To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
We are mapping 29 rotational transitions of 21 chemical and isotopic molecular species in the central Orion molecular ridge with Nyquist sampling using the new 15-element focal plane array receiver QUARRY on the FCRAO 14 m telescope. Our goal is to obtain complete, unbiased data sets for a study of the interrelated physics and chemistry in GMC cores.
The Cepheus bubble is a giant shell with a diameter of about 120pc, discovered by Kun (1987) from IRAS sky flux maps. We have imaged this 10° × 10° region in the CO J=l-0 line, using the FCRAO Quarry system with sample spacing equal to the 45” FWHM beam width. We estimate the total molecular gas mass to be ~ 105 solar masses and a total kinetic energy ~ 1051 ergs. We find 49 O and B0-B2 type stars in the Cepheus bubble region, most belong to the CepOB2 association. 120 IRAS point sources, selected according to color criteria representative of young stellar objects, fall within our map. Many of these sources are associated with the globules and filamentary structures seen in the CO emission, similar to the situation found in IC1396 (Patel et al. 1995). These stars, which are still associated with dense molecular gas plausibly represent the third and youngest generation of stars in this region.
A survey for the molecules C2H and HC3N in a variety of interstellar clouds has been completed. Both molecules are very widespread, in cold dark clouds as well as in hot clouds. C2H emission has been mapped in L1534. In cold clouds the fractional abundance X(C2H) is found to be 2-6×10−9. The ratio of abundances X(C2H)/X(HC3N) falls in the range 6-10, consistent with some gas-phase reaction schemes for these molecules.
Observations of the J=1-0 lines of 12CO have been made to determine the extent and nature of the broad secondary velocity feature in L1551 (S239) first detected by Knapp et al. (1976). L1551 is associated with an extended Herbig-Haro object, HH102 (Strom et al. 1974), and two compact HH objects, HH28 and HH29 (Herbig 1974). Two nearby stars, HL Tau and XZ Tau, show extreme T-Tauri characteristics. The broad CO velocity component is seen toward HH102. Strom et al. (1976) have detected an infrared source near the HH objects which has a luminosity and infrared colors consistent with a late B star reddened by roughly 20 magnitudes of visual extinction (Snell 1979). The infrared source lies in the direction of the core of L1551, which has a density of 105 cm-3 (Loren et al. 1979; Snell 1979). The infrared source is likely to be embedded in this dense core.
The objective of this study was to estimate heritability and crossbreeding parameters (breed and heterosis effects) of various fatty acid (FA) concentrations in milk fat of New Zealand dairy cattle. For this purpose, calibration equations to predict concentration of each of the most common FAs were derived with partial least squares (PLS) using mid-infrared (MIR) spectral data from milk samples (n=850) collected in the 2003–04 season from 348 second-parity crossbred cows during peak, mid and late lactation. The milk samples produced both, MIR spectral data and concentration of the most common FAs determined using gas chromatography (GC). The concordance correlation coefficients (CCC) between the concentration of a FA determined by GC and the PLS equation ranged from 0·63 to 0·94, suggesting that some prediction equations can be considered to have substantial predictive ability. The PLS calibration equations were then used to predict the concentration of each of the fatty acids in 26 769 milk samples from 7385 cows that were herd-tested during the 2007–08 season. Data were analysed using a single-trait repeatability animal model. Shorter chain FA (16 : 0 and below) were significantly higher (P<0·05) in Jersey cows, while longer chain, including unsaturated longer chain FA were higher in Holstein-Friesian cows. The estimates of heritabilities ranged from 0·17 to 0·41 suggesting that selective breeding could be used to ensure milk fat composition stays aligned to consumer, market and manufacturing needs.
Emergency medicine (EM) is defined, in part, by clinical excellence across an immense breadth of content and the provision of exemplary bedside teaching to a wide variety of learners. The specialty is also well-suited to a number of emerging areas of education scholarship, particularly in relation to team-based learning, clinical reasoning, acute care response, and simulation-based teaching. The success
of EM education scholarship will be predicated on systematic, collective attention to providing the infrastructure for this to occur. Specifically, as a new generation of emergency physicians prepares for education careers, academic organizations need to develop means not only to identify potential scholars but also to mentor, support, and encourage theircareers. This paper summarizes the supporting literature and presents related recommendations from a 2013 consensus conference on EM education scholarship led by the Academic Section of the Canadian Association of Emergency Physicians.
