Podcasts about anisotropy

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.31.534758v1?rss=1 Authors: Ruiz-Rizzo, A. L., Finke, K., Damoiseaux, J. S., Bartels, C., Buerger, K., Cosma, N. C., Dechent, P., Dobisch, L., Ewers, M., Fliessbach, K., Frommann, I., Glanz, W., Goerss, D., Hetzer, S., Incesoy, E. I., Janowitz, D., Kilimann, I., Laske, C., Melo van Lent, D., Munk, M. H. J., Peters, O., Priller, J., Ramirez, A., Rostamzadeh, A., Roy, N., Scheffler, K., Schneider, A., Spottke, A., Spruth, E. J., Teipel, S., Wagner, M., Wiltfang, J., Yakupov, R., Jessen, F., Duezel, E., Perneczky, R., Rauchmann, B.-S. Abstract: Background: The mechanisms in the brain that explain the benefits of adherence to the Mediterranean diet (MeDiAd) for cognition are incompletely understood. Here, we investigated whether fractional anisotropy (FA) in hippocampus-relevant white-matter tracts mediates the association between baseline MeDiAd and verbal episodic memory over four years. Methods: Participants with baseline diffusion-weighted imaging data from the DELCODE cohort study were selected, including healthy older adults with and without subjective cognitive decline and patients with mild cognitive impairment (n = 376; age: 71.47 plus-or-minus sign 6.09 years; 48.7% female). Demographic, MeDiAd, and diffusion data were obtained at baseline. Verbal episodic memory was assessed at baseline and four yearly follow-ups. The association between baseline MeDiAd and verbal episodic memory's mean and rate of change over four years and the mediation of that association by baseline white-matter tracts were tested with latent growth curve modeling. Potential mediators were selected based on the association with hippocampal volume. Results: Baseline MeDiAd was associated with verbal episodic memory four years later (latent intercept; 95% confidence interval, CI [0.01, 0.32]) but not with its rate of change (latent slope) over this period. Only baseline Fornix FA, among four potential mediators (the cingulum ventral, corticospinal tract, and superior longitudinal fasciculus II), mediated this association (latent intercept; 95% CI [0.002, 0.09]). Conclusions: Higher Fornix FA explains the association between higher baseline MeDiAd and better memory four years later in pre-dementia stages. Fornix FA may be a useful response biomarker of Mediterranean diet interventions on memory. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.28.534468v1?rss=1 Authors: Alcami, P., Castelfranco, A. Abstract: The internal resistance of axons to ionic current flow affects the speed of action potential propagation. As biological cables, axons contain mitochondria which are necessary to support axonal function with energy supply. Although we would expect mitochondria to increase the internal resistance to current flow, their impact on the conduction velocity of action potentials has remained elusive. To investigate the impact of mitochondria on action potential propagation in the small non-myelinated fibers found in the vertebrate brain, we combined computational modeling and electron microscopy from the axons found in the premotor pathway that controls the production of birdsong with submillisecond precision. Mitochondria occupancy of axonal cross-sections ranged from 5 to 73% (average: 29%) in the ~ 0.2-0.7 m diameter non-myelinated axons connecting song premotor nuclei HVC and RA in canaries. Interestingly, this occupancy depends on axonal diameter: axonal cross-section occupancy by mitochondria was larger in small axons, with an average occupancy of ~46% for axons with diameters smaller than 300 nm and ~21% for larger diameters. Computational modeling showed that when the propagating action potential meets a mitochondrion, the conduction velocity decreases and the action potential is delayed by tenths of microseconds to microseconds. This effect is stronger in small axons given their larger cross section mitochondrial occupancy and cumulates delays of tenths of milliseconds along the whole pathway linking HVC and RA. Finally, we modeled the impact of varying densities of mitochondria on action potential propagation along the songbird premotor pathway. In summary, our model shows that axonal mitochondria induce the anisotropic propagation of action potentials, and that this effect cumulates a typical delay in the order of tenths of milliseconds over distances of mms. By partially occupying axoplasm, mitochondria constitute a biological design constraint that delays information processing in the small-diameter unmyelinated axons found in the vertebrate brain. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

https://psychiatry.dev/wp-content/uploads/speaker/post-11318.mp3?cb=1672294782.mp3 Playback speed: 0.8x 1x 1.3x 1.6x 2x Download: Lower fractional anisotropy without evidence for neuro-inflammation in patients with early-phase schizophrenia spectrum disorders – Shiral S Gangadin et al. Schizophrenia Research.Full EntryLower fractional anisotropy without evidence for neuro-inflammation in patients with early-phase schizophrenia spectrum disorders –

