bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of graft copolymerization on mechanical, thermal, and chemical properties of grewia optiva/unsaturated polyester biocomposites
Authors: Singha A.S. , Rana Ashvinder K. 
Published: July 2012

AbstractPresent manuscript deals with surface modification of Grewia optiva fiber through graft copolymerization with acrylonitrile (AN). These surface modified cellulosic fibers were then used as reinforcement to prepare natural fiber reinforced unsaturated polyester matrix based biocomposites. Different reaction parameters for graft copolymerization were optimized to get the maximum graft yield (10.42%). The graft copolymers formed were characterized by FTIR, SEM, XRD, and TGA techniques. On grafting, thermal stability of fibers increased, which has been also supported by energy of activation (Ea) data obtained for both raw and grafted fiber. The grafted fibers were also subjected to evaluation of physicochemical properties. Subsequently, composites of unsaturated polyester matrix reinforced with different fiber loadings (0, 10, 20, 30, and 40% in terms of weight) of both raw and grafted fiber have been fabricated by hand lay up method. Mechanical properties of composites were studied and have been found to be higher when compared with polymer matrix. However, maximum enhancement in mechanical properties has been observed in case of grafted particle reinforced UPE composites in comparison to raw particulate reinforced composites. Further these composites were also subjected to SEM, DSC, and chemical resistance studies. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Effect of nonionizing radiation on the physicomechanical properties of banana fiber/pp composites with HEMA
Authors: Zaman Haydar U. , Khan Mubarak A. , Khan Ruhul A. 
Published: July 2012

AbstractBanana fiber‐reinforced polypropylene (PP)‐based unidirectional composites (40% fiber by weight) was manufactured by compression molding. Banana fibers and PP sheets were treated with UV radiation at different intensities and then composites were fabricated. It was found that mechanical properties of irradiated banana fiber and irradiated PP‐based composites were found to increase significantly compared to that of untreated counterparts. Irradiated banana fibers were also treated with 2‐hydroxyethyl methacrylate (HEMA) mixed with methanol (MeOH) under thermal curing method at different temperatures (30–70°C) for different curing times (20–60 min). A series of solutions of different concentrations of HEMA in methanol along with 2% benzyl peroxide were prepared. Monomer concentration, curing temperature and curing time were optimized in terms of polymer loading and mechanical properties. Composites made of 15% HEMA, 50°C and 40 min curing time showed the best mechanical properties than those of untreated composite. Scanning electron microscopy (SEM), water uptake, and simulating weathering test of the composites were also investigated. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Influence of different percentages of N‐phenylaminopropyl—poss on the degradation kinetic of epoxy resin
Authors: Pistor Vinícius , Soares Bluma Guenther , Mauler Raquel Santos 
Published: July 2012

AbstractIn the present study, nanocomposites were prepared with different contents (1, 2, 5, 10% by weight) of polyhedral oligomeric silsesquioxane—POSS n‐phenylaminopropyl in an epoxy matrix. The samples were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). TGA analyses were performed at different heating rates to allow for the prediction of the kinetic parameters of degradation. XRD analyses were used to calculate the average molecular interchain spacing. TGA analysis showed that the presence of POSS increased the thermal stability of the nanocomposites. An increase in the activation energy on degradation was evidenced through the kinetic parameters, especially for the 10% POSS. Moreover, the addition of POSS changed the kinetic mechanism of the deceleratory mode (Fn) in favor of the diffusion (Dn) process. The diffusion mechanism is corroborated by the XRD analyses that showed the increase of distance between chains when was added POSS. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
First trimester risk assessment for trisomy 21 in twin pregnancies combining nuchal translucency and first trimester biochemical markers
Authors: Prats Pilar , Rodríguez Ignacio , Comas Carmina , Puerto Bienvenido 
Published: July 2012

