bluuebunny/crossref_metadata_2025 huggingface dataset:
Analyse des déterminants de la demande d'eau potable en Algérie
Authors: Kertous Mourad
Published: November 2013

Assurer une répartition optimale de la ressource en eau est l’un des défis qui attend l’Algérie pour les années à venir. Toutefois, malgré un grave déficit, l’eau en Algérie est toujours subventionnée par l’État. En effet, avec un coût de production estimé à 28,45 DA•m‑3, le prix de vente de l’eau de la première tranche est 6,30 DA•m‑3, soit une subvention de 77 %. Cette pratique est inscrite dans l’article 138 de la Loi de l’eau de 2005, qui indique que « … la tarification des services de l’eau est basée sur les principes d’équilibre financier, de solidarité sociale, d’incitation à l’économie d’eau et de protection de la qualité des ressources en eau ». Par conséquent, cette subvention engendre, à la fois, des déficits au niveau des entreprises chargées de sa gestion et renvoie un faux signal aux abonnés (qui pensent toujours qu’elle est gratuite). Ainsi, nous proposons dans ce travail une contribution pour améliorer la gestion de ce service vital à travers la connaissance des déterminants de cette demande. Pour atteindre cet objectif, nous avons estimé une fonction de demande en eau potable, sur un échantillon de 172 abonnés et sur une période de 45 trimestres, en faisant appel à des estimations en panel dynamique. Cette estimation révèle que les abonnés de la wilaya de Bejaia sont peu sensibles aux variations des prix. L’élasticité prix, à court terme, estimée avec la spécification de Nordin (1976) donne une valeur de -0,67 (soit une élasticité -0,72 sur le long terme).

Classification JEL : L95, Q25, D12.
Optimisation de l’efficacité des graines de moringa oleifera dans le traitement des eaux de consommation en Afrique sub-saharienne
Authors: Kabore Aminata , Savadago Boubacar , Rosillon Francis , Straore Alfred S. , Dianou Dayéri
Published: November 2013

L’accès à l’eau potable demeure une très grande préoccupation en Afrique sub-saharienne, particulièrement en milieu rural où les populations sont confrontées à la gestion optimale des points d’eau, l’insuffisance d’hygiène et d’assainissement et au manque de méthodes appropriées de désinfection à l’échelle familiale. De ce fait, l’intégration de procédés biologiques de traitement des eaux de consommation pourrait être une alternative durable dans l’amélioration de la qualité des eaux de boisson, du fait de la disponibilité et de la non-toxicité des substances. La présente étude porte sur l’optimisation de l’efficacité des graines de Moringa oleifera dans l’assainissement des eaux de consommation en milieu rural au Burkina Faso. Des eaux de surface et de puits alimentant les populations ont été traitées avec différentes concentrations de coagulant de graines de M. oleifera. Le suivi de paramètres physico-chimiques et microbiologiques à différents temps de décantation a permis de déterminer les conditions optimales et d’évaluer l’efficacité des traitements. Des résultats, il est ressorti qu’en fonction des caractéristiques des eaux, les temps de décantation compris entre 1,5-2,0 h sont apparus suffisants pour éliminer la presque totalité des matières en suspension et des colloïdes. L’abattement de la turbidité obtenu était compris entre 24-96 % pour un temps de décantation de 2 h et fonction de la turbidité initiale de l’eau. Pour le même temps de décantation, l’abattement microbien était de l’ordre de 82-94 % pour les coliformes fécaux, 81-100 % pour Escherichia coli, 94-100 % pour les streptocoques fécaux et 100 % pour les kystes de Giardia intestinalis. Les traitements ont également permis de réduire les teneurs en nitrates, calcium, magnésium ainsi que la dureté totale. Par contre, une hausse des concentrations de sulfates et de matière organique a été enregistrée avec ces traitements. Ces résultats indiquent qu’en fonction des caractéristiques initiales, le traitement des eaux brutes avec les graines de M. oleifera améliore considérablement la qualité des eaux de boisson.
Étude de l’impact des variabilités climatiques sur les ressources hydriques d’un milieu tropical humide
Authors: Assemian Emile Assie , Kouame Fernand Koffi , Djagoua Éric Valère , Affian Kouadio , Jourda Jean Patrice Roger , Adja Miessan , Lasm Théophile , Biemi Jean
Published: November 2013

Cette étude vise à montrer l’apparition d’un changement climatique dans ces dernières décennies dans le département de Bongouanou, situé à l’est de la Côte d’Ivoire (milieu tropical humide) et à élucider son impact sur l'alimentation des ressources en eau souterraine. Pour ce faire, diverses méthodes statistiques et hydrologiques ont été utilisées. L'application de l’indice de Nicholson et le test de Pettitt à la série pluviométrique (1920-2005) a mis en évidence une variabilité climatique, caractérisée par deux grandes phases différentes. Les résultats montrent une rupture en 1968 qui marque une modification des régimes pluviométriques et hydrologiques. Cette rupture s'accompagne d'une diminution de la pluviométrie d’environ 19 % en moyenne et une augmentation de 0,7 °C de la température du milieu. Il s’agit donc d’un réchauffement climatique dans ce milieu tropical qui se caractérise par deux grandes périodes : une période humide de 1920 à 1968 et une période sèche ou déficitaire de 1968 à 2005. La méthode du bilan hydrique et celle de Maillet ont permis de mettre en évidence les impacts de ce réchauffement climatique sur les ressources en eau de la région. Les résultats montrent qu’avant la rupture de 1968, la recharge moyenne annuelle était estimée à 217 mm; elle est passée à 145 mm en période déficitaire, soit une baisse d'environ 33 %. Le ruissellement moyen annuel qui était de 80 mm, est réduit à 35 mm. Les coefficients de tarissement calculés montrent une vidange rapide des réserves régulatrices en période sèche (21 jours) par rapport à la période humide (27 jours). Les volumes moyens d’eau mobilisés par les aquifères chaque année ont subi une baisse de 30 %. En période humide, ce volume était estimé à environ 1,475 km3 dans la région de Bongouanou. La concordance des résultats d’évaluation des recharges et des volumes d’eau mobilisés par ces deux approches indépendantes (bilan hydrique et analyse d’hydrogrammes) avant et après la rupture, est remarquable. Cela montre aussi l’importance de précipitations importantes et régulières pour la recharge efficace des aquifères de socle.
La sociologie et la quantification au service d’Isis
Authors: Briaud Stéphanie
Published: November 2013

