scholarly journals 6. The Nature of Asteroid Surfaces, from Optical Polarimetry

1977 ◽  
Vol 39 ◽  
pp. 243-251 ◽  
Author(s):  
A. Dollfus ◽  
J. E. Geake ◽  
J. C. Mandeville ◽  
B. Zellner
Keyword(s):  
The Body ◽  
Space Weathering ◽  
Carbonaceous Chondrites ◽  
The Moon ◽  
Laboratory Measurements ◽  
Surface Textures ◽  
Lunar Samples ◽  
Dark Material ◽  
Polarization Of Light ◽  
Scanning Electron

Telescopic observations of the polarization of light by asteroids are interpreted on the basis of a systematic polarimetric analysis of terrestrial, meteoritic and lunar samples. Laboratory measurements were made using samples with different surface textures, and scanning electron microscope pictures were used to investigate the influence of microtexture and crystalline structure.It is demonstrated that asteioid surfaces do not accumulate thick regolithic layers of micro-fragments, as do the Moon and Mercury. This is because the majority of debris ejected by impacts are lost, due to the low gravitational escape velocity from these bodies. However, asteroids are not bare rocks, but are coated with a thin layer of adhesive debris. This coating apparently has the composition of the body itself. The fact that there is no indication of significant maturation by space weathering suggests that the dust which coats the surface of asteroids is frequently replaced by further impacts.Asteroids may be classified polarimetrically in several groups: those in group C are made of very dark material and behave like carbonaceous chondrites, or very dark Fe-rich basalts; Those in group S correspond to silicates and stony meteorites. A third group represented by Asteroid 21 Lutetia and 16 Psyche may be metallic.

scholarly journals Coordinated analysis of space weathering characteristics in lunar samples to understand water distribution on the Moon

2021 ◽  
Vol 27 (S1) ◽  
pp. 2260-2262
Author(s):  
Alexander Kling ◽  
Michelle Thompson ◽  
Jennika Greer ◽  
Philipp Heck
Keyword(s):  
Water Distribution ◽  
Space Weathering ◽  
The Moon ◽  
Lunar Samples

Scanning electron microscopy of freeze-fractured prescapular lymph node of caprine

1984 ◽  
Vol 42 ◽  
pp. 244-245
Author(s):  
O. Faroon ◽  
F. Al-Bagdadi ◽  
T. G. Snider ◽  
C. Titkemeyer
Keyword(s):  
Lymph Node ◽  
Lymph Nodes ◽  
Lymphatic System ◽  
Three Dimensional ◽  
Meat Products ◽  
The Body ◽  
Morphological Data ◽  
The World ◽  
Cellular Constituent ◽  
Scanning Electron

The lymphatic system is very important in the immunological activities of the body. Clinicians confirm the diagnosis of infectious diseases by palpating the involved cutaneous lymph node for changes in size, heat, and consistency. Clinical pathologists diagnose systemic diseases through biopsies of superficial lymph nodes. In many parts of the world the goat is considered as an important source of milk and meat products.The lymphatic system has been studied extensively. These studies lack precise information on the natural morphology of the lymph nodes and their vascular and cellular constituent. This is due to using improper technique for such studies. A few studies used the SEM, conducted by cutting the lymph node with a blade. The morphological data collected by this method are artificial and do not reflect the normal three dimensional surface of the examined area of the lymph node. SEM has been used to study the lymph vessels and lymph nodes of different animals. No information on the cutaneous lymph nodes of the goat has ever been collected using the scanning electron microscope.

X-ray micro tomography in the scanning electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 106-107 ◽  
Author(s):  
W. Brünger
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Target Surface ◽  
The Body ◽  
X Rays ◽  
Cross Sectional ◽  
X Ray ◽  
Micro Tomography ◽  
Scanning Electron

Reconstructive tomography is a new technique in diagnostic radiology for imaging cross-sectional planes of the human body /1/. A collimated beam of X-rays is scanned through a thin slice of the body and the transmitted intensity is recorded by a detector giving a linear shadow graph or projection (see fig. 1). Many of these projections at different angles are used to reconstruct the body-layer, usually with the aid of a computer. The picture element size of present tomographic scanners is approximately 1.1 mm2.Micro tomography can be realized using the very fine X-ray source generated by the focused electron beam of a scanning electron microscope (see fig. 2). The translation of the X-ray source is done by a line scan of the electron beam on a polished target surface /2/. Projections at different angles are produced by rotating the object.During the registration of a single scan the electron beam is deflected in one direction only, while both deflections are operating in the display tube.

The ultrastructure of the epidermis of the redia and cercaria of Parorchis acanthus, Nicoll. A study by scanning and transmission electron-microscopy

Parasitology ◽  
1971 ◽  
Vol 62 (3) ◽  
pp. 479-488 ◽  
Author(s):  
Gwendolen Rees
Keyword(s):  
Electron Micrographs ◽  
Technical Assistance ◽  
Ventral Surface ◽  
The Body ◽  
Muscle Fibres ◽  
Scanning Electron Micrographs ◽  
Large Area ◽  
Transmission Electron ◽  
Parorchis Acanthus ◽  
Scanning Electron

Scanning electron-micrographs have shown the covering of microvilli on the surface of the redia of Parorchis acanthus. In the contracted state the elongated microvilli with bulbous extremities seen in the surface grooves may be the result of compression. The surface of the epidermis of the cercaria is smooth on a large area of the ventral surface and lattice-like with microvilli, laterally, anteriorly, dorsally and on the tail. The spines on the body can be withdrawn into sheaths by the contraction of muscle fibres inserted into the basement lamina below each spine.I would like to express my sincere gratitude to Dr I. ap Gwynn of this department for preparing the scanning electron-micrographs and the School of Engineering Science, University of North Wales, Bangor for the use of their stereoscan. I should also like to thank Mr M. C. Bibby for technical assistance and Professor E. G. Gray and Dr W. Sinclair for assistance with the transmission electron-micrographs.

