bluuebunny/crossref_metadata_2025 huggingface dataset:
Validated LC–MS/MS method for quantification of agomelatine in human plasma and its application in a pharmacokinetic study
Authors: Patil Satish R. , Nerurkar Ketan K. , Kalamkar Ashok M. , Pukale Vishwas , Mangaonkar Kiran V. , Pingale Satish G.
Published: January 2012

An analytical method based on liquid–liquid extraction has been developed and validated for analysis of agomelatine in human plasma. Fluoxetine was used as an internal standard for agomelatine. A Betasil C18 (4.0 × 100 mm, 5 µm) column provided chromatographic separation of analytes followed by detection with mass spectrometry. The method involves simple isocratic chromatographic conditions and mass spectrometric detection in the positive ionization mode using an API‐4000 system. The proposed method has been validated with linear range of 0.050–8.000 ng/ml for agomelatine. The intra‐run and inter‐run precision values are within 12.12% and 9.01%, respectively, for agomelatine at the lower limit of quantification level. The overall recovery for agomelatine and fluoxetine was 67.10% and 72.96%, respectively. This validated method was used successfully for analysis of plasma samples from a pharmacokinetic study. Copyright © 2012 John Wiley & Sons, Ltd.
Bridge building within the province of proactivity
Authors: Fuller Jerry Bryan , Marler Laura E. , Hester Kim
Published: January 2012

The research questions posed in this study highlight the importance of valuing proactivity in both prompting an individual to engage in proactive behavior and encouraging the expression of that behavior. We integrate a variety of constructs from the proactivity literature to gain a deeper understanding of proactive behavior as it relates to proactive motivation and supervisory performance evaluations. First, we draw upon self‐determination theory, expectancy–value theory, and the recent integration of the proactive motivation literature to hypothesize that proactive behavior is predicted by the interaction of “can do” and “reason to” proactive motivational states. Second, on the basis of performance theory, we hypothesize that the relationship between proactive behavior and performance depends upon the extent to which the supervisor values proactivity. Specifically, we argue that supervisors with proactive personalities are more likely to value and reward subordinate proactive behavior than passive supervisors. Results provide support for both of our hypotheses. Interestingly, results show that proactive behavior did not result in negative consequences but rather that there was a cost (i.e., lower performance rating) for not taking charge for employees with proactive supervisors. Copyright © 2012 John Wiley & Sons, Ltd.
Burnout, employee engagement, and coping in high‐risk occupations
Authors: Falkoski Jennifer
Published: January 2012

This study assessed whether there were any significant relationships among burnout, type of coping, and employee engagement in a population of employees actively working in the medical and mental health fields. It also evaluated preferred workplace motivators across two overarching job categories: medical and mental health caregivers and administrative and supporting roles. The results showed that as employee burnout increased, so did the use of more harmful coping mechanisms. The study also found an inverse relationship between emotional exhaustion and employee engagement. Additionally, employee engagement and personal accomplishment were positively related. Employee‐preferred workplace motivators across two job‐overarching job categories were also assessed. The highest‐ranking employee‐preferred workplace motivators identified in the participant sample were nature of the work itself, responsibility, salary, relationship with peers, and professional growth.
A model for femininity and military leadership
Authors: Walker Karen M.
Published: January 2012

Although the concept of women as leaders is not a novelty, recent trends have women breaking through traditional “glass ceilings,” thus pioneering female leadership roles in the workplace and the military. Women in leadership is a movement, a paradigm shift. The author offers a unique leadership model calculated from an instrumental multiple case study analysis of female military officers leading in male‐dominated environments. The model proposes four principle dimensions: femininity, self‐efficacy, emotional intelligence, and teamwork (F‐SET). It has a feminist appeal, although it engages leadership theory from other innovative angles.
Evaluation of different methods of protein extraction and identification of differentially expressed proteins upon ethylene‐induced early‐ripening in banana peels
Authors: Zhang Li‐Li , Feng Ren‐Jun , Zhang Yin‐Dong
Published: January 2012

BACKGROUND: Banana peels (Musa spp.) are a good example of a plant tissue where protein extraction is challenging due to the abundance of interfering metabolites. Sample preparation is a critical step in proteomic research and is critical for good results.

RESULTS: We sought to evaluate three methods of protein extraction: trichloroacetic acid (TCA)‐acetone precipitation, phenol extraction, and TCA precipitation. We found that a modified phenol extraction protocol was the most optimal method. SDS‐PAGE and two‐dimensional gel electrophoresis (2‐DE) demonstrated good protein separation and distinct spots of high quality protein. Approximately 300 and 550 protein spots were detected on 2‐DE gels at pH values of 3–10 and 4–7, respectively. Several spots were excised from the 2‐DE gels and identified by mass spectrometry.

