Effect of Underdamped Vibration on Excitation Energy Transfer: Direct Comparison between Two Different Partitioning Schemes.

We study excitation energy transfer (EET) in a model three-site system with a mixed-quantum classical dynamics method, by focusing on the effect of an underdamped vibration. We construct two types of models where the underdamped vibration mode is included either in the quantum subsystem or in the classical bath. We show that the two models yield practically equivalent results despite the different depictions of the vibration. In particular, both models consistently demonstrate accelerations of population relaxation induced by quasi-resonant vibration. This indicates that intricate features of EET dynamics that have been frequently ascribed to the quantal nature of vibrations, such as vibronic mixing, can be successfully reproduced by using physically equivalent but classically described bath modes. The mechanism behind the observed quantum-classical correspondence is proposed. We also systematically examine how the structure of the spectating continuum phonon modes affects the vibronic resonance and observe that phonon modes with different time scales influence the resonance in different manners.

A proton transfer network that generates deprotonated tyrosine is a key to producing reactive oxygen species in phototoxic KillerRed protein.

KillerRed is the first genetically encoded photosensitizer that can induce cytotoxicity upon light exposure. Nevertheless, its phototoxicity is still lower than that of chemical photosensitizers, and the efforts to further develop KillerRed variants with enhanced phototoxicity have been impeded because the mechanism by which it generates cytotoxic reactive oxygen species (ROS) has remained elusive. To shed light on this issue, we employ quantum mechanics/molecular mechanics (QM/MM) modeling with statistical free energy analysis to examine the photo-induced electron transfer reaction occurring in KillerRed. We identify a deprotonated tyrosine residue (Tyr110) as an electron donor and further show that adjacent glutamate and serine residues play essential roles in deprotonating Tyr110. We also show that water mediation is important in the proton transfer and that protein fluctuations importantly govern the fate of the excited system. We provide clues about why KillerRed can only exhibit a low ROS yield and suggest future directions of mutagenesis toward an enhanced phototoxicity.

Two-component multi-configurational second-order perturbation theory with Kramers restricted complete active space self-consistent field reference function and spin-orbit relativistic effective core potential.

We report the formulation and implementation of KRCASPT2, a two-component multi-configurational second-order perturbation theory based on Kramers restricted complete active space self-consistent field (KRCASSCF) reference function, in the framework of the spin-orbit relativistic effective core potential. The zeroth-order Hamiltonian is defined as the sum of nondiagonal one-electron operators with generalized two-component Fock matrix elements as scalar factors. The Kramers symmetry within the zeroth-order Hamiltonian is maintained via the use of a state-averaged density, allowing a consistent treatment of degenerate states. The explicit expressions are derived for the matrix elements of the zeroth-order Hamiltonian as well as for the perturbation vector. The use of a fully variational reference function and nondiagonal operators in relativistic multi-configurational perturbation theory is reported for the first time. A series of initial calculations are performed on the ionization potential and excitation energies of the atoms of the 6p-block; the results display a significant improvement over those from KRCASSCF, showing a closer agreement with experimental results. Accurate atomic properties of the superheavy elements of the 7p-block are also presented, and the electronic structures of the low-lying excited states are compared with those of their lighter homologues.

Two-component Kramers restricted complete active space self-consistent field method with relativistic effective core potential revisited: theory, implementation, and applications to spin-orbit splitting of lower p-block atoms.

The relativistic two-component complete active space self-consistent field theory in Kramers restricted formalism (KRCASSCF) through the framework of the spin-orbit relativistic effective core potential is implemented into the KPACK package. This paper continues the development previously reported [Y. S. Kim and Y. S. Lee, J. Chem. Phys. 119, 12169 (2003)] and extends the theory by means of adding time-reversal symmetry into the relevant expressions so as to complete the course of theoretical development. We retained the usage of elementary spinor excitation operator for defining the spinor rotation operator and derived the gradient and Hessian in simpler forms than previously found. To eliminate redundant computation resulting from repeating sums in the derivatives, a suitable decomposition method is proposed, which also facilitates the implementation. The two-step near second-order approach is employed for convergence. The present implementation is applicable for both closed- and open-shell systems and is used to calculate the atoms of lower p-block. The results for 5p and 6p are in good agreement with the experiments, and those for 7p are comparable to multi-reference configuration interaction results, showing that KRCASSCF is a versatile tool for the relativistic electronic structure calculation of molecules containing moderate-weight through superheavy elements.

