Gold-nanoparticle-cored Polyferrocenyl Dendrimers: Modes of Synthesis and Functions as Exoreceptors of Biologically Important Anions and Re-usable Redox Sensors

Polyamidoferrocenylalkylthiolate-Au nanoparticles (AuNP) and AuNP-cored polyferrocenyl dendrimers have been assembled either by the ligand-substitution method from dodecanethiolate-AuNP (AB₃ units) or Brust-type direct synthesis from a 1-1 mixture of dodecanethiol and dendronized thiol (AB₉ units). The AuNP-cored polyferrocenyl dendrimers are a new type of dendrimers with a AuNP core. AuNPs containing a nonasilylferrocenyl dendron have been synthesized; they bear respectively 180 and 360 ferrocenyl units at the periphery. These AuNPs selectively recognize the anions H₂PO₄^– and adenosine-5-triphosphate (ATP^2–) with a positive dendritic effect. Recognition is monitored by the appearance of a new wave at a less positive potential in cyclic voltammetry (CV). These AuNP-cored polyferrocenyl dendrimers can form robust modified electrodes that serve as re-usable sensors of ATP^2– by simple washing with CH₂Cl₂.     

Test-retest reproducibility of a food frequency questionnaire (FFQ) and estimated effects on disease risk in the Norwegian Women and Cancer Study (NOWAC)

Background  

The Norwegian Women and Cancer Study (NOWAC) is a national population-based cohort study with 102 443 women enrolled at age 30–70 y from 1991 to 1997. The present study was a methodological sub-study to assess the test-retest reproducibility of the NOWAC food frequency questionnaire (FFQ), and to study how measurement errors in the data can affect estimates of disease risk.     

Characterization of poly(isobornyl acrylate) as a construction material for microfluidic applications

Isobornyl acrylate (IBA) is a photopolymerizable monomer that is employed in microfluidic devices because of desirable properties, such as inertness, transparency, and resolution. However, some of the mechanical properties of poly(isobornyl acrylate) are greatly affected by subtle changes in the manufacturing techniques. In this study, the parameters of exposure time, UV intensity, and aging are varied to study their effect on the material properties of thin samples of isobornyl acrylate construction material (<0.25 mm). Mechanical testing was used to obtain properties, such as elasticity, maximum strength, and maximum strain. It was observed that when using high levels of both exposure time and intensity, the polymers strength was increased. Lowering one of these two parameters immediately reduced the construction materials strength. It was also noted that aging weakens the material in as little as 1 day. In addition, an anisotropic response that produces curling in samples has been studied. It showed to have a negligible effect on the mechanical properties of the material; however it may have a major effect on device quality and shelf‐life. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Translation project adaptation for MT-enhanced computer assisted translation

The effective integration of MT technology into computer-assisted translation tools is a challenging topic both for academic research and the translation industry. In particular, professional translators consider the ability of MT systems to adapt to the feedback provided by them to be crucial. In this paper, we propose an adaptation scheme to tune a statistical MT system to a translation project using small amounts of post-edited texts, like those generated by a single user in even just one day of work. The same scheme can be applied on a larger scale in order to focus general purpose models towards the specific domain of interest. We assess our method on two domains, namely information technology and legal, and four translation directions, from English to French, Italian, Spanish and German. The main outcome is that our adaptation strategy can be very effective provided that the seed data used for adaptation is ‘close enough’ to the remaining text to be translated; otherwise, MT quality neither improves nor worsens, thus showing the robustness of our method.     

One-step methodology for the synthesis of FA picolinyl esters from intact lipids

Picolinyl derivatives are used for structural determination of FA by GC-MS. Although they provide reliable diagnostic fragments, the usual multistep methodologies applied for their preparation require TAG hydrolysis or acid chloride formation prior to picolinyl synthesis. These reaction conditions may result in the presence of artifact molecules in the samples and thus compromise analytical quality and accuracy. To address these problems, a rapid, simple and quantitative methodology for the synthesis of FA picolinyl esters from intact lipids was developed. It involves their transesterification under basecatalyzed conditions using 3-potassiooxamethylpyridine in methylene chloride. The catalyst was prepared by proton exchange between potassium tert-butoxide and anhydrous 3-hydroxymethylpyridine. Mild reaction conditions allowed complete derivatization of TAG and phospholipids in 2 min at room temperature, and of FAME in 15 min at 45°C. The proposed procedure, which can be used on a routine basis, was applied to Ipomoae imperialis seed lipids and used to confirm occurrence of γ-linoleic acid at a level of 0.9%.     

