505 research outputs found
The fossil record of early tetrapods: worker effort and the end-Permian mass extinction
It is important to understand the quality of the fossil record of early tetrapods (Tetrapoda, minus Lissamphibia and Amniota) because of their key role in the transition of vertebrates from water to land, their dominance of terrestrial faunas for over 100 million years of the late Palaeozoic and earlyMesozoic, and their variable fates during the end−Permian mass extinction. The first description of an early tetrapod dates back to 1824, and since then discoveries have occurred at a rather irregular pace, with peaks and troughs corresponding to some of the vicissitudes of human history through the past two centuries. As expected, the record is dominated by the well−sampled sedimentary basins of Europe and North America, but finds from other continents are increasing rapidly. Comparisons of snapshots of knowledge in 1900, 1950, and 2000 show that discovery of new species has changed the shape of the species−level diversification curve, contrary to earlier studies of family−level taxa. There is, however, little evidence that taxon counts relate to research effort (as counted by numbers of publications), and there are no biasing effects associated with differential study of different time intervals through the late Palaeozoic and Mesozoic. In fact, levels of effort are apparently not related to geological time, with no evidence that workers have spent more time on more recent parts of the record. In particular, the end−Permian mass extinction was investigated to determine whether diversity changes through that interval might reflect worker effort: it turns out that most records of early tetrapod taxa (when corrected for duration of geological series) occur in the Lower Triassic
Spot size measurements in the Eli-NP compton gamma source
A high brightness electron Linac is being built in the Compton Gamma Source at the ELI Nuclear Physics facility in Romania. To achieve the design luminosity, a train of 32 bunches with a nominal charge of 250 pC and 16 ns spacing , will collide with the laser beam in the interaction point. Electron beam spot size is measured with an OTR (optical transition radiation) profile moni-tors. In order to measure the beam properties, the optical radiation detecting system must have the necessary accu-racy and resolution. This paper deals with the studies of different optic configurations to achieve the magnifica-tion, resolution and accuracy desired considering design and technological constraints; we will compare several configurations of the optical detection line to justify the one chosen for the implementation in the Lina
Optical issues for the diagnostic stations for the ELI-NP compton gamma source
A high brightness electron Linac is being built in the Compton Gamma Source at the ELI Nuclear Physics facility in Romania. To achieve the design luminosity, a train of 32 bunches, 16 ns spaced, with a nominal charge of 250 pC will collide with the laser beam in the interaction point. Electron beam spot size is measured with optical transition radiation (OTR) profile monitors. In order to measure the beam properties, the optical radiation detecting system must have the necessary accuracy and resolution. This paper deals with the studies of different optic configurations to achieve the magnification, resolution and accuracy in order to measure very small beam (below 30 μm) or to study the angular distribution of the OTR and therefore the energy of the beam. Several configurations of the optical detection line will be studied both with simulation tools (e.g. Zemax) and experimentally. The paper will deal also with the sensibility of optic system (in terms of depth of field, magnification and resolution) to systematic error
When Madagascar produced natural rubber: a brief, forgotten yet informative history.
