"Magic" numbers in Smale's 7th problem

Smale's 7-th problem concerns N-point configurations on the 2-dim sphere which minimize the logarithmic pair-energy V_0(r) = -ln r averaged over the pairs in a configuration; here, r is the chordal distance between the points forming a pair. More generally, V_0(r) may be replaced by the standardized Riesz pair-energy V_s(r)= (r^{-s} -1)/s, which becomes - ln r in the limit s to 0, and the sphere may be replaced by other compact manifolds. This paper inquires into the concavity of the map from the integers N>1 into the minimal average standardized Riesz pair-energies v_s(N) of the N-point configurations on the 2-sphere for various real s. It is known that v_s(N) is strictly increasing for each real s, and for s<2 also bounded above, hence "overall concave." It is (easily) proved that v_{-2}(N) is even locally strictly concave, and that so is v_s(2n) for s<-2. By analyzing computer-experimental data of putatively minimal average Riesz pair-energies v_s^x(N) for s in {-1,0,1,2,3} and N in {2,...,200}, it is found that {v}_{-1}^x(N) is locally strictly concave, while v_s^x(N) is not always locally strictly concave for s in {0,1,2,3}: concavity defects occur whenever N in C^{x}_+(s) (an s-specific empirical set of integers). It is found that the empirical map C^{x}_+(s), with s in {-2,-1,0,1,2,3}, is set-theoretically increasing; moreover, the percentage of odd numbers in C^{x}_+(s), s in {0,1,2,3}, is found to increase with s. The integers in C^{x}_+(0) are few and far between, forming a curious sequence of numbers, reminiscent of the "magic numbers" in nuclear physics. It is conjectured that the "magic numbers" in Smale's 7-th problem are associated with optimally symmetric optimal-energy configurations.Comment: 109 pages, of which 30 are numerical data tables. Thoroughly revised version, to appear in J. Stat. Phys. under the different title: `Optimal N point configurations on the sphere: "Magic" numbers and Smale's 7th problem

Globular Clusters: DNA of Early-Type galaxies?

This paper explores if the mean properties of Early-Type Galaxies (ETG) can be reconstructed from "genetic" information stored in their GCs (i.e., in their chemical abundances, spatial distributions and ages). This approach implies that the formation of each globular occurs in very massive stellar environments, as suggested by some models that aim at explaining the presence of multi-populations in these systems. The assumption that the relative number of globular clusters to diffuse stellar mass depends exponentially on chemical abundance, [Z/H], and the presence of two dominant GC sub-populations blue and red, allows the mapping of low metallicity halos and of higher metallicity (and more heterogeneous) bulges. In particular, the masses of the low-metallicity halos seem to scale up with dark matter mass through a constant. We also find a dependence of the globular cluster formation efficiency with the mean projected stellar mass density of the galaxies within their effective radii. The analysis is based on a selected sub-sample of galaxies observed within the ACS Virgo Cluster Survey of the {\it Hubble Space Telescope}. These systems were grouped, according to their absolute magnitudes, in order to define composite fiducial galaxies and look for a quantitative connection with their (also composite) globular clusters systems. The results strengthen the idea that globular clusters are good quantitative tracers of both baryonic and dark matter in ETGs.Comment: 20 pages, 28 figures and 5 table

New poly(ionic liquid)s based on poly(azomethine-pyridinium) salts and its use as heterogeneous catalysts for CO2 conversion

A fast and simple synthetic route towards a new family of poly(ionic liquids) based on aromatic crosslinked poly(azomethine-pyridinium) salts is described. These new polymers were prepared in one step from new diamine methyl pyridinium salts and isopthaldehyde, in 30 min under microwave irradiation. By this method, poly(azomethine-pyridinium) containing chloride (Cl), bis(trifluoromethylsulfonyl)imide (TFSI) and hexaflorophosphate (PF6) as counter-anions were synthetized. This new pyridinium poly(ionic liquid)s were obtained as insoluble powders showing high thermal stability. The poly(azomethine-pyridinium)s were tested as heterogeneous catalysts in the cycloaddition of CO2 to epichlorohydrin to obtain chloropropylene carbonate. The polymers containing chloride anion shows high content of catalytically active sites and the best performance of the series, with 100% selectivity towards the chloropropylene carbonate in a reaction without solvent at 3 bar of CO2, 100 °C and low catalyst loading (0.5 mol%).Spanish Government, MINECO (Projects MAT2014-52085-C2-2-P and MAT2017-82288-C2-2-P, MAT2017-83373-R

