bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bone‐like apatite‐coated chitosan scaffolds: Characterization and osteoblastic activity
Authors: Aday Sezin , Gümüşderelioğlu Menemşe 
Published: October 2009

AbstractIn this study, porous scaffolds were prepared from chitosan (2% w/v in acetic acid and deacetylation degree: DD > 85%) by freeze‐drying method, and freshly lyophilized scaffolds were stabilized with ethanol solutions. Bone‐like apatite formation on chitosan scaffolds was achieved by immersing the scaffolds into a novel concentrated simulated body fluid (10× SBF‐like solution) for different periods, i.e., 6 and 24 h. Scanning electron microscope views showed that the 6‐h treatment in 10× SBF‐like solution led to the formation of calcium phosphate nucleation sites on chitosan scaffolds, whereas the apatite particles showed characteristic cauliflower‐like morphology at the end of 24‐h treatment. X‐ray diffraction results supported the fact that mineral phase was made of hydroxyapatite. Osteogenic activities of untreated and SBF‐treated chitosan scaffolds were examined by preosteoblastic MC3T3 cell culture studies. The mitochondrial activity test showed that apatite‐coated scaffolds stimulated cell proliferation compared with uncoated scaffolds. Alkaline phosphatase and osteocalcine levels indicated that the differentiation of the cells on all scaffolds increased significantly from 15th day of culture to the 21th day of culture, especially for the cells on 24‐h SBF‐treated scaffolds. The results of this study indicated that 10× SBF‐like solution‐treated chitosan scaffolds may be evaluated for bone tissue engineering. POLYM. COMPOS., 31:1418–1426, 2010. © 2009 Society of Plastics Engineers
Placental growth hormone and growth hormone binding protein are first trimester maternal serum markers of Down syndrome
Authors: Christiansen Michael 
Published: October 2009

AbstractBackgroundPlacental growth hormone (PGH) is synthesised by the placenta, and its function is modulated by growth hormone binding protein (GHBP). The potential of PGH and GHBP as maternal serum screening markers for Down syndrome (DS) was examined.Materials and methodsMaternal serum concentrations of PGH and GHBP were determined by ELISA in 74 DS and 261 control pregnancies in gestational week 8+0 to 13+4. Log10 MoM distributions of the markers were established. The performance of DS screening was estimated by Monte Carlo simulation.ResultsPGH log10 MoM (SD) was decreased (p < 0.001) to −0.201 (0.373) and GHBP log10 MoM to −0.116 (0.265) (p = 0.04), in DS pregnancies (n = 34) in week 8+0 to 10+0. In week 10+1 to 13+4, neither PGH (p = 0.16) nor GHBP (p = 0.13) was reduced in DS pregnancies. The detection rate (DR) for PGH in screening for DS in week 8+0 to 10+0 was 39% for a false positive rate (FPR) of 5%; increasing to 72% in combination with PAPP‐A + hCGβ. PGH + GHBP in combination with PAPP‐A + hCGβ + nuchal translucency (NT) (CUB test) had a DR of 91% compared with 80% for the CUB test.ConclusionPGH and GHBP are early first trimester maternal serum markers for DS [Correction made here after initial online publication]. Copyright © 2009 John Wiley & Sons, Ltd.
The ligand‐binding b′ domain of human protein disulphide‐isomerase mediates homodimerization
Authors: Wallis Anne Katrine , Sidhu Ateesh , Byrne Lee J. , Howard Mark J. , Ruddock Lloyd W. , Williamson Richard A. , Freedman Robert B. 
Published: October 2009

