Demographic structure across all known populations of the rheophyte Dyckia brevifolia Baker (Bromeliaceae) in the Itajaí-Açu River, Southern Brazil.

Understanding the distribution and demographic structure of populations is essential for species conservation. In Brazil, the rheophyte group has been greatly affected by the construction of hydroelectric dams. All know populations of Dyckia brevifolia Baker along Itajaí-Açu River were studied. The plants were classified as seedlings, immature or reproductive rosettes. In addition, the number of dead rosettes, except for seedlings, was determined in five populations of D. brevifolia. The total number of rosettes per population ranged from 273 to 7,185, totaling 30,443 rosettes, and 1,789 seedlings (5.9%). Only 2.4% of rosettes occurred isolated and 97.6% occurred clumped into 2,254 clumps. The number of rosettes per clump ranged from two to 339 rosettes. The percentage of reproductive rosettes per population ranged from 7.8 to 26.7%. The correlation between the number of clumps or between the total number of rosettes and the area of occupation was significant and positive (r = 0.82; P < 0.05). The production of offshoots (1-4) occurred on immature and reproductive rosettes. Dyckia brevifolia has herbivory by Hydrochaeris hydrochaeris (capybara). These rosettes die or often resprout, emitting from 1 to 20 shoots. The populations did not present a pattern of distribution of rosettes in the diametric classes, but in all populations a decrease in the number of rosettes can be observed in the classes with the largest diameter. The small area of occupation (9,185 m2) showed high environmental specificity and vulnerable to habitat loss and environmental changes. Therefore, the maintenance these sites is essential for the long-term conservation of D. brevifolia.

A longitudinal study of driving instructor guidance from an activity-oriented perspective.

The aim of this study was to provide a better understanding of the scaffolding activity of instructors during driving lessons in a French urban traffic context. It focuses on three common and risky tasks: turning right, turning left and overtaking. Data were based on fine-grained longitudinal analyses of the records of five driving lessons involving four student-instructor dyads. The instructor scaffolding activity was analyzed throughout training - an original approach in the sphere of driving. The results show that the instructors implemented the learning process using an integrative approach based on 'cutting' and 'decoupling' the driving task rather than the step-by-step method recommended in the curriculum. They transferred the responsibility of the driving components to the students in a similar order: 1) technical maneuvers, 2) situation identification and 3) goals focusing on other road-users. As expected, student autonomy and efficiency in driving increased as the training progressed. However, at the end of training, uncertainties remained with regard to the execution of basic sub-goals in complex situation; moreover, the instructors were still in charge of the navigational task. The results were discussed and suggestions were made to improve instructor training with a view to increasing their efficiency in teaching students.

Chemical modifications of laccase from white-rot basidiomycete Cerrena unicolor.

Laccases belong to the group of phenol oxidizes and constitute one of the most promising classes of enzymes for future use in various fields. For industrial and biotechnological purposes, laccases were among the first enzymes providing larger-scale applications such as removal of polyphenols or conversion of toxic compounds. The wood-degrading basidiomycete Cerrena unicolor C-139, reported in this study, is one of the high-laccase producers. In order to facilitate novel and more efficient biocatalytic process applications, there is a need for laccases with improved biochemical properties, such as thermostability or stability in broad ranges of pH. In this work, modifications of laccase isoforms by hydrophobization, hydrophilization, and polymerization were performed. The hydrophobized and hydrophilized enzyme showed enhanced surface activity and higher ranges of pH and temperatures in comparison to its native form. However, performed modifications did not appear to noticeably alter enzyme's native structure possibly due to the formation of coating by particles of saccharides around the molecule. Additionally, surface charge of modified laccase shifted towards the negative charge for the hydrophobized laccase forms. In all tested modifications, the size exclusion method led to average 80 % inhibition removal for hydrophilized samples after an hour of incubation with fluoride ions. Samples that were hydrophilized with lactose and cellobiose showed an additional 90 % reversibility of inhibition by fluoride ions after an hour of concluding the reaction and 40 % after 24 h. The hydrophobized laccase showed higher level of the reversibility after 1 h (above 80 %) and 24 h (above 70 %) incubation with fluoride ions. The addition of ascorbate to laccase solution before a fluoride spike resulted in more efficient reversibility of fluoride inhibitory effect in comparison to the treatments with reagents used in the reversed sequence.

