Reaction of graphite fluoride with NaOH-KOH eutectic

Graphite fluoride has been generally considered chemically inert against strong alkalis under ambient conditions. In the present study we demonstrate that treatment of graphite fluoride with eutectic NaOH-KOH mixture at 250 °C induces dramatic structural and textural changes in the solid as evidenced by XRD, FT-IR, Raman, UV-vis absorption and fluorescence and microscopy techniques (TEM, AFM). The reaction proceeds in the molten state leading to water-soluble, graphitized carbon particles which unlike graphite fluoride, adopt a variety of morphologies, like platy, tetragonal, triangular, discoid and spherical. The resulting carbon particles are dispersible in water and fluoresce under UV excitation.     

Synthesis of 2D Germanane (GeH): a New,Fast, and Facile Approach

Germanane (GeH), a germanium analogue of graphane, has recently attracted considerable interest because its remarkable combination of properties makes it an extremely suitable candidate to be used as 2D material for field effect devices, photovoltaics, and photocatalysis. Up to now, the synthesis of GeH has been conducted by substituting Ca by H in a β‐CaGe₂ layered Zintl phase through topochemical deintercalation in aqueous HCl. This reaction is generally slow and takes place over 6 to 14 days. The new and facile protocol presented here allows to synthesize GeH at room temperature in a significantly shorter time (a few minutes), which renders this method highly attractive for technological applications. The GeH produced with this method is highly pure and has a band gap (E_g) close to 1.4 eV, a lower value than that reported for germanane synthesized using HCl, which is promising for incorporation of GeH in solar cells.     

Solid ink-printed filter paper as a green adsorbent material for the solid-phase extraction of UV filters from water samples

This work describes the development of a new green solid-phase extraction approach, which is based on the use of low-cost extraction discs composed of plain filter papers that are covered with a synthetic wax-like coating. The filter papers are printed in a commercial solid ink printer, which dispenses a synthetic wax-like ink on the surface of the paper, to cover the hydrophilic cellulose fibre matrix with an interface of lipophilic domains where non-polar analytes can partition through hydrophobic interactions. The modified paper filters were used to extract hydrophobic organic compounds from water samples following the customary procedure of solid-phase extraction without sorbent preconditioning and needless of high-vacuum sources. As a proof-of-concept application, a series of non-polar organic UV filters were used as model analytes to optimise the extraction parameters and evaluate the performance of the method in spiked water samples. Based on this principle, a new sample preparation platform with low environmental footprint has been developed that enables extraction to be carried out using low-cost, environmental benign and non-toxic conventional materials. The advantages and disadvantages of the method, alongside with its future prospects towards the development of custom-made ‘printed extraction kits’, are envisioned and discussed.     

Serial-batching scheduling with time-dependent setup time and effects of deterioration and learning on a single-machine

This paper deals with serial-batching scheduling problems with the effects of deterioration and learning, where time-dependent setup time is also considered. In the proposed scheduling models, all jobs are first partitioned into serial batches, and then all batches are processed on a single serial-batching machine. The actual job processing time is a function of its starting time and position. In addition, a setup time is required when a new batch is processed, and the setup time of the batches is time-dependent, i.e., it is a linear function of its starting time. Structural properties are derived for the problems of minimizing the makespan, the number of tardy jobs, and the maximum earliness. Then, three optimization algorithms are developed to solve them, respectively.     

Stoicism and Alchemy in Late Antiquity: Zosimus and the Concept of Pneuma

At the beginning of the twentieth century, historians associated the alchemy of the third-century alchemist Zosimus of Panopolis with Platonism and Aristotelianism, explicating his theory of alchemical transmutation under the intellectual umbrella of these philosophical traditions. More recently, scholars of alchemy such as Christina Viano and William Newman have suggested a connection between Zosimean alchemy and Stoicism. Through a close reading of texts in Zosimus’s corpus, this paper posits a Stoic interpretation of several aspects of Zosimean alchemy, focusing on the concepts of pneuma and tension. For Zosimus, I argue, pneuma played a vital role in colouring metals, while tension conferred stability and cohesion upon metallic compounds. This interpretation suggests that Zosimus applied Stoic concepts to describe the alchemical process of tincturing metals.     

The effect of the pore structure and zeta potential of porous polymer monoliths on separation performance in ion-exchange mode

Most often, in bioseparations involving charged macromolecules, the chromatographic systems have low Reynolds and high Peclet numbers. For such systems, an expression is developed and presented in this work for evaluating the throughput in polymeric monoliths where ion-exchange adsorption occurs, as a function of (i) the pressure drop along the length of the monolith, (ii) the functional form and width of the throughpore-size distribution of the monolith, and (iii) the magnitude of the zeta potential on the surface of the throughpores of the monolith. Gaussian and log-normal throughpore-size distributions whose mean throughpore-size and standard deviation values are based on experimentally measured throughpore-size distribution data by mercury porosimetry employed on polymeric monoliths are used in this work, and their effect on the throughput relative to that obtained from a polymeric monolith having a uniform throughpore-size distribution is studied for different values of the ratio of the standard deviation to the mean throughpore-size. The results indicate that relatively modest increases in the throughput, when compared with the throughput that could be achieved in a polymeric monolith having a uniform throughpore-size distribution, could be obtained in polymeric monoliths having disperse throughpore-size distributions, and the magnitude of the increase becomes larger when the disperse distribution is skewed to larger throughpore sizes. Furthermore, the results of this work indicate that, under certain conditions, relatively modest increases in the throughput of a charged analyte could also be achieved by altering the value of the zeta potential on the surface of the throughpores of the monolith. Due to the difficulties inherent in controlling the functional form and width of the throughpore-size distribution during the synthesis of polymeric monoliths, it would appear to be more practical to increase the value of the throughput of a charged analyte by altering the value of the zeta potential through prudent selection of the ion-exchange surface functional groups and fine-tuned with the pH of the mobile phase. Thus, for ion-exchange chromatography systems, the zeta potential could be considered an important parameter for column designers and operators to manipulate, since its alteration could increase the through-put of a charged analyte in polymeric monoliths or in columns packed with charged particles.     

