Showing papers on "Literature survey published in 2002"

Plant responses to abiotic stresses: heavy metal‐induced oxidative stress and protection by mycorrhization

Abstract: The aim of this review is to assess the mode of action and role of antioxidants as protection from heavy metal stress in roots, mycorrhizal fungi and mycorrhizae. Based on their chemical and physical properties three different molecular mechanisms of heavy metal toxicity can be distinguished: (a) production of reactive oxygen species by autoxidation and Fenton reaction; this reaction is typical for transition metals such as iron or copper, (b) blocking of essential functional groups in biomolecules, this reaction has mainly been reported for non-redox-reactive heavy metals such as cadmium and mercury, (c) displacement of essential metal ions from biomolecules; the latter reaction occurs with different kinds of heavy metals. Transition metals cause oxidative injury in plant tissue, but a literature survey did not provide evidence that this stress could be alleviated by increased levels of antioxidative systems. The reason may be that transition metals initiate hydroxyl radical production, which can not be controlled by antioxidants. Exposure of plants to non-redox reactive metals also resulted in oxidative stress as indicated by lipid peroxidation, H(2)O(2) accumulation, and an oxidative burst. Cadmium and some other metals caused a transient depletion of GSH and an inhibition of antioxidative enzymes, especially of glutathione reductase. Assessment of antioxidative capacities by metabolic modelling suggested that the reported diminution of antioxidants was sufficient to cause H(2)O(2) accumulation. The depletion of GSH is apparently a critical step in cadmium sensitivity since plants with improved capacities for GSH synthesis displayed higher Cd tolerance. Available data suggest that cadmium, when not detoxified rapidly enough, may trigger, via the disturbance of the redox control of the cell, a sequence of reactions leading to growth inhibition, stimulation of secondary metabolism, lignification, and finally cell death. This view is in contrast to the idea that cadmium results in unspecific necrosis. Plants in certain mycorrhizal associations are less sensitive to cadmium stress than non-mycorrhizal plants. Data about antioxidative systems in mycorrhizal fungi in pure culture and in symbiosis are scarce. The present results indicate that mycorrhization stimulated the phenolic defence system in the Paxillus-Pinus mycorrhizal symbiosis. Cadmium-induced changes in mycorrhizal roots were absent or smaller than those in non-mycorrhizal roots. These observations suggest that although changes in rhizospheric conditions were perceived by the root part of the symbiosis, the typical Cd-induced stress responses of phenolics were buffered. It is not known whether mycorrhization protected roots from Cd-induced injury by preventing access of cadmium to sensitive extra- or intracellular sites, or by excreted or intrinsic metal-chelators, or by other defence systems. It is possible that mycorrhizal fungi provide protection via GSH since higher concentrations of this thiol were found in pure cultures of the fungi than in bare roots. The development of stress-tolerant plant-mycorrhizal associations may be a promising new strategy for phytoremediation and soil amelioration measures.

Electric load forecasting: Literature survey and classification of methods

Abstract: A review and categorization of electric load forecasting techniques is presented. A wide range of methodologies and models for forecasting are given in the literature. These techniques are classified here into nine categories: (1) multiple regression, (2) exponential smoothing, (3) iterative reweighted least-squares, (4) adaptive load forecasting, (5) stochastic time series, (6) ARMAX models based on genetic algorithms, (7) fuzzy logic, (8) neural networks and (9) expert systems. The methodology for each category is briefly described, the advantages and disadvantages discussed, and the pertinent literature reviewed. Conclusions and comments are made on future research directions.

The Lactic Acid Bacteria: A Literature Survey

Abstract: The purpose of this review article on the lactic acid bacteria grew from an early curiosity and a desire to convey and impart the broad scope of literary information on their functions as starter cultures, in the manufacture of fermentation products such as dairy products and alcoholic beverages, as well as their contribution to better health. This review article is an attempt to empower the reader and to circumvent the difficult task in acquiring and elucidating a large body of information. The intent is to familiarize the reader with the various lactic species, their habitat or source, associated food, physiological characteristics, colonial morphology, biochemical characteristics, culture media (enrichment, nonselective, and selective), classic description, and taxonomy. This review provides information on Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, Carnobacterium, and Enterococcus. Trends are presented, such as the use of nisin to extend food shelf-life and the current research premise that Probiotic strains may alter the intestinal flora and thus prevent intestinal wall penetration by pathogens.

