bluuebunny/crossref_metadata_2025 huggingface dataset:
Arthrogryposis multiplex congenita. Long-term follow-up from birth until skeletal maturity
Authors: Fassier Alice , Wicart Philippe , Dubousset Jean , Seringe Raphaël
Published: August 2009

Purpose

The aim of this retrospective long-term study was to review and present the effects of treatment for 11 children with arthrogryposis multiplex congenital, or amyoplasia, followed from birth until skeletal maturity.

Methods

We evaluated walking ability, age of beginning to walk, required ambulatory devices, age of independent walking and muscle strength.

Results

Our series showed babies with severe limb involvements without spine abnormalities. Despite the initial severity of involvement, nine patients finally became ambulators with flexion contracture of less than 20° on hips and 15° on knees, and six were independent walkers before the age of 2.5 years. The two non-ambulators presented severe scoliosis at skeletal maturity, which needed spinal fusion.

Conclusion

We conclude that long-term ambulatory status at skeletal maturity is not correlated with the severity of condition at birth. A prognosis for ambulation at skeletal maturity will be done before 2.5 years of age. We believe that early aggressive management of children with severe arthrogryposis is warranted and justified.
Fertility preferences, condom use, and concerns among HIV‐positive women in serodiscordant relationships in the era of antiretroviral therapy
Authors: Ezeanochie Michael , Olagbuji Biodun , Ande Adedapo , Oboro Victor
Published: August 2009

Objective

To assess preferences and concerns about infecting partner or child among HIV‐positive women undergoing antiretroviral therapy and whose partners are HIV‐negative.

Method

In this cross‐sectional study conducted in Nigeria, 55 HIV‐positive women undergoing antiretroviral therapy and married to seronegative men answered an anonymous questionnaire regarding whether they preferred to conceive naturally or by means of an assisted reproductive technique (ART).

Results

Compared with older women (mean age 33.6 ± 5.1 years), younger women (mean age, 29.8 ± 3.9 years) were significantly more likely to choose natural conception than ART (P = 0.02). Moreover, whereas 23 respondents (48.9%) reported consistent condom use, 11 (23.4%) reported never using condoms after initiation of antiretroviral therapy. There was a significant difference in the consistent use of condoms between those who preferred natural conception and those who preferred ART (56.8% vs 20%, P = 0.049).

Conclusion

With improving immunologic and clinical status once antiretroviral therapy is initiated, HIV‐positive women wishing to become pregnant may engage in risky sexual practices. This trend needs to be addressed because of its consequences for public health.
CENTRAL INTERPOLATION SETS FOR COMPACT GROUPS AND HYPERGROUPS
Authors: GROW DAVID , HARE KATHRYN E.
Published: August 2009

We prove that every infinite subset of the dual of a compact, connected group contains an infinite, central, weightedI0set. This yields a new proof of the fact that the duals of such groups admit infinite centralp-Sidon sets for eachp> 1. We also establish the existence of infinite, weightedI0sets in the duals of many compact, abelian hypergroups.
THE GENERALISED LIÉNARD EQUATIONS
Authors: AGHAJANI A. , MORADIFAM A.
Published: August 2009

In this paper we present sufficient conditions for all trajectories of the system

to cross the vertical isocline h(y) = F(x), which is very important in the global asymptotic stability of the origin, oscillation theory and existence of periodic solutions. Also we give sufficient conditions for all trajectories which start at a point on the curve h(y) = F(x), to cross the y-axis which is closely connected with the existence of homoclinic orbits, stability of the zero solution, oscillation theory and the centre problem. The obtained results extend and improve some of the authors' previous results and some other theorems in the literature.
THE BEST SOBOLEV TRACE CONSTANT IN PERIODIC MEDIA FOR CRITICAL AND SUBCRITICAL EXPONENTS
Authors: BONDER JULIÁN FERNÁNDEZ , ORIVE RAFAEL , ROSSI JULIO D.
Published: August 2009

In this paper we study homogenisation problems for Sobolev trace embedding H1(Ω) ↪ Lq(∂Ω) in a bounded smooth domain. When q = 2 this leads to a Steklov-like eigenvalue problem. We deal with the best constant of the Sobolev trace embedding in rapidly oscillating periodic media, and we consider H1 and Lq spaces with weights that are periodic in space. We find that extremals for these embeddings converge to a solution of a homogenised limit problem, and the best trace constant converges to a homogenised best trace constant. Our results are in fact more general; we can also consider general operators of the form aɛ(x, ∇u) with non-linear Neumann boundary conditions. In particular, we can deal with the embedding W1,p(Ω) ↪ Lq(∂Ω).
LEFT ℓ1-FACTORABLE POLYNOMIALS
Authors: CILIA RAFFAELLA , GUTIÉRREZ JOAQUÍN M.
Published: August 2009

A polynomial P ∈ (kE, F) is left ℓ1-factorable if there are a polynomial Q ∈ (kE, ℓ1) and an operator L ∈ (ℓ1, F) such that P = L ○ Q. We characterise the Radon–Nikodým property by the left ℓ1-factorisation of polynomials on L1(μ). We study the left ℓ1-factorisation of nuclear, compact and Pietsch integral polynomials. For Pietsch integral polynomials, we introduce the left integral ℓ1-factorisation property, obtaining a second polynomial characterisation of the Radon–Nikodým property and showing that it plays a role somehow comparable, in this setting, to nuclearity of operators. A characterisation of 1-spaces is also given in terms of the left compact ℓ1-factorisation of polynomials.
THE CENTRE OF THE MAXIMAL p-SUBGROUP OF (pkD2p)
Authors: GILDEA JOE
Published: August 2009

