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1.
Nat Nanotechnol ; 16(8): 869-873, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34168343

RESUMO

Nonlinear responses in transport measurements are linked to material properties not accessible at linear order1 because they follow distinct symmetry requirements2-5. While the linear Hall effect indicates time-reversal symmetry breaking, the second-order nonlinear Hall effect typically requires broken inversion symmetry1. Recent experiments on ultrathin WTe2 demonstrated this connection between crystal structure and nonlinear response6,7. The observed second-order nonlinear Hall effect can probe the Berry curvature dipole, a band geometric property, in non-magnetic materials, just like the anomalous Hall effect probes the Berry curvature in magnetic materials8,9. Theory predicts that another intrinsic band geometric property, the Berry-connection polarizability tensor10, gives rise to higher-order signals, but it has not been probed experimentally. Here, we report a third-order nonlinear Hall effect in thick Td-MoTe2 samples. The third-order signal is found to be the dominant response over both the linear- and second-order ones. Angle-resolved measurements reveal that this feature results from crystal symmetry constraints. Temperature-dependent measurement shows that the third-order Hall response agrees with the Berry-connection polarizability contribution evaluated by first-principles calculations. The third-order nonlinear Hall effect provides a valuable probe for intriguing material properties that are not accessible at lower orders and may be employed for high-order-response electronic devices.

2.
Signal Transduct Target Ther ; 6(1): 165, 2021 04 24.
Artigo em Inglês | MEDLINE | ID: mdl-33895786

RESUMO

The global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) requires an urgent need to find effective therapeutics for the treatment of coronavirus disease 2019 (COVID-19). In this study, we developed an integrative drug repositioning framework, which fully takes advantage of machine learning and statistical analysis approaches to systematically integrate and mine large-scale knowledge graph, literature and transcriptome data to discover the potential drug candidates against SARS-CoV-2. Our in silico screening followed by wet-lab validation indicated that a poly-ADP-ribose polymerase 1 (PARP1) inhibitor, CVL218, currently in Phase I clinical trial, may be repurposed to treat COVID-19. Our in vitro assays revealed that CVL218 can exhibit effective inhibitory activity against SARS-CoV-2 replication without obvious cytopathic effect. In addition, we showed that CVL218 can interact with the nucleocapsid (N) protein of SARS-CoV-2 and is able to suppress the LPS-induced production of several inflammatory cytokines that are highly relevant to the prevention of immunopathology induced by SARS-CoV-2 infection.


Assuntos
Antivirais/uso terapêutico , COVID-19/tratamento farmacológico , COVID-19/metabolismo , Simulação por Computador , Reposicionamento de Medicamentos , Modelos Biológicos , SARS-CoV-2/metabolismo , Humanos
3.
J Food Sci ; 86(5): 1835-1844, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33856047

RESUMO

This study investigated the influence of sarcoplasmic proteins (SPs) treated by the oxidation system (0.1 mmol/L FeCl3 , 0.1 mmol/L ascorbic acid, and 0, 1, 5, 10 mmol/L H2 O2 ) on the properties of pork myofibrillar proteins (MPs) gel. After oxidation treatment, the SPs showed an increased in carbonyl content and a decreased in total sulfhydryl content, coupled with the cross-linking of protein components by disulfide bonds and covalent bonds. The MPs gel with SPs oxidized at 1 mmol/L H2 O2 exhibited the maximal strength while the minimal water holding capacity (WHC). The WHC of MPs gel was significantly decreased with increasing SPs oxidation, leading to the increase of free water and the decrease of immobilized water in the gel system. The microstructures of MPs gels with moderately (1 mmol/L H2 O2 ) oxidized SPs showed a more compact and smaller pore gel network than MPs alone, suggesting adding oxidized SPs can expel water trapped in the gel. Furthermore, the environmental polarity of aliphatic C-H groups increased with SPs oxidation.


