Phonon-modulated magnetic interactions and spin Tomonaga-Luttinger liquid in the p-orbital antiferromagnet CsO2

The magnetic response of antiferromagnetic CsO2, coming from the p-orbital S=1/2 spins of anionic O2- molecules, is followed by 133Cs nuclear magnetic resonance across the structural phase transition occuring at Ts1=61 K on cooling. Above Ts1, where spins form a square magnetic lattice, we observe a huge, nonmonotonic temperature dependence of the exchange coupling originating from thermal librations of O2- molecules. Below Ts1, where antiferromagnetic spin chains are formed as a result of p-orbital ordering, we observe a spin Tomonaga-Luttinger-liquid behavior of spin dynamics. These two interesting phenomena, which provide rare simple manifestations of the coupling between spin, lattice and orbital degrees of freedom, establish CsO2 as a model system for molecular solids.Comment: 9 pages, 5 figures (with Supplemental Material), to appear in Physical Review Letter

Coeficientes culturais de consórcio milho-feijão e milho-braquiária.

Para estabelecer os riscos climáticos para consórcios milho-feijão e milho-pastagens, é necessário que se conheça os seus respectivos coeficientes culturais. Objetivando determinar esses coeficientes, foram instalados, em três épocas, ensaios de campo onde determinou-se, o consumo de água pelas cultura no consórcio por meio do balanço hídrico do solo e a demanda potencial de água por meio da metodologia proposta por Penman-Monteith. Os resultados mostraram que os coeficiente culturais dos consórcios foram muito maiores que das culturas isoladamente, o que permite concluir que o consórcio demanda maior disponibilidade de água no solo. Portanto, a implantação do consorcio dependente grandemente da distribuição das chuvas na região e da a capacidade de retenção de umidade do solo. Assim sendo haverá restrição da época e da área a ser plantada por esse sistema produtivo comparado com a cultura isolada

One-dimensional quantum antiferromagnetism in the p−p-orbital CsO2_2 compound revealed by electron paramagnetic resonance

Recently it was proposed that the orbital ordering of $\pi_{x,y}^*$ molecular orbitals in the superoxide CsO$_2$ compound leads to the formation of spin-1/2 chains below the structural phase transition occuring at $T_{\rm{s1}}=61$~K on cooling. Here we report a detailed X-band electron paramagnetic resonance (EPR) study of this phase in CsO$_2$ powder. The EPR signal appears as a broad line below $T_{\rm{s1}}$, which is replaced by the antiferromagnetic resonance below the N\'{e}el temperature $T_{\rm N}=8.3$~K. The temperature dependence of the EPR linewidth between $T_{\rm{s1}}$ and $T_{\rm{N}}$ agrees with the predictions for the one-dimensional Heisenberg antiferromagnetic chain of $S=1/2$ spins in the presence of symmetric anisotropic exchange interaction. Complementary analysis of the EPR lineshape, linewidth and the signal intensity within the Tomonaga-Luttinger liquid (TLL) framework allows for a determination of the TLL exponent $K=0.48$. Present EPR data thus fully comply with the quantum antiferromagnetic state of spin-1/2 chains in the orbitally ordered phase of CsO$_2$, which is, therefore, a unique $p-$orbital system where such a state could be studied.Comment: 6 pages, 3 figure

Numerical optimization of hybrid dielectric/HTS resonators for surface impedance evaluation of HTS films

This work describes an alternative to the traditional dielectric resonator topology used for measuring surface impedance in high temperature superconducting (HTS) films. A gap is introduced above the dielectric so that only the lower film is in direct contact with it. This arrangement has been used extensively for mechanical tuning of dielectric resonators and, when used for surface impedance measurement, it can be designed to make the losses in the upper film small relative to the overall resonator losses. Then, measured results are mostly due to one of the films and not the average of two. The specifics of a resonator design for measuring 2-inch wafers are presented. An analysis and optimization of the resonator is done using a numerically efficient mode-matching algorithm.Peer ReviewedPostprint (published version

