Joule heating effects in optimized insulator‐based dielectrophoretic devices: An interplay between post geometry and temperature rise

Insulator‐based dielectrophoresis (iDEP) is the electrokinetic migration of polarized particles when subjected to a non‐uniform electric field generated by the inclusion of insulating structures between two remote electrodes. Electrode spacing is considerable in iDEP systems when compared to electrode‐based DEP systems, therefore, iDEP systems require high voltages to achieve efficient particle manipulation. A consequence of this is the temperature increase within the channel due to Joule heating effects, which, in some cases, can be detrimental when manipulating biological samples. This work presents an experimental and modeling study on the increase in temperature inside iDEP devices. For this, we studied seven distinct channel designs that mainly differ from each other in their post array characteristics: post shape, post size and spacing between posts. Experimental results obtained using a custom‐built copper Resistance Temperature Detector, based on resistance changes, show that the influence of the insulators produces a difference in temperature rise of approximately 4°C between the designs studied. Furthermore, a 3D COMSOL model is also introduced to evaluate heat generation and dissipation, which is in good agreement with the experiments. The model allowed relating the difference in average temperature for the geometries under study to the electric resistance posed by the post array in each design.     

Insights on the cellulose pretreatment at room temperature by choline-chloride-based deep eutectic solvents: an atomistic study

Cellulose - The pretreatment or disruption of a cellulose I $$\beta $$ crystallite by four deep eutectic solvents (DES): choline-chloride ethylene glycol, choline-chloride oxalic acid,...     

Some Considerations on the <Emphasis Type="Italic">J</Emphasis>-Integral under Elastic-Plastic Conditions for Materials Obeying a Ramberg-Osgood Law

Among the approaches available for structural analysis, the J-integral has received an excellent feedback as a fracture parameter under elastic-plastic conditions. In the literature and dealing with the crack case, it is proposed to evaluate the J-integral as a sum of elastic and plastic contributions. However, some uncertainties arise when applying this method to a Ramberg-Osgood law, especially under large scale yielding conditions.The aim of the present paper is to discuss how the J-integral evaluation can be performed for elastic-plastic cracked components. Two different non-linear behaviours have been considered for the material: the Ramberg-Osgood law and power law. Numerical and finite element results from different approaches have been accurately compared, proving that the most appropriate way to evaluate the J-integral for a material obeying Ramberg-Osgood law is to perform two finite element analyses evaluating separately the elastic contribution (through a linear elastic analysis) and the plastic contribution (through a nonlinear analysis considering power law behaviour).     

Studies in the synthesis of a hexafluoropenicillamine

The known acid (F₃C)₂CC(NHCOPh)CO₂H was more fully characterized (the neutralization equivalent was one-fifth the molecular weight). Thioacetic acid did not react with it. Efforts to effect conjugate addition of $\text{α}$-toluenethiol led with piperidine only to intractable mixtures and with BF₃·Et₂O only to the thiol ester. Without catalyst, addition occurred but in the reverse sense to give 2-benzamido-2-benzylthio-3-trifluoromethyl-4,4,4-trifluorobutanoic acid. The latter was reduced by metals in liquid ammonia only to a red non-sulfur polymer but was reductively desulfurized by HBr/AcOH to 2-benzamido-3-trifluoromethyl-4,4,4-trifluorobutanoic acid (two crystalline forms).     

Regioselective one-pot synthesis of 9-alkyl-6-chloropyrido[3,2-e][1,2,4]triazolo[4,3-a]pyrazines. Reactivity of aliphatic and aromatic hydrazides

[reaction: see text] The one-pot synthesis of new 9-alkyl-6-chloropyrido[3,2-e][1,2,4]triazolo[4,3-a]pyrazines has been achieved. Hydrazides regioselectively reacted as nucleophiles with the 3-chloro substituent of 2,3-dichloropyrido[2,3-b]pyrazine. An intramolecular cyclization afforded the tricycle nonxanthine adenosine receptor antagonists.     

Cu(I)-catalyzed allylic amination of olefins

The copper(I) complex [Cu(CH₃CN)₄]PF₆ catalyzes the allylic amination of alkenes by aryl hydroxylamine in fair to moderate yields. Unsymmetrical alkenes react with high regioselectivity with N-functionalization occuring at the less substituted vinylic carbon. Trapping experiments indicate that free PhNO is not an intermediate in these reactions.     

Chemometric characterisation of Basque and French ciders according to their polyphenolic profiles

Polyphenolic compositions of Basque and French ciders were determined by HPLC-DAD following thiolysis, in order to characterise and differentiate these beverages and then develop a classification system capable of confirming the authenticities of both kinds of cider. A data set consisting of 165 cider samples and 27 measured features was evaluated using multivariate chemometric techniques, such as cluster analysis and principal component analysis, in order to perform a preliminary study of data structure. Supervised pattern recognition techniques such as linear discriminant analysis (LDA), K-nearest neighbours (KNN), soft independent modelling of class analogy (SIMCA), and multilayer feed-forward artificial neural networks (MLF-ANN) attained classification rules for the two categories using the chemical data, which produced satisfactory results. Authentication systems obtained by combining two of these techniques were proposed. We found that SIMCA and LDA or KNN models achieved 100% hit-rates, since LDA and KNN permit the detection of every Basque cider and SIMCA provides a model for Basque cider that excludes all French ciders. Polyphenolic profiles of the ciders provided enough information to be able to develop classification rules for identifying ciders according to their geographical origin (Basque or French regions). Chemical and organoleptic differences between these two types of cider are probably due to the original and distinctive cidermaking technologies used for their elaboration. Using polyphenic profiles, about 80% of French ciders could be distinguished according to their region of origin (Brittany or Normandy). Although their polyphenolic profiles did not provide enough information to achieve an authentication system for Breton and Norman ciders.Abbreviations AVI Avicularin - CQA Caffeoylquinic acid - CAF Caffeic acid - CAT (+)-catechin - CT-1, -2, -3 Unknown flavan-3-ols - DPn Average degree of polymerization of procyanidins - EC (–)-epicatechin - HCA-7 Ferulic acid - HCA-1, -2 ,-3, 4, -5, -6 Unknown hydroxycinnamic acids - HYP Hyperin - IQC Isoquercitrin - PC Total procyanidins - PCM p-Coumaric acid - PCQ p-Coumaroylquinic acid - PL Phloretin - PLG Phloridzin - PLXG phloretin-2-O-xyloglucoside - PPO Polyphenoloxidase - QCE Quercetin - QCI Quercitrin - RUT Rutin - CA Cluster analysis - KNN K-nearest neighbours - LDA Linear discriminant analysis - MLF-ANN Multilayer feed-forward-artificial neural network - PCA Principal component analysis - PC1 First principal component - PC2 Second principal component - PC3 Third principal component - RMSE Root medium square error - SD Standard deviation - SIMCA Soft independent modelling of class analogy - DAD Diode array detector - HPLC High Performance Liquid Chromatography - ND Not detected