L’isiacologie est un exemple de discipline étudiant l’Histoire de l’Antiquité, dont la méthodologie a connu de grands changements dans les années 1960-1970 conjointement à son institutionnalisation. Ici, deux grandes influences seront décrites : la sociologie et ses grands noms, comme P. Bourdieu, qui réfléchissent au concept de « science des religions » ; la quantification qui s’interroge sur l’application de cette méthode pour étudier des réalités — hautement — passées et l’histoire culturelle. La démonstration quantitative se fera en deux temps, avec une partie théorique puis pratique, à partir du catalogue SNRIS et privilégiant une étude des monnaies romaines isiaques.
L’historiographie moderne sur l’ethnographie antique : peut-on faire voler en éclats le monolithe ?
Authors: Weyland Raphaël
Published: November 2013

Les excursus faisant la description des habitudes de vie des peuples environnant le monde gréco-romain pullulent dans la littérature antique. S’ils ont longtemps été utilisés pour étudier ces peuples étrangers (Gaulois, Huns, Germains), les historiens ne leur accordent plus aujourd’hui la même valeur historique. Cet article suit l’évolution de l’historiographie du dernier siècle concernant ces documents d’ethnographie antiques, du positivisme de Félix Jacoby à sa remise en question par le post-modernisme. Nous nous efforçons aussi de proposer de nouvelles manières d’interpréter ces documents en nous inspirant des tendances récentes de cette historiographie.
Les télécommunications au premier millénaire av. J.-C. au Proche-Orient ancien
Authors: Leibovici Jacques
Published: November 2013

L’information dans l’Antiquité circulait par courrier, mais aussi par transmissions de signaux sonores ou lumineux. Après une étude documentaire des récits attestant la transmission d’informations par de tels médias au Levant aux premiers millénaires av. J.-C., l’auteur a démontré que les logiciels actuels de conception des réseaux de télécommunications peuvent suggérer des sites-relais dans le cadre étudié. Les limites techniques adéquates sont prises en compte. Il en a déduit des modèles de réseaux. Ces hypothèses ont été validées sur le terrain. Cette approche, par une synthèse originale de l’archéologie et des télécommunications, a permis de définir une méthode de préprospection en archéologie.
Historical Events as a Means of Iconographic Interpretation: The Reconstruction of Lost Greek Historical Paintings of the Fifth and Fourth Centuries B.C.
Authors: Painesi Anastasia
Published: November 2013

The disappearance of Greek monumental painting causes fundamental problems in the study of this particular form of art. Texts referring to or works of art inspired by Greek paintings seem to be frequently inadequate at the task of providing a realistic reconstruction of the painted works. Nevertheless, the reconstruction of the date and type of representation of historical paintings seems to be facilitated by texts of historical context that offer valuable informations on the events that inspired the painters of the fifth and fourth Centuries B.C. This paper will examine specific cases of Classical paintings, such as the Battle of Marathon and the Battle of Mantineia, whose iconographical reconstruction depends considerably on historiographical testimonies.
Evaluating HIV prevention efforts using semiparametric regression models: results from a large cohort of women participating in an HIV prevention trial from KwaZulu‐Natal, South Africa
Authors: Wand Handan , Ramjee Gita
Published: November 2013

Objective

To describe and quantify the differences in risk behaviours, HIV prevalence and incidence rates by birth cohorts among a group of women in Durban, South Africa.

Methods

Cross‐sectional and prospective cohort analyses were conducted for women who consented to be screened and enrolled in an HIV prevention trial. Demographic and sexual behaviours were described by five‐year birth cohorts. Semiparametric regression models were used to investigate the bivariate associations between these factors and the birth cohorts. HIV seroconversion rates were also estimated by birth cohorts.

Results

The prevalence of HIV‐1 infection at the screening visit was lowest (20.0%) among the oldest (born before 1960) cohorts, while the highest prevalence was observed among those born between 1975 and 79. Level of education increased across the birth cohorts while the median age at first sexual experience declined among those born after 1975 compared to those born before 1975. Only 33.03% of the oldest group reported ever using a condom while engaging in vaginal sex compared to 73.68% in the youngest group; however, HIV and other sexually transmitted infection (STI) incidence rates were significantly higher among younger women compared to older women.

