Near-Unity Light Absorption in a Monolayer WS2 Van der Waals Heterostructure Cavity.

Excitons in monolayer transition-metal-dichalcogenides (TMDs) dominate their optical response and exhibit strong light-matter interactions with lifetime-limited emission. While various approaches have been applied to enhance light-exciton interactions in TMDs, the achieved strength have been far below unity, and a complete picture of its underlying physical mechanisms and fundamental limits has not been provided. Here, we introduce a TMD-based van der Waals heterostructure cavity that provides near-unity excitonic absorption, and emission of excitonic complexes that are observed at ultralow excitation powers. Our results are in full agreement with a quantum theoretical framework introduced to describe the light-exciton-cavity interaction. We find that the subtle interplay between the radiative, nonradiative and dephasing decay rates plays a crucial role, and unveil a universal absorption law for excitons in 2D systems. This enhanced light-exciton interaction provides a platform for studying excitonic phase-transitions and quantum nonlinearities and enables new possibilities for 2D semiconductor-based optoelectronic devices.

Dynamic tailoring of an optical skyrmion lattice in surface plasmon polaritons: comment.

We comment on a recent paper entitled "Dynamic tailoring of an optical skyrmion lattice in surface plasmon polaritons" [Opt. Express28, 10322 (2020)10.1364/OE.384718] and disprove the assertion that Bloch-type skyrmions exist in the magnetic field of surface plasmon polaritons.

Imaging the Nonlinear Plasmoemission Dynamics of Electrons from Strong Plasmonic Fields.

We use subcycle time-resolved photoemission microscopy to unambiguously distinguish optically triggered electron emission (photoemission) from effects caused purely by the plasmonic field (termed "plasmoemission"). We find from time-resolved imaging that nonlinear plasmoemission is dominated by the transverse plasmon field component by utilizing a transient standing wave from two counter-propagating plasmon pulses of opposite transverse spin. From plasmonic foci on flat metal surfaces, we observe highly nonlinear plasmoemission up to the fifth power of intensity and quantized energy transfer, which reflects the quantum-mechanical nature of surface plasmons. Our work constitutes the basis for novel plasmonic devices such as nanometer-confined ultrafast electron sources as well as applications in time-resolved electron microscopy.

Plasmon-Polaron Coupling in Conjugated Polymer on Infrared Nanoantennas.

We propose and demonstrate a novel type of coupling between polarons in a conjugated polymer and localized surface plasmons in infrared (IR) nanoantennas. The near-field interaction between plasmons and polarons is revealed by polarized photoinduced absorption measurements, probing mid-IR polaron transitions, and infrared-active vibrational modes of the polymer, which directly gauge the density of photogenerated charge carriers. This work proves the possibility of tuning the polaronic properties of organic semiconductors with plasmonic nanostructures.

Antipsychotic effects on anthropometric outcomes in anorexia nervosa: a retrospective chart review of hospitalized children and adolescents.

BACKGROUND: Off-label antipsychotic use is not uncommon in youth with anorexia nervosa (AN), aiming to enhance suboptimal weight restoration, yet its efficacy remains debated, especially in youth. METHODS: Retrospective chart review of consecutively admitted inpatients (ages 8-18 years) with restricting/binge-purge AN, comparing youth with versus without antipsychotic treatment regarding baseline factors, treatment, and anthropometric outcome characteristics including all patients and matched subgroups. Matched subsamples were also compared regarding faster versus slower weight change (median split). Furthermore, within-subject analyses compared weight gain trajectories before versus after antipsychotic use in antipsychotic-treated youth. These results were then compared in a pre-/post design with the matched control group without antipsychotic treatment, using the mean duration until antipsychotic use in the antipsychotic-treated group as the dividing timeline, controlling for a potential order effect, in that later rather than earlier antipsychotic treatment for AN may be more successful. RESULTS: Of 294 youth with AN (median age = 15.2 (interquartile range = 14.0, 16.6) years, females = 96.6%, restricting subtype = 81.0%, hospitalization duration = 98.2 ± 43.2 days), 44 (15.0%) underwent 52 antipsychotic trials (olanzapine = 63.5%). In multivariable analyses, antipsychotic use was independently associated with younger age, childhood physical abuse history, comorbid borderline personality traits, and lower pre-antipsychotic weight gain (p < 0.0001). In unmatched groups, antipsychotic-treated versus non-treated youth had significantly lower discharge anthropometric parameters, longer inpatient treatment, and lower weight change/week (p < 0.001-p = 0.005), without significant differences between olanzapine and non-olanzapine antipsychotics (p = 0.27-0.44). Non-significant antipsychotic effects on weight outcomes were confirmed in (1) matched subgroups of antipsychotic-treated versus non-treated youth (n = 43 each), (2) youth with faster versus slower weight gain (n = 21 vs. n = 22), and (3) antipsychotic-treated youth when comparing weight change before versus after antipsychotic use (n = 31). Moreover, in antipsychotic-treated youth, weight change/week remained significantly lower versus matched non-antipsychotic-treated youth (n = 31) both before (p = 0.053) and after (p = 0.006) the median time (5 weeks) until antipsychotic use. CONCLUSIONS: In this naturalistic study, clinician's antipsychotic choice, given to a more severely ill subgroup of adolescents with AN, did not significantly improve overall worse weight change trajectories during inpatient treatment, even in matched subgroups. Randomized trials in individuals reflecting real-world samples are needed to evaluate the utility of antipsychotic treatment in youth with AN.

