Effect of Additives on UV-Activated Urethane Acrylate Polymerization Composite Coatings

An increased demand for new and improved coating systems, for environmental & health & safety and performance reasons, have appeared during the recent decades. Currently, there is new interest in preparation of thin UV curable urethane acrylate (UA) composite coatings with short-term properties. Cellulose based additives: nitrocellulose, cellulose acetate butyrate, sucrose benzoate and silica were evaluated to determine their influence on unreacted composite characteristics (viscosity, pigment suspension stability) and characteristics of cured film (ultimate tensile strength, elongation at break, surface gloss, surface scratch resistance and film adhesion loss time). The most suitable additive content was found to provide required viscosity. All additives increase surface scratch resistance, but cellulose based additives increase surface gloss values and decrease the time of adhesion loss. Silica has great effect on the interaction between linear and hyperbranched urethane acrylates, which has crucial influence on the stability of uncured pigmented mixture samples

Discovery of enzymes for toluene synthesis from anoxic microbial communities

Microbial toluene biosynthesis was reported in anoxic lake sediments more than three decades ago, but the enzyme catalyzing this biochemically challenging reaction has never been identified. Here we report the toluene-producing enzyme PhdB, a glycyl radical enzyme of bacterial origin that catalyzes phenylacetate decarboxylation, and its cognate activating enzyme PhdA, a radical S-adenosylmethionine enzyme, discovered in two distinct anoxic microbial communities that produce toluene. The unconventional process of enzyme discovery from a complex microbial community (>300,000 genes), rather than from a microbial isolate, involved metagenomics- and metaproteomics-enabled biochemistry, as well as in vitro confirmation of activity with recombinant enzymes. This work expands the known catalytic range of glycyl radical enzymes (only seven reaction types had been characterized previously) and aromatic-hydrocarbon-producing enzymes, and will enable first-time biochemical synthesis of an aromatic fuel hydrocarbon from renewable resources, such as lignocellulosic biomass, rather than from petroleum

Practical aspects in the relocation of Hermit beetle Osmoderma barnabita miropopulations in Latvia

Hermit beetle Osmoderma barnabita is a species of beetle protected in Latvia and Europe. In accordance with the data of the report to the European Commission on the situation of habitat and species protection in Latvia for 2007–2012 (Article 17 report), the population size of the Hermit beetle Osmoderma barnabita protected both in Latvia and Europe is estimated at 350–1000 localities. Specially Protected Nature Territories (hereinafter – SPNT) with Natura 2000 site status contain 71 (41 %) of population, while 103 (59 %) of population are situated outside these sites. A considerable portion of Latvia’s population inhabits parks, avenues and other plantations of residential areas, where the hollow trees are felled and removed more and more frequently. The objective of the article is to publish the experience of the research on dead trees inhabited by Osmoderma barnabita accumulated to date, methodological aspects of population relocation, as well as to provide recommendations for further research and micropopulation relocation work. The research of the trunks of broken or felled trees by dividing them into shorter spans, sieving the rotten wood, describing the structure of the hollows and counting the detected specimens of Osmoderma barnabita, was used as the main research method. Varying quantities of dead wood and numbers of Osmoderma barnabita (1–83 specimens) and Liocola lugubris (6–55 specimens) have been detected in the five examined trees. In two cases it was detected that in the time period from the felling of the tree until examination (20–40 days) the number of larvae present in the wood was reduced. The hypothesis was proposed that the internal surface area of the hollow of the tree is a significant factor that determines the number of Osmoderma barnabita specimens in the hollow. European Commission. 2013. Reporting under Article 17 of the Habitats Directive (period 2007–2012). Introduction to assessment of conservation status of habitats and species of Community interest. http://bd.eionet.europa.eu/activities/Reporting/Article_17 (Accessed 31.01.2018.)peerReviewe

Petijumi polimeru kompozitmaterialu kimija un tehnologija

In 2 partsAvailable from Latvian Academic Library / LAL - Latvian Academic LibrarySIGLELVLatvi

Characterization of cryogenically slightly crosslinked biomedical poly(vinyl alcohol) gels

