Tree Fruits for Alaska

This circular has been prepared with three major objectives in mind. 1) to define areas in which tree fruit culture is possible in Alaska and the types of fruit that can be grown in each, 2) to name and describe the varieties that at the present time seem more desirable for planting in Alaska, and 3) to point out the m?-in problems limiting tree fruit culture and suggest, rather than discuss, the probable means by which they may one day be solved. Fulfilling the first two of these objectives was a relatively simple matter, since it was only a matter of defining and description. But the third objective was not-and is not-so easy of attainment. In what may be an oversimplification, it has been stated that there are two main problems, winter hardiness and earliness of maturity, and methods have been indicated by which, it is believed, each may be overcome. However the very problems themselves are not as simple as they have been made to appear. That of winter hardiness is one of the most widely debated and investigated subject in plant science. And the characterization of the second as "earliness of maturity" makes it sound too simple, for actually the factor involved, as it applies to fruit growing in Alaska is aiding or hastening natural earliness of maturity. This is a far more complex matter. In describing the solutions of these problems, mention has been made of such factors as pruning and training, fertilization, furnishing protection to increase available heat, and limiting the water supply to the trees during the period of fruit maturation. Each of these subjects has also been the subject of numerous investigations and some of them have been the subject of textbooks. The discussion of them here has been limited to simple statements as to their merit in achieving specific objectives. Most of the statements made are based on research in Alaska. In one particular, however, they have knowingly been extended beyond the domain of research-supported conclusion. This is in advocating the withholding Qr decreasing water available to the trees during the maturation of the fruit. Some will disagree with this recommendation, for it runs counter to what is considered good orchard management in commercial fruit producing regions of the world. In these an ample water supply is advocated for this period to increase fruit size and heighten, though not to increase, coloration. In Alaska both considerations should be waived in favor of obtaining reasonable yields of fruit, suitable for culinary purposes.In all three regions of Alaska where tree fruit production is at all possible, lack of winter hardiness in the trees and failure of fruit to mature properly are the two chief limiting factors

Feasibility of the optical fiber clock

We explore the feasibility of a compact high-precision Hg atomic clock based on a hollow core optical fiber. We evaluate the sensitivity of the $^1S_0$-$^3P_0$ clock transition in Hg and other divalent atoms to the fiber inner core surface at non-zero temperatures. The Casimir-Polder interaction induced $^1S_0$-$^3P_0$ transition frequency shift is calculated for the atom inside the hollow capillary as a function of atomic position, capillary material, and geometric parameters. For $^{199}\mathrm{Hg}$ atoms on the axis of a silica capillary with inner radius $\geq 15 \,\mu \mathrm{m}$ and optimally chosen thickness $d\sim 1 \,\mu \mathrm{m}$, the atom-surface interaction induced $^1S_0$-$^3P_0$ clock transition frequency shift can be kept on the level $\delta\nu/\nu_{\mathrm{Hg}} \sim10^{-19}$. We also estimate the atom loss and heating due to the collisions with the buffer gas, lattice intensity noise induced heating, spontaneous photon scattering, and residual birefringence induced frequency shifts.Comment: 8 pages, 5 figures, submitte

Theoretical Study of Pressure Broadening of Lithium Resonance Lines by Helium Atoms

Quantum mechanical calculations are performed of the emission and absorption profiles of the lithium 2s-2p resonance line under the influence of a helium perturbing gas. We use carefully constructed potential energy surfaces and transition dipole moments to compute the emission and absorption coefficients at temperatures from 200 to 3000 K at wavelengths between 500 nm and 1000 nm. Contributions from quasi-bound states are included. The resulting red and blue wing profiles are compared with previous theoretical calculations and with an experiment, carried out at a temperature of 670 K.Comment: 10 figure