bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nuclear DNA content in the Australian Bulbine (Liliaceae)
Authors: Watson E. M. 
Published: April 2011

Nuclear DNA measurements for 17 Australian populations of Bulbine support the recognition of the four major groups already suggested by chromosome studies. Within the perennial group, Bulbine bulbosa s. lat., the tuberless, 46-chromosome (hypo-8x) "rock lily" has a similar DNA content to the hypo-4x, 24-chromosome populations of the "bulbosa" complex, which has populations at hypo-4x, -8x, and -12x levels. The "rock lily" also has substantially less DNA than another 46-chromosome entity, represented by the Kroombit population. Within the annual group, Bulbine semibarbata s. lat., the distinctions are less clear. However, the winged-seeded, 4x, 28-chromosome "alata" appears to have slightly more DNA than the closely related 26-chromosome "semibarbata." The 54-chromosome, 8x annual populations of eastern Australia have a DNA amount consistent with their proposed allopolyploid origin. The 52-chromosome "semibarbata" populations of Western Australia have, as expected, a lower DNA content than the 54-chromosome form and approximately twice the 4x "semibarbata" amount. It is suggested that some observed clinal variation in DNA content and an apparent DNA deficit in some of the higher polyploids of both perennial and annual groups may be attributable to climatic trends since the Miocene. Key words: Liliaceae, Bulbine, DNA content, polyploids, genome evolution.
The orientation behaviour of multiple chromosome configurations in acridid grasshoppers
Authors: John B. 
Published: April 2011

The existing data on the behaviour of multiple chromosome configurations arising from single interchanges between either metacentric–telocentric or telocentric–telocentric nonhomologues in 10 species of acridid grasshoppers are compared with data from four new cases. Two of these new cases involve metacentric–telocentric exchanges but the other two, for the first time in acridids, deal with a reciprocal translocation between two nonhomologous metacentrics. The combined data are used to evaluate the factors that influence multiple orientation in this family of grasshoppers and reemphasize the importance of chiasma frequency and chiasma distribution for multiple behaviour. This conclusion is reinforced by a consideration of the known cases of chain of three multiples originating from the Robertsonian fusion of nonhomologous telocentrics in acridoids. Key words: acridid grasshoppers, multiple chromosome configurations, chiasma distribution, orientation behaviour.
Trigenomic combinations for the analysis of meiotic control in the cultivated Brassica species
Authors: Busso C. , Attia T. , Röbbelen G. 
Published: April 2011

Haploid hybrids of either Brassica campestris (AA) or B. oleracea (CC) with B. nigra (BB) show a relatively low amount of chromosome pairing as compared with the level observed in the hybrid B. campestris × B. oleracea. This finding led to assume that B. nigra may carry a genic system suppressing homoeologous pairing in Brassica. To test this hypothesis, trigenomic hybrids (genome constitution ABC, 2n = 27) were synthesized, in which the effect of the B genome on the homoeologous pairing of the A and C genomes could be measured. The results indicate the inability of B. nigra to affect the level of pairing between homoeologous chromosomes of the A and C genomes. No genetic factor for a suppression of pairing was found in the B genome and there were no cytoplasmic effects on the regulation of pairing. However, cytological evidence pointed to chances of a successful transfer of economically valuable genes from B. nigra into the A and C genomes through the normal events of meiotic recombination. Key words: Brassica, triploid (trigenomic), homoeologous pairing, gene transfer.
Cytological mechanisms of thelytokous parthenogenesis in insects
Authors: Lamb Richard Y. , Willey Robert B. 
Published: April 2011

The eight female parthenogenetic mechanisms recognized in insects are organized under the broad categories "ploidy restoration" and "ploidy stasis." Each term replaces three imprecise and inappropriate existing names. Of the eight mechanisms, two are given names for the first time, and a table brings together all mechanisms in a new manner that shows the exact point in meiosis during which the DNA is doubled. Key words: insect reproduction, parthenogenesis, parthenogenetic mechanisms.
Inheritance and linkage of isozymes in Populus tremuloides (Michx.)
Authors: Hyun Jung O. , Rajora Om P. , Zsuffa Louis 
Published: April 2011

