The Social, Political, Economic, and Cultural Dimensions of Search Engines: An Introduction

Search engines are some of the most popular destinations on the Web—understandably so, given the vast amounts of information available to users and the need for help in sifting through online content. While the results of significant technical achievements, search engines are also embedded in social processes and institutions that influence how they function and how they are used. This special theme section of the Journal of Computer-Mediated Communication explores these non-technical aspects of search engines and their uses.     

Influence of dietary long-chain PUFA on premature baboon lung FA and dipalmitoyl PC composition

One of the major survival challenges of premature birth is production of lung surfactant. The lipid component of surfactant, dipalmitoyl PC (DPPC), increases in concentration in the period before normal term birth via a net shift in FA composition away from unsaturates. We investigated the influence of dietary DHA and arachidonic acid (AA) on lung FA composition and DPPC concentration in term and preterm baboons. Pregnant animals/neonates were randomized to one of four groups: breast-fed (B), term formula-fed (T⁻), preterm formulafed (P⁻), and preterm fed formula supplemented with DHA-AA (P⁺). Breast milk contained 0.68%wt DHA and the P⁺ group formula contained 0.61%wt DHA. In the preterm groups (P⁻ and P⁺), pregnant females received a course of antenatal corticosteroids. At the adjusted age of 4 wk, neonate lung tissue was harvested, and FA composition and DPPC were analyzed. Palmitate was ∼28%wt of lung total FA and no significant differences were found among the four treatment groups. In contrast, DPPC in the B group lung tissue was significantly greater than DPPC in the unsupplemented groups, but not compared with the P⁺ group. The B and P⁺ groups were not significantly different in DHA and AA, but were different compared with the unsupplemented (T, P⁻) groups. These results indicate that LCP supplementation increases lung DHA and AA, without compromising overall lung 16∶0 or DPPC. The shift in FA composition toward greater unsaturation in the groups consuming LCP supported improved surfactant lipid concentration in preterm neonate lungs.     

Clustering Empirical Failure Rate Curves for Reliability Prediction Purposes in the Case of Consumer Electronic Products

In this paper, a methodology based on the combination of time series modeling and soft computational methods is presented to model and forecast bathtub‐shaped failure rate data of newly marketed consumer electronics. The time‐dependent functions of historical failure rates are typified by parameters of an analytic model that grabs the most important characteristics of these curves. The proposed approach is also verified by the presentation of an industrial application brought along at an electrical repair service provider company. The prediction capability of the introduced methodology is compared with moving average‐based and exponential smoothing‐based forecasting methods. According to the results of comparison, the presented method can be considered as a viable alternative reliability prediction technique. Copyright © 2015 John Wiley & Sons, Ltd.     

Effects of embedded surfactants on the surface properties of PDMS; applicability for autonomous microfluidic systems

Controlled surface modification of the PDMS (polydimethylsiloxane) was developed and studied in this work to develop autonomous capillary-driven microfluidic system to be applied in bioanalytical devices. The characteristics of the PDMS surfaces were modified by embedding adequate surfactant molecules in the polymer matrix to be moved onto the free surface by diffusion. The change of the surface characteristics was studied considering the expected performance in autonomous biomicrofluidic applications and the influence on non-specific human blood protein binding also. The method was evaluated from technological aspects also, as the integrability of the microfluidic system, considering the previously published results critically. Compositions were defined to be adequate for fabrication autonomous capillary system with enhanced transport efficiency and moderated non-specific protein adsorption.     

The Irritant Effects of Pharmaceutically Applied Surfactants

Dermal or transdermal medication may lead to irritant contact dermatitis. However, little information is available on the irritant effect of surfactants which are applied in topical formulations. Our aim was to examine the irritant effect of the most frequent compounds in topical products. A murine model was applied. The following compounds were examined: sodium lauryl sulphate (SLS), polyethoxylated (40EO) hydrogenated castor oil and sucrose laurate. SLS led to severe erythema, increase in transepidermal water loss (TEWL) and induced necrosis and accumulation of neutrophylic granulocytes and lymphocytes. Exposure to sucrose laurate resulted in an elevation of TEWL, but histology did not reveal impairment of the skin structure. Application of polyethoxylated (40EO) hydrogenated castor oil was not accompanied by tissue damage. Special attention should be paid to the irritant effect of SLS. Polyethoxylated (40EO) hydrogenated castor oil seems to be a non-irritant agent and sucrose laurate is also a promising candidate for application in topical preparations.     

