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Paeonol (2-hydroxy-4-methoxyphenylacetophenone) is a natural phenolic component isolated from the root bark of peony with multiple pharmacological activities and has been proven to have anti-cancer effects. The objective of this study is to investigate the influence mechanism of paeonol on the proliferatory and apoptotic activities of ovarian cancer (OC) cells by modulating the transforming growth factor beta (TGF-ß)/Smad3 pathway. The SKOV3 cells were pretreated with various concentrations of paeonol (0, 25, 50, 100, 200, 400 µg/mL) for 48 hours to determine the optimal experimental concentration of paeonol. Following this, the TGF-ß overexpression vector was constructed and transfected into the SKOV3 cells. The assessment of cell proliferation, invasion, and migration was conducted through MTT, colony formation, flow cytometry, transwell, and wound-healing experiments. The detection of TGF-ß/Smad3 pathway-related proteins and apoptosis-related proteins (B-cell lymphoma (Bcl-2) Bcl-2-associated X protein (Bax)) was performed using Western blot analysis. Paeonol exhibited a significant inhibitory effect on SKOV3 cell viability when administered at concentrations ranging from 50-400 µg/mL, with an IC50 value of 200 µg/mL. Within the concentration range of 50 to 200 µg/mL, paeonol exhibited a dose-dependent effect on the progression of SKOV3 cells, including a reduction in the anti-apoptotic protein Bcl-2, an increase in the pro-apoptotic protein Bax (P<0.05), inhibition of cell migration and invasion (P<0.05), and promotion of cell apoptosis (P<0.05), particularly at a concentration of 200 µg/mL. These effects were found to be more pronounced. The aforementioned effects of paeonol can be ascribed to its inhibition of the TGFß/Smad3 pathway, according to a mechanistic viewpoint. It is noteworthy that the inhibitory impact of paeonol on SKOV3 cell progression is counteracted by the elevation of TGF-ß levels following overexpression. We conclude that paeonol exerts regulatory effects on the TGF-ß/Smad3 pathway, leading to the inhibition of proliferation, migration, and invasion of OC cells, thereby attenuating malignant behavior of cancer cells.
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Acetofenonas , Neoplasias Ovarianas , Humanos , Feminino , Proteína X Associada a bcl-2 , Neoplasias Ovarianas/metabolismo , Fator de Crescimento Transformador beta/farmacologia , Fator de Crescimento Transformador beta/uso terapêutico , Apoptose , Transdução de Sinais , Proliferação de Células , Linhagem Celular Tumoral , Movimento CelularRESUMO
To elucidate the role of anti-müllerian hormone (AMH) in regulating the development of ovarian follicles in laying hens, the expressions of follicle-stimulating hormone receptor (FSHR), AMH receptor type 2 (AMHR2), steroidogenic-related genes steroidogenic acute regulatory protein (STAR), cytochrome P450 side-chain cleavage (CYP11A1), and 3ß-hydroxysteroid dehydrogenase (HSD3B1) genes were measured from different sized follicles and granulosa cells. The results showed that the expressions of FSHR and AMHR2 genes were higher in small follicles and decreased after follicular selection. Oppositely, the expressions of STAR, CYP11A1, and HSD3B1 were significantly increased after follicular selection. It indicated that AMHR2 might mediate AMH suppression in the stimulating effects of follicle-stimulating hormone (FSH) on steroidogenic-related genes expression. To make sure the effects of AMH in this process, a total of 40 hens were treated (negative control, sham operation, 150 ng AMH/d or 300 ng AMH/d) for 25 d. We analyzed ovarian morphology, progesterone concentration in blood plasma, and the expressions of steroidogenic genes in ovaries and follicles. The AMH300 group had significantly lower weight of ovary and hierarchical follicles. Egg weight and ovary weight in AMH150 group were higher than those of sham operation and AMH300 groups, so did hierarchical follicles weight. The steroidogenic genes expressions showed an increase in ovarian tissue and the largest follicle of AMH150 and AMH300 groups. However, progesterone level in the blood was reduced by AMH injection with different concentrations. To further verify the above results, granulosa cells from 6 to 8 mm follicles were cultured with AMH (0, 5, 10, 20, 40, or 80 ng/mL). The results revealed that excessive AMH (80 ng/mL) exerted an inhibitory effect on progesterone synthesis and the expressions of STAR, CYP11A1, and HSD3B1. However, these genes expressions showed a significant increase in 20 ng/mL AMH-treated group. In summary, AMH inhibited the development of prehierarchical follicles in laying hens. The effects of AMH treatment with different concentrations on follicle development showed the follicle was selected by changing FSH responsiveness of prehierarchical follicles.
