Toplayer-dependent crystallographic orientation imaging in the bilayer two-dimensional materials with transverse shear microscopy

Nanocontact properties of two-dimensional (2D) materials are closely dependent on their unique nanomechanical systems, such as the number of atomic layers and the supporting substrate. Here, we report a direct observation of toplayer-dependent crystallographic orientation imaging of 2D materials with the transverse shear microscopy (TSM). Three typical nanomechanical systems, MoS₂ on the amorphous SiO₂/Si, graphene on the amorphous SiO₂/Si, and MoS₂ on the crystallized Al₂O₃, have been investigated in detail. This experimental observation reveals that puckering behaviour mainly occurs on the top layer of 2D materials, which is attributed to its direct contact adhesion with the AFM tip. Furthermore, the result of crystallographic orientation imaging of MoS₂/SiO₂/Si and MoS₂/Al₂O₃ indicated that the underlying crystalline substrates almost do not contribute to the puckering effect of 2D materials. Our work directly revealed the top layer dependent puckering properties of 2D material, and demonstrate the general applications of TSM in the bilayer 2D systems.     

Kinetic and Thermodynamic Characterization of Lysine Production Process in Brevibacterium lactofermentum

Detailed kinetic and thermodynamic parameters for lysine production from Brevibacterium lactofermentum are investigated for the first time in this study. Production of the essential amino acid, l-lysine, by B. lactofermentum was assessed in a flask and a continuously stirred tank fermentor (22 L). Maximum lysine production was achieved after 40 h of growth and at 35 °C. The effect of different nitrogen sources such as NH₄NO₃, (NH₄)₂SO₄, (NH₄)₂HPO₄, corn steep liquor, NaNO₃, and urea showed that corn steep liquor gave a better lysine yield. Lysine production was increased when dissolved oxygen was maintained at 50 % saturation. The use of dissolved oxygen was critical for high productivity. This indicates that dissolved oxygen greatly affects l-lysine productivity. Kinetic and thermodynamic parameters during lysine production from molasses and glucose mixture showed that B. lactofermentum efficiently converted the substrate mixture into cell mass and lysine. Kinetic and thermodynamic parameters were significantly higher compared with other microorganisms which may be due to the high metabolic activity of B. lactofermentum. This study will have a significant impact on future strategies for lysine production at industrial scale.     

Sol–gel synthesis of tetragonal ZrO2 nanoparticles stabilized by crystallite size and oxygen vacancies

In this letter, we present a facile route to produce metastable tetragonal zirconia (ZrO₂) nanoparticles via pH-controlled precipitation of dilute zirconyl nitrate dihydrate [ZrO(NO₃)₂·2H₂O] solution in liquid NH₃ under ambient conditions and calcination at 500 °C for 2 h. The phase pure tetragonal ZrO₂ nanoparticles are obtained at pH 9. The effect of pH on metastable phase stabilization in precipitated ZrO₂ nanoparticles is demonstrated with the help of XRD, SEM/EDX, and X-ray photoelectron spectroscopy techniques. The stability of tetragonal ZrO₂ phase is attributed to the smaller crystallite size and greater oxygen deficiency in phase-pure tetragonal ZrO₂.     

Improved Preparation and Application of Poly(Ethylene Glycol) Vinyl Sulfone

An improved synthesis of poly(ethy1ene glycol) vinyl sulfone is presented and its reactions with nucleophiles reported.     

Use of indigenous microwave system for dissolution and treatment of waste from nuclear materials

Microwave heating technique has the unique advantages of low processing time, less consumption of reagents, homogeneous heating and maintenance-free adaptability to glove box. Dissolution of thorium and plutonium containing fuel viz sintered thorium oxide, thorium-uranium oxide and thorium-plutonium oxide pellets is one of the most difficult step for their analysis and characterization. Complete dissolution of the fuel samples is a pre-requisite for the analysis of fuel material in the solution form. Even a trace level of un-dissolved particle may interfere with the accurate and precise determination in the analysis. Large volumes of liquid and solid wastes are generated during the processing and analysis of samples. These wastes being radioactive can’t be disposed directly to sea or soil. They have to be segregated and categorised and all possibilities are explored to see the feasibility of retrieving the precious nuclear material. The present paper describes an overview of all the efforts made at AFFF for rapid dissolution of nuclear materials using an indigenous microwave digestion system as well as its use for the treatment of waste being generated.     

The cooling of a low-heat-resistance stretching sheet moving through a fluid: A rejoinder

This note deals with the comments of Kuiken that appeared in the journal disputing the accuracy of the solutions of an earlier work on the cooling of a low heat resistance stretching sheet moving through a fluid. It is shown that there is no loss of accuracy in the higher order perturbations, as claimed by Kuiken. Further, a comparison of the results of Euler transformation with those of Kuiken (based on direct and inverse series) show the agreement to four places of decimal for all values of steamwise distances. The results for heat transfer not considered in earlier papers are also presented here.     

Fully developed turbulent flow in a pipe: an intermediate layer

Summary The fully developed mean turbulent pipe flow is analysed at large Reynolds number by the method of matched asymptotic expansions. From the study of various limiting processes, in the sense of Kaplun, a crucial intermediate limit is identified whose transverse dimension is of the order of geometric mean of the transverse dimensions of the classical inner and outer layers. The asymptotic expansions in the three layers (inner, intermediate and outer) are matched by the Millikan's argument leading to two overlap domains where velocity distribution is logarithmic but their slopes could be different. The measurements show that the sustantial log regions do in fact exist in the two overlap domains and the ratio of their slopes is 2.03. The present theory describes the velocity profile over a greater range when compared to the classical theory. The predictions of Reynolds stress and turbulent energy production are in remarkably good argreement with the data for almost entire turbulent flow region from the beginning of the buffer layer to the axis oj pipe.

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Voll entwickelte turbulente Rohrströmung: eine Zwischenschicht

Übersicht Die voll entwickelte turbulente Rohrströmung wird für größere Reynolds-Zahlen mit der Methode der asymptotischen Entwicklungen untersucht, wobei eine wichtige Zwischenschicht identifiziert wird. Die asymptotischen Entwicklungen für drei Schichten (innere, mittlere und äußere) werden mit Hilfe von Übergangsbedingungen nach Millikan angepaßt. Messungen zeigen, daß wesentliche logarithmische Gebiete in Wirklichkeit vorhanden sind, wobei das Verhältnis ihrer Neigungen 2.03 ist. Die vorliegende Theorie beschreibt das Geschwindigkeitsprofil über einen größeren Bereich als die klassische Theorie.