bluuebunny/crossref_metadata_2025 huggingface dataset:
Deformation and breakup of a viscoelastic drop in a Newtonian matrix under steady shear
Authors: AGGARWAL NISHITH , SARKAR KAUSIK
Published: July 2007

The deformation of a viscoelastic drop suspended in a Newtonian fluid subjected to a steady shear is investigated using a front-tracking finite-difference method. The viscoelasticity is modelled using the Oldroyd-B constitutive equation. The drop response with increasing relaxation time λ and varying polymeric to the total drop viscosity ratio β is studied and explained by examining the elastic and viscous stresses at the interface. Steady-state drop deformation was seen to decrease from its Newtonian value with increasing viscoelasticity. A slight non-monotonicity in steady-state deformation with increasing Deborah number is observed at high Capillary numbers. Transient drop deformation displays an overshoot before settling down to a lower value of deformation. The overshoot increases with increasing β. The drop shows slightly decreased alignment with the flow with increasing viscoelasticity. A simple ordinary differential equation model is developed to explain the various behaviours and the scalings observed numerically. The critical Capillary number for drop breakup is observed to increase with Deborah number owing to the inhibitive effects of viscoelasticity, the increase being linear for small Deborah number.
Two-layer quasi-geostrophic singular vortices embedded in a regular flow. Part 1. Invariants of motion and stability of vortex pairs
Authors: REZNIK GREGORY , KIZNER ZIV
Published: July 2007

The concept of a quasi-geostrophic singular vortex is extended to several types of two-layer model: a rigid-lid two-layer, a free-surface two-layer and a $2{\textstyle{1 \over 2}}$-layer model with two active and one passive layer. Generally, a singular vortex differs from a conventional point vortex in that the intrinsic vorticity of a singular vortex, in addition to delta-function, contains an exponentially decaying term. The theory developed herein occupies an intermediate position between discrete and fully continuous multilayer models, since the regular flow and its interaction with the singular vortices are also taken into account. A system of equations describing the joint evolution of the vortices and the regular field is presented, and integrals expressing the conservation of enstrophy, energy, momentum and mass are derived. Using these integrals, the initial phases of evolution of an individual singular vortex confined to one layer and of a coaxial pair of vortices positioned in different layers of a two-layer fluid on a beta-plane are described. A valuable application of the conservation integrals is related to the stability analysis of point-vortex pairs within the $1{\textstyle{1 \over 2}}$-layer model, $2{\textstyle{1 \over 2}}$-layer model, and free-surface two-layer model on the f-plane. Such vortex pairs are shown to be nonlinearly stable with respect to any small perturbation provided its regular-flow energy and enstrophy are finite.
Two-layer quasi-geostrophic singular vortices embedded in a regular flow. Part 2. Steady and unsteady drift of individual vortices on a beta-plane
Authors: REZNIK GREGORY , KIZNER ZIV
Published: July 2007

Drift of individual β-plane vortices confined to one layer of a two-layer fluid under the rigid-lid condition is considered. For this purpose, the theory of two-layer quasi-geostrophic singular vortices is employed. On a β-plane, any non-zonal displacement of a singular vortex results in the development of a regular flow. An individual singular β-plane vortex cannot be steady on its own: the vortex moves coexisting with a regular flow, be the drift steady or not. In this paper, both kinds of drift of a singular vortex are considered. A new steady exact solution is presented, a hybrid regular–singular modon. This hybrid modon consists of a dipole component and a circularly symmetric rider. The dipole is regular, and the rider is a superposition of the singular vortex and a regular circularly symmetric field. The unsteady drift of a singular vortex residing in one of the layers is considered under the condition that, at the initial instant, the regular field is absent. The development of barotropic and baroclinic regular β-gyres is examined. Whereas the barotropic and baroclinic modes of the singular vortex are comparable in magnitudes, the baroclinic β-gyres attenuate with time, making the trajectory of the vortex close to that of a barotropic monopole on a β-plane.
Turbulent spots in the asymptotic suction boundary layer
Authors: LEVIN ORI , HENNINGSON DAN S.
Published: July 2007

Amplitude thresholds for transition of localized disturbances, their breakdown to turbulence and the development of turbulent spots in the asymptotic suction boundary layer are studied using direct numerical simulations. A parametric study of the horizontal scales of the initial disturbance is performed and the disturbances that lead to the highest growth under the conditions investigated are used in the simulations. The Reynolds-number dependence of the threshold amplitude of a localized disturbance is investigated for 500≤ Re ≤ 1200, based on the free-stream velocity and the displacement thickness. It is found that the threshold amplitude scales as Re−1.5 for the considered Reynolds numbers. For Re ≤ 367, the localized disturbance does not lead to a turbulent spot and this provides an estimate of the critical Reynolds number for the onset of turbulence. When the localized disturbance breaks down to a turbulent spot, it happens through the development of hairpin and spiral vortices. The shape and spreading rate of the turbulent spot are determined for Re = 500, 800 and 1200. Flow visualizations reveal that the turbulent spot takes a bullet-shaped form that becomes more distinct for higher Reynolds numbers. Long streaks extend in front of the spot and in its wake a calm region exists. The spreading rate of the turbulent spot is found to increase with increasing Reynolds number.
Experiments on gravity currents propagating down slopes. Part 1. The release of a fixed volume of heavy fluid from an enclosed lock into an open channel
Authors: MAXWORTHY T. , NOKES R. I.
Published: July 2007