The centre of the maximal p-subgroup of (pkD2p) is described as an elementary abelian p-group, where p is a prime.
THE EXPONENTIAL DIOPHANTINE EQUATION nx + (n + 1)y = (n + 2)z REVISITED
Authors: HE BO , TOGBÉ ALAIN
Published: August 2009

Let n be a positive integer. In this paper, we consider the diophantine equation

We prove that this equation has only the positive integer solutions (n, x, y, z) = (1, t, 1, 1), (1, t, 3, 2), (3, 2, 2, 2). Therefore we extend the work done by Leszczyński (Wiadom. Mat., vol. 3, 1959, pp. 37–39) and Makowski (Wiadom. Mat., vol. 9, 1967, pp. 221–224).
ON SUBMANIFOLDS WITH TAMED SECOND FUNDAMENTAL FORM
Authors: BESSA G. PACELLI , COSTA M. SILVANA
Published: August 2009

Based on the ideas of Bessa, Jorge and Montenegro (Comm. Anal. Geom., vol. 15, no. 4, 2007, pp. 725–732) we show that a complete submanifold M with tamed second fundamental form in a complete Riemannian manifold N with sectional curvature KN ≤ κ ≤ 0 is proper (compact if N is compact). In addition, if N is Hadamard, then M has finite topology. We also show that the fundamental tone is an obstruction for a Riemannian manifold to be realised as submanifold with tamed second fundamental form of a Hadamard manifold with sectional curvature bounded below.
RATLIFF–RUSH CLOSURE OF IDEALS IN INTEGRAL DOMAINS
Authors: MIMOUNI A.
Published: August 2009

This paper studies the Ratliff–Rush closure of ideals in integral domains. By definition, the Ratliff–Rush closure of an ideal I of a domain R is the ideal given by Ĩ := ∪(In+1 :R In), and an ideal I is said to be a Ratliff–Rush ideal if Ĩ = I. We completely characterise integrally closed domains in which every ideal is a Ratliff–Rush ideal, and we give a complete description of the Ratliff–Rush closure of an ideal in a valuation domain.
MC2 RINGS AND WQD RINGS
Authors: WEI JUNCHAO , LI LIBIN
Published: August 2009

We introduce in this paper the concepts of rings characterized by minimal one-sided ideals and concern ourselves with rings containing an injective maximal left ideal. Some known results for idempotent reflexive rings and left HI rings can be extended to left MC2 rings. As applications, we are able to give some new characterizations of regular left self-injective rings with non-zero socle and extend some known results for strongly regular rings.
ON THE WARING–GOLDBACH PROBLEM FOR CUBES
Authors: BRÜDERN JÖRG , KAWADA KOICHI
Published: August 2009

We prove that almost all natural numbers satisfying certain necessary congruence conditions can be written as the sum of two cubes of primes and two cubes of P2-numbers, where, as usual, we call a natural number a P2-number when it is a prime or the product of two primes. From this result we also deduce that every sufficiently large integer can be written as the sum of eight cubes of P2-numbers.
Photo-grammetric measurements of swimming speed and body length of basking sharks observed around the Hebrides, Scotland
Authors: Lacey Claire , Leaper Russell , Moscrop Anna , Gillespie Douglas , McLanaghan Richard , Brown Steve
Published: August 2009

Photo-grammetric techniques developed for measuring body length and small scale movement patterns of cetaceans were applied to surface swimming basking sharks off the west coast of Scotland. These methods removed the need for close approaches, reducing the likelihood of disturbing the focal animal. Average swimming speed was calculated from the total path length between shark locations measured at approximately one minute intervals. These average speeds varied from 0.49 to 0.73 ms−1 for tracks of between 30 and 170 minutes' duration. Body length measurements ranged between 2.35 and 6.43 m. For ten sharks where body length and swimming speed were measured there was a significant correlation between body length (L) and swimming speed (V) expressed as V = 0.36L033.
Seasonal variation of lipid content and fatty acid composition ofSardinella auritafrom the Tunisian coast
Authors: Ben Rebah F. , Abdelmouleh A. , Kammoun W. , Yezza A.
Published: August 2009

This study was conducted to clarify the seasonal variation of the chemical composition of the TunisianSardinella auritawith a focus on the total lipid content. The chemical composition showed a large fluctuation over years in response to various factors. For the entire fish, lipid content was lower in July (2.50%), but higher in November (10.25%). It varies with seasons in inverse proportion to water content. Interestingly, it was found that red muscle have much higher lipid content than white muscle and the entire fish body. The major fatty acids inS. auritalipids were palmitic acid, palmitoleic acid, eicosapentaenoic acid, docosahexaenoic acid and myristic acid. Palmitic acid comprised the main proportion (23.9%). The high amounts of saturated and monounsaturated fatty acids in the screened species are almost in agreement with other studies. Moreover, the percentage of omega-3 fatty acids (25%) was very similar to that in oil production commercial fish.
Step Size in Stein's Method of Exchangeable Pairs
Authors: ROSS NATHAN
Published: August 2009

