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To improve the electro-optical properties of polymer-dispersed liquid crystal (PDLC) film, the size and number of liquid crystal droplets were regulated by changing component, curing method, curing...

There is a trade-off between water resistance and mechanical properties of the waterborne polyurethane film. Aiming to solve this problem, the waterborne polyurethane-acrylate (WPUBH) was prepared by post-chain extension of dithiol instead of diamine, which could improve the storage stability and reduce the water absorption rate due to the absence of urea groups, and by terminating with hydroxyethyl acrylate, which could reduce the water absorption rate and improve the mechanical properties at the same time deriving from the crosslinking of double bonds after heating. The rate of water absorption for WPUBH-2 film decreased down to 2.87%, and the tensile strength reached 8.5 MPa. The water resistance and the mechanical properties of WPUBH obtained a good balance compared with those of the carboxylate-based waterborne polyurethane-acrylate in the previous reports. They had excellent bonding properties for wood joints, and the tensile shear strength was up to 4.53 MPa.

The introduction of structured microsphere composites into hydrogels is found to improve their mechanical strength capability. Herein, chitosan microspheres were functionalized with poly(acrylamide-co-1-benzyl-3-vinylimidazolium bromide) (CS-P(AM-G)), which was synthesized through an in situ copolymerization of acrylamide and a guest functional monomer. Supramolecular hydrogels were fabricated by dynamic host-guest interactions between guest units and the host molecule cucurbit[8]uril (CB[8]). Investigations on the mechanical properties of the hydrogels show that the tensile stress and the compress stress of the hydrogels are five times higher than those of CB[8] hydrogels without CS, and the healing efficiency of the hydrogels at room temperature is 88% after 24 h. The results show that CS microspheres serve as both polyfunctional initiating and cross-linking centers, whereas the dynamic host-guest interactions endow the hydrogels with a higher self-healing property. The process provides a novel method for the production of tough and self-healing supramolecular hydrogels with various potential applications.

Eight 6FDA-TFDB polyimide (PI) samples with absolute molecular weights ranging from 1.25 × 105 g·mol−1 to 3.11 × 105 g·mol−1 are obtained by precipitation fractionation. Rheological experiments are conducted to determine the influence of molecular weight on the associating behavior of PI in N,N′-dimethylformamide (DMF) solutions in a broad volume fraction, including abnormal steady shear flow, solution heterogeneity, and scaling behavior. Abnormal flow behaviors, i.e., multi-region shear thinning and weak shear thickening, are studied, and these behaviors have not been reported in literature. The heterogeneity of PI/DMF solutions is examined by dynamic rheological test. By plotting ηsp versus ϕ/ϕη, four concentration regions of I–IV can be distinguished for all PI samples with various molecular weights. The scaling results in different concentration regions are in good agreement with the associative polymer theory proposed by Rubinstein and Semenov. The scaling exponents do not show molecular weight dependence in concentration regions I and II. In concentration regions III and IV, the scaling exponents change little when the molecular weight is below 242 k but increase when the molecular weight increases from 242 k to 311 k. This work can help us to understand polyimide solution properties from dilute to semidilute entangled solutions, and will guide the polyimide solution preparation for different processing.

Vesicular structures of block copolymers and inorganic nanoparticles with good stability have potential applications in therapeutic drug release and bioimaging. Herein, a block copolymer of polystyrene-b-poly(acrylic acid) (PS48-b-PAA67) and water-soluble AgInS2/ZnS core/shell quantum dots (QDs) capped with gelatin and thioglycolic acid were coassembled in tetrahydrofuran by adding water. The positively charged QDs bind to negatively charged PAA segments through electrostatic interaction. Numerous vesicular structures, such as uniform bilayer vesicles, flowerlike large compound vesicles, onionlike lamellar structures consisting of alternating PS and PAA&QD layers, and multilamellar vesicles with spaces between concentric vesicle layers were obtained from the coassembly of PS48-b-PAA67 with QDs. The binding of the positively charged QDs to the PAA block influenced both the intra-aggregate PAA corona conformation and the interaggregate interactions. The key parameters affecting the formation of these vesicu...

2H-NbSe2, a typical layered transition metal dichalcogenide (TMD), has attracted tremendous research interest for its higher superconducting transition temperature (Tc = 7.2 K) than Tc of other TMDs (2–4 K) and hosting of charge density wave (CDW). The van der Waals (vdW) bonding between NbSe2 layers makes it a good platform for tuning the crystal structure, CDW, and superconducting gap by intercalation. Here we report the crystal structure and superconductivity of Rb-intercalated NbSe2 prepared by solid-state reaction. For Rb intercalation with 0 ≤ x ≤ 0.025, there is only one phase with space group P63/mmc. With Rb intercalation, Tc of RbxNbSe2 decreases from 7.2 K for x = 0 to 4.2 K for x = 0.025 in an L-shaped way. The suppression rate of Tc is similar to the one with magnetic Fe doping, but much quicker than those with Li, Ga, and Cu doping. The superconducting phase diagram of RbxNbSe2 is established accordingly and is compared with those of LixNbSe2, CuxNbSe2, FexNbSe2, and GaxNbSe2. The suppression of superconductivity is discussed based on the ionic radius, valence, and magnetism of doping elements and the expansion between the NbSe2 layers.

