297 research outputs found
Shot Noise in Digital Holography
We discuss on noise in heterodyne holography in an off-axis configuration. We
show that, for a weak signal, the noise is dominated by the shot noise on the
reference beam. This noise corresponds to an equivalent noise on the signal
beam of one photoelectron per pixel, for the whole sequence of images used to
build the digital hologram
Effect of the Photon's Brownian Doppler Shift on the Weak-Localization Coherent-Backscattering Cone
We report the first observation of the dependence of the
coherent-backscattering (CBS) enhanced cone with the frequency of the
backscattered photon. The experiment is performed on a diffusing liquid
suspension and the Doppler broadening of light is induced by the Brownian
motion of the scatterers. Heterodyne detection on a CCD camera is used to
measure the complex field (i.e., the hologram) of the light that is
backscattered at a given frequency. The analysis of the holograms yield the
frequency and the propagation direction of the backscattered photons. We
observe that the angular CBS cone becomes more narrow in the tail of the
Brownian spectrum. The experimental results are in good agreement with a simple
theoretical model
Correlations between critical current density, j(sub c), critical temperature, T(sub c),and structural quality of Y1B2Cu3O(7-x) thin superconducting films
Correlations between critical current density (j(sub c)) critical temperature (T(sub c)) and the density of edge dislocations and nonuniform strain have been observed in YBCO thin films deposited by pulsed laser ablation on (001) LaAlO3 single crystals. Distinct maxima in j(sub c) as a function of the linewidths of the (00 l) Bragg reflections and as a function of the mosaic spread have been found in the epitaxial films. These maxima in j(sub c) indicate that the magnetic flux lines, in films of structural quality approachingthat of single crystals, are insufficiently pinned which results in a decreased critical current density. T(sub c) increased monotonically with improving crystalline quality and approached a value characteristic of a pure single crystal. A strong correlation between j(sub c) and the density of edge dislocations ND was found. At the maximum of the critical current density the density of edge dislocations was estimated to be N(sub D) approximately 1-2 x 10(exp 9)/sq cm
The Self Model and the Conception of Biological Identity in Immunology
The self/non-self model, first proposed by F.M. Burnet, has dominated immunology for sixty years now. According to this model, any foreign element will trigger an immune reaction in an organism, whereas endogenous elements will not, in normal circumstances, induce an immune reaction. In this paper we show that the self/non-self model is no longer an appropriate explanation of experimental data in immunology, and that this inadequacy may be rooted in an excessively strong metaphysical conception of biological identity. We suggest that another hypothesis, one based on the notion of continuity, gives a better account of immune phenomena. Finally, we underscore the mapping between this metaphysical deflation from self to continuity in immunology and the philosophical debate between substantialism and empiricism about identity
Boolean Dynamics with Random Couplings
This paper reviews a class of generic dissipative dynamical systems called
N-K models. In these models, the dynamics of N elements, defined as Boolean
variables, develop step by step, clocked by a discrete time variable. Each of
the N Boolean elements at a given time is given a value which depends upon K
elements in the previous time step.
We review the work of many authors on the behavior of the models, looking
particularly at the structure and lengths of their cycles, the sizes of their
basins of attraction, and the flow of information through the systems. In the
limit of infinite N, there is a phase transition between a chaotic and an
ordered phase, with a critical phase in between.
We argue that the behavior of this system depends significantly on the
topology of the network connections. If the elements are placed upon a lattice
with dimension d, the system shows correlations related to the standard
percolation or directed percolation phase transition on such a lattice. On the
other hand, a very different behavior is seen in the Kauffman net in which all
spins are equally likely to be coupled to a given spin. In this situation,
coupling loops are mostly suppressed, and the behavior of the system is much
more like that of a mean field theory.
We also describe possible applications of the models to, for example, genetic
networks, cell differentiation, evolution, democracy in social systems and
neural networks.Comment: 69 pages, 16 figures, Submitted to Springer Applied Mathematical
Sciences Serie
The Value of Information for Populations in Varying Environments
The notion of information pervades informal descriptions of biological
systems, but formal treatments face the problem of defining a quantitative
measure of information rooted in a concept of fitness, which is itself an
elusive notion. Here, we present a model of population dynamics where this
problem is amenable to a mathematical analysis. In the limit where any
information about future environmental variations is common to the members of
the population, our model is equivalent to known models of financial
investment. In this case, the population can be interpreted as a portfolio of
financial assets and previous analyses have shown that a key quantity of
Shannon's communication theory, the mutual information, sets a fundamental
limit on the value of information. We show that this bound can be violated when
accounting for features that are irrelevant in finance but inherent to
biological systems, such as the stochasticity present at the individual level.
