bluuebunny/crossref_metadata_2025_split huggingface dataset:
Denitrification estimates in monoculture and rotation corn as influenced by tillage and nitrogen fertilizer
Authors: Fan Ming X. , MacKenzie Angus F. , Abbott Melissa , Cadrin François 
Published: April 2011

Denitrification in agricultural soils results in loss of N for crop growth and production of N2O, a greenhouse gas. Agricultural management must be evaluated for denitrification losses in order to develop minimum N loss systems. Field estimation of denitrification losses is necessary to evaluate crop management effects. Two methods of field denitrification measurements, a soil core (SC) incubation and an in situ closed chamber (CC), were assessed in monoculture corn (Zea mays L.) and corn in rotation with soybean (Glycine max L. Merill) and alfalfa (Medicago sativa L.). Relative estimates of denitrification by the two methods depended on soil texture, with the CC method showing more treatment effects. Denitrification losses were higher with no-till than conventional tillage at one site, and were generally higher with corn than soybean. Nitrogen losses were linear with added N in monoculture corn plots, and ranged from 1.1 to 4.1% of added N. Losses were not related to added N in corn following alfalfa or soybean. Ratios of N2O/(N2O + N2) as measured with the SC method were lower at the Ste. Rosalie (1) site than at the Chicot site (0.95 to 2.84), but ratios of N2O/(N2O + N2) measured with the CC method were similar for the sites, from 0.46 to 1.20. Denitrification losses measured by either method were related to soil moisture and nitrate content in the soils. Corn production should be carried out with conventional tillage and minimum fertilizer N rates for minimum denitrification. Key words: Rotations, corn, soybean, denitrification, closed chamber, soil core
Local Differences in the Life History of the Lobster (Homarus americanus) on the Coast of the Maritime Provinces of Canada
Authors: Templeman W. 
Published: April 2011

The hatching and moulting of the lobster are earlier in waters with a high than in those with a lower summer temperature. Moulting is about one week later for each degree lower summer temperature. In such high temperature areas as Malpeque bay two moultings occur during the year in most lobsters between 14 and 22 cm. in length. In the whole southern gulf of St. Lawrence area female lobsters as small as 18 to 21 cm. in length may carry eggs, while in the Grand Manan area with a summer temperature 5 to 8 °C. lower, the smallest sexually mature females are about 34 cm. in length. The growth per moult of the female lobster falls considerably below that of the male when sexual maturity approaches, thus in the southern gulf of St. Lawrence the female growth rate slows down rapidly after 18 to 21 cm. and in southern Nova Scotia at about 30 cm. In the southern gulf area at small sizes more males than females appear in the commercial catch, at larger sizes more females and at very large sizes nearly all the lobsters caught are males. Average sizes of lobsters in the commercial catch are considerably smaller in the southern gulf area than in southern Nova Scotia and at Grand Manan.
Local Feeding of Kingfishers and Mergansers
Authors: White H. C. 
Published: April 2011

On the Margaree and Apple rivers, N.S., the belted kingfisher feeds upon those fishes most available within its feeding range. In the estuaries many species are taken, but ascending a river the number becomes less until only salmon and trout (Salvelinus), or trout alone, constitute the food. By rearing a young bird it was determined that the American merganser pursues its prey by sight under water, being able to see a distance of from 10 feet (3 m.) to 2 feet (0.6 m.) or less, depending upon the clearness of the water. The bird consumes daily on the average more than a third of its weight. In nature the broods are reared up stream where young salmon are the dominant fish and constitute the major food item, with trout next. When the supply becomes scarce they shift down stream and in the estuary take the various fishes occurring there. In contrast the young red-breasted mergansers were found feeding over areas not frequented by young salmon, and the adults were confined largely to the estuary. They fed on the species available, which sometimes consisted largely of young salmon.
Biological aspects of Amazonian fishes. IX. Cytogenetic studies in two species of the genus Semaprochilodus (Pisces, Prochilodontidae)
Authors: Feldberg Eliana , Bertollo Luiz Antonio Carlos , Toledo Lurdes Foresti de Almeida , Foresti Fausto , Filho Orlando Moreira , Santos Altair Fernandes dos 
Published: April 2011

