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1.
ACS Nano ; 16(5): 7580-7588, 2022 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-35446560

RESUMO

The combination of small coercive fields and weak magnetic anisotropy makes soft ferromagnetic films extremely useful for nanoscale devices that need to easily switch spin directions. However, soft ferromagnets are relatively rare, particularly in ultrathin films with thicknesses of a few nanometers or less. We have synthesized large-area, high-quality, ultrathin freestanding LaMnO3 films on Si and found unexpected soft ferromagnetism along both the in-plane and out-of-plane directions when the film thickness was reduced to 4 nm. We argue that the vanishing magnetic anisotropy between the two directions is a consequence of two coexisting magnetic easy axes in different atomic layers of the LaMnO3 film. Spectroscopy measurements reveal a change in Mn valence from 3+ in the film interior to approximately 2+ at the surfaces where considerable hydrogen infiltration occurs due to the water dissolving process. First-principles calculations show that protonation of LaMnO3 decreases the Mn valence and switches the magnetic easy axis from in-plane to out-of-plane as the Mn valence approaches 2+ from its 3+ bulk value. Our work demonstrates that ultrathin freestanding films can exhibit functional properties that are absent in homogeneous materials, concomitant with their convenient compatibility with Si-based devices.

2.
Front Endocrinol (Lausanne) ; 12: 754820, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34917025

RESUMO

Aim: This study aims at evaluating glycemic control during Basalin or Lantus administration in adults with controlled type 2 diabetes mellitus using continuous glucose monitoring system (CGM). Methods: 47 patients with well-controlled T2DM using both Basalin and oral hypoglycemic drugs were recruited. CGM were applied from day 1 to day 3 with the unchanged dose of Basalin and then removed from day 4. A washout was performed with Lantus at the same dose as Basalin from day 4 to day 10. Then patients were continued to install the CGM under Lantus administration from day 11 to day 13. Variables of CGM, such as the area under the curve (AUC) for both hyperglycemia and hypoglycemia, 24h mean blood glucose (24h MBG), 24h standard deviation of blood glucose (24h SDBG), 24h mean amplitude of glycemic excursion (24h MAGE), PT (percentage of time), and time in range (TIR), were calculated and compared between Basalin group and Lantus group. Results: The group of Lantus showed lower 24h MBG (p<0.01), 24h MAGE (p<0.05), and lower 24h SDBG (p<0.01) than the Basalin group. Lantus-treated patients had a lower PT and AUC when the cut-off point for blood glucose was 10 mmol/L (p<0.05) and 13.9 mmol/L (p<0.05), respectively. In this study, no patient developed symptomatic hypoglycemia, few hypoglycemia was observed and there was no difference of hypoglycemia between the two groups. Conclusion: In patients with well-controlled T2DM who were treated with insulin glargine, Lantus group showed lower MBG, GV, and lower PT (BG > 10.0 mmol/L, BG > 13.9 mmol/L) than Basalin group. In summary, for T2DM population with HbA1c ≤ 7%, Lantus may be a better choice compared with Basalin.


Assuntos
Compostos de Anilina/uso terapêutico , Diabetes Mellitus Tipo 2/tratamento farmacológico , Controle Glicêmico , Hipoglicemiantes/uso terapêutico , Insulina Glargina/uso terapêutico , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos
3.
Chem Sci ; 12(8): 2885-2889, 2021 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-34164054

RESUMO

We report on the first isolation and structural characterization of an iron phosphinoimino-borane complex Cp*Fe(η2-H2B[double bond, length as m-dash]NC6H4PPh2) by dehydrogenation of iron amido-borane precursor Cp*Fe(η1-H3B-NHC6H4PPh2). Significantly, regeneration of the amido-borane complex has been realized by protonation of the iron(ii) imino-borane to the amino-borane intermediate [Cp*Fe(η2-H2B-NHC6H4PPh2)]+ followed by hydride transfer. These new iron species are efficient catalysts for 1,2-selective transfer hydrogenation of quinolines with ammonia borane.

