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  Subjects -> ENGINEERING (Total: 2268 journals)
    - CHEMICAL ENGINEERING (190 journals)
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    - ENGINEERING (1201 journals)
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ENGINEERING (1201 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: 17)
AAPG Bulletin     Hybrid Journal   (Followers: 7)
AASRI Procedia     Open Access   (Followers: 15)
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: 247)
Acta Geotechnica     Hybrid Journal   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 2)
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: 11)
Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi     Open Access  
Adsorption     Hybrid Journal   (Followers: 4)
Advanced Engineering Forum     Full-text available via subscription   (Followers: 6)
Advanced Science     Open Access   (Followers: 5)
Advanced Science Focus     Free   (Followers: 3)
Advanced Science Letters     Full-text available via subscription   (Followers: 8)
Advanced Science, Engineering and Medicine     Partially Free   (Followers: 7)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 17)
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: 26)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Fuzzy Systems     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 10)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 22)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 26)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Natural Sciences: Nanoscience and Nanotechnology     Open Access   (Followers: 29)
Advances in Operations Research     Open Access   (Followers: 11)
Advances in OptoElectronics     Open Access   (Followers: 5)
Advances in Physics Theories and Applications     Open Access   (Followers: 12)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Remote Sensing     Open Access   (Followers: 38)
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: 31)
Ain Shams Engineering Journal     Open Access   (Followers: 5)
Akademik Platform Mühendislik ve Fen Bilimleri Dergisi     Open Access  
Alexandria Engineering Journal     Open Access   (Followers: 1)
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: 17)
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: 6)
Applied Catalysis B: Environmental     Hybrid Journal   (Followers: 16)
Applied Clay Science     Hybrid Journal   (Followers: 5)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 12)
Applied Magnetic Resonance     Hybrid Journal   (Followers: 4)
Applied Nanoscience     Open Access   (Followers: 8)
Applied Network Science     Open Access   (Followers: 1)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Physics Research     Open Access   (Followers: 3)
Applied Sciences     Open Access   (Followers: 2)
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: 7)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
ASEE Prism     Full-text available via subscription   (Followers: 3)
Asia-Pacific Journal of Science and Technology     Open Access  
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: 8)
Asian Journal of Control     Hybrid Journal  
Asian Journal of Current Engineering & Maths     Open Access  
Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 8)
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: 8)
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: 5)
Batteries     Open Access   (Followers: 5)
Bautechnik     Hybrid Journal   (Followers: 1)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 23)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 4)
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: 10)
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: 17)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 32)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 5)
Biomedical Microdevices     Hybrid Journal   (Followers: 9)
Biomedical Science and Engineering     Open Access   (Followers: 4)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 4)
BioNanoMaterials     Hybrid Journal   (Followers: 2)
Biotechnology Progress     Hybrid Journal   (Followers: 39)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription   (Followers: 1)
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: 10)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 25)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 43)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 8)
Case Studies in Thermal Engineering     Open Access   (Followers: 4)
Catalysis Communications     Hybrid Journal   (Followers: 6)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 7)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysis Today     Hybrid Journal   (Followers: 8)
CEAS Space Journal     Hybrid Journal  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
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: 11)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 14)
City, Culture and Society     Hybrid Journal   (Followers: 22)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Coal Science and Technology     Full-text available via subscription   (Followers: 3)
Coastal Engineering     Hybrid Journal   (Followers: 11)
Coastal Engineering Journal     Hybrid Journal   (Followers: 5)
Coatings     Open Access   (Followers: 4)
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: 26)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Composite Structures     Hybrid Journal   (Followers: 266)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 188)
Composites Part B : Engineering     Hybrid Journal   (Followers: 279)
Composites Science and Technology     Hybrid Journal   (Followers: 182)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access  
Computational Geosciences     Hybrid Journal   (Followers: 14)
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: 7)
Computer Science and Engineering     Open Access   (Followers: 17)
Computers & Geosciences     Hybrid Journal   (Followers: 28)
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: 10)
Computing and Visualization in Science     Hybrid Journal   (Followers: 5)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 30)
Conciencia Tecnologica     Open Access  
Concurrent Engineering     Hybrid Journal   (Followers: 3)
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 7)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 9)
Control Engineering Practice     Hybrid Journal   (Followers: 42)
Control Theory and Informatics     Open Access   (Followers: 8)
Corrosion Science     Hybrid Journal   (Followers: 25)
CT&F Ciencia, Tecnologia y Futuro     Open Access   (Followers: 1)
CTheory     Open Access  

