Pair Cross Research Articles

Multivariate associations of flavonoid and biomass accumulation in white clover (Trifolium repens) under drought.

White clover (Trifolium repens L.) is an important pasture legume in temperate regions, but growth is often strongly reduced under summer drought. Cloned individuals from a full-sib progeny of a pair cross between two phenotypically distinct white clover populations were exposed to water deficit in pots under outdoor conditions for 9 weeks, while control pots were maintained at field capacity. Water deficit decreased leaf water potential by more than 50% overall, but increased the levels of the flavonol glycosides of quercetin (Q) and the ratio of quercetin and kaempferol glycosides (QKR) by 111% and by 90%, respectively. Water deficit reduced dry matter (DM) by 21%, with the most productive genotypes in the controls showing the greatest proportional reduction. The full-sib progeny displayed a significant increase in the root:shoot ratio by 53% under water deficit. Drought-induced changes in plant morphology were associated with changes in Q, but not kaempferol (K) glycosides. The genotypes with high QKR levels reduced their DM production least under water deficit and increased their Q glycoside levels and QKR most. These data show, at the individual genotype level, that increased Q glycoside accumulation in response to water deficit stress can be positively associated with retaining higher levels of DM production.

The Effect of Stocking Densities on Reproductive Performance in Laboratory Zebrafish (Danio rerio)

Despite the growing popularity of the zebrafish model system, the optimal husbandry conditions for this animal are not well defined. The aim of this study was to examine the effect of stocking density on reproductive performance in zebrafish. In this study, undertaken by eight different zebrafish facilities, clutches of at least 200 wild-type zebrafish embryos from a single pairwise mating were produced at each participating institution and subsequently reared according to "in-house protocols" until they were 14 weeks old. Fish were then randomly assigned into treatment groups with balanced sex ratios and densities of 3, 6, or 12 fish/L. After a 1-month acclimation period, fish were spawned in pair crosses every 2 weeks for 3 months, for a total of six spawning dates. The number of viable and nonviable embryos produced in each clutch were counted at 1 day postfertilization. Although there was a great deal of variability in clutch size and percent spawning success among laboratories, there were no significant differences in average clutch size, spawning success, or percent viable among the treatment densities. These data suggest that using stocking densities as high as 12 fish/L does not have a negative impact on performance, when measured by reproductive performance.

Implications of the measurement of ultramassive boosted jets at CDF

The CDF Collaboration recently reported an upper limit on boosted top pair production and noted a significant excess above the estimated background of events with two ultramassive boosted jets. We discuss the interpretation of the measurement and its fundamental implications. In case new physics is involved, the most naive contribution is from a new particle produced with a cross section that is a few times higher than that of the top quark and a sizable hadronic branching ratio. We quantify the resulting tension of a possible larger top pair cross section with the absence of excess found in events with one massive boosted jet and missing energy. The measured planar flow distribution shows deviation from CDF's Pythia QCD prediction at high planarity, while we find a somewhat smaller deviation when comparing with other Monte Carlo tools. As a simple toy model, we analyze the case of a light gluino with R-parity violation and show that it can be made consistent with the data.

Purification of Sahdyari rice hybrid parental lines through paired crosses for nucleus seed production

The availability of genetically pure and good-quality seed is a primary prerequisite for exploiting the potential of hybrids. Lack of purity in parental lines and improper isolation conditions in seed production result in poor hybrid seed quality. Chinese scientists reported that, with every 1% decrease in the purity of hybrid seed, the eventual yield loss in F1 hybrids would be about 100 kg ha-1 (Sharma 1995). In 1998, RARS-Karjat identified and released a rice hybrid from the cross IR58025A/BR827-35-3-1-1-1R-Sahdyari- for commercial cultivation in Maharashtra State. Maintaining or improving the purity of the parental lines of Sahdyari was a major challenge. Thus, efforts were made to purify the three parental lines of Sahdyari through paired crosses.

