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1.
Phys Rev Lett ; 123(7): 074501, 2019 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-31491099

RESUMO

Inspired by electromagnetic waveguide cloaks with gradient index metamaterials, we fabricated a broadband cloak with simply a gradient depth profile on the bottom and without any other structures on the top to confine water waves in a certain area for cloaking regions. The new physics of mode conversion for water waves is first found. The experimental and numerical simulation results are in good agreement and show that the presented device has a nice performance for various situations and is feasible over a broadband of working frequencies. Being easy to construct, this design is potentially of significance for port applications.

2.
Angew Chem Int Ed Engl ; 58(44): 15757-15761, 2019 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-31454142

RESUMO

Halide double perovskites have recently bloomed as the green candidates for optoelectronic applications, such as X-ray detection. Despite great efforts, the exploration of promising organic-inorganic hybrid double perovskites toward X-ray detection remains unsuccessful. Now, single crystals of the lead-free hybrid double perovskite, (BA)2 CsAgBiBr7 (BA+ is n-butylammonium), featuring the unique 2D multilayered quantum-confined motif, enable quite large µτ (mobility-lifetime) product up to 1.21×10-3  cm2 V-1 . This figure-of-merit realized in 2D hybrid double perovskites is unprecedented and comparable with that of CH3 NH3 PbI3 wafers. (BA)2 CsAgBiBr7 crystals also exhibit other intriguing attributes for X-ray detection, including high bulk resistivity, low density of defects and traps, and large X-ray attenuation coefficient. Consequently, a vertical-structure crystal device under X-ray source yields a superior sensitivity of 4.2 µC Gyair -1 cm-2 .

3.
Prostate ; 79(11): 1226-1237, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31212363

RESUMO

BACKGROUND: We previously reported the presence of prostate-specific antigen (PSA) in the stromal compartment of benign prostatic hyperplasia (BPH). Since PSA is expressed exclusively by prostatic luminal epithelial cells, PSA in the BPH stroma suggests increased tissue permeability and the compromise of epithelial barrier integrity. E-cadherin, an important adherens junction component and tight junction regulator, is known to exhibit downregulation in BPH. These observations suggest that the prostate epithelial barrier is disrupted in BPH and E-cadherin downregulation may increase epithelial barrier permeability. METHODS: The ultra-structure of cellular junctions in BPH specimens was observed using transmission electron microscopy (TEM) and E-cadherin immunostaining analysis was performed on BPH and normal adjacent specimens from BPH patients. In vitro cell line studies using benign prostatic epithelial cell lines were performed to determine the impact of small interfering RNA knockdown of E-cadherin on transepithelial electrical resistance and diffusion of fluorescein isothiocyanate (FITC)-dextran in transwell assays. RESULTS: The number of kiss points in tight junctions was reduced in BPH epithelial cells as compared with the normal adjacent prostate. Immunostaining confirmed E-cadherin downregulation and revealed a discontinuous E-cadherin staining pattern in BPH specimens. E-cadherin knockdown increased monolayer permeability and disrupted tight junction formation without affecting cell density. CONCLUSIONS: Our results indicate that tight junctions are compromised in BPH and loss of E-cadherin is potentially an important underlying mechanism, suggesting targeting E-cadherin loss could be a potential approach to prevent or treat BPH.

4.
J Am Chem Soc ; 2019 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-31064178

RESUMO

Semiconductive metal-organic frameworks (MOFs) have attracted extraordinary research interest in recent years; however, electronic applications based on these emerging materials are still in their infancy. Herein, we show that a lanthanide-based semiconductive MOF (SCU-12) can effectively convert X-ray photons to electrical current signals under continuous hard X-ray radiation. The semiconductive MOF-based polycrystalline detection device presents a promising X-ray sensitivity with the value of 23.8 µC Gyair-1 cm-2 under 80 kVp X-ray exposure, competitive with the commercially available amorphous selenium ( α-Se) detector. The lowest detectable X-ray dose rate is 0.705 µGy s-1, representing the record value among all X-ray detectors fabricated by polycrystalline materials. This work discloses the first demonstration of hard radiation detection by semiconductive MOFs, providing a horizon that can guide the synthesis of a new generation of radiation detection materials by taking the advantages of structural designability and property tunability in the MOF system.

