Modeling the electroluminescence of atomic wires from quantum dynamics simulations.

Static and time-dependent quantum-mechanical approaches have been employed in the literature to characterize the physics of light-emitting molecules and nanostructures. However, the electromagnetic emission induced by an input current has remained beyond the realm of molecular simulations. This is the challenge addressed here with the help of an equation of motion for the density matrix coupled to a photon bath based on a Redfield formulation. This equation is evolved within the framework of the driven-Liouville von Neumann approach, which incorporates open boundaries by introducing an applied bias and a circulating current. The dissipated electromagnetic power can be computed in this context from the time derivative of the energy. This scheme is applied in combination with a self-consistent tight-binding Hamiltonian to investigate the effects of bias and molecular size on the electroluminescence of metallic and semiconducting chains. For the latter, a complex interplay between bias and molecular length is observed: there is an optimal number of atoms that maximizes the emitted power at high voltages but not at low ones. This unanticipated behavior can be understood in terms of the band bending produced along the semiconducting chain, a phenomenon that is captured by the self-consistency of the method. A simple analytical model is proposed that explains the main features revealed by the simulations. The methodology, applied here at a self-consistent tight-binding level but extendable to more sophisticated Hamiltonians such as density functional tight binding and time dependent density functional theory, promises to be helpful for quantifying the power and quantum efficiency of nanoscale electroluminescent devices.

Nanobubble Stability and Formation on Solid-Liquid Interfaces in Open Environments.

Are surface nanobubbles transient or thermodynamically stable structures? This question remained controversial until recently, when the stability of gas nanobubbles at solid-liquid interfaces was demonstrated from thermodynamic arguments in closed systems, establishing that bubbles with radii of hundreds of nanometers can be stable at modest supersaturations if the gas amount is finite. Here we develop a grand-canonical description of bubble formation that predicts that nanobubbles can nucleate and remain thermodynamically stable in open boundaries at high supersaturations when pinned to hydrophobic supports as small as a few nanometers. While larger bubbles can also be stable at lower supersaturations, the corresponding barriers are orders of magnitude above kT, meaning that their formation cannot proceed via heterogeneous nucleation on a uniform solid interface but must follow some alternative path. Moreover, we conclude that a source of growth-limiting mechanism, such as pinning or gas availability, is necessary for the thermodynamic stabilization of surface bubbles.

Fluorescence in quantum dynamics: Accurate spectra require post-mean-field approaches.

Real time modeling of fluorescence with vibronic resolution entails the representation of the light-matter interaction coupled to a quantum-mechanical description of the phonons and is therefore a challenging problem. In this work, taking advantage of the difference in timescales characterizing internal conversion and radiative relaxation-which allows us to decouple these two phenomena by sequentially modeling one after the other-we simulate the electron dynamics of fluorescence through a master equation derived from the Redfield formalism. Moreover, we explore the use of a recent semiclassical dissipative equation of motion [C. M. Bustamante et al., Phys. Rev. Lett. 126, 087401 (2021)], termed coherent electron electric-field dynamics (CEED), to describe the radiative stage. By comparing the results with those from the full quantum-electrodynamics treatment, we find that the semiclassical model does not reproduce the right amplitudes in the emission spectra when the radiative process involves the de-excitation to a manifold of closely lying states. We argue that this flaw is inherent to any mean-field approach and is the case with CEED. This effect is critical for the study of light-matter interaction, and this work is, to our knowledge, the first one to report this problem. We note that CEED reproduces the correct frequencies in agreement with quantum electrodynamics. This is a major asset of the semiclassical model, since the emission peak positions will be predicted correctly without any prior assumption about the nature of the molecular Hamiltonian. This is not so for the quantum electrodynamics approach, where access to the spectral information relies on knowledge of the Hamiltonian eigenvalues.

Management and Follow-up of Massive Fetomaternal Hemorrhage Requiring High-Dose Rh Immune Globulin: A Case Report.

