bluuebunny/crossref_metadata_2025_split huggingface dataset:
ELECTROKINETICS
Authors: Moyer Laurence S. , Bull Henry B. 
Published: May 2004

1. The question of the critical pore diameter for streaming potential is discussed.
2. The surface charge is calculated for cellulose in contact with solutions of K3PO4, K2CO3, K2SO4, KCl, and ThCl4.
3. The surface charge of cellulose in contact with a solution of 2 x 10–4 N NaCl is calculated as a function of temperature and is found to show a sharp break at 39°. This is interpreted in terms of the change of the specific heat of water.
4. A marked ion antagonism is found in NaCl:KCl, KCl:MgCl2, NaCl:MgCl2, NaCl:CaCl2, KCl:CaCl2, CaCl2:MgCl2 mixtures when the surface charge is calculated as a function of concentration.
ACETYLATION OF TYROSINE IN PEPSIN
Authors: Herriott Roger M. 
Published: May 2004

Crystalline 60 per cent active acetyl pepsin has 7 acetyl groups per mol of pepsin, 3 of which are readily hydrolyzed in acid at pH 0.0 or in weak alkali at pH 10.0.
The tyrosine-tryptophane content of this acetylated pepsin, measured colorimetrically, is less than pepsin by three tyrosine equivalents.
Hydrolysis at pH 0.0 or pH 10.0 of the 3 acetyl groups results in a concomitant increase in the number of tyrosine equivalents. In the pH 0.0 hydrolysis experiment there is also a simultaneous increase in specific activity.
The phenol group of glycyl tyrosine is acetylated by ketene under the conditions used in the acetylation of pepsin and the effect of pH on the rate of acetylation is similar in the two cases.
It is concluded that the acetyl groups in the 60 per cent active acetyl pepsin, which are responsible for the decrease in specific enzymatic activity, are 3 in number and are attached to 3 tyrosine phenol groups of the pepsin molecule.
STUDIES ON BIOLUMINESCENCE
Authors: Anderson Rubert S. 
Published: May 2004

Some solubility, oxidation, reduction, and compound-forming characteristics of extracts of Cypridina luciferin have been presented.
A method of purification has been described which increased the amount of luciferin per unit of dry weight, as measured by the total light emitted, to about two thousand times that in the dry starting material. The best yields were from 50 to 65 per cent.
THE SOLUBILITIES OF THE l-DIHALOGENATED TYROSINES IN ETHANOL-WATER MIXTURES AND CERTAIN RELATED DATA
Authors: Winner Philip S. , Schmidt Carl L. A. 
Published: May 2004

1. The solubilities of l-tyrosine, dichloro-l-tyrosine (hydrated), dibromo-l-tyrosine (anhydrous), and diiodo-l-tyrosine in ethanol-water mixtures at 25° have been determined.
2. It was found that the solubilities of the dihalogenated substitution products of l-tyrosine are increased by addition of ethanol up to a certain concentration. Further addition of ethanol leads to a decrease in solubility. The solubility of l-tyrosine is decreased by addition of ethanol.
3. Dichloro-l-tyrosine (hydrated) was found to change to the anhydrous form when allowed to stand in the presence of ethanol.
4. The apparent heat of solution of diiodo-l-tyrosine in an ethanol-water mixture has been determined.
5. The solubility of dl-thyroxine at 30° has been determined in urea solution, ethanol, dioxan, ethylene glycol, and propylene glycol.
THE FORMATION OF MILK SUGAR
Authors: Weinbach Ancel P. 
Published: May 2004

1. The mammary glands of rats in the height of lactation were frozen in situ, removed, and dried in the vacuum in the frozen state.
2. The dried gland, added to pig serum, pig serum plus glucose, pig serum plus galactose, and pig serum plus lactose, then incubated at 37.5°C., yielded a synthesis of non-fermentable, reducing material.
3. The dried gland added to glucose solution alone and incubated at 37.5°C. yielded a synthesis of a non-fermentable reducing disaccharide, having a reaction velocity of reduction resembling that of pure lactose.
4. There is a "short time" storage of some forms of lactose precursor in the active mammary gland. This precursor is non-reducing but becomes available and reducing when the gland is placed in a solution containing glucose.
IONIC TRANSFERENCE NUMBERS IN CELLOPHANE MEMBRANES
Authors: Teorell Torsten 
Published: May 2004

