Respiratory Adaptations of Prenatal Young in the Ovary of two Species of Viviparous Seaperch, Rhacochilus vacca and Embiotoca lateralis

1972 ◽  
Vol 29 (11) ◽  
pp. 1525-1542 ◽  
Author(s):  
P. W. Webb ◽  
J. R. Brett
Keyword(s):  
Flow Characteristics ◽  
Weight Ratio ◽  
Late Gestation ◽  
Ovarian Fluid ◽  
Ovary Weight ◽  
Surface Areas ◽  
Maximum Value ◽  
Embiotoca Lateralis ◽  
And Diffusion ◽  
Exchange Surface

The structure of the ovary and embryos of embiotocids is reviewed in relation to those factors that would affect the exchange of materials between ovarian and embryonic blood streams. Weight, exchange surface areas (particularly of the fins), diffusion distances, and capillary densities were measured for prenatal young and ovaries of two species of Embiotocidae, Rhacochilus vacca and Embiotoca lateralis, during middle and late gestation. Brood size and ovarian fluid volume were also measured. Changes in brood weight and ovarian fluid volumes were interpreted in relation to the load imposed on the ovary by the young. This was expressed as the brood/ovary weight ratio which was found to increase during gestation to a maximum value of eight. Changes in exchange surface areas and diffusion distances of the young and the ovary were determined and evaluated in relation to the metabolic requirements of the brood. Convection of the ovarian fluid must occur as a necessary mechanism for efficient exchange of materials with increasing brood/ovary weight ratio. It is further concluded that the supply of materials to the brood would be limited by ovarian blood-flow characteristics rather than structural considerations, except immediately prior to parturition.

ACTION ON MATTER: THE HISTORY OF THE UNIQUELY AFRICAN TAMPER AND CONCAVE ANVIL POT-FORMING TECHNIQUE

2003 ◽  
Vol 1 (1) ◽  
pp. 3-35 ◽  
Author(s):  
Judy Sterner ◽  
Nicholas David
Keyword(s):  
Historical Development ◽  
Weight Ratio ◽  
High Volume ◽  
Efficient Production ◽  
Arid Environments ◽  
Historical Evidence ◽  
Culture History ◽  
History Of ◽  
And Diffusion

The publication, largely by ethnoarchaeologists, of new data on the tamper and concave anvil technique of pot-forming (TCA) permits a reassessment of this uniquely African technique, its toolkit, and its culture history. A survey, inspired by the technologie culturelle school, of its varied expressions in the southern Saharan, Sahelian and northern Sudan zones from Mali to Sudan and extending north into Egypt emphasises the potential of the technique for the efficient production of spherical water jars of high volume to weight ratio, much appreciated in arid environments. The technique is demanding and therefore practised for the most part by specialists. The origins and diffusion of the technique are assessed in the light of the ethnological, archaeological, linguistic, and historical evidence, and a four stage historical development is sketched.

scholarly journals Estimates and relationships between aboveground and belowground resource exchange surface areas in a Sitka spruce managed forest

2010 ◽  
Vol 30 (6) ◽  
pp. 705-714 ◽  
Author(s):  
A. J. Butler ◽  
N. Barbier ◽  
J. Cermak ◽  
J. Koller ◽  
C. Thornily ◽  
...  
Keyword(s):  
Sitka Spruce ◽  
Managed Forest ◽  
Resource Exchange ◽  
Surface Areas ◽  
Exchange Surface

Effect of ZnO Particle Size on the Curing of Carboxylated NBR and Carboxylated SBR

2004 ◽  
Vol 77 (2) ◽  
pp. 214-226 ◽  
Author(s):  
G. R. Hamed ◽  
K.-C. Hua
Keyword(s):  
Zinc Oxide ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Cure Rate ◽  
Surface Areas ◽  
Diffusion Limited ◽  
Rate Of Dissolution ◽  
Oxide Particles ◽  
And Diffusion

Abstract A carboxylated nitrile rubber (XNBR) and a carboxylated SBR (XSBR) were mixed with zinc oxide particles of different specific surface areas (“S”, 35 m2/g; “M”, 3.5m2/g; “L”, 0.5 m2/g) and cure behavior at 165 ºC studied using oscillating disc rheometry. Without added zinc oxide, both raw rubbers slowly stiffen over many hours of heating. This is probably due to condensation of carboxyl groups to form anhydride crosslinks. XNBR compositions containing the finely divided “S” crosslink much more rapidly. Full cure is reached after about 10 minutes of heating. Cure rate decreases markedly as the specific surface area of the ZnO decreases. A composition containing “M” at twice stoichiometry requires about an hour to cure well, while with “L”, about 10 hours are required. In contrast, curing of the XSBR depends little on the specific surface area of the ZnO, either with “S” or “L”, curing is essentially complete after 30 minutes. After simply mixing ZnO into either rubber, it remains as a dispersed particulate. With XNBR, curing appears to be controlled by the rate of dissolution and diffusion of ZnO, while, with XSBR, reaction is not diffusion limited and may be confined to regions near particle surfaces.

