bluuebunny/crossref_metadata_2025 huggingface dataset:
Health‐promoting phytochemicals of Italian common wheat varieties grown under low‐input agricultural management
Authors: Di Silvestro Raffaella , Marotti Ilaria , Bosi Sara , Bregola Valeria , Carretero Antonio Segura , Sedej Ivana , Mandic Anamarija , Sakac Marijana , Benedettelli Stefano , Dinelli Giovanni
Published: January 2012

BACKGROUND: The increasing interest in organic food products and environmental friendly practices has emphasised the importance of selecting crop varieties suitable for the low‐input sector. Moreover, in recent years the relationship between diet and human health has gained much attention among consumers. The aim of this study was to comparatively evaluate the agronomic performance and the nutrient and phytochemical composition of old and modern Italian wheat genotypes grown under low‐input management.

RESULTS: Research highlighted that several old wheat genotypes were comparable to the modern ones in terms of agronomic performance and nutrient content. Genotype and environmental conditions (growing season), as well as their interaction, significantly affected the phytochemical composition of wheat grains for most of the analysed bioactive compounds. High variability was observed among the wheat genotypes for dietary fibre (154.7–183.3 g kg−1), polyphenol (1.94–2.77 mg g−1), tocopherol (9.1–21.2 mg kg−1) and carotenoid (701.4–3243 µg kg−1) content.

CONCLUSION: The comparative study of old and modern wheat varieties highlighted that, under low‐input conditions, ancient genotypes may equal modern ones in terms of agronomic traits and additionally provide nutraceutical value‐added wheat grains. The most promising ancient varieties for the unique phytochemical profiles are Gentil rosso, Marzuolo d'aqui and Verna. Copyright © 2012 Society of Chemical Industry
Anti‐obesity effect of a standardised ethanol extract from Curcuma longa L. fermented with Aspergillus oryzae in ob/ob mice and primary mouse adipocytes
Authors: Ho Jin‐Nyoung , Jang Ja Young , Yoon Ho‐Geun , Kim Yongjae , Kim Sunoh , Jun Woojin , Lee Jeongmin
Published: January 2012

BACKGROUND: We examined the anti‐obesity effect of fermented Curcuma longa L. (turmeric) standardised ethanol extract (FTE) in the C57BL/6J ob/ob mouse model. Mice were fed a chow diet containing FTE (0, 200, or 500 mg kg−1 body weight) for 9 weeks.

RESULTS: Supplementation with FTE significantly reduced body weight gain and retroperitoneal and epididymal adipose tissue weights compared to the ob/ob control group. Additionally, total cholesterol and triglyceride levels in serum and liver were significantly decreased in FTE‐200 and FTE‐500 groups when compared to those of the ob/ob control group, whereas the high‐density lipoprotein‐cholesterol level was significantly increased. The levels of serum adiponectin as well as mRNA expression of lipases, such as hormone sensitive lipase and adipose triglyceride lipase, were clearly increased. In primary adipocytes of C57BL/6J mice, FTE treatment caused a significant increase glycerol release and hormone sensitive lipase levels and decreased perilipin A levels.

CONCLUSION: These results suggest that supplementation of FTE has potent anti‐obesity effects by controlling body weight, fat mass, serum lipids, and hepatic lipids. Moreover, FTE could be considered a potential resource for the treatment of obesity through its promotion of lipolysis via the protein kinase A pathway. Copyright © 2012 Society of Chemical Industry
Chemical fingerprint analysis of Fritillaria delavayi Franch. by high‐performance liquid chromatography
Authors: Duan Baozhong , Huang Linfang , Chen Shilin
Published: January 2012

Bulbus of Fritillaria delavayi Franch. is the most commonly used antitussive and apophlegmatic in China and commonly prepared by water decoction. In this study, a novel and reliable method of high‐performance liquid chromatography (HPLC) was developed both for quantitative analysis of 10 bioactive compounds (uracil, cytidine, inosine, uridine, guanosine, thymidine, adenosine, hypoxanthine, adenine and 2‐deoxyadenosine) and chemical fingerprint analysis of F. delavayi Franch. In quantitative analysis, 10 compounds showed good regressions (R2 > 0.9982) within test ranges and the recovery of the method was in the range of 96.33–104.51%. In the fingerprint analysis, 11 characteristic peaks were selected to evaluate the similarities of F. delavayi Franch. samples, and the HPLC chromatograms of 16 samples from different regions of China showed similar patterns. The results from the experiment demonstrated that the combinations of the quantitative and chromatographic fingerprint analysis offer an efficient way to evaluate the quality consistency of F. delavayi Franch.
Application of solid‐phase microextraction and gas chromatography‐mass spectrometry for the determination of chlorophenols in leather
Authors: de Souza Silveira Cristine D. , Martendal Edmar , Soldi Valdir , Carasek Eduardo
Published: January 2012

