2,746 research outputs found
Laboratory and tentative interstellar detection of trans-methyl formate using the publicly available Green Bank Telescope PRIMOS survey
The rotational spectrum of the higher-energy trans conformational isomer of
methyl formate has been assigned for the first time using several pulsed-jet
Fourier transform microwave spectrometers in the 6-60 GHz frequency range. This
species has also been sought toward the Sagittarius B2(N) molecular cloud using
the publicly available PRIMOS survey from the Green Bank Telescope. We detect
seven absorption features in the survey that coincide with laboratory
transitions of trans-methyl formate, from which we derive a column density of
3.1 (+2.6, -1.2) \times 10^13 cm-2 and a rotational temperature of 7.6 \pm 1.5
K. This excitation temperature is significantly lower than that of the more
stable cis conformer in the same source but is consistent with that of other
complex molecular species recently detected in Sgr B2(N). The difference in the
rotational temperatures of the two conformers suggests that they have different
spatial distributions in this source. As the abundance of trans-methyl formate
is far higher than would be expected if the cis and trans conformers are in
thermodynamic equilibrium, processes that could preferentially form
trans-methyl formate in this region are discussed. We also discuss measurements
that could be performed to make this detection more certain. This manuscript
demonstrates how publicly available broadband radio astronomical surveys of
chemically rich molecular clouds can be used in conjunction with laboratory
rotational spectroscopy to search for new molecules in the interstellar medium.Comment: 40 pages, 7 figures, 4 tables; accepted for publication in Ap
Metastatic Crohn's Disease of the Ear
Objective. We reported a very rare case of metastatic Crohn's disease involving the retro-auricular region. Method. A case report and a review of literature concerning metastatic Crohn's disease.
Results. Metastatic Crohn's disease is an uncommon extraintestinal cutaneous manifestation of Crohn's disease and a very rare case involving the retro-auricular region is reported here. Given the limited existing literature little is known about this condition. The skin lesions appear to have a predilection for the lower trunk and genitalia regions. There is no clear association with the severity of Crohn's disease and in some cases, the cutaneous lesions predate the onset of gastrointestinal Crohn's disease. Treatment with immune-modulating medications together with the antitumour necrosis factor monoclonal antibody therapy appears to offer the best chance of remission. Conclusion. By reporting this interesting and rare condition we also hope to highlight the importance of considering underlying chronic systemic disorders, such as Crohn's disease, when presented with skin lesions resistant to simple local treatments
Volume 14. Article 1. The striped bass, Roccus saxatilis.
https://elischolar.library.yale.edu/bulletin_yale_bingham_oceanographic_collection/1151/thumbnail.jp
Studies of a Lacustrine-Volcanic Mars Analog Field Site with Mars-2020-like Instruments
On the upcoming Marsâ2020 rover two remote sensing instruments, MastcamâZ and SuperCam, and two microscopic proximity science instruments, SHERLOC and PIXL, will collect compositional (mineralogy, chemistry, and organics) data essential for paleoenvironmental reconstruction. The synergies between and limitations of these instruments were evaluated via study of a Mars analog field site in the Mojave Desert, using instruments approximating the data that will be returned by Marsâ2020. A ground truth dataset was generated for comparison to validate the results. The site consists of a succession of clayârich mudstones of lacustrine origin, interbedded tuffs, a carbonateâsilica travertine deposit, and gypsiferous mudstone strata. The major geological units were mapped successfully using simulated Marsâ2020 data. Simulated MastcamâZ data identified unit boundaries and Feâbearing weathering products. Simulated SuperCam passive shortwave infrared and green Raman data were essential in identifying major mineralogical composition and changes in lacustrine facies at distance; this was possible even with spectrally downsampled passive IR data. LIBS and simulated PIXL data discriminated and mapped major element chemistry. Simulated PIXL revealed mmâscale zones enriched in zirconium, of interest for age dating. SHERLOCâlike data mapped sulfate and carbonate at subâmm scale; silicates were identified with increased laser pulses/spot or by averaging of hundreds of spectra. Fluorescence scans detected and mapped varied classes of organics in all samples, characterized further with followâon spatially targeted deepâUV Raman spectra. Development of dedicated organics spectral libraries is needed to aid interpretation. Given these observations, the important units in the outcrop would be sampled and cached for sample return
Design of 370-ps Delay Floating-Voltage Level Shifters With 30-V/ns Power Supply Slew Tolerance
