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Biomedical subjects

C J Tucker

Publications and source records attributed to C J Tucker.

At least 19 recordsLinked to original sources
PubMed2005

Drier summers cancel out the CO2 uptake enhancement induced by warmer springs.

An increase in photosynthetic activity of the northern hemisphere terrestrial vegetation, as derived from satellite observations, has been reported in previous studies. The amplitude of the seasonal cycle of the annually detrended atmospheric CO(2) in the northern hemisphere (an indicator of biospheric activity) also increased during that period. We found, by analyzing the annually detrended CO(2) record by season, that early summer (June) CO(2) concentrations indeed decreased from 1985 to 1991, and they have continued to decrease from 1994 up to 2002. This decrease indicates accelerating springtime net CO(2) uptake. However, the CO(2) minimum concentration in late summer (an indicator of net growing-season uptake) showed no positive trend since 1994, indicating that lower net CO(2) uptake during summer cancelled out the enhanced uptake during spring. Using a recent satellite normalized difference vegetation index data set and climate data, we show that this lower summer uptake is probably the result of hotter and drier summers in both mid and high latitudes, demonstrating that a warming climate does not necessarily lead to higher CO(2) growing-season uptake, even in high-latitude ecosystems that are considered to be temperature limited.

Carbon Dioxide↗
PubMed2005

Climate-based health monitoring systems for eco-climatic conditions associated with infectious diseases.

Despite a century of confidence and optimism in modern medicine and technology inspired by their often successful prevention and control efforts, infectious diseases remain an omnipresent, conspicuous major challenge to public health. Effective detection and control of infectious diseases require predictive and proactive efficient methods that provide early warning of an epidemic activity. Of particular relevance to these efforts is linking information at the landscape and coarser scales to data at the scale of the epidemic activity. In recent years, landscape epidemiology has used satellite remote sensing and geographic information systems as the technology capable of providing, from local to global scales, spatial and temporal climatic patterns that may influence the intensity of a vector-borne disease and predicts risk conditions associated with an epidemic. This article provides a condensed, and selective look at classical material and recent research about remote sensing and GIS (geographic information system) applications in public health.

Africa, Central↗
PubMed2002

Detection of diluted gene expression alterations using cDNA microarrays.

The use of DNA microarrays has spanned numerous disciplines of life science research. Despite the volume of studies utilizing this technology, no consensus exists on basic issues such as the determination of significantly altered genes in a given experiment, often leading to either false-negative or false-positive data. In this report, we study the effect of dilution of biological alterations on the detection level of gene expression differences using cDNA microarrays. We propose that subtle alterations in transcript levels of genes below the 2-fold level should be considered when replicate hybridizations are performed, because these subtle gene expression changes may be due to a robust response in few cells. We measured the effect of dilution of gene expression and found that differences in gene expression between the two cell lines assayed (HaCaT and MCF-7) were detected even after a 20-fold dilution factor. These results better our understanding of biological alterations that comprise a relatively small percentage of an assayed organ and help in the interpretation of gene expression data.

Cell Line↗
PubMed2001

A large carbon sink in the woody biomass of Northern forests.

The terrestrial carbon sink, as of yet unidentified, represents 15-30% of annual global emissions of carbon from fossil fuels and industrial activities. Some of the missing carbon is sequestered in vegetation biomass and, under the Kyoto Protocol of the United Nations Framework Convention on Climate Change, industrialized nations can use certain forest biomass sinks to meet their greenhouse gas emissions reduction commitments. Therefore, we analyzed 19 years of data from remote-sensing spacecraft and forest inventories to identify the size and location of such sinks. The results, which cover the years 1981-1999, reveal a picture of biomass carbon gains in Eurasian boreal and North American temperate forests and losses in some Canadian boreal forests. For the 1.42 billion hectares of Northern forests, roughly above the 30th parallel, we estimate the biomass sink to be 0.68 +/- 0.34 billion tons carbon per year, of which nearly 70% is in Eurasia, in proportion to its forest area and in disproportion to its biomass carbon pool. The relatively high spatial resolution of these estimates permits direct validation with ground data and contributes to a monitoring program of forest biomass sinks under the Kyoto protocol.

Biomass↗
PubMed2001

Biospheric primary production during an ENSO transition.

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) provides global monthly measurements of both oceanic phytoplankton chlorophyll biomass and light harvesting by land plants. These measurements allowed the comparison of simultaneous ocean and land net primary production (NPP) responses to a major El Niño to La Niña transition. Between September 1997 and August 2000, biospheric NPP varied by 6 petagrams of carbon per year (from 111 to 117 petagrams of carbon per year). Increases in ocean NPP were pronounced in tropical regions where El Niño-Southern Oscillation (ENSO) impacts on upwelling and nutrient availability were greatest. Globally, land NPP did not exhibit a clear ENSO response, although regional changes were substantial.

Biomass↗
PubMed2001

Higher northern latitude normalized difference vegetation index and growing season trends from 1982 to 1999.

