3D hydrogen-like screening effect on excitons in hBN-encapsulated monolayer transition metal dichalcogenides.

We observe both s-series and p-series excitons by using sum frequency generation spectroscopy on monolayer (1L-)MX (M = Mo, W, X = S, Se) encapsulated by hexagonal boron nitride (hBN). Moreover, we perform numerical calculations with the Rytova-Keldysh potential and obtain the relative dielectric constant of hBN among other parameters. The obtained relative dielectric constant can be approximated by the high-frequency limit of the infrared dispersion even though the exciton binding energies are almost on the phonon resonances in hBN.

Ammonium carboxylates in the ammonia-Ugi reaction: one-pot synthesis of α,α-disubstituted amino acid derivatives including unnatural dipeptides.

Despite the remarkable developments of the Ugi reaction and its variants, the use of ammonia in the Ugi reaction has long been recognized as impractical and unsuccessful. Indeed, the ammonia-Ugi reaction often requires harsh reaction conditions, such as heating and microwave irradiation, and competes with the Passerini reaction, thereby resulting in low yields. This study describes a robust and practical ammonia-Ugi reaction protocol.

Ultrafast Electron-Electron Scattering in Metallic Phase of 2H-NbSe_{2} Probed by High Harmonic Generation.

Electron-electron scattering on the order of a few to tens of femtoseconds plays a crucial role in the ultrafast electron dynamics of conventional metals. When mid-infrared light is used for driving and the period of light field is comparable to the scattering time in metals, unique light-driven states and nonlinear optical responses associated with the scattering process are expected to occur. Here, we use high-harmonics spectroscopy to investigate the effect of electron-electron scattering on the electron dynamics in thin film 2H-NbSe_{2} driven by a mid-infrared field.

Ultrafast pump-probe spectroscopy via chirped-pulse up-conversion with dispersion compensation.

In this study, ultrafast transient signals were detected on a single-shot basis using chirped-pulse up-conversion spectroscopy with dispersion compensation. Unlike in the conventional time-encoding technique using chirped pulses, distortion of the ultrafast waveform was reduced by applying dispersion compensation to the chirped probe pulses and using sum-frequency generation with the chirped readout pulses. The method was applied to terahertz time-domain spectroscopy and near-infrared pump-probe spectroscopy, providing ultrafast observations with an improved temporal resolution comparable to the transform-limited pulse durations.

Diabatic and adiabatic transitions between Floquet states imprinted in coherent exciton emission in monolayer WSe.

Floquet engineering is a promising way of controlling quantum system with photon-dressed states on an ultrafast time scale. So far, the energy structure of Floquet states in solids has been intensively investigated. However, the dynamical aspects of the photon-dressed states under ultrashort pulse have not been explored yet.

Broadband sum frequency generation spectroscopy of dark exciton states in hBN-encapsulated monolayer WSe.

We demonstrate that broadband sum frequency generation (SFG) spectroscopy based on a partially incoherent supercontinuum light source can elucidate dark p-series excitons in monolayer WSe encapsulated between hexagonal boron nitride (hBN) slabs. The observed 2p exciton peak energy is a few meV higher than that predicted by the Rytova-Keldysh potential model, which is originated from the Berry phase effect. Interestingly, although the radiative relaxation of the 2p exciton is weaker, the 2p exciton peak is broader than the 1s and 2s peaks, which indicates its faster dephasing than the 1s and 2s excitons.

Influence of preoperative serum creatinine level and intraoperative volume of contrast medium on the risk of acute kidney injury after transfemoral transcatheter aortic valve implantation: a retrospective observational study.

Objective: This study aimed to determine if contrast medium volume (CMV) is a risk factor for acute kidney injury (AKI) during transcatheter aortic valve implantation (TAVI) via a transfemoral approach performed without major complications. All TAVI procedures performed at our institution between March 2014 and March 2018 were retrospectively reviewed. AKI was diagnosed using the Acute Kidney Injury Network classification based on the Valve Academic Research Consortium-2 definition.

A Peanut-Shaped Polyaromatic Capsule: Solvent-Dependent Transformation and Electronic Properties of a Non-Contacted Fullerene Dimer.

Synthesis of molecular containers capable of incorporating multiple fullerenes remains challenging. Reported here is that room-temperature mixing of metal ions with W-shaped bispyridine ligands featuring polyaromatic panels results in the quantitative formation of a peanut-shaped M L capsule. The capsule reversibly converts into two molecules of an ML double tube in response to changes in the solvent.

Open versus Closed Polyaromatic Nanocavity: Enhanced Host Abilities toward Large Dyes and Pigments.

Host functions of polyaromatic nanocavities were revealed by using an M L molecular cage and capsule. On the basis of the previously reported M L capsule with a closed polyaromatic cavity, a new M L cage (as a mixture of the isomers) was prepared by the quantitative assembly of two metal ions and four desymmetrized bispyridine ligands with a single polyaromatic panel. The obtained, open nanocavity of the cage exhibited enhanced binding abilities toward large dyes and pigments in water.

Cramming versus threading of long amphiphilic oligomers into a polyaromatic capsule.

Oligo(ethylene oxide)s are known as widely useable yet not very interactive amphiphilic compounds. Here we report that the long amphiphilic oligomers are bound by a polyaromatic capsule in two different manners, depending on the chain length. For instance, the shorter pentamer is crammed into the isolated cavity of the capsule, whereas the longer decamer is threaded into the capsule to form a 1:1 host-guest complex in a pseudo-rotaxane fashion.

Robust Nanowrapping of Reduced Graphene Oxide by Metal-Organic Network Films between Fe Ions and Tetra(Catechol-Substituted) Porphyrin.

We found the utilization of porphyrin-based metal-organic network films composed of tetra(catechol-substituted)porphyrin (cPor) and Fe ions for robust wrapping materials of graphene oxide (GO), which can keep the dispersion state under the chemical reduction of GO to reduced graphene oxide (rGO) in water. The tetra(catechol-substituted)porphyrin (cPor) was designed for soft-wrapping methods because the aromatic porphyrin moieties can be strongly adsorbed onto the surface of GO or rGO via both π-π interactions and the catechol-Fe coordination network formation. The GO sheets covered with the cPor-Fe films were reduced chemically in water under retention of the wrapped nanostructure of the cPor-Fe/GO sheets.

Hydrophilic Oligo(lactic acid)s Captured by a Hydrophobic Polyaromatic Cavity in Water.

Biologically relevant hydrophilic molecules rarely interact with hydrophobic compounds and surfaces in water owing to effective hydration. Nevertheless, herein we report that the hydrophobic cavity of a polyaromatic capsule, formed through coordination-driven self-assembly, can encapsulate hydrophilic oligo(lactic acid)s in water with relatively high binding constants (up to K =3×10  m ). X-ray crystallographic and ITC analyses revealed that the unusual host-guest behavior is caused by enthalpic stabilization through multiple CH-π and hydrogen-bonding interactions.

Protecting group free synthesis of urea-linked glycoconjugates: efficient synthesis of β-urea glycosides in aqueous solution.

A method for the protecting group free synthesis of β-urea-linked glycoconjugates has been developed. The one step process, involving reactions between urea and D-glucose, N-acetyl-D-glucosamine or D-xylose in acidic aqueous solution, furnishes the corresponding β-urea glycosides in modest yields. This simple and efficient procedure is applicable to the synthesis of β-urea tethered amino acid-carbohydrate conjugates.

Superflares on solar-type stars.

Solar flares are caused by the sudden release of magnetic energy stored near sunspots. They release 10(29) to 10(32) ergs of energy on a timescale of hours. Similar flares have been observed on many stars, with larger 'superflares' seen on a variety of stars, some of which are rapidly rotating and some of which are of ordinary solar type.

Synthesis of glycocinnasperimicin D.

The first total synthesis of amino sugar antibiotic glycocinnasperimicin D (1) has been achieved by a convergent, three-component coupling strategy. The key steps involve the Heck-Mizoroki reaction by using the iodophenyl glycoside 50 and acryl amide 32 to furnish the right core structure of 1, and the construction of the urea glycoside employing the reaction of glycosyl isocyanate 8 with amino sugar 9. Glycosyl isocyanate 8 was prepared by the oxidation of isonitrile 10, which displayed excellent reactivity in the coupling event.

Anomalous in-plane anisotropy of the onset of superconductivity in (TMTSF)2ClO4.

We report the magnetic-field amplitude and field-angle dependence of the superconducting onset temperature Tconset of the organic superconductor (TMTSF)2ClO4 in magnetic fields H accurately aligned to the conductive ab' plane. We revealed that the rapid increase of the onset fields at low temperatures occurs both for H || b' and H || a, irrespective of the carrier confinement. Moreover, in the vicinity of the Pauli-limiting field, we report a shift of a principal axis of the in-plane field-angle dependence of Tconset.

The ectopically parting cells 1-2 (epc1-2) mutant exhibits an exaggerated response to abscisic acid.

The ECTOPICALLY PARTING CELLS 1 (EPC1) gene encodes a putative retaining glycosyltransferase of the GT64 family, and epc1-1 mutant plants have a severely dwarfed phenotype. A new mutant allele of this gene, epc1-2, has been isolated. Reduced cell adhesion that has previously been reported for the epc1-1 mutant was not observed for either the epc1-1 or epc1-2 mutants grown in our conditions, suggesting that EPC1 does not affect cell adhesion but is involved in some other process affecting plant growth and development.

Nucleotide sequence of RNA2 of Lettuce big-vein virus and evidence for a possible transcription termination/initiation strategy similar to that of rhabdoviruses.

Lettuce big-vein virus (LBVV) is the type species of the genus Varicosavirus and is a two-segmented negative-sense single-stranded RNA virus. The larger LBVV genome segment (RNA1) consists of 6797 nt and encodes an L polymerase that resembles that of rhabdoviruses. Here, the nucleotide sequence of the second LBVV genome segment (RNA2) is reported.

Isolation and expression analysis of gibberellin 20-oxidase homologous gene in apple.

To characterize the gibberellin (GA) 20-oxidase gene in apple, the genomic and cDNA clone from "Fuji" apple (accession no. AB037114) was isolated. The deduced amino acid sequence of this cDNA showed 71% and 66% identity to those of GA 20-oxidase cloned from French bean and Arabidopsis, respectively.

Decreased GA1 content caused by the overexpression of OSH1 is accompanied by suppression of GA 20-oxidase gene expression.

We previously reported that overexpression of the rice homeobox gene OSH1 led to altered morphology and hormone levels in transgenic tobacco (Nicotiana tabacum L.) plants. Among the hormones whose levels were changed, GA1 was dramatically reduced.

Alteration of hormone levels in transgenic tobacco plants overexpressing the rice homeobox gene OSH1.

The rice (Oryza sativa L.) homeobox gene OSH1 causes morphological alterations when ectopically expressed in transgenic rice, Arabidopsis thaliana, and tobacco (Nicotiana tabacum L.) and is therefore believed to function as a morphological regulator gene.

Ectopic expression of a tobacco homeobox gene, NTH15, dramatically alters leaf morphology and hormone levels in transgenic tobacco.

The shoot apical meristem functions to generate the lateral organs of a plant throughout the vegetative and reproductive phases. Homeobox genes play key roles in controlling such developmental programs, but their modes of action have not been well defined. Here we describe isolation and biological functions of a novel tobacco homeobox gene, designated NTH15 (Nicotiana tabacum homeobox 15), from a tobacco shoot apex cDNA library.