Progenies of four controlled crosses were assayed electrophoretically to determine the inheritance of isozymes of 10 loci coding for six enzymes, aconitase (ACO), glutamate oxaloacetate transaminase (GOT), isocitrate dehydrogenase (IDH), phosphoglucomutase (PGM), 6-phosphogluconate dehydrogenase (6-PGD), and phosphoglucose isomerase (PGI), in roots of Populus tremuloides. Chi-square goodness of fit tests verified a single-gene Mendelian control of the segregating allozyme variants at each of five loci: Aco-1, Got, Pgm-2, 6-Pgd-2, and Pgi-2. Evidence was also obtained for a single-gene control of each of the remaining five loci (Aco-2, Idh, Pgm-1, 6-Pgd-1, and Pgi-1). ACO and PGM showed monomeric, while GOT, IDH, 6-PGD, and PGI had dimeric, banding patterns. The results of joint two-locus segregation tests indicated no linkage between 6-Pgd-2 and Pgi-2. Key words: Populus species, electrophoresis, allozymes, inheritance, linkage.
Character association analysis in common wheat (Triticum aestivum L.)
Authors: Balyan H. S. , Singh Tejbir 
Published: April 2011

Grain yield of wheat as a component characteristic of total dry matter (biological) yield is governed by harvest index (V. P. Kulshrestha and H. K. Jain. 1982. Z. Pflanzenzuecht. 89: 19–30). At the phenotypic level, both the grain and biological yields are dependent upon a number of measurable agronomic characteristics such as plant height, tiller number, spike length, and grains per spike, etc. From a breeder's point of view, it is of great value to know the relative significance of these characteristics in determining grain yield to design appropriate selection strategies. The present study evaluated the covariability of yield in relation to various agronomic traits and ascertained their direct and indirect contributions towards grain yield. Key words: wheat, grain yield.
The chromosomal location of a gene (msg) affecting megasporogenesis in durum wheat
Authors: Joppa L. R. , Williams N. D. , Maan S. S. 
Published: April 2011

An aneuploid durum wheat line (Triticum turgidum L. var. durum) having 13 chromosome pairs and 2 unpaired chromosomes at metaphase I of meiosis in pollen mother cells (i.e., monosomic for chromosomes 7A and 7D) was observed to produce some progeny plants with 2n = 40 chromosomes. These aneuploid (triploid) plants were usually weak and sterile. Triploid plants also occurred in the progeny of durum plants monosomic for chromosome 7A, or in progeny of plants that were mono-telodisomic or ditelomonotelosomic for chromosome 7Aq (13 II + 1 t II or 13 II + t II + t I) but not in the progeny of plants ditelomonotelosomic for chromosome 7Ap (13 II + t II + t 1). Therefore, there is a gene(s) on chromosome arm 7Ap that prevents the production of diploid (2n) egg cells in wheat. In the absence of 7Ap, a portion of the egg cells have 26 chromosomes, which when fertilized with a pollen nucleus with 14 chromosomes, produces progeny plants with 2n = 40 chromosomes. The data also indicated that chromosome arm 7Dp probably contains a second gene that is capable of preventing the production of triploid plants. Key words: Triticum turgidum L. var. durum, polyploidy, aneuploid, triploid, monosomic.
Doubled haploids for detecting pleiotropy and linkage of genes controlling two characters
Authors: Choo T. M. , Reinbergs E. 
Published: April 2011

A new method was developed for detecting pleiotropy and linkage of genes controlling two characters. It employs doubled-haploid lines derived from diallel crosses and permits quantification of pleiotropic effects. The method was used to study genetic correlations between five pairs of four characters (heading date, plant height, the number of spikes per hill, and grain yield) in seven varieties of barley. Results suggested that pleiotropy was present in all five pairs of characters and linkage in four pairs of characters. Key words: barley, haploids, pleiotropy, linkage.
In situ digestion of Drosophila virilis polytene chromosomes by AluI and HaeIII restriction endonucleases
Authors: Mezzanotte R. , Bianchi U. , Marchi A. 
Published: April 2011

Polytene chromosomes of Drosophila virilis were treated with AluI and HaeIII restriction endonucleases. Both enzymes were capable of extensively digesting chromosomal DNA, with the exception of some regions that contain repetitive DNAs. Moreover, a comparison was made between our data and the data already obtained with the same enzymes in D. melanogaster. On this basis, AluI digestion showed that the 5S RNA genes of D. virilis and D. melanogaster have different base composition, while digestion with HaeIII revealed resistance of the histone genes in D. virilis, contrary to what was previously found in D. melanogaster. Key words: restriction endonucleases, 5S RNA genes, histone genes, polytene chromosomes, Drosophila species.
Genetics and cytology of unreduced gametes in cultivated rye (Secale cereale L.)
Authors: Lelley T. , Mahmoud A. A. , Lein V. 
Published: April 2011

