Cellular organisation of the mature testes and stages of spermiogenesis in Danio rerio (Cyprinidae; Teleostei)--structural and ultrastructural studies

The male gonads of Danio rerio occupy a position typical of the Teleostei species. The structure of the testes corresponds to the anastomosing tubular type with unrestricted spermatogonia and represents a cystic type of spermatogenesis. The results of this study indicate that four distinct stages of cell differentiation can be identified during spermiogenesis. These stages are characterised by chromatin condensation, the development of flagellum, nuclear rotation, the formation of nuclear fossa and the elimination of excess cytoplasm. A round head and the absence of an acrosome characterise the differentiated sperm. The midpiece is short and large, and C-shaped mitochondria form a ring surrounding the initial region of the flagellum. The axoneme shows a 9 + 2 pattern. In the D. rerio spermatozoa the flagellar axis is at an angle of 110° to the nucleus diameter running through the centriole.     

Group theoretical aspects ofU B(6) ⊗U F(20) symmetry limits of IBFM related to theU B(5) andO B(6) limits of IBM

TheU ^B(6)⊗U ^F(20) Bose-Fermi dynamical symmetry of interacting boson-fermion model arises when the odd nucleon occupies single particle orbits withj=1/2, 3/2, 5/2, and 7/2. The subgroup structures ofU ^B(6)⊗U ^F(20) related to theU ^B(5) andO ^B(6) limits of sdIBM (U ^B(6)) are analysed. Broadly speaking,U ^B(6)⊗U ^F(20) admitsU ^BF(5)⊗U _s ^F (4), Spin^BF(5)⊗U _k ^F (5) andU ^BF(5)⊗U _s ^F (2) limits withU ^B(5) core and Spin^BF(6),O ^BF(5)⊗U _s ^F (4), Spin^BF(6)⊗U _k ^F (5) andO ^BF(6)⊗U _s ^F (2) limits withO ^B(6) core respectively. For each of these seven symmetry limits, group chains, quantum numbers labelling the basis states, generators and Casimir operators for the various subgroups and energy formulas are given. Recoupling coefficients (reduced Wigner coefficients) for constructing wavefunctions of low-lying states are tabulated and these will allow (together with sdIBMU ^B(5) andO ^B(6) limit results) one to calculateB(E2)’s,B(M1)’s, one and two nucleon transfer strengths etc. in the seven symmetry limits. Experimental examples for theU ^B(6)⊗U ^F(20) symmetry limits are briefly discussed.     

Centrifugal (centripetal) and Coriolis' velocities and accelerations in $$ (\bar L_n,g) $$ -spaces

The notions of centrifugal (centripetal) and Coriolis' velocities and accelerations are introduced and considered in spaces with affine connections and metrics [ -spaces] as velocities and accelerations of flows of mass elements (particles) moving in space-time. It is shown that these types of velocities and accelerations are generated by the relative motions between the mass elements. They are closely related to the kinematic characteristics of the relative velocity and relative acceleration. The centrifugal (centripetal) velocity is found to be in connection with the Hubble law. The centrifugal (centripetal) acceleration could be interpreted as gravitational acceleration as has been done in the Einstein theory of gravitation. This fact could be used as a basis for workingout new gravitational theories in spaces with affine connections and metrics.     

Morphological and ultrastructural characterization of the alimentary canal in Japanese wax scale (Ceroplastes japonicus Green)

The morphology and ultrastructure of the alimentary canal in the adult female of the Japanese wax scale, Ceroplastes japonicus Green (Hemiptera: Coccoidea: Coccidae), was investigated using light microscopy, scanning electron microscopy and transmission electron microscopy. The results showed that the foregut was subdivided into a sclerotized pharynx and an oesophagus. A pair of salivary glands attached in the middle of the foregut. The loop-shaped midgut was narrow and longer than the foregut and its inner wall lined with a thick layer of epithelia. The hindgut was divided into a narrower ileum and a broader rectum, with the well-developed filter chamber enclosed in the anterior rectum. Malpighian tubules consisted of two brownish-yellow moniliform tubules with pores, approximately 1 μm in diameter, scattered on the outer surface and many spherical crystals inside the tubules.     

The next-to-leading order (NLO) gluon distribution from DGLAP equation and the logarithmic derivatives of the proton structure functionF 2(x, Q 2) at lowx

At lowx, an analytic solution of the DGLAP equation for gluon in the next-to-leading order (NLO) is obtained by applying the method of characteristics. Its compatibility with double leading logarithmic approximation (DLLA) asymptotics is discussed and comparison with the exact ones like GRV98NLO is made. The solution is then utilized to calculate the derivatives∂F ₂ (x,Q ²)/∂ lnQ ² and ∂ lnF ₂(x,Q ²)/∂ ln (1/x) and compared with the recent HERA data. Our solution is found to reproduce most of the essential features of the data on the derivatives.     

