Potentiometric behavior of electrodes based on overoxidized polypyrrole films

Electrodes based on oxidized polypyrrole films have potentiometric selectivity toward anions. When the films are overoxidized, however, electron-rich groups are introduced on to the polymer chains, reversing the selectivity of the electrodes from anionic to cationic. In this study, electrochemically overoxidized polypyrrole film electrodes were prepared, and the conditions for film formation that lead to near-Nernstian potentiometric response were investigated. It was found that the doping ion, overoxidation solution, and pH affect the response of these electrodes. Redox interference is significantly lower for the overoxidized polypyrrole films than for polypyrrole electrodes.     

Effect of the deaeration on the adsorption of some cationic surfactants at the mercury/electrolyte solution interface

The effect of the deaeration on the adsorption of three cationic surfactants cetyldimethylbenzylammonium chloride (CDBACl), cetyltrimethylammonium bromide (CTAB) and octadecyltrimethylammonium bromide (OTAB) at the mercury/electrolyte solution interface is studied. The deaeration is studied using either nitrogen or helium and the effect of deaeration process and time is also studied. In all cases an effect of the deaeration time is found which is mainly observed at potentials where a condensed film is formed. Capacity-time curves at the potentials where the film is formed show a nucleation and growth mechanism with induction time that depends on the deaeration time. The deaeration slows down the kinetics of the film formation but does not change the equilibrium capacitance value of the film. The decrease of the dissolved gas from the water that perturbs its structure is perhaps the main reason for the behaviour observed during the adsorption of these surfactants.     

Building a new mind set in tomorrow fashion development through circular strategy models in the framework of waste management

Energy, food, and clothing are the three main components of humanity. Each one individually and all together contribute to climate change and CO₂ emissions, to the consumption of natural resources, as well as influencing social attitude and behaviour. The global trends of the fashion industry are projected to expand in value from $1.5 trillion in 2020 to about $2.25 trillion by 2025, presenting that the fashion request is on continual growth. As natural resources (e.g., water) to produce clothes and shoes are limited nowadays, more resource-efficient production pathways must be identified; moreover, natural materials must replace plastic fibres, natural colours must replace synthetic ones, and ‘buy-and throw-way philosophy’ must turn into ‘buy-less-and-these-are-needed’ as so to reduce the environmental footprint of the fashion sector. This work emphasized the necessity of developing a new business circular model for the fashion industry with the potential of providing plethora of economic opportunities in the framework of waste management. Clear vision and new strategy development in the fashion sector is proposed, including the involvement of customers, businesses and policy makers, driven by the promotion of circular economy through knowledge exchange, education as well as regulatory relief measures for a synergic transition towards the circularity of the fashion industry.     

On the adsorption and condensed film formation of binary mixtures of dodecyl-, tetradecyl-, hexadecyl-, and octadecyl-trimethylammonium bromides at the mercury–electrolyte interface

The adsorption and condensed film formation on mercury at the negative potential region for binary mixtures of dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), cetyltrimethylammonium bromide (CTAB), octadecyltrimethylammonium bromide (OTAB) is studied in KBr at various temperatures from 5 to 45 °C. The formation of the CTAB condensed film is hindered with the addition of DTAB and TTAB. There are interactions between unlike hydrophobic chains. The strong interactions between the CTAB molecules do not take place when DTAB or TTAB is present above a certain concentration. This hindering is more pronounced in the case of TTAB compared to the same DTAB concentration, i.e. the increase of the chain length hinders the film formation. The initially adsorbed molecules play a templating role in the kinetics of the film formation and in the self-assembling of the molecules. The initial induction time strongly depends on the temperature. The less surface active CTAB can hinder the OTAB film formation in binary mixtures. Also, increased interaction between OTAB and CTAB can be observed, indicating synergy effects in the film formation in some cases. The temperature range that the film is formed can be changed using mixtures of surfactants. Thus, the development of the film can become impossible, more difficult or even easier. Hysteresis phenomena are observed. The capacity versus time curves in the case that condensed film is formed are treated with the Avrami plot formulation, giving values between 1.5 and 2 indicating a progressive one dimensional nucleation with constant growth rate or a decrease of the nucleation rate during the overall film formation. There is generally a marked effect of the chain length of the alkyl chain on the film formation.     

