Pair Cross Research Articles

Top quark pair production beyond NNLO

We construct an approximate expression for the total cross section for the production of a heavy quark-antiquark pair in hadronic collisions at next-to-next-to-next-to-leading order (N$^3$LO) in $\alpha_s$. We use a technique which exploits the analyticity of the Mellin space cross section, and the information on its singularity structure coming from large N (soft gluon, Sudakov) and small N (high energy, BFKL) all order resummations, previously introduced and used in the case of Higgs production. We validate our method by comparing to available exact results up to NNLO. We find that N$^3$LO corrections increase the predicted top pair cross section at the LHC by about 4% over the NNLO.

Identifying potential heterosis in perennial ryegrass

Plant breeders aim to develop cultivars of perennial ryegrass Lolium perenne L., (PRG) that better support New Zealand farmers through improved genetic potential for key traits such as seasonal dry matter yield. Hybrid vigour (heterosis) may be one way plant breeders can increase dry matter yields, and potentially lift the long term rate of genetic gain. We report evaluation of PRG full-sibling progeny for heterosis expressed under grazing. Parents were randomly sampled from sixteen cultivars, and for each cultivar combination within mid-season and late season classes, six pair crosses were made. In 2013, replicated single row trials of parent cultivar samples and progeny were sown at two sites near Palmerston North. For 2 years, prior to each grazing, growth score (GS) data were recorded to estimate dry matter yield of each plot. Progeny GS relative to parent average GS (mid-parent heterosis, MPH), and better parent GS (high-parent heterosis, HPH) were calculated on the basis of the mean GS over years and sites. Significant (P

Pp interactions in extended air showers

Applying the recently constructed analytic representation for the pp scattering amplitudes, we present a study of p-air cross sections, with comparison to the data from Extensive Air Shower (EAS) measurements. The amplitudes describe with precision all available accelerator data at ISR, SPS and LHC energies, and its theoretical basis, together with the very smooth energy dependence of parameters controlled by unitarity and dispersion relations, permit reliable extrapolation to higher energies and to asymptotic ranges. The comparison with cosmic ray data is very satisfactory in the whole pp energy interval from 1 to 100 TeV. High energy asymptotic behaviour of cross sections is investigated in view of the geometric scaling property of the amplitudes. The amplitudes predict that the proton does not behave as a black disk even at asymptotically high enegies, and we discuss possible non-trivial consequences of this fact for pA collision cross sections at higher energies.

Pp interaction at very high energies in cosmic ray experiments

An analysis of p-air cross section data from extensive air shower measurements is presented, based on an analytical representation of the pp scattering amplitudes that describes with high precision all available accelerator data at ISR, SPS and LHC energies. The theoretical basis of the representation, together with the very smooth energy dependence of parameters controlled by unitarity and dispersion relations, permits reliable extrapolation to high energy cosmic ray (CR) and asymptotic energy ranges. Calculations of based on Glauber formalism are made using the input values of the quantities , , BI and BR at high energies, with attention given to the independence of the slope parameters, with . The influence of contributions of diffractive intermediate states, according to Good–Walker formalism, is examined. The comparison with CR data is very satisfactory in the whole pp energy interval from 1 to 100 TeV. High energy asymptotic behaviour of cross sections is investigated in view of the geometric scaling property of the amplitudes. The observed energy dependence of the ratio between p-air and pp cross sections in the data is shown to be related to the nature of the pp cross section at high energies, that does not agree with the black disk image.

Plant vigour at establishment and following defoliation are both associated with responses to drought in perennial ryegrass (Lolium perenne L.).

Periodic drought events present a significant and, with climate change, increasing constraint on temperate forage plants' production. Consequently, improving plants' adaptive response to abiotic stress is a key goal to ensure agricultural productivity in these regions. In this study we developed a new methodology, using both area-based comparison and soil water content measurements of individual non-irrigated and irrigated clones, to assess performance of perennial ryegrass (Lolium perenne L.) genotypes subjected to moisture stress in a simulated competitive environment. We applied this method to the evaluation of a full-sibling population from a pair cross between genotypes from a New Zealand cultivar and a Moroccan ecotype. Our hypothesis was that: (i) both leaf lamina regrowth after defoliation (LR) and plant vigour affect plant performance during drought and rehydration; and (ii) quantitative trait loci (QTLs) associated with plant performance under moisture stress could be identified. Differences amongst genotypes in dry matter (DM) production, early vigour at establishment, leaf elongation rate and LR were measured. LR explained most of the variation in DM production during exposure to moisture deficit and rehydration followed by plant vigour, indicated by initial DM production in both treatments and subsequent measures of DM production of irrigated clones. We identified two main QTL regions associated with DM production and LR, both during drought exposure and rehydration. Further research focused on these regions should improve our understanding of the genetic control of drought response in this forage crop and potentially other grass species with significant synteny, and support improvement in performance through molecular breeding approaches.

