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Field Methods (field + methods)
Selected AbstractsField Methods in Remote SensingTHE PHOTOGRAMMETRIC RECORD, Issue 110 2005E. D. Wallington No abstract is available for this article. [source] Using interpubic distance for sexing manakins in the fieldJOURNAL OF FIELD ORNITHOLOGY, Issue 1 2010Chase D. Mendenhall ABSTRACT Field methods for determining the sex of birds are often limited due to morphometric overlap between sexes, intermediate plumages, seasonality, and reliance on subjective age classification. Interpubic distance, characterized in birds as the distance between the distal ends of the pubic bones, has not been formally tested as a method for determining the sex of birds, despite references among parrot breeders and the frequent use of analogous measurements in mammals. We developed a harmless and easily performed field method for measuring interpubic distance in studies involving bird capture, and compared the interpubic distances of known sex White-ruffed Manakins (Corapipo altera), Orange-collared Manakins (Manacus aurantiacus), and Blue-crowned Manakins (Lepidothrix coronata) to evaluate the possible use of this measurement to determine sex. Using interpubic distance ranges based on 85% confidence intervals where overlap existed between sexes, the sex of 92.8,100% of all manakins in our study was accurately determined with no misclassification. Interpubic distance performed better than plumage-based methods that sexed 74.0% of all individuals and misclassified 1.5%. Using linear discriminant analysis, we developed classification equations that allowed us to accurately determine the sex of all individuals with 100% accuracy using mass and interpubic distance. Additionally, we compared the interpubic distances of female White-ruffed Manakins to evaluate the potential to determine age and reproductive status. Despite an apparent relationship between interpubic distance, age and reproductive status, we concluded that interpubic distance has limited use for determining age and reproductive status due to extensive overlap (31.6,100%), but shows potential in other applications. Based on these results, we endorse the use of interpubic distance to determine the sex of manakins. We encourage further study to develop additional classification equations using different morphometric measurements and to test the efficacy of interpubic distance to determine sex in other bird species. RESUMEN Los métodos del campo para distinguir el sexo de aves son limitados a causa de traslapes de medidas mórfometricas extremas entre sexos, plumajes intermedios, diferencias temporales y/o dependencia en clasificación sujeto de la edad. Distancia interpúbica, caracterizada en aves como la distancia entre los puntos distales de los huesos púbicos, no ha sido formalmente probada como un método para distinguir el sexo de las aves, a pesar de referencias por criadores de loros y uso de métodos similares en mamíferos. Diseñamos un método del campo rápido y sencillo que no tiene riesgo del daño para sacar la distancia interpúbica en estudios que capturan aves. Comparamos la distancia interpúbica de individuos de sexo conocido de Corapipo altera, Manacus aurantiacus, y Lepidothrix coronata para probar el método. Clasificamos correctamente el sexo de 92.8,100% de todos los individuos en este estudio por rangos determinados a través de intérvalos de confianza de 85%. La distancia interpúbica funcionó mejor que un método basado en plumaje, el cual que distinguió el sexo correcto de 74.0% pero falló en clasificar el sexo de 1.5% de los individuos estudiados. Usamos el análisis de discriminación linear para determinar el poder predictivo de la distancia interpúbica, longitud del ala y masa e hicimos ecuaciones de clasificación que distinguieron sexo con un 100% de éxito usando solo masa y distancia interpúbica. Además, comparamos distancia interpúbica de las hembras de C. altera para evaluar el potencial de distinguir edad y estadio reproductivo. A pesar de existir una conexión entre distancia interpúbica, edad y estadio reproductivo, concluimos que la distancia interpúbica es limitada en el contexto de distinguir edad y estadio reproductivo por traslape extensivo (31.6,100%), pero muestra potencial en otras aplicaciones. Basados en estos resultados recomendamos el uso de distancia interpúbica como un método para distinguir sexo de pipridos. Recomendamos más investigación para crear otras ecuaciones de clasificación usando medidas mórfometricas diferentes y probar la eficacia de la distancia interpúbica para distinguir el sexo de otras especies de aves. [source] Spatial pattern of downed logs and wood-decaying fungi in