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Monoamine oxidase has been isolated and purified from bovine thyroid microsomes. The general characteristics and steady-state kinetic behavior of the microsomal enzyme have been compared with those of the enzyme isolated from bovine thyroid mitochondria. The enzymes from the two sources exhibit a high degree of substrate specificity with respect to the amines oxidized. 3-Iodotyramine is a noncompetitive inhibitor of tyramine oxidation in the case of both the mitochondrial and microsomal enzymes. Product inhibition studies suggest that the enzymes from mitochondria and microsomes catalyze reactions which proceed by a similar pathway. In contrast to the mitochondrial enzyme, the enzyme isolated from microsomes is susceptible to inhibition by anions in the following order; [Formula: see text].

A muck soil, Miami silt loam and a sandy loam were treated in 1954 with lindane at rates of 10 and 100 pounds per 6-inch acre and aldrin at rates of 2,20, and 200 pounds per 6-ineh acre. Laboratory experiments were conducted, where a Miami silt loam was treated with either lindane or aldrin at a rate of 10 p.p.m. Lindane was found to break down within 2 weeks after application to a nontoxic compound, which was still detected by the colorimetric method for lindane, but not by bioassay. Two weeks after treatment the quantity estimated by bioassay amounted to 66% of that obtained by chemical analysis. Even after 3 years the same ratio was found between bioassay and chemical results. When field samples were analyzed, 3½ years after treatment, the quantity estimated by bioassay amounted to 46% of that obtained by chemical analysis. Aldrin was found to be converted into dieldrin, which first was indicated by higher recoveries obtained by bioassay. Chemical analysis for dieldrin proved the presence of this insecticide in soils. It was found that relatively more dieldrin was formed in a sandy loam and in soils which had been treated at lower concentrations and which were held at higher temperatures. Experiments conducted in the laboratory showed that 2 weeks after treatment no dieldrin was formed in a loam having; been held at 7° In soils, having; been held at 26° C. or 46° C., 4 to 8% of the recovered insecticides were found to be dieldrin. The peak of dieldrin formation was reached 56 days after treatment, followed by a decrease.

Records of sleep and wakefulness were kept on forty-six infants during their first 16 weeks of life. There was a relatively small decrease in the total hours of sleep per day. The number of hours in the longest sustained sleep period doubled, while the longest sustained wakefulness increased by one-half. In the first week there were almost equal amounts of sleep during the day and night. By the sixteenth week the distribution of sleep showed double the amount of sleep at night as compared to the day. These changes coincide with reported maturational changes in behavior and electroencephalograms, and with anatomic changes in the nervous system.*Department of Pediatrics, University ofCalifornia Medical Center, Los Angeles, Calif. 90024.

22mal wurde bei Kindern mit Polyarthritis rheumatica wahrend der Behandlung mit Butazolidin der onkotische Druck im Serum fortlaufend gemessen. Wahrend der Butazolidintherapie sank der onkotische Druck durchschnittlich um 67 mm H2O, d. h. um 16% des Ausgangswertes, um am Ende der Behandlung bzw. nach Absetzen des Medikamentes seine ursprungliche Hohe wieder zu erreichen. Der spezifische onkotische Druck lag in der gleichen Zeit um 7,5 mm H2O niedriger als vor der Behandlung (d. h. 14%ige Erniedrigung des Ausgangswertes). Die Serumeiweiswerte und der Hamatokrit zeigten kein einheitliches Verhalten. Die elektrophoretische Untersuchung der Serumeiweisfraktionen bei 6 Kindern ergab einen geringgradigen Anstieg der γ-Globuline; die ubrigen Fraktionen waren nicht einheitlich verandert. Diese Befunde machen einen kausalen Zusammenhang zwischen der depressiven Wirkung des Butazolidin auf den onkotischen Druck und der fruher beschriebenen NaCl- und Wasserretention wahrscheinlich. Eine quantitative Beziehung zwischen der Erniedrigung des onkotischen Druckes und der NaCl- und Wasserretention konnte nicht nachgewiesen werden. Es wird angenommen, das die Hyponkie einen Reiz fur bestimmte Hormonzentren (Aldosteron, Adiuretin?) darstellt, das diese Zentren jedoch in ihrer Reizbeantwortung noch durch andere Faktoren beeinflust werden. Die moglichen Ursachen fur die beobachtete Hyponkie werden diskutiert. Eine direkte Beeinflussung der Bluteiweise durch Butazolidin scheint nicht vorzuliegen, moglicherweise handelt es sich bei der Erniedrigung des onkotischen Druckes um eine Folge der Butazolidinwirkung auf den Zellstoffwechsel.

