bluuebunny/crossref_metadata_2025 huggingface dataset:
Induction of WNT11 by hypoxia and hypoxia-inducible factor-1α regulates cell proliferation, migration and invasion
Authors: Mori Hiroyuki , Yao Yao , Learman Brian S. , Kurozumi Kazuhiko , Ishida Joji , Ramakrishnan Sadeesh K. , Overmyer Katherine A. , Xue Xiang , Cawthorn William P. , Reid Michael A. , Taylor Matthew , Ning Xiaomin , Shah Yatrik M. , MacDougald Ormond A.
Published: February 2016

Changes in cellular oxygen tension play important roles in physiological processes including development and pathological processes such as tumor promotion. The cellular adaptations to sustained hypoxia are mediated by hypoxia-inducible factors (HIFs) to regulate downstream target gene expression. With hypoxia, the stabilized HIF-α and aryl hydrocarbon receptor nuclear translocator (ARNT, also known as HIF-β) heterodimer bind to hypoxia response elements (HREs) and regulate expression of target genes. Here, we report that WNT11 is induced by hypoxia in many cell types, and that transcription of WNT11 is regulated primarily by HIF-1α. We observed induced WNT11 expression in the hypoxic area of allograft tumors. In addition, in mice bearing orthotopic malignant gliomas, inhibition with bevacizumab of vascular endothelial growth factor, which is an important stimulus for angiogenesis, increased nuclear HIF-1α and HIF-2α, and expression of WNT11. Gain- and loss-of-function approaches revealed that WNT11 stimulates proliferation, migration and invasion of cancer-derived cells, and increases activity of matrix metalloproteinase (MMP)-2 and 9. Since tumor hypoxia has been proposed to increase tumor aggressiveness, these data suggest WNT11 as a possible target for cancer therapies, especially for tumors treated with antiangiogenic therapy.
Optical detection of radon decay in air
Authors: Sand Johan , Ihantola Sakari , Peräjärvi Kari , Toivonen Harri , Toivonen Juha
Published: February 2016

An optical radon detection method is presented. Radon decay is directly measured by observing the secondary radioluminescence light that alpha particles excite in air, and the selectivity of coincident photon detection is further enhanced with online pulse-shape analysis. The sensitivity of a demonstration device was 6.5 cps/Bq/l and the minimum detectable concentration was 12 Bq/m3 with a 1 h integration time. The presented technique paves the way for optical approaches in rapid radon detection, and it can be applied beyond radon to the analysis of any alpha-active sample which can be placed in the measurement chamber.
Antibacterial synergic effect of honey from two stingless bees: Scaptotrigona bipunctata Lepeletier, 1836, and S. postica Latreille, 1807
Authors: Nishio E. K. , Ribeiro J. M. , Oliveira A. G. , Andrade C. G. T. J. , Proni E. A. , Kobayashi R. K. T. , Nakazato G.
Published: February 2016

Several studies have tested antimicrobial activity of combinations of honey and various substances. In this study, we tested a combination of two stingless bee honeys against various bacterial strains. In particular: the antibacterial activity of honeys produced by Scaptotrigona bipunctata (SB) and Scaptotrigona postica (SP) was evaluated against Gram-positive and Gram-negative bacterial strains by agar well diffusion assays, minimum inhibitory concentration (MIC) assessment, construction of growth and viability curves and scanning electron microscopy (SEM). The interaction of the two honeys was also evaluated by the checkerboard assay. Inhibition zones ranged from 8 to 22 mm. The MIC values of the individual honeys ranged from 0.62 to 10% (v v−1) and decreased to 1/4 to 1/32 when the honeys were combined. SEM images showed division inhibition and cell wall disruption for the SB and SP honeys, respectively, and these alterations were observed in same field when the SB and SP honeys were combined. This study demonstrated that the natural honeys possess in vitro antimicrobial activity against Gram-positive and Gram-negative bacteria, including multidrug-resistant strains. Combination of the SB and SP honeys could lead to the development of new broad-spectrum antimicrobials that have the potential to prevent the emergence of resistant bacterial strains.
An electrochemical paracetamol sensor based on layer-by-layer covalent attachment of MWCNTs and a G4.0 PAMAM modified GCE
Authors: Zhang Yanjun , Liu Xiuhui , Li Lin , Guo Zhipan , Xue Zhonghua , Lu Xiaoquan
Published: February 2016

An electrochemical sensor for the detection of paracetamol (PAT) was reported employing multiwalled carbon nanotubes (MWCNTs) and the fourth generation poly(amidoamine) dendrimers (G4.0 PAMAM).
Palladium-mediated borylation of pentafluorosulfanyl functionalized compounds: the crucial role of metal fluorido complexes
Authors: Berg Claudia , Braun Thomas , Laubenstein Reik , Braun Beatrice
Published: February 2016

Model reactions such as the oxidative addition of SF5 aromatics at [Pd(PiPr3)2] and subsequent fluorination and borylation steps led to the development of catalytic processes for the borylation of SF5 compounds.
Influence of Ta5+ content on the crystallographic structure and electrical properties of [001]PC-oriented (Li,Na,K)(Nb,Ta)O3 single crystals
Authors: Liu Hairui , Veber Philippe , Koruza Jurij , Rytz Daniel , Josse Michael , Rödel Jürgen , Maglione Mario
Published: February 2016

