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The Attentional Networks Test for Interactions and Vigilance—executive and arousal components (ANTI-Vea) is a computerized task of 32 min duration in the standard format. The task simultaneously assesses the main effects and interactions of the three attentional networks (i.e., phasic alertness, orienting, and executive control) and two dissociated components of vigilance with reasonable reliability (executive and arousal vigilance). We present this free and publicly accessible resource (ANTI-Vea-UGR; https://anti-vea.ugr.es/) developed to easily run, collect, and analyze data with the ANTI-Vea (or its subtasks measuring some attentional and/or vigilance components embedded in the ANTI-Vea). Available in six different languages, the platform allows for the adaptation of stimulus timing and procedure to facilitate data collection from different populations (e.g., clinical patients, children). Collected data can be freely downloaded and easily analyzed with the provided scripts and tools, including a Shiny app. We discuss previous evidence supporting that attention and vigilance components can be assessed in typical lab conditions as well as online and outside the laboratory. We hope this tutorial will help researchers interested in measuring attention and vigilance with a tool useful to collect data from large sample sizes and easy to use in applied contexts. [ABSTRACT FROM AUTHOR]

Multiple theories have used perceptual sensitivity and response criterion indices to explain the decrements in performance across time on task (i.e., vigilance decrement). In a recent study, McCarley and Yamani (2021) offered conceptual and methodological advances to this debate by using a vigilance task that parametrically manipulates noise and signal and analyzes the outcomes with psychometric curves. In the present Commentary, we reanalyze data (N = 553) from a different, already existing vigilance task, the Attentional Networks Test for Interactions and Vigilance—executive and arousal components (ANTI-Vea). Psychometric curves with the ANTI-Vea showed robust changes in response criterion and lapse rate, although not in sensitivity. Our interpretation is that the need to keep the standard in memory in McCarley and Yamani's task could produce a decrease in sensitivity and be related to reduced fidelity of the memory representation rather than to a decrement in perceptual abilities across time on task. [ABSTRACT FROM AUTHOR]

The demands of today’s society for interventions that optimize cognitive abilities and prevent their decline have motivated the translation of scientific findings into applied programs. Ordinary activities such as physical exercise, chess, meditation, playing video games or a musical instrument, as well as specific cognitive programs, have witnessed the growth of evidence emphasizing their cognitive benefits. Here, we outline several issues that need consideration before speculating on the implications of this literature: (a) the magnitude and costs of the effect, (b) the robustness of the effect, (c) testing causality, (d) the identification of moderator variables, and (e) the underlying mechanisms. We consider that this would contribute to a critical appraisal of the extant findings by the interested researchers, to reduce overstatements in the media reports about the applicability and public relevance of the effects reported in scientific articles, and to potentially help designing new interventions. [ABSTRACT FROM AUTHOR]

Recent research has found that eye gaze and arrows yield opposite congruency effects in a spatial interference paradigm, arrows eliciting faster responses when their direction is congruent with their position (standard congruency effect), and gaze producing faster reaction times for incongruent conditions (reversed congruency effect). In addition, we observed by serendipity in a previous study that the standard effect with arrows was reduced when the target appeared within a complex background, presumably because of hindered figure-ground segregation. Under the same conditions, the reversed effect with gaze became more negative. To explain our previous results, we proposed the coexistence of two opposite attentional effects with eye gaze: a standard spatial interference component being common to both arrows and gaze, and a larger social-specific dimension leading to the overall reversion of the effect for gaze. Both in Experiments 1 and 2, gaze or arrow targets were presented after or concurrently with an irrelevant background (asynchronous vs. synchronous conditions, respectively). Consistent with our preregistered hypotheses, the standard effect with arrows was present in the asynchronous condition (automatic figure-ground segregation) but reduced in the synchronous one (difficult figure-ground segregation). Correspondingly with the effect on arrows interference, eye gaze triggered a significant reversed effect in the synchronous condition that decreased in the asynchronous one. These results underline the importance of the figure-ground segregation processes as modulators of the spatial conflict triggered by peripheral targets, and support our two-effect model, according to which gaze shares with nonsocial stimuli a domain-general orienting mechanism, but also triggers distinctive processes. [ABSTRACT FROM AUTHOR]

Recent evidence with a spatial interference paradigm has shown that arrows and eye gaze yield opposite congruency effects, arrow target eliciting faster responses when their direction is congruent with their position (standard congruency effect), and gaze producing faster reaction times for incongruent conditions (reversed congruency effect). But in ecological contexts eye gaze tend to be more perceptually complex (i.e., embedded in the whole face) than simple arrows. The present study aimed to replicate this dissociation using whole faces and a comparable non-social target, formed by arrows embedded in a colored geometric background. Whereas the reversed congruency effect with gaze was replicated, the standard spatial interference with arrows was surprisingly absent. A similar outcome appeared when the contrast between the arrows and the task-irrelevant background increased. The results confirm the robustness of the reversed congruency effect with eyes, regardless of whether they are presented alone or within a face. In addition, and importantly, the unexpected absence of the spatial conflict with complex arrow targets seems to be a consequence of higher figure-ground segregation demands, which extend the processing of the task-relevant spatial dimension and, in turn, cause the decay of the location code. This pattern of results, and the provided interpretation, can explain previous unexplained findings in the spatial interference literature. [ABSTRACT FROM AUTHOR]

Previous literature has shown cognitive improvements related to musical training. Attention is one cognitive aspect in which musicians exhibit improvements compared to non-musicians. However, previous studies show inconsistent results regarding certain attentional processes, suggesting that benefits associated with musical training appear only in some processes. The present study aimed to investigate the attentional and vigilance abilities in expert musicians with a fine-grained measure: the ANTI-Vea (ANT for Interactions and Vigilance—executive and arousal components; Luna et al. in J Neurosci Methods 306:77–87, https://doi.org/10.1016/j.jneumeth.2018.05.011, 2018). This task allows measuring the functioning of the three Posner and Petersen's networks (alerting, orienting, and executive control) along with two different components of vigilance (executive and arousal vigilance). Using propensity-score matching, 49 adult musicians (18–35 years old) were matched in an extensive set of confounding variables with a control group of 49 non-musicians. Musicians showed advantages in processing speed and in the two components of vigilance, with some specific aspects of musicianship such as years of practice or years of lessons correlating with these measures. Although these results should be taken with caution, given its correlational nature, one possible explanation is that musical training can specifically enhance some aspects of attention. Nevertheless, our correlational design does not allow us to rule out other possibilities such as the presence of cognitive differences prior to the onset of training. Moreover, the advantages were observed in an extra-musical context, which suggests that musical training could transfer its benefits to cognitive processes loosely related to musical skills. The absence of effects in executive control, frequently reported in previous literature, is discussed based on our extensive control of confounds. [ABSTRACT FROM AUTHOR]

