The use of photosynthesis inhibitor (DCMU) for in situ metabolic and primary production studies on soft bottom benthos

A selective chemical photosynthesis inhibitor, DCMU (Dichorophenyl-dimethylurea), dissolved in DMSO (Dimethyl sulfoxide) was substituted for the dark incubation method commonly used to measure the oxygen consumption in metabolic and primary production studies. We compared oxygen fluxes during light incubations with DCMU and dark incubations procedure, on soft bottom benthos. For this purpose, we studied the effects of different DCMU concentrations. A concentration of 5.10-5 mol 1-1 inside a clear incubation enclosure completely inhibits photosynthesis without affecting the metabolism of soft bottom benthos. (Résumé d'auteur

Oxygen and carbon dioxide fluxes at the water-sediment interface of a tropical lagoon

Oxygen demand, carbon dioxide release and total alkalinity shift were calculated from changes in oxygen, pH and total alkalinity produced by bottom dark incubations at the water-sediment interface of the 3 bottom types identified in a southwest lagoon in New Caledonia. Total sediment oxygen demand (AO?) was corrected from nonbioloyical oxygen demand (NBOD) In order to obtain the apparent biological activity (AOlO)T.o tal carbon dioxide flux (AC02)w as corrected from total alkalinity shift in order to estimate organic carbon processes. The resulting mean carbon dioxide flux (ACOzO= 2.58 mm01 m-' h-', SE = 0.12) exceeded biological oxygen demand (AO," = 1.60 mm01 m-' h-', SE = 0.08). The highly significant ratio estimates from functional regression lines of ACO," on A 0 2 and ACOzo on AOzO gave a total community respiratory quotient (CRQ) of 1.17 (SE = 0.06) and an organic respiratory quotient (CRQO)i,n volving only direct biological processes, of 1.42 (SE = 0.07) for the lagoon. The significance and the use of these ratios are discussed in order to calculate the anaerobic metabolism proportion (40.3 % of total metabolism for an aerobic respiratory quotient of 0.85). Thus, the simultaneous measurement in the field of O2 fluxes and CO2 fluxes, corrected from appropriate alkalinity changes, allows a rapid approach for estimating carbon production at the water-sediment interface of undisturbed communities

Benthic response to ammonium pulses in a tropical lagoon : implications for coastal environmental processes

In New Caledonia, the benthic communities living in the coral reef lagoon around Noumea city are subjected to regular shifts from oligotrophic conditions typical of lagoon waters to nutrient enrichment due to waste water inputs. The influence of ammonium pulses on microphytobenthos production was experimentally tested under varying light intensities in the vicinity of Noumea. Benthic oxygen, ammonium and silicon fluxes at the sediment-water interface were measured in situ using benthic enclosures. Three ammonium concentrations were tested. Gross primary production was doubled with a 13.8 mu mol 1(-1) ammonium concentration increase. Fitted PI curves showed that maximum production (F-max) was linearly related to ammonium concentration, but not the optimal irradiance (I-k). Silicon fluxes were characterized by dissolution in the absence of light, a process that declined with increasing illumination. These results were attributed to microphytobenthos activity, mainly diatoms that are nutrient-limited and strongly reactive to ammonium inputs. Production may result from a multiplication of cells, but migration up to the water sediment interface may also be involved. Oxygen consumption was also significantly influenced by ammonium concentration as a positive linear relationship with added ammonium concentration was established. Even during short-term experiments, ammonium enrichment stimulated photoautotrophic production, increasing the energy available to heterotrophs. Furthermore, microbenthic activities as well as nitrate production were increased by ammoniaoxidizing bacteria able to grow chemolithotrophically at the expense of oxygen. Therefore, in the study area, pulses of urban waste waters resulted in a decrease of plant-related autotrophy in benthic communities. (c) 2004 Elsevier B.V. All rights reserved

From thorium phosphate hydrogenphosphate hydrate to β\beta-thorium phosphate diphosphate: Structural evolution to a radwaste storage ceramic

$\beta$-Thorium phosphate diphosphate ($\beta$-TPD), considered as a very promising radwaste storage material, was obtained from thorium phosphate hydrogenphosphate hydrate (TPHPH) precursor through dehydration and hydrogen phosphate condensation. The structures of TPHPH, intermediate $\alpha$-thorium phosphate diphosphate ($\alpha$-TPD) and its hydrate ($\alpha$-TPDH) have been resolved ab initio by Rietveld analysis of their synchrotron diffraction patterns. All were found orthorhombic (space group Cmcm) and similarly composed of [ThPO$_4$]$_4^{4+}$ slabs alternating with disordered layers hosting either [HPO$_4$·H$_2$O]$_2^{4-}$ (TPHPH), [P$_2$O$_7$·2H$_2$O]$^{4-} ($\alpha$-TPDH), or [P$_2O_7$]$^{4-}$($\alpha$-TPD), unlike the 3D structure of$\beta$-TPD. The diphosphate groups of$\alpha$-TPD and$\alpha$-TPDH are strongly bent. The irreversible transition to the final$\beta$-TPD consists in a shearing of the slabs and a reduction of the interslabs cavities that explains the stability of this high-temperature form

