A novel and economical approach for the synthesis of short rod-shaped mesoporous silica nanoparticles from coal fly ash waste by Bacillus circulans MTCC 6811.

Coal fly ash (CFA) is an industrial byproduct produced during the production of electricity in thermal power plants from the burning of pulverized coal. It is considered hazardous due to the presence of toxic heavy metals while it is also considered valuable due to the presence of value-added minerals like silicates, alumina, and iron oxides. Silica nanoparticles' demands and application have increased drastically in the last decade due to their mesoporous nature, high surface area to volume ratio, etc. Here in the present research work, short rod-shaped, mesoporous silica nanoparticles (MSN) have been synthesized from coal fly ash by using Bacillus circulans MTCC 6811 in two steps. Firstly, CFA was kept with the bacterial culture for bioleaching for 25 days in an incubator shaker at 120 rpm. Secondly, the dissolved silica in the medium was precipitated with the 4 M sodium hydroxide to obtain a short rod-shaped MSN. The purification of the synthesized silica particle was done by treating them with 1 M HCl at 120 °C, for 90 min. The synthesized short rod-shaped MSN were characterized by UV-vis spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Particle size analyzer (PSA), Field emission scanning electron microscopy (FESEM), and transmission electron microscope. The microscopic techniques revealed the short rod-shaped mesoporous silica nanoparticles (MSN) for the final nano-silica, whose size varies from 40 to 80 nm, with an average size of 36 ± 5 nm. The XRD shows the crystalline nature of the synthesized MSN having a crystallite size of 36 nm. The FTIR showed the three characteristic bands in the range of 400-1100 cm-1, indicating the purity of the sample. The energy dispersive X-ray (EDX) showed 53.04 wt% oxygen and 43.42% Si along with 3.54% carbon in the final MSN. The particle size analyzer revealed that the average particle size is 368.7 nm in radius and the polydispersity index (PDI) is 0.667. Such a novel and economical approach could be helpful in the synthesis of silica in high yield with high purity from coal fly ash and other similar waste.

A Low-Cost Humidity Control System to Protect Microscopes in a Tropical Climate.

Introduction: A clean and functional microscope is necessary for accurate diagnosis of infectious diseases. In tropical climates, high humidity levels and improper storage conditions allow for the accumulation of debris and fungus on the optical components of diagnostic equipment, such as microscopes. Objective: Our objective was to develop and implement a low-cost, sustainable, easy to manage, low-maintenance, passive humidity control chamber to both reduce debris accumulation and microbial growth onto the optical components of microscopes. Methods: Constructed from easily-sourced and locally available materials, the cost of each humidity control chamber is approximately $2.35 USD. Relative humidity levels were recorded every 30 minutes over a period of 10 weeks from two chambers deployed at the Belize Vector and Ecology Center and the University of Belize. Results: The humidity control chamber deployed at the University of Belize maintained internal relative humidity at an average of 35.3% (SD = 4.2%) over 10 weeks, while the average external relative humidity was 86.4% (SD = 12.4%). The humidity control chamber deployed at the Belize Vector and Ecology Center effectively maintained internal relative humidity to an average of 54.5% (SD = 9.4%) over 10 weeks, while the average external relative humidity was 86.9% (SD = 12.9%). Conclusions: Control of relative humidity is paramount for the sustainability of medical equipment in tropical climates. The humidity control chambers reduced relative humidity to levels that were not conducive for fungal growth while reducing microscope contamination from external sources. This will likely extend the service life of the microscopes while taking advantage of low-cost, locally sourced components.

Synthesis Mechanism and Thermal Optimization of an Economical Mesoporous Material Using Silica: Implications for the Effective Removal or Delivery of Ibuprofen.