Top quark asymmetry from a non-Abelian horizontal symmetry

Motivated by the persistence of a large measured top quark forward-backward asymmetry at the Tevatron, we examine a model of non-Abelian flavor gauge symmetry. The exchange of the gauge bosons in the $t$-channel can give a large ${A}_{\mathrm{FB}}^{t}$ due to the forward Rutherford scattering peak. We address generic constraints on non-Abelian $t$-channel physics models including flavor diagonal resonances and potentially dangerous contributions to inclusive top pair cross sections. We caution on the general difficulty of comparing theoretical predictions for top quark signals to the existing experimental results due to potentially important acceptance effects. The first signature at the Large Hadron Collider can be a large inclusive top pair cross section, or like-sign dilepton events, although the latter signal is much smaller than in Abelian models. Deviations of the invariant mass distributions at the LHC will also be promising signatures. A more direct consistency check of the Tevatron asymmetry through the LHC asymmetry is more likely to be relevant at a later stage.

Short Range Correlations and the EMC Effect

This Letter shows quantitatively that the magnitude of the EMC effect measured in electron deep inelastic scattering at intermediate x(B), 0.35≤x(B)≤0.7, is linearly related to the short range correlation (SRC) scale factor obtained from electron inclusive scattering at x(B)≥1. The observed phenomenological relationship is used to extract the ratio of the deuteron to the free pn pair cross sections and F(2)(n)/F(2)(p), the ratio of the free neutron to free proton structure functions. We speculate that the observed correlation is because both the EMC effect and SRC are dominated by the high virtuality (high momentum) nucleons in the nucleus.

Simple Realizability of Complete Abstract Topological Graphs in P

An abstract topological graph (briefly an AT-graph) is a pair $A=(G,\mathcal{R})$ where G=(V,E) is a graph and $\mathcal {R}\subseteq {E \choose 2}$ is a set of pairs of its edges. An AT-graph A is simply realizable if G can be drawn in the plane in such a way that each pair of edges from $\mathcal{R}$ crosses exactly once and no other pair crosses. We present a polynomial algorithm which decides whether a given complete AT-graph is simply realizable. On the other hand, we show that other similar realizability problems for (complete) AT-graphs are NP-hard.

A 3-D Differential Method for Solving Rolling Force of PC Hot Strip Mill

The character of the deformation zone on pair cross rolls is different from that of the regular 4-high mill. Considering comprehensive influences of normal stress and shear stress in rolling direction, width direction and thickness direction, the rolling force calculation model of the PC (pair crossed) hot strip mill is built. Taking the entry stress and the exit stress of strip as the boundary conditions, the longitudinal and transverse distribution of rolling force is worked out by the differential method. Then the total rolling force is calculated, and calculated results are verified by experimental data.

Plasma disposition of capecitabine and its metabolites 5′DFCR and 5′DFUR in a standard and dose-intensified monotherapy regimen

In view of a potential gain in anticancer activity in advanced colorectal cancer (ACRC), there has been considerable interest in using a higher than the approved standard dose of capecitabine (CCB) combined with oxaliplatin. This pharmacokinetic study was designed to evaluate whether CCB is metabolized at the same extent when administered as a monotherapy in two different dose regimens, comparing standard dose (CCB 1) and intensified dose (CCB 2). Seven patients suffering from ACRC received subsequently two CCB schedules: In the standard schedule, 1,250 mg/m² CCB p.o. twice daily for 2 weeks was administered, after a pause of 1 week, a dose-intensified CCB 2 schedule was given: 1,750 mg/m² CCB p.o. twice daily for 1 week to be followed by 1 week rest. Due to this paired cross over design a direct comparison for each single patient was feasible. In both schedules, mean peak plasma concentrations of CCB occurred at about 50 min, those of metabolites shortly later (range 54-80 min). Peak plasma concentrations were about 10% (CCB, DFCR) and 40% (DFUR) higher in the CCB 2 regimen. According to the higher dose of CCB in the dose-intensified regimen (+40%), the AUC(last) values increased by 34% (CCB), 20% (DFCR) and 58% (DFUR), respectively. The results indicate that higher doses of CCB are metabolized approximately dose-dependent compared to the standard dose. No indices for a saturation of metabolizing processes or any significant delay of elimination rate was observed. The immediate 5FU precursor DFUR was formed at a 50% higher extent (expressed as AUC(last) values) than in the standard CCB 1 schedule. From the pharmacokinetic point of view, this increased formation rate suggests clinical importance in regard to metabolic activation of CCB.

