Determining the relative age of blue ballpoint ink by gas chromatography

A method for identifying the writing age of blue ballpoint pen ink has been established due to the imperative demand in forensic laboratories. The content of the volatile components in blue ballpoint pen ink were determined by gas chromatography (GC). The absorbance of dye in blue ballpoint pen ink was measured by UV-Vis spectrometry A writing age curve of the ink was established using the ratio of the content of the volatile components to the dye, based on the identification of 74 kinds of blue ballpoint pen ink of domestic and international origins. The change of benzene alcohol or phenoxetol with the writing age was also tested. Different kinds of blue ballpoint pen ink were detected and the repeatability of the experiment was investigated. The results indicate that the method is reliable, sensitive, systematic and is especially suitable for practical use. __________ Translated from Chinese Journal of Chromatography, 2005 (3)(in Chinese)     

HARVESTING AN AGE‐STRUCTURED POPULATION AS BIOMASS: DOES IT WORK?

Abstract The economics of fisheries is based heavily on describing fish populations by the surplus production model. Both economists and ecologists have different opinions on whether this approach provides an adequate biological basis for economic analysis. This study takes an age‐structured population model and shows how, under equilibrium conditions, it determines the surplus production model. The surplus production model is then used to solve an optimal feedback policy for a generic optimal harvesting problem. Next, it is assumed that the fishery manager applies this feedback policy even though the fish population actually evolves according to the age‐structured model. This framework is applied to the widow rockfish, Atlantic menhaden, and Pacific halibut fisheries. Population age‐structure contains information on future harvest possibilities. The surplus production model neglects this information and may lead to major deviations between the expected and actual outcomes especially under multiple steady states and nonlinearities.     

Backward and forward recurrence times,and their interrelationships in Bellman-Harris branching processes

Random variables are constructed for a Bellman-Harris branching process which are the extensions of backward and forward recurrence times from an ordinary renewal process. The sum of the two extended random variables is also constructed, and then the distribution functions for all three random variables are developed. The asymptotic limits for all three time-dependent distributions are also obtained.     

四爪陆龟生长的研究：Ⅲ.四爪陆龟年龄结构和年龄模型的分析

四爪陆龟的龟壳坚硬,背腹盾片上具有同心环纹,人工饲养研究表明,同心环纹就是四爪陆龟的生长年轮,饲养三年的龟体每一盾片上增加了三个同心环纹,因此一个生长年轮即为一龄。根据野生环境条件下,四爪陆龟参与繁殖的生长年轮推算,四爪陆龟性成熟的年龄雌雄不同,雌龟约为12年,雄龟约为10年,年龄结构显示雌雄性比为18:11(1984年);30:34(1991),成体龟数目远大于幼体龟的数目,利用年轮与背甲长度或体宽建立年龄模型,模型显示相同年龄的四爪陆龟,雌体生长速度大于雄体,通过年龄模型推测,背甲长度超过180mm的野生四爪陆龟的年龄可达24年,估计四爪陆龟的期望寿命为28年。     

Global Dynamics of a Multi-group SEIR Epidemic Model with Infection Age

National Natural Science Foundation of China (No. 12022113),Henry Fok Foundation for Young Teachers, China (No. 171002), Outstanding Young Talents Support Plan of Shanxi Province, Science and Engineering Research Board (SERB for short), India(No. ECR/2017/002786), UGC-BSR Research Start-Up-Grant, India (No. F.30-356/2017(BSR)), and Senior Research Fellowship from the Council of Scientific and Industrial Research (CSIR for short),India (No. 09/1131(0006)/2017-EMR-I).     

THE ECONOMICS OF CONFLICTING INTERESTS: NORTHERN BALTIC SALMON FISHERY ADAPTION TO GRAY SEAL ABUNDANCE

The successful conservation of gray seals has led to increased seal‐induced damage to the Atlantic salmon fisheries of the Baltic Sea. This paper addresses the conflict between the conservation of a formerly endangered species, the gray seal, and professional fishermen, whose livelihoods are affected by both seal‐induced damage and salmon fisheries management. We develop a bioeconomic model that incorporates the age structure of Atlantic salmon and gray seal populations. To determine the social optimum, we maximize the discounted net present value of the trap net fishery, taking into account the presence of seals in the form of seal‐induced losses, which we describe using a damage function. By choosing the optimal combination of fishing gear over time, we obtain the socially optimal fishing efforts, salmon stock size, and salmon catch. In addition, we study the private effects of introducing a technology subsidy aimed at mitigating the seal‐salmon conflict. The results suggest that technological adaptation would effectively reduce the cause of the conflict, while a technology subsidy encouraging such adaptation would shift the economic responsibility from individual fishermen to the broader public.     

一类带有感染年龄SIR模型最优化免疫策略的存在性

对于一个免疫策略来讲,付出(单位时间内接种疫苗的数量)和效果(再生数的大小)是两个重要概念.在给定的费用下找到带有最小再生数的策略和在给定的再生数下找到最小费用的策略是两个最优问题.对一个确定的免疫策略来说,人群中的易感群体和染病群体会趋于相对稳定的状态.当一种疾病侵袭已免疫人群时,用带有感染年龄的SIR模型去描述这类疾病的传播更为准确.因此,本文研究了一类带有感染年龄的SIR模型,得到了最优化策略的存在性.