277 research outputs found
Nonlinear vertical oscillations of a particle in a sheath of a rf discharge
A new simple method to measure the spatial distribution of the electric field
in the plasma sheath is proposed. The method is based on the experimental
investigation of vertical oscillations of a single particle in the sheath of a
low-pressure radio-frequency discharge. It is shown that the oscillations
become strongly nonlinear and secondary harmonics are generated as the
amplitude increases. The theory of anharmonic oscillations provides a good
qualitative description of the data and gives estimates for the first two
anharmonic terms in an expansion of the sheath potential around the particle
equilibrium.Comment: 11 pages, 4 figure
Enzymatic removal of cellulose from cotton/polyester fabric blends
The production of light-weight polyester fabrics from a polyester/cotton blended fabric, by means of the enzymatic removal of the cellulosic part of the material, was investigated. The removal of cotton from the
blended fabric yielded more than 80% of insoluble microfibrillar material by the combined action of high beating effects and cellulase hydrolysis.Other major features of this enzymatic process for converting cotton fibers into microfibrillar material are bath ratio, enzyme dosage and treatment time
Direct enzymatic esterification of cotton and Avicel with wild-type and engineered cutinases
In this work, the surface of cellulose, either Avicel or cotton fabric, was modified using cutinases without any previous treatment to swell or to solubilise the polymer. Aiming further improvement of cutinase ester synthase activity on cellulose, an engineered cutinase was investigated. Wild-type cutinase from Fusarium solani and its fusion with the carbohydrate-binding module N1 from Cellulomonas fimi were able to esterify the hydroxyl groups of cellulose with distinct efficiencies depending on the acid substrate/solvent system used, as shown by titration and by ATR-FTIR. The carbonyl stretching peak area increased significantly after enzymatic treatment during 72 h at 30 °C. Cutinase treatment resulted in relative increases of 31 and 9 % when octanoic acid and vegetable oil were used as substrates, respectively. Cutinase-N1 treatment resulted in relative increases of 11 and 29 % in the peak area when octanoic acid and vegetable oil were used as substrates, respectively. The production and application of cutinase fused with the domain N1 as a cellulose ester synthase, here reported for the first time, is therefore an interesting strategy to pursuit.This work was co-funded by the European Social Fund through the management authority POPH and FCT, Postdoctoral fellowship reference: SFRH/BPD/47555/2008. The authors also want to thank Doctor Raul Machado for his valuable help on FTIR spectral data treatment
Particles as probes for complex plasmas in front of biased surfaces
An interesting aspect in the research of complex (dusty) plasmas is the
experimental study of the interaction of micro-particles with the surrounding
plasma for diagnostic purposes. Local electric fields can be determined from
the behaviour of particles in the plasma, e.g. particles may serve as
electrostatic probes. Since in many cases of applications in plasma technology
it is of great interest to describe the electric field conditions in front of
floating or biased surfaces, the confinement and behaviour of test particles is
studied in front of floating walls inserted into a plasma as well as in front
of additionally biased surfaces. For the latter case, the behaviour of
particles in front of an adaptive electrode, which allows for an efficient
confinement and manipulation of the grains, has been experimentally studied in
dependence on the discharge parameters and on different bias conditions of the
electrode. The effect of the partially biased surface (dc, rf) on the charged
micro-particles has been investigated by particle falling experiments. In
addition to the experiments we also investigate the particle behaviour
numerically by molecular dynamics, in combination with a fluid and
particle-in-cell description of the plasma.Comment: 39 pages, 16 figures, submitted to New J. Phy
Carbohydrate metabolism genes and pathways in insects: insights from the honey bee genome
Carbohydrate-metabolizing enzymes may have particularly interesting roles in the honey bee, Apis mellifera, because this social insect has an extremely carbohydrate-rich diet, and nutrition plays important roles in caste determination and socially mediated behavioural plasticity. We annotated a total of 174 genes encoding carbohydrate-metabolizing enzymes and 28 genes encoding lipid-metabolizing enzymes, based on orthology to their counterparts in the fly, Drosophila melanogaster, and the mosquito, Anopheles gambiae. We found that the number of genes for carbohydrate metabolism appears to be more evolutionarily labile than for lipid metabolism. In particular, we identified striking changes in gene number or genomic organization for genes encoding glycolytic enzymes, cellulase, glucose oxidase and glucose dehydrogenases, glucose-methanol-choline (GMC) oxidoreductases, fucosyltransferases, and lysozymes
Current strategies for treatment of intervertebral disc degeneration: substitution and regeneration possibilities
Background: Intervertebral disc degeneration has an annual worldwide socioeconomic impact masked as low back pain of over 70 billion euros. This disease has a high prevalence over the working age class, which raises the socioeconomic impact over the years. Acute physical trauma or prolonged intervertebral disc mistreatment triggers a biochemical negative tendency of catabolic-anabolic balance that progress to a chronic degeneration disease. Current biomedical treatments are not only ineffective in the long-run, but can also cause degeneration to spread to adjacent intervertebral discs. Regenerative strategies are desperately needed in the clinics, such as: minimal invasive nucleus pulposus or annulus fibrosus treatments, total disc replacement, and cartilaginous endplates decalcification.
Main Body: Herein, it is reviewed the state-of-the-art of intervertebral disc regeneration strategies from the perspective of cells, scaffolds, or constructs, including both popular and unique tissue engineering approaches. The premises for cell type and origin selection or even absence of cells is being explored. Choice of several raw materials and scaffold fabrication methods are evaluated. Extensive studies have been developed for fully regeneration of the annulus fibrosus and nucleus pulposus, together or separately, with a long set of different rationales already reported. Recent works show promising biomaterials and processing methods applied to intervertebral disc substitutive or regenerative strategies. Facing the abundance of studies presented in the literature aiming intervertebral disc regeneration it is interesting to observe how cartilaginous endplates have been extensively neglected, being this a major source of nutrients and water supply for the whole disc.
Conclusion: Severalinnovative avenues for tackling intervertebral disc degeneration are being reported â from acellular to cellular approaches, but the cartilaginous endplates regeneration strategies remain unaddressed. Interestingly, patient-specific approaches show great promise in respecting patient anatomy and thus allow quicker translation to the clinics in the near future.The authors would like to acknowledge the support provided by the Portuguese
Foundation for Science and Technology (FCT) through the project EPIDisc
(UTAP-EXPL/BBBECT/0050/2014), funded in the Framework of the “International
Collaboratory for Emerging Technologies, CoLab”, UT Austin|Portugal Program.
The FCT distinctions attributed to J. Miguel Oliveira (IF/00423/2012 and IF/01285/
2015) and J. Silva-Correia (IF/00115/2015) under the Investigator FCT program are
also greatly acknowledged.info:eu-repo/semantics/publishedVersio
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