SEARCH · Search PubMed

Results for “environmental variability”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

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

At least 757 records · Page 42Linked to original sources

PubMed2003

Localized hypoplasia of the primary canine in bonobos, orangutans, and gibbons.

This paper extends observations by Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363; [2001] Am. J. Phys. Anthropol. 116:199-208) of localized hypoplasia of the primary canine (LHPC) among large apes to gibbons, bonobos, and orangutans. LHPC is a roughly circular area of deficient enamel on the labial surface of primary canine teeth which, on current evidence from humans, forms several months after birth due to malnutrition-induced craniofacial osteopenia, leading to crypt fenestration that exposes the dental follicle and more deep-sited ameloblasts to minor physical traumata during normal motor infant development. Our goal was to determine the prevalence of LHPC among a variety of apes which differ in body mass and socioecology, with a view to elucidating the etiology of the defect. We examined juvenile dentitions from 122 animals from three taxa: 8 Hylobates lar, 75 Pongo pygmaeus from Borneo and Sumatra, and 39 Pan paniscus from central Africa. Reported variables include taxon, sex, arcade, side, and tooth size. Presence/absence and ordinal severity of defect expression were recorded by description, microphotography, and scanning electron microscopy. Molds were taken in high-resolution dental impression materials and cast in epoxy resin. There are clear taxonomic, but no sex, differences. Prevalence ranged from 0.0% in gibbons to 61.5% in bonobos and 85.3% in orangutans. The result for orangutans is similar to that reported by Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363), while bonobos are much more affected than were the common chimpanzees (22%) described by Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363). There are no significant antimeric differences, but the lower canine is much more affected than the upper by LHPC. We show that larger teeth are more affected by LHPC and have more severe defects. Also, we encountered several instances of patent or healing canine crypt fenestrations, occasionally in direct association with LHPC. Location of the defect indicates that LHPC may occur perinatally but more usually several months postnatally. Histological examination showing the neonatal line and LHPC is required to resolve the issue of timing. We concur with Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363) that taxonomic, anatomical, and environmental variables combine to determine the occurrence and appearance of LHPC. Nevertheless, we conclude that LHPC probably reflects deficient growth of the arcades in infant apes and humans.

Animals↗

PubMed2005

Correlation of ambient inhalable bioaerosols with particulate matter and ozone: a two-year study.

In this study, we have examined the relationships between the concentrations of ambient inhalable airborne fungi and pollen with PM10, PM2.5, ozone, organic carbon, selected trace metals (cadmium, copper, lead, and zinc), temperature, and relative humidity. The database was collected in Cincinnati, Ohio, USA, during two consecutive years. Measurements of all environmental variables were performed at the same site continuously 5 days a week except during winter months. The airborne concentrations of biological and non-biological pollutants ranged as follows: total fungi: 184-16 979 spores m(-3); total pollen: 0-6692 pollen m(-3); PM10: 6.70-65.38 microg m(-3); PM2.5: 5.04-45.02 microg m(-3); and ozone: 2.54-64.17 ppb. Higher levels of total inhalable fungi and particulate matter were found during fall and summer months. In contrast, total pollen concentration showed elevated levels in spring. Peak concentrations of ozone were observed during summer and beginning of fall. Our study concluded that several types of inhalable airborne fungi and pollen, particulate matter, and ozone could be positively correlated as a result of the atmospheric temperature influence.

Aerosols↗

PubMed1997

Synechococcus diversity in the California current as seen by RNA polymerase (rpoC1) gene sequences of isolated strains.

