Subjects -> ENGINEERING (Total: 2844 journals)
    - CHEMICAL ENGINEERING (259 journals)
    - CIVIL ENGINEERING (255 journals)
    - ELECTRICAL ENGINEERING (182 journals)
    - ENGINEERING (1420 journals)
    - ENGINEERING MECHANICS AND MATERIALS (454 journals)
    - HYDRAULIC ENGINEERING (60 journals)
    - INDUSTRIAL ENGINEERING (101 journals)
    - MECHANICAL ENGINEERING (113 journals)

ENGINEERING (1420 journals)                  1 2 3 4 5 6 7 8 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 9)
3D Research     Hybrid Journal   (Followers: 22)
AAPG Bulletin     Hybrid Journal   (Followers: 11)
Abstract and Applied Analysis     Open Access   (Followers: 4)
Aceh International Journal of Science and Technology     Open Access   (Followers: 9)
ACS Nano     Hybrid Journal   (Followers: 452)
Acta Geotechnica     Hybrid Journal   (Followers: 7)
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 10)
Acta Nova     Open Access   (Followers: 1)
Acta Polytechnica : Journal of Advanced Engineering     Open Access   (Followers: 4)
Acta Scientiarum. Technology     Open Access   (Followers: 3)
Acta Universitatis Cibiniensis. Technical Series     Open Access   (Followers: 1)
Active and Passive Electronic Components     Open Access   (Followers: 8)
Adaptive Behavior     Hybrid Journal   (Followers: 9)
Adsorption     Hybrid Journal   (Followers: 5)
Advanced Energy and Sustainability Research     Open Access   (Followers: 8)
Advanced Engineering Forum     Full-text available via subscription   (Followers: 14)
Advanced Engineering Research     Open Access  
Advanced Journal of Graduate Research     Open Access   (Followers: 4)
Advanced Quantum Technologies     Hybrid Journal   (Followers: 1)
Advanced Science     Open Access   (Followers: 13)
Advanced Science Focus     Free   (Followers: 7)
Advanced Science Letters     Full-text available via subscription   (Followers: 13)
Advanced Science, Engineering and Medicine     Partially Free   (Followers: 11)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 20)
Advanced Theory and Simulations     Hybrid Journal   (Followers: 5)
Advances in Catalysis     Full-text available via subscription   (Followers: 8)
Advances in Complex Systems     Hybrid Journal   (Followers: 12)
Advances in Engineering Software     Hybrid Journal   (Followers: 31)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 20)
Advances in Fuzzy Systems     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 22)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 30)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 27)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 10)
Advances in Natural Sciences : Nanoscience and Nanotechnology     Open Access   (Followers: 36)
Advances in Operations Research     Open Access   (Followers: 14)
Advances in OptoElectronics     Open Access   (Followers: 6)
Advances in Physics Theories and Applications     Open Access   (Followers: 21)
Advances in Polymer Science     Hybrid Journal   (Followers: 54)
Advances in Porous Media     Full-text available via subscription   (Followers: 6)
Advances in Remote Sensing     Open Access   (Followers: 59)
Advances in Science and Research (ASR)     Open Access   (Followers: 8)
Aerobiologia     Hybrid Journal   (Followers: 4)
Aerospace Systems     Hybrid Journal   (Followers: 10)
African Journal of Science, Technology, Innovation and Development     Hybrid Journal   (Followers: 8)
AIChE Journal     Hybrid Journal   (Followers: 38)
Ain Shams Engineering Journal     Open Access   (Followers: 7)
Al-Nahrain Journal for Engineering Sciences     Open Access  
Al-Qadisiya Journal for Engineering Sciences     Open Access   (Followers: 2)
AL-Rafdain Engineering Journal     Open Access   (Followers: 3)
Alexandria Engineering Journal     Open Access   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
American Journal of Applied Sciences     Open Access   (Followers: 27)
American Journal of Engineering and Applied Sciences     Open Access   (Followers: 12)
American Journal of Engineering Education     Open Access   (Followers: 20)
American Journal of Environmental Engineering     Open Access   (Followers: 16)
American Journal of Industrial and Business Management     Open Access   (Followers: 31)