ABSTRACTObjectiveThe aim is to describe the performance of first‐trimester combined risk assessment in twin pregnancies.MethodsMaternal serum free beta‐human chorionic gonadotrophin and pregnancy‐associated plasma protein A (PAPP‐A) were determined at 8 to 12 weeks and fetal nuchal translucency (NT) was measured at 11 to 13+6 weeks. The individual risk was estimated for each fetus using the combined test in dichorionic twins. In monochorionic twins, the mean risk assessment of the two fetuses was used. An invasive diagnostic procedure was offered when the risk was ≥1 : 270 in either one of the fetuses.ResultsFrom February 2007 to June 2011, 447 twin pregnancies were enrolled in this study. There were 402 (89.9%) dichorionic and 45 (10.1%) monochorionic twins. In dichorionic twins, mean crown–rump length (CRL) was 63.9 mm; median NT multiples of the median (MoM) was 0.97; median Β‐hCG was MoM 1.74; median PAPP‐A was 1.72. In monochorionic twins, mean CRL was 61.9 mm; median NT MoM was 0. 98; median Β‐hCG MoM was 1.44; and median PAPP‐A was 1.51. Two pregnancies with Down syndrome were detected by first trimester screening, both in dichorionic twins. The false positive rate was 5.7% (95% confidence interval 4.1–7.3) and 4.4% (95% confidence interval 0.1–8.8%) in dichorionic and monochorionic twins, respectively.ConclusionsThe combined test in twins appears to be a good method for Down syndrome screening with a high detection rate and an acceptable false‐positive rate. © 2012 John Wiley & Sons, Ltd.
Mutagenic analysis in a pure molecular system shows that thioredoxin‐interacting protein residue Cys247 is necessary and sufficient for a mixed disulfide formation with thioredoxin
Authors: Fould Benjamin , Lamamy Véronique , Guenin Sophie‐Penelope , Ouvry Christine , Cogé Francis , Boutin Jean A. , Ferry Gilles 
Published: July 2012

AbstractThe human thioredoxin (TRX)‐interacting protein is found in multiple subcellular compartments and plays a major role in redox homeostasis, particularly in the context of metabolism (e.g., lipidemia and glycemia) and apoptosis. A molecular approach to the protein's modus operandi is still needed because some aspects of the TRX‐interacting protein‐mediated regulation of TRX are not clearly understood. To this end, His‐tagged TRX‐interacting proteins were over‐expressed in Escherichia coli. Because the protein is expressed mainly in inclusion bodies, it was denatured in high concentrations of guanidium hydrochloride, centrifuged, and purified by Ni‐NTA affinity chromatography. His‐TRX‐interacting protein was then refolded by dialysis and its restructuring monitored by circular dichroism spectrometry. This preparation resulted in the formation of a covalent complex with recombinant human TRX, demonstrating that association occurs without the intervention of other partner proteins. Multiple cysteine‐to‐serine mutants of TRX‐interacting protein were produced and purified. These mutations were efficient in limiting the formation of disulfide‐linked homo‐oligomers in an oxidizing environment. The mutants were also used to gain functional insight into the formation of the TRX‐interacting protein‐TRX complexes. These complexes were able to form in the absence of internal disulfide bridges. A mutant with all but one cysteine changed to serine (Cys247) also showed an enhanced capacity to form complexes with TRX demonstrating, in a pure molecular system, that this particular cysteine is likely responsible for the disulfide bridge between TRX‐interacting protein and TRX.
Electronic structure of interfaces with conjugated organic materials
Authors: Koch Norbert 
Published: July 2012

AbstractThe function and efficiency of most organic electronic and opto‐electronic devices greatly depend on the electronic structure of the interfaces therein. Charge injection from electrical contacts into the organic semiconductor, charge extraction, or exciton dissociation at organic semiconductor heterojunctions are crucial processes that must be optimized for high device efficiency. Consequently, the energy levels at these interfaces must be matched to allow for optimal performance. The key mechanisms that determine the energy level alignment at organic/electrode and organic/organic interfaces are reviewed, and methods to adjust the levels at such interfaces are presented. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sensitivity of analysis error covariance to the mis‐specification of background error covariance
Authors: Eyre J. R. , Hilton F. I. 
Published: July 2012