Different laboratory mouse strains show distinct coronary artery patterns

Different laboratory mouse strains show distinct coronary artery patterns. MC Fernández 1,2, A López-García 1,2, M Lorenzale 1, V Sans-Coma 1,2, AC Durán 1,2 and B Fernández 1,2. 1 Department of Animal Biology, Faculty of Science, University of Málaga, Spain. 2 Biomedical Research Institute of Málaga (IBIMA), University of Málaga, Spain. The C57BL/6 (BL/6) mouse strain is one of the most common models in research involving laboratory animals, particularly on studies of the cardiovascular system. It has been reported (Fernandez B, et al. J Anat 2008 212(1):12–18) that this strain presents an unusual coronary artery (CA) pattern, including congenital CA anomalies, which are clinically relevant in humans. The aim of the present study was to elucidate whether this pattern is strain-specific or appears in other mouse populations. We used stereomicroscopy, scanning electron microscopy, light microscopy, and a corrosion cast technique in 597 adult mice belonging to three inbred strains (BL/6, Balb/c, DBA/2), three outbred stocks (CD1, OF1, NMR1), two hybrid lines (129sv x BL/6, CD2F1) and wild mice. Lock-like ostium was only detected in BL/6 mice, whereas left septal artery, accessory ostium, high take-off, intramural course, and solitary ostium of one CA in aorta were present in different laboratory strains and in wild mice. However, each mouse population showed a specific incidence of these coronary conditions. These results should be taken into account when studying the murine coronary system, especially in CA occlusion experiments and in studies on cardiovascular development involving murine mutant lines. In addition, we propose that several laboratory mouse strains may serve as appropriate animal models to study several clinically relevant human congenital anomalies of the CAs. Our results suggest that some of these CA anomalies are subject to a simple mode of inheritance. This work was supported by P10-CTS-6068 and PI- 0888-2012.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. P10-CTS-6068. PI-0888-201

Spin-Exchange Interaction in ZnO-based Quantum Wells

Wurtzitic ZnO/(Zn,Mg)O quantum wells grown along the (0001) direction permit unprecedented tunability of the short-range spin exchange interaction. In the context of large exciton binding energies and electron-hole exchange interaction in ZnO, this tunability results from the competition between quantum confinement and giant quantum confined Stark effect. By using time-resolved photoluminescence we identify, for well widths under 3 nm, the redistribution of oscillator strengths between the A and B excitonic transitions, due to the enhancement of the exchange interaction. Conversely, for wider wells, the redistribution is cancelled by the dominant effect of internal electric fields, which dramatically reduce the exchange energy.Comment: 14 pages, 3 figure

DISTRIBUTION OF PIGMENT CELLS IN THE HEART OF THE RABBITFISH, CHIMAERA MONSTROSA (CONDRICHTHYES: HOLOCEPHALI)

El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013. Anatomical Record, Volume 296, Special Feature — 1: P-076.The study of extracutaneous cells producing and storing melanin is of interest because it may provide valuable information about the presence of neural crest elements in internal organs and tissues. Here we report, for the first time, the presence and distribution of melanophores in the heart of a chondrichthyan species, the rabbitfish, Chimaera monstrosa. Pigment cells were found in all of 20 hearts examined. Pigment cells occur mainly in the cardiac outflow tract, which consists of two anatomical components, the proximal, myocardial conus arteriosus and the distal, non-myocardial bulbus arteriosus. A few groups of dark pigmented cells were found in the apex of the ventricle of one specimen and in the atrium of two specimens. In all instances, the melanophores were located in the subepicardial space, where they could be well recognized in both unstained and stained histological sections. The distribution and intensity of the pigmentation in the cardiac outflow tract varies markedly between individuals. In all cases, however, the pigmented area is larger on the dorsal than on the ventral surface. Dorsally, the size of the pigmented area ranges from a fringe that includes the bulbus and the distal part of the conus to the whole surface of the outflow tract. Ventrally, the pigmented area does not cover the entire conus arteriosus. The intensity of the pigmentation also varies widely; in general, it is highest at the distal portion of the conus. There is no relationship between the distribution and intensity of the pigmentation and the sex and age of the animals. The functional role of the pigmented cells is unknown. If the melanophores in the heart of C. monstrosa are indeed of neural crest origin, it would suggest a notable contribution of the neural crest cells to the cardiac outflow tract in holocephalans.Proyecto CGL2010-16417/BOS; Fondos FEDER BES-2011-04690

PIGMENTATION OF THE HEART IN THE BICHIR, POLYPTERUS SENEGALUS

El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013. Anatomical Record, Volume 296, Special Feature — 1: P-078.The presence of melanin-containing cells in the heart has been documented in tetrapods, but not in fish. It has been even suggested that dark pigmented cells are exclusively associated with hearts having two atria and two ventricles. The aim here is to report the occurrence of pigment cells in the heart of the bichir, an extant representative of the polypteriformes, an ancient ray-finned fish lineage that split from the stem of the actinopterygians soon after their divergence from the sarcopterygians. The bichir heart is composed of sinus venosus, atrium, ventricle, conus arteriosus and bulbus arteriosus arranged sequentially within the pericardial cavity. Dendritic-shaped cells containing melanosomes were found in the five cardiac components of the 12 bichirs included in this study. Numerous melanophores were distributed regularly over the surface of all segments having myocardium in their walls, thus resulting in a marked pigmentation of the whole heart. The bulbus arteriosus, which in the bichir is reduced in size, showed an even more intense pigmentation. In all instances, the melanophores were localized in the subepicardial space. Pigment cells also occurred in the pericardium and ventral aorta. The functional role of melanocytes in the tetrapod heart remains obscure. Antiinflamatory activity, cytoprotection and effects on the viscoelastic properties of the cardiac tissue have been adduced as possible actions of such cells. The role of pigment cells in the bichir heart constitutes a new open question. Interestingly, however, the only cells that have been shown to form melanin-containing cells in the heart derive from the neural crest. If the melanophores of the bichir heart are indeed of neural crest origin, it would suggest a much more extensive contribution and persistence of elements from the neural crest in the primitive heart of jawed vertebrates as assumed so far in most papers devoted to vertebrate heart embryology.Proyecto CGL2010-16417/BOS; Fondos FEDER; Beca FPI ref. BES-2011-046901

