scholarly journals Gametogenesis and spawning of Spirobranchus tetraceros (Polychaeta, Serpulidae) in Abu Kir Bay, Egypt

2005 ◽  
Vol 6 (1) ◽  
pp. 89 ◽  
Author(s):  
S. A. SELIM ◽  
F. ABDEL NABY ◽  
A.A. F.A. GAB-ALLA ◽  
A. GHOBASHY
Keyword(s):  
Red Sea ◽  
Oocyte Development ◽  
Maximum Diameter ◽  
Long Period ◽  
Sperm Development ◽  
Three Stages

The serpulid polychaete Spirobranchus tetraceros of Red Sea / Indo-pacific origin, recently has succeeded to establish a foothold in Alexandria Mediterranean waters. Worms were monthly scraped from submerged iron substrates at Abu Kir Bay during the period December 2000 – November 2001. Both light and TEM were used to study gametogenesis and time of spawning of S. tetraceros.Gametogenesis was asynchronous and oogenesis could be divided into two previtellogenic, two vitellogenic and a spawning stage. Oocyte development took about 8 months, from October to June. Spawning occurred from late May - early June until October. Thus S. tetraceros is a long period spawner. The maximum diameter of ripe oocyte is 78 mm. The spermatogenic phase could be divided into three stages: spermatogonia, spermatocytes and spermatids (including spermatozoa). The duration of sperm development took about 8 months. Spermatocytes persist from October to March. By March the sperms grew rapidly until they became spermatozoa in May. The sperm could be considered ect-aquasperm with regard to its fertilization biology.

scholarly journals RESONANCE CONDITIONS IN N°.l DOCK OF LUANDA HARBOUR

1964 ◽  
Vol 1 (9) ◽  
pp. 48
Author(s):  
Fernando Manzanares Abecasis
Keyword(s):  
Experimental Study ◽  
Detailed Analysis ◽  
Analytic Study ◽  
Constant Increase ◽  
Model Studies ◽  
Long Period ◽  
General Plan ◽  
Resonance Phenomena ◽  
Port Facilities ◽  
Three Stages

About 900 m of berth length arranged around a single pier are at present available in the port of Luanda. Due to the constant increase of traffic through the port, the "Brigada de Estudos do Porto de Luanda" (Brigade of Stud ies of the Luanda Harbour) decided to prepare a general plan of extension of the port facilities. The extension planned comprises the construction of a new pier, which together with the existing one will delimit a triangular dock - dock n°-.l —, and of a se ries of rectangular basins between the new dock and the area of S.Pedro da Barra fortress (fig.l). The danger of possible resonance phenomena and the fact that this problem can be dealt with before construction begins, led the Brigade to undertake a detailed analysis of it before tak ing decisions on the extension works of the port. This analysis comprised three stages: a) Observation in nature of long-period waves in Luanda bay. b) Analytic study of the behaviour of the planned docks under the action of possible long-period waves . c) Experimental study in model of the same phenomenon. The author, as consulting engineer of the Brigade of Stud ies, programmed observations a) and analysed their results,performed the analytic study b) [l] , [2] , [3] and, as head of the Hydraulic Department of Laboratorio Nacional de Engenharia Ci vil, planned, supervised and interpreted the model studies.

scholarly journals Land rent as a factor in the modernization of the post-reform city. On the example of Nizhny Novgorod 1860–1910s

2020 ◽  
Author(s):  
A. Akasheva ◽  
Keyword(s):  
Time Series ◽  
Building Materials ◽  
Land Rent ◽  
Original Time Series ◽  
Stages Of Development ◽  
Primary Analysis ◽  
Long Period ◽  
Source Data ◽  
Three Stages ◽  
Original Time

The problem of studying prices, areas, the number of tenants, and the duration of land lease for the production of building materials – red bricks and sawn wood in Nizhny Novgorod over a long period of time is posed. The original time series in current prices were deflated. A primary analysis of the dynamics was carried out. Three stages of development of land lease processes are identified. The conclusion is made about low rates of urban modernization. The study is accompanied by online spreadsheets containing the source data, calculations and graphs.

