Metallacycle-cored luminescent ionic liquid crystals with trigonal symmetry.

Herein, we report the preparation of a series of metallacycle-cored liquid crystals with hexagonal and trigonal symmetries based on the self-assembly of tri(ethyl glycol) (TEG)-functionalized diplatinum(ii) ligands and alkyl chain-appendant tetraphenylethylene (TPE) derivatives. Interestingly, with the increase of the density of the TEG units in the metallacycles, the phase separation between TEG and alkyl chains reduces the symmetry of the columnar phase from hexagonal 6 to trigonal 31, which significantly enhances the aggregation of TPE units and thus increases the emission of the system, resulting in fluorescence quantum yield as high as 47.4% in the mesogenic phase.

Manipulation of Supramolecular Chirality in Bicontinuous Networks of Bent-Shaped Polycatenar Dimers.

Bicontinuous cubic liquid crystalline (LC) phases are of particular interest due their possible applications in electronic devices and special supramolecular chirality. Herein, we report the design and synthesis of first examples of achiral bent-shaped polycatenar dimers, capable of displaying mirror symmetry breaking in their cubic and isotropic liquid phases. The molecules have a taper-shaped 3,4,5-trialkoxybenzoate segment connected to rod-like building unit terminated with one terminal flexible chain.

Highly branched bolapolyphilic liquid crystals with a cubic A15 network at the triangle-square transition.

Rod-like bolapolyphiles with highly branched carbosilane-based side-chains self-assemble into several honeycomb structures if the oligo(-phenylene ethynylene) core is polyfluorinated, whereas for the non-fluorinated series an A15 type cubic network of rod-bundles was observed instead, suggesting a brand new pathway for the transition between triangular and square honeycomb phases.

Parameterization of the ambient aerosol refractive index with source appointed chemical compositions.

The refractive index of ambient aerosols is widely used in the climate model and remote sensing. Traditionally, the real part of the refractive index (RRI) of the ambient aerosol is calculated from the measured mass fraction of the main inorganic components with known refractive index, without full resolving the effects of variation in the RRI of organic components, which always contribute more than 50 % of the total aerosol mass. For the first time, the ambient aerosol RRI and the aerosol chemical components were measured concurrently at a suburban site Changping, in Beijing, China.

Understanding and Manipulating Helical Nanofilaments in Binary Systems with Achiral Dopants.

Here, we report the relationship between helical pitch of the helical nanofilament (HNF) phase formed by bent-core molecule NOBOW and the concentration of achiral dopants 5CB and octane, using linearly polarized resonant soft X-ray scattering (RSoXS). Utilizing theory-based simulation, which fits well with the experiments, the molecular helices in the filament were probed and the superstructure of helical 5CB directed by groove of HNFs was observed. Quantitative pitch determination with RSoXS reveals that helical pitch variation is related to 5CB concentration with no temperature dependence.

Current challenges of improving visibility due to increasing nitrate fraction in PM during the haze days in Beijing, China.

The annual mean PM mass concentration has decreased because of the stringent emission controls implemented in Beijing, China in recent years, whereas the nitrate NO mass fraction in PM increases gradually. Low-visibility events occur frequently even though PM pollution has been mitigated significantly, with the daily mean PM mass concentration mostly less than 75 μg/m. In this study, the non-linear relationship was analyzed between atmospheric visibility and PM based on chemical composition from a two-year field observation.

Asymmetric Incorporation of Silver Nanoparticles in Polymeric Assemblies by Coassembly of Tadpole-Like Nanoparticles and Amphiphilic Block Copolymers.

A general approach to asymmetrically localize nanoparticles (NPs) in larger polymeric nanostructures is demonstrated by coassembly of tadpole-like silver NPs (AgNPs) and amphiphilic block copolymers (BCPs). The tadpole-like AgNPs are prepared by template synthesis using a tailor-made A(BC) star polymer, namely poly(ethylene glycol)[poly(acrylic acid)-block-polystyrene] [PEG(PAA-b-PS) ], as template resulting in AgNPs decorated with twenty short PS chains and one long PEG chain, named Ag@PEG(PS) . The asymmetric distribution of these AgNPs in various polymeric nanostructures, e.

The particle phase state during the biomass burning events.

The phase state of biomass burning aerosols (BBA) remains largely unclear, impeding our understanding of their effects on air quality, climate and human health, due to its profound roles in mass transfer between gaseous and particulate phase. In this study, the phase state of BBA was investigated by measuring the particle rebound fraction ƒ combining field observations and laboratory experiments. We found that both ambient and laboratory-generated BBA had unexpectedly lower rebound fraction ƒ (<0.

Larger than expected variation range in the real part of the refractive index for ambient aerosols in China.

