bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic nuclear polarization-magnetic resonance imaging at low ESR irradiation frequency for ascorbyl free radicals
Authors: Ito Shinji , Hyodo Fuminori
Published: February 2016

Highly water-soluble ubiquinone-0 (CoQ0) reacts with ascorbate monoanion (Asc) to mediate the production of ascorbyl free radicals (AFR). Using aqueous reaction mixture of CoQ0 and Asc, we obtained positively enhanced dynamic nuclear polarization (DNP)-magnetic resonance (MR) images of the AFR at low frequency (ranging from 515 to 530 MHz) of electron spin resonance (ESR) irradiation. The shape of the determined DNP spectrum was similar to ESR absorption spectra with doublet spectral peaks. The relative locational relationship of spectral peaks in the DNP spectra between the AFR (520 and 525 MHz), 14N-labeled carbamoyl-PROXYL (14N-CmP) (526.5 MHz) and Oxo63 (522 MHz) was different from that in the X-band ESR spectra, but were similar to that in the 300-MHz ESR spectra. The ratio of DNP enhancement to radical concentration for the AFR was higher than those for 14N-CmP, Oxo63 and flavin semiquinone radicals. The spectroscopic DNP properties observed for the AFR were essentially the same as those for AFR mediated by pyrroloquinoline quinone. Moreover, we made a success of in vivo DNP-MR imaging of the CoQ0-mediated AFR which was administered by the subcutaneous and oral injections as an imaging probe.
Mesenchymal stem cells promote colorectal cancer progression through AMPK/mTOR-mediated NF-κB activation
Authors: Wu Xiao-Bing , Liu Yang , Wang Gui-Hua , Xu Xiao , Cai Yang , Wang Hong-Yi , Li Yan-Qi , Meng Hong-Fang , Dai Fu , Jin Ji-De
Published: February 2016

Mesenchymal stem cells (MSCs) exert a tumor-promoting effect in a variety of human cancers. This study was designed to identify the molecular mechanisms related to the tumor-promoting effect of MSCs in colorectal cancer. In vitro analysis of colorectal cancer cell lines cultured in MSC conditioned media (MSC-CM) showed that MSC-CM significantly promoted the progression of the cancer cells by enhancing cell proliferation, migration and colony formation. The tumorigenic effect of MSC-CM was attributed to altered expression of cell cycle regulatory proteins and inhibition of apoptosis. Furthermore, MSC-CM induced high level expression of a number of pluripotency factors in the cancer cells. ELISAs revealed MSC-CM contained higher levels of IL-6 and IL-8, which are associated with the progression of cancer. Moreover, MSC-CM downregulated AMPK mRNA and protein phosphorylation, but upregulated mTOR mRNA and protein phosphorylation. The NF-κB pathway was activated after addition of MSC-CM. An in vivo model in Balb/C mice confirmed the ability of MSC-CM to promote the invasion and proliferation of colorectal cancer cells. This study indicates that MSCs promote the progression of colorectal cancer via AMPK/mTOR-mediated NF-κB activation.
Estrogen replacement therapy-induced neuroprotection against brain ischemia-reperfusion injury involves the activation of astrocytes via estrogen receptor β
Authors: Ma Yulong , Guo Hang , Zhang Lixia , Tao Liang , Yin Anqi , Liu Zhaoyu , Li Yan , Dong Hailong , Xiong Lize , Hou Wugang
Published: February 2016

The incidence of ischemic stroke is significantly increased in postmenopausal women. However, the neuroprotective effects of estrogen replacement therapy (ERT) against stroke remain controversial and the role of astrocytes in ERT has rarely been explored. In this study, we investigated the effects of estrogen and selective estrogen receptor (ER) agonists on astrocytes activation and neuronal apoptosis in mice under conditions of cell culture oxygen and glucose deprivation and reperfusion (OGD-R) and global cerebral ischemia (GCI). We demonstrated that hippocampal astrocytes primarily express ERβ. In astrocytes, 2.5–20 nM 17β-estradiol (E2) or 10 nM DPN (ERβ agonist) not 10 nM PPT (ERα agonist), significantly increased GFAP expression. And 10 nM E2, DPN or E2+MPP (ERα antagonist), but not PPT or E2+PHTPP (ERβ antagonist), significantly reduced neuronal apoptosis following the subjection of astrocyte and neuronal cocultures to OGD-R. We also found that either 50 μg/kg E2 or 8 mg/kg DPN replacement (3 weeks) significantly increased GFAP expression and reduced GCI-induced neuronal apoptosis in hippocampal CA1 region of ovariectomized mice. These results indicate that estrogen-induced neuroprotection against ischemia-reperfusion injury involves activation of astrocytes via ERβ. Thus, the discovery and design of astrocyte-selective ERβ modulators may offer a new strategy for ERT of ischemic stroke.
Expression partitioning of homeologs and tandem duplications contribute to salt tolerance in wheat (Triticum aestivum L.)
Authors: Zhang Yumei , Liu Zhenshan , Khan Abul Awlad , Lin Qi , Han Yao , Mu Ping , Liu Yiguo , Zhang Hongsheng , Li Lingyan , Meng Xianghao , Ni Zhongfu , Xin Mingming
Published: February 2016