Preparation of Alcohol-Preserved Larvae of Culicidae (Diptera) for Scanning Electron Microscopy

1972 ◽  
Vol 3 (3) ◽  
pp. 181-188 ◽  
Author(s):  
Christine Dahl
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
The Body ◽  
Taxonomic Studies ◽  
Scanning Electron ◽  
Sem Studies

AbstractA method for preparation of alcohol-preserved culicid larvae for Scanning Electron Microscope (SEM) studies is described. It is based on dehydration by ethanol-xylol and fast evaporation of xylol in +8o° C. for ten minutes. For taxonomic studies such as examination of pecten teeth, comb scales and microtrichiae in magnifications up to 6oooX the method is suitable. For studies of receptor structures on hair-tufts and microstructures of the body integument alcohol preserved material is less satisfactory. The microstructure of the comb scales is figured and their function discussed. Differences in the ultrastructure of the abdominal hair-tufts are pointed out.

Porous Bioceramics (Open Cell Foams) Expanded in Vacuum

2006 ◽  
Vol 309-311 ◽  
pp. 1023-1026
Author(s):  
E.T. Uzumaki ◽  
C.S. Lambert
Keyword(s):  
Zirconium Oxide ◽  
Cell Structure ◽  
The Body ◽  
Carbon Coatings ◽  
Open Cell ◽  
Glass Foam ◽  
Open Cell Foams ◽  
Titanium Foam ◽  
Porous Bioceramics ◽  
Scanning Electron

In this study, porous bioceramics (titanium foam with diamond-like carbon coatings, glass foam and zirconium oxide foam) were produced using expansion in vacuum. The porosity, the pore size and pore morphology can be adjusted in agreement with the application. The different 3D structures were obtained by varying the parameters of the process. The microstructure and morphology of the porous materials were observed by scanning electron microscopy (SEM) and optical microscopy. The foam exhibit an open-cell structure with interconnected macropores, which provide the potential for tissue ingrowths and the transport of the body fluids.

Ionic regulation and buoyancy in some planktonic organisms

1993 ◽  
Vol 73 (1) ◽  
pp. 15-23 ◽  
Author(s):  
C. Newton ◽  
W. T. W. Potts
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
The Body ◽  
Coelomic Fluid ◽  
Ionic Regulation ◽  
High Concentration ◽  
Emission Analysis ◽  
X Ray ◽  
Scanning Electron ◽  
Gastrovascular System

Magnesium/chlorine and sulphur/chlorine ratios have been measured in the body fluids of some planktonic organisms by x-ray emission analysis of frozen hydrated specimens in a scanning electron microscope. Homarus vulgaris (Anthropoda: Decapoda) larvae excluded Mg2+ and SO42-ions from the haemolymph, but to a lesser extent than does the adult lobster. Bipinnaria larvae of Asterias (Echinodermata) excluded Mg2+ and SO42-ions from the coelomic fluid. Obelia medusae excluded Mg2+ and SO42-ions from the mesogloea but concentrate them in the gastrovascular system. The high concentration of sulphate in the gastrovascular fluid of medusae has been confirmed by rhodizonate titration in Cyanea and Rhizostoma jellyfish. Some implications of magnesium and sulphate regulation are discussed.

Impact remnants rich in carbonaceous chondrites detected on the Moon by the Chang’e-4 rover

2021 ◽  
Author(s):  
Yazhou Yang ◽  
Shuai Li ◽  
Meng-Hua Zhu ◽  
Yang Liu ◽  
Bo Wu ◽  
...  
Keyword(s):  
Carbonaceous Chondrites ◽  
The Moon

scholarly journals Bandwidth and Common Mode Optimization for Current and Voltage Sources in Bioimpedance Spectroscopy

2021 ◽  
Vol 12 (1) ◽  
pp. 135-146
Author(s):  
Tobias Menden ◽  
Jascha Matuszczyk ◽  
Steffen Leonhardt ◽  
Marian Walter
Keyword(s):  
Patient Safety ◽  
Current Source ◽  
The Body ◽  
Voltage Source ◽  
Bioimpedance Spectroscopy ◽  
Laboratory Measurements ◽  
Output Impedance ◽  
Frequency Range ◽  
Common Mode ◽  
High Bandwidth

Abstract Bioimpedance measurements use current or voltage sources to inject an excitation signal into the body. These sources require a high bandwidth, typically from 1 kHz to 1 MHz. Besides a low common mode, current limitation is necessary for patient safety. In this paper, we compare a symmetric enhanced Howland current source (EHCS) and a symmetric voltage source (VS) based on a non-inverting amplifier between 1 kHz and 1 MHz. A common mode reduction circuit has been implemented in both sources. The bandwidth of each source was optimized in simulations and achieved a stable output impedance over the whole frequency range. In laboratory measurements, the output impedance of the EHCS had its -3 dB point at 400 kHz. In contrast, the VS reached the +3 dB point at 600 kHz. On average over the observed frequency range, the active common mode compensation achieved a common mode rejection of -57.7 dB and -71.8 dB for the EHCS and VS, respectively. Our modifications to classical EHCS and VS circuits achieved a low common mode signal between 1 kHz and 1 MHz without the addition of complex circuitry, like general impedance converters. As a conclusion we found VSs to be superior to EHCSs for bioimpedance spectroscopy due to the higher bandwidth performance. However, this only applies if the injected current of the VS can be measured.

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