A Comparative Survey of Optical Wireless Technologies: Architectures and Applications

New high-data-rate multimedia services and applications are evolving continuously and exponentially increasing the demand for wireless capacity of fifth-generation (5G) and beyond. The existing radio frequency (RF) communication spectrum is insufficient to meet the demands of future high-datarate 5G services. Optical wireless communication (OWC), which uses an ultra-wide range of unregulated spectrum, has emerged as a promising solution to overcome the RF spectrum crisis. It has attracted growing research interest worldwide in the last decade for indoor and outdoor applications. OWC offloads huge data traffic applications from RF networks. A 100 Gb/s data rate has already been demonstrated through OWC. It offers services indoors as well as outdoors, and communication distances range from several nm to more than 10000 km. This paper provides a technology overview and a review on optical wireless technologies, such as visible light communication, light fidelity, optical camera communication, free space optical communication, and light detection and ranging. We survey the key technologies for understanding OWC and present state-of-the-art criteria in aspects, such as classification, spectrum use, architecture, and applications. The key contribution of this paper is to clarify the differences among different promising optical wireless technologies and between these technologies and their corresponding similar existing RF technologie

Biodétection de Legionella pneumophila par biocapteur à photocorrosion digitale à base de peptide antimicrobien

La détection de bactéries pathogènes par culture microbienne est lente, nécessite un milieu de culture spécifique pour garantir la croissance de certaines souches bactériennes fastidieuses telle que Legionella pneumophila (L. pneumophila) et en plus pourrait ne pas déceler les bactéries viables mais non cultivables mais restant dangereuse en termes de pathogénicité. Par conséquent, l’usage de biocapteurs pour la détection de L. pneumophila serait, potentiellement, une approche attrayante permettant une détection précise et rapide. Cependant, la sensibilité et la spécificité des biocapteurs dépendent fortement des molécules de bioreconnaissance utilisées. Jusqu'à présent, différents ligands tels que les anticorps, les enzymes, les acides nucléiques fonctionnels (aptamères) et les bactériophages ont été utilisés comme éléments de bioreconnaissance. En raison de leur haute spécificité, Les anticorps de mammifères ont été largement employés pour le développement de divers biocapteurs. Cependant, les anticorps sont connus pour souffrir de la variabilité des lots produits et d'une stabilité limitée, ce qui réduit l'usage et la constance des performances des biocapteurs à base d'anticorps. Au cours des dernières années, les peptides antimicrobiens (PAM) ont été de plus en plus investigués pour des applications thérapeutiques en plus d’être considérés comme des ligands de bioreconnaissance prometteurs en raison de leur grande stabilité et leurs fortes réactivités aux bactéries. Dans le but d’améliorer les performances du biocapteur à DIP, notre hypothèse reposait sur l’usage de bioarchitectures à base de PAM à courte séquence pour une capture efficace des bactéries et une détection considérablement améliorée en raison du transfert de charge plus facilitée vers dans la biopuce à base de semiconducteur III-V. Dans la première phase du projet, nous avons évalué un biocapteur à DIP consistant en une puce d’arséniure de gallium/arséniure de gallium aluminium (GaAs/AlGaAs) fonctionnalisée par le warnericine RK pour la détection directe in situ de L. pneumophila dans l’eau. Nous avons démontré une détection linéaire de L. pneumophila pour des concentrations allant de 103 à 106 CFU/mL. De plus, le nombre relativement important d'interfaces constituant la bioarchitecture d’un tel biocapteur pourrait affecter sa reproductibilité et sa sensibilité. Dans ce cas, la couche de bioreconnaissance est plus mince (~ 2 nm) permettant une distance plus courte entre les bactéries et la surface du biocapteur, ce qui pourrait jouer un rôle important dans la promotion du transfert de charge entre les bactéries et la biopuce, et ainsi nous avons pu démontrer une détection efficace de L. pneumophila à une concentration de 2 x 102 CFU/mL. Cette configuration a permis d’atteindre des LODs de 50 et 100 UFC/mL, respectivement pour de légionnelle dans du PBS et collectées d’échantillons d’eau de tour de refroidissement. Nous avons observé une détection sélective de L. pneumophila sérogroupe 1 (SG1) comparé