Infrared study of the selective oxidation of toluene and o-xylene on vanadium oxide/TiO2

Infrared spectroscopy was used to obtain information on the mechanism of the selective oxidation of toluene and o-xylene over vanadium oxide catalysts. The interaction of these aromatic hydrocarbons and the products benzaldehyde and o-tolualdehyde with the surface of a V2O5/TiO2 monolayer catalyst was investigated at different temperatures under conditions comparable to those of the catalytic reaction. The infrared results obtained for each of these compounds showed a great resemblance, indicating that their oxidation proceeds along the same reaction path. Coordinatively adsorbed aldehydes, carboxylate-like structures, and benzoate species could be identified as intermediates on the surface of the catalysts. On the basis of the spectroscopic observations a possible reaction mechanism has been proposed

Developing an SNMP agent protocol entity with object oriented Perl

The Damocles project at the University of Twente is developing an SNMP prototyping vehicle. The motivation for such a vehicle stems from the fact that the IETF will develop new versions of SNMP in response to evolving user needs. Whereas the transition to newer versions is attractive from a functional or performance point of view, the effort and cost involved in such a transition should not be underestimated. The Damocles project investigates how modular design and implementation methods and OO techniques facilitate modification and reduce the effort and cost of version transition. In this paper, we discuss an SNMP agent protocol entity written in OO Perl. We discuss the design and implementation of the protocol entity, and how this development effort contributes to the objectives of the Damocles project

Influence of phosphorus and potassium impurities on the properties of vanadium oxide supported on TiO2

The catalytic properties of vanadium oxide catalysts supported on TiO2 from Tioxide were strongly affected by phosphorus and potassium, present as impurities in the TiO2 support. The effects observed were stronaly dependent on the type of hydrocarbon oxidised. In the oxidation of toluene to benzoic acid the impurities had a large negative influence on the activity and maximum yield. For the oxidation of o-xylene to ohthalic anhydride this negative effect was only observed at relat- ively low vanadium contents. At higher contents (above monolayer coverage) improved catalytic properties were obtained for catalysts supported on the contaminated TiO2 support. When the phosphorus and potassium impurities were both largely removed by extraction with water optimum catalytic behaviour was achieved at much lower vanadium contents in both oxidation reactions. The effect of each of the two impurities separately was also investigated using vanadium oxide catalysts deliberately contaminated with various amounts of either phosphorus or potassium. From the results of the catalytic oxidation experiments it was concluded that the addition of phosphorus resulted in an increase of the surface acidity of vanadium oxide/TiO2 catalysts. The effect of potassium was much larger and was attributed to an alternation of the nature of the reactive sites, possibly because of the formation of amorphous bronzes

Ecology of foraminifera and habitat variability in an underwater cave : distinguishing anchialine versus submarine cave environments

Author Posting. © Cushman Foundation for Foraminiferal Research, 2011. This article is posted here by permission of Cushman Foundation for Foraminiferal Research for personal use, not for redistribution. The definitive version was published in Journal of Foraminiferal Research 41 (2011): 201-229, doi:10.2113/gsjfr.41.3.201.Seventy-five surface (<4 cm) sediment samples were collected throughout Green Bay Cave System, Bermuda to investigate foraminiferal ecology and habitat variability in underwater coastal caves. This cave is ideal for studying different cave environments because it consists of an anchia-line cave environment connected to a submarine cave environment. Each sediment sample was analyzed for foraminifera, {delta}13Corg, C:N, organic matter content, CaCO3, and granulometry. Measurements of pH, salinity, dissolved oxygen, and temperature in the coastal aquifer distinguished the meteoric lens and saline groundwater. Q-mode cluster analysis on the foraminifera produced a dendrogram that segregates the anchialine and submarine cave environments, and subdivides each environment into distinct habitats consistent with local hydrogeology and sedimentology. The anchialine cave environment near the sinkhole is characterized by two groups of foraminifera: 1) the Meteoric Lens Assemblage living in the brackish meteoric lens within 60 cm of sea level, and 2) the Anchialine Cave Assemblage living in the saline groundwater. Helenina anderseni, Discorinopsis aguayoi, and other marsh foraminifera can persist in the brackish meteoric lens, which transitions into a more diverse assemblage dominated by Bolivina striatula and Rosalina globularis below the halocline. The boundary between the anchialine (terrestrially dominated) and submarine cave (marine-dominated) environments is demarcated by gross foraminiferal and sedimentary changes ({delta}13Corg from –24{per thousand} to –18{per thousand}, C:N from 11.2 to 8.3) that correspond to the maximum point where terrestrial influences routinely impact the cave benthos. Three assemblages of foraminifera inhabit the submarine cave environment: 1) the Entrance Assemblage in the first ~60 m of the submarine cave, dominated by Quinqueloculina; 2) the Circulated Submarine Cave Assemblage dominated by Spirillina vivipara and Triloculina oblonga, and 3) the Isolated Submarine Cave Assemblage dominated by Spirophthalmidium emaciatum. Planktic tintinnids suggest that tidally forced saline groundwater circulation is transporting more nutrients and particulate organic matter to the Circulated Submarine Cave Assemblage than the Isolated Submarine Cave Assemblage. These results indicate that coastal caves are partitioned into specific environments that can be further subdivided into habitats by groundwater masses, sediment fluxes (terrestrial versus marine), and groundwater circulation. This implies that that cave foraminifera can be useful paleohydrogeologic, paleoclimatic, and Quaternary sea-level proxies.The research was only possible with the generous field support from the Bermuda Cavers Group (Bruce Williams, Gil Nolan, Leon Kemp, and Paul Larrett), technical support from Tom Iliffe, and support from the Tucker family. The Johanna M. Resig Fellowship from the Cushman Foundation for Foraminiferal Research and an NSERC Alexander Graham Bell Canada Graduate Scholarship to PvH provided primary research support. Student research grants to PvH from the Geologic Society of America, the Cave Research Foundation, Bermuda Zoological Society, and the Sigma Xi Scientific Research Society provided further support

