bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chromosome pairing and aneuploidy in tetraploid triticale. II. Unstabilized karyotypes
Authors: Lukaszewski Adam J. , Apolinarska Barbara , Gustafson J. Perry , Krolow K.-D. 
Published: April 2011

In the progeny of tetraploid triticale plants that segregated for either one, two, or three pairs of homoeologous wheat chromosomes, plants were selected that had 13 pairs of homologues and 1 pair of presumed wheat homoeologues. Segregation ratios of "homoeologues" were close to 1:2:1 except for group 4, where no 4B homozygotes were recovered. Aneuploid frequency among 190 progeny of the segregating plants was 4.74%. C-banding at meiosis showed that "homoeologues" paired with frequencies ranging from 0.1 to 1.74 paired arms per chromosome. The only exception was the 4A–4B pair, which did not synapse. It was concluded that the high pairing frequencies between "homoeologous" chromosomes were due to translocations that had accumulated during line development. With few exceptions, translocations could not be detected by C-banding. The results demonstrate that genome recombination in polyploid species may occur at two levels simultaneously: by segregation of complete chromosomes and by translocations between homoeologues. Key words: C-banding, homoeologous pairing, translocations.
The higher order structure of the centromere
Authors: Rattner J. B. , Lin C. C. 
Published: April 2011

The architecture of the centromere region of mouse chromosomes has been studied in cells grown in the presence of 5-azacytidine. This drug interferes with normal condensation producing elongated centromere regions. It has been found that this effect is reversible in the presence of the drug, allowing the observation of the repackaging of the extended centromere into a structure exhibiting native centromere morphology. Light microscopy as well as transmission and scanning electron microscopy of this condensation process suggests that the native centromere is formed by the helical folding of a subfiber with an approximate diameter of 100 nm. This fiber is in turn composed of loops of the 30-nm fiber class. The boundary between successive gyres of the subfiber are obscured at the completion of condensation resulting in the formation of a homogenous 250- to 300-nm fiber that is the native centromere. These observations provide evidence for an additional level of chromatin organization within the metaphase chromosome. Key words: centromere, azacytidine.
Preferential intragenomic chromosome pairing in two new diploid intergeneric hybrids between Hordeum and Secale
Authors: Gupta P. K. , Fedak George 
Published: April 2011

Intergeneric hybrids involving Hordeum californicum with Secale anatolicum and Hordeum bogdanii with Secale cereale ssp. segetale were produced at a frequency of 1.3% of pollinated florets. Chiasmata frequencies of plants ranged from 0.13 to 0.21 per cell in the first hybrid combination and from 0.30 to 0.68 per cell in the second. The paucity of heteromorphic bivalents indicated absence of a close relationship between parental genomes. The associations in bivalents could be classified into Secale–Secale (R–R), Hordeum–Hordeum (H–H), and Secale–Hordeum (R–H) on the basis of difference in size of the chromosomes of Secale and Hordeum. Using a binomial distribution, it is shown that there was preferential intragenomic (R–R, H–H) chromosome pairing, which was attributed to the presence of homologous chromosome segments on nonhomologous chromosomes of the same genome. The distribution of Hordeum and Secale chromosomes to the poles at anaphase occurred at random. Key words: Hordeum, Secale, hybrids (intergeneric), chromosome pairing.
Linkage group alignment of sorghum RFLP maps using a RIL mapping population
Authors: Subudhi Prasanta K , Nguyen Henry T 
Published: April 2011

Several molecular maps have been constructed in sorghum (Sorghum bicolor L. Moench) using a variety of probes from different grass species such as sorghum, maize, sugarcane, rice, oat, and barley. In order to enhance the utility of the existing mapping information by the sorghum research community, alignment and integration of all major molecular maps is necessary. To achieve this objective, a genetic map of 214 loci with a total map distance of 1200 cM was constructed using 98 F7sorghum recombinant inbred lines (RILs) from a cross between two inbred lines, B35 and Tx7000. Few cDNA clones of sorghum and maize related to photosynthesis and drought stress were mapped on this map for the first time. Five major restriction fragment length polymorphism (RFLP) maps independently developed in this species were used for alignment purpose. The distributions of previously mapped markers were compared with their respective sorghum maps to align each of the linkage groups. In general, consistent linear order among markers was maintained in all the linkage maps. The successful alignment of these RFLP maps will now allow selection of a large number of markers for any region of the sorghum genome with many potential applications ranging from fine mapping and marker-assisted selection to map-based cloning for the improvement of sorghum and related species.Key words: Sorghum bicolor, linkage maps, molecular markers.
Extraordinary and extensive karyotypic variation: A 48-fold range in chromosome number in the gall-inducing scale insectApiomorpha(Hemiptera: Coccoidea: Eriococcidae)
Authors: Cook Lyn G 
Published: April 2011