Investigation of Diffusion in Structured Samples using Fluorescence Pair Cross Correlation

Fluorescence Fluctuation Spectroscopy methods are powerful tools for studying diffusion both in vitro and in vivo. They are, however, limited to either homogeneous samples or to fit models that rely on generalized assumptions about the heterogeneity of the environment. Actual biological samples, however, often do not fulfill these conditions. The plasma membrane, for example, shows compartmentalization that changes dynamically [1]. This high level of complexity makes evaluation of results difficult.To better understand the effects of heterogeneities such as structures or obstacles on molecular diffusion, we monitored the diffusion of lipids in a simplified model system. We used a lipid bilayer on a nanostructured surface [2] as a simplified system to study the effect of compartmentalization on diffusion. Our samples consisted of hexagonally arranged compartments of lipid bilayers that are connected via nanometer gaps in between the metal structures. By calculating the spatial pair cross correlation functions [3] of a signal acquired while rapidly scanning over the sample, we could measure the time of diffusion of fluorescently labeled lipids between partitions. Since both diameter of the compartments and size of the gaps can be adjusted, this system allows us to study the influence of these parameters on diffusion. Furthermore, we performed Monte Carlo simulations of diffusion in similar structures. This way, we could test the effects of different interactions of the sample and the environment on the correlation functions.[1] T. Fujiwara et al., Journal of Cell Biology 2002, 157, 1071.[2] T. Lohmueller et al., Nano Letters 2012, 12, 1717.[3] M. Digman et al., Biophysical Journal 2009, 97, 665.

Higgs phenomenology in the Minimal Dilaton Model after Run I of the LHC

The Minimal Dilaton Model (MDM) extends the Standard Model (SM) by a singlet scalar, which can be viewed as a linear realization of general dilaton field. This new scalar field mixes with the SM Higgs field to form two mass eigenstates with one of them corresponding to the 125 GeV SM-like Higgs boson reported by the LHC experiments. In this work, under various theoretical and experimental constrains, we perform fits to the latest Higgs data and then investigate the phenomenology of Higgs boson in both the heavy dilaton scenario and the light dilaton scenario of the MDM. We find that: (i) If one considers the ATLAS and CMS data separately, the MDM can explain each of them well, but refer to different parameter space due to the apparent difference in the two sets of data. If one considers the combined data of the LHC and Tevatron, however, the explanation given by the MDM is not much better than the SM, and the dilaton component in the 125-GeV Higgs is less than about 20% at 2 sigma level. (ii) The current Higgs data have stronger constrains on the light dilaton scenario than on the heavy dilaton scenario. (iii) The heavy dilaton scenario can produce a Higgs triple self coupling much larger than the SM value, and thus a significantly enhanced Higgs pair cross section at hadron colliders. With a luminosity of 100 fb^{-1} (10 fb^{-1}) at the 14-TeV LHC, a heavy dilaton of 400 GeV (500 GeV) can be examined. (iv) In the light dilaton scenario, the Higgs exotic branching ratio can reach 43% (60%) at 2 sigma (3 sigma) level when considering only the CMS data, which may be detected at the 14-TeV LHC with a luminosity of 300 fb^{-1} and the Higgs Factory.