        1 2 3 4 5 6 7 | Last

Journal Cover Applied Magnetic Resonance
  [SJR: 0.358]   [H-I: 34]   [4 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  [2352 journals]
  • Six Decades of Progress in Magnetic Resonance: The Contributions of James
           S. Hyde
    • Authors: Gareth R. Eaton; Wayne L. Hubbell; Wojciech Froncisz
      Pages: 1093 - 1102
      Abstract: The development of electron paramagnetic resonance (EPR) and magnetic resonance imaging (MRI) over six decades is sketched with an emphasis on the contributions of James S. Hyde. For twenty years starting three years after the first commercial EPR spectrometer was shipped by Varian, he led commercial EPR developments, and then for more than forty years, he led development of instrumentation and biomedical applications of EPR at the Medical College of Wisconsin. It was there that he also made major contributions to MRI, and especially functional MRI.
      PubDate: 2017-12-01
      DOI: 10.1007/s00723-017-0954-1
      Issue No: Vol. 48, No. 11-12 (2017)
       
  • EPR Uniform Field Signal Enhancement by Dielectric Tubes in Cavities
    • Authors: James S. Hyde; Richard R. Mett
      Pages: 1185 - 1204
      Abstract: The dielectric tube resonator (DTR) for electron paramagnetic resonance spectroscopy is introduced. It is defined as a metallic cylindrical TE011 microwave cavity that contains a dielectric tube centered on the axis of the cylinder. Contour plots of dimensions of the metallic cylinder to achieve resonance at 9.5 GHz are shown for quartz, sapphire, and rutile tubes as a function of wall thickness and average radius. These contour plots were developed using analytical equations and confirmed by finite-element modeling. They can be used in two ways: design of the metallic cylinder for use at 9.5 GHz that incorporates a readily available tube such as a sapphire tube intended for NMR and design of a custom procured tube for optimized performance for specific sample-size constraints. The charts extend to the limiting condition where the dielectric fills the tube. However, the structure at this limit is not a dielectric resonator due to the metal wall and does not radiate. In addition, the uniform field (UF) DTR is introduced. Development of the UF resonator starting with a DTR is shown. The diameter of the tube remains constant along the cavity axis, and the diameter of the cylindrical metallic enclosure increases at the ends of the cavity to satisfy the uniform field condition. This structure has advantages over the previously developed UF TE011 resonators: higher resonator efficiency parameter Λ, convenient overall size when using sapphire tubes, and higher quality data for small samples. The DTR and UF DTR structures fill the gap between free space and dielectric resonator limits in a continuous manner.
      PubDate: 2017-12-01
      DOI: 10.1007/s00723-017-0935-4
      Issue No: Vol. 48, No. 11-12 (2017)
       