Salt stress dramatically reduces crop yield and quality, but the molecular mechanisms underlying salt tolerance remain largely unknown. To explore the wheat transcriptional response to salt stress, we performed high-throughput transcriptome sequencing of 10-day old wheat roots under normal condition and 6, 12, 24 and 48 h after salt stress (HASS) in both a salt-tolerant cultivar and salt-sensitive cultivar. The results demonstrated global gene expression reprogramming with 36,804 genes that were up- or down-regulated in wheat roots under at least one stress condition compared with the controls and revealed the specificity and complexity of the functional pathways between the two cultivars. Further analysis showed that substantial expression partitioning of homeologous wheat genes occurs when the plants are subjected to salt stress, accounting for approximately 63.9% (2,537) and 66.1% (2,624) of the homeologous genes in ‘Chinese Spring’ (CS) and ‘Qing Mai 6’ (QM). Interestingly, 143 salt-responsive genes have been duplicated and tandemly arrayed on chromosomes during wheat evolution and polyploidization events and the expression patterns of 122 (122/143, 85.3%) tandem duplications diverged dynamically over the time-course of salinity exposure. In addition, constitutive expression or silencing of target genes in Arabidopsis and wheat further confirmed our high-confidence salt stress-responsive candidates.
Spin-orbit coupling enhanced superconductivity in Bi-rich compounds ABi3 (A = Sr and Ba)
Authors: Shao D. F. , Luo X. , Lu W. J. , Hu L. , Zhu X. D. , Song W. H. , Zhu X. B. , Sun Y. P.
Published: February 2016

Recently, Bi-based compounds have attracted attentions because of the strong spin-orbit coupling (SOC). In this work, we figured out the role of SOC in ABi3 (A = Sr and Ba) by theoretical investigation of the band structures, phonon properties, and electron-phonon coupling. Without SOC, strong Fermi surface nesting leads to phonon instabilities in ABi3. SOC suppresses the nesting and stabilizes the structure. Moreover, without SOC the calculation largely underestimates the superconducting transition temperatures (Tc), while with SOC the calculated Tc are very close to those determined by measurements on single crystal samples. The SOC enhanced superconductivity in ABi3 is due to not only the SOC induced phonon softening, but also the SOC related increase of electron-phonon coupling matrix elements. ABi3 can be potential platforms to construct heterostructure of superconductor/topological insulator to realize topological superconductivity.
Bipolar versus monopolar transurethral resection of the prostate for benign prostatic hyperplasia: safe in patients with high surgical risk
Authors: Yang Er J. , Li Hao , Sun Xin B. , Huang Li , Wang Li , Gong Xiao X. , Yang Yong
Published: February 2016

Here, we compared the effects of bipolar and monopolar transurethral resection of the prostate (B-TURP, M-TURP) for treating elderly patients (≥75 years) with benign prostatic hyperplasia(BPH) who had internal comorbidities. Eligible BPH patients were aged ≥75 years and had at least one internal comorbidity. In this open-label, prospective trial, patients were assigned to B-TURP (n = 75) and M-TURP (n = 88) groups. Data on prostate volume (PV), urination and time during perioperative period were compared; data associated with urination and complications at one year postoperatively were also compared. Finally, follow-up data were available for 68 and 81 patients in the B-TURP and M-TURP group, respectively. No deaths were recorded. Intraoperative bleeding was lower and irrigation time, indwelling catheter time and hospital stay were shorter in the B-TURP group than in the M-TURP group (p < 0.001). No difference was observed with respect to operation time (p = 0.058). At one year after the operation, differences with respect to urination and complications were not significant. In conclusion, Short-term efficacy of B-TURP or M-TURP was satisfactory for elderly patients with BPH who had internal comorbidities. Besides, B-TURP is a more sensible choice because it has a lower prevalence of adverse effects.
Age-related neurogenesis decline in the subventricular zone is associated with specific cell cycle regulation changes in activated neural stem cells
Authors: Daynac Mathieu , Morizur Lise , Chicheportiche Alexandra , Mouthon Marc-André , Boussin François D.
Published: February 2016

Although neural stem cells (NSCs) sustain continuous neurogenesis throughout the adult lifespan of mammals, they progressively exhibit proliferation defects that contribute to a sharp reduction in subventricular neurogenesis during aging. However, little is known regarding the early age-related events in neurogenic niches. Using a fluorescence-activated cell sorting technique that allows for the prospective purification of the main neurogenic populations from the subventricular zone (SVZ), we demonstrated an early decline in adult neurogenesis with a dramatic loss of progenitor cells in 4 month-old young adult mice. Whereas the activated and quiescent NSC pools remained stable up to 12 months, the proliferative status of activated NSCs was already altered by 6 months, with an overall extension of the cell cycle resulting from a specific lengthening of G1. Whole genome analysis of activated NSCs from 2- and 6-month-old mice further revealed distinct transcriptomic and molecular signatures, as well as a modulation of the TGFβ signalling pathway. Our microarray study constitutes a cogent identification of new molecular players and signalling pathways regulating adult neurogenesis and its early modifications.
Combined Secretomics and Transcriptomics Revealed Cancer-Derived GDF15 is Involved in Diffuse-Type Gastric Cancer Progression and Fibroblast Activation
Authors: Ishige Takayuki , Nishimura Motoi , Satoh Mamoru , Fujimoto Mai , Fukuyo Masaki , Semba Toshihisa , Kado Sayaka , Tsuchida Sachio , Sawai Setsu , Matsushita Kazuyuki , Togawa Akira , Matsubara Hisahiro , Kaneda Atsushi , Nomura Fumio
Published: February 2016