The karyotype of Semaprochilodus insignis and Semaprochilodus taeniurus were analyzed through the conventional Giemsa staining, C-banding, and the nucleolar organizer regions. The diploid number is the same (2n = 54) in both species, but S. taeniurus shows a chromosomic system of the ZZ/ZW type. This and some other differences between the two karyotypes will be useful in further studies on the possible hybrid origin of the "jaraqui açú," a low frequency form that is observed together with S. insignis and S. taeniurus. Key words: fish, ZZ/ZW system, constitutive heterochromatin, nucleolar organizing regions.
Cytogenetic analysis of mitotic and salivary gland chromosomes in the Medfly Ceratitis capitata
Authors: Zacharopoulou A. 
Published: April 2011

The present investigation constitutes a first attempt to study the salivary gland chromosomes of Ceratitis capitata. A photographic representation of the polytene chromosomes from the salivary gland of this species is provided and the tips, as well as some important landmarks, are recognized in each arm. There is an XX/XY pair and five pairs of autosomes in the metaphases, but neither the X nor the Y are represented among the banded polytene chromosomes. Key words: Ceratitis capitata, chromosomes (polytene), chromosomes (mitotic), salivary gland chromosomes.
Experimental comparison of restricted selection index and restricted independent culling levels in Tribolium castaneum
Authors: Campo J. L. , Villanueva B. 
Published: April 2011

A selection index (I) method was compared with independent culling levels (N), with a restriction in the selection program, using two replicated single generation experiments in Tribolium castaneum, which are considered forms of antagonistic selection. The first experiment was designed to increase adult weight without changing pupal weight, while the second experiment was intended to improve egg laying without changing adult weight. In both experiments the genetic correlation between the traits involved were positive but were higher in experiment 1 than in experiment 2. The proportion of selection was 10%. In experiment 1, the effect of restriction was as expected in both lines since the changes in pupal weight were not significant. Adult weight change was positive for the I line and negative for the N line, showing that the index was a superior method to improve adult weight. In experiment 2, the effect of restriction was also as expected in both lines and changes in adult weight were not significant. Egg laying changed positively in both lines. Therefore, both selection methods were similar in this experiment, even though egg laying change was higher in the I than the N line. Key words: restricted index, restricted culling levels, antagonistic selection, Tribolium.
Recombination block in the Spore killer region of Neurospora
Authors: Campbell Joseph L. , Turner Barbara C. 
Published: April 2011

Spore killers Sk-2K and Sk-3K are chromosomal meiotic drive factors in Neurospora. In heterozygous crosses, ascospores not contining the Spore killer die. Sk-2K and Sk-3K, which differ in killing specificity, were found to be associated with suppression of recombination in a centromere-spanning region of linkage group III, and investigation of that recombination block is reported here. The block covers a region that is normally 30 to 40 map units long. A locus (r(Sk-2)) conferring resistance to Sk-2K maps to the left end of the recombination block. Recombination is normal in r(Sk-2) × Sk sensitive but blocked in Sk-2K × r(Sk-2); so the block does not depend upon killing. By selective plating, SkK stocks carrying genetic markers within the block were obtained at frequencies on the order of 10−5 or 10−6. Since this tight block is far beyond what has been observed for genetic reduction of recombination, a structural basis is assumed. No evidence of chromosome rearrangement was obtained. Crosses homozygous for Sk-2K show normal crossing-over and map order for the flanking markers cum and his-7 and three included markers (acr-7, acr-2, and leu-1). Results would be consistent with a divergence of sequence great enough to interfere with homologous pairing. Key words: meiotic drive, Neurospora, crossover suppressor.
A cytogenetical study of 7-day-old bovine embryos of poor morphological quality
Authors: King W. A. , Guay P. , Picard L. 
Published: April 2011