A series of centimeter-sized lead-free piezoelectric Li+- and Ta5+-modified (Na,K)NbO3 single crystals with an ABO3 perovskite structure was successfully grown by the top-seeded solution growth method.
New insights into the mechanism of interaction between CO2 and polymers from thermodynamic parameters obtained by in situ ATR-FTIR spectroscopy
Authors: Gabrienko Anton A. , Ewing Andrew V. , Chibiryaev Andrey M. , Agafontsev Alexander M. , Dubkov Konstantin A. , Kazarian Sergei G.
Published: February 2016

This work investigates the thermodynamics and mechanism of intermolecular interactions between CO2 and different polymers.
Solvent sensitive intramolecular charge transfer dynamics in the excited states of 4-N,N-dimethylamino-4′-nitrobiphenyl
Authors: Ghosh Rajib , Nandi Amitabha , Palit Dipak K.
Published: February 2016

Solvent sensitive excited state dynamics of DNBP is explored. In polar solvents, the ultrafast barrierless TICT process is the major relaxation pathway, whereas, in nonpolar solvents the excited state undergoes the PICT process, followed by efficient intersystem crossing to the triplet state.
(Ferrocenylpyrazolyl)nickel(ii)-catalysed ethylene oligomerisation
Authors: Obuah Collins , Jordaan Johan H. L. , Darkwa James
Published: February 2016

(Ferrocenylpyrazolyl)nickel(ii) complexes upon activation with EtAlCl2 catalyse ethylene oligomerisation reactions in chlorobenzene to isomers of butenes and C16–C64 olefins without Schulz–Flory distribution.
The single and synergistic effects of the major tea components caffeine, epigallocatechin-3-gallate andl-theanine on rat sperm viability
Authors: Dias Tânia R. , Alves Marco G. , Casal Susana , Silva Branca M. , Oliveira Pedro F.
Published: February 2016

The synergism between the main representatives of the major classes of tea components, caffeine, epigallocatechin-3-gallate (EGCG) andl-theanine, is crucial for the beneficial effects attributed to this beverage during sperm storage at room temperature.
Speciation of inorganic chromium in water samples by energy dispersive X-ray fluorescence spectrometry
Authors: Pytlakowska Katarzyna
Published: February 2016

A simple and effective speciation procedure for the determination of inorganic chromium species in water samples was developed.
Aryl and heteroaryl N-[4-[4-(2,3-substituted-phenyl)piperazine-1-yl]alkyl]carbamates with improved physico-chemical properties as dual modulators of dopamine D3 receptor and fatty acid amide hydrolase
Authors: Micoli A. , De Simone A. , Russo D. , Ottonello G. , Colombano G. , Ruda G. F. , Bandiera T. , Cavalli A. , Bottegoni G.
Published: February 2016

Improving the physico-chemical profile of a MTDL series.
Behavior of platinum(iv) complexes in models of tumor hypoxia: cytotoxicity, compound distribution and accumulation
Authors: Schreiber-Brynzak Ekaterina , Pichler Verena , Heffeter Petra , Hanson Buck , Theiner Sarah , Lichtscheidl-Schultz Irene , Kornauth Christoph , Bamonti Luca , Dhery Vineet , Groza Diana , Berry David , Berger Walter , Galanski Mathea S , Jakupec Michael A , Keppler Bernhard K
Published: February 2016

Hypoxia in solid tumors remains a challenge for conventional cancer therapeutics. As a source for resistance, metastasis development and drug bioprocessing, it influences treatment results and disease outcome. Bioreductive platinum(iv) prodrugs might be advantageous over conventional metal-based therapeutics, as biotransformation in a reductive milieu, such as under hypoxia, is required for drug activation. This study deals with a two-step screening of experimental platinum(iv) prodrugs with different rates of reduction and lipophilicity with the aim of identifying the most appropriate compounds for further investigations. In the first step, the cytotoxicity of all compounds was compared in hypoxic multicellular spheroids and monolayer culture using a set of cancer cell lines with different sensitivities to platinum(ii) compounds. Secondly, two selected compounds were tested in hypoxic xenografts in SCID mouse models in comparison to satraplatin, and, additionally, (LA)-ICP-MS-based accumulation and distribution studies were performed for these compounds in hypoxic spheroids and xenografts. Our findings suggest that, while cellular uptake and cytotoxicity strongly correlate with lipophilicity, cytotoxicity under hypoxia compared to non-hypoxic conditions and antitumor activity of platinum(iv) prodrugs are dependent on their rate of reduction.
Plasma-assisted electrolytic synthesis of In(OH)3 nanocubes for thermal transformation into In2O3 nanocubes with a controllable Sn content
Authors: Kim Tae Hyung , Eom Nu Si A. , Kang Sung-Oong , Choa Yong-Ho
Published: February 2016

Single-crystal In(OH)3 nanocubes were synthesized through a novel wet-chemical route of plasma-assisted electrolytic process and further thermally transformed into polycrystalline bixbyite-type c-In2O3 nanocubes with a controlled Sn content.
Engineering oriented hierarchical lamellar structures in SBS/PS blends via a pressure-induced flow field
Authors: Zhang Sen , Feng Xiaoling , Zhu Shu , Wang Shiwei , Wang Da , Gong Yumei , Zhang Hong , An Qingda , Guo Jing , Yu Muhuo
Published: February 2016

A hierarchical layered structure was generated using a polymer blend of polystyrene/poly(styrene–butadiene–styrene). Benefiting from the hierarchical lamellar structure, the resulting strength, stiffness and toughness were simultaneously enhanced.
Highly sensitive electrochemical detection of circulating tumor DNA based on thin-layer MoS2/graphene composites
Authors: Chu Yilan , Cai Bin , Ma Ye , Zhao Minggang , Ye Zhizhen , Huang Jingyun
Published: February 2016

