bluuebunny/crossref_metadata_2025 huggingface dataset:
Enjeux autour des flux migratoires dans les décennies à venir
Authors: Wihtol de Wenden Catherine
Published: March 2011

Enjeux autour des flux migratoires dans les décennies à venir Le phénomène des migrations internationales n’a fait que progresser au cours des dernières années et englobe aujourd’hui la quasi-totalité des pays du monde (qu’ils soient zone de départ, d’accueil, ou de transit). La situation est encore amplifiée par l’apparition de problématiques nouvelles. Parmi les enjeux déterminants pour la recomposition du paysage humain mondial en 2030 : la démographie, le risque environnemental, les inégalités ou encore les violences et les crises politiques. Face aux nouveaux modes de circulation, comment s’adapteront les gouvernements (pris entre des objectifs politiques et des impératifs économiques, sociaux et culturels) et les opinions publiques ? Comment gérer ces mouvements de population ? Et, surtout, comment vivre ensemble ? Telles sont les questions auxquelles il faudra tâcher de répondre au cours des vingt prochaines années.
Le Brésil dans le monde ou la tentation de la grandeur
Authors: Rouquié Alain
Published: March 2011

Le Brésil dans le monde ou la tentation de la grandeur Alors que l’ère Lula touche à sa fin, le Brésil semble plus que jamais en mesure d’accéder à une place prépondérante sur la scène internationale. Devenu, en l’espace de quelques années, une véritable puissance agricole – et économique en devenir -, un leader régional, fort de ses richesses en matières premières, le géant sud-américain s’est récemment illustré par une participation croissante aux dossiers géopolitiques mondiaux, et par des prises de position fermes démontrant une volonté d’affirmation de ses divergences éventuelles. Dans cet article, Alain Rouquié, ancien Ambassadeur de France au Brésil, analyse le nouveau rôle potentiel du Brésil et sa capacité à remettre en cause le statu quo international tout en assumant ses nouvelles responsabilités.
Eux et nous : quelles évolutions en Méditerranée ?
Authors: El Karoui Hakim
Published: March 2011

Eux et nous : quelles évolutions en Méditerranée ? Le développement des relations euro-méditerranéennes est aujourd’hui au point mort, principalement à cause du manque de vision des derniers projets lancés par les dirigeants européens, comme l’Union pour la Méditerranée. Devant cette absence de perspectives concrètes, Hakim El Karoui se propose d’impulser une nouvelle dynamique de partenariat via la création de structures de coopération efficaces, visant notamment l’établissement de politiques migratoires communes entre les rives nord et sud. Régulation des migrations, transferts de compétences, mobilité du travail, coresponsabilité sont autant de sujets abordés par l’auteur qui plaide pour l’émergence d’une véritable coopération développée pas à pas, a contrario des lancements déclamatoires d’organisations multilatérales vides de sens.
Les grandes puissances et le Moyen-Orient : vers une rémanence du facteur américain ?
Authors: Mikaïl Barah
Published: March 2011

Les grandespuissances et le Moyen-Orient : vers une rémanence du facteur américain ? Ouelle sera en 2030 la place des États-Unis dans la région moyen-orientale? La domination du pays est-elle si bien assise qu’on le croit ? Les États-Unis restent un acteur incontournable sur les plans diplomatique, stratégique, militaire et énergétique, mais d’autres acteurs entendent investir une région essentielle sur l’échiquier international. La Chine et la Russie en particulier semblent marquer des points, tant dans le domaine diplomatique que militaire ou commercial. Mais si ces pays profitent d’un certain affaiblissement de l’ascendant américain, celui-ci pourrat-il réellement être supplanté au Moyen-Orient ? Les conditions d’une recomposition des équilibres géopolitiques ne sont pas réunies pour une concurrence frontale entre grandes puissances et tout porte à croire qu’au cours des prochaines décennies, les États-Unis conserveront leur prédominance dans la région.
Afrique 2030 : quels futurs possibles ?
Authors: Hugon Philippe
Published: March 2011

Afrique 2030 : quels futurs possibles ? Si l’on évoque souvent l’affirmation de la Chine, de l’Inde, ou encore du Brésil, et le poids grandissant de ces pays émergents sur la scène internationale, on constate la persistance de la marginalisation de l’Afrique, en dépit des signes annonciateurs d’une véritable dynamique de développement. Au-delà des défis internes (politiques, démographiques, environnementaux et sécuritaires) qu’elle doit relever, l’Afrique doit maintenant réussir son entrée dans le concert des nations qui sera, entre autres, liée à l’évolution de sa participation à l’économie mondiale. Plusieurs scénarii, de l’intégration régionale au développement de nouveaux partenariats, notamment avec les émergents, sont ici exposés par Philippe Hugon pour mieux saisir les enjeux et problématiques de la future Afrique.
Répliquer collectivement à la tâche pour « faire du bon boulot » d'un « boulot sale »
Authors: Poussin Nadine
Published: March 2011

