46 research outputs found
The molecular emission-line spectrum of IRC +10216 between 330 and 358 GHz
We have conducted a spectral line survey of IRC + 10216 using the Caltech Submillimeter Observatory to an
average sensitivity of ≾95 mK. A deconvolution algorithm has been used to derive the continuous single-sideband
spectrum from 330.2 to 358.1 GHz. A total of 56 spectral lines were detected of which 54 have been identified
with 8 molecules and a total of 18 isotopomers. The observed lines are used to derive column densities and relative abundances for the detected species. Within this frequency range the spectral lines detected contribute the majority of the total flux emitted by IRC + 10216. We use the derived column densities and excitation temperatures to
simulate the molecular line emission (assuming LTE) at frequencies up to 1000 GHz. The observed and simulated
flux from line emission is compared to broadband total flux measurements and to dust emission assuming a power-law variation of the dust emissivity. We conclude that significant corrections for the line flux must be made
to broadband flux measurements of IRC + 10216 at wavelengths longer than ~750 µm
A Line Survey of Orion KL from 325 to 360 GHz
We present a high-sensitivity spectral line survey of the high-mass star-forming region Orion KL in the 325-360 GHz frequency band. The survey was conducted at the Caltech Submillimeter Observatory on Mauna Kea, Hawaii. The sensitivity achieved is typically 0.1-0.5 K and is limited mostly by the sideband separation method utilized. We find 717 resolvable features consisting of 1004 lines, among which 60 are unidentified. The identified lines are due to 34 species and various isotopomers. Most of the unidentified lines are weak, and many of them most likely due to isotopomers or vibrationally or torsionally excited states of known species with unknown line frequencies, but a few reach the 2-5 K level. No new species have been identified, but we were able to strengthen evidence for the identification of ethanol in Orion and found the first nitrogen sulfide line in this source. The molecule dominating the integrated line emission is SO_2, which emits twice the intensity of CO, followed by SO, which is only slightly stronger than CO. In contrast, the largest number of lines is emitted from heavy organic rotors like HCOOCH_3, CH_3CH_2CN, and CH_3OCH_3, but their contribution to the total flux is unimportant. CH_3OH is also very prominent, both in the number of lines and in integrated flux. An interesting detail of this survey is the first detection of vibrationally excited HCN in the v_2 = 2 state, 2000 K above ground. Clearly this is a glimpse into the very inner part of the Orion hot core
Molecular abundances and low-mass star formation. I: Si- and S-bearing species toward IRAS 16293-2422
Results from millimeter and submillimeter spectral line surveys of the protobinary source IRAS 16293-2422 are presented. Here we outline the abundances of silicon- and sulfur-containing species. A combination of rotation diagram and full statistical equilibrium/radiative transfer calculations is used to constrain the physical conditions toward IRAS 16293 and to construct its beam-averaged chemical composition over a 10-20" (1600-3200 AU) scale. The chemical complexity as judged by species such as SiO, OCS, and H_2S, is mtermedtate between that of dark molecular clouds such as Ll34N and hot molecular cloud cores such as Orion KL. From the richness of the spectra compared to other young stellar objects of similar luminosity, it is clear that molecular abundances do not scale simply with mass; rather, the chemistry is a strong function of evolutionary state, i.e., age
A molecular line study of NGC 1333/IRAS 4
Molecular line surveys and fully sampled spectral line maps at 1.3 and 0.87 mm are used to examine the
physical and chemical characteristics of the extreme Class I sources IRAS 4A and 4B in the L1450/NGC 1333
molecular cloud complex. A very well collimated, jetlike molecular outflow emanates from IRAS 4A, with a
dynamical age of a few thousand years. Symmetric, clumpy structure along the outflow lobes suggests that
there is considerable variability in the mass-loss rate or wind velocity even at this young age. Molecular emission
lines toward IRAS 4A and 4B are observed to be weak in the velocity range corresponding to quiescent
material surrounding the young stellar objects (YSOs). Depletion factors of 10-20 are observed for αll molecules,
including CO, even for very conservative mass estimates from the measured millimeter and submillimeter
dust continuum. However, abundances scaled with respect to CO are similar to other dark
molecular cloud cores. Such depletions could be mimicked by high dust optical depths or increased grain
emissivities at the observing frequencies of 230 and 345 GHz, but the millimeter and submillimeter spectral
energy distributions suggest that this is unlikely over the single-dish size scales of 5000-10,000 AU.
