1,788 research outputs found
Converting Endangered Species Categories to Probabilities of Extinction for Phylogenetic Conservation Prioritization
Categories of imperilment like the global IUCN Red List have been transformed to probabilities of extinction and used to rank species by the amount of imperiled evolutionary history they represent (e.g. by the Edge of Existence programme). We investigate the stability of such lists when ranks are converted to probabilities of extinction under different scenarios.Using a simple example and computer simulation, we show that preserving the categories when converting such list designations to probabilities of extinction does not guarantee the stability of the resulting lists.Care must be taken when choosing a suitable transformation, especially if conservation dollars are allocated to species in a ranked fashion. We advocate routine sensitivity analyses
Localised and unresectable neuroblastoma in infants: excellent outcome with low-dose primary chemotherapy
The pathology of familial breast cancer: The pre-BRCA1/BRCA2 era - historical perspectives
A proportion of breast carcinomas develop as a result of a genetic predispostion to the disease. Prior to cloning of the BRCA1 and BRCA2 genes a limited number of studies were carried out to identify specific histopathological characteristics of hereditary breast cancer. These studies are the subject of this review. The main finding was the association of the (atypical) medullary type of breast cancer with a family history; the most important caveat being that medullary breast cancer is found more frequently in young patients. In view of the frequent bilateral occurrence of lobular cancer, this histologic type is also likely to be associated with a predisposing genetic defect. Future investigations will have to test this hypothesis. In addition to mutations in the BRCA1 and BRCA2 genes, there are as yet unidentified genetic defects predisposing to breast cancer development, and histopathology may well help in identifying these genes in the future
The cometary composition of a protoplanetary disk as revealed by complex cyanides
Observations of comets and asteroids show that the Solar Nebula that spawned
our planetary system was rich in water and organic molecules. Bombardment
brought these organics to the young Earth's surface, seeding its early
chemistry. Unlike asteroids, comets preserve a nearly pristine record of the
Solar Nebula composition. The presence of cyanides in comets, including 0.01%
of methyl cyanide (CH3CN) with respect to water, is of special interest because
of the importance of C-N bonds for abiotic amino acid synthesis. Comet-like
compositions of simple and complex volatiles are found in protostars, and can
be readily explained by a combination of gas-phase chemistry to form e.g. HCN
and an active ice-phase chemistry on grain surfaces that advances
complexity[3]. Simple volatiles, including water and HCN, have been detected
previously in Solar Nebula analogues - protoplanetary disks around young stars
- indicating that they survive disk formation or are reformed in situ. It has
been hitherto unclear whether the same holds for more complex organic molecules
outside of the Solar Nebula, since recent observations show a dramatic change
in the chemistry at the boundary between nascent envelopes and young disks due
to accretion shocks[8]. Here we report the detection of CH3CN (and HCN and
HC3N) in the protoplanetary disk around the young star MWC 480. We find
abundance ratios of these N-bearing organics in the gas-phase similar to
comets, which suggests an even higher relative abundance of complex cyanides in
the disk ice. This implies that complex organics accompany simpler volatiles in
protoplanetary disks, and that the rich organic chemistry of the Solar Nebula
was not unique.Comment: Definitive version of the manuscript is published in Nature, 520,
7546, 198, 2015. This is the author's versio
The Universal One-Loop Effective Action
We present the universal one-loop effective action for all operators of
dimension up to six obtained by integrating out massive, non-degenerate
multiplets. Our general expression may be applied to loops of heavy fermions or
bosons, and has been checked against partial results available in the
literature. The broad applicability of this approach simplifies one-loop
matching from an ultraviolet model to a lower-energy effective field theory
(EFT), a procedure which is now reduced to the evaluation of a combination of
matrices in our universal expression, without any loop integrals to evaluate.