4.
Nano Lett ; 21(9): 3981-3988, 2021 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-33886344

RESUMO

The recent proposal of antidoping scheme breaks new ground in conceiving conversely functional materials and devices; yet, the few available examples belong to the correlated electron systems. Here, we demonstrate both theoretically and experimentally that the main group oxide BaBiO3 is a model system for antidoping using oxygen vacancies. The first-principles calculations show that the band gap systematically increases due to the strongly enhanced Bi-O breathing distortions away from the vacancies and the annihilation of Bi 6s/O 2p hybridized conduction bands near the vacancies. Our further spectroscopic experiments confirm that the band gap increases systematically with electron doping, with a maximal gap enhancement of ∼75% when the film's stoichiometry is reduced to BaBiO2.75. These results unambiguously demonstrate the remarkable antidoping effect in a material without strong electron correlations and underscores the importance of bond disproportionation in realizing such an effect.

5.
J Diabetes Res ; 2020: 6666403, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33299890

RESUMO

AIM: To evaluate the effect of an inhibitor of sodium-glucose cotransporter 2 (SGLT-2 inhibitor, dapagliflozin) on glycemic variability in type 2 diabetes mellitus (T2D) under insulin glargine combined with oral hypoglycemic drugs, using a continuous glucose monitoring system (CGMS). METHODS: This prospective, self-controlled, single-center clinical trial recruited 36 patients with T2D under combined insulin glargine and oral hypoglycemic drugs. General clinical data were collected. Fasting blood glucose (FBG), postprandial blood glucose (PBG), glycosylated hemoglobin (HbA1c), and C-peptide levels were assessed before and four weeks of dapagliflozin (10 mg per day) treatment. Blood glucose was monitored for 72 hours before and after treatment using CGMS. RESULTS: After treatment with dapagliflozin, FBG decreased from 6.74 ± 1.78 to 5.95 ± 1.13 mmol/L (p < 0.05); PBG decreased from 13.04 ± 2.99 to 10.92 ± 3.26 mmol/L (p < 0.05); HbA1c decreased from 7.37 ± 0.96% to 6.94 ± 0.80%. The proportion of patients with HbA1c < 7% increased from 27.8% to 58.3%, and the proportion of patients with HbA1c < 7% and without level 2 hypoglycemia increased from 27.8% to 55.6% (p < 0.05). CGMS data showed reduction of the 24 h MBG, MAGE, time-above-range (TAR, >10 mmol/L), high blood glucose index (HBGI), glucose management indicator (GMI), and incremental area under the curve of the glucose level more than 10 mmol/L (AUC > 10) and an increase of time-in-range (TIR, 3.9-10 mmol/L) with treatment. Homeostasis model assessment for pancreatic beta-cell function (HOMA-beta) increased significantly with treatment (p < 0.05), and fewer insulin doses were required after the treatment, without increasing in hypoglycemia and urinary tract infection. Further, a stratified analysis showed that patients with higher pretreatment HbA1c and waist-to-hip ratio (WHR) had greater improvement in glycemic control. CONCLUSION: Dapagliflozin may reduce blood glucose levels, ameliorate glycemic variability, and improve pancreatic beta-cell function in patients with T2D under insulin glargine combined with other oral hypoglycemic drugs, especially in those with poor glucose control and abdominal obesity.


Assuntos
Compostos Benzidrílicos/uso terapêutico , Glicemia/efeitos dos fármacos , Diabetes Mellitus Tipo 2/tratamento farmacológico , Glucosídeos/uso terapêutico , Controle Glicêmico , Hipoglicemiantes/uso terapêutico , Insulina Glargina/uso terapêutico , Células Secretoras de Insulina/efeitos dos fármacos , Inibidores do Transportador 2 de Sódio-Glicose/uso terapêutico , Idoso , Compostos Benzidrílicos/efeitos adversos , Biomarcadores/sangue , Glicemia/metabolismo , Peptídeo C/sangue , China , Diabetes Mellitus Tipo 2/sangue , Diabetes Mellitus Tipo 2/diagnóstico , Quimioterapia Combinada , Feminino , Glucosídeos/efeitos adversos , Hemoglobinas Glicadas/metabolismo , Controle Glicêmico/efeitos adversos , Humanos , Hipoglicemiantes/efeitos adversos , Insulina Glargina/efeitos adversos , Células Secretoras de Insulina/metabolismo , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Inibidores do Transportador 2 de Sódio-Glicose/efeitos adversos , Fatores de Tempo , Resultado do Tratamento
6.
Biomed Res Int ; 2020: 6259437, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32775431

