Experimental study of critical heat flux in open two-phase thermosyphon

Critical heat flux in an open two-phase thermosyphon has been measured employing water, R113 and R22 for a wide range ofL/D=4.8 to 960 and density ratio ofρ _L /ρ _G =6.17 to 1602. The CHF data measured, are found to be in fairly good agreement with those calculated from a criterion that the CHF takes place when reaches a maximum liquid falling rate in counter-current annular flow of liquid and vapor. Normal operation of the thermosyphon cannot be obtained at any liquid of water, R113 and R22 for a small tube diameter of less than 2 mm.     

Arrow's Theorem,Weglorz' Models and the Axiom of Choice

Applying Weglorz' mode s of set theory without the axiom of choice, we investigate Arrow‐type social we fare functions for infinite societies with restricted coalition algebras. We show that there is a reasonable, nondictatorial social welfare function satisfying “finite discrimination”, if and only if in Weglorz' mode there is a free ultrafilter on a set representing the individuals.     

Upper limit of enhancement of boiling heat transfer in a narrow vertical rectangular channel due to passing bubbles

An experimental study has been made of saturated boiling heat transfer for water and R113 in a narrow vertical rectangular channel (2 mm space, 20 mm wide, and 200 mm long) at atmospheric pressure, in which the vertical heated surface (10 mm long and 20 mm wide) is located on one side at a position of 150 mm from its entrance and bubbles are forcibly passed through it at a designated period from 0.33 to 1.0 sec. The experiment shows that the heat transfer coefficients are increased by the bubble passing through the heated surface for the value of thermal diffusivity,a, times period, T₀, of the passing bubbles above about 6×10^–9 m² (a T ₀>6×10^–9 m²) while fora T ₀< 6×10^–9 m², the heat transfer coefficients become independent of the period and the effectiveness of the enhancement of the heat transfer owing to the passing bubble disappears.

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Die obere Grenze der Verbesserung des Wärmeübergangs beim Sieden in einem vertikalen, rechteckigen Kanal infolge von aufsteigenden Blasen

Zusammenfassung Es wurden Experimente über den Wärmeübergang beim Sättigungssieden mit Wasser und R113 in einem engen, vertikalen, rechteckigen Kanal (2 mm Abstand, 20 mm Breite und 200 mm Länge) bei Umgebungsdruck durchgeführt, wobei die vertikale, beheizte Oberfläche (10 mm lang und 20 mm breit) auf der einen Seite in einem Abstand von 150 mm vom Eintritt angeordnet ist und die Blasen zwangsweise durch den Kanal sich mit einem Periodenabstand von 0,033 bis 1,0 s bewegen. Das Experiment zeigt, daß die Wärmeübergangskoeffizienten durch das Vorbeistreichen der Blasen an der beheizten Oberfläche verbessert werden, wenn das Produkt aus Temperaturleitfähigkeit,a, mal der Periode, T₀, der vorbeistreichenden Blasen größer als 6×10^–9 m² liegt, während unterhalb dieses Wertes der Wärmeübergangskoeffizient unabhängig von der Blasenperiode ist und die Effektivität der Wärmeübergangsverbesserung infolge der Blasenströmung verschwindet.

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Nomenclature a thermal diffusivity of liquid - ¯h time-averaged heat transfer coefficient - q _w heat flux at wall - T ₀ period of passing bubble - T _w(t) temperature of heated surface - T _w amplitude of heated surface temperature Greek symbols thermal conductivity - thickness of liquid film     

Pattern enrichment analysis for phage selection of stapled peptide ligands

Phage display is the most widely used technique to discover de novo peptides that bind to target proteins. However, it is associated with some challenges such as compositional bias. In this study, to overcome these difficulties, we devised a ‘pattern enrichment analysis.’ In this method, two samples (one obtained by affinity selection, the other simply amplified without selection) are prepared, and the two sequence datasets read on next-generation sequencer are compared to find the three-residue pattern most enriched in the selected sample. This allows us to compare two sequence datasets with high coverage and facilitates the identification of peptide sequences and the key residues for binding. We also demonstrated that this approach in the combination with structured peptide libraries allowed spatial mapping of the enriched sequence patterns. Here, we prepared a phage library displaying chemically stapled helical peptides with the X₁C₂X₃X₄X₅X₆X₇X₈C₉X₁₀ sequence, where X is any amino acid. To validate our method, we performed screening against the HDM2 protein. The results showed that the hydrophobic residues (Phe, Tyr, Trp and Leu) that are key to interactions with HDM2 were clearly identified by the pattern enrichment analysis. We also performed selection targeting the SARS-CoV-2 spike RBD in the same manner. The results showed that similar patterns were enriched among the hit peptides that inhibited the protein–protein interaction.

