23 research outputs found
Towards sustainable, solution-processed organic field-effect transistors using cashew gum as the gate dielectric
To realize low-cost, environmentally friendly electronic devices and circuits, there is currently a strong trend to explore plant-based dielectric materials because they can be responsibly sourced from agricultural or forest vegetation, are generally water-soluble, and possess good electrical insulator properties. In this contribution, organic field-effect transistors (OFETs) using a biopolymer dielectric obtained from exudates of Anacardium occidentale Linn. trees, namely, cashew gum (CG), are reported. To characterise the physical and dielectric properties of the gum, thin films and metal-insulator-metal (MIM) capacitors were prepared and characterized. To evaluate the materialâs performance in OFETs, bottom-gate top-contact (BGTC) p-channel poly [3,6-di(2-thien-5-yl)-2,5-di(2-octyldodecyl)-pyrrolo (3,4-c)pyrrole-1,4-dione) thieno (3,2-b) thiophene]:polymethyl methacrylate (DPPTTT:PMMA) transistors were engineered and studied. The fabricated MIM capacitors display a comparatively high areal capacitance of 260Â nF/cm2 at 1Â kHz for 130Â nm thick films. As a result, the solution-processed DPPTTT:PMMA OFETs favourably operate at 3Â V with the average saturation field-effect mobility equal to 0.20Â cm2/Vs., threshold voltage around â1.4Â V, subthreshold swing in the region of 250Â mV/dec, and ON/OFF current ratio well above 103. As such, cashew gum emerges as a promising dielectric for sustainable manufacturing of solution-processed organic FETs
Solving the Capacitated Network Design Problem in Two Steps
In this paper, we propose a two steps-based algorithm to solve the modular link version of the Capacitated Network Design Problem (CNDP) which consists to determine the optimal network that guarantees the routing of a set of commodities. In our proposition, CNDP is divided into two sub-problems: Network Design problem (NDP) and Network Loading Problem (NLP). In the first step, we solved NDP by using the genetic algorithms which select sets of network topologies. In the second step, NLP is solved with the use of Linear programming to evaluate and validate the best network topologies. Simulation results on three real network instances (Atlanta, France and Germany) show that the proposed algorithm is better and more efficient than the Iterative Local Search algorithm
Two level evolutionary algorithm for Capacitated Network Design Problem
Efficient design of networks topologies is challenging, especially with the arrival of the virtualization in these last years. In this paper, we deal with the Capacitated Network Design Problem (CNDP) with modular link capacities to design minimum cost network while satisfying the flow demands. We propose a two levels Genetic Algorithm (GA) based model that can deal with several variations of CNDP. Our proposition defines a new encoding scheme to treat the modular case. Extensive simulation results on Atlanta, France and Germany network instances show that the proposed algorithm is much more efficient than the Iterative Local Search algorithm
Genetic algorithm based model for capacitated network design problem
Efficient design of networks topologies is challenging, especially with the arrival of the virtualization in these last years. In this paper, we deal with the Capacitated Network Design Problem (CNDP) with modular link capacities to design minimum cost network while satisfying the flow demands. We propose a two levels Genetic Algorithm (GA) based model that can deal with several variations of CNDP. Our proposition defines a new encoding scheme to treat the modular case. Extensive simulation results on Atlanta, France and Germany network instances show that the proposed algorithm is much more efficient than the Iterative Local Search algorithm
Stainless steel coated with carbon nanofiber/PDMS composite as anodes in microbial fuel cells
