Paracrystalline Materials Research Articles

Morphology of the male reproductive system and sperm ultrastructure of the green lacewing, Chrysopa pallens (Rambur, 1838) (Neuroptera: Chrysopidae)

BackgroundChrysopa pallens is one of the most beneficial and effective natural predators, and is famous for its extensive distribution, wide prey spectrum, and excellent reproductive performance. This study examined the anatomy and fine structure of the C. pallens reproductive system and spermatogenesis.ResultsThe male reproductive system of C. pallens comprises a pair of testes, a vas deferens, seminal vesicles, accessory glands, and short ejaculatory ducts. The testes were already mature on the day of emergence, but the accessory glands did not mature until 5 days post-emergence. In early spermatids, the flagellum had an axoneme on one side of the two mitochondrial derivatives. The nucleus was surrounded by parallel crystalline and paracrystalline materials. The spermatid envelope extends towards the paracrystalline material in a tail-shaped wing. In mature spermatids, the axoneme is located between the two accessory bodies and mitochondrial derivative sets. The parallel-crystalline and paracrystalline materials disappeared. In the testes, the wall of seminal cysts consists of a layer of epithelium, a muscular-connective sheath, and several vesicles of different sizes. The mature seminal cysts contained 128 spermatozoa. The accessory gland is composed of six parts: ventral papilla-like protuberance, anterior glandular lobe, lateral glandular lobe, seminal cyst, posterior kidney-shaped lobe, and posterior papilla-like protuberance. Muscle fibers and secretory granules are extensive.ConclusionsThis study provides information on the reproductive system of C. pallens and offers a resource for taxonomy and reproductive biology.

Spatial correlation functions of paracrystals with radial symmetry.

We develop a phenomenological model to describe the structure of radially symmetric paracrystals whose long-range order are destroyed by propagation of particle fluctuations. General expressions are derived for the spatial correlation functions in one-, two-, and three-dimensional spaces. And the spatial correlation in paracrystals in reciprocal space is further discussed and clarified. The developed method can be used to quantitatively analyze the microstructure of paracrystalline materials in both real and reciprocal spaces via scattering experiments and computer simulations.

Solubility behavior of poly (diaminonaphthalene) doped poly (vinyl alcohol) films in different solvents and structural and electrical characterization of corresponding films

Organic conducting polymers, also recognized as para-crystalline materials, have received great attention in both fundamental and practical studies due to their conducting properties which are based on the structural and morphological changes in the parameters. In the present work poly (diaminonaphthalene) (PDAN) doped poly (vinyl alcohol) (PVA) films were prepared in two different solvents viz, acetonitrile and acrylonitrile by chemical oxidation polymerization method. The structural, morphological and electrical behaviors of the two films were investigated and the role of solvents was explored. Herein, we report irreconcilable features of PDAN doped PVA film prepared with the solvent acrylonitrile (AN). The obtained block-copolymer P(DAN-co-AN) doped PVA film offered much greater DC conductivity than that of the PDAN doped PVA film with acetonitrile as the solvent. The conducting mechanism of the two nanocomposite films was explained and compared with each other, and a conduction model was developed.

Glass transition in ferroic glass Kx(ND4)1−xD2PO4: a complete x-ray diffraction line shape analysis

Quenching of dynamic disorder in glassy systems is termed as the glass transition. Ferroic glasses belong to the class of paracrystalline materials having crystallographic order in-between that of a perfect crystal and amorphous material, a classic example of ferroic glass is the solid solution of ferroelectric deuterated potassium dihydrogen phosphate and antiferroelectric deuterated ammonium dihydrogen phosphate. Lowering temperature of this ferroic glass can lead to a glass transition to a quenched disordered state. The subtle atomic rearrangement that takes place at such a glass transition can be revealed by careful examination of the temperature induced changes occurring in the x-ray powder diffraction (XRD) patterns of these materials. Hence we report here results of a complete diffraction line shape analysis of the XRD patterns recorded at different temperatures from deuterated mixed crystals DKxA1−xDP with mixing concentration x ranging as 0 < x < 1. Changes observed in diffraction peak shapes have been explained on the basis of structural rearrangements induced by changing O–D–O hydrogen bond dynamics in these paracrystals.

Characterization of a diffraction profile using the fourth cumulant

In this study, line broadening in a diffraction intensity profile of powder crystalline materials due to particle size and lattice strain has been characterized by a new function- the fourth cumulant of the diffraction profile. Diffraction intensity profile is usually characterized in terms of half intensity width (FWHM), Fourier Transforms, second and fourth restricted moments etc. The cumulants, with addtional property of additivity[1], can be used to de-convolute the contribution of several effects such as crystallite size, lattice strain, stacking fault, dislocation, etc., to the line broadening. Since the first three cumulants are the same as the corresponding moments, we investigate the fourth cumulant, which is a function of fourth and second moments. Here, line broadening has only been due to particle size and lattice strain. Previous reports [1] showed that fourth cumulant of a Gaussian was zero, where as we now show that for Cauchy, Voigt and pseudo-Voigt distributions, the fourth cumulant is non-zero. Hence, the fourth cumulant of functions describing particle size and lattice strain for the latter types of distribution has been derived, as well as those for crystalline and para-crystalline materials. For crystalline materials, it was shown that fourth cumulant for particle size and strain (jointly) is the simple sum of the 4th cumulant for particle size and that of strain individually- thus proving the additivity of the fourth cumulant. This work illustrates the advantages of considering the fourth cumulant for characterizing line broadening in terms of particle size and strain.