What are the consequences of sharing a trainee's driving course between different trainers?

OBJECTIVES: In some driving schools in France, several trainers may successively train a single trainee. This situation can be described as a case of asynchronous collaboration. In this paper, we examine the consequences of this situation in two different studies: the first explores the trainers' activity while the second concerns the trainees. PARTICIPANTS: The participants in the first study were 6 trainers with different levels of experience, each working with 2 different trainees. Four of them met their trainees for the very first time. The second study included 150 trainees from 13 driving schools in Paris. METHODS: In the first study, the driving lessons were recorded and fully transcribed before a thematic analysis was conducted. In the second study, the trainees completed a questionnaire. We collected both socio-demographic and driver training data. RESULTS: In the first study, we observed that changing trainers during a trainee's driving course had an impact on the trainers' activity. We identified difficulties in establishing a diagnosis of the trainee's progress, and the organization of the driving lesson was altered. The second study highlighted the fact that changing trainers at the beginning of a course increased the duration of the training period. CONCLUSION: The impacts of changing trainers during a trainee's driving course are discussed with regard to both the trainers' scaffolding activity and the trainees' skill development.

Enzymatic electrodes nanostructured with functionalized carbon nanotubes for biofuel cell applications.

Nanostructured bioelectrodes were designed and assembled into a biofuel cell with no separating membrane. The glassy carbon electrodes were modified with mediator-functionalized carbon nanotubes. Ferrocene (Fc) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS) bound chemically to the carbon nanotubes were found useful as mediators of the enzyme catalyzed electrode processes. Glucose oxidase from Aspergillus niger AM-11 and laccase from Cerrena unicolor C-139 were incorporated in a liquid-crystalline matrix-monoolein cubic phase. The carbon nanotubes-nanostructured electrode surface was covered with the cubic phase film containing the enzyme and acted as the catalytic surface for the oxidation of glucose and reduction of oxygen. Thanks to the mediating role of derivatized nanotubes the catalysis was almost ten times more efficient than on the GCE electrodes: catalytic current of glucose oxidation was 1 mA cm(-2) and oxygen reduction current exceeded 0.6 mA cm(-2). The open circuit voltage of the biofuel cell was 0.43 V. Application of carbon nanotubes increased the maximum power output of the constructed biofuel cell to 100 µW cm(-2) without stirring of the solution which was ca. 100 times more efficient than using the same bioelectrodes without nanotubes on the electrode surface.

Derivatization of single-walled carbon nanotubes with redox mediator for biocatalytic oxygen electrodes.

Single-walled carbon nanotubes (SWCNTs) were covalently modified with a redox mediator derived from 2,2'-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS), and implemented in the construction of electrodes for biocatalytic oxygen reduction. The procedure is based on: covalent bonding of mediator to nanotubes, placing the nanotubes directly on the carbon electrode surface and covering the nanostructured electrode with a Nafion film containing laccase as the biocatalyst. The modified electrode is stable and the problem of mediator (ABTS) leaking from the film is eliminated by binding it covalently to the nanotubes. Three different synthetic approaches were used to obtain ABTS-modified carbon nanotubes. Nanotubes were modified at ends/defect sites or on the nanotube sidewalls and characterized by Raman spectroscopy, TGA and electrochemistry. The accessibility of differently located ABTS units by the laccase active center and mediation of electron transfer were studied by cyclic voltammetry. The surface concentrations of ABTS groups electrically connected with the electrode were compared for each of the electrodes based on the charges of the voltammetric peaks recorded in the deaerated solution. The nanotube modification procedure giving the best parameters of the catalytic process was selected.

Colour, composition and quality of M. longissimus dorsi and M. extensor carpi radialis of steers housed on straw or concrete slats or accommodated outdoors on wood-chips.

