bluuebunny/crossref_metadata_2025_split huggingface dataset:
13C NMR chemical shifts of carbonyl groups in substituted benzaldehydes and acetophenones: substituent chemical shift increments
Authors: Patterson‐Elenbaum Stephanie , Stanley John T. , Dillner Debra K. , Lin Shirley , Traficante Daniel 
Published: June 2006

Abstract13C NMR Substituent chemical shift (SCS) increments have been determined for the carbonyl carbon of a variety of substituted benzaldehydes and acetophenones. The 13C NMR chemical shift of the carbonyl carbon can be predicted for many di‐ and trisubstituted benzaldehydes and acetophenones through simple additivity of the SCS increments. The magnitude and sign of the SCS increments have been explored using Hartree‐Fock 6‐31G* calculations to determine the natural atomic charges of the carbonyl carbon. When a substituent capable of intermolecular hydrogen bonding is present, deviations from additivity on the order of 2 ppm are observed in dilution experiments; deviations of up to 6 ppm can result from intramolecular hydrogen bonding. Copyright © 2006 John Wiley & Sons, Ltd.
Alignment effect of attapulgite on the mechanical properties of poly(vinyl alcohol)/attapulgite nanocomposite fibers
Authors: Peng Zhiqin , Chen Dajun 
Published: June 2006

AbstractPoly(vinyl alcohol) (PVA)/attapulgite (AT) nanocomposite fibers have been prepared by wet spinning. The morphology and mechanical properties of the modified PVA fibers have been characterized with transmission electron microscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), birefringence measurements, and mechanical testing. The PVA/AT nanocomposite fibers show much higher tensile strength, initial modulus, and work to break than pure PVA fibers with the same draw ratio. SEM observations demonstrate that the AT nanorods can align orderly along the fiber axis by stretching and have good adhesion to the fiber matrix. The results of birefringence measurements prove that the modified fibers have higher orientation than pure PVA fibers after stretching. The results of DSC analysis indicate that the crystallinity of the PVA fibers can be increased by the addition of AT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1995–2000, 2006
Elastic and piezoelectric properties of gadolinium calcium oxoborate GdCa4O(BO3)3 crystal
Authors: Pawlaczyk C. , Markiewicz E. , Kłos A. , Hofman W. , Pajączkowska A. 
Published: June 2006

AbstractGadolinium calcium oxoborate, GdCa4O(BO3)3 (GdCOB), single crystals were grown by the Czochralski technique. The orientation of crystal was precisely determined. To estimate the complete matrices of the elastic (13) and piezoelectric (10) coefficients measurements of the complex electrical impedance for 26 suitably chosen crystal cuts were made. The step‐by‐step procedure of this estimation is described in details and the possible errors are calculated and discussed. The results are compared with the published data of other authors. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Physical properties of CdS thin films grown by pulsed laser ablation on conducting substrates: effect of the thermal treatment
Authors: Vigil‐Galán O. , Vidal‐Larramendi J. , Escamilla‐Esquivel A. , Contreras‐Puente G. , Cruz‐Gandarilla F. , Arriaga‐Mejía G. , Chavarría‐Castañeda M. , Tufiño‐Velázquez M. 
Published: June 2006

AbstractStructural, morphological and optical properties of CdS films, deposited by the pulsed laser ablation technique on SnO2:F/glass substrates, were studied as a function of time deposition. Up to our knowledge the properties of these films grown onto conducting polycrystalline substrates have not been reported before. The photoluminescence measurements showed the existence of an exciton peak at room temperature, as an indication of good crystalline quality of the layers. A thermal treatment was applied to the samples in a 100 mT Ar atmosphere at 400 °C for 30 min after the deposition of a CdCl2 layer on them. Films characterization was carried out through X‐ray diffraction, photoluminescence and atomic force microscopy measurements. The structural, optical and morphological properties as a function of growth parameters are presented and discussed. Thermal treatment makes uniform the grain size in the samples, with a tendency to increase the grain size average. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Smooth anodic TiO2 nanotubes: annealing and structure
Authors: Macak Jan M. , Aldabergerova Saule , Ghicov Andrei , Schmuki Patrik 
Published: June 2006

AbstractThe influence of an annealing process on the structure and the composition of smooth high aspect ratio TiO2 nanotube layers, grown by anodization of Ti in viscous glycerol electrolytes containing fluorides, is reported. XRD and HRTEM measurements demonstrate that the as‐formed high aspect ratio TiO2 nanotubes have an amorphous structure that can be entirely transformed to single phase – anatase – upon thermal annealing at 450 °C for 3 hours. XPS and EDX analyses furthermore show that annealing process is accompanied with an elimination of fluoride ions (present in the structure after formation). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Contribution of dislocations to carrier recombination and transport in highly excited ELO and HVPE GaN layers
Authors: Malinauskas T. , Jarašiūnas K. , Aleksiejunas R. , Gogova D. , Monemar B. , Beaumont B. , Gibart P. 
Published: June 2006