an old-growth Picea abies forestJOURNAL OF VEGETATION SCIENCE, Issue 5 2001Mattias Edman See section on Field methods Abstract. Since many wood-living forest species are influenced by the dynamics of coarse woody debris (CWD), information about the spatial pattern of CWD under natural conditions is essential to understand species distributions. In this study we examined the spatial pattern of downed logs and wood-decaying fungi in an old-growth boreal Picea abies forest in northwestern Sweden that is governed by gap-phase dynamics. The spatial pattern of wood-decaying fungi was studied to draw conclusions about species dispersal abilities. A total of 684 logs with a diameter > 10 cm were mapped and analysed with Ripley's K -function. The distribution of all logs taken together displayed a significant aggregated pattern up to 45 m. The different decay stages also deviated from random expectations. Fairly fresh logs and logs in the middle decay stage were clumped up to about 25 and 35 m respectively, and late decayed logs aggregated up to 95 m. Logs with diameters from 10,29 cm were aggregated up to 25 m, whereas logs ,30 cm diameter were randomly distributed. The result suggests that gap-dynamics do have an impact on the spatial pattern of the CWD, creating fine-scale clumping. The random distribution of large logs may result from the slightly regular spacing of large living trees. The spatial patterns of 16 species (n > 20) of wood-decaying fungi were analysed with Ripley's K -function. Three patterns were aggregated, for Gloeophyllum sepiarium, Coniophora olivacea and Vesiculomyces citrinus. These results indicate that the distribution of most species at the stand level is generally not influenced by dispersal limitations. [source] Dynamic coupled metal transport-speciation model: Application to assess a zinc-contaminated lakeENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2004Satyendra P. Bhavsar Abstract A coupled metal transport and speciation/complexation model (TRANSPEC) has been developed to estimate the speciation and fate of multiple interconverting species in surface aquatic systems. Dynamic-TRANSPEC loosely, sequentially couples the speciation/complexation and fate modules that, for the unsteady state formulation, run alternatively at every time step. The speciation module first estimates species abundance using, in this version, MINEQL+ considering time-dependent changes in water and pore-water chemistry. The fate module is based on the quantitative water air sediment interaction (QWASI) model and fugacity/aquivalence formulation, with the option of using a pseudo-steady state solution to account for past discharges. Similarly to the QWASI model for organic contaminants, TRANSPEC assumes the instantaneous equilibrium distribution of metal species among dissolved, colloidal, and particulate phases based on ambient chemistry parameters that can be collected through conventional field methods. The model is illustrated with its application to Ross Lake (Manitoba, Canada) that has elevated Zn concentrations due to discharges over 70 years from a mining operation. Using measurements from field studies, the model reproduces year-round variations in Zn water concentrations. A 10-year projection for current conditions suggests decreasing Zn remobilization and export from the lake. Decreasing Zn loadings increases sediment-to-water transport but decreases water concentrations, and vice versa. Species distribution is affected by pH such that a decrease in pH increases metal export from the lake and vice versa. [source] RELATIVE ABUNDANCE AND THE SPECIES-SPECIFIC REINFORCEMENT OF MALE MATING PREFERENCE IN THE CHRYSOCHUS (COLEOPTERA: CHRYSOMELIDAE) HYBRID ZONEEVOLUTION, Issue 12 2005Merrill A. Peterson Abstract Most studies of reinforcement have focused on the evolution of either female choice or male mating cues, following the long-held view in sexual selection theory that mating mastakes are typically more costly for females than for males. However, factors such as conspecific sperm precedence can buffer females against the cost of mating mistakes, suggesting that in some hybrid zones mating mistakes may be more costly for males than for females. Thus, the historical bias in reinforcement research may underestimate its frequency. In this study, we present evidence that reinforcement has driven the evolution of male choice in a hybrid zone between teh highly promiscuous lealf beetles chyrsochus cobaltinus and C. auratus, the hybrids of which have extremely low fitness. In addition, there is evidence for male choice in these beetles and that male mating mistakes may be costly, due to reduced opportunities to mate with conspecific females. The