SEARCH · PubMed Health

Results for “Tree building”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources

PubMed2005

Geometric modeling of the human normal cerebral arterial system.

We propose an anatomy-based approach for an efficient construction of a three-dimensional human normal cerebral arterial model from segmented and skeletonized angiographic data. The centerline-based model is used for an accurate angiographic data representation. A vascular tree is represented by tubular segments and bifurcations whose construction takes into account vascular anatomy. A bifurcation is defined quantitatively and the algorithm calculating it is given. The centerline is smoothed by means of a sliding average filter. As the vessel radius is sensitive to quality of data as well as accuracy of segmentation and skeletonization, radius outlier removal and radius regression algorithms are formulated and applied. In this way, the approach compensates for some inaccuracies introduced during segmentation and skeletonization. To create the frame of vasculature, we use two different topologies: tubular and B-subdivision based. We also propose a technique to prevent vessel twisting. The analysis of the vascular model is done on a variety of data containing 258 vascular segments and 131 bifurcations. Our approach gives acceptable results from anatomical, topological and geometrical standpoints as well as provides fast visualization and manipulation of the model. The approach is applicable for building a reference cerebrovascular atlas, developing applications for simulation and planning of interventional radiology procedures and vascular surgery, and in education.

Cerebral Arteries↗

PubMed2002

Stepwise radial complexation of imine groups in phenylazomethine dendrimers.

Dendrimers are highly branched organic macromolecules with successive layers or 'generations' of branch units surrounding a central core. Organic-inorganic hybrid versions have also been produced, by trapping metal ions or metal clusters within the voids of the dendrimers. The unusual, tree-like topology endows these nanometre-sized macromolecules with a gradient in branch density from the interior to the exterior, which can give rise to an energy gradient that directs the transfer of charge and energy from the dendrimer periphery to its core. Here we show that tin ions, Sn(2+), complex to the imine groups of a spherical polyphenylazomethine dendrimer in a stepwise fashion. This behaviour reflects a gradient in the electron density associated with the imine groups, with complexation in a more peripheral generation proceeding only after complexation in generations closer to the core has been completed. By attaching an electron-withdrawing group to the dendrimer core, we are able to change the complexation pattern, so that the core imines are complexed last. By further extending this strategy, it should be possible to control the number and location of metal ions incorporated into dendrimer structures, which might find uses as tailored catalysts or building blocks for advanced materials.

Journal Article↗

PubMed1996

Building intelligent alarm systems by combining mathematical models and inductive machine learning techniques Part 2--sensitivity analysis.

In an earlier study an approach was described to generate intelligent alarm systems for monitoring ventilation of patients via mathematical simulation and machine learning. However, ventilator settings were not varied. In this study we investigated whether an alarm system could be created with which a satisfactory classification performance could be obtained under a wide variety of ventilator settings, by varying inspiratory to expiratory time (I:E) ratio, tidal volume and respiratory rate. In a first experiment three patient data sets were modeled, each with a different I:E ratio. A part of each data set was used to construct an alarm system for each I:E ratio. The remaining part was used to test the performance of the alarm systems. The three training sets were also combined to construct one alarm system, which was tested with the three test sets. Finally, all alarm systems were tested with data generated by a patient simulator. Similar experiments were performed for the tidal volume and the respiratory rate. It was concluded that an optimally functioning alarm system should contain a library of rule sets, one for each set of ventilator settings. A second best alternative is to take all possible settings into consideration when constructing the training set. Classification performance of the trees that were trained with multiple ventilator settings ranged from 98 to 100% for all test sets. When tested with the independent patient simulator data the classification performance of these trees ranged from 80 to 100%.

Airway Resistance↗

PubMed1993

Electron microscopic study of supramolecular liquid crystalline polymers formed by molecular-recognition-directed self-assembly from complementary chiral components.

Electron microscopic observation provides insight into the nature of the polymeric supramolecular liquid crystalline species (TP2, TU2)n formed by polyassociation of the complementary components TP2 and TU2 derived from D-, L-, or meso-tartaric acid (where T is any form of tartaric acid, D is the D species, and L is the L species) and from pyridine (P) and uracil (U) derivatives. Increasing the concentration of equimolecular solutions of (LP2 + LU2) mixtures leads to the progressive assembly of very long supramolecular-polymolecular entities. The process involves successively nucleation to give small nuclei, growth to filaments, and lateral association to tree-like species, strings, and fibers. The species formed are helical; their helicity is right-handed, induced by the chirality of the components and transferred to the larger entities. The data agree with the formulation of the primary filament as a triple-helical species formed by three helically wound supramolecular strands. (DP2 + DU2) mixtures yield left-handed helical species. The helicity of the materials obtained from complementary components having different chirality is imposed by the U component, being, respectively, right- and left-handed for (DP2 + LU2) and (LP2 + DU2). No helicity is found for the meso compounds. The racemic mixture of all four L and D components yields long superhelices of opposite handedness that coexist in the same sample. This points to the occurrence of spontaneous racemate resolution by chiral selection of the components in the self-assembly of these supramolecular liquid crystalline species. The present results illustrate how extended supramolecular-polymolecular entities build up through molecular-recognition-directed polyassociation of complementary components. They also show that molecular chirality is translated into supramolecular helicity that is expressed at the level of the material on nanometric and micrometric scales.

