bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystallization and preliminary X‐ray investigation of the recombinant Trypanosoma brucei rhodesiense calmodulin
Authors: El‐Sayed Najib M. A. , Patton Curtis L. , Harkins Paul C. , Fox Robert O. , Anderson Karen
Published: May 2005

Bipyramidal crystals of the recombinant calmodulin from Trypanosoma brucei rhodesiense were obtained by vapor diffusion against 55% (v/v) 2‐methyl‐2,4‐pentanediol in 0.05 M cacodylate buffer, pH 5.6. When few nucleation events occurred, crystals grew to 0.25 × 0.25 × 1.20 mm. The space group of the crystal is I4122, with unit cell dimensions a = b = 56.88 Å, c = 230.11 Å, α = β = γ = 90°, z = 16. The molecular mass and volume of the unit cell suggest that there is one molecule in the asymmetric unit. The I/σ(I) ratio for data at 3.0 Å resolution was 3.67, indicating that the final structure can be refined at higher resolution. Molecular replacement methods and the PC‐refinement technique have not yet yielded the structure under a variety of search conditions. We are currently investigating the multiple isomorphous replacement approach to determine this crystal structure. © 1995 Wiley‐Liss, Inc.
Electron avalanche desorption: A new soft‐ionization technique for non‐volatile and/or thermally labile molecules
Authors: Zubarev R. A. , Bondarenko P. V. , Knysh A. N. , Rozynov B. V.
Published: May 2005

A new ionization technique based on a modification of the conventional plasma‐desorption mass spectrometric apparatus is described. An electron avalanche produced by the microchannel plates of a secondary electron multiplier is found to desorb a sufficient amount of (quasi‐)molecular ions of non‐volatile thermally labile molecules. Spectra of several substances with molecular masses up to 1250 u are presented. The mechanism of electron avalanche desorption is now under investigation.
Structural dependence of anion/dipole complex upon the deprotonated site in [MH]− ions of 17β‐estradiol‐17‐stearate ester in ammonia negative‐ion chemical ionization
Authors: Fournier F. , Tabet J. C. , Debrauwer L. , Rao D. , Paris A. , Bories G.
Published: May 2005

Under ammonia negative‐ion chemical ionization (NICI), of 17β‐estradiol‐17‐stearate ester, a deprotonation reaction occurs competitively at two acidic positions(i.e., the phenol and enolizable sites), demonstrated by using gas phase labelling NICI conditions which yield both [MdD]− and [MdH]− ions. Investigation under low‐energy collisionally‐activated dissociation (CAD) of both molecular species indicates that prior to dissociation, each molecular species isomerizes into different ion/dipole intermediates. These complexes can lead to labile proton exchange. Dissociation of these complexes gives rise to the formation of complementary daughter ions whose abundance depends upon the relative gas phase acidity of the corresponding neutrals.
Mass spectrometry of laser‐desorbed oligonucleotides
Authors: Tang K. , Allman S. L. , Chen C. H.
Published: May 2005

Various matrices were used for laser‐desorption ionization of mixtures of small DNA segments. Parent negative ions of 34‐mer as well as other smaller single‐stranded oligomers were observed for selected organic acids and dye compounds. Both positive and negative parent ions were observed with very little fragmentation. Effects of various matrices and the potential applications to DNA sequencing are briefly discussed.
Matrix‐assisted laser desorption/ionization mass spectrometry of synthetic oligodeoxyribonucleotides
Authors: Parr Gary R. , Fitzgerald Michael C. , Smith Lloyd M.
Published: May 2005

Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry has been used to mass analyze a variety of synthetic oligodeoxyribonucleotides ranging in size from 6 to 30 nucleotides. Molecular ions were observed almost exclusively, with little or no fragmentation and generally minor contributions from multiply charged species. Mixtures of poly d(T)12–30 with low picomole amounts of each component gave well resolved peaks. These results are encouraging for the concept of DNA sequence analysis by mass spectrometry.
Electrospray ionization tandem mass spectrometry of mixtures: Deconvolution by parent‐ion scans
Authors: Smith Philip B. , Snyder A. Peter
Published: May 2005

Electrospray ionization (ESI) mass spectra equine myoglobin and a mixture of bovine insulin, melittin and bovine growth hormone releasing factor (GHRF) were obtained on a tandem quadrupole mass spectrometer. The parent‐ion mass spectrum of m/z 171 for equine myoglobin contained all of the multiply charged molecular ions present in the conventional ESI mass spectrum. Similar results were obtained with the parent‐ion scans of selected ions for the insulin, melittin and GHRF mixture. This technique was able to differentiate between the multiply charged molecular ions produced from each of the three componenets in the mixture.
New gas‐chromatographic/mass spectrometric method for the quantitative analysis of primary aromatic amines in main‐ and side‐stream cigarette smoke. I
Authors: Pieraccini G. , Luceri F. , Moneti G.
Published: May 2005

A sensitive and accurate method to quantitate 17 primary aromatic amines in tobacco smoke has been set up. two Italian commercial brands of cigarette were smoked in a home‐made smoking machine; the amines in the smoke were trapped in dilute hudrochloric acid (containing 2H5‐aniline, 13C1‐o‐toluidine and 2H9‐4‐aminobiphenyl as internal standards) and, after extraction and purification, derivatized as pentafluoropro‐pionamides and measured by gas chromatography/mass spectrometry in the selected‐ion‐monitoring mode. Our results confirmed that side‐stream smoke contains total levels of aromatic amines about 50–60 times higher than those of main‐stream smoke of black‐tobacco cigarettes is richer in aromatic amines compared to light‐tobacco cigarettes.
Detection of γ‐aminobutyric acid in a rat brain using in vivo microdialysis‐capillary electrophoresis/mass spectrometry
Authors: Takada Yasuaki , Yoshida Motoko , Sakairi Minoru , Koizumi Hideaki
Published: May 2005