CONCLUSIONS: The protein spots identified were found to be involved in glycolysis, the tricarboxylic acid cycle, and the biosynthesis of ethylene. Several of the identified proteins may play important roles in banana ripening. Copyright © 2012 Society of Chemical Industry
Simultaneous determination of non‐steroidal anti‐inflammatory drugs in river water by gas chromatography‐mass spectrometry
Authors: Shin Ho‐Sang , Oh Jin‐Aa
Published: January 2012

The gas chromatography/mass spectrometric assay method was developed for the determination of 13 non‐steroidal anti‐inflammatory drugs (NSAIDs) in river water. Extraction was achieved by a liquid‐phase extraction procedure using methylene chloride. The extract was reacted for 30 min at 80°C based on the formation of methyl ester with 1.0 M HCl in methanol and extraction of the derivative with ethyl acetate, which was then measured by gas chromatography‐mass spectrometry. The limit of quantification of NSAIDs was 1.0–60 ng/L and the calibration curve showed linearity being greater than r=0.997. The method was used to analyze ten river water samples from various regions in Korea. Diclofenac, indoprofen, ketoprofen and loxoprofen were detected at concentration of up to 1.29 μg/L in river water. The developed method may prove valuable for use in the national monitoring project of NSAIDs in surface water.
Preparation and evaluation of thermally stable nano‐structured self‐doped polythiophene coating for analysis of phthalate ester trace levels
Authors: Mehdinia Ali , Bashour Farzane , Roohi Fateme , Jabbari Ali , Saleh Abolfazl
Published: January 2012

Nano‐structured self‐doped polythiophene (SPT) electrodeposited in the presence of fluorinated organic acid was applied as a thermally stable conductive polymer‐based solid‐phase microextraction (SPME) fiber candidate. Quantitative determination of trace levels of phthalate esters including dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), and diethylhexyl phthalate (DEHP) was carried out using this novel fiber, coupling with gas chromatography‐flame ionization detector (GC‐FID). The SPT coating was proved to be stable at high temperatures (∼350°C) with a high extraction capacity and long lifetime (more than 60 times). Improved temperature resistance was obtained by the presence of sulfonated groups in the backbone of polymer. Thermal stability of novel SPT was superior to common polythiophene (synthesized in LiClO4). The extraction procedure was optimized by means of the Taguchi orthogonal array experimental design with an OA16 (45) matrix including extraction temperature, extraction time, salt concentration, stirring rate, and headspace volume. The good linearity was obtained for most compounds with correlation coefficients (R2) of between 0.993 and 0.995. The detection limits were lower than 0.12 ng/mL for dimethyl phthalate, DEP, dibutyl phthalate, and diethylhexyl phthalate. The method was successfully applied to the analysis of water samples with the recoveries from 90±1 to 107±1%.
Molecularly imprinted polymer surfaces as solid‐phase extraction sorbents for the extraction of 2‐nitrophenol and isomers from environmental water
Authors: Guan Wei , Han Changri , Wang Xue , Zou Xiaohua , Pan Jianming , Huo Pengwei , Li Chunxiang
Published: January 2012

The novel surface molecularly imprinted polymer (MIP) with 2‐nitrophenol (2‐NP) as the template has been prepared and used as the adsorbent for the solid‐phase extraction (SPE). The selectivity of the polymer was checked toward several selected nitrophenols (NPs) such as 2‐NP, 3‐nitrophenol (3‐NP), 4‐nitrophenol (4‐NP) and 2,4,6‐trichlorophenol (2,4,6‐TCP). Under the optimized conditions, high sensitivity (detection limits: 0.07–0.12 ng/mL) and good reproducibility of analytes (2.3–4.8% for four cycles) were achieved. Then, the method was applied for the analysis of selected phenols in spiked tap, lake and river water samples. High recoveries (>83.3%) for nitrophenols (NPs) were obtained, but lower recoveries (<63.4%) were achieved for 2,4,6‐TCP. The method was found to be linear in the range of 1–300 ng/mL with correlation coefficients (R2) greater than 0.99 and repeatability relative standard deviation (RSD) below 7.2% in all cases. For analysis of 120 mL water samples, the method detection limits (LODs) ranged from 0.10 to 0.22 ng/mL and the limit of quantification (LOQs) from 0.33 to 0.72 ng/mL. These results showed the suitability of the MIP‐SPE method for the selective extraction of a group of structurally related isomeric compounds.
Application of ultra‐performance liquid chromatography coupled with mass spectrometry to metabonomic study on spontaneously hypertensive rats and intervention effects of Ping Gan prescription
Authors: Jiang Haiqiang , Nie Lei , Li Yunlun , Xie Jun
Published: January 2012

This study describes the metabonomic characters of the spontaneously hypertensive rats (SHR) and intervention effects of Ping Gan prescription. Ultra performance LC coupled with Q‐TOF MS (UPLC/MS‐Q‐TOF) was employed to develop a metabonomic method of the plasma of SHR. There was a significant difference in metabolic profiling observed between predose group of Wistar Kyoto rats and model group (SHR) by using the principal components analysis (PCA). Some significant changes in metabolites such as LysoPC(22:6), LysoPC(20:4), LysoPC(18:1), cholylglycine, PE(P‐16:0e/0:0), sphingosine‐1‐phosphate, and 2‐oxo‐4‐methylthio butanoic acid were identified. These biochemical changes were associated with the disturbance in sphingolipid metabolism and fat metabolism, which would be helpful to further understand the essence of hypertension and the therapeutic mechanism of Ping Gan prescription. This study suggests that the metabonomic method may be a valuable and feasible tool to explore the therapeutic effect and mechanism of traditional Chinese medicine (TCM).
Simultaneous determination of polyphenols and major purine alkaloids in Greek Sideritis species, herbal extracts, green tea, black tea, and coffee by high‐performance liquid chromatography‐diode array detection
Authors: Samanidou Victoria , Tsagiannidis Anastasios , Sarakatsianos Ioannis
Published: January 2012