This paper proposes a new analytical procedure based on the headspace solid‐phase microextraction (HS‐SPME) technique and gas chromatography‐selected ion monitoring‐mass spectrometry (GC‐SIM‐MS) for the determination of 16 phenols extracted from leather samples. The optimized conditions for the HS‐SPME were obtained through two experimental designs – a two‐level fractional factorial design followed by a central composite design – using the commercial SPME fiber polyacrylate 85 μm (PA). The best extraction conditions were as follows: 200 μL of derivatizing agent (acetic anhydride), 20 mL of saturated aqueous NaCl solution and extraction time and temperature of 50 min and 75°C, respectively. All optimized conditions were obtained with fixed leather sample mass (250 mg), vial volume (40 mL) and phosphate buffer pH (12) and concentration (50 mmol/L). Detection limits ranging from 0.03 to 0.20 ng/g, and relative standard deviation (RSD) lower than 10.23% (n=6) for a concentration of 800 ng/g (chlorophenols) and 1325 ng/g (2‐phenylphenol) in the splitless mode were obtained. The recovery was studied at three concentration levels by adding different amounts of phenols to the leather sample and excellent recoveries ranging from 90.0 to 107.2% were obtained. The validated method was shown to be suitable for the quantification of phenols in leather samples, as it is simple, relatively fast and sensitive.
Accurate determination of extra‐column band broadening using peak summation
Authors: Verstraeten Matthias , Liekens Anuschka , Desmet Gert
Published: January 2012

The present contribution addresses the problem of the accurate determination of the extra‐column band‐broadening dispersion by applying the method of moments (MOM) on pulse response experiments. The MOM provides the only mathematically rigorous way to determine the variance of a pulse response, but suffers from the fact that the obtained variance values usually depend very strongly and unpredictably on the selected integration boundaries. In the present study, it is investigated whether the MOM cannot be made more accurate by repeating the pulse response experiment a number of times, then add all measured peaks (after retention time alignment) and subsequently perform the integration on this summed peak. Testing this approach for a number of different integration boundary detection methods consistently more accurate results are obtained than when the different repeat response pulses are integrated individually and the variances are averaged afterwards. It was also found that adding five repeats already leads to a significant improvement of the variance estimate, whereas the addition of 10–20 repeats is needed before the variance estimate converges to a steady value.
Quantification of γ‐aminobutyric acid in the heads of houseflies (Musca domestica) and diamondback moths (Plutella xylostella (L.)), using capillary electrophoresis with laser‐induced fluorescence detection
Authors: Shi Xueyan , Liang Pei , Song Dunlun , Yang Wenling , Gao Xiwu
Published: January 2012

A novel method was developed for quantifying the levels of γ‐aminobutyric acid (GABA) in the heads of houseflies (Musca domestica) and diamondback moths (Plutella xylostella (L.)), using capillary electrophoresis with laser‐induced fluorescence detection (CE‐LIF). The GABA in sample was derivatized with 4‐chloro‐7‐nitro‐2,1,3‐benzoxadiazole (NBD‐Cl) prior to CE‐LIF analysis. In total, 32 mmol/L borate buffer, at pH 9.2 and containing 5.3 mmol/L β‐cyclodextrin (β‐CD) and 10.4 mmol/L sodium dodecyl sulfate (SDS), was determined to be the optimum CE background electrolyte (BGE) for GABA analysis. The detection limit of GABA was 0.016 μmol/L. The relative standard deviations (RSDs) of the migration time and peak area of GABA were 1.78 and 4.93%, respectively. The average recoveries of 0.97, 3.88, and 5.83 μmol/L of GABA, each added to the head sample of housefly, ranged from 88.9 to 110.5%. This method is simple and applicable to GABA assays of the heads of insects. With this newly developed CE‐LIF method, the amounts of GABA in the heads of houseflies (M. domestica) and diamondback moths (P. xylostella (L.)) were measured. The results are relevant to the understandings of some insecticides and insecticide‐resistance mechanisms in pests.
Application of counter‐current chromatography as a new pretreatment method for the determination of polycyclic aromatic hydrocarbons in environmental water
Authors: Cao Xueli , Yang Chunlei , Pei Hairun , Li Xinghong , Xu Xiaobai , Ito Yoichiro
Published: January 2012

Counter‐current chromatography (CCC) was investigated as a new sample pretreatment method for the determination of trace polycyclic aromatic hydrocarbons (PAHs) in water environmental samples. The experiment was performed with a non‐aqueous binary two‐phase solvent system composed of n‐heptane and acetonitrile. The CCC column was first filled with the upper stationary phase, and then a large volume of water sample was pumped into the column while the CCC column was rotated at 1600 rpm. Finally, the trace amounts of PAHs extracted and enriched in the stationary phase were eluted out by the lower mobile phase and determined by gas chromatography–flame ionization detector (GC‐FID) or gas chromatography–mass spectrometry (GC‐MS). The enrichment and cleanup of PAHs can be fulfilled online by this method with high recoveries (84.1–103.2%) and good reproducibility (RSDs: 4.9–12.2%) for 16 EPA PAHs under the optimized CCC pretreatment conditions. This method has been successfully applied to determine PAHs in lake water where 8 PAHs were detected in the concentration of 40.9–89.9 ng/L. The present method is extremely suitable for the preparation of large volume of environmental water sample for the determination of trace amounts of organic pollutants including PAHs as studied in this paper.
Modeling the electrophoresis of highly charged peptides: Application to oligolysines
Authors: Wu Hengfu , Allison Stuart A. , Perrin Catherine , Cottet Herve
Published: January 2012

The “coarse‐grained” bead modeling methodology, BMM, is generalized to treat electrostatics at the level of the nonlinear Poisson–Boltzmann equation. This improvement makes it more applicable to the important class of highly charged macroions and highly charged peptides in particular. In the present study, the new nonlinear Poisson–Boltzmann, NLPB‐BMM procedure is applied to the free solution electrophoretic mobility of low molecular mass oligolysines (degree of polymerization 1–8) in lithium phosphate buffer at pH 2.5. The ionic strength is varied from 0.01 to 0.10 M) and the temperature is varied from 25 to 50°C. In order to obtain quantitative agreement between modeling and experiment, a small amount of specific phosphate binding must be included in modeling. This binding is predicted to increase with increasing temperature and ionic strength.
Simultaneous determination of parabens and synthetic musks in water by stir‐bar sorptive extraction and thermal desorption‐gas chromatography‐mass spectrometry
Authors: Ramírez Noelia , Borrull Francesc , Marcé Rosa Maria
Published: January 2012

