Search

The electronic behaviour of complex oxides such as LaNiO3 depends on many intrinsic and extrinsic factors, making it challenging to identify microscopic mechanisms. Here the authors demonstrate the influence of oxygen vacancies on the thickness-dependent metal-insulator transition of LaNiO3 films.

Abstract We report on structural and electronic properties of defects in chemical vapor-deposited monolayer and few-layer MoS2 films. Scanning tunneling microscopy, Kelvin probe force microscopy, and transmission electron microscopy were used to obtain high resolution images and quantitative measurements of the local density of states, work function and nature of defects in MoS2 films. We track the evolution of defects that are formed under heating and electron beam irradiation. We observe formation of metastable domains with different work function values after annealing the material in ultra-high vacuum to moderate temperatures. We attribute these metastable values of the work function to evolution of crystal defects forming during the annealing. The experiments show that sulfur vacancies formed after exposure to elevated temperatures diffuse, coalesce, and migrate bringing the system from a metastable to equilibrium ground state. The process could be thermally or e-beam activated with estimated energy barrier for sulfur vacancy migration of 0.6 eV in single unit cell MoS2. Even at equilibrium conditions, the work function and local density of states values are strongly affected near grain boundaries and edges. The results provide initial estimates of the thermal budgets available for reliable fabrication of MoS2-based integrated electronics and indicate the importance of defect control and layer passivation.

Planar magnesium diboride Josephson junctions are fabricated using focused helium ion beam irradiation. A single track of ion irradiation with a 30 kV He+ beam with nominal beam diameter < 0.5 nm is used to create a normal-metal barrier on a MgB2 film deposited by hybrid physical-chemical vapor deposition. Josephson coupling is observed below the critical temperature of the electrodes for a He+ doses between 8x1015/cm2 to 4x1016/cm2. Analysis of the temperature dependence of the normal resistance and critical voltage of the junctions shows highly uniform barriers with nearly ideal resistively-shunted junction behavior for higher-dose junctions, while nonequilibrium effects dominate the properties of lower-dose junctions over most of the temperature range. These results demonstrate that focused helium ion beam irradiation can produce high-quality proximity-coupled MgB2 Josephson junctions with tailorable properties, promising for use in superconducting devices and circuits.

The measurement of soil total nitrogen (TN) by hyperspectral remote sensing provides an important tool for soil restoration programs in areas with subsided land caused by the extraction of natural resources. This study used the local correlation maximization-complementary superiority method (LCMCS) to establish TN prediction models by considering the relationship between spectral reflectance and TN based on spectral reflectance curves of soil samples collected from subsided land determined by synthetic aperture radar interferometry (InSAR) technology. Based on the 1655 selected effective bands of the optimal spectrum (OSP) of the first derivate differential of reciprocal logarithm ([log{1/R}]'), (correlation coefficients, P < 0.01), the optimal model of LCMCS method was obtained to determine the final model, which produced lower prediction errors (root mean square error of validation [RMSEV] = 0.89, mean relative error of validation [MREV] = 5.93%) when compared with models built by the local correlation maximization (LCM), complementary superiority (CS) and partial least squares regression (PLS) methods. The predictive effect of LCMCS model was optional in Cangzhou, Renqiu and Fengfeng District. Results indicate that the LCMCS method has great potential to monitor TN in subsided land caused by the extraction of natural resources including groundwater, oil and coal.

In this letter, we report on the structural and transport measurements of ultrathin MgB2 films grown by hybrid physical-chemical vapor deposition followed by low incident angle Ar ion milling. The ultrathin films as thin as 1.8 nm, or 6 unit cells, exhibit excellent superconducting properties such as high critical temperature (Tc) and high critical current density (Jc). The results show the great potential of these ultrathin films for superconducting devices and present a possibility to explore superconductivity in MgB2 at the 2D limit.