OBJECTIVES: Massive fetomaternal hemorrhage (FMH) is rare and reported to be the cause in approximately 3% of all fetal deaths. Maternal management of massive FMH includes prevention of Rh(D) alloimmunization in Rh(D)-negative mothers by administration of Rh(D) immune globulin (RhIG). METHODS: We describe a case of a 30-year-old O-negative, primigravida woman who presented at 38 weeks of gestation with decreased fetal movements. She underwent an emergency cesarean section and delivered an O-positive baby girl who died shortly after birth. RESULTS: The patient's FMH screen was positive, with a Kleihauer-Betke test demonstrating 10.7% fetal blood in maternal circulation. The calculated dose of 6,300 µg RhIG was given prior to discharge over 2 days using an intravenous (IV) preparation. Antibody screening a week after discharge showed anti-D and anti-C. The anti-C was attributed to acquired passive immunity from the large dose of RhIG. Anti-C reactivity waned and was negative at 6 months, but the anti-D pattern persisted at 9 months postdelivery. Negative antibody screens were noted at 12 and 14 months. CONCLUSIONS: This case highlights the immunohematology challenges of IV RhIG as well as the success in preventing alloimmunization with IV RhIG given the patient's complete resolution of anti-C and no anti-D formation, with a subsequent healthy pregnancy.

Tailoring Cooperative Emission in Molecules: Superradiance and Subradiance from First-Principles Simulations.

Cooperative optical effects provide a pathway to both the amplification (superradiance) and the suppression (subradiance) of photon emission from electronically excited states. These captivating phenomena offer a rich variety of possibilities for photonic technologies aimed at electromagnetic energy manipulation, including lasers and high-speed emitting devices in the case of superradiance or optical energy storage in that of subradiance. The employment of molecules as the building pieces in these developments requires a precise understanding of the roles of separation, orientation, spatial distribution, and applied fields, which remains challenging for theory and experiments. These questions are addressed here through ab initio quantum dynamics simulations of collective emission on the basis of a novel semiclassical formalism and time-dependent density functional theory. By establishing the configurations leading to decoherence and how the fine-tuning of a pulse can accumulate or release optical energy in H2 arrays, this report provides fundamental insight toward the design of real superradiant and subradiant devices.

Photochemical Optimization of a Silver Nanoprism/Graphene Oxide Nanocomposite's Antibacterial Properties.

Optimizing the antibacterial properties of nanocomposites is a fundamental challenge for many biomedical applications. Here, we study how we may optimize the antibacterial activity of narrow-sized anisotropically flat silver nanoprisms (S-NPs) on graphene oxide (GO) against Escherichia coli. To do so, we transformed silver nanoparticles (AgNPs) into S-NPs and anchored them to GO via a facile and low-cost photochemical reduction method by varying the irradiation wavelength during the synthesis process in the visible range (440 to 650 nm and white light). We performed a physicochemical characterization of the resulting S-NP/GO nanocomposite using a combination of UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Our results reveal a synergistic effect between the silver nanoprism and the oxygen functional groups of the GO surface. The antibacterial activity of the S-NPs/GO nanocomposite shows a significantly higher 53% inhibition efficiency after being irradiated with a 540 nm wavelength light source, compared to AgNPs with a 1% inhibition efficiency, respectively. In so doing, we have demonstrated the utility of a low-cost photoreduction method to control the structural properties of silver nanoprism on GO and, in this way, enhance the antibacterial properties of the nanocomposite. These results should be of great interest in a wide range of biomedical applications and medical devices.

Characterization data of cellulose modified by gamma irradiation to be used as template in the synthesis of a photoactive composite for environmental applications.

The following data provide evidence of the green functionalization process of a cellulose substrate by gamma radiation to be used as template in the preparation of photocatalyst composites. Functionalized cellulose, by gamma radiation treatment, improved its stability in water and exhibited a reduced size. Our data showed an intensification of carbonyl groups signal and a decrease in the thermal stability of the cellulose as result of the gamma radiation dose. Infrared and thermal data of the treated cellulose provide evidence of bond scission and the formation of functional groups that improved it is application as template. Finally, the conductive polymer poly(3,4-ethylenedioxythiophene) was deposited on the gamma irradiated cellulose to be used as photo-catalyze in the treatment of contaminated water with pharmaceutical compounds.

Enzymatic Epoxidation of Long-Chain Terminal Alkenes by Fungal Peroxygenases.