present study combines laboratory and field methods to quantify the strenght of sexual isolation, test the hypothesis of reproductive character displacement, and assess the link between relative abundance and the strenght of selection against hybridization. We document that, while sexual isolation is weak, it is sufficient to produce positive assortative mating. In addtion, reproductive character displacement was only detected in the relatively rare species. The strong postzygotic barriers in this system are sufficient to generate the bimodality that characterizes this hybrid zone, but the weak sexual isolation is not, calling into question whether strong prezygotic isolation is necessary for the maintenance of bimodality. Growing evidence that the cost of mating mistakes is sufficient to shape the evolution of male mate choice suggests that the reinforecement of male mate choice may prove to be a widespread occurrence. [source] The effect of fixed-count subsampling on macroinvertebrate biomonitoring in small streamsFRESHWATER BIOLOGY, Issue 2 2000Craig P. Doberstein Summary 1When rigorous standards of collecting and analysing data are maintained, biological monitoring adds valuable information to water resource assessments. Decisions, from study design and field methods to laboratory procedures and data analysis, affect assessment quality. Subsampling - a laboratory procedure in which researchers count and identify a random subset of field samples - is widespread yet controversial. What are the consequences of subsampling? 2To explore this question, random subsamples were computer generated for subsample sizes ranging from 100 to 1000 individuals as compared with the results of counting whole samples. The study was done on benthic invertebrate samples collected from five Puget Sound lowland streams near Seattle, WA, USA. For each replicate subsample, values for 10 biological attributes (e.g. total number of taxa) and for the 10-metric benthic index of biological integrity (B-IBI) were computed. 3Variance of each metric and B-IBI for each subsample size was compared with variance associated with fully counted samples generated using the bootstrap algorithm. From the measures of variance, we computed the maximum number of distinguishable classes of stream condition as a function of sample size for each metric and for B-IBI. 4Subsampling significantly decreased the maximum number of distinguishable stream classes for B-IBI, from 8.2 for fully counted samples to 2.8 classes for 100-organism subsamples. For subsamples containing 100,300 individuals, discriminatory power was low enough to mislead water resource decision makers. [source] The Adequacy of Household Survey Data for Evaluating the Nongroup Health Insurance MarketHEALTH SERVICES RESEARCH, Issue 4 2007Joel C. Cantor Objective. To evaluate the accuracy of household survey estimates of the size and composition of the nonelderly population covered by nongroup health insurance. Data Sources/Study Setting. Health insurance enrollment statistics reported to New Jersey insurance regulators. Household data from the following sources: the 2002 Current Population Survey (CPS)-March Demographic Supplement, the 1997 and 1999 National Surveys of America's Families (NSAF), the 2001 New Jersey Family Health Survey (NJFHS), a 2002 survey of known nongroup health insurance enrollees, a small 2004 survey testing alternative health insurance question wording. Study Design. To assess the extent of bias in estimates of the size of the nongroup health insurance market in New Jersey, enrollment trends are compared between official enrollment statistics reported by insurance carriers to state insurance regulators with estimates from three general population household surveys. Next, to evaluate possible bias in the demographic and socioeconomic composition of the New Jersey nongroup market, distributions of characteristics of the enrolled population are contrasted among general household surveys and a survey of known nongroup subscribers. Finally, based on inferences drawn from these comparisons, alternative health insurance question wording was developed and tested in a local survey to test the potential for misreporting enrollment in nongroup coverage in a low-income population. Data Collection/Extraction Methods. Data for nonelderly New Jersey residents from the 2002 CPS (n=5,028) and the 1997 and 1999 NSAF (n=6,467 and 7,272, respectively) were obtained from public sources. The 2001 NJFHS (n=5,580 nonelderly) was conducted for a sample drawn by random digit dialing and employed computer-assisted telephone interviews and trained, professional interviewers. Sampling weights are used to adjust for under-coverage