Scanning Electron Microscope Photography Research Articles

Method for taking Scanning Electron Microscope photographs of nematodes and meiofauna with the support of a low-cost and easy-made container.

This paper presents a method for capturing Scanning Electron Microscope (SEM) photographs of small specimens, including nematodes, arthropods, small insects, and other meiofauna. Our method is tailored to handle nematode specimens mounted on permanent slides, an area with relatively limited documentation. Besides, the process of transferring such delicate specimens from one solution to another has historically posed numerous challenges. To address this issue, we introduce a low-cost and easy-made container designed specifically to facilitate the aforementioned procedure, with a particular focus on SEM photography. The newly introduced container offers a practical solution that enhances the efficiency and effectiveness of specimen handling, ultimately enabling high-quality SEM imaging. This method holds significant promise for researchers working in the field of micro-scopic organism analysis, providing a valuable tool for their investigations with minimum cost.

Shock Waves as Dominant Mechanism for Cavitation Damage

Abstract In this paper, the mechanism of energy transfer from cavitation bubbles to solids is demonstrated as shock waves. To identify this mechanism, cavitation bubble structures, the corresponding damaged surface, and the wear particles in vibratory erosion tests on pure aluminum Al-99.999 using high-speed and scanning electron microscope photography were observed. The eroded surface morphology was in the form of large swellings (hundreds of micrometers), which embodies the plastic flow. Results indicate that large swelling regions formed in a few seconds are caused by shock pressure waves and not by a microjet only several micrometers in size. The observed surface erosion and falling particles make it clear that the mechanism of cavitation wear is fatigue failure.

Synthesis of CuFe2–xErxO4 nanoparticles and their magnetic, structural and dielectric properties

Erbium-doped nanocrystalline, Cu-ferrites, chemically known as CuFe2–xErxO4 (x = 0.04, 0.08, 0.12, 0.16, 0.20) were synthesized. The effects of Er3+-doped on magnetic, structural and dielectric behaviour of CuFe2O4 were studied by XRD, Scanning Electron Microscope (SEM), TGA, FTIR, VSM, and dielectric analysis. The CuFe2–xErxO4 ferrites crystallize in spinel cubic structures with ex ≤ 0.12. SEM data demonstrated that their spherical morphology and crystalline size was <50 nm. The XRD spectra of all the prepared samples exhibited peaks of single-phase spinel ferrites. The lattice parameter (A) was amplified with the ascent of Er3+ concentration in the latticework. The FTIR patterns of the synthesized ferrites described the asymmetric stretching mode of spinel transition AB2O4. SEM photography confirms that the particle size had developed up to 500 nm after doping of Er3+. The maximum saturation magnetization (Ms ~ 38.01 emug−1) was observed for CuFe2O4. It was found that the decreasing in temperature leads to the great enhancement in the magnetic properties of the examined samples. As the magnetic recording performance of the magnetic samples is enhanced for well-crystallized samples with nano-structural, the effect of Er3+ substitution appears to be particularly valuable in this respect.

Jackfruit leaf as an adsorbent of malachite green: recovery and reuse of the dye

Dry leaf powder of jackfruit (Actocarpus heterophyllus) was utilized for the removal of an industrial dye malachite green from the aqueous solution by the batch adsorption method. The parameters which effect on adsorption such as adsorption dose, contact time between adsorbent and the dye in solution, and pH of the solution were studied and standardized. The scanning electron microscope (SEM) photography of the jackfruit leaf powder (JLP) indicated that it had a large number of pores, spaces and empty sites. The SEM photography of used JLP shows that the dye is confidently attached on the JLP. Fourier-transform infrared spectroscopy analysis of the adsorbent confirmed the presence of different functional groups like –OH, –NH and C=O on its surface, which can be correlated with the fine adherence of the dye on the surface of the adsorbent. Moreover, the shifting of the functional group on the surface of adsorbed adsorbents indicates the affinity of the dye towards the adsorbent. The Freundlich isotherm model with the correlation coefficient (r2) value of 0.9880 is considered as a suitable absorption model for adsorption of dye. The pH of the aqueous solution was reduced from pH 7 to pH 5. This helped the recovery of the 80% of the attached dye. The present work concludes that jackfruit leaf powder can be used as an efficient adsorbent to remove malachite green from aqueous medium and the adsorbed dye can also be recovered for reuse from the surface of the adsorbent.