Stein's method of exchangeable pairs is examined through five examples in relation to Poisson and normal distribution approximation. In particular, in the case where the exchangeable pair is constructed from a reversible Markov chain, we analyse how modifying the step size of the chain in a natural way affects the error term in the approximation acquired through Stein's method. It has been noted for the normal approximation that smaller step sizes may yield better bounds, and we obtain the first rigorous results that verify this intuition. For the examples associated to the normal distribution, the bound on the error is expressed in terms of the spectrum of the underlying chain, a characteristic of the chain related to convergence rates. The Poisson approximation using exchangeable pairs is less studied than the normal, but in the examples presented here the same principles hold.
Weighted Interlace Polynomials
Authors: TRALDI LORENZO
Published: August 2009

The interlace polynomials introduced by Arratia, Bollobás and Sorkin extend to invariants of graphs with vertex weights, and these weighted interlace polynomials have several novel properties. One novel property is a version of the fundamental three-term formulathat lacks the last term. It follows that interlace polynomial computations can be represented by binary trees rather than mixed binary–ternary trees. Binary computation trees provide a description ofq(G) that is analogous to the activities description of the Tutte polynomial. IfGis a tree or forest then these ‘algorithmic activities’ are associated with a certain kind of independent set inG. Three other novel properties are weighted pendant-twin reductions, which involve removing certain kinds of vertices from a graph and adjusting the weights of the remaining vertices in such a way that the interlace polynomials are unchanged. These reductions allow for smaller computation trees as they eliminate some branches. If a graph can be completely analysed using pendant-twin reductions, then its interlace polynomial can be calculated in polynomial time. An intuitively pleasing property is that graphs which can be constructed through graph substitutions have vertex-weighted interlace polynomials which can be obtained through algebraic substitutions.
A REVIEW OF POSTNATAL MANAGEMENT OF CONGENITAL PULMONARY AIRWAY MALFORMATIONS
Authors: CHUANG SANDRA , SUGO ELLA , JAFFE ADAM
Published: August 2009

Congenital cystic adenomatoid malformations of the lung (CCAMs) were originally described by Ch'In and Tang in 1949 as rare lung lesions occurring in premature or stillborn infants with anasarca. In 1977 Stocker et al divided CCAM into three types based on their clinical and pathological features. The nomenclature has since changed to congenital pulmonary airway malformations (CPAMs) to reflect the possible absence of cystic changes and the probable underlying pathogenesis of different types. CPAMs are relatively rare congenital abnormalities with a reported incidence varying from 1 in 10,000 to 1 in 35,000. There is a slight male predominance, but no racial predilection has been noted. This review will outline the current nomenclature and features of different types of CPAMs, highlight possible mechanisms underlying the development of CPAMs, review current antenatal imaging modalities and interventions, address the debate surrounding the postnatal management of CPAMs, and suggest areas for future research.
Role of cations as components of jelly coats in Bufo arenarum fertilization
Authors: Medina Marcela Fátima , Crespo Claudia Alejandra , Ramos Inés , Fernández Silvia Nélida
Published: August 2009

The role of monovalent (Na+, K+) and divalent (Ca2+, Mg2+) cations in Bufo arenarum fertilization was analysed. Our results showed that the highest fertilization percentages were obtained when strings of uterine oocytes (UO) were inseminated. Under these conditions, full jelly (FJ), which represents the jelly coats surrounding the oocytes at the time of deposition, contained 68.5 ± 7.0 mM Na+, 27.4 ± 2.4 mM K+, 6.3 ± 0.9 mM Ca2+ and 6.9 ± 0.9 mM Mg2+. When the strings of oocytes were washed in deionized water, these cations diffused into the liquid medium surrounding them. There was a marked similarity between the loss of Ca2+ in the jelly and the decrease in the fertilizability of the UO. Furthermore, the use of chelating agents of divalent cations showed the importance of the Ca2+ contained in the jelly. When Ca2+ was sequestered from the jelly coats by the addition of the chelating agents to the insemination medium as well as by pretreatment of the UO strings, a decrease in fertilization percentages occurred, this effect being dose dependent and more marked with EGTA. These results demonstrate that the Ca2+ in the jelly plays a role in fertilization. Nevertheless, taking into account that during the washing of the jelly other jelly coat components were diffused and considering that the addition of Ca2+ to the insemination medium reverted significantly, but only partially, the loss of fertilizability of jellied UO (washed), the participation of other components in the fertilization mechanism is suggested.
An empirical investigation into the performance of UK pension fund managers
Authors: CLARE ANDREW , NITZSCHE DIRK , CUTHBERTSON KEITH
Published: August 2009

The UK's defined benefit pensions industry makes widespread use of pooled investment vehicles which are provided by a large number of fund management groups. In this paper, we provide the first comprehensive performance analysis of these funds. Using data on 734 actively managed pooled funds that had a combined value of just over £400bn at the end of 2007, ranging from UK equity to funds specialising in Pacific Basin equities, our results indicate that the performance of these institutional funds is generally better than those reported in the literature for managers of mutual funds. Nevertheless, with increasing numbers of UK fund managers purporting to be able to provide high alpha products to the UK's beleaguered pensions industry our results do not give us great confidence that the solution to the widespread deficits of the UK's pension fund industry lies in the hands of these active fund managers.
Securing pension benefits in DB private schemes with priority rules: an insight from contracting theory
Authors: LAVIGNE ANNE , NZE-OBAME JESUS HERELL
Published: August 2009

