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Transparent, conductive carbon nanotube films (2004)

Z. Wu ; Z. Chen ; X. Du ; [et al.]

American Association for the Advancement of Science (AAAS)

In: Science. 305(5688): 1273-6. doi: 10.1126/science.1101243.

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Publication Date: 2004-08-31

Description: We describe a simple process for the fabrication of ultrathin, transparent, optically homogeneous, electrically conducting films of pure single-walled carbon nanotubes and the transfer of those films to various substrates. For equivalent sheet resistance, the films exhibit optical transmittance comparable to that of commercial indium tin oxide in the visible spectrum, but far superior transmittance in the technologically relevant 2- to 5-micrometer infrared spectral band. These characteristics indicate broad applicability of the films for electrical coupling in photonic devices. In an example application, the films are used to construct an electric field-activated optical modulator, which constitutes an optical analog to the nanotube-based field effect transistor.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wu, Zhuangchun -- Chen, Zhihong -- Du, Xu -- Logan, Jonathan M -- Sippel, Jennifer -- Nikolou, Maria -- Kamaras, Katalin -- Reynolds, John R -- Tanner, David B -- Hebard, Arthur F -- Rinzler, Andrew G -- New York, N.Y. -- Science. 2004 Aug 27;305(5688):1273-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of Florida, Gainesville, FL 32611, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15333836" target="_blank"〉PubMed〈/a〉

Print ISSN: 0036-8075

Electronic ISSN: 1095-9203

Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics

Published by American Association for the Advancement of Science (AAAS)

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Trends in tuna carbon isotopes suggest global changes in pelagic phytoplankton communities (2019)

A Lorrain, H Pethybridge, N Cassar, A Receveur, V Allain, N Bodin, L Bopp, A C Choy, L Duffy, B Fry, N Goñi, BS Graham, A J Hobday, J M Logan, F Ménard, C Menkes, D E Olson, R J Pagendam, D Point, A T Revill, CJ Somes, J W Young

Wiley

In: Global Change Biology

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Publication Date: 2019

Description: Abstract Considerable uncertainty remains into how increasing atmospheric CO2 and anthropogenic climate changes are affecting open‐ocean marine ecosystems from phytoplankton to top predators. Biological time series data are thus urgently needed for the world’s oceans. Here, we use the carbon stable isotope composition of tuna to provide a first insight into the existence of global trends in complex ecosystem dynamics and changes in the oceanic carbon cycle. From 2000 to 2015, considerable declines in δ13C values of 0.8 to 2.5‰ were observed across three tuna species sampled globally, with more substantial changes in the Pacific Ocean compared to the Atlantic and Indian Oceans. Tunas not only recorded the Suess effect, i.e. fossil fuel‐derived and isotopically‐light carbon being incorporated into marine ecosystems, but also profound changes at the base of marine food webs. We suggest a global shift in phytoplankton community structure, e.g. a reduction of 13C‐rich phytoplankton such as diatoms, and/or a change in phytoplankton physiology during this period, while this does not prevent other concomitant changes at higher levels in the food webs. Our study establishes tuna δ13C values as a candidate essential ocean variable to assess complex ecosystem responses to climate change at regional to global scales and over decadal timescales. Finally, this time‐series will be invaluable in calibrating and validating global earth system models to project changes in marine biota.

Print ISSN: 1354-1013

Electronic ISSN: 1365-2486

Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography

Published by Wiley

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Assessment of material characteristics of ancient concretes, Grande Aula, Markets of Trajan, Rome (2010)

Jackson, M. ; Logan, J. M. ; Scheetz, B. E. ; [et al.]

