Establishment of the volatile profile of ‘Bravo de Esmolfe’ apple variety and identification of varietal markers

The volatile composition of ‘Bravo de Esmolfe’ (BE) apple was achieved by headspace-solid phase microextraction (HS-SPME) followed by gas chromatography–mass spectrometry (GC–qMS) analysis using fruits from two different rootstocks (PAJAM2 and MM106), different trees of each rootstock, and different sections of each tree (north and south). Fruits were harvested in the maturity state defined for this variety and then stored for four months at 4 °C. During this period, analyses were made monthly. α-Farnesene was the compound found in the volatile profile of BE apple with the largest GC area. A large number of esters were also detected. Rootstocks, trees, and tree sections did not have statistical significance on the volatile composition of BE apples. However, the volatile composition changed throughout the storage period. The principal component analysis (PCA) allowed distinguishing between the apples obtained immediately after harvest and those stored for 4 months. In the first case, the volatile composition was related to the occurrence of aldehydes, aromatic hydrocarbons, and phenols and, in the second case, to esters and terpenoids. Ocymene, cymene, α-bergamotene, geranyl acetone, nerolidol, and ethyl 3-(methylthio)-propionate were identified for the first time in apples. This peculiar profile allows to propose them as varietal markers of BE apple variety. However, as this methodology has only been applied to BE apple, the occurrence of these compounds in other cultivars can not be excluded.     

Temperature and water activity effects on growth and temporal deoxynivalenol production by two Argentinean strains of Fusarium graminearum on irradiated wheat grain

The ability of six strains of Pichia anomala, four strains of Pichia kluyveri and two strains of Hanseniaspora uvarum predominant during coffee processing to produce polygalacturonase (PG), pectin esterase (PE) and pectin lyase (PL) in yeast polygalacturonic acid medium (YPA) and in coffee broth (CB) was studied. For comparison, a reference strain of Kluyveromyces marxianus CCT 3172 isolated from cocoa and reported to produce high amount of PG was included.

Initial screening of PG activity using YPA medium showed that K. marxianus CCT 3172, P. anomala S16 and P. kluyveri S13Y4 had the strongest activity. Enzymatic assays showed that the four yeast species secreted PG, but none of the yeasts investigated was found to produce PE or PL. P. anomala S16 and P. kluyveri S13Y4 were found to produce higher amounts of PG when grown in CB than in YPA. When K. marxianus CCT 3172, P. anomala S16 and P. kluyveri S13Y4 were grown in YPA broth adjusted to pH of 3.0–8.0 and incubated at temperatures of 15–40 °C, the three yeast species secreted the highest amount of PG at pH 6.0 and at 30 °C. For PG secreted by K. marxianus CCT 3172 and P. anomala S16, the optimum pH and temperature for the enzymatic activity were 5.5 and 40 °C, respectively. On the other hand, PG produced by P. kluyveri S13Y4 showed the highest activity at pH 5.0 and 50 °C.

Significant differences in the extracellular activity of PG were found between the yeasts species as well as between strains within same species. High amounts of PG were produced by two strains of P. anomala and P. kluyveri. It is therefore likely that strains of those two species may be involved in the degradation of pectin during coffee fermentation.     

Isolation of alpaca anti-hapten heavy chain single domain antibodies for development of sensitive immunoassay

Some unique subclasses of Camelidae antibodies are devoid of the light chain, and the antigen binding site is comprised exclusively of the variable domain of the heavy chain (VHH). Although conventional antibodies dominate current assay development, recombinant VHHs have a high potential as alternative reagents for the next generation of immunoassay. We expressed VHHs from an immunized alpaca and developed a VHH-based immunoassay using 3-phenoxybenzoic acid (3-PBA), a major metabolite of pyrethroid insecticides as a model system. A phage VHH library was constructed, and seven VHH clones were selected by competitive binding with 3-PBA. The best immunoassay developed with one of these VHHs showed an IC(50) of 1.4 ng/mL (limit of detection (LOD) = 0.1 ng/mL). These parameters were further improved by using the phage borne VHH, IC(50) = 0.1 ng/mL and LOD = 0.01 ng/mL. Both assays showed a similar tolerance to methanol and dimethylsulfoxide up to 50% in assay buffer. The assay was highly specific to 3-PBA and its 4-hydroxylated derivative, 4-hydroxy 3-PBA, (150% cross reactivity) with negligible cross reactivity with other tested structural analogues, and the recovery from spiked urine sample ranged from 80 to 112%. In conclusion, a highly specific and sensitive VHH for 3-PBA was developed using sequences from immunized alpaca and phage display technology for antibody selection.     

