bluuebunny/crossref_metadata_2025 huggingface dataset:
Computing in Finite Time
Authors: De Vos Alexis
Published: May 2006

If a message can have n different values and all values are equally probable, then the entropy of the message is log (n). In the present paper, we discuss the expectation value of the entropy, for an arbitrary probability distribution. We introduce a mixture of all possible probability distributions. We assume that the mixing function is uniform.

• either in flat probability space, i.e. the unitary n-dimensional hypertriangle,

• or in Bhattacharyya's spherical statistical space, i.e. the unitary n-dimensional hyperoctant.

A computation is a manipulation of an incoming message, i.e. a mapping in probability space:

• either a reversible mapping, i.e. a symmetry operation (rotation or reflection) in n-dimensional space,

• or an irreversible mapping, i.e. a projection operation from n-dimensional to lower-dimensional space.

During a reversible computation, no isentropic path in the probability space can be found. Therefore we have to conclude that a computation cannot be represented by a message which merely follows a path in n-dimensional probability space. Rather, the point representing the mixing function travels along a path in an infinite-dimensional Hilbert space.
Energy Evolution in Time-Dependent Harmonic Oscillator
Authors: Robnik Marko , Romanovski Valery G.
Published: May 2006

The theory of adiabatic invariants has a long history, and very important implications and applications in many different branches of physics, classically and quantally, but is rarely founded on rigorous results. Here we treat the general time-dependent one-dimensional harmonic oscillator, whose Newton equation [Formula: see text] cannot be solved in general. We follow the time-evolution of an initial ensemble of phase points with sharply defined energy E0at time t = 0 and calculate rigorously the distribution of energy E1after time t = T, which is fully (all moments, including the variance μ2) determined by the first moment [Formula: see text]. For example, [Formula: see text], and all higher even moments are powers of μ2, whilst the odd ones vanish identically. This distribution function does not depend on any further details of the function ω(t) and is in this sense universal. In ideal adiabaticity [Formula: see text], and the variance μ2is zero, whilst for finite T we calculate [Formula: see text], and μ2for the general case using exact WKB-theory to all orders. We prove that if ω(t) is of class [Formula: see text] (all derivatives up to and including the order m are continuous) μ ∝ T-(m+1), whilst for the class [Formula: see text] it is known to be exponential μ ∝ exp (-αT).
Zn uptake by maize under the influence of AM‐fungi and Collembola Folsomia candida
Authors: Seres A. , Bakonyi G. , Posta K.
Published: May 2006

Zn uptake by maize plants may be affected by the presence of arbuscular mycorrhizal fungi (AMF). Collembola often play an important controlling role in the inter‐relationship between AMF and host plants. The objective of this experiment was to examine whether the presence of Collembola at different densities (0.4 and 1 individuals g−1 dry soil) and their activity have any effect on Zn uptake by maize through the plant–AMF system. The presence of the AMF (Glomus intraradices) and of the Collembola species Folsomia candida was studied in a laboratory microcosm experiment, applying a Zn exposure level of 250 mg kg−1 dry soil. Biomass and water content of the plants were no different when only AMF or when both AMF and Collembola were present. In the presence of AMF the Zn content of the plant shoots and roots was significantly higher than without AMF. This effect was reduced by Collembola at both low and high density. High densities of Collembola reduced the extent of AMF colonization of the plant roots and hyphal length in the soil, but low densities had no effect on either. The results of this experiment reveal that the F. candida–G. intraradices interaction affects Zn uptake by maize, but the mechanisms are still unknown.
Acute effect of β amyloid on synchronized spontaneous Ca2+ oscillations in cultured hippocampal networks
Authors: Rui Yanfang , Li Ruxin , Liu Yifu , Zhu Shaoqing , Yu Xinzhu , Sheng Zhonghua , Xie Zuoping
Published: May 2006

The effects of β amyloid (Aβ) on cytoplasmic Ca2+ ([Ca2+]c) have been studied extensively, but the current literature on this aspect is confusing. We reported that 20 μM Aβ25–35 significantly inhibited the synchronized spontaneous cytoplasmic Ca2+ transients immediately after application, whereas it had little effect on the baseline [Ca2+]c concentration in neurons. Aβ1–42 had a similar effect on the Ca2+ transients as Aβ25–35, while it increased baseline [Ca2+]c concentration gradually. However, Aβ1–40 had little effect on either Ca2+ transients or baseline [Ca2+]c. Such differential effects of Aβ on Ca2+ signals might explain, at least partially, the confusing observations from the previous studies and provide important therapeutic implications for preventing or reversing early neuron damage in Alzheimer's disease.
Behavior ontogeny in the elevated plus‐maze: prenatal stress effects
Authors: Estanislau Celio , Morato Silvio
Published: May 2006