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Hormônio Antimülleriano , Galinhas , Regulação da Expressão Gênica no Desenvolvimento , Folículo Ovariano , Animais , Hormônio Antimülleriano/farmacologia , Proteínas Aviárias/genética , Galinhas/genética , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Células da Granulosa/efeitos dos fármacos , Folículo Ovariano/efeitos dos fármacosRESUMO
Objective: To investigate the effects of down-regulation of expression of neuropilin-2 (NRP-2) by RNA interference (RNAi) technique on proliferation and apoptosis of HCT-8 colon cancer cells. Methods: NRP2-siRNA and negative control (NControl)-siRNA were transferred into HCT-8 colon cancer cells by liposomes (lip2000) as transfection group and negative control group, and phosphate buffered solution (PBS) was added as blank control group. Quantitative reverse transcription PCR (RT-qPCR) and Western blot were used to detect the transfection effect. The proliferation of cells in the three groups was examined by cell counting kit (CCK) assay, colony-forming unit assay and Ki-67 protein staining assay, respectively. Moreover, the apoptosis of cells in the three groups was determined by acridine orange/propranidine iodide (AO/PI) staining method. Results: The results of RT-qPCR and Western blot showed that the relative expression of NRP-2 mRNA and the content of NRP-2 protein in the transfer group decreased (0.46±0.05 vs 0.99±0.05 and 1.00±0.06; 1.04±0.06 vs 1.73±0.09 and 1.65±0.11) (all P<0.05). The results of CCK-8 demonstrated that the optical density of transfection group was significantly lower than that of the negative control group and the blank control group(24 h: 0.53±0.04 vs 0.82±0.07 and 0.87±0.07; 48 h: 0.54±0.05 vs 1.00±0.09 and 1.17±0.05; 72 h: 0.75±0.05 vs 1.31±0.13 and 1.50±0.03; 96 h:1.05±0.04 vs 1.46±0.09 and 1.86±0.06) (all P<0.05). The results of colony-forming unit assay indicated that the proliferation ability of the cells in the transfer group was significantly lower than that in the other two groups (134.67±8.74 vs 245.33±19.14 and 300.33±14.01, P<0.05). The results of Ki-67 protein staining assay showed that compared with the negative control group and blank control group, the expression of Ki-67 protein was significantly decreased in the transfection group (5.93±0.22 vs 8.36±0.09 and 8.70±0.21, P<0.05). The results of AO/PI assay revealed that the ratio of apoptotic cells to living cells in the transfer group was significantly higher than that in the other two groups (0.43±0.07 vs 0.14±0.04 and 0.11±0.04, P<0.05). Conclusion: The proliferation ability of HCT-8 colon cancer cells decreases, and the apoptosis ability increases by decreasing the expression of NRP-2.
