Crystallization Mechanism and Phase Transition Properties of W-doped VO2 Synthesized by Hydrothermal Method

Directory of Open Access Journals (Sweden)

LI Yao

2017-11-01

Full Text Available VO2 sol was firstly prepared using vanadyl sulfate as a vanadium source by precipitation-peptization method. Then tungsten(W doping vanadium dioxide(W-VO2 was prepared by hydrothermal crystallization of prepared sol with the presence of ammonium metatungstate. The morphologies, crystal structure of the as-prepared samples and phase transition properties were studied by X-ray diffraction(XRD, field emission scanning electron microscope(FESEMand differential scanning calorimetry(DSC analysis. The results indicate that rod-like W-VO2(B crystal with length of 1-2μm and radius of 100-200nm is firstly formed during hydrothermal treatment for 4-48h at 280℃, then the rod-like crystal dissolves gradually and sheet-like or snowflake-like crystal is formed with the phase transition from W-VO2(B to W-VO2(M and eventually, the W-VO2(M crystals can further grow up while the W-VO2(B gradually dissolves; the phase transition temperature of VO2 decreases with the increase in W doping content, and the phase transition temperature of W-VO2(M reduces to about 28℃ when the nominal dopant concentration is 6.0%(atom fraction.The "nucleation-growth-transformation-ripening" mechanism is proposed as the formation mechanism based on the hydrothermal crystallization and morphological evolution process of W-VO2(M.

Active terahertz metamaterials based on the phase transition of VO{sub 2} thin films

Energy Technology Data Exchange (ETDEWEB)

Kim, H., E-mail: heungsoo.kim@nrl.navy.mil [Materials Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 (United States); Charipar, N. [Materials Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 (United States); Breckenfeld, E. [National Research Council Fellow at the Naval Research Laboratory, Washington, DC 20375 (United States); Rosenberg, A. [NOVA Research, Inc., Alexandria, VA 22308 (United States); Piqué, A. [Materials Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 (United States)

2015-12-01

Vanadium dioxide (VO{sub 2}) thin films were prepared on single crystal sapphire substrates by pulsed laser deposition. VO{sub 2} films exhibited a significant resistivity drop (> 10{sup 4} Ω-cm) and large optical transmittance change (> 60%) in the near-infrared region across their semiconductor-to-metal transition. Hybrid metamaterial devices designed for the THz frequency regime were fabricated by combining double split-ring resonators (SRRs) with phase changing VO{sub 2} films. By changing the conductivity of VO{sub 2} via temperature, the behavior of the SRR gap was adjusted from capacitive to resistive in order to modulate the THz beam transmission at their resonance frequencies. A modulation efficiency greater than 50% was achieved at the magnetic resonance frequencies (0.3 THz and 0.7 THz) in these hybrid SRR–VO{sub 2} metamaterial devices. - Highlights: • Pulsed laser deposition of phase changing VO{sub 2} thin films • Hybrid metamaterial devices composed of split-ring resonators and phase changing VO{sub 2} • Tunable THz transmission with a modulation efficiency over 50%.

LiVO/sub 3/-Li/sub 2/Mo(W)O/sub 4/ and NaVO/sub 3/-Na/sub 2/Cr(Mo)O/sub 4/ systems

Energy Technology Data Exchange (ETDEWEB)

Belyaev, I N; Lupeiko, T G; Vyalikova, V I [Rostovskij-na-Donu Gosudarstvennyj Univ. (USSR)

1975-09-01

The systems LiVO/sub 3/-Li/sub 2/MoO/sub 4/, LiVO/sub 3/-Li/sub 2/WO/sub 4/, NaNO/sub 3/-Na/sub 2/CrO/sub 4/, NaNO/sub 3/-Na/sub 2/MoO/sub 4/ were studied with thermographic and partially visual polythermal methods of physical and chemical analyses. Except NaVO/sub 3/-Na/sub 2/MoO/sub 4/ all investigated systems are eutectic ones with limited solid solutions on the basis of some component; the eutectics melt at 542, 544, 550/sup 0/C and contain 25, 20 and 26% of Li/sub 2/MoO/sub 4/, Li/sub 2/WO/sub 4/ and Na/sub 2/CrO/sub 4/ respectively. The system NaNO/sub 3/-Na/sub 2/MoO/sub 4/ contains compound 18 NaVO/sub 3/.11Na/sub 2/MoO/sub 4/ congruently melting at 570/sup 0/C. Two eutectics of the system have melting points at 542 and 548/sup 0/C and contain 47 and 67% of Na/sub 2/MoO/sub 4/.

Max Weber, educación para las ciencias y formación democrática

Directory of Open Access Journals (Sweden)

Javier Benito Seoane Cobas

2010-04-01

Full Text Available El ensayo explora la relación que hay entre la educación para las ciencias y la educación para la democracia en el pensamiento de Max Weber, un problema no tratado por el sociólogo de Erfurt. Ello se realiza a partir del análisis del plano epistemológico y del análisis sobre la ética del científico de Weber. Al final, se elaboran dos interpretaciones razonables sobre el objeto del ensayo y se selecciona una de las mismas sobre la base de una apuesta pluralista.

SnO2@C@VO2 Composite Hollow Nanospheres as an Anode Material for Lithium-Ion Batteries.

Science.gov (United States)

Guo, Wenbin; Wang, Yong; Li, Qingyuan; Wang, Dongxia; Zhang, Fanchao; Yang, Yiqing; Yu, Yang

2018-05-02

Porous SnO 2 @C@VO 2 composite hollow nanospheres were ingeniously constructed through the combination of layer-by-layer deposition and redox reaction. Moreover, to optimize the electrochemical properties, SnO 2 @C@VO 2 composite hollow nanospheres with different contents of the external VO 2 were also studied. On the one hand, the elastic and conductive carbon as interlayer in the SnO 2 @C@VO 2 composite can not only buffer the huge volume variation during repetitive cycling but also effectively improve electronic conductivity and enhance the utilizing rate of SnO 2 and VO 2 with high theoretical capacity. On the other hand, hollow nanostructures of the composite can be consolidated by the multilayered nanocomponents, resulting in outstanding cyclic stability. In virtue of the above synergetic contribution from individual components, SnO 2 @C@VO 2 composite hollow nanospheres exhibit a large initial discharge capacity (1305.6 mAhg -1 ) and outstanding cyclic stability (765.1 mAhg -1 after 100 cycles). This design of composite hollow nanospheres may be extended to the synthesis of other nanomaterials for electrochemical energy storage.

VV and VO2 defects in silicon studied with hybrid density functional theory

KAUST Repository

Christopoulos, Stavros Richard G

2014-12-07

The formation of VO (A-center), VV and VO2 defects in irradiated Czochralski-grown silicon (Si) is of technological importance. Recent theoretical studies have examined the formation and charge states of the A-center in detail. Here we use density functional theory employing hybrid functionals to analyze the formation of VV and VO2 defects. The formation energy as a function of the Fermi energy is calculated for all possible charge states. For the VV and VO2 defects double negatively charged and neutral states dominate, respectively.

Phase coexistence in the metal-insulator transition of a VO2 thin film

International Nuclear Information System (INIS)

Chang, Y.J.; Koo, C.H.; Yang, J.S.; Kim, Y.S.; Kim, D.H.; Lee, J.S.; Noh, T.W.; Kim, Hyun-Tak; Chae, B.G.

2005-01-01

Vanadium dioxide (VO 2 ) shows a metal-insulator transition (MIT) near room temperature, accompanied by an abrupt resistivity change. Since the MIT of VO 2 is known to be a first order phase transition, it is valuable to check metallic and insulating phase segregation during the MIT process. We deposited (100)-oriented epitaxial VO 2 thin films on R-cut sapphire substrates. From the scanning tunneling spectroscopy (STS) spectra, we could distinguish metallic and insulating regions by probing the band gap. Optical spectroscopic analysis also supported the view that the MIT in VO 2 occurs through metal and insulator phase coexistence

Uncommon potential hysteresis in the Li/Li2xVO(H2-xPO4)2 (0 ≤ x ≤ 2) system

International Nuclear Information System (INIS)

Dubarry, M.; Gaubicher, J.; Guyomard, D.; Wallez, G.; Quarton, M.; Baehtz, C.

2008-01-01

Physical and electrochemical investigations of vanadium phosphates, Li 2x VO(H 2-x PO 4 ) 2 (0 + /Li + ionic exchange from VO(H 2 PO 4 ) 2 to Li 2 VO(HPO 4 ) 2 leads to grain decrepitation. Further ionic exchange toward formation of Li 4 VO(PO 4 ) 2 lowers the symmetry. As inferred from potentiodynamic cycling correlated to ex situ and in situ X-ray diffraction (XRD), the system Li/Li 4 VO(PO 4 ) 2 shows several phase transformations that are associated with thermodynamical potential hysteresis that span from roughly 15 mV to more than 1.8 V. Small hysteresis are associated with topotactic reactions and with V V /V IV and V III /V II redox couples. Large potential hysteresis values (>1 V) were observed when oxidation of V III to V IV is involved

C=C bond cleavage on neutral VO3(V2O5)n clusters.

Science.gov (United States)

Dong, Feng; Heinbuch, Scott; Xie, Yan; Bernstein, Elliot R; Rocca, Jorge J; Wang, Zhe-Chen; Ding, Xun-Lei; He, Sheng-Gui

2009-01-28

The reactions of neutral vanadium oxide clusters with alkenes (ethylene, propylene, 1-butene, and 1,3-butadiene) are investigated by experiments and density function theory (DFT) calculations. Single photon ionization through extreme ultraviolet radiation (EUV, 46.9 nm, 26.5 eV) is used to detect neutral cluster distributions and reaction products. In the experiments, we observe products (V(2)O(5))(n)VO(2)CH(2), (V(2)O(5))(n)VO(2)C(2)H(4), (V(2)O(5))(n)VO(2)C(3)H(4), and (V(2)O(5))(n)VO(2)C(3)H(6), for neural V(m)O(n) clusters in reactions with C(2)H(4), C(3)H(6), C(4)H(6), and C(4)H(8), respectively. The observation of these products indicates that the C=C bonds of alkenes can be broken on neutral oxygen rich vanadium oxide clusters with the general structure VO(3)(V(2)O(5))(n=0,1,2...). DFT calculations demonstrate that the reaction VO(3) + C(3)H(6) --> VO(2)C(2)H(4) + H(2)CO is thermodynamically favorable and overall barrierless at room temperature. They also provide a mechanistic explanation for the general reaction in which the C=C double bond of alkenes is broken on VO(3)(V(2)O(5))(n=0,1,2...) clusters. A catalytic cycle for alkene oxidation on vanadium oxide is suggested based on our experimental and theoretical investigations. The reactions of V(m)O(n) with C(6)H(6) and C(2)F(4) are also investigated by experiments. The products VO(2)(V(2)O(5))(n)C(6)H(4) are observed for dehydration reactions between V(m)O(n) clusters and C(6)H(6). No product is detected for V(m)O(n) clusters reacting with C(2)F(4). The mechanisms of the reactions between VO(3) and C(2)F(4)/C(6)H(6) are also investigated by calculations at the B3LYP/TZVP level.

Selective scanning tunneling microscope light emission from rutile phase of VO2.

Science.gov (United States)

Sakai, Joe; Kuwahara, Masashi; Hotsuki, Masaki; Katano, Satoshi; Uehara, Yoichi

2016-09-28

We observed scanning tunneling microscope light emission (STM-LE) induced by a tunneling current at the gap between an Ag tip and a VO2 thin film, in parallel to scanning tunneling spectroscopy (STS) profiles. The 34 nm thick VO2 film grown on a rutile TiO2 (0 0 1) substrate consisted of both rutile (R)- and monoclinic (M)-structure phases of a few 10 nm-sized domains at room temperature. We found that STM-LE with a certain photon energy of 2.0 eV occurs selectively from R-phase domains of VO2, while no STM-LE was observed from M-phase. The mechanism of STM-LE from R-phase VO2 was determined to be an interband transition process rather than inverse photoemission or inelastic tunneling processes.

Integrating the IA2 Astronomical Archive in the VO: The VO-Dance Engine

Science.gov (United States)

Molinaro, M.; Laurino, O.; Smareglia, R.

2012-09-01

Virtual Observatory (VO) protocols and standards are getting mature and the astronomical community asks for astrophysical data to be easily reachable. This means data centers have to intensify their efforts to provide the data they manage not only through proprietary portals and services but also through interoperable resources developed on the basis of the IVOA (International Virtual Observatory Alliance) recommendations. Here we present the work and ideas developed at the IA2 (Italian Astronomical Archive) data center hosted by the INAF-OATs (Italian Institute for Astrophysics - Trieste Astronomical Observatory) to reach this goal. The core point is the development of an application that from existing DB and archive structures can translate their content to VO compliant resources: VO-Dance (written in Java). This application, in turn, relies on a database (potentially DBMS independent) to store the translation layer information of each resource and auxiliary content (UCDs, field names, authorizations, policies, etc.). The last token is an administrative interface (currently developed using the Django python framework) to allow the data center administrators to set up and maintain resources. This deployment, platform independent, with database and administrative interface highly customizable, means the package, when stable and easily distributable, can be also used by single astronomers or groups to set up their own resources from their public datasets.

Progressive recruitment of muscle fibers is not necessary for the slow component of VO2 kinetics.

Science.gov (United States)

Zoladz, Jerzy A; Gladden, L Bruce; Hogan, Michael C; Nieckarz, Zenon; Grassi, Bruno

2008-08-01

The "slow component" of O2 uptake (VO2) kinetics during constant-load heavy-intensity exercise is traditionally thought to derive from a progressive recruitment of muscle fibers. In this study, which represents a reanalysis of data taken from a previous study by our group (Grassi B, Hogan MC, Greenhaff PL, Hamann JJ, Kelley KM, Aschenbach WG, Constantin-Teodosiu D, Gladden LB. J Physiol 538: 195-207, 2002) we evaluated the presence of a slow component-like response in the isolated dog gastrocnemius in situ (n=6) during 4 min of contractions at approximately 60-70% of peak VO2. In this preparation all muscle fibers are maximally activated by electrical stimulation from the beginning of the contraction period, and no progressive recruitment of fibers is possible. Muscle VO2 was calculated as blood flow multiplied by arteriovenous O2 content difference. The muscle fatigued (force decreased by approximately 20-25%) during contractions. Kinetics of adjustment were evaluated for 1) VO2, uncorrected for force development; 2) VO2 normalized for peak force; 3) VO2 normalized for force-time integral. A slow component-like response, described in only one muscle out of six when uncorrected VO2 was considered, was observed in all muscles when VO2/peak force and VO2/force-time were considered. The amplitude of the slow component-like response, expressed as a fraction of the total response, was higher for VO2/peak force (0.18+/-0.06, means+/-SE) and for VO2/force-time (0.22+/-0.05) compared with uncorrected VO2 (0.04+/-0.04). A progressive recruitment of muscle fibers may not be necessary for the development of the slow component of VO2 kinetics, which may be caused by the metabolic factors that induce muscle fatigue and, as a consequence, reduce the efficiency of muscle contractions.

Epitaxial growth and electronic structure of oxyhydride SrVO{sub 2}H thin films

Energy Technology Data Exchange (ETDEWEB)

Katayama, Tsukasa; Chikamatsu, Akira, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp; Yamada, Keisuke; Onozuka, Tomoya [Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Shigematsu, Kei [Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa 213-0012 (Japan); Minohara, Makoto; Kumigashira, Hiroshi [Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Ikenaga, Eiji [Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, Mikazuki-cho, Hyogo 679-5198 (Japan); Hasegawa, Tetsuya [Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa 213-0012 (Japan)

2016-08-28

Oxyhydride SrVO{sub 2}H epitaxial thin films were fabricated on SrTiO{sub 3} substrates via topotactic hydridation of oxide SrVO{sub 3} films using CaH{sub 2}. Structural and composition analyses suggested that the SrVO{sub 2}H film possessed one-dimensionally ordered V-H{sup −}-V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO{sub 2}H film was reversible to SrVO{sub 3} by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurements revealed the V{sup 3+} valence state in the SrVO{sub 2}H film, indicating that the hydrogen existed as hydride. Furthermore, the electronic density of states was highly suppressed at the Fermi energy, consistent with the prediction that tetragonal distortion induces metal to insulation transition.

Control of room-temperature defect-mediated ferromagnetism in VO{sub 2} films

Energy Technology Data Exchange (ETDEWEB)

Yang, Tsung-Han, E-mail: tyang3@ncsu.edu [NSF Center for Advanced Materials and Smart Structures, Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7907 (United States); Nori, Sudhakar; Mal, Siddhartha; Narayan, Jagdish [NSF Center for Advanced Materials and Smart Structures, Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7907 (United States)

2011-09-15

We report interesting ferromagnetic properties and their control in a vanadium-based oxide system driven by stoichiometric defects. Vanadium oxide (VO{sub 2}) thin films were grown on c-plane sapphire substrates by a pulsed laser deposition technique under different ambient conditions. The ferromagnetism of the epitaxial VO{sub 2} films can be switched on and off by altering the cooling ambient parameters. In addition, the saturated magnetic moments and coercivity of the VO{sub 2} films were found to be a function of the oxygen partial pressure during the growth process. The room-temperature ferromagnetic properties of VO{sub 2} films were correlated with the nature of the microstructure and the growth parameters. The origin of the induced magnetic properties are qualitatively understood to stem from intrinsic structural and stoichiometric defects.

Transmission of reactive pulsed laser deposited VO{sub 2} films in the THz domain

Energy Technology Data Exchange (ETDEWEB)

Émond, Nicolas; Hendaoui, Ali; Ibrahim, Akram; Al-Naib, Ibraheem; Ozaki, Tsuneyuki; Chaker, Mohamed, E-mail: chaker@emt.inrs.ca

2016-08-30

Highlights: • Synthesis of vanadium dioxide (VO{sub 2}) thin films as a function of oxygen pressure (2–25 mTorr) using Reactive Pulsed Laser Deposition (RPLD). • Characterization of RPLD-grown VO{sub 2} thin films in the THz frequency range. • THz switches and/or sensors require VO{sub 2} films deposited at low oxygen pressure (i.e. low transition temperature, large amplitude contrast of THz transmission, narrow hysteresis width). • THz optical memory applications require VO{sub 2} films deposited at high oxygen pressure (broad hysteresis width). - Abstract: This work reports on the characteristics of the insulator-to-metal transition (IMT) of reactive pulsed laser deposited vanadium dioxide (VO{sub 2}) films in the terahertz (THz) frequency range, namely the transition temperature T{sub IMT}, the amplitude contrast of the THz transmission over the IMT ΔA, the transition sharpness ΔT and the hysteresis width ΔH. XRD analysis shows the sole formation of VO{sub 2} monoclinic structure with an enhancement of (011) preferential orientation when varying the O{sub 2} pressure (P{sub O2}) during the deposition process from 2 to 25 mTorr. THz transmission measurements as a function of temperature reveal that VO{sub 2} films obtained at low P{sub O2} exhibit low T{sub IMT}, large ΔA, and narrow ΔH. Increasing P{sub O2} results in VO{sub 2} films with higher T{sub IMT}, smaller ΔA, broader ΔH and asymmetric hysteresis loop. The good control of the VO{sub 2} IMT features in the THz domain could be further exploited for the development of advanced smart devices, such as ultrafast switches, modulators, memories and sensors.

Gate-tunable gigantic lattice deformation in VO2

International Nuclear Information System (INIS)

Okuyama, D.; Hatano, T.; Nakano, M.; Takeshita, S.; Ohsumi, H.; Tardif, S.; Shibuya, K.; Yumoto, H.; Koyama, T.; Ohashi, H.; Takata, M.; Kawasaki, M.; Tokura, Y.; Iwasa, Y.; Arima, T.

2014-01-01

We examined the impact of electric field on crystal lattice of vanadium dioxide (VO 2 ) in a field-effect transistor geometry by in-situ synchrotron x-ray diffraction measurements. Whereas the c-axis lattice parameter of VO 2 decreases through the thermally induced insulator-to-metal phase transition, the gate-induced metallization was found to result in a significant increase of the c-axis length by almost 1% from that of the thermally stabilized insulating state. We also found that this gate-induced gigantic lattice deformation occurs even at the thermally stabilized metallic state, enabling dynamic control of c-axis lattice parameter by more than 1% at room temperature

A maximal cycle test with good validity and high repeatability in adults of all ages

DEFF Research Database (Denmark)

Eriksen, L; Tolstrup, J S; Larsen, Steen

2014-01-01

indirectly in both tests and measured directly in one test. Agreement between the direct measurement and the indirect estimate of VO2max and repeatability of the indirect estimates of VO2max were examined by Bland-Altman plots, limits of agreement (LOA) and coefficient of repeatability (CR). The indirect...... method (mean VO2max=3 132 ml · min(-1)) underestimated VO2max as compared to the direct method (mean VO2max=3 190 ml · min(-1)) in men (bias: 58 ml · min(-1) (95% LOA-450 and 565)) and overestimated VO2max in women (mean VO2max=2 328 vs. 2 258 ml · min(-1), bias: - 70 ml · min(-1) (95% LOA-468 and 328...

Lithiation-driven structural transition of VO2F into disordered rock-salt LixVO2F

Czech Academy of Sciences Publication Activity Database

Chen, R.; Maawad, E.; Knapp, M.; Ren, S.; Beran, Přemysl; Witter, R.; Hempelmann, R.

