bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient and Bio‐inspired Conversion of Cellulose to Formic Acid Catalyzed by Metalloporphyrins in Alkaline Solution
Authors: Liu Qiang , Zhou Doudou , Li Zongxiang , Luo Weiping , Guo Cancheng
Published: May 2017

A bio‐inspired approach for efficient conversion of cellulose to formic acid (FA) was developed in an aqueous alkaline medium. Metalloporphyrins mimicking cytochrome P450 exhibit efficiently and selectively catalytic performance in catalytic conversion of cellulose. High yield of FA about 63.7% was obtained by using sulfonated iron(III) porphyrin as the catalyst and O2 as the oxidant. Iron(III)‐peroxo species, TSPPFeIIIOO−, was involved to cleave the C‐C bonds of gluconic acid to FA in this catalytic system. This approach used relatively high concentration of cellulose and ppm concentration of catalyst. This work may provide a bio‐inspired route to efficient conversion of cellulose to FA.
Functional Ionic Liquids Promoted Double Michael Reaction of Benzofuran‐3‐one or 1‐Indone and Symmetric Dienones: Construction of Spiro[benzofuran‐2,1’‐cyclohexane]‐3‐one or Spiro[cyclohexane‐1,2’‐indene]‐1’,4(3’H)‐dione Derivatives
Authors: Liu Chunhui , Xu Yalun , Niu Songyang , Wei Liquan , Liu Yong , Wang Yanbo , Zhu Junyan , Fu Jiya , Yuan Jinfang
Published: May 2017

The double Michael reactions between benzofuran‐3‐one or 1‐indone and symmetric dienones in the presence of catalytic ionic liquids were successfully developed and spiro[benzofuran‐2,1’‐cyclohexane]‐3‐one or spiro[cyclohexane‐1,2’‐indene]‐1’,4(3’H)‐dione derivatives containing a spiro quaternary stereogenic center, which widely exist in biologically active products and building blocks in organic synthesis, were obtained in excellent yields (up to 99%). This catalytic system was also extended to the double Michael reaction of less reactive 1‐indone and the desired products were also obtained in 31%‐62% yields. The catalytic system was highly active and efficient for a broad of substrates under mild conditions.
Ionic Liquid Mediated Synthesis of Lath Shaped CuO Micro‐Assembles as Extremely Stable Anode Material for Lithium‐Ion Batteries
Authors: Wang Man , Ma Ruguang , Liu Ying , Chung C.Y. , Deng Yonghong , Lu Zhouguang
Published: May 2017

A novel lath‐shaped CuO microassemble consisting of well‐crystalized ultrafine nanocrystals was prepared by an ionothermal method with the assistance of ionic liquids (ILs, 1‐butyl‐3‐methylimidazolium tetrafluoroborate). As anode material of lithium ion batteries, the ILs‐CuO exhibits high specific capacity, durability and good rate performance, superior to bare CuO. At a high current density of 1000 mA•g−1, after 100 cycles, ILs‐CuO still retains a discharge capacity of 483.2 mAh•g−1. The improved electrochemical performances could be ascribed to the unique microscale lath‐shape CuO assembles composed of ultrafine nanostructure.
Multivariate Gaussian subspatial regression applied to predict the effect of phosphate crystallization aging on the color in silicious conglomerates
Authors: Vicente‐Palacios Victor , Iñigo Adolo Carlos , García‐Talegón Jacinta
Published: May 2017

A new methodology has been applied to the experimental data obtained about a white siliceous conglomerate from Zamora (Spain), which was subjected to 25 cycles of 2 types of aging [freezing/thawing with cooling/heating (T1) and freezing/thawing with cooling/heating + phosphate crystallization (T2)]. Our model (multivariate Gaussian subspatial regression) allows the behavior and prediction of the chromatic coordinates (L*,a*,b*), including more than 25 cycles, to be analyzed. This model is much more flexible than classical models as it allows multiple variable combinations to be predicted in a dynamic way. The final result showed that the conglomerate experiences darkening, yellowing, and reddening, as the number of cycles increase and that the darkening is much less pronounced in T2 due to phosphate crystallization.
Modulating the Kinetics of Nanoparticle Adsorption for Simple and High‐Yield Fabrication of Plasmonic Heterostructures as SERS Substrates
Authors: Pekdemir Sami , Karabel Sema , Kiremitler N. Burak , Liu Xiaoying , Nealey Paul F. , Onses M. Serdar
Published: May 2017

This work reports scalable, low‐cost, and simple fabrication of plasmonic heterostructures consisting of gold nanoparticles (NPs) of different sizes to generate intense hot‐pots over large areas to serve as substrates for molecular sensing in SERS applications. Our approach involves assembly of massively‐available colloidal gold NPs on substrates functionalized with end‐grafted poly(ethylene glycol) (PEG) brushes without need for any sophisticated tools and post‐modification of the particles and substrates. From real‐time monitoring of the adsorption process by using a quartz crystal microbalance, we identified that the cyclic deposition of citrate‐stabilized gold NPs on PEG brushes is an effective approach to modulate the kinetics of particle adsorption and greatly improves the surface coverage leading to reduced inter‐particle distances. Cyclic deposition of NPs differing in size leads to placement of the small particles in close proximity of the large ones, yielding hot‐spots as a consequence of the unique type of interaction between PEG chains and gold NPs. Assembly of heterostructures (60 nm+40 nm and 60 nm+20 nm) at optimized conditions resulted in strong SERS effects with enhancement factors as high as ≈2.0×106 and enabled detection of rhodamine 6G molecules in concentrations as low as 1 nm. The cyclic deposition of NPs also results in increase of the water contact angle without need for any post‐modification of the substrate, resulting in ≈30 fold increase in the Raman intensity of aqueous molecules. The insights gained on the adsorption of gold NPs together with the simplicity of the presented approach show great promise for surface assembly of colloidal NPs for a broad range of applications.
Toward Hyperpolarized 19F Molecular Imaging via Reversible Exchange with Parahydrogen
Authors: Shchepin Roman V. , Goodson Boyd M. , Theis Thomas , Warren Warren S. , Chekmenev Eduard Y.
Published: May 2017