Number of involved genes and heritability of clover rot (Sclerotinia trifoliorum) resistance in red clover (Trifolium pratense)

European red clover (Trifolium pratense) crops are challenged by clover rot, a devastating disease caused by Sclerotinia trifoliorum or, in some cases by S. sclerotiorum. No completely resistant cultivars are available and resistance breeding is hampered by the lack of knowledge on the number of involved resistance genes and the heritability of clover rot resistance. In this study, we estimated the number of major genes contributing to clover rot resistance by analysing 15 F1 progeny populations from pair crosses between ramets of resistant and susceptible genotypes. Parent plants were chosen from diverse, diploid populations, including wild material, landraces and cultivars. Young progeny plants were inoculated with ascospores, evaluated phenotypically and the segregation of disease scores was studied. Our results indicated that clover rot resistance may be conferred by three major effect genes, although segregation patterns suggested that there may be numerous minor effect genes involved as well. No proof was found for a maternal inheritance of clover rot resistance. To get insight in the heritability of clover rot resistance, we applied divergent selection by our high-throughput bio-test on an experimental diploid population: the original population (70.5 %), the first generation after selection for susceptibility (79.2 %) and the first generation after selection for resistance (62.3 %) differed significantly in susceptibility (p < 0.001). The second generation after selection for resistance (60.0 %) was not more resistant than the first generation after selection for resistance. In the first generation of selection the heritability (h2) was on average 0.34. In the second generation of selection h2 was 0.07. These findings have important implications for resistance breeding.

Implications of indirect response to the quantitative character of direct response rust disease resistance characters in the selection of the pair crosses peanuts

Implications of indirect response to the quantitative character of direct response rust disease resistance characters in the selection of the pair crosses peanuts

Leaf Rubisco turnover in a perennial ryegrass (Lolium perenne L.) mapping population: genetic variation, identification of associated QTL, and correlation with plant morphology and yield

This study tested the hypotheses that: (i) genetic variation in Rubisco turnover may exist in perennial ryegrass (Lolium perenne L.); (ii) such variation might affect nitrogen use efficiency and plant yield; and (iii) genetic control of Rubisco turnover might be amenable to identification by quantitative trait loci (QTL) mapping. A set of 135 full-sib F1 perennial ryegrass plants derived from a pair cross between genotypes from the cultivars 'Grasslands Impact' and 'Grasslands Samson' was studied to test these hypotheses. Leaf Rubisco concentration at different leaf ages was measured and modelled as a log-normal curve described by three mathematical parameters: D (peak Rubisco concentration), G (time of D), and F (curve standard deviation). Herbage dry matter (DM) yield and morphological traits (tiller weight (TW), tiller number (TN), leaf lamina length (LL), and an index of competitive ability (PI)) were also measured. The progeny exhibited continuous variation for all traits. Simple correlation and principal component analyses indicated that plant productivity was associated with peak Rubisco concentration and not Rubisco turnover. Lower DM was associated with higher leaf Rubisco concentration indicating that Rubisco turnover effects on plant productivity may relate to energy cost of Rubisco synthesis rather than photosynthetic capacity. QTL detection by a multiple QTL model identified seven significant QTL for Rubisco turnover and nine QTL for DM and morphological traits. An indication of the genetic interdependence of DM and the measures of Rubisco turnover was the support interval overlap involving QTL for D and QTL for TN on linkage group 5 in a cluster involving QTL for DM and PI. In this region, alleles associated with increased TN, DM, and PI were associated with decreased D, indicating that this region may regulate Rubisco concentration and plant productivity via increased tillering. A second cluster involving QTL for LL, TN, PI and DM was found on linkage group 2. The two clusters represent marker-trait associations that might be useful for marker-assisted plant breeding applications. In silico comparative analysis indicated conservation of the genetic loci controlling Rubisco concentration in perennial ryegrass and rice.

Financial Attributes and Investor Risk Tolerance at the Nairobi Securities Exchange – A Kenyan Perspective