Comparative sperm ultrastructure of three species in Siniperca (Teleostei: Perciformes: Sinipercidae)

Siniperca chuatsi, Siniperca kneri, and Siniperca scherzeri are three of the most economically important sinipercid species. The ultrastructure and morphology of the mature spermatozoa of them are examined using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The sperm consists of an acrosome-less head, a short midpiece and a long flagellum. Ultrastructurally, it has a homogeneously electron-dense nucleus in a granular pattern with nuclear lucent and a nuclear fossa excluding the centriolar complex. One to four mitochondria with lamellar cristae encircle the basal body of the flagellum in the midpiece. The cytoplasm surrounding the centrioles and the cylindric cytoplasmic channel contains glycogen granules and vesicles. Comprising the conventional 9 + 2 axoneme, vesicles and lateral fins, the sperm flagellum is inserted laterally on the nucleus, therefore the spermatozoon is asymmetrical. All of the spermatozoa of the three species are of the primitive or ect-aquasperm form and conform to the teleostean type II spermatozoa instead of the previously supposed type I. Variations in the shape of the heads, angles between the two centrioles, location of the cytoplasmic vesicles, mitochondrial number and structural characteristics of the lateral fins are notable among the three species. S. chuatsi is a sister-group of the other two species and is the most differentiated. The present study provides fresh insights to the comparative spermatology of Siniperca fishes and will be useful to the existing knowledge of the sinipercid fishes in systematic characters, biodiversity conservation and reproduction.     

Structural and ultrastructural characterization of male reproductive tracts and spermatozoa in fig wasps of the genus Pegoscapus (Hymenoptera, Chalcidoidea)

The three Pegoscapus species present the same internal reproductive tract features comprising testes with a single testicular tubule, seminal vesicles, vasa deferentia, accessory glands and an ejaculatory duct. The seminal vesicle shows two morphologically distinct portions although they do not resemble the separate chambers found in other Chalcidoidea. The anterior portion of the seminal vesicle shows a prominent epithelium and stores the mature spermatozoa, while the posterior region is formed by a thicker muscular sheath that participates on ejaculation. The sexual maturation in Pegoscapus is achieved at emergence, when the testicular degeneration occurs. The spermatozoa of Pegoscapus reveal a basic structure similar to that of other Chalcidoidea. In Pegoscapus sp1. and Pegoscapus sp2. they present the same features, whereas Pegoscapus tonduzi comprises some different characteristics. It measures approximately 160 μm in Pegoscapus sp1. and Pegoscapus sp2., while in P. tonduzi the spermatozoa measure about 360 μm. The extracellular sheath thickness is another difference among the species. While Pegoscapus sp1. and Pegoscapus sp2. show a thick extracellular sheath, in P. tonduzi this sheath is very thin resulting in a large space intervening between the extracellular sheath and the nucleus. Despite these differences, the three species analyzed share some characteristics that allow the establishment of an identity to the spermatozoon of the genus Pegoscapus: the seminal vesicle not divided in chambers; the absence of acrosomal structures in the spermatozoa; the length of the extracellular sheath; the central microtubules being the firsts to terminate in the sequence of microtubular cutoff at the final axonemal portion.     

Optical and electrical characteristics of (LiCl) x (P2O5)1 − x glass

Homogeneous (LiCl) _x (P₂O₅)_1 − x glasses were synthesised using a melt-quenching method for x = 0.1–0.6 in the interval of 0.05. The amorphous structure of the samples was evident by the X-ray diffraction spectrum. The short range structures of the binary phosphate samples were examined by Fourier transform infrared spectroscopy, whilst the density of the samples was measured as supportive data for the investigations. The results of refractive indices as measured using an ellipsometer reveal the homogeneity of samples and was found to depend on the glass composition. The electrical properties of the glasses were investigated by ac impedance spectroscopy from 10 mHz to 1 MHz for temperatures ranging from room temperature to 573 K. An estimation of the bulk resistivity was obtained by taking the intercepts on the real axis at low frequencies of the complex impedance plot. The dc conductivities derived from the reciprocal of resistivity values were found to obey the Arrhenius relationship, and its activation energy shows a decreasing trend with the increase in LiCl content in the glass. Lastly, an equivalent circuits consisting of real and complex capacitors is proposed to describe the dielectric response of the glass.     