Dense, outflowing gas is found to be kinematically, but not spatially, distinct from the quiescent material on
these size scales. If CO is used as a chemical standard for the high-velocity gas, we find substantial enhancements
in the abundances of several molecules in outflowing material, most notably CS, SiO, and CH_30H. The
SiO emission is kinematically well displaced from the bulk cloud velocity and likely arises from directly
shocked material. As is the case for CO, however, the outflow features from more volatile species are centered
near the cloud velocity and are often characterized by quite low rotational temperatures. We suggest that
grain-grain collisions induced by velocity shear zones surrounding the outflow axes transiently desorb the
grain mantles, resulting in large abundance enhancements of selected species. Similar results have recently
been obtained in several other low-mass YSOs, where the outflowing gas is often both kinematically and spatially
distinct, and are illustrative of the ability of accretion and outflow processes to simultaneously modify
the composition of the gas and dust surrounding young stars
Molecular Abundances and Low-Mass Star Formation. II. Organic and Deuterated Species toward IRAS 16293-2422
Millimeter and submillimeter line surveys of the protobinary source IRAS 16293-2422 are presented in the 230 and 345 GHz windows. In total, 265 lines belonging to 44 molecules and their isotopomers (24 chemically different species) have been detected. Here the data for organic and deuterated molecules are considered; the results for Si- and S-bearing species have been discussed in an earlier paper (Blake et al. 1994). The observations have been analyzed through a combination of rotation diagrams and full statistical equilibrium/ radiative transfer calculations. At least three physically and chemically different components can be distinguished within the 20" (3000 AU) beam. The first component is the warm (T_(kin) ≳ 80 K) and dense [^n(H_2) ≍ (0.5-1) × 10^7 cm^(-3)] gas sampled by Si- and S-containing molecules such as SiO and SO_2. This gas is found to be rich in organic molecules such as CH_3OH, CH_3CN, and H_2CO, as well. It is only 3"-10" in size (500-1500 AU) and most likely represents the interaction of the bipolar outflow(s) with the circumbinary envelope. The second component is the circumbinary envelope itself, which has T_(kin) 40 K and n(H_2) 10^6-10^7 cm^(-3) and is 10"-15" in size (2000 AU). It contains common molecules like CS, HCO^+, and H_2CO. The third component is the colder, lower density outer part of the envelope, which gradually fades into the ambient surrounding cloud core [T_(kin) ≍ 10-20 K; n(H_2)≈(3 × 10^4)-(2 × 10^5) cm^(-3)]. Radicals such as CN, C_2H, and C_3H_2 appear to reside principally in this region. The ambient cloud material is also probed through self-absorbed features in the line profiles of molecules such as HCN, HCO^+, and H^2CO. Beam-averaged abundances over a 20" scale are presented and are compared with those observed in cold dark clouds such as L134N and TMC-1 and with high-mass star-forming cores such as Orion-KL. Remarkably high deuterium fractionation ratios are found, which are more characteristic of hot core regions than of cold, quiescent clouds. As a whole, the chemical and physical regimes that can be distinguished in the low-mass young stellar object IRAS 16293-2422 are qualitatively similar to those found in high-mass star-forming regions, confirming the earlier conclusion that the chemical composition depends more on the age of the object than its mass
Evaluation of different soy protein concentrate sources on growth performance of weanling pigs
Three experiments were conducted using 486 weanling pigs (216 in Experiment 1; 210 in Experiment 2; 60 in Experiment 3) to determine the effects of different soy protein concentrate (SPC) sources on growth performance. Soy protein concentrate source 1 is dried with a torus disk following the concentration of soy proteins. This drying procedure will generate some degree of heat and possibly mechanical forces somewhat similar to extrusion processing (Soycomil P®, ADM). Soy protein concentrate source 2 is dried by a different process, and then it is moist extruded (Profine E, Central Soya). Therefore, the objective of our study was to determine the relative feeding value of the different SPC sources compared with a complex diet containing milk and other specialty proteins (no soy protein), or a diet containing 40% soybean meal. In Experiment 1, each SPC source (28.6%) replaced all the soybean meal (SBM) in the
control diet on a lysine basis. Pigs fed the diet containing 40% SBM had similar performance to pigs fed the milk-protein based diet from d 0 to 14. Pigs fed either SPC source had lower ADG and ADFI compared to pigs fed either the diet containing 40% SBM or the milkprotein based diet. Pigs fed the diet containing 40% SBM and SPC from source 2 had better F/G than pigs fed the milk-protein based diet or SPC from source 1.
