bluuebunny/crossref_metadata_2025 huggingface dataset:
Interleukin‐6 signalling regulates vascular endothelial growth factor‐C synthesis and lymphangiogenesis in human oral squamous cell carcinoma
Authors: Shinriki Satoru , Jono Hirofumi , Ueda Mitsuharu , Ota Kazutoshi , Ota Tomoko , Sueyoshi Takanao , Oike Yuichi , Ibusuki Mutsuko , Hiraki Akimitsu , Nakayama Hideki , Shinohara Masanori , Ando Yukio
Published: May 2011

Lymph node metastasis is associated with resistance to conventional therapy and poor survival of patients with oral squamous cell carcinoma (OSCC). Although lymphangiogenesis is well known to be associated with the occurrence of lymph node metastasis in various cancers, the precise mechanisms of lymphangiogenesis in OSCC are largely unknown. IL‐6, a potent pro‐inflammatory cytokine, has been shown to play active roles in various cancers, including OSCC. This study aimed to investigate the involvement of IL‐6 signalling in lymphatic metastasis and to evaluate the efficacy of tocilizumab, a humanized anti‐human IL‐6 receptor antibody, as an anti‐lymphangiogenic agent for OSCC. This investigation confirmed that levels of expression of IL‐6 protein and VEGF‐C mRNA in OSCC tissues were significantly correlated with lymph node metastasis in patients with OSCC, as assessed by immunohistochemical analysis and real‐time quantitative RT–PCR. In vitro studies showed that IL‐6 regulated VEGF‐C mRNA expression in a human OSCC cell line, SAS cells, through the phosphoinositide 3‐kinase‐Akt pathway. In addition, treatment with tocilizumab led to markedly reduced VEGF‐C mRNA expression and OSCC‐related lymphangiogenesis in SAS xenografts. Together, these data suggest that tocilizumab acted as expected: it inhibited lymph node metastasis in OSCC by reducing tumour lymphangiogenesis. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Ultra‐low concentration Na2CO3/NaHCO3 solution for texturization of crystalline silicon solar cells
Authors: Montesdeoca‐Santana Amada , Jiménez‐Rodríguez Etaín , González‐Díaz Benjamín , Borchert Dietmar , Guerrero‐Lemus Ricardo
Published: May 2011

In this work, a novel diluted carbonate/bicarbonate solution was applied for texturization of monocrystalline silicon for solar cells. The content of reactants in the solution was decreased 20 times with respect to the previously optimum found by our group and 12 times with respect to the lowest values reported in the literature as optimum. The use of this low‐cost and nonhazardous solution, free of additives as isopropyl alcohol, can reduce costs in solar cell processing. Copyright © 2011 John Wiley & Sons, Ltd.
Biodegradable thermo‐ and pH‐responsive hydrogels for oral drug delivery
Authors: Zhang Zhe , Chen Li , Deng Mingxiao , Bai Yunyan , Chen Xuesi , Jing Xiabin
Published: May 2011

In this article, novel smart hydrogels based on biodegradable pH sensitive poly(L‐glutamic acid‐g‐2‐hydroxylethyl methacrylate) (PGH) chains and temperature‐sensitive hydroxypropylcellulose‐g‐acrylic acid (HPC‐g‐AA) segments were designed and synthesized. The influence of pH and temperature on the equilibrium swelling ratios of the hydrogels was discussed. The optical transmittance of the hydrogels was also changed as a function of temperature, which reflecting that the HPC‐g‐AA part of the hydrogels became hydrophobic at the temperature above the lower critical solution temperature (LCST). At the same time, the LCST of the hydrogels had a visible pH‐dependent behavior. Scanning electron microscopic analysis revealed the morphology of the hydrogels before and after enzymatic degradation. The biodegradation rate of the hydrogels was directly related to the PGH content and the pH value. The in vitro release of bovine serum albumin from the hydrogels were investigated. The release profiles indicated that both the HPC‐g‐AA and PGH contents played important roles in the drug release behaviors. These results show that the smart hydrogels seem to be of great promise in pH–temperature oral drug delivery systems. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Effects of a single dose inhaled corticosteroid on the dynamics of airway obstruction after exercise
Authors: Driessen J.M.M. , Nieland H. , van der Palen J.A.M. , van Aalderen W.M.C. , Thio B.J. , de Jongh F.H.C.
Published: May 2011

Rationale

Exercise‐induced bronchoconstriction (EIB) is defined as a transient narrowing of the airways induced by exercise. Repetitive measurements of spirometric parameters, such as FEV1 and expiratory flows, and forced oscillation technique (FOT) measurements can be used to analyze the dynamics of EIB. A single high dose of fluticasone propionate (FP) protects against EIB. The aim of the study was to analyze the effect of FP on the dynamics of exercise‐induced airway narrowing as measured with FOT and spirometry.

Methods

Twelve children performed an exercise challenge on 2 separate days, 4 hr after inhalation of 1 mg FP (pressurized metered dose inhaler) or a placebo. Before and after the exercise flow‐volume loops as well as the FOT (frequency range: 4–32 Hz) were measured.