Gastric cancer is classified into two subtypes, diffuse and intestinal. The diffuse-type gastric cancer (DGC) has poorer prognosis, and the molecular pathology is not yet fully understood. The purpose of this study was to identify functional secreted molecules involved in DGC progression. We integrated the secretomics of six gastric cancer cell lines and gene expression analysis of gastric cancer tissues with publicly available microarray data. Hierarchical clustering revealed characteristic gene expression differences between diffuse- and intestinal-types. GDF15 was selected as a functional secreted molecule owing to high expression only in fetal tissues. Protein expression of GDF15 was higher in DGC cell lines and tissues. Serum levels of GDF15 were significant higher in DGC patients as compared with healthy individuals and chronic gastritis patients, and positively correlated with wall invasion and lymph node metastasis. In addition, the stimulation of GDF15 on NIH3T3 fibroblast enhanced proliferation and up-regulated expression of extracellular matrix genes, which were similar to TGF-β stimulation. These results indicate that GDF15 contributes to fibroblast activation. In conclusion, this study revealed that GDF15 may be a novel functional secreted molecule for DGC progression, possibly having important roles for cancer progression via the affecting fibroblast function, as well as TGF-β.
A versatile strategy for rapid conditional genome engineering using loxP sites in a small synthetic intron in Plasmodium falciparum
Authors: Jones Matthew L. , Das Sujaan , Belda Hugo , Collins Christine R. , Blackman Michael J. , Treeck Moritz
Published: February 2016

Conditional genome engineering in the human malaria pathogenPlasmodium falciparumremains highly challenging. Here we describe a strategy for facile and rapid functional analysis of genes using an approach based on the Cre/lox system and tailored for organisms with short and few introns. Our method allows the conditional, site-specific removal of genomic sequences of essential and non-essential genes by placingloxPsites into a short synthetic intron to produce a module (loxPint) can be placed anywhere in open reading frames without compromising protein expression. When duplicated, the loxPint module serves as an intragenic recombineering point that can be used for the fusion of gene elements to reporters or the conditional introduction of point mutations. We demonstrate the robustness and versatility of the system by targeting theP. falciparummerozoite surface protein 1 gene (msp1), which has previously proven refractory to genetic interrogation and the parasite exported kinase FIKK10.1.
Transformation of amorphous calcium carbonate nanoparticles into aragonite controlled by ACCBP
Authors: Su Jingtan , Zhu Fangjie , Zhang Guiyou , Wang Hongzhong , Xie Liping , Zhang Rongqing
Published: February 2016

Polymorph switching of calcium carbonate controlled by amorphous calcium carbonate-binding protein, an extrapallial fluid (EPF) protein from the pearl oyster, is investigated. The polymorph selection in nacre or pearl growth may be controlled not only by the nucleating template on the matrix but also by the physicochemical effects of EPF proteins.
Electronic energy and electron transfer processes in photoexcited donor–acceptor dyad and triad molecular systems based on triphenylene and perylene diimide units
Authors: Lee K. J. , Woo J. H. , Kim E. , Xiao Y. , Su X. , Mazur L. M. , Attias A.-J. , Fages F. , Cregut O. , Barsella A. , Mathevet F. , Mager L. , Wu J. W. , D'Aléo A. , Ribierre J.-C.
Published: February 2016

The photophysical properties of novel donor–acceptor dyad and triad molecules show an intricate interplay between energy and electron transfer processes.
A feasibility study of unconventional planar ligand spacers in chalcogenide nanocrystals
Authors: Lukose Binit , Clancy Paulette
Published: February 2016

The solar cell efficiency of chalcogenide nanocrystals (quantum dots) has been limited in the past by the insulation between neighboring quantum dots caused by intervening, often long-chain, aliphatic ligands.
Structured catalysts for dry reforming of methane
Authors: Muraleedharan Nair Mahesh , Kaliaguine Serge
Published: February 2016

This review highlights the progress in designing oxide catalysts with well defined structures for dry reforming of methane.
Natural products discovery needs improved taxonomic and geographic information
Authors: Leal Miguel C. , Hilário Ana , Munro Murray H. G. , Blunt John W. , Calado Ricardo
Published: February 2016

Marine and terrestrial organisms yield a remarkable chemical diversity and are important sources for discovery of new chemical products.
Synthesis of highly uniform Cu2O spheres by a two-step approach and their assembly to form photonic crystals with a brilliant color
Authors: Su Xin , Chang Jie , Wu Suli , Tang Bingtao , Zhang Shufen
Published: February 2016

Cu2O spheres with highly uniform sizes were obtained, which can form photonic crystal films with brilliant structural colors.
Colloidal quantum dot lasers built on a passive two-dimensional photonic crystal backbone
Authors: Chang Hojun , Min Kyungtaek , Lee Myungjae , Kang Minsu , Park Yeonsang , Cho Kyung-Sang , Roh Young-Geun , Woo Hwang Sung , Jeon Heonsu
Published: February 2016

We report the room-temperature lasing action from two-dimensional photonic crystal structures composed of a passive Si3N4 backbone with an over-coat of CdSe/CdS/ZnS colloidal quantum dots for optical gain.
Enhancing light emission efficiency without color change in post-transition metal chalcogenides
Authors: Wang Cong , Yang Shengxue , Cai Hui , Ataca Can , Chen Hui , Zhang Xinzheng , Xu Jingjun , Chen Bin , Wu Kedi , Zhang Haoran , Liu Luqi , Li Jingbo , Grossman Jeffrey C. , Tongay Sefaattin , Liu Qian
Published: February 2016