Anorexia nervosa is one of the psychiatric diseases with the highest risk of death in adolescence. People with anorexia nervosa are often severely underweight out of fear of being too "fat". Treatment is difficult. Clinicians not infrequently use off-label antipsychotic medications to improve weight gain in anorexia nervosa. Unfortunately, currently, there is little evidence of efficacy for antipsychotics, especially in children and adolescents. We examined the files of youth (8­18 years old) who were treated as inpatients between 1992 and 2015. Altogether, 44 (15%) of the 294 youth were prescribed antipsychotics, with antipsychotic use increasing over time (1992 = 0% to 2015 = 20%). Of all antipsychotic drugs, olanzapine was given most frequently (64%). Patients who received antipsychotic medications were younger and sicker than patients without antipsychotics. Also, patients prescribed antipsychotics gained less weight per week before starting antipsychotics. They also gained less weight than patients not receiving antipsychotics. Despite being treated longer as inpatients, antipsychotic-treated youth had lower discharge body weight values. We did not find differences between olanzapine and other antipsychotics regarding weight gain. In summary, we found that antipsychotics did not help with weight gain in youth with anorexia nervosa.

Ultrafast Time Dynamics of Plasmonic Fractional Orbital Angular Momentum.

The creation and manipulation of optical vortices, both in free space and in two-dimensional systems such as surface plasmon polaritons (SPPs), has attracted widespread attention in nano-optics due to their robust topological structure. Coupled with strong spatial confinement in the case of SPPs, these plasmonic vortices and their underlying orbital angular momentum (OAM) have promise in novel light-matter interactions on the nanoscale with applications ranging from on-chip particle manipulation to tailored control of plasmonic quasiparticles. Until now, predominantly integer OAM values have been investigated. Here, we measure and analyze the time evolution of fractional OAM SPPs using time-resolved two-photon photoemission electron microscopy and near-field optical microscopy. We experimentally show the field's complex rotational dynamics and observe the beating of integer OAM eigenmodes at fractional OAM excitations. With our ability to access the ultrafast time dynamics of the electric field, we can follow the buildup of the plasmonic fractional OAM during the interference of the converging surface plasmons. By adiabatically increasing the phase discontinuity at the excitation boundary, we track the total OAM, leading to plateaus around integer OAM values that arise from the interplay between intrinsic and extrinsic OAM.

Rigidifying a De Novo Enzyme Increases Activity and Induces a Negative Activation Heat Capacity.