of households without telephones and other factors. In addition, a modified version of the NJFHS was administered to a 2002 sample of known nongroup subscribers (n=1,398) using the same field methods. These lists were provided by four of the five largest New Jersey nongroup insurance carriers, which represented 95 percent of all nongroup enrollees in the state. Finally, a modified version of the NJFHS questionnaire was fielded using similar methods as part of a local health survey in New Brunswick, New Jersey, in 2004 (n=1,460 nonelderly). Principal Findings. General household sample surveys, including the widely used CPS, yield substantially higher estimates of nongroup enrollment compared with administrative totals and yield estimates of the characteristics of the nongroup population that vary greatly from a survey of known nongroup subscribers. A small survey testing a question about source of payment for direct-purchased coverage suggests than many public coverage enrollees report nongroup coverage. Conclusions. Nongroup health insurance has been subject to more than a decade of reform and is of continuing policy interest. Comparisons of unique data from a survey of known nongroup subscribers and administrative sources to household surveys strongly suggest that the latter overstates the number and misrepresent the composition of the nongroup population. Research on the nongroup market using available sources should be interpreted cautiously and survey methods should be reexamined. [source] Evaluation of Bioaccumulation Using In Vivo Laboratory and Field Studies,INTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 4 2009Annie V Weisbrod Abstract A primary consideration in the evaluation of chemicals is the potential for substances to be absorbed and retained in an organism's tissues (i.e., bioaccumulated) at concentrations sufficient to pose health concerns. Substances that exhibit properties that enable biomagnification in the food chain (i.e., amplification of tissue concentrations at successive trophic levels) are of particular concern due to the elevated long-term exposures these substances pose to higher trophic organisms, including humans. Historically, biomarkers of in vivo chemical exposure (e.g., eggshell thinning, bill deformities) retrospectively led to the identification of such compounds, which were later categorized as persistent organic pollutants. Today, multiple bioaccumulation metrics are available to quantitatively assess the bioaccumulation potential of new and existing chemicals and identify substances that, upon or before environmental release, may be characterized as persistent organic pollutants. This paper reviews the various in vivo measurement approaches that can be used to assess the bioaccumulation of chemicals in aquatic or terrestrial species using laboratory-exposed, field-deployed, or collected organisms. Important issues associated with laboratory measurements of bioaccumulation include appropriate test species selection, test chemical dosing methods, exposure duration, and chemical and statistical analyses. Measuring bioaccumulation at a particular field site requires consideration of which test species to use and whether to examine natural populations or to use field-deployed populations. Both laboratory and field methods also require reliable determination of chemical concentrations in exposure media of interest (i.e., water, sediment, food or prey, etc.), accumulated body residues, or both. The advantages and disadvantages of various laboratory and field bioaccumulation metrics for assessing biomagnification potential in aquatic or terrestrial food chains are discussed. Guidance is provided on how to consider the uncertainty in these metrics and develop a weight-of-evidence evaluation that supports technically sound and consistent persistent organic pollutant and persistent, bioaccumulative, and toxic chemical identification. Based on the bioaccumulation information shared in 8 draft risk profiles submitted for review under the United Nations Stockholm Convention, recommendations are given for the information that is most critical to aid transparency and consistency in decision making. [source] Absorption, resonance, and near-resonance Raman studies of the tetracyanoquinodimethane neutral and its monoanion in terms of density functional theory and complete active space self-consistent field methodsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 8 2006Marcin Makowski Abstract The electronic structure of the 11B1u and 12B3u excited electronic states of the tetracyanoquinodimethane (TCNQ) neutral and its charged derivative are studied within the framework of complete active space self-consistent