RESUMO

OBJECTIVE: Type 2 diabetic (T2D) male patients with low total testosterone (TT) levels are at an increasing risk of all-cause mortality. However, the levels of TT in male patients with latent autoimmune diabetes in adults (LADA) remain largely unknown. Research Design and Methods. This was a single-center, open, observational study. The inclusion criteria were male patients who were diagnosed with LADA, and sex, body mass index, C-peptide, and glycated hemoglobin (HbA1c) levels matched with those of T2D patients. Islet function/sensitivity and sex hormone concentrations were determined at baseline and 1-year follow-up. The primary endpoint was the changes in androgen levels from baseline to 1-year follow-up in patients with LADA. RESULTS: Our data showed that TT and Bio-T levels remained unchanged, while FT levels significantly decreased from baseline to 1-year follow-up in patients with T2D. However, TT, Bio-T, and FT concentrations dramatically increased in the LADA group from baseline to 1-year follow-up. Furthermore, a Spearman analysis showed that changes of TT, FT, and Bio-T levels from baseline to endpoint were significantly negatively correlated with Δ homeostasis model assessment-2 IR (ΔHOMA2-IR), respectively. CONCLUSIONS: The FT change patterns in patients with LADA may differ from those in patients with T2D. Our data also indicated the significant negative correlation between insulin sensitivity and changes of TT, FT, and Bio-T levels along with the diabetic duration in patients with T2D and LADA.


Assuntos
Diabetes Mellitus Tipo 1/sangue , Diabetes Mellitus Tipo 2/sangue , Modelos Biológicos , Testosterona/sangue , Idoso , Diabetes Mellitus Tipo 1/mortalidade , Diabetes Mellitus Tipo 2/mortalidade , Seguimentos , Hemoglobinas Glicadas/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade
7.
Int J Endocrinol ; 2020: 5947680, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32377186

RESUMO

BACKGROUND: The purpose of this study was to investigate the accuracy of the continuously stored data from the Abbott FreeStyle Libre flash glucose monitoring (FGM) system in Chinese diabetes patients during standard meal tests when glucose concentrations were rapidly changing. Subjects and Methods. Interstitial glucose levels were monitored for 14 days in 26 insulin-treated patients with type 2 diabetes using the FGM system. Standard meal tests were conducted to induce large glucose swings. Venous blood glucose (VBG) was tested at 0, 30, 60, and 120 min after standard meal tests in one middle day of the first and second weeks, respectively. The corresponding sensor glucose values were obtained from interpolating continuously stored data points. Assessment of accuracy was according to recent consensus recommendations with median absolute relative difference (MARD) and Clarke and Parkes error grid analysis (CEG and PEG). RESULTS: Among 208 paired sensor-reference values, 100% were falling within zones A and B of the Clarke and Parkes error grid analysis. The overall MARD was 10.7% (SD, 7.8%). Weighted least squares regression analysis resulted in high agreement between the FGM sensor glucose and VBG readings. The overall MTT results showed that FGM was lower than actual VBG, with MAD of 22.1 mg/dL (1.2 mmol/L). At VBG rates of change of -1 to 0, 0 to 1, 1 to 2, and 2 to 3 mg/dl/min, MARD results were 11.4% (SD, 8.7%), 9.4% (SD, 6.5%), 9.9% (SD, 7.5%), and 9.5% (SD, 7.7%). At rapidly changing VBG concentrations (>3 mg/dl/min), MARD increased to 19.0%, which was significantly higher than slow changing BG groups. CONCLUSIONS: Continuously stored interstitial glucose measurements with the FGM system were found to be acceptable to evaluate VBG in terms of clinical decision during standard meal tests. The continuously stored data from the FGM system appeared to underestimate venous glucose and performed less well during rapid glucose changes.

