SFG and DFG investigation of Au(111), Au(210), polycrystalline Au,Au–Cu and Au–Ag–Cu electrodes in contact with aqueous solutions containing KCN and 4-cyanopyridine

We report on potential-dependent in situ SFG and DFG spectroscopy carried out at Au(111), Au(210), polycrystalline Au, Au–Cu and Au–Ag–Cu electrodes in contact with aqueous solutions containing CN⁻ and 4-cyanopyridine (4CP). Spectroelectrochemical work was complemented by cyclic voltammetry. The chief stress has been placed on systematising and quantifying the interaction between 4CP and CN⁻ and the attending effects on the vibrational and electronic structures of the interface. The voltammetric behaviour of the investigated electrodes, modified by the addition of 4CP to the CN⁻ electrolyte, denote changes in the CN⁻ adsorption characteristics and effects of the adsorbed CN⁻ layer on the electrodic reactivity of 4CP. The differences among the investigated electrodes can be explained in terms of their respective degrees of atomic packing or with alloying effects on the stability of adsorbed CN⁻. The potential-dependent spectra have been analysed quantitatively with a model for the second order non linear susceptibility accounting for vibrational and electronic effects. The spectral changes induced by addition of 4CP denote interaction of the aromatic with the electrode through the CN⁻ monolayer. The non-resonant contribution yields information on the effects of 4CP on the fine structure of the bound electron density of states.     

Reaction kinetics modeling and thermal properties of epoxy–amines as measured by modulated‐temperature DSC. II. Network‐forming DGEBA + MDA

Reaction‐induced vitrification takes place in the network‐forming epoxy–amine system diglycidyl ether of bisphenol A (DGEBA) + methylenedianiline (MDA) when the glass‐transition temperature (T_g) rises above the cure temperature (T_cure). This chemorheological transition results in diffusion‐controlled reaction and can be followed simultaneously with the reaction rate in modulated‐temperature DSC (MTDSC). To predict the effect of T_cure and the NH/epoxy molar mixing ratio (r) on the reaction rate in chemically controlled conditions, a mechanistic approach was used based on the nonreversing heat flow and heat capacity MTDSC signals, in which the reaction steps of primary (E_1OH = 44 kJ mol^?1) and secondary amine (E_2OH = 48 kJ mol^?1) with the epoxy–hydroxyl complex predominating. The diffusion factor DF as defined by the Rabinowitch approach expresses whether the chemical reaction rate or the diffusion rate determines the overall reaction rate. A model based on the free volume theory together with an Arrhenius temperature dependency was used to calculate the diffusion rate constant in DF as a function of conversion (x) and T_cure. The relation between x, r, and T_g, needed in this model, can be predicted with the Couchman equation. An experimental approximation for DF is the mobility factor DF* obtained from the heat capacity signal at a modulation frequency of 1/60 Hz, normalized for the effect of the reaction heat capacity in the liquid state and the change in C_p in the glassy region with x and T_cure. In this way, an optimized set of diffusion parameters was obtained that, together with the optimized kinetic parameters set, can predict the reaction rate for different cure schedules and for stoichiometric and off‐stoichiometric mixtures. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2814–2833, 2004     

On the observation of inductive high-frequency impedance behaviour during the electrodeposition of Au—Sn alloys

Inductive high-frequency impedance behaviour is often observed in metal electrodeposition systems. This behaviour is typically attributed to equipment limitations or non-idealities in the cell set-up and electrical connections. Such instrumental artefacts would nevertheless be relevant to a frequency range which is expected to be well above that in which inductive behaviour is in fact observed (down to a few tens of Hz). In this paper some results on an acidic Au—Sn electrodeposition system are reported. Electrochemical impedance and potentiostatic transients were measured. These results suggest that the high-frequency inductive behaviour may be related to metal nucleation processes. A correlation is proposed between the pseudo-inductive potentiostatic nucleation transients and the pseudo-inductive behaviour of the impedance spectra.     

Restricted chain segment mobility in poly(amide) 6/clay nanocomposites evidenced by quasi-isothermal crystallization

Modulated temperature differential scanning calorimetry is used to explore the interactions between a poly(amide) 6 matrix and various types of clay reinforcement. During quasi-isothermal crystallization of the polymer/clay nanocomposites, an excess contribution is observed in the recorded heat capacity signal, due to reversible melting and crystallization. It is proposed that the magnitude of this excess contribution can be used to qualify the polymer/clay interfacial interaction, as it is directly linked to the segmental mobility of the polymer chains in the interphase region, where both the crystalline and amorphous polymer fractions are affected. It is shown that the interfacial interaction strongly depends on the type of clay filler used. These interactions play a key role in the development of specific material properties for the different types of nanocomposites. A simple interphase model for the poly(amide) 6/clay nanocomposites is proposed.     

