A framework for interpolating scattered data using space-filling curves

The analysis of spatial data occurs in many disciplines and covers a wide variety activities. Available techniques for such analysis include spatial interpolation which is useful for tasks such as visualization and imputation. This paper proposes a novel approach to interpolation using space-filling curves. Two simple interpolation methods are described and their ability to interpolate is compared to several interpolation techniques including natural neighbour interpolation. The proposed approach requires a Monte-Carlo step that requires a large number of iterations. However experiments demonstrate that the number of iterations will not change appreciably with larger datasets

Structural and Functional Insights into the Malaria Parasite Moving Junction Complex

Members of the phylum Apicomplexa, which include the malaria parasite Plasmodium, share many features in their invasion mechanism in spite of their diverse host cell specificities and life cycle characteristics. The formation of a moving junction (MJ) between the membranes of the invading apicomplexan parasite and the host cell is common to these intracellular pathogens. The MJ contains two key parasite components: the surface protein Apical Membrane Antigen 1 (AMA1) and its receptor, the Rhoptry Neck Protein (RON) complex, which is targeted to the host cell membrane during invasion. In particular, RON2, a transmembrane component of the RON complex, interacts directly with AMA1. Here, we report the crystal structure of AMA1 from Plasmodium falciparum in complex with a peptide derived from the extracellular region of PfRON2, highlighting clear specificities of the P. falciparum RON2-AMA1 interaction. The receptor-binding site of PfAMA1 comprises the hydrophobic groove and a region that becomes exposed by displacement of the flexible Domain II loop. Mutations of key contact residues of PfRON2 and PfAMA1 abrogate binding between the recombinant proteins. Although PfRON2 contacts some polymorphic residues, binding studies with PfAMA1 from different strains show that these have little effect on affinity. Moreover, we demonstrate that the PfRON2 peptide inhibits erythrocyte invasion by P. falciparum merozoites and that this strong inhibitory potency is not affected by AMA1 polymorphisms. In parallel, we have determined the crystal structure of PfAMA1 in complex with the invasion-inhibitory peptide R1 derived by phage display, revealing an unexpected structural mimicry of the PfRON2 peptide. These results identify the key residues governing the interactions between AMA1 and RON2 in P. falciparum and suggest novel approaches to antimalarial therapeutics

The possible role of local air pollution in climate change in West Africa

The climate of West Africa is characterized by a sensitive monsoon system that is associated with marked natural precipitation variability. This region has been and is projected to be subject to substantial global and regional-scale changes including greenhouse-gas-induced warming and sea-level rise, land-use and land-cover change, and substantial biomass burning. We argue that more attention should be paid to rapidly increasing air pollution over the explosively growing cities of West Africa, as experiences from other regions suggest that this can alter regional climate through the influences of aerosols on clouds and radiation, and will also affect human health and food security. We need better observations and models to quantify the magnitude and characteristics of these impacts

N-1 modal interactions of a three-degree-of-freedom system with cubic elastic nonlinearities

In this paper the (Formula presented.) nonlinear modal interactions that occur in a nonlinear three-degree-of-freedom lumped mass system, where (Formula presented.), are considered. The nonlinearity comes from springs with weakly nonlinear cubic terms. Here, the case where all the natural frequencies of the underlying linear system are close (i.e. (Formula presented.)) is considered. However, due to the symmetries of the system under consideration, only (Formula presented.) modes interact. Depending on the sign and magnitude of the nonlinear stiffness parameters, the subsequent responses can be classified using backbone curves that represent the resonances of the underlying undamped, unforced system. These backbone curves, which we estimate analytically, are then related to the forced response of the system around resonance in the frequency domain. The forced responses are computed using the continuation software AUTO-07p. A comparison of the results gives insights into the multi-modal interactions and shows how the frequency response of the system is related to those branches of the backbone curves that represent such interactions

Juxtamembrane Shedding of Plasmodium falciparum AMA1 Is Sequence Independent and Essential, and Helps Evade Invasion-Inhibitory Antibodies

