bluuebunny/crossref_metadata_2025 huggingface dataset:
Polyimides cross‐linked with amino group‐containing compounds
Authors: Sysel P. , Maly D. , Vysohlid J. , Friess K. , Pilnacek K. , Lanc M. , Vopicka O.
Published: February 2017

The commercially available linear polyimide Matrimid® 9725 was crosslinked with amino groups containing both high‐molecular‐weight and low‐molecular‐weight compounds. The multi‐functional amine‐terminated hyperbranched polyimide precursor (hyperbranched polyamic acid), based on 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 4,4′,4″‐triaminotriphenylmethane, and its fully imidized form (amine‐terminated hyperbranched polyimide), bifunctional amine, 4,4′‐diaminodiphenylamine and trifunctional amine, 4,4′,4″‐triaminotriphenylamine, were used as the crosslinkers. Theoretically, 10% or 20% of the Matrimid imide groups was reacted with the amino groups of the crosslinking agent during the formation of the amide groups. The insoluble content (gel) in the final materials was very low at the crosslinking temperature of 80°C and was in the 55–90% range at the crosslinking temperature of 200°. The permeability coefficients of hydrogen, carbon dioxide and methane in the self‐standing, mechanically tough film (membrane) based on the combination of Matrimid and hyperbranched polyimide were approximately 30–45% higher compared with those in the membrane made of pure Matrimid at a comparable separating ability (selectivity). POLYM. ENG. SCI., 57:1367–1373, 2017. © 2017 Society of Plastics Engineers
Rapid synthesis of titanium(IV)‐immobilized magnetic mesoporous silica nanoparticles for endogenous phosphopeptides enrichment
Authors: Yao Jizong , Sun Nianrong , Wang Jiawen , Xie Yiqin , Deng Chunhui , Zhang Xiangmin
Published: February 2017

The MALDI‐TOF MS has already been a main platform for phosphoproteome analysis. However, there are some weaknesses in direct analysis of endogenous phosphopeptides by MALDI‐TOF MS because of the serious suppression effect and poor ionization efficiency, which is brought by the excess of nonphosphopeptides and protein. It is essential to enrich endogenous phosphopeptides from complex biosamples efficiently prior to MALDI‐TOF MS analysis. Herein, we present a time‐saving and detailed protocol for the synthesis of titanium(iv)‐immobilized magnetic mesoporous silica nanoparticles (denoted as Fe3O4@mSiO2‐Ti4+), the subsequent enrichment process, and MALDI‐TOF MS analysis. We tested the LOD, size‐exclusive effect, reproducibility, and stability of Fe3O4@mSiO2‐Ti4+ nanoparticles. Furthermore, the ability of this protocol for identifying endogenous phosphopeptides in healthy human serum and saliva was investigated.
Well‐defined polymers containing high density of pendant viologen groups
Authors: Wang Zhaoxu , Tsarevsky Nicolay V.
Published: February 2017

Atom transfer radical polymerization (ATRP) of a viologen‐containing methacrylate, 1‐propyl‐1′‐[2‐(methacryloyloxy)ethyl]‐4,4′‐bipyridinium dihexafluorophosphate, is reported. To achieve good polymerization control, it was essential to use the viologen‐based monomer with a hexafluorophosphate instead of halide counterion, and 2,2′‐bipyridine as the ligand for the Cu‐based ATRP catalyst. The solubility of produced cationic polymers could be tuned by anion metathesis: the polymers with hexafluorophosphate counterions were soluble in organic solvents (e.g., acetone, DMF), and those with chloride counterions were water‐soluble. In aqueous solutions, the polymers (chloride salts) formed large aggregates, the sizes of which ranged from about 200 to about 400 nm (based on dynamic light scattering measurements) depending on the molecular weight. Upon addition of electrolytes (e.g., NaCl), the aggregates underwent dissociation. The apparent diffusion coefficients of the aggregates existing in aqueous solutions and the products of their electrolyte‐induced dissociation were measured by diffusion‐ordered NMR spectroscopy. The association–dissociation processes were also studied by fluorescence spectroscopy: the aqueous polymer solutions, which were originally fluorescent (λem = 402 nm at λex = 350 nm), lost their fluorescence in the presence of NaCl. The addition of small amounts of the viologen‐containing polyelectrolytes to solutions of inorganic salts (NaCl) altered the crystal morphology of the salts due to interaction of the multiple charged pendant groups with small ions. In the presence of reducing agents, the pendant viologen groups were converted to viologen radical‐cations, which are prone to dimerize reversibly in aqueous solutions. Indeed, marked dimerization of viologen radical cations (with absorbance maxima at 520 and 870 nm) was observed in relatively dilute aqueous solutions (4 mg mL−1) upon addition of reducing agents (hydrazine). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 55, 1173–1182
Using cluster analysis of anxiety‐depression to identify subgroups of prostate cancer patients for targeted treatment planning
Authors: Sharpley Christopher F. , Bitsika Vicki , Warren Amelia K. , Christie David R.H.
Published: February 2017

Background

To explore any possible subgroupings of prostate cancer (PCa) patients based upon their combined anxiety‐depression symptoms for the purposes of informing targeted treatments.

Methods

A sample of 119 PCa patients completed the GAD7 (anxiety) and PHQ9 (depression), plus a background questionnaire, by mail survey. Data on the GAD7 and PHQ9 were used in a cluster analysis procedure to identify and define any cohesive subgroupings of patients within the sample.