Results

The FEV1, and FEF50 fell significantly after exercise within groups; the peak fall in FEV1 after FP was significantly smaller than after placebo (respectively, 19.3 ± 14.6% and 29.2 ± 14.8%, P = 0.03, 95% CI: 0.9–18.8%). The fall in FEV1 and FEF50 peaked 3 min after exercise and showed a subsequent partial recovery. The fall in the FEV1/FVC ratio showed a later peak fall (12 min after exercise). The resistance increased while the reactance decreased significantly after exercise. FP significantly decreased the maximal increase in Rrs6 when compared to the placebo (respectively 176.5 ± 59.1% and 201.0 ± 63.8%, P = 0.05, 95% CI: 0.5–48.7%). The maximal decrease in Xrs6 was not significantly affected by FP (P = 0.06).

Conclusion

Repetitive spirometric and FOT measurements after exercise show a rapid narrowing and steady recovery of the patency of the conducting airways, and indicate a delayed and prolonged recovery of the smaller airways. A single high dose of inhaled FP seems to employ its effect mainly in the conducting airways. Pediatr. Pulmonol. 2011; 46:849–856. © 2011 Wiley‐Liss, Inc.
Abundance and functional roles of intrinsic disorder in allergenic proteins and allergen representative peptides
Authors: Xue Bin , Soeria‐Atmadja Daniel , Gustafsson Mats G. , Hammerling Ulf , Dunker A. Keith , Uversky Vladimir N.
Published: May 2011

The pathological process of allergies generally involves an initial activation of certain immune cells, tied to an ensuing inflammatory reaction on renewed contact with the allergen. In IgE‐mediated hypersensitivity, this typically occurs in response to otherwise harmless food‐ or air‐borne proteins. As some members of certain protein families carry special properties that make them allergenic, exploring protein allergens at the molecular level is instrumental to an improved understanding of the disease mechanisms, including the identification of relevant antigen features. For this purpose, we inspected a previously identified set of allergen representative peptides (ARPs) to scrutinize protein intrinsic disorder. The resulting study presented here focused on the association between these ARPs and protein intrinsic disorder. In addition, the connection between the disorder‐enriched ARPs and UniProt functional keywords was considered. Our analysis revealed that ∼ 20% of the allergen peptides are highly disordered, and that ∼ 77% of ARPs are either located within disordered regions of corresponding allergenic proteins or show more disorder/flexibility than their neighbor regions. Furthermore, among the subset of allergenic proteins, ∼ 70% of the predicted molecular recognition features (MoRFs that consist of short interactive disordered regions undergoing disorder‐to‐order transitions at interaction with binding partners) were identified as ARPs. These results suggest that intrinsic disorder and MoRFs may play functional roles in IgE‐mediated allergy. Proteins 2011; © 2011 Wiley‐Liss, Inc.
pKa predictions with a coupled finite difference Poisson–Boltzmann and Debye–Hückel method
Authors: Jim Warwicker
Published: May 2011

Modeling charge interactions is important for understanding many aspects of biological structure and function, and continuum methods such as Finite Difference Poisson–Boltzmann (FDPB) are commonly employed. Calculations of pH‐dependence have identified separate populations; surface groups that can be modeled with a simple Debye–Hückel (DH) model, and buried groups, with stronger resultant interactions that are dependent on detailed conformation. This observation led to the development of a combined FDPB and DH method for pKa prediction (termed FD/DH). This study reports application of this method to ionizable groups, including engineered buried charges, in staphylococcal nuclease. The data had been made available to interested research groups before publication of mutant structures and/or pKa values. Overall, FD/DH calculations perform as intended with low ΔpKa values for surface groups (RMSD between predicted and experimental pKa values of 0.74), and much larger ΔpKa values for the engineered internal groups, with RMSD = 1.64, where mutant structures were known and RMSD = 1.80, where they were modeled. The weaker resultant interactions of the surface groups are determined mostly by charge–charge interactions. For the buried groups, R2 for correlation between predicted and measured ΔpKa values is 0.74, despite the high RMSDs. Charge–charge interactions are much less important, with the R2 value for buried group ΔpKa values increasing to 0.80 when the term describing charge desolvation alone is used. Engineered charge burial delivers a relatively uniform, nonspecific effect, in terms of pKa. How the protein environment adapts in atomic detail to deliver this resultant effect is still an open question. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Application of the Gaussian dielectric boundary in Zap to the prediction of protein pKa values
Authors: Word J. Michael , Nicholls Anthony
Published: May 2011

The results of two rounds of blind pKa predictions for ionizable residues in staphylococcal nuclease using OpenEye's legacy protein pKa prediction program based on the Zap Poisson–Boltzmann solver were submitted to the 2009 prediction challenge organized by the Protein pKa Cooperative and first round predictions were discussed at the corresponding June 2009 Telluride conference. To better understand these results, 21 additional sets of predictions were performed with the same program, varying the internal dielectric, reference pKa, partial charge set, and dielectric boundary. The internal dielectric (ϵp) and dielectric boundary were the two most important factors contributing to the quality of the predictions. Although the lowest overall errors were observed with a molecular dielectric boundary at ϵp = 8, predictions using a smooth Gaussian dielectric boundary performed almost as well at lower ϵp values because the Gaussian boundary implicitly accounts for a significant level of solvent penetration. Improved pKa predictions with the Gaussian boundary methodology will require better prediction and modeling of structural changes due to changes in ionization state, perhaps without resorting to the more exhaustive sampling of conformational states used by other recent continuum methods. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Storage tank fire accidents
Authors: Zheng Bin , Chen Guo‐hua
Published: May 2011

