bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of pulmonary blood flow changes on oxygen‐enhanced lung magnetic resonance imaging
Authors: Lee Hye‐Jeong , Park Jaeseok , Hur Jin , Kim Young Jin , Nam Ji Eun , Choi Byoung Wook , Choe Kyu Ok
Published: July 2012

In this study, we investigated the effects of changes in pulmonary blood flow on oxygen‐enhanced lung magnetic resonance imaging. Increased pulmonary blood flow was produced by intravenous infusion of sildenafil (0.2 mg/kg) in 10 New Zealand white rabbits. Decreased pulmonary blood flow was produced by single subcutaneous injection of monocrotaline (60 mg/kg). A velocity‐encoded cine magnetic resonance imaging for pulmonary blood flow and an oxygen‐enhanced lung magnetic resonance imaging were performed at baseline, during sildenafil infusion, and after monocrotaline injection. We compared the baseline data to those obtained during sildenafil infusion and after monocrotaline injection for pulmonary blood flow changes and signal intensity enhancement ratios of oxygen‐enhanced lung magnetic resonance imaging. Wilcoxon's signed rank test was used for statistical analysis. There was a significant difference between pulmonary blood flow at baseline (418.6 ± 108.9 mL/min) and after sildenafil (491.9 ± 118.0 mL/min; P = 0.005) or between pulmonary blood flow at baseline and after monocrotaline administration (356.3 ± 85.8 mL/min; P = 0.017). However, there was no significant difference between the signal intensity enhancement ratios at baseline (23.8 ± 11.4%) and after sildenafil (24.0 ± 7.9%; P = 0.953) or the signal intensity enhancement ratios at baseline and after monocrotaline administration (22.7 ± 10.3%; P = 0.374). Changes in pulmonary blood flow had little effect on the signal intensity enhancement ratio of oxygen‐enhanced lung magnetic resonance imaging. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.
Functionalized graphene sheets‐epoxy based nanocomposite for cryotank composite application
Authors: Lee Je Kyun , Song Sangyup , Kim Byungki
Published: July 2012

Multifunctional high performance functionalized graphene sheets (FGSs) based epoxy nanocomposites were investigated to understand the feasibility that these FGSs‐epoxy nanocomposites can be applied to cryotank composite applications. The FGSs were successfully synthesized from graphite flakes through preparing graphite oxides by oxidizing graphite flakes first and next, thermally exfoliating the formed graphite oxides. These high performance FGSs were next incorporated into epoxy matrix resin system to generate the uniformly dispersed FGSs reinforced epoxy nanocomposites. The resultant FGSs‐epoxy nanocomposites significantly enhanced resin strength and toughness about 30–80% and 200–700% at room and low temperatures of −130°C, respectively, and reduced the coefficient of thermal expansion (CTE) of polymer resin at both below and above Tg about 25% at loading of 1.6 wt% FGSs, and increased Tg of polymer resin about 8°C at low loading of 0.4 wt% FGSs without deteriorating their good processability. We found that these significantly improved properties of FGSs‐reinforced epoxy nanocomposite were closely associated with high surface area and wrinkled structure of the FGSs. The further optimization will result the high performance FGSs‐epoxy nanocomposite suitable for use in the next generation multifunctional cryotank carbon fiber reinforced polymer (CFRP) composite applications, where better microcrack resistance and mechanical and dimensional stability are needed. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Effects of fly ash in composites fabricated by injection molding
Authors: Setsuda Roy , Fukumoto Isao , Kanda Yasuyuki
Published: July 2012