Seven-day-old embryos were collected from Canadian Holstein and Ayrshire heifers after superovulation with pregnant mare's serum gonadotropin (PMSG) or follicle-stimulating hormone (FSH). A total of 103 morphologically abnormal (type C) and 23 morphologically normal (type A) embryos were cytogenetically analyzed after 4, 20–24, or 44–48 h of culture in enriched phosphate-buffered saline or Eagles minimum essential medium. Twenty-one of 23 (91.3%) type A and 75 of 103 (72.8%) type C embryos had cells in metaphase. Among the 21 type C embryos produced by PMSG stimulation, 17 (80.9%) could be analyzed: 6 were mixoploid (two 2n/3n, three 2n/4n, one 2n/6n), 2 were aneuploid (61 XXY), and 9 were diploid. Among the 82 type C embryos produced by FSH stimulation, 58 (70.7%) could be analyzed: 6 were mixoploid (one n/2n, one 2n/3n, three 2n/4n, one 2n/4n/8n), 2 were polyploid (4n), and 50 were diploid. No abnormalities were observed in the type A embryos. Key words: bovine embryo, chromosome, mixoploid, aneuploid.
Genomic affinities of individual chromosomes based on C- and N-banding analyses of tetraploid Elymus species and their diploid progenitor species
Authors: Morris K. L. D. , Gill B. S. 
Published: April 2011

Giemsa C- and N-banding techniques were used to identify individual somatic chromosomes in the tetraploid (2n = 28) species Elymus trachycaulus (= Agropyron trachycaulum) (genome designation SH) and E. ciliaris (= A. ciliare) (SY) and five diploid progenitor species (2n = 14), Pseudoroegneria spicata (= A. spicatum) (S), P. libanotica (= A. libanoticum) (S), P. stipifolia (= A. stipifolium) (S), Critesion bogdanii (= Hordeum bogdanii) (H), and C. californicum (= H. californicum) (H). Comparisons based on banding patterns of E. trachycaulus and E. ciliaris with parental donor species P. spicata indicated a common S genome origin. The heterochromatin composition of several E. trachycaulus chromosomes were similar to chromosomes of both Critesion species. However, the possible origin of characteristic C- and N-banded chromosomes of E. ciliaris remained undetermined. These patterns of evolution among genomes of E. trachycaulus, E. ciliaris, and their progenitor species proved valuable for the allocation of individual chromosomes into specific genomes. This approach may be useful for the genomic allocation of wheat-Elymus addition lines. Key words: C-banding, N-banding, Elymus, Triticeae, genome.
Certation between euploid and aneuploid pollen grains from a tertiary trisomic of rye, Secale cereale L.
Authors: Janse J. 
Published: April 2011

Male transmission of the translocated extra chromosome 5R3R was studied in a tertiary trisomic of rye (Secale cereale L.) using two pollination densities. With abundant pollen, male transmission reached 4%. When a mean of four pollen grains were brought on every stigma (restricted pollination), a transmission rate of 20% was obtained. Seed set, mean seed weight, germination percentage, and the percentage of plants finally surviving were lower in the case of restricted pollination. It was concluded that certation between euploid and aneuploid pollen grains plays a decisive role in male transmission of the translocated chromosome. Although it was previously shown that aneuploid microspores have a delayed development, a large proportion must have reached maturity before anthesis. Therefore, genetic factors determining male transmission rate will primarily be expressed during pollen germination and tube growth rather than before anthesis. Key words: rye, tertiary trisomic, euploid pollen grains, aneuploid pollen grains, certation.
Evolution of a mouse Y chromosomal sequence flanked by highly repetitive elements
Authors: Nishioka Yutaka , Lamothe Estelle 
Published: April 2011

Mammalian primary sex is determined by the presence or absence of the Y chromosome. However, little is known about the molecular processes through which the Y chromosome exerts its action. We applied recombinant DNA techniques to isolate mouse Y chromosomal fragments and described previously a clone designated as AC11 (Y. Nishioka and E. Lamothe. 1986. Genetics, 113: 417–432). To obtain information on DNA sequences that flank AC11, we screened a mouse genomic library for the presence of AC11-related sequences and isolated over 50 positive clones. In this report we describe clones ACC2 and ACC3, both of which contain highly repetitive elements. Using a male-specific portion of these clones, we compared DNA's isolated from mice (Mus musculus, M. hortulanus, M. spretus, M. cookii, M. pahari, and M. platythrix), rat, hamster, and guinea pig and obtained results that agree with the phylogenetic relationships deduced from morphological and biochemical studies. The male-specific accumulation of the related sequences was found only in M. musculus, M. hortulanus, and M. spretus. Key words: mouse, Y chromosome, repetitive sequence, genome evolution.
Intergeneric hybrids between Hordeum jubatum and triticale (×Triticosecale Wittmack)
Authors: Gupta P. K. , Fedak G. 
Published: April 2011