Storage tank fires often occur together with explosion causing major losses. Fifty storage tank fires occurring during the past 50 years in China are reviewed in this article. The results show that over 64% accidents occur in petrochemical plants, petroleum refineries and oil depots. The majority of fires resulted in explosions, i.e., 82% resulted in explosions. The fire disaster occurred mostly during maintenance, repair, and loading or unloading. Twenty‐seven percent of the accidents are due to human errors including operations and maintenance. This article identified the major operating, maintenance, and management problems that resulted in storage tank accidents. © 2011 American Institute of Chemical Engineers Process Saf Prog, 2011
Towards a multi‐sensor system for the evaluation of aseptic processes employing hydrogen peroxide vapour (H2O2)
Authors: Reisert Steffen , Geissler Hanno , Flörke Rudolf , Näther Niko , Wagner Patrick , Schöning Michael J.
Published: May 2011

The presented work focuses on the development of a multi‐sensor system for the evaluation of aseptic processes employing hydrogen peroxide vapour. In a first step, selected commercially available gas sensors have been investigated on cross‐sensitivity towards hydrogen peroxide vapour and humidity. An MOX (TGS 816, Figaro) and a solid‐electrolyte gas sensor (SO‐A0‐250, Electrovac) (λ‐probe) have shown good characteristics in terms of sensitivity towards HPV, considering also reproducibility, long‐term drift and stability. Further, the sterilization effect of HPV has been investigated by means of the microbial reduction test. A correlation between the microbial reduction of Bacillus subtilis spores and the sensor response in hydrogen peroxide atmosphere has been established. Based on this correlation the microbial reduction may be estimated by means of the sensor output over a wide range of parameters.
A silicon‐based multi‐sensor chip for monitoring of fermentation processes
Authors: Bäcker M. , Pouyeshman S. , Schnitzler Th. , Poghossian A. , Wagner P. , Biselli M. , Schöning M. J.
Published: May 2011

This paper describes the design and characterization of a silicon‐based sensor chip for monitoring of fermentation processes. The sensor chip consists of three sensors using different transducer principles. A capacitive electrolyte‐insulator‐semiconductor (EIS) field‐effect structure with Ta2O5 as gate material was utilized as pH sensor. An electrolyte conductivity sensor was realized by measuring the impedance between two interdigitated electrodes (IDE). A platinum thermistor was included for temperature measurements. The EIS sensor was integrated into a bioreactor and successfully used for an inline pH measurement. The layout of the IDE has been optimized with respect to a high cell constant and a wide detectable conductivity range. The integrated platinum thermistor allowed for temperature compensation of the electrolyte conductivity measurement.
Time dependence of water‐reducing photocurrent with change of the characteristics of n‐type GaN photo‐illuminated working electrodes
Authors: Fujii Katsushi , Koike Kayo , Atsumi Mika , Goto Takenari , Itoh Takashi , Yao Takafumi
Published: May 2011

Nitride semiconductors are expected for the working electrodes of photoelectrochemical water splitting due to the chemical stability and band‐gap configuration. The p‐type nitrides are stable under photoelectrochemical conditions but the efficiency of light to hydrogen energy is low. The n‐type nitrides have relatively high energy‐conversion especially for the quantum efficiency, but the photoelectrochemical reaction is not stable because of the anodic photocorrosion. In this article, the relationships between the characteristics of n‐type GaN and the photocurrent stability are discussed. The amount of Si doping was clarified to relate to the stability. The suitable properties for stable photocurrent were different from those for high energy‐conversion efficiency at initial stage. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Next generation defect characterization in nitride HEMTs
Authors: Arehart A. R. , Malonis A. C. , Poblenz C. , Pei Y. , Speck J. S. , Mishra U. K. , Ringel S. A.
Published: May 2011

A series of constant drain current deep level transient and optical spectroscopies (CID‐DLTS/DLOS) is described, which allows characterization of deep levels with lateral spatial resolution in fully fabricated high electron mobility transistors (HEMTs). The techniques are used to examine the role of SiNx passivation in the access region of AlGaN/GaN HEMTs, in part to verify lateral resolution capabilities. Two distinct trap spectra were observed correlating to the under‐gate and access regions of the HEMT. Traps in the access region had energy levels of of EC‐0.43, EC‐1.3, EC‐2.3, and EC‐3.7 eV. The impact of each access region trap on the drain resistance before and after passivation was measured, with the total transient drain resistance change being reduced from 0.47 Ω‐mm to 0.11 Ω‐mm as a result of their partial passivation by SiNx, resulting in improved device performance. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation and selective etch of ammonothermal GaN wafers for defect evaluation
Authors: Swider Stacy , Suscavage Michael , Wang Buguo , Lynch Candace , Bliss David
Published: May 2011

Growth of bulk gallium nitride by the ammonothermal method results in thick, faceted specimens presenting polar and non‐polar surfaces. In order to investigate defect density, samples need to be cut, polished, and etched. The polishing method must remove surface damage or etch tests will be inaccurate. We examined the efficacy of different polishing and etching methods on the c, a, and m planes. Polishing methods included fixed‐grit and chemo‐mechanical solutions; results were measured by atomic force microscopy (AFM). Three etchants were tried: 85% hot phosphoric acid, hot KOH‐NaOH eutectic, and photo‐enhanced chemical (PEC) etching. The eutectic etch resulted in repeatable counts on the gallium face. The non‐polar planes did not reveal etch pits (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Progress on n‐type doping of AlGaN alloys on AlN single crystal substrates for UV optoelectronic applications
Authors: Collazo Ramón , Mita Seiji , Xie Jinqiao , Rice Anthony , Tweedie James , Dalmau Rafael , Sitar Zlatko
Published: May 2011

