Showing papers on "Literature survey published in 2004"

Animal species diversity driven by habitat heterogeneity/diversity: the importance of keystone structures

Abstract: Aim In a selected literature survey we reviewed studies on the habitat heterogeneity–animal species diversity relationship and evaluated whether there are uncertainties and biases in its empirical support. Location World-wide. Methods We reviewed 85 publications for the period 1960–2003. We screened each publication for terms that were used to define habitat heterogeneity, the animal species group and ecosystem studied, the definition of the structural variable, the measurement of vegetation structure and the temporal and spatial scale of the study. Main conclusions The majority of studies found a positive correlation between habitat heterogeneity/diversity and animal species diversity. However, empirical support for this relationship is drastically biased towards studies of vertebrates and habitats under anthropogenic influence. In this paper, we show that ecological effects of habitat heterogeneity may vary considerably between species groups depending on whether structural attributes are perceived as heterogeneity or fragmentation. Possible effects may also vary relative to the structural variable measured. Based upon this, we introduce a classification framework that may be used for across-studies comparisons. Moreover, the effect of habitat heterogeneity for one species group may differ in relation to the spatial scale. In several studies, however, different species groups are closely linked to ‘keystone structures’ that determine animal species diversity by their presence. Detecting crucial keystone structures of the vegetation has profound implications for nature conservation and biodiversity management.

The informal sector in developed and less developed countries: A literature survey *

Abstract: The main goal of this study is two-fold: (1) to provide ageneral overview of the contributions to the literature on theinformal sector, with a special focus on the public choiceapproach; and (2) to compare these contributions across twoinstitutionally different types of countries: developed andless developed (developing and transition) countries. Thepaper focuses on the criteria used to define the informalsector, the relationship between the formal and informaleconomy, tax evasion, and public choice analysis. It isstressed throughout this paper that the distinction betweenthe two types of countries is of key importance.

Response Surface Methodology: A Retrospective and Literature Survey

Abstract: The original work in response surface methodology (RSM) has been widely used in the chemical and process industries. Recent years have seen more widespread use and new developments in RSM. RMS activities since 1989 are reviewed, and areas of current and..

Conceptualising successful partnerships.

Abstract: Partnership working has become a central feature of British social welfare policy since 1997. Although this development is applicable to all areas of public welfare, nowhere is it more evident than in the planning and provision of care that overlaps health and social services. The literature survey described in the present paper focused on research examining the impact of partnership working in these areas to assess the evidence concerning its effects and to investigate how partnership 'success' is conceptualised. The literature conceptualised the success of partnerships in two main ways: (1) process issues, such as how well the partners work together in addressing joint aims and the long-term sustainability of the partnership; and (2) outcome issues, including changes in service delivery, and subsequent effects on the health or well-being of service users. The authors found that research into partnerships has centred heavily on process issues, while much less emphasis has been given to outcome success. If social welfare policy is to be more concerned with improving service delivery and user outcomes than with the internal mechanics of administrative structures and decision-making, this is a knowledge gap that urgently needs to be filled.

In vivo Near-Infrared Fluorescence Imaging of Integrin αvβ3 in Brain Tumor Xenografts

Abstract: Noninvasive visualization of cell adhesion molecule alpha(v)beta(3) integrin expression in vivo has been well studied by using the radionuclide imaging modalities in various preclinical tumor models. A literature survey indicated no previous use of cyanine dyes as contrast agents for in vivo optical detection of tumor integrin. Herein, we report the integrin receptor specificity of novel peptide-dye conjugate arginine-glycine-aspartic acid (RGD)-Cy5.5 as a contrast agent in vitro, in vivo, and ex vivo. The RGD-Cy5.5 exhibited intermediate affinity for alpha(v)beta(3) integrin (IC(50) = 58.1 +/- 5.6 nmol/L). The conjugate led to elevated cell-associated fluorescence on integrin-expressing tumor cells and endothelial cells and produced minimal cell fluorescence when coincubated with c(RGDyK). In vivo imaging with a prototype three-dimensional small-animal imaging system visualized subcutaneous U87MG glioblastoma xenograft with a broad range of concentrations of fluorescent probe administered via the tail vein. The intermediate dose (0.5 nmol) produces better tumor contrast than high dose (3 nmol) and low dose (0.1 nmol) during 30 minutes to 24 hours postinjection, because of partial self-inhibition of receptor-specific tumor uptake at high dose and the presence of significant amount of background fluorescence at low dose, respectively. The tumor contrast was also dependent on the mouse viewing angles. Tumor uptake of RGD-Cy5.5 was blocked by unlabeled c(RGDyK). This study suggests that the combination of the specificity of RGD peptide/integrin interaction with near-infrared fluorescence detection may be applied to noninvasive imaging of integrin expression and monitoring anti-integrin treatment efficacy providing near real-time measurements.