This contribution aims at enriching the debate on the priority of unfunded pension rights in the case of a sponsoring firm's bankruptcy. Starting from the idea that pension promises in DB schemes are part of a financial contract between a sponsor and participants to a sponsored pension plan, we argue that plan participants are not ordinary creditors and should be given the same priority as other claimants in the event of underfunding and a sponsoring firm's bankruptcy. We build up a model consistent with this view, which gives room for more participants' involvement in pension fund management. We assume that the sponsoring firm chooses the optimal share of a pension fund deficit that it commits to cover in case of underfunding, while participants choose the contribution rates that maximize their expected utility. We show that two regimes govern the pattern of the relationship between the optimal level of funding chosen by the sponsor and the optimal contribution rates chosen by the plan participants. Allowing plan participants to determine their desired contribution rates gives the entrepreneur the proper incentive for funding the pension plan. In a certain way, our pension contract resembles a cash-balance contract and our model suggests that more security can be given to plan participants in their pension savings by offering them a cash-balance plan which states a priority of unfunded pension rights in case of a firm's bankruptcy.
A possible generation mechanism of interplanetary rotational discontinuities
Authors: Lin C. C. , Tsai C. L. , Chen H. J. , Weng C. J. , Chao J. K. , Lee L. C.
Published: August 2009

In the present paper, we first examine some interplanetary directional discontinuities with very small Bn/B (<0.1) using intraspacecraft timing method. It is found that the velocity and magnetic field fluctuations of these directional discontinuities satisfy the Walén relation. We suggest that these directional discontinuities are rotational discontinuities. In addition, we investigate the stability of interplanetary rotational discontinuities using one‐dimensional hybrid simulations and found that rotational discontinuities with all values of Bn/B can stably exist in the solar wind. In one simulation run, we find that the rotational discontinuity (RD) is still stable when the ratio, Bn/B, equals 0.0001. Finally, from one‐dimensional hybrid simulation, we further find that the ratio is significantly reduced after interaction with interplanetary fast shocks. There are a few mechanisms for generation of RDs. Among them, two mechanisms are well accepted. One is nonlinear evolution of Alfvén waves in the solar wind, and another is magnetic reconnection near the solar surface. For magnetic reconnection, the reconnection rate, V1n/VA1(= Bn/B), in the magnetosphere and solar wind, is usually <0.2. Therefore the generated RDs also have Bn/B < 0.2. On the other hand, the nonlinear evolution of Alfvén waves in the solar wind can generate RDs at all values of Bn/B, which contradicts to the Cluster results. We suggest that interplanetary RDs with small Bn/B are likely been generated through magnetic reconnection.
Rocky Mountain evolution: Tying Continental Dynamics of the Rocky Mountains and Deep Probe seismic experiments with receiver functions
Authors: Rumpfhuber Eva‐Maria , Keller G. Randy , Sandvol Eric , Velasco Aaron A. , Wilson David C.
Published: August 2009

In this study, we have determined the crustal structure using three different receiver function methods using data collected from the northern transect of the Continental Dynamics of the Rocky Mountains (CD‐ROM) experiment. The resulting migrated image and crustal thickness determinations confirm and refine prior crustal thickness measurements based on the CD‐ROM and Deep Probe experiment data sets. The new results show a very distinct and thick lower crustal layer beneath the Archean Wyoming province. In addition, we are able to show its termination at 42°N latitude, which provides a seismic tie between the CD‐ROM and Deep Probe seismic experiments and thus completes a continuous north‐south transect extending from New Mexico into Alberta, Canada. This new tie is particularly important because it occurs close to a major tectonic boundary, the Cheyenne belt, between an Archean craton and a Proterozoic terrane. We used two different stacking techniques, based on a similar concept but using two different ways to estimate uncertainties. Furthermore, we used receiver function migration and common conversion point (CCP) stacking techniques. The combined interpretation of all our results shows (1) crustal thinning in southern Wyoming, (2) strong northward crustal thickening beginning in central Wyoming, (3) the presence of an unusually thick and high‐velocity lower crust beneath the Wyoming province, and (4) the abrupt termination of this lower crustal layer north of the Cheyenne belt at 42°N latitude.
Correlation of tremor activity with tidal stress in the northern Cascadia subduction zone
Authors: Lambert Anthony , Kao Honn , Rogers Garry , Courtier Nicholas
Published: August 2009

We analyze hourly data from five tremor episodes in the northern Cascadia subduction zone over the period 2003–2005 provided by the Tremor Activity Monitoring System (TAMS). All five tremor episodes correspond to slow slip events observed by GPS. Fourier decomposition is used to separate the hourly tremor counts for each episode into “long‐period” (0 < f < 0.8 cpd), “tidal” (0.8 < f < 2.2 cpd), and “short‐period” (f > 2.2 cpd) components. The tidal component of the observations is compared with theoretical stress variations at depths of 20, 30, and 40 km, with 40 km being the depth of the interpreted subduction thrust interface. The stress variations are predicted by a 2‐D ocean tide loading model combined with estimates of stress variations from Earth tides. We find that the shear stress in the thrust direction and the compressive normal stress on shallow dipping surfaces correlates with the data significantly better than the confining stress over the range of depths investigated. The relative amplitudes of tidal shear stress and compressive normal stress result in positive Coulomb stress favoring slip. Peak tremor activity occurs at times of maximum tidal shear stress in the thrust direction, which would assist slow slip and would suggest that tidal tremor and slip are colocated. The response of the tremor to tidal shear stress is roughly proportional to the mean activity level, controlled by tectonic conditions of stress and pore pressure. A significant, nontidal, daily variation in tremor activity of unknown origin is identified.
Mobilization and transport of in situ colloids during drainage and imbibition of partially saturated sediments
Authors: Cheng Tao , Saiers James E.
Published: August 2009