au sérogroupe 5 (SG 5). Les biocapteurs à photocorrosion digitale (DIP) en configuration sandwich PAM et Ab pourraient être une approche prometteuse pour développer un biocapteur à faible coût, hautement sensible et spécifique pour la détection rapide de L. pneumophila dans l’eau.Abstract: Culture based detection of pathogenic bacteria is time consuming, and needs specific culture medium to identify bacterial strains such as Legionella pneumophila (L. pneumophila) which does not flourish in typical growth medium. Culture based methods cannot detect viable but unculturable bacteria. Therefore, the detection of L. pneumophila with biosensors potentially could be an attractive approach enabling accurate and rapid detection. The sensitivity and specificity of biosensors depend critically on the biorecognition probes employed for the detection. Until now, different elements such as antibodies, enzymes, functional nucleic acids (aptamers) and bacteriophages have been utilized as biorecognition elements. Due to high specificity of antibodies, and the advanced technology of their production, mammalian antibodies have been widely investigated for the development of various biosensors. However, mammalian antibodies are known to suffer from batch-to-batch variation, as well as limited stability, which could reduce the consistent utility of the proposed biosensors. In recent years, antimicrobial peptides (AMPs) have been increasingly investigated for their therapeutic applications. At the same time, AMPs are considered as promising biorecognition ligands due to their high stability and multiple niches for capturing bacteria. The hypothesis was that AMP-based bioarchitectures allows for highly efficient capturing of bacteria, and the short length of the AMP would significantly enhance detection due to limited obstructive charge transfer in the charge sensing biosensor. In the first phase of the project, we investigated a warnericin RK AMP functionalized gallium arsenide/aluminum gallium arsenide (GaAs/AlGaAs) photonic biosensor for direct detection of L. pneumophila in water environments. This approach allowed for detecting a low to high concentration of L. pneumophila (103 to 106 CFU/mL) with a 103 CFU/mL limit of detection (LOD). In addition, a relatively large number of interfaces constituting the architecture of such biosensors could affect their reproducibility and sensitivity. A thinner biorecognition layer (~2 nm) resulted in a shorter distance between bacteria and the biosensor surface, which played important role in promoting charge transfer between bacteria and biochip. L. pneumophila was detected at concentrations as low of 2 x 102 CFU/mL. This configuration allowed the detection sensitivity of L. pneumophila as low as 50 CFU/mL and 100 CFU/mL in clean water and water originated from cooling tower, respectively, along with the selective detection of whole cell L. pneumophila serogroup 1 (SG1) and serogroup 5 (SG5). The proposed AMP and Ab conjugated sandwich architecture with digital photocorrosion (DIP) biosensors is a promising approach for developing low cost, highly sensitive and specific biosensors for rapid detection of L. pneumophila in water environments

Determination of genetic diversity in lentil germplasm based on quantitative traits

Genetic diversity present in a gene pool is an important determination for breeding programs and characterization is useful of building crop plant collections primarily based on the knowledge of the presence of valuable genes and traits. In Bangladesh, one of the most common problems in lentil is the narrow genetic base, which must be broadened to enhance production. So, a detailed morphological study based on quantitative traits was under taken to assess the genetic diversity in 110 lentil germplasm, including landraces, popular varieties, phenologically adapted exotic lines and selected advanced lines of lentil of diverse origin. The main aim was to identify superior genotypes to be used for future breeding program in Bangladesh. The experiments were carried out during 2006-07 and 2007-08 and eight quantitative characters were studied under international standard of characterization. The UPGMA dendrogram segregated lentil accessions into six clusters. Genotypes fell in different clusters irrespective of their origin and accessions. The accession from ICARDA gene bank showed high diversity. Group B3, B4 and F were important as they comprised accessions with higher yield per plant, higher number of pods per plant and higher number of seeds per pod separated by higher inter cluster distance, which warrant their use in the breeding program

