The Optimal Tax Rule in the Presence of Time Use

Using Mexican data on household time use and consumption, we find significant substitution between goods and time in home production and different elasticities of substitution for different household commodities. Adding these findings to the Ramsey optimal tax problem, we show it is optimal to impose higher taxes on market goods used in the production of commodities with a lower elasticity of substitution between goods and time. The reason is that government wants to minimize the distortionary substitution from market purchases toward untaxed time use in home production. This is an analog of the classical Corlett and Hague (1953-1954) result, differing in that we allow for the possibility of substitution between goods and time in the production of commodities. Leaving aside distributional considerations, we conclude that higher taxes should be imposed on market goods used in the production of `Eating` and lower taxes imposed on market goods used in the production of `Recreation`.Optimal taxation, Time use, Elasticity of substitution.

Winding vector: how to annihilate two Dirac points with the same charge

The merging or emergence of a pair of Dirac points may be classified according to whether the winding numbers which characterize them are opposite ($+-$ scenario) or identical ($++$ scenario). From the touching point between two parabolic bands (one of them can be flat), two Dirac points with the {\it same} winding number emerge under appropriate distortion (interaction, etc), following the $++$ scenario. Under further distortion, these Dirac points merge following the $+-$ scenario, that is corresponding to {\it opposite} winding numbers. This apparent contradiction is solved by the fact that the winding number is actually defined around a unit vector on the Bloch sphere and that this vector rotates during the motion of the Dirac points. This is shown here within the simplest two-band lattice model (Mielke) exhibiting a flat band. We argue on several examples that the evolution between the two scenarios is general.Comment: 5 pages, 6 figure

A short analysis on the stricter European regulations on tropical hardwood imports and their side effects

This paper analyses the side effects of the stricter regulation on tropical hardwood or timber imports. It considers the place of Europe within the global timber market, where Europe accounts only for a very limited share. It also explains the high selectivity of European markets, with its consequences. While tropical wooden furniture and other secondary processed products are not considered as timber here, their question is also discussed. The number of empirical studies specifically dealing with the side effects of EU regulations is limited, but the results are converging, showing that these regulations have a general adverse effect, contrary to the initial aim of promoting the sustainability of tropical timbers. These side effects are essentially to divert the trade towards countries with lower standards, and to add a burden on most of the producing countries which have already a set of comparative disadvantages for the production of legal or sustainable timber. The effects are positive on a limited number of companies which markets are very dependent of Europe. The question is then analysed from a broader perspective, replacing the effects of the EU regulations as an incidental factor compared to the increasing consumption of tropical timber by the three developing giants: Brazil, India and China.timber trade; trade regulation; environmental regulation, Europe; tropical timber; tropical hardwwod; side effect; adverse effect

Resolving Structure in Human Brain Organization: Identifying Mesoscale Organization in Weighted Network Representations

Human brain anatomy and function display a combination of modular and hierarchical organization, suggesting the importance of both cohesive structures and variable resolutions in the facilitation of healthy cognitive processes. However, tools to simultaneously probe these features of brain architecture require further development. We propose and apply a set of methods to extract cohesive structures in network representations of brain connectivity using multi-resolution techniques. We employ a combination of soft thresholding, windowed thresholding, and resolution in community detection, that enable us to identify and isolate structures associated with different weights. One such mesoscale structure is bipartivity, which quantifies the extent to which the brain is divided into two partitions with high connectivity between partitions and low connectivity within partitions. A second, complementary mesoscale structure is modularity, which quantifies the extent to which the brain is divided into multiple communities with strong connectivity within each community and weak connectivity between communities. Our methods lead to multi-resolution curves of these network diagnostics over a range of spatial, geometric, and structural scales. For statistical comparison, we contrast our results with those obtained for several benchmark null models. Our work demonstrates that multi-resolution diagnostic curves capture complex organizational profiles in weighted graphs. We apply these methods to the identification of resolution-specific characteristics of healthy weighted graph architecture and altered connectivity profiles in psychiatric disease.Comment: Comments welcom

Taxonomic, Genetic and Functional Diversity of Symbionts Associated with the Coastal Bivalve Family Lucinidae