Mechanical characterization of polylactic acid reinforced bagasse/basalt hybrid fiber composites

This paper focuses on the mechanical behavior of Polylatic acid reinforced Basalt and Bagasse fibers. The most important aspect in formulating this hybrid composite with better mechanical properties is the optimization of interfacial bonding between the reinforcing bagasse fiber and basalt fiber and polymer matrix. The composite of different weight proportion of the materials is compounded using twin screw extruder. The specimens were prepared by injection molding and subjected to various mechanical testing under tensile, flexural, and impact loads. It was found that 84 wt% of polylactic acid, 12 wt% of Basalt fiber and 4 wt% of Bagasse fiber composite exhibits better mechanical properties compared to other composites taken for study in this research. The better tensile, flexural, and impact strength of 52.8 MPa, 82.2 MPa, and 3.39 KJ/m2 were observed. The results show that the fiber content in weight percentage is playing a major than the fiber length on the improvement of tensile, flexural, and impact properties. The mechanical behavior obtained through experiments witnessed that Bagasse/Basalt fiber reinforcement in polylactic acid composites can be used as medium-load applications because of its low cost and ease of decomposability. The scanning electron microscope photography of the tested specimens shows better interfacial bonding between matrix and fibers. Also, the water absorption test indicates increase in fiber content increases the water absorption rate, reveals good degradation property of the composite. Additionally, the use of Bagasse fiber promotes the degradation of the material after its life time.

Effects of Curing Temperature on Glass Fiber/Urethane Composite’s Mechanical and Thermal Properties

Effects of curing temperature on glass fiber/urethane composite’s mechanical and thermal properties were investigated in this paper. L100 and curing agent C3 were mixed sufficiently with the mass ratio of 100:15 at the temperature of about 50°C, and 3 layers of glass fibers with the size of 10cm×30cm (the thickness of each layer is 0.2mm) were prepared. Then glass fabric/L100 polyurethane composites were fabricated by vacuum-assisted hand lay-up process at the temperature of 150°C, 160°C and 170°C, respectively. As the resin system is used in pultrusion process which demands the resin system can cure adequately within 5min to 15 min. The isothermal differential scanning calorimetry (DSC) method was used to investigate the curing time at the above three temperatures to testify whether the resin system can cure during a short span of time to meet the requirement. The results demonstrate that L100/C3 resin system cures within 8-10min at the temperature of 150°C and 160°C, while under 170°C, the resin system cures fully within 5min,which clearly show that the resin system meet the basic requirement of fast process. In order to better analyze the effect of curing temperature on sample’s mechanical properties, corresponding mechanical tests were conducted. The tension tests demonstrate that the tensile strength and elongation at break reduce with the rise of curing temperature. The interface strength test and field emission scanning electron microscope photography were conducted. The results show that higher curing temperature leads to lower interface strength. The decrease of the interface strength is due to the different reactivity of three reactive groups in L100. With the rising of temperature, reactivity groups tend to react with curing agent C3, but not to combine with coupling in the surface of glass fiber, hence weakens the link between resin and fiber. This assumption can be confirmed by the DSC tests, which show that curing temperatures have little effects on glass transition temperature of the samples. Additionally, the infrared spectra of the composites cured at the above three different temperatures indicate that curing temperatures exert no significant influence on the composition of the composites. Based on the above results, 150°C is chosen to be the optimal curing temperature for the glass fabric/L100 polyurethane composites.

