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Microalgae originating from wastewater has been exhibiting particularly promising results in terms of biohydrogen production and wastewater treatment. This paper aims to review the factors affecting production, pretreatment techniques to improve synthesis, advanced technologies utilized for enhancing biohydrogen production, and techno-economic feasibility evaluation of the processes at a commercial scale. Microalgae possess metabolic components to synthesize biohydrogen using photobiological and fermentative processes but must undergo pretreatment for efficient biohydrogen production. The efficiency of these processes is influenced by factors such as the microalgae species, light intensity, cell density, pH, temperature, substrates, and the type of bioreactors. Moreover, many limitations, such as oxygen sensitivity, altered thylakoid constitution, low photon conversion efficiency, light capture disruption, and the evolution of harmful by-products hinder the sustainability of biohydrogen production processes. High operational and maintenance costs serve as the major bottleneck in the scaling up of the process as an industrial technology. Therefore, future research needs to be directed towards increasing optimization of the processes by reducing energy and resource demand, recycling metabolic wastes and process components, genetically engineered microalgae to adopt more efficient routes, and conducting pilot studies for commercialization.

Improper sanitation and waste management is the number one cause for ill health, disease and death throughout the world, particularly under extremely dense living conditions in refugee camps in the global South. This paper discusses the results of a mixed-method study conducted in Rohingya refugee camps, located in Chittagong, Bangladesh, currently hosting the world's largest concentration of refugees. Our structured questionnaire, group discussion and interviews were centered on waste-borne hazards. The research has evidenced severe challenges associated with overall precarious sanitation and waste situations in the camps. Garbage littering and open defecation are widely practiced. Congested drainage systems contribute to flooding, bringing waste and contaminants into people's homes. Improvements can be made by involving camp inhabitants in decision-making processes and giving them greater ownership in everyday infrastructure maintenance. Our research suggests that community participation is the key tool to maintain proper cleanliness of drains and toilets. Creating a stronger sense of community in the camps and practicing transparency and inclusion in planning and decision-making can contribute to addressing the key threats identified in this research and also apply to other refugee camps worldwide, with similar hazardous living conditions.

Hydrogen (H2) is pivotal to phasing out fossil fuel-based energy systems. It can be produced from different sources and using different technologies. Very few studies comprehensively discuss all available state-of-the-art technologies for H2 production, the challenges facing each process, and their economic feasibility and sustainability. The current study thus addresses these gaps to effectively direct future research towards improving H2 production techniques. Many conventional methods contribute to large greenhouse gas footprints, with high production costs and low efficiency. Steam methane reforming and coal gasification dominate the supply side of H2, due to their low production costs (

Two new carboxylic acids conjugated with anthracene (1 and 2) are synthesized with a target to explore their coordination chemistry with metal ions. Compounds 1 and 2 are completely characterized by various analytical (NMR, Elemental analysis and ESI-Mass) methods. The backbone (biphenyl and phenyl) of compounds1 and 2 differs in such a way that the electronic communication between carboxylic acid and anthracene moieties can be easily modified. Compound 2 show anthracene centred emission while 1 exhibit combination of charge transfer transition and anthracene centred emissions. Preliminary fluorescence studies reveal compound 1 and 2 show different fluorescence response for first row transition metal ions.

In this paper, two different models of highly nonlinear bored core photonic crystal fibers (HNL-BCPCF) are presented and compared for attaining an ultra-high negative dispersion coefficient and high nonlinearity. We achieved this dispersion by tailoring a defect into the solid core of the two proposed models and appropriately scaling down the diameter of the neighboring airholes of the core. To investigate the optical transmission properties in the fiber, simulations were carried out employing the finite element method (FEM) having a perfectly matched layer. The simulation results exhibited large negative dispersion coefficients of − 2218 ps/(nm-km) and − 2221 ps/(nm-km) for the two proposed models, respectively, when the wavelength had been tuned to 1550 nm and the corresponding nonlinear coefficients stand out to be 117.6 W−1 km−1 and 118.4 W−1 km−1. The fabrication process had been made much more feasible as the design consists of circular airholes. In our analysis, this geometry of photonic crystal fiber is noticeably more robust for its successful achievement of an ultra-high negative dispersion with high nonlinearity and facilitates optical back propagation applications and dispersion compensation for optical transmission systems.

