bluuebunny/crossref_metadata_2025 huggingface dataset:
Cookbook versus performance SIS practices
Authors: Gentile Michela , Summers Angela E.
Published: May 2008

A safety instrumented system (SIS) is designed to achieve or maintain a safe state of the process when unacceptable process conditions are detected. An SIS is an independent protection layer that is covered by the performance‐based standard ANSI/ISA 84.00.01‐2004. The risk reduction allocated to the SIS determines its target safety integrity level (SIL). ANSI/ISA 84.00.01‐2004 allows a combination of factors to be considered in the verification of the SIL of the SIS. Performance‐based practices provide flexibility to users, yet add complexity to the design process, encouraging project teams to reinvent the wheel for even widely used process equipment.

For many engineering applications, prescriptive approaches are favored due to simplicity. These so‐called cookbook practices were very common in the process industry when ANSI/ISA 84.01‐1996 was issued. They are also the backbone of many application standards and recommended practices. The cookbook typically specifies the SIS and maximum proof test interval based on analysis and accepted practice. The user must ensure that the cookbook assumptions are met by the existing equipment and mechanical integrity program. Otherwise, the installed risk reduction may not achieve the expected performance. This article provides an example of a “cookbook” approach for a simple SIS and illustrates the effect of extending the proof test interval from 1 year to 5 years on its probability of failure on demand. © 2008 American Institute of Chemical Engineers Process Saf Prog 2008
Reflection anisotropy spectroscopy of biological molecules with the 4GLS source
Authors: Weightman P. , Bowler M. , Clarke J. A. , Farrell T. , Flavell W. , Harrison P. , Martin D. S. , Papiz M. Z. , Poole M. A. , Quinn F. , Seddon E. A. , Smith C. I. , Smith S. , Surman M.
Published: May 2008

The main characteristics of the UK Fourth Generation Light Source (4GLS) are described. It is explained how the output of 4GLS could be used in studies of biological systems using Reflection Anisotropy Spectroscopy (RAS). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reflection anisotropy spectroscopy of decanethiol adsorbed at Au(110)/liquid interfaces
Authors: Bowfield A. , Smith C. I. , Cuquerella M. C. , Farrell T. , Fernig D. G. , Edwards C. , Weightman P.
Published: May 2008

Reflection Anisotropy Spectroscopy (RAS) has been used to monitor the adsorption of decanethiol as a function of coverage on the Au(110)/ethanol interface. The coverage saturates after 60 minutes for a solution of 0.5 µM. It is found that the RAS observed after 30 minutes can be represented as a linear sum of the RAS observed after 15 minutes and after saturation coverage. This implies that the molecule does not change its orientation as function of coverage. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface strain contributions to the lineshapes of reflectance difference spectra for one‐electron and discrete‐exciton transitions
Authors: Lastras‐Martínez L. F. , Ortega‐Gallegos J. , Balderas‐Navarro R. E. , Flores‐Camacho J. M. , Chavira‐Rodríguez M. E. , Lastras‐Martínez A. , Cardona M.
Published: May 2008

Reflectance difference spectroscopy (RDS/RAS) constitutes a very sensitive tool for the study of the optical properties of semiconductors. RDS spectra comprise several components of different physical origins. One of these components is the strain induced by the surface. In the present work, we report RD spectra measured on GaAs at room temperature at around E1 and the E1+Δ1 transitions. Two cases were studied, the surface strains induced by the c (4× 4) reconstruction and by the vacancies generated by the annealing of semi insulating GaAs crystal. Fits to the line shape of the c (4× 4) reconstructed and annealed spectra were performed by using a surface strain component for one‐electron and discrete‐exciton lineshapes respectively. The character of the fits were interpreted by estimating the piezoelectric field induced by surface strain. For the c (4× 4) surface the strength of the field partially quenches the exciton while for the annealing surface this field is fifty times lower, and an excitonic lineshape is expected.We also inferred that the RD spectra include a component related to surface roughness. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reflectance‐anisotropy study of the dynamics of molecular beam epitaxy growth of GaAs and InGaAs on GaAs (001)
Authors: Ortega‐Gallegos J. , Lastras‐Martínez A. , Lastras‐Martínez L. F. , Balderas‐Navarro R. E.
Published: May 2008

Reflectance‐Anisotropy (RA) observations during the Molecular Beam Epitaxy (MBE) growth of zincblende semiconductors films were carried out using the E1 optical transition as a probe. We follow the kinetics of the deposition of GaAs and In0.3Ga0.7As on GaAs (001) at growth rates of 0.2 and 0.25 ML/s, respectively. During growth we used a constant As4 or As2 flux pressure of 5× 10–6 Torr. Clear RA‐oscillations were observed during growth with a period that nearly coincides with the growth period for a Ga‐As bilayer. RHEED was used as an auxiliary technique in order to obtain a correlation between RHEED and RA oscillations. On the basis of our results, we argue that RAS oscillations are mainly associated to periodic changes in surface atomic structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical anisotropy induced by mechanical strain around the fundamental gap of GaAs
Authors: Ortega‐Gallegos J. , Lastras‐Martínez A. , Lastras‐Martínez L. F. , Balderas‐Navarro R. E.
Published: May 2008