In this study, the effects of fly ash in composites fabricated by injection molding are examined. Taguchi design of experiment was first utilized to estimate the effects different injection molding conditions and content ratios of fly ash have on a linear low‐density polyethylene (LLDPE)‐fly ash composite. The results reveal that the content of fly ash is highly significant and contributive to the shrinkage ratio and bending strength. For these reasons, LLDPE and polypropylene (PP) composites with different size particles of fly ash were fabricated and the mechanical properties were investigated. The particle size was changed by grinding fly ash with a planetarium ball mill. The shrinkage ratio, bending strength and flexural modulus of LLDPE composites containing raw fly ash were found to improve. The shrinkage ratio and flexural modulus of PP composites containing ground fly ash were also found to improve. Homogenization analysis using the finite element method was then used to calculate the Von Mises stress distributions and homogenized elastic matrix of PP composites containing ground fly ash. The homogenized elastic matrix was used to validate the experimental flexural modulus. The results show that the homogenized elastic matrix is in good agreement with the experimental flexural modulus. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
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

Present 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

Banana 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

In 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

Objective

The aim is to describe the performance of first‐trimester combined risk assessment in twin pregnancies.

Methods

Maternal 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.

Results

From 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.

Conclusions

The 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.
Managing Political Risks of Chinese Contracted Projects in Libya
Authors: Zhang Juan , Wei William X.
Published: July 2012

The contracted project is the basic form of Sino-Libyan economic cooperation. The authors hope that Chinese constructors will learn from this case study. This article assesses the political risk for Chinese contracted projects at three levels and studies their countermeasures to this emergency and the effects of political risks on Chinese constructors in Libya. The research finds that Chinese constructors are not good at political risk management due to their traditional attitudes toward risk and the attitudes of the Chinese government toward overseas losses of Chinese state-owned enterprises (SOEs). However, Chinese SOEs are more experienced than private-owned enterprises in dealing with emergencies.
Linking Policies to Projects: The Key to Identifying the Right Public Investment Projects
Authors: Shiferaw Asmamaw Tadege , Klakegg Ole Jonny
Published: July 2012

This article reviews the merits of project governance in linking policies to projects and focuses on public investment projects in African countries. In this region, every year, huge sums of money are spent on public investment projects. It is relevant to ask whether the objectives of these projects are set and fulfilled according to the needs and priorities of the target group, or whether they are consistent with the development policies of governments in the target countries. After examining different conceptual and contextual literatures, the authors provide a project governance model to link policies to projects, a checklist for good project governance, and an outline of factors that could affect the project governance implementation.
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

The 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

The 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

Most 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

RATIONALE

Most 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.

METHODS

Using 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.

RESULTS

Comparison 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).

CONCLUSIONS

Comparison 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

RATIONALE

Amyloid 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.

METHODS

HDX‐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.

RESULTS

ESI‐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.

CONCLUSIONS

The 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

RATIONALE

Bilins 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.

METHODS

The 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.

RESULTS

The 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.

CONCLUSIONS

Based 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.
Motion planning for tree climbing with inchworm‐like robots
Authors: Lam Tin Lun , Xu Yangsheng
Published: July 2012

This paper proposes a global path‐ and motion‐planning algorithm that enables inchworm‐like robots to navigate their way up tree branches. The intuitive climbing space representation method proposed here greatly simplifies the path‐planning problem. The dynamic programming algorithm can be used to identify the optimal path leading to the target position in the target direction according to the constraints and requirements specified. The planned path can be applied in any tree‐climbing robot that utilizes the nonenclosure gripping method. An efficient motion‐planning algorithm for continuum inchworm‐like robots is then developed to enable them to climb along the planned path with a high degree of accuracy. In comparison with the method proposed in our previous study, the method proposed herein significantly improves consistency between the planned path and the motions of the robot, and therefore makes it more practical to implement the motion‐planning algorithm in trees of different shapes. The paper also describes hardware experiments in which the proposed planning algorithm is applied to enable inchworm‐like robots to climb real trees, thus validating the proposed planning algorithm in practice. © 2012 Wiley Periodicals, Inc.
Nearest‐neighbors medians clustering
Authors: Peña Daniel , Viladomat Júlia , Zamar Ruben
Published: July 2012

We 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

A 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.
ToF‐SIMS study of the behavior of thermally oxidized films formed on nickel‐based 690 alloy in high‐temperature water
Authors: Mazenc A. , Galtayries A. , Seyeux A. , Marcus P. , Leclercq S.
Published: July 2012