Coupling of in vivo microdialysis with capillary electrophoresis/mass spectrometry (MD‐CE/MS) was demonstrated. A microdialysis probe was inserted in the striatum of a rat brain and γ‐aminobutyric acid (GABA) in the brain was detected by CE/MS without any chemical treatment of the sample. MD‐CE/MS is expected to be a useful technique for analyzing brain substances, because of the relatively small damage it causes to a living structure and the high selectivity of the analytical technique.
Urinary porphyrin profiles by laser desorption/ionization time‐of‐flight mass spectrometry without the use of classical matrices
Authors: Jones Russell M. , Lamb John H. , Lim Chang Kee
Published: May 2005

A method is described for the rapid analysis of mixtures of porphyrin methyl esters using laser desorption/ionization time‐of‐flight mass spectrometry (LDI‐TOF MS). Ions corresponding to [M+H]+ for each component have been observed without the need for added matrix. LDI‐TOF MS has been applied to the analysis and characterization of porphyrin methyl esters derived from urine samples of patients suffering from various porphyrias. This technique has been shown to provide ‘fingerprint’ profiles of the porphyrins present in each urine sample, characteristic of the porphyria, which compare favourably with those obtained with the established method of high‐performance liquid chromatography. LDI‐TOF MS is a rapid and reliable method for the screening of urine from patients suffering from porphyria.
Analysis of polychlorinated biphenyls by quadrupole ion trap mass spectrometry. Part II: Comparison of mass spectrometric detection using electron impact and selected‐ion chemical ionization with electron capture detection
Authors: Lausević M. , Jiang X. , March R. E. , Metcalfc C. D.
Published: May 2005

The responses of selected‐ion monitoring of electron impact mass spectra and selected‐reagent‐ion chemical ionization mass spectra of polychlorinated biphenyls (PCBs), relative to that of congener 153, have been determined for some 60 PCBs contained in four standard mixtures. The PCB congeners examined cover a wide range of toxicities. Average responses have been determined for PCBs as a function of both the total number of chlorine substituents and the number of ortho‐substituents. Average relative responses and relative responses of individual congeners have been compared with Literature values of relative responses obtained by electron‐capture detection. Detection limits for electron ionization and C2H chemical ionization mass spectrometry, determined as the mass of congener 153 injected on column and yielding a signal‐to‐noise ratio of 5:1 were 0.76 pg and 30 pg, respectively, compared to some 70 fg for electron‐capture detection. An initial exploration and evaluation have been carried out, of the potential value of using a toxicity index to define the total toxicity of a sample; such an index is based on 39 non‐ and mono‐ortho substituted PCBs. Electron ionization, when combined with selected‐ion monitoring of both molecular and fragment ions, is the more sensitive mass‐selective method for the determination of the most toxic PCB congeners.
Matrix‐assisted laser desorption/ionization mass spectrometry of polysaccharides
Authors: Garrozzo Domenico , Impallomeni Giuseppe , Spina Emanuela , Sturiale Luisa , Zanetti Flavio
Published: May 2005

In this paper we report matrix‐assisted laser desorption/ionization (MALDI) mass spectra of dextrans up to 100 000 Da molecular weight and compare these measurements with those obtained by conventional size‐exclusion chromatography with low‐angle laser light scattering (SEC/LALLS). These results extend the usefulness of MALDI‐MS to higher molecular weight polysaccharides and give some insights into the MALDI process.
Mass spectrometric investigations of some N‐cycloalkyl and N‐aryl fluoroacetamides
Authors: Jeremić Ljiljana A. , Perić Aleksandra A. , Stojanović Nadežda D. , Petrović Slobodan D.
Published: May 2005

The electron‐ionization induced mass spectra of some N‐monosubstituted fluoroacetamides of the general formula FCH2CONHR, in which the substituent R is (C3C7) cycloalkyl, phenyl, 4‐methylphenyl, 4‐carbo‐methoxyphenyl, 4‐nitrophenyl and 4‐diethylaminophenyl, were recorded and their fragmentation patterns were studied by metastable‐ion analyses.
A simple method for removing overlapped Auger signals from ELS or low energy reflection mode EXELFS
Authors: Matsuta Hideyuki , Hirokawa Kichinosuke
Published: May 2005

Two simple techniques are described for eliminating overlapped intense Auger signals from electron energy loss spectrum. One is performed by superimposing a small oscillation on both the sample and the CMA band pass energy and detecting only signals which are not altered by the modulation, the other is performed by applying large bias voltage to the sample. These techniques can be used to extract the low energy reflection mode extended electron energy loss fine structure (EXELFS) signals.
Interfacial chemistry at real resin–metal interfaces of electronics devices
Authors: Pignataro S. , Torrisi A. , Ferla G.
Published: May 2005

An amine and an anhydride cured commercial epoxy resin were moulded to real Ag, Ni and Cu surfaces in plant conditions. The joints were mechanically broken and the two faces obtained in the fracture analysed by ESCA. The interfacial chemical compositions were found to be different with respect to that of the corresponding resin and metal bulk.

Some of the resin constituents were confined in the bulk of the resin itself. Others were found to be homogeneously distributed between the bulk of the resin and the interface. Another group of resin constituents were found to segregate to the interfacial zone, often in a chemical state different from that found in the bulk. Also some trace elements present as additives in the metals were found to migrate to the interfacial zone.