We report on a theoretical‐experimental study of reflectance anisotropy spectroscopy (RAS) of GaAs (001) crystals under uniaxial stress. The study was carried out in the energy region around the fundamental transition. RAS spectra in the energy range from 1.2‐1.7 eV were measured with a photoelastic‐modulator‐based spectrometer. To induce an optical anisotropy, the GaAs crystals were thinned down to 400 mm and an calibrated uniaxial stress was applied by deflection. RAS showed a line shape consisting of an oscillation at around E0. On the basis of a perturbative approach employing the Pikus‐Bir Hamiltonian, we calculated the RAS line shape and found a close agreement with the experimental spectra. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reflectance‐difference spectroscopy as an optical probe for in situ determination of doping levels in GaAs
Authors: Lastras‐Martínez A. , Lara‐Velázquez I. , Balderas‐Navarro R. E. , Ortega‐Gallegos J. , Guel‐Sandoval S. , Lastras‐Martínez L. F.
Published: May 2008

We report on in situ Reflectance Difference Spectroscopy measurements carried out on GaAs (001). Measurements were performed at temperatures of 580 °C and 430 °C, in both n and p‐type doped films and for both (2×4) and c(4×4) reconstructions. Samples employed were grown by Molecular Beam Epitaxy with doping levels in the range from 1016 – 1019 cm–3. We demonstrate the potential of Reflectance Difference Spectroscopy for impurity level determinations under growth conditions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AMPA receptor imaging by infrared scanning near‐field optical microscopy
Authors: Generosi J. , Kropf M. , Margaritondo G. , Hirling H. , Catsicas S. , Johnsson K. , Tolk N. H. , Piston D. W. , Cricenti A.
Published: May 2008

Infrared scanning near‐field optical microscopy is used to detect AMPA‐type glutamate receptor clusters in hippocampal neuron cells. AMPA's GluR2‐subunits were marked with the fluorophore Alexa488 and high‐resolution micrographs were taken at 6.25 µm wavelength, corresponding to the maker's strong infrared absorption. The use of infrared light avoids photobleaching and makes this approach suitable for long‐term observations; this technique can be used in general to localize different IR‐absorbing molecules over the complex background of other cell components. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pump‐probe studies of travelling coherent longitudinal acoustic phonon oscillations in GaAs
Authors: Xu Y. , Qi J. , Miller J. , Cho Y.‐J. , Liu X. , Furdyna J. K. , Shahbazyan T. V. , Tolk Norman
Published: May 2008

We report comprehensive studies of long‐lived oscillations in femtosecond optical pump‐probe measurements on GaAs based systems. The oscillations arise from a photo‐generated coherent longitudinal acoustic phonon wave at the sample surface, which subsequently travels from the surface into the GaAs substrate, thus providing information on the optical properties of the material as a function of time/depth. Wavelength‐dependent studies of the oscillations near the bandgap of GaAs indicate strong correlations to the optical properties of GaAs. We also use the coherent longitudinal acoustic phonon waves to probe a thin buried Ga0.1In0.9As layers non‐invasively. The observed phonon oscillations experience a reduction in amplitude and a phase change at wavelengths near the bandgap of the GaAs, when it passes through the thin GaxIn1‐xAs layer. The layer depth and thicknesses can be extracted from the oscillation responses. A model has been developed that satisfactorily characterizes the experimental results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence of InP: an in situ probe for characterizing nanostructured PbSe electrodeposited on InP
Authors: Gérard I. , Froment M. , Cachet H. , Etcheberry A.
Published: May 2008

PbSe electrodeposition was performed at fixed potential onto n‐InP in an EDTA electrolyte. Conditions are chosen to favour polycrystalline growth. The process was followed in situ by recording the photoluminescence (PL) of the substrate. Characteristic PL decays are observed which depend on the wavelengths of the excitations and are totally related to the PbSe growth. Estimation of the absorption coefficient at 930 nm, 850 nm and 633 nm points out a blue shift towards higher energies after comparison with data on PbSe single crystal. This suggests a quantum sizes effect which agrees to crystallite size evaluated to be in the range 10 to 20 nm by TEM observations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A novel diagnostics for polymer degradation based on near‐field two‐photon photoluminescence
Authors: Biagioni P. , Celebrano M. , Labardi M. , Polli D. , Zavelani‐Rossi M. , Cerullo G. , Lanzani G. , Finazzi M. , Duò L.
Published: May 2008

By coupling femtosecond pulses to a hollow‐pyramid aperture SNOM, we demonstrate nonlinear near‐field two‐photon photoluminescence imaging of organic semiconductors. We discover that two‐photon excitation of the blue‐emitting poly(9,9‐dioctylfluorene) (PFO) selectively addresses the keto‐defect units which are responsible for a shifted green‐orange emission. We exploit this effect to map oxidized sites in the PFO film with high contrast and spatial resolution, introducing a novel tool for characterizing oxygen‐induced degradation in electroluminescent materials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Near‐field second‐harmonic generation from gold nanoellipsoids
Authors: Celebrano M. , Biagioni P. , Finazzi M. , Duò L. , Zavelani‐Rossi M. , Polli D. , Labardi M. , Allegrini M. , Grand J. , Adam P.‐M. , Royer P. , Cerullo G.
Published: May 2008

Second‐harmonic generation from single gold nanofabricated particles is experimentally investigated by a nonlinear scanning near‐field optical microscope (SNOM). High peak power femtosecond polarized light pulses at the output of a hollow pyramid aperture allow for efficient second‐harmonic imaging, with sub‐100‐nm spatial resolution and high contrast. The near‐field nonlinear response is found to be directly related to both local surface plasmon resonances and particle morphology. The combined analysis of linear and second‐harmonic SNOM images allows one to discriminate among near‐field scattering, absorption and re‐emission processes, which would not be possible with linear techniques alone. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Second‐harmonic generation from ZnO nanowires
Authors: Pedersen K. , Fisker C. , Pedersen T. G.
Published: May 2008

