Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 95
Filtrar
Más filtros

País/Región como asunto
Tipo del documento
Intervalo de año de publicación
1.
Proc Natl Acad Sci U S A ; 120(18): e2217928120, 2023 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-37094133

RESUMEN

Topological mechanical metamaterials have enabled new ways to control stress and deformation propagation. Exemplified by Maxwell lattices, they have been studied extensively using a linearized formalism. Herein, we study a two-dimensional topological Maxwell lattice by exploring its large deformation quasi-static response using geometric numerical simulations and experiments. We observe spatial nonlinear wave-like phenomena such as harmonic generation, localized domain switching, amplification-enhanced frequency conversion, and solitary waves. We further map our linearized, homogenized system to a non-Hermitian, nonreciprocal, one-dimensional wave equation, revealing an equivalence between the deformation fields of two-dimensional topological Maxwell lattices and nonlinear dynamical phenomena in one-dimensional active systems. Our study opens a regime for topological mechanical metamaterials and expands their application potential in areas including adaptive and smart materials and mechanical logic, wherein concepts from nonlinear dynamics may be used to create intricate, tailored spatial deformation and stress fields greatly transcending conventional elasticity.

2.
Proc Natl Acad Sci U S A ; 119(40): e2208051119, 2022 10 04.
Artículo en Inglés | MEDLINE | ID: mdl-36161940

RESUMEN

Periodic networks on the verge of mechanical instability, called Maxwell lattices, are known to exhibit zero-frequency modes localized to their boundaries. Topologically polarized Maxwell lattices, in particular, focus these zero modes to one of their boundaries in a manner that is protected against disorder by the reciprocal-space topology of the lattice's band structure. Here, we introduce a class of mechanical bilayers as a model system for designing topologically protected edge modes that couple in-plane dilational and shearing modes to out-of-plane flexural modes, a paradigm that we refer to as "omnimodal polarization." While these structures exhibit a high-dimensional design space that makes it difficult to predict the topological polarization of generic geometries, we are able to identify a family of mirror-symmetric bilayers that inherit the in-plane modal localization of their constitutive monolayers, whose topological polarization can be determined analytically. Importantly, the coupling between the layers results in the emergence of omnimodal polarization, whereby in-plane and out-of-plane edge modes localize on the same edge. We demonstrate these theoretical results by fabricating a mirror-symmetric, topologically polarized kagome bilayer consisting of a network of elastic beams via additive manufacturing and confirm this finite-frequency polarization via finite element analysis and laser-vibrometry experiments.


Asunto(s)
Luz , Modelos Teóricos , Análisis de Elementos Finitos , Impresión Tridimensional , Refracción Ocular
3.
Proc Natl Acad Sci U S A ; 119(52): e2211725119, 2022 12 27.
Artículo en Inglés | MEDLINE | ID: mdl-36534795

RESUMEN

Concepts from quantum topological states of matter have been extensively utilized in the past decade to create mechanical metamaterials with topologically protected features, such as one-way edge states and topologically polarized elasticity. Maxwell lattices represent a class of topological mechanical metamaterials that exhibit distinct robust mechanical properties at edges/interfaces when they are topologically polarized. Realizing topological phase transitions in these materials would enable on-and-off switching of these edge states, opening opportunities to program mechanical response and wave propagation. However, such transitions are extremely challenging to experimentally control in Maxwell topological metamaterials due to mechanical and geometric constraints. Here we create a Maxwell lattice with bistable units to implement synchronized transitions between topological states and demonstrate dramatically different stiffnesses as the lattice transforms between topological phases both theoretically and experimentally. By combining multistability with topological phase transitions, this metamaterial not only exhibits topologically protected mechanical properties that swiftly and reversibly change, but also offers a rich design space for innovating mechanical computing architectures and reprogrammable neuromorphic metamaterials. Moreover, we design and fabricate a topological Maxwell lattice using multimaterial 3D printing and demonstrate the potential for miniaturization via additive manufacturing. These design principles are applicable to transformable topological metamaterials for a variety of tasks such as switchable energy absorption, impact mitigation, wave tailoring, neuromorphic metamaterials, and controlled morphing systems.