Prospective memory (PM) is the ability to remember to perform planned actions in a future moment and it is of fundamental importance for an independent and autonomous lifestyle from development to late adulthood. Deficits in episodic memory and executive functions, which are involved in PM are characteristic features of mild cognitive impairment (MCI) and Alzheimer’s disease (AD). Considering that the number of older adults is drastically increasing over the next decades, it is of great interest to understand how PM decline in healthy older adults and patients with different degree of cognitive decline. The present meta-analysis included 46 studies investigating PM performance in AD patients (17 studies) and people with MCI (24 studies); 5 studies included both clinical conditions in the same article. The 46 studies contributed a total of 63 independent samples and 129 effect sizes from 4668 participants (2115 patients and 2553 controls). Unlike previous reviews of the literature, our results with a larger and updated sample of studies confirmed lower PM abilities in AD compared to MCI and controls, although we did not observe conclusive differences between event-based and time-based PM in patients. Surprisingly, PM deficits shown by MCI and AD patients have decreased across years, in parallel to a reduction of the evidence of publication bias and an increase in the number of observations per task. We propose the use of more reliable research designs as one plausible explanation for the reduction of PM impairments. [ABSTRACT FROM AUTHOR]

Eye gaze conveys rich information concerning the states of mind of others, playing a critical role in social interactions, signaling internal states, and guiding others’ attention. On the basis of its social significance, some researchers have proposed that eye gaze may represent a unique attentional stimulus. However, contrary to this notion, the majority of the literature has shown indistinguishable attentional effects when eye gaze and arrows have been used as cues. Taking a different approach, in this study we aimed at finding qualitative attentional differences between gazes and arrows when they were used as targets instead of as cues. We used a spatial Stroop task, in which participants were required to identify the direction of eyes or arrows presented to the left or the right of a fixation point. The results showed that the two types of stimuli led to opposite spatial interference effects, with arrows producing faster reaction times when the stimulus direction was congruent with the stimulus position (a typical spatial Stroop effect), and eye gaze producing faster reaction times when it was incongruent (a “reversed” spatial Stroop effect). This reversed Stroop is interpreted as an eye-contact effect, therefore revealing the unique nature of eyes as special social-attention stimuli. [ABSTRACT FROM AUTHOR]

Aging is accompanied by cognitive decline, although recent research indicates that the rate of decline depends on multiple lifestyle factors. One of such factors is musical practice, an activity that involves several sensory and motor systems and a wide range of high-level cognitive processes. This paper describes the first systematic review and meta-analysis, to our knowledge, of the impact of musical practice on healthy neurocognitive aging. The inclusion criteria for the review required that studies were empirical works in English or Spanish that they explored the effects of musical practice on older people; they included an assessment of cognitive functions and/or an assessment of brain status; and they included a sample of participants aged 59 years or older with no cognitive impairment or brain damage. This review led to the selection of 13 studies: 9 correlational studies involving older musicians and non-musicians and 4 experimental studies involving short-term musical training programs. The results of the meta-analysis showed cognitive and cerebral benefits of musical practice, both in domain-specific functions (auditory perception) and in other rather domain-general functions. Moreover, these benefits seem to protect cognitive domains that usually decline with aging and boost other domains that do not decline with aging. The origin of these benefits may reside, simultaneously, in the specific training of many of these cognitive functions during musical practice (specific training mechanism), in the improvement of compensatory cognitive processes (specific compensatory mechanism), and in the preservation of general functions with a global influence on others, such as perceptual capacity, processing speed, inhibition and attention (general compensatory mechanism). Therefore, musical practice seems to be a promising tool to reduce the impact of cognitive problems associated to aging. [ABSTRACT FROM AUTHOR]

It has often been reported that mental exertion, presumably leading to mental fatigue, can negatively affect exercise performance; however, recent findings have questioned the strength of the effect. To further complicate this issue, an overlooked problem might be the presence of publication bias in studies using underpowered designs, which is known to inflate false positive report probability and effect size estimates. Altogether, the presence of bias is likely to reduce the evidential value of the published literature on this topic, although it is unknown to what extent. The purpose of the current work was to assess the evidential value of studies published to date on the effect of mental exertion on exercise performance by assessing the presence of publication bias and the observed statistical power achieved by these studies. A traditional meta-analysis revealed a Cohen's dz effect size of − 0.54, 95% CI [− 0.68, − 0.40], p <.001. However, when we applied methods for estimating and correcting for publication bias (based on funnel plot asymmetry and observed p-values), we found that the bias-corrected effect size became negligible with most of publication-bias methods and decreased to − 0.36 in the more optimistic of all the scenarios. A robust Bayesian meta-analysis found strong evidence in favor of publication bias, BFpb > 1000, and inconclusive evidence in favor of the effect, adjusted dz = 0.01, 95% CrI [− 0.46, 0.37], BF10 = 0.90. Furthermore, the median observed statistical power assuming the unadjusted meta-analytic effect size (i.e., − 0.54) as the true effect size was 39% (min = 19%, max = 96%), indicating that, on average, these studies only had a 39% chance of observing a significant result if the true effect was Cohen's dz = − 0.54. If the more optimistic adjusted effect size (− 0.36) was assumed as the true effect, the median statistical power was just 20%. We conclude that the current literature is a useful case study for illustrating the dangers of conducting underpowered studies to detect the effect size of interest. [ABSTRACT FROM AUTHOR]

Our environment is full of rhythms, which have an important predictive value as cues for the preparation and temporal orienting of attention. At the neurocognitive level, rhythms promote attentional entrainment, concentrating higher levels of attention at the moments in which the appearance of a critical event is more likely. This strategic use of attention improves performance on several cognitive tasks. It yields both perceptual and motor benefits, respectively allowing a greater stimulus processing capacity and a greater opportunity to prepare complex responses. [ABSTRACT FROM AUTHOR]

Nuestro ambiente está lleno de ritmos, los cuales tienen un importante valor predictivo como claves de preparación y de orientación temporal de la atención. Los ritmos promueven a nivel neurocognitivo una sincronización de la atención, concentrándola en los momentos en los que es más probable la aparición de un evento crítico. Este uso estratégico de la atención mejora el rendimiento en múltiples tareas cognitivas, con beneficios tanto perceptivos, permitiendo una mayor capacidad de procesamiento, como motores, ofreciendo mayor oportunidad para preparar respuestas más complejas. [ABSTRACT FROM AUTHOR]

