Revealing instability and irreversibility in nonaqueous sodium–O2 battery chemistry

2016 ◽  
Vol 52 (62) ◽  
pp. 9691-9694 ◽  
Author(s):  
Sayed Youssef Sayed ◽  
Koffi P. C. Yao ◽  
David G. Kwabi ◽  
Thomas P. Batcho ◽  
Chibueze V. Amanchukwu ◽  
...  
Keyword(s):  
Particle Size ◽  
Exposure Time

Charging kinetics and reversibility of Na–O2 batteries can be influenced greatly by the particle size of NaO2 formed upon discharge, and exposure time (reactivity) of NaO2 to the electrolyte.

scholarly journals Eco-friendly microwave-enhanced green synthesis of silver nanoparticles using Aloe vera leaf extract and their physico-chemical and antibacterial studies

2018 ◽  
Vol 7 (3) ◽  
pp. 231-240 ◽  
Author(s):  
Omid Ahmadi ◽  
Hoda Jafarizadeh-Malmiri ◽  
Naeimeh Jodeiri
Keyword(s):  
Particle Size ◽  
Silver Nanoparticles ◽  
Exposure Time ◽  
Leaf Extract ◽  
Aloe Vera ◽  
Synthesis Conditions ◽  
Stabilizing Agents ◽  
Microwave Exposure ◽  
Mean Particle Size ◽  
Vis Spectroscopy

Abstract Silver nanoparticles (AgNPs) were synthesized using Aloe vera leaf extract as both reducing and stabilizing agents via microwave irradiation method. The effects of the microwave exposure time and the amount of AgNO3 solution on the mean particle size and concentration of the synthesized AgNPs solution were investigated using response surface methodology. The synthesized AgNPs were characterized by transmission electron microscopy, UV-Vis spectroscopy, and dynamic light scattering. Well-dispersed and spherically fabricated AgNPs with mean particle size (46 nm) and maximum concentration (64 ppm) and zeta potential (+15.5 mV), were obtained at optimal synthesis conditions, using 9 ml of AgNO3 (1 mm) and 0.1 ml of Aloe vera extract during microwave exposure time of 360 s. The antibacterial activity of the synthesized AgNPs was tested using Escherichia coli and Staphylococcus aureus bacteria and the obtained results indicated their significant inhibitory effects against these two Gram-negative and Gram-positive bacteria.

Influence of the partial substitution of fine aggregate by granite powder in mortar on the process of natural carbonation

2019 ◽  
Vol 38 (3) ◽  
pp. 254-262 ◽  
Author(s):  
Júlio Lopes da Silva ◽  
Daniel Baracuy da Cunha Campos ◽  
Alberto Casado Lordsleem ◽  
Yeda Vieira Povoas
Keyword(s):  
Particle Size ◽  
Exposure Time ◽  
Time Variable ◽  
Partial Substitution ◽  
Fine Aggregate ◽  
Carbonation Depth ◽  
Experimental Planning ◽  
Carbonation Process ◽  
Granite Powder ◽  
Natural Carbonation

This article presents an evaluation of the influence on the natural carbonation process of the use of granite cutting residue as a replacement for fine aggregate in mortars. The methodology adopted consisted of replacing the fine aggregate with granite cutting residue, analysing the carbonation depth with the aid of an experimental planning matrix of 23 + 3 repetitions at the central point. The influence of the exposure time, the percentage of residue in the mixture, and the particle size of the residue used were evaluated. The exposure time variable was found to have the greatest influence on the carbonation process. Under the conditions analysed, granite residue was found to be beneficial, reducing the carbonation depth.

Microwave Accelerated Green Synthesis of Gold Nanoparticles Using Gum Arabic and their Physico-Chemical Properties Assessments

2018 ◽  
Vol 232 (3) ◽  
pp. 325-343 ◽  
Author(s):  
Maryam Eskandari-Nojehdehi ◽  
Hoda Jafarizadeh-Malmiri ◽  
Abbas Jafarizad
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Gold Nanoparticles ◽  
Exposure Time ◽  
Chemical Properties ◽  
Gum Arabic ◽  
Au Nps ◽  
Synthesis Conditions ◽  
Microwave Exposure ◽  
Physico Chemical

AbstractMicrowave enhanced gold nanoparticles (Au NPs) were synthesized using gum Arabic as both reducing and stabilizing agents. Response surface methodology was applied to study effects of the Au NPs synthesized parameters, namely, microwave exposure time (90–180 s) and the amount of AgNO3solution (1–10 mL) on the mean particle size, mixture solution color and concentration of the synthesized Au NPs. The colloidal solution containing well-dispersed and spherical fabricated Au NPs with mean particle size (22 nm) and maximum concentration (159 ppm) and color (1.12 absorbance unit, a.u.), were obtained at the optimal synthesis conditions, using 8.17 mL of HAuCl4(1 mM) and 2 mL of gum Arabic solution (4% w/v) during microwave exposure time of 180 s. The physico-chemical properties of the synthesized Au NPs at obtained optimum synthesis conditions were characterized by Fourier transform-infrared spectroscopy, UV-Vis spectroscopy, dynamic light scattering, X-ray diffraction, transmission electron microscopy and field emission scanning electron microscopy.

