Chromatographic determination of specific surface area of adsorbents by using the Jovanović equation

A new chromatographic method for calculating monolayer capacity and specific surface area has been presented. This method is based on the Jovanovi? adsorption equation.     

Charge Transportation and Chirality in Liquid Crystalline Helical Network Phases of Achiral BTBT-Derived Polycatenar Molecules

First examples of multichain (polycatenar) compounds, based on the π-conjugated [1]benzothieno[3,2-b]benzothiophene unit are designed, synthesized, and their soft self-assembly and charge carrier mobility are investigated. These compounds, terminated by the new fan-shaped 2-brominated 3,4,5-trialkoxybenzoate moiety, form bicontinuous cubic liquid crystalline (LC) phases with helical network structure over extremely wide temperature ranges (>200 K), including ambient temperature. Compounds with short chains show an achiral cubic phase with the double network, which upon increasing the chain length, is at first replaced by a tetragonal 3D phase and then by a mirror symmetry is broken triple network cubic phase. In the networks, the capability of bypassing defects provides enhanced charge carrier mobility compared to imperfectly aligned columnar phases, and the charge transportation is non-dispersive, as only rarely observed for LC materials. At the transition to a semicrystalline helical network phase, the conductivity is further enhanced by almost one order of magnitude. In addition, a mirror symmetry broken isotropic liquid phase is formed beside the 3D phases, which upon chain elongation is removed and replaced by a hexagonal columnar LC phase.     

Mesoporous drug carrier systems for enhanced delivery rate of poorly water-soluble drug: nimodipine

Journal of Porous Materials - Two mesoporous silica materials: MCM-41 and SBA-15 were applied as potential nanocarriers for poorly soluble drug—nimodipine. Drug incorporation was performed...     

MAC-layer rate control for 802.11 networks: a survey

Rate control at the MAC-layer is one of the fundamental building blocks in many wireless networks. Over the past two decades, around thirty mechanisms have been proposed in the literature. Among them, there are mechanisms that make rate selection decisions based on sophisticated measurements of wireless link quality, and others that are based on straight-forward heuristics. Minstrel, for example, is an elegant mechanism that has been adopted by hundreds of millions of computers, yet, not much was known about its performance until recently. The purpose of this paper is to provide a comprehensive survey and analysis of the existing solutions from the two fundamental aspects of rate control—metrics and algorithms. We also review how these solutions were evaluated and compared against each other. Based on our detailed studies and observations, we share important insights on future development of rate control mechanisms at the MAC-layer. This discussion also takes into account the recent developments in wireless technologies and emerging applications, such as Internet-of-Things, and shows issues that need to be addressed in the design of new rate control mechanisms suitable for these technologies and applications.

     

Novel glucose-derived gemini surfactants with a 1,1′-ethylenebisurea spacer: Preparation, thermotropic behavior, and biological properties

In the search for environmentally safe surfactants made from inexpensive and renewable sources, the interest has mainly been focused on new saccharide derivatives. This report describes the synthesis of newly designed nonionic gemini compounds comprising two reduced sugar headgroups, two alkyl tails, and a 1,1′-ethylenebisurea entity as the spacer linking two amphiphilic glucose-derived moieties. Thus, the series of N,N′-bis[(3-alkyl-3-deoxy-d-glucitol)ureido]ethylenediamines (bis(C_nGT), with C_n=n-C₉H₉, n-C₆-H₁₃, n-C₈H₁₇, n-C₁₀H₂₁, or n-C₁₂H₂₅), were prepared using a convenient procedure starting from easily accessible reagents such as d-glucose, n-alkylamines, urea, and ethylenediamine. Their structure and purity were confirmed by means of elemental analysis, electrospray ionization mass spectrometry, and ¹H and ¹³C nuclear magnetic resonance spectroscopy. Additionally, the present contribution introduces selected properties of these surfactants, including their thermotropic behavior and biological properties. The presence of two phase transition points, determined using the differential scanning calorimetry method, indicates liquid-crystalline mesophase formation upon heating. Furthermore, using the closed-bottle test (OECD Guideline 301D) as well as the biological oxygen demand test for insoluble substances for biodegradability measurements, it has been concluded that the tested glucose-derived gemini structures achieve more than 60% biodegradation after 64–75 test days. All tested surfactants were practically nontoxic to bacteria, yeast, and molds. Owing to their fitting aggregation ability as well as their nontoxicity, they constitute an interesting group of surfactants for various applications.     

Quantitative determination of the iodine values of unsaturated plant oils using infrared and Raman spectroscopy methods

Thirteen edible oils: sunflower, avocado, hemp, high-linolenic flax, low-linolenic flax, safflower, walnut, roasted sesame, rice, corn, rapeseed, pumpkin seed, and hazel were studied in this work. Their fatty acid composition, iodine, acidic, peroxide, and saponification values were determined. Infrared and Raman spectra of the oils were recorded in the range 400–3200 cm^?1. The integral intensities of the bands at about 1655 and 2852 cm^?1 corresponding to ν(C=C) and ν(CH₂) vibrations were evaluated and used to construct a relationship between the spectroscopic data and the iodine value. The following linear dependencies were obtained: I_ν(C=C)/I_ν(CH2) = 7.449 × 10^?4 × iodine value – 0.0339 and I_ν(C=C)/I_ν(CH2) = 9.299 × 10^?4 × iodine value – 0.023 for the infrared and Raman spectra with a correlation coefficient 0.988 and 0.976, respectively. These calibration lines can be used to determine the iodine value for oils with unknown unsaturation level, and may be applied for margarines and other fatty materials.     