Normalized difference vegetation index data from the polar-orbiting National Oceanic and Atmospheric Administration meteorological satellites from 1982 to 1999 show significant variations in photosynthetic activity and growing season length at latitudes above 35 degrees N. Two distinct periods of increasing plant growth are apparent: 1982-1991 and 1992-1999, separated by a reduction from 1991 to 1992 associated with global cooling resulting from the volcanic eruption of Mt. Pinatubo in June 1991. The average May to September normalized difference vegetation index from 45 degrees N to 75 degrees N increased by 9% from 1982 to 1991, decreased by 5% from 1991 to 1992, and increased by 8% from 1992 to 1999. Variations in the normalized difference vegetation index were associated with variations in the start of the growing season of -5.6, +3.9, and -1.7 days respectively, for the three time periods. Our results support surface temperature increases within the same period at higher northern latitudes where temperature limits plant growth.

Climate↗
PubMed2001

Climate-disease connections: Rift Valley Fever in Kenya.

All known Rift Valley fever(RVF) outbreaks in Kenya from 1950 to 1998 followed periods of abnormally high rainfall. On an interannual scale, periods of above normal rainfall in East Africa are associated with the warm phase of the El Niño/Southern Oscillation (ENSO) phenomenon. Anomalous rainfall floods mosquito-breeding habitats called dambos, which contain transovarially infected mosquito eggs. The eggs hatch Aedes mosquitoes that transmit the RVF virus preferentially to livestock and to humans as well. Analysis of historical data on RVF outbreaks and indicators of ENSO (including Pacific and Indian Ocean sea surface temperatures and the Southern Oscillation Index) indicates that more than three quarters of the RVF outbreaks have occurred during warm ENSO event periods. Mapping of ecological conditions using satellite normalized difference vegetation index (NDVI) data show that areas where outbreaks have occurred during the satellite recording period (1981-1998) show anomalous positive departures in vegetation greenness, an indicator of above-normal precipitation. This is particularly observed in arid areas of East Africa, which are predominantly impacted by this disease. These results indicate a close association between interannual climate variability and RVF outbreaks in Kenya.

Aedes↗
PubMed2001

Conditions of sibling support in adolescence.

This study examined the nature and extent of adolescent siblings' supportive roles and the conditions under which siblings provide support to one another about familial and nonfamilial issues. Data were collected from 185 adolescent firstborn (M age = 16 years) and second born (M age = 13 years) sibling pairs. In home interviews, siblings reported on family experiences and psychosocial functioning during the past year. In a series of 7 evening telephone interviews, siblings reported on their shared daily activities. Findings suggested that both older and younger siblings view older siblings as sources of support about nonfamilial issues such as social and scholastic activities and that siblings assume equally supportive roles about familial issues. Further, the results suggested that family background characteristics, sibling relationship qualities, and adolescents' psychosocial functioning were linked to the nature and extent of sibling support.

Adolescent↗
PubMed1999

Climate and satellite indicators to forecast Rift Valley fever epidemics in Kenya.

All known Rift Valley fever virus outbreaks in East Africa from 1950 to May 1998, and probably earlier, followed periods of abnormally high rainfall. Analysis of this record and Pacific and Indian Ocean sea surface temperature anomalies, coupled with satellite normalized difference vegetation index data, shows that prediction of Rift Valley fever outbreaks may be made up to 5 months in advance of outbreaks in East Africa. Concurrent near-real-time monitoring with satellite normalized difference vegetation data may identify actual affected areas.

Animals↗
PubMed1999

Adolescents' explanations for political issues: concordance with their views of self and society.

The relationships between adolescents' explanations for unemployment, poverty, and homelessness and their beliefs about opportunity, reports of family values, and personal aspirations were tested for 434 teenagers (mean age = 16 years 4 months). Explanations were coded for references to individual causes, societal causes, or both. Higher maternal education and average household income in the adolescent's school district were positively related to the likelihood of attributing all three problems to societal causes. When explaining unemployment, older adolescents noted both causes, and boys mentioned individual factors whereas girls mentioned societal factors. After adjustment for background factors, those endorsing individual causes were more likely to believe that all Americans enjoyed equal opportunity and that government support encouraged dependency, and they were more committed to materialist goals. In contrast, youth endorsing societal or situational causes had more altruistic life goals and reported that compassion was emphasized in their families.

Adolescent↗
PubMed1996

Remotely sensed surrogates of meteorological data for the study of the distribution and abundance of arthropod vectors of disease.

This paper gives an overview of how certain meteorological data used in studies of the population dynamics of arthropod vectors of disease may be predicted using remotely sensed, satellite data. Details are given of the stages of processing necessary to convert digital data arising from satellite sensors into ecologically meaningful information. Potential sources of error in these processing steps are also highlighted. Relationships between ground-measured meteorological variables (saturation deficit, ground temperature and rainfall) and data from both the National Oceanic and Atmospheric Administration's, polar-orbiting, meteorological satellites and the geostationary, Meteosat satellite are defined and examples detailed for Africa. Finally, the current status of existing satellite platforms and future satellite missions are reviewed and potential data availability discussed. How such satellite-based predictions have proved valuable in understanding the distribution of tsetse fly species in Côte d'Ivoire and Burkina Faso will be the subject of a future review.

