scholarly journals NATURE OF THE ACTION CURRENT IN NITELLA

1946 ◽  
Vol 30 (1) ◽  
pp. 47-59 ◽  
Author(s):  
W. J. V. Osterhout
Keyword(s):  
Surface Layer ◽  
Ionic Mobility ◽  
Complex Action ◽  
Action Current ◽  
Small Magnitude ◽  
Gradual Loss ◽  
Aqueous Surface ◽  
Aqueous Layer ◽  
Normal Potential ◽  
Made In

The experiments indicate that the protoplasm of Nitella consists of an aqueous layer W with an outer non-aqueous surface layer X and an inner non-aqueous surface layer Y. The potential at Y is measured by the magnitude of the action curve and the potential at X by the distance from the top of the action curve to the zero line. These potentials appear to be due chiefly to diffusion potentials caused by the activity gradients of KCl across the non-aqueous layers X and Y. The relative mobilities of K+ and Cl- in X and in Y can be computed and an estimate of the activity of KCl in W can be made. In the complete resting state the mobilities of K+ and Cl- in X are not very different from those in Y. The action curve is due to changes in Y which suddenly becomes very permeable, allowing potassium to move from the sap across Y into W, and thus losing its potential. A gradual loss may be due to changes in ionic mobility in Y. When recovery is incomplete and Y has not yet regained its normal potential a stimulus may cause a loss of the potential at Y giving an action curve of small magnitude. The magnitude may vary in successive action curves giving what is called a complex pattern in contrast to the simple pattern observed when recovery is complete and all the action curves are alike. Complex patterns occur chiefly in cells treated with reagents. Untreated cells usually give simple patterns. A variety of complex action patterns is discussed. It is evident that the cells of Nitella show much more variation than such highly specialized cells as muscle and nerve which give stereotyped responses. In some cases it may be doubtful whether the all-or-none law holds.

scholarly journals Shape Errors, Internal Porosity, Linear Dimensions Accuracy and Allowances for the Machining of Castings Made in the Replicast CS Process

2014 ◽  
Vol 14 (3) ◽  
pp. 25-28
Author(s):  
R. Haratym ◽  
M. Sieczka ◽  
R. Biernacki ◽  
J. Kwapisz
Keyword(s):  
Surface Layer ◽  
Comprehensive Assessment ◽  
Process Models ◽  
Modern Equipment ◽  
Internal Porosity ◽  
Linear Dimensions ◽  
Shape Errors ◽  
Measuring Machine ◽  
Made In

Abstract This research presents comprehensive assessment of the precision castings quality made in the Replicast CS process. The evaluation was made based on quality of the surface layer, shape errors and the accuracy of the linear dimensions. Studies were carried out on the modern equipment, among other things a Zeiss Calypso measuring machine and profilometer were used. Obtained results allowed comparing lost wax process models and Replicast CS process.

scholarly journals THE ROLE OF WATER IN PROTOPLASMIC PERMEABILITY AND IN ANTAGONISM

1956 ◽  
Vol 39 (6) ◽  
pp. 963-976 ◽  
Author(s):  
W. J. V. Osterhout
Keyword(s):  
Surface Layer ◽  
Water Content ◽  
Active Substance ◽  
External Medium ◽  
Surface Active Substance ◽  
Potassium Ions ◽  
Protoplasmic Surface ◽  
Outer Protoplasmic Surface ◽  
Aqueous Surface ◽  
Surface Active

