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"Chemical properties"
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Aluminum
Presents the properties of the element and its components while providing readers with resources to learn more about aluminum and how it is mined, recycled, and used in our society.
Book
Exopolysaccharides from Microalgae and Cyanobacteria: Diversity of Strains, Production Strategies, and Applications
Microalgae and cyanobacteria are photosynthetic organisms that can produce/accumulate biomolecules with industrial interest. Among these molecules, EPSs are macromolecular polysaccharidic compounds that present biological activities and physico-chemical properties, allowing to consider their valorization in diverse commercial markets, such as cosmetic, therapeutic, nutraceutic, or hydrocolloids areas. The number of microalgae and cyanobacteria strains described to produce such EPSs has increased in recent years as, among the 256 producing strains gathered in this review, 86 were published in the last 10 years (~33%). Moreover, with the rise of research on microalgae EPSs, a variety of monosaccharides compositions have been discovered, highlighting the versatility of these organisms. If some production strategies can be applied to increase EPS production yields, it appears that case by case studies are needed to promote EPS synthesis by a strain, as many responses exist. This paper proposes an up-to-date state of the art of the diversity of microalgae and cyanobacteria EPS-producing strains, associated to the variability of compositions. The strategies for the production and extraction of the polymers are also discussed. Finally, an overview of the biological activities and physico-chemical properties allow one to consider their use on several commercial markets.
Journal Article
Exploring matter & physical changes
This title provides an overview of matter and physical changes. Text includes a simple overview of matter and examines properties, states, phases, and atoms. Atomic theory is introduced. Information is explained using real-world examples and supported with graphics and photos. This book concludes with two simple, kid-friendly experiments. Aligned to Common Core standards and correlated to state standards.-- Source other than the Library of Congress.
BOOK
Urea fertilization decreases soil bacterial diversity, but improves microbial biomass, respiration, and N-cycling potential in a semiarid grassland
In this study, changes in plant diversity and aboveground biomass, soil chemical properties, microbial biomass and respiration, microbial composition, and microbial N-cycling potential (represented by the abundance of genes involved in N reaction) were studied after 3 years of urea fertilization (0, 25, 50, and 100 kg N ha−1 year−1) in a semiarid grassland in China. The microbial composition and N-cycling genes were determined using metagenome sequencing. Urea fertilization significantly decreased soil bacterial diversity, possibly through its negative effect on plant diversity, whereas it increased fungal diversity, and microbial biomass and respiration through enhancing aboveground biomass production with increases in the C input into the soil. However, above the threshold N rate of 50 kg N ha−1 year−1, microbial biomass and respiration decreased probably because of a strong N inhibitory effect on aboveground biomass. Further, urea fertilization increased the gene abundances of narH, nrfA, nirB, and napA, which are involved in dissimilatory nitrate reduction, and those of nifH and nifD, involved in N2 fixation, gdh, involved in organic N decomposition, and glnA, involved in glutamine synthesis and ureC. These findings suggested that urea addition has a positive effect on N-turnover potential. Burkholderiales and Rhizobiales play an important role in soil N cycling. Changes in plant community (diversity and biomass) were responsible for the shift in microbial diversity, biomass, and respiration, whereas alterations in inorganic N levels (exchangeable NH4+ and NO3−) potentially affected microbial N cycling. Our results show that N-mediated environmental stresses can play an important role in microbial diversity and functions, which appear to be mediated largely by plant–soil interactions.
Journal Article
Sciencia : mathematics, physics, chemistry, biology, and astronomy for all
\"From the structure of the cosmos to that of the human body, the discoveries of science over the past few hundred years have been remarkable. Sciencia spans the realms of mathematics, physics, chemistry, biology, and astronomy, offering an invaluable introduction to each. Curious about quarks, quasars, and the fantastic universe around you? Ever wanted to explore a mathematical proof? Need an introduction to biochemistry? Beautifully illustrated with engravings, woodcuts, and original drawings and diagrams, Sciencia will inspire inquisitive readers of all ages to appreciate the interconnected knowledge of the modern sciences\"--Page 4 of cover.
Book
Response of soil microbial community to afforestation with pure and mixed species
Objectives: Afforestation changes soil chemical properties over several decades. In contrast, microbial community structure can be shifted within the first decade and so, the direct effects of tree species can be revealed. The aim of this study was to determine the alteration of soil microbial community composition 10 years after afforestation by trees with contrasting functional traits. Methods: The study was conducted at the BangorDIVERSE temperate forest experiment. Soil samples were collected under single, two and three species mixtures of alder and birch, beech and oak - early and secondary successional species, respectively, and contiguous agricultural field. Soil was analysed for total carbon (C) and nitrogen (N) contents, and microbial community structure (phospholipid fatty acids (PLFAs) analysis). Results and conclusions: The total PLFAs content (370-640 nmol g⁻¹ soil) in forest plots increased for 30 to 110 % compared to the agricultural soil (290 nmol g⁻¹ soil). In contrast, soil C, N and C/N ratios were altered over 10 years much less - increased only up to 20 % or even decreased (for beech forest). Afforestation increased bacterial PLFAs by 20-120 %, whereas it had stronger impact on the development of fungal communities (increased by 50-200 %). These effects were proved for all forests, but were more pronounced under the monocultures compared to mixtures. This indicates that species identity has a stronger effect than species diversity. Principal component analysis of PLFAs revealed that under mono and three species mixtures similar microbial communities were formed. In contrast, gram-positive PLFAs and actinomycete PLFAs contributed mainly to differentiation of two species mixtures from other forests. Thus, at the early afforestation stage: i) soil biological properties are altered more than chemical, and ii) tree species identity affects more than species amount on both processes.
