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The diatoms are an ecologically important group of algae that have been extensively studied by ecologists and taxonomists. However, the large-scale patterns of diatom distribution and the factors underlying this distribution are largely unknown. The aims of this study were to identify the large-scale spatial patterns of benthic diatom assemblages in Korean streams and rivers, and to assess the importance of numerous environmental factors on diatom distribution. We classified 720 study sites based on diatom flora. Benthic diatoms, water chemistry, altitude, and riparian land cover and use were characterized by multivariate analyses, Monte Carlo permutation tests, and indicator species analysis. In total, we identified 531 diatom taxa. Diatom assemblages were mostly dominated by species of the genera Achnanthes, Navicula, Nitzschia, Cocconeis, Fragilaria (Synedra included), Cymbella, Gomphonema, and Melosira. Cluster analysis partitioned all 720 sites into eight groups based on diatom species composition. Canonical correspondence analysis indicated that altitude, land cover and use, current velocity, electrical conductivity, and nutrient levels explained a significant amount of the variation in the composition of assemblages of benthic diatoms. At the national scale, a downstream ecological gradient was apparent, from fast-flowing, mostly oligotrophic highland streams to slow-flowing, mostly eutrophic lowland rivers. Our data suggest that spatial factors explain some of the variation in diatom distribution. The present investigation of the spatial patterns of benthic diatoms, the ecological determinants of diatom occurrence, and the identification of diatom indicator species contributes to development of a program for assessing the biological integrity of lotic ecosystems in Korea.
This study investigated the relationships of three major aquatic assemblages (diatom, macroinvertebrate, and fish) and environmental variables, including sub-basin, hydrology, land cover, and water quality variables on multiple scales. Samples were collected at 720 sampling sites on the Korean nationwide scale. Geological variables, including altitude and slope, showed a strong positive correlation with proportions of forest in land cover types and cobbles in substrates, while they were negatively correlated with water quality variables, including conductivity and total phosphorus. Considering the concordance of the different assemblages, species richness of fish and macroinvertebrates displayed significant correlation, and diatoms were significantly correlated with fish. However, diatoms did not show significant correlation with macroinvertebrates. Altitude and slope showed significant correlation with all biological variables of the three assemblages. Macroinvertebrates and fish showed positive relations with large substrate sizes. Indices of diatoms and macroinvertebrates well reflected the perturbation of water quality variables. However, fish indices showed a relatively low association with water quality variables, compared with those of diatoms and macroinvertebrates. These patterns were also confirmed by the ordination and prediction of biological indices with environmental variables through the learning process of a self-organizing map as well as random forest. Overall, our study supports the concept of multi-scale habitat filters and functional organization in streams, and is consistent with the recommended use of multiple biological indices with more than one assemblage for the assessment of the biotic integrity of aquatic ecosystems.
Anthropogenic land use within watersheds has substantial effects on aquatic habitats and biological communities. From September 2006 to December 2008, we investigated the effects of land use on benthic macroinvertebrate communities by comparing Song Stream and Odae Stream, two adjacent mountain streams in Korea whose watersheds have different land use patterns. Song Stream is significantly disturbed by agricultural activities in the watershed, whereas Odae Stream is relatively undisturbed and is surrounded by a well-conserved forest area. Song Stream had significantly higher levels of all nutrients and sediment-related factors due to the adjacent agricultural area. As a result, Song Stream had markedly lower species community indices, such as taxa richness and abundance. In Song Stream, macroinvertebrate scrapers and predators were most adversely affected, whereas collector-gatherers became a dominant group. Based on correlation and multivariate analyses, total dissolved solids had the strongest negative relationship with macroinvertebrate assemblages, followed by electrical conductivity, total nitrogen, and pH. The proportion of cobble in stream substrate was positively related to the richness and abundance of macroinvertebrates. Our results indicate that disturbances caused by agricultural land use, particularly sand deposition, had significant adverse effects on macroinvertebrate habitats and on the biotic integrity of benthic macroinvertebrate communities.