Gravity currents formed by the release of heavy fluid from an enclosed lock on a sloping open channel were investigated experimentally. The experiments were conducted in a channel that had a running length of 13 lock depths, and could be inclined to a maximum angle of 17°. The release of heavy dyed salt solution from a lock with an aspect ratio (height to length) of 0.5, was examined using video images to determine the front velocity, and a particle-tracking technique was used to measure the two-dimensional velocity field in a vertical slice through the centre of the evolving current. The gravity current head velocity increased with time and downstream distance to a maximum at approximately 10 lock depths from the front of the lock. Flow visualization and the velocity measurements have shown that during the acceleration phase the head was being fed by a following current that increased its buoyancy as it propagated downstream. A modified version of the theory of P. Beghin, E. J. Hopfinger and R. E. Britter (J. Fluid Mech.vol. 107, 1981, p. 407) in which the measured increase in buoyancy was used, instead of the original assumption of constant buoyancy, gave results that agreed closely with the experimental velocity versus time histories.
On the topology of vortex lines and tubes
Authors: FUENTES O. U. VELASCO
Published: July 2007

This paper examines the widespread idea that vortex lines and tubes must either close on themselves or extend to the boundary of the fluid. A survey of the origins of this misconception, and of earlier attempts to set it right, is followed by an analysis of simple flows exhibiting vortex lines and tubes which do not fit those shapes. Two types of vortex lines are discussed:dense, which comprise open lines of infinite length but confined in a finite region, andseparatrix, which comprise lines that begin or finish within the fluid, at points where the vorticity is null. The presence of these vortex lines in a vortex tube affects its topology in the following ways. Vortex tubes formed by dense vortex lines have infinite length; they self-intersect an infinite number of times but do not close on themselves. Vortex tubes formed by separatrix vortex lines (and either closed or open vortex lines) are torn apart at the points where the vorticity is null. Vortex tubes exclusively composed of separatrix vortex lines begin or finish at points or surfaces within the fluid; in this particular situation the vortex tube has zero strength.
Gemination in Tashlhiyt Berber: an acoustic and articulatory study
Authors: Ridouane Rachid
Published: July 2007

Tashlhiyt Berber contrasts singletons and geminates in intervocalic as well as in initial and final positions. This study presents results of an investigation of the phonetic correlates that distinguish these types of segments in these three positions. A claim has been made that Tashlhiyt Berber geminates are simple segments that are distinguished from their singleton counterparts primarily by tenseness. This proposal is not supported by our data. The examination of ten temporal and non-temporal parameters shows that consonant duration is the most systematic correlate across all types of consonants and positions, even for voiceless stops after pause. Preceding vowel duration and, to a lesser degree, amplitude of the release were also found to be significantly affected by gemination. These additional characteristics, interpreted as enhancing correlates, may be present in order to increase the perceptual distance between the two phonemic categories.
F2 variation in Newcastle and Leeds English liquid systems
Authors: Carter Paul , Local John
Published: July 2007

In this paper we present a production study designed to explore the relationship between three observations which have previously been made about liquids in British English: first, that laterals have prosodically-determined ‘clear’ (syllable-initial) and ‘dark’ (syllable-final) variants; second, that some varieties of English have either clear [1] in all positions or dark [l] in all positions; third, that some varieties with clear [1] have dark [r] while some varieties with dark [1] have clear [r] (in broad phonetic transcription). We take F2 as an acoustic correlate of clearness/darkness and report on F2 variation in two representative varieties of British English, one which has clear initial [1] (Newcastle-upon-Tyne) and one with dark initial [1] (Leeds). We show that Newcastle English has higher F2 frequencies in [1] than in [r] and that the reverse pattern is found in Leeds English. These patterns can also be found in adjacent unstressed vowels but not in adjacent stressed vowels. Final [1] in both varieties has a lower F2 than initial [1]. In intervocalic contexts, these F2 distinctions in the liquids are observed in iambic words for both varieties. In trochaic words they are observed for Leeds only, though the vowel effects can be observed in both varieties. We discuss some phonological consequences of these findings.
The Belgian Limburg dialect of Hamont
Authors: Verhoeven Jo
Published: July 2007

Hamont is a small town located on the north-eastern edge of the Belgian province of Limburg, on the national border with the Netherlands. It is situated about 30 km south of Eindhoven and 15 km west of Weert in the Netherlands. The town has about 13,500 inhabitants. According to Belemans, Kruijsen & Van Keymeulen (1998), the dialect of Hamont belongs to the West Limburg dialects (subclassification: Dommellands). Limburg dialects occupy a unique position among the Belgian and Dutch dialects in that their prosodic system has a lexical tone distinction, which is traditionally referred to as SLEEPTOON ‘dragging tone’ and STOOTTOON ‘push tone’. In line with recent conventions, stoottoon is referred to as Accent 1 and transcribed as superscript 1; sleeptoon is referred to as Accent 2 and is transcribed as superscript 2 (cf. Schmidt 1986).
Tera
Authors: Tench Paul
Published: July 2007

