Agustin Anabitarteren "Einstein'en ustariak" (1923)

Ildo bitan joan da artikulu honen ekarpena. Batetik, Agustin Anabitarteren idazlan ahaztu bat berrargitaratu dugu, eta bai nabarmendu ere edukiak dituen ezaugarri nagusiak. Bestetik, gure prosa zientifikoaren aitzindarien zerrenda laburrean sartu dugu Agustin Anabitarte

Geologia 1-Fisika 0: Lur Planetaren adina

In this article I will try to show that XX. century, and especially the dominance of physics in the first half of the twentieth century, did not reach all areas. In fact, as the title suggests, Geology scored a great goal for the physicist at that time. However, as will be explained in a second article (Geology 1- Physics 1), in the last quarter of the twentieth century, when the success or efficiency of physics was not so great, physics managed to tie the game.So this article will be followed by another article entitled “Geology 1-Physics 1”.; En este artículo trataré de demostrar que el dominio de la física del siglo XX, y especialmente de la primera mitad del siglo, no llegó a todos los ámbitos. Y es que, como dice el título, Geología marcó un gran gol al físico en esa época. Sin embargo, y como se explicará en un segundo artículo ("geología 1- Física 1"), en el cuarto cuarto del siglo XX, cuando el éxito o la eficacia de la física no era tan grande, la física logró igualar la partida.Por tanto, a este artículo le seguirá otro titulado "geología 1-Física 1"; Artikulu honetan saiatuko naiz erakusten xx. mendeko, eta bereziki mendearen lehen erdiko, fisikaren nagusitasuna ez zela arlo guztietara heldu. Izan ere, izenburuak dioen bezala, Geologiak gol galanta sartu zion fisikari garai hartan. Hala ere, eta bigarren artikulu batean azalduko denez ("Geologia 1-Fisika 1" artikuluan hain zuzen), xx. mendearen laugarren laurdenean, fisikaren arrakasta edo eraginkortasuna hain handia ez zenean, fisikak partida berdintzea lortu zuen.Beraz, artikulu honi, "Geologia 1-Fisika 1" izenburua duen beste artikulu batek jarraituko dio

Geologia 1-Fisika 1: duela 65 milioi urte Lurraren aurkako meteorito baten inpaktuaren afera

This article is a continuation of the article "Geologia 1-Fisika 0", where I showed that the mastery of physics in the 20th century, and especially in the first half of the century, did not reach all areas, and in the knowledge of the age of the Earth Geology scored a great goal against physics. In this second article I will explain that in the fourth quarter of the 20th century, when the success of physics was not so great, physics tied the game, especially at the hands of. the winner of the 1968 Nobel Prize in Physics, Luis Walter Alvarez. It was largely he who proposed the theory of the impact of a meteorite on Earth about 65 million years ago. The last mass extinction occurred 65 million years ago and is used to establish the boundary between the Cretaceous and the Tertiary. This article deals with the excitement, unrest, and rich interdisciplinary scientific debate that aroused in the scientific community after the publication in 1980 in the journal Science of the aforementioned hypothesis as the cause of the last mass extinction. The article will also allow us to highlight what I call the "migrant effect" that often occurs in the world of scientific research, show the different ways of dealing with problems, the importance of people with wide curiosity, the different jealousies that can occur in different scientific communities, the “subjectivities” that may occur in the peer review process, as well as the uneasiness and reactions of experts in the field of research to a revolutionary hypothesis, if it is made by scientists outside the field.; Artikulu hau "Geologia 1-Fisika 0" artikuluaren jarraipena da, non xx. mendeko, eta bereziki mendearen lehen erdiko fisikaren nagusitasuna, ez zela arlo guztietara heldu erakutsi zen. Izan ere, Lurraren adinaren ezagutzan Geologiak gol galanta sartu zion Fisikari. Bigarren artikulu honetan, berriz, azalduko dut, xx. mendearen laugarren laurdenean, Fisikaren arrakasta hain handia ez zenean Fisikak partidua berdintzea lortu zuela, 1968ko Fisikako Nobel Saria jaso zuen Luis Walter Alvarezen eskutik bereziki. Hein handi batean bera izan baitzen Lurrak meteorito baten inpaktua duela 65 milioi urte jaso zuela proposatu zuena. Azken iraungipen/suntsipen masiboak adin hori du eta adin hori erabiltzen da Kretazeoaren eta Paleogenoaren arteko muga ezartzeko. Hipotesi hori azken suntsipen masiboaren kausa bezala 1980. urtean Science aldizkarian argitaratu ostean komunitate zientifikoan sortu zuen zirraraz, egonezinaz eta diziplina arteko eztabaida zientifiko aberatsaz arituko da artikulua. Artikuluak bide emango digu, baita ere, ikerketa zientifikoaren munduan maiz gertatzen den "migrantearen efektua" deitu dudana azaleratzeko, arazoei aurre egiteko bide desberdinak erakusteko, kuriositate zabaleko pertsonen garrantzia, komunitate zientifiko desberdinetan, eta baita bakoitzean ere, gerta daitezkeen jeloskeriak, parekideen berrikuspena prozesuan gerta daitezkeen "subjektibotasunak" eta, halaber, ikerketa arloaren adituen ezinegona eta erreakzioak hipotesi iraultzaile baten aurrean, hipotesia eremutik kanpoko zientzialariek egina bada