Uniform and position-controlled InAs nanowires on 2" Si substrates for transistor applications

This study presents a novel approach for indirect integration of InAs nanowires on 2' Si substrates. We have investigated and developed epitaxial growth of InAs nanowires on 2' Si substrates via the introduction of a thin yet high-quality InAs epitaxial layer grown by metalorganic vapor phase epitaxy. We demonstrate well-aligned nanowire growth including precise position and diameter control across the full wafer using very thin epitaxial layers (<300 nm). Statistical analysis results performed on the grown nanowires across the 2' wafer size verifies our full control on the grown nanowire with 100% growth yield. From the crystallographic viewpoint, these InAs nanowires are predominantly of wurtzite structure. Furthermore, we show one possible device application of the aforementioned structure in vertical wrap-gated field-effect transistor geometry. The vertically aligned InAs nanowires are utilized as transistor channels and the InAs epitaxial layer is employed as the source contact. A high uniformity of the device characteristics for numerous transistors is further presented and RF characterization of these devices demonstrates an f(t) of 9.8 GHz.     

Estimation of the risk for early thermal cracking for SCC containing fly ash

Cracking of concrete must be avoided during the hardening phase in order to minimize the risk of durability problems in the future, such as corrosion of the reinforcement, water tightness and damages due to frost. Estimation of the risk of early age cracking requires knowledge of the combined effects from temperature development and mechanical behaviour during the hydration. In the present paper, the influence of fly ash on the young concrete behaviour has been investigated. The concrete is based on a Swedish cement aimed for civil engineering structures, and the fly ash is of class F. A comparison of crack risks between concrete containing fly ash in different amounts with concrete without fly ash is presented. Also a previously tested concrete containing limestone filler is considered. The fly ash was added to replace a part of the aggregate, which gives a higher heat evolution. However, a numerical stress analysis showed that the risk for early age through cracking for a typical civil engineering structure is significantly decreased in the mixes containing fly ash. The denotation typical civil engineering structure is used here for concrete structures such as tunnels, bridges, and ramps of common cross-section dimensions. In the case of fly ash added to concrete by a partial replacement of cement, the crack risk will probably be further decreased. For a self-balancing structure of young concrete there is no restraint from adjacent structures, and the temperature and moisture gradients within the young concrete cause self-stresses governed by equilibrium with zero external forces for any cut. The estimated risk for surface cracking on a self-balancing wall or slab was not improved by an addition of fly ash. It is probably an effect of the increased heat development, which most likely counteracts the positive effect of the increased early age creep for concrete containing fly ash. If the heat evolution decreases when cement is partly replaced with fly ash, the use of fly ash might reduce the risk of surface cracks.     

A corrosion study of nanocrystalline copper thin films

Thin nanocrystalline, compact films, based on the copper–nitrogen system, up to 2.5 μm thickness and 3.5% nitrogen, were deposited by magnetron sputtering at different partial pressure ratios of N₂ and Ar, without formation of Cu_xN compounds, the nitrogen concentration influencing grain size (down to 30 nm) and film homogeneity. Electrochemical corrosion properties were investigated using polarization curves and electrochemical impedance spectroscopy in 0.5 M NaCl aqueous solution, and compared with pure bulk copper; morphology was examined by scanning electron microscopy. Significant variations in corrosion currents between samples were attributed to grain size and structural defects on the grain boundaries.     

