Mechano-chemical synthesis of manganese borohydride (Mn(BH4)2) and inverse cubic spinel (Li2MnCl4) in the (nLiBH4 + MnCl2) (n = 1, 2, 3, 5, 9 and 23) mixtures and their dehydrogenation behavior

Manganese borohydride (Mn(BH₄)₂) was successfully synthesized by a mechano-chemical activation synthesis (MCAS) from lithium borohydride (LiBH₄) and manganese chloride (MnCl₂) by applying high energy ball milling for 30 min. For the first time a wide range of molar ratios n = 1, 2, 3, 5, 9 and 23 in the (nLiBH₄ + MnCl₂) mixture was investigated. During ball milling for 30 min the mixtures release only a very small quantity of H₂ that increases with the molar ratio n but does not exceed ∼0.2 wt.% for n = 23. However, longer milling duration leads to more H₂ released. For the equimolar ratio n = 1 the principal phases synthesized are Li₂MnCl₄, an inverse cubic spinel phase, and the Mn(BH₄)₂ borohydride. For n = 2 a LiCl salt is formed which coexists with Mn(BH₄)₂. With the n increasing from 3 to 23 LiBH₄ is not completely reacted and its increasing amount is retained in the microstructure coexisting with LiCl and Mn(BH₄)₂. Gas mass spectrometry during Temperature Programmed Desorption (TPD) up to 450 °C shows the release of hydrogen as a principal gas with a maximum intensity around 130–150 °C accompanied by a miniscule quantity of borane B₂H₆. The intensity of the B₂H₆ peak is 200–600 times smaller than the intensity of the corresponding H₂ peak. In situ heating experiments using a continuous monitoring during heating show no evidence of melting of Mn(BH₄)₂ up to about 270–280 °C. At 100 °C under 1 bar H₂ pressure the ball milled n = 2 and 3 mixtures are capable of desorbing quite rapidly ∼4 wt.% H₂ which is a very large amount of H₂ considering that the mixture also contains 2 mol of LiCl salt. The H₂ quantities experimentally desorbed at 100 and 200 °C do not exceed the maximum theoretical quantities of H₂ expected to be desorbed from Mn(BH₄)₂ for various molar ratios n. It clearly confirms that the contribution from B₂H₆ evolved is negligibly small (if any) when desorption occurs isothermally in the practical temperature range 100–200 °C. It is found that the ball milled mixture with the molar ratio n = 3 exhibits the highest rate constant k and the lowest apparent activation energy for dehydrogenation, E_A ∼ 102 kJ/mol. Decreasing or increasing the molar ratio n below or above 3 increases the apparent activation energy. Ball milled mixtures with the molar ratio n = 2 and 3 discharge slowly H₂ during storage at room temperature and 40 °C. The addition of 5 wt.% nano-Ni with a specific surface area of 60.5 m²/g substantially enhances the rate of discharge at 40 °C.     

Determining adulteration of canned products using SNIF-NMR and IRMS: detection of undeclared addition of synthetic acetic acid

Possible adulteration of canned products containing spirit vinegar pickle by adding synthetic acetic acid is a significant problem of the food industry. Isotope analyses, which determine botanical origin of acetic acid and also can detect synthetic acid, were applied to detect undeclared addition of synthetic acetic acid to canned products. The aim of the study was to improve the extraction technique for the SNIF-NMR (²H/¹H; site-specific natural isotopic fractionation-nuclear magnetic resonance) and IRMS (¹³C/¹²C; isotope ratio mass spectrometry) isotope methods and for an atypical matrix and to determine isotope ratios in canned vegetables pickle to prove their adulteration or authenticity. The following set of canned products was analysed: pickled cucumbers (n = 16) and one vinegar pickle purchased in the Czech market and six model (cucumber) pickles. The determined ratios of ²H/¹H and ¹³C/¹²C for the pickled cucumbers proved to be authentic ranged from 89.4 to 107.0 ppm and from ?28.7 to ?15.6 ‰, respectively; for the synthetic acetic acids diluted with water they ranged from 114.2 to 129.0 ppm and from ?44.9 to ?33.4 ‰, respectively. Isotope analyses were confirmed as a reliable tool for assessing authenticity of canned products. The method enables detection of synthetic acetic acid addition into vinegars and canned vegetables containing vinegar pickle up from 20 % (of total acidity).     

Separation of selective organic acids from wastewater through a polyol supported liquid membrane

Pesticide toxicity databases usually include data on pure chemicals (active ingredients). Technical pesticides formulations, however, are mixtures with adjuvants as applied to fields/crops. Two formulations of the same pesticide can differ in their environmental fate and their toxicity. This work presents the evaluation of the toxicity of the dinitroaniline herbicide, pendimethalin by simultaneous analysis of its respiration rate and generation of a membrane potential (Δ Ψ) in rat liver mitochondria. Chromatography grade pendimethalin (8.2·10^?5 ‐ 5.47·10^?4 M or 23 – 154 ppm) caused lower enhancement of the mitochondrial respiration and decrease of the Δ Ψ than technical grade pendimethalin (Stomp), i.e. the mixture of pure ingredient and adjuvant(s). These effects are comparable to those of 2,4‐dinitrophenol. Pure and technical grade pendimethalin acts as an uncoupler of oxidative phosphorylation in mitochondria (enhances respiration and diminishes Δ Ψ). These data conflict with the statement, presented in the US EPA manual Recognition and Management of Pesticides Poisonings, that pendimethalin does not act as an uncoupler of oxidative phosphorylation.     