Conformational sampling profoundly impacts the overall activity and temperature dependence of enzymes. Peroxidases have emerged as versatile platforms for high-value biocatalysis owing to their broad palette of potential biotransformations. Here, we explore the role of conformational sampling in mediating activity in the de novo peroxidase C45. We demonstrate that 2,2,2-triflouoroethanol (TFE) affects the equilibrium of enzyme conformational states, tending toward a more globally rigid structure. This is correlated with increases in both stability and activity. Notably, these effects are concomitant with the emergence of curvature in the temperature-activity profile, trading off activity gains at ambient temperature with losses at high temperatures. We apply macromolecular rate theory (MMRT) to understand enzyme temperature dependence data. These data point to an increase in protein rigidity associated with a difference in the distribution of protein dynamics between the ground and transition states. We compare the thermodynamics of the de novo enzyme activity to those of a natural peroxidase, horseradish peroxidase. We find that the native enzyme resembles the rigidified de novo enzyme in terms of the thermodynamics of enzyme catalysis and the putative distribution of protein dynamics between the ground and transition states. The addition of TFE apparently causes C45 to behave more like the natural enzyme. Our data suggest robust, generic strategies for improving biocatalytic activity by manipulating protein rigidity; for functional de novo protein catalysts in particular, this can provide more enzyme-like catalysts without further rational engineering, computational redesign, or directed evolution.

Complete genome sequence of the myxobacterium Sorangium cellulosum.

The genus Sorangium synthesizes approximately half of the secondary metabolites isolated from myxobacteria, including the anti-cancer metabolite epothilone. We report the complete genome sequence of the model Sorangium strain S. cellulosum So ce56, which produces several natural products and has morphological and physiological properties typical of the genus. The circular genome, comprising 13,033,779 base pairs, is the largest bacterial genome sequenced to date. No global synteny with the genome of Myxococcus xanthus is apparent, revealing an unanticipated level of divergence between these myxobacteria. A large percentage of the genome is devoted to regulation, particularly post-translational phosphorylation, which probably supports the strain's complex, social lifestyle. This regulatory network includes the highest number of eukaryotic protein kinase-like kinases discovered in any organism. Seventeen secondary metabolite loci are encoded in the genome, as well as many enzymes with potential utility in industry.

Ultrafast vector imaging of plasmonic skyrmion dynamics with deep subwavelength resolution.

Plasmonic skyrmions are an optical manifestation of topological defects in a continuous vector field. Identifying them requires characterization of the vector structure of the electromagnetic near field on thin metal films. Here we introduce time-resolved vector microscopy that creates movies of the electric field vectors of surface plasmons with subfemtosecond time steps and a 10-nanometer spatial scale. We image complete time sequences of propagating surface plasmons as well as plasmonic skyrmions, resolving all vector components of the electric field and their time dynamics, thus demonstrating dynamic spin-momentum coupling as well as the time-varying skyrmion number. The ability to image linear optical effects in the spin and phase structures of light in the single-nanometer range will allow for entirely novel microscopy and metrology applications.

Spiroketal polyketide formation in Sorangium: identification and analysis of the biosynthetic gene cluster for the highly cytotoxic spirangienes.

Natural products constitute important lead structures in drug discovery. In bacteria, they are often synthesized by large, modular multienzyme complexes. Detailed analysis of the biosynthetic machinery should enable its directed engineering and production of desirable analogs. The myxobacterium Sorangium cellulosum So ce90 produces the cytotoxic spiroketal polyketide spirangien, for which we describe the identification and functional analysis of the biosynthetic pathway. The gene cluster spans 88 kb and encodes 7 type I polyketide synthases and additional enzymes such as a stand-alone thioesterase and 2 methyltransferases. Inactivation of two cytochrome P(450) monooxygenase genes resulted in the production of acyclic spirangien derivatives, providing direct evidence for the involvement of these enzymes in spiroketal formation. The presence of large DNA repeats is consistent with multiple rounds of gene duplication during the evolution of the biosynthetic gene locus.

Short-range surface plasmonics: Localized electron emission dynamics from a 60-nm spot on an atomically flat single-crystalline gold surface.

We experimentally and theoretically visualize the propagation of short-range surface plasmon polaritons using atomically flat single-crystalline gold platelets on silicon substrates. We study their excitation and subfemtosecond dynamics via normal-incidence two-photon photoemission electron microscopy. By milling a plasmonic disk and grating structure into a single-crystalline gold platelet, we observe nanofocusing of the short-range surface plasmon polariton. Localized two-photon ultrafast electron emission from a spot with a smallest dimension of 60 nm is observed. Our novel approach opens the door toward reproducible plasmonic nanofocusing devices, which do not degrade upon high light intensity or heating due to the atomically flat surface without any tips, protrusions, or holes. Our nanofoci could also be used as local emitters for ultrafast electron bunches in time-resolved electron microscopes.