Solid waste: terminological and long-term environmental risk assessment problems exemplified in a power plant fly ash study

Legal definitions exert a significant impact on the waste management strategy. Waste that is technically suitable for recovery does not automatically become a raw material if there is no market for it, or its use is not commercially effective and, hence, they should be disposed of. The majority of disposed wastes, including recyclable waste, are not environmentally safe. Waste as a freshly generated anthropogenic material is not geochemically stable. Przezchlebie fly ash surface pond (Upper Silesia, Poland) in the post-closure stage was subject to field validation of the results of laboratory leaching/extraction tests and long-term column experiments on fly ash (FA) leaching behaviour under controlled conditions for environmental risk assessment. The study showed: (i) the possibility of a discontinuous non-linear time delayed increase of pollution potential of disused 'non-hazardous' large-volume waste in the dumping sites to the hazardous level; (ii) inconsistency of the laboratory leaching tests and the actual leaching behaviour of trace metals, particularly when equilibria conditions are dictated by kinetically determined reactions where the test results reflected entirely wash-out (I) and dissolution (II) phases, but did not comprise delayed release (III) phase; and (iii) necessity of life-cycle screening/monitoring of 'non-hazardous' dumping sites for contaminant release as a function of the primary (pH-Eh, ionic strength, ionic composition of solute) and secondary controlling factors (L/S-liquid to solid ratio, water flow conditions) along the vertical profile of an anthropogenic or natural vadose zone. These data are to be used to develop long-term predictive hydrogeochemical models and their field validation, and for providing an early warning and remedial actions with respect to the particular site. The formation of pH (and Eh) as a function of time-dependent (kinetically defined) processes appeared to be a key issue for a correct prediction of the leaching behaviour of waste. The presented case study on FA shows that waste, even those considered non-hazardous and fit for use in a commercially proven applications, should not be treated the same way as a natural raw material. To facilitate waste utilisation and disposal in environmentally safe way and to prioritise its use, reliable environmental risk assessment prediction models and testing procedures, as well as special enforcement strategy and regulations, should be developed with respect to waste and not 'materials.'     

Reproducible comet assay of amorphous silica nanoparticles detects no genotoxicity

Genotoxicity of commercial colloidal and laboratory-synthesized silica nanoparticles was tested using the single cell gel electrophoresis or Comet assay. By using a carefully developed protocol and careful characterization of the nanoparticle dispersions, Comet assays were performed on 3T3-L1 fibroblasts with 3, 6, and 24 h incubations and 4 or 40 microg/ml of silica nanoparticles. No significant genotoxicity was observed for the nanoparticles tested under the conditions described, and results were independently validated in two separate laboratories, showing that in vitro toxicity testing can be quantitatively reproducible.     

Cannabis and motor function: fMRI changes following 28 days of discontinuation.

The authors hypothesized that supplementary motor cortex (SMA) and anterior cingulate cortex (ACC) activation in chronic cannabis users, studied 4 to 36 hours after their last episode of use, would disappear by Day 28 of abstinence during finger-tapping tests. Eleven cannabis users and 16 comparison subjects were scanned during right (RFT) and left (LFT) finger-tapping tasks on a GE 1.5 Tesla scanner retrofitted with a whole body echo planar coil. Image analyses were conducted in SPM99 using an ROI approach to define each Brodmann area (BA). Differences in cerebral activation were examined in the left and right primary motor cortex (BA4), SMA (BA6), and ACC (BA24 and BA32 separately). The authors found diminished activation for contralateral BA6 from Day 0 to Day 28. For LFT, the authors also found: ipsilaterally diminished BA6 activation on Day 7, but not Day 0 or Day 28; ipsilaterally diminished BA32 activation on Day 0, but not Day 7 or Day 28; contralaterally diminished BA 4 activation on Day 28, but not Day 0 or Day 7; and contralaterally diminished BA32 activation on Day 0 and Day 28, but not Day 7. For RFT, the authors found ipsilaterally diminished BA32 activation on Days 0 and 7 but not on Day 28; contralaterally diminished BA32 activation on Days 0, 7, and 28; and ipsilaterally diminished BA6 activation on Days 0, 7, and 28. These results suggest that residual diminished brain activation is still observed after discontinuing cannabis use in motor cortical circuits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modification of polyester fibers by grafting with poly(acrylic acid)

The grafting of acrylic acid on PET using benzoyl peroxide has been investigated. The influence of the main parameters of grafting, the effect of additives on the degree of grafting, and the amount of homopolymer formed during the process have been determined. Futhermore, the values of apparent activation energy have been calculated. Also, the influence of the degree of grafting on the moisture sorption and swelling of modified fibers have been determined. By an additional treatment of the grafted fibers with antibiotics it is possible to provide the fibers with antibacterial properties. Liberation of antibiotics from fibers into solutions has been examined and mathematically described. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:967–977, 1997