Coupled electron-nuclear quantum dynamics through and around a conical intersection.

In solving the time-dependent Schrödinger equation for a coupled electron-nuclear system, we study the motion of wave packets in a model which exhibits a conical intersection (CoIn) of adiabatic potential energy surfaces. Three different situations are studied. In the first case, an efficient non-adiabatic transition takes place while the wave packet passes the region of the CoIn. It is demonstrated that during these times, the nuclear probability density retains its Gaussian shape and the electronic density remains approximately constant. Second, dynamics are regarded where non-adiabatic transitions do not take place, and the nuclear dynamics follows a circle around the location of the CoIn. During this motion, the electronic density is shown to rotate. The comparison with the Born-Oppenheimer nuclear dynamics reveals the geometrical phase being associated with the circular motion. This phase is clearly revealed by an analysis of time-dependent autocorrelation functions and spectra obtained from the numerically exact and the Born-Oppenheimer calculation. The intermediate situation with a small non-adiabatic transition probability is characterized by wave-packet splitting into several fractions.

Communication: On the calculation of time-dependent electron flux within the Born-Oppenheimer approximation: A flux-flux reflection principle.

It is commonly assumed that the time-dependent electron flux calculated within the Born-Oppenheimer (BO) approximation vanishes. This is not necessarily true if the flux is directly determined from the continuity equation obeyed by the electron density. This finding is illustrated for a one-dimensional model of coupled electronic-nuclear dynamics. There, the BO flux is in perfect agreement with the one calculated from a solution of the time-dependent Schrödinger equation for the coupled motion. A reflection principle is derived where the nuclear BO flux is mapped onto the electronic flux.

Electron-nuclear wave-packet dynamics through a conical intersection.

We investigate the coupled electron-nuclear dynamics in a model system showing a conical intersection (CoIn) between two excited state potential energy surfaces. Within the model, a single electron and nucleus move in two dimensions in an external static field. It is demonstrated that the nuclear density conserves its initial Gaussian shape when directly passing the CoIn, whereas the electronic density remains approximately constant. This is in sharp contrast to the picture which evolves from an analysis within the basis of adiabatic electronic states. There, dramatic changes are seen in the dynamics of the different nuclear components of the total wave function. It is thus documented that, in the case of a highly efficient population transfer between the respective adiabatic states, neither the nuclear nor the electronic density is influenced by the existence of a CoIn. This is the case because the nuclear-electronic wave packet moves on the complete potential energy surface which changes its topology smoothly as a function of all particle coordinates.

Communication: Adiabatic and non-adiabatic electron-nuclear motion: Quantum and classical dynamics.

Using a model for coupled electronic-nuclear motion we investigate the range from negligible to strong non-adiabatic coupling. In the adiabatic case, the quantum dynamics proceeds in a single electronic state, whereas for strong coupling a complete transition between two adiabatic electronic states takes place. It is shown that in all coupling regimes the short-time wave-packet dynamics can be described using ensembles of classical trajectories in the phase space spanned by electronic and nuclear degrees of freedom. We thus provide an example which documents that the quantum concept of non-adiabatic transitions is not necessarily needed if electronic and nuclear motion is treated on the same footing.

Time-Resolved Study of 1,8-Naphthalic Anhydride and 1,4,5,8-Naphthalene-tetracarboxylic Dianhydride.

We investigate the excited electronic states of 1,8-naphthalic anhydride (NDCA) and 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA) by time- and frequency-resolved electronic spectroscopy in the gas phase using picosecond lasers and by femtosecond time-resolved transient absorption in cyclohexane. The experiments are accompanied by calculations that yield the energy of the excited singlet and triplet states as well as by surface hopping dynamics simulations and calculations of spin-orbit couplings that give insight into the photochemistry. The origin of the A (1)A1 ← X (1)A1 (ππ*) transition in isolated NDCA was found at 30 260 cm(-1), and several low-lying vibrational bands were observed. The lifetime drops sharply from 1.2 ns at the origin to around 30 ps at an excess energy of 800 cm(-1). Both internal conversion (IC) and intersystem crossing (ISC) are possible deactivation pathways as found in coupled electron-nuclear dynamics simulations. In cyclohexane solution, two time constants were observed. Deactivation of the initially excited state by ISC seems to dominate as supported by computations. For NTCDA we observed a gas phase lifetime of 16 ps upon excitation at 351 nm.

