NUMERICAL SIMULATION OF THE EFFECTS OF RESERVOIR HETEROGENEITY, FRACTURES, AND MULTI-WELL INTERFERENCE ON PRESSURE TRANSIENT RESPONSES USING MULTISTENCILS FAST MARCHING METHOD

Analysis of rate and pressure transient responses of a well in spatially heterogeneous reservoir cannot be performed using conventional well-test analytical equations. An accurate analysis of transient pressure/rate responses of wells in heterogeneous naturally fractured reservoirs requires precise characterization of the complex interactions between various reservoir and well features. These features include heterogeneity, natural and induced fractures, reservoir boundaries, and well interference. Single-stencil fast marching (SFM) method has been used for pressure transient analysis (PTA) and history matching in heterogeneous reservoirs. As an improvement to the SFM method, we develop and test the multistencils fast marching (MFM) method, which exhibits one order of magnitude higher accuracy compared to SFM method. We extensively validate the MFM method for various reservoir and wellbore scenarios by comparing its predictions against those of SFM Method, KAPPA Saphir analytical model, and KAPPA Rubis numerical model. MFM method can be effectively used to estimate pressure response not only in homogeneous reservoir with heteromorphous geometry of no-flow boundary but also in highly heterogeneous reservoir affected by high contrast permeability/porosity distribution and in the presence of induced/natural fractures or impermeable zones. Furthermore, using embedded fracture multistencils fast marching (EFMFM) method, we improve MFM method to model a discrete fracture on the cartesian reservoir girds. Through EFMFM method, pressure response data can be estimated accurately not only in a computationally efficient way, but also in an intuitive way with the visualization of the time-varying drainage volume

Lipid emulsion inhibits the cardiac toxicity caused by chloroquine via inhibition of reactive oxygen species production

Background Lipid emulsion (LE) is effective in treating intractable cardiac depression induced by the toxicity of highly lipid-soluble drugs including local anesthetics. However, the effect of LE on chloroquine (CQ)-evoked cardiac toxicity remains unclear. This study aimed to examine the effect of Lipofundin MCT/LCT, an LE, on the cardiotoxicity caused by CQ in H9c2 rat cardiomyoblasts and elucidate the underlying cellular mechanism. Methods The effects of CQ (1 × 10-4 M), LE, and the reactive oxygen species (ROS) scavengers mitotempo and N-acetyl-L-cysteine (NAC), alone or combined, on cell viability and migration, apoptosis, ROS production, calcium levels, mitochondrial membrane potential, and adenosine triphosphate (ATP) were examined. Additionally, the effects of LE on the activities of catalase (CAT), malondialdehyde (MDA), and superoxide dismutase (SOD) induced by CQ were assessed. Results Pretreatment with LE, mitotempo, or NAC reversed the reduction in cell migration and viability, mitochondrial membrane potential, and ATP levels evoked by CQ, and inhibited the increase in cleaved caspase-3, ROS, and calcium concentration induced by CQ. LE inhibited the increase in Bax expression, terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells, MDA activity, and late apoptosis, and reversed the reduction in SOD and CAT activity induced by CQ. CQ did not significantly affect cleaved caspase-8 expression, and LE did not significantly affect CQ concentration. Conclusions Collectively, these results suggest that LE (Lipofundin MCT/LCT) inhibits the cardiotoxicity and late apoptosis induced by CQ toxicity via the intrinsic mitochondrial apoptotic pathway that is associated with direct inhibition of ROS production