This study focuses on a method for simultaneously determining personal care products in a wide range of polarities in different water matrices. The method is based on stir‐bar sorptive extraction followed by thermal desorption‐gas chromatography‐mass spectrometry. Prior to extraction, the parabens were acetylated to improve their affinity for the polydimethylsiloxane phase of the stir bar. The method showed good linearity, repeatability and reproducibility between days for all compounds and limits of detection at low ng/L levels (between 0.02 and 0.3 ng/L). The proposed method is also environmentally friendly, because it does not use organic solvents, and reduces the risk of external pollution, due to the minimal manipulation of the sample required. The method developed was successfully applied for the analysis of personal care products in different kinds of water matrices: influents and effluents of urban and industrial wastewater treatment plants, effluents of a reverse osmosis treatment plant and river waters. The influents of urban treatment plants generally showed the highest values for synthetic musks, with concentrations of up to 2219 ng/L of galaxolide, whereas the highest concentrations of parabens were detected in the industrial treatment plants influents.
Effects of low‐density feeding on elk–fetus contact rates on Wyoming feedgrounds
Authors: Creech Tyler G. , Cross Paul C. , Scurlock Brandon M. , Maichak Eric J. , Rogerson Jared D. , Henningsen John C. , Creel Scott
Published: January 2012

High seroprevalance forBrucella abortusamong elk on Wyoming feedgrounds suggests that supplemental feeding may influence parasite transmission and disease dynamics by altering the rate at which elk contact infectious materials in their environment. We used proximity loggers and video cameras to estimate rates of elk‐to‐fetus contact (the primary source of brucellosis transmission) during winter supplemental feeding. We compared contact rates during high‐density and low‐density (LD) feeding treatments that provided the same total amount of food distributed over different areas. Low‐density feeding led to >70% reductions in total number of contacts and number of individuals contacting a fetus. Proximity loggers and video cameras provided similar estimates of elk–fetus contact rates. Elk contacted fetuses and random control points equally, suggesting that elk were not attracted to fetuses but encountered them incidentally while feeding. The modeled relationship between contact rate and disease prevalence is nonlinear and LD feeding may result in large reductions in brucellosis prevalence, but this depends on the amount of transmission that occurs on and off feedgrounds. © 2012 The Wildlife Society.
PRIORITISING SOIL QUALITY ASSESSMENT THROUGH THE SCREENING OF SITES: THE USE OF PUBLICLY COLLECTED DATA
Authors: Bone J. , Barraclough D. , Eggleton P. , Head M. , Jones D. T. , Voulvoulis N.
Published: January 2012

Emergence of policies dealing with concern over soil degradation and anthropogenic impacts to soil is likely to increase the requirement for assessment of soil quality and identification of soils at risk from degradation. An example is the proposed EU Soil Framework Directive, which features the identification of areas requiring protection from soil degradation. There have been some serious objections to such requirements on the grounds of resource and capital demands. To help to address these concerns, this work proposes a strategic set of indicators based on measured soil quality indicators. These can be used in screening locations to assess the likelihood of degradation and indicate areas for further detailed assessment. This will allow further emphasis to be placed on a smaller number of locations, which could lead to cost and resource efficiencies. Indicators have been used in the past in assessment of soil quality; they are parameters which can be measured and correspond to assessment criteria to measure and help monitor the status and changes. The study reviews the current state of soil quality assessment including methods and indicators that are used to collect data and approaches used to assess data to determine areas subject to soil degradation. Methods and practicalities for data collection and screening are discussed, including the need for further pilot testing and protocol development. Use of public data collection could allow more resource efficient protection of soils, in addition to benefits of public engagement, and raising awareness of the importance of soils and soil biodiversity. Copyright © 2012 John Wiley & Sons, Ltd.
Interface approximation of Darcy flow in a narrow channel
Authors: Morales Fernando , Showalter Ralph E.
Published: January 2012

A mixed formulation is introduced for the singular problem of Darcy flow in a porous medium in a region containing a narrow fracture or channel with width and high permeability . The solution converges as ε → 0 to that of Darcy flow coupled to tangential flow on the lower‐dimensional interface or boundary. Copyright © 2012 John Wiley & Sons, Ltd.
Analysis of the power law logistic population model with slowly varying coefficients
Authors: Shepherd J.J. , Stacey A. , Grozdanovski T.
Published: January 2012

We apply a multiscale method to construct general analytic approximations for the solution of a power law logistic model, where the model parameters vary slowly in time. Such approximations are a useful alternative to numerical solutions and are applicable to a range of parameter values. We consider two situations—positive growth rates, when the population tends to a slowly varying limiting state; and negative growth rates, where the population tends to zero in infinite time. The behavior of the population when a transition between these situations occurs is also considered. These approximations are shown to give excellent agreement with the numerical solutions of test cases. Copyright © 2012 John Wiley & Sons, Ltd.
Global Dynamics of the Oregonator System
Authors: You Yuncheng
Published: January 2012