Color Stable Deep Blue Multi-Resonance Organic Emitters with Narrow Emission and High Efficiency.

The development of highly efficient and deep blue emitters satisfying the color specification of the commercial products has been a challenging hurdle in the organic light-emitting diodes (OLEDs). Here, deep blue OLEDs with a narrow emission spectrum with good color stability and spin-vibronic coupling assisted thermally activated delayed fluorescence are reported using a novel multi-resonance (MR) emitter built on a pure organic-based molecular platform of fused indolo[3,2,1-jk]carbazole structure. Two emitters derived from 2,5,11,14-tetrakis(1,1-dimethylethyl)indolo[3,2,1-jk]indolo[1',2',3':1,7]indolo[3,2-b]carbazole (tBisICz) core are synthesized as the MR type thermally activated delayed fluorescence emitters realizing a very narrow emission spectrum with a full-width-at-half-maximum (FWHM) of 16 nm with suppressed broadening at high doping concentration. The tBisICz core is substituted with a diphenylamine or 9-phenylcarbazole blocking group to manage the intermolecular interaction for high efficiency and narrow emission. The deep blue OLEDs achieve high external quantum efficiency (EQE) of 24.9%, small FWHM of 19 nm, and deep blue color coordinate of (0.16, 0.04) with good color stability with increase in doping concentration. To the authors' knowledge, the EQE in this work is one of the highest values reported for the deep blue OLEDs that achieve the BT.2020 standard.

Multiple-Resonance Extension and Spin-Vibronic-Coupling-Based Narrowband Blue Organic Fluorescence Emitters with Over 30% Quantum Efficiency.

Achieving narrow-bandwidth emission and high external quantum efficiency (EQE) simultaneously is a challenge for next-generation blue-emitting organic light-emitting diodes (OLEDs). In this study, novel multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitters are developed by fusing an indolocarbazole unit with two carbazole skeletons using para-oriented nitrogen atoms. The resulting rigid and planar π-system without electron-accepting atoms exhibits pure blue photoluminescence at 470 nm, reaching a 100% quantum yield with a full-width-at-half-maximum (FWHM) of 25 nm. Higher-level quantum chemistry calculations confirm an MR effect within the extended π-conjugation and an enhanced triplet-to-singlet crossover (104 s-1 ) through a reduced energy gap (ΔEST ) coupled with large spin-vibronic coupling mediated by low-lying triplet excited states. An OLED fabricated using the MR-TADF emitter with CIE color coordinates of (0.12, 0.16) exhibits a record high EQE of 30.9% and a small FWHM of 23 nm. With further optimization of the device structure, a high EQE of 33.8% is achieved without additional outcoupling enhancements owing to the near-perfect horizontal alignment of the emitting dipoles.

Dipole Moment- and Molecular Orbital-Engineered Phosphine Oxide-Free Host Materials for Efficient and Stable Blue Thermally Activated Delayed Fluorescence.

To utilize thermally activated delayed fluorescence (TADF) technology for future displays, it is necessary to develop host materials which harness the full potential of blue TADF emitters. However, no publication has reported such hosts yet. Although the most popular host for blue TADF, bis[2-(diphenylphosphino)phenyl]ether oxide (DPEPO) guarantees high-maximum external quantum efficiency (EQEmax ) TADF devices, they exhibit very short operational lifetimes. In contrast, long-lifespan blue TADF devices employing stable hosts such as 3',5-di(9H-carbazol-9-yl)-[1,1'-biphenyl]-3-carbonitrile (mCBP-CN) exhibit much lower EQEmax than the DPEPO-employed devices. Here, an elaborative approach for designing host molecules is suggested to achieve simultaneously stable and efficient blue TADF devices. The approach is based on engineering the molecular geometry, ground- and excited-state dipole moments of host molecules. The engineered hosts significantly enhance delayed fluorescence quantum yields of TADF emitters, as stabilizing the charge-transfer excited states of the TADF emitters and suppressing exciton quenching, and improve the charge balance. Moreover, they exhibit both photochemical and electrochemical stabilities. The best device employing one of the engineered hosts exhibits 79% increase in EQEmax compared to the mCBP-CN-employed device, together with 140% and 92-fold increases in operational lifetime compared to the respective mCBP-CN- and the DPEPO-based devices.