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.12.20.521068v1?rss=1 Authors: Brabec, J., Friedjungova, M., Vasata, D., Englund, E., Bengzon, J., Knutsson, L., Szczepankiewicz, F., Sundgren, P. C., Nilsson, M. Abstract: Background: Mean diffusivity (MD) and fractional anisotropy (FA) obtained with diffusion MRI (dMRI) have been associated with cell density and tissue anisotropy across tumors, but it is unknown whether these associations persist at the microscopic level. Purpose: To quantify the degree to which cell density (CD) and structure anisotropy (SA), as determined from histology, account for the intra-tumor variability of MD and FA in meningioma tumors. Furthermore, to clarify whether histological features other than cell density account for additional intra-tumor variability of MD. Materials and Methods: We performed ex-vivo dMRI at 200 m isotropic resolution and histological imaging on 16 excised meningioma tumor samples. Diffusion tensor imaging (DTI) was used to map MD and FA, as well as the in-plane FA (FAIP). Histology images were analyzed in terms of cell nuclei density and structure anisotropy (obtained from structure tensor analysis) and were used separately in a regression analysis to predict MD and FAIP, respectively. A convolutional neural network (CNN) was also trained to predict the dMRI maps from histology patches. The association between MRI and histology was analyzed in terms of coefficient of determination (R2). Regions showing unexplained variance (large residuals) were analyzed to identify features apart from cell density and structure anisotropy that could influence MD and FAIP. Results: Cell density assessed by histology poorly explained intra-tumor variability at the mesoscopic level (200 m) in MD (median R2 = 0.06, interquartile range 0.01 - 0.29) or FAIP (median R2 = 0.19, 0.09 - 0.29). Samples with low R2 for FAIP exhibited low variations throughout the samples and thus low explainable variability, however, this was not the case for MD. Across tumors, cell density and structure anisotropy were associated with MD (R2 = 0.58) and FAIP (R2 = 0.82), respectively. In 37% of the samples (6 out of 16), cell density did not explain intra-tumor variability of MD when compared to the degree explained by the CNN. Tumor vascularization, psammoma bodies, microcysts, and tissue cohesivity were associated with bias in MD prediction when solely CD was considered. Our results support that FAIP is high in the presence of elongated and aligned cell structures, but low otherwise. Conclusion: Cell density and structure anisotropy account for variability in MD and FAIP across tumors but cell density does not explain MD variations within the tumor, which means that low or high values of MD locally may not always reflect high or low tumor cell density. Features beyond cell density need to be considered when interpreting MD. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

On the scaling and anisotropy of two subranges in the inertial range of solar wind turbulence by Honghong Wu et al. on Monday 26 September Intermittency and anisotropy are two important aspects of plasma turbulence, which the solar wind provides a natural laboratory to investigate. However, their forms and nature are still under debate, making it difficult to achieve a consensus in the theoretical interpretation. Here, we perform higher-order statistics for the observations in the fast solar wind at 1.48 au obtained by Ulysses and in the slow solar wind at 0.17 au obtained by Parker Solar Probe (PSP). We find that two subranges clearly exist in the inertial range and they present distinct features with regard to the intermittency and anisotropy. The subrange 1 with smaller scale has a multifractal scaling with the second index $xi(2) sim 2/3$ and the subrange 2 with larger scale is also multifractal but with $xi(2) sim 1/2$. The break between two subranges locates at the same spatial scale for both Ulysses and PSP observations. Subrange 1 is multifractal in the direction perpendicular to the local magnetic field with $xi_{perp}(2) sim 2/3$ and seems to be monoscaling in the parallel direction with $xi_{parallel}(2) sim 1$. Subrange 2 is multifractal in both parallel and perpendicular directions with $xi_{perp}(2) sim 1/2$ and $xi_{parallel}(2) sim 2/3$. Both subrange 1 and subrange 2 present power and wavevector anisotropies. The distinct features of two subranges suggest that a transition from weak to strong turbulence may occur and the spatial scale of the break may not evolve with the solar wind expansion. These new results update our knowledge of the inertial range and provide strong observational constraints on the understanding of intermittency and anisotropy in solar wind turbulence. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.12409v1

