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  Subjects -> ENGINEERING (Total: 2291 journals)
    - CHEMICAL ENGINEERING (192 journals)
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    - ELECTRICAL ENGINEERING (105 journals)
    - ENGINEERING (1209 journals)
    - ENGINEERING MECHANICS AND MATERIALS (385 journals)
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ENGINEERING (1209 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: 18)
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: 233)
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: 7)
Advanced Science, Engineering and Medicine     Partially Free   (Followers: 8)
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: 25)
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 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: 37)
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: 30)
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: 4)
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: 3)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 14)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 42)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 8)
Case Studies in Thermal Engineering     Open Access   (Followers: 3)
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: 262)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 183)
Composites Part B : Engineering     Hybrid Journal   (Followers: 281)
Composites Science and Technology     Hybrid Journal   (Followers: 179)
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: 6)
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  
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]   [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]
  • NMR Study Conformations of Calcium Gluconate in the Aqueous Solution
    • Authors: M. M. Akhmetov; G. N. Konygin; D. S. Rybin; V. Yu. Petukhov; G. G. Gumarov; A. B. Konov
      Pages: 971 - 979
      Abstract: Abstract Different spatial structures that arise due to rotation around simple bonds without violating the integrity of the molecule (without breaking chemical bonds) are called conformations. 1H nuclear magnetic resonance (NMR) study of the spatial structure of calcium gluconate in the aqueous solution has been carried out. It was shown that molecules of calcium gluconate exist in the form of two conformations: zigzag 1-P and cyclic 3 G +. The results of homonuclear 2D 1H NMR spectroscopy indicate the predominantly zigzag conformation. It was found that the intermolecular hydrogen bonds are formed and the spatial structure of molecules changes at the increase in the solution concentration. The observed concentration behavior of the conformation of calcium gluconate is also associated with the presence of the intramolecular hydrogen bonds –O(C4)H··O(C2).
      PubDate: 2017-10-01
      DOI: 10.1007/s00723-017-0918-5
      Issue No: Vol. 48, No. 10 (2017)
       
  • Fluid Typing: Efficient NMR Well-Logging with Interleaved CPMG Sequence at
           Different Frequencies
    • Authors: Baosong Wu; Stephen A. Altobelli; Eiichi Fukushima
      Pages: 981 - 987
      Abstract: Abstract Fluid typing in reservoirs is currently based on longitudinal relaxation and/or diffusion contrast method, the latter represented by the dual-TE method which uses two types of Carr–Purcell–Meiboom–Gill (CPMG) echo trains with short and long echo spacings. In this paper, we describe a scheme to enhance efficiency of dual-TE method by combining it with multi-frequency CPMG. We took advantage of the echo spacing in the long-TE pulse sequence and interleaved a second sequence for a different slice in the gaps to obtain information from both slices. Verification experiments were performed with a surface coil in a gradient magnetic field.
      PubDate: 2017-10-01
      DOI: 10.1007/s00723-017-0929-2
      Issue No: Vol. 48, No. 10 (2017)
       
  • Nuclear Magnetic Resonance in Gaussian Stochastic Local Field
    • Authors: F. S. Dzheparov; D. V. Lvov
      Pages: 989 - 1007
      Abstract: Abstract Anderson–Weiss–Kubo model of magnetic resonance is reconsidered to bridge the existing gaps in its applications for solutions of fundamental problems of spin dynamics and theory of master equations. The model considers the local field fluctuations as one-dimensional normal random process. We refine the conditions of applicability of perturbation theory to calculate the spin depolarization and phase relaxation. A counterexample is considered to show that in the absence of temporal fluctuations of local fields, perturbation theory is not applicable even qualitatively. It is shown that for slow fluctuations, the behavior of the longitudinal magnetization is simply related to the correlation function of the local field. Quasi-adiabatic losses are estimated.
      PubDate: 2017-10-01
      DOI: 10.1007/s00723-017-0923-8
      Issue No: Vol. 48, No. 10 (2017)
       
