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481.
The wide-ranging and rapidly evolving nature of ecological studies mean that it is not possible to cover all existing and emerging techniques for analyzing multivariate data. However, two important methods enticed many followers: the Canonical Correspondence Analysis (CCA) and the STATICO analysis. Despite the particular characteristics of each, they have similarities and differences, which when analyzed properly, can, together, provide important complementary results to those that are usually exploited by researchers. If on one hand, the use of CCA is completely generalized and implemented, solving many problems formulated by ecologists, on the other hand, this method has some weaknesses mainly caused by the imposition of the number of variables that is required to be applied (much higher in comparison with samples). Also, the STATICO method has no such restrictions, but requires that the number of variables (species or environment) is the same in each time or space. Yet, the STATICO method presents information that can be more detailed since it allows visualizing the variability within groups (either in time or space). In this study, the data needed for implementing these methods are sketched, as well as the comparison is made showing the advantages and disadvantages of each method. The treated ecological data are a sequence of pairs of ecological tables, where species abundances and environmental variables are measured at different, specified locations, over the course of time.  相似文献   
482.
It is common to fit generalized linear models with binomial and Poisson responses, where the data show a variability that is greater than the theoretical variability assumed by the model. This phenomenon, known as overdispersion, may spoil inferences about the model by considering significant parameters associated with variables that have no significant effect on the dependent variable. This paper explains some methods to detect overdispersion and presents and evaluates three well-known methodologies that have shown their usefulness in correcting this problem, using random mean models, quasi-likelihood methods and a double exponential family. In addition, it proposes some new Bayesian model extensions that have proved their usefulness in correcting the overdispersion problem. Finally, using the information provided by the National Demographic and Health Survey 2005, the departmental factors that have an influence on the mortality of children under 5 years and female postnatal period screening are determined. Based on the results, extensions that generalize some of the aforementioned models are also proposed, and their use is motivated by the data set under study. The results conclude that the proposed overdispersion models provide a better statistical fit of the data.  相似文献   
483.
This paper develops the idea that following rules of good OR practice is necessary, but not sufficient for ethical OR. Several challenges of introducing ethical aspects into OR are discussed, evidencing difficulties and ambiguities in the relationship to be established between the OR practitioner and his/her clients, decision-makers or stakeholders. It shows that neither analysis nor modelling work nor the choice of analytical tools is entirely ethically neutral; incomparability, incommensurability and incertitude must be dealt with. The purpose of this article is to detail several difficulties or dilemmas an OR practitioner may be confronted with in the course of his or her assignment. In such situations, following rules of good practice may not be sufficient to indicate how to act in a morally good way. This paper aims at stimulating reflection by structuring the debate; it may leave the reader unsettled—unsettlement being a result and even aim of many discussions in moral philosophy.  相似文献   
484.
This paper investigates the effect of linguistic diversity on redistribution in a broad cross‐section of countries. We use the notion of “linguistic distances” and show that the commonly used fractionalization index, which ignores linguistic distances, yields insignificant results. However, once distances between languages are accounted for, linguistic diversity has both a statistically and economically significant effect on redistribution. With an average level of redistribution of 9.5% of GDP in our data set, an increase byone standard deviation in the degree of diversity lowers redistribution by approximately one percentage point. We also demonstrate that other measures, such as polarization and peripheral heterogeneity, provide similar results when linguistic distances are incorporated. (JEL: D6, D74, H5, Z10)  相似文献   
485.