Prenatal stress is a putative model for studying some psychopathological disorders. Indeed, submitting pregnant animals to stress leads to enhanced anxiety in the adult offspring. However, little is known about how prenatal stress effects interacts with anxiety throughout development. To study this issue, prenatally stressed rats were tested in the elevated plus‐maze at different ages. During pregnancy female rats were submitted to uncontrollable electric foot shock sessions every other day or kept undisturbed (controls). After delivery, litters from control and stressed dams were left undisturbed from the 3rd to the 14th postnatal days. Male and female rats were tested in the elevated plus‐maze at the ages of 30, 45 or 60 days. The following measures were taken in the elevated plus‐maze: number of entries and time spent in the arms (or their extremities) and frequency and time spent in naturalistic behaviors (stretching, rearing, end exploring, grooming and head dipping). Decreases in the percentage of entries into and in the time spent (only females) in the open arms were shown by 60‐day‐old prenatally stressed rats, but not by 30‐ and 45‐day old. Increased open arm ends exploration was shown by 45‐day‐old prenatally stressed males. Rearing behavior was found to increase with age, a phenomenon more pronounced in females. Additionally, at the younger ages prenatally stressed rats were heavier than controls, an effect which disappeared at young adulthood. In conclusion, anxiogenic prenatal stress effects in the elevated plus‐maze could only be detected at early adulthood, not before. Nonetheless, at late adolescence (45 days of age) prenatal stress leaded to an anxiolytic‐like effect which can be interpreted as increased risk‐taking behavior.
Morphine exposure prevents up‐regulation of MR and GR binding sites in the brain of adult male and female rats due to prenatal stress
Authors: Rimanóczy Ágnes , Šlamberová Romana , Bar Noffar , Vathy Ilona
Published: May 2006

Our previous work demonstrated that the hormone response to stress and the negative feedback inhibition to these hormones are sex‐dependently altered by prenatal morphine exposure in adult rats. An alteration in the glucocorticoid negative feedback inhibition is mediated by glucocorticoid receptors (GR) that are distributed throughout the brain, and mineralocorticoid receptors (MR) localized mainly in the hippocampus and involved in a tonic influence of brain functions. Therefore, the present study examined the binding characteristics of MR and GR in young adult male and female rats exposed prenatally (E11–E18) to morphine (10 mg/kg/2×/day), saline or no treatment at all (controls). At 60–90 days of age, animals were adrenalectomized (ADX) 24 h prior to decapitation. The hippocampus and hypothalamus were dissected for saturation binding assays. The data demonstrate that prenatal stress due to maternal saline injections up‐regulates MR and GR binding in the hippocampus of adult male rats and this effect is prevented by prenatal morphine exposure. There is no effect of prenatal morphine exposure on GR binding in the hypothalamus of males. In female rats, prenatal morphine exposure does not affect the binding of MR and GR in the hippocampus or GR in the hypothalamus relative to controls; however, they are affected by ovarian hormone fluctuation. Moreover, prenatal stress decreases MR binding in the hippocampus of diestrous females and GR binding in the hypothalamus of estrous females. Both decreases are prevented by prenatal morphine exposure. Thus, the present study demonstrates that: (1) prenatal stress due to maternal saline injections alters MR and GR binding of adult male and female rats and is prevented by prenatal morphine exposure; (2) the MR and GR binding in adult female rats are affected by ovarian hormone fluctuations.
Comparative gene mapping in Arabidopsis lyrata chromosomes 1 and 2 and the corresponding A. thaliana chromosome 1: recombination rates, rearrangements and centromere location
Authors: HANSSON BENGT , KAWABE AKIRA , PREUSS SONJA , KUITTINEN HELMI , CHARLESWORTH DEBORAH
Published: May 2006

To add detail to the genetic map of Arabidopsis lyrata, and compare it with that of A. thaliana, we have developed many additional markers in the A. lyrata linkage groups, LG1 and LG2, corresponding to A. thaliana chromosome 1. We used a newly developed method for marker development for single nucleotide polymorphisms present in gene sequences, plus length differences, to map genes in an A. lyrata family, including variants in several genes close to the A. thaliana centromere 1, providing the first data on the location of an A. lyrata centromere; we discuss the implications for the evolution of chromosome 1 of A. thaliana. With our larger marker density, large rearrangements between the two Arabidopsis species are excluded, except for a large inversion on LG2. This was previously known in Capsella; its presence in A. lyrata suggests that, like most other rearrangements, it probably arose in the A. thaliana lineage. Knowing that marker orders are similar, we can now compare homologous, non-rearranged map distances to test the prediction of more frequent crossing-over in the more inbreeding species. Our results support the previous conclusion of similar distances in the two species for A. lyrata LG1 markers. For LG2 markers, the distances were consistently, but non-significantly, larger in A. lyrata. Given the two species' large DNA content difference, the similarity of map lengths, particularly for LG1, suggests that crossing-over is more frequent across comparable physical distances in the inbreeder, A. thaliana, as predicted.
Quantifying the genomic decay paradox due to Muller's ratchet in human mitochondrial DNA
Authors: LOEWE LAURENCE
Published: May 2006

