Deuterium on Venus: Observations from Earth

In view of the importance of the deuterium-to-hydrogen ratio in understanding the evolutionary scenario of planetary atmospheres and its relationship to understanding the evolution of our own Earth, we undertook a series of observations designed to resolve previous observational conflicts. We observed the dark side of Venus in the 2.3 micron spectral region in search of both H2O and HDO, which would provide us with the D/H ratio in Venus' atmosphere. We identified a large number of molecular lines in the region, belonging to both molecules, and, using synthetic spectral techniques, obtained mixing ratios of 34 plus or minus 10 ppm and 1.3 plus or minus 0.2 ppm for H2O and HDO, respectively. These mixing ratios yield a D/H ratio for Venus of D/H equals 1.9 plus or minus 0.6 times 10 (exp 12) and 120 plus or minus 40 times the telluric ratio. Although the detailed interpretation is difficult, our observations confirm that the Pioneer Venus Orbiter results and establish that indeed Venus had a period in its early history in which it was very wet, perhaps not unlike the early wet period that seems to have been present on Mars, and that, in contrast to Earth, lost much of its water over geologic time

Holonomic functions of several complex variables and singularities of anisotropic Ising n-fold integrals

Lattice statistical mechanics, often provides a natural (holonomic) framework to perform singularity analysis with several complex variables that would, in a general mathematical framework, be too complex, or could not be defined. Considering several Picard-Fuchs systems of two-variables "above" Calabi-Yau ODEs, associated with double hypergeometric series, we show that holonomic functions are actually a good framework for actually finding the singular manifolds. We, then, analyse the singular algebraic varieties of the n-fold integrals $\chi^{(n)}$, corresponding to the decomposition of the magnetic susceptibility of the anisotropic square Ising model. We revisit a set of Nickelian singularities that turns out to be a two-parameter family of elliptic curves. We then find a first set of non-Nickelian singularities for $\chi^{(3)}$ and $\chi^{(4)}$, that also turns out to be rational or ellipic curves. We underline the fact that these singular curves depend on the anisotropy of the Ising model. We address, from a birational viewpoint, the emergence of families of elliptic curves, and of Calabi-Yau manifolds on such problems. We discuss the accumulation of these singular curves for the non-holonomic anisotropic full susceptibility.Comment: 36 page

Paramètres gouvernant la prolifération bactérienne dans les réseaux de distribution

