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1.
Food Chem ; 448: 139086, 2024 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-38520990

RESUMO

Amanita exitialis, a deadly mushroom found in eastern Asia, causes the highest death rates among all poisonous mushrooms in China. The aim of the present study was to develop an efficient, accurate, and user-friendly PCR-based method for identifying A. exitialis that could facilitate the prevention, diagnosis, and treatment of associated food poisoning. A. exitialis-specific primers and probes were designed based on the internal transcribed spacer region variations of 27 mushroom species. Specificity was confirmed using conventional and real-time PCR for 23 non-target mushroom species, including morphologically similar and closely related species. Compared to conventional PCR, real-time PCR was more sensitive (detectable DNA concentration: 1.36 × 10-2 ng/µL vs. 1.36 × 10-3) and efficient (analysis time: 1 h vs. 40 min). Furthermore, the real-time PCR results could be immediately visualized using amplification curve analysis. The results present two robust PCR-based methods for A. exitialis identification that can facilitate food safety.


Assuntos
Amanita , DNA Fúngico , Reação em Cadeia da Polimerase em Tempo Real , Amanita/genética , Amanita/química , Amanita/classificação , DNA Fúngico/genética , Primers do DNA/genética , Reação em Cadeia da Polimerase , China , Intoxicação Alimentar por Cogumelos/diagnóstico
2.
J Affect Disord ; 343: 71-76, 2023 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-37741469

RESUMO

BACKGROUND: There was a high prevalence of overweight/obesity among patients with severe mental disorders (SMD). However, studies on the lifestyle-based interventions in patients with SMD are limited. OBJECTIVE: To examine the effects of an educational lifestyle intervention on body weight and psychological health among Chinese community-dwelling overweight/obese patients with SMD. METHODS: Community-dwelling overweight/obese patients with SMD was recruited from Shenzhen, China in October 2020. They were randomly allocated into intervention group (IG) and control group (CG). Participants in IG received a 12-month educational lifestyle intervention, while the CG was exposed to routine care. A generalized estimating equation model was used to assess the effect of the intervention over time. RESULTS: A total of 176 subjects (88 in IG and 88 in CG) aged 42.2 ± 10.9 years were included in this study. After adjusting for potential confounders, body weight (p = 0.001), body mass index (BMI, p = 0.001), and waist circumference (p = 0.027) in IG significantly decreased compared with CG after 12 months. Besides, IG had significantly higher life satisfaction than CG after intervention (p = 0.026), whereas significant reductions in depressive symptoms were observed in IG from 26.1 % at baseline to 13.6 % after the intervention (p = 0.027), and the between-group differences were marginally significant (p = 0.086). CONCLUSION: An educational lifestyle intervention can effectively reduce body weight parameters and improve psychological health in overweight/obese patients with SMD.

3.
Mol Neurobiol ; 60(11): 6373-6382, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37452221

RESUMO

The association between peripheral blood extracellular vesicles (EVs)-derived miRNAs (EVs-miRNAs) and neuropsychiatric diseases has been extensively studied. However, it remains largely unclear about the expression profile of EVs-miRNAs in schizoaffective disorder (SAD) patients. In our study, we isolated the EVs from plasma samples of patients and healthy controls, and then analyzed the expression profiles of EVs-miRNAs through small RNA sequencing. Our results identified 32 differentially expressed (DE) miRNAs (25 upregulated and 7 downregulated) in SAD patients. A module containing 42 miRNAs closely related to SAD was identified by weighted gene co-expression network analysis (WGCNA), among which has-miR-15b-5p, has-miR-301a-3p, has-miR-342-3p, has-miR-219b-5p, and has-miR-145-5p were identified as hub miRNAs. The enrichment analysis showed that the target genes of these 42 miRNAs were significantly enriched in multiple pathways related to neuropathology and located at synapses. A total of 6 DE miRNAs (has-miR-7-5p, has-miR-144-3p, has-miR-155-5p, has-miR-342-3p, has-miR-342-5p, and has-miR-487b-3p) associated with SAD were selected for qRT-PCR verification. The level of has-miR-342-3p in SAD patients was downregulated, and hsa-miR-155-5p was upregulated. Our findings support the hypothesis that dysregulation of EVs-miRNAs in plasma might be involved in the underlying neuropathology of SAD through several biological pathways and provide important preliminary evidence supporting the use of EVs-miRNAs as potential novel biomarkers in SAD.

