Comparison morphisms and the Hochschild cohomology ring of truncated quiver algebras

A main contribution of this paper is the explicit construction of comparison morphisms between the standard bar resolution and Bardzell's minimal resolution for truncated quiver algebras (TQA's). As a direct application we describe explicitely the Yoneda product and derive several results on the structure of the cohomology ring of TQA's. For instance, we show that the product of odd degree cohomology classes is always zero. We prove that TQA's associated with quivers with no cycles or with neither sinks nor sources have trivial cohomology rings. On the other side we exhibit a fundamental example of a TQA with non trivial cohomology ring. Finaly, for truncated polyniomial algebras in one variable, we construct explicit cohomology classes in the bar resolution and give a full description of their cohomology ring.Comment: 32 pages, Final Versio

Spherical Functions Associated With the Three Dimensional Sphere

In this paper, we determine all irreducible spherical functions \Phi of any K -type associated to the pair (G,K)=(\SO(4),\SO(3)). This is accomplished by associating to \Phi a vector valued function H=H(u) of a real variable u, which is analytic at u=0 and whose components are solutions of two coupled systems of ordinary differential equations. By an appropriate conjugation involving Hahn polynomials we uncouple one of the systems. Then this is taken to an uncoupled system of hypergeometric equations, leading to a vector valued solution P=P(u) whose entries are Gegenbauer's polynomials. Afterward, we identify those simultaneous solutions and use the representation theory of \SO(4) to characterize all irreducible spherical functions. The functions P=P(u) corresponding to the irreducible spherical functions of a fixed K-type \pi_\ell are appropriately packaged into a sequence of matrix valued polynomials (P_w)_{w\ge0} of size (\ell+1)\times(\ell+1). Finally we proved that \widetilde P_w={P_0}^{-1}P_w is a sequence of matrix orthogonal polynomials with respect to a weight matrix W. Moreover we showed that W admits a second order symmetric hypergeometric operator \widetilde D and a first order symmetric differential operator \widetilde E.Comment: 49 pages, 2 figure

Plasmon excitation in beryllium: inelastic x-ray scattering experiments and first-principles calculations

An experimental and theoretical study of collective electronic excitations in Be is presented. The plasmon energy and linewidth were measured by means of inelastic x-ray scattering spectroscopy. Measurements were performed on a polycrystalline sample and in a broad range of momentum transfers within the plasmon excitation regime. Theoretical plasmon dispersion and its linewidth in the whole Brillouin zone were derived from ab initio evaluations of the electron density response function. The calculations were performed with full inclusion of the electron band structure within the random-phase approximation. Good agreement of experimental plasmon energy and linewidth dispersions with direction-averaged theoretical results in all investigated q-range is obtained. We conclude that, in Be, the band structure effects alone can account for the observed finite plasmon lifetime at q = 0, as well as for the linewidth dispersion in the long-wavelength domain.The research was partially supported by LNLS (National Synchrotron Light Laboratory). Financial support from SeCyT (Universidad Nacional de Cordoba) and PRONEX/CNPq is gratefully acknowledged. VMS and EVC acknowledge partial support from the University of the Basque Country, the Departamento de Educacion del Gobierno Vasco, and the Spanish Ministerio de Ciencia y Tecnologia (MCyT) (grant no. FIS 2004-06490-C03-01), and the European Community 6th Network of Excellence NANOQUANTA (NMP4-CT-2004-500198).Peer reviewe

Synthesis of new double perovskites La 1.98 Mn 1.11 Mo 0.89 O 5.93 and La 1.92 Mn 1.29 Mo 0.71 O 5.84 : Characterization of structural and magnetic properties

International audienc

Diffraction Enhanced Imaging And X-ray Fluorescence Microtomography For Analyzing Biological Samples

