Self-Similarity of Friction Laws

The change of the friction law from a mesoscopic level to a macroscopic level is studied in the spring-block models introduced by Burridge-Knopoff. We find that the Coulomb law is always scale invariant. Other proposed scaling laws are only invariant under certain conditions.}Comment: Plain TEX. Figures not include

Improving the quality of Portuguese SMEs through competence evaluation

UIDB/04647/2020 UIDP/04647/2020Problem and goal. Since we are going through a key moment in terms of technological advances and their effect on the labour field, the investigation of the on-the-job training processes gains a predominant role. Moreover, the need to research an approach that promotes a balance between the four spheres of development of learning – economic, sustain-able, community and personal – is emerging. This study was conceived as a result of this ur-gency, aiming to respond to the following problem: to what extent does a training model, based on the VPL (Validation of Prior Learning) approach and supported by principles of the educational sciences, can contribute to individual empowerment and, consequently, to an improvement in the organizational quality of Portuguese SMEs (Small and Medium-sized Enterprises)? Methodology. The division of the research into two parts – Study 1 and Study 2 – al-lowed the collection and analysis of structural data (Study 1) that served as a basis for the defi- nition of a dynamic strategy (Study 2). Although undertaken at different times, they have thus proved to be complementary. In fact, the design of the training model was based, firstly, on the results obtained through exploratory interviews with key informants and, secondly, on the data obtained throughout the training process that involved ninety-two employees from ten Portuguese SMEs from diverse categories and sectors. Results. The training model, which emerged from the interaction between the theoreti-cal reflection and the practical context, comprises five components: distance learning, recog-nition of skills, language skills, intercultural skills and an individual action plan. Conclusion. This study, being an important contribution to the topic of on-the-job training in Portuguese SMEs, at the same time opens the way for the continuation of the research.publishersversionpublishe

Physiological response of Cistus salviifolius L. to high arsenic concentrations

Arsenic is a trace element found in the environment which can be particularly toxic to living organisms. However, some plant species such as those of the genus Cistus are able to grow in soils with high As concentrations and could be used in the sustainable rehabilitation of mining areas 19 through phytostabilization. In this work, the growth and the physiological response of Cistus salviifolius L. to As induced oxidative stress at several concentrations (reaching 30 mg L-1) in an hydroponic system were evaluated for 30 days. Several growth parameters, chlorophyll content, chemical composition, one indicator of oxidative stress (H2O2) and two of the major anti-oxidative metabolites (ascorbate and glutathione) were analyzed. The toxic effect of As was better perceived in the plants submitted to treatments with concentrations of 20 and 30 mg As L-1. Plants subjected to these treatments had higher concentration of As in roots and shoots. The concentrations of Ca, Mg, K and Fe in the plants, as well as a large part of the evaluated growth parameters were also affected. Arsenic did not interfere with the ability of the plant to perform photosynthesis, as there were no significant differences in the contents of chlorophyll a, b and total between the different treatments. Plants from all treatments accumulated higher amount of As in roots than in shoots, and it was also in the roots that the concentrations of H2O2, AsA and GSH were higher. Cistus salviifolius showed high tolerance to As up to the concentration of 5 mg L-1, which makes it a species with high potential to be used in the phytostabilization of soils contaminated with As and presenting high concentrations of the element in the soil solution.info:eu-repo/semantics/acceptedVersio

Control of flow-generated biofilms with surfactants : evidence of resistance and recovery

The action of cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulphate (SDS), a cationic and an anionic surfactant respectively, were investigated for their ability to control turbulent and laminar flow-generated biofilms formed by P. fluorescens. The disinfectant action of CTAB and SDS on biofilms was assessed by respiratory activity, variation of mass and structure, immediately, 3, 7 and 12 h after the application of the surfactants. Laminar flow-generated biofilms were more susceptible to the action of CTAB than those formed under turbulent flow. Total inactivation of the cells within the biofilms was not achieved for either type of flow- enerated biofilms. For SDS, higher concentrations promoted significant biofilm inactivation, for both turbulent and laminar flow-generated biofilms. CTAB and SDS application did not promote the detachment of biofilms from the surfaces. Post-surfactant treatment, biofilms recovered respiratory activity, in some cases, reaching values higher than those found without chemical treatment. After CTAB treatment, the recovery of respiratory activity was not affected by the hydrodynamic conditions. Conversely, turbulent flow-generated biofilms showed a higher potential to recover their metabolic activity than laminar flow-generated biofilms, when previously challenged with SDS. Concerning biofilm mass, no significant variation (increase or decrease) was detected after 12 h of surfactant treatment. This study shows that care is needed when selecting the correct procedure and agent for biofilm control and demonstrates the influence of hydrodynamic conditions on the persistent and recalcitrant properties of P. fluorescens biofilms.Fundação para a Ciência e a Tecnologia (FCT

Diagnosis of Human Leptospirosis in a Clinical Setting: Real-Time PCR High Resolution Melting Analysis for Detection of Leptospira at the Onset of Disease:

Currently, direct detection of Leptospira can be done in clinical laboratories by conventional and by real-time PCR (qRT-PCR). We tested a biobank of paired samples of serum and urine from the same patient (202 patients) presenting at the hospital in an area endemic for leptospirosis using qRT-PCR followed by high resolution melting (HRM) analysis. The results were compared with those obtained by conventional nested PCR and with the serologic gold standard microscopic agglutination test (MAT). Differences were resolved by sequencing. qRT-PCR-HRM was positive for 46 of the 202 patients (22.7%, accuracy 100%) which is consistent with known prevalence of leptospirosis in the Azores. MAT results were positive for 3 of the 46 patients (6.5%). Analysis of paired samples allowed us to identify the illness point at which patients presented at the hospital: onset, dissemination or excretion. The melting curve analysis of Leptospira species revealed that 60.9% (28/46) of patients were infected with L. interrogans and 39.1% (18/46) were infected with L. borgpetersenii, both endemic to the Azores. We validated the use of qRT-PCR-HRM for diagnosis of leptospirosis and for identification of the Leptospira species at the earliest onset of infection in a clinical setting, in less than 2 hours.publishersversionpublishe

