Influence of the Length of Kenaf Fibers on the Mechanical and Thermal Properties of Compressed Earth Blocks (CEB)

Armel B. Laibi,Philippe Poullain,Nordine Leklou,Moussa Gomina,Dominique K. C. Sohounhloué 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.2

The association of natural fibers and raw land soil has many advantages (thermal control, sound insulation, mechanical behavior, etc.). However, the major issue with the use of these materials is the lack of knowledge regarding their reliability and durability. In this work, we have evaluated the influence of kenaf fiber length on the mechanical and thermal properties of Compressed Earth Blocks (CEB). Fibers with length 10, 20 or 30 mm were used at mixing rate of 1.2% dry weight of soil; with the aim to enhance the mechanical and thermal properties of CEB fabricated starting from a plastic clayey soil mined in Benin. Analysis of the mechanical behavior of different Soil/Fiber formulations in terms of flexural strength demonstrated the beneficial effect of the fibers. However, the mechanical strength of CEB obtained by immersing fibers till saturation prior to incorporation into the soil greatly diminished. The higher flexural strength was obtained with fibers 30 mm long. The thermal conductivity of CEB decreased when the fiber length was raised. The results showed the real possibility to improve CEB mechanical and thermal properties by using fibers for reinforcement.

Application of Hybrid Polymeric Complexes to Solid State and Materials Chemistry

Josik Portier,Guy Campet,Nadine Treuil,Armel Poquet,Kim, Young Il,Kwon, Soon Jae,Kwak, Seo Young,Choy, Jin Ho Korean Chemical Society 1998 대한화학회지 Vol.42 No.4

A bird's-eye view on preparation, structure and properties of polymeric complexes in the field of Inorganic-Organic-Hybrids is presented in the view point of solid state and materials chemistry. These materials are useful precursors for preparing nanoparticles and fine grain oxides. Some of them are electroactive and are used as protonic or lithium electrolytes, electrochromic materials or membranes for sensors and actuators. New results on bio-hybrids, a class of material not far from polymeric complexes, are also described.

Fluorimetric Assay of Chitin Deacetylase Activity

( Binesh Shrestha ),( Hubert Becker ),( Willem F. Stevens ),( Francoise Le Hegarat ),( Armel Guyonvarch ) 한국키틴키토산학회 2006 한국키틴키토산학회지 Vol.11 No.2

Antibacterial phytocomplexes and compounds from Psychotria sycophylla (Rubiaceae) against drug-resistant bacteria

Olive M. F. Demgne,Judith Flore Tchuissang Mbougnia,Armel Jackson Seukep,Armelle Tsafack Mbaveng,Mathieu Tene,Paul Nayim,Brice E. N. Wamba,Michel-Gael F. Guefack,Veronique Penlap Beng,Pierre Tane,Vict 경희대학교 융합한의과학연구소 2022 Oriental Pharmacy and Experimental Medicine Vol.22 No.4

In this study, we examined the antibacterial and antibiotic-resistance reversal properties of methanol (MeOH) and ethyl acetate (EtOAc) extracts and compounds from Psychotria sycophylla aerial parts against drug-resistant bacteria. The tests were performed using the microdilution method. The mechanisms of action were investigated on growth kinetic and proton pumps of Escherichia coli. The structures of isolated compounds including oleanolic acid (1), ursolic acid (2), lupeol (3), betulinic acid (4), β-sitosterol glucoside (5), and stigmasterol (6), were established based on nuclear magnetic resonance (NMR) and electrospray ionization-mass spectrometry (ESI–MS). The extracts displayed noteworthy antibacterial activities, with recorded minimal inhibitory concentrations (MIC) ranging from 4 to 1024 μg/mL. Significant activities (MIC < 100 μg/ mL) were obtained with the MeOH extract against Providencia stuartii PS2636 and Staphylococcus aureus MRSA9 (MIC of 16 μg/mL) as well as the EtOAc extract against S. aureus MRSA3 (MIC of 32 μg/mL) and Enterobacter aerogenes EA27 (MIC of 4 μg/mL). MeOH extract displayed a broad-spectrum antibacterial activity, acting against 21 out of 22 studied bacteria. The MICs of compounds (1–6) varied from 16 to 256 μg/mL. Oleanolic acid (1) appeared to be the most effective, preventing the growth of 100% of studied bacteria. The MeOH extract significantly enhanced the efficacy of conventional antibiotics against selected multidrug-resistant Gram-negative bacteria. The mechanistic investigations showed interference of MeOH with bacterial growth kinetic (by extending the lag phase) and inhibition of proton pumps. The current study provides a strong experimental baseline to consider P. sycophylla extracts and compounds as potent antibacterial natural products.

