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1.
J Robot Surg ; 18(1): 274, 2024 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-38951387

RESUMO

Breast cancer is the most common malignant tumor worldwide, and mastectomy remains the primary strategy for treating early stage breast cancer. However, the complication rates, surgical variables, and oncologic safety of minimally invasive nipple-sparing mastectomy (MINSM) have not been fully addressed. We systematically searched PubMed, Web of Science, Embase, and the Cochrane Library for randomized-controlled trials (RCTs) and non-RCTs that compared MINSM with conventional nipple-sparing mastectomy (CNSM), both followed by Prosthesis Breast Reconstruction (PBR). The main outcomes observed included overall complications, (Grade III) complications, skin and nipple necrosis, wound dehiscence, infection, seroma, hematoma, implant loss, and oncologic safety (positive margins and recurrence). Secondary outcomes included operation time, blood loss, hospital stay, cost-effectiveness, and patient satisfaction. Binary and continuous variables were compared using odds ratios (OR) and mean differences (MD) with 95% confidence intervals (CI). A total of 10 studies involving 2,166 patients were included. There were no statistically significant differences between MINSM and CNSM in terms of skin necrosis, wound dehiscence, infection, seroma, hematoma, implant loss, or oncologic safety. However, MINSM significantly reduced overall complications (OR = 0. 74, 95% CI [0. 58, 0. 94], p = 0. 01) and (Grade III) complications (OR = 0. 47, 95% CI [0. 31, 0. 71], p = 0. 0003). Nipple necrosis events were also significantly reduced in the MINSM group (OR = 0. 49, 95% CI [0. 30, 0. 80], p = 0. 005). Patient satisfaction improved notably in the MINSM group. Additionally, compared with the CNSM group, the MINSM group had longer operating times (MD = 46. 88, 95% CI [19. 55, 74. 21], p = 0. 0008) and hospital stays (MD = 1. 39, 95% CI [0. 65, 2. 12], p < 0. 001), while intraoperative blood loss was significantly reduced (MD = -29. 05, 95% CI [-36. 20, -21. 90], p < 0. 001). Compared with CNSM, MINSM offers advantages in reducing complications and intraoperative blood loss, as well as improving aesthetic outcomes and patient satisfaction. Therefore, MINSM may become a viable option for breast surgery. Nevertheless, a long-term evaluation of the oncologic safety of this approach is necessary to ensure its efficacy and safety for patients.


Assuntos
Neoplasias da Mama , Mamoplastia , Procedimentos Cirúrgicos Minimamente Invasivos , Mamilos , Complicações Pós-Operatórias , Feminino , Humanos , Implantes de Mama , Neoplasias da Mama/cirurgia , Tempo de Internação/estatística & dados numéricos , Mamoplastia/métodos , Mastectomia/métodos , Procedimentos Cirúrgicos Minimamente Invasivos/métodos , Mamilos/cirurgia , Duração da Cirurgia , Tratamentos com Preservação do Órgão/métodos , Satisfação do Paciente , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Resultado do Tratamento
2.
Nano Lett ; 24(21): 6410-6416, 2024 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-38767286

RESUMO

CsPbI3 perovskite quantum dots (QDs) could achieve pure-red emission by reducing their size, but the increased exciton binding energy (EB) and surface defects for the small-sized QDs (SQDs) cause severe Auger and trap recombinations, thus worsening their electroluminescence (EL) performance. Herein, we utilize the dangling bonds of the SQDs as a driving force to accelerate KI dissolution to solve its low solubility in nonpolar solvents, thereby allowing K+ and I- to bond to the surface of SQDs. The EB of the SQDs was decreased from 305 to 51 meV because of the attraction of K+ to electrons, meanwhile surface vacancies were passivated by K+ and I-. The Auger and trap recombinations were simultaneously suppressed by this difunctional ligand. The SQD-based light-emitting diode showed a stable pure-red EL peak of 639 nm, an external quantum efficiency of 25.1% with low roll-off, and a brightness of 5934 cd m-2.