Herein, a high‐performance liquid chromatography‐diode array detection method has been developed for the simultaneous determination of 15 phenolic antioxidants: flavan‐3‐ols, (−)‐epigallocatechin, (+)‐catechin, (−)‐epigallocatechin gallate, (−)‐epicatechin, (−)‐epicatechin gallate, (−)‐gallocatechin, a phenolic acid (gallic acid), a hydroxycinnamic acid (chlorogenic acid), flavones (apigenin), flavonols (kaempferol, quercetin, and myricetin), and purine alkaloids (caffeine theophylline, theobromine) in different herb extracts, tea, and coffee varieties. The developed method was validated and successfully applied in order to determine the polyphenolic content to estimate the antioxidant activity of the Sideritis species commonly known as Greek mountain tea. To the best of our knowledge, this is the first report on the quantitative determination of catechins and other polyphenols in Greek mountain tea. Acidic hydrolysis was necessary for the simultaneous determination of the aglycones of the target analytes. According to our results, chlorogenic acid, myricetin, apigenin, catechin, and epicatechin gallate are found in the Sideritis species.
Quantitative structure–retention relationship of curcumin and its analogues
Authors: Zheng Xue‐Hua , Shao Yong‐Xian , Li Zhe , Liu Ming , Bu Xianzhang , Luo Hai‐Bin , Hu Xiaopeng
Published: January 2012

The natural product curcumin is widely used in Asian countries for the treatment of several diseases. However, the clinical potential of curcumins remains limited due to their relatively poor bioavailability and no experimental data about their lipophilicity for bioavailability prediction. To evaluate the retention and lipophilicity of curcumin and its 31 newly synthesized analogues, they were subjected to 3D quantitative structure–retention relationship studies by RP‐HPLC. Superior than the classical four‐variant quantitative structure–retention relationship model (conventional r2=0.734), the 3D comparative molecular similarity index analysis model with combined steric, electrostatic, and H‐bond donor fields, resulted in a robust structure–retention correlation (cross‐validated q2=0.613 and r2=0.979). The statistical analyses indicate that the electrostatic and H‐bond donor fields have a primary influence on the chromatographic retention of analytes. The predictive power and robustness of the derived comparative molecular similarity index analysis model was further confirmed by the test‐set validation (q2=0.702, r2=0.905, and the slope K=1.016) and Y‐randomization examination. Statistically significant and physically meaningful 3D‐quantitative structure–retention relationship provided better insight into understanding the retention behaviors of curcumin and its analogues, and their separation mechanism in a given RP‐HPLC system.
Micropatterns of Non‐Circular Droplets of Nanostructured PS‐b‐PEO Copolymer by Solvent‐Assisted Wetting on a Chemically Periodic Surface
Authors: Kim Tae Hee , Park Youn Jung , Song Giyoung , Kim Dong Ha , Huh June , Karthaus Olaf , Park Cheolmin
Published: January 2012

A method to fabricate micropatterns of non‐circular droplets of a self‐assembled block copolymer by solvent‐assisted wetting on chemically periodic surface is presented. The block copolymer is dewetted on a topographic pre‐pattern to form an array of microdroplets with a sphere‐capped shape and circular contact line. The droplets are then transferred onto a chemically periodic Au line pattern microcontact‐printed with two types of self‐assembled monolayers (SAMs). Solvent vapor application provides sufficient mobility to the block copolymer molecules to induce spreading of the transferred droplets, resulting in two types of non‐circular microdroplet growth. The growth behavior depends on the size of initial droplets relative to periodic line width and on the initial registries of as‐transferred droplets.
Poly(disubstituted acetylene)s With Pendant Naphthalimide‐Based Fluorophore Groups
Authors: Sivkova Radoslava , Vohlídal Jiří , Bláha Michal , Svoboda Jan , Sedláček Jan , Zedník Jiří
Published: January 2012

New stable polyacetylenes whose quantum yield of fluorescence is increased up to 62% because of the presence of pendant 4‐(piperidine‐1‐yl)‐1,8‐naphtalimide groups are described. The polymers are prepared by two‐step modification of copolymers of 1‐(4‐tert‐butylphenyl)‐6‐chlorohex‐1‐yne and 1‐phenylhex‐1‐yne consisting of the exchange of chlorine atoms at side groups for azide groups and subsequent Huisgen click reaction of the azide groups with ethynyl groups of N‐(prop‐1‐yne‐3‐yl)‐4‐(piperidine‐1‐yl)‐1,8‐naphthalimide. Modification is evidenced by 1H NMR, IR, Raman and UV–vis spectroscopy. Modified polymers show the excitation energy transfer from their main chains on fluorophores and nearly preservation of fluorescence properties of fluorophores upon their binding to polymer chains.
A discrete Fourier transform based on Simpson's rule
Authors: Singh P. , Singh V.
Published: January 2012

