Sequence Of Levels Research Articles

Authigenic uranium in Atlantic sediments of the last glacial stage — a diagenetic phenomenon

Cores from three different Atlantic localities (equatorial, Cape Verde Rise and Porcupine Abyssal Plain) are shown to have anomalous high U contents (5–8 ppm total) in sediments laid down during the last glacial stage (12–24 ky BP). Radiocarbon data demonstrate that the sediments hosting the peak U levels were accumulated at rates similar to those immediately above and below. All the cores exhibit maximum Mn levels, characteristic colour changes, and maximum U levels in the same sequence with increasing depth in core. On the evidence of the similarities between the cores, and pore water U data from a Porcupine Abyssal Plain site, it is proposed that the authigenic U enrichments are syndiagenetic and possibly active. No correlation is observed between sediment authigenic U and C org contents. The source of enrichment is bottom water U which has diffused downwards into the sediments to be sorbed at a particular redox level, located 10–30 cm below the oxic/post-oxic boundary marked by the colour change. The magnitude of the enrichments is caused by the persistence of this boundary at a particular level as a result of the decrease in mean sediment accumulation rate between the last glacial stage (5.2 up to at least 19.1 cm ky −1) and the Holocene (2.2–4.1 cm ky −1). Similar accumulation rate contrasts are expected to be widespread in the Atlantic, and the implications for previous reported work, particularly from the Mid-Atlantic Ridge, are discussed.

Transperineurial vessels in the peripheral nerves of humans

Nerve fibers in peripheral nerve (PNS) are grouped into fascicles. The perineurial (PN) sheath forms the outer cover of the fascicle and separates the epineurium from the endoneurial compartment which contains the conducting units (nerve fibers) of the PNS. The PN sheath not only serves as a physical protective layer for the vulnerable nerve fibers but also plays a role in maintaining a unique endoneurial environment with respect to endoneurial pressure and chemical composition. All blood vessels that serve the capillary plexuses of the endoneurium pass through the PN sheath. In this study on human nerves, we describe some of the anatomical relationships between PN cells and vascular elements as they pass through the PN sheath. A better understanding of the anatomical arrangement of transperineurial vessels might help explain the pathogenesis of some of the ischemic neuropathies.Segments of nerves (lumbosacral plexus, sciatic, posterior tibial, peroneal and sural) from autopsy and sural nerves from biopsy were prepared for electron microscopy. One μm serial cross-sections of nerve fascicles were stained with paragon. Thin sections for EM were taken at desired levels in the thick-section serial sequence. 3-D reconstruction of 1 μm sections was accomplished using a program provided by Dr. Kinnamon of The High Voltage Electron Microscopy Lab in Boulder, Colorado.

The human remains from Cova Negra (Valencia, Spain) and their place in European Pleistocene human evolution

The phylogenetic and chronological positions of the Cova Negra human remains are discussed. These remains include an adult right parietal bone, a juvenile right mandibular body fragment with a deciduous second molar, and an isolated permanent upper central incisor. There are 40 levels in the Cova Negra sedimentary sequence, ranging from the Riss-Würm to the beginning of the Würm III. The Cova Negra A phase (Riss-Würm) is faunally and industrially sterile. Several variants of the Mousterian (Charentian type) are known from the beginning of the Würm (Cova Negra B phase) to the end of the sequence (Cova Negra E and F phases). All human remains are assigned to the Würm. On the basis of the parietal bone, uni- and bivariate analyses show that the Cova Negra biparietal vault was very broad. The cluster analysis groups Cova Negra with the biggest Neandertal neurocrania (specimens generally sexed as males). Also, this parietal bone exhibits a subcircular profile in posterior view, a trait considered as a Neandertal autapomorphy. The mandibular fragment shows three foramina mentalia and a steep linea mylohyoidea. These and other traits lead us to include this specimen in the Neandertal group. The crown dimensions and the morphology of the deciduous molar are consistent with this taxonomic attribution. The comparative study of the crown and root dimensions of the permanent incisor, as well as the presence of traits such as a strong tuberculum linguale, well developed marginal ridges (shovelling), and the marked lingual inclination of the buccal face, lead us to attribute this tooth to the Neandertal group.

