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1.
Medicine (Baltimore) ; 103(20): e38018, 2024 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-38758855

RESUMO

Incretin-based drugs, a class of Antidiabetic medications (ADMs) used in the treatment of type 2 diabetes, may affect the incidence of prostate cancer (PCa). But real-world evidence for this possible effect is lacking. Therefore, the aim of this study is to assess the effect of incretin-based drugs on the incidence of PCa, including glucagon-like peptide-1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors. We searched PubMed, Embase, and Cochrane Library databases for eligible studies through September 2023. Two independent reviewers performed screening and data extraction. We used the Cochrane Handbook for Systematic Reviews and the Newcastle-Ottawa Scale (NOS) to assess the quality of included randomized controlled trials (RCTs) and cohort studies. We did a meta-analysis of available trial data to calculate overall risk ratios (RRs) for PCa. A total of 1238 articles were identified in our search. After screening for eligibility, 7 high-quality studies met the criteria for meta-analysis, including 2 RCTs and 5 cohort studies, with a total of 1165,738 patients. Compared with the control group, we found that incretin-based drugs reduced the relative risk of PCa by 35% (95% confidence interval (CI), 0.17-0.49; P = .0006). In subgroup analysis, the RR values for GLP-1 receptor agonists and DPP-4 inhibitors were 62% (95% CI, 0.45-0.85; P = .003) and 72% (95% CI, 0.46-1.12; P = .14), respectively. Incretin-based drugs are associated with lower incidence of prostate cancer and may have a preventive effect on prostate cancer in patients with type 2 diabetes.


Assuntos
Diabetes Mellitus Tipo 2 , Hipoglicemiantes , Incretinas , Neoplasias da Próstata , Humanos , Masculino , Neoplasias da Próstata/epidemiologia , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/epidemiologia , Incidência , Incretinas/uso terapêutico , Hipoglicemiantes/uso terapêutico , Inibidores da Dipeptidil Peptidase IV/uso terapêutico
2.
Int J STD AIDS ; : 9564624241248676, 2024 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-38644514

RESUMO

This paper seeks to determine the effect of combination anti-PD-1 and antiretroviral therapy (ART) on people living with HIV (PLWH) with advanced gastric cancer. In our case, a PLWH with recurrent locally advanced gastric cancer was treated with anti-PD-1 inhibitor and ART. A significant reduction in tumor lesions (as demonstrated by contrast-enhanced CT imaging) and a better quality of life were achieved following treatment. There have been limited studies on the treatment of PLWH with advanced gastric cancer. Chemotherapy is most often used, however, with unsatisfactory outcomes. to date, there have been no published reports on the use of PD-1 inhibitors in PLWH with advanced gastric cancer. Our report provides a valuable reference for future management of such patients.

3.
Theriogenology ; 221: 25-30, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38537318

RESUMO

The objectives of this study were to analyze the (1) effects of donor age and multiparity on development of in vitro fertilization (IVF) embryos after ovum pickup (OPU), (2) effects of repeated and consecutive OPU-IVF procedures on embryo development, and (3) embryo production from OPU-IVF in donors with differing embryo yields after multiple ovulation and embryo transfer technology (MOET) in Japanese Black cattle (Wagyu). Donors were pre-treated with low-dosage follicle-stimulating hormone (FSH; 200 IU total), and oocytes were collected via OPU and fertilized by IVF to generate blastocysts. The number of oocytes collected per OPU session per donor was lower in heifers (2-4 years old, 5.3 oocytes) than in primiparous and pluriparous cows (2-10 years old, 13.6-19.1 oocytes; P < 0.05). Rates of blastocyst development for oocytes from heifers (33.1%) were lower than for those from cows (2-10 years old, 44.1-54.3%; P < 0.05), and average blastocyst yield/OPU/animal was lower in heifers (3.7) than in 5-6 years old cows (10.1; P < 0.05). Donors undergoing five consecutive OPU-IVF sessions after low-dosage FSH showed similar oocyte retrieval (12.2-15.1 oocytes per OPU/animal), blastocyst development rates (35.6-45.0%), and embryo yield/OPU/animal (4.8-5.8; P > 0.05) across sessions. Additionally, embryo yield from OPU-IVF was significantly improved in animals with previous low embryo yield from MOET (5.9 vs. 2.6, respectively, P < 0.05). These results indicate that Wagyu cows with previous births can be more productive as OPU-IVF donors than heifers, and oocytes from donors undergoing to five consecutive OPU-IVF cycles are competent for embryo development without loss of embryo yield/OPU/animal. Moreover, OPU-IVF can be used for embryo production and breeding from all elite Japanese Black cattle, regardless of previous low embryo yield in routine MOET.