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Neoplasias do Colo , Neuropilina-2 , Apoptose , Linhagem Celular Tumoral , Proliferação de Células , Neoplasias do Colo/genética , Humanos , Neuropilina-2/genética , Interferência de RNA , RNA Interferente Pequeno , TransfecçãoRESUMO
Objective: To establish and validate a radiomics nomogram based on MR for predicting cervical lymph node metastasis in laryngeal cancer. Methods: One hundred and seventeen patients with laryngeal cancer who underwent MR examinations and received open surgery and neck dissection between January 2016 and December 2019 were included in this study. All patients were randomly divided into a training cohort (n=89) and test cohort (n=28) using computer-generated random numbers. Clinical characteristics and MR were collected. Radiological features were extracted from the MR images. Enhanced T1 and T2WI were selected for radiomics analysis, and the volume of interest was manually segmented from the Huiyihuiying radiomics cloud platform. The variance analysis (ANOVA) and the least absolute shrinkage and selection operator (LASSO) algorithm were used to reduce the dimensionality of the radiomics features in the training cohort. Then, a radiomic signature was established. The clinical risk factors were screened by using ANOVA and multivariate logistic regression. A nomogram was generated using clinical risk factors and the radiomic signature. The calibration curve and receiver operator characteristic (ROC) curve were used to confirm the nomogram's performance in the training and test sets. The clinical usefulness of the nomogram was evaluated by decision curve analysis (DCA). Furthermore, a testing cohort was used to validate the model. Results: The radiomics signature consisted of 21 features, and the nomogram model included the radiomics signature and the MR-reported lymph node status. The model showed good calibration and discrimination. The model yielded areas under the ROC curve (AUC) in the training cohort, specificity, and sensitivity of 0.930, 0.930 and 0.875. In the test cohort, the model yielded AUC, specificity and sensitivity of 0.883, 0.889 and 0.800. DCA indicated that the nomogram model was clinically useful. Conclusion: The MR-based radiomics nomogram model may be used to predict cervical lymph node metastasis of laryngeal cancer preoperatively. MR-based radiomics could serve as a potential tool to help clinicians make an optimal clinical decision.
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Neoplasias Laríngeas , Nomogramas , Humanos , Neoplasias Laríngeas/diagnóstico por imagem , Linfonodos/diagnóstico por imagem , Metástase Linfática , Estudos RetrospectivosRESUMO
OBJECTIVE: Researchers have uncovered the importance of circular RNAs (circ) in malignant tumors. Circ LARP4 has been found to serve as a tumor suppressor gene in gastric cancer. However, the exact function of circ LARP4 in non-small-cell lung cancer (NSCLC) has not been fully elucidated. The aim of this study was to uncover the role of circ LARP4 in the tumorigenesis of NSCLC. PATIENTS AND METHODS: Expression level of circ LARP4 in NSCLC tissues was detected through Real Time-quantitative Polymerase Chain Reaction (RT-qPCR). Subsequently, the association between expression and patients' prognosis was analyzed. Circ LARP4 lentivirus was constructed and transfected into NSCLC cells. The effect of circ LARP4 on NSCLC cell migration and invasion was detected by function assays. Furthermore, Western blot was performed to analyze the expression of predicted protein of circ LARP4. RESULTS: Compared with adjacent tissues, circ LARP4 was lowly expressed in NSCLC tissues. Meanwhile, expression of circ LARP4 was associated with the prognosis of NSCLC patients. Downregulated circ LARP4 was found in NSCLC cell lines as well. The migration and invasion abilities of NSCLC cells were significantly inhibited via overexpression of circ LARP4. SMAD7, the predicted protein of circ LARP4, increased remarkably via overexpression of circ LARP4. CONCLUSIONS: Circ LARP4 could suppress the metastasis of NSCLC by up-regulating SMAD7.