The inclination for optimizing returns by taking maximum risk has implications for both individual investors, as well as fund managers. For the former, risk tolerance will determine the appropriate composition of assets in a portfolio, which is optimal in terms of risk and returns relative to the needs of the individual. For fund managers, the inability to effectively determine investor risk tolerance may lead to homogeneity among investment funds. This paper investigates the extent to which financial attributes affect individual investor risk tolerance at the Nairobi Securities Exchange (NSE), Kenya. Financial attributes in this study were measured in two main aspects: individual monthly earnings income and home ownership. A sample of 500 Central Depository System (CDS) account holders was selected from a population of 932,510 investors at the NSE. Single independent variable cross tabulation on risk tolerance as well as paired cross tabulation on the dependent variable was performed. Analysis of variance was also used to determine how each group of the independent variable affects the dependent variable. Ordinal logistic regression model (OLRM) was employed to establish the contribution of financial attributes on risk tolerance. Single independent variable cross tabulation revealed that home owners were more risk tolerant than non owners. However, one way Analysis of Variance revealed that the variable had a P value of 0.710, hence not significantly affecting risk tolerance. The result of ANOVA on income was significant at a P value of 0.014 individual earnings, hence influences risk tolerance. Risk tolerance increased with earnings up to very high, except for those who earned more than 120,000 per month. OLMR fitted well with a significance level of 0.027 less than ?=5%, although it showed that home ownership is not a significant determinant at a P value of 0.761. For every single unit of home ownership for those with homes to those without, the expected log of odds increased by 0.060 as the threshold of risk tolerance increased, holding other factors constant. Income levels for those earning 90,000-120,000 per month showed a P value of 0.006, hence income was a major determinant of risk tolerance. For every single unit increase of investors earning 90,000-120,000, the expected ordered log of odds of risk tolerance reduced by 1.077 as the threshold of risk tolerance increased, holding other factors constant. Therefore fund managers, investment advisors and individual investors should consider the contribution of financial attributes in financial decision making.

Aquaculture Methods for a Genetically Managed Population of Endangered Delta Smelt

AbstractIn response to Federal listing of the Delta Smelt Hypomesus transpacificus as a threatened species in 1993, intensive fish culture techniques were developed to provide a supply of fish for research activities. The Delta Smelt was listed as endangered by the state of California in 2009, and several agencies worked quickly to develop a captive refuge population under genetic management. Captive 2‐year‐old wild‐origin Delta Smelt served as the founding population in 2008. Each year, 250 genetically selected, single pair crosses are made in vitro, and the resultant full‐sibling families are combined to rear in multifamily groups. Typically, eight families are reared together from egg to adult stage, with 80% or more of the initial families represented at the adult stage. Multifamily rearing provides an efficient way of achieving a breeding population of 500 in a smaller facility. Juvenile survival increased from 18% in 2009 to 39% in 2010, as facilities and methodologies improved. Growth rate also increased significantly from 2009 to 2010 (from 0.19 to 0.25 mm/d). Subdermal alphanumeric tags identified individuals and allowed spawning of select individuals to preserve genetic diversity in the refuge population. Group marking, by adipose fin clip, provided efficiencies in time and space. Tagging and genetic analyses enabled in vitro spawning of recommended pair crosses each year. At present, we recommend completing the majority of spawning from February to mid‐May and continuing to augment the refuge population with wild fish each year. The refuge population provides one type of safeguard against species extinction and provides an example for endangered fish culture.

Hadronic interactions and cosmic rays at ultra high energies

Observations of ultra high energy cosmic rays allow in principle to obtain information about the properties of hadronic interactions in an energy range not accessible with particle accelerators. This task is however complicated by the fact that the composition of the primary CR is not known and must be estimated from the same data set. Solving the ambiguity between composition and hadronic interaction modeling is a central problem for UHECR observations. Recently the Pierre Auger collaboration has presented an estimate of the p-air interaction length at a laboratory energy E0 � 10 18.24 eV. The interaction length is inferred from the shape of the tail of the Xmax distribution of the observed showers, following a method pioneered by the Fly's Eye group. In this work we want to analyse critically this method, and discuss its potential for further studies. composition of these particles, and at the same time to obtain information about the properties of hadronic interaction in an energy range not accessible to accelerators. These two goals are unfortunately in conflict with each other. Uncertainties in the modeling of the properties of hadronic interactions at high energy limit the precision that can be achieved in the measurement of the composition of the primary radiation; viceversa, uncertainties in the composition of the primary particles do not allow an easy determination of the properties of the showers generated by protons (or other nuclear species). The best strategy to solve this ambiguity is the object of an active field of investigations. At the present moment there is still a significant uncertainty both on the composition of cosmic rays in the UHE range, and on the quality of the description of their showers by the existing montecarlo codes. The analysis of the current situation is difficult also because the observations made by the Pierre Auger (1, 2), HiRes (3) and Telescope Array (4) collaborations are not in agreement. The HiRes and Telescope Array results appear to be consistent with a composition that is proton dominated in the entire energy range, while the data of the Pierre Auger Observatory seem to imply a composition that becomes gradually enriched in heavy nuclei with increasing energy. This disagreement is a serious obstacle in the progress of the field, since a consistent interpretation of all data is currently impossible. It is clear that a satisfactory resolution of these discrepancies is urgent and important. Recently the Pierre Auger collaboration (5) has presented a measurement of the interaction length for protons with energy E0 � 10 18.24 eV (that corresponds to a c.m. energy √ s � 57TeV for nucleon- nucleon interactions, that corresponds to a p-air cross section 505 ± 23(stat) + 28 − 36(sys)mb (this must be understood as the production cross section, that refers to interactions where at least one additional pion is produced, excluding the elastic and target fragmentation processes). Converting the