Because they are ubiquitous in a range of aquatic environments and culture methods are relatively advanced, cyanobacteria may be useful models for understanding the extent of evolutionary adaptation of prokaryotes in general to environmental gradients. The roles of environmental variables such as light and nutrients in influencing cyanobacterial genetic diversity are still poorly characterized, however. In this study, a total of 15 Synechococcus strains were isolated from the oligotrophic edge of the California Current from two depths (5 and 95 m) with large differences in light intensity, light quality, and nutrient concentrations. RNA polymerase gene (rpoC1) fragment sequences of the strains revealed two major genetic lineages, distinct from other marine or freshwater cyanobacterial isolates or groups seen in shotgun-cloned sequences from the oligotrophic Atlantic Ocean. The California Current low-phycourobilin (CCLPUB) group represented by six isolates in a single lineage was less diverse than the California Current high-phycourobilin (CCHPUB) group with nine isolates in three relatively divergent lineages. The former was found to be the closest known genetic group to Prochlorococcus spp., a chlorophyll b-containing cyanobacterial group. Having an isolate from this group will be valuable for looking at the molecular changes necessary for the transition from the use of phycobiliproteins to chlorophyll b as light-harvesting pigments. Both of the CCHPUB and CCLPUB groups included strains obtained from surface (5 m) and deep (95 m) samples. Thus, contrary to expectations, there was no clear correlation between sampling depth and isolation of genetic groups, despite the large environmental gradients present. To our knowledge, this is the first demonstration with isolates that genetically divergent Synechococcus groups coexist in the same seawater sample.

Base Sequence↗

PubMed1991

Effects of single- and multiday ozone exposures on respiratory function in active normal children.

Ventilatory function was measured twice daily on 46 healthy children aged 8-14 years on at least 7 days for each child during a 4-week period at a northwestern New Jersey residential summer camp in 1988. The highest 1-hr O3 concentration was 150 ppb, while the highest 12-hr H+ concentration (as H2SO4) was 18.6 micrograms/m3. The highest temperature-humidity index was 81 degrees F. The regressions of FVC, FEV1, FEF25-75, and PEFR on O3 in the hour preceding the afternoon function measurements yielded slopes essentially the same as those measured on other children at the same camp in 1984. Regressions of the changes in function between the late morning and late afternoon function measurements on average O3 concentration between them produced significant, but somewhat smaller effects, while regressions of morning function on O3 during the previous day indicated small but still significant effects. There were no significant correlations with other measured environmental variables including H+. Based on the results of this study and similar previous studies, we conclude that O3 exposures in ambient air produce greater lung function deficits in active young people in natural settings then does pure O3 in controlled chamber exposure studies because of: (1) longer exposures; (2) potentiation by other factors in the ambient exposures; (3) the persistence of effects from prior day's exposures; and (4) the persistence of a transient response associated with the daily peak of exposure. It follows that projections of likely effects in the real world from controlled chamber exposure studies should either have a large margin of safety, or the judgment of the extent of effects likely to occur among populations should be based directly on the effects observed in field studies.

Adolescent↗

PubMed1997

The effect of seizure type and medication on cognitive and behavioral functioning in children with idiopathic epilepsy.

Antiepileptic drugs have been reported to have a variety of adverse effects on behavior and performance in children with epilepsy. Previous studies investigating these side effects, however, have not controlled for the baseline status of the child (e.g. underlying neurological condition, seizure type, socioeconomic status, family variables), making it difficult to determine whether changes in function are attributable to the use of medication. We investigated the cognitive and behavioral profiles of 43 children, aged from 4 to 16 years, with new onset, idiopathic seizures. Twenty-six of these children participated in a 6-month follow-up study, and 12 in a 12-month follow-up study, investigating the effects of antiepileptic medications on psychological functioning. The children were of average intelligence (mean IQ 108) and had not previously been treated with antiepileptic medication. Children were classified as having either generalized convulsive, generalized non-convulsive (absence), simple partial, or complex partial seizures. Prior to the initiation of treatment, children with partial seizures were found to perform better than children with generalized seizures on measures of cognitive functioning. Children with convulsive seizures obtained significantly higher cognitive scores than those with non-convulsive seizures. Children with generalized non-convulsive seizures had lower cognitive scores than subjects with other types of seizure. No differences were found between groups at baseline prior to the initiation of antiepileptic medications. Analysis of subjects' performance after 6 and 12 months of antiepileptic therapy showed no significant deterioration attributable to medication. The differences in cognitive performance of the four seizure groups at baseline were not apparent at the time of follow-up. These results indicate that intrinsic and environmental variables may play a more significant role in predisposing certain children to cognitive and learning problems than do antiepileptic medications.

Adolescent↗

PubMedDate not supplied

[Usefulness of the geographic information system (GIS) in the identification of contributing factors to lead blood concentrations in a population of Venezuelan children].