AbstractMost data assimilation and satellite retrieval methods are based on optimal estimation theory, which assumes that the error covariances of the observations and of the a priori (background) information are known. The specification of background error covariance is crucial to the appropriate interpretation of radiance information from satellite sounders within a numerical weather prediction (NWP) data assimilation system. Uncertainties in the specification of error covariances are inevitable, but an improved understanding of the acceptable range of mis‐specification should lead to improved impact of these observations in NWP. In this study, the sensitivity of analysis error covariance to the mis‐specification of background error covariance is investigated. The linear theory for analysis error covariance is presented, both for the optimal case and for the more general suboptimal case. The theory is first applied to a simple scalar case. A ‘danger zone’ is identified, where a mis‐specification of background error variance results in analysis error variances being greater than background error variances. The boundary of the ‘danger zone’ is quantified as a function of the ratio of observation error variance to background error variance. The investigation is then extended to the vector case, and specifically to the vertical eigenmodes of a forecast error covariance matrix and to the linearized error analysis for a one‐dimensional variational (1D‐Var) retrieval analogous to the assimilation of radiances from the Infrared Atmospheric Sounding Interferometer (IASI). In the optimal case, the assimilation of IASI data can improve the analysis of the leading eigenmodes of temperature and humidity. A suboptimal case is then investigated, by assuming one representation of forecast error covariance in the analysis whilst taking another representation as truth. The analysis is shown to cross into the ‘danger zone’ for a small number of eigenmodes. Equivalent degradation of the analysis in profile space is also shown. Copyright © 2012 British Crown copyright, the Met Office. Published by John Wiley & Sons Ltd.
Elucidation of the mass fragmentation pathways of the polyether marine toxins, dinophysistoxins, and identification of isomer discrimination processes
Authors: Carey Bébhine , Sáez Maria José Fidalgo , Hamilton Brett , O'Halloran John , van Pelt Frank N. A. M. , James Kevin J. 
Published: July 2012

RATIONALEMost of the liquid chromatography/mass spectrometry (LC/MS) methods that have been developed for the analysis of Diarrhetic Shellfish Poisoning (DSP) toxins in shellfish and algae samples have been unable to differentiate the isomers okadaic acid (OA) and dinophysistoxin‐2 (DTX2), unless separated by chromatography. Since there are many bioconversion products of these compounds it is imperative to determine characteristic product ions, which can provide unequivocal identification of OA and DTX2 and their analogs.METHODSUsing electrospray ionization, the fragmentation processes for two types of precursor ions, [M+Na]+ and [M–H]–, of the polyether marine toxins, dinophysistoxins (DTXs), were studied using a hybrid linear ion trap Orbitrap mass spectrometer which provided high mass accuracy data in combination with multiple tandem mass (MSn) spectra. Three structurally related toxins were compared; okadaic acid (OA), dinophysistoxin‐2 (DTX2) and dinophysistoxin‐1 (DTX1). A quick multiple reaction monitoring (MRM) LC/MS/MS method was developed utilizing the characteristic precursor/product ion mass transitions.RESULTSComparison of the high‐resolution product ion, [M–H]–, spectra of these toxins featured dominant signals that resulted from two six‐centered rearrangements and previously proposed fragmentation pathways for the ion of m/z 321 and 293 have been corrected and identified. By contrast, the [M+Na]+ product ion spectra only revealed distinctive ions for the isomers, OA (m/z 595, 443 and 151) and DTX2 (m/z 581, 429 and 165). To illustrate the benefits of this study, a mass selective LC/MS/MS method was developed in which the isomers OA and DTX2 co‐eluted but were distinguished using the mass transitions, m/z 827/595, 827/443 (OA) and m/z 827/581, 827/429 (DTX2).CONCLUSIONSComparison of OA, DTX2 and DTX1 led to the correction of proposed negative ion mode fragmentation pathways. Through extensive study and comparison of the [M+Na]+ product ion spectra, distinctive product ions were identified which allowed for these compounds to be identified and distinguished without separation for the first time. Copyright © 2012 John Wiley & Sons, Ltd.
The role of conformational flexibility in β2‐microglobulin amyloid fibril formation at neutral pH
Authors: Hodkinson John P. , Radford Sheena E. , Ashcroft Alison E. 
Published: July 2012