As the building blocks of deep UV light emitting diode (LED) technology and high‐power electronic devices, AlGaN alloys have attracted considerable attention. In this study, AlGaN films with varying compositions doped with Si were deposited on homoepitaxial AlN layers grown on AlN single crystal substrates. The room temperature resistivity of AlGaN alloys of different compositions grown on AlN and sapphire substrates with a constant Si doping level of 6x1018 cm‐3 was compared. AlGaN films grown on AlN substrates consistently exhibited a lower n‐type resistivity than those grown on sapphire. An n‐type resistivity of 0.1 Ω cm was obtained for an AlGaN film with 80% Al content and a sheet resistance of 235 Ω/sq. for an AlGaN film with 70% Al content. The carrier activation energy as a function of Al content in AlGaN for these n‐type films was measured. For compositions below 80% Al, the activation energy was around 15 meV due to impurity potential screening. For higher Al compositions, the carrier concentration was limited by a high compensation ratio, except for AlN, which has activation energy of 250 meV. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of excess carrier dynamics in polar, semi‐polar, and non‐polar (In,Ga)N epilayers and QWs
Authors: Aleksiejūnas R. , Lubys L. , Vengris M. , Jarašiūnas K. , Wernicke T. , Hoffmann V. , Netzel C. , Knauer A. , Weyers M. , Kneissl M.
Published: May 2011

We studied carrier recombination and diffusion in GaN/sapphire templates, (In,Ga)N layers, and (In,Ga)N quantum well structures oriented along the polar [0001], semi‐polar [11‐22], and non‐polar [11‐20] orientations by means of light induced transient grating, differential transmission, and photoluminescence optical techniques. We show that the lifetime of excess carriers drops by orders of magnitude when changing the orientation from polar to non‐polar, both in GaN templates and (In,Ga)N layers. We attribute the shorter lifetime to carrier trapping by extended structural defects that are more abundant in non‐polar grown samples. In addition, we observe pronounced carrier localization effects in the semi‐ and non‐polar layers. We show that thick (In,Ga)N layers inherit the properties of the GaN templates. However, the thin quantum well structures show a lower carrier trapping activity. So, a better electrical quality can be assumed as compared to the thick (In,Ga)N layers. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polarity analysis of GaN nanorods by photo‐assisted Kelvin probe force microscopy
Authors: Wei Jiandong , Neumann Richard , Wang Xue , Li Shunfeng , Fündling Sönke , Merzsch Stephan , Al‐Suleiman Mohamed A. M. , Sökmen Ünsal , Wehmann Hergo‐H. , Waag Andreas
Published: May 2011

Polarity dependence (N‐polar (000‐1) and Ga‐polar (0001)) of surface photovoltage of epitaxially grown, vertically aligned GaN nanorods has been investigated by photo‐assisted Kelvin probe force microscopy (KPFM). Commercial GaN substrates with known polarities are taken as reference samples. The polarity of GaN substrates can be well distinguished by the change in surface photovoltage upon UV illumination in air ambient. These different behaviors of Ga‐ and N‐polar surfaces are attributed to the polarity‐related surface‐bound charges and photochemical reactivity. GaN nanorods were grown on patterned SiO2/sapphire templates by metal‐organic vapor phase epitaxy (MOVPE). In order to analyze the bottom surface of the grown GaN nanorods, a technique known from high power electronics and joining techniques is applied to remove the substrate. The top and bottom surfaces of the GaN nanorods are identified to be N‐polar and Ga‐polar according to the KPFM results, respectively. Our experiments demonstrate that KPFM is a simple and suitable method capable to identify the polarity of GaN nanorods. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Waveguides for nitride based quantum cascade lasers
Authors: Stattin Martin , Berland Kristian , Hyldgaard Per , Larsson Anders , Andersson Thorvald G.
Published: May 2011

Waveguide designs for AlGaN‐based near‐infrared quantum cascade lasers are investigated using a finite‐difference method mode solver. Because of the negligibly small refractive index difference between the AlN/GaN/AlGaN gain region and the surrounding AlGaN current injection and extraction layers, a low refractive index substrate (sapphire) and a low refractive index dielectric (SiO2) are used for vertical confinement of the optical field. A ridge waveguide with an off‐center contact metallization is used for lateral confinement. The off‐center contact allows for the propagation of a TM mode with low metal induced loss and sufficient optical confinement in the gain region. A viable waveguide design with a metal‐induced loss of 6.1 cm‐1 and a confinement factor of 0.52 is demonstrated. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of (1‐101) InGaN/GaN MQW stripe laser structure on Si substrate
Authors: Murase Tasuku , Tanikawa Tomoyuki , Honda Yoshio , Yamaguchi Masahito , Amano Hiroshi
Published: May 2011

A smooth laser structure on (1‐101) GaN microstripes was successfully fabricated on a patterned (100) 8°‐off Si substrate. The sample has a high internal quantum efficiency (IQE) compared with blue LEDs on a sapphire substrate. The high‐density excitation PL spectrum observed from the cross section of the sample shows marked narrowing, and the integral PL intensity also shows a steep increase. These results indicate the onset of stimulated emission from an InGaN‐based multi quantum well (MQW) active layer on (1‐101) GaN / (100) Si. To the best of our knowledge, this is the first report of the observation of a stimulated emission from a (1‐101) MQW on a Si substrate. We succeeded in fabricating and verifying the high‐quality laser structure on semipolar (1‐101) GaN on a Si substrate. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and characterization of InGaN for photovoltaic devices
Authors: Boney C. , Hernandez I. , Pillai R. , Starikov D. , Bensaoula A. , Henini M. , Syperek M. , Misiewicz J. , Kudrawiec R.
Published: May 2011

