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1.
Proc Natl Acad Sci U S A ; 119(15): e2119429119, 2022 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-35377791

RESUMO

Charge density waves (CDWs) have been observed in nearly all families of copper-oxide superconductors. But the behavior of these phases across different families has been perplexing. In La-based cuprates, the CDW wavevector is an increasing function of doping, exhibiting the so-called Yamada behavior, while in Y- and Bi-based materials the behavior is the opposite. Here, we report a combined resonant soft X-ray scattering (RSXS) and neutron scattering study of charge and spin density waves in isotopically enriched La1.8−xEu0.2SrxCuO4 over a range of doping 0.07≤x≤0.20. We find that the CDW amplitude is temperature independent and develops well above experimentally accessible temperatures. Further, the CDW wavevector shows a nonmonotonic temperature dependence, exhibiting Yamada behavior at low temperature with a sudden change occurring near the spin ordering temperature. We describe these observations using a Landau­Ginzburg theory for an incommensurate CDW in a metallic system with a finite charge compressibility and spin-CDW coupling. Extrapolating to high temperature, where the CDW amplitude is small and spin order is absent, our analysis predicts a decreasing wavevector with doping, similar to Y and Bi cuprates. Our study suggests that CDW order in all families of cuprates forms by a common mechanism.

2.
Nat Mater ; 21(6): 664-672, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-35301474

RESUMO

Lattice oxygen redox offers an unexplored way to access superior electrochemical properties of transition metal oxides (TMOs) for rechargeable batteries. However, the reaction is often accompanied by unfavourable structural transformations and persistent electrochemical degradation, thereby precluding the practical application of this strategy. Here we explore the close interplay between the local structural change and oxygen electrochemistry during short- and long-term battery operation for layered TMOs. The substantially distinct evolution of the oxygen-redox activity and reversibility are demonstrated to stem from the different cation-migration mechanisms during the dynamic de/intercalation process. We show that the π stabilization on the oxygen oxidation initially aids in the reversibility of the oxygen redox and is predominant in the absence of cation migrations; however, the π-interacting oxygen is gradually replaced by σ-interacting oxygen that triggers the formation of O-O dimers and structural destabilization as cycling progresses. More importantly, it is revealed that the distinct cation-migration paths available in the layered TMOs govern the conversion kinetics from π to σ interactions. These findings constitute a step forward in unravelling the correlation between the local structural evolution and the reversibility of oxygen electrochemistry and provide guidance for further development of oxygen-redox layered electrode materials.


Assuntos
Óxidos , Oxigênio , Fontes de Energia Elétrica , Eletroquímica , Oxirredução , Oxigênio/química
3.
Sci Adv ; 8(6): eabk0832, 2022 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-35138893

RESUMO

The normal state of high-Tc cuprates has been considered one of the essential topics in high-temperature superconductivity research. However, compared to the high magnetic field study of it, understanding a photoinduced normal state remains elusive. Here, we explore a photoinduced normal state of YBa2Cu3O6.67 through a charge density wave (CDW) with time-resolved resonant soft x-ray scattering, as well as a high magnetic field x-ray scattering. In the nonequilibrium state where people predict a quenched superconducting state based on the previous optical spectroscopies, we experimentally observed a similar analogy to the competition between superconductivity and CDW shown in the equilibrium state. We further observe that the broken pairing states in the superconducting CuO2 plane via the optical pump lead to nucleation of three-dimensional CDW precursor correlation. Ultimately, these findings provide a critical clue that the characteristics of the photoinduced normal state show a solid resemblance to those under magnetic fields in equilibrium conditions.

