Pool boiling heat transfer performance of Newtonian nanofluids

Experimental measurements were carried out on the boiling heat transfer characteristics of γ-Al₂O₃/water and SnO₂/water Newtonian nanofluids. Nanofluids are liquid suspensions containing nanoparticles with sizes smaller than 100 nm. In this research, suspensions with different concentrations of γ-Al₂O₃ and SnO₂ nanoparticles in water were studied under nucleate pool boiling heat transfer conditions. Results show that nanofluids possess noticeably higher boiling heat transfer coefficients than the base fluid. The boiling heat transfer coefficients depend on the type and concentration of nanoparticles.     

Simple Synthetic Routes to N-Heterocyclic Carbene Gold(I)–Aryl Complexes: Expanded Scope and Reactivity

The discovery of sustainable and scalable synthetic protocols leading to gold–aryl compounds bearing N-heterocyclic carbene (NHC) ligands sparked an investigation of their reactivity and potential utility as organometallic synthons. The use of a mild base and green solvents provide access to these compounds, starting from widely available boronic acids and various [Au(NHC)Cl] complexes, with reactions taking place under air, at room temperature and leading to high yields with unprecedented ease. One compound, (N,N′-bis[2,6-(di-isopropyl)phenyl]imidazol-2-ylidene)(4-methoxyphenyl)gold, ([Au(IPr)(4-MeOC₆H₄)]), was synthesized on a multigram scale and used to gauge the reactivity of this class of compounds towards C−H/N−H bonds and with various acids, revealing simple pathways to gold–based species that possess attractive properties as materials, reagents and/or catalysts.     

Sweeping process with regular and nonregular sets

Differential inclusions involving the normal cone to a moving set are investigated. A special attention is paid to the sweeping process associated with sets for which no regularity assumption is required.     

Broadening of the R(0) and P(2) lines in the CO fundamental by helium atoms from 300 K down to 12 K: Measurements and comparison with close-coupling calculations

We present measurements of He-broadening parameters for the R(0) and P(2) lines in the fundamental band of ¹³CO at different temperatures between 12 K and room temperature. The broadening parameters are determined, taking into account confinement narrowing, by simultaneous least-squares fitting of spectra recorded using a frequency stabilized diode laser spectrometer. The pressure broadening cross sections are deduced and compared to close-coupling calculations and earlier results obtained for rotational transitions of ¹²CO.     

Concentration dependence of the thermal boundary resistance between dilute<Superscript>3</Superscript>He−<Superscript>4</Superscript>He solutions and sintered silver powder

We have measured the³He concentration dependence of the thermal boundary resistanceR _B between³He?⁴He dilute mixtures and submicron sintered silver between 10 and 150 mK. For concentrations greater than one percent, the results for the boundary resistance per inverse volume are insensitive to the concentration and have a magnitude similar to that predicted by the acoustic mismatch theory. For concentrations less than one percent, we observe an increase ofR _B for decreasing concentrations.     

Chiroptical effects in the second harmonic signal of collagens I and IV

We performed polarization-resolved surface second harmonic generation (SHG) experiments on thin films of collagen I and IV molecules, as well as conventional CD measurements. We found that collagen IV presents little CD and no SHG optical activity, whereas collagen I exhibits large chiroptical effects involving both one-electron and excitonic coupling mechanisms. We estimated that these chiral components enhance the SHG signal from fibrillar collagen in biological tissues by typically a factor of 2. By comparing the distinct behaviors of collagens I and IV in SHG microscopy and in surface SHG experiments, we concluded that SHG microscopy is a sensitive probe of the micrometer-scale structural organization of collagen in biological tissues.     

