Uncoupling system and environment simulation cells for fast-scaling modeling of complex continuum embeddings.

Continuum solvation models are becoming increasingly relevant in condensed matter simulations, allowing to characterize materials interfaces in the presence of wet electrified environments at a reduced computational cost with respect to all atomistic simulations. However, some challenges with the implementation of these models in plane-wave simulation packages still persists, especially when the goal is to simulate complex and heterogeneous environments. Among these challenges is the computational cost associated with large heterogeneous environments, which in plane-wave simulations has a direct effect on the basis-set size and, as a result, on the cost of the electronic structure calculation. Moreover, the use of periodic simulation cells is not well-suited for modeling systems embedded in semi-infinite media, which is often the case in continuum solvation models. To address these challenges, we present the implementation of a double-cell formalism, in which the simulation cell used for the continuum environment is uncoupled from the one used for the electronic-structure simulation of the quantum-mechanical system. This allows for a larger simulation cell to be used for the environment, without significantly increasing computational time. In this work, we show how the double-cell formalism can be used as an effective periodic boundary conditions correction scheme for nonperiodic and partially periodic systems. The accuracy of the double-cell formalism is tested using representative examples with different dimensionalities, both in vacuum and in a homogeneous continuum dielectric environment. Fast convergence and good speedups are observed for all the simulation setups, provided the quantum-mechanical simulation cell is chosen to completely fit the electronic density of the system.

EUS-guided tissue samples for the diagnosis of patients with a thickened gastric wall and prior negative endoscopic biopsies.

AIM: Evaluate the diagnostic yield of biopsies obtained by EUS guidance in patients with gastric wall thickening and prior negative endoscopic biopsies. MATERIAL AND METHODS: Data collected from October 2008 to January 2016 were analyzed in a retrospective manner. All included patients had undergone at least one endoscopy with a negative biopsy and showed evidence of gastric wall thickening by tomography, confirmed by endoscopy. All patients gave their written informed consent before the procedure. Demographics and baseline characteristics, including age, sex, number of previous endoscopies, and histopathological diagnosis were recorded. Follow-up data were obtained from a review of the electronic medical records. RESULT: In total, 22 patients with previous negative endoscopic biopsies and gastric wall thickening were included. Using EUSFNA/FNB, the diagnosis was made in the first procedure in 19/22 (86.30%) cases, while in 1/22 (4.5%) patients the diagnosis was made in the second EUS-FNA. A total of 18 (81.82%) patients with EUS-FNA were assessed using a standard Echo-tip, while the remaining four (18.18%) patients underwent EUS-FNB and using a ProCore needle. All patients with a final diagnosis of malignancy had a thickened gastric wall with impaired gastric distension and a loss of wall structure determined by EUS. Of patients with a benign final diagnosis, all (n=8) showed a thickened gastric wall by EUS but with preservation of the deep layers. CONCLUSION: EUS-FNA/FNB is necessary in patients with a thickened gastric wall and prior negative biopsy on endoscopy. The procedure is safe and has a good diagnostic.

Array of biosensors for discrimination of grapes according to grape variety, vintage and ripeness.

A bioelectronic tongue based on nanostructured biosensors specific for the simultaneous detection of sugars and phenols has been developed. The array combined oxidases and dehydrogenases immobilized on a lipidic layer prepared using the Langmuir-Blodgett technique where Glucose oxidase, d-Fructose dehydrogenase, Tyrosinase or Laccase were imbibed. A phthalocyanine was co-immobilized in the sensing layer and used as electron mediator. The array thus formed has been used to analyze grapes and provides global information about the samples while providing specific information about their phenolic and their sugar content. Using Principal Component Analysis (PCA) the array of voltammetric biosensors has been successfully used to discriminate musts prepared from different varieties of grapes (Tempranillo, Garnacha, Cabernet-Sauvignon, Prieto Picudo and Mencía). Differences could be also detected between grapes of the same variety and cultivar harvested in two successive vintages (2012 and 2013). Moreover, the ripening of grapes could be monitored from veraison to maturity due to the changes in their phenolic and sugar content. Using Partial Least Squares (PLS-1) analysis, excellent correlations have been found between the responses provided by the array of biosensors and classical parameters directly related to phenols (total polyphenol index, TPI) and sugar concentration (degree Brix) measured by chemical methods with correlation coefficients close to 1 and errors close to 0. It is also worthy to notice the good correlations found with parameters associated with the pH and acidity that can be explained by taking into account the influence of the pH in the oxidation potentials of the phenols and in the enzymatic activity. This bioelectronic tongue can assess simultaneously the sugar and the phenolic content of grapes and could be used to monitor the maturity of the fruit and could be adapted easily to field analysis.

A comparative study on the effects of pindolol and propranolol on systemic and cardiac haemodynamics in hypertensive patients.