Assuntos
Oócitos , História Reprodutiva , Bovinos , Feminino , Animais , Fertilização in vitro/veterinária , Recuperação de Oócitos/veterinária , Recuperação de Oócitos/métodos , Hormônio Foliculoestimulante/farmacologia , Óvulo
4.
Molecules ; 29(5)2024 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-38474674

RESUMO

All-inorganic cesium copper halide nanocrystals have attracted extensive attention due to their cost-effectiveness, low toxicity, and rich luminescence properties. However, controlling the synthesis of these nanocrystals to achieve a precise composition and high luminous efficiency remains a challenge that limits their future application. Herein, we report the effect of oleylammonium iodide on the synthesis of copper halide nanocrystals to control the composition and phase and modulate their photoluminescence (PL) quantum yields (QYs). For CsCu2I3, the PL peak is centered at 560 nm with a PLQY of 47.3%, while the PL peak of Cs3Cu2I5 is located at 440 nm with an unprecedently high PLQY of 95.3%. Furthermore, the intermediate-state CsCu2I3/Cs3Cu2I5 heterostructure shows white light emission with a PLQY of 66.4%, chromaticity coordinates of (0.3176, 0.3306), a high color rendering index (CRI) of 90, and a correlated color temperature (CCT) of 6234 K, indicating that it is promising for single-component white-light-emitting applications. The nanocrystals reported in this study have excellent luminescence properties, low toxicity, and superior stability, so they are more suitable for future light-emitting applications.

5.
Chem Sci ; 15(8): 2954-2962, 2024 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-38404390

RESUMO

Materials with two or more fluorescence features under different excitation sources have great potential in optical applications, but luminous materials with three emission characteristics have been largely undeveloped. Here, we report a novel zero-dimensional (0D) organic-inorganic hybrid ((C2H5)4N)2ZrCl6 perovskite with multiple emissions. The zirconium-based perovskite exhibits a red emission around 620 nm, a green emission at 527 nm, and a blue emission around 500 nm. The red and green emissions come from self-trapped excitons (STEs) and the d-d transitions of Zr(iv), respectively, which are caused by distortion of the [ZrCl6]2- octahedra. The blue emission is caused by thermally activated delayed fluorescence (TADF), which is similar to that of Cs2ZrCl6. The absolute photoluminescence quantum yield (PLQY) of the red and blue double emission is up to 83% and the PLQY of the green emission is 27%. With different combinations of ((C2H5)4N)2ZrCl6 samples, we achieve a variety of applications, including a two-color luminescent anti-counterfeiting device, a white light-emitting diode (WLED) with a color rendering index (CRI) of 95 and information encryption with different excitations. We also synthesize other hybrid zirconium perovskites with tri-luminescence through a similar method. Our work provides a potential set of excitation-dependent luminescent materials and is expected to expand the basic research and practical applications of multi-luminescence materials.

6.
J Med Virol ; 96(1): e29338, 2024 01.
Artigo em Inglês | MEDLINE | ID: mdl-38163280

RESUMO

Monkeypox (mpox), a viral zoonotic disease, is spreading worldwide. However, evidence that informs prevention and control strategies in the Asia Pacific Region is very limited. Our study aims to investigate the experiences of mpox patients from infection to treatment to provide scientific basis for the prevention and control. A multicenter qualitative design was used. A total of 15 mpox patients were recruited between July 6 and July 25, 2023, from six cities in China. Semistructured interviews were conducted by telephone and analyzed using the thematic analysis. The interview was divided into two sections: patients' experiences (prediagnosis experience, treatment-seeking experience, and quarantine experience) and advice. Prediagnosis experience was summarized into three themes: symptoms, possible routes of infection, and knowledge of mpox. Treatment-seeking experience was summarized into three themes: time of visit to hospital, diagnostic difficulties, and attitude toward diagnosis. Quarantine experience was summarized into three themes: body and mind reactions, reluctance to self-disclose infection status, and factors facilitating recovery. Themes identified from patients' advice were as follows: (1) Increase in testing channels and methods, (2) Development and introduction of vaccines, (3) Adjustment of quarantine program, (4) Improvement of treatment measures, and (5) Improvement of publicity and education. To effectively curb the mpox epidemic, structured measures are urgently needed to address the mpox-related stigma and discrimination. Targeted health education should be provided to MSM, focusing on the prevention, detection, and treatment services. Hospitals should enhance the training of clinicians in key departments including infectious disease and dermatology, to improve diagnostic capability and sensitivity. Furthermore, given the absence of specific antiviral medications, supervised home quarantine may be a good option.


