Records of geomagnetic reversals from volcanic islands of French Polynesia : 1. Paleomagnetic study of a polarity transition in a lava sequence from the island of Huahine

Présentation d'une étude paléomagnétique concernant une transition du champ magnétique terrestre enregistrée par les laves de l'île de Huahin

Records of geomagnetic reversals from volcanic islands of French Polynesia : 2. Paleomagnetic study of a flow sequence (1.2-0.6 Ma) from the island of Tahiti and discussion of reversal models

Une séquence volcanique de 700 m d'épaisseur a été échantillonée dans la vallée du Punaruu (Tahiti). Les résultats de l'étude paléomagnétique montrent que la séquence a enregistré 4 inversions du champ magnétique terrestre. Les données géochronologiques (K/Ar) indiquent que l'inversion plus récente correspond à la transition de Matuyama-Brunhes, que les 2 intermédiaires correspondent à la transition Saramillo et que la plus ancienne, identifiée à la base de la séquence, correspond à la transition Cobb Mountai

Correction: Drivers of deforestation in the basin of the Usumacinta River: Inference on process from pattern analysis using generalised additive models.

[This corrects the article DOI: 10.1371/journal.pone.0222908.]

Quantitative DCE-MRI demonstrates increased blood perfusion in Hoffa’s fat pad signal abnormalities in knee osteoarthritis, but not in patellofemoral pain

Objective: Infrapatellar fat pad (IPFP) fat-suppressed T2 (T2FS) hyperintense regions on MRI are an important imaging feature of knee osteoarthritis (OA) and are thought to represent inflammation. These regions are also common in non-OA subjects, and may not always be linked to inflammation. Our aim was to evaluate quantitative blood perfusion parameters, as surrogate measure of inflammation, within T2FS-hyperintense regions in patients with OA, with patellofemoral pain (PFP) (supposed OA precursor), and control subjects. Methods: Twenty-two knee OA patients, 35 PFP patients and 43 healthy controls were included and underwent MRI, comprising T2 and DCE-MRI sequences. T2FS-hyperintense IPFP regions were delineated and a reference region was drawn in adjacent IPFP tissue with normal signal intensity. After fitting the extended Tofts pharmacokinetic model, quantitative DCE-MRI perfusion parameters were compared between the two regions within subjects in each subgroup, using a paired Wilcoxon signed-rank test. Results: T2FS-hyperintense IPFP regions were present in 16 of 22 (73%) OA patients, 13 of 35 (37%) PFP patients, and 14 of 43 (33%) controls. DCE-MRI perfusion parameters were significantly different between regions with and without a T2FS-hyperintense signal in OA patients, demonstrating higher Ktrans compared to normal IFPF tissue (0.039 min−1 versus 0.025 min−1, p = 0.017) and higher Ve (0.157 versus 0.119, p = 0.010). For PFP patients and controls no significant differences were found. Conclusions: IPFP T2FS-hyperintense regions are associated with higher perfusion in knee OA patients in contrast to identically appearing regions in PFP patients and controls, pointing towards an inflammatory pathogenesis in OA only. Key Points: • Morphologically identical appearing T2FS-hyperintense infrapatellar fat pad regions show different perfusion in healthy subjects, subjects with patellofemoral pain, and subjects with knee osteoarthritis. • Elevated DCE-MRI perfusion parameters within T2FS-hyperintense infrapatellar fat pad regions in patients with osteoarthritis suggest an inflammatory pathogenesis in osteoarthritis, but not in patellofemoral pain and healthy subjects

