bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence of exposure to potentially traumatic events in a healthy birth cohort of very young children in the northeastern United States
Authors: Briggs‐Gowan Margaret J. , Ford Julian D. , Fraleigh Lisa , McCarthy Kimberly , Carter Alice S.
Published: December 2010

Prevalence estimates of very young children's exposure to potentially traumatic events (PTEs) are limited. The study objective was to estimate the lifetime prevalence and correlates of noninterpersonal PTEs and violence exposure in a representative healthy birth cohort (ages 1–3 years) from an urban–suburban region of the United States (37.8% minority, 20.2% poverty). Parents completed 2 surveys approximately 1‐year apart. By 24–48 months of age, the prevalence of exposure was 26.3% (14.5% noninterpersonal, 13.8% violence). Exposure was common among children living in poverty (49.0% overall, 19.7% noninterpersonal, 33.7% violence). The most consistent factors associated with exposure were poverty, parental depressive symptoms, and single parenting. Findings underscore the potential for prevention and intervention in early childhood to advance public health and reduce morbidity.
Electrically Conductive Polymeric Materials with High Stretchability and Excellent Elasticity by a Surface Coating Method
Authors: Li Yongjin , Zhao Liping , Shimizu Hiroshi
Published: December 2010

Electrically conductive polymer films with high stretchability and excellent elasticity were simply fabricated by coating a conductive layer on the surface of an elastomer film. The material used for the conductive layer was a high‐shear processed poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] triblock copolymer (SEBS)/multiwalled carbon nanotubes (MWCNTs) nanocomposite with 20 wt.‐% MWCNTs loading. The nanocomposites were first dissolved in toluene to form a stable solution and then were coated onto the SEBS film by spin coating. The alignment of MWCNTs in the coated layer and the interface between the base film and the coated layer were investigated. It was found that almost all the MWCNTs are aligned parallel to the base film and that there is good adhesion between the two layers. The fabricated films show high electrical conductivity and almost same stretchability and elasticity as the base film. Moreover, the films exhibit extremely high electrical conductive retention after applying high strain.

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Composites of poly(ε‐caprolactone) and Mo6S3I6 Nanowires
Authors: Chin Seow Jecg , Hornsby Peter , Vengust Damjan , Mihailović Dragan , Mitra J. , Dawson Paul , McNally Tony
Published: December 2010

Composites of poly(ε‐caprolactone) (PCL) and molybdenum sulfur iodine (MoSI) nanowires were prepared using twin‐screw extrusion. Extensive microscopic examination of the composites revealed the nanowires were well dispersed in the PCL matrix, although bundles of Mo6S3I6 ropes were evident at higher loadings. Secondary electron imaging (SEI) showed the nanowires had formed an extensive network throughout the PCL matrix, resulting in increased electrical conductivity of PCL, by eight orders of magnitude, and an electrical percolation threshold of 6.5 × 10−3 vol%. Thermal analysis (DSC), WAXD, and hot stage polarized optical microscopy (HSPOM) experiments revealed Mo6S3I6 addition altered PCL crystallization kinetics, nucleation density, and crystalline content. A greater number of smaller spherulites were formed via heterogeneous nucleation. The onset of thermal decomposition (TGA) of PCL decreased by 70°C, a consequence of the thermal degradation of Mo6S3I6 to MoO3, which in turn accelerates the formation of volatile gases during the first stage of PCL decomposition. Copyright © 2010 John Wiley & Sons, Ltd.
Hemophagocytic lymphohistiocytosis associated with precursor B acute lymphoblastic leukemia
Authors: Kelly Caitlin , Salvi Sharad , McClain Kenneth , Hayani Ammar
Published: December 2010

We report a case of a child with precursor‐B acute lymphoblastic leukemia (ALL) who experienced refractory thrombocytopenia and massive splenomegaly during standard induction chemotherapy. He was diagnosed with hemophatocytic lymphohistiocytosis (HLH) during induction. Clinical and laboratory evaluation showed no evidence of infectious cause to HLH. Pancytopenia and HLH persisted after consolidation therapy even with remission from leukemia. After failure to control HLH with ALL‐directed therapy and HLH‐directed therapy, the patient underwent unrelated donor hematopoietic stem cell transplantation 8 months after diagnosis. He is 34 months post‐transplant and in remission from leukemia and HLH. Pediatr Blood Cancer 2011;56:658–660. © 2010 Wiley‐Liss, Inc.
Combustion properties and transference behavior of ultrafine microencapsulated ammonium polyphosphate in ramie fabric‐reinforced poly(L‐lactic acid) biocomposites
Authors: Chen Dakai , Li Jing , Ren Jie
Published: December 2010

Flame‐retardant biocomposites have attracted much attention in past decades. They can provide many advantages, such as total biodegradability and their abundant renewable sources. In the work reported, biocomposites based on poly(L‐lactic acid) (PLLA), ramie fabric (FAB) and microencapsulated ammonium polyphosphate (MCAPP) were synthesized via hot press molding using the powder‐stacking procedure. The effects of transference behavior of the flame retardant on sustaining flame retardancy of the biocomposites were investigated. Thermogravimetric analysis shows that the improved flame retardancy is due to an increased char residue at high temperature. Field emission scanning electron microscopy images and wide‐angle X‐ray diffraction data were used to investigate the hydrolysis reaction and transference behavior of ammonium polyphosphate in the biocomposites. UL‐94 testing and limiting oxygen index measurements show that the PLLA/FAB/MCAPP biocomposites retain their flame retardancy even after 21 days in UV‐irradiation hydrothermal aging tests. The good sustained flame retardancy of the PLLA/FAB/MCAPP biocomposites is attributed to the docking interactions and good distribution of MCAPP in the biocomposites. Copyright © 2010 Society of Chemical Industry
Effects of α‐cyclopropyl on heterocyclic carbenes stability at DFT
Authors: Kassaee M.Z. , Momeni M.R. , Shakib F.A. , Najafi Z. , Zandi H.
Published: December 2010