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Autoantígenos/metabolismo , Carcinoma Pulmonar de Células não Pequenas/metabolismo , Neoplasias Pulmonares/metabolismo , RNA Circular/metabolismo , Ribonucleoproteínas/metabolismo , Proteína Smad7/genética , Autoantígenos/genética , Carcinoma Pulmonar de Células não Pequenas/patologia , Células Cultivadas , Humanos , Neoplasias Pulmonares/patologia , RNA Circular/genética , Ribonucleoproteínas/genética , Proteína Smad7/metabolismo , Antígeno SS-BRESUMO
Objective: To investigate the effect of miR-27a-3p on proliferation, apoptosis and cell cycle of hepatoma cells. Methods: A quantitative real-time polymerase chain reaction (qPCR) was used to detect differential expression of miR-27a-3p in normal hepatic epithelial cells (L02) and hepatoma cells (HepG2 and PLC). Cell experiment was divided into four groups: HepG2 overexpression cells, Mi-27a-3p overexpression group (Mi-27a) and negative control group (Mi-Con); PLC knockdown cells, Mi-27a-3p knockdown group (Mi-inhibitor-27a) and negative control group (Mi-inhibitor-Con). The expression of microRNA-27a-3p in each group after transfection was detected by qPCR analysis. MTT assay was used to detect the cell proliferation. Flow cytometry was used to detect the apoptosis and cell cycle. One-way ANOVA was used for multiple comparisons, and t-test was used to compare two groups. Results: qPCR results showed that the expression levels of miR-27a-3p in L02, HepG2 and PLC increased sequentially, and the relative expression levels were 1.07 ± 0.04, 4.81 ± 0.64 and 11.31 ± 0.92, respectively (P < 0.05). MTT assay showed that the cell viability of HepG2 cells transfected with miR-27a-3p overexpression plasmid was significantly decreased compared with the negative control group (P < 0.05). The apoptosis assay showed that the apoptosis rate of miR-27a-3p overexpression group was higher than the negative control group (P < 0.05). The cell cycle results showed that the proportion of S phase cells in the miR-27a-3p overexpression cell group was significantly lower than the negative control group (P < 0.05). Furthermore, microRNA-27a-3p knockdown validation in PLC cells showed that MTT, apoptosis and cell cycle tests results were opposite to the results of HepG2 overexpression cells, and the differences were statistically significant (P < 0.05). Conclusion: miR-27a-3p can significantly inhibit the proliferation of hepatoma cells, promote cell apoptosis, alter the cell cycle distribution, and may become a potential target in hepatocellular carcinoma therapy.
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Carcinoma Hepatocelular , Neoplasias Hepáticas , Apoptose , Ciclo Celular , Linhagem Celular Tumoral , Proliferação de Células , Regulação Neoplásica da Expressão Gênica , Humanos , MicroRNAsRESUMO
Summary Head and neck carcinosarcoma leads to kinds of manifestations because of different original tumor sites, such as hoarseness and dyspnea in larynx, pharyngalgia and dysphagia in pharynx and compression in neck. Imaging examinations show specific occupying tumor sites and sometimes discover peripheral invasion. Pathological examination reveals both malignant squamous epithelium and interstitial tissue in these tumorsï¼and therefore we diagnose these tumors as carcinosarcoma.
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Carcinossarcoma , Neoplasias de Cabeça e Pescoço , Cabeça , Humanos , Laringe , Pescoço , FaringeRESUMO
Perovskites such as SrTiO3, BaTiO3, and CaTiO3 have become key materials for future energy-efficient memristive data storage and logic applications due to their ability to switch their resistance reversibly upon application of an external voltage. This resistance switching effect is based on the evolution of nanoscale conducting filaments with different stoichiometry and structure than the original oxide. In order to design and optimize memristive devices, a fundamental understanding of the interaction between electrochemical stress, stoichiometry changes and phase transformations is needed. Here, we follow the approach of investigating these effects in a macroscopic model system. We show that by applying a DC voltage under reducing conditions on a perovskite slab it is possible to induce stoichiometry polarization allowing for a controlled decomposition related to incongruent sublimation of the alkaline earth metal starting in the surface region. This way, self-formed mesoporous layers can be generated which are fully depleted by Sr (or Ba, Ca) but consist of titanium oxides including TiO and Ti3O with tens of micrometre thickness. This illustrates that phase transformations can be induced easily by electrochemical driving forces.
