Pseudo Phase Plane and Fractional Calculus Modelling of Western Global Economic Downturn

This paper applies Pseudo Phase Plane (PPP) and Fractional Calculus (FC) mathematical tools for modeling world economies. A challenging global rivalry among the largest international economies began in the early 1970s, when the post-war prosperity declined. It went on, up to now. If some worrying threatens may exist actually in terms of possible ambitious military aggression, invasion, or hegemony, countries’ PPP relative positions can tell something on the current global peaceful equilibrium. A global political downturn of the USA on global hegemony in favor of Asian partners is possible, but can still be not accomplished in the next decades. If the 1973 oil chock has represented the beginning of a long-run recession, the PPP analysis of the last four decades (1972–2012) does not conclude for other partners’ global dominance (Russian, Brazil, Japan, and Germany) in reaching high degrees of similarity with the most developed world countries. The synergies of the proposed mathematical tools lead to a better understanding of the dynamics underlying world economies and point towards the estimation of future states based on the memory of each time series

Multidimensional scaling analysis of the dynamics of a country economy

WOS:000326976400001This paper analyzes the Portuguese short-run business cycles over the last 150 years and presents the multidimensional scaling (MDS) for visualizing the results. The analytical and numerical assessment of this long-run perspective reveals periods with close connections between the macroeconomic variables related to government accounts equilibrium, balance of payments equilibrium, and economic growth. The MDS method is adopted for a quantitative statistical analysis. In this way, similarity clusters of several historical periods emerge in the MDS maps, namely, in identifying similarities and dissimilarities that identify periods of prosperity and crises, growth, and stagnation. Such features are major aspects of collective national achievement, to which can be associated the impact of international problems such as the World Wars, the Great Depression, or the current global financial crisis, as well as national events in the context of broad political blueprints for the Portuguese society in the rising globalization process.publishersversionpublishe

Effect of benzalkonium chloride residues on the initial adhesion of adapted P. aeruginosa

Bacteria have developed different strategies to sense, respond and adapt to chemical antimicrobial compounds. One of them involves bacterial adhesion to solid surfaces and subsequent biofilm formation. The biofilm lifestyle, that is usually resistant to antimicrobial treatment, is a phenomenon well noticed in almost all industrial and medical arenas. In the latter, the existence of pathogenic bacteria, that easily adhere to a surface and form biofilms, can give rise to equipment contamination and persistent infections. For instance, Pseudomonas aeruginosa has become increasingly recognized as an emerging opportunistic pathogen of clinical relevance. This bacterium, often found in a biofilm, attached to some surface, can frequently cause life-threatening infections under conditions where the host is injured and/or has the immune system compromised. Benzalkonium chloride (BZK) is a quaternary ammonium compound (QAC) used as a general clinical disinfectant and antiseptic in health care facilities and domestic households. QACs are bacteriostatic at low concentrations and bactericidal at high concentrations, thus their indiscriminate and improper use may favor the development of adaptive resistance. Therefore, they have been pointed out as the possible cause for the selection and persistence of bacterial strains with antibiotic and biocidal resistance. With this study it was aimed to characterize the adhesion ability and biofilm formation of P. aeruginosa non-adapted and adapted to BZK on polyethylene (PET) surfaces non-conditioned and pre-conditioned with BZK solution. For that purpose, bacterial hydrophobicity and changes in surface properties after conditioning were evaluated by means of contact angles determination. The initial bacterial adhesion was followed up along time (2, 4 and 6 h) by the quantification of the adhered biomass, through crystal violet (CV) and respiratory activity, using XTT. The adaptation of P. aeruginosa to BZK was attained after 6 cycles of re-inoculation every 48 h selected in TSA also supplemented with increasing doses of BZK. The free energy of adhesion of the bacteria with the PET surfaces, calculated trough the hydrophobicity components, revealed that the precontioning of the substrata increases the potential initial adhesion of P.aeruginosa, being this more significant for the adapted bacteria. Thus, it can be stated that, in the thermodynamic point of view, the initial adhesion of the P. aeruginosa adapted and non-adapted to the PET is favoured by surface preconditioning. Moreover, BZK preconditioning did not prevent or impair P.aeruginosa adhesion. In fact, the initial adhesion data showed that the accumulation of biomass increased with time, being the non-adapted bacterial cells more able to attach and establish a biofilm. The presence of BZK residues in the adhesion surfaces (preconditioning) promotes the attachment of the bacterial cells, since more biomass was determined. Concerning the activity of the adhered cells, preconditioning seem not cause any disturbance of cells, since equal or higher cellular activity was determined. The overall results suggest that preconditioning of PET surfaces with BZK promotes the attachment and activity of the bacterial cells, especially of the adapted bacteria. These evidences suggest that when the bacteria were previously exposed to a sub-lethal concentration of a chemical antimicrobial compound, they acquired some insusceptibility to that compound allowing their growth when facing adverse conditions. This study allowed gaining insights about the impact of unsuitable disinfection and rinsing procedures that might instigate the residues deposition, leading to bacteria adaptation, bacterial adhesion and biofilm development