4.
PeerJ ; 11: e15385, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37187513

RESUMO

The interactions between plant viruses and insect vectors are very complex. In recent years, RNA sequencing data have been used to elucidate critical genes of Tomato spotted wilt ortho-tospovirus (TSWV) and Frankliniella occidentalis (F. occidentalis). However, very little is known about the essential genes involved in thrips acquisition and transmission of TSWV. Based on transcriptome data of F. occidentalis infected with TSWV, we verified the complete sequence of the E3 ubiquitin-protein ligase UBR7 gene (UBR7), which is closely related to virus transmission. Additionally, we found that UBR7 belongs to the E3 ubiquitin-protein ligase family that is highly expressed in adulthood in F. occidentalis. UBR7 could interfere with virus replication and thus affect the transmission efficiency of F. occidentalis. With low URB7 expression, TSWV transmission efficiency decreased, while TSWV acquisition efficiency was unaffected. Moreover, the direct interaction between UBR7 and the nucleocapsid (N) protein of TSWV was investigated through surface plasmon resonance and GST pull-down. In conclusion, we found that UBR7 is a crucial protein for TSWV transmission by F. occidentalis, as it directly interacts with TSWV N. This study provides a new direction for developing green pesticides targeting E3 ubiquitin to control TSWV and F. occidentalis.


Assuntos
Tisanópteros , Tospovirus , Animais , Tisanópteros/genética , Tospovirus/genética , Doenças das Plantas , Insetos , Ubiquitina-Proteína Ligases/genética
5.
Medicine (Baltimore) ; 102(16): e33531, 2023 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-37083814

RESUMO

Patients with schizophrenia or bipolar disorders in community had poor psychosocial functioning, social support, and life satisfaction. However, the interaction effects of social support and depression on life satisfaction remains unclear. Thus, we examined these associations among patients with schizophrenia or bipolar disorder. This cross-sectional study was conducted from October to December 2020 in Shenzhen, China. Information on social support, depression, and life satisfaction was assessed by standardized questionnaires through a face-to-face interview. Hierarchical multiple regression analysis was performed to estimate the associations of social support and depression with life satisfaction and to explore the mediation effect of social support. A total of 293 patients aged 39.7 ±â€…11.1 years (males: 47.1 %) were included in this study. Social support was positively associated with high life satisfaction (explaining 7.2% of the variance), while depression was negatively associated with life satisfaction (explaining 17.8% of the variance). Furthermore, social support mediated 12.5% of the association between depression and life satisfaction. Social support and depression were significantly associated with life satisfaction in patients with schizophrenia or bipolar disorders. Moreover, social support mediated the association between depression and life satisfaction in this population. Health interventions that benefit social support should be promoted to alleviate the negative impact of depression on their life satisfaction.


Assuntos
Transtorno Bipolar , Esquizofrenia , Masculino , Humanos , Transtorno Bipolar/psicologia , Esquizofrenia/epidemiologia , Depressão/psicologia , Estudos Transversais , Satisfação do Paciente , Apoio Social , Satisfação Pessoal , Qualidade de Vida/psicologia
7.
Front Oncol ; 12: 877982, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35646705