  • A New Method for Determining Tight Sandstone Permeability Based on the
           Characteristic Parameters of the NMR T 2 Distribution
    • Authors: Mi Liu; Ranhong Xie; Changxi Li; Lun Gao
      Pages: 1009 - 1029
      Abstract: Abstract This paper proposes a new method to determine the permeability of tight sandstone using characteristic parameters of the nuclear magnetic resonance (NMR) transverse relaxation time (T 2) distribution. First, the Swanson parameters (T s ) and Capillary–Parachor parameters (T cp) are calculated as the percolation characteristic parameters (T c) of NMR T 2 distribution. The logarithmic mean (T lm), arithmetic mean (T am), and harmonic mean (T hm) are calculated as the pore structure characteristic parameters (T m) of NMR T 2 distribution. T x , the transverse relaxation time when the value of Y-axis is x% in the normalized accumulated T 2 distribution curve accumulated from long relaxation time part to short relaxation time part, is selected as a characteristic parameter of pore size distribution. Second, different T c, T m, T x , and NMR porosity (T por) values are selected to establish single-, double-, three-, and four- parameter models for estimating permeability. An analysis of the relationships between calculated permeabilities of different models and measured permeability in tight sandstone rocks indicated that the four-parameter model based on T cp, T 40, T am, and T por was the best model. Moreover, this model was superior to the calibrated Timur model and the calibrated SDR model for calculating permeability in tight sandstone reservoirs.
      PubDate: 2017-10-01
      DOI: 10.1007/s00723-017-0924-7
      Issue No: Vol. 48, No. 10 (2017)
       
  • MRI Contrast Enhancement Using Ferritin Genes and Its Application for
           Evaluating Anticancer Drug Efficacy in Mouse Melanoma Models
    • Authors: Jae Young Kim; Gunwoo Lee; On Seok Lee; Geo Han; Seunghan Ha; Chil Hwan Oh
      Pages: 1031 - 1041
      Abstract: Abstract The study aimed to introduce a ferritin gene probe into a mouse melanoma model to facilitate longitudinal in vivo monitoring of malignant melanoma via magnetic resonance imaging (MRI), thus creating a new prognostic tool and pharmacodynamic resource. B16 cells transfected with the human ferritin heavy chain (hFTH) and human ferritin light chain (hFTL) were subcutaneously inoculated into the dorsal areas of C57BL/6J mice for xenograft models. These xenograft models of malignant melanoma were monitored using the 4.7-T MRI system. Axial slices were acquired at the xenograft site, using T2-weighted spin-echo and T2*-weighted gradient-echo sequences. In addition, the efficacy of anticancer drugs was evaluated in the xenograft models. The hFTH- and hFTL-transfected B16 cells had significantly lower signal intensities in T2- and T2*-weighted MRI images than did the control group (w/o ferritin transfection). This was grossly correlated with tumor progression and could be visualized. The oregonin and oregonin + dacarbazine (DTIC) treated groups showed greater survival rates than the control and DTIC-only groups. We have developed an effective MRI contrast enhancement method using a ferritin gene probe. It can be applied reliably to evaluate the efficacy of drugs in preclinical and clinical trials, greatly assisting the development of new chemotherapeutics.
      PubDate: 2017-10-01
      DOI: 10.1007/s00723-017-0926-5
      Issue No: Vol. 48, No. 10 (2017)
       
  • A Rapid NMR T 2 Inversion Method Based on Norm Smoothing
    • Authors: Youlong Zou; Jun Li; Junlei Su; Aiqin Zhang
      Pages: 1043 - 1053
      Abstract: Abstract Norm smoothing is commonly used in nuclear magnetic resonance (NMR) T2 inversion and the choice of a suitable regularization parameter is a key step for obtaining a satisfactory inversion result, which is usually achieved by repeating T2 inversion multiple times. However, a greater number of inversions result in a slower speed for the inversion process. In this paper, we propose a rapid norm smoothing T2 inversion method achieved using a new selection method for the regularization parameter. First, the singular value decomposition (SVD) method is used to calculate singular values of the kernel matrix to compress the echo train data. Subsequently, a suitable regularization parameter is calculated based on the signal-to-noise ratio (SNR) of the echo train and the maximum singular value of the kernel matrix, which avoids the repetitions of the T2 inversion. Finally, a rapid T2 inversion is obtained using the Butler–Reeds–Dawson (BRD) method. Numerical simulation and logging data inversion results show that the new method can rapidly provide reasonable T2 spectra for data with different SNRs and is insensitive to the amount of the compressed data.
      PubDate: 2017-10-01
      DOI: 10.1007/s00723-017-0928-3
      Issue No: Vol. 48, No. 10 (2017)
       
