Lines Of Different Slopes Research Articles

Adaptation of the thylakoid membranes of pea chloroplasts to light intensities. II. Regulation of electron transport capacities, electron carriers, coupling factor (CF1) activity and rates of photosynthesis

The electron transport rates of photosystems II and I, amounts of electron carriers, coupling factor activity and photosynthetic rates were investigated in thylakoids isolated from pea plants grown under a wide range of light intensities (16 h light-8 h dark). The electron transport rates of PS II and PS I, as partial reactions or in whole chain, and coupling factor activity on a unit chlorophyll basis, all increased as the light intensity available for growth was altered from a very low intensity of 10 μE m(-2)s(-1) to a high intensity of 840 μE m(-2)s(-1). Similarly, there were increases in the amounts of atrazine binding sites, plastoquinine, cytochrome f and P700 per unit chlorophyll; significantly, the amounts of reaction centres of PS II and PS I were not equal at any light intensity. The rate of change of all parameters with respect to light intensity could be represented by two straight lines of different slopes which met at a transition point corresponding to approximately 200 μE m(-2)s(-1) during growth. These photoadaptations were similar to those observed for both the relative distribution of chlorophyll in chlorophyll-protein complexes and the chl a/chl b ratios [Leong and Anderson, 1984, Photosynthesis Research 5:117-128]. Since these thylakoid components and functions were affected in the same direction by light intensity during growth and all show linear relationships with chl a/chl b ratios, it indicates that they are closely regulated and markedly well co-ordinated. Plants compensate for the limited amount of low light intensities by drastically increasing the light-harvesting antenna unit size of photosystem II and to a lesser extent that of photosystem I. Changes in the composition of the thylakoid membranes exert a regulatory effect on the overall photosynthetic rate up to approximately 450 μE m(-2)s(-1).

The effect of temperature on the asymmetrical charge movement in squid giant axons.

1. Asymmetrical displacement currents ('gating currents') have been recorded in intracellularly perfused squid giant axons by averaging the currents associated with depolarizing and hyperpolarizing voltage pulses. The effect of temperature on 'gating currents' was studied and compared with the effect of temperature on Na currents. 2. Increasing the temperature in seven steps from 0 to 15 degrees C increased the area under the on- and off-response (Qon, Qoff). The average Q10 values for Qon and Qoff (measured with depolarizing pulses to 0 to 20 mV) were 1.41 and 1.62, respectively. 3. The on- and the off-response were described mathematically by the sum of two exponentials. The first component of the on-response, Qon 1, represented 80% or more of the total charge movement associated with 2.5 msec pulses; the Q10 of Qon 1 was similar to that of total Qon. The first component of the off-response, Qoff 1, represented 50--70% of total Qoff; its Q10 was smaller than that of total Qoff. 4. The temperature dependence of the rate constants (tauon 1)-1 and (tauoff 1)-1 was stronger at temperatures below 6--8 degrees C (Q10 = 3.1--6.4) than at higher temperatures (Q10 = 2.0--3.3). In an Arrhenius plot two lines of different slope were required to fit the data. 5. The effect of increasing the temperature on the Q vs. V curve can be described as an increase of Qmax or, alternatively, as a shift of the curve to more negative potentials. 6. Increasing the temperature from 0 to 15 degrees C increased the peak of the Na current (recorded in sea water with a fifth of the normal Na concentration), increased the rate constants taum-1 and tauh-1 and shifted the m3infinity and hinfinity curves to more positive potentials. 7. The Q10 of the rate constant taum-1 varied between 2.04 and 2.61 and was independent of temperature. In an Arrhenius plot the values for taum-1 could be fitted by a single line. 8. The results support the view that 'gating current' does not simply reflect changes of the Na activation variable m. The increase of Qon, Qoff with increasing temperature may be attributed to an increase in membrane fluidity. The possibility that those charges which become mobile at higher temperatures may not be related to gating is considered.