Résumé Lors d’interventions en clinique de l’activité auprès d’éboueurs, nous avons fait le constat qu’ils font preuve d’une grande inventivité dans leur travail quotidien. Ils créent notamment certains de leurs outils de travail. L’usage par catachrèse qu’ils font alors des déchets renvoie à une création de buts nouveaux en cours d’activité et permet de répondre à d’autres préoccupations que celles liées à la tâche. Ils conçoivent l’organisation du travail du binôme lors de la collecte. Laissée par le prescripteur à la main des éboueurs comme une organisation contextuelle, elle stabilise pourtant des règles de métier, des automatismes communs. Ces inventions ne sont pas indépendantes de l’organisation prescrite (que ce soient les artefacts, les règles de sécurité, l’ordre ou les modes opératoires). Elle est « en dialogue » avec cette organisation prescrite et ceux qui l’élaborent. C’est pourquoi il nous semble que cette réorganisation par les éboueurs est facilitée quand ils ont une prescription à laquelle ils peuvent répliquer et à laquelle en retour répond la prescription. Nous poserons qu’elle est la condition pour que les éboueurs puissent en tentant de « faire du bon boulot » subvertir leur « sale boulot ».
Dans les coulisses du hammam
Authors: Benhayoune Habiba
Published: March 2011

Résumé Cet article est issu d’une enquête clinique menée sur l’activité des gommeuses et masseuses de hammam à Paris. Hammam rime avec bien-être et détente. Il s’agit ici d’analyser dans un premier temps la souffrance vécue par les employées interrogées pour saisir ensuite leurs défenses pour faire face à la saleté et l’éreintement physique. Les tayabates décrivent leur activité comme elles la vivent : avec une gêne camouflée par le rire et les moments ludiques de danse et de chansons. L’ambiance à la fois conviviale et familiale joue un rôle très important.
Cardiorenal Syndrome in Acute Heart Failure Syndromes
Authors: Sarraf Mohammad , Schrier Robert W.
Published: March 2011

Impaired cardiac function leads to activation of the neurohumoral axis, sodium and water retention, congestion and ultimately impaired kidney function. This sequence of events has been termed the Cardiorenal Syndrome. This is different from the increase in cardiovascular complications which occur with primary kidney disease, that is, the so-called Renocardiac Syndrome. The present review discusses the pathogenesis of the Cardiorenal Syndrome followed by the benefits and potential deleterious effects of pharmacological agents that have been used in this setting. The agents discussed are diuretics, aquaretics, natriuretic peptides, vasodilators, inotropes and adenosineα1 receptor antagonists. The potential role of ultrafiltration is also briefly discussed.
Alzheimer′s Disease and Metals: A Review of the Involvement of Cellular Membrane Receptors in Metallosignalling
Authors: Amadoruge Pavithra C. , Barnham Kevin J.
Published: March 2011

Alzheimer′s disease (AD) is a debilitating form of dementia. The hallmark protein associated with the disease is the amyloid beta (Aβ) peptide. Aggregation of Aβ has been shown to depend on interactions with metals. The recent studies now demonstrate that metals also play additional important roles in the disease process. Consequently, there may be benefit from modulating metal homeostasis. However, the role and subcellular location of metals within neurons is not well understood. There is growing evidence to suggest that metals can act at the site of cellular membrane receptors and affect cellular signaling by modulating the signal transduction of those receptors. The glutamatergic and cholinergic receptor systems, both well‐known neurotransmitter systems affected in AD, have well‐documented metal interactions, as do the tropomyosin‐receptor kinase (Trk) family of receptors and the epidermal growth factor (EGF) receptor. In this paper, the metal interactions with these membrane receptor systems will be explored and thus the potential for membrane receptors as an intervention point in AD will be assessed.
Mitochondrial DNA Damage and Animal Longevity: Insights from Comparative Studies
Authors: Pamplona Reinald
Published: March 2011

Chemical reactions in living cells are under strict enzyme control and conform to a tightly regulated metabolic program. However, uncontrolled and potentially deleterious endogenous reactions occur, even under physiological conditions. Aging, in this chemical context, could be viewed as an entropic process, the result of chemical side reactions that chronically and cumulatively degrade the function of biological systems. Mitochondria are a main source of reactive oxygen species (ROS) and chemical sidereactions in healthy aerobic tissues and are the only known extranuclear cellular organelles in animal cells that contain their own DNA (mtDNA). ROS can modify mtDNA directly at the sugar-phosphate backbone or at the bases, producing many different oxidatively modified purines and pyrimidines, as well as single and double strand breaks and DNA mutations. In this scenario, natural selection tends to decrease the mitochondrial ROS generation, the oxidative damage to mtDNA, and the mitochondrial mutation rate in long-lived species, in agreement with the mitochondrial oxidative stress theory of aging.
Ovarian Steroid Cell Tumour: Correlation of Histopathology with Clinicopathologic Features
Authors: Mehdi Ghazala , Ansari Hena A. , Sherwani Rana K. , Rahman Khaliqur , Akhtar Nishat
Published: March 2011

Ovarian steroid cell tumours (not otherwise specified) are rare neoplasms of the ovary and are classified under lipid cell tumours. Their diagnosis can be considered as one of exclusion. Histopathologically, the tumour should carefully be evaluated for microscopic features of malignancy, but it is essential for the clinician and the pathologist to remember that in these tumours, pathologically benign histomorphology does not exclude the possibility of clinically malignant behaviour. Our case study focuses on the comparative findings in a postmenopausal female diagnosed with an ovarian steroid tumour (not otherwise specified). A careful correlation between clinical and surgical evaluation and microscopic analysis is necessary, as is a regular followup.
Source parameters of the 1963 Mw 6.1 Baffin Island earthquake
Authors: Bent A L
Published: March 2011