The observation of high mitochondrial mutation rates in human pedigrees has led to the question of how such an asexual genetic system can survive the accumulation of slightly deleterious mutations caused by Muller's ratchet. I define a null model to quantify in unprecedented detail the threat from extinction caused by Muller's ratchet. This model is general enough to explore the biological significance of Muller's ratchet in various species where its operation has been suspected. For increased precision over a wide range of parameter space I employ individual-based simulations run by evolution@home, the first global computing system for evolutionary biology. After compiling realistic values for the key parameters in human mitochondrial DNA (mtDNA) I find that a surprisingly large range of biologically realistic parameter combinations would lead to the extinction of the human line over a period of 20 million years – if accepted wisdom about mtDNA and Muller's ratchet is correct. The resulting genomic decay paradox complements a similar threat from extinction due to mutation accumulation in nuclear DNA and suggests evaluation of unconventional explanations for long-term persistence. A substantial list of potential solutions is given, including compensatory back mutations, mutation rate heterogeneity and occasional recombination in mtDNA. Future work will have to explore which of these actually solves the paradox. Nonetheless, the results presented here provide yet another reason to minimize anthropogenic increase of mutation rates.
Microsatellites reveal extensive geographical, ecological and genetic contacts between invasive and indigenous whitefly biotypes in an insular environment
Authors: DELATTE H. , DAVID P. , GRANIER M. , LETT J. M. , GOLDBACH R. , PETERSCHMITT M. , REYNAUD B.
Published: May 2006

Human-mediated bioinvasions provide the opportunity to study the early stages of contact between formerly allopatric, divergent populations of a species. However, when invasive and resident populations are morphologically similar, it may be very difficult to assess their distribution in the field, as well as the extent of ecological overlap and genetic exchanges between invasive and resident populations. We here illustrate the use of data obtained from a set of eight microsatellite markers together with Bayesian clustering methods to document invasions in a group of major tropical pests, Bemisia tabaci, which comprises several morphologically indistinguishable biotypes with different agronomic impacts. We focus on the island of La Réunion, where an invasive biotype (B) has recently been introduced and now interacts with the resident biotype (Ms). The temporal and spatial distribution, host-plant range and genetic structure of both biotypes are investigated. We showed (i) that, without prior information, clustering methods separate two groups of individuals that can safely be identified as the B and Ms biotypes; (ii) that the B biotype has invaded all regions of the island, and showed no signs of genetic founder effect relative to the Ms biotype; (iii) that the B and Ms biotypes coexist in sympatry throughout most of their geographical ranges, although they tend to segregate into different host plants; and finally (iv) that asymmetrical and locus-specific introgression occurs between the two biotypes when they are in syntopy.
Surgical debridement of craniocervical necrotizing fasciitis: the window of opportunity
Authors: Hanna B C , Delap T G , Scott K , Sinclair S
Published: May 2006

Craniocervical necrotizing fasciitis (CCNF) has a potentially high morbidity and mortality. Late presentation, shock and disseminated intravascular coagulation are associated with a particularly poor prognosis. Early recognition and aggressive treatment is advised. A case report is presented of a late presentation of necrotizing fasciitis of the face, neck and anterior thoracic wall. Despite adverse prognostic indicators, surgical debridement was performed. Intensive medical treatment included continuous renal replacement therapy and intravenous immunoglobulin. Survival in this case illustrates that the window of opportunity for surgically treating CCNF extends to the advanced stages of the disease, albeit with increased morbidity.
Tracheoinnominate fistula: surgical management of an iatrogenic disaster
Authors: Ridley R W , Zwischenberger J B
Published: May 2006

Tracheoinnominate fistula (TIF) is a rare condition with significant potential for mortality if surgical intervention is not immediate. We present two cases of successfully managed TIF. Both cases involve ligation and resection of the innominate artery at the TIF followed by a pectoralis major muscle flap. In both cases, success was largely due to a high index of suspicion and immediate control of the bleeding with transport to the operating room for surgical repair. The history, aetiology, and pathogenesis of TIF are reviewed, yielding an algorithm for recommended management of TIF.
Foreign body mimicking a nasal bone fracture
Authors: Maitra S , Hobbs C G L , Evans K L
Published: May 2006

Nasal foreign bodies are common in young children and are typically the result of intranasal placement by the child. The authors report a case of an extranasal foreign body in an adult, which presented as a nasal fracture following trauma to the nose. This uncommon presentation, previously unreported in the literature, highlights the importance of careful history taking in cases of nasal trauma and of thorough wound exploration if any penetrative injury is found.
Neuzeitliche Mythosdiskussion und altkirchliche Schriftauslegung
Authors: MEISER MARTIN
Published: May 2006

Within the current discussion of myth in New Testament theology this article reconsiders the ongoing myth debate between Greco-Roman, Jewish and Christian authors against the background not of atheism but of philosophical theology. Over against its challenges Greco–Roman authors defend the myth as exemplum within a sociologically framed accommodation theory and interpret problematic texts using allegorical exegesis. Jewish and Christian authors follow these patterns. In particular, ancient Christian commentators on the Bible use the ancient category of ‘myth as exemplum’ to understand the activities of God and Jesus Christ not only as the base but also as an exemplum for the pious life.
The Structure and Argument of 1 Corinthians:
A Biblical/Jewish Approach
Authors: CIAMPA ROY E. , ROSNER BRIAN S.
Published: May 2006

