Annual vegetation burns across the northern savanna region of Ghana: period of occurrence, area burns, nutrient losses and emissions

This study has assessed the seasonal occurrence of annual vegetation fires and defined inter-seasonally burned area for the different vegetation cover types across Ghana and the northern region of Ghana using 10-year (2001?C2010) remote sensing data. These values were used with fire induced elemental losses to estimate greenhouse gas emissions and net plant nutrient loss due to gross bush fire nutrient transfers and annual atmospheric nutrient depositions. About 21, 68, 10 and 1?% of annual burns across the northern region of Ghana take place in the months of November, December, January and February respectively. As much as 68?±?4 thousand km² (25?C32?%) and 37?±?2.6 thousand km² (46?C60?%) of dry land are annually burned across Ghana and the northern region of Ghana respectively, with 53?C56?% of the total annual burns across the country taking place in the northern region. About 10,100?C28,400 Gg of C, comprising 215?C4,700 thousand Gg of CO₂ equivalent (CO₂, CH₄) potential global warming green house gases and 48?C324 thousand Gg of local pollutants (CO, NO_x) are estimated to be released annually through bush fire occurrence across Ghana. Net negative balance for P between fire-induced nutrient transfers and, annual wet and dry nutrient deposits is of concern given the high P-sorbing mineral content of the soils. The temporal loss of P suggest an input source than wet and dry atmospheric P depositions for the sustenance of the ecosystem or predict a long term threat to regional food production.     

Serendipitous Identification of a Covalent Activator of Liver Pyruvate Kinase

Enzymes are effective biological catalysts that accelerate almost all metabolic reactions in living organisms. Synthetic modulators of enzymes are useful tools for the study of enzymatic reactions and can provide starting points for the design of new drugs. Here, we report on the discovery of a class of biologically active compounds that covalently modifies lysine residues in human liver pyruvate kinase (PKL), leading to allosteric activation of the enzyme (EC₅₀=0.29 μM). Surprisingly, the allosteric activation control point resides on the lysine residue K282 present in the catalytic site of PKL. These findings were confirmed by structural data, MS/MS experiments, and molecular modelling studies. Altogether, our study provides a molecular basis for the activation mechanism and establishes a framework for further development of human liver pyruvate kinase covalent activators.     

Synthesis and photopolymerization kinetics of new flexible diacrylate and dimethacrylate crosslinkers based on C18 diacid

A series of new di(meth)acrylate monomers was synthesized from the reactions of methyl α-hydroxymethylacrylate (MHMA), ethyl α-hydroxymethylacrylate (EHMA), hydroxyethyl acrylate (HEA) and hydroxyethylmethacrylate (HEMA) with α,ω-C18 diacid chloride. The photopolymerization behavior and reaction kinetics of the synthesized monomers were investigated using photoinitiation with differential scanning calorimetry. The polymerization rates, conversions and kinetic constants for propagation and termination were determined for each of the monomers. The maximum rate of polymerizations of the diacrylate monomers was higher than that of the dimethacrylate monomers and followed the order: HDDA (1,6-hexanediol diacrylate)>HEA-C18>EHMA-C18∼HEMA-C18>MHMA-C18. The total conversions obtained were 78, 75, 72, 64 and 69% for MHMA-C18, EHMA-C18, HEMA-C18, HEA-C18 and HDDA, respectively, indicating comparable or higher conversions for methacrylates despite their lower rates of polymerization. Propagation and termination mechanisms of the monomers were investigated by plotting propagation and termination rate constants as a function of conversion.     