In this work, breast tissue samples were investigated in order to verify the distribution of certain elements by x-ray fluorescence computed tomography (XRFCT) correlated with the characteristics and pathology of each tissue observed by diffraction enhanced imaging (DEI). The DEI system can show details in low attenuation tissues. It is based on the contrast imaging obtained by extinction, diffraction and refraction characteristics and can improve reduction in false positive and false negative diagnoses. XRFCT allows mapping of all elements within the sample, since even a minute fluorescence signal can be detected. DEI imaging techniques revealed the complex structure of the disease, confirmed by the histological section, and showed microstructures in all planes of the sample. The XRFCT showed the distribution of Zn, Cu and Fe at higher concentration. Copyright © 2007 John Wiley & Sons, Ltd.364247253Allonzi, A.M., Noia, A.L.C., Martins, L.F.L., Thuler, L.C.S., Santos, M.O., Alvez, M.R.D., Rebelo, M.S., Figueiredo, V., (2002) Atlas de Mortalidade por câncer no Brasil 1979-1999, p. 412. , INCA: Rio de Janeiro, In PortugeseFitzgerald, R., (2000) Phys. Today, 53, p. 23Pisano, D., Johnston, E., Chapman, D., Geradts, J., Lacocca, M.V., Livasy, C.A., Washburn, D.B., Thomlinson, W., (2000) Radiology, 214, p. 895Bushuev, V.A., Ingal, V.N., Beliaevskaya, E.A., (1998) Crystallogr. Rep, 43, p. 538Momose, A., (1995) Nucl. Instrum. Methods Phys, , A 352: 622Wilkins, S.W., Gureyev, T.E., Gao, D., Pogany, A., Stevenson, A.W., (1996) Nature, 384, p. 335Wu, X., Liu, H., (2004) Med. Phys, 31, p. 997Bravin, A., (2003) J. Phys. D: Appl. Phys, 36, pp. A24Chapman, D., Thomlinson, W., Arfelli, F., (1995) Rev. Sci. Instrum, p. 67. , CD Suppl, doi:10.1063/1.1147502Chapman, D., Thomlinson, W., Johnston, R., (1997) Phys. Med. Biol, 42, p. 2015Geraki, K., Farquharson, M.J., Bradley, D.A., (2004) Phys. Med. Biol, 49, p. 1Wu, T., Sempos, C.T., Freudenheim, J.L., (2004) Ann. Epidemiol, 14 (3), p. 195Hasnah, M., Oltulu, O., Zhong, Z., Chapman, D., (2002) Rev. Sci. Instrum, 73, p. 1657. , doi: 10.1063/1.1445831Lagomarsino, S., Cedola, A., X-ray microscopy and nanodiffraction (2004) Encyclopedia of Nanoscience and Nanotechnology, 10, p. 681. , American Scientific Publishers: Stevenson Ranch, CA, USAIngal, V.N., Beliaevskaya, E.A., (1995) J. Phys. D: Appl. Phys, 28, p. 2314Davis, T.J., Gao, D., Gureyev, T.E., Stevenson, A.W., Wilkins, S.W., (1995) Nature, 373, p. 595Menk, R.H., Rigon, L., Arfelli, F., (2005) Nucl. Instrum. Methods Phys. Res. A, 548, p. 213Khelashvili, G., Brankov, J.G., Chapman, D., Anastasio, M.A., Yang, Y., Zhong, O.Z., Wernick, M.N., (2006) Phys. Med. Biol, 51, p. 221. , doi:10.1088/0031-9155/ 51/2/003Wernick, M.N., Wirjadi, O., Chapman, D., Zhong, O.Z., Galatsanos, N., Yang, Y., Brankov, J.G., Muehleman, C., (2003) Phys. Med. Biol, 48, p. 3875. , doi:10.1088/0031-9155/48/23/006Dilmanian, F., Zhong, Z., Ren, B., Wu, X., Chapman, L., Orion, I., Thomlinson, W., (2000) Phys. Med Biol, 45, p. 933. , doi:10.1088/0031-9155/45/4/309Zhong Z, Thomlinson W, Chapman D, Sayers D. Nucl. Instrum. Methods Phys. Res. A. 2000A 450: 556 [doi:10.1016/S0168-9002(00)00308-9]Rigon L, Besch H, Arfelli F, et al. J. Phys. D: Appl. Phys. 200336: A107 [doi:10.1088/0022-3727/36/10A/322]Giles, C., Hönnicke, M.G., Lopes, R.T., Rocha, H.S., Gonçalves, O.D., Mazzaro, I., Cusatis, C., (2003) J. Synchrotron Radiat, 10, p. 421Rocha, H.S., Lopes, R.T., Valiante, P.M., Tirao, G., (2005) Nucl. Instrum. Methods Phys. Res. A, 548, p. 175. , doi:10.1016/j.nima.2005.03.086Hönnicke, M., Foerster, L.A., Navarro-Silva, M.A., Menk, R.H., (2005) Nucl. Instrum. Methods Phys. Res. A, 548. , 207 [doi:10.1016/j.nima, 03.091Rocha, H.S., Lopes, R.T., Pessôa, L.M., Hönnicke, M.G., (2005) Nucl. Instrum. Methods Phys. Res. A, 548. , 228 [doi:10.1016/j.nima, 03.094Connor, D.M., Sayers, D., Sumner, D.R., Zhong, Z., (2005) Nucl. Instrum. Methods Phys. Res. A, 548, p. 234Farquarson, M.J., Geraki, K., (2004) X-Ray Spectrom, 33, p. 240. , doi: 10.1002/xrs.684Chwiej, J., Sczerbowska-Boruchowska, M., Lankosz, M., (2005) Spectrochim. Acta, Part B, 60, p. 1531Braz, D., Motta, L.M.G., Lopes, R.T., (1999) Appl. Radiat, Isot, 50, p. 661Lopes, R.T., Rocha, H.S., Jesus, E.F.O., Barroso, R.C., (2003) Nucl. Instrum. Methods Phys. Res. A, , A 505: 604 [doi:10.1016/S0168-9002(03) 01157-4Cesareo, R., Mascarenhas, S., (1989) Nucl. Instrum. Methods, , A 277: 669 [doi:10.1016/0168-9002(89)90802-4Naghedolfeizi, M., Chung, J.-S., Morris, R., Ice, G.E., Yun, W.B., Cai, Z., Lai, B., (2003) J. Nucl. Mater, 312, p. 146Hogan, J.P., Gonsalves, R.A., Krieger, A.S., (1991) IEEE Trans. Nucl. Sci, 38, p. 172