Cosmic-Ray Convection-Diffusion Anisotropy by Yiran Zhang et al. on Sunday 25 September Under nonuniform convection, the distribution of diffusive particles can exhibit dipole and quadrupole anisotropy induced by the fluid inertial and shear force, respectively. These convection-related anisotropies, unlike the Compton-Getting effect, typically increase with the cosmic-ray (CR) energy, and are thus candidate contributors for the CR anisotropy. In consideration of the inertial effect, CR observational data can be used to set an upper limit on the average acceleration of the local interstellar medium in the equatorial plane to be on the order of 100 $ mu text{m}/text{s}^2 $. Using Oort constants, the quadrupole anisotropy above 200 TeV may be modeled with the shear effect arising from the Galactic differential rotation. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.01412v2

Large amplitude bidirectional anisotropy of cosmic-ray intensity observed with world-wide networks of ground-based neutron monitors and muon detectors in November, 2021 by K. Munakata et al. on Tuesday 13 September We analyze the cosmic-ray variations during a significant Forbush decrease observed with world-wide networks of ground-based neutron monitors and muon detectors during November 3-5, 2021. Utilizing the difference between primary cosmic-ray rigidities monitored by neutron monitors and muon detectors, we deduce the rigidity spectra of the cosmic-ray density (or omnidirectional intensity) and the first- and second-order anisotropies separately, for each hour of data. A clear two-step decrease is seen in the cosmic-ray density with the first $sim2%$ decrease after the interplanetary shock arrival followed by the second $sim5%$ decrease inside the magnetic flux rope (MFR) at 15 GV. Most strikingly, a large bidirectional streaming along the magnetic field is observed in the MFR with a peak amplitude of $sim5%$ at 15 GV which is comparable to the total density decrease inside the MFR. The bidirectional streaming could be explained by adiabatic deceleration and/or focusing in the expanding MFR, which have stronger effects for pitch angles near 90$^circ$, or by selective entry of GCRs along a leg of the MFR. The peak anisotropy and density depression in the flux rope both decrease with increasing rigidity. The spectra vary dynamically indicating that the temporal variations of density and anisotropy appear different in neutron monitor and muon detector data. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.05743v1

Anisotropy and characteristic scales in halo density gradient profiles by X. Wang et al. on Thursday 08 September We use a large N-body simulation to study the characteristic scales in the density gradient profiles in and around halos with masses ranging from $10^{12}$ to $10^{15} h^{-1}{rm M_odot}$. We investigate the profiles separately along the major (T_1) and minor (T_3) axes of the local tidal tensor and how the characteristic scales depend on halo mass, formation time, and environment. We find two kinds of prominent characteristic features in the gradient profiles, a deep `valley' and a prominent `peak'. We use the Gaussian Process Regression to fit the gradient profiles and identify the local extrema to determine the scales associate with these features. Around the valley, we identify three types of distinct local minima, corresponding to caustics of particles orbiting around halos. The appearance and depth of the three caustics depend significantly on the direction defined by the local tidal field, formation time and environment of halos. The first caustic is located at a radius r>0.8R_{200}, corresponding to the splashback feature, and is dominated by particles at their first apocenter after infall. The second and third caustics, around 0.6R_{200} and 0.4R_{200} respectively, can be determined reliably only for old halos. The first caustic is always the most prominent feature along T_3, but may not be the case along T_1 or in azimuthally-averaged profiles, suggesting that caution must be taken when using averaged profiles to investigate the splashback radius. We find that the splashback feature is approximately isotropic when proper separations are made between the first and the other caustics. We also identify a peak feature located at $sim$ 2.5R_{200} in the density gradient profile. This feature is the most prominent along T_1 and is produced by mass accumulations from the structure outside halos. We also discuss the origins of these features and their observational implications. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2206.12163v2