Image Mosaicing and Super-resolution

Abstract: 1 Introduction.- 1.1 Background.- 1.2 Modelling assumptions.- 1.3 Applications.- 1.4 Principal contributions.- 2 Literature Survey.- 2.1 Image registration.- 2.1.1 Registration by a geometric transformation.- 2.1.2 Ensuring global consistency.- 2.1.3 Other parametric surfaces.- 2.2 Image mosaicing.- 2.3 Super-resolution.- 2.3.1 Simple super-resolution schemes.- 2.3.2 Methods using a generative model.- 2.3.3 Super-resolution using statistical prior image models.- 3 Registration: Geometric and Photometric.- 3.1 Introduction.- 3.2 Imaging geometry.- 3.3 Estimating homographies.- 3.3.1 Linear estimators.- 3.3.2 Non-linear refinement.- 3.3.3 The maximum likelihood estimator of H.- 3.4 A practical two-view method.- 3.5 Assessing the accuracy of registration.- 3.5.1 Assessment criteria.- 3.5.2 Obtaining a ground-truth homography.- 3.6 Feature-based vs. direct methods.- 3.7 Photometric registration.- 3.7.1 Sources of photometric difference.- 3.7.2 The photometric model.- 3.7.3 Estimating the parameters.- 3.7.4 Results.- 3.8 Application: Recovering latent marks in forensic images.- 3.8.1 Motivation.- 3.8.2 Method.- 3.8.3 Further examples.- 3.9 Summary.- 4 Image Mosaicing.- 4.1 Introduction.- 4.2 Basic method.- 4.2.1 Outline.- 4.2.2 Practical considerations.- 4.3 Rendering from the mosaic.- 4.3.1 The reprojection manifold.- 4.3.2 The blending function.- 4.3.3 Eliminating seams by photometric registration.- 4.3.4 Eliminating seams due to vignetting.- 4.3.5 A fast alternative to median filtering.- 4.4 Simultaneous registration of multiple views.- 4.4.1 Motivation.- 4.4.2 Extending the two-view framework to N-views.- 4.4.3 A novel algorithm for feature-matching over N-views.- 4.4.4 Results.- 4.5 Automating the choice of reprojection frame.- 4.5.1 Motivation.- 4.5.2 Synthetic camera rotations.- 4.6 Applications of image mosaicing.- 4.7 Mosaicing non-planar surfaces.- 4.8 Mosaicing "user's guide".- 4.9 Summary.- 4.9.1 Further examples.- 5 Super-resolution: Maximum Likelihood and Related Approaches.- 5.1 Introduction.- 5.2 What do we mean by "resolution"?.- 5.3 Single-image methods.- 5.4 The multi-view imaging model.- 5.4.1 A note on the assumptions made in the model.- 5.4.2 Discretization of the imaging model.- 5.4.3 Related approaches.- 5.4.4 Computing the elements in Mn.- 5.4.5 Boundary conditions.- 5.5 Justification for the Gaussian PSF.- 5.6 Synthetic test images.- 5.7 The average image.- 5.7.1 Noise robustness.- 5.8 Rudin's forward-projection method.- 5.9 The maximum-likelihood estimator.- 5.10 Predicting the behaviour of the ML estimator.- 5.11 Sensitivity of the ML estimator to noise sources.- 5.11.1 Observation noise.- 5.11.2 Poorly estimated PSF.- 5.11.3 Inaccurate registration parameters.- 5.12 Irani and Peleg's method.- 5.12.1 Least-squares minimization by steepest descent.- 5.12.2 Irani and Peleg's algorithm.- 5.12.3 Relationship to the ML estimator.- 5.12.4 Convergence properties.- 5.13 Gallery of results.- 5.14 Summary.- 6 Super-resolution Using Bayesian Priors.- 6.1 Introduction.- 6.2 The Bayesian framework.- 6.2.1 Markov random fields.- 6.2.2 Gibbs priors.- 6.2.3 Some common cases.- 6.3 The optimal Wiener filter as a MAP estimator.- 6.4 Generic image priors.- 6.5 Practical optimization.- 6.6 Sensitivity of the MAP estimators to noise sources.- 6.6.1 Exercising the prior models.- 6.6.2 Robustness to image noise.- 6.7 Hyper-parameter estimation by cross-validation.- 6.8 Gallery of results.- 6.9 Super-resolution "user's guide".- 6.10 Summary.- 7 Super-resolution Using Sub-space Models.- 7.1 Introduction.- 7.2 Bound constraints.- 7.3 Learning a face model using PCA.- 7.4 Super-resolution using the PCA model.- 7.4.1 An ML estimator (FS-ML).- 7.4.2 MAP estimators.- 7.5 The behaviour of the face model estimators.- 7.6 Examples using real images.- 7.7 Summary.- 8 Conclusions and Extensions.- 8.1 Summary.- 8.2 Extensions.- 8.2.1 Application to digital video.- 8.2.2 Model-based super-resolution.- 8.3 Final observations.- A Large-scale Linear and Non-linear Optimization.- References.

