The development of new nonlinear optical (NLO) materials for deep‐ultraviolet (DUV) applications is in great demand. However, the synthesis of an ideal DUV NLO crystal is a serious challenge. Herein, ...three new alkali‐metal fluorooxoborates, AB4O6F (A=K, Rb, and Cs, and a mixed cation between two of them), were successfully synthesized by cation regulation. It is found that all reported compounds exhibit short UV absorption edges (<190 nm), and show second harmonic generation (SHG) responses ranging from 0.8 to 1.9 KH2PO4 (KDP). Interestingly, by judicious selection of the A‐site alkali‐metal cations, the arrangement of NLO‐active structural units is fine‐tuned to an optimal configuration, which contributes to large SHG responses.
Cation control: Three new deep‐ultraviolet nonlinear optical materials with excellent optical properties, comparable to those of KBe2BO3F2, have been obtained by cation‐controlled synthesis.
The search of new borates with improved functional properties has attracted considerable attention. Herein, a new polar fluorooxoborate, NaB4O6F (NBF) was prepared by high‐temperature solid‐state ...reaction. NBF belongs to the AB4O6F family (A=alkali metal or ammonium), a series of compounds that undergoes significant cation‐dependent structural changes. NBF is of particular interest owing to the special cation position. Temperature‐dependent ionic conductivity measurements show that NBF is a solid ionic conductor, and it has the lowest active energy of 32.5 kJ mol−1 of fluorooxoborates. NBF also shows a second‐harmonic generation (SHG) response of 0.9×KH2PO4 and 0.2×β‐BaB2O4, at 1064 and 532 nm, respectively, and it has a short UV cutoff edge below 180 nm. Based on bond valence (BV) concepts, symmetry analysis, and the first principles calculation, the unique B4O6F∞ layer can be regarded as the “multifunctional unit”, which is responsible for the observed properties of NBF.
BOF a nova: A new polar fluorooxoborate, NaB4O6F has been discovered through chemical substitution of the cation. It exhibits better ion conductivity than other alkali‐metal fluorooxoborates and excellent NLO properties.
The discovery of new nonlinear optical (NLO) materials for coherent light generation in the deep‐ultraviolet (DUV, wavelength below 200 nm) region is essential for the development of laser ...technologies. Herein, we report a new material CsB4O6F (CBF), which combines the superior structural properties of two well‐known NLO materials, β‐BaB2O4 (BBO) and KBe2BO3F2 (KBBF). CBF exhibits excellent DUV optical properties including a short cutoff edge (155 nm), a large SHG response (≈1.9×KDP), and a suitable birefringence that enables frequency doubling down to 171.6 nm. Remarkably, CBF melts congruently and shows an improved growth habit. In addition, our rational design strategy will contribute to the discovery of DUV NLO materials.
A beryllium‐free deep‐ultraviolet nonlinear optical material, CsB4O6F, combines the superior functional and structural properties of two established NLO materials, β‐BaB2O4 and KBe2BO3F2. CsB4O6F exhibits excellent DUV optical properties, a large SHG response, and a suitable birefringence that enables frequency doubling down to 171.6 nm.
Nonlinear optical materials are essential for the development of solid-state lasers. KBe2BO3F2 (KBBF) is a unique nonlinear optical material for generation of deep-ultraviolet coherent light; ...however, its industrial application is limited. Here, we report a new material NH4B4O6F, which exhibits a wide deep-ultraviolet transparent range and suitable birefringence that enables frequency doubling below 200 nm. NH4B4O6F possesses large nonlinear coefficients about 2.5 times that of KBBF. In addition, it is easy to grow bulk crystals and does not contain toxic elements.
Numerous studies on megacities have reported less air pollution in polycentric form urban than monocentric form urban. However, findings from these studies do not imply that increasing air pollution ...in region or country is accompanied by the expanding megacities. Using satellite night-light data, this study investigates the impact of polycentric urban form at the provincial level on PM
2.5
concentrations in China while controlling for variables of urban population size, energy consumption, and the weather. The results reveal that the PM
2.5
concentrations are reduced by 1.46% to 2.67%, with a 1% increase in polycentric urban form. The similar impact has also been observed in the South China, but larger in the Central China. Further studies show that the urban form-air pollution relationship mainly influenced by transportation distance and enhanced by rising per capita income. The findings suggest that regional planning and policies favoring polycentric urban patterns should be strengthened to alleviate air pollution.
First, utilising text quantitative analysis techniques, this paper analyses the smart city pilot policy in depth and clarifies its theoretical mechanism that influence the quality of new-type ...urbanisation. The revised entropy technique is then used to calculate the new-type urbanisation quality of 276 Chinese cities with a prefecture level or higher from 2007 to 2018. The above action mechanism is evaluated using the Difference-in-Difference model, employing the smart city pilot policy as a quasi-natural experiment (DID). The results indicate that the implementation of the smart city pilot policy can significantly enhance the quality of new-type urbanisation, and this conclusion is robust under a variety of conditions, including parallel trend testing, tendency score matching, exclusion of other policy interference and placebo testing. The analysis of heterogeneity indicates that the smart city pilot strategy has a greater impact on the qualitative improvement of new-type urbanisation in historic industrial bases, resource-based cities, and large-scale cities. The mechanism test confirmed that the construction of smart cities has improved the quality of new-type urbanisation primarily through the optimization and upgrading of industrial structure brought about by smart industrial policy and scientific and technological innovation fostered by smart government and smart people's livelihood policies.
