Standard reference materials for cements

The eight portland cements and two calcium aluminate cements in the Standard Reference Material (SRM) 1880 series are among the most popular SRMs in the catalog of the National Institute of Standards and Technology (NIST) Standard Reference Materials Program. Numerous laboratories rely on them for elemental analysis and qualification for ASTM C 114-00 Standard Test Methods for Chemical Analysis of Hydraulic Cement. NIST has collected new candidate materials from around the world and partnered with Construction Technology Laboratories (CTL) in their preparation and certification. This paper describes the procedures taken at NIST and CTL to prepare and test materials for certification including the homogeneity testing, the X-ray fluorescence methods and the statistical data analysis performed for value assignment.     

Field method for the determination of hexavalent chromium by ultrasonication and strong anion-exchange solid-phase extraction

A simple, fast, sensitive, and economical field method was developed and evaluated for the determination of hexavalent chromium (CrVI) in environmental and workplace air samples. By means of ultrasonic extraction in combination with a strong anion-exchange solid-phase extraction (SAE-SPE) technique, the filtration, isolation, and determination of CrVI in the presence of trivalent chromium (CrIII) and potential interferents was achieved. The method entails (1) ultrasonication in basic ammonium buffer solution to extract CrVI from environmental matrixes; (2) SAE-SPE to separate CrVI from CrIII and interferences; (3) elution/acidification of the eluate; (4) complexation of chromium with 1,5-diphenylcarbazide; and (5) spectrophotometric determination of the colored chromium-diphenylcarbazone complex. Several critical parameters were optimized in order to effect the extraction of both soluble (K2CrO4) and insoluble (PbCrO4) forms of CrVI without inducing CrIII oxidation or CrVI reduction. The method allowed for the dissolution and purification of CrVI from environmental and workplace air sample matrixes for up to 24 samples simultaneously in less than 90 min (including ultrasonication). The results demonstrated that the method was simple, fast, quantitative, and sufficiently sensitive for the determination of occupational exposures of CrVI. The method is applicable for on-site monitoring of CrVI in environmental and industrial hygiene samples.     

"Tower vertebra": a new observation in sickle cell disease

PURPOSE: We studied the frequency of testicular microlithiasis (TM) in a select group of otherwise healthy infertile men with abnormal semen. METHODS: We reviewed scrotal sonography records of 180 consecutive patients with abnormal semen who were referred for evaluation of male infertility. The pampiniform plexus was evaluated for possible varicocele, and the testes were examined for the presence or absence of intratesticular calcifications and/or masses. Five patients with more than 5 echogenic foci per transducer field in either testis were identified. The medical records and sonograms of this subgroup of patients were analyzed. RESULTS: Of the 180 patients, 5 (2.8%) had TM. Three patients with TM had concomitant small varicoceles; 2 others had a history of testicular maldescent. Two patients eventually became fertile. CONCLUSIONS: Our results indicate a higher than expected frequency of TM in otherwise healthy infertile men. We speculate that the magnitude of hypospermatogenesis in patients with TM is variable and may relate to both the degree of testicular dysgenesis and the presence or absence of concomitant scrotal pathology (eg, scrotal varicocele and cryptorchidism).     

Water Vapor Pressure over Complex Particles,I: Sulfuric Acid Solution Effect

ABSTRACT

The equilibrium vapor pressures of water are calculated for two different geometric configurations: a liquid cap formed on a single substrate sphere and a liquid pendular ring formed about the contact point of a pair of adhering, identical spheres. The substrate is a structureless, macroscopic (i.e., radius R > 50 nm), relatively hydrophobic sphere. For each configuration, pure water and sulfuric acid solution are used separately as the interface liquid. In addition to the available surface tension measurements of sulfuric acid solution against air, our calculations utilize the tabulated data of activity of water over the sulfuric acid solution and the solution density. The substrate's interfacial tension against air is treated as a parameter in these calculations. Then, by using Young's equation as a constraint in our calculation, we can determine the contact angle of the surface liquid residing on substrate spheres for both configurations. We apply Kelvin's equation in combination with both water activity of sulfuric acid solution and combining relations (semiquantitative relations describing molecular forces) to perform the calculations in the macroscopic picture. The calculations show, for example, that the equilibrium water vapor pressure over a pendular ring containing relatively dilute sulfuric acid solution (e.g., 0.5–10%) is always less than the equilibrium vapor pressure over the same configuration with only pure water when both sphere radii are 100 nm and contact angle is around 20°. The results also show that if all conditions are the same, except geometric configuration, the pendular ring of condensation has a lower equilibrium vapor pressure than the cap of condensation does. Even more significantly, the graph of equilibrium vapor pressure vs volume of condensed water for the pendular ring configuration indicates unconstrained condensational growth at subsaturation relative humidity. In contrast, in the cap configuration, condensational growth is usually limited for any subsaturation relative humidity.     

