Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 107
Filtrar
1.
PeerJ ; 12: e16874, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38406287

RESUMO

Low-grade glioma (LGG), a common primary tumor, mainly originates from astrocytes and oligodendrocytes. Increasing evidence has shown that peroxisomes function in the regulation of tumorigenesis and development of cancer. However, the prognostic value of peroxisome-related genes (PRGs) in LGG has not been reported. Therefore, it is necessary to construct a prognostic risk model for LGG patients based on the expression profiles of peroxisome-related genes. Our study mainly concentrated on developing a peroxisome-related gene signature for overall survival (OS) prediction in LGG patients. First, according to these peroxisome-related genes, all LGG patients from The Cancer Genome Atlas (TCGA) database could be divided into two subtypes. Univariate Cox regression analysis was used to find prognostic peroxisome-related genes in TCGA_LGG dataset, and least absolute shrinkage and selection operator Cox regression analysis was employed to establish a 14-gene signature. The risk score based on the signature was positively associated with unfavorable prognosis. Then, multivariate Cox regression incorporating additional clinical characteristics showed that the 14-gene signature was an independent predictor of LGG. Time-dependent ROC curves revealed good performance of this prognostic signature in LGG patients. The performance about predicting OS of LGG was validated using the GSE107850 dataset derived from the Gene Expression Omnibus (GEO) database. Furethermore, we constructed a nomogram model based on the gene signature and age, which showed a better prognostic power. Gene ontology (GO) and Kyoto Encylopedia of Genes and Genomes (KEGG) analyses showed that neuroactive ligand-receptor interaction and phagosome were enriched and that the immune status was decreased in the high-risk group. Finally, cell counting kit-8 (CCK8) were used to detect cell proliferation of U251 and A172 cells. Inhibition of ATAD1 (ATPase family AAA domain-containing 1) and ACBD5 (Acyl-CoA binding-domain-containing-5) expression led to significant inhibition of U251 and A172 cell proliferation. Flow cytometry detection showed that ATAD1 and ACBD5 could induce apoptosis of U251 and A172 cells. Therefore, through bioinformatics methods and cell experiments, our study developed a new peroxisome-related gene signature that migh t help improve personalized OS prediction in LGG patients.


Assuntos
Glioma , Peroxissomos , Humanos , Peroxissomos/genética , Glioma/genética , Domínio AAA , Adenosina Trifosfatases , Apoptose , Microambiente Tumoral/genética
2.
Cancer Rep (Hoboken) ; 6(12): e1911, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37827990

RESUMO

BACKGROUND: Carbohydrate antigen (CA) 19-9 and histological grade can serve as indicators of the biological characteristics of pancreatic ductal adenocarcinoma (PDAC). AIMS: The aim of this study was to investigate the combined impact of preoperative CA19-9 levels and histological grade on prognosis and classification accuracy in PDAC patients. METHODS AND RESULTS: A retrospective cohort study was conducted on 612 patients with PDAC who underwent curative pancreatectomy, and a biological risk model based on preoperative CA19-9 levels and histology grade was established. The prognostic importance of the biological risk model was evaluated, and its validity was confirmed through a validation cohort of 218 patients. The survival of patients with PDAC was independently associated with preoperative CA19-9 levels and histology grade, indicating a biological risk. This biological risk was incorporated into the eighth edition of the TNM staging system, leading to the development of a modified TNM (mTNM) staging system. Receiver operating characteristic (ROC) curves demonstrated that the mTNM staging system had a significantly larger area under the curve (AUC) than the TNM staging system. The discriminatory capacity of the mTNM staging system was further validated in an independent cohort. CONCLUSION: Biological risk based on preoperative CA19-9 and histological grade could predict the survival of patients with PDAC. The incorporation of biological risk into the TNM staging system has the potential to enhance the accuracy of patient classification in PDAC, predicting patient survival and enabling the development of individualized treatment plans.