International audienceModification of electrode surfaces is a promising strategy to improve microbial fuel cell (MFC) performance. Here we report a new functionalization process to improve interfacial electron transfer, biocompatibility and corrosion resistance of stainless steel (SS) electrodes used as anodes in MFCs. SS anodes prepared by surface modification with a thin layer (200 ÎŒm) of conducting composite made of polydimethylsiloxane (PDMS) doped with commercially available carbon nanofibers (CNF), are described. Electrochemical characterization showed that the corrosion rate of SS electrode in an acid solution decreased from 367 ÎŒm.y â1 to 31 ÎŒm.y â1 after CNF-PDMS coating. Electric characterization demonstrated that the maximum power density generated by MFCs after 16 days with SS/CNF-PDMS anodes (19 mW.m â2) is 5 times higher and more stable than that with unmodified SS (3.7 mW.m â2). The cyclic voltammetry analysis indicated that the electrochemical activity of the modified anode was enhanced significantly after 16 days and the electron transfer was facilitated by CNF-PDMS modification. Microscopic observations and electrochemical characterization showed that CNF-PDMS composite improved biocompatibility and corrosion resistance of the SS anode surfaces. These results confirmed that the CNF-PDMS modification is a promising approach to improve the properties of anode materials for MFC application
Oncocytoma with a vascular extension, associated with a papillary carcinoma: A case report
This is a case report about a patient which presents with two right renal tumors, one of them being an oncocytoma with typical histopathological features and renal vein extension. Recent studies show that despite renal vein thrombus being a histological sign of malignancy; when associated with renal oncocytoma, it should not alter the benign prognosis of oncocytoma, and a simple follow-up may be carried. Further explorations should be done when easily available, and when the histopathologic diagnosis of oncocytoma is uncertain, to rule out the differential diagnosis of a chromophobe renal cell carcinoma, oncocytic variant
A Decade of Improvements in Mimiviridae and Marseilleviridae Isolation from Amoeba
International audienceSince the isolation of the first giant virus, the Mimivirus, by T.J. Rowbotham in a cooling tower in Bradford, UK, and after its characterisation by our group in 2003, we have continued to develop novel strategies to isolate additional strains. By first focusing on cooling towers using our original time-consuming procedure, we were able to isolate a new lineage of giant virus called Marseillevirus and a new Mimivirus strain called Mamavirus. In the following years, we have accumulated the world's largest unique collection of giant viruses by improving the use of antibiotic combinations to avoid bacterial contamination of amoeba, developing strategies of preliminary screening of samples by molecular methods, and using a high-throughput isolation method developed by our group. Based on the inoculation of nearly 7,000 samples, our collection currently contains 43 strains of Mimiviridae (14 in lineage A, 6 in lineage B, and 23 in lineage C) and 17 strains of Marseilleviridae isolated from various environments, including 3 of human origin. This study details the procedures used to build this collection and paves the way for the high-throughput isolation of new isolates to improve the record of giant virus distribution in the environment and the determination of their pangenome
Khaya gum â a natural and eco-friendly biopolymer dielectric for low-cost organic field-effect transistors (OFETs)
Nature provides a wide range of dielectric biopolymers that can be used in electronic devices. In this work, organic field-effect transistors (OFETs) using khaya gum (KG), a natural, biodegradable biopolymer that can be directly collected from khaya senegalensis trees, as the gate dielectric are demonstrated. The fabricated bottom gate/top contact poly (3,6-di (2-thien-5-yl)-2,5-di (2-octyldodecyl)-pyrrolo [3,4-c] pyrrole-1,4-dione) thieno [3,2-b] thiophene) (DPPTTT) â(polymethylmethacrylate) (PMMA) OFETs operate at 3 V with a saturation field-effect mobility (ÎŒsat) 0.3 cm2Vâ1 sâ1, threshold voltage (Vth) -1.3 V, subthreshold swing (SS) 450 mV/dec, and current on/off ratios (ION/OFF) larger than 3âĂâ103. Significantly, the gate leakage current (IG) does not exceed 10â8 A for the gate-source voltage (VGS) â€-3 V. UVâVis spectra analysis shows that the prepared khaya gum films exhibit low absorbance and high transparency (up to 90%) with a calculated optical band gap of about 4.3 eV. Thermal characterization shows two stages of decomposition and a glass transition at around 60 °C. Characterization of metalâinsulator-metal (MIM) capacitors using khaya gum reveals that the KG-based MIM capacitors possess a relatively high capacitance per unit area (Ci) of 130â±â3 nF/cm2 at 1 kHz. As a result, khaya gum emerges as the dielectric of choice for low voltage, transparent OFETs where environmentally friendly device manufacturing is required