Point configurations that are asymmetric yet balanced

A configuration of particles confined to a sphere is balanced if it is in equilibrium under all force laws (that act between pairs of points with strength given by a fixed function of distance). It is straightforward to show that every sufficiently symmetrical configuration is balanced, but the converse is far from obvious. In 1957 Leech completely classified the balanced configurations in R^3, and his classification is equivalent to the converse for R^3. In this paper we disprove the converse in high dimensions. We construct several counterexamples, including one with trivial symmetry group.Comment: 10 page

Modeling Liquidity Risk With Implications for Traditional Market Risk Measurement and Management

Market risk management traditionally has focussed on the distribution of portfolio value changes resulting from moves in the midpoint of bid and ask prices. Hence the market risk is really in a “pure” form: risk in an idealized market with no “friction” in obtaining the fair price. However, many markets possess an additional liquidity component that arises from a trader not realizing the mid-price when liquidating her position, but rather the mid-price minus the bid-ask spread. We argue that liquidity risk associated with the uncertainty of the spread, particularly for thinly traded or emerging market securities under adverse market conditions, is an important part of overall risk and is therefore an important component to model. We develop a simple liquidity risk methodology that can be easily and seamlessly integrated into standard value-at-risk models, and we show that ignoring the liquidity effect can produce underestimates of market risk in emerging markets by as much as 25-30%. Furthermore, we show that the BIS inadvertently is already monitoring liquidity risk, and that by not modeling it explicitly and therefore capitalizing against it, banks will be experiencing surprisingly many violations of capital requirements, particularly if their portfolios are concentrated in emerging markets

Radiochemical separation of 7Be from the cooling water of the neutron spallation source SINQ at PSI

7Be is a key radionuclide for investigation of several astrophysical processes and phenomena. In addition, it is used as a tracer in wear measurements. It is produced in considerable amounts in the cooling water (D2O) of the Spallation Induced Neutron Source (SINQ) facility at PSI by spallation reactions on 16O with the generated fast neutrons. A shielded ion-exchange filter containing 100 mL of the mixed-bed ion exchanger LEWATIT was installed as a bypass for the cooling water into the cooling loop of SINQ for three months. The collected activity of 7Be was in the range of several hundred GBq. Further, the 7Be was separated and purified in a hot-cell remotely-controlled using a separation system installed. With the exception of 10Be, radioactive byproducts can be neglected, so that this cooling water could serve as an ideal source for highly active 7Be-samples. The facility is capable of producing 7Be with activities up to 1 TBq per year. The 7Be sample preparation is described in detail and the possible uses are discussed. In particular some preliminary results of 7Be ion beam production are presente

Pitfalls and Opportunities in the Use of Extreme Value Theory in Risk Management

Recent literature has trumpeted the claim that extreme value theory (EVT) holds promise for accurate estimation of extreme quantiles and tail probabilities of financial asset returns, and hence hold promise for advances in the management of extreme financial risks. Our view, based on a disinterested assessment of EVT from the vantage point of financial risk management, is that the recent optimism is partly appropriate but also partly exaggerated, and that at any rate much of the potential of EVT remains latent. We substantiate this claim by sketching a number of pitfalls associate with use of EVT techniques. More constructively, we show how certain of the pitfalls can be avoided, and we sketch a number of explicit research directions that will help the potential of EVT to be realized

Generation Of Machined Multiple Flat Surfaces On Circular Bar By Its Rotation And In Synchronism With Cutting Tool

The operation of machining by lathe is one of the most common operations in automobile and machinery industries. The process is able to generate cylindrical bars under a wider variety of diameters/staggerings and using different materials, metallic's or non-metallic's (cupper, wood, aluminum, brass, steel, etc.). However, when more complex geometries are required, additional machines are used, like milling machine and/or machines under numerical control (CNC) and multiple axles. The possibility of joining circles, polygons, angular motion and synchronism, open the mind to multiple figures (shapes) and movements, which can generate different geometries. This paper aims to demonstrate that both operations (turning and milling), can be made at the same time and at the same machine, special but simpler lathe. The studies of geometry, associated with calculus (trigonometry) and angular motion give basis and sustain this statement. Tests in bench materialize the idea and reinforce this thesis.82146155Martin, J.T., Jonathan, M.B., Patrick, R.A., (1998) Fractal Geometry In Digital Imaging, p. 1. , Academic PressLandrini, M., Colagrossi, A., Greco, M., Tulin, M.P., (2012) The Fluid Mechanics of Splashing Bow Waves On Ships: A Hybrid BEM-SPH Analysis, 53, pp. 111-127. , Ocean EngineeringKline, (1972) Mathematical Thought From Ancient to Modern Times, p. 1032. , Oxford University PressFigueiredo, D.G., (2009) Análise De Fourier E Equações Diferenciais, p. 274. , Editora Projeto Euclides, in PortugueseIório, V.M., (2010) EDP: Um Curso De Graduação, p. 275. , Editora Coleção Matemática Universitária, in portugueseIório Jr., R., Iório, V.M., (2010), p. 343. , Equações Diferenciais Parciais: Uma Introdução, Editora Projeto Euclides, in PortugueseKnobloch, E., (2011) Kaspar Schott's "encyclopedia of All Mathematical Sciences", 7, pp. 225-247. , Poiesis Prax(1998) Trigonometric Delights, , by Eli Maor, Princeton University Press, Ebook version, in PDF format, full text presented(1914) Trigonometry, , by Alfred Monroe Kenyon and Louis Ingold, The Macmillan Company, In images, full text presentedhttp://www.mfg.mtu.edu/cyberman/machining.html, The John W Sutherland Research PageLiang, S.Y., Junz Wang, J.J., (1994), pp. 1177-1190. , Milling force convolution modeling for identification of cutter axis offset, International Journal of Machine Tools and ManufactureMartelloti, M.E., An analysis of the milling process (1941) Transactions of the ASME, 63, pp. 677-700Martellotti, M.E., An analysis of the milling process, Part II-Down milling (1945) Transactions of the ASME, 67, pp. 233-251Ber, A., Feldman, D., (1974) A Mathematical Model of the Radial and Axial Throw of Square Indexable Inserts In a Face Milling Cutter, pp. 19-23. , Annals of CIRP: Manufacturing TechnologyKline, W.A., Devor, R.E., The effect of runout on cutting geometry and forces in end milling (1983) International Journal of Machine Tool Design and Research, pp. 123-140Fu, H.J., Devor, R.E., Kapoor, S.G., A mechanistic model for the prediction of force system in face milling operations (1984) Transactions of the ASME: Journal of Engineering For Industry, pp. 81-88Desai, K.A., Piyush, K.A., Rao, P.V.M., Process geometry modeling with cutter runout for milling of curved surfaces (2009) International Journal of Machine Tools & Manufacture, pp. 1015-1028Boothroyd, G., Knight, W.A., (2006) Fundamentals of Machining and Machine Tools, , CRC Press, Boca Rato

