scholarly journals Metachronism and Frequency of Beat in the Peristomial Cilia of Stentor

1956 ◽  
Vol 33 (1) ◽  
pp. 15-28 ◽  
Author(s):  
M. A. SLEIGH
Keyword(s):  
Wave Velocity ◽  
Magnesium Chloride ◽  
Wave Length ◽  
Methyl Cellulose ◽  
Aluminium Chloride ◽  
Ciliary Activity ◽  
Metachronal Wave ◽  
Low Concentrations ◽  
Two Factors ◽  
Significant Change

1. A stroboscopic method was used to determine the frequency of beat of the peristomial cilia of Stentor polymorphus (Ehrbg.). The metachronal wave-length was measured from photographs. These two values were used to calculate the rate of propagation of the metachronal wave. 2. The Arrhenius temperature characteristics for frequency and for wave velocity were calculated for the temperature range from o to 25° C. The average values found, 11,350 and 7520, were significantly different for the two factors. 3. An increase in the viscosity of the medium by addition of methyl cellulose caused a decrease in frequency, but no significant change in wave velocity. 4. The presence of magnesium chloride in low concentrations caused an increase in frequency, but no significant change in wave velocity. Aluminium chloride caused similar increases in frequency at lower concentrations than magnesium chloride. 5. The drug digitoxin had different quantitative and qualitative effects on the frequency and on the wave velocity. Small increases in frequency occurred over the concentration range in which large increases in wave velocity were recorded. The wave velocity increase reached a maximum at about 0.4 mg./l. of digitoxin and was some six times as great as the frequency increase at this concentration. 6. It is concluded that the mechanical process involved in ciliary activity functions independently of the co-ordination process. A combination of these two factors determines the magnitude of the metachronal wave-length.

scholarly journals THEORY AND MEASUREMENT OF VISUAL MECHANISMS

1941 ◽  
Vol 25 (2) ◽  
pp. 293-308 ◽  
Author(s):  
W. J. Crozier ◽  
Ernst Wolf
Keyword(s):  
Wave Length ◽  
Theoretical Interpretation ◽  
Rational Relation ◽  
Flicker Response ◽  
Foveal Region ◽  
Two Factors ◽  
Image Area ◽  
Real Test

The several parameters of the flicker response contour (F – log I) are considered as a function of wave-length composition (white, blue, and red) and light-time fraction, for an extra-foveal region (monocular, temporal retina). These data are compared with those secured for the same image area centrally fixated at the fovea. The systematic changes in the parameters are shown to be in rational relation to other relevant excitability data. Since for two retinal regions the primary contours are quite different, the systematic nature of the behavior of the parameters in the two cases is a real test of the power of the analysis proposed. Theoretical interpretation is required to deal with the properties of sets of performance contours under systematically varied conditions, and cannot rely simply on the comparison of (for example) two contours under the same arbitrary conditions at two retinal locations. In particular it is emphasized that a qualitative separation must be made of the two factors of (a) number of units and (b) the frequencies of their actions, before the wave-length problem can be dealt with effectively.

scholarly journals The role of bound potassium ions in the hydrolysis of low concentrations of adenosine triphosphate by preparations of membrane fragments from ox brain cerebral cortex

1970 ◽  
Vol 120 (1) ◽  
pp. 15-24 ◽  
Author(s):  
P. S. G. Goldfarb ◽  
R. Rodnight
Keyword(s):  
Potassium Chloride ◽  
Magnesium Chloride ◽  
Adenosine Triphosphatase ◽  
Time Course ◽  
Atp Hydrolysis ◽  
Protein Ratio ◽  
Low Concentrations ◽  
Hydrolysis Of ◽  
Emission Flame