This article argues that when the fundamentally Jewish character of 1 Corinthians is recognized, a clear structure and argument emerges. The order of the material reflects Paul's own agenda seen in patterns elsewhere in his letters. While unity is clearly a significant issue, Paul's main concern is with the purity of the church and the glory of God. The Corinthian church is part of the fulfillment of the OT expectation of worldwide worship of the God of Israel, and as God's eschatological temple they must act in a manner appropriate to their holy status by shunning pagan vices and glorifying God under the lordship of Christ.
Der ursprüngliche Kontext von 2 Kor 6.14–7.1 Zur Frage der Einheitlichkeit des 2. Korintherbriefs
Authors: SCHMELLER THOMAS
Published: May 2006

Die größten Schwierigkeiten bei dem Versuch, 2 Kor als einheitlichen Brief zu lesen, bieten zum einen der Kontextbezug und die unpaulinischen Züge von 6.14–7.1, zum anderen der Anschluss der Kap. 10–13 an den vorangehenden Kontext. Getrennt haben diese beiden Fragen bisher keine überzeugende Lösung gefunden. Die hier vertretene These lautet: Die beiden Schwierigkeiten bedingen sich gegenseitig, denn der Textabschnitt 6.14–7.1 stellte ursprünglich die jetzt fehlende Verbindung zwischen den Kap. 1–9 und 10–13 her und wurde sekundär von dort an seine jetzige Stelle versetzt. Wird diese Versetzung rückgängig gemacht, der Text also zwischen Kap. 9 und 10 eingefügt, erhält er einen klaren Kontextbezug; andererseits entsteht ein sinnvoller Übergang von 1–9 zu 10–13. Es lässt sich plausibel erklären, wie und warum der Text aus seiner ursprünglichen Kontextstellung gelöst und an seiner jetzigen Stelle eingefügt wurde.
The Perfection of ‘Love for Offspring’: Greek Representations of Maternal Affection and the Achievement of the Heroine of 4 Maccabees
Authors: DESILVA DAVID A.
Published: May 2006

A close comparison with Plutarch's De amore prolis and Aristotle's Nicomachean Ethics shows the author of 4 Maccabees to have used common topics from Greek ethical reflection on love for offspring as a means of commending Torah-observance as the means by which one is enabled to secure one's children's eternal well-being, fulfilling the natural goal of love for offspring more completely. The author shows how trust in God's future enables the mother to view even the death of her children as the fulfillment rather than the negation of her maternal investment, as in the laments of Euripides's heroines in Trojan Women and Hecuba, from which the author explicitly distances her, enabling her exemplary courage.
The Foundations of Godwinian Impartiality
Authors: LAMB ROBERT
Published: May 2006

William Godwin is often cited in contemporary philosophical discussions of ethical impartiality, within which he functions as a sort of shorthand for a particularly crude and extreme act-utilitarianism, one that contains no foundational commitments other than the maximizing of some conception of the general good. This article offers a reinterpretation of Godwin's argument, by focusing closely on the ambiguous nature of its justificatory foundations. Although utilitarian political theories seem to have two possible justifications available to them – egalitarian and teleological – there has been little effort to establish which one of them Godwin's argument for impartiality relies on. This problem becomes more complicated when it is acknowledged that Godwin actually provides two different justifications for impartiality, only one of which is consequentialist. The other seems to make a case based on the recognition of moral worth and virtue. This is something confirmed through analysis of Godwin's writings on equality and suggests his political theory is more complex than most philosophers are willing to admit.
Against Individualistic Justifications of Property Rights
Authors: CRUFT ROWAN
Published: May 2006

In this article I argue that, despite the views of such theorists as Locke, Hart and Raz, most of a person's property rights cannot be individualistically justified. Instead most property rights, if justified at all, must be justified on non-individualistic (e.g. consequentialist) grounds. This, I suggest, implies that most property rights cannot be morally fundamental ‘human rights’.
Structuring Assessments of Psychopathology
Authors: Hofstee Willem K.B. , Barelds Dick P.H. , Ten Berge Jos M.F.
Published: May 2006

Hofstee and Ten Berge (2004a) have proposed a new look at personality assessment data, based on a bipolar proportional (-1, .. . 0, .. . +1) scale, a corresponding coefficient of raw-scores likeness L = ΢XY/N, and raw-scores principal component analysis. In a normal sample, the approach resulted in a structure dominated by a first principal component, according to which most people are faintly to mildly socially desirable. We hypothesized that a more differentiated structure would arise in a clinical sample. We analyzed the scores of 775 psychiatric clients on the 132 items of the Dutch Personality Questionnaire (NPV). In comparison to a normative sample (N = 3140), the eigenvalue for the first principal component appeared to be 1.7 times as small, indicating that such clients have less personality (social desirability) in common. Still, the match between the structures in the two samples was excellent after oblique rotation of the loadings. We applied the abridged m-dimensional circumplex design, by which persons are typed by their two highest scores on the principal components, to the scores on the first four principal components. We identified five types: Indignant (1-), Resilient (1-2+), Nervous (1-2-), Obsessive-Compulsive (1-3-), and Introverted (1-4-), covering 40% of the psychiatric sample. Some 26% of the individuals had negligible scores on all type vectors. We discuss the potential and the limitations of our approach in a clinical context.
The Effect of Follower Regulatory Focus and Extraversion on Leadership Behavior
Authors: Moss Simon , Ritossa Damian , Ngu Simon
Published: May 2006