Multiplex multidimensional nanoLC-MS system for targeted proteomic analyses

The present work describes a dual-column and dual-sprayer LC-MS system for high-throughput proteomic analyses. This system consists of two precolumns for sample desalting and two analytical columns. Each column is terminated by a nanoelectrospray emitter mounted on a robotic arm enabling their sequential positioning in front of the sampling cone of the mass spectrometer. The effluent from each emitter is recorded in separate acquisition channels without detectable crosstalk. Gradient elution to both nanoLC columns is delivered by a single HPLC system via a flow splitter. The reproducibility of retention time and peak intensity of the present multiplex system were comparable to those obtainable using a single emitter configuration. Replicate injections of complex tryptic digests (n = 10) indicated that this system provided good reproducibility of retention time and peak intensity on both columns with RSD values of less than 0.9 and 18.6%, respectively. The application of this system is demonstrated for the monitoring of protein expression changes in U937 human monocyte cells with and without phorbol ester administration. Furthermore, we also demonstrated the use of this multiplex system in a 2-D LC configuration to increase sample loading and throughput for the analysis of biomarker samples of higher complexity. Variations in peptide abundance down to two-fold change were identified across salt fractions for spiked tryptic digests present at a level of 50 fmol in 1.5 microg of plasma samples.     

Structural and kinetic effects of chloride ions in the palladium-catalyzed allylic substitutions

Addition of ligands to [Pd(η³-RCHCHCH₂)(μ-Cl)]₂ or chloride ions to cationic [(η³-RCHCHCH₂)PdL₂]⁺BF₄⁻ induces the formation of neutral complexes η¹-RCHCHCH₂PdClL₂ (R=H with L=(4-ClC₆H₄)₃P, (4-CH₃C₆H₄)₃P, (4-CF₃C₆H₄)₃P or L₂=1,2-bis(diphenylphosphino)butane (dppb), 1,1′-bis(diphenylphosphino)ferrocene (dppf); R=Ph with L=(4-ClC₆H₄)₃P), instead of the expected cationic complexes [(η³-RCHCHCH₂)PdL₂]⁺Cl⁻. In the presence of chloride ions, the reaction of morpholine with the cationic complexes [(η³-allyl)Pd(PAr₃)₂]⁺BF₄⁻ (Ar=4-ClC₆H₄, 4-CH₃C₆H₄) goes slower and involves both cationic [(η³-allyl)Pd(PAr₃)₂]⁺ and neutral η¹-allyl-PdCl(PAr₃)₂ complexes as reactive species in equilibrium with Cl⁻. The cationic complex is more reactive than the neutral one. However, their relative contribution in the reaction strongly depends on the chloride concentration, which controls their relative concentration. The neutral η¹-allyl-PdCl(PAr₃)₂ may become the major reactive species at high chloride concentration. Consequently, [Pd(η³-allyl)(μ-Cl)]₂ associated with ligands or cationic [(η³-allyl)PdL₂]⁺BF₄⁻, used indifferently as precursors in palladium-catalyzed allylic substitutions, are not equivalent. In both situations, the mechanism of the Pd-catalyzed allylic substitution depends on the concentration of the chloride ions, delivered by the precursor or purposely added, that determines which species, [(η³-allyl)PdL₂]⁺ or/and η¹-allyl-PdClL₂ are involved in the nucleophilic attack with consequences on the rate of the reaction and probably on its regioselectivity. Consequently, the chloride ions of the catalytic precursors [Pd(η³-allyl)(μ-Cl)]₂ must not be considered as ‘innocent’ ligands.     

Infimal Convolution and Optimal Time Control Problem I: Fréchet and Proximal Subdifferentials

We consider a general minimal time problem with a convex constant dynamics and a lower semicontinuous extended real-valued target function defined on a Banach space. If the target function is the indicator function of a closed set, this problem is a minimal time problem for a target set, studied previously in particular by Colombo, Goncharov and Mordukhovich. We investigate several properties of the Fréchet and proximal subdifferentials for the infimum time function. Also explicit expressions of the above mentioned subdifferentials as well as various directional derivatives are obtained. We provide some examples to show the essentiality of assumptions of our theorems.