Tera is the Hausa and English name for the Nyimatli [nimaáli] people as they call themselves, and their language. Their communities lie principally in the north and east of present-day Gombe State and in the adjoining area of Borno State in north-eastern Nigeria. There are approximately 100,000 people who speak the language as their mother tongue (Gordon & Grimes 2005: 175), many of whom also use Hausa as the local lingua franca; increasing numbers are trilingual as the result of the growing importance of English in commerce and education.
Area fees and logging in tropical timber concessions
Authors: BOSCOLO MARCO , VINCENT JEFFREY R.
Published: July 2007

Area fees have become an increasingly important component of forest revenue systems in tropical developing countries. They are commonly viewed as having a neutral impact on decisions by timber concessionaires. This view is incorrect. Using both theoretical and empirical models, we demonstrate that area fees can induce concessionaires to accelerate timber harvests and to harvest more selectively. In Cameroon, area fees at recent levels create an incentive for concessionaires to harvest forests in half the estimated sustained-yield period. Countries that wish to encourage concessionaires to comply with sustained-yield requirements must implement measures that counter the depletion-accelerating effects of area fees.
Social diversity and ecological complexity: how an invasive tree could affect diverse agents in the land of the tiger
Authors: DAYAL VIKRAM
Published: July 2007

A bioeconomic model is used to study the effect of Prosopis juliflora, an exotic tree, on diverse agents in Ranthambhore National Park. Tigers prey on wild herbivores, cattle, and goats that compete with each other to feed on green biomass, i.e. leaves and grass. There are four agents: goat owner, cattle owner, wood gatherer, and park manager. It is shown that there is an inherent trade-off between the number of tigers and village livestock that are grazing. Prosopis juliflora makes management of this trade-off more difficult. The four agents have different interests in the park, and a different ranking of the four scenarios that are simulated.
False Memories
Authors: Steffens Melanie Caroline , Mecklenbräuker Silvia
Published: July 2007

Abstract. In recent years, there has been an explosion of research on false memories: The subjective experience of remembering something if that something did apparently not happen in reality. We review a range of findings concerning this phenomenon: False memories of details and of whole events by adults and children, as well as false memories of words in laboratory experiments (in the DRM paradigm). We also briefly discuss the converse phenomenon: Evidence of forgetting or repression of significant events, and evidence of recovered memories. Knowledge of both phenomena is needed for judging whether “new” memories are false, recovered, or whether both options are possible. More general as well as specific theories explaining false memories are discussed, and we close with implications for practice.
Implicit Relational Memory in Young and Older Adults
Authors: Dew Ilana T.Z. , Bayen Ute J. , Giovanello Kelly S.
Published: July 2007

Abstract. Older adults do not perform as well as young adults in explicit episodic memory tasks that require the formation and retrieval of new associations. Relatively few studies have investigated the effects of older adults' associative deficit on implicit-memory performance. After introducing the reader to the area of implicit-memory research at large, the authors review studies that have investigated young and older adults' performance in implicit associative memory tasks. Core theoretical issues and methodological challenges are discussed.
Making Memories Unavailable
Authors: Bäuml Karl-Heinz
Published: July 2007

Abstract. Research from the past decades has shown that cuing and retrieval are not always beneficial for episodic memory and can also be detrimental. Prior work assumed that these detrimental effects are caused by retrieval blocking, in which cuing and retrieval strengthen material and the repeated involuntary sampling of the strengthened material hinders subsequent recall of nonstrengthened targets. Using a new experimental paradigm and an extended range of memory tests, recent research indicates that the detrimental effects of retrieval and cuing occur across a wide range of memory tests and are likely to be the result of inhibitory processes. These inhibitory processes impair the nonretrieved and noncue items' memory representation and make these items unavailable in memory. The recent results and the new theory are reviewed and discussed.
Affective Well-Being in Old Age
Authors: Heyl Vera , Wahl Hans-Werner , Mollenkopf Heidrun
Published: July 2007

Abstract. This study investigated the relationships between tenacious goal pursuit (TGP) and flexible goal adjustment (FGA), two fundamental modes of self-regulation suggested by Brandtstädter and colleagues, and positive and negative affect (PA, NA). This was done in general terms and by considering the developmental constraint of perceived age-related visual decline. Data stem from 751 community-dwelling elders (55-98 years, 372 women, 379 men). Results support the hypothesis of differential associations of TGP and FGA, respectively, with affect: TGP was positively related to PA, and FGA was negatively related to NA. Moreover, differential moderator effects of TGP and FGA, respectively, on the relationship between subjective vision and affect emerged. FGA independently moderated the inverse relationship between subjective vision and NA. The moderator effect of TGP, however, was dependent on FGA: TGP did not alter the relationship between subjective vision and PA until FGA was high, too. It is concluded that both TGP and FGA are necessary for an adaptive self-regulation.
Perceptual Asymmetry for Chimeric Faces and Winter Disturbances in Mood and Behavior
Authors: Ennis Edel , McConville Chris
Published: July 2007