From 1891 to 1914, Madagascar, like other western African countries, was a production zone for forest rubber destined for export to Europe when Asian plantations where not yet sufficiently developed . Numerous species endemic to the forests of the three major Malagasy ecosystems were exploited, often with a view to maximising short term productivity without any consideration for the sustainable management of the resource. This episode represents one of the first cases of industrial exploitation of Madagascar's biological resources. Although Madagascar occupies a modest position on the world rubber market at that time, the exploitation of rubber bore major consequences for the island's forestry resources and, moreover, influenced the vision and discourse of scientists and politicians concerning their management. It was one of the factors triggering awareness of the value of Madagascar's biodiversity and the threat to which it might be exposed through poorly-controlled human activity. As a result, highly repressive and forcible legislation was introduced aimed at containing the activity practiced by local populations considered to be mostly to blame. But from the early days of French colonial rule, naturalists judged the outcomes of political decisions too weak to offer any guarantee of an effective defence. They responded by adopting an intentionally alarmist and catastrophist discourse with the object of provoking a reaction from the politicians, considered too lax. This discourse, in fact, took an about-turn from 1942-45 when the war effort led to a revitalisation of the Malagasy rubber sector as Asian production was mainly out of reach. A second consequence came in 1927 with the creation of a network of protected areas managed by naturalists, making Madagascar at that time, a pioneer in Africa. There was a simultaneous flurry of activity to promote the domestication of Malagasy rubber species, combined with the introduction of new species with high potential (Hevea brasiliensis, Castilloa elastica). However, with the emergence of far more profitable Asian rubber, all attempts at cultivation in Madagascar were abandoned when exploitation ceased to be profitable, and thus the Malagasy forests were redeemed. This episode demonstrates how it was in fact economic reality, by condemning an unprofitable sector, that was the real vehicle by which the survival of Malagasy rubber species was secured, and not the naturalists' discourse, nor the creation of protected zones, nor the promulgation of repressive legislations. This case study is of more than purely historical interest, in that it still has currency where, for example, the exploitation of Prunus africana is concerned
Imaging of SNR IC443 and W44 with the Sardinia Radio Telescope at 1.5 GHz and 7 GHz
Observations of supernova remnants (SNRs) are a powerful tool for
investigating the later stages of stellar evolution, the properties of the
ambient interstellar medium, and the physics of particle acceleration and
shocks. For a fraction of SNRs, multi-wavelength coverage from radio to ultra
high-energies has been provided, constraining their contributions to the
production of Galactic cosmic rays. Although radio emission is the most common
identifier of SNRs and a prime probe for refining models, high-resolution
images at frequencies above 5 GHz are surprisingly lacking, even for bright and
well-known SNRs such as IC443 and W44. In the frameworks of the Astronomical
Validation and Early Science Program with the 64-m single-dish Sardinia Radio
Telescope, we provided, for the first time, single-dish deep imaging at 7 GHz
of the IC443 and W44 complexes coupled with spatially-resolved spectra in the
1.5-7 GHz frequency range. Our images were obtained through on-the-fly mapping
techniques, providing antenna beam oversampling and resulting in accurate
continuum flux density measurements. The integrated flux densities associated
with IC443 are S_1.5GHz = 134 +/- 4 Jy and S_7GHz = 67 +/- 3 Jy. For W44, we
measured total flux densities of S_1.5GHz = 214 +/- 6 Jy and S_7GHz = 94 +/- 4
Jy. Spectral index maps provide evidence of a wide physical parameter scatter
among different SNR regions: a flat spectrum is observed from the brightest SNR
regions at the shock, while steeper spectral indices (up to 0.7) are observed
in fainter cooling regions, disentangling in this way different populations and
spectra of radio/gamma-ray-emitting electrons in these SNRs.Comment: 13 pages, 9 figures, accepted for publication to MNRAS on 18 May 201
Deep Sequencing of RNA from Blood and Oral Swab Samples Reveals the Presence of Nucleic Acid from a Number of Pathogens in Patients with Acute Ebola Virus Disease and Is Consistent with Bacterial Translocation across the Gut.
