Levoatriocardinal vein in D-transposition of the great arteries.

The levoatriocardinal vein is the embryological remnant of the connection between the pulmonary and systemic venous systems. It is a rare lesion that usually occurs in the presence of left-sided obstruction, developing as a pathway for decompression of the pulmonary veins. We report the first case of a levoatriocardinal vein in a patient with D-transposition of the great arteries.

Regarding the validity of the time-dependent Kohn-Sham approach for electron-nuclear dynamics via trajectory surface hopping.

The implementation of fewest-switches surface-hopping (FSSH) within time-dependent Kohn-Sham (TDKS) theory [Phys. Rev. Lett. 95, 163001 (2005)] has allowed us to study successfully excited state dynamics involving many electronic states in a variety of molecular and nanoscale systems, including chromophore-semiconductor interfaces, semiconductor and metallic quantum dots, carbon nanotubes and graphene nanoribbons, etc. At the same time, a concern has been raised that the KS orbital basis used in the calculation provides only approximate potential energy surfaces [J. Chem. Phys. 125, 014110 (2006)]. While this approximation does exist in our method, we show here that FSSH-TDKS is a viable option for computationally efficient calculations in large systems with straightforward excited state dynamics. We demonstrate that the potential energy surfaces and nonadiabatic transition probabilities obtained within the TDKS and linear response (LR) time-dependent density functional theories (TDDFT) agree semiquantitatively for three different systems, including an organic chromophore ligating a transition metal, a quantum dot, and a small molecule. Further, in the latter case the FSSH-TDKS procedure generates results that are in line with FSSH implemented within LR-TDDFT. The FSSH-TDKS approach is successful for several reasons. First, single-particle KS excitations often give a good representation of LR excitations. In this regard, DFT compares favorably with the Hartree-Fock theory, for which LR excitations are typically combinations of multiple single-particle excitations. Second, the majority of the FSSH-TDKS applications have been performed with large systems involving simple excitations types. Excitation of a single electron in such systems creates a relatively small perturbation to the total electron density summed over all electrons, and it has a small effect on the nuclear dynamics compared, for instance, with thermal nuclear fluctuations. In such cases an additional, classical-path approximation can be made. Third, typical observables measured in time-resolved experiments involve averaging over many initial conditions. Such averaging tends to cancel out random errors that may be encountered in individual simulated trajectories. Finally, if the flow of energy between electronic and nuclear subsystems is insignificant, the ad hoc FSSH procedure is not required, and a straightforward mean-field, Ehrenfest approach is sufficient. Then, the KS representation provides rigorously a convenient and efficient basis for numerically solving the TDDFT equations of motion.

Cardiac strangulation from epicardial pacemaker: early recognition and prevention.

Cardiac strangulation from epicardial pacemaker leads is a rare event that can be difficult to recognise and can cause serious complications such as cardiac failure or death. We describe a 3-year-old girl who received an epicardial pacing system as a neonate for complete congenital cardiac block and developed cardiac strangulation from the leads. The clinical presentation modes are reviewed and technical aspects for lead and generator positioning are discussed.

Trametinib therapy for children with neurofibromatosis type 1 and life-threatening plexiform neurofibroma or treatment-refractory low-grade glioma.

PURPOSE: To describe a series of children with extensive PNF or treatment refractory PLGG treated on a compassionate basis with trametinib. METHODS: We report on six patients with NF-1 treated with trametinib on a compassionate basis at British Columbia Children's Hospital since 2017. Data were collected retrospectively from the patient record. RAPNO and volumetric criteria were used to evaluate the response of intracranial and extracranial lesions, respectively. RESULTS: Subjects were 21 months to 14 years old at the time of initiation of trametinib therapy and 3/6 subjects are male. Duration of therapy was 4-28 months at the time of this report. All patients had partial response or were stable on analysis. Two patients with life-threatening PNF had a partial radiographic response in tandem with significant clinical improvement and developmental catch up. One subject discontinued therapy after 6 months due to paronychia and inadequate response. The most common adverse effect (AE) was grade 1-2 paronychia or dermatitis in 5/6 patients. There were no grade 3 or 4 AEs. At the time of this report, five patients remain on therapy. CONCLUSION: Trametinib is an effective therapy for advanced PNF and refractory PLGG in patients with NF-1 and is well tolerated in children. Further data and clinical trials are required to assess tolerance, efficacy and durability of response, and length of treatment required in such patients.

