bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solution‐phase submonomer diversification of aza‐dipeptide building blocks and their application in aza‐peptide and aza‐DKP synthesis
Authors: Bourguet Carine B. , Proulx Caroline , Klocek Sophie , Sabatino David , Lubell William D. 
Published: May 2010

AbstractAza‐peptides have been used as tools for studying SARs in programs aimed at drug discovery and chemical biology. Protected aza‐dipeptides were synthesized by a solution‐phase submonomer approach featuring alkylation of N‐terminal benzophenone semicarbazone aza‐Gly‐Xaa dipeptides using different alkyl halides in the presence of potassium tert‐butoxide as base. Benzophenone protected aza‐dipeptide tert‐butyl ester 31c was selectively deprotected at the C‐terminal ester or N‐terminal hydrazone to afford, respectively, aza‐dipeptide acid and amine building blocks 36c and 40c, which were introduced into longer aza‐peptides. Alternatively, removal of the benzophenone semicarbazone protection from aza‐dipeptide methyl esters 29a–c led to intramolecular cyclization to produce aza‐DKPs 39a–c. In light of the importance of aza‐peptides and DKPs as therapeutic agents and probes of biological processes, this diversity‐oriented solution‐phase approach may provide useful tools for studying peptide science. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.
Design optimization of quantum cascade laser structures at λ ∼ 11–12 µm
Authors: Ko Yeong Hwan , Yu Jae Su 
Published: May 2010

AbstractBy a simulation optimization technique, we design In0.53Ga0.47As/In0.52Al0.48As quantum cascade laser (QCL) structures, based on a four‐quantum well (QW) active region. The design of QCL structures is performed by maximizing an objective function, i.e., $z_{{\rm UL}}^2 (1 - \tau _{\rm L} /\tau _{{\rm UL}} )\tau _{\rm U}$, related to the optical gain, including dipole matrix element ($z_{{\rm UL}}$) and population inversion between subbands. For a specific lasing wavelength, each barrier/well layer in the active region can be optimized to maximize the objective function, which results from the increase in the dipole matrix element and the reduction in the lifetime ratio of $\tau _{\rm L} /\tau _{{\rm UL}}$, by an iterative procedure. The optimized QCL structures are obtained for the target wavelengths from 11 to 12 µm by a step of 0.5 µm. For a QCL structure operating at λ = 11.98, it exhibits the maximized objection function of 6.30 ps‐nm2 with a large dipole matrix element under an electric field of 45 kV/cm. The influence of the percent variation of thickness in In0.53Ga0.47As and In0.52Al0.48As layers by the change in growth rate on the lasing wavelength and objective function is also investigated.
Photoluminescent properties of the monoclinic Ba2MgSi2O7:Eu2+ phosphor prepared by the combustion‐assisted synthesis method
Authors: Yao Shanshan , Li Yuanyuan , Xue Lihong , Yan Youwei 
Published: May 2010

AbstractA blue–green emitting phosphor of the monoclinic Ba2MgSi2O7:Eu2+ was prepared by the combustion‐assisted synthesis method and an efficient bluish‐green emission under from ultraviolet to visible light was observed. The luminescence, crystallinity and particle sizes were investigated by using luminescence spectrometry, X‐ray diffractometry (XRD) and scanning electron microscopy (SEM). The emission spectrum shows a single intensive band centered at 498 nm, which corresponds to the 4f65d1 → 4f7 transition of Eu2+. The excitation spectrum is a broad extending from 260 to 465 nm, which matches the emission of ultraviolet light‐emitting diodes (UV‐LEDs). The critical quenching concentration of Eu2+ in Ba2MgSi2O7:Eu2+ phosphor is about 0.05 mol. The corresponding concentration quenching mechanism is verified to be a dipole–dipole interaction. The result indicates that Ba2MgSi2O7:Eu2+ can be potentially useful as a UV radiation‐converting phosphor for white light‐emitting diodes (LEDs).
Understanding colorations in PbMoO4 crystals through stoichiometric variations and annealing studies
Authors: Tyagi M. , Singh S. G. , Singh A. K. , Gadkari S. C. 
Published: May 2010