2D materials can take a large amount of mechanical deformation before reaching the fracture limit due to their high Young's modulus, which provides a way to tune their properties by strain engineering.
Synthesis of rocaglamide derivatives and evaluation of their Wnt signal inhibitory activities
Authors: Arai Midori A. , Kofuji Yuuki , Tanaka Yuuki , Yanase Natsuki , Yamaku Kazuki , Fuentes Rolly G. , Karmakar Utpal Kumar , Ishibashi Masami
Published: February 2016

A new class of rocaglamide derivatives were synthesized by [3 + 2] cycloaddition and their Wnt signal inhibitory activities were evaluated.
Detection and quantification of food colorant adulteration in saffron sample using chemometric analysis of FT-IR spectra
Authors: Karimi Sadegh , Feizy Javad , Mehrjo Fatemeh , Farrokhnia Maryam
Published: February 2016

The aim of present study is to investigate the combination of Fourier transform infrared spectroscopy with pattern recognition to recognize the standard saffron from those which have been adulterated with various types of food colorants.
Facile synthesis of cobalt and nitrogen co-doped graphene networks from polyaniline for oxygen reduction reaction in acidic solutions
Authors: Peng Shuqin , Jiang Hongmei , Zhang Youming , Yang Lu , Wang Shuqin , Deng Wenfang , Tan Yueming
Published: February 2016

Co and N co-doped graphene networks derived from polyaniline nanofibers can show high oxygen reduction activity in acidic solutions.
Blue upconversion emission of Cu2+ ions sensitized by Yb3+-trimers in CaF2
Authors: Aidilibike Tuerxun , Li Yangyang , Guo Junjie , Liu Xiaohui , Qin Weiping
Published: February 2016

Under 978 nm near-infrared (NIR) excitation, blue upconversion (UC) emissions from CaF2:Cu2+,Yb3+ were first observed at ∼420 nm.
Graphene enhances the magnetoresistance of FeNi3nanoparticles in hierarchical FeNi3–graphene nanocomposites
Authors: Abellán G. , Prima-García H. , Coronado E.
Published: February 2016

An increase in the giant magnetoresistance of FeNi3nanoparticles of 20 times has been observed in FeNi3–graphene nanocomposites synthesized using NiFe-layered double hydroxide hybrids as precursors.
An unusual 32-membered copper(ii) metallomacrocube based on a Cu4O3X cubic core: photocatalytic, electrocatalytic, and magnetic properties
Authors: Feng Sisi , Jia Fei , Lu Liping , Li Zhongping , Zhang Shuo
Published: February 2016

The first Cu32 cluster featuring a multi-cubane (Cu4O3X) structure exhibited excellent catalytic performance in the degradation of organic pollutant rhodamine B, good electrocatalytic activity for nitrite reduction, and strong antiferromagnetic interactions.
Development of a disaggregation-induced emission probe for the detection of RecA inteins from Mycobacterium tuberculosis
Authors: Li Xin , Jiang Hao , Luo Zhaofeng , Chang Young-Tae , Zhang Liyun
Published: February 2016

A novel fluorescent sensor with disaggregation-induced emission characteristics has been developed for the detection of RecA inteins from Mycobacterium tuberculosis.
Visible-light-induced aerobic dearomative reaction of indole derivatives: access to heterocycle fused or spirocyclo indolones
Authors: Zhang Muliang , Duan Yingqian , Li Weipeng , Cheng Yixiang , Zhu Chengjian
Published: February 2016

A highly efficient catalytic dearomatization of indoles via visible-light photocatalysis is presented. The common indole tethered alcohol at the N1 or C2 position reacts in a cascade fashion, providing facile access to diverse indolone scaffolds.
Reversible transformation of self-assemblies and fluorescence by protonation–deprotonation in pyrimidinylene–phenylene macrocycles
Authors: Xiao Duoduo , Zhang Siqi , Zhang Dengqing , Xie Dahai , Zeng Qingdao , Xiang Yunjie , Ning Ruguang , Li Xianying , Jin Wusong
Published: February 2016

Reversible transformation of nanostructures and fluorescence by protonation–deprotonation.
On couplings and excimers: lessons from studies of singlet fission in covalently linked tetracene dimers
Authors: Feng Xintian , Krylov Anna I.
Published: February 2016

Electronic factors controlling singlet fission (SF) rates are investigated in covalently linked dimers of tetracene.
Green apatites: hydride ions, electrons and their interconversion in the crystallographic channel
Authors: Hayashi Katsuro , Hosono Hideo
Published: February 2016

Hydride (H−) ions and electrons in channel sites of the lattice of calcium phosphate apatites are characterized.
Reactivity of atomically dispersed Pt2+ species towards H2: model Pt–CeO2 fuel cell catalyst
Authors: Lykhach Yaroslava , Figueroba Alberto , Camellone Matteo Farnesi , Neitzel Armin , Skála Tomáš , Negreiros Fabio R. , Vorokhta Mykhailo , Tsud Nataliya , Prince Kevin C. , Fabris Stefano , Neyman Konstantin M. , Matolín Vladimír , Libuda Jörg
Published: February 2016

