Mantle seismic structure beneath the MELT region of the east pacific rise from P and S wave tomography

Relative travel time delays of teleseismic P and S waves, recorded during the Mantle Electromagnetic and Tomography (MELT) Experiment, have been inverted tomographically for upper-mantle structure beneath the southern East Pacific Rise. A broad zone of low seismic velocities extends beneath the rise to depths of about 200 kilometers and is centered to the west of the spreading center. The magnitudes of the P and S wave anomalies require the presence of retained mantle melt; the melt fraction near the rise exceeds the fraction 300 kilometers off axis by as little as 1%. Seismic anisotropy, induced by mantle flow, is evident in the P wave delays at near-vertical incidence and is consistent with a half-width of mantle upwelling of about 100 km.     

Effect of competition between Vicia faba and Camelina sativa as a model weed in breeding for organic conditions

Weeds can have a detrimental effect on faba bean (Vicia faba) crops in organic farming. Breeding for competitive cultivars is one option for weed control in organic conditions. The aim of this study was to analyse the impact of heterozygosity and heterogeneity levels and plant height on the competitive ability of faba bean genotypes. A set of 24 genotypes, classified as genotype groups (eight inbred lines, eight polycross progenies, two inbred line bulks, two hybrid bulks and four controls), was tested under two treatments: with and without a model weed. Each group of genotypes was equally composed of tall and short genotypes. The competitive ability of the faba bean genotypes was tested with Camelina sativa (false flax) as the model weed in two German locations over the course of 2 years. Yield loss due to weed competition, as recorded per faba bean genotype, was mainly dependent on the heterozygosity level of the genotypes; hybrid bulks were the most competitive genotype group with an average loss of yield of only 6%, whereas the inbred lines were the least competitive genotype group and recorded an average yield loss of 35%. Within the genotype group, no correlations were found between either the yield performance of the genotypes or their plant height and their competitive responses. The competitive ability of faba bean against weeds was mainly determined by their level of heterozygosity; thus, highly heterozygous cultivars should be promoted for breeding.     

Effects of dietary zinc and iron supplementation on mineral excretion, body composition, and mineral status of nursery pigs

Two experiments were conducted to evaluate the effects of dietary Zn and Fe supplementation on mineral excretion, body composition, and mineral status of nursery pigs. In Exp. 1 (n = 24; 6.5 kg; 16 to 20 d of age) and 2 (n = 24; 7.2 kg; 19 to 21 d of age), littermate crossbred barrows were weaned and allotted randomly by BW, within litter, to dietary treatments and housed individually in stainless steel pens. In Exp. 1, Phases 1 (d 0 to 7) and 2 (d 7 to 14) diets (as-fed basis) were: 1) NC (negative control, no added Zn source); 2) ZnO (NC + 2,000 mg/kg as Zn oxide); and 3) ZnM (NC + 2,000 mg/kg as Zn Met). In Exp. 2, diets for each phase (Phase 1 = d 0 to 7; Phase 2 = d 7 to 21; Phase 3 = d 21 to 35) were the basal diet supplemented with 0, 25, 50, 100, and 150 mg/kg Fe (as-fed basis) as ferrous sulfate. Orts, feces, and urine were collected daily in Exp. 1; whereas pigs had a 4-d adjustment period followed by a 3-d total collection period (Period 1 = d 5 to 7; Period 2 = d 12 to 14; Period 3 = d 26 to 28) during each phase in Exp. 2. Blood samples were obtained from pigs on d 0, 7, and 14 in Exp. 1 and d 0, 7, 21, and 35 in Exp. 2 to determine hemoglobin (Hb), hematocrit (Hct), and plasma Cu, (PCu), Fe (PFe), and Zn (PZn). Pigs in Exp. 1 were killed at d 14 (mean BW = 8.7 kg) to determine whole-body, liver, and kidney mineral concentrations. There were no differences in growth performance in Exp. 1 or 2. In Exp. 1, pigs fed ZnO or ZnM diets had greater (P < 0.001) dietary Zn intake during the 14-d study and greater fecal Zn excretion during Phase 2 compared with pigs fed the NC diet. Pigs fed 2,000 mg/kg, regardless of Zn source, had greater (P < 0.010) PZn on d 7 and 14 than pigs fed the NC diet. Whole-body Zn, liver Fe and Zn, and kidney Cu concentrations were greater (P < 0.010), whereas kidney Fe and Zn concentrations were less (P < 0.010) in pigs fed pharmacological Zn diets than pigs fed the NC diet. In Exp. 2, dietary Fe supplementation tended to increase (linear, P = 0.075) dietary DMI, resulting in a linear increase (P < 0.050) in dietary Fe, Cu, Mg, Mn, P, and Zn intake. Subsequently, a linear increase (P < 0.010) in fecal Fe and Zn excretion was observed. Increasing dietary Fe resulted in a linear increase in Hb, Hct, and PFe on d 21 (P < 0.050) and 35 (P < 0.010). Results suggest that dietary Zn or Fe additions increase mineral status of nursery pigs. Once tissue mineral stores are loaded, dietary minerals in excess of the body's requirement are excreted.     

