Proper motions of the HH1 jet

We describe a new method for determining proper motions of extended objects, and a pipeline developed for the application of this method. We then apply this method to an analysis of four epochs of [S~II] HST images of the HH~1 jet (covering a period of $\sim 20$~yr). We determine the proper motions of the knots along the jet, and make a reconstruction of the past ejection velocity time-variability (assuming ballistic knot motions). This reconstruction shows an "acceleration" of the ejection velocities of the jet knots, with higher velocities at more recent times. This acceleration will result in an eventual merging of the knots in $\sim 450$~yr and at a distance of $\sim 80"$ from the outflow source, close to the present-day position of HH~1.Comment: 12 pages, 8 figure

Educational Strategies to Promote Adherence to Treatment in Patients with Cardiovascular Disease

Introduction: Educational material is a key strategy for primary health care promotion. Purpose: To design and validate educational material adapted to the population and aimed to increase knowledge about adherence to the treatment of arterial hypertension and diabetes mellitus. Methodology: Methodological study for the design of educational material for people with diabetes mellitus and high blood pressure. For the design, content validity tests were carried out, with the participation of six experts in health education and six patients with chronic diseases. Validation was performed pursuant to the attraction, understanding, engagement, and acceptance criteria. Results: The validation confirmed that all items and criteria were above the minimal expected range. Conclusion: The design and validation of educational material provide elements that improve the education of patients about their pathologies and their adherence to treatment

Spin polarons in triangular antiferromagnets

The motion of a single hole in a 2D triangular antiferromagnet is investigated using the t-J model. The one-hole states are described by strings of spin deviations around the hole. Using projection technique the one-hole spectral function is calculated. For large J/t we find low-lying quasiparticle-like bands which are well separated from an incoherent background by a gap of order J. However, for small J/t this gap vanishes and the spectrum becomes broad over an energy range of several t. The results are compared with SCBA calculations and numerical data.Comment: 4 pages, 6 figs, to be publish in PR

Hole-Hole Contact Interaction in the t-J Model

Using an analytical variational approach we calculate the hole-hole contact interaction on the N\'{e}el background. Solution of the Bethe-Salpeter equation with this interaction gives bound states in $d$- and p-waves with binding energies close to those obtained by numerical methods. At $t/J \ge 2-3$ the bound state disappears. In conclusion we discuss the relation between short range and long range interactions and analogy with the problem of pion condensation in nuclear matter.Comment: 11 pp. (LATEX), 7 figures (PostScript) appended, report N

Indications of Spin-Charge Separation at Short Distance and Stripe Formation in the Extended t-J Model on Ladders and Planes

The recently discussed tendency of holes to generate nontrivial spin environments in the extended two-dimensional t-J model (G. Martins, R. Eder, and E. Dagotto, Phys. Rev. B{\bf 60}, R3716 (1999)) is here investigated using computational techniques applied to ladders with several number of legs. This tendency is studied also with the help of analytic spin-polaron approaches directly in two dimensions. Our main result is that the presence of robust antiferromagnetic correlations between spins located at both sides of a hole either along the x or y axis, observed before numerically on square clusters, is also found using ladders, as well as applying techniques based on a string-basis expansion. This so-called "across-the-hole" nontrivial structure exists even in the two-leg spin-gapped ladder system, and leads to an effective reduction in dimensionality and spin-charge separation at short-distances, with a concomitant drastic reduction in the quasiparticle (QP) weight Z. In general, it appears that holes tend to induce one-dimensional-like spin arrangements to improve their mobility. Using ladders it is also shown that the very small J/t$\sim$0.1 regime of the standard t-J model may be more realistic than anticipated in previous investigations, since such regime shares several properties with those found in the extended model at realistic couplings. Another goal of the present article is to provide additional information on the recently discussed tendencies to stripe formation and spin incommensurability reported for the extended t-J model.Comment: 14 pages, 21 figures, LateX, submited to Phys. Rev.