Whose Space? Differences Among Users and Non‐Users of Social Network Sites

Are there systematic differences between people who use social network sites and those who stay away, despite a familiarity with them? Based on data from a survey administered to a diverse group of young adults, this article looks at the predictors of SNS usage, with particular focus on Facebook, MySpace, Xanga, and Friendster. Findings suggest that use of such sites is not randomly distributed across a group of highly wired users. A person’s gender, race and ethnicity, and parental educational background are all associated with use, but in most cases only when the aggregate concept of social network sites is disaggregated by service. Additionally, people with more experience and autonomy of use are more likely to be users of such sites. Unequal participation based on user background suggests that differential adoption of such services may be contributing to digital inequality.     

A multiple narrative approach to information systems failure: a successful system that failed

We discuss the introduction of an information system where the dominant coalition claimed project success. While the key users did not use the system as intended and the project goals were not achieved, the project committee reported success to the top management board. Using a multi-methodological approach, we can follow how different stakeholders attributed different meanings to the system introduced over time. The rhetorical tools used are analysed using a narrative methodology. We draw on the social construction of technology and use the concept of relevant social groups to understand the different interests influencing the organisational dynamics. We complement this approach by employing the concepts of organisational power and cultural fit between the new system and the different subcultures. We found that this multiple approach explains well how the acceptance of the new software processes was interpreted differently within the organisation, and also by the software supplier. Although limited, our case study reveals the process of socially constructing the success or failure of an information system using this multiple research approach. We compare our results with the literature on IS failures and we consider the value of combining constructionist and critical approaches through a narrative methodology.     

Phenylalanine Ammonia‐Lyase‐Catalyzed Deamination of an Acyclic Amino Acid: Enzyme Mechanistic Studies Aided by a Novel Microreactor Filled with Magnetic Nanoparticles

Phenylalanine ammonia‐lyase (PAL), found in many organisms, catalyzes the deamination of l ‐phenylalanine (Phe) to (E)‐cinnamate by the aid of its MIO prosthetic group. By using PAL immobilized on magnetic nanoparticles and fixed in a microfluidic reactor with an in‐line UV detector, we demonstrated that PAL can catalyze ammonia elimination from the acyclic propargylglycine (PG) to yield (E)‐pent‐2‐ene‐4‐ynoate. This highlights new opportunities to extend MIO enzymes towards acyclic substrates. As PG is acyclic, its deamination cannot involve a Friedel–Crafts‐type attack at an aromatic ring. The reversibility of the PAL reaction, demonstrated by the ammonia addition to (E)‐pent‐2‐ene‐4‐ynoate yielding enantiopure l ‐PG, contradicts the proposed highly exothermic single‐step mechanism. Computations with the QM/MM models of the N‐MIO intermediates from l ‐PG and l ‐Phe in PAL show similar arrangements within the active site, thus supporting a mechanism via the N‐MIO intermediate.     

Decohesion Kinetics of PEDOT:PSS Conducting Polymer Films

The highly conductive polymer PEDOT:PSS is a widely used hole transport layer and transparent electrode in organic electronic devices. To date, the mechanical and fracture properties of this conductive polymer layer are not well understood. Notably, the decohesion rate of the PEDOT:PSS layer and its sensitivity to moist environments has not been reported, which is central in determining the lifetimes of organic electronic devices. Here, it is demonstrated that the decohesion rate is highly sensitive to the ambient moisture content, temperature, and mechanical stress. The kinetic mechanisms are elucidated using atomistic bond rupture models and the decohesion process is shown to be facilitated by a chemical reaction between water molecules from the environment and strained hydrogen bonds. Hydrogen bonds are the predominant bonding mechanism between individual PEDOT:PSS grains within the layer and cause a significant loss in cohesion when they are broken. Understanding the decohesion kinetics and mechanisms in these films is essential for the mechanical integrity of devices containing PEDOT:PSS layers and yields general guidelines for the design of more reliable organic electronic devices.