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ENGINEERING (1202 journals)                  1 2 3 4 5 6 7 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 7)
3D Research     Hybrid Journal   (Followers: 19)
AAPG Bulletin     Full-text available via subscription   (Followers: 5)
AASRI Procedia     Open Access   (Followers: 14)
Abstract and Applied Analysis     Open Access   (Followers: 3)
Aceh International Journal of Science and Technology     Open Access   (Followers: 2)
ACS Nano     Full-text available via subscription   (Followers: 207)
Acta Geotechnica     Hybrid Journal   (Followers: 6)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 1)
Acta Scientiarum. Technology     Open Access   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Active and Passive Electronic Components     Open Access   (Followers: 7)
Adaptive Behavior     Hybrid Journal   (Followers: 10)
Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi     Open Access  
Adsorption     Hybrid Journal   (Followers: 4)
Advanced Engineering Forum     Full-text available via subscription   (Followers: 4)
Advanced Science     Open Access   (Followers: 4)
Advanced Science Focus     Free   (Followers: 3)
Advanced Science Letters     Full-text available via subscription   (Followers: 4)
Advanced Science, Engineering and Medicine     Partially Free   (Followers: 6)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 18)
Advances in Artificial Neural Systems     Open Access   (Followers: 3)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Complex Systems     Hybrid Journal   (Followers: 7)
Advances in Engineering Software     Hybrid Journal   (Followers: 25)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 14)
Advances in Fuzzy Systems     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 9)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 18)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 22)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 7)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 28)
Advances in Operations Research     Open Access   (Followers: 11)
Advances in OptoElectronics     Open Access   (Followers: 5)
Advances in Physics Theories and Applications     Open Access   (Followers: 13)
Advances in Polymer Science     Hybrid Journal   (Followers: 40)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Remote Sensing     Open Access   (Followers: 34)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aerobiologia     Hybrid Journal   (Followers: 1)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 4)
AIChE Journal     Hybrid Journal   (Followers: 28)
Ain Shams Engineering Journal     Open Access   (Followers: 5)
Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access  
Alexandria Engineering Journal     Open Access  
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 28)
American Journal of Engineering and Applied Sciences     Open Access   (Followers: 11)
American Journal of Engineering Education     Open Access   (Followers: 9)
American Journal of Environmental Engineering     Open Access   (Followers: 16)
American Journal of Industrial and Business Management     Open Access   (Followers: 23)
Analele Universitatii Ovidius Constanta - Seria Chimie     Open Access  
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Pure and Applied Logic     Open Access   (Followers: 2)
Annals of Regional Science     Hybrid Journal   (Followers: 7)
Annals of Science     Hybrid Journal   (Followers: 7)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applicable Analysis: An International Journal     Hybrid Journal   (Followers: 1)
Applied Catalysis A: General     Hybrid Journal   (Followers: 5)
Applied Catalysis B: Environmental     Hybrid Journal   (Followers: 6)
Applied Clay Science     Hybrid Journal   (Followers: 4)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Magnetic Resonance     Hybrid Journal   (Followers: 3)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Physics Research     Open Access   (Followers: 4)
Applied Sciences     Open Access   (Followers: 3)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 4)
Arabian Journal for Science and Engineering     Hybrid Journal   (Followers: 5)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 4)
Archives of Foundry Engineering     Open Access  
Archives of Thermodynamics     Open Access   (Followers: 8)
Arkiv för Matematik     Hybrid Journal  
ASEE Prism     Full-text available via subscription   (Followers: 2)
Asian Engineering Review     Open Access  
Asian Journal of Applied Science and Engineering     Open Access   (Followers: 1)
Asian Journal of Applied Sciences     Open Access   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 7)
Asian Journal of Control     Hybrid Journal  
Asian Journal of Current Engineering & Maths     Open Access  
Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 9)
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
ATZagenda     Hybrid Journal  
ATZextra worldwide     Hybrid Journal  
Australasian Physical & Engineering Sciences in Medicine     Hybrid Journal   (Followers: 1)
Australian Journal of Multi-Disciplinary Engineering     Full-text available via subscription   (Followers: 2)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 7)
Avances en Ciencias e Ingeniería     Open Access  
Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 1)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
Basin Research     Hybrid Journal   (Followers: 3)
Batteries     Open Access   (Followers: 3)
Bautechnik     Hybrid Journal   (Followers: 1)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 24)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 3)
BER : Manufacturing Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Motor Trade Survey     Full-text available via subscription   (Followers: 1)