  • Modes and Fields of Two Stacked Dielectric Resonators in a Cavity of an
           Electron Paramagnetic Resonance Probe
    • Authors: Saba M. Mattar; Sameh Y. Elnaggar
      Pages: 1205 - 1217
      Abstract: An electron paramagnetic resonance (EPR) probe consisting of two dielectric resonators (DRs) and a cavity (CV) is ideal for EPR experiments where both signal enhancement and tuning capabilities are required. The coupling of two DRs, resonating in their \({\text{TE}}_{01\delta }\) mode and a CV resonating in its \({\text{TE}}_{011}\) mode, is studied using energy-coupled mode theory (ECMT). The frequencies and eigenvectors of the three coupled modes are analytically derived. As predicted numerically, ECMT confirms that the \({\text{TE}}^{ + + - }\) and \({\text{TE}}^{ + - - }\) modes are indeed found to be degenerate at a specific distance between the two DRs \(d_{12}\) . Additionally, the condition at which degeneracy occurs is specified. For a considerable range, the calculated frequency of the \({\text{TE}}^{ + + + }\) mode changes linearly with respect to \(d_{12}\) . The \({\text{TE}}^{ + + + }\) mode showed a 500 MHz frequency change over a distance of 2 cm, when the resonance frequency is around 9.7 GHz. This enables the experimentalist to linearly tune the probe over this large frequency range. Finally the asymmetric configuration, where one of the resonators (DR2) is kept at the cavity center and the other one is allowed to move along the cavity axis, is studied. It is estimated that the frequency changes by 600 MHz over a distance of 1.5 cm. A formula for the magnitude of the magnetic field along the cavity axis, where the EPR samples are usually placed, is developed. This is crucial in determining the magnetic field in the vicinity of the sample and the probe’s filling factor.
      PubDate: 2017-12-01
      DOI: 10.1007/s00723-017-0931-8
      Issue No: Vol. 48, No. 11-12 (2017)
       
  • An X-Band Crossed-Loop EPR Resonator
    • Authors: George A. Rinard; Richard W. Quine; Joseph McPeak; Laura Buchanan; Sandra S. Eaton; Gareth R. Eaton
      Pages: 1219 - 1226
      Abstract: A copper X-band (9.22 GHz) cross-loop resonator has been constructed for use with 4 mm sample tubes. The Q for the two resonators is 380 and 350, respectively. The resonator efficiency is about 1 G per square root of watt. Operation has been demonstrated with measurement of T 1 by saturation recovery for samples of coal and an immobilized nitroxide.
      PubDate: 2017-12-01
      DOI: 10.1007/s00723-017-0945-2
      Issue No: Vol. 48, No. 11-12 (2017)
       
  • Optimization Methods for the Design of Sensitive Surface ESR Resonators
    • Authors: Yakir Ishay; Aharon Blank
      Pages: 1249 - 1262
      Abstract: Electron spin resonance (ESR) is a powerful spectroscopic technique that has many applications in a wide variety of scientific fields, including chemistry, biology, materials science, and physics. One significant drawback of conventional ESR, however, is its relatively low sensitivity compared to other spectroscopic techniques. Arguably, the most dominant element affecting ESR sensitivity is the microwave resonator used to pick up the ESR signal of the spins. Traditionally, ESR mostly employs a limited set of resonator configurations (e.g., rectangular cavity, dielectric, or loop-gap resonator) that are suboptimal with respect to a wide range of samples. In principle, a smart resonator design can be used to optimize spin sensitivity for a given sample’s properties. In this work, we make use of an efficient Genetic Algorithm (GA) approach to numerically solve, analyze, and optimize a unique class of surface microresonators. The GA is based on a method of moments code, customized directly to render the complexity of a particular resonator’s geometries in our search. The main purposes of the algorithm are to routinely generate more sensitive microresonators, optimized for a predefined sample’s dimensions, and to study the functional relations between the devices’ resonance frequency, quality, and filling factors and their topology, in order to reach a rational optimal design. Preliminary results associated with new, unique, and sensitive surface microresonators are shown and analyzed. Such resonators are cheap and easy to produce on a mass scale with an arbitrary surface geometry.
      PubDate: 2017-12-01
      DOI: 10.1007/s00723-017-0941-6
      Issue No: Vol. 48, No. 11-12 (2017)
       
  • Q-Band Loop-Gap Resonator for EPR Applications with Broadband-Shaped
           Pulses
    • Authors: Vasyl Denysenkov; Philipp van Os; Thomas F. Prisner
      Pages: 1263 - 1272
      Abstract: Recently, Q-band-pulsed electron paramagnetic resonance spectroscopy has strongly advanced its performance by the introduction of high-power microwave amplifiers and the use of shaped pulses. For such applications, the resonator Q value has to be low enough to achieve sufficient bandwidth for short microwave pulses and to reduce the ring-down time after the pulses. However, a low Q value reduces the detection sensitivity as well as the conversion efficiency of the microwave input power to the magnetic field strength at the sample position. Therefore, the resonator Q value has to be optimized for a given microwave input power and specific application. We designed a three-loop/two-gap resonator using CST Microwave Studio for such applications, and tested its performance in comparison with a standard Bruker D2 Q-band microwave resonator by accomplishing broadband SIFTER experiments on a nitroxide model compound.
      PubDate: 2017-12-01
      DOI: 10.1007/s00723-017-0930-9
      Issue No: Vol. 48, No. 11-12 (2017)
       