Use of laparoscopic surgical resection for pediatric malignant solid tumors: a case series.

BACKGROUND: Minimally invasive surgery for malignant pediatric tumors remains controversial, and few cases have been published. The present study reports on our initial experiences of laparoscopic surgical resection for selected pediatric malignant solid tumors. METHODS: We retrospectively analyzed data from ten pediatric patients who underwent laparoscopic surgical resection for malignant solid tumors at our institute between April 2005 and January 2010. RESULTS: There were four boys and six girls, including one neonate and four infants. The mean age at surgery was 23.3 months (range, 13 days-69 months). Six patients underwent laparoscopic adrenalectomy for neuroblastoma (n=5) or adrenocortical carcinoma (n=1). Two patients underwent laparoscopic partial hepatectomy for hepatoblastoma, one patient underwent a laparoscopic salpingo-oophorectomy for yolk sac tumor, and one a laparoscopic tumor excision for rhabdomyosarcoma in the pelvis. Complete tumor resection was performed in all cases. Tumors ranged from 2.5 to 5.3 cm maximum diameter. Tumors were placed inside endobags and removed safely without spillage. The mean operation time was 132 (range, 65-250) min. There were no open conversions and no postoperative complications. The mean postoperative hospital stay was 4.9 (range, 2-7) days, and all surgical wounds showed good cosmetic results. There were no local tumor recurrences during the 17.3-month median follow-up period. CONCLUSIONS: Laparoscopic surgical resection for selected pediatric malignant solid tumors was found to be feasible and safe. Long-term follow-up data are essential to confirm oncologic safety.

Surgery for hepatoblastoma: from laparoscopic resection to liver transplantation.

BACKGROUND/AIMS: Introduction of liver transplantation and the application of minimally invasive surgery for selected hepatoblastoma patients made a tailored surgical approach possible according to the tumor status. METHODOLOGY: We retrospectively evaluated clinical outcomes of 38 pediatric patients with pathologically proven hepatoblastoma who underwent surgery at our institute between 1991 and 2009. Especially, we evaluated recent changes in clinical outcomes since the commencement of liver transplantations and laparoscopic resections for hepatoblastoma patients from 2007. RESULTS: Complete hepatic tumor resections including 5 liver transplantations were performed in all patients, with 5-year overall survival and event free survival rates of 74.8% and 73.8%, respectively. From 2007, we performed 5 liver transplantations for unresectable cases. No tumor recurrences occurred in any case after a 19.9 (14.5-35.6) months median follow-up period. Totally laparoscopic partial hepatectomies were performed (2 cases) for selected patients. Both cases showed early recovery without any complications and were free of disease recurrence after 8.1 and 19.3 months follow-up period. CONCLUSIONS: Though long term follow-up data is necessary for validation, we suggest that an individualized surgical strategy based on the accurate evaluation of the tumor extent might improve the clinical outcomes of patients with hepatoblastoma.

Evolutionary design of molecules based on deep learning and a genetic algorithm.

Evolutionary design has gained significant attention as a useful tool to accelerate the design process by automatically modifying molecular structures to obtain molecules with the target properties. However, its methodology presents a practical challenge-devising a way in which to rapidly evolve molecules while maintaining their chemical validity. In this study, we address this limitation by developing an evolutionary design method. The method employs deep learning models to extract the inherent knowledge from a database of materials and is used to effectively guide the evolutionary design. In the proposed method, the Morgan fingerprint vectors of seed molecules are evolved using the techniques of mutation and crossover within the genetic algorithm. Then, a recurrent neural network is used to reconstruct the final fingerprints into actual molecular structures while maintaining their chemical validity. The use of deep neural network models to predict the properties of these molecules enabled more versatile and efficient molecular evaluations to be conducted by using the proposed method repeatedly. Four design tasks were performed to modify the light-absorbing wavelengths of organic molecules from the PubChem library.

Purely Spin-Vibronic Coupling Assisted Triplet to Singlet Up-Conversion for Real Deep Blue Organic Light-Emitting Diodes with Over 20% Efficiency and y Color Coordinate of 0.05.