AbstractIn this paper, we report on PbMoO4 crystals grown from melts of controlled stoichiometric variations under different ambient conditions. It is observed that PbMoO4 crystals of different shades not only differ in their impurity contents but their stoichiometries with regard to both cationic and anionic compositions could be different. Annealing studies in air/oxygen as well as in vacuum were carried out on the crystals for a better understanding of the defect centers responsible for the coloration. The role of nonstoichiometric giving rise to coloration is also described.
Vacancy‐mediated room‐temperature ferromagnetism in Zn1−xMnxO thin films
Authors: Gopalakrishnan N. , Balakrishnan L. , Srimathy B. , Kumar M. Senthil , Balasubramanian T. 
Published: May 2010

AbstractThe effect of oxygen vacancies on ferromagnetism (FM) in Zn1−xMnxO thin films grown by radio frequency (RF) sputtering has been investigated. The grown films at different oxygen pressures have been characterized by X‐ray diffraction (XRD), Hall effect, photoluminescence (PL) and vibrating sample magnetometry (VSM). The observed ferromagnetism/diamagnetism by the VSM measurement due to the variation of oxygen vacancies has been confirmed by XRD, PL, and Hall results. The vacancy‐mediated FM has been explained by the formation of magnetic polarons.
Role of postannealing temperature on the microstructure of Al2O3/ZnO thin films grown by atomic layer deposition for TFT applications
Authors: Jang Yong Woon , Bang Seokhwan , Jeon Hyeongtag , Lee Jeong Yong 
Published: May 2010

AbstractIn this study, the effects of postannealing on ZnO and Al2O3 films grown for a thin‐film transistor (TFT) by the atomic layer deposition (ALD) method were examined using transmission electron microscopy (TEM) and energy‐dispersion spectroscopy. Samples were subjected to rapid thermal annealing for 30 s at 610, 615, 620, and 800 °C in a N2 atmosphere. At these temperatures, the polycrystalline ZnO layer in a TFT channel rapidly degraded to amorphous, and in the Al2O3 layer of a gate oxide layer of the TFT, a ZnAl2O4 spinel structure was formed because of Al and Zn diffusion. This spinel structure was observed to be independently nucleated, and there were no specific postgrowth crystallographic orientation relations. Additionally, in electrical properties of ZnO‐TFTs with ZnO/Al2O3 layers, typical TFT characteristics was shown until the annealing temperature increased to 600 °C, and the Vth gradually decreased from 4.2, 3 to 1.8 V. However, in the 700 °C annealed case, the TFT devices are always opened, and the ZnAl2O4 generation and the ZnO layer degradation was related to the drastic changes of these ZnO‐TFTs characteristics. During postannealing, rapid degradation of the ZnO channel layer and phase transformation by means of diffusion should be carefully considered.
Charge order quenching, Griffiths phase, and magnetotransport in polycrystalline Pr0.58Ca0.42−ySryMnO3 thin films
Authors: Agarwal Vasudha , Singh M. P. , Siwach P. K. , Fournier P. , Singh H. K. 
Published: May 2010

AbstractWe report the magneto‐electrical properties of polycrystalline Pr0.58Ca0.42−ySryMnO3 thin films as function of Sr doping (y). These films (thickness ∼300 nm) prepared by spray pyrolysis on LaAlO3 (100) single crystalline substrates are single phase and have orthorhombic structure. The Sr free films show charge ordering (CO) transition at TCO ≈ 240 K and the magnetic ground state has metamagnetic nature akin to the cluster glass (CG). Sr doping quenches CO and induces paramagnetic–ferromagnetic (PM–FM) transition with a systematic destabilization of the CG state. The PM–FM transition occurs at TC ≈ 182, 218, and 250 K for y = 0.06, 0.12, and 0.22, respectively. The Sr doping induced CO quenching also gives rise to the Griffiths phase (GP) at a temperature TG > TC. The resistivity of the Sr free films shows insulating behavior typical to the CO state. An insulator–metal transition (IMT) is observed at TIM ≈ 198 K in the y = 0.06 film, which increases to 225 and 265 K at y = 0.12 and 0.22, respectively. At y = 0.12, the sharpest IMT that results in huge temperature coefficient of resistivity (TCR) ≈19%, suggests the occurrence of a bicritical state. The bicriticality is also supported by a huge low field magnetoresistance ≈40% at 3 kOe and colossal magnetoresistance ≈90% at moderate magnetic field of 10 kOe. The destabilization of the CO, the appearance of GP, and the bicritical state has been explained in terms of the phase fluctuations induced by Sr doping dependent quenched disorder.
Preface: Phys. Status Solidi C 7/5
Authors: Kulik Tadeusz , Oleszak Dariusz 
Published: May 2010