2016-01-01

Roč. 6, č. 69 (2016), s. 65112-65118 ISSN 2046-2069 R&D Projects: GA MŠk(CZ) LM2011019 EU Projects: European Commission(XE) 283883 - NMI3-II Institutional support: RVO:61389005 Keywords : Li- Ion batteries * rechargeble lithium batteries * VO2F Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.108, year: 2016

The acidic transformed nano-VO2 causes macrophage cell death by the induction of lysosomal membrane permeabilization and Ca2+ efflux

Directory of Open Access Journals (Sweden)

Shaohai Xu

2015-01-01

Full Text Available Because of its outstanding thermochromic characteristics and metal-insulator transition (MIT property, nano-vanadium dioxide (abbreviated as nano-VO2 or nVO2 has been applied widely in electrical/optical devices and design of intelligent window. However, the biological effect of nVO2 is not well understood, especially when affected by environmental factors or living organisms. For VO2 is an amphoteric oxide, we simulated pH's influence to nVO2’s physicochemical properties by exposure nVO2 in water of different pH values. We found that nVO2 transformed to a new product after exposure in acidic water for two weeks, as revealed by physicochemical characterization such as SEM, TEM, XRD, and DLS. This transformation product formed in acidic water was referred as (acidic transformed nVO2. Both pristine/untransformed and transformed nVO2 displayed no obvious toxicity to common epithelial cells; however, the acidic transformed nVO2 rapidly induced macrophage cell death. Further investigation demonstrated that transformed nVO2 caused macrophage apoptosis by the induction of Ca2+ efflux and the following mitochondrial membrane permeabilization (MMP process. And a more detailed time course study indicated that transformed nVO2 caused lysosomal membrane permeabilization (LMP at the earlier stage, indicating LMP could be chosen as an earlier and sensitive end point for nanotoxicological study. We conclude that although nVO2 displays no acute toxicity, its acidic transformation product induces macrophage apoptosis by the induction of LMP and Ca2+ efflux. This report suggests that the interplay with environmental factors or living organisms can results in physicochemical transformation of nanomaterials and the ensuing distinctive biological effects.

Insulator-metal transition in substrate-independent VO2 thin film for phase-change devices.

Science.gov (United States)

Taha, Mohammad; Walia, Sumeet; Ahmed, Taimur; Headland, Daniel; Withayachumnankul, Withawat; Sriram, Sharath; Bhaskaran, Madhu

2017-12-20

Vanadium has 11 oxide phases, with the binary VO 2 presenting stimuli-dependent phase transitions that manifest as switchable electronic and optical features. An elevated temperature induces an insulator-to-metal transition (IMT) as the crystal reorients from a monoclinic state (insulator) to a tetragonal arrangement (metallic). This transition is accompanied by a simultaneous change in optical properties making VO 2 a versatile optoelectronic material. However, its deployment in scalable devices suffers because of the requirement of specialised substrates to retain the functionality of the material. Sensitivity to oxygen concentration and larger-scale VO 2 synthesis have also been standing issues in VO 2 fabrication. Here, we address these major challenges in harnessing the functionality in VO 2 by demonstrating an approach that enables crystalline, switchable VO 2 on any substrate. Glass, silicon, and quartz are used as model platforms to show the effectiveness of the process. Temperature-dependent electrical and optical characterisation is used demonstrating three to four orders of magnitude in resistive switching, >60% chromic discrimination at infrared wavelengths, and terahertz property extraction. This capability will significantly broaden the horizon of applications that have been envisioned but remained unrealised due to the lack of ability to realise VO 2 on any substrate, thereby exploiting its untapped potential.

Prognostic impact of peakVO2-changes in stable CHF on chronic beta-blocker treatment.

Science.gov (United States)

Frankenstein, L; Nelles, M; Hallerbach, M; Dukic, D; Fluegel, A; Schellberg, D; Katus, H A; Remppis, A; Zugck, C

2007-11-15

Peak oxygen uptake (pVO2) is used for risk stratification in chronic heart failure (CHF), but little is known about the prognostic impact of pVO2-changes in patients on chronic beta-blocker (BBL) therapy. We therefore prospectively evaluated individual pVO2-changes at a 6-month interval in patients all receiving BBL. 194 patients with stable CHF on stable medication were included (V1) and underwent clinical evaluation and exercise testing. Testing was repeated (V2) at 5.7+/-1.5 months after V1 and patients were followed >12 months after V2. Death or hospitalisation due to cardiac reasons was the predefined EP (EPP, end-point positive; n=62; EPN, end-point negative; n=113). Initial characteristics did not differ between EPP and EPN. Multivariate cox regression analysis revealed that change of pVO2 (EPP: -0.6+/-2.6 ml/kg min; EPN: +2.5+/-3.3 ml/kg min; p<0.001) was independent to pVO2, LVEF, NTproBNP and NYHA at V2 for prediction of the combined end-point during follow-up. An increase of pVO2 by 10% was identified as an adequate cut-off value for risk stratification and ROC-analysis showed the significant incremental prognostic value of the determination of pVO2 changes in combination with pVO2. Serial measurements of pVO2 yield additional information for risk stratification in clinically homogenous CHF patients receiving BBL. This is the first study demonstrating this fact within a narrow predefined interval with all patients on BBL.

VO2 nanostructures based chemiresistors for low power energy consumption hydrogen sensing

CSIR Research Space (South Africa)

Simo, A

2014-05-01

Full Text Available Mott-type VO(sub2) oxide nanobelts are demonstrated to be effective hydrogen gas sensors at room temperature. These nanobelts, synthesized by hydrothermal process and exhibiting the VO(sub2) (A) crystallographic phase, display room temperature H...

Microstructure and thermochromic properties of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films

Energy Technology Data Exchange (ETDEWEB)

Khamseh, S.; Ghahari, M. [Institute for Color Science and Technology, Department of Nanomaterial and Nanocoatings, Tehran (Iran, Islamic Republic of); Araghi, H. [Islamic Azad University, Department of Materials Engineering, Science and Research Branch, Tehran (Iran, Islamic Republic of); Faghihi Sani, M.A. [Sharif University of Technology, Department of Materials Science and Engineering, Tehran (Iran, Islamic Republic of)

2016-03-15

W-doped VO{sub 2} films have been synthesized via oxygen annealing of V-W-V (vanadium-tungsten-vanadium) multilayered films. The effects of middle layer's thickness of V-W-V multilayered film on structure and properties of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films were investigated. The as-deposited V-W-V multilayered film showed amorphous-like structure when mixed structure of VO{sub 2} (M) and VO{sub 2} (B) was formed in VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films. Tungsten content of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films increased with increasing middle layer's thickness. With increasing middle layer's thickness, room temperature square resistance (R{sub sq}) of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films increased from 65 to 86 kΩ/sq. The VO{sub X}-WO{sub X}-VO{sub X} ceramic thin film with the thinnest middle layer showed significant SMT (semiconductor-metal transition) when SMT became negligible on increasing middle layer's thickness. (orig.)

Predictors of VO2Peak in children age 6- to 7-years-old

DEFF Research Database (Denmark)

Dencker, Magnus; Hermansen, Bianca; Bugge, Anna

2011-01-01

This study investigated the predictors of aerobic fitness (VO2PEAK) in young children on a population-base. Participants were 436 children (229 boys and 207 girls) aged 6.7 ± 0.4 yrs. VO2PEAK was measured during a maximal treadmill exercise test. Physical activity was assessed by accelerometers....... Total body fat and total fat free mass were estimated from skinfold measurements. Regression analyses indicated that significant predictors for VO2PEAK per kilogram body mass were total body fat, maximal heart rate, sex, and age. Physical activity explained an additional 4-7%. Further analyses showed...... the main contributing factors for absolute values of VO2PEAK were fat free mass, maximal heart rate, sex, and age. Physical activity explained an additional 3-6%....

Overspeed HIIT in Lower-Body Positive Pressure Treadmill Improves Running Performance.

Science.gov (United States)

Gojanovic, Boris; Shultz, Rebecca; Feihl, Francois; Matheson, Gordon

2015-12-01

Optimal high-intensity interval training (HIIT) regimens for running performance are unknown, although most protocols result in some benefit to key performance factors (running economy (RE), anaerobic threshold (AT), or maximal oxygen uptake (VO2max)). Lower-body positive pressure (LBPP) treadmills offer the unique possibility to partially unload runners and reach supramaximal speeds. We studied the use of LBPP to test an overspeed HIIT protocol in trained runners. Eleven trained runners (35 ± 8 yr, VO2max, 55.7 ± 6.4 mL·kg⁻¹·min⁻¹) were randomized to an LBPP (n = 6) or a regular treadmill (CON, n = 5), eight sessions over 4 wk of HIIT program. Four to five intervals were run at 100% of velocity at VO2max (vVO2max) during 60% of time to exhaustion at vVO2max (Tlim) with a 1:1 work:recovery ratio. Performance outcomes were 2-mile track time trial, VO2max, vVO2max, vAT, Tlim, and RE. LBPP sessions were carried out at 90% body weight. Group-time effects were present for vVO2max (CON, 17.5 vs. 18.3, P = 0.03; LBPP, 19.7 vs. 22.3 km·h⁻¹; P HIIT protocol at 100% vVO2max improves field performance, vVO2max, VO2max and submaximal HR in trained runners. Improvements are similar if intervals are run on a regular treadmill or at higher speeds on a LPBB treadmill with 10% body weight reduction. LBPP could provide an alternative for taxing HIIT sessions.

VO2-based radiative thermal transistor with a semi-transparent base

Science.gov (United States)

Prod'homme, Hugo; Ordonez-Miranda, Jose; Ezzahri, Younès; Drévillon, Jérémie; Joulain, Karl

2018-05-01

We study a radiative thermal transistor analogous to an electronic one made of a VO2 base placed between two silica semi-infinite plates playing the roles of the transistor collector and emitter. The fact that VO2 exhibits an insulator to metal transition is exploited to modulate and/or amplify heat fluxes between the emitter and the collector, by applying a thermal current on the VO2 base. We extend the work of precedent studies considering the case where the base can be semi-transparent so that heat can be exchanged directly between the collector and the emitter. Both near and far field cases are considered leading to 4 typical regimes resulting from the fact that the emitter-base and base-collector separation distances can be larger or smaller than the thermal wavelength for a VO2 layer opaque or semi-transparent. Thermal currents variations with the base temperatures are calculated and analyzed. It is found that the transistor can operate in an amplification mode as already stated in [1] or in a switching mode as seen in [2]. An optimum configuration for the base thickness and separation distance maximizing the thermal transistor modulation factor is found.

¿Es válido utilizar con precisión parámetros reológicos obtenidos en laboratorio para modelar aludes torrenciales a escala real?

OpenAIRE

Blanco, Armando; Rodríguez, Carmen; García, Reinaldo

2009-01-01

Para predecir el comportamiento de aludes torrenciales a escala real se utilizan modelos numéricos. Sin embargo, los parámetros reológicos que permiten representar los fluidos que componen el flujo son difíciles de obtener utilizando reómetros convencionales. En general experiencias de laboratorio son combinadas con modelos matemáticos para calibrar los modelos reológicos. Luego, el modelo numérico calibrado es utilizado para predecir el comportamiento de los aludes torrenciales en campo. Sin...

X-ray absorption spectroscopy of single-crystalline (VO)2P2O7: Electronic structure and possible exchange paths

International Nuclear Information System (INIS)

Gerhold, S.; Nu''cker, N.; Kuntscher, C. A.; Schuppler, S.; Stadler, S.; Idzerda, Y. U.; Prokofiev, A. V.; Bu''llesfeld, F.; Assmus, W.

2001-01-01

Using polarization-dependent V2p and O1s near-edge x-ray absorption spectroscopy, we studied the unoccupied electronic structure of single-crystalline (VO) 2 P 2 O 7 . It is highly anisotropic, and shows similarities to vanadium oxides like VO 2 and V 2 O 5 at the V2p edge and at the O1s threshold. The contributions from V-O and P-O orbitals could be identified. The results rule out the spin ladder model for the magnetic behavior of (VO) 2 P 2 O 7 , but are consistent with the alternating chain scenario

The electrochemical catalytic activity of single-walled carbon nanotubes towards VO2+/VO2+ and V3+/V2+ redox pairs for an all vanadium redox flow battery

International Nuclear Information System (INIS)

Li Wenyue; Liu Jianguo; Yan Chuanwei

2012-01-01

Highlights: ► SWCNT shows excellent electrochemical catalytic activity towards VO 2 + /VO 2+ and V 3+ /V 2+ redox couples. ► The anodic reactions are more sensitive to the surface oxygen atom content change compared with the cathodic reactions. ► The enhanced battery performance clearly demonstrated that the SWCNT is suitable to be used as an electrode catalyst for VRFB. - Abstract: Single-walled carbon nanotube (SWCNT) was used as an electrode catalyst for an all vanadium redox flow battery (VRFB). The electrochemical property of SWCNT towards VO 2 + /VO 2+ and V 3+ /V 2+ was carefully characterized by cyclic voltammetric (CV) and electrochemical impedance spectroscopy (EIS) measurements. The peak current values for these redox pairs were significantly higher on the modified glassy carbon electrode compared with those obtained on the bare electrode, suggesting the excellent electrochemical activity of the SWCNT. Moreover, it was proved that the anodic process was more dependent on the surface oxygen of the SWCNT than the cathodic process through changing its surface oxygen content. Detailed EIS analysis of different modified electrodes revealed that the charge and mass transfer processes were accelerated at the modified electrode–electrolyte interface, which could be ascribed to the large specific surface area, the surface defects and the oxygen functional groups of the SWCNT. The enhanced battery performance effectively demonstrated that the SWCNT was suitable to serve as an electrode catalyst for the VRFB.

A cost-effective method to fabricate VO{sub 2} (M) nanoparticles and films with excellent thermochromic properties

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hua [CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xiao, Xiudi, E-mail: xiaoxd@ms.giec.ac.cn [CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640 (China); Lu, Xuanming [CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Chai, Guanqi; Sun, Yaoming; Zhan, Yongjun; Xu, Gang [CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640 (China)

2015-07-05

Highlights: • Via solvent–thermal and pyrolysis method, VO{sub 2} (M) powder was synthesized in air. • Aiding by grinding, VO{sub 2} (M) nanoparticles with the size of 22 nm were obtained. • The VO{sub 2} films show great thermochromic properties with T{sub lum} = 62.1% and ΔT{sub sol} = 12.4%. • The haze is down to 1.9%, which is superior with films prepared by other methods. - Abstract: In this paper, high crystallinity and pure phase VO{sub 2} (M) powder is synthesized by a novel and facile method. Aiding by additional manual grinding and etching process, 22 nm high-quality VO{sub 2} (M) nanoparticles can be obtained. The structure and properties of the VO{sub 2} (M) particles were characterized by X-ray diffraction analysis, transmission electron microscopy, differential scanning calorimetry and UV–vis–NIR spectrophotometer. After mixing VO{sub 2} (M) nanoparticles with transparent polymer, thin films prepared by grinded VO{sub 2} nanoparticles show excellent thermochromic properties. The solar modulation ability is up to 12.4% with luminous transmittance of 62.7%. Moreover, The haze of films prepared by grinded VO{sub 2} (M) nanoparticles is down to 1.9%, which is far less than that of films prepared by original VO{sub 2} (Haze = 8.5%) and etched VO{sub 2} particles (Haze = 4.6%). Dramatical improvement of thermochromic property and definition indicate that it is a promising method to prepare large-scale VO{sub 2} nanoparticles and cost-effective smart window.

Phase transition study in strongly correlated VO{sub 2} based sensing systems

Energy Technology Data Exchange (ETDEWEB)

Simo, A., E-mail: alinesimo.aline@gmail.com [UNESCO-UNISA Africa Chair in Nanoscience’s/Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape Province (South Africa); Kaviyarasu, K. [UNESCO-UNISA Africa Chair in Nanoscience’s/Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape Province (South Africa); Mwakikunga, B. [Council for Scientific and Industrial Research, P.O. Box 395, Pretoria 0001 (South Africa); Madjoe, R. [Physics Department, University of Western Cape, 7535 Belville Cape Town (South Africa); Gibaud, A. [Laboratoire de Physique de l’Etat Condensé, Université du Maine Faculte des sciences, UPRESA 6087, 72085, Le Mans Cedex 9 (France); Maaza, M. [UNESCO-UNISA Africa Chair in Nanoscience’s/Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape Province (South Africa)

2017-04-15

Highlights: • At 230 °C for about 48 h to prepare successfully VO{sub 2} nanobelts. • 1D shows good sensing performance due to the large active surface of the material. • The good selectivity of methanol compared to acetone and isopropanol. • VOC compounds was observed at room temperature. - Abstract: Intermediate phase monoclinic M2 was observed by inducing in situ X-ray thermo diffraction on VO{sub 2} (M) nanoplatelets. The solid-solid phase transition occurs at around 65 °C assisted with the percolative transition metal-insulator. The existence of an intermediate crystalline phase with room temperature insulator phase and high temperature metallic phase across MIT in VO{sub 2} could be of relevance to understand structural contributions to the phase transition dynamics. In addition, pellet of VO{sub 2} nanostructures have shown to present good sensing properties to various alcohols vapors at room temperature and good selectivity of methanol with 5.54% sensitivity and limit detection below 5 ppm, compared to isopropanol 3.2% and acetone 2.4% respectively.

Capacidade funcional máxima, fração de ejeção e classe funcional na cardiomiopatia chagásica: existe relação entre estes índices? Maximal functional capacity, ejection fraction, and functional class in Chagas cardiomyopathy: are these indices related?

Directory of Open Access Journals (Sweden)

Charles Mady

2005-02-01

Full Text Available OBJETIVO: Avaliar a potencial associação entre a capacidade funcional máxima (VO2max, fração de ejeção do ventrículo esquerdo (FEVE e a classe funcional (CF pela NYHA em pacientes com cardiomiopatia chagásica. MÉTODOS: Foram estudados 104 homens, com idade média de 40.3± 9.0 anos (variação: de 18 a 65, com diagnóstico estabelecido de cardiomiopatia chagásica. A FEVE e VO2max foram classificadas em três categorias: FEVE 0.50 e VO2max 20 ml.kg-1.min-1, respectivamente. RESULTADOS: Do total, 31 (29.8% pacientes estavam em CF II, 41 (39.4% em classe funcional III, e 32 (30.8% em CF IV. Os valores correspondentes do VO2max e da FEVE para CF II, III e IV foram 21.5±4.0 ml.kg-1.min-1, 18.3±5.8 ml.kg-1.min-1 e 14.7±4.9 ml.kg-1.min-1 e 0.50±0.6, 0.35±0.9 e 0.29±0.7, respectivamente. FEVE 0.50 como também VO2max >20 ml.kg-1.min-1. CONCLUSÃO: Existe uma boa associação entre a classe funcional, a capacidade funcional máxima e a fração de ejeção do ventrículo esquerdo em pacientes com cardiomiopatia chagásica. Dados que podem ser úteis no manuseio da insuficiência cardíaca, em chagásicos.OBJECTIVE: Left ventricular ejection fraction (LVEF and maximal functional capacity (VO2max have both been shown to be related to a poor long-term survival in Chagas' disease patients. The aim of this study was to estimate the potential association of VO2max, LVEF, and NYHA functional class in patients with Chagas' disease cardiomyopathy. METHODS: One hundred four male patients, aged 40.3±9.0 years (range, 18 to 65, with a definite diagnosis of Chagas disease cardiomyopathy were studied. LVEF and VO2max were both classified into 3 degrees: LVEF 0.50 and VO2max 20 ml.kg-1.min-1, respectively. RESULTS: Thirty-one patients (29.8% were in NYHA functional class II, 41 (39.4% in functional class III, and 32 (30.8% in functional class IV. The corresponding values of VO2max and LVEF for functional classes II, III, and IV were 21.5±4.0 ml.kg-1

Genetic Correlation between Body Fat Percentage and Cardiorespiratory Fitness Suggests Common Genetic Etiology

DEFF Research Database (Denmark)

Schnurr, Theresia M; Gjesing, Anette P; Sandholt, Camilla H

2016-01-01

of twelve independent risk variants known to associate with body fat%. We assessed CRF as maximal oxygen uptake expressed in millilitres of oxygen uptake per kg of body mass (VO2max), per kg fat-free mass (VO2maxFFM), or per kg fat mass (VO2maxFM). All analyses were adjusted for age and sex, and when...... was associated with a 0.42 mL/kg/min unit decrease in VO2max per allele (p = 0.0092, age and sex adjusted). Both associations were abolished after additional adjustment for body fat%. The fat% increasing GRS and FTO risk allele were associated with decreased VO2maxFM but not with VO2maxFFM. Conclusions: Our...

VO2 microcrystals as an advanced smart window material at semiconductor to metal transition

Science.gov (United States)

Basu, Raktima; Magudapathy, P.; Sardar, Manas; Pandian, Ramanathaswamy; Dhara, Sandip

2017-11-01

Textured VO2(0 1 1) microcrystals are grown in the monoclinic, M1 phase which undergoes a reversible first order semiconductor to metal transition (SMT) accompanied by a structural phase transition to rutile tetragonal, R phase. Around the phase transition, VO2 also experiences noticeable change in its optical and electrical properties. A change in color of the VO2 micro crystals from white to cyan around the transition temperature is observed, which is further understood by absorption of red light using temperature dependent ultraviolet-visible spectroscopic analysis and photoluminescence studies. The absorption of light in the red region is explained by the optical transition between Hubbard states, confirming the electronic correlation as the driving force for SMT in VO2. The thermochromism in VO2 has been studied for smart window applications so far in the IR region, which supports the opening of the band gap in semiconducting phase; whereas there is hardly any report in the management of visible light. The filtering of blue light along with reflection of infrared above the semiconductor to metal transition temperature make VO2 applicable as advanced smart windows for overall heat management of a closure.