  • GPU-Accelerated Self-Calibrating GRAPPA Operator Gridding for Rapid
           Reconstruction of Non-Cartesian MRI Data
    • Authors: Omair Inam; Mahmood Qureshi; Shahzad A. Malik; Hammad Omer
      Pages: 1055 - 1074
      Abstract: Abstract Self-calibrating GRAPPA operator gridding (SC-GROG) is a method by which non-Cartesian (NC) data in magnetic resonance imaging (MRI) are shifted to the Cartesian k-space grid locations using the parallel imaging concept of GRAPPA operator. However, gridding with SC-GROG becomes computationally expensive and leads to longer reconstruction time when mapping a large number of NC samples in MRI data to the nearest Cartesian grid locations. This work aims to accelerate the SC-GROG for radial acquisitions in MRI, using massively parallel architecture of graphics processing units (GPUs). For this purpose, a novel implementation of GPU-accelerated SC-GROG is presented, which exploits the inherent parallelism in gridding operations. The proposed method employs the look-up-table (LUT)-based optimized kernels of compute unified device architecture (CUDA), to pre-calculate all the possible combinations of 2D-gridding weight sets and uses appropriate weight sets to shift the NC signals from multi-channel receiver coils at the nearest Cartesian grid locations. In the proposed method, LUTs are implemented to avoid the race condition among the CUDA kernel threads while shifting various NC points to the same Cartesian grid location. Several experiments using 24-channel simulated phantom and (12 and 30 channel) in vivo data sets are performed to evaluate the efficacy of the proposed method in terms of computation time and reconstruction accuracy. The results show that the GPU-based implementation of SC-GROG can significantly improve the image reconstruction efficiency, typically achieving 6× to 30× speed-up (including transfer time between CPU and GPU memory) without compromising the quality of image reconstruction.
      PubDate: 2017-10-01
      DOI: 10.1007/s00723-017-0932-7
      Issue No: Vol. 48, No. 10 (2017)
       
  • Internal Magnetic Field Gradients in Paramagnetic Shale Pores
    • Authors: M. E. Ramia; C. A. Martín
      Pages: 1075 - 1091
      Abstract: Abstract The present work involves a comprehensive study to provide a theoretical model of the internal magnetic field gradients, present in paramagnetic shale pores, to explain the main relaxation features observed by nuclear magnetic resonance transversal relaxation measurements. In the systematic analysis process of relaxation data it is necessary to know up to what extent the magnetic field gradients are generated by the logging tool and/or arise internally in the rock due to their paramagnetic impurities content. The physical model to explain the relaxation features is based on the calculation of field gradients in a planar pore with and without relaxatives walls. The results reproduce the features of the relaxation parameters in pores due to paramagnetic and tortuous walls. The mechanism that drives the relaxation process is governed by anomalous diffusion within micro-pores. These relaxation processes arise from the interactions between the protons, belonging to the liquid molecules and the pore walls, whose structure is characterized by both large tortuosity and abundance of paramagnetic impurities, giving rise to local strong time dependent magnetic field gradients. The theoretical results are compared with those obtained experimentally to validate the relaxation model. The experimental data were gathered from a sample belonging to the “Vaca Muerta” formation of the Neuquén basin, Argentina.
      PubDate: 2017-10-01
      DOI: 10.1007/s00723-017-0922-9
      Issue No: Vol. 48, No. 10 (2017)
       
  • 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: 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
       
  • Towards Determination of Distances Between Nanoparticles and Grafted
           Paramagnetic Ions by NMR Relaxation
    • Authors: A. M. Panich; N. A. Sergeev
      Abstract: Abstract We developed an approach for determining distances between carbon nanoparticles and grafted paramagnetic ions and molecules by means of nuclear spin–lattice relaxation data. The approach was applied to copper-, cobalt- and gadolinium-grafted nanodiamonds, iron-grafted graphenes, manganese-grafted graphene oxide and activated carbon fibers that adsorb paramagnetic oxygen molecules. Our findings show that the aforementioned distances vary in the range of 2.7–5.4 Å and that the fixation of paramagnetic ions to nanoparticles is most likely implemented by means of the surface functional groups. The nuclear magnetic resonance data data are compared with the results of electron paramagnetic resonance measurements and density functional theory calculations.
      PubDate: 2017-10-05
      DOI: 10.1007/s00723-017-0952-3
       
