Surface amorphization in diamond turning of silicon crystal investigated by transmission electron microscopy

Silicon crystal exhibits a ductile regime during machining prior to the onset of fracture when appropriate cutting conditions are applied. The present study shows that the ductile regime is a result of a phase transformation which is indirectly evidenced by the amorphous phase detected in the machined surface. Transmission electron microscopy (TEM) planar view studies were successfully performed on monocrystalline silicon (1 0 0) single point diamond turned. TEM electron diffraction patterns show that the machined surface presents diffuse rings along with traces of crystalline material. This is attributed to crystalline silicon immersed in an amorphous matrix. Furthermore, only diffuse rings in the diffraction patterns of the ductile chip are detected, indicating that it is totally amorphous. © 2000 Elsevier Science B.V. All rights reserved.

Scanning electron microscopy study of the choroid plexus in the monkey (Cebus apella apella)

The cells of the choroid plexus of the lateral ventricles of the monkey Cebus apella apella were examined through scanning electron microscopy at contributing to the description of such structures in primates. The animals were anesthetized previously with 3% hypnol intraperitoneally and after perfusion with 2.5% glutaraldehyde, samples of the choroid plexus were collected after exhibition of the central portion and inferior horn of the lateral ventricles. The ventricular surface of those cells presents globose form as well as fine interlaced protrusions named microvilli. Among those, it is observed the presence of some cilia. Resting on the choroid epithelial cells there is a variable number of free cells, with fine prolongations which extend from them. They are probably macrophages and have been compared to Kolmer cells or epiplexus cells, located on choroid epithelium. The choroid plexus of the encephalic lateral ventricles of the monkey Cebus apella apella at scanning electron microscopy is similar to that of other primates, as well as to that of other species of mammals mainly cats and rats, and also humans.

Corneal endothelium of the Magellanic penguin (Spheniscus magellanicus) by scanning electron microscopy

The corneal endothelium is essential for the maintenance of the corneal transparency. The aim of this study was to examine the morphology of the endothelial surface and perform morphometric analysis of the normal corneal endothelial cells of the Magellanic penguin (Spheniscus magellanicus) using scanning electron microscopy. The present work demonstrates that the corneal endothelium of the Magellanic penguin is similar to those described in other vertebrates. Copyright 2005 by American Association of Zoo Veterinarians.

Sharpening of periodontal instruments with different sharpening stones and its influence upon root debridement--scanning electronic microscopy assessment

The objective of this study was to evaluate, through scanning electronic microscopy, the effect of sharpening with different sharpening stones on the cutting angle of periodontal curettes (Gracey 5-6), and the influence on root surfaces after debridement and planing. The experimental model consisted of two different phases. In the first, the cutting angles of fifteen stainless steel Gracey 5-6 curettes were analyzed under a scanning electronic microscope after being sharpened with different types of stones. In the second phase, the root surfaces of 25 newly extracted teeth were evaluated with a scanning electronic microscope after being debrided with curettes sharpened with different stones. Analysis of the results showed that the synthetic stones (aluminum oxide and carborundum) are more abrasive and produce more irregular cutting angles, whereas Arkansas stones are less abrasive and produce smoother and more defined cutting angles. There was no significant statistical differences among the five groups tested with regard to the degree of irregularity of the root surfaces after instrumentation.

Scanning electron microscopy evaluation of the effect of etching agents on human enamel surface

Acid etching promotes microporosities on enamel surface, which provide a better bonding surface to adhesive materials. The purpose of this study was to comparatively analyze the microstructure of enamel surface after etching with 37% phosphoric acid or with two self-etching primers, Non-rinse conditioner (NRC) and Clearfil SE Bond (CSEB) using scanning electron microscopy. Thirty sound premolars were divided into 3 groups with ten teeth each: Group 1: the buccal surface was etched with 37% phosphoric acid for 15 seconds; Group 2: the buccal surface was etched with NRC for 20 seconds; Group 3: the buccal surface was etched with CSEB for 20 seconds. Teeth from Group 1 were rinsed with water; teeth from all groups were air-dried for 15 seconds. After that, all specimens were processed for scanning electron microscopy and analyzed in a Jeol 6100 SEM. The results showed deeper etching when the enamel surface was etched with 37% phosphoric acid, followed by NRC and CSEB. It is concluded that 37% phosphoric acid is still the best agent for a most effective enamel etching.