Diffraction-enhanced Imaging Microradiography Applied In Breast Samples

The diffraction-enhanced imaging (DEI) is a powerful tool to observe tumors and other diseases in breast tissue and provide more precise diagnostics. In this work DEI was used to analyze breast tissues details that have poor attenuation contrast. An X-ray imaging system with DEI techniques was developed using synchrotron radiation. The DEI experiment was performed in D10A-XRD2 beamline at the Brazilian Synchrotron-LNLS. The pre-monochromator, upstream of the beamline was adjusted to 10.7 keV. The samples were positioned between two channel-cut Si(3 3 3) in non-dispersive geometry mounted in a double axes diffractometer. A direct conversion water-cooled CCD camera of 1242 pixel × 1152 pixel of 25 μm × 25 μm each was used as a two-dimensional detector in scanning mode. The DEI system could show details in low attenuation tissues based on the contrast imaging obtained by attenuation, refraction gradient and ultra-small angle scatter characteristics. In this work the capacity to observe different types of structures and details in breast tissues were investigated. © 2008 Elsevier Ireland Ltd. All rights reserved.683 SUPPL.3740Chapman, D., Thomlinson, W., Johnston, R., Diffraction enhanced X-ray imaging (1997) Phys Med Biol, 42, pp. 2015-2025Hasnah, M., Oltulu, O., Zhong, Z., Chapman, D., Application of absorption and refraction matching techniques for diffraction enhanced imaging (2002) Rev Sci Instrum, 73, pp. 1657-1659Lagomarsino, S., Cedola, A., X-ray microscopy and nanodiffraction (2004) Encyclopedia Nanosci Nanotechnol, 10, pp. 681-710Ingal, V.N., Beliaevskaya, E.A., X-ray plane-wave topography observation of the phase contrast from a non-crystalline object (1995) J Phys D: Appl Phys, 28, pp. 2314-2317Davis, T.J., Gao, D., Gureyev, T.E., Stevenson, A.W., Wilkins, S.W., X-ray image contrast from a simple phase object (1995) Nature, 373, pp. 595-598Menk, R.H., Rigon, L., Arfelli, F., Diffraction-enhanced X-ray medical imaging at the ELETTRA synchrotron light source (2005) Nucl Instrum Methods Phys Res A, 548, pp. 213-220Dilmanian, F.A., Zhong, Z., Ren, B., Computed tomography of x-ray index of refraction using the diffraction enhanced imaging method (2000) Phys Med Biol, 45, pp. 933-946Zhong, Z., Thomlinson, W., Chapman, D., Sayers, D., Implementation of diffraction-enhanced experiments: at the NSLS and APS (2000) Nucl Instrum Methods Phys Res A, 450, pp. 556-567Rigon, L., Besch, H., Arfelli, F., A new DEI algorithm capable of investigating sub-pixel structures (2003) J Phys D: Appl Phys, 36, pp. A107-A112Giles, C., Hönnicke, M.G., Lopes, R.T., First experiments on diffraction-enhanced imaging at LNLS (2003) J Synchrotron Radiat, 10, pp. 421-423Rocha, H.S., Lopes, R.T., Valiante, P.M., Diagnosis of thyroid multinodular goiter using diffraction-enhanced imaging (2005) Nucl Instrum Methods Phys Res A, 548, pp. 175-180Rocha, H.S., Lopes, R.T., Pessôa, L.M., Diffraction-Enhanced Imaging for studying pattern recognition in cranial ontogeny of bats and marsupials (2005) Nucl Instrum Methods Phys Res A, 548, pp. 228-23

