The night float paradigm to decrease sleep deprivation: good solution or a new problem?

In the late 1980s physician residency training programs developed the night float rotation, characterized by a sequence of 5 - 15 days of night work without any daytime duties, thereby involving an abrupt reversal of the wake - sleep schedule. We examined the effect of the night float rotation on sleep, mood and performance of pediatric residents. Residents completed sleep diaries daily, and tests of mood (Profile of Mood States) and attention (Conner's Continuous Performance Test) three times a week during the two-week night float rotation, and during equivalent blocks of time of their daytime rotations. Results show that, despite having ample opportunity to sleep during the day, while on night float rotation residents slept less than during the nights of their normal daytime rotations, 6.3 h +/- 2.5 h and 7.2 h +/- 1.7 h, respectively, p < 0.0001. Also, during night float compared to daytime rotations residents had increased fatigue-inertia scores, 8.7 +/- 4.1 and 4.8 +/- 2.4, respectively, p < 0.0001, and decreased vigor-activity scores 10.7 +/- 5.4 and 14.8 +/- 5.3, respectively, p = 0.02. The scores for attention were not significantly different between night float and daytime rotations. The correlation coefficients of fatigue with measures of attention were not statistically significant for daytime rotations. However, for night float fatigue correlated with omission errors, r = 0.51, p = 0.001 and with attentiveness r = - 0.36, p = 0.03. Training programs that adopt the night float rotation must be aware of potential deleterious effects of the night float rotation as they may lead to serious consequences on residents' performance and patients' safety.     

The passport control problem or how to keep a dynamic service system load balanced?

In many real life situations (such as department stores, or passport control booths in airports) parallel queues are formed in front of control stations. Typically, some of the stations are manned while others are not. Classical queuing theory considers the configuration constant, and concentrates on the arrival process. This work explores a new line of research—the case in which the configuration is dynamic, and the customers can plan to cope with anticipated changes. Specifically, as the queues build up, management assigns additional officers to the unmanned stations. When this happens—some people move to the newly manned queues from nearby busy queues. In anticipation, people may prefer to line up in busy queues next to unmanned ones.Mathematically we discuss the problem of dynamic arrangement of the queues in a service system where at any time each server can be in either an active or an inactive mode. A balancing strategy determines how customers will be reallocated when a station becomes active. Given a balancing strategy, we seek a partition of customers to queues that minimizes the maximum wait time of a customer in each of the active stations, thereby keeping the system balanced at all times. We study two balancing strategies that we call Split and Trim. For the Split strategy we discuss a special case (the stations are ordered on a line and a single unmanned station is at one end). We show how an optimal partition can be calculated recursively. We then give partitions that approximate the minimal expected wait time within a factor of 1+O(1/N), under each of these strategies, where N is the number of stations. We obtain similar bounds (to within factor 2) for the case, where the number of active servers can be any 1⩽n⩽N−1, and the balancing strategy is Trim.     

Productivity on a weekly rotating shift system: circadian adjustment and sleep deprivation effects?

Abstract

There is little doubt that productivity and safety can be impaired on the night shift. Two main factors have been identified that may be responsible for this. On the one hand, the circadian rhythm in performance on at least simple tasks is at a low ebb at night, and adjusts only slowly over a span of night shifts. On the other, the day sleeps of shift workers taken between night shifts are of a reduced duration, and thus a cumulative sleep debt may accrue over successive night shifts. The former thus predicts that productivity should improve over a span of night duty, while the latter predicts that it should decline. We have examined the productivity of 53 female shift workers, and the sleeping habits of a sub-sample of 30 of them, on a weekly rotating shift system in order to assess the relative contribution of these two factors. Our results suggest that circadian adjustment to night work is the dominant factor for the first three or four successive nights shifts, but that sleep deprivation effects may then result in a decrease in productivity over subsequent nights. They also indicate that sleep deprivation, but not circadian adjustment, may affect the productivity of some workers when on the morning shift.     

