MINORITY THREAT AND POLICE STRENGTH FROM 1980 TO 2000: A FIXED‐EFFECTS ANALYSIS OF NONLINEAR AND INTERACTIVE EFFECTS IN LARGE U.S. CITIES*

Many studies have assessed threat theory by investigating the relationships between the size of minority populations and police strength. Yet these investigations analyzed older data with cross‐sectional designs. This study uses a fixed‐effects panel design to detect nonlinear and interactive relationships between minority presence and the per capita number of police in large U.S. cities in the last three census years. The findings show that the relationship between racial threat and the population‐corrected number of police officers has recently become considerably stronger. In accord with theoretically based expectations, tests for interactions show that segregated cities with larger African American populations have smaller departments. The coefficients on another interaction effect suggest that racial segregation leads to reductions in police strength in the South perhaps because officers are less likely to intervene in residentially isolated black neighborhoods in this region.     

亚洲货币单位与东亚货币合作的收敛性

本文使用修正的KSS非线性单位根检验方法,研究了以亚洲货币单位为计价单位的东盟及中、日、韩3国货币相对美元的收敛性问题。实证分析发现:韩元和菲律宾比索在10%显著水平上、泰铢在5%显著水平上是非线性过程收敛的;柬埔寨瑞尔、人民币、港元、日元、老挝基普、马来西亚林吉特、缅元和新加坡元均是非线性长期收敛的。总的说来,10+3国家具有创建共同汇率机制的可能。     

A Nonlinear Least Squares Approach to Time of Death Estimation Via Body Cooling

The problem of time of death (TOD) estimation by body cooling is revisited by proposing a nonlinear least squares approach that takes as input a series of temperature readings only. Using a reformulation of the Marshall–Hoare double exponential formula and a technique for reducing the dimension of the state space, an error function that depends on the two cooling rates is constructed, with the aim of minimizing this function. Standard nonlinear optimization methods that are used to minimize the bivariate error function require an initial guess for these unknown rates. Hence, a systematic procedure based on the given temperature data is also proposed to determine an initial estimate for the rates. Then, an explicit formula for the TOD is given. Results of numerical simulations using both theoretical and experimental data are presented, both yielding reasonable estimates. The proposed procedure does not require knowledge of the temperature at death nor the body mass. In fact, the method allows the estimation of the temperature at death once the cooling rates and the TOD have been calculated. The procedure requires at least three temperature readings, although more measured readings could improve the estimates. With the aid of computerized recording and thermocouple detectors, temperature readings spaced 10–15 min apart, for example, can be taken. The formulas can be straightforwardly programmed and installed on a hand‐held device for field use.     

“以债生财”还是“因债致贫”？——家庭住房债务对贫困脆弱性的影响

脱贫的长效机制应考虑到未来贫困风险问题,即应关注贫困脆弱性。随着住房债务在家庭债务中的主体地位日益显现,住房债务或将影响家庭的贫困脆弱性。基于2016年中国家庭追踪调查（CFPS）数据对两者关系展开研究,结果显示,平均而言,负有住房债务的家庭贫困脆弱性程度显著低于无住房债务的家庭,且以住房债务资产比度量的住房债务压力能够缓解贫困脆弱性。但这种缓解作用并非是持续的,而是表现出“U型”非线性特征。当住房债务资产比低于137.5%时,住房债务主要表现出净“财富效应”,存在“以债生财”的可能;在此之后,“房奴效应”将占主导地位,刺激“因债致贫”现象的发生。当然,家庭特征不同也会使这种影响产生差异。为减缓相对贫困,可进一步提高住房信贷效率、发挥住房信贷效能。     

在新条件下拟Newton迭代方法的收敛性

该文给出了在Banach空间中求解非线性方程拟Newton迭代方法的新条件,及在新条件下拟Newton迭代方法的收敛性。     

REASSESSING NONLINEARITY IN THE URBAN DISADVANTAGE/VIOLENT CRIME RELATIONSHIP: AN EXAMPLE OF METHODOLOGICAL BIAS FROM LOG TRANSFORMATION*

Sociologists and criminologists have become increasingly concerned with nonlinear relationships and interaction effects. For example, some recent studies suggest that the positive relationship between neighborhood disadvantage and violent crime is nonlinear with an accelerating slope, whereas other research indicates a nonlinear decelerating slope. The present paper considers the possibility that this inconsistency in findings is partially caused by lack of attention to an important methodological concern. Specifically, we argue that researchers have not been sensitive to the ways in which logarithmic transformation of the dependent variable can bias tests for nonlinearity and statistical interaction. We illustrate this point using demographic and violent crime data for urban neighborhoods, and we propose an alternative procedure to log transformation that involves the use of weighted least‐squares regression, heteroscedasticity consistent standard errors, and diagnostics for influential observations.     

Structure elucidation of dyes that are formed in the colorimetric detection of the improvised explosive urea nitrate

Urea nitrate (uronium nitrate, UN) is a powerful, improvised explosive that can be easily made from urea and nitric acid. It is considered the most frequently used, illegal explosive in the Israeli arena, which is responsible for the loss of more than a hundred lives in terrorist incidents. Urea nitrate is a colorless, crystalline substance that looks very much like sugar. A sensitive color test for UN was developed recently. It is based on the formation of a red dye in the reaction between p-dimethylaminocinnamaldehyde and UN under neutral conditions. A similar reaction with p-dimethylaminobezaldehyde produces a yellow dye. The two dyes have been synthesized, and their structures determined by X-ray crystallography. Both dyes are protonated Schiff bases, prevailing in the crystal in a quinoid form. They are identical to the compounds, which are obtained in the colorimetric detection of urea with the same reagents, under strong acidic conditions, whose structures have been postulated in the literature, but never fully proved experimentally.     

非线性科学及其在心理学中的应用

长期以来,心理学一直以线性的科学模型作为理论基础,追求一种简单明了的因果关系,并以此来说明人类行为的确定性规律并预测行为的变化和发展.但是,线性的方法只是在简单系统中是有效的,作为开放、演化和复杂的心理系统,我们是难以用确定性的方法来加以描述的,而非线性科学则为我们理解真实、复杂系统提供了一个新的视角.由于人的心理的本质是非线性的,所以非线性科学的概念和方法已经受到了心理学界的广泛重视,并开始运用于心理学的许多领域.