Inhomogeneous Photosusceptibility of VO_{2} Films at the Nanoscale.

Pump-probe nano-optical experiments were used to study the light-induced insulator to metal transition (IMT) in thin films of vanadium dioxide (VO_{2}), a prototypical correlated electron system. We show that inhomogeneous optical contrast is prompted by spatially uniform photoexcitation, indicating an inhomogeneous photosusceptibility of VO_{2}. We locally characterize temperature and time dependent variations of the photoexcitation threshold necessary to induce the IMT on picosecond timescales with hundred nanometer spatial resolution. We separately measure the critical temperature T_{L}, where the IMT onsets and the local transient electronic nano-optical contrast at the nanoscale. Our data reveal variations in the photosusceptibility of VO_{2} within nanoscopic regions characterized by the same critical temperature T_{L} where metallic domains can first nucleate.

[Effects of Nintedanib associated with Shenfu Injection on paraquat-induced lung injury in rats].

Objective: To study the effects of Nintedanib associated with Shenfu Injection on lung injury induced by paraquat (PQ) intoxication. Methods: In September 2021, a total of 90 SD rats were divided into 5 groups in random, namely control group, PQ poisoning group, Shenfu Injection group, Nintedanib group and associated group, 18 rats in each group. Normal saline was given by gavage route to rats of control group, 20% PQ (80 mg/kg) was administered by gavage route to rats of other four groups. 6 hours after PQ gavage, Shenfu Injection group (12 ml/kg Shenfu Injection), Nintedanib group (60 mg/kg Nintedanib) and associated group (12 ml/kg Shenfu Injection and 60 mg/kg Nintedanib) were administered with medicine once a day. The levels of serum transforming growth factor beta1 (TGF-ß1), interleukin-1 beta (IL-1ß) were determined at 1, 3 and 7 d, respectively. The pathological changes of lung tissue, the ratio of wet weight and dry weight (W/D) of lung tissue, the levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in lung tissue were observed and determined after 7 d. Western blot was used to analyse the expression levels of fibroblast growth factor receptor 1 (FGFR1), platelet derivation growth factor receptor alpha (PDGFRα), vascular endothelial growth factor receptor 2 (VEGFR2) in lung tissue after 7 d. Results: The levels of TGF-ß1, IL-1ß in all poisoning groups went up first and then went down. The levels of TGF-ß1, IL-1ß in associated group at 1, 3, 7 d were lower than that of PQ poisoning group, Shenfu Injection group and Nintedanib group at the same point (P<0.05). Pathological changes of lung tissue under the light microscopes showed that the degrees of hemorrhage, effusion and infiltration of inflammatory cells inside the alveolar space of Shenfu Injection group, Nintedanib group and associated group were milder than that of PQ poisoning group, and the midest in associated group. Compared with control group, the W/D of lung tissue was higher, the level of MDA in lung tissue was higher, while the level of SOD was lower, the expressions of FGFR1, PDGFRα and VEGFR2 in lung tissue were higher in PQ poisoning group (P<0.05). Compared with PQ poisoning group, Shenfu Injection group and Nintedanib group, the W/D of lung tissue was lower, the level of MDA in lung tissue was lower, while the level of SOD was higher, the expressions of FGFR1, PDGFRα and VEGFR2 in lung tissue were lower in associated group (P<0.05) . Conclusion: Nintedanib associated with Shenfu Injection can relieve lung injury of rats induced by PQ, which may be related to Nintedanib associated with Shenfu Injection can inhibit the activation of TGF-ß1 and the expressions of FGFR1, PDGFRα, VEGFR2 in lung tissue of rats.

Andrographolide Liquisolid using Porous-Starch as the Adsorbent with Enhanced Oral Bioavailability in Rats.