Factors that affect the fatigue life of rubber: A literature survey

Abstract: Many factors are known to influence the mechanical fatigue life of rubber components. Four major categories of factors are reviewed here: the effects of mechanical loading history, environmental effects, effects of rubber formulation, and effects due to dissipative aspects of the constitutive response of rubber. For each category, primary factors are described, and existing literature is presented and reviewed. Rubber's fatigue behavior is extremely sensitive to both the maximum and minimum cyclic load limits. Other aspects of the mechanical load history are also discussed, including the effects of static loaded periods (“annealing”), load sequence, multiaxiality, frequency, and loading waveform. Environmental factors can affect both the short and long term fatigue behavior of rubber. The effects of temperature, oxygen, ozone, and static electrical charges are reviewed. A great range of behavior is available by proper manipulation of formulation and processing variables. Effects of elastomer type...

Backward-Facing Step Flows for Various Expansion Ratios at Low and Moderate Reynolds Numbers

Abstract: This paper is concerned with the behavior of flows over a backward-facing step geometry for various expansion ratios H/h=1.9423, 2.5 and 3.0. A literature survey was carried out and it was found that the flow shows a strong two-dimensional behavior, on the plane of symmetry, for Reynolds numbers ReD=ρUbD/μ below approximately 400 (Ub= bulk velocity and D= hydraulic diameter). In this Reynolds number range, two-dimensional predictions were carried out to provide information on the general integral properties of backward-facing step flows, on mean velocity distributions and streamlines. Information on characteristic flow patterns is provided for a wide Reynolds number range, 10−4≤ReD≤800. In the limiting case of ReD→0, a sequence of Moffatt eddies of decreasing size and intensity is verified to exist in the concave corner also at ReD=1. The irreversible pressure losses are determined for various Reynolds numbers as a function of the expansion ratio. The two-dimensional simulations are known to underpredict the primary reattachment length for Reynolds numbers beyond which the actual flow is observed to be three-dimensional. The spatial evolution of jet-like flows in both the streamwise and the spanwise direction and transition to three-dimensionality were studied at a Reynolds number ReD=648. This three-dimensional analysis with the same geometry and flow conditions as reported by Armaly et al. (1983) reveals the formation of wall jets at the side wall within the separating shear layer. The wall jets formed by the spanwise component of the velocity move towards the symmetry plane of the channel. A self-similar wall-jet profile emerges at different spanwise locations starting with the vicinity of the side wall. These results complement information on backward-facing step flows that is available in the literature.