Comprehensive calculations of 4p and 4d lifetimes for the Cu sequence.

Computed lifetimes for the 4p $^{2}P_{1/2}$, 4${p}^{2}$${P}_{3/2}$, 4d $^{2}D_{3/2}$, and 4${d}^{2}$${D}_{5/2}$ levels in the copper isoelectronic sequence are presented for atomic numbers Z=29--92. These calculations agree well with recent high-precision lifetime measurements, conflict with the isoelectronic trend of single-configuration Dirac-Fock calculations, and agree at lower Z with the multiplet values of multiconfiguration Hartree-Fock calculations using experimental transition energies. Our calculations involve the inclusion of experimental energy-level data and the use of a Hartree-Slater potential to represent the ionic core. It is found that the core-polarization effects are significant and must be included to obtain agreement with experiment, at least for the lower members of the isoelectronic sequence. As part of the study, we have combined semiempirical parametrizations of the existing database with Dirac-Fock calculations to produce a set of values for the ionization potentials and the 4p and 4d excitation energies for all stable ions in this sequence.

Accurate calculations of 3pand 3dlifetimes in the Na sequence

Computed lifetimes for the 3p $^{2}P_{1/2}$, P3${p}^{2}$${P}_{3/2}$, 3d $^{2}D_{3/2}$, and 3${d}^{2}$${D}_{5/2}$ levels in the sodium isoelectronic sequence are presented for Z=11--54, 74, 79, 90, and 92. These calculations agree well with recent high-precision lifetime measurements, and conflict with some ab initio estimates which indicated lifetimes shorter than those experimentally observed. Our calculations involve the inclusion of experimental energy-level data and the use of a realistic model potential, which utilizes comprehensive spectroscopic measurements that have recently become available. We also demonstrate that the core-polarization effects are significant and must be included to obtain agreement with experiment. As part of the study, we used the existing data base and Dirac-Fock methods to determine new values for ionization potentials in this sequence.

Oscillator strengths for transitions from 3s4s and 3s4p levels calculated in the magnesium sequence, MgI–MnXIV using the multiconfiguration optimized potential model

Oscillator strengths for downward transitions from the 3s4p and 3s4s levels in the Magnesium isoelectronic sequence are reported. These, as well as lifetimes for these levels, have been calculated for MgI to MnXIV using the Multiconfiguration Optimized Potential Model (MCOPM) with inclusion of relativistic corrections. Generally, the level splittings are reasonably accurate but at certain level crossings - occurring near Sv and C1VI - considerable energy level accuracy is required to ensure accurate relativistic mixing coefficients and transition rates. Corrections have been applied to the energies in these cases.

Improved discrimination of rock units using Landsat Thematic Mapper imagery of the Oman ophiolite

The short wavelength infrared channels recorded by the Landsat Thematic Mapper make this instrument more suitable than the Landsat Multispectral Scanner for lithological mapping using enhanced imagery. The weathering mineralogy of igneous rocks causes absorption features in their reflectance spectra which are particularly characteristic in the near infrared. A Landsat Thematic Mapper band 7,5,4 red, green, blue false colour composite of part of the Oman ophiolite confirms much of the previous mapping and indicates certain hitherto unrecorded features. These include a new mafic-ultramafic late-intrusive complex and differences between deeper and near-crustal levels in the mantle sequence, which may be related to the environment in which serpentinization took place. Decorrelation stretching is an excellent means of accentuating colour variations within an image as an aid to visual interpretation.

Isoelectronic studies of the 4s4p^3PJ energy levels in the Zn sequence

Screening parameterizations of the spin–orbit and exchange energies are used to systematize available data accurately for the 4s4p configuration in the Zn isoelectronic sequence. Through the availability of precision measurements of the 4s21S0–4s4p1P1 resonance transition, these screening parameterizations are used to make accurate interpolative and extrapolative predictions of the excitation energies of the 4s4p3PJ levels for ions from Ge iii through Ba xxvii These results also provide extrapolative predictions of the magnetic-dipole, electric-quadrupole, and intercombination transitions in this system that sometimes occur in localized diagnostics of high-temperature plasmas.