field (CASSCF) and Becke's three-parameter hybrid method with Lee,Yang,Parr correlation functional (B3LYP) methods applied to the level aug-cc-p-VDZ basis set. Both CASSCF/aug-cc-p-VDZ and B3LYP/aug-cc-p-VDZ treatments provide the ground-state and the excited state geometries; these are then used to assess the Franck,Condon (FC) parameters in the 11B1u state of the neutral TCNQ and in the 12B3u state of the TCNQ monoanion. The quality of numerical results is then tested on the base of available experimental near-resonance and resonance Raman data. The studies are performed in terms of the vibronic model, which takes both FC and mode-mixing (Dushinsky) effects into account. This somewhat simplified vibronic model leads to very good agreement between the theory and the Raman experiments concerning both neutral TCNQ and its monoanion. In particular, the calculated excitation profiles of the ,2 = 2215 cm,1, ,4 = 1389 cm,1, ,5 = 1195 cm,1, and ,9 = 336 cm,1 fundamentals are shown to be in excellent agreement with those for the TCNQ monoanion. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Tropical forest tree mortality, recruitment and turnover rates: calculation, interpretation and comparison when census intervals varyJOURNAL OF ECOLOGY, Issue 6 2004SIMON L. LEWIS Summary 1Mathematical proofs show that rate estimates, for example of mortality and recruitment, will decrease with increasing census interval when obtained from censuses of non-homogeneous populations. This census interval effect could be confounding or perhaps even driving conclusions from comparative studies involving such rate estimates. 2We quantify this artefact for tropical forest trees, develop correction methods and re-assess some previously published conclusions about forest dynamics. 3Mortality rates of > 50 species at each of seven sites in Africa, Latin America, Asia and Australia were used as subpopulations to simulate stand-level mortality rates in a heterogeneous population when census intervals varied: all sites showed decreasing stand mortality rates with increasing census interval length. 4Stand-level mortality rates from 14 multicensus long-term forest plots from Africa, Latin America, Asia and Australia also showed that, on average, mortality rates decreased with increasing census interval length. 5Mortality, recruitment or turnover rates with differing census interval lengths can be compared using the mean rate of decline from the 14 long-term plots to standardize estimates to a common census length using ,corr = , × t0.08, where , is the rate and t is time between censuses in years. This simple general correction should reduce the bias associated with census interval variation, where it is unavoidable. 6Re-analysis of published results shows that the pan-tropical increase in stem turnover rates over the late 20th century cannot be attributed to combining data with differing census intervals. In addition, after correction, Old World tropical forests do not have significantly lower turnover rates than New World sites, as previously reported. Our pan-tropical best estimate adjusted stem turnover rate is 1.81 ± 0.16% a,1 (mean ± 95% CI, n = 65). 7As differing census intervals affect comparisons of mortality, recruitment and turnover rates, and can lead to erroneous conclusions, standardized field methods, the calculation of local correction factors at sites where adequate data are available, or the use of our general standardizing formula to take account of sample intervals, are to be recommended. [source] Bed Stability and Sedimentation Associated With Human Disturbances in Pacific Northwest Streams,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2009Philip R. Kaufmann Abstract:, To evaluate anthropogenic sedimentation in United States (U.S.) Pacific Northwest coastal streams, we applied an index of relative bed stability (LRBS*) to summer low flow survey data collected using the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program field methods in a probability sample of 101 wadeable stream reaches. LRBS* is the log of the ratio of bed surface geometric mean particle diameter (Dgm) to critical diameter (D*cbf) at bankfull flow, based on a modified Shield's criterion for incipient motion. We used a formulation of LRBS* that explicitly accounts for reductions in bed shear stress that result from channel form roughness due to pools and wood. LRBS* ranged from ,1.9 to +0.5 in streams within the lower quartile of human riparian and basin disturbance, and was substantially lower (,4.2 to ,1.1) in streams within the upper quartile of human disturbance. Modeling results suggest that the expected range of LRBS* in streams without human disturbances in this