Conclusions

These findings clearly suggest that demographic and sexual risk behaviours are differentially related to the birth cohorts. Significantly high HIV and STI incidence rates were observed among the younger group. Although the level of education increased, early age at sexual debut was more common among the younger group. The continuing increase in HIV and STI incidence rates among the later cohorts suggests that the future trajectory of the epidemic will be dependent on the infection patterns in younger birth cohorts.
Correlates and Changes in Empathy and Attitudes Toward Interprofessional Collaboration in Osteopathic Medical Students
Authors: Calabrese Leonard H. , Bianco Joseph A. , Mann Douglas , Massello David , Hojat Mohammadreza
Published: November 2013

Context: Many studies have reported a decline in empathy as allopathic medical students progress through medical school. Data are needed to compare the pattern of changes in empathy in osteopathic and allopathic medical students. Also, it is important to investigate the associations between measures of empathy and attitudes toward interprofessional collaboration, which are among major elements of professionalism in medicine.

Objectives: (1) To investigate correlations between empathy and interprofessional collaboration in osteopathic medical students; (2) to examine differences in empathy and interprofessional collaboration scores by sex, class year, and specialty interest; and (3) to compare empathy scores by class year between osteopathic and allopathic medical students.

Design: Correlational and comparative study.

Setting: Ohio University Heritage College of Osteopathic Medicine.

Participants: Osteopathic medical students enrolled in academic year 2011-2012.

Main Outcome Measures: The Jefferson Scale of Empathy (JSE) and the Jefferson Scale of Attitudes toward Physician-Nurse Collaboration (JSAPNC) scores.

Results: Student respondents (N=373) included 197 women (53%) and 176 men (47%). Significant correlation was found between scores on the JSE and JSAPNC (r=0.42, P<.01). Women scored higher than men on the JSE (mean scores, 117.1 and 111.9, respectively; F
1,371=19.6, P<.01) and the JSAPNC (mean scores, 50.1 and 48.7, respectively; F
1,371=6.5, P<.01). No statistically significant difference on the scores of the 2 scales was observed among students who planned to pursue “people-oriented” specialties (150 [40%]) compared with those interested in “technology/procedure-oriented” specialties (170 [45%]). No statistically significant change in empathy scores was found in different class years of the osteopathic medical students. Comparisons of empathy scores with allopathic medical students showed no significant difference in the first and second years, but osteopathic medical students had a higher mean empathy score (M=114.4) than their allopathic counterparts (M=110.9) in the third year (t
158=2.31, P<.05), and their empathy scores remained high, although not statistically significant, in the fourth year of osteopathic medical school.

Conclusion: The decline in empathy that is often reported among allopathic medical students was not observed. The present study can serve as a step toward further longitudinal research on the development of empathy and attitudes toward teamwork among osteopathic medical students.
An Unexpectedly Progressed Lumbar Herniated Disk
Authors: Lipton James A. , McLeod Geoffrey A.
Published: November 2013

The authors describe a case of a 26-year-old female military veteran who presented with low back pain that she attributed to a recent foot injury. The patient reported a history of lumbar pain while in the military that had been treated successfully with high-velocity, low-amplitude osteopathic manipulative treatment. The patient's current pain was improved with osteopathic manipulative treatment and gait correction. Several weeks after her initial presentation, the patient reported that she had had a herniated disk diagnosed 2 years earlier by means of magnetic resonance imaging. Updated magnetic resonance imaging was performed, the results of which revealed a large herniated disk that had caused severe stenosis. The patient was immediately referred to a neurosurgeon for consultation and subsequently underwent surgical treatment.
Focused Physician‐Performed Echocardiography in Sports Medicine
Authors: Yim Eugene S. , Kao Daniel , Gillis Edward F. , Basilico Frederick C. , Corrado Gianmichael D.
Published: November 2013

Objectives

The purpose of this study was to investigate whether sports medicine physicians can obtain accurate measurements of the aortic root in young athletes.

Methods

Twenty male collegiate athletes, aged 18 to 21 years, were prospectively enrolled. Focused echocardiography was performed by a board‐certified sports medicine physician and a medical student, followed by comprehensive echocardiography within 2 weeks by a cardiac sonographer. A left parasternal long‐axis view was acquired to measure the aortic root diameter at the sinuses of Valsalva. Intraclass correlation coefficients (ICCs) were used to assess inter‐rater reliability compared to a reference standard and intra‐rater reliability of repeated measurements obtained by the sports medicine physician and medical student.

Results

The ICCs between the sports medicine physician and cardiac sonographer and between the medical student and cardiac sonographer were strong: 0.80 and 0.76, respectively. Across all 3 readers, the ICC was 0.89, indicating strong inter‐rater reliability and concordance. The ICC for the 2 measurements taken by the sports medicine physician for each athlete was 0.75, indicating strong intra‐rater reliability. The medical student had moderate intra‐rater reliability, with an ICC of 0.59.

Conclusions

Sports medicine physicians are able to obtain measurements of the aortic root by focused echocardiography that are consistent with those obtained by a cardiac sonographer. Focused physician‐performed echocardiography may serve as a promising technique for detecting aortic root dilatation and may contribute in this manner to preparticipation cardiovascular screening for athletes.
Comparison of Fetal Cardiac Spatiotemporal Image Correlation Segmental Analysis Between Cardiac‐ and Body‐Based Scrolling
Authors: Jatavan Thanate , Tongsong Theera
Published: November 2013

Objectives

The purpose of this study was to compare success rates for depiction of the 5 typical transverse planes in the fetal upper thorax between cardiac‐ and body‐based scrolling techniques.