The principle of regulatory fit implies that managers should demonstrate more transformational leadership, and refrain from critical or detached behavior, if their subordinates exhibit a promotion focus or extraverted personality. Furthermore, emotional intelligence should enhance the capacity of managers to adapt their leadership style and accommodate these characteristics of employees. To assess these propositions, 263 pairs of managers and subordinates completed questionnaires that assess the emotional intelligence and leadership style of the manager as well as the regulatory focus and organizational commitment of the subordinate. Critical, detached leadership was especially likely to be inversely related to the commitment of subordinates who demonstrated a promotion focus. Nevertheless, relative to other managers, individuals who reported emotional intelligence were not more likely to demonstrate transformational leadership, or abstain from critical, detached behavior, when their subordinates focused on promotion. A second study, in which 166 pairs of nurses and their supervisors participated, revealed that managers who claimed to understand the emotions of other individuals seemed to curb their critical, detached behavior when their subordinates were extraverted. Taken together, these findings suggest that emotional intelligence might enhance the capacity of managers to adapt their leadership style appropriately, but only in some contexts.
The Acadian fold belt in the Meguma Terrane, Nova Scotia: Cross sections, fold mechanisms, and tectonic implications
Authors: Culshaw Nicholas , Lee Sharon K. Y.
Published: May 2006

Structural data and cross sections from the eastern part of the Devonian‐Carboniferous fold belt of the Meguma Terrane give insight into its structural development and crustal tectonics. The sandy Goldenville Formation, the active competent member during buckling, formed a multilayer several kilometers thick that lay beneath the denser, softer muds and silts of the Halifax Formation. Cross sections reveal 2 orders of folds: 11–18 km wavelength folds are interpreted as resulting from buckling under the influence of gravity; 4–6 km wavelength folds reflect the thickness of the multilayer with buckle shortening in the range 32–44%. Depth to detachment derived from the sections (11–13.5 km below present erosion surface) is such that given the depth of the detachment below the paleosurface during the main phase (pre‐Devonian granite) of folding, it would likely have been a relatively soft and thick shear zone that would have influenced profile geometry of the main phase folds at this stage of fold belt development. Granite production that may have been triggered by mantle delamination during continuing convergence accompanying terminal Pangean assembly and ocean basin closure was followed by rapid exhumation. Later localized deformation (Late Devonian–Carboniferous) in the fold belt took place as the Meguma Terrane was displaced along the terrane‐bounding Cobequid‐Chedabucto fault system. The characteristic asymmetric cross sections of structures of this phase are attributed to cooling and strengthening of the detachment that was a consequence of the postgranite uplift and exhumation.
Effects of charge exchange and electron impact ionization on the formation of the magnetic pileup boundary at Mars
Authors: Jin H. , Maezawa K. , Mukai T.
Published: May 2006

A relatively sharp increase in the solar wind magnetic field, Magnetic Pileup Boundary (MPB), has been observed in the inner Martian magnetosheath. We examined effects of exospheric processes, such as charge exchange reactions (CE) and electron impact ionizations (EII), on the formation of the MPB by using a newly developed two‐dimensional global MHD model coupled to Monte Carlo simulations. The CE and EII processes change the energy distribution of the solar wind plasma, causing a depletion of the thermal pressure, and thus an enhancement of magnetic pressure so as to maintain the pressure balance in the radial direction. Beside decreasing the thermal pressure, these processes decelerate the solar wind by adding mass of slow ions (protons and oxygen ions). These processes were treated self‐consistently in the new MHD model. The MHD model implicitly includes the time evolution of ion and electron distributions being deformed from Maxwellian shapes under the influence of CE and EII reactions, by making use of their reaction rate coefficients that were derived as functions of “effective temperatures” from Monte Carlo simulations. The MHD simulation results suggest that an enhancement of magnetic field magnitude occurs in the inner magnetosheath mainly due to the CE effect at the solar minimum and to the EII effect at the solar maximum. EII also decelerates the solar wind significantly through the mass‐loading effect, which lengthens the interaction time between the solar wind plasma and the exospheric atoms, resulting in an additional enhancement of magnetic field magnitude both at the solar minimum and maximum. It was also found that these exospheric processes significantly influence the ion density profiles above the upper ionosphere. The large and nearly constant scale height of total ion density as observed by past measurements can be caused by the EII process. Moreover, EII produces a large number of O+ ions above the ionopause especially at the solar maximum, which is potentially important in terms of atmospheric escape.
Comparisons between MHD model calculations and observations of Cassini flybys of Titan
Authors: Ma Yingjuan , Nagy Andrew F. , Cravens Thomas E. , Sokolov Igor V. , Hansen Kenneth C. , Wahlund Jan‐Erik , Crary Frank J. , Coates Andrew J. , Dougherty Michele K.
Published: May 2006

