scholarly journals COMPOSICIÓN Y ESTRUCTURA DE LA COMUNIDAD DE OCTOCORALES EN LOS BAJOS DE SANCHO PARDO, ARRECIFE DE LOS COLORADOS, CUBA

2011 ◽  
Vol 3 ◽  
pp. 127 ◽  
Author(s):  
Alejandro Pérez-Angulo ◽  
Daril de la Nuez Hernández
Keyword(s):  
Reef Crest ◽  
Limiting Factor ◽  
Pseudopterogorgia Elisabethae ◽  
Gorgonia Ventalina ◽  
Hydrodynamic Stress ◽  
Fore Reef ◽  
Predominant Species ◽  
Composition And Structure ◽  
Pseudopterogorgia Americana ◽  
Reef Zone

Se estudiaron la composición y estructura de las comunidades de octocorales en cinco sitios localizados en los Bajos de Sancho Pardo (arrecife de Los Colorados (NW Cuba) en agosto del 2010. Se empleó como unidad de muestreo un marco cuadrado de un metro de lado. En total se estudiaron 11 zonas del arrecife frontal, dos zonas traseras y una cresta. Se identificaron 34 especies de gorgonias de 2687 colonias. En el arrecife frontal, Pseudopterogorgia americana y Pseudopterogorgia elisabethae fueron las especies dominantes, mientras que en la zona trasera lo hicieron Briareum asbestinum y Pseudopterogorgia bipinnata. En la cresta arrecifal predominaron Gorgonia ventalina y Plexaura homomalla. Se encontraron diferencias significativas (P = 0.05) para la densidad de gorgonias entre localidades del arrecife frontal. Los resultados de los índices de heterogeneidad y de equitatividad permiten inferir que un 79% de las localidades se correspondieron con ambientes favorables o muy favorables y el 64% indicaron ambientes constantes o casi constantes. En el 79% de las localidades se infirió una tensión hidrodinámica baja y en el resto resultó entre moderada y alta en zonas someras de la cresta y el arrecife frontal. El estado general de la comunidad de octocorales fue bueno según los valores de densidad y abundancia de especies registrados, aunque se evidencia que en las zonas al oeste hay un mayor cubrimiento por macroalgas carnosas, que puede constituir un factor que limita el reclutamiento. ABSTRACTThe composition and structure of octocoral communities was studied in five locations in Bajos de Sancho Pardo (Los Colorados reefs (NW Cuba)) in August 2010. Quadrants measuring one square meter were used as sampling units. A total of 11 fore reefs, two rear zones and one reef crest were studied. Thirty-four species of gorgonians were identified in 2687 colonies. Predominant species included Pseudopterogorgia americana and Pseudopterogorgia elisabethae in the fore reef zone, Briareum asbestinum and Pseudopterogorgia bipinnata in the rear reef, and Gorgonia ventalina and Plexaura homomalla in the reef crest. Significant differences (P = 0.05) were found in the density of gorgonians between fore reef stations. Based on the results of the heterogeneity and evenness indexes, it can be inferred that 79% of the stations were consistent with favorable or very favorable environments and 64% with constant or nearly constant environments. Hydrodynamic stress was low in 79% of the stations, while it was moderate to high in shallow areas of the crest and fore reef. The overall condition of the octocoral community was good according to recorded values of species density and abundance, although it is evident that in the western areas there is greater coverage by fleshy macroalgae, which may be a limiting factor for growth.

scholarly journals ESTRUCTURA Y COMPOSICIÓN DE LAS COMUNIDADES DE GORGONIAS DE LOS ARRECIFES DEL ARCHIPIÉLAGO SABANA-CAMAGÜEY, CUBA: CONECTIVIDAD Y FACTORES DETERMINANTES

2016 ◽  
Vol 37 (1) ◽  
Author(s):  
Pedro M. Alcolado ◽  
Pedro García Parrado ◽  
Darlenys Hernández Muñoz
Keyword(s):  
Community Composition ◽  
Diversity Indices ◽  
North Central ◽  
Strong Connectivity ◽  
Fore Reef ◽  
Composition And Structure ◽  
Rocky Bottoms ◽  
Nmds Analysis ◽  
Reef Zone ◽  
Water Turbulence

