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BACKGROUND: Somatic embryogenesis (SE) exemplifies the unique developmental plasticity of plant cells. The regulatory processes, including epigenetic modifications controlling embryogenic reprogramming of cell transcriptome, have just started to be revealed. RESULTS: To identify the genes of histone acetylation-regulated expression in SE, we analyzed global transcriptomes of Arabidopsis explants undergoing embryogenic induction in response to treatment with histone deacetylase inhibitor, trichostatin A (TSA). The TSA-induced and auxin (2,4-dichlorophenoxyacetic acid; 2,4-D)-induced transcriptomes were compared. RNA-seq results revealed the similarities of the TSA- and auxin-induced transcriptomic responses that involve extensive deregulation, mostly repression, of the majority of genes. Within the differentially expressed genes (DEGs), we identified the master regulators (transcription factors - TFs) of SE, genes involved in biosynthesis, signaling, and polar transport of auxin and NITRILASE-encoding genes of the function in indole-3-acetic acid (IAA) biosynthesis. TSA-upregulated TF genes of essential functions in auxin-induced SE, included LEC1/LEC2, FUS3, AGL15, MYB118, PHB, PHV, PLTs, and WUS/WOXs. The TSA-induced transcriptome revealed also extensive upregulation of stress-related genes, including those related to stress hormone biosynthesis. In line with transcriptomic data, TSA-induced explants accumulated salicylic acid (SA) and abscisic acid (ABA), suggesting the role of histone acetylation (Hac) in regulating stress hormone-related responses during SE induction. Since mostly the adaxial side of cotyledon explant contributes to SE induction, we also identified organ polarity-related genes responding to TSA treatment, including AIL7/PLT7, RGE1, LBD18, 40, HB32, CBF1, and ULT2. Analysis of the relevant mutants supported the role of polarity-related genes in SE induction. CONCLUSION: The study results provide a step forward in deciphering the epigenetic network controlling embryogenic transition in somatic cells of plants.
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Arabidopsis , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Histonas , Ácidos Indolacéticos , Arabidopsis/genética , Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/efeitos dos fármacos , Ácidos Indolacéticos/metabolismo , Ácidos Indolacéticos/farmacologia , Acetilação , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Histonas/metabolismo , Técnicas de Embriogênese Somática de Plantas , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Transcriptoma , Ácidos Hidroxâmicos/farmacologia , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Inibidores de Histona Desacetilases/farmacologiaRESUMO
In this study, the effect of pre-slaughter handling on the content of macro- and micronutrients in blood serum and in the breast muscle of turkeys was assessed. Four different variants of pre-slaughter handling were used in the research: no transport (N-T), transport for a distance of 100 km (T-100), transport for a distance of 200 km (T-200), and transport for a distance of 300 km (T-300). In each of them, 30 female and 30 male turkeys were used. Blood was collected from the birds before slaughter, and samples of the pectoral muscle were collected after slaughter. In the obtained biological material, the content of Mg, P, Ca, Fe, Na and K was analyzed. On the basis of the obtained research results, it can be concluded that the pre-slaughter handling negatively affects the content of macro- and microelements both in the blood serum and in the pectoral muscles of experimental turkeys. Additionally, differences due to the sex of birds were observed.
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Genotype-limited plant regeneration is one of the main obstacles to the broader use of genetic transformation in barley breeding. Thus, developing new approaches that might improve responses of in vitro recalcitrant genotypes remains at the center of barley biotechnology. Here, we analyzed different barley genotypes, including "Golden Promise," a genotype commonly used in the genetic transformation, and four malting barley cultivars of poor regenerative potential. The expression of hormone-related transcription factor (TF) genes with documented roles in plant regeneration was analyzed in genotypes with various plant-regenerating capacities. The results indicated differential expression of auxin-related TF genes between the barley genotypes in both the explants and the derived cultures. In support of the role of auxin in barley regeneration, distinct differences in the accumulation of free and oxidized auxin were observed in explants and explant-derived callus cultures of barley genotypes. Following the assumption that modifying gene expression might improve plant regeneration in barley, we treated the barley explants with trichostatin A (TSA), which affects histone acetylation. The effects of TSA were genotype-dependent as TSA treatment improved plant regeneration in two barley cultivars. TSA-induced changes in plant regeneration were associated with the increased expression of auxin biosynthesis-involved TFs. The study demonstrated that explant treatment with chromatin modifiers such as TSA might provide a new and effective epigenetic approach to improving plant regeneration in recalcitrant barley genotypes.