α‐Cyclopropyl stability impacts on singlet and triplet heterocyclic carbenes with acyclic, cyclic, and cyclic‐unsaturated structures are compared and contrasted to di‐t‐butyl as well as t‐butylcyclopropylcarbenes through appropriate isodesmic reactions at B3LYP/AUG‐cc‐pVTZ level. Substitution of one of the t‐butyl groups of di‐t‐butylcarbene with a cyclopropyl alters the ground state multiplicity from triplet to singlet with a singlet–triplet energy separation (ΔEs–t) of 7.2 kcal/mol. Additional heteroatom substitution increases ΔEs–t values for the resulting α‐heteroatom cyclopropylcarbenes in the following order: amino > oxy > thio > phophino. α‐Cyclopropyl group stabilizes singlet states of all our carbenes two to three times more than their corresponding triplet states. The ΔEs–t values of all the carbenes are increased through cyclization, while the introduction of unsaturation in the rings causes small and rather random changes. To probe the kinetic stability of the species, we calculated the transition states for the opening of cyclopropyl through 1,2‐C shift. Interestingly, the 4.1 kcal/mol energy barrier in cyclopropylcarbene is significantly increased in the presence of heteroatoms to 31.2 kcal/mol for aminocyclopropylcarbene. The reactivity of the species is discussed in terms of nucleophilicity and electrophilicity issues showing our carbenes, especially acyclic ones, more nucleophilic than the common N‐heterocyclic carbenes. Copyright © 2010 John Wiley & Sons, Ltd.
A novel high‐contrast ratio electrochromic material from spiro[cyclododecane‐1,9′‐fluorene]bicarbazole
Authors: Usluer Ozlem , Koyuncu Sermet , Demic Serafettin , Janssen René A. J.
Published: December 2010

A novel electroactive spirocyclododecylfluorene monomer named 2,7‐bis(carbazol‐9‐yl)‐9,9′‐spiro[cyclododecane‐1,9′‐fluorene] (SFC) was synthesized and electrochemically polymerized to give a very stable multi‐electrochromic polymer (poly‐SFC). Two separate oxidation processes were observed for both SFC monomer and poly‐SFC that carries two carbazole units. The polymeric film of poly‐SFC was coated onto ITO/glass surface, and it shows different colors (transparent, yellowish green, green, and dark green) upon stepwise oxidations. An electrochromic device based on poly‐SFC was assembled in the sandwich cell configuration of ITO/poly‐SFC//gel electrolyte//PEDOT/ITO. Poly‐SFC exhibits 90% of transparency at neutral state and a high contrast ratio (ΔT = 58% at 800 nm). This device constructed from it represents a response time of about 1 s, high coloration efficiency (1377 cm2 C–1) and retained its performance by 96.4% even after 1000 cycles. Exhibiting high transparency at neutral state, reversible redox behavior, resistance to overoxidation, and especially high contrast ratio at near IR region can make poly‐SFC be useful and promising candidate for electrochromic applications despite having a relatively slow response time. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010
Distress trajectories at the first year diagnosis of breast cancer in relation to 6 years survivorship
Authors: Lam Wendy W. T. , Shing Yee Ting , Bonanno George A. , Mancini Anthony D. , Fielding Richard
Published: December 2010

Purpose: To explore how initial trajectories of distress experienced during the first year following diagnosis with early‐stage breast cancer (ESBC) relate to subsequent long‐term (6 years) psychosocial outcomes.

Methods: 285/303 Chinese women recruited 1‐week post‐surgery for predominantly ESBC were assessed for distress with the Chinese Health Questionnaire at 1, 4, and 8 months later. Latent growth mixture modeling revealed four distinct distress trajectories during the first 8 months following surgery (Lam et al., 2010). Six years later we reassessed 186 of these 285 women, comparing scores on the Hospital Anxiety and Depression Scale, Impact of Events Scale, and Chinese Social Adjustment Scale by first 8 months' distress trajectory.

Results: Distress trajectories over the first 8 months post‐operatively predicted psychosocial outcomes 6 years later. Women with stable low levels of distress over the first 8 months post‐operatively (resilient group) had the best 6‐year psychosocial outcomes. Women who experienced chronic distress had significantly greater longer‐term psychological distress, cancer‐related distress, and poorer social adjustment in comparison to women in the resilient group. Women in the recovered or delayed‐recovery groups were comparable to those in the resilient group, except for concerns about appearance and sexuality, and self‐image.

Conclusion: Women with an illness trajectory characterized by chronic distress over the first 8 months post‐operatively had poorest longer‐term psychosocial outcomes. Clarification of determinants of chronic distress and means for early identification of at‐risk women are needed. This will enable targeted optimization of interventions to prevent and manage chronic distress, improving ESBC rehabilitation efficiency. Copyright © 2010 John Wiley & Sons, Ltd.
In vivo characterization of renal auto‐antigens involved in human auto‐immune diseases: The case of membranous glomerulonephritis
Authors: Murtas Corrado , Bruschi Maurizio , Carnevali Maria Luisa , Petretto Andrea , Corradini Emilia , Prunotto Marco , Candiano Giovanni , degl'Innocenti Maria Ludovica , Ghiggeri Gian Marco , Allegri Landino
Published: December 2010