3.
J Am Chem Soc ; 146(20): 13934-13948, 2024 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-38741463

RESUMO

Double perovskite films have been extensively studied for ferroelectric order, ferromagnetic order, and photovoltaic effects. The customized ion combinations and ordered ionic arrangements provide unique opportunities for bandgap engineering. Here, a synergistic strategy to induce chemical strain and charge compensation through inequivalent element substitution is proposed. A-site substitution of the barium ion is used to modify the chemical valence and defect density of the two B-site elements in Bi2FeMnO6 double perovskite epitaxial thin films. We dramatically increased the ferroelectric photovoltaic effect to ∼135.67 µA/cm2 from 30.62 µA/cm2, which is the highest in ferroelectric thin films with a thickness of less than 100 nm under white-light LED irradiation. More importantly, the ferroelectric polarization can effectively improve the photovoltaic efficiency of more than 5 times. High-resolution HAADF-STEM, synchrotron-based X-ray diffraction and absorption spectroscopy, and DFT calculations collectively demonstrate that inequivalent ion plays a dual role of chemical strain (+1.92 and -1.04 GPa) and charge balance, thereby introducing lattice distortion effects. The reduction of the oxygen vacancy density and the competing Jahn-Teller distortion of the oxygen octahedron are the main phenomena of the change in electron-orbital hybridization, which also leads to enhanced ferroelectric polarization values and optical absorption. The inequivalent strategy can be extended to other double perovskite systems and applied to other functional materials, such as photocatalysis for efficient defect control.

4.
J Robot Surg ; 18(1): 136, 2024 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-38520624

RESUMO

Minimally invasive thyroidectomy (MIT) is increasingly being used for the thyroid tumors. The comparison of bilateral axillo-breast approach robotic thyroidectomy (BABART) with other MIT has not yet led to a unified conclusion with regard to surgical outcomes. To conduct a systematic review and meta-analysis of the literature on the surgical outcomes of BABART compared with MIT. We performed a systematic search in PubMed, Web of Science, Embase and Cochrane Library database for randomized control trials (RCTs) and non-RCTs that compare BABART to MIT. The primary outcomes included perioperative, postoperative complications. The odds ratio (OR) and mean difference (MD) were applied for the comparison of dichotomous and continuous variables with 95% confidence intervals (CIs). Nine studies, comprising 3645 patients, were included in the meta-analysis. Our findings indicated that there were no significant differences in hospital stay, number of retrieved lymph nodes, recurrent laryngeal nerve (RLN) injury, and vocal cord dysfunction between BABRT and MIT. However, BABART was associated with a shorter operation time (MD = - 21.45 min, 95% CI [- 47.27, 4.38], p = 0.1) and lower rate of permanent hypoparathyroidism (OR = 0.42, 95% CI [0.20, 0.88], p = 0.02). Additionally, the MIT group had reduced postoperative pain score (MD = 0.45, 95% CI [0.02, 0.88], p = 0.04) and lower rate of hypocalcemia (OR = 2.31, 95% CI [1.04, 5.13], p = 0.04) than the BABART group. In comparison with MIT, BABART exhibits better results in terms of operative time and the rate of permanent hypoparathyroidism, with no significant difference in hospital stay, number of retrieved lymph nodes, RLN injury, and vocal cord dysfunction. However, the postoperative pain score and the rate of hypocalcemia of MIT are slightly better that of BABART.


