Comparison of grain size correction procedures for organic micropollutants and heavy metals in marine sediments

Four grain size correction procedures were tested for their applicability for comparing concentrations of heavy metals and organic micropollutants (PCBs, PAHs) in sediments. A simple and straightforward procedure proved best: wet sieving of fresh sediment, isolating and analysing the < 63 m grain size fraction and expressing the pollutant concentration as a proportion of the fraction's dry weight. The total analytical errors, expressed as the variation coefficient of the average concentrations, were 3.8–7.6% for heavy metals, 12–24% for PCBs and 5.3–9.9% for PAHs.     

Synapse elimination,the size principle,and Hebbian synapses

Synapse elimination at the vertebrate neuromuscular junction reduces a polyinnervated population of muscle fibers to a monoinnervated state. The function of this developmental phenomenon (if any) is unproven. A theoretical analysis of Hebbian (correlation) rules connecting presynaptic and postsynaptic activity and synaptic strength at the neuromuscular junction is presented. The following points are demonstrated: (1) Correlational competition leads to the reduction of polyinnervation to a stable monoinnervated state; (2) the competition gives rise to the size principle over a wide range of the plausible parameter space; (3) over a significant subrange, the competition selectively eliminates topographically incorrect synapses; and (4) in cases in which topographic projection errors overwhelm the system, both error correction and the development of the size principle are disrupted. Correlational competition may explain contradictory experimental results concerning the effects of stimulating or silencing subpopulations of motor neurons. It may also explain an otherwise puzzling instance of a breakdown in the size principle seen in humans undergoing neural regeneration. Taken together, these findings suggest a novel hypothesis for the function of synapse elimination at the neuromuscular junction: the establishment of the size principle. © 1995 John Wiley & Sons, Inc.     

Polarized dosimetry method for Gafchromic EBT3

PurposeTo analyze the changes in the polarization state of the flatbed scanner light caused by the EBT3 films and to propose a new method for correcting the lateral effects.Methods and materialsThe polarization changes induced by radiochromic films are analyzed using linear polarizing film. Based on the results, the linear polarizing films are used in the scanning process of the EBT3 films. This method is tested against the conventional EBT3 dosimetry using a series of simple regular beams and 21 cases of IMRT.ResultsThe mean results are statically different from the conventional dosimetry with EBT3. Depending on the transmission axis of the polarizing sheet, the results are better or worse compared to conventional dosimetry EBT3 film. When the transmission axis of the polarizing sheet is parallel to the coating direction, the dosimetry results are better and its variability is smaller. However, when the polarizer transmission axis is perpendicular to the coating direction, results are worse as well as its variability.ConclusionUsing a polarized film with the polarization axis parallel to the coating direction of the radiochromic film, and preferably above it, significantly improves the dosimetry results and is an easy and inexpensive way to correct the lateral artifacts of the conventional EBT3 dosimetry.     

CORRECTING AERIAL SURVEY COUNTS OF HARBOR SEALS (PHOCA VITULINA RICHARDSI) IN WASHINGTON AND OREGON

Aerial surveys of harbor seals on land produce only a minimum assessment of the population; a correction factor to account for the missing animals is necessary to estimate total abundance. In 1991 and 1992, VHF radio tags were deployed on harbor seals ( n = 124) at six sites in Washington and Oregon. During aerial surveys a correction factor to account for seals in the water was determined from the proportion of radio-tagged seals on shore during the pupping season. This proportion ranged from 0.54 to 0.74. Among the six sites there was no significant difference in the proportion of animals on shore nor was there a difference in age/sex categories of seals on shore between sites. The pooled correction factor for determining total population abundance was 1.53. An additional 32 seals were radio tagged in 1993 at one of the sites used in 1991. Comparing data from the two years, we found no interannual variation. Aerial surveys of all known harbor seal haul-out sites in Washington ( n = 319) and Oregon ( n = 68) were flown during the peak of the pupping season, 1991–1993. The Washington and Oregon harbor seal population was divided into two stocks based on pupping phenology, morphometics, and genetics. Mean counts for the Washington inland stock were 8,710 in 1991, 9,018 in 1992, and 10,092 in 1993. Oregon and Washington coastal stock mean counts were 18,363 in 1991, 18,556 in 1992, and 17,762 in 1993. Multiplying the annual count by the correction factor yielded estimates of harbor seal abundance in the Washington inland stock of 13,326 (95% CI = 11,637–15,259) for 1991, 13,798 (95% CI = 11,980–15,890) for 1992, and 15,440 (95% CI = 13,382–17,814) for 1993. In the Oregon and Washington coastal stock the corrected estimate of harbor seal abundance was 28,094 (95% CI = 24,697–31,960) in 1991, 28,391 (95% CI = 24,847–32,440) for 1992, and 27,175 (95% CI = 23,879–30,926) for 1993.     

