Conservatoire national des arts et métiers

About: Conservatoire national des arts et métiers is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Context (language use). The organization has 3573 authors who have published 7127 publications receiving 141430 citations. The organization is also known as: CNAM & Conservatoire des arts et métiers.

Interrelations between populations of methanogenic archaea and sulfate-reducing bacteria in the human colon.

Abstract: In humans, CH4 is produced in the colon by methanogenic archaea and is detected in breath samples from approximately 50% of healthy adults, identified as CH4-excretors. Methanogenesis and sulfate reduction have been described as two mutually exclusive processes, potentially regulated by sulfate reduction have been described as two mutually exclusive processes, potentially regulated by sulfate availability. To determine whether microbial population balances reflected these apparently co-regulated activities, we compared sulfate-reducing bacteria, methanogenic archaea, sulfate and sulfide concentrations in faeces of 10 CH4-excretors (CH4+) and 9 non-CH4-excretors (CH4−). The mean ±SE of the logarithm of methanogenic archaea per gram wet weight were 9.0 ± 0.2 and 4.0 ± 0.7 for CH4+ and CH4−, respectively (P < 0.001). Sulfate-reducing bacterial counts were 6.5 ± 0.1 and 7.3 ± 0.2, respectively (P < 0.001). Fecal sulfate and sulfide concentrations did not differ between groups. These results suggest that a competitive interrelation between methanogenic archaea and sulfate-reducing bacteria occurs in the human colon. However, it does not lead to a complete exclusion of the two populations.

Theoretical analysis of BER performance of nonlinearly amplified FBMC/OQAM and OFDM signals

Abstract: In this paper, we introduce an analytical study of the impact of high-power amplifier (HPA) nonlinear distortion (NLD) on the bit error rate (BER) of multicarrier techniques. Two schemes of multicarrier modulations are considered in this work: the classical orthogonal frequency division multiplexing (OFDM) and the filter bank-based multicarrier using offset quadrature amplitude modulation (FBMC/OQAM), including different HPA models. According to Bussgang’s theorem, the in-band NLD is modeled as a complex gain in addition to an independent noise term for a Gaussian input signal. The BER performance of OFDM and FBMC/OQAM modulations, transmitting over additive white Gaussian noise (AWGN) and Rayleigh fading channels, is theoretically investigated and compared to simulation results. For simple HPA models, such as the soft envelope limiter, it is easy to compute the BER theoretical expression. However, for other HPA models or for real measured HPA, BER derivation is generally intractable. In this paper, we propose a general method based on a polynomial fitting of the HPA characteristics and we give theoretical expressions for the BER for any HPA model.

Efficiency of Filter Bank Multicarrier Techniques in Burst Radio Transmission

Abstract: The filter bank multicarrier (FBMC) technique has been proposed in the FP7 European research program, as an enhancement to the OFDM technique for future broadband radio systems. Besides gains in efficiency, mainly due to the absence of cyclic prefix, an important feature of FBMC is the absence of spectral leakage, which makes it particularly appealing for cognitive radio. However, in burst transmission, the filter impulse response introduces transitions which extend the length of the burst with respect to OFDM and may reduce the gains in efficiency. After a brief overview of the FBMC technique, the exploitation in burst transmission is discussed. The effect of cutting the initial and final transitions of the burst is investigated. The level of temporary spectral leakage introduced by this operation is assessed. It is shown that cuts leading to an increase in burst length of half a symbol with respect to OFDM affect the first and the last symbol only, resulting in a minor reduction in bit loading for these symbols. Application to the time division duplex access mode is considered, as well as the case of the presence of a preamble in the burst. For implementation, it is proposed to resort to a simple memory preloading technique, which has the advantage of compatibility with OFDM in dual mode systems.

Complementary feeding adequacy in relation to nutritional status among early weaned breastfed children who are born to HIV-infected mothers: ANRS 1201/1202 Ditrame Plus, Abidjan, Cote d'Ivoire

Abstract: OBJECTIVE: In high HIV prevalence resource-constrained settings, exclusive breastfeeding with early cessation is one of the conceivable interventions aimed at the prevention of HIV through breast milk. Nevertheless, this intervention has potential adverse effects, such as the inappropriateness of complementary feeding to take over breast milk. The purpose of our study first was to describe the nature and the ages of introduction of complementary feeding among early weaned breastfed infants up to their first birthday and second was to assess the nutritional adequacy of these complementary foods by creating a child feeding index and to investigate its association with child nutritional status. METHODS: A prospective cohort study in Abidjan, C?d'Ivoire, was conducted in HIV-infected pregnant women who were willing to breastfeed and had received a perinatal antiretroviral prophylaxis. They were requested to practice exclusive breastfeeding and initiate early cessation of breastfeeding from the fourth month to reduce breast milk HIV transmission. Nature and ages of introductory complementary feeding were described in infants up to their first birthday by longitudinal compilation of 24-hour and 7-day recall histories. These recalls were done weekly until 6 weeks of age, monthly until 9 months of age, and then quarterly. We created an index to synthesize the nutritional adequacy of infant feeding practices (in terms of quality of the source of milk, dietary diversity, food, and meal frequencies) ranging from 0 to 12. The association of this feeding index with growth outcomes in children was investigated. RESULTS: Among the 262 breastfed children included, complete cessation of breastfeeding occurred in 77% by their first birthday, with a median duration of 4 months. Most of the complementary foods were introduced within the seventh month of life, except for infant food and infant formula that were introduced at age 4 months. The feeding index was relatively low (5 of 12) at age 6 months, mainly as a result of insufficient dietary diversity, but was improved in the next 6 months (8.5 of 12 at 12 months of age). Inadequate complementary feeding at age 6 months was associated with impaired growth during the next 12 months, with a 37% increased probability of stunting. CONCLUSION: Adequate feeding practices around the weaning period are crucial to achieving optimal child growth. HIV-infected women should turn to early cessation of breastfeeding only when they are counseled properly to provide adequate complementary feeding to take over breast milk. Our child feeding index could contribute to the assessment of the nutritional adequacy of complementary feeding around the weaning period and therefore help to detect children who are at risk for malnutrition.