Methods

Spatiotemporal image correlation volume data sets acquired at the 4‐chamber view level were obtained from low‐risk singleton pregnancies with healthy fetuses. Each data set was analyzed by the authors using both cardiac‐ and body‐based techniques. With the cardiac‐based technique, the exact 4‐chamber view was first identified as an initial plane before scrolling, whereas with the body‐based technique, a volume data set was first manipulated to get the fetal orientation in the exact dorsal supine position as an initial plane. In both techniques, the volumes were then scrolled through the upper thorax to identify the standard planes, including the 4‐chamber, 5‐chamber, 3‐vessel, 3‐vessel and trachea, and aortic arch views.

Results

An analysis of 50 volume data sets to evaluate intraobserver and interobserver variability in the success rates for the 4‐chamber, 5‐chamber, 3‐vessel, 3‐vessel and trachea, and aortic arch views showed good agreement. In an analysis of 296 separate data sets, cardiac‐based scrolling was associated with significantly higher success rates than body‐based scrolling in all standard planes (P < .05).

Conclusions

Cardiac‐based scrolling resulted in higher success rates for obtaining the standard spatiotemporal image correlation planes than body‐based scrolling. Therefore, examiners in the early part of the learning curve should be encouraged to first identify a perfect 4‐chamber view at the start of an examination.
Absent Fetal Nasal Bone
Authors: Dukhovny Stephanie , Wilkins-Haug Louise , Shipp Thomas D. , Benson Carol B. , Kaimal Anjali J. , Reiss Rosemary
Published: November 2013

Objectives

Our purpose was to review the outcomes of singleton pregnancies in which an absent nasal bone was noted on first‐ or second‐trimester sonography and aneuploidy was not present.

Methods

We identified singleton pregnancies from 2005 to 2011 in which an absent nasal bone was noted on sonography, aneuploidy was excluded, and newborn examinations were available for review. Sonographic reports were reviewed for anomalies, growth, and amniotic fluid volume. Newborn records were reviewed for physical examinations, complications, and radiologic or genetic tests.

Results

We identified 142 fetuses with a sonographic appearance of an absent nasal bone. We excluded 52 cases with aneuploidy and 33 in which newborn examination information was unavailable. Fifty‐seven cases met inclusion criteria. For 3 euploid fetuses with an absent nasal bone on sonography, the presence of additional anomalies on second‐trimester sonography ultimately signaled an adverse outcome: the presence of multiple congenital anomalies, a microdeletion syndrome, and a specific genetic diagnosis.

Conclusions

All cases with adverse outcomes had additional prenatal sonographic findings. For the remainder, normal newborn examination findings provide some reassurance, especially in the setting of otherwise normal second‐trimester sonographic findings. A microarray as a test for microdeletion and duplication syndromes in this situation could be considered.
Screening in treatment programs for Fetal Alcohol Spectrum Disorders that could affect therapeutic progress
Authors: Grant Therese M , Novick Brown Natalie , Graham J. Christopher , Whitney Nancy , Dubovsky Dan , Nelson Lonnie A.
Published: November 2013

Grant, T., Novick Brown, N., Graham, J., Whitney, N., Dubovsky, D. , & Nelson, L. (2013). Screening in treatment programs for Fetal Alcohol Spectrum Disorders that could affect therapeutic progress. The International Journal Of Alcohol And Drug Research, 2(3), 37-49. doi:10.7895/ijadr.v2i3.116 (http://dx.doi.org/10.7895/ijadr.v2i3.116)Aims: While structured intake interviews are the standard of care in substance abuse treatment programs, these interviews often do not screen for cognitive impairments, such as those found in fetal alcohol spectrum disorders (FASD) and other brain-based developmental disorders. The research reported here supports a brief interview protocol, the Life History Screen (LHS), that screens clients unobtrusively for adverse life-course outcomes typically found in FASD, so as to guide follow-up assessments and treatment planning.Design: Two-group observational study.Setting: A three-year case management intervention program in Washington State for high-risk women who abuse alcohol and/or drugs during pregnancy.Participants: Group 1: No prenatal alcohol exposure (N = 463); Group 2: Diagnosed with FASD (Fetal Alcohol Syndrome, Alcohol Related Neurodevelopmental Disorder, fetal alcohol effects, or static encephalopathy) by a qualified physician (N = 25), or suspected of having FASD (reported prenatal alcohol exposure and displayed behaviors consistent with a clinical diagnosis of FASD) (N = 61).Measures: The Addiction Severity Index (ASI) was administered to participants at intake. We analyzed eleven ASI items that corresponded to questions on the LHS in order to assess the potential of the LHS for identifying adults with possible FASD. The Life History Screen itself was not administered.Findings: Analysis of group differences between the diagnosed FASD and suspected FASD groups supported our decision to collapse the two groups for the main analysis. The Life History Screen shows promise as an efficient pre-treatment screen, in that core items are significantly associated with FASD group membership on factors involving childhood history, maternal drinking, education, substance use, employment, and psychiatric symptomatology.Conclusions: The Life History Screen may have utility as a self-report measure that can be used at the outset of treatment to identify clients with cognitive impairments and learning disabilities due to prenatal alcohol exposure.
Case management reduces drinking during pregnancy among high-risk women
Authors: May Philip A. , Marais Anna-Susan , Gossage J. Phillip , Barnard Ronel , Joubert Belinda , Cloete Marise , Hendricks Natalie , Roux Sumien , Blom Annalien , Steenekamp Jeanetta , Alexander Theresa , Andreas Romena , Human Suzanne , Snell Cudore , Seedat Soraya , Parry Charles D. , Kalberg Wendy O. , Buckley David , Blankenship Jason
Published: November 2013

