LDR: A Package for Likelihood-Based Sufficient Dimension Reduction

We introduce a new mlab software package that implements several recently proposed likelihood-based methods for sufficient dimension reduction. Current capabilities include estimation of reduced subspaces with a fixed dimension d, as well as estimation of d by use of likelihood-ratio testing, permutation testing and information criteria. The methods are suitable for preprocessing data for both regression and classification. Implementations of related estimators are also available. Although the software is more oriented to command-line operation, a graphical user interface is also provided for prototype computations.

Analyse comparative des cadres juridiques régissant la gestion de la faune par les collectivités locales en Afrique centrale. Diversités et limites

La gestion locale de la faune peut inclure tant des zones de conservation que des zones cynégétiques. Dans ce chapitre, nous avons voulu mettre en exergue tout d'abord les régimes fonciers s'appliquant à ces zones avant de passer à l'analyse juridique des modalités de conservation de la faune et d'exercice de la chasse par les populations locales et les communautés autochtones en République démocratique du Congo (RDC), au Gabon et au Congo. En particulier, le secteur de la chasse, qui est régi à la fois par des lois spécifiques et des sections thématiques de lois forestières, présente indistinctement un problème de chevauchement et de confusion normatif. La législation régissant la chasse a tendance à contenir des normes conçues pour la chasse sportive ou scientifique qui, faute de spécificité, s'appliquent aussi à la chasse communautaire. Cela a des implications majeures sur toute la filière, de l'abattage à la détention jusqu'à la commercialisation

Characterization of the interdependency between residues that bind the substrate in a β-glycosidase

The manner by which effects of simultaneous mutations combine to change enzymatic activity is not easily predictable because these effects are not always additive in a linear manner. Hence, the characterization of the effects of simultaneous mutations of amino acid residues that bind the substrate can make a significant contribution to the understanding of the substrate specificity of enzymes. In the β-glycosidase from Spodoptera frugiperda (Sfβgly), both residues Q39 and E451 interact with the substrate and this is essential for defining substrate specificity. Double mutants of Sfβgly (A451E39, S451E39 and S451N39) were prepared by site-directed mutagenesis, expressed in bacteria and purified using affinity chromatography. These enzymes were characterized using p-nitrophenyl β-galactoside and p-nitrophenyl β-fucoside as substrates. The k cat/Km ratio for single and double mutants of Sfβgly containing site-directed mutations at positions Q39 and E451 was used to demonstrate that the effect on the free energy of ES‡ (enzyme-transition state complex) of the double mutations (∆∆G‡xy) is not the sum of the effects resulting from the single mutations (∆∆G‡x and ∆∆G‡y). This difference in ∆∆G‡ indicates that the effects of the single mutations partially overlap. Hence, this common effect counts only once in ∆∆G‡xy. Crystallographic data on β-glycosidases reveal the presence of a bidentate hydrogen bond involving residues Q39 and E451 and the same hydroxyl group of the substrate. Therefore, both thermodynamic and crystallographic data suggest that residues Q39 and E451 exert a mutual influence on their respective interactions with the substrate.FAPESPCNP

Auf der Suche nach Ursachen für das grösste Massenaussterbe-Ereignis : die Perm-Trias-Grenze der Südhemisphäre – Teil II : erforschung 260 Millionen Jahre alter Meteoriteneinschlag-verformter Sedimentgesteine im zentralen Westbrasilien