High-Efficiency, Solid-State, Dye-Sensitized Solar Cells Using Hierarchically Structured TiO₂ Nanofibers

Hwang, Daesub,Jo, Seong Mu,Kim, Dong Young,Armel, Vanessa,MacFarlane, Douglas R.,Jang, Sung-Yeon American Chemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.5

<P>High-performance, room-temperature (RT), solid-state dye-sensitized solar cells (DSSCs) were fabricated using hierarchically structured TiO<SUB>2</SUB> nanofiber (HS-NF) electrodes and plastic crystal (PC)-based solid-state electrolytes. The electrospun HS-NF photoelectrodes possessed a unique morphology in which submicrometer-scale core fibers are interconnected and the nanorods are dendrited onto the fibers. This nanorod-in-nanofiber morphology yielded porosity at both the mesopore and macropore level. The macropores, steming from the interfiber space, afforded high pore volumes to facilitate the infiltration of the PC electrolytes, whereas the mesoporous nanorod dendrites offered high surface area for enhanced dye loading. The solid-state DSSCs using HS-NFs (DSSC-NF) demonstrated improved power conversion efficiency (PCE) compared to conventional TiO<SUB>2</SUB> nanoparticle (NP) based DSSCs (DSSC-NP). The improved performance (>2-fold) of the DSSC-NFs was due to the reduced internal series resistance (<I>R</I><SUB>s</SUB>) and the enhanced charge recombination lifetime (τ<SUB>r</SUB>) determined by electrochemical impedance spectroscopy and intensity modulated photocurrent/photovoltage spectroscopy. The easy penetration of the PC electrolytes into HS-NF layers via the macropores reduces <I>R</I><SUB>s</SUB> significantly, improving the fill factor (FF) of the resulting DSSC-NFs. The τ<SUB>r</SUB> difference between the DSSC-NF and DSSC-NP in the PC electrolytes was extraordinary (∼ 14 times) compared to reported results in conventional organic liquid electrolytes. The optimized PCE of DSSC-NF using the PC electrolytes was 6.54, 7.69, and 7.93% at the light intensity of 100, 50, and 30 mW cm<SUP>−2</SUP>, respectively, with increased charge collection efficiency (>40%). This is the best performing RT solid-state DSSC using a PC electrolyte. Considering the fact that most reported quasi-solid state or nonvolatile electrolytes require higher iodine contents for efficient ion transport, our HS-NFs are a promising morphology for such electrolytes that have limited ion mass transport.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2011/aamick.2011.3.issue-5/am200092j/production/images/medium/am-2011-00092j_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am200092j'>ACS Electronic Supporting Info</A></P>

Agreement between two methods for assessment of maximal inspiratory pressure in patients weaning from mechanical ventilation

Ribeiro Emanuelle Olympia Silva,Gosselink Rik,Moura Lizandra Eveline da Silva,Correia Raissa Farias,Leite Wagner Souza,Araújo Maria das Graças Rodrigues de,Andrade Armele Dornelas de,Brandão Daniella 대한중환자의학회 2022 Acute and Critical Care Vol.37 No.4

Background: Respiratory muscle strength in patients with an artificial airway is commonly assessed as the maximal inspiratory pressure (MIP) and is measured using analogue or digital manometers. Recently, new electronic loading devices have been proposed to measure respiratory muscle strength. This study evaluates the agreement between the MIPs measured by a digital manometer and those according to an electronic loading device in patients being weaned from mechanical ventilation.Methods: In this prospective study, the standard MIP was obtained using a protocol adapted from Marini, in which repetitive inspiratory efforts were performed against an occluded airway with a one-way valve and were recorded with a digital manometer for 40 seconds (MIPDM). The MIP measured using the electronic loading device (MIPELD) was obtained from repetitively tapered flow resistive inspirations sustained for at least 2 seconds during a 40-second test. The agreement between the results was verified by a Bland-Altman analysis.Results: A total of 39 subjects (17 men, 55.4±17.7 years) was enrolled. Although a strong correlation between MIPDM and MIPELD (R=0.73, P<0.001) was observed, the Bland-Altman analysis showed a high bias of –47.4 (standard deviation, 22.3 cm H2O; 95% confidence interval, –54.7 to –40.2 cm H2O).Conclusions: The protocol of repetitively tapering flow resistive inspirations to measure the MIP with the electronic loading device is not in agreement with the standard protocol using one-way valve inspiratory occlusion when applied in poorly cooperative patients being weaned from mechanical ventilation.