Oligodeoxyribonucleotide association with single-walled carbon nanotubes studied by SPM

Studies have been performed on both as-received and chemically oxidized single-walled carbon nanotubes (SWCNTs) grown by two different growth methods to better understand the preferential association of the oligodeoxyribonucleotide T30 (ODN) with SWCNTs. Samples of T30 ODN:SWCNT were examined under ambient conditions using non-contact scanning probe microscope (SPM) techniques. The resulting images show different morphologies ranging from tangled networks of SWCNTs to individual, well-dispersed isolated SWCNTs as the sonication time is increased. SPM images of well-dispersed, as-received SWCNTs reveal isolated features that are 1.4 to 2.8 nm higher than the bare SWCNT itself. X-ray photoemission spectroscopy (XPS) confirmed these features to be T30 ODN in nature. Chemically oxidizing the SWCNTs before sonication is found to be an effective way to increase the number of T30 ODN features.     

Project governance and stakeholders: a literature review

Despite the importance of stakeholders in project governance, project management literature lacks from an inclusive framework which defines the roles, relationships and positions of internal and external stakeholders inside and outside of the organization's governance structure. This paper has the purpose to report a review on project governance literature to draw attention to the context within which the stakeholders are positioned, to extract their roles and relationships inside and outside of the organization and to develop new avenues for research regarding stakeholders in project governance. The conducted thematic analysis reveals that there are three contexts influencing organization's approaches towards stakeholders: success, megaprojects and ethics. The developed conceptual framework illustrates that organizations are in direct contact with external stakeholders at the organizational level and project level. Strategic decisions made at the organizational level are operationalised at the portfolio level and influence the approach towards external stakeholders at the project level. Considering the lack of theories to support general doctrine of stakeholder theory, this research suggests that future governance researchers adopt a broader view in selection of theoretical lenses in order to include the social and psychological aspects of the management of external stakeholders.     

Effectiveness of different surface cleaning methods on the shear bond strength of resin cement to contaminated zirconia: an in vitro study

The purpose of this in vitro study was to evaluate and compare the effectiveness of different surface cleaning methods on the shear bond strength (SBS) of zirconia ceramic surfaces. Seventy polished and cleaned zirconia disk specimens of 8 mm in diameter and 3.4 mm in thickness were immersed in fresh saliva. They were then pressed into a freshly mixed silicone disclosing medium. Six different cleaning methods were applied to the tested groups; they were airborne-particle abraded (AA), covered with a cleaning paste (Ivoclean®) (IV), etched with orthophosphoric acid (PA), immersed in alcohol (AL), rinsed with tap water only (WA), or cleaned with steam (SC). No surface cleaning was done after saliva immersion and silicone disclosing medium contamination to the control group (CC). The specimens were then bonded to an adhesive resin cement using polyethylene tubes. SBS was determined using a universal testing machine at a crosshead speed of 1 mm/min. The specimens were also examined with a scanning electron microscope and a stereomicroscope. Group AA yielded the highest SBS value (7.01 ± 1.4 MPa) among the groups, while Group WA had the lowest SBS value (3.03 ± 0.8 MPa). The SBS values of Group AA (7.01 ± 1.4 MPa) and IV (6.2 ± 1.7 MPa) were also significantly higher than those of the remaining four groups (p < 0.05). Within the limitations of this in vitro study, it was concluded that among the various cleaning methods tested, airborne-particle abrasion and Ivoclean® paste were effective in cleaning the zirconia surface.     

Simultaneous determination of pyruvate and acetate levels in xanthan biopolymer by infrared spectroscopy: effect of spectral pre-processing for solid-state analysis

A rapid, direct, and reagent-free procedure based on solid-state Fourier transform infrared spectroscopy (FT-IR) coupled with partial least squares (PLS) data analysis has been developed for simultaneous determination of pyruvate and acetate levels in a microbial xanthan biopolymer. The influences of various spectral pre-processing procedures were studied in order to eliminate effects caused by sample preparation. It was determined that the combination of first derivative and orthogonal signal correction pre-processing contributes to a significant increase in the predictive performance of PLS-1 regression models. By employing the wavenumber region 1320–1350 cm⁻¹ for pyruvate determination and 1500–1600 cm⁻¹ for acetate determination, the root mean square error of cross-validation (RMSECV) for pyruvate and acetate contents were obtained 0.13% and 0.29% w/w, respectively. Results of the proposed procedure for different real samples and those obtained by their reference methods were compared.     

Leadership: Why gender and culture matter.

For decades, understanding of leadership has been largely based on the results of studies carried out on White men in the United States. We review major theories and models of leadership as they pertain to either gender or culture. We focus on 3 approaches to leadership: trait (including leadership categorization or implicit leadership theory), behavioral (including the two-factor, transformational–transactional leadership, and leader–member exchange models), and contingency (i.e., contingency model of leadership effectiveness and normative decision making). We discuss how dynamics related to either culture or gender (e.g., stereotypes and schemas, ingroup–outgroup interaction, role expectations, power and status differentials) can have an important impact on many aspects of leadership. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adhesion Characteristics of PDMS Surfaces During Repeated Pull‐Off Force Measurements

To mimic the adhesive effects of gecko toes, artificial surfaces have been manufactured recently using polydimethylsiloxanes (PDMS). However, the effects of repeated contacts on the adhesive properties remain largely unexplored. In this paper we report on the effect of repeated pull‐off force measurements on the adhesion behavior of PDMS (polymer kit Sylgard 184, Dow Corning) tested with a borosilicate glass probe. A decrease in pull‐off force with increase in number of test cycles is found until a plateau is reached. The initial value and the rate of change in pull‐off force strongly depend on the sample preparation procedure, including curing time and cross‐linking. It is proposed that the behavior is due to steady coverage of the probe with free oligomers. The results are crucial for developing reusable, durable, and residue‐free bioinspired adhesives.     

A simple soft lithographic nanopatterning of gold on gallium arsenide via galvanic displacement

Nanoscale patterning of gold layers on GaAs substrate is demonstrated using a combination of soft lithographic molding and galvanic displacement deposition. First, an electroless deposition method has been developed to plate gold on GaAs with ease and cost-effectiveness. The electroless metallization process is performed by dipping the GaAs substrates into a gold salt solution without any reducing agents or additives. The deposition proceeds via galvanic displacement in which gold ions in the aqueous solution are reduced by electrons arising from the GaAs substrate itself. The deposition rate, surface morphology and adhesion property can be modulated by the plating parameters such as the choice of acids and the immersion time. Second, soft lithographic patterning of nanodots, nanorings, and nanolines are demonstrated on GaAs substrates with hard-polydimethylsiloxane (h-PDMS) mold and plasma etching. This method can be easily applied to the metallization and nanopatterning of gold on GaAs surfaces.     

Model‐Reference Adaptive Moment Control of Uncertain Nonlinear Stochastic Systems

In this paper, a new model‐reference adaptive moment control method is proposed to control the first and second moments of an uncertain nonlinear system with additive external stochastic excitation. This method has established a closed‐loop control system that calculates an adaptive stochastic nonlinear input by introducing a Lyapunov function and adaptive update law. The proposed adaptive structure is innovative in trying to minimize two errors simultaneously: the moments tracking error and the error between the nonlinear system output and reference model. Furthermore, the proposed method can control the expected and covariance matrices of the states without needing to solve the complicated Fokker‐Planck‐Kolmogorov differential equation or using the approximate methods. Simulation has been performed on two practical examples, which show a good performance for the designed controller.