James R. Brock (1930–2011)

Copyright 2012 American Association for Aerosol Research     

Room-Temperature Solid-Matrix Luminescence Spectroscopy of Pyrene and 1-Hydroxypyrene from Optically Clear Sugar Glasses

Room-temperature solid-matrix luminescence was investigated for two model compounds pyrene and 1-hydroxypyrene from optically clear sugar glasses. Several glasses were investigated. Novel glasses were prepared for the first time from binary mixtures of sugars for spectroscopy. Glasses were prepared from glucose/xylose and glucose/maltose. The glucose/maltose gave a superior glass compared to glucose/xylose. The glucose/maltose glass gave the best room temperature phosphorescence (RTP) for pyrene compared to glasses of glucose and maltose without a heavy atom. The RTP was weak for both pyrene and 1-hydroxypyrene without a heavy atom in the glucose glass. The addition of a heavy atom (12% NaI) gave a 44-fold increase in RTP of pyrene and a 10-fold increase in the RTP of 1-hydroxypyrene. Room temperature fluorescence (RTF) of pyrene and 1-hydroxypyrene were easily observed from all the glass systems studied. However, the pyrene RTF intensity varied with the different sugar glass systems studied. Furthermore, a polymer, polyacrylic acid (PAA), was added to the sugar matrix at the level of 1% and 2% to improve the rigidity of the glass matrix. The observed phosphorescence was weak for pyrene at both the 1% and 2% PAA concentrations. A glass prepared with 2% PAA gave the strongest RTP for pyrene. Addition of 12% NaI with 1% polyacrylic acid did improve the RTP of pyrene but it was less than the RTP of pyrene from a glucose glass with 12% NaI by a factor of 2.7. A glucose glass with 12% NaI was the best system for RTP of pyrene.     

Functional interactions of genes mediating convergent extension, knypek and trilobite, during the partitioning of the eye primordium in zebrafish

Vertebrate eye development in the anterior region of the neural plate involves a series of inductive interactions dependent on the underlying prechordal plate and signals from the midline of the neural plate, including Hedgehog. The mechanisms controlling the spatiotemporal expression pattern of hedgehog genes are currently not understood. Cyclopia is observed in trilobite (tri) and knypek (kny) mutants with affected convergent extension of the embryonic axis during gastrulation. Here, we demonstrate that tri mutants show a high frequency of partial or complete cyclopia, kny mutants exhibit cyclopia infrequently, while knym119 trim209 double-mutant embryos have dramatically reduced convergent extension and are completely cyclopic. We analyzed the relationships between the convergent extension defect, the expression of hedgehog and prechordal plate genes, and the formation of cyclopia in knym119 and trim209 mutants. Our results correlate the cyclopia phenotype with the abnormal location of hh-expressing cells with respect to the optic primordium. We show that cyclopia in these mutants is not due to an incompetence of tri and kny cells to respond to Hedgehog signaling. Rather, it is a consequence of exceeding a critical distance (>40-50 micrometer) between hedgehog-expressing cells and the prospective eye field. We hypothesize that at this distance, midline cells are not in an appropriate position to physically separate the eye field and that HH and other signals do not reach the appropriate target cells. Furthermore, tri and kny have overlapping functions in establishing proper alignment of the anterior neural plate and midline cells expressing shh and twhh genes when the partitioning of the eye primordium takes place.     

The partitioning of phosphoramide mustard and its aziridinium ions among alkylation and P-N bond hydrolysis reactions

NMR (1H and 31P) and HPLC techniques were used to study the partitioning of phosphoramide mustard (PM) and its aziridinium ions among alkylation and P-N bond hydrolysis reactions as a function of the concentration and strength of added nucleophiles at 37 degrees C and pH 7.4. With water as the nucleophile, bisalkylation accounted for only 10-13% of the product distribution given by PM. The remainder of the products resulted from P-N bond hydrolysis reactions. With 50 mM thiosulfate or 55-110 mM glutathione (GSH), bisalkylation by a strong nucleophile increased to 55-76%. The rest of the PM was lost to either HOH alkylation or P-N bond hydrolysis reactions. Strong experimental and theoretical evidence was obtained to support the hypothesis that the P-N bond scission observed at neutral pH does not occur in the parent PM to produce nornitrogen mustard; rather it is an aziridinium ion derived from PM which undergoes P-N bond hydrolysis to give chloroethylaziridine. In every buffer studied (bis-Tris, lutidine, triethanolamine, and Tris), the decomposition of PM (with and without GSH) gave rise to 31P NMR signals which could not be attributed to products of HOH or GSH alkylation or P-N bond hydrolysis. The intensities of these unidentified signals were dependent on the concentration of buffer.