Determination of dissociation degrees of K3NbF8 and K3TaF8 by thermodynamic analysis of subsystems of the KF-K2NbF7 and KF-K2TaF7 systems

A special form of the LeChatelier-Shreder equation describing the equilibrium between the crystalline phase and the melt in system A-AB in which the substance AB partially dissociates upon melting was applied to systems KF-K3NbF8, K2NbF7-K3NbF8 and to KF-K3TaF8, K2TaF7-K3TaF8 subsystems of the binary systems KF-K2NbF7 and KF-K2TaF7 in which the additive compounds K3NbF8 and K3TaF8 are formed. Using the phase diagram of the system KF-K2NbF7 determined by McCawley and Barclay (1971) and the values of the fusion enthalpy of K3NbF8 taken from literature, the intervals of the dissociation degree values of K3NbF8 for both branches of the liquidus curve of K3NbF8 were calculated. The calculated values of the dissociation degree depend on the coordinates of the liquidus curve of K3NbF8 of the pertinent phase diagram, on its used branch and section, and on the value of the fusion enthalpy of K3NbF8. For the measured fusion enthalpy of K3NbF8 (57 kJ mol−1), a common interval of the dissociation degree values of K3NbF8 for both branches of the liquidus curve of K3NbF8 is 0.71–0.72. Similarly, intervals of the dissociation degree values of K3TaF8 for both branches of the liquidus curve of K3TaF8 were calculated using the phase diagram of the system KF-K2TaF7 determined by Boča et al. (2007) and the measured fusion enthalpy of K3TaF8 ((52 ± 2) kJ mol−1). The error of the determination of the fusion enthalpy of K3TaF8, the common interval of the dissociation degree values of K3TaF8 for both branches of the liquidus curve of K3TaF8 is 0.68–0.69.

Photoperiodic and hormonal influences on fur density and regrowth in two hamster species

Temperate and boreal mammals undergo seasonal changes in pelage that facilitate thermoregulation in winter and summer. We investigated photoperiodic influences on pelage characteristics of male Siberian and Syrian hamsters. Fur density (mg fur/cm2 skin) was measured by weighing the shavings of fur patches removed from the dorsal and ventral surfaces of hamsters maintained in long days (LDs) or transferred to short days (SDs). Patches were reshaved 3 wk later to assess fur regrowth (mg regrown fur/cm2 skin). Fur density was greater in SD than in LD Siberian hamsters after 11 wk of differential phototreatment. The onset of increased fur density in SDs was accompanied by a transient increase in fur regrowth (11–14 wk on the dorsal surface and 7–10 and 11–14 wk on the ventral surface), suggestive of a seasonal molting process. Fur density, body mass, and pelage color of Siberian hamsters returned to values characteristic of LD males after a similar duration of prolonged (>27 wk) SD treatment and appear to be regulated by a similar or common interval-timing mechanism. In Syrian hamsters, dorsal fur density, fur regrowth, and hair lengths were greater in SD than in LD males. Castration increased and testosterone (T) treatment decreased dorsal and ventral fur regrowth in LD and SD hamsters, but the effects of T manipulations on fur density were limited to a decrease in dorsal fur density after T treatment. Decreased circulating T in SDs likely contributes to the seasonal molt of male hamsters by increasing the rate of fur growth during the transition to the winter pelage.

Subset-Class Relation, Common Pitches, and Common Interval Structure Guiding Estimations of Similarity

THE PRESENT STUDY EXAMINED THE importance of subsetclass relation for closeness estimations. Two experiments used set-class pairs consisting of a pentad class and a tetrad class represented by block chords, and approximately half of the pairs accomplished the subset-class relation. In the first experiment the number of common pitches was systematically varied. In the second experiment the intervals between the lowest pitch and the other pitches were either similar in both chords (except for the interval missing from the tetrachord) or dissimilar, but the chords shared no common pitches. The degree of set-class consonance was also varied. The results of the experiments indicated that the number of common pitches and the common interval structure were important factors guiding closeness estimations. The subset-class relation was important since it enabled a maximum number of common pitches, maximally similar intervals, or highly uniform voice-leading between chords.

Trifluralin (Preen) Dissipation from the Surface Layer of a Soilless Plant Growth Substrate

Southeastern U.S. container nursery crop production relies upon frequent applications of preemergence herbicides for broad-spectrum weed control. An experiment was conducted to determine the length of residual control and the sensitivity of two grass species to Preen (trifluralin) applied to the surface of a pine bark:sand (7:1 by vol) potting substrate. The experiment was conducted twice at each of two locations during 2001. Samples of the potting substrate were taken 0, 1, 3, 7, 14, 28, 42 and 56 days after treatment (DAT) for laboratory analysis. Trifluralin was extracted from the potting substrate and quantified using gas chromatographic techniques. Large crabgrass and perennial ryegrass were seeded 0, 7, 14, 28, 42 and 56 DAT to bioassay for herbicide residues. Shoot and root length were measured two weeks after each seeding date. Preen residues in the surface of the potting substrate decreased rapidly after application and leveled off approximately 21 DAT. Based on the bioassay, March applications of Preen controlled large crabgrass and perennial ryegrass for 37 days or greater while May and June applications of Preen controlled the two species for only 3 to 21 days. These results suggest that trifluralin reapplication should be more frequent than the common interval of 56 to 70 days in the southeastern United States.