Algorithmic debugging is a technique proposed in 1982 by E. Y. Shapiro in the context of logic programming. This survey shows how the initial ideas have been developed to become a widespread debugging schema fitting many different programming paradigms and with applications out of the program debugging field. We describe the general framework and the main issues related to the implementations in different programming paradigms and discuss several proposed improvements and optimizations. We also review the main algorithmic debugger tools that have been implemented so far and compare their features. From this comparison, we elaborate a summary of desirable characteristics that should be considered when implementing future algorithmic debuggers. [ABSTRACT FROM AUTHOR]

In this paper, we propose a technique for improving anonymity in screening program databases to increase the privacy for the participants in these programs. The data generated by the invitation process (screening centre, appointment date) is often made available to researchers for medical research and for evaluation and improvement of the screening program. This information, combined with other personal quasi-identifiers such as the ZIP code, gender or age, can pose a risk of disclosing the identity of the individuals participating in the program, and eventually their test results. We present two algorithms that produce a set of screening appointments that aim to increase anonymity of the resulting dataset. The first one, based on the constraint programming paradigm, defines the optimal appointments, while the second one is a suboptimal heuristic algorithm that can be used with real size datasets. The level of anonymity is measured using the new concept of generalized k-anonymity, which allows us to show the utility of the proposal by means of experiments, both using random data and data based on screening invitations from the Norwegian Cancer Registry. [ABSTRACT FROM AUTHOR]

Gaze acts from an early age as a cue to orient attention and, thereafter, to infer our social partners' intentions, thoughts, and emotions. Variants of the attentional orienting paradigm have been used to study the orienting capabilities associated to eye gaze. However, to date, it is still unclear whether this methodology truly assesses "social-specific" processes exclusively involved in attention to eye-gaze or the operation of domain-general attentional processes. The present study provides a comprehensive meta-analysis indicating that eye-gaze and non-social directional stimuli, such as arrows, produce equivalent attentional effects. This result casts doubt on the potential utility of the classic cueing task in revealing social-specific processes. On the other hand, we review behavioral evidence suggesting that eye-gaze stimuli may induce higher-order social processes when more specific experimental procedures that analyze qualitative rather than quantitative differences are used. These findings point to an integrated view in which domain-general and social specific processes both contribute to the attentional mechanisms induced by eye-gaze direction. Finally, some proposals about the social components specifically triggered by eye-gaze stimuli are discussed. • Eye gaze acts as a relevant cue to orient attention in social interactions. • Meta-analytic evidence shows no quantitative differences between gaze and arrow cues. • Identical cueing effects of eye gaze and arrows point to a common orienting mechanism. • Additional social processes might be observed with experimental procedures aiming qualitative differences. • Gaze-specific effects might be related to its ability to convey intention and mentalizing. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented which discusses various papers published within the issue, including one on project portfolio selection and scheduling with multiple criteria within a fuzzy environment, one on portfolio optimization in a stochastic context, and another on the use of an Extended Goal Programming Model in an offshore wind farm site selection problem.

The literature on musical training suggests benefits of this activity on auditory skills (i.e., near transfer) and general cognitive abilities (i.e., far transfer). However, other positions have taken those results more skeptically, rather arguing that studies with positive outcomes suffer from methodological issues that impede inferences of causality. In the context of this debate, we conducted an independent meta-analysis similar to one recently published by Neves et al.'s, also showing auditory benefits of musical training. Our meta-analysis suggests that the available evidence is not sufficient to reach firm conclusions as interventions with design-quality features (randomization and active control) are still scarce. Moreover, the reviewed studies measured auditory skills with tests based on same/different judgments that rely on short-term memory, therefore being less sensitive to changes produced by musicmaking experiences. Although the evidence is not conclusive, the results are in line with those observed with other cognitively stimulating activities and suggest a positive impact of musical training on auditory skills. Thus, the available evidence does not support extreme versions of skepticism. [ABSTRACT FROM AUTHOR]

In this paper we present two type extensions for the modeling language MiniZinc that allow the representation of some problems in a more natural way. The first proposal, called MiniZinc ⋆ , extends existing types with additional values. The user can specify both the extension of a predefined type with new values, and the behavior of the operations with relation to the new types. We illustrate the usage of MiniZinc ⋆ to model SQL-like problems with integer variables extended with NULL values. The second extension, MiniZinc + , introduces union types in the language. This allows defining recursive types such as trees, which are very useful for modeling problems that involve complex structures. A new case statement is introduced to select the different components of union type terms. The paper shows how a model defined using these extensions can be transformed into a MiniZinc model which is equivalent to the original model. [ABSTRACT FROM AUTHOR]

We present a declarative debugger for sequential Erlang programs. The tool is started when a program produces some unexpected result, and proceeds asking questions to the user about the correctness of some subcomputations until an erroneous program function is found. Then, the user can refine the granularity by zooming in the function, checking the values bound to variables and the if/case/try-catch branches taken during the execution. We show by means of an extensive benchmark that the result is a usable, scalable tool that complements already existing debugging tools such as the Erlang tracer and Dialyzer. Since the technique is based on a formal calculus, we are able to prove the soundness and completeness of the approach. [ABSTRACT FROM AUTHOR]

The present study makes a comparative analysis between two Spanish academic communities, Communication and Library and Information Sciences. The set-up of these academic programmes in Spain, along with their size and the international scientific production of each community, is briefly described and compared. These communities are relatively new, being Library and Information Sciences the more recently implemented. The numbers differ greatly, both in the universities that offer these studies and in the size of their communities; there are five times as many professors in Communication as in Library and Information Sciences. In contrast,Library and Information Sciences has an international scientific productivity three times that of Communication, with articles published in journals with a higher impact factor. [ABSTRACT FROM AUTHOR]