Optical second‐harmonic generation (SHG) from ZnO nanowires is investigated in the region around the band gap. Strong multiphoton excited luminescence and SHG appearing together in the spectra from wires are separated and the SHG part is compared to that of a bulk crystal. The spectrum of the effective second‐order nonlinear susceptibility of the nanowires is extracted from measured SHG intensity by taking into account linear optical propagation governed by effective refractive indices reflecting the volume fraction of ZnO in the nanowire film. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical second‐harmonic generation study of charge trapping dynamics in HfO2/SiO2 films on Si(100)
Authors: Price J. , An Y. Q. , Downer M. C.
Published: May 2008

Electrostatic‐Field‐Induced Second Harmonic (EFISH) generation is used to characterize laser‐induced charge trapping dynamics in thin HfO2 films deposited on chemically oxidized P‐type Si(100) substrates. We monitor EFISH generation as a function of time, HfO2 thickness and post‐deposition annealing (PDA). In as‐deposited films, the results show that electrons and holes are injected and trapped in comparable amounts, but on different time scales. In annealed films, electron dynamics dominate at all times. Quantitative details depend on film thickness. These results show that time‐dependent EFISH generation can provide an in situ, non‐destructive diagnostic of charge trapping in thin high‐k gate dielectric films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical second‐harmonic and reflectance‐anisotropy spectroscopy of molecular adsorption at Si(001) step‐edges
Authors: Ehlert Robert , Kwon Jinhee , Downer Michael C.
Published: May 2008

Reflectance‐anisotropy spectroscopy (RAS) and spectroscopic second harmonic generation (SHG) are used to probe a single‐domain reconstructed stepped Si(001) surface offcut 6° toward [110] before and after dissociative adsorption of H2 at the DB step edges. Preliminary analysis with a simplified bond hyperpolarizability model supports the mutual consistency of RA and SHG spectra and suggests that hydrogen termination redistributes oscillator strength from the chemically active step dangling bond into the step back bonds. The data provide a benchmark for first‐principles calculations of the optical response of stepped Si surfaces to step edge molecular adsorption. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Second‐harmonic spectroscopy of Si nanocrystals embedded in silica
Authors: Wirth A. , Wei J. , Gielis J. J. H. , Figliozzi P. , Rafaelsen J. , An Y. Q. , Downer M. C.
Published: May 2008

Extending previous second‐harmonic generation (SHG) single‐wavelength studies [1] of Si nanocrystals (NCs) embedded in fused silica, we implement spectroscopic cross‐polarized two‐beam SHG (XP2‐SHG) by employing an optical parametric amplifier as a source of widely tunable (1.6 ≤ Eph ≤ 2.4 eV) femtosecond pulses.

Subsequent isolation of the SH signal produced by the NCs yields the oscillator strength and phase of their nonlinear response. We obtain a broad resonance between bulk Si E1 and E2 critical points. Possible explanations for the spectroscopic result are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dipole model for the linear response of adsorbed overlayers
Authors: Vázquez‐Nava R. A. , Arzate N. , Mejía J. E. , Mochán W. L.
Published: May 2008

This paper present theoretical calculations of reflectance anisotropy spectra (RAS) for overlayers of alkali atoms adsorbed on a crystalline metallic surface. We assume that the overlayer is formed by an ordered twodimensional (2D) array of adatoms that respond to the local electric field like point‐like harmonic oscillators. We consider overlayers with several rational coverages, assuming that the adsorbates occupy high symmetry sites which form a Bravais lattice that is commensurate with the substrate [1,2]. RAS spectra are obtained for the five 2D Bravais lattices. We found that RAS can be used to observe ordered phases when the ordered phase has a rectangular, centered‐rectangular or oblique symmetry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Linear optical response of (6,0) boron nitride nanotubes adsorbed with molecular hydrogen
Authors: Arzate N. , Vázquez‐Nava R. A. , Mejía J. E.
Published: May 2008

We performed a study of the molecular adsorption of hydrogen on BN nanotubes. We present ab initio calculations for the linear optical response of single wall zigzag BN(6,0) nanotubes as a function of the hydrogen adsorption on the exterior surface of the nanotube. The calculation of the linear optical response is performed by using density functional theorywith the use of plane waves and pseudopotentials. We consider four different nanotube‐structures adsorbed with different coverage of molecular hydrogen.We find optimized atomic coordinates for such structures and calculate binding energies for the molecule of hydrogen on the nanotube.After having the linear response of the considered structures, we have calculated their energy loss function spectra. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microsynthesis and mass spectral study of Chemical Weapons Convention related 2‐alkyl‐1,3,6,2‐dioxathiaphosphocane‐2‐oxides
Authors: Palit Meehir , Mallard W. Gary , Yang Imsuk
Published: May 2008