AbstractPurified preparations of the recombinant b′x domain fragment of human protein‐disulphide isomerase (PDI), which are homogeneous by mass spectrometry and sodium dodecyl sulfate polyacrylamide gel electrophoresis, comprise more than one species when analyzed by ion‐exchange chromatography and nondenaturing polyacrylamide gel electrophoresis. These species were resolved and shown to be monomer and dimer by analytical ultracentrifugation and analytical size‐exclusion chromatography. Spectroscopic properties indicate that the monomeric species corresponds to the “capped” conformation observed in the x‐ray structure of the I272A mutant of b′x (Nguyen, Wallis, Howard, Haapalainen, Salo, Saaranen, Sidhu, Wierenga, Freedman, Ruddock, and Williamson, J Mol Biol 2008;383:1144‐1155) in which the x region binds to a hydrophobic patch on the surface of the b′ domain; conversely, the dimeric species has an “open” or “uncapped” conformation in which the x region does not bind to this surface. The larger bb′x fragment of human PDI shows very similar behavior to b′x and can be resolved into a capped monomeric species and an uncapped dimer. Preparations of recombinant b′ domain of human PDI and of the bb′ domain pair are found exclusively as dimers. Full‐length PDI is known to comprise a mixture of monomeric and dimeric species, whereas the isolated a, b, and a′ domains of PDI are found exclusively as monomers. These results show that the b′ domain of human PDI tends to form homodimers—both in isolation and in other contexts—and that this tendency is moderated by the adjacent x region, which can bind to a surface patch on the b′ domain.
The crystal structure of a TIR domain from Arabidopsis thaliana reveals a conserved helical region unique to plants
Authors: Chan Siew Leong , Mukasa Takashi , Santelli Eugenio , Low Lieh Yoon , Pascual Jaime 
Published: October 2009

AbstractPlants use a highly evolved immune system to exhibit defense response against microbial infections. The plant TIR domain, together with the nucleotide‐binding (NB) domain and/or a LRR region, forms a type of molecule, named resistance (R) proteins, that interact with microbial effector proteins and elicit hypersensitive responses against infection. Here, we report the first crystal structure of a plant TIR domain from Arabidopsis thaliana (AtTIR) solved at a resolution of 2.0 Å. The structure consists of five β‐strands forming a parallel β‐sheet at the core of the protein. The β‐strands are connected by a series of α‐helices and the overall fold mimics closely that of other mammalian and bacterial TIR domains. However, the region of the αD‐helix reveals significant differences when compared with other TIR structures, especially the αD3‐helix that corresponds to an insertion only present in plant TIR domains. Available mutagenesis data suggest that several conserved and exposed residues in this region are involved in the plant TIR signaling function.
Disulfide conformation and design at helix N‐termini
Authors: Indu S. , Kumar Senthil T. , Thakurela Sudhir , Gupta Mansi , Bhaskara Ramachandra M. , Ramakrishnan C. , Varadarajan Raghavan 
Published: October 2009

AbstractTo understand structural and thermodynamic features of disulfides within an α‐helix, a non‐redundant dataset comprising of 5025 polypeptide chains containing 2311 disulfides was examined. Thirty‐five examples were found of intrahelical disulfides involving a CXXC motif between the N‐Cap and third helical positions. GLY and PRO were the most common amino acids at positions 1 and 2, respectively. The N‐Cap residue for disulfide bonded CXXC motifs had average (ϕ,ψ) values of (−112 ± 25.2°, 106 ± 25.4°). To further explore conformational requirements for intrahelical disulfides, CYS pairs were introduced at positions N‐Cap‐3; 1,4; 7,10 in two helices of an Escherichia coli thioredoxin mutant lacking its active site disulfide (nSS Trx). In both helices, disulfides formed spontaneously during purification only at positions N‐Cap‐3. Mutant stabilities were characterized by chemical denaturation studies (in both oxidized and reduced states) and differential scanning calorimetry (oxidized state only). All oxidized as well as reduced mutants were destabilized relative to nSS Trx. All mutants were redox active, but showed decreased activity relative to wild‐type thioredoxin. Such engineered disulfides can be used to probe helix start sites in proteins of unknown structure and to introduce redox activity into proteins. Conversely, a protein with CYS residues at positions N‐Cap and 3 of an α‐helix is likely to have redox activity. Proteins 2010. © 2009 Wiley‐Liss, Inc.
Influence of temperature on the synthesis of thiol‐stabilized CdTe nanoparticles in aqueous solutions
Authors: Khalavka Y. , Mingler B. , Friedbacher G. , Okrepka G. , Shcherbak L. , Panchuk O. 
Published: October 2009