Assuntos
Adenocarcinoma , Carcinoma Ductal Pancreático , Neoplasias Pancreáticas , Humanos , Antígeno CA-19-9 , Estudos Retrospectivos , Neoplasias Pancreáticas/diagnóstico , Neoplasias Pancreáticas/cirurgia , Carcinoma Ductal Pancreático/diagnóstico , Carcinoma Ductal Pancreático/cirurgia , Prognóstico
3.
Biomed Pharmacother ; 165: 115267, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37542851

RESUMO

Cardiac ventricular arrhythmia triggered by acute myocardial infarction (AMI) is a major cause of sudden cardiac death. We have reported previously that an increased serum level of circular RNA CDR1as is a potential biomarker of AMI. However, the possible role of CDR1as in post-infarct arrhythmia remains unclear. This study in MI mice investigated the effects and underlying mechanism of CDR1as in ventricular arrhythmias associated with MI. We showed that knockdown of CDR1as abbreviated the duration of the abnormally prolonged QRS complex and QTc intervals and decreased susceptibility to ventricular arrhythmias. Optical mapping demonstrated knockdown of CDR1as also reduced post-infarct arrhythmia by increasing the conduction velocity and decreasing dispersion of repolarization. Mechanistically, CDR1as led to the depletion of NAD+ and caused mitochondrial dysfunction by directly targeting the NAMPT protein and repressing its expression. Moreover, CDR1as aggravated dysregulation of the NaV1.5 and Kir6.2 channels in cardiomyocytes, a change which was alleviated by the replenishment of NAD+. These findings suggest that anti-CDR1as is a potential therapeutic approach for ischemic arrhythmias.


Assuntos
Infarto do Miocárdio , NAD , Camundongos , Animais , Nicotinamida Fosforribosiltransferase/genética , Arritmias Cardíacas/etiologia , Morte Súbita Cardíaca/etiologia
4.
Altern Ther Health Med ; 29(8): 292-296, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37573603

RESUMO

Aim: To compare the efficacy of arthroscopic debridement and olecranon fossa augmentation plasty in patients with elbow osteoarthritis. Methods: Eighty-four patients with elbow osteoarthritis admitted to our hospital were randomly divided into two groups with 42 cases in each group. Patients in the control group received expanded olecranon fossa plasty, while those in the observation group underwent arthroscopic debridement. Then the elbow joint function, VAS score, stress level, and incidence of complications were compared between the two groups. Results: The MEPS score, ROM level, and VAS score, as well as the expression of TNF-α, IL-6, and ACTH between the two groups, were significantly different before and after surgery (P < .05). Moreover, compared to patients in the control group, the MEPS score and ROM level of patients in the observation group were higher than those in the control group after six months since surgery, while VAS score, the levels of TNF-α, IL-6, and ACTH were lower on the second day after surgery (P < .05). Conclusion: Arthroscopic cleaning is more helpful in improving elbow joint function and alleviating pain in patients with osteoarthritis of the elbow compared to olecranon fossa augmentation and reconstruction surgery.


Assuntos
Cotovelo , Osteoartrite , Humanos , Hormônio Adrenocorticotrópico , Artroscopia , Desbridamento , Úmero , Interleucina-6 , Osteoartrite/cirurgia , Amplitude de Movimento Articular , Estudos Retrospectivos , Resultado do Tratamento , Fator de Necrose Tumoral alfa
5.
Updates Surg ; 75(7): 2043-2046, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37432569

RESUMO

Presacral venous bleeding (PSVB) is an intractable situation during rectal mobilization. Till now, various methods for PSVB are introduced, but each of them has limitations. This article aims to introduce an effective approach for PSVB, which is created by Professor Xiaogang Bi. In the case of PSVB, a purse-string suture which highlighted each stitch penetrates periosteum of sacrum was performed around the bleeding site. After that, the branches of presacral venous plexus around the bleeding site were compressed to the sacrum when the stitches were tightened, the blood flow of the venous branches was blocked by the thread across them, the bleeding was controlled, and then, the knot was tied. From April 24th 2017 to November 6th 2022, ten patients who suffered PSVB during surgery accepted Bi's suture. With Bi's suture, all of the ten cases of PSVB were controlled effectively. Nine of ten cases were controlled immediately only by Bi's suture, one case which accompanied with blood oozing of sacrum wound was controlled by Bi's suture, bone wax, and pelvic gauze packing. Bi's suture is an effective approach for PSVB. It could be easily performed without the need of special materials.

6.
Food Chem ; 426: 136604, 2023 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-37348402

RESUMO

A ternary deep eutectic solvent (DES) consisting of choline chloride, lactic acid, and urea in a molar ratio of 1:2:2 was used to pretreat chamomile residue, followed by carbon dots (CDs) preparation using a one-pot solvothermal method. The CDs prepared under the suitable conditions had a high quantum yield of 47.34% and could be used as a bifunctional fluorescent probe for the detection of tartrazine and Fe(III). The concentration of tartrazine or Fe(III) had a good linear relationship with the fluorescence intensity of CDs that the determination coefficient (R2) was 0.9957 and 0.9943, and the limit of detection (LOD) was 40 nM and 119 nM, respectively. After verifying the different fluorescence quenching mechanisms of CDs by these two substances, a quantitative analysis was performed on real samples with recoveries of 90.70%∼104.29%. Overall, this study provided a promising technology for chemical conversion from low-cost chamomile residue to attractive bifunctional fluorescent probe.


