Overview of Computational Methods for Photonic Crystals

International audienc

Effect of cow diet on the ruminal microflora and its in vitro fatty acid production

The objective of this study was to investigate the effects of donor’s cow diet (hay or maize silage plus concentrates) on ruminal bacteria count, flora diversity and fatty acids profile (FA) of ruminal fluid and in vitro biohydrogenation (BH) of C18:2. Two dry cows fitted with a ruminal canula were used in a 2x2 design. Each period included three weeks of diet adaptation and two weeks of sampling. The cows were fed twice daily either a diet (H) composed of grass (38%) and alfalfa hay (62%) or an acidogenic diet (A) composed of maize silage (38%), wheat (57%) and soybean (5%) meal. Ruminal fluid was sampled and centrifugated (150g, 5min., 39°C). The ruminal fluid (80mL) was mixed with 80mL of buffer, a fermentative substrate and grape seed oil as source of C18:2 before being incubated during 6 hours at 39°C in anaerobic and dark conditions. Biodiversity was estimated by the Simpson index modified by Haegeman et al.1 after SSCP analysis, and FA were analysed by GLC. Bacteria counting was realised according to Oblinger and Koburger2 (1975). Total and cellulolytic bacteria contents were higher in inoculum A than in inoculum H (9.3.109 vs. 2.4.108/mL for total bacteria and 2.4.108 vs. 1.6.107/mL for cellulolytic bacteria). No difference in the biodiversity of the inoculums was noticed according to the cow or the diet, but diversity during period 1 tended to differ (P=0.09) from period 2, suggesting a time variation of flora biodiversity. Before incubation, the ruminal fluid from the cow receiving diet A contained significantly (P<0.01) more C18:2, trans-10 and trans-11 C18:1, and odd-chain FA than inoculum from the cow receiving diet H. After incubation, inoculum A resulted in a significantly (P<0.01) greater BH of C18:2 than inoculum H, and produced more trans-10C18:1, trans-11C18:1 and odd-chain FA (P<0.01) Trans-10 and odd-chain FA are known to be increased by a high concentrate diet, which explains that inoculum A was richer in these FA than inoculum H. The ruminal flora selected in vivo by diet A continued the production of these FA in vitro. The greater content of trans-11C18:1 and of C18:2 in the inoculum A could be explained by the greater content in C18:2 of the diet A. During incubation with added C18:2, inoculum A continued to produce more trans-11 along with a higher C18:2 BH than inoculum H, which could be due to the higher concentration of cellulolytic bacteria in the inoculum A

Preparation and electrical properties of dense micro-cermets made of nickel ferrite and metallic copper

Dense micro-cermets made of nickel ferrites and copper micrometric particles were obtained from partial reduction under hydrogenated atmosphere at 350 C of mixed copper nickel ferrites, and sintering in nitrogen at 980 C. The small copper particles are homogeneous in size and well dispersed in the spinel oxide matrix. No exudation of copper metal was observed after sintering. The micro-cermets prepared are semi-conducting materials with electrical conductivity lying from 44 to 130 S/cm at 980 C. Their overall characteristics make them interesting for inert anodes dedicated to aluminium electrolysis in melted cryolite

Facing the challenge of predicting the standard formation enthalpies of n-butyl-phosphate species with ab initio methods

Tributyl-phosphate (TBP), a ligand used in the PUREX liquid-liquid separation process of spent nuclear fuel, can form explosive mixture in contact with nitric acid, that might lead to violent explosive thermal runaway. In the context of safety of a nuclear reprocessing plant facility, it is crucial to predict the stability of TBP at elevated temperatures. So far, only the enthalpies of formation of TBP is available in the literature with a rather large uncertainties, while those of its degradation products, di-(HDBP) and mono-(H$_2$MBP}) are unknown. In this goal, we have used state-of-the art quantum chemical methods to compute the formation enthalpies and entropies of TBP and its degradation products di-(HDBP), mono-(H$_2$MBP) in gas and liquid phases. Comparisons of levels of quantum chemical theory revealed that there are significant effects of correlation on their electronic structures, pushing for the need of not only high level of electronic correlation treatment, namely local coupled cluster with single and double excitation operators and perturbative treatment of triple excitations [LCCSD(T)], but also extrapolations to the complete basis to produce reliable and accurate thermodynamics data. Solvation enthalpies were computed with the conductor like screening model for real solvents [COSMO-RS], for which we observe errors not exceeding 22 kJ mol$^{-1}$. We thus propose with final uncertainty of about 20 kJ mol$^{-1}$ standard enthalpies of formation of TBP, HDBP, and H$_2$MBP which amounts to -1281.7$\pm$24.4, -1229.4$\pm$19.6 and -1176.7$\pm$14.8 kJ mol$^{-1}$, respectively, in the gas phase. In the liquid phase, the predicted values are -1367.3$\pm$24.4, -1348.7$\pm$19.6 and -1323.8$\pm$14.8 kJ mol$^{-1}$, to which we may add about -22 kJ mol$^{-1}$ error from the COSMO-RS solvent model. From these data, we predict the complete hydrolysis of TBP to be nearly thermoneutral

Random changes in the heifer rumen in bacterial community structure,physico-chemical and fermentation parameters, and in vitro fiber degradation

The variability over time of several main ruminal characteristics was studied in heifers over 15 consecutive weeks. Three heifers were assigned to a low-fiber diet (27% NDF) and three to a high-fiber diet (44% NDF). The physico-chemical (pH and redox potential) and fermentation(volatile fatty acids and ammonia contents) parameters were determined on 1 day per week for 15 consecutive weeks. On the same days the bacterial community structure was studied using a molecular fingerprint technique and the ruminal fiber degradation was studied by in vitro incubation of a withdrawn ruminal content sample. Numerous random changes were observed from week to week for all physico-chemical and fermentative parameters and in vitro fiber degradation. The redox potential was the only parameter to show a significant interaction between diet and week. Except for the ammonia content, the amplitudes of fluctuations observed were higher for the low-fiber diet. The bacterial community structure did not differ between diets or weeks. The in vitro fiber degradation was similar for both diets, with numerous random changes throughout the study. The findings of this study indicated that most of the parameters of the ruminal ecosystem had time-related changes with random fluctuations around a mean value which reflect an unstable equilibrium. This conclusion was valid for both low- and high-fiber diets

Timed Functional Modeling for Mixed-Signal Boards in Maintenance Testing

International audienceIn the context of maintenance testing and diagnosis of faulty boards, a functional FSM (Finite State Machine)- based model for mixed-signal boards has been introduced in a precedent paper. It has been extended for dealing with time sequences aspects. In this paper, the new modeling technique is presented

Validation of a Mixed-Signal Board ATPG Method

International audienceThis paper presents the validation protocol of a mixed-signal board ATPG method. First results confirm the method fitting well with maintenance test, board modeling stage adequacy and test data generation reliability. The essential need for user-defined dedicated test strategies is highlighted in order to ensure meaningful test process and full blackbox test

Development of a regional-scale library of near infrared reflectance soil spectra for alternative assessment of soil characteristics in Southern Belgium

In Walloon Region (Southern Belgium), five routine soil laboratories are grouped within a network promoting a better quality in analysis (www.requasud.be). The harmonization of protocols as well as methodological or technical prospective are realized under scientifically supervision of our research laboratory. In this context, a study was conducted to evaluate the ability of the NIRS to predict some soil properties: CEC, TOC, TN and clay content. The initial models were elaborated upon local PLS regression on set of 1 300 soil samples. The local PLS calibration used allows an accurate prediction of the soil properties and precision of NIRS technique is comparable to reference analytical metho