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We describe the status of the problem of the electron structure of superheavy atoms with nuclear charge Z > Z_c ; here Z_c≈170 is the critical value of the nuclear charge, at which the energy of the ground state of the 1S_1/2 electron reaches the limit of the lower continuum of the solutions of the Dirac equation (∊ = - m_ec²) . We discuss the dependence of Z_c on the nuclear radius R and on the character of the distribution of the electric charge inside the nucleus, and also the form of the wave functions at Z close to Z_c . Owing to the Coulomb barrier , the state of the electron remains localized at Z > Z_c , in spite of the fact that its energy approaches the continuum. An analysis of the polarization of the vacuum in a strong Coulomb field shows that a bare nucleus with supercritical charge Z > Z_c produces spontaneously two positrons and, in addition a charge density with a total of two units of negative charge in the vacuum. The distribution of this density is localized in a region of dimension r ~ ħ/m_ec at the nucleus. The possibility of experimentally observing the effect of quasistatic production of positrons in the collision of two bare uranium nuclei (i.e., without electrons) is discussed. A brief review is presented of work on the motion of levels with increasing depth of the potential well in other relativistic equations (Kelin-Gordon, Proca, etc.).

Polarization of electrons arising as the result of radiation during extended motion in a magnetic field is considered. A calculation is made with the quasiclassical operator method of the probability of a radiative transition in a magnetic field with spin flip, including the case of a nonuniform magnetic field. The kinetic equation is obtained for polarization of electrons in an external field with inclusion of radiation effects, and this is used to analyze the kinetics of radiative polarization. Effects are discussed which lead to depolarization of an electron beam in motion in a nonuniform magnetic field, and means of suppressing these effects and also of intentional depolarization of a beam are pointed out. Means are discussed for measurement of the transverse polarization of high energy electrons, and a description is given of an experiment in which the first indication of the existence of the radiative polarization effect has been obtained.

TABLE OF CONTENTS I. Introduction 715 II. Experimental Data 716 III. The Helix-coil Transition in Homopolymers 718 IV. The Helix-coil Transition in Heteropolymers 723 V. Conclusion 732 Bibliography 734

CONTENTS Abstract 737 1. Introduction 737 2. Perturbation of the Flow of a Viscous Liquid by an Undeformed Ellipsoid 738 3. Motion of Ellipsoid in a Stream 738 4. Stress Tensor 739 5. Translational and Rotational Brownian Motion 740 6. Motion of Ellipsoid in a Stream with Allowance for Rotational Brownian Motion 741 7. Stress Tensor and Viscosity of a Suspension with Allowance for Rotational Brownian Motion of the Particles 742 8. Dielectric Ellipsoid in a Stream and an Electric Field 743 9. Stress Tensor and Viscosity of a Suspension in an Electric Field 744 10. Dielectric Tensor 745 11. Concluding Remarks 746 Cited Literature

The present review of the investigations of pulsed gas-discharge lasers is based mainly on the literature published up to the middle of 1970. Lasers utilizing transitions in neutral and ionized atoms and electronic transitions in molecules are discussed. The attention is concentrated on the systems whose efficiency is likely to be improved. The factors which determine the efficiency and the peak output power are considered. The choice of transitions likely to give high efficiencies and high peak powers is justified. A summary is given of the available information on pulsed gas-discharge lasers of two types: the lasers utilizing transitions from resonance to metastable levels in neutral and ionized atoms and the lasers using electronic transitions in diatomic molecules. The lasers using thallium, copper, and lead vapors and those utilizing transitions in nitrogen molecules are discussed in detail. Practical difficulties encountered in the construction of high-efficiency pulsed lasers are analyzed. A list is given of the transitions in other neutral and ionized atoms and molecules which can be expected to provide high-power pulsed emission. The prospects of utilization of the transitions from a resonance electronic level to the ground state of a molecule are stressed. The possibility of advance into the still unmastered vacuum ultraviolet region is discussed. Possible effects of increasing the density of the active gas are considered. Ways of going over from pulsed to continuous-wave emission in collision lasers are analyzed. It is concluded that pulsed gas-discharge lasers offer means for generating high-efficiency (up to 10%) and high-peak-power coherent pulses in a very wide range of wavelengths. It should also be possible to achieve high-efficiency continuous-wave emission in collision lasers operating at short wavelengths.

More than ten years have passed since discovery of the electric effect in paramagnetic resonance, but the number of investigations devoted to it has been large and increasing steadily. New phenomena related to this effect have been observed, and ways of its practical utilization have been indicated. The nature of the phenomenon is now understood, and the "phenomenological" description can be regarded as developed, although the quantitative theory leaves something to be desired. The article presents a review of work on the influence of the electric field on the paramagnetic-resonance spectrum. Principal attention is paid to electric effects in electron paramagnetic resonance and in electron nuclear double resonance. Effects in nuclear magnetic resonance (including quadrupole resonance), combined resonance, and optics are discussed in less detail, but all the studies known to the author are noted. The reviewed articles are grouped by topics, without observing chronological order.