Security architectures for B3G mobile networks

This paper analyzes the security architectures employed in the interworking model that integrates third-generation (3G) mobile networks and Wireless Local Area Networks (WLANs), materializing Beyond 3G (B3G) networks. Currently, B3G networks are deployed using two different access scenarios (i.e., WLAN Direct Access and WLAN 3GPP IP Access), each of which incorporates a specific security architecture that aims at protecting the involved parties and the data exchanged among them. These architectures consist of various security protocols that provide mutual authentication (i.e., user and network authentication), as well as confidentiality and integrity services to the data sent over the air interface of the deployed WLANs and specific parts of the core network. The strengths and weaknesses of the applied security measures are elaborated on the basis of the security services that they provide. In addition, some operational and performance issues that derives from the application of these measures in B3G networks are outlined. Finally, based on the analysis of the two access scenarios and the security architecture that each one employs, this paper presents a comparison of them, which aims at highlighting the deployment advantages of each scenario and classifying them in terms of: a) security, b) mobility, and c) reliability.     

Hybrid graph-based multicast traffic grooming in metro networks with quality-of-transmission considerations

This paper investigates the problem of multicast traffic grooming in optical networks utilizing a novel grooming approach that is based on the routing/grooming of multicast calls on hybrid graphs (HGs). HGs are constructed dynamically upon the arrival of each multicast call, in such a way that they consist of both the available physical links and the logical links with available capacity. Several schemes were developed for the construction of the HGs, namely the minimum free capacity light-tree first, the maximum free capacity light-tree first, the maximum overlapping light-tree first, the least-used light-tree first, and the most-used light-tree first scheme. Also, a novel hybrid Steiner tree heuristic for routing/grooming on the HGs is presented. The proposed grooming approach exhibits improved performance in terms of blocking probability compared to existing multicast grooming approaches that route/groom multicast calls by considering physical and logical links separately. Furthermore, the physical layer impairments were also considered during the provisioning phase of the newly established light-trees on the HG, in which case the proposed schemes also exhibit improved performance compared to other grooming approaches.     

Thermochemical Transition in Low Molecular Weight Substances: The Example of the Silybin Flavonoid

Silybin is a complex organic molecule with high bioactivity, extracted from the plant Silybum. As a pharmaceutical substance, silybin’s bioactivity has drawn considerable attention, while its other properties, e.g., thermodynamic properties and thermal stability, have been less studied. Silybin has been reported to exhibit a melting point, and values for its heat of fusion have been provided. In this work, differential scanning calorimetry, thermogravimetry including derivative thermogravimetry, infrared spectroscopy, and microscopy were used to provide evidence that silybin exhibits a thermochemical transition, i.e., softening occurring simultaneously with decomposition. Data from the available literature in combination with critical discussion of the results in a general framework suggest that thermochemical transition is a broad effect exhibited by various forms of matter (small molecules, macromolecules, natural, synthetic, organic, inorganic). The increased formation of hydrogen bonding contributes to this behavior through a dual influence: (a) inhibition of melting and (b) facilitation of decomposition due to weakening of chemical bonds.     

Green Metal-Free Photochemical Hydroacylation of Unactivated Olefins

Direct alkylation of C(sp²)−H bonds to convert an aldehyde into a ketone is a notorious transformation, due to the laborious challenge of the formation of ketyl or acyl radicals. Herein, we report a green, cheap, metal-free and efficient method for the hydroacylation of olefins in water. This photochemical protocol utilizes phenylglyoxylic acid, a commercially available small organic molecule, as the photoinitiator, water as the solvent and household fluorescent lamps as the irradiation source, leading to a broad substrate scope of products in moderate to good yields. A wide range of aromatic and aliphatic aldehydes, terminal and non-terminal alkenes and pharmaceutically relevant molecules can be employed, without the need of directing groups and additives or metal catalysts.     

Atomic layer deposited zirconium oxide electron injection layer for efficient organic light emitting diodes

In this work, we demonstrate efficient polyfluorene-based light emitting diodes on which conformal, thin ZrO₂ layers, formed by atomic layer deposition at a relatively low temperature (175 °C), in order to avoid introducing any damage in the organic under layer, efficiently inject electrons from their high lying conduction band to the polymer’s LUMO. An optimal thickness of 2 nm for ZrO₂ results in a threefold improvement in luminous current efficiency compared to the reference device. The relationship between the thickness of the ZrO₂ layer and the device operational characteristics is further investigated and the possible reasons for the improved device performance are discussed based on the experimental results obtained by a combination of photoemission spectroscopy and electrical/optical measurements.     