May, P., Marais, A., Gossage, J., Barnard, R., Joubert, B., Cloete, M., Hendricks, N., Roux, S., Blom, A., Steenekamp, J., Alexander, T., Andreas, R., Human, S., Snell, C., Seedat, S., Parry, C., Kalberg, W., Buckley, D., & Blankenship, J. (2013). Case management reduces drinking during pregnancy among high-risk women. The International Journal Of Alcohol And Drug Research, 2(3), 61-70. doi:10.7895/ijadr.v2i3.79 (http://dx.doi.org/10.7895/ijadr.v2i3.79)Aim: To estimate the efficacy of Case Management (CM) for women at high risk for bearing a child with Fetal Alcohol Spectrum Disorders (FASD).Design: Women were recruited from antenatal clinics and engaged in 18 months of CM.Setting: A South African community with a subculture of heavy, regular, weekend, recreational drinking and with high documented rates of FASD. Participants: Forty-one women who were at high risk for bearing a child with FASD.Measures: Statistical analysis of trends in drinking and other risk factors.Findings: At intake, 87.8% of the women were pregnant, most had previous alcohol-exposed pregnancies, 67.5% reported that most or all of their friends drank alcohol, and 50.0% had stressful lives. CM was particularly valuable for pregnant women, as statistically significant reductions in alcohol risk were obtained for them in multiple variables: total drinks on weekends after six months of CM (p = .026) and estimated peak blood alcohol concentration (BAC) at six (p < .001) and 18 months (p < .001). For participants completing 18 months of CM, AUDIT scores improved significantly by 6-month follow-up (from 19.8 to 9.7, p = .000), and although there were increases at 12 and 18 months, AUDIT scores indicate that problematic drinking remained statistically significantly lower than baseline throughout CM.  Happiness scale scores correlated significantly with reduced drinking in most time periods.Conclusions: Making an enduring change in drinking behavior is difficult in this social setting. Nonetheless, CM provided by skilled and empathic case managers reduced maternal drinking at critical times, and, therefore, alcohol exposure levels to the fetus.
National‐scale estimates of forest root biomass carbon stocks and associated carbon fluxes in Canada
Authors: Smyth C. E. , Kurz W. A. , Neilson E. T. , Stinson G.
Published: November 2013

Canada's forests play an important role in the global carbon cycle through carbon (C) storage and C exchange with the atmosphere. While estimates of aboveground biomass have been improving, little is known about belowground C storage in root biomass. Here we estimated the contribution of roots to the C budget of Canada's 2.3 × 106 km2 managed forests from 1990 to 2008 using the empirical modeling approach of the Carbon Budget Model of the Canadian Forest Sector (CBM‐CFS3) driven by detailed forestry data sets from the National Forest C Monitoring, Accounting and Reporting System. The estimated average net primary production (NPP) during this period was 809 Tg C yr−1 (352 g C m2 yr−1) with root growth and replacement of turnover contributing 39.8 % of NPP. Average heterotrophic respiration (Rh) was 738 Tg C yr−1 (321 g C m−2 yr−1), which resulted in a net ecosystem production (NEP) value of 31 g C m−2 yr−1(71 Tg C yr−1), and on average only 8.7% of NPP remained in the system as NEP. Estimated average root C stocks were 2.38 Pg (1235 g C m−2), mostly in coarse roots (≥ 5 mm diameter), and had an average root to shoot percentage (belowground to aboveground biomass) of 25.6%. Detailed monitoring of C exchange between forests and the atmosphere and an improved understanding of the belowground processes and their response to environmental changes are needed to improve our understanding of the terrestrial C budget.
A method for estimating ice mass loss from relative InSAR observations: Application to the Vatnajökull ice cap, Iceland
Authors: Zhao Wenliang , Amelung Falk , Dixon Timothy H. , Wdowinski Shimon , Malservisi Rocco
Published: November 2013

We present a new method for estimating ice mass loss from glaciers and ice sheets using Interferometric Synthetic Aperture Radar (InSAR) time‐series data. We use a linear inversion method based on observations of nearby bedrock uplift and a solution for surface loading of an elastic half‐space. The method assumes that mass loss is focused on lower elevation terminal regions of the glacier or ice sheet, and that there is an exponential decrease in thinning rate toward the higher elevation interior. We apply the method to uplift rates between 1995 and 2009 near Vatnajökull, Iceland. The data reveal up to 13 mm/yr relative line‐of‐sight (LOS) velocity around the south‐western edge of Vatnajökull. We find an ice mass loss rate of
Gt/yr, in approximate agreement with other estimates. Ice loss since 1995 is twice as fast as the loss rate estimated for the rest of the 20th century.
Two views of Hawaiian plume structure
Authors: Hofmann Albrecht W. , Farnetani Cinzia G.
Published: November 2013

