In Vitro Analysis of Bacterial Morphology by Atomic Force Microscopy of Low Level Laser Therapy 660, 830 and 904 nm

Objective: The objective of this study was to analyze the bacterial morphology by atomic force microscopy (AFM) after the application of low-level laser therapy (LLLT) in in vitro culture of Staphylococcus aureus ATCC 29213. Background data: Infections caused by S. aureus are among the highest occurring in hospitals and can often colonize pressure ulcers. LLLT is among the methods used to accelerate the healing of ulcers. However, there is no consensus on its effect on bacteria. Materials and methods: After being cultivated and seeded, the cultures were irradiated using wavelengths of 660, 830, and 904 nm at fluences of 0, 1, 2, 3, 4, 5, and 16 J/cm(2). Viable cells of S. aureus strain were counted after 24 h incubation. To analyze the occurrence of morphological changes, the topographical measurement of bacterial cells was analyzed using the AFM. Results: The overall assessment revealed that the laser irradiation reduced the S. aureus growth using 830 and 904 nm wavelengths; the latter with the greatest inhibition of the colony-forming units (CFU/mL) (331.1 +/- 38.19 and 137.38 +/- 21.72). Specifically with 660 nm, the statistical difference occurred only at a fluence of 3 J/cm(2). Topographical analysis showed small changes in morphological conformity of the samples tested. Conclusions: LLLT reduced the growth of S. aureus with 830 and 904 nm wavelengths, particularly with 904 nm at a fluence of 3 J/cm(2), where the greatest topographical changes of the cell structure occurred.

Persistent luminescence behavior of materials doped with Eu2+ and Tb3+

In this work, the persistent luminescence mechanisms of Tb3+ (in CdSiO3) and Eu2+ (in BaAl2O4) based on solid experimental data are compared. The photoluminescence spectroscopy shows the different nature of the inter- and intraconfigurational transitions for Eu2+ and Tb3+, respectively. The electron is the charge carrier in both mechanisms, implying the presence of electron acceptor defects. The preliminary structural analysis shows a free space in CdSiO3 able to accommodate interstitial oxide ions needed by charge compensation during the initial preparation. The subsequent annealing removes this oxide leaving behind an electron trap. Despite the low band gap energy for CdSiO3, determined with synchrotron radiation UV-VUV excitation spectroscopy of Tb3+, the persistent luminescence from Tb3+ is observed only with UV irradiation. The need of high excitation energy is due to the position of F-7(6) level deep below the bottom of the conduction band, as determined with the 4f(8)-> 4f(7)5d(1) and the ligand-to-metal charge-transfer transitions. Finally, the persistent luminescence mechanisms are constructed and, despite the differences, the mechanisms for Tb3+ and Eu2+ proved to be rather similar. This similarity confirms the solidity of the interpretation of experimental data for the Eu2+ doped persistent luminescence materials and encourages the use of similar models for other persistent luminescence materials. (C) 2012 Optical Society of America

Environmental effects in kelvin force microscopy of modified diamond surfaces

We have explored the effects of atmospheric environment on Kelvin force microscopy (KFM) measurements of potential difference between different regions of test polycrystalline diamond surfaces. The diamond films were deposited by microwave plasma-assisted chemical vapor deposition, which naturally produces hydrogen terminations on the surface of the films formed. Selected regions were patterned by electron-beam lithography and chemical terminations of oxygen or fluorine were created by exposure to an oxygen or fluorine plasma source. For KFM imaging, the samples were mounted in a hood with a constant flow of helium gas. Successive images were taken over a 5-h period showing the effect of the environment on KFM imaging. We conclude that the helium flow removes water molecules adsorbed on the surface of the samples, resulting in differences in surface potential between adjacent regions. The degree of water removal is different for surfaces with different terminations. The results highlight the importance of taking into account the atmospheric environment when carrying out KFM analysis. (C) 2012 Wiley Periodicals, Inc.

Periodic sterility assessment of materials stored for up to 6 months at continuous microbial contamination risk: Laboratory study

An investigation was conducted to test the hypothesis that the storage time of packaging sterility has no effect on contamination susceptibility even under deliberate bacterial exposure (Serratia marcescens). No growth of the test microorganisms was identified in the experimental group in any of the storage intervals (7, 14, 28, 90, and 180 days). Current recommendations/guidelines suggest that contamination of packaging occurs only because of events. This study, done in vitro, supports these recommendations. Copyright (c) 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Comparative study by computed radiography, histology, and scanning electron microscopy of the articular cartilage of normal goats and in chronic infection with caprine arthritis-encephalitis virus

In the northeast of Brazil, caprine arthritis-encephalitis (CAE) is one of the key reasons for herd productivity decreasing that result in considerable economic losses. A comparative study was carried out using computed radiography (CR), histological analysis (HA), and scanning electronic microscopy (SEM) of the joints of CAE infected and normal goats. Humerus head surface of positive animals presented reduced joint space, increased bone density, and signs of degenerative joint disease (DJD). The carpal joint presented no morphological alterations in CR in any of the animals studied. Tarsus joint was the most affected, characterized by severe DJD, absence of joint space, increased periarticular soft tissue density, edema, and bone sclerosis. Histological analysis showed chronic tissue lesions, complete loss of the surface zone, absence of proteoglycans in the transition and radial zones and destruction of the cartilage surface in the CAE positive animals. Analysis by SEM showed ulcerated lesions with irregular and folded patterns on the joint surface that distinguished the limits between areas of normal and affected cartilage. The morphological study of the joints of normal and CAE positive goats deepened understanding of the alteration in the tissue bioarchitecture of the most affected joints. The SEM finding sustained previous histological reports, similar to those found for rheumatoid arthritis, suggesting that the goat infected with CAE can be considered as a potential model for research in this area.