Renal auto‐immune diseases represent a major source of morbidity in humans. For many years the knowledge on mechanisms of auto‐immunity involving the kidney has been uniquely based on animal models. However, these findings often could not be readily translated to humans owing to notably difference in antigen expression by human podocytes. One example is Heymann nephritis (HN), the experimental model of human membranous glomerulonephritis (MGN), which is obtained in rats by injecting antibodies against megalin, a protein that is not present in human glomeruli. Human studies could not be done in the past since sequencing required too much material exceeding what obtainable from tissue biopsies in vivo. Research is now on the way to identify auto‐antigens and isolate specific auto‐antibodies in humans. New technology developments based on tissue microdissection and proteomical analysis have facilitated the recent discoveries, allowing direct analysis of human tissue in vivo. Major advances on the pathogenesis of MGN, the prototype for the formation and glomerular deposition of auto‐antibodies, are now in progress. Two independent groups have, in fact, demonstrated the existence of specific IgG4 against phospholipase A2 receptor, aldose reductase and Mn‐superoxide dismutase in glomerular eluates and in plasma of a prominent part of patients with MGN, suggesting a major role of these proteins as auto‐antigens in human MGN. This review will focalize these aspects outlining the contribution of proteomics in most recent developments.
Ulrich Gösele
Authors: Föll Helmut
Published: December 2010

Prof. Dr. Ulrich M. Gösele died unexpectedly and far too early in November 2009. He was invited to present a key paper to the PSST 2010, his untimely death deprived us of that pleasure. At the time of his death Prof. Ulrich Gösele was the director of a very large research department at the Max‐Planck‐Institute for Microstructure Physics in Halle, Germany. He was an outstanding scientist with a distinguished record in many fields, including porous semi‐conductor science and technology. In this contribution a personal account of his life is given, based not only on scientific collaboration but also on a longstanding friend‐ship. He will be remembered not only for his outstanding contributions to science but also as a reliable and witty friend and a highly motivating mentor.

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Prof. Dr. Ulrich M. Gösele

Jan. 26th 1949–Nov. 8th 2009
X‐ray in situ observation of oxygen precipitation in silicon confirmed with ex situ detection methods
Authors: Grillenberger Hannes , Knerer Dieter , Magerl Andreas
Published: December 2010

A focusing Laue diffractometer is used to analyze the strain field in silicon. The source for this so called strain field diffraction (SFD) setup is a high energy X‐ray tube. In the present work this setup is used to monitor the strain generated by growing oxygen precipitates (Bulk Micro Defects, BMDs) in situ at temperatures up to 1000 °C. By choosing appropriate thermal treatments a correlation of the SFD signal with BMD parameters gained with conventional analytic techniques (FT‐IR, infra red light scattering, TEM) is established. From this, the detection limit of the SFD setup for BMDs is determined at a diameter of 7 nm and a density of 1013 cm−3. This range is only covered by TEM so far. Further, the diffracted intensity provides a measure for the level of precipitation occurred.
Continuum simulation of solid phase epitaxial regrowth of amorphized silicon including most advanced physical interactions
Authors: Delalleau Julien , Pakfar Ardechir , Bazizi El‐Medhi , Simola Roberto , Tavernier Clement
Published: December 2010

Solid‐phase‐epitaxial regrowth (SPER) of Si amorphized by ion implantation is considered as a potential solution for the fabrication of highly‐activated ultra‐shallow junctions for future technology nodes of Si CMOS devices. In the frame of 32 and 22 nm technologies node development, SPER occurs after amorphizing implantations used in source/drain regions. To get an accurate simulation of dopant activation and junction depth position, a suitable continuum SPER model, implemented into a commercial simulator, is now mandatory. This TCAD model must consider the different physical effects associated with SPER: silicon regrowth rate, dopants redistribution snow plough effect, and interaction with silicon point defects. In this work, using a previously established model, we have implemented an improved physically based model for SPER and, several formulations have been developed to enable a robust/accurate modeling of the recrystallization velocity. It takes into account the direct interaction between amorphous/crystalline interface kinetics and point defects, and a regrowth rate dependent on temperature. Simulation results of dopant concentration profiles are in good agreement with experimental data and can provide important insight for optimizing the bulk silicon process as well in one dimension as two dimensions.
A stripe with a local gate potential: An efficient magnetometer?
Authors: Louis E. , Chiappe G. , Vergés J. A.
Published: December 2010

Short range impurities are known to produce dips or peaks in the magnetoconductance of a two‐dimensional electron gas. Using a tight‐binding model, we show that the width of those dips can be easily controlled in a system formed by a stripe and a local gate potential.

This opens the possibility of using such a system as an efficient magnetometer capable of measuring tiny changes in the magnetic field, and of tuning sensitivity and measuring range by changing the gate potential.
Correlation of barrier material and quantum‐well number for InGaN/(In)GaN blue light‐emitting diodes
Authors: Chang Jih‐Yuan , Kuo Yen‐Kuang , Tsai Miao‐Chan
Published: December 2010

Optical properties of the InGaN/(In)GaN light‐emitting diodes (LEDs) with varied barrier materials and quantum‐well (QW) numbers are studied numerically. The simulation results show that, for the LEDs with GaN barriers, the single quantum‐well (SQW) structure has the best optical performance. However, for the LEDs with InGaN barriers, the 5‐QW structure has less serious efficiency droop and higher output power at high current than the SQW one, which makes it a better structure for high‐power LEDs. The physical mechanisms of the aforementioned phenomena can be well explained by uniformity of carrier distribution, band‐filling effect, and overlap between the electron and hole wavefunctions.
Hierarchical nanoporous anodic alumina templates by asymmetric two‐step anodization
Authors: Santos A. , Ferré‐Borrull J. , Pallarès J. , Marsal L. F.
Published: December 2010