To effectively identify helical peptide binders from a phage library, we developed “pattern enrichment analysis,” which finds the enriched three-residue patterns by comparison with a control sample.     

Nuclear moments as a probe of electronic structure in material, exotic nuclear structure and fundamental symmetry

We report our studies in various fields of Physics through nuclear moments utilizing the β-NMR technique, including material sciences, nuclear structures and fundamental symmetries. Especially, we focus on the recent progress in the studies on the electronic structure in Pt through Knight shifts of various impurities, lattice locations of impurities, electric field gradients, the analysis of nuclear spin in terms of its components, anomaly in the spin expectation value for ⁹C-⁹Li mirror pair, the G-parity conservation law, and the Ramsey resonance on UCN for future neutron EDM measurements.     

Intramolecular cyclization of beta,beta-difluorostyrenes bearing an iminomethyl or a diazenyl group at the ortho position: synthesis of 3-fluorinated isoquinoline and cinnoline derivatives

o-Formyl-substituted beta,beta-difluorostyrenes readily react with NH(2)OH.HCl or NH(4)OAc to afford 3-fluoroisoquinoline derivatives in good yield via (i) the formation of the corresponding oximes or imines and (ii) subsequent intramolecular replacement of a vinylic fluorine by the sp(2) nitrogen of the iminomethyl group (HON=CH- or HN=CH-). Beta,beta-Difluorostyrenes bearing an o-diazenyl group (HN=N-), generated by reduction of the corresponding diazonium ions, undergo a similar substitution to afford 3-fluorinated cinnolines.     

Is CO2 fixation promoted through the formation of DBU bicarbonate salt?

The bicyclic amidines, 1,8‐diazabicyclo [5.4.0]undec‐7‐ene (DBU) and 1,5‐diazabicyclo[4.3.0] non‐5‐ene (DBN), were used for the chemical fixation of carbon dioxide. The promotion for CO₂ fixation is often reported through the formation of a thermally unstable DBU or DBN bicarbonate salt. To examine the effects of the DBU or DBN bicarbonate salt, reactions of 2‐aminobenzonitrile with the DBU salt or DBN salt in dimethylformamide (DMF) were performed at 20°C for 24 h in argon or carbon dioxide (0.1 MPa). However, in all the cases, 1H‐quinazoline‐2,4‐dione was not obtained completely. In contrast with room temperature reactions, 2‐aminobenzonitriles and DBU bicarbonate salt in DMF reacted for 4 h under high temperature (80°C) and CO₂ atmosphere (0.1 MPa) gave 1H‐quinazoline‐2,4‐diones in good to excellent yields. At high‐temperature conditions, DBU bicarbonate salt is decomposed to DBU and carbon dioxide. Also, the carbonylation of 2‐aminobenzonitrile using DBU and carbon dioxide afforded 1H‐quinazoline‐2,4‐dione in good yields under similar reaction conditions. These results suggest that the combination of DBU or DBN as a strong base and carbon dioxide is much more important than the in situ formation of DBU or DBN bicarbonate salt for the acceleration of CO₂ fixation. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:276–280, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21014     

Zinc-metal promoted selective α-haloacylation and gem-bisacylation of alkyl aldehydes in the presence of chlorotrimethylsilane

Treatment of a mixture of alkyl aldehydes (1) with acid chlorides (2) in the presence of zinc metal powder and a catalytic amount of chlorotrimethylsilane (TMSCl) in dichloromethane brought about highly facile and effective coupling to give selectively the corresponding α-haloacylation and gem-bisacylation products, α-haloalkyl carboxylates and 1,1-dicarboxylates (acylals), in good to excellent yields.