Experimental study and parameters optimization of microalgae based heavy metals removal process using a hybrid response surface methodology-crow search algorithm.

This study investigates the use of microalgae as a biosorbent to eliminate heavy metals ions from wastewater. The Chlorella kessleri microalgae species was employed to biosorb heavy metals from synthetic wastewater specimens. FTIR, and SEM/XRD analyses were utilized to characterize the microalgal biomass (the adsorbent). The experiments were conducted with several process parameters, including initial solution pH, temperature, and microalgae biomass dose. In order to secure the best experimental conditions, the optimum parameters were estimated using an integrated response surface methodology (RSM), desirability function (DF), and crow search algorithm (CSA) modeling approach. A maximum lead(II) removal efficiency of 99.54% was identified by the RSM-DF platform with the following optimal set of parameters: pH of 6.34, temperature of 27.71 °C, and biomass dosage of 1.5 g L-1. The hybrid RSM-CSA approach provided a globally optimal solution that was similar to the results obtained by the RSM-DF approach. The consistency of the model-predicted optimum conditions was confirmed by conducting experiments under those conditions. It was found that the experimental removal efficiency (97.1%) under optimum conditions was very close (less than a 5% error) to the model-predicted value. The lead(II) biosorption process was better demonstrated by the pseudo-second order kinetic model. Finally, simultaneous removal of metals from wastewater samples containing a mixture of multiple heavy metals was investigated. The removal efficiency of each heavy metal was found to be in the following order: Pb(II) > Co(II) > Cu(II) > Cd(II) > Cr(II).

Surface plasmon resonance biosensor based on hexagonal lattice dual-core photonic crystal fiber.

In this paper, the guiding properties and sensor performance are numerically investigated for a dual-core hexagonal lattice photonic crystal fiber sensor based on surface plasmon resonance (SPR). Gold is used as the active plasmonic material in order to create resonance, and it is placed outside the fiber structure to facilitate the fabrication process. The finite-element method is used to numerically investigate the characteristics of the sensor. By means of wavelength and amplitude interrogation methods, it is found that the proposed sensor shows maximum wavelength sensitivity of 16,000 nm/RIU with $6.25 \times {10^{ - 6}}\,\,{\rm RIU}$6.25×10-6RIU resolution and amplitude sensitivity of $2255\,\,{{\rm RIU}^{ - 1}}$2255RIU-1 with $4.40 \times {10^{ - 6}}\,\,{\rm RIU}$4.40×10-6RIU resolution. The proposed SPR sensor can detect the analyte refractive index ranging from 1.33 to 1.40. This work also includes an investigation of the effect of changing the gold layer thickness, air-hole diameter, and analyte layer on the sensor performance from the optimized design. The proposed sensor could be employed to detect biological and biochemical analytes because of its simple design and promising results.

Optimization of bio-cement production from cement kiln dust using microalgae.

The main aim of this study was to maximize bio-cement (CaCO3) production through a waste feedstock of cement kiln dust (CKD) as a source of calcium by deployment of microalgae sp. Chlorella kessleri. The effect of process parameters such as temperature, pH and time-intervals of microalgae cultivation, were set as criteria that ultimately subscribe to a process of optimization. In this regard, a single factor experiments integrated with response surface methodology (RSM) via central composite design (CCD) was considered. A quadratic model was developed to predict the maximum CaCO3 yield. A ceiling of 25.18 g CaCO3 yield was obtained at an optimal set of 23 °C, pH of 10.63 and day-9 of microalgae culture. Under these optimized conditions, maximum 96% calcium was extracted from CKD. FTIR, XRD and EDS analyses were conducted to characterize the CaCO3 precipitates. Compressive modes of mechanical testing seemed to hold conventional cement complimented by CaCO3 co-presence markedly superior to mere cement performance as far as compressive strength is concerned. The latter criterion exhibited further increase in correspondence with rise in cement to bio-cement ratio. This investigative endeavour at hand offers a simple pivotal platform on the basis of which a scale-up of microalgae-infested bio-cement production might be facilitated in conjunction with the added benefit of alleviation in environmental pollution through cement waste utilization.

In situ biological CO2 fixation and wastewater nutrient removal with Neochloris oleoabundans in batch photobioreactor.

Microalgae cultivation in wastewater media in phototrophic condition is a promising approach for integrated CO2 biofixation and wastewater treatment. For this, Neochloris oleoabundans was used to investigate the tertiary treatment of wastewater along with CO2 biofixation. In this investigation, biomass productivity, CO2 biofixation rate and percentage of total nitrogen (TN) and total phosphorus (TP) removal from synthetic wastewater are considered under three different operating conditions: temperature, CO2 feed concentration and nitrogen to phosphorus (NP) ratio in the media. Cultivation of N. oleoabundans was found to be highly temperature sensitive. With the increase of cultivation temperature from 25 to 45 °C, declining trends of biomass concentration, productivity and percentage of TN and TP removal were observed. Cultivation temperature of 25 °C was found to be most favorable in terms of biomass productivity, CO2 biofixation rate, percentage of TN and TP removal of 92 (mg L-1 day-1), 145 (mg L-1 day-1), 100% and 32%, respectively. Arrhenius-type kinetic model was used and the model showed good agreement with the experimental findings. Activation energy for the active stage and decay stage was found to be [Formula: see text] = 88.8 kJ mol-1 and [Formula: see text] = 8.4 kJ mol-1, respectively. With the increase of CO2 feed concentration, biomass productivity increased and the maximum biomass concentration and productivity was achieved at 6%. After that with the increase in CO2, a declining trend was observed. With the increase of NP ratio from 1:1 to 2:1, both the biomass productivity and CO2 biofixation were increased, but later were subsequently decreased with increase of NP ratio from 4:1 to 8:1. It is interesting that TP removal was increased with NP ratio and 100 percent of TP removal was achieved at 4:1 and 8:1 conditions.