RATIONALEAmyloid formation is implicated in a number of human diseases. β2‐microglobulin (β2m) is the precursor protein in dialysis‐related amyloidosis and it has been shown that partial, or more complete, unfolding is key to amyloid fibril formation in this pathology. Here the relationship between conformational flexibility and β2m amyloid formation at physiological pH has been investigated.METHODSHDX‐ESI‐MS was used to study the conformational dynamics of β2m. Protein engineering, or the addition of Cu2+ ions, sodium dodecyl sulphate, trifluoroethanol, heparin, or protein stabilisers, was employed to perturb the conformational dynamics of β2m. The fibril‐forming propensities of the protein variants and the wild‐type protein in the presence of additives, which resulted in >5‐fold increase in the EX1 rate of HDX, were investigated further.RESULTSESI‐MS revealed that HDX occurs via a mixed EX1/EX2 mechanism under all conditions. Urea denaturation and tryptophan fluorescence indicated that EX1 exchange occurred from a globally unfolded state in wild‐type β2m. Although >30‐fold increase in the HDX exchange rate was observed both for the protein variants and for the wild‐type protein in the presence of specific additives, large increases in exchange rate did not necessarily result in extensive de novo fibril formation.CONCLUSIONSThe conformational dynamics measured by the EX1 rate of HDX do not predict the ability of β2m to form amyloid fibrils de novo at neutral pH. This suggests that the formation of amyloid fibrils from β2m at neutral pH is dependent on the generation of one or more specific aggregation‐competent species which facilitate self‐assembly. Copyright © 2012 John Wiley & Sons, Ltd.
Tandem mass spectrometry of bilin tetrapyrroles by electrospray ionization and collision‐induced dissociation
Authors: Quinn Kevin D. , Nguyen Nhu Q. T. , Wach Michael M. , Wood Troy D. 
Published: July 2012

RATIONALEBilins are metabolic products of hosts and bacteria on porphyrins, and are markers of health state and human waste contamination. Although bilin tandem mass spectrometry reports exist, their fragmentation behavior as a function of structure has not been compared, nor has fragmentation been examined as a function of collision energy.METHODSThe fragmentation of bilins generated by positive ion mode electrospray ionization is examined by collision‐induced dissociation (CID). CID on a quadrupole ion trap and on a Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometer as a function of collision energy is compared. Methyl esterification was used to deduce which product ions contain the inner pyrrole rings. FT‐ICR high mass accuracy measurements were used to determine the formulas of the resultant product ions.RESULTSThe central carbon's bonding to the inner pyrrole rings influences fragmentation. Bilirubin is unique because fragmentation adjacent to the central methylene group between innermost rings predominates, and loss of a terminal pyrrole is observed only with helium collision gas. The other bilins lose the terminal pyrroles first; as CID energy is increased, additional fragmentation due to neutral losses of small molecules such as H2O, CO, CO2, and methanol occurs.CONCLUSIONSBased on these observations, fragmentation schemes for the bilins are proposed that are strongly dependent on the molecular structure and collision energy; only bilirubin fragmentation is influenced significantly by the collision gas used. This report should have value in identification of this class of molecules for biomarker detection. Copyright © 2012 John Wiley & Sons, Ltd.
Nearest‐neighbors medians clustering
Authors: Peña Daniel , Viladomat Júlia , Zamar Ruben 
Published: July 2012

AbstractWe propose a nonparametric cluster algorithm based on local medians. Each observation is substituted by its local median and this new observation moves toward the peaks and away from the valleys of the distribution. The process is repeated until each observation converges to a fixpoint. We obtain a partition of the sample based on the convergence points. Our algorithm determines the number of clusters and the partition of the observations given the proportion α of neighbors. A fast version of the algorithm where only a subset of the observations from the sample is processed is also proposed. A proof of the convergence from each point to its closest fixpoint and the existence and uniqueness of a fixpoint in a neighborhood of each mode is given for the univariate case. © 2012 Wiley Periodicals, Inc. Statistical Analysis and Data Mining, 2012
Classifying malicious activities in Honeynets using entropy and volume‐based thresholds
Authors: Sqalli Mohammed H. , Firdous Syed Naeem , Salah Khaled , Abu‐Amara Marwan 
Published: July 2012