Terminal alkenes are among the most attractive starting materials for the synthesis of epoxides, which are essential and versatile intermediate building blocks for the pharmaceutical, flavoring, and polymer industries. Previous research on alkene epoxidation has focused on the use of several oxidizing agents and/or different enzymes, including cytochrome P450 monooxygenases, as well as microbial whole-cell catalysts that have several drawbacks. Alternatively, we explored the ability of unspecific peroxygenases (UPOs) to selectively epoxidize terminal alkenes. UPOs are attractive biocatalysts because they are robust extracellular enzymes and only require H2O2 as cosubstrate. Here, we show how several UPOs, such as those from Cyclocybe (Agrocybe) aegerita (AaeUPO), Marasmius rotula (MroUPO), Coprinopsis cinerea (rCciUPO), Humicola insolens (rHinUPO), and Daldinia caldariorum (rDcaUPO), are able to catalyze the epoxidation of long-chain terminal alkenes (from C12:1 to C20:1) after an initial optimization of several reaction parameters (cosolvent, cosubstrate, and pH). In addition to terminal epoxides, alkenols and other hydroxylated derivatives of the alkenes were formed. Although all UPOs were able to convert and epoxidize the alkenes, notable differences were observed between them, with rCciUPO being responsible for the highest substrate turnover and MroUPO being the most selective with respect to terminal epoxidation. The potential of peroxygenases for epoxidizing long-chain terminal alkenes represents an interesting and green alternative to the existing synthesis technologies.

Pseudochrobactrum algeriensis sp. nov., isolated from lymph nodes of Algerian cattle.

Three Gram-negative, rod-shaped, oxidase-positive, non-spore-forming, non-motile strains (C130915_07T, C150915_16 and C150915_17) were isolated from lymph nodes of Algerian cows. On the basis of 16S rRNA gene and whole genome similarities, the isolates were almost identical and clearly grouped in the genus Pseudochrobactrum. This allocation was confirmed by the analysis of fatty acids (C19:cyclo, C18 : 1, C18 : 0, C16 : 1 and C16 : 0) and of polar lipids (major components: phosphatidylethanolamine, ornithine-lipids, phosphatidylglycerol, cardiolipin and phosphatidylcholine, plus moderate amounts of phosphatidylmonomethylethanolamine, phosphatidyldimethylethanolamine and other aminolipids). Genomic, physiological and biochemical data differentiated these isolates from previously described Pseudochrobactrum species in DNA relatedness, carbon assimilation pattern and growth temperature range. Thus, these organisms represent a novel species of the genus Pseudochrobactrum, for which the name Pseudochrobactrum algeriensis sp. nov. is proposed (type strain C130915_07T=CECT30232T=LMG 32378T).

Dissipative Equation of Motion for Electromagnetic Radiation in Quantum Dynamics.

The dynamical description of the radiative decay of an electronically excited state in realistic many-particle systems is an unresolved challenge. In the present investigation electromagnetic radiation of the charge density is approximated as the power dissipated by a classical dipole, to cast the emission in closed form as a unitary single-electron theory. This results in a formalism of unprecedented efficiency, critical for ab initio modeling, which exhibits at the same time remarkable properties: it quantitatively predicts decay rates, natural broadening, and absorption intensities. Exquisitely accurate excitation lifetimes are obtained from time-dependent DFT simulations for C^{2+}, B^{+}, and Be, of 0.565, 0.831, and 1.97 ns, respectively, in accord with experimental values of 0.57±0.02, 0.86±0.07, and 1.77-2.5 ns. Hence, the present development expands the frontiers of quantum dynamics, bringing within reach first-principles simulations of a wealth of photophysical phenomena, from fluorescence to time-resolved spectroscopies.

Advances in enzymatic oxyfunctionalization of aliphatic compounds.

Selective oxyfunctionalizations of aliphatic compounds are difficult chemical reactions, where enzymes can play an important role due to their stereo- and regio-selectivity and operation under mild reaction conditions. P450 monooxygenases are well-known biocatalysts that mediate oxyfunctionalization reactions in different living organisms (from bacteria to humans). Unspecific peroxygenases (UPOs), discovered in fungi, have arisen as "dream biocatalysts" of great biotechnological interest because they catalyze the oxyfunctionalization of aliphatic and aromatic compounds, avoiding the necessity of expensive cofactors and regeneration systems, and only depending on H2O2 for their catalysis. Here, we summarize recent advances in aliphatic oxyfunctionalization reactions by UPOs, as well as the molecular determinants of the enzyme structures responsible for their activities, emphasizing the differences found between well-known P450s and the novel fungal peroxygenases.

Clinical, environmental and histological distribution of BRAF, NRAS and TERT promoter mutations among patients with cutaneous melanoma: a retrospective study of 563 patients.

