The covariance between hourly concentration (C) and depositionvelocity (V) for various atmospheric species may act to bias the dry deposition (D) computed from the product of the weeklyaverage C and V. This is a potential problem for the CASTNet filter pack (FP) species, nitric acid (HNO3). Using ozone (O3) behavior as a surrogate for HNO3, correctionfactors (CF) are developed to estimate this bias. Weekly CF for O3 depend on both site and season, and seasonal average weekly CF for O3 at a given site may be as high as 1.25.The seasonal magnitude of this CF is generally largest in summerand is ordered: summer fall spring > winter. The CF is drivento a large extent by the diurnal correlation between C andV (i.e., both are generally higher during the day and lower at night). However, since the diurnal C profile at elevated sites is relatively constant, the resulting correlation between C and V is small, and the CF at montane sites is generally negligiblysmall. The sampling protocol using daytime integrated sampling for a week and nighttime integrated sampling for a week capturesthe diurnal correlation between C and V adequately and may be used to aggregate relatively unbiased weekly D estimates. Day-night CF for O3 are close to unity, and limited results suggest similar behavior for HNO3. Using these limited FP results, the site- and seasonally-specific weekly CF forO3are refined to estimate the corresponding CF for HNO3. Worst-case adjustments for HNO3 as high as 30% are indicated for summer periods at a given site. 相似文献
The work-conflict hypothesis (Reeve 1992) postulates that in eusocial naked mole-rat (Heterocephalus glaber) colonies there is potential conflict between the breeding female and her non-breeding colony mates over how much aid they
provide in support of her reproduction. Non-breeders may withhold aid either because they are hopeful reproductives and/or
because they have less to gain in terms of inclusive fitness. Breeding females should, therefore, preferentially direct aggression
in the form of shoving (prolonged pushes usually involving nose-to-nose contact) towards large (hopeful reproductives) and
less related non-breeders to incite them to provide aid. This study tested the following predictions of the work-conflict
hypotheses. (1) There is kin bias in the shove rate of breeding females and work rates of non-breeders; (2) Shoving activates
work in non-breeders. We found no evidence to suggest that the breeding female shove rate and the amount of colony maintenance
activities performed by non-breeders is influenced by relatedness. Body size was a better predictor of work rate and shove
rate; large animals were shoved more and worked less. Furthermore, shoving did not affect the work rate of non-breeders and
rarely incited activity in inactive mole-rats. Individual mole-rats were also more likely to be shoved when already active
than when resting in the nest. These results suggest that shoving by the breeding female may have functions other than the
incitement of activity, such as the reproductive suppression of non-breeders.
Received: 17 January 1996 / Accepted after revision: 21 September 1996 相似文献
An analysis of counts of sample size N=2 arising from a survey of the grass Bromus commutatus identified several factors which might seriously affect the estimation of parameters of Taylor's power law for such small sample sizes. The small sample estimation of Taylor's power law was studied by simulation. For each of five small sample sizes, N=2, 3, 5, 15 and 30, samples were simulated from populations for which the underlying known relationship between variance and mean was given by 2 = cd. One thousand samples generated from the negative binomial distribution were simulated for each of the six combinations of c=1,2 and 11, and d=1, 2, at each of four mean densities, =0.5, 1, 10 and 100, giving 4000 samples for each combination. Estimates of Taylor's power law parameters were obtained for each combination by regressing log10s2 on log10m, where s2 and m are the sample variance and mean, respectively. Bias in the parameter estimates, b and log10a, reduced as N increased and increased with c for both values of d and these relationships were described well by quadratic response surfaces. The factors which affect small-sample estimation are: (i) exclusion of samples for which m = s2 = 0; (ii) exclusion of samples for which s2 = 0, but m > 0; (iii) correlation between log10s2 and log10m; (iv) restriction on the maximum variance expressible in a sample; (v) restriction on the minimum variance expressible in a sample; (vi) underestimation of log10s2 for skew distributions; and (vii) the limited set of possible values of m and s2. These factors and their effect on the parameter estimates are discussed in relation to the simulated samples. The effects of maximum variance restriction and underestimation of log10s2 were found to be the most severe. We conclude that Taylor's power law should be used with caution if the majority of samples from which s2 and m are calculated have size, N, less than 15. An example is given of the estimated effect of bias when Taylor's power law is used to derive an efficient sampling scheme. 相似文献
Establishing cause-effect is critical in the field of natural resources where one may want to know the impact of management practices, wildfires, drought, etc. on water quality and quantity, wildlife, growth and survival of desirable trees for timber production, etc. Yet, key obstacles exist when trying to establish cause-effect in such contexts. Issues involved with identifying a causal hypothesis, and conditions needed to estimate a causal effect or to establish cause-effect are considered. Ideally one conducts an experiment and follows with a survey, or vice versa. In an experiment, the population of inference may be quite limited and in surveys, the probability distribution of treatment assignments is generally unknown and, if not accounted for, can cause serious errors when estimating causal effects. The latter is illustrated in simulation experiments of artificially generated forest populations using annual plot mortality as the response, drought as the cause, and age as a covariate that is correlated with mortality. We also consider the role of a vague unobservable covariate such as `drought susceptibility'. Recommendations are made designed to maximize the possibility of identifying cause-effect relationships in large-scale natural resources surveys. 相似文献
Hemispheric asymmetries and side biases have been studied in humans mostly in laboratory settings, and evidence obtained in
naturalistic settings is scarce. We here report the results of three studies on human ear preference observed during social
interactions in noisy environments, i.e., discotheques. In the first study, a spontaneous right-ear preference was observed
during linguistic exchange between interacting individuals. This lateral bias was confirmed in a quasi-experimental study
in which a confederate experimenter evoked an ear-orienting response in bystanders, under the pretext of approaching them
with a whispered request. In the last study, subjects showed a greater proneness to meet an experimenter’s request when it
was directly addressed to the right rather than the left ear. Our findings are in agreement both with laboratory studies on
hemispheric lateralization for language and approach/avoidance behavior in humans and with animal research. The present work
is one of the few studies demonstrating the natural expression of hemispheric asymmetries, showing their effect in everyday
human behavior. 相似文献
In this paper, we present a three-step methodological framework, including location identification, bias modification, and out-of-sample validation, so as to promote human mobility analysis with social media data. More specifically, we propose ways of identifying personal activity-specific places and commuting patterns in Beijing, China, based on Weibo (China’s Twitter) check-in records, as well as modifying sample bias of check-in data with population synthesis technique. An independent citywide travel logistic survey is used as the benchmark for validating the results. Obvious differences are discerned from Weibo users’ and survey respondents’ activity-mobility patterns, while there is a large variation of population representativeness between data from the two sources. After bias modification, the similarity coefficient between commuting distance distributions of Weibo data and survey observations increases substantially from 23% to 63%. Synthetic data proves to be a satisfactory cost-effective alternative source of mobility information. The proposed framework can inform many applications related to human mobility, ranging from transportation, through urban planning to transport emission modeling.