THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

1. Light and Energy. 2. Organization and Structure of Photosynthetic Systems. 3. History and Development of Photosynthesis. 4. Photosynthetic Pigments-Structure and Spectroscopy. 5. Antenna Complexes and Energy Transfer Processes. 6. Reaction Center Complexes. 7. Electron Transfer Pathways and Components. 8. Chemiosmotic Coupling and ATP Synthesis. 9. Carbon Metabolism. 10. Genetics, Assembly and Regulation of Photosynthetic. Systems. 11. Origin and Evolution of Photosynthesis. Appendix 1. Light, Energy and Kinetics

Molecular mechanisms of photosynthesis

Evolutionary information on species divergence times is fundamental to studies of biodiversity, development, and disease. Molecular dating has enhanced our understanding of the temporal patterns of species divergences over the last five decades, and the number of studies is increasing quickly due to an exponential growth in the available collection of molecular sequences from diverse species and large number of genes. Our TimeTree resource is a public knowledge-base with the primary focus to make available all species divergence times derived using molecular sequence data to scientists, educators, and the general public in a consistent and accessible format. Here, we report a major expansion of the TimeTree resource, which more than triples the number of species (>97,000) and more than triples the number of studies assembled (>3,000). Furthermore, scientists can access not only the divergence time between two species or higher taxa, but also a timetree of a group of species and a timeline that traces a species' evolution through time. The new timetree and timeline visualizations are integrated with display of events on earth and environmental history over geological time, which will lead to broader and better understanding of the interplay of the change in the biosphere with the diversity of species on Earth. The next generation TimeTree resource is publicly available online at http://www.timetree.org.

/pdf/timetree-a-resource-for-timelines-timetrees-and-divergence-4zkwez83y8.pdf

TimeTree: A Resource for Timelines, Timetrees, and Divergence Times.

Mass-independent isotopic signatures for delta(33)S, delta(34)S, and delta(36)S from sulfide and sulfate in Precambrian rocks indicate that a change occurred in the sulfur cycle between 2090 and 2450 million years ago (Ma). Before 2450 Ma, the cycle was influenced by gas-phase atmospheric reactions. These atmospheric reactions also played a role in determining the oxidation state of sulfur, implying that atmospheric oxygen partial pressures were low and that the roles of oxidative weathering and of microbial oxidation and reduction of sulfur were minimal. Atmospheric fractionation processes should be considered in the use of sulfur isotopes to study the onset and consequences of microbial fractionation processes in Earth's early history.

https://science.sciencemag.org/content/sci/289/5480/756.full.pdf

Atmospheric Influence of Earth's Earliest Sulfur Cycle

The complexity of flow and wide variety of depositional processes operating in subaqueous density flows, combined with post-depositional consolidation and soft-sediment deformation, often make it difficult to interpret the characteristics of the original flow from the sedimentary record. This has led to considerable confusion of nomenclature in the literature. This paper attempts to clarify this situation by presenting a simple classification of sedimentary density flows, based on physical flow properties and grain-support mechanisms, and briefly discusses the likely characteristics of the deposited sediments. Cohesive flows are commonly referred to as debris flows and mud flows and defined on the basis of sediment characteristics. The boundary between cohesive and non-cohesive density flows (frictional flows) is poorly constrained, but dimensionless numbers may be of use to define flow thresholds. Frictional flows include a continuous series from sediment slides to turbidity currents. Subdivision of these flows is made on the basis of the dominant particle-support mechanisms, which include matrix strength (in cohesive flows), buoyancy, pore pressure, grain-to-grain interaction (causing dispersive pressure), Reynolds stresses (turbulence) and bed support (particles moved on the stationary bed). The dominant particle-support mechanism depends upon flow conditions, particle concentration, grain-size distribution and particle type. In hyperconcentrated density flows, very high sediment concentrations (>25 volume%) make particle interactions of major importance. The difference between hyperconcentrated density flows and cohesive flows is that the former are friction dominated. With decreasing sediment concentration, vertical particle sorting can result from differential settling, and flows in which this can occur are termed concentrated density flows. The boundary between hyperconcentrated and concentrated density flows is defined by a change in particle behaviour, such that denser or larger grains are no longer fully supported by grain interaction, thus allowing coarse-grain tail (or dense-grain tail) normal grading. The concentration at which this change occurs depends on particle size, sorting, composition and relative density, so that a single threshold concentration cannot be defined. Concentrated density flows may be highly erosive and subsequently deposit complete or incomplete Lowe and Bouma sequences. Conversely, hydroplaning at the base of debris flows, and possibly also in some hyperconcentrated flows, may reduce the fluid drag, thus allowing high flow velocities while preventing large-scale erosion. Flows with concentrations <9% by volume are true turbidity flows (sensuBagnold, 1962), in which fluid turbulence is the main particle-support mechanism. Turbidity flows and concentrated density flows can be subdivided on the basis of flow duration into instantaneous surges, longer duration surge-like flows and quasi-steady currents. Flow duration is shown to control the nature of the resulting deposits. Surge-like turbidity currents tend to produce classical Bouma sequences, whose nature at any one site depends on factors such as flow size, sediment type and proximity to source. In contrast, quasi-steady turbidity currents, generated by hyperpycnal river effluent, can deposit coarsening-up units capped by fining-up units (because of waxing and waning conditions respectively) and may also include thick units of uniform character (resulting from prolonged periods of near-steady conditions). Any flow type may progressively change character along the transport path, with transformation primarily resulting from reductions in sediment concentration through progressive entrainment of surrounding fluid and/or sediment deposition. The rate of fluid entrainment, and consequently flow transformation, is dependent on factors including slope gradient, lateral confinement, bed roughness, flow thickness and water depth. Flows with high and low sediment concentrations may co-exist in one transport event because of downflow transformations, flow stratification or shear layer development of the mixing interface with the overlying water (mixing cloud formation). Deposits of an individual flow event at one site may therefore form from a succession of different flow types, and this introduces considerable complexity into classifying the flow event or component flow types from the deposits.