Toxicological Characteristics of Endocrine-Disrupting Chemicals: Developmental Toxicity, Carcinogenicity, and Mutagenicity

Abstract: It is generally accepted that endocrine-disrupting chemicals (EDCs) play a role in a variety of adverse health effects in an intact organism or its progeny as a consequence of changes in the endocrine system. Primary toxic effects of EDCs were reported to be related to infertility, reduction in sperm count, and teratogenicity, but other important toxic effects of EDCs such as carcinogenicity and mutagenicity have also been demonstrated. The aim of the present study was to systematically analyze the toxicological characteristics of EDCs in pesticides, industrial chemicals, and metals. A comprehensive literature survey on the 48 EDCs classified by the Centers for Disease Control and Prevention (CDC) was conducted using a number of databases which included Medline, Toxline, and Toxnet. The survey results revealed that toxicological characteristics of EDCs were shown to produce developmental toxicity (81%), carcinogenicity (79%, when positive in at least one animal species; 48%, when classified based on IARC evaluation), mutagenicity (79%), immunotoxicity (52%), and neurotoxicity (50%). Regarding the hormone-modulating effects of the 48 EDCs, estrogenic effects were the most predominant in pesticides, while effects on thyroid hormone were found for heavy metals. EDCs showing estrogen-modulating effects were closely related to carcinogenicity or mutagenicity with a high degree of sensitivity. Systematic information on the toxicological characteristics of the EDCs will be useful for future research directions on EDCs, the development of new screening methods, legal regulation, and for investigations of their mechanism of action.

Stand fine root biomass and fine root morphology in old-growth beech forests as a function of precipitation and soil fertility

Abstract: Only very limited information exists on the plasticity in size and structure of fine root systems, and fine root morphology of mature trees as a function of environmental variation. Six northwest German old-growth beech forests (Fagus sylvatica L.) differing in precipitation (520 – 1030 mm year−1) and soil acidity/fertility (acidic infertile to basic fertile) were studied by soil coring for stand totals of fine root biomass (0–40 cm plus organic horizons), vertical and horizontal root distribution patterns, the fine root necromass/biomass ratio, and fine root morphology (root specific surface area, root tip frequency, and degree of mycorrhizal infection). Stand total of fine root biomass, and vertical and horizontal fine root distribution patterns were similar in beech stands on acidic infertile and basic fertile soils. In five of six stands, stand fine root biomass ranged between 320 and 470 g m−2; fine root density showed an exponential decrease with soil depth in all profiles irrespective of soil type. An exceptionally small stand fine root biomass (<150 g m−2) was found in the driest stand with 520 mm year−1 of rainfall. In all stands, fine root morphological parameters changed markedly from the topsoil to the lower profile; differences in fine root morphology among the six stands, however, were remarkably small. Two parameters, the necromass/biomass ratio and fine root tip density (tips per soil volume), however, were both much higher in acidic than basic soils. We conclude that variation in soil acidity and fertility only weakly influences fine root system size and morphology of F. sylvatica, but affects root system structure and, probably, fine root mortality. It is hypothesized that high root tip densities in acidic infertile soils compensate for low nutrient supply rates, and large necromasses are a consequence of adverse soil chemical conditions. Data from a literature survey support the view that rainfall is another major environmental factor that influences the stand fine root biomass of F. sylvatica.

Prioritization of medicinal plants on the basis of available knowledge, existing practices and use value status in Uttaranchal, India

Abstract: In order to understand the pattern of indigenous uses of medicinal plants available in the Uttaranchal state of the Indian Himalaya, this study was undertaken through literature survey and fieldwork in various parts of the state. A list of all the major and most of the lesser categories of ailments was prepared and categorized with the help of medical practitioners. A total of 300 plant species used in curing 114 ailments prevailing in various ethnic and non-ethnic communities of Uttaranchal were documented. These 114 ailments were further grouped into 12 broad classes of diseases in order to project the indigenous uses of medicinal plants for various ailments. It was found that herbs contributed the highest number of medicinal plants (65%), followed by shrubs (19%) and trees (16%). The maximum number of plant species were used to cure generalized body aches and colic, followed by gastrointestinal and dermatological problems. Vitex negundo was the most important species, used for the treatment of more than 48 ailments. Azadirachta indica, Woodfordia fruticosa, Centella asiatica, Aegle marmelos, Cuscuta reflexa, Butea monosperma, Phyllanthus emblica, and Euphorbia hirta were among other important medicinal plants based on their high use values. The underground parts of the plant were used in the majority of cases. Of 300 medicinal plants, 35 were rare and endangered species, of which about 80% was restricted to the high altitude alpine region of Uttaranchal Himalaya. A priority list of 17 medicinal plant species was prepared on the basis of endemism, use value, mode of harvesting and rarity status. Strategies for long-term conservation of these valuable medicinal plants are discussed.

