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Lower Contribution (lower + contribution)
Selected AbstractsA developmental bottleneck in dispersing larvae: implications for spatial population dynamicsECOLOGY LETTERS, Issue 4 2003Daniel W. Schneider Abstract We found evidence for a critical population bottleneck at a developmental-stage transition in larvae of the zebra mussel Dreissena polymorpha Pallas from field estimates of mortality. Identification of this critical period in the field was made possible by closely tracking cohorts of larvae over 5 days of development as they dispersed 128 km in a river system. The presence of a survival bottleneck during development was confirmed in laboratory studies of zebra mussel larvae. Development-specific mortality has important implications for spatial population dynamics of the zebra mussel in particular, and all species with indirect development in general. Marine reserves that do not take development-specific mortality into account may dramatically underestimate reserve size needed to protect rare and/or exploited marine populations. Conversely, for the zebra mussel, the lower contribution of dispersing individuals to population growth downstream of reserves can lead to more feasible control through the blocking of dispersal. [source] A Theoretical Investigation of Substituent Effects on the Absorption and Emission Properties of a Series of Terpyridylplatinum(II) Acetylide ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2005Xiao-Juan Liu Abstract A comprehensive calculational investigation has been carried out on a series of complexes of the type [(terpyridyl-R1)Pt(C,C-R2)], where terpyridyl-R1 is a series of substituted 2,2':6',2"-terpyridyl ligands and C,C-R2 is a series of substituted acetylide ligands. In one series of complexes (I), the energy of the electronic excited state is varied by changing the substituents on the terpyridyl ligand (R1). In a second series of complexes (II), this electronic structure variation is obtained by changing the para substituents (R2) of the acetylide ligand. The effect of varying the substituents on the lowest-energy excited states of the complexes has been assessed by calculating their electronic structures and excitation energies. We anticipated that introduction of electron-withdrawing substituents on the terpyridyl ligand will benefit the LLCT (or MLCT) and prohibit the nonradiative pathways via d-d transitions in these complexes; introduction of electron-donating substituents on the acetylide ligand can also prohibit the nonradiative pathways by increasing the energy gaps between the HOMO,LUMO and d-d transitions. The results also reveal that the lowest-energy excitations of all complexes of series I and IIa,b complexes are dominated by a ,(C,C),,,,*(terp) (LLCT) transition mixed with some energetically d,(Pt),,,terpyridyl (MLCT) transition. However, for the complexes IIc,IId, in which phenyl rings are introduced on the acetylide ligand, the lowest-lying absorptions of IIc and IId are predominately LLCT in character, with less MLCT mixture, due to a lower contribution of the Pt(d) orbital to the HOMO, while for IIe, with a stronger donor on the acetylide, the lowest-lying absorption is completely LLCT in character. The absorption and emission calculations using the TDDFT method are based on the optimized geometries obtained at the B3LYP/LanL2DZ and CIS/LanL2DZ levels, respectively. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Y-chromosome variation in South Iberia: Insights into the North African contributionAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 3 2009Luis Alvarez Population of Pedroches Valley, a hypothetical Berber settlement, located in the northwest portion of Córdoba province (Andalusia, Spain), had been analyzed for its Y-chromosome diversity. Moreover, to contextualize this population, 127 Y-chromosomes from a general Andalusia sample and a North African Berber community (Marrakech, Morocco) were also typed. For all samples, 24 single nucleotide polymorphisms of the non-recombining portion of the Y-chromosome (NRY) were analyzed and those samples described as belonging to E3b1b-M81 haplogroup were also typed for 16 Y-chromosome short tandem repeats. Our Analysis showed low levels of North African E3b1b-M81 haplogroup in the Pedroches Valley population (1.5%), which is a lower contribution than would be expected. This result rejects the hypothesis of a gradual genetic assimilation of Berber settlers during the Islamic period. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc. [source] Exercise capacity and cardiovascular changes in patients with ,-thalassaemia majorCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2006Filippo Tocco Summary Despite the introduction of deferoxamine, 50% of thalassaemia major patients die before the age of 35 years predominantly from iron induced heart failure. Indeed, the assessment of myocardial performance may be of particular interest since it can reveal an early myocardial dysfunction. By using impedance cardiography and mass spectrometry, we studied the cardiac function and the oxygen extraction ratio (O2ER) of 14 thalassaemic patients and 15 control healthy subjects during an incremental cycle-ergometer test. The achieved mechanical power output and the relative O2 uptake did not reach any significant difference between groups. At the highest workload, O2ER reached significantly higher values in thalassaemic patients versus control subjects while the relationship between cardiac index (CI) and O2ER (CI/O2ER) decreased showing a lower contribution of cardiovascular system to maintain O2 uptake. Results of this study imply that CI/O2ER allows an early diagnosis of the iron induced myocardial dysfunction, whereas it is not clinically patent yet. To our knowledge, this is the first study revealing an O2ER pivotal role as compensatory mechanism to maintain a normal working capacity in subjects suffering from thalassaemia major. [source] The Tax Consequences of Long-Run Pension Policy,JOURNAL OF APPLIED CORPORATE FINANCE, Issue 1 2006Fischer Black A firm's pension fund is legally separate from the firm. But because pension benefits are normally independent of fund performance, pension assets impact the firm very much as if they were firm assets. Because they are worth more when times are good and less when times are bad, common stocks in the pension fund add to the sponsoring firm's leverage. They cause contributions to a pension fund to be high just when the firm can least afford to pay them. Conversely, bonds in the pension fund will make it easier for the firm to avoid default on its own bonds when times are bad all over: The more bonds a pension fund buys, the more the firm can borrow. The tax treatment accorded the pension fund differs notably from that accorded the firm. Some have argued that a firm can capitalize on the difference by accelerating the funding of its pension plan. The benefits of full funding are wasted, however, unless the added contributions to the fund are invested in bonds; higher pension contributions now mean lower contributions later, hence higher taxes later. The benefits come from earning, after taxes, the pretax interest rate on the bonds in the pension fund. If the firm wants to take advantage of the differing tax treatment of bonds without altering the level of its current pension contributions, it can (1) sell stocks in the pension fund and then buy bonds with the proceeds while (2) issuing debt in the firm and buying back its own shares with the proceeds. An investment in the firm's own stock creates no more tax liability than an investment in stocks through the pension fund. [source] | ||||||||||