Forty-five Charolais crossbred steers were offered a common diet and accommodated either outside on wood-chips (OWP, 18m(2)/head) or in a naturally-ventilated building in slatted-floor pens (SLA, 2.5m(2)/500kg bodyweight) or in straw-bedded pens (STR, 4m(2)/head) for 132 days. Carcass weight averaged 351, 362, and 372 (sed 6.63)kg (P<0.05), for SLA, STR and OWP, respectively. Accommodation system did not affect the colour, drip loss, shear force or composition of Musculus longissimus dorsi (LD) or Musculus extensor carpi radialis (ECR) muscles or the sensory characteristics of LD. The ultimate pH of ECR was highest (P<0.05) for OWP steers, while their LD was darker at 2 days post-mortem than LD from STR steers. It is concluded that accommodating cattle on OWP had a minor transient effect on beef colour and no impact on beef composition or eating quality.

Immobilization of laccase on gold, silver and indium tin oxide by zirconium-phosphonate-carboxylate (ZPC) coordination chemistry.

In this paper we present a simple method allowing for stable laccase immobilization on various conducting surfaces that retains the activity of the enzyme. The strategy for laccase immobilization presented in this paper relies on Zr(4+) ion coordination chemistry that involves -COO- terminal groups present on the protein. Using a host of techniques, including surface plasmon resonance (SPR), quartz crystal microbalance (QCM) gravimetry, atomic force microscopy (AFM), surface enhanced Raman scattering (SERS), resonance Raman scattering (RR) and electrochemical techniques, we show that laccase bound to a surface coordinatively through zirconium phosphonate/carboxylate (ZPC) functionalities forms a stable enzymatic layer with the enzyme retaining its activity to a significant extent.

Manganese peroxidase production in submerged cultures by free and immobilized mycelia of Nematoloma frowardii.

The agaric basidiomycete Nematoloma frowardii has been suggested as a good alternative for production of the extracellular ligninolytic enzyme, manganese-dependent peroxidase (MnP). Some cultural and environmental factors influencing the enzymatic activity in shaken flasks and aerated fermenter cultures were evaluated to improve the yields of the process. A low nitrogen medium (1.36 mM N added as ammonium tartrate), containing 16 g/l glucose (C/N ratio=65.3), 2mM Mn2+ and inoculated with immobilized polyurethane foam mycelium, made it possible to obtain a MnP yield of 2304 nkat/l in 8 days. Under these operational conditions, the enzyme productivity in the immobilized cells of N. frowardii was 1.4 times higher than that obtained with the free fungus. In the procedure with the reusable immobilized mycelium (semi-continuous culture) as many as three subsequent 10 day batches could be fermented by using the same carrier with no loss of MnP activity.

Influence of aromatic compounds on biodegradation of [14C]-labeled xylan and mannan by the white-rot fungus Phlebia radiata.

Radiolabeled [14C]arabinoxylan from wheat meal and [14C]galactoglucomannan from red clover meal were prepared by using 14CO2 as a precursor. Twice as much mannan was mineralized than xylan after 14 days of incubation with Phlebia radiata. Low-molecular-weight phenolic compounds structurally related to lignin increased during mineralization of both hemicellulose fractions. Veratryl alcohol increased degradation of arabinoxylan by approximately 28.5%, whereas veratric acid increased it by only 9.0%. Vanillic acid and ferulic acid also stimulated degradation by 16.6% and 34.7%, respectively. Veratryl alcohol and ferulic acid increased degradation of galactoglucomannan by approximately 75%. Veratraldehyde in both cases repressed the degradation process (23.6% arabinoxylan, 43.8% galactoglucomannan). These results indicate that the degradation of hemicelluloses, e.g., xylan and mannan, by P. radiata is enhanced by addition of aromatic compounds.

Purification and characterization of two endo-1,4-beta-xylanases and a 3-xylosidase from phlebia radiata.