Action selection and refinement in subcortical loops through basal ganglia and cerebellum

Subcortical loops through the basal ganglia and the cerebellum form computationally powerful distributed processing modules (DPMs). This paper relates the computational features of a DPM's loop through the basal ganglia to experimental results for two kinds of natural action selection. First, functional imaging during a serial order recall task was used to study human brain activity during the selection of sequential actions from working memory. Second, microelectrode recordings from monkeys trained in a step-tracking task were used to study the natural selection of corrective submovements. Our DPM-based model assisted in the interpretation of puzzling data from both of these experiments. We come to posit that the many loops through the basal ganglia each regulate the embodiment of pattern formation in a given area of cerebral cortex. This operation serves to instantiate different kinds of action (or thought) mediated by different areas of cerebral cortex. We then use our findings to formulate a model of the aetiology of schizophrenia.     

Integrating distance sampling with minimum counts to improve monitoring

Minimum counts are commonly used to estimate population size and trend for wildlife conservation and management; however, the scope of inference based on such data is limited by untestable assumptions regarding the detection process. Alternative approaches, such as distance sampling, occupancy surveys, and repeated counts, can be employed to produce detection-corrected estimates of population parameters. Unfortunately, these approaches can be more complicated and costly to implement, potentially limiting their use. We explored a conceptual framework linking datasets collected at different spatial scales under different survey designs, with the goal of improving inference. Specifically, we link landscape-scale distance sampling surveys with local-scale minimum counts in an integrated modeling framework to estimate mountain goat (Oreamnos americanus) abundance at both the local and regional scale in south-central Alaska, USA, and provide an estimate of detection probability (i.e., sightability) for the minimum counts. Estimated sightability for the minimum count surveys was 0.67 (95% credible interval [CrI] = 0.52–0.83) and abundance for the entire area was 5,600 goats (CV = 9%), both in broad agreement with estimates from previous studies. Abundance estimates at the local scale (i.e., individual min. count unit) were reasonably precise ( = 18%), suggesting the integrated approach can increase the amount of information produced at both spatial scales by linking minimum count approaches with more rigorous survey designs. We propose that our integrated approach may be implemented in the context of a modified split-panel monitoring design by altering survey protocols to include frequent minimum counts within local count units and intermittent but more rigorous survey designs with inference to the entire study area or population of interest. Doing so would provide estimates of abundance with appropriate measures of uncertainty at multiple spatial scales, thereby improving inference for population monitoring and management. © 2019 The Wildlife Society.     

利用细丝热电偶评估涡度相关系统开路分析仪表面加热效应

目前广泛使用的涡度相关系统开路CO₂/H₂O分析仪存在表面加热效应,可能影响涡动通量测量精度.以帽儿山森林生态站温带落叶林的开路涡度相关系统为例,采用细丝热电偶评估了开路CO₂/H₂O分析仪(Li-7500)的加热效应,并检验Burba方程的适用性.结果表明: 2016年4月23日至5月28日,白天Li-7500光路中部温度比环境空气温度高0.2 ℃以上,夜间二者很接近,加热峰值多出现在清晨转换期和正午或午后.Burba第4种方法的一元模型(BurbaLF)估计的感热通量加热效应(H_S,HE)日变化大体呈矩形波型,多元线性回归模型(BurbaMR)的估计值呈微弱的单峰型.与K079型细丝热电偶(单裸丝线径0.079 mm)测定(K079)和细丝热电偶模拟(K079Model)的感热通量相比,BurbaLF和BurbaMR估算的白天变化小且波峰低而宽(20 W·m^-2),昼夜过渡急剧,夜间一般低于5 W·m^-2.K079和K079Model法的H_S,HE峰值在40 W·m^-2以上,夜间H_S,HE在零值上下波动.白天Li-7500光路的感热通量增量为13.6%. K079和K079Model估算的白天加热对CO₂湍流通量影响(F_c,HC)的平均值约0.5 mg CO₂·m^-2·s^-1,是以往估值的2倍.与实测法相比,Burba方程正午由于H_S,HE不足而低估了F_c,HC,但因高估了清晨、傍晚和夜间加热效应,导致整体上高估F_c,HC.研究结果证实K079和K079Model法均可用于估计F_c,HC.