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Search Results: 1 - 10 of 1090 matches for " Etienne "
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What does the “arrow of time” stand for?  [PDF]
Etienne Klein
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.23033
Abstract: One hundred and thirty years after the work of Ludwig Boltzmann on the interpretation of the irreversibility of physical phenomena, and one century after Einstein's formulation of Special Relativity, we are still not sure what we mean when we talk of “time” or “arrow of time”. We shall try to show that one source of this difficulty is our tendency to confuse, at least verbally, time and becoming, i.e. the course of time and the arrow of time, two concepts that the formalisms of modern physics are careful to distinguish. The course of time is represented by a time line that leads us to define time as the producer of duration. It is customary to place on this time line a small arrow that, ironically, must not be confused with the “arrow of time”. This small arrow is only there to indicate that the course of time is oriented, has a well-defined direction, even if this direction is arbitrary. The arrow of time, on the other hand, indicates the possibility for physical systems to experience, over the course of time, changes or transforma-tions that prevent them from returning to their initial state forever. Contrary to what the ex-pression “arrow of time” suggests, it is there-fore not a property of time itself but a property of certain physical phenomena whose dynamic is irreversible. By its very definition, the arrow of time presupposes the existence of a well- established course of time within which – in addition – certain phenomena have their own temporal orientation. We think that it is worth-while to emphasize the difference between sev-eral issues traditionally subsumed under the label “the problem of the direction of time”. If the expressions “course of time”, “direction of time” and “arrow of time” were better defined, systematically distinguished from one another and always used in their strictest sense, the debate about time, irreversibility and becoming in physics would become clearer.
Security & Privacy Implications in the Placement of Biometric-Based ID Card for Rwanda Universities  [PDF]
Eugen Harinda, Etienne Ntagwirumugara
Journal of Information Security (JIS) , 2015, DOI: 10.4236/jis.2015.62010
Abstract: Biometric authentication systems are believed to be effective compared to traditional authentication systems. The introduction of biometrics into smart cards is said to result into biometric-based smart ID card with enhanced security. This paper discusses the biometric-based smart ID card with a particular emphasis on security and privacy implications in Rwanda universities environment. It highlights the security and implementation issues. The analysis shows that despite the necessity to implement biometric technology, absence of legal and regulatory requirements becomes a challenge to implementation of the proposed biometric solution. The paper is intended to engage a broad audience from Rwanda universities planning to introduce the biometric-based smart ID cards to verify students and staff for authentication purpose.
Further Advantages of a Unique Author Identification Number
Etienne Joly
PLOS Medicine , 2006, DOI: 10.1371/journal.pmed.0030368
Abstract:
Marker assisted selection for the improvement of two antagonistic traits under mixed inheritance
Etienne Verrier
Genetics Selection Evolution , 2001, DOI: 10.1186/1297-9686-33-1-17
Abstract: (To access the full article, please see PDF)
The existence of species rests on a metastable equilibrium between inbreeding and outbreeding. An essay on the close relationship between speciation, inbreeding and recessive mutations
Etienne Joly
Biology Direct , 2011, DOI: 10.1186/1745-6150-6-62
Abstract: I do, however, contend that, if so much speciation occurs, the most likely explanation is that there must be conditions where reproductive barriers can be directly selected for. In other words, situations where it is advantageous for individuals to reproduce preferentially within a small group and reduce their breeding with the rest of the ancestral population. This leads me to propose a model whereby new species arise not by populations splitting into separate branches, but by small inbreeding groups "budding" from an ancestral stock. This would be driven by several advantages of inbreeding, and mainly by advantageous recessive phenotypes, which could only be retained in the context of inbreeding. Reproductive barriers would thus not arise as secondary consequences of divergent evolution in populations isolated from one another, but under the direct selective pressure of ancestral stocks. Many documented cases of speciation in natural populations appear to fit the model proposed, with more speciation occurring in populations with high inbreeding coefficients, and many recessive characters identified as central to the phenomenon of speciation, with these recessive mutations expected to be surrounded by patterns of limited genomic diversity.Whilst adaptive evolution would correspond to gains of function that would, most of the time, be dominant, this type of speciation by budding would thus be driven by mutations resulting in the advantageous loss of certain functions since recessive mutations very often correspond to the inactivation of a gene. A very important further advantage of inbreeding is that it reduces the accumulation of recessive mutations in genomes. A consequence of the model proposed is that the existence of species would correspond to a metastable equilibrium between inbreeding and outbreeding, with excessive inbreeding promoting speciation, and excessive outbreeding resulting in irreversible accumulation of recessive mutations that could ultimately o
Various hypotheses on MHC evolution suggested by the concerted evolution of CD94L and MHC class Ia molecules
Etienne Joly
Biology Direct , 2006, DOI: 10.1186/1745-6150-1-3
Abstract: In a first part, I propose a highly hypothetical scenario of MHC evolution that could explain how modern day CD94L molecules can have so many diverse and well preserved biological functions. Next, I propose that MHC class I molecules evolve more rapidly and exuberantly than class II molecules because the former are subjected to more direct selective pressures, in particular from viruses. Third, I suggest that concerted evolution, by increasing inter-genic homogeneity would in turn favour further inter-allelic and inter-loci exchanges, hence resulting in a more evolvable MHC. As a fourth and last point, I propose that the high GC content of sequences coding for classical class I molecules could be a consequence of biased gene conversion.Testing of these various hypotheses should occur naturally over the coming years, with the ever increasing availability of more sequences related to MHC class I genes from various organisms. Ultimately, a better understanding of how MHC molecules evolve may help to decipher where and how our adaptive immune system arose, and keeps evolving in the face of the permanent challenge of infectious organisms.This article was reviewed by Stephan Beck, Lutz Walter and Pierre Pontarotti.Reviewed by Stephan Beck, Lutz Walter and Pierre Pontarotti.For the full reviews, please go to the Reviewers' comments section.HLA-E and/or H-2Qa1 fulfil many other roles besides that of presenting the leader peptides of class Ia molecules to NK cells. They present leader peptides derived from Hsp60 heat shock proteins of self or bacterial origin [1] to cytotoxic T cells [2]. This presentation of leader peptides from Hsps to NK cells has also been proposed to play a role in stress surveillance [3]. HLA-E also presents peptides derived from viruses [4] or bacteria [5] to CD8+ cytotoxic T cells and to NKT cells [6], and H-2Qa1 aids the resistance of mice to Salmonella infection by presenting antigens to γδ T cells [7] and regulates the activity of CD8 regulatory T
Hypothesis: could the signalling function of membrane microdomains involve a localized transition of lipids from liquid to solid state?