The Directors’ cut: a solution to collaborative multimedia management

Web 2.0 applications allow rich media contents to be exposed and shared by users. Nevertheless, usually, a multimedia is provided as an unicum, made by synchronized media items. Sound tracks, video sequences, captions, cannot be customized “on-the-fly” by users. Managing multimedia in a deep way would meet the expectations of nowadays Web prosumers (i.e. producers and consumers), and it would widen the audience. Describing and synchronizing each medium, as well as specifying different alternative contents for it, are the keystones of multimedia customization and of audience widening. This paper presents a multimedia collaborative system, which provides support to the arrangement of medium into a multi-views composed multimedia. Each prosumer can add medium by juxtaposition or by defining it as an alternative (audio, video, textual) version of an existing one. The implementation of such a system is based on SMIL 3.0 specification but implements a new and compact syntax to let users manipulate the original multimedia synchronization and their alternatives. The proposed approach has been put to test in two different scenarios.     

Intelligent agents and liability: is it a doctrinal problem or merely a problem of explanation?

The question of liability in the case of using intelligent agents is far from simple, and cannot sufficiently be answered by deeming the human user as being automatically responsible for all actions and mistakes of his agent. Therefore, this paper is specifically concerned with the significant difficulties which might arise in this regard especially if the technology behind software agents evolves, or is commonly used on a larger scale. Furthermore, this paper contemplates whether or not it is possible to share the responsibility with these agents and what are the main objections surrounding the assumption of considering such agents as responsible entities. This paper, however, is not intended to provide the final answer to all questions and challenges in this regard, but to identify the main components, and provide some perspectives on how to deal with such issue.     

Successful extreme programming: Fidelity to the methodology or good teamworking?

ContextDeveloping a theory of agile technology, in combination with empirical work, must include assessing its performance effects, and whether all or some of its key ingredients account for any performance advantage over traditional methods. Given the focus on teamwork, is the agile technology what really matters, or do general team factors, such as cohesion, primarily account for a team’s success? Perhaps the more specific software engineering team factors, for example the agile development method’s collective ownership and code management, are decisive.ObjectiveTo assess the contribution of agile methodology, agile-specific team methods, and general team factors in the performance of software teams.MethodWe studied 40 small-scale software development teams which used Extreme Programming (XP). We measured (1) the teams’ adherence to XP methods, (2) their use of XP-specific team practices, and (3) standard team attributes, as well as the quality of the project’s outcomes. We used Williams et al.’s (2004a) [33] Shodan measures of XP methods, and regression analysis.ResultsAll three types of variables are associated with the project’s performance. Teamworking is important but it is the XP-specific team factor (continuous integration, coding standards, and collective code ownership) that is significant. Only customer planning (release planning/planning game, customer access, short releases, and stand-up meeting) is positively related to performance. A negative relationship between foundations (automated unit tests, customer acceptance tests, test-first design, pair programming, and refactoring) is found and is moderated by craftsmanship (sustainable pace, simple design, and metaphor/system of names). Of the general team factors only cooperation is related to performance. Cooperation mediates the relationship between the XP-specific team factor and performance.ConclusionClient and team foci of the XP method are its critical active ingredients.     

The singular solutions to a singular quadratic minimization problem†

A number of generalizations of singular quadratic minimization theory for the finite-time case are considered. Also new stability results are derived for the infinite time problem, and novel techniques are introduced to facilitate the derivation of singular solutions for this case. Of significance is the fact that the new results make evident the duality that exists between singular control and singular filtering problems.     

Cross standard form: a solution to improve a given controller with H 2 or H ∞ specifications

This paper introduces in cross standard form (CSF) as a solution to the inverse optimal control problem. That is, the CSF is a canonical standard problem whose unique H _∞ or H ₂ optimal controller is a given controller. From the control design point of view, the general idea is to apply the CSF to a given controller in order to set up a standard problem which can be completed to handle frequency domain H ₂ or H _∞ specification. The analytical formulation of the CSF proposed in this paper can be applied to reduced-, full- or augmented-order compensators or two-degree of freedom compensations. Numerical and academic examples are given.     