Fluorinated mixed valence Fe(ii)-Fe(iii) phosphites with channels templated by linear tetramine chains. Structural and magnetic implications of partial replacement of Fe(ii) by Co(ii)

Three new fluorinated mixed valence Fe(ii)-Fe(iii) phosphites were synthesized by employing mild hydrothermal conditions. (H4baepn) 0.5[FeIII 2.3FeII 1.7(H2O)2(HPO3) 4-(x+y)(HPO4)x(PO4) yF4] (x ≃ 0.13, y ≃ 0.3) (1) (baepn = N,N′-bis(2-aminoethyl)-1,3-propanediamine (C7N 4H20)) and the Co(ii)-substituted phase with the formula (H4baepn)0.5[FeIII 2.0Fe II 0.71CoII 1.29(H2O) 2(HPO3)4-x(HPO4)xF 4] (x ≃ 0.38) (2) were studied by single crystal X-ray diffraction. The phase with the major content of Co(ii), (H4baepn) 0.5[FeIII 2.0FeII 0.62CoII 1.38(H2O) 2(HPO3)4-x(HPO4)xF 4] (x ≃ 0.38) (3) was obtained as a polycrystalline powder and studied by Rietveld refinement by using the structural model of 2. These compounds were characterized by ICP-Q-MS, thermogravimetric and thermodiffractometric analyses, and XPS, IR, UV/vis and Mössbauer spectroscopy. The single crystal data indicate that phases 1 and 2 crystallize in the P21/c space group with lattice parameters a = 13.6808(4), b = 12.6340(2), c = 12.7830(3) Å and β = 116.983(4)° for 1 and a = 13.6823(4), b = 12.6063(3), c = 12.7535(4) Å and β = 116.988(4)° for 2, with Z = 4. The reciprocal space of 1 shows satellite reflections with a modulation wavevector q = 0.284(2)a* which indicate an incommensurate long-range order. The average structure of these compounds is built up by a 3D lattice constructed by inorganic layers of Fe(iii) chains and Fe(ii) and Co(ii) dimers joined by phosphite groups partially substituted by HPO4 and PO4 tetrahedral groups. These anionic layers stack along the [100] direction encapsulating linear tetramines in eight-membered open channels involving host-guest interactions. Magnetic measurements of 1 and 3 showed antiferromagnetic coupling as the major interactions, exhibiting a weak ferromagnetic component together with a spin glass transition at low temperature in the case of 1. Heat capacity measurements showed a small anomaly at 20.5 K for 1 and a sharp magnetic peak at 28 K for 3. Unexpectedly, the small anomaly observed in 1 increased with the magnetic field and became better defined. © the Partner Organisations 2014

Observation of a charge delocalization from Se vacancies in Bi2Se3: A positron annihilation study of native defects

[EN] By means of positron annihilation lifetime spectroscopy, we have investigated the native defects present in Bi2Se3, which belongs to the family of topological insulators. We experimentally demonstrate that selenium vacancy defects (VSe1) are present in Bi2Se3 as-grown samples, and that their charge is delocalized as temperature increases. At least from 100 K up to room temperature both V0Se1and V+Se1 charge states coexist. The observed charge delocalization determines the contribution of VSe1defects to the n-type conductivity of Bi2Se3. These findings are supported by theoretical calculations, which show that vacancies of nonequivalent Se1 and Se2 selenium atoms are clearly differentiated by positron annihilation lifetime spectroscopy, enabling us to directly detect and quantify the most favorable type of selenium vacancy. In addition to open-volume defects, experimental data indicate the presence of defects that act as shallow traps, suggesting that more than one type of native defects coexist in Bi2Se3. As will be discussed, the presence of a dislocation density around 1010cm−2 could be the source of the detected shallow traps. Understanding the one-dimensional defects and the origin of the charge delocalization that leads Bi2Se3 to be an n-type semiconductor will help in the development of high-quality topological insulators based on this material.This work is supported for the Basque Government Grant IT-443-10 and partially supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under the project TEC2014-60173 and by the Generalitat Valenciana under the projects Prometeo II 2015/004 and ISIC/2012/008. I. Unzueta also wants to acknowledge financial support from the Basque Government Grant PRE-2014-214. V. Marín-Borrás thanks the University of Valencia for its pre-doctoral fellowships. Finally we would also like to thank BCMaterials for its economic support