An asymmetric two‐step anodization process is used to fabricate hierarchical nanoporous anodic alumina templates (HNAATs) with different geometric characteristics. This nanostructure consists of an outer hexagonal lattice of concavities in the interior of which pores grow. The anodization conditions (anodization voltage, and type and concentration of the acid electrolyte) between the first and the second step are considerably varied to obtain different types of templates. Two growth regimes (mild and hard), three types of acid electrolytes (phosphoric, oxalic and sulphuric) and three acid electrolyte concentrations (0.3, 0.2 and 0.1 M) are combined. In addition, the voltage ratio between the second and the first step of the anodization process is ranged from 0.11 to 0.71. By modifying these parameters, it is possible to control the fabrication process and obtain HNAATs with a wide range of morphologies.
Exciton polaritons in ZnO microcavities with different active layer thicknesses
Authors: Kawase Toshiki , Kim DaeGwi , Miyazaki Kenichi , Nakayama Masaaki
Published: December 2010

We have investigated the characteristics of exciton polaritons in ZnO microcavities with different active layer thicknesses. The microcavity was made from a bulk ZnO active layer and two distributed Bragg reflectors (DBRs) consisting of HfO2 and SiO2 layers. We adopted rf magnetron sputtering and pulsed laser deposition for the preparation of the DBR and ZnO active layer, respectively. Angle‐resolved reflectance spectra demonstrate the formation of cavity polaritons. From the analysis using a phenomenological Hamiltonian for the coupling between the cavity photon and three kinds of excitons labeled A, B, and C peculiar to ZnO, the vacuum Rabi‐splitting energies in the λ/2‐microcavity are estimated to be 30, 71, and 84 meV for the A, B, and C excitons, respectively. Moreover, we indicate the potential to control the Rabi‐splitting energy by changing the active layer thickness.
Circularly polarized photoluminescence of insulating InGaAs/GaAs heterostructures with a ferromagnetic Mn δ‐layer in the barrier
Authors: Zaitsev S. V. , Zvonkov B. N.
Published: December 2010

The photoluminescence (PL) of insulating heterostructures containing an InGaAs/GaAs quantum well (QW) and a tunneling close ferromagnetic (FM) Mn δ‐layer in the GaAs barrier has been investigated in detail. We found that a slow increase of a circular polarization degree and a Zeeman splitting of the QW emission band at high, normal to the QW plane, magnetic field B > 1 T, characteristic of non‐magnetic QWs, is preceded at low temperatures by a much faster increase at B < 1 T. The fast increase slows down with increasing temperature and disappears above a Curie temperature of the Mn δ‐layer, which evidences effective p–d exchange interaction of the QW holes with Mn ions in the FM δ‐layer.
Non‐standard anisotropy of the energy spectrum of a layered TlGaSe2 crystal
Authors: Bercha D. M. , Glukhov K. E. , Sznajder M.
Published: December 2010

The ab initio band structure calculations of the TlGaSe2 crystal in the framework of DFT, within LDA were performed using the relevant Brillouin zone for the base‐centered monoclinic lattice. It was shown that the main features of this structure can be obtained in the framework of the elementary energy bands concept, taking into account the existence of the Davydov splitting that is the consequence of structural properties of TlGaSe2.

The obtained results confirm that TlGaSe2 is an indirect band‐gap material, however, an additional local minimum of the conduction band in the Γ point is located both in a near energetic and near k‐space distance from the absolute minimum. It was shown that TlGaSe2 is the next example of a layered semiconductor for which an universal anisotropy of the energy spectrum branches that coincide with its mechanical anisotropy cannot be established.
Photoluminescence and Raman studies on tin dioxide powder and tin dioxide/single‐walled carbon‐nanotube composites
Authors: Gontia I. I. , Baibarac M. , Baltog I.
Published: December 2010

Photoluminescence (PL) and Raman spectroscopy were used to characterize the tin dioxide (SnO2) powder and the SnO2/single‐walled carbon‐nanotube (SWCNT) composites. The SnO2 powder shows a strong PL broad band centered at 1.95 eV (635 nm) under excitation at 280 nm (4.43 eV) and four PL bands peaking at: 1.95 eV (635 nm), 2.67 eV (464 nm), 2.82 eV (439 nm), and 2.98 eV (416 nm) under excitation at 350 nm (3.54 eV). PL decay‐time measurements of the SnO2 powder indicates a PL lifetime of about 1.53 ns. In the SnO2/SWCNT composites, prepared mechanicochemically, a quenching of PL is observed as the concentration of SWCNT increases. The Raman spectra were recorded at two excitation wavelengths: 514.5 and 676.4 nm. At the excitation wavelength of 676.4 nm (1.83 eV), the Raman spectrum shows a narrowed asymmetric profile of the G band (∼1585 cm−1), which indicates that in the SnO2/SWCNT composite there is an interaction between SnO2 and metallic SWCNTs.
Examination of long‐wave radiative bias in general circulation models over North Africa during May–July
Authors: Allan Richard P. , Woodage Margaret J. , Milton Sean F. , Brooks Malcolm E. , Haywood James M.
Published: December 2010

Satellite data are used to quantify and examine the bias in the outgoing long‐wave (LW) radiation over North Africa during May–July simulated by a range of climate models and the Met Office global numerical weather prediction (NWP) model. Simulations from an ensemble‐mean of multiple climate models overestimate outgoing clear‐sky long‐wave radiation (LWc) by more than 20 W m−2relative to observations from Clouds and the Earth's Radiant Energy System (CERES) for May–July 2000 over parts of the west Sahara, and by 9 W m−2for the North Africa region (20°W–30°E, 10–40°N). Experiments with the atmosphere‐only version of the High‐resolution Hadley Centre Global Environment Model (HiGEM), suggest that including mineral dust radiative effects removes this bias. Furthermore, only by reducing surface temperature and emissivity by unrealistic amounts is it possible to explain the magnitude of the bias.