Dipole Anisotropy in Gravitational Wave Source Distribution by Gopal Kashyap et al. on Wednesday 07 September Our local motion with respect to the cosmic frame of rest is believed to be dominantly responsible for the observed dipole anisotropy in the Cosmic Microwave Background Radiation (CMBR). We study the effect of this motion on the sky distribution of gravitational wave (GW) sources. We determine the resulting dipole anisotropy in GW source number counts, mass weighted number counts, which we refer to as mass intensity, and mean mass per source. The mass M dependence of the number density n(M) distribution of BBH is taken directly from the data. We also test the anisotropy in the observable mean mass per source along the direction of the CMB dipole. The current data sample is relatively small and consistent with isotropy. The number of sources required for this test is likely to become available in the near future arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2204.07472v2

Dipole Anisotropy in Gravitational Wave Source Distribution by Gopal Kashyap et al. on Wednesday 07 September Our local motion with respect to the cosmic frame of rest is believed to be dominantly responsible for the observed dipole anisotropy in the Cosmic Microwave Background Radiation (CMBR). We study the effect of this motion on the sky distribution of gravitational wave (GW) sources. We determine the resulting dipole anisotropy in GW source number counts, mass weighted number counts, which we refer to as mass intensity, and mean mass per source. The mass M dependence of the number density n(M) distribution of BBH is taken directly from the data. We also test the anisotropy in the observable mean mass per source along the direction of the CMB dipole. The current data sample is relatively small and consistent with isotropy. The number of sources required for this test is likely to become available in the near future arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2204.07472v2

This episode has a "back to school" vibe. The guys recap their field trip to Silicon Valley, including a visit to Autodesk Pier 9, an autonomous car manufacturer, and a mystery EV manufacturer. Tyler reviews some compelling research into minimizing anisotropic FDM properties, and Tate schools him on the meaning of a word that literally nobody uses correctly. The episode finishes with a brief history lesson on 3D printing technology. Read more about Anisotropy and Warm Isostatic Pressing: https://www.sciencedirect.com/science/article/pii/S2214860422002408 Watch this episode on YouTube at www.youtube.com/goengineer 

Learn about why remote workers need a "virtual commute," what happened when scientists tried growing prehistoric-sized insects, and how the solar system has not one, but two alignment planes. Separate work from home with a "virtual commute" by author Kelsey Donk MacLellan, L. (2020, October). Create boundaries when working from home with commute rituals. Quartz at Work; Quartz. https://qz.com/work/1909901/how-to-design-virtual-commute-rituals-that-energize-you/ Deighton, K. (2020, September 29). Microsoft Thinks You’ve Been Missing Your Commute in Lockdown. WSJ; The Wall Street Journal. https://www.wsj.com/articles/microsoft-thinks-youve-been-missing-your-commute-in-lockdown-11601373601 Scientists Tried Growing Prehistoric-Sized Insects, and Here's What Happenedby author Reuben Westmaas Meganeura - Encyclopedia of Life. (2020). Eol.Org. https://eol.org/pages/10511703 Largest Land-Dwelling “Bug” of All Time. (2011, January 15). Largest Land-Dwelling “Bug” of All Time. National Geographic Society Newsroom. https://blog.nationalgeographic.org/2011/01/15/largest-land-dwelling-bug-of-all-time/ Keim, B. (2010, September 29). How Plants May Have Made Large Predators Possible. WIRED. https://www.wired.com/2010/09/oxygen-and-evolution/ Mosher, D. (2010, November 2). High Oxygen Levels Spawn Monster Dragonflies. WIRED. https://www.wired.com/2010/11/huge-dragonflies-oxygen/ The Solar System Has Two Alignment Planes by Grant Currin Second alignment plane of solar system discovered. (2020). EurekAlert! https://www.eurekalert.org/pub_releases/2020-09/nion-sap092920.php ‌Higuchi, A. (2020). Anisotropy of Long-period Comets Explained by Their Formation Process. The Astronomical Journal, 160(3), 134. https://doi.org/10.3847/1538-3881/aba94d ‌Starr, M. (2020). Radical Discovery Suggests The Solar System Has Two Planes of Orbital Alignment. ScienceAlert. https://www.sciencealert.com/it-looks-like-the-solar-system-has-two-planes-of-orbital-alignment Subscribe to Curiosity Daily to learn something new every day with Ashley Hamer and Natalia Reagan (filling in for Cody Gough). You can also listen to our podcast as part of your Alexa Flash Briefing; Amazon smart speakers users, click/tap “enable” here: https://www.amazon.com/Curiosity-com-Curiosity-Daily-from/dp/B07CP17DJY See omnystudio.com/listener for privacy information.

