Biosynthesis of Quantum Dots (CdTe) and its Effect on Eisenia fetida and Escherichia coli

Biosynthesis belongs to one of the new possibilities of nanoparticles preparation, whereas its main advantage is biocompatibility. In addition, the ability of obtaining the raw material for such synthesis from the soil environment is beneficial and could be useful for remediation. However, the knowledge of mechanisms that are necessary for the biosynthesis or effect on the bio-synthesizing organisms is still insufficient. In this study, we attempted to evaluate the effect of quantum dots (QDs) not only on a model organism of collembolans, but also on another soil organism—earthworm Eisenia fetida—and in also one widespread microorganism such as Escherichia coli. Primarily, we determined 28EC₅₀ as 72.4 μmol L⁻¹ for CdTe QDs in collembolans. Further, we studied the effect of QDs biosynthesis in E. fetida and E. coli. Using determination of QDs, low-molecular thiols and antioxidant activities, we found differences between both organisms and also between ways how they behave in the presence of Cd and/or Cd and Te. The biosynthesis in earthworms can be considered as its own protective mechanism; however, in E. coli, it is probably a by-product of protective mechanisms.

     

A mesoscopic thermomechanically coupled model for thin-film shape-memory alloys by dimension reduction and scale transition

We design a new mesoscopic thin-film model for shape-memory materials which takes into account thermomechanical effects. Starting from a microscopic thermodynamical bulk model, we guide the reader through a suitable dimension reduction procedure followed by a scale transition valid for specimen large in area up to a limiting model which describes microstructure by means of parametrized measures. All our models obey the second law of thermodynamics and possess suitable weak solutions. This is shown for the resulting thin-film models by making the procedure described above mathematically rigorous. The main emphasis is, thus, put on modeling and mathematical treatment of joint interactions of mechanical and thermal effects accompanying phase transitions and on reduction in specimen dimensions and transition of material scales.     

Completion of quasi-topological groups

A topology of a quasi-topological group is induced by several natural semi-uniformities, namely right, left, two-sided and Roelcke semi-uniformities. A quasi-topological group is called complete if every Cauchy (in some sense—we examine several generalizations of Cauchy properties) filter on the two-sided semi-uniformity converges.We use the theory of Hausdorff complete semi-uniform spaces, see [B. Batíková, Completion of semi-uniform spaces, Appl. Categor. Struct. 15 (2007) 483-491], and show that Hausdorff complete quasi-topological groups form an epireflective subcategory of Hausdorff quasi-topological groups. But the reflection arrows need not be embeddings.For several types of Cauchy-like properties we show examples of quasi-topological groups that cannot be embedded into a complete group.     

A thermodynamically consistent model of shape-memory alloys

This contribution presents a non-isothermal mesoscopic model of single-crystalline shape-memory alloys within the framework of continuum mechanics. We briefly recall static mesoscopic modeling concepts as presented in e.g. [4, 5] and propose a thermomechanically consistent model featuring the heat equation and thermo-mechanical coupling. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Comprehensive two-dimensional liquid chromatography-time-of-flight mass spectrometry in the analysis of acidic compounds in atmospheric aerosols

A novel method utilising comprehensive two-dimensional liquid chromatography interfaced to electrospray ionisation time-of-flight mass spectrometry was developed for the determination of organic acids in atmospheric aerosols. The system was applied to the analysis of methanolic extracts of filters from a high volume sampler. The enhanced separation power of two-dimensional separation was demonstrated in the analysis of both rural and urban samples. Quantification was performed for compounds for which standards were available. Limit of detection was 2-200ng/ml. Average reproducibility of retention times in each dimensions was 0.1%, and average reproducibility of peak areas was 8% (10mug/ml, n=3).     

Amphiphilic conetworks. II. Novel two‐step synthesis of poly[2‐(dimethylamino)ethyl methacrylate]–polyisobutylene,poly(N‐isopropylacrylamide)–polyisobutylene,and poly(N,N‐dimethylacrylamide)–polyisobutylene hydrogels

Amphiphilic polymer conetworks consisting of hydrophilic poly[2‐(dimethylamino)ethyl methacrylate], poly(N‐isopropylacrylamide), or poly(N,N‐dimethylacrylamide) and hydrophobic polyisobutylene chains were synthesized with a novel two‐step procedure. In the first step, a methacrylate‐multifunctional polyisobutylene crosslinker was prepared by the cationic copolymerization of isobutylene with 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate. In the second step, the methacrylate‐multifunctional polyisobutylene crosslinker, with a number‐average molecular weight of 8200 and an average functionality of approximately 4 per chain, was copolymerized radically with 2‐(dimethylamino)ethyl methacrylate, N‐isopropylacrylamide, or N,N‐dimethylacrylamide into transparent amphiphilic conetworks containing 42–47 mol % hydrophilic monomer. The synthesized conetworks were characterized with solid‐state ¹³C NMR spectroscopy and differential scanning calorimetry. The amphiphilic nature of the conetworks was proved by swelling in both water and n‐heptane. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6378–6384, 2006     

Direct carbamation of cellulose fiber sheets

The paper is on introducing carbamate groups in sheets of cellulose fiber assemblies by pad-dry-cure treatments with aqueous solutions of polyethylene glycol, amide and salt. The effects of process variables—on carbamation levels and on mechanical properties of the substrate—are reported. Depending on treatment conditions, the nitrogen contents in substrates are in the range 0.668–2.252 wt%, corresponding to nominal degrees of carbamate group substitution of 0.08–0.28. The carbamation is initiated at 140 °C curing, and the levels rise with temperature up to 220 °C, but decrease at higher temperatures. The duration of curing also exerts an influence. There is a catalytic effect of sodium acetate on the carbamation, but the salt also induces a brown coloration in samples, which is likely a result of Maillard-type reactions. The treatments cause hydrolytic degradation in substrates, but there are options to adjust treatment conditions and minimize damage. Pad-dry-cure treatments are a common operation in the textile and paper industries, and the process may be adopted in commercial-scale operations to create derivatized paper or fabrics (woven, knitted or non-woven) for utilization in applications such as adsorbents for heavy metals from waste water, in hygiene products, in the creation of flame retardant products, or in creating all-cellulose composites by further treatment with alkali.