Communication: Vibrational and vibronic coherences in the two dimensional spectroscopy of coupled electron-nuclear motion.

We theoretically investigate the photon-echo spectroscopy of coupled electron-nuclear quantum dynamics. Two situations are treated. In the first case, the Born-Oppenheimer (adiabatic) approximation holds. It is then possible to interpret the two-dimensional (2D) spectra in terms of vibrational motion taking place in different electronic states. In particular, pure vibrational coherences which are related to oscillations in the time-dependent third-order polarization can be identified. This concept fails in the second case, where strong non-adiabatic coupling leads to the breakdown of the Born-Oppenheimer-approximation. Then, the 2D-spectra reveal a complicated vibronic structure and vibrational coherences cannot be disentangled from the electronic motion.

Extended quantum jump description of vibronic two-dimensional spectroscopy.

We calculate two-dimensional (2D) vibronic spectra for a model system involving two electronic molecular states. The influence of a bath is simulated using a quantum-jump approach. We use a method introduced by Makarov and Metiu [J. Chem. Phys. 111, 10126 (1999)] which includes an explicit treatment of dephasing. In this way it is possible to characterize the influence of dissipation and dephasing on the 2D-spectra, using a wave function based method. The latter scales with the number of stochastic runs and the number of system eigenstates included in the expansion of the wave-packets to be propagated with the stochastic method and provides an efficient method for the calculation of the 2D-spectra.

Situación actual de la Microcirugía en quemados. Revisión sistemática / Current status of Microsurgery in burns. Systematic review

INTRODUCCIÓN Y OBJETIVO: El empleo de transferencias de tejido libre vascularizado se ha consolidado en los últimos años dentro del tratamiento quirúrgico de los pacientes quemados. El objetivo de este trabajo es establecer conclusiones extrapolables a la práctica habitual para la optimización de resultados en el uso de colgajos libres en estos pacientes. MATERIAL Y MÉTODO: Realizamos una revisión de las bases de datos Pubmed y Scielo utilizando los términos "colgajo libre" o "microcirugía" o "transferencia tisular libre" y "quemadura" o "lesión térmica". Identificamos 1366 artículos que posteriormente revisamos para seleccionar aquellos con información relevante sobre: incidencia de colgajos libres en pacientes quemados, complicaciones, estrategias para mejorar la tasa de éxito, preparación preoperatoria, control y manejo postoperatorio. RESULTADOS: Incluimos finalmente 31 artículos. Los trabajos publicados reflejan que entre el 1.5 y el 1.8% de los pacientes con quemaduras quirúrgicas reciben cobertura mediante colgajos libres. La tasa de complicaciones mayores se eleva respecto a otros grupos de pacientes; sin embargo desciende en gran medida si la cirugía no se realiza entre los días 5 y 21 postquemadura. La realización de pruebas de imagen para la selección de vasos receptores no es indispensable. Se recomienda mantener temperatura por encima de 36 °C, normovolemia y hematocrito entre 30 y 40%, evitando la transfusión en caso de valores de hemoglobina superiores a 70 g/l. En caso de necesidad de drogas vasoactivas, serían de elección la noradrenalina o la dobutamina. CONCLUSIONES: Aunque la Microcirugía es infrecuente en el tratamiento de las quemaduras, es un recurso esencial en determinados pacientes. Esta revisión puede ser de utilidad para orientar el manejo clínico de los colgajos libres en pacientes quemados así como futuras investigaciones en este ámbito

BACKGROUND AND OBJECTIVE: The use of microvascular free tissue transplantation in burn patients has consolidated over the last years. The purpose of this article is to establish practical conclusions in order to optimize the results of free flaps in this group of patients. METHODS: A review of the PubMed and Scielo databases was performed using a combination of the search terms "free flap" or "microsurgery" or "free tissue transfer" and "burn" or "thermal injury". The search returned 1366 articles that were analyzed to include those with relevant information about: incidence of free flaps in burn patients, complications, strategies to increase success and pre-operative and post-operative management. RESULTS: Following revision 31 articles were included. Published works report an incidence of free flaps transplantations in burn patients ranging between 1.5 and 1.8%. Complication rate is high compared to other groups of patients, however, it decreases considerably if surgery is not performed between day 5 and 21 after burn injury. Imaging tests are not indispensable to select recipient vessels. It is advisable to keep body temperature over 36 °C, normovolemia and hematocrit between 30 and 40% avoiding hemoglobine values over 70 g/l. In the need of vasopressors norepinephrine and dobutamine are the drugs of choice. CONCLUSIONS: Microsurgery is uncommon but sometimes essential in burn treatment. This review may be valuable guiding not only clinical management of free flaps in burn patients but pointing towards new lines of research