1. The intrinsic Na+, K+, Mg2+ and Ca2+ contents of a preparation of membrane fragments from ox brain were determined by emission flame photometry. 2. Centrifugal washing of the preparation with imidazole-buffered EDTA solutions decreased the bound Na+ from 90±20 to 24±12, the bound K+ from 27±3 to 7±2, the bound Mg2+ from 20±2 to 3±1 and the bound calcium from 8±1 to <1nmol/mg of protein. 3. The activities of the Na++K++Mg2+-stimulated adenosine triphosphatase and the Na+-dependent reaction forming bound phosphate were compared in the unwashed and washed preparations at an ATP concentration of 2.5μm (ATP/protein ratio 12.5pmol/μg). 4. The Na+-dependent hydrolysis of ATP as well as the plateau concentration of bound phosphate and the rate of dephosphorylation were decreased in the washed preparation. The time-course of formation and decline of bound phosphate was fully restored by the addition of 2.5μm-magnesium chloride and 2μm-potassium chloride. Addition of 2.5μm-magnesium chloride alone fully restored the plateau concentration of bound phosphate, but the rate of dephosphorylation was only slightly increased. Na+-dependent ATP hydrolysis was partly restored with 2.5μm-magnesium chloride; addition of K+ in the range 2–10μm-potassium chloride then further restored hydrolysis but not to the control rate. 5. Pretreatment of the washed preparation at 0°C with 0.5nmol of K+/mg of protein so that the final added K+ in the reaction mixture was 0.1μm restored the Na+-dependent hydrolysis of ATP and the time-course of the reaction forming bound phosphate. 6. The binding of [42K]potassium chloride by the washed membrane preparation was examined. Binding in a solution containing 10nmol of K+/mg of protein was linear over a period of 20min and was inhibited by Na+. Half-maximal inhibition of 42K+-binding required a 100-fold excess of sodium chloride. 7. It was concluded (a) that a significant fraction of the apparent Na+-dependent hydrolysis of ATP observed in the unwashed preparation is due to activation by bound K+ and Mg2+ of the Na++K++Mg2+-stimulated adenosine triphosphatase system and (b) that the enzyme system is able to bind K+ from a solution of 0.5μm-potassium chloride.

scholarly journals I. On the waves produced by a single impulse in water of any depth, or in a dispersive medium

1887 ◽  
Vol 42 (251-257) ◽  
pp. 80-83 ◽  
Keyword(s):  
Wave Velocity ◽  
Dispersive Medium ◽  
Wave Length ◽  
Periodic Waves ◽  
Two Dimensional ◽  
Group A ◽  
Two Sides ◽  
The Waves

For brevity and simplicity consider only the case of two-dimensional motion . All that it is necessary to know of the medium is the relation between the wave-velocity and the wave-length of an endless procession of periodic waves. The result of our work will show us that the velocity of progress of a zero, or maximum, or minimum, in any part of a varying group of waves, is equal to the velocity of progress of periodic waves of wave-length equal to a certain length, which may be defined as the wave-length in the neighbourhood of the particular point looked to in the group (a length which will generally be intermediate between the distances from the point considered to its next-neighbour corresponding points on its two sides).

scholarly journals Factors affecting warmth comfort and stuffiness in domestic rooms

1947 ◽  
Vol 45 (4) ◽  
pp. 434-442
Author(s):  
K. W. Yarnold
Keyword(s):  
Air Temperature ◽  
Large Scale ◽  
Wave Length ◽  
Field Work ◽  
The Body ◽  
Equivalent Temperature ◽  
Factors Affecting ◽  
Two Factors ◽  
Striking Change ◽  
The Subject

One object of the investigation was to determine the ideal contributions to warmth comfort in small ‘domestic’ rooms of air heating and radiation. It was soon found that in rooms heated by fires, subjects usually complained of cold backs when the equivalent temperature was in the region of 60–65° F., the accepted standard for buildings heated by convection, and preferred equivalent temperatures above 70° F.Since large-scale trials, using many observers, were clearly necessary, the reliability of 5 min. test periods was studied; these short periods were proved reliable so long as the subject had previously been in a comfortable room for an hour or so.It was found necessary, in rooms heated by fires, to treat separately the side of the subject facing the fire and remote from it. The cooler side must be exposed to an equivalent temperature not much less than 65° F., while radiation falling on the warm side is to be regarded as a very desirable, but nonessential, bonus. These conclusions were confirmed by field work in the subjects' own homes.The eupatheoscope and globe thermometer were modified to enable conditions acting on the two sides of the body to be assessed separately.The extent to which radiation acting on the front of the body could compensate for a cold back to produce what was called ‘minimum comfort’ was also studied. It was shown that down to back equivalent temperatures of about 56° F. an increase of 2° in front equivalent temperature will compensate for a fall of 1° in back equivalent temperature, but below 56° F. compensation fails.The physical basis of sensations of stuffiness and freshness were also investigated. Throughout these experiments care was taken to ensure that the subjects were neither too hot nor too cold. In these conditions, only two factors appear to be important. First, the air temperature should be as low as possible. To obtain warmth comfort with a low air temperature some high temperature source of radiation is generally necessary. The peak wave-length of the radiation emitted by the fire is also of great importance, a striking change in the personal sensations occurring, for example, as the wave-length increases from 2 to 3μ. In general, those wavelengths which are absorbed in the outer layers of the skin cause sensations of stuffiness, and those which are not give rise to feelings of freshness. Peaks at 3, 4·1 and 4·7 μ should therefore be avoided in the design of gas and electric fires.