The Mw 6.1 earthquake of 4 September 1963 is the largest earthquake known to have occurred in the highly active seis1nic zone along the east coast of Baffin Island. Previous efforts to study this earthquake employed different subsets of the available data and did
not reach a consensus re­garding the focal mechanism, although all agree that there was a significant component of normal slip involved. The present study makes use of all the waveform data used by previous authors as well as additional seismograms that were either unused (mainly southern Canadian
data) or unavailable (data from the former Soviet Union) in the past. The preferred focal mech­anism based on waveform modeling implies nearly pure normal faulting on a roughly east-west striking plane. This solution is compatible with both the regional and teleseismic body wave data, and is similar
to some of the previously suggested mechanisms. The focal mechanis1n also appears to be consistent with the aftershock distribution. This and previous studies are in agreement with regard to the depth (7 km) and size (Mw 6.1) of the earthquake.
Sedimentation in Canada Basin, western Arctic
Authors: Mosher D C , Shimeld J , Jackson R , Hutchinson D , Chapman C B , Chian D , Childs J , Mayer L , Edwards B , Verhoef J
Published: March 2011

Canada Basin of the western Arctic Ocean is the least studied ocean basin in the World. Marine seismic field programs were conducted during the past 5 years in order to study the geology, sedimentary history and geomorphology of the region. As part of this
program, five annual icebreaker expeditions acquired bathymetric, seismic reflection and seismic refraction data on a regional scale. More than 12,000 line-km of multi-channel seismic reflection data and 120 sonobuoy seismic refraction records over abyssal plain and continental rise regions of
Canada Basin, Northwind Ridge and Alpha Ridge were acquired. The success of these programs was achieved through novel technical modifications to seismic equipment to permit towing in heavy ice conditions and through collaboration between multiple Canadian and US agencies and institutions, enabling
utilization of two ice breakers during seismic and multibeam data acquisition in heavy ice.
The seafloor of Canada Basin is remarkably flat-lying in its central region, with little bathymetric change over most of its extent. The sedimentary succession is generally flat lying with reflections extending over 100's of km. These reflections infill basement topography and onlap bathymetric
highs, such as Alpha and Northwind ridges. The sedimentary succession is thickest in the Beaufort Sea region, reaching more than 10 km, and generally thins to the north and west. Reflection characteristics suggest that sediment volume input to the Arctic Ocean has been high and dominated by
turbidity current deposition, similar to Amundsen and Nansen Basins of the Eurasian Basin. These turbidites originate from the eastern and southern continental margins. There is no evidence of contemporaneous or post-depositional reworking by bottom currents. Additionally, there is little evidence
of tectonic deformation after primary basin-forming events except in the NE quadrant, nearer Alpha Ridge.
Focal mechanisms and depths of aftershocks of the 2010 Haiti earthquake
Authors: Bent A L
Published: March 2011

The devastating magnitude 7.0 earthquake that struck Haiti on 12 January 2010 was followed by hundreds of aftershocks. The largest were recorded at regional to teleseismic distances. The smaller aftershocks were not recorded in the days immediately following
the mainshock as there was no seismic monitoring capacity within Haiti. With the installation of a real time three-station network in Haiti by the GSC in mid-February the ability to monitor the aftershocks was vastly improved. Using the new Haitian stations as well as existing stations elsewhere
in the Caribbean, focal mechanisms and depths of many of the aftershocks can be determined, both of which provide insight into the seismotectonics of the region and implications for future seismic hazard assessments. This paper summarizes the focal mechanisms and depths of the larger (magnitude ?
4.5) aftershocks determined by regional moment tensor inversion and the focal mechanisms of the smaller aftershocks determined by a composite first motion inversion. The results are consistent with the teleseismically determined focal mechanisms of the mainshock and largest aftershock and provide
further evidence for a complex faulting regime consisting of strike-slip faulting in the east of the aftershock zone where the mainshock initiated and thrust faulting in the west where the largest number of aftershocks has occurred.
The mediating effect of knowledge sharing between organisational culture and turnover intentions of professional nurses
Authors: Jacobs Everd J. , Roodt Gert
Published: March 2011

Professional nurses routinely use highly developed domain knowledge in combination with experiential knowledge to deliver quality care. However, this knowledge is often lost to employers as the migration of professional nurses from the developing countries to the developed world has become a global problem. The objective of this study therefore was to determine the relationships between organisational culture, knowledge sharing and turnover intentions and thereafter to propose knowledge sharing as a mediating variable in this relationship in order to suggest a retention strategy. A cross-sectional field survey design with questionnaires was used on a sample of professional nurses (N = 530) in private and provincial hospitals in South Africa. The tri-variate procedure of Baron and Kenny for mediation testing was adopted. The results indicated that a positive correlation exists between organisational culture and knowledge sharing, but a significant negative correlation between organisational culture and turnover intentions, as well as between knowledge sharing and turnover intentions. Finally, the results indicated that knowledge sharing mediates the relationship between organisational culture and turnover intentions, although with a small effect size.The findings suggest that turnover intentions of nurses can be actively managed through contextual variables such as organisational culture and opportunities for knowledge sharing.
Homogeneous Dynamics and Number Theory
Authors: Einsiedler Manfred , Kleinbock Dmitry , Lindenstrauss Elon , Oh Hee
Published: March 2011