Asunto(s)
Comercio , Impresión Tridimensional , Elasticidad , Miniaturización , Transición de Fase
4.
Kidney Int ; 105(5): 1020-1034, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38387504

RESUMEN

The circadian clock influences a wide range of biological process and controls numerous aspects of physiology to adapt to the daily environmental changes caused by Earth's rotation. The kidney clock plays an important role in maintaining tubular function, but its effect on podocytes remains unclear. Here, we found that podocytes expressed CLOCK proteins, and that 2666 glomerular gene transcripts (13.4%), including autophagy related genes, had 24-hour circadian rhythms. Deletion of Clock in podocytes resulted in 1666 gene transcripts with the loss of circadian rhythm including autophagy genes. Podocyte-specific Clock knockout mice at age three and eight months showed deficient autophagy, loss of podocytes and increased albuminuria. Chromatin immunoprecipitation (ChIP) sequence analysis indicated autophagy related genes were targets of CLOCK in podocytes. ChIP-PCR further confirmed Clock binding to the promoter regions of Becn1 and Atg12, two autophagy related genes. Furthermore, the association of CLOCK regulated autophagy with chronic sleep fragmentation and diabetic kidney disease was analyzed. Chronic sleep fragmentation resulted in the loss of glomerular Clock rhythm, inhibition of podocyte autophagy, and proteinuria. Rhythmic oscillations of Clock also disappeared in high glucose treated podocytes and in glomeruli from diabetic mice. Finally, circadian differences in podocyte autophagy were also abolished in diabetic mice. Deletion Clock in podocytes aggravated podocyte injury and proteinuria in diabetic mice. Thus, our findings demonstrate that clock-dependent regulation of autophagy may be essential for podocyte survival. Hence. loss of circadian controlled autophagy may play an important role in podocyte injury and proteinuria.


Asunto(s)
Diabetes Mellitus Experimental , Nefropatías Diabéticas , Podocitos , Ratones , Animales , Podocitos/metabolismo , Diabetes Mellitus Experimental/complicaciones , Privación de Sueño/complicaciones , Privación de Sueño/metabolismo , Proteinuria/genética , Proteinuria/metabolismo , Nefropatías Diabéticas/genética , Nefropatías Diabéticas/complicaciones , Ratones Noqueados , Autofagia
5.
Biochem Biophys Res Commun ; 647: 62-71, 2023 03 05.
Artículo en Inglés | MEDLINE | ID: mdl-36731335

RESUMEN

BACKGROUND: Dysfunction of pancreatic ß-cells induced by glucocorticoids contributes to diabetes mellitus development. Long noncoding RNAs (lncRNAs) have been recognized to contain short open reading frames (ORFs) that can be translated into functional small peptides. Here, we investigated whether the short peptide encoded by the lncRNA MIR7-3 host gene (MIR7-3HG) can affect dexamethasone (DEX)-induced ß-cell dysfunction. METHODS: Bioinformatics analysis was used for selection of MIR7-3HG and prediction of its protein encoding potential. The small peptide was identified by a western blot method. The cell-permeable TAT was fused into MIR7-3HG ORF to produce the cell-permeable fusion peptide (TAT-MIR7-3HG-ORF). The effects of TAT-MIR7-3HG-ORF on DEX-induced ß-cell dysfunction were evaluated by examining cell viability, apoptosis, insulin secretion, and reactive oxygen species (ROS) generation. RESULTS: DEX induced ß-TC6 cell dysfunction by impairing cell viability, insulin secretion and promoting cell apoptosis and ROS generation. The MIR7-3HG ORF could encode a 125-amino-acid-long short peptide. TAT-MIR7-3HG-ORF effectively transduced into ß-TC6 cells and attenuated DEX-induced dysfunction in ß-TC6 cells. Moreover, transduced TAT-MIR7-3HG-ORF reversed DEX-mediated inhibition of the activation of the PI3K/AKT signaling pathway. The inhibitor of the PI3K/AKT pathway partially abolished the alleviative effect of transduced TAT-MIR7-3HG-ORF on DEX-induced ß-TC6 cell dysfunction. CONCLUSION: The lncRNA MIR7-3HG encodes a short peptide, which can protect pancreatic ß-cells from DEX-induced dysfunction by activating the PI3K/AKT pathway. Our study broadens the diversity and breadth of lncRNAs in human disorders.