Influence of coating system composition on moisture dynamic performance of coated wood

Model coatings with known composition were assessed for liquid water permeability both as single coat systems and combined as primers and topcoats to form regularly used coating systems—in total 38 different systems. The water permeability of the coatings, expressed as water absorption value, was measured by a method similar to the method that now is proposed as a European standard for the assessment of liquid water permeability. During artificial weathering, the samples were measured for a water absorption value, thus showing the change in water permeability as a function of weathering. The study has shown that an excess of surfactants in the alkyd emulsions has a negative effect on the coating’s ability to exclude water from the test samples. A waterborne acrylic paint based on a dispersion of larger particle size (0.4 μm) showed a poor ability to exclude water compared to a similar paint based on smaller dispersion particles (0.1 μm). The alkyd emulsion paints, as single coats, showed high water absorption values compared to solventborne paints and acrylic paints. P.O. Box 5609, SE 114 86 Stockholm, Sweden     

Synthesis and antimicrobial activities of new water‐soluble bis‐quaternary ammonium methacrylate polymers

New methacrylate monomers containing pendant quaternary ammonium moieties based on 1,4‐diazabicyclo‐[2.2.2]‐octane (DABCO) were synthesized. The DABCO group contains either a butyl or a hexyl pendant group comprising the hydrophobic segment of the monomers and one tether group to the methacrylate moiety. The monomers were homopolymerized in water by using 2,2′‐azobis(2‐methylpropionamide) dihydrochloride (V‐50) as an initiator. The monomers and polymers were characterized by elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), FTIR, and ¹³C‐NMR. The antimicrobial activities of the corresponding small molecules (bis‐quaternary ammonium monocarboxylates) and polymers were investigated against Staphylococcus aureus and Escherichia coli. Although the small molecules did not show any antimicrobial activity, the polymers were moderately effective against both Gram‐positive and Gram‐negative bacteria. The minimum inhibitory concentration (MIC) values of the polymers with butyl and hexyl hydrocarbon chains against S. aureus and E. coli were found to be 250 and 62.5 μg/mL, respectively. The minimum bactericidal concentration (MBC) value for the polymer with the butyl group was higher than 1 mg/mL, whereas the MBC value for the polymer with hexyl group was found to be 62.5 μg/mL. Thus, an increase of the alkyl chain length from 4 to 6 significantly increased the antimicrobial activity of the polymer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 635–642, 2004     

Visualisierung der Partikelbewegung in einem Abweiseradsichter

In spite of its great importance for the dry classification of fine powders, the processes in deflector wheel classifiers are to a large extent unknown. Therefore, in the present work a commercial available classifier was modified to gain an optical access to the deflector wheel. For the first time, the obtained photographs enable an observation of the gas flow and the particle motion between the blades of the deflector wheel. Especially the importance of particle‐particle‐ and particle‐blade‐collisions could be shown.     

Metal Organic Frameworks for Natural Gas Storage in Vehicles

With the increasing demand for alternative fuels the storage of natural gas (NG) in adsorbents like metal organic frameworks (MOFs) will become more important. In order to use MOFs as storage media in fuel delivery systems, the optimization of mass and energy transfer of the system is crucial. For rapid NG filling of a tank, molecules need to reach the adsorption sites within a reasonable time while the heat of adsorption should be dissipated to the environment. In this article, mass transfer in shaped bodies of MOFs was determined by permeability measurements and pulsed field gradient (PFG) NMR spectroscopy. The heat dissipation was also experimentally measured and both data sets were used to set up a theoretical density function theory model to predict the behavior of MOFs for NG storage.     

Grafting of titanium dioxide microspheres with a temperature‐responsive polymer via surface‐initiated atom transfer radical polymerization without the use of silane coupling agents

Titania microspheres with narrow size distribution and diameters of about 1 µm were prepared and subsequently functionalized using surface‐initiated atom transfer radical polymerization (ATRP) of N‐isopropylacrylamide. The ATRP initiator was immobilized on the particle surface via acylation of surface hydroxyl groups with α‐bromoisobutyryl bromide. Subsequently, an established ATRP reaction system was used for the preparation of titania surface‐grafted poly(N‐isopropylacrylamide) (PNiPAAm). Characterization was performed with electron microscopies, X‐ray diffraction, infrared spectroscopy and dynamic light scattering. It was found that the particle size in aqueous dispersions changed reversibly with temperature as expected for a shell of PNiPAAm, a polymer with a lower critical solution temperature at 32 °C. This confirmed the successful preparation of functional, stimuli‐responsive TiO₂ microparticles via a straightforward controlled surface‐initiated polymerization method.