As emergency medicine (EM) education evolves, a more advanced understanding of education scholarship is required. This article is the first in a series of three articles that reports the recommendations of the 2013 education scholarship consensus conference of the Academic Section of the Canadian Association of Emergency Physicians. Adopting the Canadian Association for Medical Education's definition, education scholarship (including both research and innovation) is defined. A rationale for why education scholarship should be a priority for EM is discussed.
A wide variety of materials are currently used as supplementary cementitious materials (SCMs) for concrete, including natural materials and byproducts from various industries. Historically, natural SCMs, mostly derived from volcanic deposits, were common in concrete. In recent years, the dominant SCMs have been industrial by-products such as fly ash, ground granulated blast furnace slag (GGBFS), and silica fume. There is currently a resurgence of research into historic and natural SCMs, as well as other alternative SCMs for many reasons. The primary benefits of SCM use in improvement of long-term mechanical performance, durability, and sustainability are widely accepted, so local demand for these materials can exceed supply. This paper describes some of the SCMs that are attracting attention in the global research community and the properties and characteristics of these materials that affect their performance. Special attention is paid to the importance and demands of material characterization. Many SCMs do not necessarily lend themselves to characterization methods used in standardized test methods, which sometimes fail to describe the properties that are most important in predicting reactivity.
Graptolites are common fossils in Early Palaeozoic strata, but little is known of their soft-part anatomy. However, we report a long-overlooked specimen of Dicranograptus aff. ramosus from Late Ordovician strata of southern Scotland that preserves a strongly polymorphic, recalcitrant, organic-walled network hitherto unseen in graptoloid graptolites. This network displays three morphologies: proximally, a strap-like pattern, likely of flattened tubes; these transform distally into isolated, hourglass-shaped structures; then, yet more distally, revert to a (simpler) strap-like pattern. The network most likely represents a stolon-like system, hitherto unknown in graptoloids, that connected individual zooids. Its alternative interpretation, as colonial xenobionts that infested a graptoloid colony and mimicked its architecture, is considered less likely on taphonomic and palaeobiological grounds. Such polymorphism is not known in non-graptolite pterobranchs, which are less diverse and morphologically more conservative: a division of labour between graptoloid zooids for such functions as feeding, breeding and rhabdosome construction may have been the key to their remarkable evolutionary success.
We report a study of the relation between dust and gas over a 100 deg2 area in
the Taurus molecular cloud. We compare the H2 column density derived from dust
extinction with the CO column density derived from the 12CO and 13CO
J = 1 → 0 lines. We derive the visual extinction from reddening
determined from 2MASS data. The comparison is done at an angular size of 200′′,
corresponding to 0.14 pc at a distance of 140 pc. We find that the relation between visual
extinction AV and N(CO) is linear between
AV ≃ 3 and 10 mag in the region associated with the
B213–L1495 filament. In other regions the linear relation flattens for
AV ≳ 4 mag. Accounting for the observed relation between the
column density of CO and CO2 ices and AV, we find a
linear relationship between the column of carbon monoxide and dust for observed visual
extinctions up to the maximum value in our data ≃23 mag.
Objective: Pseudoaneurysms of the facial artery are an extremely rare development after blunt trauma. This paper aims to demonstrate the challenges faced during the diagnosis and subsequent management of this unusual cause of neck swelling.
Method: We report the presentation, examination, investigation, management and potential complications of a case of facial artery pseudoaneurysm secondary to blunt arterial trauma, sustained from the string of a flying kite. We also review some of the relevant literature on this subject.
Conclusions: Although a traumatic pseudoaneurysm is a rare occurrence in the facial region, the inclusion of this lesion in the differential diagnosis of soft tissue lesions caused by blunt trauma is important if the serious consequences of haemorrhage or thromboembolic disease are to be avoided. Prompt access to radiological imaging, and multi-disciplinary team input, are essential for effective diagnosis and management.
Three-millimeter-wavelength spectra of a number of nearby galaxies have been obtained at the Five College Radio Astronomy Observatory (FCRAO) using a new, very broadband receiver. This instrument, which we call the Redshift Search Receiver, has an instantaneous bandwidth of 36 GHz and operates from 74 to 110.5 GHz. The receiver has been built at UMass/FCRAO to be part of the initial instrumentation for the Large Millimeter Telescope (LMT) and is intended primarily for determination of the redshift of distant, dust-obscured galaxies. It is being tested on the FCRAO 14 m by measuring the 3 mm spectra of a number of nearby galaxies. There are interesting differences in the chemistry of these galaxies.