BACKGROUND: The distinct somatic mutations that define clinical and histopathological heterogeneity in cutaneous melanoma could be dependent on host susceptibility to exogenous factors like ultraviolet radiation. OBJECTIVES: Firstly, to characterize patients with cutaneous melanoma clinically and pathologically based on the mutational status of BRAF, NRAS and TERT promoter. Secondly, to elucidate the modified features due to the presence of TERT promoter mutations over the background of either BRAF or NRAS mutations. METHODS: We performed a retrospective study on 563 patients with melanoma by investigating somatic mutations in BRAF, NRAS and TERT promoter. RESULTS: We observed co-occurrence of TERT promoter mutations with BRAF and NRAS mutations in 26.3% and 6.9% of melanomas, respectively. Multivariate analysis showed an independent association between BRAF mutations and a decreased presence of cutaneous lentigines at the melanoma site, and an increased association with the presence of any MC1R polymorphism. We also observed an independent association between TERT promoter mutations and increased tumour mitotic rate. Co-occurrence of BRAF and TERT promoter mutations was independently associated with occurrence of primary tumours at usually sun-exposed sites, lack of histological chronic sun damage in surrounding unaffected skin at the melanoma site, and increased tumour mitotic rate. Co-occurrence of NRAS and TERT promoter mutations was independently associated with increased tumour mitotic rate. The presence of TERT promoter together with BRAF or NRAS mutations was associated with statistically significantly worse survival. CONCLUSIONS: The presence of TERT promoter mutations discriminates BRAF- and NRAS-mutated tumours and indicates a higher involvement of ultraviolet-induced damage and tumours with worse melanoma-specific survival than those without any mutation. These observations refine classification of patients with melanoma based on mutational status.

Electrochemically Generated Nanobubbles: Invariance of the Current with Respect to Electrode Size and Potential.

Gas-producing electrochemical reactions are key to energy conversion and generation technologies. Bubble formation dramatically decreases gas-production rates on nanoelectrodes, by confining the reaction to the electrode boundary. This results in the collapse of the current to a stationary value independent of the potential. Startlingly, these residual currents also appear to be insensitive to the nanoelectrode diameter in the 5 to 500 nm range. These results are counterintuitive, as it may be expected that the current be proportional to the circumference of the electrode, i.e., the length of the three-phase line where the reaction occurs. Here, we use molecular simulations and a kinetic model to elucidate the origin of current insensitivity with respect to the potential and establish its relationship to the size of nanoelectrodes. We provide critical insights for the design and operation of nanoscale electrochemical devices and demonstrate that nanoelectrode arrays maximize conversion rates compared to macroscopic electrodes with same total area.

Selective Oxygenation of Ionones and Damascones by Fungal Peroxygenases.

Apocarotenoids are among the most highly valued fragrance constituents, being also appreciated as synthetic building blocks. This work shows the ability of unspecific peroxygenases (UPOs, EC1.11.2.1) from several fungi, some of them being described recently, to catalyze the oxyfunctionalization of α- and ß-ionones and α- and ß-damascones. Enzymatic reactions yielded oxygenated products such as hydroxy, oxo, carboxy, and epoxy derivatives that are interesting compounds for the flavor and fragrance and pharmaceutical industries. Although variable regioselectivity was observed depending on the substrate and enzyme, oxygenation was preferentially produced at the allylic position in the ring, being especially evident in the reaction with α-ionone, forming 3-hydroxy-α-ionone and/or 3-oxo-α-ionone. Noteworthy were the reactions with damascones, in the course of which some UPOs oxygenated the terminal position of the side chain, forming oxygenated derivatives (i.e., the corresponding alcohol, aldehyde, and carboxylic acid) at C-10, which were predominant in the Agrocybe aegerita UPO reactions, and first reported here.

Identifying Trypanosome Protein-RNA Interactions Using RIP-Seq.

Trypanosomatids rely primarily on posttranscriptional mechanisms for the control of gene expression, with regulation of RNA processing, localization, degradation, and translation by RNA-binding proteins (RBPs). To determine the mechanisms by which RBPs control gene expression in trypanosomatids, transcriptome-wide identification of mRNA targets and mapping of the RNA-binding site is required. Here we present our most current RIP-Seq (RNA immunoprecipitation followed by high-throughput sequencing) protocol that we generally apply to elucidate RNA/protein interactions in Trypanosoma brucei. The technique provides valuable information about the workings of messenger ribonucleoprotein (mRNP) networks and trypanosome gene expression mechanisms.

