番茄遗传转化体系的建立

为了获得带有白细胞介素2基因的转基因番茄植株,本研究运用农杆菌介导法,探究了影响遗传转化的因素,建立了较完善的番茄遗传转化体系。结果表明最优化的转化条件为:Km的筛选浓度为30mg/L,头孢曲松钠的抑菌浓度为500mg/L,侵染时间采用1~2min,并且抑菌7d后加入筛选压。得到的抗性植株经PCR检测为阳性,初步证明外源基因il-2已经整合到番茄基因组中。     

B2C电子商务顾客满意度测评研究

文章在参考已有研究成果的基础上,构建了B2C电子商务顾客满意度测评模型及其评价指标体系,并运用模糊综合评判法对某电子商务公司进行实证测评,最后对测评结果进行分析,并提出相应的对策以提升顾客满意度.     

Rural/urban differentials in demographic processes: The Central Asian states

While the populations of the Central Asian successor states are extremely heterogeneous on many indicators, the issue of rural or urban residence is consistently important in terms of differentials in population growth, socio-economic status and public health. In this paper I focus on rural population trends in Kazakhstan, Kyrghyzstan, Turkmenistan, Uzbekistan and Tajikistan. I explore the relatively disadvantaged position of rural inhabitants as well as regional variations within the rural population. The differentials in fertility and mortality rates and the large projected population increases indicate that future policy interventions and data collection efforts should incorporate a specific focus on rural areas.     

C2C市场上消费者从众决策研究——基于面板数据模型

电子商务市场蓬勃发展的同时,也存在严重的信息不对称现象,给消费者带来极大的购物风险。文章基于信息不对称理论,利用淘宝网交易数据对 C2C 市场上消费者的从众决策行为进行研究。研究发现 C2C 市场上店铺的日销量在店铺间存在二八分布的特征,说明网络消费者在购买商品时有从众行为。基于面板模型对店铺市场份额的研究表明,店铺历史销量信息对消费者选择店铺的决策有显著正向影响,而店铺信用对消费者决策的影响并不显著。因此,建议 C2C 交易平台增加退货量指标、动态销量图以及销量和价格的相互对应信息等,以促进消费者理性购物。     

基于符号互动论视角下的个体生育态度探究

近年来随着人口老龄化进程的明显加快,以及不同地区、城市出现的生育率持续走低等情况,中国未来人口数量的变化成为了一个十分重要的议题。近年来,国家先后制定了“双独生二胎”、“单独生二胎”以及全面放开二胎等鼓励民众生育的相关政策;相关学者也从人口学和经济学等视角对生育问题展开了诸多研究。本研究则是从符号互动论这一微观社会学视角出发,试图了解民众（主要集中在1970年至1995年出生的群体）生育态度是否会受到社会心理因素,尤其是从小生长的家庭环境中,兄弟姊妹等手足人数、手足关系、父母对待子女公平与否和出生排行的影响;以及当前生活环境,如社会治安状况、经济发展前景和政治稳定性等方面的主观判断对生育态度的影响;最后研究还将结婚意愿、性别等因素纳入到影响个体生育态度的分析模型之中。研究结果发现,兄弟姊妹等手足越多者,未来越倾向要生孩子;手足间关系越好者,未来也越倾向于要生孩子;排行中间的比排行老大的生孩子意愿高;无论父母对自己和手足公平情况怎样,都不会影响其生育态度。此外在所有外在环境中,经济状况是影响人们生育态度的主要因素,有结婚意愿者更倾向于生育孩子,男性也显著比女性更倾向于生育孩子。     

Ethnic segregation in context: Social discrimination among native Dutch pupils and their ethnic minority classmates

Social discrimination, defined as the relative preference for intra-ethnic over inter-ethnic relationships, was studied in pupils’ networks in Dutch secondary school classes. While native Dutch pupils (ethnic majority members) mainly named fellow majority members, ethnic minority members reported ties with as many majority as minority members. Considering the ethnic composition of the classroom, however, majority members discriminated less than minorities. No strong effect of classroom ethnic composition on social discrimination was found, whereas neighborhood composition was shown to clearly influence social discrimination: ethnic minority members were more, and majority members less inclined to discriminate in neighborhoods with more ethnic presence.     

HIV testing,perceptions of AIDS risk,and condom use motivation among US women

As STD infections including HIV increase in the United States, it has become increasingly important to policy makers to ascertain the extent to which knowledge and perceptions of AIDS risk affect an individual's probability of altering their sexual or contraceptive behavior to avoid infection. This paper examines the extent to which women's perceptions of their own and their partners' risk of HIV infection affects the probability of using a condom for protection against sexually transmitted diseases. This paper also examines the extent to which HIV testing may affect motivation for condom use. Crosstabulations reveal that prophylactic condom use is more prevalent among women who have been tested for HIV and increase as perceptions of their chance (and their partner's chance) of being positive increases. The multivariate results from this study indicate that having an HIV test significantly predicts the likelihood of using a condom for STD prevention for US women. Furthermore, women who perceive themselves to be at least somewhat likely to be HIV positive have a higher probability of using a condom to prevent sexually transmitted disease, and women who perceive their partners to be HIV positive are twice as likely as other women to use a condom for STD prevention. However, women who consider themselves likely to be HIV positive are no more likely to use a condom than those who consider themselves not at risk.     

Intention to emigrate in transition countries: the case of Albania

We analyse the profile of potential emigrants from Albania using data from the Central and Eastern Europe Eurobarometer in 1992. Respondents were asked to rate on a four-point scale the likelihood that they would go to live in Western Europe. Our results show that intention to emigrate is correlated positively with males, education and certain occupations, and negatively with age. There is little relation between emigration and income. Those who support the introduction of a free market in Albania are also more likely to emigrate than those who do not. Received: 24 August 1998/Accepted: 17 April 2000     

A two phases queueing system with Bernoulli vacation schedule under multiple vacation policy

This paper deals with a single server Poisson arrival queue with two phases of heterogeneous service along with a Bernoulli schedule vacation model, where after two successive phases service the server either goes for a vacation with probability p (0≤p≤1) or may continue to serve the next unit, if any, with probability q(=1−p). Further the concept of multiple vacation policy is also introduced here. We obtained the queue size distributions at a departure epoch and at a random epoch, Laplace Stieltjes Transform of the waiting time distribution and busy period distribution along with some mean performance measures. Finally we discuss some statistical inference related issues.     

数字电视视频压缩标准

简述MPEG、JPEG与H系列图像压缩编码国际标准中与高清晰度数字电视视频相关的编码技术,并指出各自的特点、性能与应用。