Design and analysis of single-factor experiments: Analysis of variance of the effect of rice husk ash and commercial fillers in NR compounds

Summary White rice husk ash (WRHA) and black rice husk ash (BRHA) were incorporated into natural rubber (NR) using a laboratory-sized two-roll mill. A conventional vulcanization system was used for curing and physical tests of the NR vulcanized involved determining of tensile and tear resistances. For comparison purposes, precipitated silica (Zeosil-175) and carbon black (N774) were used too. Using the analysis of variance of single-factor experiments, it can be concluded that: BRHA is non-reinforcing filler and its use is limited to 20 phr; WRHA is semi-reinforcing filler and the variation of filler loading (0 up to 50 phr) causes the maximum variation upon tensile strength of NR compounds; and, that although carbon black and silica are reinforcing fillers, a real reinforcement is reached up to 20 phr for tensile strength.     

Hydrogels containing silver nanoparticles for burn wounds show antimicrobial activity without cytotoxicity

This research introduces a novel dressing for burn wounds, containing silver nanoparticles in hydrogels for infected burn care. The 2‐acrylamido‐2‐methylpropane sulfonic acid sodium salt hydrogels containing silver nanoparticles have been prepared via ultraviolet radiation. The formation of silver nanoparticles was monitored by surface plasmon bands and transmission electron microscopy. The concentration of silver nitrate loaded in the solutions slightly affected the physical properties and mechanical properties of the neat hydrogel. An indirect cytotoxicity study found that none of the hydrogels were toxic to tested cell lines. The measurement of cumulative release of silver indicated that 70%–82% of silver was released within 72 hr. The antibacterial activities of the hydrogels against common burn pathogens were studied and the results showed that 5 mM silver hydrogel had the greatest inhibitory activity. The results support its use as a potential burn wound dressing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40215.     

Classifying flexible measures in data envelopment analysis: A slack-based measure

Data envelopment analysis (DEA) has gained a wide range of applications in measuring comparative efficiency of decision making units (DMUs) with multiple incommensurate inputs and outputs. The standard DEA method requires that the status of all input and output variables be known exactly. However, in many real applications, the status of some measures is not clearly known as inputs or outputs. These measures are referred to as flexible measures. This paper proposes a flexible slacks-based measure (FSBM) of efficiency in which each flexible measure can play input role for some DMUs and output role for others to maximize the relative efficiency of the DMU under evaluation. Further, we will show that when an operational unit is efficient in a specific flexible measure, this measure can play both input and output roles for this unit. In this case, the optimal input/output designation for flexible measure is one that optimizes the efficiency of the artificial average unit. An application in assessing UK higher education institutions used to show the applicability of the proposed approach.     

Electrochemical study of corrosion inhibition of steel reinforcement in alkaline solutions containing phosphates based components

The aim of this study is to investigate the viability of use of sodium phosphate (Na₃PO₄: SP), tetrasodium pyrophosphate (Na₄P₂O₇: TSPP) and hydroxyethylidene-diphosphonic acid (C₂H₈O₇P₂: HEDP) as a non-toxic corrosion inhibitors of steel bars in alkaline media which simulate the electrolyte in the concrete pores. The effectiveness of these phosphate compounds as corrosion inhibitors was investigated by measuring the corrosion potentials, the polarization curves, the corrosion current densities, and the electrochemical impedance spectroscopy of steel bars immersed for 30 days in saturated Ca(OH)₂ solutions with and without chlorides. At the completion of the tests, the mass losses were determined in order to verify the reliability of the electrochemical results. The results showed that phosphate compounds form a protective layer on the steel surface when immersed in alkaline solution without chlorides. In the presence of chloride ions, the SP acts as an anodic inhibitor and reduces the corrosion activity on steel. The HEDP shows lower efficiency, probably due to the decrease of the pH and to the high [Cl⁻]/[inh] ratio used. Results obtained by electrochemical and gravimetric methods are in quite reasonable agreement.     