WnNim(n+m=8)团簇结构与电子性质的理论研究

采用密度泛函理论(DFT)中的B3LYP方法,在Lanl2dz基组水平上对W_nNi_m(n+m=8)团簇的各种可能构型进行了几何参数全优化,得到了它们的基态构型;并对基态构型的平均结合能、Wiberg键级(WBI)、磁学性质、NBO进行了分析,结果表明:团簇随着W原子数的增多,稳定性增强,n≥5时,结构中都含有纯钨团簇的结构基元;W-W键级高于W-Ni键和Ni-Ni键;W₅Ni₃,W₆Ni₂团簇发生了"磁矩猝灭"的现象;在W,Ni原子内部,轨道电荷发生了转移,产生了"轨道杂化"现象,W,Ni原子之间也发生了电荷转移形成了较强的化学键. 关键词： nNi_m(n+m=8)团簇')" href="#">W_nNi_m(n+m=8)团簇 几何结构 电子性质 密度泛函理论     

The power and beauty of (γ, 2e) experiments

The power and beauty of energy- and angle-resolved two-electron emission in the double photoionization of atoms is demonstrated, concentrating on the particular shapes of the angular correlation patterns of the triple differential cross section. The cases selected are direct double photoionization in helium and neon as well as sequential double photoionization in xenon, both for equal and unequal energies of the emitted electrons.     

Picosecond dynamics and mechanism of the interaction of a photoexcited Cu(II)-porphyrin with a DNA-modeling polynucleotide

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 2, pp. 110–121, March–April, 1995.     

Photon mass and the fieldB (3)

The connection between finite photon mass and the fieldB ⁽³⁾ is developed with reference to special relativity in the vacuum. The existence of the physical and longitudinal fieldB ⁽³⁾ implies that there are three degrees of polarization associated with the photon, which cannot therefore be a massless boson. The fieldB ⁽³⁾ can be observed experimentally through the magnetization of a plasma with microwave pulses, and this experiment serves to demonstrate unequivocally the existence of photon mass.     

Noether's theorem and the fieldB (3)

It is shown that the longitudinal, magnetic flux density,B ⁽³⁾ , of vacuum electromagnetic radiation can be accommodated rigorously within Noether's theorem, which relates fundamental spacetime symmetries to fundamental conservation laws. This demonstration linksB ⁽³⁾ to the canonical energy-momentum tensorT _µv that appears in Einstein's field equations of general relativity. Thus,B ⁽³⁾ provides a link between electromagnetism and gravitation which might eventually lead to an unified understanding of field theory.     

SH（D）和OH（D）自由基基态的结构与势能函数

采用QCISD（T）/ 6-311++G（3df,2pd） 和QCISD/6-311++G（3df,2pd）方法计算优化了SH（D）和OH（D）自由基分子基态X²Π的分子结构和离解能.并采用最小二乘法拟合Murrell-Sorbie 函数得到了相应的势能函数,由此计算的振转常数与实验光谱数据符合得相当好. 关键词： SH和OH自由基分子 X²Π）')" href="#">基态（X²Π） Murrell - Sorbie函数 势能函数     

Excess molar volumes, viscosities, and refractive indices for binary and ternary mixtures of {cyclohexanone (1) + N,N-dimethylacetamide (2) + N,N-diethylethanolamine (3)} at (298.15, 308.15, and 318.15) K

Densities ρ, viscosities η, and refractive indices n_D, of the binary and ternary mixtures formed by cyclohexanone + N,N-dimethylacetamide + N,N-diethylethanolamine were measured at (298.15, 308.15, and 318.15) K for the liquid region and at ambient pressure for the whole composition ranges. The excess molar volumes V_m^E, viscosity deviations Δη, and refractive index deviations Δn_D, were calculated from experimental densities and refractive indices. The excess molar volumes are positive over the mole fraction range for binary mixtures of cyclohexanone(1) + N,N-dimethylacetamide (2) and N,N-dimethylactamide (2) + N,N-diethylethanolamine (3) and increase with increasing temperatures from (298.15 to 318.15) K. The excess molar volumes of cyclohexanone (1) + N,N-diethylethanolamine (3) are S-shaped dependence on composition with negative values in the N,N-diethylethanolamine rich-region and positive values at the opposite extreme and increase with increasing temperatures from (298.15 to 318.15) K. The excess molar volumes are positive over the whole mole fraction ranges for the ternary mixtures at all temperatures. Viscosity deviations are negative over the mole fraction range for all binary and ternary mixtures and decrease with increasing temperatures from (298.15 to 318.15) K. Refractive index deviations are negative over the mole fraction range for all binary and ternary mixtures and increase with increasing temperatures from (298.15 to 318.15) K. The experimental data of constitute were correlated as a function of the mole fraction by using the Redlich–Kister equation for binary and , Cibulka, Jasinski and Malanowski , Singe et al., Pintos et al., Calvo et al., Kohler, and Jacob–Fitzner for ternary mixture, respectively. McAllister^'s three body, Hind, and Nissan–Grunberg models were used for correlating the kinematic and dynamic viscosity of binary mixtures. The experimental data of the constitute binaries are analyzed to discuss the nature and strength of intermolecular interactions in these mixtures.