Delayed sternal closure after cardiac operations in a pediatric population

AbstractObjective: The purpose of this study was to assess morbidity and mortality associated with delayed sternal closure after pediatric cardiac operations. Methods: Hospital records were reviewed of all patients with an open sternum after a cardiac operation at Children's Hospital, Boston, from January 1992 to December 1995. Results: A total of 178 patients had delayed sternal closure with an overall mortality rate of 19%. The most common diagnosis of patients with delayed sternal closure was hypoplastic left heart syndrome (29%). Although myocardial distention or chest wall edema (n = 47) was a common indication to delay sternal closure, in many patients (n = 47) the sternum was left open electively to avoid postoperative cardiac or respiratory compromise. Successful sternal closure was achieved in 158 patients (89%) at a mean of 3.4 ± 1.8 days after opening. There were significant increases in left atrial pressure (7.7 ± 3.4 to 9.8 ± 4.1 mm Hg, p = 0.00001) and right atrial pressure (8 ± 3.2 to 10.1 ± 3.3 mm Hg, p = 0.00001) with sternal closure. There was a small but statistically significant drop in pH (7.44 ± 0.05 to 7.41 ± 0.08, p < 0.0001) during sternal closure. The peak inspiratory pressure, delivered breaths per minute, and fraction of inspired oxygen all significantly increased during sternal closure. Clinical evidence of surgical site infection occurred in 12 (6.7%) of the patients with delayed sternal closure; mediastinitis developed in 7 (3.9%) patients. Conclusions: Although delayed sternal closure after complex operations for congenital heart disease is often necessary in the operating room because of edema, unstable hemodynamic conditions, or bleeding, it can also be used electively to aid in hemodynamic and respiratory stability in the initial postoperative period. Our review supports a low morbidity associated with delayed sternal closure in a pediatric population. (J Thorac Cardiovasc Surg 1997;113:886-93

Commensal Neisseria species share immune suppressive mechanisms with Neisseria gonorrhoeae

Neisseria gonorrhoeae is a highly adapted human sexually transmitted pathogen that can cause symptomatic infections associated with localized inflammation as well as asymptomatic and subclinical infections, particularly in females. Gonococcal infection in humans does not generate an effective immune response in most cases, which contributes to both transmission of the pathogen and reinfection after treatment. Neisseria gonorrhoeae is known to evade and suppress human immune responses through a variety of mechanisms. Commensal Neisseria species that are closely related to N. gonorrhoeae, such as N. cinerea, N. lactamica, N. elongata, and N. mucosa, rarely cause disease and instead asymptomatically colonize mucosal sites for prolonged periods of time without evoking clearing immunologic responses. We have shown previously that N. gonorrhoeae inhibits the capacity of antigen-pulsed dendritic cells to induce CD4+ T cell proliferation in vitro. Much of the suppressive effects of N. gonorrhoeae on dendritic cells can be recapitulated either by outer-membrane vesicles released from the bacteria or by purified PorB, the most abundant outer-membrane protein in Neisseria gonorrhoeae. We show here that three commensal Neisseria species, N. cinerea, N. lactamica and N. mucosa, show a comparable capacity to suppress dendritic cell-induced T cell proliferation in vitro through mechanisms similar to those demonstrated previously for N. gonorrhoeae, including inhibition by purified PorB. Our findings suggest that some immune-evasive properties of pathogenic N. gonorrhoeae are shared with commensal Neisseria species and may contribute to the ability of both pathogens and commensals to cause prolonged mucosal colonization in humans

Environmental consequences of Ontong Java Plateau and Kerguelen Plateau Volcanism

The mid-Cretaceous was marked by emplacement of large igneous provinces (LIPs) that formed gigantic oceanic plateaus, affecting ecosystems on a global scale, with biota forced to face excess CO2 resulting in climate and ocean perturbations. Volcanic phases of the Ontong Java Plateau (OJP) and the southern Kerguelen Plateau (SKP) are radiometrically dated and correlate with paleoenvironmental changes, suggesting causal links between LIPs and ecosystem responses. Aptian biocalcifi cation crises and recoveries are broadly coeval with C, Pb, and Os isotopic anomalies, trace metal infl uxes, global anoxia, and climate changes. Early Aptian greenhouse or supergreenhouse conditions were followed by prolonged cooling during the late Aptian, when OJP and SKP developed, respectively. Massive volcanism occurring at equatorial versus high paleolatitudes and submarine versus subaerial settings triggered very different climate responses but similar disruptions in the marine carbonate system. Excess CO2 arguably induced episodic ocean acidifi cation that was detrimental to marine calcifi ers, regardless of hot or cool conditions. Global anoxia was reached only under extreme warming, whereas cold conditions kept the oceans well oxygenated even at times of intensifi ed fertility. The environmental disruptions attributed to the OJP did not trigger a mass extinction: rock-forming nannoconids and benthic communities underwent a signifi cant decline during Oceanic Anoxic Event (OAE) 1a, but recovered when paroxysmal volcanism fi nished. Extinction of many planktonic foraminiferal and nannoplankton taxa, including most nannoconids, and most aragonitic rudists in latest Aptian time was likely triggered by severe ocean acidifi cation. Upgraded dating of paleoceanographic events, improved radiometric ages of the OJP and SKP, and time-scale revision are needed to substantiate the links between magmatism and paleoenvironmental perturbations