Annals of Civil and Environmental Engineering     Open Access   (Followers: 3)
Annals of Combinatorics     Hybrid Journal   (Followers: 3)
Annals of Pure and Applied Logic     Open Access   (Followers: 6)
Annals of Regional Science     Hybrid Journal   (Followers: 10)
Annals of Science     Hybrid Journal   (Followers: 10)
Annual Journal of Technical University of Varna     Open Access   (Followers: 1)
Antarctic Science     Hybrid Journal   (Followers: 1)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 3)
Applicable Analysis: An International Journal     Hybrid Journal   (Followers: 2)
Applications in Energy and Combustion Science     Open Access   (Followers: 4)
Applications in Engineering Science     Open Access   (Followers: 1)
Applied Catalysis A: General     Hybrid Journal   (Followers: 8)
Applied Catalysis B: Environmental     Hybrid Journal   (Followers: 22)
Applied Clay Science     Hybrid Journal   (Followers: 6)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 16)
Applied Engineering Letters     Open Access   (Followers: 5)
Applied Magnetic Resonance     Hybrid Journal   (Followers: 4)
Applied Nanoscience     Open Access   (Followers: 11)
Applied Network Science     Open Access   (Followers: 3)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 6)
Applied Physics Research     Open Access   (Followers: 7)
Applied Sciences     Open Access   (Followers: 6)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 6)
Arab Journal of Basic and Applied Sciences     Open Access  
Arabian Journal for Science and Engineering     Hybrid Journal   (Followers: 5)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 6)
Archives of Thermodynamics     Open Access   (Followers: 13)
Arctic     Open Access   (Followers: 7)
Arid Zone Journal of Engineering, Technology and Environment     Open Access   (Followers: 2)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
ArtefaCToS : Revista de estudios sobre la ciencia y la tecnología     Open Access   (Followers: 1)
Asia-Pacific Journal of Science and Technology     Open Access  
Asian Engineering Review     Open Access  
Asian Journal of Applied Science and Engineering     Open Access   (Followers: 2)
Asian Journal of Applied Sciences     Open Access   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 9)
Asian Journal of Control     Hybrid Journal  
Asian Journal of Technology Innovation     Hybrid Journal   (Followers: 7)
Assembly Automation     Hybrid Journal   (Followers: 2)
ATZagenda     Hybrid Journal  
ATZextra worldwide     Hybrid Journal  
AURUM : Mühendislik Sistemleri ve Mimarlık Dergisi = Aurum Journal of Engineering Systems and Architecture     Open Access   (Followers: 1)
Australasian Journal of Engineering Education     Hybrid Journal   (Followers: 3)
Australasian Physical & Engineering Sciences in Medicine     Hybrid Journal   (Followers: 1)
Australian Journal of Multi-Disciplinary Engineering     Hybrid Journal   (Followers: 2)
Autocracy : Jurnal Otomasi, Kendali, dan Aplikasi Industri     Open Access  
Automotive and Engine Technology     Hybrid Journal  
Automotive Experiences     Open Access  
Automotive Innovation     Hybrid Journal   (Followers: 1)
Avances en Ciencias e Ingenierías     Open Access  
Avances: Investigación en Ingeniería     Open Access   (Followers: 6)
Balkan Region Conference on Engineering and Business Education     Open Access   (Followers: 2)
Bangladesh Journal of Scientific and Industrial Research     Open Access  
Basin Research     Hybrid Journal   (Followers: 6)
Batteries     Open Access   (Followers: 11)
Batteries & Supercaps     Hybrid Journal   (Followers: 7)
Bautechnik     Hybrid Journal   (Followers: 3)
Bell Labs Technical Journal     Hybrid Journal   (Followers: 29)
Beni-Suef University Journal of Basic and Applied Sciences     Open Access   (Followers: 3)
Beyond : Undergraduate Research Journal     Open Access  
Bhakti Persada : Jurnal Aplikasi IPTEKS     Open Access  
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Bilge International Journal of Science and Technology Research     Open Access   (Followers: 1)
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 14)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 14)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 6)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 6)