Evaluation of the first year of Dental Health Partnerships: a web-based distance learning partnership between UK dental educators and students from low-resource countries.

Aim: To introduce and discuss the results of a newly-founded online, distance learning organisation, Dental Health Partnerships. The motivation behind the project is to bridge the gap between dental educators in the UK and dental students in low-resource communities. The results of the first partnership with Amoud Dental University, Somaliland, are presented. Method: Sixteen tutorials were conducted between February 2016 and June 2016 for the final year dental students via an online virtual classroom (WizIQ). Sixteen students participated in the weekly tutorials, each of which lasted for approximately 90 minutes. The students were sent online questionnaires at two stages during the study to qualitatively evaluate their experience. Results: Nine of the sixteen students responded to both questionnaires. One-hundred percent of the participants were 'very satisfied' or 'satisfied' with the programme at the end of the year. The attendance and participation rates for the weekly sessions were positive. The students had theoretical knowledge of the topics, however, the application of theoretical concepts to clinical scenarios was a challenge. Conclusion: The results of the first year of the partnership indicates the relevance of case-based tutorials to dental practice in Somaliland, equipping students with the clinical-based knowledge to be effective in the field after graduation.

Low-loss and bend-insensitive terahertz fiber using a rhombic-shaped core.

A novel porous-core photonic crystal fiber is presented, and its guiding properties are numerically investigated by using the finite element method. It is demonstrated that by introducing a rhombic-shaped core made of circular air holes inside the conventional hexagonal cladding, it is possible to obtain very low bending loss of 3.04×10-11 cm-1 at the operating frequency of 1.0 THz. In addition to this, low effective material loss of 0.089 cm-1 and very small confinement loss of 1.17×10-3 dB/cm are achieved for optimal design parameters. Other guiding properties, including effective area, dispersion, and higher order mode characteristics are also discussed thoroughly. The design of this porous fiber is relatively simple, since it contains fewer air holes and consists of circular air holes only. Due to promising wave-guiding properties, the proposed fiber would have a great potential for terahertz imaging and flexible communication applications.

Polarization-maintaining low-loss porous-core spiral photonic crystal fiber for terahertz wave guidance.

A polarization-maintaining porous-core spiral photonic crystal fiber is proposed for efficient transmission of polarization-maintaining terahertz (THz) waves. The finite element method with perfectly matched layer boundary conditions is used to characterize the guiding properties. We demonstrate that by creating artificial asymmetry in the porous core, an ultrahigh birefringence of 0.0483 can be obtained at the operating frequency of 1.0 THz. Moreover, a low effective material loss of 0.085 cm-1 and very small confinement loss of 1.91×10-3 dB/cm are achieved for the y-polarization mode with optimal design parameters. This article also focuses on some crucial design parameters such as power fraction, bending loss, and dispersion for usability in the THz regime.

Microstructure core photonic crystal fiber for gas sensing applications.

In this paper, a highly sensitive gas sensor based on the microstructure core and cladding photonic crystal fiber (PCF) is presented over the wavelength range from 1.3 to 2.2 µm, which is advantageous for sensor fabrication. The guiding properties of the proposed structure are dependent on geometrical parameters and wavelengths, which are numerically investigated by using a finite element method (FEM). Introducing the microstructure core makes it possible to obtain higher relative sensitivity and achieves low confinement loss. Moreover, it can be shown that increasing the diameter of the air holes in the microstructure core and decreasing the size of hole to hole space (pitch), the relative sensitivity is enhanced. In addition, the confinement loss is reduced by increasing the value of the diameter of the air holes in the cladding. Simulation results reveal that for the optimum design of the proposed PCF it is possible to obtain the highest relative sensitivity of about 42.27% at the wavelength λ=1.33 µm for the absorption line of methane (CH4) and hydrogen fluoride (HF) gases. In this case, the confinement loss of the fiber is 4.78345×10-6 dB/m.

Role of thallium-201 in the diagnosis of solitary bone lesions.

Thallium-201 is known to accumulate in malignant tumours. In this work we are evaluating the role of thallium in differentiating benign from malignant solitary bone lesions in 28 patients with solitary bone lesions on 99Tcm-MDP bone scans. Lesions' uptake of 201Tl was evaluated using visual assessment and lesion to background ratio. We found significant uptake with a mean lesion to background ratio of 4.27 in malignant lesions and no or faint uptake with a mean lesion to background ratio of 1.37 in benign lesions.