Color tunability of intense upconversion emission from Er3+-Yb3+ co-doped SiO2-Ta2O5 glass ceramic planar waveguides

This work reports on the infrared-to-visible CW frequency upconversion from planar waveguides based on Er3+-Yb3+-doped 100-xSiO(2)-xTa(2)O(5) obtained by a sol-gel process and deposited onto a SiO2-Si substrate by dip-coating. Surface morphology and optical parameters of the planar waveguides were analyzed by atomic force microscopy and the m-line technique. The influence of the composition on the electronic properties of the glass-ceramic films was followed by the band gap ranging from 4.35 to 4.51 eV upon modification of the Ta2O5 content. Intense green and red emissions were detected from the upconversion process for all the samples after excitation at 980 nm. The relative intensities of the emission bands around 550 nm and 665 nm, assigned to the H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2), and F-4(9/2) -> I-4(15/2) transitions, depended on the tantalum oxide content and the power of the laser source at 980 nm. The upconversion dynamics were investigated as a function of the Ta2O5 content and the number of photons involved in each emission process. Based on the upconversion emission spectra and 1931CIE chromaticity diagram, it is shown that color can be tailored by composition and pump power. The glass ceramic films are attractive materials for application in upconversion lasers and near infrared-to-visible upconverters in solar cells.

Impact of bleaching pine fibre on the fibre/cement interface

The goal of this article was to evaluate the surface characteristics of the pine fibres and its impact on the performance of fibre-cement composites. Lower polar contribution of the surface energy indicates that unbleached fibres have less hydrophilic nature than the bleached fibres. Bleaching the pulp makes the fibres less stronger, more fibrillated and permeable to liquids due to removal the amorphous lignin and its extraction from the fibre surface. Atomic force microscopy reveals these changes occurring on the fibre surface and contributes to understanding the mechanism of adhesion of the resulting fibre to cement interface. Scanning electron microscopy shows that pulp bleaching increased fibre/cement interfacial bonding, whilst unbleached fibres were less susceptible to cement precipitation into the fibre cavities (lumens) in the prepared composites. Consequently, bleached fibre-reinforced composites had lower ductility due to the high interfacial adhesion between the fibre and the cement and elevated rates of fibre mineralization.

Origin of Anomalous Activities for Electrocatalysts in Alkaline Electrolytes

Pt extended surfaces and nanoparticle electrodes are used to understand the origin of anomalous activities for electrocatalytic reactions in alkaline electrolytes as a function of cycling/time. Scanning tunneling microscopy (STM) of the surfaces before and after cycling in alkaline electrolytes was used to understand the morphology of the impurities and their impact on the catalytic sites. The nature of the contaminant species is identified as 3d-transition metal cations, and the formation of hydr(oxy)oxides of these elements is established as the main reason for the observed behavior. We find that, while for the oxygen reduction reaction (ORR) and the hydrogen oxidation reaction (HOR) the blocking of the sites by the undesired 3d-transition metal hydr(oxy)oxide species leads to deactivation of the reaction activities, the CO oxidation reaction and the hydrogen evolution reaction (HER) can have beneficial effects from the same impurities, the latter being dependent on the exact nature of the adsorbing species. These results show the significance of impurities present in real electrolytes and their impact on electrocatalysis.

Characterization of calcium oxide in root perforation sealer materials

Root perforation represents an undesirable complication that may lead to an unfavorable prognosis. The aims of this study were to characterize and to compare the presence of calcium oxide (CaO) on the chemical composition of materials used for root perforation therapy: gray and white mineral trioxide aggregate (MTA) and Portland cement (PC), gray MTA+5%CaO and gray MTA+10%CaO. The last two materials were analyzed to evaluate the increase of CaO in the final sample. CaO alone was used as a standard. Eighteen polyethylene tubes with an internal diameter of 3 mm and 3 mm in length were prepared, filled and then transferred to a chamber with 95% relative humidity and a temperature of 37ºC. The chemical compounds (particularly CaO) and the main components were analyzed by energy-dispersive X-ray microanalysis (EDX). EDX revealed the following concentrations of CaO: gray MTA: 59.28%, white MTA: 63.09%; PC: 72.51%; gray MTA+5%CaO: 63.48% and gray MTA+10%CaO: 67.55%. The tested materials presented different concentrations of CaO. Even with an increase of 5 and 10% CaO in gray MTA, the CaO levels found in the MTA samples were lower than those found in PC.

Sintering and model of thermal residual stress for getting cutting tools from functionally gradient materials

Cutting tools with higher wear resistance are those manufactured by powder metallurgy process, which combines the development of materials and design properties, features of shape-making technology and sintering. The annual global market of cutting tools consumes about US$ 12 billion; therefore, any research to improve tool designs and machining process techniques adds value or reduces costs. The aim is to describe the Spark Plasma Sintering (SPS) of cutting tools in functionally gradient materials, to show this structure design suitability through thermal residual stress model and, lastly, to present two kinds of inserts. For this, three cutting tool materials were used (Al2O3-ZrO2, Al2O3-TiC and WC-Co). The samples were sintered by SPS at 1300 °C and 70 MPa. The results showed that mechanical and thermal displacements may be separated during thermal treatment for analysis. Besides, the absence of cracks indicated coherence between experimental results and the residual stresses predicted.