Asunto(s)
Células Secretoras de Insulina , MicroARNs , ARN Largo no Codificante , Humanos , Apoptosis/genética , Dexametasona/efectos adversos , MicroARNs/genética , MicroARNs/farmacología , Péptidos/farmacología , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Especies Reactivas de Oxígeno/metabolismo , ARN Largo no Codificante/metabolismo , Transducción de Señal , Células Secretoras de Insulina/efectos de los fármacos
6.
Phys Rev Lett ; 131(25): 258201, 2023 Dec 22.
Artículo en Inglés | MEDLINE | ID: mdl-38181337

RESUMEN

Entropic self-assembly is governed by the shape of the constituent particles, yet a priori prediction of crystal structures from particle shape alone is nontrivial for anything but the simplest of space-filling shapes. At the same time, most polyhedra are not space filling due to geometric constraints, but these constraints can be relaxed or even eliminated by sufficiently curving space. We show using Monte Carlo simulations that the majority of hard Platonic solids self-assemble entropically into space-filling crystals when constrained to the surface volume of a 3-sphere. As we gradually decrease curvature to "flatten" space and compare the local morphologies of crystals assembling in curved and flat space, we show that the Euclidean assemblies can be categorized as either remnants of tessellations in curved space (tetrahedra and dodecahedra) or nontessellation-based assemblies caused by large-scale geometric frustration (octahedra and icosahedra).

7.
J Chem Phys ; 158(11): 114104, 2023 Mar 21.
Artículo en Inglés | MEDLINE | ID: mdl-36948805

RESUMEN

We investigate the spatial correlations of microscopic stresses in soft particulate gels using 2D and 3D numerical simulations. We use a recently developed theoretical framework predicting the analytical form of stress-stress correlations in amorphous assemblies of athermal grains that acquire rigidity under an external load. These correlations exhibit a pinch-point singularity in Fourier space. This leads to long-range correlations and strong anisotropy in real space, which are at the origin of force-chains in granular solids. Our analysis of the model particulate gels at low particle volume fractions demonstrates that stress-stress correlations in these soft materials have characteristics very similar to those in granular solids and can be used to identify force chains. We show that the stress-stress correlations can distinguish floppy from rigid gel networks and that the intensity patterns reflect changes in shear moduli and network topology, due to the emergence of rigid structures during solidification.

8.
Bull Environ Contam Toxicol ; 111(1): 8, 2023 Jun 24.
Artículo en Inglés | MEDLINE | ID: mdl-37354238

RESUMEN

All pesticides are toxic by nature and pose short- or long-term safety risks to human or the environment, especially when they were used extensively and absence of safety measures. As a new insecticidal active compound with a novel mechanism of action, there is a serious inadequate of information on the hydrolytic behavior of broflanilide in the aqueous environment, as well as its degradation pattern in agricultural soils. In particular, the effects of temperature and pH of the aqueous environment on its hydrolytic behaviors and the dissipation pattern in different types of agricultural soils were still in a dark box. And the further understanding and insights into this insecticidal active ingredient were being deeply conditioned by these doubts. The hydrolysis behavior of broflanilide and the dissipation pattern in soil were systematically investigated by constructing hydrolysis systems with different temperatures and pH values, and conducting spiking experiments in different types of agricultural soil in the laboratory. The obtained results showed that the longest hydrolysis half-life of 10 mg/L broflanilide at 25 °C was 43.32 h (in pH 4.0 buffer), while it was only 12.84 h in pH 9.0 buffer. In pH 7.0 buffer, the hydrolysis rate of broflanilide exhibited a significant temperature dependence, as shown by the fact that for every 10 °C increase in the system temperature, the corresponding hydrolysis rate will increase about 1.5 times. The dissipation experiments in soils showed that broflanilide was most rapidly dissipated in fluvo-aquic soil (half-life of 1.94 days), followed by lime concretion black soil (half-life of 2.53 days) and cinnamon soil (half-life of 3.11 days), and slower in paddy soil (half-life of 4.03 days). It was indicated that broflanilide was a readily degradable pesticide in both aqueous environment and agricultural soil, and it was significantly affected by the temperature and pH of the system.


