Origin of the quasi-quantized Hall effect in ZrTe5.

The quantum Hall effect (QHE) is traditionally considered to be a purely two-dimensional (2D) phenomenon. Recently, however, a three-dimensional (3D) version of the QHE was reported in the Dirac semimetal ZrTe5. It was proposed to arise from a magnetic-field-driven Fermi surface instability, transforming the original 3D electron system into a stack of 2D sheets. Here, we report thermodynamic, spectroscopic, thermoelectric and charge transport measurements on such ZrTe5 samples. The measured properties: magnetization, ultrasound propagation, scanning tunneling spectroscopy, and Raman spectroscopy, show no signatures of a Fermi surface instability, consistent with in-field single crystal X-ray diffraction. Instead, a direct comparison of the experimental data with linear response calculations based on an effective 3D Dirac Hamiltonian suggests that the quasi-quantization of the observed Hall response emerges from the interplay of the intrinsic properties of the ZrTe5 electronic structure and its Dirac-type semi-metallic character.

Evaluación de pacientes portadores de fístulas coronario-ventriculares múltiples / Assessment of patients with multiple coronary ventricular fistulas

Se presentan 4 pacientes portadoras de angina de pecho y tests funcionales positivos en las que se realizó cineangiocoronariografía, se observaron fístulas coronario-ventriculares múltiples y no se encontraron lesiones obstructivas. La prueba ergométrica consistió en una prueba de esfuerzo progresiva según protocolo de Bruce modificado. En 3 casos se realizó centellograma de perfusión miocárdica MIBI sensibilizado con esfuerzo ergométrico progresivo y en una paciente se realizó sensibilizado con dipiridamol. Las fístulas coronario-ventriculares múltiples son una alteración en la circulación coronaria que consiste en una comunicación anormal entre una de las arterias coronarias y una cámara cardíaca caracterizada por la presencia de múltiples trayectos fistulosos de pequeño calibre. Se las conoce también como microfístulas miocárdicas generalizadas. La prevalencia se estima menor a 0,2 por ciento. La angina de pecho es el síntoma principal y se ha postulado como mecanismo fisiopatológico el fenómeno de robo coronario, pero los casos con isquemia documentada son escasos. Coincidimos con la literatura internacional en la observación de pacientes con angor, tests funcionales positivos que, sin embargo, muestran ausencia de lesiones obstructivas coronarias y la presencia de fístulas coronario-ventriculares múltiples, que podrían estar en la génesis de esta sintomatología.

Antigenic analysis of bean pod mottle virus using linear and cyclized synthetic peptides.

The antigenic structure of the comovirus bean pod mottle virus (BPMV) was studied using synthetic peptides selected on the basis of the exposed location of certain regions of the viral protein. Three regions of domain A, four regions of domain B and two regions of domain C of BPMV coat protein were studied. Each of four regions were synthesized in the form of linear and cyclized peptides while the others were synthesized as linear peptides only. The peptides were tested for their ability to be recognized by antibodies directed against BPMV. The peptides were also used for producing rabbit antisera, which were tested for their ability to react with various BPMV antigens as well as with the linear and cyclized peptides. All the peptides were found to correspond to epitopes of BPMV coat protein. Several of the antigenic sites of BPMV located on exposed loops of the coat protein occupy positions which correspond to known epitopes in the structurally related picornaviruses. Only in some cases did cyclization sufficiently improve the level of conformational mimicry between peptides and the viral protein to allow cross-reactions between them to be observed.

[The treatment of chronic stable angina with isradipine. A cooperative Latin American study]. / Tratamiento de la angina crónica estable con isradipina. Estudio cooperativo latinoamericano.

In order to study the efficacy and tolerance of isradipine, a new Ca++ antagonist for the treatment of stable chronic angina, a multicentric cooperative study was carried out in eight Latin American countries (Argentine, Chile, Colombia, Ecuador, Mexico, Peru, Uruguay and Venezuela), which included 169 patients (60% men and 40% women), average age 62.6 +/- 9.7. Patients with more than 4 biweekly anginal crisis were accepted, with one or more of the following inclusion criteria: coronariographic evidence of obstruction greater than 60% in one or more vessels, IAM history, positive scintigraphy and positive effort test. The trial was single-blind, with placebo during the admission phase (2 weeks) and active treatment for 12 weeks. isradipine was administered in increasing doses of 2.5, 5, and 7 mg thrice a day, according to the presence or absence of anginal crisis. It was observed that the average frequency of weekly pains decreased from 8.2 +/- 7 under placebo to 6.3 +/- 7.5 under isradipine at low doses, and to 2.0 +/- 2.0 (p less than 0.001) under maximum doses. TNT intake decreased parallel also in a significant way. At the end of the trial, 37% of patients had become asymptomatic, and angina had reduced to less than two crisis a week in 33%. A clear relation doses-effect was observed. There was no alteration in laboratory exams neither in ECG. Seven patients had complications derived from the evolutional course of disease (2 IAM, 5 unstable angina and one sudden death). Adverse events were relatively frequent and the majority derived from vasodilator effect (tibial oedema 37%, flushing 17%, headache 23%).(ABSTRACT TRUNCATED AT 250 WORDS)

Computer-aided measuring of motor functions using pursuit tracking.

The necessity of evaluating motor functions objectively and quantitatively is discussed. Tracking tasks and their appropriateness in assessing motor performance is reviewed. Motor performance can be effectively assessed by means of tracking tasks. A simple tracking device is presented which allows the measurement of motor performance in different conditions. It is pointed out that computers are well suited for driving the stimulus in tracking tasks as well as recording the performance in experiments based on tracking tasks. Differences between open and closed loop conditions, compensatory tracking, pursuit tracking, preview tracking and cognitive tracking are discussed. A flexible computer-controlled device is presented with which diverse experiments based on tracking tasks can be performed and their results recorded. A complete description of the user-oriented, interactive programs with which the experiments can be controlled and the relevant performance data can be recorded is given. An example of their application on measuring the effects of levodopa therapy on the motor symptoms of Parkinson's disease is presented.