Formation of at least two oxygen vacancies triggers the reduction of one Pt2+ species.
Influence of adsorption strength in aqueous phase glycerol hydrodeoxygenation over Ni@Pt and Co@Pt overlayer catalysts
Authors: Zhang Chen , Lai Qinghua , Holles Joseph H.
Published: February 2016

Silica–alumina supported bimetallic overlayer catalysts of platinum on nickel (Ni@Pt) and platinum on cobalt (Co@Pt) were synthesized using the directed deposition technique.
Bimetallic Cu(i) complex with a pyridine-bridged bis(1,2,3-triazole-5-ylidene) ligand
Authors: Iwasaki Haruka , Teshima Yuta , Yamada Yuji , Ishikawa Ryuta , Koga Yuji , Matsubara Kouki
Published: February 2016

Expanded π-conjugated system catalyst for hydroboration of alkenes.
A polyamide resin based method for adsorption of anthocyanins from blackberries
Authors: Wen Yao , Chen Huaguo , Zhou Xin , Deng Qingfang , Zhao Chao , Gong Xiaojian
Published: February 2016

A polyamide resin was successfully employed for the purification of blackberry anthocyanins and this proved to be an efficient and low-cost method.
Correction: A convenient domino Ferrier rearrangement-intramolecular cyclization for the synthesis of novel benzopyran-fused pyranoquinolines
Authors: Moshapo Paseka T. , Sokamisa Mokela , Mmutlane Edwin M. , Mampa Richard M. , Kinfe Henok H.
Published: February 2016

Correction for ‘A convenient domino Ferrier rearrangement-intramolecular cyclization for the synthesis of novel benzopyran-fused pyranoquinolines’ by Paseka T. Moshapo et al., Org. Biomol. Chem., 2016, DOI: 10.1039/c5ob02536b.
Sodium ion battery anode properties of designed graphene-layers synthesized from polycyclic aromatic hydrocarbons
Authors: Hayakawa Taichi , Ishii Yosuke , Kawasaki Shinji
Published: February 2016

Structurally designed graphene-layers were synthesized by fusing two kinds of poly-aromatic hydro carbons: coronene and pentacene.
Extending the scope of oleic acid catalysis in diversity-oriented synthesis of chromene and pyrimidine based scaffolds
Authors: Ganesan Asaithampi , Kothandapani Jagatheeswaran , Subramaniapillai Selva Ganesan
Published: February 2016

Readily available, non-toxic, biodegradable oleic acid was found to catalyse 4H-chromene derivatives syntheses in good yields in a water medium.
Revisiting oxime–nitrone tautomerism. Evidence of nitrone tautomer participation in oxime nucleophilic addition reactions
Authors: Roca-López David , Darù Andrea , Tejero Tomás , Merino Pedro
Published: February 2016

Oxime–nitrone tautomerism takes place through a biomolecular mechanism. Participation of nitrone tautomer in nucleophilic addition reactions is evidenced by the first time.
Paving the way for methane hydrate formation on metal–organic frameworks (MOFs)
Authors: Casco Mirian E. , Rey Fernando , Jordá José L. , Rudić Svemir , Fauth François , Martínez-Escandell Manuel , Rodríguez-Reinoso Francisco , Ramos-Fernández Enrique V. , Silvestre-Albero Joaquín
Published: February 2016

The formation of methane hydrates on MOFs has been identified for the first time using inelastic neutron scattering and synchrotron X-ray powder diffraction.
Temperature-dependent shape-responsive fluorescent nanospheres for image-guided drug delivery
Authors: He Shawn , Tourkakis George , Berezin Oleg , Gerasimchuk Nikolay , Zhang Hairong , Zhou Haiying , Izraely Asaf , Akers Walter J. , Berezin Mikhail Y.
Published: February 2016

Nanospheres work similar to Hoberman spheres that undergo significant temperature-induced shape changes revealing large pores (holes) through which drugs released.
Linear‐assisted DC/DC regulator‐based current source for LED drivers
Authors: Martínez‐García H. , Saberkari A.
Published: February 2016

A proposal of current source based on a linear‐assisted DC/DC converter is presented, in which a linear voltage regulator assists a switching DC/DC converter in order to obtain a compact circuit with advantages of both alternatives; i.e. high efficiency (similar to the switching converter), and low output ripple and fast reaction to the load changes (similar to the linear regulator). To reduce the power dissipation in the linear regulator, it is considered as an assisted circuit for providing just a little fraction of the load current. Furthermore, this stage provides the required clock signal for the switching counterpart, resulting in reduction of the complexity in the design of the control scheme for the switching converter and a compact topology, especially for on‐chip practical implementations, since no output capacitors are required. This last advantage provides the possibility of obtaining good‐performance current‐source drivers for LED technology in lighting applications. The implementation and results indicate that the proposed linear‐assisted DC/DC regulator‐based current source can achieve a notably compacting and higher performance, while consuming less power in comparison to linear alternatives.
Wearable dual‐band stripline‐fed half‐mode substrate‐integrated cavity antenna
Authors: Pinapati S.P. , Kaufmann T. , Ranasinghe D.C. , Fumeaux C.
Published: February 2016

A low‐profile dual‐band half‐mode substrate‐integrated cavity antenna with a fully shielded textile feeding mechanism is presented for wearable applications. The antenna operates at the lower and upper microwave industrial, scientific and medical bands. The cavity geometry is accurately defined with conducting thread through computerised embroidery. Design guidelines are developed for a practical realisation. Good agreement between simulated and measured results validates the proposed structure.
Exponential stability in mean square of a singularly perturbed linear stochastic system with state‐multiplicative white‐noise perturbations and Markovian switching
Authors: Dragan Vasile , Mukaidani Hiroaki
Published: February 2016