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Publication Date: 2020-02-24

Description: The Grande Aula, or Great Hall, of the Markets of Trajan is an intact example of the sophisticated, domed, concrete architecture of imperial Rome, which records the expertise of Roman builders in formulating extraordinarily durable pozzolanic concretes between about AD 96 and 115. Petrographic, chemical, X-ray diffraction analyses and SEM images demonstrate that the pozzolanic mortars of the conglomeratic wall concretes contain strätlingite, a complex calcium aluminate cement hydrate (C2 ASH8) that gives modern cements high durability and compressive strength. It has not been previously recognized in ancient pozzolanic mortars. New methods of assessing bulk specific gravity of the porous concretes suggest unit weights of 1495 kg/m³ for the conglomeratic wall cores and 1200-1300 kg/m³ for the pumice-bearing vaulted ceiling mortar.Innovative point load tensile strength testing methods provide a means of evaluating the strengths of small samples of ancient, conglomeratic cementitious materials. Tests of coarse aggregate clasts, pozzolanic mortar, and the adhesive interfacial surfaces of coarse aggregate clasts (caementa) in contact with the mortar, suggest tensile strengths (ft) of 2.7 MPa for brick clasts, 1.2 MPa for Tufo Lionato tuff clasts, and 0.9 MPa for Tufo Giallo della Via Tiberina tuff clasts based on a tentative, approximate correlation with splitting (Brazilian) tests on these materials. The pozzolanic mortar and interfacial zones appear to have lower ft, in the range of 0.8 MPa to 0.5 MPa. The relatively low tensile strengths of the mortar and its somewhat tenuous adhesion to coarse aggregate clasts suggests that the caementa may have had a role in arresting the propagation of tensile microcracks that formed in the mortar, thereby increasing the composite tensile strength of the concrete. Roman builders evidently selected the complex aggregate mixes to optimize the performance and durability of the wall and vault masonry.

Description: Published

Description: 2481-2492

Description: 3.10. Storia ed archeologia applicate alle Scienze della Terra

Description: JCR Journal

Description: open

Keywords: ancient Rome, concrete, pozzolanic mortar, strätlingite, tensile strength, expertise of Roman builders ; 04. Solid Earth::04.01. Earth Interior::04.01.04. Mineral physics and properties of rocks

Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

Type: article

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Implications for mechanical properties of brittle faults from observations of the Punchbowl fault zone, California (1986)

Chester, F. M. ; Logan, J. M.

Springer

Pure and applied geophysics 124 (1986), S. 79-106

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ISSN: 1420-9136

Keywords: Deformation ; faults ; cataclasis ; gouge ; rock mechanics

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Abstract Field observations of the Punchbowl fault zone, an inactive trace of the San Andreas, are integrated with results from experimental deformation of naturally deformed Punchbowl fault rocks for a qualitative description of the mechanical properties of the fault and additional information for conceptual models of crustal faulting. The Punchbowl fault zone consists of a single, continuous gouge layer bounded by zones of extensively damaged host rock. Fault displacements were not only localized to the gouge layer, but also to discrete shear surfaces within the gouge. Deformation in the exposure studied probably occurred at depths of 2 to 4 km and was dominated by cataclastic mechanisms. Textural data also suggest that significant amounts of pore fluids were present during faulting, and that fluid-assisted mechanisms, such as dissolution, diffusion, and precipitation, were operative. The experimental data on specimens collected from the fault zone suggest that there is a gradual decrease in strength and elastic modulus and an increase in relative ductility and permeability toward the main gouge zone. The gouge layer has fairly uniform mechanical properites, and it has significantly lower strength, elastic modulus, and permeability than both the damaged and the undeformed host rock. For the Punchbowl fault and possibly other brittle faults, the variations in loading of the gouge zone with time are primarily governed by the morphology of the fault and the mechanical properties of the damaged host rock. In addition, the damaged zone acts as the permeable unit of the fault zone and surrounding rock. It appears that the gouge primarily governs whether displacements are localized, and it therefore may have a significant influence on the mode of slip.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00875720

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Effect of displacement rate on the real area of contact and temperatures generated during frictional sliding of Tennessee sandstone (1978)

Teufel, L. W. ; Logan, J. M.