Charge density alterations in human hair fibers: An investigation using electrostatic force microscopy

A new method for high-resolution analyses of hair surface charge density under ambient conditions is presented in this paper. Electrostatic force microscopy (EFM) is used here to analyze changes in surface charge density in virgin hair, bleached hair, and hair treated with a cationic polymer. The atomic force microscopy technique is used concomitantly to analyze morphological changes in hair roughness and thickness. The EFM images depict exactly how the polymer is distributed on the surface of the hair fiber. The EFM's powerful analytical tools enabled us to evaluate the varying degrees of interaction between the hair fiber surface charge density and the cationic polymer. The surface charge density and the polymer's distribution in the hair fibers are presented in the light of EFM measurements. © 2006 Society of Cosmetic Scientists and the Socièété Française de Cosmétologie.

Structure and properties of Brazilian peat: Analysis by spectroscopy and microscopy

Peat was taken from the Sergipe State, Brazil and characterized by several techniques: elemental and thermal analyses; Fourier infrared (FTIR) and solid state 13C nuclear magnetic resonance (NMR) spectroscopies; scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM) and X-ray diffractometry (XRD). Also, the Sergipe State peat samples were compared with other peat sample from later from Sao Paulo State, Brazil. The lowest O/C and E 4/E 6 ratios and differential thermal analysis (DTA) curves of the Santo Amaro (SAO) sample indicated that this sample had the highest degree of decomposition. FTIR results showed that Itabaiana (ITA) and São Paulo (SAP) samples presented more prominent peak at 1086 cm -1 attributed the presence of Si-O than SAO sample spectra. The SAO sample showed two more intense peaks at 2920 cm -1 and 2850 cm -1. These results were corroborated by 13C NMR and thermal gravimetric (TG) where the relative abundance of the alkyl-C groups was greater in the SAO sample. The X-ray diffractometry (XRD) of SAO sample is characteristic of amorphous matter however, the SAP and ITA samples revealed the large presence of quartz mineral. The scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) showed that the surface of peat samples have porous granules of organic material. The ITA and SAP peat samples are alike while SAO peat sample is richer in organic material. Only the SAO sample has truthful characteristics of peat. The results of this study showed that the samples are very different due to variable inorganic and organic material contents. ©2007 Sociedade Brasileira de Química.

A scanning electronic microscopy study of the action of different desensitizing agents on bovine dentin

This study sought to use scanning electronic microscopy (SEM) to evaluate the dentinal tubule occlusion potential of different desensitizing agents. Ten slices of bovine dentin were divided into six fragments, cleaned (using ultrasound), and etched for 15 seconds with a 35% phosphoric acid solution. All but one of the groups received a different desensitizing agent; the sixth group served as a control and received no additional treatment. After the agents were applied, the dentin specimens were analyzed by SEM and scores were assigned based on the extent of tubular obliteration. Only three agents demonstrated tubular sealing that was significantly different from that of the control group.

Description of eggs and nymphal instars of Triatoma baratai Carcavallo and Jurberg, 2000 based on optical and scanning electron microscopy (Hemiptera: Reduviidae: Triatominae)

Triatoma baratai Carcavallo & Jurberg, is a wild (i.e., nonperidomestic) species found in the State of Mato Grosso do Sul (Bodoquena region, county of Bonito), Brazil. Its eggs and nymphs are described here based on optical and scanning electron microscopy. The operculum and exochorion have pentagonal, hexagonal, and heptagonal cells, with small cracks and small random pits. Differences in the eggs and five nymphal instars of T. baratai allow them to be distinguished from the sympatric species Triatoma williami Galvão, Souza & Lima, and from six of the nine members of the Triatoma oliveirai complex. The most useful differentiating characters are in the color, shape of the abdomen, head, and total body length. Keys are provided to separate the eggs and nymphal instars of six of the nine members of the Triatoma oliveirai species complex. Copyright ©2009 Magnolia Press.

Scanning electron microscopy analysis of RinsEndo system and conventional irrigation for debris removal

A new device for irrigation, which presents hydrodynamic activation based on the pressure-suction technology, has recently been introduced to the market: the Rinsendo system. This study compared the efficacy of the Rinsendo system and conventional (manualdynamic) irrigation in the removal of debris from the root canal walls, using scanning electron microscopy (SEM). Twenty mandibular premolars with completely formed roots were selected and randomly divided into group 1 (irrigation with the Rinsendo system) and group 2 (conventional irrigation). The canals were irrigated with 1 ml of saline at each change of instrument. instrumentation started with a #15 K file and continued up to a #40 K file, which was standardized as the working length instrument. Then, the teeth were sectioned in buccolingual direction and the halves were sputter-coated with gold and examined by SEM. The apical, middle and cervical root canal thirds were evaluated, and the results were analyzed statistically by the Mann-Whitney test for comparison between methods, Kruskal-Wallis test for comparison among thirds, and Miller test for individual comparisons. A significance level of 5% was set for all analyses. The results did not show significant differences (p>0.05) between methods at each third and among thirds for each technique analyzed individually. in conclusion, there was no difference in the cleaning ability of the Rinsendo system and conventional irrigation.

Calcium hydroxide intracanal dressing removal with different rotary instruments and irrigating solutions: A scanning electron microscopy study

This study evaluated the efficacy of 2 types of rotary instruments employed in association with sodium hypochlorite (NaOCl) or EDTA in removing calcium hydroxide (CH) residues from root canals dentin walls. Forty-two mandibular human incisors were instrumented with the ProTaper System up to F2 instrument, irrigated with 2.5% NaOCl followed by 17% EDTA and filled with a CH intracanal dressing. After 7 days, the CH dressing was removed using 4 techniques: NiTi rotary instrument size 25, 0.06 taper (K3 Endo) and irrigation with 17% EDTA (Group 1), NiTi rotary F1 instrument (ProTaper) and irrigation with 17% EDTA (Group 2), NiTi rotary instrument size 25, 0.06 taper and irrigation with 2.5% NaOCl (Group 3) and NiTi rotary F1 instrument and irrigation with 2.5% NaOCl (Group 4). Two roots without intracanal dressing were used as negative controls. Teeth were evaluated by scanning electron microscopy, in the cervical and apical canal thirds. None of the techniques removed the CH dressing completely. In the apical and cervical thirds, F1 instrument was better than instrument size 25, 0.06 taper in removing CH residues (p<0.05), regardless of the final irrigating solution. No difference was found between the irrigating solutions in the groups of F1 instrument and of instrument size 25, 0.06 taper (p>0.05). The negative controls had no CH residues on the dentin walls. In conclusion, the ProTaper F1 instrument was better than K3 Endo instrument size 25, 0.06 taper in the removal of CH intracanal medication, regardless of irrigating solution used.

Study of ITO@PMMA composites by transmission electron microscopy

ITO nanowires were synthesized by carbothermal reduction process, using a co-evaporation method, and have controlled size, shape, and chemical composition. The electrical measurements of nanowires showed they have a resistance of about 102 Ω. In order to produce nanocomposites films, nanowires were dispersed in toluene using an ultrasonic cleaner, so the PMMA polymer was added, and the system was kept under agitation up to obtain a clear suspension. The PMMA polymer was filled with 1, 2, 5 and 10% in weight of nanowires, and the films were done by tape casting. The results showed that the electrical resistance of nanocomposites changed by over 7 orders of magnitude by increasing the amount of filler, and using 5 wt% of filler the composite resistance decreased from 1010 Ω to about 104 Ω, which means that percolation threshold of wires occurred at this concentration. This is an interesting result once for nanocomposites filled with ITO nanoparticles is necessary about 18% in weight to obtain percolation. The addition of filler up to 10 wt% decreased the resistance of the composite to 103 Ω, which is a value close to the resistance of wires. The composites were also analyzed by transmission electron microscopy (TEM), and the TEM results are in agreement with the electrical ones about percolation of nanowires. These results are promising once indicates that is possible to produce conductive and transparent in the visible range films by the addition of ITO nanowires in a polymeric matrix using a simple route. © 2011 Materials Research Society.

Effect of bleaching on sound enamel and with early artificial caries lesions using confocal laser microscopy

The aim of this study was to evaluate effect of bleaching agents on sound enamel (SE) and enamel with early artificial caries lesions (CL) using confocal laser scanning microscopy (CLSM). Eighty blocks (4 × 5 × 5 mm) of bovine enamel were used and half of them were submitted to a pH cycling model to induce CL. Eight experimental groups were obtained from the treatments and mineralization level of the enamel (SE or CL) (n=10). SE groups: G1 - unbleached (control); G2 - 4% hydrogen peroxide (4 HP); G3 - 4 HP containing 0.05% Ca (Ca); G4 - 7.5% hydrogen peroxide (7.5 HP) containing amorphous calcium phosphate (ACP). CL groups: G5 - unbleached; G6 - 4 HP; G7 - 4 HP containing Ca; G8 - 7.5 HP ACP. G2, G3, G6, G7 were treated with the bleaching agents for 8 h/day during 14 days, while G4 and G8 were exposed to the bleaching agents for 30 min twice a day during 14 days. The enamel blocks were stained with 0.1 mM rhodamine B solution and the demineralization was quantified using fluorescence intensity detected by CLSM. Data were analyzed using ANOVA and Fisher's tests (α=0.05). For the SE groups, the bleaching treatments increased significantly the demineralization area when compared with the unbleached group. In the CL groups, no statistically significant difference was observed (p>0.05). The addition of ACP or Ca in the composition of the whitening products did not overcome the effects caused by bleaching treatments on SE and neither was able to promote remineralization of CL.