Fluorine‐19 has high NMR detection sensitivity—similar to that of protons—owing to its large gyromagnetic ratio and high natural abundance (100 %). Unlike protons, however, fluorine‐19 (19F) has a negligible occurrence in biological objects, as well as a more sensitive chemical shift. As a result, in vivo 19F NMR spectroscopy and MR imaging offer advantages of negligible background signal and sensitive reporting of the local molecular environment. Here we report on NMR hyperpolarization of 19F nuclei using reversible exchange reactions with parahydrogen gas as the source of nuclear spin order. NMR signals of 3‐fluoropyridine were enhanced by ≈100 fold, corresponding to 0.3 % 19F nuclear spin polarization (at 9.4 T), using about 50 % parahydrogen. While future optimization efforts will likely significantly increase the hyperpolarization levels, we already demonstrate the utility of 19F hyperpolarization for high‐resolution hyperpolarized 19F imaging and hyperpolarized 19F pH sensing.
Ionic Liquid/Metal–Organic Framework Composites: From Synthesis to Applications
Authors: Kinik Fatma Pelin , Uzun Alper , Keskin Seda
Published: May 2017

Metal–organic frameworks (MOFs) have been widely studied for different applications owing to their fascinating properties such as large surface areas, high porosities, tunable pore sizes, and acceptable thermal and chemical stabilities. Ionic liquids (ILs) have been recently incorporated into the pores of MOFs as cavity occupants to change the physicochemical properties and gas affinities of MOFs. Several recent studies have shown that IL/MOF composites show superior performances compared with pristine MOFs in various fields, such as gas storage, adsorption and membrane‐based gas separation, catalysis, and ionic conductivity. In this review, we address the recent advances in syntheses of IL/MOF composites and provide a comprehensive overview of their applications. Opportunities and challenges of using IL/MOF composites in many applications are reviewed and the requirements for the utilization of these composite materials in real industrial processes are discussed to define the future directions in this field.
An efficient two‐party authentication key exchange protocol for mobile environment
Authors: Qi Mingping , Chen Jianhua
Published: May 2017

The primary goal of this research is to ensure secure communications by client‐server architectures in mobile environment. Although various two‐party authentication key exchange protocols are proposed and claimed to be resistant to a variety of attacks, studies have shown that various loopholes exist in these protocols. What's more, many two‐party authentication key exchange protocols use timestamp to prevent the replay attack and transmit the user's identity in plaintext form. Obviously, these methods will lead to the clock synchronization problem and user's anonymity problem. Fortunately, the three‐way challenged‐response handshake technique and masking user's original identity with a secret hash value used in our study address these problems well. Of course, the proposed protocol based on elliptic curve cryptography supports flawless mutual authentication of participants, agreement of session key, impersonation attack resistance, replay attack resistance, and prefect forward secrecy, as well. The analyses in the aspects of efficiency and security show that the proposed protocol is a better choice for mobile users.
Considerations for application‐layer multipath transport control
Authors: Zhang Wei , Lei Weimin , Guan Yunchong , Li Guangye , Yang Lei
Published: May 2017

Multipath transport faces a lot of challenges caused by path diversity, network dynamics, and service diversity. An effective end‐to‐end multipath transport control mechanism becomes essential to efficiently utilize multiple paths. On the base of the general framework of multipath transport system based on application‐level relay proposed in our previous work, this paper presents a multipath transport control mechanism supporting various applications with different transmission requirements. We propose a multipath transport protocol suite, which is extensible and suitable for various applications, and a multipath transport control model in which an application‐dependent splitting granularity named flow block is introduced. Two load distribution models are explored: the earliest idle path first load distribution for reliable data transmission to maximize the data throughput and the packet reordering‐controlled load distribution for real‐time data transmission to minimize the packet reordering thereby reducing end‐to‐end delay and packet loss rate of multipath transport. Simulation results show that the proposed models can effectively improve data throughput for applications with reliable transmission requirements and reduce the total packet loss rate of the destination for applications with real‐time transmission requirements.
Assembly of [2]Rotaxanes in Water
Authors: Aeschi Yves , Drayss‐Orth Sylvie , Valášek Michal , Raps Felix , Häussinger Daniel , Mayor Marcel
Published: May 2017