This leads us to generalize the measures of uncertainty and information usually
encountered in information theory
SUSTAINABLE DEVELOPMENT AND THE PROCESS OF JUSTIFYING CHOICES IN A CONTROVERSIAL UNIVERSE
All in all, neither the path of the generic principle nor that of the reduction to existing principles would appear to be fully satisfactory as the basis for establishing the legitimacy of sustainable development or as a way of making sustainability a principle of legitimacy by its own. We should probably resign ourselves to seeing in this idea a composite construction, still striving towards the formation of a new "superior common principle", without this principle yet being able to be completely clarified and validated. What we have here is an example of the sort of "compromise" described by Boltanski and Thévenot (1991, p.338): "In the compromise, the participants abandon the idea of clarifying the principle of their agreement but endeavour to maintain a frame of mind aiming at the common good." If we want to consolidate the compromise developing around sustainability, it would be well advised to seek the support of tests using well-formed objects. To this end, steps should be taken to move the emphasis away from long-term and unknowable sustainability requirements and closer to secondbest criteria focused on the transitional developments and possible risks of intentional human action, the ways of managing the linking of the different temporalities in play -- as regards the biophysical phenomena, their understanding and the main worlds of legitimacy (Godard, 1992) -- and the introduction of deliberation within the present generations as to what they feel best describes their identity, those things they would like to pass on
Formation and Degradation of Beta-casomorphins in Dairy Processing
Milk proteins including casein are sources of peptides with bioactivity. One of these peptides is beta-casomorphin (BCM) which belongs to a group of opioid peptides formed from b-casein variants. Beta-casomorphin 7 (BCM7) has been demonstrated to be enzymatically released from the A1 or B b-casein variant. Epidemiological evidence suggests the peptide BCM 7 is a risk factor for development of human diseases, including increased risk of type 1 diabetes and cardiovascular diseases but this has not been thoroughly substantiated by research studies. High performance liquid chromatography coupled to UV-Vis and mass spectrometry detection as well as enzymeâlinked immunosorbent assay (ELISA) has been used to analyze BCMs in dairy products. BCMs have been detected in raw cowâs milk and human milk and a variety of commercial cheeses, but their presence has yet to be confirmed in commercial yoghurts. The finding that BCMs are present in cheese suggests they could also form in yoghurt, but be degraded during yoghurt processing. Whether BCMs do form in yoghurt and the amount of BCM forming or degrading at different processing steps needs further investigation and possibly will depend on the heat treatment and fermentation process used, but it remains an intriguing unknown
First description of feline inflammatory mammary carcinoma: clinicopathological and immunohistochemical characteristics of three cases
INTRODUCTION: Inflammatory breast cancer is a special type of locally advanced mammary cancer that is associated with particularly aggressive behaviour and poor prognosis. The dog was considered the only natural model in which to study the disease because, until now, it was the only species known to present with inflammatory mammary carcinoma (IMC) spontaneously. In the present study we describe clinicopathological and immunohistochemical findings of three cats with IMC, in order to evaluate its possible value as an animal model. METHODS: We prospectively studied three female cats with clinical symptoms of IMC, identified over a period of 3 years. Clinicopathological and immunohistochemical evaluations of Ki-67, and oestrogen, progesterone and androgen receptors were performed. RESULTS: All three animals presented with secondary IMC (postsurgical) characterized by a rapid onset of erythema, severe oedema, extreme local pain and firmness, absence of subjacent mammary nodules, and involvement of extremities. Rejection of the surgical suture was observed in two of the cats. Histologically, highly malignant papillary mammary carcinomas, dermal tumour embolization of superficial lymphatic vessels, and severe secondary inflammation were observed. The animals were put to sleep at 10, 15 and 45 days after diagnosis. Metastases were detected in regional lymph nodes and lungs in the two animals that were necropsied. All tumours had a high Ki-67 proliferation index and were positive for oestrogen, progesterone and androgen receptors. CONCLUSION: Our findings in feline IMC (very low prevalence, only secondary IMC, frequent association of inflammatory reaction with surgical suture rejection, steroid receptor positivity) indicate that feline IMC could be useful as an animal model of human inflammatory breast cancer, although the data should be considered with caution
Lâusage de la poĂ©sie haĂŻku en psycho-oncologie
International audienceAbstract Aim: Our study aims to describe the discourseeffects of specific and structured protocol focused on severalhaiku poems about one patient, who have experienced cancer.Procedure: The protocol consists of 4 steps: a preliminaryexploratory interview, fifteen haiku proposed without a partof the poem (a creative writing filled in by the patient), a freeform haiku composed by the patient, and finally, a finalinterview.Clinical case: A man, D., aged 25, had tumor.Result: Using this protocol, we showed discourse variationson the illness before and after the experience of poetrywriting, by Tropes V8.4 software.Conclusion: Haiku poetry can be a useful tool in the contextof supportive interventions or as preparatory work for engagementin psychotherapeutic intervention. We believe thatthe formal structure of haikus can create conditions for aspecific poetic work composed of: poetic evocation, synthesis,and mapping of the most intimate experiences in oncologyenvironment.RĂ©sumĂ© Objectif : Cette Ă©tude qualitative et exploratoirevise Ă dĂ©crire les effets dâun protocole poĂ©tique centrĂ© surles haĂŻkus en psycho-oncologie sur lâapproche de la maladiechez un patient atteint de cancer.MatĂ©riel et mĂ©thodes : Il sâagit dâun protocole dâĂ©criturepoĂ©tique composĂ© de quatre Ă©tapes : un entretien prĂ©liminaire,la proposition de 15 haĂŻkus (sans le vers du milieu)tirĂ©s de grands auteurs japonais, la rĂ©alisation dâun poĂšmecomposĂ© librement par deux patients atteints de cancer, unentretien final sur lâexpĂ©rience de lâĂ©criture poĂ©tique.Cas clinique : Un homme, M. D., ĂągĂ© de 25 ans, qui est entraitement pour un cancer.RĂ©sultats : Nous montrons les variations discursives utilisĂ©esavant et aprĂšs lâexpĂ©rience de lâĂ©criture poĂ©tique, Ă travers lelogiciel Tropes V8.4.Conclusion : Le travail poĂ©tique avec le haĂŻku peut ĂȘtre unoutil utile, dans un contexte de support clinique en institutionou comme prĂ©paration Ă un travail de psychothĂ©rapie. Nouspensons que la structure formelle des haĂŻkus peut inviter Ă untravail poĂ©tique spĂ©cifique : Ă©vocation poĂ©tique, synthĂšse etschĂ©matisation des vĂ©cus plus intimes en milieu oncologique
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