The Cassini spacecraft passed by Titan on 26 October 2004 (Ta flyby) and 13 December 2004 (Tb flyby). In both cases the Cassini Orbiter entered Titan's ionosphere and flew through Titan's dynamic wake region. In this paper, we present our simulation results of these two flybys using our three‐dimensional multispecies MHD model. This model is a slightly updated version of the model outlined by Ma et al. (2004a); the main difference is the inclusion of magnetic diffusion into the equations. The calculations used the best available upstream plasma and magnetic field parameters obtained by the Cassini instrument complement. The calculated parameters, corresponding to the Cassini flybys near the closest approach, are compared with the relevant observed values. There is a reasonably good but clearly not perfect agreement between the measured and calculated values. Some of these differences are believed to be due to the uncertainties and time variability associated with the upstream parameters and some differences must definitely be the result of the uncertainties in the parameters selected for the model, as well as the limitations associated with the MHD approximations.
CO2 flux measurements in volcanic areas using the dynamic concentration method: Influence of soil permeability
Authors: Camarda M. , Gurrieri S. , Valenza M.
Published: May 2006

In order to evaluate the influence of soil permeability on soil CO2 flux measurements performed with the dynamic concentration method, several tests were carried out using soils characterized by different permeability values and flow rates. A special device was assembled in the laboratory to create a one‐dimensional gas flow through a soil of known permeability. Using the advective‐diffusion theory, a physical model to predict soil concentration gradients was also developed. The calculated values of CO2 concentrations at different depths were compared with those measured during the tests and a good agreement was found. Four soils with different gas permeability (3.6 × 10−2 to 1.23 × 102 μm2) were used. The CO2 flux values were varied from 0.1 kg m−2 d−1 up to 22 kg m−2 d−1. On the basis of these results, a new empirical equation for calculating very accurate soil CO2 flux from dynamic concentration and soil permeability values was proposed. As highlighted by the experimental data, the influence of soil permeability on CO2 flux measurements depends on various factors, of which the flow rate of the suction pump is the most important. Setting low values for the pumping flux (0.4–0.8 L min−1), the mean error due to soil permeability was lower than 5%. Finally, the method was tested by measuring the CO2 flux in a grid of 48 sampling sites on Vulcano (Aeolian Islands, Italy), and the global error, affecting the CO2 flux measurements in a real application, was evaluated.
Spatial distribution of zooplankton size spectra on the French continental shelf of the Bay of Biscay during spring 2000 and 2001
Authors: Sourisseau Marc , Carlotti François
Published: May 2006

During two cruises in springtime (18 March to 13 April 2000 and 27 March to 4 June 2001), the whole French continental shelf of the Bay of Biscay was sampled to obtain an overview on the zooplankton community size structure. A laboratory optical plankton counter (OPC‐1L) was used to process plankton net tow samples and estimate abundance, biovolume, and general characteristics of size spectra. In a second step, biomass estimates were extrapolated from size by using a conversion factor. Both biomass and abundance estimates show spatial patterns with a clear coastal‐open sea gradient for both years. The coastal area was characterized by the highest biomasses and abundances per volume. A first analysis of the zooplankton community size spectra was made by using the slope of the normalized biomass size spectrum. Different spatial patterns of zooplankton size spectra were highlighted for spring 2000 and 2001. The highest slopes were found for the coastal zone, showing a large ratio of small organisms, although this was less marked in the springtime 2000. Stations characterized by high proportions of large organisms were located in majority in the north of the bay and at the shelf break. A second analysis using the size probability distributions of organisms revealed a nearly permanent nonlinearity of probability distributions. This implied the community structure was not in an equilibrium state during spring and this nonlinearity could be locally related to dominant species dynamics.
Occurrence of fragile particles inferred from optical plankton counters used in situ and to analyze net samples collected simultaneously
Authors: González‐Quirós R. , Checkley D. M.
Published: May 2006

We hypothesized that the optical plankton counter (OPC) senses particles in situ that are not collected by nets and analyzed in the laboratory. An OPC was deployed in situ between 1998 and 2004 in the mouth of a bongo net with 505‐μm‐mesh nets in the upper 210 m at stations in the California Current Region. Here we compare paired data sets from the OPC in situ and the OPC analysis in the laboratory of the simultaneously collected net samples for four seasons of 2 years. We restricted our analysis to particle sizes 1.26–6.35 mm equivalent spherical diameter (ESD), a size class shown from the lab OPC data to be retained efficiently by the net. On average, 4 (3) times more particles by number (volume) were sensed in situ by the OPC than sensed in net collections by the OPC in the lab. These values varied an order of magnitude among the eight cruises examined. Time of day, distance offshore, season, year, chlorophyll a concentration, and Brunt‐Väisälä frequency each explained significant variation in these differences. The excess of particles sensed in situ over that measured in the net samples was due primarily to smaller particles in the 1.26–6.35 mm ESD range. We infer that the particles measured by the OPC in situ but not in the lab were fragile and thus not collected by the net. We hypothesize that these fragile particles are primarily aggregates and abandoned houses of larvaceans.
Spatial variability in plankton biomass and hydrographic variables along an axial transect in Chesapeake Bay
Authors: Zhang X. , Roman M. , Kimmel D. , McGilliard C. , Boicourt W.
Published: May 2006