OBJECTIVE: To identify environmental factors that contribute to blood lead levels (BPb) in children living in an urban area in Valencia, Venezuela, using a Geographical Information System (GIS) as an association tool. MATERIAL AND METHODS: An analytical-ecological study was carried out. POPULATION: 60 children. DATA COLLECTED: Demography, potential sources of environmental lead and BPb concentrations. An association was made between environmental variables and BPb, using a buffer analysis. RESULTS: There was a statistically significant difference between BPb in males (11.1+/-3.1 microg/dl) compared to females (9.5+/-2.7 microg/dl). Average BPb of children living within the buffer areas (10.7+/-3.2 microg/dl) was higher than that of the rest of the children (9.9+/-2.5 microg/dl). Children with BPb levels higher than the permissible limit who live in the southern region of the area studied had an average BPb significantly higher than the rest. The GIS enabled the identification of a soldering/welding shop as the nearest source of exposure to the male children's homes. CONCLUSIONS: GIS made it possible to recognize sources of lead exposure in the area and its association with the BPb levels of children that live near such sources. It is suggested to further evaluate additional factors that could influence the risk of lead exposure.

Child↗

PubMed2004

Spatial distribution of chromium and lead in the benthic environment of coastal areas of the Río De La Plata estuary (Montevideo, Uruguay).

Twenty-four sediment samples were collected seasonally during one year from the partially closed Montevideo Bay and the adjacent coastal zone, in Uruguay, in order to determine the impact of chromium and lead in the sediments. Analysis of related environmental variables included bottom water temperature, salinity, pH, dissolved oxygen, and several sedimentological variables such as redox potential and total organic matter. Concentrations and range of variation of these two metals were similar to those found in urbanized and industrialized estuarine environments. Metal enrichment is higher in the bay than in the adjacent coastal zone, however an important increase especially in Pb content was detected in an area previously considered as a pristine one. Considering both metal content and benthic environment characteristics, the study area can be clearly divided in at least two well-defined regions. One is the inner region of the bay near the streams, and the outermost stations of the bay and the adjacent coastal zone form the other. The first one can be considered highly polluted and the other moderately polluted. The values of the metals studied indicated that adverse biological effects are probably occurring, specially in the innermost region of Montevideo Bay.

Chromium↗

PubMed2004

Perinatal predictors of atopic dermatitis occurring in the first six months of life.

OBJECTIVE: Previous studies of predictors of atopic dermatitis have had limited sample size, small numbers of variables, or retrospective data collection. The purpose of this prospective study was to investigate several perinatal predictors of atopic dermatitis occurring in the first 6 months of life. DESIGN: We report findings from 1005 mothers and their infants participating in Project Viva, a US cohort study of pregnant women and their offspring. The main outcome measure was maternal report of a provider's diagnosis of eczema or atopic dermatitis in the first 6 months of life. We used multiple logistic regression models to assess the associations between several simultaneous predictors and incidence of atopic dermatitis. RESULTS: Cumulative incidence of atopic dermatitis in the first 6 months of life was 17.1%. Compared with infants born to white mothers, the adjusted odds ratio (OR) for risk of atopic dermatitis among infants born to black mothers was 2.41 (95% confidence interval [CI]: 1.47, 3.94) and was 2.58 among infants born to Asian mothers (95% CI: 1.27, 5.24). Male infants had an OR of 1.76 (95% CI: 1.24, 2.51). Increased gestational age at birth was a predictor (OR: 1.14; 95% CI: 1.02, 1.27, for each 1-week increment), but birth weight for gestational age was not. Infants born to mothers with a history of eczema had an OR of 2.67 (95% CI: 1.74, 4.10); paternal history of eczema also was predictive, although maternal atopic history was more predictive than paternal history. Several other perinatal, social, feeding, and environmental variables were not related to risk of atopic dermatitis. CONCLUSIONS: Black and Asian race/ethnicity, male gender, higher gestational age at birth, and family history of atopy, particularly maternal history of eczema, were associated with increased risk of atopic dermatitis in the first 6 months of life. These findings suggest that genetic and pre- and perinatal influences are important in the early presentation of this condition.

Cohort Studies↗

PubMed2005

The effects of genotype, age, and social environment on male ornamentation, mating behavior, and attractiveness.