Colloid mobilization and transport in the vadose zone have important implications to the migration of many contaminants that adsorb to mineral surfaces. The objective of this study is to elucidate the influences of transient flow events on the mobilization of in situ colloids from water‐unsaturated natural sediments. Results from our laboratory column experiments demonstrate that sand pack drainage and imbibition mobilized substantial quantities of mineral colloids and that effluent colloid concentrations peaked concomitantly with the passage of the wetting and drying fronts. In these experiments, drainage events occurred first and mobilized higher concentrations of in situ colloids than the following imbibition events, and the mass of colloids mobilized was sensitive to pore water ionic strength, as well as to the rates of imbibition and drainage. The data from the column experiments were used to test a new mathematical model that is based on the assumption that colloid mobilization is driven by pore‐scale changes in air‐water configuration that occur during porous medium drainage and imbibition. The simulated changes in air‐water configuration are predicted on the basis of the measured water retention characteristics of the porous medium. Agreement between measured and modeled concentrations of colloids is generally good, and the parameters that govern the kinetics of colloid mobilization and redeposition vary in a discernible fashion with changes in ionic strength, imbibition rates, and drainage rates.
Intercomparison of homogenization techniques for precipitation data continued: Comparison of two recent Bayesian change point models
Authors: Beaulieu Claudie , Seidou Ousmane , Ouarda Taha B. M. J. , Zhang Xuebin
Published: August 2009

In this paper, two new Bayesian change point techniques are described and compared to eight other techniques presented in previous work to detect inhomogeneities in climatic series. An inhomogeneity can be defined as a change point (a time point in a series such that the observations have a different distribution before and after this time) in the data series induced from changes in measurement conditions at a given station. It is important to be able to detect and correct an inhomogeneity, as it can interfere with the real climate change signal. The first technique is a Bayesian method of multiple change point detection in a multiple linear regression. The second one allows the detection of a single change point in a multiple linear regression. These two techniques have never been used for homogenization purposes. The ability of the two techniques to discriminate homogeneous and inhomogeneous series was evaluated using simulated data series. Various sets of synthetic series (homogeneous, with a single shift, and with multiple shifts) representing the typical total annual precipitation observed in the southern and central parts of the province of Quebec, Canada, and nearby areas were generated for the purpose of this study. The two techniques gave small false detection rates on the homogeneous series. Furthermore, the two techniques proved to be efficient for the detection of a single shift in a series. For the series with multiple shifts, the Bayesian method of multiple change point detection performed better. An application to a real data set is also provided and validated with the available metadata.
Global atmospheric As and Bi contamination preserved in 3000 year old Arctic ice
Authors: Krachler Michael , Zheng Jiancheng , Fisher David , Shotyk William
Published: August 2009

Despite its growing environmental significance, there are no detailed historical records of atmospheric As deposition for the Northern Hemisphere. Having overcome the severe analytical challenges in measuring As in polar ice, and using an Arctic ice core representing ∼16 ka of snow accumulation, we present a complete record of atmospheric As deposition for this period which reveals significant contamination beginning 3000 years ago. While Pb enrichments unequivocally increased threefold above natural background levels during Greek/Phoenician, Roman, and Medieval periods, As is elevated by a factor of 5. Previous studies showed that these periods are not only enriched in Pb but also Sb: here we show significant contamination not only by As but also Bi, Cu, and Zn. The Pb isotope data reveal declines in the ratio206Pb/207Pb which reflects the introduction Pb‐bearing aerosols from smelting of lead ores, but the metallurgy of copper ores must also have played a role. Taken together, these findings demonstrate a deeper, broader environmental significance of sulphide ore processing in antiquity, defining the origins of global atmospheric contamination for a suite of related elements and providing a new perspective on the start of the Anthropocene. In addition, the data indicate that by far the greatest As concentrations in the ice core are recorded during the Younger Dryas cold climate event centered around 12 ka B.P., demonstrating the strong link between global climate change and the atmospheric cycling of trace elements.
Ozone hole and Southern Hemisphere climate change
Authors: Son Seok‐Woo , Tandon Neil F. , Polvani Lorenzo M. , Waugh Darryn W.
Published: August 2009

Climate change in the Southern Hemisphere (SH) has been robustly documented in the last several years. It has altered the atmospheric circulation in a surprising number of ways: a rising global tropopause, a poleward intensification of the westerly jet, a poleward shift in storm tracks, a poleward expansion of the Hadley cell, and many others. While these changes have been extensively related with anthropogenic warming resulting from the increase in greenhouse gases, their potential link to stratospheric cooling resulting from ozone depletion has only recently been examined and a comprehensive picture is still lacking. Examining model output from the coupled climate models participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment (AR4), and grouping them depending on the stratospheric ozone forcing used, we here show that stratospheric ozone affects the entire atmospheric circulation in the SH, from the polar regions to the subtropics, and from the stratosphere to the surface. Furthermore, model projections suggest that the anticipated ozone recovery, resulting from the implementation of the Montreal Protocol, will likely decelerate future climate change resulting from increased greenhouse gases, although it might accelerate surface warming over Antarctica.
Slope characteristics of Europa: Constraints for landers and radar Sounding
Authors: Schenk Paul M.
Published: August 2009