Fourier analysis plays a vital role in the analysis of continuous‐time signals. In many cases, we are forced to approximate the Fourier coefficients based on a sampling of the time signal. Hence, the need for a discrete transformation into the frequency domain giving rise to the classical discrete Fourier transform. In this paper, we present a transformation that arises naturally if one approximates the Fourier coefficients of a continuous‐time signal numerically using the Simpson quadrature rule. This results in a decomposition of the discrete signal into two sequences of equal length. We show that the periodic discrete time signal can be reconstructed completely from its discrete spectrum using an inverse transform. We also present many properties satisfied by this transform. Copyright © 2012 John Wiley & Sons, Ltd.
Estimates of learning rates of regularized regression via polyline functions
Authors: Cao Feilong , Lee Joonwhoan , Zhang Yongquan
Published: January 2012

Based on the simplicity and calculability of polyline function, we consider, in this paper, the regularized regression learning algorithm associated with the least square loss and the set of polyline function . The target is the error analysis for the regression problem. The approach presented in the paper yields satisfactory learning rates. The rates depend on the approximation property of and on the capacity of measured by covering numbers. Under some certain conditions, the rates achieve m−4/5 log m. Copyright © 2012 John Wiley & Sons, Ltd.
Strong well‐posedness of a three phase problem with nonlinear transmission condition
Authors: Kotschote Matthias
Published: January 2012

We prove existence and uniqueness of strong solutions to a quasilinear parabolic‐elliptic system modelling an ionic exchanger. This chemical system consists of three phases connected with nonlinear boundary conditions. The most interesting difficulty of our problem manifests in the nonlinear transmission condition, as almost all quantities are non‐linearly involved in this boundary equation. Our approach is based on the contraction mapping principle, where maximal Lp‐regularity of the associated linear problem is used to obtain a fixed point equation of the starting problem. Copyright © 2012 John Wiley & Sons, Ltd.
Glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5) expression correlates with malignant choline phospholipid metabolite profiles in human breast cancer
Authors: Cao Maria D. , Döpkens Mailin , Krishnamachary Balaji , Vesuna Farhad , Gadiya Mayur M. , Lønning Per E. , Bhujwalla Zaver M. , Gribbestad Ingrid S. , Glunde Kristine
Published: January 2012

Altered choline phospholipid metabolism is a hallmark of cancer, leading to malignant choline metabolite profiles consisting of low glycerophosphocholine (GPC) and high phosphocholine (PC) in human breast cancers. Glycerophosphocholine phosphodiesterase (GPC‐PDE) catalyzes the degradation of GPC to free choline and glycerol‐3‐phosphate. The gene(s) encoding for the GPC‐PDE(s) responsible for GPC degradation in breast cancers have not yet been identified. Here, we demonstrate for the first time that the GPC‐PDE encoded by glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5) is associated with breast cancer malignancy. Two human breast cancer cell lines (n = 8 and n = 10) and primary human breast tumor samples (n = 19) were studied with combined MRS and quantitative reverse transcription‐polymerase chain reaction to investigate several isoforms of GDPD expression with respect to choline phospholipid metabolite levels. Of the five GDPDs tested, GDPD5 was found to be significantly overexpressed in highly malignant estrogen receptor negative (ER–) compared with weakly malignant estrogen receptor positive (ER+) human breast cancer cells (p = 0.027) and breast tumors from patients (p = 0.015). GDPD5 showed significantly positive correlations with PC (p < 0.001), total choline (tCho) (p = 0.007) and PC/GPC (p < 0.001) levels in human breast tumors. GDPD5 showed a trend towards a negative correlation with GPC levels (p = 0.130). Human breast cancers with malignant choline metabolite profiles consisting of low GPC and high PC levels highly co‐expressed GDPD5, choline kinase alpha (CHKA) and phosphatidylcholine‐specific phospholipase D1 (PLD1), whereas cancers containing high GPC and relatively low PC levels displayed low co‐expression of GDPD5, CHKA and PLD1. GDPD5, CHKA and PLD1 were significantly overexpressed in highly malignant ER– tumors in our patient cohort. Our study identified GDPD5 as a GPC‐PDE that probably participates in the regulation of choline phospholipid metabolism in breast cancer, which possibly occurs in cooperation with CHKA and PLD1. Copyright © 2012 John Wiley & Sons, Ltd.
Are the psychological needs of adolescent survivors of pediatric cancer adequately identified and treated?
Authors: Kahalley Lisa S. , Wilson Stephanie J. , Tyc Vida L. , Conklin Heather M. , Hudson Melissa M. , Wu Shengjie , Xiong Xiaoping , Stancel Heather H. , Hinds Pamela S.
Published: January 2012

Objectives

To describe the psychological needs of adolescent survivors of acute lymphoblastic leukemia (ALL) or brain tumor (BT), we examined the following: (i) the occurrence of cognitive, behavioral, and emotional concerns identified during a comprehensive psychological evaluation and (ii) the frequency of referrals for psychological follow‐up services to address identified concerns.

Methods

Psychological concerns were identified on measures according to predetermined criteria for 100 adolescent survivors. Referrals for psychological follow‐up services were made for concerns previously unidentified in formal assessment or not adequately addressed by current services.

Results

Most survivors (82%) exhibited at least one concern across domains: behavioral (76%), cognitive (47%), and emotional (19%). Behavioral concerns emerged most often on scales associated with executive dysfunction, inattention, learning, and peer difficulties. Cranial radiation therapy was associated with cognitive concerns, χ2(1, N = 100) = 5.63, p < 0.05. Lower income was associated with more cognitive concerns for ALL survivors, t(47) = 3.28, p < 0.01, and more behavioral concerns for BT survivors, t(48) = 2.93, p < 0.01. Of the survivors with concerns, 38% were referred for psychological follow‐up services. Lower‐income ALL survivors received more referrals for follow‐up, χ2(1, N = 41) = 8.05, p < 0.01. Referred survivors had more concerns across domains than non‐referred survivors, ALL: t(39) = 2.96, p < 0.01; BT: t(39) = 3.52, p < 0.01. Trends suggest ALL survivors may be at risk for experiencing unaddressed cognitive needs.