VO2 microcrystals as an advanced smart window material at semiconductor to metal transition

International Nuclear Information System (INIS)

Basu, Raktima; Pandian, Ramanathaswamy; Dhara, Sandip; Magudapathy, P; Sardar, Manas

2017-01-01

Textured VO 2 (0 1 1) microcrystals are grown in the monoclinic, M1 phase which undergoes a reversible first order semiconductor to metal transition (SMT) accompanied by a structural phase transition to rutile tetragonal, R phase. Around the phase transition, VO 2 also experiences noticeable change in its optical and electrical properties. A change in color of the VO 2 micro crystals from white to cyan around the transition temperature is observed, which is further understood by absorption of red light using temperature dependent ultraviolet–visible spectroscopic analysis and photoluminescence studies. The absorption of light in the red region is explained by the optical transition between Hubbard states, confirming the electronic correlation as the driving force for SMT in VO 2 . The thermochromism in VO 2 has been studied for smart window applications so far in the IR region, which supports the opening of the band gap in semiconducting phase; whereas there is hardly any report in the management of visible light. The filtering of blue light along with reflection of infrared above the semiconductor to metal transition temperature make VO 2 applicable as advanced smart windows for overall heat management of a closure. (paper)

Observation of reduced phase transition temperature in N-doped thermochromic film of monoclinic VO_2

International Nuclear Information System (INIS)

Wan, Meinan; Xiong, Mo; Li, Neng; Liu, Baoshun; Wang, Shuo; Ching, Wai-Yim; Zhao, Xiujian

2017-01-01

Highlights: • N-doped VO_2(M1) thin films have been synthesized by annealing in NH_3 atmosphere. • The phase purity, microstructure and optical property of VO_2 thin film can be regulated by NH_3 concentration. • First-principles calculations have been carried out to study the mechanism of N-doping on energy band structures of VO_2(M1). • The energy band gaps of VO_2(M1) are tuned by substitution N-doping or interstitial N-doping. - Abstract: Research on monoclinic (M1) phase of VO_2 has attracted a great of interest for smart coating applications due to its exceptional thermochromic property. Herein, we report the results using a novel approach to synthesize N-doped VO_2(M1) thin films with high purity by heat treatment in NH_3 atmosphere. The N dopant in the film can be regulated by varying NH_3 concentration during the annealing process. We find that the N atoms are located at the interstitial sites or substitute oxygen atoms, and the V-N bonds in the VO_2 thin films increase with NH_3 concentration. The metal to insulator transition (MIT) temperature (τ_c_,_h) of the VO_2 thin film is effectively reduced from 80.0 to 62.9 °C, while the solar modulation efficiency (ΔT_s_o_l) and the modulation efficiency at 2000 nm (ΔT_2_0_0_0_n_m) are 7.36% and 55.6% respectively. The band gap of N-doped VO_2 thin films related to MIT (E_g_1) is estimated to be as low as 0.18–0.25 eV whereas the band gap associated with the visible transparency (E_g_2) is about 1.50–1.58 eV. Based on the highly accurate first-principles calculations, the E_g_1 of VO_2 (M1) is reduced after substituted or interstitial N-doping, while the E_g_2 alters with the mode of N-doping, which is excellent agreement with experimental measurement.

Wet-etching induced abnormal phase transition in highly strained VO{sub 2}/TiO{sub 2} (001) epitaxial film

Energy Technology Data Exchange (ETDEWEB)

Ren, Hui; Chen, Shi; Chen, Yuliang; Luo, Zhenlin; Zhou, Jingtian; Zheng, Xusheng; Wang, Liangxin; Li, Bowen; Zou, Chongwen [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei (China)

2018-01-15

The metal-insulator transition (MIT) behavior in vanadium dioxide (VO{sub 2}) epitaxial film is known to be dramatically affected by interfacial stress due to lattice mismatching. For the VO{sub 2}/TiO{sub 2} (001) system, there exists a considerable strain in ultra-thin VO{sub 2} thin film, which shows a lower T{sub c} value close to room temperature. As the VO{sub 2} epitaxial film grows thicker layer-by-layer along the ''bottom-up'' route, the strain will be gradually relaxed and T{sub c} will increase as well, until the MIT behavior becomes the same as that of bulk material with a T{sub c} of about 68 C. Whereas, in this study, we find that the VO{sub 2}/TiO{sub 2} (001) film thinned by ''top-down'' wet-etching shows an abnormal variation in MIT, which accompanies the potential relaxation of film strain with thinning. It is observed that even when the strained VO{sub 2} film is etched up to several nanometers, the MIT persists, and T{sub c} will increase up to that of bulk material, showing the trend to a stress-free ultra-thin VO{sub 2} film. The current findings demonstrate a facial chemical-etching way to change interfacial strain and modulate the phase transition behavior of ultrathinVO{sub 2} films, which can also be applied to other strained oxide films. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Preparation and Characterization of Epitaxial VO2 Films on Sapphire Using Postepitaxial Topotaxy Route via Epitaxial V2O3 Films

Science.gov (United States)

Yamaguchi, Iwao; Manabe, Takaaki; Tsuchiya, Tetsuo; Nakajima, Tomohiko; Sohma, Mitsugu; Kumagai, Toshiya

2008-02-01

Epitaxial VO2 films were prepared on the C-planes of α-Al2O3 substrates by a metal organic deposition (MOD) process. It was difficult to obtain the single phase of (010)M-oriented VO2 films, in which the subscript M refers to the monoclinic indices, by the heat treatment of amorphous precursor films in the VO2-stable region after the pyrolysis of the coating solution. The product films consisted of discontinuous circular grains of 1-2 µm size on the substrate surface. Therefore, we prepared the (010)M-oriented epitaxial VO2 films using postepitaxial topotaxy (PET), that is, topotactic oxidation of (0001)-oriented epitaxial V2O3 films. First, epitaxial V2O3(0001) films were obtained by MOD starting with a vanadium naphthenate solution. Second, the epitaxial V2O3(0001) films were topotactically oxidized at 500 °C in an Ar-O2 gas mixture with pO2 = 10-4 atm to obtain (010)M-oriented epitaxial VO2 films. The epitaxial relationships were VO2(010)M ∥ α-Al2O3(0001) and VO2[100]M ∥ α-Al2O3[0110], [1010], [1100]. The VO2(010)M films exhibited metal-semiconductor transitions with hysteresis loops at 60-80 °C. The resistivity change before and after the transition of the VO2(010)M film oxidized for 6 h was three orders of magnitude.

Supercapacitors based on two dimensional VO2 nanosheet electrodes in organic gel electrolyte

KAUST Repository

Rakhi, R.B.

2016-10-16

VO2 is a low band-gap semiconductor with relatively high conductivity among transition metal oxides, which makes it an interesting material for supercapacitor electrode applications. The performance of VO2 as supercapacitor electrode in organic electrolytes has never been reported before. Herein, two-dimensional nanosheets of VO2 are prepared by the simultaneous solution reduction and exfoliation from bulk V2O5 powder by hydrothermal method. A specific capacitance of 405 Fg−1 is achieved for VO2 based supercapacitor in an organic electrolyte, in three electrode configuration. The symmetric capacitor based on VO2 nanosheet electrodes and the liquid organic electrolyte exhibits an energy density of 46 Wh kg−1 at a power density of 1.4 kW kg−1 at a constant current density of 1 Ag−1. Furthermore, flexible solid-state supercapacitors are fabricated using same electrode material and Alumina-silica based gel electrolyte. The solid-state device delivers a specific capacitance of 145 Fg−1 and a device capacitance of 36 Fg−1 at a discharge current density of 1 Ag−1. Series combination of three solid state capacitors is capable of lighting up a red LED for more than 1 minute.

Firma de la aplicación paralela para predecir el rendimiento

OpenAIRE

Wong, Alvaro

2013-01-01

Evaluar el rendimiento de una aplicación paralela es cada vez más complejo. Una vez terminado el desarrollo, cuando una aplicación pasa a producción, el rendimiento y la eficiencia son fundamentales para los usuarios y administradores. Por ello, cada vez es más importante ser capaz de tener información para seleccionar adecuadamente cuál es el sistema más apropiado para ejecutar la aplicación, o cuánto tiempo de ejecución llevará ejecutar la aplicación entera, a fin de tener una previsión que...

Broadband terahertz generation using the semiconductor-metal transition in VO2

Directory of Open Access Journals (Sweden)

Nicholas A. Charipar

2016-01-01

Full Text Available We report the design, fabrication, and characterization of broadband terahertz emitters based on the semiconductor-metal transition in thin film VO2 (vanadium dioxide. With the appropriate geometry, picosecond electrical pulses are generated by illuminating 120 nm thick VO2 with 280 fs pulses from a femtosecond laser. These ultrafast electrical pulses are used to drive a simple dipole antenna, generating broadband terahertz radiation.

Supercapacitors based on two dimensional VO2 nanosheet electrodes in organic gel electrolyte

KAUST Repository

Baby, Rakhi Raghavan; Nagaraju, Doddahalli H.; Beaujuge, Pierre; Alshareef, Husam N.

2016-01-01

VO2 is a low band-gap semiconductor with relatively high conductivity among transition metal oxides, which makes it an interesting material for supercapacitor electrode applications. The performance of VO2 as supercapacitor electrode in organic

Hydrothermal route to VO2 (B) nanorods: controlled synthesis and characterization

Science.gov (United States)

Song, Shaokun; Huang, Qiwei; Zhu, Wanting

2017-10-01

One-dimensional vanadium dioxides have attracted intensive attention owing to their distinctive structure and novel applications in catalysis, high energy lithium-ion batteries, chemical sensors/actuators and electrochemical devices etc. In this paper, large-scale VO2 (B) nanorods have been successfully synthesized via a versatile and environment friendly hydrothermal strategy using V2O5 as vanadium source and carbohydrates/alcohols as reductant. The obtained samples are characterized by XRD, FT-IR, TEM, and XPS techniques to investigate the effects of chemical parameters such as reductants, temperature, and time of synthesis on the structure and morphology of products. Results show that pure B phase VO2 with homogeneous nanorod-like morphology can be prepared easily at 180 °C for 3 days with glycerol as reluctant. Typically, the nanorod-like products are 0.5-1 μm long and 50 nm width. Furthermore, it is also confirmed that the products are consisted of VO2, corresponding to the B phase. More importantly, this novel approach is efficient, free of any harmful solvents and surfactants. Therefore, this efficient, green, and cost-saving route will have great potential in the large-scale fabrication of 1D VO2 (B) nanorods from the economic and environmental point of view.

Modelos multivariables para predecir el extractable de níquel por la composición química de la mena tecnológica en el proceso Caron

Directory of Open Access Journals (Sweden)

Jorge Arce-Molina

2006-03-01

Full Text Available La  investigación  tuvo el propósito de determinar los modelos que con mayor efectividad puedan predecir el extractable de Ni al variar la composición química-mineral de la mena tecnológica que  alimenta a los Hornos Herreshoff. Se realizó en una Loza (8 hornos de la planta  de Punta Gorda para turnos de 8 horas durante tres  meses  aproximadamente. El procesamiento estadístico de las Bases de Datos se realizó en EXCEL. Como resultado, se obtuvieron varios modelos  multi-variables con efectividades de pronóstico del  extractable de Ni  superiores que  95 % para ser probados en el escalado  hacia toda la Planta de Horno; se demostró la elevada efectividad del pronóstico del extractable de Ni,  al organizar la limpieza o el filtrado de las BD Sucias por intervalos de la relación Limonita / Serpentina (R5 en lugar de la relación de contenidos de Fe*Ni/ Mg*Si (No. Mineral; Se confirmó la validez del procedimiento de filtrado de Datos para ajustar los modelos multi-variables  en  el  caso particular de la Tostación reductora de menas lateríticas  de Ni  y  Co,  el cual puede ser empleado para crear un software integrado con la información existente en la INTRANET de una empresa para su uso en tiempo real. Se fundamentaron  las regularidades en el comportamiento de  los signos y valores de los coeficientes de regresión y correlación, al ser comparados los mejores modelos de las BD de composición química y mineralógica, enfatizando en las contradicciones de las variables: Fe, Al y sus minerales, así como el Ni.

Optical switching properties of VO2 films driven by using WDM-aligned lasers

International Nuclear Information System (INIS)

Tsai, K.Y.; Wu, F.-H.; Shieh, H.-P.D.; Chin, T.-S.

2006-01-01

Vanadium dioxide (VO 2 ) film had been demonstrated a high speed IR shutter driven by total optical modulation. However, it usually required a higher power heating laser of high power and precise optical systems to cover the probe beam on the sample with a heating beam of larger area. A new optical system, simply composed of wavelength division multiplexing (WDM), fiber lens or convex lens system, and a glass sheet with VO 2 thin film on it, was easily assembled to utilize VO 2 film as an IR shutter, implying the possibility to highly miniaturize the VO 2 -based optical shutter. A permanent low-transmittance (PLT) region forms on the film within the probe beam, resulting in a decrease in average power of the probe beam. Another ring-type switching area (switching ring) forms around the PLT region, resulting in the transmittance switching of the probe beam synchronously with the heating signal. VO 2 films can be switched with the highest rate of a continuous square heating signal of 3 mW at 120 kHz. A heating pulse of 0.7 ns and 13 mW can be used to stimulate an IR pulse with fiber lens

Supercritical temperature synthesis of fluorine-doped VO2(M) nanoparticle with improved thermochromic property

Science.gov (United States)

Riapanitra, Anung; Asakura, Yusuke; Cao, Wenbin; Noda, Yasuto; Yin, Shu

2018-06-01

Fluorine-doped VO2(M) nanoparticles have been successfully synthesized using the hydrothermal method at a supercritical temperature of 490 °C. The pristine VO2(M) has the critical phase transformation temperature of 64 °C. The morphology and homogeneity of the monoclinic structure VO2(M) were adopted by the fluorine-doped system. The obtained particle size of the samples is smaller at the higher concentration of anion doping. The best reduction of critical temperature was achieved by fluorine doping of 0.13% up to 48 °C. The thin films of the fluorine-doped VO2(M) showed pronounced thermochromic property and therefore are suitable for smart window applications.

Studies on high-pressure reaction of Er/sub 2/O/sub 3/ or Yb/sub 2/O/sub 3/ with VO/sub 2/

Energy Technology Data Exchange (ETDEWEB)

Shin-ike, T [Osaka Dental Coll., Hirakata (Japan); Adachi, G; Shiokawa, J; Shimada, M; Koizumi, M

1980-12-01

The reaction of erbium sesquioxide (Er/sub 2/O/sub 3/) or ytterbium sesquioxide (Yb/sub 2/O/sub 3/) with vanadium dioxide (VO/sub 2/) at 1400/sup 0/C and 50 kbar and 30 kbar pressures was studied. Quadrivalent vanadium ions were reduced to the trivalent state, erbium vanadate (ErVO/sub 3/) or ytterbium vanadate (YbVO/sub 3/) being obtained. The crystal structure of ErVO/sub 3/ obtained at 50 kbar pressure was vaterite-type isostructural with ErBO/sub 3/ belonging to a hexagonal system, and that obtained at 30 kbar calcite-type belonging to a rhombohedral (pseudo-hexagonal) system. In the reaction of Yb/sub 2/O/sub 3/ with VO/sub 2/ at high pressure, a perovskite-type crystal was obtained. The electrical and magnetic properties of the vaterite- and the calcite-type ErVO/sub 3/ were studied.

Ultrafast electron-lattice coupling dynamics in VO2 and V2O3 thin films

Science.gov (United States)

Abreu, Elsa; Gilbert Corder, Stephanie N.; Yun, Sun Jin; Wang, Siming; Ramírez, Juan Gabriel; West, Kevin; Zhang, Jingdi; Kittiwatanakul, Salinporn; Schuller, Ivan K.; Lu, Jiwei; Wolf, Stuart A.; Kim, Hyun-Tak; Liu, Mengkun; Averitt, Richard D.

2017-09-01

Ultrafast optical pump-optical probe and optical pump-terahertz probe spectroscopy were performed on vanadium dioxide (VO2) and vanadium sesquioxide (V2O3 ) thin films over a wide temperature range. A comparison of the experimental data from these two different techniques and two different vanadium oxides, in particular a comparison of the spectral weight oscillations generated by the photoinduced longitudinal acoustic modulation, reveals the strong electron-phonon coupling that exists in both materials. The low-energy Drude response of V2O3 appears more amenable than VO2 to ultrafast strain control. Additionally, our results provide a measurement of the temperature dependence of the sound velocity in both systems, revealing a four- to fivefold increase in VO2 and a three- to fivefold increase in V2O3 across the insulator-to-metal phase transition. Our data also confirm observations of strong damping and phonon anharmonicity in the metallic phase of VO2, and suggest that a similar phenomenon might be at play in the metallic phase of V2O3 . More generally, our simple table-top approach provides relevant and detailed information about dynamical lattice properties of vanadium oxides, paving the way to similar studies in other complex materials.

Gate-tunable gigantic lattice deformation in VO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Okuyama, D., E-mail: okuyama@riken.jp, E-mail: nakano@imr.tohoku.ac.jp, E-mail: iwasa@ap.t.u-tokyo.ac.jp; Hatano, T. [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Nakano, M., E-mail: okuyama@riken.jp, E-mail: nakano@imr.tohoku.ac.jp, E-mail: iwasa@ap.t.u-tokyo.ac.jp [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Takeshita, S.; Ohsumi, H.; Tardif, S. [RIKEN SPring-8 Center, Hyogo 679-5148 (Japan); Shibuya, K. [National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8562 (Japan); Yumoto, H.; Koyama, T.; Ohashi, H. [Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan); Takata, M. [RIKEN SPring-8 Center, Hyogo 679-5148 (Japan); Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan); Kawasaki, M.; Tokura, Y.; Iwasa, Y., E-mail: okuyama@riken.jp, E-mail: nakano@imr.tohoku.ac.jp, E-mail: iwasa@ap.t.u-tokyo.ac.jp [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Quantum-Phase Electronics Center and Department of Applied Physics, University of Tokyo, Tokyo 113-8656 (Japan); Arima, T. [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); RIKEN SPring-8 Center, Hyogo 679-5148 (Japan); Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561 (Japan)

2014-01-13

We examined the impact of electric field on crystal lattice of vanadium dioxide (VO{sub 2}) in a field-effect transistor geometry by in-situ synchrotron x-ray diffraction measurements. Whereas the c-axis lattice parameter of VO{sub 2} decreases through the thermally induced insulator-to-metal phase transition, the gate-induced metallization was found to result in a significant increase of the c-axis length by almost 1% from that of the thermally stabilized insulating state. We also found that this gate-induced gigantic lattice deformation occurs even at the thermally stabilized metallic state, enabling dynamic control of c-axis lattice parameter by more than 1% at room temperature.

Cardio-respiratory capacity as an important biomarker of health

Directory of Open Access Journals (Sweden)

Jaroslav Novák

2016-12-01

Full Text Available Background: Cardio-respiratory capacity is an important factor in human health. It's quality depends on many objective factors (such as age and gender, but it can be influenced also by others (physical activity, nutrition. Low level of cardio-respiratory capacity significantly correlates with numerous health failures. Objective: Evaluation of the cardio-respiratory capacity in athletes enables a prediction of performance. In a non-sporting population a critically low level of cardio-respiratory capacity could be a warning signal of a high risk of diseases. The Spiroergometric examination needs very sophisticated technical equipment including O2-CO2 analyzer. The aim of the study was to examine the possibility of how to replace direct measurement of oxygen consumption by the method. Methods: 2 777 protocols from the data base of examinations performed in the period of 1994 till 2015 were used. Cardio-respiratory capacity in all examinations was evaluated according to maximal oxygen uptake VO2max, physical working capacity W170 and maximal performance on the cyclo-ergometer. Step-vice increased workload on cyclo-ergometer based on procedure used in International Biological Program was applied to obtain the characteristics of cardio-respiratory capacity of each subject (2 015 men and 762 women. Results: Correlation coefficients r and regression equations of cardio-respiratory capacity characteristics (W170, W170/kg, VO2max, VO2max/kg, Wmax, Wmax/kg were calculated. The highest correlation was found between VO2max and Wmax and between VO2max/kg and Wmax/kg, both in men and women (r = .89 in men and r = .85 in women for VO2max and Wmax. The most important regression equations are: (men VO2max = 0.0095 . Wmax + 0.54 (l/min (r = .89, VO2max/kg = 8.3 . Wmax/kg + 13 (ml/min/kg (r = .83; (women VO2max = 0.0083 . Wmax + 0.67 (l/min (r = .85, VO2max/kg = 8.0 . max/kg + 13 (ml/min/kg (r = .83. Conclusions: It was proved that VO2max and VO2max/kg values

Metal-Insulator Phase Transition in Quasi-One-Dimensional VO2 Structures

Directory of Open Access Journals (Sweden)

Woong-Ki Hong

2015-01-01

Full Text Available The metal-insulator transition (MIT in strongly correlated oxides has attracted considerable attention from both theoretical and experimental researchers. Among the strongly correlated oxides, vanadium dioxide (VO2 has been extensively studied in the last decade because of a sharp, reversible change in its optical, electrical, and magnetic properties at approximately 341 K, which would be possible and promising to develop functional devices with advanced technology by utilizing MITs. However, taking the step towards successful commercialization requires the comprehensive understanding of MIT mechanisms, enabling us to manipulate the nature of transitions. In this regard, recently, quasi-one-dimensional (quasi-1D VO2 structures have been intensively investigated due to their attractive geometry and unique physical properties to observe new aspects of transitions compared with their bulk counterparts. Thus, in this review, we will address recent research progress in the development of various approaches for the modification of MITs in quasi-1D VO2 structures. Furthermore, we will review recent studies on realizing novel functional devices based on quasi-1D VO2 structures for a wide range of applications, such as a gas sensor, a flexible strain sensor, an electrical switch, a thermal memory, and a nonvolatile electrical memory with multiple resistance.

Broadband modulation of terahertz waves through electrically driven hybrid bowtie antenna-VO2 devices.

Science.gov (United States)

Han, Chunrui; Parrott, Edward P J; Humbert, Georges; Crunteanu, Aurelian; Pickwell-MacPherson, Emma

2017-10-05

Broadband modulation of terahertz (THz) light is experimentally realized through the electrically driven metal-insulator phase transition of vanadium dioxide (VO 2 ) in hybrid metal antenna-VO 2 devices. The devices consist of VO 2 active layers and bowtie antenna arrays, such that the electrically driven phase transition can be realized by applying an external voltage between adjacent metal wires extended to a large area array. The modulation depth of the terahertz light can be initially enhanced by the metal wires on top of VO 2 and then improved through the addition of specific bowties in between the wires. As a result, a terahertz wave with a large beam size (~10 mm) can be modulated within the measurable spectral range (0.3-2.5 THz) with a frequency independent modulation depth as high as 0.9, and the minimum amplitude transmission down to 0.06. Moreover, the electrical switch on/off phase transition depends very much on the size of the VO 2 area, indicating that smaller VO 2 regions lead to higher modulation speeds and lower phase transition voltages. With the capabilities in actively tuning the beam size, modulation depth, modulation bandwidth as well as the modulation speed of THz waves, our study paves the way in implementing multifunctional components for terahertz applications.