Two [2]rotaxanes have been assembled in water from modular subunits through CuI‐catalyzed azide–alkyne “click” chemistry. For this purpose, 2,6‐disubstituted naphthalene axles with solubilizing oligo(ethylene glycol) (OEG) chains (n = 1–5) and propargyl terminal groups were synthesized and examined for their propensity to form inclusion complexes with a dicationic Diederich‐type cyclophane host. The dependence of pseudorotaxane formation on the linkers between the naphthalene core and OEG chains, and in the case of ester linkers on different spacer lengths, was analyzed by titration experiments. In addition, the inclusion complexes of two [2]rotaxanes were trapped by using a water‐soluble azide‐functionalized stopper. Repetitive chromatography finally enabled the isolation of both mechanically interlocked [2]rotaxanes.
Post‐fire hydrological response and suspended sediment transport of a terraced Mediterranean catchment
Authors: García‐Comendador Julián , Fortesa Josep , Calsamiglia Aleix , Calvo‐Cases Adolfo , Estrany Joan
Published: May 2017

In July 2013, a wildfire severely affected the western part of the island of Mallorca (Spain). During the first three post‐fire hydrological years, when the window of disturbance tends to be more open, the hydrological and sediment delivery processes and dynamics were assessed in a representative catchment intensively shaped by terracing that covered 37% of its surface area. A nested approach was applied with two gauging stations (covering 1.2 km2 and 4.8 km2) built in September 2013 that took continuous measurements of rainfall, water and sediment yield. Average suspended sediment concentration (1503 mg L−1) and the maximum peak (33 618 mg L−1) were two orders of magnitude higher than those obtained in non‐burned terraced catchments of Mallorca. This factor may be related to changes in soils and the massive incorporation of ash into the suspended sediment flux during the most extreme post‐fire event; 50 mm of rainfall in 15 min, reaching an erosivity of 2886 MJ mm ha−1 h−1. Moreover, hysteretic counter‐clockwise loops were predominant (60%), probably related to the increased sensitivity of the landscape after wildfire perturbation. Though the study period was average in terms of total annual precipitation (even higher in intensities), minimal runoff (2%) and low sediment yield (6.3 t km−2 y−1) illustrated how the intrinsic characteristics of the catchment, i.e. calcareous soils, terraces and the application of post‐fire measures, limited the hydrosedimentary response despite the wildfire impact. Copyright © 2017 John Wiley & Sons, Ltd.
Preparation and studies of new phosphorus‐containing diols as potential flame retardants
Authors: Wang Kui , Morgan Alexander B. , Benin Vladimir
Published: May 2017

Several new phosphorus‐containing potential flame retardants (FRs) were prepared and evaluated for heat release reduction potential, by incorporation of the molecules into polyurethane samples, generated from methylene diphenyl diisocyanate and 1,3‐propane diol. The potential FRs were all prepared from commercial diisocyanates, with the phosphorus‐containing substructure introduced as a semicarbazone. All of the target structures were diols, to facilitate their incorporation into a polyurethane main chain. The polyurethane samples were prepared via copolymerization, and analysis clearly demonstrated that the potential FRs were chemically incorporated, prior to heat release testing. The heat‐release reduction potential of these substances was evaluated using the microcombustion calorimeter. Results demonstrated that both heat release reduction potential and char formation were structure dependent. Some of the compounds containing an aromatic core had more effect on char formation (higher char yields) and peak heat‐release rate (lowered heat release) than just phosphorus content alone.
Chemosensory characterization of virgin olive oils obtained from organic and conventional practices during fruit ripening
Authors: Jiménez Brígida , Rivas Ana , Lorenzo María Luisa , Sánchez‐Ortiz Araceli
Published: May 2017

The current increase in demand for organic products by consumers, including virgin olive oils (VOO), makes it necessary to study the characteristics of these types of foods. Moreover, the higher quality of organic products versus that of conventional products is controversial. In this regard, the chemosensory qualities of several virgin olive oils produced from fruit grown in an experimental orchard at four different stages of maturation under organic and conventional management systems were analysed. The resulting oils were subjected to sensory and chemical analyses. According to the data organic virgin olive oils showed higher concentrations of volatile compounds synthesized throughout lipoxygenase (LOX) pathway, responsible for green grass and olive fruity sensory attributes and showed lower concentrations of phenols, related to bitter and pungent attributes. Sensorily, conventional oils were more bitter and richer in green‐leaf character, while organic oils were sweeter. Multivariate analysis showed that 10 sensory descriptors and 6 compositional parameters clearly discriminate between Picual and Hojiblanca cultivars and between organic and conventional samples. These results could be useful to clarify the different sensory characteristic between virgin olive oils obtained by conventional and organic olive crops.
Nickel Depletion and Agglomeration in SOFC Anodes During Long‐Term Operation
Authors: Zekri A. , Herbrig K. , Knipper M. , Parisi J. , Plaggenborg T.
Published: May 2017

Low degradation is a key feature for a successful commercialization of solid oxide fuel cell (SOFC) systems. A variety of degradation mechanisms influences the overall degradation rate. Nickel depletion, agglomeration and coarsening in anodes during operation are considered as an important degradation mechanism. In this work, the microstructure of SOFC anodes of electrolyte‐supported cells with operation times up to 20,000 hours (850 °C) were analyzed. The examined anodes consist of a porous cermet of nickel and gadolinium doped ceria. Scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX) analysis were used to investigate the nickel distribution in the anode. The results show nickel depletion at the electrolyte/anode interface, which becomes more noticeable for increased operation time. In addition, nickel agglomeration in the contact layer and in the functional layer was found. A relationship between nickel agglomeration and depletion was deduced.
Biocompatibility of four common orthopedic biomaterials following neuroelectromyostimulation: Anin‐vivostudy
Authors: Lecocq Mathieu , Felix Marie‐Solenne , Bernard Cécile , Linares Jean‐Marc , Chaves‐Jacob Julien , Decherchi Patrick , Dousset Erick
Published: May 2017