Condition monitoring techniques for electrical equipment-a literature survey

Abstract: Increasing interest has been seen in condition monitoring (CM) techniques for electrical equipment, mainly including transformer, generator, and induction motor in power plants, because CM has the potential to reduce operating costs, enhance the reliability of operation, and improve power supply and service to customers. Literature is accumulated on developing intelligent CM systems with advanced practicability, sensitivity, reliability, and automation. A literature survey is felt necessary with an aim to reflect the state-of-the-art development in this important area. After introducing the concepts and functions of CM, this paper describes the popular monitoring methods for and research status of CM on transformers, generators, and induction motors, respectively. The paper also points out the potential benefits through the utilization of advanced signal processing and artificial intelligence techniques in developing novel CM schemes.

The value of synovial fluid assays in the diagnosis of joint disease: a literature survey

Abstract: Objective: To carry out a critical appraisal of the literature in an attempt to assess the current value of synovial fluid (SF) analysis in the diagnosis of joint disease. Methods: A literature search was undertaken using the Medline, Biomed, Bids, Pubmed, and Embase electronic databases using the keywords: synovial fluid (SF) analysis, SF crystals, joint sepsis, acute arthritis, and SF cell counts, cytology, biomarkers, and microbiology. Results: Publications fell into three main categories. Firstly, reports assessing the value of the three traditional assays (microbiology, white blood cell counts, and microscopy for pathogenic crystals). For these quality control evidence was found to be sparse, and tests for sensitivity, specificity, and reliability showed worrying variations. These poor standards in SF analysis may be due to lack of inclusion of some tests within routine pathology services. Secondly, claims for the usefulness of "new" assays (cytology and biochemical markers). For cytology, the supporting evidence was mainly anecdotal and there were no reports on specificity, sensitivity, and reliability. Interpretation difficulties are a major hindrance to the clinical use of biochemical assays, which remain primarily research tools. Finally, work on the diagnostic value of SF analysis in general. The appraisal confirmed that SF analysis remains of major diagnostic value in acute arthritis, where septic arthritis or crystal arthropathy is suspected, and in intercritical gout. Conclusions: Given the importance of SF tests, rationalisation of their use, together with improved quality control, should be immediate priorities. Further investigation is recommended into the contribution of SF inspection and white cell counts to diagnosis, as well as of the specificity and sensitivity of SF microbiological assays, crystal identification, and cytology.

Sex chromosomes and sexual selection in poeciliid fishes.

Abstract: We propose that the evolution of female preferences can be strongly influenced by linkage of attractive male traits to the Y chromosome and female preferences to the X chromosome in male heterogametic species. Such linkage patterns are predicted by models of the evolution of sexually antagonistic genes. Subsequent recombination of attractive male characters from the Y to the X would create physical linkage between attractive male trait and preference. A literature survey shows that Y linkage of potentially sexually antagonistic traits is common in poeciliid fishes and other species with sex chromosomes that are not well differentiated, but may also occur in taxa with degenerate Y chromosomes. In the guppy, attractive male traits are primarily Y and X linked; a literature review of the inheritance of sex‐limited attractive male characters suggests that 16 are Y linked, 24 recombine between the X and Y, two are X linked, and two are autosomal. Crosses and backcrosses between high female preference...