Gate voltage controlled humidity sensing using MOSFET of VO2 particles

CSIR Research Space (South Africa)

Akande, Amos A

2017-01-01

Full Text Available (A), VO2 (AH) [4], [5] and M2 the intermediate phase between M1 and R phase. These phases have been generally useful in technologies such as thermal switch (thermochromic window), thermal/infrared sensors, A.A Akande holds PhD studentship...) is 272.1, A1 and A2 are respectively 0.118 and 12096 with a correlation coefficient, R2, of 0.925. These results suggest that the VO2 sensor is very resilient to humidity such that it does not saturate even when humidity approaches 100%. This sensor...

Uncommon potential hysteresis in the Li/Li{sub 2x}VO(H{sub 2-x}PO{sub 4}){sub 2} (0 {<=} x {<=} 2) system

Energy Technology Data Exchange (ETDEWEB)

Dubarry, M. [Institut des Materiaux Jean Rouxel, 2 rue de la Houssiniere, BP32229, 44322 Nantes Cedex 3 (France); Gaubicher, J. [Institut des Materiaux Jean Rouxel, 2 rue de la Houssiniere, BP32229, 44322 Nantes Cedex 3 (France)], E-mail: joel.gaubicher@cnrs-imn.fr; Guyomard, D. [Institut des Materiaux Jean Rouxel, 2 rue de la Houssiniere, BP32229, 44322 Nantes Cedex 3 (France); Wallez, G.; Quarton, M. [Laboratoire de Cristallochimie du Solide, Universite Pierre et Marie Curie-Paris VI, 4 place Jussieu, 75252 Paris Cedex 05 (France); Baehtz, C. [Deutsches Elektronen Synchrotron HASYLAB, Notkestr. 85, 22607 Hamburg (Germany)

2008-05-20

Physical and electrochemical investigations of vanadium phosphates, Li{sub 2x}VO(H{sub 2-x}PO{sub 4}){sub 2} (0 < x < 2), have been undertaken. H{sup +}/Li{sup +} ionic exchange from VO(H{sub 2}PO{sub 4}){sub 2} to Li{sub 2}VO(HPO{sub 4}){sub 2} leads to grain decrepitation. Further ionic exchange toward formation of Li{sub 4}VO(PO{sub 4}){sub 2} lowers the symmetry. As inferred from potentiodynamic cycling correlated to ex situ and in situ X-ray diffraction (XRD), the system Li/Li{sub 4}VO(PO{sub 4}){sub 2} shows several phase transformations that are associated with thermodynamical potential hysteresis that span from roughly 15 mV to more than 1.8 V. Small hysteresis are associated with topotactic reactions and with V{sup V}/V{sup IV} and V{sup III}/V{sup II} redox couples. Large potential hysteresis values (>1 V) were observed when oxidation of V{sup III} to V{sup IV} is involved.

Downregulation of MDM2 expression by RNAi inhibits LoVo human colorectal adenocarcinoma cells growth and the treatment of LoVo cells with mdm2siRNA3 enhances the sensitivity to cisplatin

International Nuclear Information System (INIS)

Yu Yan; Sun Ping; Sun Lichun; Liu Guoyi; Chen Guohua; Shang Lihua; Wu Hongbo; Hu Jing; Li Yue; Mao Yinling; Sui Guangjie; Sun Xiwen

2006-01-01

To investigate the biological effect of mdm2 in human colorectal adenocarcinoma LoVo cells, three mdm2siRNA constructions were recombinated and transient transfected into human colorectal adenocarcinoma LoVo cells with low differentiation character in vitro. The results showed that mdm2siRNA3 reduced mRNA level of mdm2 and protein level of mdm2, leading to proliferation inhibition on LoVo cells, and reduced tumor growth in nude mice. It was found that depletion of MDM2 in this pattern promoted apoptosis of LoVo cells and Cisplatin (DDP) treated in the mdm2siRNA3 transfected cell population would result in a substantial decrease by MTT colorimetry. Decreasing the MDM2 protein level in LoVo cells by RNAi could significantly inhibit tumor growth both in vitro and in vivo, which indicated that mdm2 gene played a definite role in the development and aggressiveness of human colon carcinoma. It also could be a therapeutic target in colorectal carcinoma. The synergistic activation of RNAi and cell toxicity agents indicated that the combination of chemotherapy and gene therapy will be a promising approach in the future

Slow VO2 off-kinetics in skeletal muscle is associated with fast PCr off-kinetics--and inversely.

Science.gov (United States)

Korzeniewski, Bernard; Zoladz, Jerzy A

2013-09-01

The computer model of the bioenergetic system in skeletal muscle, developed previously, was used to study the effect of the characteristic decay time of the parallel activation of oxidative phosphorylation [τ(OFF)] during muscle recovery on the muscle oxygen consumption rate (Vo2) and phosphocreatine (PCr) work-to-rest transition (off)-kinetics and on the relationship between the Vo2 and PCr rest-to-work transition (on)- and off-kinetics in moderate and heavy exercise. An increase in τ(OFF) slows down the initial phase of the muscle Vo2 off-kinetics and accelerates the PCr off-kinetics. As a result, the relationship between the initial phase of the Vo2 off-kinetics (lasting approximately 3-60 s in computer simulations) and the PCr off-kinetics is inverse: the slower the former, the faster the latter. A faster initial phase of the Vo2 off-kinetics is associated with a slower late phase of the Vo2 off-kinetics, and as a result, the integral of Vo2 above baseline during recovery, representing the oxygen debt, is identical in all cases [values of τ(OFF)] for a given PCr decrease. Depending on τ(OFF), the muscle Vo2 on-kinetics was either equally fast or slower than the Vo2 off-kinetics in moderate exercise and always slower in heavy exercise. PCr on-kinetics was always faster than PCr off-kinetics. This study clearly demonstrates that τ(OFF) has a pronounced impact on the mutual relations between the muscle Vo2 and PCr on- and off-kinetics.

Influence of lattice distortion on phase transition properties of polycrystalline VO{sub 2} thin film

Energy Technology Data Exchange (ETDEWEB)

Lin, Tiegui [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Wang, Langping, E-mail: aplpwang@hit.edu.cn [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Wang, Xiaofeng; Zhang, Yufen [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Yu, Yonghao, E-mail: yhyu@hit.edu.cn [Academy of Fundamental and Interdisciplinary Science, Harbin Institute of Technology, Harbin 150001 (China)

2016-08-30

Highlights: • Polycrystalline VO{sub 2} thin films were fabricated by high power impulse magnetron sputtering. • The reported lowest phase transition temperature for undoped polycrystalline VO{sub 2} thin film was reduced to 32 °C by this research. • XRD patterns at varied temperatures revealed that the main structual change was a gradual shift in interplanar spacing with temperature. - Abstract: In this work, high power impulse magnetron sputtering was used to control the lattice distortion in polycrystalline VO{sub 2} thin film. SEM images revealed that all the VO{sub 2} thin films had crystallite sizes of below 20 nm, and similar configurations. UV–vis-near IR transmittance spectra measured at different temperatures showed that most of the as-deposited films had a typical metal–insulator transition. Four-point probe resistivity results showed that the transition temperature of the films varied from 54.5 to 32 °C. The X-ray diffraction (XRD) patterns of the as-deposited films revealed that most were polycrystalline monoclinic VO{sub 2}. The XRD results also confirmed that the lattice distortions in the as-deposited films were different, and the transition temperature decreased with the difference between the interplanar spacing of the as-deposited thin film and standard rutile VO{sub 2}. Furthermore, a room temperature rutile VO{sub 2} thin film was successfully synthesized when this difference was small enough. Additionally, XRD patterns measured at varied temperatures revealed that the phase transition process of the polycrystalline VO{sub 2} thin film was a coordinative deformation between grains with different orientations. The main structural change during the phase transition was a gradual shift in interplanar spacing with temperature.

Excitations and possible bound states in the S = 1/2 alternating chain compound (VO)2P2O7

International Nuclear Information System (INIS)

Tennant, D.A.; Nagler, S.E.; Sales, B.C.

1997-01-01

Magnetic excitations in an array of (VO) 2 P 2 O 7 single crystals have been measured using inelastic neutron scattering. Until now, (VO) 2 P 2 O 7 has been thought of as a two-leg antiferromagnetic Heisenberg spin ladder with chains running in the a-direction. The present results show unequivocally that (VO) 2 P 2 O 7 is best described as an alternating spin-chain directed along the crystallographic b-direction. In addition to the expected magnon with magnetic zone-center energy gap Δ = 3.1 meV, a second excitation is observed at an energy just below 2Δ. The higher mode may be a triplet two-magnon bound state. Numerical results in support of bound modes are presented

A cost-effective process to prepare VO2 (M) powder and films with superior thermochromic properties

International Nuclear Information System (INIS)

Xiao, Xiudi; Zhang, Hua; Chai, Guanqi; Sun, Yaoming; Yang, Tao; Cheng, Haoliang; Chen, Lihua; Miao, Lei; Xu, Gang

2014-01-01

Graphical abstract: Combining codeposition and short time post annealing, VO 2 (M) with high quality and excellent phase transition performance is obtained. After mixing the VO 2 powder with acrylic resin, the composite films deposited on glass show superior visible transmission and solar modulation, which can be used as an excellent candidate of low cost smart window in energy saving field. - Highlights: • The VO 2 powder obtained by short time thermolysis method is high purity and crystallinity with superior phase transition performance. • The maximum decreasing efficiency of phase transition temperature is about −30 K/at% with w = 0.4 at%. • After mixing VO 2 powder with acrylic resin, the maximal visible transmission of the composite films is 48% and the transmission modulation at 2000 nm is 37.3% with phase transition temperature of 66.2 °C. • Though the phase transition performance is weakened by tungsten doping, the film prepared by 1.3 at% tungsten doped VO 2 still show superior transmission modulation about 26.4%, which means that it is a potential candidate as smart windows. - Abstract: VO 2 powder with superior phase transition performance was prepared by convenient thermolysis method. The results illustrated that VO 2 powder show high purity and crystallinity. VO 2 particles are transformed from cluster to quasi-sphere with the increase of annealing temperature. The DSC analysis proves that VO 2 show superior phase transition performance around 68 °C. The phase transition temperature can be reduced to 33.5 °C by 1.8 at% tungsten doping. The maximum decreasing efficiency of phase transition temperature is about −30 K/at% with w = 0.4 at%. After mixing VO 2 powder with acrylic resin, the maximal visible transmission of the composite thin films on glass is 48% and the transmission modulation at 2000 nm is 37.3% with phase transition temperature of 66.2 °C. Though the phase transition performance is weakened by tungsten doping, the film

Comprehensive picture of VO2 from band theory

KAUST Repository

Zhu, Zhiyong; Schwingenschlö gl, Udo

2012-01-01

The structural, electronic, and magnetic features of the metal-insulator transition from the tetragonal rutile (R) to the monoclinic (M1) phase of VO2 are well reproduced by band theory using the modified Becke-Johnson exchange potential. Based

Metal-semiconductor phase transition of order arrays of VO2 nanocrystals

Science.gov (United States)

Lopez, Rene; Suh, Jae; Feldman, Leonard; Haglund, Richard

2004-03-01

The study of solid-state phase transitions at nanometer length scales provides new insights into the effects of material size on the mechanisms of structural transformations. Such research also opens the door to new applications, either because materials properties are modified as a function of particle size, or because the nanoparticles interact with a surrounding matrix material, or with each other. In this paper, we describe the formation of vanadium dioxide nanoparticles in silicon substrates by pulsed laser deposition of ion beam lithographically selected sites and thermal processing. We observe the collective behavior of 50 nm diameter VO2 oblate nanoparticles, 10 nm high, and ordered in square arrays with arbitrary lattice constant. The metal-semiconductor-transition of the VO2 precipitates shows different features in each lattice spacing substrate. The materials are characterized by electron microscopy, x-ray diffraction, Rutherford backscattering. The features of the phase transition are studied via infrared optical spectroscopy. Of particular interest are the enhanced scattering and the surface plasmon resonance when the particles reach the metallic state. This resonance amplifies the optical contrast in the range of near-infrared optical communication wavelengths and it is altered by the particle-particle coupling as in the case of noble metals. In addition the VO2 nanoparticles exhibit sharp transitions with up to 50 K of hysteresis, one of the largest values ever reported for this transition. The optical properties of the VO2 nanoarrays are correlated with the size of the precipitates and their inter-particle distance. Nonlinear and ultra fast optical measurements have shown that the transition is the fastest known solid-solid transformation. The VO2 nanoparticles show the same bulk property, transforming in times shorter than 150 fs. This makes them remarkable candidates for ultrafast optical and electronic switching applications.

Atomic layer deposition of VO{sub 2} films with Tetrakis-dimethyl-amino vanadium (IV) as vanadium precursor

Energy Technology Data Exchange (ETDEWEB)

Lv, Xinrui [Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Cao, Yunzhen, E-mail: yzhcao@mail.sic.ac.cn [Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China); Yan, Lu; Li, Ying; Song, Lixin [Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China)

2017-02-28

Highlights: • VO{sub 2} film was easily deposited by ALD using novel vanadium precursor V(NMe{sub 2}){sub 4}. • Deposition and annealing condition were systematically investigated. • Comparable transition properties of VO{sub 2} film on resistance and spectral transmittance were studied. - Abstract: VO{sub 2} thin films have been grown on Si(100) (VO{sub 2}/Si) and fused silica substrates (VO{sub 2}/SiO{sub 2}) by atomic layer deposition (ALD) using tetrakis-dimethyl-amino vanadium (IV) (TDMAV) as a novel vanadium precursor and water as reactant gas. The quartz crystal microbalance (QCM) measurement was performed to study the ALD process of VO{sub 2} thin film deposition, and a constant growth rate of about 0.95 Å/cycle was obtained at the temperature range of 150–200 °C. XRD measurement was performed to study the influence of deposition temperature and post-annealing condition on the crystallization of VO{sub 2} films, which indicated that the films deposited between 150 and 200 °C showed well crystallinity after annealing at 475 °C for 100 min in Ar atmosphere. XPS measurement verified that the vanadium oxidation state was 4+ for both as-deposited film and post-annealed VO{sub 2}/Si film. AFM was applied to study the surface morphology of VO{sub 2}/Si films, which showed a dense polycrystalline film with roughness of about 1 nm. The resistance of VO{sub 2}/Si films deposited between 150 °C and 200 °C as a function of temperature showed similar semiconductor-to-metal transition (SMT) characters with the transition temperature for heating branch (T{sub c,h}) of about 72 °C, a hysteresis width of about 10 °C and the resistance change of two orders of magnitude. The increase of T{sub c,h} compared with the bulk VO{sub 2} (68 °C) may be attributed to the tensile stress along the c-axis in the film. Transmittance measurement of VO{sub 2}/SiO{sub 2} films showed typical thermochromic property with a NIR switching efficiency of above 50% at 2 μm across

Apple F-box Protein MdMAX2 Regulates Plant Photomorphogenesis and Stress Response

Directory of Open Access Journals (Sweden)

Jian-Ping An

2016-11-01

Full Text Available MAX2 (MORE AXILLARY GROWTH2 is involved in diverse physiological processes, including photomorphogenesis, the abiotic stress response, as well as karrikin and strigolactone signaling-mediated shoot branching. In this study, MdMAX2, an F-box protein that is a homolog of Arabidopsis MAX2, was identified and characterized. Overexpression of MdMAX2 in apple calli enhanced the accumulation of anthocyanin. Ectopic expression of MdMAX2 in Arabidopsis exhibited photomorphogenesis phenotypes, including increased anthocyanin content and decreased hypocotyl length. Further study indicated that MdMAX2 might promote plant photomorphogenesis by affecting the auxin signaling as well as other plant hormones. Transcripts of MdMAX2 were noticeably up-regulated in response to NaCl and Mannitol treatments. Moreover, compared with the wild type, the MdMAX2-overexpressing apple calli and Arabidopsis exhibited increased tolerance to salt and drought stresses. Taken together, these results suggest that MdMAX2 plays a positive regulatory role in plant photomorphogenesis and stress response.

Surface charge sensing by altering the phase transition in VO2

Science.gov (United States)

Kumar, S.; Esfandyarpour, R.; Davis, R.; Nishi, Y.

2014-08-01

Detection of surface charges has various applications in medicine, electronics, biotechnology, etc. The source of surface charge induction may range from simple charge-polarized molecules like water to complicated proteins. It was recently discovered that surface charge accumulation can alter the temperature at which VO2 undergoes a Mott transition. Here, we deposited polar molecules onto the surface of two-terminal thin-film VO2 lateral devices and monitored the joule-heating-driven Mott transition, or conductance switching. We observed that the power required to induce the conductance switching reduced upon treatment with polar molecules and, using in-situ blackbody-emission direct measurement of local temperature, we show that this reduction in power was accompanied by reduction in the Mott transition temperature. Further evidence suggested that this effect has specificity to the nature of the species used to induce surface charges. Using x-ray absorption spectroscopy, we also show that there is no detectable change in oxidation state of vanadium or structural phase in the bulk of the 40 nm VO2 thin-film even as the phase transition temperature is reduced by up to 20 K by the polar molecules. The ability to alter the phase transition parameters by depositing polar molecules suggests a potential application in sensing surface charges of different origins and this set of results also highlights interesting aspects of the phase transition in VO2.

Two-Dimensional SiO2/VO2 Photonic Crystals with Statically Visible and Dynamically Infrared Modulated for Smart Window Deployment.

Science.gov (United States)

Ke, Yujie; Balin, Igal; Wang, Ning; Lu, Qi; Tok, Alfred Iing Yoong; White, Timothy J; Magdassi, Shlomo; Abdulhalim, Ibrahim; Long, Yi

2016-12-07

Two-dimensional (2D) photonic structures, widely used for generating photonic band gaps (PBG) in a variety of materials, are for the first time integrated with the temperature-dependent phase change of vanadium dioxide (VO 2 ). VO 2 possesses thermochromic properties, whose potential remains unrealized due to an undesirable yellow-brown color. Here, a SiO 2 /VO 2 core/shell 2D photonic crystal is demonstrated to exhibit static visible light tunability and dynamic near-infrared (NIR) modulation. Three-dimensional (3D) finite difference time domain (FDTD) simulations predict that the transmittance can be tuned across the visible spectrum, while maintaining good solar regulation efficiency (ΔT sol = 11.0%) and high solar transmittance (T lum = 49.6%). Experiments show that the color changes of VO 2 films are accompanied by NIR modulation. This work presents a novel way to manipulate VO 2 photonic structures to modulate light transmission as a function of wavelength at different temperatures.

Physical Activity Enhances Metabolic Fitness Independently of Cardiorespiratory Fitness in Marathon Runners

Directory of Open Access Journals (Sweden)

M. J. Laye

2015-01-01

Full Text Available High levels of cardiovascular fitness (CRF and physical activity (PA are associated with decreased mortality and risk to develop metabolic diseases. The independent contributions of CRF and PA to metabolic disease risk factors are unknown. We tested the hypothesis that runners who run consistently >50 km/wk and/or >2 marathons/yr for the last 5 years have superior metabolic fitness compared to matched sedentary subjects (CRF, age, gender, and BMI. Case-control recruitment of 31 pairs of runner-sedentary subjects identified 10 matched pairs with similar VO2max (mL/min/kg (similar-VO2max. The similar-VO2max group was compared with a group of age, gender, and BMI matched pairs who had the largest difference in VO2max (different-VO2max. Primary outcomes that defined metabolic fitness including insulin response to an oral glucose tolerance test, fasting lipids, and fasting insulin were superior in runners versus sedentary controls despite similar VO2max. Furthermore, performance (velocity at VO2max, running economy, improved exercise metabolism (lactate threshold, and skeletal muscle levels of mitochondrial proteins were superior in runners versus sedentary controls with similar VO2max. In conclusion subjects with a high amount of PA have more positive metabolic health parameters independent of CRF. PA is thus a good marker against metabolic diseases.

Enhanced Visible Transmittance of Thermochromic VO2 Thin Films by SiO2 Passivation Layer and Their Optical Characterization

Directory of Open Access Journals (Sweden)

Jung-Hoon Yu

2016-07-01

Full Text Available This paper presents the preparation of high-quality vanadium dioxide (VO2 thermochromic thin films with enhanced visible transmittance (Tvis via radio frequency (RF sputtering and plasma enhanced chemical vapor deposition (PECVD. VO2 thin films with high Tvis and excellent optical switching efficiency (Eos were successfully prepared by employing SiO2 as a passivation layer. After SiO2 deposition, the roughness of the films was decreased 2-fold and a denser structure was formed. These morphological changes corresponded to the results of optical characterization including the haze, reflectance and absorption spectra. In spite of SiO2 coating, the phase transition temperature (Tc of the prepared films was not affected. Compared with pristine VO2, the total layer thickness after SiO2 coating was 160 nm, which is an increase of 80 nm. Despite the thickness change, the VO2 thin films showed a higher Tvis value (λ 650 nm, 58% compared with the pristine samples (λ 650 nm, 43%. This enhancement of Tvis while maintaining high Eos is meaningful for VO2-based smart window applications.

Lattice relaxation and ferromagnetic character of (LaVO3)m/SrVO3 superlattices

KAUST Repository

Schuster, Cosima B.

2013-08-01

The experimental observation that vanadate superlattices (LaVO 3)m/SrVO3 show ferromagnetism up to room temperature (Lüders U. et al., Phys. Rev. B, 80 (2009) 241102(R)) is investigated by means of density functional theory, and the band structure for m = 5 and 6 is calculated. A buckling of the interface VO2 layers is found in both cases, but subtle differences in bond length lead to very different properties for even and odd values of m: in the even case, the two interface VO2 layers effectively decouple from the adjacent LaO layers due to a strong bond length enhancement. This results into a local inversion of the orbital occupancy and to the confinement of the charge carriers. In the odd case, the amplitude of the bond length variation is smaller, so that the charge carriers spill into the deeper-lying VO2 layers, and spin-polarised interfaces are obtained. © Copyright EPLA, 2013.

