scholarly journals Morphological and histopathological studies of Thelandros chalcidae (Oxyuroidea: Pharyngodonidae) infecting Chalcides ocellatus from Egypt

2021 ◽  
Vol 82 (1) ◽  
Author(s):  
Mona F. Fol ◽  
Nesma A. Mostafa
Keyword(s):  
Gastrointestinal Nematode ◽  
The Body ◽  
Maximum Width ◽  
Leukocytic Infiltration ◽  
Body Level ◽  
Electron Microscopes ◽  
Histopathological Studies ◽  
Scanning Electron Microscopes ◽  
Chalcides Ocellatus ◽  
Gastrointestinal Nematode Parasite

Abstract Background Thelandros (Pharyngodonidae) is a gastrointestinal nematode parasite with a life cycle including lizards as main hosts. Thelandros chalcidae collected from the large intestine of the Egyptian ocellated skink, Chalcides ocellatus were described and illustrated by light and scanning electron microscopes. Seven out of fifteen (46.66%) of the examined lizards were found to be naturally infected. Also, host intestinal tissues were evaluated from hematoxylin/eosin-stained sections to describe any histopathological changes. Results Microscopic examinations revealed that the recovered pharyngodonid species characterized by mouth with triangular opening and surrounded by six simple lips, the cuticle had regular transverse annulations extending from the posterior margin of the lips to the end of the body. Male was cylindrical with distinct truncated posterior end and measured 1.59–1.86 (1.64 ± 0.10) long and 0.29–0.37 (0.32 ± 0.01) in maximum width at the level of mid-body. Female measured 1.72–2.43 (1.85 ± 0.2) long and 0.36–0.49 (0.42 ± 0.01) maximum width at the mid-body level, terminated posteriorly in a short, stout spike. Histological studies observed structural alterations represented by leukocytic infiltration, villi atrophy, and muscularis degeneration. These changes were indicative of inflammatory and degenerative reaction due to Thelandros chalcidae infection. Conclusion The present morphological study revealed that the recovered pharyngodonid species was Thelandros chalcidae causing pathological alterations in Chalcides ocellatus intestinal tissues.

Effects of Mechanical Alloying on the Structure and Properties of Iron Powders

2015 ◽  
Vol 364 ◽  
pp. 132-138
Author(s):  
F. Lemdani ◽  
Mohammed Azzaz ◽  
K. Taïbi ◽  
A. Lounis
Keyword(s):  
Magnetic Behavior ◽  
High Energy ◽  
The Body ◽  
X Ray Diffraction ◽  
Laser Scattering ◽  
Different Types ◽  
Bcc Structure ◽  
Electron Microscopes ◽  
Diffraction Patterns ◽  
Scanning Electron Microscopes

A nanostructured iron, elaborated from pure elemental powders by mechanical milling at high energy was characterized by different types of technical of analysis. Scanning electron microscopes (SEM) and laser scattering machine have showed the variation in the size and the shape of particles according to different milling times. Powders obtained were characterized with X-ray diffraction (XRD) , the latter diffraction patterns indicated the body centered cubic (bcc) structure. The crystalline grain was about 13 nm size after only a few hours of milling time. The measurement of both coercive field (Hc) and maximal magnetization (Ms) revealed a change in the magnetic behavior of our samples.

scholarly journals A new species of Exogone Ørsted, 1845 (Annelida: Syllidae: Exogoninae) from Brazilian waters

2019 ◽  
Vol 59 ◽  
pp. e20195947 ◽  
Author(s):  
Marcelo Veronesi Fukuda ◽  
Andrezza Ribeiro Menezes-Moura ◽  
Carmen Regina Parisotto Guimarães ◽  
Christine Ruta
Keyword(s):  
New Species ◽  
The Body ◽  
Anterior Body ◽  
Electron Microscopes ◽  
Polychaete Family ◽  
Scanning Electron Microscopes ◽  
A New Species ◽  
Scanning Electron

We describe herein a new species of the abundant polychaete family Syllidae, Exogone brasiliensis sp. nov. The new species is characterized by a peculiar morphology of anterior body falcigers, with shafts and blades modified specially in chaetigers 1 and 2; falcigers until chaetiger 5 different from those of the rest of the body; and dorsal simple chaetae from midbody onwards unique in the genus, nearly straight, subdistally swollen in one side only, distally rounded. Exogone brasiliensis sp. nov. is described based on detailed morphological analyses under optical and scanning electron microscopes, and compared to its most similar congeners.