Hybrids of Hordeum jubatum (4x) were produced with two isogenic lines of 6x triticale (×Triticosecale Wittmack) cv. DRIRA, one carrying the normal heterochromatic block on the long arm of 7R (cv. DRIRA HH) and the other lacking 90% of it (cv. DRIRA EE). The two hybrids were produced at relative frequencies of 1.1 and 0.9% of pollinated florets, respectively. The chromosome pairing in both of these hybrids was negligible (chiasmata frequencies 0.11 and 0.15), indicating that heterochromatin on 7R had no effect on chromosome pairing in H. jubatum and that the expected autosyndetic pairing between two related genomes of H. jubatum was absent in this combination. Key words: wide crosses, intergeneric hybrids, triticale, Hordeum jubatum, chromosome pairing.
Identification of a 5S rDNA spacer type specific toTriticum urartuand wheats containing theT. urartugenome
Authors: Allaby Robin G , Brown Terence A 
Published: April 2011

A PCR system was designed to amplify 5S spacer rDNA specifically from homeologous chromosome 1 in a variety of species representative of the Aegilops and Triticum genera. Two polymerase chain reaction (PCR) primer combinations were used, one of which appears to be apomorphic in nature and specific to chromosome 1A in Triticum urartu and tetraploid and hexaploid wheats containing the AA genome donated by T. urartu. The value of studying single repeat types to investigate the molecular evolution of 5S-rDNA arrays is considered.Key words: 5S rDNA, polymerase chain reaction, Triticum, wheat.
Hamiltonian and BRST formulations of the two-dimensional Abelian Higgs model
Authors: Kulshreshtha Usha 
Published: April 2011

The Hamiltonian and BRST formulations of the Abelian Higgs model in one-space one-time dimensions are investigated. PACS Nos.: 03.65+, 03.70tk, 11.10lm, 11.10Ef, 11.30Rd
An introduction to physics education research
Authors: Aalst Jan van 
Published: April 2011

At a number of U.S. universities, some physicists are focusing their research effort on physics education research (PER). This paper examines this development in terms of the knowledge of teaching and learning, curriculum projects and practices it has produced. First, a selective review of research and curriculum development projects provides an introduction to PER for readers unfamiliar with it. Studies based on surveys and interviews are emphasized, as well as curriculum projects that make use of microcomputer-based laboratory tools (MBL). Other efforts are mentioned more briefly, but illustrate the breath of research and development activity. Following the review, I examine the evidence for the effectiveness of some of the curricula discussed, and identify three areas in which greater interaction between the PER and educational researchers working in other fields should be fostered: (a) statistical data analysis, (b) micro-analysis of learning situations, and (c) ways in which subject matter knowledge in physics can contribute to school-based projects and educational research. The concluding section of the paper argues for multi-disciplinary graduate programs in physics education, which are intended to provide a solid base in physics as well as research and innovation in education. PACS Nos.: 01.40.Fk, 01.50.Ht
Preprofessional students' beliefs about learning physics
Authors: Aalst Jan van , Key Tony 
Published: April 2011

We report results obtained with the Maryland Physics Expectations (MPEX) survey in: (a) a course for students who have not previously taken a second course in physics in high school; (b) physics for the life sciences; (c) honors physics; and (d) physics for engineers. Comparing the responses with a group of experienced teachers Redish et al. call the ``expert group'', we find that (i) overall, agreement with experts decreased after the two semesters of instruction, and (ii) there were significant differences between the response patterns for students in the first two courses, compared with the last two. The data suggest that the context of learning, i.e., a program in physical science versus one in the life sciences must be taken into account in research on students' beliefs about learning physics. PACS No.: 01.40Fk
Time-dependent angular and energy distributions of sputtered copper atoms
Authors: Vichev R G , Karpuzov D S 
Published: April 2011

Time reference was introduced in the TRIM computer simulation code without changing the "event-driven" logic of the program. The code was applied to model the atomic collision cascades and sputtering of amorphous copper targets caused by bombardment of keV ions of different masses (Be, Ne, Ar, Cu, Xe, Au). Time-dependent characteristics of ion-induced processes such as mean number and energy of moving target atoms, number of collisions and vacancies (or) recoils created, sputtering yield, mean energy and angle of ejection of sputtered atoms were obtained, and their dependence on the ion/atom mass ratio is discussed. PACS No.: 79.20-m
Mathematical methods for the characterization of ultrasound in anisotropic materials
Authors: O'Neill B , Maev R Gr. 
Published: April 2011