Assuntos
Géis/química , Proteínas Musculares/química , Miofibrilas/química , Carne de Porco/análise , Retículo Sarcoplasmático/química , Sus scrofa , Animais , Fenômenos Químicos , Oxirredução , Compostos de Sulfidrila/análise , Água/química
5.
Food Chem ; 345: 128849, 2021 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-33601660

RESUMO

The study was to investigate the role of direct current magnetic field (DC-MF) for water-holding capacity (WHC) of myofibrillar protein gels and to understand potential mechanisms. Samples were subjected to DC-MF with different intensities (3.5, 3.8, 9.5 and 10.4 mT), and DC-MF treatment significantly improved WHC compared with control (46.09%), reaching the maximum value of 50.36% at 3.8 mT. The main reason for the increase in WHC might be that DC-MF modified the protein structure via unfolding, re-crosslinking and aggregation of proteins, which was supported by the increased intensity of tyrosine, aliphatic and tryptophan residues, and reduced reactive sulfhydryl (2.97 to 1.94). And the re-crosslinking between molecules was maintained mainly through hydrophobic interactions and disulfide bonds. Besides, DC-MF treatment helped to generate a relatively loose and uniform microstructure to trap more water as shown by electron microscope image, which was consistent with the highest WHC at 3.8 mT.


Assuntos
Géis/química , Proteínas Musculares/química , Água/química , Animais , Dissulfetos/química , Interações Hidrofóbicas e Hidrofílicas , Microscopia Eletrônica , Nefelometria e Turbidimetria , Ressonância Magnética Nuclear Biomolecular , Agregados Proteicos , Solubilidade , Suínos
6.
Sci Total Environ ; 770: 144838, 2021 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-33517008

RESUMO

This study assesses the impacts of climate change on net livestock revenue, grazing intensity, and net revenue per livestock, based on a panel dataset of 959 herder households from 18 counties in three major pastoral provinces in China. The Ricardian model and the Hsiao two-step method are applied to quantify the impacts on household-level livestock production made by long-term changes of temperature and precipitation and short-term occurrence of natural disasters. The results indicate that long-term temperature leads to decreased net livestock revenue and net revenue per livestock, whereas long-term precipitation improves revenue per livestock. Next, both long-term annual temperature and precipitation result in an increase of grazing intensity. A further analysis based on the simulation of future climate change predicts that the future increase in temperature will have a negative influence on both net revenue and net revenue per livestock, while the precipitation increment will have a positive effect on livestock production.

7.
Food Chem ; 343: 128557, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33199125

RESUMO

This study explored effects of radio frequency (RF, 27.12 MHz, 3 kW) heating replacing the first stage (electrode gaps of 120, 140 and 160 mm) or/and the second stage (95 mm) of the water bath heating on water distribution and structural characteristics of grass carp myofibrillar proteins gels. Compared with control, RF heating (140) during the first stage significantly reduced the total time to prepare gels from 70 min to 45.3 min and increased springiness and water holding capacity from 62.9% to 68.3%. It may be attributed to the appropriate RF heating contributing to α-helix turning into random coil and cross-linking via hydrophobic interactions and disulfide bonds, thus forming smooth gels with clear network structures. Structural changes further affected water distribution (immobilized water increasing from 97.8% to 98.7%). Namely, RF (140 mm) heating improved water distribution and structural characteristics of gels, which provided basic information for RF heating surimi gels.


Assuntos
Carpas/metabolismo , Proteínas de Peixes/química , Géis/química , Água/química , Animais , Dissulfetos/química , Interações Hidrofóbicas e Hidrofílicas , Microscopia Eletrônica de Varredura , Ondas de Rádio , Análise Espectral Raman , Temperatura
8.
ACS Omega ; 5(49): 31831-31844, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-33344837

RESUMO

Shale oil reserves play an important role in the oil & gas industry. The investigation of oil transport behavior in shale nanopores is crucial in the successful exploitation of shale oil reservoirs. However, the transport mechanisms of oil in shale nanopores are still not understood. In this paper, a model for oil transport through a single nanopore was established by considering mixed wettability, surface roughness, varying viscosity, and the effects triggered by adsorbed organic matter. The organic surface ratio of a single nanopore was used to quantify mixed wettability, while the effects of adsorbed organic matter were estimated by the surface coverage and the adsorption thickness. The entire mathematical model was simplified into several equations to discuss the contributions of each mechanism. The results showed that to accurately predict the oil transport properties in mixed wettability shale nanopores, it is necessary to consider varying viscosity, wettability alteration, and the oil molecule structure. Adsorbed organic matter led to increase in oil flow capacity by altering the surface wettability. However, the oil flow capacity was greatly reduced when varying viscosity was considered. Additionally, the contributions of each mechanism varied with the pore type. Furthermore, increasing surface roughness significantly reduced the oil flow capacity in both organic and inorganic nanopores. This work provides a better understanding of oil transport behavior in mixed-wettability shale nanopores and a quantitative framework for future research.

