bluuebunny/crossref_metadata_2025_split huggingface dataset:
Closed‐form expressions for flip angle variation that maximize total signal in T1‐weighted rapid gradient echo MRI
Authors: Drobnitzky Matthias , Klose Uwe 
Published: January 2017

PurposeMagnetization‐prepared rapid gradient‐echo (MPRAGE) sequences are commonly employed for T1‐weighted structural brain imaging. Following a contrast preparation radiofrequency (RF) pulse, the data acquisition proceeds under nonequilibrium conditions of the relaxing longitudinal magnetization. Variation of the flip angle can be used to maximize total available signal. Simulated annealing or greedy algorithms have so far been published to numerically solve this problem, with signal‐to‐noise ratios optimized for clinical imaging scenarios by adhering to a predefined shape of the signal evolution. We propose an unconstrained optimization of the MPRAGE experiment that employs techniques from resource allocation theory. A new dynamic programming solution is introduced that yields closed‐form expressions for optimal flip angle variation.MethodsFlip angle series are proposed that maximize total transverse magnetization () for a range of physiologic T1 values. A 3D MPRAGE sequence is modified to allow for a controlled variation of the excitation angle. Experiments employing a T1 contrast phantom are performed at 3T. 1D acquisitions without phase encoding permit measurement of the temporal development of . Image mean signal and standard deviation for reference flip angle trains are compared in 2D measurements. Signal profiles at sharp phantom edges are acquired to access image blurring related to nonuniform development.ResultsA novel closed‐form expression for flip angle variation is found that constitutes the optimal policy to reach maximum total signal. It numerically equals previously published results of other authors when evaluated under their simplifying assumptions. Longitudinal magnetization () is exhaustively used without causing abrupt changes in the measured MR signal, which is a prerequisite for artifact free images. Phantom experiments at 3T verify the expected benefit for total accumulated k‐space signal when compared with published flip angle series.ConclusionsDescribing the MR signal collection in MPRAGE sequences as a Bellman problem is a new concept. By means of recursively solving a series of overlapping subproblems, this leads to an elegant solution for the problem of maximizing total available MR signal in k‐space. A closed‐form expression for flip angle variation avoids the complexity of numerical optimization and eases access to controlled variation in an attempt to identify potential clinical applications.
Metabolic phenotyping of human plasma by 1H‐NMR at high and medium magnetic field strengths: a case study for lung cancer
Authors: Louis Evelyne , Cantrelle Francois‐Xavier , Mesotten Liesbet , Reekmans Gunter , Bervoets Liene , Vanhove Karolien , Thomeer Michiel , Lippens Guy , Adriaensens Peter 
Published: January 2017

Accurate identification and quantification of human plasma metabolites can be challenging in crowded regions of the NMR spectrum with severe signal overlap. Therefore, this study describes metabolite spiking experiments on the basis of which the NMR spectrum can be rationally segmented into well‐defined integration regions, and this for spectrometers having magnetic field strengths corresponding to 1H resonance frequencies of 400 MHz and 900 MHz. Subsequently, the integration data of a case–control dataset of 69 lung cancer patients and 74 controls were used to train a multivariate statistical classification model for both field strengths. In this way, the advantages/disadvantages of high versus medium magnetic field strength were evaluated. The discriminative power obtained from the data collected at the two magnetic field strengths is rather similar, i.e. a sensitivity and specificity of respectively 90 and 97% for the 400 MHz data versus 88 and 96% for the 900 MHz data. This shows that a medium‐field NMR spectrometer (400–600 MHz) is already sufficient to perform clinical metabolomics. However, the improved spectral resolution (reduced signal overlap) and signal‐to‐noise ratio of 900 MHz spectra yield more integration regions that represent a single metabolite. This will simplify the unraveling and understanding of the related, disease disturbed, biochemical pathways. Copyright © 2017 John Wiley & Sons, Ltd.
Computation of higher‐order moments of generalized polynomial chaos expansions
Authors: Savin É. , Faverjon B. 
Published: January 2017