BER : Retail Sector Survey     Full-text available via subscription   (Followers: 2)
BER : Retail Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Manufacturing : An Executive Summary     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Retail : An Executive Summary     Full-text available via subscription   (Followers: 3)
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biofuels Engineering     Open Access  
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 8)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 16)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 31)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 8)
Biomedical Science and Engineering     Open Access   (Followers: 4)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 4)
BioNanoMaterials     Hybrid Journal   (Followers: 1)
Biotechnology Progress     Hybrid Journal   (Followers: 40)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription  
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access   (Followers: 2)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 10)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 14)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 3)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Full-text available via subscription   (Followers: 14)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 40)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 7)
Case Studies in Thermal Engineering     Open Access   (Followers: 4)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 3)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 5)
CEAS Space Journal     Hybrid Journal  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 4)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 6)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Engineering     Open Access   (Followers: 2)
Chinese Science Bulletin     Open Access   (Followers: 1)
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access   (Followers: 1)
Ciencias Holguin     Open Access   (Followers: 1)
CienciaUAT     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 10)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 13)
City, Culture and Society     Hybrid Journal   (Followers: 20)
Clay Minerals     Full-text available via subscription   (Followers: 8)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Coal Science and Technology     Full-text available via subscription   (Followers: 4)
Coastal Engineering     Hybrid Journal   (Followers: 10)
Coastal Engineering Journal     Hybrid Journal   (Followers: 3)
Coatings     Open Access   (Followers: 2)
Cogent Engineering     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 1)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 13)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 13)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 2)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 23)
Composite Interfaces     Hybrid Journal   (Followers: 5)
Composite Structures     Hybrid Journal   (Followers: 242)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 174)
Composites Part B : Engineering     Hybrid Journal   (Followers: 216)
Composites Science and Technology     Hybrid Journal   (Followers: 159)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access  
Computational Geosciences     Hybrid Journal   (Followers: 12)
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computational Science and Discovery     Full-text available via subscription   (Followers: 2)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 6)
Computer Science and Engineering     Open Access   (Followers: 16)
Computers & Geosciences     Hybrid Journal   (Followers: 25)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 5)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 4)
Computers and Geotechnics     Hybrid Journal   (Followers: 8)
Computing and Visualization in Science     Hybrid Journal   (Followers: 6)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 25)
Conciencia Tecnologica     Open Access  
Concurrent Engineering     Hybrid Journal   (Followers: 3)
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 6)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 7)
Control Engineering Practice     Hybrid Journal   (Followers: 40)
Control Theory and Informatics     Open Access   (Followers: 7)
Corrosion Science     Hybrid Journal   (Followers: 24)
CT&F Ciencia, Tecnologia y Futuro     Open Access  
CTheory     Open Access  
Current Applied Physics     Full-text available via subscription   (Followers: 4)

        1 2 3 4 5 6 7 | Last

Journal Cover Applied Magnetic Resonance
  [SJR: 0.358]   [H-I: 34]   [3 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1613-7507 - ISSN (Online) 0937-9347
   Published by Springer-Verlag Homepage  [2335 journals]
  • Electron-Spin Relaxation Measurements of Biological [2Fe-2S] Cluster
           System in View of Electron Spin Quantum Bits
    • Authors: Amgalanbaatar Baldansuren
      Pages: 275 - 286
      Abstract: At 20 K, as long as \(T_m\sim 800-1000\)  ns were measured for the [2Fe-2S] cluster in its intrinsic protein environment. Such relaxations are a relatively long coherence time for the low-spin \(S=1/2\) system. For this biological cluster, the phase memory time was found significantly affected by the nuclear hyperfine interactions of \(^{14}\) N with \(I=1\) . When labeling the surrounding ligands with the \(^{15}\) N isotope uniformly, \(T_m\) are enhanced between \({\sim }1.1-1.4~\upmu\) s at the canonical orientations. This is already an order of magnitude longer than the duration of a single-spin qubit manipulation \({\sim }10-100\)  ns. While \(T_1\) are of the order of \({\sim }130\) \(\upmu\) s at the canonical orientations, the transient nutation experiments reflect on the coherent manipulation of the electron spin.