Limited Galileo‐derived topographic mapping of four major terrain types on Europa provides slope characteristics useful for designing spacecraft instruments and for terrain comparisons. Topographic data are derived using stereo and photoclinometric analysis of Galileo images at resolutions of 10 to 200 m (with a few sites sampled at ∼500 m resolution). Similar data are also presented for dark and bright terrains on Ganymede as well as preliminary results for polar terrains on Enceladus. RMS slopes for ridged plains, matrix, and crater deposits on Europa are typically between 10 and 15° at 10–100 m length scales, significantly steeper overall than typical landing sites on Mars. Terrains on Ganymede may be even rougher. Smooth dilational bands on Europa, however, have RMS slopes of ∼5°, the shallowest slope statistics of any major terrain type on Europa. Aside from these areas almost no smooth areas larger than a few kilometers across occur on Europa.
A new perspective on MST radar observations of stratospheric intrusions into‐troposphere associated with tropical cyclone
Authors: Das Siddarth Shankar
Published: August 2009

This paper presents the first ever evidence of stratospheric intrusion into troposphere during the passage of tropical cyclone using mesosphere‐stratosphere‐troposphere (MST) radar located at Gadanki (13.5°N, 79.2°E). The most significant and new observation is the enhanced signal‐to‐noise ratio (SNR) of thickness ∼1 km, extended from 16–13 km, when the cyclone is located close to the radar site. Small‐scale turbulence and strong downdraft followed by weak updraft are also observed from spectral‐width and vertical velocity, respectively. Further analysis of global data shows low out‐going long wave radiation (<170 W m−2), low tropopause temperature (<191 K), enhanced potential vorticity (∼1 PVU) in the upper/middle troposphere, and low specific humidity (∼2 × 10−4 kg/kg) at 300 hPa pressure level, occurs over the radar site. These observations clearly indicate the evidence of stratospheric intrusion into troposphere during the passage of tropical cyclone. The results are presented and discussed in the light of present understanding.
Recent biomass burning in the tropics and related changes in tropospheric ozone
Authors: Ziemke J. R. , Chandra S. , Duncan B. N. , Schoeberl M. R. , Torres O. , Damon M. R. , Bhartia P. K.
Published: August 2009

Biomass burning in the tropics is set intentionally during dry season each year to destroy agricultural waste and clear land for human expansion. These burning activities cause pollution including atmospheric particulates and trace gases which are harmful to human health. Measurements from the Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) from October 2004–November 2008 are used to evaluate the effects of biomass burning on tropical tropospheric ozone in the context of the Global Modeling Initiative (GMI) chemical transport model. The impact of biomass burning on ozone is significant within and near the burning regions with increases of ∼10–25% in tropospheric column ozone relative to average background concentrations. Globally the model indicates increases of ∼4–5% in ozone, ∼7–9% in NOx (NO + NO2), and ∼30–40% in CO.
Plasmaspheric dynamics resulting from the Hallowe'en 2003 geomagnetic storms
Authors: Kale Z. C. , Mann I. R. , Waters C. L. , Vellante M. , Zhang T. L. , Honary F.
Published: August 2009

Cross‐phase‐derived plasma mass density trends during the Hallowe'en 2003 geomagnetic storms are presented for 38° ≲ magnetic latitude ≲ 63° (1.61 ≤ L ≤ 5.10), using data from the SAMNET (Subauroral Magnetometer Network), BGS (British Geological Survey), and SEGMA (South European Geomagnetic Array), ground‐based magnetometer arrays in Europe. At all latitudes monitored, a rapid increase of total mass density is observed immediately following the initial storm sudden commencement at 0611 UT on 29 October, believed to be due to rapid ionospheric O+ outflow. Plasmaspheric density depletion to at least 50° magnetic latitude (L ∼ 2.4) took place over the next 3 days. Poststorm refilling began on 2 November. Following the sudden commencement of another storm on 4 November, a density enhancement was monitored at 2.79 ≤ L ≤ 3.84, with subsequent plasmaspheric depletion occurring by 6 November. Plasma mass density values are compared to empirical plasmapause location model predictions, with reasonable agreement for most days, but density depletion and refilling were monitored 1 day after they are predicted. During poststorm plasmaspheric refilling, some extremely low early morning resonance frequencies are monitored and appear be due to quarter mode standing waves. This study also highlights that care must be taken in the choice of assumed geomagnetic field geometry when deriving plasma mass densities from observed field line resonances during severe geomagnetic storms.
Energy dissipation and ion heating at the heliospheric termination shock
Authors: Wu P. , Winske D. , Gary S. P. , Schwadron N. A. , Lee M. A.
Published: August 2009

