Economic advantages of using bacterial biopreparations in agricultural crops

The ecological, genetic, biological approach proposed by agricultural specialists in order to protect plants and crops has a role in reducing the impact of pests through the process of selection and improvement of genetic resources in the processes of planting, development and introduction of biological means to combat pests in agricultural ecosystems. The strategies proposed by the specialists in the agricultural field aim not at the total extermination of the pests from the agricultural crops but at keeping the pest populations at the optimal damage threshold. The most important advantages of these biological processes are those of the evolutionary stability of the crop systems, the ecological stabilization of the pest and crop populations as well as the assurance of a superior quality of the resulting agricultural products.The present paper aims to present the main advantages of using bacterial biopreparations in agricultural ecosystems (research conducted in agricultural research stations in Romania), reducing soil pollution, environmental crops, use of alternative fertilization and cultivation technologies as well as obtaining additional, ecological productions.The aim of this paper is to present the economic advantages of using bacterial biopreparations in agricultural research and development stations, reducing costs in agriculture and the processes that these bacterial biopreparations have on the agricultural ecosystem, the environment and humans and animals

Remote activation by green-light irradiation of shape memory epoxies containing gold nanoparticles

Shape memory epoxies (SMEs) that can be remotely activated by the use of green light, are described. An epoxy matrix based on on diglycidylether of bisphenol A (DGEBA cured with a mixture of n-dodecylamine (DA) and m-xylylenediamine (MXDA), exhibits excellent shape memory properties as described in a previous paper (Leonardi et al., 2011). Au NPs with an average diameter close to 5 nm could be uniformly dispersed in this matrix using poly(ethylene oxide) (PEO) chains as stabilizer. These NPs showed a significant photothermal effect even at very low concentrations (0.01 wt% as metallic gold), when irradiated with a 532 nm laser at a power close to 2 W/cm2. Under these conditions, a bended bar (1.4-mm thickness) recovered its initial shape in a few seconds. This formulation may be used to build up devices with the necessary mechanical strength and with the possibility to produce shape recovery by remote activation using green light. A second example was analyzed employing an amphiphilic epoxy matrix to produce a uniform dispersion of Au NPs stabilized with dodecyl chains (average diameter close to 3 nm). A bar (1.4-mm thickness) of the SME with 0.04 wt% Au NPs (as metallic gold) showed a fast recovery of its initial shape by irradiation with a 532 nm laser at a power close to 2 W/cm2. This example shows the feasibility of adapting the epoxy chemistry to disperse Au NPs stabilized with different ligands and obtained through robust synthetic methods.Fil: Leonardi, Agustina Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Puig, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Antonacci, Julian. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Arenas, Gustavo Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Zucchi, Ileana Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Hoppe, Cristina Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Reven, Linda. McGill University; CanadáFil: Zhu, Liu. Peking University Shenzhen Graduate School; ChinaFil: Toader, Violeta. McGill University; CanadáFil: Williams, Roberto Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Reprogramming the assembly of unmodified DNA with a small molecule

The ability of DNA to store and encode information arises from base pairing of the four-letter nucleobase code to form a double helix. Expanding this DNA ‘alphabet’ by synthetic incorporation of new bases can introduce new functionalities and enable the formation of novel nucleic acid structures. However, reprogramming the self-assembly of existing nucleobases presents an alternative route to expand the structural space and functionality of nucleic acids. Here we report the discovery that a small molecule, cyanuric acid, with three thymine-like faces reprogrammes the assembly of unmodified poly(adenine) (poly(A)) into stable, long and abundant fibres with a unique internal structure. Poly(A) DNA, RNA and peptide nucleic acid all form these assemblies. Our studies are consistent with the association of adenine and cyanuric acid units into a hexameric rosette, which brings together poly(A) triplexes with a subsequent cooperative polymerization. Fundamentally, this study shows that small hydrogen-bonding molecules can be used to induce the assembly of nucleic acids in water, which leads to new structures from inexpensive and readily available materials