Assuntos
Hipocalcemia , Hipoparatireoidismo , Procedimentos Cirúrgicos Robóticos , Disfunção da Prega Vocal , Humanos , Tireoidectomia/efeitos adversos , Tireoidectomia/métodos , Procedimentos Cirúrgicos Robóticos/métodos , Complicações Pós-Operatórias/epidemiologia , Dor Pós-Operatória/etiologia
5.
Adv Mater ; 36(24): e2308550, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38478729

RESUMO

The development of ultrathin, stable ferroelectric materials is crucial for advancing high-density, low-power electronic devices. Nonetheless, ultrathin ferroelectric materials are rare due to the critical size effect. Here, a novel ferroelectric material, magnesium molybdenum oxide (Mg2Mo3O8) is presented. High-quality ultrathin Mg2Mo3O8 crystals are synthesized using chemical vapor deposition (CVD). Ultrathin Mg2Mo3O8 has a wide bandgap (≈4.4 eV) and nonlinear optical response. Mg2Mo3O8 crystals of varying thicknesses exhibit out-of-plane ferroelectric properties at room temperature, with ferroelectricity retained even at a 2 nm thickness. The Mg2Mo3O8 exhibits a relatively large remanent polarization ranging from 33 to 52 µC cm- 2, which is tunable by changing its thickness. Notably, Mg2Mo3O8 possesses a high Curie temperature (>980 °C) across various thicknesses. Moreover, the as-grown Mg2Mo3O8 crystals display remarkable stability under harsh environments. This work introduces nolanites-type crystal into ultrathin ferroelectrics. The scalable synthesis of stable ultrathin ferroelectric Mg2Mo3O8 expands the scope of ferroelectric materials and may prosper applications of ferroelectrics.

6.
Nat Commun ; 15(1): 693, 2024 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-38267445

RESUMO

Ferroelectric tunnel junctions are promising towards high-reliability and low-power non-volatile memories and computing devices. Yet it is challenging to maintain a high tunnelling electroresistance when the ferroelectric layer is thinned down towards atomic scale because of the ferroelectric structural instability and large depolarization field. Here we report ferroelectric tunnel junctions based on samarium-substituted layered bismuth oxide, which can maintain tunnelling electroresistance of 7 × 105 with the samarium-substituted bismuth oxide film down to one nanometer, three orders of magnitude higher than previous reports with such thickness, owing to efficient barrier modulation by the large ferroelectric polarization. These ferroelectric tunnel junctions demonstrate up to 32 resistance states without any write-verify technique, high endurance (over 5 × 109), high linearity of conductance modulation, and long retention time (10 years). Furthermore, tunnelling electroresistance over 109 is achieved in ferroelectric tunnel junctions with 4.6-nanometer samarium-substituted bismuth oxide layer, which is higher than commercial flash memories. The results show high potential towards multi-level and reliable non-volatile memories.

7.
Mater Horiz ; 10(10): 4389-4397, 2023 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-37465904

RESUMO

Polarization rotation caused by various strains, such as substrate and/or chemical strain, is essential to control the electronic structure and properties of ferroelectric materials. This study proposes anion-induced polarization rotation with chemical strain, which effectively improves ferroelectricity. A method for the sulfurization of BiFeO3 thin films by introducing sulfur anions is presented. The sulfurized films exhibited substantial enhancement in room-temperature ferroelectric polarization through polarization rotation and distortion, with a 170% increase in the remnant polarization from 58 to 100.7 µC cm-2. According to first-principles calculations and the results of X-ray absorption spectroscopy and high-angle annular dark-field scanning transmission electron microscopy, this enhancement arose from the introduction of S atoms driving the re-distribution of the lone-pair electrons of Bi, resulting in the rotation of the polarization state from the [001] direction to the [110] or [111] one. The presented method of anion-driven polarization rotation might enable the improvement of the properties of oxide materials.