The "apparent" cation transference number within cellophane is determined for HCl, KCl, NH4Cl, NaCl, and LiCl.
The method consists in measuring the E.M.F. in a concentration chain employing Ag:AgCl electrodes or calomel electrodes and calculating from formulas derived for cases of simple, unconstrained diffusion.
The transference numbers and the cation mobilities relative to the chloride ion were found to be higher in the cellophane (relative cation mobilities increased about 40 per cent).
The effect of the membrane is discussed. It is emphasized that with the introduction of a membrane as a liquid junction new factors are introduced, which are not considered in the formulas ordinarily used. Such factors may be activity changes due to dimensional or other reasons and particularly electrical effects exhibited by the membrane upon the ionic diffusion. Accordingly the transference number, as determined, may lack well defined physical significance.
INTERMITTENT STIMULATION BY LIGHT
Authors: Hecht Selig , Shlaer Simon 
Published: May 2004

1. An optical system is described which furnishes large flickering fields whose brightness, even when reduced with monochromatic filters, is capable of covering the complete range of the relation between critical frequency and intensity.
2. For a centrally located test field of 19° diameter, with light from different parts of the spectrum, the data divide into a low intensity section identified with rod function, and a high intensity section identified with cone function. The transition between the two sections is marked by an inflection point which is sharp, except for 450 and 490 mµ where, though clearly present, it is somewhat rounded.
3. The intensity range covered by the flicker function is smallest in the red, and increases steadily as the wave-length decreases. The increase is due entirely to the extent of the low intensity, rod section which is smallest (non-existent for S. S.) in the red and largest in the violet. The high intensity cone portion for all colors is in the same position on the intensity axis, and the only effect of decreasing wave-length is to shift the rod section to lower intensities without changing its shape.
4. The measurements are faithfully described by two similar equations, one for the rods and one for the cones, both equations being derived from the general stationary state equation already used for various visual functions.
INTERMITTENT STIMULATION BY LIGHT
Authors: Hecht Selig , Smith Emil L. 
Published: May 2004

1. In the retina, central areas whose diameter is less than 2° possess only cones, while larger areas have rods and cones. In conformity with this, the relation of critical fusion frequency to intensity is a single function for centrally fixated areas below 2°, and a double function for similarly fixated, larger areas. The two sections of such data are easily identified with rod activity at low intensities and with cone activity at high intensities.
2. The curves describing the rod data are the same for all areas, differing only in the values of the associated dimensional constants which control the location of the curves on the coordinate axes. Similarly, the curves for the cone data are the same for all areas; the tendency for an increase in maximal frequency with area is the expression merely of the value of a constant which determines the position of the data on the frequency axis. Area, therefore, does not influence the fundamental nature of the flicker relation through each receptor system, but merely alters the extraneous constants of the relation.
3. The curves which describe the measurements are represented by two equations, one for rods and one for cones; both equations are derived from the stationary state descriptive of the initial event in the photoreceptor process.
INTENSITY DISCRIMINATION IN THE HUMAN EYE
Authors: Steinhardt Jacinto 
Published: May 2004

New measurements of the brightness difference sensibility of the eye corroborate the data of previous workers which show that ΔI/I decreases as I increases. Contrary to previous report, ΔI/I does not normally increase again at high intensities, but instead decreases steadily, approaching a finite limiting value, which depends on the area of the test-field and on the brightness of the surrounding field.
On a logarithmic plot, the data of ΔI/I against I for test-fields below 2° are continuous, whereas those for test-fields above 2° show a sharp discontinuity in the region of intensity in which ΔI/I decreases rapidly. This discontinuity is shown to divide the data into predominantly rod function at low intensities, and predominantly cone function at high intensities. Fields below 2° give higher values of ΔI/I at all intensities, when compared with larger fields. Fields greater than one or two degrees differ from one another principally on the low intensity side of the break. Changes in area above this limit are therefore mainly effective by changing the number of rods concerned. This is confirmed by experiments controlling the relative numbers of rods and cones with lights of different wavelength and with different retinal locations.
At high intensities ΔI/I is extremely sensitive to changes in brightness of surrounding visual fields, except for large test-fields which effectually furnish their own surrounds. This sensitivity is especially marked for fields of less than half a degree in diameter. Although the effect is most conspicuous for high intensities, the surround brightness seems to affect the relation between variables as a whole, except in very small fields where absence of a surround of adequate brightness results in the distortion of the theoretical relation otherwise found.
The theoretical relationship for intensity discrimination derived by Hecht is shown to fit practically all of the data. Changes in experimental variables such as retinal image area, wavelength, fixation, and criterion may be described as affecting the numerical quantities of this relationship.
A DESEEDED AVENA TEST METHOD FOR SMALL AMOUNTS OF AUXIN AND AUXIN PRECURSORS
Authors: Skoog Folke 
Published: May 2004