Analysis of biocide and surfactant influencing detachment of bacterial cells

Adhesion and chemical induced detachment kinetics of Pseudomonas fluorescens ATCC 13525T to glass surface were conducted in situ under flow conditions in a well-controlled parallel plate flow chamber (PPFC). Ortho-phthalaldehyde (OPA) and cetyltrimethyl ammonium bromide (CTAB), respectively, an aldehyde-based biocide and a cationic surfactant were applied at several concentrations to the glass attached bacteria. At the end of the chemical treatment the remaining adhered bacteria were characterized in terms of viability and cellular size. Simultaneously, planktonic cell surface characterization was conducted in order to correlate PPFC results with thermodynamic approaches for adhesion prevision and to evaluate the surface free energy of chemically treated cells and its relevance for adhesion strength. It was observed that about 2.8×106 cells/cm2 adhered to the glass surface after 30 min of bacterial flow through the PPFC, besides thermodynamic analyses demonstrate unfavourable adhesion of P. fluorescens to glass (ΔGadhesion = 30 mJ/m2). The application of OPA and CTAB promoted bacterial detachment in a small extent ( 0.1). For CTAB, apolar characteristics increased with concentration (P < 0.05), switching from hydrophilic to hydrophobic for concentrations near the critical micellar concentration. The overall results emphasize the role of the adhesion process and the chemical stress on cellular physiological induced response. OPA and CTAB were markedly inefficient in the removal of glass attached P. fluorescens, demonstrating that bacteria can be non-viable but remain attached to the adhesion surface

Determination of rutin and narcissin in marigold extract and topical formulations by liquid chromatography: applicability in skin penetration studies

A chromatographic technique for determination of rutin and narcissin in marigold extract and topical formulations was developed and validated. The method shows linearity over the concentration range of 0.2 - 6.0 &#956;g/mL of rutin (r = 0.9986) and 0.8 - 12.0 &#956;g/mL of narcissin (r = 0.9951). The values obtained for precision and accuracy are in agreement with ICH guidelines. Both the formulation excipients and the porcine ear skin samples did not interfere with the flavonoids determination. The recovery of rutin and narcissin in skin samples added with marigold extract was 81.41% and 83.35%, respectively, which demonstrate the applicability of this method to perform skin penetration studies.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Dilemmas of girls and women in engineering: a study in Portugal

The reason that girls and women withdraw from science and technology education and careers has been a universal concern in the social sciences. This study investigated how gendered constructions of identity are translated into the barriers and fears that female students and professional women experience in decision-making about their careers. We conducted interviews with 63 girls and 39 women in academic and professional engineering careers, focusing on their interpersonal relationships with boys and men in their school and occupational engineering settings, respectively. Participant discourse highlighted the difficulties women face when managing the antagonistic discourses of femininity and masculinity in a social environment in which they are frequently forced to submit to hegemonic masculinity. The consequences of women’s differing discourses about the “masculine world” and the “feminine world” are discussed, and some strategies for creating more equalitarian relational environments in school and work settings are discussed.Fundação para a Ciência e a Tecnologia (FCT

Antagonism between bacillus cereus and pseudomonas fluorescens in planktonic systems and in biofilms

In the environment, many microorganisms coexist in communities competing for resources, and they are often associated as biofilms. The investigation of bacterial ecology and interactions may help to improve understanding of the ability of biofilms to persist. In this study, the behaviour of Bacillus cereus and Pseudomonas fluorescens in the planktonic and sessile states was compared. Planktonic tests were performed with single and dual species cultures in growth medium with and without supplemental FeCl3. B. cereus and P. fluorescens single cultures had equivalent growth behaviours. Also, when in co-culture under Fe-supplemented conditions, the bacteria coexisted and showed similar growth profiles. Under Fe limitation, 8 h after co-culture and over time, the number of viable B. cereus cells decreased compared with P. fluorescens. Spores were detected during the course of the experiment, but were not correlated with the decrease in the number of viable cells. This growth inhibitory effect was correlated with the release of metabolite molecules by P. fluorescens through Fe-dependent mechanisms. Biofilm studies were carried out with single and dual species using a continuous flow bioreactor rotating system with stainless steel (SS) substrata. Steadystate biofilms were exposed to a series of increasing shear stress forces. Analysis of the removal of dual species biofilms revealed that the outer layer was colonised mainly by B. cereus. This bacterium was able to grow in the outermost layers of the biofilm due to the inhibitory effect of P. fluorescens being decreased by the exposure of the cells to fresh culture medium. B. cereus also constituted the surface primary coloniser due to its favourable adhesion to SS. P. fluorescens was the main coloniser of the middle layers of the biofilm. Single and dual species biofilm removal data also revealed that B. cereus biofilms had the highest physical stability, followed by P. fluorescens biofilms. This study highlights the inadequacy of planktonic systems to mimic the behaviour of bacteria in biofilms and shows how the culturing system affects the action of antagonist metabolite molecules because dilution and consequent loss of activity occurred in continuously operating systems. Furthermore, the data demonstrate the biocontrol potential of P. fluorescens on the planktonic growth of B. cereus and the ability of the two species to coexist in a stratified biofilm structure.Fundação para a Ciência e a Tecnologia (FCT