scholarly journals Flow Characteristics Analysis of the Decontamination Device with Mixing and Diffusion Using Radio-Isotopes Tracer

2017 ◽  
Vol 39 (5) ◽  
pp. 282-287 ◽  
Author(s):  
Daemin Oh ◽  
Sungwon Kang ◽  
Youngsug Kim ◽  
Sunghee Jung ◽  
Jinho Moon ◽  
...  
Keyword(s):  
Flow Characteristics ◽  
Characteristics Analysis ◽  
And Diffusion ◽  
Radio Isotopes

scholarly journals Modeling of human breath: conceptual and mathematical statements

2016 ◽  
Vol 11 (1) ◽  
pp. 64-80 ◽  
Author(s):  
П.В. Трусов ◽  
P.V. Trusov
Keyword(s):  
Mathematical Model ◽  
Flow Characteristics ◽  
Quiet Breathing ◽  
Ansys Fluent ◽  
Proposed Model ◽  
Joint Problem ◽  
Large Airways ◽  
Further Development ◽  
And Diffusion ◽  
Joint Problem Solving

The article is devoted to the main aspects of the development of a mathematical model of the human respiratory system taking into account the effects of environmental factors. The proposed model is a submodel of "meso-level" multilayered mathematical model of the evolution of functional disorders of the human body. The conceptual and mathematical formulations of the problem are discussed. The breathing is considered as a set of synchronized processes of gas dynamics, deformation of the porous medium and diffusion. The results of the calculation of the air flow characteristics during quiet breathing and forced breath in the first four generations of large airways were obtained by using software ANSYS Fluent. Further development of the model involves the joint problem solving of changes in lung configuration and in gasdynamic processes in the human airway.

scholarly journals 2D Numerical Study of Heat Transfer Enhancement Using Fish-Tail Locomotion Vortex Generators

2021 ◽  
Vol 8 (3) ◽  
pp. 386-392
Author(s):  
Ahmed Hashim Yousif ◽  
Hakim T. Kadhim ◽  
Kadhim K. Idan Al-Chlaihawi
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Flow Characteristics ◽  
Vortex Generators ◽  
Transfer Enhancement ◽  
Number Range ◽  
Maximum Value ◽  
Fluid Flow Characteristics

In this paper, a numerical simulation is performed to study the effect of two types of concave vortex generators (VGs), arranged as fish-tail locomotion in a rectangular channel. The heat transfer and fluid flow characteristics with and without VGs are examined over the Reynolds number range 200≤Re≤2200.The two proposed types of the VGs are selected based on the speed of the fish movement which is arranged in different distances between them (d/H=0.6, 1, 1.3). The results show that the use of VGs can significantly enhance the heat transfer rate, but also increases the friction factor. The heat transfer performance is enhanced by (4-21.1%) reaching the maximum value by using the first type of the VGs at (d/H=1.3) due to better mixing of secondary flow and the new arrangement of the VGs which lead to decreasing the friction factor with an easy flow of fluid.

Fetal canine cardiac Purkinje fibers: electrophysiology and ultrastructure

1984 ◽  
Vol 246 (2) ◽  
pp. H250-H260
Author(s):  
P. Danilo ◽  
R. F. Reder ◽  
O. Binah ◽  
M. J. Legato
Keyword(s):  
Action Potential ◽  
Fetal Development ◽  
Late Gestation ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Purkinje Fibers ◽  
Ultrastructural Studies ◽  
Surface Areas ◽  
Cardiac Purkinje Fibers ◽  
External Potassium