The main results presented in this article may be summarized as follows:
1. A test method with deseeded Avena seedlings for small concentrations of auxin and precursors of auxin has been described.
2. This method makes possible quantitative determinations of about ten times as low concentrations of hormone as can be obtained with the standard method, (a) Through an increase in the time of the test, so that nearly all the hormone applied can be utilized. (b) Through an increase in sensitivity of deseeded plants to unilaterally applied small concentrations of hormone.
3. The effect of deseeding in relation to curvature growth is primarily the prevention of auxin regeneration through the removal of the material for auxin synthesis, and in addition the prevention of physiological aging.
4. The mechanism of auxin synthesis in the tip of the coleoptile and the mechanism of auxin regeneration in the new physiological tip have been shown to be identical.
5. The application of the deseeded method is illustrated by determinations of auxin in primary leaves and coleoptile sections of Avena seedlings.
6. The deseeded method has been used as a test method for precursors of auxin obtainable from the coleoptile and from other sources. The method further makes possible a distinction between auxins and these substances which may become activated by the plant.
7. Evidence for the existence of a precursor of auxin in the plant is given (a) indirectly by determinations of the decrease in auxin synthesis in deseeded plants. (b) Directly by its isolation from the plant.
8. Precursors of hetero-auxin are demonstrated; their chemical nature and activation are briefly considered.
TEMPERATURE AND CRITICAL ILLUMINATION FOR REACTION TO FLICKERING LIGHT
Authors: Crozier W. J. , Wolf Ernst , Zerrahn-Wolf Gertrud 
Published: May 2004

The curve of mean critical illumination (Im) for response to flicker as a function of flicker frequency (F) for the larvae of the dragonfly Anax junius is progressively shifted toward higher intensities the lower the temperature. The maximum flicker frequency (one half the cycle time of light and no light) and the maximum intensity with which it is associated are very little if at all affected by change of temperature.
These facts are in agreement with the requirements of the conception that recognition of critical illumination for reaction to flicker involves and depends upon a kind of intensity discrimination, namely between the effects of flashes and the after effects of these flashes during the intervals of no light. The shift of the F-Im curve with change of temperature is quite inconsistent with the stationary state conception of the determination of the shape of the curve.
The dispersion (P.E.II1) of the measurements of I1 is directly proportional to Im, but the factor of proportionality is less at high and at low temperature than at an intermediate temperature; the scatter of the values of P.E.II1 is also a function of the temperature. These facts can also be shown to be concordant with the intensity discrimination basis for marginal recognition of flicker.
SPECTROSCOPY OF CATALASE
Authors: Stern Kurt G. 
Published: May 2004

