The State of the State: Introduction

Systemic Practice and Action Research -     

高分辨率雷达检测——预研课题和潜在应用

文献[1]介绍了高分辨力雷达在改善目标检测中的潜在优点,强调了根据期望的目标径向距离分布图来形成发射波形和接收处理器的概念,并给出了性能预测。为克服先验信息的不足,本文提出并评估了一个自适应方案,用它来联机估算目标距离分布图。此外,引入了一个更一般性的、基于统计描述的目标冲击响应模型,讨论了相应的处理方案和检测性能。     

Competency-Based Model Through It: An Action Research Project

Competency-based management is a strategic approach for Human Resources Management and organizational change. Additionally, in business environment, information technologies competencies are a significant factor to organizational success (Bharadwaj, MIS Q 24(1):169–196, 2006). However the implementation of a model of competency-based management in business environment is difficult and complex (Lawler, J Organ Behav 15(1):3–15, 1993). In this context, Information systems are a suitable tool to manage individual and organizational knowledge (Alavi and Leidner, MIS Q 25(1):107–136, 2001; Bowman, Inf Syst Manag 19(3):32–40, 2002). This paper introduces a dynamic approach to a competency-based model through IT. We validate such approach through an action research project in RTVE, the largest company and reference public corporation of radio and television in Spain. The action research process in this organization is presented, and the findings highlight the potential benefits of the proposed model, and may be used in facilitating organizational change.     

The CRISPR/Cas bacterial immune system cleaves bacteriophage and plasmid DNA

Bacteria and Archaea have developed several defence strategies against foreign nucleic acids such as viral genomes and plasmids. Among them, clustered regularly interspaced short palindromic repeats (CRISPR) loci together with cas (CRISPR-associated) genes form the CRISPR/Cas immune system, which involves partially palindromic repeats separated by short stretches of DNA called spacers, acquired from extrachromosomal elements. It was recently demonstrated that these variable loci can incorporate spacers from infecting bacteriophages and then provide immunity against subsequent bacteriophage infections in a sequence-specific manner. Here we show that the Streptococcus thermophilus CRISPR1/Cas system can also naturally acquire spacers from a self-replicating plasmid containing an antibiotic-resistance gene, leading to plasmid loss. Acquired spacers that match antibiotic-resistance genes provide a novel means to naturally select bacteria that cannot uptake and disseminate such genes. We also provide in vivo evidence that the CRISPR1/Cas system specifically cleaves plasmid and bacteriophage double-stranded DNA within the proto-spacer, at specific sites. Our data show that the CRISPR/Cas immune system is remarkably adapted to cleave invading DNA rapidly and has the potential for exploitation to generate safer microbial strains.     

Extensive halogen-mediated ozone destruction over the tropical Atlantic Ocean

Increasing tropospheric ozone levels over the past 150 years have led to a significant climate perturbation; the prediction of future trends in tropospheric ozone will require a full understanding of both its precursor emissions and its destruction processes. A large proportion of tropospheric ozone loss occurs in the tropical marine boundary layer and is thought to be driven primarily by high ozone photolysis rates in the presence of high concentrations of water vapour. A further reduction in the tropospheric ozone burden through bromine and iodine emitted from open-ocean marine sources has been postulated by numerical models, but thus far has not been verified by observations. Here we report eight months of spectroscopic measurements at the Cape Verde Observatory indicative of the ubiquitous daytime presence of bromine monoxide and iodine monoxide in the tropical marine boundary layer. A year-round data set of co-located in situ surface trace gas measurements made in conjunction with low-level aircraft observations shows that the mean daily observed ozone loss is approximately 50 per cent greater than that simulated by a global chemistry model using a classical photochemistry scheme that excludes halogen chemistry. We perform box model calculations that indicate that the observed halogen concentrations induce the extra ozone loss required for the models to match observations. Our results show that halogen chemistry has a significant and extensive influence on photochemical ozone loss in the tropical Atlantic Ocean boundary layer. The omission of halogen sources and their chemistry in atmospheric models may lead to significant errors in calculations of global ozone budgets, tropospheric oxidizing capacity and methane oxidation rates, both historically and in the future.     

Mobility of screw dislocations in BCC crystals: A review on modelling methods

This article reviews the methods employed in modelling the various aspects of mobility of screw dislo¬cations in the body-centred cubic (BCC) structure. The behaviour of straight dislocation cores at 0 K has been well-un¬derstood following the application of traditional 2-D atomistic simulation in the past few decades. Kink-pair activation at non-zero temperatures has been classically treated by Volterra-type line tension models, but these have been superseded in recent years by a semi-continuum approach based on the Peierls-Nabarro framework. The use of 3-D atomistic simula¬tion techniques in studying kink-pair related problems is also emerging. There is now the prospect that engineering-ori¬ented phenomena such as brittle-to-ductile transition and the strain-rate sensitivity of deformation textures in BCC metals can be investigated at a more fundamental level involving dislocation core behaviour.     

Crystal structure of the specificity domain of ribonuclease P

RNase P is the only endonuclease responsible for processing the 5' end of transfer RNA by cleaving a precursor and leading to tRNA maturation. It contains an RNA component and a protein component and has been identified in all organisms. It was one of the first catalytic RNAs identified and the first that acts as a multiple-turnover enzyme in vivo. RNase P and the ribosome are so far the only two ribozymes known to be conserved in all kingdoms of life. The RNA component of bacterial RNase P can catalyse pre-tRNA cleavage in the absence of the RNase P protein in vitro and consists of two domains: a specificity domain and a catalytic domain. Here we report a 3.15-A resolution crystal structure of the 154-nucleotide specificity domain of Bacillus subtilis RNase P. The structure reveals the architecture of this domain, the interactions that maintain the overall fold of the molecule, a large non-helical but well-structured module that is conserved in all RNase P RNA, and the regions that are involved in interactions with the substrate.