Here, we report the crystal structures and properties of RbxNbSe2, with 0 ≤ x ≤ 0.5. With Rb intercalation, RbxNbSe2 evolves from 2H (Phase I) for 0 ≤ x ≤ 0.025, to 6R (Phase II) for x ∼ 0.2 with s...

We report a new type of MAX phase (M=transition metals, A=main group elements, and X=C/N), Nb3 As2 C, designated as 321 phase. It differs from all the previous Mn+1 AXn phases in that it consists of an alternate stacking of one MX layer and two MA layers in its unit cell, while only one MA layer is allowed in usual MAX phases. The new 321 phase exhibits a bulk modulus of Nb3 As2 C up to 225(3) GPa as determined by high-pressure synchrotron X-ray diffraction, one of the highest values among MAX phases. Isostructural 321 phases V3 As2 C, Nb3 P2 C, and Ta3 P2 C are also found to exist. First-principles calculations reveal the outstanding elastic stiffness in 321 phases. Among all 321 phases, Nb3 P2 C is predicted to have the highest elastic properties. These 321 phases, represented by a chemical formula Mn+1 An X, were added as new members to the MAX family and their other properties deserve future investigations.

Numerous nodal-line semimetal candidates have been predicted and experimentally examined. To realize a genuine nodal-line semimetal, the Dirac nodes must be robust against spin-orbit coupling and must lie close to the Fermi level so as to allow for the manifestation of the novel properties. By performing band structure calculations and angle-resolved photoemission measurements, direct evidence is provided here for the realization of a genuine nodal-line semimetal in LaSbTe. This finding creates new opportunity for exploring novel phenomena in topological materials.

Near-term quantum computers are noisy, and therefore must run algorithms with a low circuit depth and qubit count. Here we investigate how noise affects a quantum neural network (QNN) for state discrimination, applicable on near-term quantum devices as it fulfils the above criteria. We find that when simulating gradient calculation on a noisy device, a large number of parameters is disadvantageous. By introducing a new smaller circuit ansatz we overcome this limitation, and find that the QNN performs well at noise levels of current quantum hardware. We also show that networks trained at higher noise levels can still converge to useful parameters. Our findings show that noisy quantum computers can be used in applications for state discrimination and for classifiers of the output of quantum generative adversarial networks., Comment: 8 pages, 9 figures

Recent practical approaches for the use of current generation noisy quantum devices in the simulation of quantum many-body problems have been dominated by the use of a variational quantum eigensolver (VQE). These coupled quantum-classical algorithms leverage the ability to perform many repeated measurements to avoid the currently prohibitive gate depths often required for exact quantum algorithms, with the restriction of a parameterized circuit to describe the states of interest. In this work, we show how the calculation of zero-temperature dynamic correlation functions defining the linear response characteristics of quantum systems can also be recast into a modified VQE algorithm, which can be incorporated into the current variational quantum infrastructure. This allows for these important physical expectation values describing the dynamics of the system to be directly converged on the frequency axis, and they approach exactness over all frequencies as the flexibility of the parameterization increases. The frequency resolution hence does not explicitly scale with gate depth, which is approximately twice as deep as a ground state VQE. We apply the method to compute the single-particle Green's function of ab initio dihydrogen and lithium hydride molecules, and demonstrate the use of a practical active space embedding approach to extend to larger systems. While currently limited by the fidelity of two-qubit gates, whose number is increased compared to the ground state algorithm on current devices, we believe the approach shows potential for the extraction of frequency dynamics of correlated systems on near-term quantum processors., Comment: 13 pages, 4 figures. Added new citations

Solving for molecular excited states remains one of the key challenges of modern quantum chemistry. Traditional methods are constrained by existing computational capabilities, limiting the complexity of the molecules that can be studied or the accuracy of the results that can be obtained. Several quantum computing methods have been suggested to address this limitation. However, these typically have hardware requirements which may not be achieved in the near term. We propose a variational quantum machine learning based method to determine molecular excited states aiming at being as resilient as possible to the defects of early noisy intermediate scale quantum computers and demonstrate an implementation for ${\mathrm{H}}_{2}$ on IBM Quantum Computers. Our method uses a combination of two parametrized quantum circuits, working in tandem, combined with a variational quantum eigensolver to iteratively find the eigenstates of a molecular Hamiltonian.

Cold atmospheric plasma (CAP) applications can potentially lead to effective therapy for numerous skin diseases. Our aim is to systematically review the available data and map the use of CAP in dermatology. PubMed, Embase and Web of science were explored before 2020 for studies regarding the use of CAP in dermatology. A total of 166 studies were finally included. 74.1% of these studies used indirect CAP sources. Most studies used plasma jet (67.5%). Argon was the mostly used working gas (48.2%). Plasma application itself could be direct (89.2%) and indirect (16.3%). The proportion of studies with in vivo results remained 57.2%, of which most concerned direct plasma treatment (97.9%). Analyses performed indicate that CAP has been beneficial in many skin disorders. While, most CAP applications were focused on wound healing and melanoma treatment. This study provides a brief overview of CAP sources and relative medical applications in dermatology.