9.
Phys Rev Lett ; 125(14): 143001, 2020 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-33064518

RESUMO

Unconventional Weyl points (WPs), carrying topological charge 2 or higher, possess interesting properties different from ordinary charge-1 WPs, including multiple Fermi arcs that stretch over a large portion of the Brillouin zone. Thus far, such WPs have been observed in chiral materials and acoustic metamaterials, but there has been no clean demonstration in photonics in which the unconventional photonic WPs are separated from trivial bands. We experimentally realize an ideal symmetry-protected photonic charge-2 WP in a three-dimensional topological chiral microwave metamaterial. We use field mapping to directly observe the projected bulk dispersion, as well as the two long surface arcs that form a noncontractible loop wrapping around the surface Brillouin zone. The surface states span a record-wide frequency window of around 22.7% relative bandwidth. We demonstrate that the surface states exhibit a novel topological self-collimation property and are robust against disorder. This work provides an ideal photonic platform for exploring fundamental physics and applications of unconventional WPs.

10.
Clin Transl Med ; 10(3): e129, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32722861

RESUMO

Esophageal squamous cell carcinoma (ESCC) is more prevalent than esophageal adenocarcinoma in Asia, especially in China, where more than half of ESCC cases occur worldwide. Many studies have reported that the automatic detection of lymph node metastasis using semantic segmentation shows good performance in breast cancer and other adenocarcinomas. However, the detection of squamous cell carcinoma metastasis in hematoxylin-eosin (H&E)-stained slides has never been reported. We collected a training set of 110 esophageal lymph node slides with metastasis and 132 lymph node slides without metastasis. An iPad-based annotation system was used to draw the contours of the cancer metastasis region. A DeepLab v3 model was trained to achieve the best fit with the training data. The learned model could estimate the probability of metastasis. To evaluate the effectiveness of the detection model of learned metastasis, we used another large cohort of clinical H&E-stained esophageal lymph node slides containing 795 esophageal lymph nodes from 154 esophageal cancer patients. The basic authenticity label for each slide was confirmed by experienced pathologists. After filtering isolated noise in the prediction, we obtained an accuracy of 94%. Furthermore, we applied the learned model to throat and lung lymph node squamous cell carcinoma metastases and achieved the following promising results: an accuracy of 96.7% in throat cancer and an accuracy of 90% in lung cancer. In this work, we organized an annotated dataset of H&E-stained esophageal lymph node and trained a deep neural network to detect lymph node metastasis in H&E-stained slides of squamous cell carcinoma automatically. Moreover, it is possible to use this model to detect lymph nodes metastasis in squamous cell carcinoma from other organs. This study directly demonstrates the potential for determining the localization of squamous cell carcinoma metastases in lymph node and assisting in pathological diagnosis.

11.
Nat Nanotechnol ; 15(8): 661-667, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32572230

RESUMO

Interface engineering by local polarization using piezoelectric1-4, pyroelectric5,6 and ferroelectric7-9 effects has attracted considerable attention as a promising approach for tunable electronics/optoelectronics, human-machine interfacing and artificial intelligence. However, this approach has mainly been applied to non-centrosymmetric semiconductors, such as wurtzite-structured ZnO and GaN, limiting its practical applications. Here we demonstrate an electronic regulation mechanism, the flexoelectronics, which is applicable to any semiconductor type, expanding flexoelectricity10-13 to conventional semiconductors such as Si, Ge and GaAs. The inner-crystal polarization potential generated by the flexoelectric field serving as a 'gate' can be used to modulate the metal-semiconductor interface Schottky barrier and further tune charge-carrier transport. We observe a giant flexoelectronic effect in bulk centrosymmetric semiconductors of Si, TiO2 and Nb-SrTiO3 with high strain sensitivity (>2,650), largely outperforming state-of-the-art Si-nanowire strain sensors and even piezoresistive, piezoelectric and ferroelectric nanodevices14. The effect can be used to mechanically switch the electronics in the nanoscale with fast response (<4 ms) and high resolution (~0.78 nm). This opens up the possibility of realizing strain-modulated electronics in centrosymmetric semiconductors, paving the way for local polarization field-controlled electronics and high-performance electromechanical applications.

