The Life History of Folsomia Candida (Willem) (Collembola: Isotomidae) Relative to Temperature

The parthenogenetic mode of reproduction in Collembola, although frequently questioned in the past (Schaller, 1953; Mayer, 1957; Falkenhan, 1932), has only recently been recorded and confirmed for several species; Onychiutus parthenogeneticus Choudhuri (Choudhuri, 1958), Folsomia candida (Willem) (Goto, 1960; Marshall and Kevan, 1962; Green, 1964; Husson and Paldvody, 1967), Folsomia cavicola Cassagnau and Delamare (Goto, 1960), Tullbergia krausbaueri (Bomer) (Hale, 1966; Petersen, 1971), and Isotoma notabilis Schaffer (Petersen, 1971). Sex-ratios in populations of the above cited species are often unknown. Existing data indicate that the composition of a population may vary with the geographical distribution of the species. Populations of Folsomia candida (Willem), known to be bisexual in England (Goto, 1960), have been found so far to consist entirely of females in Canada (Sharma and Kevan, 1963a) and in Michigan (Snider, 1973). Similar to I. notabilis and T. krausbaueri (Petersen, 1971), investigations throughout the year and over larger geographic areas are necessary before northern USA and Canada F. candida may be labeled as obligatory parthenogenetic. Snider (1973) recorded in detail the life cycle of F. candida at 21°C. The present study provides information on the influence of temperature on the bionomics of the species

Development of advanced composite structures

Composite structure programs: the L-1011 Advanced Composite Vertical Fin (ACVF), the L-1011 Advanced Composite Aileron, and a wing study program were reviewed. These programs were structured to provide the technology and confidence for the use of advanced composite materials for primary and secondary structures of future transport aircraft. The current status of the programs is discussed. The results of coupon tests for both material systems are presented as well as the ACVF environmental (moisture and temperature) requirements. The effect of moisture and temperature on the mechanical properties of advanced composite materials is shown. The requirements set forth in the FAA Certification Guidelines for Civil Composite Aircraft Structures are discussed as they relate to the ACVF

Constraints on the Symmetry Energy Using the Mass-Radius Relation of Neutron Stars

The nuclear symmetry energy is intimately connected with nuclear astrophysics. This contribution focuses on the estimation of the symmetry energy from experiment and how it is related to the structure of neutron stars. The most important connection is between the radii of neutron stars and the pressure of neutron star matter in the vicinity of the nuclear saturation density $n_s$. This pressure is essentially controlled by the nuclear symmetry energy parameters $S_v$ and $L$, the first two coefficients of a Taylor expansion of the symmetry energy around $n_s$. We discuss constraints on these parameters that can be found from nuclear experiments. We demonstrate that these constraints are largely model-independent by deriving them qualitatively from a simple nuclear model. We also summarize how recent theoretical studies of pure neutron matter can reinforce these constraints. To date, several different astrophysical measurements of neutron star radii have been attempted. Attention is focused on photospheric radius expansion bursts and on thermal emissions from quiescent low-mass X-ray binaries. While none of these observations can, at the present time, determine individual neutron star radii to better than 20% accuracy, the body of observations can be used with Bayesian techniques to effectively constrain them to higher precision. These techniques invert the structure equations and obtain estimates of the pressure-density relation of neutron star matter, not only near $n_s$, but up to the highest densities found in neutron star interiors. The estimates we derive for neutron star radii are in concordance with predictions from nuclear experiment and theory.Comment: 24 pages, 13 figure

General training by firms, apprentice contracts, and public policy

Workers will not pay for general on-the-job training if contracts are not enforceable. Firms may if there are mobility frictions. Private information about worker productivities, however, prevents workers who quit receiving their marginal products elsewhere. Their new employers then receive external benefits from their training. Training firms increase profits by offering apprenticeships committing them to high wages for trainees retained on completion. At those wages, only good workers are retained, which signals their productivity and reduces the external benefits if they subsequently quit. Regulation of apprenticeship length (a historically important feature) can enhance efficiency, as can appropriate subsidies.

Lakshmi Planum: A distinctive highland volcanic province

Lakshmi Planum, a broad smooth plain located in western Ishtar Terra and containing two large oval depressions (Colette and Sacajawea), has been interpreted as a highland plain of volcanic origin. Lakshmi is situated 3 to 5 km above the mean planetary radius and is surrounded on all sides by bands of mountains interpreted to be of compressional tectonic origin. Four primary characteristics distinguish Lakshmi from other volcanic regions known on the planet, such as Beta Regio: (1) high altitude, (2) plateau-like nature, (3) the presence of very large, low volcanic constructs with distinctive central calderas, and (4) its compressional tectonic surroundings. Building on the previous work of Pronin, the objective is to establish the detailed nature of the volcanic deposits on Lakshmi, interpret eruption styles and conditions, sketch out an eruption history, and determine the relationship between volcanism and the tectonic environment of the region