SummaryBecause of the complexity of fluid flow solvers, non‐intrusive uncertainty quantification techniques have been developed in aerodynamic simulations in order to compute the quantities of interest required in an optimization process, for example. The objective function is commonly expressed in terms of moments of these quantities, such as the mean, standard deviation, or even higher‐order moments. Polynomial surrogate models based on polynomial chaos expansions have often been implemented in this respect. The original approach of uncertainty quantification using polynomial chaos is however intrusive. It is based on a Galerkin‐type formulation of the model equations to derive the governing equations for the polynomial expansion coefficients. Third‐order, indeed fourth‐order moments of the polynomials are needed in this analysis. Besides, both intrusive and non‐intrusive approaches call for their computation provided that higher‐order moments of the quantities of interest need to be post‐processed. In most applications, they are evaluated by Gauss quadratures and eventually stored for use throughout the computations. In this paper, analytical formulas are rather considered for the moments of the continuous polynomials of the Askey scheme, so that they can be evaluated by quadrature‐free procedures instead. Matlab© codes have been developed for this purpose and tested by comparisons with Gauss quadratures. Copyright © 2017 John Wiley & Sons, Ltd.
RP‐HPLC‐DAD‐ESI‐QTOF‐MS based metabolic profiling of the potential Olea europaea by‐product “wood” and its comparison with leaf counterpart
Authors: Ammar Sonda , Contreras Maria del Mar , Gargouri Boutheina , Segura‐Carretero Antonio , Bouaziz Mohamed 
Published: January 2017

AbstractIntroductionOlea europaea L. organs such as leaves, stems and roots have been associated with numerous in vivo and in vitro biological activities and used for traditional medicinal purposes. However, tree wood is an untapped resource with little information about their chemical composition.ObjectiveThat is why, the objective of this study is to increase the knowledge about phytochemicals from ‘Chemlali’ olive wood by means of mass spectrometry‐based analyses. Its comparison with by‐products derived from leaves was also studied.MethodologyHydromethanol extracts from wood and leaves with stems of ‘Chemlali’ olive cultivar were analysed using reversed‐phase (RP) high‐performance liquid chromatography (HPLC) coupled to two detection systems: diode‐array detection (DAD) and quadrupole time‐of‐flight (QTOF) mass spectrometry (MS) in negative ion mode. Tandem MS experiments were performed to establish the chemical structure of olive phytochemicals.ResultsA total of 85 compounds were characterised in the studied olive parts and classified as: sugars (3), organic acids (5), one phenolic aldehyde, simple phenolic acids (6), simple phenylethanoids (5), flavonoids (14), coumarins (3), caffeoyl phenylethanoid derivatives (6), iridoids (5), secoiridoids (32), and lignans (5). To our knowledge, the major part of these metabolites was not previously reported in olive tree wood, and 10 olive chemical constituents were identified for the first time in the Oleaceae family.ConclusionThe results presented here demonstrated the usefulness of the methodology proposed, based on RP‐HPLC‐DAD‐ESI‐QTOF‐MS and MS/MS, to develop an exhaustive metabolic profiling and to recover new biologically active compounds in olive wood with pharmacologic and cosmetic potential. Copyright © 2017 John Wiley & Sons, Ltd.
Prediction of neonatal respiratory distress in pregnancies complicated by fetal lung masses
Authors: Girsen Anna I. , Hintz Susan R. , Sammour Rami , Naqvi Aasim , El‐Sayed Yasser Y. , Sherwin Katie , Davis Alexis S. , Chock Valerie Y. , Barth Richard A. , Rubesova Erika , Sylvester Karl G. , Chitkara Ritu , Blumenfeld Yair J. 
Published: January 2017

AbstractObjectiveThe objective of this article is to evaluate the utility of fetal lung mass imaging for predicting neonatal respiratory distress.MethodPregnancies with fetal lung masses between 2009 and 2014 at a single center were analyzed. Neonatal respiratory distress was defined as intubation and mechanical ventilation at birth, surgery before discharge, or extracorporeal membrane oxygenation (ECMO). The predictive utility of the initial as well as maximal lung mass volume and congenital pulmonary airway malformation volume ratio by ultrasound (US) and magnetic resonance imaging (MRI) was analyzed.ResultsForty‐seven fetal lung mass cases were included; of those, eight (17%) had respiratory distress. The initial US was performed at similar gestational ages in pregnancies with and without respiratory distress (26.4 ± 5.6 vs 22.3 ± 3 weeks, p = 0.09); however, those with respiratory distress had higher congenital volume ratio at that time (1.0 vs 0.3, p = 0.01). The strongest predictors of respiratory distress were maximal volume >24.0 cm3 by MRI (100% sensitivity, 91% specificity, 60% positive predictive value, and 100% negative predictive value) and maximal volume >34.0 cm3 by US (100% sensitivity, 85% specificity, 54% positive predictive value, and 100% negative predictive value).ConclusionUltrasound and MRI parameters can predict neonatal respiratory distress, even when obtained before 24 weeks. Third trimester parameters demonstrated the best positive predictive value. © 2017 John Wiley & Sons, Ltd.
Silicificated polymer arrays based on a strong adhesive polymer for antifouling coatings
Authors: Du Mengmeng , Jin Qiaoqiao , Chai Mengsha , Ji Peijun 
Published: January 2017