In this work, the existence and properties of a global attractor for the solution semiflow of the Oregonator system are proved. The Oregonator system is the mathematical model of the celebrated Belousov–Zhabotinskii reaction. A rescaling and grouping estimation method is developed to show the absorbing property and the asymptotic compactness of the solution trajectories of this three‐component reaction–diffusion system with quadratic nonlinearity. It is also proved that the fractal dimension of the global attractor is finite and an exponential attractor exists for the Oregonator semiflow. Copyright © 2012 John Wiley & Sons, Ltd.
Smoothed aggregation solvers for anisotropic diffusion
Authors: Schroder Jacob B.
Published: January 2012

A smoothed aggregation‐based algebraic multigrid solver for anisotropic diffusion problems is presented. Algebraic multigrid is a popular and effective method for solving sparse linear systems that arise from discretizing partial differential equations. However, although algebraic multigrid was designed for elliptic problems, the case of non‐grid‐aligned anisotropic diffusion is not adequately addressed by existing methods. To achieve scalable performance, it is shown that neither new coarsening nor new relaxation strategies are necessary. Instead, a novel smoothed aggregation approach is developed that combines long‐distance interpolation, coarse‐grid injection, and an energy‐minimization strategy that finds the interpolation weights. Previously developed theory by Falgout and Vassilevski is used to discern that existing coarsening strategies are sufficient, but that existing interpolation methods are not. In particular, an interpolation quality measure tracks ‘closeness’ to the ideal interpolant and guides the interpolation sparsity pattern choice. Although the interpolation quality measure is computable for only small model problems, an inexact, but computable, measure is proposed for larger problems. This paper concludes with encouraging numerical results that also potentially show broad applicability (e.g., for linear elasticity). Copyright © 2012 John Wiley & Sons, Ltd.
On condition numbers for Moore–Penrose inverse and linear least squares problem involving Kronecker products
Authors: Diao Huaian , Wang Weiguo , Wei Yimin , Qiao Sanzheng
Published: January 2012

In this paper, we investigate the normwise, mixed, and componentwise condition numbers and their upper bounds for the Moore–Penrose inverse of the Kronecker product and more general matrix function compositions involving Kronecker products. We also present the condition numbers and their upper bounds for the associated Kronecker product linear least squares solution with full column rank. In practice, the derived upper bounds for the mixed and componentwise condition numbers for Kronecker product linear least squares solution can be efficiently estimated using the Hager–Higham Algorithm. Copyright © 2012 John Wiley & Sons, Ltd.
Mechanisms and Möbius strips: understanding dynamic processes in annulenes
Authors: Castro Claire , Karney William L.
Published: January 2012

Exploratory computational studies on annulenes with planar, Möbius, and two‐twist topologies have resulted in new mechanisms to explain facile thermal configuration change (cis‐trans isomerization) for medium‐sized annulenes ([12]‐ to [16]annulene). Möbius π‐bond shifting through both aromatic and antiaromatic transition states, two‐twist π‐bond shifting, and planar nondegenerate π‐bond shifting can all be invoked to explain experimental results. Moreover, a simple bond‐shift rule, which is based on the change in number of trans CC double bonds (Δtrans), was developed that predicts the topology of the transition state(s) necessary to effect the desired cis‐trans isomerization. The bond‐shift rule was also applied to configuration change in dehydro[12]annulene. Finally, extensive investigation of the [14]annulene hypersurface revealed that numerous Möbius minima exist within 10 kcal/mol of the global minimum. Copyright © 2012 John Wiley & Sons, Ltd.
Computational investigations into new fluorescence quenching process induced by complexation of alkali metal ion
Authors: Xia Yong , Wang Xueye , Zhang Yu , Luo Benhua
Published: January 2012

A novel fluorescent switchable chemosensor 1, which is composed of an anthracene‐modified calix[4]crown in the 1,3‐alternate conformation, was calculated by density functional theory and time‐dependent density functional theory method. Geometries, molecular orbitals and binding thermal energies were evaluated at the restricted hybrid Becke's three‐parameter exchange functional using 6‐31 G(d) basis set and relativistic effective core potentials. The metal–ligand and cation–π interactions were investigated acting as two main types of driving force. Our calculations clearly show that solvent effects strongly influence cation selectivity, and K+ selectivity is recovered when even a few waters of hydration are considered. The calculations indicate that because of the photoinduced electron transfer effect, the addition of alkali metal ions have hardly any effect on the fluorescence of ligand 1 under neutral or basic conditions. Also, the high selectivity of ligand 1 for K+ and Rb+, under acidic conditions, the complexed metal ion can result in ammonium ion deprotonation, which leads to quenching of fluorescence of 1•H+. Copyright © 2012 John Wiley & Sons, Ltd.
Excited state mixed valence in a dual‐bridged three‐chromophore system
Authors: Dibrelle Marcelle , Hoekstra Ryan , Weaver Michael N. , Okada Keiji , Nelsen Stephen F. , Zink Jeffrey I.
Published: January 2012