By integrating thin-layer molybdenum disulfide (MoS2) and graphene through a hydrothermal process and an ultrasonic method, a label-free, amplification-free and ultrasensitive circulating tumor DNA electrochemical sensor was made.
Multicolor nanoprobes based on silica-coated gadolinium oxide nanoparticles with highly reduced toxicity
Authors: Atabaev Timur Sh. , Lee Jong Ho , Han Dong-Wook , Choo Ki Seok , Jeon Ung Bae , Hwang Jae Yeon , Yeom Jeong A. , Kang ChulHee , Kim Hyung-Kook , Hwang Yoon-Hwae
Published: February 2016

Multicolor core-shell nanoprobes were developed for molecular imaging of living cells using optical and MRI technique.
Triplet excited state properties in variable gap π-conjugated donor–acceptor–donor chromophores
Authors: Cekli Seda , Winkel Russell W. , Alarousu Erkki , Mohammed Omar F. , Schanze Kirk S.
Published: February 2016

Intersystem crossing in π-conjugated donor–acceptor–donor chromophores is controlled by the strength of the donor–acceptor interaction.
Highly efficient blue thermally activated delayed fluorescent OLEDs with record-low driving voltages utilizing high triplet energy hosts with small singlet–triplet splittings
Authors: Zhang Dongdong , Cai Minghan , Bin Zhengyang , Zhang Yunge , Zhang Deqiang , Duan Lian
Published: February 2016

High-triplet-energy hosts with favorable carrier injection/transporting abilities are realized, endowing efficient blue TADF devices with record-low voltages.
Precious-metal free photoelectrochemical water splitting with immobilised molecular Ni and Fe redox catalysts
Authors: Rosser Timothy E. , Gross Manuela A. , Lai Yi-Hsuan , Reisner Erwin
Published: February 2016

Splitting water into hydrogen and oxygen with 3d transition metal molecular catalysts and light has been accomplished.
Insight into the mechanism and outcoupling enhancement of excimer-associated white light generation
Authors: Chen Ying-Hsiao , Tang Kuo-Chun , Chen Yi-Ting , Shen Jiun-Yi , Wu Yu-Sin , Liu Shih-Hung , Lee Chun-Shu , Chen Chang-Hsuan , Lai Tzu-Yu , Tung Shih-Huang , Jeng Ru-Jong , Hung Wen-Yi , Jiao Min , Wu Chung-Chih , Chou Pi-Tai
Published: February 2016

Fundamental insight into excimer formation ofCz9PhAn, achieving a single-component, high-performance WOLED.
Intrinsic defect processes and O migration in PrBa(Co/Fe)2O5.5
Authors: Akande Salawu Omotayo , Boulfrad Samir , Schwingenschlögl Udo
Published: February 2016

Co → Fe substitution in PrBa(Co/Fe)2O5.5 strongly affects the formation of defects and consequently the O migration.
A general non-CH3NH3X (X = I, Br) one-step deposition of CH3NH3PbX3 perovskite for high performance solar cells
Authors: Zhang Taiyang , Guo Nanjie , Li Ge , Qian Xufang , Li Liang , Zhao Yixin
Published: February 2016

High quality CH3NH3PbI3/CH3NH3PbI2Br perovskite films were facilely deposited by spin coating HI + PbI2/HBr + PbI2 solution in CH3NH2 atmospheres.
Determination of boron in water samples by dispersive liquid–liquid microextraction based on the solidification of a floating organic drop coupled with a fluorimetric method
Authors: Peng Guilong , He Qiang , Li Haifang , Mmereki Daniel , Lu Ying , Zheng Yongzan , Zhong Zhihui , Lin Jin-Ming
Published: February 2016

Dispersive liquid–liquid microextraction based on the solidification of a floating organic drop (DLLME-SFO) prior to fluorescence spectra analysis.
Regioselective iodoamination of terminal ynamides for the synthesis of α-amino-β,β-diiodo-enamides
Authors: Huang Hai , Tang Luning , Han Xiaobo , He Guangke , Xi Yang , Zhu Hongjun
Published: February 2016

We developed the intermolecular iodoamination of terminal ynamides for the synthesis of α-amino-β,β-diiodo-enamides.
Inverted molecular cups: 1-D and 2-D Ag(i) coordination polymers from resorcinarene bis-thiacrowns
Authors: Helttunen Kaisa , Nissinen Maija
Published: February 2016

Exo-cavity binding into resorcinarene based inverted molecular cups creates 1-D and 2-D silver coordination polymers with argentophilic interactions.
Computer simulations of 3C-SiC under hydrostatic and non-hydrostatic stresses
Authors: Guedda H. Z. , Ouahrani T. , Morales-García A. , Franco R. , Salvadó M. A. , Pertierra P. , Recio J. M.
Published: February 2016

Uniaxial [001] stress induces a semiconductor–metal transition in 3C-SiC.
Identifying the redox activity of cation-disordered Li–Fe–V–Ti oxide cathodes for Li-ion batteries
Authors: Chen Ruiyong , Witte Ralf , Heinzmann Ralf , Ren Shuhua , Mangold Stefan , Hahn Horst , Hempelmann Rolf , Ehrenberg Helmut , Indris Sylvio
Published: February 2016

Combined element-sensitive techniques reveal the redox activity of mixed transition metals in cation disordered rock-salt oxide cathodes.
Co@Co3O4 core–shell particle encapsulated N-doped mesoporous carbon cage hybrids as active and durable oxygen-evolving catalysts
Authors: Li Xinzhe , Fang Yiyun , Wen Lixin , Li Feng , Yin Guanlin , Chen Wanmin , An Xingcai , Jin Jun , Ma Jiantai
Published: February 2016

