Development of the drag coefficient of a sphere translating through a viscoelastic fluid

Presentation at 15th OpenFOAM Workshop, June 22-25, 2020, Arlington, VA, USA

Effect of peak power on microstructure, mechanical and tribological properties of W-Ti-C-N(O) ceramic films produced by hybrid sputtering

This research investigates the impact of peak power (from 44 to 105 kW) on the structural and tribological properties of W-Ti-C-N(O) films. Chemical analysis of the coatings, using energy-dispersive spectroscopy and Raman spectroscopy, indicates that increasing target power results in a rise in the oxygen (from 2.6 to 12.0 at%), carbon (from 19.7 to 32.4 at%), and sp3 (from 9.8% to 24.3%) content. Morphological and topographical analysis reveal that an increase in target power causes a transition from a columnar structure (with nodular grains) to a dense structure (with textured grains). The indentation and dry sliding tests demonstrate that the maximum level of H/E2 (0.00047 GPa-1) is achieved, along with a low wear rate of 8.1 × 10-7 mm3/N.m.info:eu-repo/semantics/publishedVersio

Advanced polymer simulation and processing

[Excerpt] Polymer processing techniques are of paramount importance in the manufacture of polymer parts. The key focus is on producing parts with the desired quality, which usually refers to mechanical performance, dimensional conformity, and appearance. To maximize the overall efficiency of polymer processing techniques, advanced modeling codes are needed along with experimental setups to simulate and optimize the processes. [...]This research was funded by FEDER through the COMPETE 2020 Programme and National Funds through FCT-Portuguese Foundation for Science and Technology under the projects UIDB/05256/2020 and UIDP/05256/2020. It was also funded by FCT through CMAT (Centre of Mathematics of the University of Minho) through projects UIDB/00013/2020 and UIDP/00013/2020

Gene silencing based on RNA-guided catalytically inactive Cas9 (dCas9): a new tool for genetic engineering in Leptospira

International audienceLeptospirosis is a worldwide zoonosis caused by pathogenic bacteria of the genus Leptospira, which also includes free-living saprophyte strains. Many aspects of leptospiral basic biology and virulence mechanisms remain unexplored mainly due to the lack of effective genetic tools available for these bacteria. Recently, the type II CRISPR/Cas system from Streptococcus pyogenes has been widely used as an efficient genome engineering tool in bacteria by inducing double-strand breaks (DSBs) in the desired genomic targets caused by an RNA-guided DNA endonuclease called Cas9, and the DSB repair associated machinery. In the present work, plasmids expressing heterologous S. pyogenes Cas9 in L. biflexa cells were generated, and the enzyme could be expressed with no apparent toxicity to leptospiral cells. However, L. biflexa cells were unable to repair RNA-guided Cas9-induced DSBs. Thus, we used a catalytically dead Cas9 (dCas9) to obtain gene silencing rather than disruption, in a strategy called CRISPR interference (CRISPRi). We demonstrated complete gene silencing in L. biflexa cells when both dCas9 and single-guide RNA (sgRNA) targeting the coding strand of the β-galactosidase gene were expressed simultaneously. Furthermore, when the system was applied for silencing the dnaK gene, no colonies were recovered, indicating that DnaK protein is essential in Leptospira. In addition, flagellar motor switch FliG gene silencing resulted in reduced bacterial motility. To the best of our knowledge, this is the first work applying the CRISPRi system in Leptospira and spirochetes in general, expanding the tools available for understanding leptospiral biology

Effect of storage on quality features of local onion landrace ‘Vatikiotiko’

‘Vatikiotiko’ is a Greek landrace of Allium cepa L. of the Liliaceae family, cultivated only in the region of Vatika, in Lakonia prefecture as a short day onion. The dry bulbs are a quality product highly sought after in Greek market, since this is the earliest onion that comes out during Spring. However, so far the production is limited and the potential of this landrace is not fully developed. In the present study we examined the effect of storage at two temperatures (23±1 and 5±1°C) and 60-70% RH (relative humidity) on marketability and quality features of dry bulbs of ‘Vatikiotiko’ landrace and ‘Sivan F1’ which is also cultivated in the specific region. The experiments were carried out at the University of Thessaly, Greece during the period 2014-2015. The quality features that were recorded during storage included fresh weight loss, bulb firmness, antioxidants and sugar’s composition. The measurements were taken at regular intervals and the storage was completed when either bulbs had not marketable quality or sprouting occurred. So far the results have shown that ‘Vatikiotiko’ onion can be stored for 7 months at both temperatures, whereas at 5±1°C storage could be prolonged for almost 8 months without significant marketability and quality loss. Similarly, ‘Sivan F1’ sprouting occurred after 5 and 6 months at 23±1 and 5±1°C, respectively. Therefore, the fact that ‘Vatikiotiko’ landrace is a storage onion allows for further valorization in order to increase total production and yield, since the stored product could cover the market needs that arise throughout the year, whereas breeding is needed in order to minimize the genetic variability of the landrace and increase uniformity of the final product.info:eu-repo/semantics/publishedVersio