We illustrate the relationship of our results to the Standard Model (SM) EFT,
using as an example the supersymmetric stop and sbottom squark Lagrangian and
extracting from our universal expression the Wilson coefficients of
dimension-six operators composed of SM fields.Comment: 30 pages, v2 contains additional comments and corrects typos, version
accepted for publication in JHE
The Role of Bile in the Regulation of Exocrine Pancreatic Secretion
As early as 1926 Mellanby (1) was able to show that introduction of bile into the duodenum of anesthetized cats produces a copious flow of pancreatic juice. In conscious dogs, Ivy & Lueth (2) reported, bile is only a weak stimulant of pancreatic secretion. Diversion of bile from the duodenum, however, did not influence pancreatic volume secretion stimulated by a meal (3,4). Moreover, Thomas & Crider (5) observed that bile not only failed to stimulate the secretion of pancreatic juice but also abolished the pancreatic response to intraduodenally administered peptone or soap
Problematic Instagram use: the role of perceived feeling of presence and escapism
The use of social networking sites is becoming increasingly popular. Although there are many studies investigating the problematic use of social networking sites such as Facebook, little is known about problematic Instagram use (PIU) and factors related to it. The present study developed a complex model in order to examine the mediating role of perceived feeling of presence (i.e., social, spatial, and co-presence) and escapism between using different Instagram features and PIU. A total of 333 Instagram users from a high school and a state university, aged between 14 and 23 years (Mage = 17.74 years, SD = 2.37, 61% female), completed a "paper-and-pencil" questionnaire comprising measures of social presence, spatial presence, co-presence, Instagram escapism, and PIU. In addition, frequency of use of five different Instagram features (i.e., watching live streams; watching videos; looking at posted photographs; liking, commenting on others' posts; and getting likes and comments from others) were assessed using a 7-point Likert scale. Analysis indicated that watching live streams was indirectly associated with PIU via escapism, spatial presence, and co-presence. Leaving likes and comments on others' posts was both directly and indirectly associated with PIU via co-presence and escapism. Escapism mediated the relationships between social and spatial presence and co-presence and PIU. The findings of the present study appear to indicate that a minority of individuals use Instagram problematically and that problematic Instagram use is associated with the frequency of watching live streams, liking, and commenting on others’ posts on Instagram, being able to feel a higher sense of presence using Instagram, and using Instagram as an escape from reality
Circumstellar discs: What will be next?
This prospective chapter gives our view on the evolution of the study of
circumstellar discs within the next 20 years from both observational and
theoretical sides. We first present the expected improvements in our knowledge
of protoplanetary discs as for their masses, sizes, chemistry, the presence of
planets as well as the evolutionary processes shaping these discs. We then
explore the older debris disc stage and explain what will be learnt concerning
their birth, the intrinsic links between these discs and planets, the hot dust
and the gas detected around main sequence stars as well as discs around white
dwarfs.Comment: invited review; comments welcome (32 pages
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A practitioner's guide to Bayesian estimation of discrete choice dynamic programming models
This paper provides a step-by-step guide to estimating infinite horizon discrete choice dynamic programming (DDP) models using a new Bayesian estimation algorithm (Imai et al., Econometrica 77:1865–1899, 2009a) (IJC). In the conventional nested fixed point algorithm, most of the information obtained in the past iterations remains unused in the current iteration. In contrast, the IJC algorithm extensively uses the computational results obtained from the past iterations to help solve the DDP model at the current iterated parameter values. Consequently, it has the potential to significantly alleviate the computational burden of estimating DDP models. To illustrate this new estimation method, we use a simple dynamic store choice model where stores offer “frequent-buyer” type rewards programs. Our Monte Carlo results demonstrate that the IJC method is able to recover the true parameter values of this model quite precisely. We also show that the IJC method could reduce the estimation time significantly when estimating DDP models with unobserved heterogeneity, especially when the discount factor is close to 1
Thermal Properties of Graphene, Carbon Nanotubes and Nanostructured Carbon Materials
Recent years witnessed a rapid growth of interest of scientific and
engineering communities to thermal properties of materials. Carbon allotropes
and derivatives occupy a unique place in terms of their ability to conduct
heat. The room-temperature thermal conductivity of carbon materials span an
extraordinary large range - of over five orders of magnitude - from the lowest
in amorphous carbons to the highest in graphene and carbon nanotubes. I review
thermal and thermoelectric properties of carbon materials focusing on recent
results for graphene, carbon nanotubes and nanostructured carbon materials with
different degrees of disorder. A special attention is given to the unusual size
dependence of heat conduction in two-dimensional crystals and, specifically, in
graphene. I also describe prospects of applications of graphene and carbon
materials for thermal management of electronics.Comment: Review Paper; 37 manuscript pages; 4 figures and 2 boxe
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