The theory of flows on homogeneous spaces of Lie groups has emerged as a distinct, rapidly advancing subject over the last few decades incorporating ergodic theory, geometry and number theory. The workshop showcased the latest advances in the subject as well as a wide range of applications.
Calculus of Variations
Authors: De Lellis Camillo , Huisken Gerhard , McCann Robert J.
Published: March 2011

Since its invention by Newton, the calculus of variations has formed one of the central techniques for studying problems in geometry, physics, and partial differential equations. This trend continues even today. On the one hand, slow but steady progress is made on long-standing questions concerning minimal surfaces, curvature flows, and related geometric objects. Basic questions also remain in such areas as mathematical physics and general relativity. On the other hand, new types of question emerge, driven by applications from economics and engineering to materials science, whose solution will depend on developing ideas and techniques in this classical branch of analysis. The July 2010 Oberwolfach workshop on the Calculus of Variations showcased a blend of continued progress in traditional areas with surprising developments which emerged from the exploration of new lines of research.
Cohomology of Finite Groups: Interactions and Applications
Authors: Adem Alejandro , Carlson Jon F. , Krause Henning
Published: March 2011

The cohomology of finite groups is an important tool in many subjects including representation theory and algebraic topology. This meeting was the third in a series that has emphasized the interactions of group cohomology with other areas.
Mathematical Theory and Modelling in Atmosphere-Ocean-Science
Authors: Majda Andrew J. , Stevens Bjorn , Klein Rupert
Published: March 2011

Participants from around the world gathered to review application and development of mathematics in relation to problems in the atmospheric, oceanic and climate sciences.
Mini-Workshop: Exploiting Symmetry in Optimization
Authors: Kaibel Volker , Liberti Leo , Schürmann Achill , Sotirov Renata
Published: March 2011

The feasible regions of mathematical optimization models quite often exhibit a high degree of symmetry. In recent years, several groups of researchers have independently worked on algorithmic approaches to exploit such symmetries in a variety of contexts. Many of the techniques that have been developed are related or rely on similar computational tools. The workshop brought together researchers working on symmetry aspects in different areas of optimization. The exchange of state-of-the-art knowledge between these areas lead to identification of important directions for future research activities.
Global parametrices for the Schrödinger propagator and geometric approach to the Hamilton-Jacobi equation
Authors: Graffi Sandro , Zanelli Lorenzo
Published: March 2011

A result is announced concerning a family of semiclassical Fourier Integral Operators representing a global parametrix for the Schrödinger propagator when the potential is quadratic at infinity. The construction is based on the geometrical approach of the corresponding Hamilton-Jacobi equation and thus sidesteps the problem of the caustics generated by the classical flow. Moreover, a detailed study of the real phase function allows us to recover a WKB semiclassical approximation which necessarily involves the multivaluedness of the graph of the Hamiltonian flow past the caustics.
An obstacle problem with gradient term and asymptotically linear reaction
Authors: Abdellaoui Boumediene , Bouguima Sidi Mohamed , Peral Ireneo
Published: March 2011

We will consider the following obstacle problem

\int_{\Omega}\nabla u\nabla T_{k}(v-u)dx +\int_{\Omega }h(u)\left\vert \nabla u\right\vert ^{q}T_{k}(v-u)dx\geq \int_{\Omega }\left(g(x,u)+f\right) T_{k}(v-u)dx,

with the condition that

u\geq\psi

a.e in

\Omega .

Under suitable condition relating

g

,

h

and

q

, we show the existence of a solution for all

f \in L^1(\Omega)

.

The main feature is, assuming that

g(x,s)

is asymptotically linear as

|s|\to \pm\infty

and independently of the values of

\lim\limits_{s\to \pm\infty }\dfrac{g(x,s)}{s},

to obtain a solution for all

\lambda>0

and

f\in L^1(\Omega)

. In this sense we could say that the first order term break down any resonant effect.
Variational methods for nonlinear perturbations of singular $ϕ$-Laplacians
Authors: Bereanu Cristian , Jebelean Petru , Mawhin Jean
Published: March 2011

Motivated by the existence of radial solutions to the Neumann problem involving the mean extrinsic curvature operator in Minkowski space

\mathrm{div}\left(\frac{\nabla v}{\sqrt{1-|\nabla v|^2}}\right)=g(|x|,v) \quad \text{in} \quad \mathcal A, \quad \frac{\partial v}{\partial \nu}=0 \quad \text{on} \quad \partial\mathcal A,

where

0 \leq R_1 < R_2

,

\mathcal A=\{ x\in \mathbb{R}^N: R_1\leq |x|\leq R_2\}

and

g:[R_1,R_2]\times \mathbb{R}\to\mathbb{R}

is continuous, we study the more general problem

[r^{N-1} \phi(u')]' =r^{N-1}g(r,u), \quad u'(R_1)=0=u'(R_2),

where

\phi:=\Phi':(-a,a) \to \mathbb{R}

is an increasing homeomorphism with

\phi(0)=0

and the continuous function

\Phi:[-a,a] \to \mathbb{R}

is of class

C^1

on

(-a,a)

. The associated functional in the space of continuous functions over

[R_1,R_2]

is the sum of a convex lower semicontinuous functional and of a functional of class

C^1

. Using the critical point theory of Szulkin, we obtain various existence and multiplicity results for several classes of nonlinearities. We also discuss the case of the periodic problem.
Creation of a Hyponatremia Registry Supported by an Industry-Derived Quality Control Methodology
Authors: Fuentes N. , Pazo V. , Posadas-Martínez M. L. , Michellangelo H. , Waisman G. , González Bernaldo De Quirós F. , Giunta D.
Published: March 2011

Background: A clinical registry encompasses a selective set of rigorously collected and stored clinical data focused on a specific condition. Hyponatremia has multiple, complex underlying causes and is one of the most frequent laboratory abnormalities. No systematic registries of hyponatremic patients have been reported in the medical literature. The purpose of this project was to create a registry for hyponatremia in order to obtain epidemiological data that will help to better understand this condition.