Application of Electroporation Technique in Biofuel Processing

Biofuels production is mostly oriented with fermentation process, which requires fermentable sugar as nutrient for microbial growth. Lignocellulosic biomass (LCB) represents the most attractive, low-cost feedstock for biofuel production, it is now arousing great interest. The cellulose that is embedded in the lignin matrix has an insoluble, highly-crystalline structure, so it is difficult to hydrolyze into fermentable sugar or cell protein. On the other hand, microbial lipid has been studying as substitute of plant oils or animal fat to produce biodiesel. It is still a great challenge to extract maximum lipid from microbial cells (yeast, fungi, algae) investing minimum energy. Electroporation (EP) of LCB results a significant increase in cell conductivity and permeability caused due to the application of an external electric field. EP is required to alter the size and structure of the biomass, to reduce the cellulose crystallinity, and increase their porosity as well as chemical composition, so that the hydrolysis of the carbohydrate fraction to monomeric sugars can be achieved rapidly and with greater yields. Furthermore, EP has a great potential to disrupt the microbial cell walls within few seconds to bring out the intracellular materials (lipid) to the solution. Therefore, this study aims to describe the challenges and prospect of application of EP technique in biofuels processing

Augmentation of Air Cathode Microbial Fuel Cell Performance using Wild Type Klebsiella Variicola

In the present work, simultaneous power generation and wastewater treatment in the single chamber air cathode microbial fuel cell (MFC) have been enhanced by introducing wild-type Klebsiella variicola (K. variicola) as an efficient inoculum for the anode operated with palm oil mill effluent (POME). K. variicola was isolated from municipal wastewater (MWW) and identified using BIOLOG gene III analysis, PCR and sequencing. The performance of K. variicola in MFC was evaluated by polarization curve measurement, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) analysis. The MFC with K. variicola achieved a maximum power density of about 1.7 W m−3 which is comparatively higher than most widely used anaerobic sludge (215 mW m−3) as an inoculum whereas COD removal efficiency is (43%) lower than anaerobic sludge (74%). Moreover, K. variicola has the ability to produce electron shuttles and to form biofilms on the electrode surface which helps to significantly reduce the anode charge transfer (Rct) resistance compared to the anaerobic sludge. These results revealed the potential of K. variicola to be used in MFC

Ultrasound Driven Biofilm Removal for Stable Power Generation in Microbial Fuel Cell

Anodic biofilm plays a crucial role in bioelectrochemical system to make it sustainable for long-term performance. However, the accumulation of dead cells over time within the anode biofilm can be particularly detrimental for current generation. In this study, the effect of ultrasound on anode biofilm thickness was investigated in microbial fuel cells (MFCs). Ultrasonic treatment was employed for different durations to evaluate its ability to control the thickness of the biofilm to maintain stable power generation. Cell viability count and field emission scanning electron microscopy (FESEM) analysis of the biofilms over time showed that the number of dead cells increased with the increase of biofilm thickness, and eventually exceeded the number of live cells by many-fold. Electrochemical impedance spectroscopy (EIS) analysis indicated that the high polarization resistance appeared due to the dead layer formation, and thus the catalytic efficiency was reduced in MFCs. The stable power generation was achieved by employing ultrasonic treatment for 30 min every 6 days with some initial exception. The low frequency ultrasound treatment successfully dislodged the ineffective biofilm from the surface of the anode. Moreover, the ultrasound could increase the mass transfer rate of the nutrients and cellular waste through the biofilm leading to the increase in cell growth. Therefore, ultrasonic treatment is verified as an efficient method to control the thickness of the biofilm as well as enhance the cell viability in biofilm thereby maintaining the stable power generation in the MFC