Alloy 690 is a high‐chromium nickel alloy widely used for steam generator tubes in pressurized water reactors. We have applied an optimized thermal oxidation treatment to alloy 690 consisting of 4 h at 500 °C (0.6 at% O2 in Ar) to make an improved diffusion barrier layer limiting the release of Ni during processing. The efficiency of such a treatment was tested by immersion in simulated pressurized water reactor primary water for 9 weeks. This work also explores the use of time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) to characterize the oxidized films formed after different treatments. Reference spectra were acquired by analyzing thermally oxidized Ni, Cr, and Ni‐30Cr samples as well as hydroxides and spinel powders [Ni(OH)2 and NiFe2O4]. ToF‐SIMS spectra of model oxides have allowed the selection of a set of ionic intensity ratios to be used for data processing of the spectra and profiles, obtained after the different oxidation steps applied on alloy 690. Thus, the following information was obtained: (i) the oxide layer structure is triplex; (ii) an intermediate layer is composed of Cr2O3, on which surface coverage depends on treatment; (iii) the outer layer is Ni‐ and Fe‐rich, whereas the inner layer is most probably constituted by a NiCr spinel oxide; and (iv) the total oxide layer grown during thermal oxidation is thinner than the one directly formed in primary water. If similar in thickness, the thermally grown oxide layer has a different composition once exposed to primary water. This ToF‐SIMS strategy was very fruitful in such a surface tube characterization. Copyright © 2012 John Wiley & Sons, Ltd.
The effect of the addition of talc on tribological properties of aramid fiber‐reinforced polyimide composites under high vacuum, ultraviolet or atomic oxygen environment
Authors: Zhao Gai , Liu Baixing , Wang Qihua , Wang Tingmei
Published: July 2012

The aramid fibers‐reinforced polyimide composites filled with talc were fabricated by means of a hot press molding technique, and mechanical and tribological behaviors were comparatively investigated. Experimental results showed that the elastic modulus of the composites increased with an increase of the talc, but the impact intensity and loss factor decreased. Besides, the coefficient of friction decreased with the increase of the talc content. To contrast the effects of the ultrahigh vacuum (VC), ultraviolet (UV) or atomic oxygen (AO) on the composites, experiments without irradiation or after UV or AO irradiation were conducted. Scanning electron microscopy and X‐ray photoelectron spectroscopy (XPS) analysis showed that UV or AO irradiation can change the surface structure and chemical composition of the polymer because of the photooxidation and chemical erosion. 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

This 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

This 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.
Prussian Blue Analogues of Reduced Dimensionality
Authors: Gengler Régis Y. N. , Toma Luminita M. , Pardo Emilio , Lloret Francesc , Ke Xiaoxing , Van Tendeloo Gustaaf , Gournis Dimitrios , Rudolf Petra
Published: July 2012

Mixed‐valence polycyanides (Prussian Blue analogues) possess a rich palette of properties spanning from room‐temperature ferromagnetism to zero thermal expansion, which can be tuned by chemical modifications or the application of external stimuli (temperature, pressure, light irradiation). While molecule‐based materials can combine physical and chemical properties associated with molecular‐scale building blocks, their successful integration into real devices depends primarily on higher‐order properties such as crystal size, shape, morphology, and organization. Herein a study of a new reduced‐dimensionality system based on Prussian Blue analogues (PBAs) is presented. The system is built up by means of a modified Langmuir–Blodgett technique, where the PBA is synthesized from precursors in a self‐limited reaction on a clay mineral surface. The focus of this work is understanding the magnetic properties of the PBAs in different periodic, low‐dimensional arrangements, and the influence of the “on surface” synthesis on the final properties and dimensionality of the system.
Inertial Manipulation and Transfer of Microparticles Across Laminar Fluid Streams
Authors: Gossett Daniel R. , Tse Henry Tat Kwong , Dudani Jaideep S. , Goda Keisuke , Woods Travis A. , Graves Steven W. , Di Carlo Dino
Published: July 2012