The malarial life cycle involves repeated rounds of intraerythrocytic replication interspersed by host cell rupture which releases merozoites that rapidly invade fresh erythrocytes. Apical membrane antigen-1 (AMA1) is a merozoite protein that plays a critical role in invasion. Antibodies against AMA1 prevent invasion and can protect against malaria in vivo, so AMA1 is of interest as a malaria vaccine candidate. AMA1 is efficiently shed from the invading parasite surface, predominantly through juxtamembrane cleavage by a membrane-bound protease called SUB2, but also by limited intramembrane cleavage. We have investigated the structural requirements for shedding of Plasmodium falciparum AMA1 (PfAMA1), and the consequences of its inhibition. Mutagenesis of the intramembrane cleavage site by targeted homologous recombination abolished intramembrane cleavage with no effect on parasite viability in vitro. Examination of PfSUB2-mediated shedding of episomally-expressed PfAMA1 revealed that the position of cleavage is determined primarily by its distance from the parasite membrane. Certain mutations at the PfSUB2 cleavage site block shedding, and parasites expressing these non-cleavable forms of PfAMA1 on a background of expression of the wild type gene invade and replicate normally in vitro. The non-cleavable PfAMA1 is also functional in invasion. However – in contrast to the intramembrane cleavage site - mutations that block PfSUB2-mediated shedding could not be stably introduced into the genomic pfama1 locus, indicating that some shedding of PfAMA1 by PfSUB2 is essential. Remarkably, parasites expressing shedding-resistant forms of PfAMA1 exhibit enhanced sensitivity to antibody-mediated inhibition of invasion. Drugs that inhibit PfSUB2 activity should block parasite replication and may also enhance the efficacy of vaccines based on AMA1 and other merozoite surface proteins

Short-Lived Trace Gases in the Surface Ocean and the Atmosphere

The two-way exchange of trace gases between the ocean and the atmosphere is important for both the chemistry and physics of the atmosphere and the biogeochemistry of the oceans, including the global cycling of elements. Here we review these exchanges and their importance for a range of gases whose lifetimes are generally short compared to the main greenhouse gases and which are, in most cases, more reactive than them. Gases considered include sulphur and related compounds, organohalogens, non-methane hydrocarbons, ozone, ammonia and related compounds, hydrogen and carbon monoxide. Finally, we stress the interactivity of the system, the importance of process understanding for modeling, the need for more extensive field measurements and their better seasonal coverage, the importance of inter-calibration exercises and finally the need to show the importance of air-sea exchanges for global cycling and how the field fits into the broader context of Earth System Science

Effect of nasal valve surgery by open-septorhinoplasty and lateral cartilage grafts (spreader grafts) on snoring among a population of single snorers. Preliminary report.

Snoring is traditionally considered more of a social nuisance than disease. The observation that nasal obstruction may modify breathing during sleep and daytime behavior and our clinical observations suggesting that some single snorer patients who had undergone surgery of the nasal valve for nasal obstruction complaints had presented a decrease in their snoring, led us to make a retrospective study on twenty nine patients. Eight of them were simple snorers. They underwent a surgery of the nasal valve under general anesthesia through an open septorhinoplasty during which lateral graft cartilages (modified spreader grafts) were set in place between septolateral cartilage and the anterior and superior edge of the nasal septum. Active anterior rhinomanometry (AAR), posterior active rhinomanometry (PAR) and a self-assessment of the nasal patency by the patient himself on a visual analog scale (VAS) were compared before and one year after surgery. Snoring was assessed by both bed partners according to a four step scale (none, slight, moderate and severe). No significant differences were found between AAR or between PAR. But significant differences were measured with VAS (for the left (p < 0.0001) and the right sides (p < 0.001). All patients but one demonstrated substantially decreased snoring. As there is no clear cut evidence of changes in nasal resistances measured by rhinomanometry, we suggest that the observed decrease in snoring may be induced by changes in the direction of the nasal airflow against the nasal mucosa which may produce by a reflex between mecanoreceptors of the nasal mucosa and muscles of the pharynx, an increased tonus of the muscles of the pharynx

Sensitivity and reliability analysis of articulated heavy vehicle

SIA, MULHOUSE, FRANCE, 04-/10/2011 - 06/10/2011The aim of this paper is to develop a stochastic based approach to prevent rollover and jackkning risk of articulated heavy vehicle. A specific 6-DOF heavy vehicle model is developed and safety criteria are used. Parameters involved in the model are modeled by random variables or stochastic processes in order to take into account incertainties. These parameters are deduced from two different sensitivity analysis methods. Then, structural reliability methods are employed to assess the probability of failure and compared to Monte-Carlo based method

Damping identification in multi-degree-of freedom system via a wavelet-logarithmic decrement - Part 2:Study of a civil engineering building

International audienceIn a previous paper entitled "Damping identification in multi-degree-of-freedom (m.d.o.f.) systems via wavelet-logarithmic decrement--Part 1: theory", a wavelet-logarithmic decrement formula was established to estimate damping in multi-degree-of-freedom systems from time-domain responses. Numerical validation was then investigated using the dynamic response of exact single-degree-of-freedom systems that were artificially perturbed with a Gaussian noise. Part 2 is now dedicated to the application of the wavelet procedure to identify the damping of in situ dynamic responses of a civil engineering building excited with both harmonic and shock testings