Eerst weekend! Wiskunde in dienst van een sociaal leven

Het sociale leven - sportactiviteiten, verjaardagsbezoeken, het ontmoeten van vrienden - vindt vooral in de weekeinden plaats. Dit maakt werken in het weekend voor veel mensen onaantrekkelijk. In sectoren waar de dienstverlening 7 dagen in de week en 24 uur per dag beschikbaar moet zijn, zoals in de gezondheidszorg en de beveiligingssector, dienen medewerkers wel in het weekend te werken. Het maken van goede dienstroosters voor het weekend is een uitdaging: medewerkers hebben vaak heel specifieke voorkeuren terwijl de werkgever moet zorgen dat er voldoende mensen worden ingezet. Het maken van goede dienstroosters wordt verder bemoeilijkt doordat er rekening moet worden gehouden met de Arbeidstijdenwetgeving (ATW) en omdat werkgevers de diensten 'eerlijk' over de medewerkers willen verdelen

Shift rostering using decomposition: assign weekend shifts first

This paper introduces a shift rostering problem that surprisingly has not been studied in literature: the weekend shift rostering problem. It is motivated by our experience that employees’ shift preferences predominantly focus on the weekends, since many social activities happen during weekends. The Weekend Rostering Problem (WRP) addresses the rostering of weekend shifts, for which we design a problem specific heuristic. We consider the WRP as the first phase of the shift rostering problem. To complete the shift roster, the second phase assigns the weekday shifts using an existing algorithm. We discuss effects of this two-phase approach both on the weekend shift roster and on the roster as a whole. We demonstrate that our first-phase heuristic is effective both on generated instances and real-life instances. For situations where the weekend shift roster is one of the key determinants of the quality of the complete roster, our two-phase approach shows to be effective when incorporated in a commercially implemented algorithm

Informatienet 2003 in zicht: Totstandkoming en kwaliteit van de steekproef land- en tuinbouwbedrijven van het Bedrijven- Informatienet

The EU Farm Accountancy Data Network (FADN) requires the Netherlands to yearly sent bookkeeping data of 1,500 farms to Brussels. This task is carried out by LEI and CEI. The data send to Brussels mainly involves technical and financial economic information. For national policy purposes additional data is collected, such as pesticide use, manure production, nature management, non-farm income and rural development. This report explains the background of the farm sample for the year 2003. The report mainly focuses on the Dutch contribution to the European Farm Accountancy Data Network. All phases from the determination of the selection plan, the recruitment of farms to the quality control of the final sample are described in this report. Mede voor de Europese Unie organiseren het CEI en het LEI jaarlijks de verzameling van technische en financieel-economische gegevens van circa 1.500 bedrijven in de akkerbouw, tuinbouw en veehouderij. Voor nationaal beleidsgericht onderzoek wordt die informatie aangevuld met gegevens over bijvoorbeeld milieubelasting, natuurbeheer en plattelandsontwikkeling. Alle gegevens worden vastgelegd in het Bedrijven-Informatienet. In dit rapport wordt verantwoording afgelegd over de steekproef 2003, toegespitst op de Nederlandse bijdrage aan het Farm Accountancy Data Network van de Europese Unie. De diverse fasen, van het opstellen van het selectieplan, het werven van de bedrijven tot het beoordelen van de kwaliteit van de resulterende steekproef worden beschreven.Agricultural Finance,

Cost-efficient staffing under annualized hours

We study how flexibility in workforce capacity can be used to efficiently match capacity and demand. Flexibility in workforce capacity is introduced by the annualized hours regime. Annualized hours allow organizations to measure working time per year, instead of per month or per week. An additional source of flexibility is hiring employees with different contract types, like full-time, part-time, and min-max, and by hiring subcontractors. We propose a mathematical programming formulation that incorporates annualized hours and shows to be very flexible with regard to modeling various contract types. The objective of our model is to minimize salary cost, thereby covering workforce demand, and using annualized hours. Our model is able to address various business questions regarding tactical workforce planning problems, e.g., with regard to annualized hours, subcontracting, and vacation planning. In a case study for a Dutch hospital two of these business questions are addressed, and we demonstrate that applying annualized hours potentially saves up to 5.2% in personnel wages annually

