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491.
    
Anomalous transport of topological semimetals has generated significant interest for applications in optoelectronics, nanoscale devices, and interconnects. Understanding the origin of novel transport is crucial to engineering the desired material properties, yet their orders of magnitude higher transport than single-particle mobilities remain unexplained. This work demonstrates the dramatic mobility enhancements result from phonons primarily returning momentum to electrons due to phonon-electron dominating over phonon–phonon scattering. Proving this idea, proposed by Peierls in 1932, requires tuning electron and phonon dispersions without changing symmetry, topology, or disorder. This is achieved by combining de Haas - van Alphen (dHvA), electron transport, Raman scattering, and first-principles calculations in the topological semimetals MX2 (M = Nb, Ta and X = Ge, Si). Replacing Ge with Si brings the transport mobilities from an order magnitude larger than single particle ones to nearly balanced. This occurs without changing the crystal structure or topology and with small differences in disorder or Fermi surface. Simultaneously, Raman scattering and first-principles calculations establish phonon–electron dominated scattering only in the MGe2 compounds. Thus, this study proves that phonon-drag is crucial to the transport properties of topological semimetals and provides insight to engineer these materials further.  相似文献   
492.
    
Chitosan-based edible coatings represent an eco-friendly and biologically safe preservative tool to reduce qualitative decay of fresh and ready-to-eat fruits during post-harvest life due to their lack of toxicity, biodegradability, film-forming properties, and antimicrobial actions. Chitosan-based coatings modulate or control oxidative stress maintaining in different manner the appropriate balance of reactive oxygen species (ROS) in fruit cells, by the interplay of pathways and enzymes involved in ROS production and the scavenging mechanisms which essentially constitute the basic ROS cycle. This review is carried out with the aim to provide comprehensive and updated over-view of the state of the art related to the effects of chitosan-based edible coatings on anti-oxidant systems, enzymatic and non-enzymatic, evaluating the induced oxidative damages during storage in whole and ready-to-eat fruits. All these aspects are broadly reviewed in this review, with particular emphasis on the literature published during the last five years.  相似文献   
493.
    