The Influence of Wall Stress on AAA Growth and Biomarkers

2010 ◽  
Author(s):  
Lambert Speelman ◽  
Femke A. Hellenthal ◽  
E. Marielle H. Bosboom ◽  
Jaap Buth ◽  
Marcel Breeuwer ◽  
...  
Keyword(s):  
Growth Rate ◽  
Surgical Procedure ◽  
Surgical Repair ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Long Period ◽  
Abdominal Aortic ◽  
Risk Of Rupture

In the decision for surgical repair of abdominal aortic aneurysms (AAAs), the risk of rupture is weighed carefully against the risk of the surgical procedure. The risk of rupture is estimated based on the maximum diameter and the growth rate of the AAA. Previous studies indicate that AAA growth rate increases with the diameter of the AAA [1, 2]. However, this growth rate is not the same for each AAA, as some AAA’s remain stable over a long period of time, while others show a fast growth or grow discontinuously.

scholarly journals Reproduction of Oligosarcus hepsetus (Cuvier, 1829) (Characiforms) in the Serra do Mar State Park, São Paulo, Brazil

2008 ◽  
Vol 68 (1) ◽  
pp. 187-192 ◽  
Author(s):  
LM. Gomiero ◽  
L. Garuana ◽  
FMS. Braga
Keyword(s):  
Sao Paulo ◽  
Reproductive Period ◽  
Volumetric Method ◽  
Period Length ◽  
Oocyte Development ◽  
São Paulo ◽  
Gonadal Maturation ◽  
Serra Do Mar ◽  
Long Period

The purpose of this study was to characterize the reproduction of Oligosarcus hepsetus in the Grande river (Santa Virginia Unit - Serra do Mar State Park) based on the reproductive period, length of first gonadal maturation for both sexes, sexual proportion, oocyte development, type of spawn and fecundity. The Grande river was sampled monthly from January through December 2004. The numerical frequency of the stages of maturity and the volumetric method were utilized to determine the reproductive period and fecundity, respectively. The reproduction of Oligosarcus hepsetus was characterized by a long period, relatively low fecundity, precocious length of first gonadal maturation and parceled spawning.

On nearly-commensurable periods in the restricted problem of three bodies, with calculations of the long-period variations in the interior 2:1 case

1966 ◽  
Vol 25 ◽  
pp. 197-222 ◽  
Author(s):  
P. J. Message
Keyword(s):  
Periodic Solution ◽  
Periodic Solutions ◽  
Large Amplitude ◽  
Restricted Problem ◽  
Small Amplitude ◽  
Minor Planets ◽  
Long Period ◽  
Numerical Integrations ◽  
Period Variations ◽  
The Mean

An analytical discussion of that case of motion in the restricted problem, in which the mean motions of the infinitesimal, and smaller-massed, bodies about the larger one are nearly in the ratio of two small integers displays the existence of a series of periodic solutions which, for commensurabilities of the typep+ 1:p, includes solutions of Poincaré'sdeuxième sortewhen the commensurability is very close, and of thepremière sortewhen it is less close. A linear treatment of the long-period variations of the elements, valid for motions in which the elements remain close to a particular periodic solution of this type, shows the continuity of near-commensurable motion with other motion, and some of the properties of long-period librations of small amplitude.To extend the investigation to other types of motion near commensurability, numerical integrations of the equations for the long-period variations of the elements were carried out for the 2:1 interior case (of which the planet 108 “Hecuba” is an example) to survey those motions in which the eccentricity takes values less than 0·1. An investigation of the effect of the large amplitude perturbations near commensurability on a distribution of minor planets, which is originally uniform over mean motion, shows a “draining off” effect from the vicinity of exact commensurability of a magnitude large enough to account for the observed gap in the distribution at the 2:1 commensurability.