Immunochemical studies on the combining site of the blood group H-Specific lectin 1 from Ulex europeus seeds

The specificity of purified Ulex lectin I has been studied by quantitative precipitin, quantitative precipitin inhibition, and competitive binding assays using tritium-labeled hog mucin H substance. The lectin is precipitated by human and hog H substances, by human A 2 substances, by a cow substance with A activity, and by B substances of human and horse origin. The lectin did not precipitate with A 1 substances, with Le a substances, with a precursor substance with I activity, or with PI fractions obtained by mild acid hydrolysis of blood group B substance. Ulex lectin I was most specific for the blood group H oligosaccharide HR L 0.75, having the structure lFucαl ↓ 2 dGalβ1 → 4 dGlcNAcβ1 → 6R; this was determined by inhibition of precipitation of the lectin with a human H substance and by inhibition of the binding of tritiated hog H substance to the Ulex lectin I coupled to Sepharose beads using blood group and milk oligosaccharides as inhibitors. The lectin was also reactive with lFucα1 → 2 dGalβ1 → 4[ lFucαl → 3] dGlcNAcβ1 → 6R, 2′-fucosyllactose, lactodifucotetraose, and methyl α lFuc, all of which had essentially parallel slopes by each assay method. lFuc and fucosyl oligosaccharides with type 1 chains gave lines of different slopes but had the same range of activity. The Ulex lectin I site differs from the Lotus tetragonolobus site, which does not react at all with H oligosaccharides with the type 1 chain. Inhibition assays using tritiated hog H substance and various oligosaccharides were about 60 to 80 times more sensitive than assays by inhibition of precipitation.

Hydrolysis of pentosans in bagasse pith

AbstractWork has been conducted on the hydrolysis of pentosans in bagasse pith as the first part of a study of the chemistry of bagasse processing aimed at establishing an integrated industry. Bagasse pith is the fine part screened out and discarded as waste during the preparation of raw material for bagasse pulping plant. By using dilute sulphuric acid at a concentration less than 2% by weight and at a temperature lower than 165°C, pith is hydrolysed to pentoses in a yield of 80–90% based on potential pentoses in pith. Hydrolysis of pentosans in pith, within the scope of experiment, seems to be a first order reaction. However, the semi‐logarithmic time plot for the hydrolysis of potential pentoses in the residue consists of two straight lines of different slope. This may be explained on the assumption that bagasse pith contains two major fractions of pentosans that are hydrolysed at different rates. Saeman's equation for hydrolysis of wood with sulphuric acid may be adapted to represent dependence of rate constant K on acid concentration C and reaction temperature T in hydrolysis of the two major parts of pentosans in bagasse pith.

Hydrolysis of pentosans in bagasse pith

AbstractWork has been conducted on the hydrolysis of pentosans in bagasse pith as the first part of a study of the chemistry of bagasse processing aimed at establishing an integrated industry. Bagasse pith is the fine part screened out and discarded as waste during the preparation of raw material for bagasse pulping plant. By using dilute sulphuric acid at a concentration less than 2% by weight and at a temperature lower than 165°C, pith is hydrolysed to pentoses in a yield of 80–90% based on potential pentoses in pith. Hydrolysis of pentosans in pith, within the scope of experiment, seems to be a first order reaction. However, the semi‐logarithmic time plot for the hydrolysis of potential pentoses in the residue consists of two straight lines of different slope. This may be explained on the assumption that bagasse pith contains two major fractions of pentosans that are hydrolysed at different rates. Saeman's equation for hydrolysis of wood with sulphuric acid may be adapted to represent dependence of rate constant K on acid concentration C and reaction temperature T in hydrolysis of the two major parts of pentosans in bagasse pith.K1 = 6.4 × 105C1.02 exp (−6378/T)K2 = 10.7C0.363 exp (‐ 2826/T)

アルミニウムの多孔質アノード酸化皮膜のｐｏｒｅ‐ｆｉｌｌｉｎｇ

Aluminium specimens anodized to form porous oxide films in an oxalic acid solution were reanodized in a neutral boric acid-borate solution (pH=7.4, 20°C) at a constant c.d. of 0.5mA/cm2 and changes in the anodizing voltage and geometrical structure of the film were examined. An automatic apparatus was used for the current-controlled electrolysis and an ultra-thin sectioning technique was utilized in electron-microscopy. It was found that the oxide formation occurs both at the barrier oxide/solution and oxide/metal interphases. The former which leads to pore-filling is due to the transport of Al3+ ions through the barrier oxide whereas the latter is caused by the O2- ion transportation. The voltagetime relationship is represented by two successive straight lines of different slopes and the pore-filling was found to be completed at the time when the slope changes. Apparent transport numbers for Al3+ and O2- ions were determined respectively to be 0.40 and 0.60 and they were almost independent of the applied c.d. It is shown that the porosity and thickness of the film could be estimated by an analysis of the voltage-time relationship using the above transport numbers.

