Anisotropic structure building unit involving diverse chemical bonds: a new opportunity for high-performance second-order NLO materials.

We define the anisotropic structure building unit that encompasses diverse chemical bonds (ABUCB). The ABUCB is highly likely to cause anisotropy in both crystallographic structure and spatial electron distribution, ultimately resulting in enhanced macroscopic optical anisotropy. Accordingly, the (PO3F)2- or (SO3F)- tetrahedron involving the unique P-F or S-F bond serves as such an ABUCB. The distinct chemical bond effectively alters the microscopic nature of the structure building unit, such as polarizability anisotropy, hyperpolarizability, and geometry distortion; this consequently changes the macroscopic second-order nonlinear optical (2nd-NLO) properties of the materials. In this review, we summarize both typical and newly emerged compounds containing ABUCBs. These compounds encompass approximately 90 examples representing six distinct categories, including phosphates, borates, sulfates, silicates, chalcogenides and oxyhalides. Furthermore, we demonstrate that the presence of ABUCBs in DUV/UV NLO compounds contributes to an increase in birefringence and retention of a large band gap, facilitating phase matching in high-energy short-wavelength spectral ranges. On the other hand, the inclusion of ABUCBs in IR NLO compounds offers a feasible method for increasing the band gap and consequently enhancing the larger laser-induced damage threshold. This review consolidates various trial-and-error explorations and presents a novel strategy for designing 2nd-NLO compounds, potentially offering an opportunity for the development of high-performance 2nd-NLO materials.

Overdamped Phonon Diffusion and Nontrivial Electronic Structure Leading to a High Thermoelectric Figure of Merit in KCu5Se3.

Thermoelectric copper selenides are highly attractive owing to not only their constituent nontoxic, abundant elements but also their ultralow liquid-like lattice thermal conductivity (κlat). For the first time, the promising thermoelectric properties of the new KCu5Se3 are reported herein, showing a high power factor (PF = 9.0 µWcm-1 K-2) and an intrinsically ultralow κlat = 0.48 Wm-1 K-1. The doped K1-xBaxCu5Se3 (x = 0.03) realizes a figure-of-merit ZT = 1.3 at 950 K. The crystallographic structure of KCu5Se3 allows complex lattice dynamics that obey a rare dual-phonon transport model well describing a high scattering rate and an extremely short phonon lifetime that are attributed to interband phonon tunneling, confinement of the transverse acoustic branches, and temperature-dependent anharmonic renormalization, all of which generate an unprecedently high contribution of the diffusive phonons (70% at 300 K). The overall weak chemical bonding feature of KCu5Se3 gives K+ cations a quiescence behavior that further blocks the heat flux transfer. In addition, the valence band edge energy dispersion of KCu5Se3 is quasilinear that allows a large Seebeck coefficient even at high hole concentrations. These in-depth understandings of the ultralow lattice thermal conductivity provide new insights into the property-oriented design and synthesis of advanced complex chalcogenide materials.

Inorganic Solid-State Nonlinear Optical Switch with a Linearly Tunable Tc Spanning a Wide Temperature Range.

Nonlinear optical (NLO) switch materials that turn on/off second-harmonic generation (SHG) at a phase transition temperature (Tc ) are promising for applications in the fields of photoswitching and optical computing. However, precise control of Tc remains challenging, mainly because a linearly tunable Tc has not been reported to date. Herein, we report a unique selenate, tetragonal P 4 ‾ ${\bar{4}}$ 21 c [Ag(NH3 )2 ]2 SeO4 with a=b=8.5569(2) Šand c=6.5208(2) Šthat exhibits a strong SHG intensity (1.3×KDP) and a large birefringence (Δnobv. =0.08). This compound forms a series of isostructural solid-solution crystals [Ag(NH3 )2 ]2 Sx Se1-x O4 (x=0-1.00) that exhibit excellent NLO switching performance and an unprecedented linearly tunable T c , x , e x p . = T 0 - k x ${{T}_{\left(c,{\rm \ }x\right),{\rm \ }\left({\rm e}{\rm x}{\rm p}.\right)}{\rm \ }={T}_{0}-kx}$ spanning 430 to 356 K. The breaking of localized hydrogen bonds between SeO4 2- and the cation triggers a phase transition accompanied by hydrogen bond length changes with increasing x and a linear change in the enthalpy Δ H x = Δ U 1 - Δ U 2 x + Δ U 2 ${{{\rm { \Delta{}}}H}_{x}=\left({\rm { \Delta{}}}{U}_{1}-{\rm { \Delta{}}}{U}_{2}\right)x+{\rm { \Delta{}}}{U}_{2}}$ .