To know the gorgonian community composition and structure of coral reefs in the Archipelago Sabana-Camagüey (north central Cuba) and the factors governing them, sampling was carried out in 10 transects, which include the rear zone (about 1 m in depth) and the fore reef zone (between 5 m and 20 m in depth). The most dominant and frequent species was Pseudopterogorgia americana, followed by Eunicea flexuosa, Eunicea mammosa, Plexaurella dichotoma, and Plexaura kuekenthali. The first one is typical of rocky bottoms with accumulated sediments, while the others are considered resistant to water turbulence, except the last one. According the nMDS analysis, water turbulence was the only direct factor that explained in a significant way the gorgonian community composition and structure. Ordination of stations reveals a strong connectivity within the study area. Diversity indices H’ and J’suggest the dominance of favorable and quasi constant to constant physical environmental conditions for gorgonian communities.

An assessment of whether energy was the first factor limiting production of dairy cows grazing kikuyu grass pasture

1979 ◽  
Vol 19 (100) ◽  
pp. 530 ◽  
Author(s):  
KW Moir ◽  
HG Dougherty ◽  
PJ Goodwin ◽  
FJ Humphreys ◽  
PR Martin
Keyword(s):  
Dairy Cows ◽  
Dry Matter ◽  
Body Weight Loss ◽  
Metabolizable Energy ◽  
Energy Concentration ◽  
Limiting Factor ◽  
Dietary Energy ◽  
Predominant Species ◽  
Kikuyu Grass ◽  
Whole Plants

Whole plants of kikuyu grass were taken at intervals over a 9-month period from four commercial dairy farms on which this grass was the predominant species. The plants were separated into leaf and stem fractions and their metabolizable energy (ME) concentrations were estimated from their cell-wall contents. The overall mean ME in the dry matter of leaf and stem on each farm was of the order of 11 and 9 MJ kg DM-1, respectively. From considerations of appetite limits depending upon whether energy was derived mainly from leaf or stem, and taking into account ME supplied from supplementary feeds, and ME requirements for milk production, it was concluded that the production of the herd with the highest mean production cow-1 (4140 kg lactation-1) was limited by dietary energy concentration, although the genetic capacity of the cows to produce milk at the expense of body weight loss overcame this limitation to some extent. On the other farms with low to intermediate levels of productivity, the amount of food on offer was the first limiting factor.

scholarly journals FACIES DISTRIBUTION OF KAIS FORMATION IN “X” FIELD, SALAWATI BASIN, WEST PAPUA, INDONESIA

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Rifky Nuraza Putra ◽  
Moehammad Ali Jambak
Keyword(s):  
Reef Crest ◽  
Back Reef ◽  
Fore Reef ◽  
Facies Distribution ◽  
Reef System ◽  
West Papua ◽  
Papua Barat

<p class="Abstract">Daerah penelitian lapangan “X” terletak di Formasi Kais, Cekungan Salawati, Papua Barat, Indonesia. Maksud dan tujuan dari penelitian ini adalah untuk menginterpretasikan fasies karbonat, beserta penyebarannya, baik secara vertikal maupun horizontal. Penelitian dimulai dengan penafsiran <em>litostratigrafi</em> menggunakan data <em>log</em> dan sayatan tipis, untuk membuat <em>type log</em>. Dilanjut dengan analisis sikuen stratigrafi dan <em>reef system</em> untuk menentukan penyebaran, dengan bantuan data seismik untuk dikorelasikan dengan sumur-sumur lainnya. Dari hasil analisis, terdapat 5 fasies pada daerah penelitian, yaitu: <em>Skeletal Debris Packstone-Wackestone, Coral Algal Grainstone – Boundstone, Skeletal Wackestone, Skeletal Packstone dan Coral Algal Packstone</em>. Terdapat pula 4 <em>reef system</em>, yaitu; <em>Back reef, reef crest, fore reef dan off reef</em>. Untuk mencapai tujuan akhir dari penelitian ini, maka dibuat peta penyebaran fasies.</p>

scholarly journals Influence of reef flat submergence on infra-gravity wave energy and resonance over the fringing reef