In this study, samples from the 2013-2016 West African Ebola virus outbreak from patients in Guinea with Ebola virus disease (EVD) were analyzed to discover and classify what other pathogens were present. Throat swabs were taken from deceased EVD patients, and peripheral blood samples were analyzed that had been taken from patients when they presented at the treatment center with acute illness. High-throughput RNA sequencing (RNA-seq) and bioinformatics were used to identify the potential microorganisms. This approach confirmed Ebola virus (EBOV) in all samples from patients diagnosed as acute positive for the virus by quantitative reverse transcription-PCR in deployed field laboratories. Nucleic acid mapping to Plasmodium was also used on the patient samples, confirming results obtained with an antigen-based rapid diagnostic test (RDT) conducted in the field laboratories. The data suggested that a high Plasmodium load, as determined by sequence read depth, was associated with mortality and influenced the host response, whereas a lower parasite load did not appear to affect outcome. The identifications of selected bacteria from throat swabs via RNA-seq were confirmed by culture. The data indicated that the potential pathogens identified in the blood samples were associated with translocation from the gut, suggesting the presence of bacteremia, which transcriptome data suggested may induce or aggravate the acute-phase response observed during EVD. Transcripts mapping to different viruses were also identified, including those indicative of lytic infections. The development of high-resolution analysis of samples from patients with EVD will help inform care pathways and the most appropriate general antimicrobial therapy to be used in a resource-poor setting. IMPORTANCE Our results highlight the identification of an array of pathogens in the blood of patients with Ebola virus disease (EVD). This has not been done before, and the data have important implications for the treatment of patients with EVD, particularly considering antibiotic stewardship. We show that EVD patients who were also infected with Plasmodium, particularly at higher loads, had more adverse outcomes than patients with lower levels of Plasmodium. However, the presence of Plasmodium did not influence the innate immune response, and it is likely that the presence of EBOV dominated this response. Several viruses other than EBOV were identified, and bacteria associated with sepsis were also identified. These findings were indicative of bacterial translocation across the gut during the acute phase of EVD
Reciprocity as a foundation of financial economics
This paper argues that the subsistence of the fundamental theorem of contemporary financial mathematics is the ethical concept ‘reciprocity’. The argument is based on identifying an equivalence between the contemporary, and ostensibly ‘value neutral’, Fundamental Theory of Asset Pricing with theories of mathematical probability that emerged in the seventeenth century in the context of the ethical assessment of commercial contracts in a framework of Aristotelian ethics. This observation, the main claim of the paper, is justified on the basis of results from the Ultimatum Game and is analysed within a framework of Pragmatic philosophy. The analysis leads to the explanatory hypothesis that markets are centres of communicative action with reciprocity as a rule of discourse. The purpose of the paper is to reorientate financial economics to emphasise the objectives of cooperation and social cohesion and to this end, we offer specific policy advice
Who’s afraid of the predicate theory of names?
This essay is devoted to an analysis of the semantic significance of a fashionable view of proper names, the Predicate Theory of names (PT), typically developed in the direction of the Metalinguistic Theory of names (MT). According to MT, ‘syntactic evidence supports the conclusion that a name such as ‘Kennedy’ is analyzable in terms of the predicate (general term) ‘individual named ‘Kennedy’’. This analysis is in turn alleged to support a descriptivist treatment of proper names in designative position, presumably in contrast with theories of names as ‘directly referring rigid designators’. The main aim of this essay is that of questioning the significance of PT and MT as theories of designation: even granting for the argument’s sake that names are analyzable as (metalinguistic) predicates, their designative occurrences may be interpreted in consonance with the dictates of Direct Reference—indeed, in consonance with the radically anti-descriptivist version of Direct Reference I call Millianism
Multi-messenger observations of a binary neutron star merger
On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta
STEM through Authentic Research and Training Program (START) for Underrepresented Communities: Adapting to the COVID-19 Pandemic
The STEM Through Authentic Research and Training (START) Program is a new program integrating academic, social, and professional experiences, in the theme of exomedicine, to build a pipeline into college for first generation and traditionally underrepresented students by providing year-round authentic opportunities and professional development for high school students and teachers. In response to the COVID-19 pandemic, the START Program has worked with the local Fayette County public school and community partners to provide content to over 300 students through: virtual laboratory tours with community partner Space Tango, meet a scientist discussions, and online near-peer student demonstrations aimed at making the practice of STEM disciplines approachable. Furthermore, the START Program has partnered with Higher Orbits to provide at-home, space-themed learning kits for students to develop teamwork, communication, and STEM principles while engaging in online content with teachers, professionals, and astronauts. Finally, the START Program has moved its training platforms online, including receiving College Reading and Learning Association (CRLA) Peer Educator accreditation for our near-peer mentoring and coaching training. As a result, the START Program is better positioned to address this critical need in STEM education, while reaching more students in the community than possible with face-to-face interactions alone
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