Aldrin was applied at 5 lb per acre to Carrington silt loam plots, employing 4 application variables: 1) emulsion left on the soil surface, 2) emulsion incorporated into the soil, 3) granules left on the soil surface, and 4) granules incorporated into the soil. Carrots were grown in these soils, to study the effect of mode of application on the rate of translocation of insecticidal residues into the crop tissue. The greatest loss of residues occurred in soils where the insecticidal was left on the soil surface following an emulsion application. The greatest persistence of residues was noticed after granules had been incorporated into the upper 4-5-inch soil layer. Forty to 62% of the applied dosage was recovered in the form of aldrin or dieldrin 1 year after the insecticide had been incorporated into the soil. Only 6.5 to 13% of the applied dosage was recovered from soils where aldrin was left on the surface. The highest rate of aldrin epoxidation occurred in emulsion-treated soils. The greatest residues in carrots were found in those grown in soils into which the insecticide had been incorporated as an emulsion, although the comparable granule-treated soil contained 1.5 times more toxicants. Residue levels in carrots grown on the 4 differently treated plots did not vary as much as did the soil residue levels.

Dyfonate® ( O -ethyl S -phenyl ethylphosphonodithioate) was applied to soils as broadcast or band treatments at the high dosage of 10 pounds per acre to study: (I) the rate of decline of Dyfonate residues over a 22-month period, (2) the potential conversion of the applied compound into metabolic products, (3) the absorbance of Dyfonate into carrots and potatoes grown in the treated soil, and (4) the movement of Dyfonate from granule- or emulsion-treated bands into the surrounding untreated soil. Half the amount of Dyfonate, applied as an emulsion into the upper 5-inch soil layer, disappeared from the soil after 28 days. The amount of insecticide lost during 2 successive growing seasons was 76% of the insecticide concentration found in the soil each spring. No compounds, other than Dyfonate, could be detected by thin-layer or gas chromatography. The concentration of Dyfonate in the carrots was not related to the insecticide concentration in the soil. The extremely low residue level (0.001 ppm) in whole potatoes was in contrast to residue levels found in potatoes that were grown in soils containing residues of chlorinated hydrocarbon insecticides. Although the insecticide was applied at a high concentration in 3 narrow bands, no appreciable movement of the insecticide from the applied band was detected in either direction by chemical assay. It appears from these data that in actual agricultural practice, leaching of Dyfonate into lower soil strata is unlikely. Based on Drosophila melanogaster Meigen bioassay, Dyfonate could control insects in an area up to 2 to 4 inches away from the band.

1. 1. Monoamine oxidase (monoamine:O2 oxidoreductase, EC 1.4.3.4) has been partially purified from bovine thyroid mitochondria. The enzyme appeared to require Cu2+ and sulfhydryl groups for activity. Unlike the plasma oxidase, the thyroid enzyme was not inhibited by carbonyl reagents which suggests that the thyroid enzyme may not contain pyridoxal phosphate. Flavin analogs were inhibitory. 2. 2. Thyroid monoamine oxidase exhibited a rather high degree of substrate specificity. Of the amines tested, only tyramine and phenylethylamine were oxidized at an appreciable rate. 3-Iodotyramine was not oxidized, but was a potent non-competitive inhibitor. Enzymic activity was insensitive to 0.5 M urea, but this concentration of urea obviated iodotyramine inhibition. 3. 3. A tentative reaction mechanism has been proposed based on initial velocity and product inhibition studies.

Because of the structural similarity to DDT-related compounds, II plasticizers were tested for their toxicological interaction with dieldrin and DDT. Many of these polychlorinated biphenyl compounds were toxic to Draso Phila melanogaster Meigen and house flies, Musca domestica L.., but to a lesser extent than dieldrin or DDT. Their toxicity increased with a decrease in their chlorine content. Moreover, sub lethal dosages of several of the plasticizers increased the toxicity of dieldrin and DDT. Since plasticizers are in the environment, their potential effects on biological systems, especially in combination with other synthetic chemicals, should not be disregarded.