In this work we present the growth and characterization of InxGa1–xN‐based materials and solar cells with x up to 0.39. The bandgap of the layers is determined by contactless electroreflectance, which indicates a substantial Stokes shift compared to photoluminescence measurements. Time‐resolved photo‐luminescence was used to confirm the existence of carrier localization phenomenon in the films. Fabricated p‐n devices are then studied for photo‐response under simulated AM0 spectral conditions and under wavelength‐dependent conditions to evaluate solar cell characteristics. All of the p‐n junctions exhibited photoresponse in the regions above their respective bandgaps. However, the dark and illuminated J‐V results indicate the existence of significant shunt and series resistances arising from material defects and non‐optimized device designs. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Selective MOVPE growth of InGaN/GaN MQW on microfacet GaN stripes
Authors: Tanikawa Tomoyuki , Murase Tasuku , Honda Yoshio , Yamaguchi Masahito , Amano Hiroshi
Published: May 2011

We demonstrated the effects of growth conditions such as growth pressure and growth temperature during the selective growth of InGaN/GaN multiple quantum wells (MQWs) on semipolar GaN microstripes on Si substrates. Grown layers exhibited the ridge growth, which indicates the thickness fluctuation, owing to the source supply from the apexes of the GaN microstructure. Ridge growth was suppressed by increasing growth pressure and decreasing growth temperature. Cathode luminescence (CL) analysis showed uniform luminescence. As a result, high pressure and low temperature are suitable for obtaining uniform heterostructures in the selective growth of InGaN/GaN MQWs on GaN microstripes. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
C‐plane bowing in free standing GaN crystals grown by HVPE on GaN‐sapphire substrates with photolithographically patterned Ti masks
Authors: Łucznik Bolesław , Sochacki Tomasz , Sarzyński Marcin , Kryśko Marcin , Dzięcielewski Igor , Grzegory Izabella , Porowski Sylwester
Published: May 2011

It is suggested that final bowing of {0001} planes in free standing GaN depends mostly on the nucleation mechanism at the beginning of the growth in the presented approach. Typical growth process in this study, includes formation of pyramidal islands through the openings in the mask, growth of the islands on their semi‐polar faces, the coalescence, smoothening of the layer and finally, bulk growth on the c‐plane of the crystal. The initial layer containing large fraction of material grown on semi‐polar faces is strongly n‐type (n > 1019 cm‐3) due to enhanced incorporation of oxygen. In contrast, the growth on c‐plane, after smoothening of the layer, results in much lower electron concentration (n < 1017 cm‐3) thus a corresponding lattice mismatch appears between semi‐polar and c‐plane growth regions. There are three results suggesting that this mismatch is an important source of stress leading to the observed c‐plane bowing: (i) relatively strong dependence of bowing radius on diameter and distance of openings in the mask, (ii) dramatic increase of the bowing radius (R = 10–80 m) if the crystallization front remains rough (entire crystal is strongly n‐type), (iii) agreement of the observed bowing radii (0.9–3 m) with theoretical estimations (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of GaN in a planetary MOCVD hotwall system
Authors: Fahle D. , Behmenburg H. , Mauder C. , Kalisch H. , Jansen R. H. , Kitahata H. , Brien D. , Strauch G. , Schmitz D. , Heuken M. , Vescan A.
Published: May 2011

We report on a new planetary hotwall research system with independent control of the ceiling and susceptor temperatures. This allows a study of the influence of an actively heated ceiling during a MOCVD process. It was found that the temperature profile across the substrate becomes more uniform when the ceiling temperature is increased while maintaining the same susceptor surface temperature.

The parasitic coating on the ceiling was found to be stable and no source of particles up to 1050 °C. The influence of the ceiling temperature on the depletion profile and the possibility to manipulate it was investigated. Good thickness homogeneity of 1.35% (1·σ) on a 4″ sapphire wafer was achieved with excellent XRD results of 206 arcsec for the (0002) reflex and 272 arcsec for the (10‐12) reflex for a 4.7 µm thick GaN film. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Masking photochromic films for nanolithography technology
Authors: Ayt Anton , Barachevsky Valery , Kobeleva Olga , Valova Tatyana , Gorelik Alexander , Krayushkin Michail , Komlenok Maksim , Kononenko Vitaly
Published: May 2011

One of the problems for modern photolithography is a resolution increase of images recorded on photoresists. For this goal a method of photochromic masking using reversible photochemical transformations of organic systems may be developed. More than 150 photochromic compounds from 11 classes have been studied in solutions and several photochromic compounds exhibiting the best value of the photoindused change of an optical density (ΔOD) at 193 nm have been chosen for the following investigations in the polymer binder and solid films. The method of testing of the photochromic polymer and solid films in operating conditions has been developed. For the testing, a preparation technology of thin photochromic polymer films using the spin‐coating technique has been worked out. It was shown that the polymer and the photochrome should be at an optimal mass ratio in a thin film to reach the maximum of ΔOD. The best result (ΔOD = 0.87) was received for the polymer film based on one of photochromic diarylethenes and poly(methyl)‐methacrylate (at the concentration ratio as 90/10 mass%) of a thickness 450±50 nm under 193 nm laser irradiation at exposure doses about 525 mJ/cm2. An application of these photochromic layers may allow to increase a resolution on the photoresist layer up to 22 nm and more with 193 nm photolithography double‐exposure method. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Heat treatment to prevent image defect occurrence in amorphous Se doped with Te avalanche multiplication photoconductive film
Authors: Ohkawa Yuji , Miyakawa Kazunori , Matsubara Tomoki , Kikuchi Kenji , Tanioka Kenkichi , Kubota Misao , Egami Norifumi , Kobayashi Akira
Published: May 2011

