Detailed stratigraphic correlation of the Neogene sedimentary sequences on the Ontong Java Plateau by well logging; ODP Sites 803, 805, 806, 807, and DSDP Site 586

We used well logs, in some cases combined with shipboard physical properties measurements to make more complete profiles and to correlate between sites on the Ontong Java Plateau. By comparing sediment bulk density, velocity, and resistivity logs from adjacent holes at the same site, we showed that even subtle features of the well logs are reproducible and are caused by variations in sedimentation. With only minor amounts of biostratigraphic information, we could readily correlate these sedimentary features across the entire top of the Ontong Java Plateau, demonstrating that for most of the Neogene the top of the plateau is a single sedimentary province. We found it more difficult, but still possible, to correlate in detail sites from the top of the plateau to those drilled on the flanks. The pattern of sedimentation rate variation down the flank of the plateau cannot be interpreted as simply controlled by dissolution. Site 805, in particular, oscillates between accumulating sediment at roughly the same rate as cores on top of the Ontong Java Plateau, and accumulating sediment as slowly as Site 803, 200 m deeper in the water column. These oscillations do not match earlier reconstructions of central Pacific carbonate compensation depth variations

Thermodynamic identities and particle number fluctuations in weakly interacting Bose--Einstein condensates

We derive exact thermodynamic identities relating the average number of condensed atoms and the root-mean-square fluctuations determined in different statistical ensembles for the weakly interacting Bose gas confined in a box. This is achieved by introducing the concept of {\it auxiliary partition functions} for model Hamiltonians that do conserve the total number of particles. Exploiting such thermodynamic identities, we provide the first, completely analytical prediction of the microcanonical particle number fluctuations in the weakly interacting Bose gas. Such fluctuations, as a function of the volume V of the box are found to behave normally, at variance with the anomalous scaling behavior V^{4/3} of the fluctuations in the ideal Bose gas.Comment: 5 pages, 1 figur

The Globular Clusters of the Small Magellanic Cloud in the general Diagram Magnitude-Diameter

In the magnitude-diameter diagram the globular clusters in the Small Magellanic Cloud lie parallel to the line of the galactic globular clusters. As a result, the magnitudes and diameters of these clusters appear lower than in our galactic system.Asociación Argentina de Astronomí

The Globular Clusters of the Small Magellanic Cloud in the general Diagram Magnitude-Diameter

In the magnitude-diameter diagram the globular clusters in the Small Magellanic Cloud lie parallel to the line of the galactic globular clusters. As a result, the magnitudes and diameters of these clusters appear lower than in our galactic system.Asociación Argentina de Astronomí

Investigations on finite ideal quantum gases

Recursion formulae of the N-particle partition function, the occupation numbers and its fluctuations are given using the single-particle partition function. Exact results are presented for fermions and bosons in a common one-dimensional harmonic oscillator potential, for the three-dimensional harmonic oscillator approximations are tested. Applications to excited nuclei and Bose-Einstein condensation are discussed.Comment: 13 pages, 7 postscript figures, uses 'epsfig.sty'. Submitted to Physica A. More information available at http://obelix.physik.uni-osnabrueck.de/~schnack

Variations of porosity in calcareous sediments from the Ontong Java Plateau

Based on index properties measurements made on board the JOIDES Resolution, we studied porosity changes with depth in the fairly homogeneous deep-sea calcareous sediments cored during Ocean Drilling Program Leg 130 on the Ontong Java Plateau. Using Leg 130 data, we present evidence that the rate of porosity decrease with burial in calcareous oozes and chalks is related to the depth of deposition and thus probably depends on the conditioning of calcareous sediments by winnowing or dissolution processes during the time of deposition. The ooze-to-chalk transition is not clearly reflected in porosity profiles. In the ooze-chalk sections studied (the upper 600 mbsf), mechanical compaction is most likely the major process controlling the porosity decrease with depth of burial, whereas the chalk-limestone transition (at about 1100 mbsf at Site 807) is characterized by an intense chemical compaction leading to a drastic decrease in porosity values within 100 m. In oozes and chalks, porosity values were corrected to original (uncompacted) values using site-specific empirical regression equations. When plotted vs. age, corrected porosity profiles appear to correlate quite well from site to site in the sediments deposited during the last 15 m.y. This observation has considerable implications for seismic stratigraphy. Our attempt to correlate variations in porosity (or wet-bulk density) profiles with changes in carbonate content remained unsatisfactory. Index properties changes are likely caused by changes in the foraminifer content. If this is the case, we propose that large-scale porosity fluctuations that correlate from site to site are the result of changes in the surface productivity that lead to changes in the foraminifers-to-nannofossils ratio