4.
Environ Pollut ; 267: 115583, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33254689

RESUMO

In this study, a metal organic framework MIL-100(Fe) was synthesized for rhodamine B (RB) removal from aqueous solutions. An experimental design was conducted using a central composite design (CCD) method to obtain the RB adsorption data (n = 30) from batch experiments. In the CCD approach, solution pH, adsorbent dose, and initial RB concentration were included as input variables, whereas RB removal rate was employed as an output variable. Response surface methodology (RSM) and artificial neural network (ANN) modeling were performed using the adsorption data. In RSM modeling, the cubic regression model was developed, which was adequate to describe the RB adsorption according to analysis of variance. Meanwhile, the ANN model with the topology of 3:8:1 (three input variables, eight neurons in one hidden layer, and one output variable) was developed. In order to further compare the performance between the RSM and ANN models, additional adsorption data (n = 8) were produced under experimental conditions, which were randomly selected in the range of the input variables employed in the CCD matrix. The analysis showed that the ANN model (R2 = 0.821) had better predictability than the RSM model (R2 = 0.733) for the RB removal rate. Based on the ANN model, the optimum RB removal rate (>99.9%) was predicted at pH 5.3, adsorbent dose 2.0 g L-1, and initial RB concentration 73 mg L-1. In addition, pH was determined to be the most important input variable affecting the RB removal rate. This study demonstrated that the ANN model could be successfully employed to model and optimize RB adsorption to the MIL-100(Fe).


Assuntos
Estruturas Metalorgânicas , Adsorção , Dietilamida do Ácido Lisérgico/análogos & derivados , Redes Neurais de Computação , Projetos de Pesquisa
5.
Rev Sci Instrum ; 91(8): 083904, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32872965

RESUMO

Resonant elastic x-ray scattering has been widely employed for exploring complex electronic ordering phenomena, such as charge, spin, and orbital order, in particular, in strongly correlated electronic systems. In addition, recent developments in pump-probe x-ray scattering allow us to expand the investigation of the temporal dynamics of such orders. Here, we introduce a new time-resolved Resonant Soft X-ray Scattering (tr-RSXS) endstation developed at the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL). This endstation has an optical laser (wavelength of 800 nm plus harmonics) as the pump source. Based on the commissioning results, the tr-RSXS at PAL-XFEL can deliver a soft x-ray probe (400 eV-1300 eV) with a time resolution of ∼100 fs without jitter correction. As an example, the temporal dynamics of a charge density wave on a high-temperature cuprate superconductor is demonstrated.

6.
Rev Sci Instrum ; 90(11): 113101, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31779391

RESUMO

We present results obtained with a new soft X-ray spectrometer based on transition-edge sensors (TESs) composed of Mo/Cu bilayers coupled to bismuth absorbers. This spectrometer simultaneously provides excellent energy resolution, high detection efficiency, and broadband spectral coverage. The new spectrometer is optimized for incident X-ray energies below 2 keV. Each pixel serves as both a highly sensitive calorimeter and an X-ray absorber with near unity quantum efficiency. We have commissioned this 240-pixel TES spectrometer at the Stanford Synchrotron Radiation Lightsource beamline 10-1 (BL 10-1) and used it to probe the local electronic structure of sample materials with unprecedented sensitivity in the soft X-ray regime. As mounted, the TES spectrometer has a maximum detection solid angle of 2 × 10-3 sr. The energy resolution of all pixels combined is 1.5 eV full width at half maximum at 500 eV. We describe the performance of the TES spectrometer in terms of its energy resolution and count-rate capability and demonstrate its utility as a high throughput detector for synchrotron-based X-ray spectroscopy. Results from initial X-ray emission spectroscopy and resonant inelastic X-ray scattering experiments obtained with the spectrometer are presented.

7.
Phys Rev Lett ; 122(14): 147601, 2019 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-31050473

RESUMO

Ba(Ni_{1-x}Co_{x})_{2}As_{2} is a structural homologue of the pnictide high temperature superconductor, Ba(Fe_{1-x}Co_{x})_{2}As_{2}, in which the Fe atoms are replaced by Ni. Superconductivity is highly suppressed in this system, reaching a maximum T_{c}=2.3 K, compared to 24 K in its iron-based cousin, and the origin of this T_{c} suppression is not known. Using x-ray scattering, we show that Ba(Ni_{1-x}Co_{x})_{2}As_{2} exhibits a unidirectional charge density wave (CDW) at its triclinic phase transition. The CDW is incommensurate, exhibits a sizable lattice distortion, and is accompanied by the appearance of α Fermi surface pockets in photoemission [B. Zhou et al., Phys. Rev. B 83, 035110 (2011)PRBMDO1098-012110.1103/PhysRevB.83.035110], suggesting it forms by an unconventional mechanism. Co doping suppresses the CDW, paralleling the behavior of antiferromagnetism in iron-based superconductors. Our study demonstrates that pnictide superconductors can exhibit competing CDW order, which may be the origin of T_{c} suppression in this system.