Investigation of electrochemical machining characteristics of 20MnCr5 alloy steel using potassium dichromate mixed aqueous NaCl electrolyte and optimization of process parameters

Electrochemical machining is a modern machining technique that plays an important role in the applications of aerospace, die and electronic industries. Electrochemical machining is used to machine difficult-to-machine materials and complex shapes. Machining of alloy steels especially 20MnCr5 is very important for its wide variety of applications such as piston bolts, spindles, camshafts, gears, shafts and other mechanical controlling parts. Machining of the above components with conventional machine tools is a burdensome task. Hence, in this work, an investigation was made to study the electrochemical machining characteristics of 20MnCr5 alloy steel. Two electrolytes, namely, aqueous sodium chloride (NaCl) and potassium dichromate (K2Cr2O7) mixed aqueous NaCl, were used to investigate the machining performance. K2Cr2O7 was selected for its oxidizing characteristics and was included in small proportions in aqueous NaCl bath. The influence of predominant electrochemical machining process parameters such as applied voltage (V), inter electrode gap and electrolyte concentration was studied on the material removal rate and surface roughness (Ra). Scanning electron microscope photography of surface of the 20MnCr5 specimen machined with electrochemical machining was studied to understand the effect of electrolytes during the machining. The contour plots were generated to study the effect of process parameters as well as their interactions. It was noted in the study that the presence of K2Cr2O7 in aqueous NaCl electrolyte increases the material removal rate significantly. The process parameters are optimized through genetic algorithm-desirability function. Optimized operating conditions were found to be quite close with experimental results.

Effects of Poly-MVA on the rheological properties of blood after in-vivo exposure to gamma radiation

This study aims to examine the radio-prophylactic effects of poly-MVA against exposure to acute dose of gamma radiation. Adult male rats, weighing 200 gm, were exposed to 6 Gy gamma radiation from Cs-137 source. The animals received daily oral administration of 2 ml/kg body weight of poly-MVA for different time intervals. The prophylactic effect was examined by two modes of administration: two weeks before irradiation and another group which received continuous administration for two weeks before and two other weeks after irradiation (total time of administration 28 days). Different parameters were performed, which include determination of cellular antioxidant enzymes (Glutathione (GSH), catalase and superoxide dismutase) in hepatic cells, the rheological properties of blood, osmotic fragility and scanning electron microscope photography of red blood cells. Exposure to radiation resulted in a significant decrease in cellular antioxidant enzymes (GSH, Catalase and SOD) and decrease in Bingham viscosity, yield stress and aggregation index of blood. Furthermore it induced slightly increase in average osmotic fragility of red blood cells accompanied by decrease in osmotic dispersion and remarkable modification of red blood cell morphology. Administration of Poly-MVA showed markedly elevation in GSH, Catalase and SOD content in liver cells in all treated groups. It also showed improvement in all observed parameters. The obtained results showed that oral uptake of poly MVA posses a radio-prophylactic effect that might be used in planned radiation exposure in diagnosis and radiotherapy.

도토리묵 제조용 조전분의 수입 원산지별 호화 특성

Gelatinization properties of crude starches from acorns harvested in various countries (domestic (KAS), Chinese (CAS), and North Korea (NAS)) were analyzed, especially blue value, amylose contents, amylogram, particle size, and SEM (scanning electron microscope). Amylose contents of NAS, KAS, and CAS were 33.65%, 32.00%, and 30.48%, respectively, and a similar tendency was observed in blue value. According to amylogram, initial paste temperature was for NAS and CAS and for KAS, whereas peak viscosity was 580 BU for KAS and NAS and 570 BU for CAS. The cooling viscosity and setback of NAS and CAS were higher than those of KAS. The average particle size was 23.17 microns for KAS, 23.53 microns for CAS, and 82.14 microns for NAS; particle size ranging from 5~40 microns was highly distributed in KAS (68.9%) and CAS (73.8%), whereas 57.1% distribution was observed for 5~40 microns and 27.2% for >80 microns in NAS. Gelatinization ranges of SEM photography of CAS and NAS showed a more swollen, extremely disintegrated, and folded structure than that of KAS. From these results, gelatinization properties, especially viscosity, setback of amylogram, particle size, and SEM photography, differed according to the country.