Andrographolide (AGL) is the major component of Andrographispaniculata. The poor water solubility and low dissolution strongly affect its oral absorption. Liquisolid technology has been used to improve its dissolution and oral bioavailability. Liquisolid powders of AGL (AGL-LS-PSG) were obtained by firstly dissolving AGL in the mixture of NMP, PEG 6000 and Soluplus®, and solidified by absorption of the blend in porous starch. Angle of repose, Carr index and Hauser ratio presented good powder fluidity and compressibility characteristics of AGL-LS-PSG. The results of optical microscopic observation, PXRD and DSC analysis indicated that AGL has been completely adsorbed in porous starch granules and existed in an amorphous or molecularly dispersing state. AGL-LS-PSG can obviously increase the drug dissolution rate compared to commercial guttate pills and raw drug. In vivo pharmacokinetic behavior of AGL-LS-PSG was investigated following a single oral administration to rats. The Cmax (0.37 ± 0.06 µg mL-1) and AUC0-2h (13.55 ± 2.67 µg h mL-1) of AGL-LS-PSG were evidently increased compared to commercial guttate pills (Cmax = 0.30 ± 0.21 µg mL-1, AUC0-2h = 9.88 ± 3.57 µg h mL-1). This study indicated great potential of liquisolid technology in effectively improving the dissolution and bioavailability of AGL.

[Therapeutic effect of different surgical methods for congenital small intestine atresia].

Objective: To compare and analyze the curative effect of three surgical methods in the treatment of small intestine atresia, and to provide evidence for individualized surgical treatment of children with small intestine atresia. Methods: The clinical diagnosis and treatment of 168 children with small intestine Ⅱ, Ⅲ, Ⅳ type atresia in our hospital from January 2008 to September 2017 were retrospectively analyzed and they were divided into different types according to the operation. The three groups were end-to-end anastomosis group (EEA, n=58), end oblique anastomosis group (EOA, n=68), and proximal end-end anastomosis group (PEA, n=42). The EEA group and the EOA group were further divided into group a (EEA-a/EOA-a) with a proximal intestinal tube diameter greater than 4.0 times the distal end and a group b ((EEA-b/EOA-b) with a diameter less than or equal to 4.0 times the distal intestinal tube diameter. The gender, gestational age, birth weight, type of atresia, and postoperative defecation time, postoperative feeding time, postoperative hospital stay and postoperative follow-up complications were compared. Results: There was no significant difference in gender, gestational age and birth weight between the groups (P>0.05). The PEA group was better than EEA-a group and EOA-a group in postoperative defecation time, postoperative feeding time, postoperative hospital stay and complications (P<0.05). The postoperative defecation time, postoperative feeding time, postoperative hospital stay and complications of the EOA-a group were better than those of the EEA-a group (P<0.05). There was no statistically significant difference in postoperative defecation time, postoperative feeding time, and complications between the EEA-b group and the EOA-b group (P>0.05), but the postoperative hospital stay in the EEA-b group was longer than that in the EOA-b group (P<0.05). Conclusion: PEA is recommended for children with a proximal intestinal canal diameter greater than 4.0 times greater than the distal end because of the rapid recovery and fewer complications; EOA is recommended for children with a proximal intestinal canal diameter of 4.0 or less because of its advantage of shorter hospital stay than EEA surgery. Congenital intestinal atresia has a better effect according to the specific conditions of the child.

Chiral terahertz wave emission from the Weyl semimetal TaAs.

Weyl semimetals host chiral fermions with distinct chiralities and spin textures. Optical excitations involving those chiral fermions can induce exotic carrier responses, and in turn lead to novel optical phenomena. Here, we discover strong coherent terahertz emission from Weyl semimetal TaAs, which is demonstrated as a unique broadband source of the chiral terahertz wave. The polarization control of the THz emission is achieved by tuning photoexcitation of ultrafast photocurrents via the photogalvanic effect. In the near-infrared regime, the photon-energy dependent nonthermal current due to the predominant circular photogalvanic effect can be attributed to the radical change of the band velocities when the chiral Weyl fermions are excited during selective optical transitions between the tilted anisotropic Weyl cones and the massive bulk bands. Our findings provide a design concept for creating chiral photon sources using quantum materials and open up new opportunities for developing ultrafast opto-electronics using Weyl physics.