Finding narrow-band, ultrapure blue thermally activated delayed fluorescence (TADF) materials is extremely important for developing highly efficient organic light-emitting diodes (OLEDs). Here, spin-vibronic coupling (SVC)-assisted ultrapure blue emitters obtained by joining two carbazole-derived moieties at a para position of a phenyl unit and performing substitutions using several blocking groups are presented. Despite a relatively large singlet-triplet gap (∆EST ) of >0.2 eV, efficient triplet-to-singlet crossover can be realized, with assistance from resonant SVC. To enhance the spin crossover, electronic energy levels are fine-tuned, thereby causing ∆EST to be in resonance with a triplet-triplet gap (∆ETT ). A sizable population transfer between spin multiplicities (>103 s-1 ) is achieved, and this result agrees well with theoretical predictions. An OLED fabricated using a multiple-resonance-type SVC-TADF emitter with CIE color coordinates of (0.15, 0.05) exhibits ultrapure blue emissions, with a narrow full-width-at-half-maximum of 21 nm and a high external quantum efficiency of 23.1%.

Three States Involving Vibronic Resonance is a Key to Enhancing Reverse Intersystem Crossing Dynamics of an Organoboron-Based Ultrapure Blue Emitter.

The recently developed narrow-band blue-emitting organoboron chromophores based on the multiple-resonance (MR) effect have now become one of the most important components for constructing efficient organic light emitting diodes (OLEDs). While they basically emit through fluorescence, they are also known for showing substantial thermally activated delayed fluorescence (TADF) even with a relatively large singlet-triplet gap (ΔE ST). Indeed, understanding the reverse intersystem crossing (RISC) dynamics behind this peculiar TADF will allow judicious molecular designs toward achieving better performing OLEDs. Explaining the underlying nonadiabatic spin-flip mechanism, however, has often been equivocal, and how the sufficiently fast RISC takes place even with the sizable ΔE ST and vanishingly small spin-orbit coupling is not well understood. Here, we show that a vibronic resonance, namely the frequency matching condition between the vibration and the electronic energy gap, orchestrates three electronic states together and this effect plays a major role in enhancing RISC in a typical organoboron emitter. Interestingly, the mediating upper electronic state is quite high in energy to an extent that its thermal population is vanishingly small. Through semiclassical quantum dynamics simulations, we further show that the geometry dependent non-Condon coupling to the upper triplet state that oscillates with the frequency ΔE ST/ℏ is the main driving force behind the peculiar resonance enhancement. The existence of an array of vibrational modes with strong vibronic rate enhancements provides the ability to sustain efficient RISC over a range of ΔE ST in defiance of the energy gap law, which can render the MR-emitters peculiar in comparison with more conventional donor-acceptor type emitters. Our investigation may provide a new guide for future blue emitting molecule developments.

Complications and risk factors of infection in pediatric hemato-oncology patients with totally implantable access ports (TIAPs).

BACKGROUND: Totally implantable access ports (TIAPs) are widely used in pediatric hematology-oncology patients. We investigated the incidence of complications, causes of TIAP removal, and risk factors for infection. PROCEDURE: We retrospectively analyzed the clinical, demographic, and surgical characteristics in 225 pediatric hematology-oncology patients implanted with 238 TIAPs between January 2004 and December 2005. RESULTS: Except for 20 patients lost to follow-up, the mean maintenance period was 724.8 +/- 500.6 days (range: 17-2,124). Mechanical complications occurred in seven patients (2.9%). The causes of TIAP removal were termination of use in 130 patients (59.6%), death from primary disease with TIAP in situ in 35 (14.7%), infection in 35 (14.7%), and obstruction in 4 (1.8%). Early infections occurred in nine patients at mean 37.77 +/- 16.44 days (range: 17-56). Late infections occurred in 26 patients at mean 334.5 +/- 257.82 days (range: 68-997). Univariate analysis showed that the risk factors of early infection were re-implantation (P = 0.022) and long operation time (P = 0.045). The risk factors of late infection were ANC <500/mm(3) (P = 0.011) and platelet count <50,000/mm(3) (P < 0.001). In multivariate analysis, re-implantation was a significant risk factor of early infection (P = 0.033, OR 4.528) and low platelet count (<50,000/mm(3)) was the independent risk factor for late infection (P = 0.005, OR 4.24). CONCLUSIONS: Correct procedure and careful use decreases the incidence of early infection and leads to the prevention of re-implantation. Initial thrombocytopenia was attributable to bone marrow suppression caused by hematologic malignancies or severe infection. Thus, this condition is of value in predicting late infection.