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Methylenedioxyphenyl synergists (sesamex, piperonyl cyelonene, piperonyl butoxide, sulfoxide and n-propyl isome) added to aldrin-treated loam soils blocked the conversion of aldrin to dieldrin and increased the persistence of the residues by factors of 1.5 to 1.8 within 4 months of soil incubation at 37±1° C. With no synergists, 21% of the applied insecticide was recovered in the form of aldrin and 25% in the form of dieldrin. Soil samples treated also with synergists at 250 times the concentration of aldrin, still contained 60 to 65% of the applied aldrin and only 7 to 23% in the form of dieldrin. Sesamex inhibited the conversion of aldrin to dieldrin more than any of the other methylenedioxyphenyl compounds. The addition of corn oil to aldrin-treated soil increased the conversion of aldrin to dieldrin. Sesamol, which is a breakdown product of sesamex, and a known antioxidant, caused no significant inhibition of dieldrin formation. Sesamex also reduced populations of microorganisms when added to pure cultures, soil suspension, or soils. Thornton’s culture medium, treated with aldrin and inoculated with a suspension of a silt loam, contained 10 to 30% of thc recovered residues as dieldrin. No dieldrin was formed when sesamex and aldrin were added to the media inoculated with microorganisms. Moreover, the persistence of aldrin increased 4- or 10-fold after 2 or 4 weeks of incubation at 37° C.

The effects of application methods of phorate at 10 lb/acre on its metabolism, toxicity, and translocation into crops were studied under field conditions. Residues were least persistent when phorate was applied solely to the soil surface; 6 days were required until 1/2 of the applied dosage could no longer be detected in the form of phorate and its metabolites. Residues were more persistent after the insecticide had been mixed with the upper 4- to 5-in. soil layer, and 30 days were required until 1/2 of the applied dosage could no longer be detected. Less than 1.6% of the applied phorate was measured 14 and 30 days after its application to the soil surface or the upper 4- to 5-in. soil layer, respectively. Highest amounts of phorate sulfoxide (3.2 and 4.88 lb. acre) were recovered from both field soils 6 days after phorate application. subsequently, the concentration of phorate sulfoxide in these soils declined rapidly, while the amounts of phorate sulfone increased, until they in turn reached their peak (1.44 and 3.5 lb/acre) at one month after soil treatment. Residues consisting entirely of phorate sulfone were found 2 months after application of phorate to the soil surface but 5 months after mixing of the insecticide with the upper soil layer. Insect mortalities were obtained with both field soils. Potatoes grown in these soils during 1971 and 1972 did not contain measurable insecticide residues. Corn silage contained phorate sulfone at 0.03 and 0.18 ppm in 1971, but no measurable residues in 1972. Carrots from both field plots contained in 1971 phorate sulfone at 0.12 and 0.50 ppm and in 1972 at 0.04 ppm after growing in the soil whose upper layer had originally been mixed with the insecticide.

A connection matrix is defined for an enzyme reaction sequence. This formulation allows one to derive the rate equation in coefficient form for the reaction either by manual means directly from the matrix or from a computer program described by the algorithm presented in the text. As an example, the rate equation for a particular nine-node two-substrate, two-product reaction with multiple reaction paths consists of 576 terms in the numerator and 4320 terms in the denominator and was derived in a few minutes on a digital computer. The connection matrix formulation allows one to predict the influence of the various reactants on the observed kinetics of the reaction. In the case of multireaction systems, this includes the effect of each substrate on the initial rate and makes possible the prediction of product inhibition patterns. The algorithm can be modified to derive the equation for the initial rate of isotopic exchange in an enzyme-catalyzed reaction.

After a single i.v. administration of 50 mg/kg of Trimethoprim (TM) to rats in late pregnancy, a diffusion equilibrium of the folic acid inhibitor in the foetal organs is reached after 30–60 min. The TM levels in maternal as well as in foetal organs can have an inhibitory effect on folic acid reductase activity. The elimination of TM is lower in pregnant than in non-pregnant animals. The TM elimination of the foeti is dependent on the elimination capacity of the mother. Three-days-old rats eliminate TM some four times slower than mature animals owing to their reduced kidney development.