Morphology and Physical Studies of Nanostructured Fe64Cr36 Alloy Elaborated by Ball Milling

2013 ◽  
Vol 26 ◽  
pp. 75-81 ◽  
Author(s):  
S. Triaa ◽  
L. Faghi ◽  
F. Kali-Ali ◽  
M. Azzaz
Keyword(s):  
Milling Time ◽  
High Energy ◽  
The Body ◽  
Analysis Method ◽  
X Ray Diffraction ◽  
Bcc Structure ◽  
Iron Phase ◽  
Electron Microscopes ◽  
Xrd Patterns ◽  
Scanning Electron Microscopes

Nanostructured iron based alloy, elaborated from pure elemental powders by mechanical milling at high energy was studied. The materials obtained were characterized by several techniques, such as X-ray diffraction (XRD), which allowed the dissolution of chromium in the iron phase as a function of milling time. The peaks indicate that the obtained solid solution has the body centred cubic (bcc) structure, for a speed of 250 rpm after 24 hours milling time. The Williamson - Hall analysis method was used to exploit the recorded XRD patterns. The crystallite size of about 14 nm and the microstrain of about 0.90% were obtained for 48 hours of milling. Scanning electron microscopes (SEM) and EDX analysis have confirmed the refining of milled particles as a function of milling time and the homogenization of our powders. The measurement of reflection coefficient has revealed an increase in the microwave absorption versus milling time and has confirmed the formation of our alloy during 24 hours of milling.

Study of Mechanical Properties of Magnesium Oxide Doped Alumina (Al2O3) and Yttria Stabilized Zirconia (YSZ) Composite for Medical Applications

2012 ◽  
Vol 506 ◽  
pp. 521-524 ◽  
Author(s):  
A. Phothawan ◽  
K. Nganvongpanit ◽  
T. Tunkasiri ◽  
Sukum Eitssayeam
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Magnesium Oxide ◽  
Sintering Temperature ◽  
The Body ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Electron Microscopes ◽  
Pin On Disk ◽  
Scanning Electron Microscopes

The aim of this research is to study the mechanical properties such as hardness ,wear resistance etc , of the magnesium oxide (MgO) doped alumina (Al2O3) and yttria stabilized zirconia (YSZ) composite, We first prepared MgO-doped Al2O3(denoted as Al4) by mixing Al2O3powder and 0.4 wt% of MgO powder. After that Al4powder was mixed YSZ powder, with the formula [(x)Al4- (100-x)YS when x was varied from 0 - 100 by wt%. The samples were sintered at 1450, 1500, 1550, 1600 and 1650 °C. In addition, microstructure of the surface was studied employing both optical and scanning electron microscopes. The hardness of the surface was investigated by Vickers indentation technique and pin on disk apparatus was employed for wear rate measurement. The results showed that the density and volume shrinkage decreased with the increase of Al4content. The grain size and porosity of the specimens tend to decrease when the sintering temperature increases. The hardness and wear resistance of the samples increased with the increase of Al4up to 90 %. It was also found that the material is not toxic to the body.