Effect of exposure time, particle size and uptake pathways in immune cell lysosomal cytotoxicity of mussels exposed to silver nanoparticles

2017 ◽  
Vol 41 (2) ◽  
pp. 169-174 ◽  
Author(s):  
Younes Bouallegui ◽  
Ridha Ben Younes ◽  
Faten Turki ◽  
Amine Mezni ◽  
Ridha Oueslati
Keyword(s):  
Particle Size ◽  
Silver Nanoparticles ◽  
Exposure Time ◽  
Immune Cell

An Engineering Approach Investigating the Uptake and Phytotoxicity of One Type of Engineered Nanoparticle (CdSe/ZnS Quantum Dots) by Solanum Lycopersicum

2013 ◽  
Author(s):  
Lynsey A. M. Salverson ◽  
Nader Saniei ◽  
Mel Mendelson ◽  
Michelle Lum
Keyword(s):  
Quantum Dots ◽  
Particle Size ◽  
Solanum Lycopersicum ◽  
Exposure Time ◽  
Engineered Nanoparticles ◽  
Water Soluble ◽  
Microscopy Imaging ◽  
Tomato Seedlings ◽  
Time Interaction ◽  
Tomato Seeds

The novel and extraordinary physiochemical properties of engineered nanoparticles (ENPs) is certain, yet, at the same time, their unique characteristics raise growing concerns regarding potentially adverse effects on biological and ecological systems. It is becoming increasingly evident, that before the full potential of nanotechnology can be realized, standardized characterization of ENPs behavior, fate, and their effects in the ecosystem are essential, to ensure the safe manufacturing and use of ENP products. Otherwise, the promise of such extraordinary advancements may find itself limited to applications such as electronics, and sporting equipments, industries in which it currently resides. The current toxicity profile of engineered nanomaterials is not only preliminary, but highly variable amongst researchers. Emphasizing the great need to develop a highly organized, efficient, and precise approach to assess the hazardous potential ENPs may pose, and address the safety concerns surrounding and limiting nanotechnology. In response to such concerns, the present study took an engineering approach, in an otherwise traditionally viewed discipline, to assess the potential impact of engineered nanoparticles on tomato (Solanum lycopersicum) seedlings, by implementing a full factorial design of experiment (FDOE) in an effort to identify what factors, and their interactions, have a significant (p ≤ 0.05) effect on root and shoot elongation, and if any observed effects are a result of particle uptake, evaluated via fluorescence microscopy imaging. Therefore, the goal of our study was to design and implement an efficient, effective, and precise method to assess the effect of one type of ENP, water-soluble CdSe/ZnS quantum dots, using Solanum lycopersicum as our model organism, one of 10 species recommended by the Unites States Environmental Protection Agency (US EPA) for use in phytotoxicity studies, via a methodology we believe novel to nanotechnology. By implementing factorial experimental design methodologies, not only are we efficiently identifying the factors that affect phytotoxicity, we are providing, for the first time to our knowledge, the first scientific data to report the significant interaction effects between the factors responsible for ENP toxicity. Water soluble (MUA) CdSe/ZnS quantum dots used in our study had a negative influence on root and shoot lengths of tomato seeds exposed for 3 and 6 days. The observed influence depended on (MUA) CdSe/ZnS concentration and QD exposure time. The importance of the factor effects were examined via analysis of variance (ANOVA), t-tests, confidence intervals, and normal plot statistical analyses. The findings concluded that factors B, C, and the BC-interaction (CdSe/ZnS: Exposure time, concentration, and exposure time–concentration interaction) significantly (p ≤ 0.05) affected root and shoot lengths of tomato seedlings. Thus, factors A, AB, AC, and ABC (CdSe/ZnS QD: Size, size–concentration, size-exposure time, and size-concentration-exposure time interactions) were not found to have a significant effect on root and shoot lengths of tomato seedlings, and ultimately eliminated from our model. After analyzing the interaction plots, it became evident that low percentages of root reduction are obtained at low concentration levels for short lengths of time; thus, to obtain the least amount of phytotoxic effects one would set factors B (concentration) and C (exposure time) to their low levels, 125 mg/L for 3 days, respectively. Alternatively, high percentages of root reduction are obtained at high concentration levels for long lengths of time; thus, to obtain the greatest phytotoxic effect one would set factors B and C to their high levels, 1000 mg/L for 6 days, respectively. This indicates that as exposure time increases, root reduction increases; thus, phytotoxicity increases. Since our study attempted to realize which factors minimize phytotoxicity effects of one type of ENP, these findings suggest that to minimize phytotoxicity effects (i.e. maximize root length or minimize percent of root reduction) of (MUA) CdSe/ZnS QDs on tomato seeds, set factors B and C (QD concentration and exposure time) to their low levels; that is, expose tomato seeds to 125 mg/L of QD solution for a maximum of 3 days. These settings will yield the least amount of root reduction (5.15%) and; thus, phytotoxicity effects will be minimized. With regard to tomato roots ability to uptake MUA QDs, our results contribute to the literature by reporting uptake possible. Although we did see particles inside the root, it was sporadic and difficult to quantify. As to whether it was intracellular (within the cell) or intercellular (in the spaces between the cells, i.e., outside the cells) we could not conclude with certainty, although we suspect the QDs were intercellular. Thus, we highly recommend future experiments involving cross sections and more in-depth microscopy imaging. Additionally, although the results of our experiment failed to support that particle size (t = 2.13; d.f. = 1; p = 0.065) or the particle size-exposure time interaction (t = 2.17; d.f. = 1; p = 0.062) had a significant effect on root and shoot lengths of tomato seedlings, due to the small p-value associated with both test statistics, it is our belief that particle size and the particle size-exposure time interaction may, in fact, be a real effect; thus, further investigation is recommended.

