3,236 research outputs found
Modelling radiation emission in the transition from the classical to the quantum regime
An emissivity formula is derived using the generalised
Fermi-Weizacker-Williams method of virtual photons which accounts for the
recoil the charged particle experiences as it emits radiation. It is found that
through this derivation the formula obtained by Sokolov et al using QED
perturbation theory is recovered. The corrected emissivity formula is applied
to nonlinear Thomson scattering scenarios in the transition from the classical
to the quantum regime, for small values of the nonlinear quantum parameter
\chi. Good agreement is found between this method and a QED probabilistic
approach for scenarios where both are valid. In addition, signatures of the
quantum corrections are identified and explored.Comment: 11 pages, 4 figures, submitted for publicatio
Application of a 235 rRNA Fluorescent In Situ Hybridization method for rapid detection of Salmonella sp. in slaughtered pigs
Pork products contamination during the slaughter process represents an important vehicle of Salmonella sp. dissemination to humans. It\u27s urgent to develop rapid, sensitive and accurate methods that allow the detection of a large number of Sa/monel/a-positive samples, in order to control these risks efficiently and in a practical time. This study evaluates the suitability of Fluorescent In Situ Hybridization (FISH) method as a rapid screening tool for Salmonella sp. deteclton in pork carcasses, as well in some risk tissues (ileum, ileocolic and mandibular lymph nodes and tonsils), which could be involved in Salmonella contamination during slaughter process. For that, FISH was comparatively analysed with the labour intenstve reference microbiological culture method (ISO 6579:2002) whose results were previously published by the same authors
Astrometry of mutual approximations between natural satellites. Application to the Galilean moons
Typically we can deliver astrometric positions of natural satellites with
errors in the 50-150 mas range. Apparent distances from mutual phenomena, have
much smaller errors, less than 10 mas. However, this method can only be applied
during the equinox of the planets. We developed a method that can provide
accurate astrometric data for natural satellites -- the mutual approximations.
The method can be applied when any two satellites pass close by each other in
the apparent sky plane. The fundamental parameter is the central instant
of the passage when the distances reach a minimum.
We applied the method for the Galilean moons. All observations were made with
a 0.6 m telescope with a narrow-band filter centred at 889 nm with width of 15
nm which attenuated Jupiter's scattered light. We obtained central instants for
14 mutual approximations observed in 2014-2015. We determined with an
average precision of 3.42 mas (10.43 km). For comparison, we also applied the
method for 5 occultations in the 2009 mutual phenomena campaign and for 22
occultations in the 2014-2015 campaign. The comparisons of determined by
our method with the results from mutual phenomena show an agreement by less
than 1-sigma error in , typically less than 10 mas. This new method is
particularly suitable for observations by small telescopes.Comment: 13 pages, 11 figures and 8 tables. Based on observations made at the
Laborat\'orio Nacional de Astrof\'isica (LNA), Itajub\'a-MG, Brazi
Composite coatings of chitosan and alginate emulsions with olive oil to enhance postharvest quality and shelf life of fresh figs (Ficus carica L. cv. Pingo De Mel)
Fresh figs are very appreciated and have been associated with health benefits. However,
these fruits are highly perishable. In this study, edible coatings were studied envisaging their positive
effect in enhancing figs’ shelf-life. Fig fruits cv. ‘Pingo de mel’ were harvested at commercial ripening
stage and single emulsion-based coatings, composed of chitosan + olive oil and alginate + olive oil,
were applied. After coatings application by dipping each fruit in the emulsion-based solutions at 4 C
and drying, the coated fruits were sprayed with crosslinking solutions (6% tripolyphosphate and 1%
calcium chloride for chitosan and alginate-based coatings, respectively). Then, were maintained at
4 C and analyzed after 1, 7, 14 and 19 days of storage. After each time interval, fruits were further