We have been developing an amorphous selenium (a‐Se) avalanche multiplication photoconductive film, named HARP (high‐gain avalanche rushing amorphous photoconductor), for the purpose of making a high‐sensitivity video camera useful for broadcasting, x‐ray medical diagnosis, etc. The HARP film used for the red channel in a colour camera is doped with tellurium (Te) to improve its red‐light sensitivity. However, doping a‐Se with Te generates impurity levels that trap electrons, and the built‐in‐field formed by these trapped electrons causes image defects. We devised a heat treatment to prevent the occurrence of these defects. We suppose that the thermal energy of the heat treatment releases the originally trapped electrons, and that the energy makes it difficult for moving electrons to be trapped during operation. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Kinetics of photodarkening at room and liquid He temperatures in a‐As45Se 55 thin film
Authors: Barik A. R. , Adarsh K. V. , Naik Ramakanta , Ganesan R. , Sangunni K. S. , Zhao Donghui , Jain Himanshu
Published: May 2011

We report experimental results that compare the magnitude and kinetics of photodarkening (PD) in a‐As45Se55 thin film at 4.2 K vs. at 300 K. Overall the magnitude of PD increases with decreasing temperature, however the kinetics become slower when compared to the same effects at room temperature. The large change in PD and its kinetics are successfully explained based on the photon assisted site switching (PASS) model (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observation and modelling of gap flow and wake formation on Svalbard
Authors: Barstad Idar , Adakudlu Muralidhar
Published: May 2011

Aircraft observations, satellite information and model simulations are presented for an episode with significant local disturbances in the vicinity of Spitsbergen, on the Svalbard archipelago in the Barents Sea. Relative weak upstream winds from the east gave rise to strong local winds in the Hinlopen Strait which separates Spitsbergen from Nordaustlandet Island. The aircraft data included wind lidar, water vapour lidar and dropsonde observations. The aircraft flew through the Hinlopen Strait and found winds near 20 m s−1 in magnitude close to the surface. This is a factor of about four above the upstream wind magnitude. In the lee of the terrain, a wake with return currents was formed and this was clearly documented by the lidar observations. The model simulations reproduced the episodes with a high degree of fidelity. In the lee of the mountains, small‐scale cloud features appeared both in the lidar data and in the satellite observations. For wind directions with easterly and northerly components, these features are frequently observed on satellite pictures downstream of Spitsbergen. In the model framework, the cloud streamers were further investigated. Through sensitivity tests and more idealized simulations, it was found that the features plausibly stem from vertical circulations set up by the terrain and maintained by the positive buoyancy gained downstream over the relatively warm water. Copyright © 2011 Royal Meteorological Society
Developing a model‐based sampling plan
Authors: Negrin Itay , Parmet Yisrael , Schechtman Edna
Published: May 2011

Statistical process modeling is widely used in industry for forecasting the production outcomes, for process control and for process optimization. Applying a prediction model in a production process allows the user to calibrate/predict the mean of the distribution of the process outcomes and to partition the overall variation in the distribution of the process outcomes into explained (by the model) and unexplained (residuals) variations; thus, reducing the unexplained variability. The additional information about the process behavior can be used prior to the sampling procedure and may help to reduce the required sample size to classify a lot. This research focuses on the development of a model‐based sampling plan based ontextitCpk (process capability index). It is an extension of a multistage acceptance sampling plan also based on Cpk (Negrin et al., Quality Engineering 2009; 21:306–318; Quality and Reliability Engineering International 2011; 27:3–14). The advantage of this sampling plan is that the sample size needed depends directly and quantitatively on the quality of the process (Cpk), whereas other sampling plans such as MIL‐STD‐414 (Sampling Procedures and Tables for Inspection by Variables for Percent Defective, Department of Defense, Washington, DC, 1957.) use only qualitative measures. The objective of this paper is to further refine the needed sample size by using a predictive model for the lot's expectation. We developed model‐based sample size formulae which depend directly on the quality of the prediction model (as measured by R2) and adjust the ‘not model‐based’ multistage sampling plan developed in Negrin et al. (Quality Engineering 2009; 21:306–318; Quality and Reliability Engineering International 2011; 27:3–14) accordingly. A simulation study was conducted to compare between the model‐based and the ‘not model‐based’ sampling plans. It is found that when R2 = 0, the model‐based and ‘not model‐based’ sampling plans require the same sample sizes in order to classify the lots. However, as R2 becomes larger, the sample size required by the model‐based sampling plan becomes smaller than the one required by the ‘not model‐based’ sampling plan. In addition, it is found that the reduction of the sample size achieved by the model‐based sampling plan becomes more significant as Cpk tends to 1 and can be achieved without increasing the proportion of the classification errors. Finally, the suggested sampling plan was applied with areal data set from a chemicals manufacturing process for illustration. Copyright © 2011 John Wiley & Sons, Ltd.
Theoretical study of the polarized infrared spectra of the hydrogen bond in 2‐furoic acid crystal dimer
Authors: Ghalla Houcine , Issaoui Noureddine , Oujia Brahim
Published: May 2011