Results

Three distinct clusters of patients were identified and were found to be significantly different in the severity of their GAD7 and PHQ9 responses, and also by the profile of symptoms that they exhibited.

Conclusions

The presence of these 3 clusters of PCa patients indicates that there is a need to extend assessment of anxiety and depression in these men beyond simple total score results. By applying the clustering profiles to samples of PCa patients, more focussed treatment might be provided to them, hopefully improving outcome efficacy.
Stereo‐Electronic, Molecular Connectivity, and Geometric Configuration Approaches towards Designing Antibacterial Agents from 1, 3, 4‐Thiadiazole as the Starting Molecular Template
Authors: Yusuf Mohammad , Khan Riaz A. , Khan Maria , Ahmed Bahar
Published: February 2017

New 5‐amino‐1,3,4‐thiadiazole‐2‐thiol derivatives have been synthesized based on molecular target designs derived from various molecular descriptors involving configurational geometry, molecular size, and stereoelectronic effects of the desired sub‐structural templates using molecular connectivity design approach. The approach generated fragment‐based pharmacophore sub‐units in comparison to fluoroquinolone template to yield comparable leads with medium molecular size, and nearly flat‐plane molecular geometry framework. The product, namely, 5‐{[‐1‐(4‐chlorophenyl)‐5‐phenyl penta‐2,4‐dien‐1‐ylidene] amino}‐1,3,4‐thiadiazole‐2‐thiol (2 f) showed potent antibacterial activity against both gram‐positive and, gram‐negative strains to validate the design.
Atomically Precise Noble Metal Clusters Harvest Visible Light to Produce Energy
Authors: Jeseentharani V. , Pugazhenthiran N. , Mathew Ammu , Chakraborty Indranath , Baksi Ananya , Ghosh Jyotirmoy , Jash Madhuri , Anjusree G. S. , Deepak T. G. , Nair A. Sreekumaran , Pradeep T.
Published: February 2017

Atomically precise gold and silver clusters are a new class of sensitizers which can be used as substitutes for dyes in the classical dye‐sensitized solar cells (DSCs). Here noble metal clusters protected by proteins and thiols (Au30@BSA, Au25SBB18, and Ag44MBA30) have been used for photovoltaic studies. These metal clusters were used as sensitizers for the photoanodes fabricated using TiO2 nanotubes (NTs) and the commercial P25 TiO2 nanoparticles. The TiO2, clusters and the solar cells were characterized by spectroscopy, microscopy, current‐voltage (I‐V) and incident photon‐to‐current conversion efficiency (IPCE) measurements. A systematic I‐V study revealed a conversion efficiency of 0.35 % for the Au30@BSA sensitized solar cell made from TiO2 NTs which showed an IPCE maximum of 3 % at ∼ 400 nm.
AIE Nanodots Obtained from a Pyrene Schiff Base and Their Applications
Authors: Srinivasan Venkatesan , Jhonsi Mariadoss Asha , Dhenadhayalan Namasivayam , Lin King‐Chuen , Jaccob Madhavan , Kathiravan Arunkumar
Published: February 2017

Developing the aggregation indcued emission (AIE) nanodots as alternates to the conventional inorganic quantum dots is a contemporary research interest towards assorted applications. Herein, we have designed and synthesized a tripodal structured pyrene Schiff base (PS) and it is characterized by 1H NMR, 13C NMR and ESI‐MS techniques. The developed PS exhibit an excellent AIE property in THF:water (10:90) ratio. The formed PS aggregates were meticulously characterized by HR‐SEM, HR‐TEM and AFM measurements. The results reveal that the PS aggregates are spherical in shape with an average diameter of ∼ 1 nm. Hence, the PS aggregates are expressed as AIE nanodots. Intriguingly, the AIE nanodots has high fluorescence lifetime (4 ns) and quantum yield of 54 %, which are adequate to compete with the commercial fluorophores. In addition, molecular structure dependent nano shapes have also been investigated. The PS based AIE nanodots were successfully utilized as a fluorescent probe for several applications such as in‐vitro bioimaging, detection of picric acid and photoinduced electron transfer studies. The confocal fluorescence images of nanodots in HeLa and HEK live cells exhibit higher fluorescence signal which clearly reveal that AIE nanodots can be used as a promising probe for in‐vitro bio‐imaging application. Moreover, the AIE nanodots are employed to detect the picric acid through fluorescence quenching method. Towards the commercial application, the low‐cost fluorescent test strips have also been developed for the detection of picric acid. We have also investigated the electron transfer nature of AIE nanodots with benzyl viologen towards the energy related applications.
A Case of Folding Pattern in Flexible Tripodal of N‐Substituted Bisethylenamine Bridged Pyridazinone Dimers
Authors: Kumar Ranjeet , Gaurav Archana , Pal Shiv , Tewari Ashish Kumar
Published: February 2017

Present manuscript reports three tripodal molecules for their special structural and conformational properties. Interestingly, X‐ray structure revealed that all these molecules adopt folded conformation in solid state. Further, these molecules are flexible due to linker, may exist in various conformations, the studies have been carried out with different conformers through theoretical calculation in gaseous state.
Olive Biophenols as New Antioxidant Additives in Food and Beverage
Authors: Ciriminna Rosaria , Meneguzzo Francesco , Delisi Riccardo , Pagliaro Mario
Published: February 2017