Ab initio nonadiabatic molecular dynamics of wet-electrons on the TiO(2) surface.

The electron transfer (ET) dynamics of wet-electrons on a TiO(2) surface is investigated using state-of-the-art ab initio nonadiabatic (NA) molecular dynamics (MD). The simulations directly mimic the time-resolved experiments [Science 2005, 308, 1154] and reveal the nature of ET in the wet-electron system. Focusing on the partially hydroxylated TiO(2) surface with 1-monolayer water coverage, and including electronic evolution, phonon motions, and electron-phonon coupling, the simulations indicate that the ET is sub-10 fs, in agreement with the experiment. Despite the large role played by low frequency vibrational modes, the ET is fast due to the strong coupling between the TiO(2) surface and water. The average ET for the system has equal contributions from the adiabatic and NA mechanisms, even though a very broad range of individual ET events is seen in the simulated ensemble. Thermal phonon motions induce a large fluctuation of the wet-electron state energy, generate frequent crossings of the donor and acceptor states, and drive the adiabatic mechanism. The rapid phonon-assisted NA tunneling from the wet-electron state to the TiO(2) surface is facilitated by the strong water-TiO(2) electronic interaction. The motions of molecular water have a greater effect on the ET dynamics than the hydroxyl vibrations. The former contribute to both the wet-electron state energy and the water-TiO(2) electronic coupling, while the latter changes only the energy and not the coupling. Delocalized over both water and TiO(2), wet-electrons are supported by a new type of state that is created at the interface due to the strong water-TiO(2) interaction and that cannot exist separately in either material. Similar states are present in a number of other systems with strong interfacial coupling, including certain dye-sensitized semiconductors and metal-liquid interfaces. The ET dynamics involving such interfacial states share many universal features, such as an ultrashort time scale and weak-dependence on temperature, surface defects, and other system details.

Imaging of a carotid aneurysm in two patients following extracorporeal membrane oxygenation therapy.

Following extracorporeal membrane oxygenation (ECMO), two patients subsequently developed carotid aneurysms at the site of cannulation. Given the invasive nature of ECMO, vascular ultrasound and/or computerized tomographic imaging should be considered to rule out cannulation-site complications post-ECMO.

Temperature independence of the photoinduced electron injection in dye-sensitized TiO2 rationalized by ab initio time-domain density functional theory.

Time-domain density functional theory simulations resolve the apparent conflict between the central role that thermal fluctuations play in the photoinduced chromophore-TiO 2 electron transfer (ET) in dye-sensitized semiconductor solar cells [J. Am. Chem. Soc. 2005, 127, 18234; Isr. J. Chem. 2003, 42, 213] and the temperature independence of the ET rate [e.g., Annu. Rev. Phys. Chem. 2005, 56, 119]. The study, performed on the alizarin-TiO 2 interface at a range of temperatures, demonstrates that the ET dynamics, both adiabatic and nonadiabatic (NA), are dependent on the temperature, but only slightly. The adiabatic rate increases with temperature because a fluctuation toward a transition state (TS) becomes more likely. A classical TS theory analysis of the adiabatic ET gives a Gibbs energy of activation that is equal to k B T at approximately 50 K, and a prefactor that corresponds to multiple ET pathways. The NA rate increases as a result of changes in the distribution of photoexcited-state energies and, hence, in the density of accessible TiO 2 levels, as expressed in the Fermi Golden Rule. In the system under investigation, the photoexcited state lies close to the bottom of the TiO 2 conduction band (CB), and the chromophore-semiconductor coupling is strong, resulting in primarily adiabatic ET. By extrapolating the simulation results to chromophores with excited states deeper inside the CB and weaker donor-acceptor coupling, we conclude that the interfacial ET is essentially independent of temperature, even though thermal ionic motions create a widespread of initial conditions, determine the distribution of injected electron energy, and drive both adiabatic and NA ET.

Electronic structure and spectra of catechol and alizarin in the gas phase and attached to titanium.

