A New Caged‐Glutamine Derivative as a Tool To Control the Assembly of Glutamine‐Containing Amyloidogenic Peptides

We present the design, synthesis, and characterization of a novel photocaged glutamine derivative (modified on the side chain of glutamine), and describe its use in enhancing peptide stability and solubility. Our results demonstrate that this approach can be used to develop molecular switches to control the folding and β‐sheet formation of amyloidogenic peptides.     

Epidemic theory and data survivability in unattended wireless sensor networks: Models and gaps

Information survivability is the capability of a system to fulfill its mission, in a timely manner, and even in the presence of attacks, failures, or accidents. In this paper, we provide a preliminary assessment of epidemic-domain inspired approaches to model the information survivability in UWSNs. In particular, we show that epidemic models can be used to devise solutions enabling the information to survive, once the maximal compromising power of an attacker is estimated. However, we also point out that the mere application of these models is not always the right choice. Indeed, our results show that these deterministic models are not accurate enough, and “unlikely” events—usually met when striving to optimize resource usage—can cause the loss of the datum; furthermore, we highlight that when translating these models into real applications, geometric constraints (such as communication radius and deployment area) can hinder the applicability of epidemic models. We propose a simple but effective solution to these issues. Finally, extensive simulations support our results.     

Microstructure observation using MeV-electron-irradiation-induced amorphization

MeV electron irradiation can stimulate solid-state amorphization in some intermetallic compounds. The irradiation induced amorphization phenomenon facilitates a clearer observation of the composite microstructure of the compounds. MeV electron irradiation is applied to a composite structure containing intermetallic compound “A,” which undergoes solid-state amorphization and crystalline phase “B,” which does not undergo amorphization. The composite structure transforms into a mixture of amorphous and crystalline phases by the irradiation. The distribution of A and B in the structure can hence be easily determined. High-voltage electron microscopy (HVEM) offers a unique microstructure observation technique that uses the difference between the sensitivities of compounds to undergo solid-state amorphization when MeV electron irradiation is applied to them.     

Colossal Permittivity in Microwave‐Sintered Barium Titanate and Effect of Annealing on Dielectric Properties

Colossal permittivity (ε′ = 301,484 at room temperature and 1 kHz) of barium titanate was induced in ceramics synthesized using the microwave sintering method. Three different sintering processes (conventional, spark plasma, and microwave) were performed to better understand colossal permittivity in sintered barium titanate. The dielectric permittivity measurements revealed that the appearance of colossal permittivity has strong dependence on the sintering temperature and atmosphere, and less on the grain size of the sintered ceramics. However, the as‐sintered barium titanate samples produced by microwave sintering show high dielectric loss (tanδ > 1) consistent with oxygen reduction during the microwave sintering process and consequent accumulation of oxygen vacancies and associated charge carriers at the grain boundary. Since the highly conductive state of as‐sintered ceramics precludes their use in dielectric applications, thermal annealing at different conditions was performed to recover insulating characteristics. Microwave‐sintered barium titanate with post annealing process (950°C for 12 h in air) showed low dielectric loss (tanδ = 0.045) at room temperature and 1 kHz, while still showing a much higher permittivity (ε′ = 36,055) than conventionally sintered barium titanate (ε′ = 3500).     

Spectrophotometric study of the copigmentation of malvidin 3-O-glucoside with p-coumaric,vanillic and syringic acids

Anthocyanins are a natural source of pigments in plants and their processed food products have become attractive and excellent candidates to replace the synthetic colourants due to their characteristic intense colours and associated health benefits. The intermolecular copigmentation between anthocyanins and other colourless compounds has been reported to be an important way to enhance and stabilise the colour intensity of aqueous solutions. In the present work we report the equilibrium constant, stoichiometric ratio and the thermodynamic parameters (ΔG°, ΔH° and ΔS°) related to the intermolecular copigmentation reactions of the anthocyanin malvidin 3-O-glucoside with one hydroxycinnamic acid (p-coumaric acid) and two O-methylated hydroxybenzoic acids (vanillic and syringic acid). Different factors which affect their interactions such as copigment concentration, pH and temperature of the medium are examined at two pH levels (pH = 2.50 and 3.65) corresponding to those of the major food mediums where these reactions take place (fruit juices, wine, jams etc.).     

Domain Wall Displacement is the Origin of Superior Permittivity and Piezoelectricity in BaTiO3 at Intermediate Grain Sizes

The dielectric and piezoelectric properties of ferroelectric polycrystalline materials have long been known to be strong functions of grain size and extrinsic effects such as domain wall motion. In BaTiO₃, for example, it has been observed for several decades that the piezoelectric and dielectric properties are maximized at intermediate grain sizes (≈1 μm) and different theoretical models have been introduced to describe the physical origin of this effect. Here, using in situ, high‐energy X‐ray diffraction during application of electric fields, it is shown that 90° domain wall motion during both strong (above coercive) and weak (below coercive) electric fields is greatest at these intermediate grain sizes, correlating with the enhanced permittivity and piezoelectric properties observed in BaTiO₃. This result validates the long‐standing theory in attributing the size effects in polycrystalline BaTiO₃ to domain wall displacement. It is now empirically established that a doubling or more in the piezoelectric and dielectric properties of polycrystalline ferroelectric materials can be achieved through domain wall displacement effects; such mechanisms are suggested for use in the design of new ferroelectric materials with enhanced properties.     

Processing and Structure Relationships in Electrospinning of Ceramic Fiber Systems

During the last years, several groups across the world have concentrated on the adaptation and further development of electrospinning (e-spinning) to enable ceramic fiber synthesis. Thus far, more than 20 ceramic systems have been synthesized as micro- and nanofibers. These fibers can be amorphous, polycrystalline, dense, porous, or hollow. This article reviews the experimental and theoretical basis of ceramic e-spinning. Furthermore, it introduces an expanded electro hydrodynamic (EHD) theory that allows the prediction of fired fiber diameter for lanthanum cuprate fibers. It is hypothesized that this expanded EHD theory is applicable to most ceramic e-spinning systems. Furthermore, electroceramic nanofibers produced via e-spinning are presented in detail along with an overview of electrospun ceramic fibers.     

Signalling analysis in integrated 4G networks

Scarce radio resources and the ambition to increase the number of mobile customers with a guarantee of service are pushing mobile communication systems from homogeneous non‐service convergent 2G and convergent‐service 2.5G and 3G wireless systems to heterogeneous integrated and convergent service 4G networks. This evolution has had several consequences from network design, control and service management points of view. In the emerging integrated 4G networks one of the issues is the signalling of information related to different control purposes such as QoS, mobility and security signalling. In fact, some questions such as which are the candidate signalling protocols, and which approach of integrated signalling to be adopted (unified versus non‐unified) need to be considered in the context of the emerging 4G integrated network. This is precisely the scope of this paper. We first identify the requirements related to mobility, security/AAA and QoS signalling, then we consider candidate signalling protocols and we propose possible approaches in the integration of signalling in the context of 4G networks. Copyright © 2006 John Wiley & Sons, Ltd.     

The molecular basis of working mechanism of natural polyphenolic antioxidants

In this review, we present a summary of the research work performed so far using high accuracy quantum chemical methods on polyphenolic antioxidant compounds. We have reviewed the different groups of polyphenols, which mostly belong to the Mediterranean food culture, i.e. phenolic acids, flavonoids and stilbenes. The three main proposed mechanisms through which the antioxidants may play their protective role, which is the H atom transfer, the single electron transfer and the metals chelation, have been analysed and discussed in details. This work represents a further important contribution to the elucidation of the beneficial effects on health of these substances.