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Histonas , Hordeum , Ácidos Hidroxâmicos , Histonas/genética , Histonas/metabolismo , Hordeum/genética , Acetilação , Melhoramento Vegetal , Ácidos Indolacéticos/farmacologia , Regeneração/genética , Epigênese GenéticaRESUMO
Despite numerous studies and recommendations, the acceptance of treatments involving medicinal maggots in many clinics has been slow. Several factors may account for this, including the gender of nurses administering the treatment, their level of work experience, and their perceived level of personal stress. The aim of the study was to assess the impact of selected variables (gender, work experience, stress level) on the readiness of nurses to administer maggot debridement therapy (MDT), which is a form of biodebridement. The study population was a cohort of 290 wound care nurses providing specialist care for patients with chronic wounds. It was assumed that the identified variables may determine the implementation of larval therapy in everyday professional practice. A subsample of 35 men and 35 women was further analyzed to determine if gender, work experience, and/or personal stress levels were correlated with attitudes towards the utilization of maggots in biodebridement. Assessment tools included the Perceived Stress Scale (PSS-10) and the MDT 10 Perception Assessment Questionnaire, a protocol by which the subject ranked six wound photographs in order of repulsiveness and responded to questions regarding demographic variables, which include education and work experience. The visual perception of pictures of a wound with larvae is indirectly an indicator of the attitude towards larval therapy. Selection of the photograph with maggots on the wound as the most repulsive image was associated with a personal appraisal of not being ready to implement maggot therapy (chi-square = 8.430, p = 0.015). Low work experience (chi-square = 14.039, df = 4, p = 0.007), and low readiness for MDT (chi-square = 8.430, df = 2, p = 0.015) were also associated with unpreparedness to administer maggot therapy. Neither gender nor perceived stress level were exclusively associated with disgust for maggots or lack of readiness to implement MDT. Low professional experience and a deficit of knowledge in maggot therapy may negatively affect the readiness of nurses to administer biodebridement. Gender and personal stress levels do not affect nurses' readiness to utilize larval therapy.
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The cap at the 5'terminus of mRNA is a key determinant of gene expression in eukaryotic cells, which among others is required for cap dependent translation and protects mRNA from degradation. These properties of cap are mediated by several proteins. One of them is 4E-Transporter (4E-T), which plays an important role in translational repression, mRNA decay and P-bodies formation. 4E-T is also one of several proteins that interact with eukaryotic initiation factor 4E (eIF4E), a cap binding protein which is a key component of the translation initiation machinery. The molecular mechanisms underlying the interactions of these two proteins are crucial for mRNA processing. Studying the interactions between human eIF4E1a and the N-terminal fragment of 4E-T that possesses unstructured 4E-binding motifs under non-reducing conditions, we observed that 4E-T preferentially forms an intramolecular disulphide bond. This "disulphide loop" reduces affinity of 4E-T for eIF4E1a by about 300-fold. Considering that only human 4E-T possesses two cysteines located between the 4E binding motifs, we proposed that the disulphide bond may act as a switch to regulate interactions between the two proteins.
