Wetting of cholesteric liquid crystals

We investigate theoretically the wetting properties of cholesteric liquid crystals at a planar substrate. If the properties of substrate and of the interface are such that the cholesteric layers are not distorted the wetting properties are similar to those of a nematic liquid crystal. If, on the other hand, the anchoring conditions force the distortion of the liquid crystal layers the wetting properties are altered, the free cholesteric-isotropic interface is non-planar and there is a layer of topological defects close to the substrate. These deformations can either promote or hinder the wetting of the substrate by a cholesteric, depending on the properties of the cholesteric liquid crystal

Control of biofilms using surfactants: persistence and regrowth

The action of the cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), respectively, a cationic and an anionic surfactant were investigated to control mature biofilms formed under turbulent and laminar flow, by P.fluorescens. The sanitizer action of the surfactants on biofilms was assessed by means of respiratory activity and variation of biofilm mass, immediately, 3, 7 and 12 h after the treatment of the chemicals. The latter experimental times were tested in order to assess the biofilm regrowth. The structure of the biofilms was assessed before and after surfactant treatment by SEM. The results showed that, laminar biofilms were more susceptible to the action of CTAB than those formed under turbulent flow. Concerning SDS, both biofilms showed analogous susceptibility to the surfactants. However, total inactivation of the cells within the biofilms was not achieved for both types of biofilms. CTAB application by itself did not promoted the detachment of biofilms from the surface. Regarding SDS, higher concentrations applied promoted significant biofilm inactivation. Turbulent and laminar flow had analogous susceptibility to SDS application. However, SDS did not promoted the detachment of biofilms from the metal surfaces. The structure of the biofilms was changed after the application of both surfactants. It was found that after CTAB and SDS application, the biofilms recovered its respiratory activity, reaching, in same situations, higher values than the ones found before chemical treatment. The CTAB application promoted similar recovery in the respiratory activity for both biofilms. Concerning biofilm behaviour after SDS treatment, turbulent biofilms showed a higher potential to recover their metabolic activity than laminar biofilms. Biofilm mass did not experienced any significant variation after the treatment, for both surfactants tested. This study highlights the need of care in choosing the correct procedure for biofilm control and the recalcitrant properties of biofilms.Fundação para a Ciência e a Tecnologia (FCT

Effects of the interactions between glutaraldehyde and the polymeric matrix on the efficacy of the biocide against pseudomonas fluorescens biofilms

Glutaraldehyde (GTA) is a widely used biocide due to its high effectiveness. The experimental work reported here was carried out to assess the effectiveness of GTA in controlling biofilms formed by Pseudomonas fluorescens on stainless steel slides, and to compare efficacy against both planktonic and sessile microrganisms. The tests were performed using two concentrations of GTA (50 and 100mg L-1), biofilms of two ages (7 and 15 d), several pH values (5, 7 and 9) and a range of exposure times (from 0 (control) to 1, 3, 7 and 24 h). The action of GTA on biofilm and planktonic populations was assessed by means of activity tests, zeta potential, and the wet weight of the biofilms. Biofilms were not completely removed after treatment with GTA in any of the conditions studied. The higher GTA concentration was more effective in reducing the bacterial activity of the biofilm. The biocide proved to be more effective for longer exposure times. GTA showed good antimicrobial activity against P. fluorescens in suspension, with higher activity at pH 9. The findings of this study suggest that when GTA is used to control biofilms, it reacts with one of the components of the matrix, the proteins, thereby reducing its antimicrobial action.Instituto de Biotecnologia e Química Fina (IBQF)

Role of the polymeric matrix constituents on the performance of a biocide against pseudomonas fluorescens biofilms

The effectiveness of glutaraldehyde – a very common biocide – to control biofilms formed by Pseudomonas fluorescens on stainless steel slides, was investigated. The tests were performed using two concentrations of the biocide (50 and 100 mg Lˉ¹), biofilms of two ages (7 and 15 days), several pH values (5, 7 and 9) and a range of exposure times (from 0 to 1, 3, 7 and 24 hours). The GTA action on biofilm and planktonic populations was assessed by means of activity tests and wet weight of the biofilms. The results showed that biofilms were not completely removed after the treatment with biocide, in all the situations studied. The higher concentration was more effective in reducing the bacterial activity of the biofilm. The biocide proved to be more effective for longer exposure times. GTA showed good antimicrobial activity against P. fluorescens in suspension, with higher activity for pH 9. The findings of this study suggest that when GTA is used to control biofilms, it reacts with one of the components of the matrix – the proteins – thereby reducing its antimicrobial action.Instituto de Biotecnologia e Química Fina (IBQF)