Two different endo-1,4-beta-xylanases, designated XA-1 and XA-2, and one beta-xylosidase (XD-1) have been purified by column chromatography to apparent homogeneity from the extracellular culture fluid of Phlebia radiata grown on wheat bran. The molecular masses of XA- 1, XA-2 and XD-1 were 18.6, 15.8 kDa, and 27 kDa, respectively. The isoelectric points for the xylanases were 6.7 and 4.1 and for the xylosidase - 5.9. The Km and Vmax values with larchwood xylan as substrate were 4.86 mg ml(-1) and 0.17 micromol min(-1) mg(-1) for XA-1; 2.7 mg ml(-1) and 3.91 micromol min(-1) mg(-1) for XA-2, whereas with pNPK as a substrate the Km and Vmax for XD-1 was 1.28 mM and 7.41 micromol min(-1) mg(-1). All the above enzymes are glycoproteins and the carbohydrate contents are for- XA-1 and XA-2 (6.70%, 3.58%) and for XD-1 (12.8%). Endoxylanase XA-1 and XA-2 were not able to release arabinose from rye arabinoxylan and birch xylan. Both enzymes were endo-acting, as revealed by their hydrolysis product profiles on xylan substrates.

Fungal laccase: properties and activity on lignin.

The sources of ligninocellulose that occur in various forms in nature are so vast that they can only be compared to those of water. The results of several, more recent experiments showed that laccase probably possesses the big ability for "lignin-barrier" breakdown of ligninocellulose. The degradation of this compound is currently understood as an enzymatic process mediated by small molecules, therefore, this review will focus on the role of these mediators and radicals working in concert with enzymes. The fungi having a versatile machinery of enzymes are able to attack directly the "lignin-barrier" or can use a multienzyme system including "feed-back" type enzymes allowing for simultaneous transformation of lignin and carbohydrate compounds.

Production of lignolytic and feed-back type enzymes by Phlebia radiata on different media.

Low molecular-weight compounds, structurally related to lignin, increase the production of laccase, lignin peroxidase, manganese dependent peroxidase, and feed-back type enzymes such as glucose oxidase, cellobioso-quinone oxidoreductase, and glyoxal oxidase in the culture of the white rot fungus Phlebia radiata growing on different carbon sources.

Demethylation of [14C]-labelled veratric acid and oxidation of methanol and formaldehyde by the white-rot fungus Phlebia radiata.

Veratric acids 14C-labelled in carboxyl group, 3-OCH3, 4-OCH3, or aromatic ring together with unlabelled veratric acid were supplemented in the cultures of the white-rot fungus Phlebia radiata. The effect of various carbon sources on the release of 14CO2 was studied. Veratric acid was readily decarboxylated, maximally already on day 1 from the addition of [14COOH]-veratric acid. High amounts (4%) of glucose slightly repressed the decarboxylation. In medium supplemented with cellulose the methoxyl group in position 4 was much more readily mineralized to CO2 than the group in position 3. The maximum evolution was achieved on day 5, two days from the addition. Cellulose did not repress methanol oxidation but repression of methanol oxidation by glucose was detected in media supplemented with [O14CH3]-veratric acids and 14CH3OH. However, glucose did not repress oxidation of H14CHO. The apparent uptake of 14C by fungal mycelium, especially from methoxyl groups, but also from the aromatic ring, may partially be due to the strong slime formation observed in cellobiose medium. Also in cellobiose medium apparent uptake of 14C from 14C-labelled methoxyl groups was observed.

Biodegradation of lignin by white rot fungi.

A review is presented related to the biochemistry of lignocellulose transformation. The biodegradation of wood constituents is currently understood as a multienzymatic process with the mediation of small molecules; therefore, this review will focus on the roles of these small molecular compounds and radicals working in concert with enzymes. Wood rotting basidiomycetous fungi penetrate wood and lead to more easily metabolized, carbohydrate constituents of the complex. Having a versatile machinery of enzymes, the white rot fungi are able to attack directly the "lignin barrier." They also use a multienzyme system including so-called "feed back" type enzymes, allowing for simultaneous transformation of both lignin and cellulose. These enzymes may function separately or cooperatively.