Cobalt-based nanomaterials are promising candidates as efficient, affordable, and sustainable alternative electrocatalysts for the oxygen evolution reaction (OER).
Recent developments in synthetic methods for benzo[b]heteroles
Authors: Wu Bin , Yoshikai Naohiko
Published: February 2016

This review summarizes recent developments in synthetic methods for benzoheterole compounds of significant potential for applications in materials science.
Assembly of substituted phenanthridines via a cascade palladium-catalyzed coupling reaction, deprotection and intramolecular cyclization
Authors: Ge Jun , Wang Xiaojian , Liu Tianqi , Shi Zeyu , Xiao Qiong , Yin Dali
Published: February 2016

A practical method for one-pot synthesis of substituted phenanthridines is described. Via this method, a series of substituted phenanthridines are obtained in good yields with remarkable functional groups compatibility.
Handling and managing bleeding wounds using tissue adhesive hydrogel: a comparative assessment on two different hydrogels
Authors: T Thiruselvi , Raja S Thirupathi Kumara , R Aravindhan , S. K Shanuja , A Gnanamani
Published: February 2016

The present study explores the preparation and a comparative assessment on the physical, mechanical and biological properties of two different tissue adhesive hydrogels (TAHs) for the management of bleeding wounds.
ε-Caprolactone polymerization using titanium complexes immobilized onto silica based materials functionalized with ionic liquids: insights into steric, electronic and support effects
Authors: Cruz Paula , Pérez Yolanda , Hierro Isabel del , Fernández-Galán Rafael , Fajardo Mariano
Published: February 2016

Heterogeneous catalysts comprised of titanium immobilized on silica imidazolium-based systems have been synthesized for the ring opening polymerization of ε-caprolactone.
Small molecule regulated dynamic structural changes of human G-quadruplexes
Authors: Debnath Manish , Ghosh Shirsendu , Panda Deepanjan , Bessi Irene , Schwalbe Harald , Bhattacharyya Kankan , Dash Jyotirmayee
Published: February 2016

A carbazole derivative (BTC) regulates the dynamics of unstructured humanc-MYCandh-TELOsequences by folding them into compact quadruplex structures.
Carbogenic nanodots derived from organo-templated zeolites with modulated full-color luminescence
Authors: Mu Ying , Wang Ning , Sun Zaicheng , Wang Jing , Li Jiyang , Yu Jihong
Published: February 2016

Dual modulated luminescence of carbogenic nanodots derived from zeolites has been acquired by controlling the concentration and pH value of CND aqueous dispersions.
Dopant-free 3,3′-bithiophene derivatives as hole transport materials for perovskite solar cells
Authors: Gong Genfei , Zhao Ning , Ni Debin , Chen Jianyou , Shen Yan , Wang Mingkui , Tu Guoli
Published: February 2016

We report three hole transport materials featuring “X” swivel-cruciform structures for stable perovskite solar cells.
Ternary CuSbSe2 chalcostibite: facile synthesis, electronic-structure and thermoelectric performance enhancement
Authors: Zhang Dan , Yang Junyou , Jiang Qinghui , Fu Liangwei , Xiao Ye , Luo Yubo , Zhou Zhiwei
Published: February 2016

A single phase CuSbSe2 polycrystalline chalcostibite compound has been facilely synthesized through mechanical alloying for the first time, and the phase evolution has been revealed in detail.
Thermoelectric properties of Bi-based Zintl compounds Ca1−xYbxMg2Bi2
Authors: Shuai Jing , Liu Zihang , Kim Hee Seok , Wang Yumei , Mao Jun , He Ran , Sui Jiehe , Ren Zhifeng
Published: February 2016

Bi-based Zintl compounds, Ca1−xYbxMg2Bi2 with the structure of CaAl2Si2, have been successfully prepared by mechanical alloying followed by hot pressing.
Genetic algorithm‐optimised structure of convolutional neural network for face recognition applications
Authors: Rikhtegar Arash , Pooyan Mohammad , Manzuri‐Shalmani Mohammad Taghi
Published: February 2016

Proposing a proper method for face recognition is still a challenging subject in biometric and computer vision applications. Although some reliable systems were introduced under relatively controlled conditions, their recognition rate is not satisfactory in the general settings. This is especially true when there are variations in pose, illumination, and facial expression. To alleviate these problems, a hybrid face recognition system is proposed which benefits from the superiority of both convolutional neural network (CNN) and support vector machine (SVM). To this end, first a genetic algorithm is employed to find the optimum structure of CNN. Then, the performance of the system is improved by replacing the last layer of CNN with an ensemble of SVMs. Finally, using concepts of error correction, decision is made. The potential of CNN as a trainable feature extractor provides a flexible recognition system that can recognise faces with variations in pose and illumination. Simulation results show that the system achieves good recognition rate and is robust against variations in terms of facial expressions, occlusion, noise, and illuminations.
Analysis of electric field influence on buildings under high‐voltage transmission lines
Authors: Tong Ziyuan , Dong Zhaoyang , Ashton Trevor
Published: February 2016

