Journal of research of the National Bureau of Standards最新文献

{"title":"Ortho-Para Catalysis In Liquid-Hydrogen Production","authors":"D. Weitzel, W. V. Loebenstein, J. Draper, O., Park","doi":"10.6028/jres.060.026","DOIUrl":"https://doi.org/10.6028/jres.060.026","url":null,"abstract":"A series of selected or specially prepared catalysts were s tud ied fo r t heir abili ty to accelerate the ortho to para conversion of hydrogen . The results of t his st udy a re presented and the performance of various catalyst s are compared with t hat of chrom ic oxide on alu: mina pellets. An outstanding cata.lyst, u~supported hydrous J erric oxide g ra nules, was selected for further study and used 111 the liquefi ers of t he NatIOnal Burea u of Standards Cr yogenic Engineering Laboratory. One and one-half liters of t his catalyst has now bee n used to convert more t han 100,000 li ters of liquid hydrogen to 90 to 95 percent para at an average rate of about 235 liters of liquid per hour. There is to date no ev id ence of decrea se in effici ency with continued use.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71360833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetic Studies Using a Highly Sensitive Microphone Detector","authors":"W. Braun, P. Dagaut, B. Cadoff","doi":"10.6028/jres.093.157","DOIUrl":"https://doi.org/10.6028/jres.093.157","url":null,"abstract":"A very sensitive microphone detector is used to study fast kinetic rate processes in the gas phase resulting in the generation of heat. The rate of heat evolution in turn produces a short duration pressure pulse which drives the microphone. The frequency response of the microphone is somewhat slower than required to record these pulses as they actually appear at the detector. The theory of the method used for the data reduction is presented. It is based upon the Green’s Function method which expresses the time dependent microphone signal, X, (t), as the convolution of the pressure pulse function, f(t), by the microphone’s impulse response function, G(t). A Fourier analysis of X(t) and the two relevant functions, f(t) and G(t), at a single frequency, allows direct determination of the rate constant for the kinetic process under study. The method is demonstrated by applying it to the study of vibrational energy relaxation of pentafluorobenzene in argon buffer gas and gives results in agreement with other experimental methods.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"643 - 654"},"PeriodicalIF":0.0,"publicationDate":"1988-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363038","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Solvent-Free Injection in Supercritical Fluid Chromatography Using Sintered Glass Deposition","authors":"T. Bruno","doi":"10.6028/jres.093.158","DOIUrl":"https://doi.org/10.6028/jres.093.158","url":null,"abstract":"Sample injection in supercritical fluid chromatography (SFC) is usually performed using a combination of apparatus from liquid chromatography and capillary gas chromatography. The device most often consists of an injection valve (of the type used in liquid chromatography) followed by a flow splitter controlled by a restrictor. It is sometimes desirable to inject samples in the absence of a solvent, as in physicochemical applications of SFC. In this article, two simple modifications to a conventional sampling valve system are presented which allow solvent-free injection. Using these devices, sample (in a solvent) is deposited on a sintered glass bed. After removal of the solvent by mild heating and evacuation, the sample loop is filled with the supercritical carrier and the valve is switched to the inject position.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"655 - 658"},"PeriodicalIF":0.0,"publicationDate":"1988-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Conferences/Events: U.S.-JAPAN PANEL ON WIND AND SEISMIC EFFECTS National Bureau of Standards, Gaithersburg, MD, May 17–20, 1988","authors":"N. Raufaste","doi":"10.6028/jres.093.162","DOIUrl":"https://doi.org/10.6028/jres.093.162","url":null,"abstract":"","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"671 - 671"},"PeriodicalIF":0.0,"publicationDate":"1988-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Liposome-Based Flow Injection Immunoassay System","authors":"L. Locascio-Brown, A. Plant, R. Durst","doi":"10.6028/jres.093.160","DOIUrl":"https://doi.org/10.6028/jres.093.160","url":null,"abstract":"The development of many biochemical assays is dependent upon the specific interaction of an antigen with its antibody. This interaction is usually monitored using secondary labels with the most popular immunoassays employing fluorescent or radioactive tracers for detection of a single binding event. We are developing a novel flow injection analysis (FIA) system which contains an immunospecific reactor column and utilizes liposomes for detection. The