Although the fundamental equations for the propagation of elastic and acoustic waves in anisotropic materials have not changed in more than a 100 years, the last few decades have seen a surge in interest in the topic. Much of this interest stems from the growing need for characterization of an increasing number of exotic materials. The intent of this paper is to review, for the benefit of beginning researchers in acoustics and ultrasonics, the fundamental phenomena related to elastic wave propagation in anisotropic media. We also present the most common and interesting theoretical methods developed over the past 20 years to model bulk wave propagation in such media. The methods discussed include plane wave superpositions, ray asymptotic theory, paraxial beams, and Green's functions. More peripheral issues, including anisotropic effects combined with various other exotic effects, are dealt with in the bibliography. PACS No.: 43.90
Charged-particle pseudorapidity (rapidity) distribution in nucleusnucleus collisions at alternating-gradient synchrotron energy
Authors: Liu F -H 
Published: April 2011

The charged-particle pseudorapidity (rapidity) distributions in nucleusnucleus collisions at the alternating-gradient synchrotron energy (1115A GeV) have been described by the thermalized cylinder picture. The calculated results are in agreement with the experimental data of the reactions 28Si + Au, Ag, Cu, and Al at 14.6A GeV/c bombarding energy. It is shown that the target stopping power (the leading participant target nucleon rapidity shift with respect to the projectile) increases with the target size, and the projectile penetrating power (the leading participant projectile nucleon rapidity shift with respect to the target) decreases with the increasing of target size. PACS Nos.: 25.75-q, 25.75Dw, and 24.10pa
Analytical expressions for the energies of anharmonic oscillators
Authors: Fernández F M , Tipping R H 
Published: April 2011

We propose a systematic construction of algebraic approximants for the bound-state energies of anharmonic oscillators. The approximants are based on the Rayleigh-Schrödinger perturbation series and take into account the analytical behavior of the energies at large values of the perturbation parameter. A simple expression obtained from a low-order perturbation series compares favorably with alternative approximants. Present approximants converge in the large-coupling limit and are suitable for the calculation of the energy of highly excited states. Moreover, we obtain some branch points of the eigenvalues of the anharmonic oscillator as functions of the coupling constant. PACS No.: 03.65Ge
The motion of a curling rock: Analytical approach
Authors: Shegelski M R 
Published: April 2011

A simplified version of a previously proposed model is presented and used to illustrate the salient features of the motion of a slowly rotating curling rock. A one-parameter model is presented. Analytical approximations for the chief aspects of the motion are derived. The simplified analytical model accounts quite well for the principal features of the motion of a slowly rotating curling rock, in particular that most of the curl occurs in the final few metres of the rock's motion. A discussion is also given concerning a popular misconception as to why curling rocks curl. PACS No.: 46.00
Plasma waves in two-dimensional conductors with impurity electron states
Authors: Haghighi B , Ermolaev A M 
Published: April 2011

The dispersion relation and the damping of plasma waves in two-dimensional conductors are calculated under the condition of localization of electrons by impurity atoms. It has been shown that localization of electrons decreases plasma-wave frequency as well as causing their damping when the frequency exceeds some threshold value. The data obtained resulted in an explanation of experiments on electromagnetic wave absorption in inversion layers of silicon and silicon dioxide interfaces. PACS Nos.: 73.20Mf, 73.40Qv, 72.10Bg
Low-lying electronic states of CuBr
Authors: Hirao T , Bernath P F 
Published: April 2011

The A1Π  X1Σ+ and B1Σ+  X1Σ+ transitions of copper monobromide, CuBr, were recorded with a Fourier transform spectrometer. The emission was generated by using a hollow cathode discharge of Ar buffer gas and a mixture of Cu and CuBr powders. The mass-dependent Dunham expansion formula was used to obtain improved molecular constants for the ground, A and B states. These molecular constants provided RKR potential curves and FranckCondon factors for the AX and BX transitions.PACS No. 35.80 transitions. PACS No. 35.80