In this episode, host Andrew Geary speaks with author Vladimir Grechka on his latest book, Anisotropy and Microseismics: Theory and Practice. Vladimir highlights why anisotropy and microseismics are a great pairing, how the shift from P-waves to shear waves changed the industry, and reflects on what we will find in seismology books in the next decade. Each chapter of the book starts with a question, followed by what's exciting about it, where the mystery might lie, and what could be the potential value of answering the question. Vladimir shares what question he was most excited to explore and what has yet to be fully answered. This is a conversation not to miss! Visit https://seg.org/podcast for the complete show notes. BIOGRAPHY Vladimir Grechka received an MSc degree (1984) in geophysical exploration from Novosibirsk State University, Russia, and a Ph.D. (1990) in geophysics from the Institute of Geophysics, Novosibirsk, Russia. He worked in the same institute from 1984 to 1994 as a research scientist. He was a graduate student at the University of Texas at Dallas from 1994 to 1995. Then, Vladimir joined the department of Geophysics at Colorado School of Mines, where he was an associate research professor and a co-leader of the Center for Wave Phenomena. From 2001 to 2012, Vladimir was a senior staff geophysicist at Shell, and from 2012 to 2019 a senior technical consultant at Marathon Oil. Since 2019, Vladimir has been a senior adviser at Borehole Seismic, focusing on novel uses of microseismic and VSP for reservoir characterization. He received the East European Award from the European Geophysical Society (1992), the J. Clarence Karcher Award (1997) from SEG, Honorable Recognition Award from EAGE (2010), and the Best Paper in The Leading Edge Award (2013) from SEG. Vladimir teaches courses on seismic anisotropy for SEG and EAGE. BOOK ABSTRACT Downhole microseismic monitoring of stimulation and production of unconventional reservoirs has resulted in renewed industry interest in seismic anisotropy. This occurred not only because anisotropy of hydrocarbon-bearing shales is among the strongest in rocks but also because of downhole microseismics shifts the focus from the standard exploration of P-waves to shear waves. The consequences of the difference in wave type are profound for geophysicists because everyone involved – from theoreticians to developers and users of microseismic data-processing software – must be aware of shear-wave splitting, singularities, and multivalued wavefronts, which have been largely irrelevant for P-waves propagating in relatively simple geologic settings. Anisotropy and Microseismics leads readers on a path of discovery of rarely examined wave phenomena and their possible usage. Most of the chapters begin by formulating a question, followed by explanations of what is exciting about it, where the mystery might lie, and what could be the potential value of answering the question. Importantly, the findings entail useful applications, as showcased by the unmistakably practical flavor of the chapters on microseismic event location, moment tensor inversion, and imaging. As an investigation of microseismic methodologies and techniques is conducted, it often yields unexpected results. CREDITS Original music by Zach Bridges. This episode was hosted, edited, and produced by Andrew Geary at 51 features, LLC. Thank you to the SEG podcast team: Ted Bakamjian, Jennifer Crockett, Ally McGinnis, and Mick Swiney.

