Dynamic control of a single-server system with abandonments

In this paper, we discuss the dynamic server control in a two-class service system with abandonments. Two models are considered. In the first case, rewards are received upon service completion, and there are no abandonment costs (other than the lost opportunity to gain rewards). In the second, holding costs per customer per unit time are accrued, and each abandonment involves a fixed cost. Both cases are considered under the discounted or average reward/cost criterion. These are extensions of the classic scheduling question (without abandonments) where it is well known that simple priority rules hold. The contributions in this paper are twofold. First, we show that the classic c-μ rule does not hold in general. An added condition on the ordering of the abandonment rates is sufficient to recover the priority rule. Counterexamples show that this condition is not necessary, but when it is violated, significant loss can occur. In the reward case, we show that the decision involves an intuitive tradeoff between getting more rewards and avoiding idling. Secondly, we note that traditional solution techniques are not directly applicable. Since customers may leave in between services, an interchange argument cannot be applied. Since the abandonment rates are unbounded we cannot apply uniformization-and thus cannot use the usual discrete-time Markov decision process techniques. After formulating the problem as a continuous-time Markov decision process (CTMDP), we use sample path arguments in the reward case and a savvy use of truncation in the holding cost case to yield the results. As far as we know, this is the first time that either have been used in conjunction with the CTMDP to show structure in a queueing control problem. The insights made in each model are supported by a detailed numerical study. © 2010 Springer Science+Business Media, LLC

Introduction revisiting the Argentine crisis a decade on: changes and continuities

This introductory chapter to the book "Argentina Since the 2001 Crisis Recovering the Past, Reclaiming the Future" analyses crisis and its associated responses and subsequent recovery in the context of Argentina’s multiple implosion of 2001-02 whilst also assessing its legacies for the country’s social, cultural, economic and political realms during the last decade. It recognises that "crisis" is a term that is much used in the post-Lehman Brothers world and that the subsequent responses and associated recoveries (or lack of) have been the subject of a cascade of academic, government, media, and think-tank investigation ever since. The chapter instead seeks to understand the nature of how crisis and its impacts should be investigated and interrogated, by rejecting false dichotomies of ‘old’ and ‘new’ and synthesising understanding to form an analysis that draws both elements of continuity and elements of change. Secondly, it argues that crisis manifests itself in a number of realms, and that heuristic devices employed to investigate them must subsequently also be drawn from across a range of disciplinary perspectives. Thirdly, it examines how the 2001-02 crisis in Argentina led to a series of responses that both rejected the neoliberal model yet also recovered elements of it. Finally it outlines the structure of the rest of the book, briefly summarising the chapters in turn

Fermion-Boson Interactions and Quantum Algebras

Quantum Algebras (q-algebras) are used to describe interactions between fermions and bosons. Particularly, the concept of a su_q(2) dynamical symmetry is invoked in order to reproduce the ground state properties of systems of fermions and bosons interacting via schematic forces. The structure of the proposed su_q(2) Hamiltonians, and the meaning of the corresponding deformation parameters, are discussed.Comment: 20 pages, 10 figures. Physical Review C (in press

Attentional bias for threat: Evidence for delayed disengagement from emotional faces

The present paper reports three new experiments suggesting that the valence of a face cue can influence attentional effects in a cueing paradigm. Moreover, heightened trait anxiety resulted in increased attentional dwell-time on emotional facial stimuli, relative to neutral faces. Experiment 1 presented a cueing task, in which the cue was either an "angry", "happy", or "neutral" facial expression. Targets could appear either in the same location as the face (valid trials) or in a different location to the face (invalid trials). Participants did not show significant variations across the different cue types (angry, happy, neutral) in responding to a target on valid trials. However, the valence of the face did affect response times on invalid trials. Specifically, participants took longer to respond to a target when the face cue was "angry" or "happy" relative to neutral. In Experiment 2, the cue-target stimulus onset asynchrony (SOA) was increased and an overall inhibition of return (IOR) effect was found (i.e., slower responses on valid trials). However, the "angry" face cue eliminated the IOR effect for both high and low trait anxious groups. In Experiment 3, threat-related and jumbled facial stimuli reduced the magnitude of IOR for high, but not for low, trait-anxious participants. These results suggest that: (i) attentional bias in anxiety may reflect a difficulty in disengaging from threat-related and emotional stimuli, and (ii) threat-related and ambiguous cues can influence the magnitude of the IOR effect