  • 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: 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
       
  • Determination of Carbon Chain Lengths of Fatty Acid Mixtures by Time
           Domain NMR
    • Authors: E. Nikolskaya; Y. Hiltunen
      Abstract: Abstract Average carbon chain length is a key parameter that defines the quality of liquid biofuels. In this paper, a method for the determination of carbon chain lengths of fatty acid mixtures is presented. The approach is based on proton relaxation rates measured by time domain nuclear magnetic resonance. The spin–spin relaxation rates R 2 were used for the estimation of the carbon chain lengths. The method was examined for the set of samples with different mean lengths of the main linear carbon chain. Samples were prepared using four different fatty acids and mixtures of two, three or four of these fatty acids. The correlation coefficient between the known and measured values was equal to 0.994. Based on the relaxation theory, a linear-like dependence between the relaxation rate and carbon chain length was briefly shown, which endorses the experimental results. The developed methodology for determining carbon chain lengths offers robustness and rapidity, which are significant advantages when it comes to online use of the method in real industrial environments.
      PubDate: 2017-09-30
      DOI: 10.1007/s00723-017-0953-2
       
  • 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: 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: 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
       
  • The Effect of Shape and Concentration on Translational Diffusion of
           Proteins Measured by PFG NMR
    • Authors: A. M. Kusova; A. E. Sitnitsky; B. Z. Idiyatullin; D. R. Bakirova; Yu. F. Zuev
      Abstract: Abstract The concentration dependences of self-diffusion coefficient for irregular-shaped fibrinogen, for globular, spheroidal trypsin and α-chymotrypsin were studied by pulsed field gradient nuclear magnetic resonance. The experimental data were analyzed in a view of two known theoretical approaches—the hydrodynamic model of rigid spheres by Tokuyama and Oppenheim and the phenomenological approach based on the frictional formalism of non-equilibrium thermodynamics by Vink. The detailed discussion of their merits and drawbacks is presented. Our results testify that the Vink’s approach is quite universal, providing a satisfactory description of experimental data for proteins of complicated structure and different shape while the model of Tokuyama and Oppenheim is applicable only to proteins of more regular shape.
      PubDate: 2017-09-23
      DOI: 10.1007/s00723-017-0957-y
       
  • 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: 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: 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
       
  • Optimizing Image Reconstruction in SENSE Using GPU
    • Authors: Sohaib A. Qazi; Saima Nasir; Abeera Saeed; Hammad Omer
      Abstract: Abstract Parallel magnetic resonance imaging (MRI) (pMRI) uses multiple receiver coils to reduce the MRI scan time. To accelerate the data acquisition process in MRI, less amount of data is acquired from the scanner which leads to artifacts in the reconstructed images. SENSitivity Encoding (SENSE) is a reconstruction algorithm in pMRI to remove aliasing artifacts from the undersampled multi coil data and recovers fully sampled images. The main limitation of SENSE is computing inverse of the encoding matrix. This work proposes the inversion of encoding matrix using Jacobi singular value decomposition (SVD) algorithm for image reconstruction on GPUs to accelerate the reconstruction process. The performance of Jacobi SVD is compared with Gauss–Jordan algorithm. The simulations are performed on two datasets (brain and cardiac) with acceleration factors 2, 4, 6 and 8. The results show that the graphics processing unit (GPU) provides a speed up to 21.6 times as compared to CPU reconstruction. Jacobi SVD algorithm performs better in terms of acceleration in reconstructions on GPUs as compared to Gauss–Jordan method. The proposed algorithm is suitable for any number of coils and acceleration factors for SENSE reconstruction on real time processing systems.
      PubDate: 2017-09-21
      DOI: 10.1007/s00723-017-0951-4
       
  • Six Decades of Progress in Magnetic Resonance: The Contributions of James
           S. Hyde
    • Authors: Gareth R. Eaton; Wayne L. Hubbell; Wojciech Froncisz
      Abstract: 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: 2017-09-21
      DOI: 10.1007/s00723-017-0954-1
       
  • High-Pressure EPR Spectroscopy Studies of the E. coli Lipopolysaccharide
           Transport Proteins LptA and LptC
    • Authors: Kathryn M. Schultz; Candice S. Klug
      Abstract: 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: 2017-09-21
      DOI: 10.1007/s00723-017-0948-z
       
 
 
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