The optical and resonance Raman spectra of the 2,2′: 6′,2″:6″,6‐trioxytriphenyl‐amine cation are measured and interpreted. This molecule contains two simultaneous types of coupling between three chromophores and two types of bridging atoms. The first and conventional coupling involves a single nitrogen bridge that couples all three aryl groups. The second is provided by the three oxygen atoms, each of which bridges two adjacent aryl groups. There are two bands in the visible region of the optical absorption spectrum; their assignment and the interpretation of the contributing orbitals and electronic states are described in terms of the neighboring orbital model that explains the effects of the two types of coupling. The bonding changes that take place in the excited electronic states are probed by resonance Raman spectroscopy intensities and analyzed using the time‐dependent theory of resonance Raman spectroscopy. The optical absorption spectrum was fit using the measured vibrational frequencies and excited state distortions. The distortions correlate well with the bonding changes predicted by the neighboring orbital model. The resonance Raman data and neighboring orbital model analysis reveal that the two optical absorption bands correspond to charge transfers from aryl groups with different nodal structures in their pi orbitals. Copyright © 2012 John Wiley & Sons, Ltd.
N = 1. Why People Matter in Medicines – an RCP report
Authors: Chaplin Steve
Published: January 2012

N = 1. Why People Matter in Medicines was produced by an RCP subgroup tasked with investigating the patient's perspective in medicines usage. Here, Steve Chaplin discusses the findings of the report and its key recommendations. Copyright © 2012 Wiley Interface Ltd
Effective surface passivation of AlGaN/GaN heterostructures by using PH3 plasma treatment and HfO2 dielectric
Authors: Zhang Chunfu , Hao Yue , Feng Qian
Published: January 2012

Different surface passivation methods of AlGaN/GaN heterostructures were investigated in this work. C‐V measurement shows that very high trap density (Dit) of 1.51×1013cm‐2eV‐1 exists at the AlGaN/GaN surface, which has activation energy of 0.765 eV. The surface treatment by using O2 plasma treatment and HfO2 dielectric can efficiently lower Dit to 3.57×1012cm‐2eV‐1 and 1.06×1012cm‐2eV‐1, repectively. To reduce these deep trap states further, a more effective passivation method is presented here. By using the PH3 plasma treatment before the HfO2 deposition, Dit was further greatly reduced and reached a very low value of 1.37×1011cm‐2eV‐1. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Relationship between residual carrier density and phase purity in InN grown by pressurized‐reactor MOVPE
Authors: Prasertsuk Kiattiwut , Hirata Masaki , Liu Yuhuai , Kimura Takeshi , Zhang Yuantao , Iwabuchi Takuya , Katayama Ryuji , Matsuoka Takashi
Published: January 2012

We have studied the relationship between the residual carrier density and the phase purity of the InN films grown on α‐Al2O3 substrate by pressurized‐reactor metalorganic vapour phase epitaxy. As simple and non‐destructive measurement methods of carrier density (ne), the plasmon dispersion analysis by the IR reflection spectra, and the estimation by the absorption edge of the IR transmission spectra have been adopted for the epitaxial InN films at room temperature, using Fourier transform infrared (FT‐IR) spectrometer. With increasing the growth temperature, plasma frequency estimated from the reflectance analysis shifts to the lower frequency which means the decrease of ne associated with the improvement of the crystal quality. Especially in case of zincblende containing InN grown at low temperature, the discrepancy occurred between ne derived from two methods. The ne analyzed in terms of the electronic band filling effect was found to be underestimated due to the use of bandgap energy of wurtzite phase instead of zincblende, since the bandgap energy of the latter has been reported to be 0.48 eV, much smaller than that of wurtzite, 0.68 eV. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sequential tunneling transport in GaN/AlGaN quantum cascade structures
Authors: Sudradjat Faisal F. , Zhang Wei , Driscoll Kristina , Liao Yitao , Bhattacharyya Anirban , Thomidis Christos , Zhou Lin , Smith David J. , Moustakas Theodore D. , Paiella Roberto
Published: January 2012

We demonstrate electronic sequential tunneling transport through the ground‐state subbands of GaN/Al0.15Ga0.85N quantum cascade structures grown on free‐standing GaN substrates. A pronounced transition from a high‐ to a low‐resistance state is observed as the applied voltage is increased. The measured current‐voltage characteristics are found to vary with temperature, structure design, and polarity of the applied bias, in a way that is fully consistent with theoretical expectations. The dominant transport mechanism is determined to be scattering‐assisted tunneling. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Highly enhanced migration in Pt‐catalyst‐assisted MOVPE InN by controlling the catalyst temperature
Authors: Sugita K. , Hotta T. , Hironaga D. , Mihara A. , Bhuiyan A. G. , Hashimoto A. , Yamamoto A.
Published: January 2012

This paper reports on the catalyst‐assisted metal‐organic vapor phase epitaxy (CA‐MOVPE) growth of InN with an independent control of catalyst temperature. When the catalyst temperature is increased above the growth temperature of InN, the grain size becomes large and full width at half maximum (FWHM) of X‐ray rocking curve (XRC) is drastically decreased The migration of precursors is highly enhanced and the crystal quality is improved by CA‐MOVPE with an independent heating system of the catalyst. This CA‐MOVPE system will open the possibility of the growth of high‐quality InN and In containing alloys especially with the higher In content (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improved crystalline quality and light output power of GaN‐based light‐emitting diodes grown on Si substrate by buffer optimization
Authors: Zou Xinbo , Wong Ka Ming , Yu Naisen , Chen Peng , Lau Kei May
Published: January 2012