Results of the CEO Project - WWW Management

This report contains the result of a ‘proof of concept’ study that was performed by the CTIT of the University of Twente, together with ESYS Limited (Guildford, UK) for the Institute of Remote Sensing Applications of the Joint Research Centre (JRC) of the EC (Ispra, Italy). The study is part of the ‘Centre of Earth Observation’ (CEO) programme. The subject of the study was the design and implementation of tools that allow status and utilisation monitoring of networks and distributed information servers. In the specific case of the CEO programme, these information servers are accessible via the WWW and contain large amounts of earth observation data (e.g. satellite pictures). The work division within the project was that ESYS investigated the management applications, which had to run on top of HP-Openview, and the CTIT designed and implemented the management agents. These agents had to include the following Management Information Bases (MIBs): • A HTTP-MIB, with detailed information concerning the WWW document transfer protocol. • A Retrieval Service (RS) MIB, with high level information concerning the WWW document transfer service. • An Information Store (IS) MIB, with information concerning the WWW server and the documents provided by that server. The specifications of these MIBs were presented to the IETF and provided a good starting point for subsequent standardization activities. The agents were implemented as sub-agents of the EMANATE extensible agent package and are currently being tested in a number of field trials

Preparation of supported vanadium and molybdenum oxide catalysts using metal acetylacetonate complexes

Supported vanadium and molybdenum oxide catalysts were prepared by reaction of the corresponding acetylacetonate complex in a non-aqueous solution with the surface hydroxyl groups of the carrier. Continuous or batch adsorption of the metal acetylacetonate from toluene, as well as wet impregnation from ethanol, resulted in a uniform coverage of the support. The applied metal oxide was probably present on the surface as a monomolecular dispersion. When readsorption or reimpregnation from toluene was carried out with TiO2 as support, metal oxide crystallites were formed, which could readily be detected with laser Raman spectroscopy. Reimpregnation from ethanol led to a complete occupancy of the surface hydroxyl groups of the carrier without the formation of metal oxide multilayers or crystallites

Reconstructing 7000 years of North Atlantic hurricane variability using deep-sea sediment cores from the western Great Bahama Bank

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 28 (2013): 31–41, doi:10.1002/palo.20012.Available overwash records from coastal barrier systems document significant variability in North Atlantic hurricane activity during the late Holocene. The same climate forcings that may have controlled cyclone activity over this interval (e.g., the West African Monsoon, El Niño–Southern Oscillation (ENSO)) show abrupt changes around 6000 yrs B.P., but most coastal sedimentary records do not span this time period. Establishing longer records is essential for understanding mid-Holocene patterns of storminess and their climatic drivers, which will lead to better forecasting of how climate change over the next century may affect tropical cyclone frequency and intensity. Storms are thought to be an important mechanism for transporting coarse sediment from shallow carbonate platforms to the deep-sea, and bank-edge sediments may offer an unexplored archive of long-term hurricane activity. Here, we develop this new approach, reconstructing more than 7000 years of North Atlantic hurricane variability using coarse-grained deposits in sediment cores from the leeward margin of the Great Bahama Bank. High energy event layers within the resulting archive are (1) broadly correlated throughout an offbank transect of multi-cores, (2) closely matched with historic hurricane events, and (3) synchronous with previous intervals of heightened North Atlantic hurricane activity in overwash reconstructions from Puerto Rico and elsewhere in the Bahamas. Lower storm frequency prior to 4400 yrs B.P. in our records suggests that precession and increased NH summer insolation may have greatly limited hurricane potential intensity, outweighing weakened ENSO and a stronger West African Monsoon—factors thought to be favorable for hurricane development.This research was supported by awards from the Division of Ocean Sciences and the Division of Atmospheric and Geospace Sciences of the National Science Foundation to William B. Curry and an NSERC Post-Doctoral Fellowship to Peter van Hengstum.2013-09-1

