Self‐Assembly of Mechanoplasmonic Bacterial Cellulose–Metal Nanoparticle Composites

Nanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC–NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self‐assembly strategy is described for fabrication of complex and well‐defined BC–NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self‐assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near‐field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.     

A Protein-Adsorbent Hydrogel with Tunable Stiffness for Tissue Culture Demonstrates Matrix-Dependent Stiffness Responses

Although tissue culture plastic has been widely employed for cell culture, the rigidity of plastic is not physiologic. Softer hydrogels used to culture cells have not been widely adopted in part because coupling chemistries are required to covalently capture extracellular matrix (ECM) proteins and support cell adhesion. To create an in vitro system with tunable stiffnesses that readily adsorbs ECM proteins for cell culture, a novel hydrophobic hydrogel system is presented via chemically converting hydroxyl residues on the dextran backbone to methacrylate groups, thereby transforming non-protein adhesive, hydrophilic dextran to highly protein adsorbent substrates. Increasing methacrylate functionality increases the hydrophobicity in the resulting hydrogels and enhances ECM protein adsorption without additional chemical reactions. These hydrophobic hydrogels permit facile and tunable modulation of substrate stiffness independent of hydrophobicity or ECM coatings. Using this approach, it is shown that substrate stiffness and ECM adsorption work together to affect cell morphology and proliferation, but the strengths of these effects vary in different cell types. Furthermore, it is revealed that stiffness-mediated differentiation of dermal fibroblasts into myofibroblasts is modulated by the substrate ECM. The material system demonstrates remarkable simplicity and flexibility to tune ECM coatings and substrate stiffness and study their effects on cell function.     

Understanding Why Scholars Hold Different Views on the Influences of Video Games on Public Health

Despite decades of research, no scholarly consensus has been achieved regarding the potential impact of video games on youth aggression or other public health concerns. In recent years, hypotheses have been raised that scholarly opinions on video games may resemble past moral panics, with attitudes reflective of generational conflicts. These hypotheses are tested in a sample of 175 criminologists, psychologists, and media scholars, examining both overall negative attitudes about video games and perceived linkages with youth assaults specifically. Results reflected continued lack of scholarly consensus on the issue of video game influences with only 15.3% of scholars endorsing the view that violent video games contribute to youth assaults. As hypothesized, older scholars endorsed more negative views of video games generally, although this appeared to be related to experience with games rather than age per se. Scholars with more negative attitudes toward youth themselves were also more negative about games. Criminologists and media scholars were more skeptical of violent video games contributing to youth assaults than were psychologists. These results are discussed in relation to Moral Panic Theory.     

Self‐Healing Fibre Reinforced Composites via a Bioinspired Vasculature

This paper demonstrates the first steps towards self‐healing composites that exploit a design philosophy inspired by the damage tolerance and self‐repair functions of bone. Cracking in either fibre reinforced polymers (FRP) or bone, if left unattended, can grow under subsequent cyclic stresses eventually leading to catastrophic failure of the structure. On detection of cracks, an FRP component must be repaired or completely replaced, whereas bone utilises a series of complex processes to repair such damage. Under normal circumstances, these processes allow the skeleton to continually perform over the lifespan of the organism, a highly desirable aspiration for engineering materials. A simple vasculature design incorporated into a FRP via a “lost wax” process was found to facilitate a self‐healing function which resulted in an outstanding recovery (≥96%) in post‐impact compression strength. The process involved infusion of a healing resin through the vascule channels. Resin egress from the backface damage, ultrasonic C‐scan testing, and microscopic evaluation all provide evidence that sufficient vascule–damage connectivity exists to confer a reliable and efficient self‐healing function.     

Very Low Degree of Energetic Disorder as the Origin of High Mobility in an n‐channel Polymer Semiconductor

Charge transport is investigated in high‐mobility n‐channel organic field‐effect transistors (OFETs) based on poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2), Polyera ActivInk? N2200) with variable‐temperature electrical measurements and charge‐modulation spectroscopy. Results indicate an unusually uniform energetic landscape of sites for charge‐carrier transport along the channel of the transistor as the main reason for the observed high‐electron mobility. Consistent with a lateral field‐independent transport at temperatures down to 10 K, the reorganization energy is proposed to play an important role in determining the activation energy for the mobility. Quantum chemical calculations, which show an efficient electronic coupling between adjacent units and a reorganization energy of a few hundred meV, are consistent with these findings.     

The distribution of the sample correlation from a complex normal

We obtain the density of the distribution of the sample correlation from a complex normal using a complex version of Cochran's theorem. We give “small sample” asymptotic expansions for its distribution.     

