Computational aspects of minimizing conditional value-at-risk

Abstract.: We consider optimization problems for minimizing conditional value-at-risk (CVaR) from a computational point of view, with an emphasis on financial applications. As a general solution approach, we suggest to reformulate these CVaR optimization problems as two-stage recourse problems of stochastic programming. Specializing the L-shaped method leads to a new algorithm for minimizing conditional value-at-risk. We implemented the algorithm as the solver CVaRMin. For illustrating the performance of this algorithm, we present some comparative computational results with two kinds of test problems. Firstly, we consider portfolio optimization problems with 5 random variables. Such problems involving conditional value at risk play an important role in financial risk management. Therefore, besides testing the performance of the proposed algorithm, we also present computational results of interest in finance. Secondly, with the explicit aim of testing algorithm performance, we also present comparative computational results with randomly generated test problems involving 50 random variables. In all our tests, the experimental solver, based on the new approach, outperformed by at least one order of magnitude all general-purpose solvers, with an accuracy of solution being in the same range as that with the LP solver

Better off without? Benefits and costs of resolving goal conflict through goal shelving and goal disengagement

Pursuing multiple goals with limited time often leads to goal conflicts that can be resolved by prioritizing some goal pursuits over others. This research examines proximal outcomes of two approaches to goal prioritization: Goal shelving (temporarily withdrawing from a goal) and goal disengagement (permanently withdrawing from a goal). We conducted an experiment (N = 214) to compare motivational and emotional consequences of resolving goal conflict through goal shelving and disengagement. Results suggest that goal shelving and disengagement are similarly effective at reducing different facets of experienced goal conflict, but people regret shelving goals less than disengaging from them. Together, these findings provide first evidence that goal shelving may allow people to “have their cake and eat it too:” to reap the benefits of goal prioritization while minimizing its costs

Analysis of the Security and Memorability of the Password Card

Choosing and remembering secure passwords poses a problem to users. The password card is a proposal intended to help users to cope with this problem. It is a paper card with a grid of random letters, numbers, and symbols, on which users choose a starting point and a walk of adjacent cells. The characters on the traversed cells form the new password. We analyze the security and memorability of passwords created this way. We find that users mostly choose predictable walks and starting points. At the same time, memorability of the passwords seems low. Thus, the password card seems to fail in helping users to choose and remember secure passwords

Managing Organizational Identity Challenges Caused By AI Implementation: The Role Of AI Principles

Alongside growing external pressure for implementation of Artificial Intelligence (AI) technologies, multi-stakeholder demands for responsible conduct have led to an increasing number of organizational AI principles. As previous research on AI principles has mainly focused on their content, restrictions, and external functions, little is known about their relevance for organization-internal stakeholders. Concurrently, while organizational identity was shown to play a central role in technology implementation’s success or failure, with respect to AI implementation, the concept has remained unexplored. Building on 25 expert interviews as part of an ongoing research that involves a qualitative, cross-industry multiple-case study with 13 organizations, we reveal AI principles’ capacities for managing organizational identity towards AI implementation by: (1) redefining organizational identity, and (2) aligning organizational identity’s facets. Our findings accentuate the relevance of organizational identity for AI implementation, and indicate AI principles’ role as a tool to manage this transformative change in an identity-conforming way

Temporal Evolution and Strength of Neural Activity in Parietal Cortex during Eye and Hand Movements

The role of area 7a in eye-hand movement was studied by recording from individual neurons while monkeys performed 7 different tasks, aimed at assessing the relative influence of retinal, eye, and hand information on neural activity. Parietal cell activity was modulated by visuospatial signals about target location, as well as by information concerning eye and/or hand movement, and position. The highest activity was elicited when the hand moved to the fixation point. The population activities across different memory tasks showed common temporal peaks when aligned to the visual instruction (visuospatial peak) or Go signal (motor peak) for eye, hand, and coordinated eye-hand movement. The motor peak was higher for coordinated eye-hand movement, and it was absent in a No-Go task. Two activation maxima were also observed during visual reaching. They had the same latency of the visuospatial and motor peaks seen in the memory tasks. Therefore, area 7a seems to operate through a common neural mechanism underlying eye, hand, or combined eye-hand movement. This mechanism is revealed by invariant temporal activity profiles and is independent from the effector selected and from the presence or absence of a visible target during movement. For comparative purposes, we have studied the temporal evolution of the population activity in the superior parietal lobule (SPL) during the same reaching tasks and during a saccade task. In SPL, the population activity was characterized by a single peak, time locked to the Go signal for eye, hand, or combined eye-hand movement. As in IPL, the time of occurrence of this peak was effector independent. The population activity remained unchanged when the position of the eye changed, suggesting that SPL is mostly devoted to the hand motor behavior

Regulation of cell cycle and DNA damage response in mouse oocytes.