Evaluation of semi-hybrid perennial ryegrass populations

The yield potential of modern forage cultivars is a limit to production from pasture- based agriculture, and may influence profitability. Hybrid vigour has increased yield in a range of plant species, but is only partially captured in conventional forage breeding systems. The objective of this research was to assess the potential for harnessing hybrid vigour in a semi-hybrid breeding system for perennial ryegrass (Lolium perenne). Paired crosses among eight parental sources, including four cultivars and four ecotypes, were used to create 28 semi-hybrid populations. Parents, semi-hybrids and check cultivars were trialled in pure grass plots under rotational grazing for 2 years in the Manawatu. Dry matter yield data were used to estimate cumulative and seasonal patterns of hybrid vigour expression for cultivar x cultivar semi-hybrid combinations. The mean level of high parent heterosis was less than 2%. However, one combination exhibited significant (p

Measurement of the proton-air cross section with ARGO-YBJ

In this work the results of p-air cross section measurements with the ARGO-YBJ experiment are reported. The analysis is based on the different flux attenuation for different atmospheric depths (i.e. zenith angles), by exploiting the detector capabilities in selecting the shower development stage by means of the size, hit density and lateral profile measurements. The systematic errors introduced by fluctuations in shower development and heavier primaries have been taken into account. The results can give useful insights on p-air interactions at energies where hadronic interaction models start to give significantly different expectations and allow to infer the p-p total cross section in the energy region ( s = 80 GeV − 500 GeV ) not covered by experiments at accelerators.

Dissection of the genetic basis of heterosis in an elite maize hybrid by QTL mapping in an immortalized F2 population

The genetic basis of heterosis for grain yield and its components was investigated at the single- and two-locus levels using molecular markers with an immortalized F(2) (IF(2)) population, which was developed by pair crosses among recombinant inbred lines (RILs) derived from the elite maize hybrid Yuyu22. Mid-parent heterosis of each cross in the IF(2) population was used to map heterotic quantitative trait loci. A total of 13 heterotic loci (HL) were detected. These included three HL for grain yield, seven for ear length, one for ear row number and two for 100-kernel weight. A total of 143 digenic interactions contributing to mid-parent heterosis were detected at the two-locus level involving all three types of interactions (additive x additive = AA, additive x dominance = AD or DA, dominance x dominance = DD). There were 25 digenic interactions for grain yield, 36 for ear length, 31 for ear row number and 51 for 100-kernel weight. Altogether, dominance effects of HL at the single-locus level as well as AA interactions played an important role in the genetic basis of heterosis for grain yield and its components in Yuyu22.

Theoretical top quark cross section at the Fermilab Tevatron and the CERN LHC

We present results for the top quark pair cross section at the Tevatron and the LHC. We use the resummed double differential cross section, employing the fully kinematics-dependent soft-anomalous-dimension matrices, to calculate the soft-gluon contributions at next-to-next-to-leading order (NNLO). We improve and update our previous estimates by refining our methods, including further subleading terms, and employing the most recent parton distribution function sets. The NNLO soft corrections significantly enhance the NLO cross section while considerably reducing the scale dependence. We provide a detailed discussion of all theoretical uncertainties in our calculation, including kinematics, scale, and parton distribution uncertainties, and clarify the differences between our work and other approaches in the literature.

Selection for salt tolerance and its genetic basis in perennial ryegrass (Lolium perenne L.)

Salt tolerance of two selected lines of Lolium perenne L. (high selection and low selection) was assessed in comparison with control unselected line after three weeks growth in solution culture at 0, 50, 100, 150, 200, 250, and 300 mol m-3 NaCl. The high selection line had significiantly higher root growth compared with the low selection and unselected lines at all salt concentrations. In order to assess the usefulness of a second cycle of selection, 8000 seeds of each of the high selection and unselected (control) lines were screened after three weeks growth in 325 mol m-3 NaCl. A large number of individuals in the high selection line produced remarkably longer roots than the control lines. Pair crosses were made between the high selection and the low selection in order to investigate additive genetic component at two NaCl treatments, 150 and 250 mol m-3, Additive genetic component was quite high at both the salt treatments.