Asunto(s)
Insecticidas , Plaguicidas , Contaminantes del Suelo , Humanos , Suelo/química , Hidrólisis , Agricultura , Agua , Contaminantes del Suelo/análisis
9.
J Cell Mol Med ; 26(16): 4453-4462, 2022 08.
Artículo en Inglés | MEDLINE | ID: mdl-35808902

RESUMEN

Activated B cells contribute to heart diseases, and inhibition of B-cell activating factor (BAFF) expression is an effective therapeutic target for heart diseases. Whether activated B cells participate in the development and progression of hyperthyroid heart disease, and what induces B cells activation in hyperthyroidism are unknown. The present study aimed to determine the roles of BAFF overexpression induced by high concentrations of triiodothyronine (T3) in the pathogenesis of hyperthyroid heart disease. Female C57BL/6J mice were subcutaneously injected with T3 for 6 weeks, and BAFF expression was inhibited using shRNA. Protein and mRNA expression of BAFF in mouse heart tissues evaluated via immunohistochemistry, western blotting and polymerase chain reaction (PCR). Proportions of B cells in mouse cardiac tissue lymphocytes were quantified via flow cytometry. Morphology and left ventricle function were assessed using pathological sections and echocardiography, respectively. Here, we demonstrate that compared with the control group, the proportion of myocardial B cells was larger in the T3 group; immunohistochemistry, western blotting and PCR analyses revealed increased protein and mRNA expression levels of TNF-α and BAFF in heart tissues of the T3 group. Compared with the normal controls group, in the T3 group, the diameter of myocardial cells and some echocardiographic values significantly increased and hypertrophy and structural disorder were noticeable. Our results revealed that elevated levels of circulating T3 can promote the expression of BAFF in myocardial cells and can lead to B-cell activation, an elevated inflammatory response and ventricular remodelling.


Asunto(s)
Factor Activador de Células B , Hipertiroidismo , Animales , Factor Activador de Células B/genética , Factor Activador de Células B/metabolismo , Cardiomegalia/genética , Femenino , Ratones , Ratones Endogámicos C57BL , ARN Mensajero/genética , Triyodotironina
10.
Phys Rev Lett ; 129(8): 088002, 2022 Aug 19.
Artículo en Inglés | MEDLINE | ID: mdl-36053689

RESUMEN

Periodic lattices in hyperbolic space are characterized by symmetries beyond Euclidean crystallographic groups, offering a new platform for classical and quantum waves, demonstrating great potential for a new class of topological metamaterials. One important feature of hyperbolic lattices is that their translation group is nonabelian, permitting high-dimensional irreducible representations (irreps), in contrast to abelian translation groups in Euclidean lattices. Here we introduce a general framework to construct wave eigenstates of high-dimensional irreps of infinite hyperbolic lattices, thereby generalizing Bloch's theorem, and discuss its implications on unusual mode counting and degeneracy, as well as bulk-edge correspondence in hyperbolic lattices. We apply this method to a mechanical hyperbolic lattice, and characterize its band structure and zero modes of high-dimensional irreps.

11.
Biosci Biotechnol Biochem ; 86(8): e1-e13, 2022 Sep 05.
Artículo en Inglés | MEDLINE | ID: mdl-31791206

RESUMEN

The role of linc00472 in lung cancer (LC) has been rarely reported. We aimed to study the role of linc00472 in LC progression. Expressions of linc00472 and miR-196b-5p in LC cell lines were measured by qRT-PCR. The targeting relationship between linc00472 and miR-196b-5p was determined by Starbase and dual-luciferase reporter. The viability, migration, invasion, and apoptosis of LC cells were determined using CCK-8 assay, scratch test, transwell assay, and flow cytometry, respectively. The levels of epithelial-to-mesenchymal transition (EMT)-related proteins and apoptosis-related proteins in LC cells were determined by western blot. Down-regulated linc00472 was observed in five LC cell lines. Linc00472 overexpression suppressed viability, migration, invasion and EMT process, but elevated apoptotic rate in LC cells. MiR-196b-5p mimic promoted viability, migration, invasion, and EMT process, but decreased apoptotic rate, which was reversed by up-regulated linc00472. Linc00472 functioned as a cancer suppressor via negatively regulating miR-196b-5p of LC cells.