Mesoporous silica materials (MSMs) were synthesized economically using silica (SiO2) as a precursor via a modified alkaline fusion method. The MSM prepared at 500°C (MSM-500) had the highest surface area, pore size, and volume, and the results of isotherms and the kinetics of ibuprofen (IBP) removal indicated that MSM-500 had the highest sorption capacity and fastest removal speed vs. SBA-15 and zeolite. Compared with commercial granular activated carbon (GAC), MSM-500 had a ~100 times higher sorption rate at neutral pH. IBP uptake by MSM-500 was thermodynamically favorable at room temperature, which was interpreted as indicating relatively weak bonding because the entropy (∆adsS, -0.07 J mol(-1) K(-1)) was much smaller. Five times recycling tests revealed that MSM-500 had 83-87% recovery efficiencies and slower uptake speeds due to slight deformation of the outer pore structure. In the IBP delivery test, MSM-500 drug loading was 41%, higher than the reported value of SBA-15 (31%). The in vitro release of IBP was faster, almost 100%, reaching equilibrium within a few hours, indicating its effective loading and unloading characteristics. A cost analysis study revealed that the MSM was ~10-70 times cheaper than any other mesoporous silica material for the removal or delivery of IBP.

Lead sorption performance on active silica derived from fly ash.

The object of this study was to estimate the sorption property of active silica derived from fly ash after separation of silica and aluminum. The specific surface area of active silica enlarged to 115 m(2)/g was compared with the original fly ash (4 m(2)/g). Field emission scanning electron microscopy displayed the active silica, which looked like a honeycomb or curly layer with many lamellae that formed many mesopores. The uptake kinetics indicated that the residual concentration of Pb(2+) in the aqueous solution decreased rapidly from the initial 1.25 mg/L to less than 10 µg/L within 45 min. The removal efficiency of Pb(2+) on active silica was pH dependent. The increase in pH value promoted Pb(2+) removal because the negative surface provided more electrostatic attraction sites. A stepwise non-linear isotherm was obtained because the lamellae of active silica provided a heterogeneous surface with various kinds of active sites. The maximum sorption amount of Pb on active silica was more than 90 mg/g, which was better than some pristine-activated carbon.

Análise de custo-efetividade de métodos preventivos para superfície oclusal de acordo com o risco de cárie: resultados de um ensaio clínico controlado / Cost-effectiveness analysis of preventive methods for occlusal surface according to caries risk: results of a controlled clinical trial / Análisis del coste-efectividad de los métodos preventivos para una superficie oclusal según el riesgo de caries: resultados de un ensayo clínico controlado

Este estudo apresenta o resultado de uma avaliação de custo-efetividade conduzida ao longo de um ensaio clínico controlado para avaliar a efetividade do selamento com ionômero de vidro modificado por resina (Vitremer, 3M ESPE) e da aplicação de verniz fluoretado (Duraphat, Col-gate) em superfícies oclusais de primeiros molares permanentes, em crianças de 6 a 8 anos (N = 268), segundo o risco de cárie (alto risco; baixo risco). As crianças foram examinadas semestralmente, ao longo de 24 meses, pelo mesmo dentista calibrado, após alocação em seis grupos: controle alto risco e baixo risco (educação em saúde bucal trimestral); verniz alto risco e baixo risco (educação em saúde bucal trimestral + aplicação semestral de verniz); e selante alto risco e baixo risco (educação em saúde bucal trimestral + única aplicação do selante). A análise mostrou que o selamento de primeiros molares permanentes em crianças de alto risco apresentou razão de C/E de R$ 225,21(US$ 119,80) por superfície oclusal salva, e razão incremental de C/E de R$ 203,71(US$ 108,36) por superfície oclusal adicional salva. Conclui-se que uma única aplicação de selante, em escolares de alto risco, foi a intervenção mais custo-efetiva.

This study presents the results of a cost-effectiveness analysis in a controlled clinical trial on the effectiveness of a modified glass ionomer resin sealant ( Vitremer, 3M ESPE) and the application of fluoride varnish (Duraphat, Colgate) on occlusal surfaces of first permanent molars in children 6-8 years of age (N = 268), according to caries risk (high versus low). Children were examined semiannually by the same calibrated dentist for 24 months after allocation in six groups: high and low risk controls (oral health education every three months); high and low risk with varnish (oral health education every three months + varnish biannually); and high and low risk with sealant (oral health education every three months + a single application of sealant). Economic analysis showed that sealing permanent first molars of high-risk schoolchildren showed a C/E ratio of US$ 119.80 per saved occlusal surface and an incremental C/E ratio of US$ 108.36 per additional saved occlusal surface. The study concluded that sealing permanent first molars of high-risk schoolchildren was the most cost-effective intervention.