Chemical Weapons Convention (CWC)‐related compounds where the phosphorus atom is part of a ring have very limited representation in mass spectral libraries and the open literature. Here we report electron ionization (EI), chemical ionization (CI) and electrospray ionization tandem mass spectrometry (ESI‐MSn) spectra and retention indices for 2‐alkyl‐1,3,6,2‐dioxathiaphosphocane‐2‐oxides (alkyl C1 to C3) which are new cyclic chemicals covered under the CWC. The EI mass spectra show a pattern of ion fragmentation that is similar to that of other cyclic phosphonates in that loss of the alkylphosphonic acid as a neutral loss is more important than the presence of the protonated alkylphosphonic acid. In contrast to other cyclic phosphonates, the 2‐alkyl‐1,3,6,2‐dioxathiaphosphocane‐2‐oxides show almost no protonated alkylphosphonic acid and as a result the spectra do not carry the same distinctive signature of the phosphorus–carbon bond that is required for the chemical to be covered under the CWC. Copyright © 2008 John Wiley & Sons, Ltd.
Comparison of high‐ and low‐resolution electrospray ionization mass spectrometry for the analysis of naphthenic acid mixtures in oil sands process water
Authors: Martin Jonathan W. , Han Xiumei , Peru Kerry M. , Headley John V.
Published: May 2008

The oil sands regions of Northern Alberta, Canada, contain an estimated 1.7 trillion barrels of oil in the form of bitumen, representing the second largest deposit of crude oil in the world. A rapidly expanding industry extracts surface‐mined bitumen using alkaline hot water, resulting in large volumes of oil sands process water (OSPW) that must be contained on site due to toxicity. The toxicity has largely been attributed to naphthenic acids (NAs), a complex mixture of naturally occurring aliphatic and (poly‐)alicyclic carboxylic acids. Research has increasingly focused on the environmental fate and remediation of OSPW NAs, but an understanding of these processes necessitates an analytical method that can accurately characterize and quantify NA mixtures. Here we report results of an interlaboratory comparison for the analysis of pure commercial NAs and environmental OSPW NAs using direct injection electrospray ionization mass spectrometry (ESI‐MS) and high‐pressure liquid chromatography/high‐resolution mass spectrometry (HPLC/HRMS). Both methods provided very similar characterization of pure commercial NA mixture; however, the m/z selectivity of HPLC/HRMS was essential to prevent substantial false‐positive detections and misclassifications in OSPW NA mixtures. For a range of concentrations encompassing those found in OSPW (10–100 mg/L), both methods produced linear response, although concentrations of commercial NAs above 50 mg/L resulted in slight non‐linearity by HPLC/HRMS. A three‐fold lower response factor for total OSPW NAs by HPLC/HRMS was largely attributable to other organic compounds in the OSPW, including hydroxylated NAs, which may explain the substantial misclassification by ESI‐MS. For the quantitative analysis of unknown OSPW samples, both methods yielded total NA concentrations that correlated with results from Fourier transform infrared (FTIR), but the coefficients of determination were not high. Quantification by either MS method should therefore be considered semi‐quantitative at best, albeit either method has substantial value in environmental fate experiments where relative concentration changes are the desired endpoints rather than absolute concentrations. Copyright © 2008 John Wiley & Sons, Ltd.
Grain‐scale heterogeneities in the stable carbon and oxygen isotopic compositions of the international standard calcite materials (NBS 19, NBS 18, IAEA‐CO‐1, and IAEA‐CO‐8)
Authors: Ishimura Toyoho , Tsunogai Urumu , Nakagawa Fumiko
Published: May 2008

We determined grain‐scale heterogeneities (from 6 to 88 µg) in the stable carbon and oxygen isotopic compositions (δ13C and δ18O) of the international standard calcite materials (NBS 19, NBS 18, IAEA‐CO‐1, and IAEA‐CO‐8) using a continuous‐flow isotope ratio mass spectrometry (CF‐IRMS) system that realizes a simultaneous determination of the δ13C and the δ18O values with standard deviations (S.D.) of less than 0.05‰ for CO2 gas. Based on the S.D. of the δ13C and δ18O values determined for CO2 gases evolved from the different grains of the same calcite material, we found that NBS 19, IAEA‐CO‐1, and IEAE‐CO‐8 were homogeneous for δ13C (less than 0.10‰ S.D.), and that only NBS 19 was homogeneous for δ18O (less than 0.14‰ S.D.). On the level of single grains, we found that both IAEA‐CO‐1 and IAEA‐CO‐8 were heterogeneous for δ18O (1.46‰ and 0.76‰ S.D., respectively), and that NBS 18 was heterogeneous for both δ13C and δ18O (0.34‰ and 0.54‰ S.D., respectively). Closer inspection of NBS 18 grains revealed that the highly deviated isotopic compositions were limited to the colored grains. By excluding such colored grains, we could also obtain the homogeneous δ13C and δ18O values (less than 0.18‰ and less than 0.16‰ S.D., respectively) for NBS 18. We conclude that NBS 19, IAEA‐CO‐1, or pure grains in NBS 18 are suitable to be used as the standard reference material for δ13C, and that either NBS 19 or pure grains in NBS 18 are suitable to be used as the reference material for δ18O during the grain‐scale isotopic analyses of calcite. Copyright © 2008 John Wiley & Sons, Ltd.
Determination of disulfide bond patterns in laminin β1 chain N‐terminal domains by nano‐high‐performance liquid chromatography/matrix‐assisted laser desorption/ionization time‐of‐flight/time‐of‐flight mass spectrometry
Authors: Kalkhof Stefan , Haehn Sebastian , Ihling Christian , Paulsson Mats , Smyth Neil , Sinz Andrea
Published: May 2008