Assuntos
Pontos Quânticos , Tartrazina , Tartrazina/análise , Compostos Férricos , Pontos Quânticos/química , Carbono/química , Corantes Fluorescentes/química , Camomila , Espectrometria de Fluorescência/métodos
7.
Chem Commun (Camb) ; 59(31): 4680-4683, 2023 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-36995105

RESUMO

Possessing dual-targeted agents toward the lysosome and cancer cells, a ternary supramolecular assembly was constructed by a morpholine-modified permethyl ß-cyclodextrin, sulfonated porphyrin, and folic acid-modified chitosan via multivalent interactions. As compared with free porphyrin, the obtained ternary supramolecular assembly showed promoted photodynamic effect and achieved dual-targeted precise imaging in cancer cells.


Assuntos
Antineoplásicos , Nanopartículas , Porfirinas , beta-Ciclodextrinas , Antineoplásicos/farmacologia , Porfirinas/farmacologia , Morfolinas/farmacologia
8.
Oper Neurosurg (Hagerstown) ; 24(4): 341-349, 2023 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-36716051

RESUMO

BACKGROUND: Percutaneous trigeminal rhizotomy (PTR) is a widely used procedure for trigeminal neuralgia. However, comprehensive analyses that combine anatomic, radiological, and surgical considerations are rare. OBJECTIVE: To present high-quality anatomic dissections and radiological studies that highlight the technical nuances of this procedure. METHODS: Six silicon-injected postmortem heads underwent PTR. The surgical corridors were dissected, and the neurovascular relationships were studied. In addition, 20 dried human skulls and 50 computed tomography angiography and MRI scans were collected to study the anatomic relationships for a customized puncture corridor. RESULTS: The PTR corridor was divided into 3 segments: the buccal segment (length, 34.76 ± 7.20 mm), the inferior temporal fossa segment (length, 42.06 ± 6.92 mm), and the Meckel cave segment (length, 24.75 ± 3.34 mm). The puncture sagittal (α) and axial (ß) angles measured in this study were 38.32° ± 4.62° and 19.13° ± 2.82°, respectively. The precondylar reference line coincided with the foramen ovale in 75% of the computed tomography angiography scans, and the postcondylar line coincided with the carotid canal in 70% of the computed tomography angiography scans; these lines serve as the intraoperative landmarks for PTR. The ovale-carotid-pterygoid triangle, delineated by drawing a line from the foramen ovale to the carotid canal and the lateral pterygoid plate, is a distinguished landmark to use for avoiding neurovascular injury during fluoroscopy. CONCLUSION: Knowledge of the anatomic and radiological features of PTR is essential for a successful surgery, and a customized technical flow is a safe and effective way to access the foramen ovale.


Assuntos
Rizotomia , Neuralgia do Trigêmeo , Humanos , Rizotomia/métodos , Radiografia , Neuralgia do Trigêmeo/diagnóstico por imagem , Neuralgia do Trigêmeo/cirurgia , Osso Esfenoide , Cadáver
9.
Phys Rev Lett ; 129(23): 237202, 2022 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-36563188

RESUMO

Competition among exchange interactions is able to induce novel spin correlations on a bipartite lattice without geometrical frustration. A prototype example is the spiral spin liquid, which is a correlated paramagnetic state characterized by subdimensional degenerate propagation vectors. Here, using spectral graph theory, we show that spiral spin liquids on a bipartite lattice can be approximated by a further-neighbor model on the corresponding line-graph lattice that is nonbipartite, thus broadening the space of candidate materials that may support the spiral spin liquid phases. As illustrations, we examine neutron scattering experiments performed on two spinel compounds, ZnCr_{2}Se_{4} and CuInCr_{4}Se_{8}, to demonstrate the feasibility of this new approach and expose its possible limitations in experimental realizations.

