Evaluation of sectioning techniques for Electron Microscopic analyses of low-density polyethylene foams

1986 ◽  
Vol 44 ◽  
pp. 880-881
Author(s):  
P. L. McCarthy ◽  
C. W. Price
Keyword(s):  
Cell Walls ◽  
Surface Preparation ◽  
Structural Features ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Electron Microscopic ◽  
Freeze Fracturing ◽  
Planar Surfaces ◽  
Carbon Coated ◽  
Sem Analyses

Cell sizes of low-density polyethylene foams in the range of 0.5 to 5μm are most conveniently measured by SEM analyses. Unfortunately, the cell walls are relatively weak and fragile membranes that either collapse or are severely distorted by conventional surface preparation and sectioning techniques. Sectioning damage can be circumvented to some extent by freeze fracturing. However, fractures tend to propagate through the weakest structural features, they can be associated with severe deformation, even at liquid nitrogen temperatures, and they frequently do not yield planar surfaces for reliable statistical measurements. Therefore, alternate sectioning techniques were evaluated. The most promising techniques are vibrotome sectioning and ultramicrotomy. These techniques are compared with freeze fracturing using SEM examinations of carbon-coated specimens prepared from the same batch of foam.

Characterization of machined polystyrene foam

1989 ◽  
Vol 47 ◽  
pp. 372-373
Author(s):  
C. W. Price ◽  
E. F. Lindsey ◽  
R. M. Franks ◽  
M. A. Lane
Keyword(s):  
Surface Finish ◽  
Cell Walls ◽  
Surface Structures ◽  
Efficient Technique ◽  
Low Density ◽  
Polystyrene Foam ◽  
Planar Surfaces ◽  
Machining Characteristics

Diamond-point turning is an efficient technique for machining low-density polystyrene foam, and the surface finish can be substantially improved by grinding. However, both diamond-point turning and grinding tend to tear and fracture cell walls and leave asperities formed by agglomerations of fragmented cell walls. Vibratoming is proving to be an excellent technique to form planar surfaces in polystyrene, and the machining characteristics of vibratoming and diamond-point turning are compared.Our work has demonstrated that proper evaluation of surface structures in low density polystyrene foam requires stereoscopic examinations; tilts of + and − 3 1/2 degrees were used for the stereo pairs. Coating does not seriously distort low-density polystyrene foam. Therefore, the specimens were gold-palladium coated and examined in a Hitachi S-800 FESEM at 5 kV.

scholarly journals Microbial consortiums of putative degraders of low-density polyethylene-associated compounds in the ocean

2021 ◽  
Author(s):  
Maria Pinto ◽  
Zihao Zhao ◽  
Katja Klun ◽  
Eugen Libowitzky ◽  
Gerhard J Herndl
Keyword(s):  
Relative Abundance ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Alkane Hydroxylase ◽  
Alkane Degradation ◽  
Electron Microscopic ◽  
Genes Encoding ◽  
Diverse Community ◽  
Metagenomics Analysis ◽  
Over Time

Polyethylene (PE) is one of the most abundant plastics in the ocean. The development of a biofilm on PE in the ocean has been reported, yet whether some of the biofilm-forming organisms can biodegrade this plastic in the environment remains unknown. Via metagenomics analysis, we taxonomically and functionally analysed three biofilm communities using low-density polyethylene (LDPE) as their sole carbon source for two years. Several of the taxa that increased in relative abundance over time were closely related to known degraders of alkane and other hydrocarbons. Alkane degradation has been proposed to be involved in PE degradation, and most of the organisms increasing in relative abundance over time harboured genes encoding proteins essential in alkane degradation, such as the genes alkB and CYP153, encoding an alkane monooxygenase and a cytochrome P450 alkane hydroxylase. Weight loss of PE sheets when incubated with these communities and chemical and electron microscopic analyses provided evidence for alteration of the PE surface over time. Taken together, these results provide evidence for the utilization of LDPE-associated compounds by the prokaryotic communities. This study identifies a group of genes potentially involved in the degradation of the LDPE polymeric structure and/or associated plastic additives in the ocean and describes a phylogenetically diverse community of plastic biofilm-dwelling microbes with the potential of utilizing LDPE-associated compounds as carbon and energy source.

