Résumé
Les auteurs analysent l'effet du télétravail (effectué depuis le domicile) sur le fonctionnement familial en se fondant sur les vagues 2001–2013 d'une enquête australienne auprès des ménages ...(enquête HILDA), plus précisément sur les réponses fournies par le partenaire du télétravailleur. L'analyse, qui repose sur quarante‐huit modèles multivariés, établit à certains égards l'effet bénéfique du télétravail sur les relations intrafamiliales et le partage des responsabilités en présence d'enfants. Les externalités négatives mises en évidence sont limitées et surviennent surtout lorsque c'est l'homme qui travaille – beaucoup – depuis le domicile. Globalement, l'analyse confirme les résultats des études précédentes selon lesquelles le télétravail faciliterait la conciliation travail‐vie personnelle.
Sparse and redundant representation modeling of data assumes an ability to describe signals as linear combinations of a few atoms from a pre-specified dictionary. As such, the choice of the ...dictionary that sparsifies the signals is crucial for the success of this model. In general, the choice of a proper dictionary can be done using one of two ways: i) building a sparsifying dictionary based on a mathematical model of the data, or ii) learning a dictionary to perform best on a training set. In this paper we describe the evolution of these two paradigms. As manifestations of the first approach, we cover topics such as wavelets, wavelet packets, contourlets, and curvelets, all aiming to exploit 1-D and 2-D mathematical models for constructing effective dictionaries for signals and images. Dictionary learning takes a different route, attaching the dictionary to a set of examples it is supposed to serve. From the seminal work of Field and Olshausen, through the MOD, the K-SVD, the Generalized PCA and others, this paper surveys the various options such training has to offer, up to the most recent contributions and structures.
PPO, constitutive or induced by jasmonate, in coded for by multiple genes. It oxidizes mono- or dihydroxy phenols to the corresponding quinones. The products of its action have a function in ...resistance to pathogens and herbivores. PPO may be involved in biosynthesis processes.
The more recent reports on polyphenol oxidase in plants and fungi are reviewed. The main aspects considered are the structure, distribution, location and properties of polyphenol oxidase (PPO) as well as newly discovered inhibitors of the enzyme. Particular stress is given to the possible function of the enzyme. The cloning and characterization of a large number of PPOs is surveyed. Although the active site of the enzyme is conserved, the amino acid sequence shows very considerable variability among species. Most plants and fungi PPO have multiple forms of PPO. Expression of the genes coding for the enzyme is tissue specific and also developmentally controlled. Many inhibitors of PPO have been described, which belong to very diverse chemical structures; however, their usefulness for controlling PPO activity remains in doubt. The function of PPO still remains enigmatic. In plants the positive correlation between levels of PPO and the resistance to pathogens and herbivores is frequently observed, but convincing proof of a causal relationship, in most cases, still has not been published. Evidence for the induction of PPO in plants, particularly under conditions of stress and pathogen attack is considered, including the role of jasmonate in the induction process. A clear role of PPO in a least two biosynthetic processes has been clearly demonstrated. In both cases a very high degree of substrate specificity has been found. In fungi, the function of PPO is probably different from that in plants, but there is some evidence indicating that here too PPO has a role in defense against pathogens. PPO also may be a pathogenic factor during the attack of fungi on other organisms. Although many details about structure and probably function of PPO have been revealed in the period reviewed, some of the basic questions raised over the years remain to be answered.
A wide range of phylogenetically diverse microorganisms couple the reductive dehalogenation of organohalides to energy conservation. Key enzymes of such anaerobic catabolic pathways are corrinoid and ...Fe-S cluster-containing, membrane-associated reductive dehalogenases. These enzymes catalyze the reductive elimination of a halide and constitute the terminal reductases of a short electron transfer chain. Enzymatic and physiological studies revealed the existence of quinone-dependent and quinone-independent reductive dehalogenases that are distinguishable at the amino acid sequence level, implying different modes of energy conservation in the respective microorganisms. In this review, we summarize current knowledge about catabolic reductive dehalogenases and the electron transfer chain they are part of. We review reaction mechanisms and the role of the corrinoid and Fe-S cluster cofactors and discuss physiological implications.
Object tracking is a key enabling technology in the context of computer-assisted medical interventions. Allowing the continuous localization of medical instruments and patient anatomy, it is a ...prerequisite for providing instrument guidance to subsurface anatomical structures. The only widely used technique that enables real-time tracking of small objects without line-of-sight restrictions is electromagnetic (EM) tracking. While EM tracking has been the subject of many research efforts, clinical applications have been slow to emerge. The aim of this review paper is therefore to provide insight into the future potential and limitations of EM tracking for medical use. We describe the basic working principles of EM tracking systems, list the main sources of error, and summarize the published studies on tracking accuracy, precision and robustness along with the corresponding validation protocols proposed. State-of-the-art approaches to error compensation are also reviewed in depth. Finally, an overview of the clinical applications addressed with EM tracking is given. Throughout the paper, we report not only on scientific progress, but also provide a review on commercial systems. Given the continuous debate on the applicability of EM tracking in medicine, this paper provides a timely overview of the state-of-the-art in the field.