Tribology of enzymatically degraded cartilage mimicking early osteoarthritis

Healthy cartilage is a water-filled super lubricious tissue. Collagen type II provides it structural stability, and proteoglycans absorb water to keep the cartilage in a swollen condition, providing it the ability to creep and provide weeping lubrication. Osteoarthritis (OA) is a degenerative and debilitating disorder of diarthrodial joints, where articular cartilage damage originates from enzymatic degradation and mechanical damage (wear). The objective of this research is to observe the level of cartilage damage present in knee arthroplasty patients and to understand the friction and creep behavior of enzymatically degraded bovine cartilage in vitro. Lateral (Lat) and medial (Med) condylar cartilages from OA patients undergoing total knee arthroplasty showed signs of enzymatic degradation and mechanical damage. Bovine cartilages were exposed to collagenase III and chondroitinase ABC to degrade collagen and proteoglycans, respectively. The loss of proteoglycans or collagen network and morphological changes were observed through histology and the atomic force microscope (AFM), respectively. A significant effect on creep due to enzymatic treatment was not observed. But the enzymatic treatment was found to significantly decrease the coefficient of friction (COF) at 4 N, while higher COF was shown from chondroitinase ABC degraded cartilage at 40 N. Collagenase III treatment leads to the release of intact proteoglycans at the sliding interface, while chondroitinase ABC treatment leads to the loss of chondroitin sulfate (CS) from the proteoglycans. Chondroitinase ABC-digested bovine cartilage mimicked patient samples the best because of the similar distributions of proteoglycans, collagen network, and friction behavior.[Figure not available: see fulltext.].</p

Association between workarounds and medication administration errors in bar-code-assisted medication administration in hospitals

Objective: To study the association of workarounds with medication administration errors using barcode-assisted medication administration (BCMA), and to determine the frequency and types of workarounds and medication administration errors. Materials and Methods: A prospective observational study in Dutch hospitals using BCMA to administer medication. Direct observation was used to collect data. Primary outcome measure was the proportion of medication administrations with one or more medication administration errors. Secondary outcome was the frequency and types of workarounds and medication administration errors. Univariate and multivariate multilevel logistic regression analysis were used to assess the association between workarounds and medication administration errors. Descriptive statistics were used for the secondary outcomes. Results: We included 5793 medication administrations for 1230 inpatients. Workarounds were associated with medication administration errors (adjusted odds ratio 3.06 [95% CI: 2.49-3.78]). Most commonly, procedural workarounds were observed, such as not scanning at all (36%), not scanning patients because they did not wear a wristband (28%), incorrect medication scanning, multiple medication scanning, and ignoring alert signals (11%). Common types of medication administration errors were omissions (78%), administration of non-ordered drugs (8.0%), and wrong doses given (6.0%). Discussion: Workarounds are associated with medication administration errors in hospitals using BCMA. These data suggest that BCMA needs more post-implementation evaluation if it is to achieve the intended benefits for medication safety. Conclusion: In hospitals using barcode-assisted medication administration, workarounds occurred in 66% of medication administrations and were associated with large numbers of medication administration errors

The Relation Between Trait Anger and Impulse Control in Forensic Psychiatric Patients

Inhibitory control is considered to be one of the key factors in explaining individual differences in trait anger and reactive aggression. Yet, only a few studies have assessed electroencephalographic (EEG) activity with respect to response inhibition in high trait anger individuals. The main goal of this study was therefore to investigate whether individual differences in trait anger in forensic psychiatric patients are associated with individual differences in anger-primed inhibitory control using behavioral and electrophysiological measures of response inhibition. Thirty-eight forensic psychiatric patients who had a medium to high risk of recidivism of violent and/or non-violent behaviors performed an affective Go/NoGo task while EEG was recorded. On the behavioral level, we found higher scores on trait anger to be accompanied by lower accuracy on NoGo trials, especially when anger was primed. With respect to the physiological data we found, as expected, a significant inverse relation between trait anger and the error related negativity amplitudes. Contrary to expectation, trait anger was not related to the stimulus-locked event related potentials (i.e., N2/P3). The results of this study support the notion that in a forensic population trait anger is inversely related to impulse control, particularly in hostile contexts. Moreover, our data suggest that higher scores on trait anger are associated with deficits in automatic error-processing which may contribute the continuation of impulsive angry behaviors despite their negative consequences

Two-year outcome of quality of life and health status for the elderly with chronic limb-threatening ischemia