Assuntos
Mpox , Humanos , China/epidemiologia , Ásia , Antivirais , Cidades
7.
J Med Virol ; 95(10): e29198, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-37881113

RESUMO

Human mpox is occurring worldwide, however, evidence from the Asian Pacific Region is limited. In this multicenter cross-sectional study, information of confirmed mpox cases diagnosed between June 1 and July 31, 2023 in China. Information included demographic and epidemiological characteristics, and clinical manifestations, laboratory results, and mental health status of mpox cases. A total of 115 confirmed mpox cases were enrolled. All cases were men. A total of 102 (90.3%) identified as homosexual. The median age was 31.0 years (interquartile range 27.0-36.5). A total of 65 (56.5%) were HIV-positive, of whom 92.3% were receiving antiretroviral therapy (ART). A total of 19/39 (40.4%) had a CD4 cell count <500 cells/µL. Systemic features such as fever (73.0%), lymphadenopathies (49.6%), and myalgia (28.7%) were commonly observed. Skin lesions were present in all participants: 49.6% in the genital area and 27.0% in the perianal area. Vesicular rash (78.3%) and papular rash (44.3%) were the most common lesion morphologies. People living with HIV were more likely to have anxiety than those living without HIV. The majority of mpox cases had primary genital lesions and sexual activities before diagnosis, which supports the likelihood of sexual contact transmission. Guidelines on hospitalization and isolation protocols for mpox patients necessitate further confirmation.


Assuntos
Exantema , Infecções por HIV , Mpox , Adulto , Humanos , Masculino , China/epidemiologia , Estudos Transversais , Nível de Saúde , Infecções por HIV/tratamento farmacológico , Infecções por HIV/epidemiologia
8.
Chem Sci ; 14(20): 5309-5315, 2023 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-37234884

RESUMO

Recently, lead halide perovskite nanocrystals (NCs) have attracted extensive attention due to their unique optical properties. However, the toxicity of lead and the instability to moisture obstruct their further commercial development. Herein, a series of lead-free CsMnX3 (X = Cl, Br, and I) NCs embedded in glasses were synthesized by a high temperature solid-state chemistry method. These NCs embedded in glass can remain stable after soaking in water for 90 days. It is found that increasing the amount of cesium carbonate in the synthesis process can not only prevent the oxidation of Mn2+ to Mn3+ and promote the transparency of glass in the 450-700 nm region, but also significantly increase its photoluminescence quantum yield (PLQY) from 2.9% to 65.1%, which is the highest reported value of the red CsMnX3 NCs so far. Using CsMnBr3 NCs with a red emission peak at 649 nm and full-width-at-half-maximum (FWHM) of 130 nm as the red light source, a white light-emitting diode (LED) device with International Commission on illumination (CIE) coordinates of (0.33, 0.36) and a color rendering index (CRI) of 94 was obtained. These findings, together with future research, are likely to yield stable and bright lead-free NCs for the next generation of solid-state lighting.

