bluuebunny/crossref_metadata_2025_split huggingface dataset:
Population cytogenetics of Chorthippus vagans. I. Polymorphisms for pericentric inversion and for heterochromatin deletion
Authors: Cabrero Josefa , Camacho Juan Pedro M. 
Published: April 2011

Two different polymorphisms have been identified in natural populations of the grasshopper Chorthippus vagans. One of these involved an inversion polymorphism in the M7 chromosome and was present in two populations from Granada. In one of these, from Prados del Pinar, the frequency of this polymorphism was constant over three consecutive generations, and meiotic studies of heterozygous individuals indicated that this inversion had not effect on male fertility. The second polymorphism involved a deletion of the distal C-band of the short arm of the M4 chromosome, which was observed in three different populations. From the observed difference between its frequency in adults and embryos in one of these populations, that of Prados del Pinar, it would appear that this deletion is strongly selected against. Despite this, its frequency was maintained in adult individuals of this population over 2 consecutive years. Complete meiotic drive in favour of the M4–d chromosomes in heterozygous females would explain the maintenance of its frequency despite the fact that it is counterselected. Key words: Chorthippus, inversion, heterochromatin, polymorphism (chromosome), meiotic drive.
Genetic and cytogenetic analyses of the A genome of Triticum monococcum. IV. Synaptonemal complex formation in autotetraploids
Authors: Gillies C. B. , Kuspira J. , Bhambhani R. N. 
Published: April 2011

Electron microscopy of synaptonemal complex spreads from autotetraploid Triticum monococcum (2n = 4x = 28) revealed a minimum mean of 3.59 multivalents per zygotene–pachytene nucleus. The range of values was from 1 to 6 multivalents per nucleus. Most of the multivalents were quadrivalents with single, medially located pairing partner switch points. Lateral element pairing switches, particularly the few multiple switches, were often accompanied by extensive asynapsis around the switch point. The synaptonemal complex multivalent frequency is considerably higher than the metaphase I quadrivalent frequency previously reported for the same material. Calculations of expected pachytene quadrivalent frequency from metaphase I data, using several published theoretical models, gave values that did not agree with the results obtained here. The difference between the multivalent frequencies at pachytene and metaphase I does not appear to be the result of a correction process. Instead, it could be caused by a combination of preferential pairing or crossing-over and the effects of the position of partner switches and asynapsis associated with switches. Key words: autotetraploid, multivalents, synaptonemal complex, pairing effects.
Genome size variation in North American minnows (Cyprinidae). II. Variation among 20 species
Authors: Gold J. R. , Amemiya C. T. 
Published: April 2011

Genome sizes (nuclear DNA contents) from 200 individuals representing 20 species of North American cyprinid fishes (minnows) were examined spectrophotometrically. The distributions of DNA values of individuals within populations of the 20 species were essentially continuous and normal; the distribution of DNA values among species was continuous and overlapping. These observations suggest that changes in DNA quantity in cyprinids are small in amount, involve both gains and losses of DNA, and are cumulative and independent in effect. Significant heterogeneity in mean genome size occurs both between individuals within populations of species and among species. The former averages maximally around 6% of the cyprinid genome and is nearly the same as the amount of DNA theoretically needed for the entire cyprinid structural gene component. The majority of the DNA content variation among the 20 species is distributed above the level of individuals within populations. Comparisons of average genome size difference or distance between individuals drawn from different levels of taxonomic organization indicate that considerably greater divergence in genome size has occurred in the extremely speciose cyprinid genus Notropis as compared with other North American cyprinid genera. This may suggest that genome size change is concentrated in speciation episodes. Finally, no associations were found between interspecific variation in genome size and five life-history characters. This suggests that much of the variation in genome size within and among the 20 species may be phenotypically inconsequential. Key words: genome size, North American cyprinid fishes, evolution.
Incidence and inheritance of the 1/29 and 14/20 Robertsonian translocations in Canadian beef cattle
Authors: McWhir J. , Church R. B. , Coulter G. H. , Lin C. C. 
Published: April 2011

