Third-order Axis Research Articles

Weak ferromagnetism along the third-order axis of the FeBO3 crystals caused by Fe2+ impurity ions

Using the single-ion approximation, the weak ferromagnetic moment σZ(Fe2+) along the third-order axis of FeBO3 crystals, which is caused by the contribution of Fe2+ ions, has been investigated in the framework of the model Fe2+ impurity ion –BO3 vacancy. The extreme low-temperature behavior of the total magnetic moment due to the strong dependence of the Fe2+ion contribution is predicted.

Response of thermoelectric parameters of Bi0.5Sb1.5Te3 films to secondary recrystallization

Flash evaporation is used to grow Bi0.5Sb1.5Te3 films 1200 nm thick on mica substrates. The average lateral crystallite sizes in the as-grown films are ~800 nm. The (0001) plane in the crystallites is preferentially parallel to the substrate plane. After heat treatment in an argon atmosphere, the effective lateral size of crystallites in which the third-order axis is perpendicular to the substrate plane increased by a factor of 3–5. The crystallites were preferentially oriented in the substrate plane as well. The thermoelectric-power parameter of Bi0.5Sb1.5Te3 films after their heat treatment in an inert environment increased approximately twofold to values close to that of the corresponding single crystals.

A new diminutive euphyllophyte from the Middle Devonian of West Junggar, Xinjiang, China and its evolutionary implications

Xu, H.-H., Wang, Y., Tang, P. & Wang, Y., May 2017. A new diminutive euphyllophyte from the Middle Devonian of West Junggar, Xinjiang, China and its evolutionary implications. Alcheringa 41, 524–531. ISSN 0311-5518.A diminutive euphyllophyte, Douaphyton levigata gen. et sp. nov., is described from the upper Middle Devonian (Givetian) Hujiersite Formation of West Junggar, Xinjiang, China. The plant consists of more than three orders of axis branching, each axis being less than 2 mm wide. The second-order axes are short, laterally and alternately attached to the main axis. The third-order axes are paired and anisotomously divided, bearing the vegetative appendages or the fertile units. The fertile unit consists of a short recurved axis giving off up to four short pedicels along one side, each of which bears one to four pairs of terminal sporangia. Douaphyton has a three-dimensional branching system that has an intermediate form in the evolutionary context of euphyllophytes and lignophytes. It is also proposed that complex branching developed in multiple groups in the Middle Devonian.*Hong-He Xu [hhxu@nigpas.ac.cn], Yao Wang [yaowang@nigpas.ac.cn], Peng Tang [pengtang@nigpas.ac.cn], Yi Wang [yiwang@nigpas.ac.cn] State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210,008, PR China. Yao Wang [yaowang@nigpas.ac.cn] University of Science and Technology of China. 96 Jinzhai Road, Hefei, Anhui Province, 230,026, PR China.

Raman scattering under structural and magnetic phase transitions in terbium ferroborate

The Raman scattering spectrum of single crystal TbFe3(BO3)4 was studied in the frequency range 3–500 cm−1 at temperatures from 2 to 300 K. It was found that in high- and low-temperature phases there exist additional phonon lines which were not known before. In the high-temperature phase, these lines originate from LO–TO splitting of polar phonons. Appearance of the additional lines in the low temperature phase is due to both a reduction of the crystal symmetry under the phase transition and an increase of the primitive cell volume. It was established that the frequencies of some phonon lines in the magneto-ordered phase are shifted towards the high-energy region upon applying an external magnetic field along the third-order axis. The spectrum of two-magnon Raman scattering was investigated. It was shown that at low temperatures the two-magnon band has a complex shape that reflects specific features in the density of state of the magnon branches. The magnon energy at the Brillouin zone boundary was determined.

A new euphyllophyteKunia venustagen. et sp. nov. from the Middle Devonian of Yunnan, South China

Abstract Kunia venusta gen. et sp. nov. is reported from the late Middle Devonian (Givetian) Haikou Formation near Kunming City, Yunnan Province, China. This plant has three orders of naked axes that divide pseudomonopodially. The second- and third-order axes occur in a helix. Fertile appendages are distantly spaced and helically inserted to the third-order axis; they comprise equally dichotomous branches terminated by two clusters of paired and fusiform sporangia. Sterile appendages are dichotomous and distally recurved. A comparison is made with the basal euphyllophytes including the trimerophytes, cladoxylopsids, zygopterids, stauropterids, and some relevant genera of uncertain affinity. The new plant resembles them in dichotomous appendages with terminal elongated sporangia, but differs mainly in the three orders of pseudomonopodial axes bearing helical laterals. It is thus placed in the Euphyllophytina as incertae sedis. It is suggested that an evolutionary divergence in the branching pattern and appendage morphology might have occurred in the Middle Devonian euphyllophytes, that is, maintaining three dimensions versus yielding more or less planation.

Application of X-ray photoelectron spectroscopy for studying the molecular structure of corrosion inhibitor — Zinc complex of 1-hydroxyethylidene diphosphonic acid

The molecular structure of zinc complex of 1-hydroxyethylidene diphosphonic acid was studied by X-ray photoelectron spectroscopy. The obtained data were compared with IR absorption spectrum of the same substance to acquire new information on the molecular structure. It was shown that coordination of the phosphonate group by zinc atom retains the localization of P-O π bond, the phosphonate group does not have a third-order axis of symmetry, and Zn atom can occupy positions with different coordination. Thermal destruction of the complex is accompanied by decomposition of hetero-organic ligand with detachment of the hydrocarbon fragment along C-P bonds and formation of inorganic zinc salts.