8.
Front Oncol ; 13: 1112687, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37056328

RESUMO

Purpose: In this study, we aimed to develop and validate nomograms for predicting the survival outcomes in patients with T1-2N1 breast cancer to identify the patients who could not benefit from postmastectomy radiotherapy (PMRT). Methods: Data from 10191 patients with T1-2N1 breast cancer were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Of them, 6542 patients who had not received PMRT formed the training set. Concurrently, we retrospectively enrolled 419 patients from the Affiliated Hospital of North Sichuan Medical College (NSMC), and 286 patients who did not undergo PMRT formed the external validation set. The least absolute shrinkage and selection operator (LASSO) and multivariate Cox regression analyses were used for selecting prognostic factors in the training set. Using the selected factors, two prognostic nomograms were constructed. The nomograms' performance was assessed using the concordance index (C-index), calibration curves, decision curve analysis (DCA), and risk subgroup classification. The stabilized inverse probability of treatment weights (IPTWs) was used to balance the baseline characteristics of the different risk groups. Finally, the survival outcomes and effectiveness of PMRT after IPTW adjustment were evaluated using adjusted Kaplan-Meier curves and Cox regression models. Results: The 8-year overall survival (OS) and breast cancer-specific survival (BCSS) rates for the SEER cohort were 84.3% and 90.1%, with a median follow-up time of 76 months, while those for the NSMC cohort were 84.1% and 86.9%, with a median follow-up time of 73 months. Moreover, significant differences were observed in the survival curves for the different risk subgroups (P < 0.001) in both SEER and NSMC cohorts. The subgroup analysis after adjustment by IPTW revealed that PMRT was significantly associated with improved OS and BCSS in the intermediate- (hazard ratio [HR] = 0.72, 95% confidence interval [CI]: 0.59-0.88, P=0.001; HR = 0.77, 95% CI: 0.62-0.95, P = 0.015) and high- (HR=0.66, 95% CI: 0.52-0.83, P<0.001; HR=0.74, 95% CI: 0.56-0.99, P=0.039) risk groups. However, PMRT had no significant effects on patients in the low-risk groups. Conclusion: According to the prognostic nomogram, we performed risk subgroup classification and found that patients in the low-risk group did not benefit from PMRT.

9.
Research (Wash D C) ; 6: 0073, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36930756

RESUMO

Semiconductor quantum dots have been emerging as one of the most ideal materials for artificial photosynthesis. Here, we report the assembled ZnS-CdS hybrid heterostructure for efficient coupling cooperative redox catalysis toward the oxidation of 1-phenylethanol to acetophenone/2,3-diphenyl-2,3-butanediol (pinacol) integrated with the reduction of protons to H2. The strong interaction and typical type-I band-position alignment between CdS quantum dots and ZnS quantum dots result in efficient separation and transfer of electron-hole pairs, thus distinctly enhancing the coupled photocatalyzed-redox activity and stability. The optimal ZnS-CdS hybrid also delivers a superior performance for various aromatic alcohol coupling photoredox reaction, and the ratio of electrons and holes consumed in such redox reaction is close to 1.0, indicating a high atom economy of cooperative coupling catalysis. In addition, by recycling the scattered light in the near field of a SiO2 sphere, the SiO2-supported ZnS-CdS (denoted as ZnS-CdS/SiO2) catalyst can further achieve a 3.5-fold higher yield than ZnS-CdS hybrid. Mechanistic research clarifies that the oxidation of 1-phenylethanol proceeds through the pivotal radical intermediates of •C(CH3)(OH)Ph. This work is expected to promote the rational design of semiconductor quantum dots-based heterostructured catalysts for coupling photoredox catalysis in organic synthesis and clean fuels production.

10.
Science ; 379(6638): 1218-1224, 2023 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-36952424

RESUMO

Atomic-scale ferroelectrics are of great interest for high-density electronics, particularly field-effect transistors, low-power logic, and nonvolatile memories. We devised a film with a layered structure of bismuth oxide that can stabilize the ferroelectric state down to 1 nanometer through samarium bondage. This film can be grown on a variety of substrates with a cost-effective chemical solution deposition. We observed a standard ferroelectric hysteresis loop down to a thickness of ~1 nanometer. The thin films with thicknesses that range from 1 to 4.56 nanometers possess a relatively large remanent polarization from 17 to 50 microcoulombs per square centimeter. We verified the structure with first-principles calculations, which also pointed to the material being a lone pair-driven ferroelectric material. The structure design of the ultrathin ferroelectric films has great potential for the manufacturing of atomic-scale electronic devices.