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.08.332353v1?rss=1 Authors: Shenoy Handiru, V., Alivar, A., Selvan, S. E., Hoxha, A., Saleh, S., Yue, G. H., Allexandre, D. Abstract: Traumatic Brain Injury (TBI) often results in postural instability, thus affecting the daily activities of living. In this study, we investigated the postural instability in a group of 12 TBI patients vs 9 healthy controls (HC) by studying their brain's response to an external perturbation of the computerized dynamic posturography platform. A 64-channel EEG was used to noninvasively record the brain's anticipatory response while the participant was performing the dynamic posturography task. We used the global graph-theoretic network measures (global efficiency and modularity) derived from source-space EEG connectivity in different frequency bands as quantitative measures of the functional integration and segregation of the brain network during the task. The center of pressure (COP) displacement and the Berg Balance Scale (BBS) were used as balance outcomes. Furthermore, we used the Diffusion Tensor Imaging (DTI) data from all the participants to explore the association between the measures of the structural integrity of the white matter (Fractional Anisotropy, Mean Diffusivity, and Mode of Anisotropy) and the balance outcomes. Our findings revealed significant changes in functional segregation between the TBI group and controls during the task and group-level differences in DTI measures. Also, we observed significant differences between theta-band modularity and global efficiency during rest vs. task within both the groups (TBI and HC). In terms of the neural correlates, we observed a distinct role played by different frequency bands; increase in theta-band modularity during the task was shown to be highly correlated with the poorer COP displacement and BBS in the TBI group; alpha-band and beta-band graph-theoretic measures were correlated with the measures of structural integrity. In terms of the regions of interest pertaining to the postural control, we noticed a significant cortical activity during the task in the paracentral lobule, post-central gyrus, cingulate gyrus, superior parietal gyrus, and other regions often reported to be involved in postural stability. Our study, although limited by small sample size, provides insights into the neural correlates of the balance deficits due to brain injury. Our future studies will focus on the larger sample size and also the effect of stabilometry platform training on the functional brain network modulation in TBI. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.13.196824v1?rss=1 Authors: Schintu, S., Cunningham, C. A., Freedberg, M., Taylor, P., Gotts, S. J., Shomstein, S., Wassermann, E. M. Abstract: Hemispatial neglect is thought to result from disruption of interhemispheric equilibrium. Right hemisphere lesions deactivate the right frontoparietal network and hyperactivate the left via release from interhemispheric inhibition. Support for this theory comes from neuropsychological evidence as well as transcranial magnetic stimulation (TMS) studies in healthy subjects, in whom right posterior parietal cortex (PPC) inhibition causes neglect-like, rightward, visuospatial bias. Concurrent TMS and fMRI after right PPC TMS show task-dependent changes but may fail to identify effects of stimulation in areas not directly activated by the specific task, complicating interpretations. We used resting-state functional connectivity (RSFC) after inhibitory TMS over the right PPC to examine changes in the networks underlying visuospatial attention. In a crossover experiment in healthy individuals, we delivered continuous theta burst TMS to the right PPC and vertex as control condition. We hypothesized that PPC inhibitory stimulation would cause a rightward visuospatial bias, decrease PPC connectivity with frontal areas, and increase PPC connectivity with the attentional network in the left hemisphere. We also expected that individual differences in fractional anisotropy (FA) in white matter connections between the PPCs would account for variability in TMS-induced RSFC changes. As expected, TMS over the right PPC caused a rightward shift in line bisection judgment and increased RSFC between the right PPC and the left superior temporal gyrus. This effect was inversely related to FA in the posterior corpus callosum. Local inhibition of the right PPC reshapes connectivity in the attentional network and depends on interhemispheric connections. Copy rights belong to original authors. Visit the link for more info

In this episode, host Andrew Geary previews Lisa Gavin's upcoming Honorary Lecturer tour in the Pacific South on seismic azimuthal anisotropy. Lisa and Andrew discuss the 3 main reasons it's important to be aware of seismic azimuthal anisotropy, why you should account for it in 4-D seismic interpretation, who this lecture is for, and what excites her about the future of this topic. Visit https://seg.org/podcast/Post/8762 for the complete show notes and links to her upcoming tour dates. BIOGRAPHY Lisa Gavin is a geophysicist with academic and industry experience in the oil and gas industry. She has worked as a geophysicist at Fugro Seismic Imaging, Chevron, and is currently at Woodside Energy in Perth, Australia. She has interests in seismic anisotropy, quantitative interpretation, 4D seismic, and rock physics and holds a Ph.D. in geophysics from the University of Western Australia. Credits Original music by Zach Bridges. This episode was hosted, edited, and produced by Andrew Geary. Thank you to the SEG podcast team: Jennifer Crockett, Ally McGinnis, and Mick Swiney.