Comparing simulations from the Met Office NWP model with satellite observations from Geostationary Earth Radiation Budget (GERB) instruments suggests that the model overestimates the LW by 20–40 W m−2during North African summer. The bias declines over the period 2003–2008, although this is likely to relate to improvements in the model and inhomogeneity in the satellite time series. The bias in LWc coincides with high aerosol dust loading estimated from the Ozone Monitoring Instrument (OMI), including during the GERBILS field campaign (18–28 June 2007) where model overestimates in LWc greater than 20 W m−2and OMI‐estimated aerosol optical depth (AOD) greater than 0.8 are concurrent around 20°N, 0–20°W. A model‐minus‐GERB LW bias of around 30 W m−2coincides with high AOD during the period 18–21 June 2007, although differences in cloud cover also impact the model–GERB differences. Copyright © Royal Meteorological Society and Crown Copyright, 2010
Determination of distinctive carbohydrate signatures obtained from the Aeromonas hydrophila (chemotype II) core oligosaccharide pinpointing the presence of the 4‐O‐phosphorylated 5‐O‐linked Kdo reducing end group using electrospray ionization quadrupole orthogonal time‐of‐flight mass spectrometry and tandem mass spectrometry
Authors: Sioud Salim , Jahouh Farid , Nashed Mina , Joly Nicolas , Banoub Joseph H.
Published: December 2010

The electrospray quadrupole orthogonal time‐of‐flight mass spectrometric (ESI‐QqTOF‐MS) structural elucidation of the core oligosaccharide of Aeromonas hydrophila (chemotype II) lipopolysaccharide has been investigated and it was demonstrated that it contained an 4‐O‐phosphorylated Kdo reducing end group, which was glycosylated by the remaining outer core oligosaccharide through its O‐5 position. After releasing the core oligosaccharide from the native LPS with acid, the phosphorylated Kdo residue eliminated phosphoric acid, to produce a core oligosaccharide containing a mixture of diastereomeric 4,8‐ and 4,7‐anhydro‐α‐keto acids and an open‐chain olefinic Kdo residue. The characteristic glycone sequence was elucidated by collision‐induced dissociation tandem mass spectrometry (CID‐MS/MS) of the protonated molecule of the native core oligosaccharide.

In addition, the analysis of the Hakomori permethylated core oligosaccharide was carried out by electrospray ionization quadrupole orthogonal time‐of‐flight mass spectrometry (ESI‐QqTOF‐MS) and matrix‐assisted laser desorption/ionization (MALDI)‐QqTOF‐MS analyses. The presence of more than nine isobaric isomers of this core was detected. The CID‐MS/MS analysis of the various protonated permethylated core oligosaccharide molecules showed a similar and diagnostic fragmentation pattern. The over‐methylation of the permethylated core oligosaccharide containing either the 4,7‐ or the 4,8‐anhydro‐α‐keto acid unit and the open‐chain olefinic Kdo unit was reported. It was realized that the extra minor satellite signals obtained in the ESI‐QqTOF‐MS and MALDI‐TOF‐MS analyses were dimethyl sulfoxide (DMSO) stable covalent addition products, which have occurred by a Michael addition on the 4,8‐Kdo exocyclic double bond. The occurrence of this series of covalent addition products during the MS analysis of a permethylated core oligosaccharide should be considered as ‘carbohydrate‐distinctive signatures’ establishing and confirming the presence of a 4‐O‐phosphorylated‐5‐O‐linked Kdo reducing end group. Copyright © 2010 John Wiley & Sons, Ltd.
δ15N of soil N and plants in a N‐saturated, subtropical forest of southern China
Authors: Koba K. , Isobe K. , Takebayashi Y. , Fang Y.T. , Sasaki Y. , Saito W. , Yoh M. , Mo J. , Liu L. , Lu X. , Zhang T. , Zhang W. , Senoo K.
Published: December 2010

We investigated the δ15N profile of N (extractable NH, NO, and organic N (EON)) in the soil of a N‐saturated subtropical forest. The order of δ15N in the soil was EON > NH > NO. Although the δ15N of EON had been expected to be similar to that of bulk soil N, it was higher than that of bulk soil N by 5‰. The difference in δ15N between bulk soil N and EON (Δ15Nbulk‐EON) was correlated significantly with the soil C/N ratio. This correlation implies that carbon availability, which determines the balance between N assimilation and dissimilation of soil microbes, is responsible for the high δ15N of EON, as in the case of soil microbial biomass δ15N. A thorough δ15N survey of available N (NH, NO, and EON) in the soil profiles from the organic layer to 100 cm depth revealed that the δ15N of the available N forms did not fully overlap with the δ15N of plants. This mismatch in δ15N between that of available N and that of plants reflects apparent isotopic fractionation during N uptake by plants, emphasizing the high N availability in this N‐saturated forest. Copyright © 2010 John Wiley & Sons, Ltd.
Limitations of mass spectrometric methods for the characterization of polydisperse materials
Authors: Herod Alan A.
Published: December 2010

This paper is a review of work on the characterization of coal liquids and petroleum residues and asphaltenes over several decades in which various mass spectrometric methods have been investigated. The limitations of mass spectrometric methods require exploration in order to understand what the different analytical methods can reveal about environmental pollution by these kinds of samples and, perhaps more importantly, what they cannot reveal.