Phase transitions in planar bilayer membranes

Temperature-dependent structural changes in planar bilayer membranes formed from glycerol monooleate (GMO) dispersed in various n-alkane solvents (C12-C17) have been studied using precise measurements of specific geometric capacitance (Cg). Cg generally increases as temperature (T) decreases. A change in the slope of Cg(T) occurs between 15 and 18 degrees C for all solvent systems examined. Measurements of the interfacial tension (gamma) of the bulk GMO-alkane dispersions against 0.1 M NaCl show that gamma generally decreases with decreasing temperature. The data can be fitted with two straight lines of different slope which intersect on the average at 17 degrees C. Pagano et al. (1973, Science (Wash. D.C.). 181:557) have shown using calorimetry that GMO has a phase transition at about 15 degrees C. Thus, the changes in Cg and gamma with temperature are likely to result from a GMO phase transition. A second structural change is observed to occur between 5 and 10 degrees C which has not been detected calorimetrically. Calculations of Cg based on various estimates of the hydrocarbon dielectric coefficient (epsilon-b) and/or hydrocarbon thickness (delta-b) leads to models for the structure of the bilayer above and below the phase transition temperature.

Interaction of ophidian L-amino acid oxidase with its substrates and inhibitors: role of molecular geometry and electron distribution. Communication 6 on ophidian L-amino acid oxidases.

AbstractMolecular activities, determined polarographically for the degradation of phenylalanine and 21 meta‐ and para‐substituted derivatives by crystalline L‐amino acid oxidase, yielded a linear Hammett plot of positive slope. However, the presence of large moieties in the para‐position led to negative deviations which were linearly correlated with van der Waals' radius of the substituent. This suggested that the large substituents cause the substrate molecules to be displaced from their normal (eutopic, productive) position at the active site, resulting in lower velocities. In analogous experiments with competitive inhibitors (ring‐substituted benzoic and phenylacetic acids), the logarithm of K1 was found to be a linear function of Hansch's hydrophobic constant π. Lines of different slope characterized the meta‐ and para‐derivatives, suggesting that the nature of the substituent affects the strength of hydrophobic binding, while the locus determines the orientation of the inhibitor on the active site. An analysis of the data reported here and in the literature for meta‐ and para‐compounds supports the idea that the geometry of the ring‐substituted substrate affects the orientation of the molecule on the active site, which may in turn determine which step of the reaction sequence becomes rate‐limiting.

GPC Separation and Molecular Wcight Distribution of Benzene Soluble Components from Coal Derivatives

