ABSTRACT
Miniature batteries can accelerate the development of mobile electronics by providing sufficient energy to power small devices. Typical microbatteries commonly use thin-film inorganic electrodes based on Li-ion insertion reaction. However, they rely on the complicated thin-film synthesis method of inorganics containing many elements. Graphene, one atomic layer thick carbon sheet, has diverse physical and chemical properties and is compatible with conventional micron-scale device fabrication. Here, we study the use of chemical vapor deposition (CVD) grown monolayer graphene in a two-dimensional configuration, as a future Li-oxygen microbattery cathode. By maximizing the dissolution of discharge intermediates, we obtain 2610 Ah/ggraphene of capacity corresponding to 20% higher areal cathode energy density and 2.7 times higher cathode specific energy than that can be derived from the same volume or mass of conventional Li-ion battery cathode material. Furthermore, a clear observation on the discharge reaction on composite electrodes and their role in the charging reaction was made, thanks to the two-dimensional monolayer graphene Li-oxygen battery cathode. We demonstrate an easy integration of two-dimensional CVD graphene cathode into microscale devices by simply transferring or coating the target device substrate with flexible graphene layers. The ability to integrate and use monolayer graphene on arbitrary device substrates as well as precise control over a chemical derivation of the carbon interface can have a radical impact on future energy-storage devices.
ABSTRACT
AIM: To determine the validity and the reliability of the Prenatal Breastfeeding Self-Efficacy Scale. MATERIAL AND METHODS: This was a methodologic study. The sample of the research comprised 200 pregnant women who presented to the outpatient clinic of Gynecology between April and June 2015. An introductory information form and the Prenatal Breast Self-Efficacy Scale were used to collect the data. In the analysis of the data, descriptive statistics, content validity index for coverage validity, exploratory factor analysis, and confirmatory factor analysis for construct validity, and Cronbach-alfa α for reliability were used. RESULTS: In the explanatory factor analysis of the scale, the Kaiser-Meyer-Olkin floor number was 0.84 and the Barlett's sphericity test results were χ2=1812.608; df=171; p<0.001. The contribution of the factors to total variance was 59.06%. According to confirmatory factor analysis of the scale, the Chi-square test result was as follows: χ2=254.23 (p<0.001, SD=146). The model fit indices were as follows: χ2/SD=1.74, Root Mean Square Error of Approximation=0.06, Comparative Fit Index=0.96, Normed Fit Index=0.92, Non-Normed Fit Index=0.96, Goodness of Fit Index=0.88 and Adjusted Goodness of Fit Index=0.85. The internal consistency reliability coefficient of Prenatal Breastfeeding Self-Efficacy Scale was 0.86. CONCLUSION: The Prental Breastfeeding Self-Efficacy Scale is a valid and reliable scale which is applicable to Turkish culture and an appropriate tool which can be used by all healthcare workers who wish to design and evaluate interventions to support breastfeeding in the prenatal period.
ABSTRACT
Synthetic porogens provide an easy way to create porous structures, but their usage is limited due to synthetic difficulties, process complexities and prohibitive costs. Here we investigate the use of bacteria, sustainable and naturally abundant materials, as a pore template. The bacteria require no chemical synthesis, come in variable sizes and shapes, degrade easier and are approximately a million times cheaper than conventional porogens. We fabricate free standing porous multiwalled carbon nanotube (MWCNT) films using cultured, harmless bacteria as porogens, and demonstrate substantial Li-oxygen battery performance improvement by porosity control. Pore volume as well as shape in the cathodes were easily tuned to improve oxygen evolution efficiency by 30% and double the full discharge capacity in repeated cycles compared to the compact MWCNT electrode films. The interconnected pores produced by the templates greatly improve the accessibility of reactants allowing the achievement of 4,942 W/kg (8,649 Wh/kg) at 2 A/ge (1.7 mA/cm2).