Rapid Synthesis of Si-Rich SSZ-13 Zeolite under Fluoride-Free Conditions.

Rapid synthesis of Si-rich (SiO2/Al2O3 > 100) SSZ-13 zeolite under fluoride-free conditions is highly desirable but still challenging. Herein, we for the first time report a rapid synthesis of all silica and aluminosilicate (SiO2/Al2O3 > 100) SSZ-13 zeolite without the addition of fluoride species. The crystallization could be fully completed at 160 °C for 4 h when the aging of the starting gel is 3 h at room temperature after the addition of a zeolite seed. The key to success is the formation of more basic building units (4- and 6-membered rings) in the initial gel with the aging time of 3 h after the addition of a zeolite seed, leading to the successful rapid synthesis of Si-rich SSZ-13 zeolite. The obtained Si-rich SSZ-13 zeolite displays high crystallinity, uniform cubic morphology with a nanoparticle feature, and a large surface area. More importantly, the obtained Si-rich SSZ-13 zeolite displays excellent performance in the adsorption of ethanol and methanol-to-olefin reaction.

Advances in the Synthesis of Crystalline Metallosilicate Zeolites via Interlayer Expansion.

Given the numerous industrial applications of zeolites as adsorbents, catalysts, and ion-exchangers, the development of new zeolite structures is highly desired to expand their practical applications. Currently, a general route to develop new zeolite structures is to use interlayer expansion agents to connect layered silicates. In this review, we briefly summarize the novel zeolite structures constructed from the lamellar precursor zeolites MWW, RUB-36, PREFER, Nu-6(1), COK-5, and PLS-1 via interlayer expansion. The contents of the summary contain detailed experiments, physicochemical characterizations, possible expansion mechanisms, and catalytic properties. In addition, the insertion of metal heteroatoms (such as Ti, Fe, Sn) into the layered zeolite precursor through interlayer expansion, which could be helpful to modify the catalytic function, is discussed.

[Ag(NH3 )2 ]2 SO4 : A Strategy for the Coordination of Cationic Moieties to Design Nonlinear Optical Materials*.

Over recent decades, guided by the anionic group theory of nonlinear optical (NLO) materials, rational design strategies have been primarily focused on anionic moieties; consequently, structural modification and design of cationic moieties have long been neglected. Herein, we report a strategy for the coordination of cationic moieties that substantially enhances the optical properties of NLO materials. For an example with well-known crystal structure, [Ag(NH3 )2 ]2 SO4 , we demonstrate that the coordination of the Ag+ cation by the neutral ligand drives the formation of a noncentrosymmetric tetragonal P 4 ‾ 21 c structure as a positive uniaxial crystal. The bending of the [Ag(NH3 )2 ]+ cationic moiety parallel to the z-axis generates an anisotropic arrangement of the dipoles, i.e., a dipole of 0.12 D along the z-direction, yet zero dipole in the xy-plane, which interacts anisotropically with the incident light oscillating electromagnetic wave, leading to optical anisotropy with a large birefringence. The incident beam of 589.3 nm normal to the (110) crystal plane measures Δnobv. =0.08, and [Ag(NH3 )2 ]2 SO4 also exhibits a phase-matching NLO response 1.4 times that of KH2 PO4 (KDP) (obv. 1.4×KDP @1064 nm; cal. d36 =1.50 pm V-1 ).