The traits thought to advertise genetic quality are often highly susceptible to environmental variation and prone to change with age. These factors may either undermine or reinforce the potential for advertisement traits to signal quality depending on the magnitude of age-dependent expression, environmental variation, and genotype-age and genotype-environment interaction. Measurements of the magnitude of these effects are thus a necessary step toward assessing the implications of age dependence and environmental variability for the evolution of signals of quality. We conducted a longitudinal study of male guppies (Poecilia reticulata) from 22 full-sibling families. Each fish was assigned at maturity to one of three treatments in order to manipulate his allocation of resources to reproduction: a control in which the male was kept alone, a courtship-only treatment in which he could see and court a female across a clear partition, and a mating treatment in which he interacted freely with a female. We measured each male's size, ornamental color patterns, courtship, attractiveness to females, and mating success at three ages. Size was influenced by treatment and age-treatment interactions, indicating that courtship and mating may impose costs on growth. Tail size and color patterns were influenced by age but not by treatment, suggesting fixed age-dependent trajectories in these advertisement traits. By contrast, display rate and attempted sneak copulation rate differed among treatments but not among ages, suggesting greater plasticity of these behavioral traits. As a result of the different patterns of variation in ornamentation and behavior, male attractiveness and mating success responded to male age, treatment, and the interaction between age and treatment. Neither age nor treatment obscured the presence of genetic variation, and the genetic relationship between male ornamentation and attractiveness remained the same among treatments. Our findings suggest that neither age-dependent variation nor environmentally induced variation in reproductive effort is likely to undermine the reliability of male signaling.

Age Factors↗

PubMed1993

Spatial and temporal patterns of airborne metal pollution: the value of low technology sampling to an environmental epidemiology study.

To investigate an epidemic of respiratory cancer in Armadale, central Scotland, its air pollution was studied. During a period of 18 months, low technology samplers were exposed at 47 sites in the town to monitor the local variations in contamination by atmospheric metals. The samplers were two types of lichen and two types of moss, one of each type being a transplant and the other an in situ sampler. Following each exposure, the comparability of the samplers' uptake and retention of the metals was assessed. The sources of the metals and the effects of environmental variables on the pollution patterns were investigated through statistical analyses of spatial and temporal trends in the data. The spatial patterns of the metals indicated the steel foundry in the town as the major source of most of the pollutants. The temporal patterns, although less statistically significant, suggested the pollution might have been affected by some meteorological factors and by the foundry's output, but not by the output of the other main industry in the town, i.e. a brickworks. The types of sampler showed a general similarity of pollution pattern, but with some differences which indicated that some types of sampler were more suitable than others for particular forms of survey. Low technology sampling can provide information about short-distance and short-term changes in the patterns of airborne pollution by metals, thereby assisting the interpretation of epidemiological patterns of respiratory disease.

Air Pollutants↗

PubMed2006

Epidemiology of undernutrition in adults in Dhaka slum households, Bangladesh.

OBJECTIVES: To identify socioeconomic, demographic and environmental factors that predict undernutrition in adults in a Dhaka slum population. DESIGN: A panel survey, conducted between 1995 and 1997. A random sample of households was selected. Socioeconomic, demographic and environmental variables were collected monthly by questionnaire and nutritional status was assessed. SETTING: Dhaka slums in Bangladesh. SUBJECTS: A total of 1097 adults surveyed during September-December 1996. MAIN OUTCOME MEASURES: Body mass index (BMI) less than 18.5 kg/m(2). RESULTS: There was a sex difference with female subjects having a significant odds ratio for low BMI compared with male subjects (P<0.03). There was no difference by age for males, but there was a difference by age for female subjects, with women aged 30-39 and 40-49 years having the worst BMI (P<0.04; P<0.04). The Beri Bahd area of residence had the worst BMI (P<0.001). Deficit situation as the self-reported financial situation had the worst BMI (P<0.03). Casual wage workers, unskilled and dependent self-employed individuals had the worst BMI (P<0.005; P<0.003). Not being involved in credit organizations and NGO credit organizations was associated with worst BMI (P<0.008; P<0.03). Those households that had an income of 2000-2499 Taka had the worst BMI (P<0.07). Households with a floor area of 5 m(2) or more per consumption unit had the best BMI (P<0.01). Households without electricity had the worst BMI (P<0.007). Households with tube well water had the worst BMI compared with those with tap water (P<0.001). CONCLUSIONS: Under nutrition was related to demographic, economic, social and environmental factors.