The application of mass spectrometry to environmental problems generally requires the detection and determination of the concentration of specific pollutants released into the environment by accident or design. The release of crude petroleum or coal liquids into the environment can be detected and tracked during biodegradation processes through specific chemicals such as alkanes or polyaromatic hydrocarbons (PAHs). However, petroleum asphaltenes are polydisperse materials of unknown mass range and chemical structures and, therefore, there are no individual chemicals to detect. It is necessary to determine methods of detection and the ranges of mass of such materials. This can only be achieved through fractionation to reduce the polydispersity of the initial sample. Comparison of mass spectrometric results with results from an independent analytical method such as size‐exclusion chromatography with a suitable eluent is advisable to confirm that all the sample has been detected and mass discrimination effects avoided. Copyright © 2010 John Wiley & Sons, Ltd.
Minimization of sample requirement for δ18O in benzoic acid
Authors: Hagopian William M. , Jahren A. Hope
Published: December 2010

The measurement of the oxygen stable isotope content in organic compounds has applications in many fields, ranging from paleoclimate reconstruction to forensics. Conventional High‐Temperature Conversion (HTC) techniques require >20 µg of O for a single δ18O measurement. Here we describe a system that converts the CO produced by HTC into CO2 via reduction within a Ni‐furnace. This CO2 is then concentrated cryogenically, and 'focused' into the isotope ratio mass spectrometry (IRMS) source using a low‐flow He carrier gas (6–8 mL/min). We report analyses of benzoic acid (C7H6O2) reference materials that yielded precise δ18O measurement down to 1.3 µg of O, suggesting that our system could be used to decrease sample requirement for δ18O by more than an order of magnitude. Copyright © 2010 John Wiley & Sons, Ltd.
Role of 2‐oxo and 2‐thioxo modifications on the proton affinity of histidine and fragmentation reactions of protonated histidine
Authors: Lam Adrian K. Y. , Hutton Craig A. , O'Hair Richard A. J.
Published: December 2010

A combination of electrospray ionisation (ESI), multistage and high‐resolution mass spectrometry experiments was used to compare the gas‐phase chemistry of the amino acids histidine (1), 2‐oxo‐histidine (2), and 2‐thioxo‐histidine (3). Collision‐induced dissociation (CID) of all three different proton‐bound heterodimers of these amino acids led to the relative gas‐phase proton affinity order of: histidine >2‐thioxo‐histidine >2‐oxo‐histidine. Density functional theory (DFT) calculations confirm this order, with the lower proton affinities of the oxidised histidine derivatives arising from their ability to adopt the more stable keto/thioketo tautomeric forms. All protonated amino acids predominately fragment via the combined loss of H2O and CO to yield a1 ions. Protonated 2 and 3 also undergo other small molecule losses including NH3 and the imine HN=CHCO2H. The observed differences in the fragmentation pathways are rationalised through DFT calculations, which reveal that while modification of histidine via the introduction of the oxygen atom in 2 or the sulfur atom in 3 does not affect the barriers against the loss of H2O+CO, barriers against the losses of NH3 and HN=CHCO2H are lowered relative to protonated histidine. Copyright © 2010 John Wiley & Sons, Ltd.
Ionspray microchip
Authors: Pól Jaroslav , Kauppila Tiina J. , Franssila Sami , Kotiaho Tapio , Kostiainen Risto
Published: December 2010

An ionspray microchip is introduced. The chip is based on the earlier presented nebulizer microchip that consists of glass and silicon plates bonded together. A liquid inlet channel, nebulizer gas inlet, and nozzle are etched on the silicon plate and a platinum heater is integrated on the glass plate. The nebulizer microchip has been previously used in atmospheric pressure chemical ionization, atmospheric pressure photoionization, sonic spray ionization, and thermospray ionization modes. In this work we show that the microchip can be operated also in ionspray mode by introducing high voltage to the silicon plate of the microchip. The effects of operation parameters (voltage, nebulizer gas pressure, sample solution flow rate, solvent composition, and analyte concentration) on the performance of the ion spray microchip were studied. Under optimized conditions the microchip provides efficient ionization of small and large compounds and good quantitative performance. The feasibility of the ion spray microchip in liquid chromatography/mass spectrometry (LC/MS) was demonstrated by the analysis of tryptic peptides of bovine serum albumin. Copyright © 2010 John Wiley & Sons, Ltd.
Electron ionisation mass spectrometry of the pentafluoropropionate esters of trichothecene analogues and culmorin compounds from Fusarium species
Authors: Langseth Wenche , Rundberget Thomas , Uhlig Silvio
Published: December 2010

This paper reports the mass spectra, obtained after electron ionisation (EI) at 70 eV, of 34 trichothecenes and five culmorin compounds after acylation with pentafluoropropionic anhydride. The derivatised fungal metabolites were separated by gas chromatography, and the mass spectra were obtained by scanning of a single quadrupole mass filter in the scan range m/z 200‐900. The fragmentation pathways of three trichothecenes (triacetyl‐deoxynivalenol, 4,15‐diacetoxy‐scirpenol, T‐2 toxin) have been studied in more detail by linked scan – high‐resolution mass spectrometry. The most common trichothecenes are today more often routinely analysed using LC/MS‐based methodologies. However, EI‐MS may give complementary structural information, and the data that are summarised in this article may help to identify analogues of one of the largest class of mycotoxins, the tricothecenes, as well as culmorin compounds that are commonly co‐produced by Fusarium culmorum and F. graminearum in cultures or naturally contaminated samples. Copyright © 2010 John Wiley & Sons, Ltd.
Quantitation of a de‐fluorinated analogue of Casopitant Mesylate by normal‐phase liquid chromatography/mass spectrometry
Authors: Dams Riet , Bernabe Elena , Nicoletti Anna , Loda Claudio , Martini Luca , Papini Damiano
Published: December 2010