Replacing synthetic phenols, sulfites and other synthetic antioxidants and antimicrobials, olive biophenols can be successfully used as multipurpose additives in foodstuffs and beverages. Are these natural phenolics suitable for large‐scale replacement of synthetic additives? This study aims to provide an answer to this and related questions of significant health and environmental significance.
Silver Nanoparticles Modified Graphitic Carbon Nitride Nanosheets as a Significant Bifunctional Material for Practical Applications
Authors: Veerakumar Pitchaimani , Dhenadhayalan Namasivayam , Lin King‐Chuen , Liu Shang‐Bin
Published: February 2017

Amine‐functionalized graphitic carbon nitride (NH2/GCN) nanosheets photoluminescence, catalytic properties and excellent water dispersion stability were prepared and characterized by a variety of different analytical and spectroscopic techniques. The well‐dispersed NH2/GCN nanosheets were found to exhibit remarkable pH sensing sensitivity at an ambient temperature with desirable broad detection range (1 ≤ pH ≤ 12). Moreover, upon incorporating silver nanoparticles (Ag NPs), the Ag‐NH2/GCN nanocomposites showed excellent performances for catalytic reduction of 4‐nitrophenol (4‐NP) in NaBH4 with a superior rate constant (k) of 0.1594 s‐1 within as short as 30 s. The NH2/GCN and Ag‐NH2/GCN nanocomposites reported herein therefore render prospective applications as sensitive pH and practical catalytic applications.
Facile Transformation of Nitriles into Thioamides: Application to C‐Glycosyl Nitrile Derivatives
Authors: Ghosh Tamashree , Si Anshupriya , Kumar Misra Anup
Published: February 2017

An effective reaction condition for the rapid transformation of nitrile derivatives into thioamide derivatives has been developed by the treatment with a combination of carbon disulfide and sodium sulfide. The reaction condition is equally effective for the transformation of alkyl, aryl nitriles. C‐Glycosyl nitriles also furnished C‐glycosyl thioamide derivatives in satisfactory yield under the reported reaction condition. The reaction condition is simple, high yielding and suitable for scaled up.
Microwave‐Assisted Ligand‐Free Nickel‐Catalyzed β‐Boration of α,β‐Unsaturated Carbonyl Compounds with Bis(pinacolato)diboron
Authors: Huang Xi , Wang Mingming , Wu Mengying , Wang Jiayi , Peng Yanqing , Song Gonghua
Published: February 2017

A simple and efficient ligand‐free nickel‐based catalytic system has been developed for the β‐boration of α,β‐unsaturated carbonyl compounds with bis(pinacolato)diboron. With catalyst loading of 10–15 mol%, a series of β‐boration products from chalcones and cinnamates was obtained rapidly in moderate to excellent yields within 3–30 minutes under a nitrogen atmosphere and microwave irradiation. The combination of hydroboration with microwave irradiation provided a convenient and rapid method to afford a boronate group at the β‐position of carbonyl.
SiGeSn Ternaries for Efficient Group IV Heterostructure Light Emitters
Authors: von den Driesch Nils , Stange Daniela , Wirths Stephan , Rainko Denis , Povstugar Ivan , Savenko Aleksei , Breuer Uwe , Geiger Richard , Sigg Hans , Ikonic Zoran , Hartmann Jean‐Michel , Grützmacher Detlev , Mantl Siegfried , Buca Dan
Published: February 2017

SiGeSn ternaries are grown on Ge‐buffered Si wafers incorporating Si or Sn contents of up to 15 at%. The ternaries exhibit layer thicknesses up to 600 nm, while maintaining a high crystalline quality. Tuning of stoichiometry and strain, as shown by means of absorption measurements, allows bandgap engineering in the short‐wave infrared range of up to about 2.6 µm. Temperature‐dependent photoluminescence experiments indicate ternaries near the indirect‐to‐direct bandgap transition, proving their potential for ternary‐based light emitters in the aforementioned optical range. The ternaries' layer relaxation is also monitored to explore their use as strain‐relaxed buffers, since they are of interest not only for light emitting diodes investigated in this paper but also for many other optoelectronic and electronic applications. In particular, the authors have epitaxially grown a GeSn/SiGeSn multiquantum well heterostructure, which employs SiGeSn as barrier material to efficiently confine carriers in GeSn wells. Strong room temperature light emission from fabricated light emitting diodes proves the high potential of this heterostructure approach.
Recent Advances of Electrospun Nanofibrous Membranes in the Development of Chemosensors for Heavy Metal Detection
Authors: Zhang Nan , Qiao Ruirui , Su Jing , Yan Juan , Xie Zhiqiang , Qiao Yiqun , Wang Xichang , Zhong Jian
Published: February 2017

It is critical to detect and analyze the heavy metal pollutions in environments and foods. Chemosensors have been widely investigated for fast detection of analytes such as heavy metals due to their unique advantages. In order to improve the detection sensitivity of chemosensors, recently electrospun nanofibrous membranes (ENMs) have been explored for the immobilization of chemosensors or receptors due to their high surface‐to‐volume ratio, high porosity, easiness of fabrication and functionalization, controllability of nanofiber properties, low cost, easy detection, no obvious pollution to the detection solution, and easy post‐treatment after the detection process. The purpose of this review is to summarize and guide the development and application of ENMs in the field of chemosensors for the detection of analytes, especially heavy metals. First, heavy metals, chemosensors, and four types of preparation methods for ENM‐immobilized chemosensors/receptors are briefly introduced. And then, ENM‐immobilized chemosensors/receptors and their application progresses for optical, electro, and mass detections of heavy metals are reviewed according to the four types of preparation methods. Finally, the application of ENM‐immobilized chemosensors/receptors is summarized and an outlook is provided. The review will provide an instruction to the research and development of ENM‐immobilized chemosensors/receptors for the detection of analytes.
Review of DFIG wind turbine impact on power system dynamic performances
Authors: Ngamroo Issarachai
Published: February 2017