A novel medium for the enhanced cell growth and production of prodigiosin from Serratia marcescens isolated from soil

Abstract: Prodigiosin produced by Serratia marcescens is a promising drug owing to its reported characteristics of having antifungal, immunosuppressive and antiproliferative activity. From an industrial point of view the necessity to obtain a suitable medium to simultaneously enhance the growth of Serratia marcescens and the pigment production was the aim of this work. The usage of individual fatty acid as substrate in industries would be cost-effective in the long run and this paved the way for us to try the effect of different fatty acid-containing seeds and oils of peanut, sesame and coconut as source of substrate. The addition of sugars only showed slight enhancement of prodigiosin production in nutrient broth but not in fatty acid containing seed medium. The powdered peanut broth had supported better growth of Serratia marcescens and higher yield of prodigiosin when compared with the existing nutrient broth and peptone glycerol broth. A block in prodigiosin production was seen above 30°C in nutrient broth, but the fatty acid seed medium used by us supported prodigiosin production upto 42°C though the yields were lower than what was obtained at 28°C. From the results, the fatty acid form of carbon source has a role to play in enhanced cell growth and prodigiosin production. We conclude by reporting that the powdered and sieved peanut seed of different quality grades were consistent in yielding a fourty fold increase in prodigiosin production over the existing media. A literature survey on the composition of the different media components in nutrient broth, peptone glycerol broth and the fatty acid containing seeds and oils enabled us to propose that the saturated form of fatty acid has a role to play in enhanced cell growth and prodigiosin production. This work has also enabled us to report that the temperature related block of prodigiosin biosynthesis varies with different media and the powdered peanut broth supports prodigiosin production at higher temperatures. The medium suggested in this work is best suitable from an industrial point of view in being economically feasible, in terms of the higher prodigiosin yield and the extraction of prodigiosin described in this paper is simple with minimal wastage.

Tight-binding calculations of stacking energies and twinnability in fcc metals

Abstract: We calculate the material properties needed to evaluate the tendency of a face-centered-cubic (fcc) metal to plastically deform by forming crystallographic twins as opposed to dislocation-mediated slip. We refer to this property as the twinnability of the metal. We use a formulation for twinnability derived from a coupling of continuum mechanics with an atomistic stress-slip relation. The essential quantities for evaluating the twinnability are elastic constants, which are measurable experimentally, and energies for various stacking sequences of the fcc (111) planes. These stacking sequences include the intrinsic stacking fault configuration as well as the unstable-stacking energy and unstable-twinning energy configurations which can only be determined computationally. We use a tight-binding model to evaluate the necessary stacking energies, as well as the extrinsic stacking fault energy and twin-boundary energy, for eight fcc metals. The accuracy of the tight-binding parameters is established by comparing them with first-principles values obtained through an extensive study of the literature. The results of the literature survey are included in the paper as a resource for the reader. We show that the ranking of these metals in order of twinnability agrees with available experimental results. We reproduce the low incidence of deformation twinning in Al, and explain it in terms of the material parameters using an approximation to the twinnability expression. We also predict that Pd, which has not been studied experimentally, should twin as easily as Cu.

Lanthanide alkylidene and imido complexes.

Abstract: In stark contrast to the transition metals, examples of imido or alkylidene complexes of the lanthanides remain scarce. A recent literature survey reveals that only nine examples of lanthanide imido complexes have been reported, and the majority of these have arisen serendipitously. Concrete examples of species containing lanthanide–carbon multiple bonds are even more sparse. Recently, some rational approaches to the synthesis of lanthanide complexes containing LnX functionalities have been detailed (X = C, N). Additionally, a DFT (Density Functional Theory) study of a samarium imido complex has provided insight into the electronic and steric factors that may be necessary to support these unusual reactive groups. This Perspective reviews the work in this field and offers some suggestions to expand this potentially useful class of compounds.

