Scanning Electrone Microscopy Research Articles

In vitro evaluation of wear resistance, microhardness and superficial roughness of different fissure sealants after aging.

The aim of this study was to compare the aging effects on wear, surface roughness and microhardness of fissure sealants having varying contents. Four fissure sealant types were used in the study: Aegis (Bosworth, USA) (Group A), Beautisealant (Shofu, Japan) (Group B), Clinpro (3M, USA) (Group C), and Ultraseal XT/Hydro (Ultradent, USA) (Group U). Hundred disc-shaped specimens (5 mm diameter/3 mm width) were designed according to the manufacturer's instructions and assigned for microhardness/Vickers Hardness (VHN), surface roughness, and wear tests. Thermocycling (10,000 times/5-55 °C ± 2 °C/20 s) and chewing simulator (75,000 times/49 N) were applied as the aging procedures. Measurements were made before and after the aging procedures. The specimens were examined by Scanning Electrone Microscopy (SEM). Data was statistically analyzed through Kruskal Wallis, Wilcoxon and Welch tests. The highest and the lowest changes in mean microhardness values were obtained for Group U (9.88 ± 1.46) and Group A (4.40 ± 0.46), respectively; and a significant difference (p < 0.001) was found between the mean changes in microhardness numbers (U > B > C > A). The median roughness values had no significant difference; the surface roughness had the highest mean differences in Groups U and C (U = C > A > B). Significant difference was found between the mean changes in wear/weight values (p < 0.001); the highest and the lowest mean weight losses were recorded in Group U (0.0097 ± 0.0003 gr), and Group C (0.0041 ± 0.0006 gr), respectively (U > B > A > C). The highest physical changes were determined in Group U after the aging procedures. It is concluded that the aging procedures affect physical structures of all test materials with varying degrees, however Ultraseal XT/Hydro is the most affected. The individual treatment needs and material properties must be considered to select a fissure sealant material.

Effect of Plasticizer and Concentration on Characteristics of Bioplastic Based on Cellulose Acetate from Kapok (Ceiba pentandra) Fiber

The synthetic plastics that made from petroleum material have been widely used in all industrial sectors. They cause some serious problems for the environment. There are semi-synthetic plastics or biodegradable plastics which are made from natural polymers such as cellulose to mitigate this problem. Biodegradable plastics can fulfill the needs of society because they can be decomposed easily into the environment. This research used laboratory experimental methods through several processes: kapok fiber isolation, cellulose acetate production and purification, and manufacture of bioplastics. The characteristics of bioplastics was analyzed using some parameters such as density, tensile strength, elongation, Young's modulus, water absorption, biodegradability, compound group analysis using Fouier-Transform Infrared Spectrometer (FTIR) and bioplastic morphology analysis by using Scanning electrone microscopy (SEM). This study aimed to determine the effect of the plasticizer type and concentration on the bioplastics characteristics that was divided into several different concentrations of glycerol and sorbitol plasticizers (20%, 30%, and 40%). The fabrication of composite bioplastics used the cellulose acetat from kapok fiber, starch, and types of plasticizer (glycerol, and sorbitol). The results of the study showed that the addition of different plasticizers, such as glycerol and sorbitol gave distinct effects on the bioplastics product characteristics. The optimum concentration of glycerol addition affected the bioplastic characteristics with the best results were 40% concentration generate density of 0.836 g/mL, tensile strength of 0.818 MPa, water absorption value of 22.23%, and degradation plastic mass about 39.7%. The addition of sorbitol also affected the bioplastic characteristics, where the best results were 40% concentration produced bioplastic density of 0.941 g/mL, percent elongation at 3.94%, young’s modulus of 0.726 MPa, and degradarion mass of 32.05%. The morphology of bioplastic showed the high homogeneity on concentrations of 40% glycerol and 30% sorbitol.

