Competency rallying in electronic markets: implications for open source project success

This paper studies the success of Open Source Software (OSS) projects in attracting developer interest and achieving project efficiency. The focus of our study is on examining the relationship between the four sets of capabilities proposed in the Theory of Competency Rallying (TCR) and the success of OSS projects. The data collected from 607 OSS projects mainly confirm that the capabilities proposed in the TCR are necessary for the success of OSS projects. The results of this study show that in order to succeed, OSS projects should constantly identify their market??s quality and functionality needs. Ability of OSS project managers to know which developers possess certain skills required to meet a particular market need is also found to be critical. Another capability that is recognised to be crucial in predicting project success is the ability of OSS developers in effectively addressing market needs and continuously learning from such experiences. Finally, the ability of stakeholders involving in addressing a particular market need to efficiently collaborate and fulfil that specific market need is found to be another essential capability required for OSS projects to succeed. Implications of the results for practitioners and the research community are presented.     

The development, validity and reliability of TPACK-deep: A technological pedagogical content knowledge scale

The purpose of this study is to develop a TPACK (technological pedagogical content knowledge) scale based on the centered component of TPACK framework in order to measure preservice teachers’ TPACK. A systematic and step-by-step approach was followed for the development of the scale. The validity and reliability studies of the scale were carried out with 995 Turkish preservice teachers. The sample was split into two subsamples on random basis (n1 = 498, n2 = 497). The first sample was used for Exploratory Factor Analysis (EFA) and the second sample for Confirmatory Factor Analysis (CFA). After the EFA, the TPACK-deep scale included 33 items and had four factors. These factors were design, exertion, ethics and proficiency. The Cronbach’s alpha coefficient for the whole scale was found to be .95, whereas the values of Cronbach’s alpha coefficient for individual factors of the scale ranged between .85 and .92. The CFA was conducted within the scope of the validity study of the scale. In this way, this structure of the 4-factor scale was confirmed. In addition, the test-retest reliability coefficient of the scale was calculated as .80. The findings revealed that the TPACK-deep scale was a valid and reliable instrument for measuring TPACK. Consequently, various suggestions were put forward regarding the use the TPACK-deep scale for applied research and for future studies.     

Antecedents to IT personnel's intentions to leave: A systematic literature review

This paper undertakes a systematic review to gain insight into existing studies on the turnover of information technology (IT) personnel. Our systematic review of 72 studies from 1980 to 2008 examines the background and trend of research into IT personnel's intentions to leave their workplaces, in addition to providing a taxonomy of the determinants of their intentions to quit as captured in IT literature. We note a huge growth in the number of academic papers on the topic since 1998. Moreover, most of the research on IT turnover has been undertaken in North America, followed by Asia. Based on the 72 extracted studies, we found a total of 70 conceptually distinct IT turnover drivers. We classified them into the 5 broad categories of individual, organisational, job-related, psychological, and environmental, each containing three to four sub-categories. Finally, this paper presents insightful recommendations for IT practitioners as well as for the research community.     

Academic self-efficacy and academic procrastination as predictors of problematic internet use in university students

Although computers and the internet, indispensable tools in people’s lives today, facilitate life on the one hand, they have brought new risks with them on the other. Internet dependency, or problematic internet use, has emerged as a new concept of addiction. Parallel to this increasing in society in general, it is also on the rise among university students and is widely believed to have a negative impact on their lives. The aim of this study was to investigate whether academic self-efficacy and academic procrastination can act as predictors of problematic internet use among university students. The study group consisted of 398 students attending education, medicine, architecture and economics programs at the Karadeniz Technical University in Turkey. The Problematic Internet Use Scale, Academic Self-efficacy Scale, Academic Procrastination Scale and a Personal Data Form were used as scaling instruments. Pearson’s correlation coefficient, multiple regression analysis, independent samples t-test and one-way ANOVA were used to analyze the data collected. The results show a significant negative correlation between academic self-efficacy and problematic internet use, while the relation between problematic internet use and academic procrastination was not statistically significant. Furthermore, academic self-efficacy was determined to be a significant predictor of problematic internet use. The results also show a significant difference in problematic internet use in terms of students’ programs, though levels of problematic internet use did not differ in terms of sex or ownership of a computer. These findings are discussed in the light of the relevant literature and some new directions for further studies are suggested.     

The synthesis of nonporous poly(isobutyl methacrylate) microspheres by suspension polymerization technique and investigation of their swelling properties

Poly(isobutyl methacrylate) (PiBMA) microspheres with different crosslinking densities were synthesized by suspension polymerization technique in aqueous medium and their characterization and swelling behaviors in different solvents were investigated. PiBMA spheres with a 800‐ to 1500‐μm‐diameter range were obtained by using benzoyl peroxide (BPO) as polymerization initiator, 1/5 ratio of monomer/water in volume, tricalcium phosphate (TCP), and poly(N vinyl‐2‐pyrrolidone) (PVP) as suspension stabilizer with 350 rpm stirring rate in nitrogen atmosphere. The influence of type and amount of crosslinking agent on the swelling properties and diffusional behavior, diffusion coefficient, and network properties of the spheres were examined in pentane, hexane, heptane, and gasoline. Dynamic swelling behaviors of crosslinked spheres were determined by measuring the diameter of the sphere as a function of time by an optical microscope. Swelling behaviors and network properties were found to be dependent on the diameter, crosslinking density of the sphere, and crosslinking agent and solvent. The results of this study indicate that the crosslinked PiBMA microsphere can be swollen in gasoline very well and retains a high ratio (1500% of its volume) of gasoline in their structure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 349–356, 2002     

