Visual Evaluation of Urban Streetscape Design Supported by Multisource Data and Deep Learning.

This paper integrates classical design theory, multisource urban data, and deep learning to explore an accurate analytical framework in a new data environment, providing a scientific analysis path for the "where" and "how" of greenways in a high-density built environment. The analysis is based on street view data and location service data. Through the integration of multiple data sources such as street scape data, location service data, point-of-interest data, structured web data, and refined built environment data, a systematic measurement of the key elements of density, diversity, design, accessibility to destinations, and distance to transport facilities as defined in the Five Elements of High Quality Built Environment (5D) theory is achieved. The assessment of alignment potential was carried out. The key factors influencing the aesthetics of the street were identified. Based on an extensive landscape perception-based survey, it was found that although different respondents had different views and preferences for the same street scape, their preferences were overwhelmingly influenced by the visual quality of the street scape aesthetics itself, with higher aesthetic quality of the landscape.

Pressure-Induced Local Excitation Promotion: New Route toward High-Efficiency Aggregate Emission Based on Multimer Excited State Modulation.

Achieving high-efficiency solid state emission is essential for practical applications of organic luminescent materials. However, intermolecular interactions generally induce formation of multimeric aggregate excited states with deficient emissive ability, making it extremely challenging to enhance emission in aggregated states. Here we demonstrate a novel strategy of continuously regulating multimeric excitation constituents with a high-pressure technique successfully enhancing the emission in a representative organic charge-transfer material, Laurdan (6-lauroyl-N,N-dimethyl-2-naphthylamine). The Laurdan crystal exhibits distinct emission enhancement up to 4.1 GPa accompanied by a shift in the emission color from blue to cyan. Under compression, the π-π interplanar distance in Laurdan multimers is reduced, and intermolecular wave function diffusion is demonstrated to be improved simultaneously, which results in local excitation promotion and thus enhanced emission. Our findings not only provide new insights into multimeric excited state emission modulation but also pave the way for the further design of high-performance aggregated luminophores.

Experimental Observation of the High Pressure Induced Substitutional Solid Solution and Phase Transformation in Sb2S3.

The substitutional solid solutions composed of group VA-VIA nonmetallic elements has attracted considerable scientific interest since they provide a pressure-induced route to search for novel types of solid solutions with potential applications. Yet, the pressure-induced solid solution phase is unprecedented in the sulfide family. In this paper, the structural behavior of antimony trisulfide, Sb2S3, has been investigated in order to testify whether or not it can also be driven into the substitutional solid solution phase by high pressures. The experiments were carried out by using a diamond anvil cell and angle dispersive synchrotron X-ray diffraction up to 50.2 GPa at room temperature. The experimental results indicate that Sb2S3 undergoes a series of phase transitions at 5.0, 12.6, 16.9, 21.3, and 28.2 GPa, and develops ultimately into an Sb-S substitutional solid solution, which adopts a body-centered cubic disordered structure. In this structure, the Sb and S atoms are distributed randomly on the bcc lattice sites with space group Im-3m. The structural behavior of Sb2S3 is tentatively assigned by comparison within the A2B3 (A = Sb, Bi; B = Se, Te, S) series under high pressures.

Nanodiamonds: a critical component of anodes for high performance lithium-ion batteries.

Detonation nanodiamonds (DNDs) have been introduced into a carbonaceous anode for improving the performance of lithium ion batteries (LIBs). The lithium storage capacity, cycling performance and stability of the LIBs are increased and this is related to the DNDs' unique characteristics of chemical inertness, a larger surface area, low expansion, and high lithium adsorption capacity.

Molecular Mechanisms for High Hydrostatic Pressure-Induced Wing Mutagenesis in Drosophila melanogaster.

Although High hydrostatic pressure (HHP) as an important physical and chemical tool has been increasingly applied to research of organism, the response mechanisms of organism to HHP have not been elucidated clearly thus far. To identify mutagenic mechanisms of HHP on organisms, here, we treated Drosophila melanogaster (D. melanogaster) eggs with HHP. Approximately 75% of the surviving flies showed significant morphological abnormalities from the egg to the adult stages compared with control flies (p < 0.05). Some eggs displayed abnormal chorionic appendages, some larvae were large and red, and some adult flies showed wing abnormalities. Abnormal wing phenotypes of D. melanogaster induced by HHP were used to investigate the mutagenic mechanisms of HHP on organism. Thus 285 differentially expressed genes associated with wing mutations were identified using Affymetrix Drosophila Genome Array 2.0 and verified with RT-PCR. We also compared wing development-related central genes in the mutant flies with control flies using DNA sequencing to show two point mutations in the vestigial (vg) gene. This study revealed the mutagenic mechanisms of HHP-induced mutagenesis in D. melanogaster and provided a new model for the study of evolution on organisms.