Studies on a New Earliest Carboniferous Plant: Coenosophyton tristichus gen. et sp. nov. from China

A new plant fossil from the earliest Carboniferous of Anhui, China, is described. This species, known only from compression, consists of three orders of branching and dichotomous appendages. The first-order axis represents the morphology of a stem or small trunk. Lateral organs are attached along the primary axis in three ranks. The appendages are arranged along the third-order axis in three ranks and divided into sterile and fertile appendages. The sterile appendages are dichotomized two times with a pointed tip. The fertile appendages are made of paired erect sporangia on the supporting axial system with two dichotomies. A dense terminal branching system is attached at the end of first- and second-order axes. Based on comparison with and differences from established taxa, this plant is named Coenosophyton tristichus gen. et sp. nov. The relationships with the known plant fossils of Devonian, Carboniferous, and Permian are discussed.

Effect of centrifugation on the crystal structure of barium nitrate

The structure of barium nitrate crystals grown from supersaturated aqueous solutions under normal conditions and during centrifugation at 11.8×103g is studied for the first time by a high-precision powder neutron diffraction method. It is established for the first time that centrifuging leads to displacement of the nitrate oxygen atoms in the xy plane (resulting in rotation of the NO3 trigonal prism about the third-order axis) and to variation of the bond lengths and angles in the coordination polyhedron of Ba atoms. The latter changes result in the appearance of a torsional mode in the phonon spectrum of barium nitrate and in increasing stiffness of the crystal lattice, as evidenced by a significant increase in microhardness of the samples grown in the centrifuge.

Anapaulia moodyi gen. et sp. nov.: a probable iridopteridalean compression fossil from the Devonian of western Venezuela

Compression fossils of a new plant, Anapaulia moodyi Berry et Edwards, gen. et sp. nov., are described from the Middle or Upper Devonian of western Venezuela. The main novel characteristic of this plant is that the monopodial main axis has both large second-order axes as well as smaller dichotomizing branches inserted in a predominantly whorled arrangement, the whorls being separated by long internodes. Third-order axes and small fourth-order axes are borne in compressed helices and helices. Small ultimate branching systems, which dichotomize up to four times, are borne on the third- and fourth-order axes in helices and compressed helices. Elliptical sporangia are borne upon the recurved tips of ultimate branching systems otherwise similar to the sterile examples. The entire plant up to the second or third divisions of the ultimate branching systems is covered with fine spines. The nature of the whorled arrangement of branching in the first-order axes sets the plant apart from the Trimerophytina and other contemporary and earlier land plants. A close comparison can be drawn with permineralized stems from the Middle Devonian of North America belonging to Iridopteridales Stein, which show anatomical traits which may correspond to the branching patterns found in Anapaulia. There are morphological similarities to compression fossils of the iridopteridalean Ibyka Skog et Banks, for which both permineralizations and a limited amount of compression material was described. Anapaulia is thus tentatively assigned to the Iridopteridales.

Solitons in models of an alpha -helix: influence of symmetry

Solitons in an alpha -helix are studied within the framework of a modified Davydov model which takes into account third-order axis symmetry. It is shown that antisymmetric solitons with one vanishing amplitude do not satisfy this demand. The result is confirmed by perturbational calculation for the static solitons.

Disorder of the sublattice of terminal groups and phase transition in octa (vinylsilsesquioxane)

Octa(vinylsilsesquioxane) is one of the members of a series of materials which are important for microelectronics, viz., the organylsilsesquioxanes with the general formula (RSiO/sub 1.5/)/sub n/, where R is an organic substituent, and exists in the form of a molecular crystal consisting of (C2H3SiO/sub 1.5)9 molecules. The almost cubic silicon-oxygen skeleton is slightly extended along the C3 axis. According to the data from x-ray diffraction analysis, at room temperature there is disordering of the terminal C/sub US / carbon atoms of the substituent in the compound: among three positions for substituents lying on the third-order axis and among two positions for those in positions which are not symmetry centers. However, the question of the nature of the disordering (whether it is static or dynamic) remained open. In the present work the authors used the method of proton NMR (PMR), NMR relaxation, and precision calorimetry to establish that dynamic disordering appears in octa(vinylsilsesquioxane) at T = 230K in the sublattice of the terminal groups of atoms and that it is accompanied by a phase transition in the system.

Development of the female flower and gynecandrous partial inflorescence of Myrica californica

Organogenesis of the female flower and gynecandrous partial inflorescence is described. Approximately 25 first-order inflorescence bracts are formed in an acropetal sequence. A second-order inflorescence axis, the partial inflorescence, develops in the axil of each bract. Third-, fourth-, and fifth-order axes arise in the axils of second-, third-, and fourth-order bracts. A gynoecium terminates a second-order axis and sometimes a distal third-order axis. A gynoecium consists of two stigmas and one basal, unitegmic, orthotropous ovule. The wall enclosing the ovule, the circumlocular wall, is comprised distally of gynoecial tissue and proximally of tissue of the inflorescence axis and its appendages. The latter portion of the wall is formed by zonal growth. Androecial members, formed proximal to the gynoecium on the partial inflorescence, are carried onto the circumlocular wall by zonal growth. A stamen may develop from the last-formed primordium before gynoecial inception or from a potentially stigmatic primordium. The papillae of the flower and fruit arise as emergences and from potentially bracteate, axial, and staminate primorida during the development of the circumlocular wall. The term circumlocular wall is used in a neutral sense to describe this unique structure. Since the gynoecium is composed of gynoecial appendages and inflorescence axis and appendages, a functional definition of gynoecium must be expanded to include any tissue, including an inflorescence, that surrounds the ovule(s) and forms the fruit(s).