The use of adjoint equations to solve a variational adjustment problem with advective constraints

A methodology is developed to guarantee time continuity in a sequence of analyses. Coupling is accomplished by requiring the least squares minimization of adjustment to the analyses subject to dynamic constraints. In this paper, the analyses are assumed to be governed by advective constraints such as those used in vorticity conservation models; however, the method can easily be applied to other constraints. The results correspond to the application of a strong constraint as introduced by Sasaki, but the procedure used to accomplish the minimization is an alternative to the traditional methods for solution of the Euler-Lagrange equation. The method allows easier inclusion of more time levels in the analysis sequence as well as accommodation of more complicated constraints. The method is tested using both simulated and real data. The simulated data studies use a one-dimensional advection equation with progressively more complicated dynamics: constant advection velocity, spatially varying advection velocity, and nonlinear advection. The real data case study uses an advection of quasi-geostrophic potential vorticity constraint to examine the height adjustment process for three time periods on 6 March 1982. Separate studies are made for analyses derived from VAS and RAOB data. The results of this study indicate the method has excellent potential to reduce the random component of the analysis errors. DOI: 10.1111/j.1600-0870.1985.tb00430.x

The representation of higher-order relativistic corrections in the MCDF-EAL method

The MCDF-EAL method is shown to be closely related to the procedure used to solve the Bethe-Salpeter equation by Douglas and Kroll (1974) in their study of helium 3P fine structure. The authors interpret the former as a method based on a well defined effective Hamiltonian derived from QED which yields a solution within a finite set of CSF which is exact to all orders of perturbation theory. This interpretation allows one to examine the contribution of higher-order terms in the perturbation series for 23P in helium-like F VIII, 1s2p2 4P levels in the lithium isoelectronic sequence and 1s22s22p2 3P levels in the carbon isoelectronic sequence. These terms are shown to be essential if the theoretical predictions are to match the precision obtainable in current experiments. In the case of the carbon sequence, the authors identify discrepancies due to missing (non-relativistic) correlation contributions, and show how these may be taken into account in some cases.

A Methodology for Assessment of Wind Turbine Noise Generation

The detailed analysis of a series of acoustic measurements taken near several large wind turbines (100 kW and above) has identified the maximum acoustic energy as being concentrated in the low-frequency audible and subaudible ranges, usually less than 100 Hz. These measurements have also shown any reported community annoyance associated with turbine operations has often been related to the degree of coherent impulsiveness present and the subsequent harmonic coupling of acoustic energy to residential structures. Thus, one technique to assess the annoyance potential of a given wind turbine design is to develop a method which quantifies this degree of impulsiveness or coherency in the radiated acoustic energy spectrum under a wide range of operating conditions. Experience has also shown the presence of annoying conditions is highly time dependent and nonstationary, and, therefore, any attempts to quantify or at least classify wind turbine designs in terms of their noise annoyance potential must be handled within the proper probabilistic framework. A technique is described which employs multidimensional, joint probability analysis to establish the expected coincidence of acoustic energy levels in a contiguous sequence of octave frequency bands which have been chosen because of their relationship to common structural resonant frequencies in residential buildings. Evidence is presented to justify the choice of these particular bands. Comparisons of the acoustic performance and an estimate of the annoyance potential of several large wind turbine designs using this technique is also discussed.

Effects of variations in glutamic acid decarboxylase activity on acute oxygen poisoning.

A study was made to test the influence of rapid variations in glutamic acid decarboxylase (GAD) activity on the susceptibility of rats to hyperbaric oxygen (HBO). GAD was inhibited by the convulsant drug unsymmetrical dimethylhydrazine (UDMH) and reactivated by pyridoxine (PYR) after onset of convulsive activity. There was a relatively long induction period after UDMH injection until the onset of convulsions and the predictable interictal periods between successive periodic convulsions made it possible to study the impact of variations in GAD activity on survival rates, suspectibility to HBO and brain glycogen levels in a time sequence after UDMH administration. The experiments showed that UDMH interferes with aerobic metabolism in brain in such a way that profound alterations in resistance to acute oxygen poisoning resulted. An accumulation of substrate proximal to the enzyme block is assumed to develop during UDMH poisoning. The protective effect against HBO toxicity that was achieved after reactivation of GAD by PYR injection, as well as the rapid re-establishment of glycogen levels, is believed to speak in favour of this hypothesis.