The crystallite size-disorder relationship based on the spiral paracrystal.

A simple physical model of the relationship between crystallite size and disorder for paracrystalline materials is presented, based on the spiral paracrystal and distortion of the lattice cells. Simulations show that the model leads to relationships similar to the alpha* rule. Average crystallite sizes predicted by the model are in agreement with experimental data and also allow crystallite-size distributions to be proposed. The model provides a more satisfactory and complete explanation of this relationship than do current descriptions.

Microparacrystals: The intermediate stage between crystalline and amorphous

It has been established that “microparacrystals” are the building blocks of materials in the intermediate stage between crystalline and amorphous. A simplified review of the Theory of Paracrystallinity will be given. The analytical procedure for the determination of the paracrystalline distortion parameter,ghkl, and evidence of the existence of paracrystalline structure in various types of materials will be included.g-values > 0 and < 15% characterize the world of paracrystalline materials, which range from catalysts (g ≃ 1%) to polymers (g ≃ 3%), graphites (g ≃ 6%), glasses (g ≃ 12%) and molten metals (g ≃ 15%). Extensive studies ofg and-N, the average number of netplane layers which build up the paracrystal, have led to a fundamental empirical relationα*=N 1/2 g ≃ 0.15. This relation implies physically that the growth of paracrystals in a particular material is controlled appreciably by the level ofg in the netplane structure. Examples on the impact ofg on the behaviour of materials will be given. Relationships betweeng, the crystallinity, and the mechanical properties in polymers will be discussed. The results of our recent investigations on high-modulus Kevlar fibres will be used to demonstrate these relationships.

Presence of only eupyrene spermatozoa in adult males of the genus Micropterix hübner and its phylogenetic significance (Lepidoptera : Zeugloptera, Micropterigidae)

The morphology of the male genital organs and sperm ultrastructure were studied by light and transmission electron microscopy in adult males of two species of the genus Micropterix (Micropterigidae; Zeugloptera; Lepidoptera). The results are compared with findings from other primitive Lepidoptera and Trichoptera, and evaluated from a phylogenetic viewpoint. Both Micropterix species examined agree with regard to essential characters of the male genital organs. The paired testes are separate and show no internal compartmentalization. The male genital organs contain only mature nucleate (eupyrene) spermatozoa. Anucleate (apyrene) spermatozoa characteristically found in all other Lepidoptera were not observed. The eupyrene spermatozoa are filiform, measure 100 μm in length, and contain an elongated nucleus, 2 mitochondrial derivatives without paracrystalline materials, and a 9 + 2 axoneme without accessory tubules; the nucleus extends for almost the entire length of the spermatozoa. The absence of apyrene spermatozoa in Micropterix is in contrast to their presence in another species of the same family.

One possible explanation for the ?* relation in non-crystalline materials

The existence of natural occurring paracrystals, as an intermediate state of non-crystalline matter lying between crystals and gases, has been convincingly supported in recent years [1-3]. Paracrystalline materials can be detected by X-ray, neutron or electron diffraction and sometimes by electron microscopy [4]. One basic feature of real paracrystals is that they exhibit limited colloidal dimensions [2]. Paracrystalline materials cannot grow to macroscopic sizes mainly because of the gradual increase in the fluctuation of lattice points due to the presence of three dimensional statistically distributed motifs disturbing the lattice packing. When the lattice fluctuations reach values which are of the order of the average lattice spacing, d, the paracrystal has essentially reached its limiting coherent lattice size, /)=Nd. The study of non-crystalline materials showing a paracrystaUine behaviour has given rise to an empirical relation which states: the product of the square root of the number of N lattice planes within a paracrystal, N 1/2, times the value of the relative distance fluctuation (degree of distortion), g = Aa/cT, (A1 is the distance fluctuation between two neighbouring lattice planes)gN 1/2, is nearly a constant o~*. Fig. 1 illustrates the linear increase

Ultrastructure of the Spermatozoon of an Opisthobranch, Tornatina sp. (Mollusca, Gastropoda, Retusidae)

The spermatozoon of Tornatina sp. has been studied with phase-contrast light microscopy and transmission electron microscopy. The head of the spermatozoon consists of an elongate acrosome which caps the apex of an unusually complex, helical nucleus. This elaborate nuclear morphology has not been previously reported, but possibly is found in other opisthobranch gastropod spermatozoa. An axoneme is inserted deeply into the base of the nucleus whilst posterior from the nucleus, the axoneme is ensheathed successively by the mitochondrial derivative (midpiece) and 'glycogen' granules (glycogen piece). The midpiece exhibits fine structure similar to that observed in other euthyneuran spermatozoa (paracrystalline and matrix materials) and possesses a single helical compartment filled with what are probably glycogen granules. A dense ring structure occurs at the junction of the midpiece and glycogen piece. The spermatozoon of Tornatina and other gastropods (prosobranch and euthyneuran) are compared.