Ecotourism, a sustainable form of tourism, is increasingly being viewed as a tool that can promote global biodiversity and forest conservation. This study explored the scope of ecotourism in forest conservation practices in the developing context by taking the Sitakunda Botanical Garden and Ecopark (SBGE), Bangladesh’s first ecopark established in 2000, as a case study. Using GIS and remote sensing technology, NDVI analysis revealed that, unlike the anticipated outcomes of the SBGE project, after a brief increase in vegetation coverage of 84.6% from 1995 to 2000, the vegetation coverage fell drastically from 2000 to 2015, wherein 33.4% of vegetation had been completely removed, and much of the dense and medium vegetation had been converted to sparse vegetation or other land uses. Anthropogenic activities, namely, unplanned urbanization, are suggested as the major contributors to this decline. From the period of 2015 to 2020, however, vegetation was seen to regenerate, potentially due to the decelerating urbanization or the possible manifestation of the ‘U’ shape relationship between the changes in vegetation and rates of urbanization. Sustainable land-use policies may help attain the targets of the project and lead the SBGE to emerge as a success story of the Bangladeshi ecotourism industry.

International audience; Biogas production is rising in the context of fossil fuel decline and the future circular economy, yet raw biogas requires purification steps before use. Here, we review biogas upgrading using physical, chemical and biological methods such as water scrubbing, physical absorption, pressure swing adsorption, cryogenic separation, membrane separation, chemical scrubbing, chemoautotrophic methods, photosynthetic upgrading and desorption. We also discuss their techno-economic feasibility. We found that physical and chemical upgrading technologies are near-optimal, but still require high energy and resources. Biological methods are less explored despite their promising potential. High-pressure water scrubbing is more economic for small-sized plants, whereas potassium carbonate scrubbing provides the maximum net value for largesized plants.

The expeditious and world pandemic viral disease of new coronavirus (SARS-CoV-2) has formed a prompt urgency to discover auspicious target-based ligand for the treatment of COVID-19. Symptoms of novel coronavirus disease (COVID-19) typically include dry cough, fever, and shortness of breath. Recent studies on many COVID-19 patients in Italy and the United Kingdom found increasing anosmia and ageusia among the COVID-19-infected patients. SARS-CoV-2 possibly infects neurons in the nasal passage and disrupts the senses of smell and taste, like other coronaviruses, such as SARS-CoV and MERS-CoV that could target the central nervous system. Developing a drug based on the T2Rs might be of better understanding and worth finding better molecules to act against COVID-19. In this research, we have taken a taste receptor agonist molecule to find a better core molecule that may act as the best resource to design a drug or corresponding derivatives. Based on the computational docking studies, the antibiotic tobramycin showed the best interaction against 6LU7 COVID-19 main protease. Aromatic carbonyl functional groups of the molecule established intermolecular hydrogen bonding interaction with GLN189 amino acid and it showed the two strongest carbonyl interactions with receptor protein resulting in a glide score of −11.159. To conclude, depending on the molecular recognition of the GPCR proteins, the agonist molecule can be recognized to represent the cell secondary mechanism; thus, it provides enough confidence to design a suitable molecule based on the tobramycin drug.