Synergistic effect of intumescent flame retardant and zinc borate on linear low‐density polyethylene

AbstractA series of novel intumescent flame retardant (IFR) based on melamine, neopentyl glycol, and aluminum diethylphosphinate were prepared and tested. In addition, the synergistic effect of the novel IFR and zinc borate (ZB) on the flame retardancy of LLDPE composites was investigated. The structures of novel IFR and ZB were characterized by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The limiting oxygen index (LOI) increased from 19.3% for the pure LLDPE to 27% for the 25 wt% IFR/5 wt% ZB composites and the composites achieved the desired V‐0 rating in the UL‐94 test. Thermogravimetric analysis showed that the addition of IFR/ZB reduced the pyrolysis rate of the LLDPE composites at high temperatures and increased the amount of the char residues, and the char residue of LLDPE‐5 reached 12.1 wt% at 700°C. Cone calorimetry (CCT) data showed that the peak of total heat release, heat release rate, and fire growth index were comparatively reduced, indicating that the addition of IFR/ZB decreased the fire hazard of LLDPE composites. The formation of a compact and thermally stable char layer on the surfaces of LLDPE composites was revealed from the scanning electrone microscopy images and digital photographs of the char residue after the CCT tests.

Coral reef-associated bryozoans of Jamaica.

As part of a long-term ecological study of the cryptic comunity of Jamaican coral reefs carried out by Jeremy B.C. Jackson and associates during the 1970s and early 1980s, collections were made of reef bryozoans found at 14 sites around the island. Space occupied by bryozoans on undercoral surfaces is dominated by relatively few species. However, during scanning electrone microscopy study and monograph preparation a diverse assortment of relatively rare species was discovered. Of the 132 species found, 56%, 74 species (70 cheilostomes and 4 cyclostomes) are new, as are one family (Inversiscaphidae) and 5 genera (Planospinella, Caribaria, Spirocoleopora, Gemellitheca, and Palliocella).

Institute of Geological Sciences, NAS of Ukraine

The aim of the research is to substantiate the expediency of themineral and radiogeochemical composition comprehensive study of phosphate raw materials from domestic deposits in connection with their promising use in agro-industrial production. Phosphates from five levels of phosphate accumulation (Vendian (Ediacaran), Visean, Alb-Cenomanian, Santon-Campanian and Eocene) from Ukraine territory were studied, as well as for the purpose of comparison –phosphorites from deposits in Syria, Belarus, Russia and Kazakhstan. Optical polarization, scanning electrone microscopy with energy dispersive analysis, X-ray diffractometric analysis and the method of semiconductor gamma spectrometry were used. Study results of phosphate mineral raw materials processing by different methods, including with the involvement of biotechnological methods (using the environmentally friendly leaching agents of microbial origin) are represented. The results obtained are the basis for determining the quality criteria of phosphate raw materials and assessing the prospects for industrial production of phosphorites from domestic deposits of various types. In turn, the improvement of phosphorite processing technology, as well as the involvement of modern biotechnological methods in the production will significantly reduce the cost of mineral fertilizers and related products, which is of economic interest in various sectors of the national economy.

New Ecological Solutions Involved in the Cleaning of a 19th Century Icon

Cleaning of old icons requires special attention to selecting the processes and systems compatible with the chemical nature and adhesions of the deposits, to not affect the polychrome layer or their conservation status. The study was carried out on a 19th century icon made in fat tempera, on a thin layer of preparation that presents fouling. The cleaning was done using extracts obtained from sage, St. John’s Wort, and, respectively, licorice root teas obtained through different extraction processes: microwave, ultrasound, boiling, and room temperature, respectively. The washing capacity of the new system used was analyzed by analytical methods of assessing the cleaning degree: UV-Vis reflection, reflective colorimetry type CIE L*a*b*, co-assisted with optical microscopy and scanning electrone microscopy (SEM-EDX).

Microchannel fabrication and metallurgical characterization on titanium by nanosecond fiber laser micromilling

ABSTRACTLaser micromilling technique is used to manufacture microchannel on metals and nonmetals. Microfeatures ≤100 µm are still challenging for fabrication by common methods. Nanosecond fiber laser micromachining has become more popular owing to its prospective implementation in laser micromilling. Microchannel application relies on its geometric dimension, profile, and surface quality. In this study, an attempt was made to explore the impact of process parameters scanning times, scanning velocity, pulse repetition rate, and assist gas pressure on top kerf width, taper, surface roughness, and metal removal rate in laser micromilling experimentally. Microchannel width varied between 45.5 and 70.9 µm. A regression model has been developed for each response. ANOVA (analysis of variance) has been carried out to remove insignificant parameters. Thermal stress analyzed by surface cracks inside microchannel by Scanning Electrone Microscopy (SEM) images. Higher PRR, lower no. of scans, higher scanning speed and high air pressure found suitable for lesser surface cracks. Redeposition observed at slower scanning velocity and minimum scanning times. Oxidation zone from boundary of channel varies between 37 and 58 µm. Oxide formed on Ti surface which increases oxygen content toward center of channel from 51.08 to 76.22% compared to outside surroundings.