MYOCARDIAL STRUCTURE AND VASCULARIZATION OF THE HEART VENTRICLE IN HOLOCEPHALI: IMPLICATIONS FOR HEART EVOLUTION

El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013. Anatomical Record, Volume 296, Special Feature — 1: P-075.It has been classically assumed that the ventricle of the primitive vertebrate heart is composed of spongy myocardium, supplied exclusively by oxygen-poor, luminal blood. This idea is on two facts: (1) extant agnathans have a spongy ventricular myocardium, and (2) in avian and mammalian embryos, the formation of trabeculated myocardium precedes the appearance of compact myocardium. Recently, it has been proposed that, like elasmobranchs, the early gnathostomes possess a fully vascularised ventricle composed of mixed myocardium. We tested this idea by studying the structure and vascularisation of the ventricular myocardium in four holocephalan species of the families Chimaeridae and Rhinochimaeridae. Chimaera monstrosa, Hidrolagus affinis and Harriotta raleighana have a spongy myocardium covered by a thin layer of cardiac muscle. In H. raleighana, the compacta is reduced to an extremely fine rim. In all three species there is a well-developed coronary artery system consisting of subepicardial vessels which give off branches that penetrate the myocardial trabeculae. Rhinochimaera atlantica has no compacta and its ventricular coronary artery system is reduced to subepicardial vessels that do not enter the spongy layer. This report is the first to show that in wild living vertebrates, a coronary artery system supplying the whole myocardium exists in the absence of a well-developed compacta, which supports experimental work that shows that myocardial cell proliferation and coronary vascular growth rely on genetically separated programs. We conclude that the mixed ventricular myocardium is primitive for chondrichthyans, and that the lack of compacta in some holocephalans is a derived character. Moreover our results support the hypotheses that the mixed myocardium is the primitive condition in gnathostomes, and that the absence of a compacta in different actinopterygian taxa is the result of its repeated loss during evolution.Proyecto CGL2010-16417/BOS; Fondos FEDE

The bulbus arteriosus of the holocephalan heart

El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013.Anatomical Record, Volume 296, Special Feature — 1: P-074.Previous work has shown that the outflow tract of the elasmobranch heart, namely the cardiac portion intercalated between the ventricle and the ventral aorta, does not consist of a single component, the conus arteriosus, as has classically been assumed, but two, the myocardial conus arteriosus and the non-myocardial bulbus arteriosus. From the evolutionary perspective, knowledge of the anatomy of the cardiac outflow tract of the holocephali is important, as they are the sister group of elasmobranchs. Our aim is to describe the cardiac outflow tract of four holocephalan species, two of them, Chimaera monstrosa and Hydrolagus affinis of the family Chimaeridae, and the other two, Harriotta raleighana and Rhinochimaera atlantica, of the family Rhinochimaeridae. The cardiac outflow tract of the four species consisted of a myocardial conus arteriosus, furnished with valves, and a bulbus arteriosus devoid of cardiac muscle. Both the bulbus and conus are tubular in shape. The length of the bulbus relative to the total length of the outflow tract is somewhat smaller in the rhinochimaerids (15%-19%) than in the chimaerids (19%-23%). The bulbus is covered by epicardium and is crossed by the main coronary artery trunks. Histologically, the bulbus is mainly composed of elastin and collagen, and, to a lesser extent, by smooth muscle. This suggests that in holocephalans, the bulbus actively helps to protect the gill vasculature from exposure to high-pressure pulses of blood. Our results prove that the bulbus arteriosus is common to chondrichthyans. In addition, they support the hypothesis that the cardiac outflow tract consisted of a conus arteriosus and a bulbus arteriosus from the beginning of the jawed vertebrate radiation, contributing to our understanding of the morphological changes that have occurred at the arterial pole of the heart in both actinopterygians and sarcopterygians.Proyecto CGL2010-16417/BOS; Fondos FEDE