Comparison results of NSGL21, IADM MFL, and SLEP.

<p>The x-axes represents the number of iterations and the y-axes represents the relative error.</p

Dynamical Correlation Effects on Photoisomerization: Ab Initio Multiple Spawning Dynamics with MS-CASPT2 for a Model <i>trans</i>-Protonated Schiff Base

We investigate the photoisomerization of a model retinal protonated Schiff base (<i>trans</i>-PSB3) using <i>ab initio</i> multiple spawning (AIMS) based on multistate second order perturbation theory (MSPT2). Discrepancies between the photodynamical mechanism computed with three-root state-averaged complete active space self-consistent field (SA-3-CASSCF, which does not include dynamic electron correlation effects) and MSPT2 show that dynamic correlation is critical in this photoisomerization reaction. Furthermore, we show that the photodynamics of <i>trans</i>-PSB3 is not well-described by predictions based on minimum energy conical intersections (MECIs) or minimum energy conical intersection (CI) seam paths. Instead, most of the CIs involved in the photoisomerization are far from MECIs and minimum energy CI seam paths. Thus, both dynamical nuclear effects and dynamic electron correlation are critical to understanding the photochemical mechanism

Comparison results of NSGL21 with IADM_MFL and SLEP.

<p>Comparison results of NSGL21 with IADM_MFL and SLEP.</p

Comparison results of NSGL21, IADM MFL, and SLEP.

<p>The x-axes represents the CPU time in seconds and the y-axes represents the relative error.</p

Photodecarbonylation Mechanism of Cyclopropenone in the Gas Phase: Electronic Structure Calculation and AIMS Dynamics Simulation

In this article, structures and energies of cyclopropenone in the low-lying electronic states have been determined by the CASSCF and MS-CASPT2 calculations with different basis sets. Two minimum-energy conical intersections (CI-1 and CI-2) between S₀ and S₁ were obtained and their topographic characters were characterized by the SA4-CAS­(10,9) calculated energy gradients and nonadiabatic coupling vectors. The AIMS method was used to carry out nonadiabatic dynamics simulation with ab initio calculation performed at the SA4-CAS­(10,9) level. On the basis of time evolution of wave functions simulated here, the S₁ lifetime is fitted to be 125 fs with a pure exponential decay for the S₁ electronic population. The CI-1 intersection is mainly responsible for ultrafast S₁→S₀ nonadiabatic transition and the photoinduced decarbonylation is a sequential process, where the first CC bond is broken in the S₁ state and fission of the second CC bond occurs in the S₀ state as a result of the S₁→S₀ internal conversion via the CI-1 region. As a minor channel through the CI-2 region, the decarbonylation proceeds in an asynchronous concerted way. Effects of the S₁ excess energies and the S₁–S₀ energy gap on the nonadiabatic dynamics were examined, which reveals that the S₁→S₀ nonadiabatic transition occurs within a small energy gap and high-energy conical intersection regions can play an important role. The present study provides new insights into mechanistic photochemistry of cyclopropenones and reveals that the AIMS dynamics simulation at a high-accuracy ab initio level is a powerful tool for exploring a mechanism of an ultrafast photochemical reaction

Efficient Interface for Online Coupling of Capillary Electrophoresis with Inductively Coupled Plasma–Mass Spectrometry and Its Application in Simultaneous Speciation Analysis of Arsenic and Selenium