For potential applications in superconducting RF cavities, we have investigated the properties of polycrystalline MgB2 films, including the thickness dependence of the lower critical field Hc1. MgB2 thin films were fabricated by hybrid physical-chemical vapor deposition on (0001) SiC substrate either directly (for epitaxial films) or with a MgO buffer layer (for polycrystalline films). When the film thickness decreased from 300 nm to 100 nm, Hc1 at 5 K increased from around 600 Oe to 1880 Oe in epitaxial films and to 1520 Oe in polycrystalline films. The result is promising for using MgB2/MgO multilayers to enhance the vortex penetration field.

Superconductor magnesium diboride is considered one of the viable materials to substitute bulk niobium for superconducting radio frequency cavities. Utilizing a MgB_{2} coating on the inner wall of a copper cavity will allow operation at higher temperatures (20–25 K) than Nb cavities due to the high transition temperature of MgB_{2} (39 K) and the high thermal conductivity of Cu. In this paper, we present results of MgB_{2} coating on Cu tubes with similar dimensions to a 3 GHz cavity, as the first step towards coating the actual cavity, using the hybrid physical chemical vapor deposition technique. The results show successful coating of a uniform MgB_{2} layer on the inner wall of the Cu tubes with T_{c} as high as 37 K.

We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD). To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB_{2} films on these substrates showed uniformly good superconducting properties including T_{c} of 37–40 K, residual resistivity ratio of up to 14, and root-mean-square roughness R_{q} of 20–30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB_{2} by the HPCVD technique, an important step towards superconducting rf cavities with MgB_{2} coating.

The high transition temperature and low surface resistance of MgB_{2} attracts interest in its potential application in superconducting radio frequency accelerating cavities. However, compared to traditional Nb cavities, the viability of MgB_{2} at high rf fields is still open to question. Our approach is to study the nonlinear electrodynamics of the material under localized rf magnetic fields. Because of the presence of the small superconducting gap in the π band, the nonlinear response of MgB_{2} at low temperature is potentially complicated compared to a single-gap s-wave superconductor such as Nb. Understanding the mechanisms of nonlinearity coming from the two-band structure of MgB_{2}, as well as extrinsic sources of nonlinearity, is an urgent requirement. A localized and strong rf magnetic field, created by a magnetic write head, is integrated into our nonlinear-Meissner-effect scanning microwave microscope [T. Tai et al., IEEE Trans. Appl. Supercond. 21, 2615 (2011)ITASE91051-822310.1109/TASC.2010.2096531]. MgB_{2} films with thickness 50 nm, fabricated by a hybrid physical-chemical vapor deposition technique on dielectric substrates, are measured at a fixed location and show a strongly temperature-dependent third harmonic response. We propose that several possible mechanisms are responsible for this nonlinear response.

The development and synthesis of a new configuration of the dual-heater reactor for hybrid physical-chemical vapor decomposition of [MgB.sub.2] thin films are being discussed. The new reactor allows the growth of thick films, as well as thin films at lower substrate temperatures.

The study explains the various properties of the polycrystalline [MgB.sub.2] films that are deposited on flexible yttium-stabilized zirconia (YSZ) substrates grown by hybrid physical-chemical vapor deposition. These films can be widely used in superconducting digital circuits.

Several measurements are conducted to study the mechanism of light detection in various current-biased superconducting [MgB.sub.2] microbridges.

The analysis presents and explains the effects of neutron irradiation on the normal state and superconducting properties of the magnesium diboride ([MgB.sub.2]) thin films. The results show that the irradiation causes a high increase in the residual resistivity of the films.

A series of films grown by hybrid physical chemical vapor deposition (HPCVD) that are neutron irradiated at different fluences up to [10.sup.20] [cm.sup.-2] is reported. The measured critical field values are extremely high and turn out to be rather independent of the experimental resistivity at least at low fluences.