Family variables and drug addiction

Este trabalho teve como objectivo avaliar o impacto das variáveis familiares: coesão, adaptabilidade, recursos familiares, satisfação familiar e exaustão familiar no toxicodependente e família, no sentido de contribuir para a elaboração de futuros programas de intervenção na área da educação para a saúde. Para o efeito foi utilizada uma amostra constituída por 208 indivíduos: 113 toxicodependentes e 95 familiares, divididos em 3 grupos: primeira vez em tratamento, recaídas e reabilitados. Os dados foram recolhidos no Projecto Homem em Braga. Os instrumentos utilizados foram: “Escala da Adaptabilidade e Coesão Familiar” (Faces II) de Olson, Portner & Bell (1982); “Questionário Satisfação Familiar” (FSS) de Olson & Wilson (1982) e “Questionário Recursos Familiares” de Olson, Larsen & McCubbin (1982). Verificamos maior nível de coesão, adaptabilidade, satisfação familiar e mais recursos familiares nos toxicodependentes reabilitados. Os familiares dos toxicodependentes reabilitados percebem a família como mais adaptável quando comparados com os outros dois grupos. Por sua vez, os toxicodependentes percepcionam menos satisfação familiar, coesão e recursos do que o seu familiar. As implicações dos resultados são abordadas.The current project assesses the impact of family variables: cohesion, adaptability, family strengths, family satisfaction, burden assessment in drug users and families with the intent of contributing to elaborate future intervention programs in the field of health education. The sample of our study is composed of 208 subjects: 113 drug users and 95 family members, divided into 3 groups: drug users who were in treatment for the first time, relapsed drug users and rehabilitated drug users. The data was gathered at “Projecto Homem” in Braga. The following instruments were used: “Family Cohesion and Adaptability Scales” (Faces II) by Olson, Portner & Bell; “Family Satisfaction Scale” (FSS) by Olson & Wilson (1982) and “Family Strengths” by Olson, Larsen & McCubbin (1982). Results showed greater level of cohesion, adaptability, family satisfaction and more family resources in the rehabilitated drug users. Family members of rehabilitated drug users perceive more adaptability in the family than family members from the other two groups. Drug users perceive less family satisfaction, cohesion and resources than their family member. Implications of results are addressed

Comparison of upper body strength gains between men and women after 10 weeks of resistance training

Resistance training (RT) offers benefits to both men and women. However, the studies about the differences between men and women in response to an RT program are not conclusive and few data are available about upper body strength response. The aim of this study was to compare elbow flexor strength gains in men and women after 10 weeks of RT. Forty-four college-aged men (22.63 +/- 2.34 years) and forty-seven college-aged women (21.62 +/- 2.96 years) participated in the study. The RT program was performed two days a week for 10 weeks. Before and after the training period, peak torque (PT) of the elbow flexors was measured with an isokinetic dynamometer. PT values were higher in men in comparison to women in pre-and post-tests (p 0.05). Effect sizes were 0.57 and 0.56 for men and women, respectively. In conclusion, the present study suggests that men and women have a similar upper body strength response to RT

Action of a cationic surfactant on the activity and removal of bacterial biofilms formed under different flow regimes

The action of the cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated to control biofilms (aged 7 d) formed by Pseudomonas fluorescens on stainless-steel slides, using flow cells reactors, under turbulent and laminar flow. The effect of CTAB was also investigated using planktonic cells in the presence and absence of BSA, by measuring the cellular respiratory activity and the ATP released. The action of CTAB on biofilms was assessed by means of cellular respiratory activity and variation of biofilm mass, immediately and 3, 7 and 12 h after the application of CTAB. The physical stability of the biofilm was also assessed using a rotating device, where the effect of the surfactant on the biofilm stability was evaluated through the variation of the mass remaining on the surface. CTAB significantly reduced the activity of the planktonic cells probably due to the rupture of the cells. This effect was significantly reduced in the presence of BSA. Planktonic cells were more easily inactivated than bacteria in biofilms. Biofilms formed under laminar flow were more susceptible than those formed under turbulent flow, but in both cases total inactivation was not achieved. Biofilm recovery was observed, in terms of respiratory activity, in almost all the cases studied. CTAB application by itself did not promote the detachment of biofilms. The physical stability tests showed that the synergistic action of the surfactant and the application of high shear stress to the biofilm increase its detachment.Fundação para a Ciência e Tecnologia (FCT

Validation of respirometry as a short-term method to assess the efficacy of biocides

This study shows that a short-term respirometric measurement based on the rate of oxygen uptake needed to oxidize glucose is a reliable and fast method to assess biocide efficacy against P. fluorescens cells. Respiratory activity using oxygen consumption rate, the determination of viable and nonviable cells using Live/Dead® BacLightTM kit and colony formation units (CFU), were compared as indicators of the biocidal efficacy of ortho-phthalaldehyde (OPA). The results showed tha determining the effect of OPA against P. fluorescens using the different methods leads to different conclusions. The minimum bactericidal concentration (MBC) was 80 mg l-¹, 100 mg l-¹ and 65 mg l-¹ respectively, using respiratory activity, viability using BacLight counts and culturability. The plate count method was shown to underestimate the biocidal action of OPA, whilst data from respirometry and viability using Live/Dead BacLight kit correlated strongly and were not statistically different when yellow cells were considered nonviable. Respirometry therefore represents an expeditious, non-destructive and accurate method to determine the antimicrobial action of biocides against aerobic heterotrophic bacteria.Fundação para a Ciência e a Tecnologia (FCT