Metaphase chromosomes were prepared from peripheral leukocyte cultures of 253 beef animals representing 21 breeds. A total of 10 Robertsonian translocations were identified. Nine were 1/29 fusions and one was a stable 14/20 fusion identified in several Simmentals. To our knowledge, the only other case of this translocation reported was also in the Simmental breed, suggesting that this fusion may be unique to the breed. A further 54 relatives of known 1/29 and 14/20 carriers were examined, revealing that both fusions were inherited by 50% of offspring of the heterozygous carrier. Heterozygous male 1/29 carriers left fewer calves than karyotypically normal bulls when used in natural service. Key words: Robertsonian translocation, cattle, chromosomes, fertility.
Pattern of nucleolar organizer region activity during male meiosis in Callicrania seoanei (Orthoptera) as analyzed by silver staining: evidences for a possible reactivation in the period between the two meiotic divisions
Authors: Santos J. , Sentis C. , Fernandez-Piqueras J. 
Published: April 2011

Silver staining of spermatocytes and early spermatid nuclei from the neo XY race of the Tettigonioid species Callicrania seoanei reveals an active nucleolar organizer region (NOR) located proximally in a medium-sized bivalent. Ag-positive material was present at the NOR in all stages of male meiosis. However, the results obtained indicate that transcriptional activity of ribosomal cistrons (rDNA) is not maintained throughout spermatogenesis, but that NOR reactivation might occur in the period between the two meiotic divisions in addition to the more general postmeiotical reactivation in the early spermatid nuclei. Key words: NOR activity, silver staining, male meiosis, Callicrania seoanei (Orthoptera).
Correlations, epistasis, and heterosis of plant height and internode length in barley
Authors: Vazquez J. F. , Sanchez-Monge E. 
Published: April 2011

The correlation between total height and its components, and between these and yield components, and the presence of nonallelic interactions and heterosis were studied in barley by means of a 6 × 6 diallel cross. The estimation of interaction and heterosis parameters were made in P1, P2, F1, F2, B1, and B2 generations according to the Jinks and Jones model. Total height had a positive correlation with each internode length. The values of such correlations seemed to indicate that peduncle length could be a good index of total height. The plants with short basal internodes had less total height and longer intermediate internodes. The positive correlation of total height with yield and its components suggests that the selection for short culm and short basal internodes would be to the detriment of yield. The predominant interaction was of the duplicate type, the total height being the character with greater epistasis. In the crosses with heterosis, this was always positive. 'Albacete' × M-168 and A.1.-2 × M-168 were the crosses where the selection for short culm and lodging resistance would be most effective. Key words: diallel cross, correlations, epistasis, heterosis, barley.
Segmental pycnotic reversion of facultative heterochromatin during the second male meiosis in tettigonioid species (Orthoptera)
Authors: Piqueras J. Fernández , Sentís C. 
Published: April 2011

The X chromosome invariably exhibits isopycnosis during the most condensed stages of male meiosis after conventional staining procedures in all studied species of Tettigonioidea (Orthoptera). However, differential negative staining of the X chromosome can be achieved during these stages by a silver impregnation method after extraction of chromosomal proteins with 2 × SSC. This differential response to silver may be indicative of a distinctive chromatin organization in the X chromosome with respect to that of the autosomes. Following 2 × SSC – silver impregnation treatment, pycnotic reversion of part of the X chromosome can be observed from the metaphase II stage on in tettigonioids. Pycnotic reversion is initiated from the telomeric region of the X chromosome in the subfamily Ephyppigerinae, while in the subfamily Pycnogastrinae pycnotic reversion occurs at the centromeric region of this chromosome. These two modes of segmental pycnotic reversion may indicate the onset of a reversion of the facultative heterochromatinized state of the X chromosome (euchromatinization) during male meiosis in tettigonioids. An initiation center may be postulated for this process that is located either at the end distal to or proximal to the centromere of the X chromosome. This hypothesis is supported by the observed pycnotic behaviour of neo-X chromosomes in two different neo-XY systems, one involving centric and the other tandem fusion. Facultative heterochromatinization never involves the autosomally derived segments (XR) of the neo-X chromosomes. Occasional failures in the heterochromatinization process of part of the X chromosome, as well as of the neo-X chromosome, in two species suggests that both facultative heterochromatinization and its reversion are two processes that act segmentally. Key words: male meiosis, X chromosome, facultative heterochromatin, segmental euchromatinization.
The orientation of multivalents at meiotic metaphase I: a workshop report
Authors: Sybenga J. , Rickards G. K. 
Published: April 2011