Micellisation and gelation of diblock copolymers of ethylene oxide and propylene oxide in aqueous solution, the effect of P-block length

The aqueous solution properties of five diblock copolymers prepared by sequential anionic copolymerisation (i.e. E₁₀₂P₃₇, E₁₀₄P₅₂, E₉₂P₅₅, E₁₀₄P₆₀ and E₉₈P₇₃ where E denotes oxyethylene and P denotes oxypropylene) were studied across a wide range of concentration. The techniques used to study micellisation and micellar properties in dilute solution were static and dynamic light scattering, surface tension, and eluent gel-permeation chromatography. The gelation of concentrated solutions was also investigated. As expected, the critical micelle concentration (CMC) was lowered and the association number of the micelles was increased by an increase in P-block length. In contrast, the critical gel concentration was unchanged, consistent with the constant E-block length leading to micelles with essentially identical E-block fringes. Comparison of the CMCs of the diblock copolymers with those of triblock E_mP_nE_m copolymers with the same P-block length shows the diblock copolymers to micellise more efficiently. A similar comparison of the CMCs of the diblock copolymers with those of E_mB_n copolymer (B denotes oxybutylene) shows the hydrophobicity of a P unit to be one-sixth that of a B unit. The possibility is explored of correlating the limiting association number of a spherical micelle with the hydrophobe block length of its constituent copolymer. Of the five copolymers, only dilute solutions of E₉₈P₇₃ were predominantly micellar at both room temperature and body temperature, and this copolymer must be a prime candidate in any consideration of the potential application of E_mP_n copolymers in the solubilisation and controlled release of drugs.     

A single hop architecture exploiting cooperative beamforming for wireless sensor networks

In this paper, we propose a single hop architecture for a cooperative wireless sensor network and analyze the attained distributed beamforming gain performance using the theory of random arrays. All nodes in the system transmit a single carrier such that the signals add up constructively towards the direction of the fusion center. The potential directive beamforming gains are investigated for different sensor network densities which are expressed as the number of nodes per carrier wavelength squared. The multiple access capability of the sensor network is achieved by employing an on-off keying orthogonal signaling technique, which is usually employed in atmospheric optical systems. Finally, we investigate the average loss in directivity gain when the received signal from each sensor node follows a Ricean distribution. The results show that high directive gains can be achieved in practical wireless sensor networks using simple sensor nodes.     

Formation and photodecomposition of cationic titanium oxide clusters

In this paper we report on the titanium oxide cluster cations Ti _x O _y ⁺, generated by laser ablation of a titanium target in the region of the nozzle expansion of oxygen. The mass distribution of the clusters produced is recorded with a time-of-flight mass spectrometer. Three different series, namely TiO(TiO₂) _n ⁺ , TiO(TiO₂) _n O₂⁺, and (TiO₂) _n ⁺, appear in the spectra. Two different ablation wavelengths (infrared at 1064 nm and ultraviolet at 308 nm) are used to generate the titanium oxide clusters. At the shorter wavelength the maximum size of the clusters formed decreases. The interaction of the UV photons with the Ti _x O _y ⁺ clusters is further investigated in a separate two-laser arrangement with an IR laser for ablation and after some mm downstream with an UV system for the cluster beam irradiation. These studies indicate that the intensity of the T _x O _y ⁺ clusters with x≥4, y≥7 is strongly influenced by the absorption of UV photons. This is attributed mainly to dissociation into smaller ones.     

Surface conductivity of hydrogenated diamond films

The experimentally observed high surface conductivity of hydrogenated diamond films is explained through ab initio results as well as model calculations based on the tight-binding molecular dynamics method. Our results support the previously reported experimental results indicating that the surface conductivity of the hydrogenated diamond surfaces is due to the surface adsorption of a H(3)O(+) monolayer. Specifically, it is shown that the presence of the H(3)O(+) adlayer results in the formation of an electrostatic surface dipole moment which makes the potential of the surface H layer effectively more attractive. This, in turn, ignites charge transfer from the diamond lattice to the surface layer creating, thus, the necessary charge carriers (holes) for the observed high conductivity.     

Synchronized reneging in queueing systems with vacations

In this paper we present a detailed analysis of queueing models with vacations and impatient customers, where the source of impatience is the absence of the server. Instead of the standard assumption that customers perform independent abandonments, we consider situations where customers abandon the system simultaneously. This is, for example, the case in remote systems where customers may decide to abandon the system, when a transport facility becomes available.