      PubDate: 2017-03-01
      DOI: 10.1007/s00723-016-0857-6
      Issue No: Vol. 48, No. 3 (2017)
  • Unexpected Features of the Intramolecular Spin Exchange in Imidazoline
           Nitroxide Biradicals Dissolved in Ionic Liquids
    • Authors: A. I. Kokorin; B. Y. Mladenova-Kattnig; I. A. Grigor’ev; G. Grampp
      Pages: 287 - 296
      Abstract: Three imidazoline-type nitroxide biradicals of the similar composition R 5 NO –CH=N–N=CH–R 5 N , B1, R 5 NO –CH=N–N=C(CH3)–R 5 N , B2, and R 5 N –C(CH3)=N–N=C(CH3)–R 5 N , B3, with R 5 N and R 5 NO denoting, respectively, the nitroxide rings 1-oxyl-2,2,5,5-tetramethyl-3-imidazoline and 1-oxyl-2,2,5,5-tetramethyl-3-N–oxide imidazoline, have been studied by X-band electron paramagnetic resonance (EPR) spectroscopy. Variations of the intramolecular electron spin exchange in these biradicals dissolved in ethanol and the room temperature ionic liquid bmimBF4 were characterized as a function of temperature by means of the analysis of the EPR lines shape. Thermodynamic parameters of the conformational rearrangements in ethanol were calculated. Analyzing the EPR spectra of these biradicals in bmimBF4, it was revealed that the two-conformational model does not describe their conformational transitions. Moreover, the observed EPR spectra are not central symmetric especially at low temperatures that cannot be described and explained in the framework of the current theory of the intramolecular spin exchange. Probable reasons of this “strange” behavior are discussed.
      PubDate: 2017-03-01
      DOI: 10.1007/s00723-016-0858-5
      Issue No: Vol. 48, No. 3 (2017)
  • 23 Na and 27 Al NMR Study of Structure and Dynamics in Mordenite
    • Authors: N. A. Sergeev; M. Paczwa; M. Olszewski; A. M. Panich
      Pages: 115 - 124
      Abstract: Temperature dependencies of 27Al and 23Na nuclear magnetic resonance spectra and spin–lattice relaxations in mordenite have been studied in static and magic angle spinning regimes. Our data show that the spin–lattice relaxations of the 23Na and 27Al nuclei are mainly governed by interaction of nuclear quadrupole moments with electric field gradients of the crystal, modulated by translational motion of water molecules in the mordenite channels. At temperatures below 200 K, the dipolar interaction of nuclear spins with paramagnetic impurities becomes an important relaxation mechanism of the 23Na and 27Al nuclei.
      PubDate: 2017-02-01
      DOI: 10.1007/s00723-016-0847-8
      Issue No: Vol. 48, No. 2 (2017)
  • Visualization of Magnetization Transfer Effect in Polyethylene Glycol
           Impregnated Waterlogged Wood
    • Authors: Yuki Kanazawa; Tetsuya Yamada; Aki Kido; Koji Fujimoto; Kyoko Takakura; Hiroaki Hayashi; Yasutaka Fushimi; Satoshi Kozawa; Koji Koizumi; Makiko Okuni; Naomi Ueda; Kaori Togashi
      Pages: 125 - 134
      Abstract: To visualize the condition of impregnation of polyethylene glycol (PEG) in waterlogged wood, we demonstrated magnetic transfer (MT) magnetic resonance imaging (MRI) through a series of process of PEG impregnation. Three different samples were examined; reference wood, 10 cm cut wood, and 5 cm cut wood. During this study, the upper section sample was kept immersed in water, for the middle and lower sections the concentration of PEG solution was changed at 20 wt% intervals from 20 to 100 wt%. The impregnated periods of each PEG solution concentration were 14 days. Then, MR imaging were performed with/without MT pulse. The MTR value for both 10 cm- and 5 cm-samples were shown to decrease at 20 wt% PEG at peak concentration. When the sample volume was large, e.g., 10 cm-sample, the MTR value decreased to 100 wt% PEG concentration. In contrast, when a sample volume was small, e.g., 5 cm-sample, MTR value decreased to 60 wt% PEG concentration. In conclusion, MTR analysis makes it possible to nondestructively visualize and evaluate the inner condition concerning the PEG impregnation method for waterlogged wood.