Abstract. Different affective disturbances are related to brain activity, and, thus, to perceptual bias in very specific ways ( Keller et al., 2000 ). During the winter months, approximately 90% of people report lowered levels of mood and increased levels of anxiety to varying degrees (e.g., Magnusson, 2000 ). The current study examines the relationship between such winter mood disturbances and perceptual asymmetry on the chimeric-face task using a nonclinical sample (38 males and 92 females). Because of the suggested influence of symbolic light on cognitive processing of seasonal depressives ( Bouhuys, Meesters, Jansen, & Bloem, 1994 ), chimeric faces were presented on both symbolic bright and dark backgrounds. Face processing demonstrated the expected left hemifacial perceptual bias. However, the magnitude of individuals' perceptual bias bore no relation to subjectively reported seasonality, depressed mood, or anxiety. This was regardless of whether the faces were displayed on symbolic bright or dark backgrounds. Methodological factors must be considered. However, results are discussed in terms of the importance of clarifying the distinct nature of the psychological and neurobiological profile associated with winter disturbances in mood, and the possible influences of symbolic light on cognitive processing.
A Qualitative Study of Adaptation to the Euro in the Republic of Ireland
Authors: Ranyard Rob , Routh David A. , Burgoyne Carole B. , Saldanha Gabriela
Published: July 2007

Abstract. This is the second of two reports using semistructured interviews to explore the current and recollected experiences of Irish people for the period before, during, and after the introduction of Euro notes and coins (1 January 2002). A total of 24 adults were interviewed between October 2002 and February 2003. Most people felt they were adapting well although their knowledge of new prices tended to be fairly sparse. Some reported still experiencing confusion with notes and coins or making errors associated with habitual behavior based on the value of the former currency, the punt. Initially respondents had routinely attempted to make mental or electronic comparisons of Euro and punt prices, although this had become more selective. One year after the transition, some respondents claimed to be thinking in Euros, while others were still thinking in punts. People's reported experience appeared to reveal an adaptation strategy comprising at least two stages, initially involving currency conversion, but later focusing on the relearning of reference prices for certain exemplars.
Privacy Needs in Office Environments
Authors: Haans Antal , Kaiser Florian G. , de Kort Yvonne A.W.
Published: July 2007

Abstract. In this paper, we develop two behavior-based privacy-need measures for office environments. These two new scales are designed as objective measures, since they try to avoid introspection. One scale assesses people's motivation to withdraw from social interaction (i.e., the Need-For-Privacy [NFP]) and the other the motivation to seek social exchange (i.e., the Need-For-Socializing [NFS]). Based on survey data from 204 bank employees, our newly-developed measures demonstrated reasonable reliabilities (> .70). Regarding construct validity, we found our NFP scale to overlap (R2 > 25%) with an established NFP measure ( Kaya & Weber, 2003 ) and a need-for-solitude instrument ( Pedersen, 1988 ). The results also corroborate the fact that people's NFP and their NFS are relatively distinct motives (R2 = 10%).
Social Support and Successful Aging
Authors: Gow Alan J. , Pattie Alison , Whiteman Martha C. , Whalley Lawrence J. , Deary Ian J.
Published: July 2007

Abstract. Social networks or support may contribute to successful aging. The Lothian Birth Cohort 1921 had their mental ability assessed at age 11 and 79. Almost 500 participants also rated their life satisfaction, social networks, and support at age 80. After controlling for age-11 IQ, sex, years of education, and social class, loneliness was the only social network/support characteristic adding significantly to the prediction of age-79 IQ, explaining about 2% of the variance; in old age, increased loneliness was associated with lower cognitive ability. Social network/support factors accounted for 23% of the variance in satisfaction with life ratings, with the greatest contributions from reduced loneliness (~12%) and having someone to talk to (~6%). Social network/support characteristics explained a greater proportion of the variance in life satisfaction ratings compared with later life cognition, although an individual's level of loneliness emerged as the largest single social support predictor of both outcomes. Possible causal pathways for these associations, which need to be studied in future research, are discussed.
Brief Versions of the NEO-PI-3
Authors: McCrae Robert R. , Costa, Jr. Paul T.
Published: July 2007

Abstract. Self-report (Form S) and observer rating (Form R) versions of two short forms of the NEO Personality Inventory-3 (NEO-PI-3) were evaluated. The NEO Five-Factor Inventory-3 is a 60-item instrument that assesses the five factors. The NEO-PI-3 First Half consists of the first 120 items of the NEO-PI-3, selected to optimally assess its 30 facet scales. Internal consistencies were systematically lower for the brief scales than for the parent scales, but both brief instruments replicated the factor structure and showed cross-observer validity. They appeared to work well in both adolescent and adult samples, and adequately in a middle school-age sample. Norms for the NEO-FFI-3 are provided and it was shown that NEO-PI-3 norms can be used for NEO-PI-3 First Half scores if they are simply doubled. Uses of the NEO-PI-3 First Half are discussed.
Differential Effects of Incongruent Anger Expression on Memory Performance
Authors: Perbandt Kerstin
Published: July 2007