AbstractWe have investigated the evolution of thiol‐capped cadmium telluride nanocrystals prepared in aqueous solutions at low and room temperature followed by heating at 50–100 °C. The UV–visible absorption spectra, as well as transmission electron microscopy, atomic force microscopy, and dynamic light scattering observations made it possible to reveal differences in size and structure originating from different heating temperatures. It was shown that minimization of the nucleation process temperature provided formation of larger nanoparticles than at higher temperatures.
Growth of ultralong ZnO microwire and its application in isolatable and flexible piezoelectric strain sensor
Authors: Sun Kaitong , Zhang Heqiu , Hu Lizhong , Yu Dongqi , Qiao Shuangshuang , Sun Jingchang , Bian Jiming , Chen Xi , Zhang Lingxuan , Fu Qiang , Zhao Ziwen 
Published: October 2009

AbstractUltralong ZnO piezoelectric‐fine‐wires (PFWs) with a perfect hexagonal structure have been prepared by an upstream growing chemical vapor deposition (CVD) method. Furthermore, isolatable and flexible piezoelectric strain sensors based on individual ZnO PFWs have been fabricated by a simple and reliable technique. The whole device was fully packaged by epoxy polymeric resin (EPR). The I–V characteristic of the isolatable sensor is highly sensitive to the strain applied on it, which was well interpreted in terms of variation in Schottky barrier height (SBH) caused by strain induced band structure change and piezoelectric effect. The sensor exhibited excellent stability and fine reversibility, and a remarkably high gauge factor up to 1010 had been achieved. It is expected that the isolatable and flexible piezoelectric strain sensor demonstrated here will have applications in detection of external mechanical forces, as well as electromechanical switch with a high ON/OFF ratio.
Polarization of eigenmodes in laser diode waveguides on semipolar and nonpolar GaN
Authors: Rass Jens , Wernicke Tim , Scheibenzuber Wolfgang G. , Schwarz Ulrich T. , Kupec Jan , Witzigmann Bernd , Vogt Patrick , Einfeldt Sven , Weyers Markus , Kneissl Michael 
Published: October 2009

AbstractRecent calculations of the eigenmodes in waveguides grown on semipolar GaN suggest that the optical polarization of the emitted light as well as the optical gain depends on the orientation of the resonator. Our measurements on separate confinement heterostructures on semipolar (11$ \bar 2 $2) and (10$ \bar 1 $2) GaN show that for laser resonators along the semipolar [11$ \bar 2 \bar 3 $] and [0$ \bar 1 $11] directions (i.e. the projection of the c‐axis onto the plane of growth) the threshold for amplified spontaneous emission is lower than for the nonpolar direction and that the stimulated emission is linearly polarized as TE mode. For the waveguide structures along the nonpolar [1$ \bar 1 $00] or [11$ \bar 2 $0] direction on the other hand, birefringence and anisotropy of the optical gain in the plane of growth leads not only to a higher threshold but alsoto a rotation of the optical polarization which is not any more TE‐ or TM‐polarized but influenced by the ordinary and extraordinary refractive index of the material. We observe stimulated emission into a mode which is linearly polarized in extraordinarydirection nearly parallel to the c‐axis. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rapid drug detection in oral samples by porous silicon assisted laser desorption/ionization mass spectrometry
Authors: Lowe Rachel D. , Guild Georgia E. , Harpas Peter , Kirkbride Paul , Hoffmann Peter , Voelcker Nicolas H. , Kobus Hilton 
Published: October 2009

AbstractThe demand for analysis of oral fluid for illicit drugs has arisen with the increased adoption of roadside testing, particularly in countries where changes in legislation allow random roadside testing of drivers for the presence of a palette of illicit drugs such as methamphetamine (MA), 3,4‐methylenedioxymethamphetamine (MDMA) and Δ9‐tetrahydrocannabinol (THC). Oral samples are currently tested for such drugs at the roadside using an immunoassay‐based commercial test kit. Positive roadside tests are sent for confirmatory laboratory analysis, traditionally by means of gas chromatography/mass spectrometry (GC/MS). We present here an alternative rapid analysis technique, porous silicon assisted laser desorption/ionization time‐of‐flight mass spectrometry (pSi LDI‐MS), for the high‐throughput analysis of oral fluids. This technique alleviates the need for sample derivatization, requires only sub‐microliter sample volumes and allows fast analysis (of the order of seconds). In this study, the application of the technique is demonstrated with real samples from actual roadside testing. The analysis of oral samples resulted in detection of MA and MDMA with no extraction and analysis of THC after ethyl acetate extraction. We propose that, subject to miniaturization of a suitable mass spectrometer, this technique is well suited to underpin the deployment of oral fluid testing in the clinic, workplace and on the roadside. Copyright © 2009 John Wiley & Sons, Ltd.
Precursor ion scans for the targeted detection of stable‐isotope‐labeled peptides
Authors: Colzani Mara , Bienvenut Willy V. , Faes Eveline , Quadroni Manfredo 
Published: October 2009