Bright-rimmed clouds (BRCs) are logical laboratories in which to study triggered star formation, however it is difficult in any single cloud to definitively show that star formation was triggered. In this study we compare the hydrodynamic models produced by Vanhala & Cameron (1998) that treat the problems of star-formation triggered by wind-driven implosion to millimeter and submillimeter molecular line observations of BRCs with embedded IRAS sources. These latter sources are derived from a catalog by Sugitani, Fukui, & Ogura (1991) In order to make an accurate comparison we implement a radiative transfer model based on the Sobolev or LVG approximation, and generate molecular line maps which can be directly compared to our observations. We observed several millimeter and submillimeter transitions of CO, C 18O, HCO+, and H13CO+ using the FCRAO, SMT, CSO, and SMA observatories (De Vries, Narayanan, & Snell 2002). We compare these observations with 3 hydrodynamic models of wind-driven shock fronts interacting with pre-existing, but unbound cloud cores. In two cases these model cores are triggered to collapse under the influence of the external wind.
The distribution of the arboreal ant community plus a termite species of the genus Nasutitermes was inventoried on 938 red mangrove, Rhizophora mangle L., trees in a completely flooded mangrove forest of the Sian Ka'an Biosphere Reserve, Quintana Roo, Mexico. Colonies sheltered in dry hollow branches of the trees and the pseudobulbs of the epiphytic orchid, Myrmecophila christinae. Two size classes of dry hollow tree branches were categorized in order to test differences in ant distribution. As some trees remained unoccupied by either an ant or a termite colony, we deduced that the competition for nesting sites was low. Differences in the composition of the ant community corresponded to the nature of the shelters (i.e. diameter of the hollow branches or orchid pseudobulbs). The ant fauna was richer in the large dry hollow branches of R. mangle than in the smaller ones, with certain ant species belonging to the subfamilies Ponerinae and Formicinae being significantly more frequent in the large dry hollow branches than in the small ones. Cephalotes and Pseudomyrmex were the most frequent ant genera inhabiting the dry branches of R. mangle, while Dolichoderus bispinosus was the most frequent ant species inhabiting the orchid pseudobulbs. Arboreal Nasutitermes sp. selected mostly the orchid pseudobulbs and thus indirectly interfered with ant nest-site selection. Our results highlight niche differentiation through the selection of nest sites among different types of shelter.
This paper reports the results of computations to obtain the spatial
distributions of the charged particles in a bounded active plasma dominated by
negative ions. Using the fluid model with a constant collision frequency for
electrons, positive ions and negative ions the cases of both detachment-dominated gases (such as oxygen) and recombination-dominated gases (such as
chlorine) are examined. It is concluded that it is valid to use a Boltzmann relation
ne = ne0exp(eV/kT)
for the electrons of density ne, where the
temperature T is approximately the electron temperature Te, and that the
density nn of the negative ions at low pressures obeys
nn = nn0exp(eV/kTn),
where Tn is the negative-ion temperature. However, at high pressure in
detachment-dominated gases where the ratio of negative-ion density to electron
density is constant and greater than unity, and when the attachment rate is
larger than the ionization rate, the negative ions are distributed with the same
effective temperature as the electrons. In all other cases there is no simple
relationship. Thus to put nn/ne = const,
nn = ne0exp(eV/kTe) and
nn = nn0exp(eV/kTn)
simultaneously is mathematically inconsistent and physically
unsound. Accordingly, expressions deduced for ambipolar diffusion coefficients
based on these assumptions have no validity. The correct expressions for the
situation where nn/ne = const
are obtained without invoking a Boltzmann relation for the negative ions.
Macromolecular X-ray crystallography underpins the vigorous field of structural molecular biology having yielded many protein, nucleic acid and virus structures in fine detail. The understanding of the recognition by these macromolecules, as receptors, of their cognate ligands involves the detailed study of the structural chemistry of their molecular interactions. Also these structural details underpin the rational design of novel inhibitors in modern drug discovery in the pharmaceutical industry. Moreover, from such structures the functional details can be inferred, such as the biological chemistry of enzyme reactivity. There is then a vast number and range of types of biological macromolecules that potentially could be studied. The completion of the protein primary sequencing of the yeast genome, and the human genome sequencing project comprising some 105 proteins that is underway, raises expectations for equivalent three dimensional structural databases.