Chromosome number reflects strong constraints on karyotype evolution, unescaped by the majority of animal taxa. Although there is commonly chromosomal polymorphism among closely related taxa, very large differences in chromosome number are rare. This study reports one of the most extensive chromosomal ranges yet reported for an animal genus. Apiomorpha Rübsaamen (Hemiptera: Coccoidea: Eriococcidae), an endemic Australian gall-inducing scale insect genus, exhibits an extraordinary 48-fold variation in chromosome number with diploid numbers ranging from 4 to about 192. Diploid complements of all other eriococcids examined to date range only from 6 to 28. Closely related species of Apiomorpha usually have very different karyotypes, to the extent that the variation within some species- groups is as great as that across the entire genus. There is extensive chromosomal variation among populations within 17 of the morphologically defined species of Apiomorpha indicating the existence of cryptic species-complexes. The extent and pattern of karyotypic variation suggests rapid chromosomal evolution via fissions and (or) fusions. It is hypothesized that chromosomal rearrangements in Apiomorpha species may be associated with these insects' tracking the radiation of their speciose host genus, Eucalyptus.Key words: Apiomorpha, cytogenetics, chromosomal evolution, holocentric.
Molecular cytogenetic analysis of supernumerary heterochromatic segments in Rumex acetosa
Authors: Shibata Fukashi , Hizume Masahiro , Kuroki Yuzo 
Published: April 2011

The dioecious plant Rumex acetosa shows intraspecific karyotype variation, caused by supernumerary heterochromatic segments or DAPI (4',6-diamidino-2 phenylindole)-bands at the ends of the short arms of three pairs of autosomes. A DNA sequence (RAE730) specific to the supernumerary heterochromatic segments was cloned and sequenced. RAE730 was about 730 bp and AT-rich (71% AT-content). Using fluorescence in situ hybridization (FISH), RAE730 was localized in the supernumerary DAPI-positive heterochromatic segments on several mitotic chromosomes and chromocenters in interphase nuclei, but not in the DAPI-bands of Y or B chromosomes. RAE730 was tandemly arranged in the genome, and the copy number varied between plants from 40 000 to 304 000 copies per 2C, corresponding to the relative amount of supernumerary heterochromatic segments per genome. These results indicate that the karyotype variation caused by the supernumerary heterochromatic segment was generated by amplification or reduction of the tandem repeats of RAE730. Key words: Rumex acetosa, repetitive sequence, supernumerary heterochromatic segment, intraspecific karyotype variation, DAPI-band.
Genomic in situ hybridization (GISH) reveals high chromosome pairing affinity between Lolium perenne and Festuca mairei
Authors: Cao Mingshu , Sleper David A , Dong Fenggao , Jiang Jiming 
Published: April 2011

Intergeneric hybridizations have been made between species of Lolium and Festuca. It has been demonstrated, largely through conventional cytogenetic analysis, that the genomes of the two genera are related, however, much information is lacking on exactly how closely related the genomes are between the two species. We applied genomic in situ hybridization (GISH) techniques to the F1 hybrids of tetraploid Festuca mairei with a genomic constitution of M1M1M2M2 and diploid Lolium perenne with a genomic constitution of LL. It was shown in the triploid hybrids (LM1M2) that the chromosomes of M1 and M2 from F. mairei could pair with each other, and it was further discovered that L chromosomes of L. perenne paired with M1 and M2 chromosomes. Our results showed that meiocytes of Lolium-Festuca are amenable to GISH analysis, and provided direct evidence for the hypothesis that the chromosomes of Lolium and Festuca may be genetically equivalent and that reciprocal mixing of the genomes may be possible. Key words: Lolium, Festuca, in situ hybridization, meiosis.
Some applications of the Lambert W  function to physics
Authors: Valluri S R , Jeffrey D J , Corless R M 
Published: April 2011

