Synergistic effect of dual flocculation between inorganic salts and chitosan on harvesting microalgae Chlorella vulgaris

© 2020 Elsevier B.V. The flocculation efficiency of microalgae Chlorella vulgaris for subsequent harvesting was investigated using single flocculants of inorganic salts, synthetic polymer, chitosan and dual flocculants of inorganic salts and chitosan. Synthetic polymer (FlopamTM) could achieve over 90% optical density removal (OD680removal) at a low flocculant dose (20 to 40 mg polymer per litre of algal suspension) through the bridging mechanism and charge neutralisation. Inorganic salts (i.e. ferric chloride and aluminium sulphate) and chitosan individually resulted in low flocculation efficiency (80% flocculation efficiency, significantly higher than the sum of each individual flocculation. The improvement in flocculation efficiency was 57 and 24% respectively for ferric chloride/chitosan and aluminium sulphate/chitosan. Charge neutralisation of microalgal cells by ferric chloride or aluminium sulphate combined with bridging by chitosan produced the synergy

Adsorption mechanism of hexavalent chromium onto layered double hydroxides-based adsorbents: A systematic in-depth review

© 2019 Elsevier B.V. An attempt has been made in this review to provide some insights into the possible adsorption mechanisms of hexavalent chromium onto layered double hydroxides-based adsorbents by critically examining the past and present literature. Layered double hydroxides (LDH) nanomaterials are typical dual-electronic adsorbents because they exhibit positively charged external surfaces and abundant interlayer anions. A high positive zeta potential value indicates that LDH has a high affinity to Cr(VI) anions in solution through electrostatic attraction. The host interlayer anions (i.e., Cl−, NO3−, SO42−, and CO32−) provide a high anion exchange capacity (53–520 meq/100 g) which is expected to have an excellent exchangeable capacity to Cr(VI) oxyanions in water. Regarding the adsorption-coupled reduction mechanism, when Cr(VI) anions make contact with the electron-donor groups in the LDH, they are partly reduced to Cr(III) cations. The reduced Cr(III) cations are then adsorbed by LDH via numerous interactions, such as isomorphic substitution and complexation. Nonetheless, the adsorption-coupled reduction mechanism is greatly dependent on: (1) the nature of divalent and trivalent salts utilized in LDH preparation, and the types of interlayer anions (i.e., guest intercalated organic anions), and (3) the adsorption experiment conditions. The low Brunauer–Emmett–Teller specific surface area of LDH (1.80–179 m2/g) suggests that pore filling played an insignificant role in Cr(VI) adsorption. The Langmuir maximum adsorption capacity of LDH (Qomax) toward Cr(VI) was significantly affected by the natures of used inorganic salts and synthetic methods of LDH. The Qomax values range from 16.3 mg/g to 726 mg/g. Almost all adsorption processes of Cr(VI) by LDH-based adsorbent occur spontaneously (ΔG° 0) and increase the randomness (ΔS° >0) in the system. Thus, LDH has much potential as a promising material that can effectively remove anion pollutants, especially Cr(VI) anions in industrial wastewater

Factors governing microalgae harvesting efficiency by flocculation using cationic polymers.

This study aims to elucidate the mechanisms governing the harvesting efficiency of Chlorella vulgaris by flocculation using a cationic polymer. Flocculation efficiency increased as microalgae culture matured (i.e. 35-45, 75, and > 97% efficiency at early, late exponential, and stationary phase, respectively. Unlike the negative impact of phosphate on flocculation in traditional wastewater treatment; here, phosphorous residue did not influence the flocculation efficiency of C. vulgaris. The observed dependency of flocculation efficiency on growth phase was driven by changes in microalgal cell properties. Microalgal extracellular polymeric substances (EPS) in both bound and free forms at stationary phase were two and three times higher than those at late and early exponential phase, respectively. Microalgae cells also became more negatively charged as they matured. Negatively charged and high EPS content together with the addition of high molecular weight and positively charged polymer could facilitate effective flocculation via charge neutralisation and bridging

Une course sans répit : l’évolution des paramètres des candidats à la résidence en oto-rhino-laryngologie – chirurgie cervico-faciale au fil du temps

