Coercive field of ultrathin PbZr0.52Ti0.48O3 epitaxial films

The polarization reversal in single-crystalline ferroelectric films has been investigated experimentally and theoretically. The hysteresis loops were measured for Pb(Zr0.52Ti0.48)O-3 films with thicknesses ranging from 8 to 250 nm. These films were grown epitaxially on SrRuO3 bottom electrodes deposited on SrTiO3 substrates. The measurements using Pt top electrodes showed that the coercive field E-c increases drastically as the film becomes thinner, reaching values as high as E(c)approximate to1200 kV/cm. To understand this observation, we calculated the thermodynamic coercive field E-th of a ferroelectric film as a function of the misfit strain S-m in an epitaxial system and showed that E-th strongly depends on S-m. However, the coercive field of ultrathin films, when measured at high frequencies, exceeds the calculated thermodynamic limit. Since this is impossible for an intrinsic coercive field E-c, we conclude that measurements give an apparent E-c rather than the intrinsic one. An enormous increase of apparent coercive field in ultrathin films may be explained by the presence of a conductive nonferroelectric interface layer. (C) 2003 American Institute of Physics

Fabrication of 2D based pn junctions with improved performance by selective laser annealing

There is a growing body of research on transistors based on nanomaterials such as 2D transition metal dichalcogenides (TMDs) (WS2, MoS2, etc.) and carbon nanotubes (CNTs). Here we co-deposited MoS2 and WS2 as PN junctions. The deposition could be performed on a PCB (printed circuit board) with Cu electrodes. The current-voltage characteristics were obtained using an Arduino board. The effect of laser irradiation could be investigated by studying the IV curves and light sensitivity for the same kind of devices in which one of the Cu electrodes was modified by a laser. The IV curves from the devices with and without laser treatment could be compared to quantify the changes in performance

The constant-velocity highly collimated outflows of the planetary nebula He 2-90

We present high-dispersion echelle spectroscopic observations and a narrow-band [N II] image of the remarkable jet-like features of He 2-90. They are detected in the echelle spectra in the H-alpha and [N II] lines but not in other nebular lines. The [N II]/H-alpha ratio is uniformly high, ~1. The observed kinematics reveals bipolar collimated outflows in the jet-like features and shows that the southeast (northwest) component expands towards (away from) the observer at a remarkably constant line-of-sight velocity, 26.0+-0.5 km/s. The observed expansion velocity and the opening angle of the jet-like features are used to estimate an inclination angle of ~5 degrees with respect to the sky plane and a space expansion velocity of ~290 km/s. The spectrum of the bright central nebula reveals a profusion of Fe lines and extended wings of the H-alpha line, similar to those seen in symbiotic stars and some young planetary nebulae that are presumed to host a mass-exchanging binary system. If this is the case for He 2-90, the constant velocity and direction of the jets require a very stable dynamic system against precession and warping.Comment: 8 pages (emulate ApJ), 5 figure, 1 tabl

Development of Thiophene Compounds as Potent Chemotherapies for the Treatment of Cutaneous Leishmaniasis Caused by Leishmania major

Leishmania major (L. major) is a protozoan parasite that causes cutaneous leishmaniasis. About 12 million people are currently infected with an annual incidence of 1.3 million cases. The purpose of this study was to synthesize a small library of novel thiophene derivatives, and evaluate its parasitic activity, and potential mechanism of action (MOA). We developed a structure–activity relationship (SAR) study of the thiophene molecule 5A. Overall, eight thiophene derivatives of 5A were synthesized and purified by silica gel column chromatography. Of these eight analogs, the molecule 5D showed the highest in vitro activity against Leishmania major promastigotes (EC50 0.09 ± 0.02 µM), with an inhibition of the proliferation of intracellular amastigotes higher than 75% at only 0.63 µM and an excellent selective index. Moreover, the effect of 5D on L. major promastigotes was associated with generation of reactive oxygen species (ROS), and in silico docking studies suggested that 5D may play a role in inhibiting trypanothione reductase. In summary, the combined SAR study and the in vitro evaluation of 5A derivatives allowed the identification of the novel molecule 5D, which exhibited potent in vitro anti-leishmanial activity resulting in ROS production leading to cell death with no significant cytotoxicity towards mammalian cells

High Levels of Academic Procrastination do not Influence the Academic Performance of Nursing Students during Internship

Introducción: La procrastinación académica (AP) es un fenómeno global que afecta significativamente a los estudiantes universitarios, influyendo potencialmente en su rendimiento académico y bienestar mental. Objetivo: Investigar la relación entre los niveles de procrastinación académica y el rendimiento académico de estudiantes de enfermería durante su pasantía en el Perú. Métodos: Se realizó un estudio transversal, involucrando a 112 pasantes de enfermería, de 18 años y más, matriculados en el semestre 2019-I. Los participantes completaron la Escala de Procrastinación Académica (EPA), una escala tipo Likert que consta de 12 ítems, que midió dos dimensiones: autorregulación académica (9 ítems) y procrastinación de actividades (3 ítems). Se utilizó una puntuación umbral de 36 puntos para identificar altos niveles de procrastinación académica. El rendimiento académico se evaluó en una escala de 0 a 10 (reprobado), 11 a 14 (aprobado), 15 a 17 (notable) y 18 a 20 (sobresaliente). Resultados: La edad media de los participantes fue de 29 años, siendo el 88,4% mujeres. El estudio encontró que el 72,3% de los estudiantes de enfermería exhibieron niveles más altos de AP, particularmente entre las mujeres (62,5%) y los estudiantes más jóvenes (59,8%). A escala global, el 70,3% de los estudiantes obtuvo una calificación notable, y el 51,8% de estos estudiantes también exhibió un alto nivel de AP. Sin embargo, no se encontraron diferencias significativas en el rendimiento académico según el nivel de AP (p=0,918). Conclusión: Aunque los estudiantes de enfermería mostraron un mayor nivel de AP, este estudio no encontró una asociación significativa entre la procrastinación académica y el rendimiento académico durante el período de prácticas. Sin embargo, es crucial monitorear la AP en estudiantes de enfermería a lo largo de sus estudios para identificar factores potenciales que puedan contribuir a su impacto y desarrollar estrategias para mitigar sus efectos