CHEMISTRY AND CLAY MINERALOGY OF ANDO SOILS, BROWN FOREST SOILS, AND PODZOLIC SOILS FORMED FROM RECENT TOWADA ASHES, NORTHEASTERN JAPAN

We conducted chemical and clay mineralogical studies on Ando soils, Brown forest soils, and Podzolic soils that had been formed mainly from felsic Towada-a (1000 B.P.) and Chuseri (4000 B.P.) ashes under different climates and vegetation. Organic carbon accumulated remarkably in the humus horizons of all the soils and contributed to the high CEC of the soils. Soil acidity was observed to be in the order of Ando soils < Brown forest soils < Podzolic soils, reflecting the differences in base saturation and clay mineralogy of these soils, and to have a tendency to decrease with depth within the same profiles. Diagnostic properties of soil samples, such as pH(NaF), phosphate absorption, pyrophosphate-soluble Fe(Fep)/dithionite-citrate-soluble Fe(Fed), pyrophosphate-soluble Al(Alp)/dithionite-citrate-soluble Al(Ald), Fep + Alp/percent clay, Fep + Alp/Fed + Ald, etc., were studied in detail. None of these chemical criteria, however, could distinguish satisfactorily among Ando soils, Brown forest soils, and Podzolic soils formed from Towada ashes. It was noted that both Fep/Fed and Alp/Ald ratios increase with decrease in the soil pH(H2O). Notable differences in clay mineralogy were observed between soil groups. Ando soils had mostly clay fractions dominated by amorphous materials consisting mainly of allophane and imogolite. Nonexpansible chloritized 2:1 mineral, which was major among the crystalline clay minerals, was present in relatively large amounts only in the surface horizons. Brown forest soils showed a diversity in clay mineralogy within the same soil profiles. The clay fractions of the surface soils showed an abundance of chloritized 2:1 mineral with high expansibility and an absence of allophane and imogolite. The subsoils showed major amorphous and paracrystalline materials with minor 2:1 layer silicates. The clay fractions of the Podzolic soils, except those of IIB horizon soils, were characterized by the abundance of chloritized 2:1 mineral varying widely in expansibility and by the absence of allophane and imogolite. The IIB horizons from Chuseri ash had clay fractions dominated by amorphous materials consisting mainly of free iron and alumina. Laminar opaline silica was found in almost all the humus horizons and was relatively abundant in the modern humus horizons of Brown forest soils. We concluded that formation of allophane and imogolite, as well as chloritization of 2:1 layer silicates, is related primarily to soil acidity. Allophane and imogolite formed only in the soils having pH(H2O) >4.9, irrespective of differences in soil groups and soil horizons. The 2:1 layer silicates were considered to have formed largely by alteration of volcanic glass. Chloritization of 2:1 layer silicates was observed to proceed with formation of allophane and imogolite. The formation of laminar opaline silica in the surface soil was considered to be suppressed not only in the Ando soils containing large amounts of allophane and imogolite, but also in the Podzolic soils, which are subject to strong leaching.

The longitudinal Young's modulus of Pinus radiata

The variation of the longitudinal Young's modulus with mean cellulose microfibril angle of the wood substance of the earlywood of a softwood has been determined from small clear samples. The longitudinal Young's modulus falls steeply as the angle between the longitudinal axis and the mean microfibril direction in the cell walls increases. The variation has been explained in both form and magnitude by applying the elastic theory of a fibre composite material with distributed fibre directions to a model of the experimental material. It confirms the two phase concepts of the plant cell wall, as far as the elastic properties are concerned, of rigid crystalline microfibrils embedded in an isotropic matrix of amorphous and paracrystalline materials.

Crystalline and Paracrystalline Order in High Polymers

The mathematical treatment of light scattering by regular and random arrays of points is outlined. The diffraction patterns of two-dimensional models are compared with patterns from ideal crystals, imperfect crystals, and paracrystalline lattices. The effects of various types of crystalline imperfections and paracrystalline order on the diffraction pattern are analyzed and examples are presented. It is shown that both natural and synthetic polymers can be treated as paracrystalline materials. The diffraction patterns of polyethylene after various thermal and mechanical treatments are discussed. A detailed model of the structure of polyethylene is presented and various features of the structure of other polymers are pointed out.