Top quark forward-backward asymmetry and W ′-boson with general couplings

The measured forward-backward asymmetry in top pair events at the Fermilab Tevatron collider deviates significantly from the standard model expectation. Several models have been proposed to describe the observed asymmetry which grows with the rapidity difference of the top pairs and also with the $t\bar{t}$ invariant mass. The presence of a heavy charged gauge boson $W'$ with the coupling $W'-t-d$ (left-handed, right-handed, and a mixture of left and right-handed couplings) could generate the desired top forward-backward asymmetry keeping the top pair cross section consistent with the standard model prediction. Such $W'$-boson makes contribution to the electric dipole moment of the neutron through contribution to the $d$-quark electric dipole moment, recently measured charge asymmetry ($A_{C}$) by the LHC experiments, and the total cross section of top pair at the LHC and Tevatron. We show that the upper bounds on neutron and top electric dipole moments disfavour any $W'$ with a mass below 240 GeV which could explain the Tevatron forward-backward asymmetry. It is shown that the charge asymmetry provides an allowed region in the parameters space with no overlap with the allowed region where the asymmetry could be described.

Measurement of the top quark pair cross section with ATLAS in pp collisions at [formula omitted] using final states with an electron or a muon and a hadronically decaying τ lepton

A measurement of the cross section of top quark pair production in proton–proton collisions recorded with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 7 TeV is reported. The data sample used corresponds to an integrated luminosity of 2.05 fb−1. Events with an isolated electron or muon and a τ lepton decaying hadronically are used. In addition, a large missing transverse momentum and two or more energetic jets are required. At least one of the jets must be identified as originating from a b quark. The measured cross section, σtt¯=186±13(stat.)±20(syst.)±7(lumi.) pb, is in good agreement with the Standard Model prediction.

Inheritance of an extended diapause trait in theNorthern corn rootworm,Diabrotica barberi(Coleoptera:Chrysomelidae)

AbstractDiapause is an adaptive trait that delays development or reproduction under unfavourable circumstances. The northern corn rootworm,Diabrotica barberiSmith &amp;Lawrence, an important maize,Zea maysL., pest in the Diabroticite species complex, overwinters in diapause during the egg stage. SomeNCRpopulations are adapted to crop rotation by expressing an extended diapause (ED) trait that delays embryonic development for 2 years. ThisEDtrait has increased in frequency and geographic distribution since first reported inIllinois in 1932. Reciprocal single pair crosses among beetles from a laboratory colony with the ancestral 1‐year diapause trait and field collected beetles with the 2‐yearEDtrait indicated thatEDfemales laid significantly moreEDeggs than did females with the 1‐year diapause trait regardless of male genotype. TheEDtrait was highly heritable [realized heritability (h2) = 0.698 ± 0.314], with genetic dominance (D) of the trait strongly influenced by female genotype. Selection of theEDtrait and maintenance of polymorphic diapause phenotypes within maize‐soybean cropping systems is discussed in relation to response to a fluctuating environment and as a potentially advantageous life history adaptation.