Catalase is resistant to oxidizing agents; e.g., ferricyanide. It is also resistant to reducing agents; e.g., catalytically activated hydrogen, hydrosulfite, ferrotartrate, cysteine. The hemin group of the enzyme will combine with cyanide, sulfides, nitric oxide, fluoride. It will not combine with carbon monoxide. Catalase is therefore a ferric complex. The stability of the ferric iron in the enzyme toward reducing agents is not due to the structure of the porphyrin with which it is combined. This porphyrin is the protoporphyrin of the blood pigment. In combination with globin (methemoglobin) the ferric iron is readily reduced by the same reagents which have no effect on catalase. The stability of the ferric iron in the enzyme is therefore due to the protein component. It may be that the type of hematin-protein linkage in catalase is the reason for this phenomenon. The suggestion of Bersin (31), that sulfur may participate in this linkage, is interesting but, as yet, has no experimental basis.
Hydrazine or pyridine and hydrosulfite convert catalase into hemochromogens containing ferrous iron. But in these hemochromogens the hematin is no longer attached to the protein. This has been replaced by the nitrogenous bases hydrazine and pyridine. Both hemochromogens combine reversibly with carbon monoxide. Photo-dissociation has only been demonstrated in the case of the pyridine hemochromogen.
The positions of the absorption bands of catalase and its derivatives are listed in Table II.
The main absorption band (Soret's band) of hemin complexes with nitrogenous substances (nitrogen bases, proteins) is situated at the border between the visible and the ultraviolet region of the spectrum. It has now been found that the spectrum of purified liver catalase has a well defined maximum of high extinction in this range, at 409 mµ. This is further evidence for the hemin nature of the enzyme.
THE QUANTUM YIELD OF HYDROGEN AND CARBON DIOXIDE ASSIMILATION IN PURPLE BACTERIA
Authors: French C. S. 
Published: May 2004

1. The effect of H2 tension, CO2 tension, pH, time, light intensity, density of suspension, salt content of the medium, and certain spectral regions on the rate of photoassimilation of H2 and CO2 by Streptococcus varians has been studied.
2. The method of making light absorption measurements with thin suspensions of bacteria is described.
3. A light source, optical system, and filter for isolating 852 mµ with 894 mµ in sufficient intensity for photochemical work and an improved design of thermostat are given.
4. The photoassimilation of 2H2 with 1CO2 apparently involves little over all energy change but nevertheless requires 4 quanta.
THE KINETICS OF PENETRATION
Authors: Jacques A. G. 
Published: May 2004

When 0.1 M NaI is added to the sea water surrounding Valonia iodide appears in the sap, presumably entering as NaI, KI, and HI. As the rate of entrance is not affected by changes in the external pH we conclude that the rate of entrance of HI is negligible in comparison with that of NaI, whose concentration is about 107 times that of HI (the entrance of KI may be neglected for reasons stated).
This is in marked contrast with the behavior of sulfide which enters chiefly as H2S. It would seem that permeability to H2S is enormously greater than to Na2S. Similar considerations apply to CO2. In this respect the situation differs greatly from that found with iodide.
NaI enters because its activity is greater outside than inside so that no energy need be supplied by the cell.
The rate of entrance (i.e. the amount of iodide entering the sap in a given time) is proportional to the external concentration of iodide, or to the external product [N+]o [I-lo, after a certain external concentration of iodide has been reached. At lower concentrations the rate is relatively rapid. The reasons for this are discussed.
The rate of passage of NaI through protoplasm is about a million times slower than through water. As the protoplasm is mostly water we may suppose that the delay is due chiefly to the non-aqueous protoplasmic surface layers. It would seem that these must be more than one molecule thick to bring this about.
There is no great difference between the rate of entrance in the dark and in the light.
A PHASE RULE STUDY OF THE PROTEINS OF BLOOD SERUM: THE EFFECT OF CHANGES IN CERTAIN VARIABLES
Authors: Jameson Eloise 
Published: May 2004

Changes were studied in the standard solubility curve of fresh serum proteins by alterations in pH, temperature, concentration of protein, and nature of the salt used for precipitation.
The principal factor affecting the precipitation of protein fractions was a change in temperature. In order to investigate the proteins in their original states low temperatures are necessary.
Protein fraction A is altered by a change in pH and with the use of (NH4)2SO4 as a precipitant, fraction B by a change in pH and temperature, and use of (NH4)2SO4, C by a change in temperature and concentration of the protein, and D by a change in temperature and pH.
The solubility of D is independent of the amount of protein in solution in high concentrations of salt.
CRITICAL ILLUMINATION AND FLICKER FREQUENCY IN RELATED FISHES
Authors: Crozier W. J. , Wolf E. , Zerrahn-Wolf Gertrud 
Published: May 2004