Despite the worldwide high prevalence of total joint arthroplasty (TJA), life expectancy of prosthesis remains limited by mechanical and chemical constraint which promote wear debris production, surrounding tissues damage and finally prosthesis loosening. Such results could be amplified by neuro‐myoelectrostimulation (NMES; widely used to reduce neuromuscular deficits observed following TJA surgery). It was previously described in anin vivoexperiment that interactions between NMES and Ti6Al4V implant are deleterious for both implant and surrounding muscles. The purpose of the present study was to compare the biocompatibility of four common orthopedic biomaterials, two metallic (Ti6Al4V, CrCo) and two nonmetallic (PEEK, Al2O3) alloys, fixed on rat tibial crest in which the surrounding muscles were electrostimulated. Muscle cell death rate was not found significantly increased, with or without electrical stimulation for nonmetallic implants. Contrary to Ti6Al4V alloy, the CrCo implant did not induce destruction of the surrounding muscle. However, cell viability decreased for both metallic alloys when NMES was applied but within a greater significant extent for Ti6Al4V implant. Otherwise, when NMES was applied, implant‐to‐bone adhesion significantly decreased for Ti6Al4V while no significant difference was found for PEEK, Al2O3, and CrCo. Statistical analyses reveal also a lesser adhesion strength for Ti6Al4V compared with CrCo when NMES was applied. Selecting the most suitable material in term of biocompatibility remains a major concern and non‐metallic materials seems to be more appropriated in regard to electrical currents used for post TJA care. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1156–1164, 2018.
Male‐on‐male sexual assault: Victim, offender and offence characteristics
Authors: Ioannou Maria , Hammond Laura , Machin Laura
Published: May 2017

Unlike male‐on‐female sexual assaults, little is known about the nature of male‐on‐male sexual assault, especially in terms of victim, offender and offence characteristics. The present paper systematically reviews the limited research into male‐on‐male sexual offences in order to ascertain the current state of knowledge with regards to these issues. An extensive search resulted in the identification of 15 empirical studies, with a total of 5,112 cases of male‐on‐male sexual assaults, for inclusion in the analyses. Findings revealed that, in the main, both victims and offenders of this type of offence tend to be young and heterosexual. Offenders tend to act alone during the assault and to be previously acquainted with the victim. Most male‐on‐male sexual assaults are violent in nature, taking place in either the victim's or the offender's home. Victims are subjected to various sexual acts, with anal penetration being the most frequent, and victims are frequently forced to perform oral sex on the offender. The implications of these findings, as well as limitations of the reviewed studies and directions for future research, are discussed.
Multiscale and macroscopic modeling of magneto‐elastic behavior of soft magnetic steel sheets
Authors: Vanoost Dries , Steentjes Simon , Peuteman Joan , De Gersem Herbert , Pissoort Davy , Hameyer Kay
Published: May 2017

This paper compares different energy‐based magneto‐mechanical models, which describe the magnetization changes that a magnetostrictive and anisotropic material undergoes when subjected to a quasi‐static H‐field excitation and tensile or compressive external stress. The magnetic behavior is either characterized by considering the phenomenological energy‐based Hauser hysteresis model or by the recently introduced hysteresis energy. The effect of mechanical stress is included naturally in the energy summation of the multiscale models. Properties of the different models, such as accuracy and parameter identification, are illustrated by comparison with experimental data for a nonoriented FeSi3% electrical steel grade.
Sometimes Less is More: Establishing the Core Symptoms of PTSD
Authors: Walton Jessica L. , Cuccurullo Lisa‐Ann J. , Raines Amanda M. , Vidaurri Desirae N. , Allan Nicholas P. , Maieritsch Kelly P. , Franklin C. Laurel
Published: May 2017

Historically, the symptoms of posttraumatic stress disorder (PTSD) have garnered attention and controversy due to symptom overlap with other disorders. To improve diagnostic specificity, researchers have proposed to reformulate PTSD symptoms into a parsimonious set of core criteria. The core symptoms consisted of recurrent distressing dreams or flashbacks; internal or external avoidance; and hypervigilance or exaggerated startle. The purpose of this study was to examine a previously proposed set of “core” PTSD criteria in identifying cases of PTSD within a veteran sample. Veterans (N = 383) presenting to a Veterans Affairs (VA) Medical Center PTSD clinic for psychological services were assessed using the Clinician Administered PTSD Scale for DSM‐5 (CAPS‐5). A logistic regression analysis revealed that the core criteria accurately identified 79% of veterans with PTSD (OR = 11.57). Findings support a parsimonious set of core criteria in the assessment and diagnosis of PTSD. Future studies should replicate these findings in diverse, nonveteran samples.
Lentigo maligna melanoma with a history of cosmetic treatment: Prevalence, surgical outcomes and considerations
Authors: Hibler Brian P. , Connolly Karen L. , Lee Erica H. , Rossi Anthony M. , Nehal Kishwer S.
Published: May 2017

Introduction

Lentigo maligna (LM) is melanoma in situ on sun‐damaged skin and presents diagnostic challenges due to overlapping features with benign pigmented lesions. Cosmetic treatments may be inadvertently performed on LM. The aim of this study is to estimate the prevalence of LM with prior cosmetic treatment, and evaluate surgical outcomes.