10.
Front Public Health ; 10: 1029962, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36568781

RESUMO

Introduction: We aim to explore the association between chronic kidney disease (CKD) and cataracts. Methods: A total of 121,380 participants with adequate information collected from 29 community-based recruitment centers since 2008 were analyzed. The association between CKD and self-reported diagnosed cataracts was examined in a cross-sectional cohort and was validated in a longitudinal cohort of 25,263 participants without cataracts at baseline. Results and discussion: Of all participants, cataracts occurred in 503/1,947 (26%) and 10,464/119,433 (9%) subjects in the CKD and non-CKD groups, respectively. Multivariate logistic regression showed that CKD was significantly associated with a higher prevalence of self-reported diagnosed cataracts. In the validation cohort, a higher incidence of cataracts was also noted in the CKD group (65/317, 21%) compared to the non-CKD group (1,964/24,252, 8%) during a mean 47-month follow-up. After adjusting for confounders, subjects with CKD had a 1.498-fold higher risk of incident cataracts than those without CKD (95% confidence interval = 1.114 to 2.013, p value = 0.007). We found that CKD was associated with a higher prevalence of cataracts as well as incident cataracts, which suggests CKD patients and their primary physicians should be aware of this disease and can provide a clue for further exploration of the possible mechanisms and treatments.


Assuntos
Catarata , Insuficiência Renal Crônica , Humanos , Estudos Longitudinais , Estudos Transversais , Fatores de Risco , Taxa de Filtração Glomerular , Insuficiência Renal Crônica/epidemiologia , Catarata/epidemiologia
11.
Rev Sci Instrum ; 93(10): 103903, 2022 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-36319315

RESUMO

M-STAR is a next generation polarized neutron reflectometer with advanced capabilities. A new focusing guide concept is optimized for samples with dimensions down to a millimeter range. A proposed hybrid pulse-skipping chopper will enable experiments at constant geometry at one incident angle in a broad range of wavevector transfer Q up to 0.3 A-1 for specular, off-specular, and GISANS measurements. M-STAR will empower nanoscience and spintronics studies routinely on small samples (∼2 × 2 mm2) and of atomic-scale thickness using versatile experimental conditions of magnetic and/or electric fields, light, and temperature applied in situ to novel complex device-like nanosystems with multiple buried interfaces. M-STAR will enable improved grazing incidence diffraction measurements, as a surface-sensitive depth-resolved probe of, e.g., the out-of-plane component of atomic magnetic moments in ferromagnetic, antiferromagnetic, and more complex structures as well as in-plane atomic-scale structures inaccessible with contemporary diffractometry and reflectometry. New horizons will be opened by the development of an option to probe near-surface dynamics with inelastic grazing incidence scattering in the time-of-flight mode. These novel options in combination with ideally matched parameters of the second target station will place M-STAR in the world's leading position for high resolution polarized reflectometry.

12.
Int J Med Sci ; 19(10): 1596-1602, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36185328

RESUMO

We aimed to investigate the association between habitual tea consumption and the risk of developing cataracts in a large community-based cohort study. We prospectively collected volunteers from 29 recruitment centers that were ≧ 55 years old with no history of cataracts at the beginning of the study. There were 12,080 participants with available information in our study and were divided into two groups according to habitual tea consumption; non-tea-drinking and tea-drinking groups. The mean age was 59 years. Compared to the non-tea-drinking group, the tea-drinking group had a significantly lower incidence of developing cataracts (15.5% vs 12.1%) during follow-up of 46 months. In multivariate Cox proportional hazards regression analysis, the relative risk (RR) of incident cataracts was lower in the tea-drinking group than the non-tea-drinking group (RR = 0.848; 95% confidence interval [CI] = 0.751 to 0.957). Participants with ≧ 2 cups per day were associated with almost 16% reduction in the risk of developing cataracts compared with the non-tea-drinking group (RR = 0.844; 95% CI = 0.741 to 0.961). Our study suggests that habitual tea consumption can reduce the incidence of cataracts and raises the possibility that the tea content may slow the progression of cataracts.


Assuntos
Catarata , Catarata/epidemiologia , Catarata/etiologia , Catarata/prevenção & controle , Estudos de Coortes , Humanos , Incidência , Estudos Longitudinais , Pessoa de Meia-Idade , Risco , Fatores de Risco
13.
J Mater Chem B ; 10(39): 8058-8063, 2022 10 12.
Artigo em Inglês | MEDLINE | ID: mdl-36111529