The disulfide bonding patterns in the N‐terminal (LN) domains of the basement membrane protein laminin β1 have not been investigated so far. We report an in‐depth mass spectrometric analysis using offline nano‐high‐performance liquid chromatography/matrix‐assisted laser desorption/ionization time‐of‐flight/time‐of‐flight mass spectrometry (nano‐HPLC/MALDI‐TOF/TOF‐MS) for determining the disulfide bond patterns in the LN‐domain of recombinant mouse laminin β1 chain for the first time. Mass spectra were recorded and the putatively disulfide‐linked peptides were subjected to LIFT‐TOF/TOF‐MS to confirm the disulfide bond. Screening the fragment ion mass spectra of disulfide‐linked peptides for characteristic 66‐amu patterns (34 u +32 u), arising from symmetric and asymmetric cleavage of disulfide bonds, facilitated their identification. Using various enzymes for proteolytic digestion of a recombinant laminin β1 chain N‐terminal protein fragment, a linear bonding pattern of the eight cysteine residues in the LN‐domain of the laminin β1 chain was observed with a (1‐2, 3‐4, 5‐6, 7‐8) connectivity of cysteines. The identical disulfide‐bonding pattern was found in E4, the N‐terminal laminin β1 chain fragment derived by elastase digestion of mouse tumor laminin‐111, confirming that this pattern also occurs in native laminin. Copyright © 2008 John Wiley & Sons, Ltd.
Identification of the related substances of tilmicosin by liquid chromatography/ion trap mass spectrometry
Authors: Stoev Georgi , Nazarov Valeri
Published: May 2008

Structures of seven impurities of the veterinary drug tilmicosin have been elucidated by multiple fragmentation with ion trap tandem mass spectrometry. All related compounds possess the main lactone ring of tilmicosin. The differences in their structures are due to the hydroxyl, mycaminose, 3,5‐dimethylpiperidine and mycinose groups connected to C3, C5, C6, C14 of the lactone ring, respectively. The following compounds of the impurity profile of tilmicosin were identified: B – tilmicosin with a hydroxyl group at C3; C – tilmicosin without a methyl group at the N‐atom connected to C3 of the mycaminose ring; D – tilmicosin with a hydroxyl group at C6 of the mycaminose ring; E – tilmicosin with a methoxy group at C3, F – desmicosin; G – 20‐dihydrodesmicosin; and H – tilmicosin without a mycaminose ring. Isomers of the compounds B, C, D, E and H were identified by their mass chromatograms and retention times. The concentrations of the impurities varied in the range of 0.1% to 2.9%. Copyright © 2008 John Wiley & Sons, Ltd.
Two‐pulse delayed 532‐nm laser ionization of metals using collinear sub‐threshold beams
Authors: Alcántara José F. , Vadillo José M. , Laserna J. Javier
Published: May 2008

Two frequency‐doubled Nd:YAG lasers collinearly aligned were used to ionize different metals at specific interpulse delays. The beams were independently operated in order to attain full control over the energy. Each laser beam was always set at fluences below the ionization threshold and an evaluation of the effect that the interpulse delay has on the material ionization and the LIMS signal was performed. The different metallic targets studied (Cu, Si, Al, Ti, Fe, 314 AISI stainless steel) exhibit a characteristic ionization feature consisting of a clear enhancement in the ionization yield at interpulse delays around 60 ns when analyzed as pure foils. In addition, an improvement in the spectral resolution is observed at the specific interpulse delay. Our results indicate that proper control of the energy allows optimization of the different steps in the ionization process and they suggest that the effect of the first laser pulse impinging on the surface enhances the way in which the second pulse interacts with the solid. Copyright © 2008 John Wiley & Sons, Ltd.
Succinylmonocholine analytics as an example for selectivity problems in high‐performance liquid chromatography/tandem mass spectrometry, and resulting implications for analytical toxicology
Authors: Kuepper Uta , Musshoff Frank , Madea Burkhard
Published: May 2008

The determination and quantitation of drugs in biological matrices using high‐performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) is becoming increasingly popular in analytical toxicology, while at the same time a growing awareness for the limits of this technique can be observed. Our group previously developed a rapid HPLC/ESI‐MS/MS method for the detection and quantitation of succinylcholine (SUX) and succinylmonocholine (SMC) using ion‐pairing extraction of samples with subsequent separation by gradient chromatography on a Synergi Hydro RP C18 column (4 µm, 150 × 2 mm). Identification of analytes was achieved in the multiple reaction monitoring (MRM) mode, using two characteristic ion transitions each, the respective analytes' retention time as well as co‐elution of stable isotopic analogues.

In both native serum as well as urine an interference with the main MRM transition of SMC was found to co‐elute with this analyte, thus severely compromising the identification and quantitation of this target analyte. The interference was further shown to be eliminated from serum and urine by exposure to alkaline conditions and hence proven to share a key physicochemical property with SMC. The observed absence of the second and third most intense ion transitions of SMC in the unknown substance was the only useful distinction between both compounds.

The detailed presentation of selectivity problems encountered during method development is intended to initiate further discussion on this yet underrepresented issue in HPLC/MS/MS. The present work emphasizes the need to monitor more than just one ion transition to confidently rule out signal interferences, ensure correct analyte identification as well as quantitation, and thus avoid false‐positive results. In this context, the employment of minor MRM transitions for the quantitation and identification of a given analyte is presented as a satisfactory solution to HPLC/MS/MS selectivity problems, and proposed as a possible alternative to previously published approaches. Copyright © 2008 John Wiley & Sons, Ltd.
Atomic force microscopy application for degradation diagnostics in library heritage
Authors: Coluzza Carlo , Bicchieri Marina , Monti Michela , Piantanida Giovanna , Sodo Armida
Published: May 2008

