Positive ion temperatures above the F-layer maximum

Positive ion temperatures above F layer maximum from Ariel I satellite ion mass analyze

Interaction of a Modulated Electron Beam with a Plasma

The results of a theoretical and experimental investigation of the high-frequency interaction of an electron beam with a plasma are reported. An electron beam, modulated at a microwave frequency, passes through a uniform region of a mercury arc discharge after which it is demodulated. Exponentially growing wave amplification along the electron beam was experimentally observed for the first time at a microwave frequency equal to the plasma frequency. Approximate theories of the effects of 1) plasma-electron collision frequencies, 2) plasma-electron thermal velocities and 3) finite beam diameter, are given. In a second experiment the interaction between a modulated electron beam and a slow electrostatic wave on a plasma column has been studied. A strong interaction occurs when the velocity of the electron beam is approximately equal to the velocity of the wave and the interaction is essentially the same as that which occurs in traveling-wave amplifiers, except that here the plasma colum replaces the usual helical slow-wave circuit. The theory predicting rates of growth is presented and compared with the experimental results

Studies of Soil Microorganisms, Inuvik, Northwest Territories

A study of soil microorganisms of the Inuvik area (68°21'N, 133°40'W) was carried out during the summer of 1964. In almost all samples taken, psychrophilic, mesophilic, and especially thermophilic bacteria were found in greater numbers than in samples obtained from northern and southwestern Alaska. These studies also demonstrated that the soil microflora in this area was more varied physiologically and metabolically than in its Alaskan counterpart, and that the Canadian soils were warmer, had better drainage, and had certain chemical and physical properties that could account for the differences in bacterial numbers.Études sur les microorganismes du sol, Inuvik, T. du N.-O.  Au cours de l’été de 1964, on a mené une étude des microorganismes du sol dans la région d’Inuvik (68°21'N., 133°40'W.).  Dans tous les échantillons recueillis les bactéries psychrophiles, mésophiles et surtout thermophiles ont été trouvées en plus grand nombre que dans des échantillons provenant du Nord et du sud-ouest de l’Alaska.  Ces études ont aussi démontré que dans cette région, la microflore du sol était physiologiquement et métaboliquement plus variée que son équivalent alaskien, et que les sols canadiens étaient plus chauds et mieux drainés, et possédaient certaines propriétés chimiques et physiques qui pourraient expliquer ces différences dans les comptages de bactéries

Microbiological Studies of Aquatic Habitats of the Area of Inuvik, Northwest Territories

Results of chemical analyses and bacterial counts of waters in eight lakes and the Mackenzie River at Inuvik, show a uniform chemical composition throughout the ice-free period (Jun-Aug), an increase in psychrophilic and mesophilic bacteria, and low counts of thermophilic bacteria and molds. Water supplied to Inuvik from the Mackenzie River, has been pumped into Hidden Lake during freeze-up, allowed to settle, then filtered and chlorinated. This system is described and problems of circulation and sewage disposal noted, with tabulated data on microbial and chemical properties of the sewage lagoons.Études microbiologiques d'habitats aquatiques de la région d'inuvik, T.N.-O. Les auteurs ont mené des études chimiques et microbiologiques dans des lacs et des mares et sur le fleuve Mackenzie, au voisinage d'Inuvik. Sauf pour quelques exceptions, la composition chimique de la plupart de ces eaux était uniforme tout au long de la période pendant laquelle elles étaient libres de glace. Dans tous les cas, le nombre de bactéries psychrophiles et mésophiles augmentait, mais pas nécessairement au même moment; les comptages de bactéries thermophiles et de moisissures donnèrent des chiffres assez bas. Des études auxiliaires furent aussi menées sur l'eau de ruissellement et sur les réseaux d'adduction d'eau et d'égouts de la ville

The Bovine Placenta In Health and Disease

Extensive histologic changes of the endometrium are already well under way at the time the fertilized ovum enters the uterine cavity. During estrus the endometrium becomes hyperemic and edematous, while degeneration of a vacuolar type affects the surface epitl\u27l.elium. In the postestrous period the endometrium becomes markedly thickened, and the uterine glands increase in size and activity. In pregnancy there is further modification of the endometrium, particularly in the carunculae, which serve as a means of attachment for the fetal placenta. The carunculae, more familiarly known as cotyledons, constitute the maternal placenta. The above described changes which provide for the formation of the maternal placenta are initiated by the fertilized ovum and the estrogenic hormones, estrone and progesterone. These hormones, though differing clinically and functionally, are thought to be synergistic. This supposition seems quite logical inasmuch as the cells that form the graafian follicle later give formation to the corpus luteum. The first few days of the fertilized ovum within the uterine cavity may be regarded as difficult ones, largely from the standpoint of nutrition. The secretion from the uterine glands, known as uterine milk, is believed to provide nourishment for a brief period or until contact is made between the fetal and maternal placenta

Stochastic properties of systems controlled by autocatalytic reactions II

We analyzed the stochastic behavior of systems controlled by autocatalytic reaction A+X -> X+X, X+X -> A+X, X -> B provided that the distribution of reacting particles in the system volume is uniform, i.e. the point model of reaction kinetics introduced in arXiv:cond-mat/0404402 can be applied. Assuming the number of substrate particles A to be kept constant by a suitable reservoir, we derived the forward Kolmogorov equation for the probability of finding n=0,1,... autocatalytic particles X in the system at a given time moment. We have shown that the stochastic model results in an equation for the mean value of autocatalytic particles X which differs strongly from the kinetic rate equation. It has been found that not only the law of the mass action is violated but also the bifurcation point is disappeared in the well-known diagram of X particle- vs. A particle-concentration. Therefore, speculations about the role of autocatalytic reactions in processes of the "natural selection" can be hardly supported.Comment: 17 pages, 6 figure

Zitterbewegung of optical pulses in nonlinear frequency conversion

Pulse walk-off in the process of sum frequency generation in a nonlinear $\chi^{(2)}$ crystal is shown to be responsible for pulse jittering which is reminiscent to the Zitterbewegung (trembling motion) of a relativistic freely moving Dirac particle. An analytical expression for the pulse center of mass trajectory is derived in the no-pump-depletion limit, and numerical examples of Zitterbewegung are presented for sum frequency generation in periodically-poled lithium niobate. The proposed quantum-optical analogy indicates that frequency conversion in nonlinear optics could provide an experimentally accessible simulator of the Dirac equation.Comment: to be published in Journal of Physics B: Atomic, Molecular & Optical Physic

Slow light with integrated gain and large pulse delay

We demonstrate slow and stored light in Rb vapor with a combination of desirable features: minimal loss and distortion of the pulse shape, and large fractional delay (> 10). This behavior is enabled by: (i) a group index that can be controllably varied during light pulse propagation; and (ii) controllable gain integrated into the medium to compensate for pulse loss. Any medium with the above two characteristics should be able to realize similarly high-performance slow light.Comment: 5 pages, 4 figures; abstract is shortened, some typo correcte

Cavity Nonlinear Optics at Low Photon Numbers from Collective Atomic Motion

We report on Kerr nonlinearity and dispersive optical bistability of a Fabry-Perot optical resonator due to the displacement of ultracold atoms trapped within. In the driven resonator, such collective motion is induced by optical forces acting upon up to $10^5$ $^{87}$Rb atoms prepared in the lowest band of a one-dimensional intracavity optical lattice. The longevity of atomic motional coherence allows for strongly nonlinear optics at extremely low cavity photon numbers, as demonstrated by the observation of both branches of optical bistability at photon numbers below unity.Comment: 4 pages, 3 figures. Modifed following reviewer comment