Consumption and digestion of suspended microbes by juvenile Pacific white shrimp Litopenaeus vannamei

Microalgae hold a key role in the diet of the world's highest-valued seafood species, Pacific white shrimp Litopenaeus vannamei, but ingestion, digestion, and feeding mechanisms employed for consuming suspended microbes are not well studied. The goal of this work was to determine whether juvenile L. vannamei could consume and digest several microbes of varying sizes and structures in suspended monocultures. Diatoms Thalassiosira weissflogii and Amphiprora sp., eustigmatophyte Nannochloropsis salina, and cyanobacterium Synechococcus bacillarus were chosen based upon their common occurrence in intensive shrimp aquaculture systems. Juvenile 2 g L. vannamei, previously starved for 24 h, were individually stocked in aerated flasks containing axenic monocultures of T. weissflogii, Amphiprora sp., N. salina or S. bacillarus for 15, 30, 60, and 90 min. After designated immersion times, shrimp were dissected for collection of stomach and intestine content samples. Fluorometry was used to measure chlorophyll a (μg/g) within the stomach and intestine contents at each time increment. Counts of intact cells (cells/g) within the stomach and intestine contents were completed for shrimp that had been immersed for 60 min. Shrimp demonstrated a sweeping behavior of the third maxillipeds during submersion in some algal cultures, which led to examination through scanning electron microscope photography. Counts of intact cells and chlorophyll a levels in the stomach and intestine indicated that juvenile shrimp actively ingested and digested T. weissflogii and Amphiprora sp. from suspended monocultures. Diatom consumption and digestion were evident across all immersion times, with increasing levels of chlorophyll a in stomach samples up to but not significantly beyond 60 min, indicating that the experimental time period represented a continuous feeding period and spanned the gut passage time. Shrimp were able to ingest S. bacillarus and N. salina to a very limited degree, but there was no evidence of digestion of these cells. Examination under the scanning electron microscope revealed that the third maxillipeds have net-like setae which could potentially select for microorganism > 10 μm in size. Since this cell size reflected the difference between those cells consumed or not consumed in this study, we hypothesize that these appendages may be used by juvenile L. vannamei to filter food particles. These observations provide valuable insight regarding this shrimp's ability to capture and digest microalgae both within its natural environment and in aquaculture systems.

Acquisition, retention and dispersal of soilborne plant pathogenic fungi by fungus gnats and moth flies

AbstractAdult fungus gnats and moth flies were experimentally demonstrated to function as potential above‐ground vectors for three soilborne plant pathogens: Verticillium dahliae, Fusarium acuminatum and Thielaviopsis basicola. The adult insects externally acquired the conidia of the pathogens after exposure to the cultures as confirmed by scanning electron microscope photography. The intestinal contents and frass deposits of larvae exposed to fungal cultures contained viable fungal propagules. Internally infested larvae developed into internally infested pupae; however, the emerging adults were free of fungal structures. Because of the maintenance of a high level of inoculum on the external body surface and the ability of these adult insects to fly, they can be a significant factor in the dispersal of soilborne fungi in greenhouse agriculture. The rate of dispersal of T. basicola by adult fungus gnats was 1.78 cm2 h−1 per insect and by adult moth flies was 1.17 cm2 h−1 per insect. The area over which the pathogen was dispersed by the adult insects increased with the increase in exposure time. The study demonstrated that adult insects are efficient distributors of soilborne plant pathogenic fungal propagules.