Study Design and Methods

Retrospective review of biopsy‐proven LM presenting over a 10‐year‐period (2006–2015). Prior cosmetic treatment and biopsies were recorded. Records were reviewed for demographic data, clinical characteristics, and surgical outcomes.

Results

37/503 (7.4%) patients with LM reported prior cosmetic therapy. Most (95%) were on the head and neck; mean size 1.9 cm. Most patients reported cryotherapy (73%), followed by laser (29.7%), topical bleaching agents (18.9%), and electrodessication, and/or curettage (5.3%). Ten patients (27%) received two or more modalities. Eight patients (21.6%) reported prior benign biopsies. Six patients (16%) had invasive disease, two on initial biopsy and 4/34 (11.7%) upstaged upon excision. Average margin for clearance was 9.1 mm.

Conclusion

Prior cosmetic treatment of LM is not uncommon, and may delay diagnosis and obscure borders, resulting in wider surgical margins. Clinicians should consider a biopsy confirming the benign nature of equivocal lesions prior to cosmetic treatment. Lasers Surg. Med. 49:819–826, 2017. © 2017 Wiley Periodicals, Inc.
Demonstration of the utility of biomarkers for dietary intake assessment; proline betaine as an example
Authors: Gibbons Helena , Michielsen Charlotte J. R. , Rundle Milena , Frost Gary , McNulty Breige A. , Nugent Anne P. , Walton Janette , Flynn Albert , Gibney Michael J. , Brennan Lorraine
Published: May 2017

Scope

There is a dearth of studies demonstrating the use of dietary biomarkers for determination of food intake. The objective of this study was to develop calibration curves for use in quantifying citrus intakes in an independent cohort.

Methods and results

Participants (n = 50) from the NutriTech food‐intake study consumed standardized breakfasts for three consecutive days over three consecutive weeks. Orange juice intake decreased over the weeks. Urine samples were analyzed by NMR‐spectroscopy and proline betaine was quantified and normalized to osmolality. Calibration curves were developed and used to predict citrus intake in an independent cohort; the Irish National Adult Nutrition Survey (NANS) (n = 565). Proline betaine displayed a dose‐response relationship to orange juice intake in 24 h and fasting samples (p < 0.001). In a test set, predicted orange juice intakes displayed excellent agreement with true intake. There were significant associations between predicted intake measured in 24 h and fasting samples and true intake (r = 0.710–0.919). Citrus intakes predicted for the NANS cohort demonstrated good agreement with self‐reported intake and this agreement improved following normalization to osmolality.

Conclusion

The developed calibration curves successfully predicted citrus intakes in an independent cohort. Expansion of this approach to other foods will be important for the development of objective intake measurements.
A novel multilayer MV imager computational model for component optimization
Authors: Myronakis Marios , Star‐Lack Josh , Baturin Paul , Rottmann Joerg , Morf Daniel , Wang Adam , Hu Yue‐Houng , Shedlock Daniel , Berbeco Ross I.
Published: May 2017

Purpose

A novel Megavoltage (MV) multilayer imager (MLI) design featuring higher detective quantum efficiency and lower noise than current conventional MV imagers in clinical use has been recently reported. Optimization of the MLI design for multiple applications including tumor tracking, MV‐CBCT and portal dosimetry requires a computational model that will provide insight into the physics processes that affect the overall and individual components’ performance. The purpose of the current work was to develop and validate a comprehensive computational model that can be used for MLI optimization.

Methods

The MLI model was built using the Geant4 Application for Tomographic Emission (GATE) application. The model includes x‐ray and charged‐particle interactions as well as the optical transfer within the phosphor. A first prototype MLI device featuring a stack of four detection layers was used for model validation. Each layer of the prototype contains a copper buildup plate, a phosphor screen and photodiode array. The model was validated against measured data of Modulation Transfer Function (MTF), Noise‐Power Spectrum (NPS), and Detective Quantum Efficiency (DQE). MTF was computed using a slanted slit with 2.3° angle and 0.1 mm width. NPS was obtained using the autocorrelation function technique. DQE was calculated from MTF and NPS data. The comparison metrics between simulated and measured data were the Pearson's correlation coefficient (r) and the normalized root‐mean‐square error (NRMSE).

Results

Good agreement between measured and simulated MTF and NPS values was observed. Pearson's correlation coefficient for the combined signal from all layers of the MLI was equal to 0.9991 for MTF and 0.9992 for NPS; NRMSE was 0.0121 for MTF and 0.0194 for NPS. Similarly, the DQE correlation coefficient for the combined signal was 0.9888 and the NRMSE was 0.0686.

Conclusions

A comprehensive model of the novel MLI design was developed using the GATE toolkit and validated against measured MTF, NPS, and DQE data acquired with a prototype device featuring four layers. This model will be used for further optimization of the imager components and configuration for clinical radiotherapy applications.
Two‐step inversion with a logarithmic transformation for microwave breast imaging
Authors: Meaney Paul M. , Geimer Shireen D. , Paulsen Keith D.
Published: May 2017

Purpose

The authors have developed a new two‐step microwave tomographic image reconstruction process specifically designed to incorporate logarithmic transformed microwave imaging algorithms as a means of significantly improving spatial resolution and target property recovery. Log transform eliminates the need for a priori information, but spatial filtering often integrated as part of the regularization required to stabilize image recovery, generally smooths image features and reduces object definition. The new implementation begins with this smoothed image as the first step, but then utilizes it as the starting estimate for a second step which continues the iterative process with a standard weighted Euclidean distance regularization. The penalty term of the latter restricts the new image to a multi‐dimensional location close to the original but allows the algorithm to optimize the image without excessive smoothing.