Biodegradability of chlorinated solvents and related chlorinated aliphatic compounds

Abstract: The biodegradability of chlorinated methanes, chlorinated ethanes, chlorinated ethenes, chlorofluorocarbons (CFCs), chlorinated acetic acids, chlorinated propanoids and chlorinated butadienes was evaluated based on literature data. Evidence for the biodegradation of compounds in all of the compound categories evaluated has been reported. A broad range of chlorinated aliphatic structures are susceptible to biodegradation under a variety of physiological and redox conditions. Microbial biodegradation of a wide variety of chlorinated aliphatic compounds was shown to occur under five physiological conditions. However, any given physiological condition could only act upon a subset of the chlorinated compounds. Firstly, chlorinated compounds are used as an electron donor and carbon source under aerobic conditions. Secondly, chlorinated compounds are cometabolized under aerobic conditions while the microorganisms are growing (or otherwise already have grown) on another primary substrate. Thirdly, chlorinated compounds are also degraded under anaerobic conditions in which they are utilized as an electron donor and carbon source. Fourthly, chlorinated compounds can serve as an electron acceptor to support respiration of anaerobic microorganisms utilizing simple electron donating substrates. Lastly chlorinated compounds are subject to anaerobic cometabolism becoming biotransformed while the microorganisms grow on other primary substrate or electron acceptor. The literature survey demonstrates that, in many cases, chlorinated compounds are completely mineralised to benign end products. Additionally, biodegradation can occur rapidly. Growth rates exceeding 1 d-1 were observed for many compounds. Most compound categories include chlorinated structures that are used to support microbial growth. Growth can be due to the use of the chlorinated compound as an electron donor or alternatively to the use of the chlorinated compound as an electron acceptor (halorespiration). Biodegradation linked to growth is important, since under such conditions, rates of degradation will increase as the microbial population (biocatalyst) increases. Combinations of redox conditions are favorable for the biodegradation of highly chlorinated structures that are recalcitrant to degradation under aerobic conditions. However, under anaerobic conditions, highly chlorinated structures are partially dehalogenated to lower chlorinated counterparts. The lower chlorinated compounds are subsequently more readily mineralized under aerobic conditions.

Biomedical conflicts of interest: a defence of the sequestration thesis—learning from the cases of Nancy Olivieri and David Healy

Abstract: No discussion of academic freedom, research integrity, and patient safety could begin with a more disquieting pair of case studies than those of Nancy Olivieri and David Healy. The cumulative impact of the Olivieri and Healy affairs has caused serious self examination within the biomedical research community. The first part of the essay analyses these recent academic scandals. The two case studies are then placed in their historical context-that context being the transformation of the norms of science through increasingly close ties between research universities and the corporate world. After a literature survey of the ways in which corporate sponsorship has biased the results of clinical drug trials, two different strategies to mitigate this problem are identified and assessed: a regulatory approach, which focuses on managing risks associated with industry funding of university research, and a more radical approach, the sequestration thesis, which counsels the outright elimination of corporate sponsorship. The reformist approach is criticised and the radical approach defended.

Emission of Hexanal and Carbon Monoxide from Storage of Wood Pellets, a Potential Occupational and Domestic Health Hazard

Abstract: Objectives: The objective of the present study was to investigate and describe the emissions of volatile compounds, particularly hexanal and carbon monoxide, from large- and small-scale storage of wood pellets. Methods: Air sampling was performed with Fourier transform infrared spectroscopy and adsorbent sampling in pellet warehouses, domestic storage rooms, lumber kiln dryers and experimental set-ups. Literature studies were included to describe the formation of hexanal and carbon monoxide and the toxicology of hexanal. Results: A geometric mean aldehyde level of 111 ± 32 mg/m 3 was found in one warehouse, with a peak reading of 156 mg/m 3 . A maximum aldehyde reading of 457 mg/m 3 was recorded at the surface of a pellet pile. Hexanal (70–80% w/w) and pentanal (10–15% w/w) dominated, but acetone (83 ± 24 mg/m 3 ), methanol (18 ± 7 mg/m 3 ) and carbon monoxide (56 ± 4 mg/m 3 ) were also found. The emissions in a domestic storage room varied with the ambient temperature and peaked after 2 months storage in the midst of the warm season. Aldehyde levels of 98 ± 4 mg/m 3 and carbon monoxide levels of 123 ± 10 mg/m 3 were recorded inside such storage rooms. Elevated levels of hexanal (0.084 mg/m 3 ) were recorded inside domestic housing and 6m g/m 3 in a room adjacent to a poorly sealed storage area. Experimental laboratory studies confirmed the findings of the field studies. A field study of the emissions from industrial lumber drying also showed the formation of aldehydes and carbon monoxide. Conclusions: High levels of hexanal and carbon monoxide were strongly associated with storage of wood pellets and may constitute an occupational and domestic health hazard. The results from lumber drying show that the emissions of hexanal and carbon monoxide are not limited to wood pellets but are caused by general degradation processes of wood, facilitated by drying at elevated temperature. Emission of carbon monoxide from wood materials at low temperatures (<100°C) has not previously been reported in the literature. We postulate that carbon monoxide is formed due to autoxidative degradation of fats and fatty acids. A toxicological literature survey showed that the available scientific information on hexanal is insufficient to determine the potential risks to health. However, the data presented in this paper seem sufficient to undertake preventive measures to reduce exposure to hexanal.