AbstractEvery year in September, the European Materials Research Society organizes the Fall Meeting at War‐saw University of Technology. The 2009 Meeting was held from 14 to 18 September. This issue of physica status solidi contains proceedings of the Symposium H: Bulk Amorphous and Nanocrystalline Materials.Amorphous and nanocrystalline alloys represent a unique group of materials exhibiting better or new properties in comparison with traditional polycrystal‐line materials. However, in many cases their applica‐tion is limited due to the small volume of the fabri‐cated alloys as a consequence of the technological processes. Recently, new types of alloys and new processing routes have appeared which enable the production of amorphous and nanocrystalline alloys and their composites in bulk form. They provide new technological potential for novel applications. The second main topic of the symposium was fabrication of bulk nanostructured materials by severe plastic de‐formation techniques. The symposium also highlighted advances in the development of nanoparticles with a special focus on fabrication methods, technologies and properties.The symposium brought together researchers from various fields, including contributions from ma‐terials science and engineering, physics, chemistry, electronics and manufacturing.We would like to take the opportunity to thank the Co‐Organizers of this symposium R. Yavari, J. Eckert and P. Svec. We also thank everyone in‐volved in the organization of this meeting: the Local Organizing Committee, the reviewers and especially all the participants whose contributions assured the high scientific level of this symposium (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tilt of InGaN layers on miscut GaN substrates
Authors: Kryśko M. , Domagala J. Z. , Czernecki R. , Leszczynski M. , Perlin P. , Suski T. , Grzanka Sz. , Targowski G. , Grzegory I. , Boćkowski M. , Porowski S. 
Published: May 2010

AbstractWe report on the crystallographic orientation of InGaN layers grown on GaN substrates with a miscut with respect to c ‐planes up to 2.5°. The samples were examined using high‐resolution X‐ray diffraction (HRXRD) and atomic force microscopy (AFM). Because of the large (up to about 2% in this study) lattice mismatch between InGaN and GaN, an additional tilt between the c lattice planes of InGaN and GaN was observed and explained by using the Nagai model [J. Appl. Phys. 45, 3789 (1974)]. We observed that for part of the samples, this tilt is about 10% smaller compared to the one predicted by the model. The experimental data are important for understanding the microstructure of InGaN layers grown on substrates of non‐perfect morphology. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The survival of glycine in interstellar ices: A coupled investigation using NEXAFS experiments and theoretical calculations
Authors: Lattelais M. , Risset O. , Pilme J. , Pauzat F. , Ellinger Y. , Sirotti F. , Silly M. , Parent Ph. , Laffon C. 
Published: May 2010

AbstractComplex organic molecules have been observed in the interstellar medium in comets and meteorites. Among these compounds are the building blocks that may have led to prebiotic systems and ultimately to the origin of life. In the panspermia hypothesis, the survival and the transfer of the amino acids from space to planets is a necessary condition for the appearance of life, and, especially, their resistance to the solar UV radiation in ice is a key issue. The case of glycine, which is the smallest molecule in the amino acid family, is presented here. To improve our knowledge on the decomposition mechanisms of glycine, we have undertaken a coupled experimental and computational study. On the one hand, it has been performed a near‐edge X‐ray absorption spectroscopy (NEXAFS) study at the oxygen K‐edge of solid glycine and of glycine diluted into H2O ice, and irradiated at 30 K with soft X‐rays. However, extensive quantum chemical simulations using density functional theory have been realized at the B3LYP/cc‐pVQZ level. A systematic investigation of the most plausible fragmentations has been performed for neutral glycine itself, ionized glycine, doubly ionized glycine, protonated glycine, and zwitterionic glycine, the well known stable form of glycine trapped in ices. We show that glycine easily decomposes under irradiation. Water does not enhance or protect glycine from photodecomposition, but it increases the production of CO2 in the secondary photoreactions. The concentration of glycine tends to a limit of ∼30% of the initial load in the ice. The role of water ice appears to be that of a containment environment allowing the fragments to remain close, thus leading to reformation of glycine in situ. Under these conditions, it can be concluded that glycine is partially, but not entirely, protected by ice during its journey to the Earth. It is a strong point to be credited to the panspermia hypothesis. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Normalized mass mapping of Orbitrap data to define complex, polyglycerol‐based raw material compositions
Authors: Strife Robert J. , Mangels Michele L. 
Published: May 2010