As the world attempts to transition from fossil fuels, lignocellulosic biomass (LCB) serves as a promising alternative due to its high abundance. Hydrolysing LCB can generate various bioproducts, such as biofuels and value-added chemicals. However, the presence of lignin inhibits the solubilization of LCBs, presenting a major techno-economic challenge in the biorefinery concept. Therefore, this paper addresses the gaps left by most of the recent review works that fail to comprehensively review different pretreatment methods and the full scope of applications of LCBs, and do not incorporate techno-economic considerations of the technologies, the latter being the greatest bottleneck in the commercialization of the processes. The literature review revealed that while many of the physical and chemical pretreatment methods exhibit great effectiveness, they have a huge dependence on energy, chemicals, water, and/or specialized equipment, and produce harmful waste and inhibitory compounds. The pretreatment of lignocellulosic biomass can account for 40% of total production costs. Biological pretreatment can address these challenges but is limited by long incubation times. For instance, the bacterial pretreatment can noticeably reduce sawdust cellulose, hemicelluloses, and lignin contents by 35.8%, 37.1%, and 46.2%, respectively. Recently, integrated/coupling (hybrid) methods, such as chemical-assisted liquid hot water/steam and microwave or ultrasound-assisted alkaline pretreatment, have been gaining popularity due to their potential to improve chemical yield, but at the expense of the high cost of operation. To make pretreatment processes more techno-economically feasible, there is a need for process integration and the standardization and optimization of process parameters.

In this paper, an asymmetric photonic crystal fiber (PCF) working on surface plasmon resonance (SPR) has been proposed and demonstrated using the wavelength interrogation method and lower birefringence peak method. The proposed sensor contains a D-shaped analyte channel that can detect unknown analytes within the sensing range of 1.42–1.47 refractive index units (RIU) of the analytes. The structural asymmetry induces orthogonal x and y polarization modes. The numerical investigations with the finite element method (FEM) reveal that the sensor has a maximum wavelength sensitivity of 80,000 nm/RIU with a sensor resolution of 1.25 × 10−6 RIU for the y polarization mode and the maximum figure of merit (FOM) is found to be of 370.4 RIU−1. For the x polarization mode, the sensor exhibits a maximum wavelength sensitivity of 53,000 nm/RIU with a resolution of 1.89 × 10−6 RIU, having a maximum figure of merit (FOM) of 351 RIU−1. These results are found by using the wavelength interrogation method via confinement loss. On the other hand, the lower birefringence peak method-based analysis reveals a maximum wavelength sensitivity of 50,000 nm/RIU with a resolution of 2 × 10−6 RIU. As such, it is highly suitable for organic chemical detections and medical diagnostics. In addition, this paper studies the fabrication tolerance on the sensor performance.

A novel PCF sensor based on surface plasmon resonance (SPR) to detect pH levels of Acetic acid aqueous solution is proposed in this paper. This proposed sensor has a sensing range for 1%-25% acetic acid aqueous solution (2.51-1.90 in pH level). Gold layer is used as plasmonic metal along with a TiO 2 layer for better plasmonic excitation and enhancing evanescent field. Analyte is passed through a rectangular channel in center and a channel surrounding the metal layer. For some analyte samples of refractive index(RI) ranging in between 1.33-1.37, we have investigated effective RI, relative sensitivity in x and y polarizations, confinement loss and effective area via Finite Element Method (FEM). As a result of proper optimization maximum wavelength sensitivity of 10,000 nm/RIU and wavelength resolution of $1\times 10^{-5}$ RIU is achieved at 1.3620 RI level which secures excessive detection reliability of minute RI changes. This sensor evinces moderated confinement loss which certifies simplicity in fabricating the design. Relation of confinement loss, relative sensitivity and effective area against wavelength show eminent indication of better sensing capability for various pH levels of acetic acid.

A Dual core surface plasmon resonance (SPR) based photonic crystal fiber (PCF) biosensor functioning in the infrared (IR) range for biosensing applications is proposed and illustrated in this paper. Using gold as the plasmonic metal, the proposed sensor is able to detect analytes with higher refractive index, ranging from 1.46-1.50. The sensor design comes up with a hexagonal lattice accompanied by two analyte channels. Considering the wavelength interrogation method, this design exhibits a maximum wavelength sensitivity of 1000nm/RIU, along with a sensor resolution of $1\times 10^{-4}$ RIU. The fabrication method has been highlighted, along with the analysis of the impact of fabrication tolerance on the design structure. The proposed sensor is highly suitable for biological and chemical analyte detection.

