Memory for the spatial layout of the everyday physical environment: Factors affecting rate of acquisition

That a memory representation of the spatial layout of a large-scale environment may be acquired very fast was shown in two experiments in which subjects (48 undergraduates and high-school students) were taken on tours through a residential area with which they were unfamiliar. Memory for the path traversed was almost perfect after the first trial, as indicated by almost perfect recall of the order in which a number of designated landmarks had been passed. Memory for the locations of the same landmarks appeared to reach an asymptotic level after the second of three trials. The memory representation of the locations were however not perfectly accurate, thus the asymptotic level might have been an acquisition plateau. The rate of acquisition was slightly faster for subjects driven in a car slowly through the area than for those who walked the same path. Men tended to improve slightly faster than women if they were driven by car but there were no other sex differences. Finally, the acquired memory representation appeared to be resistant to forgetting. Re-learning after a one-week retention interval was faster and rate of learning was not negatively affected whether the trials were massed or distributed with one week in between. The results are discussed in terms of hypotheses concerning the order in which different types of information about spatial layouts (landmarks, paths, and locations) are acquired. The bearing of the results on the question of why memory representations of the spatial layout are often found to be distorted is also discussed.     

Foreign direct investment and institutional obstacles: The case of Russian forestry

This article examines why, in spite of vast forest resources, Russia has been unable to attract foreign investors into its forest industry. A survey of 32 influential Western European forest companies indicates that purely economic factors, such as labour or raw material costs, are not the main reasons these companies refrain from investing. Instead, the companies identify a number of institutional factors: ambiguous legal systems; difficulties in negotiating with local authorities; unfair tax enforcement; and general political instability as the main impediments to FDI in the sector. These factors have led many companies to abandon previously considered investments in Russia, and also to terminate existing business relationships with Russian partners. The survey results also indicate that, while many investors in forestry were attracted by the potential for a growing Russian market in the early days of the transition period, they have become more and more aware of the many institutional obstacles challenging growth in the sector. The article concludes, therefore, that FDI in the Russian forestry sector is likely to remain low until a fundamental change takes place in the legal and political systems.     

Transport and biodegradation of creosote compounds in clayey till, a field experiment

The transport and biodegradation of 12 organic compounds (toluene, phenol, o-cresol, 2,6-, 3,5-dimethylphenol, naphthalene, 1-methylnaphthalene, benzothiophene, dibenzofuran, indole, acridine, and quinoline) were studied at a field site located on the island of Funen, Denmark, where a clayey till 10–15 m deep overlies a sandy aquifer. The upper 4.8 m of till is highly fractured and the upper 2.5 m contains numerous root and worm holes. A 1.5–2 m thick sand lens is encountered within the till at a depth of 4.8 m. Sampling points were installed at depths of 2.5 m, 4 m, and in the sand lens (5.5 m) to monitor the downward migration of a chloride tracer and the organic compounds. Water containing organic compounds and chloride was infiltrated into a 4 m×4.8 m basin at a rate of 8.8 m³ day⁻¹ for 7 days. The mass of naphthalene relative to chloride was 0.39–0.98 for the sampling points located at a depth of 2.5 m, 0.11–0.61 for the sampling points located at a depth of 4 m, and 0–0.02 for the sampling points located in the sand lens. A similar pattern was observed for eight organic compounds for which reliable results were obtained (toluene, phenol, o-cresol, 2,6-, 3,5-dimethylphenol, 1-methylnaphthalene, benzothiophene, and quinoline). This shows that the organic compounds were attenuated during the downward migration through the till despite the high infiltration rate. The attenuation process may be attributed to biodegradation.     