Fundamental studies on the separation of coal derivatives by means of gel permeation chromatography (GPC) are reported on (1) the chromatographic conditions for preparative GPC separation for structural analyses of coal and (2) basic experiments to odtain the molecular weight distributtion from analytical GPC elution curves using the chloroform soluble qart (γ-part) of pyridine extract from Akabira coal. On the basis of this informaton, the distributions of molecularweight of oil and asphaltene obtained from hydrogenolysis of Akabira coal are investigated by GPC analyses and their variation with reaction temperature is discussed.The petroleum soluble portion (γ1-part) and the insoluble portion (γ2-4-part) from the γ-part were selected as the sample for the discussion of the optimum conditions for GPC separation, such as pore size of gel and elution solvent. From the experimental results, it is obvious that separation by preparative GPC is achieved, odtaining fractions of considerably narrow molecular weight distribution. This contributed remarkably to the resolution of thechemical structure of coal. The relationship detween the elution volume (Ve) of the analytical GPC and average molecular weight (M) estimated by vapor pressure osmometry is fairly good for the fractionation products from preparative GPC (Fig. 9, 10). The M-Ve correlation lines of the 1- and the 2-4-parts were straight lines of different slope. Therefore it was assumed that the difference was due to a difference in structural type on the components. Consequently, these γ relationships of log M-Ve can be applied to the estimation of the molecular weight distribution from analytical GPC chromatograms as the correlation lines of high-molecular and low-molecular weight components respectively for the coal derived liquids.Oil and asphaltene in hydrogenolysis products werealso separated into fraction on the basis of molecular weight by preparative GPC and each fraction was correlated by elution counts of analytical GPC and average molecular weight. The results of these relationships were in fairly good agreement with correlation lines of log M-Ve odtained from the γ1 and the γ2-4 componets respectively (Fig. 13, 14). From the elution curves of analytical GPC for oil and asphaltene of varying reaction temperature, it is recognized that the distribution of molecular wight for asphaltene shifts gradually in the direction of a lower molecular weight distribution as the reaction temperature increases. On the other hand, the distribution of moleclar weight of oil changes only slightly and tends to converge to the constant distribution of low molecular weight components.

Ionic Conduction in Alkali and Thallium Silicate Glasses

Electrical conductivities of binary alkali and thallous silicate glasses have been measured as a function of composition, temperature, and frequency. The best approximation to the activation energy for dc conduction can probably be obtained by extrapolating its frequency dependence to zero frequency, although values obtained at frequencies below 2500 hz do not differ greatly from the dc values. The plot of activation energy for conduction against modifier content consists of two straight lines of different slope. For all the alkali silicate glasses the break in slope occurs near 25 mole % alkali oxide and at an activation energy near 14.7 kcal/mole. The slope of the line below 25 mole % alkali oxide is proportional to the alkali ion radius. The behavior of thallous silicate glass is similar but not identical to that of the alkali silicates. It is concluded that (1) the reported conduction behavior does not result primarily from phase separation, (2) the principal contribution to the activation energy is probably the work required for a mobile ion to pass through the glass network rather than to leave its initial position, and (3) a structural change independent of the nature of the modifier cation occurs near a modifier content of 25 mole %.

Rapid colorimetric micromethod for free fatty acids

Free fatty acids (FFA), the uranyl ion, and the basic dye Rhodamine B form colored complexes, which are extractable into toluene or benzene. Fatty acids of different chain lengths above C(10) and different degrees of unsaturation gave constant molar yield. Complexes in toluene alone are unstable, especially in the light, but a small amount of aqueous uranyl acetate stabilizes them sufficiently for determination. At constant uranyl and Rhodamine B concentrations, a plot of optical density vs. FFA concentration yields two straight lines of different slope, i.e., a biphasic standard curve. Phospholipids interfere, and must be removed with zeolite during FFA extraction. Recovery of FFA added to rat plasma was very similar to that with titration. Assay of rat and dog plasma samples under fasting and fed conditions gave good agreement with the titration method. Values of human plasma samples tended to be higher by the colorimetric procedure; a few samples gave significant disagreement. The method compares well with previous methods in sensitivity and accuracy, and offers advantages in speed, simplicity, and possibly specificity.

Flow Properties of Molten EVA Copolymer

The flow properties of molten EVA copolymer in the region of compratively higher shear rate were measured in connection with investigation of the behaviors and forming mechanism of melt fracture by means of a capillary type rheometer. The relation between the actual shear rate and viscosity obtained by means of the differential method indicates that their flow pattern is non-Newtonian and viscosity decreases with increase of shear rate.They are described by two straight lines of different slope. The shear rate at their intersecting point corresponds to the critical shear rate where melt fracture forms.The EVA copolymer differs slightly in the flow curve from low density polyethylene; it seems, however, that their difference is due to the difference in molecular weight distribution rather than in the materials themselves.And also, the fluidity of the molten EVA copolymer having about 3 in the ratio of Mw/Mn may be equivalent to that of low density polyethylene having from 4 to 7 and, generally, EVA copolymer has higher fluidity than low density polyethylene does. It is expected that the fluidity will increase with incroporation of vinylacetate in the same molecular weight distribution and the same average molecular weight.The critical shear rate increases with the melt index and temperature. It can not be found that the materials themselves and the molecular weight distribution gives direct influence to the critical point of melt fracture forming as far as the melt index is defined as the parameter. The critical viscosity ηc where melt fracture forms decreases almost in a straight line with increase of melt index.It is found from the studies of end correction and behavior of formation of melt fracture that melt fracture occurs at inlet of the die, and it supposed that formation of melt fracture has been caused by the result of the elastic turbulence of flow pattern due to failure of recoverable shear strain at inlet of the die.

