We present in this paper, new resolution methods for the selective maintenance problem. This problem consists in finding the best choice of maintenance actions to be performed on a multicomponent ...system, so as to maximize the system reliability, within a time window of a limited duration. When the number of components of the system is important, this combinatorial problem is not easy to solve, in particular because of the nonlinear objective function modeling the system reliability. This problem did not receive much attention yet. Consequently, rare are the effective resolution methods that are offered to the user. We thus developed heuristics and an exact method based on a branch and bound procedure, which we apply to various system configurations. We compare the obtained results, and we evaluate the best method to be used in various situations.
Summary
Background
Two algorithms based on sequential measurements of liver and spleen stiffness using two‐dimensional shearwave elastography (2D‐SWE) have been recently proposed to estimate ...clinically significant portal hypertension (hepatic venous pressure gradient HVPG ≥10 mm Hg) in patients with cirrhosis, with excellent diagnostic accuracy.
Aim
To validate externally these algorithms in a large cohort of patients with cirrhosis.
Methods
One hundred and ninety‐one patients with stable cirrhosis (Child‐Pugh class A 39%, B 29% and C 31%) who underwent liver and spleen stiffness measurements using 2D‐SWE at the time of HVPG measurement were included. Diagnostic accuracy of the 2 algorithms was assessed by calculating sensitivity, specificity, positive and negative predictive values.
Results
The first algorithm, using liver stiffness <16.0 kilopascals (kPa) and then spleen stiffness <26.6 kPa, was used to rule‐out HVPG ≥10 mm Hg. In our population, its sensitivity and negative predictive value were 95% and 63% respectively. The second algorithm, using liver stiffness >38.0 kPa, or liver stiffness ≤38.0 kPa but spleen stiffness >27.9 kPa, was used to rule‐in HVPG ≥10 mm Hg. In our population, its specificity and positive predictive value were 52% and 83% respectively. Restricting the analyses to the 74 patients without any history of decompensation of cirrhosis or to the 65 patients with highly reliable liver stiffness measurement did not improve the results.
Conclusion
In our population, diagnostic accuracies of non‐invasive algorithms based on sequential measurements of liver and spleen stiffness using 2D‐SWE were acceptable, but not good enough to replace HVPG measurement or to base clinical decisions.
Linked ContentThis article is linked to Thiele and Krag paper. To view this article visit https://doi.org/10.1111/apt.14536.
Maintenance problems are crucial aspect of nowadays industrial problems. However, the quest of the efficient periodicity of maintenance for all components of a system is far from an easy task to ...accomplish when considering all the antagonistic criteria of the maintenance and production views of a production system. Thus, the objective is to simultaneously ensure a low frequency of failures by an efficient periodic preventive maintenance and minimize the unavailability of the system due to preventive maintenance. This implies a minimum impact on the production. In this paper, several tools are combined to collaborate in order to optimize multi-component preventive maintenance problems. The structure of the maintenance-production system is modeled thanks to a framework inspired by our previous research projects. The dynamic aspects are modeled by a combination of timed petri-nets and PDEVS models and implemented in our VLE simulator. The parameters of the resulting simulation model are optimized via a Nelder–Mead (Simplex) Method.
This paper reports a study of water dynamics in a carbonate vadose zone (VZ). This study is performed in the experimental natural site of Saint-Emilion located in an underground quarry (Gironde, ...France). For this, two geophysical properties are used: the time domain reflectometry method (TDR) which provides the volumetric water content and electrical properties which provides the spatial water distribution. The dephasing and amplitude attenuation of the water content front were measured and modelled. Physical properties of the porous medium (porosity, permeability and effective diffusivity) can explain the water transfer process in VZ. The electrical resistivity tomography (ERT) gives a series of 2D images of water dynamics in VZ. Variations in water content induce changes in the electrical properties of the medium such as electrical resistivity. Using the time-lapse method, it is possible to model the evolution of saturation over time. The reliability of these electrical tools was confirmed by laboratory measurements.