An inbred genotype of cultivated rye was found that produces unreduced gametes in a very regular fashion. In the cross progeny of this line with another inbred line, which did not show unreduced gametes, the inheritance of this phenomenon was studied. The formation of unreduced gametes appears to be a recessive trait controlled by more than one gene. Chiasma frequency in 4n PMCs is exactly twice that in 2n PMCs. In first metaphase of 4n PMCs only bivalents (no multivalents) were seen. The possible mechanism leading to unreduced gametes and its evolutionary implications are discussed. Key words: rye, unreduced gametes, polyploidy, genetic control, chiasma frequency.
Sequence conservation and expression of theSex-lethalhomologue in the flyMegaselia scalaris
Authors: Sievert Volker , Kuhn Sylvia , Paululat Achim , Traut Walther 
Published: April 2011

Sex-lethal (Sxl) is Drosophila melanogaster's key regulating gene in the sex-determining cascade. Its homologue in Megaselia scalaris, the chromosome 3 gene Megsxl, codes for a protein with an overall similarity of 77% with the corresponding D. melanogaster sequence. Expression in M. scalaris, however, is very unlike that in D. melanogaster. Megsxl transcripts with a long ORF occur in both sexes. Differential splicing is conserved but not sex-specific. There are several splice variants, among them one is common to gonads and somatic tissues of all developmental stages investigated, one is specific for ovaries and embryos, and a third one is not found in ovaries. In the ovary, Megsxl is heavily transcribed in nurse cells and transported into eggs. These results suggest a non-sex-determining function during early embryogenesis; the presence of Megsxl RNA in testes and somatic tissues calls for other (or more) functions.Key words: sex determination, RNA-binding domain, differential splicing, RNA in situ hybridization.
Identification and chromosomal localization of a transcriptionally active retrotransposon of Ty3-gypsy type in rice
Authors: Li Zi-Yin , Chen Shou-Yi , Zheng Xian-Wu , Zhu Li-Huang 
Published: April 2011

A DNA fragment representing a transcriptionally active retrotransposon of Ty3-gypsy type was isolated and characterized from rice (Oryza sativa L.). The fragment (named RIRE9) includes the coding sequences for the C-terminal part of the RNase H domain and the N-terminal part of the integrase domain in the polyprotein region. Northern blot hybridization indicated that this element was expressed in rice leaves and stems, suggesting that it is potentially active to transpose under normal growth conditions. Using dot-blot hybridization, the copy number of RIRE9 was estimated to be about 1600 copies per haploid rice genome. Five homologous copies of RIRE9 were assigned to five distinct positions of four chromosomes by restriction fragment length polymorphism (RFLP) mapping approach using an indica-japonica rice doubled-haploid (DH) population and its molecular linkage map. Key words: Oryza sativa L., Ty3-gypsy-like retrotransposon, copy number, chromosomal location.
Organization, nucleotide sequence, and chromosomal mapping of a tandemly repeated unit containing the four core histone genes and a 5S rRNA gene in an isopod crustacean species
Authors: Barzotti Rita , Pelliccia Franca , Bucciarelli Elisabetta , Rocchi Angela 
Published: April 2011

A tandemly repeated unit of 6553 bp containing a copy of the four core histone genes H2B, H2A, H3, and H4, and also a 5S rRNA gene, was amplified by PCR from genomic DNA of the isopod crustacean Asellus aquaticus. The linkage between 5S rRNA genes and histone genes has been so far observed in only one other organism, the anostrac crustacean Artemia salina. The gene cluster was cloned and sequenced. The histone genes, in their 3' flanking region, have the interesting feature of possessing two different mRNA termination signals, the stem-loop structure and the AATAAA sequence. A part of the PCR product was used as a probe in FISH experiments to locate the gene cluster on an inter-individually variable number of chromosomes from 6 to 12 per diploid cell, always in a terminal position and never associated with the heterochromatic areas. Fluorescence in situ hybridization (FISH) was also performed on preparations of released chromatin and the reiteration level of the gene cluster was determined as approximately 200-300 copies per haploid genome. Key words: Asellus, Isopoda, Crustacea, histone genes, 5S rRNA gene.
A comparison of the multigroup and collocation methods for solving the low-energy neutron Boltzmann equation
Authors: Clowdsley M S , Heinbockel J H , Kaneko H , Wilson J W , Singleterry R C , Shinn J L 
Published: April 2011

