scholarly journals Spirals: their orientation and description

1994 ◽  
Vol 13 (1) ◽  
pp. 54-54
Author(s):  
Stefan A. Revets
Keyword(s):  
Cross Sections ◽  
Oxford English Dictionary ◽  
Circular Motion ◽  
Lower Side ◽  
Spiral Coil

Abstract. The trochoid coiling mode is the most dominant amongst hyaline foraminifera. The parallels in shape with especially gastropods neatly explains the use of the same terms to describe the spiral coiling. Other terms came in use, at first well-defined, but gradually losing their precision. Because of growing demands of systematics and changes in stress of use and value of characters, the inadequacy of this terminology has become a stumbling block. The terms ventral/dorsal and spiral/umbilical denote different things and are therefore all useful: the latter pair should not be relinquished as suggested (Haynes, 1990: 512). Historically, the terms ventral/dorsal and upper and lower side have been used by most students of the foraminifera with only few exceptions (notably Reuss and Loeblich & Tappan). Despite the protist nature of foraminifera, dorsal and ventral continued to be used, analogous to terms used to describe, for example gastropods. Far fewer problems beset the terms spiral and umbilical, which arc generally defined (Oxford English Dictionary) as: spiral a.. n. & v. 1. a. Coiled; winding about a centre in an enlarging or decreasing circular motion, either on a flat plane or rising in a cone. spire n. Spiral, coil; single twist of this; upper part of spiral shell [F. f. Lf. Gk speira coil] umbilical a. 1. Of, situated near, affecting, the umbilicus 2. Centrally placed. umbilicus n. Navel; (Bot. & Zool.) navel-like formation; (Geom.) point in a surface through which all cross-sections have same curvature [I., rel. to Gk omphalos]ORIENTATION: A GEOMETRICAL . . .

Cernes manquants et houppier vivant chez le pin laricio (Pinus nigra Arn. ssp. laricio (Poir.) Maire)

1998 ◽  
Vol 76 (12) ◽  
pp. 2051-2060
Author(s):  
Céline Meredieu ◽  
Yves Caraglio
Keyword(s):  
Cross Sections ◽  
Cambial Activity ◽  
Pinus Nigra ◽  
Point Of View ◽  
Lower Side ◽  
Growth Rings ◽  
Branch Growth ◽  
Crown Characteristics ◽  
Pinus Laricio ◽  
Tree Development

During a study on the live crown characteristics of Pinus laricio (Pinus nigra Arn. ssp. laricio (Poir.) Maire), the observation of branch cross-sections allowed us to work on the problem of the discontinuance of cambial activity. This work points out the existence of missing rings with a histologic point of view and establishes the generality of the phenomenon for this species. In addition to the observations at the base of living branches, the cross-sections in all the successive growth units of the branch were observed to establish the distribution of the annual wood layers along the branch and to ascertain the dissymmetry between the upper side and the lower side of the branch. The occurrence of this phenomenon in the upper part of the crown raises the problem of the contribution of these branches to tree development and its implication in forest management.Key words: growth rings, Pinus nigra Arn. ssp. laricio (Poir.) Maire, missing rings, anatomy, branch growth, crown.

Influence of Working Fluid on a Novel Solar Pond Coil

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
M. Yakubu ◽  
S. Z. Shuja ◽  
B. S. Yilbas ◽  
M. Al-Qahtani
Keyword(s):  
Graphene Oxide ◽  
Cross Sections ◽  
Pressure Loss ◽  
Working Fluid ◽  
Functionalized Graphene ◽  
Graphene Nanoplatelet ◽  
Spiral Coil ◽  
Solar Pond ◽  
Aspect Ratios ◽  
Selection Of

Abstract A design configuration and selection of working fluid for solar absorption remain critical for high performance of energy harvesting process in solar pond. In this study, heating and pressure loss characteristics in a novel designed spiral-coil geometry pertinent to salt-gradient solar pond (SGSP) is examined and the thermal performance of nanofluids in the coil is assessed. Nanofluids possessing graphene, functionalized graphene nanoplatelet (fGnP), and graphene oxide (GO) at 0.06% volume concentration are considered as the working fluids in the system. In order to achieve a novel design of a spiral coil, the circular cross-sectional geometries with aspect ratios (AR) of 0.5, 1, and 2 are incorporated in the analysis. The selection of the aspect ratios of 0.5, 1, and 2 results in elliptic, circular, and oval cross sections of the coil, respectively. The findings reveal that heat transfer enhances and pressure loss reduces via increasing the mass flowrate. This is due to the formation of a stable secondary flow which causes mixing enhancement while shortening the thermal entry length. Circular and elliptic cross sections resulted in the maximum and the smallest normalized average Nusselt numbers, respectively, for low rates of flow. This is because of thermal resistance created under the large surface area-to-volume ratio; however, this effect varnishes for high mass flowrates. Graphene oxide and functionalized graphene nanoplatelet have the highest and the lowest normalized average pressure drops, respectively, for all flow rates.

scholarly journals Hydrogen motions in the central region of the Galaxy

1964 ◽  
Vol 20 ◽  
pp. 183-186 ◽  
Author(s):  
B. F. Burke ◽  
M. A. Tuve
Keyword(s):  
Radio Telescope ◽  
Cross Sections ◽  
Central Region ◽  
Galactic Plane ◽  
Circular Motion ◽  
Galactic Centre ◽  
Strong Deviation ◽  
The Galaxy

The 21-cm hydrogen radiation near the galactic plane exhibits strong deviation from circular motion over longitudes within 30° or so of the galactic centre. In order to extend the observations first made by Rougoor and Oort,* the Carnegie multichannel H-line spectrograph was used with our 60-foot radio telescope at Derwood, Maryland, in order to confirm the Leiden work and extend observations to more southern longitudes. Cross-sections extending ±2° in latitude were taken every 2° in longitude from lII=−26°8 to lII=+2°2 and a series of points along the galactic equator were taken every 1° over the same range. Effort has been concentrated on the southern extension of the observations, which agree well with the Leiden observations over the section in common, but which carry the observations nearly 20° farther south in longitude.