High‐voltage cables especially bare cables generate intense electric fields. Within certain distances, the fields could have strong effects on human health. Since of housing planning factors, it is inevitable that there will be buildings located under bare cables. Whether the intensity of electric field exceeds safety level (5 kV/m at 50 Hz) has been a concern for both land agents and residents. To address the concerns, this study studies the electric field of 500 kV overhead transmission line exerted on building and proposes the scheme for field intensity reduction. The authors study shows that when overhead cable and building are in different relative locations, the maximum intensity and influence range in the window regions can be highly variable, which suggests an optimal building orientation to minimise the electric field generated by overhead transmission lines. They also studied the field distribution in window regions on each floor in two models. The results provide design basis for safe distance between buildings and transmission lines. A shielding scheme for building construction is proposed to reduce the field intensity. Experiment result shows that with shielding on the building roof at a certain angle, the influence of electric field can be effectively reduced.
Arachnoid Cyst with a Non-traumatic Acute Subdural Hematoma in an Eleven-year-old Patient
Authors: Cavasana Gabriel , Mendonça Rodrigo , Zanini Fabricio
Published: February 2016

A non-traumatic intra-cystic hemorrhage in an arachnoid cyst is a rare event, with few cases reported in the literature. We present a case of an eleven-year-old boy patient, which presented a spontaneous acute subdural hematoma and intra-cystic hemorrhage after a strong headache episode. The results were evidenced by a computed tomography (CT) scan and surgical findings. We perform a brief literature review on the arachnoid cyst and its suggested treatments. In our case, the patient underwent a surgical treatment with a complete resolution of the case.
Direct growth of CdSe semiconductor quantum dots in glass matrix by femtosecond laser beam
Authors: Bell G. , Filin A. I. , Romanov D. A. , Levis R. J.
Published: February 2016

Controllable, spatially inhomogeneous distributions of CdSe nanocrystals smaller than the exciton Bohr radius are grown in a glass matrix under combined action of sample heating (below the transformation temperature) and focused high-repetition femtosecond (fs) laser beam. Selective quantum dot precipitation is evidenced by position-dependent absorption and Raman spectra. The particle size is estimated as r=2.1±0.3 nm by comparing the measured absorption and Raman spectra with those obtained from the samples grown in glass by traditional heat-treatment procedure. Direct growth of CdSe quantum dots in glass is enabled by nonlinear excitation using a focused fs duration laser beam (as differentiated from other methods), and this opens an avenue for adjustable selective growth patterns.
Electrostatically defined silicon quantum dots with counted antimony donor implants
Authors: Singh M. , Pacheco J. L. , Perry D. , Garratt E. , Ten Eyck G. , Bishop N. C. , Wendt J. R. , Manginell R. P. , Dominguez J. , Pluym T. , Luhman D. R. , Bielejec E. , Lilly M. P. , Carroll M. S.
Published: February 2016

Deterministic control over the location and number of donors is crucial to donor spin quantum bits (qubits) in semiconductor based quantum computing. In this work, a focused ion beam is used to implant antimony donors in 100 nm × 150 nm windows straddling quantum dots. Ion detectors are integrated next to the quantum dots to sense the implants. The numbers of donors implanted can be counted to a precision of a single ion. In low-temperature transport measurements, regular Coulomb blockade is observed from the quantum dots. Charge offsets indicative of donor ionization are also observed in devices with counted donor implants.
Stability and scalability of piezoelectric flags
Authors: Wang Xiaolin , Alben Silas , Li Chenyang , Young Yin Lu
Published: February 2016

We investigate the effect of piezoelectric material on the flutter speed, vibration mode and frequency, and energy harvesting power and efficiency of a flexible flag in various fluids. We develop a fully coupled fluid-solid-electric model by combining the inviscid vortex sheet model with a linear electro-mechanical coupling model. A resistance only circuit and a resonant resistance-inductance (RL) circuit are considered. For a purely resistive circuit, an increased electro-mechanical coupling factor results in an increased flutter speed, vibration frequency, averaged electric power, and efficiency. A consistent optimal resistance is found that maximizes the flutter speed and the energy harvesting power. For a resonant RL circuit, by tuning the inductance to match the circuit frequency to the flag’s vibration frequency, the flutter speed can be greatly decreased, and a larger averaged power and efficiency are obtained. We also consider a model scale setup with several commonly used commercial materials for operating in air and water. Typical ranges of dimensionless parameters are obtained for four types of material that span a wide range of solid density and rigidity values. We find that the resistance only circuit is more effective when the flag is placed in a lighter fluid (e.g., air), while the RL circuit is able to reduce the flutter speed when the flag is placed in a heavier fluid (e.g., water).
An amorphous-to-crystalline phase transition within thin silicon films grown by ultra-high-vacuum evaporation and its impact on the optical response
Authors: Orapunt Farida , Tay Li-Lin , Lockwood David J. , Baribeau Jean-Marc , Noël Mario , Zwinkels Joanne C. , O'Leary Stephen K.
Published: February 2016

A number of thin silicon films are deposited on crystalline silicon, native oxidized crystalline silicon, and optical quality fused quartz substrates through the use of ultra-high-vacuum evaporation at growth temperatures ranging from 98 to 572 °C. An analysis of their grazing incidence X-ray diffraction and Raman spectra indicates that a phase transition, from amorphous-to-crystalline, occurs as the growth temperature is increased. Through a peak decomposition process, applied to the Raman spectroscopy results, the crystalline volume fractions associated with these samples are plotted as a function of the growth temperature for the different substrates considered. It is noted that the samples grown on the crystalline silicon substrates have the lowest crystallanity onset temperature, whereas those grown on the optical quality fused quartz substrates have the highest crystallanity onset temperature; the samples grown on the native oxidized crystalline silicon substrates have a crystallanity onset temperature between these two limits. These resultant dependencies on the growth temperature provide a quantitative means of characterizing the amorphous-to-crystalline phase transition within these thin silicon films. It is noted that the thin silicon film grown on an optical quality fused quartz substrate at 572 °C, possessing an 83% crystalline volume fraction, exhibits an optical absorption spectrum which is quite distinct from that associated with the other thin silicon films. We suggest that this is due to the onset of sufficient long-range order in the film for wave-vector conservation to apply, at least partially. Finally, we use a semi-classical optical absorption analysis to study how this phase transition, from amorphous-to-crystalline, impacts the spectral dependence of the optical absorption coefficient.
Nonrelativistic limit of standing waves for pseudo-relativistic nonlinear Schrödinger equations
Authors: Choi Woocheol , Seok Jinmyoung
Published: February 2016