En este estudio se presentan los resultados de una evaluación de costo-efectividad (C/E) durante un ensayo clínico controlado para evaluar la efectividad de la obturación con ionómero de vidrio modificado con resina (Vitremer, 3M ESPE) y la aplicación de barniz de flúor (Duraphat, Colgate) en las superficies oclusales de los primeros molares permanentes, para niños de 6-8 años (N = 268) de edad, de acuerdo con el riesgo de caries (alto riesgo-bajo riesgo). Los niños fueron examinados cada seis meses por el mismo dentista calibrado, durante 24 meses, después de haberle sido asignados seis grupos: control alto riesgo y bajo riesgo (educación de salud bucal cada tres meses); barniz alto riesgo y bajo riesgo (educación de salud bucal cada tres meses + barniz semestralmente); obturación alto riesgo y bajo riesgo (educación de salud bucal cada tres meses + una sola aplicación de ionómero de vidrio). El análisis económico mostró que la obturación de los primeros molares permanentes de escolares de alto riesgo presenta una relación C/E de US$ 119.80 de ahorro por superficie oclusal y una ratio C/E incremental de US$ 108.36 de ahorro adicional por superficie oclusal.

[Cost-effectiveness analysis of preventive methods for occlusal surface according to caries risk: results of a controlled clinical trial]. / Análise de custo-efetividade de métodos preventivos para superfície oclusal de acordo com o risco de cárie: resultados de um ensaio clínico controlado.

This study presents the results of a cost-effectiveness analysis in a controlled clinical trial on the effectiveness of a modified glass ionomer resin sealant ( Vitremer, 3M ESPE) and the application of fluoride varnish (Duraphat, Colgate) on occlusal surfaces of first permanent molars in children 6-8 years of age (N = 268), according to caries risk (high versus low). Children were examined semiannually by the same calibrated dentist for 24 months after allocation in six groups: high and low risk controls (oral health education every three months); high and low risk with varnish (oral health education every three months + varnish biannually); and high and low risk with sealant (oral health education every three months + a single application of sealant). Economic analysis showed that sealing permanent first molars of high-risk schoolchildren showed a C/E ratio of US$ 119.80 per saved occlusal surface and an incremental C/E ratio of US$ 108.36 per additional saved occlusal surface. The study concluded that sealing permanent first molars of high-risk schoolchildren was the most cost-effective intervention.

A cost-effective growth of SiO(x) thin films by reactive sputtering: photoluminescence tuning.

We present a new cost-effective method to produce substoichiometric SiO2 thin films by means of a simple sputter-coater operated at a base pressure of 1 x 10(-3) mbar. During sputtering air is introduced through a fine valve so that the sputtering gas is a mixture of air/Ar. High-resolution electron microscopy shows the formation of amorphous SiO(x) thin films for the as-deposited samples. The index x approaches 1 when the ratio of the partial pressure of air/Ar tends to 0.1. On the other hand, pure silica is formed when the ratio of the partial pressure of air/Ar approaches 0.5. The films in the as-deposited state show intense green-yellow photoluminescence. This fades away with short annealing under air at 950 degrees C. If on the other hand, prolonged annealing is performed under Argon atmosphere at 1000 degrees C, red-infrared photoluminescence is recorded due to the formation of Si nanocrystals embedded in SiO2. This simple method could be suitable for the production of thin SiO(x) films with embedded nanocrystals for optoelectronic or photovoltaic applications.

Fishing for ancient DNA.

The major problems concerning ancient DNA studies are related to the amount of extractable DNA and the precautions needed to avoid contamination. From the very first step of the analyses, the DNA extraction, these problems must be confronted. There are several extraction methods available for DNA in ancient tissue; several of them are complicated and time consuming, and none of the methods have reached an acceptance level such that they are routinely used on a widespread basis. Here we investigate the efficiency of two methods, one based on magnetic separation of the targeted molecules, and one based on silica binding. The efficiency rate of these two on the material studied seems to be identical. The silica binding method has the benefit of relative simplicity, but the magnetic separation technique also has advantages. For example, it is possible to reuse the extract several times for different loci, and it is possible to concentrate all extracted DNA from one locus into one PCR.

A low cost route to hexagonal mesostructured carbon molecular sieves.

A mesoporous carbon molecular sieve with a hexagonal framework structure (denoted C-MSU-H) has been prepared using a MSU-H silica template that can be assembled from a low cost soluble silicate precursor at near-neutral pH conditions.