First direct measurement of the total cross section of 12C(alpha,gamma)16O

The total cross section of 12C(alpha,gamma)16O was measured for the first time by a direct and ungated detection of the 16O recoils. This measurement in inverse kinematics using the recoil mass separator ERNA in combination with a windowless He gas target allowed to collect data with high precision in the energy range E=1.9 to 4.9 MeV. The data represent new information for the determination of the astrophysical S(E) factor.Comment: 5 pages, 3 figures, 1 table, accepted for publication Eur.Phys.J. A (Online first available

The Evolution of a High Copy Gene Array in Arabidopsis

Local gene duplication is a prominent mechanism of gene copy number expansion. Elucidating the mechanisms by which local duplicates arise is necessary in understanding the evolution of genomes and their host organisms. Chromosome one of Arabidopsis thaliana contains an 81-gene array subdivided into 27 triplet units (t-units), with each t-unit containing three pre-transfer RNA genes. We utilized phylogenetic tree reconstructions and comparative genomics to order the events leading to the array’s formation, and propose a model using unequal crossing-over as the primary mechanism of array formation. The model is supported by additional phylogenetic information from intergenic spacer sequences separating each t-unit, comparative analysis to an orthologous array of 12 t-units in the sister taxa Arabidopsis lyrata, and additional modeling using a stochastic simulation of orthologous array divergence. Lastly, comparative phylogenetic analysis demonstrates that the two orthologous t-unit arrays undergo concerted evolution within each taxa and are likely fluctuating in copy number under neutral evolutionary drift. These findings hold larger implications for future research concerning gene and genome evolution

The arabidopsis DNA polymerase δ has a role in the deposition of transcriptionally active epigenetic marks, development and flowering

DNA replication is a key process in living organisms. DNA polymerase α (Polα) initiates strand synthesis, which is performed by Polε and Polδ in leading and lagging strands, respectively. Whereas loss of DNA polymerase activity is incompatible with life, viable mutants of Polα and Polε were isolated, allowing the identification of their functions beyond DNA replication. In contrast, no viable mutants in the Polδ polymerase-domain were reported in multicellular organisms. Here we identify such a mutant which is also thermosensitive. Mutant plants were unable to complete development at 28°C, looked normal at 18°C, but displayed increased expression of DNA replication-stress marker genes, homologous recombination and lysine 4 histone 3 trimethylation at the SEPALLATA3 (SEP3) locus at 24°C, which correlated with ectopic expression of SEP3. Surprisingly, high expression of SEP3 in vascular tissue promoted FLOWERING LOCUS T (FT) expression, forming a positive feedback loop with SEP3 and leading to early flowering and curly leaves phenotypes. These results strongly suggest that the DNA polymerase δ is required for the proper establishment of transcriptionally active epigenetic marks and that its failure might affect development by affecting the epigenetic control of master genes.Fil: Iglesias, Francisco Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; ArgentinaFil: Bruera, Natalia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; ArgentinaFil: Dergan Dylon, Leonardo Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; ArgentinaFil: Marino, Cristina Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; ArgentinaFil: Lorenzi, Hernán. J. Craig Venter Institute; Estados UnidosFil: Mateos, Julieta Lisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; Argentina. Max Planck Institute for Plant Breeding Research; AlemaniaFil: Turck, Franziska. Max Planck Institute for Plant Breeding Research; AlemaniaFil: Coupland, George. Max Planck Institute for Plant Breeding Research; AlemaniaFil: Cerdan, Pablo Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; Argentina. Fundación Instituto Leloir; Argentina. Universidad de Buenos Aires. Departamento de Ciencias Exactas; Argentin