A

Abstract:&nbsp; INTRODUCTION: In most instances, the physiopathology of exercise-triggered headache remains ill defined.&nbsp; We present the modifications of visual cortex activity evaluated using EEG in a patient suffering from headache induced by exercise, before and after exertion. CASE PRESENTATION: We present a 36 years old otherwise healthy male under evaluation for headache crises with migrainous features (with intense photophobia) provoked by physical activity. Attacks respond to ergotamine-containing compounds, but cannot be prevented using common anti-migraine prophylactics. Laboratory tests, magnetic resonance angiography and cardiac and neck blood vessels Doppler ultrasound were normal. An electroencephalographic recording was performed at rest and during 3 consecutive blocks of visual stimulation (checkboard pattern-reversal) before and after a graduated ergometric evaluation.&nbsp; Independent components of EEG activity were extracted to assess visual cortex activity in the frequency domain. The electrophysiological patterns observed were similar to those previously described on migraineurs in-between and during headaches. CONCLUSIONS: If replicated in an adequately sized sample, our findings may suggest that exercise-induced headache in subjects without any vascular, structural, or cerebrospinal fluid dynamic alterations and migraine may share a common physiopathological background.Resumen:&nbsp; INTRODUCCIÓN:&nbsp;&nbsp; En la mayoría de los casos, la fisiopatogenia de la cefalea inducida por el ejercicio no puede ser determinada a ciencia cierta.Presentamos los resultados del análisis de la actividad en la corteza visual de un paciente con cefalea inducida por el ejercicio antes y después de una prueba de actividad física. PRESENTACIÓN&nbsp; DEL CASO:&nbsp;Paciente de sexo masculino de 36 años de edad, sin antecedentes médicos de relevancia, en estudio por crisis de cefalea de características migrañosas (marcada fotofobia) desencadenadas por la actividad física. Las crisis responden adecuadamente a compuestos con ergotamina,&nbsp; pero no pueden ser prevenidas con profilácticos antimigrañosos clásicos. Los análisis de laboratorio, la angio-resonancia magnética nuclear de cerebro y la ecografía Doppler cardíaca y de vasos&nbsp; del&nbsp; cuello fueron normales. Se le realizó un registro electroencefalograáfico en reposo, seguido de 3 bloques de 5 minutos de estimulación visual con damero antes y después de una prueba ergométrica graduada, del cual se extrajeron los componentes independientes de la señal para luego comparar la actividad espectral a nivel de la corteza visual.&nbsp;Los patrones electrofisiológicos observados fueron similares a aquellos que han sido descriptos previamente en pacientes con migraña entre medio y durante las crisis. CONCLUSIONES:&nbsp; En caso de poder ser replicados en una muestra de tamaño adecuado, nuestros hallazgos sugieren que la fisiopatogenia de la cefalea inducida por el ejercicio podría ser similar a la de la migraña en pacientes sin alteraciones vasculares, estructurales o de la dinámica de líquido cefalorraquídeo.

The Brazil-Argentina gemini group for the study of globular cluster systems (BAGGs GCs): Flamingos-2 and GMOS data for NGC 1395

In this letter, we present preliminary results of the analysis of Flamingos-2 and GMOS-S photometry of the globular cluster (GC) system of the elliptical galaxy NGC1395. This is the first step of a long-term Brazilian-Argentinian collaboration for the study of GC systems in early-type galaxies. In the context of this collaboration, we obtained deep NIR photometric data in two different bands (J and Ks), which were later combined with high quality optical Gemini + GMOS photometry previously obtained by the Argentinian team. This allowed us to obtain different color indices, less sensitive to the effect of horizontal branch (HB) stars for several hundreds of GC candidates, and to make an initial assessment of the presence or absence of multiple GC populations in colors in NGC1395.Instituto de Astrofísica de La PlataMuseo de Astronomía y Geofísic

The Brazil-Argentina gemini group for the study of globular cluster systems (BAGGs GCs): Flamingos-2 and GMOS data for NGC 1395