8.
DNA Cell Biol ; 37(10): 850-860, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30227079

RESUMO

The role of chemotherapeutic agents in tumor immunotherapy is still controversial. In this study, we test using a TC-1 tumor model whether gemcitabine plus E7 peptide vaccine regimens (E7 peptides+CpG-ODN+anti-4-1BB Abs) may result in tumor cure in mice with large established tumors, with a focus on their effects on Ag-specific cytotoxic T lymphocyte (CTL) and myeloid-derived suppressor cell levels. Gemcitabine inhibited tumor growth by its direct cytotoxicity to tumor cells in vivo. E7 peptide vaccine regimens enhanced Ag-specific CTL lytic and antitumor therapeutic activity. Initial combination therapy using gemcitabine and E7 peptide vaccine regimens resulted in tumor regression with tumor relapse in animals with large established tumors, which appeared to result from the suppression of Ag-specific CTL activity by gemcitabine treatment. However, optimization of gemcitabine therapy by reducing its dose and frequency led to complete tumor regression without any recurring tumors in all tested mice even after discontinuation of therapy, possibly due to Ag-specific CTL responses. Thus, this study shows that the optimal dose and therapy frequency of gemcitabine are critical for achieving tumor cure in tumor-bearing animals undergoing E7 peptide vaccine regimen therapy, mainly by preventing CTL suppression. These findings may have implications for designing peptide-based therapeutic vaccines in cancer patients undergoing chemotherapy.


Assuntos
Adenocarcinoma/terapia , Antimetabólitos Antineoplásicos/farmacologia , Vacinas Anticâncer/administração & dosagem , Terapia Combinada/métodos , Desoxicitidina/análogos & derivados , Linfócitos T Citotóxicos/efeitos dos fármacos , Adenocarcinoma/genética , Adenocarcinoma/imunologia , Adenocarcinoma/patologia , Animais , Anticorpos/farmacologia , Antígenos de Neoplasias/administração & dosagem , Antígenos de Neoplasias/química , Vacinas Anticâncer/química , Linhagem Celular Tumoral , Citotoxicidade Imunológica/efeitos dos fármacos , Desoxicitidina/farmacologia , Tratamento Farmacológico/métodos , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/imunologia , Células Epiteliais/patologia , Feminino , Humanos , Imunização , Imunoterapia/métodos , Camundongos , Camundongos Endogâmicos C57BL , Transplante de Neoplasias , Oligodesoxirribonucleotídeos/administração & dosagem , Oligodesoxirribonucleotídeos/síntese química , Peptídeos/administração & dosagem , Peptídeos/síntese química , Linfócitos T Citotóxicos/imunologia , Linfócitos T Citotóxicos/patologia , Carga Tumoral/efeitos dos fármacos , Membro 9 da Superfamília de Receptores de Fatores de Necrose Tumoral/antagonistas & inibidores , Membro 9 da Superfamília de Receptores de Fatores de Necrose Tumoral/genética , Membro 9 da Superfamília de Receptores de Fatores de Necrose Tumoral/imunologia
9.
Nanomaterials (Basel) ; 8(8)2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30071684

RESUMO

The production of a large amount of high-quality transition metal dichalcogenides is critical for their use in industrial applications. Here, we demonstrate the scalable exfoliation of bulk molybdenum disulfide (MoS2) powders into single- or few-layer nanosheets using the Taylor-Couette flow. The toroidal Taylor vortices generated in the Taylor-Couette flow provide efficient mixing and high shear stresses on the surfaces of materials, resulting in a more efficient exfoliation of the layered materials. The bulk MoS2 powders dispersed in N-methyl-2-pyrrolidone (NMP) were exfoliated with the Taylor-Couette flow by varying the process parameters, including the initial concentration of MoS2 in the NMP, rotation speed of the reactor, reaction time, and temperature. With a batch process at an optimal condition, half of the exfoliated MoS2 nanosheets were thinner than ~3 nm, corresponding to single to ~4 layers. The spectroscopic and microscopic analysis revealed that the exfoliated MoS2 nanosheets contained the same quality as the bulk powders without any contamination or modification. Furthermore, the continuous exfoliation of MoS2 was demonstrated by the Taylor-Couette flow reactor, which produced an exfoliated MoS2 solution with a concentration of ~0.102 mg/mL. This technique is a promising way for the scalable production of single- or few-layer MoS2 nanosheets without using hazardous intercalation materials.

