A comparison of efficient methods for the computation of Born gluon amplitudes

We compare four different methods for the numerical computation of the pure gluonic amplitudes in the Born approximation. We are in particular interested in the efficiency of the various methods as the number n of the external particles increases. In addition we investigate the numerical accuracy in critical phase space regions. The methods considered are based on (i) Berends-Giele recurrence relations, (ii) scalar diagrams, (iii) MHV vertices and (iv) BCF recursion relations.Comment: 20 page

Lived experiences of routine antenatal dietetic services among women with obesity: A qualitative phenomenological study

Objective: To understand the lived experiences and views of being referred to an antenatal dietetic service from the perspective of pregnant women with obesity.Design: A qualitative, interpretive approach using one-to-one in-depth interviews to explore the lived experience of pregnant women with obesity following referral to an antenatal dietetics service. Thematic content analysis was carried out by two researchers independently to develop data-driven themes.Setting: One NHS Trust maternity and dietetic services, North East England, UKParticipantsFifteen pregnant women with a booking body mass index ≥30 kg/m2 attending an obesity-specific antenatal dietetic service. All women were White, parity between 0–2, and BMI range 30–51 kg/m2.Findings: Four themes were identified within this concept. 1) Women's overall experience of the service: experiences were predominately positive with only two negative cases identified. 2) Process of referral: women placed importance on informative and in-person communication about the service, with health professionals, at the point of referral. 3) Delivery of the service: dietitians were considered to be the experts and women wanted more frequent contact. 4) Content of the service: tailored advice enabled behaviour change, and women desired increased physical activity support and weight monitoring.Key conclusions: Women reported an overall positive experience and thought that dietitians were the expert health professionals to support them. Women in this study felt that tailoring advice specific to their personal circumstances helped them implement changes, and had a strong interest in the nutritional benefits for fetal development. Women considered weight monitoring to be a positive element of the service; however, further research is required given the limited and conflicting evidence-base.Implications for practice: It is important to incorporate women's experiences in the development and delivery of antenatal weight management services to facilitate person-centred care. Communication by health professionals at the point of referral is particularly important to provide accurate expectations of services and to reduce anxieties. Dietitians are considered to be appropriate experts to deliver these services, although they may need additional support to address women's physical activity needs in pregnancy

Complete mitochondrial genome of the grey reef shark, Carcharhinus amblyrhynchos (Carcharhiniformes: Carcharhinidae)

We report the first mitochondrial genome sequences for the gray reef shark, Carcharhinus amblyrhynchos. Two specimens from the British Indian Ocean Territory were sequenced independently using two different next generation sequencing methods, namely short read sequencing on the Illumina HiSeq and long read sequencing on the Oxford Nanopore Technologies’ MinION sequencer. The two sequences are 99.9% identical and are 16,705 base pairs (bp) and 16,706 bp in length. The mitogenome contains 22 tRNA genes, two rRNA genes, 13 protein-coding genes and two non-coding regions; the control region and the origin of light-strand replication (OL)

Short-range order and precipitation in Fe-rich Fe-Cr alloys: Atomistic off-lattice Monte Carlo simulations

Short-range order (SRO) in Fe-rich Fe-Cr alloys is investigated by means of atomistic off-lattice Monte Carlo simulations in the semi-grand canonical ensemble using classical interatomic potentials. The SRO parameter defined by Cowley [Phys. Rev. B 77, 669 (1950)] is used to quantify the degree of ordering. In agreement with experiments a strong ordering tendency in the Cr distribution at low Cr concentrations (~< 5%) is observed, as manifested in negative values of the SRO parameters. For intermediate Cr concentrations (5% ~< c_Cr ~< 15%) the SRO parameter for the alpha-phase goes through a minimum, but at the solubility limit the alpha-phase still displays a rather strong SRO. In thermodynamic equilibrium for concentrations within the two-phase region the SRO parameter measured over the entire sample therefore comprises the contributions from both the alpha and alpha-prime phases. If both of these contributions are taken into account, it is possible to quantitatively reproduce the experimental results and interpret their physical implications. It is thereby shown that the inversion of the SRO observed experimentally is due to the formation of stable (supercritical) alpha-prime precipitates. It is not related to the loss of SRO in the alpha-phase or to the presence of unstable (subcritical) Cr precipitates in the alpha-phase.Comment: 9 pages, 8 figure

On-shell recursion relations for all Born QCD amplitudes

We consider on-shell recursion relations for all Born QCD amplitudes. This includes amplitudes with several pairs of quarks and massive quarks. We give a detailed description on how to shift the external particles in spinor space and clarify the allowed helicities of the shifted legs. We proof that the corresponding meromorphic functions vanish at z --> infinity. As an application we obtain compact expressions for helicity amplitudes including a pair of massive quarks, one negative helicity gluon and an arbitrary number of positive helicity gluons.Comment: 30 pages, minor change

Color-dressed recursive relations for multi-parton amplitudes

Remarkable progress inspired by twistors has lead to very simple analytic expressions and to new recursive relations for multi-parton color-ordered amplitudes. We show how such relations can be extended to include color and present the corresponding color-dressed formulation for the Berends-Giele, BCF and a new kind of CSW recursive relations. A detailed comparison of the numerical efficiency of the different approaches to the calculation of multi-parton cross sections is performed.Comment: 31 pages, 4 figures, 6 table

First-principles study of ternary fcc solution phases from special quasirandom structures

In the present work, ternary Special Quasirandom Structures (SQSs) for a fcc solid solution phase are generated at different compositions, $x_A=x_B=x_C=\tfrac{1}{3}$ and $x_A=\tfrac{1}{2}$, $x_B=x_C=\tfrac{1}{4}$, whose correlation functions are satisfactorily close to those of a random fcc solution. The generated SQSs are used to calculate the mixing enthalpy of the fcc phase in the Ca-Sr-Yb system. It is observed that first-principles calculations of all the binary and ternary SQSs in the Ca-Sr-Yb system exhibit very small local relaxation. It is concluded that the fcc ternary SQSs can provide valuable information about the mixing behavior of the fcc ternary solid solution phase. The SQSs presented in this work can be widely used to study the behavior of ternary fcc solid solutions.Comment: 20 pages, 7 figure