The persistence and metabolism of azinphosmethyl (Guthion®) in soils was studied under field and laboratory conditions. The insecticide was least persistent after field application in an emulsion and when left on the soil surface (50% loss within 12 days after soil treatment) and was most persistent (50% loss within 28 days) after its incorporation in granular form into the upper 4-5 inches of the soil. One year after soil treatment with azinphosmethyl granules, 13% of the applied dosage was recovered in the form of azinphosmethyl, and the derivatives mercaptomethyl benzazimide, N -methyl benzazimide and N -methyl benzazimide sulfide or N -methyl benzazimide disulfide. In addition, benzazimide plus 4 unknown compounds were detected. However, toxic effects observed with Drosophila melanogaster Meigen flies or with larvae of the yellow-fever mosquito, Aedes aegpti (L,) were due only to azinphosmethyl Nearly all the insecticide, although applied at the relative high dosage of 5 lb per acre, was degraded in 1 year into non-toxic products, and more azinphosmethyl derivatives than azinphosmethyl were present at that time. Two years after the insecticidal application, only traces of azinphosmethyl were left in the soil, and concentrations of azinphosmethyl derivatives had also declined. The amount of 14-azinphosmethyl applied to soils under laboratory conditions declined over a 10-week period, while the amounts of several nontoxic and more polar derivatives increased during that time.

Unter Verwendung eines neuen weitgehend durchlassigen Kittes gelingt es, chromatisch und spharisch gut korrigierte Systeme fur UR herzustellen, wenn man die in unverkittetem Zustand nicht haltbaren Substanzen Steinsalz, Sylvin u. a. neben den schon bekannten (Quarz, schweres Flint) heranzieht.

Parathion, methyl parathion, and malathion were applied at 5 lb/acre to Carrington silt loam plots. Residue levels of approximately 0.1 ppm (3.1% of the applied dosage) were reached under field conditions with malathion within 8 days, with methyl parathion within 30 days, and with parathion within 90 days after the insecticidal application to the soil. Under laboratory conditions (30° C), 95% of the applied methyl parathion and 30% of the parathion were lost within 12 days after application to a loam soil. The effects of moisture and microorganisms on the persistence and metabolism of parathion in Carrington silt loam soil were tested under laboratory conditions at 30° C. The insecticide was most persistent in dry soil and least persistent in soils with a high moisture content. Parathion was not lost through volatilization, as is the case with some insecticides of the chlorinated hydrocarbon group. Degradation of parathion was either by hydrolysis or by reduction to its amino form depending on populations of soil microorganisms. In soils of low numbers of microorganisms (autoclaved soil) or of low microorganism activity (dry soils) , parathion persisted for a relatively long time. No amino parathion was formed in autoclaved soils. Yeast was primarily responsible for the reduction of parathion in soil to aminoparathion. Bacteria apparently had no effect on this reduction. Para-oxon was hydrolyzed within 12 hours after its application at 20 ppm to loam soil. During that time the amount of para-oxon constantly decreased while the amount of p -nitrophenol produced increased. Amino parathion or p .nitrophenol, added to soils, disappeared within 2 and 16 days, respectively.

1. Implantation of morphine pellets in guinea-pigs produced a high degree of tolerance and dependence within 3 days. 2. The contractions of the longitudinal muscle induced by electrical stimulation of the myenteric plexus-longitudinal muscle preparations obtained from tolerant animals were less depressed by morphine than the contractions evoked in preparations from non-tolerant animals. 3. Naloxone did not alter the size of the evoked twitch but antagonized the depressant action of morphine in tolerant and in non-tolerant animals. When given to tolerant guinea-pigs, naloxone caused an increase in intestinal activity in vivo. 4. The contractile response of the longitudinal muscle to acetylcholine was the same in preparations obtained from tolerant and non-tolerant animals. Electrically evoked contractions of the myenteric plexus-longitudinal muscle preparations from tolerant animals showed reduced sensitivity to the depressant effects of adrenaline, isoprenaline, and particularly, dopamine.