5.
Nat Commun ; 10(1): 2326, 2019 05 24.
Artigo em Inglês | MEDLINE | ID: mdl-31127119

RESUMO

Phase gradient metagratings (PGMs) have provided unprecedented opportunities for wavefront manipulation. However, this approach suffers from fundamental limits on conversion efficiency; in some cases, higher order diffraction caused by the periodicity can be observed distinctly, while the working mechanism still is not fully understood, especially in refractive-type metagratings. Here we show, analytically and experimentally, a refractive-type metagrating which can enable anomalous reflection and refraction with almost unity efficiency over a wide incident range. A simple physical picture is presented to reveal the underlying diffraction mechanism. Interestingly, it is found that the anomalous transmission and reflection through higher order diffraction can be completely reversed by changing the integer parity of the PGM design, and such phenomenon is very robust. Two refractive acoustic metagratings are designed and fabricated based on this principle and the experimental results verify the theory.

6.
Opt Express ; 27(6): 7857-7867, 2019 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-31052613

RESUMO

Goos-Hänchen (GH) effect is a fundamental phenomenon in optics. Here we demonstrate theoretically that the surface modes at Parity-time (PT) symmetric interfaces, can induce a giant GH shift at a specific incident angle. It is found that the amplitude of the GH shift can be tuned by adjusting the thickness of the bilayer, and as the thickness grows, its maximum value can go to infinity in theory. The physical mechanism behind this interesting feature is that the surface modes at PT interfaces are quasi-bound states in continuum (BICs), which lead to rapid variation in the phase of the scattered waves. Our work enriches the previous studies about GH effect in PT bilayer structures and provides a way in turn to explore the BICs in non-Hermitian photonic systems.

7.
Curr Mol Med ; 19(1): 54-75, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30854966

RESUMO

OBJECTIVE: The relationship between OCT4 and clinicopathological features in lung cancer is shown to be controversial in recent publications. Therefore, we conducted this meta-analysis to quantitatively investigate the prognostic and clinicopathological characteristics of OCT4 in lung cancer. METHODS: A comprehensive literature search of the PubMed, EMBASE, Cochrane Library, WOS, CNKI and Wanfang databases was performed to identify studies. Correlations between OCT4 expression and survival outcomes or clinicopathological features were analyzed using meta-analysis methods. RESULTS: Twenty-one studies with 2523 patients were included. High OCT4 expression showed a poorer overall survival (OS) (univariate: HR= 2.00, 95% CI = (1.68, 2.39), p<0.0001; multivariate: HR= 2.43, 95% CI = (1.67, 3.55), p<0.0001) and median overall survival (MSR = 0.51, 95% CI = (0.44, 0.58), p < 0.0001), disease-free survival (DFS) (HR= 2.18, 95% CI = (1.30, 3.67), p = 0.003) and poorer disease-specific survival (DSS) (HR= 2.23, 95% CI = (1.21, 4.11), p = 0.010). Furthermore, high OCT4 expression was found to be related with lower 5 year disease-specific survival rate (OR= 0.24, 95% CI = (0.14, 0.41), p<0.0001) and 10 year overall survival rate (OR= 0.22, 95% CI = (0.12, 0.40), p=0.0001). Additionally, OCT4-high expression was also strongly associated with higher clinical TNM stage, lymph node metastasis, tumor distant metastasis, higher histopathologic grade, but not related with gender, smoking status, tumor size and histologic type of lung cancer. CONCLUSION: OCT4 over-expression in lung cancer was strongly related to poorer clinicopathological features and worse survival outcomes, which suggests that OCT4 could be a valuable prognostic marker in lung cancer.

8.
Prostate ; 79(6): 657-666, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30714180

RESUMO

BACKGROUND: DHX15 is a member of the DEAH-box (DHX) RNA helicase family. Our previous study identified it as an AR coactivator which contributes to prostate cancer progression. METHODS: We investigated DHX15 expression in castration resistant prostate cancer specimens and the influence of DHX15 on the responsiveness of prostate cancer cells to DHT stimulation. We also explored the role DHX15 played in enzalutamide resistance and the interacting domain in DHX15 with AR. DHX15 expression level in human CRPC specimens and prostate cancer specimens was detected by tissue microarray (TMA) immunostaining analysis. Colony formation assay was performed to determine the proliferation of cells treated with enzalutamide or DHT. siRNAs were used to knockdown DHX15. The interactions between DHX15 and AR were detected using co-immunoprecipitation assay. RESULTS: The expression level of DHX15 was upregulated in human CRPC specimens compared with hormone naïve prostate cancer specimens. DHX15 knockdown reduced AR sensitivity to low DHT concentrations in C4-2 cells. Inactivation of DHX15 sensitizes the enzalutamide treatment in C4-2 cells. Deletion mutagenesis indicated that DHX1 5 interacts with AR through its N terminal domain. CONCLUSIONS: These findings suggest that DHX15 contributes to prostate cancer progression. DHX15 is required for androgen receptor sensitivity to low DHT concentrations and contributes to enzalutamide resistance in C4-2 cells. Targeting DHX15 may improve the ADT treatment.

