Differential, Partial Cross Sections for Electron Excitation of the Sodium 3P State

Using a powerful laser-based experimental method, the cross section for electron excitation of Na(3S) atoms to the Na(3P) state has been decomposed into partial components with respect to changes in the spin and angular momentum of the atomic electron, and these partial cross sections are further reduced to their differential character with respect to the electron scattering angle. Partial, differential cross sections are reported for electron collision energies from threshold 2.1 to 3.6 eV, and compared to available calculations

Spin-Exchange Cross Section for Electron Excitation of Na 3S 3P Determined by a Novel Spectroscopic Technique

An experimental technique is described which enables determination of the partial cross sections for electron excitation of atoms as a function of changes in spin and orbital angular momentum. This method provides a good signal-to-noise ratio in the energy region near threshold, and could be used to study long- or short-lived excited states of many atomic systems. Measurements for Na 3S−3P, near-threshold excitation are reported here. The results are generally in good agreement with the close-coupling calculations of D. L. Moores and D. W. Norcross [J. Phys. B 5, 1482 (1972)] for the largest ΔmS and ΔmL components of the cross section, but not for the component with |ΔmS|=1 and |ΔmL|=1, indicating that the exchange interaction is larger than previously recognized

NLL soft and Coulomb resummation for squark and gluino production at the LHC

We present predictions of the total cross sections for pair production of squarks and gluinos at the LHC, including the stop-antistop production process. Our calculation supplements full fixed-order NLO predictions with resummation of threshold logarithms and Coulomb singularities at next-to-leading logarithmic (NLL) accuracy, including bound-state effects. The numerical effect of higher-order Coulomb terms can be as big or larger than that of soft-gluon corrections. For a selection of benchmark points accessible with data from the 2010-2012 LHC runs, resummation leads to an enhancement of the total inclusive squark and gluino production cross section in the 15-30 % range. For individual production processes of gluinos, the corrections can be much larger. The theoretical uncertainty in the prediction of the hard-scattering cross sections is typically reduced to the 10 % level.Comment: 45 pages, 16 Figures, LaTex. v2: published version. Grids with numerical results for the NLL cross sections for squark and gluino production at the 7/8 TeV LHC are included in the submission and are also available at http://omnibus.uni-freiburg.de/~cs1010/susy.htm

Scalar diagrammatic rules for Born amplitudes in QCD

We show that all Born amplitudes in QCD can be calculated from scalar propagators and a set of three- and four-valent vertices. In particular, our approach includes amplitudes with any number of quark pairs. The quarks may be massless or massive. The proof of the formalism is given entirely within quantum field theory.Comment: 20 pages, references adde

Unitarity, BRST Symmetry and Ward Identities in Orbifold Gauge Theories

We discuss the use of BRST symmetry and the resulting Ward identities for orbifold gauge theories as consistency checks in an arbitrary number of dimensions. We verify that both the usual orbifold symmetry breaking and the recently proposed Higgsless symmetry breaking are consistent with the nilpotency of the BRST transformation. Imposing the Ward identities resulting from the BRST symmetry on the 4-point functions of theory, we obtain relations on the coupling constants that are shown to be equivalent to the conditions for tree level unitarity. We present the complete set of these sum rules also for inelastic scattering and discuss applications to 6-dimensional models and to incomplete matter multiplets on orbifold fixed points.Comment: 34 pages, LaTeX (feynmf.sty, url.sty and thophys.sty included), v2:references added, v3:typos corrected, sec.3 revise

Spinor formalism for massive fields with half-integral spin

In this article, we extend the %Weyl-van der Waerden spinor technique for calculating helicity amplitudes to general massive fields of half-integer spins. We find that the little group generators can be represented as first-order differential operators in the spinor formalism. We use the spinor forms of the generators to get the explicit form of the massive fields of any spin and any helicity. We also deal with the three-particle S-matrix by these spinor form generators, and find that we are able to extend the explicit form of the three-particle vertex obtained by Benincasa and Cachazo to the massive case. We present the explicit expressions for the amplitudes with external particles of the lowest helicities up to -3/2. Group theory, in the form of raising operators of the little group, then dictates other amplitudes with higher helicity in the same spin multiplets. The formalism allows, in principle, to determine the electromagnetic form-factors of charged particles of arbitrary helicities, without additional assumptions about the underlying lagrangian. We find that restrictions which follow from gauge and Lorentz invariance are nearly as restrictive as in the massless case.Comment: 21 pages, 1 figure