Biotype B of the sweetpotato whitefly (SPWF), Bemisia tabaci (Gennadius) (also known as the silverleaf whitefly, B. argentifolii Bellows & Perring), is the key pest of tomatoes in south Florida, primarily as a vector of the begomovirus Tomato yellow leaf curl virus (TYLCV). Insecticides are most often used to manage the SPWF and TYLCV. A resistance monitoring program that was initiated in Florida in 2000 was continued from 2008 to 2010 and included 4 neonicotinoid insecticides (imidacloprid, thiamethoxam, dinotefuran, and acetamiprid), the insect growth regulator buprofezin, the pyrethroid bifenthrin, and the organochlorine endosulfan. Ten field populations in 2008 and 9 each in 2009 and 2010 were established with nymphal infested foliage and were tested for susceptibility using a systemic uptake, cut-leaf petiole bioassay with adults for the neonicotinoids; a leaf-dip bioassay with 2nd instars for buprofezin; and a vial bioassay with adults for bifenthrin and endosulfan. Each field population was exposed to the LC50 and LC95 of a known susceptible laboratory colony for each respective insecticide and mortality was compared with that at the same doses predicted from probit analyses of field populations tested in 2007. T-tests were used to determine the significance of differences between the mean mortality at the LC values of each field collected colony compared to the respective LC values of the laboratory susceptible strain. T-tests were also used to determine the significance of differences between the mean of the predicted mortality at the LC values of field collected populations in 2007 and the means of the LC values of field collected populations in 2008-2010 for each insecticide. Results indicated that, based on mortality averaged over all populations evaluated, all of the neonicotinoids indicated decreases in average susceptibility in 2008 and 2009 compared with the 2007 values, although the differences were less for dinotefuran and acetamiprid. The lowest average of mortality at both the LC50 and LC95 in 2008 and 2009 occurred for imidacloprid and thiamethoxam. These neonicotinoids had been in use longer than either of the other two. Mortality values for bifenthrin suggested an overall increase in field susceptibility in 2008 and 2009 while values for endosulfan suggested no change. There were no data predicted for buprofezin in 2007, but the 2008 average mortalities at the LC50 and LC95 were 0.438 and 0.802, respectively, indicating that field susceptibility was at an acceptable level. In 2010 the average susceptibility to the neonicotinoids appeared to have increased compared with previous years; however, the field populations tended to be evaluated after they had been reared in the laboratory without exposure to insecticides for more generations than in previous years. Despite this, average susceptibility to endosulfan appeared to decrease. The results showed the utility of using predicted LC50 and LC95 values, over the use of full dose range, for monitoring changes in susceptibility in field populations thru time. The data presented here provide important information aid to growers and producers in making decisions on insecticide usage. [ABSTRACT FROM AUTHOR]

Chlorantraniliprole 200 mg ai L-1 (Rynaxypyr® 200 SC) is the first xylem systemic insecticide in the new chemistry class, anthranilic diamides. A laboratory systemic bioassay using cut stems of cotton seedlings was developed to quantify the baseline susceptibility of the sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype B, to chlorantraniliprole. Bioassays were conducted for a susceptible laboratory colony and for 11 field populations collected in 2008 and 2009 in Southern Florida. Baseline data of the susceptible colony (targeting first instar nymphs with initial exposure at the egg stage) for chlorantraniliprole in 2008 and 2009, revealed a pooled LC50 and slope values of 0.033 mg ai L-1 and 1.186, correspondingly. With the implementation of the stabilization period in the bioassay method in 2009, the susceptible colony generated LC50 and slope values of 0.182 mg ai L-1 and 0.972, respectively. LC50 and slope values of field collected populations (targeting nymphs as above) ranged from 0.016 to 0.046 mg ai L-1 and 0.889 to 1.595, respectively, in 2008 and 2009. Resistance ratio values at 50% mortality (RR50) on nymphs of field colonies ranged from 0.496 to 1.377. LC50 and slope values of the last 3 field collected populations of 2009, using the stabilization period, ranged from 0.117 to 0.251 mg ai L-1 and 0.885 to 1.395, respectively, and RR50 values ranging from 0.645 to 1.381. The overlapping of the fiducial limits of the LC50 values, the low RR50 values, and no significant differences in the slopes of the probit lines between the laboratory and field colonies, indicate that B. tabaci populations collected in Florida in 2008 and 2009 were highly susceptible to chlorantraniliprole. This anthranilic diamide insecticide is a promising tool in integrated pest management programs for B. tabaci, particularly where field populations have developed resistance to other insecticide groups. The baseline information developed in the present study confirmed the susceptibility of field populations in Florida and represents the basis for future susceptibility monitoring programs to help ensure the continued viability of chlorantraniliprole for B. tabaci management. [ABSTRACT FROM AUTHOR]

The min-max vehicle routing problem (VRP) is a variant of the classical VRP in which the objective is to minimize the duration of the longest route. Examination of the VRP literature indicates that the min-max VRP has received less attention than other variants have over the years. However, the problem has important practical applications, such as those related to routing school buses. In this setting, in addition to the min-max criterion imposed on the time it takes to complete the longest route, school districts are concerned with the minimization of the total distance traveled, which is the objective of the classical VRP. Hence, the problem is formulated as a bi-objective optimization model that trades off service (i.e., the minimization of the longest route) and operational cost (i.e., the minimization of the total distance traveled). We develop a solution procedure for this problem by applying tabu search within the framework of Multiobjective Adaptive Memory Programming and compare it to an implementation of the Non-dominated Sorting Genetic Algorithm--a well-known approach to multiobjective optimization. We also assess the merit of the solution method by comparing our approximations with solution frontiers obtained with an-constraint implementation. [ABSTRACT FROM AUTHOR]

In the current situation, involving a global economic crisis, national economies are under a high pressure. Greek and Irish bailouts have prompted many people to wonder about the economic situation in other countries. The global crisis is causing First World countries need help from institutions such as the IMF or the ECB. The goal of this paper is to analyze the risk that these countries have to be rescued by the economic institutions. In order to prepare this ranking, we are going to use two synthetic indicators. The first one is called Distance Principal Components (DPC) and the other one Goal Programming Synthetic Indicator (GPSI). We develop this indicator taking into account variables from both the public economy and the financial markets. Concerning the public economy, we use variables such as the public debt ratio and its total amount (% of GDP), public revenues, public deficit, real GDP growth and unemployment rate. We strongly believe that the soundness of an economy in the long-term depends on the behavior of these variables. Therefore, if they show a positive trend, other variables exposed to speculation in the financial markets should present a proper behavior as well. With this we mean two variables negotiated in the markets: debt risk premium and credit default swap levels. This paper will bring easily understandable results that will let us know what the bankruptcy situation is in the rest of the countries analyzed. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology for obtaining a synthetic indicator to facilitate decision making in practical situations. It is based on goals provided by the users, which will be included in a synthetic indicator by a goal-programming approach. This methodology facilitates interpreting the values of the synthetic indicator, and thus helps in the decision-making process. We not only formulate these indicators, but also analyze their properties and apply them to the analysis of a complex concept, sustainable tourism. We use this methodology to study the case of coastal areas of Andalusia (Spain), attempting to identify the main characteristics of the different elements, their weakness and strengths. [Copyright &y& Elsevier]