maintained at 25 C for 2 days. The results have shown that coatings were effective on delaying
fungal decay and postharvest ripening indicators (respiration rate, mass loss, softening and total
soluble solids/titratable acidity ratio). The results foresee a fruits’ shelf life between 14 and 19 days
under refrigeration at 4 C that may be followed up to 2 days at ambient temperature, higher than
that estimated for uncoated fruits (less than 14 days at 4 C plus to 2 days at ambient temperature)info:eu-repo/semantics/publishedVersio
Design of chitosan and alginate emulsion-based formulations for the production of monolayer crosslinked edible films and coatings
This study aimed to develop edible monolayer emulsion-based barriers with polysaccharides
as film-forming components (chitosan and sodium alginate), soy lecithin as a surfactant and
olive oil as a hydrophobic barrier. Monolayer barriers in the form of films were prepared by casting
filmogenic emulsions composed of 2% w/v chitosan (dissolved in lactic acid 1% v/v) or 1% w/v
sodium alginate, with different lipid contents (25, 50 and 100% w/w biopolymer basis) and different
surfactant concentrations (5, 10 and 25% w/w, lipid basis). Glycerol was used as a plasticizer (25 %
w/w, biopolymer basis). After the emulsion drying process, the obtained stand-alone films were
sprayed with a crosslinking solution, achieving an optimized crosslinker content of 3.2 mgCa2+/cm2
alginate film and 4 mg tripolyphosphate/cm2 chitosan film. The effect of oil and lecithin contents,
as well the presence of crosslinking agents, on the film’s water vapour permeability (WVP), water
vapour sorption capacity, mechanical properties and colour parameters, was evaluated. The results
have shown that the lowest WVP values were obtained with formulations containing 25% lipid and
25% surfactant for chitosan films, and 100% lipid and 25% surfactant for alginate films. The application
of the crosslinking agents decreased even further the WVP, especially for chitosan films (by 30%).
Crosslinking also increased films’ resistance to deformation under tensile tests. Overall, the films
developed present a good potential as polysaccharide-based barriers with increased resistance to
water, which envisages the use of the designed formulations to produce either edible/biodegradable
films or edible coatingsinfo:eu-repo/semantics/publishedVersio
Application of an Eco-Friendly Antifungal Active Package to Extend the Shelf Life of Fresh Red Raspberry (Rubus idaeus L. cv. ‘Kweli’)
The main objective of this study was to extend the shelf life of fresh red raspberry
(Rubus idaeus. L. cv. ‘Kweli’) by using active film-pads inside commercial compostable packages. The
pads were produced with chitosan (Ch) with the incorporation of green tea (GTE) and rosemary
(RSME) ethanolic extracts as natural antifungal agents. Pads were placed on the bottom of commercial
fruit trays underneath the fruits, and the trays were heat-sealed with a polyacid lactic (PLA) film.
Preservation studies were carried out over 14 days of storage at refrigeration temperature (4 C).
Raspberry samples were periodically analyzed throughout storage, in terms of quality attributes
(fungal decay, weight loss, firmness, surface color, pH, total soluble solids), total phenolic content
and antioxidant activity. Gas composition inside the packages was also analyzed over time. From
the packaging systems tested, the ones with active film-pads Ch + GTE and Ch + RSME were highly
effective in reducing fungal growth and decay of raspberry during storage, showing only around
13% and 5% of spoiled fruits after 14 days, respectively, in contrast with the packages without pads
(around 80% of spoiled fruits detected). In addition, fruits preserved using packages with Ch + RSME
active film-pads showed lower mass loss (5.6%), decreased firmness (3.7%) and reduced antioxidant
activity (around 9% and 15% for DPPH and FRAP methods, respectively). This sustainable packaging
presents a potential strategy for the preservation of raspberries and other highly perishable
small fruitsinfo:eu-repo/semantics/publishedVersio
Comparison of different lipid extraction procedures applied to three microalgal species