Effect of substrate bias voltage on structural and tribological properties of W-Ti-C-N thin films produced by combinational HiPIMS and DCMS co-sputtering

Protective multi-component thin films at the surface of cutting tools have been significantly developed to reduce wear and friction. The present work investigates the effect of substrate bias voltage on the structural-tribological relations of W-Ti-C-N thin films produced by HiPIMS and DCMS co-sputtering. Chemical analysis of the coatings is obtained and composite phase structure is revealed. Morphology of the coatings illustrates that defectless surfaces may be achieved. Topographical parameters are investigated by employing graphical software. Indentation, scratch and pin-on-disk tests (pin is AISI 52100 steel) are applied to study mechanical behaviors of the films. To produce a wear-resistant film, a median bias voltage ( 60 V) and as a result, optimum content of tungsten concentration (19.2 at. %), grain size (42.8 nm) and average peak interval (188 nm) is required. Finally, a model based on the representative volume element is developed to show crack propagation and delamination.info:eu-repo/semantics/publishedVersio

Food preservation under pressure (hyperbaric storage) as a possible improvement/alternative to refrigeration

Food preservation is highly dependent on refrigeration, which is limited by its high energy costs. Among alternatives being developed, this review focused on hyperbaric storage (food preservation under pressure). This new preservation methodology has as main objective microbial growth inhibition similarly to freezing and refrigeration, showing a great potential to lower energy costs since refrigerated/room temperatures (RT) can be used. This, even at variable (uncontrolled) RT (up to 37 C), has been shown to preserve foods and thus achieving significant energy savings. Covering the earliest up to the more recent studies, this review aimed to gather information about the state of art of hyperbaric storage at refrigerated and RTs, with the primary objective of showing it potential and possible future applications of this new preservation method based on microbial growth inhibition under pressure, using pressure as the main variable to slow down microbial growth

The role of deformation history on stress relaxation and stress memory of filled rubber

Although the magnitudes of inelastic and viscoelastic effects in filled rubbers are small relative to that of the elastic response, these effects are nevertheless critical in applications such as gaskets, seals and dampers. This study investigates the role of deformation history on relaxation of rubber through time-dependent experiments following a range of deformation histories. Two grades of carbon-black filled EPDM were subjected to uniaxial tensile deformation followed by stress-relaxation or stress memory at fixed deformation. Stress relaxation was found to be highly dependent on strain levels following a single loading. When an additional load-unload cycle was added to the history, the rubbers relaxed an approximately constant fraction of stress after a given time, provided that the strain at stress relaxation was smaller than the historical maximum. This fraction was independent of both the applied strain and of the maximum strain, and suggests that the relaxation process is independent of scragging procedures used to control the modulus. Stress memory observed following load-unload cycles was also approximately independent of strain history

Preservation of sliced cooked ham at 25, 30 and 37°C under moderated pressure (hyperbaric storage) and comparison with refrigerated storage

The feasibility of hyperbaric storage (HS) to substitute refrigeration as a lower energetic cost alternative to refrigeration, for sliced cooked ham preservation was assessed by using temperatures and pressures ranging 25–37◦C and 25–150 MPa for 4 and 8 h. At microbiological level, storage at 25 ◦C, 30 ◦C, and 37 ◦C, showed no effect on microbial growth at 25 MPa reaching levels similar to atmospheric pressure storage, around 5 log CFU/g for both total aerobic mesophiles (TAM) and lactic acid bacteria (LAB). Nevertheless, the storage at 50 MPa and 30 ◦C resulted in microbial growth inhibition, resulting in TAM and LAB counts similar to refrigeration, of about 3.8 log CFU/g for both the microorganisms. Additionally, the increase of the storage pressure to 100–150 MPa resulted in microbial inacti-vation, leading to microbial loads of almost 1 log CFU/g lower than refrigeration. In general, hyperbaric stored sliced cooked ham showed physicochemical parameters similar to the refrigerated samples. In conclusion, these results show that HS at uncontrolled (naturally variable room tem-perature conditions at 25–37 ◦C) is a promising alternative to refrigeration for cooked ham preservation. To this new preservation technology, no energetic costs are associated throughout storage, compared to refrigeration, needing only energy to generate the pressure and decompress, since no energy is required to maintain the pressure