AbstractWe report a novel approach for the preparation of multilayer polymers for protein and bacterial antifouling. Stainless steel (SS) was used as the model substrate. SS was first coated with a hybrid polymer film, which was formed by simultaneous hydrolytic polycondensation of 3‐aminopropyltriethoxysilane and polymerization of dopamine (HPAPD). Then p‐phenylenediamine was chemically bound to SS–HPAPD. The amino groups of p‐phenylenediamine were used as anchors for the growth of polyaniline nanofiber arrays by polymerization of aniline in situ. The nanofibers were further silicificated using 3‐aminopropyltriethoxysilane, 3‐mercaptopropyltriethoxysilane, vinyltrimethoxysilane and octyltrimethoxysilane, conferring various functional groups. The silicificated polyaniline nanofiber arrays (SPNAs) become hydrophobic. Separate tests for the adsorption of proteins of small (54 kDa) and large (2 × 90 kDa) molecular weights and Escherichia coli on the SPNAs were performed. The results show that the SPNAs can resist the adhesion of the proteins with an average efficiency of 96.3 ± 3.2%, and the SPNAs can resist the adhesion and colonization of Escherichia coli with an average efficiency of 97.5 ± 3.8%. The methodology of forming SPNAs on SS is of general utility and has wide application potential. © 2017 Society of Chemical Industry
Azahelicenes as visible light photoinitiators for cationic and radical polymerization: Preparation of photoluminescent polymers and use in high performance LED projector 3D printing resins
Authors: Al Mousawi Assi , Dumur Frédéric , Garra Patxi , Toufaily Joumana , Hamieh Tayssir , Goubard Fabrice , Bui Thanh‐Tuân , Graff Bernadette , Gigmes Didier , Pierre Fouassier Jean , Lalevée Jacques 
Published: January 2017

ABSTRACTIn this article, novel azahelicenes (AZs) were synthesized and proposed as high performance visible light photoinitiators for both the free radical polymerization of acrylates and the cationic polymerization (CP) of epoxides upon visible light exposure using Light Emitting Diodes (LEDs) @405, @455, and @470 nm. Excellent polymerization initiating abilities are found and high final conversions were obtained. Remarkably, an exceptional long lifetime photoluminescence property of the polymer films was observed when synthesized in presence of AZs. A full picture of the involved chemical mechanisms is given. AZs being high performance photoinitiators, their use in new cationic LED 3D printing resins will be also presented, that is, the cationic process upon LED projector @405 nm can be useful to reduce the shrinkage usually observed for radical polymerization. LED projector printing is very interesting compared to laser writing as this technology projects the profile of an entire layer of a 3D object at one time. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 55, 1189–1199
Modeling ionomer swelling dynamics of a sulfonated polyphenylene, pentablock copolymers, and nafion
Authors: Wang Donghui , Cornelius Chris J. 
Published: January 2017