9.
Heliyon ; 9(2): e13613, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36852051

RESUMO

Background: Adrenocortical carcinoma (ACC) represents the rare urological epithelial cancer of urinary tract, which has a large mass and is usually diagnosed at the advanced stage, thus inducing the poor prognosis. As a result, early detection and diagnosis are more important for the prognosis rather than the treatment of ACC. There is evidence supporting the association of Sulfatase2 (SULF2) with bladder cancer. However, the relationships of SULF2 with the clinical features and immune infiltration of ACC remain unclear. Methods: This work comprehensively investigated the different expression levels of SULF2 within ACC and its prognostic significance through various databases including Gene Expression Profiling Interaction Analysis (GEPIA), Tumor Immune Estimation Resource (TIMER), The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), Kaplan-Meier (KM) plotter and UALCAN. Besides, SULF2 levels within different tumor and paraneoplastic tissues were examined based on Human Protein Atlas (HPA) and TIMER. Afterwards, this study identified differentially expressed genes (DEGs) in high-compared with low-SULF2-expression groups. To predict the possible interaction between SULF2 and its targets, a protein-protein interaction (PPI) network was constructed based on relevant data collected in STRING database. Besides, the SULF2 functional annotation was carried out, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and GSEA. In addition, gene mutation analysis was also performed based on the cBioPortal database. The relation of SULF2 with immune infiltration was analyzed from various aspects by using the resources of various databases including TIMER, TISIDB, and GEPIA, which was first reported in this work. Finally, R package was utilized to plot the receiver operating characteristic (ROC) curves of diagnosis, time-dependent survival, and the association of SULF2 with cancer stage and the nomogram model. Finally, CellMiner dataset was adopted for SULF2 correlation as well as drug sensitivity analysis. Results: Relative to healthy people, SULF2 level markedly elevated within ACC tissues. Besides, SULF2 up-regulation significantly predicted the dismal prognostic outcome, which may be an important prognostic factor. Afterwards, the PPI network was constructed, and the possible link of SULF2 with the corresponding targets was predicted. Besides, up-regulated SULF2 expression was tightly related to immune regulation and tumor-infiltration immune cell (TIICs), including CD8+, CD4+ and mast cells. Finally, SULF2 expression was speculated to help determine the sensitivity of certain drugs. Conclusions: SULF2 may offer a new therapeutic target for ACC patients and become an important potential prognostic biomarker.

10.
J Phys Chem Lett ; 14(7): 2006-2011, 2023 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-36794832

RESUMO

The absorption and photoluminescence (PL) of CsMnBr3 with Mn(II) in octahedral crystal fields are extremely weak due to a d-d forbidden transition. Herein, we introduce a facile and general synthetic procedure that can prepare undoped and heterometallic doped CsMnBr3 NCs at room temperature. Importantly, both PL and absorption of CsMnBr3 NCs were significantly improved after doping a small amount of Pb2+ (4.9%). The absolute photoluminescence quantum yield (PL QY) of Pb-doped CsMnBr3 NCs is up to 41.5%, 11-fold higher than undoped CsMnBr3 NCs (3.7%). The PL enhancement is attributed to the synergistic effects between [MnBr6]4- units and [PbBr6]4- units. Furthermore, we verified the similar synergistic effects between [MnBr6]4- units and [SbBr6]4- units in Sb-doped CsMnBr3 NCs. Our results highlight the potential of tailoring luminescence properties of manganese halides through heterometallic doping.

11.
Chemistry ; 29(10): e202202675, 2023 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-36599805

RESUMO

In order to achieve a high color-rendering index (CRI) and low correlated color temperature (CCT) indoor lighting, single-component phosphors with broad-band dual emission are in high demand for white-light-emitting diodes (WLEDs). However, phosphors with such fluorescent properties are rare at present. Herein, we report a facile solid-state chemical method for the synthesis of single-component phosphor with broad-band emission and a large Stokes shift that can meet the requirements of future white-light sources. These new tetrabutylammonium copper halides phosphors have excellent warm white emission characteristics, and their luminescence peaks are located at 494 and 654 nm. The optimized photoluminescence (PL) quantum yield can reach 93.7 %. The typical CIE coordinate of the as-fabricated WLED is at (0.3620, 0.3731) with a CRI of 89 and low CCT of 4516 K.

12.
Nanoscale ; 15(4): 1661-1668, 2023 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-36598774

RESUMO

The synthesis of α-CsPbI3 perovskite quantum dots (QDs) with pure red emission around 630 nm is in high demand for display backlight application. However, the phase transition of α-CsPbI3 to yellow non-emitting δ-CsPbI3 has been proven to be a great challenge for the classic colloidal synthesis route for perovskite QDs in octadecene (ODE). Herein, we report a novel colloidal synthesis route by replacing ODE with lauryl methacrylate (LMA) as the reaction solvent to improve the solubility of precursors, resulting in small sized α-CsPbI3 QDs with a diameter of only 4.2 nm, which are the smallest red PQDs reported so far. The corresponding CsPbI3 QD films exhibit a tunable photoluminescence (PL) emission peak in the bright pure red region of 627 to 638 nm. The CsPbI3 QD polymer composite films with PL emission at 630 nm exhibit a superior photoluminescence quantum yield (PLQY) and photostability to mixed halide CsPbBrI2 films under intense illumination. Perovskite light emitting diodes (LED) with the color gamut reaching 96% of the Rec. 2020 standard are achieved using these films. This study provides a high-performance pure red fluorescent material with a robust, low-cost, and reproducible colloidal chemistry that will pave the way for the adoption of perovskite QDs in display backlight application.

