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。     

Future Climate in the Yellowstone National Park Region and Its Potential Impact on Vegetation

Biotic responses to future changes in global climate are difficult to project for a particular region because the responses involve processes that operate at many spatial scales. This difficulty is exacerbated in mountainous regions, where future vegetation changes are often portrayed as simple upward displacements of vegetation zones in response to warming. We examine the scope of future responses that may occur in a mountainous area by illustrating the potential distributions of selected tree taxa in the region of Yellowstone National Park. The output of a coarse-resolution climate model that incorporated a doubling of carbon dioxide concentration in the atmosphere was interpolated onto a 5-minute grid of topographically adjusted climate data. The output was also used as input into statistical relationships between the occurrence of individual taxa and climate. The simulated vegetation changes include a combination of elevational and directional range adjustments. The range of high-elevation species decreases, and some species become regionally extirpated. The new communities have no analogue in the present-day vegetation because they mix low-elevation montane species currently in the region with extralocal species from the northern and central Rocky Mountains and Pacific Northwest. The projected climate changes within the Yellowstone region and the individualism displayed by species in their potential range adjustments are equal or greater than the changes seen in the paleoecologic record during previous warming intervals. Although the results support conservation strategies that include habitat connectivity, the magnitude of the changes may exceed the ability of species to adjust their ranges. The predicted patterns call into question the adequacy of current management objectives to cope with the scope of future changes.     

Female mate choice in the zebra finch — the effect of male beak colour and male song

Studies of female mate preference in zebra finches (Taenopygia guttata) have shown that male beak colour and song rate are important. However, the two characters are correlated. Here the effect of beak colour and song rate on female choice are examined independently. In mate choice tests involving two males, beak colour was manipulated artificially using nail varnish. The results showed that females showed a significant preference for males with a high song rate, but not with a red beak. Females did not prefer males with a red beak if song rate was low and females preferred males with orange beaks who expressed a high song rate. Female preference for males with red beaks was not found when beak and song characters were no longer correlated.     

Semicontinuous PM2.5 sulfate and nitrate measurements at an urban and a rural location in New York: PMTACS-NY summer 2001 and 2002 campaigns

Several collocated semicontinuous instruments measuring particulate matter with particle sizes < or =2.5 microm (PM2.5) sulfate (SO4(2-)) and nitrate (NO3-) were intercompared during two intensive field campaigns as part of the PM2.5 Technology Assessment and Characterization Study. The summer 2001 urban campaign in Queens, NY, and the summer 2002 rural campaign in upstate New York (Whiteface Mountain) hosted an operation of an Aerosol Mass Spectrometer, Ambient Particulate Sulfate and Nitrate Monitors, a Continuous Ambient Sulfate Monitor, and a Particle-Into-Liquid Sampler with Ion Chromatographs (PILS-IC). These instruments provided near real-time particulate SO4(2-) and NO3- mass concentration data, allowing the study of particulate SO4(2-)/NO3- diurnal patterns and detection of short-term events. Typical particulate SO4(2-) concentrations were comparable at both sites (ranging from 0 to 20 microg/m3), while ambient urban particulate NO3- concentrations ranged from 0 to 11 microg/m3 and rural NO3- concentration was typically less than 1 microg/m3. Results of the intercomparisons of the semicontinuous measurements are presented, as are results of the comparisons between the semicontinuous and time-integrated filter-based measurements. The comparisons at both sites, in most cases, indicated similar performance characteristics. In addition, charge balance calculations, based on major soluble ionic components of atmospheric aerosol from the PILS-IC and the filter measurements, indicated slightly acidic aerosol at both locations.     

Evaluation of pesticides and metals in fish of the Dniester River, Moldova

The Dniester River is one of the largest rivers in Eastern Europe and receives input from numerous anthropogenic activities. In October 2001, fish samples (Abramis brama, Rutilus rutilus heckeli, Perca fluviatilis, Chondrostoma nasus, Carassius auratus gibelio, and Cyprinus carpio) were collected and analyzed for metals and various pesticides. Maximum total DDT pesticide concentrations were between 27.7 and 34.2 ng/g wet weight in muscles and gonads, respectively. DDE isomers comprised up to 70% of total DDT measurement in fish tissues, indicating historical rather than recent DDT pollution. Chlordane and lindane were also detected in amounts up to 37 and 76 ng/g wet weight in gonads, respectively. Among organophosphorous pesticides, malathion showed extremely high concentrations--3 microg/g wet weight in muscles and 46 microg/g wet weight in gonads, indicating recent exposure. Copper concentrations in muscles (1.8-7.2 microg/g) exceeded Threshold Effect Concentrations for copper in fish. Detection of high concentrations of malathion and copper in fish tissues indicated potential anthropogenic stress for more sensitive aquatic biota, likely from agricultural sources in the Dniester River.     