Toward High-Resolution Low-Voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 218-219
Author(s):  
Zhifeng Shao
Keyword(s):  
Low Voltage ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Limiting Factor ◽  
Operating Voltage ◽  
Probe Radius ◽  
Non Local ◽  
Electron Microscopes ◽  
Image Position ◽  
Scanning Electron Microscopes

Recently, low voltage (≤5kV) scanning electron microscopes have become popular because of their unprecedented advantages, such as minimized charging effects and smaller specimen damage, etc. Perhaps the most important advantage of LVSEM is that they may be able to provide ultrahigh resolution since the interaction volume decreases when electron energy is reduced. It is obvious that no matter how low the operating voltage is, the resolution is always poorer than the probe radius. To achieve 10Å resolution at 5kV (including non-local effects), we would require a probe radius of 5∽6 Å. At low voltages, we can no longer ignore the effects of chromatic aberration because of the increased ratio δV/V. The 3rd order spherical aberration is another major limiting factor. The optimized aperture should be calculated as

Current State of Biological High-Resolution Scanning Electron Microscopy

1988 ◽  
Vol 46 ◽  
pp. 180-181 ◽  
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Performance ◽  
Low Voltage ◽  
Backscattered Electrons ◽  
Lens Position ◽  
Low Voltage Operation ◽  
Signal Collection ◽  
Probe Size ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

A new generation of high performance field emission scanning electron microscopes (FSEM) is now commercially available (JEOL 890, Hitachi S 900, ISI OS 130-F) characterized by an "in lens" position of the specimen where probe diameters are reduced and signal collection improved. Additionally, low voltage operation is extended to 1 kV. Compared to the first generation of FSEM (JE0L JSM 30, Hitachi S 800), which utilized a specimen position below the final lens, specimen size had to be reduced but useful magnification could be impressively increased in both low (1-4 kV) and high (5-40 kV) voltage operation, i.e. from 50,000 to 200,000 and 250,000 to 1,000,000 x respectively.At high accelerating voltage and magnification, contrasts on biological specimens are well characterized1 and are produced by the entering probe electrons in the outmost surface layer within -vl nm depth. Backscattered electrons produce only a background signal. Under these conditions (FIG. 1) image quality is similar to conventional TEM (FIG. 2) and only limited at magnifications >1,000,000 x by probe size (0.5 nm) or non-localization effects (%0.5 nm).

Chromatic aberration and low-voltage SEM

1987 ◽  
Vol 45 ◽  
pp. 546-547
Author(s):  
Zhifeng Shao ◽  
A.V. Crewe
Keyword(s):  
Electron Energy ◽  
Low Voltage ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Primary Electron ◽  
Probe Size ◽  
Non Local ◽  
Optical Treatment ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes

For scanning electron microscopes, it is plausible that by lowering the primary electron energy, one can decrease the volume of interaction and improve resolution. As shown by Crewe /1/, at V0 =5kV a 10Å resolution (including non-local effects) is possible. To achieve this, we would need a probe size about 5Å. However, at low voltages, the chromatic aberration becomes the major concern even for field emission sources. In this case, δV/V = 0.1 V/5kV = 2x10-5. As a rough estimate, it has been shown that /2/ the chromatic aberration δC should be less than ⅓ of δ0 the probe size determined by diffraction and spherical aberration in order to neglect its effect. But this did not take into account the distribution of electron energy. We will show that by using a wave optical treatment, the tolerance on the chromatic aberration is much larger than we expected.

High-resolution observation of sintered alumina (Al2O3) using the specimen-heated and electron-beam-induced conductivity method in a UHR-SEM

1994 ◽  
Vol 52 ◽  
pp. 1046-1047
Author(s):  
K. Ogura ◽  
T. Suzuki ◽  
C. Nielsen
Keyword(s):  
Electron Beam ◽  
High Resolution ◽  
Specimen Preparation ◽  
Conductivity Method ◽  
Fine Grain ◽  
Grain Structures ◽  
Resolution Observation ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Charging Effect

