一种改进的多学习教与学优化算法

针对传统教与学算法在解决复杂多峰函数优化问题时,具有局部最优且搜索开发能力较差的缺点,提出了一种改进的多学习教与学优化算法,新算法为学员的每一维加入不同的教学因子,设计了基于学员均值比较的教师选择策略和向教师及学员学习的多学习策略。基于多个单峰和多峰函数的仿真结果表明,新算法跟传统的、改进的教与学算法相比,在稳定性、寻优精度和收敛速度方面更具优势。     

Prenatal diagnosis of de novo (7;19)(q11.2;q13.3) translocation associated with a thick corpus callosum and Wilms tumor of the kidneys

We present a case of prenatal diagnosis of a de novo (7;19)(q11.2;q13.3) translocation associated with ultrasound features, including enlarged cisterna magna, normal vermis, thick corpus callosum, micrognathia, small and low-set ears and right hyperechogenic kidney. Karyotyping was performed at 24 weeks of gestation. Termination of pregnancy was accepted at the parents' request. Postmortem examination confirmed the prenatal findings, but revealed bilateral Wilms tumors of the kidneys. Parental karyotype was normal. Copyright © 2005 John Wiley & Sons, Ltd.     

Consequences for Protaphorura armata (Collembola: Onychiuridae) following exposure to genetically modified Bacillus thuringiensis (Bt) maize and non-Bt maize

Studies on the effect of genetically modified Bacillus thuringiensis (Bt) crops on true soil dwelling non-target arthropods are scarce. The objective of this study was to assess the influence of a 4-week exposure to two Bt maize varieties (Cry1Ab) Cascade and MEB307 on the collembolan Protaphorura armata. For comparison three non-Bt maize varieties, Rivaldo (isogenic to Cascade), Monumental (isogenic to MEB307) and DK242, and two control diets based on baker's yeast (uncontaminated and contaminated with Bt toxin Cry1Ab) were also tested. Due to a lower C:N ratio, individuals reared on yeast performed significantly better in all of the measured endpoints than those reared on maize. P. armata performed equally well when reared on two Bt and three non-Bt maize varieties. Although there were no negative effects of Bt maize in this experiment, we recommend future studies on Bt crops to focus on species interactions in long-term, multi-species experiments.     

Three lessons for gender equity in biodiversity conservation

Amid a growing global agenda, biodiversity conservation has embraced gender equity as a pillar of equitable and effective practice. Gender equity has become enshrined in the global environment and development agenda through global commitments, policy and funding. However, for various reasons, conservation biodiversity often takes a simplistic view of gender as synonymous with women or as a dualism between women and men. This narrow view risks promoting inequitable processes and ineffective outcomes. Deeper engagement with feminist theory, and feminist political ecology in particular, could help advance biodiversity conservation's approach to how gender is understood, framed and integrated. Engaging with lessons from feminist political ecology can help advance gender equity in conservation through attention to power dynamics, intersectionality, and subjectivity.     

The persistence of chronically accumulated hydrocarbons in the hard shell clam Mercenaria mercenaria

Hard shell clams, Mercenaria mercenaria, from the chronically polluted environment of the Providence River, USA, were transferred to a clean laboratory system located in lower Narragansett Bay, Rhode Island. The hydrocarbon contents of these transplanted clams were monitored for 120 days after transfer. After this period only slight depuration had occurred. A 41.9 g g wet weight^-1 average initial hydrocarbon burden decreased to 29.3 g g^-1, a decrease that became statistically significant (P<0.1) only after 120 days. At most, only 30% of the clams' hydrocarbons were lost. These findings indicate that the duration of the exposure period and the chemical nature of the source hydrocarbons are both instrumental in determining the persistence of these compounds in filter-feeding bivalves. Chronically accumulated petroleum hydrocarbons are strongly retained by the organisms and are only very slowly depurated.     

Studies on the digestive lipase of the surf clam Spisula solidissima

Crude molluscan lipase was prepared by homogenizing in tris buffer either fresh or lyophilized crystalline styles of Spisula solidissima. Both preparations showed specific activities less than 2% of standard hog pancreatic lipase, and pH and temperature optima of 8.0 and 20°C, respectively. When compared with mammalian hog pancreatic lipase, the clam lipase was found to be the more versatile enzyme on primary wax esters as well as methyl esters. Neither lipase was capable of hydrolyzing the oleate or palmitate esters of the secondary alcohols of glycerol, cholesterol or isopropyl alcohol; however, both showed activity on the oleate ester of isobutyl alcohol, a primary alcohol. S. solidissima lipase, hog pancreatic lipase, and a lipase isolated from the pancreas of the skate Raja erinacea, all demonstrated an inability to hydrolyze the methyl esters of eicosatetraenoic, eicosapentaenoic and docosahexaenoic acids. The lipase-resistant polyunsaturated fatty acid esters are discussed in terms of their role in the lipid biochemistry of marine organisms.     

Uptake and depuration of organic contaminants by blue mussels (Mytilus edulis) exposed to environmentally contaminated sediment

Experiments were designed to expose blue mussels (Mytilus edulis) to contaminated sediment collected from Narragansett Bay, Rhode Island, USA in 1982. Measurements were taken to allow comparisons of the uptake and depuration of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). In addition, concentration factors in the mussels were calculated separately against the dissolved and particulate phase concentrations and the results from the exposure and control systems were compared. Both PAHs and PCBs were rapidly accumulated by the mussels exposed to the contaminated sediment. After the mussels were transferred to control seawater, individual PAHs were depurated with half-lives ranging from 12 to 30 d. Individual PCBs showed depuration half-lives which ranged from 16 to 46 d. Concentration factors in the mussels calculated against the particulate phase concentrations were very different in the exposure and control systems. Concentration factors calculated using only the dissolved phase concentrations (bioconcentration factors) showed excellent agreement in the two systems, possibly an indication that the dissolved phase was the direct source of the contaminants accumulated by the mussels. The bioconcentration factors for PCBs were higher than those of PAHs when compounds with similar n-octanol/water partition coefficients were compared.