Ecology,evolution, and management strategies of northern pike populations in the Baltic Sea

Baltic Sea populations of the northern pike (Esox lucius) have declined since the 1990s, and they face additional challenges due to ongoing climate change. Pike in the Baltic Sea spawn either in coastal bays or in freshwater streams and wetlands. Pike recruited in freshwater have been found to make up about 50 % of coastal pike stocks and to show natal homing, thus limiting gene flow among closely located spawning sites. Due to natal homing, sub-populations appear to be locally adapted to their freshwater recruitment environments. Management actions should therefore not involve mixing of individuals originating from different sub-populations. We offer two suggestions complying with this advice: (i) productivity of extant freshwater spawning populations can be boosted by modifying wetlands such that they promote spawning and recruitment; and (ii) new sub-populations that spawn in brackish water can potentially be created by transferring fry and imprinting them on seemingly suitable spawning environments.     

基于层次分析法的城市河流生态修复评估

城市的发展改变了许多河流的自然水文环境,并导致河流生态系统中水质、物理生境和生物完整性下降。评估受损河流水体修复的效果,需要结合物理、化学的参数,以及对生物结构、多样性和过程的影响。构建了包含河流水力、水质、水生生物、河岸带及物理结构5个方面15个指标的城市河流生态修复评估指标体系,运用群组决策的层次分析法(AHP),确定了各指标的权重,重要性排序前5位依次为：水质污染指数、鱼类IBI、水源补给量、藻类多样性、透明度。并以我国南方城市岐江河整治修复状况为例进行综合评价,结果表明,河流生态系统修复评估结果为可以接受,体现了河流整治工程使河流水质、生态的状况有所改善,但河流生态系统恢复需要较长的周期,修复初期生态系统仍处于受损状态。〖     

Symptoms and Clinical Findings From the Musculoskeletal System Among Operators at a Call Centre in Sweden—A 10-Month Follow-Up Study

The musculoskeletal health among 57 operators at 1 call centre in Sweden was studied with 10 monthly follow-ups, parallel to a reference group of 1,226 professional computer users in other occupations. Operators at this call centre were more symptom-loaded than the other professional computer users in spite of their younger age and shorter exposure to computer work. Symptoms were long-lasting or recurrent. Muscle tenderness and nerve affections in the neck- shoulder region were the most common specific findings and diagnoses at medical examination of incident symptom cases. More extensive studies should be done on the working conditions and health status among call centre workers.     

Effects of enhanced UVB radiation on a marine benthic diatom mat

In order to study the ecophysiological response of a natural diatom-dominated microbial mat to an enhanced level of ultraviolet-B radiation (UVBR), intact sediment cores from a shallow microtidal bay on the Swedish west coast were incubated in an outdoor flow-through system and exposed to either no UVBR or to an artificially enhanced level of UVBR. The microbial mat was cohesive and dominated by the large (≈ 400 μm) motile diatom Gyrosigma balticum. Functional response to UVBR was assessed by measuring carbon fixation (¹⁴C) and allocation of photosynthetic products. Sediment oxygen microprofiles were measured as indicators of the balance between the photosynthetic and respiratory activity of the community. Structural variables included biomass and composition of microalgae, pigment composition (HPLC), content of UV-absorbing compounds, and composition of fatty acids. An enhanced level of UVBR resulted in significant functional changes in the microalgal community. Significantly decreased carbon fixation and lower net oxygen production (as calculated from oxygen microprofiles) suggest that primary productivity in the type of microbial mat studied is potentially sensitive to an enhanced level of UVBR. The pattern of carbon allocation hinted a change as to the photosynthetically active part of the community when exposed to UVBR, indicating a differential sensitivity among algal cells. Despite significant functional effects, pigment or algal composition were not significantly affected by enhanced UVBR. The concentration of UV-absorbing compounds was low and did not increase at UVBR exposure. Due to the short duration of the experiment (4 d), a change in algal biomass or composition was not to be expected. Moreover, the thickness of the sampled sediment layer, may have contributed to the lack of observed structural effects of enhanced UVBR. Visual observations suggested that UVBR affected the motility of G. balticum. This study, as well as other experiments with a similar diatom mat, suggest that vertical migration is a key mechanism to be further studied in relation to UVBR exposure of diatom-dominated microbial mats. Received: 7 September 1996 / Accepted: 8 October 1996