Eight out-patients with essential hypertension participated in a comparative, placebo-controlled study with a cross-over design. Pindolol and propranolol were administered orally in doses of 20.0 +/- 3.13 mg/d (mean +/- SEM) and 125.0 +/- 19.17 mg/d respectively. Pindolol reduced mean blood pressure by 11.9 mmHg; pre-ejection period index by 8.1 msec; total peripheral resistance by 3.1 mmHg min/L; and limb vascular resistance by 3.28 mmHg min 100 g/ml. Heart rate, cardiac output, plasma renin activity and urinary norepinephrine excretion rate were not altered by pindolol. Propranolol reduced mean blood pressure by 14.0 mmHg; heart rate by 9.1 beats/min; cardiac output by 0.57 L/min; limb blood flow by 1.06 ml/100 g.min; and plasma renin activity by 1.44 ng/ml/h; and increased pre-ejection period index by 8.7 msec. Total peripheral resistance, limb vascular resistance and urinary norepinephrine excretion rate were not altered by propranolol. It was concluded that: (1) the drugs, pindolol and propranolol, are equally effective as antihypertensive agents; (2) heart function and plasma renin activity are decreased by propranolol and unaltered by pindolol; (3) total peripheral resistance is decreased by pindolol and unaltered by propranolol; and (4) these findings may be explained by the intrinsic sympathomimetic activity exhibited by pindolol only.

On the electrocardiographic diagnosis of biventricular infarctions.

To diagnose posterior and anterior biventricular infarctions it is necessary to record from right and left thoracic and high abdominal unipolar leads. These supplementary leads are dependable, can be repeated as many times as needed and show the evolution from signs of myocardial injury to those of dead tissue (Q waves of 0.04 sec or more). This electrocardiographic evolution increases the diagnostic value of the electrical exploration, since the injury current can be observed also in other conditions. The diagnosis of right ventricular infarction can be established even in the presence of RBBB. Signs of a dead zone in the free right ventricular wall are more frequently observed in posterior biventricular infarctions than in anterior ones. In these cases, the signs of subepicardial injury are more accentuated in the right thoracic unipolar leads than in V3, indicating anterior right ventricular involvement. These signs are also observed in experimental studies made in animals. This electrocardiographic exploration opens a wide field for the diagnosis of myocardial infarction, particularly in biventricular involvement, including old myocardial scars, and in discarding signs of pericarditis manifested only by the upward displacement of the ST segment. A review of the medical literature concerning diagnosis of biventricular infarctions is presented.

Effects of verapamil in ventricular tachycardias. An experimental and clinical study.

To determine the effect of verapamil in ventricular tachycardias, we performed an experimental and clinical study. Experimental ventricular tachycardias (VT) were produced in dog hearts with minute aconitine crystals introduced into the periphery of a left ventricular area, damaged by intramural injection of 1.0-1.5 ml phenol. The response of these tachycardias to 0.2 mg/kg verapamil was analyzed. Verapamil was infused into the superior vena cava over 15-20 min. Leads II, aVL, intraventricular right and left unipolar records, as well as one of the superior vena cava, were registered under control conditions, in the presence of VT, and after application of verapamil. Recordings were obtained at constant intervals, waiting for the recovery of sinus rhythm (SR) and the posterior reappearance of tachycardia. Experiments were performed for 6 to 8 h under continuous infusion of Hartmann's solution. Throughout these periods, variations in systemic systolic pressure were recorded. From 75 animals submitted to this treatment, 30 (40%) recovered transiently the SR, whereas the drug exerted no antiarrhythmic effect in 19 (25%), and arterial systolic pressure fell importantly in 10 (13%) animals. In two more groups, of 15 dogs each, the VT response to verapamil was compared with the response to lidocaine and flecainide. Endovenous verapamil (5-10 mg) was administered to 10 patients, coursing with VT and having a structurally normal heart, after this arrhythmia was induced by electrical stimulation. The response to verapamil was satisfactory in nine patients (90%), in which VT originated in the septal and apical regions of the left ventricle. Verapamil seems to be effective in experimental and clinical ventricular tachycardias related to calcium-dependent potentials, in which the sustaining mechanism could either be triggered activity or reentry.

[The control of respiration in pulmonary fibrosis. The effect of O2 and CO2]. / Contrôle de la respiration dans les fibroses pulmonaires. Effets de l'O2 et du CO2.

We have studied the mode of ventilation and chemosentivity in 10 patients suffering from pulmonary fibrosis. The total lung capacity was on average 63.5 +/- 8% of the predicted. Their static compliance was 0.078 +/- 0.05 l.cm of water. The patients were studied in the prone position breathing ambient air then on hyperoxia. The response to CO2 was assessed according to the rebreathing method of Read. The results of these patients were compared with those of 11 normal subjects. The ventilation at rest was normal, with a shortened respiratory time and a Ti/Ttot ratio which was lowered. The occlusion pressure (P0.1) was very much higher than that in normal subjects. This rise was correlated with an increase in pulmonary elastance and a reduction in vital capacity. The correction of hypoxia was without effect on the respiratory parameters. In relation to normal subjects the ventilatory response to carbon dioxide in fibrotics was decreased whilst the response of the P0.1 was increased expressing central hyperactivity. In conclusion, fibrotic patients have normal ventilation in spite of an increase in inspiratory work. This normal ventilation results from hyperactivity of the respiratory centre, as in the hyperventilation induced by carbon dioxide when at rest.

