3,225 research outputs found
The fossil record of ichthyosaurs, completeness metrics and sampling biases
Ichthyosaurs were highly successful marine reptiles with an abundant and well-studied fossil record. However, their occurrences through geological time and space are sporadic, and it is important to understand whether times of apparent species richness and rarity are real or the result of sampling bias. Here, we explore the skeletal completeness of 351 dated and identified ichthyosaur specimens, belonging to all 102 species, the first time that such a study has been carried out on vertebrates from the marine realm. No correlations were found between time series of different skeletal metrics and ichthyosaur diversity. There is a significant geographical variation in completeness, with the well-studied northern hemisphere producing fossils of much higher quality than the southern hemisphere. Medium-sized ichthyosaurs are significantly more complete than small or large taxa: the incompleteness of small specimens was expected, but it was a surprise that larger specimens were also relatively incomplete. Completeness varies greatly between facies, with fine-grained, siliciclastic sediments preserving the most complete specimens. These findings may explain why the ichthyosaur diversity record is low at times, corresponding to facies of poor preservation potential, such as in the Early Cretaceous. Unexpectedly, we find a strong negative correlation between skeletal completeness and sea level, meaning the most complete specimens occurred at times of global low sea level, and vice versa. Completeness metrics, however, do not replicate the sampling signal and have limited use as a global-scale sampling proxy
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Firm-specific, country-specific and region-specific competitive advantages: the case of emerging economy MNEs - Thailand
Increasing levels of regional economic integration have created a new source of international competitiveness for MNEs from an emerging economy, Thailand, in the context of ASEAN economic integration. Building on the theoretical framework of firm-specific advantages (FSAs) and country-specific advantages (CSAs) grounded in internalization theory, we introduce region-specific advantages (RSAs) and advance a novel regional dual-double-diamond model to analyse regional competitiveness. Using both primary and secondary data we find that most Thai firms derive their international competitiveness from CSAs rather than FSAs, and will benefit from ASEAN RSAs. Our study significantly advances the literature on international competitiveness of emerging-economy MNEs
Relativistic ejecta from XRF 060218 and the rate of cosmic explosions
Over the last decade, long-duration gamma-ray bursts (GRBs) including the
subclass of X-ray flashes (XRFs) have been revealed to be a rare variety of
Type Ibc supernova (SN). While all these events result from the death of
massive stars, the electromagnetic luminosities of GRBs and XRFs exceed those
of ordinary Type Ibc SNe by many orders of magnitude. The essential physical
process that causes a dying star to produce a GRB or XRF, and not just an SN,
remains the crucial open question. Here we present radio and X-ray observations
of XRF 060218 (associated with SN 2006aj), the second nearest GRB identified
to-date, which allow us to measure its total energy and place it in the larger
context of cosmic explosions. We show that this event is 100 times less
energetic but ten times more common than cosmological GRBs. Moreover, it is
distinguished from ordinary Type Ibc SNe by the presence of 10^48 erg coupled
to mildly-relativistic ejecta, along with a central engine (an accretion-fed,
rapidly rotating compact source) which produces X-rays for weeks after the
explosion. This suggests that the production of relativistic ejecta is the key
physical distinction between GRBs/XRFs and ordinary SNe, while the nature of
the central engine (black hole or magnetar) may distinguish typical bursts from
low-luminosity, spherical events like XRF 060218.Comment: To appear in Nature on August 31 2006 (15 pages, 3 figures, 1 table,
including Supplementary Information
The sub-energetic GRB 031203 as a cosmic analogue to GRB 980425
Over the six years since the discovery of the gamma-ray burst GRB 980425,
associated with the nearby (distance, ~40 Mpc) supernova 1998bw, astronomers
have fiercely debated the nature of this event. Relative to bursts located at
cosmological distances, (redshift, z~1), GRB 980425 was under-luminous in
gamma-rays by three orders of magnitude. Radio calorimetry showed the explosion
was sub-energetic by a factor of 10. Here, we report observations of the radio
and X-ray afterglow of the recent z=0.105 GRB 031203 and demonstrate that it
too is sub-energetic. Our result, when taken together with the low gamma-ray
luminosity, suggest that GRB 031203 is the first cosmic analogue to GRB 980425.
We find no evidence that this event was a highly collimated explosion viewed
off-axis. Like GRB 980425, GRB 031203 appears to be an intrinsically
sub-energetic gamma-ray burst. Such sub-energetic events have faint afterglows.
