Systematic observations of enhanced oil recovery and associated changes at carbonate-brine and carbonate-petroleum interfaces.

Enhanced oil recovery (EOR) from carbonates is obtained by injection of controlled ionic strength brines containing "active ions" (e.g., SO42-, Mg2+, Ca2+). It is generally believed that this occurs through the interaction of the active ions at the carbonate-brine interface (e.g., within a thin brine layer separating the petroleum and the carbonate phases). Here, in-situ observations show how one active ion, SO42-, alters behavior at the carbonate-petroleum interface. Displacement of petroleum from initially oil-wet carbonate rocks using brines with variable SO4 concentrations systematically changes oil recovery, in situ contact angles, and connectivity of the oil phase, confirming that the active ion alters interactions at the oil/brine/carbonate interface, as expected. Measurements of model calcite-fluid interfaces show that there is no measurable sorption of SO4 to carbonate-brine interfaces but reveals that the carbonate-petroleum interface is altered by previous exposure to SO4-containing brines. These results suggest that EOR in carbonates is controlled indirectly by active ions. We propose that this may be due to a reduced oleophilicity of the carbonate caused by chemical complexation between the active ion and petroleum's acidic and basic functional groups. This mechanism explains how both anions and cations act as active ions for EOR in carbonates.

Copper-Catalyzed Enantioselective C1,N-Dipolar (3+2) Cycloadditions of 2-Aminoallyl Cations with Indoles.

2-Aminoallyl cations are versatile 1,3-dipoles that could potentially be used for diverse (3+n) cycloaddition reactions. Despite some preliminary studies, the asymmetric catalytic transformation of these species is still underdeveloped. We herein report a binuclear copper-catalyzed generation of 2-aminoallyl cations from ethynyl methylene cyclic carbamates and their enantioselective (3+2) cycloaddition reaction with indoles to construct chiral pyrroloindolines. This transformation features a novel C1,N-dipolar reactivity for 2-aminoallyl cations.

Exercise modalities for type 2 diabetes: A systematic review and network meta-analysis of randomized trials.

AIMS: We aimed to determine the effects of different exercise modalities in patients with type 2 diabetes mellitus (T2DM). METHODS: We searched PubMed, Embase, and the Cochrane Library from their inception until July 2020 to identify randomised controlled trials (RCTs) on exercise in adults with T2DM. Paired reviewers independently performed study selection, data extraction, and risk of bias assessment. The certainty of the evidence was assessed using the Confidence in Network Meta-Analysis (CINeMA) framework. RESULTS: A total of 106 RCTs that enroled eight exercise modalities with 7438 patients were included. Six exercise modalities, except unsupervised aerobic/resistance exercise, significantly reduced glycosylated haemoglobin (HbA1c), with mean differences (MDs) ranging from 0.71 (95% confidence interval [CI]: 0.34-1.08) to 0.34 (95% CI: 0.17-0.52), low to high certainty, in comparison with no exercise. The evidence of low to moderate certainty showed that supervised aerobic/resistance exercise improved glycaemic control, body weight, blood pressure, and blood lipid profiles compared with no exercise. Flexibility exercise may be associated with glycaemic control (HbA1c: MD = 0.71, 95% CI: 0.34-1.08); fasting plasma glucose (MD = 1.48, 95% CI: 0.78-2.17), and weight loss (MD = 1.80, 95% CI: 0.85-2.75) compared with controls, but not blood pressure and lipid profiles. Balance exercise showed the largest benefit in improving total cholesterol (MD = 52.81, 95% CI: 28.47-77.16) and low certainty. We found no significant differences between exercises and the triacylglycerol (TG) level. CONCLUSIONS: Overall, our network meta-analyses support the recommendation for exercise in patients with T2DM, especially supervised exercises. Limited evidence supports the benefits of flexibility and balance exercises. The effectiveness of exercise modalities for TG reduction remains unclear.