The Tethering Assay: A Simple Method for the Characterization of mRNA-Fate Regulators.

In trypanosomatids, posttranscriptional controls are very important in regulation of individual gene expression. These are achieved through combinatorial sets of RNA-binding proteins (RBPs) which recognize RNA regulatory motifs or regions of secondary structure within RNAs. To analyze the potential functional impact of an RBP on their mRNA targets, we have applied a robust technique called tethering assay. In this method, the protein under study is attached to an mRNA reporter through an artificial RNA-protein interaction. Therefore, the functional activity of a protein can be analyzed independently of its intrinsic ability to bind to RNA. By making use of a cell line expressing a chloramphenicol acetyltransferase (CAT) reporter mRNA, we have characterized dozens of novel mRNA-fate regulators in cultured Trypanosoma brucei. After induction of the candidate fusion protein, the effect on the reporter expression is determined by a rapid CAT assay. The protocol is simple and typically takes one working day for analysis of a single protein and controls. In this chapter, we provide a description of materials and methods for the tethering method and should allow the assay to be successfully deployed in any laboratory with minimal user training.

The Search for Quorum Sensing in Botrytis cinerea: Regulatory Activity of Its Extracts on Its Development.

Botrytis cinerea is a phytopathogenic fungus that causes large crop and post-harvest losses. Therefore, new and effective strategies are needed to control the disease and to reduce resistance to fungicides. Modulating pathogenicity and virulence by manipulating microbial communication is a promising strategy. This communication mechanism, called Quorum Sensing (QS), has already been reported in bacteria and yeasts; however, it has not yet been studied in B. cinerea. To establish the existence of this biochemical process in B. cinerea, we prepared extracts at different growth times (D1-D12), which were applied to fresh cultures of the same fungi. The chemical analysis of the extracts obtained from several fermentations showed different compositions and biological activities. We confirmed the presence of several phytotoxins, as well as compounds 1-phenylethanol and 3-phenylpropanol. Day five extract (0.1%) inhibited conidia germination and elongation of germ tubes, day seven extract (1%) produced the greatest phytotoxic effect in tomato leaves, and day nine extract (0.1%) was a sporulation inhibitor. In contrast, the extracts from days 7, 9, and 12 of fermentation (0.1% and 0.01%) promoted pellet and biofilm formation. Sporulation was slightly induced at 0.01%, while at 0.1% there was a great inhibition. At the highest extract concentrations, a biocidal effect was detected, but at the lowest, we observed a QS-like effect, regulating processes such as filamentation, morphogenesis, and pathogenesis. These results of the biological activity and composition of extracts suggest the existence of a QS-like mechanism in B. cinerea, which could lead to new non-biocidal alternatives for its control through interference in the pathogenicity and virulence mechanisms of the fungi.

Influence of a Retentive Shoulder Design to Prevent Early Failure of Three Core Build-Ups.

This study evaluated the influence of a retentive shoulder design to prevent early failure of three resin composite build-ups on molars. Ninety-six intact extracted human maxillary third molars were assigned to two groups (n=48) based on occlusal, buccal cusps only and all cusps reduction. The groups were divided into two subgroups: pin retained and non-pin retained build-ups resulting in four groups (n=24), according the cusps reduction: pin retained/partial, pin retained/complete, non-pin retained/partial, non-pin retained/complete. Occlusal reduction was 3 mm with a semi-lunar retentive shoulder of 3 mm and an axial wall height of 1.5 mm. Groups were restored using a microhybrid, flowable or titanium reinforced resin composite. Modified self-curing acrylic resin provisional crowns were fabricated, cemented with non-eugenol temporary cement and thermal cycled. An instron machine applied tension to the provisional crowns parallel to the long axis of the tooth until dislodgement. A three-way analysis of variance was conducted on the influence of the variables on the retention of the core build-up. Ninety-three build-ups were retained under tensile load, while three core build-ups without pins were dislodged. Three-way analysis of variance showed no statistically significant difference between core build-ups using a retentive shoulder and pin retained core build-ups when tested under tensile load. With the advent of adhesive systems, increased surface area and retentive shoulder design can provide a retentive core foundation to prevent early failures of core build-ups during indirect restoration fabrication which will contribute to the longevity of final restorations.