  • High-Pressure EPR Spectroscopy Studies of the E. coli Lipopolysaccharide
           Transport Proteins LptA and LptC
    • Authors: Kathryn M. Schultz; Candice S. Klug
      Pages: 1341 - 1353
      Abstract: The use of pressure is an advantageous approach to the study of protein structure and dynamics, because it can shift the equilibrium populations of protein conformations toward higher energy states that are not of sufficient population to be observable at atmospheric pressure. Recently, the Hubbell group at the University of California, Los Angeles, reintroduced the application of high pressure to the study of proteins by electron paramagnetic resonance (EPR) spectroscopy. This methodology is possible using X-band EPR spectroscopy due to advances in pressure intensifiers, sample cells, and resonators. In addition to the commercial availability of the pressure generation and sample cells by Pressure Biosciences Inc., a five-loop–four-gap resonator required for the initial high-pressure EPR spectroscopy experiments by the Hubbell group, and those reported here, was designed by James S. Hyde and built and modified at the National Biomedical EPR Center. With these technological advances, we determined the effect of pressure on the essential periplasmic lipopolysaccharide (LPS) transport protein from Escherichia coli, LptA, and one of its binding partners, LptC. LptA unfolds from the N-terminus to the C-terminus, binding of LPS does not appreciably stabilize the protein under pressure, and monomeric LptA unfolds somewhat more readily than oligomeric LptA upon pressurization to 2 kbar. LptC exhibits a fold and relative lack of stability upon LPS binding similar to LptA, yet adopts an altered, likely monomeric, folded conformation under pressure with only its C-terminus unraveling. The pressure-induced changes likely correlate with functional changes associated with binding and transport of LPS.
      PubDate: 2017-12-01
      DOI: 10.1007/s00723-017-0948-z
      Issue No: Vol. 48, No. 11-12 (2017)
       
  • Saturation Recovery EPR Spin-Labeling Method for Quantification of Lipids
           in Biological Membrane Domains
    • Authors: Laxman Mainali; Theodore G. Camenisch; James S. Hyde; Witold K. Subczynski
      Pages: 1355 - 1373
      Abstract: The presence of integral membrane proteins induces the formation of distinct domains in the lipid bilayer portion of biological membranes. Qualitative application of both continuous wave (CW) and saturation recovery (SR) electron paramagnetic resonance (EPR) spin-labeling methods allowed discrimination of the bulk, boundary, and trapped lipid domains. A recently developed method, which is based on the CW EPR spectra of phospholipid (PL) and cholesterol (Chol) analog spin labels, allows evaluation of the relative amount of PLs (% of total PLs) in the boundary plus trapped lipid domain and the relative amount of Chol (% of total Chol) in the trapped lipid domain (Raguz et al. Exp Eye Res 140:179–186, 24). Here, a new method is presented that, based on SR EPR spin-labeling, allows quantitative evaluation of the relative amounts of PLs and Chol in the trapped lipid domain of intact membranes. This new method complements the existing one, allowing acquisition of more detailed information about the distribution of lipids between domains in intact membranes. The methodological transition of the SR EPR spin-labeling approach from qualitative to quantitative is demonstrated. The abilities of this method are illustrated for intact cortical and nuclear fiber cell plasma membranes from porcine eye lenses. Statistical analysis (Student’s t test) of the data allowed determination of the separations of mean values above which differences can be treated as statistically significant (P ≤ 0.05) and can be attributed to sources other than preparation/technique.
      PubDate: 2017-12-01
      DOI: 10.1007/s00723-017-0921-x
      Issue No: Vol. 48, No. 11-12 (2017)
       