AbstractNonequilibrium carrier dynamics has been investigated in ELO and HVPE grown GaN layers in a wide temperature and excitation range by using the time‐resolved picosecond FWM technique. Carrier lifetime in the samples at 300 K increased up to 2.8–5.1 ns in accordance with the decreasing threading dislocation density from 4 × 107 cm–2 (ELO) to mid 106 cm–2 in HVPE layers. At T < 100 K, the hyperbolic shape of FWM kinetics indicated carrier density dependent radiative lifetimes, which gradually decreased at lower temperatures to a few hundreds of ps. The dominance of bimolecular recombination in HVPE layers at 10–40 K was demonstrated by the exposure characteristic of FWM, that has shown a sublinear growth of carrier density with excitation, N ∝ I1/2. Numerical fitting of the set of FWM kinetics at various T confirmed the temperature dependence of bimolecular recombination coefficient B ∝ T–1.5 and provided its value B = 2 × 10–11 cm3/s at 300 K and 3.2 × 10–9 cm3/s at 9 K. The measured bipolar diffusion coefficients allowed determination of carrier diffusion length of 0.8–1 μm at 300 K and its dependence on dislocation density and temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Undoped and rare‐earth doped GaN quantum dots on AlGaN
Authors: Hori Yuji , Andreev Thomas , Florian Thomas , Bellet‐Amalric Edith , Le Si Dang Daniel , Tanaka Mitsuhiro , Oda Osamu , Daudin Bruno 
Published: June 2006

AbstractWe study the self organized growth of GaN quantum dots deposited by molecular beam epitaxy on AlxGa1–xN, with x varying between 1 and 0.21. As a result of the specific strain relaxation mechanism of AlxGa1–xN on AlN, it is found that dots can be formed for an Al content as low as about 30%. Monopolar devices have been realized by depositing Schottky contacts on n‐type doped Al0.5Ga0.5N. Finally, electroluminescence of Eu‐doped GaN quantum dots embedded in n‐type Al0.5Ga0.5N has been demonstrated, emphasizing the potentialities of such an active layer for room temperature visible light emission. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman and transmission electron microscopy characterization of InN samples grown on GaN/Al2O3 by molecular beam epitaxy
Authors: Arvanitidis J. , Katsikini M. , Ves S. , Delimitis A. , Kehagias Th. , Komninou Ph. , Dimakis E. , Iliopoulos E. , Georgakilas A. 
Published: June 2006

AbstractRaman spectroscopy and transmission electron microscopy were employed to study the vibrational properties and the microstructure of epitaxially grown InN films on GaN/Al2O3 templates. The variations of the InN lattice constants, as deduced by electron diffraction analysis, along with the red‐shifted E22 mode frequency reveal that InN films exhibit residual tensile stress, strongly dependent on the epilayer growth temperature. Threading dislocations are the dominant structural defects in the films, having a density in the order of 109–1010 cm–2. Profile analysis of the E22 Raman peak by means of the Spatial Correlation Model provides useful information concerning the effective mean length for free phonon propagation (L), which is a measure of the structural quality of the samples. In all the studied samples, L monotonically increases with decreasing threading dislocation density of pure screw and mixed type character. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of AlN nanowires by metal organic chemical vapour deposition
Authors: Cimalla V. , Foerster Ch. , Cengher D. , Tonisch K. , Ambacher O. 
Published: June 2006

AbstractAlN nanowires with a diameter of 20 nm were grown stochastically by the vapour‐liquid‐solid (VLS) method. At low temperatures below 1000 °C the Kirkendall effect during the alloying of aluminium and the catalyst resulted in the formation of three‐dimensional nanostructures like lamellas and nano flowers. The high temperatures above 1000 °C, which are necessary to grow the nanowires complicate the control of their formation. Small catalyst droplets of 20 nm diameter are not stable due to their evaporation. Thus, in contrast to the classical approach to grow a single nano wire out of one droplet, we grew dense networks of nanowires inside larger 3D structures with diameters up to 5 µm. Depending on the growth temperature and the droplet geometry the nanowires inside of these networks are connected by angles of 90° (“cubic”) or 120° (“hexagonal”). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low density GaN quantum dots on AlGaN
Authors: Pakuła K. , Bożek R. , Surowiecka K. , Stępniewski R. , Wysmolek A. , Baranowski J. M. 
Published: June 2006