L'étude a permis de suivre l'évolution des caractéristiques physico-chimiques et microbiologiques des eaux dans un réseau de distribution expérimental de taille industrielle, afin de comparer d'une part l'effet du chlore et de la monochloramine sur la biomasse présente dans le système à l'équilibre et d'autre part d'établir des relations quantitatives entre prolifération bactérienne, oxydant et matière organique biodégradable.Dès les premières heures de transit dans le réseau, une consommation des oxydants est constatée, avec toutefois une plus grande stabilité de la monochloramine (vitesse de consommation de 0,05 mgCl2 l-1h-1 et 0,02 mgCl2 l-1h-1 respectivement pour le chlore et la monochloramine).Même en présence d'un désinfectant résiduel, il est possible de noter une accumulation de bactéries-à ta surface des tuyaux de distribution (105 à 106 cellules. cm-2, dont environ 1 % est cultivable sur gélose) qui augmente avec la diminution de concentration du désinfectant résiduel. Les relations logarithmiques entre densité cellulaire (phase eau ou biofilm) et oxydant résiduel montrent d'une part que pour inactiver totalement les bactéries en suspension dans l'eau il convient de maintenir une chloration en continu avec un résiduel constant supérieur ou égal à 0,5 mgCl2 l-1 et, d'autre part que les chloramines sont au moins 2,5 fois moins efficaces que le chlore, même vis-à-vis des bactéries fixées.La présence de matière organique biodégradable dans les eaux explique la prolifération des bactéries dans le système de distribution. Ainsi une concentration additionnelle de 100 µg.l-1 de carbone organique dissous biodégradable (CODB) dans l'eau entrant dans le réseau de distribution occasionne en 24 heures et à 20°C une augmentation du nombre de bactéries fixées (+7,5.105 cellules.cm-2) ou en suspension (+ 4.104 cellules.ml-1) dans le réseau de distribution, à l'équilibre, déjà largement colonisé par des micro-organismes.Ainsi le contrôle de la fraction biodégradable de la matière organique apparaît toujours comme un objectif primordial.This study was carried out in order to evaluate the variations in the physicochemical characteristics of the water in an experimental distribution system.The primary objectives of the study were :- to compare the disinfectant efficiency of chlorine and monochloramine- to establish quantitative correlations among bacterial density, concentration of residual disinfectant, and concentration of biodegradable organic matter.The finished waters were obtained from a water treatment pilot plant characterized by : prechlorination (average treatment rate : 1.4 mgCl2 l-1 and residual alter sand filtration : 0.08 mgCl2 l-1), coagulation-flocculation-sedimentation (FeCl3 treatment rate : 30 to 60 mg l-1 adjusted to the raw water turbidity below 0.3 NTU), sand filtration (filtration rate : 6 h-1) and post-disinfection with chloramine (average treatment rate : 1.8 mgCl2 l-1) or chloramine (average treatment rate : 1.66 mgCl2 l-1). The concentrations of post-disinfectant used were chosen in order to maintain chlorine at 0.2 to 0.5 mgCl2 l-1 and monochloramine at 1 mgC2 l-1 after the first 24 hours residence time in the experimental distribution system.The experimental distribution system is composed of three parallel loops connected in series (31 m length, 100 mm diameter, cement lined cast iron, water velocity : 1m s-1). The configuration and operation of the system permitted a residence time of 24 hours in each loop (that is 72 hours for the whole system). Appropriate sample tap locations facilitated removal of bulk water samples. Special sampling parts also permitted sampling of cement coupons for determination of attached biofilm.The measured parameters were : residual oxidant (DPD method), DOC, BDOC (28 days of incubation at 28 °C with a bacterial inoculum), cell density in the bulk water phase (CFU ml-1) and in the biofilm (CFU cm-2) after 15 days of incubation at 20-22 °C. Total cells were enumerated using the epifluorescence direct count technique.For each experiment, all the sampling sequences were carried out on each of three days, after quasi steady-state was achieved in the system (4 to 6 weeks after starting each experiment). The data were analysed in order to characterize the treated and distributed waters; the results discussed here are based on the averages of the measured parameters tram the water samples and biofilm samples taken after the system achieved quasi steady-state.Characteristics of the treated watersThe treated waters were characterized by important variations at the DOC, BDOC and cell density. For example, the concentrations of DOC showed a seasonal variation ranging from 0.8 to 1.3 mg Cl-1 in winter to 1.6 to 2.6 mg Cl-1 in summer.The treated waters contained approximately the same concentrations of residual disinfectant, averaging 1.6 mgCl2 l-1 for chlorine and 1.5 mgCl2 l-1 for monochloramine.However, a significant difference cell density was found between the two post-disinfectants. Cell densities by the epifluorescence direct count technic were 1.6 x 103 ml-1 (0.3 % of CFU ml-1) with chlorine and 6.3 x 104 ml-1 (0.03 % of CFU ml-1) with monochloramine. The difference on cell density between the post-chlorination and the post-chloramination treatments has been observed systematically, and may be explained either as cellular lysis with chlorine or an interference when using epifluorescence counting for chlorinated waters.Characteristics of the distributed watersWhatever the season, depletion of oxidant (chlorine or monochloramine), and elimination of dissolved organic matter (DOC, BDOC) occured during the first hours of circulation of water in the distribution system. The net result was an increase in bacterial cell density.During the first hours of circulation of the waters in the distribution system, depletion of the disinfectant occured. Depletion was more rapid for chlorine (-0.05 mgCl2 l-1 h-1) titan for monochloramine (-0.02 mgCl2 l-1 h-1), winch is considered more stable titan chlorine.Even in the presence of a residual disinfectant in the distribution system, microorganisms are present in the water phase (104 to 106 cells ml-1 by epifluorescence direct count; 1 % CFU ml-1 after 15 days of incubation at 20-22 °C) and in the biofilm (105 to 106 cells cm-2 by epifluorescence direct count; 1 % CFU ml-1 after 15 days of incubation at 20-22 °C). The bacterial density increased white the disinfectant residual decreased. The apparent growth rate of the attached biomass (µfix) in loop 2 of the chlorinated distribution system (equivalent to 48 hours detention), was close to the µfix calculated for loop 2 of the chloraminated distribution system : the values were 0.0043 h-1 and 0.005 h-1 respectively.In addition, the change in the organic matter (expressed as DOC) occured in two steps :- a slight increase in DOC during the 24 first hours of residence time (loop 1), when increased residual disinfectant were present.- a bacterial consumption of DOC after 24 hours of residence time (loops 2 and 3), even in the presence of small concentrations of disinfectants.In loop 2 (48 hours residence time of the water in the system; chlorine : 0.01 mgCl2 l-1, chloramine : 0.3 mgCl2 l-1 h-1), the rates of DOC elimination averaged 13 mgCl2 l-1 h-1 and 0.42, mgCl2 l-1 h-1, respectively in the chlorinated and chloraminated distribution systems. This decrease in DOC concentrations was related to the increase in bacterial density.Relationships between cell density, oxidant and organic matterLinear relationships between the concentration of residual oxidant (chlorine or monochloramine) and the cell density in the water phase or in the biofilm show that :- whichever oxidant was used, the pipe loop sections without residual disinfectants were characterized by about 5 x 106 attached cells per cm2 (4 to 10% were able to grow on agar medium in 15 days at 20-22 °C) and by 4 x 105 planktonic cells per ml (1 % CFU ml-1);- consistently, in the sections of the system with a residual disinfectant, the bacteria (CFU and epilluorescence counting) in the water phase were more sensitive to the residual disinfectant (chlorine or monochloramine) than the bacteria attached to the pipe walls (biofilm).However, there was a difference in effectiveness between the two disinfectants; chlorine was more efficient in controlling planktonic bacteria and biofilm bacteria than was monochloramine.For example, to achieve complete inactivation of the planktonic bacteria (CFU ml-1) a constant chlorine residual of 0.5 mgCl2 l-1 was required throughout the whole distribution system, compared to 2.5 times more chloramine to achieve the same efficiency.Finally, with equivalent concentrations of residual disinfectant, the microbiological quality of the chlorinated distribution waters was better than that of the chloraminated distribution waters.From loop to loop, linear relationships between ∆DOC and cell density pointed out that the presence of biodegradable organic matter can explain the bacterial proliferation in the distribution system. For example, a concentration of BDOC as low as 0.1 mgC l-1 resulted in an increase in the cell density : an additional accumulation of 7.5 x 105 attached cells cm-2 and 4 x 104 planktonic cells ml-1 was observed in the experimental distribution system at quasi steady-state.Consequently, the control of the biodegradable organic carbon remains one of the prime objectives in order to achieve biologically stable distribution waters