Previous studies have reported that flue gas desulfurization (FGD) gypsum can be used as an amendment for saline-alkali soils. However, little information is available regarding the effects of FGD gypsum on soil quality and crop production at large scales. Thus, we evaluated the changes in the soil salinity, sodicity, soluble ion levels, paddy rice (Oryza sativa L.) yield and heavy metal levels in soil and rice after reclamation with FGD gypsum and paddy planting over three years. Data (90 samples) were also collected from three neighbouring saline-sodic fields (1780 ha). As expected, soil salinity and sodicity decreased significantly after two years of reclamation. The levels of electrical conductivity (EC) and the sodium absorption ratio (SAR) decreased rapidly in the first year, and the pH and exchangeable sodium percentage (ESP) decreased substantially in the second year. Averaged across the experimental sites, the mean EC, pH, ESP and SAR levels of the soils two years after reclamation decreased by 38.6%, 14.6%, 61.2% and 87.8%, respectively, compared to those of the initial soils. In addition, the concentrations of water-soluble Na+ and CO32− + HCO3− were 97.5% and 96.8% lower, respectively, two years after reclamation than the concentrations before reclamation. The paddy rice yield increased over time with reclamation; the mean level in the second year was 7.4 t ha−1 or 80% of the yield harvested from the managed fields of neighbouring farmers. Moreover, the heavy metal (Cd, Cr, Hg, Pb and As) contents of both soils and rice were lower than the established standards and below detectable limits after FGD gypsum application. These results confirm that FGD gypsum is a safe and effective way to reclaim saline-sodic soils and worthy of widespread application on the Songnen Plain in Northeast China and in similar ecological areas.

NbTe2 crystal is quasi-2D layered semimetal with charge density wave ground state showing a distorted-1T structure at room temperature. Here we report the anisotropic magneto-transport properties of NbTe2. An anomalous linear magnetoresistance up to 30% at 3 K in 9 T was observed, which can be well explained by quantum linear magnetoresistance model. Our results reveal that a large quasi-2D Fermi surface and small Fermi pockets with linearly dispersive bands coexist in NbTe2. The comparison with the isostructural material TaTe2 provides more information about the electronic structure evolution with charge density wave transitions in NbTe2 and TaTe2., 5 pages, 4 figures

We report a new type of amide bond-bearing cathepsin B-sensitive gemcitabine (GEM) prodrugs, capable of in situ covalently targeting circulating albumin and then making a hitchhike to the tumor. Specially, less plasma-enzyme deactivation, long plasma half-life, independence on nucleoside transporters, outstanding tumor targeting, and site-specific drug release are achieved, and as such these multifunctional advantages contribute to the dramatically increased in vivo antitumor efficacy.

Rational design of prodrugs for efficient albumin binding shows distinct advantages in drug delivery in terms of drug availability, systemic circulation, and potential targeting effect. And fatty acids are good candidates due to their high affinity to albumin. However, how the alkyl chain length of fatty acids affects the binding dynamics between prodrugs and albumin, despite its importance, is still unclear. In the present study, three prodrugs of didanosine (DDI) and fatty acids were designed and synthesized to evaluate the effect of the alkyl chain length on prodrug-albumin binding process, including capric acid-didanosine (CA-DDI), myristic acid-didanosine (MA-DDI), and stearic acid-didanosine (SA-DDI). The binding dynamics between these prodrugs with bovine serum albumin (BSA) were studied by fluorometry, circular dichroism (CD), UV analysis, and molecular docking. It turned out that DDI itself showed poor binding affinity to BSA. In contrast, CA-DDI, MA-DDI, and SA-DDI demonstrated significantly improved binding affinity. Interestingly, the binding affinity between DDI prodrugs and BSA was correlated with the alkyl chain length of fatty acids, and the binding constant significantly increased with the extension of alkyl chain length (KCA-DDI = 5.86 × 103 M−1, KMA-DDI = 8.57 × 103 M−1, and KSA-DDI = 11.42 × 103 M−1 at 298 K).

In this study, we show that the polymorph type of cellulose is an important factor for its pyrolysis behavior. By using TGA, XRD and FTIR, we characterized the pyrolysis kinetics and char yields of amorphous cellulose, cellulose II and cellulose I. All these celluloses with various polymorphs were regenerated from the same source material, microcrystalline cellulose; thus, the lattice difference among these samples was the only factor affecting their thermal pyrolysis. We found that the char yield of cellulose I was the highest among all cellulose polymorphs. With the addition of 5% phosphoric acid, the char yield of cellulose I at 800 °C was as high as 37.4%. The char yield of cellulose I at 800 °C is more than 10% higher than that of cellulose II regardless the addition of additives. This study highlights that the lattice structures of cellulose affects both its thermal pyrolysis kinetics and the char yield. For improving the char yield of cellulose, both structural factors and impregnated additives play independent and important roles.