Introducing semantic variables in mixed distance measures: Impact on hierarchical clustering

Today, it is well known that taking into account the semantic information available for categorical variables sensibly improves the meaningfulness of the final results of any analysis. The paper presents a generalization of mixed Gibert’s metrics, which originally handled numerical and categorical variables, to include also semantic variables. Semantic variables are defined as categorical variables related to a reference ontology (ontologies are formal structures to model semantic relationships between the concepts of a certain domain). The superconcept-based distance (SCD) is introduced to compare semantic variables taking into account the information provided by the reference ontology. A benchmark shows the good performance of SCD with respect to other proposals, taken from the literature, to compare semantic features. Mixed Gibert’s metrics is generalized incorporating SCD. Finally, two real applications based on touristic data show the impact of the generalized Gibert’s metrics in clustering procedures and, in consequence, the impact of taking into account the reference ontology in clustering. The main conclusion is that the reference ontology, when available, can sensibly improve the meaningfulness of the final clusters.     

Diagnosis of bubble distribution in a three-phase bubble column reactor for dehydration of ortho-boric acid

For the practical application of a three-phase bubble column as a reactor in the dehydration of ortho-boric acid, we investigated the bubble distribution and its effects on the reaction in a three-phase bubble column reactor (0.102 m IDx2.0 m in height) operating at relatively low pressure (below the atmospheric pressure). Effects of reaction time, temperature, gas velocity, particle size and gas injection mode (even, wall-side, central and asymmetric distribution) on the fractional conversion of the reaction were determined. The complicated bubble distribution as well as bubbling phenomena in the reactor were diagnosed and interpreted by means of the attractor trajectories and correlation dimension which were obtained from the resultant pressure fluctuations. The fractional conversion was closely related to the attractor shape or correlation dimension of the pressure fluctuations in the reactor. The fractional conversion in the case of even distribution of gas injection exhibited the highest value in all cases studied, at which the attractor of pressure fluctuations was less scattered in the phase space, while their correlation dimension had the lowest value. When the gas was injected by means of wall-side distribution, the conversion level was higher than that in case of central or asymmetric distribution mode. Although a fluid-solid heterogeneous reaction model can be applicable to the reaction, deviations from the model become considerable when the gas injection mode changes from even to wall-side, central or asymmetric mode, orderly.     

Automated parameter estimation of the Hodgkin-Huxley model using the differential evolution algorithm: application to neuromimetic analog integrated circuits

We propose a new estimation method for the characterization of the Hodgkin-Huxley formalism. This method is an alternative technique to the classical estimation methods associated with voltage clamp measurements. It uses voltage clamp type recordings, but is based on the differential evolution algorithm. The parameters of an ionic channel are estimated simultaneously, such that the usual approximations of classical methods are avoided and all the parameters of the model, including the time constant, can be correctly optimized. In a second step, this new estimation technique is applied to the automated tuning of neuromimetic analog integrated circuits designed by our research group. We present a tuning example of a fast spiking neuron, which reproduces the frequency-current characteristics of the reference data, as well as the membrane voltage behavior. The final goal of this tuning is to interconnect neuromimetic chips as neural networks, with specific cellular properties, for future theoretical studies in neuroscience.     

Kinetics of radical polymerization

Summary The effect of N-nitroso compounds on free radical polymerization has been studied in the temperature range of 30–70 °C. The comparison with the effect of C-nitroso compounds shows that not only the inhibitor effectivity but the inhibition mechanism are different in the case of N-nitroso compounds. The detailed kinetic investigations proved that the thermal dissociation product of N-nitroso compounds can act as scavengers of macroradicals.