Adult↗

PubMed2026

Targeted population genomics uncovers demographic history and genetic divergence in north American wild cranberry.

Wild populations of North American cranberry (Vaccinium macrocarpon Aiton) are reservoirs of genetic variation that may contribute to the improvement of breeding-relevant traits. However, the extent to which wild genetic variation is geographically structured and represented in elite germplasm remains unclear. We analysed 179 wild cranberry accessions from the upper Midwest and Eastern North America to estimate nucleotide diversity (π), population structure, and loci associated with genetic differentiation and environmental variables using a genome-informed targeted genotyping panel. Additionally, 14 demographic scenarios were evaluated using site-frequency-spectrum-based inference to identify historical events that could explain current genetic diversity. We observed extremely low nucleotide diversity within the targeted panel (π = 5 × 10-6). Rare allele distributions strongly influenced π and Tajima's D values, suggesting constrained diversity in the genomic regions assayed that is not captured by heterozygosity-based estimates alone. However, we interpreted these results as conservative lower bounds on genome-wide neutral diversity because the targeted panel is enriched for genic and conserved regions. A clear separation between the Midwest and East populations was observed, with inbreeding coefficients ranging from -0.13 to 0.15. Furthermore, site frequency spectrum inference from the targeted panel supported a demographic scenario consistent with a significant population reduction ≈15-14 thousand years ago (kya), followed by a divergence between the two regions ≈12 kya, and an asymmetric gene flow ≈1.3 kya. We detected 254 candidate loci showing regional allele-frequency differentiation. Several of these loci colocalized with candidate genes linked to stress response, development, and metabolic processes. To evaluate the representation of geographically differentiated wild alleles in a breeding context, we analysed Rutgers breeding materials (n = 484) and found that this panel is enriched for common alleles in Eastern wild populations. These findings indicate regionally structured allele-frequency variation in wild cranberry, with potential relevance to environmental response and breeding. This study extends prior wild cranberry population-genetic research by providing targeted-panel estimates of diversity, comparisons of demographic models, and breeding insights on geographically differentiated alleles, while highlighting the importance of conserving wild cranberry germplasm for use in modern breeding programs.

Journal Article↗

PubMed2003

Benthos abundance pattern and species composition in conditions of pollution in Amursky Bay (the Peter the Great Bay, the Sea of Japan).

Multivariate statistical analysis of data on environmental variables and benthic macrofauna, of 30 sites from four surveys done between 1986 and 1989 in Amursky Bay, is presented. The purpose of this study is to investigate a contamination gradient, assess effects on benthic fauna and evaluate quantitative and qualitative benthic parameters. Contamination was assessed using chemical data from PCA-ordination analysis. Clear patterns were found using three categories, moderate, severe and gross. Significant changes in the number of taxa, density and ecological indices are observed between severe and moderate levels. Changes in these parameters, excluding the number of species, were also detected between gross and moderate levels. Only biomass differs non-significantly. However results of cluster analysis and MDS ordination indicate that two benthic communities exist in Amursky Bay. The most "contaminant insensitive" species polychaetes are Tharyx pacifica, Dorvillea (Schistomeringos) japonica, Dipolydora cardalia, Capitella capitata, phoronid Phoronopsis harmeri. Contaminant sensitive species include Maldane sarsi, Lumbrineris sp. and Scoloplos armiger.

Animals↗

PubMed2026

Engineering cold stress resilience in capsicum annuum through functional genomics and precision breeding.