Journal Article↗

PubMed2003

Roadside measurements of deforestation in the Amazon area of Bolivia.

This study describes the deforestation impact from three settlements, 5 de Junio, El Tigre, and 30 de Agosto, near the Madidi National Park in Bolivia. First deforestation rates along the road that connects the settlements and then deforestation within each settlement are examined. Landsat Thematic Mapper (TM) imagery from 1987, 1997, and 2000 were used to measure the deforestation. Face-to-face interviews were also used to collect detailed social and land-use information. Road-building and farming have been the major causes of deforestation in this region. The TM measurements indicate a high increase in the deforestation rate along the road in the area of study. The results also show a rapidly escalating deforestation rate in 5 de Junio, a potential high future deforestation rate in El Tigre, and a gradual deforestation increase in 30 de Agosto. The information provided by the settlers about clearing was compared with the imagery analysis. Generally, the settler's estimates were lower than the deforestation as derived from the imagery.

Bolivia↗

PubMed1985

Allergy to weeping fig--a new occupational disease.

During the last decade green plants have become more common in interior decoration. There are companies specializing in the leasing of green plants to public buildings and offices. Weeping fig is one of the most popular green plants. Dust and dry components of the plant are usually removed by vigorous shaking. In this way the allergen becomes airborne. During a few months we have seen several plant keepers who have developed airway allergy to weeping fig. Two of them have been thoroughly investigated. Both are atopics. Extracts were made from leaves and branches and both patients had positive skin prick tests and RAST. The risk of sensitization in plant keepers who work with weeping fig is probably considerable.

Adult↗

PubMed2006

An XML-based system for synthesis of data from disparate databases.

Diverse data sets have become key building blocks of translational biomedical research. Data types captured and referenced by sophisticated research studies include high throughput genomic and proteomic data, laboratory data, data from imagery, and outcome data. In this paper, the authors present the application of an XML-based data management system to support integration of data from disparate data sources and large data sets. This system facilitates management of XML schemas and on-demand creation and management of XML databases that conform to these schemas. They illustrate the use of this system in an application for genotype-phenotype correlation analyses. This application implements a method of phenotype-genotype correlation based on phylogenetic optimization of large data sets of mouse SNPs and phenotypic data. The application workflow requires the management and integration of genomic information and phenotypic data from external data repositories and from the results of phenotype-genotype correlation analyses. Our implementation supports the process of carrying out a complex workflow that includes large-scale phylogenetic tree optimizations and application of Maddison's concentrated changes test to large phylogenetic tree data sets. The data management system also allows collaborators to share data in a uniform way and supports complex queries that target data sets.

Animals↗

PubMed2001

The Area Production Model: a tool and concept for sustainable land-use and forest-resource management.

In developing countries, planning in the forestry sector has been seen as an appropriate instrument to prepare and implement government policies and programs. Despite its potential and recent advancements in, for example, remote sensing and infrastructure, tropical forest land-use planning is often formal and non-integrated with agriculture. It rarely involves all legitimate stakeholders and neglects taking into account actual land-use. The socio-economic and environmental consequences of these shortcomings emphasise the need for alternative ways of approaching planning. This article summarises the idea, structure and current status of the Area Production Model (APM), originally developed in the 1980s, which is now gaining interest as a land-use planning tool in Africa and Asia. It describes the development over time of production and consumption in agriculture and forestry within a defined geographical area operating under different assumptions on management, land use and socio-economic and macro-economic changes. From a narrow perspective, the APM is a fairly simple computerised tool for generating scenarios. In a broad sense, it is a concept comprising the whole planning process including organisation, inventory, data analysis, consensus building and strategy. A case-study in Laos, based on verified data for a historical period of 45 years, and a review of different APM applications in the world over the last 15 years are presented as a base for conclusions about its potential and shortcomings. In some cases where the APM concept was used in training courses and planning exercises involving stakeholders, it generated a strong interest in collecting and analysing relevant information. It provides the means of addressing a number of shortcomings in current planning.