Abstract. There is growing evidence that certain strategies of emotion regulation may lead to impaired cognitive performance. The present study investigated the impact of manipulated discrepancy between felt and displayed anger on cognitive performance and how it is modulated by extraversion. Fifty-six female participants were asked to solve two blocks of anagrams. Additionally, half of the subjects were instructed to show an angry emotional expression while solving the second block of anagrams, the remaining half were asked to keep their expression neutral. Before the second anagram trial, half of the participants were provoked, half of them were not. The subsequent unexpected memory test revealed a detrimental effect of the incongruent anger expression on the recall of the anagram solutions seen in the second trial. Compared to participants low on extraversion, high extraverts appeared to profit from showing an emotional display that was congruent with their feelings.
Patterns of Neuroticism, Work-Family Stress, and Resources as Determinants of Personal Distress
Authors: Schneewind Klaus A. , Kupsch Melanie
Published: July 2007

Abstract. Based on a sample of 632 German-speaking dual-earner couples from three European countries (Austria, Germany, and Switzerland) with at least one child aged 1 to 5 years, three different clusters representing specific risk patterns of low vs. high levels in (1) personality (neuroticism), (2) work- and family-related stress, and (3) personal and social resources were identified and related to the level of personal distress expressed by the corresponding female and male risk groups. At the individual level, the results showed marked differences in personal distress depending on which risk pattern the persons belong to. Moreover, compensatory effects that reduce the impact of high neuroticism on personal distress were found. Gender differences in personal distress were significant, albeit relatively small, for all three risk groups. At the couple level, when analyzing different within-couple constellations of risk patterns showed that concordant within-couple risk patterns corroborate both partners' gender-specific levels of personal distress whereas in discordant-couple constellations, with one partner belonging to a high and the other to a low individual risk pattern, no buffering partner-effects were found. Differential intervention strategies for reducing the level of personal distress are suggested.
Global mantle flow and the development of seismic anisotropy: Differences between the oceanic and continental upper mantle
Authors: Conrad Clinton P. , Behn Mark D. , Silver Paul G.
Published: July 2007

Viscous shear in the asthenosphere accommodates relative motion between Earth's surface plates and underlying mantle, generating lattice‐preferred orientation (LPO) in olivine aggregates and a seismically anisotropic fabric. Because this fabric develops with the evolving mantle flow field, observations of seismic anisotropy can constrain asthenospheric flow patterns if the contribution of fossil lithospheric anisotropy is small. We use global viscous mantle flow models to characterize the relationship between asthenospheric deformation and LPO and compare the predicted pattern of anisotropy to a global compilation of observed shear wave splitting measurements. For asthenosphere >500 km from plate boundaries, simple shear rotates the LPO toward the infinite strain axis (ISA, the LPO after infinite deformation) faster than the ISA changes along flow lines. Thus we expect the ISA to approximate LPO throughout most of the asthenosphere, greatly simplifying LPO predictions because strain integration along flow lines is unnecessary. Approximating LPO with the ISA and assuming A‐type fabric (olivine a axis parallel to ISA), we find that mantle flow driven by both plate motions and mantle density heterogeneity successfully predicts oceanic anisotropy (average misfit 13°). Continental anisotropy is less well fit (average misfit 41°), but lateral variations in lithospheric thickness improve the fit in some continental areas. This suggests that asthenospheric anisotropy contributes to shear wave splitting for both continents and oceans but is overlain by a stronger layer of lithospheric anisotropy for continents. The contribution of the oceanic lithosphere is likely smaller because it is thinner, younger, and less deformed than its continental counterpart.
High frequency of occurrence of large solar energetic particle events prior to 1958 and a possible repetition in the near future
Authors: McCracken K. G.
Published: July 2007

It is shown that the >4 GeV fluence of large solar energetic particle events was a factor of 10 greater and the frequency of occurrence a factor of four greater prior to 1958 than during the space era. There were two events in 1946 and 1949 with >4 GeV fluences similar to that of 23 February 1956, suggesting that the >4 GeV fluence of the largest probable event for a similar period would be ∼3 times greater. The historic cosmic ray and glaciological records indicate that the fluences and probability of occurrence of such large events at both high and low energies are greatest in periods of low long‐term solar activity and anticorrelated with the estimated strength of the heliospheric magnetic field. A working model is proposed where the factors controlling the occurrence of large SEP events are (1) the occurrence of a large solar flare or CME and (2) the heliomagnetic field being <6.5 nT near Earth. A theoretical basis for this model is discussed. It is proposed that the next Gleissberg minimum of solar activity will lead to a repetition of the pre‐1958 era of high‐frequency, high‐fluence GLE and SEP events. Two predictive indicators of higher SEP activity are proposed: (1) the Climax neutron monitor rate at solar minimum rises >5% compared to 1954 and (2) the measured heliomagnetic field near Earth remains <6.5 nT for ≥2 years into a new solar cycle, or alternatively it is substantially less than 5 nT at sunspot minimum.
Wavelet‐based multifractal analysis of field scale variability in soil water retention
Authors: Zeleke Takele B. , Si Bing C.
Published: July 2007