The migration phenomena were found to selectively depend on the chemical nature of the metal and resin respectively. Dramatic chemical composition differences were found between the two faces obtained in the fracture.

The effect of time and moulding temperature on the interfacial chemistry was studied. Proof of various chemical reactions taking place at the interfaces with time or moulding temperature could be obtained.

The results are discussed also in terms of performance of the electronic devices where the studied interfaces are present.
Glow discharge sputtering of alloys observed by atomic absorption spectroscopy
Authors: Teo W. B. , Hirokawa K.
Published: May 2005

Sputtering procedures are often employed in the field of material preparation such as thin films and surface analysis. In this report the atomic absorption spectroscopic technique is applied to observe sputtering phenomena of typical binary alloys of copper–nickel and coppersilver, as occurring in a hollow cathode glow discharge. A parameter μα−β correlating the composition of the sample with the composition of the produced plasma which was measured with atomic absorption spectroscopy, is used to monitor changes in the surface composition. Measurements at a natural high surface temperature of the sample during glow discharge and at a lower temperature by cooling with liquid nitrogen were performed. AES analysis of the glow discharge sputtered surfaces of uncooled samples show that a very deep altered layer can be produced.
An AES and ELS study of InP (100) surface subjected to argon ion bombardment
Authors: Jardin C. , Robert D. , Achard B. , Gruzza B. , Pariset C.
Published: May 2005

Auger electron spectroscopy (AES) and electron loss spectroscopy (ELS) have been performed in order to investigate a (100) InP surface subjected to argon ion bombardment at low energy. It has been found that preferential sputtering of phosphorus‐impurities species during the cleaning stage results in the formation of a In0.57P0.43 disordered layer. Within the sampling depth of the In MNN Auger electrons, about 1/4 of the total In atoms are of metallic type. Our experimental results are not consistent with the formation of pure In islands over a stoichiometric InP surface. If In clusters are present in the disordered surface, they are associated with adsorbed phosphorus. Prolonged ion bombardment increases the surface roughness as detected by ELS and scanning electron microscopy (SEM).
Ni surface chemistry and quality of the Al/Ni bond in electronic devices
Authors: Torrisi A. , Cavallaro A. , Licciardello A. , Perniciaro A. , Pignataro S.
Published: May 2005

Four chemically different nickel surfaces, as revealed by ESCA, have been ultrasonically bonded to Al/Mg wires. Under normal conditions there was found to be very little difference in the pull strength of the various surfaces; there were small variations when the samples were tested in stress conditions such as high temperature storage (200 ° C), or a water vapour pressure environment (121 °C, 1.04 atm). However, the bonds have been found to be reliable for the four surfaces and when tested in the encapsulating resin environment of an actual electronic device. The thickness of nickel chemical species overlaying the nickel substrate was estimated to range from 5 to 13 Å for the four nickel surfaces simulating possible plant conditions. This relatively low thickness is considered to be responsible for the above positive results. These results are compared with those previously obtained for the Al/Cu joints.
XPS and AES studies of halofluorocarbon plasma etched surfaces
Authors: Occhiello E. , Garbassi F.
Published: May 2005

In situ AES and ex situ XPS studies have been performed on surfaces treated with haloflurocarbon plasmas. The quartz crystal microbalance (QCM) technique has been used to measure the corresponding etch rates.

Silicon dioxide, polystyrene (PS) and polymethylmethacrylate (PMMA) show comparable trends in etch rates, they seem to react preferentially with fluorine. On the surface of silicon dioxide a silicon oxyfluoride layer is formed as a consequence of plasma treatment. Such a layer is virtually unaffected by the change in the discharge gas.

PS and PMMA surfaces react also with chlorine and bromine, to give derivatization. The reactivity of polystyrene is higher, probably owing to the presence of aromatic rings allowing addition and electrophylic reactions, while in polymethylmethacrylate only substitution reactions are possible.
An energy‐resolved, electron‐stimulated desorption study of hydrogen from cleaned and oxidized Si(100)
Authors: Corallo Cheryl F. , Hoflund Gar B.
Published: May 2005

Electron‐stimulated desorption (ESD) was used to study the hydrogen present on cleaned and oxidized Si(100), Cleaning the surface by ion bombardment and annealing does not completely remove hydrogen from a Si(100) surface. Kinetic energy analysis of the hydrogen ions emitted through ESD shows that multiple states of adsorbed hydrogen are present. Electron beam exposure results in a depopulation of higher energy states. These states are repopulated upon annealing suggesting that the bulk silicon is a source of hydrogen. Oxygen exposure also results in a depopulation of the higher energy desorption states. Angle‐resolved, energy‐resolved ESD spectra of H+ from the cleaned Si(100) surface were also collected. They show that different hydrogen bonding states desorb at different angles relative to the surface plane with differing energy distributions.
Rheology of PVC compounds. III. Effect of modifying resins on fusion
Authors: Krzewki Rudolf J. , Collins Edward A.
Published: May 2005

A rheological method quantifies effects of processing additives on progression of fusion of polyvinyl chloride compounds. It offers a way for tailoring compound composition to attain maximum optimum fusion characteristics for a specific process and/or final physical properties.
The additive heat history of PVC stability
Authors: Brown Randy
Published: May 2005

A thermal stability test can determine the amount of residual stability remaining in a polyvinyl chloride compound after processing. Once the percentage of a compound's stability consumed in a given process is known, any regrind material can be tested to determine if it has sufficient residual stability to be reprocessed. Thermal processing also affects weathering, so the test can predict safe weathering limits.
A new method for judging efficiency of PVC impact modifiers
Authors: Goldman Theodore D.
Published: May 2005

