Sequence Of Levels Research Articles

Influence of the two-electron transitions on the radiative lifetimes of excited levels in the boron isoelectronic sequence

The ions of the boron isoelectronic sequence (7⩽Z⩽45) are investigated using the configuration interaction method on the basis of transformed radial orbitals with a variable parameter. The energy spectra and the radiative lifetimes of the levels of configurations 2s2 2p, 2s2p2, 2p3 and 2s2 3l are obtained. The aim of the present work is the investigation of the influence of the two-electron transitions on the radiative lifetimes of levels of configuration 2s23p. It has been shown that the two-electron transitions are crucial for radiative lifetimes of these levels. The dependence of the influence on Z is discussed. The E2 transitions from 2s23p are also calculated for ions Z⩾25.

An EPR Spin Label Study of the Quinol Oxidase, E. coli Cytochrome bo3: A Search for Redox Induced Conformational Changes

A search for conformational changes at the cytosolic entrance to the proton channels of the heme-copper quinol oxidase (QO), cytochrome bo3, E. coli, has been carried out using site directed nitroxide spin labeling (SDSL) of cysteine residues. These were positioned at R134 and R309, on loops that link helices II and III and VI and VII at the entrances to the D and K proton channels, respectively. The motional characteristics of both labels have been determined using X- and W-band EPR spectroscopy at room temperature in selected redox levels in the reaction sequence of QO with oxygen, namely, the mixed valence carbon monoxide form (COMV), the oxidized (O) and super-oxidized (PM) states. The O to PM step is accompanied by the uptake of protons through the K pathway. We find no evidence for changes in the motional characteristics of either label that are expected to be associated with helical motions at the entrances to the channels. Because kinetic studies of mutants show that the redox gating of protons occurs deep within the D channel close to the heme-copper site, the present study implies that no motion is transmitted to the ends of the helices.

Late Pleistocene desiccation of Lake Tana, source of the Blue Nile

High-resolution seismic data from Lake Tana, the source of the Blue Nile in northern Ethiopia, reveal a deep sedimentary sequence divided by four strong reflectors. Data from nearshore cores show that the uppermost strong reflector represents a stiff silt unit, interpreted as a desiccation surface. Channel cuts in this surface, bordered by levee-like structures, are apparent in the seismic data from near the lake margin, suggesting fluvial downcutting and over-bank deposition during seasonal flood events. Periphytic diatoms and peat at the base of a core from the deepest part of the lake overlie compacted sediments, indicating that desiccation was followed by development of shallow-water environments and papyrus swamp in the central basin between 16,700 and 15,100cal BP. As the lake level rose, open-water evaporation from the closed lake caused it to become slightly saline, as indicated by halophytic diatoms. An abrupt return to freshwater conditions occurred at 14,750cal BP, when the lake overflowed into the Blue Nile. Further reflection surfaces with downcut structures are identifiable in seismic images of the overlying sediments, suggesting at least two lesser lake-level falls, tentatively dated to about 12,000 and 8000cal BP. Since Lake Victoria, the source of the White Nile, was also dry until 15,000cal BP, and did not reach overflow until 14,500cal BP, the entire Nile system must have been reduced to intermittent seasonal flow until about 14,500cal BP, when baseflow was re-established with almost simultaneous overflow of the headwater lakes of both the White and Blue Nile rivers. Desiccation of the Nile sources coincides with Heinrich event 1, when cessation of northward heat transport from the tropical Atlantic disrupted the Atlantic monsoon, causing drought in north tropical Africa. The strong reflectors at deeper levels in the seismic sequence of Lake Tana may represent earlier desiccation events, possibly contemporaneous with previous Late Pleistocene Heinrich events.

The Persian Gulf Basin: Geological history, sedimentary formations, and petroleum potential

The Persian Gulf Basin is the richest region of the World in terms of hydrocarbon resources. According to different estimates, the basin contains 55–68% of recoverable oil reserves and more than 40% of gas reserves. The basin is located at the junction of the Arabian Shield and Iranian continental block that belong to two different (Arabian and Eurasian) lithospheric plates. Collision of these plates at the Mesozoic/Cenozoic boundary produced the Zagros Fold Belt and the large Mesopotamian Foredeep, which is a member of the Persian Gulf Basin. During the most part of the Phanerozoic, this basin belonged to an ancient passive margin of Gondwana, which was opened toward the Paleotethys Ocean in the Paleozoic and toward the Neotethys in the Mesozoic. Stable subsidence and the unique landscape-climatic conditions favored the accumulation of a very thick sedimentary lens of carbonate rocks and evaporites (up to 12–13 km and more). Carbonate rocks with excellent reservoir properties are widespread, while the evaporites play the role of regional fluid seals. Organicrich rocks, which can generate liquid and gaseous hydrocarbons (HC), are present at different levels in the rock sequence.