Ab initio electronic structure calculations elucidate the dramatic differences observed in the electronic spectra of the catechol and alizarin molecules upon binding to titanium. Catechol and alizarin are similar chromophores with analogous electronic spectra in the free state. Binding alizarin to titanium red-shifts the spectrum. The binding of catechol to titanium produces a new optically active transition, at the same time preserving the features of the free catechol spectrum. By examining the details of the calculations, we can rationalize the spectral differences in the catechol and alizarin systems by the positioning of the catechol and alizarin pi molecular orbitals relative to the conduction band of TiO(2).

Nonadiabatic molecular dynamics study of electron transfer from alizarin to the hydrated Ti4+ ion.

Ab initio real-time nonadiabatic (NA) molecular dynamics (MD) simulations are performed in order to investigate the photoinduced electron transfer (ET) from alizarin to the hydrated Ti4+ ion and compare it with the ET into bulk TiO2 that forms the basis of the Grätzel type solar cell. The experimental data and electronic structure calculations indicate that the photoexcitation spectra of alizarin attached to either bulk TiO2 or the Ti4+ ion in solution are very similar. In contrast, the NAMD simulations at ambient temperature predict marked differences between the ET dynamics that follow the photoexcitation in the two systems. The simulation of ET between alizarin and the TiO2 surface shows predominantly adiabatic transfer that occurs within 8 fs (Duncan et al. J. Am. Chem. Soc. 2005, 127, 7941), in agreement with the time-resolved experimental data. The simulation of alizarin attached to the hydrated Ti4+ ion reported presently predicts that the ET does occur, but on a slower 30 fs time scale, with a substantially reduced amplitude and by a predominantly NA mechanism. The differences are attributed to the disparity in the acceptor states of bulk TiO2 and the Ti4+ ion in solution. It is shown that the predicted alizarin-Ti4+ ET dynamics can be verified experimentally.

Cardiac strangulation following epicardial pacemaker implantation: a rare pediatric complication.

OBJECTIVES: The aim of our study was 2-fold: to determine the incidence of cardiac strangulation (CS) and to develop a clinical pathway to aid in the diagnosis and prognosis of CS. In <2 years, 2 cases of CS occurred in our institution, which caused much alarm and led to the study's objectives. METHODS: All patients who underwent implantation of an epicardial pacemaker from January 1992 to March 2012 were included. There were no exclusion criteria. Health records were used to locate all subjects and gather all retrospective data. Prospectively, subjects without a chest radiograph from the previous 2 years were approached for imaging. RESULTS: This study included 86 patients retrospectively, and 84 patients prospectively. There was a 2.3% incidence, and a 1.2% mortality, related to CS. A pattern of posterior looping of the ventricular lead was seen in radiographs of both CS-diagnosed patients. Five variables were significantly associated with an outcome of CS (P = .0153). CONCLUSIONS: Our data indicate that the 2 cases of CS were not caused by a lack of follow-up but by a lack of consistent imaging for diagnosis. This conclusion is supported by the 8 cases of CS found in the English-language literature. If the patient is age ≤6 months at the time of implantation, particular attention should be given to the placement of leads and follow-up.

Diagnosis and outcome of dextrocardia diagnosed in the fetus.

A retrospective review of 5,539 fetal echocardiograms over a 22-year period revealed 85 cases of dextrocardia. In primary dextrocardia (46 cases), the incidence of situs solitus, inversus, and ambiguous, was similar and associated with a high incidence of complex cardiac malformations in situs solitus and situs ambiguous. Secondary dextrocardia (39 cases) was due to intrathoracic displacement and, when caused by diaphragmatic hernia, was associated with cardiac malformations in 31% of cases. Even in complex cases, fetal echocardiography was highly accurate; therefore, specific counseling can be given to parents.

Clipped tube fenestration after extracardiac Fontan allows for simple transcatheter coil occlusion.