Low-input and large scale grazing systems (LSGS) in Europe are at a crossroads and are facing two contrasting threats: intensification and abandonment (the most extreme form of extensification). Paradoxically, these LSGS constitute large tracts of European rural land in the less favored areas (LFA), which harbor a great part of high nature value (HNV) farmland. Natural and cultural values depend on continuity of the traditional farming practices and this on the social and economic sustainability of the respective farming systems. In this report, we argue that understanding the social dynamic and main binding constraints of particular LSGS is a precedent to institutional reforms and devising sensible schemes of policy support. A community-based research approach with stakeholders' participation was devised within the EU-funded LACOPE research project and applied to five European LSGS. A more structured approach with three phases of the diagnostic methodology and corresponding data is presented for the cereal-sheep farming system of Castile-La Mancha (South-Central Spain). Comparative data are presented for other four European LSGS: the reindeer herding in northernmost Fennoscandia (Northern Sapmi); sheep grazing in the Carpathian (Tatra) mountains of Poland; and heifers' rearing on the Alps in the UNESCO Biosphere Reserve Entlebuch (Switzerland) and Upper Bavaria (Germany). Results in the cereal-sheep systems showed congenial views (social consensus) on the main constraints between the two principal stakeholders, but uncooperative attitudes and lack for social cohesion. Comparative results indicated a common ground of abandonment of the less-favored and far-reaching grazing areas with causes related to inter-Scandinavian border barriers (Northern Sapmi), intensification of more-favored lowland farms (Entlebuch and Upper Bavaria) and lack of social cohesion and structural constraints (Tatra and Castile-La Mancha). A social sustainability tier should be included into the Rural Development guidelines of the EU for actions in HNV farmland, but regional strategy plans should be adapted to particular social dynamic of European LSGS. [ABSTRACT FROM AUTHOR]

European biodiversity significantly depends on large-scale livestock systems with low input levels. In most countries forms of grazing are organized in permanent or seasonal cooperations (land-owner/land-user agents) and covers different landscape such as alpine areas, forest, grasslands, mires, and even arable land. Today, the existence of these structures is threatened due to changes in agricultural land use practices and erratic governmental policies. The present chapter investigates six low-input livestock systems of grassland management with varying degrees of arrangements in different European countries and landscapes. These large-scale grazing systems (LSGS) are reindeer husbandry in Northern Sapmi (Fennoscandia), sheep grazing in the Polish Tatra mountains, cattle grazing in the Swiss and German Alps, cattle, sheep, and pig grazing in Baixo Alentejo, Southern Portugal, and sedentary sheep grazing in Central Spain. These systems showed very heterogeneous organizational patterns in their way of exploiting the pastoral resources. At the same time, these LSGS showed at least some of the following weaknesses such as poor economic performance, social fragility, and structural shortcomings for proper grazing management. Lack of proper mobility of herds/flocks or accession to specific grazing grounds can be a cause of environmental hazards. The surveyed LSGS are mostly dependent on public handouts for survival, but successive policy schemes have only showed mixed effects and, in particular study areas, clear inconsistencies in their aim to stop the general declining trend of LSGS. This research assumed that detailed system research may open the way for better-focused policy intervention, but policymakers need to take advantage of this period of support to push ahead for reforms. Recent European Union (EU) guidelines (2007-2013) on Rural Development Policy (RDP) and its operative scale of high nature value (HNV) farmland can easily fit the structure and functions of low-input grazing systems and LSGS. [ABSTRACT FROM AUTHOR]

Implementation of improved irrigation schedules in some semiarid zones improve water efficiency and can be recommended where occasional periods of heavy rainfall may remove some of the accumulated salts. We hypothesized, however, that the leaching pattern of the main ions may differ regarding their potential contribution to the total salt discharge. The experiment was conducted near Madrid in Spain on a typical Xerofluvent soil with sandy-loam texture in the first 0.5 m. For 4 years, a traditional crop rotation of corn–wheat–corn–oat ( Zea mays L.– Triticum aestivum L.– Zea mays L.– Avena sativa L.) was planted and two irrigation treatments (traditional and improved) were applied only to the corn. In an experimental set-up of 24 plots, samples of the soil solutions were extracted 61 times during the experiment at soil depths of 0.4, 0.9 and 1.4 m. During the experiment, drainage volume was estimated in plots under the two irrigation schedules. Main ions in the soil solution were SO, Cl−, Ca2+, Na+ and HCO. These solutes accounted for 88% of total salt discharge under the two irrigation treatments. Two main patterns of salt leaching were observed. For most main ions, except HCO, the input to discharge ratio was lower than one. Also for HCO, the irrigation treatment did not affect the leaching pattern (higher input than discharge under the two irrigation treatments). Improved irrigation schedules can be implemented without increasing the total salt load, but attention should be paid to specific leaching patterns of individual ions. [ABSTRACT FROM AUTHOR]

The article discusses the application of goal programming with linear fractional criteria to a forest problem. It states that the proposed model to calculate the area to be harvested in a forest plantation in Cuba ensures a balanced age class distribution by the end of the planning horizon. It says that the proposed model allows the calculation of the number of hectares undergoing various treatments to identify the net present value generated by the management planning and reduce clearcutting.

This study proposes a methodology to serve as a guiding mechanism for the allocation and management of university financial resources taking efficiency as its objective. Specifically, an aid model is provided for decision making, so that the planning of staff policy within a university guarantees an equal treatment of all the teaching and research units, greater transparency in the allocation of financial resources, as well as a rational monitoring of the allocations made and their effects on the university efficiency levels. The model we provide is based on the use of two quantitative techniques: data envelopment analysis (DEA) and multiple criteria decision making (MCDM), both techniques being linked in a way which makes it possible to transfer information from one to the other. [Copyright &y& Elsevier]

Extensive livestock farming systems in the Less Favored Areas (LFA) of the European Union (EU) are under social stress and requirement to adapt their production practices to new economic and social realities. This research argues that a restructuring plan for the cereal-sheep system of Castile-La Mancha may represent economic and ecological synergies. The potential implementation of a technical strat- egy (integrating cereal and sheep farming and increasing acreage of annual forage legumes) has been tested within a community-based research project carried out over three phases. Factual and empirical structural and social data were collected, proposal of reforms were submitted for consideration to local agricultural staff and farmers, and a set of guidance standards for restructuring developed. Results showed that both cereal and sheep farming, although carried out in the same land units, were not integrated. The agropastoral system was endangered mainly because the pastoralists (sheep owners) are land-less, while the cultivators (land owners) have a low stake in the grazing operation to enforce the law. Constraints related to the labor factor were more important than grazing land availability. Young farmers rejected the current sheep operation because of the harsh working conditions. Restructuring of the grazing system would require a new legal and institutional framework, a small land redistribution plan, and a new policy scenario that would link the Common Agricultural Policy (CAP) support instrument to structural reforms. [ABSTRACT FROM AUTHOR]

Presents a study which assessed the environmental performance of a traditional grazing system, the cereal-sheep mixed production system of Castile-La Mancha, south central Spain. Information on the traditional mixed-farming system; Structure of the traditional grazing system; Modeling response of farmers to improved grazing practices.