High‐quality crack‐free GaN‐based light‐emitting diodes (LEDs) were grown on patterned Si substrate using a flow modulation method and a high‐temperature (HT)‐AlN/AlGaN superlattice structure (SLs) interlayer. The effects of these two techniques on material properties and device performance were studied. The enhanced crystalline quality can be attributed to a 3D to 2D coalescence process with fewer dislocations initiated from the interlayers. The light output power of blue LEDs was improved by 66% after successful implementation of flow modulation and new interlayers. After substrate removal and packaging, the optical power of circle LEDs with diameter of 300 μm could reach as high as 6.30 mW at 20 mA. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐efficiency AlGaN deep‐UV LEDs fabricated on a‐ and m‐axis oriented c‐plane sapphire substrates
Authors: Fujikawa Sachie , Hirayama Hideki , Maeda Noritoshi
Published: January 2012

We demonstrated high‐efficiency 270 nm‐band AlGaN deep‐ultraviolet (DUV) light‐emitting diodes (LEDs) fabricated on 0.15° off a‐ and m‐axis oriented c‐plane (0001) sapphire substrates grown by low‐pressure metal organic chemical‐vapor deposition (LP‐MOCVD). An approximately 4.5 μm‐thick low threading dislocation density (TDD) AlN template was grown on the sapphire substrate by using an NH3 pulsed‐flow multilayer (ML) growth method. We found that atomically flat surface can be easily obtained for AlN layer grown on a‐axis oriented sample. On the other hand, a step‐bunching was observed for the surface of AlN layer grown on m‐axis oriented sample. We found, from these results, that a‐axis oriented (0001) sapphire is more suitable for obtaining a flat surface in AlN template without step‐bunching. We also found that shorter wavelength LED can be obtained by using an a‐axis oriented (0001) sapphire, because an Al incorporation in AlGaN is slightly high for the growth on a‐axis oriented (0001) sapphire. We achieved high‐efficiency AlGaN quantum well (QW) DUV LEDs on AlN templates grown on both a‐ and m‐axis oriented sapphire substrates. The peak wavelengths of the LEDs fabricated on a‐ and m‐axis oriented sapphire were 270 and 277 nm, respectively. The maximum external quantum efficiencies (EQEs) of the LEDs fabricated on a‐ and m‐axis oriented sapphire were 3.8 and 3.2%, respectively, measured under room temperature (RT) continuous wave (CW) operations. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies of efficiency droop in GaN based LEDs
Authors: Phillips W. A. , Thrush E. J. , Zhang Y. , Humphreys C. J.
Published: January 2012

EL measurements have been made on a number of commercial LEDs as a function of drive current density “J” and temperature “T”. For one type of LED, (sample A), the magnitude of the peak in quantum efficiency (QE) is almost independent of temperature and the QE as a function of J can be successfully modelled in terms of the well‐known J=An+Bn2+Cn3 expression using the same relative magnitudes of B and C at different temperatures, with A alone increasing with increasing temperature. In another type, the peak in QE occurs at values of J that decrease with decreasing temperature but in this sample there is evidence of quantum well inhomogeneity. The weak temperature dependence of the C coefficient in sample A is strong evidence against thermally activated current leakage, mid‐gap trapping centres or intra‐band Auger recombination being dominant mechanisms for droop. The EL spectra show strong phonon replicas at low temperatures, but a lineshape analysis allows the main emission linewidth to be derived as a function of J and T. A model based on inhomogeneous broadening provides a good explanation for the results, and provides a link between the value of B and the effective 2D density of states. The results suggest that the most likely mechanism for droop in these devices is an indirect Auger effect mediated by phonons or localised states (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of 100 nm gate AlGaN/GaN HEMT and MMIC technology suitable for mm‐wave applications
Authors: Brückner Peter , Kiefer R. , Haupt C. , Leuther A. , Müller S. , Quay R. , Schwantuschke D. , Mikulla M. , Ambacher O.
Published: January 2012

In this paper a Gallium Nitride MMIC technology for RF‐ and microwave and high power amplifiers based on 100 nm gate technology is presented. The MMIC technology includes alloyed ohmic contacts, T‐shaped 100 nm gates, air‐bridges, MIM capacitors, inductors, and a full through wafer viahole backside process. As a key element for a high MMIC yield, we'll present low ohmic contact resistances with a high yield on several wafers in different processing batches and low leakage currents for a reliable device performance, respectively. Single HEMT performance exhibits PAE values of up to 60% and power densities of 1.3 W/mm. For a single stage power amplifier with a WG = 4 × 45 µm dual‐gate HEMT configuration, a gain beyond 10 dB at 60 GHz is presented. By using only one transistor for the amplifier stage, a maximum output power of more than 21 dBm and a PAE of 9.3% is achieved. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations on Si‐doped AlGaN: Below and above the Mott density
Authors: Forghani Kamran , Gharavipour Mohammadreza , Scholz Ferdinand , Thonke Klaus
Published: January 2012

Si doped AlxGa1‐xN layers with x ranging from 0 to 45% have been grown by metal‐organic vapour phase epitaxy in order to study their electrical properties. The Si doping concentration was varied over a wide range below and above the theoretically expected Mott density. By per­forming variable temperature Hall‐effect measurements on such epilayers, we could evaluate the donor ionization energy as a function of the Al content x and the Si doping concentration. As expected, we observed a very low ionization energy for Si concentrations above the Mott density (for which the conductivity changes towards metallic conductivity). The evaluated ionization energies for low carrier concentrations fit well with the predicted Si ionization energies (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Distribution of built‐in electric field in GaN(cap)/AlGaN/GaN(buffer) transistor heterostructures with various AlGaN thicknesses
Authors: Gladysiewicz M. , Kudrawiec R.
Published: January 2012

