Efficient Population Transfer in a Λ-Type Quantum System Coupled to a Gold Nanoparticle Using STIRAP Shortcuts

A theoretical investigation on the population transfer in a Λ-type quantum system near a spherical gold nanoparticle under application of two stimulated Raman adiabatic passage (STIRAP) shortcuts and efficiency comparison with conventional STIRAP. It combines the density matrix approach for system dynamics, with classical electromagnetic calculations used to obtain the modified electric field amplitudes of the applied pulses and the Purcell factor of the quantum system due to the presence of the nanoparticle. The efficiency of population transfer is investigated by varying the distance between the quantum system and the nanoparticle, the free-space decay rate of quantum states, the mutual polarization, and the Rabi frequencies of each STIRAP shortcut pulses. In all cases, at least one of the applied shortcuts is more efficient than conventional STIRAP, while in most cases both perform better. When the pump and Stokes fields of the shortcuts have radial and tangential polarizations with respect to the nanoparticle surface, respectively, high transfer efficiency is obtained for small distances of the quantum system to the nanoparticle, moderate free space decay rates and large Rabi frequencies of the fields, while when the pulse polarizations are interchanged, the transfer becomes highly efficient only at large distances.     

Changes in Light Energy Utilization in Photosystem II and Reactive Oxygen Species Generation in Potato Leaves by the Pinworm Tuta absoluta

We evaluated photosystem II (PSII) functionality in potato plants (Solanum tuberosum L.) before and after a 15 min feeding by the leaf miner Tuta absoluta using chlorophyll a fluorescence imaging analysis combined with reactive oxygen species (ROS) detection. Fifteen minutes after feeding, we observed at the feeding zone and at the whole leaf a decrease in the effective quantum yield of photosystem II (PSII) photochemistry (Φ_PSII). While at the feeding zone the quantum yield of regulated non-photochemical energy loss in PSII (Φ_NPQ) did not change, at the whole leaf level there was a significant increase. As a result, at the feeding zone a significant increase in the quantum yield of non-regulated energy loss in PSII (Φ_NO) occurred, but there was no change at the whole leaf level compared to that before feeding, indicating no change in singlet oxygen (¹O₂) formation. The decreased Φ_PSII after feeding was due to a decreased fraction of open reaction centers (q_p), since the efficiency of open PSII reaction centers to utilize the light energy (Fv′/Fm′) did not differ before and after feeding. The decreased fraction of open reaction centers resulted in increased excess excitation energy (EXC) at the feeding zone and at the whole leaf level, while hydrogen peroxide (H₂O₂) production was detected only at the feeding zone. Although the whole leaf PSII efficiency decreased compared to that before feeding, the maximum efficiency of PSII photochemistry (Fv/Fm), and the efficiency of the water-splitting complex on the donor side of PSII (Fv/Fo), did not differ to that before feeding, thus they cannot be considered as sensitive parameters to monitor biotic stress effects. Chlorophyll fluorescence imaging analysis proved to be a good indicator to monitor even short-term impacts of insect herbivory on photosynthetic function, and among the studied parameters, the reduction status of the plastoquinone pool (q_p) was the most sensitive and suitable indicator to probe photosynthetic function under biotic stress.     

Electrochemical Determination of Neomycin and Norfloxacin at a Novel Polymer Nanocomposite Electrode in Aqueous Solution

Organic compounds such as antibiotics that are not effectively removed by modern-day treatment technology are a growing threat to water quality and health. The emergence of antibiotics in the aquatic environment is a matter of concern as they may induce bacterial resistance, a major threat to health-care management and an increasing economic crisis. The current methods that are used to detect antibiotics are expensive and time consuming due to the sample preparation necessary for the determination of low concentrations of antibiotics in water and the instruments used. Electrochemical sensors and biosensors are simple systems, with high selectivity and sensitivity for individual measurements and low cost. In this study, we present a novel polyamic acid/graphene oxide electrode that was prepared for electrochemical screening of selected antibiotic residues in aqueous solution. Polyamic acid and graphene oxide were synthesized independently and characterized using microscopic, spectroscopic, and voltammetric approaches. A polyamic acid/graphene oxide/screen-sprinted carbon electrode was prepared in situ by electrochemical deposition of polyamic acid/graphene (0.03?mg/mL 50:50 mass ratio) on screen-printed carbon electrodes using five cycles between ?1000 and 1000?mV at 50?mV/s. The polyamic acid/graphene oxide/screen-printed carbon electrode provided limits of detection of 0.034?µM for norfloxacin and 1.07?µM for neomycin. Recovery studies on synthetic urine showed good inter-day and intra-day coefficients of variation (n?=?3).     