Random Matrix Theory and Classical Statistical Mechanics. I. Vertex Models

A connection between integrability properties and general statistical properties of the spectra of symmetric transfer matrices of the asymmetric eight-vertex model is studied using random matrix theory (eigenvalue spacing distribution and spectral rigidity). For Yang-Baxter integrable cases, including free-fermion solutions, we have found a Poissonian behavior, whereas level repulsion close to the Wigner distribution is found for non-integrable models. For the asymmetric eight-vertex model, however, the level repulsion can also disappearand the Poisson distribution be recovered on (non Yang--Baxter integrable) algebraic varieties, the so-called disorder varieties. We also present an infinite set of algebraic varieties which are stable under the action of an infinite discrete symmetry group of the parameter space. These varieties are possible loci for free parafermions. Using our numerical criterion we have tested the generic calculability of the model on these algebraic varieties.Comment: 25 pages, 7 PostScript Figure

Near-forward Raman selection rules of the phonon-polariton created by alloying in (Zn,Be)Se

The Raman selection rules of the (ZnSe, BeSe) mixed phonon polariton created by alloying in the three mode (1ZnSe, 2BeSe) ZnBeSe system, whose dramatic S like dispersion covers the large frequency gap between the ZnSe and BeSe spectral ranges, is studied in its wave vector dependence by near forward scattering. Both the collapse regime away from the Brillouin zone centre and the reinforcement regime near the Brillouin zone centre are addressed, using appropriate laser lines and Be contents. We find that in both regimes the considered phonon polariton, in fact a transverse mode with mixed mechanical and electrical character, obeys the same nominal Raman selection rules as its purely mechanical variant commonly observed in the backscattering geometry. Besides, marked differences in the phonon polariton Raman lineshapes in the two regimes give a hint about how the phonon polariton electrical field E develops while descending the S like dispersion towards the Brillouin zone centre. In the reinforcement regime E is large, leading to intramode on top of intermode transfers of oscillator strength mediated by E between the two BeSe modes, that both exhibit a fine structure on account of the alloy disorder. In contrast, in the collapse regime E remains weak, as testified by the absence of intramode transfer. The discussion is supported by contour modeling of the multi phonon polariton Raman lineshapes in their wave vector dependence within the linear dielectric approach.Comment: 16 pages, 7 figure