This study deals with a stabilisation problem for a class of singularly perturbed linear stochastic systems with state‐multiplicative white‐noise and Markovian jumping parameters. Based on the Lyapunov‐ type operator, an exponential stability in mean square is discussed intensively. First, after decomposing the full‐order stochastic Lyapunov differential equations, the conditions that the reduced‐order systems are both mean square stable are established. Second, it is shown that there exist small perturbation parameters that cause the original stochastic systems to be mean square stable. Moreover, it is also shown that the parameter‐independent composite stabilising controller is established by solving the linear matrix inequalities.
Stabilisation of unstable cascaded heat partial differential equation system subject to boundary disturbance
Authors: Kang Wen , Guo Bao‐Zhu
Published: February 2016

In this study, the authors consider boundary stabilisation for a cascade of unstable heat partial differential equation systems with interconnection at one end and general external disturbance at the control end. An unknown input type observer is first designed by sliding mode control method to estimate the state, and its Filippov type solution is determined. To design an output feedback, they need to know a state feedback which could be realised by the backstepping transformation. The transformation transforms the system into an equivalent target system where the governing equations are stable. To deal with the disturbance, they apply the active disturbance rejection control to estimate the disturbance by output. Based on observer and disturbance estimator, an output feedback control is then designed. The existence of solution to the closed‐loop system is proved and the stability is concluded. Finally, some numerical simulations are presented for illustration.
Output‐based disturbance rejection control for non‐linear uncertain systems with unknown frequency disturbances using an observer backstepping approach
Authors: Yang Jun , Ding Zhengtao , Chen Wen‐Hua , Li Shihua
Published: February 2016

This study is concerned with the output feedback control design for a class of non‐linear uncertain systems subject to multiple sources of disturbances including model uncertainties, unknown constant disturbances, harmonic disturbances with unknown frequency and amplitude. The total disturbances and uncertainties are delicately represented by a compact exogenous model first. By incorporating the adaptive internal model principle, a set of dynamic estimators are developed for both state and disturbance observations. By means of observer backstepping technique, a composite output feedback controller is constructed based on the disturbance and state estimations. The stability of the closed‐loop system is rigorously established based on Lyapunov stability criterion. A missile roll stabilisation example is finally investigated to validate the effectiveness of the proposed control approach.
Reduced‐order observer design for one‐sided Lipschitz time‐delay systems subject to unknown inputs
Authors: Cuong Nguyen Minh , Trinh Hieu
Published: February 2016

This study addresses the observer design problem for a class of one‐sided Lipschitz time‐delay systems in the presence of unknown inputs. The non‐linearities are assumed to satisfy the one‐sided Lipschitz and quadratically inner‐bounded conditions; hence, a wider class of non‐linear systems is investigated in this work. A novel approach for the non‐linear observer design problem subject to time delays and disturbances is proposed. Both H∞ observer design and asymptotic observer design with reduced‐order are introduced. To deal with the time‐delay issue, Wirtinger‐based integral inequality, which encompasses the Jensen inequality, is employed to derive less conservative synthesis conditions in linear matrix inequalities form. Two numerical examples are given to illustrate the effectiveness and the edge of the authors' results over other relevant works in the literature.
Multi‐objective restoration optimisation of power systems with battery energy storage systems
Authors: Liu Weijia , Sun Lei , Lin Zhenzhi , Wen Fushuan , Xue Yusheng
Published: February 2016

The applications of battery energy storage systems (BESSs) in power systems have been paid increasing attention in recent years. Apart from all the benefits that BESSs can bring to the power systems, their potential applications in assisting power system restoration after a major blackout have not yet been systematically investigated. The flexible charging and discharging characteristics of BESSs could help maintain the balance between power supply and demand during the system restoration process, thus the recovery speed of the power system concerned after a blackout could be accelerated. Given this background, the applications of BESSs in power system restoration is investigated. First, the potential applications of BESSs during power system restoration process are discussed. A multi‐objective optimisation model is next proposed, aiming at minimising the number of circuit breaker operations and outage durations of both the non‐black‐start generating units and the important loads. Meanwhile, the application of intermittent renewable energy sources for improving power system restoration is also discussed. The operation strategy of BESSs will also be optimised after the system restoration scheme is attained through the multi‐objective optimisation. The proposed method is demonstrated by numerical tests on the IEEE 30‐bus and 162‐bus test systems.
Modular input‐parallel output‐series DC/DC converter control with fault detection and redundancy
Authors: Lian Yiqing , Adam Grain , Holliday Derrick , Finney Stephen
Published: February 2016

Large offshore wind farms require extensive sub‐sea cables within the collection network. Present solutions are based around medium‐voltage AC collection networks. Recent studies have highlighted the potential benefits of DC collection networks. However, achieving DC/DC conversion at the required voltage and power levels presents a significant challenge for wind‐turbine power electronics. This study proposes an alternative DC collection network based around a modular DC/DC converter with input‐parallel output‐series connection. This modular topology can overcome the limitations imposed by semiconductor voltage ratings and provides fault‐tolerant operation. Small‐signal analysis of the converter is presented to be used to facilitate controller design for the converter input and output stages. A new master–slave control scheme and distributed voltage sharing controllers are proposed that ensure power sharing under all operating conditions, including during failure of a master module. This control scheme achieves fault‐tolerant operation by allowing the status of master module to be reallocated to any healthy module. The proposed control scheme is validated using simulation and experimentation, considering active power sharing between modules with parameter mismatch.
New control strategy of decoupling the AC/DC voltage offset for modular multilevel converter
Authors: Zhang Fan , Xu Jianzhong , Zhao Chengyong
Published: February 2016