Background: There has been an increasing number of Canadian medical graduates who have gone unmatched in the residency selection process. Medical students have been engaging in extracurricular activities outside the formal curriculum which may help to distinguish themselves from their peers in the selection process. To understand how competitiveness in residency selection shapes applicant demographic characteristics and behaviours, this study set out to explore the demographic characteristics and prevalence of reported extra-curricular activities by applicants to Canadian Otolaryngology – Head & Neck Surgery (OTL-HNS) residency across time. Methods: A retrospective, descriptive study reviewed specific sections of the curriculum vitae (CV) of applicants to OTL-HNS programs in Canada.  These sections were self-reported, and included research productivity, involvement in volunteer and leadership activities, membership in associations, and honours or awards granted.  Data was quantified and analyzed descriptively. Results: Between 2013 to 2017, a total of 267 applicants reported a median of 12.6 research publications, 9.6 volunteer activities, six leadership activities, six association memberships and 9.8 honours/awards. Applicants were younger over time, with proportions of applicants over 30 years old decreasing from 56% in 2013 to 9% in 2017. Conclusion: Applicants to Canadian OTL-HNS residency programs are reporting consistently high numbers of extracurricular activities and were of increasingly younger ages. Medical students are investing significant time and energy to pursue these activities which are above and beyond the formal curriculum, possibly contributing to decreased diversity in applicants for competitive residencies, increasing the likelihood of misrepresentation in residency applications, and likely contributing to medical student burnout.Contexte : De plus en plus de diplômés en médecine canadiens demeurent non jumelés à l’issue du processus de sélection des résidents. Certains font des activités hors programme afin de se distinguer de leurs pairs dans le processus de sélection. Pour comprendre comment la compétition dans la sélection de résidents influence les caractéristiques démographiques et les comportements des candidats, cette étude visait à explorer l’évolution des caractéristiques démographiques et la prévalence d’activités hors programme déclarées par les candidats à la résidence en oto-rhino-laryngologie – chirurgie cervico-faciale (ORL-CCF) à travers le temps. Méthodes : Dans le cadre d’une étude rétrospective et descriptive, nous avons parcouru des sections pertinentes du curriculum vitae (CV) des candidats aux programmes d'oto-rhino-laryngologie et chirurgie cervico-faciale au Canada. Ces sections étaient auto-déclarées et comprenaient les activités de recherche, la participation à des activités de bénévolat et de leadership, l'appartenance à des associations et les prix et distinctions obtenus. Les données ont été quantifiées et analysées de manière descriptive. Résultats : Entre 2013 et 2017, un total de 267 candidats ont déclaré une médiane de 12,6 publications de recherche, 9,6 activités de bénévolat, 6 activités de leadership, 6 adhésions à des associations et 9,8 prix et distinctions. Au fil du temps, on observe que les candidats sont de plus en plus jeunes ; ainsi, la proportion de candidats âgés de 30 ans et plus a diminué de 56 % en 2013 à 9 % en 2017. Conclusion : Les candidats aux programmes de résidence en ORL-CCF au Canada déclarent d’une année à l’autre un nombre élevé d'activités hors programme et sont de plus en plus jeunes. Les étudiants en médecine investissent beaucoup de temps et d'énergie dans ces activités qui vont au-delà du programme d'études officiel. Cela pourrait nuire à la diversité des candidats aux programmes de résidence fortement contingentés, augmenter la probabilité de fausses déclarations dans les demandes de résidence et probablement contribuer à l'épuisement professionnel des étudiants en médecin

Removal of various contaminants from water by renewable lignocellulose-derived biosorbents: a comprehensive and critical review

© 2019, © 2019 Taylor & Francis Group, LLC. Contaminants in water bodies cause potential health risks for humans and great environmental threats. Therefore, the development and exploration of low-cost, promising adsorbents to remove contaminants from water resources as a sustainable option is one focus of the scientific community. Here, we conducted a critical review regarding the application of pristine and modified/treated biosorbents derived from leaves for the removal of various contaminants. These include potentially toxic cationic and oxyanionic metal ions, radioactive metal ions, rare earth elements, organic cationic and anionic dyes, phosphate, ammonium, and fluoride from water media. Similar to lignocellulose-based biosorbents, leaf-based biosorbents exhibit a low specific surface area and total pore volume but have abundant surface functional groups, high concentrations of light metals, and a high net surface charge density. The maximum adsorption capacity of biosorbents strongly depends on the operation conditions, experiment types, and adsorbate nature. The absorption mechanism of contaminants onto biosorbents is complex; therefore, typical experiments used to identify the primary mechanism of the adsorption of contaminants onto biosorbents were thoroughly discussed. It was concluded that byproduct leaves are renewable, biodegradable, and promising biosorbents which have the potential to be used as a low-cost green alternative to commercial activated carbon for effective removal of various contaminants from the water environment in the real-scale plants

Stability of white matter changes related to Huntington's disease in the presence of imaging noise: a DTI study.

Movement artifacts and other sources of noise are a matter of concern particularly in the neuroimaging research of movement disorders such as Huntington's disease (HD). Using diffusion weighted imaging (DWI) and fractional anisotropy (FA) as a compound marker of white matter integrity, we investigated the effect of movement on HD specific changes in magnetic resonance imaging (MRI) data and how post hoc compensation for it affects the MRI results. To this end, we studied by 3T MRI: 18 early affected, 22 premanifest gene-positive subjects, 23 healthy controls (50 slices of 2.3 mm thickness per volume, 64 diffusion-weighted directions (b = 1000 s/mm2), 8 minimal diffusion-weighting (b = 100 s/mm2)); and by 1.5 T imaging: 29 premanifest HD, 30 controls (40 axial slices of 2.3 mm thickness per volume, 61 diffusion-weighted directions (b = 1000 s/mm2), minimal diffusion-weighting (b = 100 s/mm2)). An outlier based method was developed to identify movement and other sources of noise by comparing the index DWI direction against a weighted average computed from all other directions of the same subject. No significant differences were observed when separately comparing each group of patients with and without removal of DWI volumes that contained artifacts. In line with previous DWI-based studies, decreased FA in the corpus callosum and increased FA around the basal ganglia were observed when premanifest mutation carriers and early affected patients were compared with healthy controls. These findings demonstrate the robustness of the FA value in the presence of movement and thus encourage multi-center imaging studies in HD

Solvent-dependent photophysics of a red-shifted, biocompatible coumarin photocage

Controlling the activity of biomolecules with light-triggered photocages is an important research tool in the life sciences. We describe here a coumarin photocage that unusually combines the biocompatible optical properties of strong absorption at a long wavelength close to 500 nm and high photolysis quantum yields. The favourable properties are achieved by synthetically installing on the photocage scaffold a diethyl amino styryl moiety and a thionoester group rather than the lactone typical for coumarins. The photocage's photophysics are analysed with microsecond transient absorption spectroscopy to reveal the nature of the excited state in the photolysis pathway. The excited state is found to be strongly dependent on solvent polarity with a triplet state formed in DMSO and a charge-separated state in water that is likely due to aggregation. A long triplet lifetime is also correlated with a high photolysis quantum yield. Our study on the biocompatible photocage reveals fundamental insight for designing advanced photocages such as longer wavelengths in different solvent conditions tailored for applications in basic and applied research