AbstractA new method of the growth of low‐density GaN quantum dots on AlGaN by MOVPE is reported. The method bases on in‐situ etching of the AlGaN surface in the presence of silane (SiH4) and subsequent growth of randomly nucleated GaN nano‐crystallites. Investigation of successive growth stages with atomic force microscopy (AFM) shows that density of the GaN crystallites is of the order of 108 cm–2. Micro‐photoluminescence (µPL) measurements show sharp emission lines originating from single quantum dots without any artificial masks or mesa structures. This gave unique possibility for advanced studies on optical and electrical properties of single GaN quantum dots in AlGaN. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of high‐In‐content InGaN multiple quantum disk nanocolumns on Si(111) by RF plasma‐assisted molecular‐beam epitaxy
Authors: Kouno Tetsuya , Kikuchi Akihiko , Kishino Katsumi 
Published: June 2006

AbstractSelf‐organized InxGa1–xN nanocolumns with high‐In‐contents of x = 0.86–1.0 and In0.86Ga0.14N/ In0.79Ga0.21N multiple quantum disk (MQD) nanocolumns were successfully grown on Si(111) substrates by rf plasma‐assisted molecular beam epitaxy. The InxGa1–xN nanocolumns showed room‐temperature photoluminescence (RT‐PL) emission and the emission peak wavelength varied from 1500 to 1920 nm with increasing In content from 0.86 to 1.0. The In0.86Ga0.14N/In0.79Ga0.21N MQD nanocolumns showed a satellite peak in X‐ray diffraction spectra that indicates the growth of a good periodic structure. RT‐PL emission was also observed and the emission peak wavelength shifted from 1450 to 1620 nm with changing In0.86Ga0.14N well layer thickness from 1.5 to 3.0 nm. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure and role of ultrathin AlN layers for improving optical activation of rare earth implanted GaN
Authors: Wójtowicz T. , Gloux F. , Ruterana P. , Nouet G. , Bodiou L. , Braud A. , Lorenz K. , Alves E. 
Published: June 2006

AbstractIn this work we carry out characterization of GaN implanted with Tm and Eu ions by scanning and transmission electron microscopy. Structural investigation is supported by optical measurements. We have investigated samples implanted at room temperature with different energies (150–300 keV) and fluences (1–7 × 1015 at/cm2). High temperature annealing was performed at 1200 °C and 1300 °C with the GaN surface protected by a 10nm thick AlN cap grown by MOCVD prior to the implantation. Direct implantation in GaN, results in the formation of a high density of stacking faults in the damaged surface layer and a nanocrystalline surface layer when a critical dose is exceeded. Implanting through the AlN capping layer prevents the formation of the nanocrystalline layer even for high fluences but the stacking faults are still generated. The AlN cap also protects the surface during high temperature annealing. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transition energies and Stokes shift analysis for In‐rich InGaN alloys
Authors: Schley P. , Goldhahn R. , Winzer A. T. , Gobsch G. , Cimalla V. , Ambacher O. , Rakel M. , Cobet C. , Esser N. , Lu H. , Schaff W. J. 
Published: June 2006

AbstractThe absorption and emission properties of In‐rich InGaN alloys were studied by spectroscopic ellipsometry and photoluminescence spectroscopy, respectively. Films grown on a GaN buffer layer show a much sharper increase of the imaginary part of the dielectric function around the band gap and a slightly reduced Stokes shift compared to layers grown directly on AlN buffers. It is attributed to a reduced electron concentration and improved structural quality of the films. By fitting the third derivatives of the dielectric functions up to 9.5 eV we determine for the first time the compositional dependences (bowing param‐eters) of the transition energies for at least four critical points of the band structure. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN/AlGaN superlattices for optoelectronics in the mid‐infrared
Authors: Guillot F. , Monroy E. , Gayral B. , Bellet‐Amalric E. , Jalabert D. , Gérard J.‐M. , Dang Le Si , Tchernycheva M. , Julien F. H. , Monnoye S. , Mank H. 
Published: June 2006

AbstractIn this work we discuss the optical properties of a GaN/Al0.11Ga0.89N multiple‐quantum‐well structure grown on 4H‐SiC by plasma‐assisted molecular‐beam epitaxy. Photoluminescence lines related to the fundamental and excited electronic levels are identified, in good agreement with simulations of the electronic structure. Temperature dependence studies reveal an anomalous behaviour with quenching of the e1–hh1 while the e2–hh1 line becomes dominant at room temperature. This behaviour could be explained by the increasing thermal population of the e2 state and the higher radiative efficiency of the e2–hh1 transition compared to the e1–hh1 transition due to the intense electric field in the well. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray diffraction reciprocal lattice space mapping of a‐plane AlGaN on GaN
Authors: Tsuda Michinobu , Furukawa Hiroko , Honshio Akira , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu 
Published: June 2006