For its notable advantages, the modular multilevel converter (MMC) has become a hot topic in high‐voltage direct current (HVDC) research and construction. Based on the existing MMC configuration and double‐loop control strategy, there is a coupling between AC/DC voltage offset, which brings a series of problems in different engineering background. This study proposes solutions to decouple this coupling with two steps: (i) a principle of the arm sub‐module configuration is proposed to change the topology of MMC arms; MMC with the new changes of configuration is defined as asymmetrical MMC. (ii) The asymmetrical MMC is modelled and analysed, and a new control strategy is designed for it. Two two‐terminal active MMC‐HVDC simulation models with different configuration are established in PSCAD/EMTDC and the efficiency of the proposed topology and control strategy is validated.
Interaction between the voltage‐droop and the frequency‐droop control for multi‐terminal HVDC systems
Authors: Akkari Samy , Dai Jing , Petit Marc , Guillaud Xavier
Published: February 2016

Multi‐terminal DC systems must provide a high level of reliability and may have to support the interconnected AC grids. This can be achieved by providing AC/DC converters with a dual controller combining both the voltage‐droop and the frequency‐droop control techniques. In this article, the coupling between those droops is theoretically investigated and quantified, and a proposed corrected value of the frequency‐droop parameter allows the system to comply with the TSO's requirements with regards to the frequency support of the AC grids despite the unintended interaction of the two droops. A dynamic frequency‐droop parameter is then proposed to also cope with the controller limits. Finally, an electromagnetic transient study of a five‐terminal HVDC grid is performed to validate the theoretical results.
Short‐term wind speed forecasting using the wavelet decomposition and AdaBoost technique in wind farm of East China
Authors: Shao Haijian , Deng Xing , Cui Fang
Published: February 2016

The accurate and reliable short‐term wind speed forecasting can benefit the stability of the grid operation. However, it is a challenging issue to generate consistently accurate forecasts due to the complex and stochastic nature of wind speed distribution in meteorological interactions. In this study, a novel solution using AdaBoost neural network in combination with wavelet decomposition is proposed to solve the defects of the lower accuracy and enhance the model robustness. Based on the real data provided by sampling device weak wind turbine (type‐FD77) in a wind farm plant of East China, the experimental evaluation demonstrates that the proposed strategy can significantly enhance model robustness and effectively improve the prediction accuracy.
Fast localised active contour for inhomogeneous image segmentation
Authors: Duc Bui Toan , Ahn Chunsoo , Shin Jitae
Published: February 2016

The localised active contour framework has been widely used for image segmentation because it provides reliable results for inhomogeneous images. However, its computational complexity remains an issue. In this study, the authors introduce a fast algorithm based on the localised active contour framework. A key concept of the proposed algorithm is its consideration of the curve evolution based on the speed function only at active points that change across time, rather than at all points in a narrow band. This approach reduces computational time in the localised active contour. The authors additionally propose a modified speed function to address inhomogeneous image segmentation. The experimental results demonstrate significant advantages of the proposed method over existing methods, both in terms of computational efficiency and segmentation accuracy, for homogeneous and inhomogeneous images.
Spatiotemporal feature extraction for facial expression recognition
Authors: Kamarol Siti Khairuni Amalina , Jaward Mohamed Hisham , Parkkinen Jussi , Parthiban Rajendran
Published: February 2016

A key issue regarding feature extraction is the capability of a technique to extract distinctive features to represent facial expressions while requiring a low computational complexity. In this study, the authors propose a novel approach for appearance‐based facial feature extraction to perform the task of facial expression recognition on video sequences. The proposed spatiotemporal texture map (STTM) is capable of capturing subtle spatial and temporal variations of facial expressions with low computational complexity. First, face is detected using Viola–Jones face detector and frames are cropped to remove unnecessary background. Facial features are then modelled with the proposed STTM, which uses the spatiotemporal information extracted from three‐dimensional Harris corner function. A block‐based method is adopted to extract the dynamic features and represent the features in the form of histograms. The features are then classified into classes of emotion by the support vector machine classifier. The experimental results demonstrate that the proposed approach shows superior performance compared with the state‐of‐the‐art approaches with an average recognition rate of 95.37, 98.56, and 84.52% on datasets containing posed expressions, spontaneous micro‐expressions, and close‐to‐real‐world expressions, respectively. They also show that the proposed algorithm requires low computational cost.
Matching cost function using robust soft rank transformations
Authors: Dinh Vinh Quang , Pham Cuong Cao , Jeon Jae Wook
Published: February 2016