Biomedical Microdevices     Hybrid Journal   (Followers: 9)
Biomedical Science and Engineering     Open Access   (Followers: 8)
Biomicrofluidics     Open Access   (Followers: 7)
Biotechnology Progress     Hybrid Journal   (Followers: 44)
Black Sea Journal of Engineering and Science     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)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 13)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 15)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers Droit, Sciences & Technologies     Open Access   (Followers: 1)
Calphad     Hybrid Journal   (Followers: 2)
Canadian Geotechnical Journal     Hybrid Journal   (Followers: 30)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 50)
Carpathian Journal of Electronic and Computer Engineering     Open Access  
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 6)
Case Studies in Thermal Engineering     Open Access   (Followers: 8)
Catalysis Communications     Hybrid Journal   (Followers: 7)
Catalysis Letters     Hybrid Journal   (Followers: 3)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 9)
Catalysis Science and Technology     Hybrid Journal   (Followers: 13)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysis Today     Hybrid Journal   (Followers: 8)
CEAS Space Journal     Hybrid Journal   (Followers: 6)
Cell Reports Physical Science     Open Access  
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 2)
Central European Journal of Engineering     Hybrid Journal  
CFD Letters     Open Access   (Followers: 8)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 3)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chaos, Solitons & Fractals : X     Open Access   (Followers: 1)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 3)
Chinese Journal of Engineering     Open Access   (Followers: 2)
Chinese Journal of Population, Resources and Environment     Open Access  
Chinese Science Bulletin     Open Access   (Followers: 1)
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access   (Followers: 1)
Ciencia y Tecnología     Open Access  
Ciencias Holguin     Open Access   (Followers: 2)
CienciaUAT     Open Access   (Followers: 1)
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Hybrid Journal   (Followers: 11)
CIRP Journal of Manufacturing Science and Technology     Hybrid Journal   (Followers: 14)
City, Culture and Society     Hybrid Journal   (Followers: 27)
Clay Minerals     Hybrid Journal   (Followers: 9)
Coal Science and Technology     Full-text available via subscription   (Followers: 4)
Coastal Engineering     Hybrid Journal   (Followers: 14)
Coastal Engineering Journal     Hybrid Journal   (Followers: 9)
Coastal Engineering Proceedings : Proceedings of the International Conference on Coastal Engineering     Open Access   (Followers: 2)
Coastal Management     Hybrid Journal   (Followers: 30)
Coatings     Open Access   (Followers: 4)
Cogent Engineering     Open Access   (Followers: 3)
Cognitive Computation     Hybrid Journal   (Followers: 3)
Color Research & Application     Hybrid Journal   (Followers: 4)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 18)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 21)
Communications Faculty of Sciences University of Ankara Series A2-A3 Physical Sciences and Engineering     Open Access  
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 2)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 28)
Composite Interfaces     Hybrid Journal   (Followers: 10)
Composite Structures     Hybrid Journal   (Followers: 335)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 279)
Composites Part B : Engineering     Hybrid Journal   (Followers: 312)
Composites Part C : Open Access     Open Access   (Followers: 3)
Composites Science and Technology     Hybrid Journal   (Followers: 247)
Comptes Rendus : Mécanique     Open Access   (Followers: 2)
Computation     Open Access   (Followers: 1)
Computational Geosciences     Hybrid Journal   (Followers: 20)
Computational Optimization and Applications     Hybrid Journal   (Followers: 11)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 6)
Computer Science and Engineering     Open Access   (Followers: 21)