6th International Conference on Energy and Environment ResearchThe increase in the world’s energy demand has contributed to the emergence of new sustainable energy sources, such as microalgae, with their great potential to provide biofuels and other high value co-products for the food and health’s markets. However, current biorefinery methodologies are either too complex to extract the targeted components such as high-value products, or require solvents with toxicity for humans and the environment. This work aims to evaluate different lipid extraction approaches applied to three microalgal species: Chlorella zofingiensis, Phaeodactylum tricornutum, and Arthrospira platensis, while employing less toxic and more economical solvents for the lipids extraction. Experimental results showed a promising outcome to tune current biorefinery methodologies, enhancing product yield as well as decreasing potential hazards.Authors thank the financial support of the project IF/01093/2014/CP1249/CT0003 and research grantsIF/01093/2014 and SFRH/BPD/112003/2015 funded by national funds through FCT/MCTES, Portugal, and projectUID/EQU/00305/2013 - Center for Innovation in Engineering and Industrial Technology - CIETI, Portugal. This work was financially supported by : project UID/EQU/00511/2019 - Laboratory for Process Engineering, Environment, Biotechnology and Energy - LEPABE funded by national funds through FCT/MCTES (PIDDAC), Portugal; Project POCI-01-0145-FEDER-006939 (Laboratory for Process Engineering, Environment, Biotechnology and Energy - LEPABE, UID/EQU/00511/2013) funded by FEDER, Portugal through COMPETE2020-POCI and by national funds through FCT, Portugal; Project “LEPABE-2-ECO-INNOVATION” - NORTE-01-0145-FEDER-000005, funded by Norte Portugal Regional Operational Programme (NORTE 2020), Portugal , under PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). Authors also acknowledge the “Grupo Interdisciplinario de Biotecnología Marina (GIBMAR) and “Convenio de Desempeño Ciencia, Tecnología e Innovación para la Bioeconomía” from University of Concepción, Chile, for providing the support to P. tricornutum biomass production.info:eu-repo/semantics/publishedVersio
Magnetic control of particle-injection in plasma based accelerators
The use of an external transverse magnetic field to trigger and to control
electron self-injection in laser- and particle-beam driven wakefield
accelerators is examined analytically and through full-scale particle-in-cell
simulations. A magnetic field can relax the injection threshold and can be used
to control main output beam features such as charge, energy, and transverse
dynamics in the ion channel associated with the plasma blowout. It is shown
that this mechanism could be studied using state-of-the-art magnetic fields in
next generation plasma accelerator experiments.Comment: 10 pages, 3 figure
Contribuição da Microscopia Confocal In Vivo para o Diagnóstico e Follow-Up de Neoplasias Conjuntivais Intraepiteliais
Objectivo: Analisar o contributo da microscopia confocal in vivo para o diagnóstico efollow-up de neoplasias conjuntivais intraepiteliais.
Métodos: Avaliámos 5 doentes com neoplasia conjuntival intraepitelial unilateral com o Heidelberg Retina Tomograph II, Rostock Cornea Module. Três doentes foram submetidos a excisão com crioterapia adjuvante, um doente a excisão com crioterapia adjuvante e ciclos de IFN-a2b e um doente a excisão simples e ciclos de IFN-a2b. As imagens de microscopia confocal foram comparadas com a histologia das mesmas lesões. 0 follow-up clínico, através de fotografias do segmento anterior, foi comparado com os achados da microscopia confocal.
Resultados: Três dos doentes foram identificados histologicamente como neoplasia intraepitelial de alto grau e dois como carcinoma in situ. As características histológicas descritas correlacionam-
se bem com as visíveis à microscopia confocal: alteração da estrutura do epitélio com acantose, disqueratose, pleomorfismo celular, aumento da refletibilidade celular e nuclear, com relação núcleo/citoplasma aumentada e por vezes binucleação. A lesão é bem delimitada e os plexos nervosos sob a lesão não são visíveis. A microscopia confocal identificou uma recidiva e
demonstrou-se útil na monitorização da resposta ao tratamento.
Conclusão: A microscopia confocal ill vivo pode ter um papel importante não só no diagnóstico
inicial como também na deteção de recidivas e na avaliação da resposta ao tratamento, de uma forma minimamente invasiva
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