Fundamentally contradictory interpretations of the isotopic compositions of Hawaiian basalts persist, even among authors who agree that the Hawaiian hotspot is caused by a deep‐mantle plume. One view holds that the regional isotopic pattern of the volcanoes reflects large‐scale heterogeneities in the basal thermal boundary layer of the mantle. These are drawn into the rising plume conduit, where they are vertically stretched and ultimately sampled by volcanoes. The alternative view is that the plume resembles a “uniformly heterogeneous plum pudding,” with fertile plums of pyroxenite and/or enriched peridotite scattered in a matrix of more refractory peridotite. In a rising plume, the plums melt before the matrix, and the final melt composition is controlled significantly by the bulk melt fraction. Here we show that the uniformly heterogeneous plum pudding model is inconsistent with several geochemical observations: (1) the relative melt fractions inferred from La/Yb ratios in shield‐stage basalts of the two parallel (Kea‐ and Loa‐) volcanic chains, (2) the systematic Pb‐isotopic differences between the chains, and the absence of such differences between shield and postshield phases, (3) the systematic shift to uniformly depleted Nd‐isotopic compositions during rejuvenated volcanism. We extend our previous numerical simulation to the low melt production rates calculated far downstream (200–400 km) from shield volcanism. Part of these melts, feeding rejuvenated volcanism, are formed at pressures of ∼5 GPa in the previously unmelted underside of the plume, from material that originally constituted the uppermost part of the thermal boundary layer at the base of the mantle.
Finite‐differencePwave travel time seismic tomography of the crust and uppermost mantle in the Italian region
Authors: Gualtieri L. , Serretti P. , Morelli A.
Published: November 2013

We present a 3‐DPwave velocity model of the crust and shallowest mantle under the Italian region, that includes a revised Moho depth map, obtained by regional seismic travel time tomography. We invert 191,850PnandPgwave arrival times from 6850 earthquakes that occurred within the region from 1988 to 2007, recorded by 264 permanent seismic stations. We adopt a high‐resolution linear B‐spline model representation, with 0.1° horizontal and 2 km vertical grid spacing, and an accurate finite‐difference forward calculation scheme. Our nonlinear iterative inversion process uses the recent European reference 3‐D crustal model EPcrust as a priori information. Our resulting model shows two arcs of relatively low velocity in the crust running along both the Alps and the Apennines, underlying the collision belts between plates. Beneath the Western Alps we detect the presence of the Ivrea body, denoted by a strong highPwave velocity anomaly. We also map the Moho discontinuity resulting from the inversion, imaged as the relatively sharp transition between crust and mantle, wherePwave velocity steps up to values larger than 8 km/s. This simple condition yields an image quite in agreement with previous studies that use explicit representations for the discontinuity. We find a complex lithospheric structure characterized by shallower Moho close by the Tyrrhenian Sea, intermediate depth along the Adriatic coast, and deepest Moho under the two mountain belts.
Isotopes of nitrogen on Mars: Atmospheric measurements by Curiosity's mass spectrometer
Authors: Wong Michael H. , Atreya Sushil K. , Mahaffy Paul N. , Franz Heather B. , Malespin Charles , Trainer Melissa G. , Stern Jennifer C. , Conrad Pamela G. , Manning Heidi L. K. , Pepin Robert O. , Becker Richard H. , McKay Christopher P. , Owen Tobias C. , Navarro‐González Rafael , Jones John H. , Jakosky Bruce M. , Steele Andrew
Published: November 2013

The Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) measured a Mars atmospheric14N/15N ratio of 173 ± 11 on sol 341 of the mission, agreeing with Viking's measurement of 168 ± 17. The MSL/SAM value was based on Quadrupole Mass Spectrometer measurements of an enriched atmospheric sample, with CO2 and H2O removed. Doubly ionized nitrogen data at m/z 14 and 14.5 had the highest signal/background ratio, with results confirmed by m/z 28 and 29 data. Gases in SNC meteorite glasses have been interpreted as mixtures containing a Martian atmospheric component, based partly on distinctive14N/15N and40Ar/14N ratios. Recent MSL/SAM measurements of the40Ar/14N ratio (0.51 ± 0.01) are incompatible with the Viking ratio (0.35 ± 0.08). The meteorite mixing line is more consistent with the atmospheric composition measured by Viking than by MSL.
Major effusive eruptions and recent lava fountains: Balance between expected and erupted magma volumes at Etna volcano
Authors: Bonaccorso A. , Calvari S.
Published: November 2013

Over the last four decades Etna has shown a high output rate through numerous eruptions. The volcano has displayed two eruptive behaviors. The first is characterized by effusive eruptions that efficiently drained the storage system and emitted large volumes of magma; the second behavior is related to lava fountains, erupting small magma batches, which are normally with high frequency and have been considered as precursors of major effusive eruptions. In this paper, we present an updated estimation of emitted volumes from Etna eruptions, which include the 38 lava fountain episodes that occurred from January 2011 to April 2013. These recent explosive episodes have been frequent, discharging significant magma volumes. Observing the steady trend of magma output over time, we present insights on expected erupted volumes. We highlight that the January 2011 to April 2013 lava fountains efficiently drained the intermediate‐shallow storage system and favored a balance between the incoming and outgoing magma.
The effect of large‐scale shear‐velocity heterogeneity on SS precursor amplitudes
Authors: Bai L. , Ritsema J.
Published: November 2013

