Casein and Caseinogen.

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Chemical aspects of kidney growth

1. The estimation of kidney hypertrophy has been placed on a more quantitative basis by using the DNA content of the kidney as a measure of the cell number; an indication of the average cell composition has then been obtained by relating the other cellular components to DNA. This approach has been used to compare the hypertrophy following unilateral nephrectomy with the variation in kidney size and composition produced by variations in the diet. In addition, changes in RNA biosynthesis of the remaining kidney have been examined in the first 12 hours after unilateral nephrectomy. 2. In normal rats the right kidney is, on the average, about 7% heavier than the left and contains about 7% more RNA and DNA. The two kidneys have almost identical RNA and protein contents per cell. 3. There is a very good correlation between the weights of the right and left kidneys of normal rats. There is also a good correlation between right kidney weight and body weight. The correlation between total renal weight and body weight is slightly better then either that between right kidney weight and body weight or that between total renal weight and liver weight. 4. There is good correlation between the total contents of DNA, RNA and protein of the right kidney and the body weight of the animal. There is no correlation between the DNA concentration, RNA content per cell and protein content per cell on the one hand and body weight on the other. 5. After unilateral nephrectomy the surviving kidney increases steadily in wet and dry weight, in rate and in mice, for the first 4 days after the operation. This is accompanied by a much slower increase in cell number by a small increase in protein content per cell end by a dramatic increase in RNA content per cell, These changes are accompenied by an increase in the activity of deoxy- ribonuclease I and II. There is no consistent change in the activity of DNA deoxynucleotidyltransferase activity after unilateral nephrectomy end no detectable change in serum sodium, potassium or chloride or in blood haematocrit. 6. Changes in kidney weight and in total contents of DNA, RNA, protein and lipid phosphorus can also be produced by varying the protein content of the diet. These effects were found to be of approximately the same magnitude as the effects of unilateral nephrectomy on the remaining kidney 4 days post-operatively. More over the two effects seem to be independent of each other end approximately additive. 7. Starvation does not significantly affect the mean cell mass or content of RNA per cell of the surviving kidney in the first 36 hours after unilateral nephrectomy, but it does apparently abolish the increase in protein content per cell. 8. The feeding of a diet containing 10% of urea by weight for 4 days increases the mean cell mass, RNA content per cell and protein content per cell of the kidneys of normal intact rats. Although these changes are similar to the effects produced in the remaining kidney after unilateral nephrectomy, they are only about one third as great, 9. The feeding of a diet containing 3% by weight of ammonium chloride for 6 days increases kidney weight by 25%, mean cell mass by 18%, RNA per cell by 19% and protein per cell by 18%. Equivalent amounts of ammonium citrate or sodium chloride do not produce these effects. The action of ammonium chloride would seem to be related to its acidotic effect rather than to the contribution it makes to either nitrogen excretion or electrolyte balance. 10. Decapsulation of the left kidney at the time of right unilateral nephrectomy does not affect the changes in weight or composition of the remaining kidney. 11. No consistent results could be obtained on RNA biosynthesis in the remaining kidney after unilateral nephrectomy using [3H] adenine as a precursor. The incorporation of [3H] erotic acid into the DNA of the surviving kidney was from 100 to 300 fold greater then the incorporation of [3H] adenine 4 hours pest-operatively. Unilateral nephrectomy did not produce any qualitative changes in the pattern of incorporation of [3H] orotic acid into kidney RNA as demonstrated by the sucrose density gradient technique. Quentitatively, however, the ratio of the specific activity of kidney RNA to that of liver RNA was 25% to 120% greater in unilaterally nephrectomized than in control animals at all times studied. 12. The RNA content per cell of the liver is increased substantially 2 days after removal of a 10% biopsy but is not affected by unilateral nephrectomy

EPR identification of defects responsible for thermoluminescence in Cu-doped lithium tetraborate (Li2B4O7) crystals