Conclusions

Many adolescent survivors of cancer experience psychological difficulties that are not adequately managed by current services, underscoring the need for long‐term surveillance. In addition to prescribing regular psychological evaluations, clinicians should closely monitor whether current support services appropriately meet survivors' needs, particularly for lower‐income survivors and those treated with cranial radiation therapy. Copyright © 2012 John Wiley & Sons, Ltd.
Adherence with antiosteoporosis medications: a primary‐care study
Authors: McGowan Bernie , Bennett Kathleen
Published: January 2012

The authors describe the results of a study of adherence and persistence in all and new users of anti‐osteoporosis therapies in general practice in Ireland. Copyright © 2012 Wiley Interface Ltd
Photoluminescence properties of Al‐rich AlXGa1‐XN grown on AlN/sapphire template by MOCVD
Authors: Zeng Jianping , Yan Jianchang , Wang Junxi , Cong Peipei , Li Jinmin , Sun Shuaishuai , Tao Ye
Published: January 2012

Optical properties of the un‐doped and the Si‐doped AlGaN epilayers have been studied by using the deep ultraviolet photoluminescence (PL) spectrum. The samples were grown under the same conditions on a HT‐AlN template by low pressure metal‐organic chemical vapour deposition (LP‐MOCVD). The Al composition and the relaxation status were detected to be 0.654 and 42% for the un‐doped AlGaN, 0.657 and 63% for the Si‐doped AlGaN by use the high resolution XRD. The temperature dependent PL spectra of both AlGaN epilayers reveal a typical energy broadband around 2.85 eV involving the deep level impurity transitions and the different peak shift behaviour of localized excitons around 4.97 eV with temperature increasing from 13 K to 120 K. The luminescence intensity of the excitons in both samples indicated a thermal quenching process with two activation energies. The two activation energies Eact1 and Eact2 were assigned to the thermal barrier resulting from the strong composition fluctuation in AlGaN and the binding energy of the excitons, respectively. The different PL oscillation properties of two samples at the 2.85 eV emission band indicate the Si‐doped AlGaN epilayer has significant interference of interface and surface. The significant oscillations were attributed to less centres of nucleation in the Si‐doped AlGaN, as has been supported by atomic force microscopy (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of nitrogen precursor and its flow rate on the quality and the residual doping in GaN grown by molecular beam epitaxy
Authors: Cordier Yvon , Natali Franck , Chmielowska Magdalena , Leroux Mathieu , Chaix Catherine , Bouchaib Pierre
Published: January 2012

This work is dedicated to the growth of GaN layers by molecular beam epitaxy. Plasma assisted and ammonia growth techniques are compared. The influence of the nitrogen source (NH3 or N2 plasma) as well as its flow rate is investigated. In particular, we show how the amount of donors incorporated in the layers depends on the growth conditions. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN on sapphire mesa technology
Authors: Herfurth Patrick , Men Yakiv , Rösch Rudolph , Carlin Jean‐Francois , Grandjean Nicolas , Kohn Erhard
Published: January 2012

This contribution reports on a GaN on sapphire mesa technology for lattice matched InAlN/GaN HEMTs similar to a silicon on insulator technology. Ultrathin buffer layers between 500 nm and 100 nm have been deep mesa etched down to the substrate to avoid cross talk between devices through the buffer and provide full transparency outside the active device area (of special interest to biochemical sensor applications).The heterostructure characteristics were: NS > 1.6 x 1013 cm‐2, Rsh < 600 Ω/□. 0.25 µm gate length HEMT device characteristics are moderate, but essentially similar down to 200 nm buffer thickness. Devices on 100 nm buffer layer are still difficult to reproduce. Ion/Ioff was up to 109 and sub‐threshold slopes down to 90 mV/dec (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Residual strain in recessed AlGaN/GaN heterostructure field‐effect transistors evaluated by micro photoluminescence measurements
Authors: Mikulics Martin , Hardtdegen Hilde , Winden Andreas , Fox Alfred , Marso Michel , Sofer Zdeněk , Lüth Hans , Grützmacher Detlev , Kordoš Peter
Published: January 2012

The residual strain in AlGaN/GaN heterostructure field‐effect transistors (HFETs) with recessed gates and their non‐recessed counterparts were investigated by micro photoluminescence measurements (µ‐PL). It is found that strain relaxation accounts for the observed sheet carrier density reduction after gate recessing. The usefulness of the method for device processing optimization is demonstrated. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of the optical properties of InGaN/GaN nanorods with different indium composition
Authors: Wang Q. , Bai J. , Gong Y. P. , Wang T.
Published: January 2012