Cache Based Power Analysis Attacks on AES

International audienceThis paper describes possible attacks against software implementations of AES running on processors with cache mechanisms, particularly in the case of smart cards. These attacks are based on sidechannel information gained by observing cache hits and misses in the current drawn by the smart card. Two dierent attacks are described. The first is a combination of ideas proposed in [2] and [11] to produce an attack that only requires the manipulation of the plain text and the observation of the current. The second is an attack based on specific implementations of the xtime function [10]. These attacks are shown to also work against algorithms using Boolean data masking techniques as a DPA countermeasure

Flux d'oxygène et de sels nutritifs à l'interface eau-sédiment dans le lagon sud-ouest de Nouvelle-Calédonie : enrichissements en ammonium et action d'un inhibiteur de la photosynthèse : méthodes et recueil des données

Le présent document regroupe les méthodes utilisées et les résultats obtenus lors de la mission effectuée par le N.O. ALIS dans le lagon sud-ouest de Nouvelle-Calédonie, du 9 juillet au 10 août 1990. Des enceintes d'incubation ont été mises en oeuvre pour : 1-évaluer le métabolisme aérobie et calculer les flux de sels nutritifs à l'interface eau-sédiment; 2-estimer les flux d'ammonium après enrichissement du milieu; 3-juger de l'action d'un inhibiteur de la photosynthèse, le DCMU (Dichlorophenyl-dimethylurée). La concencration en oxygène de chaque enceinte a été mesurée par une sonde polarographique (YSI 58) reliée à un oxymètre protégé dans un caisson étanche. Au total, 15 stations réparties sur les trois types de fonds reconnus dans le lagon (fonds envasés, fonds de sables gris et fonds de sables blancs) ont été échantillonnées. En premier lieu, trois incubations ont été réalisées à l'obscurité pendant deux heures sur chaque station, pour mesurer les flux d'oxygène et de sels nutritif

An insight into polarization states of solid-state organic lasers

The polarization states of lasers are crucial issues both for practical applications and fundamental research. In general, they depend in a combined manner on the properties of the gain material and on the structure of the electromagnetic modes. In this paper, we address this issue in the case of solid-state organic lasers, a technology which enables to vary independently gain and mode properties. Different kinds of resonators are investigated: in-plane micro-resonators with Fabry-Perot, square, pentagon, stadium, disk, and kite shapes, and external vertical resonators. The degree of polarization P is measured in each case. It is shown that although TE modes prevail generally (P>0), kite-shaped micro-laser generates negative values for P, i.e. a flip of the dominant polarization which becomes mostly TM polarized. We at last investigated two degrees of freedom that are available to tailor the polarization of organic lasers, in addition to the pump polarization and the resonator geometry: upon using resonant energy transfer (RET) or upon pumping the laser dye to an higher excited state. We then demonstrate that significantly lower P factors can be obtained.Comment: 12 pages, 12 figure

Electrochromic and electrofluorochromic properties of a new boron dipyrromethene–ferrocene conjugate

A new boron dipyrromethene–ferrocene (BODIPY–Fc) conjugate with pentafluorophenyl as the meso substituent and two Fc termini was synthesized and its spectroscopic and electrochemical features were analyzed. An intramolecular charge transfer from the donor Fc to the acceptor BODIPY has been predicted by theory and confirmed experimentally, leading to efficient fluorescence quenching when the dyad is in the neutral state. Fluorescence can be triggered by oxidizing both ferrocenyl units either chemically or electrochemically. Eventually, a fully reversible fluorescence switch is evidenced by coupling TIRF microscopy with electrolysis in an electrochemical cell

Analysis and Improvement of the Random Delay Countermeasure of CHES 2009

Random delays are often inserted in embedded software to protect against side-channel and fault attacks. At CHES 2009 a new method for generation of random delays was described that increases the attacker's uncertainty about the position of sensitive operations. In this paper we show that the CHES 2009 method is less secure than claimed. We describe an improved method for random delay generation which does not suffer from the same security weakness. We also show that the paper's criterion to measure the security of random delays can be misleading, so we introduce a new criterion for random delays which is directly connected to the number of acquisitions required to break an implementation. We mount a power analysis attack against an 8-bit implementation of the improved method verifying its higher security in practice