Two standard physics problems are solved in terms of the Lambert W  function, to show the applicability of this recently defined function to physics. Other applications of the function are cited, but not described. The problems solved concern Wien's displacement law and the fringing fields of a capacitor, the latter problem being representative of some problems solved using conformal transformations. The physical content of the solutions remains unchanged, but they gain a new elegance and convenience. PACS No.: 41.10F
Amplitude ratios near a Lifshitz point
Authors: Abdel-Hady A 
Published: April 2011

The susceptibility amplitude ratio in the neighborhood of an m-fold Lifshitz point is calculated using the field theoretical techniques of the renormalization group, in one-loop order. A simple expression for the amplitude associated with the helical (ferromagnetic) AH (AF) branches near a Lifshitz point is also calculated. A comparison between our calculations and the available theoretical results is presented. PACS No.: 75.40Cx
Approach to equilibrium in the micromaser
Authors: Leary D , Yau S , Carrington M , Kobes R , Kunstatter G 
Published: April 2011

We examine the approach to equilibrium of the micromaser. Analytic methods are first used to show that for large times (i.e., many atoms) the convergence is governed by the next-to-leading eigenvalue of the corresponding discrete evolution matrix. The model is then studied numerically. The numerical results confirm the phase structure expected from analytic approximation methods and agree for large times with the analysis of Elmfors et al. in terms of the ``continuous master equation.'' For short times, however, we see evidence for interesting new structure not previously reported in the literature. PACS No.: 42.55Sa
A realistic quasi-physical model of the 100 m dash
Authors: Mureika J R 
Published: April 2011

A quasi-physical model (having both physical and mathematical roots) of sprint performances is presented, accounting for the influence of drag modification via wind and altitude variations.The race-time corrections for world class male sprinters are discussed, and theoretical estimates for the associated drag areas are presented. The corrections are consistent with constant-wind estimates of previous authors. At sea level, world class men's race times are adjusted by about 0.10 s for a wind speed w = 2 m s-1, while every 1000 m of altitude provides an advantage of roughly 0.030.04 s. Corrections are provided for a wide range of wind speeds (-5 to +5 m s-1) and altitudes (02500 m), as well as for variable winds whose time-averaged value does not realistically reflect the ambient conditions. A simplified algebraic expression is also presented to correct 100 m sprint times for ambient wind and altitude effects. The primary aim is to demonstrate the utility and robustness of the full model in making such predictions, after which accurate measurement of each parameter can help to fine-tune these results. As a practical example of its utility, the nullified World Record and 1988 Olympic 100 m race of Ben Johnson is studied, and compared with the present World Record of 9.79 s. PACS Nos.: 01.80, 02.60L
Damage profile and mode observation in LiTaO3 by low-energy H+ ions
Authors: Wang K -M , Hu H , Chen F , Lu F , Zhang J -H , Liu X -D , Liu J -T , Shi B -R 
Published: April 2011

LiTaO3 samples were implanted with 50, 80, 120, and 150 keV H + ions. The damage profiles in LiTaO3 induced by H+ ions were investigated using the Rutherford backscattering/channeling technique. We used TRIM (transport of ions in matter) to simulate it. It was found that the shape of the experimental damage profile was similar to one predicted by TRIM'98, but the experimental damage ratio (NDN) was higher than the calculated damage ratio based on TRIM'98. The modes in LiTaO3 were measured by a prism-coupling method for all samples. The modes were observed only for LiTaO3 implanted with 80, 120, and 150 keV H+ ions. The present result shows that optical wave guides in LiTaO3 can be formed by lower energy H+ ions. PACS Nos.: 61.72-y, 61.82-d, 61.85+p, 78.20Ci
The motion of rapidly rotating cylinders sliding on smooth surfaces
Authors: Shegelski M R.A. 
Published: April 2011

An analytical calculation is presented and used to illustrate the principal features of the motion of rapidly rotating cylinders sliding over smooth surfaces. In particular, the time dependences of the angle rotated through, the distance traveled, and the lateral deflection of the cylinder are calculated. Examples of cylinders are given for which rotation and sliding stop at different times. The theoretical results are also compared to observed motions of curling rocks sliding on "pebbled" ice. PACS No.: 46.00
On temperature-dependent frequency factor in thermoluminescence measured with a hyperbolic heating profile
Authors: Singh W S , Bhattacharya M , Singh S D , Mazumdar P S 
Published: April 2011