Performance on timing tasks changes with age. Whether these changes reflect a real "clock" problem due to aging or a secondary effect of the reduced cognitive resources of older adults is still an unsettled question. Research on processing of time in aged populations marked by severe mnemonic and/or attentional deficits, such as patients with Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI), may help elucidate the role of cognitive resources in age-related temporal distortions. To this end, we conducted a systematic review and meta-analysis of timing studies in AD and MCI patients; both prospective and retrospective timing tasks were considered and analysed separately. As concerns prospective timing, a first random-effect model showed a medium overall effect of neurodegeneration on timing performance. When considering the role of moderator variables(i.e., neurodegenerative condition, type of measure, participants' age and years of education, interval length, and type of timing task), mean score appeared to be a less sensitive measure than accuracy and variability, and the observed temporal impairment was smaller in older samples. In addition, AD patients only exhibited medium-to-high impairment on prospective timing tasks, whereas MCI patients did not significantly differ from controls. However, assuming a mean age of 70 years old and absolute error as dependent variable, a second fitted meta-regression model predicted a significant outcome also for MCI patients. Concerning retrospective timing, a significant but small effect of neurodegeneration was observed for retrospective judgments. None of the moderators, however, explained between-studies variability. Collectively, our findings highlight a clear deficit in prospective timing for AD patients and underscore several issues that future work should carefully consider to better investigate the effect of MCI on prospective temporal judgements. Results from retrospective timing also point to a possible impairment of retrospective judgments in neurodegenerative conditions, albeit more studies are needed to substantiate this finding. [ABSTRACT FROM AUTHOR]

Comments on the integrated sheep-farming cereal-based system being practiced in Castile-La Mancha. Indicators in evaluating the farming system; Consequences of the farming system; Constraints to the implementation of the farming system.

In an attempt to assess the level of integration of annual forage legumes into the cropping systems of the Mediterranean region, a survey instrument was sent to a broad-specbum of representative experts. Responses characterized respondents by countries and study areas. The questionnaire posed specific questions related to the main physical determinants of the study area, the forage legumes use, the ability of forage legumes acreage to cover the seasonality of natural resources and the qualitative opinions of representative experts on the role of forage legumes, agricultural policy and structural limitation to current sheep production methods. A total of 23 questionnaires were returned with a rate of response of 34 oer cent. Greater than 70 ver cent of resuondents considered that cro&livestock systems are askxiated. ~owkver, a forage deficit was detected in all but one of the study areas. Respondents considered that fann size and fragmentation is the main limitation to the transition from open and hard-working systems to semi-enclosed sheep production methods. Most respondents (95 per cent) agreed that social attitudes toward current methods of sheep and goat farming are preventing a positive approach of fanners toward forage legumes cultivation. [ABSTRACT FROM PUBLISHER]

Attention comprises a wide set of processes such as phasic alertness, orienting, executive control, and the executive (i.e., detecting infrequent targets) and arousal (i.e., sustaining a fast reaction) vigilance components. Importantly, the effects of transcranial direct current stimulation (tDCS) over attentional functioning have been mostly addressed by measuring these processes separately and by delivering offline tDCS with low precision over the stimulation region. In the current study, we examined the effects of online High-Definition tDCS (HD-tDCS) over the behavioral and electrophysiological functioning of attentional and vigilance components. Participants (N = 92) were randomly assigned to one of three stimulation groups: right dorsolateral prefrontal cortex stimulation, right posterior parietal cortex (PPC) stimulation, and sham. All of them performed – in combination with the HD-tDCS protocol – an attentional networks task (ANTI-Vea) suitable to measure the executive and arousal components of vigilance along with three typical attentional functions: phasic alertness, orienting, and executive control. In addition, EEG was registered at the baseline and at the post-stimulation period. We observed that, regardless the stimulation region, online HD-tDCS: (a) reduced phasic alertness (p =.008), but did not modulated the orienting and executive control functioning; and (b) mitigated the executive vigilance decrement (p =.011), but did not modulated arousal vigilance across time-on-task. Interestingly, only HD-tDCS over PPC reduced considerably the increment of alpha power observed across time-on-task (p =.009). The current study provides further evidence for both an empirical dissociation between vigilance components and the cortical regions underlying attentional processes. We highlight the advantages of using online HD-tDCS to examine the stimulation effects on attentional and vigilance functioning. • Further evidence on the dissociation of executive and arousal vigilance is provided. • The executive vigilance decrement was reduced by online HD-tDCS. • The arousal vigilance decrement was not modulated by online HD-tDCS. • Online HD-tDCS modulated phasic alertness but not orienting and/or executive control. • Alpha power shifts across time in the parietal cortex were modulated by HD-tDCS. [ABSTRACT FROM AUTHOR]

• Considering a real routing problem and modeling it with 4 objective functions. • Solving system combining metaheuristics with achievement scalarizing function. • Developing the methodology to apply iterated greedy to a multi objective problem. • Performing exhaustive experimentation to test the method. • Improving both the currently implemented solution and NSGA-II. In the last few years, the application of decision making to logistic problems has become crucial for public and private organizations. Efficient decisions clearly contribute to improve operational aspects such as cost reduction or service improvement. The particular case of waste collection service considered in this paper involves a set of economic, labor and environmental issues that translate into difficult operational problems. They pose a challenge to nowadays optimization technologies since they have multiple constraints and multiple objectives that may be in conflict. We therefore need to resort to multiobjective approaches to model and solve this problem, providing efficient solutions in short computational times. In particular, we consider four different objectives to model the waste collection problem: travel cost, route length balance, route time balance, and number of routes. We propose an iterated greedy algorithm coupled with a variable neighborhood search to minimize an achievement function to determine a good approximation to the Pareto front. The performance of our method is empirically analyzed on a set of instances (both generated and real), and compared with the well-known NSGA-II and SPEA2 methods. The comparison favors our proposal. [ABSTRACT FROM AUTHOR]