A simple and highly efficient online system coupling of capillary electrophoresis to inductively coupled plasma–mass spectrometry (CE-ICP-MS) for simultaneous separation and determination of arsenic and selenium compounds was developed. CE was coupled to an ICP-MS system by a sprayer with a novel direct-injection high-efficiency nebulizer (DIHEN) chamber as the interface. By using this interface, six arsenic species, including arsenite (As­(III), arsenate (As­(V)), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), and arsenocholine (AsC) and five selenium species (such as sodium selenite (Se­(IV)), sodium selenate (Se­(VI)), selenocysteine (SeCys), selenomethionine (SeMet), and Se-methylselenocysteine (MeSeCys)) were baseline-separated and determined in a single run within 9 min under the optimized conditions. Minimum dead volume, low and steady sheath flow liquid, high nebulization efficiency, and high sample transport efficiency were obtained by using this interface. Detection limits were in the range of 0.11–0.37 μg L^–1 for the six arsenic compounds (determined as ⁷⁵As at <i>m</i>/<i>z</i> 75) and 1.33–2.31 μg L^–1 for the five selenium species (determined as ⁸²Se at <i>m</i>/<i>z</i> 82). Repeatability expressed as the relative standard deviations (RSD, <i>n</i> = 6) of both migration time and peak area were better than 2.68% for arsenic compounds and 3.28% for selenium compounds, respectively. The proposed method had been successfully applied for the determination of arsenic and selenium species in the certified reference materials DORM-3, water, urine, and fish samples

The batches of foetal bovine serum tested by real-time RT-PCR.

a<p>Sequence has not been determined.</p

Nonradiative Relaxation of Photoexcited Black Phosphorus Is Reduced by Stacking with MoS₂: A Time Domain ab Initio Study

Black phosphorus (BP) is an appealing material for applications in electronics and optoelectronics because of its tunable direct band gap and high charge carrier mobility. For real optoelectronic device utilization, nonradiative electron–hole recombination should be slow because it constitutes a major pathway for charge and energy losses. Using time-domain density functional theory combined with nonadiabatic (NA) molecular dynamics, we show that nonradiative electron–hole recombination occurs within several tens of picoseconds in bilayer BP, agreeing well with experimental data. When a single layer of BP is stacked with monolayer MoS₂, the recombination is reduced because of the increased band gap and reduced electron–phonon NA coupling compared to bilayer BP. The slow electron–phonon energy losses in BP-MoS₂ van der Waals heterojunction relative to bilayer BP indicate that rationally stacking BP with other two-dimensional materials is an attractive route for designing novel and efficient photovoltaic materials

Neighbor-Joining analysis of a 249-bp fragment of the 5′UTR sequences under Kimura 3-parameter model.

<p>The sequences are labelled with sample ID (-number of clone)/country or region of origin. AU, Australia; BR, Brazil; CA, Canada; CO, Colombia; DK, Denmark; DR, Dominican Republic; EU, European Union; FR, France; MX, Mexico; NI, not identified by supplier; NZ, New Zealand; SA, South American; US, USA; ZA, South Africa. Numbers are percentage of bootstrap values (1000 replicates) for major clades. Bar indicates changes per site. The GenBank accession numbers for reference strains are DQ075210, NC_001461, U97481, AF026781, AB359927, AF049221, AY363096 and FJ493479 for BVDV-1, AY763053 and NC_002032 for BVDV-2, and NC_012812 for BVDV-3.</p

Lewis Base Passivation of Hybrid Halide Perovskites Slows Electron–Hole Recombination: Time-Domain Ab Initio Analysis

Nonradiative electron–hole recombination plays a key role in determining photon conversion efficiencies in solar cells. Experiments demonstrate significant reduction in the recombination rate upon passivation of methylammonium lead iodide perovskite with Lewis base molecules. Using nonadiabatic molecular dynamics combined with time-domain density functional theory, we find that the nonradiative charge recombination is decelerated by an order of magnitude upon adsorption of the molecules. Thiophene acts by the traditional passivation mechanism, forcing electron density away from the surface. In contrast, pyridine localizes the electron at the surface while leaving it energetically near the conduction band edge. This is because pyridine creates a stronger coordinative bond with a lead atom of the perovskite and has a lower energy unoccupied orbital compared with thiophene due to the more electronegative nitrogen atom relative to thiophene’s sulfur. Both molecules reduce two-fold the nonadiabatic coupling and electronic coherence time. A broad range of vibrational modes couple to the electronic subsystem, arising from inorganic and organic components. The simulations reveal the atomistic mechanisms underlying the enhancement of the excited-state lifetime achieved by the perovskite passivation, rationalize the experimental results, and advance our understanding of charge-phonon dynamics in perovskite solar cells