Post-conventional moral reasoning and reputation

Kohlberg’s theory of moral development conceives conventional and post-conventional moral reasoning as consecutive levels in a developmental sequence. This claim was examined in terms of the relationship between preference for these two styles of reasoning on the one hand and moral identity as perceived by others (reputation) and as self-perceived and on the other. Participants ( n = 172), in groups of four mutual acquaintances, provided ratings of one another’s standing, and estimates of their own standing and reputation, on four trait dimensions (moral responsibility, consideration for others, respect for authority, and political orientation). Post-conventional moral reasoning, assessed using the Defining Issues Test, was not significantly related either to reputation or to self-rating on any dimension except political orientation. Conventional reasoning was related to politics though in the opposite direction, but additionally to both self- and other-ratings of moral responsibility and to the corresponding ratings of respect for authority. Findings do not support the view that the conventional/post-conventional distinction in moral reasoning is a developmental difference. An alternative proposed is that these are independent domains of moral thought, related to quite different aspects of social behaviour and political attitudes.

Quadriphasic waveforms are superior to triphasic waveforms for transthoracic defibrillation in a cardiac arrest swine model with high impedance

We have demonstrated previously that triphasic waveform shocks were superior to biphasic waveform shocks for transthoracic defibrillation. Our purpose was to compare the efficacy and safety of quadriphasic versus triphasic shocks for transthoracic defibrillation in a porcine model. Sixteen adult swine (19-25 kg, mean: 21.5 kg) were deeply anesthetized and intubated. To simulate impedance of the human chest, fixed electrical resistors (25 or 50 ohms) was placed in series with the defibrillator and the chest of each pig. After 30 s of electrically induced VF, each pig received transthoracic shocks, using either a truncated exponential triphasic waveform (5 ms positive pulse duration, 5 ms negative pulse duration and 5 ms positive pulse duration, total waveform duration 15 ms) or a quadriphasic waveform (5/5/5/5 ms, total waveform duration 20 ms). Each pig received transthoracic triphasic and quadriphasic shocks at three selected energy levels (50, 100 and 150 J) in random sequence. Four shocks were delivered at each energy level to construct an energy versus % success curve. Success was defined as VF termination at 5 s after shock. The total shocks were divided into three groups based on the delivered energy actually delivered to the animal: <40, 40-65 and >65 J. Delivered energy = (animal impedance/total impedance) times selected energy of the shock. For high-impedance animals (86-102 ohms), quadriphasic waveform shocks achieved significantly higher percent shock success than triphasic shocks for the termination of VF at the energy levels of >65 J actually delivered (quadriphasic 72.7+/-12.2%, triphasic 38.9+/-7.7%, p<0.02). No differences in the shock success between quadriphasic and triphasic waveforms were found for other two energy levels. There were no differences in ventricular tachycardia or asystole after shocks between quadriphasic and triphasic waveforms. In this porcine model, 20 ms (5/5/5/5) quadriphasic shocks were superior to 15 ms (5/5/5) triphasic shocks for transthoracic defibrillation in animals with impedances that simulated high impedance in humans.

Behavioral neuroendocrinology of vasotocin and vasopressin and the sensorimotor processing hypothesis

Vasotocin (AVT) and vasopressin (AVP) are potent modulators of social behaviors in diverse species of vertebrates. This review addresses questions about how and where AVT and AVP act to modulate social behaviors, focusing on research with an amphibian model ( Taricha granulosa). In general, the behaviorally important AVT and AVP neurons occur in the forebrain and project to sites throughout the brain. Social behaviors are modulated by AVT and AVP acting at multiple sites in the brain and at multiple levels in the behavioral sequence. This review proposes that AVT and AVP can act on sensory pathways to modulate the responsiveness of neurons to behaviorally relevant sensory stimuli and also can act on motor pathways in the brainstem and spinal cord to modulate the neuronal output to behavior-specific pattern generators. This neurobehavioral model, in which AVT and AVP are thought to modulate social behaviors by affecting sensorimotor processing, warrants further research.

Speech segment detection and word recognition

In a speech segment detection method, a sequence of speech samples is provided from an input speech signal and a sequence of feature vectors is provided from the speech samples, the feature vectors having respective speech power levels. A minimum speech power among the speech power levels in the feature vector sequence is detected. Normalized speech power levels are computed based on the speech power levels and the minimum speech power. Each of the normalized speech power levels is compared with a predetermined threshold value to detect speech segments in the input speech signal. Further, a speech recognition system and method and a computer-readable medium, using the speech segment detection method, are also disclosed.