The preparation of specific sorbents with polyclonal antibodies as a ligand for purification of human antithrombin III.

Antithrombin III (AT III) is a serine protease inhibitor active against thrombin, factor X and factor VII. Major hematolytic abnormalities such as disseminated intravascular closing, coagulative vein inflammation, embolism in lungs or brain etc. frequently occur when the level of AT III is low. As a drug AT III is separated from blood preparations by bioselective sorption on sorbents containing heparine as a complementary ligand interacting with AT III molecules. The present paper describes the preparation procedures and the properties of sorbents with chemically bonded AT III antigen. The chromatographic ability of the prepared sorbents to separate AT III from human plasma are discussed in relation to the bonding procedure which was used for AT III antigen immobilization.

Purification of extracellular catalase from Aspergillus niger.

The extracellular catalase (EC 1.11.1.6) produced by Aspergillus niger culture in 5-liter fermentor was isolated and purified by ion-exchange chromatography on DEAE Sepharose (fast flow) column, hydrophobic interaction on phenyl-Sepharose column and chromatofocusing on PBE 94 column. Some physico-chemical properties of two purified catalase forms were also determined (molecular weight, isolelectric point, polysaccharides contents, Km, and Ea).

Co-operation processes in dynamic environment management: evolution through training experienced pilots in flying a highly automated aircraft.

Dynamic environment management (process control, aircraft piloting, etc.) increasingly implies collective work components. Pragmatic purposes as well as epistemological interests raise important questions on collective activities at work. In particular, linked to the technological evolution in flight management, the role of the 'collective fact' appears as a key point in reliability. Beyond the development of individual competencies, the quality of the 'distributed' crew activity has to be questioned. This paper presents an empirical study about how experienced pilots co-ordinate their information and actions during the last period of training on a highly automated cockpit. A task of disturbance management (engine fire during takeoff) is chosen as amplifying cognitive requirements. Analysis focuses on the transitions between the main task and the incident to be managed. Crew performance and co-operation between two pilots are compared in three occurrences of the same task: the results are coherent with the hypothesis of a parallel evolution of the crew performance and its internal co-operation, and show that prescribed explicit co-operation is more present on action than on information about the 'state of the world'. Methodological issues are discussed about the possible effects of the specific situation of training, and about the psychological meaning of the results.

Seeds as natural matrices for immobilization of Aspergillus niger mycelium producing pectinases.

A simple method for the immobilization of Aspergillus niger mycelium producing polygalacturonase (PG) and pectinesterase (PE) is described. Fungal conidia were immobilized on wheat, rye, barley, peas, buckwheat and mustards seeds. Spongy mycelia overgrowing the seed surfaces on mineral medium with pectin produced extracellular PG and PE; the highest production was reached on the wheat carrier. Some of the variables influencing the enzymatic activity have been optimized. After every 24 h, a culture liquid with 6.8-7.8 U of PG ml-1 and 7.0-10.1 U of PE ml-1 was obtained. This procedure also made possible repeated batch enzyme production and, as many as eight subsequent 24-h batches could be fermented by using the same carrier without any loss of PG activity. The addition of sodium orthovanadate (1 mmol) into the medium with pectin caused a significant increase in PG and PE activity produced by free cells of A. niger (by 1.59-fold and 1.67-fold respectively), and only 0.47-fold of PG activity in case of the immobilized mycelium.

Analysing communication in complex distributed decision-making.

This paper analyses emergency tasks within the theoretical framework of dynamic environment management with distributed decision-making (DDM). Models of task and work organization are used to analyse verbal exchanges in order to infer collective strategies. A cross-analysis method serves to analyse communication from the standpoint of both semantics and structure of the exchanges. The findings of two empirical comparative studies show that invariants vs differences in the organization and the semantics of exchanges are associated with invariants vs differences in parameters of the situations themselves (initial state and final result of actions). Efficient strategies were linked with well-structured flow of communication and roles distribution.