Top-down versus bottom-up control of autotrophic biomass—a meta-analysis on experiments with periphyton

Abstract: Nutrient supply and herbivore presence can regulate plant biomass. The relative impact of both of these factors, and their interactions, on periphyton biomass were examined in a quantitative meta-analysis. A literature survey revealed 85 experiments with factorial and replicated manipulation of grazer access and nutrient supply. Two measures of effect sizes were calculated for each experiment, one based on final biomass yields (Hedges’ d) and the other on rates (Δr). Grazers significantly reduced periphyton biomass across all experiments, whereas nutrient addition significantly increased periphyton biomass. Effect sizes were very large for both factors. Thus, periphyton can be viewed as highly controlled by top-down and bottom-up mechanisms. Grazer effects were greater than nutrient effects. This result would be expected because nutrient enrichment represents a relative relief from nutrient limitation, whereas grazer exclusion represents a categorical removal of grazing pressure. Moreover, nutrien...

Protean nature of mass sociogenic illness: From possessed nuns to chemical and biological terrorism fears

Abstract: Background Episodes of mass sociogenic illness are becoming increasingly recognised as a significant health and social problem that is more common than is presently reported. Aims To provide historical continuity with contemporary episodes of mass sociogenic illness in order to gain a broader transcultural and transhistorical understanding of this complex, protean phenomenon. Method Literature survey to identify historical trends. Results Mass sociogenic illness mirrors prominent social concerns, changing in relation to context and circumstance. Prior to 1900, reports are dominated by episodes of motor symptoms typified by dissociation, histrionics and psychomotor agitation incubated in an environment of preexisting tension. Twentieth-century reports feature anxiety symptoms that are triggered by sudden exposure to an anxiety-generating agent, most commonly an innocuous odour or food poisoning rumours. From the early 1980s to the present there has been an increasing presence of chemical and biological terrorism themes, climaxing in a sudden shift since the 11 September 2001 terrorist attacks in the USA. Conclusions A broad understanding of the history of mass sociogenic illness and a knowledge of episode characteristics are useful in the more rapid recognition and treatment of outbreaks.

Lingual and buccal mandibular bone depressions: a review based on 583 cases from a world-wide literature survey, including 69 new cases from Japan

Abstract: OBJECTIVES To review present knowledge of so-called lingual and buccal mandibular bone depressions (n = 583) based on studies of 247 contemporary and 267 archaeological cases from a world-wide literature survey in addition to 69 new cases from Japan. METHODS The 69 cases from Japan were retrieved through examination of 42,600 consecutive panoramic radiographs. RESULTS Bone depressions can be divided into four topographical variants: (1) lingual anterior mandibular body (incisor-canine- premolar area) above the mylohyoid muscle; (2) posterior to the mandibular angle-first permanent molar area, below the mandibular canal, and a third located to the ascending, lingual mandibular ramus, posterior to the lingual foramen, just below the neck of the condyle. An excessively rare fourth variant is located to the buccal aspects of the ascending mandibular ramus. CONCLUSIONS The present concept favours that all variants have a common origin: a hyperplastic/hypertrophic lobe (or aberrant lobe) of the sublingual, subm...

Vehicle control and drowsiness

Abstract: This report consists of 2 parts. The 1st part is a literature study aimed at identifying the most relevant indicators for predicting and detecting fatigue-induced impaired driving. The aim was to identify possible performance-based technologies, such as lateral control of the car. Thus, less attention was given to psychophysiological measures like EEG. A large number of research reports describing various approaches were reviewed. The survey clearly indicates that no single indicator can be used to detect drowsy driving. A combination of different measures is suggested (analysis of lateral control performance and eye blink pattern). Furthermore, it should be noted that to date, there is no commercial system available that provides a sufficiently reliable method to detect a drowsy driver. In the 2nd part, experimental data from previous driving simulator experiments was analyzed by means of signal processing and statistical analyses. Specific attention was paid to investigate the potential of lateral vehicle position data as a means of estimating driver drowsiness. The analysis of experimental data did not reveal any clear answer as to what indicators are the most prominent with respect to detecting drowsy driving behavior. Further study and analysis of driving behavior data is needed. However, the data analysis conforms in large measure to findings of the literature survey.

