morphological transition
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Author(s):  
Hannes Schürmann ◽  
Gordon Schmidt ◽  
Frank Bertram ◽  
Christoph Berger ◽  
Sebastian Metzner ◽  
...  

Abstract We report on the formation process of GaN/AlN quantum dots which arises after the deposition of 1 - 2 monolayers of GaN on an AlN/sapphire template followed by a distinct growth interruption. The influence of the duration of a growth interruption on structural and optical properties of the GaN layer has been systematically investigated. Quantum dots develop from initially bulky GaN islands, which nucleate in close vicinity to bundles of threading dislocations. For prolonged growth interruptions a decreasing island size is observed which is consistent with a systematic blue shift of the emission wavelength. In addition, a fragmentation of the bulky GaN islands into several smaller islands occurs, strongly depending on local strain fields caused by threading dislocations as well as on a different facet orientation of the islands. This morphological transition during growth interruption eventually leads to GaN quantum dot formation which assemble as clusters with a density of 108 cm-2. Desorption of GaN is identified as the major source for this morphological transition. The growth interruption time allows for tuning of the quantum dot emission wavelength in the UV spectral range.


2021 ◽  
Vol 920 (1) ◽  
pp. L24
Author(s):  
Motoki Kino ◽  
Kotaro Niinuma ◽  
Nozomu Kawakatu ◽  
Hiroshi Nagai ◽  
Gabriele Giovannini ◽  
...  

2021 ◽  
Vol 12 ◽  
Author(s):  
Silvia Moschin ◽  
Sebastiano Nigris ◽  
Ignacio Ezquer ◽  
Simona Masiero ◽  
Stefano Cagnin ◽  
...  

Nymphaeaceae are early diverging angiosperms with large flowers characterized by showy petals and stamens not clearly whorled but presenting a gradual morphological transition from the outer elements to the inner stamens. Such flower structure makes these plant species relevant for studying flower evolution. MADS-domain transcription factors are crucial components of the molecular network that controls flower development. We therefore isolated and characterized MADS-box genes from the water lily Nymphaea caerulea. RNA-seq experiments on floral buds have been performed to obtain the transcript sequences of floral organ identity MADS-box genes. Maximum Likelihood phylogenetic analyses confirmed their belonging to specific MADS-box gene subfamilies. Their expression was quantified by RT-qPCR in all floral organs at two stages of development. Protein interactions among these transcription factors were investigated by yeast-two-hybrid assays. We found especially interesting the involvement of two different AGAMOUS-like genes (NycAG1 and NycAG2) in the water lily floral components. They were therefore functionally characterized by complementing Arabidopsis ag and shp1 shp2 mutants. The expression analysis of MADS-box genes across flower development in N. caerulea described a complex scenario made of numerous genes in numerous floral components. Their expression profiles in some cases were in line with what was expected from the ABC model of flower development and its extensions, while in other cases presented new and interesting gene expression patterns, as for instance the involvement of NycAGL6 and NycFL. Although sharing a high level of sequence similarity, the two AGAMOUS-like genes NycAG1 and NycAG2 could have undergone subfunctionalization or neofunctionalization, as only one of them could partially restore the euAG function in Arabidopsis ag-3 mutants. The hereby illustrated N. caerulea MADS-box gene expression pattern might mirror the morphological transition from the outer to the inner floral organs, and the presence of transition organs such as the petaloid stamens. This study is intended to broaden knowledge on the role and evolution of floral organ identity genes and the genetic mechanisms causing biodiversity in angiosperm flowers.


Antibiotics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1074
Author(s):  
Priscilla Augusta de Sousa Fernandes ◽  
Josefa Carolaine Pereira da Silva ◽  
Débora Lima Sales ◽  
Paulo Riceli Vasconcelos Ribeiro ◽  
Edy Sousa de Brito ◽  
...  

Croton heliotropiifolius Kunth (Euphorbiaceae), whose occurrence has already been registered in the most varied Brazilian biomes, is commonly found in the Chapada do Araripe, Ceará. The species is traditionally used to treat fungal, parasitic, and degenerative diseases. This study investigated the chemical composition and pharmacological potential (antioxidant, antifungal, antiparasitic, and cytotoxic) of an aqueous extract obtained from the roots of C. heliotropiifolius. Following a qualitative phytochemical screening, the chemical constituents were identified by ultra-efficiency liquid chromatography coupled witha quadrupole/time-of-flight system (UPLC-QTOF). The antioxidant potential was verified by thin-layer chromatography (TLC). The direct and combined antifungal activity of the extract against opportunistic Candida strains was investigated using the microdilution method. The minimal fungicidal concentration (MFC) was determined by subculture, while the modulation of the morphological transition (fungal virulence) was evaluated by light microscopy. The in vitro antiparasitic activity was analyzed using epimastigotes of Trypanosoma cruzi and promastigotes of Leishmania braziliensis and Leishmania infantum, while cytotoxicity was determined in cultures of mouse fibroblasts. The phytochemical analysis identified the presence of acids, terpenes, flavonoids, lignans, and alkaloids. Among these constituents, the presence of polar and non-polar phenolic compounds with known antioxidant action washighlighted. While the extract showed clinically ineffective antifungal effects, it could enhance the effectiveness of fluconazole, in addition to inhibiting the morphological transition associated with increased virulence in Candida strains. Although the extract showed low cytotoxicity against fibroblasts, it also had weak antiparasitic effects. In conclusion, Croton heliotropiifolius is a source of natural products with antifungal and antioxidant potential.


2021 ◽  
pp. 117313
Author(s):  
Yong Lu ◽  
Benjamin Derby ◽  
Sriram Hariharan ◽  
Kamal Kadirvel ◽  
Cuiping Wang ◽  
...  

Author(s):  
Lei Qiu ◽  
Tong-Sheng Zhang ◽  
Ji-Zheng Song ◽  
Jing Zhang ◽  
Ze Li ◽  
...  

As a well-known entomopathogenic fungus, Beauveria bassiana has a complex life cycle and involves transformations among single-cell conidia, blastospores, and filamentous hyphae. This study provides new insight into the regulation of the fungal cell morphological transitions by simulating three models.


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