Rapid electron transfer reactions associated with oxygen evolution in photosystem II preparations from spinach and Phormidium laminosum

AbstractWe have measured the nanosecond kinetics of Chl-a+II reduction in oxygen-evolving detergent preparations of PS II from the cyanobacterium Phormidium laminosum and from higher plants (spinach) at 824 and 680 nm. Compared to earlier studies at 680 nm with higher plant material, we obtained an improved signal: noise ratio for measurements on a ns to ms time scale. The kinetics of Chl-a+II reduction in the ns range are consistent in the two preparations and are comparable to other studies of higher plant and cyanobacterial material. The ns kinetics are tightly connected to the ability for O2 evolution. Analysis of the μs kinetics indicates three phases: (a) the slow phase (t12 ~ 150 μs in spinach and ~ 500 μs in Phormidium) reflects the back reaction between Chl-a+II and Q−; (b) the phase with t125–10 μs is probably due to a donor which is not connected to an intact water oxidation system; (c) the intermediate μs component (t12 30–40 μs) may be related to water oxidation

Analysis of cybersecurity threats in Industry 4.0: the case of intrusion detection

Nowadays, industrial control systems are experiencing a new revolution with the interconnection of the operational equipment with the Internet, and the introduction of cutting-edge technologies such as Cloud Computing or Big data within the organization. These and other technologies are paving the way to the Industry 4.0. However, the advent of these technologies, and the innovative services that are enabled by them, will also bring novel threats whose impact needs to be understood. As a result, this paper provides an analysis of the evolution of these cyber-security issues and the requirements that must be satis ed by intrusion detection defense mechanisms in this context.Springer ; Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

SPRWeb: preserving subjective responses to website colour schemes through automatic recolouring

Colours are an important part of user experiences on the Web. Colour schemes influence the aesthetics, first impressions and long-term engagement with websites. However, five percent of people perceive a subset of all colours because they have colour vision deficiency (CVD), resulting in an unequal and less-rich user experience on the Web. Traditionally, people with CVD have been supported by recolouring tools that improve colour differentiability, but do not consider the subjective properties of colour schemes while recolouring. To address this, we developed SPRWeb, a tool that recolours websites to preserve subjective responses and improve colour differentiability - thus enabling users with CVD to have similar online experiences. To develop SPRWeb, we extended existing models of non-CVD subjective responses to CVD, then used this extended model to steer the recolouring process. In a lab study, we found that SPRWeb did significantly better than a standard recolouring tool at preserving the temperature and naturalness of websites, while achieving similar weight and differentiability preservation. We also found that recolouring did not preserve activity, and hypothesize that visual complexity influences activity more than colour. SPRWeb is the first tool to automatically preserve the subjective and perceptual properties of website colour schemes thereby equalizing the colour-based web experience for people with CVD.Engineering and Applied Science

Antecedents and consequences of effectuation and causation in the international new venture creation process

The selection of the entry mode in an international market is of key importance for the venture. A process-based perspective on entry mode selection can add to the International Business and International Entrepreneurship literature. Framing the international market entry as an entrepreneurial process, this paper analyzes the antecedents and consequences of causation and effectuation in the entry mode selection. For the analysis, regression-based techniques were used on a sample of 65 gazelles. The results indicate that experienced entrepreneurs tend to apply effectuation rather than causation, while uncertainty does not have a systematic influence. Entrepreneurs using causation-based international new venture creation processes tend to engage in export-type entry modes, while effectuation-based international new venture creation processes do not predetermine the entry mod

Cultura de Inovação: Conceitos e Modelos Teóricos

This study portrays the state of the art in scientific literature on the culture of innovation, with the objective of characterizing its meaning and especially describing different theoretical models that seek to understand how it occurs in an organizational environment. To enrich the analysis, research results show the relationship between organizational culture and innovation. The literature review was carried out in 2011 using the following databases: Coordination for the Improvement of Higher Education Personnel (CAPES), Proquest and Directory of Open Access Journals (DOAJ). The keywords used were the expression culture of innovation and the joint terms culture and innovation, only full articles were included in the research. Culture of innovation articles that were cited in the papers identified in the literature search were also considered. The analysis consisted of 40 articles, based on the predefined criteria, and showed that this is a topic of interest for researchers in different world regions. It is a complex theme determined by factors with a systemic character. There is a predominance of quantitative research and strong evidence of a relationship between organizational culture and innovation, which requires further research to test the theoretical models proposed by these different authors

Industry 4.0 as enabler of sustainability diffusion in supply chain: analysis of influential strength of drivers in emerging economy

Industry 4.0 (I4.0) and sustainability are recent buzzwords in manufacturing environments. However, the connection between these two concepts is less explored in the literature. In the current business context, the future generation of manufacturing systems is greatly influenced by the rapid advancement of information technology. Therefore, this study aims to examine the drivers of I4.0 to diffuse sustainability in Supply Chains (SCs). This research identifies the most relevant drivers through the literature and discusses them with area experts. Afterwards, an empirical analysis is conducted to validate the key drivers. Finally, the Grey based DEMATEL method is employed to examine the influential strength of the identified drivers and to build an interrelationship diagram. ‘Government supportive policies’ and ‘Collaboration and transparency among supply chain members’ were reported as highly significant drivers of I4.0. This study is an initial effort that investigates the key drivers of I4.0 to achieve high triple bottom line (ecological-economic-social) gains in SCs by taking an example from an emerging economy, i.e. India. This study may help managers, practitioners and policy makers interested in I4.0 applications to diffuse sustainability in SCs.N/

