An exact extended formulation for the unrelated parallel machine total weighted completion time problem

The plethora of research on NP-hard parallel machine scheduling problems is focused on heuristics due to the theoretically and practically challenging nature of these problems. Only a handful of exact approaches are available\udin the literature, and most of these suffer from scalability issues. Moreover, the majority of the papers on the subject are restricted to the identical parallel machine scheduling environment. In this context, the main contribution of this work is to recognize and prove that a particular preemptive relaxation for the problem of minimizing the total weighted completion time (TWCT) on a set of unrelated parallel machines naturally admits a non-preemptive optimal solution and gives rise to an exact mixed integer linear programming formulation of the problem. Furthermore, we exploit the structural properties of TWCT and attain a very fast and scalable exact Benders decomposition-based algorithm for solving this formulation. Computationally, our approach holds great promise and may even be embedded into iterative algorithms for more complex shop scheduling problems as instances with up to 1000 jobs and 8 machines are solved to optimality within a few seconds

Sulfur Poisoning and Regeneration Behavior of Perovskite-Based NO Oxidation Catalysts

SOx uptake and release properties of LaMnO3, Pd/LaMnO3, LaCoO3 and Pd/LaCoO3 perovskites were investigated via in situ Fourier transform infrared (FTIR) spectroscopy, temperature programmed desorption and X-ray photoelectron spectroscopy. Sulfation of the perovskite leads to the formation of surface sulfite/sulfate and bulk-like sulfate species. Pd addition to LaMnO3 and LaCoO3 significantly increases the sulfur adsorption capacity. Pd/LaMnO3 sample accumulates significantly more sulfur than LaMnO3; however it can also release a larger fraction of the accumulated SOx species in a reversible fashion at elevated temperatures in vacuum. This is not the case for Co-based materials, where thermal regeneration of bulk sulfates on poisoned LaCoO3 and Pd/LaCoO3 is extremely ineffective under similar conditions. However, in the presence of an external reducing agent such as H2 (g), Pd/LaMnO3 requires much lower temperature (873 K) for complete sulfur regeneration as compared to that of Pd/LaCoO3 (973 K). Sequential CO and SOx adsorption experiments performed via in situ FTIR indicate that in the presence of carbonyls and/or carbonates, Pd adsorption sites may have a stronger affinity for SOx as compared to that of the perovskite surface, particularly in the early stages of sulfur poisoning.

Critical submergence for isolated and dual rectangular intakes

This study examined critical submergence for isolated and dual rectangular intakes. It is shown that the critical submergence for an isolated intake can be predicted by disregarding whole boundary blockages on the complete imaginary critical sink surface that is the combination of imaginary complete critical cylindrical and hemi-spherical sink surfaces. It is proposed that this theory can be applied to the rectangular intakes located in general geometrical and flow conditions (i.e., intake in still water, circulation imposed flow, non-developed cross-flow, multiple intakes, etc.) and that it does not require computation of blockages caused from flow boundaries. The concept of complete sink surface (disregarding whole boundary blockages) developed for an isolated intake was also applied to dual rectangular intakes. The agreement between available test data and theoretical results was found to be satisfactory.

Effective intake for critical submergence in the case of more than one intake

Comparison of different methods of nasogastric tube insertion in anesthetized and intubated patients

BackgroundNasogastric tube insertion may be difficult in anesthetized and intubated patients with head in the neutral position. Several techniques are available for the successful insertion of nasogastric tube. The primary aim of this study was to investigate the difference in the first attempt success rate of different techniques for insertion of nasogastric tube. Secondary aim was to investigate the difference of the duration of insertion using the selected technique, complications during insertion such as kinking and mucosal bleeding.Material and methodsTwo hundred adult patients, who received general anesthesia for elective abdominal surgeries that required nasogastric tube insertion, were randomized into four groups: Conventional group (Group C), head in the lateral position group (Group L), endotracheal tube assisted group (Group ET) and McGrath video laryngoscope group (Group MG). Success rates, duration of insertion and complications were noted.ResultsSuccess rates of nasogastric tube insertion in first attempt and overall were lower in Group C than Group ET and Group MG. Mean duration and total time for successful insertion of NG tube in first attempt were significantly longer in Group ET. Kinking was higher in Group C. Mucosal bleeding was statistically lower in Group MG.ConclusionUse of video laryngoscope and endotracheal tube assistance during NG tube insertion compared with conventional technique increase the success rate and reduce the kinking in anaesthetized and intubated adult patients. Use of video laryngoscope during nasogastric tube insertion compared to other techniques reduces the mucosal bleeding in anaesthetized and intubated adult patients