Experimental Investigation of the Properties of Lime-Based Plaster-Containing PCM for Enhancing the Heat-Storage Capacity of Building Envelopes

Experimental analysis of a wide range of properties of a lightweight plaster which should enhance the heat-storage capacity of building envelopes is presented. The basic physical characteristics, namely, the bulk density, matrix density, total open porosity, and pore-size distribution are measured at first. Then, the compressive strength is determined for an assessment of mechanical performance of the plaster. The thermal conductivity and thermal diffusivity are studied using an impulse technique. Differential scanning calorimetry measurements are performed as well, in order to identify the temperature range and latent heat of the phase change and to determine the specific heat capacity as a function of temperature. Durability properties are assessed using the measurement of the water absorption coefficient and sorption and desorption isotherms. The experimental results indicate a good capability of the designed plaster to moderate effectively the interior climate of buildings.     

Development of a solid self-microemulsifying drug delivery system (SMEDDS) for solubility enhancement of naproxen

Context: Comparative evaluation of liquid and solid self-microemulsifying drug delivery systems (SMEDDS) as promising approaches for solubility enhancement.

Objective: The aim of this work was to develop, characterize, and evaluate a solid SMEDDS prepared via spray-drying of a liquid SMEDDS based on Gelucire® 44/14 to improve the solubility and dissolution rate of naproxen.

Material and methods: Various oils and co-surfactants in combination with Gelucire® 44/14 were evaluated during excipient selection study, solubility testing, and construction of (pseudo)ternary diagrams. The selected system was further evaluated for naproxen solubility, self-microemulsification ability, and in vitro dissolution of naproxen. In addition, its transformation into a solid SMEDDS by spray-drying using maltodextrin as a solid carrier was performed. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to evaluate the physical characteristics of the solid SMEDDS obtained.

Results: The selected formulation of SMEDDS was comprised of Miglyol 812®, Peceol?, Gelucire® 44/14, and Solutol® HS 15. The liquid and solid SMEDDS formed a microemulsion after dilution with comparable average droplet size and exhibited uniform droplet size distribution. In the solid SMEDDS, liquid SMEDDS was adsorbed onto the surface of maltodextrin and formed smooth granular particles with the encapsulated drug predominantly in a dissolved state and partially in an amorphous state. Overall, incorporation of naproxen in SMEDDS, either liquid or solid, resulted in improved solubility and dissolution rate compared to pure naproxen.

Conclusion: This study indicates that a liquid and solid SMEDDS is a strategy for solubility enhancement in the future development of orally delivered dosage forms.     

Reconstructing the microstructure of polyimide–silicalite mixed‐matrix membranes and their particle connectivity using FIB‐SEM tomography

Properties of a composite material made of a continuous matrix and particles often depend on microscopic details, such as contacts between particles. Focusing on processing raw focused‐ion beam scanning electron microscope (FIB‐SEM) tomography data, we reconstructed three mixed‐matrix membrane samples made of 6FDA‐ODA polyimide and silicalite‐1 particles. In the first step of image processing, backscattered electron (BSE) and secondary electron (SE) signals were mixed in a ratio that was expected to obtain a segmented 3D image with a realistic volume fraction of silicalite‐1. Second, after spatial alignment of the stacked FIB‐SEM data, the 3D image was smoothed using adaptive median and anisotropic nonlinear diffusion filters. Third, the image was segmented using the power watershed method coupled with a seeding algorithm based on geodesic reconstruction from the markers. If the resulting volume fraction did not match the target value quantified by chemical analysis of the sample, the BSE and SE signals were mixed in another ratio and the procedure was repeated until the target volume fraction was achieved. Otherwise, the segmented 3D image (replica) was accepted and its microstructure was thoroughly characterized with special attention paid to connectivity of the silicalite phase. In terms of the phase connectivity, Monte Carlo simulations based on the pure‐phase permeability values enabled us to calculate the effective permeability tensor, the main diagonal elements of which were compared with the experimental permeability. In line with the hypothesis proposed in our recent paper (?apek, P. et al. (2014) Comput. Mater. Sci. 89 , 142–156), the results confirmed that the existence of particle clusters was a key microstructural feature determining effective permeability.     

Guided-wave Electro-optic X-type Switches: Symmetry,Switching Characteristics and Cross-talk

Abstract

The influence of branching asymmetry and electrode offset on the switching characteristics and cross-talk of X-type switches is analysed theoretically. The relationship between the switch symmetry (i.e. the existence of a plane or centre of inversion) and the switching characteristics is found. Cross-talk levels of slightly asymmetric Ti:LiNbO₃ switches are calculated.     

Extraction of Bitter Acids from Hops and Hop Products Using Pressurized Solvent Extraction (PSE)

The EBC method 7.7, currently used for determination of bitter acids in hop products, is a time‐consuming and laborious extraction technique. In this paper, our aim was to propose a new extraction method based on Pressurized Solvent Extraction (PSE) sometimes also called Pressurized Fluid Extraction (PFE) or Accelerated Solvent Extraction (ASE). Compared to conventional extractions, PSE offers a number of important benefits. PSE on OnePSE^® automated extractor was used for extraction of α‐ and β‐acids from hops and hop products and the parameters influencing extraction efficiency and the influence of the sample preparation method were studied. The quantitative determination of α‐ and β‐acids in the extracts was accomplished by using an HPLC apparatus equipped with diode array detector. The experimental results were compared with those obtained by the standard EBC 7.7 method and the two methods were found to be fully compatible