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Fator de Iniciação 4E em Eucariotos , Biossíntese de Proteínas , Humanos , Ligação Proteica , RNA Mensageiro/genética , Fator de Iniciação 4E em Eucariotos/química , Fator de Iniciação 4E em Eucariotos/genética , Fator de Iniciação 4E em Eucariotos/metabolismoRESUMO
The importance of amorphous and nanocrystalline Fe-based soft magnetic materials is increasing annually. Thus, characterisation of the chemical compositions, alloying additives, and crystal structures is significant for obtaining the appropriate functional properties. The purpose of this work is to present comparative studies on the influence of Nb (1, 2, 3 at.%) and Mo (1, 2, 3 at.%) in Fe substitution on the thermal stability, crystal structure, and magnetic properties of a rapidly quenched Fe79.4Co5Cu0.6B15 alloy. Additional heat treatments in a vacuum (260-640 °C) were performed for all samples based on the crystallisation kinetics. Substantial improvement in thermal stability was achieved with increasing Nb substitution, while this effect was less noticeable for Mo-containing alloys. The heat treatment optimisation process showed that the least lossy states (with a minimum value of coercivity below 10 A/m and high saturation induction up to 1.7 T) were the intermediate state of the relaxed amorphous state and the nanocomposite state of nanocrystals immersed in the amorphous matrix obtained by annealing in the temperature range of 340-360 °C for 20 min. Only for the alloy with the highest thermal stability (Nb = 3%), the α-Fe(Co) nanograin grows, without the co-participation of the hard magnetic Fe3B, in a relatively wide range of annealing temperatures up to 460 °C, where the second local minimum in coercivity and core power losses exists. For the remaining annealed alloys, due to lower thermal stability than the Nb = 3% alloy, the Fe3B phase starts to crystallise at lower annealing temperatures, making an essential contribution to magneto-crystalline anisotropy, thus the substantial increase in coercivity and induction saturation. The air-annealing process tested on the studied alloys for optimal annealing conditions has potential use for this type of material. Additionally, optimally annealed Mo-containing alloys are less lossy materials than Nb-containing alloys in a frequency range up to 400 kHz and magnetic induction up to 0.8 T.
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Solution-based processing offers advantages for producing thin films due to scalability, low cost, simplicity, and benignity to the environment. Here, we develop conductive and photoactivated self-cleaning reduced graphene oxide (rGO)/Ti3CNTx MXene thin films via spin coating under ambient conditions. The addition of a thin rGO layer on top of Ti3CNTx resulted in up to 45-fold improvement in the environmental stability of the film compared to the bare Ti3CNTx film. The optimized rGO/Ti3CNTx thin film exhibits an optical transmittance of 74% in the visible region of the spectrum and a sheet resistance of 19 kΩ/sq. The rGO/Ti3CNTx films show high rhodamine B discoloration activity upon light irradiation. Under UV irradiation, the electrically conductive MXene in combination with in situ formed semiconducting titanium oxide induces photogenerated charge carriers, which could potentially be used in photocatalysis. On the other hand, due to film transparency, white light irradiation can bleach the adsorbed dye via photolysis. This study opens the door for using MXene thin films as multifunctional coatings with conductive and potentially self-cleaning properties.
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Two-dimensional (2D) transition metal carbides/nitrides (MXenes) are potential antibacterial agents. However, their activity against microorganisms is not fully understood. It could relate to MXenes' surface which further influences their biocidal action. Herein, we report no continuous biocidal activity for delaminated 2D niobium-based MXenes (Nbn+1XnTx) such as Nb2CTx and Nb4C3Tx prepared with HF/TMAOH protocol. Biocidal activity towards Bacillus subtilis and Staphylococcus aureus microorganisms was achieved by surface-functionalization with lysozyme macromolecule. MXenes' engineering with lysozyme changed MXene's surface charge from negative into positive thus enabling the elimination of bacteria cells during 48 h of incubation. In contrast, Nb4C3Tx functionalized with collagen stimulated the growth of Bacillus subtilis by 225 %, showing MXene's biocompatibility towards this particular strain. Altogether, our results show that MXenes are incredibly bio-tunable. Opposing bio-effects such as antimicrobial or growth-stimulating can be achieved towards various microorganisms with rational surface engineering.