A simple and rapid UPLC–MS/MS method to simultaneously determine gemcitabine and its L-carnitine ester derivative (2'-deoxy-2', 2'-difluoro-N-((4-amino-4-oxobutanoyl) oxy)-4-(trimethyl amm-onio) butanoate-cytidine, JDR) in rat plasma was developed and validated. The conventional plasma sample preparation method of nucleoside analogues is solid-phase extraction (SPE) which is time-consuming and cost-expensive. In this study, gradient elution with small particles size solid phase was applied to effectively separate gemcitabine and JDR, and protein precipitation pretreatment was adopted to remove plasma protein and extract the analytes with high recovery(>81%). Method validation was performed as per the FDA guidelines, and the standard curves were found to be linear in the range of 5–4000 ng/ml for JDR and 4–4000 ng/ml for gemcitabine, respectively. The lower limit of quantitation (LLOQ) of gemcitabine and JDR was 4 and 5 ng/ml, respectively. The intra-day and inter-day precision and accuracy results were within the acceptable limits. Finally, the developed method was successfully applied to investigate the pharmacokinetic studies of JDR and gemcitabine after oral administration to rats.

Amphiphilic polyurethanes based on methoxy poly(ethylene glycol) (mPEG) and poly(ϵ-caprolactone) diol (PCL) with different arm numbers such as two, three and four were successfully synthesized. Their structures were confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR) and gel permeation chromatography (GPC). The effects of arm number on properties of amphiphilic polyurethanes were studied. Pyrene fluorescence probe technique and dynamic light scattering (DLS) analyses showed that the CMC value and the micellar size of the resultant amphiphilic polyurethanes decreased and the micellar stability against dilution enhanced with increasing the arm number of polyurethane. Using indometacin (IMC) as a model drug, the results indicated that the drug loading capacity and in vitro drug sustained release effect of polyurethane with four arms were better than those of polyurethanes with two and three arms.

Distinguishing SiC (0001) Si-face from SiC (000-1) C-face without any damages is extremely important because the two polar faces have different physical and chemical properties which seriously influence the quality of a homoepitaxy or heteroepitaxy thin film on it. Here, a convenient and nondestructive detection method is developed to distinguish the Si-face and C-face of a (0001) oriented SiC wafer by employing a pull-off force measurement using atomic force microscopy. It is found that the pull-off force from a Si-face of 6H-SiC is about two times of that from a C-face, no matter it is a two-face chemical mechanical polishing or etched 6H-SiC wafer. The method developed here is suitable to identify polar faces of materials only if the two polar faces having different surface energy.

Our previous work has demonstrated that soluble polyimide with relatively weak interaction can be transformed from neutral polymer to associative polymer by increasing molecular weight. Thus, it is necessary to find another way to vary the relatively weak interaction strength, i.e. variation of solvent quality. Herein, viscoelastic behaviors are examined for 2,2-bis(3,4-dicarboxy-phenyl) hexafluoropropane dianhydride (6FDA)-2,2′-bis(trifluoromethyl)-4,4′-diam (TFDB) polyimide (PI), with a relatively low molecular weight (Mw) of 88 000 g mol−1, dissolved in cyclohexanone (CYC). The scaling relationship between viscosity (η0–ηs) and volume fraction is in good agreement with the associative polymer theory proposed by Rubinstein and Semenov. Oscillatory rheological results indicate that the PI solution tends to become a gel with increased volume fraction. The synchrotron radiation small-angle X-ray scattering results imply the existence of dense aggregates in the concentrated PI/CYC solutions. Shear thickening and thinning behaviors are observed in the solutions, and the shear thickening behavior of polyimide solution has not been reported in literature. Their mechanisms are studied by conducting dynamic and steady rheological experiments. Thus, enhancing the relatively weak interaction strength can also make the low Mw polyimide show associative polymer behavior. This work can help us to gain deep insight into polyimide solution properties from dilute to semidilute entangled solutions, and will guide the preparation of polyimide solutions for different processing.

Solvent species influence the interactions of dissolved polymers in solution and consequently induce changes in solution properties. A soluble polyimide was synthesized through polycondensation, and four solvents, namely, N,N-dimethylacetamide (DMAc), N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), were selected to investigate systematically the influence of solubility parameter on solution power law behaviors. The power law relationship between specific viscosity and concentration was established using rheology and applying concepts from the Zimm, Rouse-Zimm, and Doi-Edwards models. All power law exponents were higher than theoretical predictions, and in the three concentration regions, i.e. dilute, semidilute unentangled, and semidilute entangled, the exponents increase, decrease, and increase, respectively, with respect to solubility parameter. Arguments derived from the listed models are proposed to explain these trends. The influences of solubility parameter on the overlap and entanglement concentrations are also discussed.