RESUMO

Background: Hepatocellular carcinoma (HCC) is inflammation-related cancer. Persistent inflammatory injury of the liver is an important factor mediating the occurrence and development of liver cancer. Hepatic macrophages play an important role in the inflammatory microenvironment, which mediates tumor immune escape, tumor growth, and metastasis. Previous studies have suggested that L-3,5,3-triiodothyronine (T3) can regulate inflammation; however, its use is associated with serious cardiac side effects, and its role in hepatocarcinogenesis remains unclear. In this study, we aimed to develop an effective T3 delivery system with reduced cardiac toxicity and to explore its effects on HCC occurrence. Methods: T3 liposomes (T3-lipo) were prepared using the thin-film hydration method, and their characteristics, including particle size, polydispersity index, zeta potential, encapsulation efficiency, drug loading, drug release, and stability, were evaluated in vitro. We assessed the effect of T3-lipo on hepatocarcinogenesis in diethylnitrosamine (DEN)-induced primary HCC in rats and examined the biodistribution of T3 and T3-lipo by high-performance liquid chromatography-mass spectrometry. Furthermore, we explored the potential molecular mechanism of T3-lipo in hepatocarcinogenesis by immunohistochemistry and immunofluorescence analyses, Bio-Plex assays, real-time polymerase chain reaction analysis, and Western blotting assays. Results: Compared with T3, T3-lipo had an enhanced inhibitory effect on hepatocarcinogenesis and reduced cardiac side effects in DEN-induced primary HCC in rats. Mechanistically, T3-lipo were absorbed by hepatic macrophages and regulated the secretion of inflammatory cytokines in macrophages by inhibiting inflammatory signaling pathways. Conclusions: T3-lipo may suppress hepatocarcinogenesis by regulating the inflammatory microenvironment in the liver and reduce the cardiac side effects meanwhile.

8.
Front Plant Sci ; 13: 844918, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35755651

RESUMO

Phytolacca is the largest genus of Phytolaccaceae. Owing to interspecific hybridization, infraspecific variation, and apparent weak genetic control of many qualitative characters, which have obscured boundaries between species, the classification and phylogenetic relationships of this genus are unclear. Native Phytolacca is disjunctly distributed in America, eastern Asia, and Africa, and the biogeographic history of the genus remained unresolved. In this study, we used the whole chloroplast genome and three markers (nrDNA, rbcL, and matK) to reconstruct phylogenetic relationships within Phytolacca, analyze divergence times, and infer biogeographic histories. The phylogenetic results indicate that Phytolacca is monophyletic, which is inconsistent with the infrageneric classification based on morphology. According to the divergence time estimation, Phytolacca began to diversify at approximately 20.30 Ma during the early Miocene. Central America, including Mexico, Costa Rica, and Colombia, is the center of species diversity. Biogeographical analysis indicated five main dispersal events and Phytolacca originated from Central and South America. Birds may be the primary agents of dispersal because of the fleshy fruiting of Phytolacca. This study extended sampling and added more genetic characteristics to infer the evolutionary history of Phytolacca, providing new insights for resolving the classification and elucidating the dispersal events of Phytolacca.

9.
Nanoscale ; 13(29): 12659-12668, 2021 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-34477616

RESUMO

We study the theoretical properties of a parabolic hBN/MoS2/hBN heterostructure quantum dot potential generated via electrostatic gates and its interaction with a cobalt nano chevron. We demonstrate that such an example system can undergo electric dipole spin resonance for a single electron isolated to the K' valley within the MoS2 monolayer, and such a system can achieve pi-rotation times of approximately 5.5 ns under the influence of a 20.89 GHz driving field. Our proposed system requires operating conditions easily achievable with current experimental methods and would allow for the all-electrical control of a spin-qubit within an MoS2 device. Our results show that such a system is experimentally feasible and would have comparable properties to that of more traditional silicon based spin-qubits. Furthermore, the design of the device can be applied to other material systems beyond MoS2 and cobalt. In theory, the proposed structure could make use of any 2D material that experiences strong proximity exchange interactions with other magnetic materials, which makes our proposed design highly general.