      PubDate: 2017-02-01
      DOI: 10.1007/s00723-016-0850-0
      Issue No: Vol. 48, No. 2 (2017)
  • The Oil-Swelling Processes Characterization in Rubbers Studied by 1 H NMR
    • Authors: Roman R. Bavin; Dmitry I. Furtsov; Vladimir A. Zabrodin; Victor P. Tarasov; Vitaly I. Volkov
      Pages: 135 - 142
      Abstract: The swelling processes of rubbers on the basis of ethylene–propylene SKEPT-40, butadiene–nitrile SKN-18, and fluorine SKF-26 caoutchoucs in transformer oil GK were investigated by 1H nuclear magnetic resonance spectroscopy and 1H NMR relaxation techniques. The main rubber-swelling singularities were developed. It was shown that polymeric affinity to oil decreases in the next rubber row—ethylene–propylene, fluorine, and butadiene–nitrile. The oil molecular mobility is on the contrary increased in the same row. The surface NMR probe express test of oil amount in real production was introduced.
      PubDate: 2017-02-01
      DOI: 10.1007/s00723-016-0851-z
      Issue No: Vol. 48, No. 2 (2017)
  • Magnetic Resonance Study of Fe-Implanted TiO 2 Rutile
    • Authors: C. Okay; I. R. Vakhitov; V. F. Valeev; R. I. Khaibullin; B. Rameev
      Abstract: Single-crystal (100) and (001) TiO2 rutile substrates have been implanted with 40 keV Fe+ at room temperature with high doses in the range of (0.5–1.5) × 1017 ions/cm2. A ferromagnetic resonance (FMR) signal has been observed for all samples with the intensity and the out-of-plane anisotropy increasing with the implantation dose. The FMR signal has been related to the formation of a percolated metal layer consisting of close-packed iron nanoparticles in the implanted region of TiO2 substrate. Electron spin resonance (ESR) signal of paramagnetic Fe3+ ions substituting Ti4+ positions in the TiO2 rutile structure has been also observed. The dependences of FMR resonance fields on the DC magnetic field orientation reveal a strong in-plane anisotropy for both (100) and (001) substrate planes. An origin of the in-plane anisotropy of FMR signal is attributed to the textured growth of the iron nanoparticles. As result of the nanoparticle growth aligned with respect to the structure of the rutile host, the in-plane magnetic anisotropy of the samples reflects the symmetry of the crystal structure of the TiO2 substrates. Crystallographic directions of the preferential growth of iron nanoparticles have been determined by computer modeling of anisotropic ESR signal of substitutional Fe3+ ions.
      PubDate: 2017-03-20
      DOI: 10.1007/s00723-017-0868-y
  • Influence of Defects on Photoconductivity and Photocatalytic Activity of
           Nitrogen-Doped Titania
    • Authors: A. A. Minnekhanov; N. T. Le; E. A. Konstantinova; P. K. Kashkarov
      Abstract: Samples of nitrogen-doped titanium dioxide (anatase, 0.2 ≤ N ≤ 1.0 wt%) prepared by the sol–gel method were investigated using X-band electron paramagnetic resonance spectroscopy, photoconductivity, and photocatalysis measurements. N· and NO· paramagnetic defects in N-TiO2 have been observed; their concentrations and spin-Hamiltonian parameters were calculated. An increase both in the rate of the generation of free charge carriers and in the rate of photocatalysis was found in N-TiO2 in contrast with non-doped titania under visible light. The correlation of the density of the observed radicals with the photoconductivity and photocatalysis data is discussed.