13.
Materials (Basel) ; 15(23)2022 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-36499961

RESUMO

Understanding the coupling between electrons and phonons in iron chalcogenides FeTexSe1-x has remained a critical but arduous project in recent decades. The direct observation of the electron-phonon coupling effect through electron dynamics and vibrational properties has been lacking. Here, we report the first pressure-dependent ultrafast photocarrier dynamics and Raman scattering studies on an iron chalcogenide FeTe0.5Se0.5 to explore the interaction between electrons and phonons in this unconventional superconductor. The lifetime of the excited electrons evidently decreases as the pressure increases from 0 to 2.2 GPa, and then increases with further compression. The vibrational properties of the A1g phonon mode exhibit similar behavior, with a pronounced frequency reduction appearing at approximately 2.3 GPa. The dual evidence reveals the enhanced electron-phonon coupling strength with pressure in FeTe0.5Se0.5. Our results give an insight into the role of the electron-phonon coupling effect in iron-based superconductors.

14.
Heliyon ; 8(10): e10884, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36267366

RESUMO

Objective: To evaluate the effectiveness and safety of transurethral resection of the prostate (TURP), holmium laser enucleation of the prostate (HoLEP) and thulium laser enucleation of the prostate (ThuLEP) in the treatment of benign prostatic hyperplasia using a network Meta-analysis. Methods: Randomized controlled trials of TURP, HoLEP and ThuLEP for benign prostatic hyperplasia were collected by computerized searches of databases including CNKI, WANFANG, VIP, PubMed, The Cochrane Library, the Web of Science and Embase, with a search time frame of build to January 2022. The literature was screened and data was extracted by two investigators separately, while the risk of bias of the included studies was evaluated before systematic evaluation and network meta-analysis using ADDIS 1.16.8 software and RevMan 5.3 software. Results: A total of 27 RCTs with a total of 3335 patients were involved. The results of the network meta-analysis showed that ThuLEP was better than the remaining two procedures in terms of enhancing patients' subjective perception and improving objective indicators, and the incidence of adverse events such as postoperative urethral stricture and urinary incontinence was lower compared with that of conventional TURP in both short- and long-term postoperative follow-ups. Conclusion: As ThuLEP is effective, safe, and featured with few postoperative complications, it can be the preferred surgical procedure for prostate enlargement. Nevertheless, because of the limited number of studies included, more-sample, multicenter, double-blind clinical randomized controlled trials are required in the future to further verify the findings of the present study.

15.
Front Oncol ; 12: 923307, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36172162

RESUMO

Alterations in tryptophan (Trp) metabolism facilitate the continuous modulation of tumor progression, including tumor growth, distant metastasis, and chemoresistance development. Although there is a high correlation between Trp metabolism and tumor progression, it is unknown whether and how Trp metabolism affects the development of prostate cancer. In this study, we reported that the overexpression of Trp hydroxylase 1 (TPH1) caused the upregulation of Trp hydroxylation and mediated the production of 5-hydroxytryptamine (5-HT), contributing to tumor growth and poor prognosis in patients with prostate cancer. An increase in 5-HT levels triggered the activation of the Axin 1/ß-catenin signaling pathway, thus enhancing cell proliferation and migration. Consequently, ß-catenin cooperated with the Krüppel-type zinc finger family transcription factor ZBP-89 to upregulate TPH1 expression, further promoting Trp hydroxylation and forming the TPH1/5-HT/ß-catenin/ZBP-89/THP1 positive feedback signaling loop. Interruption of the signaling loop by the THP1 inhibitor 4-chloro-dl-phenylalanine (PCPA) significantly improved anticancer effects and suppressed lung metastasis in prostate cancer-bearing mice. Our findings revealed a mechanism by which TPH1 promotes prostate cancer growth by inducing Trp hydroxylation and identified a novel THP1 target for an innovative prostate cancer therapeutic strategy.

16.
Nat Mater ; 20(12): 1650-1656, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34413490

RESUMO

Emergent relativistic quasiparticles in Weyl semimetals are the source of exotic electronic properties such as surface Fermi arcs, the anomalous Hall effect and negative magnetoresistance, all observed in real materials. Whereas these phenomena highlight the effect of Weyl fermions on the electronic transport properties, less is known about what collective phenomena they may support. Here, we report a Weyl semimetal, NdAlSi, that offers an example. Using neutron diffraction, we found a long-wavelength helical magnetic order in NdAlSi, the periodicity of which is linked to the nesting vector between two topologically non-trivial Fermi pockets, which we characterize using density functional theory and quantum oscillation measurements. We further show the chiral transverse component of the spin structure is promoted by bond-oriented Dzyaloshinskii-Moriya interactions associated with Weyl exchange processes. Our work provides a rare example of Weyl fermions driving collective magnetism.