During a workshop with 13 participants, several aspects of multivalent orientation at meiotic (pro)metaphase were discussed in an attempt to resolve some of the most prominent controversies with respect to terminology, interpretation of observations, and the validity of hypotheses and theories. For several terms and concepts, descriptive definitions were formulated that are recommended for general use. In the analysis of the behaviour of the multivalent in meiosis preprometaphase shape and position as important factors in final orientation were discussed, as well as the first contact between spindle and kinetochores and the role of reorientation. Specific characteristics of different multivalents and expected frequencies of different orientation types were considered. Finally, a few remarks on data collection and analytical procedures were made Key words: meiosis, multivalents, orientation, workshop.
DNA base composition heterogeneity in the grass genus Briza L.
Authors: King G. J. , Ingrouille M. J. 
Published: April 2011

Intragenomic DNA base composition heterogeneity is determined for eight species of Briza L. (Poaceae). High-resolution first-derivative DNA denaturation profiles, recording base composition distribution, provide a "fingerprint" of a species genome. Differences in base composition between species may be explained by chromosome loss or recent sequence amplification events and correlate with relationships established by traditional biosystematic methods. The complex polyphasic profiles can be deconvoluted into a small number of Gaussian curves that accurately represent the complex profile. The physical basis of this representation is demonstrated by affinity chromatography of DNA fragments of at least 600 base pairs, which separates a number of components. Key words: Briza, DNA base composition, genome heterogeneity, grass systematics, thermal denaturation.
Cytological evidence of terminal deficiencies produced by the r-X1 deletion in maize
Authors: Lin Bor-yaw 
Published: April 2011

In addition to monosomes and trisomes, the r-X1 deletion generates chromosome deficiencies of parts of an arm; these deficiencies now have been identified cytologically. Of eight japonica plants produced from the cross of r-X1/R-r as female with the Mangelsdorf's tester, five were complete and three were partial monosomes. The isolated partial monosomes had chromosome breaks in the region between the centromere and the japonica locus. Their breakpoints were at the 0.33, 0.30, and 0.25 positions, respectively, on the long arm of chromosome 8. Additionally, a liguleless plant produced from the same cross carried a partial monosome with a breakpoint at the 0.09 position on the short arm of chromosome 2. Although partial monosomes associated with other chromosome arms have not been investigated, it is evident that the action of the r-X1 deletion is not restricted to the centromeric region of maize chromosomes. Key words: maize, r-X1 deletion, terminal deficiencies, monosomes.
Inheritance and RAPD tagging of multiple genes for resistance to net blotch in barley
Authors: Molnar S J , James L E , Kasha K J 
Published: April 2011

A doubled haploid barley (Hordeum vulgare L.) population that was created from a cross between cultivars 'Léger' and 'CI 9831' was characterized by RAPD (random amplified polymorphic DNA) markers for resistance to isolate WRS857 of Pyrenophora teres Drechs. f. sp. maculata Smedeg., the causal agent of the spot form of net blotch. Resistance, which initially appeared to be conferred by a single gene from the approximate 1:1 (resistant : susceptible) segregation ratio of the doubled-haploid (DH) progeny, was found to be associated with three different genomic regions by RAPD analysis. Of 500 RAPD random primers that were screened against the parents, 195 revealed polymorphic bands, seven showed an association to the resistance in bulks, and these seven markers were mapped to three unlinked genomic regions. Two of these regions, one of which was mapped to chromosome 2, have major resistance genes. The third region has some homology to the chromosome 2 region. This study demonstrates the simultaneous location of markers for more than one gene governing a trait by using RAPD and bulked segregant analysis (BSA).Key words: net blotch, RAPD markers, bulked segregant analysis, barley, doubled haploids.
Isolation of large terminal sequences of BAC inserts based on double-restriction-enzyme digestion followed by anchored PCR
Authors: Yang Zhong-Nan , Mirkov T Erik 
Published: April 2011