This paper provides an overview of the development and application of the National Aquatic Ecological Monitoring Program (NAEMP) in Korea, which uses biological and habitat–riparian criteria for river/stream and watershed management. Development of NAEMP began in 2003, with recognition by the Korean Ministry of Environment (MOE) of the limitations of applying chemical parameters (e.g., biochemical oxygen demand (BOD)) as the principal targets of water environment management. Ecosystem health criteria under NAEMP were developed from 2003 to 2006. Candidate sites for monitoring were also screened and established across the country. NAEMP was implemented in 2007, and since then a standard protocol of nationwide monitoring based on multi-criteria has been implemented to assess the ecological condition of rivers and streams. The monitoring results indicate that many Korean rivers and streams are severely degraded, with biological conditions that are much worse than their water chemistry suggests. In 2009, 24% of rivers and streams were in classes C (Fair) and D (Poor) for BOD, but more than 71, 53, and 27% were categorized as Fair to Poor according to fish, diatom, and benthic macroinvertebrate assemblages, respectively. NAEMP is promising in that the results have already had great impacts on policy making and scientific research relevant to lotic water environment and watershed management in Korea. In the future, NAEMP results will be used to develop more aggressive regulations for the preservation and restoration of rivers/streams, riparian buffer areas and watersheds. Another future aim of the NAEMP is to develop aquatic ecological modeling based on the monitoring results.
Despite numerous previous studies, relationships between watershed land use and adjacent streams and rivers at various scales in Korea remain unclear. This study investigated the relationships between land uses and the physical, chemical, and biological characteristics of 720 sites of streams and rivers across the country. The land uses at two spatial scales, including a 1-km buffer and the base watershed management region (BWMR), were computed in a geographical information system (GIS) with a digital land use/land cover map. Characteristics of land uses at two spatial scales were then correlated with the monitored multidimensional characteristics of the streams and rivers. The results of this study indicate that land use types have significant effects on stream and river characteristics. Specifically, most characteristics were negatively correlated with the proportions of urban, rice paddy, agricultural, and bare soil areas and positively correlated with the amount of forest. The site-scale and BWMR-scale analyses suggest that BWMR land use patterns were more strongly related to ecological integrity than they were to site land use patterns. Improving our understanding of land use effects will largely depend on relating the results of site-specific studies that use similar response techniques and measures to evaluate ecological integrity. In addition, our results clearly indicate that the characteristics of streams and rivers are closely linked and that land use types differentially affect those characteristics. Thus, effective restoration and management for ecological integrity of lotic system should consider the physical, chemical, and biological factors in combination.
To determine the appropriateness of antibiotic prophylaxis regimens for major surgery in Korea.
Retrospective study using a written survey for each patient who underwent arthroplasty, colon surgery, or hysterectomy.
Six tertiary hospitals in Seoul and Gyeonggi Province.
From each hospital, a maximum of 150 patients who underwent each type of surgery were randomly chosen for the study.
Of 2,644 eligible patients, 1,914 patients were included in the analysis; 677 of these patients underwent arthroplasty, 578 underwent colon surgery, and 659 underwent hysterectomy. Nineteen patients were excluded from the analyses of the class and number of antibiotics used for prophylaxis because they underwent multiple surgeries at different sites. For each of the 1,895 remaining patients, antibiotic prophylaxis involved a mean ( ± SD) of 2.8 ± 0.9 classes of antibiotics. The most commonly prescribed agents were cephalosporins (prescribed for 1,875 [98.9%] of the patients) and aminoglycosides (1,404 [74.1%]). A total of 1,574 (83.1%) of patients received at least 2 classes of antibiotics simultaneously. Only 15 (0.8%) of 1,895 patients received antibiotic prophylaxis in accordance with published guidelines. Of 506 patients for whom the initial dose of antibiotics was evaluated, 374 (73.9%) received an appropriate initial dose. Of the 1,676 patients whose medical records included information about antibiotic administration relative to the time of surgery, only 188 (11.2%) received antibiotic prophylaxis an hour or less before the surgical incision was made. Of the 1,748 patients whose medical records included information about duration of surgery, antibiotic prophylaxis was discontinued 24 hours or less after surgery for only 3 (0.2%) of the patients.