2021 ◽  
Vol 72 (1) ◽  
pp. 16-24
Author(s):  
Anh Pham Lan
Keyword(s):  
Gravity Wave ◽  
Wave Energy ◽  
Reef Flat ◽  
Surf Zone ◽  
Low Frequency ◽  
Resonant Mode ◽  
Reef Crest ◽  
Swash Zone ◽  
Frequency Wave ◽  
Fore Reef

Fringing reefs which are common nearshore islands with coral reef growth have special topography of very steep slope on the fore-reef and mild slope on the wide flat. When incident waves propagate from a very deep water region (from hundreds of meters to thousands of meters of depth) to approaching the reef they abruptly commence a very shallow water (only few centimeters to several meters of depth) and create strong hydrodynamic processes on the reef flat. Due to shallow depth, waves feel the bottom and break in the area of fore-reef slope and reef crest and partial reef flat. Infra-gravity waves (IG), other name as bound long waves or surf beat, which belong to low-frequency wave type (0.002Hz ¸ 0.04Hz) are generated by the varying-breaking point mechanism on the shallow reef flat. On the flat, short wave energy is almost dissipated; low-frequency waves are strongly dominated over the surf zone till swash zone. Wave set-up causing an increase of water level on the flat combines with the run-up at the shoreline which can lead to coastal flooding. Besides, if the reef flat length is in the order of one fourth of wavelength the first oscillation resonant mode with standing wave occurs. This component is resonantly amplified at the shoreline relative to the incident infra-gravity wave energy at the reef crest.

Utilizing Dark Field Electron Microscopy to Produce Lantern Slides

1974 ◽  
Vol 32 ◽  
pp. 116-117
Author(s):  
J. N. Meador ◽  
C. N. Sun ◽  
H. J. White
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Dark Field ◽  
Limiting Factor ◽  
Clinical Laboratories ◽  
Field Electron ◽  
Time Element ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Dark Field Micrographs

The electron microscope is being utilized more and more in clinical laboratories for pathologic diagnosis. One of the major problems in the utilization of the electron microscope for diagnostic purposes is the time element involved. Recent experimentation with rapid embedding has shown that this long phase of the process can be greatly shortened. In rush cases the making of projection slides can be eliminated by taking dark field electron micrographs which show up as a positive ready for use. The major limiting factor for use of dark field micrographs is resolution. However, for conference purposes electron micrographs are usually taken at 2.500X to 8.000X. At these low magnifications the resolution obtained is quite acceptable.

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

Crystal Structure Analysis of Cu-Zr Alloys by Convergent Beam Diffraction

1981 ◽  
Vol 39 ◽  
pp. 354-355
Author(s):  
A. F. Marshall ◽  
J. W. Steeds ◽  
D. Bouchet ◽  
S. L. Shinde ◽  
R. G. Walmsley
Keyword(s):  
Crystal Structure ◽  
Point Group ◽  
Intermetallic Phase ◽  
Three Dimensional ◽  
Crystal Structure Analysis ◽  
Ion Milling ◽  
Composition And Structure ◽  
Unit Cells ◽  
Sputter Deposited ◽  
Convergent Beam

Convergent beam electron diffraction is a powerful technique for determining the crystal structure of a material in TEM. In this paper we have applied it to the study of the intermetallic phases in the Cu-rich end of the Cu-Zr system. These phases are highly ordered. Their composition and structure has been previously studied by microprobe and x-ray diffraction with sometimes conflicting results.The crystalline phases were obtained by annealing amorphous sputter-deposited Cu-Zr. Specimens were thinned for TEM by ion milling and observed in a Philips EM 400. Due to the large unit cells involved, a small convergence angle of diffraction was used; however, the three-dimensional lattice and symmetry information of convergent beam microdiffraction patterns is still present. The results are as follows:1) 21 at% Zr in Cu: annealed at 500°C for 5 hours. An intermetallic phase, Cu3.6Zr (21.7% Zr), space group P6/m has been proposed near this composition (2). The major phase of our annealed material was hexagonal with a point group determined as 6/m.