Abstract. Poly(vinyl alcohol) gels, prepared by the freezing/thawing technique, were studied. Poly(vinyl alcohol) water solutions were exposed to 1-3 subsequent cycles of freezing (12 h at -20 °C) followed by thawing (12 h at 20 °C). Water content (weight and volume fraction) and degree of swelling α at the equilibrium state were determined. Average molecular weights of polymer chains between crosslinks M C (using the Flory-Rehner approach) were calculated. Values of α and M C considerably decrease with the growth of the number of freezing/thawing cycles n C . The modulus of elasticity E, tensile strength σ B , and elongation at brake ε B were determined from experimental stress-strain relationships of swollen gels. The E and σ B and values considerably increase with n C : up to 6-8 times for E and almost by an order for tensile strength σ B . More concentrated water solutions provide almost two times greater E and σ B values. Strengthdeformation characteristics for gels prepared at n C = 2-3 are acceptable for their application in potential drug delivery systems. To assess the stability of crosslinked structures, gels were subjected to subsequent drying (at 25, 60, and 105 °C) and water sorption (at 25 °C) cycles. Reduction of the swelling degree and respective calculated M C values as well as lessening of the initial rate of water sorption after each drying cycle indicate the formation of additional crosslinks

Diastereoselective Hydroxymethylation of Cyclic N-tert-Butanesulfinylketimines Using Methoxymethanol as Formaldehyde Source

A stable and easy-to-handle source of anhydrous monomeric formaldehyde is used

TitleThe First Step Towards Generic Modelling Tool

Abstract: The foundation of a generic modelling tool is its flexible diagramming facility. The paper proposes a universal graphical editor definition language based on logical metamodel extended by presentation classes. Some more advanced diagram definition facilities such as patterns and diagram cores are also introduced. Implementation principles of this language, based on Graphical Diagramming Engine are briefly described. Key words: modelling tool, graphical editor, metamodel, editor definition language 1

Diastereoselective Hydroxymethylation of Cyclic <i>N</i>-<i>tert</i>-Butanesulfinylketimines Using Methoxymethanol as Formaldehyde Source

Hydroxymethylation of cyclic <i>tert</i>-butanesulfinylketimine-derived lithium enamides with methoxymethanol proceeds with excellent diastereoselectivity (99:1 dr). Methoxymethanol is a stable and easy-to-handle source of anhydrous monomeric formaldehyde in the reaction with lithium enamides. Cyclic α-hydroxymethyl ketimines undergo highly diastereoselective reduction to <i>syn</i>- or <i>anti</i>-1,3-amino alcohols

Diastereoselective Hydroxymethylation of Cyclic <i>N</i>-<i>tert</i>-Butanesulfinylketimines Using Methoxymethanol as Formaldehyde Source

Hydroxymethylation of cyclic <i>tert</i>-butanesulfinylketimine-derived lithium enamides with methoxymethanol proceeds with excellent diastereoselectivity (99:1 dr). Methoxymethanol is a stable and easy-to-handle source of anhydrous monomeric formaldehyde in the reaction with lithium enamides. Cyclic α-hydroxymethyl ketimines undergo highly diastereoselective reduction to <i>syn</i>- or <i>anti</i>-1,3-amino alcohols

Zero Emission and Bio-refineries for Natural Fibres, Biomaterials and Energy: Genesis of Concepts. Review

Depletion of world recourses, increasing pollution, and climate change make us to shift from linear economy to system economy-an economy of technologies integrated to reach a system of non-pollution zero emission production. Transition to renewable resources requires replacing the present crude oil refinery by biomass refinery. Along with conventional biomass refinery technologies bioengineering and nano-technologies become significant players in systems designed as clusters of integrated bio-refinery technologies. The authors consider a number of case studies of biomass conversion into value-added shemicals and courses of energy, the steam explosion auto-hydrolysis (SEA) in particulars. Research of wood and non-wood (hemp,etc.) fibres demonstrates feasibility, for example, of value added textiles, self-binding bio-composite boards, heat insulation micro- and nano-materials. Serious breakthroughts require revision of the structures of fundamental natural macromolecules, particularly the complexity, scaning and fractality of lignin