morphological modification
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Author(s):  
Bassam Abdallah ◽  
M. Kakhia ◽  
W. Zetoune ◽  
M. Alwazzeh

ZnS nanostructure films were deposited by a thermal evaporation method. Two films were prepared; the first was zinc sulfide (undoped ZnS) and the second was Pb-doped zinc sulfide (Pb:ZnS). X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) techniques were employed to investigate the element contents of the two films; they were found to be stoichiometric. Surface and growth evolution of films were explored by SEM images and found to have morphological development from spherical forms into nanostructure lookalike Taraxacum erythrospermum (Dandelion) with increasing the Pb from 0 wt.% to 12 wt.%. A structural study was performed using XRD patterns. The films have ZnS hexagonal structure (002) preferential orientation with various Pb percentages. In the doped sample, ZnS nanostructure and pores and nanowires (NWs) were formed with a mean diameter less than 50 nm; the undoped film had dense structure and was thin. This study illustrated the influence of Pb doped on the morphological modification of ZnS films.


2021 ◽  
Vol 122 ◽  
pp. 111658
Author(s):  
Eka Nurfani ◽  
Yeli Krisdayanti Lature ◽  
Mohamad Samsul Anrokhi

Author(s):  
Nguyen Hoc Thang ◽  
Nguyen Thuc Boi Huyen

In the 21st century, mankind has witnessed the rapidly development of all industries with a lot of new products in a variety of types and designs. However, this development has been also causing many problems with the society and the ecological environment such as a wasteful excess of products, exhaustive exploitation of natural resources, indiscriminate deforestation, and waste pollution affecting the living environment, ecosystem, and human health. Many organizations and governments are calling for environmental protection, limit waste emissions, and find good solutions to use the recycled materials as raw materials in production plants. This study would like to provide a solution which not only utilizes waste packaging Pinaceae wood for recycling as raw material but also supplies to the market with a green product responding to the durability requirements in fact. Pinaceae wood packaging residues were chemically processed through two stages. The amount of lignin extract from Pinaceae was determined by the method of Tappi 222 om-02 which was significantly influenced by the extraction parameters such as temperature, time and concentration of the treatment solution. Morphological modification of wood materials was analyzed by SEM micrographs. In particular, the mechanical properties of the Epoxy/TPW2 composite green material have been significantly improved with increasing up to 206–540 % compared to the original Pinaceae wood. The optical properties of the wood have completely changed from opaque pine wood with the optical transmittance of 8 % into transparent composite material with the optical transmittance up to 85 % using UV-vis spectroscopy analysis.


2021 ◽  
Author(s):  
Fabio Andrade Machado ◽  
Gabriel Marroig ◽  
Alex Hubbe

The prevalence of stasis on paleontological and comparative data has been classically taken as evidence of the strong role of stabilizing selection in shaping morphological evolution. When confronted against biologically informed predictions, empirical rates of evolution tend to fall below what is expected under genetic drift, suggesting that the signal for directional selection is erased at longer time scales. However, empirical tests of these claims are few and tend to focus on univariate traits, ignoring the potential roles of trait covariances in constraining evolution. Here we investigated the multivariate rates of morphological evolution in a fossil lineage that underwent extreme morphological modification, the glyptodonts. Contrary to what was expected, biologically informed models of evolution suggest a preeminent role of directional selection on the divergence of glyptodonts from living armadillos. Furthermore, the reconstruction of selection patterns shows that traits selected to generate a glytodont morphology are markedly different from those necessary to explain the extant armadillos' morphological diversity. Changes in both direction and magnitude of selection are probably tied to the invasion of a specialist-herbivore adaptive zone by glyptodonts. These results suggest that directional selection might have played a more important role in the evolution of extreme morphologies than previously imagined.


2021 ◽  
Vol 54 (4) ◽  
Author(s):  
Yao Liu ◽  
Huilin He ◽  
Yanjun Liu

Crystal growth speeds, crystal sizes and the morphology of sodium acetate (CH3COONa) crystals in the presence of polymaleic acid and polyacrylic acid with different concentrations were investigated in supersaturated solutions of sodium acetate. The technique of non-photochemical laser-induced nucleation (NPLIN) was used to produce initial crystallites of anhydrous CH3COONa. The anhydrous CH3COONa crystal growth in solution after laser irradiation resembled the formation of dandelion seed heads. Even though NPLIN could offer temporal–spatial control of crystal nucleation without the addition of acidic polymers, the crystal growth rates were heterogeneous for crystallites along the laser pathway, which led to irregular crystalline sizes and morphologies. Here, a controllable approach from crystal nucleation to crystal growth has been designed through the addition of acidic polymers in the laser-induced growth of anhydrous CH3COONa crystals. In the presence of an acidic polymer, both the crystal growth and the morphological modification were controlled from tuft-shaped crystals to dandelion-like crystals. As bulk solid thicknesses and crystal growth speeds can be modified by different mass fractions of acidic polymer, a mathematical model was established to analyse the dynamics of crystal growth under the effect of acidic polymers. The model reproduces remarkably well the experimental trend and predicts experimental results. The changes in supersaturation and the number of nuclei through the addition of acidic polymers were analysed to investigate the underlying mechanism of morphological difference.


Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 247
Author(s):  
Mattia Giuliano ◽  
Maria Carmen Valsania ◽  
Pierfrancesco Ticali ◽  
Enrico Sartoretti ◽  
Sara Morandi ◽  
...  

Ageing of automotive catalysts is associated to a loss of their functionality and ultimately to a waste of precious resources. For this reason, understanding catalyst ageing phenomena is necessary for the design of long lasting efficient catalysts. The present work has the purpose of studying in depth all the phenomena that occur during ageing, in terms of morphological modification and deactivation of the active materials: precious metal particles and oxidic support. The topic was deeply investigated using specific methodologies (FT-IR, CO chemisorption, FE-SEM) in order to understand the behavior of metals and support, in terms of their surface properties, morphology and dispersion in the washcoat material. A series of commercial catalysts, aged in different conditions, have been analyzed, in order to find correlations between real and simulated ageing conditions. The characterization highlights a series of phenomena linked to the deactivation of the catalysts. Pd nanoparticles undergo a rapid agglomeration, exhibiting a quick loss of dispersion and of active sites with an increase of particles size. The evolution of the support allows highlighting also the contribution of chemical ageing effects. These results were also correlated with performance tests executed on synthetic gas bench, underlining a good correspondence between vehicle and laboratory aged samples and the contribution of chemical poisoning to vehicle aged ones. The collected data are crucial for the development of accelerated laboratory ageing protocols, which are instrumental for the development and testing of long lasting abatement systems.


2021 ◽  
Author(s):  
Eugenio Azpeitia ◽  
Gabrielle Tichtinsky ◽  
Marie Le Masson ◽  
Antonio Serrano-Mislata ◽  
Veronica Gregis ◽  
...  

AbstractThe arrangement of plant organs, called phyllotaxis, produce remarkable spiral or whorled patterns. Cauliflowers present a unique phyllotaxis with a multitude of spirals over a wide range of scales. How such a self-similar fractal organization emerges from developmental mechanisms has remained elusive. Combining experimental assays with modeling, we found that cauliflowers arise due to the hysteresis of the bistable floral network that generates inflorescences imprinted by a transient floral state. We further show how additional mutations affecting meristem growth dynamics can induce the production of conical phyllotactic structures reminiscent of the conspicuous fractal Romanesco shape. This study reveals how the spectacular morphological modification of the inflorescences in cauliflower and Romanesco shape arises from the hysteresis of the genetic programs controlling inflorescence development.One Sentence SummaryThe molecular making of cauliflowers


2021 ◽  
Vol 8 ◽  
Author(s):  
Wissam El Hazzat ◽  
Hicham Benyahia ◽  
Fatima Zaoui

Introduction : A double tooth can be a consequence of fusion or gemination and is characterized by a size increasing of the tooth and a morphological modification. This anomaly concerns the anterior teeth and occurs in temporary and permanent dentition. Double teeth causes various problems (easthetic, occlusal, endodontic, orthodontic, periodontal…). The management of clinical situations involving such abnormalities is often complex. Our aim is to present reasoned analysis based on a systematic review of  therapeutic attitudes used in different clinical situations when the abnormal tooth is located at the anterior maxillary region. Material and methods : we carried out an electronic research via Pubmed and Sciencedirect to collect case reports published during the 20 recent years (1999-2020).  We included 46 articles corresponding to 57 relevant case report that we classified based on Aguilo and coll. Classification (1999). Results : Partial crown and root section is indicated for type I. Stipping is indicated for type II. The management of type III is compromised by the canal morphology .Extraoral and entraoral hemisection are only incated for type IV. Coronoplasty is usually unavoidable. Endodontic, orthodontic or periodontal treatment can be indicated depending on the situation. The extraction is considered as a last resort, the space is restored by autotransplantation of a supernumarary tooth, a prosthetic restauration or an implant by the end of the craniofacial growth. Conclusion : The managment of double teeth is a therapeutic challenge, every case is different, a multidisciplinary approach is recommended.


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