HIS report summarizes the findings to date of a follow-up study of 1,908 cases of tinea capitis (ringworm of scalp) who were treated by x-ray epilation and 1,801 cases of tinea capitis who did not receive x-ray therapy. Both groups were treated at the Skin and Cancer Unit of the New York University Hospital between 1940 and 1958. The purpose of the study is to characterize the nature and magnitude of chronic radiation injury due to x-ray epilation. It was motivated by the current need in the field of radiological health protection for quantitative data on the relationship of radiation dose to chronic injury. Although x-ray epilation has been used for many decades and involves substantial doses of ionizing radiation to the scalp, brain, and associated head structures of children, only a few follow-up studies of a limited nature have been done.1'2 The opportunity for a long-term follow-up study at this institution seemed favorable for the following reasons: (1) a registry which included 2,500 irradiated cases had been maintained for many years, and (2) the distribution of radiation dose in the head could be defined with considerable accuracy since the x-ray equipment was always carefully calibrated, the treatment procedure was well standardized and virtually all of the x-ray epilations were done by one technician or under her supervision. At the present time there are several facets to the program: (1) an evaluation of the medical experience of the irradiated and control populations by means of a health questionnaire, (2) a clinical and laboratory examination of a representative sample of the irradiated and control populations, and (3) a study of the x-ray dose to the various head structures associated with the Adamson-Keinbock technic.

Es wird der Lichtweg durch eine Folge gleicher gleichabstandiger Linsen bestimmt und die Brennweite eines solchen Systems berechnet. Ferner wird gezeigt, welche Bedingung erfullt sein mus, damit ein radial geschichteter Zylinder gleiche optische Wirkung aufweist.

The homogeneous gas‐phase reaction H+p‐H2=o‐H2+H has been studied in the temperature range 300° to 444°K. Within this range the results fitted the equation log10k1 = 15.454 − 3.490×103/T+3.836×105/T2 cm3 mole−1 sec−1. The results were interpreted in terms of activated‐complex theory with quantum‐mechanical tunneling. From the information about the tunneling factors provided by the curvature of the Arrhenius plot it was possible to calculate the imaginary frequency of the asymmetric vibration of the complex corresponding to its coordinate of decomposition on the assumption of a truncated parabolic barrier. The value obtained was 1213i cm−1. For the same model ΔE0° was found to be 9.7 kcal mole−1. The almost exponential dependence of the tunneling factor on 1/T for Eckart barriers made it impossible to interpret the curvature in terms of such a barrier except for considerably larger values of barrier height and/or imaginary frequency than have been found in recent theoretical calculations.

Die geometrische Optik aspharischer Flachen kann erweitert werden. Fur technische Zwecke kommen auser den einfachen Kegelschnitten zunachst bestimmte Kurven hoheren Grades in Betracht, fur wissenschaftliche Fragen ergibt sich ein Weg zur Einbeziehung der Optik von Medien mit kontinuierlich variablem Brechungsindex.

DL-β-aminoisobutyric acid-β- 14 C was synthesized and administered intraperitoneally to rats. Radioactivity was incorporated into all vascular tissues. Maximum radioactivity was found in rat livers and kidneys within 30 minutes after injection. β-Aminoisobutyric acid-β- 14 C was readily converted to 14 CO 2 . In two hours, about 20% of the injected dose appeared as 14 CO 2 . Approximately 17% of the injected radioactivity was excreted in the urine in 24 hours. Fractionation of the urine by ion exchange chromatography revealed the presence of several radioactive peaks. Two peaks have been identified, one as unchanged β-aminoisobutyric acid and the other as N-acetyl-β-aminoisobutyric acid. When β-aminoisobutyric acid-β- 14 C together with an overload of succinate was given intraperitoneally to rats, succinate- 14 C was isolated from the urine. Degradation of urinary- 14 C-succinate by the Schmidt reaction revealed the presence of about 80% of the 14 C in the carboxyl carbons and 20% in the methylene carbons. When valine-4- 14 C and an overload of cold β-aminoisobutyric acid was given intraperitoneally to rats, β-aminoisobutyric acid- 14 C was isolated from the urine. These results indicate that succinate is an end produce of β-aminoisobutyric acid catabolism by the rat and that β-aminoisobutyric acid is in equilibrium with the pathway by which valine is metabolized.