Seismic modelling and paleoceanography at DSDP Site 574

The analysis of high-resolution watergun seismic profiles collected in support of DSDP Leg 85 drilling reveals sev eral major, regionally traceable reflectors that can be correlated over more than 360,000 km2 in the central equatorial Pacific. Synthetic seismograms generated from shipboard physical property measurements (carefully corrected to in situ values) for DSDP Site 574 show excellent agreement with the field records; the agreement suggests that the traveltime to-depth conversion is accurate and permits the precise (± 5 m) location of reflectors in the cored section. The reflectors can be dated (±0.5 Ma) as follows: Orange, 21.5 to 22.5 Ma; Yellow, 20.5 to 21.5 Ma; Lavender, 16 to 17 Ma; Red, 13.5 to 14.5 Ma; Purple, 11 to 12 Ma; Brown, 7 to 8 Ma; and Green, 3 to 4 Ma. Similar analyses at the other Leg 85 sites result in identical ages. The reflectors are thus time surfaces; this chapter relates them to major paleoceanographic events and changes in the relative sea-level curve. The Orange and Yellow reflectors are associated with a marked increase in δ 1 3C, a major change in planktonic foraminiferal assemblages, the development of the deep Circum-Antarctic Current, and the establishment of steep thermal gradients between tropical and polar regions. This reorganization of the oceanic circulation system was probably a response to the opening of the Drake Passage, and it resulted in changes in the chemistry of tropical Pacific waters that caused the induration (and thus impedance contrasts) associated with these reflectors. The Lavender reflector is associated with a large carbonate minimum, the Chron 16 carbon shift, a widespread hiatus (NH2), major eustatic sea-level fluctuations, and a significant increase in silica deposition in the Pacific. It is not associated with 18O enrichment or climatic cooling. We conclude that this event represents an intensification in Antarc tic Bottom Water (AABW) circulation and the partitioning of silica between the Atlantic and the Pacific, caused by the introduction of North Atlantic Deep Water (NADW) in response to paleobathymetric and tectonic events. The Red re flector is associated with a subdued carbonate minimum, a widespread hiatus (NH3), a sea-level drop, significant changes in microfossil assemblages, and a major increase in δ 1 8 that has been linked with the buildup of Antarctic ice. Detailed isotopic analyses reveal that this isotopic shift occurred within an interval of 30,000 yr. and precisely at the depth of the Red reflector. The Purple reflector is associated with an extremely large carbonate minimum, a change in the style of carbonate deposition in the Pacific, a major lithologic boundary, a widespread hiatus (NH4), an increase in the provincialism be tween low and high latitudes in all planktonic microfossil assemblages, an apparent fall in eustatic sea level, an enrich ment in δ 1 8 , and a major North Atlantic reflector interpreted as representing an intensification of North Atlantic bot tom-water circulation. The Brown reflector is roughly associated with a small carbonate minimum, an enrichment in δ 1 8 , the late Miocene 1 3C depletion, a drop in the relative sea-level curve, and major faunal changes. The Green reflector is associated with a large carbonate minimum, an enrichment in δ 1 8 , a major western North Atlantic erosional event, and a widespread eastern Atlantic seismic reflector. The bulk of evidence supports correlation with the onset of Northern Hemisphere glaciation, but detailed isotopic analyses indicate that this isotopic event may be linked to the establishment of colder bottom waters without major ice-sheet development. Several types of reflectors have been identified. The reflectors in the older section result from diagenetic effects; the regionally correctable reflectors are associated with global events. In the younger (post-18 Ma) section, local reflectors are characterized by velocity contrasts, whereas regional reflectors are associated with density contrasts caused by car bonate minima. Two modes of generation of carbonate minima (and thus of reflectors) spanning the equatorial Pacific are (1) the intensification of AABW without the concurrent intensification of NADW and so without fractionation of silica between the Atlantic and the Pacific; this mode results in the less extreme carbonate minima; and (2) the intensifi cation of AABW in response to the intensification of NADW; this mode results in extreme carbonate minima and a cor relation of equatorial Pacific reflectors with North Atlantic events

