RESUMEN

The superfluid density or superconducting (SC) carrier concentrationnscof cuprates has been the subject of intense investigations but there is not any single theory capable to explain all the available data. Here we show that the behavior ofnscin under and overdoped cuprates are a consequence of an SC interaction based on charge fluctuations in the incommensurate charge-density-waves (CDW) domains. We have shown that this interaction scales with the CDW amplitude or the pseudogap (PG) energy, yielding local SC amplitudes and Josephson currents. The average Josephson energyEJis proportional to the phase stiffness or superfluid densityρsc∝nsc. We find thatnsc(p) increases almost linearly with dopingpin the underdoped region and in the charge abundant overdoped only a few fractions of the holes condense leading to two kinds of carriers, a recently confirmed feature. The calculations and theρscdata uncover how the PG-CDW-SC intertwined orders operate to yield cuprates properties.

RESUMEN

A unified phenomenological description framework is proposed for the evaluation of some of the most important observables of the cuprate superconductors: the pseudogap (PG) ΔPG, the local superconducting amplitudes ΔSC(r i ), the critical temperature T c and charge ordering (CO) parameters. Recent detailed measurements of CO structures and CO wavelengths λ CO are faithfully reproduced by solutions of a Cahn-Hilliard differential equation with a free energy potential V GL that produces alternating small charge modulations. The charge oscillations induce atomic fluctuations that mediate the SC pair interaction proportional to the V GL amplitude. The local SC amplitude and phase θ i are connected by Josephson coupling E J(r ij ) and the SC long-range order transition occurs when [Formula: see text]. The calculated results of the wavelength λ CO, ΔPG, [Formula: see text] and T c calculations are in good agreement with a variety of experiments.

RESUMEN

The observations of quantum oscillations frequencies in overdoped cuprates were in agreement with a charge density contained in a cylindrical Fermi surface but the measured frequencies of underdoped compounds were much smaller than expected. This was attributed to a topological transition into small pockets of Fermi surface associated with the existence of charge density waves. On the other hand, spectroscopic measurements suggested that the large two-dimensional Fermi surface changes continuously into a set of four disconnected arcs. Here we take into account the effect of the pseudogap that limits the available k-space area where the Landau levels are developed on the Luttinger theorem and obtain the correct total carrier densities. The calculations show how the disconnected arcs evolve into a closed Fermi surface reconciling the experiments.

RESUMEN

Impurity doping using Zn atoms was largely studied in cuprates because this process substantially reduces the superconducting critical temperature T(c) without any effect on the pseudogap onset T*. Earlier theories missed the recently established ubiquitous presence of incommensurate charge modulations in these materials. The charge order is a consequence of a phase separation transition which we describe by a continuity equation of the local free energy density. The Zn atoms generate a local magnetic moment, freezing their neighbors' spins, slowing down the electronic segregation process. Then the Zn-doped properties are that of a granular superconductor whose size of the charge order modulations are dictated by the degree of phase separation.

RESUMEN

We present a theoretical framework for understanding recent transverse field muon spin rotation (TF-µSR) experiments on cuprate superconductors in terms of localized regions of phase-coherent pairing correlations above the bulk superconducting transition temperature Tc. The local regions of phase coherence are associated with a tendency toward charge ordering, a phenomenon found recently in hole-doped cuprates. We use the Cahn-Hilliard equation as a means to phenomenologically model the inhomogeneous charge distribution of the electron system observed experimentally. For this system we perform self-consistent superconducting calculations using the Bogoliubov-deGennes method. Within this context we explore two possible scenarios: (i) the magnetic field is diamagnetically screened by the sum of varying shielding currents of isolated small-sized superconducting domains. (ii) These domains become increasingly correlated by Josephson coupling as the temperature is lowered and the main response to the applied magnetic field is from the sum of all varying tunneling currents. The results indicate that these two approaches may be used to simulate the TF-µSR data but case (ii) yields better agreement.

RESUMEN

To deal with the physics of cuprate superconductivity we propose an electronic phase separation transition that segregates the holes into high and low density domains. The calculated grain boundary potential favors the development of intragrain superconducting amplitudes. The zero resistivity transition arises only when the intergrain Josephson coupling E(J) is of the order of the thermal energy and phase locking takes place among the superconducting grains. We show that this approach explains the pseudogap and superconducting phases and it also reproduces some recent scanning tunneling microscopy data.

RESUMEN

This study describes the cardiac size and function of patients with sickle cell anaemia, in Segipe, Brazil, and its association to the clinical severity, duration of illness and haemoglobin levels. Heart measurements were obtained by echocardiography from 38 children and adolescents and compared to international reference values. Sickle cell patients had increased left atrial and ventricular dimensions in systole and an increased end diastolic septal and left ventricular free wall thickness. These findings correlated with age. There were no abnormalities in the ejection or shortening fractions. These results suggest early haemodynamic changes with progressive cardiac chamber dilation and diastolic dysfunction that become increasingly abnormal with growth.

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RESUMEN

Sickle cell disease (SCD) is the most prevalent inherited monogenic pathology in South America. Although children with SCD have normal birthweight, weight deficit is often seen from early childhood. On the other hand, paradoxically, normal final height associated with delayed puberty has been reported from Brazil and Jamaica. This cross-sectional study describes the growth pattern by age and sex in 76 children and adolescents with SCD in Sergipe, north-east Brazil with a median age of 110 months. Median weights and heights for age were below the NCHS standards. The weight and height deficits were statistically significant for boys of all ages, except for 7-year-olds. Most girls have median weights and heights below the NCHS standards but this only becomes statistically significant at 15 years of age. Family channels were calculated from the parents' heights. The observed height was lower than the expected percentile value for the family in seven (41%) children, equal to expected family height in six (35%) and above expected family height in four (24%) of 17 teenagers. Our findings suggest that Brazilian children with SCD do not attain normal height and weight. It is therefore likely that, although maximum height and weight velocity occur significantly later than normal due to delayed puberty, the magnitude of this spurt is less than normal.

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We have studied the morphological and quantitative aspects of the myenteric plexus neurons of the proximal colon in rats (Rattus norvegicus of Wistar strain) submitted to a protein deprivation during prenatal and lactation periods. Twenty pregnant dams were divided in four groups labeled according to the kind of nourishment they were given: Group NN, normal diet; Group DN, low protein diet during prenatal period, and normal diet during lactation period; Group ND, normal diet during prenatal period, and low protein diet during lactation period; Group DD, low protein diet during prenatal and lactation periods. Histological analyses were developed with proximal colon segments using the haematoxylin and eosin staining method. Membrane preparations were stained by Giemsa's method. The statistical analysis has demonstrated no significant difference among the means of neurons found in the four studied groups. It was noticed that the animals under protein deprivation during prenatal and lactation periods presented greater quantity of large and strongly basophilic myenteric neurons. This suggests that neurons have accumulated protein in the cytoplasm.

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