Weak temperature dependence of P (+) H A (-) recombination in mutant Rhodobacter sphaeroides reaction centers

International audienceIn contrast with findings on the wild-type Rhodobacter sphaeroides reaction center, biexponential P (+) H A (-) → PH A charge recombination is shown to be weakly dependent on temperature between 78 and 298 K in three variants with single amino acids exchanged in the vicinity of primary electron acceptors. These mutated reaction centers have diverse overall kinetics of charge recombination, spanning an average lifetime from ~2 to ~20 ns. Despite these differences a protein relaxation model applied previously to wild-type reaction centers was successfully used to relate the observed kinetics to the temporal evolution of the free energy level of the state P (+) H A (-) relative to P (+) B A (-) . We conclude that the observed variety in the kinetics of charge recombination, together with their weak temperature dependence, is caused by a combination of factors that are each affected to a different extent by the point mutations in a particular mutant complex. These are as follows: (1) the initial free energy gap between the states P (+) B A (-) and P (+) H A (-) , (2) the intrinsic rate of P (+) B A (-) → PB A charge recombination, and (3) the rate of protein relaxation in response to the appearance of the charge separated states. In the case of a mutant which displays rapid P (+) H A (-) recombination (ELL), most of this recombination occurs in an unrelaxed protein in which P (+) B A (-) and P (+) H A (-) are almost isoenergetic. In contrast, in a mutant in which P (+) H A (-) recombination is relatively slow (GML), most of the recombination occurs in a relaxed protein in which P (+) H A (-) is much lower in energy than P (+) H A (-) . The weak temperature dependence in the ELL reaction center and a YLH mutant was modeled in two ways: (1) by assuming that the initial P (+) B A (-) and P (+) H A (-) states in an unrelaxed protein are isoenergetic, whereas the final free energy gap between these states following the protein relaxation is large (~250 meV or more), independent of temperature and (2) by assuming that the initial and final free energy gaps between P (+) B A (-) and P (+) H A (-) are moderate and temperature dependent. In the case of the GML mutant, it was concluded that the free energy gap between P (+) B A (-) and P (+) H A (-) is large at all times

Mutational Analysis of Photosystem I of Synechocystis sp. PCC 6803: The Role of Four Conserved Aromatic Residues in the j-helix of PsaB

Photosystem I is the light-driven plastocyanin-ferredoxin oxidoreductase in the photosynthetic electron transfer of cyanobacteria and plants. Two histidyl residues in the symmetric transmembrane helices A-j and B-j provide ligands for the P700 chlorophyll molecules of the reaction center of photosystem I. To determine the role of conserved aromatic residues adjacent to the histidyl molecule in the helix of B-j, we generated six site-directed mutants of the psaB gene in Synechocystis sp. PCC 6803. Three mutant strains with W645C, W643C/A644I and S641C/V642I substitutions could grow photoautotrophically and showed no obvious reduction in the photosystem I activity. Kinetics of P700 re-reduction by plastocyanin remained unaltered in these mutants. In contrast, the strains with H651C/L652M, F649C/G650I and F647C substitutions could not grow under photoautotrophic conditions because those mutants had low photosystem I activity, possibly due to low levels of proteins. A procedure to select spontaneous revertants from the mutants that are incapable to photoautotrophic growth resulted in three revertants that were used in this study. The molecular analysis of the spontaneous revertants suggested that an aromatic residue at F647 and a small residue at G650 may be necessary for maintaining the structural integrity of photosystem I. The (P700+ - P700) steady-state absorption difference spectrum of the revertant F647Y has a ∼5 nm narrower peak than the recovered wild-type, suggesting that additional hydroxyl group of this revertant may participate in the interaction with the special pair while the photosystem I complexes of the F649C/G650T and H651Q mutants closely resemble the wild-type spectrum. The results presented here demonstrate that the highly conserved residues W645, W643 and F649 are not critical for maintaining the integrity and in mediating electron transport from plastocyanin to photosystem I. Our data suggest that an aromatic residue is required at position of 647 for structural integrity and/or function of photosystem I

Robust Metabolic Responses to Varied Carbon Sources in Natural and Laboratory Strains of Saccharomyces cerevisiae

Understanding factors that regulate the metabolism and growth of an organism is of fundamental biologic interest. This study compared the influence of two different carbon substrates, dextrose and galactose, on the metabolic and growth rates of the yeast Saccharomyces cerevisiae. Yeast metabolic and growth rates varied widely depending on the metabolic substrate supplied. The metabolic and growth rates of a yeast strain maintained under long-term laboratory conditions was compared to strain isolated from natural condition when grown on different substrates. Previous studies had determined that there are numerous genetic differences between these two strains. However, the overall metabolic and growth rates of a wild isolate of yeast was very similar to that of a strain that had been maintained under laboratory conditions for many decades. This indicates that, at in least this case, metabolism and growth appear to be well buffered against genetic differences. Metabolic rate and cell number did not co-vary in a simple linear manner. When grown in either dextrose or galactose, both strains showed a growth pattern in which the number of cells continued to increase well after the metabolic rate began a sharp decline. Previous studied have reported that O2 consumption in S. cerevisiae grown in reduced dextrose levels were elevated compared to higher levels. Low dextrose levels have been proposed to induce caloric restriction and increase life span in yeast. However, there was no evidence that reduced levels of dextrose increased metabolic rates, measured by either O2 consumption or CO2 production, in the strains used in this study