Structural evolution of protein-biofilms: Simulations and experiments

The control of biofilm formation is a challenging goal that has not been reached yet in many aspects. One unsolved question is the role of van der Waals forces and another is the importance of mutual interactions between the adsorbing and the adsorbed biomolecules ("critical crowding"). In this study, a combined experimental and theoretical approach is presented, which fundamentally probes both aspects. On three model proteins-lysozyme, α-amylase, and bovine serum albumin-the adsorption kinetics is studied experimentally. Composite substrates are used enabling a separation of the short- and the long-range forces. Although usually neglected, experimental evidence is given for the influence of van der Waals forces on the protein adsorption as revealed by in situ ellipsometry. The three proteins were chosen for their different conformational stabilities in order to investigate the influence of conformational changes on the adsorption kinetics. Monte Carlo simulations are used to develop a model for these experimental results by assuming an internal degree of freedom to represent conformational changes. The simulations also provide data on the distribution of adsorption sites. By in situ atomic force microscopy we can also test this distribution experimentally, which opens the possibility to, e.g., investigate the interactions between adsorbed proteins.     

Preface to Special Topic: Papers from the 13th International Conference on Surface and Colloid Science (ICSCS) and the 83rd ACS Colloid and Surface Science Symposium, Columbia University, New York, 2009

This Special Topic section is a compilation of several original contributions covering both fundamental and practical aspects of electrokinetic microfluidic phenomena that were presented during the Electrokinetics and Microfluidics sessions held at the conference.Electrokinetics is currently the mechanism of choice for the manipulation of fluids as well as colloidal and biological particles at microscale and nanoscale dimensions.¹ The popularity of electrokinetics is perhaps not so surprising as electrodes are easy to fabricate and embed into microfluidic chips, thus allowing the entire fluid and particle actuation mechanism to be completely integrated into the device. In addition, driving microfluidics with electric fields is relatively straightforward and allows for precise actuation. Nevertheless, considerable challenges remain in understanding the complex mechanisms associated with the hydrodynamics of conducting and dielectric fluids and particles under the influence of electric fields. Concomitantly, there has been an exponential increase in research and development in this field along both fundamental and applied themes in the past five years.This sustained growth in the microfluidics community of electrokinetics research has led to a sequel to the first Electrokinetic Phenomena and Microfluidics session at the 82nd ACS Colloid and Surface Science Symposium in Raleigh, NC, in 2008, and which we hope will now be a regular feature at successive ACS Colloid and Surface Science meetings. This year at the combined 2009 13th International Conference on Surface and Colloid Science (ICSCS) and the 83rd ACS Colloid and Surface Science Symposium in New York, the Electrokinetics and Microfluidics symposium proved to be extremely popular, with three keynote lectures presented by Professor Howard Stone, Professor Hsueh-Chia Chang, and Professor Thomas Healy, and 44 oral presentations. In both 2008 and 2009, Biomicrofluidics has organized a special issue to cover some of the contributions reported at these meetings.²The growing interest in using electric fields to manipulate biological entities such as cells, DNA, and even single molecules is reflected in this year’s collection of papers with dielectrophoretic (DEP) phenomena comprising the bulk of the contributions. In Ref. ³, a new theory to describe Stern layer conductance along the surface of nanocolloids is proposed, forming the basis for the derivation of a more accurate prediction of the DEP crossover frequency. This theory is then employed to determine the conformation and, hence, optimum coverage of oligonucleotides on the surface of nanocolloid functionalized molecular probes during DNA hybridization under the influence of DEP, which can be exploited for biomolecular sensing. Other fundamental DEP papers include the investigation of particle motion under DEP induced optically via a photoconductor, in which Zhu et al.⁴ characterized the frequency dependence of the motion through the synchronous velocity spectra of the particles, and a numerical study of particle trapping at the throat of converging-diverging microchannels under the influence of negative DEP using a transient arbitrary Lagrangian–Eulerian finite element method.⁵ A more practical implementation is, on the other hand, reported by Yang et al.⁶ in which the negative DEP is exploited to separate colorectal cancer cells from other cells in a microfluidic device as a demonstration of a portable cancer detection tool.Continuing along the separation theme, but with regard to DNA separation using pulsed-field gel electrophoresis aided by sparse but regularly ordered microfabricated arrays of nanoposts, is a Brownian dynamics simulation model reported by Ou et al.⁷ in which DNA channeling, which predicts that the motion of DNA is undisturbed by the presence of arrays for large spacing to DNA equilibrium size ratios and when the field lines are straight, is predicted, consistent with experimental observations. In another fundamental paper, a direct numerical simulation model is presented to predict the current-voltage relationship across conducting pores along cell membranes, which is of fundamental importance in the electroporation process.⁸We hope that you will enjoy reading the contributions in this special topic and that it encourages you to participate in future Electrokinetics and Microfluidics meetings at the ACS Colloid and Surface Science Symposia, which we definitely hope will continue on a regular basis.     