We present here measurements carried out by using a dielectrically loaded copper cavity operating at 7 GHz on MgB2 thin films synthesized by hybrid physical-chemical vapor deposition. Microwave data on samples having critical temperatures above 41 K, very low resistivity values, and residual resistivity ratio between 15 and 17, are presented. The dependence of the nonlinear surface losses and of the third order intermodulation products on the power feeding the cavity is analyzed, with the aim of shedding a light on the primary dissipation mechanisms. At low power, data from both power dependence and third order products seem to indicate that we are observing a nonlinear response which is inherent to the conventional s-wave nature of this novel compound. At intermediate-to-high circulating power values, vortex penetration appears to be the limiting mechanism for the power handling capability of MgB2 films. [ABSTRACT FROM AUTHOR]

In order to reveal the character of ammonia emission in senescent tobacco (Nicotiana tabacum), the content of NH4 +, total nitrogen, and soluble protein, and the activities of nitrogen metabolism-related enzymes were measured in leaves of a quick-leaf-senescence phenotype ZY90 and a slow-leaf-senescence phenotype NC89. Compared with NC89, ZY90 had a higher NH4 + accumulation, a lower glutamine synthetase activity, and a significantly higher stomatal ammonia compensation point, and ammonia emission during 40 to 60 d after leaf emergence. During senescence, the quick-leafsenescence phenotype was characterized by nitrogen re-transfer by ammonia emmission, whereas the slow-leafsenescence phenotype by nitrogen re-assimilation. The ammonia emission was primarily regulated by glutamine synthetase activity, apoplastic pH, and NH4 + content.

Increasing cost and scarcity of maize has stimulated the use of alternative feed sources (AFS) in the diets of cattle. In this study, we investigated the effects of partial or total replacement of maize on nutrient digestibility, growth performance, blood metabolites, and economics in Limousin crossbred feedlot cattle. Forty-five Limousin×Luxi crossbred bulls were randomly assigned to the three treatment groups, orthodox diet (OD; 45.0% maize), partial replacement diet (PRD; 15% maize, 67% AFS), total replacement diet (TRD; 0% maize, 100% AFS). The growth feeding trial lasted for 98 days. Dry matter intake (DMI) and average daily gain (ADG) were recorded. The digestion trial was carried out after the end of the growth trial. Total faeces and feed samples were measured daily. Digestibilities of dry matter (DM) and organic matter (OM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were calculated. After the feeding trial, blood metabolites were measured in 12 animals from each group. Initial and final body weights did not differ significantly among treatment groups (p>0.05). The ADG and DMI were 1.72 and 8.66, 1.60 and 9.10, and 1.40 and 9.11 kg/d for OD, PRD, and TRD, respectively. The PRD and TRD exhibited lower ADG (p0.5). Feed efficiency of PRD and TRD were lower than OD (p0.05). Blood urea nitrogen (mg/dL) in PRD and TRD was higher than OD (p0.05), although TRD showed the highest economic benefits overall (p

We report a real-time observation of strain relaxation during in situ growth of SrTiO[sub 3] thin films by measuring the in-plane lattice constant at the film surface using reflection high-energy electron diffraction. The initial misfit strain in the SrTiO[sub 3] film is tensile on MgO and compressive on LaAlO[sub 3] as expected from the lattice mismatches between the film and the substrates. Strain relaxation begins immediately after the deposition starts, but is not complete until the film thickness reaches 500–2500 Å depending on the substrate and the deposition temperature. The strain relaxation at the growth temperature influences the film strain at room temperature, which is compressive for both substrates for thin SrTiO[sub 3] films. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