9.
ACS Appl Mater Interfaces ; 11(7): 7522-7528, 2019 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-30693756

RESUMO

An important factor for the high performance of light-harvesting devices is the presence of surface trappings. Therefore, understanding and controlling the carrier recombination of the organic-inorganic hybrid perovskite surface is critical for the device design and optimization. Here, we report the use of aluminum zinc oxide (AZO) as the anode to construct a p-n junction structure MAPbBr3 nuclear radiation detector. The AZO/MAPbBr3/Au detector can tolerate an electrical field of 500 V·cm-1 and exhibit a very low leakage current of ∼9 nA, which is 1 order of magnitude lower than that of the standard ohmic contact device. The interface state density of AZO/MAPbBr3 contact was reduced from 2.17 × 1010 to 8.7 × 108 cm-2 by annealing at 100 °C under an Ar atmosphere. Consequently, a photocurrent to dark current ratio of 190 was realized when exposed to a green light-emitting diode with a wavelength of 520 nm (∼200 mW·cm-2). Simultaneously, a high X-ray sensitivity of ∼529 µC·Gyair-1 cm-2 was achieved under 80 kVp X-ray at an electric field of 50 V·cm-1. These results demonstrate the use of surface engineering to further optimize the performance of MAPbBr3 detectors, which have many potential applications in medical and security detection with low radiation dose brought to the human body.

10.
Sci Rep ; 8(1): 16188, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30385792

RESUMO

The Luneburg lens is a spherically symmetrical gradient refractive index (GRIN) device with unique imaging properties. Its wide field-of-view (FoV) and minimal aberration have lead it to be successfully applied in microwave antennas. However, only limited realizations have been demonstrated in acoustics. Previously proposed acoustic Luneburg lenses are mostly limited to inherently two-dimensional designs at frequencies from 1 kHz to 7 kHz. In this paper, we apply a new design method for scalable and self-supporting metamaterials to demonstrate Luneburg lenses for airborne sound and ultrasonic waves. Two Luneburg lenses are fabricated: a 2.5D ultrasonic version for 40 kHz and a 3D version for 8 kHz sound. Imaging performance of the ultrasonic version is experimentally demonstrated.

11.
ACS Nano ; 2018 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-30427653

RESUMO

Three-dimensional (3D) cellular graphene structures have wide applications in energy storage, catalysis, polymer composites, electromagnetic shielding, and many others. However, the current strategies to form cellular graphene are only able to realize limited structure control and are hard to achieve the construction of 3D hierarchical architectures with complex, programmed configurations, limiting the design capabilities to satisfy various next-generation device applications. In addition, cellular graphene usually exhibits limited electromechanical properties, and its electrical and electrochemical performances are dramatically affected by mechanical deformations, constraining its applications in emerging wearable electronics and energy devices. Herein, we report a simple, general, and effective route to 3D hierarchical architectures of cellular graphene with desired geometries through the use of a mechanically guided, 3D assembly approach to overcome the aforementioned two challenges. Demonstrations include more than 10 3D hierarchical architectures with diverse configurations, ranging from mixed tables and tents, to double-floor helices, to kirigami/origami-inspired structures, and to fully separated multilayer architectures. The LED arrays interconnected with 3D helical coils and 3D interdigital supercapacitors fabricated with solid-state electrolytes provide prototypic examples of wearable devices that exhibit outstanding electromechanical properties and can maintain stable performances with little change in the electrical and electrochemical responses under extreme deformations, in both the static and cyclic loading conditions.