Flows Through Charged Membranes. I. Flip-Flop Current vs Voltage Relation

Flow processes in a (porous) charged membrane separating two solutions of different concentration of the same electrolyte are studied theoretically, using a capillary model for the membrane and the Debye—Hückel approximation for the calculation of ion distributions in the double layer formed near fixed charges on the capillary wall. Steady-state solutions to the continuity equations derived are obtained subject to the external conditions that there is the passage of a constant forced electric current I through the membrane, the salt concentrations on both sides of the membrane are held constant, and a constant pressure is imposed on the more concentrated solution. The results yield a characteristic I vs transmembrane potential Δφ relation, which consists of two nearly straight lines of different slopes involving a discontinuous transition between them. This feature well compares to the experimental data obtained recently by Tasaki et al. with sintered glass membranes and thought by them to be significance in relation to the physiology of nerve excitation. It is shown that, in the framework of the theory presented, the occurrence of a discontinuous change in I at a certain particular potential mainly stems from the dependence of the electro-osmotic coefficient on salt concentration. The probable causes for the discrepancies between theory and experiment are discussed briefly.

Investigation of the influence of the structures of solid and liquid phases on the solubility of salts in water

1. Solubility in the systems NH4NO3−NH4I−H2O and KNO3−KI−H2O at 25° was studied. 2. Solubility in the systems named was compared with the structures of the component salts and their saturated solutions. 3. The varying solubility of salts in the studied systems is determined to a certain degree by the relative stability of the ionic close order taking part in the crystallization of salts from saturated solutions: the more stable this order is, the less soluble is the salt. 4. Joint solubility in both systems is characterized by a linear relation between xo−x (moles of salted-out salt) andy (moles of dissolved salt). 5. The linear relation between xo−x andy, its representation for KNO3 by two straight lines of different slope, and the difference in displacement coefficients indicate with one accord, that joint solubility is determined by the structural state of saturated solutions.

Cupric tetramminosulphate. II. Dissociation pressures

AbstractThe dissociation pressure of cupric tetramminosulphate was measured at different temperatures. Log10 P is plotted against 1/T, gave a curve which could be divided into two intersecting lines of different slopes, indicating that the two molecules of ammonia liberated in the decomposition of the tetrammine to give the diammine are set free in two stages; at temperatures lower than 50° the tetrammine decomposes giving the triammine; at higher temperatures, it gives the diammine directly. The heat content change of the system “Δ H” was calculated for each step and found to be 6.1 and 25.5 kcals per molecule for the liberation of the first and second molecules ammonia respectively at low temperatures.The heat of formation of CuSO4.3NH3 was calculated as 285.3 kcals per molecule.

Spectrophotometric Titrations with Nitrous Acid I. : The Estimation Of Procaine Hydrochloride, Propoxycaine Hydrochloride; and Tetracaine Hydrochloride

Spectrophotometric titrations of three aromatic amines with nitrous acid are described. Measurements made during the course of a given titration are dependent on the presence or absence of the nitrous acid spectrum, or on the presence or absence of diazo or nitroso derivative spectra. The point of intersection of straight lines of different slope, occurring prior to and after reaction completion, is a measure of amine equivalency. In particular, measurements of procaine hydrochloride, propoxycaine hydrochloride, tetracaine hydrochloride, and the combination of procaine hydrochloride with tetracaine hydrochloride are discussed.