10.
Stem Cell Res Ther ; 12(1): 342, 2021 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-34112239

RESUMO

BACKGROUND: The liver possesses a powerful regeneration ability, which is correlated with the stemness of hepatocytes in the portal vein (PV). However, the mechanism underlying the maintenance of hepatocyte stemness has not been elucidated. Here, we hypothesized that high levels of lipopolysaccharide from the portal vein might maintain the stemness of hepatocytes in the PV area. METHODS: First, we examined the location of hepatic stem cells and the concentration of lipopolysaccharide (LPS) in the portal vein and inferior vena cava. Then, we assessed the effect of LPS on stemness maintenance in mice by using antibiotics to eliminate LPS and knocking out the LPS receptor, TLR4. In vitro, the effect of LPS on the stemness of hepatocytes was investigated by colony and sphere formation assays and assessment of pluripotent and stem cell marker expression. Furthermore, we studied the mechanism by which LPS regulates the stemness of hepatocytes. Finally, we ligated the portal vein branch to further verify the effect of LPS. RESULTS: We found that a high level of LPS from the portal vein was correlated with the location of hepatic stem cells in the PV area, and elimination of LPS by antibiotics inhibited the expression of the stemness marker. LPS promoted colony and sphere formation and induced the upregulation of pluripotent and stem cell markers in AML12 cells. Furthermore, in the reprogramming medium, LPS facilitated the dedifferentiation of mature hepatocytes into hepatic progenitor-like cells, which exhibited a bipotent differentiation capacity in vivo and in vitro. Mechanistically, LPS bound TLR4 to regulate stemness of hepatocytes via the activation of YAP1 signaling, and blockade of YAP1 abolished the LPS-induced cell stemness and upregulation of pluripotent markers. CONCLUSIONS: Our study implies a correlation between LPS/TLR4/YAP1 signaling and cell stemness, and LPS was shown to be involved in stemness maintenance of hepatocytes in the PV area. LPS might be used to induce the dedifferentiation of mature hepatocytes into progenitor-like cells for repair of liver injury.


Assuntos
Hepatócitos , Lipopolissacarídeos , Animais , Lipopolissacarídeos/farmacologia , Fígado , Camundongos , Transdução de Sinais , Células-Tronco
11.
Cancer Lett ; 517: 46-54, 2021 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-34102284

RESUMO

Hepatocellular carcinoma (HCC) usually occurs at the late stage of chronic liver injury. Oncostatin M (OSM) is a tumor-associated cytokine highly expressed in cirrhosis and HCC patients; however, its role in hepatocarcinogenesis has not been clearly elucidated. In this study, we investigated the effect of OSM on HCC occurrence in a rat model of N-diethylnitrosamine-induced HCC. OSM overexpression significantly increased the number of tumor nodules and shortened the overall survival of the rats. Notably, OSM promoted HPC activation in vivo but did not directly regulate the proliferation of the HPC cell line in vitro. Further, OSM induced tumor necrosis factor-α (TNF-α) secretion and CD68+ macrophage accumulation, which were positively correlated with HPC activation. Additionally, TNF-α or macrophage depletion inhibited the promoting effect of OSM on hepatocarcinogenesis and HPC activation. Furthermore, OSM expression in the peritumoral tissues of HCC was positively correlated with poor overall survival of patients. In conclusion, OSM plays an important role in hepatocarcinogenesis by regulating the liver inflammation environment. Hence, OSM could be used as a potential target for HCC prevention and therapy or as an indicator of HCC prognosis.