12.
Adv Mater ; : e1804327, 2018 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-30306662

RESUMO

Soft on-skin electronics have broad applications in human healthcare, human-machine interface, robotics, and others. However, most current on-skin electronic devices are made of materials with limited gas permeability, which constrain perspiration evaporation, resulting in adverse physiological and psychological effects, limiting their long-term feasibility. In addition, the device fabrication process usually involves e-beam or photolithography, thin-film deposition, etching, and/or other complicated procedures, which are costly and time-consuming, constraining their practical applications. Here, a simple, general, and effective approach for making multifunctional on-skin electronics using porous materials with high-gas permeability, consisting of laser-patterned porous graphene as the sensing components and sugar-templated silicone elastomer sponges as the substrates, is reported. The prototype device examples include electrophysiological sensors, hydration sensors, temperature sensors, and joule-heating elements, showing signal qualities comparable to conventional, rigid, gas-impermeable devices. Moreover, the devices exhibit high water-vapor permeability (≈18 mg cm-2 h-1 ), ≈18 times higher than that of the silicone elastomers without pores, and also show high water-wicking rates after polydopamine treatment, up to 1 cm per 30 s, which is comparable to that of cotton. The on-skin devices with such attributes could facilitate perspiration transport and evaporation, and minimize discomfort and inflammation risks, thereby improving their long-term feasiblity.

13.
Cent Eur J Immunol ; 43(2): 123-131, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30135623

RESUMO

Previous fundamental or clinical trials of dendritic cell (DC) vaccine against pancreatic ductal adenocarcinoma (PDAC) revealed the burgeoning neoadjuvant immunotherapy. Microarray studies indicated that multiple ingredients of the transfer growth factor beta (TGF-ß) pathway were overexpressed in PDAC, which inhibited the intratumoral immune response. To explore whether the DC volume in tumor microenvironment contributes to the differentiation of T cell cohort and test the hypothesis that combining DC vaccine with TGF-ß inhibitors will elevate the anti-tumor immune response, we managed to co-culture T cells in vitro with pancreatic cancer cells and DCs in different concentrations, and combine TGF-ß blockage with DC vaccine therapy in a murine model of pancreatic cancer. In in vitro studies, we discovered that CD8+ T cytotoxic cell (Tc) presented a significant advantage and lower volume of CD4+ T helper cell (Th) existed with a certain elevated DC concentration (p < 0.05), associated with declined interleukin (IL)-10 and increased interferon (IFN)-γ, which suggested with the DC volume increasing, the enhancing immune effect may represent a great advantage in such a system (p < 0.05). When interfered with anti-TGF-ß antibody or TGF-ß cytokine, respectively, in the co-culture system, we found IFN-γ producing was extremely higher and T cell apoptosis relatively descent with TGF-ß blockage (p < 0.05). The murine PDAC model demonstrated a survival advantage treated with anti-TGF-ß antibody combined with DC vaccine when compared with monotherapy controls (p < 0.05). Therefore, these findings indicated that, through neutralizing TGF-ß associated with DC vaccine, the anti-tumor immunity is highly elevated and this combinational therapy will provide an efficacious prospect.

14.
J Biomed Inform ; 84: 164-170, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30009990

RESUMO

Attention Deficit Hyperactive Disorder (ADHD) is one of the most common diseases in school aged children. In this paper, we consider using fMRI data with classification techniques to aid the diagnosis of ADHD and propose a bi-objective ADHD classification scheme based on L1-norm support vector machine (SVM). In our classification model, two objectives, namely, the margin of separation and the empirical error are considered at the same time. Then the normal boundary intersection (NBI) method of Das and Dennis is used to solve the bi-objective optimization problem. A representative nondominated set which reflects the entire trade-off information between the two objectives is obtained. Each representative nondominated point in the set corresponds to an efficient classifier. Finally a decision maker can choose a final efficient classifier from the set according to the performance of each classifier. Our scheme avoids the trial and error process for regularization hyper-parameter selection. Experimental results show that our bi-objective optimization classification scheme for ADHD diagnosis performs considerably better than some traditional classification methods.