scholarly journals Changes in the Raman spectrum of sulphuric acid on dilution

1934 ◽  
Vol 144 (851) ◽  
pp. 129-143 ◽  
Keyword(s):  
Sulphuric Acid ◽  
Raman Effect ◽  
Wave Length ◽  
Frequency Shifts ◽  
Low Concentrations ◽  
Intensity Changes ◽  
Continuous Background ◽  
Length Determination ◽  
Detailed Interpretation ◽  
Two Stages

The results of previous workers upon the Raman effect of sulphuric acid show a considerable lack of agreement, due no doubt in part to the intensity of the accompanying continuous background and the apparent diffuseness of certain of the lines. Thus both Nisi and Woodward found that change of the concentration of the add greatly modified the appearance of the spectrum, influencing both the positions and the relative intensities of the lines. Wood-ward gave photometer carves of the spectra for concentrations ranging from 100% to 25% by volume, and attributed the observed intensity changes to tho successive stages of ionization of the acid. The lines Δ v = 910 and 1140 cm. -1 (approximate values), which were strong in the 100% acid, became weaker and shifted somewhat as the concentration decreased; while a new line Δ v = 1046 cm. -1 made its appearance and increased correspondingly in intensity. At low concentrations this last line became double, a companion appearing at 982 cm. -1 . The frequencies 910 and 1110 were regarded as characteristic of the H 2 SO 4 molecule, 1016 of the HSO' 4 ion, and 982 of the SO" 4 ion. Other diffuse lines also showed frequency shifts. Bell and Fredrickson. however, whose measurements were made not only with a prism spectrograph but also with a grating, failed to find any appreciable shifts of the line with dilution. Moreover, they stated that on their plates the 1016 line gave no indication of becoming double at low concentrations, but merely grew more diffuse. The findings of other workers are referred to in the discussion of our results (see below). In view of the conflicting nature of the above evidence regarding the two stages of ionisation of the acid, it was thought, desirable to repeat tho investigations using a higher dispersion than that employed by Woodward ( loc. cit .), the object of the work being to obtain more conclusive photometer curves of the spectra. The curves we have actually obtained not only give a clear picture of the intensity changes involved, but have also been used in a rational method of wave-length determination, the adoption of which has made it possible for us to propose a somewhat more detailed interpretation of the spectra than has hitherto been attempted.

scholarly journals Effect of aluminium toxicity on the development of poplar (Populus tremula L. x P. alba L.) cultured in vitro

2014 ◽  
Vol 68 (4) ◽  
pp. 245-250 ◽  
Author(s):  
Krystyna Bojarczuk
Keyword(s):  
Aluminium Toxicity ◽  
Inhibitory Effect ◽  
Populus Tremula ◽  
Aluminium Chloride ◽  
Adventitious Bud ◽  
Aluminium Sulphate ◽  
Low Concentrations ◽  
The Media ◽  
High Concentrations

Adventitious bud cultures were established using vegetative buds from selected clones of poplar (<em>Populus tremula</em> L. x <em>P</em>. <em>alba</em> L.) as initial explants. For multiplication of shoots a modified Murashige and Skoog medium (MS) was used. Aluminium salts (aluminium sulphate and aluminium chloride) were added to the media. It was found that the pH of the medium had no effect on the development of cultures at low concentrations of nutrients (1/2 or 1/4 MS). Low concentrations of aluminium (Al 25mg•dm<sup>-3</sup> supplied as aluminium sulphate, Al 15 mg•dm<sup>-3</sup> as aluminium chloride) had no inhibitory effect on shoot development but decreased regeneration of adventitious roots. High concentrations of aluminium inhibited the development of shoots and roots, especially in a medium at pH 4.5. Microcuttings rooted in the highest percentage and formed the strongest rooting system on 1/4 strength MS medium at pH 4.5. It was found that there was no difference between the rooting of shoots excised from cultures cultivated with or without A1 in this medium at pH 5.5.

scholarly journals Doubling of Group Velocity near the Coast due to Storm Surge, Tides or Tsunami: An Analytical Study

2021 ◽  
Vol 9 (VI) ◽  
pp. 567-574
Author(s):  
Ramkrishna Datta
Keyword(s):  
Group Velocity ◽  
Storm Surge ◽  
Wave Velocity ◽  
Deep Sea ◽  
Analytical Study ◽  
Perturbation Technique ◽  
Wave Length ◽  
Coastal Region ◽  
Slight Variation ◽  
Harmonic Waves