In this paper, we study standing waves for pseudo-relativistic nonlinear Schrödinger equations. In the first part, we find ground state solutions. We also prove that they have one sign and are radially symmetric. The second part is devoted to take nonrelativistic limit of the ground state solutions in H1(ℝn) space.
Magnetic phase transition and giant anisotropic magnetic entropy change in TbFeO3 single crystal
Authors: Cao Yiming , Xiang Maolin , Zhao Weiyao , Wang Guohua , Feng Zhenjie , Kang Baojuan , Stroppa Alessandro , Zhang Jincang , Ren Wei , Cao Shixun
Published: February 2016

The magnetocaloric effect (MCE) is an intrinsic property of magnetic materials that enable magnetic refrigeration devices without using the traditional vapour-compression. Temperature sensitive and anisotropic magnetic solids might give rise to a large rotating MCE for building compact and efficient magnetic cooling systems by simply rotating the sample. Here, we report an unprecedented maximal refrigeration capacity of 497.36 J/kg (at 70 kOe) in perovskite TbFeO3 single crystal, resulting from its giant anisotropic magnetic entropy change along a axis. Our paper reveals that interaction between Fe-3d and Tb-4f electrons drives extremely interesting spin reorientation transition, which is highly sensitive to magnetic field and temperature. These findings highlight potential applications of an emerging material for high efficient low temperature magnetic refrigeration, which is compact and quiet, and does not use ozone-depleting coolant gases.
Characteristics of energy exchange between inter- and intramolecular degrees of freedom in crystalline 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) with implications for coarse-grained simulations of shock waves in polyatomic molecular crystals
Authors: Kroonblawd Matthew P. , Sewell Thomas D. , Maillet Jean-Bernard
Published: February 2016

In this report, we characterize the kinetics and dynamics of energy exchange between intramolecular and intermolecular degrees of freedom (DoF) in crystalline 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). All-atom molecular dynamics (MD) simulations are used to obtain predictions for relaxation from certain limiting initial distributions of energy between the intra- and intermolecular DoF. The results are used to parameterize a coarse-grained Dissipative Particle Dynamics at constant Energy (DPDE) model for TATB. Each TATB molecule in the DPDE model is represented as an all-atom, rigid-molecule mesoparticle, with explicit external (molecular translational and rotational) DoF and coarse-grained implicit internal (vibrational) DoF. In addition to conserving linear and angular momentum, the DPDE equations of motion conserve the total system energy provided that particles can exchange energy between their external and internal DoF. The internal temperature of a TATB molecule is calculated using an internal equation of state, which we develop here, and the temperatures of the external and internal DoF are coupled using a fluctuation-dissipation relation. The DPDE force expression requires specification of the input parameter σ that determines the rate at which energy is exchanged between external and internal DoF. We adjusted σ based on the predictions for relaxation processes obtained from MD simulations. The parameterized DPDE model was employed in large-scale simulations of shock compression of TATB. We show that the rate of energy exchange governed by σ can significantly influence the transient behavior of the system behind the shock.
Local structure, composition, and crystallization mechanism of a model two-phase “composite nanoglass”
Authors: Chattopadhyay Soma , Kelly S. D. , Shibata Tomohiro , Balasubramanian M. , Srinivasan S. G. , Du Jincheng , Banerjee Rajarshi , Ayyub Pushan
Published: February 2016

We report a detailed study of the local composition and structure of a model, bi-phasic nanoglass with nominal stoichiometry Cu55Nb45. Three dimensional atom probe data suggest a nanoscale-phase-separated glassy structure having well defined Cu-rich and Nb-rich regions with a characteristic length scale of ≈3 nm. However, extended x-ray absorption fine structure analysis indicates subtle differences in the local environments of Cu and Nb. While the Cu atoms displayed a strong tendency to cluster and negligible structural order beyond the first coordination shell, the Nb atoms had a larger fraction of unlike neighbors (higher chemical order) and a distinctly better-ordered structural environment (higher topological order). This provides the first experimental indication that metallic glass formation may occur due to frustration arising from the competition between chemical ordering and clustering. These observations are complemented by classical as well as ab initio molecular dynamics simulations. Our study indicates that these nanoscale phase-separated glasses are quite distinct from the single phase nanoglasses (studied by Gleiter and others) in the following three respects: (i) they contain at least two structurally and compositionally distinct, nanodispersed, glassy phases, (ii) these phases are separated by comparatively sharp inter-phase boundaries, and (iii) thermally induced crystallization occurs via a complex, multi-step mechanism. Such materials, therefore, appear to constitute a new class of disordered systems that may be called a composite nanoglass.
Surface waves propagating on a turbulent flow
Authors: Gutiérrez Pablo , Aumaître Sébastien
Published: February 2016