Precursors to the SS wave have been analyzed extensively to characterize seismic discontinuities in the upper mantle. We examine the influence of shear‐velocity heterogeneity on the amplitude of underside shear wave reflections off the 410 (i.e., S410S) and 660 (i.e., S660S) discontinuities using waveform data from global seismic networks and spectral element method synthetics for four tomographic models of the crust and mantle. On average, the S660S/SS amplitude ratio is smaller than values predicted for the Preliminary Reference Earth Model (PREM) and tomographic models of shear velocity perturbations from PREM. The variation of S410S/SS and S660S/SS ratios determined for the 3‐D models is significant. Its amplitude depends on the amplitude of shear‐velocty heterogeneity in the mantle and on the incorporated model for the crust. The S410S/SS and S660S/SS amplitude variations are stronger in the data and do not correlate spatially with the simulated ratios. It is therefore not certain that the spatial variation of S410S/SS and S660S/SS, as expressed by cap averaging, can be related to compositional heterogeneity in the mantle, given the profound influence of the heterogeneous crust and mantle.
Effect of the northward turning of the interplanetary magnetic field on the dipolarization
Authors: Peng Z. , Wang C.
Published: November 2013

An outstanding question in magnetospheric physics is whether the association between the northward turning of the interplanetary magnetic field (IMF) and the substorm onset is a random relation or a causal relation. In this work, we investigate the effect of the northward turning of the IMF on the dipolarization in the magnetotail by using the global PPMLR‐MHD simulation model and observations. Four simulation runs are carried out: (1) a dipolarization under steady IMF conditions, (2) a dipolarization associated with a northward turning of the IMF, (3) an observed event under steady IMF conditions, and finally (4) an observed event associated with IMF northward turning. Our results show that (1) the northward turning of the IMF can enhance and prolong the dipolarization initiated by internal trigger, which is consistent with the statistical studies, and (2) the event simulations are similar to the observations. All these indicate that the northward turning of the IMF could play an important role in substorm triggering; however, it does not mean that it is necessary.
Variability in tropical cyclone heat potential over the Southwest Indian Ocean
Authors: Malan N. , Reason C. J. C. , Loveday B. R.
Published: November 2013

Tropical cyclone heat potential (TCHP) has been proposed as being important for hurricane and typhoon intensity. Here, a climatology of TCHP is developed for the Southwest Indian Ocean, a basin that experiences on average 11–12 tropical cyclones per year, many of which impact on Mauritius, Reunion and Madagascar, and Mozambique. SODA data and a regional ocean model forced with the GFDL‐CORE v.2b reanalysis winds and heat fluxes are used to derive TCHP values during the 1948–2007 period. The results indicate that TCHP increases through the austral summer, peaking in March. Values of TCHP above 40 kJ cm−2, suggested as the minimum needed for tropical cyclone intensification, are still present in the northern Mozambique Channel in May. A time series of TCHP spatially averaged over the Seychelles‐Chagos thermocline ridge (SCTR), an important area for tropical cyclones, is presented. The model time series, which agrees well with XBT‐based observations (r = 0.82, p = 0.01), shows considerable interannual variability overlaying an upward tendency that matches with an observed increase in severe tropical cyclone days in the Southwest Indian Ocean. Although an increase in severe storms is seen during 1997–2007, the increasing TCHP tendency time series after 1997 coincides with a decrease in total cyclone numbers, a mismatch that is ascribed to increased atmospheric anticyclonicity over the basin. Seasons of increased (decreased) TCHP over the SCTR appear to be associated with dry (wet) conditions over certain areas of southern and East Africa and are linked with changes in zonal wind and vertical motion in the midtroposphere.
Distribution and composition of suspended biogenic particles in surface waters across Subarctic and Arctic Seas
Authors: Wyatt Shea N. , Crawford David W. , Wrohan Ian A. , Varela Diana E.
Published: November 2013

Suspended biogenic particles were examined across Subarctic and Arctic Seas during the Canada‐Three‐Oceans (C3O) program in the summers of 2007 and 2008. Particulate organic carbon (POC) and nitrogen (PON), biogenic silica (bSiO2), and size‐fractionated chlorophyll a (chl a) concentrations were measured within the euphotic zone throughout five domains: Eastern Subarctic North Pacific (ESNP), Bering and Chukchi Seas (BE‐CH), Southern Beaufort Sea and Canada Basin (BS‐CB), Canadian Arctic Archipelago (CAA), and Baffin Bay and Labrador Sea (BB‐LS). Despite large variability along the sampling transect and vertically throughout the euphotic zone, domain averages of depth‐integrated POC and PON were relatively invariant across the ESNP, BE‐CH, CAA, and BB‐LS, ranging from 546 to 670 mmol m−2 (POC) and 101 to 154 mmol m−2 (PON), but were much lower in BS‐CB (199 and 78 mmol m−2, respectively). In contrast, depth‐integrated bSiO2 averages were highest in BE‐CH and CAA (>100 mmol m−2), intermediate in ESNP and BB‐LS (34–48 mmol m−2), and low in BS‐CB (6 mmol m−2). Similarly to the bSiO2 distribution, the biomass of the >5 μm chl a size‐fraction averaged 68–69% of total chl a in BE‐CH and CAA, 56% in BB‐LS, and 22–23% in ESNP and BS‐CB. Ratios of bSiO2:PON averaged 1.10–1.30 in BE‐CH and CAA, 0.30–0.34 in ESNP and BB‐LS, and 0.08 in BS‐CB. This study highlights the relative importance of siliceous phytoplankton such as diatoms in BE‐CH and CAA, smaller nonsiliceous cells in BS‐CB and ESNP, and a mixed assemblage of variably sized phytoplankton with a less siliceous component in BB‐LS.
The effect of basal channels on oceanic ice‐shelf melting
Authors: Millgate Thomas , Holland Paul R. , Jenkins Adrian , Johnson Helen L.
Published: November 2013