Characteristics of one-year observation of VOCs, NOx, and O3 at an urban site in Wuhan, China.

A continuous online observation of ozone and its precursors (NOx, VOCs) was carried out in central urban Wuhan from September 2016 to August 2017. The concentration levels of ozone, NOx, VOCs and their variations in urban Wuhan were analyzed, as well as effects of VOCs on ozone photochemical generation and the main controlling factors for ozone production. During the observation period, the average concentrations of ozone and NOx in Wuhan was 22.63 and 30.14 ppbv, respectively, and the average concentration of VOCs was 32.61 ppbv (42.3% alkanes, 13.0% alkenes, 10.0% aromatics, 7.3% acetylene, 9.9% OVOCs, and 10.5% halohydrocarbons). Ozone concentration was higher in spring and summer as compared with autumn and winter, wheras VOCs and NOx concentratios were lower in spring and summer but higher in autumn and winter. Aromatics and alkenes, two of VOCs species, showed the highest contributions to ozone formation potential in Wuhan (35.7% alkenes, 35.4 aromatics, 17.5% alkanes, 8.6% OVOCs, 1.6% halogenated hydrocarbons, and 1.4% acetylene). Among all VOCs species, those with the highest contribution were ethylene, m-xylene, toluene, propylene and o-xylene. The contribution of these five compounds to the total ozone formation potential concentration was 43.90%. Ozone-controlling factors in Wuhan changed within one day; during the early morning hours (6:00-9:00), VOCs/NOx was low, and ozone generation followed a VOCs-limited regime. However, during the peak time of ozone concentration (12:00-16:00), the ratio of VOCs/NOx was relatively high, suggesting that ozone generation followed a NOx-limited regime.

Enhanced dewaterability of sewage sludge with zero-valent iron-activated persulfate oxidation system.

The potential benefits of zero-valent iron-activated persulfate (Na2S2O8) oxidation in enhanced dewaterability of sludge, along with the associated mechanisms were investigated in this study. The sludge dewaterability was evaluated in terms of specific resistance to filtration (SRF) and water content. Based on these indexes, it was observed that ZVI-S2O8(2) oxidation effectively improved sludge dewaterability. The optimal conditions to give preferable dewaterability were found when the molar ratio of ZVI/S2O8(2-) was 5:1 and pH value was 3.0. The most important mechanism was proposed to be the degradation of extracellular polymeric substances (EPS) incorporated in sludge flocs and rupture of microbial cells. Three-dimensional excitation-emission matrix fluorescence spectra revealed that the powerful SO4- and ·OH generated from ZVI-S2O8(2-) system destroyed the particular functional groups of fluorescing substances (aromatic protein-like and tryptophan protein-like substances), resulting in the release of bound water and the subsequent enhancement of dewaterability. Therefore, ZVI/S2O8(2-) oxidation is an alternative approach showing great potential to be applied in sludge treatment plants.

A risk prediction model for efficient intubation in the emergency department: A 4-year single-center retrospective analysis.

Objective: To analyze the risk factors associated with intubated critically ill patients in the emergency department (ED) and develop a prediction model by machine learning algorithms. Methods: This study was conducted in an academic tertiary hospital in Hangzhou, China. Critically ill patients admitted to the ED were retrospectively analyzed from May 2018 to July 2022. The demographic characteristics, distribution of organ dysfunction, parameters for different organs' examination, and status of mechanical ventilation were recorded. These patients were assigned to the intubation and non-intubation groups according to ventilation support. We used the eXtreme Gradient Boosting (XGBoost) algorithm to develop the prediction model and compared it with other algorithms, such as logistic regression, artificial neural network, and random forest. SHapley Additive exPlanations was used to analyze the risk factors of intubated critically ill patients in the ED. Results: Of 14,589 critically ill patients, 10,212 comprised the training group and 4377 comprised the test group; 2289 intubated patients were obtained from the electronic medical records. The mean age, mean scores of vital signs, parameters of different organs, and blood oxygen examination results differed significantly between the two groups (p < 0.05). The white blood cell count, international normalized ratio, respiratory rate, and pH are the top four risk factors for intubation in critically ill patients. Based on the risk factors in different predictive models, the XGBoost model showed the highest area under the receiver operating characteristic curve (0.84) for predicting ED intubation. Conclusions: For critically ill patients in the ED, the proposed model can predict potential intubation based on the risk factors in the clinically predictive model.

