4,854 research outputs found
Recommended from our members
Stereolithography Epoxy Resins SL 5170 and SL 5180: Accuracy, Dimensional Stability, and Mechanical Properties
No full textStereolithography (SL) resins based on epoxy chemistry provide significantly improved overall
part accuracy, dimensional stability, and mechanical properties relative to the earlier acrylate SL resins.
In July, 1993, epoxy-based SL 5170 resin was introduced for use on the SLA-250 system. In March,
1994, the epoxy-based resin for the SLA-500 system, SL 5180, was also released. These epoxy resins
have minima11aser-cure and post-cure shrinkage, resulting in extremely low curl and distortion. Overall
dimensional accuracy has also improved. Standard User-Parts built in SL 5170 on the SLA-250, and
now, SL 5180 on the SLA-500, have recently achieved the highest level of dimensional accuracy from a
statistically significant number of measurements taken in the x, y, and z directions. Diagnostic test results
presented in this paper show that these epoxy-based resins are now capable of producing extremely flat
parts when required. SL parts built in these resins also exhibit superb dimensional stability in the lasercured
state, as demonstrated by the "Green" Creep Distortion diagnostic test. Dimensional stability in the
laser-cured state is critical, especially for SL parts having the characteristic quasi-hollow internal
structure, generated using the QuickCast™ build style. Creep results are presented in this paper.
Furthermore, the overall mechanical properties of these epoxy resins were measured according to the
ASTM standards for plastics. Tensile, flexural, and impact properties for the epoxy-based and acrylatebased
SL resins are presented in this paper. Mechanical properties ofthermoplastics, acrylic plastic
(PMMA) and medium impact polystyrene, are also presented for comparison. The data shows that the
mechanical properties of epoxy-based SL 5170 and SL 5180 are comparable to, or exceed those of acrylic
plastic and medium impact polystyrene.
For applications that require greater mechanical strengths than SL 5170 and SL 5180, metal
parts can be obtained using QuickCast. QuickCast, made possible with the development of these epoxybased
SL resins, is the key to successfully utilizing SL parts for shell investment casting applications, and
the generation of precision metal components directly from SL parts. Furthermore, when a "negative"
core and cavity pair of a part geometry is produced in metal using QuickCast, tooling is obtained.
Prototype, and eventually, production functional parts may then be ultimately injection molded in the
QuickCast tooling, using the desired engineering thermoplastic material.Mechanical Engineerin
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
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
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
The Laurent Extension of Quantum Plane: a Complete List of Uq(sl₂)-Symmetries
No full textThis work finishes a classification of Uq(sl₂)-symmetries on the Laurent extension Cq[x±¹,y±¹] of the quantum plane. After reproducing the partial results of a previous paper of the author related to symmetries with non-trivial action of the Cartan generator(s) of Uq(sl₂) and the generic symmetries, a complete collection of non-generic symmetries is presented. Together, these collections constitute a complete list of Uq(sl₂)-symmetries on Cq[x±¹,y±¹].The author would like to thank the anonymous referees for a large number of comments and suggestions that substantially improved the initial version of this paper
Dinuclear niobium(III), tantalum(III) and tantalum(IV) complexes with thioether and selenoether ligands
No full textMagnesium reduction of MCl5 (M = Nb or Ta) in the presence of R2S (R = Me or nBu) affords the complexes [M2Cl4(R2S)2(μ-Cl)2(μ-R2S)]. The X-ray structures of those complexes where M = Nb or Ta, R = nBu2S, and of a new polymorph of [Ta2Cl4(Me2S)2(μ-Cl)2(μ-Me2S)], show that they have confacial bi-octahedral structures with M=M double bonds. The reactions of [Nb2Cl4(R2S)2(μ-Cl)2(μ-R2S)] with MeSCH2CH2SMe, MeSeCH2CH2SeMe or MeSeCH2CH2CH2SeMe produce the edge-linked dimers [Nb2Cl4(MeSCH2CH2SMe)2(μ-Cl)2] and [Nb2Cl4{MeSe(CH2)nSeMe}2(μ-Cl)2], all with M=M double bonds (M26+). The tantalum diselenoether complex, [Ta2Cl4(MeSeCH2CH2SeMe)2(μ-Cl)2], is similar. Two “dimer of dimers”, [{Nb2Cl4(μ-Cl)2(μ-Me2S)}2(μ-MeSeCH2CH2CH2SeMe)2] and [{Ta2Cl4(μ-Cl)2(μ-Me2S)}2(μ-nBuSeCH2CH2CH2SenBu)2], containing confacial bi-octahedra linked by diselenoether bridges, were obtained as minor by-products and were identified via their X-ray crystal structures. The xylyl-linked diselenoether, o-C6H4(CH2SeMe)2, gave a complex mixture of products, including [Ta2Cl4{o-C6H4(CH2SeMe)2}2(μ-Se)2]. The complexes were characterised by microanalysis, IR and UV–visible spectroscopy. X-ray crystal structures are reported for [Nb2Cl6(nBu2S)3], [Ta2Cl6(nBu2S)3], [Ta2Cl8(Me2S)2], [Ta2Cl6(Me2S)3], [Ta2Cl4{o-C6H4(CH2SeMe)2}2(Se)2], [{Ta2Cl6(Me2S)(nBuSeCH2CH2CH2SenBu)}2] and [Ta2Cl4(Me2S)4(S)2]
Constructing Thin Subgroups in SL(4, R)
No full textWe give a construction for new families of thin subgroups inside SL(4,R). In particular, we show that the fundamental group of a closed hyperbolic 3-manifold can be isomorphic to a thin subgroup of a lattice. © The Author(s) 2013
- …