Methods

The overall approach is based on a Gauss‐Newton iterative scheme which incorporates a log transformation as a way of making the reconstruction more linear. It has been shown to be robust and not require a priori information as a condition for convergence, but does produce somewhat smoothed images as a result of associated regularization. The new two‐step process utilizes the previous technique to generate a smoothed initial estimate and then uses the same reconstruction process with a weighted Euclidean distance penalty term. A simple and repeatable method has been implemented to determine the weighting factor without significant computational burden. The reconstructions are assessed according to conventional parameter estimation metrics.

Results

We apply the approach to phantom experiments using large, high contrast canonical shapes followed by a set of images recovered from an actual patient exam. The image improvements are substantial in regards to improved property recovery and feature delineation without inducing unwanted artifacts. Analysis of the residual vector after the reconstruction process further emphasizes that the minimization criterion is efficient with minimal biases.

Conclusions

The outcome is a novel synergism of an established stable reconstruction algorithm with a conventional regularization technique. It maintains the ability to recover high quality microwave tomographic images without the bias of a priori information while substantially improving image quality. The results are confirmed on both phantom experiments and patient exams.
Simplified derivation of stopping power ratio in the human body from dual‐energy CT data
Authors: Saito Masatoshi , Sagara Shota
Published: May 2017

Purpose

The main objective of this study is to propose an alternative parameterization for the empirical relation between mean excitation energies (I‐value) and effective atomic numbers (Zeff) of human tissues, and to present a simplified formulation (which we called DEEDZ‐SPR) for deriving the stopping power ratio (SPR) from dual‐energy (DE) CT data via electron density (ρe) and Zeff calibration.

Methods

We performed a numerical analysis of this DEEDZ‐SPR method for the human‐body‐equivalent tissues of ICRU Report 46, as objects of interest with unknown SPR and ρe. The attenuation coefficients of these materials were calculated using the XCOM photon cross‐sections database. We also applied the DEEDZ‐SPR conversion to experimental DECT data available in the literature, which was measured for the tissue‐characterization phantom using a dual‐source CT scanner at 80 kV and 140 kV/Sn.

Results

It was found that the DEEDZ‐SPR conversion enables the calculation of SPR simply by means of the weighted subtraction of an electron‐density image and a low‐ or high‐kV CT image. The simulated SPRs were in excellent agreement with the reference values over the SPR range from 0.258 (lung) to 3.638 (bone mineral‐hydroxyapatite). The relative deviations from the reference SPR were within ±0.6% for all ICRU‐46 human tissues, except for the thyroid that presented a −1.1% deviation. The overall root‐mean‐square error was 0.21%. Application to experimental DECT data confirmed this agreement within the experimental accuracy, which demonstrates the practical feasibility of the method.

Conclusions

The DEEDZ‐SPR conversion method could facilitate the construction of SPR images as accurately as a recent DECT‐based calibration procedure of SPR parameterization based directly on the CT numbers in a DECT data set.
A robust diffusion tensor model for clinical applications of MRI to cartilage
Authors: Ferizi Uran , Ruiz Amparo , Rossi Ignacio , Bencardino Jenny , Raya José G.
Published: May 2017

Purpose

Diffusion tensor imaging (DTI) of articular cartilage is a promising technique for the early diagnosis of osteoarthritis (OA). However, in vivo diffusion tensor (DT) measurements suffer from low signal‐to‐noise ratio (SNR) that can result in bias when estimating the six parameters of the full DT, thus reducing sensitivity. This study seeks to validate a simplified four‐parameter DT model (zeppelin) for obtaining more robust and sensitive in vivo DTI biomarkers of cartilage.

Methods

We use simulations in a substrate to mimic changes during OA; and analytic simulations of the DT drawn from a range of fractional anisotropies (FA) measured with high‐quality DT data from ex vivo human cartilage. We also use in vivo data from the knees of a healthy subject and two OA patients with Kellgren‐Lawrence (KL) grades 1 and 2.

Results

For simulated in vivo cartilage SNR (∼25) and anisotropy levels, the estimated mean values of MD from the DT and zeppelin models were identical to the ground truth values. However, zeppelin's FA is more accurate in measuring water restriction. More specifically, the FA estimations of the DT model were additionally biased by between +2% and +48% with respect to zeppelin values. Additionally, both mean diffusivity (MD) and FA of the zeppelin had lower parameter variance compared to the full DT (F‐test, P < 0.05). We observe the same trends from in vivo values of patient data.