fluorophore-loaded liposomes used in this assay can be made to provide signal enhancement in the range of one thousand to one million times per binding event making fluorescent assays competitive in sensitivity with radioimmunoassays. Liposomes are spherical structures composed of phospholipid bilayers that form spontaneously when phospholipid molecules are dispersed in water. The interior and exterior environments of liposomes are aqueous and, therefore, liposomes can be prepared with large numbers of water-soluble marker molecules trapped in their internal aqueous space. Liposomes are prepared by the injection method [1] from a mixture of dimyristoylphosphatidylcholine: cholesterol: dicetyl phosphate with a molar ratio of 5:4:1. Approximately 1 X 103 carboxyfluorescein molecules are encapsulated inside each liposome when the liposomes are formed in 3 mmol/L carboxyfluorescein solution. The liposomes may be \"sensitized\" to a particular antigen through covalent binding of that antigen to the polar head group of a phospholipid molecule which is incorporated into the lipid mixture at about 1 mol % prior to liposome formation. When the liposome is formed in water, approximately half of the antigen will be exposed to the external solution, and, therefore, will be available to interact with antibody binding sites. The combining of antigen on these \"sensitized\" liposomes with antibody can","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"663 - 665"},"PeriodicalIF":0.0,"publicationDate":"1988-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Conferences/Events: WORKSHOP ON MICROSTRUCTURE AND MACROMOLECULAR RESEARCH WITH COLD NEUTRONS National Bureau of Standards, Gaithersburg, MD, April 21–22, 1988","authors":"C. Glinka, J. Gotaas, C. O’Connor","doi":"10.6028/jres.093.161","DOIUrl":"https://doi.org/10.6028/jres.093.161","url":null,"abstract":"On April 21-22, 1988, over 160 scientists, including 25 from industry, 70 from universities and 30 from government laboratories and agencies (not including NBS), gathered at NBS, Gaithersburg, for a Workshop on Microstructure and Macromolecular Research with Cold Neutrons. This workshop was one of a series, each devoted to a major area of research with cold neutrons, that are being held in conjunction with the development of the Cold Neutron Research Facility (CNRF) at the NBS 20 MW research reactor as a national, useroriented research facility. The dual aims of this workshop were to highlight research opportunities in the application of cold neutron techniques to the study of submicron structure in materials and macromolecular systems, and to inform and involve the scientific community in the planning for instrumentation for the CNRF. The long wavelength neutrons that are produced by a cold moderator, such as the 40 K D2 0-ice moderator recently installed in the NBS reactor, are a powerful probe of both the structure and dynamics of materials. The emphasis of this workshop was on the structural applications of cold neutrons. Thus techniques such as small angle neutron scattering (SANS), which probes structure in bulk materials on the 1 to 100 nm scale, and the relatively new technique of neutron reflectometry, which probes near surface structure to depths of tenths of microns, were discussed in detail. For both of these techniques, cold neutrons substantially extend the distance scale probed and improve the spatial resolution beyond what has been possible with thermal neutrons. The first morning session of the workshop on Scientific Opportunities with Cold Neutrons opened with a review by T. Russell (IBM Almaden Research Center) of the impact SANS has had on Polymer Science in general, and on the understanding of the interactions and correlations in polymer mixtures in particular. Russell also discussed recent developments, important to the development of polymer composites, in the use of grazing incidence neutron and x-ray scattering for the evaluation of conformation changes and concentration gradients in polymer mixtures near surfaces and at interfaces. The use of scattering methods to characterize such seemingly dissimilar materials as porous rock and agglomerated colloids was the subject of the talk by S. K. Sinha (Exxon Research and Engineering Co.). Sinha presented a general formalism which unified the concepts of surface and mass fractals and showed how the selfsimilar nature of fractal structures is most directly revealed through scattering measurements. Several examples were presented which underscored the need for scattering instruments which probe a wide range of length scales in order to accurately determine the nature and limits of fractal behavior. The second half of this session was devoted to applications of neutron reflectometry, reviewed by","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"667 - 669"},"PeriodicalIF":0.0,"publicationDate":"1988-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enzyme-Enhanced