12.
Food Chem ; 326: 126896, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32416422

RESUMO

This study investigated the combined effects of low frequency magnetic field (LF-MF) (3.8 mT) and pH (5-7) on pork myofibrillar protein (MP) gel quality. With LF-MF applying, the water ratio and migration rate both changed to varying extents. LF-MF modified secondary structure of MP by exposing tryptophan and tyrosine residues to participate in hydrogen bonding with water, as well changing α-helix and ß-sheet to varying extents; LF-MF also drove molecular rearrangement and crosslinking. LF-MF brought gel larger and more ordered network to trap more water. And the water holding capacity of gels significantly increased by 2.50% and 2.47% when LF-MF involved at appropriate pH (pH 6.5 and 7.0). Collectively, our results support an optimum treatment (pH 6.5 or 7.0 with applying LF-MF) for the improvement in gel quality of pork MP, and the combination of physical and chemical treatments casts a new light into improving product quality during meat processing.


Assuntos
Proteínas Musculares/química , Miofibrilas/química , Animais , Géis/química , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Campos Magnéticos , Imageamento por Ressonância Magnética , Espectroscopia de Ressonância Magnética , Carne de Porco , Estrutura Secundária de Proteína , Análise Espectral Raman , Suínos
13.
Food Chem ; 321: 126728, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32259736

RESUMO

The effects of low-frequency magnetic field combined with different heating rates on pork myofibrillar protein (MP) gels were investigated. Samples were treated under different heating rates (1 °C/min and 2 °C/min) in the presence or absence of 9.5 mT low-frequency magnetic field. The highest levels of intermolecular and intramolecular ionic and hydrogen bonds in MP were observed at the heating rate of 2 °C/min under the 9.5 mT magnetic field. These bonds resulted in decreasing the α-helix and increasing the ß-sheet and ß-turn, which promoted the formation of a more uniform microstructure. It also increased the proportion of bound water, increasing the ability of MP to bind with water. This effect, combined with the weaker hydrophobic interactions, as confirmed by the reduced content of tryptophan and aliphatic residues, explained well the high water-holding capacity of MP induced by heating at 2 °C/min under the 9.5 mT magnetic field.


Assuntos
Géis/química , Campos Magnéticos , Proteínas Musculares/química , Miofibrilas/química , Carne de Porco , Animais , Calefação , Ligação de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Reologia , Água/química
14.
Int J Neuropsychopharmacol ; 23(3): 181-191, 2020 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-31990032

RESUMO

BACKGROUND: Both the clinical and preclinical studies have suggested embryonic or infant exposure to ketamine, a general anesthetic, pose a great threat to the developing brain. However, it remains unclear how ketamine may contribute to the brain dysfunctions. METHODS: A mouse model of prenatal exposure to ketamine was generated by i.m. injection and continuous i.p. infusion of pregnant mice. Open field test and elevated plus maze test were used to analyze the behavioral alterations induced by ketamine. Immunostaining by c-Fos was used to map the neuron activity. Chemogenetic modulation of the neurons was used to rescue the abnormal neuron activity and behaviors. RESULTS: Here we show that mice prenatally exposed to ketamine displayed anxiety-like behaviors during adulthood, but not during puberty. C-Fos immunostaining identified abnormal neuronal activity in Bed Nucleus of the Stria Terminalis, the silencing of which by chemogenetics restores the anxiety-like behaviors. CONCLUSIONS: Taken together, these results demonstrate a circuitry mechanism of ketamine-induced anxiety-like behaviors.


Assuntos
Anestésicos Dissociativos/farmacologia , Ansiedade/induzido quimicamente , Ketamina/farmacologia , Efeitos Tardios da Exposição Pré-Natal/induzido quimicamente , Núcleos Septais/efeitos dos fármacos , Fatores Etários , Anestésicos Dissociativos/administração & dosagem , Animais , Ansiedade/fisiopatologia , Comportamento Animal/fisiologia , Modelos Animais de Doenças , Feminino , Técnicas Genéticas , Ketamina/administração & dosagem , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Gravidez , Efeitos Tardios da Exposição Pré-Natal/fisiopatologia , Maturidade Sexual/fisiologia
15.
Adv Mater ; 31(51): e1905436, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31643113