In spite of the complicated specimen preparation, Transmission Electron Microscopes (TEM) have traditionally been used for the investigation of the fine grain structures of sintered ceramics. Scanning Electron Microscopes (SEM) have not been used much for the same purpose as TEM because of poor results caused by the specimen charging effect, and also the lack of sufficient resolution. Here, we are presenting a successful result of high resolution imaging of sintered alumina (pure Al2O3) using the Specimen Heated and Electron Beam Induced Conductivity (SHEBIC) method, which we recently reported, in an ultrahigh resolution SEM (UHR-SEM). The JSM-6000F, equipped with a Field Emission Gun (FEG) and an in-lens specimen position, was used for this application.After sintered Al2O3 was sliced into a piece approximately 0.5 mm in thickness, one side was mechanically polished to get a shiny plane for the observation. When the observation was started at 20 kV, an enormous charging effect occured, and it was impossible to obtain a clear Secondary Electron (SE) image (Fig.1).

High resolution at low voltage: A new approach

1989 ◽  
Vol 47 ◽  
pp. 76-77
Author(s):  
Arthur V. Jones
Keyword(s):  
Low Voltage ◽  
Emission Sources ◽  
New Approach ◽  
Design Concepts ◽  
Probe Diameter ◽  
Low Voltage Operation ◽  
Sufficient Intensity ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Immersion Type

With the introduction of field-emission sources and “immersion-type” objective lenses, the resolution obtainable with modern scanning electron microscopes is approaching that obtainable in STEM and TEM-but only with specific types of specimens. Bulk specimens still suffer from the restrictions imposed by internal scattering and the need to be conducting. Advances in coating techniques have largely overcome these problems but for a sizeable body of specimens, the restrictions imposed by coating are unacceptable.For such specimens, low voltage operation, with its low beam penetration and freedom from charging artifacts, is the method of choice.Unfortunately the technical dificulties in producing an electron beam sufficiently small and of sufficient intensity are considerably greater at low beam energies — so much so that a radical reevaluation of convential design concepts is needed.The probe diameter is usually given by

Observation of GaAs/AlAs Superlattice Structures in both Secondary and Backscattcred Electron Imaging Modes with an Ultrahigh Resolution Scanning Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 404-405
Author(s):  
K. Ogura ◽  
A. Ono ◽  
S. Franchi ◽  
P.G. Merli ◽  
A. Migliori
Keyword(s):  
Gaas Layer ◽  
Objective Lens ◽  
Superlattice Structure ◽  
Backscattered Electron ◽  
Instrumental Resolution ◽  
Electron Microscopes ◽  
Superlattice Structures ◽  
Electron Imaging ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

In the last few years the development of Scanning Electron Microscopes (SEM), equipped with a Field Emission Gun (FEG) and using in-lens specimen position, has allowed a significant improvement of the instrumental resolution . This is a result of the fine and bright probe provided by the FEG and by the reduced aberration coefficients of the strongly excited objective lens. The smaller specimen size required by in-lens instruments (about 1 cm, in comparison to 15 or 20 cm of a conventional SEM) doesn’t represent a serious limitation in the evaluation of semiconductor process techniques, where the demand of high resolution is continuosly increasing. In this field one of the more interesting applications, already described (1), is the observation of superlattice structures.In this note we report a comparison between secondary electron (SE) and backscattered electron (BSE) images of a GaAs / AlAs superlattice structure, whose cross section is reported in fig. 1. The structure consist of a 3 nm GaAs layer and 10 pairs of 7 nm GaAs / 15 nm AlAs layers grown on GaAs substrate. Fig. 2, 3 and 4 are SE images of this structure made with a JEOL JSM 890 SEM operating at an accelerating voltage of 3, 15 and 25 kV respectively. Fig. 5 is a 25 kV BSE image of the same specimen. It can be noticed that the 3nm layer is always visible and that the 3 kV SE image, in spite of the poorer resolution, shows the same contrast of the BSE image. In the SE mode, an increase of the accelerating voltage produces a contrast inversion. On the contrary, when observed with BSE, the layers of GaAs are always brighter than the AlAs ones , independently of the beam energy.

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