The behavior of the cell depends to a large extent on the permeability of the outer non-aqueous surface layer of the protoplasm. This layer is immiscible with water but may be quite permeable to it. It seems possible that a reversible increase or decrease in permeability may be due to a corresponding increase or decrease in the water content of the non-aqueous surface layer. Irreversible increase in permeability need not be due primarily to increase in the water content of the surface layer but may be caused chiefly by changes in the protoplasm on which the surface layer rests. It may include desiccation, precipitation, and other alterations. An artificial cell is described in which the outer protoplasmic surface layer is represented by a layer of guaiacol on one side of which is a solution of KOH + KCl representing the external medium and on the other side is a solution of CO2 representing the protoplasm. The K+ unites with guaiacol and diffuses across to the artificial protoplasm where its concentration becomes higher than in the external solution. The guaiacol molecule thus acts as a carrier molecule which transports K+ from the external medium across the protoplasmic surface. The outer part of the protoplasm may contain relatively few potassium ions so that the outwardly directed potential at the outer protoplasmic surface may be small but the inner part of the protoplasm may contain more potassium ions. This may happen when potassium enters in combination with carrier molecules which do not completely dissociate until they reach the vacuole. Injury and recovery from injury may be studied by measuring the movements of water into and out of the cell. Metabolism by producing CO2 and other acids may lower the pH and cause local shrinkage of the protoplasm which may lead to protoplasmic motion. Antagonism between Na+ and Ca++ appears to be due to the fact that in solutions of NaCl the surface layer takes up an excessive amount of water and this may be prevented by the addition of suitable amounts of CaCl2. In Nitella the outer non-aqueous surface layer may be rendered irreversibly permeable by sharply bending the cell without permanent damage to the inner non-aqueous surface layer surrounding the vacuole. The formation of contractile vacuoles may be imitated in non-living systems. An extract of the sperm of the marine worm Nereis which contains a highly surface-active substance can cause the egg to divide. It seems possible that this substance may affect the surface layer of the egg and cause it to take up water. A surface-active substance has been found in all the seminal fluids examined including those of trout, rooster, bull, and man. Duponol which is highly surface-active causes the protoplasm of Spirogyra to take up water and finally dissolve but it can be restored to the gel state by treatment with Lugol solution (KI + I). The transition from gel to sol and back again can be repeated many times in succession. The behavior of water in the surface layer of the protoplasm presents important problems which deserve careful examination.

scholarly journals In Vitro Tissue Culture in Brachypodium: Applications and Challenges

2020 ◽  
Vol 21 (3) ◽  
pp. 1037 ◽  
Author(s):  
Alexander Betekhtin ◽  
Karolina Hus ◽  
Magdalena Rojek-Jelonek ◽  
Ewa Kurczynska ◽  
Candida Nibau ◽  
...  
Keyword(s):  
Tissue Culture ◽  
Transformation Efficiency ◽  
Brachypodium Distachyon ◽  
Low Frequency ◽  
Transformation Techniques ◽  
Bioenergy Grasses ◽  
Embryogenic Potential ◽  
Gradual Loss ◽  
Made In

Brachypodium distachyon has become an excellent model for plant breeding and bioenergy grasses that permits many fundamental questions in grass biology to be addressed. One of the constraints to performing research in many grasses has been the difficulty with which they can be genetically transformed and the generally low frequency of such transformations. In this review, we discuss the contribution that transformation techniques have made in Brachypodium biology as well as how Brachypodium could be used to determine the factors that might contribute to transformation efficiency. In particular, we highlight the latest research on the mechanisms that govern the gradual loss of embryogenic potential in a tissue culture and propose using B. distachyon as a model for other recalcitrant monocots.

Vertical Temperature Distribution in the Great Lakes

1952 ◽  
Vol 9 (7) ◽  
pp. 325-328 ◽  
Author(s):  
H. B. Hachey
Keyword(s):  
Surface Layer ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Great Lakes ◽  
Fresh Water ◽  
Maximum Density ◽  
Maximum Depth ◽  
Vertical Temperature ◽  
Vertical Temperature Distribution ◽  
Made In

On the basis of temperature observations made in the Great Lakes in the summer months it has been shown that: (a) the maximum depth of the thermocline does not exceed 50 feet, (b) the temperature gradient within the thermocline may be as much as 26 degrees Fahrenheit in 10 feet, (c) the thickness of the surface layer varies considerably with time and position, and can under certain circumstances be entirely removed from an area, and (d) the temperature of the deeper waters approximates to that of the maximum density of fresh water.

scholarly journals Jumping Wave Characteristic during Low Plasticity Burnishing Process

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1441
Author(s):  
Stefan Dzionk ◽  
Michal Dobrzynski ◽  
Bogdan Ścibiorski
Keyword(s):  
Surface Layer ◽  
Soft Materials ◽  
Additional Structure ◽  
Wave Characteristic ◽  
Processed Material ◽  
Low Plasticity Burnishing ◽  
Wave Forms ◽  
Burnishing Process ◽  
Parametric Description ◽  
Made In

During the low plasticity burnishing process of soft materials such as carbon steel with a hardness of up to 40 HRC (Rockwell grade) a raised structure of the material known as the Jumping Wave forms in front of the tool roll. This phenomenon significantly disturbs the burnishing process, but is very poorly described in the literature. This article presents studies of this phenomenon on the example of burnished 1.0562 steel. The research concerns the changes in the surface structure of the processed material as well as changes in the structure of the material during this process. The research shows changes in the geometric structure of the surface made in the 3D system and their parametric description. Moreover, the work presents an analysis of the metallographic structure in the tool zone. The research showed occurrence of material slippages in the wave in front of the tool, which creates an additional structure on the surface. These tests make it possible to better understand the process of changes that take place in the surface layer of the processed element in the low plasticity burnishing process.