region might be generally between ,0.7 and +0.5 in either sedimentary or volcanic lithology. However, streams draining relatively soft, erodible sedimentary lithology showed greater reductions in LRBS* associated with disturbance than did those having harder, more resistant volcanic (basalt) lithology with similar levels of basin and riparian disturbance. At any given level of disturbance, smaller streams had lower LRBS* than those with larger drainages. In sedimentary lithology (sandstone and siltstone), high-gradient streams had higher LRBS* than did low-gradient streams of the same size and level of human disturbance. High gradient streams in volcanic lithology, in contrast, had lower LRBS* than low-gradient streams of similar size and disturbance. Correlations between Dgm and land disturbance were stronger than those observed between D*cbf and land disturbance. This pattern suggests that land use has augmented sediment supplies and increased streambed fine sediments in the most disturbed streams. However, we also show evidence that some of the apparent reductions in LRBS*, particularly in steep streams draining small volcanic drainages, may have resulted in part from anthropogenic increases in bed shear stress. The synoptic survey methods and designs we use appear adequate to evaluate regional patterns in bed stability and sedimentation and their general relationship to human disturbances. More precise field measurements of channel slope, cross-section geometry, and bed surface particle size would be required to use LRBS* in applications requiring a higher degree of accuracy and precision, such as site-specific assessments at individual streams. [source] Design and field methods for sighting surveys of cetaceans in coastal and riverine habitatsMAMMAL REVIEW, Issue 1 2008STEVE DAWSON ABSTRACT 1Dolphins and porpoises in coastal and/or riverine habitats face serious conservation threats, yet surveys of their abundance are often especially difficult due to the challenges imposed by the habitats. Because many of these species occur in developing countries, lack of resources imposes a further set of challenges. 2We offer advice on designing and conducting line-transect surveys with a focus on sound, practical, design rather than analytical sophistication, and we attempt, where possible, to offer simple, inexpensive solutions. 3We guide the reader through the questions of what kind of survey should be done, whether by boat or aircraft, and we discuss ways to avoid bias and increase precision. 4Our treatment of field methods focuses especially on robust, but low-cost, approaches. We provide two case studies to illustrate the implementation of these ideas. [source] Computational chemistry study of the environmentally important acid-catalyzed hydrolysis of atrazine and related 2-chloro- s -triazinesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 8 2002Phillip Sawunyama Abstract Many chlorine-containing pesticides, for example 2-chloro- s -triazines, are of great concern both environmentally and toxicologically. As a result, ascertaining or predicting the fate and transport of these compounds in soils and water is of current interest. Transformation pathways for 2-chloro- s -triazines in the environment include dealkylation, dechlorination (hydrolysis), and ring cleavage. This study explored the feasibility of using computational chemistry, specifically the hybrid density functional theory method, B3LYP, to predict hydrolysis trends of atrazine (2-chloro- N4 -ethyl- N6 -isopropyl-1,3,5-triazine-2,4-diamine) and related 2-chloro- s -triazines to the corresponding 2-hydroxy- s -triazines. Gas-phase energetics are described on the basis of calculations performed at the B3LYP/6-311++G(d,p)//B3LYP/6-31G* level of theory. Calculated free energies of hydrolysis (,hG298) are nearly the same for simazine (2-chloro- N4,N6 -diethyl-1,3,5-triazine-2,4-diamine), atrazine, and propazine (2-chloro- N4,N6 -di-isopropyl-1,3,5-triazine-2,4-diamine), suggesting that hydrolysis is not significantly affected by the side-chain amine-nitrogen alkyl substituents. High-energy barriers also suggest that the reactions are not likely to be observed in the gas phase. Aqueous solvation effects were examined by means of self-consistent reaction field methods (SCRF). Molecular structures were optimized at the B3LYP/6-31G* level using the Onsager model, and solvation energies were calculated at the B3LYP/6-311++G(d,p) level using the isodensity surface polarizable continuum model (IPCM). Although the extent of solvent stabilization was greater for cationic species than neutral ones, the full extent of solvation is underestimated, especially for the transition state structures. As