INFLUENCE OF THE SIZE OF METHYLENE SPACERS ON THE THERMAL BEHAVIOR OF SEVERAL ALIPHATIC-AROMATIC POLYESTERS

Polyesters have a wide range of technical applications and therefore their processing is of the utmost importance. Since polyesters are usually processed by melting, their thermal stability is an extremely important characteristic for the exact determination of the operational parameters. The thermal analysis was carried out using a MOM-Budapest derivatograph at the 10 C/min heating speed, aluminum oxide the reference material, and the air conditions were static. The study lead to conclusions on the thermal stability and degradation mechanism depending on the number of methylene groups in the spacer. Thermal stability is supported by the increase in the number of methylene groups in the spacer. The degradation mechanism is complex through successive reactions. The spacer size influences the nature of the micromolecules formed by spacer fragmenting and by the number of carbon atoms, respectively

Microcantilevers Bend to the Pressure of Clustered Redox Centers

The redox-activated deflection of microcantilevers has attracted interest for nanoactuation and chemical sensing. Microcantilever sensors are devices that transduce (bio)­chemical reactions into a quantifiable nanomechanical motion via surface stress changes. Despite promising applications in analytical science, poor signal-to-noise ratios and a limited understanding of the molecular origins of the surface stress changes that cause the observed deflections remain obstacles to cantilever-based sensing becoming an established (bio)­detection method, such as surface plasmon resonance and electrochemistry. We use phase-separated, binary self-assembled monolayers (SAMs) of ferrocenyldodecanethiolate and <i>n</i>-undecanethiolate as a model system to study the effect of the steric crowding of the redox centers on the surface stress change and cantilever deflection produced by the electrochemical oxidation of the surface-tethered ferrocene to ferrocenium. We correlate the measured surface stress change to the fraction of the clustered ferrocenyldodecanethiolate phase in the binary SAMs. The pairing of anions with the sterically crowded clustered ferroceniums induces a collective molecular reorientation which drives the cantilever deflection. The results provide fundamental insights into the response mechanism of microcantilever-based actuating and sensing technologies

¹H Solid State NMR Study of Poly(methacrylic acid) Hydrogen-Bonded Complexes

The hydrogen bond structure of a series of poly­(methacrylic acid) (PMAA) complexes was studied by solid-state NMR. ¹³C and ²H labeled PMAA samples were complexed with poly­(ethylene oxide) (PEO), poly­(vinyl methyl ether) (PVME), poly­(acrylamide) (PAAM), poly­(vinyl caprolactam) (PVCL) and poly­(vinylpyrrolidone) (PVPon). The presence and relative strengths of PMAA’s hydrogen bonds with itself versus those with the complementary polymer was assessed by combining ¹³C CP-MAS NMR, ¹H–¹³C HETCOR, 1D and 2D DQ ¹H MAS NMR experiments. Analyses of ¹H DQ spinning sideband patterns gave estimates of the proton–proton distances. Only the polyether–PMAA complexes, PEO and PVME, show resolved ¹³C and ¹H resonances. This spectral resolution is proposed to be due to the selective disruption and stabilization of PMAA’s open and cyclic dimers, respectively. Residual PMAA dimers are detected by ¹H NMR for the polylactam complexes, PVCL and PVPon, but both types dimers are weakened, reflecting the greater amount of interpolymer linkages. The PAAM–PMAA complex maintains more of the weaker hydrogen bonds. The role of the different hydrogen bond structures in the relative stabilities and dynamic properties within this series of PMAA complexes and multilayers is assessed