Synthesis of Hollow ß-Phase GeO2 Nanoparticles.

We fabricated mono-dispersed hollow waxberry shaped ß-quartz GeO2 by a facile one-step synthesis in emulsion at room temperature. TEM images indicated that hollow waxberry shaped GeO2 were consisted of nano-sphere whose average size were estimated to be 20 nm. The growth mechanism and optical properties of the products were also investigated. It was found that addition of n-butanol and PVP were crucial factors to control the morphology of GeO2. The possible formation mechanism of the hollow interior is proposed as the Ostwald ripening. The optical properties of the ß-GeO2 nanoparticles with hollow shapes were also studied with photoluminescence spectrum, which reveals a broad emission, suggesting potential applications in electronic and optoelectronic nanodevices. These attractive results provide us a new simple method further used to fabricate other specific hollow structure and indicate hollow waxberry shaped GeO2 may have potential applications in light-emitting nanodevices.

A Protocol to Fabricate Nanostructured New Phase: B31-Type MnS Synthesized under High Pressure.

Synthesis of nanomaterials with target crystal structures, especially those new structures that cannot be crystallized in their bulk counterparts, is of considerable interest owing to their strongly structure-dependent properties. Here, we have successfully synthesized and identified new-phase nanocrystals (NCs) associated with orthorhombic MnP-type (B31) MnS by utilizing an effective high-pressure technique. It is particularly worth noting that the generated new structured MnS NCs were captured as expected by quenching the high-pressure phase to the ambient conditions at room temperature. Likewise, the commercially available bulk rocksalt (RS) MnS material underwent unambiguously a reversible phase transition when the pressure was released completely. First-principles calculations further supported that the B31-MnS was more energetically preferable than the RS one under high pressure, which can be plausibly interpreted by the structural buckling with respect to zigzagged arrangements within B31 unit cell. Our findings represent a significant step forward in a deeper understanding of the high-pressure phase diagram of MnS and even provide a promising strategy to prepare desired nanomaterials with new structures that do not exist in their bulk counterparts, thus greatly increasing the choice of materials for a variety of applications.

Reactions of xenon with iron and nickel are predicted in the Earth's inner core.

Studies of the Earth's atmosphere have shown that more than 90% of the expected amount of Xe is depleted, a finding often referred to as the 'missing Xe paradox'. Although several models for a Xe reservoir have been proposed, whether the missing Xe could be contained in the Earth's inner core has not yet been answered. The key to addressing this issue lies in the reactivity of Xe with Fe/Ni, the main constituents of the Earth's core. Here, we predict, through first-principles calculations and unbiased structure searching techniques, a chemical reaction of Xe with Fe/Ni at the temperatures and pressures found in the Earth's core. We find that, under these conditions, Xe and Fe/Ni can form intermetallic compounds, of which XeFe3 and XeNi3 are energetically the most stable. This shows that the Earth's inner core is a natural reservoir for Xe storage and provides a solution to the missing Xe paradox.

Robust diamond meshes with unique wettability properties.

Robust diamond meshes with excellent superhydrophobic and superoleophilic properties have been fabricated. Superhydrophobicity is observed for water with varying pH from 1 to 14 with good recyclability. Reversible superhydrophobicity and hydrophilicity can be easily controlled. The diamond meshes show highly efficient water-oil separation and water pH droplet transference.

Unexpected room-temperature ferromagnetism in nanostructured Bi2Te3.

There is an urgent need for the development in the field of the magnetism of topological insulators, owing to the necessity for the realization of the quantum anomalous Hall effect. Herein, we discuss experimentally fabricated nanostructured hierarchical architectures of the topological insulator Bi2Te3 without the introduction of any exotic magnetic dopants, in which intriguing room-temperature ferromagnetism was identified. First-principles calculations demonstrated that the intrinsic point defect with respect to the antisite Te site is responsible for the creation of a magnetic moment. Such a mechanism, which is different from that of a vacancy defect, provides new insights into the origins of magnetism. Our findings may pave the way for developing future Bi2Te3-based dissipationless spintronics and fault-tolerant quantum computation.

Pressure-induced isosymmetric phase transition in sulfamic acid: a combined Raman and x-ray diffraction study.