Isolation of the terminal portions of genomic DNA cloned in bacterial artificial chromosomes (BACs) is an important step in map-based cloning, and several methods have been developed. Here, we present a new method based on double-restriction-enzyme digestion followed by anchored PCR. BAC DNA was digested with two enzymes: NotI and one of four enzymes (EcoRV, HpaI, StuI, or XmnI) that produce blunt termini. After dephosphorylation, these digestions were ligated to NotI- and EcoRV-digested pMSK, a new cloning vector developed in this work that is derived from pBluescript SK(+). PCR products representing the left- and right-terminal sequences of BAC inserts were obtained using a primer complementary to pMSK and a primer complementary to sequences in either the left arm or the right arm of the BAC vector pBeloBAC11. We have tested this method with 15 different BAC clones, and PCR products representing both the left- and right-terminal sequences have been obtained from all 15 BAC clones. This method is simple, fast, reproducible, and uses the same set of primers for any restriction enzyme used. With some modifications, it can also be used for isolating the terminal portions of genomic DNA cloned in yeast artificial chromosomes and P1-derived artificial chromosomes.Key words: BAC, anchored PCR, terminal sequence isolation, chromosome walk.
Interacting fermions in a two-dimensional trap and fractional exclusion statistics
Authors: Srivastava M K , Bhaduri R K , Law J , Murthy M.V.N. 
Published: April 2011

We consider N fermions in a two-dimensional harmonic oscillator potential interacting with a very short-range repulsive pair-wise potential. The ground-state energy of this system is obtained by performing a Thomas-Fermi as well as a self-consistent Hartree-Fock calculation. The two results are shown to agree even for a small number of particles. We next use the finite-temperature Thomas-Fermi method to demonstrate that in the local density approximation, these interacting fermions are equivalent to a system of noninteracting particles obeying the Haldane-Wu fractional exclusion statistics. It is also shown that mapping onto a system of N noninteracting quasiparticles enables us to predict the energies of the ground and excited states of the N-body system. PACS Nos.: 05.30-d, 73.20Dx
Hiemenz magnetic flow of a non-Newtonian fluid of second grade with heat transfer
Authors: Attia H A 
Published: April 2011

The steady laminar flow of an incompressible viscous electrically conducting non-Newtonian fluid of second grade impinging normal to a plane wall with heat transfer is investigated. An externally applied uniform magnetic field is applied normal to the wall, which is maintained at a constant temperature. A numerical solution for the governing momentum and energy equations is obtained. The effect of the characteristics of the non-Newtonian fluid and the magnetic field on both the flow and heat transfer is outlined. PACS Nos.: 47.50 and 47.15
Response above a plane-conducting earth to a pulsed vertical magnetic dipole at the surface
Authors: Abo-Seida O M , Bishay S T 
Published: April 2011

A theoretical study of the pulsed electromagnetic radiation from a vertical magnetic dipole placed on a plane-conducting earth is presented. The application of a Laplace transformation in time and a Fourier transformation in the two orthogonal, horizontal, spatial components leads, under consideration of initial, boundary, and transition conditions, to an integral representation of the solution of the wave equation in frequency space. A modified Cagniard method is then used to derive closed-form expressions for the magnetic Hertz vector anywhere above the conducting earth. The method is used to perform numeric calculations of the magnetic Hertz vector, for different source-receiver distances, as well as different values of the earth's conductivity and permittivity. PACS Nos.: 41.20Jb, 42.25Bs, 42.25Gy, 44.05+e
Role of democratic SU2 x n dual-group carrier space and group structure in the superboson quantum-Liouville physics of identical spin ensembles: Maximal n tensor product reduction, via symbolic algebraic combinatorics
Authors: Temme F P 
Published: April 2011