        1 2 3 4 5 6 7 8 | Last

Similar Journals
Journal Cover
Applied Magnetic Resonance
Journal Prestige (SJR): 0.319
Citation Impact (citeScore): 1
Number of Followers: 4  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1613-7507 - ISSN (Online) 0937-9347
Published by Springer-Verlag Homepage  [2658 journals]
  • Two-Frequency Planar Gradiometer for Distant NQR Detection of Explosives

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      Abstract: The experimental realization of the two-frequency 14N nuclear quadrupole resonance (NQR) technique with use of the gradiometer radiofrequency (RF) probe for applications in the remote detection of explosives and other substances has been proposed. The planar two-frequency gradiometer has been designed, modeled and manufactured. The regions, where the RF magnetic fields are nearly orthogonal to each other, have been determined by finite-element modeling studies. The two-frequency experiments have been carried out for the detection of hexahydro-1,3,5-trinitro-s-triazine C3H6N6O6 (RDX). The possibility of the combined use of the two-frequency 14N NQR technique and the gradiometer RF probe in practice for detection of explosives hidden under clothes or underground has been also discussed.
      PubDate: 2021-10-07
       
  • Selected Applications of Magnetic Resonance

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      PubDate: 2021-09-23
       
  • The Effect of MRI Parameters on the Sensitivity and Dose Resolution of
           PASSAG Polymer Gel Dosimeter

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      Abstract: Magnetic resonance imaging (MRI) system is used as one of the most common methods to read out the response of polymer gel dosimeters. The imaging protocols can have a remarkable effect on the response of polymer gel dosimeters; hence, the impact of imaging parameters on the response of each type of polymer gel dosimeter should be addressed. This study aims to investigate the effect of MRI parameters on PASSAG polymer gel dosimeter response. PASSAG gel dosimeter was first fabricated and then, these gel samples were irradiated by a 6 MV X-rays. Thereafter, the MRI responses (R2) of the gel samples were analyzed. In addition, the impact of MRI parameters, including number of echoes (NOE), echo spacing (ES), repetition time (TR), and matrix size, on the sensitivity and dose resolution of the gel samples were evaluated. The findings showed that the highest R2–dose sensitivity belongs to the gel samples imaged with 32 NOE. It was also found that the dose resolution value improves with the increase of NOE. The R2–dose sensitivities and dose resolution values obtained from PASSAG gel samples imaged with ESs of 16.8, 22.0, and 27.2 ms were almost the same. Furthermore, the R2–dose sensitivities of gel vials imaged with TRs of 2000, 4000, and 6000 ms are almost the same (a 0.00–0.80% difference range), while the R2–dose sensitivity of gel vials imaged with 8000 ms was remarkably different from the sensitivities of gel vials imaged with other TRs (a 7.85–8.65% difference range). In addition, the dose resolution values of PASSAG gel dosimeter are almost the same for the evaluated TRs. There was a 0.80–11.58% difference range between the R2–dose sensitivities of gel vials at different matrix sizes, as these findings represent that the R2–dose sensitivity of PASSAG gel dosimeter is dependent on the matrix size. In addition, the dose resolution values of PASSAG gel dosimeter vary over the matrix size. According to the obtained results, it can be concluded that the TR and matrix size affect the response (R2–dose sensitivity and dose resolution) of PASSAG gel dosimeter more than the NOE and ES.
      PubDate: 2021-09-23
       
  • Pitfalls in Sample Preparation of Metalloproteins for Low-Temperature EPR:
           The Example of Alkaline Myoglobin

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      Abstract: Due to fast relaxation processes of transition metal ions, electron paramagnetic resonance (EPR) spectroscopy of metalloproteins needs to be performed at cryogenic temperatures. To avoid damaging the biological system upon freezing, a cryoprotectant is generally added to the sample as a glassing agent. Even though cryoprotectants are expected to be inert substances, evidences in literature show their non-innocent role in altering the shape of EPR spectra of proteins and biological objects in general. In this work we conduct a systematic study on the impact of several experimental factors—such as buffer composition, choice of cryoprotectant, pH and temperature—on the EPR spectrum of myoglobin, taken as a reference system for being a well-characterized heme-containing protein. We focus on high-pH buffers to induce and investigate the alkaline transition of ferric myoglobin (pKa ~ 8.9). A combined approach of continuous-wave EPR and UV–visible absorption spectroscopy shows that using particular pairs of buffers and cryoprotectants determines a considerable pH variation in the sample and that this effect is enhanced at cryogenic temperature. In addition, phase memory times were measured to evaluate the efficiency of different cryoprotectants and compared with spectral linewidths in continuous-wave EPR. Our findings suggest that among the selected cryoprotectants ethylene glycol is rather effective, even more than the widely used glycerol, without having unwanted effects.
      PubDate: 2021-09-23
       