Combined tide and wave influence on sedimentation patterns in the Upper Jurassic Swift Formation, south‐eastern Alberta

In south‐eastern Alberta, the Oxfordian Swift Formation comprises two unconformity‐bounded sequences. Sequence 1 consists of the shale member. It unconformably overlies Bathonian calcareous shale of the Rierdon Formation and consists dominantly of shale with uncommon hum‐ mocky cross‐stratified siltstone. The shale member comprises up to four parasequences that show a subtle upward‐fining stacking pattern, suggesting overall deepening in a storm‐dominated fully marine basin. Deposition of the shale member was terminated by a fall in relative sea‐level, which in turn initiated sequence 2. During lowstand, a network of north‐east‐ to south‐west‐trending meandering channels incised the top of sequence 1. Despite the preserved morphology of these channels, observations in core suggest that lowstand deposits are absent. These strata were most likely thoroughly reworked by ravinement processes associated with the ensuing transgression and are recorded only by a thin chert pebble lag. Also associated with transgression were significant changes in the physical and ecological conditions in the local Swift basin. These changes were related to modifications in basin configuration and the development of a low‐energy strait, which probably formed as a result of uplift of the Sweetgrass Arch. Within this newly configured basin, brackish‐water conditions prevailed, and sedimentation was dominated by suspension deposition of mud. Bed‐load sediment, composed mostly of very fine and fine sand, made up only a small part of the total sediment flux into the area and was transported principally by low‐energy combined flows with variable‐speed microtidal currents and a low‐energy oscillatory component related to storm waves. Sand was generally deposited in the form of small, discontinuous sand ridges that developed locally throughout the study area – it is these features that form the principal hydrocarbon reservoir bodies in the Swift Formation in the study area. After initiation, ridges built upwards and migrated laterally in response to transport and preferential local deposition of bed‐load sediment. Although common near the unconformity along the top of sequence 1, sand ridges also occur at several higher stratigraphic levels in sequence 2. These latter ridges, however, are not associated with regionally correlatable discontinuities but, instead, were initiated by local bed irregularities, possibly related to breaking internal waves, and were supplied with new sediment transported into the study area. The origin of these sand ridges is therefore not related to changes in relative sea‐level but, instead, to intrabasinal processes in a low‐energy strait.

Optimization of the step-and-shoot leaf sequence for delivery of intensity modulated radiation therapy using a variable division scheme

To deliver an intensity modulated radiation therapy (IMRT) plan by multileaf collimator (MLC) it is necessary to convert beam profiles, generated from the inverse treatment planning algorithm, into a series of instructions that the MLC control system can execute. An idealized IMRT beam profile can be regarded as a continuously varying two-dimensional function and is usually represented by an intensity map, i.e., a discretized description in space and in intensity of the beam profile. It is common to assume that the intensity map be defined over a regular grid with N steps and equal increments of intensity levels. In reality, this may not be the optimal representation of the beam profile and may introduce unnecessary discrepancies between the intensity pattern delivered and that ideally required. We have implemented an algorithm capable of minimizing the difference between the two patterns on a beam specific basis. In other words, it can produce optimized intensity maps, individually produced to suit the (continuous function) intensity profile they are intended to approximate. This enhancement in conformation is achieved by allowing variable step size and unconstrained intensity levels in the final leaf sequence.

Measurements and predictions of the6s6p1,3P1lifetimes in the Hg isoelectronic sequence

Experimental and theoretical values for the lifetimes of the ${6s6p}^{1}{P}_{1}$ and ${}^{3}{P}_{1}$ levels in the Hg isoelectronic sequence are examined in the context of a data-based isoelectronic systematization. New beam-foil measurements for lifetimes in Pb III and Bi IV are reported and included in a critical evaluation of the available database. These results are combined with ab initio theoretical calculations and linearizing parametrizations to make predictive extrapolations for ions with $84&lt;~Z&lt;~92.$

A Recent History of 14C, 137Cs, 210Pb, and 241Am Accumulation at Two Irish Peat Bog Sites: an East Versus West Coast Comparison