Etienne Joly
BMC Cell Biology , 2004, DOI: 10.1186/1471-2121-5-3
Abstract: The core of the hypothesis presented here is that resting cells may actively maintain their plasma membrane in liquid phase, corresponding to a metastable thermodynamic state. Following a physiological stimulus such as ligands binding to their membrane receptors, the tendency of membrane components to undergo a localised transition towards a gel state would increase, resulting in initial minute solid structures. These few membrane components having undergone a liquid to solid state transition, would then act as seeds for the specific recruitment of additional membrane components whose properties are compatible with the crystalline growth of these initial docks. Cells could therefore be using the propensity of lipids to assemble selectively to generate stable platforms of particular cellular components either for intra-cellular transport or for signal transduction.could presumably be done via biophysical approaches such as EPR spin labelling, X-ray diffraction or FRET coupled to direct microscopic observation of cells to which very localized stimuli would be delivered.Such a model of selective growth of membrane docks would provide an explanation for the existence of different types of microdomains, and for the fact that, depending on the state of the cells and on the procedures used to isolate them, membrane microdomains can vary greatly in their properties and composition. Ultimately, a thorough understanding of how and why lipid domains are assembled in biological membranes will be essential for many aspects of cell biology and medicine.The very existence of lipid rafts was initially proposed to explain the selective sorting of lipids and GPI-anchored molecules in polarised cells [1]. This conceptual definition has however evolved towards a more biochemical one, and the term raft is nowadays most often used to describe a fraction of cellular membranes that remain insoluble in non-ionic detergents at 4°C, have a lipid composition rich in cholesterol and sphingolipi
Hypophosphatasia
Etienne Mornet
Orphanet Journal of Rare Diseases , 2007, DOI: 10.1186/1750-1172-2-40
Abstract: The symptoms are highly variable in their clinical expression, which ranges from stillbirth without mineralized bone to early loss of teeth without bone symptoms. Depending on the age at diagnosis, six clinical forms are currently recognized: perinatal (lethal), perinatal benign, infantile, childhood, adult and odontohypophosphatasia. In the lethal perinatal form, the patients show markedly impaired mineralization in utero. In the prenatal benign form these symptoms are spontaneously improved. Clinical symptoms of the infantile form are respiratory complications, premature craniosynostosis, widespread demineralization and rachitic changes in the metaphyses. The childhood form is characterized by skeletal deformities, short stature, and waddling gait, and the adult form by stress fractures, thigh pain, chondrocalcinosis and marked osteoarthropathy. Odontohypophosphatasia is characterized by premature exfoliation of fully rooted primary teeth and/or severe dental caries, often not associated with abnormalities of the skeletal system.The disease is due to mutations in the liver/bone/kidney alkaline phosphatase gene (ALPL; OMIM# 171760) encoding the tissue-nonspecific alkaline phosphatase (TNAP). The diagnosis is based on laboratory assays and DNA sequencing of the ALPL gene. Serum alkaline phosphatase (AP) activity is markedly reduced in hypophosphatasia, while urinary phosphoethanolamine (PEA) is increased. By using sequencing, approximately 95% of mutations are detected in severe (perinatal and infantile) hypophosphatasia.Genetic counseling of the disease is complicated by the variable inheritance pattern (autosomal dominant or autosomal recessive), the existence of the uncommon prenatal benign form, and by incomplete penetrance of the trait. Prenatal assessment of severe hypophosphatasia by mutation analysis of chorionic villus DNA is possible. There is no curative treatment for hypophosphatasia, but symptomatic treatments such as non-steroidal anti-inflammatory dru
Utilisation d'un espace forestier par un troupeau: à chaque échelle spatio-temporelle son modèle
M. Etienne
Mappemonde , 1990,
Abstract: Une approche chorématique de l’utilisation d’un réseau de pare-feu par un troupeau de brebis est illustré à différentes échelles.
Asymmetries in the Social Responsible Investment Agendas: From an NGO Driven World to a Stakeholders Dialogue.
Etienne Coerwinkel
Philosophica , 2007,
Abstract: NGOs have taken a dominant position in setting the agendas of Corporate Responsibility and Socially Responsible Investment matters, thereby skewing the efforts of corporates to limit negative externalities towards their own agendas. As the latter remain to a certain extent unpredictable, corporates must deal with an information asymmetry. This situation can be explained by the historically defensive nature of Corporate Responsibility codes established by companies under pressure of the NGOs. In this paper, I contend that only a new approach to Corporate Responsibility could reverse this asymmetry: one where the social responsibility matters are articulated in a political debate between all stakeholders of a company and where conflicting interests are addressed in a deliberative process. To this end, the corporate world and the NGOs need to understand the need for a larger debate that includes all relevant stakeholders defined as the Public in the sense of Dewey. Latour and the Actor-Network theory provide us with a workable framework to structure such a dialogue, where participants have the authority and legitimacy to speak for the Public.
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