NiCrSiBC alloy: microstructure and hardness of coatings processed by arc and laser

The processing technique is decisive for the characteristics of a coating. This is because the heat supply, which depends on the technique and on the parameters, has an influence on the dilution and the solidification rate. In alloys with low metallurgical complexity, the effect of processing with deposition techniques that give a higher cooling rate may be translated into refining of the microstructure. A more refined microstructure is expected to result in higher mechanical strength of the coating. However, in the deposition of alloys that are more complex metallurgically this does not always occur, because the high cooling rate may suppress formation/precipitation of phases responsible for strength. The influence of processing on the microstructure and hardness of coatings of alloy Colmonoy-6^® was assessed in this study. The alloy was processed by plasma transferred arc and high-power diode laser on plates of AISI 304 with two levels of dilution. In both cases, good-quality, defect-free coatings were obtained. Increase in Fe content (dilution) and different cooling rates result from processing with different parameters and techniques. This leads to significant changes in microstructure and hardness of the coatings, associated with the distribution, morphology and chemical composition of the carbides and particularly of the borides.     

Reaction zone formed during diffusion bonding of TiNi to Ti6Al4V using Ni/Ti nanolayers

This study investigated the interfacial structure of solid state diffusion bonding of TiNi to Ti6Al4V using reactive Ni/Ti multilayer thin films. The TiNi and Ti6Al4V surfaces were modified by sputtering, by deposition of alternated Ni and Ti nanolayers, to increase the diffusivity at the interface. Bonding experiments were performed at 750, 800 and 900 °C at a pressure of 10 MPa with a dwell time of 60 min. The reaction zone was characterized by high-resolution scanning and transmission electron microscopy. Joints free from porosity and cracks were produced with Ni/Ti reactive multilayer thin films. Several phases formed at the interface, ensuring the bonding of these alloys. The reaction zone was constituted by columnar grains of Ti₂Ni and AlNi₂Ti, close to the Ti6Al4V base material, and by alternate layers of Ti₂Ni and TiNi equiaxed grains. The grain size decreased from Ti6Al4V to TiNi base materials. Nanometric grains were observed in the layers closest to the TiNi base material.     

Discovery of novel non-cyclam polynitrogenated CXCR4 coreceptor inhibitors

HIV cell fusion and entry have been validated as targets for therapeutic intervention against infection. Bicyclams were the first low-molecular-weight compounds to show specific interaction with CXCR4. The most potent bicyclam was AMD3100, in which the two cyclam moieties are tethered by a 1,4-phenylenebis(methylene) bridge. It was withdrawn from clinical trials owing to its lack of oral bioavailability and cardiotoxicity. We have designed a combinatorial library of non-cyclam polynitrogenated compounds by preserving the main features of AMD3100. At least two nitrogen atoms on each side of the p-phenylene moiety, one in the benzylic position and the other(s) in the heterocyclic system were maintained, and the distances between them were similar to the nitrogen atom distances in cyclam. A selection of diverse compounds from this library were prepared, and their in vitro activity was tested in cell cultures against HIV strains. This led to the identification of novel potent CXCR4 coreceptor inhibitors without cytotoxicity at the tested concentrations.     

The corrin moiety of coenzyme B12 is the determinant for switching the btuB riboswitch of E. coli

Riboswitches are regulatory elements in the 5'-untranslated region (5'-UTR) of bacterial mRNAs that bind certain metabolites with high specificity and affinity. The 202 nucleotide (nt)-long btuB riboswitch RNA of E. coli interacts specifically with coenzyme B12 and its derivatives thereby leading to changes in the RNA structure and hence to an altered expression of the downstream btuB gene. We report the investigations of the rearrangement of the three-dimensional structure of the btuB riboswitch upon binding to four different B12 derivatives: coenzyme B12, vitamin B12, adenosyl factor A and adenosyl-cobinamide. In-line probing experiments have shown that the corrin ring plays the crucial role in switching the three-dimensional riboswitch structure. Instead, the apical ligands influence only the binding affinity of the B12 derivative to the btuB riboswitch.