Influence of material type and surface benzalkonium chloride preconditioning on biofilm formation and activity

This study investigates the potential of benzalkonium chloride (BC), a cationic surfactant, on the prevention of biofilm formation on stainless steel ASI 316 and silicone rubber, two distinct surfaces currently used on food processing facilities. The surfaces were preconditioned with several concentration of BC for 30 min. Treated surfaces were characterized by the sessile drop method, demonstrating that surfactant pre-treatment increased the hydrophobicity of the surfaces, this increase being a function of BC concentration increase applied for preconditioning. In order to ascertain the preventive effect in biofilm formation, the treated surfaces where inserted in a chemostat continuously inoculated with P. fluorescens in the exponential phase of growth, being the biofilm allowed to grow for 6 days. The results showed that BC preconditioning did not prevent or impair biofilm formation. In fact, biofilms developed on the treated surfaces presented higher biomass and respiratory activity than the ones formed on the untreated surfaces, this phenomenon being more evident for silicone than for stainless steel and for surfaces treated with higher BC concentrations. Scanning electron microscopy and biochemical analysis reveal that the difference of surface type and surface preconditioning, by itself, gave rise to the formation of structural and biochemical distinct biofilms. The overall results suggest that preconditioning of stainless steel and silicone rubber surfaces with BC allowed the formation of biofilms with more recalcitrant properties than the ones found on untreated surfaces

Role of benzalkonium chloride surface preconditioning in the increased resistance of biofilms to removal and disinfection

The main goals of the present study was to ascertain the role of surface preconditioning in the biofilm sanitation (removal and disinfection) ability of the cationic surfactant benzalkonium chloride (BC) and to investigated whether BC preconditioning can be a factor of the increased resistance of the Pseudomonas fluorescens biofilms to the surfactant. Prior to biofilm formation, coupons of two distinct materials (stainless steel and silicone rubber) currently used on medical and industrial processing facilities were exposed to several sub-effective concentrations of BC for 30 min. Afterwards, these conditioned coupons were used as the surfaces to form biofilms in a chemostat for 6 days. The antimicrobial action of BC on the biofilms was assessed by means of respiratory activity, due to oxygen consumption, and biofilm mass. The results showed that BC preconditioning, by itself, did not prevent or impair biofilm formation. In general, the mass and respiratory activity of the biofilms developed on the conditioned coupons increased with the increase of the BC concentration used in the preconditioning. The data related with BC application to the bacterial biofilms formed on the conditioned metal and rubber coupons showed that biofilms became more difficult to inactivate, especially those that have been developed in the coupons preconditioned with the higher BC concentrations. Thus, it can be concluded that the antimicrobial ability of BC was considerably disturbed when the surfaces are preconditioned with the surfactant. Based merely on this data, it can be speculated that, in the initial adhesion stage, the contact of the P. fluorescens with the BC residues adsorbed on the coupons surface, due to preconditioning, induces bacteria resistance when they are entrapped in a developed biofilm and submitted to BC aggression.IBQF, and the Portuguese Foundation for Science and Technology (FCT

Application of Fractional Calculus in the Dynamical Analysis and Control of Mechanical Manipulators

Mathematics Subject Classification: 26A33, 93C83, 93C85, 68T40Fractional Calculus (FC) goes back to the beginning of the theory of differential calculus. Nevertheless, the application of FC just emerged in the last two decades. In the field of dynamical systems theory some work has been carried out but the proposed models and algorithms are still in a preliminary stage of establishment. This article illustrates several applications of fractional calculus in robot manipulator path planning and control

The role of antimicrobial stress on Pseudomonas aeruginosa colony morphology diversity, tolerance and virulence

