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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 05 March 2013, Vol.110(10), pp.3755-9
    Description: Newly developed high-speed, synchrotron-based X-ray computed microtomography enabled us to directly image pore-scale displacement events in porous rock in real time. Common approaches to modeling macroscopic fluid behavior are phenomenological, have many shortcomings, and lack consistent links to elementary pore-scale displacement processes, such as Haines jumps and snap-off. Unlike the common singular pore jump paradigm based on observations of restricted artificial capillaries, we found that Haines jumps typically cascade through 10-20 geometrically defined pores per event, accounting for 64% of the energy dissipation. Real-time imaging provided a more detailed fundamental understanding of the elementary processes in porous media, such as hysteresis, snap-off, and nonwetting phase entrapment, and it opens the way for a rigorous process for upscaling based on thermodynamic models.
    Keywords: Porous Materials -- Properties ; Cat Scans -- Methods ; Flow (Dynamics) -- Research ; Particle Dynamics -- Research;
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: Journal of Chemical Education, November 2013, Vol.90(11), p.1446
    Description: In a recent article by the authors, the suggestion was made that arrow pushing, a widely used tool in organic chemistry, could also be profitably employed in the teaching of introductory inorganic chemistry. A number of relatively simple reactions...
    Keywords: Science Instruction ; College Science ; Inorganic Chemistry ; Teaching Methods ; Undergraduate Study ; Graduate Study ; Scientific Concepts ; Inquiry ; Education ; Chemistry
    ISSN: 0021-9584
    E-ISSN: 1938-1328
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  • 3
    Language: English
    In: Journal of Chemical Education, December 2011, Vol.88(12), p.1663
    Description: Inorganic chemistry at core consists of a vast array of molecules and chemical reactions. To master the subject, students must learn to think intelligently about this vast body of facts, a feat seldom accomplished in an introductory course. All too often, young undergraduate students perceive...
    Keywords: Undergraduate Students ; Introductory Courses ; Student Attitudes ; Organic Chemistry ; Inorganic Chemistry ; Teaching Methods ; Science Instruction ; Science Education ; Learner Engagement ; College Science ; Education ; Chemistry
    ISSN: 0021-9584
    E-ISSN: 1938-1328
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  • 4
    Language: English
    In: Physical review letters, 12 January 2018, Vol.120(2), pp.028005
    Description: We use confocal microscopy to measure velocity and interfacial tension between a trapped wetting phase with a surfactant and a flowing, invading nonwetting phase in a porous medium. We relate interfacial tension variations at the fluid-fluid interface to surfactant concentration and show that these variations localize the destabilization of capillary forces and lead to rapid local invasion of the nonwetting fluid, resulting in a Haines jump. These spatial variations in surfactant concentration are caused by velocity variations at the fluid-fluid interfaces and lead to localization of the Haines jumps even in otherwise very uniform pore structure and pressure conditions. Our results provide new insight into the nature of Haines jumps, one of the most ubiquitous and important instabilities in flow in porous media.
    ISSN: 00319007
    E-ISSN: 1079-7114
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  • 5
    Language: English
    In: European Journal of Inorganic Chemistry, August 2015, Vol.2015(24), pp.4138-4144
    Description: Oxygen atom transfer (OAT) between main‐group elements is pivotal to a number of industrial processes such as the synthesis of thionyl chloride (SO + SCl → SO + SOCl) and sodium chlorate (3 NaOCl → NaClO + 2 NaCl), as well as the historic method of CO detection in mines via its reaction with IO (IO + 5 CO → I + 5 CO). Surprisingly, little is known about the mechanisms of these and other OAT reactions involving main‐group elements. Even the basic question as to whether such reactions are one‐step, S2‐like displacements or multistep, involving oxo‐bridged intermediates, remains largely unanswered. Extensive density functional theory calculations reported herein indicate a direct, S2‐like pathway as the norm for such processes. In the major quantum chemical study of oxygen atom transfer between main‐group element centers, DFT calculations unequivocally indicate a one‐step, S2‐like pathway as the normative mechanism, as opposed to a two‐step associative‐dissociative sequence that is common for transition metals.
    Keywords: Oxygen Atom Transfer ; Oxidation ; Main‐Group Elements ; Iodine ; Sulfur ; Oxygen
    ISSN: 1434-1948
    E-ISSN: 1099-0682
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  • 6
    Language: English
    In: Inorganic chemistry, 17 September 2012, Vol.51(18), pp.9911-6
    Description: A first major study of undecaphenylcorrole (UPC) derivatives is presented. Three different Cu-UPC derivatives with different para substituents X (X = CF(3), H, CH(3)) on the β-aryl groups were synthesized via Suzuki-Miyaura coupling of Cu[Br(8)TPC] and the appropriate arylboronic acid. A single-crystal X-ray structure of the X = CF(3) complex revealed a distinctly saddled macrocycle conformation with adjacent pyrrole rings tilted by ~60-66° relative to one another (within the dipyrromethane units), which is somewhat higher than that observed for β-unsubstituted Cu-TPC derivatives but slightly lower than that observed for Cu[Br(8)TPC] (~70°) derivatives. Electrochemical and electronic absorption measurements afforded some of the first comparative insights into meso versus β substituent effects on the copper corrole core. The Soret maxima of the Cu-UPC complexes (~440-445 nm), however, are comparable to those of Cu[Br(8)TPC] derivatives and are considerably red-shifted relative to Cu-TPC derivatives. Para substituents on the β-phenyl groups were found to tune the redox potentials of copper corroles more effectively than those on meso-phenyl substituents, a somewhat surprising observation given that neither the HOMO nor LUMO has significant amplitudes at the β-pyrrolic positions.