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Muramidase , Nióbio , Antibacterianos/farmacologia , Bacillus subtilisRESUMO
OBJECTIVE: The driver fatigue detection using multi-channel electroencephalography (EEG) has been extensively addressed in the literature. However, the employment of a single prefrontal EEG channel should be prioritized as it provides users with more comfort. Furthermore, eye blinks from such channel can be analyzed as the complementary information. Here, we present a new driver fatigue detection method based on simultaneous EEG and eye blinks analysis using an Fp1 EEG channel. METHODS: First, the moving standard deviation algorithm identifies eye blink intervals (EBIs) to extract blink-related features. Second, the discrete wavelet transform filters the EBIs from the EEG signal. Third, the filtered EEG signal is decomposed into sub-bands, and various linear and nonlinear features are extracted. Finally, the prominent features are selected by the neighbourhood components analysis and fed to a classifier to discriminate between fatigue and alert driving. In this paper, two different databases are investigated. The first one is used for parameters' tuning of proposed method for the eye blink detection and filtering, nonlinear EEG measures, and feature selection. The second one is solely used for testing the robustness of the tuned parameters. MAIN RESULTS: The comparison between the obtained results from both databases by the AdaBoost classifier in terms of sensitivity (90.2% vs. 87.4%), specificity (87.7% vs. 85.5%), and accuracy (88.4% vs. 86.8%) indicates the reliability of the proposed method for the driver fatigue detection. SIGNIFICANCE: Considering the existence of commercial single prefrontal channel EEG headbands, the proposed method can be used to detect the driver fatigue in real-world scenarios.
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Eletroencefalografia , Análise de Ondaletas , Humanos , Reprodutibilidade dos Testes , Eletroencefalografia/métodos , Algoritmos , Bases de Dados FactuaisRESUMO
Skin sensitization is a term used to refer to the regulatory hazard known as allergic contact dermatitis (ACD) in humans or contact hypersensitivity in rodents, an important health endpoint considered in chemical hazard and risk assessments. Information on skin sensitization potential is required in various regulatory frameworks, such as the Directive of the European Parliament and the Council on Registration, Evaluation and Authorization of Chemicals (REACH). The identification of skin-sensitizing chemicals previously required the use of animal testing, which is now being replaced by alternative methods. Alternative methods in the field of skin sensitization are based on the measurement or prediction of key events (KE), i.e., (i) the molecular triggering event, i.e., the covalent binding of electrophilic substances to nucleophilic centers in skin proteins; (ii) the activation of keratinocytes; (iii) the activation of dendritic cells; (iv) the proliferation of T cells. This review article focuses on the current state of knowledge regarding the methods corresponding to each of the key events in skin sensitization and considers the latest trends in the development and modification of these methods.
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Resumo Desde a primeira descrição da tetralogia de Fallot (ToF) em 1671 por Niels Stensen e em 1888 por Étienne-Louis Arthur Fallot, vários trabalhos relataram essa anomalia juntamente com suas variantes e anomalias cardiovasculares concomitantes. A artéria subclávia direita aberrante (ASDA) é a anomalia do arco aórtico mais comum. Diferentemente da artéria subclávia esquerda aberrante, a ocorrência de ASDA em pacientes com ToF só foi relatada casuisticamente. Apresentamos dois pacientes de ToF com ASDA. É importante notar que o conhecimento da coexistência das duas anomalias tem pontos muito práticos durante correções endovasculares ou cirúrgicas de defeitos cardíacos congênitos (inclusive ToF).
Abstract Since the first description of Tetralogy of Fallot (ToF) in 1671 by Niels Stensen and in 1888 by Étienne-Louis Arthur Fallot, numerous papers have reported on this anomaly, along with its variants and concomitant cardiovascular anomalies. Aberrant right subclavian artery (ARSA) is the most common anomaly of the aortic arch. Different from the left aberrant subclavian artery, occurrence of ARSA in ToF-patients has only casuistically been reported so far. The present study reports on two ToF-patients with ARSA. It is important to note that knowledge of the coexistence of both anomalies has highly practical points during surgical or endovascular corrections of congenital heart defects (including ToF).