Infrared spectroscopic study of neutral water clusters is crucial to understanding of the hydrogen-bonding networks in liquid water and ice. Here we report infrared spectra of size-selected neutral ...water clusters, (H₂O)n (n = 3–6), in the OH stretching vibration region, based on threshold photoionization using a tunable vacuum ultraviolet free-electron laser. Distinct OH stretch vibrational fundamentals observed in the 3,500–3,600-cm−1 region of (H₂O)₅ provide unique spectral signatures for the formation of a noncyclic pentamer, which coexists with the global-minimum cyclic structure previously identified in the gas phase. The main features of infrared spectra of the pentamer and hexamer, (H₂O)n (n = 5 and 6), span the entire OH stretching band of liquid water, suggesting that they start to exhibit the richness and diversity of hydrogenbonding networks in bulk water.
Osteosarcoma is the most common primary sarcoma of the bone. Lung osteosarcoma metastases at diagnosis have a significantly poor prognosis, even when surgery plus chemotherapy are performed. Our goal ...was to analyze clinical and sarcoma characteristics that could help identify factors related to an increased rate of lung metastasis and to identify different modes of treatment and its correlation with survival.
The Surveillance, Epidemiology, and End Results (SEER) database was used to identify all osteosarcoma patients diagnosed from 2010 to 2015. Patient characteristics such as age, sex, ethnicity, marital status, tumor location, histologic grade, surgery, chemotherapy, radiation therapy, SEER cause-specific death classification, survival, and lung metastasis were collected. These factors were analyzed using Univariate and multivariate regression models in survival analyses.
A total of 1057 osteosarcoma patients diagnosed from 2010 to 2015 were included, of which 176 were patients with lung metastasis. Substantial disparities in the rate of lung metastasis existed when osteosarcoma patients were stratified according to tumor location (P = 0.0002) and tumor size (P < .001). Using a Multivariate Cox regression model, being older than 30 years (vs. younger than 30, HR = 2.171, 95% CI = 1.623–2.905, P < .0001), having a tumor >5–10 cm (vs. <5 cm, HR = 2.046, 95% CI = 1.153–3.632, P = 0.0014) and >10 cm (vs. <5 cm, HR = 3.610, 95% CI = 2.066–6.310, P < .0001) were related to an increased HR for all-cause death. The HR decreased in patients with surgery (vs. no surgery, HR = 0.189, 95% CI = 0.138–0.260, P < 0.0001) and osteosarcoma. As for osteosarcoma patients with lung metastases, Multivariate Cox regressions revealed that an increased HR was associated with being older than 30 years (vs. younger than 30 years, HR = 2.142, 95% CI = 1.273–3.605, P = .0041) and married (vs. no marriage, HR = 2.418, 95% CI = 1.400–4.176, P= .0015), while a decreased HR was related to having had surgery (vs. no surgery, HR = 0.282, 95% CI = 0.171–0.464, P < .0001) and chemotherapy (vs. no chemotherapy, HR = 0.107, 95% CI = 0.050–0.229, P < .0001).
Advanced age (older than 30 years) and large tumors were related to a higher risk of lung metastases in osteosarcoma patients. Therefore, patients who were diagnosed at advanced age or had large tumors should receive comprehensive chest CT scans. Surgery and chemotherapy can significantly improve the survival of metastatic patients, while radiotherapy did not improve survival in these patients.
Infrared (IR) spectroscopy provides detailed structural and dynamical information on clusters at the fingerprint level. Herein, we demonstrate the capability of a tunable vacuum ultraviolet free ...electron laser (VUV-FEL) for selective detection of a wide variety of neutral water clusters and for recording the size-dependent IR spectra. The present technique does not require the presence of an ultraviolet chromophore or a dipole moment and is generally applicable for IR spectroscopy of neutral clusters free from confinement. To show the features of our technique, we report here the IR spectra of neutral water dimer in the OH stretch region, providing benchmarks for theoretical study of the accurate description of hydrogen bonding structures involved in liquid water and ice. Quantum mechanical calculations on a 12-dimensional ab initio potential energy surface are utilized to simulate the anharmonic vibrational spectra of water dimer. These results help to resolve the controversy of the exact vibrational assignment of each band feature of the water dimer.
Abstract
The water octamer with its cubic structure consisting of six four-membered rings presents an excellent cluster system for unraveling the cooperative interactions driven by subtle changes in ...the hydrogen-bonding topology. Despite prediction of many distinct structures, it has not been possible to extract the structural information encoded in their vibrational spectra because this requires size-selectivity of the neutral clusters with sufficient resolution to identify the contributions of the different isomeric forms. Here we report the size-specific infrared spectra of the isolated cold, neutral water octamer using a scheme based on threshold photoionization using a tunable vacuum ultraviolet free electron laser. A plethora of sharp vibrational bands features are observed. Theoretical analysis of these patterns reveals the coexistence of five cubic isomers, including two with chirality. The relative energies of these structures are found to reflect topology-dependent, delocalized multi-center hydrogen-bonding interactions. These results demonstrate that even with a common structural motif, the degree of cooperativity among the hydrogen-bonding network creates a hierarchy of distinct species. The implications of these results on possible metastable forms of ice are speculated.
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