    Keywords: Chemical Bonds -- Analysis ; Copper Compounds -- Chemical Properties ; Copper Compounds -- Structure ; Phenyl Compounds -- Chemical Properties ; Phenyl Compounds -- Structure ; Redox Potential -- Measurement ; Substitution Reactions -- Analysis;
    ISSN: 00201669
    E-ISSN: 1520-510X
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  • 7
    Language: English
    In: Physical review. E, Statistical, nonlinear, and soft matter physics, October 2013, Vol.88(4), pp.043010
    Description: Drainage is typically understood as a process where the pore space is invaded by a nonwetting phase pore-by-pore, the controlling parameters of which are represented by capillary number and mobility ratio. However, what is less understood and where experimental data are lacking is direct knowledge of the dynamics of pore drainage and the associated intrinsic time scales since the rate dependencies often observed with displacement processes are potentially dependent on these time scales. Herein, we study pore drainage events with a high speed camera in a micromodel system and analyze the dependency of interfacial velocity on bulk flow rate and spatial fluid configurations. We find that pore drainage events are cooperative, meaning that capillary pressure differences which extend over multiple pores directly affect fluid topology and menisci dynamics. Results suggest that not only viscous forces but also capillarity acts in a nonlocal way. Lastly, the existence of a pore morphological parameter where pore drainage transitions from capillary to inertial and/or viscous dominated is discussed followed by a discussion on capillary dispersion and time scale dependencies. We show that the displacement front is disperse when volumetric flow rate is less than the intrinsic time scale for a pore drainage event and becomes sharp when the flow rate is greater than the intrinsic time scale (i.e., overruns the pore drainage event), which clearly shows how pore-scale parameters influence macroscale flow behavior.
    ISSN: 15393755
    E-ISSN: 1550-2376
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  • 8
    In: Geophysical Research Letters, 16 April 2015, Vol.42(7), pp.2189-2195
    Description: Direct observations of oil‐water‐rock contacts are key for improving our understanding of multiphase flow phenomena in mixed‐wet reservoir rocks. In this study we imaged pore‐scale fluid‐fluid‐solid contacts in sandstone with nanometer resolution using cryogenic broad ion‐beam polishing in combination with scanning electron microscopy and phase identification by energy‐dispersive X‐ray analysis. We observed, as expected, the nonwetting oil phase separated from quartz surfaces by a thin brine film, but also direct contacts between oil and rock at asperities and clay aggregates, which act as pinning points and cause discontinuous motion of the oil‐water‐solid contact line. For the rare classical configuration of a three‐phase contact the microscopic contact angle has been determined by serial sectioning. Our results call for improvements in models of multiphase pore‐scale flow in digital rocks. Nanoscale imaging of pore‐scale fluid‐fluid‐rock contacts Cryo‐BIB‐SEM enables contact line imaging Clay aggregates cause discontinuous contact line motion
    Keywords: Multiphase Flow ; Contact Line ; Contact Angle ; Nanoscale ; Pore Scale ; Digital Rock Modeling
    ISSN: 0094-8276
    E-ISSN: 1944-8007
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  • 9
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  • 10
    Language: English
    In: Sensors & Actuators: B. Chemical, Jan, 2013, Vol.176, p.368(6)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.snb.2012.09.088 Byline: Christian Leiterer (a), Steffen Berg (a), Antti-Pekka Eskelinen (b), Andrea Csaki (a), Matthias Urban (a), Paivi Torma (b), Wolfgang Fritzsche (a) Keywords: Gold nanoparticle; Dielectrophoresis; Sensor; Bioanalytics; Micro integration; Nano transducer Abstract: Here we present the utilization of gold nanoparticle (AuNP) chains assembled between two electrodes using an AC electrical field as a potential nanosensor for molecular detection. We describe an easy way to assemble, monitor and characterize the resulting nanoparticle chains electrically. Furthermore, parallelizability and sensing ability of the assembled structures will be addressed. The assembled pearl-chain like structures have the potential to recognize binding events of small molecules with DC current. Bound molecules influencing the charge transfer along the particle chain and therefore generate a signal that can be read electrically. We demonstrate that the produced AuNP-chains can be used for molecular sensing, by measuring the resistances changes due to the interaction with thiols, which are known to bind strongly to gold. The resulting signal was monitored in end-point as well as real-time measurements. Author Affiliation: (a) Institute of Photonic Technology, Albert-Einstein-Stra[sz]e 9, 07745 Jena, Germany (b) Aalto University, Applied Physics, FI-00076 Aalto, Finland Article History: Received 9 August 2012; Revised 25 September 2012; Accepted 26 September 2012
    Keywords: Thiols -- Usage ; Thiols -- Electric Properties
    ISSN: 0925-4005
    Source: Cengage Learning, Inc.
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