Synthesis,characterization, and comparison of self‐doped,doped, and undoped forms of polyaniline,poly(o‐anisidine), and poly[aniline‐co‐(o‐anisidine)]

Polyaniline (PANI), poly(o‐anisidine), and poly[aniline‐co‐(o‐anisidine)] were synthesized by chemical oxidative polymerization with ammonium persulfate as an oxidizing reagent in an HCl medium. The viscosities, electrical conductivity, and crystallinity of the resulting polymers (self‐doped forms) were compared with those of the doped and undoped forms. The self‐doped, doped, and undoped forms of these polymers were characterized with infrared spectroscopy, ultraviolet–visible spectroscopy, and a four‐point‐probe conductivity method. X‐ray diffraction characterization revealed the crystalline nature of the polymers. The observed decrease in the conductivity of the copolymer and poly(o‐anisidine) with respect to PANI was attributed to the incorporation of the methoxy moieties into the PANI chain. The homopolymers attained conductivity in the range of 3.97 × 10^?3 to 7.8 S/cm after doping with HCl. The conductivity of the undoped forms of the poly[aniline‐co‐(o‐anisidine)] and poly(o‐anisidine) was observed to be lower than 10^?5 J/S cm^?1. The conductivity of the studied polymer forms decreased by the doping process in the following order: self‐doped → doped → undoped. The conductivity of the studied polymers decreased by the monomer species in the following order: PANI → poly[aniline‐co‐(o‐anisidine)] → poly(o‐anisidine). All the polymer samples were largely amorphous, but with the attachment of the pendant groups of anisidine to the polymer system, the crystallinity region increased. The undoped form of poly[aniline‐co‐(o‐anisidine)] had good solubility in common organic solvents, whereas doped poly[aniline‐co‐(o‐anisidine)] was moderately crystalline and exhibited higher conductivity than the anisidine homopolymer. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Double bound method for solving the p-center location problem

We give a review of existing methods for solving the absolute and vertex restricted p-center problems on networks and propose a new integer programming formulation, a tightened version of this formulation and a new method based on successive restrictions of the new formulation. A specialization of the new method with two-element restrictions obtains the optimal p-center solution by solving a series of simple structured integer programs in recognition form. This specialization is called the double bound method. A relaxation of the proposed formulation gives the tightest known lower bound in the literature (obtained earlier by Elloumi et al., [1]). A polynomial time algorithm is presented to compute this bound. New lower and upper bounds are proposed. Problems from the OR-Library [2] and TSPLIB [3] are solved by the proposed algorithms with up to 3038 nodes. Previous computational results were restricted to networks with at most 1817 nodes.     

Differential Responses to Bioink-Induced Oxidative Stress in Endothelial Cells and Fibroblasts

A hydrogel system based on oxidized alginate covalently crosslinked with gelatin (ADA-GEL) has been utilized for different biofabrication approaches to design constructs, in which cell growth, proliferation and migration have been observed. However, cell–bioink interactions are not completely understood and the potential effects of free aldehyde groups on the living cells have not been investigated. In this study, alginate, ADA and ADA-GEL were characterized via FTIR and NMR, and their effect on cell viability was investigated. In the tested cell lines, there was a concentration-dependent effect of oxidation degree on cell viability, with the strongest cytotoxicity observed after 72 h of culture. Subsequently, primary human cells, namely fibroblasts and endothelial cells (ECs) were grown in ADA and ADA-GEL hydrogels to investigate the molecular effects of oxidized material. In ADA, an extremely strong ROS generation resulting in a rapid depletion of cellular thiols was observed in ECs, leading to rapid necrotic cell death. In contrast, less pronounced cytotoxic effects of ADA were noted on human fibroblasts. Human fibroblasts had higher cellular thiol content than primary ECs and entered apoptosis under strong oxidative stress. The presence of gelatin in the hydrogel improved the primary cell survival, likely by reducing the oxidative stress via binding to the CHO groups. Consequently, ADA-GEL was better tolerated than ADA alone. Fibroblasts were able to survive the oxidative stress in ADA-GEL and re-entered the proliferative phase. To the best of our knowledge, this is the first report that shows in detail the relationship between oxidative stress-induced intracellular processes and alginate di-aldehyde-based bioinks.     

Effect of Conductivity, pH, and Elution Buffer Salinity on Glycomacropeptide Recovery from Whey Using Anion Exchange Chromatography

ABSTRACT: The objective of this study was to investigate the effect of whey conductivity, pH, and the salt concentration of the elution buffer on glycomacropeptide recovery and its extent of contamination using anion exchange chromatography. Glycomacropeptide was isolated from Mozzarella whey. Samples were analyzed for glycomacropeptide and contaminating whey proteins. Mass balances and percent recoveries were calculated from these data. Glycomacropeptide recovery increased substantially with decreasing conductivity and increasing pH of the whey feed stream. Increasing the pH, but not increasing the conductivity, increased contamination of the glycomacropeptide by primarily beta-lactoglobulin. Salt concentration of at least 0.1 M was required for complete elution of bound glycomacropeptide. These data define conditions needed for glycomacropeptide recovery by a process chromatography system that uses food-grade buffers, operates at industrially relevant flow rates, and achieves up to 98% recovery.