The vertical movement and persistence of aldrin and parathion in agricultural loam soils were investigated under leaching and nonleaching conditions. The effect of the detergents ABS (alkyl benzene sulfonate) and LAS (linear alkyl benzene sulfonate) and sodium chloride in water, or of a complete plant nutrient solution, on the movement of the insecticides in the soil also was studied. The water, after its percolation through insecticide-treated soil and through lower insecticide-free soil layers, was analyzed for insecticidal residues. Quartz sand of no sorptive capacity and minimal microbiological activity was used as a control. The effects of the sorptive capacities of a loam soil became evident. After its percolation through loam soil, water that had been treated at a rate of 2 lb per 6-inch acre did not contain measurable amounts of aldrin but contained small amounts of parathion. The amount of parathion in percolated water was a function of the concentration of the insecticide in the soil. Detergents, having increased the persistence of parathion in soil, indirectly increased the amount of parathion within the percolated water. Aldrin moved within soils in the absence of percolated water, while parathion moved to a lesser extent. After the percolation of water or water + LAS through insecticide-treated (20 lb per 6-inch acre) soil and through lower untreated soil layers, small amounts of aldrin (0.1 to 0.2 ppb) and parathion (0.2 to 0.8 ppb) were found in the water samples. These amounts were far below the water solubility of these insecticides and the water was not toxic to mosquito larvae. The presence of salts prevented the appearance of aldrin residues in the percolated water and reduced the amount of parathion residues. It appears unlikely that water in deeper soil strata could be contaminated with insecticidal residues from the upper agricultural soil layers.

The increased level of folic acid reductase activity in rats during the perinatal period is inhibited following the oral administration of 5 or 50 mg/kg Trimethoprim. When the enzyme activity was tested in vitro, the highest sensitivity to the antimetabolite was displayed by the liver reductase isolated from rats the 20th day of pregnancy, the lowest was observed in the foetal liver extract. It is proposed that the stimulated reductase activity during the pregnancy is caused by a newly synthesized, Trimethoprim-sensitive enzyme form. The results of the in vitro experiments could contribute to the suggested hypothesis.

To determine, the effect of mode of application and a cover Crop on the persistence and vertical distribution of insecticides in soils, field tests were conducted over a 3-year period. Aldrin and heptachlor were applied either to the soil surface only or incorporated into the soil by rototilling to approximately 5 inches. Recoveries of insecticidal residues ranged from 2.7% to 5.3% of the applied dosages, 4 months after a soil-surface application. However, incorporation of insecticidal deposits into the upper soil layers increased the persistence of the residues by a factor of 10. One year after treatment of the upper soil layers, 90% of the recovered residues were located within the upper 3 inches of the soil. The highest concentration of the insecticides was found within the second in the of the soil layer. A deeper penetration and a more equal distribution of the insecticidal residues was noticed 3 year after soil treatment. Two to 3 times more insecticidal residues were recovered from alfalfa-covered plots than from fallowed ones. Volatilization appears to be the major factor in the loss of insecticidal residues. Their longer persistence after having been incorporated into the soil, may be extended by reducing the volatilization of the insecticides at the soil-air interface with a dense cover crop.

Field and laboratory experiments were conducted to determine the influence of soil type, rate of application, and temperature on the persistence of some chlorinated hydrocarbons in soils. Three and a half years after treatment 1.43 times more DDT, 4.25 times more aldrin and 8.45 times more lindane were recovered from a muck soil than from comparably treated .Miami silt loam. A field plot (Miami silt loam) treated at a rate of 100 pounds per 6-inch acre contained—3 ½ years after treatment—2.03 times more DDT than the plot treated at a rate of 10 pounds per 6-inch acre. The comparable figure for lindane was found to be 3.50. Under laboratory conditions, figures comparable to field results were obtained when soils were incubated at 46° C. for a period of 56 days. Soil temperatures were found to be an important factor in the persistence of insecticides in soils. No insecticide loss was found in frozen soils. At a temperature of 6° C. aldrin and heptachlor (16% to 27%) were lost during a period of 56 days and only 2% to 14% of the initial insecticides were found after 56 days, when held at a temperature of 46° C.