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While doping is widely used for tuning physical properties of perovskites in experiments, it remains a challenge to exactly know how doping achieves the desired effects. Here, we propose an empirical and computationally tractable model to understand the effects of doping with Fe-doped BaTiO3 as an example. This model assumes that the lattice sites occupied by a Fe ion and its nearest six neighbors lose their ability to polarize, giving rise to a small cluster of defective dipoles. Employing this model in Monte Carlo simulations, many important features such as reduced polarization and the convergence of phase transition temperatures, which have been observed experimentally in acceptor doped systems, are successfully obtained. Based on microscopic information of dipole configurations, we provide insights into the driving forces behind doping effects and propose that active dipoles, which exist in proximity to the defective dipoles, can account for experimentally observed phenomena. Close attention to these dipoles is necessary to understand and predict doping effects.
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Since the first report of porcine kobuvirus (PKV) in 2008, it has been confirmed that PKV is widely present in several countries and plays an important role in diarrhoea outbreak in pigs. Studies have shown that the biggest difference among PKVs is the presence or absence of a specific 30-amino acid (aa) sequence in the 2B region of the polyprotein gene. Based on this unique feature, most PKV sequences could be divided into two groups (Group 1 without deletion and Group 2 with deletion), but a few sequences did not follow this rule due to possible recombination. In this study, two PKV genome sequences, designated JXAT2015 (8,123 nucleotide) and JXJC2015 (8,120 nucleotide), were identified on two different commercial swine farms with the severe diarrhoea outbreak accompanying with highly PKV infection (90%, 18/20) and moderate infection (40%, 8/20) of porcine bocavirus 1 (PBoV1) in Jiangxi province of China. Sequence analysis based on the polyprotein gene showed that they shared low nucleotide similarity (86.3%-88.1%) with other known PKVs. Although both possessed the 30-aa deletion in the 2B region, phylogenetic analysis showed that JXJC2015 was distinct from Group 1 and even Group 2, and formed a new Group (designated Group 3). The findings of this study further revealed genetic diversity and the possible pathogenic role of PKV in conjunction with other pathogens in piglets.
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Diarreia/veterinária , Kobuvirus/isolamento & purificação , Infecções por Picornaviridae/veterinária , Doenças dos Suínos/virologia , Sequência de Aminoácidos , Animais , China/epidemiologia , DNA Viral/genética , Diarreia/patologia , Diarreia/virologia , Variação Genética , Kobuvirus/genética , Filogenia , Infecções por Picornaviridae/epidemiologia , Infecções por Picornaviridae/virologia , Análise de Sequência de DNA , Suínos , Doenças dos Suínos/epidemiologia , Doenças dos Suínos/patologiaRESUMO
Previously, we identified three porcine circovirus type 2 (PCV2) strains in buffalo meat samples from southern China. In this study, we confirmed the reappearance of those buffalo-origin-like PCV2 strains in swine herds in this region, which supported the possible cross-species infection of PCV2 between buffalos and pigs under field conditions.
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Coupling between lattice and order parameters, such as polarization in ferroelectrics and/or polarity in polar structures, has a strong impact on surface relaxation and reconstruction. However, up to now, surface structures that involve the termination of both matrix polarization and polar atomic planes have received little attention, particularly on the atomic scale. Here, we study surface structures on a BiFeO3 thin film using atomic-resolution scanning transmission electron microscopy and spectroscopy. Two types of surface structure are found, depending on the polarization of the underlying ferroelectric domain. On domains that have an upward polarization component, a layer with an Aurivillius-Bi2O2-like structural unit is observed. Dramatic changes in local properties are measured directly below the surface layer. On domains that have a downward polarization component, no reconstructions are visible. Calculations based on ab initio density functional theory reproduce the results and are used to interpret the formation of the surface structures.
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We suggest and demonstrate via large scale numerical simulations an electrically operated spin-wave inducer based on composite multiferroic junctions. Specifically, we consider an interfacially coupled ferromagnetic/ferroelectric structure that emits controllably spin waves in the ferromagnets if the ferroelectric polarization is poled by an external electric field. The roles of geometry and material properties are discussed.