12.
BMC Nephrol ; 23(1): 398, 2022 12 10.
Artículo en Inglés | MEDLINE | ID: mdl-36496400

RESUMEN

BACKGROUND: Thyroid dysfunction is common in patients with nephrotic syndrome, especially patients with primary membranous nephropathy (pMN). In view of both MN and thyroid dysfunction are associated with autoimmunity, the current study aimed to elucidate the significance of thyroid dysfunction in patients with pMN. METHODS: Four hundred and twenty patients with biopsy-proven pMN from 2018-2021 were retrospectively enrolled. Clinical and pathological parameters, and treatment response of patients with and without thyroid dysfunction were analyzed. RESULTS: Ninety-one (21.7%) patients with pMN suffered from thyroid dysfunction, among which subclinical hypothyroidism (52.7%) was the main disorder. Compared to patients with normal thyroid function, patients with thyroid dysfunction presented with a higher level of proteinuria, a lower level of serum albumin, a higher level of serum creatinine and more severe tubulointerstitial injury at the time of biopsy. But the positive rate and level of circulating anti-phospholipase A2 receptor (PLA2R) antibody were comparable between these two groups. Though following the similar treatment, the percentage of no response to treatment were significantly higher in the patients with thyroid dysfunction (38.6 vs. 20.0%, P = 0.003). Similar to the urinary protein and the positivity of anti-PLA2R antibody, multivariate COX analysis showed thyroid dysfunction was also identified as an independent risk factor for the failure to remission (HR = 1.91, 95%CI, 1.07-3.40, P = 0.029). CONCLUSION: In conclusion, thyroid dysfunction is common in the patients with pMN and might predict a severe clinical manifestation and a poor clinical outcome, which indicated that the thyroid dysfunction might be involved in the disease progression of pMN.


Asunto(s)
Glomerulonefritis Membranosa , Glándula Tiroides , Humanos , Estudios Retrospectivos , Glándula Tiroides/patología , Glomerulonefritis Membranosa/tratamiento farmacológico , Receptores de Fosfolipasa A2 , Proteinuria/tratamiento farmacológico , Autoanticuerpos
13.
J Clin Lab Anal ; 36(10): e24701, 2022 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-36097969

RESUMEN

BACKGROUND: Elevated thyroid hormone (TH) levels have been suggested to be associated with the pathological progression of Graves' disease (GD). However, direct evidence from clinical studies remains unclear. METHODS: Peripheral blood samples were collected from patients with or without the recurrence of Graves' hyperthyroidism (GH) and healthy donors. Thyroid tissue samples were obtained from patients with benign thyroid nodules. To assess the differentiation of autoreactive B cells, the expression of B-cell-activating factor (BAFF) and the proportion of CD11c+/-IgG+/- subsets of B cells stimulated by high levels of triiodothyronine (T3) in vivo and in vitro were examined by ELISA, flow cytometry, western blotting, and qRT-PCR. RESULTS: Serum BAFF levels in patients with GD were significantly and positively correlated with FT3, FT4, and TRAb levels. Furthermore, the ratio of abnormally differentiated CD11c+ autoreactive B cells positively correlated with BAFF and TRAb. High levels of triiodothyronine (T3) induced BAFF overexpression in thyroid follicular cells and mononuclear cells of the normal thyroid in vitro, thereby promoting the differentiation of CD11c+IgG+ autoreactive secretory B cells (ASCs). However, the precise knockdown of BAFF expression significantly inhibited the abnormal differentiation of ASCs. CONCLUSION: The pathological progression of GD was prolonged and exacerbated by autoimmune positive feedback modulation caused by high TH levels. BAFF could be considered a potential target for localized thyroid immunosuppressive treatment of Graves' hyperthyroidism recurrence.


Asunto(s)
Enfermedad de Graves , Hipertiroidismo , Enfermedad de Graves/genética , Humanos , Inmunoglobulina G , Interleucina-4 , Tiroxina , Triyodotironina
14.
Zhong Nan Da Xue Xue Bao Yi Xue Ban ; 47(2): 244-251, 2022 Feb 28.
Artículo en Inglés, Zh | MEDLINE | ID: mdl-35545415

