7,339 research outputs found
The Sound of Silence: What Do We Know When Insiders Do Not Trade?
We examine the phenomenon of insider silence, periods when corporate insiders do not trade. Our evidence strongly supports the jeopardy hypothesis that regulations inhibit insiders from trading on extreme information, implying a relation between insider silence and extreme future returns. First, insiders of merger targets refrain from buying in the months before the merger announcement, and insiders of bankruptcy firms refrain from selling before the bankruptcy filing. Second, among firms that are likely to have bad news, insider silence predicts significant negative future returns, which are even lower than when insiders net sell. Further, the negative information in insider silence is gradually incorporated into stock prices, and a significant portion of it is released around quarterly earnings announcements. Finally, the price inefficiency due to insider silence is pervasive, and market frictions make it worse
Institutional Ownership and Return Predictability Across Economically Unrelated Stocks
We document strong weekly lead-lag return predictability across stocks from different industries with no customer-supplier linkages (economically unrelated stocks). Between 1980 and 2010, the industry-neutral long-short hedge portfolio earns an average of over 19 basis points per week. This return predictability arises exclusively from pairs of stocks in which there are common institutional owners. This predictability is a new phenomenon which does not originate from the slow information diffusion underlying previously documented lead-lag effects, weekly reversals, momentum, nonsynchronous trading, or other known factors. Our findings suggest that institutional portfolio reallocations can induce return predictability among otherwise unrelated stocks
ALMA [NII] 205 micron Imaging Spectroscopy of the Interacting Galaxy System BRI 1202-0725 at Redshift 4.7
We present the results from Atacama Large Millimeter/submillimeter Array
(ALMA) imaging in the [NII] 205 micron fine-structure line (hereafter [NII])
and the underlying continuum of BRI 1202-0725, an interacting galaxy system at
4.7, consisting of an optical QSO, a sub-millimeter galaxy (SMG) and two
Lyman- emitters (LAEs), all within 25 kpc of the QSO. We detect
the QSO and SMG in both [NII] and continuum. At the (or 6.6 kpc)
resolution, both QSO and SMG are resolved in [NII], with the de-convolved major
axes of 9 and 14 kpc, respectively. In contrast, their continuum
emissions are much more compact and unresolved even at an enhanced resolution
of . The ratio of the [NII] flux to the existing CO (76) flux is
used to constrain the dust temperature () for a more accurate
determination of the FIR luminosity . Our best estimated equals K for both galaxies (assuming an emissivity index
). The resulting ratios are
statistically consistent with that of local luminous infrared galaxies,
confirming that traces the star formation (SF) rate (SFR) in
these galaxies. We estimate that the on-going SF of the QSO (SMG) has a SFR of
5.1 yr ( 30%) assuming Chabrier
initial mass function, takes place within a diameter (at half maximum) of 1.3
(1.5) kpc, and shall consume the existing 5 of
molecular gas in 10 years.Comment: 4 pages, 1 table, 4 figures; accepted for publication in the ApJ
Letter
Graph Annotations in Modeling Complex Network Topologies
The coarsest approximation of the structure of a complex network, such as the
Internet, is a simple undirected unweighted graph. This approximation, however,
loses too much detail. In reality, objects represented by vertices and edges in
such a graph possess some non-trivial internal structure that varies across and
differentiates among distinct types of links or nodes. In this work, we
abstract such additional information as network annotations. We introduce a
network topology modeling framework that treats annotations as an extended
correlation profile of a network. Assuming we have this profile measured for a
given network, we present an algorithm to rescale it in order to construct
networks of varying size that still reproduce the original measured annotation
profile.
Using this methodology, we accurately capture the network properties
essential for realistic simulations of network applications and protocols, or
any other simulations involving complex network topologies, including modeling
and simulation of network evolution. We apply our approach to the Autonomous
System (AS) topology of the Internet annotated with business relationships
between ASs. This topology captures the large-scale structure of the Internet.
