places a severe strain on the simplest afterglow models involving spherical
blast waves in a homogeneous medium. Instead, the rapid observed temporal decay
is more consistent with models of expansion into a medium of density n(r)
proportional to r^{-2}, or with predictions of the evolution of a jet after it
slows down and spreads laterally. The jet model would relax the energy
requirements on some of the more extreme GRBs, of which GRB 980519 is likely to
be an example because of its large gamma-ray fluence and faint host galaxy.Comment: 13 pages, submitted to ApJ Letter
Observational Prospects for Afterglows of Short Duration Gamma-ray Bursts
If the efficiency for producing -rays is the same in short duration
(\siml 2 s) Gamma-Ray Bursts (GRBs) as in long duration GRBs, then the
average kinetic energy of short GRBs must be times less than that of
long GRBs. Assuming further that the relativistic shocks in short and long
duration GRBs have similar parameters, we show that the afterglows of short
GRBs will be on average 10--40 times dimmer than those of long GRBs. We find
that the afterglow of a typical short GRB will be below the detection limit
(\siml 10 \microJy) of searches at radio frequencies. The afterglow would be
difficult to observe also in the optical, where we predict R \simg 23 a few
hours after the burst. The radio and optical afterglow would be even fainter if
short GRBs occur in a low-density medium, as expected in NS-NS and NS-BH merger
models. The best prospects for detecting short-GRB afterglows are with early
(\siml 1 day) observations in X-rays.Comment: 5 pages, 2 figures, submitted to ApJ lette
Objects that Sound
In this paper our objectives are, first, networks that can embed audio and
visual inputs into a common space that is suitable for cross-modal retrieval;
and second, a network that can localize the object that sounds in an image,
given the audio signal. We achieve both these objectives by training from
unlabelled video using only audio-visual correspondence (AVC) as the objective
function. This is a form of cross-modal self-supervision from video.
To this end, we design new network architectures that can be trained for
cross-modal retrieval and localizing the sound source in an image, by using the
AVC task. We make the following contributions: (i) show that audio and visual
embeddings can be learnt that enable both within-mode (e.g. audio-to-audio) and
between-mode retrieval; (ii) explore various architectures for the AVC task,
including those for the visual stream that ingest a single image, or multiple
images, or a single image and multi-frame optical flow; (iii) show that the
semantic object that sounds within an image can be localized (using only the
sound, no motion or flow information); and (iv) give a cautionary tale on how
to avoid undesirable shortcuts in the data preparation.Comment: Appears in: European Conference on Computer Vision (ECCV) 201
Purification and Partial Characterization of Relaxin and Relaxin Precursors from the Hamster Placenta
Previous immunological studies have indicated that the molecular structure of hamster relaxin is
quite different from that of porcine relaxin. In the present study, hamster relaxin was purified from
placentas and characterized in order to investigate its biochemical properties. Placentas from Days
14 and 15 of gestation were homogenized in 0.26 N HCl-62.5% acetone containing protease
inhibitors. After centrifugation, soluble proteins were acetone precipitated. Soluble proteins were
applied to a carboxymethyl cellulose ion-exchange column and bound proteins were eluted with 0.1
and 0.3 M NaCl. Western blot analysis detected 16.5-, 18.7-, and 36.0-kDa relaxin-immunoreactive
(IR) proteins within the 0.1 M NaCl eluant and detected a 5.6-kDa relaxin-IR protein within the 0.3
M NaCl eluant. The 5.6-kDa protein was purified to homogeneity by gel filtration (Sephadex G-50),
ion-exchange HPLC, and C18 -HPLC. Reduction of the 5.6-kDa protein prior to electrophoresis
resulted in a single band of lower molecular mass, suggesting that hamster relaxin consists of two
chains of approximately equal molecular mass. Isoelectric point of the 5.6-kDa protein was 7.78.
The 16.5- and 18.7-kDa IR proteins were copurified by gel filtration and ion-exchange HPLC. At
least five isoelectric point variants were observed for the 16.5- and 18.7-kDa proteins. The N-terminal
amino acid for the 5.6 and 18.7 relaxin-IR proteins was arginine, and subsequent cycles indicated an
identical partial sequence that was consistent with that for relaxins from other species. Originally published Biology of Reproduction, Vol. 49, No. 1, July 199
A search for solar neutrons on a long duration balloon flight
The EOSCOR 3 detector, designed to measure the flux of solar neutrons, was flown on a long duration RACOON balloon flight from Australia during Jan. through Feb, 1983. The Circum-global flight lasted 22 days. No major solar activity occurred during the flight and thus only an upper limit to the solar flare neutrons flux is given. The atmospheric neutron response is compared with that obtained on earlier flights from Palestine, Texas
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