Flicker response curves have been obtained at 21.5°C. for three genera of fresh water teleosts: Enneacanthus (sunfish), Xiphophorus (swordtail), Platypoecilius (Platy), by the determination of mean critical intensities for response at fixed flicker frequencies, and for a certain homogeneous group of backcross hybrids of swordtail x Platy (Black Helleri).
The curves exhibit marked differences in form and proportions. The same type of analysis is applicable to each, however. A low intensity rod-governed section has added to it a more extensive cone portion. Each part is accurately described by the equation
F = Fmax./(1 + e-p log-p logI/Ii),
where F = flicker frequency, I = associated mean critical intensity, and Ii is the intensity at the inflection point of the sigmoid curve relating F to log I.
There is no correlation between quantitative features of the rod and cone portions. Threshold intensities, p, Ii, and Fmax. are separately and independently determined.
The hybrid Black Helleri show quantitative agreement with the Xiphophorus parental stock in the values of p for rods and cones, and in the cone Fmax.; the rod Fmax. is very similar to that for the Platy stock; the general level of effective intensities is rather like that of the Platy form. This provides, among other things, a new kind of support for the duplicity doctrine. Various races of Platypoecilius maculatus, and P. variatus, give closely agreeing values of Im at different flicker frequencies; and two species of sunfish also agree. The effect of cross-breeding is thus not a superficial thing. It indicates the possibility of further genetic investigation.
The variability of the critical intensity for response to flicker follows the rules previously found to hold for other forms. The variation is the expression of a property of the tested organism. It is shown that, on the assumption of a frequency distribution of receptor element thresholds as a function of log I, with fluctuation in the excitabilities of the marginally excited elements, it is to be expected that the dispersion of critical flicker frequencies in repeated measurements will pass through a maximum as log I is increased, whereas the dispersion of critical intensities will be proportional to Im; and that the proportionality factor in the case of different organisms bears no relation to the form or position of the respective curves relating mean critical intensity to flicker frequency. These deductions agree with the experimental findings.
THE RATE OF CO2 ASSIMILATION BY PURPLE BACTERIA AT VARIOUS WAVE LENGTHS OF LIGHT
Authors: French C. S. 
Published: May 2004

1. The relative absorption spectrum of the pigments in their natural state in the photosynthetic bacterium Spirillum rubrum is given from 400 to 900 mµ. The position of the absorption maxima in the live bacteria due to each of the pigments is: green pigment, 420, 590, 880; red pigment, 490, 510, 550.
2. The relative absorption spectrum of the green pigment in methyl alcohol has been determined from 400 to 900 mµ. Bands at 410, 605, and 770 mµ were found.
3. The wave length sensitivity curve of the photosynthetic mechanism has been determined and shows maxima at 590 and about 900 mµ.
4. It is concluded that the green bacteriochlorophyll alone and not the red pigment can act as a light absorber for photochemical CO2 reduction.
VISUAL ADAPTATION AND CHEMISTRY OF THE RODS
Authors: Wald George , Clark Anna-Betty 
Published: May 2004

1. The reality of a chemical cycle proposed to describe the rhodopsin system is tested with dark adaptation measurements.
2. The first few minutes of rod dark adaptation are rapid following short, slower following long irradiation. As dark adaptation proceeds, the slow process grows more prominent, and occupies completely the final stages of adaptation.
3. Light adaptation displays similar duality. As the exposure to light of constant intensity lengthens, the visual threshold rises, and independently the speed of dark adaptation decreases.
4. These results conform with predictions from the chemical equations.
CRITICAL ILLUMINATION FOR RESPONSE TO FLICKERED LIGHT, WITH DRAGONFLY LARVAE (ANAX), IN RELATION TO AREA OF EYE
Authors: Crozier W. J. , Wolf E. , Zerrahn-Wolf G. 
Published: May 2004

Arthropods with large convex eyes provide curves of critical illumination for response as a function of flicker frequency (or of visual acuity) which depart from the probability integral type characteristically found for F – log I with vertebrates. By means of experiments with Anax nymphs in which various parts of the eye have been opaqued it is shown that the special shape of the flicker curve is due to the mechanical disadvantage of the periphery of the eye in the reception of light, which is overcome by higher intensities. It is not due to a fixed spatial pattern of intrinsic individual excitabilities of the ommatidia.
Reduction of retinal area decreases Fmax., and increases log I for F/Fmax. = 50 per cent. The direct proportionality of Im to P.E.1I is independent of area. Certain relations of these facts to the theory of response to flicker have been discussed.