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Tibetan chickens have good adaptation to hypoxic conditions, which can be reflected by higher hatchability than lowland breeds when incubated at high altitude. The objective of this trial was to study changes in egg composition and metabolism with regards the adaptation of Tibetan chickens to high altitude. We measured the dry weight of chicken embryos, egg yolk, and egg albumen, and the activity of lactate dehydrogenase (LDH) and succinic dehydrogenase (SDH) in breast muscle, heart, and liver from embryos of Tibetan chicken and Dwarf chicken (lowland breed) incubated at high (2,900 m) and low (100 m) altitude. We found that growth of chicken embryos was restricted at high altitude, especially for Dwarf chicken embryos. In Tibetan chicken, the egg weight was lighter, but the dry weight of egg yolk was heavier than that of Dwarf chicken. The LDH activities of the three tissues from the high altitude groups were respectively higher than those of the lowland groups from d 15 to hatching, except for breast muscle of Tibetan chicken embryos on d 15. In addition, under the high altitude environment, the heart tissue from Tibetan chicken had lower LDH activity than that from Dwarf chicken at d 15 and 18. The lactic acid content of blood from Tibetan chicken embryos was lower than that of Dwarf chicken at d 12 and 15 of incubation at high altitude. There was no difference in SDH activity in the three tissues between the high altitude groups and the lowland groups except in three tissues of hatchlings and at d 15 of incubation in breast muscle, nor between the two breeds at high altitude except in the heart of hatchlings. Consequently, the adaptation of Tibetan chicken to high altitude may be associated with higher quantities of yolk in the egg and a low metabolic oxygen demand in tissue, which illuminate the reasons that the Tibetan chicken have higher hatchability with lower oxygen transport ability.
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Adaptação Biológica , Proteínas Aviárias/genética , Galinhas/fisiologia , L-Lactato Desidrogenase/genética , Succinato Desidrogenase/genética , Altitude , Animais , Proteínas Aviárias/metabolismo , Embrião de Galinha/enzimologia , Embrião de Galinha/fisiologia , Galinhas/genética , L-Lactato Desidrogenase/metabolismo , Especificidade de Órgãos , Óvulo/enzimologia , Óvulo/fisiologia , Succinato Desidrogenase/metabolismo , TibetRESUMO
The experiment was conducted to investigate the influence of different levels of zinc (Zn) on cashmere growth, plasma testosterone and Zn profile in male Cashmere goats. Twenty-eight male Liaoning Cashmere goats, 3 years old and body weight at 56.2 ± 2.45 kg, were assigned to four groups. The animals were fed a basal diet containing of 45.9 mg Zn/kg dry matter (DM) basis and supplemented with 0, 20, 40 or 80 mg Zn (reagent grade ZnSO4 ·7H2 O) per kg DM for 90 days. There was no significant effect on growth and diameter of cashmere fibre for Zn supplemented in diets. However, the length and growth rate of wool were improved (p < 0.05) with dietary Zn. The length and growth rate of wool were higher (p < 0.05) for the groups supplemented with 40 or 80 mg Zn/kg DM compared with that of 20 mg Zn/kg DM treatment group. Plasma testosterone concentration was increased for Zn supplemented in diets, and the testosterone concentration was higher (p < 0.05) in goats fed on the diet supplemented with 40 or 80 mg Zn/kg DM compared with those fed on basal diet. Plasma Zn concentrations increased (p < 0.05) with increasing dietary Zn and supplemented with 40 and 80 mg Zn/kg DM groups improved plasma Zn concentration (p < 0.05) more than 20 mg Zn/kg DM group. Fibre Zn content was higher (p < 0.05) in groups supplemented with 40 or 80 mg Zn/kg DM compared with control group, but no difference between Zn-supplemented groups (p > 0.05). The activity of plasma alkaline phosphatase was increased (p < 0.05) due to dietary Zn supplementation; however, no difference was found between supplemented treatment groups (p > 0.05). In conclusion, Zn content (45.9 mg Zn/kg DM) in control diet was insufficient for optimal wool growth performance, and we recommended the level of dietary Zn for such goats is 86 mg/kg DM during the breeding season and cashmere fibre growing period.