Atomic Force Microscopy was used on pure cotton cellulose paper to characterize the relationship between surface topographies and cellulose degradation patterns. Whatman N.1 chromatography paper and Fabriano Umbria paper artificially aged with different procedures and then naturally aged‐were evaluated together with a sample from an original book. Evidence is found of a clear distinction between surface heights distribution of chiefly oxidised samples with respect to those where hydrolysis is the dominant process. In both cases, deteriorated paper shows surface features well different from the paper in good preservation state, in agreement to results from previous experiments. This is a first step that could open the way to AFM application as a qualitative diagnostic tool for library materials. The only way to achieve such a goal is to extend the experimentation to a wider population of paper samples, so to improve the statistical evaluation. Copyright © 2008 John Wiley & Sons, Ltd.
Mesoporous Silica Nanoparticles Improve Magnetic Labeling Efficiency in Human Stem Cells
Authors: Liu Hon‐Man , Wu Si‐Han , Lu Chen‐Wen , Yao Ming , Hsiao Jong‐Kai , Hung Yann , Lin Yu‐Shen , Mou Chung‐Yuan , Yang Chung‐Shi , Huang Dong‐Ming , Chen Yao‐Chang
Published: May 2008

Tumblerlike magnetic/fluorescein isothiocyanate (FITC)‐labeled mesoporous silica nanoparticles, Mag‐Dye@MSNs, have been developed, which are composed of silica‐coated core–shell superparamagnetic iron oxide (SPIO@SiO2) nanoparticles co‐condensed with FITC‐incorporated mesoporous silica. Mag‐Dye@MSNs can label human mesenchymal stem cells (hMSCs) through endocytosis efficiently for magnetic resonance imaging (MRI) in vitro and in vivo, as manifested by using a clinical 1.5‐T MRI system with requirements of simultaneous low incubation dosage of iron, low detection cell numbers, and short incubation time. Labeled hMSCs are unaffected in their viability, proliferation, and differentiation capacities into adipocytes and osteocytes, which can still be readily detected by MRI. Moreover, a higher MRI signal intensity decrease is observed in Mag‐Dye@MSN‐treated cells than in SPIO@SiO2‐treated cells. This is the first report that MCM‐41‐type MSNs are advantageous to cellular uptake, as manifested by a higher labeling efficiency of Mag‐Dye@MSNs than SPIO@SiO2.
A SERS‐Active Nanocrystalline Pd Substrate and its Nanopatterning Leading to Biochip Fabrication
Authors: Bhuvana Thiruvelu , Kulkarni Giridhar U.
Published: May 2008

Nanocrystalline metallic Pd films have been produced by thermolysis of Pd hexadecanethiolate deposited on a Si surface. The particle size was in the range of 50–60 nm based on electron and atomic force microscopy. The Pd surface produced was found to be surface‐enhanced Raman scattering (SERS) active with an enhancement factor of ≈105. The electron‐resist behavior of Pd thiolate is exploited in conceptualizing a prototype chip with patterned Pd regions that are SERS active, called “SERS bits”, which host different biomolecules.
Fluorescent Bionanoprobes to Characterize Cytoadhesion and Cytoinvasion
Authors: Fillafer Christian , Friedl Daniela S. , Wirth Michael , Gabor Franz
Published: May 2008

To overcome current limitations in diagnostic imaging and targeted drug delivery, a highly versatile tool is presented that can be used to representatively investigate the effects of submicroparticles intended for the use in biological systems. An effective approach to render colloids trackable is developed by stable attachment of the fluorescent probe BODIPY 493/503 (BOD: 4,4‐difluoro‐1,3,5,7,8‐pentamethyl‐4‐bora‐3a,4a‐diaza‐s‐indacene) to a biodegradable and biocompatible particle core matrix. BOD submicroparticles are shown to be stable, can be surface modified, and exhibit high fluorescence emission. Upon conjugation with human serum albumin (nonspecific) and wheat germ agglutinin (biorecognitive) as model ligands explicit differences are found in the cytoadhesive and cytoinvasive characteristics of the submicroparticles using Caco‐2 cells. These results demonstrate the potency of BOD‐labeled colloids as a versatile analytical platform for a multifaceted investigation of cell‐particle interactions in biological systems.
Frictional contact models with local compliance: semismooth formulation
Authors: Pang J.‐S.
Published: May 2008

A complementarity‐based, 3‐dimensional frictional contact model with local compliance and damping was introduced in the Ph.D. thesis [45] and the paper [47] and was subsequently studied extensively in [31, 49]. In this paper, we examine a variant of this model where there is no damping in the normal contact forces but there is coupled stiffness between the normal and tangential forces via body deformations. We show that this frictional contact model admits a formulation as an ordinary differential equation with a boundedly Lipschitz continuous, albeit implicitly defined, semismooth right‐hand side with global linear growth. Several major consequences follow from such a formulation: (a) existence and uniqueness of a continuously differentiable solution trajectory originated from an arbitrary initial state, (b) finite contact forces that are semismooth functions of the system state, (c) semismooth dependence of the trajectory on the initial state, and (d) convergence of a shooting method for solving two‐point boundary problems. The derived results are valid for both a dynamic model and a quasistatic model, the latter being one in which inertia effects are ignored, and for a broad class of friction cones that include the well‐known quadratic Coulomb cone and its polygonal approximations. Part II of this work establishes the absence of Zeno states in such a frictional contact model.
An inverse problem for a linear Schrödinger equation in the presence of inhomogeneities of small volumes
Authors: Khelifi A.
Published: May 2008

