6,454 research outputs found
Investigation into boiler corrosion on the historic vessel SL Dolly.
No full textWhen SL Dolly was recovered from Ullswater after being submerged for 67 years,
the wrought iron boiler was found to have surprisingly little corrosion. This
article describes the results of a project to investigate the reasons for this
behaviour and determine whether it was a property of the wrought iron or a
consequence of the lakebed environment. Weight loss measurements and
electrochemical impedance spectroscopy were used to compare the corrosion rates
of wrought iron and modern boiler steel exposed to tap water and samples of lake
water and lakebed sediment. A corrosion probe was used to make in situ linear
polarisation resistance measurements at the spot where Dolly sank. The corrosion
rate of wrought iron on the lakebed was estimated to be in the range
0à ·018â  0à ·030 mm year-1, which corresponds to a metal loss of 1à ·2â  2à ·0 mm
over the 67 year period; this metal loss is consistent with the condition of the
boiler. The effects of microstructure, material composition and water chemistry
are considered in detail, and it is concluded that the low oxygen content and
the low concentration of dissolved solids in the lake water were the underlying
causes of the observed corrosion b
Conformal mechanics on rotating Bertotti-Robinson spacetime
No full text20 pages, Latex. Minor corrections. To be published in Nuclear Physics BInternational audienceWe investigate conformal mechanics associated with the rotating Bertotti-Robinson (RBR) geometry found recently as the near-horizon limit of the extremal rotating Einstein-Maxwell-dilaton-axion black holes. The solution breaks the symmetry of Bertotti-Robinson (BR) spacetime to and breaks supersymmetry in the sense of supergravity as well. However, it shares with BR such properties as confinement of timelike geodesics and discreteness of the energy of test fields on the geodesically complete manifold. Conformal mechanics governing the radial geodesic motion coincides with that for a charged particle in the BR background (a relativistic version of the De Alfaro-Fubini-Furlan model), with the azimuthal momentum playing the role of a charge. Similarly to the BR case, the transition from Poincaré to global coordinates leads to a redefinition of the Hamiltonian making the energy spectrum discrete. Although the metric does not split into a product space even asymptotically, it still admits an infinite-dimensional extension of as asymptotic symmetry. The latter is shown to be given by the product of one copy of the Virasoro algebra and U(1), the same being valid for the extremal Kerr throat
CR1 Knops blood group alleles are not associated with severe malaria in the Gambia
No full textThe Knops blood group antigen erythrocyte polymorphisms have been associated with reduced falciparum malaria-based in vitro rosette formation (putative malaria virulence factor). Having previously identified single-nucleotide polymorphisms (SNPs) in the human complement receptor 1 (CR1/CD35) gene underlying the Knops antithetical antigens Sl1/Sl2 and McC(a)/McC(b), we have now performed genotype comparisons to test associations between these two molecular variants and severe malaria in West African children living in the Gambia. While SNPs associated with Sl:2 and McC(b+) were equally distributed among malaria-infected children with severe malaria and control children not infected with malaria parasites, high allele frequencies for Sl 2 (0.800, 1,365/1,706) and McC(b) (0.385, 658/1706) were observed. Further, when compared to the Sl 1/McC(a) allele observed in all populations, the African Sl 2/McC(b) allele appears to have evolved as a result of positive selection (modified Nei-Gojobori test Ka-Ks/s.e.=1.77, P-valu
On the Hypersurface Orbital Varieties of sl(N,C)
No full textAbstractWe study the structure of hypersurface orbital varieties of sl(N,C) (those that are hypersurfaces in the nilradical of some parabolic subalgebra) and how information about this structure is encoded in the standard Young tableau associated to it by the Robinson–Schensted algorithm. We present a conjecture for the exact form of the unique non-linear defining equations of hypersurface orbital varieties and proofs of the conjecture in certain cases
Quantum and its irreducible representations
No full textWe define for real a unital -algebra
quantizing the universal enveloping
-algebra of . The -algebra
is realized as a -subalgebra of the
Drinfeld double of and its dual Hopf -algebra
, generated by the equatorial Podle\'s sphere coideal
-subalgebra of and
its associated orthogonal coideal -subalgebra . We then classify all the irreducible
-representations of .Comment: 22 pages; author accepted manuscrip
On the sheaf-theoretic SL(2, C) Casson–Lin invariant
No full textWe prove that the (τ-weighted, sheaf-theoretic) SL(2, C) Casson–Lin invariant introduced by Manolescu and the first author is generically independent of the parameter τ and additive under connected sums of knots in integral homology 3-spheres. This addresses two questions asked by Manolescu and the first author. Our arguments involve a mix of topology and algebraic geometry, and rely crucially on the fact that the SL(2, C) Casson–Lin invariant admits an alternative interpretation via the theory of Behrend functions.</p
A study of SL-resolution for automatic theorem-proving
No full textAutomatic theorem-proving by resolution was first proposed by J. A. Robinson in 1965. Since then, quite a number of restricted versions of resolution have been proposed all with the aim of providing more efficient proof procedures. In this paper, SL-resolution - linear resolution with selection function - recently proposed by Kowalski and Keuhner, is studied. A version of SL-resolution was implemented by means of a LISP program, and its efficiency tested on a number of examples. In the original paper, a long and tedious proof for the completeness of this inference system was given. A more elegant proof is given here, using the basic technique developed by Anderson and Bledsoe.Computer Science, Department o
Candidatus Rhetoricae (or Novus Candidatus).