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Ração Animal/análise , Dieta/veterinária , Cabras/crescimento & desenvolvimento , Cabelo/crescimento & desenvolvimento , Testosterona/sangue , Zinco/farmacologia , Fenômenos Fisiológicos da Nutrição Animal , Animais , Relação Dose-Resposta a Droga , Cabras/sangue , Masculino , Zinco/sangueRESUMO
Although the overall atomic structure of a nanoscale crystal is in principle accessible by modern transmission electron microscopy, the precise determination of its surface structure is an intricate problem. Here, we show that aberration-corrected transmission electron microscopy, combined with dedicated numerical evaluation procedures, allows the three-dimensional shape of a thin MgO crystal to be determined from only one single high-resolution image. The sensitivity of the reconstruction procedure is not only sufficient to reveal the surface morphology of the crystal with atomic resolution, but also to detect the presence of adsorbed impurity atoms. The single-image approach that we introduce offers important advantages for three-dimensional studies of radiation-sensitive crystals.
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The dislocations created by mechanical polishing of SrTiO3 (100) single crystals were investigated by means of transmission electron microscopy (TEM) techniques combined with scanning TEM (STEM) techniques. A high density of dislocations was observed in the surface layer with a thickness of about 5 µm. These dislocations were found to be straight and highly aligned along the ã111ã directions. In most cases they appear in pairs or as a bundle. The nature of the dislocations was determined as mixed ã110ã-type with the line vector t=ã111ã. They are ã110ã-type 35.26° dislocations. The isolated ã110ã-type 35.26° dislocations possess a compact core structure with a core spreading of ~0.5 nm. Dissociation of the dislocation occurs on the {1−10} glide plane, leading to the formation of two b=a/2ã110ã partials separated by a stacking fault. The separation of the two partials was estimated to be 2.53 ± 0.32 nm based on a cross-correlation analysis of atomic-resolution images. Our results provide a solid experimental evidence for this special type of dislocation in SrTiO3. The high density of straight and highly ã111ã-orientated dislocations is expected to have an important influence on the anisotropy in electrical and mass transport properties.
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Microscopia Eletrônica de Transmissão e Varredura/métodos , Microscopia Eletrônica de Transmissão/métodos , Óxidos/química , Estrôncio/química , Titânio/química , CristalizaçãoRESUMO
The atomic structure of dislocation cores is decisive for the understanding of plasticity in crystalline solids. The core structure of dislocations in sapphire introduced by high-temperature plastic deformation has been investigated with the use of the negative spherical-aberration imaging technique. The ability of this technique to discriminate oxygen columns from aluminum (Al) columns, combined with reproduction of subtle contrast features by image simulation, leads to a markedly detailed atomic model of the dislocation cores. The partial dislocations are Al-terminated, with electrical neutrality being achieved because half of the Al columns are missing. These partials also undergo core spreading, which results in random occupancy of both tetrahedrally and octahedrally coordinated sites, though Al in tetrahedral coordination never occurs in a perfect crystal. Unusual dislocation core structures may be present in other technologically important nonmetallic solids.
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We study, on an atomic scale, the influence of a single dislocation in a SrTiO3 sublayer on the local ferroelectric polarization of the neighboring ferroelectric PbZr0.2Ti0.8O3 (PZT) sublayer in an epitaxial SrTiO3/PbZr0.2Ti0.8O3/SrTiO3 three-layer heterostructure. The strain field of the dislocation in the SrTiO3 layer propagates across the interface into the PZT layer and leads to a strong variation of the c-lattice parameter of the PZT layer. Accompanying a strong reduction of the c-lattice parameter, the off-center displacements of the Zr/Ti atoms away from the center of the oxygen octahedra are also strongly decreased, resulting in a decrease of the local spontaneous polarization by up to 48%.