Hydrogen-Bonded Liquid Crystal Nanocomposites

Nanoparticle-liquid crystal (NP-LC) composites based on hydrogen bonding were explored using a model system. The ligand shells of 3 nm diameter zirconium dioxide nanoparticles (ZrO₂ NPs) were varied to control their interaction with 4-<i>n</i>-hexylbenzoic acid (6BA). The miscibility and effect of the NPs on the nematic order as a function of particle concentration was characterized by polarized optical microscopy (POM), fluorescence microscopy and ²H NMR spectroscopy. Nonfunctionalized ZrO₂ NPs have the lowest miscibility and strongest effect on the LC matrix due to irreversible binding of 6BA to the NPs via a strong zirconium carboxylate bond. The ZrO₂ NPs were functionalized with 6-phosphonohexanoic acid (6PHA) or 4-(6-phosphonohexyloxy)­benzoic acid (6BPHA) which selectively bind to the ZrO₂ NP surface via the phosphonic acid groups. The miscibility was increased by controlling the concentration of the pendant CO₂H groups by adding hexylphosphonic acid (HPA) to act as a spacer group. Fluorescence microscopy of lanthanide doped ZrO₂ NPs showed no aggregates in the nematic phase below the NP concentration where aggregates are observed in the isotropic phase. The functionalized NPs preferably concentrate into LC defects and any remaining isotropic liquid but are still present throughout the nematic liquid at a lower concentration

¹³C MAS NMR Study of Poly(methacrylic acid)–Polyether Complexes and Multilayers

Hydrogen-bonded interpolymer complexes are widely used as stimuli-responsive materials. This solid-state ¹³C MAS NMR spectroscopy study examines the influence of water and temperature on the hydrogen bond structures of ¹³C-labeled poly­(methacrylic acid) (PMAA) complexes with poly­(ethylene oxide) (PEO) and poly­(vinyl methyl ether) (PVME). The spatial variation of the inter- and intrapolymer hydrogen bonds in the dried bulk complexes and supported multilayers was measured by 2D ¹³C exchange (EXSY) NMR. In contrast to earlier studies of PAA complexes, the cross-peak intensities of the PMAA complexes are primarily due to ¹³C spin exchange rather than H-bond exchange due to the use of ¹³C-labeled PMAA and slower dynamics. The ¹³C–¹³C spin diffusion between the carbonyl groups with intra- versus interpolymer hydrogen bonds indicates interatomic distances of <7 Å, consistent with interpolymer and the different intra-PMAA hydrogen bonds occurring together along the PMAA chain segments or in nanodomains in close proximity rather than isolated clusters. The fractional population involved in the spin diffusion corresponded to the population of the stronger cyclic dimer, such that PMAA–PEO complex > PVME complex > PEO supported multilayers > PVME supported multilayers. For the multilayer films, there are fewer of the stronger, more ordered cyclic dimer hydrogen bonds due to the disordering effect of the interfaces

The Role of Organic Linkers in Directing DNA Self-Assembly and Significantly Stabilizing DNA Duplexes

We show a simple method to control both the stability and the self-assembly behavior of DNA structures. By connecting two adjacent duplexes with small synthetic linkers, factors such as linker rigidity and DNA strand orientation can increase the thermal denaturation temperature of 17 base-pair duplexes by up to 10 °C, and significantly increase the cooperativity of melting of the two duplexes. The same DNA sequence can thus be tuned to melt at vastly different temperatures by selecting the linker structure and DNA-to-linker connectivity. In addition, a small rigid <i>m</i>-triphenylene linker directly affects the self-assembly product distribution. With this linker, changes in the orientation of the linked strands (e.g., 5′3′ vs 3′3′) can lead to dramatic changes in the self-assembly behavior, from the formation of cyclic dimer and tetramer to higher-order oligomers. These variations can be readily predicted using a simple strand-end alignment model

Micromechanical Redox Actuation by Self-Assembled Monolayers of Ferrocenylalkanethiolates: Evens Push More Than Odds

Microcantilever transducers can be valuable tools for the investigation of physico­chemical processes in organized molecular films. Gold-coated cantilevers are used here to investigate the electro­chemo­mechanics of redox-active self-assembled monolayers (SAMs) of ferrocenyl­alkane­thiolates (Fc­(CH₂)_<i>n</i>S) of different alkyl chain lengths. A significant odd–even effect is observed in the surface stress and cantilever movement generated by the oxidation of the SAM-confined ferrocenes as the number of methylene units <i>n</i> in the SAM backbone is varied. We demonstrate that stronger alkyl chain–chain interactions are at the origin of the larger surface stresses generated by SAMs with an even versus odd <i>n</i>. The findings highlight the impact of subtle structural effects and weak van der Waals interactions on the mechanical actuation produced by redox reactions in self-assembled systems