8.
Sci Adv ; 6(15): eaay0114, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32300646

RESUMO

Engineering magnetic anisotropy in two-dimensional systems has enormous scientific and technological implications. The uniaxial anisotropy universally exhibited by two-dimensional magnets has only two stable spin directions, demanding 180° spin switching between states. We demonstrate a previously unobserved eightfold anisotropy in magnetic SrRuO3 monolayers by inducing a spin reorientation in (SrRuO3)1/(SrTiO3) N superlattices, in which the magnetic easy axis of Ru spins is transformed from uniaxial 〈001〉 direction (N < 3) to eightfold 〈111〉 directions (N ≥ 3). This eightfold anisotropy enables 71° and 109° spin switching in SrRuO3 monolayers, analogous to 71° and 109° polarization switching in ferroelectric BiFeO3. First-principle calculations reveal that increasing the SrTiO3 layer thickness induces an emergent correlation-driven orbital ordering, tuning spin-orbit interactions and reorienting the SrRuO3 monolayer easy axis. Our work demonstrates that correlation effects can be exploited to substantially change spin-orbit interactions, stabilizing unprecedented properties in two-dimensional magnets and opening rich opportunities for low-power, multistate device applications.

9.
Inorg Chem ; 59(8): 5546-5557, 2020 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-32223228

RESUMO

We report imine- and amine-based dinucleating ligands bearing a bisphenol backbone and explore their coordination chemistry with zinc to form zinc alkyl, alkoxide, acetate, and amide complexes. Full characterization of the complexes shows that this ligand framework can support dinuclear and trinuclear complexes. We explore the reactivity of the zinc alkyl and alkoxide complexes as catalysts for the ring opening polymerization of lactide and compared this reactivity to analogous mononuclear complexes. We show that 1) The amine-based complexes are more reactive than the imine-based analogues; 2) The trinuclear zinc alkyl species show unusual control and reproducibility for lactide polymerization; and 3) The extent of bimetallic cooperation is hampered by the ability of the ligand framework to form trinuclear clusters.

10.
Org Biomol Chem ; 18(8): 1572-1576, 2020 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-32039418

RESUMO

Using an air-stable cobalt catalyst [Cp*Co(1,2-Ph2PC6H4S)(NCMe)]BF4 (1, Cp* = Me5C5-), we have achieved catalytic regioselective hydrohydrazination of epoxides to 1,1-hydrazinoalcohols in an atom-economical manner. The catalysis involves a cobalt-hydrazine intermediate, in which the NH2 group of the hydrazine binds to the metal center, inhibiting its nucleophilic reactivity and allowing the NH group to participate in the regioselective hydrohydrazination.

11.
Natl Sci Rev ; 7(1): 84-91, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34692020

RESUMO

Complex oxides with tunable structures have many fascinating properties, though high-quality complex oxide epitaxy with precisely controlled composition is still out of reach. Here we have successfully developed solution-based single-crystalline epitaxy for multiferroic (1-x)BiTi(1-y)/2Fe y Mg(1-y)/2O3-(x)CaTiO3 (BTFM-CTO) solid solution in large area, confirming its ferroelectricity at the atomic scale with strong spontaneous polarization. Careful compositional tuning leads to a bulk magnetization of 0.07 ± 0.035 µB/Fe at room temperature, enabling magnetically induced polarization switching exhibiting a large magnetoelectric coefficient of 2.7-3.0 × 10-7 s/m. This work demonstrates the great potential of solution processing in large-scale complex oxide epitaxy and establishes novel room-temperature magnetoelectric coupling in epitaxial BTFM-CTO film, making it possible to explore a much wider space of composition, phase, and structure that can be easily scaled up for industrial applications.

12.
Diabetes Metab Res Rev ; 35(4): e3126, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30614187

RESUMO

BACKGROUND: Testosterone affects insulin resistance, but the effect of testosterone treatment on type 2 diabetes (T2D) remains controversial. We aimed to investigate the association between circulating total testosterone (TT) and glycaemic variability using continuous glucose monitoring (CGM) in patients with T2D. METHODS: A total of 248 men with T2D were enrolled in the study. Clinical characteristics and plasma for glycated haemoglobin (HbA1c) and C-peptide assessment were collected. TT was measured using a chemiluminescent immunometric assay. All patients were subjected to a 3-day CGM before making adjustments for hypoglycaemic therapy. RESULTS: TT positively correlated with the standard deviation of mean blood glucose (SDBG) (P < 0.05), especially in older patients. Linear regression analysis showed that SDBG was associated with HbA1c (ß = 0.354, P < 0.001) and TT (ß = 0.164, P = 0.008) after adjusting for age, duration of diabetes, body mass index, fasting/postprandial C-peptide, and use of different hypoglycaemic drugs. The cut-off value of TT for predicting glycaemic variability was 14.76 mmol/L according to receiver operating characteristic (ROC) analysis. SDBG, the coefficient of variation, the incremental area under the curve of glucose (AUC) > 10 mmol/L, and AUC night were increased in the group with TT > 14.76 nmol/L (P < 0.01 for all variables). Body mass index and fasting/postprandial C-peptide were lower in the group with TT > 14.76 nmol/L than in the group with TT ≤ 14.76 nmol/L (P < 0.05). CONCLUSIONS: Circulating TT levels should be assessed in patients with T2D in addition to HbA1c for predicting glycaemic variability. More frequent blood glucose monitoring or CGM is suggested for patients with T2D and high testosterone levels. CLINICAL TRIALS REGISTRATION: NCT03519529, ClinicalTrials.gov.