ARTICLE Animal species diversity driven by habitat heterogeneity/diversity: the importance of keystone structures

Abstract: Aim In a selected literature survey we reviewed studies on the habitat heterogeneity–animal species diversity relationship and evaluated whether there are uncertainties and biases in its empirical support. Location World-wide. Methods We reviewed 85 publications for the period 1960–2003. We screened each publication for terms that were used to define habitat heterogeneity, the animal species group and ecosystem studied, the definition of the structural variable, the measurement of vegetation structure and the temporal and spatial scale of the study. Main conclusions The majority of studies found a positive correlation between habitat heterogeneity/diversity and animal species diversity. However, empirical support for this relationship is drastically biased towards studies of vertebrates and habitats under anthropogenic influence. In this paper, we show that ecological effects of habitat heterogeneity may vary considerably between species groups depending on whether structural attributes are perceived as heterogeneity or fragmentation. Possible effects may also vary relative to the structural variable measured. Based upon this, we introduce a classification framework that may be used for across-studies comparisons. Moreover, the effect of habitat heterogeneity for one species group may differ in relation to the spatial scale. In several studies, however, different species groups are closely linked to ‘keystone structures’ that determine animal species diversity by their presence. Detecting crucial keystone structures of the vegetation has profound implications for nature conservation and biodiversity management.

Review of radio frequency microelectromechanical systems technology

Abstract: A review of radio frequency microelectromechanical systems (RF MEMS) technology, from the perspective of its enabling technologies (e.g. fabrication, RF micromachined components and actuation mechanisms) is presented. A unique roadmap is given that shows how enabling technologies, RF MEMS components, RF MEMS circuits and RF microsystems packaging are linked together; leading towards enhanced integrated subsystems. An overview of the associated fabrication technologies is given, in order to distinguish between the two distinct classes of RF microsystems' component technologies; non-MEMS micromachined and true MEMS. An extensive literature survey has been undertaken and key papers have been cited; from these, the motivations behind different RF MEMS technologies are highlighted. The importance of understanding the limitations for realising new and innovative ideas in RF MEMS is discussed. Finally, conclusions are drawn as to where future RF MEMS technology may lead. It is likely that the switch will continue to be the most important RF MEMS component, with future work investigating its enhanced functionality, subsystem integration and volume production. The focus of RF MEMS circuits will shift from the digital phase shifter to high-Q tuneable filters.

Female post-reproductive lifespan: a general mammalian trait

Abstract: Traditional explanations for the evolution of menopause and post-reproductive lifespan in human females have been based on the benefits of maternal or grand-maternal care outweighing the cost of lost reproduction. These explanations assume an evolutionary origin of menopause since human divergence with the most recent common ancestor. In this study, I conduct a literature survey of studies of 42 mammal species from eight orders, showing that post-reproductive lifespan appears to be widespread among mammals. I then propose an alternative to traditional hypotheses: following accepted theories of trade-offs and senescence, I suggest that the cost of extending reproductive lifespan might be relatively high in female mammals. Somatic and reproductive senescence appear to follow separate trajectories, so it is not surprising that the two processes should occur on different schedules. The timing of each process is probably determined by maximization of reproductive performance and survival early in adulthood, with consequent trajectories resulting in a post-reproductive lifespan. The early end of reproduction relative to lifespan may be due to the cost of production and/or maintenance of oocytes, which decline exponentially over time. Oocyte number below a threshold may trigger an end to normal hormonal cycling.