Ultrasonic shear wave velocities of MgSiO3 perovskite at 8 GPa and 800 K and lower mantle composition

Ultrasonic interferometric measurements of the shear elastic properties of MgSiO3 perovskite were conducted on three polycrystalline specimens at conditions up to pressures of 8 gigapascals and temperatures of 800 kelvin. The acoustic measurements produced the pressure (P) and temperature (T) derivatives of the shear modulus (G), namely ( partial differentialG/ partial differentialP)T = 1.8 +/- 0.4 and ( partial differentialG/ partial differentialT)P = -2.9 +/- 0.3 x 10(-2) gigapascals per kelvin. Combining these derivatives with the derivatives that were measured for the bulk modulus and thermal expansion of MgSiO3 perovskite provided data that suggest lower mantle compositions between pyrolite and C1 carbonaceous chondrite and a lower mantle potential temperature of 1500 +/- 200 kelvin.     

Yield Stability in Faba Bean,Vicia faba L. 1. Variation Among Inbred Lines*

Cultivation of faba beans (Vicia faba L.) is hampered by poor yield stability. The genetic variation at the homozygous level for yield stability in the gene pool of the small-seeded and indeterminate European faba beans and the usefulness of auxiliary traits for the improvement of yield stability were investigated. The concept of stability, based on the regression technique, was applied. A sample of 36 faba bean lines was tested in 16 environments and a subsample of eight lines was tested in 11 additional environments. Significant differences were found between lines for yield stability parameters, but the repeatability of the results was limited. Early maturity correlated markedly (r = 0.51^**) with one of the yield stability parameters (deviation from regression). Although lodging resistance was not correlated with the stability parameters, it proved to be a safety factor for performance.     

Yield Stability in Faba Bean,Vicia faba L. 2. Effects of Heterozygosity and Heterogeneity*

In order to evaluate the effects of heterogeneity and heterozygosity on yield stability in faba beans, genotypes were generated with contrasting population structures, differing only in their levels of heterogeneity and heterozygosity. All entries were based on either eight or 36 inbred lines, respectively. The population structures tested consisted of pure stands of the inbred lines (1) and of their F₁,-hybrids (2), blends of the inbred lines (3) and of their F₁ hybrids (4), four-component synthetics in different Syngenerations (5), the open-pollinated source varieties (6) and 36 polycross progenies (7). Five different entry sets (= data sets), each covering several of the seven population structures listed, were grown during 1986 to 1991 in at least four different environments in Western Germany and tested for yield. Stability parameters, i.e., the regression coefficient and deviation from regression (EBERHART and RUSSELL 1966), and the ecovalence (WRICKE 1962), revealed that yield stability of the different population structures was improved by increasing heterozygosity as well as heterogeneity. But the impact of both factors of diversity on yield stability varied between the different data sets. Positive effects of both factors on yield stability seemed to be additively combined in the hybrid blends (data set I). The same proved to be partly true for the four different Syn-generations of the nine synthetics tested. Yield advantage of the different heterozygous variety structures over the homozygous ones in creased with increasing yield level at test sites, as indicated by regression coefficients larger than 1.