The Los Alamos hybrid simulation code is used to examine heating and the partition of dissipation energy at the perpendicular heliospheric termination shock in the presence of pickup ions. The simulations are one‐dimensional in space but three‐dimensional in field and velocity components, and are carried out for a range of values of pickup ion relative density. Results from the simulations show that because the solar wind ions are relatively cold upstream, the temperature of these ions is raised by a relatively larger factor than the temperature of the pickup ions. An analytic model for energy partition is developed on the basis of the Rankine‐Hugoniot relations and a polytropic energy equation. The polytropic index γ used in the Rankine‐Hugoniot relations is varied to improve agreement between the model and the simulations concerning the fraction of downstream heating in the pickup ions as well as the compression ratio at the shock. When the pickup ion density is less than 20%, the polytropic index is about 5/3, whereas for pickup ion densities greater than 20%, the polytropic index tends toward 2.2, suggesting a fundamental change in the character of the shock, as seen in the simulations, when the pickup ion density is large. The model and the simulations both indicate for the upstream parameters chosen for Voyager 2 conditions that the pickup ion density is about 25% and the pickup ions gain the larger share (approximately 90%) of the downstream thermal pressure, consistent with Voyager 2 observations near the shock.
A reassessment of spectralTeestimation in continental interiors: The case of North America
Authors: Kirby J. F. , Swain C. J.
Published: August 2009

Conventional spectralTestudies use the real part of the admittance between gravity anomalies and topography or, alternatively, the square of the magnitude of the coherency (i.e., coherence). Here we show the utility of treating both the admittance and coherency as complex quantities. Inverting the real parts to estimateTe, we use the imaginary parts to tell if the inversion is biased by noise. One method inverts the square of the real coherency, with the internal‐to‐total load ratioFderived (as a function of wave number) directly from the gravity and topography. The other method inverts the real part of the admittance assuming thatFis wave number‐independent. We test the methods using synthetic elastic plate models loaded at the surface and Moho in such a way that the final relief is the actual North American topography. In some of the models we add gravity noise generated by a model having both surface and internal loads such that the final topography is zero and find that both methods are susceptible to noise. Application of the two methods to North America givesTemaps showing substantial agreement except in regions affected by noise, but these are not a dominant part of the total area. Given the suggested mechanisms by which noise might arise, it is not surprising that it is not a more widespread feature of the North American craton. Importantly, both methods show that large parts of the Canadian Shield are characterized byTe> 100 km.
Hydrological modeling of groundwater disturbances to observed gravity: Theory and application to Asama Volcano, Central Japan
Authors: Kazama T. , Okubo S.
Published: August 2009

The gravity disturbance caused by groundwater is derived based on hydrological physics by solving nonlinear hydrological diffusion equations for three‐dimensional and temporal groundwater distributions. The gravity disturbance is then estimated by the spatial integral of the groundwater distributions. This approach aims to resolve the problems of previous methods for the correction of groundwater disturbances in gravity data, such as instrumental drift of relative gravimeters, empirical estimation of gravity assuming a linear gravity response to precipitation, and the use of lower‐dimensional water transfer models. The disturbance estimated using the proposed model is consistent with the observed gravity change at Asama Volcano in Central Japan during the rainy summer of 2006. The model reproduces the rapid increase and subsequent gradual decrease in gravity following rainfall events. The water mass within 150 m of the gravimeter is shown to dominate the observed gravity change during precipitation. It is also demonstrated that the use of adequately representative soil parameters is essential in order to accurately estimate the groundwater distributions and consequent gravity variations. This study shows that correcting for hydrological disturbances requires a more sophisticated model of water movements, particularly during heavy rainfall.
Statistics of nonlinear waves generated in an offshore wave basin
Authors: Cherneva Z. , Tayfun M. A. , Guedes Soares C.
Published: August 2009

This study analyzes waves generated in a deepwater wave basin and characterized by modulational instabilities induced by third‐order nonlinear interactions among freely propagating waves, which can cause the statistics of various surface features to deviate significantly from the predictions based on the linear Gaussian and second‐order models. Comparisons are provided between the statistics of wave envelopes and phases, wave heights, and crest and trough amplitudes observed for various theoretical approximations based on Gram‐Charlier expansions. The results suggest that the comparisons for the wave envelopes tend to be somewhat poor, particularly in the presence of relatively strong instabilities. In contrast, the comparisons for wave phases, crest‐to‐trough heights, and crest and trough amplitudes all indicate that the theoretical approximations represent the empirical distributions observed reasonably well, for the most part. Furthermore, the heights and crests of the largest waves do not exceed Miche‐Stokes‐type upper bounds.
Is transverse macrodispersivity in three‐dimensional groundwater transport equal to zero? A counterexample
Authors: Janković Igor , Steward David R. , Barnes Randal J. , Dagan Gedeon
Published: August 2009