To determine the efficiency difference between impact modifiers, S‐shaped polyvinyl chloride impact curves are compared. But in highly variable scatter regions, the position of the curves is uncertain. A new method focuses on the scatter region by statistically comparing percent ductility for different impact modifiers. If a sufficient number of samples are tested, percent ductility is a sensitive and reproducible function of impact modifier concentration and testing temperatures.
Effect of a variable diffusivity on the migration of vinyl chloride from poly(vinyl chloride) pipe
Authors: Vinson C. G. , Banzer J. D.
Published: May 2005

Measurements of the extent of vinyl chloride migration from specimens of processed poly(vinyl chloride) (PVC) are used to calculate the diffusivity of vinyl chloride in PVC pipe compound. The migration is strongly affected by temperature and is slightly larger into water than into air. The equation for calculating vinyl chloride migration from PVC must be generalized to recognize a variable diffusivity to be useful for non‐isothermal situations, as in the case of the measurements. The diffusivities calculated from the data with the generalized equation were confirmed by migration measurements from one in. pipe. Predictions with the calculated diffusivities and the generalized equation show that PVC pipe with a 3 mg/kg concentration of residual vinyl chloride will not release quantitatively detectable amounts of vinyl chloride (< .002 mg/kg) in a realistic time frame in potable water distribution.
PVC—gelation model
Authors: Parey J. , Menges G.
Published: May 2005

The plasticization of polyvinyl chloride proceeds in two stages. In the first stage, the PVC dry‐blend, under the influence of temperature and particularly of shear, changes into a material capable of gelling. In the second stage, mainly through the effect of temperature, this material becomes gelled. The shear serves here only to homogenize the material. Tests show that the stages do not necessarily have to follow one another directly in an extruder, but can take place separately in terms of both time and space.
Effects of preparation on physical properties of flexible PVC
Authors: Harrison William H. , Johnston William R. , Wadey Brian L.
Published: May 2005

Conditions used to prepare samples of flexible polyvinyl chloride for physical property testing were found to be very critical, particularly when a compound must meet certain requirements. Of the conditions tested, mill temperature had the greatest effect on physical properties: increases in mill temperatures led to increases in tensile strength. Press temperature, which depended on plasticizer and filler levels, had a minor effect. As the filler level increased or plasticizer level decreased, the effects of both mill and press temperatures decreased. There appears to be less scatter in the data with higher durometer and higher filled compounds.
Basic studies of smoke reduction in rigid poly(vinylchloride)
Authors: Guyot Alain , Michel Alain , Bert Michel , Van Hoang Tran
Published: May 2005

A review of recent results in the literature and from our laboratory lead to drive a general picture of the combustion or rigid PVC as well as to the mechanism by which the most powerful additive can reduce the production of smoke. It is shown that, in smoldering condition the black smoke comes chiefly from direct volatilization of heavy tar molecules from the decomposing residue. The additives change the degradation process of the PVC by catalysis of the intermolecular crosslinking reactions, which compete with the intramolecular reactions leading to formation of benzene. Whatever their initial nature, they are at least partly transformed into chlorides and then into oxides during the combustion process. The oxide of Cu, Fe and also Zn are catalysts of the oxidation of the char residue, which may be partially inhibited by phosphorous compounds. The catalytic effects seem less pronounced in flaming conditions, which cause the productions of soots from the initial tars.
Investigation of multiphase polymeric systems of PVC
Authors: Singh Y. P. , Shaw S. , Singh R. P.
Published: May 2005

Graft copolymers of chlororubber‐20‐g‐(ethylacrylate‐co‐acrylonitrile (2:1)) and chlororubber‐20‐g‐(styrene‐co‐vinyl acetate‐co‐acrylonitrile [1:1:1]) have been synthesized by solution precipitation polymerization technique. The graft copolymers have been characterized by elemental analysis, IR spectroscopy, and viscometry. The graft copolymers have been melt blended with PVC. The mechanical properties, such as flexural, tensile strength, and impact strength, of the blends have been studied to evaluate the relative performance of various graft copolymer blends of PVC as impact modified systems. Mechanical properties of the blends have been discussed in terms of morphology of impact fractured samples.
Thermal‐mechanical properties of PVC flame retarded alloys
Authors: Burke Dennis M.
Published: May 2005

Several segments of the plastics conversion industry are concerned with meeting critical functional and performance demands. Relevant concerns include flame spread, smoke generation, and toxicity. In recent decades, the transportation and electrical/electronics industries have consumed tremendous quantities of polymeric materials. Many of these plastics have been extensively modified to meet flammability criteria, processability demands, and other functional requirements. Aircraft and electronics applications of these materials include printed circuit boards, electrical connectors, wiring, wire harnesses, and aircraft cabin flooring, ceiling, paneling, carpeting, and cargo storage bins. The traditional mechanism for imparting flame retarding properties is to incorporate external additives, which alter burning characteristics, but at the expense of functional properties. An alternate solution to flame retarding that has gained much attention in recent years is the alloying, or blending, of flammable polymers with inherently flame retarded polymers. ASTM protocol has established dynamic mechanical testing (DMT) techniques to evaluate the rheological properties of such materials. This paper exhibits how DMT can be used to monitor the solid properties of various flame retarded alloys.
Processable intrinsically conductive polymer blends
Authors: Kulkarni V. G. , Mathew W. R. , Campbell J. C. , Dinkins C. J. , Durbin P. J.
Published: May 2005