In this paper we prove that the knowledge of the partial (on part of the boundary) dynamic boundary measurements for the Schrödinger equation on any open subset Γ of the boundary determines uniquely the potential. Using a global Carleman estimate, we also derive a stability result with appropriate norms provided that Γ satisfies a suitable geometrical condition.
Spectrum of an operator arising elastic system with local K‐V damping
Authors: Xu G.Q. , Mastorakis N.E.
Published: May 2008

In this paper, we analyze the spectrum of an operator arising in elastic system with local K‐V damping, whose vibration is modelled as the Euler–Bernoulli beam. Suppose that the beam is clamped at both ends, at its internal bonded a patch made of smart material that produces the Kelvin–Voigt damping. Our aim is to study the spectrum of the operator determined by such a system. By a detail analysis, we show that the spectrum consists of the point spectrum and continuous spectrum, in which the point spectrum is a denumerable set, and the continuous spectrum is a segment on the real axis. Under certain conditions, the continuous spectrum is possibly the whole half line, and also degenerates possibly one point. For a special case, we give the asymptotic expression of the point spectrum.
Oscillations of a magneto‐sensitive elastic sphere
Authors: Altenbach H. , Brigadnov I.A. , Eremeyev V.A.
Published: May 2008

Magneto‐sensitive (MS) or magnetorheological (MR) elastomers are smart materials whose mechanical properties change instantly by the application of a magnetic field. MS elastomers are widely used in the practice as elements of MEMS (sensors, actuators, etc.), for example, in medical devices. The behavior of MS elastomers under time‐dependent magnetic field is a complex process and till now is not investigated in all details. Here we present the statements of the dynamic boundary‐value problem of a MS elastomer and demonstrate the special features of the dynamic behavior of such system. As an example both the nonlinear and the linear oscillations of a MS elastic sphere are considered. The control of radially symmetric oscillations of MS elastic sphere by a homogeneous magnetic field is investigated. The presented results can be used for control and generation of radially symmetric acoustic waves using magnetic field excitation.
Homotopy analysis of unsteady boundary‐layer flow started impulsively from rest along a symmetric wedge
Authors: Xu H. , Pop I.
Published: May 2008

An investigation of the velocity boundary‐layer growth resulting from an impulsively started wedge is presented in this paper. By introducing a new set of scaled coordinates, the governing equations describing the impulsively set into motion Falkner‐Skan flows is transformed to a partial differential equation but the number of independent variables are reduced from three to two. Note that the new time scaling avoids the appearance of the singularity resulting from the logarithmic function ln(1‐ξ), thus reducing the difficulties of computations. Analytical approximations for the momentum boundary layer are obtained, which are valid for all time. The results are then matched numerically using the Keller‐Box method.
Energy integral in fracture mechanics (J‐integral) and Gauss‐Bonnet Theorem
Authors: Yamasaki K. , Nagahama H.
Published: May 2008

The J‐integral (a path‐independent energy integral) formalism is the standard method of analyzing nonlinear fracture mechanics. It is shown that the energy density of deformation fields in terms of the homotopy operator corresponds to the J‐integral for dislocation‐disclination fields and gives the force on dislocation‐disclination fields as a physical interpretation. The continuum theory of defects gives a natural framework for understanding the topological aspects of the J‐integral. This geometric interpretation gives that the J‐integral is an alternative expression of the well‐known theorem in differential geometry, i.e., the Gauss‐Bonnet theorem (with genus = 1). The geometrical expression of the J‐integral shows that the Eshelby's energy‐momentum (the physical quantity of the material space) is closely related to the Einstein 3‐form (the geometric objects of the material space).
Application of Continuum Damage Mechanics in discontinuous crack formation: Forward extrusion chevron predictions
Authors: Soyarslan C. , Tekkaya A.E. , Akyuz U.
Published: May 2008

Materializing Continuum Damage Mechanics (CDM), numerical modeling of discrete internal cracks, namely central bursts, in direct forward extrusion process is presented. Accordingly, in a thermodynamically consistent setting, a local Lemaitre variant damage model with quasi‐unilateral evolution is coupled with hyperelastic‐plasticity. The formulations are constructed in the principal axes where simultaneous local integration schemes are efficiently developed. To this end, the framework is implemented as ABAQUS/VUMAT subroutine to be used in an explicit FE solution scheme, and utilized in direct forward extrusion simulations for bearing steel, 100Cr6. Discontinuous cracks are obtained with the element deletion procedure, where the elements reaching the critical damage value are removed from the mesh. The periodicity of the cracks shows well accordance with the experimental facts. The investigations reveal that, application of the quasi‐unilateral conditions together with the crack closure parameter has an indispensable effect on the damage accumulation zones by determining their internal or superficial character.
Fatty acids—Synthetic or agrichemical
Authors: Fineberg Herbert
Published: May 2008

Abstract and Summary

The cost of producing fatty acids from agricultural products and the cost of producing them from petroleum and natural gas both depend heavily on the cost and availability of energy. The costs of the agrichemical acids and of the petrochemical acids will probably increase at the same rate in the future. Therefore, the choice of which one to use will depend at least as much on chemical composition and performance as on price.
Historical and marketing trends of natural/synthetic fatty acids
Authors: Johanson Arnold G.
Published: May 2008