On the universality of the long-/short-range separation in multiconfigurational density-functional theory

In many cases, the dynamic correlation can be calculated quite accurately and at a fairly low computational cost in Kohn-Sham density-functional theory (KS-DFT), using current standard approximate functionals. However, in general, KS-DFT does not treat static correlation effects (near degeneracy) adequately which, on the other hand, can be described in wave-function theory (WFT), for example, with a multiconfigurational self-consistent field (MCSCF) model. It is therefore of high interest to develop a hybrid model which combines the best of both WFT and DFT approaches. The merge of WFT and DFT can be achieved by splitting the two-electron interaction into long-range and short-range parts. The long-range part is then treated by WFT and the short-range part by DFT. In this work the authors consider the so-called "erf" long-range interaction erf(micror12)/r12, which is based on the standard error function, and where mu is a free parameter which controls the range of the long-/short-range decomposition. In order to formulate a general method, they propose a recipe for the definition of an optimal microopt parameter, which is independent of the approximate short-range functional and the approximate wave function, and they discuss its universality. Calculations on a test set consisting of He, Be, Ne, Mg, H2, N2, and H2O yield microopt approximately 0.4 a.u.. A similar analysis on other types of test systems such as actinide compounds is currently in progress. Using the value of 0.4 a.u. for micro, encouraging results are obtained with the hybrid MCSCF-DFT method for the dissociation energies of H2, N2, and H2O, with both short-range local-density approximation and PBE-type functionals.     

Transport of wetting liquid plugs in bifurcating microfluidic channels

A plug of wetting liquid is driven at constant pressure through a bifurcation in a microchannel. For a plug advancing in a straight channel, we find that the viscous dissipation in the bulk may be estimated using Poiseuille's law while Bretherton and Tanner's laws model the additional dissipation occurring at the rear and front interfaces. At a second stage, we focus on the behavior of the plug flowing through a T-junction. Experiments show the existence of a threshold pressure, below which the plug remains blocked at the entrance of the junction. Above this required pressure, the plug enters the bifurcation and either ruptures or splits into two daughter plugs, depending on the applied pressure and on the initial length of the plug. By means of geometrical arguments and the previously cited laws, we propose a global model to predict the transitions between the three observed behaviors.     

Suzuki-miyaura cross-coupling of 1,1-dichloro-1-alkenes with 9-alkyl-9-BBN

We addressed an unexplored application of the Suzuki-Miyaura protocol to the cross-coupling of 1,1-dichloro-1-alkenes with 9-alkyl-9-BBN. The use of bisphosphine ligands with a large P-Pd-P bite angle allowed us to synthesize Z-chlorinated internal alkenes in good yields resulting from a selective monocoupling process, a recurrent challenge with 1,1-dichloro-1-alkenes. Moreover, these monochlorinated olefins could be further transformed providing stereospecifically trisubstituted olefins.     

Modified Julia fluoroolefination: selective preparation of fluoroalkenoates

The modified Julia olefination reaction has been applied to develop a stereoselective synthesis of fluoroalkenoate derivatives from a fluorobenzothiazolyl sulfone and aldehydes or a ketone. The olefination reaction can be achieved by using a variety of bases. DBU and DBU in the presence of MgBr2 were found to be the most efficient systems to prepare either (Z)- or (E)-alkenoates in moderate to excellent stereoselectivity.     

First example of an Ugi type reaction on phenylsulfinimine-avermectin B1 derivatives

A short synthesis of 4″-(S)-4″-deoxy-4″-trifluoroacetylamino-4″-alkylcarbamoyl-avermectin B₁4 has been developed through the diastereoselective Ugi reaction to an phenylsulfinimide intermediate.     

Changing the oxothiomolybdate ring from an anionic to a cationic receptor

The ionic recognition properties of neutral oxothiomolybdenum wheels can be changed from anionic to cationic through ionization of the internal aquo ligands. In the solid state, [Mo8O8S8(OH)10(H2O)]2- (1) interacts with two Cs+ cations to give a close supramolecular host-guest arrangement. Such interactions appear to be maintained in solution as a labile association.