High‐resolution, axial sampling surveys were conducted in Chesapeake Bay during April, July, and October from 1996 to 2000 using a towed sampling device equipped with sensors for depth, temperature, conductivity, oxygen, fluorescence, and an optical plankton counter (OPC). The results suggest that the axial distribution and variability of hydrographic and biological parameters in Chesapeake Bay were primarily influenced by the source and magnitude of freshwater input. Bay‐wide spatial trends in the water column‐averaged values of salinity were linear functions of distance from the main source of freshwater, the Susquehanna River, at the head of the bay. However, spatial trends in the water column‐averaged values of temperature, dissolved oxygen, chlorophyll‐a and zooplankton biomass were nonlinear along the axis of the bay. Autocorrelation analysis and the residuals of linear and quadratic regressions between each variable and latitude were used to quantify the patch sizes for each axial transect. The patch sizes of each variable depended on whether the data were detrended, and the detrending techniques applied. However, the patch size of each variable was generally larger using the original data compared to the detrended data. The patch sizes of salinity were larger than those for dissolved oxygen, chlorophyll‐a and zooplankton biomass, suggesting that more localized processes influence the production and consumption of plankton. This high‐resolution quantification of the zooplankton spatial variability and patch size can be used for more realistic assessments of the zooplankton forage base for larval fish species.
Lensing effect on underwater levels of UV radiation
Authors: Deckert R. , Michael K. J.
Published: May 2006

In the austral spring/summer the Antarctic ozone hole can cause enhanced UVB radiation events in the photic zone of the Southern Ocean. If these events coincide with rich shallow‐water algal blooms in the marginal ice zone, a high mortality rate can result. The contribution to the sub‐surface radiation field of UVB light flashes created through the focusing of collimated solar radiation by surface waves is sought. A three‐dimensional Monte Carlo model with cyclic boundaries was developed to investigate the intensity and temporal characteristics of UVB light flashes. The model accounts for reflection, refraction, absorption and scattering of photons, and is based on a data set of ocean optical properties from 280 to 700 nm. The model includes the effect of biogenic particles and covarying yellow substance. Model runs were performed with collimated light for both 350 and 300 nm. Runs for a flat ocean surface revealed a rapid increase of statistical fluctuations (noise) with depth. This increase was more pronounced at 300 nm. Model runs with sinusoidal surface waves showed significant light flashes which were stronger and penetrated more deeply at 350 nm. At 300 nm, the flashes could exceed the collimated part of surface irradiance for 25% of the time, but were negligible at depths greater than 3.7 m. Small sinusoidal waves produced a more intense focus at a shallower depth than larger sinusoidal waves of the same steepness. Model runs with a more complex ocean surface were less conclusive, as the light flashes were disguised by variations in the water elevation.
Application of window functions for full spectrum inversion of cross‐link radio occultation data
Authors: Lohmann Martin S. , Jensen Arne Skov , Benzon Hans‐Henrik , Nielsen Alan Steen
Published: May 2006

The full spectrum inversion (FSI) technique allows for effective retrieval of profiles of bending angle and optical depth. These profiles are directly derived from a Fourier transform of a measured radio occulation (RO) signal. Though the entire signal is used in the FSI Fourier transform, only some fraction of the signal contributes significantly to each pair of bending angle and optical depth, whereas noise and disturbances throughout the signal contribute to the errors for all pairs of bending angle and optical depth. The impact from noise and other disturbances may be reduced if window functions are applied in the computation of individual Fourier components. In this study, it is demonstrated how window functions can be applied to the FSI technique. In the approach described here, the window functions are applied in the frequency domain, and it is demonstrated that this technique can be applied in an iterative way to further reduce the impact of noise and disturbances. To assess the merits of using window functions, we apply the windowed FSI to simulated cross‐link signals. The results from the simulations show that application of window functions in the FSI technique results in some noise reduction for both white noise and a spike in the signal, whereas iterative use of the window functions was found to significantly reduce the errors from these noise sources, as compared to standard FSI retrieval. It was also found that in terms of relative errors, retrieved derivatives of optical depth are far more sensitive to signal disturbances than retrieved bending angles.
Perils of the GPS phase scintillation index (σϕ)
Authors: Beach Theodore L.
Published: May 2006

The phase scintillation index (σϕ), equal to the standard deviation of measured phase, is often used to characterize Global Positioning System (GPS) observations in ionospheric environments that may be scintillated. Since σϕ is dominated by large‐scale fluctuations, questions of usage and interpretation exist as will be illustrated here. Beyond traditional concerns with detrending, multipath and receiver phase noise, there are at least two issues to be considered. The first is the marginal suitability of σϕ to characterize a power law phase screen with a poorly defined low‐frequency component (e.g., outer scale). Second, observed σϕ parameters may not be relevant to GPS receiver tracking impacts. These arguments are outlined here in greater detail and are illustrated with simple one‐dimensional phase screen propagation modeling results. The conclusion is that GPS σϕ values depend critically on the circumstances of measurement and are difficult to compare among observations without additional knowledge, particularly of relative ionospheric drift and irregularity orientation, that may not be available from an isolated GPS receiver. The development of suitable alternative measures requires careful consideration of the elements of GPS scintillation and its impacts. The broader GPS scintillation community should take an active role in developing suitable replacement measures for σϕ.
Spatial organization and ecohydrological interactions in oxygen‐limited vegetation ecosystems
Authors: Marani Marco , Silvestri Sonia , Belluco Enrica , Ursino Nadia , Comerlati Andrea , Tosatto Omar , Putti Mario
Published: May 2006