Various catastrophic and/or episodic events have been suggested to have caused the end-Permian mass extinction close to the Permo-Triassic Boundary (PTB). The theories and extinction-scenarios are however predominantly based on the sedimentary rock record and fossil record of the Northern Hemisphere – the Southern Hemisphere and in particular the fossil fish record worldwide being least well explored. In this second of four contributions we briefly present a little-known meteorite-impact crater relatively close to the PTB on the border of the States of Goiás and Mato Grosso in central west-Brazil. We discuss the occurrence of neighbouring Permian sedimentary rocks, a selection of accessible outcrops, fossil content and their potential to contribute to the discussion around the end-Permian extinction event. _______________________________________________________________________________________________ ABSTRAKTVerschiedene katastrophenhafte und/oder episodische Ereignisse sind als Ursachen für das Massenaussterbe- Ereignis am Ende des Perms in der Nähe der Perm-Trias-Grenze (PTB) vorgeschlagen worden. Die Theorien und Aussterbe-Szenarien gründen allerdings mehrheitlich auf dem Sedimentgestein- und Fossilbeleg der Nordhemisphäre, während die Südhemisphäre und speziell der fossile Fisch-Beleg weltweit am wenigsten gründlich erforscht sind. In diesem zweiten von vier Beiträgen stellen wir einen wenig bekannten Meteoriten-Einschlagkrater relativ nahe der PTB an der Grenze der Staaten Goiás und Mato Grosso im zentralen West-Brasilien vor. Wir diskutieren das Auftreten benachbarter permischer Sedimentgesteine, eine Auswahl zugänglicher Aufschlüsse, Fossilinhalte und ihr Potential zur Diskussion um das Aussterbe-Ereignis am Ende des Perms beizutragen

Molecular line emissions from pre main sequence objects

We present some preliminary results obtained with the LWS G.T. programme on the study of young objects driving molecular outflows. In particular, we discuss the importance of molecular emission in these sources and address the role of the H20 cooling

A Long-Term Control Project for an Invasive Plant: Assessment of Phragmites Australis Reduction and Redevelopment of Native Vegetation in Interdunal Swales of Sandy Neck Barrier Beach, Cape Cod, Massachusetts

Phragmites australis is a perennial wetland grass that is native to North America. However, salt marshes, estuaries, and other wetlands throughout the northeast USA and Canada have witnessed a dramatic range expansion and population increase of the introduced genetic variant Phragmites australis haplotype M (Saltonstall 2002), with loss of native vegetation through competitive exclusion. Within the dune system of Sandy Neck Barrier Beach, freshwater wetland swales form in low elevation areas, which harbor a diverse wetland plant community dominated by shrubs, and sedges -- and including some rare and endangered species. To conserve and protect these wetland plant associations, annual herbicide applications were initiated in 2002 in a control program targeting the expanding populations of Phragmites M in the interdunal swales. To determine whether herbicide applications have reduced Phragmites infestations, estimated density and abundance scores from 2002-2009 were analyzed using a linear mixed model regression. Phragmite presence/absence data from the same time period was analyzed through binary logistic regression to determine whether herbicide applications were eradicating Phragmites from swales. The number of herbicide applications has significantly reduced the number of Phragmites stems within invaded swales, but the plant persists in all but a few of the treated swales. Data from a vegetation survey of 28 swales in 2010 were analyzed through cluster and multidimensional scaling analysis to investigate whether the composition of the plant communities differs between Phragmites-invaded swales versus swales never invaded by Phragmites. The vegetation found in uninvaded swales is distinctly different than that found in invaded swales. Additionally, the analysis of the survey data was used to determine whether reducing Phragmites in treated swales produces a vegetational shift toward non-Phragmites community structure. The analysis does not show that swales with reduced Phragmites plants have had a redevelopment of swale vegetation, similar to that found in uninvaded swales. More time or more herbicide applications may be necessary before changes to the plant community become evident