$\mathrm{N}{\mathrm{a}}_{0.35}{({\mathrm{C}}_{3}{\mathrm{N}}_{2}{\mathrm{H}}_{10})}_{0.426}\mathrm{F}{\mathrm{e}}_{2}\mathrm{S}{\mathrm{e}}_{2}$ exhibits a large orthorhombic distortion at room temperature without magnetic ordering, hence providing an ideal platform to investigate the correlation between nematicity and superconductivity. We show that its nematicity is stabilized by ``nematic'' ordered 1,3-diaminopropane (1,3- DIA) molecules in between the FeSe layers, and the C2 twofold rotational symmetry is preserved down to 10 K without phase transition. The superconductivity occurs at 46.5 K even though the orthorhombic distortion is much larger than that for \ensuremath{\beta}-FeSe and most of the other pnictide superconductors at low temperatures. First principles calculations reveal that this ``artificial'' orthorhombic distortion has a selective effect on the band structure, which behaves differently on splitting the iron $3{d}_{xz}$ and $3{d}_{yz}$ orbitals around the \cyrchar\CYRG{} and M points in the Brillouin zone. Our finding strongly supports that the nematic state is irrelevant to the emergent superconductivity, at least in high-${T}_{c}$ iron selenide superconductors.

Transition metal dichalcogenides (TMDs), an emerging optical limiting material, exhibit excellent optical limiting properties for high energy laser. Generally, TMDs materials showed better laser protection with the decrease of lateral sizes. However, in this work, TiS2 nanosheets showed exceptional lateral size-dependent optical limiting property contrary to the reported TMDs nanosheets. TiS2 nanosheets with similar thickness and varied lateral sizes of 50 nm, 100 nm, 150 nm, 350 nm were obtained. Larger size TiS2 nanosheets displayed better optical limiting performance and TiS2 nanosheets with ultra-low normalized transmittance (as low as 12%) were developed. It was interesting to find that both two-photon absorption (TPA) and reverse saturable absorption (RSA) were exhibited in large TiS2 nanosheets (350 nm) with a bandgap of 2.67 eV, while in small TiS2 nanosheets (50 nm) with a bandgap of 3.51 eV, only TPA existed. Furthermore, the TiS2 nanosheets incorporated polymethyl methacrylate (PMMA) sample with an extremely low content of 0.066 wt‰ TiS2 nanosheets exhibited a low normalized transmittance of 18%, along with a low initial threshold (0.03 J/cm2) and low optical threshold (0.57 J/cm2), which showed great potential for practical use of the TiS2 nanosheets in optical limiting field.

A challenge to polymer scientists is to design new materials with superior overall performance in heat-resistance, cold-resistance, strength, and toughness. Here we report the synthesis of hyperbranched polymers containing epoxy and imide structure (EHPI-n, n = 6, 12, and 24) with various molecular weights and degrees of branching using a new synthetic diimide dicarboxylic acid. EHPI-n significantly decreases the gelation time and accelerates the curing of EHPI-n/diglycidyl ether of bisphenol-A (DGEBA). Both EHPI-6 and EHPI-12 significantly reduce the viscosity, activation energy, and average particle size of EHPI-n/DGEBA blends due to the disentangling function and compatibility of the EHPI-n. The toughness property, including elongation at break, impact strength, critical strain energy value (GIC) and critical stress intensity factor (KIC) of 12 wt % EHPI-12/DGEBA composites are improved over the neat DGEBA, by 144.72 %, 197.9 %, 168.4 % and 72.6 %, respectively, while their mechanical properties, including tensile strength, storage modulus and flexural strength are enhanced by 61.2 %, 89.9 %, 44.2 %. The heat-resistant index and β-relaxation peak temperatures of the composites are improved 14 °C and 15 °C, respectively, indicating both outstanding high-temperature resistance and outstanding low-temperature resistance. The simultaneous improvement on multiple performances is attributable to an in-situ homogeneous reinforcing and toughening mechanism, which is explained by free volume fraction, microstructure and surface micrograph. The EHPI-n present great potential as advanced materials for aerospace and wind turbine.

The shape memory polyurethane/sepiolite nanocomposites were prepared with sepiolite dispersed uniformly in polyurethane based on poly(e-caprolactone). The influence of sepiolite on the structure of polyurethane was investigated by dynamic mechanical analysis, differential scanning calorimetry, X-ray diffraction, and polarized optical microscopy. The results show that sepiolite has little effect on the ordering of hard segments, but can act as a nucleating agent enhancing the crystallinity of soft segments. The maximum crystallinity of soft segments can be achieved when the content of sepiolite is 3 wt%. The results of shape memory test demonstrate that the addition of sepiolite improves the shape fixity ratio of polyurethane. The shape fixity ratio of polyurethane composite with 3 wt% of sepiolite reaches the maximum of 86.2%. The crystallinity of the soft segments can be adjusted by varying sepiolite content, which has a potential to realize controllability of shape memory properties. POLYM. COMPOS., 2016. © 2016 Society of Plastics Engineers

The Lenglongling Mountains (LLM) located in northeastern part of the Tibet Plateau, belong to a marginal area of the East Asian summer monsoon (EASM) and are sensitive to monsoon dynamics. Two tree-ring width chronologies developed from six sites of Picea crassifolia in the LLM were employed to study the regional drought variability. Correlation and temporal correlation analyses showed that relationships between the two chronologies and self-calibrated Palmer Drought Severity Index (sc_PDSI) were significant and stable across time, demonstrating the strength of sc_PDSI in modeling drought conditions in this region. Based on the relationships, the mean sc_PDSI was reconstructed for the period from 1786 to 2013. Dry conditions prevailed during 1817-1819, 1829-1831, 1928-1931 and 1999-2001. Relatively wet periods were identified for 1792-1795 and 1954-1956. Spatial correlations with other fourteen precipitation/drought reconstructed series in previous studies revealed that in arid regions of Northwest China, long-term variability of moisture conditions was synchronous before the 1950s at a decadal scale (1791-1954). In northwestern margin of the EASM, most of all selected reconstructions had better consistency in low-frequency variation, especially during dry periods, indicating similar regional moisture variations and analogous modes of climate forcing on tree growth in the region.