Better understanding of spatial variability of soil hydraulic parameters and their relationships to other soil properties is essential to scale‐up measured hydraulic parameters and to improve the predictive capacity of pedotransfer functions. The objective of this study was to characterize scaling properties and the persistency of water retention parameters and soil physical properties. Soil texture, bulk density, organic carbon content, and the parameters of the van Genuchten water retention function were determined on 128 soil cores from a 384‐m transect with a sandy loam soil, located at Smeaton, SK, Canada. The wavelet transform modulus maxima, or WTMM, technique was used in the multifractal analysis. Results indicate that the fitted water retention parameters had higher small‐scale variability and lower persistency than the measured soil physical properties. Of the three distinct scaling ranges identified, the middle region (8–128 m) had a multifractal‐type scaling. The generalized Hurst exponent indicated that the measured soil properties were more persistent than the fitted soil hydraulic parameters. The relationships observed here imply that soil physical properties are better predictors of water retention values at larger spatial scales than at smaller scales.
Coupled moisture and microbial dynamics in unsaturated soils
Authors: Maggi F. , Porporato A.
Published: July 2007

A continuum‐scale mathematical model which couples water flow and bacterial dynamics explores the process of biological clogging in unsaturated soils. The impact of biomass dynamics on soil water flow is assumed to take place through the changes in porosity and the structural properties of the medium by suitable modifications of the pore size distribution, water retention, and hydraulic conductivity functions. The feedback of soil moisture on biomass is taken into account by including the effect of water stress on microbial growth. The model is calibrated against existing laboratory experimental data for an artificial porous medium in saturated conditions, and it is used to analyze the hydraulic behavior of unsaturated soils when subject to biological clogging and plant water uptake. The results of this analysis show that this feedback may have a substantial impact on the net water flow, the soil water‐holding capacity, and the soil moisture and biomass space‐time distributions.
Magnesium and strontium distributions within valves of a recent marine ostracode, Neonesidea oligodentata: Implications for paleoenvironmental reconstructions
Authors: Morishita Tomoaki , Tsurumi Atsushi , Kamiya Takahiro
Published: July 2007

Ostracodes are bivalved microcrustaceans that live in nearly all types of aquatic environments. The chemical compositions of the calcified part of their carapaces are frequently used as an empirical proxy in paleoenvironmental reconstructions. We investigated the compositions and the distribution of Mg and Sr within valves of a recent ostracode, Neonesideaoligodentata, using an electron microprobe analyzer. Each of the investigated valves displayed large variations in Mg and Sr concentrations compared to the variations in Ca (and probably O). There were no systematic chemical differences between right and left valves of each carapace, and between male and female carapaces. Although there were some deviations, the valves consisted of, at least, three chemical bands: (1) a narrow (usually <10 μm) high‐Mg, Sr outer band (Outer Band), (2) a heterogeneous low‐Mg, Sr middle band (Middle Band), and (3) a high‐Mg, low‐Sr inner band (Inner Band). The high‐Mg, low‐Sr Inner Band was well developed at the inner part of the margin, including the marginal infold. The high‐Mg, Sr Outer Band is thought to be formed during the early stage of carapace formation when the calcification rate is high, whereas other parts formed at later stages with a relatively slow calcification rates. Since bairdioidean ostracodes, exemplified by Neonesidea oligodentata, have a long geological history and are abundant in many regions, further studies on the mechanism of the Mg/Ca distribution in these ostracodes will provide a suitable tool to estimate paleotemperatures in various marine environments.
Rayleigh‐wave group‐velocity of the Icelandic crust from correlation of ambient seismic noise
Authors: Gudmundsson Ó. , Khan A. , Voss P.
Published: July 2007

By cross‐correlating 2 years of ambient seismic noise from 31 broadband stations distributed across Iceland, we have been able to measure Rayleigh wave group velocity in three discrete frequency bands centered on 4, 7 and 17 s, sensitive to approximately the top 6, 10 and 25 km of the crust, for 289, 420 and 139 station‐to‐station paths, respectively. These are inverted to yield tomographic group velocity maps of the Icelandic crust. The results correlate with the major tectonic features on Iceland, and agree well with earlier seismic studies based on traditional methods (active source and earthquake). Specifically, we obtain low velocities in the central parts of Iceland, coinciding with the rift zones and young crust. In contrast, the parts of Iceland covered with older Tertiary volcanics reveal relatively higher velocities. At the shorter periods (4 and 7 s) this correlation reflects porosity, degree of fracturing and alteration. At the longest period (17 s), i.e. at greater depth, this correlation may reflect the thermal state of the crust, with warm and seismically slow material near the rifts and cooler and seismically faster material beneath the Tertiary formations to the east and west.
Optimized stomatal conductance and the climate sensitivity to carbon dioxide
Authors: Kleidon A.
Published: July 2007