High‐Mobility and Low Turn‐On Voltage n‐Channel OTFTs Based on a Solution‐Processable Derivative of Naphthalene Bisimide

In organic electronics solution‐processable n‐channel field‐effect transistors (FETs) matching the parameters of the best p‐channel FETs are needed. Progress toward the fabrication of such devices is strongly impeded by a limited number of suitable organic semiconductors as well as by the lack of processing techniques that enable strict control of the supramolecular organization in the deposited layer. Here, the use of N,N′‐bis(4‐n‐butylphenyl)‐1,4,5,8‐naphthalenetetracarboxylic‐1,4:5,8‐bisimide (NBI‐4‐n‐BuPh) for fabrication of n‐channel FETs is described. The unidirectionally oriented crystalline layers of NBI‐4‐n‐BuPh are obtained by the zone‐casting method under ambient conditions. Due to the bottom‐contact, top‐gate configuration used, the gate dielectric, Parylene C, also acts as a protective layer. This, together with a sufficiently low LUMO level of NBI‐4‐n‐BuPh allows the fabrication and operation of these novel n‐channel transistors under ambient conditions. The high order of the NBI‐4‐n‐BuPh molecules in the zone‐cast layer and high purity of the gate dielectric yield good performance of the transistors.     

Superhydrophobic polymer‐particle composite films produced using various particle sizes

Hydrophilic alumina (Al₂O₃) nanoparticles (25, 35, and 150 nm) are dispersed in different concentrations in solutions of a commercial hydrophobic poly(alkyl siloxane) (Silres BS‐290), and the suspensions are sprayed on glass surfaces. Static contact angles (θ_S), measured on surfaces of siloxane‐nanoparticle composite films that were prepared from dilute dispersions, increase rapidly with particle concentration. Composite films prepared from concentrated dispersions exhibit a maximum, constant θ_S (at saturation θ_S is 160°), which is not affected by the size of the particles. These films exhibit also very small contact angle hysteresis (5°), which is also independent of the particle size. Consequently, the same superhydrophobic character can be induced in siloxane films using nanoparticles, which can range from a few up to several tenths of nanometers. However, the particle size and more precisely the particle specific surface area affects dramatically the minimum critical particle concentration, which must be used in the dispersions to induce superhydrophobicity on the surface of the composite films, that is, to achieve θ_S = 150°. It is shown that critical particle concentration decreases exponentially with specific surface area. This result can be important for manufacturers of superhydrophobic surfaces who are interested in having a good control on the wettability of the composite films. Copyright © 2012 John Wiley & Sons, Ltd.     

Questioning the Feasibility of UMTS-GSM Interworking Attacks

Recently, Ahmadian et?al. (Security enhancements against UMTS-GSM interworking attacks, Elsevier, Amsterdam, 2010) presented and analyzed three different attacks that can be performed in UMTS-GSM interworking networks: (a) a real-time eavesdropping attack, (b) an offline eavesdropping attack, and (c) an impersonation attack. In this letter we question the feasibility of these attacks. In particular, we pinpoint and analyze that these attacks are based on some erroneous and misleading assumptions that the authors have made regarding the security functionality of the UMTS-GSM interworking networks. Based on this analysis, we deduce that these three attacks cannot be performed.     

Photoorganocatalytic One‐Pot Synthesis of Hydroxamic Acids from Aldehydes

An efficient one‐pot synthesis of hydroxamic acids from aldehydes and hydroxylamine is described. A fast, visible‐light‐mediated metal‐free hydroacylation of dialkyl azodicarboxylates was used to develop the subsequent addition of hydroxylamine hydrochloride. A range of aliphatic and aromatic aldehydes were employed in this reaction to give hydroxamic acids in high to excellent yields. Application of the current methodology was demonstrated in the synthesis of the anticancer medicine vorinostat.     

Proline dipeptides containing fluorine moieties as oganocatalysts for the asymmetric aldol reaction

A series of dipeptide analogues consisting of proline, phenylalanine and aniline- or phenol-fluorine derivatives were synthesized. Their catalytic ability was evaluated in the intermolecular asymmetric aldol reaction, both in organic and aqueous media. Aniline-fluorine derivatives proved to be superior and the best results were obtained, when 2-CF₃ aniline was employed. A diverse substrate scope consisting of both aromatic and aliphatic aldehydes, as well as different ketones was demonstrated, where aromatic aldehydes afforded products in high yields (up to 100%) with excellent diastereo- (up to 95:5) and enantioselectivities (up to 97%), whereas the aliphatic aldehydes afforded also excellent selectivities, but relatively low yield. A simple addition of fluorine to a dipeptide analogue affords organocatalysts with new interesting properties that can catalyze the aldol reaction more efficiently.