Electron paramagnetic resonance (EPR) is used to identify the electron and hole traps responsible for thermoluminescence (TL) peaks occurring near 100 and 200 ◦C in copper-doped lithium tetraborate (Li2B4O7) crystals. As-grown crystals have Cu+ and Cu2+ ions substituting for lithium and have Cu+ ions at interstitial sites. All of the substitutional Cu2+ ions in the as-grown crystals have an adjacent lithium vacancy and give rise to a distinct EPR spectrum. Exposure to ionizing radiation at room temperature produces a second and different Cu2+ EPR spectrum when a hole is trapped by substitutional Cu+ ions that have no nearby defects. These two Cu2+ trapped-hole centers are referred to as Cu2+-VLi and Cu2+active, respectively. Also during the irradiation, two trapped-electron centers in the form of interstitial Cu0 atoms are produced when interstitial Cu+ ions trap electrons. They are observed with EPR and are labeled Cu0A and Cu0B. When an irradiated crystal is warmed from 25 to 150 ◦C, the Cu2+active centers have a partial decay step that correlates with the TL peak near 100 ◦C. The concentrations of Cu0A and Cu0B centers, however, increase as the crystal is heated through this range. As the crystal is futher warmed between 150 and 250 ◦C, the EPR signals from the Cu2+active hole centers and Cu0A and Cu0B electron centers decay simultaneously. This decay step correlates with the intense TL peak near 200 ◦C

Oxygen Vacancies in LiAlO\u3csub\u3e2\u3c/sub\u3e Crystals

Singly ionized oxygen vacancies are produced in LiAlO2 crystals by direct displacement events during a neutron irradiation. These vacancies, with one trapped electron, are referred to as V+O centers. They are identified and characterized using electron paramagnetic resonance (EPR) and optical absorption. The EPR spectrum from the V+O centers is best monitored near 100 K with low microwave power. When the magnetic field is along the [001] direction, this spectrum has a g value of 2.0030 and well-resolved hyperfine interactions of 310 and 240 MHz with the two 27Al nuclei that are adjacent to the oxygen vacancy. A second EPR spectrum, also showing hyperfine interactions with two 27Al nuclei, is attributed to a metastable state of the V+O center. An optical absorption band peaking near 238 nm is assigned to V+O centers. Bleaching light from a Hg lamp converts a portion of the V+O centers to V0O centers (these latter centers are oxygen vacancies with two trapped electrons). The V0O centers have an absorption band peaking near 272 nm, a photoluminescence band peaking near 416 nm, and a photoluminescence excitation band peaking near 277 nm. Besides the oxygen-vacancy EPR spectra, a holelike spectrum with a resolved, but smaller, hyperfine interaction with one 27Al nucleus is present in LiAlO2 after the neutron irradiation. This spectrum is tentatively assigned to doubly ionized aluminum vacancies

Copper Doping of ZnO Crystals by Transmutation of \u3csup\u3e64\u3c/sup\u3eZn to \u3csup\u3e65\u3c/sup\u3eCu: An Electron Paramagnetic Resonance and Gamma Spectroscopy Study

Transmutation of 64Zn to 65Cu has been observed in a ZnO crystal irradiated with neutrons. The crystal was characterized with electron paramagnetic resonance (EPR) before and after the irradiation and with gamma spectroscopy after the irradiation. Major features in the gamma spectrum of the neutron-irradiated crystal included the primary 1115.5 keV gamma ray from the 65Zn decay and the positron annihilation peak at 511 keV. Their presence confirmed the successful transmutation of 64Zn nuclei to 65Cu. Additional direct evidence for transmutation was obtained from the EPR of Cu2+ ions (where 63Cu and 65Cu hyperfine lines are easily resolved). A spectrum from isolated Cu2+ (3d9) ions acquired after the neutron irradiation showed only hyperfine lines from 65Cu nuclei. The absence of 63Cu lines in this Cu2+ spectrum left no doubt that the observed 65Cu signals were due to transmuted 65Cu nuclei created as a result of the neutron irradiation. Small concentrations of copper, in the form of Cu+-H complexes, were inadvertently present in our as-grown ZnO crystal. These Cu+-H complexes are not affected by the neutron irradiation, but they dissociate when a crystal is heated to 900 °C. This behavior allowed EPR to distinguish between the copper initially in the crystal and the copper subsequently produced by the neutron irradiation. In addition to transmutation, a second major effect of the neutron irradiation was the formation of zinc and oxygen vacancies by displacement. These vacancies were observed with EPR