Preparation of Multi-Walled Carbon Nanotubes Supported Zinc Oxide Catalyst for Transesterification of Kesambi (Schleichera oleosa) Oil

In this work, multi-walled carbon nanotubes supported zinc oxide (ZnO/MWCNTs) as a heterogeneous catalyst for transesterification had been successfully prepared via the modified Stober-like synthesis method. The effect of calcination temperature during the catalyst preparation towards reaction was investigated. These catalyst was also characterized by X-ray diffraction (XRD) analysis, N2 adsorption-desorption analysis followed by Brunauer- Emmett-Teller (BET) calculation to determine the total surface area, and scanning electrone microscopy with energy dispersive x-ray spectroscopy (SEM-EDX). Transesterification of kesambi (Schleichera oleosa) oil also had been done to test the activity of the prepared catalysts. However, the quantity of dispersed zinc oxide (ZnO) on multi-walled carbon nanotubes (MWCNTs) are quite small that is lower than 5 %wt. It produces low conversion of transesterification after 3 hours reaction that is under 15% of conversion.

Rapid Detection of Ara h2 Using Single Walled Carbon Nanotube Based Biosensor for Peanut Allergen Control

Peanut protein Ara h2 is one of the serious food allergens contributing to the allergic reaction, causing the common reasons for food-related life threating problems over the world. The objective of this study is to develop single-walled carbon nanotubes (SWCNTs) based biosensor using 1-pyrenibutanoic acid succinimidyl ester (1-PBASE) as a linker for rapid detecting peanut allergen Ara h2 in foods. The detection principal of this biosensor was based upon the binding of Ara h2 to the anti-Ara h2 on the linker-modified SWCNTs connecting gold electrode in biosensor silicon template. The measurements of each step were achieved using linear sweep voltammetry (LSV) with a potentiostat for Ara h2 detection. The application of anti-Ara h2 as pAbs on linker immobilized SWCNTs surface increased the sensor resistance values. The developed biosensor showed significant resistance response with the increase in the concentration of Ara h2 from 0 to 1000 ng/mL. Indirect enzyme-linked immunosorbent assay (ELISA) was successfully applied to confirm the specificity of antibodies using 96-well microplates. Scanning electrone microscopy (SEM) confirmed the microstructure of SWCNTs. Sensor sensitivity and specificity were tested with different peanut allergens and the detection range (1-1000 ng/mL).

Flexural strength and modulus of autopolimerized poly (methyl methacrylate) with nanosilica

Background/Aim. Autopolymerized, or cold polymerized poly(methyl methacrylate) class of materials have a lower mechanical properties compared to hot polymerized poly(methyl methacrylate), due to a limited time of mixing before the polymerization process begins. The aim of this study was to test the effect of different relatively low nanosilica contents, in improving mechanical properties of the cold polymerized poly(methyl methacrylate). Methods. A commercially available autopolymerized poly(methyl methacrylate) denture reline resin methyl methacrylate liquid component was mixed with 7 nm after treated hydrophobic fumed silica and subsequently mixed with poly(methyl methacrylate) powder. Three nanosilica loadings were used: 0.05%, 0.2% and 1.5%. Flexural modulus and strength were tested, with one way ANOVA followed by Tukey?s test. Furthermore, zeta potential, differential scanning calorimetry, scaning electrone microscopy and energy dispersive X-ray analyses were performed. Results. Flexural modulus and strength of poly(methyl methacrylate) based nanocomposites were statistically significantly increased by the addition of 0.05% nano-SiO2. The increase in nanosilica content up to 1.5% does not contribute to mechanical properties tested, but quite contrary. The main reason was agglomeration, that occurred before mixing of the liquid and powder component and was proved by zeta potential measurement, and after mixing, proved by scanning electrone microscopy and energy dispersive x-ray analyses. Conclusions. Addition of 7 nm 0.05% SiO2 is the most effective in increasing flexural modulus and strength of autopolimerized poly(methyl methacrylate).