In this paper, we investigate the consequences of the temperature dependence of the frequency factor on thermoluminescence peaks recorded in a hyperbolic heating profile. The temperature dependence of the frequency factor leads to nonuniqueness in the symmetry factor for a particular order of kinetics (b) and causes an error of the order of 5% in the determination of b and an error of the order of 10% in the determination of activation energy (E). PACS No.: 78.60Kn
Magnetohydrodynamic compressible laminar boundary-layer adiabatic flow with adverse pressure gradient and continuous or localized mass transfer
Authors: Xenos M , Kafoussias N , Karahalios G 
Published: April 2011

The problem of magnetohydrodynamic compressible boundary-layer flow over a flat plate, in the presence of an adverse pressure gradient, is studied numerically. The fluid is assumed to be Newtonian, electrically conducting and the magnetic field is constant and applied transversely to the direction of the flow. The fluid flow is subjected to a constant velocity of suction and (or) injection, continuous or localized, and there is no heat transfer between the plate and the fluid (adiabatic flow). The system of partial differential equations, describing the problem under consideration, is solved numerically by applying a modification of the Keller box technique. Numerical calculations are carried out for different values of the free-stream Mach number and the magnetic parameter for continuous or localized suction and (or) injection imposed at the wall. The results obtained are shown in the figures and their analysis shows that the flow field can be controlled by the application of a magnetic field as well as by continuous or localized suction and (or) injection. PACS Nos.: 51.00, 52.00
Chiral bosonic field theories and the quantum Hall effect
Authors: Bracken P 
Published: April 2011

The gauge-transformation properties of the actions of certain scalar and ChernSimons theories are investigated, including contributions from the boundary. By imposing chirality constraints on the fields, these types of theories can be used to describe the quantum Hall effect. It is shown that the corresponding equation of motion for the associated current for the theory generates an anomaly, which can be related directly to the Hall conductivity. PACS Nos.: 73.43, 03.70, 11.10, 11.30R
Polarizabilities and other properties of the tdµ molecular ion
Authors: Bhatia A K , Drachman R J 
Published: April 2011

Wave functions of the Hylleraas type were used earlier to calculate energy levels of muonic systems. Recently, we found in the case of the molecular ions H2+, D2+, and HD+ that it was necessary to include high powers of the internuclear distance in the Hylleraas functions to localize the nuclear motion when treating the ions as three-body systems without invoking the BornOppenheimer approximation. We tried the same approach in a muonic system, tdµ (triton, deuteron, and muon). Improved convergence was obtained for J = 0 and 1 states for shorter expansions when we used this type of generalized Hylleraas function, but as the expansion length increased the high powers were no longer useful. We obtained good energy values for the two lowest J = 0 and 1 states and compared them with the best earlier calculations. Expectation values were obtained for various operators, the Fermi contact parameters, and the permanent quadrupole moment. The cusp conditions were also calculated. The polarizability of the ground state was then calculated using second-order perturbation theory with intermediate J = 1 pseudostates. (It should be possible to measure the polarizability by observing Rydberg states of atoms with tdµ acting as the nucleus.) In addition, the initial sticking probability (an essential quantity in the analysis of muon catalyzed fusion) was calculated and compared with earlier results. PACS Nos.: 30.00, 36.10-k, 02.70-c
κ(BEDTTTF)2X organic crystals: Superconducting versus anti-ferromagnetic instabilities in the Hubbard model on an anisotropic triangular lattice
Authors: Tsai S -W , Marston J B 
Published: April 2011

A Hubbard model at half-filling on an anisotropic triangular lattice has been proposed as the minimal model to describe conducting layers of κ(BEDTTTF)2X organic materials. The model interpolates between the square lattice and decoupled chains. The κ(BEDTTTF)2X materials have many similarities with cuprates, such as the presence of unconventional metallic properties and the close proximity of superconducting and anti-ferromagnetic phases. As in cuprates, spin fluctuations are expected to play a crucial role in the onset of superconductivity. We perform a weak-coupling renormalization-group analysis to show that a superconducting instability occurs. Frustration in the anti-ferromagnetic couplings, which arises from the underlying geometrical arrangement of the lattice, breaks the perfect nesting of the square lattice at half-filling. The spin-wave instability is suppressed and a superconducting instability predominates. For the isotropic triangular lattice, there are again signs of long-range magnetic order, in agreement with studies at strong-coupling. PACS Nos.: 74.30G, 76.50
Analog to the 4He melting curve in a model geometrically frustrated magnet
Authors: Tsui Y K , Snyder J , Schiffer P 
Published: April 2011