AbstractKendrick Mass Mapping of complex sample compositions, via data derived by Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) at 1 000 000 resolution, is becoming more common. The Orbitrap mass spectrometer (Fourier Transform Axially Harmonic Orbital Trapping) also uses FT methods and indirect detection, though operating at a maximum resolution of 100 000. We define the more general case of Normalized Mass Mapping to any repeating oligomer unit (e.g., C3H6O2) and apply it to Orbitrap‐based mapping of a complex polyglycerol ester, 'green' raw material. Mass measurement errors showed sub‐ppm precision and accuracy in many cases, parameters that are critical to obtaining well‐defined maps. Map‐derived, raw‐material‐characterization parameters such as iodine value are compared with wet‐chemical results and show reasonable agreement for our purposes. The methodology appears applicable to raw material control and eliminates wet chemical methods. Copyright © 2010 John Wiley & Sons, Ltd.
The application of gas chromatography/atmospheric pressure chemical ionisation time‐of‐flight mass spectrometry to impurity identification in Pharmaceutical Development
Authors: Bristow Tony , Harrison Mark , Sims Martin 
Published: May 2010

AbstractAccurate mass measurement (used to determine elemental formulae) is an essential tool for impurity identification in pharmaceutical development for process understanding. Accurate mass liquid chromatography/mass spectrometry (LC/MS) is used widely for these types of analyses; however, there are still many occasions when gas chromatography (GC)/MS is the appropriate technique. Therefore, the provision of robust technology to provide accurate mass GC/MS (and GC/MS/MS) for this type of activity is essential. In this report we describe the optimisation and application of a newly available atmospheric pressure chemical ionisation (APCI) interface to couple GC to time‐of‐flight (TOF) MS.To fully test the potential of the new interface the APCI source conditions were optimised, using a number of standard compounds, with a variety of structures, as used in synthesis at AstraZeneca. These compounds were subsequently analysed by GC/APCI‐TOF MS. This study was carried out to evaluate the range of compounds that are amenable to analysis using this technique. The range of compounds that can be detected and characterised using the technique was found to be extremely broad and include apolar hydrocarbons such as toluene. Both protonated molecules ([M + H]+) and radical cations (M+.) were observed in the mass spectra produced by APCI, along with additional ion signals such as [M + H + O]+.The technique has been successfully applied to the identification of impurities in reaction mixtures from organic synthesis in process development. A typical mass accuracy of 1–2 mm/zunits (m/z 80–500) was achieved allowing the reaction impurities to be identified based on their elemental formulae. These results clearly demonstrate the potential of the technique as a tool for problem solving and process understanding in pharmaceutical development. The reaction mixtures were also analysed by GC/electron ionisation (EI)‐MS and GC/chemical ionisation (CI)‐MS to understand the capability of GC/APCI‐MS relative to these two firmly established techniques. Copyright © 2010 John Wiley & Sons, Ltd.
Carbon isotope fractionation of benzene and toluene by progressive evaporation
Authors: Shin Woo‐Jin , Lee Kwang‐Sik 
Published: May 2010

AbstractEvaporation is one of the key attenuation processes for near‐surface volatile organic compounds (VOCs) in the upper soil zone. Evaporation experiments were performed to investigate the carbon isotope fractionation of benzene and toluene during progressive and non‐equilibrium evaporation at room temperature. Considerable carbon isotope fractionation occurred during evaporative enrichment of benzene and toluene. The carbon isotope compositions of residual compounds increased exponentially with increasing evaporation. Thus, the remaining liquids become isotopically heavier, and the process follows a Rayleigh trend. This result is compatible with the direction of isotopic changes associated with both microbial degradation and volatilization of hydrocarbons previously observed in soil columns, but shows exactly the opposite behavior to previous equilibrium volatilization findings. Copyright © 2010 John Wiley & Sons, Ltd.
Identification of explosives and explosive formulations using laser electrospray mass spectrometry
Authors: Brady John J. , Judge Elizabeth J. , Levis Robert J. 
Published: May 2010