Browsers for distributed systems: Universal paradigm or siren's song?

Webbased browsers are quickly becoming ubiquitous in the workplace. Software development managers are quick to incorporate browsers into a broad range of software development projects, often inappropriately. The purpose of this paper is to examine the technical issues relevant to incorporating browsers as a component of a commercial offtheshelf (COTS)based solution. Issues examined include portability, performance, functionality, security, human factors, distribution, installation, upgrading, componentbased development, runtime configuration management, and licensing.     

Multi-objective mitigation budget allocation problem and solution approaches: The case of İstanbul

İstanbul is the financial, commercial, industrial, cultural and educational center of Turkey. However, İstanbul is also an earthquake-prone city that has experienced many earthquakes throughout its history; and it is threatened with a high probability of a devastating earthquake in the next 30 years. In this study, we propose three financial allocation strategies and their multi-objective models related to building reinforcement, with the purpose of reducing the risk of disaster in Istanbul. The study aims to answer three important questions: (1) How should the mitigation budget be distributed among Istanbul’s districts? (2) Which building types should be mitigated, and how? (3) Can Pareto-efficient solutions be sorted? Pareto-efficient solutions for all of the proposed models were obtained and analyzed. The proposed superefficiency model has the ability to rank the Pareto-optimal solutions.     

How to construct small probabilistic roadmaps with a good coverage?

We investigate how we can construct small probabilistic roadmaps in a reasonable time while still keeping a good coverage and connectivity. We propose a new neighborhood-based method that can reduce the size of the roadmaps by filtering out unnecessary nodes. We then experimentally test it against a basic probabilistic roadmap planner and a visibility-based planner. We use both a uniform sampling and a bridge test sampling in our tests. The results show that the neighborhood-based method can reduce the number of nodes considerably. The neighborhood-based method is simple to implement, it works well with a uniform sampling, and it does not need any additional parameters when compared with the basic planner.     

The flooding sink — a new approach to local area networking

A new local area networking technology is presented. The approach is based on an old routing algorithm called flooding — forward messages to all neighbouring nodes. The problem with this algorithm is that the network is deluged with duplicate messaes. The solution is a simple device which uses local memory to detect and ignore redundant messages, thus also acting as a message sink. Networks based on this device can be more flexible and reliable than current networks. Flooding also has the advantage that any messages lost due to transmission errors are quickly replaced by one of the copies. This can make low-level protocols unnecessary. When the low-level protocols are omitted, significant performance improvements are achieved. Simulation results are presented which show that this flooding technology can perform better than current CSMA and ring technologies.     

An approximate solution to an initial boundary value problem: Rakib–Sivashinsky equation

The construction of an approximate solution to an initial boundary value problem for the Rakib–Sivashinsky equation is of concern. The Fourier method is combined with the Adomian decomposition method in order to provide the approximate solution. The variables are separated by the Fourier method and the approximate solution to the nonlinear system of ordinary differential equations is obtained by the Adomian decomposition method. One example of application is presented.     

On typing delimited continuations: three new solutions to the printf problem

In “Functional Unparsing” (J. Funct. Program. 8(6):621–625, 1998), Danvy presented a type-safe printf function using continuations and an accumulator to achieve the effect of dependent types. The key technique employed in Danvy’s solution is the non-standard use of continuations: not all of its calls are tail calls, i.e., it uses delimited continuations. Against this backdrop, we present three new solutions to the printf problem: a simpler one that also uses delimited continuations but that does not use an accumulator, and the corresponding two in direct style with the delimited-control operators, shift and reset. These two solutions are the direct-style counterparts of the two continuation-based ones. The last solution pinpoints the essence of Danvy’s solution: shift is used to change the answer type of delimited continuations. Besides providing a new application of shift and reset, the solutions in direct style raise a key issue in the typing of first-class delimited continuations and require Danvy and Filinski’s original type system. The resulting types precisely account for the behavior of printf.