The introduction of Quality by Design (QbD) in Drug Development has resulted in a greater emphasis on chemical process understanding, in particular on the origin and fate of impurities. Therefore, the identification and quantitation of low level impurities in new Active Pharmaceutical Ingredients (APIs) play a crucial role in project progression and this has created a greater need for sensitive and selective analytical methodology. Consequently, scientists are constantly challenged to look for new applications of traditional analytical techniques. In this context a normal‐phase liquid chromatography/electrospray ionization mass spectrometry (LC/ESI‐MS) method was developed to determine the amount of a de‐fluorinated analogue impurity in Casopitant Mesylate, a new API under development in GlaxoSmithKline, Verona. Normal‐phase LC provided the selectivity needed between our target analyte and Casopitant, while a single quadrupole mass spectrometer was used to ensure the sensitivity needed to detect the impurity at <0.05%w/w. Standard solutions and samples were prepared in heptane/ethanol (50:50, v/v) containing 1% of 2 M NH3 in ethanol; the mobile phase consisted of heptane/ethanol (95:5, v/v) with isocratic elution (flow rate: 1.0 mL/min, total run time: 23 min). To allow the formation of ions in solutions under normal‐phase (apolar) conditions, a post‐column infusion of a solution of 0.1% v/v of formic acid in methanol was applied (flow rate: 200 µL/min). The analysis was carried out in positive ion mode, monitoring the impurity by single ion monitoring (SIM). The method was fully validated and its applicability was demonstrated by the analysis of real‐life samples. This work is an example of the need for selective and accurate methodology during the development of a new chemical entity in order to develop an appropriate control strategy for impurities to ultimately ensure patient safety. Copyright © 2010 John Wiley & Sons, Ltd.
Analysis of epoxyeicosatrienoic acids by chiral liquid chromatography/electron capture atmospheric pressure chemical ionization mass spectrometry using [13C]‐analog internal standards
Authors: Mesaros Clementina , Lee Seon Hwa , Blair Ian A.
Published: December 2010

The metabolism of arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs) is thought to be mediated primarily by the cytochromes P450 (P450s) from the 2 family (2C9, 2C19, 2D6, and 2J2). In contrast, P450s of the 4 family are primarily involved in omega oxidation of AA (4A11 and 4A22). The ability to determine enantioselective formation of the regioisomeric EETs is important in order to establish their potential biological activities and to asses which P450 isoforms are involved in their formation. It has been extremely difficult to analyze individual EET enantiomers in biological fluids because they are present in only trace amounts and they are extremely difficult to separate from each other. In addition, the deuterium‐labeled internal standards that are commonly used for stable isotope dilution liquid chromatography/mass spectrometry (LC/MS) analyses have different LC retention times when compared with the corresponding protium forms. Therefore, quantification by LC/MS‐based methodology can be compromised by differential suppression of ionization of the closely eluting isomers. We report the preparation of [13C20]‐EET analog internal standards and the use of a validated high‐sensitivity chiral LC/electron capture atmospheric pressure chemical ionization (ECAPCI)‐MS method for the trace analysis of endogenous EETs as their pentafluorobenzyl (PFB) ester derivatives. The assay was then used to show the exquisite enantioselectivity of P4502C19‐, P4502D6‐, P4501A1‐, and P4501B1‐mediated conversion of AA into EETs and to quantify the enantioselective formation of EETs produced by AA metabolism in a mouse epithelial hepatoma (Hepa) cell line. Copyright © 2010 John Wiley & Sons, Ltd.
Structural characterization and identification of oleanane‐type triterpene saponins in Glycyrrhiza uralensis Fischer by rapid‐resolution liquid chromatography coupled with time‐of‐flight mass spectrometry
Authors: Zheng Yun‐Feng , Qi Lian‐Wen , Zhou Jian‐Liang , Li Ping
Published: December 2010

Oleanane‐type triterpene saponins (OTS) are major active ingredients in Glycyrrhiza uralensis. In this work, a rapid‐resolution liquid chromatography with time‐of‐flight mass spectrometry (RRLC/TOF‐MS) method has been developed to characterize and identify OTS from G. uralensis. The major diagnostic ions and fragmentation pathways from thirteen OTS have been characterized for the first time. At a low fragmentor voltage of 120 V in positive ion mode, the precursor ion [M + H]+ or/and [M + Na]+ was obtained for accurate determination of molecular formula. When the fragmentor voltage was increased to 425 V, abundant characteristic fragment ions were observed for structural characterization. Neutral losses of sugar moieties, such as glucuronic acid (GlcA, 176 Da), glucose (Glc, 162 Da) and rhamnose (Rha, 146 Da), were commonly observed in the MS spectra for prediction of the sugar number and sequences. Other typical losses included AcOH (60 Da), CH2O (30 Da), 2 × H2O (2 × 18 Da) and HCOOH (46 Da) from [Aglycone + H–H2O]+ (named [B]+), corresponding to the presence of a C22‐acetyl group, C24‐hydroxyl group, C22‐hydroxyl group or C30‐carboxyl group on the aglycone moiety, respectively. In particular, characteristic ring cleavages of the aglycone moieties on A‐ and B‐rings were observed. Based on the fragmentation patterns of reference compounds, nineteen OTS have been identified in an extract of G. uralensis, thirteen of which were unambiguously identified and the other six were tentatively assigned. Copyright © 2010 John Wiley & Sons, Ltd.
o‐(Pentafluorobenzyloxycarbonyl)benzoyl chloride: a novel electrophoric derivatisation reagent for amino compounds designed for negative ion chemical ionisation mass spectrometry
Authors: Leis Hans J. , Windischhofer Werner
Published: December 2010