Computer averaging of lattice images of poly-4-methyl-pentene-1 (P4mp1): Noise created artifacts

1987 ◽  
Vol 45 ◽  
pp. 388-389
Author(s):  
P. Pradère ◽  
J.F. Revol ◽  
R. St. John Manley
Keyword(s):  
Low Dose ◽  
Polymer Concentration ◽  
Processing System ◽  
Limiting Factor ◽  
Dilute Solution ◽  
New Techniques ◽  
Dose Unit ◽  
Lattice Images ◽  
Dose Imaging ◽  
Imaging Conditions

Although radiation damage is the limiting factor in HREM of polymers, new techniques based on low dose imaging at low magnification have permitted lattice images to be obtained from very radiation sensitive polymers such as polyethylene (PE). This paper describes the computer averaging of P4MP1 lattice images. P4MP1 is even more sensitive than PE (total end point dose of 27 C m-2 as compared to 100 C m-2 for PE at 120 kV). It does, however, have the advantage of forming flat crystals from dilute solution and no change in d-spacings is observed during irradiation.Crystals of P4MP1 were grown at 60°C in xylene (polymer concentration 0.05%). Electron microscopy was performed with a Philips EM 400 T microscope equipped with a Low Dose Unit and operated at 120 kV. Imaging conditions were the same as already described elsewhere. Enlarged micrographs were digitized and processed with the Spider image processing system.

Parathyroid gland before and after cisplatin treatment

1987 ◽  
Vol 45 ◽  
pp. 860-861
Author(s):  
S.K. Aggarwal ◽  
J.M. Fadool
Keyword(s):  
Parathyroid Gland ◽  
Wistar Rats ◽  
Antitumor Agent ◽  
The Body ◽  
Cross Linking ◽  
Limiting Factor ◽  
Hormonal Changes ◽  
Primary Mechanism ◽  
Before And After ◽  
Dna Strands

Cisplatin (CDDP) a potent antitumor agent suffers from severe toxic side effects with nephrotoxicity being the major dose-limiting factor, The primary mechanism of its action has been proposed to be through its cross-linking DNA strands. It has also been shown to inactivate various transport enzymes and induce hypocalcemia and hypomagnesemia that may be the underlying cause for some of its toxicities. The present is an effort to study its influence on the parathyroid gland for any hormonal changes that control calcium levels in the body.Male Swiss Wistar rats (Crl: (WI) BR) weighing 200-300 g and of 60 days in age were injected (ip) with cisplatin (7mg/kg in normal saline). The controls received saline injections only. The animals were injected (iv) with calcium (0.5 ml of 10% calcium gluconate/day) and were killed by decapitation on day 1 through 5. Trunk blood was collected in heparinized tubes.

Resolution assessment from spectral signal-to-noise ratios

1987 ◽  
Vol 45 ◽  
pp. 746-747
Author(s):  
M. Unser ◽  
B.L. Trus ◽  
A.C. Steven
Keyword(s):  
Electron Microscopy ◽  
Limiting Factor ◽  
Biological Macromolecules ◽  
Signal To Noise ◽  
Differential Phase ◽  
Traditional Measure ◽  
Spectral Signal ◽  
Two Measures ◽  
Diffraction Patterns ◽  
Averaging Techniques

Since the resolution-limiting factor in electron microscopy of biological macromolecules is not instrumental, but is rather the preservation of structure, operational definitions of resolution have to be based on the mutual consistency of a set of like images. The traditional measure of resolution for crystalline specimens in terms of the extent of periodic reflections in their diffraction patterns is such a criterion. With the advent of correlation averaging techniques for lattice rectification and the analysis of non-crystalline specimens, a more general - and desirably, closely compatible - resolution criterion is needed. Two measures of resolution for correlation-averaged images have been described, namely the differential phase residual (DPR) and the Fourier ring correlation (FRC). However, the values that they give for resolution often differ substantially. Furthermore, neither method relates in a straightforward way to the long-standing resolution criterion for crystalline specimens.

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