In this episode, host Andrew Geary speaks with Heloise Lynn on her upcoming North American Honorary Lecturer tour starting 5 September. Andrew and Heloise discuss Leon Thomsen's famous deck of cards from SEG 1986, the controversy surrounding her recent published paper, how anisotropy can be understood by all geophysicists, what would happen if azimuthal P-P seismic measurements reached its full potential, and more. This interview isn't to be missed. Learn more about her tour at https://seg.org/Education/Lectures/Honorary-Lectures/2019-HL-Lynn. Interviewee biography Heloise Bloxsom Lynn is a geophysical consultant and instructor with Petroskills and Nautilus World. She started working in seismic reflection data in 1975, processing U.S. onshore data for Texaco in Houston. Lynn worked for Texaco, Amoco, BP, and then in 1984, she and her husband, Walt, formed Lynn Incorporated. Her consulting experience includes working in North America, Hungary, Qatar, Kuwait, Saudi Arabia, Pakistan, Australia, Thailand, China, and Japan. She specializes in the use of 3D multiazimuth and/or multicomponent data to obtain structure, lithology, porosity, pore fluids, in-situ stress, and aligned porosity (aka natural fractures). She also includes conventional VSP data processed for split-shear waves in these projects because there is nearly always a source-generated S-wave or a near-source mode-converted S-wave, and/or mode-conversions at impedance boundaries. In the fall of 2004, she was the SEG/AAPG Distinguished Lecturer, speaking on “The Winds of Change – anisotropic rocks, their preferred direction of fluid flow, and their associated seismic signatures.” She has described her research findings in many oral presentations and in 47 published papers that collectively create an invaluable knowledge base for scientists, researchers, students, teachers, and exploration geophysicists. She earned a BA in geology-math from Bowdoin College, Maine; an MSc in exploration geophysics from Stanford University; and a PhD in geophysics from Stanford University. She is a member of SEG, EAGE, the Geophysical Society of Houston (GSH), AAPG, and SPE. Credits Interview: Heloise Lynn Original music by Zach Bridges. This episode was hosted, edited, and produced by Andrew Geary. Special thanks to the SEG podcast team: Jennifer Crockett, Ally McGinnis, and Mick Swiney. If you enjoy the show, please subscribe to the podcast on Spotify, Google Podcasts, or Apple Podcasts to be the first to know about new episodes!

The Italian imprint @Hidden-Tapes is back with an EP full of dark and experimental sounds. The label's third release features six orininal tracks by @DarkDivision as well as two remixes. Monument premieres PRG/M's (@progra_m) "tritone paradox" remix of track Anisotropy of the Void. The CMBR EP is out on November 12th.

Hansen, L (University of Oxford) Friday 15th April 2016 - 14:30 to 15:30

Tommasi, A [CNRS (Centre national de la recherche scientifique), Université de Montpellier] Friday 15th April 2016 - 16:00 to 17:00

Ribe, N [CNRS (Centre national de la recherche scientifique), Université Paris-Sud 11] Friday 15th April 2016 - 13:30 to 14:30

Cherdantsev, M (Cardiff University) Friday 27 March 2015, 13:30-14:30

Fri, 13 Jul 2012 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/14571/ https://edoc.ub.uni-muenchen.de/14571/1/Wack_Michael.pdf Wack, Michael Richard ddc:550, ddc:500, Fakultät für Geowissenschaften

Through-space interaction between magnets of fixed strength and orientation averages to zero during random molecular tumbling, suggesting that the local field about a proton should be sensitive only to electrons that orbit about itself. The chemical shift can be sensitive to electrons orbiting elsewhere if the amount of orbiting varies with molecular orientation. This “diamagnetic anisotropy” is commonly used to rationalize the unusual chemical shifts of protons in acetylene and in aromatic and antiaromatic compounds. The other source of a proton’s local field is nearby magnetic nuclei, which can be counted by the splitting multiplicity. Unlike chemical shift, which is measured in fractional units because it depends on the strength of the applied field, this spin-spin splitting (J), measured in Hz, is dependent only on molecular structure. J depends not on spatial proximity, but on orbital overlap, which, remarkably, is larger for anti- than for eclipsed conformations. Complete course materials are available at the Open Yale Courses website: http://oyc.yale.edu This course was recorded in Spring 2011.