Semi-Empirical Calculations of Fine Structure Splittings and Ionisation Potentials in the MgI Isoelectronic Sequence

A semi-empirical parametrisation of the singlet-triplet and fine structure splittings for available measurements of the 3s3p 1,3P levels in the MgI isoelectronic sequence has revealed regularities which are useful for interpolation and extrapolation. By combining an extrapolation of the empirical gross energies, Slater integrals and spin-orbit splitting factors to highly ionised members of this sequence with available measurements for the 3s2 1S-3s3p 1P transitions, the positions of the members of the 3s3p 3P multiplets and the ionisation potentials can be predicted.

An examination of prerequisite relations, positive transfer among learning tasks, and variations in instruction for a seriation hierarchy

This study investigated the hypothesis that prerequisite skills in a seriation learning hierarchy mediate positive transfer for superordinate skills. In addition, the effect of instructional conditions involving modeling combined with variations in feedback on skill acquisition at different levels in the seriation sequence was examined. Application of the White and Clark test of inclusion revealed a close correspondence between hypothesized and observed prerequisite relations in the seriation hierarchy. However, structural analysis of the data revealed that positive transfer did not occur in many instances in which it was expected. In addition, instructional variations were found not to be uniformly effective at all levels in the sequence.

Geological setting of the Skorovas orebody within the allochthonous volcanic stratigraphy of the Gjersvik Nappe, central Norway

Synopsis The Skorovas orebody is one of the chief stratiform basemetal deposits within the allochthonous greenstone belt of the Central Norwegian Caledonides. It is contained in the volcanic level of a complex eruptive association of Lower to Middle Ordovician age defined as the Gjersvik Nappe. The rocks of this nappe are contained as a depressed segment of the larger Köli Nappe and defined to the north and south, respectively, by the Börgefjell and Grong-Olden basement culminations. The principal components of this nappe are a plutonic infrastructure of composite gabbroic intrusions within which has been emplaced a series of dioritic to granodioritic (trondhjemitic) bodies that form the roots of a consanguineous submarine polygenic volcanic sequence. The eruptive rocks are overlain unconformably by a sequence of polymict conglomerates and calcareous flysch sediments, the composition of which suggests immediate derivation by erosion from the underlying igneous complex. Pre-tectonic segregations, veins and vesicle fillings of epidote, albite, chlorite, carbonate and quartz related to primary volcanic flow structures in the lava pile provide evidence of pervasive in-situ sea-floor metamorphism, and this interpretation is verified by the abundance of nearly monomineralic epidote clasts in the derived conglomerates. The relationship of the eruptive and sedimentary suites is interpreted in terms of the evolution of an ensimatic island arc, of Lower to Middle Ordovician age, which underwent uplift and erosion prior to emplacement on the Fennoscandian basement during the climactic stages of collision tectonism of the Caledonian Orogeny in Silurian times. The entire igneous and sedimentary assemblage has been affected by the tectonic stages of allochthonous emplacement, but the gross differences in competence between the component lithologies has resulted in a particularly heterogeneous style of deformation in which folding, componental sliding, fracturing and penetrative metamorphic refabrication have been governed largely by the geometry of the most competent lithologies, notably gabbro, diorite and granodiorite (trondhjemite) intrusives and, within the extrusive sequence, compact dacitic flows and their spilitized aphanitic equivalents (keratophyres). The heterogeneous pattern of deformation is resolved in terms of two main stages of folding complicated by componental sliding movements. Mineralization occurs at two levels in the eruptive sequence. The layered gabbros and lensoid metagabbros of the plutonic infrastructure contain small cumulus bodies of nickel-, copper- and platinum-bearing pyrrhotite-pyrite-magnetite ore of magmatic derivation. Mineralization of this type is at present only known in sub-economic quantities. The Skorovas orebody, in common with other widely dispersed volcanic exhalites in the Gjersvik Nappe, occurs within the volcanic sequence at a level marked by episodes of explosive dacitic volcanism and associated fumarolic activity. The Skorovas orebody consists of approximately 10 000 000 tons of massive and disseminated predominantly pyritic ore with an approximate average grade of 1.3% Zn and 1.0% Cu, together with trace amounts of Pb, As and Ag. The complex lensoid geometry of the orebody is resolved in terms of the disjunction of a single stratiform unit by tight isoclinal folding and componental movements, probably involving both translation and rotation. Enrichment of sphalerite, chalcopyrite and, locally, galena within the magnetite-pyrite ores at the stratigraphic top and margins of the ore lenses is interpreted as a primary feature. The banded magnetite-pyrite ores are commonly associated with magnetitic cherts or jaspers and are thus transitional in aspect to the thin, iron- and silica-rich, basemetal-depleted, exhalative sedimentary horizons that occur extensively within the extrusive sequence of the Gjersvik Nappe. These are interpreted as the products of settling of colloidal iron and silica hydrosols following explosive dispersal into an oxidizing submarine environment. They are valuable time-stratigraphic markers and indicators of way-up in complicated structures and are a potentially valuable tool in exploration for massive sulphide bodies formed in limited reducing environments.