Surface-Enhanced Raman Scattering (SERS) of Microorganisms

Normal Raman (NR) spectra and surface-enhanced Raman scattering (SERS) spectra were obtained for the bacterium Escherichia coli and were compared with those of two other microorganisms, Haloferax volcanii and Thiobacillus neapolitanus. It was found that at 514 nm the SERS of E. coli was similar to that of flavin adenine dinucleotide (FAD). Upon increasing the excitation wavelength, contributions from other cell components became evident, and they were attributed to nicotinamide adenine dinucleotide (NAD) or other adenine-containing molecules in the bacterium. A comprehensive study of FAD, riboflavin (RF), NAD, and adenine under various experimental conditions was thus performed to shed light on the features in the SERS obtained for E. coli. Comparison of NR and SERS measurements of the various samples enabled a better understanding of the SERS spectra and their sensitivity to the specific experimental conditions (excess metal ion concentration and laser excitation wavelengths and intensity). It was concluded that SERS is a highly sensitive technique and that careful examination of the spectra can provide important chemical information.     

Efficient and mild synthesis of ortho-hydroxyaryl ketones catalyzed by zinc chloride under solvent-free condition and microwave irradiation

Preparation of ortho-hydroxyaryl ketones was regioselectively carried out from phenol and naphthol derivatives, in reaction with various organic acids by using a ZnCl₂ as catalyst, under microwave and solvent-free mild conditions. In this reaction, the products were obtained in very high yields and very short reaction times.     

Moisture absorption by epoxy resins: The reverse thermal effect

Experiments are reported on the variations in moisture absorption properties of an epoxy resin produced by sudden changes in temperature. Where the temperature change occurred when only a little water had been absorbed, the change in moisture absorption was determined by the change in diffusivity. Where a temperature change occurred when near saturation, a reverse thermal effect was observed. An attempt has been made to understand the results in terms of thermodynamics. Results obtained for the swelling changes accompanying sudden changes in moisture content suggest that it is the more tightly bound water in the polymer which takes part in the reverse thermal effect.     

Comparison and validation of tissue modelization and statistical classification methods in T1-weighted MR brain images

This paper presents a validation study on statistical nonsupervised brain tissue classification techniques in magnetic resonance (MR) images. Several image models assuming different hypotheses regarding the intensity distribution model, the spatial model and the number of classes are assessed. The methods are tested on simulated data for which the classification ground truth is known. Different noise and intensity nonuniformities are added to simulate real imaging conditions. No enhancement of the image quality is considered either before or during the classification process. This way, the accuracy of the methods and their robustness against image artifacts are tested. Classification is also performed on real data where a quantitative validation compares the methods' results with an estimated ground truth from manual segmentations by experts. Validity of the various classification methods in the labeling of the image as well as in the tissue volume is estimated with different local and global measures. Results demonstrate that methods relying on both intensity and spatial information are more robust to noise and field inhomogeneities. We also demonstrate that partial volume is not perfectly modeled, even though methods that account for mixture classes outperform methods that only consider pure Gaussian classes. Finally, we show that simulated data results can also be extended to real data.     

Calcium lactate effect on the shelf life of osmotically dehydrated guavas

The effect of calcium lactate on osmodehydrated guavas in sucrose and maltose solutions was monitored during storage under passive modified atmosphere for 24 d at 5 °C. Sample texture and color characteristics, microbial spoilage, sensory acceptance, structural changes, and gas composition inside the packages were periodically evaluated. Calcium lactate inhibited microbial growth on guavas, with yeast and mold counts in the order of 10(2) CFU/g throughout storage. The calcium salt reduced respiration rate of guava products, showing O(2) and CO(2) concentrations around 18% and 3% inside the packages. A firming effect on fruit texture, with up to 5 and 2 times higher stress and strain at failure values and tissue structure preservation could also be attributed to calcium lactate use. However, fruits treated with calcium lactate, osmodehydrated in maltose and sucrose solutions, showed sensory acceptance scores below the acceptability limit (4.5) after 13 and 17 d of storage, respectively.