Simulation of adsorption and desorption phenomena in a gas chromatography microcolumn

International audienceThe main goal of the present work is to optimize the micro-column for the gas chromatography analysis device, which is the device used in the real-time monitoring of atmospheric BTEX concentration for indoor environments. The BTEX group of molecules (Benzene, Toluene, Ethylbenzene and Xylenes) is, among volatile organic compounds (VOC), the most widely found in indoor air and its main sources are the cleaning products, building materials and outdoor air supply [1]. Among the BTEX compounds, Benzene is the most dangerous one, since it has been proven as a carcinogenic component [2]. The European Commission report [3] stated that the limit concentration of Benzene in an indoor environment should be 5μg/m³. Therefore, it is really important to measure the concentration of these species in indoor environments. The separation of BTEX takes place inside the micro-column is due to the adsorption and desorption phenomena. The relative rates of adsorption and desorption onto and off the stationary phase inside the chromatographic column allow chemicals in the analyzed samples to be separated and then quantified. Aiming to have a good performance of chemical detection, it is always important to have well-separated analytes in the GC column, hence designing an efficient column is crucial to the success of the microchemical detection system [4]. Usually, the micro-columns used in gas-chromatographs are silica tubes of about 150 to 300 microns in diameter and about 20 meters long [5]. These columns have a thin stationary phase layer coated onto the walls of about 1μm thick. The different adsorption and desorption rates between the species to be separated with the stationary phase will generate different interactions between them, and each species will reach the outlet of the micro-column in a distinct instant. Placed after the micro-column, another component of the gas chromatography device, called detector, is accountable for measuring the concentration of each specie in tested air sample. The final output provided by the gas chromatograph analyzed in the present work is a graph containing the concentration of the BTEX compounds species in time, called chromatogram. In a very long and narrow channel and under isothermal conditions, the pressure and density could change considerably between the inlet and outlet in the function of the applied end conditions. Therefore, the velocity of the flow in the outlet cross-section of the column is higher than the velocity nearby the inlet. Consequently, even though the flow velocity is much smaller than the sound speed, the compressibility effect and the flow velocity variation with the position have to be considered. The working conditions of our micro-column are: outlet pressure of 1atm and temperature of 65°C. Under these conditions, the mean free path of Nitrogen, th

Research challenges on energy-efficient networking design

The networking research community has started looking into key questions on energy efficiency of communication networks. The European Commission activated under the FP7 the TREND Network of Excellence with the goal of establishing the integration of the EU research community in green networking with a long perspective to consolidate the European leadership in the field. TREND integrates the activities of major European players in networking, including manufacturers, operators, research centers, to quantitatively assess the energy demand of current and future telecom infrastructures, and to design energy-efficient, scalable and sustainable future networks. This paper describes the main results of the TREND research community and concludes with a roadmap describing the next steps for standardization, regulation agencies and research in both academia and industry.The research leading to these results has received funding from the EU 7th Framework Programme (FP7/2007–2013) under Grant Agreement No. 257740 (NoE TREND)

Prevalence of Group A beta-haemolytic Streptococcus isolated from children with acute pharyngotonsillitis in Aden, Yemen.

OBJECTIVES: To estimate the prevalence of Group A beta-haemolytic streptococcus (GAS) and non-GAS infections among children with acute pharyngotonsillitis in Aden, Yemen, to evaluate the value of a rapid diagnostic test and the McIsaac score for patient management in this setting and to determine the occurrence of emm genotypes among a subset of GAS isolated from children with acute pharyngotonsillitis and a history of acute rheumatic fever (ARF) or rheumatic heart disease (RHD). METHODS: Group A beta-haemolytic streptococcus infections in school-aged children with acute pharyngotonsillitis in Aden, Yemen, were diagnosed by a rapid GAS antigen detection test (RADT) and/or GAS culture from a throat swab. The RADT value and the McIsaac screening score for patient management were evaluated. The emm genotype of a subset of GAS isolates was determined. RESULTS: Group A beta-haemolytic streptococcus pharyngotonsillitis was diagnosed in 287/691 (41.5%; 95% CI 37.8-45.3) children. Group B, Group C and Group G beta-haemolytic streptococci were isolated from 4.3% children. The RADT had a sensitivity of 238/258 (92.2%) and specificity of 404/423 (95.5%) against GAS culture. A McIsaac score of ≥4 had a sensitivity of 93% and a specificity of 82% for confirmed GAS infection. The emm genotypes in 21 GAS isolates from children with pharyngitis and a history of ARF and confirmed RHD were emm87 (11), emm12 (6), emm28 (3) and emm5 (1). CONCLUSION: This study demonstrates a very high prevalence of GAS infections in Yemeni children and the value of the RADT and the McIsaac score in this setting. More extensive emm genotyping is necessary to understand the local epidemiology of circulating strains