a consequence, the calculated hydrolysis barrier for protonated atrazine is exaggerated compared with the experimentally determined one. Overall, the hydrolysis reactions follow a concerted nucleophilic aromatic substitution (SNAr) pathway. Published in 2002 for SCI by John Wiley & Sons, Ltd [source] Relationships between plasma leptin levels and body composition parameters measured by different methods in postmenopausal womenAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2003Toivo Jürimäe The aim of this study was to determine the effects of body composition measured by different methods with different measurement errors on fasting plasma leptin level in normal body mass and obese postmenopausal women. It was hypothesized that the relationship between plasma leptin concentration and body fat is higher using more sophisticated laboratory methods (dual energy X-ray absorptiometry, DXA) in comparison with field methods (bioelectrical impedance analysis, BIA, or skinfold thickness) for body fat measurement because of the greater precision of DXA measurements. Thirty-five postmenopausal (55,83 years of age) healthy Estonian women were divided into two groups: BMI < 27kg/m2 as non obese (n = 18) and BMI> 27kg/m2 as obese (n = 17). Body composition was determined using DXA (total body, arms, legs, and trunk fat percent, fat mass, and LBM) and BIA methods. Body fat percent was significantly higher using the DXA method. Subcutaneous adipose tissue distribution was determined by measuring nine skinfold thicknesses. Body fat distribution was defined as the ratio of waist-to-hip (WHR) and waist-to-thigh (WTR) circumferences. Leptin was determined by means of radioimmunoassays. Leptin concentration was not significantly different between groups (19.0 ± 13.3 and 21.5 ± 21.5ng/ml in non obese and obese groups, respectively). Body fat percent and fat weight measured by DXA or BIA methods and all measured skinfold thickness values, except biceps and abdominal, were higher in obese women. Body height did not correlate significantly with leptin concentrations. The relationships between leptin concentration were highest with body weight (r = 0.67) and BMI (r = 0.73) values in the obese group. All measured body fat parameters using DXA or BIA methods correlated significantly with plasma leptin concentration in the obese group. LBM did not influence the leptin concentration in postmenopausal women. Stepwise multiple regression analysis indicated that the body fat percent measured using the DXA method was highly related to plasma leptin concentration in the obese group (63.2%; R2 × 100). When absolute fat mass parameters were considered, leptin concentration was related to the mass of arms fat tissue in the obese group of women (62.3%). Body fat percent measured by BIA was highly related to plasma leptin concentration in the obese group (63.3%). Only biceps skinfold thickness was related to leptin concentration (22.5% and 58.9%, in the nonobese and obese groups, respectively) from the nine measured skinfold thicknesses. WHR and WTR did not reflect leptin concentration in different groups of postmenopausal women. It was concluded that different methods of body composition estimation generate different correlations with plasma leptin concentration. Body fat percent and especially fat mass measured by DXA are the main predictors relating to plasma leptin concentration in obese, but not in nonobese, postmenopausal women. In addition, fat mass in arms measured by DXA and biceps skinfold thickness were also highly related to leptin concentration. Am. J. Hum. Biol. 15:628,636, 2003. © 2003 Wiley-Liss, Inc. [source] New model for the hydroxyapatite,octacalcium phosphate interfaceACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2003M. E. Fernández Some experimental results have indicated that hydroxyapatite (HA) and octacalcium phosphate (OCP) can form an epitaxic interface. Subsequently the OCP,HA interface has become of great biological interest in the context of mineralized tissue formation. In this work a new OCP,HA interface model based on Brown's proposed configuration [Brown (1962), Nature, 197, 1048,1050] and using the minimum interface free-energy optimization is presented. This new model is formed by half a unit cell of HA and one unit cell of OCP, as in Brown's model, but in our case [110] of HA is `glued' with [010] of OCP. Therefore, the relationship found was: [000]HA parallel to [001]OCP and [110]HA parallel to [010]OCP. Self-consistent field methods were used for the analysis of Brown's model and ours. It is shown that the atoms in our model have similar environments as in the HA and OCP unit cells and that, as a result of the differences