Different escape modes in two-photon double ionization of helium

The quadrupole channel of two-photon double ionization of He exhibits two distinctly different modes of correlated motion of the photoelectron pair. The mode associated with the center-of-mass motion favors a large total momentum which is maximazed at a parallel emission. However, the mode associated with the relative motion favors an antiparallel emission. This difference is manifested in a profoundly different width of the angular correlation functions corresponding to the center-of-mass and relative motion modes.Comment: 4 pages, 3 figure

Exclusive quasielastic production of dijets at hadronic colliders

We critically re-examine the calculation of central production of dijets in quasi-elastic hadronic collisions. We find that the process is not dominated by the perturbative contribution, and discuss several sources of uncertainties in the calculation.Comment: 4 pages, talk given at Diffraction-2008, La Londe-les-Maures, France, 9-14 Sept 200

TMD PDF's: gauge invariance, RG properties and Wilson lines

The UV divergences associated with transverse-momentum dependent (TMD) parton distribution functions (PDF) are calculated together with the ensuing one-loop anomalous dimensions in the light-cone gauge. Time-reversal-odd effects in the anomalous dimensions are observed and the role of Glauber gluons is discussed. A generalized renormalization procedure of TMD PDFs is proposed, relying upon the renormalization of contour-dependent operators with obstructions.Comment: 4 pages, 1 figure. Talk presented at the International Workshop on Diffraction in High Energy and Nuclear Physics, La Londe-les-Maures, France, 9-14 Sept 2008. v2: 5 pages, preprint number and e-mail addresses adde

gamma* -> rhoT impact factor with twist three accuracy

We evaluate the impact factor of the transition gamma* -> rhoT taking into account the twist 3 contributions. We show that a gauge invariant expression is obtained with the help of QCD equations of motion. Our results are free of end-point singularities. This opens the way to a consistent treatment of factorization for exclusive processes with a transversally polarized vector meson.Comment: 4 pages, 1 figure; To appear in the proceedings of Diffraction 2008: International Workshop on Diffraction in High-Energy Physics, La Londe-les-Maures, France, September 9-14, 200

Molecular Cloning of a Bovine Immunoglobulin Lambda Chain cDNA

A cDNA library of the bovine mammary gland constructed in pBR322 was screened by mRNA hybrid-selected translation and by differential hybridization. Several immunoglobulin (Ig) λ light-chain clones were identified and sequenced. Nucleotide sequence comparison of bovine and human Ig λ chains showed a high degree of homology for constant regions and for J regions. The amino acid (aa) sequence encoded by the constant region of the bovine Ig λ chain cDNA contains 107 aa with differences at 24 aa positions from the human Ig A chain. Three complementarity-determining regions (CDR1,2,3) characteristic of the variable region of bovine Ig λ chain cDNA can be distinguished. The bovine and human sequences display good homology in the framework region 3 (FR3) but only patches of homology throughout the FR2 region. The 5′ end of the bovine Ig λ chain cDNA fragment of clone 1-14E contains five stop codons: two in CDR1, one in FR1 and two in the hydrophobic prepeptide region. These data suggest that the Igλ mRNA of clone 1-14E is transcribed from the Vλ pseudogene

Abelian symmetries in multi-Higgs-doublet models

N-Higgs doublet models (NHDM) are a popular framework to construct electroweak symmetry breaking mechanisms beyond the Standard model. Usually, one builds an NHDM scalar sector which is invariant under a certain symmetry group. Although several such groups have been used, no general analysis of symmetries possible in the NHDM scalar sector exists. Here, we make the first step towards this goal by classifying the elementary building blocks, namely the abelian symmetry groups, with a special emphasis on finite groups. We describe a strategy that identifies all abelian groups which are realizable as symmetry groups of the NHDM Higgs potential. We consider both the groups of Higgs-family transformations only and the groups which also contain generalized CP transformations. We illustrate this strategy with the examples of 3HDM and 4HDM and prove several statements for arbitrary N.Comment: 33 pages, 2 figures; v2: conjecture 3 is proved and becomes theorem 3, more explanations of the main strategy are added, matches the published versio

Investigation of vibratory drilling model with adaptive control. Part 2: mixed control of peak-to-peak vibration displacement and cutting continuity index

Chip segmentation is important condition for deep drilling efficiency improving. Chip segmentation could be ensured by sustaining stable axial self-excited vibrations of a drill. Vibrations are excited by regenerative effect when cutting edges move along the surface formed by previous passes. The conditions required for reliable chip segmentation could be created by using of a special vibratory head with an elastic element, providing tool additional axial flexibility. To maintain stable vibro-process with amplitude sufficient for chip segmentation, it’s suggested to use the vibratory head with a special actuator for adaptive feedback control proportional to a tool vibration velocity. Two algorithms of the feedback gain adaptation are proposed in the present paper: the adaptation by peak-to-peak displacement and the mixed adaptation by peak-to-peak displacement with cutting continuity index. The investigation of effectiveness of the proposed algorithms applicable to the model, described in [9], is also presented