15.
Huan Jing Ke Xue ; 39(2): 758-764, 2018 Feb 08.
Artigo em Chinês | MEDLINE | ID: mdl-29964839

RESUMO

Aiming at the low pollutant removal efficiency of constructed wetlands (CWs) at low temperature in winter, three laboratory-scale vertical-flow CWs, namely unplanted CWs, ordinary CWs, and internal-electrolysis CWs, were used to investigate the nitrogen removal efficiency of municipal secondary effluent when the water temperature was 3-12℃. Moreover, the mechanism of enhanced denitrification of the new wetland was revealed through analysis of the microbial community diversity and community structure. The results showed that the internal-electrolysis CWs could make better use of the carbon sources in the municipal secondary effluent and had a higher removal rate. The effluent TN concentration was maintained at about (9±0.29) mg·L-1. The average TN removal rate was 42.27%, which was 17.91% and 17.33% higher than those of the unplanted CWs and ordinary CWs, respectively. The microbial activity was detected using fluorescein diacetate (FDA), and the result revealed that the microbial activity of the internal-electrolysis CWs could reach 0.224 mg·g-1, which was 2.6 times and 3.4 times of that of the unplanted CWs and ordinary CWs, respectively. The microbial denitrification intensity of the internal-electrolysis CWs was 2.8 times and 3.3 times of that of the unplanted and ordinary CWs, respectively. The results of high-throughput sequencing showed that the microbial community diversity of the internal electrolysis CWs was higher than those of the unplanted and ordinary CWs. Denitrification microorganisms were detected, mainly Dechloromonas, Rhizobium, Hyphomicrobium, and Rhodobacter, as well as Thiobacillus, which is an autotrophic denitrifying bacterium. There were obvious advantages in the total amount of denitrifying microorganisms in the internal-electrolysis CWs, as the denitrification microorganisms accounted for 7.13% of the total microbial biomass, which was 3.8 times and 8.7 times of that of the unplanted CWs and ordinary CWs, respectively.

16.
Sci Adv ; 4(6): eaas8660, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29868645

RESUMO

This work demonstrates markedly modified spin dynamics of magnetic insulator (MI) by the spin momentum-locked Dirac surface states of the adjacent topological insulator (TI), which can be harnessed for spintronic applications. As the Bi concentration x is systematically tuned in 5-nm-thick (Bi x Sb1-x )2Te3 TI films, the weight of the surface relative to bulk states peaks at x = 0.32 when the chemical potential approaches the Dirac point. At this concentration, the Gilbert damping constant of the precessing magnetization in 10-nm-thick Y3Fe5O12 MI films in the MI/TI heterostructures is enhanced by an order of magnitude, the largest among all concentrations. In addition, the MI acquires additional strong magnetic anisotropy that favors the in-plane orientation with similar Bi concentration dependence. These extraordinary effects of the Dirac surface states distinguish TI from other materials such as heavy metals in modulating spin dynamics of the neighboring magnetic layer.

17.
Nano Lett ; 18(6): 3580-3585, 2018 06 13.
Artigo em Inglês | MEDLINE | ID: mdl-29852737

RESUMO

Spin-orbit coupling (SOC) in graphene can be greatly enhanced by proximity coupling it to transition metal dichalcogenides (TMDs) such as WSe2. We find that the strength of the acquired SOC in graphene depends on the stacking order of the heterostructures when using hexagonal boron nitride ( h-BN) as the capping layer, i.e., SiO2/graphene/WSe2/ h-BN exhibiting stronger SOC than SiO2/WSe2/graphene/ h-BN. We utilize photoluminescence (PL) as an indicator to characterize the interaction between graphene and monolayer WSe2 grown by chemical vapor deposition. We observe much stronger PL quenching in the SiO2/graphene/WSe2/ h-BN stack than in the SiO2/WSe2/graphene/ h-BN stack and, correspondingly, a much larger weak antilocalization (WAL) effect or stronger induced SOC in the former than in the latter. We attribute these two effects to the interlayer distance between graphene and WSe2, which depends on whether graphene is in immediate contact with h-BN. Our observations and hypothesis are further supported by first-principles calculations, which reveal a clear difference in the interlayer distance between graphene and WSe2 in these two stacks.