Recently, the variable‐speed wind turbine with doubly fed induction generator (DFIG) has drawn significant attention because of its many advantages such as small power converter rating, the ability to control the output power, etc. Nevertheless, the large penetration of DFIG wind turbines may affect the power system dynamics. This paper provides a general review of the DFIG wind turbine's impact on power system dynamic performances such as frequency stability, transient stability, small‐signal stability, and voltage stability. Besides, ancillary services from the DFIG wind turbine for the power grid, such as frequency support, reactive power, and voltage support, are explained. Especially, the survey emphasizes power oscillation damping methods by the DFIG wind turbine. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Novel topology of DC circuit breaker and current interruption in HVDC networks
Authors: Guo Qinglei , Yoon Minhan , Park Jungsoo , Jang Gilsoo
Published: February 2017

With the emerging growth of high‐voltage direct current (HVDC) transmission in modern power systems, the HVDC grid has become a hot topic in recent academic research and real projects. In the DC grid, DC faults can have very serious consequences, and so the faulty DC parts need to be rapidly isolated from the system. Compared to the full‐bridge converters for the DC grid, DC circuit breakers are preferred to deal with this problem economically. In this paper, the self‐excited resonant DC circuit breaker is reviewed. Then, a novel scheme of hybrid DC circuit breaker is introduced, and the operation principle of the proposed circuit breaker is described in detail. Finally, a four‐terminal HVDC grid based on a modular multilevel converter (MMC) is used as the DC test system in PSCAD/EMTDC to verify the validity of the proposed DC circuit breaker. From the simulation results, it is seen that the proposed DC circuit breaker has advantages on current interruption time, voltage on DC circuit breaker, investment, etc. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
STATCOMversusSSSCfor power system stabilization
Authors: Hafez Ahmed A. A.
Published: February 2017

Flexible alternating current transmission systems (FACTS) are gaining more attention in power utilities because of their advantages of controllability, reliability, and operation over a wide range. Static synchronous compensator (STATCOM)and static series synchronous compensator (SSSC) are prominentFACTStopologies; they have the ability to instantaneously regulate active/reactive powers and stabilize the power system following severe disturbances. In this paper,STATCOMandSSSCare compared with regard to their damping action on power system oscillations. The comparison is extended to the controller design strategies. Two distinct meta‐heuristic optimization approaches, namely chaos (CO) and simulated annealing (SA), are recommended for the optimal design of theSSSCandSTATCOMdamping controller. To assess the promisingFACTStopology, a single‐machine infinite bus system is subjected to several disturbances while operating at different loading levels. MATLAB/Simulink is used as a platform to investigate the dynamic performance of the system under consideration withSTATCOMandSSSC. Simulation results reveal the superiority ofSSSCin damping power system oscillations in terms of response speed and stability margin. Moreover, the CO optimization scheme seems to outperform the SA algorithm in terms of computation requirements and global optimal convergence. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
QPR and duty ratio feed‐forward control for vienna rectifier of HVDC supply system
Authors: Dang Chaoliang , Tong Xiangqian , Huang Jingjing , Wang Qian , Zhang Hao
Published: February 2017

The grid current of a Vienna rectifier will change from the continuous conduction mode (CCM) to the discontinuous conduction mode (DCM) when the load current or the inductance decreases. This deteriorates the grid current. Therefore, a strategy based on the variable duty ratio feed‐forward and quasi‐proportional‐resonant (QPR) combined control is put forward, by introducing the needed duty ratio to the original output of current inner loop, whereby the pressure of the inner loop is effectively reduced. The working mechanism of the Vienna rectifier is first analyzed. The transfer functions of CCM and DCM between duty ratio and grid current are then built. At the same time, the parallel multi‐QPR harmonic compensators are adopted in the current inner loop to effectively eliminate the specific harmonic pollution. To verify the correctness and effectiveness of the proposed strategy, a 5.3‐kW prototype under digital control is established. The simulation and experimental results show that both the steady and transient performance of the proposed strategy are better under the fixed current inner loop parameters, the current zero crossing distortion can be eliminated, and the current quality acquired under the transformation between CCM to DCM can be further improved.
Risk assessment and bi‐level optimization dispatch of virtual power plants considering renewable energy uncertainty
Authors: Zhang Gao , Jiang Chuanwen , Wang Xu , Li Bosong
Published: February 2017

Aiming at the effective management of distributed energy resources (DERs), we propose a bi‐level optimization dispatch model which consists of a virtual power plant (VPP) and an independent system operator (ISO) in order to achieve a coordinated dispatch between the upper level objective function of minimizing system's operation cost and the lower level objective function of maximizing the VPP's net profit. However, the VPP's dispatch strategy is variable due to the threat from unavoidable uncertainties including unit outage, load forecast deviation, and renewable energy forecasting error. In order to evaluate the influences of these risks on VPP's dispatch strategy, a proper definition of expected energy not supplied (EENS) and its relationship with VPP's reserve capacity are provided. Also, chance‐constrained programming (CCP) is adopted during the analysis. By including VPP's risk cost into the dispatch model, VPP's dispatch strategy is able to keep a balance between the potential risk and economic profit. In addition, a further discussion regarding the risk cost is conducted in view of renewable energy capacity proportion and the VPP capacity proportion. Based on the analysis results of the case study provided, the proposed model serves as a foundation for VPP's economic and risk‐balanced dispatch.
Multiple roles coordinated control of battery storage units in a large‐scale island microgrid application
Authors: Wen Yeting , Dai Yuxing , Zhou Xiwei , Qian Fei
Published: February 2017