Assuntos
Biomarcadores/análise , Glicemia/análise , Diabetes Mellitus Tipo 2/sangue , Hiperglicemia/sangue , Hipoglicemia/sangue , Testosterona/sangue , Adulto , Idoso , Automonitorização da Glicemia , China , Estudos Transversais , Diabetes Mellitus Tipo 2/complicações , Seguimentos , Hemoglobinas Glicadas/análise , Humanos , Hiperglicemia/epidemiologia , Hiperglicemia/etiologia , Hipoglicemia/epidemiologia , Hipoglicemia/etiologia , Incidência , Resistência à Insulina , Masculino , Pessoa de Meia-Idade , Prognóstico , Curva ROC
13.
Nat Mater ; 17(12): 1081-1086, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30397308

RESUMO

Two-dimensional (2D) topological materials, including quantum spin/anomalous Hall insulators, have attracted intense research efforts owing to their promise for applications ranging from low-power electronics and high-performance thermoelectrics to fault-tolerant quantum computation. One key challenge is to fabricate topological materials with a large energy gap for room-temperature use. Stanene-the tin counterpart of graphene-is a promising material candidate distinguished by its tunable topological states and sizeable bandgap. Recent experiments have successfully fabricated stanene, but none of them have yet observed topological states. Here we demonstrate the growth of high-quality stanene on Cu(111) by low-temperature molecular beam epitaxy. Importantly, we discovered an unusually ultraflat stanene showing an in-plane s-p band inversion together with a spin-orbit-coupling-induced topological gap (~0.3 eV) at the Γ point, which represents a foremost group-IV ultraflat graphene-like material displaying topological features in experiment. The finding of ultraflat stanene opens opportunities for exploring two-dimensional topological physics and device applications.

14.
Dalton Trans ; 47(44): 15757-15764, 2018 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-30351329

RESUMO

Diphosphinodithio ligated complexes of nickel(0), nickel(i) and nickel(ii)-alkyl with a reactivity relevant to the C-C bond formation were described. Stoichiometric reactions of the nickel(0) complex, [(P2S2)Ni] ([1]0, P2S2 = (Ph2PC6H4CH2S)2(C2H4)), with alkyl halides (RX) such as C6H5CH2Br, C2H3CH2Br, C2H5I and (CH3)2CHI were investigated, from which the products were found to be highly dependent on the nature of RX used. Oxidative addition of C2H3CH2Br to [1]0 provides the stable Ni(ii)-alkyl complexes [1-allyl]+. The reaction of [1]0 with C6H5CH2Br proceeds through a radical pathway resulting in the formation of the nickel(i) complex [1]+ and an organic homo-coupled product 1,2-diphenylethane. Oxidative addition of C2H5I or (CH3)2CHI to [1]0 can be achieved but it competes with the halogen atom abstraction reaction as found for C6H5CH2Br. [1]0 was shown to be an active catalyst for the coupling reactions of primary halides and alkyl Grignard reagents.

