Opposite effects of maternal and paternal grandmothers on infant survival in historical Krummhörn

On the basis of church register entries from the Krummhörn region (Ostfriesland, Germany, 1720-1874) we looked at whether the existence of grandmothers had an impact on the reproductive success of a family. We found that fertility measured by parity progression ratios was influenced by grandmothers, though only in exceptionally large families, while fertility measured by intervals between births was not influenced by grandmothers. However, maternal grandmothers reduced infant mortality when the children were between 6 and 12 months of age. During these 6 months, the relative risk of dying was approximately 1.8 times higher if the maternal grandmother was dead at the time of the child's birth compared to if she was alive. Interestingly, the existence of paternal grandmothers approximately doubled the relative risk of infant mortality during the 1st month of life. We interpret this as being the result of a tense relationship between mother- and daughter-in-laws. We found that Krummhörn grandmothers could be both helpful and a hindrance at the same time. Geographic proximity increased the effects found. If this ambivalent impact of grandmothers on familial reproduction could be generalized beyond the Krummhörn population, the hypothesis that the evolution of the postgenerative life span could be explained by grandmotherly kin-effects would have to be stated more precisely: the costs of social stress in the male descendency would have to be subtracted from the benefits of aid and assistance in the female descendency.     

Age-related foetal sex ratio bias in Iberian red deer (<Emphasis Type="Italic">Cervus elaphus hispanicus</Emphasis>): are male calves too expensive for growing mothers?

Several theories predict offspring biases towards males or females with increasing reproductive resources of the mother to maximize reproductive returns by offspring, or as a result of prohibitive cost of the most expensive sex for young mothers or those in poor condition. This study examines foetus sex of 221 harvested hinds in a food-supplemented game estate for 10 years, according to hind age class (yearlings, subadults or adults), precise age, body mass and condition, and jaw length. A logistic model showed that hinds had a greater probability of bearing a male foetus with increasing age class, but not with any other variable. The greatest bias was found in yearling hinds. After controlling for age class and mass, jaw length was smaller in pregnant compared to non-pregnant yearlings and subadults, which suggests a trade-off between reproduction and growth. The bias towards females in yearlings increased as gestation proceeded, which suggests that the bias might be a result of selective abortion of male foetuses. Although results do not exclude an investment in males to increase number of grand-offspring, they suggest that young hinds may produce daughters as a trade-off between low energetic-cost offspring and their need to grow.Communicated by S. Krackow     

Female pied flycatchers Ficedula hypoleuca choose male characteristics in homogeneous habitats

Summary The paper reports the results of a 2-year study of pairing success of male pied flycatchers in a homogeneous habitat. A handicapping experiment was carried out in which certain wing and tail feathers were removed from randomly selected males. Handicapped males had reduced pairing success, they lost weight, and they sang less frequently than control males. Male pairing success was positively correlated with the darkness of the plumage, body-size, and previous breeding experience. Earlier studies on the same species have failed to detect any relationships between pairing success and male characteristics, possibly because of habitat heterogeneity and variation in nest site quality. The evolutionary basis for female choice of male characteristics is discussed. There are reports that males with attractive traits (e.g. black plumage) provide a high quality of parental care. However, the fact that male pairing success was related to male conspicuousness makes it difficult to discriminate between active and passive female choice.     

The Impact of the Hyperacid Ijen Crater Lake. Part II: A Total Diet Study

In Asembagus (East Java, Indonesia), surface water is contaminated with effluent from the hyperacid Ijen Crater Lake. In a previous study, we reported that food crops irrigated with this water had increased concentrations of various elements. Here, we present a total diet study for adults and 6-year-old children to determine if the mean daily intake of a broad range of elements is safe and adequate. For children, the intake of B, Mg, Mn and V is high with Hazard Quotients (HQ) of 1.1 (B), 1.4 (Mn) and 1.4 (V), respectively (no TDI is available for Mg). For Mn, the daily intake is high due to the consumption of locally produced rice. Drinking water is the main source of B, Mg and V. For adults, the intake of Mg, Mn and V is also high but HQ values are ≤0.7. For both children and adults, the intake of Ca, Zn and particularly Fe is below the RNI (Fe intake is 90% below the RNI for women). It is concluded the mean intake of elements is unbalanced and Fe deficiency is probably the most serious health problem. Toxic effects cannot be fully excluded since deficiency of essential elements such as Ca, Fe and Zn can increase the absorption and retention of various elements.     

电偶极辐射场的另一种计算方法

研究电偶极辐射问题的出发点是推迟势公式,本文先用格林函数法求解达朗贝尔方程组,得出推迟势公式;再用特殊函数理论对推迟势公式作展开,得出电偶极辐射场,并对远场和近场分别进行讨论。这种计算方法既能对电偶极辐射问题有一个较全面而且准确的认识,又能将数学思想与物理理论相结合,做到学以自用,融会贯通。