Assuntos
Carcinogênese/metabolismo , Macrófagos/metabolismo , Oncostatina M/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Adulto , Idoso , Animais , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patologia , Linhagem Celular , Proliferação de Células/fisiologia , Feminino , Humanos , Fígado/metabolismo , Fígado/patologia , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patologia , Macrófagos/patologia , Masculino , Pessoa de Meia-Idade , Prognóstico , Ratos , Adulto Jovem
12.
Environ Toxicol ; 36(4): 665-674, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33258555

RESUMO

Numerous studies have shown that endocrine-disrupting chemicals are one of the important pathogenic factors in women with polycystic ovary syndrome. Our previous study has revealed that bisphenol A (BPA) can cause steroid hormone imbalance, polycystic ovary, and estrus cycle disorder. In this study, we aimed to explore the effect of BPA, a typical environmental estrogen, on the synthesis of steroid hormones in human ovarian granulosa KGN cells. Exposure of KGN cells to BPA (0.5, 5, 50, and 500 µg/L) resulted in the decrease of progesterone (P), estradiol (E2), and the ratio of estradiol to testosterone (E2/T). BPA affected the expression of genes related to steroid hormone synthesis in KGN cells, including the decreased expression of the steroidogenic acute regulatory protein, ferredoxin, and ferredoxin reductase genes during progesterone synthesis; upregulating the expression of cytochrome p450 oxidoreductase gene associated with E2 and T synthesis; and the downregulated cytochrome P450 family 1 subfamily A member 1 and cytochrome P450 family 1 subfamily B member 1 in E2 degradation. BPA also reduced the expression of stimulatory G proteins (GS) in follicle-stimulating hormone receptor (FSHR)/GS/adenylate cyclase (AC) signaling pathway. In summary, our research has demonstrated that environment-relevant level of BPA exposure leads to steroid hormone synthesis disorder in human ovarian granulosa cells, which might cause the reduction of gene expression in hormone synthesis and the suppression of the FSHR/GS/AC signaling pathway.


Assuntos
Compostos Benzidrílicos/toxicidade , Disruptores Endócrinos/toxicidade , Estradiol/biossíntese , Células da Granulosa/efeitos dos fármacos , Fenóis/toxicidade , Progesterona/biossíntese , Testosterona/biossíntese , Animais , Técnicas de Cultura de Células , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/genética , Relação Dose-Resposta a Droga , Regulação para Baixo , Feminino , Expressão Gênica/efeitos dos fármacos , Humanos , Regulação para Cima
13.
Endocr Pract ; 26(6): 585-594, 2020 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-31968198

RESUMO

Objective: Early diagnosis and treatment of children with congenital hypothyroidism (CH) through newborn screening can effectively prevent delayed development. This study was designed to investigate the pathogenesis and factors that influence CH in urban areas of China between 2009 and 2018. Methods: A retrospective analysis of newborn screening data and diagnosis and treatment information for CH diagnosed in the information database of the neonatal disease screening center in one of China's five special economic zones from 2009 to 2018. Results: Of the 947,258 newborns screened between 2009 and 2018, 829 (406 girls) were diagnosed with CH at birth (1 diagnosis/1,136 births). Among the 608 cases of CH diagnosed at birth and re-evaluated at the age of 3 years, 487 were permanent congenital hypothyroidism (PCH, 1/1,429), and 121 were transient congenital hypothyroidism (TCH, 1/5,882). A total of 83.2% of infants with PCH (405/487) underwent thyroid imaging in the neonatal period, of which thyroid dysgenesis accounted for 28.64% (116/405) and functional defects accounted for 71.36% (289/405). The incidence of CH changed significantly in infants with initial serum thyroid-stimulating hormone concentrations of 41 to 100 mIU/L and ≥100 mIU/L, whereas the incidence of mild CH showed a slight increase. The incidence of CH was significantly higher in postterm infants (1/63) and low-birth-weight infants (1/370). Conclusion: In the past decade, the incidence of CH has increased, mainly due to the increase in the incidence of PCH and TCH. The incidence of mild CH has increased slightly. Postterm birth and low birth weight are important factors affecting the incidence of CH. Abbreviations: CH = congenital hypothyroidism; FT4 = free thyroxine; L-T4 = levothyroxine sodium; PCH = permanent congenital hypothyroidism; TCH = transient congenital hypothyroidism; TSH = thyroid-stimulating hormone; TT4 = total thyroxine.


