Micro-Determination of Nitrogen

Fleck, A.; Davidson, J.

doi:10.1080/10408347408542672

Cited by 22 publications

(28 citation statements)

References 80 publications

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“…Digest samples (made up to 250 rn1 with deionised water) contained 1·85 mmol/l mercuric oxide (HgO), 0·22 mol/l sulphuric acid (H2S04) (Aristar), and 106 mmol/l potassium sulphate (K2S04). To make up an analogue of a digested sample, 2·4 g K2S04, 2·0 rn1 5 % (w/v) HgO in 2M H2S04, and 3 rn1 concentrated H2S04 were made up to 250 ml with deionised water (Fleck, 1974).…”

Section: Standardsmentioning

confidence: 99%

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Optimal Conditions for the Estimation of Ammonium by the Berthelot Reaction

1978

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SUMMARY A technique for optimising reagent concentrations on the AutoAnalyzer has been applied to the estimation of ammonia by the Berthelot reaction in the determination of urea and organic nitrogen. Comparison of the use of phenol and salicylate revealed that the optimum concentration of the latter is about four times that of the former. The optimum concentration of hypochlorite is five times greater with salicylate than with phenol, and for the catalyst, sodium nitroprusside, the factor is two. The precision obtained with the different methods is similar.

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Section: Standardsmentioning

confidence: 99%

“…Lorentz (1967) also used this method for urea estimation but employed salicylate in place of phenol. A survey of descriptions and applications of the Berthelot reaction revealed a wide variety of reagents (Fleck, 1974). Because of this, an investigation of the optimal concentrations seemed justified.…”

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confidence: 99%

Optimal Conditions for the Estimation of Ammonium by the Berthelot Reaction

1978

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“…Observationally, Padoan et al (2003) show that the structure of the Taurus and Perseus MCs is hierarchical at scales of 0.3–3 pc. Given the universality of turbulence (Heyer & Brunt 2004), it is perhaps unsurprising that the observed CMFs exhibit similarities between different star‐forming regions, and there exists in the literature a number of models for describing how these clumps can form (Fleck 1982; Elmegreen 1993; Padoan 1995; Padoan, Nordlund & Jones 1997; Myers 2000; Klessen 2001; Padoan & Nordlund 2002). The similarities between the CMF and the IMF then naturally lead to the suggestion that the two are related (Motte et al 1998; Lada et al 2008; Myers 2008).…”

Section: Discussion Of Global Propertiesmentioning

confidence: 99%

The structure of molecular clouds and the universality of the clump mass function

Smith

Clark

Bonnell

2008

Monthly Notices of the Royal Astronomical Society

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Using a smoothed particle hydrodynamics (SPH) simulation of a star‐forming region in a molecular cloud, we show that the emergence of a clump mass function (CMF) resembling the stellar initial mass function (IMF) is a ubiquitous feature of molecular cloud structure, but caution against its overinterpretation. We employ three different techniques to extract the clumps in this study. In the first two, we interpolate the SPH particle data to two‐ and three‐dimensional grids before performing the clump‐find, using position–position (PP) and position–position–velocity (PPV) information, respectively. In the last technique, the clump‐finding is performed on the SPH data directly, making use of the full three‐dimensional position information. Although the CMF is typically similar to that observed in regions of nearby star formation, the individual clumps and their masses are found to be unreliable since they depend strongly on the parameters and the method of the clump‐finding. In particular, we find that the resolution and orientation of the data make a significant difference to the resulting properties of the identified clumps in the PP and PPV cases. We conclude that making comparisons between a CMF and the stellar IMF should be done with caution, since the definition of a clump boundary, and hence the number of clumps and their properties, is arbitrary in the extraction method. This is especially true if molecular clouds are truly scale free.

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“…Observations suggest that there is a characteristic mass M ch for stars in the solar vicinity. Kroupa, 2001Larson, 2003Mac Low and Klessen, 2004Fleck, 1982Padoan, 1995Padoan et al, 1997Klessen et al, 1998Klessen et al, 2000Klessen, 2001aPadoan and Nordlund, 2002Schmeja and Klessen, 2004Jappsen and Klessen, 2004Bodenheimer, 1995Papaloizou and Lin, 1995Lin and Papaloizou, 1996 There are many ways to approach the formation of stars and star clusters from a theoretical point of view. The IMF has a nearly power-law form for larger masses and declines rapidly towards smaller masses (Scale 1998;.…”

Section: Introductionmentioning

confidence: 99%

“…The IMF has a nearly power-law form for larger masses and declines rapidly towards smaller masses (Scale 1998;. The interplay between turbulent motion and self-gravity of the cloud leads to a process we call gravoturbulent fragmentation: Supersonic turbulence generates strong density fluctuations with gravity taking over in the densest and most massive regions (e.g., Fleck 1982;Padoan 1995;Padoan et al 1997;Klessen et al 1998Klessen et al , 2000Klessen 2001;Padoan & Nordlund 2002). Initial conditions in star forming regions can vary considerably.…”

Section: Introductionmentioning

confidence: 99%