      PubDate: 2017-03-10
      DOI: 10.1007/s00723-017-0870-4
  • T 1 – T 2 Correlation and Biopolymer Diffusion Within Human
           Osteoarthritic Cartilage Measured with Nuclear Magnetic Resonance
    • Authors: Sarah E. Mailhiot; Nathan H. Williamson; Jennifer R. Brown; Joseph D. Seymour; Sarah L. Codd; Ronald K. June
      Abstract: Cartilage is a load-bearing tissue that provides smooth articulation during motion of human joints like the knee and hip. Cartilage deterioration in the form of osteoarthritis (OA) causes painful joint motion in more than 100 million patients worldwide, and thus there is great interest in improving our understanding of cartilage to further clinical treatment. Previous studies have examined many aspects of cartilage mechanics, including the flow of interstitial water and repulsion of neighboring glycosaminoglycan chains. However, the contributions of specific molecules to overall tissue properties remain unclear. In this study, we use nuclear magnetic resonance (NMR) diffusometry and relaxometry to examine the molecular dynamics of water and cartilage polymers in OA human articular cartilage. To our knowledge, this is the first identification of two macromolecular populations corresponding to collagen and proteoglycan in human cartilage through their diffusive properties. Further, we performed NMR T 1–T 2 correlation studies on human cartilage and observed two populations of water distinguished by differing NMR relaxation corresponding to a solid-like component and a liquid-like component. These results provide fundamental insight on the water behavior and polymeric interactions that drive the functional mechanics of cartilage. This study provides a basis to both expand our understanding of basic cartilage mechanics and provide molecular dynamics data for design of novel biomaterials to improve joint health.
      PubDate: 2017-03-10
      DOI: 10.1007/s00723-017-0869-x
  • β-Phosphorus Hyperfine Coupling Constant in Nitroxides: Conformational
           Effects in 6-Membered Ring Nitroxides
    • Authors: Lionel Bosco; Teddy Butscher; Sylvain R. A. Marque
      Abstract: Recently, we reported a significant solvent effect on the phosphorus hyperfine coupling constant a P in β-phosphorylated 6-membered ring nitroxides (∆a P = 24 G in Org. Biomol. Chem. 2015). Thus, it led us to investigate the effect of solvent for several 6-membered ring nitroxides. Although smaller than mentioned above, a change of 5–7 G in a P with the polarity of solvent was still observed for these nitroxides. As for other β-phosphorylated nitroxides, a N increases with the polarity/polarizability π* and the Hydrogen Bond Donating α properties of the solvent whereas a P exhibits the reverse trends. The change of a P with the solvent depends a lot on a subtle interplay between the destabilizing steric hindrance due to the bulkiness of the substituents and the stabilizing hyperconjugation interactions SOMO → σ*C–P between the anti-bonding orbitals of the C–P bond and the SOMO.
      PubDate: 2017-03-10
      DOI: 10.1007/s00723-017-0867-z
  • Accelerated 3D Coronary Vessel Wall MR Imaging Based on Compressed Sensing
           with a Block-Weighted Total Variation Regularization
    • Authors: Zhongzhou Chen; Xiaoyong Zhang; Caiyun Shi; Shi Su; Zhaoyang Fan; Jim X. Ji; Guoxi Xie; Xin Liu
      Abstract: Coronary vessel wall magnetic resonance (MR) imaging is important for heart disease diagnosis but often suffers long scan time. Compressed sensing (CS) has been previously used to accelerate MR imaging by reconstructing an MR image from undersampled k-space data using a regularization framework. However, the widely used regularizations in the current CS methods often lead to smoothing effects and thus are unable to reconstruct the coronary vessel walls with sufficient resolution. To address this issue, a novel block-weighted total variation regularization is presented to accelerate the coronary vessel wall MR imaging. The proposed regularization divides the image into two parts: a region-of-interest (ROI) which contains the coronary vessel wall, and the other region with less concerned features. Different penalty weights are given to the two regions. As a result, the small details within ROI do not suffer from over-smoothing while the noise outside the ROI can be significantly suppressed. Results with both numerical simulations and in vivo experiments demonstrated that the proposed method can reconstruct the coronary vessel wall from undersampled k-space data with higher qualities than the conventional CS with the total variation or the edge-preserved total variation.