AbstractMass analysis is demonstrated for the detection of sub‐microgram quantities of explosive samples on a metallic surface at atmospheric pressure using laser electrospray mass spectrometry (LEMS). A non‐resonant femtosecond duration laser pulse vaporizes native samples for subsequent electrospray ionization and transfer into a time‐of‐flight mass spectrometer. LEMS was used to detect 2,3‐dimethyl‐2,3‐dinitrobutane (DMNB), 1,3,5‐trinitroperhydro‐1,3,5‐triazine (RDX), 3,4,8,9,12,13‐hexaoxa‐1,6‐diazabicyclo[4.4.4]tetradecane (HMTD), and 3,3,6,6,9,9‐hexamethyl‐1,2,4,5,7,8‐hexaoxacyclononane (TATP) deposited on a steel surface. LEMS was also used to directly analyze composite propellant materials containing an explosive to determine the molecular composition of the explosive pellets at atmospheric pressure. Copyright © 2010 John Wiley & Sons, Ltd.
A solvent‐free matrix application method for matrix‐assisted laser desorption/ionization imaging of small molecules
Authors: Goodwin R. J. , MacIntyre L. , Watson D. G. , Scullion S. P. , Pitt A. R. 
Published: May 2010

AbstractMatrix application continues to be a critical step in sample preparation for matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI). Imaging of small molecules such as drugs and metabolites is particularly problematic because the commonly used washing steps to remove salts are usually omitted as they may also remove the analyte, and analyte spreading is more likely with conventional wet matrix application methods. We have developed a method which uses the application of matrix as a dry, finely divided powder, here referred to as dry matrix application, for the imaging of drug compounds. This appears to offer a complementary method to wet matrix application for the MALDI‐MSI of small molecules, with the alternative matrix application techniques producing different ion profiles, and allows the visualization of compounds not observed using wet matrix application methods. We demonstrate its value in imaging clozapine from rat kidney and 4‐bromophenyl‐1,4‐diazabicyclo(3.2.2)nonane‐4‐carboxylic acid from rat brain. In addition, exposure of the dry matrix coated sample to a saturated moist atmosphere appears to enhance the visualization of a different set of molecules. Copyright © 2010 John Wiley & Sons, Ltd.
Depth profiling by cluster projectiles as seen by computer simulations
Authors: Postawa Z. , Rzeznik L. , Paruch R. , Russo M. F. , Winograd N. , Garrison B. J. 
Published: May 2010

AbstractMolecular dynamics computer simulations are used to probe the development of the surface morphology and the processes that determine the depth resolution in depth profiling experiments performed by secondary ion and neutral mass spectrometry (SIMS/SNMS). The Ag(111) surface is irradiated by an impact of 20‐keV Au3, C60 and Ar872 clusters that represent a broad range of cluster projectiles used in SIMS/SNMS experiments. Improvements in the simulation protocol including automation and optimal sample shape allow for at least 1000 consecutive impacts for each set of initial conditions. This novel approach allows to shrink the gap between single‐impact simulations and real experiments in which numerous impacts are used. Copyright © 2010 John Wiley & Sons, Ltd.
Geospatial visualization with VisTracks
Authors: Eick Stephen G. 
Published: May 2010

AbstractRecently with the widespread emergence of personal navigation devices and growth of mobile networks, large quantities of time‐stamped, location data have become available. To analyze real‐time spatial movement data, we have developed a Web 2.0 platform called VisTracks®. The platform includes spatial servers for generating maps, performing navigation, and tracking moving assets and a flexible Silverlight visual analytics web client. Using VisTracks, it is possible to develop rich visual analytics web applications for understanding location, movement, tracking, and analytics through time. Copyright © 2010 John Wiley & Sons, Inc.This article is categorized under:

Statistical and Graphical Methods of Data Analysis > Statistical Graphics and Visualization
[Sn9HgSn9]6–: An Intermetalloid Zintl Ion with Two Sn9 Connected by Heteroatom
Authors: Yong Li , Boeddinghaus M. Bele , Fässler Thomas F. 
Published: May 2010

AbstractThe title compound [K([2,2,2]crypt)]12[Sn9]2[Sn9HgSn9] has been obtained by reaction of elemental mercury with the binary phase K4Sn9 in ethylenediamine after addition of [2,2,2]crypt and layering with toluene. The X‐ray single crystal analysis shows that the compound consists of two isolated Sn9 clusters and two Sn9 clusters connected by a mercury atom.