Blends of intrinsically conductive polymers (ICPs) with conventional thermo‐plastics exhibit conductivities approaching those of neat ICPs and can be processed using conventional thermoplastic processing equipment. They display good environmental stability and mechanical properties suitable for commercial applications.
Recent developments in analysing crystals for X‐ray spectrometry
Authors: Jenkins R.
Published: May 2005

The usefulness of the analysing crystal is generally governed by its angular dispersion and reflecting power. This is particularly so today where the increasing requirement for more speed and greater accuracy can often only be obtained by the availability of higher net intensities. Although the performance of the conventional X‐ray spectrometer is satisfactory in the middle portion of the wavelength range, it lacks dispersion at the short wavelength end and sensitivity at the long wavelength end. For this reason, there is a continuing search for crystals which offer more angular dispersion in the 0.2 to 2 Å range and better reflecting power in the 5 to 20 Å region.

This paper discusses results obtained with some of the newer analysing crystals which have become available during the past couple of years. These crystals include pyrolitic graphite, rubidium acid phthalate, sorbitol hexa‐acetate, and the (420) and the (422) cuts of lithium fluoride.
X‐ray tube excited fluorescence method using critical absorbers
Authors: Puumalainen P.
Published: May 2005

Critical absorbers were employed to shape a quasi‐discrete excitation beam for X‐ray fluorescence analysis from the primary spectrum of an X‐ray tube. Also the elimination of the Compton scattered excitation peak seen by the detector was made adapting critical absorbers. In single heavy metal analyses the irradiation times needed in the present method were diminished by a factor of several orders of magnitude, with the same accuracy, compared with those needed in the conventional 241Am excited X‐ray analysis.
X‐ray production by 5.2–27 MeV alpha particles
Authors: Bădică T. , Ciortea C. , Dima S. , Petrovici A. , Popescu I. , Neacşu V.
Published: May 2005

K‐shell ionization cross‐sections for Ni, Cu, Ge, Ag and Sn and L‐shell ionization cross‐sections for Sn, Au and Pb induced by α particles have been determined at 5.2, 16.5 and 27 MeV. Results have been compared with the predictions of the plane‐wave Born approximation (PWBA) and binary encounter approximation (BEA).
Pile‐up rejection: Limitations and corrections for residual errors in energy‐dispersive spectrometers
Authors: Statham Peter J.
Published: May 2005

Pile‐up rejection is commonly achieved through use of an auxiliary inspection channel with short time constants but low energy events can be missed because of electronic noise. A formula is derived to predict the detection efficiency of such a channel and the effect of adjusting the discriminator threshold or changing the time constants is demonstrated. When pulses are missed, spectrum distortion and counting losses are greater than would be predicted from the specified pulse pair resolution time so it is important to optimize the inspector adjustment. A mathematical analysis leads to formulae which can be used to correct for residual counting losses and sum peaks, and the relationship between empirical parameters obtained for these formulae and time constants in the electronics is demonstrated. The present state of the art in noise performance dictates that 1 μs is about the best resolution time that can be achieved for 1 ke V pulses. For further improvements, a fast beam switching technique could be used which would improve pulse pair resolution by a factor of three or more and thus afford adequate protection for the very low energy pulses that would be encountered with thin‐window or windowless solid‐state detectors.
Correction for matrix effects in x‐ray fluorescence analysis of finite media
Authors: Ben‐Haim Yakov
Published: May 2005

A procedure is presented for constructing calibration curves of X‐ray fluorescence activity versus analyte concentration for finite multicomponent media. The composition must be known for all components other than the low‐concentration analyte. If these compositions are not known, the system's mass absorption coefficient must be measured. The analyte must be present in low enough concentration so that it does not contribute significantly to the total mass absorption coefficient. The calibration curve for a multicomponent system is constructed numerically from data on analyte activity versus secondary component composition in binary systems (analyte plus one secondary component). Thus calibration curves for any system containing the analyte and n secondary components are constructed from data on the n corresponding binary systems. The method is found to reproduce measured activities of uranium solutions with an accuracy of 5–7%.
Quantitative röntgenfluoreszenzanalyse mit hilfedes linearen und quadratischen hybridmodells
Authors: Kloyber H. , Ebel H. , Mantler M. , Koitz S.
Published: May 2005

Das Konzept der hybriden Röntgenfluoreszenzanalytk ermöglicht die quantitative Bestimmlung einer Probenzusammensetzung mit Hilfe einzigen Standardpprobe und der Kenntnis von theoretischen Zusammenhängen im Sinne der fundamentalen Parameterrechnung. Die gesuchten Konzentrationen werden aus einem Differentialausdruck berechnet, der die Zählratenänderungen als Funktion von Konzentrationsänderungen beschreibt. Im Fall des Linermodells wird diese Funktion liner approximiert, im quadratischen Modell durch eine Funktion zweiter Ordnung. Die vorliegende Arbeit geht von dem Linearmodell aus, das von Kramer, Ebel und Tschismarov vorgestellt wurde und ergänzt es zur verbesserten Bestimmbarkeit kleiner Konzentrationen. Die Ergebnisse der Theoretischen Gegenöberstellung von linerarem und quadratischem Modell werden mit experimentellen Ergebnissen belegt.
A practical relation between atomic numbers and alpha coefficients
Authors: Lachance G. R.
Published: May 2005

