VERTEX program

G. A. Knauer, J. H. Martin and others, VERtical Transport and Exchange (VERTEX) program Pioneering research on the relationships between particulate matter production, export and remineralization tracer studies particle-associated nitrification trace element (Fe) controls on primary production establishment of an 18-month ocean time-series at 33°N, 139°W... 

As one component of the decade-long VERTEX program, an oceanic time-series station (33°N, 139°W) was occupied for an 18-month period from October 1986 to May 1988. During this observation period, the site was visited on 7 occasions ( 90-day interval) for approximately 1 week per expedition to retrieve and redeploy a free-drifting sediment trap array, to collect water samples and to conduct experiments relevant to C- and N-cycle processes (Harrison et al., 1992 Knauer et al., 1990). The uptake and assimilation of NOa and NH4 substrates were measured during incubation experiments that were designed to assess, and correct for, isotope dilution of the added tracers. Photoautotrophic N assimilation was measured using the into protein method, described later in this section. Measurements were also made of the concentrations of NOs , NH4, DON, PON, total microbial biomass, autotrophic biomass, heterotrophic biomass, primary productivity and the export of particulate matter (Harrison et al, 1992). In many ways this was, at that time, the most comprehensive study of the marine N-cycle ever conducted in the North Pacific trades biome. 

Figure l6.8 N assimilation data from the VERTEX program time-series station at 33°N, 139°W (adapted from Harrison et al., 1992). Shown are (A) Upper water column density, expressed as sigma-T showing changes in stratification of the water column, C-HC03 -based primary production, autotrophic N-uptake based on the C-HC03 into protein method (see text for details) and (B) N03 and NH4 uptake rates based on tracer experiments and calculated f-ratios. 

Martin et al. (1987) published an initial formulation of a redissolution curve for organic carbon, which has extremely been influential in the ocean modeling community. Their formulation was based on sediment trap data from the North East Pacific Ocean (the VERTEX program) and described the sinking flux of organic matter as a power law ... 

The fact that the extremum of a linear program always occurs at a vertex of the feasible region is the single most important property of linear programs. It is true for any number of variables (i.e., more than two dimensions) and forms the basis for the simplex method for solving linear programs (not to be confused with the simplex method discussed in Section 6.1.4). 

Linear programs always solve to a global optimum. The optimum must lie on the boundary at an intersection between constraints, which is known as a vertex of the feasible region. The inequality constraints that intersect at the optimum are said to be active and have fi(x) = 0, where x is the vector of decision variables. 

A linear discriminant function can be found using a linear programming approach (48,49). The objective function to be optimized consists of the fraction of the training set correctly classified. If two vertices have the same classification ability, then the vertex with the smaller sum of distances to misclassified points is taken as better. 

The coordination sequences and the vertex symbol are unique for a particular framework topology, i.e. they can be used to distinguish between different zeolite framework types unambiguously. In this way, frameworks with the same topologies can be easily identified. Currently, it is easier to calculate the coordination sequences and vertex symbol using computer program based on crystallographic data. 

Methods for regiospecific introduction of halogens at boron vertices in 7-vertex MC2B4 clusters, and for organosubstitution at boron in n/do-MCaBs compounds, have been developed in recent years and are summarized in Scheme 1. The approaches shown, combined with available routes to C-substituted derivatives, have been used to advantage in preparing B- and C-functionalized multidecker complexes and linked dimers. However, recent synthetic objectives in our program require more versatility in... 

---