15.
Nanoscale ; 10(21): 10041-10049, 2018 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-29774918

RESUMO

Inducing magnetism in a topological insulator (TI) by exchange coupling with a ferromagnetic insulator (FMI) will break the time-reversal symmetry of topological surface states, offering possibilities to realize several predicted novel magneto-electric effects. Seeking suitable FMI materials is crucial for the coupling of heterojunctions, and yet is challenging as well and only a few kinds have been explored. In this report, we introduce epitaxial LaCoO3 thin films on a SrTiO3 substrate, which is an insulating ferromagnet with a Curie temperature of TC ∼ 85 K, to be combined with TIs for proximity coupling. Thin films of the prototype topological insulator, Bi2Se3, are successfully grown onto the (001) surface of LaCoO3/SrTiO3, forming a high-quality TI/FMI heterostructure with a sharp interface. The magnetic and transport measurements manifest the emergence of a ferromagnetic phase in Bi2Se3 films, with additional induced moments and a suppressed weak antilocalization effect, while preserving the carrier mobility of the intrinsic Bi2Se3 films at the same time. Moreover, a signal of an anomalous Hall effect is observed and persists up to temperatures above 100 K, paving the way towards spintronic device applications.

16.
Sci Rep ; 8(1): 5888, 2018 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-29651052

RESUMO

To compare the continuous subcutaneous insulin infusion (CSII) or insulin glargine based multiple injections (MDI) therapy on glycemic variations in diabetic patients receiving PN outside of intensive care settings. This was a single-center, randomized, open-label trial. Patients with type 2 diabetes (T2D) who were receiving parenteral nutrition (PN) were recruited. After baseline data were collected, recruited patients were then randomized 1:1 to a CSII group or a MDI group. All patients were subjected to a 4-day retrospective Continuous Glucose Monitoring (CGM). The primary endpoint was the differences of the 24-hrs mean amplitude of glycemic excursion (MAGE) in patients receiving the PN therapy between the two groups. A total of 102 patients with T2D receiving PN were recruited. Patients in the CSII group had a significantly decreased mean glucose level (MBG), the standard deviation of MG (SDBG), MAGE, and the coefficient of variation (CV%) compared to those in MDI group (all P < 0.01). Furthermore, we found that the patients who received a bolus insulin dose required maintaining euglycemic control was gradually decreased during the PN period in both groups at the endpoint. The administration of insulin via CSII led to a significant decrease in glycemic variations in patients receiving PN.


Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Insulina Glargina/uso terapêutico , Insulina/uso terapêutico , Nutrição Parenteral , Idoso , Glicemia/metabolismo , Automonitorização da Glicemia , Diabetes Mellitus Tipo 2/sangue , Diabetes Mellitus Tipo 2/fisiopatologia , Esquema de Medicação , Feminino , Humanos , Injeções Subcutâneas , Masculino , Pessoa de Meia-Idade , Pacientes Ambulatoriais , Estudos Retrospectivos
17.
Opt Express ; 26(6): 7842-7851, 2018 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-29609332

RESUMO

Two (La0.7Sr0.3MnO3)n/(SrTiO3)m superlattices with different superlattice period but the same total thickness were deposited on LaAlO3 substrates by pulsed laser deposition. Dielectric properties of these samples were investigated by means of terahertz time-domain spectroscopy (THz-TDS) under external continuous wave green laser excitation and optical-pump terahertz-probe spectroscopy (OPTP) at room temperature. Experimental results show that the real part of the permittivity for both superlattices increases significantly with increasing green laser pump power, which indicates the decrease of the plasma frequency, along with the increase of the electron scattering rate, soft mode eigenfrequency and oscillator strength in the Drude-Lorentz model. Furthermore, it's observed that the insulating superlattice exhibits a more significant dielectric tunability than the metallic superlattice. Besides, the carrier lifetime of superlattices is much shorter than the La0.7Sr0.3MnO3 thin film in the OPTP measurements, indicating that the electrons excited in the La0.7Sr0.3MnO3 layers may be trapped by the defects located in the interfaces of La0.7Sr0.3MnO3 and SrTiO3 or the SrTiO3 layers. With the optical field-induced tunability of dielectric properties, (La0.7Sr0.3MnO3)n/(SrTiO3)m superlattices show great potential in the actively tunable devices in the THz range.