Drake, J (Maryland) Monday 26 July 2010, 10:00-10:40

Passot, T (Observatoire de la Côte d' Azur) Wednesday 21 July 2010, 11:30-12:15

To become biologically active, most proteins need to fold into precise three dimensional structures. It has been well established that all the folding information is contained within the primary structure of a protein. However, the mechanisms utilized by proteins to avoid sampling the extraordinarily large amount of possible conformations during their folding process are just beginning to be understood. Molecular chaperones assist the folding of newly synthesized and denatured proteins in acquiring their native state in the crowded intracellular environment. As a nascent chain leaves the ribosome, it is captured first by the upstream chaperones and then possibly transferred to the downstream chaperonins. GroEL-GroES, the Hsp-60 of E.coli, is one of the best studied chaperone systems. An appreciable amount of data is available providing information regarding its structure and function. GroEL encapsulates the substrate into the central cavity where folding occurs unimpaired by aggregation and unwanted inter-molecular interactions. Nevertheless, many important aspects of the GroEL mechanism remain to be addressed. Some of the open questions we have addressed in this study include: In what conformation does a substrate protein bind to the apical domains of GroEL; how is it that GroEL is able to accelerate the rate of folding of certain proteins, and how do the conformational properties of the substrate change as it undergoes repeated cycling. By using ensemble FRET and Sp-FRET (Single Pair-Fluorescence Resonance Energy Transfer), we have probed the conformation of the model substrate DM-MBP (Double Mutant Maltose Binding Protein) during different stages of the functional cycle of GroEL. With Sp-FRET coupled to PIE (Pulsed Interleaved Excitation), we have been able to explore the heterogeneity of the GroEL bound substrate protein and observed a bimodal conformational distribution. One of the two populations is as compact as the native state, whereas the other is as extended as the unfolded protein in denaturant. This unfolding is a local phenomena and can also be observed when the substrate is transferred from DnaK/J system (bacterial Hsp70) to GroEL, indicating the possibility of the existence of this conformational heterogeneity in vivo as the protein follows the cellular chaperone pathway. Subsequent to GroEL binding, there is a transient expansion of the protein upon binding of ATP to GroEL, followed by compaction when GroES triggers the encapsulation of the protein inside the chaperonin cage. This transient expansion is however found not to be a necessary event for the rate acceleration of DM-MBP folding, since ADP-AlFx (transition state analogue of ATP hydrolysis) results in a much slower rate of expansion, which does not cause a change in the folding rate. Anisotropy measurements, probing the freedom of motion of different regions of the GroEL bound protein, revealed that there is a segmental release of the substrate protein from the GroEL surface upon binding of ATP and GroES. As a consequence, the hydrophobic collapse of the protein upon encapsulation by GroES follows a step-wise mechanism. In this process, less hydrophobic regions are released upon binding of ATP, prior to more hydrophobic ones which are released only by GroES binding. Thus, the order of Hydrophobic collapse is reversed as compared to spontaneous folding possibly resulting in conformationally different folding intermediates. Evidence that the folding pathway inside the cage differs from that of spontaneous folding was obtained by observing the effect of external perturbations (e.g. mutations in substrate protein and use of different solvent conditions) on the rate of spontaneous and GroEL assisted folding reactions. These two folding reactions respond differently to the introduced perturbations. Kinetic data obtained from ensemble FRET measurements suggest that the conformation of refolding intermediate is altered by the GroEL cavity, which leads to a folding pathway that is different from the spontaneous refolding pathway. In summary, this study revealed significant novel aspects of the GroEL folding mechanism and provided insights into the basis of rate acceleration of the substrate protein by the chaperonin. This work may thus contribute to advance our fundamental knowledge of the chaperonin system and the basic mechanism of protein folding.

Polarization pump-probe femtosecond spectroscopy was used to investigate photoinduced optical density changes in allophycocyanin (APC) trimers at 635–690 nm after excitation with 230-fs pulses at 618 nm. The initial bleaching observed at λ < 645 nm is followed by subpicosecond absorption recovery corresponding to 430 ± 40 fs recovery kinetics measured at 615 nm with 70-fs pulses. Only the red part of the APC absorption band remains strongly bleached at 3 ps after excitation. The spectral and kinetic results can be described in terms of two different models of interaction between neighbouring α-80 and β-81 chromophores of APC trimers. According to the first one, the observed subpicosecond kinetics corresponds to relaxation between the levels of excitonically coupled, spectrally identical α-80 and β-81 chromophores. Excited state absorption to doubly excited excitonic state should in this case contribute to the measured difference spectra. According to the second one, the femtosecond excitation energy transfer in APC trimers takes place between a donor chromophore absorbing predominantly at 620 nm and an acceptor chromophore absorbing at 650 nm. The high anisotropy value observed at 615 nm during the first 1.2 ps is in good agreement with the donor-acceptor model. Anisotropy values calculated in the 635–675 nm spectral region at 3 ps after excitation are in the 0.1–0.25 range corresponding to an angle of 30°–45° between donor and acceptor transition dipole orientations. The high anisotropy obtained at 658 nm during the excitation is probably due to stimulated emission of the donor chromophore.