Cytoplasmic and Genomic Effects on Meiotic Pairing in Brassica Hybrids and Allotetraploids from Pair Crosses of Three Cultivated Diploids

Interspecific hybridization and allopolyploidization contribute to the origin of many important crops. Synthetic Brassica is a widely used model for the study of genetic recombination and "fixed heterosis" in allopolyploids. To investigate the effects of the cytoplasm and genome combinations on meiotic recombination, we produced digenomic diploid and triploid hybrids and trigenomic triploid hybrids from the reciprocal crosses of three Brassica diploids (B. rapa, AA; B. nigra, BB; B. oleracea, CC). The chromosomes in the resultant hybrids were doubled to obtain three allotetraploids (B. juncea, AA.BB; B. napus, AA.CC; B. carinata, BB.CC). Intra- and intergenomic chromosome pairings in these hybrids were quantified using genomic in situ hybridization and BAC-FISH. The level of intra- and intergenomic pairings varied significantly, depending on the genome combinations and the cytoplasmic background and/or their interaction. The extent of intragenomic pairing was less than that of intergenomic pairing within each genome. The extent of pairing variations within the B genome was less than that within the A and C genomes, each of which had a similar extent of pairing. Synthetic allotetraploids exhibited nondiploidized meiotic behavior, and their chromosomal instabilities were correlated with the relationship of the genomes and cytoplasmic background. Our results highlight the specific roles of the cytoplasm and genome to the chromosomal behaviors of hybrids and allopolyploids.

PollenCALC: Software for estimation of pollen compatibility of self-incompatible allo- and autotetraploid species

BackgroundSelf-incompatibility (SI) is a biological mechanism to avoid inbreeding in allogamous plants. In grasses, this mechanism is controlled by a two-locus system (S-Z). Calculation of male and female gamete frequencies is complex for tetraploid species. We are not aware of any software available for predicting pollen haplotype frequencies and pollen compatibility in tetraploid species.ResultsPollenCALC is a software tool written in C++ programming language that can predict pollen compatibility percentages for polyploid species with a two-locus (S, Z) self-incompatibility system. The program predicts pollen genotypes and frequencies based on defined meiotic parameters for allo- or autotetraploid species with a gametophytic S-Z SI system. These predictions can be used to obtain expected values for for diploid and for (allo- or autotetraploidy SI grasses.ConclusionThe information provided by this calculator can be used to predict compatibility of pair-crosses in plant breeding applications, to analyze segregation distortion for S and Z genes, as well as linked markers in mapping populations, hypothesis testing of the number of S and Z alleles in a pair cross, and the underlying genetic model.

Co-Localized or Randomly Distributed? Pair Cross Correlation of In Vivo Grown Subgingival Biofilm Bacteria Quantified by Digital Image Analysis

The polymicrobial nature of periodontal diseases is reflected by the diversity of phylotypes detected in subgingival plaque and the finding that consortia of suspected pathogens rather than single species are associated with disease development. A number of these microorganisms have been demonstrated in vitro to interact and enhance biofilm integration, survival or even pathogenic features. To examine the in vivo relevance of these proposed interactions, we extended the spatial arrangement analysis tool of the software daime (digital image analysis in microbial ecology). This modification enabled the quantitative analysis of microbial co-localization in images of subgingival biofilm species, where the biomass was confined to fractions of the whole-image area, a situation common for medical samples. Selected representatives of the disease-associated red and orange complexes that were previously suggested to interact with each other in vitro (Tannerella forsythia with Fusobacterium nucleatum and Porphyromonas gingivalis with Prevotella intermedia) were chosen for analysis and labeled with specific fluorescent probes via fluorescence in situ hybridization. Pair cross-correlation analysis of in vivo grown biofilms revealed tight clustering of F. nucleatum/periodonticum and T. forsythia at short distances (up to 6 µm) with a pronounced peak at 1.5 µm. While these results confirmed previous in vitro observations for F. nucleatum and T. forsythia, random spatial distribution was detected between P. gingivalis and P. intermedia in the in vivo samples. In conclusion, we successfully employed spatial arrangement analysis on the single cell level in clinically relevant medical samples and demonstrated the utility of this approach for the in vivo validation of in vitro observations by analyzing statistically relevant numbers of different patients. More importantly, the culture-independent nature of this approach enables similar quantitative analyses for “as-yet-uncultured” phylotypes which cannot be characterized in vitro.

$t\bar t$ and single top cross sections at the Tevatron

We present a summary of the latest measurements of the top pair and single top cross sections performed by the CDF and D0 collaborations at the Fermilab Tevatron collider.