Spin-Vibronic Model for Quantitative Prediction of Reverse Intersystem Crossing Rate in Thermally Activated Delayed Fluorescence Systems.

Computationally predicting reverse intersystem crossing (RISC) rates is important for designing new thermally activated delayed fluorescence (TADF) materials. We report a method that can quantitatively predict RISC rates by explicitly considering the spin-vibronic coupling mechanism. The coupling element of the spin-vibronic Hamiltonian is obtained by expanding the spin-orbit and the non-Born-Oppenheimer terms to second order and is then brought into the Golden Rule rate under the Condon approximation. The rate equation is solved directly in the time domain using a correlation function approach. The contributions of the first-order direct spin-orbit coupling and the second-order spin-vibronic coupling to an RISC rate can be quantitatively analyzed in a separate manner. We demonstrate the utility of the method by applying it to a representative TADF system, where we observe that the spin-vibronic portion is substantial but not dominant especially with a relatively small triplet-singlet energy gap. Likewise, our method may elucidate the physical background of efficient nonradiative transitions from the lowest triplet to a higher lying singlet in other purely organic TADF systems, and it will be of great utility toward designing new such molecules.

Orbital Optimization in the Active Space Decomposition Model.

We report the derivation and implementation of orbital optimization algorithms for the active space decomposition (ASD) model, which are extensions of complete active space self-consistent field (CASSCF) and its occupation-restricted variants in the conventional multiconfiguration electronic-structure theory. Orbital rotations between active subspaces are included in the optimization, which allows us to unambiguously partition the active space into subspaces, enabling application of ASD to electron and exciton dynamics in covalently linked chromophores. One- and two-particle reduced density matrices, which are required for evaluation of orbital gradient and approximate Hessian elements, are computed from the intermediate tensors in the ASD energy evaluation. Numerical results on 4-(2-naphthylmethyl)-benzaldehyde and [36]cyclophane and model Hamiltonian analyses of triplet energy transfer processes in the Closs systems are presented. Furthermore, model Hamiltonians for hole and electron transfer processes in anti-[2.2](1,4)pentacenophane are studied using an occupation-restricted variant.

Clinical experience with persistent cloaca.

PURPOSE: Persistent cloaca is one of the most severe types of anorectal malformation. Appropriate initial drainage is difficult due to their various malformations and hydrocolpos or dilated urinary bladder. Corrective surgery also differs among individual patients. We describe our experiences with the surgical management of children with persistent cloaca. METHODS: We retrospectively reviewed 16 children diagnosed with persistent cloaca at Asan Medical Center. RESULTS: Sixteen patients were managed in their neonatal period. Twelve patients had enlarged bladder or vagina at birth. Three patients, who did not undergo cystostomy or vaginostomy at first operation, had earlier complications after surgery or required drainage tube insertion. One patient who did not undergo hydrocolpos drainage died of sepsis and complications. Nine patients underwent corrective surgery; posterior sagittal anorectovaginourethroplasty using the Pena method. Three patients required additional operations due to complications after surgery. CONCLUSION: Patients found to have anatomical malformations before colostomy, as well as hydrocolpos and bladder enlargement, require a vaginostomy with or without a cystostomy to reduce complications. Follow-up is required in patients with hydrocolpos and bladder enlargement to determine whether vaginal drainage improves dilated bladder. Continuous long-term follow-up examination is required to determine the long-term results of corrective surgery.

Avulsion of wandering spleen after traumatic torsion.

Wandering spleen usually causes clinical symptoms by torsion. Cases of torsion or hemorrhage after blunt trauma are reported. The authors experienced avulsion of wandering spleen after traumatic torsion in the victim of pedestrian injury. The spleen had been located in the left upper quadrant on the time of torsion, but it moved into the right paracolic gutter after avulsion. The avulsed spleen was removed, and the postoperative course was uneventful.