Structural aspects of superboson mappings and their dual group-based carrier spaces inherent in quantum-Liouville NMR formalisms are presented for their conceptual role in understanding the transformational properties and the spin dynamics of identical [A]n([Formula: see text]n) spin ensembles or [AX]n systems, given in terms of {Tkq (υ)} º  {|kqυ > >} tensorial bases. Interest in the explicit democratic labelling of the Liouvillian carrier subspaces of [A]n spin ensembles, prompts an examination of the inner products (ITPs) that define the projective carrier space associated with superbosons. A weak-branching (WB) limit (for (bipartite) partitions λ [Formula: see text] n, for n-indexed (SU2 ×)[Formula: see text]n) ITPs gives rise to: (i) maximal coefficient sets for [µ] [Formula: see text] [µ']([Formula: see text]n) irrep products (in Butler's notation), under a sufficiently high (n [Formula: see text] 4µ, 4µ') indexed [Formula: see text]n group, or (ii) to identical numerical {c[Formula: see text], λ' } sequence-ordered sets of reduction coefficients over similar, displaced-sequence fields  on augmenting ITP to [µ] [Formula: see text] [µ''], where µ'' > µ' > µ,  or else (iii) to some (sequence-displaced) subset of the latter. The origins of the decompositional WB limit as part of group structure may be traced to an algorithmic similarity between the LittlewoodRichardson and Young(III) combinatorial rules. Alternative approaches to the bipartite product decompositional mappings are possible, using both (subspatial-restricted) Schur-function techniques of Wybourne and [Formula: see text]16[Formula: see text]n[Formula: see text]28 symbolic algorithmic enumerations based on the SYMMETRICA discrete-maths. package of Kerber et al. (J. Symbolic Comput. 14, 195 (1993)). The nature of maximal sets and scaling in ITP decompositions is established and recognition given to the role of combinatorics, [Formula: see text]n algorithms and the superboson algebras of the SU(2) × [Formula: see text]n group in (multiple) quantized spin physics. PACS Nos.: 02.10, 03.65Ca, 33.20Vq, 33.25+k
Wave scattering from rough cylinders
Authors: Hillion P 
Published: April 2011

We present a nonconventional integral equation approach to the scattering of harmonic waves by a smooth or rough perfectly conducting circular cylinder and by a cylinder with a surface impedance. As an application, the case of a corrugated cylinder is investigated. PACS Nos.: 03.50De, 41.20Jb, 41.60Bq
On the calculation of charge-exchange effects in a relativistic model for (γ n) reactions
Authors: Lotz G M , Sherif H S 
Published: April 2011

The charge-exchange contribution to photoneutron emission is calculated in a relativistic model. The emission is regarded as a two-step process consisting of a direct electromagnetic knockout of a proton followed by a (p,n) charge-exchange reaction. The latter step is effected by the isovector components of the scalar and vector mean field optical potentials. A novel procedure, in which the pertinent integral is reduced to a simpler integral in combination with a differential equation, is adopted to evaluatethe transition amplitude. We find that the charge-exchange contribution is comparable in magnitude to the direct contribution over a range of photon energies. There is some dependence on the optical and binding potentials used to calculate nucleon wave functions. As expected, the sum of direct and charge-exchange contributions is not sufficient to account for the observed cross sections, confirming the importance of including meson exchange and isobar currents. PACS Nos.: 25.20Lj, 25.40Kv, 24.10Jv
The perturbative β-function in the Zumino model
Authors: Clarkson R , McKeon D.G.C. 
Published: April 2011

We consider the perturbative β-function in a supersymmetric model in four-dimensional Euclidean space formulated by Zumino. It turns out to be equal to the β-function for N = 2 supersymmetric YangMills theory despite differences that exist in the two models. PACS No.: 12.60Jv
Positron impact ionization of hydrogen and the noble gases
Authors: Campeanu R I , McEachran R P , Stauffer A D 
Published: April 2011

Based on our previous experience with positron ionization, we propose a simple distorted-wave model for this process and apply it to the ionization of atomic and molecular hydrogen as well as the noble gases. The advantage of having a single method that produces reliable results in all cases is discussed. PACS No.: 34.85+x
Low-lying spin-wave spectrum of the triangular anti-ferromagnet: A finite-size study
Authors: Trumper A E , Capriotti L , Sorella S 
Published: April 2011

We developed a finite-size spin-wave calculation on the Heisenberg anti-ferromagnet on the triangular lattice, which, to order 1/s, favors a singlet (for an even number of sites) ground state. Furthermore, we implement the computation of the low-energy excitation spectrum E (S) where S is the total spin. For s=1/2, the good agreement with the exact diagonalization and quantum Monte Carlo results strengthens the validity of the spin-wave expansion to describe the low-energy spin excitations of the Heisenberg model even in the presence of frustration. PACS No.: 75.10-b