Thermal Deformations of Crystal Structures in the L-Aspartic Acid/L-Glutamic Acid System and DL-Aspartic Acid

The method of temperature-resolved powder X-ray diffraction (TRPXRD) was used to determine the elevated temperature behavior of L-aspartic acid (L-asp), DL-aspartic acid (DL-asp), L-glutamic acid (L-glu), and an L-asp0.25,L-glu0.75 solid solution. These amino acids were not found to undergo any solid-phase (polymorph) transformations. When heated, they all experienced only thermal deformations. The corresponding parameters of the monoclinic cells of L-asp and DL-asp, and the orthorhombic cells of L-glu and L-asp0.25,L-glu0.75, were calculated for the entire range of studied temperatures (up to 220 °C). The data obtained were used to calculate the parameters of the thermal deformation tensors, and to plot the figures of their thermal expansion coefficients. A correlation between the maximum and minimum values of thermal expansion coefficients and the length, type, direction, and number of hydrogen bonds in the crystal structures of the investigated amino acids was established. The observed negative thermal expansion (contraction) of crystal structures of L-asp and DL-asp along the ac plane can be explained as a result of shear deformations occurring in monoclinic crystals with a non-fixed angle β. The studies were related to the presence of amino acids in various natural and technological processes occurring at different temperatures

Limits of Solid Solutions and Thermal Deformations in the L-Alanine–L-Serine Amino Acid System

The limits of solid solutions and thermal deformations in the L-alanine–L-serine (L-ala–L-ser) amino acid system have been determined. Thirteen amino acid mixtures with various proportions of the components L-ser/L-ala were studied using powder X-ray diffraction techniques. It was found that the regions of solid solutions in the system are rather limited and cover less than 10 mol. % from each component side. The thermal behavior of the components L-ser and L-ala and the composition L-ser/L-ala = 90/10 were studied by temperature-resolved powder X-ray diffraction. The heating of L-ser and L-ala only causes thermal deformations, while two-phase mixtures with the 90/10 L-ser/L-ala ratio form solid solutions at elevated temperatures. Additionally, the parameters of the thermal deformation tensor for L-ser and L-ala were calculated, and the figures of their thermal expansion coefficients were plotted and analyzed. The study conducted is of high applicability, since amino acids are active components of various biological, geological, and technological processes, including those at elevated temperatures, and have numerous applications in life-science industries

Identification of Boundary Conditions Using Natural Frequencies

The present investigation concerns a disc of varying thickness of whose flexural stiffness $D$ varies with the radius $r$ according to the law $D=D_0 r^m$, where $D_0$ and $m$ are constants. The problem of finding boundary conditions for fastening this disc, which are inaccessible to direct observation, from the natural frequencies of its axisymmetric flexural oscillations is considered. The problem in question belongs to the class of inverse problems and is a completely natural problem of identification of boundary conditions. The search for the unknown conditions for fastening the disc is equivalent to finding the span of the vectors of unknown conditions coefficients. It is shown that this inverse problem is well posed. Two theorems on the uniqueness and a theorem on stability of the solution of this problem are proved, and a method for establishing the unknown conditions for fastening the disc to the walls is indicated. An approximate formula for determining the unknown conditions is obtained using first three natural frequencies. The method of approximate calculation of unknown boundary conditions is explained with the help of three examples of different cases for the fastening the disc (rigid clamping, free support, elastic fixing). Keywords: Boundary conditions, a disc of varying thickness,inverse problem, Plucker condition.Comment: 19 page

Predictability problems of global change as seen through natural systems complexity description. 2. Approach

Developing the general statements of the proposed global change theory, outlined in Part 1 of the publication, Kolmogorov's probability space is used to study properties of information measures (unconditional, joint and conditional entropies, information divergence, mutual information, etc.). Sets of elementary events, the specified algebra of their sub-sets and probability measures for the algebra are composite parts of the space. The information measures are analyzed using the mathematical expectance operator and the adequacy between an additive function of sets and their equivalents in the form of the measures. As a result, explanations are given to multispectral satellite imagery visualization procedures using Markov's chains of random variables represented by pixels of the imagery. The proposed formalism of the information measures application enables to describe the natural targets complexity by syntactically governing probabilities. Asserted as that of signal/noise ratios finding for anomalies of natural processes, the predictability problem is solved by analyses of temporal data sets of related measurements for key regions and their background within contextually coherent structures of natural targets and between particular boundaries of the structures