Tratamiento quirúrgico del paciente gran quemado: casuística de siete años en el Hospital Universitario y Politécnico la Fe de Valencia, España / Tratamento cirúrgico do paciente grande queimado: casuística de sete anos do Hospital Universitario y Politécnico la Fe de Valência, Espanha / Surgical treatment of the major burn: seven years experience in the University and Polytechnic La Fe Hospital of Valencia, Spain

Objetivo: Caracterizar los casos atendidos en el Hospital Universitario y Politécnico la Fe de Valencia, España, en el transcurso de 7 años de uso de un protocolo quirúrgico para pacientes con quemaduras de más del 50% de superfície corporal quemada (SCQ). Métodos: Se ha realizado un análisis descriptivo de los pacientes con quemaduras mayores al 50% de SCQ, tratados entre enero de 2011 y enero de 2017, en la Unidad de Quemados del Hospital La Fe (Valencia, España). Todos los pacientes fueron tratados de acuerdo al protocolo quirúrgico establecido en nuestra unidad para el paciente gran quemado. Resultados: Se trataron 35 pacientes, 25 varones y 10 mujeres, con edad media de 51,3±16,2 años. La llama fue el agente lesional más frecuente. La SC media afecta por quemadura fue 66,9±13,5%. La tasa de mortalidad (TM) neta fue del 55%, siendo el shock por quemadura la causa de muerte predominante en las primeras 48h y la sepsis tras las 48h. Conclusiones: El paciente gran quemado supone un reto terapéutico donde un enfoque multidisciplinar es determinante para su adecuada evolución. En nuestra serie, la estandarización del tratamiento quirúrgico mediante un protocolo ha permitido un adecuado manejo de los pacientes con una TM inferior a la estimada y comparable a la informada en la literatura.

Objetivo: Caracterizar os casos atendidos no Hospital Universitário y Politécnico la Fe de Valencia, Espanha, no transcurso de sete anos de uso de um protocolo cirúrgico para pacientes com queimaduras de superfície corporal queimada (SCQ) superior a 50%. Método: foi realizada análises descritiva dos casos de pacientes com SCQ superior a 50%, tratados entre janeiro de e janeiro de 2017, na Unidade de Queimados do Hospital La Fe (Valência, Espanha). Todos os pacientes foram tratados de acordo com o protocolo cirúrgico estabelecido na unidade para o paciente grande queimado. Resultados: Foram tratados 35 pacientes, 25 homens e 10 mulheres, com idade média de 51,3±16,2 anos. A chama foi o agente causador mais frequente. A SCQ media foi de 66,9±13,5%. A taxa de mortalidade (TM) foi de 55%, sendo o choque por queimadura a causa de morte predominante nas primeiras 48h e a sepses após 48h. Conclusões: O paciente grande queimado representa um desafio terapêutico no qual o foco multidisciplinar é determinante para sua adequada evolução. Nos casos estudados, a padronização do tratamento cirúrgico por meio de um protocolo permitiu um adequado manejo dos pacientes com una TM inferior à estimada e comparável à informada na literatura.

Objective: To characterize the cases treated at the University and Polytechnic la Fe Hospital in Valencia, Spain, over the course of 7 years with the use of a surgical protocol for patients with burns greater than 50% of total body surface area (TBSA). Methods: From January 2011 to January 2017, 35 patients with burns greater than 50% TBSA were treated in our Burn Unit. All patients were treated according to our major burn surgical protocol. Results: A total of 35 patients were treated, 25 men and 10 women, with a mean age of 51.3±16.2 years. Flame burn was the most common etiology. The mean TBSA affected was 66.9±13.5%. The mortality rate was 55%, with burn shock being the main cause of death in the first 48 hours. Conclusion: Patients with burns greater than 50% TBSA suppose a therapeutic challenge where a multidisciplinary approach is essential for its adequate evolution. In our series, the treatment standardization with a protocol has allowed an adequate management of the patients with a mortality rate similar to the literature report and lower than our estimated rate.