Cross-Resistance and Genetics of Resistance to Indoxacarb in <I>Spodoptera litura</I> (Lepidoptera: Noctuidae)

Bioassays (at generation G1) with a newly collected field population of Spodoptera litura (F.) (Lepidoptera: Noctuidae) from Multan, Pakistan, showed resistance ratios of 15, 23, 37, and 16 for indoxacarb, spinosad, abamectin, and emamectin, respectively, compared with a laboratory susceptible population, Lab-PK. At G1, the field population was selected with indoxacarb by using single pair crosses. For Indoxa-SEL, bioassay at G4 found that selection increased resistance ratio to 95 for indoxacarb compared with Lab-PK. Selection with indoxacarb significantly increased resistance to spinosad and emamectin; however, resistance to abamectin was observed to drop. A significant reduction in the resistance to indoxacarb was observed in Indoxa-SEL at G9, indicating unstable resistance to indoxacarb; however, it was stable for fipronil. Synergism tests with microsomal oxidase and esterase-specific inhibitors suggested that the indoxacarb resistance was associated with microsomal oxidase. Reciprocal genetic crosses between Indoxa-SEL and Lab-PK populations indicated that resistance was autosomal and incompletely dominant. Tests of monogenic inheritance suggested that resistance to indoxacarb was controlled by more than one locus.

Cross-Resistance and Genetics of Resistance to Indoxacarb in Spodoptera litura (Lepidoptera: Noctuidae)

Bioassays (at generation G1) with a newly collected field population of Spodoptera litura (F.) (Lepidoptera: Noctuidae) from Multan, Pakistan, showed resistance ratios of 15, 23, 37, and 16 for indoxacarb, spinosad, abamectin, and emamectin, respectively, compared with a laboratory susceptible population, Lab-PK. At G1, the field population was selected with indoxacarb by using single pair crosses. For Indoxa-SEL, bioassay at G4 found that selection increased resistance ratio to 95 for indoxacarb compared with Lab-PK. Selection with indoxacarb significantly increased resistance to spinosad and emamectin; however, resistance to abamectin was observed to drop. A significant reduction in the resistance to indoxacarb was observed in Indoxa-SEL at G9, indicating unstable resistance to indoxacarb; however, it was stable for fipronil. Synergism tests with microsomal oxidase and esterase-specific inhibitors suggested that the indoxacarb resistance was associated with microsomal oxidase. Reciprocal genetic crosses between Indoxa-SEL and Lab-PK populations indicated that resistance was autosomal and incompletely dominant. Tests of monogenic inheritance suggested that resistance to indoxacarb was controlled by more than one locus.

Heterosis for yield and crossbreeding of the Pacific oyster Crassostrea gigas

Hybrid vigor or heterosis for growth and survival was demonstrated in experimental crosses of inbred Pacific oysters by Hedgecock et al. [Hedgecock, D., McGoldrick, D.J., Bayne, B.L., 1995. Hybrid vigor in Pacific oysters: an experimental approach using crosses among inbred lines. Aquaculture 137, 285–298.]. Substantial evidence for the pervasiveness of heterosis accumulated since then suggests a role for crossbreeding in commercial improvement. Here, we summarize evidence for yield heterosis in juvenile (seed) and adult oysters resulting from four diallel mating experiments. In pair crosses of parental inbred lines, we quantify heterosis by potence, hp=Q/L>1.0, where Q is twice the deviation of a hybrid from the mid-parent value and L is the absolute difference between the mean trait-values of the two parental inbred lines, these contrasts being estimated from ANOVA. For larger incomplete diallel crosses, in which partially inbred parental lines were not reared, we present estimates of Griffing's [Griffing, B., 1956. Concept of general and specific combining ability in relation to diallel crossing systems. Aust. J. Biol. Sci. 9, 463–493.] general and specific combining abilities (GCA, SCA) and, where possible, reciprocal hybrid effects (R). GCA is significant in two of four crosses analyzed, while SCA is significant in all four crosses, particularly at the seed stage, and R is significant in all three crosses, in which reciprocal comparisons were possible. The reciprocal effect is partitioned into maternal (extra-nuclear) and non-maternal (extra-nuclear×nuclear interaction) effects; the latter are significant in 4 of 5 cases, while maternal effects are significant in only 2 of 5 cases. Improvement of commercial oyster seed can be achieved by a combination of selection among inbred lines and crossbreeding of elite inbred lines; pervasive differences between reciprocal hybrids may constrain the direction of interline crosses. Because correlation of seed and adult yield is positive but weak, we propose to retain top inbred parent lines based on seed yield and to re-test the most promising crosses on a much larger production scale.