Journal Article
Prediction of antimicrobial peptides toxicity based on their physico-chemical properties using machine learning techniques
Background
Antimicrobial peptides are promising tools to fight against ever-growing antibiotic resistance. However, despite many advantages, their toxicity to mammalian cells is a critical obstacle in clinical application and needs to be addressed.
Results
In this study, by using an up-to-date dataset, a machine learning model has been trained successfully to predict the toxicity of antimicrobial peptides. The comprehensive set of features of both physico-chemical and linguistic-based with local and global essences have undergone feature selection to identify key properties behind toxicity of antimicrobial peptides. After feature selection, the hybrid model showed the best performance with a recall of 0. 876 and a F1 score of 0. 849.
Conclusions
The obtained model can be useful in extracting AMPs with low toxicity from AMP libraries in clinical applications. On the other hand, several properties with local nature including positions of strand forming and hydrophobic residues in final selected features show that these properties are critical definer of peptide properties and should be considered in developing models for activity prediction of peptides. The executable code is available at
https://git.io/JRZaT
.
Journal Article
Effects of drying on the nutrient content and physico-chemical and sensory characteristics of the edible kelp Saccharina latissima
The effects of convective air-drying at 25, 40, and 70 °C and freeze-drying on the quality of the edible kelp Saccharina latissima to be used for food were investigated. Based on the analysis of the carbohydrate and amino acid profiles, as well as polyphenol, fucoxanthin, and ash contents, no significant differences were detected among sample groups, and air-drying up to 70 °C results in equally nutritious products at shorter processing times. Only the iodine content was found lower in freeze-dried compared to air-dried samples. The swelling capacity of the air-dried samples was significantly lower than in freeze-dried samples, particularly at high temperatures (40 and 70 °C), reflecting alteration of the physico-chemical properties of the seaweed during air-drying (attributed to product shrinkage) and reduced capacity of the final product to rehydrate. Structural differences between air-dried products at 25 and 70 °C may explain the differences in mouthfeel perception (dissolving rate) among the two sample groups observed during a sensory evaluation. Overall, the drying temperature within this range did not alter neither the aroma (i.e. odor) nor the flavor intensity of the product. In food applications where the product’s mechanical properties (e.g. porosity) are essential, freeze-drying, and to a lesser extent, air-drying at low temperatures, will result in higher quality products than air-drying at higher temperatures.
Journal Article
Effects of Soil Physico-Chemical Properties on Plant Species Diversity Along an Elevation Gradient Over Alpine Grassland on the Qinghai-Tibetan Plateau, China
Elevation gradient can reflect the effects of soil physico-chemical properties on plant species diversity. Alpine grassland on the QTP has suffered from a serious decline in plant species diversity. In this study, we investigated 112 sites recording plant community characteristics and collecting soil samples along an elevation gradient (3,500–5,200 m asl) in alpine meadow on the QTP. We analyzed the effects of soil physico-chemical properties on plant species composition and diversity by canonical ordination and spatial regression along an elevation gradient. The results showed that species richness of the overall plant communities decreased with the increasing elevation, and the Simpson dissimilarity index ( β sim ) had a maximum at low elevation (3,500–4,000 m) with the value of 0.37. Soil available nitrogen content was the primary soil parameter affecting plant species composition and diversity in alpine grassland. The effect of soil available nitrogen content on plant species richness varied at different elevations. For Gramineae plants (G), plant species richness declined with the increase in soil available nitrogen content at low elevation (3,500–4,000 m), but rose at middle elevation (4,000–4,500 m). Soil available nitrogen content had a more significant limiting effect on species richness at high elevation (>4,500 m). These findings increase our understanding about the drivers of plant species diversity changes in alpine grassland on the QTP, and will provide insights into grassland restoration and sustainable management.
Journal Article
Soils naturally suppressive to banana Fusarium wilt disease harbor unique bacterial communities
AIMS: Banana Fusarium wilt disease is caused by the Fusarium oxysporum f. sp. cubense race 4 fungus and is a vast problem for global banana production. Suppressive and conducive soils were analyzed to characterize important microbial populations and soil chemical properties that contribute to disease suppressiveness. METHODS: Soil bacteria communities from the two banana orchards with excellent Fusarium disease suppression (suppressive soil) after long-term monoculture and two adjacent banana orchards with serious Fusarium wilt disease (conducive soils) were compared using deep 16S RNA barcode pyrosequencing. RESULT: Compared to the conducive soils within the same field site, higher (P < 0.05) richness and diversity indices were observed in both suppressive soils. Moreover, more operational taxonomic units (OTUs) were observed in the two suppressive soils. Hierarchical cluster analyses showed that bacterial community membership and structure in disease-suppressive soils differed from disease-conducive soils. The Acidobacteria phylum was significantly (P < 0.05) elevated, but Bacteroidetes was significantly (P < 0.05) reduced in suppressive soils. The Gp4, Gp5, Chthonomonas, Pseudomonas, and Tumebacillus genera were significantly (P < 0.05) enriched in suppressive soils, but Gp2 was significantly (P < 0.05) reduced in suppressive soils. Furthermore, the enrichment of Gp5 and Pseudomonas as well as the soil physicochemical properties of available phosphorus were significantly (P < 0.05) correlated with disease suppression. CONCLUSIONS: Naturally disease suppressive soils to banana Fusarium wilt disease harbor unique bacterial communities.
Journal Article