In order to build a large‐scale island microgrid with 100% penetration intermittent photovoltaic power generation as the only power source, a structure with multiple role battery energy storage systems (BESSs) is proposed in this paper based on the analysis of energy storage demand in the island microgrid and performance comparison of two types of batteries. The storage system in the proposed structure is composed of three types of functional BESSs. In detail, the master control units (MCUs) with LiFePO4 batteries are responsible for the voltage and frequency stability and instantaneous power balance, slave storage units (SSUs) with lead‐acid batteries are responsible for daily energy storage, and multi‐function units (MFUs) with LiFePO4 batteries are used for short‐time energy regulation. A hierarchical control structure is adopted in the system. At the local level, the converters of the MCUs are controlled as the voltage sources in paralleled mode as grid‐forming units, and those of SSUs and MFUs are controlled in the current source mode as grid‐feeding units. At the system level, a real‐time power balance coordinated control strategy is proposed, which has the capability of efficient and orderly operation of different types of BESSs. Simulation and practical operation analysis of the Qumalai 7.023 MW microgrid demonstrate the practicality and effectiveness of the research methods of the island microgrid. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Impacts of DFIG‐based wind farm integration on its tie line distance protection and countermeasures
Authors: Chen Xu , Yin Xianggen , Zhang Zhe
Published: February 2017

Modern power grids, especially high‐voltage grids, are increasingly integrated with wind farms. The correct action of distance protection for the wind farm tie line plays an important role in the safe and stable operation of the power system. However, based on the fault characteristics of wind farms based on the doubly fed induction generator, considering crowbar action and weak infeed properties, this paper reveals some serious defects of conventional distance protection. The result shows that, due to the influences of mixed data window and damped current component with near‐rotor‐speed frequency, the fault distance calculation result obtained by the fundamental‐component‐based distance protection is inaccurate. To tackle this problem, a transient‐based distance protection countermeasure along with a faulted phase selection technique is proposed. Specifically, the transient phase voltage characteristic for different fault types is analyzed to select the faulted phase. Considering the effect of high‐frequency components, pre‐fault voltage compensation, and transducer characteristics, a distance calculation procedure including a low‐pass filter, the reconstruction of voltage at the fault point, and an iterative fault distance calculation is proposed. The comprehensive performance of the proposed method is validated by the simulation case studies using the PSCAD/EMTDC software. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
The detection of lightning from space
Authors: Labrador Lorenzo
Published: February 2017

Earth orbit offers a unique vantage point from which to study and monitor the phenomenon of lightning. Space‐borne lightning detection sensors are capable of detecting total lightning activity during both day and night, over land and sea, potentially filling in data gaps in areas of poor or no radar coverage or where ground‐based lightning detection networks offer low detection resolution. For over four decades, studies using different types of satellite‐borne lightning detectors have resulted in significant advances in our understanding of the global distribution and frequency of lightning. The advent of a new generation of lightning‐observing instruments in geostationary orbit in the near future will usher in a new era not only in our understanding of the phenomenon, but also of continuous, routine monitoring of lightning from space for practical applications such as improved severe weather warnings for communities on the ground and improved weather warnings for aviation. In this paper, a historical perspective of the study and monitoring of lightning from space, as well as a glimpse of the future, is offered.
Nanoescapology: progress toward understanding the endosomal escape of polymeric nanoparticles
Authors: Selby Laura I. , Cortez‐Jugo Christina M. , Such Georgina K. , Johnston Angus P.R.
Published: February 2017

Using nanoparticles to deliver drugs to cells has the potential to revolutionize the treatment of many diseases, including HIV, cancer, and diabetes. One of the major challenges facing this field is controlling where the drug is trafficked once the nanoparticle is taken up into the cell. In particular, if drugs remain localized in an endosomal or lysosomal compartment, the therapeutic can be rendered completely ineffective. To ensure the design of more effective delivery systems we must first develop a better understanding of how nanoparticles and their cargo are trafficked inside cells. This needs to be combined with an understanding of what characteristics are required for nanoparticles to achieve endosomal escape, along with methods to detect endosomal escape effectively. This review is focused into three sections: first, an introduction to the mechanisms governing internalization and trafficking in cells, second, a discussion of methods to detect endosomal escape, and finally, recent advances in controlling endosomal escape from polymer‐ and lipid‐based nanoparticles, with a focus on engineering materials to promote endosomal escape. WIREs Nanomed Nanobiotechnol 2017, 9:e1452. doi: 10.1002/wnan.1452

This article is categorized under:

Nanotechnology Approaches to Biology > Nanoscale Systems in Biology
One‐Step Concentration of Highly Unsaturated Fatty Acids from Tuna Oil by Low‐Temperature Crystallization
Authors: Zhang Yu , Wang Xiaosan , Xie Dan , Li Yongru , Wang Xingguo
Published: February 2017