This work presents a theoretical simulation of νOH and νOD band shapes in the polarized infrared spectra of 2‐furoic acid dimer crystals measured at liquid‐nitrogen temperature. The line shapes are studied theoretically within the framework of the anharmonic couplings between low‐frequency hydrogen‐bond vibrations and degenerate excited states of high‐frequency hydrogen vibrations in hydrogen‐bonded dimers and the anharmonic coupling between the first excited state of the fast mode and the harmonics or band combinations of some low‐frequency bending modes, which lead to Fermi resonances.This approach takes into account the adiabatic approximation, the intrinsic anharmonicity of the low‐frequency mode through a Morse potential, Davydov coupling triggered by resonance exchange between the excited states of the fast modes of the two hydrogen bonds involved in the cyclic dimer, and the direct and indirect damping of the fast‐stretching modes of the hydrogen bonds and of the bending modes. The infrared spectral density was calculated within the linear response theory by Fourier transform of the autocorrelation function of the transition dipole moment operator of the fast mode. Numerical results show that mixing of all these effects allows satisfactory reproduction of the main features of the experimental IR line shapes of crystalline H‐ and D‐bonded 2‐furoic acid at liquid‐nitrogen temperature and for different polarizations. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012
Theoretical study of the effects of substitution, solvation, and structure on the interaction between nitriles and methanol
Authors: Raissi Heidar , Farzad Farzaneh , Nadim Emad Saleh , Yoosefian Mehdi , Farsi Hossein , Nowroozi Alireza , Loghmaninejad Danial
Published: May 2011

We report an investigation on intermolecular interactions in RCN···HOCH3(R = H, CH3, F, Cl, NO2, OH, SH, SCH3, CHO, COCH3, CH2Cl, CH2F, CH2OH, CH2COOH, CF3, SCOCH3, SCF3, OCHF2, CH2CF3, CH2OCH3, and CH2CH2OH) complexes using density functional theory. The calculations were conducted on B3LYP/6‐311++G** level of theory for optimization of geometries of complexes and monomers. An improper hydrogen bonding (HB) in the H3COH···NCR complexes was observed in that N atom of the nitriles functions acts as a proton acceptor. Furthermore, quantum theory of “Atoms in Molecules” (AIM) and natural bond orbital (NBO) method were applied to analyze H‐bond interactions in respective complexes. The electron density (ρ) and Laplacian (∇2ρ) properties, estimated by atoms in molecules calculations, indicate that H···N bond possesses low ρ and positive ∇2ρ values, which are in agreement with partially covalent character of the HBs, whereas OH bonds have negative ∇2ρ values. In addition, the weak intermolecular force due to dipole–dipole interaction (U) is also considered for analysis. The examination of HB in these complexes by quantum theory of NBO method fairly supports the ab initio results. Natural population analysis data, the electron density, and Laplacian properties, as well as, the ν(OH) and γ(OH) frequencies of complexes, calculated at the B3LYP/6‐311++G** level of theory, are used to evaluate the HB interactions. The calculated geometrical parameters and conformational analysis in water phase solution show that the H3COH···NCR complexes in water are more stable than that in gas phase. The obtained results demonstrated a strong influence of the R substituent on the properties of complexes. Numerous correlations between topological, geometrical, thermodynamic properties, and energetic parameters were also found. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012
Systematic comparison of δ13C measurements of testosterone and derivative steroids in a freeze‐dried urine candidate reference material for sports drug testing by gas chromatography/combustion/isotope ratio mass spectrometry and uncertainty evaluation using four different metrological approaches
Authors: Munton Ellaine , Murby John , Hibbert D. Brynn , Santamaria‐Fernandez Rebeca
Published: May 2011

An alternative calibration procedure for use when performing carbon isotope ratio measurements by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) has been developed. This calibration procedure does not rely on the corrections in‐built in the instrument software, as the carbon isotope ratios of a sample are calculated from the measured raw peak areas. The method was developed for the certification of a urine reference material for sports drug testing, as the estimation of measurement uncertainty is greatly simplified. To ensure that the method is free from bias arising from the choice of calibration material and instrument, the carbon isotope ratios of steroids in urine extracts were measured using two different instruments in different laboratories, and three different reference materials (CU/USADA steroid standards from Brenna Laboratory, Cornell University; NIST RM8539 mineral oil; methane calibrated against NIST RM8560 natural gas). The measurements were performed at LGC and the Australian National Measurement Institute (NMI). It was found that there was no significant difference in measurement results when different instruments and reference materials were used to measure the carbon isotope ratio of the major testosterone metabolites androsterone and etiocholanolone, or the endogenous reference compounds pregnanediol, 11‐ ketoetiocholanolone and 11β‐hydroxyandrosterone. Expanded measurement uncertainties at the 95% coverage probability ranged from 0.21‰ to 1.4‰, depending on analyte, instrument and reference material. The measurement results of this comparison were used to estimate a measurement uncertainty of δ13C for the certification of the urine reference material being performed on a single instrument using a single reference material at NMI. Copyright © 2011 John Wiley & Sons, Ltd.
Development of a liquid chromatography/mass spectrometry methodology to separate, detect, characterize and quantify PEG‐resveratrol prodrugs and the conjugation reaction precursors and intermediates
Authors: Basavaraj S. , Benson Heather A. E. , Cruickshank Christopher , Brown David H. , Chen Yan
Published: May 2011

