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111.
The Euroconference on Coastal Management Research held in San-Feliu de Guixols, Spain, in December 1997 brought together scientists
from a great variety of disciplines in the natural and social sciences, in a search for modes of transdisciplinary cooperation
in the context of integrated coastal management. During the conference the participants discussed which interactions among
disciplines are required for different coastal issues. Discussion groups each focused on a particular type of coastal environment,
characterized by a particular type and degree of development. The group discussions were inspired by background papers which
were prepared for this purpose by invited speakers. A selection of these background papers were redrafted on the basis of
the conference outcome, and are published in this issue of theJournal of Coastal Conservation. The reports of the discussion groups are published in a conference proceedings booklet issued by EMAPS (1998), the European
Polar and Marine Sciences Secretariat. A synthesis of ideas on the challenge of transdisciplinarity, expressed during the
discussion group sessions, is presented in this introduction. The statements reflect opinions or suggestions which received
broad support from the participants; they should not be taken as proven knowledge. 相似文献
112.
By scoring the chromosome number of developing embryos, we show that the sex ratio bias of the African social spider Stegodyphus dumicola Pocock is the result of an overproduction of female embryos. Only 17% of 585 embryos sexed from 14 egg sacs were male, a
significant departure from a 1:1 sex ratio. We also explored the possibility of direct control of the sex of individual offspring
in this species by examining the variance in the number of males per sac and the spatial distribution of male and female embryos
within the sacs. We postulated that a variance in the number of males per sac lower than binomial (i.e., underdispersed or
precise sex ratios) or a non-random distribution of male embryos within the sacs would suggest direct control of the sex of
individual offspring. We found that the variance in the number of males per sac was indistinguishable from binomial and significantly
larger than expected under exact ratios. Likewise, the spatial distribution of male embryos within three sacs examined was
no more clustered than expected by chance. The sex ratio biasing mechanism in this species, therefore, apparently only allows
control of the mean sex ratio but not of its variance. We present randomization and Monte Carlo methods that can be applied
to test for departures from a random spatial arrangement of male and female embryos in an egg mass and for departures from
binomial or exact ratios when not all members of a clutch have been sexed.
Received: 21 October 1998 / Received in revised form: 23 March 1999 / Accepted: 26 April 1999 相似文献
113.
Encounter rate and task allocation in harvester ants 总被引:7,自引:0,他引:7
As conditions change, social insect colonies adjust the numbers of workers engaged in various tasks, such as foraging and
nest work. This process of task allocation operates without central control; individuals respond to simple, local cues. This
study investigates one such cue, the pattern of an ant's interactions with other workers. We examined how an ant's tendency
to perform midden work, carrying objects to and sorting the refuse pile of the colony, is related to the recent history of
the ant's brief antennal contacts, in laboratory colonies of the red harvester ant, Pogonomyrmex barbatus. The probability that an ant performed midden work was related to its recent interactions in two ways. First, the time an
ant spent performing midden work was positively correlated with the number of midden workers that ant had met while it was
away from the midden. Second, ants engaged in a task other than midden work were more likely to begin to do midden work when
their rate of encounter per minute with midden workers was high. Cues based on interaction rate may enable ants to respond
to changes in worker numbers even though ants cannot count or assess total numbers engaged in a task.
Received: 1 July 1998 / Accepted: 15 November 1998 相似文献
114.
Chemical defense and evolutionary trends in biosynthetic capacity among dorid nudibranchs (Mollusca: Gastropoda: Opisthobranchia) 总被引:5,自引:0,他引:5
Summary. An evolutionary scenario incorporating recent advances in phylogenetic research begins with an opisthobranch-pulmonate common
ancestor that was herbivorous and had some diet-derived chemical defense. The Nudibranchia and their closest relatives, the
Notaspidea, form a lineage the ancestors of which had switched to feeding upon sponges and deriving protection from metabolites
contained in them. Subsequently there have been repeated shifts in food and defensive metabolites, and trends are evident
in the ability to detoxify, sequester and utilize metabolites from food, as well as to synthesize defensive compounds de novo. The Notaspidea display a minor adaptive radiation that foreshadows a more extensive one in the various lineages of nudibranchs.