In this paper, the optical properties of our nanorod array structures fabricated from InGaN/GaN multiple quantum wells (MQWs) epiwafers with two different kinds of indium compositions have been investigated. The optical performance of our nanorod samples are significantly enhanced compared to the as‐grown epiwafers, in particular, such improvement is much more pronounced in the nanorod array structure with a higher indium composition. This is mainly attributed to effective strain relaxation as a result of fabrication into nanorod structure, leading to significant reduction in quantum confined Stark effect (QCSE). X‐ray reciprocal space mapping (RSM) measurements have been performed in order to quantitatively evaluate the stain relaxation in the nanorod samples, confirming that the majority of the strain in InGaN/GaN MQWs can be relaxed as a result of fabrication into nanorods. Finally, excitation‐power dependant photoluminescence measurements performed at a low temperature also support the conclusion (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the origin of blue‐green emission from heteroepitaxial nonpolar a‐plane InGaN quantum wells
Authors: Kappers M. J. , Badcock T. J. , Hao R. , Moram M. A. , Hammersley S. , Dawson P. , Humphreys C. J.
Published: January 2012

The optical and structural properties of nonpolar a‐plane InGaN/GaN multiple quantum wells grown on r‐plane sapphire substrates were investigated as a function of defect density. The photoluminescence spectrum is characterised by a peak at 380 nm (3.24 eV) and a blue‐green emission band from 425‐550 nm (2.25‐3.10 eV). The near‐UV peak is assigned to carrier recombination in the quantum wells lying on the a‐plane. On the basis of microscopy, photoluminescence spectroscopy and cathodoluminescence imaging, the blue‐green emission band is attributed to emission from sidewall quantum wells formed on the various semipolar facets of small (∼100 nm) surface pits which form during quantum well growth at the lower temperatures and high NH3 flow in a nitrogen atmosphere. The density of the surface pits equals that of partial dislocations and threading dislocations in the quantum wells structure. Thus, the 300 K photoluminescence spectrum is dominated by the blue‐green emission band at a high defect density (>1010 cm‐2) and its intensity is reduced with lower defect densities. For a spectrum with a single emission from the nonpolar a‐plane InGaN/GaN quantum wells the defect density needs to be below ∼109 cm‐2. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Self‐assembled m ‐plane InGaN quantum dots: formation and shape evolution
Authors: Yang Xuelin , Arita Munetaka , Kako Satoshi , Arakawa Yasuhiko
Published: January 2012

The authors report the formation and shape evolution of m ‐plane InGaN quantum dots grown on GaN substrates. The formation of the quantum dots is enabled by introducing AlGaN/AlN interlayers prior to the GaN layer. The introduced compressive strain in the GaN layer promotes a growth mode transition during layer growth, from smooth InGaN layer to three dimensional quantum dot structures. The structural transition is consistent with optical properties. Furthermore, we also discuss the shape evolution with different growth conditions and find that the InGaN quantum dots are elongated with decreasing the indium concentration (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of carrier gas ratio and growth temperature on MOVPE growth of AlN
Authors: Miyagawa Reina , Yang Shibo , Miyake Hideto , Hiramatsu Kazumasa
Published: January 2012

The strong demand for high‐efficiency light‐emitting diodes in the deep‐ultraviolet region and for sensors has led to renewed interest in the growth of high‐quality AlN. However, the growth of high‐quality AlN is extremely difficult owing to the low surface migration rate of Al adatoms. In this study, the effects of the carrier gas ratio and growth temperature on the growth rate of AlN are examined with the aim of optimizing the growth conditions of high‐temperature AlN. AlN epilayers were grown on sapphire substrates by metal‐organic vapor phase epitaxy (MOVPE) at a growth temperature of 1430 °C with a medium‐temperature AlN layer grown at 1100 °C. A combination of H2 and N2 was used as the carrier gas in the growth of AlN, and the ratio of H2 to N2 in the carrier gas was changed to examine its effect on the growth of AlN. Under all growth conditions, crack‐free and smooth surfaces at the atomic level with an extremely small tilt were obtained. The growth rate decreased with increasing growth temperature and ratio of H2 in the carrier gas. This suggests that the high temperature and the H2 carrier gas inhibit the adsorption of atoms. Also, with increasing ratio of N2 in the carrier gas, the radius of curvature of the AlN layer increased and the compressive strain decreased. The reduction of compressive strain and increase in curvature of the AlN layer were due to an increase in the number of dislocations. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Teaching strategic thinking using system dynamics: lessons from a strategic development course
Authors: Kunc Martin
Published: January 2012

The use of System Dynamics within strategy courses aims to teach students dynamic theories to explain firm performance. This paper presents an analysis of the development of students' strategic systems thinking skills after taking a course on strategic development processes. Students that achieved the best performance employed graphs representing the performance of key variables, described how the strategy worked using verbal explanations of feedback processes, and validated the results obtained to detect poor or unreasonable strategies. However, a large group of students did not follow System Dynamics practices and performed poorly in their strategies. We extract two lessons: more emphasis on the areas shown by the best students, which are along the modeling for learning practices, are needed to improve students' strategic systems thinking skills, and it is important to adopt multidimensional tools to evaluate systems thinking skills given the diversity in learning preferences. Copyright © 2012 System Dynamics Society.
Bot detection evasion: a case study on local‐host alert correlation bot detection methods
Authors: Shirley Brandon , Babu Lokesh , Mano Chad
Published: January 2012