Hole-mask colloidal nanolithography combined with tilted-angle-rotation evaporation: A versatile method for fabrication of low-cost and large-area complex plasmonic nanostructures and metamaterials.

Many nano-optical applications require a suitable nanofabrication technology. Hole-mask colloidal nanolithography has proven to be a low-cost and large-area alternative for the fabrication of complex plasmonic nanostructures as well as metamaterials. In this paper, we describe the fabrication process step by step. We manufacture a variety of different plasmonic structures ranging from simple nano-antennas over complex chiral structures to stacked composite materials for applications such as sensing. Additionally, we give details on the control of the nanostructure lateral density which allows for the multilayer-fabrication of complex nanostructures. In two accompanying movies, the fabrication strategy is explained and details are being demonstrated in the lab. The movies can be found at the website of Beilstein TV.

Large-area 3D chiral plasmonic structures.

We manufacture large-area plasmonic structures featuring 3-dimensional chirality by colloidal nanohole lithography. By varying the polar rotating speed of the samples during gold evaporation, we can fabricate spiral-type ramp nanostructures. The optical properties show chiroptical resonances in the 100 to 400 THz frequency region (750 to 3000 nm), with circular dichroism values of up to 13%. Our method offers a simple low-cost manufacturing method of cm(2)-sized chiral plasmonic templates for chiroptical applications such as stereochemical enantiomer sensors.

Hole-mask colloidal nanolithography for large-area low-cost metamaterials and antenna-assisted surface-enhanced infrared absorption substrates.

We use low-cost hole-mask colloidal nanolithography to manufacture large-area resonant split-ring metamaterials and measure their infrared optical properties. This novel substrate is employed for antenna-assisted surface-enhanced infrared absorption measurements using octadecanethiol (ODT) and deuterated ODT, which demonstrates easy adjustability of our material to vibrational modes. Our method has the potential to make resonant plasmon-enhanced infrared spectroscopy a standard lab tool in biology, pharmacology, and medicine.

Large-area high-quality plasmonic oligomers fabricated by angle-controlled colloidal nanolithography.

We introduce angle-controlled colloidal nanolithography as a fast and low-cost fabrication technique for large-area periodic plasmonic oligomers with complex shapes and tunable geometry parameters. We investigate the optical properties and find highly modulated plasmon modes in oligomers with triangular building blocks. Fundamental modes, higher-order modes, as well as Fano resonances due to coupling between bright and dark modes within the same complex structure are present, depending on polarization and structure geometry. Our process is well-suited for mass fabrication of novel large-area plasmonic sensing devices and nanoantennas.

From genetic diversity to metabolic unity: studies on the biosynthesis of aurafurones and aurafuron-like structures in myxobacteria and streptomycetes.

The myxobacterial polyketide secondary metabolites aurafuron A and B were identified by genome mining in the myxobacterial strain Stigmatella aurantiaca DW4/3-1. The compounds contain an unusual furanone moiety and resemble metabolites isolated from soil-dwelling and marine actinobacteria, a fungus and mollusks. We describe here the cloning and functional analysis of the aurafuron biosynthetic gene cluster, including site-directed mutagenesis and feeding studies using labeled precursors. The polyketide core of the aurafurones is assembled by a modular polyketide synthase (PKS). As with many such systems described from myxobacteria, the aurafuron PKS exhibits a number of unusual features, including the apparent iterative use of a module, redundant modules and domains, a trans acting dehydratase and the absence of a terminal thioesterase domain. Four oxidoreductases are encoded within the gene locus, some of which likely participate in formation of the furanone moiety via a Baeyer-Villiger type oxidation. Indeed, inactivation of a gene encoding a cytochrome P(450) monooxygenase completely abolished production of both compounds. We also compare the complete gene locus to biosynthetic gene clusters from two Streptomyces sp., which produce close structural analogues of the aurafurones. A portion of the post-PKS biosynthetic machinery is strikingly similar in all three cases, in contrast to the PKS genes, which are highly divergent. Phylogenetic analysis of the ketosynthase domains further indicates that the PKSs have developed independently (polyphyletically) during evolution. These findings point to a currently unknown but important biological function of aurafuron-like compounds for the producing organisms.