We studied the ontogenesis of the transmembrane action potential and the ultrastructure of fetal canine Purkinje fibers. Fetal hearts were obtained from fetuses just after implantation to end gestation. Using standard microelectrode recording techniques, we found that action potential characteristics varied linearly over this period of development. Maximum diastolic potential (MDP) ranged from -65 to -85 mV; action potential amplitude (AMP) varied from 100 to 120 mV; maximum upstroke velocity (Vmax) increased from 200 to 550 V/s. Action potential duration measured to 50% repolarization (APD50) increased from 15 to 156 ms while duration measured at full repolarization (APD100) similarly increased from 75 to 236 ms. The relationship between external potassium concentration and membrane potential was equivalent across all stages of fetal development. Tetrodotoxin (TTX, 7.7 X 10(-7) to 1.6 X 10(-5) M) caused concentration-dependent decreases in AMP, Vmax, and APD50. Verapamil (1 X 10(-7) to 1 X 10(-5) M) decreased Vmax and APD50 in a concentration-dependent manner. The effects of both TTX and verapamil were statistically equivalent across all stages of fetal development. Ultrastructural studies of fetal Purkinje fibers showed that myocytes at the earliest stages of development (Purkinje fibers were not visually distinct at this time) were arranged as a tightly packed mosaic with a rounded shape, with a large amount of glycogen, small sparse mitochondria, and relatively large nuclei. Mitotic cells were observed frequently. Purkinje fibers when first identified grossly had fewer myofilaments than working myocardial cells and sarcomeres without M lines. By late gestation, intercalated disks appeared with an increase in surface areas; desmosomes occurred more frequently. Myofilaments are organized around Z bands into rudimentary sarcomeres that still lack M lines. These data indicate that, although the fetal canine Purkinje fiber undergoes marked developmental changes in ultrastructure, cellular electrophysiological changes are more subtle. The action potential has a qualitative appearance similar to those of the neonatal or adult fiber. At no time during fetal development could we find slow-response action potentials.

Ventilation Frequency Reveals the Roles of Exchange Surface Areas in Metabolic Scaling

2020 ◽  
Vol 93 (1) ◽  
pp. 13-22 ◽  
Author(s):  
Yiping Luo ◽  
Qian Li ◽  
Xiaoling Zhu ◽  
Jing Zhou ◽  
Cong Shen ◽  
...  
Keyword(s):  
Metabolic Scaling ◽  
Ventilation Frequency ◽  
Surface Areas ◽  
Exchange Surface

scholarly journals Microwave Heating Behavior in SiC Fiber-MO2 Mixtures (M = Ce, Zr)—Selective Heating of Micrometer-Sized Fibers Facilitated by ZrO2 Powder

Processes ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 47 ◽  
Author(s):  
Keiichiro Kashimura ◽  
Jun Fukushima ◽  
Tomoaki Namioka ◽  
Takashi Fujii ◽  
Hirotsugu Takizawa ◽  
...  
Keyword(s):  
High Temperature ◽  
Hot Spots ◽  
Weight Ratio ◽  
Temperature Gradients ◽  
Maximum Temperature ◽  
Selective Heating ◽  
Sic Fiber ◽  
Maximum Value ◽  
Rate Maximum ◽  
Heating Behavior

SiC fiber-MO2 (M = Ce, Zr) mixtures with various compositions were heated by applying an 80 W microwave electric field, to investigate their heating rate, maximum temperature, and dielectric constant. For the SiC fiber-CeO2 mixture, all three parameters continued to increase as the weight ratio of the SiC fiber increased; in contrast, for the SiC fiber-ZrO2 mixture, these parameters reached a maximum value at a certain composition. A thermal gradient of 500 °C was observed at a microlevel in the SiC fiber-ZrO2 mixture, and hot spots were located in regions with a certain composition. This result not only contributes to designing a novel good microwave absorber but also presents new aspects with regard to high-temperature microwave processing, including the mechanism behind the high-temperature gradients on the order of micrometers as well as engineering applications that utilize these high-temperature gradients.

Study of Mechanical Properties of Friction Stir Welded Armour Grade Aluminium Alloy Plates

2020 ◽  
Author(s):  
Umesh Kumar Singh ◽  
Avanish Kumar Dubey
Keyword(s):  
Tensile Strength ◽  
Aluminium Alloy ◽  
Research Work ◽  
Weight Ratio ◽  
Input Rate ◽  
Friction Stir ◽  
Maximum Value ◽  
Shoulder Diameter ◽  
Tool Tilt Angle ◽  
Tungsten Carbide Tool

Abstract In present research work, friction stir welding of armour grade aluminium alloy, which is having excellent strength to weight ratio, has been done at low heat input rate (rotational speed of 600 rpm, travelling speed of 75 mm/min) and tool tilt angle of 2.5°. Tungsten carbide tool with a shoulder diameter of 15 mm was used to produce the joint. Tensile strength and microhardness of welded sample were measured at three different locations i.e. at the start, middle and end of the weld. The lowest value of tensile strength was obtained at the start of the weld while the maximum tensile strength was observed at middle of the weld and having the value of 378.672 MPa which is 82.32% of base metal along with 15.26% elongation. There is a large gap between the lower and the maximum value of tensile strength. The middle of the weld has less fluctuation in microhardness value as compared to the start and end of the weld. While the maximum value of microhardness was obtained on the advancing side at the start of the weld with the value of 187.4 Hv. Microstructural image shows the presence of craters and segregation in the weld surface. XRD result signify the presence of intermetallic compound Al12Mg17 in the welded zone.

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