Objective: This paper describes the creation of a registry for hyponatremia within a single institution that employs industry-based approaches for quality management to optimize data accuracy and completeness.

Methods: A prospective registry of incident hyponatremia cases was created for this study. A formalized statistically based quality control methodology was developed and implemented to analyze and monitor all the process indicators that were developed to ensure data quality.

Results: Between December 2006 and April 2009, 2443 episodes of hyponatremia were included. Six process indicators that reflect the integrity of the system were evaluated monthly, looking for variation that would suggest systematic problems. The graphical representation of the process measures through control charts allowed us to identify and subsequently address problems with maintaining the registry.

Conclusion: In this project we have created a novel hyponatremia registry. To ensure the quality of the data in this registry we have implemented a quality control methodology based on industrial principles that allows us to monitor the performance of the registry over time through process indicators in order to detect systematic problems. We postulate that this approach could be reproduced for other registries.
Evolution of organic aerosol mass spectra upon heating: implications for OA phase and partitioning behavior
Authors: Cappa C. D. , Wilson K. R.
Published: March 2011

Abstract. Vacuum Ultraviolet (VUV) photoionization mass spectrometry has been used to measure the evolution of chemical composition for two distinct organic aerosol types as they are passed through a thermodenuder at different temperatures. The two organic aerosol types considered are primary lubricating oil (LO) aerosol and secondary aerosol from the α-pinene + O3 reaction (αP). The evolution of the VUV mass spectra for the two aerosol types with temperature are observed to differ dramatically. For LO particles, the spectra exhibit distinct changes with temperature in which the lower m/z peaks, corresponding to compounds with higher vapor pressures, disappear more rapidly than the high m/z peaks. In contrast, the αP aerosol spectrum is essentially unchanged by temperature even though the particles experience significant mass loss due to evaporation. The variations in the LO spectra are found to be quantitatively in agreement with expectations from absorptive partitioning theory whereas the αP spectra suggest that the evaporation of αP derived aerosol appears to not be governed by partitioning theory. We postulate that this difference arises from diffusivity within the αP particles being sufficiently slow that they do not exhibit the expected liquid-like behavior and perhaps exist in a glassy state. To reconcile these observations with decades of aerosol growth measurements, which indicate that OA formation is described by equilibrium partitioning, we present a conceptual model wherein the secondary OA is formed and then rapidly converted from an absorbing form to a non-absorbing form. The results suggest that, although OA growth may be describable by equilibrium partitioning theory, the properties of organic aerosol once formed may differ significantly from the properties determined in the equilibrium framework.
Controls of carbon dioxide concentrations and fluxes above central London
Authors: Helfter C. , Famulari D. , Phillips G. J. , Barlow J. F. , Wood C. R. , Grimmond C. S. B. , Nemitz E.
Published: March 2011

Abstract. Eddy-covariance measurements of carbon dioxide fluxes were taken continuously between October 2006 and May 2008 at 190 m height in central London (UK) to quantify emissions and study their controls. Inner London, with a population of 8.2 million (~5000 inhabitants per km2) is heavily built up with 8% vegetation cover within the central boroughs. CO2 emissions were found to be mainly controlled by fossil fuel combustion (e.g. traffic, commercial and domestic heating). The measurement period allowed investigation of both diurnal patterns and seasonal trends. Diurnal averages of CO2 fluxes were found to be correlated with traffic but also exhibited an inverse dependency on atmospheric stability in the near-neutral range, with higher fluxes coinciding with unstable stratification during most seasons and perhaps reflecting how changes in heating-related natural gas consumption and, to a lesser extent, photosynthetic activity controlled the seasonal variability. Despite measurements being taken at ca. 22 times the mean building height, coupling with street level was adequate, especially during daytime. Night-time saw a higher occurrence of stable or neutral stratification, especially in autumn and winter, which resulted in data loss in post-processing and caused the tower to become decoupled from street level. CO2 fluxes observed at night were not always correlated with traffic counts, probably reflecting this decoupling, but also the fact that at night heating was always a larger source than traffic. No significant difference was found between the annual estimate of net exchange of CO2 for the expected measurement footprint and the values derived from the National Atmospheric Emissions Inventory (NAEI), with daytime fluxes differing by only 3%. This agreement with NAEI data also supported the use of the simple flux footprint model which was applied to the London site; this also suggests that individual roughness elements did not significantly affect the measurements due to the large ratio of measurement height to mean building height.
Changes in organic aerosol composition with aging inferred from aerosol mass spectra
Authors: Ng N. L. , Canagaratna M. R. , Jimenez J. L. , Chhabra P. S. , Seinfeld J. H. , Worsnop D. R.
Published: March 2011