In this paper, we propose a photonic crystal fiber sensor to detect analytes based on their refractive indexes. We modeled the fiber structure based on Surface Plasmon Resonance using gold as the plasmonic material. The Finite Element Method (FEM) has been used to evaluate the sensing performance and to investigate other characteristics. We arranged the airholes of the structure in a 5-ring hexagonal manner. The central airhole filled with benzene has a layer of gold coating to create the plasmonic mode and improve the sensing capability of the sensor. We changed the parameters of the structure to find the optimum results. The proposed sensor could successfully detect the change in the refractive index varies from 1.45 to 1.49 with a maximum sensor resolution of $3.33\times 10^{-5}$ , an Amplitude sensitivity(AS) of 439.9 $RIU^{-1}$ and a Wavelength sensitivity(WS) of 9000 nm/RIU. This sensor shows high sensitivity in detecting a small change in refractive index, which makes it highly applicable in the field of biosensing.

In this paper, a highly sensitive miniaturized surface plasmon resonance (SPR) based photonic crystal fiber (PCF) sensor is presented for a wide range of analyte sensing. Gold is selected as the plasmonic metal for its higher chemical stability and titanium oxide works as the adhesive layer for gold attachment on silica. The plasmonic metal and the sensing medium are placed exterior to the surface of the sensor design to make it fitting for practical applications. By a careful arrangement of the periodic arrangement of the refractive index in the design, the generation of the evanescent fields is fine-tuned to obtain the phase matching between the leaky core guided mode and the surface plasmon polariton (SPP) mode. Numerical simulations have been carried out by employing the finite element method (FEM) with the consideration of a perfectly matched layer (PML) to absorb surface radiations. The proposed sensor shows a maximum wavelength sensitivity of 34,000 nm/RIU (refractive index units) and a maximum amplitude sensitivity of 331 RIU−1, investigated by using the wavelength and the amplitude interrogation methods, respectively, for the analyte sensing range of 1.16 to 1.37 RI (refractive index). The sensor also exhibits a wavelength resolution of 2.94×10−6 RIU which indicates a high detection accuracy. On that, the proposed sensor would be an excellent candidate for a wide range of RI detection, applicable for various purposes such as chemical detections, medical diagnostics, bio-sensing, and other low RI analytes.

Arsenic is a highly toxic metalloid that is extensively distributed in soils and water bodies, resulting in a variety of toxicity mechanisms and harmful effects on humans and environmental health. This paper comprehensively reviews the technological development in arsenic (As) removal from wastewater and contaminated soil, and provides insights into the challenges in effective arsenic removal from the environmental compartments. The arsenic removal efficiency of the available technologies is also discussed in terms of their principle of operation, efficiency, advantages, and shortcomings. Many of the existing technologies are not found economically feasible for the regions of interest or are not applicable at the community level. Some of the techniques are often responsible for producing toxic by-products. Overall, the adsorption technique demonstrated high efficiency of almost 100% and a maximum of 95% in removing arsenic from water and soil, respectively. Novel methods such as the application of nanotechnology and polymeric ligand exchangers have also been gaining traction but also seem to possess limitations similar to conventional and non-conventional techniques.

We demonstrate an ultra-low loss photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR)in this paper. In this refractive index (RI) sensor, we explored hexagonal-arrangement of airholes and employed only two different sizes of it. The formation of airholes makes the confinement loss (CL) surprisingly low. The maximum CL is as low as 10.71 and 28.58 dB/cm for x and y-pol modes, respectively within a range of refractive indices 1.33-1.40. The maximum gained amplitude sensitivity is -1212 RIU−1 and -2430 RIU−1, and the maximum figure of merit is as high as 583 and 467 respectively for x and y-polarization (pol) modes respectively. In addition to that, we got a maximum wavelength sensitivity, Sw of 14,000nm/RIU for both x and y-pol modes with a minimum sensor resolution of 7.143x10−6. Gold is preferred over other materials as the plasmonic material for its inert behaviour and higher chemical stability. The analysis was carried out using the finite element method (FEM). This sensor, with its elegant configuration, fabrication feasibility, ultra-low loss, stands out to be an effective and eminent prospect in the current burgeoning SPR sensor realm and also prompts further creative exploration in its hexagonal lattice arrangements.