Most patients who had major surgery in Korea received inappropriate antibiotic prophylaxis. Measures to improve the appropriateness of antibiotic prophylaxis are urgently required.
Proper selection of an osteotome for nasal osteotomy is important for minimizing soft tissue trauma. Radiographic analysis of the facial bony lateral wall thickness was performed to suggest a guideline for an appropriate osteotome size for Asians. Facial bone computed tomography (CT) of 100 patients (50 male, 50 female) were studied. The thickness of the facial bony lateral wall at three points along the track of a lateral osteotomy, and two points along the track of a medial osteotomy and intermediate osteotomy were measured. The average bony thickness along the track of a lateral osteotomy was 2.61 ± 0.66 mm at the low level, 2.75 ± 0.76 mm at the middle level, and 2.72 ± 0.53 mm at the high level in subjects. The average bony thickness along the track of an intermediate osteotomy were 1.26 ± 0.34 mm at the low level, and 1.31 ± 0.32 mm at the high level in the subjects. The average bony thickness along the track of the medial osteotomy were 2.54 ± 0.31 mm at the lowlevel, and 2.77 ± 0.30 mm at the high level in subjects. These results may provide a guideline for choosing an osteotome of appropriate size for the Asian population.
Recently, inorganic/inorganic and organic/inorganic heterostructured materials have attracted considerable research interest, due to their unusual physicochemical properties, which cannot be achieved by conventional solid-state reactions. In order to develop new hybrid materials, various synthetic approaches, such as vacuum deposition, Langmuir–Blodgett films, selfassembly, and intercalation techniques, have been explored. Among them, the intercalation reaction technique—that is, the reversible insertion of guest species into the two-dimensional host lattice—is expected to be one of the most effective tools for preparing new layered heterostructures because this process can provide a soft chemical way of hybridizing inorganic/inorganic, organic/inorganic, or biological/inorganic compounds. In fact, the intercalation/deintercalation process allows us to design high-performance materials in a solution at ambient temperature and pressure, just as “soft solution processing” provides a simple and economical route for advanced inorganic materials by means of an environmentally benign, lowenergy method. These unique advantages of the intercalation technique have led to its wide application to diverse fields of the solid-state sciences, namely, secondary (rechargeable) batteries, electrochromic systems, oxidation–reduction catalysts, separating agents, sorbents, and so on. Through these extensive studies, many kinds of low-dimensional compounds have been developed as host materials for the intercalation reaction, including graphite, transition-metal chalcogenides, transitionmetal oxides, aluminosilicates, metal phosphates, metal chalcogenohalides, and so on. Recently, the area of intercalation chemistry has been extended to high-Tc superconducting copper oxides, resulting in remarkable structural anisotropy.
Structure and composition of the ferroelectric Pb(Zr, Ti)O3 layers in a capacitor of the ferroelectric random-access memory (FeRAM) device having a density of 64 k were investigated by transmission electron microscopy (TEM) together with the energy-dispersive spectroscopy (EDS) technique. The 250 nm thick PZT layer derived by the sol-gel route showed a 2–3% Pb-deficient, 3–4% Ti-deficient, and 5–7% Zr-excess composition at the top electrode interface compared to the bulk composition when they were as-fabricated. The local compositional nonuniformity became more critical as the integration process proceeded, which seriously degraded the ferroelectric hysteresis and the device yield. The major cause of the compositional variation was the outward diffusion of Pb through the capping barrier TiO2 layer during annealing at 650 °C. The AlN capping barrier layer was also not effective in suppressing the diffusion of Pb. However, the Al2O3/TiO2 double capping layer was very effective in suppressing the outward diffusion of Pb, and excellent ferroelectric characteristic was expected.
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