Neptune's eccentricity and the nature of the kuiper belt

The small eccentricity of Neptune may be a direct consequence of apsidal wave interaction with the trans-Neptune population of debris called the Kuiper belt. The Kuiper belt is subject to resonant perturbations from Neptune, so that the transport of angular momentum by density waves can result in orbital evolution of Neptune as well as changes in the structure of the Kuiper belt. In particular, for a belt eroded out to the vicinity of Neptune's 2:1 resonance at about 48 astronomical units, Neptune's eccentricity can damp to its current value over the age of the solar system if the belt contains slightly more than an earth mass of material out to about 75 astronomical units.     

Post-cambrian trilobite diversity and evolutionary faunas

A cluster analysis of the stratigraphic distribution of all Ordovician trilobite families, based on a comprehensive taxonomic database, identified two major faunas with disjunct temporal diversity trends. The Ibex Fauna behaved as a cohort, declining through the Ordovician and disappearing at the end-Ordovician mass extinction. In contrast, the Whiterock Fauna radiated rapidly during the Middle Ordovician and gave rise to all post-Ordovician trilobite diversity. Its pattern of diversification matches that of the Paleozoic Evolutionary Fauna; hence, trilobites were active participants in the great Ordovician radiations. Extinction patterns at the end of the Ordovician are related to clade size: Surviving trilobite families show higher genus diversity than extinguished families.     

Measuring the spin polarization of a metal with a superconducting point contact

A superconducting point contact is used to determine the spin polarization at the Fermi energy of several metals. Because the process of supercurrent conversion at a superconductor-metal interface (Andreev reflection) is limited by the minority spin population near the Fermi surface, the differential conductance of the point contact can reveal the spin polarization of the metal. This technique has been applied to a variety of metals where the spin polarization ranges from 35 to 90 percent: Ni0.8Fe0.2, Ni, Co, Fe, NiMnSb, La0.7Sr0.3MnO3, and CrO2.     

Hormonal response to dobutamine cardiac stress testing in a conscious canine model of early left ventricular dysfunction induced by chronic rate overload

The aims of this study were to investigate (1) hormonal activation before and during dobutamine cardiac stress testing (DST) in a canine model of early left ventricular dysfunction (ELVD) induced by rapid right ventricular pacing (RRVP) and (2) the relationship between this hormonal profile and carnitine concentrations.Before the pacing period, the 6 dogs were assigned to 2 groups according their baseline total plasma carnitine concentration. A DST was performed on each dog before activation of the pacemaker and every 3 to 4 days during development of 3 progressive stages of ELVD (stages 1, 2 and 3). Plasma atrial natriuretic factor (ANF), angiotensin II (ANG II) and endothelin-1 (ET-1) levels were measured at the start and at the end of each DST. Effects of ELVD, DST and plasma carnitine concentration on these measurements were tested.The RRVP induced a significant increase of ANF and ANG II and a non significant trend toward increase of ET-1 in all dogs.Before the pacing period, ANF remained constant during the DST in dogs with normal total plasma carnitine concentration, while it significantly decreased in dogs with low total plasma carnitine concentration. Dobutamine stress testing induced a significant decrease in ANF in all dogs in ELVD. Dobutamine infusion induced a significant increase in ANG II in all dogs before as well as during the pacing period while ET-1 was unchanged.These results suggest that investigation of the hormonal profile before and after a dobutamine challenge might provide important diagnostic information in dogs with asymptomatic or mildly symptomatic cardiac dysfunction of different origins.     