Gadolinium gallium garnet, Gd3Ga5O12 (GGG) has an extraordinary low-temperature phase diagram. Although the CurieWeiss temperature of GGG is ~2 K, GGG shows no long-range order down to T ~ 0.4 K. At low temperatures GGG has a spin-glass phase at low fields ([Formula: see text] 0.08 T), a field-induced long-range-ordered anti-ferromagnetic (AFM) phase at fields of between 0.7 and 1.3 T, and, at intermediate fields, an apparent spin-liquid (SL) phase without long-range order. We have performed specific heat, magnetocaloric, and static magnetization measurements near the SL/AFM phase boundary. Our results show that the lower field boundary of the AFM phase has a distinct minimum at T ~ 0.2 K, in analogy to the minimum in the melting curve of 4He. PACS Nos.: 75.30Kz, 75.50Ee
Lanczos study of the S = 1/2 frustrated square-lattice anti-ferromagnet in a magnetic field
Authors: Honecker A 
Published: April 2011

We study the zero-temperature phase diagram of the frustrated square-lattice S = 1/2 anti-ferromagnet in an external magnetic field numerically with the Lanczos algorithm. For strong frustration, we find disordered phases at high (and low) magnetic fields. Between these two disordered phases, we find a plateau in the magnetization curve at half of the saturation magnetization, which corresponds to a state with up-up-up-down (uuud) spin order. This and other considerations (M.E. Zhitomirsky, A. Honecker, and O.A. Petrenko. Phys. Rev. Lett. 85, 3269 (2000).) suggest an unusual ordering scenario. There is an ordered phase with a spin gap (the plateau) and disordered magnetically gapless phases above and below. The transition to saturation is studied in further detail and problematic conclusions in earlier investigations of this region are pointed out. PACS Nos.: 75.50Ee, 75.40Mg, 75.45+j
Chiral-ordered phases in a frustrated S = 1 chain with uniaxial single-ion-type anisotropy
Authors: Hikihara T 
Published: April 2011

The ground-state phase transitions of a frustrated S = 1 Heisenberg chain with the uniaxial single-ion-type anisotropy and the frustrating next-nearest-neighbor coupling are studied. For the system, it has been shown that there are gapless and gapped chiral phases in which the chirality κl = Slx Syl+1  Sly Sxl+1 exhibits a finite long-range order (LRO) and the spin correlation decays either algebraically or exponentially. In this study, the transitions between the Haldane and chiral phases and between the large-D (LD) and chiral phases are investigated using the infinite-system density-matrix renormalization group method. It is found that there exist two types of gapped chiral phases, "chiral Haldane" and "chiral LD" phases, in which the string LRO coexists with the chiral LRO and the string correlation decays exponentially, respectively. PACS No.: 75.30
Search for spin liquid state in sub-monolayer 3He adsorbed on HD-preplated graphite
Authors: Ikegami H , Masutomi R , Obara K , Ishimoto H 
Published: April 2011

NMR studies of sub-monolayer solid 3He adsorbed on a bilayer of HD-preplated graphite have been made down to 100 µK, which is more than one order of magnitude smaller than the exchange energy (J). In the highly frustrated anti-ferromagnetic region, the magnetization obeys a CurieWeiss law even at temperatures around J and then increases gradually down to 100 µK. Nevertheless, it does not show any anomalous behavior corresponding to the existence of the spin gap. The normalized magnetization versus the reduced temperature (T/J) is independent of the density just after solidification. This fact is consistent with the result in the high-temperature region where the main multiple spin exchanges have a similar density dependence in the present density region. PACS Nos.: 67.80Jd, 67.70+n, 75.10Jm
Exact diagonalization studies of two-dimensional frustrated anti-ferromagnet models
Authors: Lhuillier C , Sindzingre P , Fouet J -B 
Published: April 2011

We describe the four kinds of behavior found in two-dimensional isotropic quantum anti-ferromagnets. Two of them display long-range order at T = 0: the Néel state and the valence bond crystal. The last two are spin liquids. Properties of these different states are briefly described and open questions are underlined. PACS Nos.: 75.10Jm, 75.50Ee, 75.40-s