The synthesis of a novel electrophoric derivatisation reagent, o‐(pentafluorobenzyloxycarbonyl)benzoyl chloride, is described. The reagent was tested against selected primary and secondary amino compounds as analytical targets. The derivatives exhibit excellent mass spectral properties under negative ion chemical ionisation (NICI), i.e. reduced fragmentation and thus high ion current for the targeted m/z during analysis. Since the reagent bears a pentafluorobenzyl ester group, resulting mass NICI mass spectra were expectedly dominated by dissociative resonance electron capture typically observed with these compounds. The reagent is suitable for detecting volatile primary and secondary amines with high sensitivity. Background is reduced by a shift in detected m/z and retention time, as demonstrated for the analysis of the drug methylphenidate from human plasma. Copyright © 2010 John Wiley & Sons, Ltd.
Mass spectrometric characterization of black tea thearubigins leading to an oxidative cascade hypothesis for thearubigin formation
Authors: Kuhnert Nikolai , Drynan J. Warren , Obuchowicz Jaczek , Clifford Michael N. , Witt Matthias
Published: December 2010

Thearubigins are the most abundant group of phenolic pigments found in black tea, accounting for an estimated 60–70% of the solids in a typical black tea infusion. Fifty years ago the term thearubigins was first introduced and to date the chemical nature of the thearubigins remains largely unresolved, if not mysterious, despite numerous attempts made to clarify their structure. Thearubigins isolated from 15 commercial black teas have been analyzed using a strategy combining standard chemical characterization along with a series of modern complementary mass spectrometry techniques, including MALDI‐TOF‐MS, FTICR‐MS, LC/TOF‐MS and LC/MS/MS. Fifteen molecular formulas have been matched to constituents of fresh tea leaf that have survived processing and 21 to dimeric transformation products such as theasinensins, theaflavins, theaflavates, theanaphthoquinones, theacitrins and oolongtheanins, which were further confirmed by ESI MS/MS. MALDI‐TOF‐MS data revealed an average of 5000 additional thearubigin components in the mass range between m/z 1000 to 2100 clearly defining the molecular weight range of the thearubigin fraction. Six selected samples have for the first time been analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR‐MS). FT‐ICR‐MS data revealed the presence of a maximum of 9428 peaks in the mass range 300 to 1000 m/z and molecular formulas were assigned to 1517 of them. Data interpretation strategies developed for petrolomics studies (van Krevelen and Kendrick analyses) have for the first time been applied to black tea thearubigins and a novel interpretation protocol has been developed to refine these procedures for the investigation of complex mixtures, leading to a novel hypothesis for the formation and structure of the black tea thearubigins named oxidative cascade hypothesis. Copyright © 2010 John Wiley & Sons, Ltd.
Azo‐group reduction during the matrix‐assisted laser desorption/ionization process in the presence of 2,5‐dihydroxybenzoic acid
Authors: Svoboda Martin , Kodíček Milan
Published: December 2010

Some time ago, we published an announcement that the azo group that closes model cyclic peptides is often reduced in matrix‐assisted laser desorption/ionization mass spectrometry (MALDI MS) in the presence of 2,5‐dihydroxybenzoic acid (2,5‐DHB) as the matrix. In this work, we demonstrate that these peptides are ionized in all DHB matrix isomers, although threshold ionization laser energies as well as the reduction ratios differ in each matrix. Using a NALDI plate, we confirmed that their reduction depends on the presence of DHB matrix and that the hydrogen atoms participating in the reaction come from the DHB matrix hydroxyl group. We show that the reduction ratio is affected by the overall covalent structure of the peptide, by the presence of a free carboxyl group in DHB matrix, by the mutual position of the hydroxyl and carboxyl groups, as well as the laser beam intensity. Based on these results, it can be concluded that the azo‐group reduction in cyclic peptides is a very complex process and we are far from fully understanding its nature. We hope that our experimental results will help to shed some light on the MALDI process that still remains mysterious in some of its aspects. Copyright © 2010 John Wiley & Sons, Ltd.
Multiple levels of PKR inhibition during HIV‐1 replication
Authors: Clerzius Guerline , Gélinas Jean‐François , Gatignol Anne
Published: December 2010

Recent therapeutic approaches against HIV‐1 include IFN in combination therapy for patients with coinfections or as an alternative strategy against the virus. These treatment options require a better understanding of the weak efficacy of the IFN‐stimulated genes, such as the protein kinase RNA‐activated (PKR), which results in viral progression. Activated PKR has a strong antiviral activity on HIV‐1 expression and production in cell culture. However, PKR is not activated upon HIV‐1 infection when the virus reaches high levels of replication, due to viral and cellular controls. PKR is activated by low levels of the HIV‐1 trans‐activation response (TAR) RNA element, but is inhibited by high levels of this double‐stranded RNA. The viral Tat protein also counteracts PKR activation by several mechanisms. In addition, HIV‐1 replicates only in cells that have a high level of the TAR RNA binding protein (TRBP), a strong inhibitor of PKR activation. Furthermore, increased levels of adenosine deaminase acting on RNA (ADAR1) are observed when HIV‐1 replicates at high levels and the protein binds to PKR and inhibits its activation. Finally, the PKR activator (PACT) also binds to PKR during HIV‐1 replication with no subsequent kinase activation. The combination of all the inhibiting pathways that prevent PKR phosphorylation contributes to a high HIV‐1 production in permissive cells. Enhancing PKR activation by counteracting its inhibitory partners could establish an increased innate immune antiviral pathway against HIV‐1 and could enhance the efficacy of the IFN treatment. Copyright © 2010 John Wiley & Sons, Ltd.