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Rapidly developing nanotechnologies and their integration in daily applications may threaten the natural environment. While green methods of decomposing organic pollutants have reached maturity, remediation of inorganic crystalline contaminants is major problem due to their low biotransformation susceptibility and the lack of understanding of material surface-organism interactions. Herein, we have used model inorganic 2D Nb-based MXenes coupled with a facile shape parameters analysis approach to track the mechanism of bioremediating 2D ceramic nanomaterials with green microalgae Raphidocelis subcapitata. We have found that microalgae decomposed the Nb-based MXenes due to surface-related physicochemical interactions. Initially, single and few-layered MXene nanoflakes attached to microalgae surfaces, which slightly reduced algal growth. But with prolonged surface interaction, the microalgae oxidized MXene nanoflakes and further decomposed them into NbO and Nb2O5. Since these oxides were nontoxic to microalgal cells, they consumed Nb-oxide nanoparticles by an uptake mechanism thus enabling further microalgae recovery after 72 h of water treatment. The uptake-associated nutritional effects were also reflected by cells' increased size, smoothed shape and changed growth rates. Based on these findings, we conclude that short- and long-term presence of Nb-based MXenes in freshwater ecosystems might cause only negligible environmental effects. Notably, by using 2D nanomaterials as a model system, we show evidence of the possibility of tracking even fine material shape transformations. In general, this study answers an important fundamental question about the surface interaction-associated processes that drive the mechanism of 2D nanomaterials' bioremediation as well as provides the fundamental basis for further short- and long-term investigations on the environmental effects of inorganic crystalline nanomaterials.
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Microalgas , Poluentes Químicos da Água , Biodegradação Ambiental , Ecossistema , Microalgas/metabolismo , Nióbio , Poluentes Químicos da Água/metabolismoRESUMO
Since the first description of Tetralogy of Fallot (ToF) in 1671 by Niels Stensen and in 1888 by Étienne-Louis Arthur Fallot, numerous papers have reported on this anomaly, along with its variants and concomitant cardiovascular anomalies. Aberrant right subclavian artery (ARSA) is the most common anomaly of the aortic arch. Different from the left aberrant subclavian artery, occurrence of ARSA in ToF-patients has only casuistically been reported so far. The present study reports on two ToF-patients with ARSA. It is important to note that knowledge of the coexistence of both anomalies has highly practical points during surgical or endovascular corrections of congenital heart defects (including ToF).
Desde a primeira descrição da tetralogia de Fallot (ToF) em 1671 por Niels Stensen e em 1888 por Étienne-Louis Arthur Fallot, vários trabalhos relataram essa anomalia juntamente com suas variantes e anomalias cardiovasculares concomitantes. A artéria subclávia direita aberrante (ASDA) é a anomalia do arco aórtico mais comum. Diferentemente da artéria subclávia esquerda aberrante, a ocorrência de ASDA em pacientes com ToF só foi relatada casuisticamente. Apresentamos dois pacientes de ToF com ASDA. É importante notar que o conhecimento da coexistência das duas anomalias tem pontos muito práticos durante correções endovasculares ou cirúrgicas de defeitos cardíacos congênitos (inclusive ToF).
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Cardiopatias Congênitas , Tetralogia de Fallot , Aorta Torácica/anormalidades , Anormalidades Cardiovasculares , Humanos , Artéria Subclávia/anormalidades , Artéria Subclávia/diagnóstico por imagem , Tetralogia de Fallot/complicações , Tetralogia de Fallot/diagnóstico por imagem , Tetralogia de Fallot/cirurgiaRESUMO
Many in vitro methods can be used to classify eye irritation or damage caused by exposure to a substance. In this study, a recently described method called the Cytotoxicity Assay to Assess Eye Irritation (CEI) was compared with other selected in vitro methods adopted in the OECD guidelines. Furthermore, the influence of combining more than one in vitro method was investigated. Basic performance indices were considered and a risk assessment based on the number of correct and incorrect results (overestimated or underestimated) was performed. The CEI results were similar to those of other in vitro tests, however, the CEI can also directly classify substances irritating to the eyes. When the CEI preceded an eye irritation test based reconstructed human corneal-like epithelium, there were fewer underestimates compared with other method combinations. This combination can better protect human health and provides results comparable to those obtained in animal tests.