In depth understanding of this structure and tools to model it are cornerstones
of research on future Internet architectures and designs. We find that our
techniques are able to accurately capture the structure of annotation
correlations within this topology, thus reproducing a number of its important
properties in synthetically-generated random graphs
Measuring Star-formation Rate and Far-Infrared Color in High-redshift Galaxies Using the CO (7-6) and [NII] 205 micron Lines
To better characterize the global star formation (SF) activity in a galaxy,
one needs to know not only the star formation rate (SFR) but also the
rest-frame, far-infrared (FIR) color (e.g., the 60-to-100 m color,
] of the dust emission. The latter probes the average intensity of
the dust heating radiation field and scales statistically with the effective
SFR surface density in star-forming galaxies including (ultra-)luminous
infrared galaxies [(U)LIRGs]. To this end, we exploit here a new spectroscopic
approach involving only two emission lines: CO\,(76) at 372 m and [NII]
at 205 m. For local (U)LIRGs, the ratios of the CO (76) luminosity
() to the total infrared luminosity (; 81000
m) are fairly tightly distributed (to within 0.12 dex) and show
little dependence on . This makes a good SFR
tracer, which is less contaminated by active galactic nuclei (AGN) than and may also be much less sensitive to metallicity than . Furthermore, the logarithmic [NII] 205 m to CO (76)
luminosity ratio is fairly steeply (at a slope of ) correlated with
, with a modest scatter (0.23 dex). This makes it a useful
estimator on with an implied uncertainty of 0.15 [or
4 K in the dust temperature () in the case of a
graybody emission with K and a dust emissivity index
]. Our locally calibrated SFR and estimators are shown
to be consistent with the published data of (U)LIRGs of up to 6.5.Comment: 6 pages, 3 figures, 1 table; accepted for publication in the ApJ
Lette
Purely-long-range bound states of HeHe
We predict the presence and positions of purely-long-range bound states of
HeHe near the atomic
limits. The results of the full multichannel and approximate models are
compared, and we assess the sensitivity of the bound states to atomic
parameters characterizing the potentials. Photoassociation to these
purely-long-range molecular bound states may improve the knowledge of the
scattering length associated with the collisions of two ultracold
spin-polarized He atoms, which is important for studies of
Bose-Einstein condensates.Comment: 16 pages, 5 figure
A low-cost, wireless near-infrared spectroscopy device detects the presence of lower extremity atherosclerosis as measured by computed tomographic angiography and characterizes walking impairment in peripheral artery disease
Background Patients with peripheral artery disease (PAD) who experience intermittent claudication report a range of symptoms. Patients with symptoms other than classically described intermittent claudication may be at the highest risk for functional decline and mobility loss. Therefore, technologies allowing for characterization of PAD severity are desirable. Near-infrared spectroscopy (NIRS) allows for measurements of muscle heme oxygen saturation (StO2) during exercise. We hypothesized lower extremities affected by PAD would exhibit distinct NIRS profiles as measured by a low-cost, wireless NIRS device and that NIRS during exercise predicts walking limitation. Methods We recruited 40 patients with PAD and 10 control participants. All patients with PAD completed a computed tomographic angiography, 6-minute walk test, and a standardized treadmill test. Controls completed a 540-second treadmill test for comparison. StO2 measurements were continuously taken from the gastrocnemius during exercise. Variables were analyzed by Fischer\u27s exact, χ2, Wilcoxon rank-sum, and Kruskal-Wallis tests as appropriate. Correlations were assessed by partial Spearman correlation coefficients adjusted for occlusive disease pattern. Results Patients with PAD experienced claudication onset at a median of 108 seconds with a median peak walking time of 288 seconds. The baseline StO2 was similar between PAD and control. The StO2 of PAD and control participants dropped below baseline at a median of 1 and 104 seconds of exercise, respectively (P \u3c .0001). Patients with PAD reached minimum StO2 earlier than control participants (119 seconds vs 522 seconds, respectively; P \u3c .001) and experienced a greater change in StO2 at 1 minute of exercise (−73.2% vs 8.3%; P \u3c .0001) and a greater decrease at minimum exercise StO2 (−83.4% vs −16.1%; P \u3c .0001). For patients with PAD, peak walking time, and 6-minute walking distance correlated with percent change in StO2 at 1 minute of exercise (r = −0.76 and -0.67, respectively; P \u3c .001) and time to minimum StO2 (r = 0.79 and 0.70, respectively; P \u3c .0001). Conclusions In this initial evaluation of a novel, low-cost NIRS device, lower extremities affected by PAD exhibited characteristic changes in calf muscle StO2, which differentiated them from healthy controls and were strongly correlated with walking impairment. These findings confirm and expand on previous work demonstrating the potential clinical value of NIRS devices and the need for further research investigating the ability of low-cost NIRS technology to evaluate, diagnose, and monitor treatment response in PAD
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