居住区内植物叶面尘中重金属累积特征

选取城区居住区内大叶女贞等7种绿化树种叶片为研究材料,测定其单位叶面积滞尘量、叶面尘中和叶内重金属含量,并分析两者的相关性,研究不同绿化树种对大气粉尘中各重金属的吸附滞留能力。结果表明,单位叶面积滞尘量大小表现为海桐(2.50 g/m^(2))>金森女贞(2.26 g/m^(2))>桂花(2.01 g/m^(2))>大叶女贞(1.50 g/m^(2))>广玉兰(1.20 g/m^(2))>香樟(1.11 g/m^(2))>大叶黄杨(0.97 g/m^(2))。叶片中重金属含量高低排序为Mn(49.026 mg/kg)>Cr(5.308 mg/kg)>Cu(5.138 mg/kg)>Ni(2.436 mg/kg)>Pb(1.986 mg/kg)>As(0.359 mg/kg)>Cd(0.063 mg/kg)。叶面尘中Cr-Ni、Cr-Cu、Mn-Ni、Mn-Cu、Mn-Cd、Ni-Cu、As-Pb以及叶内Cr-Ni、Mn-Cu、Cu-Cd之间均存在明显相关性(P<0.01);叶面尘中Cr-Mn、Cr-As、Ni-As、Cu-Cd以及叶内Cr-Cd、Cu-As存在相关关系(P<0.05)。海桐对大气粉尘的滞尘能力和吸附大气重金属能力较强,可作为城市绿化优选树种。

智能网关技术及发展趋势

随着社会的进步与信息技术的发展,用户对各类新兴家庭数字业务的需求也在逐步增加。传统的家庭网关已无法满足信息化时代的要求,智能网关应运而生。本文从智能网关的需求出发,对其内部架构和功能模块进行了详细介绍,并从宽带化、数字化以及NFV化三方面对未来智能网关的技术发展趋势进行了分析讨论。

Prefrontal attention and multiple reference frames during working memory in primates

The prefrontal cortex (PFC) is responsible for executive functions, including planning, goal setting, problem solving, inhibitory control, monitoring, and action adjusting. Executive functions also include selective attention and the flexibility or switching of attention; therefore, attention is an executive function in which the PFC participates. Working memory (WM), which is the temporary maintenance and processing of particular information, is usually considered to be a basic neural mechanism underlying the executive functions. This review systematically discusses the relationship between the prefrontal WM and attention and empha- sizes two forms of prefrontal attention. The first form occurs in the dlPFC, which encodes the location of objects with respect to the position of the head, thereby providing a frame of reference from which the focus of attention can be centered. The second occurs in the inferior convexity of the prefrontal cortex (IFC), which encodes the different attributes (shape, texture, color) of objects to enable the ability to focus on one or to switch attention between sensory attributes of objects.