In this letter, we present preliminary results of the analysis of Flamingos-2 and GMOS-S photometry of the globular cluster (GC) system of the elliptical galaxy NGC1395. This is the first step of a long-term Brazilian-Argentinian collaboration for the study of GC systems in early-type galaxies. In the context of this collaboration, we obtained deep NIR photometric data in two different bands (J and Ks), which were later combined with high quality optical Gemini + GMOS photometry previously obtained by the Argentinian team. This allowed us to obtain different color indices, less sensitive to the effect of horizontal branch (HB) stars for several hundreds of GC candidates, and to make an initial assessment of the presence or absence of multiple GC populations in colors in NGC1395.Instituto de Astrofísica de La PlataMuseo de Astronomía y Geofísic

Attributing scientific and technical progress: the case of holography

Holography, the three-dimensional imaging technology, was portrayed widely as a paradigm of progress during its decade of explosive expansion 1964–73, and during its subsequent consolidation for commercial and artistic uses up to the mid 1980s. An unusually seductive and prolific subject, holography successively spawned scientific insights, putative applications and new constituencies of practitioners and consumers. Waves of forecasts, associated with different sponsors and user communities, cast holography as a field on the verge of success—but with the dimensions of success repeatedly refashioned. This retargeting of the subject represented a degree of cynical marketeering, but was underpinned by implicit confidence in philosophical positivism and faith in technological progressivism. Each of its communities defined success in terms of expansion, and anticipated continual progressive increase. This paper discusses the contrasting definitions of progress in holography, and how they were fashioned in changing contexts. Focusing equally on reputed ‘failures’ of some aspects of the subject, it explores the varied attributes by which success and failure were linked with progress by different technical communities. This important case illuminates the peculiar post-World War II environment that melded the military, commercial and popular engagement with scientific and technological subjects, and the competing criteria by which they assessed the products of science

La primera enana ultra-compacta confirmada en el grupo de NGC5044

En el siguiente trabajo confirmamos como miembro del grupo NGC5044, un objeto que por sus propiedades fotométricas constituye la primer Enana ultra-compacta “UCD” (por sus siglas en inglés) detectada en dicho grupo. La misma se encuentra asociada a la galaxia masiva NGC5044 y fue identificada empleando datos Gemini+GMOS. Se presentan los resultados preliminares de un análisis de poblaciones estelares, basado en espectros obtenidos mediante el mismo instrumento. Dicho análisis indica que se trata de un objeto masivo (MV ∼ -12.3 mag), con una edad mayor a 10×109 años, con metalicidades y abundancias [Z/H] ∼ -1 y [α/Fe] ∼ 0.3, respectivamente.In the present work we confirm as a member of the group NGC5044, an object which due to its photometric properties constitutes the first UCD detected in this group. It is associated with the massive galaxy NGC5044 and was identified using Gemini+GMOS data. We present the preliminary results of an analysis of stellar populations, based on spectra obtained by the same instrument. This analysis indicates that this is a massive object (MV ∼ -12.3 mag), older than 10×109 years, with metallicity and abundances [Z/H] ∼ -1 and [α/Fe]∼ 0.3, respectively.Trabajo publicado en Actas de las Terceras Jornadas de Astrofísica Estelar. La Plata, Asociación Argentina de Astronomía, 2018.Facultad de Ciencias Astronómicas y Geofísica

Triggered metal ion release and oxidation: ferrocene as a mechanophore in polymers

The introduction of mechanophores into polymers makes it possible to transduce mechanical forces into chemical reactions that can be used to impart functions such as self‐healing, catalytic activity, and mechanochromic response. Here, an example of mechanically induced metal ion release from a polymer is reported. Ferrocene (Fc) was incorporated as an iron ion releasing mechanophore into poly(methyl acrylate)s (PMAs) and polyurethanes (PUs). Sonication triggered the preferential cleavage of the polymers at the Fc units over other bonds, as shown by a kinetic study of the molar mass distribution of the cleaved Fc‐containing and Fc‐free reference polymers. The released and oxidized iron ions can be detected with KSCN to generate the red‐ colored [Fe(SCN)n(H2O)6−n)](3−n)+ complex or reacted with K4[Fe(CN)6] to afford Prussian blue