[Value of serum matrix metalloproteinase 3 in the assessment of early rheumatoid arthritis].

OBJECTIVE: To investigate the expression level of serum matrix metalloproteinase 3 (MMP3) in early rheumatoid arthritis (ERA) patients with normal C-reaction protein (CRP) or erythrocyte sedimentation rate (ESR), and the significance in disease assessment. METHODS: In the study, 133 cases of early RA patients, 25 osteoarthritis (OA) patients and 60 healthy controls in Peking University People's Hospital from 2011 to 2015 were included. The RA patients were further divided into 4 groups according to levels of CRP and ESR: 88 patients with increased CRP and increased ESR, 15 patients with normal CRP and normal ESR, 17 patients with normal CRP but increased ESR, and 13 patients with increased CRP but normal ESR. All the clinical information of the patients was collected, and the serum MMP3 levels of both patients and healthy controls were detected by enzyme-linked immune sorbent assay (ELISA). RESULTS: The serum MMP3 level of RA patients with normal CRP and/or normal ESR [(72.89±6.34) µg/L] was obviously higher than that of OA patients [(42.87±4.14) µg/L] (P=0.002) and healthy controls [(31.62±2.88) µg/L] (P<0.001). The serum MMP3 levels of the patients with normal CRP and normal ESR [(47.04±9.64) µg/L] were higher than those of the healthy controls, and there was statistical significance between the two groups (P<0.05). The serum MMP3 levels of the patients with increased CRP but normal ESR [(94.18±9.11) µg/L] and the patients with normal CRP but increased ESR [(79.42±10.60) µg/L] were both higher than those of the OA patients and healthy controls, and there was obvious statistical difference (P<0.05). In the early RA patients with normal CRP and/or normal ESR, the serum MMP3 level was positively correlated with the CRP level (r=0.336, P=0.024). The positive rate of MMP3 in the patients with normal CRP and/or normal ESR was 44.44%, higher than the positive rate of CRP (28.89%) and the positive rate of ESR (37.78%). In these early RA patients, the positive rate was 52.94% in the patients with normal CRP but increased ESR and 53.85% in the patients with increased CRP but normal ESR. CONCLUSION: The detection of the serum MMP3 level was significant in the assessment of early RA patients within 2-year duration who had normal CRP or ESR value.

Broadband Terahertz Generation via the Interface Inverse Rashba-Edelstein Effect.

Novel mechanisms for electromagnetic wave emission in the terahertz frequency regime emerging at the nanometer scale have recently attracted intense attention for the purpose of searching next-generation broadband THz emitters. Here, we report broadband THz emission, utilizing the interface inverse Rashba-Edelstein effect. By engineering the symmetry of the Ag/Bi Rashba interface, we demonstrate a controllable THz radiation (∼0.1-5 THz) waveform emitted from metallic Fe/Ag/Bi heterostructures following photoexcitation. We further reveal that this type of THz radiation can be selectively superimposed on the emission discovered recently due to the inverse spin Hall effect, yielding a unique film thickness dependent emission pattern. Our results thus offer new opportunities for versatile broadband THz radiation using the interface quantum effects.

Ultraconfined Plasmonic Hotspots Inside Graphene Nanobubbles.

We report on a nanoinfrared (IR) imaging study of ultraconfined plasmonic hotspots inside graphene nanobubbles formed in graphene/hexagonal boron nitride (hBN) heterostructures. The volume of these plasmonic hotspots is more than one-million-times smaller than what could be achieved by free-space IR photons, and their real-space distributions are controlled by the sizes and shapes of the nanobubbles. Theoretical analysis indicates that the observed plasmonic hotspots are formed due to a significant increase of the local plasmon wavelength in the nanobubble regions. Such an increase is attributed to the high sensitivity of graphene plasmons to its dielectric environment. Our work presents a novel scheme for plasmonic hotspot formation and sheds light on future applications of graphene nanobubbles for plasmon-enhanced IR spectroscopy.

Edge and Surface Plasmons in Graphene Nanoribbons.