11.
Clin. transl. oncol. (Print) ; 24(11): 2136-2145, noviembre 2022.
Artigo em Inglês | IBECS | ID: ibc-210141

RESUMO

To investigate the subcellular localization of ANXA2 in breast cancer of different cell densities in humans and its relationship with the clinicopathological features of patients. To investigate the differences in ANXA2 subcellular localization in MDA-MB-231 cells of different cell densities. To compare the proliferation, invasion, and migration ability of MDA-MB-231 cells under different ANXA2 subcellular localization.MethodsImmunohistochemistry was applied to detect the subcellular localization of ANXA2 in tissue sections of 60 breast cancer patients, and the association with ANXA2 subcellular localization was verified in conjunction with cell density. To investigate the relationship between cell density and clinicopathological data of breast cancer patients. To establish high- and low-density models of MDA-MB-231 breast cancer cell lines and verify the subcellular localization of ANXA2 using immunofluorescence and observation under confocal microscopy. The proliferation, migration, and invasion ability of MDA-MB-231 cells under different subcellular localization of ANXA2 were detected and compared using CCK-8 assay and Transwell assay. After changing the subcellular localization of ANXA2 in high-density MDA-MB-231 cells with PY-60, changes in biological behaviors of the compared MDA-MB-231 cells were observed. Two different 4T1 cell lines with high and low densities were implanted subcutaneously in nude mice to observe the effects of different cell densities on tumor growth in nude mice.ResultsThe clinical data showed that breast cancer with high cell density had higher T stage and higher TNM stage, and the cell density was positively correlated with breast cancer mass size. ANXA2 was mainly localized to the cell membrane when the cell density of breast cancer cells was high and to the cytoplasm when the cell density was low. (AU)


Assuntos
Humanos , Animais , Anexina A2 , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Proliferação de Células , Sincalida/metabolismo , Movimento Celular , Camundongos
12.
Chem Commun (Camb) ; 58(59): 8282-8285, 2022 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-35791826

RESUMO

The reaction of cyclopropenes with compounds containing Mg-Mg bonds is reported. 1,2-Dimagnesiation occurs exclusively by syn-addition to the least hindered face of the alkene forming a single diastereomeric product. DFT calculations support a concerted and stereoselective mechanism. These findings shed new light on the stereochemistry of reactions involving magnesium reagents.

13.
Clin Transl Oncol ; 24(11): 2136-2145, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-35778647

RESUMO

OBJECTIVE: To investigate the subcellular localization of ANXA2 in breast cancer of different cell densities in humans and its relationship with the clinicopathological features of patients. To investigate the differences in ANXA2 subcellular localization in MDA-MB-231 cells of different cell densities. To compare the proliferation, invasion, and migration ability of MDA-MB-231 cells under different ANXA2 subcellular localization. METHODS: Immunohistochemistry was applied to detect the subcellular localization of ANXA2 in tissue sections of 60 breast cancer patients, and the association with ANXA2 subcellular localization was verified in conjunction with cell density. To investigate the relationship between cell density and clinicopathological data of breast cancer patients. To establish high- and low-density models of MDA-MB-231 breast cancer cell lines and verify the subcellular localization of ANXA2 using immunofluorescence and observation under confocal microscopy. The proliferation, migration, and invasion ability of MDA-MB-231 cells under different subcellular localization of ANXA2 were detected and compared using CCK-8 assay and Transwell assay. After changing the subcellular localization of ANXA2 in high-density MDA-MB-231 cells with PY-60, changes in biological behaviors of the compared MDA-MB-231 cells were observed. Two different 4T1 cell lines with high and low densities were implanted subcutaneously in nude mice to observe the effects of different cell densities on tumor growth in nude mice. RESULTS: The clinical data showed that breast cancer with high cell density had higher T stage and higher TNM stage, and the cell density was positively correlated with breast cancer mass size. ANXA2 was mainly localized to the cell membrane when the cell density of breast cancer cells was high and to the cytoplasm when the cell density was low. The CCK-8 assay showed that the proliferation rate of MDA-MB-231 cells increased (P < 0.05) after shifting the subcellular localization of ANXA2 from the cell membrane to the cytoplasm. Transwell invasion assay and Transwell migration assay showed that the invasion and migration ability of MDA-MB-231 cells increased significantly after the subcellular localization of ANXA2 was transferred from the cell membrane to the cytoplasm (P < 0.05). The animal experiments showed that high-density breast cancer cells could promote the growth of subcutaneous tumors in nude mice relative to low-density breast cancer cells. CONCLUSION: Cell density can regulate the subcellular localization of ANXA2, and changes in the subcellular localization of ANXA2 are accompanied by the changes in the biological behavior of breast cancer.


