Directed Evolution: A Historical Exploration into an Evolutionary Experimental System of Nanobiotechnology, 1965–2006

This study explores the history of nanotechnology from the perspective of protein engineering, which differs from the history of nanotechnology that has arisen from mechanical and materials engineering; it also demonstrates points of convergence between the two. Focusing on directed evolution—an experimental system of molecular biomimetics that mimics nature as an inspiration for material design—this study follows the emergence of an evolutionary experimental system from the 1960s to the present, by detailing the material culture, practices, and techniques involved. Directed evolution, as an aspect of nanobiotechnology, is also distinct from the dominant biotechnologies of the 20th century. The experimental systems of directed evolution produce new ways of thinking about molecular diversity that could affect concepts concerning both biology and life.

Constraints on visual exploration of youth football players during 11v11 match-play: The influence of playing role,pitch position and phase of play

ABSTRACT

Visual exploratory action, in which football players turn their head to perceive their environment, improves prospective performance with the ball during match-play. This scanning action, however, is relevant for players throughout the entire match, as the information perceived through visual exploration is needed to guide movement around the pitch during both offensive and defensive play. This study aimed to understand how a player’s on-pitch position, playing role and phase of play influenced the visual exploratory head movements of players during 11v11 match-play. Twenty-two competitive-elite youth footballers (M = 16.25 years) played a total of 1,623 minutes (M = 73.8). Inertial measurement units, global positioning system units and notational analysis were used to quantify relevant variables. Analyses revealed that players explored more extensively when they were in possession of the ball, and less extensively during transition phases, as compared to team ball-possession and opposition ball-possession phases of play. Players explored most extensively when in the back third of the pitch, and least when they were in the middle third of the pitch. Playing role, pitch position and phase of play should be considered as constraints on visual exploratory actions when developing training situations aimed at improving the scanning actions of players.     

The Preservation and Maintenance of Special Research Collections in Public Libraries:

Whether or not, or under what circumstances, public libraries should house special-subject research collections is examined with respect to: (1) feasibility of community participation in administrative decisionmaking and allocation of funds: (2) reliability of library/collection use statistics as measures of performance: (3) rationales for and costs of maintaining special collections. Literature on local history and performing arts research collections is discussed to illustrate practical administrative considerations. Creation of community participation opportunities, either through formal analyses of library communities or other methods, is advocated as essential with respect to the preservation and maintenance of special subject research collections in public libraries.     

盲人智能拐杖的设计与制作

SHEN Qing-yang;YU Bao-qi(School of Electrical and Informational Engineering, Liaoning Institute of Science and Technology, Benxi, Liaoning, 117004, China)     

Effects of light curing modes and ethanol-wet bonding on dentin bonding properties

Objective

This study explored the effects of different light curing modes and ethanol-wet bonding on dentin bonding strength and durability.

Methods

A total of 54 molars were randomly divided into three groups: Single Bond 2, Gluma Comfort Bond, and N-Bond. Based on the three light-curing modes and presence or absence of ethanol pretreatment, the samples were assigned to six subgroups: high-light mode, ethanol pretreatment+high-light mode, soft-start mode, ethanol pretreatment+soft-start mode, standard mode, and ethanol pretreatment+standard mode. All samples were bonded with resin based on the experimental groups. After 24 h and 6 months of water storage, a universal testing machine was used to measure microtensile bond strength. Scanning electron microscopy (SEM) was applied to observe mixed layer morphology.

Results

The 24-h and 6-month microtensile bond strengths of the ethanol pretreatment groups were significantly higher than those of the non-ethanol pretreatment groups at the same light modes (P<0.05). With or without ethanol pretreatment, the microtensile bond strengths of the high-light modes were significantly lower than those of the soft-start modes and standard modes (P<0.05). The microtensile bond strengths of samples from the 6-month water storage group significantly decreased compared with those of samples from the 24-h water storage group (P<0.05). The soft-start groups and standard groups formed better mixed layers than the high-light mode groups, whereas the ethanol pretreatment groups formed more uniform mixed layers than those without ethanol pretreatment.

Conclusions

Ethanol-wet bonding technique, soft-start, and standard modes could improve dentin bonding properties.

     

Examining Patterns and Motivations for Drug-Related Information Seeking and Scanning Behavior: A Cross-National Comparison of American and Israeli College Students

The current study uses a grounded theory approach to explore dimensions and bi-national comparisons of active information seeking efforts (seeking) for and passive information acquisition (scanning) of drug-related information among two college student samples from the United States (N = 25) and Israel (N = 39). Specifically, the study focuses on seeking and scanning related to amphetamines and marijuana, two frequently used drugs among college populations, about which information is easily accessible. Results of semi-structured interviews suggest that information scanning and seeking about marijuana and amphetamines are common, particularly from peers and from the Internet. The analysis uncovers themes relating to young adults’ drug-related, information-seeking behaviors, including cross-source information acquisition across interpersonal and media sources, and motivations for engaging in active efforts to seek drug-related information. These findings extend research on information seeking and scanning and suggest future research should examine predictors and effects of these behaviors in the context of substance use.     

麝毛被扫描电镜观察和机能意义探讨

麝毛被由长针毛和短针毛组成,无绒毛。长针毛的髓部和皮部由致密纵横膈分隔成气室,气室连续贯穿毛干,毛小皮呈菱形。短针毛髓部为气室,皮部为致密角质物,毛小皮呈扁平形。毛干气室发达充盈体表温度,毛被层形成体表保温层,具保温御寒功能。     

从图式理论的视角看如何提高四级快速阅读能力

因为缺乏正确的理论指导,学生面对改革后的四级考试新题型——快速阅读理解时不知所措。论文诠释了图式理论的渊源、发展与内容,揭示了人们已有的知识结构对阅读理解存在着重要影响的论点。论文认为依照图式理论来指导快速阅读理解,培养学生建立和调用图式的技巧,结合正确的阅读方法,学生可以大大提高阅读的速度与理解的效度。     

中国天南星科花粉形态的研究

利用扫描电镜对天南星科Araceae22属28种(除Arum maculatum产自德国外，其余均产自中国) 及菖蒲科Acoraceae 1属2种植物的花粉形态进行了观察。结果显示天南星科花粉形态在科内变异很 大。花粉粒形状从球形、近球形、椭球形到扁球形和橄榄形；萌发孔类型有散孔型、具薄壁区型、环沟型 或无萌发孔；外壁纹饰为小穴状、网状、肋条状、条纹状、疣状、具刺或光滑。主要依据花粉形态方面的证 据探讨了崖角藤属Rhaphidophora、麒麟叶属Epipremnam 、龟背竹属Monstera 3属的属间关系以及犁头尖属Typhonium属下分类中存在的一些问题。