Abstract. Organic aerosols (OA) can be separated with factor analysis of aerosol mass spectrometer (AMS) data into hydrocarbon-like OA (HOA) and oxygenated OA (OOA). We develop a new method to parameterize H:C of OOA in terms of f43 (ratio of m/z 43, mostly C2H3O+, to total signal in the component mass spectrum). Such parameterization allows the transformation of large database of ambient OOA components from the f44 (mostly CO2+, likely from acid groups) vs. f43 space ("triangle plot") (Ng et al., 2010) into the Van Krevelen diagram (H:C vs. O:C). Heald et al. (2010) suggested that the bulk composition of OA line up in the Van Krevelen diagram with a slope ~ −1; such slope can potentially arise from the physical mixing of HOA and OOA, and/or from chemical aging of these components. In this study, we find that the OOA components from all sites occupy an area in the Van Krevelen space, with the evolution of OOA following a shallower slope of ~ −0.5, consistent with the additions of both acid and alcohol functional groups without fragmentation, and/or the addition of acid groups with C-C bond breakage. The importance of acid formation in OOA evolution is consistent with increasing f44 in the triangle plot with photochemical age. These results provide a framework for linking the bulk aerosol chemical composition evolution to molecular-level studies.
Ozone-driven photochemical formation of carboxylic acid groups from alkane groups
Authors: Liu S. , Day D. A. , Shields J. E. , Russell L. M.
Published: March 2011

Abstract. Carboxylic acids are ubiquitous in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were highly associated with trajectories from an industrial region with high organic mass (OM), likely from fossil fuel combustion emissions. The concentration of carboxylic acid groups peaked during daytime, suggesting a photochemical secondary formation mechanism. This daytime increase in concentration was tightly correlated with O3 mixing ratio, indicating O3 was the likely driver in acid formation. Based on the diurnal cycles of carboxylic acid and alkane groups, the covariation of carboxylic acid groups with O3, and the composition of the Combustion factor resulted from the factor analyses, gas-phase alkane oxidation by OH radicals to form dihyfrofuran followed by further oxidation of dihydrofuran by O3 is the likely acid formation mechanism. Using the multi-day average of the daytime increase of carboxylic acid group concentrations and m/z 44-based Aged Combustion factor, we estimated the lower-bound contributions of secondary organic aerosol (SOA) formed in 12-h daytime of processing in a single day to be 30% of the carboxylic acid groups and 25–45% of the Combustion factor concentration. These unique ambient observations of photochemically-driven acid formation suggest that gas-phase alkanes might be important sources of SOA formation in this coastal region.
Satellite-based evidence of wavelength-dependent aerosol absorption in biomass burning smoke inferred from ozone monitoring instrument
Authors: Jethva H. , Torres O.
Published: March 2011

Abstract. We provide satellite-based evidence of the spectral dependence of absorption in biomass burning aerosols over South America using near-UV measurements made by Ozone Monitoring Instrument (OMI) during 2005–2007. Currently, OMAERUV aerosol algorithm characterizes carbonaceous aerosol as "gray" aerosol, meaning no wavelength dependence in aerosol absorption. With this assumption, OMI-derived aerosol optical depth (AOD) is found to be over-estimated significantly compared to that of AERONET at several sites during intense biomass burning events (August–September). The assumption on height of aerosols and other parameters seem to be reasonable and unable to explain large discrepancy in the retrieval. The specific ground-based studies have revealed strong spectral dependence in aerosol absorption in the near-UV region that indicates the presence of organic carbon. A new set of OMI aerosol retrieval with assumed wavelength-dependent aerosol absorption in the near-UV region (Absorption Angstrom Exponent λ−2.5 to −3.0) provided much improved retrieval of AOD with significantly reduced bias. Also, the new retrieval of single-scattering albedo is in better agreement with those of AERONET within the uncertainties (Δω=±0.03). The new smoke aerosol model was also found to be valid over the biomass burning region of central Africa and northern India. Together with suggesting vast improvement in the retrieval of aerosol properties from OMI, present study demonstrates the near-UV capabilities of OMI in separating aerosols containing organics from pure black carbon through OMI-AERONET integrated measurements.
A geostationary thermal infrared sensor to monitor the lowermost troposphere: O3 and CO retrieval studies
Authors: Claeyman M. , Attié J.-L. , Peuch V.-H. , El Amraoui L. , Lahoz W. A. , Josse B. , Ricaud P. , von Clarmann T. , Höpfner M. , Orphal J. , Flaud J.-M. , Edwards D. P. , Chance K. , Liu X. , Pasternak F. , Cantié R.
Published: March 2011