AbstractStable isotope labels are routinely introduced into proteomes for quantification purposes. Full labeling of cells in varying biological states, followed by sample mixing, fractionation and intensive data acquisition, is used to obtain accurate large‐scale quantification of total protein levels. However, biological processes often affect only a small group of proteins for a short time, resulting in changes that are difficult to detect against the total proteome background. An alternative approach could be the targeted analysis of the proteins synthesized in response to a given biological stimulus. Such proteins can be pulse‐labeled with a stable isotope by metabolic incorporation of ‘heavy’ amino acids. In this study we investigated the specific detection and identification of labeled proteins using acquisition methods based on Precursor Ion Scans (PIS) on a triple‐quadrupole ion trap mass spectrometer. PIS‐based methods were set to detect unique immonium ions originating from labeled peptides. Different labels and methods were tested in standard mixtures to optimize performance. We showed that, in comparison with an untargeted analysis on the same instrument, the approach allowed a several‐fold increase in the specificity of detection of labeled proteins over unlabeled ones. The technique was applied to the identification of proteins secreted by human cells into growth media containing bovine serum proteins, allowing the preferential detection of labeled cellular proteins over unlabeled bovine ones. However, compared with untargeted acquisitions on two different instruments, the PIS‐based strategy showed some limitations in sensitivity. We discuss possible perspectives of the technique. Copyright © 2009 John Wiley & Sons, Ltd.
Inoperability input‐output modeling (IIM) of disruptions to supply chain networks
Authors: Wei Hairui , Dong Ming , Sun Shuyu 
Published: October 2009

AbstractIn this paper, the Inoperability Input‐Output Model (IIM) is deployed for assessing the impacts of disruptive events on supply chain networks under an unsafe environment. The IIM for supply chain networks has been proposed, based on the original IIM used in macro‐economics. A new method called the OWA (Ordered Weighted Averaging) Operator has been formulated to evaluate the interdependency matrix, a key component of the IIM. Similar to the capability of the basic IIM to describe the propagation impacts of disruptions to macroeconomic systems, the IIM for supply chain networks is capable of describing the propagation effects of disruptions to interdependent supply chain components. IIM assesses the impacts of disruptions to supply chain networks with “inoperability” and “economic losses” metrics, which can provide helpful insights for risk management of supply chain networks. An example supply chain network is used to illustrate the application of IIM for systemic risk assessment of supply chains under an unsafe environment. A risk mitigation strategy by increasing the number of suppliers has been considered to reduce the adverse effects caused by the supply reduction of the single secondary supplier in the example supply chain network. In addition, a simulation model integrated with Monte Carlo simulation method has been developed to validate the accuracy of the IIM for supply chain. The example shows that the application of IIM can provide useful guidance toward supply chain risk management or mitigation strategies and it could also be used to test the effectiveness of these strategies. © 2009 Wiley Periodicals, Inc. Syst Eng
Evolving the INCOSE reference curriculum for a graduate program in systems engineering
Authors: Squires Alice , Cloutier Robert 
Published: October 2009

AbstractThis paper suggests an evolution to the graduate level systems engineering curriculum framework documented in an International Council on Systems Engineering (INCOSE) report in October of 2007 [Jain and Verma, INCOSE‐PP‐2007‐001‐01, Seattle, WA, 2007]. This evolution leverages the International Organization for Standardization (ISO)/International Electrotechnical Commission (IEC) 15288 Systems and Software Engineering—System Life Cycle Processes standard [ISO/IEC 15288, International Organization for Standardization, Geneva, 2008] as a guide. The evolved framework is presented and consists of six levels of course categories: prerequisite, introductory, technical system life cycle processes, project planning system life cycle processes, infrastructure processes and other broad areas, and capstone courses. Next, 18 systems engineering centric online masters degrees offered by 17 distinct universities are identified as part of a growing base of graduate level systems engineering degrees offered globally through distance education. Specific examples for applying the framework using three of the universities that provide online systems engineering masters programs globally are included. © 2009 Wiley Periodicals, Inc.
Credit markets: Tumultuous and opportunistic— navigating the shifting terrain of debt markets
Authors: Wittlin Roger 
Published: October 2009