Ultrastructural analysis of early pre-messenger RNA processing events using the Miller chromatin spreading method

1992 ◽  
Vol 50 (1) ◽  
pp. 554-555
Author(s):  
Ann Beyer ◽  
Yvonne Osheim
Keyword(s):  
Rna Processing ◽  
Messenger Rna ◽  
Structural Features ◽  
Ultrastructural Analysis ◽  
Electron Microscopic ◽  
Mrna Transcripts ◽  
Carbon Coated ◽  
Nascent Transcripts ◽  
Active Genes

We use the Miller chromatin spreading technique for electron microscopic visualization of transcriptionally active genes. In this method, cells are hypotonically disrupted and cellular contents are diluted into water at pH 8-9 and fixed with formaldehyde. The dispersed cellular contents are centrifuged onto a carbon-coated EM grid; the majority of the material that is deposited on the grid consists of entangled masses of dispersed chromatin, some regions of which are transcriptionally active (Fig 1). Our interests lie in ultrastructural analysis of co-transcriptional RNA processing events on pre-mRNA transcripts, which we analyze by mapping structural features on successive nascent transcripts on a given gene. The two processing events that we have been able to study by this approach are the removal of introns by splicing and generation of the 3’ end of the transcript.

scholarly journals Surface Mechanical Characterization of Carbon Nanofiber Reinforced Low-Density Polyethylene by Nanoindentation and Comparison with Bulk Properties

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1357 ◽  
Author(s):  
Peyman Nikaeen ◽  
Dilip Depan ◽  
Ahmed Khattab
Keyword(s):  
Tensile Test ◽  
Carbon Nanofiber ◽  
Surface Preparation ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Force Microscopy ◽  
Atomic Force ◽  
Macro Scale ◽  
Data Points

Surface mechanical properties of low-density polyethylene (LDPE) reinforced by carbon nanofibers (CNFs) up to 3% weight load were investigated using nanoindentation (NI). Surface preparation of the nanocomposite was thoroughly investigated and atomic force microscopy (AFM) was used to analyze the surface roughness of the polished surfaces. The dispersion of nanofillers in the LDPE matrix was examined using scanning electron microscopy (SEM). The effect of various penetration loads on the results and scattering of the data points was discussed. It was found by NI results that the addition of 3% weight CNF increased the elastic modulus of LDPE by 59% and its hardness up to 12%. The nano/micro-scale results were compared with macro-scale results obtained by the conventional tensile test as well as the theoretical results calculated by the Halpin-Tsai (HT) model. It was found that the modulus calculated by nanoindentation was twice that obtained by the conventional tensile test which was shown to be in excellent agreement with the HT model. Experimental results indicated that the addition of CNF to LDPE reduced its wear resistance property by reducing the hardness to modulus ratio. SEM micrographs of the semicrystalline microstructure of the CNF/LDPE nanocomposite along with the calculated NI imprints volume were examined to elaborate on how increasing the penetration depth resulted in a reduction of the coefficient of variation of the NI data/more statistically reliable data.

Scanning Electron Microscopic and Electrophoretic Observations on Barium Sulphate Used to Adsorb Clotting Factors

1975 ◽  
Vol 33 (02) ◽  
pp. 256-270
Author(s):  
R. M Howell ◽  
S. L. M Deacon
Keyword(s):  
Electron Microscopy ◽  
Factor Xa ◽  
Barium Sulphate ◽  
High Density ◽  
Low Density ◽  
Factor X ◽  
Clotting Factors ◽  
Electron Microscopic ◽  
Complementary Techniques ◽  
Scanning Electron

SummaryElectron microscopy and particle electrophoresis were found to be complementary techniques with which to complete the physical data from an earlier study on barium sulphates used to adsorb clotting factors from serum. The differences revealed by scanning electron microscopy (S. E. M.) in the physical shape of low and high density grades of barium sulphate particles appear to be of greater significance than charge as expressed by electrophoretic mobility, in determining whether or not precursor or preformed factor Xa is eluted.This conclusion was based on the finding that at pH values close to 7, where the adsorption from serum occurs, all samples with the exception of natural barytes were uncharged. However as the high-density, or soil-grade, was found by S. E. M. to consist of large solid crystals it was suggested that this shape might induce activation of factor X as a result of partial denaturation and consequent unfolding of the adsorbed protein. In contrast, uptake of protein into the centre of the porous aggregates revealed by S. E. M. pictures of low-density or X-ray grade barium sulphate may afford protection against denaturation and exposure of the enzyme site.The porous nature of particles of low-density barium sulphate compared with the solid crystalline forms of other grades accounts not only for its lower bulk density but also for its greater surface/gram ratio which is reflected by an ability to adsorb more protein from serum.Neither technique produced evidence from any of the samples to indicate the presence of stabilising agents sometimes used to coat particles in barium meals.

Biodegradation of low density polyethylene/starch films exposed to soil burial

2009 ◽  
Vol 34 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Souad Djellalia ◽  
Nassima Benmahmoud ◽  
Tahar Sadoun
Keyword(s):  
Low Density Polyethylene ◽  
Low Density ◽  
Soil Burial ◽  
Starch Films
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