Inelastic X-ray scattering and first-principles study of electron excitations in MgB2

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)An experimental and theoretical study of electronic excitations in MgB2 covering the domain of large energy and momentum transfers is reported. Energy-loss spectra for several values of momentum transfers were measured in a polycrystalline sample by means of inelastic X-ray scattering spectroscopy. Ab initio calculations of the dielectric function as well as the energy-loss function were performed in the frame of the time-dependent local density approximation with inclusion of crystal local-field effects. We obtained very good agreement between the experimental and the theoretical energy dispersion of the peak maximum of the loss function. We found that crystal local-field effects are responsible for this agreement at large momenta. Fine structure observed in the measured spectra was interpreted in terms of strong interband transitions predicted by the calculations in the Gamma A and Gamma K directions. The theoretical dispersion of these features is in good accordance with the experimental data. Further spectral features in the measured spectra due to Mg 2s and 2p core electron excitations are also discussed. (c) 2009 Elsevier Ltd. All rights reserved.14939-4017061711SeCyT (Universidad Nacional de Cordoba, Argentina)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)University of the Basque Country [GIC07IT36607]Departamento de Educacion del Gobierno VascoSpanish Ministerio de Ciencia y Technologia (MCyT) [FIS200766711C0101]IKERBASQUE FoundationLNLS-Brazilian Synchrotron Light Laboratory/MCTFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)University of the Basque Country [GIC07IT36607]Spanish Ministerio de Ciencia y Technologia (MCyT) [FIS200766711C0101

Diagnosis Of Thyroid Multinodular Goiter Using Diffraction-enhanced Imaging

Diffraction-enhanced images (DEI) have been obtained using two silicon crystals. A first channel-cut silicon crystal using the Si(3 3 3) reflection is employed to reduce the divergence of the pre-monochromated Si(1 1 1) beam of the light line to 60 microradian (12 arcsec). A second channel-cut Si(3 3 3) crystal was used as a Bragg analyzer to obtain bright and dark field images by changing its angular position. This technique is ideally suited for soft-tissue imaging or objects with the same absorption coefficient interfaces. DEI was developed at the XRD-2 beamline at the Brazilian Synchrotron (LNLS) in Campinas - Brazil. Feasibility tests on acquired images, which allow the diagnosis of thyroid nodular goiter, were performed. This disease is ordinary. The tissue developed on the cervical area causes compression of the nearby structures and undesirable aesthetic deformities with worldwide distribution. DEI of the tissues were taken to observe their morphology and to compare with the microscopic analysis (histopathological). This technique allows cutting sections a hundred times thicker than conventional histological techniques allowing a complete vision of the disease morphology. DEI show details not clearly seen with conventional techniques. © 2005 Elsevier B.V. All rights reserved.5481-2175180Ramelli, F., (1982) Am. J. Pathol., 109, p. 215Cotran, R.S., (1999) Robbins Pathologic Basis of Disease, , W.B. Saunders Company BostonGureyev, T.E., Mayo, S., (2001) Phys. Rev. Lett., 86, p. 5827Momose, A., Takeda, T., (1998) Synchrotron Radiat. News, 11 (5), p. 27Zhong, Z., Thomlinson, W., (2000) Nucl. Instr. and Meth. A, 450, p. 556Giles, C., Hönnicke, M.G., (2003) J. Synchrotron Radiat., 10, p. 421Wilkins, S.W., Gureyev, T.E., (1996) Nature, 384, p. 335Gureyev, T.E., Mayo, S., (2001) Phys. Rev. Lett., 86, p. 5827Ingal, V.N., Beliaevskaya, E.A., (1997) Nuovo Cimento, 19, p. 553Li, J., (2003) J. Anat., 202, p. 463Takeda, T., Itai, Y., (1998) J. Synchrotron Radiat., 5, p. 326Mori, K., Hyodo, K., (1999) J. Appl. Phys., 38 (11), pp. L1339Kotre, C.J., Birch, I.P., (1999) Phys. Med. Biol., 44, p. 2853Hasnah, M., (2002) Rev. Sci. Instrum., 73, p. 165