SiP(系统级封装)技术的应用与发展趋势(上)

一,SiP技术的产生背景 系统级封装SiP(System-In-Package)是将一个电子功能系统,或其子系统中的大部分内容,甚至全部都安置在一个封装内.这个概念看起来很容易理解,熟悉封装技术,又对电子装置或电子系统有所了解的人们一般都能够理解SiP的含义.但是如果试图对SiP使用严格的名词术语,进行精确的定义,却非常困难.SiP这一术语出现至今,虽然已经有好几年了,但是仍然没有,能够被广泛认同的定义;一般只是指出其包含的内容,或者指出其所具有的特征.Amkor公司认为SiP技术包括以下内容,或具有以下特征:     

Modular Ligation of Thioamide Functional Peptides onto Solid Cellulose Substrates

Hetero Diels‐Alder (HDA) cycloaddition – as an effective modular conjugation approach – is employed to graft thioamide endfunctional oligopeptides onto solid cyclopentadienyl (Cp) functional cellulose substrates generating cellulose‐peptide hybrid materials. The highly reactive Cp moieties serve as diene functionality in the consecutive HDA reaction on the biosubstrate surface. Oligopeptides (i.e., the model peptide Gly‐Gly‐Arg‐Phe‐Pro‐Trp‐Trp‐Gly and the antimicrobial peptide tritrpticin) are functionalized at their N‐termini employing strongly electron deficient thiocarbonyl thio compounds resulting in biomacromolecules bearing a thioamide endgroup. The dienophile‐ functional peptides readily undergo HDA reactions at ambient temperature and under mild conditions in solution with synthetic polymers as well as on solid (bio)substrates. An in‐depth investigation is provided of the influence of the temperature, the Lewis acid catalysis and the side group exchange of thioamide functional oligopeptides reacting with Cp terminated poly(methyl methacrylate) (M_n = 2100 g·mol^?1, PDI = 1.1) in homogenous solution as well as Cp functionalized cellulose in a heterogeneous system. To assess the success of the grafting reaction, the soluble samples were subjected to characterization methods such as size exclusion chromatography (SEC) and SEC‐electrospray ionization mass spectrometry (SEC‐ESI‐MS). The heterogeneous “grafting‐to” reactions were monitored using high resolution attenuated total reflection (ATR) Fourier transform infrared microscopy (HR‐FTIRM) imaging, X‐ray photoelectron spectroscopy (XPS) and elemental analysis. Evaluation via elemental analysis leads to quantitative peptide cellulose surface loading capacities.     

Environmental effects on the electrical behavior of pentacene thin-film transistors with a poly(methyl methacrylate) gate insulator

The electrical properties of top-contact pentacene thin-film transistors (TFTs) with a poly(methyl methacrylate) (PMMA) gate dielectric were analyzed in air and vacuum environments. Compared to the vacuum case, the pentacene TFT in air exhibited lower drain currents and more pronounced shifts in the threshold voltage upon reversal of the gate voltage sweep direction, together with a decrease in the field-effect mobility. These characteristic variations were explained in terms of two distinctive actions of polar H₂O molecules in pentacene TFT. H₂O molecules were suggested to diffuse under the source and drain contacts and interrupt the charge injection into the pentacene film, whereas those that permeate at the pentacene/PMMA interface retard hole depletion in and around the TFT channel. The diffusion process was much slower than the permeation process. The degraded TFT characteristics in air could be recovered mostly by storing the device under vacuum, which suggests that the air instability of TFTs is due mainly to the physical adsorption of H₂O molecules within the pentacene film.     

Interpolation techniques for building a continuous map from discrete wireless sensor network data

Wireless sensor networks (WSNs) typically gather data at a discrete number of locations. However, it is desirable to be able to design applications and reason about the data in more abstract forms than in points of data. By bestowing the ability to predict inter‐node values upon the network, it is proposed that it will become possible to build applications that are unaware of the concrete reality of sparse data. This interpolation capability is realised as a service of the network. In this paper, the ‘map’ style of presentation has been identified as a suitable sense data visualisation format. Although map generation is essentially a problem of interpolation between points, a new WSN service, called the map generation service, which is based on a Shepard interpolation method, is presented. A modified Shepard method that aims to deal with the special characteristics of WSNs is proposed. It requires small storage, can be localised and integrates the information about the application domain to further reduce the map generation cost and improve the mapping accuracy. Empirical analysis has shown that the map generation service is an accurate, a flexible and an efficient method. Copyright © 2011 John Wiley & Sons, Ltd.