BACKGROUND: Expensive devices are increasingly used to close a patent fenestration after a modified Fontan operation. We report our 5-year institutional experience of clipped tube fenestration after extracardiac Fontan operation, which allows for simple transcatheter coil occlusion. METHODS: We retrospectively reviewed 30 children, median age of 4.0 years (range, 2.4 to 8.8 years) who underwent extracardiac Fontan operation between May 1996 and May 2001, and were fenestrated using a 4- to 8-mm diameter clipped tube graft. RESULTS: Ten children had a patent fenestration occluded by transcatheter placement of 15 detachable coils (5- to 8-mm diameter). Aortic oxygen saturations increased on average by 5.5% (2% to 14%) and mean pressures in the Fontan circuit by 2.5 mm Hg (0 to 3 mm Hg). Four had immediate complete occlusion angiographically and 6 had trivial residual shunt, but complete occlusion by echocardiography at follow-up. There have been no immediate complications, late coil embolizations, thromboembolic events, or documented hemolysis within a follow-up after coil implantation of 1.7 years (0.4 to 4.5 years). Spontaneous fenestration closure was documented in 8 patients at cardiac catheterization and 9 patients by echocardiography with consistent improvement in resting transcutaneous oxygen saturation. Two children with a patent fenestration have been considered inappropriate for closure, and there was one early surgical death. There have been no complications related to the tube fenestration modification within a follow-up postoperation of 2.6 years (0.1 to 5.5 years). CONCLUSIONS: Clipped tube fenestration after extracardiac Fontan operation is a useful surgical modification that allows for simple transcatheter coil occlusion.

Synthesis, Structure, and Properties of a Model for Galactose Oxidase.

An active-site analog of the radical copper enzyme galactose oxidase has been prepared from a synthetic tripod chelate ((2-pyridylmethyl)[(2-hydroxy-3,5-dimethylphenyl)methyl][(2-hydroxy-5-methyl-3-(methylthio)phenyl)methyl]amine, duncamine (dnc)) that binds a single Cu(II) ion through phenolate, thioether-substituted phenolate, and pyridylamine arms. The Cu complex crystallizes as a dinucleated dimer bridged by phenolate oxygens, and the structure has been determined by X-ray crystallography. Addition of pyridine (or other coordinating bases) dissociates the complex into a monomeric derivative that has been characterized spectroscopically (optical absorption and EPR) and electrochemically. The model provides insight into the properties of a mutant form of galactose oxidase which retains the same copper ligand complement as the wild type protein but lacks catalytic activity.

Echocardiographic tools for pacemaker optimization of ventricular function in an infant following surgical repair for double outlet right ventricle.

A case of an infant, following surgical repair for double outlet right ventricle, who developed low cardiac output syndrome and complete heart block that required insertion of a pacemaker is presented. The infant underwent optimization of his ventricular function to determine whether pacing the right ventricle or left ventricle or both would improve cardiac function. Using standard two-dimensional echocardiography and Doppler imaging, tissue synchronization imaging, and two-dimensional speckle-tracking strain analysis, improvement in cardiac output and function was demonstrated. The present case highlights the usefulness of newer echocardiographic techniques in pacemaker optimization in the acute postoperative setting.

The challenge of diagnosing arrhythmogenic right ventricular cardiomyopathy in the young.

We report two cases of arrhythmogenic right ventricular cardiomyopathy (ARVC) in the pediatric age group. In both cases, the diagnosis was considered and pursued but would not be made utilizing Task Force Criteria. The diagnosis was made based on the morphology of a single beat during exercise testing. We illustrate the difficulty of diagnosing ARVC in the young even with a heightened index of suspicion.

Dynamics of the photoexcited electron at the chromophore-semiconductor interface.

Electron dynamics at molecular-bulk interfaces play a central role in a number of different fields, including molecular electronics and sensitized semiconductor solar cells. Describing electron behavior in these systems is difficult because it requires a union between disparate interface components, molecules and solid-state materials, that are studied by two different communities, chemists and physicists, respectively. This Account describes recent theoretical efforts to bridge that gap by analyzing systems that serve as good general models of the interfacial electron dynamics. The particular systems that we examine, dyes attached to TiO2, are especially important since they represent the key component of dye-sensitized semiconductor solar cells, or Gratzel cells. Gratzel cells offer a cheap, efficient alternative to traditional Si-based solar cells. The chromophore-TiO2 interface is a remarkably good target for theorists because it has already been the subject of many excellent experimental investigations. The electron dynamics in the chromophore-semiconductor systems are surprisingly rich and involve a great variety of processes as illustrated in the scheme above. The exact rates and branching ratios depend on the system details, including the semiconductor type, its bulk phase, and its exposed surface, the chromophore type, the presence or absence of a chromophore-semiconductor bridge, the alignment of the chromophore and semiconductor energy levels, the surface termination, the active vibrational modes, the solvent, the type of electrolyte, the presence of surface defects, etc. Still, the general principles governing the electron dynamics at the bulk-semiconductor interface can be understood and formulated by considering a few specific examples. The ultrafast time scale of the electronic and vibrational processes at the molecule-bulk interface make it difficult to invoke traditional theories. Instead, we perform explicit time-domain simulations with an atomistic representation of the interface. This approach most directly mimics the time-resolved experimental data and provides a detailed description of the processes as they occur in real time. The simulations described in this Account take into consideration the chemical structure of the system, determine the role of the vibrational motion and non-adiabatic coupling, uncover a vast variety of electron dynamics scenarios, and ultimately, allow us to establish the basic criteria that provide an understanding of this complicated physical process. The insights attained in the theoretical studies let us formulate a number of practical suggestions for improving the properties of the dye-sensitized semiconductor solar cell and for controlling the electron transfer across molecular-bulk interfaces.