This review synthesizes the molecular mechanisms of cold tolerance in pepper, integrating multi-omics data,genome editing, and precision breeding strategies to accelerate the development of cold-resilient cultivars. Cold stress is a significant environmental factor that affects the growth, productivity, and fruit quality of Capsicum annuum by impairing membrane integrity photosynthesis and cellular redox homeostasis. Although pepper has several endogenous cold-responsive regulators such as CaNAC035 and CabHLH035, along with antioxidant defense systems, its cold tolerance remains limited due to low transcriptional activation of key regulators, functional redundancy among cold-responsive genes, and the polygenicity of cold tolerance. These complexities, combined with low genetic diversity and linkage drag, have hindered the improvement of cold-resistant cultivars through conventional breeding. This review brings together the recent progress in understanding the molecular mechanisms of cold stress perception, signal transduction, transcriptional regulation, metabolic reprogramming, and phytohormone interactions in pepper. Precision Breeding 2.0 is a new innovation that combines the integration of multi-omics-based target identification with next-generation genome-editing techniques, allowing precise and multiplex engineering of complex and interconnected regulatory networks instead of single genes. We cover new approaches such as engineering the DREB/CBF pathway, allele-specific editing and targeted disruption of negative regulators to enhance the pathway(s) involved in cold response. Moreover, we propose a roadmap for integration of transcriptomics, proteomics, metabolomics, high-throughput phenomics, and speed breeding to accelerate the identification, validation, and deployment of superior alleles to boost cold tolerance. This review provides a foundation for developing climate-resilient pepper cultivars by connecting functional genomics with precision genome engineering approaches to maintain productivity under variable environmental conditions.

Capsicum↗

PubMed2002

Calibrating the uptake kinetics of semipermeable membrane devices in water: impact of hydrodynamics.

The use of lipid-containing semipermeable membrane devices (SPMDs) is becoming commonplace, but the potential effects of environmental variables affecting the accumulation of contaminants into SPMDs had not been characterized sufficiently, yet. To characterize the effect of hydrodynamic conditions on the contaminant uptake kinetics, accumulation of pentachlorobenzene, hexachlorobenzene, and hexachlorocyclohexane isomers from water into SPMD was studied at various water flow rates. The accumulation kinetics of hydrophobic compounds (log Kow > 4) are governed by the aqueous boundary layer in linear flow velocity range from 0.06 to 0.28 cm s(-1) and sensitive to slight changes in flow rate. The effect of flow velocity on the exchange kinetics increases with increasing hydrophobicity. Under faster, but still laminar flow conditions (0.28-1.14 cm s(-1)), the sensitivity to changes in flow decreases to a nonsignificant level for the substances under consideration. The results of this study confirm that the use of the laboratory-derived calibration data for estimation of analyte concentrations in the ambient environment is limited unless flow-sensitive performance reference compounds are used.

Calibration↗

PubMed2002

Longitudinal processes in Salto Grande Reservoir (Americana, SP, Brazil) and its influence in the formation of compartment system.

Studies on the longitudinal processes in reservoirs, involving physical, chemical and biological processes have been thoroughly appraised, suggesting the existence of a longitudinal organization controlled by the entrance and circulation of water which inserts modifications in the structuring of the system. To evaluate this effect, the Salto Grande reservoir (Americana, SP) was analyzed in 11 sampling stations in its longitudinal axis, in the rainy and dry seasons of 1997 considering the physical chemical and biological variables. Analyzing the results in agreement with the declining concentration degree of the river-barrage direction, a more significant correlation was verified in the dry period for total phosphorus (r2 = 0.86), dissolved total phosphate (r2 = 0.83), nitrite (r2 = 0.93), inorganic phosphate (r2 = 0.89), ammonium (r2 = 0.84) and suspended material (r2 = 0.85). In the rainy period, only nitrite (r2 = 0.90) and conductivity (r2 = 0.89) presented correlation with the distance of the dam, which demonstrates the effects of precipitation and the operational mechanism of the dam, as well as the distinction among the physical (sedimentation), chemical (oxidation) and biological (decomposition) processes in spatial heterogeneity of the system. These factors were decisive in the organization of these communities, with higher occurrence of rotifers and copepods in relation to cladocerans, the first ones being more abundant in the entrance of the Atibaia river, decreasing towards the dam direction, while copepods presented an inverse pattern. A distribution pattern similar to Copepoda was also verified for the Cladocera, evidencing a tendency to increase the density of organisms in the stations distant to the entrance of the Atibaia river, not being registered, however, a distribution gradient in the longitudinal axis, as observed for rotifers and copepods. In relation to the trophic degree a longitudinal gradient was also verified from eutrophic to oligotrophic depending on the location of the sampling station in relation to the longitudinal axis and period of analysis. The differences obtained, relating to the distribution of the environmental variables, demonstrate a characteristic pattern for reservoirs, with a longitudinal gradient in the sense river-barrage that inserts changes in the physical and chemical composition of the water, contributing to the differentiated establishing of biological communities.