We report on nano-infrared (IR) imaging studies of confined plasmon modes inside patterned graphene nanoribbons (GNRs) fabricated with high-quality chemical-vapor-deposited (CVD) graphene on Al2O3 substrates. The confined geometry of these ribbons leads to distinct mode patterns and strong field enhancement, both of which evolve systematically with the ribbon width. In addition, spectroscopic nanoimaging in the mid-infrared range 850-1450 cm(-1) allowed us to evaluate the effect of the substrate phonons on the plasmon damping. Furthermore, we observed edge plasmons: peculiar one-dimensional modes propagating strictly along the edges of our patterned graphene nanostructures.

Sum-rule constraints on the surface state conductance of topological insulators.

We report the Drude oscillator strength D and the magnitude of the bulk band gap E_{g} of the epitaxially grown, topological insulator (Bi,Sb)_{2}Te_{3}. The magnitude of E_{g}, in conjunction with the model independent f-sum rule, allows us to establish an upper bound for the magnitude of D expected in a typical Dirac-like system composed of linear bands. The experimentally observed D is found to be at or below this theoretical upper bound, demonstrating the effectiveness of alloying in eliminating bulk charge carriers. Moreover, direct comparison of the measured D to magnetoresistance measurements of the same sample supports assignment of the observed low-energy conduction to topological surface states.

Tunneling Plasmonics in Bilayer Graphene.

We report experimental signatures of plasmonic effects due to electron tunneling between adjacent graphene layers. At subnanometer separation, such layers can form either a strongly coupled bilayer graphene with a Bernal stacking or a weakly coupled double-layer graphene with a random stacking order. Effects due to interlayer tunneling dominate in the former case but are negligible in the latter. We found through infrared nanoimaging that bilayer graphene supports plasmons with a higher degree of confinement compared to single- and double-layer graphene, a direct consequence of interlayer tunneling. Moreover, we were able to shut off plasmons in bilayer graphene through gating within a wide voltage range. Theoretical modeling indicates that such a plasmon-off region is directly linked to a gapped insulating state of bilayer graphene, yet another implication of interlayer tunneling. Our work uncovers essential plasmonic properties in bilayer graphene and suggests a possibility to achieve novel plasmonic functionalities in graphene few-layers.

Graphene on hexagonal boron nitride as a tunable hyperbolic metamaterial.

Hexagonal boron nitride (h-BN) is a natural hyperbolic material, in which the dielectric constants are the same in the basal plane (ε(t) ≡ ε(x) = ε(y)) but have opposite signs (ε(t)ε(z) < 0) in the normal plane (ε(z)). Owing to this property, finite-thickness slabs of h-BN act as multimode waveguides for the propagation of hyperbolic phonon polaritons--collective modes that originate from the coupling between photons and electric dipoles in phonons. However, control of these hyperbolic phonon polaritons modes has remained challenging, mostly because their electrodynamic properties are dictated by the crystal lattice of h-BN. Here we show, by direct nano-infrared imaging, that these hyperbolic polaritons can be effectively modulated in a van der Waals heterostructure composed of monolayer graphene on h-BN. Tunability originates from the hybridization of surface plasmon polaritons in graphene with hyperbolic phonon polaritons in h-BN, so that the eigenmodes of the graphene/h-BN heterostructure are hyperbolic plasmon-phonon polaritons. The hyperbolic plasmon-phonon polaritons in graphene/h-BN suffer little from ohmic losses, making their propagation length 1.5-2.0 times greater than that of hyperbolic phonon polaritons in h-BN. The hyperbolic plasmon-phonon polaritons possess the combined virtues of surface plasmon polaritons in graphene and hyperbolic phonon polaritons in h-BN. Therefore, graphene/h-BN can be classified as an electromagnetic metamaterial as the resulting properties of these devices are not present in its constituent elements alone.

Subdiffractional focusing and guiding of polaritonic rays in a natural hyperbolic material.

Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. In such materials, light propagation is unusual leading to novel and often non-intuitive optical phenomena. Here we report infrared nano-imaging experiments demonstrating that crystals of hexagonal boron nitride, a natural mid-infrared hyperbolic material, can act as a 'hyper-focusing lens' and as a multi-mode waveguide. The lensing is manifested by subdiffractional focusing of phonon-polaritons launched by metallic disks underneath the hexagonal boron nitride crystal. The waveguiding is revealed through the modal analysis of the periodic patterns observed around such launchers and near the sample edges. Our work opens new opportunities for anisotropic layered insulators in infrared nanophotonics complementing and potentially surpassing concurrent artificial hyperbolic materials with lower losses and higher optical localization.

Tunable phonon polaritons in atomically thin van der Waals crystals of boron nitride.

van der Waals heterostructures assembled from atomically thin crystalline layers of diverse two-dimensional solids are emerging as a new paradigm in the physics of materials. We used infrared nanoimaging to study the properties of surface phonon polaritons in a representative van der Waals crystal, hexagonal boron nitride. We launched, detected, and imaged the polaritonic waves in real space and altered their wavelength by varying the number of crystal layers in our specimens. The measured dispersion of polaritonic waves was shown to be governed by the crystal thickness according to a scaling law that persists down to a few atomic layers. Our results are likely to hold true in other polar van der Waals crystals and may lead to new functionalities.

Electronic and plasmonic phenomena at graphene grain boundaries.

Graphene, a two-dimensional honeycomb lattice of carbon atoms of great interest in (opto)electronics and plasmonics, can be obtained by means of diverse fabrication techniques, among which chemical vapour deposition (CVD) is one of the most promising for technological applications. The electronic and mechanical properties of CVD-grown graphene depend in large part on the characteristics of the grain boundaries. However, the physical properties of these grain boundaries remain challenging to characterize directly and conveniently. Here we show that it is possible to visualize and investigate the grain boundaries in CVD-grown graphene using an infrared nano-imaging technique. We harness surface plasmons that are reflected and scattered by the graphene grain boundaries, thus causing plasmon interference. By recording and analysing the interference patterns, we can map grain boundaries for a large-area CVD graphene film and probe the electronic properties of individual grain boundaries. Quantitative analysis reveals that grain boundaries form electronic barriers that obstruct both electrical transport and plasmon propagation. The effective width of these barriers (∼10-20 nm) depends on the electronic screening and is on the order of the Fermi wavelength of graphene. These results uncover a microscopic mechanism that is responsible for the low electron mobility observed in CVD-grown graphene, and suggest the possibility of using electronic barriers to realize tunable plasmon reflectors and phase retarders in future graphene-based plasmonic circuits.

Anisotropic electronic state via spontaneous phase separation in strained vanadium dioxide films.

We resolved the enigma of anisotropic electronic transport in strained vanadium dioxide (VO2) films by inquiring into the role that strain plays in the nanoscale phase separation in the vicinity of the insulator-to-metal transition. The root source of the anisotropy was visualized as the formation of a peculiar unidirectional stripe state which accompanies the phase transition. Furthermore, nanoscale infrared spectroscopy unveils distinct facets of electron-lattice interplay at three different stages of the phase transition. These stages include the initial formation of sparse nonpercolating metallic domains without noticeable involvement of the lattice followed by an electron-lattice coupled anisotropic stripe state close to percolation which ultimately evolves into a nearly isotropic rutile metallic phase. Our results provide a unique mesoscopic perspective for the tunable macroscopic phenomena in strained metal oxide films.

Photoinduced phase transitions by time-resolved far-infrared spectroscopy in V2O3.

Using time-resolved far-infrared spectroscopy, we observe multiple routes for photoinduced phase transitions in V(2)O(3). This includes (i) a photothermal antiferromagnetic to paramagnetic transition and (ii) an incipient strain-generated paramagnetic metal to paramagnetic insulator transition, which manifests as coherent oscillations in the far-infrared conductivity. The ∼100 ps conductivity oscillation results from coherent acoustic phonon modulation of the bandwidth W. Our results indicate that poor metals are particularly amenable to coherent strain control of their electronic properties.