A first approximation indicates that fundamental alpha coefficients for a given analyte vary as a function of the ratio of their respective atomic number raised to a power. This simple rule applies mainly at the limits (i.e., when the weight fraction of analytei, wi is of the order of 0.0 or 1.0) in cases of absorption and weak enhancement. The relation thus provides a means of generating coefficients for the system i‐k from experimental data obtained on system i‐j and a means of verifying experimental alphas, since arrays of coefficients must show a high degree of concordance.
Analysis of geologic materials using an automated x‐ray fluorescence system
Authors: Schroeder Brian , Thompson Geoffrey , Sulanowska Margaret , Ludden John N.
Published: May 2005

The use of an automated, software‐controlled X‐ray fluorescence spectrometer (Phillips AXS System)for analysis of geologic materials gives rapid, precise results. Fluorescence intensities are corrected for background and peak overlap and for mass absorption, and ratioed to a standard rock analyzed at frequent intervals. Major element determinations show precision and accuracy in the 0.5–3% range and are based on calibration with a wide variety of international reference rocks. Determinations for major elements are done on specially fused rock powders. Precision and accuracy for trace elements are generally in the 1–5% range. Calibration is also by use of reference rocks but the determinations are done directly on pressed rock powders.
Multielement thin film standards for XRF analysis
Authors: Billiet J. , Dams R. , Hoste J.
Published: May 2005

Multielement thin film standards are made by mixing a solution of different elements and a radioactive tracer (24Na) with the water soluble polymer mehtylcellulose. A film is produced by spreading the liquid mixture evenly on glass plates and letting it dry. Standards of the desired size and shape are punched out. The concentrations of the elements are calculated from the tracer activity. Ten sets of standards containing the elements Na, Mg, Al, Si, P, S, Cl, K, Cs, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Ag, Cd, Sn, Sb, Ba and Pb in different groupings have been prepared. Homogeneity and accuracy oof the standards are extensively discussed. The accuracy is also estimated by the alalysis of the standards using several techniques. The precision of the analysis factors derived from the standards is better than 1–2%, while the accuracy for the elements Al, Cl, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Br, Sb, Ba and Pb is found to be better than 5%.
Intensity for cubic particles in x‐ray fluorescence analysis
Authors: Bonetto R. D. , Riveros J. A.
Published: May 2005

Particle size effects constitute a major source of error in the x‐ray fluorescence of granular material. Different models have been proposed to account for the influence of particle size on the characteristic x‐ray intensity leaving the sample. Important points in these models are the granular distribution from each grain. Berry et al. proposed a model which is in reasonable agreement with experimental values. In this work, fluorescent intensity calculations for a cubic particle with different geometries were carried out. The intensity values obtained through this model were compared with the Berry et al. model. There is better agreement with the experimental values when the expression obtained is used in order to find the total fluorescent intensity using heterogeneous samples consisting of fluorescent and non‐fluorescent components of particle size d.
Quantitative light element analysis using an energy‐dispersive detector: 2—continuum removal and peak deconvolution
Authors: Bloomfield D. J. , Love G.
Published: May 2005

Techniques for analysing light elements by energy‐dispersive spectrometry are discussed and a new approach is proposed. Firstly, a method for predicting the x‐ray continuum level is developed. It is based on the use of a reference standard and, unlike other methods, is accurate below 1.5 ke V. When combined with methods for dealing with spectrum artefacts, this approach allows the calculation of background levels down to 0.1 ke V. Attention is then given to the problem of overlap, which is particularly important in light element analysis. Various methods for deconvolution of peaks are considered and a technique is adopted based on least‐squares fitting of standard peak profiles. The effects of count statistics and computational accuracy on the final results are discussed. Some practical overlap situations are examined to discover the level of accuracy which can be expected.
Quantitative x‐ray diffraction analysis on thin samples deposited on cellulose membrane filters
Authors: Battaglia S.
Published: May 2005

Experimental mass absorption coefficients on thin‐layer samples deposited on membrane disc filters, consisting of mixtures of cellulose acetate and cellulose nitrate, were determined from the attenuation of a reflection of the crystalline material supporting the membranes. These mass absorption coefficients were used to carry out a quantitative x‐ray diffraction analysis on the same thin samples.
Inverse formulations of the Sherman equation for x‐ray spectrometry: A review of existing algorithms
Authors: Vrebos B. , Helsen J. A.
Published: May 2005

A series of 12 correction algorithms for quantitative XRF analysis have been compared. The algorithms are applied to intensities, calculated by the NRLXRF program for hypothetical binary, tertiary and one more complex alloy. The influence coefficients are determined by a least‐squares procedure. It is shown that, when both enhancement and absorption occur, at least a two‐coefficient model is necessary and for more complex samples cross‐effect terms reduce the maximum errors substantially.
Some features of the Lachance‐Traill equation
Authors: Kuczumow A. , Helsen J. A.
Published: May 2005

All currently known changes in the values of the α coefficients in the Lachance‐Traill equation occurring under the influence of different factors are considered. These factors include the change in composition in connection with the enhancement phenomenon, the change in radious of grains (or lamellae) in a non‐homogeneous environment and the change of angle of the analytical surface slope relative to the ideal flat surface. Changes in the α coefficients are found to be always of hyperbolic character. A new version of the Lachance‐Traill equation has been derived.
Effects of chemical combination on x‐ray Kα emission spectra of chromium
Authors: Sarode P. R.
Published: May 2005