Increased hurricane frequency near Florida during Younger Dryas Atlantic Meridional Overturning Circulation slowdown

Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Geology 45 (2017): 1047-1050, doi:10.1130/G39270.1.The risk posed by intensification of North Atlantic hurricane activity remains controversial, in part due to a lack of available storm proxy records that extend beyond the relatively stable climates of the late Holocene. Here we present a record of storm-triggered turbidite deposition offshore the Dry Tortugas, south Florida, USA, that spans abrupt transitions in North Atlantic sea-surface temperature and Atlantic Meridional Overturning Circulation (AMOC) during the Younger Dryas (12.9–11.7 k.y. B.P.). Despite potentially hostile conditions for cyclogenesis in the tropical North Atlantic at this time, our record and numerical experiments suggest that strong hurricanes may have regularly impacted Florida. Less severe surface cooling at mid-latitudes (~20–40°N) than across much of the tropical North Atlantic (~10–20°N) in response to AMOC reduction may best explain strong hurricane activity during the Younger Dryas near the Dry Tortugas and, potentially, along the entire southeastern coast of the United States.This work was supported by the U. S. Geological Survey Climate and Land Use Change Research and Development Program (Toomey), the Woods Hole Oceanographic Institution Ocean and Climate Change Institute (Toomey) and National Science Foundation grants (OCE-1356708 to Donnelly; 1356509 to van Hengstum)

<i>Xibalbanus cozumelensis</i>, a new species of Remipedia (Crustacea) from Cozumel, Mexico, and a molecular phylogeny of <i>Xibalbanus </i>on the Yucatán Peninsula

A new species belonging to the crustacean class Remipedia is described from an anchialine cave system on the island of Cozumel (Mexico), and is illustrated and compared morphologically and molecularly (CO1 and 16S) with closely related taxa. Xibalbanus cozumelensis sp. nov., the first remipede described from Cozumel, is morphologically similar to Xibalbanus tulumensis (Yager, 1987) from the Yucatán Peninsula, but the two species are genetically separate from each other (about 10% in CO1). A phylogenetic (Bayesian) analysis of Yucatán remipede populations based on CO1 and 16S placed them in a monophyletic Xibalbanus (in Xibalbanidae fam. nov.), with X. cozumelensis as most closely related to X. tulumensis. The Yucatán Peninsula and Cozumel have been separate since approx. early Cenozoic (~65 Ma), which suggests allopatric speciation for X. cozumelensis sp. nov. and X. tulumensis. However, the comparatively low genetic divergence between the two species may indicate that there has been gene flow between ‘mainland’ Yucatán and Cozumel long after the geological separation of the two landmasses, e.g., in cave systems under the sea bed, either continuously or sporadically, for example during the Last Glacial Maximum when the sea level was about 120 m lower than today

Human arrival and landscape dynamics in the northern Bahamas

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fall, P. L., van Hengstum, P. J., Lavold-Foote, L., Donnelly, J. P., Albury, N. A., & Tamalavage, A. E. Human arrival and landscape dynamics in the northern Bahamas. Proceedings of the National Academy of Sciences of the United States of America, 118(10), (2021): e2015764118, https://doi.org/10.1073/pnas.2015764118.The first Caribbean settlers were Amerindians from South America. Great Abaco and Grand Bahama, the final islands colonized in the northernmost Bahamas, were inhabited by the Lucayans when Europeans arrived. The timing of Lucayan arrival in the northern Bahamas has been uncertain because direct archaeological evidence is limited. We document Lucayan arrival on Great Abaco Island through a detailed record of vegetation, fire, and landscape dynamics based on proxy data from Blackwood Sinkhole. From about 3,000 to 1,000 y ago, forests dominated by hardwoods and palms were resilient to the effects of hurricanes and cooling sea surface temperatures. The arrival of Lucayans by about 830 CE (2σ range: 720 to 920 CE) is demarcated by increased burning and followed by landscape disturbance and a time-transgressive shift from hardwoods and palms to the modern pine forest. Considering that Lucayan settlements in the southern Bahamian archipelago are dated to about 750 CE (2σ range: 600 to 900 CE), these results demonstrate that Lucayans spread rapidly through the archipelago in less than 100 y. Although precontact landscapes would have been influenced by storms and climatic trends, the most pronounced changes follow more directly from landscape burning and ecosystem shifts after Lucayan arrival. The pine forests of Abaco declined substantially between 1500 and 1670 CE, a period of increased regional hurricane activity, coupled with fires on an already human-impacted landscape. Any future intensification of hurricane activity in the tropical North Atlantic Ocean threatens the sustainability of modern pine forests in the northern Bahamas.This research was supported by NSF Awards GSS-1118340 (P.L.F.), OCE-1356509 (P.J.v.H.), OCE-1703087 (P.J.v.H.), and OCE-1356708 (J.P.D.)