Tsunami may cause due to storm surge, earthquake at coastal region or at under the sea (obviously Hypocenter of earthquake must be within the earth’s crust or below). Each cases a wave packet which develops a set of simple harmonic motion of different wave lengths. These simple harmonic waves have been analyzed analytically. The velocity of propagation of waves depends upon the wave lengths. So the waves of nearly equal wave lengths can be considered as a group. This group of waves will propagate with nearly equal velocity which is known as group velocity. On considering two consecutive simple harmonic waves of same amplitude, we can find two equations describing simple harmonic motions having slightly different wave lengths and time periods. The combination of these two said SHM’s we can find another resultant SHM with different amplitude than of the previous two SHM’s. This new SHM has a slight variation in wave length and time period than that of that of the said earlier two SHM’s. Then using the perturbation technique on this resultant equation of SHM, we can find a new wave velocity (group velocity) in differential notation of wave velocity. This differential notation of wave velocity has been eliminated from the relation between the wave velocity on the surface of water and the depth of the sea. Then we get a relation between group velocity and wave velocity depending with depth of the sea. The application of boundary conditions on depth of deep sea and that of at the sea shore, we can find the group velocity at each region respectively. It is seen from the analysis that the group velocity at the sea shore is as much as double that of at the deep sea. Several recent cases of tsunamis or storm surges have been studied and it is found that the results depicted the same implementation through devastation that established by analytical study.

Experimental Study of Mix Proportion of Magnesium Oxychloride Cement

2012 ◽  
Vol 188 ◽  
pp. 183-188 ◽  
Author(s):  
Zhan Hong Qiu ◽  
Jin Rong Feng ◽  
Lei Xiao ◽  
Zhi Yong Zeng
Keyword(s):  
Magnesium Oxide ◽  
Magnesium Chloride ◽  
Bending Strength ◽  
Influence Factor ◽  
Immersion Test ◽  
Magnesium Chloride Solution ◽  
Two Factors ◽  
Magnesium Oxychloride ◽  
Magnesium Oxychloride Cement ◽  
Oxychloride Cement

Based on the results of compression and bending tests of fifty eight magnesium oxychloride cement test cubes, the influences of two factors on compression and bending strength have been analyzed which includes the mole ratio of magnesium oxide and magnesium chloride and Baum degree of magnesium chloride solution. Softening coefficient of magnesium oxychloride cement and its influence factor have been studied by immersion test of twelve test cubes. The results show when the mole ratio of magnesium oxide and magnesium chloride is 7.0, the strength and water resistance performance of magnesium oxychloride cement is best. This work is very important to the application and dissemination of magnesium oxychloride cement bearing structural member in southern wetter areas of china.

scholarly journals STUDY OF VISCOSITY OF AQUEOUS SOLUTIONS OF NATURAL POLYSACCHARIDES

2016 ◽  
pp. 11-19 ◽  
Author(s):  
Lyudmila Asyakina ◽  
Lyudmila Asyakina ◽  
Lyubov Dyshlyuk ◽  
Lyubov Dyshlyuk
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Biodegradable Polymers ◽  
Raw Materials ◽  
Hydroxypropyl Methylcellulose ◽  
Methyl Cellulose ◽  
Preparation Temperature ◽  
Low Concentrations ◽  
Wide Range ◽  
Solution Preparation

One of the steps of synthesis of biodegradable polymers is preparation of an aqueous solution of raw materials. Formulation of biodegradable films with optimum characteristics requires to undertake a separate rheological study of each aqueous solution. An essential parameter in this step is a uniform thickness, which is achieved by means of specified viscosity parameters. Viscosity of solutions depends on many parameters, among which are composition and concentration of components in a solution, solution preparation temperature, pH of the finished medium, and presence of free ions. This article describes studies and results on study of viscosity parameters of aqueous solutions of natural polysaccharides: agar-agar, hydroxypropyl methyl cellulose and carrageenan. For aqueous solutions of carrageenan and hydroxypropyl methylcellulose, viscosity was measured at 25°C. In addition, viscosity parameters were measured for 1.5% hhydroxypropyl methylcellulose solutions at 40°C and 60°C. Depending on the gel formation temperature, viscosity of agar-agar solutions was measured at 50°C or 70°C. According to the results of experiments, it was found that viscosity of 1.0-1.5% hydroxypropyl methylcellulose aqueous solutions is in the range of 8.0-80.0 cP. Heating to 100°C at pH 6 results in irreversible destruction of hydroxypropylmethylcellulose molecules. Aqueous solutions of agar-agar are similar to hydroxypropyl methylcellulose solutions but agar-agar is able to gelate at sufficiently low concentrations (from 0.5%). Viscosity of 3.0- 5.0% carrageenan aqueous solutions varies within a wide range: 1.5-1400.0 cP. Thus, rheological properties allow to adjust viscosity of the process mixture in the production of biodegradable polymers in the desired range and in different directions.

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