Genetic Variants in P-Selectin and C-Reactive Protein Influence Susceptibility to Cognitive Decline After Cardiac Surgery

ObjectivesWe hypothesized that candidate gene polymorphisms in biologic pathways regulating inflammation, cell matrix adhesion/interaction, coagulation-thrombosis, lipid metabolism, and vascular reactivity are associated with postoperative cognitive deficit (POCD).BackgroundCognitive decline is a common complication of coronary artery bypass graft (CABG) surgery and is associated with a reduced quality of life.MethodsIn a prospective cohort study of 513 patients (86% European American) undergoing CABG surgery with cardiopulmonary bypass, a panel of 37 single-nucleotide polymorphisms (SNPs) was genotyped by mass spectrometry. Association between these SNPs and cognitive deficit at 6 weeks after surgery was tested using multiple logistic regression accounting for age, level of education, baseline cognition, and population structure. Permutation analysis was used to account for multiple testing.ResultsWe found that minor alleles of the CRP1059G/C SNP (odds ratio [OR] 0.37, 95% confidence interval [CI] 0.16 to 0.78; p = 0.013) and the SELP1087G/A SNP (OR 0.51, 95% CI 0.30 to 0.85; p = 0.011) were associated with a reduction in cognitive deficit in European Americans (n = 443). The absolute risk reduction in the observed incidence of POCD was 20.6% for carriers of the CRP1059C allele and 15.2% for carriers of the SELP1087A allele. Perioperative serum C-reactive protein (CRP) and degree of platelet activation were also significantly lower in patients with a copy of the minor alleles, providing biologic support for the observed allelic association.ConclusionsThe results suggest a contribution of P-selectin and CRP genes in modulating susceptibility to cognitive decline after cardiac surgery, with potential implications for identifying populations at risk who might benefit from targeted perioperative antiinflammatory strategies

Painted flowers: Eluta generates pigment patterning in Antirrhinum

*In the early 1900s, Erwin Baur established Antirrhinum majus as a model system, identifying and characterising numerous flower colour variants. This included Picturatum /Eluta, which restricts the accumulation of magenta anthocyanin pigments, forming bullseye markings on the flower face. *We identified the gene underlying the Eluta locus by transposon-tagging, using an Antirrhinum line that spontaneously lost the non-suppressive el phenotype. A candidate MYB repressor gene at this locus contained a CACTA transposable element. We subsequently identified plants where this element excised, reverting to a suppressive Eluta phenotype. El alleles inhibit expression of anthocyanin biosynthetic genes, confirming it to be a regulatory locus. The modes of action of Eluta were investigated by generating stable transgenic tobacco lines, biolistic transformation of Antirrhinum petals and by promoter activation/repression assays. *Eluta competes with MYB activators for promoter cis-elements, and also by titrating essential co-factors (bHLH proteins) to reduce transcription of target genes. Eluta restricts the pigmentation established by the R2R3-MYB factors, Rosea and Venosa, with greatest repression on those parts of the petals where Eluta is most highly expressed. *Baur questioned the origin of heredity units determining flower colour variation in cultivated A. majus. Our findings support introgression from wild species into cultivated varieties. <br/

Testing the theory of immune selection in cancers that break the rules of transplantation

Modification of cancer cells likely to reduce their immunogenicity, including loss or down-regulation of MHC molecules, is now well documented and has become the main support for the concept of immune surveillance. The evidence that these modifications, in fact, result from selection by the immune system is less clear, since the possibility that they may result from reorganized metabolism associated with proliferation or from cell de-differentiation remains. Here, we (a) survey old and new transplantation experiments that test the possibility of selection and (b) survey how transmissible tumours of dogs and Tasmanian devils provide naturally evolved tests of immune surveillance