  • ELDOR-detected NMR at Q-Band
    • Authors: Thilo Hetzke; Alice M. Bowen; Thomas F. Prisner
      Pages: 1375 - 1397
      Abstract: In recent years, electron–electron double resonance detected nuclear magnetic resonance (EDNMR) has gained considerable attention as a pulsed electron paramagnetic resonance technique to probe hyperfine interactions. Most experiments published so far were performed at W-band frequencies or higher, as at lower frequencies detection of weakly coupled low-γ nuclei is hampered by the presence of a central blind spot, which occurs at zero frequency. In this article we show that EDNMR measurements and a meaningful data analysis is indeed possible at intermediate microwave frequencies (Q-band, 34 GHz), once experimental parameters have been optimized. With highly selective detection pulses and Gaussian shaped electron–electron double resonance (ELDOR) pulses it is possible to detect low-γ nuclei coupled to paramagnetic Mn2+. Weakly coupled 14N resonances, which are separated from the zero frequency by only 2.8 MHz, were readily detected. In systems where different spin active nuclei are coupled to the electron spin, particular care has to be taken when using higher powered ELDOR pulses, as combination frequencies from the two nuclei (∆m S = ±1, ∆m I,1 = ±1, ∆m I,2 = ±1) can lead to severe line broadening and complicated EDNMR spectra. We also compare the EDNMR spectra of 13C-labeled Mn–DOTA to 13C-Mims electron–nuclear double resonance to get a better insight into the similarities and differences in the results of the two techniques for 13C hyperfine coupling.
      PubDate: 2017-12-01
      DOI: 10.1007/s00723-017-0927-4
      Issue No: Vol. 48, No. 11-12 (2017)
       
  • ODMR Spectroscopy of NV − Centers in Diamond Under High MW Power
    • Authors: I. V. Zhukov; S. V. Anishchik; Yu. N. Molin
      Pages: 1461 - 1469
      Abstract: We have studied negatively charged nitrogen vacancy centers (NV \(^-\) centers) in diamond using the technique of optically detected magnetic resonance (ODMR). Due to the use of the MW power amplifier we have easily observed in the ODMR spectrum all the lines known to date, including the lines of the excited state of the NV \(^-\) centers. The g values and the hyperfine interaction constants of the ground and the excited triplet states of the NV \(^-\) center are given. Hamiltonian parameters of the ground and the excited triplet states of the NV \(^-\) center at ambient temperature have been confirmed and refined. In addition, an evidence of a slight g value asymmetry of the excited state of the NV \(^-\) center has been obtained.
      PubDate: 2017-12-01
      DOI: 10.1007/s00723-017-0933-6
      Issue No: Vol. 48, No. 11-12 (2017)
       
  • Refining Spin–Spin Distance Distributions in Complex Biological Systems
           Using Multi-Gaussian Monte Carlo Analysis
    • Authors: Ivan O. Timofeev; Olesya A. Krumkacheva; Matvey V. Fedin; Galina G. Karpova; Elena G. Bagryanskaya
      Abstract: Pulse dipolar electron paramagnetic resonance spectroscopy provides means of distance measurements in the range of ~ 1.5–10 nm between two spin labels tethered to a biological system. However, the extraction of distance distribution between spin labels is an ill-posed mathematical problem. The most common approach for obtaining distance distribution employs Tikhonov regularization method, where a regularization parameter characterizing the smoothness of distribution is introduced. However, in case of multi-modal distance distributions with peaks of different widths, the use of a single regularization parameter might lead to certain distortions of actual distribution shapes. Recently, a multi-Gaussian Monte Carlo approach was proposed for eliminating this drawback and verified for model biradicals [1]. In the present work, we for the first time test this approach on complicated biological systems exhibiting multi-modal distance distributions. We apply multi-Gaussian analysis to pulsed electron–electron double resonance data of supramolecular ribosomal complexes, where the 11-mer oligoribonucleotide (MR) bearing two nitroxide labels at its termini is used as a reporter. Calculated distance distributions reveal the same conformations of MR as those obtained by Tikhonov regularization, but feature the peaks having different widths, which leads to a better resolution in several cases. The advantages, complications, and further perspectives of application of Monte-Carlo-based multi-Gaussian approach to real biological systems are discussed.
      PubDate: 2017-11-10
      DOI: 10.1007/s00723-017-0965-y
       