Abstract. This paper describes the capabilities of a nadir thermal infrared (TIR) sensor proposed for deployment onboard a geostationary platform to monitor ozone (O3) and carbon monoxide (CO) for air quality (AQ) purposes. To assess the capabilities of this sensor we perform idealized retrieval studies considering typical atmospheric profiles of O3 and CO over Europe with different instrument configuration (signal to noise ratio, SNR, and spectral sampling interval, SSI) using the KOPRA forward model and the KOPRA-fit retrieval scheme. We then select a configuration, referred to as GEO-TIR, optimized for providing information in the lowermost troposphere (LmT; 0–3 km in height). For the GEO-TIR configuration we obtain ~1.5 degrees of freedom for O3 and ~2 for CO at altitudes between 0 and 15 km. The error budget of GEO-TIR, calculated using the principal contributions to the error (namely, temperature, measurement error, smoothing error) shows that information in the LmT can be achieved by GEO-TIR. We also retrieve analogous profiles from another geostationary infrared instrument with SNR and SSI similar to the Meteosat Third Generation Infrared Sounder (MTG-IRS) which is dedicated to numerical weather prediction, referred to as GEO-TIR2. We quantify the added value of GEO-TIR over GEO-TIR2 for a realistic atmosphere, simulated using the chemistry transport model MOCAGE (MOdèle de Chimie Atmospherique à Grande Echelle). Results show that GEO-TIR is able to capture well the spatial and temporal variability in the LmT for both O3 and CO. These results also provide evidence of the significant added value in the LmT of GEO-TIR compared to GEO-TIR2 by showing GEO-TIR is closer to MOCAGE than GEO-TIR2 for various statistical parameters (correlation, bias, standard deviation).
Two-dimensional performance of MIPAS observation modes in the upper-troposphere/lower-stratosphere
Authors: Carlotti M. , Castelli E. , Papandrea E.
Published: March 2011

Abstract. In this paper we analyze the performance of the three MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) observation modes that sound the Upper-Troposphere/Lower-Stratosphere (UT/LS) region. The two-dimensional (2-D) tomographic retrieval approach is assumed to derive the atmospheric field of geophysical parameters. For each observation mode we have calculated the 2-D distribution of the information load quantifier relative to the main MIPAS targets. The performance of the observation modes has been evaluated in terms of strength and spatial coverage of the information-load distribution along the full orbit. The indications of the information-load analysis has been validated with simulated retrievals based on the observational parameters of real orbits. In the simulation studies we have assessed the precision and the spatial (both horizontal and vertical) resolution of the retrieval products. The performance of the three observation modes has been compared for the MIPAS main products in both the UT/LS and the extended altitude range. This study shows that the two observation modes that were specifically designed for the UT/LS region are actually competitive with the third one, designed for the whole stratosphere, up to altitudes that far exceed the UT/LS. In the UT/LS the performance of the two specific observation modes is comparable even if the best performance in terms of horizontal resolution is provided by the observation mode that was excluded by the European Space Agency (ESA) from the current MIPAS duty cycle. This paper reports the first application of the information-load analysis and highlights the worthiness of this approach to make qualitative considerations about retrieval potential and selection of retrieval grid.
A broadband optical cavity spectrometer for measuring weak near-ultraviolet absorption spectra of gases
Authors: Chen J. , Venables D. S.
Published: March 2011

Abstract. Accurate absorption spectra of gases in the near–ultraviolet (300 to 400 nm) are essential in atmospheric observations and laboratory studies. This paper describes a novel incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instrument for measuring very weak absorption spectra from 335 to 375 nm. The instrument performance was validated against the 3B1-X1A1 transition of SO2. The measured absorption varied linearly with SO2 column density and the resulting spectrum agrees well with published spectra. Using the instrument, we report new absorption cross-sections of O3, acetone, 2-butanone, and 2-pentanone in this spectral region, where literature data diverge considerably. In the absorption minimum between the Huggins and Chappuis bands, our absorption spectra fall at the lower range of reported ozone absorption cross-sections. The spectra of the ketones agree with prior spectra at moderate absorptions, but differ significantly at the limits of other instruments' sensitivity. The collision-induced absorption of the O4 dimer at 360.5 nm was also measured and found to have a maximum cross-section of ca. 4.0×10−46 cm5 molecule−2. We demonstrate the application of the instrument to quantifying low concentrations of the short-lived radical, BrO, in the presence of stronger absorptions from Br2 and O3.
Identification and localization of layers in the ionosphere using the eikonal and amplitude of radio occultation signals
Authors: Pavelyev A. G. , Zhang K. , Wickert J. , Schmidt T. , Liou Y.-A. , Gubenko V. N. , Pavelyev A. A. , Salimzjanov R. R. , Kuleshov Y.
Published: March 2011

Abstract. Conditions for communication, navigation, and remote sensing in the ionosphere and atmosphere depend strongly on the ionospheric impact on the radio waves propagation. By use of the CHAllenge Minisatellite Payload (CHAMP) radio occultation (RO) data a description of different types of the ionospheric contributions to the RO signals at the altitudes 30–90 km of the RO ray perigee is introduced and compared with results of measurements obtained earlier in the communication link satellite-to-Earth at frequency 1.5415 GHz. An analytical model is introduced for description of the radio waves propagation in a stratified medium consisting of sectors having the spherically symmetric distributions of refractivity. Model presents analytical expressions for the phase path and refractive attenuation of radio waves. Model is applied for analysis of the radio waves propagation effects along a prolonged path including the atmosphere and two parts of the ionosphere. Model explains significant amplitude and phase variations at the altitudes 30–90 km of the RO ray perigee as connected with influence of the inclined ionospheric layers. An innovative eikonal acceleration technique is described and applied for the identification of the inclined ionospheric layers contributions and their location. Possibility to separate the influence of layered structures from contributions of irregularities and turbulence is analyzed.
On cloud ice induced absorption and polarisation effects in microwave limb sounding
Authors: Eriksson P. , Rydberg B.
Published: March 2011