Stereo correspondence is a challenging task because stereo images are affected by many factors such as radiometric distortion, sun and rain flares, flying snow, occlusions and object boundaries. However, most of the existing stereo correspondence methods use simple matching cost functions. As a result, their performance is degraded significantly when operating with real‐world stereo images whose intensities of corresponding pixels can be arbitrarily transformed. In this study, the authors propose a novel matching cost function based on the order relations between pixel pairs that can operate accurately under various conditions of transformed intensities between stereo images. The proposed matching cost function is an improvement of the soft rank transform (SRT) and can tolerate local, monotonically non‐linear changes in intensities between the left and right images. The proposed function significantly reduces the error rate from 24.7 to 12.7% in the Middlebury dataset, and from 19.8 to 7.1% in the KITTI dataset as compared with the SRT. The qualitative and quantitative experimental results obtained using stereo images in different datasets under various conditions show that the proposed matching cost function outperforms the state‐of‐the‐art matching cost functions in indoor and outdoor stereo images.
Design of leaky‐wave antenna with wide beam‐scanning angle and low cross‐polarisation using novel miniaturised composite right/left‐handed transmission line
Authors: Wu Guo‐Cheng , Wang Guang‐Ming , Peng Hua‐Xia , Gao Xiang‐Jun , Liang Jian‐Gang
Published: February 2016

In this study, a novel periodic leaky‐wave antenna (LWA) with wide beam‐scanning angle and low cross‐polarisation is proposed by using miniaturised composite right/left‐handed transmission line (CRLH TL). By introducing the metallic holes loaded in the interdigital lines of the miniaturised CRLH TL, not only the parasitic resonant modes can be eliminated, but also the miniaturisation is realised. Considering the continuous phase constants from negative to positive values of the balanced CRLH TL, a continuous beam‐scanning property from backward to forward of the resultant LWA can be obtained. For verification, a periodic LWA, which consists of 20 unit cells of the balanced CRLH TL, is fabricated and measured; the measured and simulated results are in good agreements with each other, indicating that the fabricated LWA operates from 3.90 to 4.90 GHz (a bandwidth of 22.7%), and has a wide continuous beam‐scanning capability from backward −61° to forward 67° (including the broadside) within the operating band. Moreover, it also has very low cross‐polarisation, which remains at a level of at least 25 dB below the co‐polarisation across the entire radiation region. As a result, the presented LWA should find promising applications in modern wireless communication systems and the high‐resolution radar system due to these wonderful electromagnetic performances.
Vector selection approach‐based hexagonal hysteresis space vector current controller for a three phase diode clamped MLI with capacitor voltage balancing
Authors: Bharatiraja C. , Jeevananthan Seenithangam , Latha Ramachandran , Mohan V.
Published: February 2016

The purpose of this study is to provide a broad idea about current control scheme and equilibrating voltages in DC‐link capacitors of the neutral‐point clamped multilevel inverter (NPC‐MLI), using an innovative hexagonal space vector hysteresis current control (SVHCC) scheme. The main ideology is to force the literal current vector to reach the reference current vector through an appropriate voltage vector selection sequence. This proposed scheme defines two hexagonal hysteresis bands encompassing the error vector, as a first step. With respect to the error vector location, the selection of the adjacent vector is acted to minimise the error vector. In addition to the error vector selection, the capacitor voltage is also equilibrated by controlling the degree of freedom available in selecting the switching vectors. The SVHCC scheme is intelligent in performing modulation depth dependent selection of switching vectors between the groups namely closest three vector and preferred three vector (PTV). This scheme balances the DC‐link capacitors’ voltages within a tolerance limit for any value of modulation index. The proposed scheme is asserted through MATLAB/Simulink software. The superiority of the proposed technique is validated through the 2 kW NPC‐MLI supported with SPARTAN III 3AN –XC3S400 field programmable gate array.
Power amplifier linearisation using digital predistortion and multi‐port techniques
Authors: Beikmirza Mohammad Reza , Mohammadi Abbas , Mirzavand Rashid
Published: February 2016

Power amplifiers are essential components in communication systems and are inherently non‐linear. The non‐linearity creates spectral growth (broadening) beyond the signal bandwidth, which interferes with adjacent channels. It also causes distortions within the signal bandwidth, which decreases the bit error rate at the receiver. This study reports an adaptive digital predistorter with fast convergence rate and low complexity and cost to alleviate these problems. In this design, a lookup table‐based adaptive digital predistortion (DPD) technique using a five‐port receiver instead of traditional heterodyne and homodyne architectures is proposed to realise the linearisation loop for this amplifier. The five‐port receiver is implemented by use of passive microwave circuits and detector diodes. This approach highly reduces the cost and complexity of the linearisation system. Simulation and measurement results obtained are presented for a laterally diffused metal–oxide–semiconductor‐based high‐power amplifier biased in class AB operation with wideband code‐division multiple access input signal to demonstrate the effectiveness of this novel DPD design. Moreover, these results are compared with DPD technique using homodyne receiver in feedback path.
Study on dynamics of the bubble in transformer oil under non‐uniform electric field
Authors: Tao Zhao , Yunpeng Liu , Fangcheng Lü , Ruihong Du
Published: February 2016

This study explores the dynamics of gas bubbles in liquid dielectric theoretically and experimentally. A numerical model is introduced for the bubble motion in the transformer oil under non‐uniform electric field. Moreover, the bubble trajectory is obtained through the force calculation of the bubble under the non‐uniform electric field. The numerical calculations for different bubble sizes and applied voltages are also done. Notably, trajectories calculated indicate the bubble aggregation in concentrated area of the electric field between the needle‐plane electrodes. It is concluded that the bubble can play a catalytic role in the breakdown of the oil gap. An experiment is finally conducted on the bubble motion in transformer oil gap submitted to a high divergent electric field and the suspension and aggregation of bubbles are observed before the oil gap breakdown, which confirms the results of numerical calculation.