Inter-satellite coordinated impulsive collision avoidance strategies

LAUREA MAGISTRALEL'aumento dei detriti spaziali nella zona vicino alla Terra pone significative sfide alla sicurezza e alla sostenibilità delle operazioni spaziali. Lo sviluppo di strategie efficaci per evitare le collisioni diventa fondamentale all'aumentare della probabilità di collisioni tra satelliti attivi e detriti. Inoltre, la maggiore presenza di costellazioni incrementa la necessità di manovre di anti-collisione (CAM) coordinate in scenari attivo vs attivo, che sono l'obiettivo di questa tesi. Questa ricerca esplora metodi numerici e analitici per ideare strategie robuste di CAM impulsive con tre diversi parametri impostati come obiettivo. In primo luogo, la CAM viene risolta formulandola come un problema di Non-Linear Programming (NLP) con il vincolo finale che agisce sulla Miss Distance (MD) 2D-3D o sulla Probabilità di Collisione (PoC) al Time of Closest Approach (TCA). Il metodo numerico si concentra sul trovare gli impulsi ottimali all'interno di limiti definiti a partire dalla soluzione del problema non coordinato. Il metodo analitico, invece, fornisce una soluzione attraverso la derivazione matematica. Inoltre, questa tesi offre una valutazione approfondita del TCA reale, inclusi il calcolo dello spostamento del punto di contatto dovuto alla manovra e la valutazione dei vincoli rilevanti in quel punto specifico. Sia la soluzione numerica che quella analitica vengono quindi migliorate incorporando l'aggiornamento del TCA nel processo di ottimizzazione per garantire delle manovre efficienti ed efficaci in scenari realistici. I risultati principali di questo studio includono lo sviluppo di una pipeline completa per l'implementazione di CAM coordinate, testata in diversi regimi orbitali e condizioni iniziali. I risultati sottolineano l'efficienza computazionale del metodo analitico, in grado di mantenere un livello di precisione simile rispetto a quello numerico pur impiegando in media circa dieci volte meno tempo. Inoltre, l'inclusione del processo di aggiornamento del TCA nella pipeline della soluzione della CAM si è rivelata benefica nel garantire che i valori imposti di MD o PoC siano rispettati. Questa ricerca contribuisce al campo della sicurezza spaziale, offrendo soluzioni pratiche alla crescente sfida della gestione dei detriti spaziali e più specificamente delle CAM coordinate. Le metodologie sviluppate offrono un punto di partenza per migliorare le capacità di evitamento delle collisioni, garantendo la sostenibilità a lungo termine delle attività spaziali e il prosperare della collaborazione tra satelliti.The increasing number of space debris in the near-Earth environment poses significant challenges to the safety and sustainability of space operations. Developing effective collision avoidance strategies becomes fundamental as the probability of collisions between active satellites and debris grows. Moreover, the presence of more and more constellations raises the need for coordinated collision avoidance manoeuvres (CAMs) in active vs active scenarios, which is the focus of this thesis. This research delves into numerical and analytical impulsive CAM methods to devise robust strategies with three different target parameters. Firstly, CAM is solved by formulating it as a Non-Linear Programming (NLP) problem with the final constraint acting on the 2D-3D Miss Distance (MD) or the Probability of Collision (PoC) at the Time of Closest Approach (TCA). The numerical method aims at finding the optimal impulses inside a predefined boundary starting from the solution of the non-coordinated problem. The analytical method, on the other hand, provides a solution through mathematical derivation. Furthermore, this thesis offers an in-depth evaluation of the real TCA, including the calculation of the shift in the closest approach point induced by the manoeuvre and the assessment of relevant constraints at that specific point. Both numerical and analytical solutions are then enhanced by incorporating the TCA update within the optimization process to ensure effective and efficient CAMs in realistic scenarios. The primary outcomes of this study include the development of a comprehensive pipeline for implementing coordinated CAMs, tested on different orbital regimes and initial conditions. The results underscore the computational efficiency of the analytical method, capable of maintaining a similar level of accuracy with respect to the numerical one while being ten times less taxing. Moreover, the inclusion of the TCA update process into the CAM solution pipeline has proven to be beneficial in ensuring that the MD or PoC comply with the imposed values. This research contributes valuable insights into the field of space safety, offering practical solutions to the growing challenge of space debris management and more specifically coordinated CAMs. The developed methodologies provide a starting point for enhanced collision avoidance capabilities, ensuring the long-term sustainability of space activities and the prosperity of inter-satellite collaboration