In Experiment 2, either all or half of the soybean meal was replaced by the 28.6 or 14.3% SPC from source 1 and 2. From d 0 to
14 and d 0 to 28, an SPC source by level interaction was observed for ADG (P<0.01) and
ADFI (P<0.07). Replacing soybean meal with SPC from source 1 did not influence pig performance. However, replacing soybean meal
with SPC from source 2 resulted in a quadratic (P<0.05) improvement in ADG with performance being improved for the diet containing 14.3% SPC, but no benefit to replacing all the soybean meal with SPC. Replacing soybean meal with SPC from either source influenced feed efficiency in a quadratic (P<0.01) manner with feed efficiency being optimal for pigs consuming the diet with half the soybean meal replaced by SPC. Because replacing all of the soybean meal with SPC reduced ADFI in Experiments 1 and 2, we hypothesized that pigs may not prefer the taste of a diet with a high inclusion rate of SPC (28.6%). To test this theory, a 7-day preference test was conducted to determine feed intake of weanling pigs provided the option of consuming diets containing either 40% soybean meal or 28.6% SPC (from source 2).
Average daily feed intake was 0.41 and 0.01
lb for the 40% soybean meal and 28.6% soy
protein concentrate diets, respectively (P<0.0001). The poor intake of the SPC diet may indicate a palatability problem when high
levels of SPC are included in the diet. Our results suggest replacing a portion of the soybean meal in the diet with SPC from source 2 improves ADG and feed efficiency; however, high levels (28.6%) of SPC should not be included in the diet
Evaluation of the effects of wheat gluten source and animal plasma blends on the growth performance of nursery pigs
A total of 472 weanling pigs (initially 13.5 lb) were used in two experiments to evaluate the effects of wheat gluten source (WG) and combinations with spray-dried animal plasma (SDAP) on growth performance of nursery pigs. In Exp. 1, the five dietary treatments included a control diet containing 6% SDAP, wheat gluten that was enzymatically hydrolyzed (Source 1), and a non-hydrolyzed wheat gluten (Source 2). The wheat gluten sources replaced L-lysine HCl and replaced 50% or 100% of the spray-dried animal plasma. From d 0 to 7, 7 to 14, and 0 to 21, increasing wheat gluten decreased (linear; P\u3c0.05) ADG. There were no differences between wheat gluten sources. Average daily feed intake decreased similar to ADG, with the exception that ADFI of pigs fed wheat gluten Source 2 had only a slight decreasing trend (P\u3c0.11) from d 0 to 7. Pigs fed the diet containing 6% SDAP had the greatest ADG and ADFI from d 0 to 21. When the SDAP was replaced with either wheat gluten source, ADG and ADFI linearly decreased (P\u3c0.01) but F/G improved (P\u3c0.04). When pigs were fed the common diet from d 21 to 35, there were no differences (P\u3c0.05) in ADG, ADFI or F/G. In Exp. 2, the six dietary treatments included a negative control with no SDAP or WG (0:0 ratio), 9% WG (100:0 ratio), 6.75% WG and 1.25% SDAP (75:25 ratio) combination, 4.5% WG and 2.5% SDAP (50:50 ratio) combination, 2.25% WG and 3.75% SDAP (25:75 ratio) combination, and a positive control with 5% SDAP (0:100 ratio). The wheat gluten (Source 1) was enzymatically hydrolyzed, but from a different lot than Exp. 1. From d 0 to 14, pigs fed 6% SDAP had numerically greater ADG and ADFI compared to pigs fed the negative control diet. However, replacing SDAP with increasing amounts of WG tended to decrease (P\u3c0.10) ADG and ADFI. These results confirm the improved ADG and ADFI of pigs fed SDAP immediately after weaning. In these experiments, replacing SDAP with WG resulted in decreased ADG.; Swine Day, Manhattan, KS, November 14, 200
Coal and Climate Change
This overview adopts a critical social science perspective to examine the state of play and potential futures for coal in the context of climate change. It introduces key trends in coal consumption, production and trade, before appraising the relevant literature. Finding surprisingly little literature directly focussed on coal and climate change compared with related fields, it appraises existing work and highlights key areas for future work. In addition to established bodies of work on the situated politics of coal and the political economy of coal, new work calling for demand side policies to be supplemented with supply side policies highlights the increasing importance of how normative contestations drive debates over coal, suggesting that future work needs to engage not only much more directly with climate change as an issue, but particularly with the place of coal in a just transition. Because of coal’s mammoth contribution to climate change and the complex political economy which drives its production and consumption, it is likely that coal will remain at the centre of difficult questions about the relationship between climate action and development for some time