Cancer risk assessment for oral exposure to PAH mixtures.

Abstract: Cancer risk estimates for oral uptake of polycyclic aromatic hydrocarbons (PAHs) currently are based on risk estimates for benzo[a]pyrene (BAP). The potency of PAH mixtures often is calculated using relative potency values (BAP equivalency factors). We used recent oral carcinogenicity studies with BAP and coal tar mixtures, as well as older studies for a critical reappraisal of the current practice. A literature survey identified several carcinogenicity studies with oral and dermal exposure and lung implantation that allow a direct comparison of the carcinogenic potency of pure BAP and PAH mixtures. Moreover, when the PAH composition of the mixture has been analysed, prediction of the potency of PAH mixtures by BAP equivalency factors could be compared with the observed PAH potency. The analysis indicates that BAP equivalency factors do not describe adequately the potency of PAH mixtures and lead to underestimations of carcinogenic potency in most cases. Evaluation of several studies with various PAH mixtures revealed that the potency ratio between pure BAP and the PAH mixture in the same assay is highly dependent on the exposure pathway and the target organ, therefore potency estimates for PAH mixtures should be derived separately for oral, dermal and inhalative exposure using data from studies with the relevant pathway. A cancer slope factor for oral PAH exposure was derived based on data from a recent feeding study with coal tar mixtures. By using incidence data for all exposure-related tumours, a slope factor for humans of 11.5 (human excess risk per oral lifetime exposure with 1 mg BAP kg(-1)day(-1) in a PAH mixture) was obtained. Our analysis led to the conclusion that the contribution of BAP to the carcinogenic potency of the mixture depends on the exposure pathway and type of cancer observed but is relatively constant for various PAH mixtures from industrial sources. Thus, the derived oral slope factor is recommended to be used for the risk assessment of PAH-contaminated soils.

Hydraulic constraints in the functional scaling of trees

Abstract: I conducted a literature survey to assess the available information on relationships between size--expressed in terms of diameter and dry biomass--and hydraulic efficiency of woody structures at different scales, from stem segments to whole trees. Three data sets were constructed: the first described the relationship between segment diameter and hydraulic conductivity (k(h); kg m s(-1) MPa(-1)) in four species; the second, for the same four species, described the intraspecific trajectories of change in total hydraulic conductance (G; kg s(-1) MPa(-1)) during ontogeny, i.e., from saplings to mature trees, thereby providing a comparison between allometric scaling laws at the scales of segments and whole trees; the third comprised pooled means for nine species that described the interspecific trajectory of change in G with tree size. The scaling coefficients obtained were compared with predictions made with an architectural fractal-like model incorporating tissue-specific hydraulic architecture parameters (West et al. 1999). When data on segment k(h) were examined, the fractal-like model closely predicted the scaling of k(h) with segment diameter in four species. However, the model failed to predict accurately in all species the intraspecific scaling at the branch and whole-tree levels, and consistently overestimated the scaling coefficients. The results suggest that ontogenetic changes in tree size during the life cycle of one tree may result in tradeoffs between optimal hydraulic supply to the existing leaf area and maintenance costs of the supporting xylem tissue. The model of West et al. (1999) may be useful for understanding broad interspecific patterns, but not for understanding more subtle ontogenetic changes.

Revisión de los conceptos de alfabetización informacional y alfabetización digital

Abstract: The concepts of ‘information literacy’ and ‘digital literacy’ are described, and reviewed, by way of a literature survey and analysis. Related concepts, including computer literacy, library literacy, network literacy, internet literacy and hyperliteracy are also discussed, and their relationships elucidated. After a general introduction, the paper begins with the basic concept of ‘literacy’, which is then expanded to include newer forms of literacy, more suitable for complex information environments. Some of these, for example library, media and computer literacies, are based largely on specific skills, but have some extension beyond them. They lead to general concepts, such as information literacy and digital literacy, which are based on knowledge, perceptions and attitudes, though reliant on the simpler skills-based literacies