Theoretical studies of photoinduced electron transfer in dye-sensitized TiO2.

This review describes recent research into the properties of the chromophore-TiO2 interface that forms the basis for photoinduced charge separation in dye-sensitized semiconductor solar cells. It focuses particularly on an atomistic picture of the electron-injection dynamics. The interface offers an excellent case study, pertinent as well to a variety of other photovoltaic systems, photo- and electrochemistry, molecular electronics, analytical detection, photography, and quantum confinement devices. The differences between chemists' and physicists' models for describing molecules and bulk materials, respectively, create challenges for the characterization of interfaces that include both of these components. We give an overall picture of the interface by starting with a description of the properties of the chromophores and semiconductor separately, and then by discussing the coupled system, including the chromophore-semiconductor binding, electronic structure, and electron-injection dynamics. Explicit time-dependent modeling is particularly valuable for an understanding of the ultrafast electron injection because it shows a variety of individual injection events with well-defined dynamical features that cannot be made apparent by an average reaction-rate description.

Time-domain ab initio study of charge relaxation and recombination in dye-sensitized TiO2.

In order to investigate the electron dynamics at the alizarin/I2-/TiO2 interface this study uses a novel state-of-the-art quantum-classical approach that combines time-dependent density functional theory with surface hopping in the Kohn-Sham basis. Representing the dye-sensitized semiconductor Grätzel cell with the I-/I3- mediator, the system addresses the problems of an organic/inorganic, molecule/bulk interface that are commonly encountered in molecular electronics, photovoltaics, and photoelectrochemistry. The processes studied include the relaxation of the injected electron inside the TiO2 conduction band (CB), the back electron transfer (ET) from TiO2 to alizarin, the ET from the surface to the electrolyte, and the regeneration of the neutral chromophore by ET from the electrolyte to alizarin. Developing a theoretical understanding of these processes is crucial for improving solar cell design and optimizing photovoltaic current and voltage. The simulations carried out for the entire system that contains many electronic states reproduce the experimental time scales and provide detailed insights into the ET dynamics. In particular, they demonstrate the differences between the optimized geometric and electronic structure of the system at 0 K and the experimentally relevant structure at ambient temperature. The relaxation of the injected electron inside the TiO2 CB, which affects the solar cell voltage, is shown to occur on a 100 fs time scale and occurs simultaneously with the electron delocalization into the semiconductor bulk. The transfer of the electron trapped at the surface to the ground state of alizarin proceeds on a 1 ps time scale and is facilitated by vibrational modes localized on alizarin. If the electrolyte mediator is capable of approaching the semiconductor surface, it can form a stable complex and short-circuit the cell by accepting the photoexcited electron on a subpicosecond time scale. The ET from TiO2 to both alizarin and the electrolyte diminishes the solar cell current. Finally, the simulations show that the electrolyte can efficiently regenerate the neutral chromophore. This is true even though the two species do not form a chemical bond and, therefore, the electronic coupling between them is weaker than in the TiO2-chromophore and TiO2-electrolyte donor-acceptor pairs. The chromophore-electrolyte coupling can occur both directly through space and indirectly through bonding to the semiconductor surface. The ET events involving the electrolyte are promoted primarily by the electrolyte vibrational modes.