Concepts in Magnetic Resonance Part A最新文献_第7页

Variational Bayesian analysis of nonuniformly sampled NMR data 非均匀采样核磁共振数据的变分贝叶斯分析

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-09-16 DOI: 10.1002/cmr.a.21428

Bradley Worley

引用次数: 0

Advances in alternative sampling and processing 替代取样和处理的进展

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-09-16 DOI: 10.1002/cmr.a.21458

David Rovnyak, Adam D. Schuyler

引用次数: 2

Conservation of energy, density of states, and spin lattice relaxation 能量守恒，态密度和自旋晶格弛豫

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-07-15 DOI: 10.1002/cmr.a.21457

Navin Khaneja

{"title":"Conservation of energy, density of states, and spin lattice relaxation","authors":"Navin Khaneja","doi":"10.1002/cmr.a.21457","DOIUrl":"https://doi.org/10.1002/cmr.a.21457","url":null,"abstract":"The starting point of all NMR experiments is a spin polarization which develops when we place the sample in static magnetic field B0. There are excess of spins aligned along B0 (spin up with lower energy) than spins aligned opposite (spin down with higher energy) to the field B0. A natural question is what is the source of this excess spin polarization because relaxation mechanisms can flip a up spin to a down spin and vice-versa. The answer lies in the density of states. When a molecule with spin down flips to spin up it loses energy. This energy goes into increasing the kinetic energy of the molecule in the gas/solution phase. At this increased kinetic energy, there are more rotational-translational states accessible to the molecule than at lower energy. This increases the probability the molecule will spend in spin up state (higher kinetic energy state). This is the source of excess polarization. In this article, we use an argument based on equipartition of energy to explicitly count the excess states that become accessible to the molecule when its spin is flipped from down to up. Using this counting, we derive the familiar Boltzmann distribution of the ratio of up vs down spins. Although prima facie, there is nothing new in this article, we find the mode counting argument for excess states interesting. Furthermore, the article stresses the fact that spin polarization arises from higher density of states at increased kinetic energy of molecules.","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"46A 3","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21457","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91838675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

NMR Concepts 核磁共振的概念

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-06-26 DOI: 10.1002/cmr.a.21436

引用次数: 0

DVD Review DVD的评论

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-06-26 DOI: 10.1002/cmr.a.21368

引用次数: 0

Steady-state free precession signals of arbitrary dephasing order and their sensitivity to T2∗ 任意减相阶的稳态自由进动信号及其对T2 *的敏感性

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-06-13 DOI: 10.1002/cmr.a.21435

Jochen Leupold

{"title":"Steady-state free precession signals of arbitrary dephasing order and their sensitivity to T2∗","authors":"Jochen Leupold","doi":"10.1002/cmr.a.21435","DOIUrl":"10.1002/cmr.a.21435","url":null,"abstract":"A simple approach how to calculate analytical expressions for unbalanced steady-state free precession (ubSSFP) signals of arbitrary dephasing order is presented. Dephasing order is the number of effective gradient dephasing cycles that magnetization immediately after an RF-pulse has experienced during the ubSSFP sequence. Based on the obtained equations, which are in accordance with existing literature, the sensitivity of ubSSFP signals to T2∗ is derived under the assumption of a Lorentzian frequency distribution resulting from static field inhomogeneities. Further, the phases of all ubSSFP signals are calculated and a general expression of how to use them for B0-fieldmapping is given. The derivation is supported by the extended phase graph (EPG) model, and as such the work also acts as a comprehensive introduction to the formal description of SSFP. In addition, the balanced SSFP (bSSFP) sequence is explored. The connection of bSSFP to ubSSFP is shown, and potential T2∗-sensitivity of bSSFP is examined based on numerical simulations. It is shown that ubSSFP signals with negative dephasing order have a refocusing character and behave similar to spin-echo signals. Conversely, ubSSFP signals with zero or positive dephasing order can be regarded as T2∗-weighted. The behavior of bSSFP depends largely on the exact distribution of frequencies. For instance, for a narrow spherical distribution, bSSFP acts like a spin-echo sequence, while for a Lorentzian distribution a refocusing behavior does not occur.","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"46A 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21435","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87722707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Continuous wave electron paramagnetic resonance of nitroxide biradicals in fluid solution 流体溶液中氮氧化物双基的连续波电子顺磁共振

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-05-25 DOI: 10.1002/cmr.a.21426

Sandra S. Eaton, Lukas B. Woodcock, Gareth R. Eaton

引用次数: 15

DVD Review DVD的评论

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-04-29 DOI: 10.1002/cmr.a.21431

引用次数: 0

A tribute to Alexander Davidson Bain: An NMR pioneer and mentor at McMaster University 致敬亚历山大·戴维森·贝恩:麦克马斯特大学的核磁共振先驱和导师

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-04-29 DOI: 10.1002/cmr.a.21418

Christopher Anand, Bob Berno, Stephen Boulton, Michael A. Brook, Richard Epand, Timothy R. Field, Gillian R. Goward, Paul Hazendonk, Giuseppe Melacini

{"title":"A tribute to Alexander Davidson Bain: An NMR pioneer and mentor at McMaster University","authors":"Christopher Anand, Bob Berno, Stephen Boulton, Michael A. Brook, Richard Epand, Timothy R. Field, Gillian R. Goward, Paul Hazendonk, Giuseppe Melacini","doi":"10.1002/cmr.a.21418","DOIUrl":"10.1002/cmr.a.21418","url":null,"abstract":"In this tribute to our friend, mentor and colleague Alexander Davidson Bain we have collectively recapitulated the milestones of his career at McMaster university. We start from Alex's scientific and educational achievements and continue with his accomplishments as a community and infrastructure builder. We attempt to provide a sense of the breadth and depth of his seemingly endless scientific contributions while at McMaster by briefly summarizing selected representative examples from his body of work. Following Alex's lead, the scientific account is mixed with anecdotes and “bits of wisdom” we fondly remember from our interactions and collaborations with him. We also touch upon his brilliant and nurturing educational style and his “aggregator” role within the McMaster and wider NMR communities. We conclude with a more personal picture of Alex D. Bain, in which his scientific excellence and profound intellect are inextricably tied to his kind, nurturing and optimistic character and to his uniquely wry humor. He was not just a “good guy,” he was the epitome of the “good guy.”","PeriodicalId":55216,"journal":{"name":"Concepts in Magnetic Resonance Part A","volume":"45A 6","pages":""},"PeriodicalIF":0.6,"publicationDate":"2018-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/cmr.a.21418","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81401056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Solid-state NMR studies of chemical exchange in ion conductors for alternative energy applications 离子导体中用于替代能源应用的化学交换的固态核磁共振研究

IF 0.6 4区化学

Concepts in Magnetic Resonance Part A Pub Date : 2018-04-29 DOI: 10.1002/cmr.a.21419

Danielle L. Smiley, Gillian R. Goward

引用次数: 7