The rheological behavior of waterborne polyurethane dispersion (PUD) thickened by the hyperbranched waterborne polyurethane (HWPU) was studied by rheological measurements. The results showed that the flow activation energy depended on the structure and concentration of HWPU. Based on the relationship between the structure, concentration and flow activation energy, we could infer that during HWPU associating thickening process PUD experienced Duckweed state (appropriate HWPU-latex particles linker), 3D network structure (HWPU-latex particles three-dimensional network) or Bead-like texture (HWPU monomolecular micelles or multi-molecular micelles). The role of interaction between particles in the structure of thickening system was explored by dynamic light scattering, refraction analysis and fluorescence spectroscopy. The combination of hydrophobic groups of HWPU with latex particles resulted in associating thickening, while the intramolecular or intermolecular association of HWPU might lead to a decrease in thickening efficiency or no thickening.

Tantalum arsenide is experimentally verified as a Weyl semimetal recently. However, it is difficult to grow large TaAs single crystals due to the decomposition prior to reaching its melting point. Here we report an improved chemical vapor transport method using iodine as an agent to get large-size, high-quality TaAs single crystals up to 1 cm. X-ray diffraction confirmed that they are tetragonal TaAs. Specific heat of TaAs was measured from 2 K to room temperature, and hence the entropy and enthalpy were obtained, which are helpful in designing the optimal growth conditions. The as-grown crystals exhibit polyhedral morphology consisting of {101}, {001}, {103}, and {112} facets. The key points in crystal growth include using tantalum in the form of foils instead of powder as the starting material, tilting ampule to enhance convections and controlling the concentration of agent iodine. These measures should be applicable to the growth of other transition metal arsenides and phosphides.

This study focused on the preparation of wearable polyacrylonitrile (PAN)/phase-change material (PCM) sheath/core nano-fibers by coaxial electro-spinning technology. PAN was used as the sheath material to make fibers comfortable to human skin, and isopropyl palmitate and paraffin oil were used as sample PCMs. The electro-spinning conditions are critical for encapsulating a PCM by a PAN shell and forming a uniform sheath–core structure. Our experiments show that these PCMs could be well encapsulated in PAN hollow fibers and function to stabilize environmental temperature in a narrow range. This study provides a versatile and feasible way to fabricate PAN/PCM sheath/core homo-thermal nano-fibers with various temperature stabilization windows. Using these homo-thermal nano-fibers as clothing materials will be able to abate people’s discomfort during a sudden environmental temperature change.

It is very important to optimize rheological properties of polyimide (PI) solution for film casting or fiber spinning. Herein, a soluble 2,2-bis(3,4-di-carboxyphenyl) hexafluoro propane dianhydride-2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl PI sample with high absolute molecular weight of 390,000 g/mol was obtained by precipitation fractionation. The viscoelastic behavior of PI in cyclohexanone solution was investigated at different concentrations (0.1–12 wt%). PI gel can form at a suitable concentration. Analysis of viscoelastic storage and loss moduli, G ' and G ' ' , based on the Winter and Chambon model gives the gel concentration c g = 4 wt% and the critical relaxation exponent n = 0.56. The scaling relations such as zero-shear viscosity η 0 and equilibrium modulus G e against relative distance from the gel point e , that is η 0 ∝ e − γ and G e ∝ e z , were examined in the vicinity of c g , where a fractal dimension d f = 2.54 indicates formation of a compact gel structure. Addition of N,N-dimethylformamide (DMF) strongly decrosslinks the PI solution, suggesting a screening of the interchain dipole–dipole interactions by the highly polar DMF solvent.

Recently, cold atmospheric pressure plasmas (CAPs) have provided many new opportunities in dermatology by providing a multimodal action of reactive agents (RA). This review critically examines the generation, transport, and physical effects induced by CAPs in dermatologic treatments. We introduce the most suitable plasma sources, which provide a multitude of physical effects on the skin without any electric or thermal shocks. The mechanisms of generation and transport of the key reactive species are introduced and examined from the viewpoint of their applications in dermatology. Special attention is paid to study the “plasmaporation” effect, which enables RA penetration through healthy and damaged skin. Plausible physical mechanisms involved in the CAP treatment of some of the most common skin diseases are analyzed.