This review emphasizes changes that have occurred within the Holohepatica, or dorid nudibranchs (order Doridacea). Their sister-group,
the Cladohepatica, consists of three other orders, Dendronotacea, Arminacea, and Aeolidiacea, in which there has been a shift
from sponges to Cnidaria as food. The Dendronotacea often feed upon Octocorallia, which combine spicules, chemical defense,
and stinging capsules and thereby suggest a transition from feeding on sponges. A previous diet of Octocorallia is suggested
by the defensive use of prostaglandins in the dendronotacean Tethys fimbria, which eats crustaceans. A shift to bryozoans in some Arminacea is accompanied by use of different metabolites. Dorid nudibranchs
evidently began as sponge-feeders, but some lineages have shifted to a variety of other food organisms, and others have specialized
in the kind of sponges they feed on and how they do it. There have been shifts to bryozoans (Ectoprocta) and ascidians (Chordata:
Urochordata) that track metabolites rather than the taxonomy of the food. There is a crude correlation between the genealogy
and the defensive metabolites of the sponge-feeding dorids. De novo synthesis is well documented in this order and the metabolites are appropriately positioned so as to have an adaptive effect.
The hypothesis that the capacity for de novo synthesis was acquired by gene transfer across lineages is rejected, partly on the basis of different chirality of metabolites
in the nudibranchs and their food organisms. Instead it is proposed that there has been a preadaptive phase followed by evolution
in a retrosynthetic mode, with selection favoring enzymes that enhance the yield of end products that are already present
in the food.
Received 5 February 1999; accepted 26 July 1999 相似文献
115.
Otto Klemm Holger Lange 《Environmental science and pollution research international》1999,6(4):193-199
We analyzed 13 years of hourly measurements of SO2, NOx, and O3, at forest ecosystem research sites in SE Germany. A quasi-continuous data record was obtained by combining data sets from
two locations. Before interpreting trends in the combined data set, we analyzed if the change of location introduced a systematic
bias. We employed autocorrelation functions, Hurst statistics, complexity analysis, and recurrence quantification and found
that the partial data sets exhibited no indication of the presence of any bias. For SO2, we also compared the data from the forest sites with data obtained in nearby cities and also found no indications for any
systematic effects. Applying nonparametric trend statistics we found a significant decrease of the SO2. Most of the observed decrease is due to the reductions of SO2 emissions in eastern Germany, but reductions in western Germany and the Czech Republic also played important roles. For O3, we observed a significant increase, the causes of which are unclear from our data alone. No trend was identified for NOx. 相似文献
116.
为了解台州市市区大气降水化学成分组成特征及变化规律,对2010—2019年台州市市区降水监测数据进行了统计分析。结果表明:2010—2019年降水样品pH为4.20~4.84夏高冬低,强酸性降水频率下降显著,电导率平均值为3.16 mS/cm。SO_4~(2-)和NO_3~-是降水中最主要的阴离子,NH_4~+和Ca~(2+)是降水中最主要的阳离子。Ca~(2+)浓度在2018年开始有所抬升,SO_4~(2-)和NO_3~-浓度整体呈波动下降趋势。SO_4~(2-)与NO_3~-浓度比均值为1.50,呈下降趋势,同大气中SO_2与NO_2的质量浓度比变化趋势基本一致。SO_4~(2-)和NO_3~-相关性显著,Cl~-、Na~+及Mg~(2+)三者之间具有较好相关性。降水与气态污染物相关性不大,对颗粒物有明显冲刷去除作用。SO_2和NO_x的排放量显著下降,酸雨污染呈现改善过程。 相似文献
117.