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Alternativas aos Testes com Animais , Irritantes , Animais , Córnea , Olho , Técnicas In Vitro , Irritantes/toxicidade , Testes de Toxicidade/métodosRESUMO
Somatic embryogenesis (SE), which is a process that involves the in vitro-induced embryogenic reprogramming of plant somatic cells, requires dynamic changes in the cell transcriptome. These changes are fine-tuned by many genetic and epigenetic factors, including posttranslational histone modifications such as histone acetylation. Antagonistically acting enzymes, histone acetyltransferases (HATs) and deacetylases (HDACs), which control histone acetylation in many developmental processes, are believed to control SE. However, the function of specific HAT/HDACs and the genes that are subjected to histone acetylation-mediated regulation during SE have yet to be revealed. Here, we present the global and gene-specific changes in histone acetylation in Arabidopsis explants that are undergoing SE. In the TSA (trichostatin A)-induced SE, we demonstrate that H3 and H4 acetylation might control the expression of the critical transcription factor (TF) genes of a vital role in SE, including LEC1, LEC2 (LEAFY COTYLEDON 1; 2), FUS3 (FUSCA 3) and MYB118 (MYB DOMAIN PROTEIN 118). Within the HATs and HDACs, which mainly positively regulate SE, we identified HDA19 as negatively affecting SE by regulating LEC1, LEC2 and BBM. Finally, we provide some evidence on the role of HDA19 in the histone acetylation-mediated regulation of LEC2 during SE. Our results reveal an essential function of histone acetylation in the epigenetic mechanisms that control the TF genes that play critical roles in the embryogenic reprogramming of plant somatic cells. The results implicate the complexity of Hac-related gene regulation in embryogenic induction and point to differences in the regulatory mechanisms that are involved in auxin- and TSA-induced SE.
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Proteínas de Arabidopsis , Arabidopsis , Acetilação , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Desenvolvimento Embrionário , Regulação da Expressão Gênica de Plantas , Histona Desacetilases/genética , Histona Desacetilases/metabolismo , Histonas/metabolismo , Plantas/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
BACKGROUND: It is unclear whether patients with adult congenital heart disease (ACHD) should be considered as an increased risk population with poor outcomes when suffering from COVID-19. AIMS: This study aimed to collect clinical outcome data and to identify risk factors of a complicated course of COVID-19 among ACHD patients. METHODS: Among all outpatients who came to medical attention via telemedicine or direct physician contact at our institution between September 1, 2020 and March 31, 2021, we included all with a COVID-19 diagnosis. The incidence of COVID-19, a clinical course of the disease, and outcome were determined. RESULTS: One hundred and four (8.7%) out of 1 197 patients who were seen at our outpatient clinic for ACHD patients met the definition of COVID-19. Most of them reported a mild course of COVID-19 (99 [95.5%]). Five patients (4.5%) experienced severe symptoms and needed hospitalization. Two patients (1.9% of all with a confirmed diagnosis, 40% with severe infection) died. In the multivariable analysis, decreased systemic ventricular systolic function and any significant valve stenosis were predictors of a complicated disease course. CONCLUSIONS: Our study confirmed previous results showing that a physiology-based model, rather than an anatomy-based model, better predicted COVID-19 outcomes among ACHD patients, which is of importance for patients and healthcare providers during the COVID-19 pandemic.
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COVID-19 , Cardiopatias Congênitas , Adulto , Teste para COVID-19 , Cardiopatias Congênitas/complicações , Cardiopatias Congênitas/epidemiologia , Humanos , Pandemias , SARS-CoV-2RESUMO
OBJECTIVE: Blink-related features derived from electroencephalography (EEG) have recently arisen as a meaningful measure of driver's cognitive state. Combined with band power features of low-channel prefrontal EEG data, blink-derived features enhance the detection of driver drowsiness. Yet, it remains unanswered whether synergy of combined blink and EEG band power features for the detection of driver drowsiness may be further boosted if a proper eye blink removal is also applied before EEG analysis. This paper proposes an algorithm for simultaneous eye blink feature extraction and elimination from low-channel prefrontal EEG data. METHODS: Firstly, eye blink intervals (EBIs) are identified from the Fp1 EEG channel using variational mode extraction, and then blink-related features are derived. Secondly, the identified EBIs are projected to the rest of EEG channels and then filtered by a combination of principal component analysis and discrete wavelet transform. Thirdly, a support vector machine with 10-fold cross-validation is employed to classify alert and drowsy states from the derived blink and filtered EEG band power features. MAIN RESULTS: When compared the synergy of eye blink and EEG features before and after filtering by the proposed algorithm, a significant improvement in the mean accuracy of driver drowsiness detection was achieved (71.2% vs. 78.1%, p 0.05). SIGNIFICANCE: This paper validates a novel view of eye blinks as both a source of information and artifacts in EEG-based driver drowsiness detection.