      PubDate: 2017-03-01
      DOI: 10.1007/s00723-017-0866-0
  • Influence of Pressure on the Intramolecular Spin Exchange in a Short
           Imidazolium-Nitroxide Biradical
    • Authors: Boryana Mladenova-Kattnig; Günter Grampp; Alexander I. Kokorin
      Abstract: A short-chain imidazoline-type nitroxide biradical R 5 NO –CH=N–N=C(CH3)–R 5 N , B2, with nitroxide rings R 5 N and R 5 NO as 1-oxyl-2,2,5,5-tetramethyl-3-imidazoline and 1-oxyl-2,2,5,5-tetramethyl-3-N-oxide imidazoline, respectively, has been studied using X-band electron paramagnetic resonance (EPR) spectroscopy in CH3CN solutions at variable temperature T and pressure P. Changes of the solution viscosity on the intramolecular electron spin exchange in B2 is characterized by calculating the value of the exchange integral J/a , where a denotes the 14N hyperfine splitting (hfs) constant. It is revealed that the intramolecular dynamics in B2 do not follow the Debye–Stokes–Einstein law, while the Arrhenius dependence is fulfilled. Probable reasons of such behavior are discussed.
      PubDate: 2017-02-15
      DOI: 10.1007/s00723-017-0865-1
  • A Degenerate Birdcage with Integrated Tx/Rx Switches and Butler Matrix for
           the Human Limbs at 7 T
    • Authors: Riccardo Stara; Gianluigi Tiberi; Fabio Morsani; Mark Symms; Maria Evelina Fantacci; Massimo Marletta; Virna Zampa; Mihir Pendse; Alessandra Retico; Brian K. Rutt; Michela Tosetti
      Abstract: The theoretically known degeneracy condition of the band-pass birdcage coil has rarely been exploited in transmit coil designs. We have created an eight-channel degenerate birdcage for the human limbs at 7 T, with dedicated Tx/Rx switches and a Butler matrix. The coil can be split into two half cylinders, as required for its application to patients with limited mobility. The design of the coil, the Butler matrix, and Tx/Rx switches relied on a combination of analytical, circuital, and numerical simulations. The birdcage theory was extended to the degenerate case. The theoretical and practical aspects of the design and construction of the coil are presented. The performance of the coil was demonstrated by simulations, workbench, and scanner measurements. The fully assembled prototype presents good performance in terms of efficiency, B1 homogeneity, and signal-to-noise ratio, despite the asymmetry introduced by the splittable design. The first in vivo images of the knee are also shown. A novel RF coil design consisting of an eight-channel splittable degenerate birdcage has been developed, and it is now available for 7 T MRI applications of the human lower limbs, including high-resolution imaging of the knee cartilages and of the patellar trabecular structure.
      PubDate: 2017-02-15
      DOI: 10.1007/s00723-017-0864-2
  • Relaxation Model and Mapping of Magnetic Field Gradients in MRI
    • Authors: Alexey V. Protopopov
      Abstract: The purpose of the work is development of algorithms for separate mapping of T 2 relaxation time and gradients, using gradient recalled echo (GRE) sequence. Application of three-dimensional (3D) model of gradients and their volumetric averaging within a voxel lead to analytical model of relaxation function, which is consistent with experimental data for both regular macroscopic and randomized micro- and mesoscopic gradients. The model is verified by fitting into experimental data obtained on specially made phantoms. Verification of algorithms is completed by comparing gradient maps obtained on specially made cylindrical phantoms with theoretical maps of their exact 3D electro-dynamic solutions. Analytical model of relaxation function proved to be in good agreement with experimental relaxation curves. On the basis of this model, fast and unambiguous fittingless algorithms were developed. Gradient maps measured on special cylindrical phantoms are in good qualitative agreement with theory. 3D statistical model and fittingless algorithms provide the basis for separating the GRE signal into two meaningful parameters—T 2 and gradients, thus doubling information from magnetic resonance imaging.
      PubDate: 2017-02-13
      DOI: 10.1007/s00723-017-0863-3
  • Validation of MRI-Based Fiber-Tracking Results
    • Authors: K. A. Il’yasov; L. V. Konopleva; O. V. Nedopekin
      Abstract: A new approach to estimating the probability of the fiber-track existence has been developed and validated on the basis of digital phantoms and diffusion-weighted magnetic resonance imaging measurements on human brain. The proposed approach includes two parameters—the local probability of the tract direction and the Shannon entropy. The local probability of the tract direction characterizes how well tracts “fit” the direction information in a voxel. The Shannon entropy characterizes the shape of diffusivity in the voxel. Calculations on digital phantoms and in vivo data showed that the combination of these parameters makes it possible to verify fiber-tracking results.