Survey the effect of aerobic exercise on aerobic capacity in patients with coronary artery disease (cad)

International Nuclear Information System (INIS)

Kalyani, M. N.; Ebadi, A.

2007-01-01

Increased aerobic exercise capacity appears to reduce both all-cause mortality and cardiovascular disease mortality. Physical exercise to improve maximal oxygen consumption (VO/sub 2max/) is thus strongly recommended, however evidence regarding the most efficient training intensity for patients with coronary artery disease (CAD) is still lacking. The purpose of this randomized study was to assess the effects of aerobic exercise for increasing VO/sub 2max/ in stable CAD-patients. Thirty stable CAD-patients were randomized to supervised walking 30 min three times a week for 10 weeks. Before and after training VO/sub 2max/ was predicted from Bruce treadmill test. Before training VO/sub 2max/ was 35.2+-4.32 ml/kg/min and after training the mean VO/sub 2max/ was 43.1+-3.4 ml/kg/min. This difference was significant (p<0.05). Aerobic exercise is effective for increasing VO/sub 2max/ in stable CAD-patients. As VO/sub 2max/ seems to reflect a continuum between health and cardiovascular disease and death, the present data may be useful in designing effective training programmes for improved health in the future. (author)

Instantaneous band gap collapse in VO{sub 2} caused by photocarrier doping

Energy Technology Data Exchange (ETDEWEB)

Herzog, Marc; Wegkamp, Daniel; Wolf, Martin; Staehler, Julia [Fritz-Haber-Institut der MPG, Berlin (Germany); Xian, Lede; Cudazzo, Pierluigi [Univ. del Pais Vasco, San Sebastian (Spain); European Theoretical Spectroscopy Facility (ETSF) (France); Gatti, Matteo [European Theoretical Spectroscopy Facility (ETSF) (France); Ecole Polytechnique, Palaiseau (France); McGahan, Christina L.; Marvel, Robert E.; Haglund, Richard F. [Vanderbilt Univ., Nashville, Tennessee (United States); Rubio, Angel [Fritz-Haber-Institut der MPG, Berlin (Germany); Univ. del Pais Vasco, San Sebastian (Spain); European Theoretical Spectroscopy Facility (ETSF) (France); MPI for the Structure and Dynamics of Matter, Hamburg (Germany)

2015-07-01

We have investigated the controversially discussed mechanism of the insulator-to-metal transition (IMT) in VO{sub 2} by means of femtosecond time-resolved photoelectron spectroscopy (trPES). Our data show that photoexcitation transforms insulating monoclinic VO{sub 2} quasi-instantaneously into a metal without an 80 fs structural bottleneck for the photoinduced electronic phase transition. First-principles many-body perturbation theory calculations reveal an ultrahigh sensitivity of the VO{sub 2} band gap to variations of the dynamically screened Coulomb interaction thus supporting the fully electronically driven isostructural IMT indicated by our trPES results. We conclude that the ultrafast band structure renormalization is caused by photoexcitation of carriers from localized V 3d valence states, strongly changing the screening before significant hot-carrier relaxation or ionic motion has occurred.

VO₂ thin films synthesis for collaborators and various applications.

Energy Technology Data Exchange (ETDEWEB)

Johnson, Raegan Lynn [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Clem, Paul G. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

2016-11-01

Vanadium dioxide (VO₂) is an attractive material for a variety of applications due to its metal-to-insulator transition (MIT) observed at modest temperatures. This transition takes VO₂ from its low temperature insulating monoclinic phase to a high temperature (above 68°C) metallic rutile phase. This transition gives rise to a change in resistivity up to 5 orders of magnitude and a change in complex refractive index (especially at IR wavelengths), which is of interest for radar circuit protection and tunable control of infrared signature. Recently, collaborations have been initiated between CINT scientists and external university programs. The Enhanced Surveillance funds help fund this work which enabled synthesis of VO₂ films for several collaborations with internal and external researchers.

Effects of training status and exercise intensity on phase II VO2 kinetics.

Science.gov (United States)

Koppo, Katrien; Bouckaert, Jacques; Jones, Andrew M

2004-02-01

To test the hypotheses that: 1) the time constant for the fast component of .VO2 kinetics (tau1) at exercise onset would be faster in trained than in untrained subjects for both moderate and heavy exercise, and that 2) tau1 would become progressively slower in untrained subjects at higher power outputs but be invariant in trained subjects. Eight untrained subjects (.VO2peak: 42.9 +/- 5.1 mL.kg-1.min-1) and seven trained cyclists (.VO2peak: 66.6 +/- 2.5 mL.kg-1.min-1) completed square-wave transitions to power outputs requiring 60% and 80% of gas exchange threshold (GET), and 50% of the difference between GET and .VO2 peak (50%Delta) from a baseline of "unloaded" cycling. .VO2 was measured breath-by-breath and individual responses were modeled using nonlinear regression techniques. A repeated measures ANOVA revealed that the tau1 was significantly smaller (i.e., the kinetics were faster) in the trained compared with the untrained subjects and that tau1 became significantly greater (i.e., the kinetics were slowed) at higher power outputs both in the untrained (60%GET: 17.8 +/- 3.8 s, 80%GET: 21.5 +/- 6.6 s, and 50%Delta: 23.5 +/- 2.8 s) and the trained (60%GET: 8.9 +/- 1.3 s, 80%GET: 11.7 +/- 2.5 s, and 50%Delta: 15.2 +/- 2.0 s) subjects (P exercise intensity domain (recruitment of higher threshold motor units.

Assessment of cardiorespiratory fitness using submaximal protocol in older adults with mood disorder and Parkinson's disease

Directory of Open Access Journals (Sweden)

Natacha Alves de Oliveira

2013-01-01

Full Text Available BACKGROUND: Evidence has shown benefits for mental health through aerobic training oriented in percentage of VO2max, indicating the importance of this variable for clinical practice. OBJECTIVE: To validate a method for estimating VO2max using a submaximal protocol in elderly patients with clinically diagnosis as major depressive disorder (MDD and Parkinson's disease (PD. METHODS: The sample comprised 18 patients (64.22 ± 9.92 years with MDD (n = 7 and with PD (n = 11. Three evaluations were performed: I disease staging, II direct measurement of VO2max and III submaximal exercise test. Linear regression was performed to verify the accuracy of estimation in VO2max established in ergospirometry and the predicted VO2max from the submaximal test measurement. We also analyzed the correlation between the Bland-Altman procedures. RESULTS: The regression analysis showed that VO2max values estimated by submaximal protocol associated with the VO2max measured, both in absolute values (R² = 0.65; SEE = 0.26; p < 0.001 and the relative (R² = 0.56; SEE = 3.70; p < 0.001. The Bland-Altman plots for analysis of agreement of showed a good correlation between the two measures. DISCUSSION: The VO2max predicted by submaximal protocol demonstrated satisfactory criterion validity and simple execution compared to ergospirometry.

Electronic transport in VO2—Experimentally calibrated Boltzmann transport modeling

International Nuclear Information System (INIS)

Kinaci, Alper; Rosenmann, Daniel; Chan, Maria K. Y.; Kado, Motohisa; Ling, Chen; Zhu, Gaohua; Banerjee, Debasish

2015-01-01

Materials that undergo metal-insulator transitions (MITs) are under intense study, because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO 2 has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of electronic transport in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach with Hubbard U correction (DFT + U) to model electronic transport properties in VO 2 in the semiconducting and metallic regimes, focusing on band transport using the Boltzmann transport equations. We synthesized high quality VO 2 films and measured the transport quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable transport properties

Mg-doped VO2 nanoparticles: hydrothermal synthesis, enhanced visible transmittance and decreased metal-insulator transition temperature.

Science.gov (United States)

Zhou, Jiadong; Gao, Yanfeng; Liu, Xinling; Chen, Zhang; Dai, Lei; Cao, Chuanxiang; Luo, Hongjie; Kanahira, Minoru; Sun, Chao; Yan, Liuming

2013-05-28

This paper reports the successful preparation of Mg-doped VO2 nanoparticles via hydrothermal synthesis. The metal-insulator transition temperature (T(c)) decreased by approximately 2 K per at% Mg. The Tc decreased to 54 °C with 7.0 at% dopant. The composite foils made from Mg-doped VO2 particles displayed excellent visible transmittance (up to 54.2%) and solar modulation ability (up to 10.6%). In addition, the absorption edge blue-shifted from 490 nm to 440 nm at a Mg content of 3.8 at%, representing a widened optical band gap from 2.0 eV for pure VO2 to 2.4 eV at 3.8 at% doping. As a result, the colour of the Mg-doped films was modified to increase their brightness and lighten the yellow colour over that of the undoped-VO2 film. A first principle calculation was conducted to understand how dopants affect the optical, Mott phase transition and structural properties of VO2.

VoIP Security

OpenAIRE

Fontanini, Piero

2008-01-01

VOIP or Voice Over Internet Protocol is a common term for phone service over IP based networks. There are much information about VoIP and some of how VoIP can be secured. There is however no standard for VoIP and no general solution for VoIP Security. The security in VoIP systems today are often non existing or in best case weak and often based on proprietary solutions. This master thesis investigates threats to VoIP system and describes existing alternatives for securing Vo...

Observation of reduced phase transition temperature in N-doped thermochromic film of monoclinic VO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Wan, Meinan; Xiong, Mo [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Li, Neng, E-mail: lineng@whut.edu.cn [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Liu, Baoshun; Wang, Shuo [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Ching, Wai-Yim [Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, MO 64110 (United States); Zhao, Xiujian, E-mail: opluse@whut.edu.cn [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China)

2017-07-15

Highlights: • N-doped VO{sub 2}(M1) thin films have been synthesized by annealing in NH{sub 3} atmosphere. • The phase purity, microstructure and optical property of VO{sub 2} thin film can be regulated by NH{sub 3} concentration. • First-principles calculations have been carried out to study the mechanism of N-doping on energy band structures of VO{sub 2}(M1). • The energy band gaps of VO{sub 2}(M1) are tuned by substitution N-doping or interstitial N-doping. - Abstract: Research on monoclinic (M1) phase of VO{sub 2} has attracted a great of interest for smart coating applications due to its exceptional thermochromic property. Herein, we report the results using a novel approach to synthesize N-doped VO{sub 2}(M1) thin films with high purity by heat treatment in NH{sub 3} atmosphere. The N dopant in the film can be regulated by varying NH{sub 3} concentration during the annealing process. We find that the N atoms are located at the interstitial sites or substitute oxygen atoms, and the V-N bonds in the VO{sub 2} thin films increase with NH{sub 3} concentration. The metal to insulator transition (MIT) temperature (τ{sub c,h}) of the VO{sub 2} thin film is effectively reduced from 80.0 to 62.9 °C, while the solar modulation efficiency (ΔT{sub sol}) and the modulation efficiency at 2000 nm (ΔT{sub 2000nm}) are 7.36% and 55.6% respectively. The band gap of N-doped VO{sub 2} thin films related to MIT (E{sub g1}) is estimated to be as low as 0.18–0.25 eV whereas the band gap associated with the visible transparency (E{sub g2}) is about 1.50–1.58 eV. Based on the highly accurate first-principles calculations, the E{sub g1} of VO{sub 2} (M1) is reduced after substituted or interstitial N-doping, while the E{sub g2} alters with the mode of N-doping, which is excellent agreement with experimental measurement.

VV and VO2 defects in silicon studied with hybrid density functional theory

KAUST Repository

Christopoulos, Stavros Richard G; Wang, Hao; Chroneos, Alexander I.; Londos, Charalampos A.; Sgourou, Efstratia N.; Schwingenschlö gl, Udo

2014-01-01

The formation of VO (A-center), VV and VO2 defects in irradiated Czochralski-grown silicon (Si) is of technological importance. Recent theoretical studies have examined the formation and charge states of the A-center in detail. Here we use density

Gate-tunable gigantic changes in lattice parameters and optical properties in VO2

Science.gov (United States)

Nakano, Masaki; Okuyama, Daisuke; Shibuya, Keisuke; Ogawa, Naoki; Hatano, Takafumi; Kawasaki, Masashi; Arima, Taka-Hisa; Iwasa, Yoshihiro; Tokura, Yoshinori

2014-03-01

The field-effect transistor provides an electrical switching function of current flowing through a channel surface by external gate voltage (VG). We recently reported that an electric-double-layer transistor (EDLT) based on vanadium dioxide (VO2) enables electrical switching of the metal-insulator phase transition, where the low-temperature insulating state can be completely switched to the metallic state by application of VG. Here we demonstrate that VO2-EDLT enables electrical switching of lattice parameters and optical properties as well as electrical current. We performed in-situ x-ray diffraction and optical transmission spectroscopy measurements, and found that the c-axis length and the infrared transmittance of VO2 can be significantly modulated by more than 1% and 40%, respectively, by application of VG. We emphasize that these distinguished features originate from the electric-field induced bulk phase transition available with VO2-EDLT. This work was supported by the Japan Society for the Promotion of Science (JSPS) through its ``Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program).''

EVALUATION AND DEVELOPMENT OF THE VO2 OF ATHLETES THAT ATTEND A SOCCER SCHOOL

Directory of Open Access Journals (Sweden)

Felipe Bittencourt Oliveira

2012-11-01

Full Text Available The goal of this study was to identify the effects from technical and physical activities on the VO2, of male athletes aged 14 to 15, participants of a soccer school, in the municipality of Rio Pardo - RS. The semi-experimental research involved 10 male adolescents. For the VO2 evaluation the 12 minute Cooper test was used. Interval-training work was applied, at which the athletes exercised 75% of their maximum speed, in 60-meter runs. After training for two months (at least two sessions a week the Cooper post-test was applied to check the improvement of the VO2. As results of this study, we can draw the conclusion that all adolescents involved in this training showed considerable improvement in their maximum VO2, especially the 15-year-old teens, who managed to obtain a much higher percentage level.

V-dotO2max prediction from multi-frequency bioelectrical impedance analysis

International Nuclear Information System (INIS)

Stahn, Alexander; Strobel, Günther; Terblanche, Elmarie

2008-01-01

Bioelectrical impedance analysis (BIA) has been shown to be highly related to skeletal muscle mass and blood volume, both of which are important determinants of maximal oxygen uptake (V-dotO 2max ). The aim of the present study was therefore to investigate the ability of whole-body and segmental multi-frequency BIA to improve current nonexercise V-dotO 2max prediction models. Data for V-dotO 2max (mL min −1 ), anthropometry, self-reported physical activity (PA-R) and BIA were collected in 115 men and women. Multiple linear regression analysis (MLR) was used to develop the most parsimonious prediction model. Segmental BIA was not superior to whole-body measurements. Correlation coefficients between V-dotO 2max and resistance indices were significantly higher at 500 kHz compared to 50 kHz (p 2max (r = 0.89). After adjusting for age, gender and PA-R, MLR revealed that the inclusion of intracellular resistance index was slightly, but significantly (p 2max ( −1 ). In short, whole-body BIA marginally improves the accuracy of nonexercise V-dotO 2max prediction models and its advantage is most pronounced in individuals with particularly low V-dotO 2max

F-doped VO2 nanoparticles for thermochromic energy-saving foils with modified color and enhanced solar-heat shielding ability.

Science.gov (United States)

Dai, Lei; Chen, Shi; Liu, Jianjun; Gao, Yanfeng; Zhou, Jiadong; Chen, Zhang; Cao, Chuanxiang; Luo, Hongjie; Kanehira, Minoru

2013-07-28

F-doped VO2 (M1) nanoparticles were prepared via one-pot hydrothermal synthesis. The F-doping can minimise the size of the VO2 (M1) nanoparticles, induce a homogeneous size distribution and effectively decrease the phase transition temperature to 35 °C at 2.93% F in VO2. VO2 smart glass foils obtained by casting these nanoparticles exhibit excellent thermochromism in the near-infrared region, which suggests that these foils can be used for energy-efficient glass. Compared to a pure VO2 foil, the 2.93% F-doped VO2 foil exhibits an increased solar-heat shielding ability (35.1%) and a modified comfortable colour, while still retaining an excellent solar modulation ability (10.7%) and an appropriate visible transmittance (48.7%). The F-doped VO2 foils are the first to simultaneously meet the requirements of a reduced phase transition temperature, diluted colour and excellent thermochromic properties, and these properties make the further improved F-doped VO2 foils suitable for commercial applications in energy efficient glass.

Mechanisms of Attenuation of Pulmonary V'O2 Slow Component in Humans after Prolonged Endurance Training.

Directory of Open Access Journals (Sweden)

Jerzy A Zoladz

Full Text Available In this study we have examined the effect of prolonged endurance training program on the pulmonary oxygen uptake (V'O2 kinetics during heavy-intensity cycling-exercise and its impact on maximal cycling and running performance. Twelve healthy, physically active men (mean±SD: age 22.33±1.44 years, V'O2peak 3198±458 mL ∙ min-1 performed an endurance training composed mainly of moderate-intensity cycling, lasting 20 weeks. Training resulted in a decrease (by ~5%, P = 0.027 in V'O2 during prior low-intensity exercise (20 W and in shortening of τp of the V'O2 on-kinetics (30.1±5.9 s vs. 25.4±1.5 s, P = 0.007 during subsequent heavy-intensity cycling. This was accompanied by a decrease of the slow component of V'O2 on-kinetics by 49% (P = 0.001 and a decrease in the end-exercise V'O2 by ~5% (P = 0.005. An increase (P = 0.02 in the vascular endothelial growth factor receptor 2 mRNA level and a tendency (P = 0.06 to higher capillary-to-fiber ratio in the vastus lateralis muscle were found after training (n = 11. No significant effect of training on the V'O2peak was found (P = 0.12. However, the power output reached at the lactate threshold increased by 19% (P = 0.01. The power output obtained at the V'O2peak increased by 14% (P = 0.003 and the time of 1,500-m performance decreased by 5% (P = 0.001. Computer modeling of the skeletal muscle bioenergetic system suggests that the training-induced decrease in the slow component of V'O2 on-kinetics found in the present study is mainly caused by two factors: an intensification of the each-step activation (ESA of oxidative phosphorylation (OXPHOS complexes after training and decrease in the ''additional" ATP usage rising gradually during heavy-intensity exercise.

Mechanisms of Attenuation of Pulmonary V'O2 Slow Component in Humans after Prolonged Endurance Training.

Science.gov (United States)

Zoladz, Jerzy A; Majerczak, Joanna; Grassi, Bruno; Szkutnik, Zbigniew; Korostyński, Michał; Gołda, Sławomir; Grandys, Marcin; Jarmuszkiewicz, Wiesława; Kilarski, Wincenty; Karasinski, Janusz; Korzeniewski, Bernard

2016-01-01

In this study we have examined the effect of prolonged endurance training program on the pulmonary oxygen uptake (V'O2) kinetics during heavy-intensity cycling-exercise and its impact on maximal cycling and running performance. Twelve healthy, physically active men (mean±SD: age 22.33±1.44 years, V'O2peak 3198±458 mL ∙ min-1) performed an endurance training composed mainly of moderate-intensity cycling, lasting 20 weeks. Training resulted in a decrease (by ~5%, P = 0.027) in V'O2 during prior low-intensity exercise (20 W) and in shortening of τp of the V'O2 on-kinetics (30.1±5.9 s vs. 25.4±1.5 s, P = 0.007) during subsequent heavy-intensity cycling. This was accompanied by a decrease of the slow component of V'O2 on-kinetics by 49% (P = 0.001) and a decrease in the end-exercise V'O2 by ~5% (P = 0.005). An increase (P = 0.02) in the vascular endothelial growth factor receptor 2 mRNA level and a tendency (P = 0.06) to higher capillary-to-fiber ratio in the vastus lateralis muscle were found after training (n = 11). No significant effect of training on the V'O2peak was found (P = 0.12). However, the power output reached at the lactate threshold increased by 19% (P = 0.01). The power output obtained at the V'O2peak increased by 14% (P = 0.003) and the time of 1,500-m performance decreased by 5% (P = 0.001). Computer modeling of the skeletal muscle bioenergetic system suggests that the training-induced decrease in the slow component of V'O2 on-kinetics found in the present study is mainly caused by two factors: an intensification of the each-step activation (ESA) of oxidative phosphorylation (OXPHOS) complexes after training and decrease in the ''additional" ATP usage rising gradually during heavy-intensity exercise.

Enhanced photoelectrochemical response of plasmonic Au embedded BiVO4/Fe2O3 heterojunction.

Science.gov (United States)

Verma, Anuradha; Srivastav, Anupam; Khan, Saif A; Rani Satsangi, Vibha; Shrivastav, Rohit; Kumar Avasthi, Devesh; Dass, Sahab

2017-06-14

The effect of embedding Au nanoparticles (NPs) in a BiVO 4 /Fe 2 O 3 heterojunction for photoelectrochemical water splitting is studied here for the first time. The present nanostructured heterojunction offers three major advantages over pristine BiVO 4 and Fe 2 O 3 : (i) the formation of a heterojunction between BiVO 4 and Fe 2 O 3 enhances the charge carrier separation and transfer, (ii) the layer of Fe 2 O 3 provides protection to BiVO 4 from photocorrosion and, (iii) the Au NPs possessing surface plasmon resonance (SPR) enhance the photoelectrochemical response by transferring energy to metal oxides by hot electron transfer (HET) and plasmon resonant energy transfer (PRET). The present study reveals that the heterojunction ITO/BiVO 4 /Fe 2 O 3 (with 32% v/v Au solution in both layers) gives the best performance and mitigates the limitations of both pristine Fe 2 O 3 and BiVO 4 . A thirteen-fold increment in applied bias photon-to-current conversion efficiency (ABPE) was observed at 1.24 V vs. RHE under the condition of 1 Sun illumination. Monochromatic incident photon-to-current conversion efficiency (IPCE) measurements indicated that an Au embedded heterojunction is more effective in harvesting visible light in comparison to a heterojunction without Au NPs.