AbstractIn this study, the anisotropic strain in a‐plane AlGaN on GaN was investigated by X‐ray diffraction (XRD) analysis using AlGaN/GaN heterostructure grown on r‐plane sapphire. An a‐plane GaN layer is compressively strained, particularly in the m‐axis direction. According to XRD reciprocal lattice space mapping, the AlGaN layer was strained under tensile stress and grown almost coherently to the underlying GaN layer. The tensile stress in the AlGaN layer in the c‐axis direction is approximately 1.7 times larger than that in the m‐axis direction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum transport in high mobility AlGaN/GaN 2DEGs and nanostructures
Authors: Schmult S. , Manfra M. J. , Sergent A. M. , Punnoose A. , Chou H. T. , Goldhaber‐Gordon D. , Molnar R. J. 
Published: June 2006

AbstractHigh mobility two‐dimensional electron systems in GaN/AlGaN heterostructures have been realized by plasma assisted molecular beam epitaxy on GaN templates. In the density range of 1011 cm–2 to 1012 cm–2, mobility values exceeding 160000 cm2/Vs have been achieved. Scattering mechanisms that presently limit the production of higher mobility samples are discussed. We present results of a systematic study of the weak localization and antilocalization corrections to the classical conductivity at very low magnetic fields. The unambiguous observation of a conductivity maximum at B = 0 suggests that spin–orbit scattering is not negligible in GaN heterostructures as one might expect for a wide‐bandgap system. We have recently realized electron transport through GaN nanostructures. We report on the transport properties of the first quantum point contacts (QPCs) in GaN. These devices are used to study one‐dimensional transport in the Nitride system. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A‐plane (11$ \bar 2 $0) InN growth on nitridated R‐plane (10$ \bar 1 $2) sapphire by ECR‐MBE
Authors: Kumagai Y. , Tsuyuguchi A. , Naoi H. , Araki T. , Na H. , Nanishi Y. 
Published: June 2006

AbstractA‐plane (11$ \bar 2 $0) InN has been successfully grown on R‐plane (10$ \bar 1 $2) sapphire substrate by electron cyclotron resonance (ECR) plasma‐exited molecular beam epitaxy through substrate nitridation process. The substrate nitridation of R‐plane sapphire by ECR nitrogen plasma was carried out at 430 °C for 10 and 15 min. The results of reflection high‐energy electron diffraction (RHEED), X‐ray diffraction (XRD), and scanning electron microscopy indicated the formation of A‐plane InN on R‐plane sapphire. Inclusion of cubic InN was also observed together with A‐plane InN through RHEED and XRD measurements in case of A‐plane InN layer grown on 10 min nitridated substrate. However, when the nitridation time of R‐plane sapphire by ECR nitrogen plasma increased to 15 min, it is confirmed that formation of cubic InN was successfully suppressed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of single non‐polar GaN quantum dots
Authors: Rol F. , Gayral B. , Founta S. , Daudin B. , Eymery J. , Gérard J.‐M. , Mariette H. , Dang Le Si , Peyrade D. 
Published: June 2006

AbstractWe present a microphotoluminescence study of non polar GaN/AlN quantum dots (QDs) grown along the [11$ \bar 2 $0] axis. Despite the high QD density, single exciton lines could be isolated on the high energy side of the spectral distribution of the QD array emission. Linewidths down to 0.5 meV are reported, which is one order of magnitude lower than previously reported linewidths for polar GaN/AlN QDs. This difference is attributed to the drastic reduction of the internal field in non‐polar quantum dots. Temperature dependent measurements were performed up to 180 K. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Paramagnetic resonance of Shungite – a natural nano‐structured carbonaceous material
Authors: Yablokov M. Yu. , Augustyniak‐Jabłokow M. A. , Kempiński W. , Stankowski J. , Yablokov Yu. V. 
Published: June 2006