The presence of ice‐shelf basal channels has been noted in a number of Antarctic and Greenland ice shelves, but their impact on basal melting is not fully understood. Here we use the Massachusetts Institute of Technology general circulation model to investigate the effect of ice‐shelf basal channels on oceanic melt rate for an idealized ice shelf resembling the floating tongue of Petermann Glacier in Greenland. The introduction of basal channels prevents the formation of a single geostrophically balanced boundary current; instead the flow is diverted up the right‐hand (Coriolis‐favored) side of each channel, with a return flow in the opposite direction on the left‐hand side. As the prescribed number of basal channels is increased the mean basal melt rate decreases, in agreement with previous studies. For a small number of relatively wide channels the subice flow is found to be a largely geostrophic horizontal circulation. The reduction in melt rate is then caused by an increase in the relative contribution of weakly melting channel crests and keels. For a larger number of relatively narrow channels, the subice flow changes to a vertical overturning circulation. This change in circulation results in a weaker sensitivity of melt rates to channel size. The transition between the two regimes is governed by the Rossby radius of deformation. Our results explain why basal channels play an important role in regulating basal melting, increasing the stability of ice shelves.
Comparison of aerosol optical depth between CALIOP and MODIS‐Aqua for CALIOP aerosol subtypes over the ocean
Authors: Kim Man‐Hae , Kim Sang‐Woo , Yoon Soon‐Chang , Omar Ali H.
Published: November 2013

The Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol optical depth (AOD) has been compared with the Moderate Resolution Imaging Spectroradiometer (MODIS)‐Aqua AOD using Level 2 products of both instruments. Such comparisons have been performed for five different aerosol subtypes classified by CALIOP algorithm, namely clean marine, dust, polluted dust, polluted continental, and biomass burning, over the ocean from June 2006 to December 2010. MODIS AOD at 550 nm (0.111 ± 0.079) for the collocated data pairs is about 63% higher than CALIOP AOD at 532 nm (0.068 ± 0.073). For clean marine, MODIS AOD (0.110 ± 0.064) is almost twice the CALIOP AOD (0.056 ± 0.038), and the difference between the AOD values has a strong latitude dependence likely related to the surface wind speed over the ocean. The difference in AOD for dust (13%) is observed to be the lowest among the five aerosol types under consideration, but it shows a slight regional variation. The discrepancy of AOD for dust also shows strong dependency on the layer mean of the particulate depolarization ratio. CALIOP AOD is higher than MODIS AOD for both polluted dust and polluted continental by 15% and 29%, respectively, for most of the ocean. One of the possible reasons for the difference is the misclassification of clean marine (or marine + dust) as polluted dust and polluted continental in the CALIOP algorithm. For biomass burning, uncertainty in the layer base altitude is thought to be one of the main reasons for the lower value of CALIOP AOD.
Dissipation at tidal and seismic frequencies in a melt‐free, anhydrous Mars
Authors: Nimmo F. , Faul U. H.
Published: November 2013

The measured inward motion of Phobos provides a constraint on the tidal dissipation factor, Q, within Mars. We model viscoelastic dissipation inside a convective Mars using a modified Burgers model based on laboratory experiments on anhydrous, melt‐free olivine. The model tidal Q is highly sensitive to the mantle potential temperature and grain size assumed but relatively insensitive to the bulk density and rigidity structure. Q thus provides a tight constraint on the Martian interior temperature. By fitting the observed tidal Q and tidal Love number (k2) values and requiring present‐day melt generation, we estimate that for a grain size of 1 cm the current mantle potential temperature is 1625±75 K, similar to that of the Earth. This estimate is consistent with recent petrologically derived determinations of mantle potential temperature but lower than estimates in some thermal evolution models. The presence of water in the Martian mantle would reduce our estimated temperature. Our preferred mantle grain size of ≈1 cm is somewhat larger than that of the Earth's upper mantle. The predicted mantle seismic Q is about 130 and is almost independent of depth. The Martian lithosphere represents a high seismic velocity lid, which should be readily detectable with future seismological observations.
Physical mechanisms controlling self‐aggregation of convection in idealized numerical modeling simulations
Authors: Wing Allison A. , Emanuel Kerry A.
Published: November 2013

We elucidate the physics of self‐aggregation by applying a new diagnostic technique to the output of a cloud resolving model. Specifically, the System for Atmospheric Modeling is used to perform 3‐ D cloud system resolving simulations of radiative‐convective equilibrium in a nonrotating framework, with interactive radiation and surface fluxes and fixed sea surface temperature (SST). We note that self‐aggregation begins as a dry patch that expands, eventually forcing all the convection into a single clump. Thus, when examining the initiation of self‐aggregation, we focus on processes that can amplify this initial dry patch. We introduce a novel method to quantify the magnitudes of the various feedbacks that control self‐aggregation within the framework of the budget for the spatial variance of column‐integrated frozen moist static energy. The absorption of shortwave radiation by atmospheric water vapor is found to be a key positive feedback in the evolution of aggregation. In addition, we find a positive wind speed‐surface flux feedback whose role is to counteract a negative feedback due to the effect of air‐sea enthalpy disequilibrium on surface fluxes. The longwave radiation feedback can be either positive or negative in the early and intermediate stages of aggregation; however, it is the dominant positive feedback that maintains the aggregated state once it develops. Importantly, the mechanisms that maintain the aggregate state are distinct from those that instigate the evolution of self‐aggregation.