We study the propagation of monochromatic surface waves on a turbulent flow of liquid metal, when the waves are much less energetic than the background flow. Electromagnetic forcing drives quasi-two-dimensional turbulence with strong vertical vorticity. To isolate the surface-wave field, we remove the surface deformation induced by the background turbulent flow using coherent-phase averaging at the wave frequency. We observe a significant increase in wavelength, when the latter is smaller than the forcing length scale. This phenomenon has not been reported before and can be explained by multiple random wave deflections induced by the turbulent velocity gradients. The shift in wavelength thus provides an estimate of the fluctuations in deflection angle. Local measurements of the wave frequency far from the wavemaker do not reveal such systematic behavior, although a small shift is visible. Finally, we quantify the damping enhancement induced by the turbulent flow and compare it to the existing theoretical predictions. Most of them suggest that the damping increases as the square of the Froude number, whereas our experimental data show a linear increase with the Froude number. We interpret this linear relationship as a balance between the time for a wave to cross a turbulent structure and the turbulent mixing time. The larger the ratio of these two times, the more energy is extracted from the wave. We conclude with possible mechanisms for energy exchange.
Direct numerical simulation of the flow around an aerofoil in ramp-up motion
Authors: Rosti Marco E. , Omidyeganeh Mohammad , Pinelli Alfredo
Published: February 2016

A detailed analysis of the flow around a NACA0020 aerofoil at Rec = 2 × 104 undergoing a ramp up motion has been carried out by means of direct numerical simulations. During the manoeuvre, the angle of attack is linearly varied in time between 0° and 20° with a constant rate of change of α̇rad=0.12U∞/c. When the angle of incidence has reached the final value, the lift experiences a first overshoot and then suddenly decreases towards the static stall asymptotic value. The transient instantaneous flow is dominated by the generation and detachment of the dynamic stall vortex, a large scale structure formed by the merging of smaller scales vortices generated by an instability originating at the trailing edge. New insights on the vorticity dynamics leading to the lift overshoot, lift crisis, and the damped oscillatory cycle that gradually matches the steady condition are discussed using a number of post-processing techniques. These include a detailed analysis of the flow ensemble average statistics and coherent structures identification carried out using the Q-criterion and the finite-time Lyapunov exponent technique. The results are compared with the one obtained in a companion simulation considering a static stall condition at the final angle of incidence α = 20°.
Droplet spreading on rough surfaces: Tackling the contact line boundary condition
Authors: Chamakos Nikolaos T. , Kavousanakis Michail E. , Boudouvis Andreas G. , Papathanasiou Athanasios G.
Published: February 2016

The complicated dynamics of the contact line of a moving droplet on a solid substrate often hamper the efficient modeling of microfluidic systems. In particular, the selection of the effective boundary conditions, specifying the contact line motion, is a controversial issue since the microscopic physics that gives rise to this displacement is still unknown. Here, a sharp interface, continuum-level, novel modeling approach, accounting for liquid/solid micro-scale interactions assembled in a disjoining pressure term, is presented. By following a unified conception (the model applies both to the liquid/solid and the liquid/ambient interfaces), the friction forces at the contact line, as well as the dynamic contact angle are derived implicitly as a result of the disjoining pressure and viscous effects interplay in the vicinity of the substrate’s intrinsic roughness. Previous hydrodynamic model limitations, of imposing the contact line boundary condition to an unknown number and reconfigurable contact lines, when modeling the spreading dynamics on textured substrates, are now overcome. The validity of our approach is tested against experimental data of a droplet impacting on a horizontal solid surface. The study of the early spreading stage on hierarchically structured and chemically patterned solid substrates reveal an inertial regime where the contact radius grows according to a universal power law, perfectly agreeing with recently published experimental findings.
Up- and downstream sheaths in an ion-beam-plasma system
Authors: Wei Zi-an , Ma J. X.
Published: February 2016

Ion sheaths formed in the up- and downstream sides of a negatively biased metal plate/mesh in an ion-beam-background-plasma system were experimentally investigated in a double plasma device. Measured potential profiles near the plate exhibit asymmetric structure, showing thicker sheath in the downstream side. The presence of the ion beam causes the shrink of the sheaths on both sides. The sheath thickness decreases with the increase of beam energy and density. Furthermore, the sheaths near the mesh are substantially thinner than that near the plate because of the partial transmission of the mesh to the ions. In addition, the increase of neutral gas pressure leads to the reduction of the beam energy and density, resulting in the increase of the sheath thickness.
Rayleigh-Taylor instability in non-uniform magnetized rotating strongly coupled viscoelastic fluid
Authors: Prajapati R. P.
Published: February 2016

The Rayleigh-Taylor instability (RTI) in an incompressible strongly coupled viscoelastic fluid is investigated considering the effects of inhomogeneous magnetic field, density gradient, and uniform rotation. The generalized hydrodynamic equations have been formulated, and linear dispersion relation is derived taking appropriate density and magnetic field profiles for the considered system. The gravity induced stable and unstable configurations of RTI are analyzed in hydrodynamic and kinetic limits. In the kinetic limit, shear wave modified dispersion relation and the condition of RTI are derived in terms of magnetic-viscoelastic Mach number and viscoelastic Froude number. The criteria of RTI and critical wavenumber for the growth of RTI to be unstable are estimated numerically for white dwarf and inertial confinement fusion target. It is observed that magnetic field, rotation, and viscoelastic effects play a significant role in the suppression of RTI in these systems. The stabilizing influence of magnetic field, rotation, and magnetic-viscoelastic Mach number while the destabilizing influence of viscoelastic Froude on the growth rate of RTI number is observed graphically. The growth rate of RTI decreases faster in kinetic limit as compared to the hydrodynamic limit.
Large eddy simulation predictions of absolutely unstable round hot jet
Authors: Boguslawski A. , Tyliszczak A. , Wawrzak K.
Published: February 2016