  • Simulation of Multiple-Quantum NMR Dynamics of Spin Dimer on Quantum
           Computer

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      Abstract: Dynamics of spin dimers in multiple quantum NMR experiment is studied on the 5-qubit superconducting quantum processor of IBM Quantum Experience for the both pure ground and thermodynamic equilibrium (mixed) initial states. The work can be considered as a first step towards an application of quantum computers to solving problems of magnetic resonance. This article is dedicated to Prof. Klaus Möbius and Prof. Kev Salikhov on the occasion of their 85th birthdays.
      PubDate: 2021-09-23
       
  • Local Environment of Superoxide Radical Formed on the TiO2 Surface
           Produced From Ti(OiPr)4 Exposed to H2O2

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      Abstract: A selective heterogeneous catalyst with the superoxide anion O2•− stable at room temperature, generated by treating Ti(OR)4 (R = iPr, nBu) with H2O2, was previously reported and used for the oxidation of organic compounds. It was proposed that exceptional stability of the O2•− is resulted from its stabilization near Ti+4 cation on the TiO2 surface with the participation of water molecules and/or OH groups. In this article, we performed high-resolution pulsed EPR study on the O2•− in this catalyst with the aim to obtain quantitative information about its interactions with the surrounding molecules. Our data has shown that the O2•− is involved in weak hyperfine interactions with protons in the nearest environment, which do not exceed a value of 2 MHz. It corresponds to an Os…H distance of  ≥ 3 Å that excludes the formation of hydrogen bonds. The analysis of possible structures of O2•− adsorption on TiO2 surface taking into account our results and lack of radical mobility at room temperature previously observed in EPR spectra led us to suggest that the O2•− is stabilized in the form of superoxo bridge coordinated with two titanium atoms.
      PubDate: 2021-09-17
       
  • To a Question on Possibilities of High-Resolution NMR Spectroscopy in the
           Earth’s Magnetic Field

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      Abstract: The low signal-to-noise ratio is a characteristic feature of NMR experiments in the Earth’s magnetic field. The main problem of such studies is the ineffectiveness of signal accumulation due to fluctuations of the Earth’s magnetic field because of magnetic interferences from laboratory equipment and other magnetic field sources. Taking into account the fact that generally in the Earth’s magnetic field, proton-containing liquids have spectra with a strong central line, a relatively simple method has been developed to neutralize the influence of Larmor frequency fluctuations. The NMR signal processing algorithm is described. The home-built NMR-equipment allows us to clearly register the splitting in proton spectra, for example, due to the J-interaction with such nuclei as 29Si or 13C at their natural abundance (4.7 and 1.1%, respectively).
      PubDate: 2021-09-17
       
  • Special Issues of AMR on the Occasion of the 85th Birthday of Harold M.
           Swartz

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      PubDate: 2021-09-17
       
  • Correction to: Oxygenation Status of Malignant Tumors vs. Normal Tissues:
           Critical Evaluation and Updated Data Source Based on Direct Measurements
           with pO2 Microsensors

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      PubDate: 2021-09-14
       
  • Atomistic Simulations Modify Interpretation of Spin-Label Oximetry Data.
           Part 1: Intensified Water–Lipid Interfacial Resistances