Purpose:  In elderly patients with chronic limb-threatening ischemia (CLTI), there is little scientific understanding of the long-term changes of quality of life (QoL) and health status (HS) after treatment. The primary goal of this study was to provide long-term QoL and HS results for elderly CLTI patients after therapy. Treatments consisted of endovascular revascularization, surgical revascularization, or conservative treatment. Furthermore, the aim of this study was to identify the distinctive trajectories of QoL and HS. Patients and Methods:  CLTI patients aged >= 70 years were included in a prospective observational cohort study with a two-year follow-up. The WHOQOL-BREF was used to asses QoL. The 12-Item Short Form Health Survey was used to measure HS. The QoL and HS scores were compared to the scores in the general elderly Dutch population. Latent class trajectory analysis was used. Results:  A total of 195 patients were included in this study. After two years, in all treatment groups patients showed significantly higher physical QoL score compared to baseline and there was no significant difference with the corresponding values in the elderly Dutch population. In the latent class trajectory analysis, there were no overlapping risk factors for poorer QoL or HS. Conclusion:  This study shows that QoL levels in surviving elderly CLTI patients in the long-term do not differ from the corresponding values for elderly in the general population. There were no disparities in sociodemographic, clinical and treatment characteristics associated with poorer QoL and HS. This study was carried out to encourage further analysis of the influence of biopsycho social characteristics on QoL and HS in elderly CLTI patients

Mortality after major amputation in elderly patients with critical limb ischemia

Background: Owing to the aging population, the number of elderly patients with critical limb ischemia (CLI) has increased. The consequence of amputation is immense. However, at the moment, information about the mortality after amputation in the elderly vascular patients is unknown. For this reason, this study evaluated mortality rates and patient-related factors associated with mortality after a major amputation in elderly patients with CLI. Methods: From 2006 to 2013, we included patients aged >70 years who were treated for chronic CLI by primary or secondary major amputation within or after 3 months of initial therapy (revascularization or conservative management). Outcome measurements were mortality after major amputation and factors associated with mortality (age, comorbidity and timing of amputation). Results: In total, 168/651 patients (178 legs; 26%) underwent a major amputation. Patients were stratified by age: 70–80 years (n=86) and > 80 years (n=82). Overall mortality after major amputation was 44%, 66% and 85% after 1, 3 and 5 years, respectively. The 6-month and 1-year mortality in patients aged 80 years or older was, respectively, 59% or 63% after a secondary amputation 3 months. Per year of age, the mortality rate increased by 4% (P=0.005). No significant difference in mortality after major amputation was found in the presence of comorbidity or according to Rutherford classification. Conclusion: Despite developments in the treatment of CLI by revascularization, amputation rates remain high and are associated with tremendous mortality rates. Secondary amputation after a failed attempt of revascularization causes a higher mortality. Further research concerning timing of amputation and patient-related outcome is needed to evaluate if selected patients might benefit from primary amputation

practice of mechanical ventilation in cardiac arrest patients and effects of targeted temperature management a substudy of the targeted temperature management trial

Aims: Mechanical ventilation practices in patients with cardiac arrest are not well described. Also, the effect of temperature on mechanical ventilation settings is not known. The aims of this study were 1) to describe practice of mechanical ventilation and its relation with outcome 2) to determine effects of different target temperatures strategies (33 °C versus 36 °C) on mechanical ventilation settings. Methods: This is a substudy of the TTM-trial in which unconscious survivors of a cardiac arrest due to a cardiac cause were randomized to two TTM strategies, 33 °C (TTM33) and 36 °C (TTM36). Mechanical ventilation data were obtained at three time points: 1) before TTM; 2) at the end of TTM (before rewarming) and 3) after rewarming. Logistic regression was used to determine an association between mechanical ventilation variables and outcome. Repeated-measures mixed modelling was performed to determine the effect of TTM on ventilation settings. Results: Mechanical ventilation data was available for 567 of the 950 TTM patients. Of these, 81% was male with a mean (SD) age of 64 (12) years. At the end of TTM median tidal volume was 7.7 ml/kg predicted body weight (PBW)(6.4–8.7) and 60% of patients were ventilated with a tidal volume ≤ 8 ml/kg PBW. Median PEEP was 7.7cmH2O (6.4–8.7) and mean driving pressure was 14.6 cmH2O (±4.3). The median FiO2 fraction was 0.35 (0.30–0.45). Multivariate analysis showed an independent relationship between increased respiratory rate and 28-day mortality. TTM33 resulted in lower end-tidal CO2 (Pgroup = 0.0003) and higher alveolar dead space fraction (Pgroup = 0.003) compared to TTM36, while PCO2 levels and respiratory minute volume were similar between groups. Conclusions: In the majority of the cardiac arrest patients, protective ventilation settings are applied, including low tidal volumes and driving pressures. High respiratory rate was associated with mortality. TTM33 results in lower end-tidal CO2 levels and a higher alveolar dead space fraction compared to TTTM36