Highly unsaturated fatty acids (HUFA), including eicosapentaenoic acid (EPA, 20:5n‐3), docosapentaenoic acid (DPA, 22:5n‐3 and 22:5n‐6) and docosahexaenoic acid (DHA, 22:6n‐3), play an important role in human health and nutrition. In this study, concentration of HUFA in free fatty acids (FFA) form by low‐temperature crystallization was investigated. For this purpose, tuna oil (7.1% EPA, 26.8% DHA) was first converted into corresponding FFA. Subsequently, crystallization conditions of various solvent types, the ratio of FFA to acetonitrile, operation temperature and crystallization time were optimized at a small scale of 2 g tuna oil fatty acids. Taking purity and yield into account, the optimum conditions were a 1:10 ratio of FFA to acetonitrile (w/v), −60 °C, and 1 h. The optimal conditions resulted in concentrations of EPA, DHA and HUFA of 15.1, 58.4 and 79.6%, respectively, with corresponding yields of 61.5, 61.8 and 60.7%, respectively. Crystallization was carried out under the optimal conditions at a large scale of 200 g tuna oil FFA, and a similar concentration result was achieved. After evaporating away the solvent, the residual amount of acetonitrile met the US Pharmacopoeia requirement of <410 ppm. The process for enrichment of HUFA is readily scalable, effective and time‐saving.
A prenatal nicotine exposure mouse model of methylphenidate responsive ADHD‐associated cognitive phenotypes
Authors: Zhu Jinmin , Fan Fangfang , McCarthy Deirdre M. , Zhang Lin , Cannon Elisa N. , Spencer Thomas J. , Biederman Joseph , Bhide Pradeep G.
Published: February 2017

Prenatal exposure to nicotine via cigarette smoke or other forms of tobacco use is a significant environmental risk factor for attention deficit hyperactivity disorder (ADHD). The neurobiological mechanisms underlying the link between prenatal nicotine exposure (PNE) and ADHD are not well understood. Animal models, especially rodent models, are beginning to bridge this gap in knowledge. Although ADHD is characterized by hyperactivity, inattention, impulsivity and working memory deficits, the majority of the animal models are based on only one or two ADHD associated phenotypes, in particular, hyperactivity or inattention. We report a PNE mouse model that displays the full range of ADHD associated behavioral phenotypes including working memory deficit, attention deficit and impulsive‐like behavior. All of the ADHD‐associated phenotypes respond to a single administration of a therapeutic equivalent dose of methylphenidate. In an earlier study, we showed that PNE produces hyperactivity, frontal cortical hypodopaminergic state and thinning of the cingulate cortex. Collectively, these data suggest that the PNE mouse model recapitulates key features of ADHD and may be a suitable preclinical model for ADHD research.
Parametric investigation on an industrial electromagnetic continuous casting mould performance
Authors: Zhang Lintao , Deng Anyuan , Cameron Ian , Wang Engang , Sienz Johann
Published: February 2017

This research aimed at conducting a quantitative investigation of process parameters on the magnetic field contribution in an electromagnetic continuous casting mould. The Taguchi method (4 factors and 3 factor value levels: L9 orthogonal array) was adopted to design matrix of the simulation runs and the analysis of variance was used to evaluate the contributions of each control factor. The simulations were conducted based on the finite element method and the numerical set-up was validated by the designed experiment. The results showed that the applied alternating current magnitude contributed most (76.64%) to the magnetic field level in the mould, compared to the other control factors. It was followed by the slit length (17.72%), the alternating current frequency (4.17%) and the slit width (1.57%).

Highlights Numerical system was validated by the designed experiment. A quantitative investigation of process parameter on the magnetic field in contribution an EMCC mould was conducted. The current value was the most influential factor, followed by the slit length, current frequency and the slit width.
Stabilization of second order evolution equations by unbounded nonlinear feedback
Authors: Conrad Francis , Pierre Michel
Published: February 2017

For an abstract evolution equation of the form

u_{tt} + Au + ∂ψ(u_t) \ni 0

, general conditions on the “unbounded” feedback are given, that ensure strong asymptotic stability. Essentially the directions determined by the convex of the minima of the functional

ψ

should not intersect the eigenspaces of

A

. Equivalently, the feedback on the velocity must dissipate enough energy, in the sense that the kernel of the form

\langle ∂ψ(·), ·\rangle

is not larger than the kernel of a “strategic” observation operator, for the uncontrolled system. The particular case where the control operator is the dual of the observation operator is specifically considered: the condition then corresponds to more classical rank conditions on the observation operator. The interest of the present framework is that it applies to boundary controls and to interior controls on thin sets (of zero measure but positive capacity). Several examples, including wave, beam and plate equations are considered.

Pour un problème d’évolution abstrait de la forme

u_{tt} + Au + ∂ψ(u_t) \ni 0

, on donne des conditions générales sur le feedback « non borné » pour assurer la stabilité asymptotique forte. Essentiellement les directions déterminées par le convexe des minima de

ψ

ne doivent pas être des directions propres de l’opérateur

A

. De façon équivalente, il faut que le bouclage sur la vitesse soit suffisamment dissipatif, en ce sens que le noyau de la forme

\langle ∂ψ(·), ·\rangle

ne doit pas être plus gros que le noyau d’un observateur « stratégique », pour le système non contrôlé. Le cas particulier où l’opérateur de contrôle est l’adjoint de l’opérateur d’observation est étudié; la condition se ramène alors à des conditions plus classiques de rang sur l’opérateur d’observation. Le cadre proposé ici englobe le cas de contrôles frontières ou intérieurs, distribués ou ponctuels, ainsi que des contrôles unilatéraux. Divers exemples concernant les équations des ondes, des poutres ou des plaques, éventuellement avec des contrôles sur des ensembles « fins », sont proposés.
The existence of Ginzburg–Landau solutions on the plane by a direct variational method
Authors: Yang Yisong
Published: February 2017