RESUMEN

OBJECTIVES: Low dose computed tomography (LDCT) is the best method for early diagnosis of lung cancer. Even though it has been widely used in clinic, the selection of screening objects and the management scheme of pulmonary nodules are still not unified among research institutions. This study aims to evaluate the effect of LDCT in detection effect and follow-up process for pulmonary nodules in asymptomatic participants. METHODS: A total of 1 600 asymptomatic participants (37 to 82 years old), who came from Yantian District People's Hospital, Southern University of Science and Technology, received LDCT. The lung nodules were categorized into positive nodules and semi-positive nodules, and according to the density of positive nodules they were categorized into 4 types: solid nodules (SN), partial solid nodules (pSN), pure ground glass nodules (pGGN), and pleural nodules (PN). The number, detection rate, imaging findings, follow-up change of lung nodules, and the postoperative pathological results of positive nodules were recorded and analyzed. RESULTS: Lung nodules were found in 221 cases by LDCT. The total detection rate of lung nodule was 13.8% (221/1 600), and the detection rate in positive nodules was 4.9% (79/1 600). The detected nodules were mainly single (173 cases), solid (133 cases) and semi-positive nodules (142 cases). Most of nodules (177 cases) had no change in the follow-up process. The enlargement and/or increased density of nodules (5 cases) were lung cancer. Pathological results were obtained in 10 cases, 8 cases were malignant (1 small cell lung cancer and 7 adenocarcinomas), 2 cases were benign (cryptococcal infection and alveolar epithelial dysplasia). The detection rate of lung cancer was 0.5% (8/1 600), and the proportion of early lung cancer was 75% (6/8). CONCLUSIONS: LDCT screening can identify and increase the detection rate in the early lung cancer, which is an effective screening method. It is safe and feasible to take regular follow-up and re-examination for nodules with diameter less than 5 mm. When the size and or density of nodule increases, it indicates the malignant prognosis of the nodule and timely clinical intervention is needed.


Asunto(s)
Adenocarcinoma , Neoplasias Pulmonares , Adulto , Anciano , Anciano de 80 o más Años , Detección Precoz del Cáncer/métodos , Humanos , Neoplasias Pulmonares/diagnóstico por imagen , Neoplasias Pulmonares/patología , Tamizaje Masivo/métodos , Persona de Mediana Edad , Tomografía Computarizada por Rayos X/métodos
15.
Phys Rev Lett ; 127(9): 098001, 2021 Aug 27.
Artículo en Inglés | MEDLINE | ID: mdl-34506176

RESUMEN

We show that minimal-surface non-Euclidean elastic plates share the same low-energy effective theory as Haldane's dimerized quantum spin chain. As a result, such elastic plates support fractional excitations, which take the form of charge-1/2 solitons between degenerate states of the plate, in strong analogy to their quantum counterpart. These fractional excitations exhibit properties similar to fractional excitations in quantum fractional topological states and in Haldane's dimerized quantum spin chain, including deconfinement and braiding, as well as unique new features such as holographic properties and diodelike nonlinear response, demonstrating great potentials for applications as mechanical metamaterials.

16.
Soft Matter ; 17(29): 6929-6934, 2021 Jul 28.
Artículo en Inglés | MEDLINE | ID: mdl-34180465

RESUMEN

Rheological measurements of model colloidal gels reveal that large variations in the shear moduli as colloidal volume-fraction changes are not reflected by simple structural parameters such as the coordination number, which remains almost a constant. We resolve this apparent contradiction by conducting a normal-mode analysis of experimentally measured bond networks of gels of colloidal particles with short-ranged attraction. We find that structural heterogeneity of the gels, which leads to floppy modes and a nonaffine-affine crossover as frequency increases, evolves as a function of the volume fraction and is key to understanding the frequency-dependent elasticity. Without any free parameters, we achieve good qualitative agreement with the measured mechanical response. Furthermore, we achieve universal collapse of the shear moduli through a phenomenological spring-dashpot model that accounts for the interplay between fluid viscosity, particle dissipation, and contributions from the affine and non-affine network deformation.

17.
Soft Matter ; 17(38): 8624-8641, 2021 Oct 06.
Artículo en Inglés | MEDLINE | ID: mdl-34505853

RESUMEN

Recent advances in topological mechanics have revealed unusual phenomena such as topologically protected floppy modes and states of self-stress that are exponentially localized at boundaries and interfaces of mechanical networks. In this paper, we explore the topological mechanics of epithelial tissues, where the appearance of these boundary and interface modes could lead to localized soft or stressed spots and play a role in morphogenesis. We consider both a simple vertex model (VM) governed by an effective elastic energy and its generalization to an active tension network (ATN) which incorporates active adaptation of the cytoskeleton. By analyzing spatially periodic lattices at the Maxwell point of mechanical instability, we find topologically polarized phases with exponential localization of floppy modes and states of self-stress in the ATN when cells are allowed to become concave, but not in the VM.