To determine the equilibrium constant for ferroselite (FeSe2(cr)) dissolution reaction, FeSe2(cr) solubility experiments were performed at 298 ± 1 K from both the over- and under-saturation directions with Fe–Se precipitates that were aged at 348 K. X-ray diffraction (XRD) analysis detected only FeSe2(cr) as the Se solid phase in the equilibrated precipitates. The Eh values of the equilibrated suspensions ranged from ?188.6 to ?4.9 mV vs. standard hydrogen electrode (SHE) and the pH values ranged from 6.00 to 8.76. Based on the available thermodynamic data, Se42? and Fe2+ are thermodynamically stable within this Eh–pH range. Agreement between the solubility data obtained from the over- and under-saturation directions lends credence to the attainment of equilibrium at 298 ± 1 K. The thermodynamic interpretations using the specific ion interaction theory (SIT) model showed that Eh values and the concentrations of Se and Fe are well represented by the 2FeSe2(cr) solubility reaction (2FeSe2(cr) ? 2Fe2+ + Se42? + 2e?) with log10K = ?17.09 ± 0.28. The obtained log10K value falls within the uncertainty limits of the log10K value calculated from the available thermodynamic data.  相似文献   
494.
Summary The effect of small concentrations of dicumyl peroxide (DCP) on the modification of a linear low density polyethylene (LLDPE) during a reactive extrusion process was investigated. The experiments were arranged in a two level factorial design in order to evaluate the effect of temperature zones (X1), peroxide concentration (X2) and screw rpm (X3) on the modification of LLDPE. The melt flow index (MFI) was used as a response variable. It was verified that the thermal properties, crystalline melting temperature (Tm), the heat of fusion (Hmelt) and the crystallinity degree (X%) decrease with the increasing of the peroxide concentration. The crystallization temperature (Tc) increased up to 0.05% w/w peroxide, whereafter the level stays almost constant. The gel content of the samples however indicated that a three-dimensional network was negligible in the experimental conditions used.  相似文献   
495.
The necessity of planning the activities related to quarries developed in the metropolitan area of Sao Paulo, in accordance with the directions fixed by the metropolitan planning led to the preparation of a PDM-PLANO DIRECTOR DE MINERAÇAO-(guiding Plan for Quarrying). This project includes contributions from SNM—Secretaria dos negocios metropolitanos do estado de Sao Paulo—as well as from D.N.P.M.—Departmento Nacional da Produçao Mineral; from Emplasa—Empresa metropolitana de planejamento da grande Sao Paulo and from C.P.R.M.—Companhia de Pesquisa de Recursos Minerais. This work was a natural consequence of what was agreed upon between S.N.M. and D.N.P.M., on september the 28th, 1976. Such an agreement proved to be necessary when the conflicts between the quarrying activities and the plans for use and occupation of the metropolitan soils tended to increase, as there was an incompatibility between quarrying activities development and the areas which had been selected for agriculture, implantation of industrial districts, urban expansion or even for environmental protection. The elaboration of the PDM required hard field work including a survey of mineral potential areas, the situation of the market; a check-up of local conditions for quarrying; the methods of quarrying which were used and the possibilities of recovering the mined areas. It also requried experts from different fields, such as architects, civil and mining engineers, geoligists, geographers and lawyers who worked together, in an attempt to find an integrated solution for the problem. The execution and implantation of the PDM led to the conclusion that quarrying activities had to be considered as a significant way of using the soil, contrary to what had been done so far. It also tried to integrate it with other uses of the soil, in the metropolitan planning.  相似文献   
496.
The research evidences the importance of linking chemical and sensory data for the wine characterization; in particular, the Italian white wine made from Inzolia grapes has been considered. Inzolia is one of the most widespread native white grapes in Sicily (Italy), and wine samples from two different areas (Monreale and Sambuca di Sicilia) have been analyzed. A headspace solid-phase microextraction/gas chromatography–mass spectroscopy method has been developed, and 56 volatile components, esters, fatty acids, alcohols, and terpenes have been identified; the method allows also the quantification of the main components, namely, ethyl octanoate (banana, fruit, fat) (257.2–541.6 mg/l) and ethyl decanoate (fruity, oily, floral; 171.8–272.0 mg/l). A good repeatability in terms of retention times and peak areas resulted. Sensory analysis was performed by ten trained judges that evaluated eight attributes: two referring to appearance (yellow color and yellow reflex), four referring to aroma (fruity, banana, ripened apple, and floral), and two referring to oral perception (acid and pungent). The volatile constituents and the aroma sensory attributes were in agreement.  相似文献   
497.
A method was developed to differentiate between Bacillus cereus, Bacillus mycoides and Bacillus thuringiensis using the polymerase chain reaction combined with a restriction endonuclease (PCR-RE) technique. This fast and simple protocol, applied to pure culture strains, was developed using the gyrB DNA sequence, as previously proposed by other authors. Strains from international collections were used to optimize the method which was then applied to the identification of strains isolated from food samples. Amplifications were specific for the B. cereus group. Only Staphylococcus aureus gave the same size PCR product, but it was easily differentiated from strains in the B. cereus group by using restriction analysis, based on digestion with the RsaI, Sau3AI and EcoRI endonucleases. Specific amplifications and good differentiations were obtained using pure strains, suggesting the possibility of using the method described to identify the B. cereus group directly in food samples.  相似文献   
498.
Due to their increasing use in agriculture, the presence of pesticide residues in food and water currently represents one of the major issues for the food safety. Among the pesticides, organophosphate and carbamate species are the most used, and their toxicity is mainly due to their inhibitory effect on acetylcholinesterase (AChE). For this reason, a monoenzymatic acetylcholinesterase impedimetric biosensor was developed in order to sensitively detect carbamate and organophosphate compounds with a very fast response. The working principle of the AChE biosensor exploits the capability of carbamate and organophosphate pesticides to form a stable complex with the enzyme, which causes an impedimetric change. The impedimetric biosensor showed a linearity between 5 and 170 ppb for carbamates and 2.5–170 ppb for organophosphate compounds, with a reproducibility (RSD%) interelectrode equal to 4.8 and 3.1% for organophosphates and carbamates, respectively. Moreover, the common amperometric evaluation of AChE inhibition degree was correlated to the impedimetric changes of the electrode surface, showing a good correlation (R 2 = 0.99 for carbamates and R 2 = 0.98 for organophosphates) between the two methods. In contrast to amperometric evaluation that needs a response time of 20 min, impedimetric detection requires only 4 min. Finally, the impedimetric biosensor was used to measure carbaryl and dichlorvos spiked in different concentrations in tap water and lettuce samples, showing a recovery near to 100% for all concentrations and for both pesticides.  相似文献   
499.
The effects of drying by microwave and convective heating at 60 and 70 °C on colour change, degradation of β‐carotene and the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) scavenging activity of apricots were evaluated. Microwave heating reduced significantly the drying time (up to 25%), if compared with convective one, also owing to the higher temperature reached during the last phase of the process, as monitored by infrared thermography. Colour changes of apricot surface, described with lightness and hue angle, in both drying methods followed a first‐order reaction (0.927 ≤ R2 ≤ 0.996). The apricots dried by microwave were less affected by the darkening phenomena. The evolution of β‐carotene in fresh apricots (61.2 ± 5.6 mg kg?1 d.w.) during the drying highlighted a wider decrease (about 50%) when microwave heating was employed for both the temperatures used. Radical scavenging activity increased (P < 0.05) in all dried samples except for hot‐air dried apricots at 60 °C.  相似文献   
500.
Bioconversion of isoflavone glucosides and antioxidant activity by probiotic strain (Bifidobacterium longum) during soymilk fermentation was investigated, as well as partial characterisation of the produced enzyme β‐glucosidase. The enzyme has higher affinity for genistin than for other substrates assayed. Maximum activity occurred at 42 °C and at pH 6.0; keeping 70–80% of activity for 60 days stored at low temperatures. Bifidobacterium longum grew well in soymilk (8.26 log CFU mL?1 and pH of 3.9 at 24 h) and were produced in good quantities of organic acids. High hydrolysis degree of isoflavone glucosides (81.2%) was observed at 24 h. Enhancements in bioactivity were assessed in fermented soymilk by monitoring the radical‐scavenging activity, antioxidant activity and DNA protective action. The use of probiotic Bifidobacterium strain as β‐glucosidase producer increased bioactive isoflavone content and demonstrated that this enzyme plays a key role in the bioavailability of soymilk isoflavones, reducing the bioconversion time compared to other studies.  相似文献   
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