Dietary Self-Selection by Laying Hens Offered Choices of Feed

A short telm dietary self-selection experiment (28 days) was conducted with laying hens fed three treatments (Tl-T3) consisting of a commercially available layer feed (1'1, single choice), commercially available layer feed and oyster shell grit offered separately (T2, two choices) and a com mixture, soyabean meal mixture and oyster shell grit offered sejJarately (T3, three choices). Measurement of feed intake was divided into three feeding periods, from 0800-1200h, 1200-1600h and 1600-0800h. Feed and water' were available ad Ii bitum. Hens were raised under' 15 hour Photo period. Feed, energy and protein intakes were significantly better' on the commercial diet and lower in the other' two treatments. Calcium intake was significantly lower on the single choice and three choice diets. In all treatments, the hens tended to consume more feed during the pel10d between 1600-0800h (40.8-45.8% feed consumed), that is very late in the evening and very early in the morning. Similar amounts of feed (26.2-29.7% of feed consumed) were consumed between 0800-1200h and 1200-1600h. egg production, egg mass and feed conversion were significantly better' on the two and three-choice diets as compared to the single diet. There was no difJeI'ence in egg weight among the three treatments

The suppression of magnetism and the development of superconductivity within the collapsed tetragonal phase of Ca0.67Sr0.33Fe2As2 at high pressure

Structural and electronic characterization of (Ca0.67Sr0.33)Fe2As2 has been performed as a func- tion of pressure up to 12 GPa using conventional and designer diamond anvil cells. The compound (Ca0.67Sr0.33)Fe2As2 behaves intermediate between its end members-CaFe2As2 and SrFe2As2- displaying a suppression of magnetism and the onset of superconductivity. Like other members of the AEFe2As2 family, (Ca0.67Sr0.33)Fe2As2 undergoes a pressure-induced isostructural volume collapse, which we associate with the development of As-As bonding across the mirror plane of the structure. This collapsed tetragonal phase abruptly cuts off the magnetic state, giving rise to superconductivity with a maximum Tc=22.2 K. The maximum Tc of the superconducting phase is not strongly correlated with any structural parameter, but its proximity to the abrupt suppression of magnetism as well as the volume collapse transition suggests that magnetic interactions and structural inhomogeneity may play a role in its development. The pressure-dependent evolution of the ordered states and crystal structures in (Ca,Sr)Fe2As2 provides an avenue to understand the generic behavior of the other members of the AEFe2As2 family.Comment: 9 pages, 9 figure

Diurnal and seasonal variations of <i>hm</i>F2 deduced from digitalionosonde over New Delhi and its comparison with IRI 2001

International audienceUsing digital ionosonde observations at a low mid-latitude station, New Delhi (28.6°N, 77.2°E, dip 42.4°N), we have derived hourly monthly values of hmF2 (the real height corresponding to the peak electron density in the F2-region), employing both the Dudeney (1983) and Bilitza (1990) empirical formulations for the period from January 2001 to August 2002. The diurnal and seasonal variations of hmF2 are analyzed. Further, to assess the predictability of the latest available model, International Reference Ionosphere, (IRI-2001), we have obtained the median values of hmF2 derived from M(3000)F2 for each hour during different seasons and compare these with the model. Our results show that both the Dudeney (1983) and Bilitza (1990) formulations reveal more or less a similar diurnal trend of hmF2, with higher values around midnight and lower during sunrise, in all the seasons. It is also noted that the hmF2 shows a larger variability around midnight than by daytime, in all the seasons. Further, the study shows that median values of observed hmF2, using both formulations, are somewhat larger than those predicted by the IRI, in all seasons and at all local times. During summer, the IRI values agree comparatively well with the observations, especially during daytime. Major discrepancies occur when the IRI underestimates observed hmF2 for local times from about 14:00 LT to 18:00 LT and 04:00 LT to 05:00 LT during winter and equinox, where the percentage deviation of the observed hmF2 values with respect to the IRI model varies from 15 to 25%. The difference between the model and observations, outside this time period, remains less than 20% during all the seasons. Key words. Ionosphere (modelling and forecasting; equatorial ionosphere

Pressure-induced superconductivity in the giant Rashba system BiTeI

At ambient pressure, BiTeI is the first material found to exhibit a giant Rashba splitting of the bulk electronic bands. At low pressures, BiTeI undergoes a transition from trivial insulator to topological insulator. At still higher pressures, two structural transitions are known to occur. We have carried out a series of electrical resistivity and AC magnetic susceptibility measurements on BiTeI at pressure up to ~40 GPa in an effort to characterize the properties of the high-pressure phases. A previous calculation found that the high-pressure orthorhombic P4/nmm structure BiTeI is a metal. We find that this structure is superconducting with Tc values as high as 6 K. AC magnetic susceptibility measurements support the bulk nature of the superconductivity. Using electronic structure and phonon calculations, we compute Tc and find that our data is consistent with phonon-mediated superconductivity.Comment: 7 pages, 7 figure