A general strategy for controlling particle movement across streams would enable new capabilities in single‐cell analysis, solid‐phase reaction control, and biophysics research. Transferring cells across streams is difficult to achieve in a well‐controlled manner, since it requires precise control of fluid flow along with external force fields or precisely manufactured mechanical structures. Herein a strategy is introduced for particle transfer based on passive inertial lift forces and shifts in the distribution of these forces for channels with shifting aspect ratios. Uniquely, use of the dominant wall‐effect lift parallel to the particle rotation direction is explored and utilized to achieve controllable cross‐stream motion. In this way, particles are positioned to migrate across laminar streams and enter a new solution without significant disturbance of the interface at rates exceeding 1000 particles per second and sub‐millisecond transfer times. The capabilities of rapid inertial solution exchange (RInSE) for preparation of hematological samples and other cellular assays are demonstrated. Lastly, improvements to inline flow cytometry after RInSE of excess fluorescent dye and focusing for downstream analysis are characterized. The described approach is simply applied to manipulating cells and particles and quickly exposing them to or removing them from a reacting solution, with broader applications in control and analysis of low affinity interactions on cells or particles.
Vasculogenic and Osteogenesis-Enhancing Potential of Human Umbilical Cord Blood Endothelial Colony-Forming Cells
Authors: Liu Yuchun , Teoh Swee-Hin , Chong Mark S. K. , Lee Eddy S. M. , Mattar Citra N. Z. , Randhawa Nau'shil Kaur , Zhang Zhi-Yong , Medina Reinhold J. , Kamm Roger D. , Fisk Nicholas M. , Choolani Mahesh , Chan Jerry K. Y.
Published: July 2012

Umbilical cord blood-derived endothelial colony-forming cells (UCB-ECFC) show utility in neovascularization, but their contribution to osteogenesis has not been defined. Cocultures of UCB-ECFC with human fetal-mesenchymal stem cells (hfMSC) resulted in earlier induction of alkaline phosphatase (ALP) (Day 7 vs. 10) and increased mineralization (1.9×; p < .001) compared to hfMSC monocultures. This effect was mediated through soluble factors in ECFC-conditioned media, leading to 1.8–2.2× higher ALP levels and a 1.4–1.5× increase in calcium deposition (p < .01) in a dose-dependent manner. Transcriptomic and protein array studies demonstrated high basal levels of osteogenic (BMPs and TGF-βs) and angiogenic (VEGF and angiopoietins) regulators. Comparison of defined UCB and adult peripheral blood ECFC showed higher osteogenic and angiogenic gene expression in UCB-ECFC. Subcutaneous implantation of UCB-ECFC with hfMSC in immunodeficient mice resulted in the formation of chimeric human vessels, with a 2.2-fold increase in host neovascularization compared to hfMSC-only implants (p = .001). We conclude that this study shows that UCB-ECFC have potential in therapeutic angiogenesis and osteogenic applications in conjunction with MSC. We speculate that UCB-ECFC play an important role in skeletal and vascular development during perinatal development but less so in later life when expression of key osteogenesis and angiogenesis genes in ECFC is lower.
Modulating Glypican4 Suppresses Tumorigenicity of Embryonic Stem Cells While Preserving Self-Renewal and Pluripotency
Authors: Fico Annalisa , De Chevigny Antoine , Egea Joaquim , Bösl Michael R. , Cremer Harold , Maina Flavio , Dono Rosanna
Published: July 2012