Improving Lifetime of Organic Solar Cells for Green Energy Generation

Organic photovoltaic devices (OPVs) have been progressively developed as a promising green energy source. The solar-to-electrical power conversion efficiency (PCE) of the OPVs has been steadily enhanced in the last few decades by advanced chemical designs and device structures/architectures. A state-of-the-art class of photoactive materials recently contributed to a drastic increase in PCEs, reaching almost 20%. Compared to the other PVs such as inorganic-based and perovskite PVs, the OPVs have unique merits: thinness, lightweight, flexibility, and ease to tune color and transparency. These characteristics have attracted the commercialization of the OPVs in various fields (e.g. incorporating with clothing and aesthetic windows). However, in contrast to the remarkable PCE improvements, the OPVs are still suffering from short lifetime under environmental operating conditions (e.g. intense sunlight, high temperature, etc.), which is a hurdle to encourage wide-ranging commercial products of the OPVs. The lack of understanding of fundamental degradation processes and mechanisms within an entire OPV has delayed the development of long-term stable OPVs. In the aspect of chemical synthesis, many efforts have introduced durable photoactive materials (thermally stable and/or photostable chemicals), but synthetic steps often require complicated processes and high cost, and provide low yield and toxicity which is another potential environmental issue. This dissertation demonstrates a comprehensive understanding of possible degradation mechanisms within an OPV device, and suggests a facile method to improve the lifetime of the OPVs based on existing materials. In the first study, we discussed both the physical and chemical degradation processes of layers, especially, at interfaces between adjacent layers within an OPV. Molecular-level insights are provided into the impact of different metal top electrodes (the most commonly used aluminum (Al) and silver (Ag)) on the interfacial morphology and stability of photoactive layers in PM6:Y6 bulk-heterojunction (BHJ) OPVs. OPVs with an Al top electrode exhibit inferior stability compared to Ag electrode devices upon thermal aging, whereby thermal stress induces the diffusion of both Al and Ag atoms to the PM6:Y6 BHJ layer. Multiscale characterizations (X-ray photoelectron, solid-state nuclear magnetic resonance, and electron paramagnetic resonance spectroscopy) suggest the different local chemical environments of PM6 and Y6 moieties in PM6:Y6/Al-contact. By comparison, the Ag atoms do not adversely affect PM6:Y6 BHJ morphology and the associated device physics. Next, a common cross-linking method is applied for the organic BHJ photoactive to address a fundamental morphological stability issue with high performing small molecule non-fullerene acceptors (NFAs). The molecular diffusion and/or aggregation of the NFAs due to thermal energy alter optimum BHJ morphology which is required to yield high PCE, leading to undesirable morphology and hence reducing PCE. Herein, a photochemically activated multi-bridged azide cross-linker (6Bx) restricts molecular aggregation and crystallization of the Y6, a representative high performing NFA, in solid state. Solid-state magnetic resonance and infrared spectroscopy analyses demonstrate that the 6Bx molecules closely interact with Y6 moieties within the PM6:Y6 blend, facilitating molecularly cross-linked Y6 regions. Consequently, 0.05 wt% 6Bx cross-linked PM6:Y6 BHJ OPVs retain 93.4% of initial power conversion efficiency upon thermal aging at 85 °C for 1680 h. This dissertation comprehensively examines physical and chemical reactions/interactions within an entire OPV device by multiscale characterizations and device physics, therefore will provide guidance to develop stable and efficient organic electronics

Modelling of failure and fracture development of the Callovo-Oxfordian claystone during an in-situ heating experiment associated with geological disposal of high-level radioactive waste

To ensure the safety of geological disposal of high-level radioactive waste, in-situ experiments have been carried out to examine the behavior of rocks in underground research laboratories (URLs). At the Meuse/Haute-Marne URL in France, the French National Radioactive Waste Management Agency (Andra) has been assessing the Callovo-Oxfordian claystone (COx) as potential host rock of geological disposal by subjecting the COx to in-situ heating mimicking exothermic radioactive waste. Results of the in-situ experiments are used to validate and bolster the numerical simulators for predicting the thermo-hydromechanically (THM) coupled behavior of the COx. The numerical simulators are, however, yet to be tested for predicting the failure and fracture development of the COx during heating, which is of paramount importance to the safety of the geological disposal. In this research, we modelled a recently carried out in-situ experiment at the Meuse/Haute-Marne URL using the TOUGH-FLAC simulator to predict the failure and fracture development of the COx during heating. The objectives are to examine the effects of (i) the weak bedding planes, (ii) the softening rate of matrix/weak plane strengths, and (iii) the stiffness anisotropy of the COx on the development of shear and tensile fractures during heating. Results show that considering failure along the weak planes enabled accurate predictions of fracture development. Also, fracture development intensified at a softening rate beyond a threshold level and the geometry of fractures was significantly affected by the stiffness anisotropy. These results will help boost the reliability of the safety and performance assessment of geological disposal in claystone

Validation of strongly coupled geomechanics and gas hydrate reservoir simulation with multiscale laboratory tests

We validate a coupled flow-geomechanics simulator for gas hydrate deposits, named T+MAM, performing two meter-scale laboratory experiments of gas hydrates for production by depressurization, replicating the gas hydrate deposit in the Ulleung Basin, East Sea, South Korea. The first experiment with a sand-only specimen is a 1D 1 m-scale depressurization test based on the excess gas method, which represents the grain coating hydrate growth. On the other hand, the second is a 3D 1.5 m-scale test with the excess water method for a sand–mud alternating layer system, representing the pore filling hydrate growth. We measure production and displacement at the top with different depressurization levels. In particular, the 3D test exhibits high coupling strength of substantial deformation induced by incompressibility of water and high deformability of the specimen. For validation, we match pressure, flow rate, and displacement between the experimental data and numerical results. Thus, we identify that T+MAM is a reliable simulator, which can be applied to fields in both permafrost and deep oceanic hydrate deposits of strongly coupled flow and geomechanics systems. This validation also implies that other coupled simulators based on the same coupling formulation as T+MAM can be validated when individual flow and geomechanics simulators are stable and reliable