10.
Clin Exp Vaccine Res ; 7(2): 119-128, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30112351

RESUMO

PURPOSE: The goal of this study was to purify and characterize Ebola virus glycoprotein (GP)-specific IgG antibodies from hybridoma clones. MATERIALS AND METHODS: For hybridoma production, mice were injected by intramuscular-electroporation with GP DNA vaccines, and boosted with GP vaccines. The spleen cells were used for producing GP-specific hybridoma. Enzyme-linked immunosorbent assay, Western blot assay, flow cytometry, and virus-neutralizing assay were used to test the ability of monoclonal IgG antibodies to recognize GP and neutralize Ebola virus. RESULTS: Twelve hybridomas, the cell supernatants of which displayed GP-binding activity by enzyme-linked immunosorbent assay and the presence of both IgG heavy and light chains by Western blot assay, were chosen as a possible IgG producer. Among these, five clones (C36-1, D11-3, D12-1, D34-2, and E140-2) were identified to secrete monoclonal IgG antibodies. When the monoclonal IgG antibodies from the 5 clones were tested for their antigen specificity, they recognized GP in an antigen-specific and IgG dose-dependent manner. They remained reactive to GP at the lowest tested concentrations (1.953-7.8 ng/mL). In particular, IgG antibodies from clones D11-3, D12-1, and E140-2 recognized the native forms of GP expressed on the cell surface. These antibodies were identified as IgG1, IgG2a, or IgG2b kappa types and appeared to recognize the native forms of GP, but not the denatured forms of GP, as determined by Western blot assay. Despite their GP-binding activity, none of the IgG antibodies neutralized Ebola virus infection in vitro, suggesting that these antibodies are unable to neutralize Ebola virus infection. CONCLUSION: This study shows that the purified IgG antibodies from 5 clones (C36-1, D11-3, D12-1, D34-2, and E140-2) possess GP-binding activity but not Ebola virus-neutralizing activity.

11.
J Am Chem Soc ; 140(34): 10710-10720, 2018 08 29.
Artigo em Inglês | MEDLINE | ID: mdl-30028604

RESUMO

Non-noble-metal, thin-film oxides are widely investigated as promising catalysts for oxygen evolution reactions (OER). Amorphous cobalt oxide films electrochemically formed in the presence of borate (CoBi) and phosphate (CoPi) share a common cobaltate domain building block, but differ significantly in OER performance that derives from different electron-proton charge transport properties. Here, we use a combination of L edge synchrotron X-ray absorption (XAS), resonant X-ray emission (RXES), resonant inelastic X-ray scattering (RIXS), resonant Raman (RR) scattering, and high-energy X-ray pair distribution function (PDF) analyses that identify electronic and structural factors correlated to the charge transport differences for CoPi and CoBi. The analyses show that CoBi is composed primarily of cobalt in octahedral coordination, whereas CoPi contains approximately 17% tetrahedral Co(II), with the remainder in octahedral coordination. Oxygen-mediated 4 p-3 d hybridization through Co-O-Co bonding was detected by RXES and the intersite dd excitation was observed by RIXS in CoBi, but not in CoPi. RR shows that CoBi resembles a disordered layered LiCoO2-like structure, whereas CoPi is amorphous. Distinct domain models in the nanometer range for CoBi and CoPi have been proposed on the basis of the PDF analysis coupled to XAS data. The observed differences provide information on electronic and structural factors that enhance oxygen evolving catalysis performance.