Phylogenetic relationship and comparative analysis of the main Bupleuri Radix species in China.

Background: Bupleuri Radix (Chaihu) is a famous traditional Chinese medicine derived from Bupleurum, Apiaceae. The origin of cultivated Chaihu germplasm in China is unclear, which has led to unstable Chaihu quality. In this study, we reconstructed the phylogeny of the main Chaihu germplasm species in China and identified potential molecular markers to authenticate its origin. Methods: Three Bupleurum species (eight individuals), B. bicaule, B. chinense, and B. scorzonerifolium, were selected for genome skimming. Published genomes from B. falcatum and B. marginatum var. stenophyllum were used for comparative analysis. Results: Sequences of the complete plastid genomes were conserved with 113 identical genes ranging from 155,540 to 155,866 bp in length. Phylogenetic reconstruction based on complete plastid genomes resolved intrageneric relationships of the five Bupleurum species with high support. Conflicts between the plastid and nuclear phylogenies were observed, which were mainly ascribed to introgressive hybridization. Comparative analysis showed that noncoding regions of the plastomes had most of the variable sequences. Eight regions (atpF-atpH, petN-psbM, rps16-psbK, petA-psbJ, ndhC-trnV/UAC and ycf1) had high divergence values in Bupleurum species and could be promising DNA barcodes for Chaihu authentication. A total of seven polymorphic cpSSRs and 438 polymorphic nSSRs were detected across the five Chaihu germplasms. Three photosynthesis-related genes were under positive selection, of which accD reflected the adaptation fingerprint of B. chinense to different ecological habitats. Our study provides valuable genetic information for phylogenetic investigation, germplasm authentication, and molecular breeding of Chaihu species.

Recent Advances in the Seed-Directed Synthesis of Zeolites without Addition of Organic Templates.

Zeolites have been widely employed in fields of petroleum refining, fine chemicals and environmental protection, but their syntheses are always performed in the presence of organic templates, which have many drawbacks such as high cost and polluted wastes. In recent years, the seed-directed synthesis of zeolites has been paid much attention due to its low-cost and environmentally friendly features. In this review, the seed-directed synthesis of Al-rich zeolites with homonuclear and heteronuclear features, the seed-directed synthesis of Si-rich zeolites assisted with ethanol and the utility of seed-directed synthesis have been summarized. This review could help zeolite researchers understand the recent progress of seed-directed synthesis.

Hydrogen Bond-Driven Order-Disorder Phase Transition in the Near-Room-Temperature Nonlinear Optical Switch [Ag(NH3)2]2SO4.

Herein, we report a near-room-temperature nonlinear optical (NLO) switch material, [Ag(NH3)2]2SO4, exhibiting switching performance with strong room-temperature second harmonic generation (SHG) intensity that outperforms the UV-vis spectral region industry standard KH2PO4 (1.4 times stronger). [Ag(NH3)2]2SO4 undergoes a reversible phase transition (T c = 356 K) from the noncentrosymmetric room-temperature phase (P4̅21 c, RTP) to a centrosymmetric high-temperature phase (I4/mmm, HTP) where both the SO4 2- anions and [Ag(NH3)2]+ cations are highly disordered. The weakening of hydrogen bond interactions in the HTP is also evidenced by the lower energy shift of the stretching vibration of the N-H···O bonds revealed by the in situ FT-IR spectra. Such weakening leads to an unusual negative thermal expansion along the c axis (-3%). In addition, both the atomic displacement parameters of the single-crystal diffraction data and the molecular dynamics-simulated mean squared displacements suggest the motions of the O and N atoms. Such a structural disorder not only hinders the phonon propagation and dramatically drops the thermal conductivity to 0.22 W m-1 K-1 at 361 K but also significantly weakens the optical anisotropy and SHG as verified by the DFT theoretical studies.