Botnets have continuously evolved since their inception as a malicious entity. Attackers come up with new botnet designs that exploit the weaknesses in existing defense mechanisms and continue to evade detection. It is necessary to analyze the weaknesses of existing defense mechanisms to find out the lacunae in them. This research exposes a weakness found in an existing bot detection method (BDM) by implementing a specialized P2P botnet model and carrying out experiments on it. Weaknesses that are found and validated can be used to predict the development path of botnets, and as a result, detection and mitigation measures can be implemented in a proactive fashion. The main contribution of this work is to demonstrate the exploitation pattern of an inherent weakness in local‐host alert correlation (LHAC) based methods and to assert that current LHAC implementations could allow pockets of cooperative bots to hide in an enterprise size network. This work suggests that additional monitoring capabilities must be added to current LHAC‐based methods in order for them to remain a viable bot detection mechanism. Copyright © 2012 John Wiley & Sons, Ltd.
Efficient identity‐based hierarchical access authentication protocol for mobile network
Authors: Liu He , Liang Mangui
Published: January 2012

This paper presents a secure and efficient hierarchical identity‐based access authentication protocol for mobile network. First, a new mobile scheme is constructed to improve the registration performance by the port‐based vector switching; especially when there are multihops and bandwidth between the user and home network, the registration delay is greatly reduced. Second, an access authentication protocol is proposed by combining the designed mobile proposal with hierarchical identity‐based signature. It has the characteristics of identity based, local verification, concurrency and hierarchy. The whole authenticating process is divided into two phrases to precompute some time‐consuming parameters, which are important to decrease the effects of the signing/verifying. Besides, a new access router selection algorithm is given for the mobile user to choose optimal access point in this paper. The theoretical analysis and simulating results show that the proposed authentication protocol outperforms the previous ones in terms of the handover delay integrating the authentication with its security enhanced. For example, the falling speed of the new protocol's total latency is reduced about 50% and 83%, respectively, compared with the existing identity‐based‐signature‐based and Rivest–Shamir–Adleman‐based schemes. Copyright © 2012 John Wiley & Sons, Ltd.
Estimating net survival: the importance of allowing for informative censoring
Authors: Danieli Coraline , Remontet Laurent , Bossard Nadine , Roche Laurent , Belot Aurélien
Published: January 2012

Net survival, the one that would be observed if cancer were the only cause of death, is the most appropriate indicator to compare cancer mortality between areas or countries. Several parametric and non‐parametric methods have been developed to estimate net survival, particularly when the cause of death is unknown. These methods are based either on the relative survival ratio or on the additive excess hazard model, the latter using the general population mortality hazard to estimate the excess mortality hazard (the hazard related to net survival). The present work used simulations to compare estimator abilities to estimate net survival in different settings such as the presence/absence of an age effect on the excess mortality hazard or on the potential time of follow‐up, knowing that this covariate has an effect on the general population mortality hazard too. It showed that when age affected the excess mortality hazard, most estimators, including specific survival, were biased. Only two estimators were appropriate to estimate net survival. The first is based on a multivariable excess hazard model that includes age as covariate. The second is non‐parametric and is based on the inverse probability weighting. These estimators take differently into account the informative censoring induced by the expected mortality process. The former offers great flexibility whereas the latter requires neither the assumption of a specific distribution nor a model‐building strategy. Because of its simplicity and availability in commonly used software, the nonparametric estimator should be considered by cancer registries for population‐based studies. Copyright © 2012 John Wiley & Sons, Ltd.
Grammatical and context‐sensitive error correction using a statistical machine translation framework
Authors: Ehsan Nava , Faili Heshaam
Published: January 2012

Producing electronic rather than paper documents has considerable benefits such as easier organizing and data management. Therefore, existence of automatic writing assistance tools such as spell and grammar checker/correctors can increase the quality of electronic texts by removing noise and correcting the erroneous sentences. Different kinds of errors in a text can be categorized into spelling, grammatical and real‐word errors. In this article, we present a language‐independent approach based on a statistical machine translation framework to develop a proofreading tool, which detects grammatical errors as well as context‐sensitive spelling mistakes (real‐word errors). A hybrid model for grammar checking is suggested by combining the mentioned approach with an existing rule‐based grammar checker. Experimental results on both English and Persian languages indicate that the proposed statistical method and the rule‐based grammar checker are complementary in detecting and correcting syntactic errors. The results of the hybrid grammar checker, applied to some English texts, show an improvement of about 24% with respect to the recall metric with almost similar value for precision. Experiments on real‐world data set show that state‐of‐the‐art results are achieved for grammar checking and context‐sensitive spell checking for Persian language. Copyright © 2012 John Wiley & Sons, Ltd.
A threat model‐based approach to security testing
Authors: Marback Aaron , Do Hyunsook , He Ke , Kondamarri Samuel , Xu Dianxiang
Published: January 2012

Software security issues have been a major concern in the cyberspace community, so a great deal of research on security testing has been performed, and various security testing techniques have been developed. Threat modeling provides a systematic way to identify threats that might compromise security, and it has been a well‐accepted practice by the industry, but test case generation from threat models has not been addressed yet. Thus, in this paper, we propose a threat model‐based security testing approach that automatically generates security test sequences from threat trees and transforms them into executable tests. The security testing approach we consider consists of three activities in large: building threat models with threat trees; generating security test sequences from threat trees; and creating executable test cases by considering valid and invalid inputs. To support our approach, we implemented security test generation techniques, and we also conducted an empirical study to assess the effectiveness of our approach. The results of our study show that our threat tree‐based approach is effective in exposing vulnerabilities. Copyright © 2012 John Wiley & Sons, Ltd.
Estimating the annual probability of failure using improved progressive incremental dynamic analysis of structural systems
Authors: Kayhani Hossein , Azarbakht Alireza , Ghafory‐Ashtiany Mohsen
Published: January 2012