Further isolation of AFLP and LMS markers for the mapping of the Ol-2 locus related to powdery mildew ( Oidium neolycopersici) resistance in tomato ( Solanum lycopersicum L.)

Tomato powdery mildew ( Oidium neolycopersici) is a new plant disease that in recent years has frequently occurred in open field and protected environments to cause serious damage to tomato crops. Currently, the development of resistant cultivars appear to be the best eco-compatible solution to control the fungus. Several studies are in progress to increase knowledge on a recessive gene named ol-2 that confers complete resistance to powdery mildew. In this paper, we report results of research aimed at further isolation of new PCR-based markers linked to ol-2. This goal was pursued by means of bulk segregant analysis (BSA) applied to an F 2 population segregating for the ol-2 gene and derived from the pair cross between a resistant line of Solanum lycopersicum L. var. cerasiforme and the susceptible cultivar Super Marmande. Eight new amplified fragment length polymorphism (AFLP) markers tightly linked to ol-2 were isolated, adding useful mapping information to the chromosome four region where Ol-2 locus is located. Results from the application of the ligation-mediated suppression PCR (LMS-PCR) technique are also reported for the first time in plant material. These results, combined with those obtained applying low ionic strength single strand conformation polymorphism (LIS-SSCP) analysis, were of value to detect polymorphism between parents characterised by high genetic similarities and also useful in avoiding “linkage drag” during marker assisted selection (MAS) programs.

Segregation and Linkage Analysis of 75 Novel Microsatellite DNA Markers in Pair Crosses of Japanese Abalone (Haliotis discus hannai) Using the 5′-Tailed Primer Method

We present novel microsatellite markers of the Japanese abalone (Haliotis discus hannai) for general mapping studies in this species. A total of 75 microsatellite markers were developed, and the allele-transmission patterns of these markers were studied in three families generated by pair crosses. For allele scoring, we employed the 5'-tailed primer polymerase chain reaction (PCR) technique, which substantially reduces the cost for fluorescent labeling of primers. Of the 225 possible marker-family combinations (75 markers x 3 families), 18 cases of informative null-allele segregation were inferred. When such null-allele segregations were allowed, more than 70% of the 75 markers in the families turned out to be markers with an expected segregation ratio of 1:1:1:1, allowing maximal exploitation of the codominant nature of microsatellite markers. There were 16 instances of segregation distortion at the 5% significance level. The test for independence of segregation assigned the 75 markers into 17 linkage groups, which is in close agreement with the haploid chromosome number of H. discus hannai (n = 18). Six markers could not be placed into any linkage group. We suggest that these markers could help construct a H. discus hannai linkage map.

The Elusive p-air cross section

For the \(\bar pp\) and pp systems, we have used all of the extensive data of the Particle Data Group [K. Hagiwara et al. (Particle Data Group), Phys. Rev. D 66, 010001 (2002)]. We then subject these data to a screening process, the “Sieve” algorithm [M. M. Block, physics/0506010], in order to eliminate “ outliers” that can skew a χ2 fit. With the “Sieve” algorithm, a robust fit using a Lorentzian distribution is first made to all of the data to sieve out abnormally high Δχ 2 i , the individual ith point’s contribution to the total χ2. The χ2 fits are then made to the sieved data. We demonstrate that we cleanly discriminate between asymptotic ln s and ln2 s behavior of total hadronic cross sections when we require that these amplitudes also describe, on average, low energy data dominated by resonances. We simultaneously fit real analytic amplitudes to the “sieved” high energy measurements of \(\bar pp\) and pp total cross sections and ρ-values for \(\sqrt s \) ≥ GeV, while requiring that their asymptotic fits smoothly join the the σ pp and σpp total cross sections at \(\sqrt s \) = 4.0 GeV—again both in magnitude and slope. Our results strongly favor a high energy ln2 s fit, basically excluding a ln s fit. Finally, we make a screened Glauber fit for the p-air cross section, using as input our precisely-determined pp cross sections at cosmic ray energies.