This paper studies the existence and the minimization problem of the solutions of the Ginzburg-Landau equations in

\mathbf R^2

coupled with an external magnetic field or a source current. The lack of a suitable Sobolev inequality makes it necessary to consider a variational problem over a special admissible space so that the space norms of the gauge vector fields of a minimization sequence can be controlled by the corresponding energy upper bound and a solution may be obtained as a minimizer of a modified energy of the problem. Asymptotic properties and flux quantization are established for finite-energy solutions. Besides, it is shown that the solutions obtained also minimize the original Ginzburg–Landau energy when the admissible space is properly chosen.

Le but de ce travail est d’étudier l’existence et le problème de minimisation des solutions des équations de Ginzburg-Landau dans

\mathbf R^2

, couplées avec un champ magnétique externe ou une source de courant. L’absence d’une inégalité convenable de Sobolev amène à considérer un problème variationnel sur un espace admissible spécial. Sur cet espace, les normes des champs de vecteurs de la gauge d’une suite minimisante peuvent être contrôlées par la borne supérieure de l’énergie correspondante. Aussi, une solution peut être obtenue comme un minimiseur d’une énergie modifiée du problème. Des propriétés asymptotiques et une quantification de flux sont établies par des solutions d’énergie finie. Entre autres, il est prouvé que les solutions obtenues minimisent aussi l’énergie originale de Ginzburg–Landau lorsque l’espace admissible est convenablement choisi.
A characterization of families of function sets described by constraints on the gradient
Authors: Esposito Antonio Corbo , De Arcangelis Riccardo
Published: February 2017

One of the results proved in the paper deals with a characterization of the families

\{K (Ω) : Ω \text{ bounded open set}\}

of subsets of

W_{\mathrm{loc}}^{1,\:p}\:(ℝ^{n})\ (p \in [1, + ∞])

whose elements can be described as

K\:(\mathrm{\Omega }) = \{u \in W_{\mathrm{loc}}^{1,\:p}\:(ℝ^{n}):Du\:(x) \in C \text{ for a.e. }x \text{ in }Ω\}

,

C

being a closed convex subset of

ℝ^n

.

Characterizations similar to the above mentioned but for families of subsets of

BV_{\mathrm{loc}}\:(ℝ^{n})

and

L_{\mathrm{loc}}^{p}\:(ℝ^{n})

are also proved.

These results are deduced by a general characterization theorem for families of subsets of a Hausdorff locally convex topological vector subspace of

L_{\mathrm{loc}}^{1}\:(ℝ^{n})

.

An application to the problem of the homogenization of the elastic-plastic torsion of a cylindrical bar is given.

Un des résultats démontrés dans notre travail concerne une caractérisation des familles

\{K (Ω) : Ω, \text{ ensemble ouvert borné}\}

des sous-ensembles de

W_{\mathrm{loc}}^{1,\:p}\:(ℝ^{n})\:\:(p \in [1, + ∞])

dont les éléments peuvent être décrits comme

K(\mathrm{\Omega }) = \{u \in W_{\mathrm{loc}}^{1,\:p}\:(ℝ^{n}):Du\:(x) \in C \text{ pour presque chaque }x \text{ en }Ω\}

,

C

étant un sous-ensemble convexe fermé de

ℝ^{n}

.

On prouve aussi des caractérisations similaires pour des familles de sous-ensembles de

BV_{\mathrm{loc}}\:(ℝ^{n})

et de

L_{\mathrm{loc}}^{p}\:(ℝ^{n})

.

Nos résultats sont dérivés par un théorème général de caractérisation pour des familles de sous-ensembles d’un sous-espace vectoriel topologique de Hausdorff localement convexe de

L_{\mathrm{loc}}^{1}\:(ℝ^{n})

.

On donne une application pour le problème d’homogénéisation de la torsion élastoplastique d’une barre cylindrique.
The Cauchy problem for semilinear weakly hyperbolic equations in Hilbert spaces
Authors: D’Ancona Piero
Published: February 2017

We consider an abstract nonlinear second order equation, whose principal part satisfies some conditions inspired by Oleinik’s conditions on degenerate hyperbolic equations. We prove local existence and regularity results in suitable scales of abstract Sobolev spaces. Several applications to concrete equations are given.

On considère une équation abstraite du second ordre, nonlinéaire, dont la partie principale satisfait à des conditions inspirées par celles de Mme Oleinik pour les équations hyperboliques dégénérées. On obtient des résultats d’existence locale et de régularité dans des échelles d’espaces de Sobolev abstraits. Plusieurs applications aux équations concrètes sont données.
Construction of the Leray-Schauder degree for elliptic operators in unbounded domains
Authors: Volpert A.I. , Volpert V.A.
Published: February 2017

This paper is devoted to a construction of the Leray–Schauder degree for quasilinear elliptic operators in unbounded domains. The main problem here is that such operators can not be reduced to compact ones and the usual theory (
see
[1]) can not be applied. In [2, 3] the Leray–Schauder degree was constructed in one dimensional case. To do this certain lower estimates of the operators were obtained and the approach of Skrypnik [4] was applied. In this paper we generalize these results to the multidimensional case. When the degree is defined the Leray–Schauder method can be used to prove the existence of solutions [3].