Assuntos
Hipotireoidismo Congênito , Criança , China , Hipotireoidismo Congênito/epidemiologia , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Estudos Retrospectivos , Fatores de Risco , Tireotropina , Tiroxina
14.
Obes Facts ; 12(4): 476-488, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31394543

RESUMO

BACKGROUND: Childhood overweight and obesity have become some of the most serious public health problems in the 21st century and have a significant impact on affected children as they grow into adulthood. OBJECTIVE: The purpose of this study was to evaluate the overweight and obesity status and their main influencing factors in preschool children aged 2-7 years in urban areas of China between 2011 and 2017. METHODS: A stratified cluster random sampling method was used to conduct a sample survey of children aged 2-7 years in Xiamen, one of China's five special economic zones. The 56,738 participants (29,444 boys, 27,294 girls) were examined at three time points (15,757 in 2011, 19,098 in 2014, and 21,883 in 2017), and were analyzed for factors influencing obesity. RESULTS: Between 2011 and 2017, the prevalence of overweight and obesity in preschool children between 2 and 7 years old was 10.91 and 5.66%, respectively. The overweight and obesity rates were higher in boys (11.85 and 7.11%) than in girls (9.90 and 4.09%), and the difference was statistically significant (p < 0.01). In the past 7 years, the overweight and obesity rates showed a downward trend in both boys and girls (p < 0.01). The peak ages for overweight were 6 years in boys and 2 years in girls, while the obesity rate peaked at 6 years. In those children with obesity, the proportion of those with moderate to severe obesity decreased from 40.70% in 2011 to 32.80% in 2017. Multiple stepwise regression analysis showed that children who were averse to sports activities preferred greasy foods and had earlier introduction of solid foods as infants, as well as those who were born at a high birth weight, ate fast, and those with parents with obesity were more likely to have obesity themselves (p < 0.05). CONCLUSIONS: Although preventative and control measures for childhood obesity have achieved initial results, Chinese preschool children remain to have high levels of overweight and obesity. It is therefore necessary to strengthen monitoring of overweight and obesity in preschool-aged children and implement appropriate interventions when necessary.


Assuntos
Sobrepeso/epidemiologia , Obesidade Infantil/epidemiologia , Povo Asiático/estatística & dados numéricos , Peso ao Nascer , Criança , Pré-Escolar , China/epidemiologia , Feminino , Humanos , Masculino , Obesidade Mórbida/epidemiologia , Prevalência , Inquéritos e Questionários
15.
Chemosphere ; 231: 151-160, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31129395

RESUMO

The development of polycystic ovary syndrome (PCOS) could be caused by exposure to environmental endocrine disrupting chemicals (EDCs). In the current study, two commonly found EDCs, bisphenol A (BPA) and tributyltin (TBT), were investigated for their effects on PCOS occurrence in neonatal female rats. TBT (10 and 100 ng kg-1 d-1), BPA (50 µg kg-1 d-1), and a mixture of the two (TBT 100 ng kg-1 d-1 with BPA 50 µg kg-1 d-1) were administered to female rats from postnatal day 1-16. TBT, BPA, and TBT + BPA treatment resulted in an irregular estrus cycle and disturbed ovarian development, with less corpora lutea and antral follicles, but more atretic follicles and cysts. In addition, serum testosterone and luteinizing hormone levels were significantly elevated, whereas a reduced level of serum sex hormone-binding globulin was observed after TBT100, BPA50, and TBT + BPA treatments. Moreover, gene expression analyses identified significant differential expression of the genes involved in a variety of biological pathways, such as lipid transport and steroidogenesis. Moreover, the expression level of proteins regulating lipid and androgen biosynthesis was elevated after the treatments. In conclusion, this study demonstrated that exposure to TBT, BPA, and a mixture of the two in newborn rats could contribute to a PCOS-like syndrome. The mechanism of PCOS pathogenesis caused by exposure to TBT and BPA is likely to be mediated by the lipid metabolism and steroidogenesis pathways. Our results provide novel insight into female reproduction affected by EDCs, which may be helpful for revealing the pathogenesis of PCOS.


