The preparation and investigation of some hetero-atom onium ions and their use in organic synthesis

A short review of cases where acyl- or alkoxycarbonyl onium salts have been prepared or postulated as intermediates is presented. The reaction of trialkylamines with chloroformate esters and acyl halides has been re-examined. Chloride ion proved to be too nucleophilic an anion to be able to isolate the salts. The route of decomposition is discussed in detail. The reaction of amines with chloroformates in the presence of antimony pentachloride has been investigated. Chloride ion exchange using triethyloxonium tetrafluoroborate has been achieved in the reaction of phenyl chloroformate with triethylamine, and the 13C nmr spectrum of this salt is discussed in detail. [Continues.

Pathways of Pacific water across the Chukchi Sea : a numerical model study

Author Posting. © American Geophysical Union, 2004. 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 109 (2004): C03002, doi:10.1029/2003JC001962.Pathways of Pacific Water flowing from the North Pacific Ocean through Bering Strait and across the Chukchi Sea are investigated using a two-dimensional barotropic model. In the no-wind case, the flow is driven only by a prescribed steady northward flow of 0.8 Sv through Bering Strait. The resulting steady state circulation consists of a broad northeasterly flow, basically following the topography, with a few areas of intensified currents. About half of the inflow travels northwest through Hope Valley, while the other half turns somewhat toward the northeast along the Alaskan coast. The flow through Hope Valley is intensified as it passes through Herald Canyon, but much of this flow escapes the canyon to move eastward, joining the flow in the broad valley between Herald and Hanna Shoals, another area of slightly intensified currents. There is a confluence of nearly all of the flow along the Alaskan coast west of Pt. Barrow to create a very strong and narrow coastal jet that follows the shelf topography eastward onto the Beaufort shelf. Thus in this no-wind case, nearly all of the Pacific Water entering the Chukchi Sea eventually ends up flowing eastward along the narrow Beaufort shelf, with no discernable flow across the shelf edge toward the interior Canada Basin. Travel times for water parcels to move from Bering Strait to Pt. Barrow vary tremendously according to the path taken; e.g., less than 6 months along the Alaskan coast, but about 30 months along the westernmost path through Herald Canyon. This flow field is relatively insensitive to idealized wind-forcing when the winds are from the south, west or north, in which cases the shelf transports tend to be intensified. However, strong northeasterly to easterly winds are able to completely reverse the flows along the Beaufort shelf and the Alaskan coast, and force most of the throughflow in a more northerly direction across the Chukchi Sea shelf edge, potentially supplying the surface waters of the interior Canada Basin with Pacific Water. The entire shelf circulation reacts promptly to changing wind conditions, with a response time of ~2–3 days. The intense coastal jet between Icy Cape and Pt. Barrow implies that dense water formed here from winter coastal polynyas may be quickly swept away along the coast. In contrast, there is a relatively quiet nearshore region to the west, between Cape Lisburne and Icy Cape, where dense water may accumulate much longer and continue to become denser before it is carried across the shelf.Financial support was provided to PW by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution (WHOI), the Swedish Foundation for International Cooperation in Research and Higher Education (STINT), and the J. Seward Johnson Fund. Funding for DCC came through a grant from the Coastal Ocean Institute at WHOI

Programs for computing properties of coastal-trapped waves and wind-driven motions over the continental shelf and slope

2nd ed.Documentation and listings are presented for a sequence of computer programs to be used for problems in continental shelf dynamics. Three of the programs are to be used for computing properties of free and forced coastal-trapped waves. A final program may be used to compute wind-driven fluctuations over the continental shelf and slope. This second edition includes several minor revisions and corrections in the computer code and the documentation.Funding was provided by the National Science Foundation under Grant OCE-0856

Programs for computing properties of coastal-trapped waves and wind-driven motions over the continental shelf and slope

Documentation and listings are presented for a sequence of computer programs to be used for problems in continental shelf dynamics. Three of the programs are to be used for computing properties of free and forced coastal-trapped waves. A final program may be used to compute wind-driven fluctuations over the continental shelf and slope.Funding was provided by the National Science Foundation under grant Number OCE 84-08563

Alien plant invasions in South Africa: Driving forces and the human dimension

Invasive alien plants pose a substantial threat to the rich biodiversity of South Africa, and to the sustained delivery of a wide range of ecosystem services. Biological invasions are driven by human activities and mediated by culturally shaped values and ethics. This paper explores the human dimensions of alien plant invasions in South Africa. We consider four primary forces, those which directly influence the likelihood and rate of invasion — arrival of propagules; changes in disturbance regimes; changes in the availability of limiting factors; and fragmentation of the landscape — and the roles of 22 secondary driving forces in shaping the outcomes of the four primary driving forces. Human societies and their dynamics and activities are an integral part of each of the secondary driving forces. A map of the interactions between and among the primary and secondary driving forces shows how they are interlinked and influence each other — either positively or negatively, or switching between the two. There are two key points for intervention: prevention of the introduction of propagules of potentially invasive species and developing collaborative initiatives with enterprises that rely largely on alien species (for example, horticulture, agriculture and forestry, including community forestry) to minimize the introduction and use of potentially invasive species. An example of the first type of intervention would be to implement more effective inspection systems at international border and customs posts. This type of intervention can only be effective if those who are directly affected — whether businessmen, tourists or migrants — understand the requirement for these measures, and collaborate. The need to build public awareness of the critical importance of the human dimension of invasions emerges as a key theme from this analysis and is the basis for better-informed decisions, more effective control programmes and a reduction of further invasions