A low-energy neutron transport algorithm for use in space-radiation protection is developed. The algorithm is based upon a multiple energy group analysis of the straight ahead Boltzmann equation utilizing a mean value theorem for integrals. The algorithm developed is then verified by using a collocation method solution on the same straight ahead Boltzmann equation. This algorithm was then coupled to the existing NASA Langley HZETRN (high charge and energy transport) code through the evaporation source term. Evaluation of the neutron fluence generated by the February 23, 1956 solar particle event for an aluminum-water shield-target configuration is then compared with the LAHET Monte Carlo calculation for the same shield-target configuration. The algorithm developed showed a great improvement in results over the unmodified HZETRN solution. A bidirectional modification of the evaporation source produced further improvement of the fluence. PACS Nos.; 87.50N, 25.40D, 28.20G
On classical and quantum harmonic potentials
Authors: Mohazzabi P 
Published: April 2011

To date, the only potential energy function that has been demonstrated to be classical harmonic but not quantum harmonic is that of the asymmetrically matched harmonic oscillator. By investigating the accurate quantum mechanical energy levels of the potential V = V0 [Formula: see text], we demonstrate that this is the second member of the class. PACS No.: 03.65Ge
Energy and time as conjugate dynamical variables
Authors: Grigorescu M 
Published: April 2011

The energy and time variables of the elementary classical dynamical systems are described geometrically, as canonically conjugate coordinates of an extended phase-space. It is shown that the Galilei action of the inertial equivalence group on this space is canonical, but not Hamiltonian equivariant. Although it has no effect at a classical level, the lack of equivariance makes the Galilei action inconsistent with the canonical quantization. A Hamiltonian equivariant action can be obtained by assuming that the inertial parameter in the extended phase-space is quasi-isotropic. This condition leads naturally to the Lorentz transformations between moving frames as a particular case of symplectic transformations. The limit speed appears as a constant factor relating the two additional canonical coordinates to the energy and time. Its value is identified with the speed of light by using the relationship between the electromagnetic potentials and the symplectic form of the extended phase-space. PACS Nos.: 45.20Jj, 11.30Cp, 03.50De
Classical harmonic oscillator approach of a helical-wiggler free-electron laserwith axial guide field
Authors: Rhimi M N , El-Bahi R , Cheikhrouhou A W 
Published: April 2011

Electron beam dynamics in a helical-wiggler free-electron laser (FEL) with a uniform axial guide magnetic field are studied using a three-dimensional Hamiltonian approach. The basic feature of the analysis is the definition of a rotational variable, [Formula: see text], that plays the primordial role in lowering to the half the dimension of the quadratic Hamiltonian as a system of two uncoupled oscillators with definite frequencies and amplitudes. It is through applying this variable in the vicinity of a fixed point that the Heisenberg picture of the dynamics of the particles comes to light, leading thus to the association of the steady-state ideal helical trajectories with arbitrary trajectories. The approach recognized the usual two constants of motion, one being the total energy while the other is the canonical axial angular momentum, Pz'. If the value of the latter is such that a fixed point exists, the Hamiltonian is expanded about the fixed point up to second order. The so-obtained oscillator characteristic frequencies allowed one to study the different modes of propagation and to identify, and then avoid the problematic operating conditions of the FEL concerned. On the other hand, the amplitudes of the oscillations, which do depend on the frequencies, are fortunately found to be constants of motion and then controlled by the boundary conditions (initial conditions). PACS Nos.: 52.40-w, 52.60+h, 42.55.Tb, 52.75Ms
Spectroscopy of the C2 molecule: Valence and Rydberg states in the 710 eV region. An ab initio study
Authors: Bruna P J , Grein F 
Published: April 2011