ABSTRACTThe water swelling behavior of Nafion, sulfonated poly(phenylene) (sPP), and poly[t‐butyl styrene‐b‐hydrogenated isoprene‐b‐sulfonated styrene‐b‐hydrogenated isoprene‐b‐t‐butyl styrene) was studied in order to understand microscopic molecular interactions. Ionomer swelling was modeled using the Flory‐Rehner relationship to predict solvent‐ionomer interaction parameter (χ12) and effective number of elastically active chains (n). Water swollen PBC had a decreasing χ12 from 1.146 to 0.516 when its ion‐exchange capacity (IEC) increased from 1.0 to 2.0. Nafion 117 and sPP χ12 values were 0.93 and 0.807 at an IEC of 0.91 and 1.8. Polymer water uptake was inversely dependent upon n and IEC or sulfonic acid‐group concentration. The following trend was noted for ionomer type, n, and water uptake: PBC‐2.0 (159 wt % and 7.89e‐4 mol/cm3) > sPP (48.6 wt % and 1.40e‐3 mol/cm3) > Nafion 117 (23 wt % and 1.24e‐3 mol/cm3). The ionomer's Gibb's total free change (ΔGTot) due to water swelling for Nafion 117 was −15.3 J, sPP was −28.5 J, and PBC‐2.0 was −53.2 J. An empirical equation was created to estimate a material's total solubility parameter (δ); and dispersion (δd), dipolar (δp,), and hydrogen bonding (δh) forces. The δ values for Nafion 117, sPP, and PBC‐2.0 were 19.9 (J/cm3)1/2, 21.3 (J/cm3)1/2, and 21.0 (J/cm3)1/2. Idealized swelling within an ionomer due to solvent. Ion domains are comprised of fixed sulfonated acid groups (SO3H) along the polymer's backbone. These functional groups provide interaction sites for molecules to diffusion and swell chains. The total change in free energy ΔG is dominated by ΔGmix that is attributed to hydrogen bonding and the concentration of elastically active chains n, which directly impacts its chemical potential Δμ. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 435–443
X‐ray reflectivity method for the characterization of InGaN/GaN quantum well interface
Authors: Massabuau Fabien , Piot Nicolas , Frentrup Martin , Wang Xiuze , Avenas Quentin , Kappers Menno , Humphreys Colin , Oliver Rachel 
Published: January 2017

AbstractA method to characterize the interface of InGaN/GaN quantum wells by X‐ray reflectivity is presented. The interface roughness can be obtained from the ratio of diffuse to specular scatterings obtained on a transverse ‐scan. Rotation around the azimuthal angle allows for information about the directionality of the roughening mechanisms to be obtained. The method allows for quick identification of the presence or absence of gross well width fluctuations in the quantum well, providing that the interface is chemically sharp. When the interface exhibits chemical grading, compositional fluctuations across the terraced structure of the quantum well surface lead to aggravated roughness as the barrier is grown, which may be misinterpreted as gross well width fluctuations. This method carries promises for complementing analysis by transmission electron microscopy as it is non‐destructive, fast, and allows multi‐directional characterization of the roughness. It would therefore be particularly useful to detect process deviation in a production line, where prior knowledge of the sample is already available.
Robust sliding mode‐based extremum‐seeking controller for reaction systems via uncertainty estimation approach
Authors: Lara‐Cisneros Gerardo , Femat Ricardo , Dochain Denis 
Published: January 2017

SummaryThis paper deals with the design of a robust sliding mode‐based extremum‐seeking controller aimed at the online optimization of a class of uncertain reaction systems. The design methodology is based on an input–output linearizing method with variable‐structure feedback, such that the closed‐loop system converges to a neighborhood of the optimal set point with sliding mode motion. In contrast with previous extremum‐seeking control algorithms, the control scheme includes a dynamic modelling‐error estimator to compensate for unknown terms related with model uncertainties and unmeasured disturbances. The proposed online optimization scheme does not make use of a dither signal or a gradient‐based optimization algorithm. Practical stabilizability for the closed‐loop system around to the unknown optimal set point is analyzed. Numerical experiments for two nonlinear processes illustrate the effectiveness of the proposed robust control scheme. Copyright © 2017 John Wiley & Sons, Ltd.
Evaluating the Framework of a New River Bird Survey Method
Authors: Call E. M. , Hunter M. L. 
Published: January 2017