A specific feature of mammalian oocytes is a long prophase I arrest, which can be maintained for many years in humans. The oocytes must ensure robust mechanisms, which can keep them in prophase I, but effectively trigger meiotic resumption when required. Consequently, throughout the maturation of an oocyte, non-erroneous chromosome segregation is a prerequisite for the generation of healthy offspring. In this study we aimed to investigate the new roles of Aurora A (AURKA) and polo-like kinase 1 (PLK1) in the regulation of the cell cycle progression. For this purpose, we used transgenic mice that specifically overexpress wild type (WT-) or kinase-dead (KD-) AURKA in oocytes only, and to study PLK1 we treated oocytes with BI2536, a small molecule inhibitor known to specifically inhibit PLK1 in somatic cells. Our data show, that both AURKA and PLK1 are not essential for meiotic resumption, however they participate in this process. Active AURKA regualtes the increase in microtubule organizing centers (MTOC) in prophase I, which is the first visible marker of resumption of meiosis in oocytes. AURKA activation is biphasic, and the initial increase in MTOC is transient, while full AURKA activation needed for the stability of MTOC requires the activity of Cyclin-dependent kinase 1 (CDK1). We show that PLK1...Buněčný cyklus savčích oocytů je dočasně zastaven v průběhu profáze I. meiotického dělení a v tomto stádiu mohou oocyty přetrvávat až několik desítek let. V oocytech proto musí fungovat účinné mechanismy, které je udržují v profázi I a umožňují znovuzahájení meiózy, když je potřeba. Následně, správná segregace chromozomů během maturace oocytů je podmínkou pro vývoj zdravých potomků. Naším cílem bylo zjistit nové role AURKA a PLK1 kináz v regulaci buněčného cyklu. Použili jsme transgenní myši, které nadprodukují wild type (WT-) nebo neaktivní (kinase- dead, KD-) AURKA pouze v oocytech, a ke studiu PLK1 kinázy jsme použili specifický inhibitor BI2536, jehož účinnost je ověřená v somatických buňkách. Naše data ukazují, že jak AURKA tak PLK1 nejsou nezbytné pro znovuzahájení meiózy, i když obě kinázy se tohoto procesu účastní. Aktivní AURKA reguluje proces multiplikace mikrotubuly organizujících center (MTOC) v profázi I, což je první viditelná známka znovuzahajení meiózy. Aktivace AURKA je bifázní, proto primární nárůst počtu MTOC je tranzientní. Plná aktivace AURKA, která je potřebná pro stabilitu MTOC, vyžaduje aktivitu Cyklin-dependentní kinázy 1 (CDK1). Ukázali jsme, že PLK1 se účastní rozpadu jaderné membrány během znovuzahájení meiózy. Jak AURKA tak PLK1 se podílí na akumulaci centrozomálních...Department of Cell BiologyKatedra buněčné biologieFaculty of SciencePřírodovědecká fakult

Veränderungen in der subchondralen Knochenplatte am Tibiaplateau des Kaninchen nach Meniskektomie

Ziel der tierexperimentellen Studie war es Veränderungen in der Mineralisierungsverteilung in der subchondralen Knochenplatte in der frühen Phase nach Arthoseinduktion mittels Meniskektomie zu untersuchen. Die Mineralisierungs-verteilung spiegelt die Beanspruchung einer Gelenkfläche wieder. Mit Hilfe der Methode der CT-OAM war es möglich die Mineralisierungsverteilung der tibialen Gelenkfläche flächenhaft darzustellen und quantitativ auszuwerten. Diese Mehtode kann auch an kleinen Gelenken angewendet werden. Zur Analyse der Mineralisierungsverteilung wurde ein intraindividueller Vergleich gewählt. Zur Dokumentation des zeitlichen Ablaufes der Veränderungen in der subchondralen Knochenplatte nach mechanischer Arthroseinduktion wurde ein Beobachtungszeitraum von 2,4,8,12 und 24 Wochen festgelegt. Es hat sich gezeigt, dass die subchondrale Knochenplatte frühzeitig mit einer Umverteilung der Mineralisierung reagiert, was als Anpassung des Knochens auf die veränderte Beanspruchung anzusehen ist

More than a feeling: A unified view of stress measurement for population science.

Stress can influence health throughout the lifespan, yet there is little agreement about what types and aspects of stress matter most for human health and disease. This is in part because "stress" is not a monolithic concept but rather, an emergent process that involves interactions between individual and environmental factors, historical and current events, allostatic states, and psychological and physiological reactivity. Many of these processes alone have been labeled as "stress." Stress science would be further advanced if researchers adopted a common conceptual model that incorporates epidemiological, affective, and psychophysiological perspectives, with more precise language for describing stress measures. We articulate an integrative working model, highlighting how stressor exposures across the life course influence habitual responding and stress reactivity, and how health behaviors interact with stress. We offer a Stress Typology articulating timescales for stress measurement - acute, event-based, daily, and chronic - and more precise language for dimensions of stress measurement

The Role Of Higher Education In Personal Relationships

The roles within personal relationships have evolved throughout the years. What was once a “traditional” role within a household is now considered outdated and old-fashioned. These roles have been influenced by many factors, one of those being higher education. A study was conducted to examine how those roles have been influenced by higher education. In the late 1940’s, many U.S. women stayed home, raised their children and did not work outside the home unless there was a missing male figure to provide for the family. Although women may have wanted to venture into the workforce, it wasn’t widely accepted.  However, a Census Bureau study in 1948 found that 17 million women were in the paid labor force (Walker 1998)