Continuing medical education and continuing professional development have been affected by the ongoing 2019 novel coronavirus disease (COVID-19) pandemic. Therefore, we developed the 2020 International Web-Based Neurosurgery Congress (2020 IWBNC), which became the first successful virtual neurosurgical congress. The aim of this article was to describe the experience designing and organizing a web congress by the 2020 IWBNC method. The 2020 IWBNC was organized by the Center for Research and Training in Neurosurgery (Centro de Investigación y Entrenamiento en Neurocirugía [CIEN]) in a record time of 4 weeks. Eight committees were created and assigned a specific task. The event followed a strict protocol based on the double-room method, which consisted of 2 virtual rooms (A and B) hosted from 4 different physical locations to avoid lecture overlapping and connection drops. Quality and impact were measured by a videoconferencing platform and social media parameters as well as an audience perception survey. High quality was achieved in academic standards, worldwide assistance, schedule adherence, and security. The 2020 IWBNC hosted 25 internationally renowned speakers and offered 30 top-of-the-line multidisciplinary conferences. There were 3096 participants from 125 countries, and 22,266 live-stream views were registered. No technical or cybersecurity-related issues occurred. Web-based academic meetings will continue to be a helpful educational tool for continuing medical education and continuing professional development. The 2020 IWBNC double-room method represents an alternative design that may be replicated by the academic community planning web congresses and similar events. [ABSTRACT FROM AUTHOR]

Serious games have proven to be a powerful tool in education to engage, motivate, and help students learn. However, the change in student knowledge after playing games is usually measured with traditional (paper) prequestionnaires–postquestionnaires. We propose a combination of game learning analytics and data mining techniques to predict knowledge change based on in‐game student interactions. We have tested this approach in a case study for which we have conducted preexperiments–postexperiments with 227 students playing a previously validated serious game on first aid techniques. We collected student interaction data while students played, using a game learning analytics infrastructure and the standard data format Experience API for Serious Games. After data collection, we developed and tested prediction models to determine whether knowledge, given as posttest results, can be accurately predicted. Additionally, we compared models both with and without pretest information to determine the importance of previous knowledge when predicting postgame knowledge. The high accuracy of the obtained prediction models suggests that serious games can be used not only to teach but also to measure knowledge acquisition after playing. This will simplify serious games application for educational settings and especially in the classroom easing teachers' evaluation tasks. Lay Description: What is currently known about the subject matter Serious games are a powerful tool to engage, motivate, and help students learn.Pre‐post experiments are commonly used to measure knowledge acquisition.Game learning analytics can be applied to interaction data from games. What this paper adds We present a two‐step approach combining game learning analytics and data mining to predict players' performance in serious games based on their interactions.The approach is tested in a case study with pre‐post experiments collecting interaction data with 227 students playing a serious game to determine if performance can be accurately predicted.The comparison of prediction models has helped to determine if pretest information is essential.The highly accurate prediction models obtained suggest that games can be used to teach and measure knowledge acquisition after playing. Implications of study findings for practitioners The approach aims to simplify the measurement of players' learning with serious games.It may be generalized at least to similar scenarios (e.g., games for procedural learning or game‐likesimulations) where similar interaction data are feasible.Game mechanics and educational design should define the interaction data to capture.Using an accepted standard tracking profile is a clear recommendation. [ABSTRACT FROM AUTHOR]

Collet-Sicard syndrome (CSS) is the unilateral palsy of the cranial nerves (CN) IX, X, XI, and XII. To our knowledge, no review describes the characteristics of patients diagnosed with CSS. Therefore, this review aims to collect and describe all cases in the literature labeled as CSS. We performed a scoping review of the literature and conducted a database search in Embase and PubMed. We included articles and abstracts with case reports or case series of patients with CSS diagnosis. We classified the cases into two groups: "CSS", referring to patients presenting exclusively with IX-XII nerve involvement, and "CSS-plus", which corresponds to cases with CSS and other neurological impairments. We included 135 patients from 126 articles, of which 84 (67.7%) were male. The most common clinical manifestations reported were dysphagia and dysphonia. The most common etiology was tumoral in 53 cases (39.6%) and vascular in 37 cases (27.6%). The majority of patients showed partial or total improvement, with just over half receiving conservative treatment. The most frequent anatomic space was the jugular foramen (44.4%) and the parapharyngeal retrostyloid space (28.9%). Approximately 21% of the patients had other CN impairments, with the seventh and eighth CN most frequently compromised. We conclude that although there is a need for greater rigor in CSS reporting, the syndrome has a clear utility in identifying the localization of jugular foramen and parapharyngeal retrostyloid space pathology. [ABSTRACT FROM AUTHOR]

It has been proposed that attention triggered by eye-gaze may represent a unique attentional process, different from that triggered by non-social stimuli such as arrows. To investigate this issue, in the present study we compared the temporal dynamics of the conflict processing triggered by eye-gaze and arrow stimuli. We investigated the electrophysiological activity during a task in which participants were required to identify the direction of laterally presented eye-gaze or arrow targets. Opposite behavioural effects were observed: while arrows produced the typical effect, with faster responses when they were congruent with their position, eye-gaze targets produced a reversed effect with faster responses when they were incongruent. Event-related potentials showed common and dissociable congruency modulation: whereas eye-gaze and arrows showed similar effects on earlier ERP components (P1 and N1), they led to opposite effects in later components such as N2 and P3. This represents the first electrophysiological demonstration of both early shared and later dissociable congruency effects for eye-gaze and arrow stimuli. • We compared the temporal dynamics of the conflict triggered by gaze and arrows. • These stimuli led to opposite behavioural interference effects. • P1 and N170 potentials displayed common interference modulation for both stimuli. • Later stages, indexed by the N2 and the P3, reflected opposite conflict effects. [ABSTRACT FROM AUTHOR]

Currently, water and sewer companies face the challenge of improving their quality of service to customers (QSC). Performance indicators are essential to monitor and benchmark the QSC of water companies; however, individual indicators do not provide a holistic evaluation of the quality of water and sewer services provided to customers. This study proposes an innovative QSC index based on distance-function techniques that makes it possible to compare changes in the QSC of water companies among locations and temporal periods. A case study assesses changes in QSC for a sample of Chilean water and sewer companies from 2007 to 2014. The results show that in spite of the efforts made by the water regulator, QSC has remained almost constant over a number of years, with 2010 having the best performance. The methodology proposed in this study is useful for water regulators to benchmark water companies when developing policies that prompt QSC improvements. [ABSTRACT FROM AUTHOR]