Self-renewal and differentiation of stem cell depend on a dynamic interplay of cell-extrinsic and -intrinsic regulators. However, how stem cells perceive the right amount of signal and at the right time to undergo a precise developmental program remains poorly understood. The cell surface proteins Glypicans act as gatekeepers of environmental signals to modulate their perception by target cells. Here, we show that one of these, Glypican4 (Gpc4), is specifically required to maintain the self-renewal potential of mouse embryonic stem cells (ESCs) and to fine tune cell lineage commitment. Notably, Gpc4-mutant ESCs contribute to all embryonic cell lineages when injected in blastocyts but lose their intrinsic tumorigenic properties after implantation into nude mice. Therefore, our molecular and functional studies reveal that Gpc4 maintains distinct stemness features. Moreover, we provide evidence that self-renewal and lineage commitment of different stem cell types is fine tuned by Gpc4 activity by showing that Gpc4 is required for the maintenance of adult neural stem cell fate in vivo. Mechanistically, Gpc4 regulates self-renewal of ESCs by modulating Wnt/β-catenin signaling activities. Thus, our findings establish that Gpc4 acts at the interface of extrinsic and intrinsic signal regulation to fine tune stem cell fate. Moreover, the ability to uncouple pluripotent stem cell differentiation from tumorigenic potential makes Gpc4 as a promising target for cell-based regenerative therapies.
The GCTM-5 Epitope Associated with the Mucin-Like Glycoprotein FCGBP Marks Progenitor Cells in Tissues of Endodermal Origin
Authors: Stamp Lincon A. , Braxton David R. , Wu Jun , Akopian Veronika , Hasegawa Kouichi , Chandrasoma Parakrama T. , Hawes Susan M. , McLean Catriona , Petrovic Lydia M. , Wang Kasper , Pera Martin F.
Published: July 2012

Monoclonal antibodies against cell surface markers are powerful tools in the study of tissue regeneration, repair, and neoplasia, but there is a paucity of specific reagents to identify stem and progenitor cells in tissues of endodermal origin. The epitope defined by the GCTM-5 monoclonal antibody is a putative marker of hepatic progenitors. We sought to analyze further the distribution of the GCTM-5 antigen in normal tissues and disease states and to characterize the antigen biochemically. The GCTM-5 epitope was specifically expressed on tissues derived from the definitive endoderm, in particular the fetal gut, liver, and pancreas. Antibody reactivity was detected in subpopulations of normal adult biliary and pancreatic duct cells, and GCTM-5-positive cells isolated from the nonparenchymal fraction of adult liver expressed markers of progenitor cells. The GCTM-5-positive cell populations in liver and pancreas expanded greatly in numbers in disease states such as biliary atresia, cirrhosis, and pancreatitis. Neoplasms arising in these tissues also expressed the GCTM-5 antigen, with pancreatic adenocarcinoma in particular showing strong and consistent reactivity. The GCTM-5 epitope was also strongly displayed on cells undergoing intestinal metaplasia in Barrett's esophagus, a precursor to esophageal carcinoma. Biochemical, mass spectrometry, and immunochemical studies revealed that the GCTM-5 epitope is associated with the mucin-like glycoprotein FCGBP. The GCTM-5 epitope on the mucin-like glycoprotein FCGBP is a cell surface marker for the study of normal differentiation lineages, regeneration, and disease progression in tissues of endodermal origin.
Dendrimers—revolutionary drugs for infectious diseases
Authors: Lazniewska Joanna , Milowska Katarzyna , Gabryelak Teresa
Published: July 2012

Over recent years innovative nanomolecules in a form of dendrimers have been gaining increasing interest. These compounds can be designed and modified in many ways giving a molecule which meets required expectations. For this reason dendrimers are the object of intensive studies in many fields of nanoscience including one of the most thriving—biomedicine. Numerous studies provide evidence that some dendrimers exhibit activities against many species/strains of viruses, bacteria, fungi, and prions. These types of dendritic nanostructures which are distinguished by antipathogenic properties and low cytotoxicity to eukaryotic cells may be potentially applied in medicine as novel drugs for various infectious diseases, especially those which are persistent, marked by high mortality rate, or untreatable. Dendrimers can exert their effect via different mechanisms of action, which are, in most cases, related to multivalency of the nanomolecule. The application of dendrimers is likely to be a breakthrough in prevention and treatment of infectious diseases which still beset humanity and may significantly improve the quality of people's life.WIREs Nanomed Nanobiotechnol2012, 4:469–491. doi: 10.1002/wnan.1181