Stomatal conductance shapes the exchange of water and carbon of vegetated land surfaces. Previous studies have demonstrated that optimized stomatal functioning that maximizes productivity provides a realistic description of how stomata operate. Here I investigate the role of optimum stomatal functioning for the sensitivity of terrestrial productivity and land surface climate to concentrations of atmospheric carbon dioxide (pCO2). I conduct sensitivity simulations with a coupled vegetation‐climate system model with different values of maximum stomatal conductance at different prescribed levels of pCO2. The optimum in stomatal conductance shifts to lower values with increasing pCO2, which is consistent with observed sensitivities of stomatal density of leaves. If this change in optimum conditions is not taken into account, the climate sensitivity shows (1) a general underestimation of terrestrial productivity under altered pCO2, and (2) different sensitivities of key climatic variables to pCO2. The climate sensitivity of land temperature for a doubling of pCO2 ranges from ΔT = 2.7 K to ΔT = 3.2 K, depending on whether stomata adapt optimally or not at all. These results demonstrate that the assumed ability of vegetation to adapt to its environment can have important consequences for the simulated climate system sensitivity to pCO2.
Variable SO2 emission rates for Anatahan volcano, the Commonwealth of the Northern Mariana Islands: Implications for deriving arc‐wide volatile fluxes from erupting volcanoes
Authors: Hilton D. R. , Fischer T. P. , McGonigle A. J. S. , de Moor J. M.
Published: July 2007

We report new spectroscopic‐derived SO2 emission rates for Anatahan volcano, Mariana Islands. Measurements of SO2 fluxes reveal large fluctuations over the 2003–2005 period ‐ from 78 kg s−1 which occurred on the same day as resurgent volcanic activity (March, 2005) to 50 kg s−1 and 25 kg s−1 made days/weeks after the start of eruptive sequences in 2003 and 2004 respectively. Even the lowest values make Anatahan a major global source of SO2 over the past decade. These SO2 emission rates are used to estimate the CO2 flux from the arc as a whole (=3.6 − 40 × 107 mol km−1 yr−1). Such values are significantly higher than estimates derived using other approaches: they are also high compared to other convergent margins (e.g., Central America) where the input flux of CO2 is substantially greater. Our results caution against including volatile fluxes from actively‐degassing volcanoes to produce volatile outputs considered representative of entire arc fronts.
Cluster observations of broadband ULF waves near the dayside polar cap boundary: Two detailed multi‐instrument event studies
Authors: Matsui H. , Puhl‐Quinn P. A. , Torbert R. B. , Baumjohann W. , Farrugia C. J. , Mouikis C. G. , Lucek E. A. , Décréau P. M. E. , Paschmann G.
Published: July 2007

We study two examples of broadband ultra‐low frequency (ULF) waves observed near the dayside polar cap boundary using data from multiple instruments on Cluster. These waves lie in a frequency range of ∼1–100 mHz with variable amplitudes. We have focused on their characteristics around the lowest frequency end. In the first event, the magnetic variations consist of oscillations mainly transverse to the background field. These waves are inferred to be the shear Alfvén waves whose phase velocity is approximately perpendicular to the magnetic field. A possible source is located in reconnection, probably of transient variety. In the second event, the magnetic variations include compressional components. These waves are suggested to be fast mode waves. It is possible that the waves are generated by the pressure variations in the solar wind impinging on the magnetosphere. The estimated wave modes and generation mechanisms of these two events are different, even though the waves have broadband spectra at similar spacecraft locations. The results from our observations may be useful when comparing with theories in realistic situations.
Quantum superintegrable systems with quadratic integrals on a two dimensional manifold
Authors: Daskaloyannis C. , Tanoudis Y.
Published: July 2007

There are two classes of quantum integrable systems on a manifold with quadratic integrals, the Liouville and the Lie integrable systems, as it happens in the classical case. The quantum Liouville quadratic integrable systems are defined on a Liouville manifold and the Schrödinger equation can be solved by separation of variables in one coordinate system. The Lie integrable systems are defined on a Lie manifold and are not generally separable ones but can be solved. Therefore, there are superintegrable systems with two quadratic integrals of motion not necessarily separable in two coordinate systems. The quantum analogs of the two dimensional superintegrable systems with quadratic integrals of motion on a manifold are classified by using the quadratic associative algebra of the integrals of motion. There are six general fundamental classes of quantum superintegrable systems corresponding to the classical ones. Analytic formulas for the involved integrals are calculated in all the cases. All the known quantum superintegrable systems are classified as special cases of these six general classes. The coefficients of the associative algebra of the general cases are calculated. These coefficients are the same as the coefficients of the classical case multiplied by −ℏ2 plus quantum corrections of orders ℏ4 and ℏ6.
Photofragment angular momentum distribution beyond the axial recoil approximation: Predissociation
Authors: Kuznetsov Vladislav V. , Vasyutinskii Oleg S.
Published: July 2007