Analysis of STEM micrographs of thick objects

1978 ◽  
Vol 36 (2) ◽  
pp. 106-107
Author(s):  
S. Golladay
Keyword(s):  
Inelastic Scattering ◽  
Multiple Scattering ◽  
Mass Distribution ◽  
Cross Sections ◽  
Phase Contrast ◽  
Image Point ◽  
Contrast Effects ◽  
Total Cross Sections ◽  
Elastic And Inelastic Scattering

The theory of multiple scattering has been worked out by Groves and comparisons have been made between predicted and observed signals for thick specimens observed in a STEM under conditions where phase contrast effects are unimportant. Independent measurements of the collection efficiencies of the two STEM detectors, calculations of the ratio σe/σi = R, where σe, σi are the total cross sections for elastic and inelastic scattering respectively, and a model of the unknown mass distribution are needed for these comparisons. In this paper an extension of this work will be described which allows the determination of the required efficiencies, R, and the unknown mass distribution from the data without additional measurements or models. Essential to the analysis is the fact that in a STEM two or more signal measurements can be made simultaneously at each image point.

Direct Observation of Heat Exchanger Deposits by Cross Sectioning

1967 ◽  
Vol 25 ◽  
pp. 364-365
Author(s):  
R. W. Anderson ◽  
D. L. Senecal
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Heat Exchanger ◽  
Direct Observation ◽  
Cross Sections ◽  
Preparation Method ◽  
Specimen Preparation ◽  
Flowing Water ◽  
Transmission Electron ◽  
Deposit Layer

A problem was presented to observe the packing densities of deposits of sub-micron corrosion product particles. The deposits were 5-100 mils thick and had formed on the inside surfaces of 3/8 inch diameter Zircaloy-2 heat exchanger tubes. The particles were iron oxides deposited from flowing water and consequently were only weakly bonded. Particular care was required during handling to preserve the original formations of the deposits. The specimen preparation method described below allowed direct observation of cross sections of the deposit layers by transmission electron microscopy.The specimens were short sections of the tubes (about 3 inches long) that were carefully cut from the systems. The insides of the tube sections were first coated with a thin layer of a fluid epoxy resin by dipping. This coating served to impregnate the deposit layer as well as to protect the layer if subsequent handling were required.

An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 486-487
Author(s):  
Mihir Parikh
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Sections ◽  
Resolving Power ◽  
Peak Intensity ◽  
Molecular Film ◽  
Resolution Electron ◽  
Dissociation Cross Section ◽  
High Resolution Electron Microscope ◽  
The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

Surface ultrastructure of danazol treated rat endometrium: A SEM study

1983 ◽  
Vol 41 ◽  
pp. 556-557
Author(s):  
R.P. Apkarian ◽  
J.S. Sanfilippo
Keyword(s):  
Cross Sections ◽  
Reproductive Tract ◽  
Preliminary Investigation ◽  
Breast Disease ◽  
Distal Segment ◽  
Uterine Horn ◽  
Female Reproductive Tract ◽  
Ultrastructural Changes ◽  
Cycle Phase ◽  
Sprague Dawley

The synthetic androgen danazol, is an isoxazol derivative of ethisterone. It is utilized in the treatment of endometriosis, fibrocystic breast disease, and has a potential use as a contraceptive. A study was designed to evaluate the ultrastructural changes associated with danazol therapy in a rat model. The preliminary investigation of the distal segment of the rat uterine horn was undertaken as part of a larger study intended to elucidate the effects of danazol on the female reproductive tract.Cross-sections (2-3 mm in length) of the distal segment of the uterine horn from sixteen Sprague-Dawley rats were prepared for SEM. Ten rats in estrus served as controls and six danazol treated rats were noted to have alterations of the estrus cycle i.e. a lag in cycle phase or noncycling patterns. Specimens were fixed in 3% glutaraldehyde in 0.05M phosphate buffer containing CaCl2 at pH 7.0-7.4 and chilled to 4°C. After a brief wash in distilled water, specimens were passed through a graded series of ethanol, critical point dryed in CO2 from absolute ethanol, and coated with 6nm Au. Observations were made with an IS1-40 SEM operated at 15kV.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Oxygen K near edge structures studied with multiple scattering calculations

1988 ◽  
Vol 46 ◽  
pp. 504-505
Author(s):  
Xudong Weng ◽  
Peter Rez
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Partial Cross Section ◽  
Energy Window ◽  
Edge Structure ◽  
Fine Structures ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
Quantitative Chemical

In electron energy loss spectroscopy, quantitative chemical microanalysis is performed by comparison of the intensity under a specific inner shell edge with the corresponding partial cross section. There are two commonly used models for calculations of atomic partial cross sections, the hydrogenic model and the Hartree-Slater model. Partial cross sections could also be measured from standards of known compositions. These partial cross sections are complicated by variations in the edge shapes, such as the near edge structure (ELNES) and extended fine structures (ELEXFS). The role of these solid state effects in the partial cross sections, and the transferability of the partial cross sections from material to material, has yet to be fully explored. In this work, we consider the oxygen K edge in several oxides as oxygen is present in many materials. Since the energy window of interest is in the range of 20-100 eV, we limit ourselves to the near edge structures.

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