Assuntos
Anexina A2 , Neoplasias da Mama , Animais , Neoplasias da Mama/patologia , Contagem de Células , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Feminino , Humanos , Camundongos , Camundongos Nus , Invasividade Neoplásica
14.
Sci Adv ; 8(13): eabm8550, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35363530

RESUMO

The orthorhombic rare-earth manganates and ferrites multiferroics are promising candidates for the next generation multistate spintronic devices. However, their ferroelectric polarization is small, and transition temperature is far below room temperature (RT). The improvement of ferroelectricity remains challenging. Here, through the subtle strain and defect engineering, an RT colossal polarization of 4.14 µC/cm2 is achieved in SmFeO3-δ films, which is two orders of magnitude larger than its bulk and is also the largest one among the orthorhombic rare-earth manganite and ferrite family. Meanwhile, its RT magnetism is uniformly distributed in the film. Combining the integrated differential phase-contrast imaging and density functional theory calculations, we reveal the origin of this superior ferroelectricity in which the purposely introduced oxygen vacancies in the Fe-O layer distorts the FeO6 octahedral cage and drives the Fe ion away from its high-symmetry position. The present approach can be applied to improve ferroelectric properties for multiferroics.

15.
Inorg Chem ; 60(20): 15190-15195, 2021 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-34605633

RESUMO

The monoclinic phase has received a lot of research because of its importance in explaining the origin of high piezoelectric and ferroelectric performances around the morphotropic phase boundary. In the present study, we have investigated the detailed structural evolution in monoclinic PbZr0.535Ti0.465O3 ferroelectric ceramics induced by an electric field with in situ high-energy synchrotron diffraction combined with two-dimensional (2D) geometry scattering technology. It has been discovered that an electric-field-induced single monoclinic MB phase persists indefinitely. The lattice, unit cell volume, and spontaneous polarization of the monoclinic MB structure exhibit significant and flexible responses to the external electric field, i.e., the spontaneous polarization rotates continuously and the lattice and unit cell volume present a butterfly form under the influence of the bipolar electric field. Particularly, direct experimental evidence demonstrates that the macropolarization of PbZr0.535Ti0.465O3 is derived from the spontaneous polarization rotation rather than domain switching, and its volume expansion plays a vital role in the piezoelectric response.

16.
J Am Chem Soc ; 143(17): 6491-6497, 2021 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-33900066

RESUMO

Although BaTiO3 is one of the most famous lead-free piezomaterials, it suffers from small spontaneous and low Curie temperature. Chemical pressure, as a mild way to modulate the structures and properties of materials by element doping, has been utilized to enhance the ferroelectricity of BaTiO3 but is not efficient enough. Here, we report a promoted chemical pressure route to prepare high-performance BaTiO3 films, achieving the highest remanent polarization, Pr (100 µC/cm2), to date and high Curie temperature, Tc (above 1000 °C). The negative chemical pressure (∼-5.7 GPa) was imposed by the coherent lattice strain from large cubic BaO to small tetragonal BaTiO3, generating high tetragonality (c/a = 1.12) and facilitating large displacements of Ti. Such negative pressure is especially significant to the bonding states, i.e., hybridization of Ba 5p-O 2p, whereas ionic bonding in bulk and strong bonding of Ti eg and O 2p, which contribute to the tremendously enhanced polarization. The promoted chemical pressure method shows general potential in improving ferroelectric and other functional materials.

