Interaction of Silver Nanoparticles and Chitin Powder with Different Sizes and Surface Structures: The Correlation with Antimicrobial Activities

Silver nanoparticles (Ag NPs) were  nm in diameter, and four <5% deacetylated chitins (A, B, C, and D) differing in size of powder and surface structure properties were used in the study. Chitin/Ag NP composites were synthesized by mixing Ag NP suspensions with each chitin powder at room temperature for 30 min. The Ag NPs were homogenously dispersed and stably adsorbed onto the chitins A and B powders. The resulting chitin/Ag NP composites were brown; darker composites were obtained when larger amounts of Ag NPs were reacted with chitin. Approximately, 26 and 22 μg of Ag NPs maximally adsorbed to 1 mg of chitins A and B, respectively, whereas only 2.5 and 1.5 μg of Ag NPs maximally adsorbed to chitins C and D, respectively. As the bactericidal and antifungal activities of the chitin/Ag NP composites increased with increasing amounts of Ag NPs adsorbed to the chitin, the antimicrobial activity of chitins A and B/Ag NP composites was much higher than that of chitins C and D/Ag NP composites. These results suggest that the particle size and surface structure of the chitin powder critically influence both the adsorption and antimicrobial activity of Ag NPs

Making a Better Magnetic Map

A new version of the World Digital Magnetic Anomaly Map, released last summer, gives greater insight into the structure and history of Earth's crust and upper mantle.Published1A. Geomagnetismo e PaleomagnetismoN/A or not JC

Submersible study of an oceanic megamullion in the central North Atlantic

Author Posting. © American Geophysical Union, 2001. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 106, no. B8 (2001): 16145–16161, doi:10.1029/2001JB000373.Recently discovered megamullions on the seafloor have been interpreted to be the exhumed footwalls of long-lived detachment faults operating near the ends of spreading segments in slow spreading crust. We conducted five submersible dives on one of these features just east of the rift valley in the Mid-Atlantic Ridge at 26°35′N and obtained visual, rock sample, gravity, and heat flow data along a transect from the breakaway zone (where the fault is interpreted to have first nucleated in ∼2.0–2.2 Ma crust) westward to near the termination (∼0.7 Ma). Our observations are consistent with the detachment fault hypothesis and show the following features. In the breakaway zone, faulted and steeply backtilted basaltic blocks suggest rotation above a deeper shear zone; the youngest normal faults in this sequence are interpreted to have evolved into the long-lived detachment fault. In younger crust the interpreted detachment surface rises as monotonously flat seafloor in a pair of broad, gently sloping domes that formed simultaneously along isochrons and are now thinly covered by sediment. The detachment surface is locally littered with basaltic debris that may have been clipped from the hanging wall. The domes coincide with a gravity high that continues along isochrons within the spreading segment. Modeling of on-bottom gravity measurements and recovery of serpentinites imply that mantle rises steeply and is exposed within ∼7 km west of the breakaway but that rocks with intermediate densities prevail farther west. Within ∼5 km of the termination, small volcanic cones appear on the detachment surface, indicating melt input into the footwall. We interpret the megamullion to have developed during a phase of limited magmatism in the spreading segment, with mantle being exhumed by the detachment fault <0.5 m.y. after its initiation. Increasing magmatism may eventually have weakened the lithosphere and facilitated propagation of a rift that terminated slip on the detachment fault progressively between ∼1.3 m.y. and 0.7 m.y. Identifiable but low-amplitude magnetic anomalies over the megamullion indicate that it incorporates a magmatic component. We infer that much of the footwall is composed of variably serpentinized peridotite intruded by plutons and dikes.B. Tucholke's research was supported by NSF grant OCE-9503561 and by an award from the Andrew W. Mellon Foundation Endowed Fund for Innovative Research and the Henry Bryant Bigelow Chair in Oceanography at Woods Hole Oceanographic Institution. G. Hirth acknowledges support by NSF grant OCE-9907244

Description of manganese nodules and crust collected from the Hakurei Maru Cruise GH76-2, March-May, 1976, in Northwestern Pacific Ocean

The cores and dredges described in this report were taken on the GH76-2 Expedition in March-May, 1976 by the Geological Survey of Japan from the R/V Hakurei Maru. A total of 47 cores and dredges sites have been visited. The survey covered the whole of the Pacific side of the Tohoku Arc, the southern part of the Kurile Arc and the northern margin of the Izu-Ogasawara (Bonin) Arc. The surveyed area covered the continental shelves, slopes, trenches and Pacific basin along the trenches

Cenozoic motion between East and West Antarctica

The West Antarctic rift system is the result of late Mesozoic and Cenozoic extension between East and West Antarctica, and represents one of the largest active continental rift systems on Earth. But the timing and magnitude of the plate motions leading to the development of this rift system remain poorly known, because of a lack of magnetic anomaly and fracture zone constraints on seafloor spreading. Here we report on magnetic data, gravity data and swath bathymetry collected in several areas of the south Tasman Sea and northern Ross Sea. These results enable us to calculate mid-Cenozoic rotation parameters for East and West Antarctica. These rotations show that there was roughly 180 km of separation in the western Ross Sea embayment in Eocene and Oligocene time. This episode of extension provides a tectonic setting for several significant Cenozoic tectonic events in the Ross Sea embayment including the uplift of the Transantarctic Mountains and the deposition of large thicknesses of Oligocene sediments. Inclusion of this East–West Antarctic motion in the plate circuit linking the Australia, Antarctic and Pacific plates removes a puzzling gap between the Lord Howe rise and Campbell plateau found in previous early Tertiary reconstructions of the New Zealand region. Determination of this East–West Antarctic motion also resolves a long standing controversy regarding the contribution of deformation in this region to the global plate circuit linking the Pacific to the rest of the world