户外运动服装的开发及发展趋势探析 总被引:2,自引:1,他引:1
马俊淑 《中国个体防护装备》2010,(3):28-31
随着生活方式的多元化发展,户外运动受到越来越多人的关注和喜爱。户外运动用品店如雨后春笋应运而生。因此具有防护功能的户外运动服装特别受到青睐。本文综述了户外运动服装的需求和分类,分析了户外运动服装的结构和功能性设计思路,并论述了未来户外运动服装的发展趋势。 相似文献
118.
ABSTRACTMost scholarly accounts of social licence define it as a public relations strategy to legitimate resource development. In Canadian pipeline politics, however, it has had the opposite effect, crystallizing widespread concerns about industry capture of regulatory processes and affirming the democratic rights of local communities. This assessment of the concept’s critical, counter-hegemonic potential to challenge the policies, practices and logic of state-sponsored extractivist development situates social licence as a key discursive battleground in the struggle between politicization (which accents agonistic confrontation between competing alternative futures) and de-politicization (which defuses conflict and builds consensus around the perception of common interests). Frame analysis of news media and advocacy group texts is used to investigate how opponents of a pipeline project bridged the idea of social licence with movement frames concerning identity, injustice and democratic agency to transform the concept from a public relations term meant to enable corporate activity into a critical trope used to constrain it. 相似文献
119.
Long‐Term Trends of Nutrients and Sediment from the Nontidal Chesapeake Watershed: An Assessment of Progress by River and Season
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Qian Zhang Damian C. Brady Walter R. Boynton William P. Ball 《Journal of the American Water Resources Association》2015,51(6):1534-1555
To assess historical loads of nitrogen (N), phosphorus (P), and suspended sediment (SS) from the nontidal Chesapeake Bay watershed (NTCBW), we analyzed decadal seasonal trends of flow‐normalized loads at the fall‐line of nine major rivers that account for >90% of NTCBW flow. Evaluations of loads by season revealed N, P, and SS load magnitudes have been highest in January‐March and lowest in July‐September, but the temporal trends have followed similar decadal‐scale patterns in all seasons, with notable exceptions. Generally, total N (TN) load has dropped since the late 1980s, but particulate nutrients and SS have risen since the mid‐1990s. The majority of these rises were from Susquehanna River and relate to diminished net trapping at the Conowingo Reservoir. Substantial rises in SS were also observed, however, in other rivers. Moreover, the summed rise in particulate P load from other rivers is of similar magnitude as from Susquehanna. Dissolved nutrient loads have dropped in the upland (Piedmont and above) rivers, but risen in two small rivers in the Coastal Plain affected by lagged groundwater input. In addition, analysis of fractional contributions revealed consistent N trends across the upland watersheds. Finally, total N:total P ratios have declined in most rivers, suggesting the potential for changes in nutrient limitation. Overall, this integrated study of historical data highlights the value of maintaining long‐term monitoring at multiple watershed locations. 相似文献
120.
This study investigated the water quality variation spanning 30 years (1986–2017) in 16 catchments of Hong Kong against different urbanization indices, namely, built area fraction; population; and product of population and built area fraction. Pearson correlations of three different periods of time (1988–1990, 1998–2000, and 2015–2017) indicated that water quality trends were dependent on the urbanization index. Total solids, nitrite-nitrogen, total phosphorus, electrical conductivity, dissolved oxygen, and flow rate had significant deteriorative trends (Pearson r > 0.5 and p < 0.05) with population and product of built area and population. Results also interpreted that built area fraction and product of built area and population were the worst and best indices that represented urbanization and/or its impacts, respectively. Mann-Kendall test for the entire 30 year period showed that water quality had improved with time with respect to certain water quality parameters (e.g., dissolved oxygen, ammoniacal nitrogen and total suspended solids). The results portrayed that although the urbanization of catchments had increased with time, the river water quality with respect to many parameters showed signs of improvement and the legislative measures implemented seemed to be effective in controlling pollution. 相似文献