A computer-based algorithm to derive the rate equation of an enzyme-catalyzed reaction under the assumption of steady state is the basis for additional algorithms that provide the enzyme kineticist with powerful tools to investigate models of the reaction. These algorithms include one to define kinetic constants associated with the mechanism and one to reformulate the rate equation from coefficient form to kinetic form. The reformulation algorithm is a nonnumeric, combinatorial, algebraic expander. A model of the reaction need not be unique. By using a rational approximation to fit experimental data, one can obtain uniqueness of a model to within an equivalence class of models defined in terms of the rational approximation. The ability to derive and reformulate the rate equation on a computer allows the kineticist to propose several models from which he may select those to study further through experimental means. After experimental data are obtained and the model is fitted by a rational approximation, further refinements may be made by iterating the foregoing procedure. The final model is unique to within the equivalence class defined by the rational approximation and order of accuracy prescribed.

Computer-based algorithms to derive the rate equation for an enzyme-catalysed reaction model, to define kinetic constant, and to reformulate the rate equation in terms of the kinetic constants are discussed. These algorithms are based on notations that are algebratic rather than geometric in nature. Computer programs for the derivation, kinetic constant definition and rate equation reformulation have been implemented in Fortran IV.

An all-glass differential microrespirometer is described, which is designed to measure the respiration of actively growing cellsin vitro. The actual growing of the cells was carried outin situ in the respirometer to avoid injury by a transfer of the living cells.

Aldrin was applied to Quartz sand, Plainfield sand, Carrington loam and muck soils in order to study its persistence and epoxidation. In addition autoclaved-wet and nonautoclaved dry sand and loam soils were used. Aldrin was readily transformed into dieldrin in a wet-nonautoclaved Carrington loam, but less rapidly so in a muck soil. The amounts of aldrin and dieldrin recovered from aldrin-treated Carrington loam soils were equal 3.3 months after treatment under laboratory conditions at 37• C. and 16 months after treatment under field conditions. In soils containing a low number of microorganisms (autoc1aved loam, Plainfield sand) or in dry soils the amount of dieldrin formed was small. After heptachlor had been applied to a Carrington loam it was found that this insecticide persisted slightly longer than aldrin, but the amount of heptachlorepoxide formed was smaller than that of dieldrin. A similar study on lindane persistence in a Miami silt loam is also reported.

Cucumbers were grown in 1962 and 1963 on Carrington silt loam soils which contained various amounts of aldrin or heptachlor residues. The experiment provided that some of the developing cucumber fruits were lying on the ground while others developed without touching the soil. Similar insecticidal residue concentrations were found in all these cucumbers, as well as in the lower halves as compared with the upper halves of fruits lying on the ground. Insecticidal residues apparently penetrated through the root system and were then translocated into the cucumber fruits. Third cuttings of fresh alfalfa, grown in 1964 on aldrinor heptachlor-treated soils, were analyzed by gas-liquid chromatography and bioassay procedures. No mortalities were obtained with vinegar flies, Drosophila melanogaster Meigen, during a 48-hr exposure period to purified extracts of alfalfa from soils that contained 0.2–0.7 lb/6-in. acre of aldrin and dieldrin or heptachlor and heptachlorepoxide (2,3 epoxy-1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro- 4,7-methanoindene) residues. Extracts of 70–100 g of alfalfa grown on soils of higher insecticidal residue concentrations were toxic to the insects and also contained measurable amounts of these chemicals. Residue concentrations in or on alfalfa grown on aldrin-treated soils were 0.88% ± 0.23 of their concentrations in the soil at harvest time, and 3.01% ± 0.85 for alfalfa grown on heptachlor-treated soils.

The reaction D+H2=HD+H has been studied in the gas phase in the temperature range 274° to 468°K. By attributing the curvature in the Arrhenius plot to quantum‐mechanical tunneling and interpreting the results in terms of absolute reaction rate theory the rate constant was given by the expression k3=3.63×1015T−12Γexp(−9.40×103/RT). The results obtained previously for the reaction H+p‐H2=o‐H2+H fitted the equation k1=1.18×1015T−12Γ exp(−9.21×103/RT). The tunneling factors Γ were calculated on the assumption of a truncated parabolic barrier and gave almost identical values for the force constant of the asymmetric stretching vibration of the complex. The results are compared with recent theoretical calculations.

The authors have measured the rate constant for the reaction H + D2 = HD + D in the temperature range 368–68° K. This was found to be given by the relation:[Formula: see text]A comparison is made with previous experimental and theoretical work on the reaction.

We call this an explanatory bibliography of research. The authors in presenting their references explain how that particular reference fits into what we know about children's choices.