  • EPR Study of Sc 2 SiO 5 :Nd 143 Isotopically Pure Impurity Crystals
    • Authors: R. M. Eremina; V. F. Tarasov; K. B. Konov; T. P. Gavrilova; A. V. Shestakov; V. A. Shustov; S. A. Kutovoi; Yu. D. Zavartsev
      Abstract: The Sc2SiO5 single crystals doped with 0.001 at.% of the 143Nd3+ ion were studied by continuous-wave and pulse electron paramagnetic resonance methods. The g-tensors and hyperfine structure tensors for two magnetically non-equivalent Nd ions were obtained. The spin–spin and spin–lattice relaxation times were measured at 9.82 GHz in the temperature range from 4 to 10 K. It was established that three relaxation processes contribute to the spin–lattice relaxation processes. There are one-phonon spin–phonon interaction, two-phonon Raman interaction and two-phonon Orbach–Aminov relaxation processes. It was established that spin–spin relaxation time is of the same magnitude for neodymium ion doped in Sc2SiO5 and in Y2SiO5.
      PubDate: 2017-11-09
      DOI: 10.1007/s00723-017-0966-x
       
  • Autobiography of James S. Hyde
    • Authors: James S. Hyde
      Abstract: The papers, book chapters, reviews, and patents by James S. Hyde in the bibliography of this document have been separated into EPR and MRI sections and within each section by topics. Within each topic, publications are listed chronologically. A brief summary is provided for each patent listed. A few publications and patents that do not fit this schema have been omitted. This list of publications is preceded by a scientific autobiography that focuses on selected topics that are judged to have been of most scientific importance. References to many of the publications and patents in the bibliography are made in the autobiography.
      PubDate: 2017-10-27
      DOI: 10.1007/s00723-017-0950-5
       
  • Jim Hyde and the ENDOR Connection: A Personal Account
    • Authors: Klaus Möbius; Wolfgang Lubitz; Anton Savitsky
      Abstract: In this minireview, we report on our year-long EPR work, such as electron–nuclear double resonance (ENDOR), pulse electron double resonance (PELDOR) and ELDOR-detected NMR (EDNMR) at X-band and W-band microwave frequencies and magnetic fields. This report is dedicated to James S. Hyde and honors his pioneering contributions to the measurement of spin interactions in large (bio)molecules. From these interactions, detailed information is revealed on structure and dynamics of macromolecules embedded in liquid-solution or solid-state environments. New developments in pulsed microwave and sweepable cryomagnet technology as well as ultra-fast electronics for signal data handling and processing have pushed the limits of EPR spectroscopy and its multi-frequency extensions to new horizons concerning sensitivity of detection, selectivity of molecular interactions and time resolution. Among the most important advances is the upgrading of EPR to high magnetic fields, very much in analogy to what happened in NMR. The ongoing progress in EPR spectroscopy is exemplified by reviewing various multi-frequency electron–nuclear double-resonance experiments on organic radicals, light-generated donor–acceptor radical pairs in photosynthesis, and site-specifically nitroxide spin-labeled bacteriorhodopsin, the light-driven proton pump, as well as EDNMR and ENDOR on nitroxides. Signal and resolution enhancements are particularly spectacular for ENDOR, EDNMR and PELDOR on frozen-solution samples at high Zeeman fields. They provide orientation selection for disordered samples approaching single-crystal resolution at canonical g-tensor orientations—even for molecules with small g-anisotropies. Dramatic improvements of EPR detection sensitivity could be achieved, even for short-lived paramagnetic reaction intermediates. Thus, unique structural and dynamic information is revealed that can hardly be obtained by other analytical techniques. Micromolar concentrations of sample molecules have become sufficient to characterize stable and transient reaction intermediates of complex molecular systems—offering exciting applications for physicists, chemists, biochemists and molecular biologists.
      PubDate: 2017-10-23
      DOI: 10.1007/s00723-017-0959-9
       