ABSTRACTA Honeynet is a network designed by the Honeynet Project organization to gather information on security threats and attacks. Honeynets are being used by numerous institutions to proactively improve network security by identifying malicious and unauthorized activities in production and private networks. A Honeynet captures a substantial amount of network data and logs. The analysis of these datasets to identify malicious activities is a challenging task. The main aim of the work in this paper is to employ an anomaly detection technique to classify different types of malicious activities present in Honeynet. In particular, we use feature‐based and volume‐based schemes for Honeynet data classification. A detailed analysis of various traffic features is carried out, and the most appropriate ones for Honeynet traffic are selected. The classification of malicious activities is achieved by applying entropy‐based distributions and traffic volume distributions. Entropy‐based distributions are used for feature‐based parameters, whereas traffic volume distributions are used for volume‐based parameters. The behavior of various anomalies or malicious activities is classified using the selected features and their respective threshold values. Finally, we propose a mapping between the various anomalies and their associated behavior, which can be further used to identify similar anomalies in other Honeynet data sets. Copyright © 2012 John Wiley & Sons, Ltd.
Microfluidic Devices Modulate Tumor Cell Line Susceptibility to NK Cell Recognition
Authors: Perozziello Gerardo , La Rocca Rosanna , Cojoc Gheorghe , Liberale Carlo , Malara Natalia , Simone Giuseppina , Candeloro Patrizio , Anichini Andrea , Tirinato Luca , Gentile Francesco , Coluccio Maria Laura , Carbone Ennio , Di Fabrizio Enzo 
Published: July 2012

AbstractThis study aims to adoptively reduce the major histocompatibility complex class I (MHC‐I) molecule surface expression of cancer cells by exposure to microfluid shear stress and a monoclonal antibody. A microfluidic system is developed and tumor cells are injected at different flow rates. The bottom surface of the microfluidic system is biofunctionalized with antibodies (W6/32) specific for the MHC‐I molecules with a simple method based on microfluidic protocols. The antibodies promote binding between the bottom surface and the MHC‐I molecules on the tumor cell membrane. The cells are injected at an optimized flow rate, then roll on the bottom surface and are subjected to shear stress. The stress is localized and enhanced on the part of the membrane where MHC‐I proteins are expressed, since they stick to the antibodies of the system. The localized stress allows a stripping effect and consequent reduction of the MHC‐I expression. It is shown that it is possible to specifically treat and recover eukaryotic cells without damaging the biological samples. MHC‐I molecule expression on treated and control cell surfaces is measured on tumor and healthy cells. After the cell rolling treatment a clear reduction of MHC‐I levels on the tumor cell membrane is observed, whereas no changes are observed on healthy cells (monocytes). The MHC‐I reduction is investigated and the possibility that the developed system could induce a loss of these molecules from the tumor cell surface is addressed. The percentage of living tumor cells (viability) that remain after the treatment is measured. The changes induced by the microfluidic system are analyzed by fluorescence‐activated cell sorting and confocal microscopy. Cytotoxicity tests show a relevant increased susceptibility of natural killer (NK) cells on microchip‐treated tumor cells.
Microfluidic Automation Using Elastomeric Valves and Droplets: Reducing Reliance on External Controllers
Authors: Kim Sung‐Jin , Lai David , Park Joong Yull , Yokokawa Ryuji , Takayama Shuichi 
Published: July 2012

AbstractThis paper gives an overview of elastomeric valve‐ and droplet‐based microfluidic systems designed to minimize the need of external pressure to control fluid flow. This Concept article introduces the working principle of representative components in these devices along with relevant biochemical applications. This is followed by providing a perspective on the roles of different microfluidic valves and systems through comparison of their similarities and differences with transistors (valves) and systems in microelectronics. Despite some physical limitation of drawing analogies from electronic circuits, automated microfluidic circuit design can gain insights from electronic circuits to minimize external control units, while implementing high‐complexity and high‐throughput analysis.