Conclusion

The zeppelin is more robust than the full DT for cartilage diffusion anisotropy and SNR at levels typically encountered in clinical applications of articular cartilage. Magn Reson Med 79:1157–1164, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
Optimization and characterization of electrospun chitosan/poly(vinyl alcohol) nanofibers as a phenol adsorbent via response surface methodology
Authors: Yousefi Abdolmaleki Aliyeh , Zilouei Hamid , Nouri Khorasani Saied , Abdolmaleki Amir
Published: May 2017

Fabrication and characterization of chitosan/poly(vinyl alcohol) electrospun nanofibers for adsorption of phenol from water were investigated. The effects of voltage (15–30 kV), solution injection flow rate (0.5–1.5 ml/hr), distance of needle and collector (10–20 cm) and chitosan/poly(vinyl alcohol) ratio (25/75, 50/50, 75/25) were studied to obtain the optimum electrospinning conditions for the maximum adsorption capacity of phenol. Central composite design (CCD) was used to investigate and optimize the processing factors for production of chitosan/poly(vinyl alcohol) nanofibers from aqueous solutions. The nanofibers were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR). Uniform beadless nanofibers with the minimum diameters of 3–11 nm were obtained at chitosan/poly(vinyl alcohol) ratio of 50/50, voltage of 22.5 kV, distance of 15 cm and injection flow rate of 1.99 ml hr−1. Fourier transform infrared spectrum of chitosan/poly(vinyl alcohol) exhibited the existence of relevant functional groups of both poly(vinyl alcohol) and chitosan in the blends. Results of CCD show that among all processing factors, rate of electrospinning will highly affect the nanofiber adsorption. The response surface quadratic order model presented correlation coefficient explaining 69.5% of the variability in the adsorption. Copyright © 2017 John Wiley & Sons, Ltd.
Synthesis and characterization of silica–polyvinyl imidazole core–shell nanoparticles via combination of RAFT polymerization and grafting‐to method
Authors: Gargari Jafar Ettehadi , Shakeri Alireza , Kalal Hossein Sid , Khanchi Alireza , Rashedi Hamid
Published: May 2017

The silica–polyvinyl imidazole core–shell nanoparticles (silica/PVI NPs) with controlled shell thickness and narrow distribution size were fabricated via “grafting‐to” method. First, O‐ethyl xanthate terminated PVI with various chain lengths was produced via the reversible addition–fragmentation chain transfer (RAFT) polymerization using O‐ethyl‐S‐phenyl dithiocarbonate (EPDC) as RAFT agent. Next, three synthesized PVI of different molecular weights (3.4, 6.6, and 11 kg/mol) were successfully grafted to the methacrylate modified silica NPs from solution by radical mediated grafting‐to method. These core–shell NPs were then characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectrum measurements (XPS), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). Polyvinyl imidazole molecular weight, reaction time, polymer concentration, and reaction temperature were all used to control the grafting reaction for PVI grafting densities and shell thicknesses. The highest grafting density obtained was close to 1.2 chains/nm2 and was achieved for 3.4 kg/mol PVI at 80°C. The prepared silica/PVINP displayed efficient antifouling properties and stability in concentrated sodium chloride aqueous solutions over a broad pH range for a period of at least 7 days. Copyright © 2017 John Wiley & Sons, Ltd.
Investigating interaction between CNT and polymer using cohesive zone model
Authors: Rafiee Roham , Ghorbanhosseini Amin
Published: May 2017

The main goal of this research is to analyze mechanical properties of embedded carbon nanotubes (CNTs) in polymer using continuum modeling. A 3D finite element model of long CNT, polymer and the interface between CNT and polymer is constructed. Cohesive zone modeling is employed to capture the non‐bonded van der Waals interactions between CNT and polymer. Appropriate constitutive law is used for mathematical description of the adhesion between CNT and polymer occurring at the interface region. Constructed FE model is subjected to five different load cases to extract mechanical properties of CNT/polymer at micro scale in the presence of CNT‐polymer interface. The embedded CNT and the interface are replaced with an equivalent fiber. Observing transversely isotropic behavior, calculated mechanical properties of the virtual equivalent fiber are in a very good agreement with other reported values in literature. Finally, an investigation of CNT length effect on the reinforcement is carried out using a unit‐cell containing embedded short‐CNT in polymer. POLYM. COMPOS., 39:3903–3911, 2018. © 2017 Society of Plastics Engineers
Optical, mechanical, and transport studies of nanodiamonds/poly(phenylene oxide) composites
Authors: Polotskaya Galina A. , Avagimova Natalia V. , Toikka Alexander M. , Tsvetkov Nikolai V. , Lezov Alexei A. , Strelina Irina A. , Gofman Iosif V. , Pientka Zbinek
Published: May 2017

Considerable progress in the development of new materials is achieved due to the modification of polymer materials by carbon nanoparticles of various kinds. In this work new composites of nanodiamonds (ND) and poly (phenylene oxide) (PPO) were prepared by solid phase dispersing. Their solutions and dense nonporous films were studied by different techniques. The structure of the PPO/ND composites was examined by atomic force microscopy, dynamic light scattering, and birefringence. The increase of ND content in the film leads to a more complex structure because of accumulation of aggregates containing ND particles and PPO molecules. The physical and mechanical properties were exhaustively evaluated by measuring intrinsic viscosity, density, surface tension, the Young's modulus, yield stress, tensile strength, and ultimate strain. Gas transport properties were determined by measuring H2, CO2, N2, CH4, and O2 permeation. The gas permeability coefficients decrease slightly with an increase of the ND content in composites, but the ideal selectivity of gas separation increases at the same time. POLYM. COMPOS., 39:3952–3961, 2018. © 2017 Society of Plastics Engineers
Effect of addition of organomodified montmorillonite nanoclay on three‐body abrasive wear behavior of maleic anhydride grafted polyethylene compatibilized ethylene‐co‐vinyl acetate/high density polyethylene nanocomposites
Authors: Namdeo Rajeev , Tiwari Sudhir , Manepatil Smita , Chand Navin
Published: May 2017