This article is categorized under:

Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease
The molecular circuitry underlying pluripotency in embryonic stem cells
Authors: Warmflash Aryeh , Arduini Brigitte L. , Brivanlou Ali H.
Published: July 2012

Cells in the pluripotent state have the ability to self‐renew indefinitely and to differentiate to all the cells of the embryo. These cells provide an in vitro window into development, including human development, as well as holding extraordinary promise for cell‐based therapies in regenerative medicine. The recent demonstration that somatic cells can be reprogrammed to the pluripotent state has raised the possibility of patient and disease‐specific induced pluripotent cells. In this article, we review the molecular underpinning of pluripotency. We focus on the transcriptional and signaling networks that underlie the state of pluripotency and control differentiation. In general, the action of each of the molecular components and pathways is dose and context dependent highlighting the need for a systems approach to understanding pluripotency. WIREs Syst Biol Med 2012. doi: 10.1002/wsbm.1182

This article is categorized under:

Biological Mechanisms > Cell Fates

Biological Mechanisms > Cell Signaling

Developmental Biology > Stem Cell Biology and Regeneration
(Dys)Zphilia or a custodial breaking Higgs at the LHC
Authors: Farina Marco , Grojean Christophe , Salvioni Ennio
Published: July 2012

Abstract

Electroweak precision measurements established that custodial symmetry is preserved to a good accuracy in the gauge sector after electroweak symmetry breaking. However, recent LHC results might be interpreted as pointing towards Higgs couplings that do not respect such symmetry. Motivated by this possibility, we reconsider the presence of an explicitly custodial breaking coupling in a generic Higgs parameterization. After briefly commenting on the large UV sensitivity of the T parameter to such a coupling, we perform a fit to results of Higgs searches at LHC and Tevatron, and find that the apparent enhancement of the ZZ channel with respect to WW can be accommodated. Two degenerate best-fit points are present, which we label ‘Zphilic’ and ‘dysZphilic’ depending on the sign of the hZZ coupling. Finally we highlight some measurements at future linear colliders that may remove such degeneracy.
A Meta‐Analysis of Perioperative Outcomes of Laparoscopic Splenectomy for Hematological Disorders
Authors: Bai Yan‐Nan , Jiang Hui , Prasoon Pankaj
Published: July 2012

Background

Due to changes in surgical trends, laparoscopic splenectomy (LS) has become the standard approach for most splenectomies performed for hematological disorders, barring any contraindications. The perioperative outcomes of LS for this indication have not been updated for several years. Controversy still surrounds whether LS should be performed for massive splenomegaly. The purpose of this meta‐analysis was to evaluate the perioperative outcomes of laparoscopic splenectomy for hematological disorders.

Methods

Literature searches were conducted to identify studies comparing the perioperative outcomes of the laparoscopic and open approaches for hematological disorders. The results were pooled by using standard meta‐analysis methods.

Results

Thirty‐eight studies with a total of 2,914 patients comparing LS to open splenectomy (OS) for hematological disorders were identified. Mortality was low in both groups. The pooled complications of the LS group were significantly fewer than those of the OS group (−0.11, p < 0.001), and the NNT was 9 (95 % confidence interval, 6–20). For massive spleens, a similar result was observed (−0.12, p = 0.009). Accessory spleen resection and blood loss also were comparable between the two approaches. Additionally, LS was associated with longer operative times (57.38 min, p < 0.00001) and shorter hospital stays (2.48 days, p < 0.00001).

Conclusions

LS is preferred compared to OS, based on lower complication rates and better handling of comorbid conditions. LS is associated with shorter hospital stays but longer operative times. We conclude that LS may be considered an acceptable option even in cases of a massive spleen. To strengthen the clinical evidence, more high‐quality clinical trials on different issues are necessary.