Drivers of deforestation in the basin of the Usumacinta River: Inference on process from pattern analysis using generalised additive models.

Quantifying patterns of deforestation and linking these patterns to potentially influencing variables is a key component of modelling and projecting land use change. Statistical methods based on null hypothesis testing are only partially successful for interpreting deforestation in the context of the processes that have led to their formation. Simplifications of cause-consequence relationships that are difficult to support empirically may influence environment and development policies because they suggest simple solutions to complex problems. Deforestation is a complex process driven by multiple proximate and underlying factors and a range of scales. In this study we use a multivariate statistical analysis to provide contextual explanation for deforestation in the Usumacinta River Basin based on partial pattern matching. Our approach avoided testing trivial null hypotheses of lack of association and investigated the strength and form of the response to drivers. As not all factors involved in deforestation are easily mapped as GIS layers, analytical challenges arise due to lack of a one to one correspondence between mappable attributes and drivers. We avoided testing simple statistical hypotheses such as the detectability of a significant linear relationship between deforestation and proximity to roads or water. We developed a series of informative generalised additive models based on combinations of layers that corresponded to hypotheses regarding processes. The importance of the variables representing accessibility was emphasised by the analysis. We provide evidence that land tenure is a critical factor in shaping the decision to deforest and that direct beam insolation has an effect associated with fire frequency and intensity. The effect of winter insolation was found to have many applied implications for land management. The methodology was useful for interpreting the relative importance of sets of variables representing drivers of deforestation. It was an informative approach, thus allowing the construction of a comprehensive understanding of its causes

The Relativistic Factor in the Orbital Dynamics of Point Masses

There is a growing population of relativistically relevant minor bodies in the Solar System and a growing population of massive extrasolar planets with orbits very close to the central star where relativistic effects should have some signature. Our purpose is to review how general relativity affects the orbital dynamics of the planetary systems and to define a suitable relativistic correction for Solar System orbital studies when only point masses are considered. Using relativistic formulae for the N body problem suited for a planetary system given in the literature we present a series of numerical orbital integrations designed to test the relevance of the effects due to the general theory of relativity in the case of our Solar System. Comparison between different algorithms for accounting for the relativistic corrections are performed. Relativistic effects generated by the Sun or by the central star are the most relevant ones and produce evident modifications in the secular dynamics of the inner Solar System. The Kozai mechanism, for example, is modified due to the relativistic effects on the argument of the perihelion. Relativistic effects generated by planets instead are of very low relevance but detectable in numerical simulations

Trajectories of university adjustment in the United Kingdom: Emotion management and emotional self-efficacy protect against initial poor adjustment

Little is known about individual differences in the pattern of university adjustment. This study explored longitudinal associations between emotional self-efficacy, emotion management, university adjustment, and academic achievement in a sample of first year undergraduates in the United Kingdom (N=331). Students completed measures of adjustment to university at three points during their first year at university. Latent Growth Mixture Modeling identified four trajectories of adjustment: (1) low, stable adjustment, (2) medium, stable adjustment, (3) high, stable adjustment, and (4) low, increasing adjustment. Membership of the low, stable adjustment group was predicted by low emotional self-efficacy and low emotion management scores, measured at entry into university. This group also had increased odds of poor academic achievement, even when grade at entry to university was controlled. Students who increased in adjustment had high levels of emotion management and emotional self-efficacy, which helped adaptation. These findings have implications for intervention