In this experimental study, effect of addition of organomodified montmorillonite (OMMT) nanoclay in increasing quantity, viz. 0, 1, 2, 3, and 4 parts per hundred on three‐body abrasive wear behavior of maleic anhydride grafted polyethylene compatibilized ethylene‐co‐vinyl acetate/high‐density polyethylene (EVA/HDPE/MA‐g‐PE) nanocomposites have been investigated. Experiments were conducted on rubber wheel abrasion tester, which was in‐house developed according to ASTM G65‐04 standard. Comparative wear volume loss and specific wear rate of polymer nanocomposites were evaluated at different loads and sliding distances with 300 µm sand abrasive size particles. It was observed that both wear volume loss and specific wear rate were increased with increase in loads. Wear volume loss was increased with increase in sliding distance while specific wear rate was decreased. Taguchi (L18) design of experiment and analysis of variance were used to optimize control factors and determine statistical significance and percentage contribution of control factors. Scanning electron microscopic images showed surface fatigue and microploughing wear mechanism on surface matrix. The aim of this study is to establish the prospects of studied polymer nanocomposites in automobile, aerospace, and similar industrial applications, where three‐body abrasive wear is dominating. POLYM. COMPOS., 39:3962–3968, 2018. © 2017 Society of Plastics Engineers
Strengthening Network of Polyacrylic Acid/Silica Nanocomposite Hydrogels
Authors: Liu Zilu , Du Juan , Tan Yun , Cao Liqin , Xu Shimei , Huang Jianbin
Published: May 2017

The polyacrylic acid (PAA)/silica nanocomposite hydrogels with high mechanical property were prepared by combining sol‐gel process and in situ free radical polymerization using 3‐methacryloxypropyltrimethoxysilane (MPTMS) as silane and acrylic acid (AA) as monomers. The structure‐property relationship of nanocomposite hydrogels was characterized by FT‐IR, DMA, TGA, XRD, TEM, and static mechanical testing. The dependence of mechanical property on the network parameter was investigated. The elastic modulus and compression fracture stress of PAA/silica nanocomposite hydrogels reached 1.27 and 1.35 MPa at molar ratio of MPTMS to AA of 0.034. The enhancement of mechanical property was attributed to the multiple cross‐linking networks between MPTMS and AA by covalent bonding and hydrogen bonding. POLYM. COMPOS., 39:3969–3976, 2018. © 2017 Society of Plastics Engineers
Synthesis and characterization of UHMWPE nanocomposite fibers containing carbon nanotubes coated with a PVP surfactant layer
Authors: Hulsey Stephanie , Absar Saheem , Sultana Quazi Nahida , Sabet Seyed Morteza , Mahfuz Hassan , Khan Mujibur
Published: May 2017

Ultra‐high‐molecular‐weight polyethylene (UHMWPE) nanocomposite fibers were fabricated using solution spinning, consisting of surface modified single‐walled carbon nanotubes (SWCNTs) embedded into the fiber matrix. The SWCNTs were modified using polyvinylpyrrolidone (PVP) noncovalent functionalization process, which acts as a surfactant and has the ability to enhance the dispersion of CNTs in the base polymer matrix by reducing aggregation and promoting interfacial adhesion with the fiber polymer matrix. Tensile testing of fibers containing PVP‐coated SWCNTs showed substantial improvements in the tensile strength and fracture strain by 125% and 137%, respectively, compared to fibers containing pristine CNTs. The amount of PVP coated onto the surfaces of CNTs was determined to be about 32.5% using thermogravimetric analysis (TGA). Differential scanning calorimetry (DSC) analysis of the nanocomposite fibers showed significant increase in crystallinity and upshift in the melting point compared to that of neat UHMWPE fibers. Fourier transform infrared spectroscopy (FTIR) analysis showed the presence of characteristic absorbance bands of PVP functional groups (CN @ 1289 cm−1 and CO @ 1651 cm−1) on the modified CNTs. Scanning electron microscopy (SEM) imaging of modified CNTs and nanocomposite fibers showed an increase in average tube diameter and reduced aggregate formation compared to pristine CNTs, indicating the successful coating of the nanotubes with PVP. Preferential alignment of the modified CNTs along the direction of fiber extrusion and crack bridging of the fiber by nanotubes were also observed. POLYM. COMPOS., 39:E1025–E1033, 2018. © 2017 Society of Plastics Engineers
Glass Fiber Epoxy Matrix Composites Containing Zero and Two Dimensional Carbonaceous Nanoreinforcements
Authors: Khurram Aqeel A. , Khan Ajmal , Gul Iftikhar H. , Subhani Tayyab
Published: May 2017

An approach to enhance the dispersion state of graphene nanoplatelets (GNPs) has been proposed by the incorporation of nanodiamond (ND) particles. The ND particles act as nanoseparators between individual graphene sheets to suppress the van der Waals interactions among individual sheets as well as GNPs. Glass fiber/epoxy composites filled with equal amount of UV ozone treated GNPs and ND particles in 0.1, 0.3, and 0.5 wt% were manufactured by vacuum compression. The effect of hybrid nanofillers on the mechanical and dielectric properties of composites were evaluated by tensile and short beam shear testing and free space dielectric measurements. The results have shown an enhancement in the mechanical properties of glass fiber/epoxy composites at lower wt% of graphene with ND particles as dispersion enhancers. The inclusion of ND with GNPs did not enhance the dielectric properties of the composites due to their small surface area and lower conductivity. POLYM. COMPOS., 39:E2056–E2063, 2018. © 2017 Society of Plastics Engineers