Intensive follow-up of faint bursts with smooth gamma-ray light curves (common
to both GRBs 031203 and 980425) may enable us to reveal their expected large
population.Comment: To Appear in Nature, August 5, 200
Reduced length of hospital stay in colorectal surgery after implementation of an enhanced recovery protocol.
BACKGROUND: Enhanced recovery after surgery (ERAS) is a multimodal approach to perioperative care that combines a range of interventions to enable early mobilization and feeding after surgery. We investigated the feasibility, clinical effectiveness, and cost savings of an ERAS program at a major U. S. teaching hospital. METHODS: Data were collected from consecutive patients undergoing open or laparoscopic colorectal surgery during 2 time periods, before and after implementation of an ERAS protocol. Data collected included patient demographics, operative, and perioperative surgical and anesthesia data, need for analgesics, complications, inpatient medical costs, and 30-day readmission rates. RESULTS: There were 99 patients in the traditional care group, and 142 in the ERAS group. The median length of stay (LOS) was 5 days in the ERAS group compared with 7 days in the traditional group (P < 0.001). The reduction in LOS was significant for both open procedures (median 6 vs 7 days, P = 0.01), and laparoscopic procedures (4 vs 6 days, P < 0.0001). ERAS patients had fewer urinary tract infections (13% vs 24%, P = 0.03). Readmission rates were lower in ERAS patients (9.8% vs 20.2%, P = 0.02). DISCUSSION: Implementation of an enhanced recovery protocol for colorectal surgery at a tertiary medical center was associated with a significantly reduced LOS and incidence of urinary tract infection. This is consistent with that of other studies in the literature and suggests that enhanced recovery programs could be implemented successfully and should be considered in U.S. hospitals
InterFace : A software package for face image warping, averaging, and principal components analysis
We describe InterFace, a software package for research in face recognition. The package supports image warping, reshaping, averaging of multiple face images, and morphing between faces. It also supports principal components analysis (PCA) of face images, along with tools for exploring the “face space” produced by PCA. The package uses a simple graphical user interface, allowing users to perform these sophisticated image manipulations without any need for programming knowledge. The program is available for download in the form of an app, which requires that users also have access to the (freely available) MATLAB Runtime environment
Evanescent light-matter Interactions in Atomic Cladding Wave Guides
Alkali vapors, and in particular rubidium, are being used extensively in
several important fields of research such as slow and stored light non-linear
optics3 and quantum computation. Additionally, the technology of alkali vapors
plays a major role in realizing myriad industrial applications including for
example atomic clocks magentometers8 and optical frequency stabilization.
Lately, there is a growing effort towards miniaturizing traditional
centimeter-size alkali vapor cells. Owing to the significant reduction in
device dimensions, light matter interactions are greatly enhanced, enabling new
functionalities due to the low power threshold needed for non-linear
interactions. Here, taking advantage of the mature Complimentary
Metal-Oxide-Semiconductor (CMOS) compatible platform of silicon photonics, we
construct an efficient and flexible platform for tailored light vapor
interactions on a chip. Specifically, we demonstrate light matter interactions
in an atomic cladding wave guide (ACWG), consisting of CMOS compatible silicon
nitride nano wave-guide core with a Rubidium (Rb) vapor cladding. We observe
the highly efficient interaction of the electromagnetic guided mode with the
thermal Rb cladding. The nature of such interactions is explained by a model
which predicts the transmission spectrum of the system taking into account
Doppler and transit time broadening. We show, that due to the high confinement
of the optical mode (with a mode area of 0.3{\lambda}2), the Rb absorption
saturates at powers in the nW regime.Comment: 10 Pages 4 Figures. 1 Supplementar
Laryngeal tuberculosis presenting as a supraglottic carcinoma: a case report and review of the literature
<p>Abstract</p> <p>Introduction</p> <p>Laryngeal tuberculosis used to be a common complication in advanced pulmonary tuberculosis. However, it has become a rare occurrence in developed countries since the introduction of antituberculous agents. Moreover, the pattern of the disease has changed over the years. Nowadays, it more closely resembles a laryngeal carcinoma than any other laryngeal illness.</p> <p>Case presentation</p> <p>We describe the case of a 50-year-old Caucasian man who presented with the clinical picture of laryngeal cancer, but which turned out to be tuberculosis. We illustrate the difficulty of recognizing laryngeal tuberculosis both clinically and even with radiological examination.</p> <p>Conclusion</p> <p>Although laryngeal tuberculosis is uncommon, especially in developed countries, it still occurs and should be considered as a differential diagnosis in any laryngeal disease, in particular in the case of a laryngeal carcinoma.</p
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