We present observations of ammonia emission lines toward the interstellar filament WB~673 hosting the dense clumps WB~673, WB~668, S233-IR and G173.57+2.43. LTE analysis of the lines allows us to ...estimate gas kinetic temperature (\(\lesssim\) 30~K in all the clumps), number density (\(7-17\times10^3\)~cm\(^{-3}\)), and ammonia column density (\(\approx 1-1.5\times 10^{15}\)~cm\(^{-2}\)) in the dense clumps. We find signatures of collapse in WB 673 and presence of compact spatially unresolved dense clumps in S233-IR. We reconstruct 1D density and temperature distributions in the clumps and estimate their ages using astrochemical modelling. Considering CO, CS, NH\(_3\) and N\(_2\)H\(^+\) molecules (plus HCN and HNC for WB~673), we find a chemical age of \(t_{\rm chem}=1-3\times 10^5\)~yrs providing the best agreement between the simulated and observed column densities in all the clumps. Therefore, we consider \(t_{\rm chem}\) as the chemical age of the entire filament. A long preceding low-density stage of gas accumulation in the astrochemical model would break the agreement between the simulated and observed column densities. We suggest that rapid star formation over a \(\sim 10^5\)~yrs timescale take place in the filament.
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A controlled reaction of a mixture of structural isomers of diacylglycerol (DAG) with N,N-disuccinimidyl carbonate and then with b-alanine provided intermediates of 1,2-diacylglycerol ...(1,2-DAG) which were further modified with carboxy- and amino-terminated oligoethylene glycol spacer arms of different length. As an example of bioactive molecules intended for the incorporation in lipid bilayer of artificial or cell membranes, 1,2-DAGs bearing tetrasaccharide Sialyl Lewis X or triglycine at the terminus of polar spacer were synthesized. The synthetic scheme can be readily scaled-up by the use of DAGs from food industry.
We present results of a multi-line study of the filamentary infrared dark cloud G351.78-0.54 in the 1.3 and 0.8 mm wavelength bands. The lines of the three isotopologues of carbon monoxide CO, ...N\(_2\)H\(^+\), CH\(_3\)CCH and HNCO were observed. The aim was to study the general structure of the filamentary cloud, its fragmentation and physical parameters with the emphasis on properties of dense clumps in this cloud. Several dense clumps are identified from the N\(_2\)H\(^+\) (3-2) data, their masses and virial parameters are determined using the C\(^{18}\)O (2-1) line. Temperatures of some clumps are estimated from the CH\(_3\)CCH and HNCO data. Almost all clumps appear to be gravitationally unstable. The density estimates obtained from the C\(^{18}\)O (3-2)/(2-1) and N\(_2\)H\(^+\) (3-2)/(1-0) intensity ratios are in the range \(n \sim (0.3-3)\times 10^5\) cm\(^{-2}\). The HNCO emission is detected exclusively toward the first clump which contains the luminous IR source IRAS 17233-3606, and indicates an even higher density. It is observed in the outflow, too. The velocity shift of the higher excitation HNCO lines may indicate a movement of the hot core relative the surrounding medium. In some clumps there is a velocity shift \(\sim 1\) km s\(^{-1}\) between N\(_2\)H\(^+\) (3-2) and CO isotopologues. The large widths of the N\(_2\)H\(^+\) (3-2) line in the clumps indicate an increase of the velocity dispersion in their dense interiors, which may be related to the star formation process. The N\(_2\)H\(^+\) abundance drops toward the luminous IR source.