RESUMO

Highly efficient discrimination between cancer cells and normal cells is full of challenges for precise diagnosis. Herein, we report an effective in situ-activated phosphorescence energy transfer supramolecular assembly constructed by a bromophenyl pyridine derivative (BPPY), cucurbit[8]uril (CB[8]), and rhodamine B-grafted hyaluronic acid (HAR) through noncovalent interaction. As compared with BPPY, CB[8] encapsulated two BPPY molecules, resulting in a biaxial pseudorotaxane supramolecular assembly showing purely organic room-temperature phosphorescence induced by macrocyclic confinement, which when further co-assembled with HAR, formed a multivalent supramolecular assembly with phosphorescence energy transfer. Benefitting from the targeting of hyaluronic acid and the cyclolactam ring ON-OFF reaction of HAR, such supramolecular assembly with an open ring presents red delayed fluorescence through phosphorescence energy transfer in cancer cells, while the assembly showed only green phosphorescence in normal cells, realizing highly efficient discrimination between cancer and normal cells. This supramolecular assembly is responsive to the physiological environment and provides a supramolecular platform for precise diagnosis.


Assuntos
Neoplasias , Rotaxanos , Hidrocarbonetos Aromáticos com Pontes , Transferência de Energia , Ácido Hialurônico , Imidazóis , Neoplasias/diagnóstico por imagem , Piridinas
14.
J Med Chem ; 65(19): 13473-13481, 2022 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-36102846

RESUMO

The advent of macrocycle-based supramolecular chemistry can offer powerful strategies for regulating vital bioactivities in living systems and bring about emerging technology in biomedical science. Herein, we construct a supra-biomacromolecular nanosystem involving microtubules, cell-permeable porphyrins, and antimitotic peptide-decorated permethyl-ß-cyclodextrins for promoting cell apoptosis in a cooperative manner. Through specific polypeptide-tubulin recognition, cyclodextrin moieties are capable of anchoring to the tubulin surface and providing abundant hydrophobic microenvironments to accommodate the photosensitive porphyrins. Consequently, spherical tubulin aggregates are formed, and reactive oxygen species can be efficiently generated via the host-guest complexation. The combined usage of complexation-promoted photodynamic efficacy and tubulin aggregation gives more serious cell apoptosis under light irradiation in vitro and in vivo. To be envisioned, this supramolecularly enhanced photodynamic performance together with controlled aggregation of natural biomacromolecules may be developed as an innovative approach to improve the therapeutic potency against many diseases.


Assuntos
Antimitóticos , Ciclodextrinas , Neoplasias , Porfirinas , beta-Ciclodextrinas , Ciclodextrinas/química , Humanos , Neoplasias/tratamento farmacológico , Peptídeos/farmacologia , Porfirinas/química , Porfirinas/farmacologia , Medicina de Precisão , Espécies Reativas de Oxigênio , Tubulina (Proteína) , Microambiente Tumoral , beta-Ciclodextrinas/química
15.
Rev Sci Instrum ; 93(7): 073901, 2022 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-35922293

RESUMO

PIONEER is a high Q-resolution, single-crystal, polarized neutron diffractometer at the Second Target Station (STS), Oak Ridge National Laboratory. It will provide the unprecedented capability of measuring tiny crystals (0.001 mm3, i.e., x-ray diffraction size), ultra-thin films (10 nm thickness), and weak structural and magnetic transitions. PIONEER benefits from the increased peak brightness of STS cold-neutron sources and uses advanced Montel mirrors that are able to deliver a focused beam with a high brilliance transfer, a homogeneous profile, and a low background. Monte Carlo simulations suggest that the optimized instrument has a high theoretical peak brilliance of 2.9 × 1012 n cm-2 sr-1 Å-1 s-1 at 2.5 Å at the sample position, within a 5 × 5 mm2 region and a ±0.3° divergence range. The moderator-to-sample distance is 60 m, providing a nominal wavelength band of 4.3 Å with a wavelength resolution better than 0.2% in the wavelength range of 1.0-6.0 Å. PIONEER is capable of characterizing large-scale periodic structures up to 200 Å. With a sample-to-detector distance of 0.8 m, PIONEER accommodates various sample environments, including low/high temperature, high pressure, and high magnetic/electric field. A large cylindrical detector array (4.0 sr) with a radial collimator is planned to suppress the background scattering from sample environments. Bottom detector banks provide an additional 0.4 sr coverage or can be removed if needed to accommodate special sample environments. We present virtual experimental results to demonstrate the scientific performance of PIONEER in measuring tiny samples.