Direct, mediator-free transfer of electrons between a microbial cell and a solid phase in its surrounding environment has been suggested to be a widespread and ecologically significant process. The ...high rates of microbial electron uptake observed during microbially influenced corrosion of iron Fe(0) and during microbial electrosynthesis have been considered support for a direct electron uptake in these microbial processes. However, the underlying molecular mechanisms of direct electron uptake are unknown. We investigated the electron uptake characteristics of the Fe(0)-corroding and electromethanogenic archaeon Methanococcus maripaludis and discovered that free, surface-associated redox enzymes, such as hydrogenases and presumably formate dehydrogenases, are sufficient to mediate an apparent direct electron uptake. In genetic and biochemical experiments, we showed that these enzymes, which are released from cells during routine culturing, catalyze the formation of H2 or formate when sorbed to an appropriate redox-active surface. These low-molecular-weight products are rapidly consumed by M. maripaludis cells when present, thereby preventing their accumulation to any appreciable or even detectable level. Rates of H2 and formate formation by cell-free spent culture medium were sufficient to explain the observed rates of methane formation from Fe(0) and cathode-derived electrons by wild-type M. maripaludis as well as by a mutant strain carrying deletions in all catabolic hydrogenases. Our data collectively show that cell-derived free enzymes can mimic direct extracellular electron transfer during Fe(0) corrosion and microbial electrosynthesis and may represent an ecologically important but so far overlooked mechanism in biological electron transfer.
The intriguing trait of some microbial organisms to engage in direct electron transfer is thought to be widespread in nature. Consequently, direct uptake of electrons into microbial cells from solid surfaces is assumed to have a significant impact not only on fundamental microbial and biogeochemical processes but also on applied bioelectrochemical systems, such as microbial electrosynthesis and biocorrosion. This study provides a simple mechanistic explanation for frequently observed fast electron uptake kinetics in microbiological systems without a direct transfer: free, cell-derived enzymes can interact with cathodic surfaces and catalyze the formation of intermediates that are rapidly consumed by microbial cells. This electron transfer mechanism likely plays a significant role in various microbial electron transfer reactions in the environment.
Microbial uptake of free cathodic electrons presents a poorly understood aspect of microbial physiology. Uptake of cathodic electrons is particularly important in microbial electrosynthesis of ...sustainable fuel and chemical precursors using only CO
and electricity as carbon, electron and energy source. Typically, large overpotentials (200 to 400 mV) were reported to be required for cathodic electron uptake during electrosynthesis of, for example, methane and acetate, or low electrosynthesis rates were observed. To address these limitations and to explore conceptual alternatives, we studied defined co-cultures metabolizing cathodic electrons. The Fe(0)-corroding strain IS4 was used to catalyze the electron uptake reaction from the cathode forming molecular hydrogen as intermediate, and Methanococcus maripaludis and Acetobacterium woodii were used as model microorganisms for hydrogenotrophic synthesis of methane and acetate, respectively. The IS4-M. maripaludis co-cultures achieved electromethanogenesis rates of 0.1-0.14 μmol cm
h
at -400 mV vs standard hydrogen electrode and 0.6-0.9 μmol cm
h
at -500 mV. Co-cultures of strain IS4 and A. woodii formed acetate at rates of 0.21-0.23 μmol cm
h
at -400 mV and 0.57-0.74 μmol cm
h
at -500 mV. These data show that defined co-cultures coupling cathodic electron uptake with synthesis reactions via interspecies hydrogen transfer may lay the foundation for an engineering strategy for microbial electrosynthesis.
A full-rank matrix ${\bf A}\in {\Bbb R}^{n\times m}$ with n < m generates an underdetermined system of linear equations Ax = b having infinitely many solutions. Suppose we seek the sparsest solution, ...i.e., the one with the fewest nonzero entries. Can it ever be unique? If so, when? As optimization of sparsity is combinatorial in nature, are there efficient methods for finding the sparsest solution? These questions have been answered positively and constructively in recent years, exposing a wide variety of surprising phenomena, in particular the existence of easily verifiable conditions under which optimally sparse solutions can be found by concrete, effective computational methods. Such theoretical results inspire a bold perspective on some important practical problems in signal and image processing. Several well-known signal and image processing problems can be cast as demanding solutions of undetermined systems of equations. Such problems have previously seemed, to many, intractable, but there is considerable evidence that these problems often have sparse solutions. Hence, advances in finding sparse solutions to undetermined systems have energized research on such signal and image processing problems--to striking effect. In this paper we review the theoretical results on sparse solutions of linear systems, empirical results on sparse modeling of signals and images, and recent applications in inverse problems and compression in image processing. This work lies at the intersection of signal processing and applied mathematics, and arose initially from the wavelets and harmonic analysis research communities. The aim of this paper is to introduce a few key notions and applications connected to sparsity, targeting newcomers interested in either the mathematical aspects of this area or its applications.
Without election or re-election motivations, what factors have impacted public goods preferences in an authoritarian country such as China? More specifically, what makes political elites be devoted ...to or not be devoted to local public goods provision? This study, using basic education provision as an example, intends to gauge the impact of leadership selection on public goods provision in China. It is found that career trajectories of politicians have a bearing on basic education provision. The findings suggest that even under a top-down appointment system, homegrown politicians are more willing to cater to local preferences, especially on basic education provision, which suggests an extension of Riker's theory, applied in a non-democratic regime. Numerous studies have examined the impacts of decentralization on a variety of aspects of public governance in different contexts. Nevertheless, the unique contribution of this study is its policy implication that political centralization may not be an effective solution for local public governance even in an authoritarian context.
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