between HA and OCP unit-cell parameters, this interface presents misfit-dislocation-like features. High-resolution transmission electron microscopy (HREM) simulated images for the new interface model have been included and, when they are compared with the experimental ones, the similarity is quite good. [source] Single crystal structure and molecular dynamics analysis of a myo -inositol derivativeACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2000Jan Dillen The crystal structure of 5- O - tert -butyldimethylsilyl-3,4- O -carbonyl-1,2- O -cyclohexylidene-2-oxo-3-oxa-4-bornanylcarbonyl- d - myo -inositol has been studied by single-crystal X-ray diffraction at both room temperature and 173,K. At room temperature, the tert -butyldimethylsilyl group exhibits dynamical disorder. A molecular dynamics simulation was used to model the disorder and this indicates that the group librates between two stable conformations in the crystal. Approximate relative energies of the different forms and energy barriers for the transition were obtained by empirical force field methods. Calculations of the thermal motion of the atoms are in good qualitative, but fair to poor quantitative agreement with the X-ray data. [source] Estimating population parameters in a threatened arctic fox population using molecular tracking and traditional field methodsANIMAL CONSERVATION, Issue 4 2008T. Meijer Abstract Comprehensive population parameter data are useful for assessing effective conservation actions. The Fennoscandian arctic fox Alopex lagopus is critically endangered and the population size is estimated at 120 individuals that are fragmented into four isolated populations. Here, we use molecular tracking and visual observations to estimate population size and survival in one of the populations on the Swedish mountain tundra during a year of low food availability. We collected 98 arctic fox faecal samples during the winter of 2006 and recorded visual observations of ear-tagged individuals during the summer of 2005 and 2006. The faecal samples were analysed for variation in nine microsatellite loci and matched to the genetic profiles of previously ear-tagged individuals from 2001 to 2005. During winter 2006, the minimum number alive was 12 individuals using visual observations, 30 using molecular tracking and 36 by combining the datasets. Population size was estimated through mark,recapture for the molecular tracking and visual observation datasets and through rarefaction analyses for molecular tracking data. The mark,recapture estimate for visual observations was uninformative due to the large confidence interval (CI) (i.e. 6,212 individuals). Based on the molecular tracking dataset combined with the minimum number alive for visual observations and molecular tracking, we concluded a consensus population size of 36,55 individuals. We also estimated the age-specific finite survival rate during 1 year (July 2005 to July 2006) by combining molecular tracking with visual observations. Juvenile survival on a yearly basis was 0.08 (95% CI 0.02,0.18) while adults had a survival of 0.59 (95% CI 0.39,0.82). Juveniles displayed a lower survival than the adults during autumn (P<0.01) whereas no age-specific survival difference during spring was found. The risk of negative effects due to the small population size and low juvenile survival is accordingly considerable. [source] A new potential field method for mobile robot path planning in the dynamic environmentsASIAN JOURNAL OF CONTROL, Issue 2 2009Lu Yin Abstract A new potential field method for mobile robot path planning is proposed in this paper. At present, most potential field methods are designed to be applied in the stationary environment, and several improved potential functions have brought in the velocity factors in the dynamic circumstances. Based on the consideration that the moving trend of the robot in the dynamic environments is also necessary to produce more reasonable path, this paper defines new attractive potential function with respect to the relative position, velocity, and acceleration between the robot and the goal, as well as the repulsive potential function with respect to the relative positions, velocities, and accelerations between the robot and the obstacles. The virtual forces are calculated to make the robot plan its motion, not only with right positions, but also with suitable velocities. Furthermore, the robot will keep a similar moving trend with the goal and contrary trends with the obstacles. Finally, some methodic simulations are carried out to validate and demonstrate the effectiveness of the new potential field method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] | |||||||||||||||||||