  • The Current State of Measuring Bimolecular Spin Exchange Rates by the EPR
           Spectral Manifestations of the Exchange and Dipole–Dipole Interactions
           in Dilute Solutions of Nitroxide Free Radicals with Proton Hyperfine
           Structure
    • Authors: Barney L. Bales; M. M. Bakirov; R. T. Galeev; I. A. Kirilyuk; A. I. Kokorin; K. M. Salikhov
      Abstract: Experimental studies of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (Tempol) in 60 wt% aqueous glycerol were carried out for temperatures from 273 to 340 K. Selective isotope substitution allowed comparisons between the experimental spectral manifestations of spin exchange and dipole–dipole interactions for protonated, deuterated, 15N, and 14N Tempol. Theoretical spectra were computed from a rigorous theory specifically formulated to include proton hyperfine interactions over a wide range of spin exchange and dipole–dipole interactions to compare with the experimental data. For spin exchange and dipole–dipole interactions small compared with the proton hyperfine coupling constant, spectra were calculated with perturbation theory to gain insight into the behavior of individual proton lines. The theoretical and experimental spectra were analyzed by least-squares fitting to Voigt shapes or by a new two-point method. For most accessible experimental designs, the comparisons are rather good; however, for an experiment constrained to low concentrations and high viscosities, the methods are less accurate.
      PubDate: 2017-10-09
      DOI: 10.1007/s00723-017-0958-x
       
  • Analysis of Saturation Recovery Amplitudes to Characterize Conformational
           Exchange in Spin-Labeled Proteins
    • Authors: Michael D. Bridges; Zhongyu Yang; Christian Altenbach; Wayne L. Hubbell
      Abstract: Analysis of saturation recovery data from spin-labeled proteins is extended to include the amplitudes in addition to the recovery rates for two-site exchange. It is shown that the recovery amplitudes depend strongly on the exchange rate between states as well as their populations and this dependence provides a simple criterion to identify exchange rates in the 10–1000 kHz range. Analysis of experimental SR relaxation curves via the uniform penalty (UPEN) method allows for reliable identification of single, double, or other multiple-component traces, and global fitting of a set of relaxation curves using both relaxation rates and amplitudes determined from the UPEN fits allows for the estimation of exchange rate in the above domain. The theory is tested on simple model systems, and applied to the determination of conformational exchange rates in spin-labeled mutants of T4 Lysozyme and intestinal fatty acid binding protein. Finally, an example of T 1-weighted spectral editing is provided for systems in the slow exchange limit.
      PubDate: 2017-10-05
      DOI: 10.1007/s00723-017-0936-3
       
  • Uniform Field Re-entrant Cylindrical TE $$_{01\text {U}}$$ 01 U Cavity for
           Pulse Electron Paramagnetic Resonance Spectroscopy at Q-band
    • Authors: Jason W. Sidabras; Edward J. Reijerse; Wolfgang Lubitz
      Abstract: Uniform field (UF) resonators create a region-of-interest, where the sample volume receives a homogeneous microwave magnetic field ( \(B_1\) ) excitation. However, as the region-of-interest is increased, resonator efficiency is reduced. In this work, a new class of uniform field resonators is introduced: the uniform field re-entrant cylindrical TE \(_{\text {01U}}\) cavity. Here, a UF cylindrical TE \(_{\text {01U}}\) cavity is designed with re-entrant fins to increase the overall resonator efficiency to match the resonator efficiency maximum of a typical cylindrical TE \(_{011}\) cavity. The new UF re-entrant cylindrical TE \(_{\text {01U}}\) cavity is designed for Q-band (34 GHz) and is calculated to have the same electron paramagnetic resonance (EPR) signal intensity as a TE \(_{011}\) cavity, a 60% increase in average resonator efficiency \(\Lambda _\mathrm{ave}\) over the sample, and has a \(B_1\) profile that is 79.8% uniform over the entire sample volume (98% uniform over the region-of-interest). A new H-type T-junction waveguide coupler with inductive obstacles is introduced that increases the dynamic range of a movable short coupler while reducing the frequency shift by 43% during over-coupling. The resonator assembly is fabricated and tested both on the bench and with EPR experiments. This resonator provides a template to improve EPR spectroscopy for pulse experiments at high frequencies.
      PubDate: 2017-09-30
      DOI: 10.1007/s00723-017-0955-0
       
