Search results for "Quantum"

Predicting 19F NMR Chemical Shifts: A Combined Computational and Experimental Study of a Trypanosomal Oxidoreductase–Inhibitor Complex

2020

Abstract The absence of fluorine from most biomolecules renders it an excellent probe for NMR spectroscopy to monitor inhibitor–protein interactions. However, predicting the binding mode of a fluorinated ligand from a chemical shift (or vice versa) has been challenging due to the high electron density of the fluorine atom. Nonetheless, reliable 19F chemical‐shift predictions to deduce ligand‐binding modes hold great potential for in silico drug design. Herein, we present a systematic QM/MM study to predict the 19F NMR chemical shifts of a covalently bound fluorinated inhibitor to the essential oxidoreductase tryparedoxin (Tpx) from African trypanosomes, the causative agent of African sleepi…

Coulomb blockade thermometry

1996

One dimensional arrays of normal metal tunnel junctions have been found to exhibit properties which are very suitable for primary and secondary thermometry in a lithographically adjustable temperature range which extends over about two decades. The thermometer is remarkably insensitive to nonuniformities in the actual pattern and to even strong magnetic fields. We also discuss the behaviour of this device at very low temperatures where the hot electron effect due to poor electron phonon coupling ultimately takes over and at very high temperatures where the finite tunnel barrier effects appear. Short arrays, and especially single tunnel junctions show interesting deviations from the universa…

Magnetic nanoparticles between electrodes of tunnel junction: anomalous tunnel conductance

2002

Abstract Magnetic particles of microscopic size can be created in the process of Ni, Fe and Co mechanically controllable break junctions fabrication and trapped between the electrodes by magnetic dipole forces. Tunneling between the protruding nanoparticle and the sample electrode shows clear distinctions from the usual junctions: heavy deviation of the current–distance I(z) dependence from the expected exponential behavior at electrode separations z below 4.0– 4.5 A and on numerous occasions a sudden jump-like decrease of the tunnel current at z≈1.5– 2.0 A . Possible mechanisms behind observed anomalies including the short-range magnetic exchange coupling are discussed.

Probing the electronic states of high-TMR off-stoichiometric Co2MnSi thin films by hard x-ray photoelectron spectroscopy

2014

The tunnel magnetoresistance ratio (TMR) of fully epitaxial magnetic tunnel junctions with an off-stoichiometric Co${}_{2}$MnSi Heusler alloy has been shown to exhibit a systematic dependence on Mn content, reaching 1135% at 4.2 K for Co${}_{2}$Mn${}_{1.29}$Si. In this paper, we explain the behavior of the observed TMR ratio using ab initio calculations and hard x-ray photoelectron spectroscopy (HAXPES). For the Mn-deficient samples, we show that the the drop of the TMR is caused by Co antisite atoms, which impose extra states into the minority-spin band gap. On the other hand, Mn-excess composition shows nearly half-metallic behavior. This result can be intuitively understood since both Co…

Stark ionization of atoms and molecules within density functional resonance theory

2013

We show that the energetics and lifetimes of resonances of finite systems under an external electric field can be captured by Kohn–Sham density functional theory (DFT) within the formalism of uniform complex scaling. Properties of resonances are calculated self-consistently in terms of complex densities, potentials, and wave functions using adapted versions of the known algorithms from DFT. We illustrate this new formalism by calculating ionization rates using the complex-scaled local density approximation and exact exchange. We consider a variety of atoms (H, He, Li, and Be) as well as the H2 molecule. Extensions are briefly discussed.

Critical Phenomena and Diffusion in Complex Systems

2008

Training pre-service and in-service secondary school teachers: Analysis of changes in perceptions about quantum physics concepts and NoS views

2016

In this work we focus on the study of the changes in perceptions about Quantum Physics concepts and Nature of Science (NoS) Views of secondary school teachers attending three different typologies of professional development courses on Modern Physics . An open-ended questionnaire has been properly developed and administered in order to investigate Quantum Mechanics conceptual issues, NoS views and motivational aspects for all involved teachers. The same questionnaire has been submitted to the teachers both prior-to and after the courses. The analysis of teachers’ pre-instruction answers highlights that the majority of them show several difficulties on both conceptual knowledge and epistemolo…

Lecture Notes on Quantum Field Theory I

2022

El documento ha sido corregido por el Servicio de Política Linguística de la Universidad de Valencia. Material docente preparado para la asignatura Teoría Cuántica de Campos en el Master de Física Avanzada. These lectures notes are based on the material covered in the course on Quantum Field Theory I in the Master in Advanced Physics at the University of Valencia, delivered in the years 2017-2021.

Rational design and modelling of f-block molecular nanomagnets

2016

Los imanes monomoleculares o moléculas imán, por sus siglas en inglés SMMs, han suscitado una gran atención en los últimos años debido a sus extraordinarias propiedades físicas. Los cristales de este tipo de moléculas se caracterizan por presentar relajación lenta de la magnetización a baja temperatura, así como curvas de histeresis magnética. Estas moléculas se encuentran entre las entidades con comportamiento magnético más complejas, mostrando fenómenos cuánticos tales como efecto túnel en la magnetización, coherencia cuántica o interferencia cuántica. Por esto, se han postulado como candidatos prometedores para el diseño de bits cuánticos (qubits) de espín en computación cuántica. La pri…

Chiral Low-Energy Constants: Status and Prospects

2007

7 pages.-- PACS nrs.: 11.15.Pg, 12.38.-t, 12.39.Fe.-- ISI Article Identifier: 000252187200017.-- ArXiv pre-print available at: http://arxiv.org/abs/0710.4405