AbstractRiver bird assemblages can serve as beacons of environmental change associated with restoration or degradation. River birds regularly rely on riverine resources at some point in their life cycle, vary in the scale of temporal and spatial of use and forage at multiple levels of the food web (e.g. fish, aquatic plants, aquatic or emergent insects). We present a novel river bird survey method that is more easily employed and less intrusive than riverbank transect or boat surveys and encompasses a wide suite of species and a year‐round time frame. We evaluate the relative efficacy of different levels of survey duration (20, 15, 10 or 5 min), number of surveys (every 2 weeks in spring and fall and every 3 weeks in summer and winter) and number of sites on the survey's ability to document species richness and bird abundance. We used two statistical approaches, species accumulation curves (for duration, number of surveys and number of sites) and first‐order Jackknifes (for duration). We conclude that a biweekly or triweekly survey, 25 sites in the focal river, and a survey duration of at least 15 min are sufficient to meet our objectives. This logistically efficient survey approach facilitates monitoring complex and long‐term change such as that associated with river restoration and dam removal. Copyright © 2017 John Wiley & Sons, Ltd.
Bringing Together Reading and Writing: An Experimental Study of Writing Intensive Reading Comprehension in Low‐Performing Urban Elementary Schools
Authors: Collins James L , Lee Jaekyung , Fox Jeffery D. , Madigan Timothy P. 
Published: January 2017

AbstractThis study examined the hypothesis that assisted writing during reading improves reading comprehension. The hypothesis was derived from sociocognitive and constructivist theory and research and implemented in the form of a curricular intervention called Writing Intensive Reading Comprehension after its main feature of bringing together reading comprehension and writing. The study used instruction with interactive thinksheets to provide sustained, focused, and assisted writing experiences to help students in low‐performing urban schools construct understandings of their reading. The study used a cluster randomized trial design. Results support the hypothesis that bringing together reading and writing through instruction using thinksheets produces levels of reading comprehension superior to traditional instruction. Hierarchical linear modeling analyses of pretest and posttest data from 1,062 fourth‐ and fifth‐grade students in 50 classrooms and 10 schools (four 2‐year experimental, three 1‐year experimental, and three control schools) also revealed greater effects for special education and low‐income students in the experimental group. The study also revealed uneven improvement among experimental classrooms with regard to students’ grade level, length of exposure to the intervention, and teachers’ fidelity of implementation. The results imply that the upper grade students with the longer treatment and higher fidelity of implementation benefited more from the intervention. The study extends theory and research on reading–writing connections and suggests additional research and practical applications using assisted writing to improve reading comprehension.
Direct Conversion of Human Fibroblasts into Schwann Cells that Facilitate Regeneration of Injured Peripheral Nerve In Vivo
Authors: Sowa Yoshihiro , Kishida Tsunao , Tomita Koichi , Yamamoto Kenta , Numajiri Toshiaki , Mazda Osam 
Published: January 2017

Abstract
Schwann cells (SCs) play pivotal roles in the maintenance and regeneration of the peripheral nervous system. Although transplantation of SCs enhances repair of experimentally damaged peripheral and central nerve tissues, it is difficult to prepare a sufficient number of functional SCs for transplantation therapy without causing adverse events for the donor. Here, we generated functional SCs by somatic cell reprogramming procedures and demonstrated their capability to promote peripheral nerve regeneration. Normal human fibroblasts were phenotypically converted into SCs by transducing SOX10 and Krox20 genes followed by culturing for 10 days resulting in approximately 43% directly converted Schwann cells (dSCs). The dSCs expressed SC-specific proteins, secreted neurotrophic factors, and induced neuronal cells to extend neurites. The dSCs also displayed myelin-forming capability both in vitro and in vivo. Moreover, transplantation of the dSCs into the transected sciatic nerve in mice resulted in significantly accelerated regeneration of the nerve and in improved motor function at a level comparable to that with transplantation of the SCs obtained from a peripheral nerve. The dSCs induced by our procedure may be applicable for novel regeneration therapy for not only peripheral nerve injury but also for central nerve damage and for neurodegenerative disorders related to SC dysfunction.
Security of VoIP traffic over low or limited bandwidth networks
Authors: Alouneh Sahel , Abed Sa'ed , Ghinea George 
Published: January 2017

AbstractThe early days of voice over IP (VoIP) adoption were characterized by a lack of concern and awareness about security issues related to its use. Indeed, service providers and users were mostly preoccupied with issues related to its quality, functionality, and cost. Now that VoIP is a mainstream communication technology, security has become a major issue. This paper investigates the major security threats for VoIP communications and proposes a multipath approach solution, especially targeted for low bandwidth networks. Results show that security has an effect on VoIP quality especially for a large distance between communicating nodes and packet size. Results also show that our proposed multipath solution reduces significantly packet losses and performs better than single routing techniques in networks with low bandwidth capacities. Copyright © 2017 John Wiley & Sons, Ltd.