China implemented systematic air pollution control measures during the 2008 Beijing Summer Olympics and Paralympics to improve air quality. This study used a versatile mobile laboratory to conduct in situ monitoring of on-road air pollutants along Beijing's Fourth Ring Road on 31 selected days before, during, and after the Olympics air pollution control period. A suite of instruments with response times of less than 30 s was used to measure temporal and spatial variations in traffic-related air pollutants, including NOx, CO, PM1.0 surface area (S(PM1)), black carbon (BC), and benzene, toluene, the sum of ethylbenzene, and m-, p-, and o-xylene (BTEX). During the Olympics (8–23 August, 2008), on-road air pollutant concentrations decreased significantly, by up to 54% for CO, 41% for NOx, 70% for SO2, 66% for BTEX, 12% for BC, and 18% for SPM1, compared with the pre-control period (before 20 July). Concentrations increased again after the control period ended (after 20 September), with average increases of 33% for CO, 42% for NOx, 60% for SO2, 40% for BTEX, 26% for BC, and 37% for S(PM1), relative to the control period. Variations in pollutants concentrations were correlated with changes in traffic speed and the number and types of vehicles on the road. Throughout the measurement periods, the concentrations of NOx, CO, and BTEX varied markedly with the numbers of light- and medium-duty vehicles (LDVs and MDVs, respectively) on the road. Only after 8 August was a noticeable relationship found between BC and S(PM1) and the number of heavy-duty vehicles (HDVs). Additionally, BC and S(PM1) showed a strong correlation with SO2 before the Olympics, indicating possible industrial sources from local emissions as well as regional transport activities in the Beijing area. Such factors were identified in measurements conducted on 6 August in an area southwest of Beijing. The ratio of benzene to toluene, a good indicator of traffic emissions, shifted suddenly from about 0.26 before the Olympics to approximately 0.48 after the Olympics began. This finding suggests that regulations on traffic volume and restrictions on the use of painting solvents were effective after the Olympics began. This study demonstrated the effectiveness of air pollution control measures and identified local and regional pollution sources within and surrounding the city of Beijing. The findings will be invaluable for emission inventory evaluations and model verifications.

We have investigated the normal-state and superconducting properties of Co-doped BaFe2As2 (Ba122) and MgB2 thin films irradiated at room temperature using a 30 keV focused He+ ion beam with doses between 1012 and 1017 cm2. We show that superconductivity is suppressed and the normal-state resistivity is increased upon irradiation. The critical dose for the complete suppression of superconductivity is ∼5 × 1014 cm−2 for Ba122 and ∼8 × 1015 cm−2 for MgB2. The dependence of the normal-state and superconducting properties on irradiation dose is discussed, taking into account the spatial distribution of ion-induced damage. Hillock formation due to the substrate swelling, arising from the He+ ions stopped in the substrate, is also observed. The findings provide guidelines for exploiting focused He+ ion beam irradiation in fabricating iron pnictide and MgB2 planar Josephson junctions. [ABSTRACT FROM AUTHOR]

We report on the growth of high quality MgB2 thin films on silicon and silicon-on-insulator substrates by hybrid physical chemical vapor deposition. A boron buffer layer was deposited on all sides of the Si substrate to prevent the reaction of Mg vapor and Si. Ar ion milling at a low angle of 1° was used to reduce the roughness of the boron buffer layer before the MgB2 growth. An Ar ion milling at low angle of 1° was also applied to the MgB2 surface to reduce its roughness. The resultant MgB2 films showed excellent superconducting properties and a smooth surface. The process produces thin MgB2 films suitable for waveguide-based superconducting hot electron bolometers and other MgB2-based electronic devices. [ABSTRACT FROM AUTHOR]

Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (Tc) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg–Cu alloy layer with occasional intrusion of Mg–Cu alloy regions. High Tc values of around 37 K and high critical current density (Jc) on the order of 107 A cm−2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high Tc and showed a quality factor (Q0) much higher than for Cu and close to that of Nb. [ABSTRACT FROM AUTHOR]

Several theoretical analyses of the two superconducting energy gaps of magnesium diboride, and , predict substructures within each energy gap. We report additional experimental evidence for these features, in tunneling conductance data using multiple samples measured at very low temperatures. The absence of these features in c-axis tunneling, and a sharp peak in the subgap (associated with the counterelectrode material), support the conclusion that these features are intrinsic to MgB2. By demonstrating the inadequacy of a simple two-gap model in fitting the data, we illustrate that distinctions between theoretical models of energy gap substructures are experimentally accessible. [ABSTRACT FROM AUTHOR]