Modo borderline e mundo do trabalho: um ensaio sobre implicações e perspectivas atuais

Resumo Partindo do pressuposto de que o modo border line parece constituir uma nova "normalidade" atualmente, este artigo busca discutir a sociedade contemporânea em seus modos de vida e o impacto sobre o mundo do trabalho. A busca constante pelo sucesso e pela realização profissional atravessa, consequentemente, as relações de trabalho, que constituem o sujeito. Não há tempo para vazios! É preciso produzir. Considera-se para a discussão o que chamamos de "modo borderline", pensado a partir de sua dimensão fenomenológica e não estrutural, portanto, não a partir do paradigma da psicopatologia individual, mas como sintoma da cultura, em uma sociedade marcada pela im pulsividade, fragilidade dos laços sociais e pela chamada "cultura do narcisismo". Através de uma abordagem psicanalítica e com breve descrição da evolução dos modos de trabalho e produção ao longo dos anos, propõe-se uma discussão a respeito dessas novas configurações de vida implicadas no mundo do trabalho, pensando, sobretudo, em como se dá essa relação na contemporaneidade, em pleno capitalismo flexível

Enhanced Processing of Threat Stimuli under Limited Attentional Resources

The ability to process stimuli that convey potential threat, under conditions of limited attentional resources, confers adaptive advantages. This study examined the neurobiology underpinnings of this capacity. Employing an attentional blink paradigm, in conjunction with functional magnetic resonance imaging, we manipulated the salience of the second of 2 face target stimuli (T2), by varying emotionality. Behaviorally, fearful T2 faces were identified significantly more than neutral faces. Activity in fusiform face area increased with correct identification of T2 faces. Enhanced activity in rostral anterior cingulate cortex (rACC) accounted for the benefit in detection of fearful stimuli reflected in a significant interaction between target valence and correct identification. Thus, under conditions of limited attention resources activation in rACC correlated with enhanced processing of emotional stimuli. We suggest that these data support a model in which a prefrontal “gate” mechanism controls conscious access of emotional information under conditions of limited attentional resources

Auditory-Visual Object Recognition Time Suggests Specific Processing for Animal Sounds

cote interne IRCAM: Suied09bNone / NoneNational audienceAuditory-visual object recognition time suggests specific processing for animal sound

Do Associations Support Authoritarian Rule? Tentative Answers from Algeria, Mozambique, and Vietnam

Whether associations help to democratise authoritarian rule or support those in power is a contested issue that so far lacks a cross-regional perspective. Drawing on relational sociology, this paper explores the impact of state power in Algeria, Mozambique, and Vietnam on associations and vice versa. We focus on decision-making in associations and on three policy areas - welfare policy concerning HIV/AIDS, economic policy concerning small and mediumsized enterprises, policies concerning gender equality and the rights of women and sexual minorities - to assess the relations between associations and the state's infrastructural and discursive power. Most associations interviewed by us in the three countries accept or do not openly reject the state's and/or the state ruling party's various forms of interference in internal decision-making processes. Whereas associations in Algeria and Vietnam help to maintain the state's control through welfare provision, associations in Mozambique can weaken this form of infrastructural state power. Moreover, business and professionals' associations in all three countries help maintain the state's control through limited participation, i.e. another form of infrastructural state power. Finally, associations in all three countries support the state's discourse and policies in the area of gender equality and women's rights, though in all three countries at least some NGOs help weaken this form of state power

Brief Report: Attenuated Emotional Suppression of the Attentional Blink in Autism Spectrum Disorder: Another Non-Social Abnormality?

Twenty-five individuals with Autism Spectrum Disorder and 25 typically developed individuals participated in an Attentional Blink paradigm to determine whether emotional words would capture attention similarly in the two groups. Whilst the emotionality of words facilitated attention in typical comparison participants, this effect was attenuated in the ASD group. The magnitude of the emotional modulation of attention in ASD also correlated significantly with participants’ VIQ, which was not observed for the comparison group. Together these observations replicate and extend the findings of Corden et al. (J Autism Develop Disord 38:1072–1080, 2008) and implicate abnormalities in emotional processes outside the broader context of social cognition in ASD. We discuss our findings in relation to possible abnormalities in amygdala function that may underlie the disorder