A Wrapped Approach Using Unlabeled Data for Diabetic Retinopathy Diagnosis

Large-scale datasets, which have sufficient and identical quantities of data in each class, are the main factor in the success of deep-learning-based classification models for vision tasks. A shortage of sufficient data and interclass imbalanced data distribution, which often arise in the medical domain, cause modern deep neural networks to suffer greatly from imbalanced learning and overfitting. A diagnostic model of diabetic retinopathy (DR) that is trained from such a dataset using supervised learning is severely biased toward the majority class. To enhance the efficiency of imbalanced learning, the proposal of this study is to leverage retinal fundus images without human annotations by self-supervised or semi-supervised learning. The proposed approach to DR detection is to add an auxiliary procedure to the target task that identifies DR using supervised learning. The added process uses unlabeled data to pre-train the model that first learns features from data using self-supervised or semi-supervised learning, and then the pre-trained model is transferred with the learned parameter to the target model. This wrapper algorithm of learning from unlabeled data can help the model gain more information from samples in the minority class, thereby improving imbalanced learning to some extent. Comprehensive experiments demonstrate that the model trained with the proposed method outperformed the one trained with only the supervised learning baseline utilizing the same data, with an accuracy improvement of 4~5%. To further examine the method proposed in this study, a comparison is conducted, and our results show that the proposed method also performs much better than some state-of-the-art methods. In the case of EyePaCS, for example, the proposed method outperforms the customized CNN model by 9%. Through experiments, we further find that the models trained with a smaller but balanced dataset are not worse than those trained with a larger but imbalanced dataset. Therefore, our study reveals that utilizing unlabeled data can avoid the expensive cost of collecting and labeling large-scale medical datasets

Effect of Dosing Interval on Compliance of Osteoporosis Patients on Bisphosphonate Therapy: Observational Study Using Nationwide Insurance Claims Data

Only a few studies are available on the effect of the dosing interval of bisphosphonate on drug compliance. We analyzed the data of patients who were newly prescribed bisphosphonate using a national insurance claims database. Drug compliance was assessed by calculating medication possession ratio (MPR) over a minimum of a 1-year follow-up. This analysis included 281,996 new bisphosphonate users with a mean age of 68.9 years (92% women). The patients were divided into daily, weekly, monthly, 3-monthly, and switch groups (who changed the drug to other dosing intervals). The average MPR was the highest in the switch group (66%), and the longer the dosing interval, the higher the compliance (3-monthly, 56% vs. daily, 37%). “Non-compliant” was defined as an MPR under 80%. Various factors which were possibly associated with “non-compliant” MPR were investigated using multiple regression analysis. Multivariate analysis showed that male patients were more likely to be non-compliant with pharmacotherapy than female patients, with as odds ratio of 1.389. Younger patients had a significantly lower likelihood of being non-compliant than older patients for age 60–69 vs. age 80+. Long dosing intervals were recommended to improve compliance and special attention was given to older and male patients

Influences of Metal Electrodes on Stability of Non‐Fullerene Acceptor‐Based Organic Photovoltaics

International audienceUnderstanding chemical degradation at the interface between different layers in an organic photovoltaic device (OPV) is crucial to improving the long‐term stability of OPVs. Herein, molecular‐level insights are provided into the impact of different metal top electrodes on the interfacial morphology and stability of photoactive layers in PM6:Y6 bulk‐heterojunction (BHJ) OPVs. OPVs with an aluminum (Al) top electrode exhibit inferior stability compared to silver (Ag) electrode devices upon thermal annealing, whereby thermal stress induces the diffusion of both Al and Ag atoms to the PM6:Y6 BHJ layer. The diffused Al atoms cause surface recombination at the interface between the photoactive layer and an interlayer. Specifically, X‐ray photoelectron spectroscopy suggests the different local chemical environments of PM6 and Y6 moieties in PM6:Y6/Al‐contact devices. These results are corroborated by solid‐state nuclear magnetic resonance and electron paramagnetic resonance spectroscopy measurements, indicating the formation of ionic and organo‐metallic‐like species at the sub‐layers of the PM6:Y6 BHJ morphology, which are estimated to be less than 5 wt% of the PM6:Y6/Al blend. By comparison, the Ag atoms do not adversely affect PM6:Y6 BHJ morphology and the associated device physics. The investigation of reactive electrode‐BHJ interfaces by multiscale characterization techniques and device physics is expected to provide guidance to future interfacial engineering strategies to develop stable and efficient OPVs

Media 3: Lamina 3D display: projection-type depth-fused display using polarization-encoded depth information

Originally published in Optics Express on 20 October 2014 (oe-22-21-26162