Data on radiocarbon (14C), 137Cs, 210Pb, and 241Am levels in an ombrotrophic peat sequence from a montane site on the east coast of Ireland are compared with data from a similar sequence at an Atlantic peatland site on the west coast. The 14C profiles from the west and east coasts show a broadly similar pattern. Levels increase from 100 pMC or less in the deepest horizons examined, to peak values at the west and east coast sites of 117 ± 0.6 pMC and 132 ± 0.7 pMC, respectively (corresponding to maximal fallout from nuclear weapons testing around 1964), thereafter diminishing to levels of 110–113 pMC near the surface. Significantly, peak levels at the east coast site are considerably higher than corresponding levels at the west coast site, though both are lower than reported peak values for continental regions. The possibility of significant 14C enrichment at the east coast site due to past discharges from nuclear installations in the UK seems unlikely. The 210Pbex inventory at the east coast site (6500 Bq m−2) is significantly higher than at the west coast (5300 Bq m−2) and is consistent with the difference in rainfall at the two sites. Finally, 137Cs and 241Am inventories at the east coast site also exceed those at the west coast site by similar proportions (east:west ratio of approximately 1:1.2).

Predictive data-based exposition of5s5p1,3P1lifetimes in the Cd isoelectronic sequence

Experimental and theoretical values for the lifetimes of the $5s5p{}^{1}{P}_{1}$ and ${}^{3}{P}_{1}$ levels in the Cd isoelectronic sequence are examined in the context of a data-based isoelectronic systematization. Lifetime and energy-level data are combined to account for the effects of intermediate coupling, thereby reducing the data to a regular and slowly varying parametric mapping. This empirically characterizes small contributions due to spin-other-orbit interaction, spin dependences of the radial wave functions, and configuration interaction, and yields accurate interpolative and extrapolative predictions. Multiconfiguration Dirac-Hartree-Fock calculations are used to verify the regularity of these trends, and to examine the extent to which they can be extrapolated to high nuclear charge.

Mildly alkaline basalts from Pavagadh Hill, India: Deccan flood basalts with an asthenospheric origin

Of twelve flows at Pavagadh Hill, the two three-phenocryst-basalt flows with Mg#∼0.70 and Ni/MgO∼33 are the most primitive and perhaps as primitive as any basalts in the Deccan province. Scatter on variation diagrams and the occurrence of primitive flows at two different levels in the volcanic sequence implies that most rocks are probably not, strictly speaking, comagmatic. Nevertheless, mass balance calculations indicate a generalized differentiation scheme from primitive basalt to hawaiite that involved removal of olivine, augite, plagioclase and Fe-Ti oxides in the proportions 40:33:22:5 with ∼ 50% of the magma remaining. Crustal assimilation had a minimal effect on evolution of the basalts but rhyolites at the top of the volcanic sequence may have been produced by crustal melting following prolonged heat release from alkali basalt pooled along fault zones in the continental crust. Major element based calculations indicate that the most primitive basalts were generated by 7 to 10% melting of mantle peridotite. These low percentages of melting, typical of alkali basalts, are consistent with the steep slopes on chondrite-normalized REE diagrams. Low heavy REE concentrations point to residual garnet in the source region. Incompatible element concentrations (e.g. Rb, Ba, Zr, La) in Pavagadh basalts exceed those in Deccan tholeiitic basalts but are substantially lower than those reported for some other Deccan alkali basalts. Obviously Pavagadh basalts do not reflect the lowest percentages of melting and greatest amount of source region metasomatic enrichment attained in the Deccan province. Deccan tholeiitic and alkali basalts are largely characterized by low La/Nb ratios and high La/Ba ratios similar to those in oceanic island basalts. This indicates minimal involvement of the subcontinental lithospheric mantle in their petrogenesis. Comparison with continental mafic magma provinces where a subcontinental lithospheric mantle imprint is common indicates long periods of extension and/or melting of mantle lithosphere still hot from pre-extension subduction are more likely to produce magmas bearing the lithospheric imprint.

Diameter dependence of myogenic tone of human pial arteries. Possible relation to distensibility.