Extant bivalve members from the family Lucinidae harbor chemosynthetic gammaproteobacterial gill endosymbionts capable of thioautotrophy. These endosymbionts are environmentally acquired and belong to a paraphyletic group distantly related to other marine chemosymbionts. In coastal habitats, lucinid chemosymbionts participate in facilitative interactions with their hosts and surrounding seagrass habitat that results in symbiotic sulfide detoxification, oxygen release from seagrass roots, carbon fixation, and/or symbiotic nitrogen fixation. Currently, the structural and functional complexity of whole lucinid gill microbiomes, as well as their interactions with lucinid bivalves and their surrounding environment, have not been comprehensively characterized. This dissertation focuses on the taxonomic, genetic, and functional diversity in the gill microbiomes of three Floridian coastal lucinid bivalve species, Phacoides pectinatus, Ctena orbiculata, and Stewartia floridana, in the context of environmental data where appropriate. Analyses of these lucinid gill microbiomes showed taxonomic diversity that was unaffected by spatial distribution patterns. Phacoides pectinatus gill microbiomes sampled from a coastal mangrove habitat contained, in order of relative abundances, a chemosynthetic symbiont species that was taxonomically and functionally distinct from seagrass-associated chemosynthetic lucinid symbionts, a heterotrophic Kistimonas-like species, and a heterotrophic Spirochaeta-like species. In comparison, gill microbiomes of a seagrass-dwelling C. orbiculata population comprised four strains of chemosymbionts that belonged to two separate species and low abundances of an uncharacterized Endozoicomonas-like operational taxonomy unit (OTU). Gill microbiomes of a separate seagrass-dwelling S. floridana population consisted of another chemosynthetic symbiont species and low abundances of a heterotrophic Spirochaeta-like species that was distantly related to the Spirochaeta-like species in P. pectinatus. Functional characterization of host- and microbiome-related genes/transcripts in these bivalve species revealed previously unreported C1-compound oxidation functions in some chemosymbionts and other functions relevant to microbe-microbe competition, symbiont selection, metabolism support, and symbiont-to-host nutrient transfer. Preliminary differential expression analyses on host- and microbiome genes across micro-habitats with different vegetation coverages showed potential upregulation of C. orbiculata functions involved in aerobic respiration, aerobic stress, electron transport, and mitochondrial sulfide detoxification, as well as downregulation of a sulfurtransferase gene encoded by its chemosynthetic symbionts, in a seagrass-covered quadrat compared to an algae-covered quadrat. In comparison, very few genes mappable to S. floridana and its chemosymbiont were differentially expressed between predominantly sand-covered and seagrass-covered quadrats, but the Spirochaeta-like species over-expressed carbon, nitrogen, phosphate, transport, synthesis, transcriptional regulation, and protein degradation functions in predominantly sand-covered quadrats. These findings reaffirm the overlooked notion of heterogeneous lucinid gill microbiomes that can vary within and between host species and populations. At the same time, this project advances understanding of the functional diversity across chemosynthetic lucinid symbionts and offers insights on lucinid-microbiome-environment interactions

A short analysis on the stricter European regulations on tropical hardwood imports and their side effects

This paper analyses the side effects of the stricter regulation on tropical hardwood or timber imports. It considers the place of Europe within the global timber market, where Europe accounts only for a very limited share. It also explains the high selectivity of European markets, with its consequences. While tropical wooden furniture and other secondary processed products are not considered as timber here, their question is also discussed. The number of empirical studies specifically dealing with the side effects of EU regulations is limited, but the results are converging, showing that these regulations have a general adverse effect, contrary to the initial aim of promoting the sustainability of tropical timbers. These side effects are essentially to divert the trade towards countries with lower standards, and to add a burden on most of the producing countries which have already a set of comparative disadvantages for the production of legal or sustainable timber. The effects are positive on a limited number of companies which markets are very dependent of Europe. The question is then analysed from a broader perspective, replacing the effects of the EU regulations as an incidental factor compared to the increasing consumption of tropical timber by the three developing giants: Brazil, India and China.timber trade, trade regulation, environmental regulation, Europe, tropical timber, tropical hardwwod, side effect, adverse effect

Multi-residues analysis of pre-emergence herbicides in fluvial sediments : application to the mid-Garonne River

Contamination of man and ecosystems by pesticides has become a major environmental concern. Whereas many studies exist on contamination from agriculture, the effects of urban sources are usually omitted. Fluvial sediment is a complex matrix of pollutants but little is known of its recent herbicide content. This study proposes a method for a fast and reliable analysis of herbicides by employing the accelerated solvent extractor (ASE). The aim of the study is to show the impact of a major town (Toulouse) on the herbicide content in the river. In this study, three herbicide families (i.e. s-triazine, substituted ureas and anilides) were analysed in fluvial sediment fractions at 11 sampling sites along the mid-Garonne River and its tributaries. River water contamination by herbicides is minor, except for at three sites located in urban areas. Among the herbicidal families studied, urban and suburban areas are distinguished from rural areas and were found to be the most contaminated sites during the study period, a winter low-water event. The herbicide content of the coarse sediment fractions is about one third of that found in the fine fractions and usually ignored. The distribution of pesticide concentrations across the whole range of particle sizes was investigated to clarify the role of plant remains on the significant accumulation in the coarse fractions

The optimal tax rule in the presence of time use

Using Mexican data on household time use and consumption, we find significant substitution between goods and time in home production and different elasticities of substitution for different household commodities. Adding these findings to the Ramsey optimal tax problem, we show it is optimal to impose higher taxes on market goods used in the production of commodities with a lower elasticity of substitution between goods and time. The reason is that government wants to minimize the distortionary substitution from market purchases toward untaxed time use in home production. This is an analog of the classical Corlett and Hague (1953-1954) result, differing in that we allow for the possibility of substitution between goods and time in the production of commodities. Leaving aside distributional considerations, we conclude that higher taxes should be imposed on market goods used in the production of `Eating' and lower taxes imposed on market goods used in the production of `Recreation'

Integration of organisational aspects into learning from experience : illustration with a case study

International audienceIn a recent study on learning from experience, INERIS acknowledged the organisational dimensions of major hazard accidents. The aim of this paper is to introduce the approach advocated in order to take into account the organisational aspects of accidents. This approach is based on a review of the literature on the organisational side of major accidents as well as on accident investigation methods. Among the methods, the Accimap (J. Rasmussen, I. Svedung, 2000) was chosen to illustrate the global dimension of accident, and a method (MORT for management oversight and risk tree, Johnson, 1980) has been chosen as a tool to be developed at INERIS, with the collaboration of the Noordwijk Risk Initiative Foundation. This method integrates a normative organisational model and an approach to the accident investigation process, based on the principle of barriers. These two methods, though not completely compatible, have shown to be relevant for serving different objectives of INERIS