Effect of GAPT extract on expression of tau protein and its phosphorylation related enzymes in hippocampal neurons of APPV717I transgenic mice.

OBJECTIVE: To investigate the effect of GAPT, an extract mixture from Radix Ginseng, Rhizoma Acor tatarinowii, Radix Polygalae and Radix Curcuma (containing ingredient of turmeric), etc. on expression of tau protein and its phosphorylation related enzyme in hippocampal neurons of APPV717I transgenic mice. METHODS: Sixty three-month-old APPV717I transgenic mice were randomly divided into model group, donepezil group [0.92 mg/(kg•d)], the low, medium and high dosage of GAPT groups [0.075, 0.15, 0.30 g/(kg•d), 12 in each group], and 12 three-month-old C57BL/6J mice were set as a normal control group, treatments were administered orally once a day respectively, and both the normal group and model group were given 0.5% sodium carboxymethyl cellulose solution. Immunohistochemistry (IHC) and Western blot analysis were used to detect the expression of total tau protein (Tau-5), cyclin-dependent kinase 5 (CDK5) and protein phosphatase 2A (PP2A) in hippocampal neurons of experimental mice after 8-month drug administration (11 months old). RESULTS: In the model group, the expression of Tau-5 and CDK5 were increased, whereas the expression of PP2A was decreased in hippocampal neurons, which were signifificantly different compared with that in the normal group (all P<0.01). IHC test indicated the number and area of either Tau-5 or CDK5 positive cells were decreased with a dose-depended way in GAPT groups, and an increase of PP2A. Compared with the model group, the changes were signifificant in GAPT groups (P<0.05 or P<0.01). Similar results were shown by Western blot. CONCLUSION: GAPT could attenuate abnormal hyperphosphorylation of tau protein in hippocampal neurons of APPV717I transgenic mice via inhibiting the expression of CDK5 and activating the expression of PP2A.

Molar mass and molar mass distribution of polystyrene particle size standards.

Monodisperse polystyrene microspheres and nanospheres are often used as particle size standards for calibration of size-measuring instruments. They are potentially useful as the mass standards for particle mass spectrometry as well. We demonstrated in this work that it is possible to achieve high-precision mass determination for single polystyrene spheres using a quadrupole ion trap. We introduced the particles into the trap by laser-induced acoustic desorption and probed them with light scattering. Mass-to-charge ratios of the individual particles were determined from applied trap-driving frequencies, voltage amplitudes and the observed starlike oscillatory trajectories projected on the radial plane. Creation of one-electron differentials through charge-state changes by electron bombardment allowed determination for the absolute mass of a single trapped particle to a precision better than 0.1%. Both molar mass and molar mass distribution were deduced from a large number of measurements for NIST polystyrene particle size standards (SRMs 1690 and 1691). Our results are in excellent agreement with the size measurement for the 0.895-microm spheres (NIST SRM 1690), but a small discrepancy (4%) in number-average mass was found for the 0.269-microm spheres (NIST SRM 1691).

Measuring masses of single bacterial whole cells with a quadrupole ion trap.

A novel method has been developed to precisely measure the masses of single bacterial whole cells using a quadrupole ion trap as an electrodynamic balance. The bacterial cells were introduced into the ion trap by matrix-assisted laser desorption/ionization, confined in space by audio frequency ac fields, and detected by elastic light scattering. Mass measurement accuracy approaching 0.1% was achieved for Escherichia coli K-12 with a mass distribution of +/-3% from 60 repetitive measurements of the particles and their clusters. This is the first high-precision mass measurement reported for any intact microorganisms with masses greater than 1 x 1010 Da. The method opens new avenues for high-precision mass measurement of single microbial particles and offers an alternative approach for rapid identification of microorganisms by mass spectrometry.