Conservation of Natural Resources↗

PubMed2004

Finding optimal decision scores by evolutionary strategies.

OBJECTIVE: Severeness of illness is often rated by physicians at admission time. For this purpose, medical scores have been developed as 'objective' rating methods. When considering their classification performance, it is not assumed that such an expert-driven score is an optimal one. Our aim is to design an optimized data-driven score. In particular, we compare classical scores with a new data-driven score for abdominal septic shock patients. METHODS AND MATERIAL: Medical scores are used as ratings for different aspects of a patient's health status. The medical score indicates either a more critical or a healthier condition. For example, physicians rate organ conditions for different organs. We consider four different scores, SOFA, APACHE II, SAPS II, and MODS. Beyond the use of such classical scores, we propose an evolutionary strategy, that is suitable for score design, to find optimized data-driven scores. A database of 282 patients is used to optimize a new score for abdominal septic shock patients. Classification performance is compared by a ROC analysis. RESULTS: We give a general instruction for building optimized scores, i.e. we define individuals and operators for the evolutionary score design task. We apply this instruction to abdominal septic shock patient data. When compared to the SOFA score, it has similar classification performance, but it is more performant than APACHE II, SAPS II, and MODS. It can be used as a daily bedside score. CONCLUSIONS: We argue that evolutionary strategies should be used for optimizing purposes in the medical score design process. Using abdominal septic shock patient data, we show that evolutionary score design is a feasible and performant method that can complement or replace expert knowledge, provided that qualitative data is available.

Abdomen↗

PubMed2006

[Forest distribution pattern and land use strategy along urban-rural gradient].

According to the buffers and urban fringes of Nanjing in 1988 and 2003, and by using landsat TM images and DEM data, 8 urban-rural gradient zones called I, II, III,......, VIII in this city were marked off, and the forest distribution pattern as well as the land use strategies along these gradient zones were studied. The results showed that in each of these zones, there was a significant positive correlation between the coverage of mountainous area and forest, and the forest coverages were obviously higher in mountainous than in flat area, with a distribution pattern of I > II, II < III, III approximately equal to IV, IV > V > VI > VII > VIII. In urbanizing area, there were three major landuse types, i. e. , urban building, ecological regulation (mainly forest stand), and agricultural production (mainly crop land). The potential value of a certain land use type became the leading cause of land use type selection. Inner city area had very low forest coverage because of its high exploitation value, and the ecological value of the outskirts within 10 km beyond the urban fringe was comparatively outstanding, with the forest coverage increased significantly. The forest coverage declined with the increasing distance to urban, because of the dominant station of the production value.

China↗

PubMed2006

Season effects on leaf nitrogen partitioning and photosynthetic water use efficiency in mango.

The key parameters of photosynthetic capacity (maximum carboxylation rate (V(cmax)), electron transport capacity (J(max)) and dark respiration rate (R(d))) and the slope (m) of the stomatal conductance model of Ball et al. [Progress in photosynthetic research, Martinus Nijhoff, Dordrecht, 1987] were measured for a whole growing season in fully expanded leaves of 12-year-old mango trees cv. Cogshall in La Réunion island. Leaf nitrogen partitioning into carboxylation (P(c)) and bioenergetic (P(b)) pools were computed according to the model of Niinemets and Tenhunen [Plant Cell Environ 1997;20: 845-66]. V(cmax), J(max), R(d), P(c) and P(b) remained relatively stable over the whole study period, with the exception of the period of linear fruit growth when J(max), R(d) and P(b) were slightly lower, and leaf non-structural carbohydrate content higher. During the pre-floral and floral periods, m decreased by more than 50%, indicating an increase in photosynthetic water use efficiency and m increased again during the period of linear fruit growth. Our results show that, in tropical orchard conditions characterized by mild seasonal climatic changes and non-limiting water supply, leaf nitrogen partitioning is rather stable. Our results also advocate for more studies on the effect of phenology on m and photosynthetic water use efficiency, which is of paramount importance for building coupled biochemical models of photosynthetic carbon assimilation.

Climate↗

PubMed2003

[Africanized bees in a metropolitan area of Brazil: shelters and climatic influences].