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      Abstract: The role of membrane cholesterol in cellular function and dysfunction has been the subject of much inquiry. A few studies have suggested that cholesterol may slow oxygen diffusive transport, altering membrane physical properties and reducing oxygen permeability. The primary experimental technique used in recent years to study membrane oxygen transport is saturation-recovery electron paramagnetic resonance (EPR) oximetry, using spin-label probes targeted to specific regions of a lipid bilayer. The technique has been used, in particular, to assess the influence of cholesterol on oxygen transport and membrane permeability. The reliability of such EPR recordings at the water–lipid interface near the phospholipid headgroups has been challenged by all-atom molecular dynamics (MD) simulation data that show substantive agreement with spin-label probe measurements throughout much of the bilayer. This work uses further MD simulations, with an updated oxygen model, to determine the location of the maximum resistance to permeation and the rate-limiting barrier to oxygen permeation in 1-palmitoyl,2-oleoylphosphatidylcholine (POPC) and POPC/cholesterol bilayers at 25 and 35 °C. The current simulations show a spike of resistance to permeation in the headgroup region that was not detected by EPR but was predicted in early theoretical work by Diamond and Katz. Published experimental nuclear magnetic resonance (NMR) oxygen measurements provide key validation of the MD models and indicate that the positions and relative magnitudes of the phosphatidylcholine resistance peaks are accurate. Consideration of the headgroup-region resistances predicts bilayer permeability coefficients lower than that estimated in EPR studies, giving permeabilities lower than the permeability of unstirred water layers of the same thickness. Here, the permeability of POPC at 35 °C is estimated to be 13 cm/s, compared to 10 cm/s for POPC/cholesterol and 118 cm/s for simulation water layers of similar thickness. The value for POPC is 12 times lower than that estimated from EPR measurements, while the value for POPC/cholesterol is 5 times lower. These findings underscore the value of atomic resolution models for guiding the interpretation of experimental probe-based measurements.
      PubDate: 2021-09-12
       
  • The Interaction of Water-Soluble Nitroxide Radicals with Photosystem II

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      Abstract: In this work, we investigated the redox transients of a number of water-soluble spin labels upon their interactions with Photosystem II (PS II) core complexes isolated from spinach leaves. We have found that the reactivity of nitroxide radicals, determined by the rate of their reduction upon illumination of PS II, depends on the chemical structure of radicals and the capability of their coming close to low-potential redox centers of photoactive PS II complexes. An enhanced capability of nitroxide radicals to accept electrons from PS II correlates with their chemical structure. Nitroxide radicals NTI (2,2,5,5-tetramethyl-4-nitromethylene-3-imidazolidine-N-oxyl) and Tacet (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl-acetate), containing polar groups, appear to be most efficient acceptors of electrons donated by PS II compared to neutral (TEMPOL, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl) or positively charged (Tamine, 4-amino-2,2,6,6-tetramethylpiperidine-l-oxyl) spin labels. We assume that enhanced reactivities of polar nitroxide radicals, NTI and Tacet, are determined (1) by their relatively high redox potentials, providing the possibility to accept electrons from PS II, and (2) by their affinities to the closest binding sites on the surface of PS II in the vicinity of the primary plastoquinone acceptor PQA (12–14 Å) or/and in the intraprotein cavity for the secondary plastoquinone PQB (~ 22 Å).
      PubDate: 2021-09-09
       
  • Kinetic Analysis and Resolution of Overlapping EPR Spectra

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      Abstract: A new method for the resolution and quantitative kinetic analysis of overlapping electron paramagnetic (EPR) spectra, based on a combination of smoothing by B-splines and/or discrete cosine transformation and linear algebra methods for finding eigenvalues and eigenvectors of the covariance matrix using the Frobenius normal form with subsequent final basis adjustment by the Moore–Penrose pseudo-inverse matrix, is proposed. This algorithm does not require the use of the time-consuming multiple iterations of the least squares method. Our approach has been tested on several specific chemical systems including stable organic radicals and paramagnetic V4+ and VO2+ ions. In all the cases, the analysis of experimental EPR spectra demonstrated that the new approach produces good results.
      PubDate: 2021-09-09
       