Animals↗

PubMed2004

Experimental and numerical test of the micrometeorological mass difference technique for the measurement of trace gas emissions from small plots.

Micrometeorological methods for measuring fluxes of gases between the land surface and the atmosphere are non-invasive: in fact, they do not interfere with natural processes of gas exchange. The Micrometeorological Mass Difference (MMD) approach can be used for many environmental monitoring purposes, such as to measure methane and carbon dioxide emission from landfills, methane production by grazing animals, trace gas emission from waste products and from agricultural soils, photosynthesis, and transpiration of plant canopies. The purpose of this study is to adapt the MMD technique, originally developed in Australia, to monitor CO2 and trace gases exchange rate at the plot level. Comparison of different treatments in replicated experiments requires plots of few rather than tens of meters. The tests reported here were performed on a square area (4 m x 4 m) in the meteorological field of the experimental farm of CNR-ISAFOM located in Vitulazio, province of Caserta, Italy (40 degrees 07' N, 14 degrees 50' E, 25 m above sea level) and consisted of the release of pure CO2 at different rates (1.7, 1.3, 0.6 L min(-1)) from a single source on the ground in the center of the experimental area and the consequent measurement of the environmental variables (wind speed and direction, CO2 concentration) at different times at four heights (up to 1.2 m) in order to compute the mass balance according to MMD technique. Measured flow rates well accounted for the mass of CO2 released. A flow underestimation occurred when wind speed dropped below 1.5 m s(-1), in accord with the previous findings obtained in Australia: this happened because anemometers can stall at low speeds, and their measurements are unreliable and because of significant loss of mass from the top of the apparatus. The experimental results were compared with outputs of Computational Fluid Dynamic (CFD) simulations. The commercial CFD package Fluent was used to evaluate performances and sources of errors. According to the experimental and numerical results, the MMD apparatus in our present configuration is suitable to be used for the monitoring of trace gas emissions of experimental plots. Advantages and limits of the present approach are discussed.

Air Pollutants↗

PubMed2006

Use of the pupal survey technique for measuring Aedes aegypti (Diptera: Culicidae) productivity in Puerto Rico.

The hypothesis tested was that most pupae of Aedes aegypti are produced in a few types of containers so that vector control efforts could concentrate on eliminating the most productive ones and thus prevent dengue outbreaks. Pupal surveys were conducted twice in 2004 in an urban area in southern Puerto Rico. A total 35,030 immature mosquitoes (III and IV instars, pupae) was counted in 1,367 containers found with water in 624 premises during the first survey. Only pupae were counted in the second survey in 829 premises, 257 of which had containers with water, and 124 contained Ae. aegypti pupae (15%, 22% in the first survey). We found fewer (583) containers with water than in the first survey, but 202 had pupae (35%; 18.5% in first survey). Containers yielded 3,189 Ae. aegypti pupae, which was slightly fewer than those found in the first survey (3,388 pupae). The hypothesis was supported by the data, showing that 7 of 18 types of containers contained 80% of all female pupae. The most productive containers generally were also common. We used several criteria (i.e., container use, two-step cluster analysis based on environmental variables of containers and premises) to classify the containers and premises and to evaluate pupal distribution at various spatial scales (container, premise, and residences versus public areas). Most pupae were in 4 of 10 types of container usage categories. The cluster technique showed that most pupae were in unattended, rain-filled containers in the yards, particularly in receptacles in the shade of trees that received rainfall through foliage and had lower water temperatures. Pupal counts were adjusted to a negative binomial distribution, confirming their highly aggregated dispersal pattern. Cluster analysis showed that 61.3% of female pupae were in 40 (6.4%) of 624 premises that had in common their larger yards, number of trees, and container water volume. Using number of Ae. aegypti larvae, Breteau Index, or the presence of immature forms as indicators of pupal productivity is not as efficient in identifying the most productive types of containers as direct pupal counts.

Aedes↗