AbstractHistoric events battered both the financial markets and the real economy throughout 2008 and the first quarter of 2009. On Wall Street, the destruction was most evident through the bankruptcy of Lehman Brothers; the acquisitions of Bear Stearns, Merrill Lynch, and Wachovia; and the implosions of AIG, Fannie Mae, and Freddie Mac. And Main Street wasn't spared, as the declines in home prices, large federal involvement in the banking and the automobile industries, a rapid rise in unemployment, and the explosion of the U.S. federal budget deficit have shaped millions of lives and will dramatically alter the country's economic future. © 2009 Wiley Periodicals, Inc.
Effects of waste ground rubber tire powder (WGRT) and chemical blowing agent content on the cell morphology and physicomechanical properties of injection‐molded polypropylene/WGRT foams
Authors: Xin Zhen Xiang , Zhang Zhen Xiu , Pal Kaushik , Kang Dong Jin , Lee Sung Hyo , Kim Jin Kuk 
Published: October 2009

AbstractMicrocellular polypropylene (PP)/WGRT blends, a new outlet for the recycling of waste tire rubber, were prepared in an injection‐molding process by using a chemical blowing agent. The effects of WGRT content and chemical blowing agent content on the density, cell morphology, and physicomechanical properties of the foamed PP/WGRT blends were investigated. The foam morphologies were characterized in terms of void fraction, average cell size, and cell density. The results indicated that both the WGRT and the blowing agent content had huge effects on the cell morphology and tensile properties of the PP/WGRT foams. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers
Robust and distributed control of a smart blade
Authors: Rice Justin K. , Verhaegen Michel 
Published: October 2009

AbstractFor the next generation of larger off‐shore wind turbines, it has been suggested to use feedback to actively control the blade vibrations, thus decreasing fatigue damage and increasing the life of the machine. Because of both practical engineering difficulties and fundamental control theoretic limitations, it seems that individual pitch actuation may not be well suited for this type of control, prompting researchers to investigate other forms, such as tip actuation and the ‘smart blade’ concept. Most research in this area has been on the design of cheap, reliable and effective actuators and sensors, which are necessary for economic viability of the concept. We will argue that the design of a robust feedback controller is just as critical to the success of the smart blade concept, but has been so far overlooked because of the complexities of modeling and computation involved therein.In this paper, we take the first step in demonstrating how to build blade models with a distributed bounded uncertainty structure, in a framework appropriate for robust control analysis and design. We then discuss recent progress in distributed computationally efficient robust control techniques, scalable for very fine discretizations, and show that for coarse discretizations, even centralized techniques can be employed to design high‐performance feedback controllers for a smart blade system, with guaranteed closed loop stability and performance for a variety of operating conditions and model mismatches. Copyright © 2009 John Wiley & Sons, Ltd.
Simulating Feedback Linearization control of wind turbines using high‐order models
Authors: Kumar A. , Stol K. 
Published: October 2009

AbstractAs wind turbines are becoming larger, wind turbine control must now encompass load control objectives as well as power and speed control to achieve a low cost of energy. Due to the inherent non‐linearities in a wind turbine system, the use of non‐linear model‐based controllers has the potential to increase control performance. A non‐linear feedback linearization controller with an Extended Kalman Filter is successfully used to control a FAST model of the controls advanced research turbine with active blade, tower and drive‐train dynamics in above rated wind conditions. The controller exhibits reductions in low speed shaft fatigue damage equivalent loads, power regulation and speed regulation when compared to a Gain Scheduled Proportional Integral controller, designed for speed regulation alone. The feedback linearization controller shows better rotor speed regulation than a Linear Quadratic Regulator (LQR) at close to rated wind speeds, but poorer rotor speed regulation at higher wind speeds. This is due to modeling inaccuracies and the addition of unmodeled dynamics during simulation. Similar performance between the feedback linearization controller and the LQR in reducing drive‐train fatigue damage and power regulation is observed. Improvements in control performance may be achieved through increasing the accuracy of the non‐linear model used for controller design. Copyright © 2009 John Wiley & Sons, Ltd.