Cet article est consacré à la construction du degré de Leray–Schauder pour les opérateurs elliptiques dans les domaines non bornés. Le problème essentiel ici est que ces opérateurs ne peuvent pas être réduits à des compacts. Par conséquent, on ne peut pas utiliser la théorie habituelle [1]. Dans [2, 3] le degré est construit pour les cas monodimen-sionnel. Pour cette construction, certaines estimations des opérateurs sont obtenues, et l’approche de Skrypnik [4] est utilisée. Dans cet article, nous généralisons ces résultats pour le cas multidimensionnel. Quand le degré est déterminé, la méthode de Leray–Schauder peut être appliquée pour prouver l’existence de solutions [3].
A uniqueness result in the theory of stereo vision: Coupling Shape from Shading and Binocular Information allows Unambiguous Depth Reconstruction
Authors: Chambolle Antonin
Published: February 2017

We study here the mathematical consistency of coupling two classical methods in the theory of vision and surface reconstruction, namely the
shape from shading
theory and the theory of stereo vision. It is known that each of these approaches by itself is incomplete and leads to ill posed problems and multiple solutions, even under drastic simplifying assumptions. We show in this paper that, from a mathematical point of vue, these ambiguities disappear when both theories are cooperatively implemented. In section 2 we state our assumptions; then part 3 is devoted to the presentation of the binocular vision theory. Section 4 eventually studies, in the one and two dimensional case, how introducing the
shape from shading
tool leads to the uniqueness of the solution. In the annex (section 6), a few mathematical results are explained, and some experiments (in 1 D) are presented.

Nous étudions ici la consistance mathématique du couplage de deux méthodes classiques de reconstruction visuelle, à savoir la théorie du
shape from shading
, qui vise à retrouver le relief d’une surface à partir des ombres et variations d’intensité lumineuse de son image, et la théorie de la vision binoculaire (la « vision stéréo » au sens usuel). Chacune de ces approches est incomplète et conduit à des problèmes mal posés à solutions multiples. Dans cet article nous montrons que d’un point de vue mathématique ces inconvénients disparaissent lorsqu’on met à contribution de manière coopérative les deux méthodes.

Dans la section 2 on établit un certain nombre d’hypothèses simplificatrices, puis la partie suivante 3 est consacrée à la présentation de notre modèle de vision binoculaire. Finalement nous montrons (section 4) dans les cas uni- et bidimensionnel, comment l’introduction du
shape from shading
supprime les ambiguités. Le détail des résultats mathématiques de trouve en annexe, ainsi que la présentation de quelques résultats de simulations numériques (en dimension un).
A notion of total variation depending on a metric with discontinuous coefficients
Authors: Amar M. , Bellettini G.
Published: February 2017

Given a function

u:\mathrm{\Omega } \subseteq ℝ^{n}\rightarrow ℝ

, we introduce a notion of total variation of

u

depending on a possibly discontinuous Finsler metric. We prove some integral representation results for this total variation, and we study the connections with the theory of relaxation.

Étant donnée une fonction

u:\mathrm{\Omega } \subseteq ℝ^{n}\rightarrow ℝ

, on définit une notion de variation totale de

u

, dépendant d’une métrique Finslérienne discontinue. On démontre quelques résultats de représentation intégrale pour cette variation totale et ses relations avec la théorie de la relaxation.
On the singular support of the distributional determinant
Authors: Müller Stefan
Published: February 2017

Let

Ω ⊂ ℝ^n

be bounded and open, let

p ≧ n^2/(n + 1)

and let

u: Ω → ℝ^n

be in the Sobolevspace

W^{1, n} (Ω; ℝ^n)

. This paper discusses the singular part of the distributional determinant

\mathrm{Det\, D}u

and shows the existence of functions

u

for which that singular part is supported in a set of prescribed Hausdorff-dimension

α \in (0, n)

. For

n = 2

and simply connected

Ω

the problem is equivalent to analyzing

\mathrm{div} (bv) − b.\mathrm Dv

where

v\in W^{1, p} (Ω; ℝ^2)

with

\mathrm{div} b = 0

.

Soit

Ω ⊂ ℝ^n

un ouvert borné, soit

p ≧ n^2/(n + 1)

et soit

u: Ω → ℝ^n

dans l’espace de Sobolev

W^{1, p} (Ω; ℝ^n)

. On construit des applications

u

dont le déterminant au sens de distributions

\mathrm{Det\, D}u

est une mesure de Radon positive, portée par un ensemble singulier dont la dimension de Hausdorff est arbitraire, strictement entre

0

et

n

.
Finite element analyses of pure Ni cold spray particles impact related to coating crack behaviour
Authors: Cavaliere Pasquale , Silvello Alessio
Published: February 2017

Cold spray processing parameters governing particle velocity and impact energy are analysed in the present paper for pure Ni sprayed on IN718 substrates. The study is conducted by employing finite element modelling used to calculate the particle behaviour as a function of gas temperature and pressure and particles properties. In the present paper, the possibility of repairing cracks, in superalloys sheets, through cold spray is demonstrated. An IN718 panel, with a surface 30° V notch, was repaired with pure Ni particles via cold spray. The crack behaviour, of the V-notched sheets subjected to bending loading, was studied by FEM and mechanical experiments. Cold spray repair can contribute to the increase of the global fatigue life of cracked structures, in fact, the resistance of repaired panels is increased of more than eight times.