Bootstrap confidence intervals for adaptive cluster sampling design based on Horvitz–Thompson type estimators

Perez and Pontius (J Stat Comput Simul 76:755–764, 2006) introduced several bootstrap methods under adaptive cluster sampling using a Horvitz–Thompson type estimator. Using a simulation study, they showed that their proposed methods provide confidence intervals with highly understated coverage rates. In this article, we first show that their bootstrap methods provide biased bootstrap estimates. We then define two bootstrap methods, based on the method of Gross (Proceeding of the survey research methods section. American Statistical Association, Alexandria, VA, pp 181–184, 1980) and Bootstrap With Replacement, that provide unbiased bootstrap estimates of the population mean with bootstrap variances matching the corresponding unbiased variance estimator. Using a simulation study, we show that the bootstrap confidence intervals based on our proposed methods have better performance than those based on available bootstrap methods, in the sense of having coverage proportion closer to the nominal coverage level. We also compare the proposed intervals to empirical likelihood based intervals in small samples.     

Bioaccumulation and toxic effects of copper on growth and oxygen consumption by the postlarvae of Penaeus indicus

The aim of this study was to assess the toxic impact of copper on postlarvae (PL) of the penaeid shrimp Penaeus indicus. Tolerance, growth, oxygen consumption and metal accumulation were investigated in these PL on exposure to copper. Tolerance studies were conducted for 96 h to assess the tolerance limits of P. indicus PL exposed to different concentrations of copper using static renewal bioassay tests. Using the Probit method, the regression equation was calculated as Y=0.4899+2.3562 X, with a correlation coefficient of 0.9707. The 96 h LC₅₀ was 0.8204 ppm. The effect of sublethal (one-fifth of 96 h LC₅₀) copper on PL for short- and long-term exposures revealed a significant (p<0.05) decrease in the rate of oxygen consumption, metabolic rate, mean length, wet and dry weight of the exposed PL over their respective controls which can be attributed to a gradual and time-dependent accumulation of the metal, as noticed in the exposed PL through accumulation studies. Overall, the data suggest that on chronic exposure even sublethal concentrations of copper can reduce the metabolic rate and growth in P. indicus PL. This is perhaps the first attempt to use the wild P. indicus PL as a bioindicator of copper toxicity.     

Protein Metabolic Response to Carbon Tetrachloride in A Freshwater Fish,Sarotherodon Mossambicus

Exposure of a freshwater teleost, Sarotherodon mossambicus, to a sublethal concentration (26 ppm) of carbon tetrachloride for periods up to 30 days led to significant changes in the soluble protein fractions (albumin and globulins) and free amino acid content. the decrease in total protein content was greater in liver than in muscle. the protein loss was expected due to the impairement of protein synthetic activity during stress conditions.     

Wastewater management for hazardous chemicals ‐ disposal of ammonium perchlorate wastes from propellant production for space vehicles

An attempt to depict the wastewater treatment system for the production of ammonium perchlorate, a component of solid propellant used in space vehicles, has been made. The waste‐water management system uses solar ponds and seawater dilution for the retention and disposal of the undesirable constituents of the wastewater. The details of the wastewater generation and its treatment are highlighted in this paper.     

稀有鮈鲫细胞凋亡相关基因的克隆及序列分析

细胞凋亡是调控机体发育和维护内环境稳定的重要机制。在克隆了稀有鮈鲫(Gobiocypris rarus)肝脏组织中凋亡相关的bcl-2、apaf-1、caspase-3和caspase-9基因的部分cDNA片段之后,进行了序列分析。结果表明,caspase-3和caspase-9基因片段与唐鱼(Tanichthys albonubes)相对应的核苷酸序列同源性最高,而bcl-2、apaf-1基因片段则分别与鮈鱼(Gobio gobio)和鲤鱼(Cyprinus carpio)相对应的核苷酸序列同源性最高,为99%和89%。基于稀有鮈鲫和已知物种的caspase-3基因核苷酸序列构建了系统发育树,发现稀有鮈鲫与唐鱼、斑马鱼(Danio rerio)的亲缘关系最近,而与金头鲷(Sparus aurata)、红鳍东方鲀(Takifugu rubripes)的亲缘关系较远。本研究为深入理解外源性化学物质对鱼类的毒理学机制及其生态健康风险评价提供科学数据,同时也为稀有鮈鲫在鲤科鱼类的分类及进化地位的研究提供分子水平的重要参考。     

Rehabilitation of degraded community lands for sustainable development in Himalaya: a case study in Garhwal Himalaya,India

SUMMARY

An approach to the rehabilitation of degraded community lands built on people's perceptions and traditional knowledge was developed, implemented on a small scale (6 ha plot), and evaluated in terms of economic and ecological costs and benefits over a period of 5 years in a mid-altitude (1200 m) village of Garhwal Himalaya. Rehabilitation comprised establishment of water harvesting tanks, organic management of soil, agroforestry (native multipurpose trees t traditional crops), and decision making by the whole village community. Costs and benefits under irrigated and unirrigated conditions were compared. The total cost of establishing the irrigated agroforestry system was 1.23 fold that of the unirrigated one, whereas the total benefit was 2.09 fold. The average standing above-ground biomass of the 4-year-old plantation in the irrigated agroforestry system was 11.69 t/ha compared to 8.34 t/ha in the unirrigated system. Improvement in soil properties was more pronounced in the irrigated system than in the unirrigated one. Nutrient input, an input derived largely from forest biomass, in the unirrigated system was nearly 3 times higher than that in the irrigated system. It is concluded that, considering the local and national/regional/global interests in an integrated manner, agroforestry incorporating water management would be a more effective option for rehabilitating degraded community lands than the afforestation currently being attempted by the government in the mid-altitudes of Indian Himalaya.     