ANALYSIS OF SURFACE MICROGEOMETRY AND STRUCTURE OF LAYERED BIOMATERIALS USED FOR PROSTHETIC CONSTRUCTIONS IN DIGITAL TECHNOLOGIES

Tribologia ◽  
2019 ◽  
Vol 287 (5) ◽  
pp. 101-113
Author(s):  
Wojciech RYNIEWICZ ◽  
Anna M. RYNIEWICZ ◽  
Łukasz BOJKO ◽  
Beata LESZCZYŃSKA-MADEJ ◽  
Andrzej RYNIEWICZ
Keyword(s):  
Surface Roughness ◽  
Surface Layer ◽  
Digital Technologies ◽  
Metal Powders ◽  
Roughness Parameters ◽  
Complex Load ◽  
Stomatognathic System ◽  
Surface Microgeometry ◽  
Load Conditions ◽  
Made In

Veneering layers of prosthetic substructures are responsible for tribological cooperation with opposite teeth in the stomatognathic system (SS). Investigations of microgeometry and structure of veneering layers are aimed at checking to what extent these layers replicate enamel parameters, which, under complex load conditions, are characterized by the phenomenon of resistance to tribological wear. Ceramic veneering layers are dedicated for substructures made in digital technologies from factory fittings by milling and laser sintering of metal powders. Using a confocal microscope, contactless tests of the surface layer stereometry were performed and surface roughness parameters were determined on samples of ceramics veneering of prosthetic substructures. The analysis was performed in comparison to the natural enamel of premolars and molars. The shaping of the surface of materials veneering the substructures is similar to the regularity determined in the statistical analysis of the enamel roughness. Layers facing samples from milling technology are characterized by lower values of roughness parameters than layers created on substructures made of SLM technology.

Effects of Noise on Access to Recent Memory

1978 ◽  
Vol 47 (1) ◽  
pp. 168-170 ◽  
Author(s):  
B. Lord ◽  
D. C. Finlay
Keyword(s):  
Ambient Noise ◽  
Original Learning ◽  
Intensity Noise ◽  
Mental Function ◽  
Noise Condition ◽  
Complex Action ◽  
Distraction Effect ◽  
Low Intensity ◽  
Learning Trials ◽  
Made In

Two experiments are described. The first demonstrated the effects of relatively low intensity noise on recall of a previously learned list of nonsense syllables. Significant differences were found between recall under noise and recall under ambient noise conditions with the noise condition producing more errors. Exp. 2 yielded a high correlation between number of errors made in the original learning trials and the number of errors made in recall under noise. The relationships suggest a quite complex action of noise on mental function, one which is other than a peripheral distraction effect.

scholarly journals Note on Ripples in a Viscous Liquid

1891 ◽  
Vol 17 ◽  
pp. 110-115 ◽  
Author(s):  
Tait
Keyword(s):  
Surface Tension ◽  
Surface Layer ◽  
Free Surface ◽  
Boundary Conditions ◽  
Viscous Liquid ◽  
Tuning Fork ◽  
Cartesian Coordinates ◽  
A Current ◽  
Made In

The following investigation was made in consequence of certain peculiarities in the earlier results of some recent measurements of ripples by Prof. Michie Smith, in my Laboratory, which will, I hope, soon be communicated to the Society. These seemed to suggest that viscosity might have some influence on the results, as might also the film of oxide, &c, which soon gathers on a free surface of mercury. I therefore took account of the density, as well as of possible rigidity, of this surface layer, in addition to the surface tension which, was the object of Prof. Smith's work. The later part of the paper, where Cartesian coordinates are employed, runs somewhat on the lines of an analogous investigation in Basset's Hydrodynamics. My original object, however, was different from his, as I sought the effects of viscosity on waves steadily maintained by means of a tuning-fork used as a current interruptor; not on waves once started and then left to themselves. Besides obtaining his boundary conditions in a singular manner, I think that in his § 521 Mr Basset has made an erroneous investigation of the effects of very great viscosity.

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