High-pressure behaviors of hydrogen-bonded molecular crystal, sulfamic acid (NH3(+)SO3(-), SA), have been investigated using Raman spectroscopy and synchrotron X-ray diffraction (XRD) techniques up to the pressure of ~20 GPa. Under ambient conditions, molecules of SA are arranged in puckered layers and held together by hydrogen bonding and electrostatic interactions. It is proved by the Raman results that SA undergoes the molecular conformation changes in the pressure range 8.1-10.2 GPa. Then between 10.2 and 12.7 GPa, a phase transition is observed in both Raman and XRD patterns. Both the ambient and high-pressure phases of SA crystallize in Pbca symmetry with similar unit-cell dimensions. The mechanism of the phase transition involves relative movements of adjacent hydrogen-bonded molecules, accompanied by the rearrangement of hydrogen bonds and the enhancement of electrostatic interactions.

Resonant tunneling modulation in quasi-2D Cu(2)O/SnO(2) p-n horizontal-multi-layer heterostructure for room temperature H(2)S sensor application.

Heterostructure material that acts as resonant tunneling system is a major scientific challenge in applied physics. Herein, we report a resonant tunneling system, quasi-2D Cu(2)O/SnO(2) p-n heterostructure multi-layer film, prepared by electrochemical deposition in a quasi-2D ultra-thin liquid layer. By applying a special half-sine deposition potential across the electrodes, Cu(2)O and SnO(2) selectively and periodically deposited according to their reduction potentials. The as-prepared heterostructure film displays excellent sensitivity to H(2)S at room temperature due to the resonant tunneling modulation. Furthermore, it is found that the laser illumination could enhance the gas response, and the mechanism with laser illumination is discussed. It is the first report on gas sensing application of resonant tunneling modulation. Hence, heterostructure material act as resonant tunneling system is believed to be an ideal candidate for further improvement of room temperature gas sensing.

Controlled synthesis of hollow Cu2-x Te nanocrystals based on the Kirkendall effect and their enhanced CO gas-sensing properties.

This paper develops a facile solution-based method to synthesize hollow Cu2-x Te nanocrystals (NCs) with tunable interior volume based on the Kirkendall effect. Transmission electron microscopy images and time-dependent absorption spectra reveal the temporal growth process from solid copper nanoparticles to hollow Cu2-x Te NCs. Furthermore, the as-prepared hollow Cu2-x Te NCs show enhanced sensitivity for the detection of carbon monoxide (CO), which is often referred to as the "silent killer". The response and recovery time of the as-prepared sensor for the detection of 100 ppm CO gas are estimated to be about 21 and 100 s, respectively, which are sufficient to render it a promising candidate for effective CO gas-sensing applications. Such enhanced performance is achieved owing to the small grain size and large specific area of the hollow nanostructures. Therefore, the obtained hollow NCs based on the Kirkendall effect may have the potential as new functional blocks for high-performance gas sensors.

Size-controlled synthesis of bifunctional magnetic and ultraviolet optical rock-salt MnS nanocube superlattices.

Wide-band-gap rock-salt (RS) MnS nanocubes were synthesized by the one-pot solvent thermal approach. The edge length of the nanocubes can be easily controlled by prolonging the reaction time (or aging time). We systematically explored the formation of RS-MnS nanocubes and found that the present synthetic method is virtually a combination of oriented aggregation and intraparticle ripening processes. Furthermore, these RS-MnS nanocubes could spontaneously assemble into ordered superlattices via the natural cooling process. The optical and magnetic properties were investigated using measured by UV-vis absorption, photoluminescence spectra, and a magnetometer. The obtained RS-MnS nanocubes exhibit good ultraviolet optical properties depending on the size of the samples. The magnetic measurements suggest that RS-MnS nanocubes consist of an antiferromagnetic core and a ferromagnetic shell below the blocking temperatures. Furthermore, the hysteresis measurements indicate these RS-MnS nanocubes have large coercive fields (e.g., 1265 Oe for 40 nm nanocubes), which is attributed to the size and self-assembly of the samples.

Exploration of the pyrazinamide polymorphism at high pressure.

We report the high-pressure response of three forms (α, δ, and γ) of pyrazinamide (C(5)H(5)N(3)O, PZA) by in situ Raman spectroscopy and synchrotron X-ray diffraction techniques with a pressure of about 14 GPa. These different forms are characterized by various intermolecular bonding schemes. High-pressure experimental results show that the γ phase undergoes phase transition to the ß phase at a pressure of about 4 GPa, whereas the other two forms retain their original structures at a high pressure. We propose that the stabilities of the α and δ forms upon compression are due to the special dimer connection that these forms possess. On the other hand, the γ form, which does not have this connection, prefers to transform to the closely related ß form when pressure is applied. The detailed mechanism of the phase transition together with the stability of the three polymorphs is discussed by taking molecular stacking into account.

Compression studies of face-to-face π-stacking interaction in sodium squarate salts: Na2C4O4 and Na2C4O4●3H2O.