Antennal and Cephalic organelles in the social wasp Paravespula germanica (Hymenoptera, Vespinae): Form and possible function

This paper deals with hairs and organelles present on the head and antennae of the German wasp, Paravespula germanica, and their possible role in sensing the physical and chemical ambience, as well as in intercommunicating both while in flight outside or in the nest. Via scanning electron microscope photography, we detected on the frons plate of the wasp's head, hairs that were about 300 microm long and comprised the longest hairs on the body of the wasps. Additionally, the two antennae bore along their entire length photoreceptors, placoids, campaniforms, trichoids, and agmons. These organelles are located at high but variable density along the antennal segments. The paper provides the dimensions of each of the mentioned organelles, and discusses the possible functions of the organelles as well as of the hairs on the frons. Photographs taken via atomic force microscope reveal that the epicuticle of the antenna is of two typical shapes; one, bearing both longitudinal stripes as well as transverse bands that are about 1 mum in width, and a second granulated form. Conceivably, the wasp uses the various organelles mentioned to communicate with its mates that are some distance away, somewhat like the use of radar by humans.

Late Pliocene Diatoms in a Diatomite from Prydz Bay, East Antarctica

Very well-preserved Pliocene diatoms from a diatomite unit interbedded within glacial sediments at Ocean Drilling Program Site 742 in Prydz Bay, Antarctica are documented and illustrated. The presence of Thalassiosira kolbei, T torokina, Actinocyclus actinochilus, A. karstenii and the absence of Nitzschia interfrigidaria. T insigna and T vulnifica in Sample 119-742A-15R-4, 44-46cm constrain its age to ca. 2.2-1.8 Ma (late Pliocene). Diatoms associated with sea ice constitute 35% of the Pliocene diatom assemblage, compared with 71% of the modem sediment assemblage at the site, suggesting that sea ice was present during the late Pliocene period of deposition of the sample, although it probably was not the significant feature it is today. Thalassiosira ellitipora (Donahue) Fenner is described and illustrated in detail and is validly published. An expanded description and numerous illustrations are also presented for T. torokina Brady. INTRODUCTION During Ocean Drilling Program Leg 119 on the continental shelf in Prydz Bay, Antarctica, a 60-cm-thick unit of distinctive greenish gray to gray diatomite (lithologic Subunit IIIB) was recovered within a thick (300+m) sequence of coarse-grained glacial diamictite in Core 15R of Hole 742A at 67?32.98'S, 75?24.27'E and a water depth of 426.2m (text-fig. 1) (Shipboard Scientific Party 1989). The abundant Pliocene diatoms found in this diatomite were apparently deposited during a period of enhanced biologic productivity in a distal glaciomarine setting, possibly during an interglacial period warmer than today (Shipboard Scientific Party 1989). The presence of well-preserved Pliocene diatoms within otherwise glacial sediments that typify the Antarctic shelf is relatively rare and offers an opportunity to study a nearshore environment of East Antarctica during an interval of the late Pliocene. A study of the diatoms of this Pliocene diatomite may provide evidence that bears on the hypothesis of Webb et al. (1984) and Webb and Harwood (1991) that calls for large scale deglaciation of East Antarctica during parts of the early and late Pliocene. In addition, the well-preserved nature of the diatoms in this deposit allows their study under the scanning electron microscope(SEM) and may contribute to solving some of the numerous problems of taxonomic confusion that currently plagues the study of Pliocene Antarctic diatoms (Harwood and Maruyama 1992). MATERIALS AND METHODS Sample 119-742A-15R-4, 44-46cm was collected from the 60cm-thick diatomite unit. The sample was processed for light microscopy (LM) and SEM by the Van der Werff (1955) hydrogen peroxide method. Strew slides were mounted in Hyrax for LM with individual species ringed for identification and photographic reference. Examination of taxa was made using a Leitz Ortholux II and an Olympus IMT at magnifications of x500 and x1250. SEM examination and photography was made using a Cambridge 250 mark II SEM at the U.S. Geological Survey (Menlo Park) and a Hitachi S520 at the California Academy of Sciences. Diatom terminology follows that of Ross et al. (1979). Sample material (CAS number 613278, ODP 119-742A-15R-4, 44-46cm) and slides (CAS numbers 217016-217018, 217022, 217026, 217027, 217029) are deposited at the California Academy of Sciences. TEXT-FIGURE 1 Location of ODP Site 742 in Prydz Bay, East Antarctica, and other sites cores by ODP Leg 119. Contours in meters. micropaleontology, vol. 42, no. 3, pp. 285-302, text-figure 1, plates 1-8, table 1, 1996 285 This content downloaded from 157.55.39.138 on Tue, 19 Apr 2016 06:51:08 UTC All use subject to http://about.jstor.org/terms Albert D. Mahood and John A. Barron: Late Pliocene Diatoms in a Diatomite from Prydz Bay, East Antarctica TABLE 1 Tabulation of diatom taxa in Pliocene Sample ODP-119-742A-15R-4, 44-46cm and their relative percentage compared with the relative percentage of taxa recorded in surface sediment at the site by Stockwell et al. (1991). * = extinct; ( ) = possible decendent.