18.
ACS Appl Mater Interfaces ; 10(22): 19143-19152, 2018 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-29766720

RESUMO

Highly efficient electromagnetic shielding materials entailing strong electromagnetic wave absorption and low reflection have become an increasing requirement for next-generation communication technologies and high-power electronic instruments. In this study, a new strategy is employed to provide flexible waterborne polyurethane composite films with an ultra-efficient electromagnetic shielding effectiveness (EMI SE) and low reflection by constructing gradient shielding layers with a magnetic ferro/ferric oxide deposited on reduced graphene oxide (rGO@Fe3O4) and silver-coated tetraneedle-like ZnO whisker (T-ZnO/Ag) functional nanoparticles. Because of the differences in density between rGO@Fe3O4 and T-ZnO/Ag, a gradient structure is automatically formed during the film formation process. The gradient distribution of rGO@Fe3O4 over the whole thickness range forms an efficient electromagnetic wave absorption network that endows the film with a strong absorption ability on the top side, while a thin layer of high-density T-ZnO/Ag at the bottom constructs a highly conductive network that provides an excellent electromagnetic reflection ability for the film. This specific structure results in an "absorb-reflect-reabsorb" process when electromagnetic waves penetrate into the composite film, leading to an excellent EMI shielding performance with an extremely low reflection characteristic at a very low nanofiller content (0.8 vol % Fe3O4@rGO and 5.7 vol % T-ZnO/Ag): the EMI SE reaches 87.2 dB against the X band with a thickness of only 0.5 mm, while the shielding effectiveness of reflection (SER) is only 2.4 dB and the power coefficient of reflectivity ( R) is as low as 0.39. This result means that only 39% of the microwaves are reflected in the propagation process when 99.9999998% are attenuated, which is the lowest value among the reported references. This composite film with remarkable performance is suitable for application in portable and wearable smart electronics, and this method offers an effective strategy for absorption-dominated EMI shielding.

19.
Sci Total Environ ; 626: 807-816, 2018 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29396342

RESUMO

Air pollution epidemiology studies of ambient fine particulate matter (PM2.5) often use outdoor concentrations as exposure surrogates, which can induce exposure error. The goal of this study was to improve ambient PM2.5 exposure assessments for a repeated measurements study with 22 diabetic individuals in central North Carolina called the Diabetes and Environment Panel Study (DEPS) by applying the Exposure Model for Individuals (EMI), which predicts five tiers of individual-level exposure metrics for ambient PM2.5 using outdoor concentrations, questionnaires, weather, and time-location information. Using EMI, we linked a mechanistic air exchange rate (AER) model to a mass-balance PM2.5 infiltration model to predict residential AER (Tier 1), infiltration factors (Finf_home, Tier 2), indoor concentrations (Cin, Tier 3), personal exposure factors (Fpex, Tier 4), and personal exposures (E, Tier 5) for ambient PM2.5. We applied EMI to predict daily PM2.5 exposure metrics (Tiers 1-5) for 174 participant-days across the 13 months of DEPS. Individual model predictions were compared to a subset of daily measurements of Fpex and E (Tiers 4-5) from the DEPS participants. Model-predicted Fpex and E corresponded well to daily measurements with a median difference of 14% and 23%; respectively. Daily model predictions for all 174 days showed considerable temporal and house-to-house variability of AER, Finf_home, and Cin (Tiers 1-3), and person-to-person variability of Fpex and E (Tiers 4-5). Our study demonstrates the capability of predicting individual-level ambient PM2.5 exposure metrics for an epidemiological study, in support of improving risk estimation.


Assuntos
Poluição do Ar em Ambientes Fechados/análise , Diabetes Mellitus , Exposição Ambiental/análise , Monitoramento Ambiental , Material Particulado/análise , Poluentes Atmosféricos , Humanos , Modelos Teóricos , North Carolina , Tamanho da Partícula
20.
Inorg Chem ; 57(5): 2730-2735, 2018 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-29446937

RESUMO

The triangular lattice Na xRhO2 contains a 4d Rh element with large spin-orbit coupling, and the electron-electron correlation effect is expected to have some novel physical properties. Here we report NaRhO2 crystal growth by Na2CO3 vapor growth and a series of Na xRhO2 (0.25 ≤ x ≤ 1) crystals prepared using the chemical desodiation method. Na xRhO2 reveals a layer structure with the space group R3̅ m, and the lattice parameter a evolves from 3.09 to 3.03 Å and c from 15.54 to 15.62 Å when x decreases from 1.0 to 0.2. Decreasing potassium concentration leads to a contraction of the RhO6 octahedral layers, which may be attributed to a higher covalency of Rh-O bonds. More important, the metal-insulator transition in Na xRhO2 was observed in resistivity along the ab plane. The conducting mechanism of Na xRhO2 is strongly dependent on x. Two-dimensional variable range hopping (VRH) mechanisms (0.67 ≤ x ≤ 1) and metallic behaviors (0.42 and 0.47) are observed in temperature-dependent resistivity. The origin of this metal-insulator transition was discussed on the basis of the Ioffe-Regel criterion. Our work demonstrates the strong correlation between sodium concentration and physical properties of Na xRhO2.

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