Electrochemical Immunoassay for Phenytoin","authors":"M. Umaña, J. Waller, M. Wani, C. Whisnant, E. Cook","doi":"10.6028/jres.093.159","DOIUrl":"https://doi.org/10.6028/jres.093.159","url":null,"abstract":"Research Triangle Institute Post Office Box 12194 Research Triangle Park, NC 27709-2194 drug to be effective and safe, plasma levels must be between 5 and 20 mg/L [11]. Thus, the development of easy, real-time assays for this and other critical-level drugs is highly desirable. This paper also describes preliminary results on the electron-transfer mediation of ferrocene derivatives to polypyrrole-immobilized GOx. The goal of these experiments is to couple the polypyrrole-immobilized GOx to the ferrocene-DPH system to produce a reagentless electrochemical immunoassay sensor, so that easy, real-time determinations may be realized. Introduction","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"29 1","pages":"659 - 661"},"PeriodicalIF":0.0,"publicationDate":"1988-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71363052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diffraction Imaging (Topography) with Monochromatic Synchrotron Radiation","authors":"B. Steiner, M. Kuriyama, R. Dobbyn, U. Laor","doi":"10.6028/jres.093.151","DOIUrl":"https://doi.org/10.6028/jres.093.151","url":null,"abstract":"Structural information of special interest to crystal growers and device physicists is now available from high resolution monochromatic synchrotron diffraction imaging (topography). In this review, the importance of superior resolution in momentum transfer and in space is described, and illustrations are taken from a variety of crystals: gallium arsenide, cadmium telluride, mercuric iodide, bismuth silicon oxide, and lithium niobate. The identification and detailed understanding of local variations in crystal growth processes are shown. Finally, new experimental opportunities now available for exploitation are indicated.","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"577 - 601"},"PeriodicalIF":0.0,"publicationDate":"1988-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Convective Velocity Effects on a Thermistor in Water","authors":"S. Domen","doi":"10.6028/jres.093.152","DOIUrl":"https://doi.org/10.6028/jres.093.152","url":null,"abstract":"Electrical powers from 5 to 150 μW were dissipated in a thermistor, causing it to rise to equilibrium temperatures above the stagnant surrounding water. Natural convection was then simulated by forced convection of water flowing up or down at known rates from 1.3 to 17 mm/min. The disturbances of the equilibrium temperatures were measured, and are presented as effects of equivalent absorbed dose and absorbed dose rates, positive and “negative.”","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"603 - 612"},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Octacalcium Phosphate Solubility Product from 4 to 37 °C","authors":"M. Tung, N. Eidelman, B. Sieck, W. E. Brown","doi":"10.6028/jres.093.153","DOIUrl":"https://doi.org/10.6028/jres.093.153","url":null,"abstract":"Octacalcium phosphate (OCP) is proving to be an important intermediary in the formation of tooth and bone mineral and various pathological calcifications. Before this mineral can form, its solubility product must be exceeded. Thus, a knowledge of its precise values under various conditions is required for a basic understanding of calcification processes. The methodology suitable for measuring the solubility of metastable phases was developed and used to determine the negative logarithms of the solubility products of OCP, pKsp(OCP), at 4, 4.8, 6, 18, 23.5, and 37 °C. This methodology includes (1) the use of high solid-to-liquid ratio, 10 mg/mL, to minimize the effects of hydrolysis, (2) frequent sampling during equilibration to detect possible effects of hydrolysis, (3) equilibration from supersaturation and from undersaturation, and (4) equilibration in the absence and presence of a CO2-containing atmosphere. The resulting pKsp(OCP) values are 48.3±0.2, 48.3±0.2, 48.2, 48.3, 48.4±0.1 and 48.7±0.2 at 4, 4.8, 6, 18, 23.5, and 37 °C. A 5.5% CO2 atmosphere did not change the apparent pKsp(OCP) value significantly. The value of pKsp(OCP) obtained by approaching equilibrium from supersaturation was essentially the same as that from undersaturation. The effects of (1) the use of different ionic models, (2) OCP hydrolysis, and (3) differences in equilibrium constants on the apparent pKsp(OCP) values are described; the latter two contribute significantly to the differences in pKsp(OCP).","PeriodicalId":17082,"journal":{"name":"Journal of research of the National Bureau of Standards","volume":"93 1","pages":"613 - 624"},"PeriodicalIF":0.0,"publicationDate":"1988-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71362983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}