Asymmetry indices, chemical shifts and full widths at half maximum intensity (FWHM) of the chromium Kα1 and Kα2 x‐ray emission lines were studied in chromium metal, some of its divalent, trivalent, tetravalent and hexavalent compounds, and minerals, catalysts and glassy materials by an x‐ray fluorescence excitation method. The asymmetry indices were found to depend on the number of unpaired 3d electrons. The chemical shifts, spin—orbit splittings, asymmetry indices and the half‐widths of both the X‐ray emission lines show interesting trends with the oxidation state of chromium.
SEM and EDX analyses of the scales formed on Fe—24Cr—5V—Pd and Fe—24Cr—5Mo—Pd alloy systems
Authors: Tjong S. C. , Chung C. K.
Published: May 2005

SEM and EDX analyses were used to characterize the morphologies of the scales formed on the Fe—24Cr—5V—Pd and Fe—24Cr—5Mo—Pd alloy systems in air at 900°C. SEM observations revealed that porous and non‐protective FeCr2O4 scales were formed on the Fe—24Cr—5V—Pd alloy system. Addition of Pd has no influence on the oxidation performance of the Fe—24Cr—5V alloy. However, thin and adherent Cr2O3 scales were formed on the Fe—24Cr—5Mo—Pd alloy system. The EDX analyses showed that Pd was enriched at the oxide—alloy interface of the Fe—24Cr—5Mo—3Pd alloy. This Pd‐enriched layer provided a fast diffusion path for Cr to form Cr2O3 oxide scales.
RPB7, one of two dissociable subunits of yeast RNA polymerase II, is essential for cell viability
Authors: McKune Keith , Richards Kristy L. , Edwards Aled M. , Young Richard A. , Woychik Nancy A.
Published: May 2005

The Saccharomyces cerevisiae RNA polymerase II subunit gene RPB7 was isolated and sequenced. RPB7 is a single copy gene whose sequence predicts a 19,000 Dalton protein of 171 amino acids. RPB7 is known to dissociate from RNA polymerase II as an RPB4/RPB7 subcomplex in vitro. RPB7 also appears to interact with RNA polymerase II in a manner dependent upon RPB4, since RNA polymerase II purified from cells lacking RPB4 also lacks RPB7. Previous results have demonstrated that deletion of the RPB4 results in slow growth and cold‐ and temperature‐sensitivity. In contrast, deletion of the RPB7 gene revealed that it is essential for cell growth and viability. Loss of both the RPB4 and the RPB7 genes causes lethality. These results suggest that RPB7 contributes to the function of RNA polymerase II in the absence of RPB4 either in a manner independent of its association with the enzyme or by directly binding to the enzyme in a manner independent of its association with RPB4.
XIV. Yeast sequencing reports. The sequence of a 44 420 bp fragment located on the left arm of chromosome XIV from Saccharomyces cerevisiae
Authors: Bergez Patricia , Doignon Francois , Crouzet Marc
Published: May 2005

We have determined the complete nucleotide sequence of a 44 420 bp DNA fragment from chromosome XIV of Saccharomyces cerevisiae. The sequence data revealed 23 open reading frames (ORFs) larger than 300 bp, covering 73·5% of the sequence. The ORFs N2418, N2441, N2474 and N2480 correspond to previously sequenced S. cerevisiae genes coding respectively for the mitochondrial import protein Mas5, the nucleolar protein Nop2, the outer mitochondrial membrane porin Por1, the cytochrome c oxidase polypeptide VA precursor CoxA and the yeast protein tyrosine phosphatase Msg5. Translation products of three other ORFs N2406, N2411 and N2430 exhibit similarity to previously known S. cerevisiae proteins: the ribosomal protein YL9A, the protein Nca3 involved in the mitochondrial expression of subunits 6 and 8 of the ATP synthase and actin; in addition N2505 presents strong similarity to an ORF of chromosome IX. The predicted protein products of ORFs N2417 and N2403 present similarities with domains from proteins of other organisms: the Candida maltosa cycloheximide‐resistance protein, the human interleukin enhancer‐binding factor (ILF‐2). The 12 remaining ORFs show no significant similarity to known proteins. In addition, we have detected a DNA region very similar to the yeast transposon Ty 1–15 of which insertion has disrupted a tRNAAsp gene. The sequence has been deposited in the GenBank database with the Accession Number U12141.
XIV. Yeast sequencing reports. An 8·2 kb DNA segment from chromosome XIV carries the RPD3 and PAS8 genes as well as the Saccharomyces cerevisiae homologue of the thiamine‐repressed nmt1 gene and a Chromosome III‐duplicated gene for a putative aryl‐alcohol dehydrogenase
Authors: van Dyck Luc , Pascual‐Ahuir Amparo , Purnelle Benedicte , Goffeau Andre
Published: May 2005

An 8·2 kb DNA segment from the left arm of Saccharomyces cerevisiae chromosome XIV (GenBank/EMBL accession number: X83226) encompasses four open reading frames (ORFs) longer than 100 residues. The ORF N0295 is highly similar to the Aspergillus parasiticus and Schizosaccharomyces pombe nmt1 gene products, which are involved in thiamine biosynthesis and are strongly repressed by thiamine. N0300 is 76% identical to YCR107w, a hypothetical protein of yeast chromosome III, and 55% identical to a ligninolytic aryl‐alcohol dehydrogenase from the white‐rot fungus Phanerochaete chrysosporium. In addition, this fragment encodes Rpd3, a pleiotropic transcription factor (Vidal and Gaber, 1991), and part of Pas8, a protein essential for the biogenesis of peroxisomes (Voorn‐Brouwer) et al., (1993). The sequence of the right flanking region has already been submitted to the EMBL data library under Accession Number Z46259 (Maftahi et al., 1995).
Chemischer Transport fester Lösungen. 20 [1] Der Chemische Transport von Mischphasen in den Systemen CdS/CdTe und CdSe/CdTe
Authors: Hotje U. , Binnewies M.
Published: May 2005