Childhood tuberculosis: progress requires an advocacy strategy now

Childhood tuberculosis (TB) is a preventable and curable infectious disease that remains overlooked by public health authorities, health policy makers and TB control programmes. Childhood TB contributes significantly to the burden of disease and represents the failure to control transmission in the community. Furthermore, the pool of infected children constitutes a reservoir of infection for the future burden of TB. It is time to prioritise childhood TB, advocate for addressing the challenges and grasp the opportunities in its prevention and control. Herein, we propose a scientifically informed advocacy agenda developed at the International Childhood TB meeting held in Stockholm, Sweden, from March 17 to 18, 2011, which calls for a renewed effort to improve the situation for children affected by Mycobacterium tuberculosis exposure, infection or disease. The challenges and needs in childhood TB are universal and apply to all settings and must be addressed more effectively by all stakeholders

Turbo décodage de code produit haut débit utilisant un code BCH étendu (128,106,8) t=3

- Cet article propose une nouvelle architecture de turbo décodage de codes BCH (128,106,8) à entrées et sorties pondérées corrigeant 3 erreurs. En utilisant le concept de parallélisme et les propriétés de la matrice générée par un code produit, cet article présente la conception et la complexité de trois décodeurs capables de traiter 2, 4 et 8 données en même temps pour obtenir le haut débit dans le décodage. Pour comparer les performances et la complexité entre les différents décodeurs, le langage C a été utilisé pour les simulations, le langage VHDL pour les simulations fonctionnelles et Synopsys Design Compiler pour la synthèse. Les résultats ainsi obtenus ouvrent la possibilité d'intégration sur le silicium de turbo décodeurs à fort pouvoir de correction (distance de 64, rendement de 0,8) et à haut débit (6,4Gbits/s)

Visualizing landscapes of the superconducting gap in heterogeneous superconductor thin films: geometric influences on proximity effects

The proximity effect is a central feature of superconducting junctions as it underlies many important applications in devices and can be exploited in the design of new systems with novel quantum functionality. Recently, exotic proximity effects have been observed in various systems, such as superconductor-metallic nanowires and graphene-superconductor structures. However, it is still not clear how superconducting order propagates spatially in a heterogeneous superconductor system. Here we report intriguing influences of junction geometry on the proximity effect for a 2D heterogeneous superconductor system comprised of 2D superconducting islands on top of a surface metal. Depending on the local geometry, the superconducting gap induced in the surface metal region can either be confined to the boundary of the superconductor, in which the gap decays within a short distance (~ 15 nm), or can be observed nearly uniformly over a distance of many coherence lengths due to non-local proximity effects.Comment: 17 pages, 4 figure

Organizational linkages for new product development: Implementation of innovation projects

Effective external and internal organization linkage characterizes new product development. Although prior research covers the external linkages to gain operational efficiencies and develop new products, the current body of scholarship on internal cross-functional linkages requires further attention. This study provides a certain level of inquiry into the antecedents of such internal linkages and presents a framework to establish the relationship between two internal functions at major fast-moving consumer goods (FMCG). The study examines the implementation of 150 innovation projects in 6 different countries over a period of three years. The objective is to study the influence of trust dimension on the perceived effectiveness of cross-functional linkage to highlight how organizational mechanisms like the amount and quality of shared communication affect trust and relationship between two functions

Sub-national prevalence survey of tuberculosis in rural communities of Ethiopia

Abstract Background Tuberculosis is a major public health problem with varying prevalence in different settings. National prevalence surveys provide evidence for planning and decision making. However, they lack the capacity to estimate subnational magnitude that affected the capacity to make selected intervention based on the prevalence. Ethiopia is among high TB burden countries with estimated prevalence of 108 per 100,000 population varying by regions. We aimed to study sub national prevalence of smear-positive TB in rural communities of southern Ethiopia. Methods This cross-sectional study, enrolled community members aged over 14 years who had cough of at least two weeks duration. Two sputum samples were collected and examined by using smear microscopy. Results 38,304 eligible people were enumerated (10,779 from Hadiya, 10,059 from Gurage and 17,466 from Sidama) and indentified 960 presumptive cases. 16, 14 and 14 smear-positive pulmonary TB cases were identified respectively. The point prevalence of smear-positive TB were 148 per 100,000 population (95% CI: 91–241) in Hadiya, 139 per 100,000 population (95% CI: 83–234) in Gurage and 80/100,000 population (95%CI: 48–135) in Sidama zone. Gurage zone had the highest prevalent to notified cases of seven to one. Conclusions The prevalence of smear positive TB varies by districts and is high in rural southern Ethiopia compared to the estimated national prevalence. More TB patients remain missed and unreached, impacting negatively on health outcomes. TB case finding approaches should be revisited and innovative approaches and tools to identify missing people with TB should be scaled up