The selection of the most appropriate wastewater treatment (WWT) technology is a complex problem since many alternatives are available and many criteria are involved in the decision-making process. To deal with this challenge, the analytic network process (ANP) is applied for the first time to rank a set of seven WWT technology set-ups for secondary treatment in small communities. A major advantage of ANP is that it incorporates interdependent relationships between elements. Results illustrated that extensive technologies, constructed wetlands and pond systems are the most preferred alternatives by WWT experts. The sensitivity analysis performed verified that the ranking of WWT alternatives is very stable since constructed wetlands are almost always placed in the first position. This paper showed that ANP analysis is suitable to deal with complex decision-making problems, such as the selection of the most appropriate WWT system contributing to better understand the multiple interdependences among elements involved in the assessment. [ABSTRACT FROM AUTHOR]

General equilibrium macroeconomic models are a basic tool for understanding how the economy functions, how the main macroeconomic variables are related, and the final outcome of economic policies. The teaching of these models is essentially achieved through a system of mathematical equations accompanied by the use of concatenated graphs representing the markets involved in the economy. However, the way these graphs are traditionally taught does not allow the learner to easily understand how they are related or for changes in a model's graphical outputs (curves) to be visualized. Here, a simulation program is presented and the effectiveness of its application to a group of macroeconomics students at the University of Seville during the 2011/12 academic year is evaluated. Analysis of variance (ANOVA) of all students' scores and some complementary statistical tests were applied with a view to distinguishing between students who used the simulator with the aid of a teacher, students who used the simulator without this assistance, and students who studied the topic in a conventional manner in the classroom. The average score obtained by the first-mentioned group in a model comprehension test was significantly higher than that of the second group, which in turn was higher than that of the third group taught using the conventional approach. [Copyright &y& Elsevier]

Perimeter detection systems detect intruders penetrating protected areas, but modern solutions require the combination of smart detectors, information networks and controlling software to reduce false alarms and extend detection range. The current solutions available to secure a perimeter (infrared and motion sensors, fiber optics, cameras, radar, among others) have several problems, such as sensitivity to weather conditions or the high failure alarm rate that forces the need for human supervision. The system exposed in this paper overcomes these problems by combining a perimeter security system based on CEMF (control of electromagnetic fields) sensing technology, a set of video cameras that remain powered off except when an event has been detected. An autonomous drone is also informed where the event has been initially detected. Then, it flies through computer vision to follow the intruder for as long as they remain within the perimeter. This paper covers a detailed view of how all three components cooperate in harmony to protect a perimeter effectively, without having to worry about false alarms, blinding due to weather conditions, clearance areas, or privacy issues. The system also provides extra information of where the intruder is or has been, at all times, no matter whether they have become mixed up with more people or not during the attack. [ABSTRACT FROM AUTHOR]

The tourist sector has undergone many changes in recent years due to technological progress and demographic change. On the one hand, there have been immense advances in communication technology and easy access to the Internet, which have led to the globalization of tourist information and greater numbers of tourists being able to access information on a huge number of products. On the other hand, a substantial change has taken place in tourist preferences and behaviour, with a move away from standard trips to other more personalized options, where customer preferences are taken into account. They are not only looking for sun and beach activities, but are also interested in culture and heritage, thus distributing their time between cultural visits and relaxation and leisure. When planning a tour, the tourist's objectives may be in conflict because, among other factors, the most important attractions are usually the most expensive, and thus the tourist is clearly faced with a multiobjective problem. We develop a model to solve this problem, taking into account the diverse economic costs (transport, the cost of different activities, lodging, etc), the timing of the different activities, and his/her particular preferences. [ABSTRACT FROM AUTHOR]

• Eco-efficiency assessment of municipalities in the provision of solid waste services. • Eco-efficiency evaluation integrates unsorted waste as undesirable output. • Global inefficiency and individual inefficiency scores were computed. • Exogenous variables affecting eco-efficiency scores were investigated. Improving the eco-efficiency of municipalities in the provision of municipal solid waste (MSW) services is fundamental in the context of a circular economy. This study evaluates the eco-efficiency of a sample of Spanish municipalities, integrating the total cost as input, recyclable waste as desirable output, and unsorted waste as undesirable output. Following a pioneering approach, the weighted Russell directional distance model (a non-radial data envelopment analysis model) was employed, which allowed us to obtain a global inefficiency score and individual inefficiency scores for each variable integrated in the model. In the second stage of analysis, the potential factors affecting the previously computed inefficiency scores were investigated. The results indicated that one third of the municipalities evaluated were eco-efficient in the provision of MSW services with the total cost being the variable in which the municipalities exhibited the best performance. Moreover, the size of the municipalities, population served, population density, tourism, and availability of containers for separative collection of paper, glass, and plastic significantly affect the eco-efficiency of the municipalities. The findings of this study provide detailed information to support decision-making for the policy makers to improve the eco-efficiency of the municipalities in managing MSW. [ABSTRACT FROM AUTHOR]

Activation of the oncogenic potential of ras oncogenes occurs by point mutations at codons 12, 13, 59, 61, and 63 of the sequences that codify for its product, a 21-kDa protein designated as p21. This activation has been postulated by computer models as modifiers of the structure of the protein, which may alter its biochemical and biological activities. We have expressed in bacteria the normal ras p21 and five mutated p21 proteins with mutations at positions 12, 59, 61, 12 plus 59, and 12 plus 61. Purification was carried out by solubilization from bacterial pellets in 7 M urea and chromatography through a Sephadex G-100 column to obtain >95% purified proteins. Circular dichroic (CD) spectra showed that the normal protein and that activated by substitution of Ala59 to Thr59 are very similar in their overall structure. By contrast, point mutations affecting either 12 or 61 residues substantially altered the structure of the proteins. When the parameters of Chen et al. [Biochemistry 11, 4120-4131 (1972)] were applied to the CD spectra, both normal and thr59-mutated ras proteins showed a less organized structure than mutated proteins at position 12 or 61. Since the Thr59 mutant has a more similar transforming activity than other activated proteins, but a GTPase activity similar to that of the normal protein, our results support the hypothesis that there is more than one mechanism of activation of the ras p21 protein. One of these mechanisms involves important structural alterations by point mutations at position 12 or 61 which reduce the GTPase activity of the protein. Another mechanism will be that induced by a substitution of Ala59 to Thr59 which does not substantially alter the protein conformation. A putative alternative mechanism for the activation of this mutant is discussed. [ABSTRACT FROM AUTHOR]