Thermodynamic fermion-boson symmetry in harmonic oscillator potentials

A remarkable thermodynamic fermion-boson symmetry is found for the canonical ensemble of ideal quantum gases in harmonic oscillator potentials of odd dimensions. The bosonic partition function is related to the fermionic one extended to negative temperatures, and vice versa.Comment: 7 pages, no figures, submitted to PHYSICA A. More information available at http://www.physik.uni-osnabrueck.de/makrosysteme

High School Mathematics Preparation for College Calculus: Is the Story the same for Males and Females?

Using data from the first national study on high school preparation for college calculus, the Factors Including College Success in Mathematics (FICSMath) project, this paper connects males’ (n=3,648) and females’ (n=2,033) instructional experiences from their senior level high school precalculus or calculus course to their college calculus performance. A hierarchical linear model identifies several significant instructional experiences that predict college calculus performance. Our findings show that high school instructional practices affect college calculus performance similarly for males and females. GOAL/OUTCOME #1 Present the long time perceived differences in mathematics performance across gender. GOAL/OUTCOME #2 Consider the transition across high school mathematics to college calculus relative to gender and performance. GOAL/OUTCOME #3 Share a model, including 3,648 males and 2,033 females, that reveals similar high school pedagogical experiences and predictors of performance in college calculus

Determining Shear Wave Velocities in Soft Marine Sediments

The inversion technique presented in this volume (Cheng, 1987) that simultaneously inverts full waveform acoustic logs for shear wave velocity (V[subscript 3]) and compressional wave attenuation (Q[subscript p]) was applied to selected full waveform acoustic logs taken in soft sediments from Deep Sea Drilling Project Site 613. Besides V[subscript 3] and Q[subscript p], the sensitivity of the inversion to perturbations in the fixed parameters, P-wave velocity (V[subscript p]), fluid velocity (V[[subscript f]), borehole diameter, bulk density (P[subscript b]), and borehole fluid attenuation (Q[subscript f]), were tested. Our study shows that the inversion technique is most sensitive to the estimate of V[subscript p] because the inversion is based on the P leaky mode energy portion of the spectrum. The Poisson's ratio, however, which primarily controls the amplitude of the waveforms, is rather stable with different estimates in V[subscript p]. The inversion technique is less sensitive to small perturbations in borehole diameter, P[subscript b], V[subscript f], and Q[subscript f] The shear wave velocities inferred from these inversions correlate well with the attendant velocity logs run at Site 613 and the diagenetic changes identified by shipboard stratigraphers. For example, there is an increase in both V[subscript p] and V[subscript 3] at the diagenetic boundary between siliceous nannofossil oozes and porcellanite. This boundary is responsible for a sharp seismic reflector in a USGS. seismic line run nearby. Over the depth interval that we analyzed, from 390.0 to 582.0 meters below sea floor, we determined shear wave velocities ranging from 0.74 to 1.06 km/sec corresponding to compressional wave velocities from 1.70 to 2.20 km/sec.Massachusetts Institute of Technology. Full Waveform Acoustic Logging ConsortiumNational Science Foundation (U.S.) (Grant OCE84-08761)Chevron (Fellowship