The potential curves of selected valence and Rydberg states of C2 lying in the 710 eV region are reported for the first time. The states studied, using MRCI wave funtions, include (25)3,1Πu, (13)3Σ+g, (25)3Σg, (13)3Δg, and relevant quintet states. The f 3Σg, g3Δg, and F1Πu states observed in absorption from 8.88 to 9.25 eV by Herzberg et al. have originally been assumed to be πu ® 3s Rydberg states, with respect to a 3Πu(13Πu) for the triplets and to X1Σg+ for the singlet. Our calculations partially support such assignments: f 3 Σg corresponding to 33Σg has mixed valence σuσgπu 3πg and Rydberg σu 2σgπu 23s character, g 3Δg corresponding to 23 Δg has a valence σuσgπu 3πg structure, while F 1 Πu(21Πu) is confirmed to be a σu 2πu 33s state. The calculated f00-values for these bands are 0.027 for f¬ a, 0.051 for g ¬ a, and 0.098 for F ¬ X. The singletsinglet transition F ¬ X constitutes the strongest absorption band reported so far for C2. Our theoretical value agrees with f00(F¬X) = 0.10 ± 0.01 derived indirectly from interstellar data collected by the Hubble Space Telescope. The 13Σg+ (σuσgπu 3πg) state at Te = 7.57 eV lies much higher than expected by experimentalists. PACS Nos.: 31.20T, 31.50, 33.20N, 33.70. PACS Nos.: 31.20T, 31.50, 33.20N, 33.70.
Nonresonant multiphoton excitation spectra of atomic 7Li
Authors: Ballard M K , Bernheim R A , Bicchi P 
Published: April 2011

The nonresonant multiphoton laser-induced fluorescence excitation spectrum of isotopically purified 7Li was obtained with a tunable, pulsed, nanosecond laser scanned between 13 600 and 14 500 cm1. The measured Rydberg series include n 2P [Formula: see text] 2 2S, n 2F [Formula: see text] 2 2S, n 2P [Formula: see text]2 2P, and n 2F [Formula: see text] 2 2P, and term values up to 14 2P and 28 2F were determined. Features due to the ac Stark effect become prominent for the high Rydberg states, but can be eliminated by using circular instead of plane-polarized radiation. Quantum defect values for the n 2P, n 2D, and n 2F levels were determined. Those for the n 2F states cover a range of principal quantum numbers not previously investigated. PACS Nos.: 32.80Rm, 32.30Jc, 32.70Jz
Modelling the far wings of collision-induced translational spectral profiles
Authors: Glaz W , Tabisz G C 
Published: April 2011

By comparing three model spectral profiles to precise line shapes obtained from quantum calculations, we assess the suitability of the various models for describing the far wings of translational collision-induced spectra. A profile obtained based on a generalized Langevin approach can give a better fit to the quantum shape than the widely used BirnbaumCohen model; the fit given by the six-parameter extended BirnbaumCohen profile proves to be the best of all three functions. PACS No.: 32.70Jz
The pion cut and the negative-energy behaviour of neutronproton effective-range functions near threshold
Authors: Dijk W van , Kermode M W 
Published: April 2011

We study the effect of the pion cut on the negative-energy effective-range parameters of the 3S1  3D1 neutronproton interaction. Utilizing an approach involving one-pion-exchange potentials truncated at large distances, we demonstrate that the mixing parameter at negative energies between zero and the deuteron energy is practically independent of presence or absence of the pion cut. At the same time, the analysis gives some interesting insight into the behaviour of the mixing parameter and other effective-range functions at more negative energies. This work complements our earlier result that the positive-energy mixing parameter is independent of the pioncut. PACS Nos.: 0.3.80+r, 11.55Bq, 13.75C, 21.30-x
Convective heat transfer past a continuously moving plate embedded in a non-Darcian porous medium in the presence of a magnetic field
Authors: Abo-Eldahab E M , El Gendy M S 
Published: April 2011

In the present study, free-convection and heat-transfer behavior of an electrically conducting fluid is investigated near a stretching sheet embedded in a non-Darcian medium. The temperature of the stretching sheet is varied. The sheet is stretched linearly with variable velocity and temperature. Boundary-layer equations are derived. The resulting approximate nonlinear ordinary differential equations are solved numerically. Velocity and temperature profiles as well as the local Nusselt number and skin-friction coefficient are computed for various values of the magnetic field, the Prandtl number, the free convective parameter, and the inertia parameter. PACS No.: 44.30+v
WKB quantization rules for three-dimensional confinement
Authors: Sinha A , Roychoudhury R , Varshni Y P 
Published: April 2011

Confined quantum systems have been studied by various authors over the past decades, by using various mathematical techniques. In this work, we derive the WKB quantization rules for quantum systems confined in an impenetrable spherical box of radius r0. We apply the proposed method to two systems explicitly, viz., the confined harmonic oscillator and the confined hydrogen atom. The results are found to be in reasonable agreement with those obtained by other methods. PACS No.: 03.65