A theoretical approach supported by experimental data (i.e., measurements of built‐in electric field in AlGaN layer and two dimensional electron gas (2DEG) concentration at the AlGaN/GaN interface) has been proposed to determine the distribution of built‐in electric field in undoped polar GaN(cap)/AlGaN/GaN(buffer) heterostructures. In this method the Schrodinger and Poisson equations are solving self consistently for various boundary conditions. It is clearly shown that the built‐in electric field in AlGaN layer depends mainly on the surface boundary condition whereas the concentration of 2DEG at AlGaN/GaN interface depends on two boundary conditions (i.e., the Fermi‐level position on GaN(cap) surface and inside GaN(buffer) layer). Comparing the measured built‐in electric field in AlGaN layer with this one calculated for various Fermi‐level position on GaN surface it is possible to determine the Fermi‐level pinning on GaN(cap) surface. Next it is possible to determine the Fermi‐level position in GaN(buffer) layer at a given distance from AlGaN/GaN interface. For this purpose the measured 2DEG concentration was compared with this one calculated for the fixed Fermi‐level position on GaN(cap) surface and the varied Fermi‐level position in GaN buffer layer. In this way the distribution of built‐in electric can be determined for real heterostructures for which the built‐in electric field in AlGaN layer is measured by electromodulation spectroscopy and 2DEG concentration is extracted from Hall measurements. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron holography of an in‐situ biased GaN‐based LED
Authors: Liu L. Z.‐Y. , McAleese C. , Sridhara Rao D. V. , Kappers M. J. , Humphreys C. J.
Published: January 2012

Electron holography was used to measure the electrostatic potential distribution in an LED chip at high spatial resolution, from which the internal polarization field can be derived. A cross‐sectional TEM lamella on a workable LED die containing five InGaN/GaN quantum wells (QWs) connected to electrodes that fit into an in‐situ biasing TEM holder was prepared using a focused ion beam (FIB). Off‐axis electron holography under Lorentz mode was carried out to study the p ‐MQW‐n region and phase profiles were derived at different reverse biasing conditions. p ‐n contrast has been shown in the calibrated electrostatic potential mapping. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of GaN and AlGaN on (100) β‐Ga2O3 substrates
Authors: Ito Shun , Takeda Kenichiro , Nagata Kengo , Aoshima Hiroki , Takehara Kosuke , Iwaya Motoaki , Takeuchi Tetsuya , Kamiyama Satoshi , Akasaki Isamu , Amano Hiroshi
Published: January 2012

The crystalline quality of GaN and Al0.08Ga0.92N epitaxial layers on (100) β‐Ga2O3 substrates was significantly improved by the facet‐controlled growth method. The facets were controlled by changing the nitrogen ambient thermal annealing temperature. We demonstrated the high‐crystalline‐quality GaN and Al0.08Ga0.92N on β‐Ga2O3 substrates, which were comparable to GaN and AlGaN on sapphire substrates using low‐temperature buffer layers. This method is useful for the fabrication of vertical‐type ultraviolet (UV) light‐emitting diodes (LEDs) on β‐Ga2O3 substrates. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of InGaN/GaN epitaxial layers by aberration corrected TEM/STEM
Authors: Amari Houari , Ross Ian M. , Wang Tao , Walther Thomas
Published: January 2012

In this study, the thickness, interface quality, and elemental composition of InGaN/GaN epitaxial layers are investigated. Samples were grown by Metal‐Organic Chemical Vapour Deposition (MOCVD) on sapphire (0001) substrates. The structure was designed to form In0.1Ga0.9N quantum wells (QWs) with thicknesses decreasing from 8 nm to 0.25 nm embedded between 10 nm GaN barriers. Scanning transmission electron microscopy (S)TEM, energy‐dispersive X‐ray spectroscopy (EDXS) and electron energy loss spectroscopy (EELS) have been applied using both a JEOL 2010F field‐emission gun (FEG) TEM/STEM microscope and the newly developed spherical aberration‐corrected JEOL R005 cold FEG (S)TEM. The peak indium concentration of the widest QWs was determined to lie between 0.12 and 0.15 (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and stacking fault reduction in semi‐polar GaN films on planar Si(112) and Si(113)
Authors: Ravash Roghaiyeh , Veit Peter , Müller Mathias , Schmidt Gordon , Dempewolf Anja , Hempel Thomas , Bläsing Jürgen , Bertram Frank , Dadgar Armin , Christen Jürgen , Krost Alois
Published: January 2012

We report on metal organic vapor phase epitaxy of semi‐polar growth of nearly (1$ \bar 1 $06) oriented GaN films on Si(112) and (1$ \bar 1 $05) and (1$ \bar 1 $04) GaN on Si(113). We analyze the GaN crystallites by field emission‐scanning electron microscopy (FE‐SEM), scanning transmission electron microscopy (STEM), photoluminescence (PL), and cathodoluminescence (CL). A correlation between optical properties and microstructure is presented. Our studies reveal a significant reduction of basal plane stacking faults (BSFs) in semi‐polar GaN grown on planar Si(112) by applying a low temperature (LT) AlN interlayer. We find that the insertion of the LT‐AlN interlayer can eliminate the stacking faults in the upper GaN layer, when the LT‐AlN interlayer is inserted on a smooth GaN buffer. The LT‐AlN interlayer results in lattice relaxation due to misfit dislocation formation at the GaN/LT–AlN interface. In comparison, GaN grown on Si(113) with same growth conditions and a rough GaN surface does not show any BSF reduction while it is reduced for a smooth GaN layer (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐Markovian State‐Space Models in Dependability Evaluation
Authors: Distefano Salvatore , Trivedi Kishor S.
Published: January 2012