  • Pentacene in 1,3,5-Tri(1-naphtyl)benzene: A Novel Standard for Transient
           EPR Spectroscopy at Room Temperature

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      Abstract: Testing and calibrating an experimental setup with standard samples is an essential aspect of scientific research. Single crystals of pentacene in p-terphenyl are widely used for this purpose in transient electron paramagnetic resonance (EPR) spectroscopy. However, this sample is not without downsides: the crystals need to be grown and the EPR transitions only appear at particular orientations of the crystal with respect to the external magnetic field. An alternative host for pentacene is the glass-forming 1,3,5-tri(1-naphtyl)benzene (TNB). Due to the high glass transition point of TNB, an amorphous glass containing randomly oriented pentacene molecules is obtained at room temperature. Here we demonstrate that pentacene dissolved in TNB gives a typical “powder-like” transient EPR spectrum of the triplet state following pulsed laser excitation. From the two-dimensional data set, it is straightforward to obtain the zero-field splitting parameters and relative populations by spectral simulation as well as the \(B_{1}\) field in the microwave resonator. Due to the simplicity of preparation, handling and stability, this system is ideal for adjusting the laser beam with respect to the microwave resonator and for introducing students to transient EPR spectroscopy.
      PubDate: 2021-09-07
       
  • Comparative Study of the Intensity of Nitric Oxide Production and Copper
           Content in Hippocampus of Rats After Modeling of Hemorrhagic Stroke and
           Brain Injury

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      Abstract: A comparative experimental analysis of intensity of nitric oxide (NO) production and the copper content in the tissues of hippocampus of male Wistar rats after modeling of hemorrhagic stroke and brain injury was conducted using EPR spectroscopy. Modeling of hemorrhagic stroke was carried out by microinjection of 500 nl of autologous blood into the brain to a depth of 5.0 mm (hippocampus) on the left side. Brain injury was performed by removing a piece of nerve tissue from 5.0 mm depth on the left side of hippocampus. It was registered a significant decrease in the NO content in hippocampus by 36 ± 17% on the 3rd day after modeling of hemorrhagic stroke together with decrease by an average of 24 ± 14% of the copper content. There were no significant changes in the NO level in hippocampus found neither on the 3rd day nor on the 7th day after brain injury modeling. There was also no change in copper content. Thus, it was experimentally demonstrated that modeling of brain injury, in contrast to hypoxia induced by hemorrhagic stroke, was not accompanied with significant changes in NO production in hippocampus of rat.
      PubDate: 2021-09-07
       
  • Neuroglobin Provides a Convenient Scaffold to Investigate the
           Triplet-State Properties of Porphyrins by Time-Resolved EPR Spectroscopy
           and Magnetophotoselection

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      Abstract: The photo-excited triplet state of Zn-protoporphyrin IX located in the heme pocket of human neuroglobin has been investigated by time-resolved EPR coupled to magnetophotoselection. The triplet state in the protein matrix has been compared with the model complex in organic glass, considering both non-coordinating and coordinating solvent mixtures. The protein matrix plays an important role in stabilizing the coordination of the embedded chromophore, resulting in a more homogeneous environment relative to that of the chromophore in a glassy solvent, even in the presence of an axial nitrogenous ligand like pyridine. The EPR spectral parameters point out a slow Jahn–Teller interconversion between slightly different triplet states, both in organic solvent and in the protein matrix. The EPR-magnetophotoselection allows us to propose a reinterpretation of the assignment of the Q bands in the electronic absorption spectrum.
      PubDate: 2021-09-04
       
  • The Effect of N, Nʹ-Methylene-bis-acrylamide Removal from a Polymer Gel
           Dosimeter Formulation: Spin–Spin Relaxation Rate Investigation and
           Post-irradiation Time Instability