12.
Polymers (Basel) ; 10(6)2018 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-30966683

RESUMO

A simple and cost-effective fabrication method for plasmonic nanolens arrays (PNA) with a narrow gap has been proposed for fabricating enhanced fluorescence substrates, in which the fluorophores interacting with the enhanced electromagnetic field generated by localized surface plasmons provide a higher fluorescence signal. The PNA was fabricated by the sequential depositions of the SiO2 and Ag layers on a UV-nanoimprinted nanodot array with a pitch of 500 nm, a diameter of 250 nm, and a height of 100 nm. During the deposition processes, the shape of the nanodots changed to that of nanolenses, and the gap between the nanolenses was decreased via sidewall deposition. To examine the feasibility of the fabricated PNA for enhanced fluorescence application, a streptavidin-Cy5 (SA-Cy5) conjugate dissolved in a saline buffer solution was spotted on the PNA, and the fluorescence signals of the SA-Cy5 were measured and compared with those on a bare glass substrate. The enhancement factor was affected by the gap between the nanolenses, and the maximum enhancement factor of ~128 was obtained from the PNA with a SiO2 layer thickness of 150 nm and an Ag layer thickness of 100 nm. Finally, an electromagnetic field analysis was used to examine the fluorescence signal enhancement, and was conducted using rigorous coupled wave analysis.

13.
J Phys Ther Sci ; 28(10): 2975-2978, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27821972

RESUMO

[Purpose] The purpose of this study was to examine the effect of the Schroth method (three-dimensional convergence exercise) of emphasis of active holding on pain and Cobb's angle in patients with scoliosis. [Subjects and Methods] It applied the Schroth method program of emphasis of active holding individually to three subjects three time per week for 15 weeks. All subject were measured Cobb's angle and pain. [Results] After 15 weeks, pain and Cobb's angle decreased compared to values before. [Conclusion] These results demonstrate the benefit of the Schroth exercise program of emphasis of active holding on decreasing pain and Cobb's angle in patients with idiopathic scoliosis.

14.
Nat Mater ; 13(7): 682-7, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24813420

RESUMO

Heavy-fermion metals exhibit a plethora of low-temperature ordering phenomena . Among these are the so-called hidden-order phases that, in contrast to conventional magnetic order, are invisible to standard neutron diffraction experiments. One of the structurally most simple hidden-order compounds, CeB6, has been intensively studied for an elusive phase that was attributed to the antiferroquadrupolar ordering of cerium-4f moments . As the ground state of CeB6 is characterized by a more conventional antiferromagnetic (AFM) order , the low-temperature physics of this system has generally been assumed to be governed solely by AFM interactions between the dipolar and multipolar Ce moments . Here we overturn this established picture by observing an intense ferromagnetic (FM) low-energy collective mode that dominates the magnetic excitation spectrum of CeB6. Inelastic neutron-scattering data reveal that the intensity of this FM excitation significantly exceeds that of conventional spin-wave magnons emanating from the AFM wavevectors, thus placing CeB6 much closer to a FM instability than previously anticipated. This propensity for ferromagnetism may account for much of the unexplained behaviour of CeB6, and should lead to a re-examination of existing theories that have so far largely neglected the role of FM interactions.

15.
Phys Rev Lett ; 106(4): 047203, 2011 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-21405356

RESUMO

Based on the detailed Mn L(2,3)-edge x-ray resonant scattering results, we report a new complexity in the magnetic order of multiferroic orthomangnites, which has been considered as the simple A-type cycloid order inducing ferroelectricity. The Dzyaloshinskii-Moriya interaction involved in the orthorhombic distortion brings on F-type canting from the A type, and the ordering type becomes the off-phase synchronized bc cycloid in TbMnO(3) or the tilted antiphase ab cycloid in Eu(3/4)Y(1/4)MnO(3). The F-type canting is responsible for the magnetic field-driven multiferroicity to weak ferromagnetism transition.

16.
Sensors (Basel) ; 9(9): 6897-912, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-22399978

RESUMO

In this paper, a new method for the detection of apnea/hypopnea periods in physiological data is presented. The method is based on the intelligent combination of an integrated sensor system for long-time cardiorespiratory signal monitoring and dedicated signal-processing packages. Integrated sensors are a PVDF film and conductive fabric sheets. The signal processing package includes dedicated respiratory cycle (RC) and QRS complex detection algorithms and a new method using the respiratory cycle variability (RCV) for detecting apnea/hypopnea periods in physiological data. Results show that our method is suitable for online analysis of long time series data.

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