Relative Numerousness Judgment and Summation in Young and Old Western Lowland Gorillas.

The relationship between age, relative numerousness judgment, and summation was investigated in 11 Western lowland gorillas (Gorilla gorilla gorilla). Experiments 1 and 2 evaluated the gorillas' ability to select the larger of 2 food quantities before and with training. The majority of gorillas did not reliably select the larger quantity in Experiment 1 until receiving training to do so in Experiment 2. Experiment 3 evaluated their ability to select the larger of 2 pairs of quantities. All gorillas selected the larger pair more often than chance, and the old were less accurate and slower than were the young. For most gorillas, performance in relative numerousness judgment with training and summation was comparable with previous reports in chimpanzees and orangutans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low-temperature transport properties of RERh4B4 compounds (RE=Sm,Ho, Er,Lu)

We have measured the low-temperature electrical resistivity ρ and thermal conductivity λ of a selection of RERh₄B₄ compounds. The compound LuRh₄B₄ served as the standard material concerning superconductivity and HoRh₄B₄ as that for magnetic ordering. For ErRh₄B₄ we studied, in particular, the transition from the superconducting to the normal state with decreasing temperature. In SmRh₄B₄ both ρ(T) and λ(T) reveal the strong interaction between the magnetic moments of the Sm³⁺ ions and the conduction electrons, which is partly quenched at the transition to the antiferromagnetic state. Depending on the material considered, the thermal conductivity data are analyzed using theoretical calculations due to Bardeen, Rickayzen, and Tewordt; Kadanoff and Martin; and Ambegaokar and Griffin.     

Normal and superconducting properties of EuMo6S8 in high magnetic fields

The variation of the electrical resistanceR of EuMo₆S₈ with temperatureT and applied magnetic fieldH was determined at pressuresP to 19 kbar. At ambient pressure, the results are in agreement with previous work on samples of similar quality, where it was determined that variations of the carrier concentration were responsible for the very strong dependence ofR onT andH. AtP=8.5 kbar, the magnetoresistance is determined by the freezing out of the Eu²⁺ spins asH increases. ForP>13 kbar, EuMo₆S₈ exhibits bulk superconductivity, and we investigated the upper critical magnetic fieldH _c2(T). The analysis of these results shows that our EuMo₆S₈ samples are clean superconductors. We observe thatH _c2 is strongly reduced by pressure, perhaps due to an increase of the carrier concentration with pressure.     

Negative effects of a high level of nutrient intake on mammary gland development of prepubertal goats

Ten French Alpine kids were used to determine whether mammary development was altered by level of nutrient intake during the prepubertal period. At 6 wk of age, kids were paired on the basis of BW and assigned to an ad libitum or restricted diet of milk from Jersey cows. Kids on the restricted diet were fed 70% of their pair mate's milk intake for 4 wk and then 50% for 9 wk. Low quality grass hay was available for all kids. The ADG was greater for kids fed for ad libitum intake. Kids fed for ad libitum intake had larger mammary glands and increased adipose deposition. Measurement of hydroxyproline indicated that connective tissue increased with gland size. Kids on the restricted diet had more DNA and protein per gram of mammary gland, indicating greater secretory development. Goats can be used as a model to study the effect of level of nutrient intake on hormones and growth factors that regulate mammary gland development.     

Ferromagnetism in the RERh4B4 compounds

The magnetic ordering temperatures of the primitive tetragonal rare earth (RE) rhodium boride compounds exhibit a peak at DyRh₄B₄, rather than GdRh₄B₄ as predicted from ordering via the indirect RKKY exchange interaction. This deviation is analyzed in terms of the depression of the superconducting transition temperature of LuRh₄B₄ by dilute amounts of RE impurity ions and the magnetic heat capacities of the RERh₄B₄ compounds for RE = Gd, Tb, Dy, and Ho. The strength of anisotropic crystalline electric field forces, as inferred from magnetic entropy considerations, may be the origin of the anomalous magnetic ordering temperatures. In addition, the depression of the superconducting transition temperatures of ErRh₄B₄ and TmRh₄B₄ from that of LuRh₄B₄ is shown to arise primarily from elastic exchange scattering of the conduction electrons by the magnetic RE ions.This research was supported by the U.S. Department of Energy under Contract EY-76-S-03-0034-PA227-3 (HBM, LDW, MBM) and by the National Science Foundation under Grant NSF/DMR77-08469 (DCJ).