A simple and reliable liquid chromatography/mass spectrometry (LC/MS) method to monitor pegylation of resveratrol is described. The developed LC/MS method can separate and quantify unmodified MeO‐PEG‐OH, carboxylic acid terminated PEG, resveratrol and PEG‐resveratrol prodrugs. This methodology was able to monitor and determine the extent of conversion of MeO‐PEG‐OH into respective acidic functional derivatives such as MeO‐PEG succinylester acid (MeO‐PEGO‐SuccOH), which was found to be complete. The developed method was also utilised to determine the extent of conjugation of resveratrol to carboxylic acid terminated PEG. The conversion of carboxylic acid terminated PEG into a PEG‐resveratrol conjugate was found to be 100% and 73%, respectively, for MeO‐PEG succinylamide resveratrol (MeO‐PEGN‐Succ‐RSV) and MeO‐PEG succinylester resveratrol (MeO‐PEGO‐Succ‐RSV). The 100% conjugation of MeO‐PEGN‐Succ‐RSV is consistent with the result obtained from a nuclear magnetic resonance (NMR) study. The average molecular weights determined by LC/MS for MeO‐PEG‐OH, MeO‐PEGO‐SuccOH and MeO‐PEGO‐Succ‐RSV were found to be 2108, 2321 and 2423 Da, respectively. These data correlate well with the theoretical values. This methodology proved to be simple and effective in determining the extent of functionalisation of PEG and its conjugation to resveratrol. Overall our LC/MS method coupled with NMR permitted complete characterisation of the polymeric prodrug pegylated‐resveratrol and the reaction precursors. Copyright © 2011 John Wiley & Sons, Ltd.
Two‐dimensional Fourier transform ion cyclotron resonance mass spectrometry: reduction of scintillation noise using Cadzow data processing
Authors: van Agthoven Maria A. , Coutouly Marie‐Aude , Rolando Christian , Delsuc Marc‐André
Published: May 2011

In two‐dimensional Fourier transform ion cyclotron resonance mass spectrometry (2D FTICR‐MS), scintillation noise, caused mostly by fluctuations in the number of ions in the ICR cell, is the leading cause for errors in spectrum interpretation. In this study, we adapted an algorithm based on singular value decomposition and first introduced by Cadzow et al. (IEE Proceedings Pt. F 1987, 134, 69) to 2D FTICR‐MS and we measured its performance in terms of noise reduction without losing signal information in the 2D mass spectrum. Copyright © 2011 John Wiley & Sons, Ltd.
Identification of multiple components in Guanxinning injection using hydrophilic interaction liquid chromatography/time‐of‐flight mass spectrometry and reversed‐phase liquid chromatography/time‐of‐flight mass spectrometry
Authors: Chen Xiaofei , Lou Ziyang , Zhang Hai , Tan Guangguo , Liu Zhirui , Li Wuhong , Zhu Zhenyu , Chai Yifeng
Published: May 2011

An approach for the identification of multiple components in traditional Chinese medicine injections (TCMIs) using a combination of hydrophilic interaction chromatography (HILIC) and reversed‐phase liquid chromatography (RPLC) coupled with time‐of‐flight mass spectrometry (TOFMS) was developed for the quality control of Guanxinning injection (GXNI), a widely used TCMI, composed of Salvia miltiorrhiza and Ligusticum Chuanxiong. A total of 50 compounds from five compound classes, including saccharides, amino acids, organic acids, phenolic acids and phthalides, were identified or tentatively characterized on the basis of accurate mass measurements and subsequent TOFMS product ions. Six groups of isomers of phenolic acids and saccharides were tentatively distinguished. It was observed that the ESI‐TOFMS fragmentation behavior of phthalides was different in negative and positive ion mode, and the fragmentation pathways were tentatively elucidated using structurally‐relevant product ions. Several highly polar constituents were characterized for the first time from GXNI by HILIC/TOFMS. In addition, all the constituents identified from GXNI were further assigned in the two individual crude drugs. The integrated strategy has provided a powerful approach for the separation and identification of the multiple components in GXNI, and it has also assisted in the establishment of methods for the comprehensive safety and quality evaluation of TCMIs. Copyright © 2011 John Wiley & Sons, Ltd.
Surface‐activated chemical ionization combined with electrospray ionization and mass spectrometry for the analysis of cannabinoids in biological samples. Part I: Analysis of 11‐nor‐9‐carboxytetrahydro‐cannabinol
Authors: Conti Matteo , Tazzari Valeria , Bertona Maria , Brambilla Maura , Brambilla Paolo
Published: May 2011

Recently, electrospray ionization mass spectroscopy (ESI‐MS) has been widely used for the identification of drugs of abuse and their metabolites in biological samples. However, the sensitivity and selectivity of this technique are commonly inadequate for the analysis of tetrahydrocannabinol (THC) and its metabolites at very low levels, such as those sometimes required in forensic and clinical‐legal applications. We coupled electrospray ionization and surface‐activated chemical ionization (ESI‐SACI) to various types of mass analyzers (ion trap, triple quadrupole and orbitrap) (ESI‐SACI‐MS) to improve the detection of 11‐nor‐9‐carboxy‐tetrahydrocannabinol (THC‐COOH), the most common marker of THC abuse. The benefits of this approach in terms of sensitivity and selectivity compared with a common ESI‐MS approach are clearly demonstrated. Copyright © 2011 John Wiley & Sons, Ltd.