Neutron Scattering as a Powerful Tool to Investigate Magnetic Shape Memory Alloys: A Review

Magnetic shape memory alloys (MSMAs) are an interesting class of smart materials characterized by undergoing macroscopic deformations upon the application of a pertinent stimulus: temperature, stress and/or external magnetic fields. Since the deformation is rapid and contactless, these materials are being extensively investigated for a plethora of applications, such as sensors and actuators for the medical, automotive and space industries, energy harvesting and damping devices, among others. These materials also exhibit a giant magnetocaloric effect, whereby they are very promising for magnetic refrigeration. The applications in which they can be used are extremely dependent on the material properties, which are, in turn, greatly conditioned by the structure, atomic ordering and magnetism of a material. Particularly, exploring the material structure is essential in order to push forward the current application limitations of the MSMAs. Among the wide range of available characterization tools, neutron scattering techniques stand out in acquiring advanced knowledge about the structure and magnetism of these alloys. Throughout this manuscript, a comprehensive review about the characterization of MSMAs using neutron techniques is presented. Several elastic neutron scattering techniques will be explained and exemplified, covering neutron imaging techniques—such as radiography, tomography and texture diffractometry; diffraction techniques—magnetic (polarized neutron) diffraction, powder neutron diffraction and single crystal neutron diffraction, reflectometry and small angle neutron scattering. This will be complemented with a few examples where inelastic neutron scattering has been employed to obtain information about the phonon dispersion in MSMAs.This work has been carried out with the financial support of the Spanish Ministry of Science, Innovation and Universities (project RTI2018-094683-B-C53-54) and Basque Government Department of Education (project IT1245-19). N.A.R.-L. wants to thank the Basque Government (Department of Education) for providing funding under the specific investigation PFPI grant

Low temperature magnetic properties of a Ni50Mn34In16 ball-milled metamagnetic shape memory alloy

[EN] The effect of the atomic disorder induced by ball-milling on the structure and the magnetic properties has been analyzed in a Ni50Mn34In16 metamagnetic shape memory alloy. The as-milled samples displayed an amorphous structure which crystallizes to a disordered B2 structure on annealing. On further annealing, several recovery processes leading to the austenitic L21 structure and the subsequent martensitic transformation are observed. As a result of the recovery processes, the magnetic order drastically varies concurrent with the long-range atomic order. In particular, the magnetism evolves from a frustrated magnetic state compatible with a canonical spin-glass, observed in the amorphous structure, to the well-developed ferromagnetic state.This work has been carried out with the financial support of the Spanish “Ministerio de Economía y Competitividad” and FEDER funding, projects no. MAT2012-37923 and MAT2015-65165-C2-R. I. Unzueta acknowledges financial support from the Basque Government Grant nos. IT-443-10 and PRE_2014_214

Identification of Ni-vacancy defect in Ni-Mn-Z (Z = Ga, Sn, In): An experimental and DFT positron annihilation study

[EN] By means of experimental positron-annihilation-lifetime measurements and theoretical density functional theory (DFT) positron-lifetime calculations, vacancy-type defects in Ni50Mn50−xSnx (x=25, 20,15,13,10) and Ni50Mn50−xInx (x=25,20,16,13) systems are systematically studied. The study is extended to Ni-Mn-Ga systems as well. Experimental results are complemented with electron-positron DFT calculations carried out within the local density approximation and generalized gradient approximation, where five different parametrizations accounting for the γ(r) enhancement factor are analyzed. Theoretical results indicate that the Boronski-Nieminen parametrization of γ(r) is the one that best predicts the experimental results, which ultimately enables us to identify VNi as the vacancy present in the studied samples. The characteristic positron lifetime related to VNi ranges between 181 and 191 ps in Ni-Mn-Sn/In systems. Positron-annihilation-lifetime spectroscopy results in these two systems delimit the lower bound of the achievable vacancy concentration, which is much larger compared with the reported values in Ni-Mn-Ga systems. The present work, along with setting the basis for positron simulations in Ni-Mn based Heusler alloys, delimits the effect that the variation of vacancies has in the martensitic transformation in Ni-Mn-Sn systemsThis work is supported by the Basque Government and Spanish Ministry of Economy and Competitiveness under grants IT-1005-16, IT-756-13 and MAT2015-65165-C2-R (MINECO/FEDER). I. Unzueta also wants to acknowledge the Basque Government Grant PRE-2014-214