Reference Correlations for the Thermal Conductivity of 13 Inorganic Molten Salts.

The available experimental data for the thermal conductivity of 13 inorganic molten salts have been critically examined with the intention of establishing thermal conductivity reference correlations. All experimental data have been categorized into primary and secondary data according to the quality of measurement specified by a series of criteria. Standard reference correlations are proposed for the following molten salts (with estimated uncertainties at the 95 % confidence level given in parentheses): LiNO3 (7 %), NaNO3 (7 %), KNO3 (15 %), NaBr (15 %), KBr (15 %), RbBr (15 %), LiCl (17 %), NaCl (20 %), KCl (17 %), RbCl (17%), CsCl (10 %), NaI (17 %), and RbI (20 %).

Reference Values and Reference Correlations for the Thermal Conductivity and Viscosity of Fluids.

In this paper, reference values and reference correlations for the thermal conductivity and viscosity of pure fluids are reviewed. Reference values and correlations for the thermal conductivity and the viscosity of pure fluids provide thoroughly evaluated data or functional forms and serve to help calibrate instruments, validate or extend models, and underpin some commercial transactions or designs, among other purposes. The criteria employed for the selection of thermal conductivity and viscosity reference values are also discussed; such values, which have the lowest uncertainties currently achievable, are typically adopted and promulgated by international bodies. Similar criteria are employed in the selection of reference correlations, which cover a wide range of conditions, and are often characterized by low uncertainties in their ranges of definition.

Reference Correlation for the Thermal Conductivity of n-Hexadecane from the Triple Point to 700 K and up to 50 MPa.

This paper presents a new wide-ranging correlation for the thermal conductivity of n-hexadecane based on critically evaluated experimental data. The correlation is designed to be used with a recently published equation of state, and it is valid from the triple point up to 700 K and pressures up to 50 MPa. We estimate the uncertainty at a 95% confidence level to be 4% over the aforementioned range, with the exception of the dilute-gas range where the uncertainty is 2.7% over the temperature range 583 to 654 K. The correlation behaves in a physically reasonable manner when extrapolated to the full range of the equation of state, but the uncertainties are larger outside of the validated range, and also in the critical region.

Reference Correlation for the Viscosity of Ammonia from the Triple Point to 725 K and up to 50 MPa.

This paper presents a new wide-ranging correlation for the viscosity of ammonia based on critically evaluated experimental data. The correlation is designed to be used with a recently developed equation of state, and it is valid from the triple point to 725 K, at pressures up to 50 MPa. The estimated uncertainty varies depending on the temperature and pressure, from 0.6% to 5%. The correlation behaves in a physically reasonable manner when extrapolated to 100 MPa, however care should be taken when using the correlations outside of the validated range.

Reference Correlations for the Viscosity and Thermal Conductivity of n-Undecane.

This paper presents new wide-ranging correlations for the viscosity and thermal conductivity of n-undecane based on critically evaluated experimental data. The correlations are designed to be used with a recently published equation of state that is valid from the triple point to 700 K, at pressures up to 500 MPa, with densities below 776.86 kg m-3. The estimated uncertainty for the dilute-gas viscosity is 2.4%, and the estimated uncertainty for viscosity in the liquid phase for pressures up to 60 MPa over the temperature range 260 K to 520 K is 5%. The estimated uncertainty is 3% for the thermal conductivity of the low-density gas, and 3% for the liquid over the temperature range from 284 K to 677 K at pressures up to 400 MPa. Both correlations behave in a physically reasonable manner when extrapolated to the full range of the equation of state, however care should be taken when using the correlations outside of the validated range. The uncertainties will be larger outside of the validated range, and also in the critical region.

Reference Correlations for the Thermal Conductivity of Liquid Bismuth, Cobalt, Germanium and Silicon.

The available experimental data for the thermal conductivity of liquid bismuth, cobalt, germanium and silicon have been critically examined with the intention of establishing thermal conductivity reference correlations. All experimental data have been categorized into primary and secondary data according to the quality of measurement specified by a series of criteria. The proposed standard reference correlations for the thermal conductivity of liquid bismuth, cobalt, germanium, and silicon are respectively characterized by uncertainties of 10, 15, 16 and 9.5% at the 95% confidence level.

Correlations for the Viscosity and Thermal Conductivity of Ethyl Fluoride (R161).

This paper presents new wide-ranging correlations for the viscosity and thermal conductivity of ethyl fluoride (R161) based on critically evaluated experimental data. The correlations are designed to be used with a recently published equation of state that is valid from 130 K to 450 K, at pressures up to 100 MPa. The estimated uncertainty at a 95% confidence level is 2% for the viscosity of low-density gas (pressures below 0.5 MPa), and 3% for the viscosity of the liquid over the temperature range from 243 K to 363 K at pressures up to 30 MPa. The estimated uncertainty is 3% for the thermal conductivity of the low-density gas, and 3% for the liquid over the temperature range from 234 K to 374 K at pressures up to 20 MPa. Both correlations may be used over the full range of the equation of state, but the uncertainties will be larger, especially in the critical region.