A methodology based on the progressive incremental dynamic analysis has been introduced in this paper to estimate the structural response and the corresponding annual probability of failure. The proposed methodology employs the genetic algorithm optimisation technique and an equivalent single‐degree‐of‐freedom system corresponding to the first‐mode period of a considered structure. The proposed methodology can significantly reduce the number of ground motion records needed for estimating the annual probability of failure. The numerical results indicate that the proposed method can effectively reduce the computational effort needed for computation of probability of failure for the first‐mode dominated structures, which is advantageous as the structure becomes larger. A relatively huge set of single‐degree‐of‐freedom systems as well as three multi‐degree‐of‐freedom systems including 3, 8 and 12 storeyed reinforced concrete structures was taken into account to test the proposed methodology. It has been shown that the probability of failure can be estimated within ±15% error with 95% confidence. The proposed method can speed up the decision‐making process in the probability‐based seismic performance assessment of structures, and it also incorporates the randomness of strong ground motions explicitly. Copyright © 2012 John Wiley & Sons, Ltd.
Autonomous aggregation in location aware ad hoc wireless networks
Authors: Geibig Joanna , Bradler Dirk
Published: January 2012

Gossip‐based epidemic protocols are used to aggregate data in distributed systems. This fault‐tolerant approach neither require maintenance of any global network state nor knowledge of network structure. However, although gossip‐based aggregation algorithms scale well for graphs with good expansion, their efficiency for sparse graphs is unexamined. In this paper, we analyze the feasibility and efficiency of a gossip aggregation protocol in wireless networks with low expansion. We propose a modification of the existing aggregation algorithm for use in locality‐aware, sparse, and static wireless networks. Our protocol terminates autonomously, uses less bandwidth than the original version, and removes the need for the leader election process while counting network nodes. Aggregates are calculated only over nodes placed in the vicinity, and nodes communicate only with their immediate neighbors by using a wireless broadcast. We evaluate our approach by simulation on sparse, irregular graphs with low expansion for the simplified system model. Furthermore, we analytically assess the worst‐case convergence time of this protocol for sparse wireless networks and also for the simplified system model. The proposed protocol can be used in the monitoring and alarming applications in wireless networks. Copyright © 2012 John Wiley & Sons, Ltd.
Understanding protein unfolding from molecular simulations
Authors: Toofanny Rudesh D. , Daggett Valerie
Published: January 2012

Experimental biophysical techniques can probe the native, transition, intermediate, and denatured states of proteins. The characterization of these states and the conversion between states provide us with information about folding, dynamics, misfolding, and the origin of mechanical strength in response to force. Molecular dynamics (MD) simulations are a complementary theoretical technique that provides atomic detail to the experimental measurements particularly through careful benchmarking and validation against experiment. Furthermore, MD simulations often correctly predict the outcome of experiments and provide new and interesting avenues of investigation. Our understanding of protein unfolding is being pushed forward by the symbiosis of experimental and theoretical methods. Here, we review investigations of several protein systems and highlight the close interplay between experiment and simulation in providing an atomic resolution view of protein unfolding, which provide us with the general principles for folding and the origin of mechanical strength. © 2012 John Wiley & Sons, Ltd.

This article is categorized under:

Structure and Mechanism > Reaction Mechanisms and Catalysis
Controversies Concerning the Use of Neoadjuvant Systemic Therapy for Primary Breast Cancer
Authors: Kaufmann Manfred , Karn Thomas , Ruckhäberle Eugen
Published: January 2012

The major aim of neoadjuvant systemic therapy is to improve prognosis by individualizing treatment. The proven benefits of neoadjuvant systemic therapy include reducing tumor burden, higher breast‐conserving surgery, and the possibility of in vivo monitoring of response to treatment. Other goals of neoadjuvant treatment are the detection of new prognostic and predictive biomarkers and the investigation of new drugs and imaging modalities. Although many prospective trials have answered important questions regarding neoadjuvant systemic therapy, several topics remain controversial.
Evliya Celebi’s Description of the Removal of a Musket Ball From the Brain of a Habsburg Prince: An Interesting Excerpt From the “Seyahatname”
Authors: Bilsel Yilmaz
Published: January 2012

In the 17th century an Ottoman traveler, Evliya Celebi, was inspired by a dream to embark on a journey across the Ottoman Empire. He traveled far and wide across Europe and North Africa and wrote extensively about his adventures in the Seyahatname. The Seyahatname, or “Book of Travels,” is the longest and most detailed travel account in Islamic (if not world) literature. It is a vast panorama of the Ottoman world in the mid‐17th century. This article is concerned with Celebi’s description of several surgeries that he claimed to have witnessed in Vienna during the year 1665. He describes several procedures, the first and most detailed of which is a fascinating brain operation that seems to be a highly unusual procedure for the time. His impressions of Central European medicine, as viewed by a Muslim from the East, offer an unexplored perspective. We examine what his description tells us about the perceptions and images of surgery and medicine.