A comprehensive microstructural study was conducted on optimally-doped epitaxial Ba(Fe1−xCox)2As2 thin films grown by pulsed laser deposition on various substrates of a wide range of lattice constants: SrTiO3, LaAlO3, (La,Sr)(Al,Ta)O3, MgO, CaF2, and BaF2. We found that epitaxial strain directly affects the superconductivity in the film, with the transition temperature decreasing linearly with increasing in-plane lattice constant of the film. However, the strain is not determined by the lattice mismatch between the film and substrate. Instead, the mosaic spread of the grain orientation in the film and the thermal expansion coefficient of the substrate were found to correlate well with the in-plane lattice constant of the film. The result confirms the importance of structural distortions to the superconductivity in the Ba(Fe1−xCox)2As2 films. [ABSTRACT FROM AUTHOR]

We report that C-doped MgB2 thin films deposited by hybrid physical-chemical vapor deposition (HPCVD) using CH4 as the carbon source have Hc2(0 K)[?]60 T, similar to that of HPCVD films obtained using (MeCp)2Mg for the carbon. Using transmission electron microscopy, we show that in the films doped using CH4 there is a MgB2C2 layer on top of the MgB2 film, which does not degrade the MgB2 connectivity or Jc. We also find a high density of coherent MgO nanoplatelets in the MgB2 which create strain fields which may give rise to strong p-band scattering and the very high Hc2. [ABSTRACT FROM AUTHOR]

Phase pure and clean MgB2 films have been fabricated on different types of single-crystal substrate, including SiC, sapphire, MgO, LaAlO3, SrTiO3, and yttrium-stabilized ZrO2 (YSZ), via the hybrid physical-chemical vapor deposition (HPCVD) technique. Pure MgB2 films with different structural textures are obtained by selecting the substrate and its orientation, such as off-axis epitaxial MgB2 on MgO(211) or textured MgB2 on YSZ(110) substrates. Films show Tc(0) in the range 37-41 K, and residual resistivity r(42 K) between 0.3 and 5 µO cm as the substrate and film thickness are varied. The crystal structures and film morphologies are presented and discussed. Further investigations are focused on c-axis epitaxial films. Epitaxial MgB2 films with thickness about 300 nm manifest Tc(0) = 41.2 K and residual resistivity r(42 K) = 0.35 µO cm on SiC(0001) while Tc(0) = 39.5 K and r(42 K) = 0.27 µO cm on c-cut sapphire, reflecting that the films are of high quality and in the 'clean limit'. Low upper critical field H_{\mathrm {c}2}^{ \parallel ab}(0) and large anisotropy of the upper critical field g comparable to the results from MgB2 single crystals are also revealed. The smooth surface of the epitaxial films, with root-mean-square (RMS) roughness less than 5 nm, makes them well qualified for device applications. Microwave performance measurements are carried out using a coplanar resonator on a 300 nm thick film on sapphire substrate and no power dependence of unloaded quality factor in the output power range of [?]10-25 dB is found. [ABSTRACT FROM AUTHOR]

Low residual resistivity in superconducting thin films is required for their applications in radio frequency (RF) cavities. Here we report on clean epitaxial MgB2 films fabricated by the ex situ annealing of B films, grown by chemical vapour deposition, in Mg vapour. The films show sharp superconducting transitions at about 40 K and a high residual resistivity ratio of about 10. The result indicates that a clean precursor B film and a contamination-free annealing procedure are important for a viable MgB2 film fabrication process for RF cavity applications. [ABSTRACT FROM AUTHOR]

