The paper presents an approach to the solution of the problem of assessing the probabilistic characteristics of echo signals of ground penetration radar (GPR). This allows performing the synthesis of ...decisive statistical rules in the problems of detection and recognition of subsurface objects.
A crystallographic analysis of two structures, monoclinic Nа
8
{Re
4
(PO)
4
}(CN)
12
⋅18H
2
O⋅CH
3
OH (
I
) and orthorhombic (C
6
H
5
)
4
P
4
Ta
6
I
12
(CN
6
) (
II
), in which clusters of heavy ...atoms are significantly rarefied in space, so that their mutual arrangement cannot be explained only in terms of chemical interaction, has been performed. In structure
I
the crystallographic planes with a high atomic density (“skeletal” planes) are located in the regions with
d
hkl
= 10–5.5 Å and
d
hkl
< 3 Å. The planes in which atomic groups Re
4
(PO)
4
(playing the role of unified bulk objects) are concentrated are in fact selected in the first region. In the second region, ordering is implemented at the level of individual atoms. A crystallographic analysis showed that the structure basis is determined by the sites of heavy Re cations. A striking fact is that there are 1152 subcells and only 32 Re atoms per unit cell in this structure; i.e., only the fraction of 1/144 provides the basis of structure stability. In structure
II
“skeletal” planes are also absent in the range of
d
hkl
from ∼7 to ∼4 Å. The planes in the range of large
d
hkl
characterize cluster ordering, whereas the planes in the range of small
d
hkl
characterize ordering of separate atoms. The geometry and local symmetry of the cluster group (Та
6
octahedron) dictates the basis of translational symmetry—unified sublattice of sites, most of which are free of these atoms. The considered structures demonstrate the key role of heavy atoms in the formation of translational symmetry—the fundamental difference of the crystalline state from other condensed states. The newly formed structure retains partially local symmetry of cores (templates) of atomic groups, bound by strong chemical interactions, including the interactions between heavy and light atoms. The process of formation of a crystal structure from randomly oriented and randomly located templates—coherence assembly—is implemented according to the laws of dynamics of elastic media, where masses of atoms rather than their chemical characteristics are important.
The crystallographic analysis of the structures of compounds Na
2
FePO
4
F (
I
), NaFePO
4
(
II
), and LiVOPO
4
(
III
) reveals that there are vacant channels in “honeycomb” constructions of their ...cation frameworks. In these structures, the stability is based on a sequence of embedded (according to the “matryoshka” principle) pseudosymmetry-related pseudo-hexagonal configurations. Ordering of cation positions creates their configuration approaching highly symmetrical sublattices that are close in geometry to face-centered (
F
cube
) and body-centered (
I
cube
) cubic sublattices. The equivalent positions are occupied by different atoms and vacancies.
A novel kind of composite material is presented that contains two indicators incorporated into a single polymer matrix, thus allowing simultaneous determination of oxygen partial pressure and ...temperature. The temperature‐sensitive dye (ruthenium tris‐1,10‐phenanthroline) was chosen for its highly temperature‐dependent luminescence which is the highest among the RuII polypyridyl complexes. A fluorinated palladium(II) tetraphenylporphyrin served as the oxygen probe. The indicators were incorporated into either poly(styrene‐co‐acrylonitrile) microparticles (to sense oxygen) or into poly(acrylonitrile) (for temperature sensing, since this polymer is virtually impermeable to oxygen). The luminescence of both dyes can be separated either spectrally (due to different absorption and emission spectra of the indicators) or via luminescence decay time. The material is suitable for temperature‐compensated oxygen sensing, for example, in high‐resolution oxygen profiling, and for imaging temperature in the range between 0 and 60 °C. This enables one to “see” (rather than to “feel”) temperature in this important range. Simultaneous imaging of pressure and temperature also has been achieved. It enables contactless imaging of the two parameters, for example, in wind tunnels. Due to the use of a biocompatible hydrogel matrix, the material conceivably is suited for biomedical applications.
Noninvasive, simultaneous temperature and oxygen sensing using luminescent probes incorporated into, respectively, organic copolymer microparticles and a biocompatible hydrogel polymer matrix are described. The material is suitable for temperature‐compensated oxygen sensing, and for imaging temperature in the range 0–60 °C. This enables one to “see” (rather than “feel”) temperature in this important range (see figure).
The article considers some problems of mechanics about the rolling of a wheel with impacts and one-way constraints under dry friction. Such tasks are often encountered in practice when a vehicle ...wheel collides with or leaves an obstacle. The contact of the wheel with the road is assumed to be point, the dry friction model is the classical Euler-Coulomb model. A complete analysis of various cases of impact and post-impact movements of the wheel is given.
The effect of symmetry ordering of sites of material particles (atoms, chemically strong atomic groups) is shown on characteristic examples. This ordering leads to reduction of the degrees of their ...freedom and, therefore, minimizes the energy of a system during crystallization. The geometry of Fedorov groups, supplemented with the symmetry energy function, determines the processes occurring in condensed atomic medium (“Kingdom of crystals,” according to E.S. Fedorov). Criteria are proposed for comparative estimation of the stability of structures, including the structural stencils (structure types of tourmaline, apatite, et al.) abundant in nature.
Widely known and some other structural types as well as mechanisms of structural transformations are considered in the framework of the idea that stability of crystal structures is caused by ...translational and point spatial symmetries, which reduce the degree of freedom and, therefore, the energy of material particles (atoms, chemically stable atomic groups). The role of highly symmetric spatial “stencils” of atomic arrangement in the solution of the
composition—structure
problem is shown. Criteria of relative stability of crystal structures are proposed.
The interpretation of translational symmetry as a consequence of the formation of a complex of standing planar elastic oscillations in atomic systems explains the stability of crystalline state. It ...supplements conventional crystallography with the energetic function of spatial symmetry, as well as reveals the mechanisms and sequence of atomic-site ordering. The standard technique of crystallographic analysis is demonstrated on the example of orthoborate structures: trigonal and monoclinic modifications of H
3
BO
3
and hexagonal modification of Tl
3
BO
3
.
The first (arylsulfonylureido)-substituted derivatives of tricyclic diterpenoids were synthesized by the reaction of isopimaric acid isocyanate with sulfonamides of various structures. The molecular ...structures of
11c
and
12
were proved by X-ray crystal structure analyses. The anti-inflammatory activity was studied in a histamine inflammatory edema model. The activity depended significantly on the substituent in the sulfonylureido fragment.
The article presents the algorithms for demodulating binary channels of data transmission lines with frequency multiplexing used in remote control and warning systems. The noise immunity of the ...algorithms were investigated. It is shown that significant simplification and significant noise immunity increasing can be obtained by applying the majority decision rule.
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