Asunto(s)
Células Epiteliales , Modelos Biológicos , Células Epiteliales/citología , Células Epiteliales/fisiología
18.
Eur Phys J E Soft Matter ; 44(11): 137, 2021 Nov 15.
Artículo en Inglés | MEDLINE | ID: mdl-34782959

RESUMEN

Epithelial cell clusters often move collectively on a substrate. Mechanical signals play a major role in organizing this behavior. There are a number of experimental observations in these systems which await a comprehensive explanation. These include: the internal strains are tensile even for clusters that expand by proliferation; the tractions on the substrate are often confined to the edges of the cluster; there can exist density waves within the cluster; and for cells in an annulus, there is a transition between expanding clusters with proliferation and the case where cells fill the annulus and rotate around it. We formulate a mechanical model to examine these effects. We use a molecular clutch picture which allows "stalling"-inhibition of cell contraction by external forces. Stalled cells are passive from a physical point of view and the un-stalled cells are active. By attaching cells to the substrate and to each other, and taking into account contact inhibition of locomotion, we get a simple picture for many of these findings as well as predictions that could be tested.


Asunto(s)
Inhibición de Contacto , Modelos Biológicos , Movimiento Celular
19.
Surg Innov ; 28(5): 590-599, 2021 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-33339487

RESUMEN

Objective. This study was to combine endobronchial ultrasound elastography (UE) with computed tomography (CT) to identify benign and malignant thoracic lymph nodes (LNs) more objectively and accurately. Methods. A total of 42 patients with intrathoracic lymphadenopathy required for endobronchial ultrasound with real-time guided transbronchial needle aspiration (EBUS-TBNA) examination were enrolled. All patients were examined by enhanced chest CT, B-mode ultrasound, and endobronchial ultrasound (EBUS)-guided elastography before EBUS-TBNA. Each lymph node was assessed by describing the characteristics of CT image (short diameter, texture, shape, boundary, and mean CT value), B-mode ultrasound (short diameter, echo characteristic, shape, and boundary), and elastography (image type, grading score, strain rate, and blue area ratio). The pathological results were used as the gold standard. The characteristics were compared alone and in combination between benign and malignant LNs. Results. The blue area ratio of elastography combined with CT had better diagnostic value in differentiating benign and malignant LNs than elastography alone, with the accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) being 92%, 96%, 80%, 94%, and 86% vs 81%, 77%, 93%, 97%, and 56%, respectively. Elastography combined with B-mode ultrasound and CT characteristics showed the highest diagnostic value. Accuracy, sensitivity, specificity, PPV, and NPV were all 100%. Conclusions. Endobronchial UE combined with CT and B-mode ultrasound imaging shows a greater diagnostic value in differentiating benign and malignant intrathoracic LNs than either imaging alone.


Asunto(s)
Diagnóstico por Imagen de Elasticidad , Neoplasias Pulmonares , Broncoscopía , Endosonografía , Humanos , Ganglios Linfáticos/diagnóstico por imagen , Sensibilidad y Especificidad , Tomografía Computarizada por Rayos X
20.
Water Sci Technol ; 84(1): 77-88, 2021 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-34280156

RESUMEN

Bi4O5Br2 with irregular flake shape was synthesized by a facile and energy-saving hydrolysis method. Its band gap energy (Eg) was 2.1 eV. The formation mechanism was proposed. The Bi4O5Br2 exhibited superb visible-light-induced photocatalytic activity (>90%) toward the oxidation of carbamazepine. The kinetics rate constant (k) attained 0.0196 min-1. The effect of Bi4O5Br2 dosage, initial solution pH value, and inorganic anions on carbamazepine degradation was investigated. During the oxidation process, photogenerated holes (h+) and superoxide radical anions (•O2-) were the main active species. Based on the reaction intermediates results determined through a combined system of liquid chromatography and mass spectrometry, a possible reaction mechanism was speculated. The degree of contamination of carbamazepine solution after treatment was evaluated through the teratogenic effect experiment. After 120 min of visible light exposure, the carbamazepine solution is free of pollution. Also, the as-synthesized Bi4O5Br2 maintains good chemical stability and could be reused in the photodegradation process, indicating its potential in practical applications.


Asunto(s)
Carbamazepina , Luz , Catálisis , Oxidación-Reducción , Fotólisis
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA