Transport efficiency and dynamics of hydraulic fracture networks

Acknowledgments This study is carried out within the framework of DGMK (German Society for Petroleum and Coal Science and Technology) research project 718 “Mineral Vein Dynamics Modeling,” which is funded by the companies ExxonMobil Production Deutschland GmbH, GDF SUEZ E&P Deutschland GmbH, RWE Dea AG and Wintershall Holding GmbH, within the basic research programme of the WEG Wirtschaftsverband Erdöl- und Erdgasgewinnung e.V. We thank the companies for their financial support and their permission to publish our results. We further acknowledge support by Deutsche Forschungsgemeinschaft and Open Access Publishing Fund of University of Tübingen.Peer reviewedPublisher PD

Progress and Opportunities in the Characterization of Cellulose – An Important Regulator of Cell Wall Growth and Mechanics

The plant cell wall is a dynamic network of several biopolymers and structural proteins including cellulose, pectin, hemicellulose and lignin. Cellulose is one of the main load bearing components of this complex, heterogeneous structure, and in this way, is an important regulator of cell wall growth and mechanics. Glucan chains of cellulose aggregate via hydrogen bonds and van der Waals forces to form long thread-like crystalline structures called cellulose microfibrils. The shape, size, and crystallinity of these microfibrils are important structural parameters that influence mechanical properties of the cell wall and these parameters are likely important determinants of cell wall digestibility for biofuel conversion. Cellulose–cellulose and cellulose-matrix interactions also contribute to the regulation of the mechanics and growth of the cell wall. As a consequence, much emphasis has been placed on extracting valuable structural details about cell wall components from several techniques, either individually or in combination, including diffraction/scattering, microscopy, and spectroscopy. In this review, we describe efforts to characterize the organization of cellulose in plant cell walls. X-ray scattering reveals the size and orientation of microfibrils; diffraction reveals unit lattice parameters and crystallinity. The presence of different cell wall components, their physical and chemical states, and their alignment and orientation have been identified by Infrared, Raman, Nuclear Magnetic Resonance, and Sum Frequency Generation spectroscopy. Direct visualization of cell wall components, their network-like structure, and interactions between different components has also been made possible through a host of microscopic imaging techniques including scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. This review highlights advantages and limitations of different analytical techniques for characterizing cellulose structure and its interaction with other wall polymers. We also delineate emerging opportunities for future developments of structural characterization tools and multi-modal analyses of cellulose and plant cell walls. Ultimately, elucidation of the structure of plant cell walls across multiple length scales will be imperative for establishing structure-property relationships to link cell wall structure to control of growth and mechanics

A new stylolite classification scheme to estimate compaction and local permeability variations

This study was carried out within the framework of DGMK (German Society for Petroleum and Coal Science and Technology) research project 718 “Mineral Vein Dynamics Modeling”, which is funded by the companies ExxonMobil Production Deutschland GmbH, GDF SUEZ E&P Deutschland GmbH, DEA Deutsche Erdoel AG and Wintershall Holding GmbH, within the basic research program of the WEG Wirtschaftsverband Erdoel- und Erdgasgewinnung e.V. We thank the companies for their financial support and their permission to publish these results. This work has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 31688. The Zechstein data were collected with the help of Simon Gast. We thank Jean-Pierre Gratier and an anonymous reviewer for their comments that improved an earlier version of the manuscript.Peer reviewedPostprin

Using Student Ambassadors to Relay Themes from Changing the Conversation in Engineering First Year Seminars

This paper describes the efforts at a large mid-Atlantic university to integrate themes from Changing the Conversation into First Year Seminars. Changing the Conversation, a 2008 book by the National Academy of Engineering, found that both male and female students were more attracted to messages describing engineering in terms relating to societal impact, such as the phrases, Engineering makes a world of difference and Engineering is essential to our health, happiness, and safety. Although the research was conducted with younger students, the potential for using these themes in the undergraduate curricula could have the potential to impact persistence in engineering, especially for female students or those from other underrepresented groups. The purpose of the initiative described in the paper, which uses engineering students from a group called the Engineering Ambassadors to relay these messages in freshmen level courses, is to impact student perceptions of engineering and to provide information to students that will be critical in making career decisions. In the Fall of 2011, a pilot program was launched in two sections of a Chemical Engineering First Year Seminar. Engineering Ambassadors made four separate visits to each section, focusing on the following topics: 1) An overview of College of Engineering Majors, 2) Options within Chemical Engineering, 3) Student experiences in the College of Engineering, and 4) How to be a successful engineering student. Woven through each presentation were themes from Changing the Conversation, focusing on how engineers are essential to health, happiness and safety. The students were mentored by a faculty member whose background is in Communication. The quality of student presentations was high, utilizing the assertion-evidence method of slide design. Data was collected to determine whether the following project objectives were met: 1) Students in the First Year Seminars will have a greater understanding of the possible careers in engineering as well as the engineering majors; and 2) Students will be more likely to define engineering in terms associated with health, happiness, and safety. The data showed that the students had a very positive reaction to the Engineering Ambassador visits, although a larger sample size would be necessary to more clearly understand the impact

Pure spin current manipulation in antiferromagnetically exchange coupled heterostructures

We present a model to describe the spin currents generated by ferromagnet/spacer/ferromagnet exchange coupled trilayer systems and heavy metal layers with strong spin-orbit coupling. By exploiting the magnitude of the exchange coupling (oscillatory RKKY-like coupling) and the spin-flop transition in the magnetization process, it has been possible to produce spin currents polarized in arbitrary directions. The spin-flop transition of the trilayer system originates pure spin currents whose polarization vector depends on the exchange field and the magnetization equilibrium angles. We also discuss a protocol to control the polarization sign of the pure spin current injected into the metallic layer by changing the initial conditions of magnetization of the ferromagnetic layers previously to the spin pumping and inverse spin Hall effect experiments. The small differences in the ferromagnetic layers lead to a change in the magnetization vector rotation that permits the control of the sign of the induced voltage components due to the inverse spin Hall effect. Our results can lead to important advances in hybrid spintronic devices with new functionalities, particularly, the ability to control microscopic parameters such as the polarization direction and the sign of the pure spin current through the variation of macroscopic parameters, such as the external magnetic field or the thickness of the spacer in antiferromagnetic exchange coupled systems.Fil: Avilés Félix, L.. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Butera, Alejandro Ricardo. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Resonancias Magnéticas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: González Chávez, D. E.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Sommer, R. L.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Gomez, Javier Enrique. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Resonancias Magnéticas; Argentin

Fluid mixing from below in unconformity-related hydrothermal ore deposits

This research was partly funded by German Research Foundation (DFG) grant BO 1776/8 and was carried out within the framework of DGMK (German Society for Petroleum and Coal Science and Technology) project 718, funded by the companies ExxonMobil Production Deutschland GmbH, GDF SUEZ E&P Deutschland GmbH, RWE Dea AG, and Wintershall Holding GmbH. Assistance by Simone Kaulfuss, Gabi Stoschek, Sara Ladenburger, Mathias Burisch, and Bernd Steinhilber with sample preparation and crush-leach analyses is gratefully acknowledged. We thank Steve Cox and two anonymous reviewers for their critical comments.Peer reviewedPostprin

Statistics of Core Lifetimes in Numerical Simulations of Turbulent, Magnetically Supercritical Molecular Clouds

We present measurements of the mean dense core lifetimes in numerical simulations of magnetically supercritical, turbulent, isothermal molecular clouds, in order to compare with observational determinations. "Prestellar" lifetimes (given as a function of the mean density within the cores, which in turn is determined by the density threshold n_thr used to define them) are consistent with observationally reported values, ranging from a few to several free-fall times. We also present estimates of the fraction of cores in the "prestellar", "stellar'', and "failed" (those cores that redisperse back into the environment) stages as a function of n_thr. The number ratios are measured indirectly in the simulations due to their resolution limitations. Our approach contains one free parameter, the lifetime of a protostellar object t_yso (Class 0 + Class I stages), which is outside the realm of the simulations. Assuming a value t_yso = 0.46 Myr, we obtain number ratios of starless to stellar cores ranging from 4-5 at n_thr = 1.5 x 10^4 cm^-3 to 1 at n_thr = 1.2 x 10^5 cm^-3, again in good agreement with observational determinations. We also find that the mass in the failed cores is comparable to that in stellar cores at n_thr = 1.5 x 10^4 cm^-3, but becomes negligible at n_thr = 1.2 x 10^5 cm^-3, in agreement with recent observational suggestions that at the latter densities the cores are in general gravitationally dominated. We conclude by noting that the timescale for core contraction and collapse is virtually the same in the subcritical, ambipolar diffusion-mediated model of star formation, in the model of star formation in turbulent supercritical clouds, and in a model intermediate between the previous two, for currently accepted values of the clouds' magnetic criticality.Comment: 25 pages, 8 figures, ApJ accepted. Fig.1 animation is at http://www.astrosmo.unam.mx/~e.vazquez/turbulence/movies/Galvan_etal07/Galvan_etal07.htm

Strain and vorticity analysis using small-scale faults and associated drag folds

This work was financed through the PhD grant BES-2003-0755 to EGR and research project CGL2004-03657, both funded by the Spanish Ministry of Education and Science. We thank Jens Becker and Anne Peschler for their help with the BASIL modelling. We gratefully acknowledge D. Jiang and T. Bell, whose constructive reviews greatly improved the manuscript.Peer reviewedPostprin

Dynamic Structural Change of Plant Epidermal Cell Walls under Strain

The molecular foundations of epidermal cell wall mechanics are critical for understanding structure-function relationships of primary cell walls in plants and facilitating the design of bioinspired materials. To uncover the molecular mechanisms regulating the high extensibility and strength of the cell wall, the onion epidermal wall is stretched uniaxially to various strains and cell wall structures from mesoscale to atomic scale are characterized. Upon longitudinal stretching to high strain, epidermal walls contract in the transverse direction, resulting in a reduced area. Atomic force microscopy shows that cellulose microfibrils exhibit orientation-dependent rearrangements at high strains: longitudinal microfibrils are straightened out and become highly ordered, while transverse microfibrils curve and kink. Small-angle X-ray scattering detects a 7.4 nm spacing aligned along the stretch direction at high strain, which is attributed to distances between individual cellulose microfibrils. Furthermore, wide-angle X-ray scattering reveals a widening of (004) lattice spacing and contraction of (200) lattice spacing in longitudinally aligned cellulose microfibrils at high strain, which implies longitudinal stretching of the cellulose crystal. These findings provide molecular insights into the ability of the wall to bear additional load after yielding: the aggregation of longitudinal microfibrils impedes sliding and enables further stretching of the cellulose to bear increased loads

Depositional and structural controls on a fault-related dolostone formation (Maestrat Basin, E Spain)

Acknowledgments This research was funded by the Natural Environment Research Council (NERC) Centre for Doctoral Training (CDT) in Oil & Gas, through a PhD grant to EH. Equinor ASA are thanked for providing additional support. Additional funding was provided by the Grup Consolidat de Recerca “Geologia Sedimentària” (2017SGR-824) and DGICYT Spanish Projects CGL2017-85532-P, PGC2018-093903-B-C22 and PID2020-118999GB-I00, all funded by the Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER). EGR acknowledges the Spanish Ministry of Science, Innovation and Universities for the “Ramón y Cajal” fellowship RYC2018-026335-I. EH, EGR, JDM and JN conceived the idea and provided funding whilst field data was collected by EH, EGR, and JDM. EH organised the sampling for geochemical analysis (supervised by JDM) and RS and JG provided the regional stratigraphic context and structural cross-section. Petrographic data was collected by EH (supervised by JN). EH wrote the manuscript with edits and contributions provided by all co authors.Peer reviewedPublisher PD