Triply excited states of three-electron atomic systems

A formalism is discussed whereby many-electron systems may be described by a great number of product functions of different configurations in a manageable way. Calculations are made to find triply excited energy levels of three-electron atomic systems, using products of hydrogenic functions with a $Z$ equal to that of the nucleus. Results for the lowest $^{2}P^{o}$ and $^{2}S^{e}$ levels in the Li isoelectronic sequence, $Z=1 \mathrm{to} 10$, are presented. The results of calculations for the energies of $^{2}D^{e}$ triply excited states in ${\mathrm{He}}^{\ensuremath{-}}$ are also reported. The calculated energies are compared with available experimental and other theoretical values. Finally, the lowest $^{2}S^{e}$ and two lowest $^{2}P^{o}$ energy levels in the isoelectronic sequence are fitted by a $\frac{1}{Z}$ perturbation expansion. It is seen that this expansion can be used to estimate the energy levels of such states for higher nuclear charges.

Genesis of bauxite deposits in the Boolarra‐Mirboo area of Gippsland, victoria

Abstract Bauxite deposits in Gippsland are small, low in grade, and buried under a thick cover of Tertiary sands. Occurring at various stratigraphic levels in the Thorpdale volcanic sequence, they are also texturally and compositionally primitive and hence now presumably fossilised. Although broadly comparable with deposits in Tasmania and New England, they show few obvious analogies with other Australian bauxites. Profile studies reveal a somewhat erratic vertical mineralogical zonation which can, at least in part, be accounted for by assuming a degree of post‐bauxitisation planation so that some profiles are now truncated. Some profiles show gibbsite increasing with depth and at least in the Boolarra profile this has significant genetic implications. Here, during submergence of the lateritic surface, rising carbonated connate waters precipitated scarbroite and this, with subsequent renewed leaching, decomposed initially to form nordstrandite, and finally gibbsite.

Mean life measurements of 2p 2p 0 levels in the lithium sequence

Mean lives of 2p 2p 0 levels in Li I, Be II and B III belonging to the lithium isoelectronic sequence have been measured. The evaluated oscillator strengths are compared with theoretical estimates for the lithium sequence.

Palaeomagnetic Pole Positions, Part I.