Three form potential in (special) minimal supergravity superspace and supermembrane supercurrent

This contribution begins the study of the complete superfield Lagrangian description of the interacting system of D=4 N=1 supergravity (SUGRA) and supermembrane. Firstly, we review a 'three form supergravity' by Ovrut and Waldram, which we prefer to call 'special minimal supergravity'. This off-shell formulation of simple SUGRA is appropriate for our purposes as the supermembrane action contains the so-called Wess-Zumino term given by the integral over a three form potential in superspace, C3. We describe this formulation in the frame of Wess--Zumino superfield approach, showing how the basic variations of minimal SUGRA are restricted by the conditions of the existence of a three-form potential C3 in its superspace. In this language the effect of dynamical generation of cosmological constant, known to be characteristic for this formulation of SUGRA, appears in its superfield form, first described by Ogievetsky and Sokatchev in their formulation of SUGRA as a theory of axial vector superfield. Secondly, we vary the supermembrane action with respect to the special minimal SUGRA superfields (basic variations) and obtain the supercurrent superfields as well as the supergravity superfield equations with the supermembrane contributions.Comment: 18 pages, no figures. V2: Important references added. The abstract and presentation have been changed to reflect the overloop with that. Submitted to the QTS7 Proceedings. J. Phys. style use

Interpreting Attoclock Measurements of Tunnelling Times

Resolving in time the dynamics of light absorption by atoms and molecules, and the electronic rearrangement this induces, is among the most challenging goals of attosecond spectroscopy. The attoclock is an elegant approach to this problem, which encodes ionization times in the strong-field regime. However, the accurate reconstruction of these times from experimental data presents a formidable theoretical challenge. Here, we solve this problem by combining analytical theory with ab-initio numerical simulations. We apply our theory to numerical attoclock experiments on the hydrogen atom to extract ionization time delays and analyse their nature. Strong field ionization is often viewed as optical tunnelling through the barrier created by the field and the core potential. We show that, in the hydrogen atom, optical tunnelling is instantaneous. By calibrating the attoclock using the hydrogen atom, our method opens the way to identify possible delays associated with multielectron dynamics during strong-field ionization.Comment: 33 pages, 10 figures, 3 appendixe

Curare alkaloids from Matis Dart Poison: Comparison with d-tubocurarine in interactions with nicotinic, 5-HT3 serotonin and GABAA receptors.

Several novel bisbenzylisoquinoline alkaloids (BBIQAs) have recently been isolated from a Matis tribe arrow poison and shown by two-electrode voltage-clamp to inhibit mouse muscle nicotinic acetylcholine receptors (nAChR). Here, using radioligand assay with Aplysia californica AChBP and radioiodinated α-bungarotoxin ([125I]-αBgt), we show that BBIQA1, BBIQA2, and d-tubocurarine (d-TC) have similar affinities to nAChR orthosteric site. However, a competition with [125I]-αBgt for binding to the Torpedo californica muscle-type nAChR revealed that BBIQAs1, 2, and 3 are less potent (IC50s = 26.3, 8.75, and 17.0 μM) than d-TC (IC50 = 0.39 μM), while with α7 nAChR in GH4C1 cells, BBIQA1 was less potent that d-TC (IC50s = 162 μM and 7.77 μM, respectively), but BBIQA2 was similar (IC50 = 5.52 μM). In inhibiting the Ca2+ responses induced by acetylcholine in Neuro2a cells expressing the mouse adult α1β1εδ nAChR or human α7 nAChR, BBIQAs1 and 2 had similar potencies to d-TC (IC50s in the range 0.75-3.08 μM). Our data suggest that BBIQA1 and BBIQA2 can inhibit adult muscle α1β1εδ nAChR by both competitive and noncompetitive mechanisms. Further experiments on neuronal α3β2, α4β2, and α9α10 nAChRs, expressed in Xenopus laevis oocytes, showed that similar potencies for BBIQAs1, 2, and d-TC. With α3β2γ2 GABAAR currents were almost completely inhibited by d-TC at a high (100 μM) concentration, but BBIQAs1 and 2 were less potent (only 40-50% inhibition), whereas in competition with Alexa Fluor 546-α-cobratoxin for binding to α1β3γ2 GABAAR in Neuro2a cells, d-TC and these analogs had comparable affinities. Especially interesting effects of BBIQAs1 and 2 in comparison with d-TC were observed for 5-HT3AR: BBIQA1 and BBIQA2 were 5- and 87-fold less potent than d-TC (IC50 = 22.63 nM). Thus, our results reveal that these BBIQAs differ from d-TC in their potencies towards certain Cys-loop receptors, and we suggest that understanding the reasons behind this might be useful for future drug design.The work of ENS, IAI, DSK, IVS, AIG, LVS, and VIT was supported by the Russian Science Foundation Grant 16-14-00215 (http://rscf. ru/en). The work of IEK was supported by the Russian Foundation for Basic Research Grant 18- 04-01366 (http://www.rfbr.ru/rffi/eng). The work of SCRL was supported by a Medical Research Council Grant MR L021676 (https://mrc.ukri.org/)