Assuntos
Compostos Benzidrílicos/toxicidade , Disruptores Endócrinos/toxicidade , Fenóis/toxicidade , Síndrome do Ovário Policístico/induzido quimicamente , Compostos de Trialquitina/toxicidade , Animais , Exposição Ambiental/análise , Feminino , Humanos , Recém-Nascido , Folículo Ovariano/efeitos dos fármacos , Síndrome do Ovário Policístico/sangue , Gravidez , Efeitos Tardios da Exposição Pré-Natal , Ratos , Reprodução/efeitos dos fármacos
16.
J Phys Condens Matter ; 30(43): 435701, 2018 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-30210060

RESUMO

We analytically establish an anomalous transverse flow of heat in 8- Pmmn borophene, one of the several two-dimensional allotropes of Boron. The dispersion of this allotrope contains a pair of anisotropic and tilted Dirac cones which are gapped by placing the 2D B sheet under an intense circularly-polarized illumination. A gap in the Dirac dispersion leads to a finite Berry curvature and connected anomalous Hall effects. In the case of thermoelectrics, this manifests as a heat current perpendicular to the temperature gradient-the thermal Hall effect. A quantitative calculation of the attendant thermal Hall conductivity reveals dependence on the intrinsic anisotropy and tilt of the Dirac cone. Further, by estimating the longitudinal thermal conductivity using the Wiedemann-Franz law, we also outline steps to compute the thermal Hall angle that gauges the generation efficiency of such transverse heat processes. Finally, we touch upon the idea of thermal rectification wherein the direction of flow of the anomalous heat reverses through a simple switch of the polarization of incident light and is of interest in thermal logic circuits.

17.
Sci Rep ; 8(1): 5972, 2018 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-29654241

RESUMO

A semi-classical analysis of magneto-thermopower behaviour, namely, the Seebeck and Nernst effect (NE) in quantum wells of IV-VI lead salts with significant extrinsic Rashba spin-orbit coupling (RSOC) is performed in this report. In addition to the spin-dependent Seebeck effect that has been observed before, we also theoretically predict a similar spin-delineated behavior for its magneto-thermal analog, the spin-dependent NE. The choice of lead salts follows from a two-fold advantage they offer, in part, to their superior thermoelectric properties, especially PbTe, while their low band gaps and high spin-orbit coupling make them ideal candidates to study RSOC governed effects in nanostructures. The calculations show a larger longitudinal magneto-thermopower for the spin-up electrons while the transverse components are nearly identical. In contrast, for a magnetic field free case, the related power factor calculations reveal a significantly higher contribution from the spin-down ensemble and suffer a reduction with an increase in the electron density. We also discuss qualitatively the limitations of the semi-classical approach for the extreme case of a high magnetic field and allude to the observed thermopower behaviour when the quantum Hall regime is operational. Finally, techniques to modulate the thermopower are briefly outlined.