Reference Correlation of the Thermal Conductivity of Cyclohexane from the Triple Point to 640 K and up to 175 MPa.

New, wide-range reference equations for the thermal conductivity of cyclohexane as a function of temperature and density are presented. The equations are based in part upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible. We estimate the uncertainty (at the 95% confidence level) for the thermal conductivity of cyclohexane from the triple point (279.86 K) to 650 K at pressures up to 175 MPa to be 4% for the compressed liquid and supercritical phases. For the low-pressure gas phase (up to 0.1 MPa) over the temperature range 280 K to 680 K, the estimated uncertainty is 2.5%. Uncertainties in the critical region are much larger, since the thermal conductivity approaches infinity at the critical point and is very sensitive to small changes in density.

Reference Correlations of the Thermal Conductivity of Ethene and Propene.

New, wide-range reference equations for the thermal conductivity of ethene and propene as a function of temperature and density are presented. The equations are based in part upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible. For ethene, we estimate the uncertainty (at the 95% confidence level) for the thermal conductivity from 110 K to 520 K at pressures up to 200 MPa to be 5% for the compressed liquid and supercritical phases. For the low-pressure gas phase (to 0.1 MPa) over the temperature range 270 K to 680 K, the estimated uncertainty is 4%. The correlation is valid from 110 K to 680 K and up to 200 MPa, but it behaves in a physically reasonable manner down to the triple point and may be used at pressures up to 300 MPa, although the uncertainty will be larger in regions where experimental data were unavailable. In the case of propene, data are much more limited. We estimate the uncertainty for the thermal conductivity of propene from 180 K to 625 K at pressures up to 50 MPa to be 5% for the gas, liquid, and supercritical phases. The correlation is valid from 180 K to 625 K and up to 50 MPa, but it behaves in a physically reasonable manner down to the triple point and may be used at pressures up to 100 MPa, although the uncertainty will be larger in regions where experimental data were unavailable. For both fluids, uncertainties in the critical region are much larger, since the thermal conductivity approaches infinity at the critical point and is very sensitive to small changes in density.

Reference Correlation of the Thermal Conductivity of Carbon Dioxide from the Triple Point to 1100 K and up to 200 MPa.

This paper contains new, representative reference equations for the thermal conductivity of carbon dioxide. The equations are based in part upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the dilute-gas thermal conductivity, we incorporated recent theoretical calculations to extend the temperature range of the experimental data. Moreover, in the critical region, the experimentally observed enhancement of the thermal conductivity is well represented by theoretically based equations containing just one adjustable parameter. The correlations are applicable for the temperature range from the triple point to 1100 K and pressures up to 200 MPa. The overall uncertainty (at the 95% confidence level) of the proposed correlation varies depending on the state point from a low of 1% at very low pressures below 0.1 MPa between 300 K and 700 K, to 5% at the higher pressures of the range of validity.

Interlocking box jejunostomy: a new technique for enteral feeding.

A new jejunostomy tube placement technique is described and compared to traditional methods. The interlocking box technique was compared to a simple purse-string with jejunopexy and an inverting serosal tunnel (Witzel technique) with jejunopexy. Procedures performed in fresh canine cadavers were fluid pressure tested following tube removal. Mean+/-standard deviation (SD) intraluminal pressure necessary to induce leakage at the jejunopexy site of the interlocking box group (87.63+/-40.56 cm H2O) was significantly greater (p less than 0.001) than the simple purse-string (43.17+/-31.69 cm H2O) and serosal tunnel (46.33+/-23.60 cm H2O) groups. Significant differences were not identified between the latter groups. The interlocking box technique resisted leakage following acute removal better than conventional techniques and should be tested clinically.

Assessment of current techniques for determining tracheal luminal stenosis in dogs.

OBJECTIVE: To assess the accuracy of current antemortem and postmortem techniques for determining tracheal luminal stenosis. ANIMALS: 15 dogs. PROCEDURE: Percentage of tracheal luminal stenosis (PTLS) was determined by 6 methods, using measurements obtained by radiography, tracheoscopy, and necropsy after selected tracheostomy techniques were performed. To calculate PTLS, dorsoventral tracheal diameter was measured from preoperative and postoperative lateral cervical radiographic views. Preoperative or normal tracheal segments adjacent to the stenotic area were used to obtain normal tracheal diameter measurements. Planimetrically determined cross-sectional area (CSA), obtained from pre- and postoperative tracheoscopic photographs, was used to calculate PTLS. The CSA of tracheal specimens obtained at necropsy was determined, using the formula for an ellipse. Percentage of luminal stenosis was calculated, using CSA of the stenotic site and of segments craniad and caudad to the site obtained at necropsy or at surgery. All methods were compared with the control method of planimetrically determined CSA of sections obtained at necropsy of the tracheostomy and segments craniad and caudad to the site. RESULTS: Correlation was poor for radiographic and tracheoscopic techniques (r = 0.146 to 0.458, P > 0.05) The formula for an ellipse accurately predicted PTLS when measurements obtained at surgery (r = 0.516, P = 0.049) or segments craniad and caudad (r = 0.853, P < 0.001) to the site were used. CONCLUSION: Antemortem methods of assessing PTLS did not correlate with control planimetric methods. Methods using CSA determined by tracheal diameter were weakly correlated to control planimetric techniques. CLINICAL RELEVANCE: Accurate measurement of the degree of tracheal stenosis cannot be made in clinical patients using current techniques.