The physical character of subaqueous sedimentary density flows and their deposits

Comment and Reply on “Pseudoconglomerate and a re-examination of some paleoenvironmental controversies” COMMENT

Provenance and paleogeography of Archean Fig Tree siliciclastic rocks in the East-Central Barberton Greenstone Belt, South Africa

Sandstones of the 3.22 Ga Archean Moodies Group represent one of the world's oldest quartz-rich sedimentary sequences. The provenance of this unit is unresolved because its quartz and common microcline can be sourced both from either now eroded or covered granitoid plutons outside the Barberton Greenstone Belt (BGB) or, alternatively and perhaps more controversially, (rhyo-)dacitic (sub-)volcanic rocks within the BGB. We compiled 31 detrital zircon data sets (n = 2588) from sandstones, reworked tuffs and conglomerate of the Moodies Group in order to constrain its age and provenance. After selection using quality criteria, the remaining zircons (n = 1621) in nearly all samples show a distribution corresponding to the four known major pulses of felsic magmatism in the BGB: 1) the ca. 3550 to 3530 Ma Theespruit and Sandspruit Formations at the base of the Onverwacht Group; 2) the ca. 3440 to 3410 Ma rhyo-dacites of the upper Hooggenoeg Formation, Onverwacht Group; 3) the ca. 3300 to 3280 Ma thin felsic tuffs in the Mendon Formation; and 4) the ca. 3260 to 3215 Ma felsic volcanic and shallow intrusive rocks of the Auber Villiers, Bien Venue and Schoongezicht Formations of the upper Fig Tree Group and the Moodies Group as well as their co-magmatic plutonic counterparts. Almost all data sets also contain near-concordant younger zircons as young as 2820 Ma, which can be attributed to one of six tectonic or magmatic events affecting the young Kaapvaal Craton in post-BGB time, causing the partial or complete resetting of the U-Pb system in some grains. The youngest (near-)concordant zircon clusters yield ages of ca. 3220 Ma in most locations, and the youngest discordant group of zircons from a reworked tuff near the top of the Moodies Group at 3212 ± 13 Ma agrees well with previous estimates of the maximum depositional age. With very few exceptions, the oldest zircons (ca. 3564 Ma) are only slightly older than the oldest rocks in the BGB stratigraphy (ca. 3550 Ma). Subtle regional and stratigraphic differences in age spectra may indicate localized or nearby sediment sources within a synorogenic setting. Preliminary age spectra along vertical stratigraphic profiles show little systematic variation, possibly indicating that intrabasinal recycling was dominant over considerable time periods of the basin's evolution. Extra-basinal plutonic sources of similar age and composition as the intra-BGB sources appear to be required to provide quartz and some feldspar to Moodies Group sandstones, although zircon age spectra, limited zircon Hf isotope data, sandstone petrography, facies analysis, and the high variability in Moodies conglomerate clast composition are consistent with uplift, deformation and erosion of several intra-BGB sources, but in particular from the region of the Onverwacht Anticline. Zircon populations, conglomerate clasts, and sandstone composition show no evidence that high-grade metamorphic rocks from the adjacent Ancient Gneiss Complex (AGC) contributed significantly to the Moodies Group.

Donald R. Lowe

Papers

Comment and Reply on “Pseudoconglomerate and a re-examination of some paleoenvironmental controversies” COMMENT

Provenance and paleogeography of Archean Fig Tree siliciclastic rocks in the East-Central Barberton Greenstone Belt, South Africa

Detrital zircon provenance of the Archean Moodies Group, Barberton Greenstone Belt, South Africa and Eswatini

Sedimentology and Architecture of Coarse-grained, Submarine Channel Fills, Lobitos Village, Peru

High Resolution Tephra and U/Pb Chronology of the 3.33-3.26 Ga Mendon Formation, Barberton Greenstone Belt, South Africa