Abstract. Detailed simulations of microwave limb sounding in the presence of ice clouds have been performed. It is clarified that, while particle absorption normally gives no significant change of the measured radiance for down-looking measurements, this is not the case for limb sounding. The particles were treated as horizontally aligned oblate spheroids and for this assumption on particle shape, and comparable situations, no significant degree of circular polarisation is generated. Differences between the brightness temperature of the ±45° polarisation components up to 4 K were found, but this difference appears to be small as long as single scattering conditions apply. The cloud extinction is the smallest for the vertically polarised component, but it should be more beneficial to observe any of the ±45° and circularly polarised components if ice water content is also a target of the retrievals. These latter pairs of orthogonal components also make it easier to combine information measured from different positions and with different polarisations. The results indicate that single scattering can be assumed for cloud optical thicknesses below about 0.1, which is thus an important threshold with respect to the complexity and accuracy of retrievals. The representation of particle sizes during the retrieval is discussed.
Assimilation of GPS radio occultation data at DWD
Authors: Anlauf H. , Pingel D. , Rhodin A.
Published: March 2011

Abstract. We describe the status of the assimilation of bending angles from GPS radio occultations in the 3D-Var for DWD's operational global forecast model GME ("Global Model for Europe"). Experiments show that the assimilation of GPSRO data leads to a significant reduction of biases in the analyses of temperature, humidity and wind in the upper troposphere and the stratosphere, as well as a better r. m. s. fit in the comparison to radiosondes. The impact on forecasts is most prominent in the data sparse Southern Hemisphere, but is also quite notable in the Northern Hemisphere extra-tropics, where we also see a slightly positive impact on surface pressure. The positive results found in the impact experiments lead to the implementation of the assimilation of GPS radio occultations from GRACE-A, FORMOSAT-3/COSMIC and GRAS/MetOp-A into the operational suite on 3 August 2010. We also show some initial results from assimilation experiments using radio occultation data from the German research satellite TerraSAR-X.
Evidence for microbial dissolution of pyrite from the Lower Cambrian oolitic limestone, South China
Authors: Liu W. , Zhang X.-L.
Published: March 2011

Abstract. The oxidative dissolution of the sulphide mineral pyrite (FeS2) has been of significant interest since it affects global geochemical cycles, generates acid mine drainage, and is used in industrial metal extraction. Several different groups of prokaryotes are known to catalyze the dissolution of pyrite and use the free energy generated from the oxidation, which may result in the dissolution of the mineral and the precipitation of the secondary ferric iron minerals either on the cell surface or is separated from the cells. However, straightforward evidence for such metabolic process in the ancient sediments is rare. Here we report pyrite crystals from the Lower Cambrian oolitic limestones that show indications of microbial erosion in various degrees. Erosion pits and tubular micro-tunnels with characteristic shapes and sizes in our samples are generally similar to those obtained from the laboratory studies on the oxidative dissolution of pyrite by iron-oxidizing bacteria. Diagenetic examination demonstrates that the bioerosion predates the consolidation of the limestone. In addition, bacillus-sized and -shaped microfossils encrusted with iron oxides are present in our samples, which are very likely to be fossilized sheaths produced by iron-oxidizing bacteria. Our findings indicate that the microbial oxidative dissolution of pyrite existed in the Cambrian shallow marine carbonate sediments. Furthermore, we suggest that characteristic pitting patterns on the pyrite crystals from ancient sediments are an important clue to trace the evolution of life, in particular, the evolution of metabolism like microbial iron oxidation in the remote past on our planet, independent of biomarkers, isotopic signals and body fossils as well.
Impact of extreme precipitation and water table change on N2O fluxes in a bio-energy poplar plantation
Authors: Zona D. , Janssens I. A. , Verlinden M. S. , Broeckx L. S. , Cools J. , Gioli B. , Zaldei A. , Ceulemans R.
Published: March 2011

Abstract. A large fraction of the West European landscape is used for intensive agriculture. Several of these countries have very high nitrous oxide (N2O) emissions, because of substantial use of fertilizers and high rates of atmospheric nitrogen deposition. N2O production in soils is controlled by water-filled pore space (WFPS) and substrate availability (NO3). Here we show that extreme precipitation (80 mm rainfall in 48 h) after a long dry period, led to a week-long peak in N2O emissions (up to about 2200 μg N2O-N m−2 h−1). In the first four of these peak emission days, N2O fluxes showed a pronounced diurnal pattern correlated to daytime increase in temperature and wind speed. It is possible that N2O was transported through the transpiration stream of the poplar trees and emitted through the stomates. However, during the following three high emission days, N2O emission was fairly stable with no pronounced diurnal trend, and was correlated with wind speed and WFPS (at 20 and 40 cm depth) but no longer with soil temperature. We hypothesized that wind speed facilitated N2O emission from the soil to the atmosphere through a significant pressure-pumping. Successive rainfall events and similar WFPS after this first intense precipitation did not lead to N2O emissions of the same magnitude. These findings suggest that climate change-induced modification in precipitation patterns may lead to high N2O emission pulses from soil, such that sparser and more extreme rainfall events after longer dry periods could lead to peak N2O emissions. The cumulative effects of more variable climate on annual N2O emission are still largely uncertain and need further investigation.