17.
Phys Rev Lett ; 126(10): 107203, 2021 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-33784157

RESUMO

Neutron spectroscopy on the classical triangular-lattice frustrated antiferromagnet h-YMnO_{3} reveals diffuse, gapless magnetic excitations present both far below and above the ordering temperature. The correlation length of the excitations increases as the temperature approaches zero, bearing a strong resemblance to critical scattering. We model the dynamics in the ordered and correlated disordered phase as critical spin correlations in a two-dimensional magnetic state. We propose that our findings may provide a general framework to understand features often attributed to classical spin liquids.

18.
Nat Mater ; 20(7): 977-983, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33723420

RESUMO

Lead halide perovskites exhibit structural instabilities and large atomic fluctuations thought to impact their optical and thermal properties, yet detailed structural and temporal correlations of their atomic motions remain poorly understood. Here, these correlations are resolved in CsPbBr3 crystals using momentum-resolved neutron and X-ray scattering measurements as a function of temperature, complemented with first-principles simulations. We uncover a striking network of diffuse scattering rods, arising from the liquid-like damping of low-energy Br-dominated phonons, reproduced in our simulations of the anharmonic phonon self-energy. These overdamped modes cover a continuum of wave vectors along the edges of the cubic Brillouin zone, corresponding to two-dimensional sheets of correlated rotations in real space, and could represent precursors to proposed two-dimensional polarons. Further, these motions directly impact the electronic gap edge states, linking soft anharmonic lattice dynamics and optoelectronic properties. These results provide insights into the highly unusual atomic dynamics of halide perovskites, relevant to further optimization of their optical and thermal properties.

19.
Phys Rev Lett ; 127(27): 277206, 2021 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-35061439

RESUMO

Reentrance, the return of a system from an ordered phase to a previously encountered less-ordered one as a controlled parameter is continuously varied, is a recurring theme found in disparate physical systems, yet its microscopic cause is often not investigated thoroughly. Here, through detailed characterization and theoretical modeling, we uncover the microscopic mechanism behind reentrance in the strongly frustrated pyrochlore antiferromagnet Er_{2}Sn_{2}O_{7}. We use single crystal heat capacity measurements to expose that Er_{2}Sn_{2}O_{7} exhibits multiple instances of reentrance in its magnetic field B vs temperature T phase diagram for magnetic fields along three cubic high symmetry directions. Through classical Monte Carlo simulations, mean field theory, and classical linear spin-wave expansions, we argue that the origins of the multiple occurrences of reentrance observed in Er_{2}Sn_{2}O_{7} are linked to soft modes. These soft modes arise from phase competition and enhance thermal fluctuations that entropically stabilize a specific ordered phase, resulting in an increased transition temperature for certain field values and thus the reentrant behavior. Our work represents a detailed examination into the mechanisms responsible for reentrance in a frustrated magnet and may serve as a template for the interpretation of reentrant phenomena in other physical systems.

20.
Phys Rev Mater ; 5(2)2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38487078

RESUMO

The coupling between the organic CH3NH3+ cations and inorganic perovskite PbBr3- framework in a large single crystal of (CH3NH3)PbBr3 weighting 13 g was studied using neutron diffraction and inelastic neutron scattering. Two lattice incommensurate (ICM) phases were found, one at higher temperatures, marked ICMHT, which appeared between 147 and 135 K. The second one, marked ICMLT, developed below 143 K and remained at 75 K. The transition from the ICMLT to ICMHT phase upon warming gave rise to extremely large lattice shrinking, followed by extremely large lattice expansion of the tetragonal basal plane of the PbBr3 lattice. There was a progressive decrease in the width of the Bragg peaks from the PbBr3 lattice upon warming, which can be described using a critical exponent for each type of Bragg peak to show complete ordering of the atoms into a (CH3NH3)PbBr3 lattice at 194 K. (CH3NH3)PbBr3 exhibits six definitive acoustic-like phonon branches at 75 K. The six branches renormalizes into two at 200 K, with the frequencies of both the transverse and longitudinal modes greatly enhanced. The asymmetric structure of the CH3NH3 ions helps to understand the observed behaviors.

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