The paper presents a novel view on the absolute instability phenomenon in heated variable density round jets. As known from literature the global instability mechanism in low density jets is released when the density ratio is lower than a certain critical value. The existence of the global modes was confirmed by an experimental evidence in both hot and air-helium jets. However, some differences in both globally unstable flows were observed concerning, among others, a level of the critical density ratio. The research is performed using the Large Eddy Simulation (LES) method with a high-order numerical code. An analysis of the LES results revealed that the inlet conditions for the velocity and density distributions at the nozzle exit influence significantly the critical density ratio and the global mode frequency. Two inlet velocity profiles were analyzed, i.e., the hyperbolic tangent and the Blasius profiles. It was shown that using the Blasius velocity profile and the uniform density distribution led to a significantly better agreement with the universal scaling law for global mode frequency.
Shock interaction with deformable particles using a constrained interface reinitialization scheme
Authors: Sridharan P. , Jackson T. L. , Zhang J. , Balachandar S. , Thakur S.
Published: February 2016

In this paper, we present axisymmetric numerical simulations of shock propagation in nitromethane over an aluminum particle for post-shock pressures up to 10 GPa. We use the Mie-Gruneisen equation of state to describe both the medium and the particle. The numerical method is a finite-volume based solver on a Cartesian grid, that allows for multi-material interfaces and shocks, and uses a novel constrained reinitialization scheme to precisely preserve particle mass and volume. We compute the unsteady inviscid drag coefficient as a function of time, and show that when normalized by post-shock conditions, the maximum drag coefficient decreases with increasing post-shock pressure. We also compute the mass-averaged particle pressure and show that the observed oscillations inside the particle are on the particle-acoustic time scale. Finally, we present simplified point-particle models that can be used for macroscale simulations. In the Appendix, we extend the isothermal or isentropic assumption concerning the point-force models to non-ideal equations of state, thus justifying their use for the current problem.
Metal-insulator-metal metamaterial absorbers consisting of proximity-coupled resonators with the control of the fundamental and the second-order frequencies
Authors: Ito Kota , Toshiyoshi Hiroshi , Iizuka Hideo
Published: February 2016

Metal-insulator-metal metamaterial thermal emitters or absorbers have been widely investigated, and the fundamental and higher-order modes are generally excited in these metamaterial resonators. In this paper, we propose a methodology to widen the frequency interval between the fundamental and the second-order modes by enhancing coupling between resonators in close-proximity. At the second-order mode, antiparallel magnetic fields are excited in the insulating layer of rectangular resonators. A diagonal arrangement of rectangles allows destructive interaction between neighboring resonators, resulting in higher second-order frequency. The maximum frequency interval between the two modes is achieved when resonators are shifted by half a period. Furthermore, we suggest a possibility to split the second-order mode by adjusting the arrangement of rectangles. Measured reflection spectra of fabricated metamaterial absorbers agree well with numerical simulations.
Electron trapping mechanisms in magnetron injection guns
Authors: Pagonakis Ioannis Gr. , Piosczyk Bernhard , Zhang Jianhua , Illy Stefan , Rzesnicki Tomasz , Hogge Jean-Philippe , Avramidis Konstantinos , Gantenbein Gerd , Thumm Manfred , Jelonnek John
Published: February 2016

A key parameter for the gyrotron operation and efficiency is the presence of trapped electrons. Two electron trapping mechanisms can take place in gyrotrons: (i) the adiabatic trap and (ii) the magnetic potential well. Their influence on the gyrotron operation is analyzed. Two gun design criteria are then proposed to suppress both mechanisms in order to minimize the risk of possible problems. Experimental results of three high power gyrotrons are presented and their performance is correlated to the presence of populations of trapped electrons. Finally, some very general gun design principles are presented for the limitation of harmful electron trapping.
Superconducting proximity effect in NiBi3-Ni-NiBi3 trilayer system with sharp superconductor-ferromagnet boundaries
Authors: Siva Vantari , Pradhan Paresh C. , Santosh Babu G. , Nayak Maheswar , Sahoo Pratap K. , Senapati Kartik
Published: February 2016

We have studied the superconducting proximity effect in a series of e-beam evaporated Bi-Ni-Bi trilayers, where diffusion of Bi into Ni spontaneously formed superconducting NiBi3 layers at both Ni-Bi interfaces, effectively resulting in superconductor-ferromagnet-superconductor (S-F-S) trilayers. The thickness of top and bottom superconducting layers was found to be different with slightly different transition temperatures. Both resistive transition temperatures in the series of S-F-S trilayers showed 0-π crossover as a function of ferromagnetic Ni thickness. The zero bias conductance calculated from the in-plane current-voltage measurements also confirmed the 0-π crossovers. The possibility of proximity effect in the superconducting fluctuation regime, above transition temperature, was investigated via in-plane magneto-transport measurements at 4 K. We observed clear modulations in magneto-resistance (MR) and in low-field MR-hysteresis at 4 K, in contrast to their monotonic behavior at 10 K. Although the period of these modulations was commensurate with the observed periodicity of 0-π crossovers, the nature of these modulations was found to be the same in both 0 and π regimes. This observation suggested that in the superconducting fluctuation regime the apparent modulations of MR and MR-hysteresis were due to the variations in densities of superconducting fluctuations in individual NiBi3 layers, and not due to the proximity coupling between the superconducting layers.