OBJECTIVE: Africanized bees are the most aggressive bees, form swarms several times a year and build their nests in a great variety of places different from European bees. This behavior brings them into closer contact with human populations, thus giving rise to a larger number of injuries. A study was carried out to gain greater knowledge on these bees' behavior and thus create more efficient strategies for dealing with them and educating the population on this regard. METHODS: Data consisted of 3,061 registries of requests to the Center for the Control of Animal Diseases of S o Paulo for removing bee colonies and wandering swarms in the period between 1994 and 1997. An evaluation of the most frequent nesting sites and their correlation with climatic variables was conducted using Pearson's coefficient. RESULTS: There were 3,061 requests in the study period and the daily volume had a positive correlation with average temperature and degree of insolation and a negative correlation with relative humidity and rainfall. The colonies showed a likelihood for nesting in artificial constructions and the wandering swarms for nesting in trees. CONCLUSIONS: Those periods of the year characterized by high temperatures and low rainfall are related to greater activity of bees and a larger number of wandering swarms, thus giving rise to increased contact with human populations. Items such as boxes and oil-drums should not be left outdoors and ceilings and walls should be sealed off, as they are potential nesting sites for colonies and swarms. Wooded areas may harbor swarms, thus care should always be taken when in the proximity of such areas. No attempt should be made to handle swarms.

Animals↗

PubMed2004

Intact polar membrane lipids in prokaryotes and sediments deciphered by high-performance liquid chromatography/electrospray ionization multistage mass spectrometry--new biomarkers for biogeochemistry and microbial ecology.

Lipids from prokaryotic cell membranes can serve as sources of information on the biogeochemistry and microbial ecology of natural ecosystems. Traditionally, apolar derivatives of the intact polar membrane molecules, e.g., fatty acids, have been the major target of lipid-based biogeochemical studies. However, when still intact, i.e., as glycerol esters and ethers with attached polar headgroups, membrane lipids are diagnostic for living prokaryotes, which makes them excellent biomarkers for the study of in situ microbial processes in geological systems such as sediments or soils. Intact polar lipids (IPLs) are attractive analytical targets because they are taxonomically more specific than their apolar derivatives and avoid exclusion of signals from prokaryotes that primarily build their membranes with ether-bound lipids such as archaea and some bacteria. Here we report results from analyses of IPLs in pure cultures of biogeochemically relevant prokaryotes and marine sediments by high-performance liquid chromatography/electrospray ionization ion-trap mass spectrometry (HPLC/ESI-IT-MSn). This technique is suitable for screening of biomass and environmental samples for distinctive taxonomic structural features such as distribution of polar lipid headgroups, types of bonds between alkyl moiety and glycerol backbone, and the chain length and degree of unsaturation in the alkyl moieties. We present analytical protocols to decipher structural information from mass spectral data. The IPL contents in selected archaeal and bacterial species are diverse and qualify as molecular fingerprints. Applied to marine sediments, the approach provided detailed information on the dominant microbial groups. The IPLs from bacterial members of anaerobic methanotrophic communities in surface sediments at Hydrate Ridge resemble those found in Desulfosarcina variabilis. The presence of dietherglycerophospholipids, however, suggests the presence of other bacteria possibly affiliated with the deepest phylogenetic branches in the tree of life. Sediments from approximately 90 m below the seafloor on the Peruvian continental margin are dominated by intact archaeal tetraethers with glycosidically bound hexoses as headgroups, consistent with a significant fraction of the community being archaea. Additional calditol-based tetraethers imply that the sedimentary archaea are taxonomically linked to the crenarchaeal Sulfolobales.

Biomarkers↗

PubMed2005

Exposure to moulds in flats and the prevalence of allergic diseases--preliminary study.

The presented study concerned mycological analysis of buildings in Lódź and evaluation of the role between filamentous fungi contaminated flats and inhabitants health (allergic airway diseases). 49 inhabitants of 20 flats with signs of moulds contamination were examined. Air samples were collected in houses and outdoors. In all inhabitants skin prick tests (SPT) to common allergens and to standardized particular fungal extracts were performed. Moreover, total and serum specific IgE to moulds, rest spirometry were measured in all subjects. Level of moulds contamination in the air of flats was high and in 75% cases exceed accepted limits. The most frequent species isolated from examined rooms were: Penicillium, Cladosporium, Aspergillus, Acremoniu and Alternaria. The most frequent symptoms reported by examined subjects were rhinitis (N = 29, 59.2%), conjunctivitis (N = 29, 59.2%), chronic cough (N = 24, 49%), dyspnea (N = 15, 30.6%) and skin symptoms (N = 24, 49%). Elevated IgE level was found in 12 subjects (24.5%) and in three patients (6.1%) mould specific serum IgE were detected. Nineteen out of all subjects (38.8%) had positive SPT to common allergens (house dust mites, grass and tree pollens). Eight out of these patients (16.3% of the group) were sensitized to moulds (Candida albicans, Alternaria alternata, Botrytis cinerea, Trichophyton mentagrophytes, Helminthosporium halodes, Aspergillus). In all cases sensitisation to moulds was accompanied by allergy to other common allergens. No isolated hypersensitivity to moulds was found. Although the frequency of self-reported symptoms was high, the prevalence of atopy and allergic diseases seems to be similar to that found in general population, but that statement must be confirmed by comparison of the control group.