Predictability problems of global change as seen through natural systems complexity description. 1. General Statements

The overall problem of global change is considered as the mathematical discrete dynamics discipline that deals with the sets, measures and metrics (SMM) categories in information sub-spaces. The SMM conception enables to unify techniques of data interpretation and analysis and to explain how effectively the giant amounts of information from multispectral satellite radiometers and ground-based instruments are to be processed. It is shown that Prigogine's chaos/order theory and Kolmogorov's probability space are two milestones in understanding the predictability problems of global change. The essence of the problems is maintained to be in filtering out a “useful signal” that would spread from key regions of the globe as compared to their background. Global analysis, interpretation and modelling issues are outlined in the framework of incorrect mathematical problems and of the SMM categories, which contribute to solving the comparability problem for different sets of observations

Printed Graphene Circuits

we have fabricated transparent electronic devices based on graphene materials with thickness down to one single atomic layer by the transfer printing method. The resulting printed graphene devices retain high field effect mobility and have low contact resistance. The results show that the transfer printing method is capable of high-quality transfer of graphene materials from silicon dioxide substrates, and the method thus will have wide applications in manipulating and delivering graphene materials to desired substrate and device geometries. Since the method is purely additive, it exposes graphene (or other functional materials) to no chemical preparation or lithographic steps, providing greater experimental control over device environment for reproducibility and for studies of fundamental transport mechanisms. Finally, the transport properties of the graphene devices on the PET substrate demonstrate the non-universality of minimum conductivity and the incompleteness of the current transport theory.Comment: 10 pages, 3 figure

Piezo-Responsive Hydrogen-Bonded Frameworks Based on Vanillin-Barbiturate Conjugates

A concept of piezo-responsive hydrogen-bonded π-π-stacked organic frameworks made from Knoevenagel-condensed vanillin–barbiturate conjugates was proposed. Replacement of the substituent at the ether oxygen atom of the vanillin moiety from methyl (compound 3a) to ethyl (compound 3b) changed the appearance of the products from rigid rods to porous structures according to optical microscopy and scanning electron microscopy (SEM), and led to a decrease in the degree of crystallinity of corresponding powders according to X-ray diffractometry (XRD). Quantum chemical calculations of possible dimer models of vanillin–barbiturate conjugates using density functional theory (DFT) revealed that π-π stacking between aryl rings of the vanillin moiety stabilized the dimer to a greater extent than hydrogen bonding between carbonyl oxygen atoms and amide hydrogen atoms. According to piezoresponse force microscopy (PFM), there was a notable decrease in the vertical piezo-coefficient upon transition from rigid rods of compound 3a to irregular-shaped aggregates of compound 3b (average values of d33 coefficient corresponded to 2.74 ± 0.54 pm/V and 0.57 ± 0.11 pm/V), which is comparable to that of lithium niobate (d33 coefficient was 7 pm/V). © 2022 by the authors.2.1.06.03, 20211572; Russian Foundation for Basic Research, РФФИ: 20-53-00043-Bel_a; Ministry of Science and Technology, Taiwan, MOST: 19-52-06004 MNTI_a; Ural Federal University, UrFU: 2968; Ministry of Science and Higher Education of the Russian Federation: 075-15-2021-677The work was supported by the Russian Foundation for Basic Research (RFBR, project no. 20-53-00043-Bel_a) and the PFM measurements were done under RFBR and MOST project no. 19-52-06004 MNTI_a. The equipment of the Ural Center for Shared Use “Modern nanotechnology” Ural Federal University (Reg. No. 2968), which is supported by the Ministry of Science and Higher Education RF (project No. 075-15-2021-677), was used. T.V.S. acknowledges the support from the State Program of Scientific Researchers of Belarus (research issue 2.1.06.03, state registration number: 20211572)