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      Abstract: The extreme toxicity of the monomers used in polymer gel dosimeters (PGDs) has caused some limitations in producing, applying, and storing these valuable tools. This study aimed to investigate the response of a new PGD produced by a less toxic monomer of 2-acrylamido-2-methyl-propane-sulfonic-acid potassium salt. Furthermore, in this new formulation, the highly toxic cross-linker, N, Nʹ-methylene-bis-acrylamide, was not used. The new formulation was named PAGPOT. A clinical linac system was used to irradiate the gel dosimeters. The response of irradiated PGDs was read-out using magnetic resonance imaging (MRI). Additionally, the response of the produced PGD was evaluated for different post-irradiation times and read-out temperatures. Results showed a maximum sensitivity of 0.08 s−1 Gy−1 for the PAGPOT PGD. The change in sensitivity as a function of temperature is negligible compared to the uncertainty of the measurement. Results showed that the sensitivity and dose resolution of the PAGPOT PGD are functions of time elapsed post-irradiation. Furthermore, results showed a significant dependence of the R2 response of the PAGPOT PGD on the post-irradiation time. However, it was noticeably less toxic compared with other PGDs.
      PubDate: 2021-09-01
       
  • Temperature Coefficient Optimization of the Physics Package of Rubidium
           Atomic Clock

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      Abstract: The vapor-cell rubidium atomic clock is widely used in Global Navigation Satellite System (GNSS) and telecommunications. The sensitivity of temperature is one of the most important factors affecting the performance of rubidium Atomic Frequency Standards (RAFS). It plays a significant role in the long-term frequency stability of the rubidium atomic clock, and largely depends on the Physics Package (PP). In this paper, we attempt to reduce the temperature sensitivity of RAFS in a specific environment of vacuum and extraterrestrial temperature. We achieve this by studying the theory of light shift, collision shift, and magnetic frequency shift in RAFS. By combining this with our engineering expertise, we have proposed a single method on three parameters to optimize the temperature coefficient of PP of the rubidium atomic clock, which can not only optimize the temperature coefficient of PP, but can also improve the long-term frequency stability of the rubidium atomic clock. Some related experiments, by the proposed method, further demonstrate a significant reduction in the temperature coefficient of PP, suggesting that the performance of RAFS can be improved.
      PubDate: 2021-09-01
       
  • Magneto-uniaxial Nanoparticle and Nano-lattice Magnetization Reversal
           Under the Additional Effect of Noise

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      Abstract: The magnetic moment response of an isolated nanoparticle of a uniaxial anisotropy and plane lattice composed of nanoparticles is being studied under the action of a longitudinal alternating field and a Gaussian pulse with an additional noise signal. The modes of partial and complete magnetization reversal of dipole systems implemented only in the presence of noise have been revealed. The periodic dependence of the magnetic moment response and magnetization reversal processes on the pulse duration has been studied. The conditions under which the pulsed magnetization reversal is most and least sensitive to the action of the noise signal have been revealed.
      PubDate: 2021-09-01
       
  • Temperature Dependencies of the Spin Relaxation Times for the Isotopically
           Pure Chromium Impurity 53Cr3+ in the Yttrium Orthosilicate Single Crystal
           Y228SiO5

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      Abstract: The temperature dependencies of the spin–lattice relaxation time and the phase relaxation time of 53Cr3+ ion in the Y228SiO5 single crystal are measured at the anti-crossing point via pulsed electron paramagnetic resonance technique at X-band frequencies and in the temperature range from 5 to 80 K. It is found that the phase relaxation time does not change rapidly near the anti-crossing point, whereas in optical experiments with rare-earth ions, the phase relaxation time decreases significantly with a slight deviation of the magnetic field from the anti-crossing point. The effect of spin dynamical decoupling on the phase relaxation time is measured using the Carr–Purcell–Meiboom–Gill (CPMG) multi-pulse sequence.
      PubDate: 2021-09-01
       
  • Magnon Quantization in the Magnetic Field Qradient

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      Abstract: The article is devoted to the study of quantization of magnons in yttrium iron garnet film in the magnetic field gradient. Detected energy levels correspond to the quantization of particles in triangular potential. These energy levels are not equidistant. Therefore, they can be used to create a magnon quantum qubits.
      PubDate: 2021-09-01
       
 
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