A knowledge management perspective on Art Education

This paper applies concepts drawn from KM to Art Education. Specifically, the purpose of this paper is to study the knowledge types, knowledge sources, knowledge processes as well as factors affecting these processes in Art Education. The research was carried out using an interpretative case study methodology in Singapore. Apart from 26 one-to-one interviews conducted with various stakeholders of the Art Education community, on-site observations were made at 19 different Art Education events. Four major findings emerged. One, the knowledge types of Art Education in Singapore were a blend of different knowledge domains. Two, perceptible knowledge sources were those which conveyed an appearance of authority. Three, knowledge processes in Art Education were steeply humanistic. Finally, factors that affected knowledge processes were (i) the highly competitive Singapore education system, (ii) management support and policies, (iii) personal values and interests, (iv) workload and (v) the absorptive capacity of Art teachers. This paper concludes with a number of research and practical implications.     

The solution of the Bagley-Torvik equation with the generalized Taylor collocation method

In this paper, the Bagley-Torvik equation, which has an important role in fractional calculus, is solved by generalizing the Taylor collocation method. The proposed method has a new algorithm for solving fractional differential equations. This new method has many advantages over variety of numerical approximations for solving fractional differential equations. To assess the effectiveness and preciseness of the method, results are compared with other numerical approaches. Since the Bagley-Torvik equation represents a general form of the fractional problems, its solution can give many ideas about the solution of similar problems in fractional differential equations.     

The Subject Matter Knowledge in Physics Related Topics of Hong Kong Junior Secondary Science Teachers

The subject matter competence in physics related topics of 147 inservice junior secondary science teachers in Hong Kong was identified using a true-or-false instrument based on a framework conceptualized by the authors. The findings of this study showed that teachers are weak both in factual knowledge and conceptions in these topics. Although physics majors outperform nonphysics majors significantly in the test, their own performance is by no means satisfactory on criterion referenced terms. Items incorrectly answered by over 40% of the teachers are listed with corrections given. The sources of conceptual mistakes and specific remedial measures were elaborated for items incorrectly answered by more than 60% of the teachers. General implications and possibilities for improvement in tertiary education, science teaching, and teacher education were discussed.     

影响矩作为测度单篇论著影响力的评价指标探讨

把评价视向由针对学术主体转向针对学术客体,提出着眼于单篇论著影响力评价的影响矩指标。影响矩M被定义为单篇论著影响学者力A及其影响跨度D的乘积,M越大,影响越大。通过对测算样本集和校验样本集的数据分析,显示影响矩M与总被引C及h指数的相关系数都在0.6以上,表明影响矩可以作为测评单篇论著影响力的独立指标。     

Coherent Resonant Tunneling through Double Metallic QuantumWell States

<正>Due to its far-reaching scientific impact and broad applications, coherent resonant tunneling effect in magnetic tunnel junctions has aroused intensive interest from spintronic and semiconductor communities. Actually, resonant tunneling effect has been verified and utilized in semiconductor-based multiquantum wells, such as resonant tunneling diode and light-emitting diodes with multiple quantum wells and etc. However, coherent resonant tunneling effect through metallic multi-quantum wells has been rarely reported     

Cultural Diplomacy and Internationalization of Higher Education: The Experience of Three Confucius Institutes in Canada

This paper is based on a study of three Confucius Institutes in Canada. The research aims to explore the nature of operations at Confucius Institutes, ranging from the selection of partnering Chinese universities, to the program planning at each individual site. Specifically, it focuses on the perceived impacts of the Confucius Institute partnership on the Canadian hosting institutions. Data was collected through interviews with key administrative staff from three Canadian universities. The theoretical framework of constructivism from international relations theory and concepts drawn from the literature on the internationalization of higher education were used to analyze the findings. Key issues revealed from the data include the host’s perception of Confucius Institutes as China’s cultural diplomacy and soft power strategy, the progression of partnerships between Canada and China over time, and university autonomy.     

A stabilization policy for an economy with some unknown characteristics

A stabilization policy is developed for an economy with unknown and possibly unknowable characteristics. Uniform asymptotic stability is guaranteed for all initial states and for all admissible uncertainties. Welfare loss over the infinite horizon is bounded by a level dependent on the initial state. The policy is robust, with a simple structure. A simple example sheds some light on the fiscalist-monetarist debate.