      PubDate: 2017-02-10
      DOI: 10.1007/s00723-017-0859-z
  • Structural Phase Transition of Perovskite-Type N(CH 3 ) 4 CdBr 3 Studied
           by MAS NMR and Static NMR
    • Authors: Ae Ran Lim
      Abstract: The structural geometry change in the perovskite-type N(CH3)4CdBr3 single crystal near the phase transition temperature of T C = 390 K was investigated using magic angle spinning nuclear magnetic resonance techniques. For 1H and 13C nuclei, the temperature dependences of their chemical shift, spectral intensity, and spin–lattice relaxation time (T 1ρ) in the rotating frame were obtained and analyzed. While the chemical shift and T 1ρ of 1H showed change near T C, those of 13C did not. In addition, the 113Cd spin–lattice relaxation time T 1 in the laboratory frame near T C show no evidence of anomalous change near the phase transition temperature, which coincides with the measured changes in the 1H T 1ρ. The driving force for this phase transition was connected to the 1H in the CH3 groups.
      PubDate: 2017-02-01
      DOI: 10.1007/s00723-017-0861-5
  • Line Profile Measure as a Stopping Criterion in CG-SENSE Algorithm
    • Authors: Mahwish Khan; Taquwa Aslam; Hassan Shahzad; Hammad Omer
      Abstract: Conjugate gradient SENSE (CG-SENSE) is a parallel magnetic resonance imaging reconstruction algorithm which solves the inversion problem of SENSE iteratively. One major limitation of CG-SENSE is the appropriate choice of the number of iterations required for good reconstruction results. Fewer iterations result in aliasing artifacts and too many iterations result in an increased noise level. This paper proposes a novel method to define the stopping criterion of CG-SENSE algorithm which is based on the use of correlation measure between the line profiles of the reconstructed images in the current and the previous iterations. The results are compared with Bregman distance-stopping criterion. Artifact power and peak signal-to-noise ratio are used to quantify the quality of the reconstructed images. The results demonstrate that the line profile correlation measure acts as an effective stopping criterion in CG-SENSE.
      PubDate: 2017-01-19
      DOI: 10.1007/s00723-017-0860-6
  • Mimicking the Electromagnetic Distribution in the Human Brain: A
           Multi-frequency MRI Head Phantom
    • Authors: Ana L. Neves; Lisa Leroi; Nicolas Cochinaire; Redha Abdeddaim; Pierre Sabouroux; Alexandre Vignaud
      Abstract: The purpose of this study was to fabricate and test a multi-frequency human brain-mimicking phantom for magnetic resonance imaging (MRI) assessment purposes. An anatomically realistic human head phantom was elaborated, for different Larmor frequencies, which allows rapid quantification of \({\text{B}}_{1}^{ + }\) . It is a simple alternative solution in time and cost as compared to numerical simulations to validate simulation when the coil geometry and components cannot be known as a unique solution. The permittivity \(\varepsilon^{{\prime }}\) and conductivity \(\sigma\) of sucrose/salt/agar aqueous solutions of varying concentrations were determined; a solution with these components and having the adequate concentration to obtain the brain’s dielectric properties at 3, 7 and 11.7T was manufactured. An anthropomorphic polymeric skull was filled with this mixture. To check the behavior of this phantom in a MRI configuration, both numerical and experimental validations were done: a \({\text{B}}_{1}^{ + }\) field distribution inside the phantom was calculated with CST Microwave Studio inside a birdcage coil at 7T; the same mapping was assessed in a 7T MRI. The feasibility of a multi-MRI static field phantom was demonstrated. A solution composed by 54.7 wt% of sucrose, 3.1 wt% of salt and 3.1 wt% of agar was fabricated with good permittivity and conductivity matching for 3, 7 and 11.7T. The results were confirmed by both numerical simulation and MRI acquisition. This work has shown the possibility of manufacturing a head phantom with accessible and cheap components for MRI evaluation, having an adequate \({\text{B}}_{1}^{ + }\) field distribution and the dielectric properties of the human brain.