Effects of acute and 2-week administration of oral salbutamol on exercise performance and muscle strength in athletes

DEFF Research Database (Denmark)

Hostrup, Morten; Kalsen, Anders; Auchenberg, Michael

2016-01-01

Our objective was to investigate effects of acute and 2-week administration of oral salbutamol on repeated sprint ability, exercise performance, and muscle strength in elite endurance athletes. Twenty male elite athletes [VO2max : 69.4 ± 1.8 (Mean ± SE) mL/min/kg], aged 25.9 ± 1.4 years, were....... deltoideus were measured, followed by three repeated Wingate tests. Exercise performance at 110% of VO2max was determined on a bike ergometer. Acute administration of salbutamol increased peak power during first Wingate test by 4.1 ± 1.7% (P ....05) peak power during first and second Wingate test by 6.4 ± 2.0 and 4.2 ± 1.0%. Neither acute nor 2-week administration of salbutamol had any effect on MVC, exercise performance at 110% of VO2max or on isometric endurance. No differences were observed in the placebo group. In conclusion, salbutamol...

[Is physical activity an elixir?].

Science.gov (United States)

Lacza, Gyöngyvér; Radák, Zsolt

2013-05-19

Physical exercise has systemic effects, and it can regulate all the organs. The relative maximal aerobic oxygen uptake (VO2max) could have been important in the evolution of humans, since higher VO2max meant better hunting abilities for the Stone Age man. However, it appears that high level of VO2max is also important today, in the 21st century to prevent cardiovascular diseases, cancer and neurodegenerative diseases. High level of VO2max is not just preventive against a wide spectrum of diseases, but it associated with better function of many organs. Relevant data suggest that high level of VO2max is a key factor in prevention of diseases and survival even at the modern civilized world.

Capacity Evaluation for IEEE 802.16e Mobile WiMAX

Directory of Open Access Journals (Sweden)

Chakchai So-In

2010-01-01

Full Text Available We present a simple analytical method for capacity evaluation of IEEE 802.16e Mobile WiMAX networks. Various overheads that impact the capacity are explained and methods to reduce these overheads are also presented. The advantage of a simple model is that the effect of each decision and sensitivity to various parameters can be seen easily. We illustrate the model by estimating the capacity for three sample applications—Mobile TV, VoIP, and data. The analysis process helps explain various features of IEEE 802.16e Mobile WiMAX. It is shown that proper use of overhead reducing mechanisms and proper scheduling can make an order of magnitude difference in performance. This capacity evaluation method can also be used for validation of simulation models.

Tuning the work function of VO_2(1 0 0) surface by Ag adsorption and incorporation: Insights from first-principles calculations

International Nuclear Information System (INIS)

Chen, Lanli; Wang, Xiaofang; Shi, Siqi; Cui, Yuanyuan; Luo, Hongjie; Gao, Yanfeng

2016-01-01

Graphical abstract: - Highlights: • After adsorption, there is a charge transfer from Ag to VO_2(1 0 0) surface, which thus increases the electron concentration in VO_2 thin film. • Ag adsorption on VO_2(1 0 0) surface process is an exothermic chemical process, and the adsorption system is stable. • The work function can be tuned by Ag adsorption on and incorporation into the VO_2(1 0 0) surface, which in turn regulates the phase transition temperature of VO_2. - Abstract: VO_2 is an attractive material for application to thermochromic optoelectronic devices such as smart windows, and Ag/VO_2 double-layered structure can effectively decrease the phase transition temperature (T_c) of VO_2 thin film, which is very important for practical application of VO_2. Previous works has shown that the decrease in phase transition temperature (T_c) seems to be relevant with the work function of VO_2 in Ag/VO_2 double-layered thin film, although the underlying mechanism of tuning its T_c by Ag incorporation and adsorption on the VO_2(1 0 0) surface has been rarely investigated. Our first-principles calculations reveal that the adsorption of Ag atoms on the VO_2(1 0 0) surface rather than incorporation of Ag exhibits a lower work function, which is ascribed to an integrated effect of charge transfer from Ag to VO_2(1 0 0) surface and enhanced surface dipole moment. The results suggest that the decrease in work function of VO_2 with Ag adsorption favors the reduction in T_c. The current findings are helpful to understand the fundamental mechanism for yielding high-efficiency VO_2-based optoelectronic devices.

Securing VoIP keeping your VoIP network safe

CERN Document Server

(Bud) Bates, Regis J Jr

2015-01-01

Securing VoIP: Keeping Your VoIP Network Safe will show you how to take the initiative to prevent hackers from recording and exploiting your company's secrets. Drawing upon years of practical experience and using numerous examples and case studies, technology guru Bud Bates discusses the business realities that necessitate VoIP system security and the threats to VoIP over both wire and wireless networks. He also provides essential guidance on how to conduct system security audits and how to integrate your existing IT security plan with your VoIP system and security plans, helping you prevent

Aerobic Capacity Following Long Duration International Spaces Station (ISS) Missions: Preliminary Results

Science.gov (United States)

Moore, Alan D.; Lee, S.M.C.; Everett, M.E.; Guined, J.R.; Knudsen, P.

2010-01-01

Maximum oxygen uptake (VO2max) is reduced immediately following space flights lasting 6%. WRmax also decreased on R+1/2 compared to preflight (Pre: 245+/-69, R+1/2: 210+/-45 W). On R+10, VO2max was 2.86+/-0.62 L(dot)/min, with 2 subjects still demonstrating a loss of > 6% from preflight. WRmax on R+10 was 240+/-49 W. HRmax did not change from pre to post-flight. Conclusions: These preliminary results, from the first 5 of 12 planned subjects of an ongoing ISS study, suggest that the majority of astronauts will experience a decrease in VO2max after long-duration space-flight. Interestingly, the two astronauts with the highest preflight VO2max had the greatest loss on R+1/2, and the astronaut with the lowest preflight VO2max increased by 13%. Thus, maintenance of VO2max may be more difficult in astronauts who have a high aerobic capacity, perhaps requiring more intense in-flight exercise countermeasure prescriptions.

Graphene-Nanowall-Decorated Carbon Felt with Excellent Electrochemical Activity Toward VO2+/VO2+ Couple for All Vanadium Redox Flow Battery.

Science.gov (United States)

Li, Wenyue; Zhang, Zhenyu; Tang, Yongbing; Bian, Haidong; Ng, Tsz-Wai; Zhang, Wenjun; Lee, Chun-Sing

2016-04-01

3D graphene-nanowall-decorated carbon felts (CF) are synthesized via an in situ microwave plasma enhanced chemical vapor deposition method and used as positive electrode for vanadium redox flow battery (VRFB). The carbon fibers in CF are successfully wrapped by vertically grown graphene nanowalls, which not only increase the electrode specific area, but also expose a high density of sharp graphene edges with good catalytic activities to the vanadium ions. As a result, the VRFB with this novel electrode shows three times higher reaction rate toward VO 2 + /VO 2+ redox couple and 11% increased energy efficiency over VRFB with an unmodified CF electrode. Moreover, this designed architecture shows excellent stability in the battery operation. After 100 charging-discharging cycles, the electrode not only shows no observable morphology change, it can also be reused in another battery and practical with the same performance. It is believed that this novel structure including the synthesis procedure will provide a new developing direction for the VRFB electrode.

Graphene‐Nanowall‐Decorated Carbon Felt with Excellent Electrochemical Activity Toward VO2 +/VO2+ Couple for All Vanadium Redox Flow Battery

Science.gov (United States)

Li, Wenyue; Zhang, Zhenyu; Bian, Haidong; Ng, Tsz‐Wai

2015-01-01

3D graphene‐nanowall‐decorated carbon felts (CF) are synthesized via an in situ microwave plasma enhanced chemical vapor deposition method and used as positive electrode for vanadium redox flow battery (VRFB). The carbon fibers in CF are successfully wrapped by vertically grown graphene nanowalls, which not only increase the electrode specific area, but also expose a high density of sharp graphene edges with good catalytic activities to the vanadium ions. As a result, the VRFB with this novel electrode shows three times higher reaction rate toward VO2 +/VO2+ redox couple and 11% increased energy efficiency over VRFB with an unmodified CF electrode. Moreover, this designed architecture shows excellent stability in the battery operation. After 100 charging–discharging cycles, the electrode not only shows no observable morphology change, it can also be reused in another battery and practical with the same performance. It is believed that this novel structure including the synthesis procedure will provide a new developing direction for the VRFB electrode. PMID:27774399

Creatine Kinase and Lactate Dehydrogenase Responses After Different Resistance and Aerobic Exercise Protocols

Directory of Open Access Journals (Sweden)

Callegari Gustavo A.

2017-08-01

Full Text Available The aim of this study was to investigate the responses of creatine kinase (CK and lactate dehydrogenase (LDH after performing different resistance and aerobic exercise protocols. Twelve recreationally trained men (age, 23.2 ± 5.6 years; body mass, 84.3 ± 9.3 kg; body height, 178.9 ± 4.5 cm; and BMI, 26.3 ± 2.3 kg·m2 volunteered to participate in this study. All subjects were randomly assigned to four experimental protocols (crossover: (a aerobic training at 60% of VO2max, (b aerobic training at 80% of VO2max, (c a resistance exercise (RE session with a bi-set protocol, and (d an RE session with a multiple sets protocol. Blood samples were collected before, immediately after and 24 hours following the experimental protocols. After 24 hours, there was a significant increase in CK for the 80% of VO2max protocol vs. the bi-set RE session (p = 0.016. Immediately after the protocols, we observed a significant increase in LDH among certain groups compared to others, as follows: multiple sets RE session vs. 60% of VO2max, bi-set RE session vs. 60% of VO2max, multiple sets RE session vs. 80% of VO2max, and bi-set RE session vs. 80% of VO2max (p = 0.008, p = 0.013; p = 0.002, p = 0.004, respectively. In conclusion, aerobic exercise performed at 80% of VO2max appears to elevate plasma CK levels more than bi-set RE sessions. However, the bi-set and multiple sets RE sessions appeared to trigger greater levels of blood LDH compared to aerobic protocols performed at 60% and 80% of VO2max.

EPR and optical absorption studies of VO2+ doped L-alanine (C3H7NO2) single crystals

International Nuclear Information System (INIS)

Biyik, Recep

2009-01-01

VO 2+ doped L-alanine (C 3 H 7 NO 2 ) single crystals and powders are examined by electron paramagnetic resonance (EPR) and optical absorption spectroscopy. Three magnetically different sites are resolved from angular variations of L-alanine single crystal EPR spectra. In some specific orientations each VO 2+ line splits into three superhyperfine lines with intensities of 1:2:1 and maximum splitting value of 2.23 mT. The local symmetries of VO 2+ complex sites are nearly axial. The optical absorption spectra show three bands. Spin Hamiltonian parameters are measured and molecular orbital coefficients are calculated by correlating EPR and optical absorption data for the central vanadyl ion.

Speciation in the aqueous H+/H2VO4-/H2O2/citrate system of biomedical interest.

Science.gov (United States)

Gorzsás, András; Getty, Kendra; Andersson, Ingegärd; Pettersson, Lage

2004-09-21

The speciation in the quaternary aqueous H+/H2VO4-/H2O2/citrate (Cit3-) and H+/H2VO4-/Cit3-/L-(+)-lactate (Lac-) systems has been determined at 25 degrees C in the physiological medium of 0.150 M Na(Cl). A combination of 51V NMR integral intensities and chemical shift (Bruker AMX500) as well as potentiometric data (glass electrode) have been collected and evaluated with the computer program LAKE, which is able to treat multimethod data simultaneously. The pKa-values for citric acid have been determined as 2.94, 4.34 and 5.61. Altogether six vanadate-citrate species have been found in the ternary H+/H2VO4-/Cit3- system in the pH region 2-10, only two of which are mononuclear. Reduction of vanadium(V) becomes more pronounced at pH acidic solutions limited the final model to pH > 4. In the quaternary H+/H2VO4-/Cit3-/Lac- system, two mixed-ligand species have been determined, with the compositions V2CitLac2- and V2CitLac3- (pKa = 5.0). To our knowledge, this is the first time such complexes have been reported for vanadium(V). 51V NMR chemical shifts, compositions and formation constants are given, and equilibrium conditions are illustrated in distribution diagrams as well as the fit of the model to the experimental data. When suitable, structural proposals are given, based on 13C NMR measurements and available literature data of related compounds.

Influence of nitrate supplementation on VO(2) kinetics and endurance of elite cyclists

DEFF Research Database (Denmark)

Christensen, Peter Møller; Nyberg, Michael Permin; Bangsbo, Jens

2013-01-01

The present study examined if an elevated nitrate intake would improve VO(2) kinetics, endurance, and repeated sprint capacity in elite endurance athletes. Ten highly trained cyclists (72¿±¿4¿mL O(2) /kg/min, mean¿±¿standard deviation) underwent testing for VO(2) kinetics (3¿×¿6¿min at 298¿±¿28¿W...... juice. Plasma NOx (nitrate¿+¿nitrite) levels were higher (P¿......The present study examined if an elevated nitrate intake would improve VO(2) kinetics, endurance, and repeated sprint capacity in elite endurance athletes. Ten highly trained cyclists (72¿±¿4¿mL O(2) /kg/min, mean¿±¿standard deviation) underwent testing for VO(2) kinetics (3¿×¿6¿min at 298¿±¿28¿W......), endurance (120¿min preload followed by a 400-kcal time trial), and repeated sprint capacity (6¿×¿20¿s sprints, recovery 100¿s) during two 6-day periods in randomized order with a daily ingestion of either 0.5¿L beetroot (BR) juice to increase nitrate levels or a 0.5¿L placebo (PLA) drink with blackcurrant...

Synthesis of vanadium oxides 5 wt.%VO2–MxOy by sol–gel process ...

Indian Academy of Sciences (India)

Experimental results indicated that the VO2–SiO2 catalysts .... crucible, which was supported by the beam of a balance in the oven. ... Epoxidation of cyclohexene on VO2–Mx Oy (M = Si, Al, Ti). 1189 ... tially amorphous nature of silica.

Hydrothermal Synthesis of VO2 Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows.

Science.gov (United States)

Li, Ming; Magdassi, Shlomo; Gao, Yanfeng; Long, Yi

2017-09-01

Vanadium dioxide (VO 2 ) is a widely studied inorganic phase change material, which has a reversible phase transition from semiconducting monoclinic to metallic rutile phase at a critical temperature of τ c ≈ 68 °C. The abrupt decrease of infrared transmittance in the metallic phase makes VO 2 a potential candidate for thermochromic energy efficient windows to cut down building energy consumption. However, there are three long-standing issues that hindered its application in energy efficient windows: high τ c , low luminous transmittance (T lum ), and undesirable solar modulation ability (ΔT sol ). Many approaches, including nano-thermochromism, porous films, biomimetic surface reconstruction, gridded structures, antireflective overcoatings, etc, have been proposed to tackle these issues. The first approach-nano-thermochromism-which is to integrate VO 2 nanoparticles in a transparent matrix, outperforms the rest; while the thermochromic performance is determined by particle size, stoichiometry, and crystallinity. A hydrothermal method is the most common method to fabricate high-quality VO 2 nanoparticles, and has its own advantages of large-scale synthesis and precise phase control of VO 2 . This Review focuses on hydrothermal synthesis, physical properties of VO 2 polymorphs, and their transformation to thermochromic VO 2 (M), and discusses the advantages, challenges, and prospects of VO 2 (M) in energy-efficient smart windows application. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Size and composition-controlled fabrication of VO2 nanocrystals by terminated cluster growth

Energy Technology Data Exchange (ETDEWEB)

Anders, Andre; Slack, Jonathan

2013-05-14

A physical vapor deposition-based route for the fabrication of VO2 nanoparticles is demonstrated, consisting of reactive sputtering and vapor condensation at elevated pressures. The oxidation of vanadium atoms is an efficient heterogeneous nucleation method, leading to high nanoparticle throughtput. Fine control of the nanoparticle size and composition is obtained. Post growth annealing leads to crystalline VO2 nanoparticles with optimum thermocromic and plasmonic properties.

Eu-emission quenching by electron screening in VO2 thin films

International Nuclear Information System (INIS)

Liu, H.; Lysenko, S.; Rua, A.; Vikhnin, V.; Vasquez, O.; Fernandez, F.E.

2006-01-01

As a kind of phase transition functional material, Vanadium dioxide (VO 2 ) thin films deposited on fused quartz substrate were fabricated using pulsed laser deposition (PLD) technique. Europium was introduced for structure study. By laser excitation at 526 nm, VO 2 thin film undergoes a reversible and ultrafast phase transition from semiconductor to metallic state, which results in a change of optical properties. In fluorescence measurement, Eu emission was found severely quenched in all as-grown thin films. After annealing the sample in air, a red Eu-emission appeared. The emission spectrum is characterized by a pronounced twin peak, centered at 617 nm ( 5 D - 7 F 2 ), surrounded by a set of broad, but relatively weaker bands (emission from 5 D to 7 F j manifold). The emission lifetime increased when the sample annealed at higher temperature for longer time. Each spectral component is actually a doublet which is the spectral overlap of emissions from Eu 3+ situated in two sites with different configurations. One is a linear h-Eu 3+ -h, where h stands for holes. Another is a right-angle configuration of h-Eu 3+ -h with Eu 3+ in the corner. In as-grown VO 2 film, Eu 3+ ions can either substitute V 4+ , leaving a negative charge around (Eu 3+ -O) - , or substitute V 5+ , leaving two negative charges around (Eu 3+ -O) -- . Due to trapped electrons in a large radius state, it covers Eu 3+ V 4+ -V 5+ complexes. It suggests that the screening by degenerate electronic gas may result in switching off the Eu-related optical response for a wide spectral region, causing emission quenching in VO 2 films

Effects of V2O3 buffer layers on sputtered VO2 smart windows: Improved thermochromic properties, tunable width of hysteresis loops and enhanced durability

Science.gov (United States)

Long, Shiwei; Cao, Xun; Sun, Guangyao; Li, Ning; Chang, Tianci; Shao, Zewei; Jin, Ping

2018-05-01

Vanadium dioxide (VO2) is one of the most well-known thermochromic materials, which exhibits a notable optical change from transparent to reflecting in the infrared region upon a metal-insulator phase transition. For practical applications, VO2 thin films should be in high crystalline quality to obtain a strong solar modulation ability (ΔTsol). Meanwhile, narrow hysteresis loops and robust ambient durability are also indispensable for sensitivity and long-lived utilization, respectively. In this work, a series of high-quality V2O3/VO2 bilayer structures were grown on quartz glass substrates by reactive magnetron sputtering. Basically, the bottom V2O3 acts as the buffer layer to improve the crystallinity of the top VO2, while the VO2 serves as the thermochromic layer to guarantee the solar modulation ability for energy-saving. We observed an obvious increase in ΔTsol of 76% (from 7.5% to 13.2%) for VO2 films after introducing V2O3 buffer layers. Simultaneously, a remarkable reduction by 79% (from 21.9 °C to 4.7 °C) in width of hysteresis loop was obtained when embedding 60 nm V2O3 buffer for 60 nm VO2. In addition, VO2 with non-stoichiometry of V2O3±x buffer demonstrates a broadening hysteresis loops width, which is derived from the lattice distortion caused by lattice imperfection. Finally, durability of VO2 has been significantly improved due to positive effects of V2O3 buffer layer. Our results lead to a comprehensive enhancement in crystallinity of VO2 and shed new light on the promotion of thermochromic property by homologous oxides for VO2.

Characteristics of the Current-Controlled Phase Transition of VO2 Microwires for Hybrid Optoelectronic Devices

Directory of Open Access Journals (Sweden)

Arash Joushaghani

2015-08-01

Full Text Available The optical and electrical characteristics of the insulator-metal phase transition of vanadium dioxide (VO2 enable the realization of power-efficient, miniaturized hybrid optoelectronic devices. This work studies the current-controlled, two-step insulator-metal phase transition of VO2 in varying microwire geometries. Geometry-dependent scaling trends extracted from current-voltage measurements show that the first step induced by carrier injection is delocalized over the microwire, while the second, thermally-induced step is localized to a filament about 1 to 2 μm wide for 100 nm-thick sputtered VO2 films on SiO2. These effects are confirmed by direct infrared imaging, which also measures the change in optical absorption in the two steps. The difference between the threshold currents of the two steps increases as the microwires are narrowed. Micron- and sub-micron-wide VO2 structures can be used to separate the two phase transition steps in photonic and electronic devices.

Light-induced ultrafast phase transitions in VO2 thin film

International Nuclear Information System (INIS)

Lysenko, S.; Rua, A.J.; Vikhnin, V.; Jimenez, J.; Fernandez, F.; Liu, H.

2006-01-01

Vanadium dioxide shows a passive and reversible change from a monoclinic insulator phase to a metallic tetragonal rutile structure when the sample temperature is close to and over 68 deg. C. As a kind of functional material, VO 2 thin films deposited on fused quartz substrates were successfully prepared by the pulsed laser deposition (PLD) technique. With laser illumination at 400 nm on the obtained films, the phase transition (PT) occurred. The observed light-induced PT was as fast as the laser pulse duration of 100 fs. Using a femtosecond laser system, the relaxation processes in VO 2 were studied by optical pump-probe spectroscopy. Upon a laser excitation an instantaneous response in the transient reflectivity and transmission was observed followed by a relatively longer relaxation process. The alteration is dependent on pump power. The change in reflectance reached a maximum value at a pump pulse energy between 7 and 14 mJ/cm 2 . The observed PT is associated with the optical interband transition in VO 2 thin film. It suggests that with a pump laser illuminating on the film, excitation from the d θ,ε - state of valence band to the unoccupied excited mixed d θ,ε -π* - state of the conduction band in the insulator phase occurs, followed by a resonant transition to an unoccupied excited mixed d θ,ε -π* - state of the metallic phase band

Maximum oxygen uptake and objectively measured physical activity in Danish children 6-7 years of age: the Copenhagen school child intervention study

DEFF Research Database (Denmark)

Eiberg, Stig; Hasselstrøm, Henriette; Grønfeldt, Vivian

2005-01-01

Objectives: To provide normative data on maximum oxygen uptake (V·O2MAX) and physical activity in children 6-7 years of age and analyse the association between these variables. Methods: VO2MAX was measured in 366 boys (mean (SD) 6.8 (0.4) years of age) and 332 girls (6.7 (0.4) years of age) from.......5 (6.0) v 44.8 (5.6) ml/kg/min (+8%); pgirls. The difference in VO2MAX between boys and girls decreased to +2% when expressed relative to lean body mass (LBM). Absolute VO2MAX was related to LBM, body mass, and stature (all pBoys were more physically active than girls (mean counts...... +9.4%, pboys and girls with the same VO2MAX were compared, boys were more active. The difference in physical activity between the sexes was higher when sustained activity of higher intensity was compared. Conclusions: VO2MAX is higher in boys than girls (+11%), even when...