Robust and sensitive high-performance liquid chromatographic-UV detection technique for the determination of tigecycline in rabbit plasma

An isocratic HPLC method with detection at 248 nm was developed and fully validated for the determination of tigecycline in rabbit plasma. Minocycline was used as an internal standard. A Hypersil BDS RP-C18 column (250 x 4.6 mm, 5 microm particle size) was used with the mobile phase phosphate buffer (pH 7.10, 0.070 M)-acetonitrile (76 + 24, v/v) at a flow rate of 1.0 mL/min. The elution time of tigecycline and minocycline was approximately 8.1 and 9.9 min, respectively. Calibration curves of tigecycline were linear in the concentration range of 0.021-3.15 microg/mL in plasma. The LOD and LOQ in plasma were estimated as 7 and 21 ng/mL, respectively. The intraday and interday precision values of the method were in the range of 5.0-7.1 and 5.6-9.1%, while the corresponding accuracy values were in the ranges of 92.8-111.1 and 97.6-102.3%, respectively. At the LOQ, the intraday precision was 18.7%, while intraday and interday accuracy values were 97.3 and 98.0%, respectively. Robustness of the proposed method was studied using a Plackett-Burman experimental design. A pharmacokinetic profile is presented for confirmation of the applicability of the method to pharmacokinetic studies.     

Physicochemical study of the ‘anatase/electrolyte solution’ interface in suspension and closely packed particles of the solid

The electric double layer (EDL) developed at the interface of anatase in contact with aqueous electrolyte solutions was investigated at 25 °C. Potentiometric titrations (PT), measurements of the electrophoretic mobility (EM) in suspensions, and streaming potential (SP) measurements were taken. The surface charge over a wide pH range (ca. 3–10) and the point of zero charge (pzc = 6.3 ± 0.1) of anatase was easily determined by means of the suspension titration curve and the blank one, obtained at a single ionic strength value. Streaming potential measurements were conducted in anatase particles appropriately packed to form plugs. Two different plugs were prepared differing in the degree of particles' packing and, consequently, in the respective porosities. It was found that surface conductivity is lower at higher packing (lower porosity), because of the reduction of the total surface area in contact with the electrolyte. Moreover, it was found that the surface conductivity of the anatase samples increased at pH values away from pzc, while the mobility of the counter ions behind the shear plane decreased. This trend was attributed to the increase of the absolute surface charge. This increase caused an increase in the amount of the counter ions and, therefore, in the conductivity due to these ions. On the other hand, stronger electrostatic interactions between the surface of the solid and the counter ions reduced their mobility. The packing density of the anatase particles in the respective plugs, affected the values of ζ‐potential calculated from SP measurements when the effect of surface conductivity was neglected. Copyright © 2010 John Wiley & Sons, Ltd.     

Identification of the Binding Site of Brucella VirB8 Interaction Inhibitors

Secretion systems translocate virulence factors of many bacterial pathogens, enabling their survival inside the host organism. Consequently, inhibition strongly attenuates pathogenicity and can be considered a target for novel antimicrobial drugs. The type IV secretion system (T4SS) of the intracellular pathogen Brucella is a prerequisite for its virulence, and in this work we targeted the interactions of the?essential assembly factor protein, VirB8, using small-molecule inhibitors. High-throughput screening identified several potent and specific inhibitors, and the target-binding site of these inhibitors was identified by X-ray crystallography, in?silico docking, and analysis of the derivates of the inhibitor B8I-2. VirB8 interaction inhibitors bind to a surface groove opposite to the dimerization interface, and by varying the binding-site residues, we were able to determine which residues are required for inhibitor activity. E115 and K182 were found to be especially important, and changes at R114, Y229, and L151 also reduced inhibitor efficiency.     

Novel Technology Development through Thermal Drying of Encapsulated Kluyveromyces marxianus in Micro- and Nano-tubular Cellulose in Lactose Fermentation and Its Evaluation for Food Production

A novel technology development based on the production of a low-cost starter culture for ripening of cheeses and baking is reported in the present study. The starter culture comprises thermally dried cells of Kluyveromyces marxianus encapsulated in micro- and nano-tubular cellulose. For production of a low-cost and effective biocatalyst, whey was used as raw material for biomass production and thermal drying methods (convective, conventional, and vacuum) were applied and evaluated at drying temperatures ranging from 35 to 60?°C. The effect of drying temperature of biocatalysts on fermentability of lactose and whey was evaluated. Storage stability and suitability of biocatalysts as a commercial starter cultures was also assessed and evaluated. All thermally dried biocatalysts were found to be active in lactose and whey fermentation. In all cases, there was sugar conversion ranging from 92 to 100?%, ethanol concentration of up to 1.47?% (v/v), and lactic acid concentrations ranged from 4.1 to 5.5?g/l. However, convective drying of the encapsulated cells of K. marxianus in micro- and nano-tubular cellulose was faster and a more effective drying method while drying at 42?°C appear to be the best drying temperature in terms of cell activity, ethanol, and lactic acid formation. Storage of the biocatalysts for 3?months at 4?°C proved maintenance of its activity even though fermentation times increased by 50?C100?% compared with the fresh dried ones.