METEOR ECHO DURATION AND RADIO WAVE LENGTH

The durations of radar echoes from meteors have been observed simultaneously on 9.22 m. and 5.35 m., and also on 9.22 m. and 2.83 m. The ratio of durations on two wave lengths decreases with increasing duration by a factor of two over the observed range, deviating significantly from the accepted square law of wave length. Plotting the log of the ratio against the log of the duration yields two straight lines of different slopes, one in the short-duration range and the other applying to the longer echoes. General empirical formulae are developed to predict the echo duration on one radio equipment in terms of the duration of the same echo recorded by another apparatus of different sensitivity and wave length.

BIOASSAY SYSTEMS FOR THE PYRETHRINS: V. EXPERIMENTS WITH A RESISTANT STRAIN OF CALANDRA GRANARIA L.

Some principles of testing for resistance in wild and laboratory stocks of insects are discussed, and experiments with Calandra granaria L. are described in which these insects are selected for pyrethrum resistance.A new method is described of expressing relative tolerances when the relevant regression lines are not parallel, based on the ‘generalized distance’ of Mahalanobis. The method may equally be used for the comparison of two insecticides giving rise to lines of different slope. A limited increase in resistance occurred on selection. Non‐random oscillatory sequences of slopes were observed when the resistant strain was assayed, and regression parameters computed. The nature of these oscillations is considered.

Electrical Properties of Ceramics as Influenced by Temperature

Data on dielectric strength, resistivity and power factor are presented for a high-tension porcelain, a zircon porcelain celain and an alumina porcelian. Additional data on mica and fused silica taken from the literature are included for comparison purposes. The temperature range covered in the experimental work extends from 25 to 1000 degrees centigrade. When the logarithms of the dielectric strength, resistivity or power factor are plotted against the reciprocal of the absolute temperature, two straight lines of different slopes result in each case. The intersection of these two lines define a transition temperature between the disruptive and thermal regions of electric breakdown. An interesting feature of this investigation is the discovery that the transition temperatures as determined by the dielectric strength coincide approximately with those determined by resistivity or power factor. The transition temperature gives some indication of the maximum temperature beyond which the material should not be used in practice. Considerable advantage of zircon and alumina porcelains over high tension porcelain for high temperature applications are indicated. The data are discussed in the light of existing conduction and electric breakdown theories.

The Influence of Intensity, Color and Retinal Location on the Fusion Frequency of Intermittent Illumination

1. Nature of Problem.-The flickering sensation produced by regularly interrupted illumination disappears when the frequency of interruptions is made sufficiently high. Under controlled conditions the determination of this critical fusion frequency may be made with considerable accuracy; its precise value, however, depends on a variety of conditions, of which the most effective is the intensity of the illumination. The relation between these two variables is not wholly clear at present. Though the dependence of the critical frequency on illumination was recognized over one hundred years ago, it was only forty years ago that Ferry' formulated what has since become known as the Ferry-Porter law, namely, that the critical frequency is proportional to the logarithm of the illumination intensity. Ferry's published measurements distinctly do not support this generalization, but the later data of Porter2 do. Porter, however, found that when the critical fusion frequency-as cycles of light and dark per second-is plotted against the logarithm of the intensity the data fall on two straight lines instead of one. The two lines intersect at an illumination of about 0.25 meter candles, and the slope of the lower is 1.56 while that of the upper is 12.4. These findings were corroborated by Ives3 in 1912. Ives's data for different parts of the spectrum show a dual logarithmic relation similar to that for white light. However, the slope of the straight lines and their point of intersection seem to vary with the wave-length of the light, the upper and lower limbs of the relationship varying in different ways. In addition Ives found the extraordinary fact that for blue light, the lower line becomes horizontal. These peculiarities are difficult to reconcile with the obvious interpretation of Porter's data which is generally given in terms of the Duplicity Theory, that is, that the lower limb describes the function of the rods while the upper limb describes the function of the cones. This difficulty has been emphasized by Allen4 whose flicker studies in general confirm Porter and Ives, though differing from them in particulars. Thus Allen draws through his measurements about five short straight lines of different slope, instead of the two drawn by Porter and by Ives. In our estimation, the data presented by Allen do not justify such treatment. The points seem to lie on a continuously curving line, and deviate from it no more than would be expected when special precautions are