Closing of dentinal tubules by glutardialdehyde treatment, a scanning electron microscopy study

The properties of dentin are strongly influenced by the so-called smear layer. This layer is always present on the dentin surface after cutting, drilling, sawing, etc. The smear layer can be removed by various chemical treatments, such as those of acid etching or ethylenediaminetetraacetic acid (EDTA). These treatments remove the smear layer and open the tubules. In this paper, the effect on the smear layer of human dentin of treatment with a 2% glutardialdehyde (GDA) solution at pH 3.5 for 2 min and a 0.5-M EDTA solution at pH 7.4 for 4 min was investigated by scanning electron microscope (SEM). The dentin samples were dried by air or critical-point drying before SEM photography was employed. The number of open dentin tubules was quantified on micrographs of EDTA- and GDA+EDTA-treated dentin. The results show that the GDA treatment fixed part of the smear layer and the superficial dentin surface in such a way that at least 50% of the tubules remained closed after EDTA treatment. By closing the dentinal tubules, the GDA-fixed layer might have a positive effect on dentin hypersensitivity, root caries, and bonding of composite to dentin.

The impact of soil structure and confining stress on the hydraulic conductivity of clays in brine environments

Numerous studies have been completed in recent years on the alteration of the hydraulic conductivity of clayey soils as a result of exposure to concentrated organic or inorganic permeants. These hydraulic conductivity changes have been attributed to either changes in microstructure, due to contraction of the diffuse double layer, or to the alteration of the macrostructure, as a result of volume changes leading to shrinkage fractures or fissures. In this paper, the change in hydraulic conductivity of a highly plastic natural clay during exposure to a concentrated sodium chloride (NaCl) solution is described. The performance of samples with three different initial soil structures, prepared by slurry, static compaction, and kneading compaction, were investigated under various levels of confining stress. Hydraulic conductivity tests were carried out before and after the samples were exposed to the NaCl solutions. Scanning electron microscope photography was used to compare the soil structures before and after brine permeation. The test results show that the alteration of hydraulic conductivity is strongly related to the initial soil structure and the level of confining stress. No significant change in the microfabric of the clay was observed; however, the size of the interaggregate pores appeared to increase as a result of the physicochemical volume change that occurred during brine permeation. The increase in hydraulic conductivity that occurred during brine permeation could be prevented by increasing the level of confining stress. The stress levels at which significant increases in hydraulic conductivity occurred appeared to be coincident with low levels of vertical stress which allowed the sample to undergo lateral shrinkage and a subsequent loss of confinement. Key words : hydraulic conductivity, clay soils, osmotic consolidation, sodium chloride brine, soil structure, scanning electron microscope.

Studies on male genitalia of sarcophagidae (Diptera) based on scanning electron microscope observations

Male genitalia of Oxyvinia exicisa (Lopes), Oxysarcodexia thomax (Walker), O. fluminensis Lopes, Sarcodexia lambens (Wiedemann), Peckia chrysostoma (Wiedemann) and Liopygia ruficornis (Fabricius) were studied based on scanning electron microscope photography. Some important details were evidentiated with this method.