This list contains the pole determinations available up to 1959 September, with the exception of some results from Russia. Further parts will appear, approximately every half year, as new determinations are made. The Russian results will be given in a future issue. The results are presented as a table with rg columns. The details given in originals has not always been sufficient to allow entries in all columns. Polar identification numbers are entered in column 2. The numbers in each part are arranged approximately according to age. It is felt that this number, prefixed by the part number, will be useful for identification purposes and in figure illustrations, and also as a key to the original. For instance, the pole determination from the Rosehill Formation has the reference number 1/117, the first number referring to Part I of the list and the second to the position within the part where a reference to the original may be found. Information about the rock unit from which the pole determination has been made is given in columns 3 and 4. Its geological age is specified by these period symbols: Quaternary Q, Tertiary T, Cretaceous K, Jurassic J, Triassic ‘R, Permian P, Carboniferous C, Devonian D, Silurian S, Ordovician 0, Cambrian e, and Pre-Cambrian pe. Subdivisions of periods from Cambrian to Cretaceous, where recognized, are denoted by u, m or 1. Epochs within the Tertiary (Palaeocene, Eocene, etc.) are denoted by Tpa, Te, To, T m and Tp. The Quaternary is divided into Recent Qr, and Pleistocene Qp. Subdivision of the Pre-Cambrian is not attempted. If it is thought that a rock formation was magnetized long after formation the probable “magnetic age” is entered in brackets after the geological age. Where possible, a distinction is made between a collecting site which is thought of as the particular place (say a quarry) from which a specimen is collected, and a collecting IocaZity which refers to a more general area (for example, a canyon section) which may comprise several sites at different levels in a rock sequence. However, the variation in sampling schemes used by different workers does not always allow this distinction to be made. The thickness of the rock unit which has been sampled is given in column 5 and in column 6 the spread of sampling localities (or sites) is indicated either as an area, or as a distance between extreme localities in those cases where the localities are few or are distributed along a zone rather than over an area. Pieces of rock, separately orientated, are referred to as samples, and from them one or more specimens are cut. The numbers of these samples and specimens are entered in columns 7 and 8. The distinction between samples and specimens has not always been made in originals, and in cases of doubt the entry is made in column 7.

Hokonui Stratigraphy of the Awakino-Mahoenui area, South West Auckland

Summary Trias-Jura rocks of the Awakino-Mahoenui area constitute part of the western limb of the Kawhia Syncline in its southern-most exposure. The syncline is approximately meridional in alignment and pitches northwards at a low angle. Strata have dips varying from nearly vertical in the west of the area to about 15° east at the top of the succession in the east. The strata form the Herangi Range which originated as a north-south fold or the peneplained surface resulting from the post-Hokonui orogeny. This fold is believed to be faulted on its western edge, but while this is also the case on the eastern limb farther north, in the Awakino-Mahoenui area faulting seems not to have occurred at the surface. The oldest beds exposed are 7,000 ft of Oretian (lower Carnian) which are believed to be the equivalent of 2,100 ft of strata above the Moeatoa conglomerate at Marakopa. These are followed conformably by 2,200 ft of Otamitan strata (Carnian), 1,800 ft to 2,300 ft of Warepan (Norian), 2,800 ft of Otapirian (Rhaetian), 2,500 ft of Aratauran (Hettangian-Sinemurian), about 2,000 it of Ururoan (Pliensbachian-Toarcian), about 4,000 ft of Temaikan (Bajocian-Oxfordian), and 4,300 ft of Heterian (Kimeridgian), giving a total of 14,000 ft of Triassic and 12,000 it of Jurassic strata. Beds of. Heterian age make up a greater thickness than in other North Island localities. On the south shore of Kawhia Harbour there are some 500 ft of beds, including Temaikan, between the type Temaikan and the black, gritty sandstone of Totara Peninsula, whereas below the Palmer Creek Shellbed (the same horizon as the black sandstone) there are 3,500 ft of Heterian strata. The sediments are mainly bedded sandstones and siltstones, with scattered and widespread tuffaceous material. True conglomerates are rare and thin, but grits are more common. Carbonaceous beds occur in the Otapirian and Heterian and accompany thin coals in the Oretian, but no non-marine beds typical of the type Temaikan sequence were observed in strata of Temaikan age. Calcareous beds are found at various levels in the Jurassic sequence but only Aratauran strata were found to contain microfossils. Marine fossils are widespread and allow closer subdivision of some stages. Warepan beds contain numerous forms of Monotis whose stratigraphic distribution enables four subdivisions to be recognized in the area. M. richmondiana is found in the older beds; M. calvata. is confined to the upper Warepan; while middle Warepan strata contain a very varied fauna including forms recognized by Trechmann (1918) and others recorded from New Caledonia (Avias, 1953). The Otapirian Stage is divided after Campbell (1956) although his basal fauna was not recognized in the area. Ururoan beds are divided into those containing Pseudaucella (Pliensbachian) and those with Dactylioceras (Toarcian). This ammonite was not found, but the fauna enables ready correlation wi'th the beds containing it at Ururoa Point.