Realizing the reliable modulation of the carrier type and density in graphene is a challenging task, especially for epitaxial graphene (EG) grown in situ on SiC via thermal decomposition. In this process, doping is seldom adopted for substrate pretreatment, and the residual carriers in EG are determined by the properties of the SiC substrate and the random defects in EG. Here, we demonstrate a simple and effective technique for hole doping in EG on the Si-face of SiC (0001) implanted with boron ions. P-type EG with a carrier concentration of approximately 1–2 × 1012 cm−2 and a room-temperature mobility of 100–300 cm2/V s was achieved at the boron ion dose of approximately 1 × 1015 cm−2 at a centroid depth of approximately 140 nm from the SiC surface. These transport properties are comparable with the data reported for unintentionally doped P-type EG on the Si-face of SiC [Tedesco et al., Appl. Phys. Lett. 95, 122102 (2009)], for which the Hall device size was 40 times smaller compared to our device. The formation of P-type EG on the Si-face of SiC (0001) in this study was attributed to the synergetic effects of boron doping in EG and the transfer of electrons from EG into SiC. The detailed mechanisms are studied and discussed in this paper. The method demonstrated herein can be universally applied to downshift the Fermi level of EG on SiC, regardless of the crystallization orientation or polytype. The developed method is also compatible with modern semiconductor procedures.Realizing the reliable modulation of the carrier type and density in graphene is a challenging task, especially for epitaxial graphene (EG) grown in situ on SiC via thermal decomposition. In this process, doping is seldom adopted for substrate pretreatment, and the residual carriers in EG are determined by the properties of the SiC substrate and the random defects in EG. Here, we demonstrate a simple and effective technique for hole doping in EG on the Si-face of SiC (0001) implanted with boron ions. P-type EG with a carrier concentration of approximately 1–2 × 1012 cm−2 and a room-temperature mobility of 100–300 cm2/V s was achieved at the boron ion dose of approximately 1 × 1015 cm−2 at a centroid depth of approximately 140 nm from the SiC surface. These transport properties are comparable with the data reported for unintentionally doped P-type EG on the Si-face of SiC [Tedesco et al., Appl. Phys. Lett. 95, 122102 (2009)], for which the Hall device size was 40 times smaller compared to our device. The f...

Gapless surface states (SSs) are features of topological semimetals and are extensively observed. Nowadays, the emerging question is whether the SSs possess exotic and applicable properties. Here, associated with the symmetrical selection rule for nonlinear optical materials, the surface nonlinear optics on a centrosymmetric Dirac nodal-line semimetal ZrSiS crystal is studied and it is found that the SSs bring record nonlinear susceptibilities. The unprecedented conversion efficiencies for second and third harmonic generations are 0.11‰ and 0.43‰, respectively, more than ten orders of magnitude larger than the typical surface second harmonic generation. This work discovers a new route toward studying the SSs for applications in nonlinear photonics.

Quantum mechanics fundamentally forbids deterministic discrimination of quantum states and processes. However, the ability to optimally distinguish various classes of quantum data is an important primitive in quantum information science. In this work, we train near-term quantum circuits to classify data represented by non-orthogonal quantum probability distributions using the Adam stochastic optimization algorithm. This is achieved by iterative interactions of a classical device with a quantum processor to discover the parameters of an unknown non-unitary quantum circuit. This circuit learns to simulates the unknown structure of a generalized quantum measurement, or Positive-Operator-Value-Measure (POVM), that is required to optimally distinguish possible distributions of quantum inputs. Notably we use universal circuit topologies, with a theoretically motivated circuit design, which guarantees that our circuits can in principle learn to perform arbitrary input-output mappings. Our numerical simulations show that shallow quantum circuits could be trained to discriminate among various pure and mixed quantum states exhibiting a trade-off between minimizing erroneous and inconclusive outcomes with comparable performance to theoretically optimal POVMs. We train the circuit on different classes of quantum data and evaluate the generalization error on unseen mixed quantum states. This generalization power hence distinguishes our work from standard circuit optimization and provides an example of quantum machine learning for a task that has inherently no classical analogue., 19 pages, 10 figures

A novel polyamic acid (PAA from BAPMPO-BPDA) organogel was synthesized and characterized via dynamic light scattering (DLS), a classical rheometer, and diffusion wave spectroscopy (DWS). In situ monitoring was performed using a classical rheometer to observe the formation of the PAA organogel. The rheological curves confirm the formation of the PAA gel network and the origin of hydrogen bonding from the -NH- group (donor) and P[double bond, length as m-dash]O group (acceptor). The autocorrelation functions of PAA under different conditions (pure gel, gel with NaNO3, gel with formamide) are measured via DLS, and different characteristic times are obtained via the CONTIN method. Three different relaxation modes of the PAA gel, i.e., fast, intermediate and slow modes, are observed. The fast and intermediate modes show a diffusive behaviour (τ ∼ q-2), whereas the slow mode did not. When enough formamide is added into the PAA gel, the fast mode disappears; addition of enough salt (NaNO3) leads to disappearance of the slow mode. The relationship between characteristic time and diffusion vector demonstrates that the different decorrelation modes consisted of two homodyne and two heterodyne components. Two single-exponential functions and two stretched exponential functions were used, and the different decorrelation modes of the PAA gel are expressed with a non-linear function, which fits the autocorrelation function very well. And the different decorrelation modes are also discussed. DWS results in the high-frequency region not only demonstrate the formation of a PAA gel network but also indicate that the semiflexible chains of PAA are due to electrostatic interaction. The DWS results at different time scales are analyzed by applying the de Gennes' reptation model.

