Structural interpretation of site-directed mutagenesis and specificity of the catalytic subunit of protein kinase CK2 using comparative modelling

The catalytic subunit of protein kinase casein kinase 2 (CK2),which has specificity for both ATP and GTP, shows significantamino acid sequence similarity to the cyclin-dependent kinase2 (CDK2). We constructed site-directed mutants of CK2 and useda three-dimensional model to investigate the basis for the dualspecificity. Introduction of Phe and Gly at positions 50 and51, in order to restore the pattern of the glycine-rich motif,did not seriously affect the specificity for ATP or GTP. Weshow that the dual specificity probably originates from theloop situated around the position His115 to Asp120 (HVNNTD).The insertion of a residue in this loop in CK2 subunits, comparedwith CDK2 and other kinases, might orient the backbone to interactwith the base A and G; this insertion is conserved in all knownCK2. The mutant N118, the design of which was based on the modelling,showed reduced affinity for GTP as predicted from the model.Other mutants were intended to probe the integrity of the catalyticloop, alter the polarity of a buried residue and explore theimportance of the carboxy terminus. Introduction of Arg to replaceAsn189, which is mapped on the activation loop, results in amutant with decreased k_cat, possibly as a result of disruptionof the interaction between this residue and basic residues inthe vicinity. Truncation at position 331 eliminates the last60 residues of the subunit and this mutant has a reduced catalyticefficiency compared with the wild-type. Catalytic efficiencyis restored in the truncation mutant by the replacement of apotentially buried Glu at position 252 by Lys, probably owingto a higher stability resulting from the formation of a saltbridge between Lys252 and Asp208.     

View Planning for Multi-View Stereo 3D Reconstruction Using an Autonomous Multicopter

Multi-view stereo algorithms are an attractive technique for the digital reconstruction of outdoor sites. Concerning the data acquisition process a vertical take off and landing UAV carrying a digital camera is a suitable platform in terms of mobility and flexibility in viewpoint placement. We introduce an automated UAV based data acquisition and outdoor site reconstruction system. A special focus is set on the problem of model based view planning using a coarse digital surface model (DSM) with minimal data preprocessing. The developed view planning heuristic considers a coverage, a maximum view angle and an overlapping constraint imposed by multi-view stereo reconstruction techniques. The time complexity of the algorithm is linear with respect to the size of the area of interest. We demonstrate the efficiency of the entire system in two scenarios, a building and a hillside.     

Predicting users' return to virtual worlds: a social perspective

Virtual worlds or three‐dimensional computer‐based simulated environments have received considerable attention as platforms for entertainment, education and commerce. In contrast to a web site, for example, where a user interacts with a two‐dimensional site, virtual worlds provide a platform in which users can interact with other individuals, sometimes including strangers, within three‐dimensional environments. Virtual worlds afford a form of ‘socialness’ unlike many other technologies, often motivating a user – by virtue of these social experiences – to return. Drawing on the Spatial Model of Interaction and Awareness‐Attention Theory, we demonstrate that besides social aspects, which include social awareness and social perception, flow experience, which is the mental state of being fully absorbed and somewhat lost in time, is an essential ingredient in an individual's decision to return to a virtual world. We also demonstrate how characteristics of the technology are linked to the social aspects experienced in virtual worlds. A laboratory study conducted in a virtual world, Second Life, supports our assertions and identifies state predictors of flow that influence individuals' intentions to return to the virtual world environment.     

Business–IT fit in e-procurement systems: evidence from high-technology firms in China

Abstract.  Because of the influence of globalization and updated information technologies (IT), firms in China face an urgent need to adopt e-procurement systems (EP) to deal with their daily procurement activities. However, implementing EP in China encounters various uncertainties from internal and external business environments. To address this issue, this research aims to examine the fit between business and the IT environment and to study its impact on system performance. The literature review allows the proposal of two internal business environmental uncertainties and two external business environmental uncertainties covering the perspectives of process, knowledge, partnership and environment. Based on a multiple-case study performed in four Chinese firms that supply various personal computer components to a Taiwanese original equipment manufacturer via an EP, it was found that the firms' external and internal uncertainty factors affected the performance of EP. In addition, an EP with a low level of integration – the EP type used most frequently in China – can only achieve great performance when the adopting firms faced a low uncertainty of environment, partnership and process, and had low levels of IT knowledge. It was also observed that lack of fit between the business environment and EP produced extra burdens and costs in the buyer–supplier relationship. This significantly reduced the system performance of the Chinese firms. Hence, the contribution of this research can be twofold. First, practitioners in China can use this framework to diagnose their environmental conditions and then choose the appropriate type of EP to implement. Second, researchers can build upon this model to further examine the impact of fit on EP performance and generalize the results.     

OPM vs. UML--Experimenting with Comprehension and Construction of Web Application Models

Object-Process Methodology (OPM), which is a holistic approach to modeling and evolving systems, views objects and processes as two equally important entities that describe the system's structure and behavior in a single model. Unified Modeling Language (UML), which is the standard object-oriented modeling language for software systems, separates the system model into various aspects, each of which is represented in a different view (diagram type).The exponential growth of the Web and the progress of Internet-based architectures have set the stage for the proliferation of a variety of Web applications, which are classified as hybrids between hypermedia and information systems. Such applications require a modeling approach that is capable of clearly specifying aspects of their architecture, communication, and distributive nature. Since UML and OPM are two candidates for this task, this study has been designed to establish the level of comprehension and the quality of the constructed Web application models using each one of these two approaches.In the experiment we carried out, third year undergraduate information systems engineering students were asked to respond to comprehension and construction questions about two representative Web application models. The comprehension questions related to the system's structure, dynamics, and distribution aspects. The results suggest that OPM is better than UML in modeling the dynamics aspect of the Web applications. In specifying structure and distribution aspects, there were no significant differences. The results further suggest that the quality of the OPM models students built in the construction part was superior to that of the corresponding UML models.     

Individuals and their interactions in demand planning processes: an agent-based,computational testbed

The demand planning process in semiconductor supply chains faces many challenges. In this process, individuals, their properties such as sensing capabilities and their interactions play a crucial role. This paper shows how agent-based modelling (ABM) can provide a computational testbed to investigate these aspects with respect to forecast accuracy. Based on the requirements of the demand planning context, we develop an empirically validated agent-based model of the demand planning process. In this model, we incorporate different concepts from behavioural science and the distributed cognition perspective. We show the usefulness of this agent-based computational testbed by using a case study from the semiconductor industry. Our model shows that demand planning accuracy does not depend on the planning capabilities of planners alone, but that the interactions of the individuals, emerging from the planning process design, may both positively and negatively affect accuracy.     

Utilizing domain models for application design and validation

Domain analysis enables identifying families of applications and capturing their terminology in order to assist and guide system developers to design valid applications in the domain. One major way of carrying out the domain analysis is modeling. Several studies suggest using metamodeling techniques, feature-oriented approaches, or architectural-based methods for modeling domains and specifying applications in those domains. However, these methods mainly focus on representing the domain knowledge, providing insufficient guidelines (if any) for creating application models that satisfy the domain rules and constraints. In particular, validation of the application models which include application-specific knowledge is insufficiently dealt. In order to fill these lacks, we propose a general approach, called Application-based DOmain Modeling (ADOM), which enables specifying domains and applications similarly, (re)using domain knowledge in application models, and validating the application models against the relevant domain models. In this paper we present the ADOM approach, demonstrating its application to UML 2.0 class and sequence diagrams.