Springer

Pure and applied geophysics 116 (1978), S. 840-865

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ISSN: 1420-9136

Keywords: Frictional sliding ; Stick-up ; Temperature measurements

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Physics

Notes: Summary The real area of contact has been determined, and measurements of the maximum and average surface temperatures generated during frictional sliding along precut surfaces in Tennessee sand-stone have been made, through the use of thermodyes. Triaxial tests have been made at 50 MPa confining pressure and constant displacement rates of 10−2 to 10−6 cm/sec, and displacements up to 0.4 om. At 0.2 cm of stable sliding, the maximum temperature decreases with decreasing nominal displacement rate from between 1150° to 1175°C at 10−2 cm/sec to between 75° to 115°C at 10−3 cm/sec. The average temperature of the surface is between 75 and 115°C at 10−2 cm/sec, but shows no rise from room temperature at 10−3 cm/sec. At 0.4 cm displacement, and in the stick-slip mode, as the nominal displacement rate decreases from 10−3 to 10−6 cm/sec, the maximum temperature decreases from between 1120° to 1150°C to between 1040° to 1065°C. The average surface temperature is 115° to 135°C at displacement rates from 2.6×10−3 to 10−4 cm/sec. With a decrease in the displacement rate from 10−2 to 10−6 cm/sec, the real area of contact increases from about 5 to 14 percent of the apparent area; the avergge area of asperity contact increases from 2.5 to 7.5×10−4 cm2. Although fracture is the dominate mechanism during stick-up thermal softening and creep may also contribute to the unstable sliding process.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00876541

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Direct measurement of antiferromagnetic domain fluctuations (2007)

Isaacs, E. D. ; Logan, J. M. ; Feng, Yejun ; [et al.]

[s.l.] : Nature Publishing Group

Nature 447 (2007), S. 68-71

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ISSN: 1476-4687

Source: Nature Archives 1869 - 2009

Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics

Notes: [Auszug] Measurements of magnetic noise emanating from ferromagnets owing to domain motion were first carried out nearly 100 years ago, and have underpinned much science and technology. Antiferromagnets, which carry no net external magnetic dipole moment, yet have a periodic arrangement of the ...

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1038/nature05776

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The progression from damage to localization of displacement observed in laboratory testing of porous rocks (2007)

Logan, J. M.

In: Geological Society Special Publication 289: 75-87.

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Publication Date: 2007-11-05

Description: Laboratory experiments suggest that fault zones form in porous rocks through the extension and coalescence of fractures of predictable geometries. These fractures form in an array of Riedel fractures in R1, R2, P and Y orientations. Displacement along closely spaced fractures leads to the formation of comminuted fault gouge. Localization of displacement within the fault gouge progresses from distributed shearing to comminution and compaction of the fault rock material culminating in fractures in the Riedel orientations. Colour boundaries within the simulated gouge zones show the change in accommodation of displacement to fractures in the Y orientation as shear strain progresses. Clayquartz mixtures demonstrate that the clay inhibits localization and the achievement of steady-state sliding as well as stick-slip. A reduction in the coefficient of friction does not occur until about 30% of the clay is present and continues to decrease until about 70% is reached. Localization of slip appears as a necessary condition for steady-state sliding as well as unstable behaviour. Field studies show the implication of grain-size reduction in the localization process by porosity decrease inhibiting fluid flow normal to the fault zone. The pervasive Y fractures, however, facilitate fluid migration parallel to some faults.

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Textural controls on the brittle deformation of dolomite: the transition from brittle faulting to cataclastic flow (2007)

Austin, N. J. ; Kennedy, L. A. ; Logan, J. M. ; [et al.]

In: Geological Society Special Publication 243: 51-66.

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Publication Date: 2007-10-08

Description: To investigate the role of texture on the brittle deformation of dolomite, 23 triaxial deformation experiments were performed at confining pressures of 25, 50, and 100 MPa, dry, at room temperature, on dolomite from three texturally distinct sample suites. The variations in the mechanical response of these mineralogically and chemically similar dolomites, and the ensuing microstructures, indicate that grain boundary textures promote or inhibit the ability of grains to shear and rotate with respect to one another, whereas the presence of intragranular flaws, such as cleavage, that act as weaknesses, promote intragranular deformation. In samples with porosities greater than c. 7%, inelastic pore collapse controls the transition from brittle faulting to extensive intragranular deformation and cataclastic flow. This porosity is much higher than has been observed at the onset of pore collapse in calcite, as a consequence of the inability of dolomite to deform by crystal plastic processes at room temperature. Combined, these textural features may dictate the transition from brittle faulting to cataclastic flow in brittle rocks in the upper crust.

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