18.
J Chem Phys ; 148(10): 104701, 2018 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-29544322

RESUMO

We study a thermal gradient induced current Ith flow in potassium-doped two-dimensional anisotropic black phosphorus (BP) with semi-Dirac dispersion. The prototype device is a BP channel clamped between two contacts maintained at unequal temperatures. The choice of BP lies in the predicted efficient thermoelectric behaviour. A temperature-induced difference in the Fermi levels of the two contacts drives the current (typified by the electro-thermal conductance) which we calculate using the Landauer transport equation. The current shows an initial rise when the device is operated at lower temperatures. The rise stalls at progressively higher temperatures and Ith acquires a plateau-like flat profile indicating a competing effect between a larger number of transmission modes and a corresponding drop in the Fermi level difference between the contacts. The current is computed for both n- and p-type BP, and the difference thereof is attributed to the particle-hole asymmetry. The utility of such calculations lie in conversion of the heat produced in a miniaturized chip to useful thermopower via a prototypical Seebeck power generator. Unlike the flow of Ith that purportedly utilizes the additional removable heat in a nanoscale device heat, the ability of a material to maintain a steady temperature is reflected in its heat capacity through effective absorption of thermal energy. The heat capacity is formulated in this work for BP via a Sommerfeld expansion. In the concluding part, we draw a microscopic connection between the two seemingly disparate processes of heat removal and absorption by pinning down their origin to the underlying density of states. Finally, a qualitative analysis of a Carnot-like efficiency of the considered thermoelectric engine is performed drawing upon the previous results on thermal current and heat capacity.

19.
J Phys Condens Matter ; 29(40): 405701, 2017 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-28862996

RESUMO

We study the low temperature thermal conductivity of single-layer transition metal dichalcogenides (TMDCs). In the low temperature regime where heat is carried primarily through transport of electrons, thermal conductivity is linked to electrical conductivity through the Wiedemann-Franz law (WFL). Using a k.p Hamiltonian that describes the [Formula: see text] and [Formula: see text] valley edges, we compute the zero-frequency electric (Drude) conductivity using the Kubo formula to obtain a numerical estimate for the thermal conductivity. The impurity scattering determined transit time of electrons which enters the Drude expression is evaluated within the self-consistent Born approximation. The analytic expressions derived show that low temperature thermal conductivity (1) is determined by the band gap at the valley edges in monolayer TMDCs and (2) in presence of disorder which can give rise to the variable range hopping regime, there is a distinct reduction. Additionally, we compute the Mott thermopower and demonstrate that under a high frequency light beam, a valley-resolved thermopower can be obtained. A closing summary reviews the implications of results followed by a brief discussion on applicability of the WFL and its breakdown in context of the presented calculations.

20.
BMC Genomics ; 15: 861, 2014 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-25282613

RESUMO

BACKGROUND: The genus Liposcelis (Psocoptera: Troctomorpha) has more than 120 species with a worldwide distribution and they pose a risk for global food security. The organization of mitochondrial (mt) genomes varies between the two species of booklice investigated in the genus Liposcelis. Liposcelis decolor has its mt genes on a single chromosome, like most other insects; L. bostrychophila, however, has a multipartite mt genome with genes on two chromosomes. RESULTS: To understand how multipartite mt genome organization evolved in the genus Liposcelis, we sequenced the mt genomes of L. entomophila and L. paeta in this study. We found that these two species of booklice also have multipartite mt genomes, like L. bostrychophila, with the mt genes we identified on two chromosomes. Numerous pseudo mt genes and non-coding regions were found in the mt genomes of these two booklice, and account for 30% and 10% respectively of the entire length we sequenced. In L. bostrychophila, the mt genes are distributed approximately equally between the two chromosomes. In L. entomophila and L. paeta, however, one mt chromosome has most of the genes we identified whereas the other chromosome has largely pseudogenes and non-coding regions. L. entomophila and L. paeta differ substantially from each other and from L. bostrychophila in gene content and gene arrangement in their mt chromosomes. CONCLUSIONS: Our results indicate unusually fast evolution in mt genome organization in the booklice of the genus Liposcelis, and reveal different patterns of mt genome fragmentation among L. bostrychophila, L. entomophila and L. paeta.


Assuntos
Genoma Mitocondrial , Insetos/genética , Animais , Sequência de Bases , Cromossomos de Insetos , DNA Mitocondrial/classificação , DNA Mitocondrial/metabolismo , Insetos/classificação , Proteínas Mitocondriais/classificação , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Dados de Sequência Molecular , Filogenia , Pseudogenes/genética , Alinhamento de Sequência , Regiões não Traduzidas/genética
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