In advective transport through weakly heterogeneous aquifers of random stationary and isotropic three‐dimensional permeability distribution, transverse macrodispersivity αT is found to be zero. This was determined in the past by solving the transport equation at first order in the log conductivity variance σY2. However, field findings indicate the presence of small but finite αT. The aim of the paper is to determine αT for highly heterogeneous formations using a model that contains inclusions of conductivity K, submerged in a matrix of conductivity K0, for large κ = K/K0. In the dilute medium approximation, valid for small volume fraction n, but arbitrary κ, and for spherical inclusions, it is found that αT = 0 because of the axisymmetry of flow past a sphere. A medium made up of rotational ellipsoids of arbitrary random orientation, macroscopically isotropic, and of the same κ and n is devised as a counterexample. It is found that because of the intertwining of streamlines αT > 0, being of order (κ − 1)4 for κ → 1. These findings are confirmed by accurate numerical simulations of flow through a large number of interacting inclusions; for κ = 10 and n = 0.2 (jamming limit), the large value αT/αL ≃ 0.15 is attained. The numerical simulations display the strong permanent deformation of stream tubes responsible for this phenomenon, coined as “advective mixing.” The two‐point covariance, used in practice in order to characterize the aquifer structure, is not able to detect the structures that produce advective mixing. Nevertheless, the presence of high‐conductivity lenses inclined with respect to the mean flow may explain the occurrence of finite αT in field applications.
A Class of Mutant CHO Cells Resistant to Cholera Toxin Rapidly Degrades the Catalytic Polypeptide of Cholera Toxin and Exhibits Increased Endoplasmic Reticulum‐Associated Degradation
Authors: Teter Ken , Jobling Michael G. , Holmes Randall K.
Published: August 2009

After binding to the eukaryotic cell surface, cholera toxin undergoes retrograde transport to the endoplasmic reticulum. The catalytic A1 polypeptide of cholera toxin (CTA1) then crosses the endoplasmic reticulum membrane and enters the cytosol in a process that may involve the quality control mechanism known as endoplasmic reticulum‐associated degradation. Other toxins such as Pseudomonas exotoxin A and ricin are also thought to exploit endoplasmic reticulum‐associated degradation for entry into the cytosol. To test this model, we mutagenized Chinese hamster ovary cells and selected clones that survived a prolonged coincubation with Pseudomonas exotoxin A and ricin. These lethal endoplasmic reticulum‐translocating toxins bind different surface receptors and target different cytosolic substrates, so resistance to both would likely result from disruption of a shared trafficking or translocation event. Here we characterize two Pseudomonas exotoxin A/ricin‐resistant clones that exhibited increased endoplasmic reticulum‐associated degradation. Both clones acquired the following unselected traits: (i) resistance to cholera toxin; (ii) increased degradation of an endoplasmic reticulum‐localized CTA1 construct; (iii) increased degradation of an established endoplasmic reticulum‐associated degradation substrate, the Z variant of α1‐antitrypsin (α1AT‐Z); and (iv) reduced secretion of both α1AT‐Z and the transport‐competent protein α1AT‐M. Proteosome inhibition partially rescued the α1AT‐M secretion deficiencies. However, the mutant clones did not exhibit increased proteosomal activity against cytosolic proteins, including a second CTA1 construct that was expressed in the cytosol rather than in the endoplasmic reticulum. These results suggested that accelerated endoplasmic reticulum‐associated degradation in the mutant clones produced a cholera toxin/Pseudomonas exotoxin A/ricin‐resistant phenotype by increasing the coupling efficiency between toxin translocation and toxin degradation.
Recycling Compartments and the Internal Vesicles of Multivesicular Bodies Harbor Most of the Cholesterol Found in the Endocytic Pathway
Authors: Möbius W. , Van Donselaar E. , Ohno‐Iwashita Y. , Shimada Y. , Heijnen H. F. G. , Slot J. W. , Geuze H. J.
Published: August 2009

We employed our recently developed immuno‐electron microscopic method (W. Möbius, Y. Ohno‐Iwashita, E. G. van Donselaar, V. M. Oorschot, Y. Shimada, T. Fujimoto, H. F. Heijnen, H. J. Geuze and J. W. Slot, J Histochem Cytochem 2002; 50: 43–55) to analyze the distribution of cholesterol in the endocytic pathway of human B lymphocytes. We could distinguish 6 categories of endocytic compartments on the basis of morphology, BSA gold uptake kinetics and organelle marker analysis. Of all cholesterol detected in the endocytic pathway, we found 20% in the recycling tubulo‐vesicles and 63% present in two types of multivesicular bodies. In the multivesicular bodies, most of the cholesterol was contained in the internal membrane vesicles, the precursors of exosomes secreted by B cells. Cholesterol was almost absent from lysosomes, that contained the bulk of the lipid bis(monoacylglycero)phosphate, also termed lysobisphosphatidic acid. Thus, cholesterol displays a highly differential distribution in the various membrane domains of the endocytic pathway.
Phospholipase A2 (PLA2) Enzymes in Membrane Trafficking: Mediators of Membrane Shape and Function
Authors: Brown William J. , Chambers Kimberly , Doody Anne
Published: August 2009

Since the mid‐1990s, there have been tremendous advances in our understanding of the roles that lipid‐modifying enzymes play in various intracellular membrane trafficking events. Phospholipases represent the largest group of lipid‐modifying enzymes and accordingly display a wide range of functions. The largest class of phospholipases are the phospholipase A(2) (PLA2) enzymes, and these have been most extensively studied for their roles in the generation lipid signaling molecules, e.g. arachidonic acid. In recent years, however, cytoplasmic PLA2 enzymes have also become increasingly associated with various intracellular trafficking events, such as the formation of membrane tubules from the Golgi complex and endosomes, and membrane fusion events in the secretory and endocytic pathways. Moreover, the ability of cytoplasmic PLA2 enzymes to directly affect the structure and function of membranes by altering membrane curvature suggests novel functional roles for these enzymes. This review will focus on the role of cytoplasmic PLA2 enzymes in intracellular membrane trafficking and the mechanisms by which they influence membrane structure and function.