17.
J Am Chem Soc ; 143(9): 3571-3582, 2021 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-33621095

RESUMO

The study of new C-H silylation reagents and reactions remains an important topic. We reported that under Rh catalysis, silacyclobutanes (SCBs) for the first time were able to react with C(sp2)-H and C(sp3)-H bonds, however the underlying reasons for such a new reactivity were not understood. Through this combined computational and experimental study on C-H silylation with SCBs, we not only depict a reaction pathway that fully accounts for the reactivity and all the experimental findings but also streamline a more efficient catalyst that significantly improves the reaction rates and yields. Our key findings include: (1) the active catalytic species is a [Rh]-H as opposed to the previously proposed [Rh]-Cl; (2) the [Rh]-H is generated via a reductive elimination/ß-hydride (ß-H) elimination sequence, as opposed to previously proposed endocyclic ß-H elimination; (3) the regio- and enantio-determining steps are identified; (4) and of the same importance, the discretely synthesized [Rh]-H is shown to be a more efficient catalyst. This work suggests that the [Rh]-H/diphosphine system should find further applications in C-H silylations involving SCBs.

18.
Inorg Chem ; 59(18): 13632-13638, 2020 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-32862641

RESUMO

In situ diffraction investigations have played an important role in experimentally revealing the mechanism of piezoelectric and ferroelectric properties. In this study, a pure tetragonal ferroelectric ceramic of La-doped PbZr0.5Ti0.5O3 (LaPZT50) was investigated to eliminate the complex influence of phase coexistence. The electric field evolutions of the crystal structure, domain switching, and lattice deformation of the tetragonal phase have been revealed by in situ high-energy synchrotron X-ray diffraction. We found that the crystal structure of LaPZT50 is quite stable, showing a negligible change in the Pb-O bond length, unit cell volume, and spontaneous polarization upon application of an in situ external electric field. Importantly, the maximum macroscopic polarization of tetragonal LaPZT50 is defined by the 111-oriented grains. As determined by the intensity difference, the switching of non-180° domains plays a more significant role in contributing to the macroscopic strain than lattice deformation. These results further imply that the phase coexistence around the morphotropic phase boundary facilitates domain wall motion in the tetragonal phase and improves the ferroelectric and piezoelectric properties.

19.
Org Lett ; 22(10): 3799-3803, 2020 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-32337987

RESUMO

To expand the toolbox for the synthesis of ortho-phenolic sulfilimines, sigmatropic rearrangements were introduced to the field of sulfilimine chemistry. Herein we report a N-H sulfenylation/[2,3]-sigmatropic rearrangement cascade reaction. This mild reaction enables commercially available thiols to serve as the sulfenylation reagent and generates water as the sole byproduct. Moreover, the reaction has a wide substrate scope and can be conducted on a gram scale with excellent reaction efficiency.

20.
Nano Lett ; 20(2): 881-886, 2020 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-31887059

RESUMO

The coupling strain in nanoscale systems can achieve control of the physical properties in functional materials, such as ferromagnets, ferroelectrics, and superconductors. Here, we directly demonstrate the atomic-scale structure of super-tetragonal PbTiO3 nanocomposite epitaxial thin films, including the extraordinary coupling of strain transition and the existence of the oxygen vacancies. Large strain gradients, both longitudinal and transverse (∼3 × 107 m-1), have been observed. The original non-magnetic ferroelectric composites notably evoke ferromagnetic properties, derived from the combination of Ti3+ and oxygen vacancies. The saturation ferromagnetic moment can be controlled by the strain of both the interphase and substrate, optimized to a high value of ∼55 emu/cc in 10-nm thick nanocomposite epitaxial thin films on the LaAlO3 substrate. Strain engineering provides a route to explore multiferroic systems in conventional non-magnetic ferroelectric oxides and to create functional data storage devices from both ferroelectrics and ferromagnetics.

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