Tuning the work function of VO{sub 2}(1 0 0) surface by Ag adsorption and incorporation: Insights from first-principles calculations

Energy Technology Data Exchange (ETDEWEB)

Chen, Lanli; Wang, Xiaofang [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Shi, Siqi, E-mail: sqshi@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Cui, Yuanyuan [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Luo, Hongjie [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Gao, Yanfeng, E-mail: yfgao@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China)

2016-03-30

Graphical abstract: - Highlights: • After adsorption, there is a charge transfer from Ag to VO{sub 2}(1 0 0) surface, which thus increases the electron concentration in VO{sub 2} thin film. • Ag adsorption on VO{sub 2}(1 0 0) surface process is an exothermic chemical process, and the adsorption system is stable. • The work function can be tuned by Ag adsorption on and incorporation into the VO{sub 2}(1 0 0) surface, which in turn regulates the phase transition temperature of VO{sub 2}. - Abstract: VO{sub 2} is an attractive material for application to thermochromic optoelectronic devices such as smart windows, and Ag/VO{sub 2} double-layered structure can effectively decrease the phase transition temperature (T{sub c}) of VO{sub 2} thin film, which is very important for practical application of VO{sub 2}. Previous works has shown that the decrease in phase transition temperature (T{sub c}) seems to be relevant with the work function of VO{sub 2} in Ag/VO{sub 2} double-layered thin film, although the underlying mechanism of tuning its T{sub c} by Ag incorporation and adsorption on the VO{sub 2}(1 0 0) surface has been rarely investigated. Our first-principles calculations reveal that the adsorption of Ag atoms on the VO{sub 2}(1 0 0) surface rather than incorporation of Ag exhibits a lower work function, which is ascribed to an integrated effect of charge transfer from Ag to VO{sub 2}(1 0 0) surface and enhanced surface dipole moment. The results suggest that the decrease in work function of VO{sub 2} with Ag adsorption favors the reduction in T{sub c}. The current findings are helpful to understand the fundamental mechanism for yielding high-efficiency VO{sub 2}-based optoelectronic devices.

Formation of VO{sub 2} by rapid thermal annealing and cooling of sputtered vanadium thin films

Energy Technology Data Exchange (ETDEWEB)

Ba, Cheikhou O. F., E-mail: cheikhou.ba.1@ulaval.ca; Fortin, Vincent; Bah, Souleymane T.; Vallée, Réal [Centre d' optique, photonique et laser (COPL), Université Laval, Québec G1V 0A6 (Canada); Pandurang, Ashrit [Thin Films and Photonics Research Group (GCMP), Department of Physics and Astronomy, Université de Moncton, Moncton, New Brunswick E1A 3E9 (Canada)

2016-05-15

Sputtered vanadium-rich films were subjected to rapid thermal annealing-cooling (RTAC) in air to produce vanadium dioxide (VO{sub 2}) thin films with thermochromic switching behavior. High heating and cooling rates in the thermal oxidation process provided an increased ability to control the film's microstructure. X-ray diffraction patterns of the films revealed less intense VO{sub 2} peaks compared to traditional polycrystalline samples fabricated with a standard (slower) cooling time. Such films also exhibit a high optical switching reflectance contrast, unlike the traditional polycrystalline VO{sub 2} thin films, which show a more pronounced transmittance switching. The authors find that the RTAC process stabilizes the VO{sub 2} (M2) metastable phase, enabling a rutile-semiconductor phase transition (R-M2), followed by a semiconductor–semiconductor phase transition (M2-M1).

High performance of solvothermally prepared VO2(B as anode for aqueous rechargeable lithium batteries

Directory of Open Access Journals (Sweden)

Milošević Sanja

2015-01-01

Full Text Available The VO2 (B was synthesized via a simple solvothermal route at 160oC in ethanol. The initial discharge capacity of VO2 (B anode, in saturated aqueous solution of LiNO3, was 177 mAh g-1 at a current rate of 50 mA g-1. After 50 cycles capacity fade was 4%, but from 20th-50th cycle no capacity drop was observed. The VO2 (B has shown very good cyclability at current rate of even 1000 mA g-1 with initial discharge capacity of 92 mAh g-1. The excellent electrochemical performance of VO2 (B was attributed to the stability of micro-nano structures to repeated intercalation /deintercalation process, very good electronic conductivity as well as the very low charge transfer resistance in the aqueous electrolyte. [Projekat Ministarstva nauke Republike Srbije, br. III45014

Respostas fisiológicas e metabólicas em escolares submetidos a aulas de educação física voltadas ao desenvolvimento da aptidão cardiorespiratória

Directory of Open Access Journals (Sweden)

Sandra Fachineto

2012-05-01

Full Text Available Bons níveis dos componentes da aptidão física relacionada à saúde representam boas condições de vida, longevidade e menor risco de adquirir doenças hipocinéticas. Assim, este estudo teve por objetivo analisar as respostas fisiológicas - VO2max, Frequência cardíaca de repouso (FC, pressão arterial sistólica (PAS e diastólica de repouso (PAD e metabólicas - gasto energético de repouso (GER antes e após um programa orientado de atividades aeróbias em 22 adolescentes do 2º ano do ensino médio de uma escola Pública de Mondaí/SC. O resultado no Teste t pareado mostrou que quando comparados os valores médios das variáveis fisiológicas e metabólicas em relação a todo o grupo de alunos, foram constatadas diferenças significativas para todas as variáveis (VO2max, PAS e FC de repouso, GE de repouso com exceção para a PAD. Já na análise por gênero, observaram-se diferenças significativas no VO2máx e na PAD nos meninos e no VO2máx, FC e PAS nas meninas. Quanto ao gasto energético, não houve mudança significativa para ambos os gêneros. A partir disso, pode-se inferir que com um programa orientado de atividade física voltado para a saúde durante as aulas de Educação Física, é possível contribuir na saúde dos escolares.

VO2 thermochromic smart window for energy savings and generation

Science.gov (United States)

Zhou, Jiadong; Gao, Yanfeng; Zhang, Zongtao; Luo, Hongjie; Cao, Chuanxiang; Chen, Zhang; Dai, Lei; Liu, Xinling

2013-10-01

The ability to achieve energy saving in architectures and optimal solar energy utilisation affects the sustainable development of the human race. Traditional smart windows and solar cells cannot be combined into one device for energy saving and electricity generation. A VO2 film can respond to the environmental temperature to intelligently regulate infrared transmittance while maintaining visible transparency, and can be applied as a thermochromic smart window. Herein, we report for the first time a novel VO2-based smart window that partially utilises light scattering to solar cells around the glass panel for electricity generation. This smart window combines energy-saving and generation in one device, and offers potential to intelligently regulate and utilise solar radiation in an efficient manner.

Synthesis of boron and nitrogen co-doped carbon nanofiber as efficient metal-free electrocatalyst for the VO"2"+/VO_2"+ Redox Reaction

International Nuclear Information System (INIS)

Shi, Lang; Liu, Suqin; He, Zhen; Yuan, Hao; Shen, Junxi

2015-01-01

Boron or nitrogen mono-doped carbon nanofiber (CNF), and boron, nitrogen co-doped CNF are intentionally prepared as positive electrodes in a vanadium redox flow battery (VRFB). The structures and electrochemical properties of the materials are investigated by Scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry and electrochemical impendence spectroscopy. The experimental results indicate that either B or N mono-doped CNF shown better electrochemical performance than untreated one. Interestingly, for the B and N co-doped CNF, the separated case exhibited an outstanding electrochemical activity better than either B or N mono-doped case, while the bonded case leading to a sharp drop in conductivity and shown poor electrochemical performances. These results demonstrated that not the total amount of incorporated B and N but how the B and N are incorporated into carbon nanostructures determines the catalytic activity toward VO"2"+/VO_2"+ reaction. Moreover, the individual mechanism of the nitrogen and boron containing functional groups act as active sites have been analyzed.

Fourier transform infrared study of the phase transitions in (NH4)3VO2FO4

Science.gov (United States)

de Waal, D.; Heyns, A. M.

1994-01-01

Ammonium oxofluorovanadate compounds are known to show some potential as ferroelectric materials. The whole series of ammonium and sodium oxofluorovanadate compounds including Na3VO2F4 have already been prepared and investigated by means of various techniques including x-ray diffraction, EPR, and vibrational spectroscopy. It was established that the pure ammonium compound shows the two above mentioned transitions from phase A (below 200 K) to phase B (between 200 and 400 K) and phase C (above 400 K) while Na(NH4)2VO2F4 has only one transition from phase A to phase B around 400 K4. In the present study various aspects regarding the nature of the structures of (NH4)3VO2F3 and Na(NH4)2VO2F4 and its influence on the phase transitions have been investigated.

Synthesis and supercapacitor electrode of VO{sub 2}(B)/C core–shell composites with a pseudocapacitance in aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yifu, E-mail: yfzhang@dlut.edu.cn; Zheng, Jiqi; Hu, Tao; Tian, Fuping; Meng, Changgong

2016-05-15

Highlights: • A facile one-pot hydrothermal method was used to synthesize VO{sub 2}(B)/C core–shell composites. • VO{sub 2}(B)/C composites consisted of the crystal VO{sub 2}(B) phase and the amorphous carbon phase. • The supercapacitor property of VO{sub 2}(B)/C composites was improved by this novel structure. - Abstract: VO{sub 2}(B)/C core–shell composites were successfully prepared using commercial V{sub 2}O{sub 5}, glucose and water as the starting materials by a facile one-pot hydrothermal method. The composition of the products was characterized by the techniques including X-ray powder diffraction, infrared spectroscopy, Raman, energy-dispersive X-ray spectrometer and elemental analysis. The morphology of the products was observed by scanning electron microscopy and transmission electron microscopy tests. The results showed the products consisted of the crystal VO{sub 2}(B) phase and the amorphous carbon phase. The amorphous carbon contained lots of organic groups, such as −OH, C−H, C=O and C=C, etc., which suggested that the carbon here was organic carbon. The morphology of the as-obtained VO{sub 2}(B)/C composites was well-defined nanobelts, and each VO{sub 2}(B) core was encapsulated into carbon. Furthermore, the electrochemical properties of VO{sub 2}(B)/C core–shell composites were investigated by cyclic voltammetry and galvanostatic charge–discharge. The results showed the measured capacitance of VO{sub 2}(B)/C composites was mainly based on the pseudocapacitance. VO{sub 2}(B)/C composites displayed the specific capacitance of 203, 190, 182, 173, 164, and 147 F g{sup −1} at the current density of 0.2, 0.5, 1, 5, 10 and 20 A g{sup −1}, respectively. They also showed an excellent energy density of 198.9 W h kg{sup −1} at a power density of 504.5 W kg{sup −1} and a rapidly reversible redox Faraday response.

Phase evolution and infrared transmittance in monophasic VO{sub 2} synthesized by a rapid non-equilibrium process

Energy Technology Data Exchange (ETDEWEB)

Rajeswaran, Bharathi, E-mail: rajeswaran.bharathi@gmail.com; Umarji, A.M.

2017-04-01

VO{sub 2} displays a semiconducting to metallic (SMT) transition accessible near room temperature. This makes it one of the most sought after materials for electrical and optical switching. But this can be utilized only when the synthesis process yields phase pure VO{sub 2} without other oxides of vanadium. Across the SMT, VO{sub 2} exhibits difference crystal structures with a rich phase behavior of insulating monoclinic M1, M2 and T phases. The objective of this study is to synthesize phase pure VO{sub 2} and to investigate its structural evolution and infrared switching during the transition. In this work, a rapid non-equilibrium process namely Solution Combustion Synthesis (SCS) was employed. The structural phase transition (SPT) of VO{sub 2} nanostructures synthesized by SCS was investigated by in-situ temperature controlled XRD across the SMT. Gaussian curve fittings for measured XRD patterns revealed that competing phases of M1 and R significantly contribute to the observed pattern at every increase in temperature. The powders were further characterized by FTIR, DSC and DC electrical conductivity. These studies show that a sharp SMT was observed at 68–70 °C. Infrared transmittance experiments pinpointed the transition. Carrier density and mobility of VO{sub 2} were calculated. This suggests that this VO{sub 2} thus synthesized displays excellent phase transition behavior and can be utilized in optical and electrical switching. - Highlights: • VO{sub 2} has been synthesized by an easy, rapid, cost-effective, two-step, novel reaction. • High temperature XRD and DSC showed first order phase transition. • IR transmittance showed a decrease in transmittance at high temperatures enabling it to be used for IR sensing.

The epitaxial growth and interfacial strain study of VO{sub 2}/MgF{sub 2} (001) films by synchrotron based grazing incidence X-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Fan, L.L. [Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology, Yancheng 224051 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Chen, S. [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Liu, Q.H. [Science and Technology on Electro-optical Information Security Control Laboratory, Tianjin 300300 (China); Liao, G.M.; Chen, Y.L.; Ren, H. [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Zou, C.W., E-mail: czou@ustc.edu.cn [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China)

2016-09-05

High quality VO{sub 2} films with different thickness were epitaxially grown on MgF{sub 2} (001) substrates by oxide molecular beam epitaxy method. The evolution of interfacial strain was investigated by synchrotron based grazing incidence X-ray diffraction. By adjusting the incidence angles, the penetration depth of X-ray in VO{sub 2} film could be controlled and the thickness-depend lattice distortion in the epitaxial VO{sub 2} film was investigated. Due to the lattice mismatching, the pronounced tensile strain was observed in ultra-thin VO{sub 2} film. As the film thickness increasing, the interfacial strain relaxed gradually and became fully relaxed for thick VO{sub 2} films. Combined with the electric transport measurement, it was revealed that the phase transition temperature of ultra-thin VO{sub 2} film decreased greatly. The effect of interfacial strain induced phase transition modulation and the intrinsic mechanism was systematically discussed. - Highlights: • We prepared high quality VO{sub 2} epitaxial films on MgF{sub 2} (001) substrates by oxide molecular beam epitaxy method. • Synchrotron radiation grazing incidence X-ray diffraction was employed to detect evolution of strain along depth profile. • Based on a classic band structure model, the mechanism of strain controlled phase transition of VO{sub 2} was discussed.

Exercício aeróbio: Aspectos bioenergéticos, ajustes fisiológicos, fadiga e índices de desempenho

Directory of Open Access Journals (Sweden)

Fabrizio Caputo

2009-01-01

Full Text Available http://dx.doi.org/10.5007/1980-0037.2009v11n1p94   O objetivo deste trabalho foi trazer informações atuais e relevantes a respeito dos aspectos fisiológicos determinantes do rendimento e treinamento dos esportes aeróbios. Diferente do que se tem sido comumente apresentado, o metabolismo aeróbio responde rapidamente a demanda energética, com um exercício máximo de 75 s, apresentando iguais contribuições do sistema aeróbio e anaeróbio para a produção total de energia. No entanto, em exercícios acima dessa duração, os possíveis mecanismos da fadiga relacionados ao metabolismo anaeróbio ainda são os principais determinantes da tolerância ao exercício. Em durações mais prolongadas (acima de 60 min, a depleção de glicogênio, o desequilíbrio hídrico e eletrolítico, elevação da temperatura corporal terão um papel decisivo no rendimento. As mais importantes variáveis do desempenho aeróbio têm sido organizadas em um modelo que integra fatores como o consumo máximo de oxigênio (VO2max, limiares relacionados à resposta do lactato ao exercício e a eficiência muscular. Para atletas de elite, observa-se que em adição a um elevado valor de VO2max, o sucesso em eventos aeróbios também requer uma capacidade de se exercitar por um tempo prolongado a uma alta porcentagem do VO2max, bem como, uma eficiente conversão da energia produzida para a forma de trabalho muscular. Dependendo da duração da modalidade que se compete, os treinos deverão objetivar uma melhora da IVO2max, capacidade anaeróbia lática e tolerância à acidose, para as competições mais curtas, capacidade aeróbia para durações intermediárias e a melhora da capacidade de estocar glicogênio e aumentar a utilização de gordura, nas modalidades muito prolongadas.

Raman scattering and x-ray diffractometry studies of epitaxial TiO2 and VO2 thin films and multilayers on α-Al2O3(11 bar 20)

International Nuclear Information System (INIS)

Foster, C.M.; Chiarello, R.P.; Chang, H.L.M.; You, H.; Zhang, T.J.; Frase, H.; Parker, J.C.; Lam, D.J.

1993-01-01

Epitaxial thin films of TiO 2 and VO 2 single layers and TiO 2 /VO 2 multilayers were grown on (11 bar 20) sapphire (α-Al 2 O 3 ) substrates using the metalorganic chemical vapor deposition technique and were characterized using Raman scattering and four x-ray diffractometry. X-ray diffraction results indicate that the films are high quality single crystal material with well defined growth plane and small in-plane and out-of-plane mosaic. Single-layer films are shown to obey the Raman selection rules of TiO 2 and VO 2 single crystals. The close adherence to the Raman selection rules indicates the high degree of orientation of the films, both parallel and perpendicular to the growth plane. Selection rule spectra of two and three layer TiO 2 /VO 2 multilayers are dominated by the VO 2 layers with only minimal signature of the TiO 2 layers. Due to the low band gap of semiconducting vanadium dioxide, we attribute the strong signature of the VO 2 layers to resonant enhancement of the VO 2 Raman component accompanied with absorption of the both the incident and scattered laser light from the TiO 2 layers

Investigation of the physical, optical, and photocatalytic properties of CeO2/Fe-doped InVO4 composite

Science.gov (United States)

Chaison, Jindaporn; Wetchakun, Khatcharin; Wetchakun, Natda

2017-12-01

The CeO2/Fe-doped InVO4 composites with various Fe concentrations (0.5, 1.0, 2.0, 5.0 and 6.0 mol%) was synthesized by homogeneous precipitation and hydrothermal methods. The as-synthesized samples were characterized by powder X-ray diffraction (XRD), Brunauer Emmett and Teller (BET)-specific surface area, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy (DRS). Fe-doping into InVO4 crystal induces the distortion of the crystalline structure, the transformation of InVO4 morphology, and the new energy subband level generation of Fe between the CB and VB edge of InVO4. The electron excitation from the VB to Fe orbitals results in the decreased band gap and the extended absorption of visible-light, and thus enhances its photocatalytic performance. Visible-light-driven photocatalytic degradation of Rhodamine B (RhB) dye in water was used to evaluate the photocatalytic performance of CeO2/Fe-doped InVO4 composites. The results revealed that there is an optimum Fe (5.0 mol %) doping level. The composite with the optimum doping level obtains high photocatalytic activity of CeO2/Fe-doped InVO4 composite compared to pure CeO2 and pure InVO4 host. The increase of photocatalytic activity of CeO2/Fe-doped InVO4 composite was ascribed to the surface area, crystal defect, and band gap energy. Moreover, the photocatalytic enhancement is also because iron ions act as a trapping site, which results in the higher separation efficiency of photogenerated electrons and holes pairs in the CeO2/InVO4 composite. The evaluation of radical scavengers confirmed that hydroxyl radical was the main active species during the photodegradation of RhB. These synergistic effects are responsible for the enhanced photocatalytic activity of CeO2/Fe-doped InVO4 composite. Furthermore, the possible enhanced photocatalytic mechanism

Un nuevo modelo fenomenológico y diferencial para predecir la respuesta mecánica de materiales metálicos policristalinos sometidos a deformación en caliente

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Castellanos, J.

2012-10-01

Full Text Available This paper presents a new phenomenological and differential model (that use differential equations to predict the flow stress of a metallic polycrystalline material under hot working. The model, called MCC, depends on six parameters and uses two internal variables to consider the strain hardening, dynamic recovery and dynamic recrystallization processes that occur under hot working. The experimental validation of the MCC model has been carried out by means of stress-strain curves from torsion tests at high temperature (900 ºC a 1200 ºC and moderate high strain rate (0.005 s^-1 to 5 s^-1 in a high nitrogen steel. The results reveal the very good agreement between experimental and predicted stresses. Furthermore, the Garofalo a-parameter and the strain to reach 50 % of recrystallized volume fraction have been employed as a control check being a first step to the physical interpretation of variables and parameters of the MCC model.

Este trabajo presenta un nuevo modelo fenomenológico y diferencial (que emplea ecuaciones diferenciales para predecir la respuesta mecánica de un material metálico policristalino sometido a deformación en caliente. El modelo, llamado MCC, depende de seis parámetros y utiliza dos variables internas para considerar los procesos de endurecimiento por deformación, restauración y recristalización dinámicas. La validación experimental del modelo MCC se ha realizado empleando curvas tensión-deformación procedentes de ensayos de torsión a alta temperatura (900 ºC a 1.200 ºC y moderadamente alta velocidad de deformación (0,005 s^-1 a 5 s^-1 sobre un acero de alto contenido en nitrógeno. Los resultados obtenidos revelan la concordancia significativa entre las tensiones experimentales y predichas. Además el parámetro a de Garofalo y la deformación para el 50 % de volumen recristalizado se han utilizado como elementos de control para realizar un primer paso en la

Cardioprotective Effect of High Intensity Interval Training and Nitric Oxide Metabolites (NO2 (-), NO3 (-)).