Wetlands are characterized by extremely high biodiversity and primary productivity (comparable to tropical rain forests), provide critical habitats for rare and endangered vegetation and animal species, and mediate the effects of floods and the action of the sea on the coast. A deep understanding of wetland system functioning cannot be acquired by simply reducing its dynamics to a collection of parts but requires the explicit description of wetland physical and ecological processes as fully interacting components. In fact, the complex spatial ecohydrological patterns characterizing wetland areas arise as a result of the coupled evolution of their ecological, hydrological, and morphological features. Here we examine observations of prominent spatial patterns in wetland vegetation and link them to the relevant hydrological and ecological processes. We describe the limitations to vegetation development due to scarce soil oxygen availability and implement a mathematical model, based on Richards' equation, coupling subsurface water flow and plant water uptake in a tidal salt marsh. The soil aeration patterns arising from such interactions highlight the central role of vegetation in increasing soil aeration, possibly inducing the establishment of a permanently aerated soil layer (in spite of tidal flooding), and the influence of different soil characteristics on soil oxygen availability. Finally, we discuss how ecohydrological interactions can contribute to explain patterns of vegetation colonization and spatial heterogeneity.
Effect of impurity on the elasticity of perovskite and postperovskite: Velocity contrast across the postperovskite transition in (Mg,Fe,Al)(Si,Al)O3
Authors: Tsuchiya Taku , Tsuchiya Jun
Published: May 2006

We calculated the acoustic velocity contrasts between perovskite and postperovskite in MgSiO3, FeSiO3 and Al2O3 compounds, using the planewave pseudopotential method for a pressure range of the Earth's lower mantle. Both FeSiO3 and Al2O3 pv and ppv have about 20% smaller shear moduli than Mg‐phases at deep mantle pressures, though the bulk moduli are comparable, consistent with previous studies. For the relative variations of shear to compressional velocities, bulk to shear velocities and density to shear velocity at constant pressure due to variations in Fe and Al content up to 20 mol%, we find RS/P of 1.5∼2.2, RΦ/S of 0.1∼0.4 and Rρ/S of −1.0∼−0.2. Both Fe and Al influence elasticity of ppv more than that of pv. Therefore velocity contrasts across the postperovskite phase change would decrease with increasing Fe and Al content. We find that positive velocity variations are hardly produced in pv with the MORB composition.
Three‐dimensional structures and dynamics in the deep mantle: Effects of post‐perovskite phase change and deep mantle layering
Authors: Nakagawa Takashi , Tackley Paul J.
Published: May 2006

Three‐dimensional numerical simulations of thermo‐chemical mantle convection with multiple phase transitions (olivine‐spinel‐perovskite‐post perovskite) are used to investigate the morphology of compositional and post‐perovskite (PPV) boundary structures above the core‐mantle boundary (CMB). Compositionally‐dense subducted MORB partially segregates above the CMB forming ridge‐like dense piles, morphologically similar to structures in previous spherical or Cartesian studies in which a dense layer was inserted a priori. An anti‐correlation is observed between regions where a thick post‐perovskite layer occurs and regions containing piles of dense material, as in our previous two‐dimensional study. Lateral variations in the thickness or occurrence of a PPV layer cause very strong seismic shear‐wave velocity anomalies which may dominate thermal or composition‐related seismic heterogeneity in the depth range where the variable PPV boundary occurs, and also generate sharp‐sided structures as observed seismologically. Both compositional and PPV effects may be necessary to simultaneously explain large‐scale heterogeneity and the global distribution of the discontinuity atop D″.
Observed radar reflectivity in convectively coupled Kelvin and mixed Rossby‐gravity waves
Authors: Swann A. , Sobel A. H. , Yuter S. E. , Kiladis G. N.
Published: May 2006

Propagating disturbances in the tropical atmosphere exhibiting characteristics of linear equatorial waves have been shown to be “coupled” to convection. In some cases, a rain event at a specific location can be associated with a particular wave of sufficiently large amplitude. Rain events spanning three years at Kwajalein Atoll, Republic of the Marshall Islands, 8.72°N 167.73°E, are classified by associated wave type (i.e. Kelvin or mixed Rossby‐gravity (MRG)) using space‐time spectral‐filtered outgoing longwave radiation (OLR). Contoured frequency by altitude diagrams (CFADs) of radar for the classified dates were compared between the two groups. The Kelvin wave accumulated CFAD has a distribution shifted to lower reflectivities compared to MRG suggesting that Kelvin storms likely contain a larger fraction of stratiform to convective area compared to MRG storms.