On the Symmetries of Integrability

We show that the Yang-Baxter equations for two dimensional models admit as a group of symmetry the infinite discrete group $A_2^{(1)}$. The existence of this symmetry explains the presence of a spectral parameter in the solutions of the equations. We show that similarly, for three-dimensional vertex models and the associated tetrahedron equations, there also exists an infinite discrete group of symmetry. Although generalizing naturally the previous one, it is a much bigger hyperbolic Coxeter group. We indicate how this symmetry can help to resolve the Yang-Baxter equations and their higher-dimensional generalizations and initiate the study of three-dimensional vertex models. These symmetries are naturally represented as birational projective transformations. They may preserve non trivial algebraic varieties, and lead to proper parametrizations of the models, be they integrable or not. We mention the relation existing between spin models and the Bose-Messner algebras of algebraic combinatorics. Our results also yield the generalization of the condition $q^n=1$ so often mentioned in the theory of quantum groups, when no $q$ parameter is available.Comment: 23 page

Critical manifold of the kagome-lattice Potts model

Any two-dimensional infinite regular lattice G can be produced by tiling the plane with a finite subgraph B of G; we call B a basis of G. We introduce a two-parameter graph polynomial P_B(q,v) that depends on B and its embedding in G. The algebraic curve P_B(q,v) = 0 is shown to provide an approximation to the critical manifold of the q-state Potts model, with coupling v = exp(K)-1, defined on G. This curve predicts the phase diagram both in the ferromagnetic (v>0) and antiferromagnetic (v<0) regions. For larger bases B the approximations become increasingly accurate, and we conjecture that P_B(q,v) = 0 provides the exact critical manifold in the limit of infinite B. Furthermore, for some lattices G, or for the Ising model (q=2) on any G, P_B(q,v) factorises for any choice of B: the zero set of the recurrent factor then provides the exact critical manifold. In this sense, the computation of P_B(q,v) can be used to detect exact solvability of the Potts model on G. We illustrate the method for the square lattice, where the Potts model has been exactly solved, and the kagome lattice, where it has not. For the square lattice we correctly reproduce the known phase diagram, including the antiferromagnetic transition and the singularities in the Berker-Kadanoff phase. For the kagome lattice, taking the smallest basis with six edges we recover a well-known (but now refuted) conjecture of F.Y. Wu. Larger bases provide successive improvements on this formula, giving a natural extension of Wu's approach. The polynomial predictions are in excellent agreement with numerical computations. For v>0 the accuracy of the predicted critical coupling v_c is of the order 10^{-4} or 10^{-5} for the 6-edge basis, and improves to 10^{-6} or 10^{-7} for the largest basis studied (with 36 edges).Comment: 31 pages, 12 figure

Activation of PKA via asymmetric allosteric coupling of structurally conserved cyclic nucleotide binding domains

Cyclic nucleotide-binding (CNB) domains allosterically regulate the activity of proteins with diverse functions, but the mechanisms that enable the cyclic nucleotide-binding signal to regulate distant domains are not well understood. Here we use optical tweezers and molecular dynamics to dissect changes in folding energy landscape associated with cAMP-binding signals transduced between the two CNB domains of protein kinase A (PKA). We find that the response of the energy landscape upon cAMP binding is domain specific, resulting in unique but mutually coordinated tasks: one CNB domain initiates cAMP binding and cooperativity, whereas the other triggers inter-domain interactions that promote the active conformation. Inter-domain interactions occur in a stepwise manner, beginning in intermediate-liganded states between apo and cAMP-bound domains. Moreover, we identify a cAMP-responsive switch, the N3A motif, whose conformation and stability depend on cAMP occupancy. This switch serves as a signaling hub, amplifying cAMP-binding signals during PKA activation

On the complexity of some birational transformations

Using three different approaches, we analyze the complexity of various birational maps constructed from simple operations (inversions) on square matrices of arbitrary size. The first approach consists in the study of the images of lines, and relies mainly on univariate polynomial algebra, the second approach is a singularity analysis, and the third method is more numerical, using integer arithmetics. Each method has its own domain of application, but they give corroborating results, and lead us to a conjecture on the complexity of a class of maps constructed from matrix inversions