Fabrication and characterization of elastomeric polyester/carbon nanotubes nanocomposites for biomedical application.

A novel biodegradable polymer elastomer nanocomposite composing of poly(1,8-octanediol-citrate) (POC) polymer matrix and carbon nanotubes (CNTs) additive was successfully fabricated and systematically investigated using Fourier transform infrared (FT-IR), X-ray diffractometer (XRD), differential scanning calorimetry (DSC), tensile test, incubation and cytotoxicity tests. It was found that the addition of CNTs in POC elastomer did not result in any noticeable change in its chemical structure and the amorphous state. However, the tensile strength and elongation at break were greatly improved by the addition of CNTs in POC polymer matrix. It revealed that the swelling ratio and percentage of weight loss of POC/CNTs nanocomposite were lower, compared with the pure POC material. Moreover, the adsorption amount of bovine serum albumin (BSA) increased with an increase of the CNTs mass content in POC matrix revealing the enhanced hydrophilicity of POC/CNTs nanocomposites contributed by the carboxyl of the CNTs. Additionally, the cytotoxicity tests with L929 cell line revealed that the experimental POC/CNTs nanocomposites possessed good in vitro biocompatibility.

Origin of the reduced attracting force between a rotating dielectric particle and a stationary one.

Recently Tao and Lan [Phys. Rev. E. 72, 041508 (2005)] experimentally reported that the rotation of a dielectric particle can reduce significantly the attracting interparticle force between the rotating dielectric particle and a stationary one in argon gas. We develop the Gu-Yu-Hui theory of relaxation [J. Chem. Phys. 116, 24 (2002)] to account for the Tao-Lan observations. Excellent agreement between the theoretical results and the Tao-Lan experimental data shows that the reduction in the attracting interparticle force is due to the effect of charge relaxation. We also show that the relaxation time of touching rotating particles can be accurately determined with the aid of the developed theory, for which, however, the well-known Maxwell-Wagner relaxation time is no longer valid.

CD14-dependent activation of protein kinase C and mitogen-activated protein kinases (p42 and p44) in human monocytes treated with bacterial lipopolysaccharide.

To investigate mechanisms of mononuclear phagocyte cell signaling, the effects of bacterial LPS on protein kinase activities in normal human peripheral blood monocytes were examined. Incubation of intact monocytes with LPS brought about time- and concentration-dependent increases in myelin basic protein (MBP) phosphotransferase activity in high speed supernatants of cell lysates. Anion-exchange chromatography on Mono Q demonstrated that LPS treatment resulted in two principal peaks of stimulated MBP kinase activity. Evidence was obtained to indicate that the first eluted peak of MBP kinase activity is accounted for by p42 and p44 mitogen-activated protein (MAP) kinases. Thus, 1) MBP kinase activity within peak 1 was quantitatively precipitated by anti-MAP kinase Abs, 2) the enzyme effectively phosphorylated a specific peptide substrate, 3) peak 1 contained proteins of subunit size M(r) 42,000 and M(r) 44,000 that reacted specifically with anti-MAP kinase Abs, and that 4) were recognized by anti-phosphotyrosine Abs only after stimulation of cells with LPS. Studies of the second peak of LPS-stimulated MBP kinase activity indicate that it is an isoform of protein kinase C (PKC) because: 1) enzyme activity was quantitatively immunoprecipitated by anti-PKC Abs, 2) the activity of the enzyme was potently and selectively inhibited by a specific peptide modeled on the autoinhibitory domain of PKC, and 3) the presence of a protein of subunit size M(r) 80,000 recognized by anti-PKC Abs. Because the second peak of MBP kinase activity (like the first) was active in the absence of added calcium and in the presence of 2 mM EGTA, it appears to be a type II, calcium-independent isoform of PKC. Abs to CD14 completely abrogated LPS-induced activation of both Mono Q peaks of MBP phosphotransferase activity. These results indicate that LPS coordinately activates both an apparently calcium-independent PKC and MAP kinase in mononuclear phagocytes and these responses appear to be initiated by signaling through the cell surface receptor, CD14.