AbstractShungites Sh‐III and Sh‐IV (∼50% and 20% of carbon) have been studied by X‐band EPR method in the range 4.2–293 K. The week signal of Dyson shape (a /b = 2.25–2.40) observed from a bulk sample of Sh‐III has been observed to transform into an intensive Lorentzian line (ΔB = 1.99 mT, g = 2.0020) after sample grinding. The number of EPR responsible spins (2 × 1019 g–1) and the depth of penetration δ (∼60 µm) have been estimated. The shape of the signals (Dysonian or Lorentzian) is independent of T . ΔB and the g values decrease below 80 K to 1.15 mT and 2.0012. The signal intensity is independent of T down to 150 K. Isolated complexes of C60(C70)–n with K+(Na+) have been found in Sh‐IV. Analysis of the EPR spectra has been made taking into consideration the properties of the conductive materials such as metals and graphite. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Use of electrospray ionization mass spectrometry for the study of Ln(III) complexation and extraction speciation with calixarene‐CMPO in the fuel partitioning concept
Authors: Lamouroux C. , Rateau S. , Moulin C. 
Published: June 2006

AbstractThe calixarene‐bearing CMPO groups belong to a family of extracting agents recently developed for nuclear reprocessing. These molecules exhibit specific properties to separate actinides(III) from lanthanides(III) in nitric acid solution. Speciation of two distinct calixarene‐CMPO (carbamoyl phosphine oxide), substituted either in the wide rim or in the narrow rim with lanthanides (La, Eu, Yb), was undertaken. The complexation behaviour in single phase or in liquid‐liquid extraction was examined with two different electrospray spectrometer source geometries. The stoichiometries of the different complexes were reported and the selectivity of these calixarenes towards lanthanides was determined. The results obtained were concordant for the two spectrometers and confirm that electrospray mass spectrometry is a useful tool to study non‐covalently bonded complexes. Copyright © 2006 John Wiley & Sons, Ltd.
Determination of calcium in complex samples using functional magnetic beads combined with electrodeless/sheathless electrospray ionization mass spectrometry
Authors: Wu Yi‐Ting , Chen Yu‐Chie 
Published: June 2006

AbstractConventionally, electrospray ionization ion trap mass spectrometry (ESI‐ITMS) is not used for the analysis of metal ions because metal ions may be of too low mass to be trapped by the mass analyzer. Furthermore, metal ions can easily precipitate during ESI processes because of their poor volatilities. We present an approach for solving these two problems using milk as the sample to demonstrate the feasibility of using ESI‐ITMS as the detection method for metal ions. Iron oxide magnetic beads with nitrilotriacetic acid (NTA) immobilized on their surface were used as affinity probes for calcium ions from dairy drinks. Ethylenediaminetetraacetic acid (EDTA) was used for the elution of the metal ions chelated by NTA on the beads. The EDTA eluent was analyzed by electrodeless/sheathless ESI‐ITMS. The use of functional magnetic beads to trap metal ions from complex samples can effectively reduce the interference from sample matrix. Using the EDTA eluent as the sample avoids the problem of the low volatility of metal ions during ESI‐ITMS analysis. This method gives measurements of calcium ions in dairy drinks quantitatively very close to the true values (<4% error). Copyright © 2006 John Wiley & Sons, Ltd.
The metabolism and excretion of 2‐methylaminoethoxycarbonyl‐4,4′‐dimethoxy‐5,6,5′,6′‐dimethylenedioxybiphenyl‐2′‐carboxylic acid (DDB‐S) in rats and human
Authors: Yoo Hye Hyun , Son Junghyun , Lee Jaeick , Kim Nam Sun , Shin Myungyoup , Kang Min‐Jung , Kim Dong‐Hyun 
Published: June 2006

AbstractThe metabolism and excretion of 2‐methylaminoethoxycarbonyl‐4,4′‐dimethoxy‐5,6,5′,6′‐dimethylenedioxybiphenyl‐2′‐carboxylic acid (DDB‐S) were investigated in both rats and humans using liquid chromatography/electrospray ion trap mass spectrometry (LC/ESI‐MS/MS). In rats, DDB‐S was rapidly eliminated from the body after a single 50 mg/kg intravenous injection, with urine being a major excretion route. DDB‐S was metabolically stable; approximately 96% of the administered dose was recovered in the form of the parent compound. Nevertheless, 12 metabolites were detected in the urine and feces collected from DDB‐S‐treated rats. The structural characterizations of the metabolites were elucidated from the MSn spectral analysis. Because DDB‐S has a pseudo‐symmetrical methylenedioxy biphenyl structure, regioselective deuterium‐substituted DDB‐S (d5‐DDB‐S) was used to assign the metabolic modification. The major metabolic pathways of DDB‐S were identified as demethylenation of the methylenedioxy moiety, O‐demethylation of the methoxy moiety and glucuronidation. In addition, N‐demethylation of the methylaminoethyl group was also detected as a minor reaction. Copyright © 2006 John Wiley & Sons, Ltd.