      PubDate: 2017-01-19
      DOI: 10.1007/s00723-017-0862-4
  • ESR Study on Scavenging Effect of Squalene on Free Radicals in Mainstream
           Cigarette Smoke
    • Authors: Yuan Liang; Zhang Yuxia; Jin Yabo; Hu Yajie; Wei Jianyu; Chen Zepeng; Jiang Dingxin
      Abstract: Radicals in mainstream cigarette smoke (MCS) have been proposed to contribute to the harm caused by cigarette smoking. In the present study, we used natural antioxidant, squalene, to treat cigarette filters and tobacco for scavenging gas- and particulate-phase free radicals in MCS. The scavenging activities of cigarette filter and tobacco containing squalene against gas and particulate-phase free radicals were detected and quantified using spin-trapping or directly electron spin resonance spectroscopy method. The results revealed that squalene could significantly scavenge gas- and particulate-phase free radicals in MCS in a dose-dependent manner. The radical-scavenging activity of cigarette filter treatment was higher than that of tobacco treatment, irrespective of either gas-phase free radicals, or particulate-phase free radicals in MCS. Among them, 3 mg squalene/filter treatment showed that the highest scavenging effects against gas- and particulate-phase free radicals were 35.9 and 35.4%, respectively. The use of squalene as potential scavenger for reducing free radicals in cigarette smoke is discussed.
      PubDate: 2017-01-02
      DOI: 10.1007/s00723-016-0856-7
  • EPR Line Shifts and Line Shape Changes Due to Spin Exchange Between
           Nitroxide Free Radicals in Liquids 10. Spin-Exchange Frequencies of the
           Order of the Nitrogen Hyperfine Interaction: A Hypothesis
    • Authors: Barney L. Bales; Miroslav Peric
      Abstract: The behavior of electron paramagnetic resonance spectra due to 15N and 14N nitroxide free radicals undergoing spin exchange in liquids at frequencies \(\omega_{\text{ex}}\) that are high, of the same order of magnitude as the nitrogen hyperfine coupling constant \(A_{0}\) , is investigated. The well-known features are reconfirmed: (1) at low values of \(\omega_{\text{ex}}\) where the lines broaden, shift toward the center of the spectrum, and change shape due to the introduction of a resonance of the form of a dispersion component; (2) at values of \(\omega_{\text{ex}}\) comparable to \(A_{0}\) , where the lines merge into one; and (3) at values much larger than \(A_{0}\) , where the merged line narrows. It is found that each line of a spectrum may be decomposed into an admixture of a single absorption and a single dispersion component of Lorentzian shape. These two- or three-line absorption–dispersion admixtures, for 15N and 14N, respectively, retain their individual identities even after the spectrum has merged and has begun to narrow. For both isotopes, the average broadening and integrated intensities are equal to the predictions of perturbation theory although, in the case of 14N, the outer lines broaden faster than the central line and intensity moves from the outer lines to the central line. In fact, the outer line intensity becomes zero and then negative at higher values of \(\omega_{\text{ex}}\) which is compensated by the central line becoming more intense than the overall integrated intensity. For both isotopes, the dispersion components and the line shifts depart from the perturbation predictions. The results are presented in terms of measurable quantities normalized to \(A_{0}\) so that they may be applied to any two- or three-line spectrum.
      PubDate: 2016-12-03
      DOI: 10.1007/s00723-016-0854-9
  • Magnetic Resonance Study of the Bi 2 Te 3 Doped with Manganese
    • Authors: Yu. Talanov; V. Sakhin; E. Kukovitskii; N. Garif’yanov; G. Teitel’baum
      Abstract: Crystals of 3D topological insulators, bismuth telluride Bi2Te3, doped with manganese were studied using electron spin resonance (ESR) spectroscopy together with the SQUID magnetometry, transport measurements, and X-ray characterization. The obtained ESR data, such as the temperature and the angular dependence of the resonance field, reveal the specific critical behavior and confirm the ferromagnetic ordering of Mn spins even at modest doping. In addition to the studies of the critical behavior of diluted ferromagnet Bi2−x Mn x Te3, we also discuss the effects of the limited solubility of Mn ions giving rise to microscopic inclusions of the spurious magnetic phases which were revealed using ESR technique.
      PubDate: 2016-12-02
      DOI: 10.1007/s00723-016-0853-x
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