In natural environments, as well as in infections, bacteria faced several stresses like starvation, heat exposure, antimicrobials and host defense after entry in human body. The ability to quickly adapt to a new environment is critical to bacteria and the underlying mechanisms are not fully understood. One of the strategies adopted by bacteria is a high frequency of phenotype switching by a mechanism called phase variation. A sign of these bacterial changes is the altered colony morphology on solid media. Several colony morphologies have been isolated from clinical strains, being the best-studied the small colony variants, the rugose small colony variants and the mucoid phenotype. It was aimed to study the prevalence and diversity of colony morphologies from planktonic and sessile P. aeruginosa (Pa) ATCC, chemically stressed, and to compare with the ones developed by a P. aeruginosa isolated from a medical device (Pa I). Pa is one of the most important opportunistic pathogen commonly found in clinical arena being often responsible for acute and chronic infections. Planktonic and sessile Pa and Pa I were in vitro stressed by continuous exposure to benzalkonium chloride (BZK) and peroxide hydrogen and by attack with the same products. The stressed bacteria were collected, serial diluted and plated onto TSA to inspect colony morphology variants. Each predominant bacterial morphology was harvested and reserved for further phenotypic and motility characterization. The results demonstrated that cells coming from biofilm and planktonic growth of Pa, regardless they were stressed or not or the type of stress implemented, develop colonies mostly with the same morphotype, type II, characterized by big and regular colony circumference, with small and dark center and wrinkled surface. This colony type showed to have a good ability to form biofilms, although the colonies from the stressed cultures developed biofilms with higher biomass accumulated. The Pa I gave rise to high diversity of colony morphotypes, being 3 of them more prevalent and cataloged as type XVII, XXIII, XXVIII. The types XVII and XXVIII are characterized by regular colony circumferences with craters in the center. However their superficial area presented different colors. Type XXIII has irregular colony shape with craters in the center. These 3 morphotypes showed similar biofilm formation ability between them but lower than type II. Nonetheless the phenotypic differences found between the several morphotypes, all of them generated biofilms with identical tolerance to antimicrobials (BZK and the fluoroquinolone antibiotic ciprofloxacin-CIP). However, the cells resulting from the planktonic growth of Pa I morphotypes demonstrated two-fold tolerance to BZK and CIP than their Pa counterparts. Regarding bacteria motility, results highlighted that all Pa I morphotypes had impaired swimming motilities compared to type II. This result seems to indicate that the capacity of adhesion or invasion of Pa I morphotypes to, respectively, surfaces or tissues was compromised, which may interfere with their virulence. Although, the latter is not sustained by the susceptibility patterns, emphasizing the ambiguous relationship between virulence and antimicrobial resistance. The morphologies described are not similar with previous reports and the colony morphologies more prevalent seemed to be less virulent than typical ones. Among the various colony morphologies detected, no Pa I morphotype match with Pa type. So, it can be concluded that phase variation is an adaptive strategy of bacteria to respond to fluctuating environment leading to mixed populations where the chances for survival is higher. The generation of varied bacterial phenotypes may be the sum of previous and successive adaptations suffer by Pa I as an attempt to adjust to adverse habitats.IBB-CEB and FCT, for the financial support (Project PTDC/SAUESA/64609/2006; PhD Grant SFRH/BD/31065/2006

In vitro adaptation of P. aeruginosa: colony morphology variants selection and virulence characterization

One of the bacterial strategies to respond to environmental pressures is the switch of their phenotypic traits by a mechanism called phase variation. This reversible process provides the generation of varied bacterial phenotypes, leading to a mixed population and colony diversity. In this work it was aimed to isolate and characterize the virulence of colony morphology variants selected by environmental pressures from planktonic and sessile P.aeruginosa, in order to understand the biological significance of phase variation in virulent-bacteria selection. Bacteria were in vitro stressed by continuous exposure to increased concentrations of benzalkonium chloride (BZK) and by heat and peroxide hydrogen shock. The stressed bacteria were suspended, serial diluted and plated onto TSA to inspect and collect colony morphology variants. It was observed, for planktonic and biofilm states, that adaptation and heat and chemical shocks selected different colony morphologies. These differences were in colony circumference and outer edge (smooth or irregular), surface texture and surface shape (craters). All the colony morphotypes were collected and used to evaluate their biofilm formation ability and its susceptibility to some antimicrobials. Data revealed that some morphotypes shown less ability to form biofilms but were more tolerant to BZK. Other morphotypes, with more ability to form biofilms, were resistant to Ciprofloxacin, and others were susceptible to Ciprofloxacin but resistant to Erytromicine. It can be concluded that P.aeruginosa is capable to undertake phenotypic changes when facing stress pressure. These different morphology variants may play a significant role in P.aeruginosa antimicrobial resistance, contributing its increased pathogenicity

Application of lean approaches and techniques in an automotive company

In this paper are applied lean approaches and techniques in an industrial environment at Preh Portugal, Lda., a Company involved in the automotive sector located in Trofa, Portugal. This work makes use of the action-research methodology, aiming to diagnose the production system and to implement lean production procedures in order to optimize the Mizusumashi that supplies several production sections, about plastic Injection, cutting and painting. The results obtained enabled to obtain significant improvements on this Company at several factory management and operational levels.This work was supported by FCT “Fundação para a Ciência e a Tecnologia” under the program: PEst20152020.info:eu-repo/semantics/publishedVersio