RESUMO

Tunneling junction is used in many devices such as high-frequency oscillators, nonvolatile memories, and magnetic field sensors. In these devices, modulation on the barrier width and/or height is usually realized by electric field or magnetic field. Here, a new piezotronic tunneling junction (PTJ) principle, in which the quantum tunneling is controlled/tuned by externally applied mechanical stimuli, is proposed. In these metal/insulator/piezoelectric semiconductor PTJs, such as Pt/Al2 O3 /p-GaN, the height and the width of the tunneling barriers can be mechanically modulated via the piezotronic effect. The tunneling current characteristics of PTJs exhibit critical behavior as a function of external mechanical stimuli, which results in high sensitivity (≈5.59 mV MPa-1 ), giant switching (>105 ), and fast response (≈4.38 ms). Moreover, the mechanical controlling of tunneling transport in PTJs with various thickness of Al2 O3 is systematically investigated. The high performance observed with these metal/insulator/piezoelectric semiconductor PTJs suggest their great potential in electromechanical technology. This study not only demonstrates dynamic mechanical controlling of quantum tunneling, but also paves a way for adaptive interaction between quantum tunneling and mechanical stimuli, with potential applications in the field of ultrasensitive press sensor, human-machine interface, and artificial intelligence.

16.
Food Res Int ; 121: 678-683, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31108795

RESUMO

Isolated myofibrillar protein (MP) was treated by the oxidation system of FeCl3 (0.01 mM) at four different H2O2 concentrations (0, 1, 10, 20 mM). The oxidation degree was determined by measuring the carbonyl and total sulphydryl values. The structure and physicochemical properties of MP gels were investigated by water holding capacity (WHC) evaluation, sodium dodecyl sulfate-polyacryl amide gel electrophoresis (SDS-PAGE), texture profile analysis (TPA), Raman spectroscopy, and NMR transverse relaxation (T2). The results of carbonyls and total sulphydryls indicated that oxidation degree of MP increased with increasing H2O2 concentration. TPA showed that moderate oxidation (10 mM H2O2) could improve the hardness, springiness, gumminess and cohesiveness of MP gels, but not contribute to the maintenance of their WHC, probably due to severe depolymerization of MPs, unfolding of α-helix, exposure of the hydrophobic groups and the migration of protein-associated water (T2b) and intra-myofibrillar water (T21) to the longer relaxation time.


Assuntos
Géis/química , Estresse Oxidativo , Carne Vermelha/análise , Animais , Eletroforese em Gel de Poliacrilamida , Peróxido de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Espectroscopia de Ressonância Magnética , Proteínas de Carne/análise , Oxirredução , Análise Espectral Raman , Compostos de Sulfidrila/análise , Suínos , Água/química
17.
Cell Rep ; 24(3): 713-723, 2018 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-30021167

RESUMO

Protein phosphatase 2A (PP2A) inhibition causes hyperphosphorylation of tau and APP in Alzheimer's disease (AD). However, the mechanisms underlying the downregulation of PP2A activity in AD brain remain unclear. We demonstrate that Cancerous Inhibitor of PP2A (CIP2A), an endogenous PP2A inhibitor, is overexpressed in AD brain. CIP2A-mediated PP2A inhibition drives tau/APP hyperphosphorylation and increases APP ß-cleavage and Aß production. Increase in CIP2A expression also leads to tau mislocalization to dendrites and spines and synaptic degeneration. In mice, injection of AAV-CIP2A to hippocampus induced AD-like cognitive deficits and impairments in long-term potentiation (LTP) and exacerbated AD pathologies in neurons. Indicative of disease exacerbating the feedback loop, we found that increased CIP2A expression and PP2A inhibition in AD brains result from increased Aß production. In summary, we show that CIP2A overexpression causes PP2A inhibition and AD-related cellular pathology and cognitive deficits, pointing to CIP2A as a potential target for AD therapy.


Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Autoantígenos/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas de Membrana/metabolismo , Transtornos da Memória/metabolismo , Sinapses/patologia , Proteínas tau/metabolismo , Doença de Alzheimer/complicações , Doença de Alzheimer/patologia , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Células HEK293 , Hipocampo/patologia , Hipocampo/fisiopatologia , Humanos , Potenciação de Longa Duração , Transtornos da Memória/complicações , Transtornos da Memória/patologia , Camundongos Endogâmicos C57BL , Degeneração Neural/metabolismo , Degeneração Neural/patologia , Neurônios/metabolismo , Neurônios/patologia , Fosforilação , Proteína Fosfatase 2/antagonistas & inibidores , Proteína Fosfatase 2/metabolismo , Ratos Sprague-Dawley , Sinapses/metabolismo
18.
World J Gastroenterol ; 24(25): 2776-2784, 2018 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-29991881