Systematic significance of anatomy and trichome morphology in Lamium (Lamioideae; Lamiaceae)

Lamium (Lamiaceae, Lamioideae) is a widespread and taxonomically complex genus. A comparative anatomical study of the root, stem, leaf and petioles in 33 taxa assigned to this genus is carried out in order to address generic delimitation, subgeneric classification and species delimitation. Using light and scanning electrone microscopy, anatomical features and indumentum characteristics are investigated. In addition, the phylogenetic implication of the observed variations are discussed. Anatomical characters of taxonomic interest are as follows: the presence or absence of collenchyma at the corners of stems and petioles, the number of pith rays in the root, shape of the vascular bundles in petioles and characteristics of leaf mesophyll. Non-glandular trichomes can be short or long, while the glandular trichomes are stalked, subsessile or sessile. The indumentum is taxonomically significant, particularly in discrimination of taxa in “L. garganicum complexˮ and their delimitation from L. armenum. Trichome characters are also important in distinguishing the alpine Turkish endemic L. eriocephalum from other taxa in L. sect. Amplexicaule. Our analyses partly corroborate the findings of recent phylogenetic investigations and support also partly the current infrageneric classification of the genus. Anatomical features and trichome characters reject accepting Galeobdolon and Wiedemaniana as distinct genera. In general, Our investigations reveal the usefulness of such characters in taxon delimitation at various ranks, especially at the specific and partly at the sectional level.

Chitosan‐carbon Nanofiber Modified Single‐use Graphite Electrodes Developed for Electrochemical Detection of DNA Hybridization Related to Hepatitis B Virus

AbstractChitosan (CHIT) and carbon nanofiber (CNF) modified pencil graphite electrodes (PGEs) were developed for the first time in the present study for enhanced monitoring of DNA hybridization. CHIT‐CNF modified PGE, CHIT modified PGE and unmodified PGE were firstly characterized by scanning electrone microscopy (SEM), and the electrochemical behaviour of each electrode was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The optimization of experimental studies; CNF concentration, or DNA probe concentration was performed by differential pulse voltammetry (DPV) technique. The sequence‐selective DNA hybridization related to Hepatitis B virus (HBV) was then performed in the case of hybridization between HBV probe and its target DNA, or different non‐complementary DNA sequences (NC1 and NC2), and also the hybridization case in the mixture samples containing both target and NC sequences in the ratio of 1 : 1. CHIT‐CNF‐PGEs presented very effective discrimination of HBV DNA hybridization, which also presented high sensitivity and better reproducibility due to the unique chemical and structural properties of CNF.

Synthesis, characterization, and drug release properties of macroporous dual stimuli responsive stereo regular nanocomposites gels of poly(N-isopropylacrylamide) and graphene oxide

Nanocomposite stereoregular hybrid gels of poly(N-isopropylacrylamide) were prepared in 1:1 methanol–water mixture in the presence rare earth yttrium trifluoromethanesulfonate Lewis acid and graphene oxide (GO). The nanocomposite gels were characterized by swelling ratio measurements at different temperatures and different pH, deswelling kinetics, scanning electrone microscopy, FTIR, thermogravimetric analysis, powder XRD, Raman spectroscopy, LCST measurement by DSC etc. Drug release experiments also done by using tramadol hydrochloride as a model drug to check their suitability in application. All results were explained on the basis of porosity, cononsolvency of the synthesis solvents, hydrophilicity, isotacticity, pH effect, interactions between solvents and polymer molecules, interactions between polymer and GO or interactions between GO and solvents etc.

Variability of Local Corrosion Attack Morphology of AISI 316Ti Stainless Steel in Aggressive Chloride Environment

AISI 316Ti is Cr-Ni-Mo austenitic stainless steel stabilized by Ti, recommended for construction of various industrial and medicine devices. In spite of its high Pitting Equivalent Resistance Number (PREN=23.688) it underlies local corrosion namely pitting in aggressive chloride environment. Appearance and extent of AISI 316Ti corrosion damage in a particular chloride solution depends strongly on temperature and surface treatment. One part of tested specimens is surface untreated the second part is treated by nitric acid passivation. Specimens are immersed for 24 hours at the temperatures of 30, 50 and 80 °C in 0.3M FeCl3 solution to induce pitting. Pitting corrosion morphology (shape and size of corrosion pits) is observed viewed from above and in profile as well, by optical metallographic microscope and scanning electrone microscopy SEM. Shape and size of corrosion pits is compared in dependence on temperature and surface finish of specimens.

Sintering and microstructure characteristics of 42CrMo4 steel processed by spark plasma sintering

Rapidly solidified micron sized 42CrMo4 steel powder with a size range of 150–250 μm produced by plasma rotating electrode process was consolidated using a recently developed spark plasma sintering (SPS) process. The relationship between sintering parameters (temperature and soaking time) and microstructural properties was investigated. The effect of slow and high heating regimes on the consolidation of sintered compacts has been also investigated. Maximum relative density (99.2%) was obtained at 1000 °C, under 50 MPa pressure, with 8 min holding time and 200 °C/min heating rate. The microstructure of sintered steel was influenced by carburization occuring inside the graphite SPS process die. The diffusion of carbon produced martensite structure near the surface region and hardened the surface. This effect was investigated in detail using optical microscopy and hardness measurement. Scanning electrone microscopy was also used to examine the fracture surface of sintered compacts. High heating rate promoted the relative density at low temperature compared to high temperature.

Caval involvement of renal cell carcinoma.

Department of Cardiothoracic Surgery, Helsinki University Hospital, FinlandKey words: Renal cell carcinoma; venous invasion; caval extension; surgery; prognosisin all cases (6). Immunohistochemical markers likeantifactor-VIII have proven to be useful in the searchof microscopic venous invasion (6, 7). Increasing thenumber of samples and slides per sample also im-proves the detection rate (6). Microvascular invasionhas turned out to be an independent prognosticfactor with adverse impact on disease-free survival(7, 8, 9). On the contrary and somewhat unexpected-ly, caval extension as such seems not to be an inde-pendent prognostic factor, if the tumour is comple-tely removed (4, 10, 11, 12). Hanke and coworkersexamined the surface structure of caval tumourthrombi with light- and scanning electrone micro-scopy and immunohistochemically by Q-band factorVIII marking (13). They found that the free floatingparts of the venous thrombi were covered with en-dothelium and compared this phenomen to abdomi-nal hernia covered with peritoneum.Thus microscopic venous invasion may result fromdifferent cellular mechanisms compared with mac-roscopic renal vein and caval extension.The speed of growth of the venous extension is notknown. Many patients with caval tumour thrombusand simultaneous metastatic disease will not under-go operation and die relatively quickly of the gener-alized tumour burden with no documentation of thegrowth speed of the venous part. The upwards prop-agation of the thrombus and its circumferential ex-pansion are most likely slow processes because inmany patients venous collaterals have time to be-come wide and there is no swelling of the lower ex-tremities. The tumour thrombus is for the most partloose from the caval wall but may invade the orifi-ces of the renal and hepatic veins, which has to betaken into account when planning the surgery (14).The terms extension and invasion should not bemixed. In cases of true invasion of the caval wall thisis also evident in microscopic examination (15). How-ever, wall invasion seems not to depend on the levelof the free thrombus (11).It is not clear how much blood circulation to thecells of the tumour thrombus comes from the renalarterial inflow, compared with possible diffusion

Effects of hypovolaemia on acid-induced duodenal mucosal damage in the rat.

Modest acute hypovolaemia in rats markedly decreases the duodenal mucosal alkaline secretion via neurohumoral links. The present study was undertaken to investigate if such a procedure influences the morphological changes observed following an acid challenge of the duodenal mucosa. Experiments were performed on anaesthetized male Sprague-Dawley rats. HCl (10 or 100 mM) was infused during 15 min into the duodenum via a luminally situated catheter. Time controls were compared with animals bled 10% of total blood volume. Mucosal damage was evaluated by light microscopic morphometry on transverse sections and by scanning electron microscopy of the luminal surface. Perfusion with either 10 mM or 100 mM HCl reduced villus length by about 30%. The villus area was unaffected by 10 mM HCl, but was reduced significantly by 10% by 100 mM HCl as compared with NaCl time controls. Hypovolaemia did not influence the morphometrical changes induced by 10 mM HCl but reduced significantly both villus length (-28%) and villus area (-10%) as compared with the unbled 100 mM HCl group. Scanning electrone microscopy (SEM)-based visual damage score was not influenced by the hypovolaemia procedure in any of the acidities. Morphological changes of the duodenal mucosa, induced by moderate intra-luminal acidity (10 mM HCl), is not influenced by hypovolaemia. However, at higher acidities (100 mM HCl) the hypovolaemia contributes to more severe mucosal damage.

O44--a solvent for silicone oil adhesions on intraocular lenses

To examine the efficiency of O44, a partial fluorinated octane, as a solvent for silicone oil adhesions on intraocular lenses. After placing silicone- and PMMA-lenses in silicone oil, the adhesions were treated with O44. The extent of silicone oil adhesions and the effectiveness of O44 were studied by gross microscopy by scanning electrone microscopy (SEM) and combined energy dispersive spectrometry (EDX). Furthermore an explanted silicone lens with oil adhesions was treated with O44 and examined. To simulate the effect of adhesion proteins PMMA- and silicone lenses were placed in silicone oil and human plasma. With EDX it was possible to prove that O44 is able to remove silicone oil adhesions from PMMA-lenses. The removal from an explanted silicone lens by O44 could be demonstrated by light microscopy. Silicone oil adhesions on intraocular lenses (IOL's) in vitro showed a different oil coverage than the IOL in vivo. Silicone lenses in vitro were often covered by a homogenous oil film and therefore the demonstration of the silicone adhesions and of the efficacy of O44 was difficult. The adhesions of IOL's placed additional in human plasma did not show any differences. O44 may be a successful intraoperative tool to remove silicone oil adhesions avoiding explantation of silicone oil contaminated IOL's. Silicone oil adhesions in vivo seem to be influenced by adhesive proteins.

Stylar trimorphism in four functionally andromonoeciousProsopis species (Mimosaceae)

The reproductive system ofProsopis chilensis, P. pugionata, P. flexuosa, andP. torquata is described. Observations were made of floral morphology, stigmatic receptivity, pollen grain viability, and the nature of pollen reserves. Scanning electrone microscopy and statistical analysis were carried out. The results allow us to conclude that: 1) The studied species have three distinct floral morphs characterized by significantly different style lengths and, to a lesser extent, different stamen lengths; 2) style precocity found in all species does not indicate protogyny; 3) flowers with shortest styles are not receptive; 4) the pollen grains of all floral morphs showed high viability; 5) peroxidase is present in both the pollen and pistil; 6) viable pollen grains invariably have both starch and pollenkitt; 7) the studied species are andromonoecious.

In vitro development of aggregate embryos obtained by pairing the microsurgically halved morulae of mice and rats, and observations on their aggregation process in scanning electrone and fluorescence microscopies.

Using the halved morulae of rats and mice obtained with microsurgical technique, the following items were investigated:1) Production of aggregate embryos by the method of MINTZ1) and investigation on the subsequent development.2) Observation on aggregation and fusion of the paired demi-embryos by scanning elec-trone microscopy (SEM).3) Fluorescent vital staining (FITC & TRIT) of the paired demi-embryos and investga-tion on distribution of the dyes during development in the aggregate embryo in vitro.Out of 107 pairs of rat's demi-embryos, 87 were successfully aggregated, of which 63 (58%) developed to the blastocyst stage. While, 85 out of 127 pairs of mouse demi-embryos suc-cessfully aggregated, of which 71 (56%) developed to late morulae and 14 (11%) to blasto-cysts. These rat and mouse aggregate blastocysts were slightly small in size but were found to have inner cell masses.The observation by SEM revealed that the fused embryo at late morula stage had the structure of a linear sulcus running around the equatorial surface. The location of this sulcus seemed to be the border where the paired demi-embryos made contact to fuse each other.The distribution of the fluorescent dyes showed that two hemispherical cell masses with different colors made contact at the central plane of the morula, and that in the blastocyst the inner cell mass was also consisted of two cell populations with different colors confront-ing either vertically or horizontally.These observations suggested that two groups of cell mass might seldom mingle each other in the aggregate embryo during early developmental period until the blastocyst stage, thereafter two groups of blastomeres of different origin seem to begin mixing.