18.
Proc Natl Acad Sci U S A ; 115(12): 2873-2877, 2018 03 20.
Artigo em Inglês | MEDLINE | ID: mdl-29507211

RESUMO

Ferromagnetic insulators are required for many new magnetic devices, such as dissipationless quantum-spintronic devices, magnetic tunneling junctions, etc. Ferromagnetic insulators with a high Curie temperature and a high-symmetry structure are critical integration with common single-crystalline oxide films or substrates. So far, the commonly used ferromagnetic insulators mostly possess low-symmetry structures associated with a poor growth quality and widespread properties. The few known high-symmetry materials either have extremely low Curie temperatures (≤16 K), or require chemical doping of an otherwise antiferromagnetic matrix. Here we present compelling evidence that the LaCoO3 single-crystalline thin film under tensile strain is a rare undoped perovskite ferromagnetic insulator with a remarkably high TC of up to 90 K. Both experiments and first-principles calculations demonstrate tensile-strain-induced ferromagnetism which does not exist in bulk LaCoO3 The ferromagnetism is strongest within a nearly stoichiometric structure, disappearing when the Co2+ defect concentration reaches about 10%. Significant impact of the research includes demonstration of a strain-induced high-temperature ferromagnetic insulator, successful elevation of the transition over the liquid-nitrogen temperature, and high potential for integration into large-area device fabrication processes.

19.
RSC Adv ; 8(30): 16937-16946, 2018 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-35540545

RESUMO

Aurivillius oxides with an intergrowth structures have been receiving increasing interest because of their special structures and potential outstanding ferroelectric properties. In this work, Bi3LaTiNbFeO12-Bi5Ti3FeO15 and Bi3TiNbO9-Bi3LaTiNbFeO12 compounds were successfully synthetised using a simple solid-state reaction method. X-Ray diffraction patterns and scanning transmission electron microscopy high angle annular dark field (STEM-HAADF) images confirm the 2-3 and the 3-4 intergrowth structures in Bi3TiNbO9-Bi3LaTiNbFeO12 and Bi3LaTiNbFeO12-Bi5Ti3FeO15 compounds, respectively. A superlattice-like distortion in these oxides was proposed resulting from the combination of sub-lattices with different a and b parameters, which was validated by XRD refinements and Raman spectra. Polarization-electric field tests and pulsed polarization positive-up negative-down measurements demonstrate that such superlattice-like structures can effectively enhance the intrinsic ferroelectric polarization and coercive field of these oxides, especially when compared with their component oxides Bi3TiNbO9, Bi3LaTiNbFeO12 and Bi5Ti3FeO15. Simultaneously, ferroelectric Curie temperatures of Bi3TiNbO9-Bi3LaTiNbFeO12 and Bi3LaTiNbFeO12-Bi5Ti3FeO15 oxides are lowered because of the internal stress in the superlattice-like structure. Nevertheless, the paramagnetism of the samples is hardly influenced by their structure, while mainly related to their iron content, in which iron has a similar effective magnetic moment around 3.4-3.9.

20.
Sci Rep ; 7(1): 16382, 2017 11 27.
Artigo em Inglês | MEDLINE | ID: mdl-29180640

RESUMO

It is unknown whether YOD (young onset diabetes) and LOD (late onset diabetes) require similar insulin doses for intensive insulin therapy with a metformin add-on to achieve glycemic control. We analyzed data from our two previously performed randomized, controlled open-label trials. Patients were randomized to receive either continuous subcutaneous insulin infusion (CSII) therapy or CSII combined with metformin therapy for 4 weeks. The studies concentrated on the differences in the insulin doses used for the two groups. We included 36 YOD (age < 40 yrs) and 152 LOD (age > 40 yrs) patients. YOD patients who received metformin combined with CSII therapy required significantly lower insulin doses to maintain euglycemic control compared to patients with LOD. A multivariate analysis, controlled for gender and the fasting blood concentration, was performed to determine the significance of the differences between groups, particularly with respect to the total and basal insulin doses. There was a trend toward improvement in ß-cell function and insulin resistance in terms of ΔHOMA-B and ΔHOMA-IR in patients with YOD compared to those with LOD. Newly diagnosed T2D patients with YOD required significantly lower insulin doses, particularly basal insulin doses, to maintain glycemic control compared to the LOD patients.


Assuntos
Idade de Início , Diabetes Mellitus Tipo 2/tratamento farmacológico , Hipoglicemiantes/uso terapêutico , Metformina/uso terapêutico , Adulto , Biomarcadores , Glicemia , Diabetes Mellitus Tipo 2/sangue , Diabetes Mellitus Tipo 2/diagnóstico , Quimioterapia Combinada , Feminino , Humanos , Insulina/administração & dosagem , Masculino , Pessoa de Meia-Idade , Ensaios Clínicos Controlados Aleatórios como Assunto , Resultado do Tratamento
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