16.
Neurosci Bull ; 38(11): 1277-1291, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-35788510

RESUMO

The choice of females to accept or reject male courtship is a critical decision for animal reproduction. Serotonin (5-hydroxytryptamine; 5-HT) has been found to regulate sexual behavior in many species, but it is unclear how 5-HT and its receptors function to regulate different aspects of sexual behavior. Here we used Drosophila melanogaster as the model animal to investigate how 5-HT and its receptors modulate female sexual receptivity. We found that knockout of tryptophan hydroxylase (Trh), which is involved in the biosynthesis of 5-HT, severely reduced virgin female receptivity without affecting post-mating behaviors. We identified a subset of sexually dimorphic Trh neurons that co-expressed fruitless (fru), in which the activity was correlated with sexual receptivity in females. We also found that 5-HT1A and 5-HT7 receptors regulate virgin female receptivity. Our findings demonstrate how 5-HT functions in sexually dimorphic neurons to promote virgin female receptivity through two of its receptors.


Assuntos
Proteínas de Drosophila , Drosophila , Animais , Masculino , Feminino , Drosophila/fisiologia , Drosophila melanogaster/fisiologia , Serotonina , Proteínas de Drosophila/fisiologia , Comportamento Sexual Animal/fisiologia , Fatores de Transcrição , Proteínas do Tecido Nervoso
18.
Proc Natl Acad Sci U S A ; 119(28): e2119942119, 2022 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-35787036

RESUMO

We report results of low-temperature heat-capacity, magnetocaloric-effect, and neutron-diffraction measurements of TmVO4, an insulator that undergoes a continuous ferroquadrupolar phase transition associated with local partially filled 4f orbitals of the thulium (Tm[Formula: see text]) ions. The ferroquadrupolar transition, a realization of Ising nematicity, can be tuned to a quantum critical point by using a magnetic field oriented along the c axis of the tetragonal crystal lattice, which acts as an effective transverse field for the Ising-nematic order. In small magnetic fields, the thermal phase transition can be well described by using a semiclassical mean-field treatment of the transverse-field Ising model. However, in higher magnetic fields, closer to the field-tuned quantum phase transition, subtle deviations from this semiclassical behavior are observed, which are consistent with expectations of quantum fluctuations. Although the phase transition is driven by the local 4f degrees of freedom, the crystal lattice still plays a crucial role, both in terms of mediating the interactions between the local quadrupoles and in determining the critical scaling exponents, even though the phase transition itself can be described via mean field. In particular, bilinear coupling of the nematic order parameter to acoustic phonons changes the spatial and temporal fluctuations of the former in a fundamental way, resulting in different critical behavior of the nematic transverse-field Ising model, as compared to the usual case of the magnetic transverse-field Ising model. Our results establish TmVO4 as a model material and electronic nematicity as a paradigmatic example for quantum criticality in insulators.

19.
Nat Commun ; 13(1): 3073, 2022 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-35654798

RESUMO

Quantum phase transitions in quantum matter occur at zero temperature between distinct ground states by tuning a nonthermal control parameter. Often, they can be accurately described within the Landau theory of phase transitions, similarly to conventional thermal phase transitions. However, this picture can break down under certain circumstances. Here, we present a comprehensive study of the effect of hydrostatic pressure on the magnetic structure and spin dynamics of the spin-1/2 ladder compound C9H18N2CuBr4. Single-crystal heat capacity and neutron diffraction measurements reveal that the Néel-ordered phase breaks down beyond a critical pressure of Pc ∼ 1.0 GPa through a continuous quantum phase transition. Estimates of the critical exponents suggest that this transition may fall outside the traditional Landau paradigm. The inelastic neutron scattering spectra at 1.3 GPa are characterized by two well-separated gapped modes, including one continuum-like and another resolution-limited excitation in distinct scattering channels, which further indicates an exotic quantum-disordered phase above Pc.

20.
Phys Rev Lett ; 128(22): 227201, 2022 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-35714254

RESUMO

Spiral spin liquids are correlated paramagnetic states with degenerate propagation vectors forming a continuous ring or surface in reciprocal space. On the honeycomb lattice, spiral spin liquids present a novel route to realize emergent fracton excitations, quantum spin liquids, and topological spin textures, yet experimental realizations remain elusive. Here, using neutron scattering, we show that a spiral spin liquid is realized in the van der Waals honeycomb magnet FeCl_{3}. A continuous ring of scattering is directly observed, which indicates the emergence of an approximate U(1) symmetry in momentum space. Our work demonstrates that spiral spin liquids can be achieved in two-dimensional systems and provides a promising platform to study the fracton physics in spiral spin liquids.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...