Science.gov (United States)

Fallahi, Aliasghar; Gaeini, Abbasali; Shekarfroush, Shahnaz; Khoshbaten, Ali

2015-09-01

The aim of this study was to investigate the effects of High-Intensity Interval Training (HIIT) on nitric oxide metabolites (NO2(-), NO3(-)) and myocardial infarct size after Ischemia/Reperfusion (I/R) injury in healthy male rats. A total of 44 Wistar rats were randomly divided into 4 groups including HIIT (n=8), HIIT + IR protocol (n=14), control (n=8), and control + IR (n=14). Each training session of HIIT consisted of 1 hour of exercise in three stages: 6-minute running at 50-60% VO2max for warm-up; 7 intervals of 7-minute running on treadmill with a slope of 5° to 20° (4 minutes with an intensity of 80-100% VO2max and 3 minutes at 50-60% VO2max); and 5-minute running at 50-60% VO2max for cool-down. The control group did not participate in any exercise program. Nitric Oxide (NO) and its metabolites were measured by using Griess reaction test. The results showed that eight weeks of exercise training exerted a significantly increasing effect on nitrite (8.55 μmol per liter, equivalent to 34.79%), nitrate (62.02 μmol per liter, equivalent to 149.48%), and NOx (66 μmol per liter, equivalent to 98.11%) in the HIIT group compared with the control group. The results showed myocardial infract size (IS) was significantly smaller (23.2%, PHIIT program can protect the heart from I/R injury and decrease myocardial infarction.

Anomalous optical switching and thermal hysteresis during semiconductor-metal phase transition of VO2 films on Si substrate

International Nuclear Information System (INIS)

Leahu, G.; Li Voti, R.; Sibilia, C.; Bertolotti, M.

2013-01-01

We present a detailed infrared study of the semiconductor-to-metal transition (SMT) in a vanadium dioxide (VO 2 ) film deposited on silicon wafer. The VO 2 phase transition is studied in the mid-infrared region by analyzing the transmittance and the reflectance measurements, and the calculated emissivity. The reflectance has been measured in two configurations: from the side of the VO 2 film and from that of Si wafer. The results show a strong asymmetry between the emissivity in the two configurations, and the fact that the emissivity dynamic range from the silicon side is twice as large than that from the VO 2 side. The temperature behaviour of the emissivity during the SMT put into evidence the phenomenon of the anomalous absorption in VO 2 , which has been explained by applying the Maxwell Garnett effective medium approximation theory

Experimental investigation of the EPR parameters and molecular orbital bonding coefficients for VO{sup 2+} ion in NaH{sub 2}PO{sub 4}·2H{sub 2}O single crystals

Energy Technology Data Exchange (ETDEWEB)

Kalfaoğlu, Emel [Ondokuz Mayıs University, Faculty of Sciences, Department of Physics, 55139 Kurupelit-Samsun (Turkey); Karabulut, Bünyamin, E-mail: bbulut@omu.edu.tr [Ondokuz Mayıs University, Faculty of Engineering, Department of Computer Engineering, 55139 Kurupelit-Samsun (Turkey)

2016-09-15

Electron paramagnetic resonance (EPR) spectra of VO{sup 2+} ions in NaH{sub 2}PO{sub 4}·2H{sub 2}O single crystal have been studied. The spin-Hamiltonian parameters and molecular orbital bonding coefficients were calculated. The angular variation of the EPR spectra shows two different VO{sup 2+} complexes. These are located in different chemical environment and each environment contains four magnetically inequivalent VO{sup 2+} sites. The crystal field around VO{sup 2+} ion is approximately axially symmetric since a strong V=O bond distorts the crystal lattice. Spin Hamiltonian parameters and molecular orbital bonding coefficients were calculated from the EPR data and the nature of bonding in the complex was discussed together.

Relation of oxygen uptake to work rate in prepubertal healthy children - reference for VO2/W-slope and effect on cardiorespiratory fitness assessment.

Science.gov (United States)

Tompuri, Tuomo; Lintu, Niina; Laitinen, Tomi; Lakka, Timo A

2017-08-09

Exercise testing by cycle ergometer allows to observe the interaction between oxygen uptake (VO 2 ) and workload (W), and VO 2 /W-slope can be used as a diagnostic tool. Respectively, peak oxygen uptake (VO 2 PEAK ) can be estimated by maximal workload. We aim to determine reference for VO 2 /W-slope among prepubertal children and define agreement between estimated and measured VO 2 PEAK . A total of 38 prepubertal children (20 girls) performed a maximal cycle ergometer test with respiratory gas analysis. VO 2 /W-slopes were computed using linear regression. Agreement analysis by Bland and Altman for estimated and measured VO 2 PEAK was carried out including limits of agreement (LA). Determinants for VO 2 /W-slopes and estimation bias were defined. VO2/W-slope was in both girls and boys ≥9·4 and did not change with exercise level, but the oxygen cost of exercise was higher among physically more active children. Estimated VO 2 PEAK had 6·4% coefficient of variation, and LA varied from 13% underestimation to 13% overestimation. Bias had a trend towards underestimation along lean mass proportional VO 2 PEAK . The primary determinant for estimation bias was VO2/W-slope (β = -0·65; PW-slope among healthy prepubertal children were similar to those published for adults and among adolescents. Estimated and measured VO 2 PEAK should not be considered to be interchangeable because of the variation in the relationship between VO 2 and W. On other hand, variation in the relationship between VO 2 and W enables that VO 2 /W-slope can be used as a diagnostic tool. © 2017 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Electronic transport in VO{sub 2}—Experimentally calibrated Boltzmann transport modeling

Energy Technology Data Exchange (ETDEWEB)

Kinaci, Alper; Rosenmann, Daniel; Chan, Maria K. Y., E-mail: debasish.banerjee@toyota.com, E-mail: mchan@anl.gov [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kado, Motohisa [Higashifuji Technical Center, Toyota Motor Corporation, Susono, Shizuoka 410-1193 (Japan); Ling, Chen; Zhu, Gaohua; Banerjee, Debasish, E-mail: debasish.banerjee@toyota.com, E-mail: mchan@anl.gov [Materials Research Department, Toyota Motor Engineering and Manufacturing North America, Inc., Ann Arbor, Michigan 48105 (United States)

2015-12-28

Materials that undergo metal-insulator transitions (MITs) are under intense study, because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO{sub 2} has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of electronic transport in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach with Hubbard U correction (DFT + U) to model electronic transport properties in VO{sub 2} in the semiconducting and metallic regimes, focusing on band transport using the Boltzmann transport equations. We synthesized high quality VO{sub 2} films and measured the transport quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable transport properties.

The Impact of Firefighter Personal Protective Equipment and Treadmill Protocol on Maximal Oxygen Uptake

Science.gov (United States)

Lee, Joo-Young; Bakri, Ilham; Kim, Jung-Hyun; Son, Su-Young; Tochihara, Yutaka

2015-01-01

This study investigated the effects of firefighter personal protective equipment (PPE) on the determination of maximal oxygen uptake (VO2max) while using two different treadmill protocols: a progressive incline protocol (PIP) and a progressive speed protocol (PSP), with three clothing conditions (Light-light clothing; Boots-PPE with rubber boots; Shoes-PPE with running shoes). Bruce protocol with Light was performed for a reference test. Results showed there was no difference in VO2max between Bruce Light, PIP Light, and PSP Light. However, VO2max was reduced in Boots and Shoes with shortened maximal performance time (7 and 6 min reduced for PIP Boots and Shoes, respectively; 11 and 9 min reduced for PSP Boots and Shoes, respectively), whereas the increasing rate of VO2 in Boots and Shoes during submaximal exercise was greater compared with Light. Wearing firefighter boots compared with wearing running shoes also significantly affected submaximal VO2 but not VO2max. These results suggest that firefighters’ maximal performance determined from a typical VO2max test without wearing PPE may overestimate the actual performance capability of firefighters wearing PPE. PMID:23668854

A detailed study of the dehydration process in synthetic strelkinite, Na[(UO2)(VO4)] . nH2O (n = 0, 1, 2)

International Nuclear Information System (INIS)

Suleimanov, Evgeny V.; Somov, Nikolay V.; Chuprunov, Evgeny V.; Mayatskikh, Ekaterina F.; Depmeier, Wulf

2012-01-01

Synthetic strelkinite Na[(UO 2 )(VO 4 )] . nH 2 O (n = 0, 1, 2) was systematically investigated by single crystal X-ray diffraction and thermoanalytical methods. The anhydrous form and two hydrates were isolated as single crystals and the structures of these phases solved: Na[(UO 2 )(VO 4 )], monoclinic, P2 1 /c, a = 6.0205(1) Aa, b = 8.3365(1) Aa, c = 10.4164(2) Aa, β = 100.466(2) , V = 514.10(1) Aa 3 , R 1 = 0.0337; Na[(UO 2 )(VO 4 )] . H 2 O, monoclinic, P2 1 /c, a = 7.722(2) Aa, b = 8.512(1) Aa, c = 10.480(4) Aa, β = 113.18(3) , V = 633.3(3) Aa 3 , R 1 = 0.1658; Na[(UO 2 )(VO 4 )] . 2 H 2 O, monoclinic, P2 1 /n, a = 16.2399(5) Aa, b = 8.2844(2) Aa, c = 10.5011(2) Aa, β = 97.644(2) , V = 1400.24(6) Aa 3 , R 1 = 0.0776. A possible mechanism of the structural transformation processes during dehydration is proposed based on the structures of the anhydrous phase and the hydrates. (orig.)

In healthy elderly postmenopausal women variations in BMD and BMC at various skeletal sites are associated with differences in weight and lean body mass rather than by variations in habitual physical activity, strength or VO2max.

Science.gov (United States)

Schöffl, I; Kemmler, W; Kladny, B; Vonstengel, S; Kalender, W A; Engelke, K

2008-01-01

The objective of this study was an integrated cross-sectional investigation for answering the question whether differences in bone mineral density in elderly postmenopausal women are associated with differences in habitual physical activity and unspecific exercise levels. Two hundred and ninety nine elderly women (69-/+3 years), without diseases or medication affecting bone metabolism were investigated. The influence of weight, body composition and physical activity on BMD was measured at multiple sites using different techniques (DXA, QCT, and QUS). Physical activity and exercise level were assessed by questionnaire, maximum strength of the legs and aerobic capacity. Variations in physical activity or habitual exercise had no effect on bone. The only significant univariate relation between strength/VO(2)max and BMD/BMC that remained after adjusting for confounding variables was between arm BMD (DXA) and hand-grip strength. The most important variable for explaining BMD was weight and for cortical BMC of the femur (QCT) lean body mass. Weight and lean body mass emerge as predominant predictors of BMD in normal elderly women, whereas the isolated effect of habitual physical activity, unspecific exercise participation, and muscle strength on bone parameters is negligible. Thus, an increase in the amount of habitual physical activity will probably have no beneficial impact on bone.

New intelligent multifunctional SiO2/VO2 composite films with enhanced infrared light regulation performance, solar modulation capability, and superhydrophobicity.

Science.gov (United States)

Wang, Chao; Zhao, Li; Liang, Zihui; Dong, Binghai; Wan, Li; Wang, Shimin

2017-01-01

Highly transparent, energy-saving, and superhydrophobic nanostructured SiO 2 /VO 2 composite films have been fabricated using a sol-gel method. These composite films are composed of an underlying infrared (IR)-regulating VO 2 layer and a top protective layer that consists of SiO 2 nanoparticles. Experimental results showed that the composite structure could enhance the IR light regulation performance, solar modulation capability, and hydrophobicity of the pristine VO 2 layer. The transmittance of the composite films in visible region ( T lum ) was higher than 60%, which was sufficient to meet the requirements of glass lighting. Compared with pristine VO 2 films and tungsten-doped VO 2 film, the near IR control capability of the composite films was enhanced by 13.9% and 22.1%, respectively, whereas their solar modulation capability was enhanced by 10.9% and 22.9%, respectively. The water contact angles of the SiO 2 /VO 2 composite films were over 150°, indicating superhydrophobicity. The transparent superhydrophobic surface exhibited a high stability toward illumination as all the films retained their initial superhydrophobicity even after exposure to 365 nm light with an intensity of 160 mW . cm -2 for 10 h. In addition, the films possessed anti-oxidation and anti-acid properties. These characteristics are highly advantageous for intelligent windows or solar cell applications, given that they can provide surfaces with anti-fogging, rainproofing, and self-cleaning effects. Our technique offers a simple and low-cost solution to the development of stable and visible light transparent superhydrophobic surfaces for industrial applications.

The Effects of Free-Living Interval-Walking Training on Glycemic Control, Body Composition, and Physical Fitness in Type 2 Diabetes Patients

DEFF Research Database (Denmark)

Karstoft, Kristian; Winding, Kamilla; Knudsen, Sine H

2013-01-01

at moderate intensity, whereas interval walkers alternated 3-min repetitions at low and high intensity. Before and after the 4-month intervention, the following variables were measured: VO(2)max, body composition, and glycemic control (fasting glucose, HbA(1c), oral glucose tolerance test, and continuous...... glucose monitoring [CGM]).RESULTSTraining adherence was high (89 ± 4%), and training energy expenditure and mean intensity were comparable. VO(2)max increased 16.1 ± 3.7% in the interval-walking group (P

Estimated Prestroke Peak VO2 Is Related to Circulating IGF-1 Levels During Acute Stroke.

Science.gov (United States)

Mattlage, Anna E; Rippee, Michael A; Abraham, Michael G; Sandt, Janice; Billinger, Sandra A

2017-01-01

Background Insulin-like growth factor-1 (IGF-1) is neuroprotective after stroke and is regulated by insulin-like binding protein-3 (IGFBP-3). In healthy individuals, exercise and improved aerobic fitness (peak oxygen uptake; peak VO 2 ) increases IGF-1 in circulation. Understanding the relationship between estimated prestroke aerobic fitness and IGF-1 and IGFBP-3 after stroke may provide insight into the benefits of exercise and aerobic fitness on stroke recovery. Objective The purpose of this study was to determine the relationship of IGF-1 and IGFBP-3 to estimated prestroke peak VO 2 in individuals with acute stroke. We hypothesized that (1) estimated prestroke peak VO 2 would be related to IGF-1 and IGFBP-3 and (2) individuals with higher than median IGF-1 levels will have higher estimated prestroke peak VO 2 compared to those with lower than median levels. Methods Fifteen individuals with acute stroke had blood sampled within 72 hours of hospital admission. Prestroke peak VO 2 was estimated using a nonexercise prediction equation. IGF-1 and IGFBP-3 levels were quantified using enzyme-linked immunoassay. Results Estimated prestroke peak VO 2 was significantly related to circulating IGF-1 levels (r = .60; P = .02) but not IGFBP-3. Individuals with higher than median IGF-1 (117.9 ng/mL) had significantly better estimated aerobic fitness (32.4 ± 6.9 mL kg -1 min -1 ) than those with lower than median IGF-1 (20.7 ± 7.8 mL kg -1 min -1 ; P = .03). Conclusions Improving aerobic fitness prior to stroke may be beneficial by increasing baseline IGF-1 levels. These results set the groundwork for future clinical trials to determine whether high IGF-1 and aerobic fitness are beneficial to stroke recovery by providing neuroprotection and improving function. © The Author(s) 2016.

Interação de variáveis biomecânicas na composição de "feedback" visual aumentado para o ensino do ciclismo Interacción de variables biomecánicas en la composición de feedback visual aumentado para el enseñanza del ciclismo Interaction of biomechanical variables in the composition of visual augmented feedback for learning cycling

Directory of Open Access Journals (Sweden)

Guilherme Garcia Holderbaum

2012-12-01

Full Text Available O objetivo deste estudo foi testar uma metodologia para o ensino da técnica da pedalada do ciclismo utilizando variáveis biomecánicas para desenvolver um sistema de "feedback" visual aumentado (FVA. Participaram do estudo 19 indivíduos, sem experiência no ciclismo , divididos em grupo experimental (n = 10 e controle (n = 9. Inicialmente foi realizado um pré-teste para determinar o consumo máximo de oxigênio (VO2máx bem como a carga de trabalho utilizada nas sessões práticas que correspondeu a 60% do VO2máx. Em seguida foram realizadas sete sessões de prática. O grupo experimental foi submetido ao FVA e o grupo controle ao "feedback" aumentado (FA. O teste de retenção mostrou um aumento de 21 % na média do índice de efetividade (IE do grupo experimental quando comparado ao grupo controle. Os resultados mostraram que variáveis biomecánicas são apropriadas para o desenvolvimento de FVA e podem contribuir no processo de ensino-aprendizagem da técnica da pedalada do ciclismo.El objetivo de este estudio fue probar una metodología para enseñar la técnica de el ciclismo mediante la utilización de variables biomecánicas para desarrollar un sistema de feedback visual aumentado (FVA. Fue aplicado en 19 personas sin experiencia en el ciclismo, divididos en dos grupos (experimental = 10 y control = 9. Inicialmente se realizó un pre-test para determinar el consumo máximo de oxígeno (VO2max y la carga de trabajo utilizada en las sesiones de práctica que correspondía al 60% del VO2máx. El grupo experimental fue sometido a la FVA y el control a la feedback aumentado (FA. El ensayo de retención mostró un aumento del 21% en la media del índice de eficacia (IE en el grupo experimental en comparación con el grupo control. Los resultados mostraron que las variables biomecánicas son apropiadas para el desarrollo de la FVA y puede contribuir al proceso de enseñanza y aprendizaje del ciclismo.The aim of this study was to test a

Registration of cytoplasmic male-sterile oilseed sunflower genetic stocks CMS GIG2 and CMS GIG2-RV, and fertility restoration lines RF GIG2-MAX 1631 and RF GIG2-MAX 1631-RV

Science.gov (United States)

Two cytoplasmic male-sterile (CMS) oilseed sunflower (Helianthus annuus L.) genetic stocks, CMS GIG2 (Reg. No. xxx, PI xxxx), and CMS GIG2-RV (Reg. No. xxx, PI xxxx), and corresponding fertility restoration lines RF GIG2-MAX 1631 (Reg. No. xxx, PI xxxx) and RF GIG2-MAX 1631-RV (Reg. No. xxx, PI xxx...

High-performance thermal sensitive W-doped VO{sub 2}(B) thin film and its identification by first-principles calculations

Energy Technology Data Exchange (ETDEWEB)

Wan, Dongyun; Xiong, Ping; Chen, Lanli [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Shi, Siqi, E-mail: sqshi@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Ishaq, Ahmad [National Center for Physics, Quaid-I-Azam University, Islamabad 44000 (Pakistan); Luo, Hongjie [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Gao, Yanfeng, E-mail: yfgao@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China)

2017-03-01

Graphical abstract: VO{sub 2}(B) thin films with high TCR and suitable resistance were first achieved by W doping. The mechanism for performance improvement was studied by first-principles calculations. The two-dimensional octahedral structure of VO{sub 2}(B) favors the strain control with W-doping for achieving a large TCR, which overcomes the contradiction between the high conductivity and large TCR generated by dopants in VO{sub 2}(M). - Highlights: • High performance W-doped VO{sub 2}(B) thin films were first achieved by co-sputtering. • Mechanism for performance improvement was studied by first-principles calculations. • The two-dimensional octahedral structure of VO{sub 2} (B) favors the strain control. • Achieved VO{sub 2} films possess high thermal sensitivity (TCR: −3.9%/K & R{sub 0}: 32.7 kΩ). - Abstract: VO{sub 2}(B) is currently a preferred phase structure for the application as bolometer material, which, however, suffers from low temperature-coefficient-of-resistance (TCR) values and large resistances. Here we present the combined experimental and first-principles calculations study on both doped and undoped VO{sub 2}(B) thin films enabling us to attain high TCR (−3.9%/k) and suitable square-resistance (32.7 kΩ) by controlled W doping employing the widely used magnetron sputtering technique. The TCR value is 50% larger than reported ones at the similar resistance. The underlying microscopic mechanism for the performance improvement was studied and results indicated that the introduction of extra electrons and the variation in the band structure resulting from the incorporation of W{sup 6+} ions in the VO{sub 2}(B) crystal lattice contribute to the enhancement of the electronic conductivity. Moreover, the special two-dimensional octahedral structure of monoclinic (C2/m) B-phase VO{sub 2} favors the strain control with W-doping for achieving a large TCR, which overcomes the analogous predicament between the high conductivity and large TCR

Visual Impairment does not Limit Training Effects in Development of Aerobic and Anaerobic Capacity in Tandem Cyclists

Directory of Open Access Journals (Sweden)

Malwina Kamelska Anna

2015-12-01

Full Text Available The study aimed to investigate the differences in the effects of 7-month training on aerobic and anaerobic capacity in tandem cycling athletes with and without visual impairment. In this study, Polish elite (n=13 and sub-elite (n=13 visually impaired (VI (n=13; 40.8 ±12.8 years and properly sighted (PS (n=13; 36.7 ±12.2 years tandem-cycling athletes participated voluntarily in 7-month routine training. The following pre-/post-training measurements were conducted on separate days: maximal oxygen uptake (VO2max was estimated with age correction using the Physical Working Capacity test on a bicycle ergometer according to the Astrand-Ryhming method. Maximal power output (Pmax was evaluated using the Quebec test on a bicycle ergometer. At baseline, VO2max (47.8 ±14.1 vs 42.0 ±8.3 ml/kg/min, respectively and Pmax (11.5 ±1.5 vs 11.5 ±1.0 W/kg did not differ significantly between PS and VI cyclists. However, differences in aerobic capacity were considered as clinically significant. Two-way ANOVA revealed that after 7 month training, there were statistically significant increases in VO2max (p=0.003 and Pmax (p=0.009 among VI (VO2max, +9.1%; Pmax, +6.3% and PS (VO2max, +9.1%; Pmax, +11.7% cyclists, however, no time x visual impairment interaction effect was found (VO2max, p=0.467; Pmax, p=0.364. After training, VO2max (p=0.03, but not Pmax (p=0.13, was significantly greater in elite compared to sub-elite tandem cyclists. VI and PS tandem cyclists showed similar rates of improvement in VO2max and Pmax after 7-month training. VO2max was a significant determinant of success in tandem cycling. This is one of the first studies providing reference values for aerobic and anaerobic capacity in visually impaired cyclists.