Outbursts of comet Schwassmann-Wachmann 1, and the cloud of interplanetary boulders

1974 ◽  
Vol 22 ◽  
pp. 307 ◽  
Author(s):  
Zdenek Sekanina
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Interplanetary Space ◽  
Porous Matrix ◽  
Maximum Diameter ◽  
Expansion Velocity ◽  
Solid Constituent ◽  
Meteoric Material ◽  
Periodic Comet

AbstractIt is suggested that the outbursts of Periodic Comet Schwassmann-Wachmann 1 are triggered by impacts of interplanetary boulders on the surface of the comet’s nucleus. The existence of a cloud of such boulders in interplanetary space was predicted by Harwit (1967). We have used the hypothesis to calculate the characteristics of the outbursts – such as their mean rate, optically important dimensions of ejected debris, expansion velocity of the ejecta, maximum diameter of the expanding cloud before it fades out, and the magnitude of the accompanying orbital impulse – and found them reasonably consistent with observations, if the solid constituent of the comet is assumed in the form of a porous matrix of lowstrength meteoric material. A Monte Carlo method was applied to simulate the distributions of impacts, their directions and impact velocities.

Discussion following the presentation by F. Deubner

1977 ◽  
Vol 36 ◽  
pp. 69-74
Keyword(s):  
List Type ◽  
The Sun ◽  
Type Number ◽  
Harmonic Motion ◽  
Locally Excited ◽  
Long Period ◽  
Coherent Wave ◽  
Short Period ◽  
Global Modes

The discussion was separated into 3 different topics according to the separation made by the reviewer between the different periods of waves observed in the sun :1) global modes (long period oscillations) with predominantly radial harmonic motion.2) modes with large coherent - wave systems but not necessarily global excitation (300 s oscillation).3) locally excited - short period waves.

Design of objective lens for 200-kV high-resolution electron microscopes

1983 ◽  
Vol 41 ◽  
pp. 314-315
Author(s):  
K. Tsuno ◽  
T. Honda ◽  
Y. Harada ◽  
M. Naruse
Keyword(s):  
Optical Properties ◽  
Computer Technology ◽  
Axial Magnetic Field ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Resolution Electron ◽  
Correction Of Astigmatism ◽  
Three Stages ◽  
Electron Microscopes ◽  
Stage 1

Developement of computer technology provides much improvements on electron microscopy, such as simulation of images, reconstruction of images and automatic controll of microscopes (auto-focussing and auto-correction of astigmatism) and design of electron microscope lenses by using a finite element method (FEM). In this investigation, procedures for simulating the optical properties of objective lenses of HREM and the characteristics of the new lens for HREM at 200 kV are described.The process for designing the objective lens is divided into three stages. Stage 1 is the process for estimating the optical properties of the lens. Firstly, calculation by FEM is made for simulating the axial magnetic field distributions Bzc of the lens. Secondly, electron ray trajectory is numerically calculated by using Bzc. And lastly, using Bzc and ray trajectory, spherical and chromatic aberration coefficients Cs and Cc are numerically calculated. Above calculations are repeated by changing the shape of lens until! to find an optimum aberration coefficients.

The growth of mica polytypes as studied by conventional and high-resolution TEM

1983 ◽  
Vol 41 ◽  
pp. 174-177
Author(s):  
A. Baronnet ◽  
M. Amouric
Keyword(s):  
Water Pressure ◽  
Point Of View ◽  
Temperature Fields ◽  
Natural Occurrence ◽  
Growth Mechanisms ◽  
Long Period ◽  
High Resolution Tem ◽  
Layer Stacking ◽  
Experimental Works ◽  
Potential Use

The origin of mica polytypes has long been a challenging problem for crystal- lographers, mineralogists and petrologists. From the petrological point of view, interest in this field arose from the potential use of layer stacking data to furnish further informations about equilibrium and/or kinetic conditions prevailing during the crystallization of the widespread mica-bearing rocks. From the compilation of previous experimental works dealing with the occurrence domains of the various mica "polymorphs" (1Mr, 1M, 2M1, 2M2 and 3T) within water-pressure vs temperature fields, it became clear that most of these modifications should be considered as metastable for a fixed mica species. Furthermore, the natural occurrence of long-period (or complex) polytypes could not be accounted for by phase considerations. This highlighted the need of a more detailed kinetic approach of the problem and, in particular, of the role growth mechanisms of basal faces could play in this crystallographic phenomenon.

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