The real part of the refractive index (RRI) of ambient aerosol, which is widely used in remote sensing and atmospheric models, is one of the key factors determining its particles' optical properties. The characteristics of ambient aerosol RRI in China have not yet been well studied owing to a lack of observations. For the first time, the properties of aerosol RRI were studied based on field measurements in China at four sites with different atmospheres.

Explosive Secondary Aerosol Formation during Severe Haze in the North China Plain.

Severe haze events with exceedingly high-levels of fine aerosols occur frequently over the past decades in the North China Plain (NCP), exerting profound impacts on human health, weather, and climate. The development of effective mitigation policies requires a comprehensive understanding of the haze formation mechanisms, including identification and quantification of the sources, formation, and transformation of the aerosol species. Haze evolution in this region exhibits distinct physical and chemical characteristics from clean to polluted periods, as evident from increasing stagnation and relative humidity, but decreasing solar radiation as well as explosive secondary aerosol formation.

A preliminary investigation of COVID-19 transmission in the United States by incorporating social media sentiments.

COVID-19 has now become a global pandemic. During the widespread of COVID-19, Twitter, as an online social media platform, has been a preferred channel for interaction and communication. As a result, it provides huge amount of information from which latent signals such as sentiments can be mined for a better understanding of COVID-19 transmission patterns.

Intensity-noise suppression in 1950-nm single-frequency fiber laser by bidirectional amplifier configuration.

In this Letter, a bidirectional amplifier configuration suppressing the relative intensity noise in a 1950-nm linearly polarized single-frequency fiber laser (SFFL) is proposed. The scheme to amplify the signal in a nonlinear saturated amplification regime with low gain distribution for suppressing the RIN is theoretically analyzed. By optimizing the input power level and reflectivity of the bidirectional power-amplifier, the RIN is decreased maximally by >24 within the frequency range of 200 kHz.

Noise-sideband-free and narrow-linewidth photonic microwave generation based on anoptical heterodyne technique of low-noise fiber lasers.

Noise-sideband-free and narrow-linewidth photonic microwave generation based on an optical heterodyne technique is demonstrated experimentally. By beating a self-injection-locking low-noise single-frequency fiber laser and a Brillouin fiber laser, a 9.4 GHz microwave is produced, and its noise sidebands are completely suppressed.

55 W kilohertz-linewidth core- and in-band-pumped linearly polarized single-frequency fiber laser at 1950 nm.

Based on core- and in-band-pumped polarization-maintaining ${{\rm Tm}^{3 + }}$Tm-doped single-cladding fiber (PM-TSF, the core diameter is 9 µm) by a 1610 nm fiber laser and a distributed Bragg reflector seed laser, a linearly polarized single-frequency fiber laser (LP-SFFL) at 1950 nm with an output power of 55.3 W and a laser linewidth of 6.95 kHz is demonstrated.

Luminescent Metallacycle-Cored Liquid Crystals Induced by Metal Coordination.

Two rhomboidal metallacycles based on metal-coordination-driven self-assembly are presented. Because metal-coordination interactions restrict the rotation of phenyl groups on tetraphenylethene units, these metallacycles were emissive both in solution and in solid state, and their aggregation-induced emission properties were well-retained. Moreover, the rhomboidal metallacyclic structures offer a platform for intermolecular packing beneficial for the formation of liquid crystalline phases.

Enhancement in Particulate Organic Nitrogen and Light Absorption of Humic-Like Substances over Tibetan Plateau Due to Long-Range Transported Biomass Burning Emissions.

To elucidate the influence of long-range transported biomass burning organic aerosols (BBOA) on the Tibetan Plateau, the molecular compositions and light absorption of HUmic-Like Substances (HULIS), major fractions of brown carbon, were characterized during the premonsoon season. Under the significant influence of biomass burning, HULIS concentrations increased to as high as 26 times of the background levels, accounting for 54% of water-soluble organic carbon (WSOC) and 50% of organic carbon (OC). The light absorption of HULIS also enhanced up to 42 times of the background levels, contributing 61% of the WSOC absorption and 50% of OC absorption.

New insight into PM pollution patterns in Beijing based on one-year measurement of chemical compositions.

In recent years, air pollution has become a major concern in China, especially in the capital city of Beijing. Haze events occur in Beijing over all four seasons, exhibiting distinct characteristics. In this study, the typical evolution patterns of atmospheric particulate matter with a diameter of less than 2.

Temporal and spatial distribution of PM chemical composition in a coastal city of Southeast China.

Rapid economic development and urbanization in China has been concentrated in coastal cities, resulting in haze and photochemical smog issues, especially in the densely-populated Yangtze River Delta. In this study, we explore particulate matter (specifically PM) pollution in a city in Zhejiang Province (Ningbo), chosen to represent a typical, densely-populated urban city with residential and industrial sections. PM samples were collected at five sites in four seasons from Dec.