New Pt(II) complexes with the bidentate bridging ligand dipyrido(2,3-
a:3′,2′-
h)phenazine (dpop) have been prepared and studied. Absorption, electrochemical and spectroelectrochemical results are ...presented and discussed.
Three new complexes Pt(dpop)(Cl)
2, (Cl)
2Pt(dpop)Pt(Cl)
2 and (bpy)
2Ru(dpop)Pt(Cl)
2(PF
6)
2 (dpop
=
dipyrido(2,3-a:3′,2′-h)phenazine) were prepared and studied. The electronic absorption spectra of the complexes display Pt dπ
→
dpop π* and Ru dπ
→
dpop π* MLCT transitions at longer wavelengths than for previously reported similar complexes. Results of cyclic voltammograms show reversible dpop centered reductions while for the mixed metal (bpy)
2Ru(dpop)Pt(Cl)
2
2+ an irreversible Pt(II) oxidative wave precedes the Ru(II) oxidation/reduction couple. Spectroelectrochemical results show that all oxidative and reductive processes are completely reversible. The (Cl)
2Pt(dpop)Pt(Cl)
2 complex cleaves in solution with pseudo-first order kinetics resulting in loss of the Pt dπ
→
dpop π* MLCT transition at 545 nm.
All published distributional data on recent benthic foraminifera of the North American Atlantic continental margin were archived into computerized catalogs. Cluster analysis of these data delimited ...seven large, marginally overlapping provinces exhibiting a congruous relationship with western North Atlantic water masses. The single major latitudinal faunal change occurs at Cape Hatteras.
The age, origin, and geologic development of outcropping sedimentary units of the continental slope and rise of the Wilmington Canyon region are assessed from analysis of foraminifera. DSRV Alvin was ...used to core outcrops and subcrops of strata in the walls and floors of Wilmington, South Wilmington, and North Heyes Canyons. Planktonic and benthic foraminifera were identified and counted in 34 samples and analyzed using Q-mode cluster analysis. Planktonic foraminifera were used to determine age of outcropping strata and surficial watermass conditions at the time of deposition. Benthic foraminifera were used to determine water depth of the unit at the time of original deposition. Pleistocene sedimentary units exposed by canyon incision into the continental slope appear to be in place within the resolution possible for depth assignments based on benthic foraminifera. In contrast, on the upper continental rise, units exposed in the north wall and floor of South Wilmington Canyon clearly represent a sequence of displaced blocks, three of which originated from shal-lower depths. The base of the north wall sequence consists of strata derived from inner and middle neritic depths (<100 m) which is overlain by a unit either slumped from nearby or deposited in situ at lower bathyal to abyssal depths. The lower bathyal to abyssal unit is overlain by a unit derived from the middle to outer neritic which is overlain, in turn, by a unit displaced from upper to middle bathyal depths. The Pleistocene strata of the canyon floor and north wall of South Wilmington Canyon are capped by a thin dusting of Recent contourite deposits. South Wilmington Canyon was incised into the upper rise during the Pleistocene after emplacement of the last slumped block. The age, climatic, and paleodepth data derived from foraminiferal information suggest that mass movement on the slope and rise is related to Pleistocene sea level lowstands and that the present morphology of South Wilmington Canyon and perhaps some other canyons in this region is a result of relatively recent canyon incision, presumably by erosional processes of turbidity flow, during the latter part of the Pleistocene.
Supposed Upper Proterozoic strata in the southwest Taoudeni Basin, Guinea and Senegal, and from the Mauritanide fold belt, Mauritania, have yielded mostly poorly preserved small skeletal fossils of ...metazoan and protistan origin. Problematic, but possible echinoderm material and spicules of the heteractinid sponge Eiffelia dominate the Taoudeni Basin assemblage. The age of the material is not certain but the paleontologic data suggest an Early Cambrian age for the stratigraphically lowest faunas, and a Middle Cambrian age is possible for the stratigraphically highest collections.
The weight ratio of either cholesterol or phospholipid to protein contents in 7 different cell lines, growing exponentially at 37 degrees, correlates positively with increasing resistance of the ...cells to subsequent hyperthermic cell killing. The relative heat resistance of each cell line is derived from survival curves obtained when the different cell lines are exposed to 43 degrees. Cholesterol and phospholipid amounts in the particulate fraction correlate with survival sensitivity to 43 degrees when the values are expressed per mg protein but not when expressed per cell number. Also, cholesterol:phospholipid molar ratios and the amount of protein in the particulate fraction do not display linear correlations with sensitivity of the respective cell lines to 43 degrees-induced cell killing. The relative degree of fatty acid saturation at 37 degrees also is independent of whether cells show a higher degree of heat resistance. These data suggest that lipid (both cholesterol and phospholipid):protein weight ratios correlate with increasing resistance of cells to an elevation in temperature. The major implication of these data is that major membrane components can influence and perhaps predict cellular survival to hyperthermia.
The distribution of benthic foraminifera around the continental margins of North America is extensively documented. Data from 2673 localities consists of a synonomized list of 2329 species (S) and ...61369 occurrences (n). Here, the margins are divided into five geographical regions: Pacific (PA), S = 965, sn = 19014; Arctic (AR), S = 458, n = 7342; Atlantic (AT), S = 878, n = 10034; Gulf of Mexico (GM), S = 849, n = 18011; Caribbean (CR), S = 1188, N = 6968. As for many other organisms, species richness is lowest in the Arctic and highest in the Caribbean. In each region, the distribution of species richness and occurrences is a log series. Consequently, the entire series of species occurrences is predicted by the single proportionality constant, α. After log series rarefaction, differences in species richness among areas are nearly all accounted for by species occurring ≤ 10 times. Most of the differences are accounted for by species occurring once, less by twice, and so on. For example, species occurring once account for 81% of the difference in species richness between the Atlantic and Caribbean, and those occurring once and twice account for 87% of the difference. Most rare species have no fossil record and most endemic species are rare. Probably most of these species evolved recently indicating more origination in species-rich areas. High origination might also be coupled with less extinction. Although each of the five regions can easily be distinguished by differences in composition, in all regions the 10 most abundantly occurring species exhibit nearly equal proportions of occurrences. No region is dominated by only one or two species. All regions exhibit the log series distribution, have nearly equal proportions for abundant species, and differ only in the number of rare species that coexist. Thus, from the point of view of the distribution of occurrences, the most striking aspect is the similarity among regions.
Several very large, taxonomically standardized data sets have been compiled and utilized to investigate biogeographic and evolutionary patterns of continental margin benthic foraminifera. Mean ...partial species durations for 87 frequently occurring and 180 rarely occurring species on the Atlantic continental margin of North America are the same, namely 21 m.y. The global fossil record of these species indicates no center or centers of origin and indicates very rapid dispersal. The Miocene had the greatest number of first occurrences with 46%, followed by the Pleistocene, Pliocene and Oligocene with approximately 13% each. The remaining 14% first occur in the Eocene, Paleocene, and Cretaceous. Species with a wide geographic distribution often exhibit longer species durations than those with narrow geographic ranges. The vast majority of endemic species (150 of 175) occur rarely and have no fossil record.
Average species durations were estimated for 131 commonly occurring modern species. The duration of species occurring at depths of less than 200 meters is 16 million years, while for those at greater ...than 200 meters and at all depths it is 25 to 26 million years. Species (less than 200 meters) distributed from Florida to Newfoundland and from Florida to Cape Hatteras have about the same durations (18 to 20 million years). The duration for species restricted to north of Cape Hatteras is only 7 million years. The data suggest that evolutionary rates are greater in shallower than in deeper depths and greatest in the shallower northern area.
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