[Spirometric modifications induced by bronchography. Effects of Salbutamol]. / Modifications spirométriques induites par la bronchographie. Effets du Salbutamol.

Bronchography enables an appreciation of the morphology and dynamics of the bronchi inaccessible to the fibroscope. However, this examination may aggravate pulmonary function in patients with chronic airflow obstruction. We have studied the effects of bronchography on forced expiration in order to identify and quantify possible spirometric changes. Thus spirometric tests were done at different times during the examination (V.C., F.E.V., flow-volume curves): before and after anaesthetizing the upper airways with xylocaine, after the introduction of contrast to the bronchi and finally after a Salbutamol aerosol. Spirometric values were unaffected by anaesthesia of the upper airways. On the other hand, the introduction of contrast led to a clear and constant fall in maximum expiratory flow, associated with a fall in forced vital capacity. These changes could not be reversed either after inhalation of Salbutamol or sub-cutaneous Terbutaline. The mechanisms producing the spirometric changes which we report does not seem to involve either the adrenergic system or the irritant receptors. Bronchial obstruction produced by the contrast does not alone appear to explain the changes induced by bronchography. Other mechanisms, not yet identified, probably contribute to the decrease in maximum expiratory flow.

[Rational electrovectorcardiography]. / En torno a la electrovectocardiografía racional.

The mental process of electrocardiographists to adjust the electrocardiogram's or vectorcardiogram's interpretation with the sequence of myocardial depolarization and repolarization can be accomplished in two ways. The first one is through vectorial analysis and the second concerns the analysis of unipolar morphologies. The most suitable is to follow both ways. The first procedure constitutes the classic method accepted since Einthoven's time and refers to the vectorial representation of the electrical charges of the heart. This representation approaches the electrical moment of a unique dipole, when cardiac exploration is performed at the smallest adequate distance. This allows to establish the spatial position of the instantaneous vectors, or of the mean vector, by using different leads. The study of unipolar morphologies permits to know the distribution of the mentioned charges in the conducting medium. The adjustment of the electrical charges depends on the location of the wave fronts. These charges produce potential variations in the physical sense--Gaussian type--at the epicardial surface and also at any point of the conducting medium surrounding the heart as far as the skin. This procedure requires the use of Poisson's integral, based on the principle of Helmholtz' electromotive surface. Thereafter, it is mandatory to perform another adjustment for the results of both procedures and to scrutinize the inner cellular metabolic process, which can explain the behavior of the observed electrical phenomena and suggest the adequate treatment.

[Usefulness of vector analysis of the electrocardiogram]. / Utilidad del análisis vectorial del electrocardiograma.

An electrocardiogram corresponding to an obese, hypertensive woman 52 years old, is presented. It shows a left bundle branch block of advanced degree and the AQRSF at 70 degrees. In this case, the key of the electrocardiographic diagnosis is that the second vector originated by depolarization of the lower left septal mass is oriented downward, which is unusual in the presence of left bundle branch block. This fact may be due to a marked clockwise rotation. Therefore, it is possible that right ventricle pathologic conditions be associated to those involving the left ventricle. Cardiopulmonary tests determined the existence of a chronic pulmonary emphysema. Furthermore the study of this case shows the usefulness of vectorcardiographic exploration in clinical practice.

The rational approach to the electrical exploration of the heart.

A rational approach is inevitable in any scientific activity. Such an approach is opposed not only to irrationality, at all inadmissible in scientific thinking, but also to empiric reasoning. Many years ago, Sodi Pallares introduced the rational method in the electrical exploration of the heart based on experimental findings obtained in his laboratory. This method has progressively been accepted and used with good results for diagnoses and has led to logical therapeutic inferences. To confirm the results from the logical interpretation of electrical tracings, we present some examples of its application in three fields: arrhythmias, myocardial infarction, and left ventricular hypertrophy. In the studied cases--two with tachycardia, one with a posterior infarct, and two with left ventricular hypertrophy--a very satisfactory correlation has been observed between the electrical exploration findings and those obtained through direct examination of the heart. It is desirable, and even profitable, to analyze in this way the electrical tracings to get as close as possible to reality, rejecting the stereotyped aspects of a simple routine exploration, which often induce errors and lead to some fallacious asseverations.

Characterization of textile electrodes and conductors using standardized measurement setups.

Textile electrodes and conductors are being developed and used in different monitoring scenarios, such as ECG or bioimpedance spectroscopy measurements. Compared to standard materials, conductive textile materials offer improved wearing comfort and enable long-term measurements. Unfortunately, the development and investigation of such materials often suffers from the non-reproducibility of the test scenarios. For example, the materials are generally tested on human skin which is difficult since the properties of human skin differ for each person and can change within hours. This study presents two test setups which offer reproducible measurement procedures for the systematic analysis of textile electrodes and conductors. The electrode test setup was designed with a special skin dummy which allows investigation of not only the electrical properties of textile electrodes but also the contact behavior between electrode and skin. Using both test setups, eight textile electrodes and five textile conductors were analyzed and compared.