为了研究龙眼果皮酶促褐变产物的最佳提取工艺、稳定性和抗氧化活性,以样品中总蒽醌含量为指标,通过单因素和正交试验法,考察乙醇的浓度、料液比、提取时间、提取温度4个因素对应用回流法提取褐变产物的影响,探讨提取龙眼果皮中酶促褐变产物的最佳工艺条件.采用分光光度法对褐变产物的稳定性和体外抗氧化活性进行了测定.结果表明,回流法提取酶促褐变产物最佳工艺条件为:乙醇浓度为70%,提取时间为8h,料液比为1∶2,提取温度为40℃.在试验温度范围内,酶促褐变产物比较稳定;但对光照比较敏感,尤其是在紫外光下稳定性较差;在酸性条件下的稳定性比在碱性和中性条件下好;在4种不同种类添加剂影响下,其稳定性均变差.体外抗氧化试验结果表明,龙眼果皮总蒽醌浓度为9.55 μg/mL时,对1,1-二苯基-2-三硝基苯肼自由基(DPPH·)清除率为74.1%;浓度为4.55 μg/mL时,羟基自由基(·OH)清除率达81.6%;浓度为6.70 μg/mL时,超氧阴离子自由基(·O2-)清除率达86.1%.回流法可提取龙眼果皮中酶促褐变产物.温度对酶促褐变产物稳定性影响不明显,光照、pH、食品添加剂因素影响其稳定性.酶促褐变产物具有一定的清除DPPH·、·OH和·O2-自由基的能力.  相似文献   
486.
严修是中国近代著名教育理论家和实践家,其教育主张及教育实践极大促进了直隶教育的近代化。他提出了改革进而废除科举制的主张,这为直隶教育向近代化方向迈进清除了最大的障碍;在学部主政期间他创立新的教育体制,为直隶教育近代化奠定了制度基础;此外,他兴办了各级各类的新式学堂,形成了直隶近代教育体系的雏形。  相似文献   
487.
1957年在晋宁石寨山出土了"滇王印",证实了古代"滇国"的存在,古滇国的青铜器种类十分繁杂,具有浓烈的地方色彩,"滇"本身就是一个神秘的古国,其艺术的生动真实常常唤起一种经历的记忆与想象。给予我们美的享受。古滇青铜雕刻与图饰的题材内容非常广泛,充满了生活气息。生活实践,是古滇国青铜器艺术生动大胆的表现力、强悍灵动风格的基础。在古滇国青铜器中,雕刻图饰与器物是融为一体的,是古滇青铜艺术特有的构成形式。古滇国青铜器的艺术风格是非常写实的,布局上,疏密节奏的安排赋予韵律感与装饰美。  相似文献   
488.
We investigate how choices for uncertain gain and loss prospects are affected by the decision maker’s perceived level of knowledge about the underlying domain of uncertainty. Specifically, we test whether Heath and Tversky’s (J Risk Uncertain 4:5–28, 1991) competence hypothesis extends from gains to losses. We predict that the commonly-observed preference for high knowledge over low knowledge prospects for gains reverses for losses. We employ an empirical setup in which participants make hypothetical choices between gain or loss prospects in which the outcome depends on whether a high or low knowledge event occurs. We infer decision weighting functions for high and low knowledge events from choices using a representative agent preference model. For gains, we replicate the results of Kilka and Weber (Manage Sci 47:1712–1726, 2001), finding that decision makers are more attracted to choices that they feel more knowledgeable about. However, for losses, we find limited support for our extension of the competence effect.  相似文献   
489.
国民经济恢复时期基层的乡级财政还不是一级完备的财政。各地乡级财政存在不少问题:收支不平衡、行政事业经费开支比例过大、任意摊派,从而影响了乡级政权工作的开展。其中的经验教训对目前的乡村政权建设以及财政体制改革仍有一定的启示。  相似文献   
490.
Therapeutic residential care (TRC) is the name given to specialized children's homes for treating cases with severe emotional and behavioural problems that have been placed in residential care. A recent international review has revealed great diversity in the referral criteria of cases and in the models of intervention carried out. The goal of this study is to describe the population treated in these types of facilities in Spain and the therapeutic coverage given. The sample is made up of 215 young people in children's homes, of whom 93 are in TRC. The cases referred to TRC have been in residential care for less time but have gone through a greater number of placements. These young people also exhibit more problems of drug use, and there is a larger percentage of clinical‐range cases in the Child Behaviour Checklist scales of attention problems and aggressive behaviour. Nevertheless, the results of logistic regression indicate that the only variables that significantly increase the probability of being referred to TRC are drug use and changes of care placements. With regard to therapeutic care, there is a higher percentage in the TRC group receiving psychiatric care, and the sessions are also more frequent.  相似文献   
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