A new design method for producing high-performance and power-rail slew-tolerant floating-voltage level shifters is presented, offering increased speed, reduced power consumption, and smaller layout area compared with previous designs. The method uses an energy-saving pulse-triggered input, a high-bandwidth current mirror, and a simple full latch composed of two inverters. A number of optimizations are explored in detail, resulting in a presented design with a dVdd slew immunity of 30 V/ns, and near-zero static power dissipation in a 180-nm technology. Experimental results show a delay of below 370 ps for a level-shift range of 8-20 V. Postlayout simulation puts the energy consumption at 2.6 pJ/bit at 4 V and 7.2 pJ/bit at 20 V, with near symmetric rise and fall delays
Sub-Arc Second 2 Centimeter Continuum and SiO Spectral Line Observations of R Aquarii
ub-arc second (- 0\u27.\u2715) VLA observations at 2 em have resolved the previously reported 6 em H II region, which engulfs the R Aquarii binary system, into two components. The stronger 2 em component is itself partially resolved (distorted in shape), which may be a consequence of the long-period variable (LPV) wind being subjected to the intense ionizing radiation field of the hot companion\u27s accretion disk, which we suspect is precessing. The distorted radio contours of the central H II region may also suggest that one hemisphere of the extended LPV envelope is directly illuminated by the intense radiation field of the accretion disk, owing to the orientation of the disk. The accretion disk can be formed by tidal mass exchange between the LPV and hot companion, which results in blobs of material periodically being expelled primarily in the northeast direction. Together with the VLA results, we report SiO observations obtained with the Hat Creek interferometer that suggest maser action occurs in the circumbinary nebulosity far removed from the LPV photosphere
Titanite petrochronology linked to phase equilibrium modelling constrains tectono-thermal events in the Akia Terrane, West Greenland
GeoHistory Facility instruments (part of the John de Laeter Centre) were funded via an Australian Geophysical Observing System (AGOS) grant provided to AuScope by the AQ44 Australian Education Investment Fund.The Mesoarchean Akia Terrane in West Greenland contains a detailed magmatic and metamorphic mineral growth record from 3.2 Ga to at least c. 2.5 Ga. This time span makes this region an important case study in the quest to track secular changes in geodynamic style which may ultimately inform on the development of plate tectonics as a globally linked system of lateral rigid plate motions. The common accessory mineral titanite has recently become recognised as a powerful high temperature geochronometer whose chemistry may chart the thermal conditions of its growth. Furthermore, titanite offers the potential to record the time-temperature history of mafic lithologies, which may lack zircon. Although titanite suffers from higher levels of common Pb than many other UPb chronometers, we show how measurement of 207Pb/206Pb in texturally coeval biotite may assist in the characterization of the appropriate common Pb composition in titanite. Titanite extracted from two samples of mafic gneisses from the Akia Terrane both yield UPb ages of c. 2.54 Ga. Although coeval, their chemistry implies growth under two distinctly different processes. In one case, the titanite has elevated total REE, high Th/U and grew from an in-situ partial melt, consistent with an identical date to granite dyke zircon. In contrast, the second titanite sample contains greater common Pb, lower total REE, lower Th/U, and grew from dominantly hydrothermal fluids. Zr-in-titanite thermometry for partial melt-derived titanite, with activities constrained by phase equilibrium modelling, indicates maxima of c. 690 °C. Elsewhere in the Akia Terrane, coeval metamorphism linked to growth of hydrothermal titanite is estimated at temperatures of c. 670 °C. These new results when coupled with existing findings indicate punctuated, repeated metamorphic events in the Akia Terrane, in which high temperature conditions (re)occurred at least three times between 3.0 and 2.5 Ga, but crucially changed in style across a c. 3.0 Ga change point. We interpret this change in metamorphism as reflecting a fundamental shift in geodynamic style in West Greenland at 3.0 Ga, consistent with other estimates for the onset of widespread plate tectonic-type processes.Publisher PDFPeer reviewe
Origins of order in cognitive activity
Most cognitive scientists have run across The War of the Ghosts, a Native American story used by The origin of order in cognition is the topic of this chapter. We begin with a discussion of how order is explained within a traditional approach of information processing. Taking the shortcomings of this account seriously, we then turn to other disciplines -those that have framed the question of order more successfully. The answers have relied on the concept of self-organization, the idea that order can emerge spontaneously from the nonlinear interaction of a system's components. In the remainder of the chapter, we discuss empirical evidence for self-organization in cognition. The accumulated evidence in reasoning, speaking, listening, reading, and remembering motivates a complex system approach to cognition. 20
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