Evaluation of acidity in late Permian outcrop coals and its association with endemic fluorosis in the border area of Yunnan,Guizhou, and Sichuan in China

The junction area of Yunnan, Guizhou, and Sichuan provinces is the heaviest coal-burning endemic fluorosis zones in China. To better understand the pathogenicity of endemic fluorosis in this area, 87 coal samples from the late Permian outcrop or semi-outcrop coal seams were collected in eight counties of the junction area of Yunnan, Guizhou, and Sichuan provinces. The total fluorine and sulfate content, etc. in the coal was determined using combustion-hydrolysis/fluoride-ion-selective electrode method and ion chromatography, respectively. The results show that the total fluorine concentrations in the samples ranged from 44 to 382 µg g^?1, with an average of 127 µg g^?1. The average pH of the coals is 5.03 (1.86–8.62), and the sulfate content varied from 249 to 64,706 µg g^?1 (average 7127 µg g^?1). In addition, the coals were medium- and high-sulfur coals, with sulfur mass fraction ranging from 0.08 to 13.41%. By heating the outcrop coals, HF release from the coal was verified quantitatively without exception, while simulated combustion directly confirmed the release of sulfuric acid (H₂SO₄). The acid in coal may be in the form of acidic sulfate (\({\text{HSO}}_{4}^{ - }\)/H₂SO₄) because of a positive relationship between pH and \(p\left( {{\text{SO}}_{4}^{2 - } } \right)\) in the acidic coal. The possible reaction mechanism would be that a chemical reaction between the acid (H₂SO₄ or \({\text{HSO}}_{4}^{ - }\)) and fluorine in the coal occurred, thereby producing hydrogen fluoride (HF), which would be the chemical form of fluorine released from coal under relatively mild conditions. The unique chemical and physical property of HF may bring new insight into the pathogenic mechanism of coal-burning endemic fluorosis. The phenomenon of coal-burning fluorosis is not limited to the study area, but is common in southwest China and elsewhere. Further investigation is needed to determine whether other endemic fluorosis areas are affected by this phenomenon.     

Historical trends of organochlorine pesticides (OCPs) recorded in sediments across the Tibetan Plateau

Sediment cores from four lakes across the Tibetan Plateau were used as natural archives to study the time trends of organochlorine pesticides (OCPs). The total concentrations of dichlorodiphenyltrichloroethane (ΣDDT) and hexachlorocyclohexane isomers (ΣHCH) were in the range of 0.04–1.61 and 0.08–1.88 ng/g based on dry weight (dw), while the input fluxes were in the range of 0.3–236 and 0.7–295 pg/cm²/y in the core sediments, respectively. The input fluxes of ΣDDT and ΣHCH generally peaked in sediment layers corresponding to the 1970s–1990s and peaked in top sediment layers. The ratio of α/γ-HCH decreased in the top layer sediments, implying that the contribution of lindane (pure γ-HCH) has been increasing in recent years. In addition, the ratio of o,p′-DDT/p,p′-DDT increased significantly over the last 15–20 years, suggesting that dicofol (characterized by high ratio of o,p′-DDT/p,p′-DDT about 7.0) has recently become a relatively more important source of DDT compared to technical DDT itself. The time trends of OCPs recorded in lake sediments examined the impact on such remote alpine regions by human activities.     

医疗废物高温蒸汽集中处置工艺设计

以某市医疗废物集中处置中心为例,介绍8 t/d规模的高温蒸汽系统工艺设计,包括工艺流程以及产生的有害物质的处理,并对医疗废物高温蒸汽处理系统的设计技术进行探讨。     

Empirical likelihood confidence intervals for adaptive cluster sampling

Adaptive cluster sampling (ACS) is an efficient sampling design for estimating parameters of rare and clustered populations. It is widely used in ecological research. The modified Hansen-Hurwitz (HH) and Horvitz-Thompson (HT) estimators based on small samples under ACS have often highly skewed distributions. In such situations, confidence intervals based on traditional normal approximation can lead to unsatisfactory results, with poor coverage properties. Christman and Pontius (Biometrics 56:503–510, 2000) showed that bootstrap percentile methods are appropriate for constructing confidence intervals from the HH estimator. But Perez and Pontius (J Stat Comput Simul 76:755–764, 2006) showed that bootstrap confidence intervals from the HT estimator are even worse than the normal approximation confidence intervals. In this article, we consider two pseudo empirical likelihood functions under the ACS design. One leads to the HH estimator and the other leads to a HT type estimator known as the Hájek estimator. Based on these two empirical likelihood functions, we derive confidence intervals for the population mean. Using a simulation study, we show that the confidence intervals obtained from the first EL function perform as good as the bootstrap confidence intervals from the HH estimator but the confidence intervals obtained from the second EL function perform much better than the bootstrap confidence intervals from the HT estimator, in terms of coverage rate.