RESUMO

Liposarcoma of the stomach is extremely rare, and only 37 cases have been reported worldwide. We herein report two cases of liposarcoma of the stomach. The first patient was referred to our hospital with upper abdominal discomfort. The endoscopic examination revealed a tumor mass about 3 cm in diameter. The patient underwent a partial gastrectomy and had an uneventful recovery. The histopathological examination revealed a well-differentiated liposarcoma. The second patient had symptoms of upper abdominal discomfort combined with nausea and anorexia. Several palpable masses were found with endoscopy. Endoscopic submucosal dissection was the treatment used, and the postoperative course was uneventful. The histopathological diagnosis was a well-differentiated liposarcoma. The two patients did not undergo any adjuvant therapy. They are both currently in good condition without recurrence. Therefore, we believe that the outcome of liposarcoma of the stomach is positive, and surgical resection may be the first choice for treatment at present.


Assuntos
Lipossarcoma/diagnóstico , Doenças Raras/diagnóstico , Neoplasias Gástricas/diagnóstico , Estômago/patologia , Ressecção Endoscópica de Mucosa/métodos , Endossonografia , Feminino , Gastrectomia/métodos , Gastroscopia , Humanos , Lipossarcoma/patologia , Lipossarcoma/cirurgia , Masculino , Pessoa de Meia-Idade , Doenças Raras/patologia , Doenças Raras/cirurgia , Estômago/diagnóstico por imagem , Estômago/cirurgia , Neoplasias Gástricas/patologia , Neoplasias Gástricas/cirurgia , Tomografia Computadorizada por Raios X , Resultado do Tratamento
19.
ACS Nano ; 12(5): 4903-4908, 2018 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-29701956

RESUMO

Because silicon transistors are rapidly approaching their scaling limit due to short-channel effects, alternative technologies are urgently needed for next-generation electronics. Here, we demonstrate ultrathin ZnO piezotronic transistors with a ∼2 nm channel length using inner-crystal self-generated out-of-plane piezopotential as the gate voltage to control the carrier transport. This design removes the need for external gate electrodes that are challenging at nanometer scale. These ultrathin devices exhibit a strong piezotronic effect and excellent pressure-switching characteristics. By directly converting mechanical drives into electrical control signals, ultrathin piezotronic devices could be used as active nanodevices to construct the next generation of electromechanical devices for human-machine interfacing, energy harvesting, and self-powered nanosystems.

20.
Curr Biol ; 28(6): 859-871.e5, 2018 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-29502952

RESUMO

Defensive responses to threatening stimuli are crucial to the survival of species. While expression of these responses is considered to be instinctive and unconditional, their magnitude may be affected by environmental and internal factors. The neural circuits underlying this modulation are still largely unknown. In mice, looming-evoked defensive responses are mediated by the superior colliculus (SC), a subcortical sensorimotor integration center. We found that repeated stress caused an anxiety-like state in mice and accelerated defensive responses to looming. Stress also induced c-fos activation in locus coeruleus (LC) tyrosine hydroxylase (TH)+ neurons and modified adrenergic receptor expression in SC, suggesting a possible Th::LC-SC projection that may be involved in the accelerated defensive responses. Indeed, both anterograde and retrograde neural tracing confirmed the anatomical Th::LC-SC projection and that the SC-projecting TH+ neurons in LC were activated by repeated stress. Optogenetic stimulation of either LC TH+ neurons or the Th::LC-SC fibers also caused anxiety-like behaviors and accelerated defensive responses to looming. Meanwhile, chemogenetic inhibition of LC TH+ neurons and the infusion of an adrenergic receptor antagonist in SC abolished the enhanced looming defensive responses after repeated stress, confirming the necessity of this pathway. These findings suggest that the Th::LC-SC pathway plays a key role in the sophisticated adjustments of defensive behaviors induced by changes in physiological states.


Assuntos
Mecanismos de Defesa , Estresse Psicológico/metabolismo , Animais , Ansiedade/fisiopatologia , Medo/fisiologia , Genes fos/genética , Instinto , Locus Cerúleo/metabolismo , Locus Cerúleo/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Vias Neurais/fisiologia , Neurônios/fisiologia , Norepinefrina/metabolismo , Optogenética , Receptores Adrenérgicos/metabolismo , Colículos Superiores/fisiologia , Tirosina 3-Mono-Oxigenase/genética , Tirosina 3-Mono-Oxigenase/metabolismo
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