High-pressure Raman scattering and synchrotron X-ray diffraction measurements of sodium squarate (Na(2)C(4)O(4), SS) are performed in a diamond anvil cell. SS possesses a rare, but typical structure, which can show the effect of face-to-face π-stacking without interference of other interactions. At ~11 GPa, it undergoes a phase transition, identified as a symmetry transformation from P2(1)/c to P2(1). From high-pressure Raman patterns and the calculated model of SS, it can be proved that the phase transition results from the distorted squarate rings. We infer it is the enhancement of π-stacking that dominates the distortion. For comparison, high-pressure Raman spectra of sodium squarate trihydrate (Na(2)C(4)O(4)●3H(2)O, SST) are also investigated. The structure of SST is determined by both face-to-face π-stacking and hydrogen bonding. SST can be regarded as a deformation of SS. A phase transition, with the similar mechanism as SS, is observed at ~10.3 GPa. Our results can be well supported by the previous high-pressure studies of ammonium squarate ((NH(4))(2)C(4)O(4), AS), and vice versa. High-pressure behaviors of the noncovalent interactions in SS, SST, and AS are compared to show the impacts of hydrogen bonding and the role of electrostatic interaction in releasing process.

Synthesis and high-pressure transformation of metastable wurtzite-structured CuGaS2 nanocrystals.

The metastable wurtzite nanocrystals of CuGaS(2) have been synthesized through a facile and effective one-pot solvothermal approach. Through the Rietveld refinement on experimental X-ray diffraction patterns, we have unambiguously determined the structural parameters and the disordered nature of this wurtzite phase. The metastability of wurtzite structure with respect to the stable chalcopyrite structure was testified by a precise theoretical total energy calculation. Subsequent high-pressure experiments were performed to establish the isothermal phase stability of this wurtzite phase in the pressure range of 0-15.9 GPa, above which another disordered rock salt phase crystallized and remained stable up to 30.3 GPa, the highest pressure studied. Upon release of pressure, the sample was irreversible and intriguingly converted into the energetically more favorable and ordered chalcopyrite structure as revealed by the synchrotron X-ray diffraction and the high-resolution transmission electron microscopic measurements. The observed phase transitions were rationalized by first-principles calculations. The current research surely establishes a novel phase transition sequence of disorder → disorder → order, where pressure has played a significant role in effectively tuning stabilities of these different phases.

Calcium with the ß-tin structure at high pressure and low temperature.

Using synchrotron high-pressure X-ray diffraction at cryogenic temperatures, we have established the phase diagram for calcium up to 110 GPa and 5-300 K. We discovered the long-sought for theoretically predicted ß-tin structured calcium with I4(1)/amd symmetry at 35 GPa in a s mall low-temperature range below 10 K, thus resolving the enigma of absence of this lowest enthalpy phase. The stability and relations among various distorted simple-cubic phases in the Ca-III region have also been examined and clarified over a wide range of high pressures and low temperatures.

Pressure-induced phase transition in N-H···O hydrogen-bonded molecular crystal oxamide.

The effect of high pressure on the structural stability of oxamide has been investigated in a diamond anvil cell by Raman spectroscopy up to ∼14.6 GPa and by angle-dispersive X-ray diffraction (ADXRD) up to ∼17.5 GPa. The discontinuity in Raman shifts around 9.6 GPa indicates a pressure-induced structural phase transition. This phase transition is confirmed by the change of ADXRD spectra with the symmetry transformation from P1 to P1. On total release of pressure, the diffraction pattern returns to its initial state, implying this transition is reversible. We discuss the pressure-induced variations in N-H stretching vibrations and the amide modes in Raman spectra and propose that this phase transition is attributed to the distortions of the hydrogen-bonded networks.

Effect of high pressure on the typical supramolecular structure of guanidinium methanesulfonate.

We report the high-pressure response of guanidinium methanesulfonate (C(NH(2))(3)(+)·CH(3)SO(3)(-), GMS) using in situ Raman spectroscopy and synchrotron X-ray diffraction (XRD) techniques up to the pressures of ~11 GPa. GMS exhibits the representative supramolecular structure of two-dimensional (2D) hydrogen-bonded bilayered motifs under ambient conditions. On the basis of the experimental results, two phase transitions were identified at 0.6 and 1.5 GPa, respectively. The first phase transition, which shows the reconstructive feature, is ascribed to the rearrangements of hydrogen-bonded networks, resulting in the symmetry transformation from C2/m to Pnma. The second one proves to be associated with local distortions of methyl groups, accompanied by the symmetry transformation from Pnma to Pna2(1). The cooperativity of hydrogen bonding, electrostatic, and van der Waals interactions, as well as mechanisms for the phase transitions is discussed by means of the local nature of the structure.