  • High-Bandwidth Q-Band EPR Resonators
    • Authors: Rene Tschaggelar; Frauke D. Breitgoff; Oliver Oberhänsli; Mian Qi; Adelheid Godt; Gunnar Jeschke
      Abstract: The emerging technology of ultra-wide-band spectrometers in electron paramagnetic resonance—enabled by recent technological advances—provides the means for new experimental schemes, a broader range of samples, and huge gains in measurement time. Broadband detection does, however, require that the resonator provides sufficient bandwidth and, despite resonator compensation schemes, excitation bandwidth is ultimately limited by resonator bandwidth. Here, we present the design of three resonators for Q-band frequencies (33–36 GHz) with a larger bandwidth than what was reported so far. The new resonators are of a loop-gap type with 4–6 loops and were designed for 1.6 mm sample tubes to achieve higher field homogeneity than in existing resonators for 3 mm samples, a feature that is beneficial for precise spin control. The loop-gap design provides good separation of the B 1 and E field, enabling robust modes with powder samples as well as with frozen water samples as the resonant behavior is largely independent of the dielectric properties of the samples. Experiments confirm the trends in bandwidth and field strength and the increased B 1 field homogeneity predicted by the simulations. Variation of the position of the coupling rod allows the adjustment of the quality factor Q and thus the bandwidth over a broad range. The increased bandwidth of the loop-gap resonators was exploited in double electron–electron resonance measurements of a Cu(II)-PyMTA ruler to yield significantly higher modulation depth and thus higher sensitivity.
      PubDate: 2017-09-23
      DOI: 10.1007/s00723-017-0956-z
       
  • Resonators for In Vivo Imaging: Practical Experience
    • Authors: George A. Rinard; Richard W. Quine; Laura A. Buchanan; Sandra S. Eaton; Gareth R. Eaton; Boris Epel; Subramanian V. Sundramoorthy; Howard J. Halpern
      Abstract: Resonators for preclinical electron paramagnetic resonance imaging have been designed primarily for rodents and rabbits and have internal diameters between 16 and 51 mm. Lumped-circuit resonators include loop-gap, Alderman–Grant, and saddle coil topologies and surface coils. Bimodal resonators are useful for isolating the detected signal from incident power and reducing dead time in pulse experiments. Resonators for continuous wave, rapid scan, and pulse experiments are described. Experience at the University of Chicago and University of Denver in design of resonators for in vivo imaging is summarized.
      PubDate: 2017-09-22
      DOI: 10.1007/s00723-017-0947-0
       
  • Unseen Coherences Can Be Felt
    • Authors: Alexander G. Maryasov; Michael K. Bowman
      Abstract: Forbidden transitions are not observed in the continuous-wave electron paramagnetic resonance (EPR) spectrum nor in the free induction decay because, unlike allowed transitions, their coherences have no observable magnetic moment and are spectroscopically silent. Yet, the paramagnetic relaxation described by Redfield theory can cause coherence transfer between any types of transitions. Coherence transfer between allowed transitions is now known to cause noticeable changes in EPR spectra, but coherence transfer involving forbidden transitions has long been considered to be negligible because those coherences are silent and unseen. However, our simulations of a simple model system indicate that coherence transfer with silent transitions can introduce new features into EPR spectra. The EPR-silent coherence of a forbidden transition can be transferred to an allowed transition by paramagnetic relaxation. A silent coherence can have consequences felt in the EPR spectrum.
      PubDate: 2017-09-21
      DOI: 10.1007/s00723-017-0949-y
       
 
 
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