A spectroscopic atlas of post-AGB stars and planetary nebulae selected from the IRAS Point Source Catalogue

Aims: We study the optical spectral properties of a sample of stars showing far infrared colours similar to those of well-known planetary nebulae. The large majority of them were unidentified sources or poorly known in the literature at the time when this spectroscopic survey started, some 15 years ago. Methods: We present low-resolution optical spectroscopy, finding charts and improved astrometric coordinates of a sample of 253 IRAS sources. Results: We have identified 103 sources as post-AGB stars, 21 as ``transition sources'', and 36 as planetary nebulae, some of them strongly reddened. Among the rest of sources in the sample, we were also able to identify 38 young stellar objects, 5 peculiar stars, and 2 Seyfert galaxies. Up to 49 sources in our spectroscopic sample do not show any optical counterpart, and most of them are suggested to be heavily obscured post-AGB stars, rapidly evolving on their way to becoming planetary nebulae. Conclusions: An analysis of the galactic distribution of the sources identified as evolved stars in the sample is presented together with a study of the distribution of these stars in the IRAS two-colour diagram. Finally, the spectral type distribution and other properties of the sources identified as post-AGB in this spectroscopic survey are discussed in the framework of stellar evolution.Comment: 69 pages, 413 figures. Accepted by Astronomy and Astrophysic

Incidence of human granulocytic anaplasmosis in returning travellers with fever.

Although tick-borne pathogens have been reported as an important cause of imported fever, the incidence of Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis (HGA), in travellers is unknown. We conducted a prospective cohort study to investigate the aetiologies of fever in returning travellers (November 2017-July 2019). Polymerase chain reaction for msp2 gene amplification and indirect immunofluorescence assay for A. phagocitophilum were performed in all returning travellers with undifferentiated non-malarial fever. Among 141 travellers included, 8 patients were diagnosed with probable or confirmed HGA. The overall incidence rate of HGA was 19.9 cases/1000 person-week of travel. The main destination of travel was Asia, accounting for 62.5% patients with HGA. Co-infections were found in 37.5% of patients with HGA. Diagnosis of HGA and empirical treatment with doxycycline should be considered in travellers with fever

Revival of the spin-Peierls transition in Cu_xZn_(1-x)GeO_3 under pressure

Pressure and temperature dependent susceptibility and Raman scattering experiments on single crystalline Cu_xZn_(1-x)GeO_3 have shown an unusually strong increase of the spin-Peierls phase transition temperature upon applying hydrostatic pressure. The large positive pressure coefficient (7.5 K/GPa) - almost twice as large as for the pure compound (4.5 K/GPa) - is interpreted as arising due to an increasing magnetic frustration which decreases the spin-spin correlation length, and thereby weakens the influence of the non-magnetic Zn-substitution.Comment: LaTeX, 15 pages, 5 eps figures, Phys. Rev. B, to appea

Doped bilayer antiferromagnets: Hole dynamics on both sides of a magnetic ordering transition

The two-layer square lattice quantum antiferromagnet with spins 1/2 shows a magnetic order-disorder transition at a critical ratio of the interplane to intraplane couplings. We investigate the dynamics of a single hole in a bilayer antiferromagnet described by a t-J Hamiltonian. To model the spin background we propose a ground-state wave function for the undoped system which covers both magnetic phases and includes transverse as well as longitudinal spin fluctuations. The photoemission spectrum is calculated using the spin-polaron picture for the whole range of the ratio of the magnetic couplings. This allows for the study of the hole dynamics of both sides of the magnetic order-disorder transition. For small interplane coupling we find a quasiparticle with properties known from the single-layer antiferromagnet, e.g., the dispersion minimum is at (pi/2,pi/2). For large interplane coupling the hole dispersion is similar to that of a free fermion (with reduced bandwidth). The cross-over between these two scenarios occurs inside the antiferromagnetic phase which indicates that the hole dynamics is governed by the local environment of the hole.Comment: 14 pages, 11 figs, minor changes, discussion of spin correlations added, accepted for publication in PR