Onset of puberty and duration of the breeding season in Suffolk, Rambouillet, Finnish Landrace, Dorset and Finn-Dorset ewe lambs

Sixty ewe lambs, 12 each of Suffolk, Dorset, Finnish Landrace, Finn-Dorset and Rambouillet born in January and February were used in a study of puberty and duration of the first breeding season. Ovulation was monitored via progesterone assay of weekly blood samples beginning in July, and estrus via daily checking with vasectomized rams. All 60 ewes ovulated but three, one Dorset and two Rambouillet failed to show estrus although each had five to seven ovulatory cycles. Several ewes showed small progesterone rises, 300 to 500 pg/ml, before first ovulation and six (10%) failed to initiate regular cyclicity following the first ovulation as defined by progesterone greater than 500 pg/ml. Mean number of ovulatory events before the first behavioral estrus ranged from 1.25 for Finnish Landrace to 2.20 for Rambouillet ewe lambs (P less than .1). Rambouillets were older (277 d; P less than .05) at first estrus than Finns (258 d) and Finn-Dorsets (260 d), but differences in age at first ovulation were not significant: Finn-Dorset, 233 d; Dorset, 234 d; Finn, 235 d; Rambouillet, 240 d; Suffolk, 245 d. Most cycles were of normal length, with 91.4% between 14 and 20 d. Repeatability of cycle length within breed group was .38. Suffolks had significantly shorter cycles (16.1 d) than the other four groups (17.0 to 17.4 d). Finnish Landrace and Finn-Dorset ewes continued to cycle much longer than the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of induced parturition in dairy cows on the incidence of mortality in calves from commercial herds in south-western Victoria

SUMMARY The effects of induced parturition on calf mortality rates were studied in 24 winter-calving, pasture-fed, dairy herds in south-western Victoria. Parturition was induced when most cows were between 27 and 35 weeks of pregnancy. Control groups were selected from cows in the same herds in which calving was not induced. The incidence of mortality within 7 days of birth was much higher among calves from cows in induced groups relative to those in control groups (estimated median herd mortality incidence 72% and 7%, respectively). The incidence of calf mortality was high among groups induced at all stages of pregnancy that were investigated. However, differences in calf mortality incidence, relative to controls, were increased among groups induced at earlier stages of pregnancy.     

Composition of growth in mice with a major gene for rapid postweaning gain

Previous research from this laboratory identified the existence of a major gene for rapid growth in mice. This trait is expressed as rapid postweaning growth and is inherited as a single recessive gene, designated hg. The hg/hg males and females had greater (P less than .05) body weights at 49-d of age as compared with their Hg/-counterparts; 45.6 +/- .64 and 34.0 +/- .64 vs 33.2 +/- .23 and 27.3 +/- .15 g, respectively. Twenty-four male littermate pairs (hg/hg and Hg/-) were euthanized at 49 d of age for determination of carcass composition. Percentage body water was not affected by genotype (hg/hg, 66.7 +/- .5; Hg/-, 67.8 +/- .3). However, there was a decrease (P less than .05) in percentage body protein (20.2 +/- .1 vs 20.8 +/- .1) and body ash (3.4 +/- .01 vs 3.7 +/- .01) in hg/hg males as compared with Hg/- males, while percentage lipid was significantly increased in hg/hg males (8.7 +/- .5 vs 6.7 +/- .3). When carcass weights were adjusted for differences in dry weight, only body protein was significantly affected by genotype, being greater for hg/hg males (8.54 +/- .19 vs 7.70 +/- .19 g). All other components of body composition were not affected by genotype. The regression coefficient for the covariate of dry weight was significantly different from zero for all carcass components. However, there was no significant difference in the regression coefficient between Hg/- and hg/hg males for each component.(ABSTRACT TRUNCATED AT 250 WORDS)     

Determination of growth loss of Pinus taeda L. caused by Heterobasidion annosus (Fr.) Bref.

The root system of 350 loblolly pine trees in 14 plots were excavated utilizing a bulldozer and evaluated according to the annosus root rot (Heterobasidion annosus) symptom expression of the roots, i. e. resin soaked and stringy. The annual increments of the healthy (<1% colonized) and diseased (<1% colonized) groups of trees were compared for each of the last five years growth. There was a significant growth difference between healthy and diseased trees for each of these last five years at about 4% per year or about 19% for the five year total.