Aim: To investigate the prognostic value of the composite posterior circulation Acute Stroke Prognosis Early Computed tomography (CT) Score (ASPECTS)-Collaterals (pcASCO) score, which combines diffusion-weighted imaging (DWI) posterior circulation ASPECTS (pcASPECTS) and the magnetic resonance angiography (MRA)-collateral circulation score at baseline among patients with acute posterior circulation ischaemic stroke after mechanical thrombectomy., Materials and Methods: Patients with acute posterior circulation ischaemic stroke who underwent mechanical thrombectomy were analysed retrospectively. The DWI-pcASPECTS and MRA-collateral circulation score before treatment and the modified Rankin Scale (mRS) at 90 days after treatment were used as the endpoints. An mRS ≤2 was defined as a good prognosis, and an mRS ≥3 was defined as a poor prognosis. Multivariate logistic regression was used to analyse independent predictors of functional outcome 90 days after mechanical thrombectomy., Results: Mechanical thrombectomy was performed in 57 patients; 38 patients had a good prognosis, 19 patients had a poor prognosis, and 33 patients were successfully recanalised. Univariate logistic regression found that National Institute of Health Stroke Scale (NIHSS) score (OR: 1.18, p<0.001), pcASPECTS (OR: 1.91, p=0.028) and pcASCO score (OR: 0.51, p=0.001) were factors of good functional outcome. Receiver operating characteristic curve (ROC curve) analysis showed that the diagnostic efficiency of the NIHSS and pcASCO was better (AUC = 0.88, 0.83, p<0.05) than that of the pcASPECTS (AUC = 0.65). The prediction model was established by age, NIHSS, and pcASCO, and the diagnostic efficiency of the prediction model was better (AUC = 0.94)., Conclusions: The composite MR-pcASCO score can be used as an important predictor of the prognosis of patients with acute posterior circulation ischaemic stroke after mechanical thrombectomy., (Copyright © 2023. Published by Elsevier Ltd.)

Objective: This study aimed to analyze the potential correlation between chronic endometritis (CE) and intrauterine adhesions (IUA) with its associated risk factors., Patients and Methods: We retrospectively analyzed data from 131 patients who underwent hysteroscopic transcervical resection of adhesions (TCRA) for intrauterine adhesions at our hospital between February 2020 and February 2021. General clinical data were collected and analyzed using univariate, multifactorial, and logistic regression analyses. Patients with mild, moderate, and severe IUA were divided into two groups based on whether they coincided with CE (CE group) or not (NCE group). Logistic regression analysis of the factors associated with IUA was performed, and the recurrence rates of IUA after TCRA in the CE and NCE groups were registered., Results: The risk of severe IUA was higher in patients with a higher number of abortions, higher number of indolent abortions, and CD138 positivity. In addition, the incidence of IUA combined with chronic CE varied when comparing the different IUA stages: 10.70% (3/28) for patients with mild IUA, 25.00% (7/28) for patients with moderate IUA, and 64.30% (18/28) for patients with severe IUA. The recurrence rates of IUA after TCRA in the CE and NCE groups were 69.20% (9/26) and 30.08% (4/67), respectively, in patients with moderate to severe IUA, and the differences were statistically significant (χ2=12.782, p=0.001)., Conclusions: A correlation was observed between CE and IUA. Patients presenting both conditions had more severe IUA stage and higher recurrence rates after TCRA.

The quality of Moutai-flavour Baijiu is highly dependent on Moutai-flavour Daqu (MTDQ), which needs to be stored for 6 months before using. It brings abundant bacterium, which can metabolize various enzymes and favour compounds. But the reasonable storage time of MTDQ prepared in different seasons is still uncertain. To this end, the study revealed a detailed bacterial profile of storage MTDQ prepared in three different seasons (specifically, they were stored start from spring, summer and autumn) by using high-throughput sequencing approach (next generation sequencing). Results showed that major phyla of storage MTDQ were Firmicutes, Proteobacteria, Actinobacteria, Bacteroidetes and Fusobacteria. The advantages of Firmicutes were Thermoactinomyces and Bacillaceae. Significant differences in bacterial community structures of MTDQ from different seasons and storage time were observed. Compared with summer and autumn MTDQ, the decrease of Thermoactinomyces and increase of Desmospora in spring MTDQ were the main differences and bacterial community structures of summer and autumn MTDQ were more similar. The variation trends of the bacteria community indicated that the effective time of storage period was appropriately 6 months for spring MTDQ, 2 months for summer MTDQ and more than 6 months for autumn MTDQ. These results showed that the length of storage time was associated with the season and it is reasonable to adjust the storage time of MTDQ with the season., (© 2022 Society for Applied Microbiology.)