Africa↗
PubMed1996

Use of weather data and remote sensing to predict the geographic and seasonal distribution of Phlebotomus papatasi in southwest Asia.

Sandfly fever and leishmaniasis were major causes of infectious disease morbidity among military personnel deployed to the Middle East during World War II. Recently, leishmaniasis has been reported in the United Nations Multinational Forces and Observers in the Sinai. Despite these indications of endemicity, no cases of sandfly fever and only 31 cases of leishmaniasis have been identified among U.S. veterans of the Persian Gulf War. The distribution in the Persian Gulf of the vector, Phlebotomus papatasi, is thought to be highly dependent on environmental conditions, especially temperature and relative humidity. A computer model was developed using the occurrence of P. papatasi as the dependent variable and weather data as the independent variables. The results of this model indicated that the greatest sand fly activity and thus the highest risk of sandfly fever and leishmania infections occurred during the spring/summer months before U.S. troops were deployed to the Persian Gulf. Because the weather model produced probability of occurrence information for locations of the weather stations only, normalized difference vegetation index (NDVI) levels from remotely sensed Advanced Very High Resolution Radiometer satellites were determined for each weather station. From the results of the frequency of NDVI levels by probability of occurrence, the range of NDVI levels for presence of the vector was determined. The computer then identified all pixels within the NDVI range indicated and produced a computer-generated map of the probable distribution of P. papatasi. The resulting map expanded the analysis to areas where there were no weather stations and from which no information was reported in the literature, identifying these areas as having either a high or low probability of vector occurrence.

Animals↗
PubMed1990

Application of polar-orbiting, meteorological satellite data to detect flooding of Rift Valley Fever virus vector mosquito habitats in Kenya.

Measurements of green-leaf vegetation dynamics recorded by the advanced very high resolution radiometer instruments onboard National Oceanic and Atmospheric Administration satellites 7 and 9 were used to derive ground moisture and rainfall patterns in Kenya and monitor resultant flooding of mosquito larval habitats (dambos) likely to support Rift Valley Fever virus vector mosquitoes (Aedes and Culex spp.). Satellite-derived data from mid-1981 to December 1988 have been analysed with corresponding rainfall, flooding and vector population data as they relate to Rift Valley Fever virus ecology. Single (7 x 7 km) and multiple grid-cell image analysis (200 x 300 km) in small localized areas and large geographical regions, respectively, of vegetation data were used to quantify the potential for flooding of mosquito breeding habitats. The ability to detect accurately parameters, such as ground moisture, that determine flooding could provide local officials with sufficient warning to allow for implementation of specific mosquito control measures before a disease outbreak.

Animals↗
PubMed1988

Measuring migration distances: self-reporting and indirect methods.

Methods of determining distance covered in migration are discussed. "Two approaches for doing so are simply to ask movers how far they moved or to infer distance from localities of origin and destination. The former has been used in Health Interview Surveys, and the latter is applied to Current Population Surveys; both are national surveys conducted by the U.S. Census Bureau. The two approaches appear to produce consistent results and offer ways of increasing comparability of data and research findings on geographical mobility."

Americas↗
PubMed1988

Migration distances: an international comparison.

Comparing the level or amount of migration within different countries has been a longstanding problem because the local administrative areas commonly used as the basis for measuring migration vary greatly in size and significance within and between countries. Distance moved is a critical aspect of most concepts of migration, and measuring it would facilitate cross-national comparisons. Apparently only the United States, Great Britain, and Sweden have measured migration distances for the country as a whole, and this information is used as the basis for comparative analysis of spatial mobility.

Adolescent↗
PubMed1987

Detection of Rift Valley fever viral activity in Kenya by satellite remote sensing imagery.

Data from the advanced very high resolution radiometer on board the National Oceanic and Atmospheric Administration's polar-orbiting meteorological satellites have been used to infer ecological parameters associated with Rift Valley fever (RVF) viral activity in Kenya. An indicator of potential viral activity was produced from satellite data for two different ecological regions in Kenya, where RVF is enzootic. The correlation between the satellite-derived green vegetation index and the ecological parameters associated with RVF virus suggested that satellite data may become a forecasting tool for RVF in Kenya and, perhaps, in other areas of sub-Saharan Africa.

Animals↗
PubMed1987

Frequency of geographic mobility: findings from the National Health Interview Survey.

Age stands out as an important factor in multiple moves over a relatively short period of time. In addition, in the NHIS data whites show a higher tendency to be multiple movers than do blacks. It was also found that persons defined as interstate migrants moved more often than either intrastate migrants or local movers, but it is impossible to conclude anything more definitive about that relationship. In conclusion, mobility defined as a move rather than as a mover is clearly higher than estimates derived from five-year census data or the CPS, which only use the idea of a mover. On the whole, though, over three-year periods most persons do not move at all or they move and then return. Of those who do change residence, the majority move only once. By far the bulk of moves is accounted for by a relatively small segment of Americans. Of 34,000 moves reported in the NHIS, more than one-half were made by a small number of persons--4,400--who not only constituted scarcely one-fourth of all movers but were less than 1 out of every 11 Americans.

Adolescent↗