Summary
Background
Beta‐blockers may have to be interrupted in patients with cirrhosis. The concept of a rebound after interruption of beta‐blockers is based on an animal study and on isolated case ...reports of variceal bleeding.
Aim
To determine if a rebound occurs in patients with cirrhosis following abrupt interruption of beta‐blockers.
Methods
We prospectively included all consecutive patients with cirrhosis undergoing right heart and hepatic vein catheterisation. Four groups were defined: ‘no beta‐blockers’ including patients not receiving beta‐blockers; ‘≤1 day’, ‘2–3 days’ and ‘≥4 days’ classified according to the time patients had interrupted beta‐blockers before catheterisation. Results were expressed as median (interquartile range).
Results
A total of 150 patients were included. Among the 25 patients in the groups ‘2–3 days’ and ‘≥4 days’, median duration of beta‐blockers interruption was 4 (3–6) days. No gastrointestinal bleeding occurred during that period, nor during the following month. Hepatic venous pressure gradient was not different among patients in usually treated with beta‐blockers. After adjustment, beta‐blockers interruption was not associated with hepatic venous pressure gradient. Cardiac index was higher in the ‘≥4 days’ group 4.6 L/min/m2 (3.5–5.1) than in the ‘≤1 day’ group 3.4 (2.6–4.0); P = 0.001 or in the ‘2–3 days’ group 3.1 (2.7–3.7); P = 0.007, but not different from the ‘no beta‐blockers’ group.
Conclusions
Abrupt interruption of beta‐blockers is associated neither with an apparent increase in the risk of variceal bleeding nor with a haemodynamic rebound. Thus, interruption of beta‐blockers in patients with cirrhosis may not require particular dosing or surveillance.
Because insects are ectotherms, their physiology, behaviour and fitness are influenced by the ambient temperature. Any changes in environmental temperatures may impact the fitness and life history ...traits of insects and, thus, affect population dynamics. Here, we experimentally tested the impact of heat shock on the fitness and life history traits of adults of the aphid parasitoid Aphidius avenae and on the later repercussions for their progeny. Our results show that short exposure (1 h) to an elevated temperature (36 degrees C), which is frequently experienced by parasitoids during the summer, resulted in high mortality rates in a parasitoid population and strongly affected the fitness of survivors by drastically reducing reproductive output and triggering a sex-dependent effect on lifespan. Heat stress resulted in greater longevity in surviving females and in shorter longevity in surviving males in comparison with untreated individuals. Viability and the developmental rates of progeny were also affected in a sex-dependent manner. These results underline the ecological importance of the thermal stress response of parasitoid species, not only for survival, but also for maintaining reproductive activities.
The aim of this study was to determine the efficacy of percutaneous vertebroplasty in treating painful spinal osteoporotic collapse.
Twenty-three cases of vertebral collapse were evaluated with CT ...and MR imaging to determine osteoporotic origin and recent evolution. Percutaneous vertebroplasties were performed using CT guidance. The 20 patients included in the study (17 women, 3 men; 62-92 years old) had acute pain of less than 1 month's duration that hindered ambulation and required treatment with narcotic drugs. They underwent this procedure for analgesic purposes. The analogic visual scale of Huskisson was used for pain when scoring assessment.
In 15 patients (75%), pain relief was complete within 24 hr after injection. Analgesic administration was stopped in 14 patients. Mild pain persisted in three (15%) of the remaining five patients. In one other patient (5%), crural pain was observed with cement leakage in the psoas muscle. In the fifth patient (5%), pain recurred after the patient was lifted. The pain was related to a new acute collapse of an adjacent vertebrae.
Vertebroplasty for the treatment of osteoporotic vertebral collapse is a minimally invasive procedure that provides immediate pain relief and enables the patient to become quickly mobile.
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