Chiral materials have attracted significant research interests as they exhibit intriguing physical properties, such as chiral optical response, spin-momentum locking, and chiral induced spin selectivity. Recently, layered transition metal dichalcogenide 1T-TaS&#95;{2} has been found to host a chiral charge density wave (CDW) order. Nevertheless, the physical consequences of the chiral order, for example, in electronic structures and the optical properties, are yet to be explored. Here, we report the spectroscopic visualization of an emergent chiral electronic band structure in the CDW phase, characterized by windmill-shaped Fermi surfaces. We uncover a remarkable chirality-dependent circularly polarized Raman response due to the salient in-plane chiral symmetry of CDW, although the ordinary circular dichroism vanishes. Chiral Fermi surfaces and anomalous Raman responses coincide with the CDW transition, proving their lattice origin. Our Letter paves a path to manipulate the chiral electronic and optical properties in two-dimensional materials and explore applications in polarization optics and spintronics.

Objectives: To investigate the correlation of parameters of magnetic resonance perfusion-weighted imaging (MR-PWI) with the expression of vascular endothelial growth factor (VEGF), hypoxia-inducible factor-1α (HIF-1α) and microvessel density (MVD) in nasopharyngeal carcinoma (NPC) so as to explore the value of predicting radiosensitivity., Design: A prospective study., Setting: Department of Head-and-neck radiotherapy in Hunan Cancer Hospital., Participants: Ninety-four patients of NPC were included between December 2013 and December 2014., Main Outcome Measures: The expression of VEGF, MVD and HIF-1α was studied by immunohistochemistry, and magnetic resonance perfusion-weighted imaging (MR-PWI) was performed before and after undergoing radiotherapy (20 Gy dose). Parameters of MR-PWI, volume of primary tumour and rate of tumour remission were measured and calculated. Patients with primary local tumour were then divided into completely response group (CR group) and partially response group (non-CR group) according to tumour regression condition. Relevant parameters were analysed by Spearman, and diagnostic efficiency of radiosensitivity was analysed by receiver operating characteristic curve (ROC)., Results: The expression of VEGF was positively correlated with MVD (r = .322,P < .05), but the expression of HIF-1α was no significant correlations with VEGF and MVD. The expression VEGF was in positive correlation with fractional plasma volume (fpv) (r = .339, P = .05) before radiotherapy. There was a significant difference in the quantitative parameters of MR-PWI between CR group and non-CR group during the course of radiotherapy and at the end of radiotherapy treatment. The change of blood reflux constant (Δkep20) and extravascular extracellular space volume fraction (ΔVe20) before and after treatment was positively correlated with primary local tumour remission condition after 3 month treatment; Δkep and ΔVe were negatively correlated with primary local tumour remission condition after 3 months. Tumour regression rate was only positively correlated with Ve and the average volume of primary tumour after 2 week treatment (V1). ROC curve showed that R20 ≥ 65.69%, and was considered as a threshold to predict primary local tumour remission, with a sensitivity of 0.84 and specificity of 0.69, and area under the curve was 0.819 (P = .000)., Conclusions: The parameters of MR-PWI with the expression of VEGF, HIF-1α and MVD could be guidance for predicting radiosensitivity in NPC., (© 2017 John Wiley & Sons Ltd.)