Who and what links to the Internet Archive

The Internet Archive’s (IA) Wayback Machine is the largest and oldest public Web archive and has become a significant repository of our recent history and cultural heritage. Despite its importance, there has been little research about how it is discovered and used. Based on Web access logs, we analyze what users are looking for, why they come to IA, where they come from, and how pages link to IA. We find that users request English pages the most, followed by the European languages. Most human users come to Web archives because they do not find the requested pages on the live Web. About 65 % of the requested archived pages no longer exist on the live Web. We find that more than 82 % of human sessions connect to the Wayback Machine via referrals from other Web sites, while only 15 % of robots have referrers. Most of the links (86 %) from Websites are to individual archived pages at specific points in time, and of those 83 % no longer exist on the live Web. Finally, we find that users who come from search engines browse more pages than users who come from external Web sites.     

Provable security of a pairing-free one-pass authenticated key establishment protocol for wireless sensor networks

Designing efficient as well as secure cryptographic protocols for resource-constrained applications is a challenging task. In this paper, we formally analyze the security of an efficient one-pass authenticated key establishment protocol, the 1P-AKE protocol, which is primarily proposed for resource-constrained sensor nodes devices in wireless sensor networks (WSNs). In contrast to the existing identity-based one-pass key establishment protocols, the 1P-AKE protocol does not require any bilinear pairing computation in order to establish a key. This feature makes it really attractive for resource-constrained application environments, such as WSNs, where pairing computations are too expensive. We show that in the random oracle model, the 1P-AKE protocol is a secure authenticated one-pass key establishment protocol under the computational Diffie–Hellman assumption. The performance of the 1P-AKE protocol is also discussed and compared with the existing relevant protocols.     

Designing biomass supply chains within planetary boundaries

The design of sustainable supply chains, which recently emerged as an active area of research in process systems engineering, is vital to ensure sustainable development. Despite past and ongoing efforts, the available methods often overlook impacts beyond climate change or incorporate them via standard life cycle assessment metrics that are hard to interpret from an absolute sustainability viewpoint. We here address the design of biomass supply chains considering critical ecological limits of the Earth—planetary boundaries—which should never be surpassed by anthropogenic activities. Our method relies on a mixed-integer linear program that incorporates a planetary boundaries-based damage model to quantify absolute sustainability precisely. We apply this approach to the sugarcane-to-ethanol industry in Argentina, identifying the optimal combination of technologies and network layout that minimize the impact on these ecological boundaries. Our framework can find applications in a wide range of supply chain problems related to chemicals and fuels production, energy systems, and agriculture planning.     

Detecting off-topic pages within TimeMaps in Web archives

Web archives have become a significant repository of our recent history and cultural heritage. Archival integrity and accuracy is a precondition for future cultural research. Currently, there are no quantitative or content-based tools that allow archivists to judge the quality of the Web archive captures. In this paper, we address the problems of detecting when a particular page in a Web archive collection has gone off-topic relative to its first archived copy. We do not delete off-topic pages (they remain part of the collection), but they are flagged as off-topic so they can be excluded for consideration for downstream services, such as collection summarization and thumbnail generation. We propose different methods (cosine similarity, Jaccard similarity, intersection of the 20 most frequent terms, Web-based kernel function, and the change in size using the number of words and content length) to detect when a page has gone off-topic. Those predicted off-topic pages will be presented to the collection’s curator for possible elimination from the collection or cessation of crawling. We created a gold standard data set from three Archive-It collections to evaluate the proposed methods at different thresholds. We found that combining cosine similarity at threshold 0.10 and change in size using word count at threshold ?0.85 performs the best with accuracy = 0.987, \(F_{1}\) score = 0.906, and AUC \(=\) 0.968. We evaluated the performance of the proposed method on several Archive-It collections. The average precision of detecting off-topic pages in the collections is 0.89.     

Dual‐Action Cancer Therapy with Targeted Porous Silicon Nanovectors

There is a pressing need to develop more effective therapeutics to fight cancer. An idyllic chemotherapeutic is expected to overcome drug resistance of tumors and minimize harmful side effects to healthy tissues. Antibody‐functionalized porous silicon nanoparticles loaded with a combination of chemotherapy drug and gold nanoclusters (AuNCs) are developed. These nanocarriers are observed to selectively deliver both payloads, the chemotherapy drug and AuNCs, to human B cells. The accumulation of AuNCs to target cells and subsequent exposure to an external electromagnetic field in the microwave region render them more susceptible to the codelivered drug. This approach represents a targeted two‐stage delivery nanocarrier that benefits from a dual therapeutic action that results in enhanced cytotoxicity.