Hepatopulmonary Syndrome in Patients With Cystic Fibrosis and Liver Disease

Hepatopulmonary syndrome (HPS) is a liver-induced lung disorder defined as a triad of liver disease, pulmonary vascular dilatation, and a defect in oxygenation. It can complicate chronic liver disease of any etiology, but is most commonly associated with portal hypertension. Severe liver disease with portal hypertension is present in 2% to 8% of patients with cystic fibrosis (CF), but to date, to our knowledge, only one patient with CF has been reported to suffer from HPS. Here, we describe two patients with CF diagnosed with HPS, one subsequent to unresolved hypoxemia and the other following screening for HPS performed in our center. We speculate that HPS is underdiagnosed in patients with CF because of their coexisting respiratory morbidity, and we advocate routine screening for every patient with CF who has liver disease and portal hypertension.

Knowns and unknowns in metabolomics identified by multidimensional NMR and hybrid MS/NMR methods

Metabolomics continues to make rapid progress through the development of new and better methods and their applications to gain insight into the metabolism of a wide range of different biological systems from a systems biology perspective. Customization of NMR databases and search tools allows the faster and more accurate identification of known metabolites, whereas the identification of unknowns, without a need for extensive purification, requires new strategies to integrate NMR with mass spectrometry, cheminformatics, and computational methods. For some applications, the use of covalent and non-covalent attachments in the form of labeled tags or nanoparticles can significantly reduce the complexity of these tasks.

Motile-Cilia-Mediated Flow Improves Sensitivity and Temporal Resolution of Olfactory Computations

Motile cilia are actively beating hair-like structures that cover the surface of multiple epithelia. The flow that ciliary beating generates is utilized for diverse functions and depends on the spatial location and biophysical properties of cilia. Here we show that the motile cilia in the nose of aquatic vertebrates are spatially organized and stably beat with an asymmetric pattern, resulting in a robust and stereotypical flow around the nose. Our results demonstrate that these flow fields attract odors to the nose pit and facilitate detection of odors by the olfactory system in stagnant environments. Moreover, we show that ciliary beating quickly exchanges the content of the nose, thereby improving the temporal resolution of the olfactory system for detecting dynamic changes of odor plumes in turbulent environments. Altogether, our work unravels a central function of ciliary beating for generating flow fields that increase the sensitivity and the temporal resolution of olfactory computations in the vertebrate brain.

A hybrid Integer Programming and Variable Neighbourhood Search algorithm to solve Nurse Rostering Problems

The Nurse Rostering Problem (NRP) is defined as assigning a number of nurses to different shifts during a specified planning period, considering some regulations and preferences. This is often very difficult to solve in practice particularly by applying a sole approach. In this paper, we propose a novel hybrid algorithm combining the strengths of Integer Programming (IP) and Variable Neighbourhood Search (VNS) algorithms to design a hybrid method for solving the NRP. After generating the initial solution using a greedy heuristic, the solution is further improved by employing a Variable Neighbourhood Descent algorithm. Then IP, deeply embedded in the VNS algorithm, is employed within a ruin-and-recreate framework to assist the search process. Finally, IP is called again to further refine the solution during the remaining time. We utilize the strength of IP not only to diversify the search process, but also to intensify the search efforts. To identify the quality of the current solution, we use a new generic scoring scheme to mark the low-penalty parts of the solution. Based on the computational tests with 24 instances recently introduced in the literature, we obtain better results with our proposed algorithm, where the hybrid algorithm outperforms two state-of-the-art algorithms and Gurobi in most of the instances. Furthermore, we introduce 11 randomly generated instances to further evaluate the efficiency of the hybrid algorithm, and we make these computationally challenging instances publicly available to other researchers for benchmarking purposes

To disclose or not to disclose: How global competition for foreign direct investment influences transparency reforms in extractive industries

In the last decade, the Extractive Industries Transparency Initiative (EITI) has grown in both popularity and influence. The ascendance of EITI is surprising because traditionally, leaders of resource-rich states prefer to tightly control their extractive industries. This paper investigates the underlying causes of EITI membership in order to understand its acceptance, even among some of the most authoritarian regimes. The paper argues that leaders of resource-rich countries use the EITI to consolidate their international prestige as eager reformers, which serves to both maintain and lure foreign investment. The cross-national and interrupted time series analyses reveal that EITI members not only have higher FDI levels compared to non-members, but these investments increase once countries join the initiative.