Abstract and Summary

As long as a substantial portion of raw materials for natural fatty acids are relatively inexpensive by‐products of other major industries, natural fatty acids should fulfill the world's projected needs at least through 1985. Production of synthetic fatty acids may also increase; however, at the present time the cost of their raw material and processing has made them largely noncompetitive, except in a few cases. Synthetic organic acid manufacturers currently supplying short chain products will continue their efforts to enter the detergent range fatty acid market area. We expect some breakthrough in synthetics during the life of our forecast. However, potential producers have yet to develop an economically competitive synthetic fatty acid as a replacement for natural fatty acids in the U.S. Petroleum‐based products include odd, even, and branched chain acids whose performance must be proven. Finally, the petroleum base for synthetic fatty acids no longer has the price stability we have been accustomed to in the past. Recent changes in price of ethylene and forecasts are evidence of this trends for the future.
Fats and oils in agriculture
Authors: Abramitis W. W.
Published: May 2008

Abstract and Summary

Fats, oils, and their derivatives are reviewed, in their roles as emulsifiers and surfactants and as pesticide derivatives, and in their activity per se. As emulsifiers and surfactants they offer a wide range of hydrophile‐lipophile balance (HLB) values to assist formulators in developing saleable products. Their lipoid solubilities aid in evaporation retardation, plant penetration, and absorption. Often they greatly improve the performance of the active ingredients. Nitrogen derivatives such as amines and quaternaries, fatty alcohols, acid esters, and other agricultural chemicals are reviewed. Examples are cited on the effect of the length of the carbon chain and their number in such herbicides as 2,4‐D and dalapon, as well as the biological properties of various aliphatic groups in insect larvicides, plant growth regulators, and fungicides. The role vegetable oils can play in the looming energy shortages as petroleum oil substitutes is discussed. They offer a challenging future in agricultural applications.
Oxidation of alkenes with use of phase transfer catalysis
Authors: Foglia T. A. , Barr P. A. , Malloy A. J.
Published: May 2008

Abstract and summary

The use of phase transfer catalysis (PTC) as an aid in the oxidation of long chain olefins with aqueous potassium permanganate (KMnO4) in neutral and alkaline media and with aqueous ruthenium tetroxide (RuO4) is reported. The phase transfer catalysts (PTCT) were either quaternary ammonium halides or crown ethers. The long chain olefins studied were 1‐pentadecene, 9‐octadecene, and methyl oleate. PTC not only increases the rate of these reactions but also gives good yields of reaction products. For example,cis‐9‐octadecene in methylene chloride reacted with aqueous KMnO4 to give either dihydroxyoctadecane (80%) or pelargonic, acid (80%) depending upon pH, when tetrabutylammonium bromide was used as the PTCT. When RuO4 in conjunction with a PTCT was used as the oxidant, a quantitative yield of myristic acid was obtained from 1‐pentadecene. The RuO4 oxidant was conveniently regenerated in situ from RuO2 and sodium hypochlorite. This regeneration is facilitated with a PTCT.
Phase transfer agents. I. Transfer of permanganate, periodate, and cyanate ions from aqueous to organic phases. Preparation of quaternary onium periodates
Authors: Okimoto Tomoyuki , Swern Daniel
Published: May 2008

Abstract and Summary

Several quaternary ammonium and phosphonium halides have been shown to be useful phase transfer agents (PTA) for the efficient transport of permanganate, periodate, and cyanate ions from aqueous to organic phases (benzene and/or methylene chloride). Chemical and spectral methods of analysis were used to measure ion transfer quantitatively and to assess the relative efficiency of PTA.
Catalytic hydroformylation and hydrocarboxylation of unsaturated fatty compounds
Authors: Frankel E. N. , Pryde E. H.
Published: May 2008

Abstract and Summary

The two catalyst systems rhodium‐triphenylphosphine and palladium chloride‐triphenylphosphine were investigated for the respective hydroformylation and hydrocarboxylation of oleic acid or ester to produce C‐19 bifunctional compounds. Compared to conventional cobalt carbonyl for making formylstearate, rhodium‐triphenylphosphine permits lower pressures (1000–2000 psi vs. 3000–4000 psi), higher conversions (95% vs. 80%), and no loss of functionality (vs. 15% hydrogenation with cobalt). Although palladium chloride‐triphenylphosphine for hydrocarboxylation introduces the carboxyl function directly into the fatty acid chain, CO pressures of 3000–4000 psi and corrosion‐resistant equipment are necessary. When applied to polyunsaturated fatty acids, both rhodium and palladium catalyst systems have the outstanding advantage of introducing functionality at each double bond position to produce polyformyl‐ and polycarboxystearates. Selected formyl derivatives were converted in excellent yield to acetals, to acids and their esters, to hydroxymethyl compounds and their esters, and also to aminomethyl compounds that could be condensed to polyamides. Several of the esters and acetals were effective primary plasticizers for poly(vinyl chloride) that had outstanding low volatility characteristics. Other applications for these new and highly versatile derivatives included rigid urethane foams, urethane‐modified coatings, ester lubricants, and a shrink‐resist treatment for wool.
Diffusion properties of lipids—Pure and in seeds
Authors: Anderson R. , Osredkar R. , Žagar V.
Published: May 2008

Abstract and Summary

Diffusion constants of some fatty acids and triglycerides in pure form and also in seeds have been measured at different temperatures in order to elucidate the motion and organization of triglyceride molecules in oils. The size of the oil storage cavity (droplet) in seeds has been estimated to be 0.8 μ. Temperature dependences of the proton T1 relaxation time in some samples have been measured by pulsed nuclear magnetic resonance (NMR). From these measurements it is concluded that since activation energies for the relaxation mechanism, diffusion, is the same in seeds as in pure oils, 0.22 eV, the nature of the motion is similar.