Chemical Vapor Transport of Solid Solutions. 20, Chemical Vapor Transport of Mixed Phases in the Systems CdS/CdTe and CdSe/CdTe

By means of CVT methods using iodine as transport agent (900 → 800 °C) in the systems CdS/CdTe and CdSe/CdTe mixed crystals could be prepared. The system CdS/CdTe shows a broad miscibility gap. Sulfur rich mixed crystals as well as tellurium rich ones could be prepared. The system CdSe/CdTe shows complete miscibility for all Se/Te ratios. In both systems congruent transport has been observed.
[C10N2H10][ZnCl(HPO4)]2: A New Templated Zincophosphate Containing Tetrahedral Nets with 63 Topology
Authors: Natarajan Srinivasan , Ewald Bastian , Prots Yurii , Kniep Rüdiger
Published: May 2005

The crystal structure of [C10N2H10][ZnCl(HPO4)]2 contains corrugated tetrahedral layers $^{2}_{\infty}\rm [ZnCl(HPO_{4})^{-}]$ with 63 topology. Charge balance is achieved by insertion of diprotonated 4,4′‐bipyridine between the layers. Crystal data: monoclinic, P21/n (no. 14), a = 4.8832(2) Å, b = 22.673(2) Å, c = 8.1643(4) Å, β = 104.02(1)°; V = 877.0(1) Å3; Z = 4; R1 = 0.041 and wR2 = 0.088 for 1836 reflections [I > 2σ(I)]. Tetrahedral layers $^{2}_{\infty}\rm [ZnCl(HPO_{4})^{-}]$ are also observed in other organo‐ammonium templated compounds. However, their topologies are characterized by 4.82 nets. With the title compound a layered tetrahedral net $^{2}_{\infty}\rm [ZnCl(HPO_{4})^{-}]$ with 63‐topology is reported for the first time.
Some New Molecular Hydrides Stabilized and Characterized with the Aid of the Matrix‐Isolation Technique
Authors: Himmel Hans‐Jörg
Published: May 2005

New molecular hydrides have been prepared and characterized with the aid of the matrix isolation technique. These hydrides are products of spontaneous or photoactivated reactions taking place in the matrix. They show a remarkable structural variety reflecting the ability of H atoms to be positively or negatively polarized and to be engaged in terminal as well as bridging bonds. In addition to the academic interest in these molecules, the findings are of interest for applications. Thus the results will be discussed especially in the light of the increasing effort to fabricate new molecular hydrogen storage materials.
Synthese und Kristallstruktur von Cadmium‐Dodekahydro‐closo‐Dodekaborat‐Hexahydrat, Cd(H2O)6[B12H12]
Authors: Tiritiris Ioannis , Schleid Thomas
Published: May 2005

Synthesis and Crystal Structure of Cadmium Dodecahydro closo‐Dodecaborate Hexahydrate, Cd(H2O)6[B12H12]

Through neutralization of the aqueous free acid (H3O)2[B12H12] with cadmium carbonate (CdCO3) and after isothermic evaporation of the resulting solution, colourless lath‐shaped single crystals of Cd(H2O)6[B12H12] are obtained. Cadmium dodecahydro closo‐dodecaborate hexahydrate crystallizes at room temperature in the monoclinic system (space group: C2/m) with the lattice constants a = 1413.42(9), b = 1439.57(9), c = 749.21(5) pm and β = 97.232(4)° (Z = 4). The crystal structure of Cd(H2O)6[B12H12] can be regarded as a monoclinic distortion variant of the CsCl‐type structure. Two crystallographically different [Cd(H2O)6]2+ octahedra (d(Cd–O) = 227–230 pm) are present which only differ in their relative orientation. The intramolecular bond lengths for the quasi‐icosahedral [B12H12]2− cluster anions range in the intervals usually found for dodecahydro closo‐dodecaborates (d(B–B) = 177–179 pm, d(B–H) = 103–116 pm). The hydrogen atoms of the [B12H12]2− clusters have no direct coordinative influence on the Cd2+ cations. Due to the fact that no “zeolitic” crystal water molecules are present, a stabilization of the lattice takes place mainly via the B–Hδ−···+δH–O hydrogen bonds.
Synthesis and Crystal Structure of the Nitridosilicates Ca5[Si2N6] and Ca7[NbSi2N9]
Authors: Ottinger Frank , Nesper Reinhard
Published: May 2005

Ca5[Si2N6] and Ca7[NbSi2N9] were obtained by reaction of Ca3N2, Ca2N and Si3N4 (with addition of niobium powder in case of Ca7[NbSi2N9]) in closed tantalum ampoules at temperatures at 1060 °C and 1000 °C, respectively. Ca5[Si2N6] is monoclinic C2/c with a = 983.6(2) pm, b = 605.2(1) pm, c = 1275.7(3), β = 100.20(3)° and Z = 4 crystallising homotypically to Ba5[Si2N6]. The crystal structure contains pairs of edgesharing SiN4 tetrahedra forming isolated nitridosilicate anions of [Si2N6]10−. Ca7[NbSi2N9] is monoclinic P21/m with a = 605.1(1), b = 994.6(2), c = 899.7(2), β = 92.10(1)°, Z = 2 and crystallises in an hitherto unknown structure type. Ca7[NbSi2N9] contains isolated anions [NbSi2N9]14− which are composed of two edgesharing SiN4 tetrahedra and an edge‐sharing NbN5 pyramid. So far, such a pseudotrisilicate unit has not been observed in the family of silicates.