The purpose of this paper is to provide an up‐to‐date treatment of advanced analytic, state‐space based techniques to study dependability models with non‐exponential distributions. We first provide an overview of different techniques for the solution of non‐Markovian state‐space based models, including phase‐type expansion and a general framework which allows us to deal with renewal, semi‐Markov, and Markov‐regenerative processes, trying to characterize them on dependability contexts. In the last part of the paper, we illustrate these techniques by means of some examples dealing with common non‐exponential reliability behaviors. Our aim is to provide a reference for practising engineers, researchers, and students in state‐space dependability modeling and evaluation. Copyright © 2012 John Wiley & Sons, Ltd.
Allergen Arrays for Antibody Screening and Immune Cell Activation Profiling Generated by Parallel Lipid Dip‐Pen Nanolithography
Authors: Sekula‐Neuner Sylwia , Maier Jana , Oppong Emmanuel , Cato Andrew C. B. , Hirtz Michael , Fuchs Harald
Published: January 2012

Multiple‐allergen testing for high throughput and high sensitivity requires the development of miniaturized immunoassays that allow for a large test area and require only a small volume of the test analyte, which is often available only in limited amounts. Developing such miniaturized biochips containing arrays of test allergens needs application of a technique able to deposit molecules at high resolution and speed while preserving its functionality. Lipid dip‐pen nanolithography (L‐DPN) is an ideal technique to create such biologically active surfaces, and it has already been successfully applied for the direct, nanoscale deposition of functional proteins, as well as for the fabrication of biochemical templates for selective adsorption. The work presented here shows the application of L‐DPN for the generation of arrays of the ligand 2,4‐dinitrophenyl[1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐[6‐[(2,4‐dinitrophenyl)amino]hexanoyl] (DNP)] onto glass surfaces as a model system for detection of allergen‐specific Immunoglobin E (IgE) antibodies and for mast cell activation profiling.
Structural insight into RNA recognition motifs: versatile molecular Lego building blocks for biological systems
Authors: Muto Yutaka , Yokoyama Shigeyuki
Published: January 2012

‘RNA recognition motifs (RRMs)’ are common domain‐folds composed of 80–90 amino‐acid residues in eukaryotes, and have been identified in many cellular proteins. At first they were known as RNA binding domains. Through discoveries over the past 20 years, however, the RRMs have been shown to exhibit versatile molecular recognition activities and to behave as molecular Lego building blocks to construct biological systems. Novel RNA/protein recognition modes by RRMs are being identified, and more information about the molecular recognition by RRMs is becoming available. These RNA/protein recognition modes are strongly correlated with their biological significance. In this review, we would like to survey the recent progress on these versatile molecular recognition modules. WIREs RNA 2012, 3:229–246. doi: 10.1002/wrna.1107

This article is categorized under:

RNA Interactions with Proteins and Other Molecules > Protein–RNA Recognition

RNA Interactions with Proteins and Other Molecules > RNA–Protein Complexes
Hadronic top-quark pair-production with one jet and parton showering
Authors: Alioli Simone , Moch Sven-Olaf , Uwer Peter
Published: January 2012

Abstract

We present a calculation of heavy-flavor production in hadronic collisions in association with one jet matched to parton shower Monte Carlo programs at next-to-leading order in perturbative QCD. Top-quark decays are included and spin correlations in the decay products are taken into account. The calculation builds on existing results for the radiative corrections to heavy-quark plus one jet production and uses the POWHEG BOX for the interface to the parton shower programs PYTHIA or HERWIG. A broad phenomenological study for the Large Hadron Collider and the Tevatron is presented. In particular we study — as one important sample application — the impact of the parton shower on the top-quark charge asymmetry.
Risky Business: Risk Perception and the Use of Medical Services among Customers of DTC Personal Genetic Testing
Authors: Kaufman David J. , Bollinger Juli M. , Dvoskin Rachel L. , Scott Joan A.
Published: January 2012

Direct‐to‐consumer genetic testing has generated speculation about how customers will interpret results and how these interpretations will influence healthcare use and behavior; however, few empirical data on these topics exist. We conducted an online survey of DTC customers of 23andMe, deCODEme, and Navigenics to begin to address these questions. Random samples of U.S. DTC customers were invited to participate. Survey topics included demographics, perceptions of two sample DTC results, and health behaviors following DTC testing. Of 3,167 DTC customers invited, 33% (n = 1,048) completed the survey. Forty‐three percent of respondents had sought additional information about a health condition tested; 28% had discussed their results with a healthcare professional; and 9% had followed up with additional lab tests. Sixteen percent of respondents had changed a medication or supplement regimen, and one‐third said they were being more careful about their diet. Many of these health‐related behaviors were significantly associated with responses to a question that asked how participants would perceive their colon cancer risk (as low, moderate, or high) if they received a test result showing an 11% lifetime risk, as compared to 5% risk in the general population. Respondents who would consider themselves to be at high risk for colon cancer were significantly more likely to have sought information about a disease (p = 0.03), discussed results with a physician (p = 0.05), changed their diet (p = 0.02), and started exercising more (p = 0.01). Participants’ personal health contexts—including personal and family history of disease and quality of self‐perceived health—were also associated with health‐related behaviors after testing. Subjective interpretations of genetic risk data and personal context appear to be related to health behaviors among DTC customers. Sharing DTC test results with healthcare professionals may add perceived utility to the tests.