A new type of regeneration method of cellulose I was developed, and the regenerated cellulose I has a crystallinity as high as 84.7%. This mild and processable method makes it possible to shape cellulose I into various shapes, for example aerogels and fibers.

Polyimde (PI) samples with different molecular weights were synthesized. Based on SEC coupled with multidetectors measurement and Yamakawa-Fujii-Yoshizaki (YFY) model, eight soluble samples with absolute Mw from 40,600 g/mol to 197,000 g/mol are chosen and applied to investigate the influence of molecular weight on scaling exponents and critical concentrations at 20–45 °C in dilute, semidilute unentangled, and semidilute entangled solutions. Most of the scaling exponents are higher than the theoretical values in three concentration regions, and scaling exponent increases with molecular weight; overlap concentration (C*) increases and entanglement concentration (Ce) decreases with molecular weight. Considering bead-bead interaction, corrected bead-spring model can explain the related results. Finally, the relationship among C*, Ce, and molecular weight is established at different temperatures (from 20 °C to 45 °C), and two linear equations are available at each temperature. Thus, both C* and Ce are calculated at a fixed molecular weight. And from C/C* and C/Ce ratios, the morphology of PI fiber during electrospinning can be controlled. These results are helpful to guide the preparation of polyimide solutions for different processing.

We present a quasiparticle interference study of clean and Mn surface-doped TaAs, a prototypical Weyl semimetal, to test the screening properties as well as the stability of Fermi arcs against Coulomb and magnetic scattering. Contrary to topological insulators, the impurities are effectively screened in Weyl semimetals. The adatoms significantly enhance the strength of the signal such that theoretical predictions on the potential impact of Fermi arcs can be unambiguously scrutinized. Our analysis reveals the existence of three extremely short, previously unknown scattering vectors. Comparison with theory traces them back to scattering events between large parallel segments of spin-split trivial states, strongly limiting their coherence. In sharp contrast to previous work [R. Batabyal et al., Sci. Adv. 2, e1600709 (2016)], where similar but weaker subtle modulations were interpreted as evidence of quasiparticle interference originating from Femi arcs, we can safely exclude this being the case. Overall, our results indicate that intra- as well as inter-Fermi arc scattering are strongly suppressed and may explain why---in spite of their complex multiband structure---transport measurements show signatures of topological states in Weyl monopnictides.

TaTe2 is a quasi-2D charge density wave (CDW) compound with distorted-1T–type structure exhibiting double-zigzag chains. Here we report the Fermi surface topology of a low-temperature phase of TaTe2 (LT-TaTe2) by anisotropic magneto-transport and magnetic measurements on high-quality single crystals. An anomalous large linear magnetoresistance up to 140% at 3 K in 9 T was observed, suggesting the existence of a small Fermi pocket in the Dirac cone state in quantum transport models. Moreover, strong magnetic anisotropy was observed for B⊥(001) and B∥(001). Angle-dependent magnetoresistance and de Hass-van Alphen oscillations suggest the anisotropy of the normal Fermi surface and the small Fermi pocket in Dirac cone state.

To improve the depth of plasma active species in the skin, it is very important to develop skin disease treatment using plasma. In this article, an air plasma source was used to work directly with the skin of a mouse. A tortuous pathway, hair follicles, electroporation and a microneedle do not aid the transdermal delivery of gaseous plasma active species, therefore these gaseous plasma active species cannot penetrate mouse skin with a thickness of ~0.75 mm. The plasma activated water (PAW) produced by the air plasma source was used to study the transdermal penetration of the aqueous plasma activated species. This aqueous plasma activated species can penetrate the skin through hair follicles, intercellular and transcellular routes. The pH of the PAW did not affect the penetration efficiency of the aqueous plasma active species.

Amorphous indium gallium zinc oxide (a-IGZO) powder was prepared by typical solution-based process and post-annealing process. The sample was used as sensor for detecting C₂H₅OH, H₂, and CO. Gas-sensing performance was found to be highly sensitive to C₂H₅OH gas in a wide range of concentration (0.5-1250 ppm) with the response of 2.0 towards 0.5 ppm and 89.2 towards 1250 ppm. Obvious difference of response towards C₂H₅OH, H₂, and CO was found that the response e.g., was 33.20, 6.64, and 2.84 respectively at the concentration of 200 ppm. The response time and recovery time of was 32 s and 14 s respectively towards 200 ppm concentration of C₂H₅OH gas under heating voltage of 6.5 V.

A self-powered graphene-based photodetector with high performance is particularly useful for device miniaturization and to save energy. Here, we report a graphene/silicon carbide (SiC)-based self-powered ultraviolet photodetector that exhibits a current responsivity of 7.4 mA/W with a response frequency of over a megahertz under 325-nm laser irradiation. The built-in photovoltage of the photodetector is about four orders of magnitude higher than previously reported results for similar devices. These favorable properties are ascribed to the ingenious device design using the combined advantages of graphene and SiC, two terminal electrodes, and asymmetric light irradiation on one of the electrodes. Importantly, the photon energy is larger than the band gap of SiC. This self-powered photodetector is compatible with modern semiconductor technology and shows potential for applications in ultraviolet imaging and graphene-based integrated circuits.