Branched-chain fatty acids produced by mutants of Streptomyces fradiae, putative precursors of the lactone ring of tylosin.

Three branched-chain fatty acids (7-hydroxy-4,6-dimethylnona-2,4-dienoic acid [compound 1], its 7-epimer [compound 2], and 7-keto-4,6-dimethylnona-2,4-dienoic acid [compound 3]) and a ketone (9-hydroxy-6,8-dimethylundeca-4,6-dien-3-one [compound 4]) were isolated from the culture broth of mutants of Streptomyces fradiae which were blocked in the biosynthesis of the macrolide antibiotic tylosin. Two phenotypic classes of mutants of this organism which were blocked in the addition of mycaminose to tylactone (compound 6) accumulated these compounds. These compounds were not produced by mutants which were blocked in lactone synthesis, in steps beyond mycaminose addition, or by the wild-type strain. Synthesis of these compounds, like synthesis of tylosin, was inhibited by the addition of cerulenin. Compounds 1, 2, and 3 were partially interconvertible by these mutants; but they were not produced from the degradation of tylactone and they were not directly incorporated into tylosin by intact cells. The structures of compounds 1 and 2 were equivalent to that of a predicted intermediate (S. Yue, J. S. Duncan, Y. Yamamoto, and C. R. Hutchinson, J. Am. Chem. Soc. 109:1253-1255, 1987) in the biosynthesis of tylactone. The ketone (compound 4) reported previously (N. D. Jones, M. O. Chaney, H. A. Kirst, G. M. Wild, R. H. Baltz, R. L. Hamill, and J. W. Paschal, J. Antibiot. 35:420-425, 1982) appears to be the decarboxylation product of the intermediate following that represented by compound 1. This represents the first report of the isolation of putative precursors of tylactone from tylosin-producing organisms.

Cloning of spiramycin biosynthetic genes and their use in constructing Streptomyces ambofaciens mutants defective in spiramycin biosynthesis.

Several cosmid clones from Streptomyces ambofaciens containing the spiramycin resistance gene srmB were introduced into S. fradiae PM73, a mutant defective in tylosin synthesis, resulting in tylosin synthesis. The DNA responsible for this complementation was localized to a 10.5-kilobase EcoRI fragment. A 32-kilobase DNA segment which included the srmB spiramycin resistance gene and DNA which complemented the defect in strain PM73 were mutagenized in vivo with Tn10 carrying the gene for Nmr (which is expressed in Streptomyces spp.) or in vitro by insertional mutagenesis with a drug resistance gene (Nmr) cassette. When these mutagenized DNA segments were crossed into the S. ambofaciens chromosome, three mutant classes blocked in spiramycin synthesis were obtained. One mutant accumulated two precursors of spiramycin, platenolide I and platenolide II. Two mutants, when cofermented with the platenolide-accumulating mutant, produced spiramycin. Tylactone supplementation of these two mutants resulted in the synthesis of a group of compounds exhibiting antibiotic activity. Two other mutants failed to coferment with any of the other mutants or to respond to tylactone supplementation.

Production of a hybrid macrolide antibiotic in Streptomyces ambofaciens and Streptomyces lividans by introduction of a cloned carbomycin biosynthetic gene from Streptomyces thermotolerans.

The structurally related macrolide antibiotics carbomycin (Cb) and spiramycin (Sp) are produced by Streptomyces thermotolerans and Streptomyces ambofaciens, respectively. Both antibiotics contain 16-membered lactone rings to which deoxysugars are attached. There are three sugars in Sp (forosamine, mycaminose and mycarose) and two sugars in Cb (mycaminose and a derivative of mycarose containing an isovaleryl group at position 4). We have identified the gene from S. thermotolerans (designated carE), which appears to encode an enzyme that acylates this mycarose sugar, and have shown that recombinant strains containing carE can use Sp as a substrate and convert it to the hybrid antibiotic, isovaleryl Sp (ivSp). Expression of carE was demonstrated in two heterologous hosts: in S. ambofaciens, where endogenously synthesized Sp was converted to ivSp, and in Streptomyces lividans where exogenously added Sp was converted to ivSp. The carE gene was isolated on a cosmid that also encodes genes required for Cb-lactone formation. These genes reside on a DNA segment of about 70 kb and are part of a Cb biosynthetic gene cluster that is flanked by two Cb-resistance genes, carA and carB. Mapping studies and nucleotide sequence analysis revealed that carE is located at one end of this gene cluster, immediately adjacent to the carB gene. Genes carB and carE are transcribed convergently and may share a common transcriptional terminator sequence.