Responses to changes in intraluminal pressure of isolated human pial arteries (200 to 1200 microns i.d.) obtained from patients undergoing neurosurgery were measured. The vessels were cannulated and pressurized (60 mm Hg); vascular diameter and intraluminal pressure were recorded simultaneously. After spontaneous development of steady state tone, intraluminal pressure was changed to both higher and lower levels in random sequence. Human pial arteries exhibited myogenic responses and maintained their diameter over the pressure range of 20 to 100 mm Hg. The level of myogenic tone observed at 30 mm Hg did not vary significantly with artery diameter. In contrast, at 60 and 90 mm Hg, the extent of myogenic tone increased as the diameter decreased (up to 70% to 80% of maximum in 200-microns i.d. arteries). The arteries contracted to KCl 30 mmol/L, norepinephrine 1 mumol/L, and vasopressin 0.1 mumol/L and relaxed to acetylcholine 3 mumol/L. The extent of these responses did not vary with the diameter of the artery. Arterial distensibility, represented by the slope of the tangent of the passive pressure-diameter curve at lower pressures (5 to 50 mm Hg), increased as arteries became smaller. This is consistent with the possibility that the level of myogenic tone is related to vessel distensibility. Human omental arteries of comparable size did not develop myogenic tone but contracted to KCl and norepinephrine and relaxed to acetylcholine to an extent similar to pial arteries. There is a specific gradient of myogenic responsiveness in human pial arteries that varies inversely with their diameter. This tone does not develop in all vascular beds. These levels of tone in the pial circulation would be expected to be of profound functional significance by allowing blood flow to vary widely.

Quadrupole and hexadecapole correlations in rotating nuclei studied within the single-jshell model

The influence of quadrupole and hexadecapole residual interactions on rotational bands is investigated in a single-$j$ shell model. An exact shell-model diagonalization of the quadrupole-plus-hexadecapole Hamiltonian demonstrates that the hexadecapole-hexadecapole interaction can sometimes produce a staggering of energy levels in the yrast sequence; however, long and regular $\ensuremath{\Delta}I=2$ sequences are not obtained. The shell-model results are discussed in terms of the intrinsic deformations extracted by means of the self-consistent Hartree-Fock method. The angular momentum dependence of intrinsic quadrupole and hexadecapole moments ${Q}_{2\ensuremath{\mu}}$ and ${Q}_{4\ensuremath{\mu}}$ is investigated.

Relativistic oscillator strengths for excited state transitions in some ions of the silver isoelectronic sequence

The relativistic quantum defect orbital method has been applied to the study of fine structure 5p2P-nd2D and 5p2P-ns2S (n≥5) transitions (some of them involving highly excited upper levels) in the silver isoelectronic sequence. The resulting oscillator strengths are analyzed in terms of other relativistic results and some available experimental data.

Empirical lifetimes for 4s4p P1,31∘ levels in the zinc isoelectronic sequence

Empirical predictions are reported for the lifetimes of the 4s2–4s4p resonance and intercombination transitions in the Zn isoelectronic sequence. The approach uses a direct-mapping reduction of available energy-level and lifetime data and imposes no theoretical assumptions or restrictions. Measured spectroscopic energy-level data are used to characterize intermediate coupling effects in terms of an effective singlet–triplet mixing angle, which is then used to convert lifetime data into mixing-reduced effective line strength factors. Through a linearizing screening parameterization, these reduced line strength factors are found to exhibit regularities permit accurate interpolation, extrapolation, and smoothing and also provide a convenient exposition for that sensitive comparison between experimental results and ab initio calculations.

Calculations of 2p lifetimes in the Li sequence.

Lifetime predictions for the 2{ital p} {sup 2}{ital P}{sub 1/2} and 2{ital p} {sup 2}{ital P}{sub 3/2} levels in the lithium isoelectronic sequence have been computed for atomic numbers {ital Z}=3--92 using the semiempirical Coulomb approximation with a Hartree-Slater core. This extends our earlier studies of the sodium and copper sequences, and the results agree well with critically selected experimental lifetime measurements. The calculations involve the inclusion of experimental energy level, ionization potential, and core-polarizability data, and we also report here a comprehensive and reliable data base developed through semiempirical parametrizations of spectroscopic measurements and {ital ab} {ital initio} calculations.

Spectra of Cd, In, Sb and Te in laser produced plasmas (5-9.2 Å) and survey of 2p6 nl energy levels in the sodium isoelectronic sequence (Zn XX-Nd L)

The emission spectra of plasma produced by frequency-doubled Nd: YAG laser irradiation (0.53 µm, 600 ps, 5 × 1014W cm−2) of Cd, In, Sb and Te have been photographed in the region 5.0-9.2 Å by means of a flat crystal spectrograph. The transitions from 2p6nl(n = 4-7) to 2p63l' in sodium-like ions are identified by comparison between experimental wavelengths λexp and predictions λREL of the relativistic parametric potential method. By extending these comparisons to the levels of lower-Z elements, systematic trends of Eexp - EREL = f(Z) are derived. The resulting semi-empirical energies are listed from Zn XX to Nd L and lead to recommended wavelengths and to ionization limits. Some features of magnesium-like ion spectra (Cd36+ through Te40+) which overlap sodium-like ion spectra, are briefly described.