Progress In The Practical Application Of Automated Image Analysis To Tem Negatives

1977 ◽  
Vol 35 ◽  
pp. 214-217
Author(s):  
F. A. Heckman ◽  
E. Redman ◽  
J.E. Connolly
Keyword(s):  
Image Analysis ◽  
Image Quality ◽  
Exposure Time ◽  
Image Contrast ◽  
Automated Image Analysis ◽  
Practical Application ◽  
Factors Affecting ◽  
High Image Quality ◽  
Qualitative Evidence ◽  
Comprehensive Study

In our initial publication on this subject1) we reported results demonstrating that contrast is the most important factor in producing the high image quality required for reliable image analysis. We also listed the factors which enhance contrast in order of the experimentally determined magnitude of their effect. The two most powerful factors affecting image contrast attainable with sheet film are beam intensity and KV. At that time we had only qualitative evidence for the ranking of enhancing factors. Later we carried out the densitometric measurements which led to the results outlined below.Meaningful evaluations of the cause-effect relationships among the considerable number of variables in preparing EM negatives depend on doing things in a systematic way, varying only one parameter at a time. Unless otherwise noted, we adhered to the following procedure evolved during our comprehensive study:Philips EM-300; 30μ objective aperature; magnification 7000- 12000X, exposure time 1 second, anti-contamination device operating.

Structure images of Si, Ge and Mos2 crystals and some application to radiation damage studies

1978 ◽  
Vol 36 (1) ◽  
pp. 292-293 ◽  
Author(s):  
K. Izui ◽  
T. Nishida ◽  
S. Furuno ◽  
H. Otsu ◽  
S. Kuwabara
Keyword(s):  
Radiation Damage ◽  
Exposure Time ◽  
Gaussian Distribution ◽  
Intensity Distribution ◽  
Chromatic Aberration ◽  
Magnetic Lens

Recently we have observed the structure images of silicon in the (110), (111) and (100) projection respectively, and then examined the optimum defocus and thickness ranges for the formation of such images on the basis of calculations of image contrasts using the n-slice theory. The present paper reports the effects of a chromatic aberration and a slight misorientation on the images, and also presents some applications of structure images of Si, Ge and MoS2 to the radiation damage studies.(1) Effect of a chromatic aberration and slight misorientation: There is an inevitable fluctuation in the amount of defocus due to a chromatic aberration originating from the fluctuations both in the energies of electrons and in the magnetic lens current. The actual image is a results of superposition of those fluctuated images during the exposure time. Assuming the Gaussian distribution for defocus, Δf around the optimum defocus value Δf0, the intensity distribution, I(x,y) in the image formed by this fluctuation is given by

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