No full textThis little book is a find whatever it finally turns out to be! For now it seems to be a Jesuit collegium text in rhetoric following the Progymnasmata of Aphthonius. If one works from the back of the book, there is an apparently independent 48-page work, Angelus Pacis by Nicolas Caussini (Latinized name), S.J. The rest of the book seems to be a commentary on or presentation of Aphthonius' Progymnasmata in 3 parts covering 435 pages, followed by a T of C and an AI, which is often one page off. Pars II is titled Rhetoricae Praecepta, Pars III De Panegyrico seu Laudatione. Pars I seems to be Apparatus ad Fabulam et Narrationem. Fable is handled on 15-31. After the famous Greek definition of Theion done into Latin ( sermo falsus veritatem effingens ), the author distinguishes rational (human) and moral (animal) fables, with mixed fables including both. He holds (19) that the sense of the fable generally needs to be expressed; otherwise people often miss the point of a fable. His Latin for promythium is praefabulatio, for epimythium affabulatio. Apologus and parabola are identical for him with fabula. After describing the qualities and uses of fables, the author presents some nine fables that exemplify various levels of style, twice telling the same stories on two levels (WL and FC). The last example is of the florid style: The Silkworm and the Spider takes four pages to tell! I found this book sitting in a box of disparate, unmarked, old books. It pays to look!This is a hardbound book (hard cover)Language note: Bilingual: Greek/LatinElzevers
Searches for New Physics effects in b →sl-sl+ transitions
No full textThe dissertation aims at presenting the current situation in the measurements of electroweak
penguin diagrams dominated decays: b → sl−l+1 . These decays have been a smoking gun
for hunting for New Physics effects over many years, but in the last three years the research
on these phenomena has intensified due to new measurements. Enormous progress has
been made both on the theoretical and the experimental sides to understand the measured
deviations from the current Standard Model predictions, referred to in what follows as
“anomalies”. The author of this dissertation has been one of the main authors of the angular analysis
of B0→ K∗ 0µ+µ− decay in the LHCb experiment, which has been widely regarded as one
of the most important results of the flavour physics sector in recent years. He has proposed
a method called “the method of moments” to measure the angular terms of this decay,
which he has later successfully applied in the measurement itself. Moreover, he has been
the driving force behind the two other important analyses in LHCb: the measurement of
the angular distribution and branching ratio of the B0→ K∗ 0 (1430)µ+µ− decay, where again the method of moments has been used to obtain the angular coefficients, and the search for the light scalar particle that can be produced in the b → s transitions and that decays to a dimuon pair. In this case no signal has been observed and the upper limits on the branching fraction have been set, later to be used for constraining the inflaton model.
The dissertation is organized as follows: the brief introduction is followed by, the second
chapter devoted to a theoretical description of rare B decays, where the effective field
theory formalism is introduced. Furthermore, the author discusses the current theoretical
problems in calculating the Standard Model predictions for the b → sl−l+ processes. Last but not least, the optimised angular observables that are less dependent on the form
factors uncertainness are derived. The third chapter describes the experimental apparatus
used in the b → sl−l+ measurements. Special focus is put on the sub-detectors that play
an important role in the studies of b → sl−l+ transitions. Chapters 4, 5, 6 are devoted to
describing the data analyses performed by the author in the LHCb experiment. In Chapter 7
the global analysis of electroweak penguin decays is presented. This kind of global analysis
has become extremely popular in the past few years as it helps to constrain and pin down those New Physics models that are likely to be responsible for the observed anomalies. The
author of this monograph is involved in one of the biggest collaborations performing New
Physics fits, where he is the convenor of the Flavour Working group. Furthermore, the
author presents his own study on separating the long distance effects in the B0→ K∗ 0µ+µ−decay. This is the state of the art way of determining those contributions. The chapter ends with a description of possible New Physics models that can explain the observed discrepancies
contravariant function-valued valuations on polytopes
No full textWe present a complete classification of contravariant,
-valued valuations on polytopes, without any
additional assumptions.It extends the previous results of the second author
[Int. Math. Res. Not. 2020] which have a good connection with the and
Orlicz Brunn-Minkowski theory. Additionally, our results deduce a complete
classification of contravariant symmetric-tensor-valued
valuations on polytopes
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