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Piscadela , Eletroencefalografia , Algoritmos , Artefatos , Humanos , Vigília , Análise de OndaletasRESUMO
In this study, high-density magnesium diboride (MgB2) bulk superconductors were synthesized by spark plasma sintering (SPS) under pressure to improve the field dependence of the critical current density (Jc-B) in MgB2 bulk superconductors. We investigated the relationship between sintering conditions (temperature and time) and Jc-B using two methods, ex situ (sintering MgB2 synthesized powder) and in situ (reaction sintering of Mg and B powder), respectively. As a result, we found that higher density with suppressed particle growth and suppression of the formation of coarse particles of MgB4 and MgO were found to be effective in improving the Jc-B characteristics. In the ex situ method, the degradation of MgB2 due to pyrolysis was more severe at temperatures higher than 850 °C. The sample that underwent SPS treatment for a short time at 850 °C showed higher density and less impurity phase in the bulk, which improved the Jc-B properties. In addition, the in situ method showed very minimal impurity with a corresponding improvement in density and Jc-B characteristics for the sample optimized at 750 °C. Microstructural characterization and flux pinning (fP) analysis revealed the possibility of refined MgO inclusions and MgB4 phase as new pinning centers, which greatly contributed to the Jc-B properties. The contributions of the sintering conditions on fP for both synthesis methods were analyzed.
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In the present work, we investigated in detail the thermal/crystallization behavior and magnetic properties of materials with Fe84.5-xCoxNb5B8.5P2 (x = 0, 5, 10, 15 and 20 at.%) composition. The amorphous ribbons were manufactured on a semi-industrial scale by the melt-spinning technique. The subsequent nanocrystallization processes were carried out under different conditions (with/without magnetic field). The comprehensive studies have been carried out using differential scanning calorimetry, X-ray diffractometry, transmission electron microscopy, hysteresis loop analyses, vibrating sample magnetometry and Mössbauer spectroscopy. Moreover, the frequency (up to 300 kHz) dependence of power losses and permeability at a magnetic induction up to 0.9 T was investigated. On the basis of some of the results obtained, we calculated the values of the activation energies and the induced magnetic anisotropies. The X-ray diffraction results confirm the surface crystallization effect previously observed for phosphorous-containing alloys. The in situ microscopic observations of crystallization describe this process in detail in accordance with the calorimetry results. Furthermore, the effect of Co content on the phase composition and the influence of annealing in an external magnetic field on magnetic properties, including the orientation of the magnetic spins, have been studied using various magnetic techniques. Finally, nanocrystalline Fe64.5Co20Nb5B8.5P2 cores were prepared after transverse thermo-magnetic heat treatment and installed in industrially available portable heating equipment.
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Abnormal repetitive behaviors often pose problems for dog owners. Such behaviors are considered undesirable if they pose a nuisance or a danger to humans. Ancient dog breeds are intelligent, sociable, active, boisterous and need regular outdoor exercise, but are also independent and reluctant to follow commands. This study aimed to identify factors (breed, sex, origin, housing conditions) and situations that contribute to undesirable behaviors, such as aggression towards humans and other dogs/animals, separation anxiety, excessive vocalization, and oral and locomotion behaviors in Akita, Alaskan Malamute, Basenji, Samoyed and Siberian husky. Undesirable behaviors in dogs were analyzed based on the results of 897 questionnaires. Breed influenced aggressive behavior towards other dogs/animals, aggression towards humans, undesirable oral and locomotion behaviors, and excessive vocalization. Aggressive behaviors were more prevalent in females than in males. Housing conditions were linked with aggression towards other dogs/animals, aggression at mealtime, and excessive vocalization. Undesirable behaviors were most frequently reported in Akitas, Siberian huskies and Samoyeds, and they were more prevalent in males than in females and dogs living indoors with or without access to a backyard. Aggressive behaviors towards other dogs and animals, excessive vocalization and undesirable motor activities posed the greatest problems in ancient dog breeds.