We present the quantum mechanical expressions for the angular momentum distribution of the photofragments produced in slow predissociation. The paper is based on our recent theoretical treatment [J. Chem. Phys. 123, 034307 (2005)] of the recoil angle dependence of the photofragment multipole moments which explicitly treat the role of molecular axis rotation on the electronic angular momentum polarization of the fragments. The electronic wave function of the molecule was used in the adiabatic body frame representation. The rigorous expressions for the fragment state multipoles which have been explicitly derived from the scattering wave function formalism have been used for the case of slow predissociation where a molecule lives in the excited quasibound state much longer than a rotation period. Possible radial nonadiabatic interactions were taken into consideration. The optical excitation of a single rotational branch and the broadband incoherent excitation of all possible rotational branches have been analyzed in detail. The angular momentum polarization of the photofragments has been treated in the high-J limit. The polarization of the photofragment angular momenta predicted by the theory depends on photodissociation mechanism and can in many cases be significant.
A computational study of axial dispersion in segmented gas-liquid flow
Authors: Muradoglu Metin , Günther Axel , Stone Howard A.
Published: July 2007

Axial dispersion of a tracer in a two-dimensional gas-liquid flow is studied computationally using a finite-volume/front-tracking method. The effects of Peclet number, capillary number, and segment size are examined. At low Peclet numbers, the axial dispersion is mainly controlled by the convection through the liquid films between the bubbles and channel walls. In this regime, the computational results are found to be in a very good agreement with the existing model due to Pedersen and Horvath [Ind. Eng. Chem. Fundam. 20, 181 (1981)]. At high Peclet numbers, the axial dispersion is mainly controlled by the molecular diffusion, with some convective enhancement. In this regime, a new model is proposed and found to agree well with the computational results. These Peclet number regimes are shown to persist for different slug lengths. The axial dispersion is found to depend weakly on the capillary number in the diffusion-controlled regime. Finally, computational simulations are performed for the cases of six bubbles to mimic bubble trains, and results are compared with the theoretical models.
Influence of molecular topology on the static and dynamic properties of single polymer chain in solution
Authors: Fu Cuiliu , Ouyang Wenze , Sun Zhaoyan , An Lijia
Published: July 2007

The influence of molecular topology on the structural and dynamic properties of polymer chain in solution with ring structure, three-arm branched structure, and linear structure are studied by molecular dynamics simulation. At the same degree of polymerization (N), the ring-shaped chain possesses the smallest size and largest diffusion coefficient. With increasing N, the difference of the radii of gyration between the three types of polymer chains increases, whereas the difference of the diffusion coefficients among them decreases. However, the influence of the molecular topology on the static and the dynamic scaling exponents is small. The static scaling exponents decrease slightly, and the dynamic scaling exponents increase slightly, when the topology of the polymer chain is changed from linear to ring-shaped or three-arm branched architecture. The dynamics of these three types of polymer chain in solution is Zimm-like according to the dynamic scaling exponents and the dynamic structure factors.
Existence of boundary layers to the Boltzmann equation with cutoff soft potentials
Authors: Wang Weike , Yang Tong , Yang Xiongfeng
Published: July 2007

When the Boltzmann equation is used to study a physical problem with boundary, there usually exists a layer of the width in the order of the Knudsen number along the boundary. There have been extensive studies on the existence and stability of boundary layers to the Boltzmann equation in different physical settings. Based on the previous work, in this paper, we consider the existence of boundary layer solutions to the Boltzmann equation for the cutoff soft potentials when its parameter γ satisfying −2<γ⩽0. The boundary condition is imposed on the incoming particles of Dirichlet type, and the solution is assumed to approach to a global Maxwellian at the far field. As for the hard sphere model and the cutoff hard potentials, the existence of solutions is shown to depend on the Mach number of the far field Maxwellian. Moreover, there is an implicit solvability condition on the boundary data which gives the codimension of the boundary data related to the number of the positive characteristic speeds. In the following analysis, even though the weight function of both the position and velocity introduced in [Chen, C.-C., Liu, T. P., and Yang, T., “Existence of boundary layer solutions to the Boltzmann equation,” Anal. Appl. 2, 337–363 (2004)]. plays an important role, the result in this paper extends the previous works on the existence and the classification of the boundary data for the hard sphere model and cutoff hard potentials to the cutoff soft potentials with weaker collisional interactions.
Modeling sawtooth stabilization by energetic ions from neutral beam injection
Authors: Chapman I. T. , Pinches S. D. , Appel L. C. , Hastie R. J. , Hender T. C. , Saarelma S. , Sharapov S. E. , Voitsekhovitch I. , Graves J. P.
Published: July 2007

Recent advances in modeling the effects of anisotropic energetic ion distributions have enabled the development of a complete coherent physics explanation of sawtooth stabilization in both conventional and spherical tokamaks. As an example, a complete model has been developed to explain the asymmetric stabilization of sawteeth with respect to neutral beam injection direction in the Joint European Torus. This asymmetric sawtooth stabilization [M. Nave et al., Phys. Plasmas 13, 014503 (2006)] arises because of both the destabilizing contribution from the counterpassing ions and the strong modification of the stabilizing contribution of the nonadiabatic trapped ions due to flow shear. The fast particle effects including pressure anisotropy, sheared flows, and the adiabatic response to the internal kink mode have been modeled in general toroidal geometry for the first time.