Carotenoid-based status signalling in red-shouldered widowbirds (<Emphasis Type="Italic">Euplectes axillaris</Emphasis>): epaulet size and redness affect captive and territorial competition

In breeding plumage, the African male red-shouldered widowbirds (Euplectes axillaris) are black except for red carotenoid-based epaulets ('shoulder patches'), similar to the well-studied American red-winged blackbirds (Agelaius phoeniceus). To experimentally test the signal function of the red epaulets in male red-shouldered widowbirds, we manipulated epaulet colour and size (within natural variation), and observed the effects in two competitive contexts. First, in captivity, unfamiliar males with epaulets of different size or redness were staged in dyadic contests over food. Only epaulet manipulations significantly affected contest outcome; red epaulet males out-competed orange and control males, which in turn dominated blackened (no epaulet) males. Epaulet size manipulations had particularly strong effects; enlarged epaulet males vigorously defeated smaller epaulet males within colour treatments, whereas the independent effect of 'redness' (i.e., within size treatments) was much weaker. Second, in a field experiment, epaulets were manipulated prior to territory establishment. Males with enlarged epaulets acquired territories, whereas most males with blackened or reduced signals failed to obtain territories. Furthermore, among the territorial males, birds with enlarged epaulets defended larger territories and spent less time in boundary signalling, yet they received fewer intrusions from conspecifics. In contrast, epaulet manipulations had no effect on either female visitation rates or subsequent female settlement. These results concur with recent studies and suggest that the carotenoid-based epaulets of red-shouldered widowbirds are status signals, sexually selected through male contest competition for territories.     

Waterbird Communities and Habitat Relationships in Coastal Pastures of Northern California

We examined waterbird assemblages (diversity, composition, and species' densities) in 20 pastures near Humboldt Bay, California, in relation to habitat characteristics (vegetation height, soil penetrability, water depth), abundance of invertebrates (worms and other invertebrates), and presence of livestock. From October 1991 to May 1992 we observed 29 species and 10,776 birds, most (78%) of which foraged. Nonrandom pasture use by birds resulted in a highly clumped spatial distribution (s²:{ovbar>x} ratio = 42.1). Habitat characteristics of pastures correlated with this nonrandom pattern: waterbird diversity and densities of three sandpiper species and one gull species correlated negatively ( r = −0.61 and r = −0.44 to −0.67, respectively) with vegetation height; densities of two plover species correlated negatively ( r = −0.39 and −0.45) with soil penetrability; and waterfowl densities correlated positively with water depth ( r = 0.97). Species composition varied among pastures. Wading birds used pastures with tall vegetation, shorebirds and gulls frequented short-grass pastures, and waterfowl used flooded pastures of waterbirds and their densities increased in association with livestock.In coastal areas where much intertidal habitat has been reclaimed as postureland, pastures offered valuable habitats to nonbreeding waterbirds. We suggest that grazing in coastal pastures can be used to provide a mosaic of vegetation heights, which would yield greater waterbird diversity as well as higher densities of some species.     

Grief and mid-trimester fetal loss

Fetal loss through miscarriage or termination of pregnancy for genetic reasons often provokes the grief of bereavement. This is not fully understood, and the extent of the distress is often underestimated by professionals and family alike. We have examined elements of the normal bereavement process and have found that they may occur in specific and accentuated forms in mid-trimester fetal loss. We discuss our findings in the light of the attachment theory—a psychodynamic model for understanding grief reactions.     

The accumulation of a chemical cue: nest-entrance trail in the German yellowjacket, Vespula germanica

Vespine wasps have been shown to deposit an attractive chemical in the nest entrance. Foragers use this to help locate the nest when returning to it. We determined how many individuals need to track (pass through) the entrance before the chemical is recognized. We found a logistic response as the number of tracks increased. At 200 tracks and above there was a 75–90% positive response rate to the chemical. We found no evidence of trail-marking behavior performed by foragers inside the nest entrance. We conclude that the trail is not an evolved signal, but is a cue composed of an accumulation of hydrocarbons deposited from the legs or feet of workers as they walk on a substrate. This is the first quantitative measurement of the attractiveness of the nest-entrance chemical in a social wasp.