A study of living plant specimens by low‐temperature scanning electron microscopy

AbstractYoung fresh Tradescantia reflexa stamen hair cells were used to clarify the optimal conditions for direct viewing and taking photographs with a scanning electron microscope (SEM) equipped with a cryo‐system. The rate of protoplasmic streaming in the cells was measured under an optical microscope after examining and photographing them in the SEM over a period of a few minutes. Almost the same rate of streaming (5.5 μm/second, 20°C) was observed in nonirradiated control cells and irradiated cells photographed in the SEM using an accelerating voltage of 10 kV with the cryo‐stage at a temperature of – 15°C. (The specimen holder and specimen were not at this temperature, but, rather, probably somewhat higher.) Fresh plant organs, tissues, and cells were also tested under the same conditions. The fine structure was well preserved in detail. The procedures were as follows: (1) prompt attachment of fresh plant materials on an aluminum specimen holder with double‐faced adhesive Scotch tape or a small amount of plastic adhesive for woodcraft; (2) setting the holder on the cryo‐stage cooled to –15°C in advance and rapid evacuation; and (3) quick SEM examination and photography (within several minutes). The advantages of this method are summarized as follows: (1) high possibility of viewing living materials; (2) minimal artifacts: freedom from chemical fixation and additional procedures utilized in ordinary SEM specimen preparation; and (3) simplicity, speediness, and economy in preparation for viewing. Since the specimens were not likely to be frozen during quick examination and photography, this method might well be called “low‐temperature SEM” (LT‐SEM) as distinguished from “cryo‐SEM”.

Plasma display panel MgO thin film properties and their modification by low energy ion bombardment

This paper contributes to a phenomenological understanding of the low energy ion bombardment induced changes of MgO thin films inside plasma display panels. SEM (scanning electron microscope) and optical photography are utilized to delineate local MgO changes such as densification and stress reversal at the operated gas panel cell site. MgO surface transformation is shown to be influenced by the presence of contaminants, surface topography, ion current and panel operating time. The implications of some of these with respect to panel operation are discussed. MgO thin film growth behaviour using electron-beam deposition and MgO film properties are dealt with in order to understand better the observed surface changes.

Reverse osmosis characteristics of cellulose acetate butyrate membranes

AbstractCellulose acetate butyrate membranes were cast from five different formulations. The pure water flux through the membrane increased with evaporation period. The separation of 4000 ppm NaCl aqueous solution remained unchanged until it reached a critical flux; at that point, separation decreased inversely proportional to the flux. Scanning electron microscope photography of the membranes corresponding to each evaporation period is reported.

Surface smoothness and marginal fit with phosphate-bonded investments

Two phosphate-bonded investments and one calcium sulfate investment were evaluated for the surface smoothness and marginal fit they impart to gold castings. A modified technique was also evaluated for each phosphate-bonded investment, where the silica sol was not diluted and the spatulation time was reduced. The results of this study lead to the following conclusions: 1. The marginal fits obtained with all four phosphate-bonded methods were comparable to each other and superior to that obtained with the calcium sulfate investment. 2. The presence of nodules on the surface of the castings was more prevalent with the phosphate-bonded investments. However, this effect was not statistically significant. 3. Clinical assessment of the roughness of the castings revealed that all the methods tested produced clinically acceptable castings. 4. Visual observation by five dentists revealed that both the recommended and modified techniques for one of the phosphate-bonded investments (Ceramigold) produced a smoother surface than any other investment tested. Rating of scanning electron microscope photographs (X600) revealed no difference in the surface roughness between any of the castings. Consequently, no definitive relation between investment type or technique and surface roughness was established. 5. No correlation was demonstrated between surface roughness, as evaluated by either clinical observation or scanning electron microscope photography, and marginal fit of the castings.