Adolescent↗

PubMed1991

Object-oriented design and programming in medical decision support.

The concept of object-oriented design and programming has recently received a great deal of attention from the software engineering community. This paper highlights the realisable benefits of using the object-oriented approach in the design and development of clinical decision support systems. These systems seek to build a computational model of some problem domain and therefore tend to be exploratory in nature. Conventional procedural design techniques do not support either the process of model building or rapid prototyping. The central concepts of the object-oriented paradigm are introduced, namely encapsulation, inheritance and polymorphism, and their use illustrated in a case study, taken from the domain of breast histopathology. In particular, the dual roles of inheritance in object-oriented programming are examined, i.e., inheritance as a conceptual modelling tool and inheritance as a code reuse mechanism. It is argued that the use of the former is not entirely intuitive and may be difficult to incorporate into the design process. However, inheritance as a means of optimising code reuse offers substantial technical benefits.

Adult↗

PubMed1992

[Emission and control of gases and odorous substances from animal housing and manure depots].

Agricultural animal production in increasingly regarded as a source of gases which are both aggravating and ecologically harmful. An overview of the origin, number and quantity of trace gases emitted from animal housing and from manure stores is presented and possible means of preventing or reducing them are discussed. Of the 136 trace gases in the air of animal houses, odorous substances, ammonia and methane are most relevant to the environment. The role played by the remaining gases is largely unknown. Quantitative information is available for 23 gases. The gases are emitted principally from freshly deposited and stored faeces, from animal feed and from the animals themselves. Future work should determine sources and quantities of the gases emitted from animal housing more precisely and should aim to investigate the potential of these gases to cause damage in man, animals and environment. Odorous substances have an effect on the area immediately surrounding the animal housing. They can lead to considerable aggravation in humans. For years, VDI1 guidelines (3471/72), which prescribe distances between residential buildings and animal housing, have been valuable in preventing odour problems of this kind. Coverings are suitable for outside stores. The intensity of the odour from animal housing waste air increases from cattle through to hens and pigs; it is also further affected by the type of housing, the age of the animals and the purpose for which they are being kept. Methods of cleaning waste air (scrubbers/biofilters) are available for problematic cases. The need for guidelines to limit emissions from individual outside manure stores (lagoons) is recognised. Total ammonia emissions from animal production in the Federal Republic of Germany (up to 1989) are estimated at approximately 300,000 to 600,000 t/year. There is a shortage of satisfactory and precise research on the extent of emissions, in particular on those from naturally ventilated housing. It is calculated that between 12 and 21 kg/ha of nitrogen a year enter the soil via the air, the average of which is higher than the average "critical loads" for most natural habitats. Ammonia has a direct effect on the trees in the area surrounding animal housing and is transported long distances through the air causing eutrophication and acidification of water and vegetation. This frequently results in changes in plant sociology. Reduction measures must begin with the housing and manure removal systems and with feeding and management.(ABSTRACT TRUNCATED AT 400 WORDS)

Air Pollution↗

PubMed1999

Decision support systems in health economics.

This article describes a system addressed to different health care professionals for building, using, and sharing decision support systems for resource allocation. The system deals with selected areas, namely the choice of diagnostic tests, the therapy planning, and the instrumentation purchase. Decision support is based on decision-analytic models, incorporating an explicit knowledge representation of both the medical domain knowledge and the economic evaluation theory. Application models are built on top of meta-models, that are used as guidelines for making explicit both the cost and effectiveness components. This approach improves the transparency and soundness of the collaborative decision-making process and facilitates the result interpretation.

Computer Simulation↗

PubMed1999

Building syntactic structure in speaking.

We investigated how people produce simple and complex phrases in speaking using a newly developed immediate recall task. People read and tried to memorize a target sentence, then read a prime sentence, then did a distractor task involving the prime sentence. Despite the delay and activity between memory and recall, people could still recall the target sentence although the syntactic form of the recalled sentence was influenced by the syntactic form of the prime sentence. This result replicates the syntactic priming effect found with other experimental paradigms. Using this task, we tested how people used abstract syntactic plans to produce simple and complex noun phrases. We found syntactic priming both when targets and prime sentences matched in complexity and when they did not match, suggesting that simple and complex noun phrases are built by the same syntactic routines during speech production.

Humans↗