Identification of the Zinc-oxygen Divacancy in ZnO Crystals

An electron paramagnetic resonance (EPR) spectrum in neutron-irradiated ZnO crystals is assigned to the zinc-oxygen divacancy. These divacancies are observed in the bulk of both hydrothermally grown and seeded-chemical-vapor-transport-grown crystals after irradiations with fast neutrons. Neutral nonparamagnetic complexes consisting of adjacent zinc and oxygen vacancies are formed during the irradiation. Subsequent illumination below ∼150 K with 442 nm laser light converts these (V2−Zn − V2+O)0 defects to their EPR-active state (V−Zn − V2+O)+ as electrons are transferred to donors. The resulting photoinduced S = 1/2 spectrum of the divacancy is holelike and has a well-resolved angular dependence from which a complete g matrix is obtained. Principal values of the g matrix are 2.00796, 2.00480, and 2.00244. The unpaired spin resides primarily on one of the three remaining oxygen ions immediately adjacent to the zinc vacancy, thus making the electronic structure of the (V−Zn − V2+O)+ ground state similar to the isolated singly ionized axial zinc vacancy. The neutral (V2−Zn − V2+O)0 divacancies dissociate when the ZnO crystals are heated above 250 °C. After heating above this temperature, the divacancy EPR signal cannot be regenerated at low temperature with light

EPR identification of defects responsible for thermoluminescence in Cu-doped lithium tetraborate (Li2B4O7) crystals

Electron paramagnetic resonance (EPR) is used to identify the electron and hole traps responsible for thermoluminescence (TL) peaks occurring near 100 and 200 ◦C in copper-doped lithium tetraborate (Li2B4O7) crystals. As-grown crystals have Cu+ and Cu2+ ions substituting for lithium and have Cu+ ions at interstitial sites. All of the substitutional Cu2+ ions in the as-grown crystals have an adjacent lithium vacancy and give rise to a distinct EPR spectrum. Exposure to ionizing radiation at room temperature produces a second and different Cu2+ EPR spectrum when a hole is trapped by substitutional Cu+ ions that have no nearby defects. These two Cu2+ trapped-hole centers are referred to as Cu2+-VLi and Cu2+active, respectively. Also during the irradiation, two trapped-electron centers in the form of interstitial Cu0 atoms are produced when interstitial Cu+ ions trap electrons. They are observed with EPR and are labeled Cu0A and Cu0B. When an irradiated crystal is warmed from 25 to 150 ◦C, the Cu2+active centers have a partial decay step that correlates with the TL peak near 100 ◦C. The concentrations of Cu0A and Cu0B centers, however, increase as the crystal is heated through this range. As the crystal is futher warmed between 150 and 250 ◦C, the EPR signals from the Cu2+active hole centers and Cu0A and Cu0B electron centers decay simultaneously. This decay step correlates with the intense TL peak near 200 ◦C

Identification of electron and hole traps in lithium tetraborate (Li2B4O7) crystals: Oxygen vacancies and lithium vacancies

Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify and characterize electrons trapped by oxygen vacancies and holes trapped by lithium vacancies in lithium tetraborate (Li2B4O7) crystals. Our study includes a crystal with the natural abundances of 10B and 11B and a crystal highly enriched with 10B. The as-grown crystals contain isolated oxygen vacancies, lithium vacancies, and copper impurities, all in nonparamagnetic charge states. During an irradiation at 77 K with 60 kV x-rays, doubly ionized oxygen vacancies trap electrons while singly ionized lithium vacancies and monovalent copper impurities trap holes. The vacancies return to their preirradiation charge states when the temperature of the sample is increased to approximately 90 K. Hyperfine interactions with 10B and 11B nuclei, observed between 13 and 40 K in the radiation-induced EPR and ENDOR spectra, provide models for the two vacancy-related defects. The electron trapped by an oxygen vacancy is localized primarily on only one of the two neighboring boron ions while the hole stabilized by a lithium vacancy is localized on a neighboring oxygen ion with nearly equal interactions with the two boron ions adjacent to the oxygen ion

Dual Role of Sb Ions as Electron Traps and Hole Traps in Photorefractive Sn2P2S6 Crystals

Doping photorefractive single crystals of Sn2P2S6 with antimony introduces both electron and hole traps. In as-grown crystals, Sb3+ (5s2 ) ions replace Sn2+ ions. These Sb3+ ions are either isolated (with no nearby perturbing defects) or they have a chargecompensating Sn2+ vacancy at a nearest-neighbor Sn site. When illuminated with 633 nm laser light, isolated Sb3+ ions trap electrons and become Sb2+ (5s2 5p1 ) ions. In contrast, Sb3+ ions with an adjacent Sn vacancy trap holes during illumination. The hole is primarily localized on the (P2S6) 4− anionic unit next to the Sb3+ ion and Sn2+ vacancy. These trapped electrons and holes are thermally stable below ∼200 K, and they are observed with electron paramagnetic resonance (EPR) at temperatures below 150 K. Resolved hyperfine interactions with 31P, 121Sb, and 123Sb nuclei are used to establish the defect models