Nutritional Recommendations for Type 2 Diabetes: An International Review of 15 Guidelines.

OBJECTIVES: Recommendations from clinical practice guidelines (CPGs) for individuals with type 2 diabetes mellitus (T2DM) may be inconsistent, and little is known about their quality. Our aim in this study was to systematically review the consistency of globally available CPGs containing nutritional recommendations for T2DM and to assess the quality of their methodology and reporting. METHODS: PubMed, China Biology Medicine and 4 main guideline websites were searched. Four researchers independently assessed quality of the methodology and reporting using the Appraisal of Guidelines for Research and Evaluation, second edition (AGREE II) instrument and the Reporting Items for Practice Guidelines in HealThcare (RIGHT) checklist. RESULTS: Fifteen CPGs include 65 nutritional recommendations with 6 sections: 1) body weight and energy balance; 2) dietary eating patterns; 3) macronutrients; 4) micronutrients and supplements; 5) alcohol; and 6) specific, functional foods. Current nutritional recommendations for individuals with T2DM on specific elements and amounts are not completely consistent in different CPGs and fail to assign the specific supporting evidence and strength of recommendations. To use nutritional recommendations to guide and manage individuals with T2DM, it is important to address the current challenges by establishing a solid evidence base and indicating the strength of recommendations. Overall, 8 CPGs classified as recommended for clinical practice used AGREE II. Fifteen CPGs adhere to <60% of RIGHT checklist items. CONCLUSIONS: High-quality evidence is needed to potentially close knowledge gaps and strengthen the recommendation. The AGREE II instrument, along with the RIGHT checklist, should be endorsed and used by CPG developers to ensure higher quality and adequate use of their products.

Lewis-Acid-Promoted Ligand-Controlled Regiodivergent Cycloaddition of Pd-Oxyallyl with 1,3-Dienes: Reaction Development and Origins of Selectivities.

For nearly 30 years, considerable research effort has been focused on the development of methods for catalytic (3 + 2) cycloaddition reactions of palladium-oxyallyl species with alkenes. However, because C-O bond formation is kinetically favored, the (3 + 2) cycloadditions achieved to date have involved C-O reductive elimination. We herein report a method of lithium triflate-promoted (3 + 2) cycloaddition reactions of palladium-oxyallyl species with 1,3-dienes that proceed via a pathway terminated with C-C bond formation to give a five-membered carbocycle. Coordination of the lithium ion with the alkoxide moiety disrupts the C-O reductive elimination and forms a metal-enolate tethered π-allyl-Pd. The π-allyl-Pd moiety then accepts intramolecular allylic attack from the enolate moiety to form carbocyclic products. Furthermore, by tuning the steric properties of the palladium ligand, we could also accomplish the competing (4 + 3) cycloadditions, and thus this method provides regiodivergent access to both cyclopentanones and cycloheptanones. The reaction mechanism was investigated by DFT calculation and the origins of the regioselectivities of the cycloaddition were rationalized.

Enantioselective Inverse Electron Demand (3 + 2) Cycloaddition of Palladium-Oxyallyl Enabled by a Hydrogen-Bond-Donating Ligand.

Cycloaddition reactions between oxyallyl cations and alkenes are important transformations for the construction of ring systems. Although (4 + 3) cycloaddition reactions of oxyallyl cations are well-developed, (3 + 2) cycloadditions remain rare, and an asymmetric version has not yet been developed. Moreover, because oxyallyl cations are highly electrophilic, only electron-rich olefins can be used as cycloaddition partners. We herein report a method for enantioselective (3 + 2) cycloaddition reactions between palladium-oxyallyl species and electron-deficient nitroalkenes. This transformation was enabled by a rationally designed hydrogen-bond-donating ligand (FeUrPhos) and proceeded via an inverse electron demand pathway. Using this method, we could assemble cyclopentanones with up to three contiguous stereocenters with high enantioselectivity and good to excellent diastereoselectivity.

Coronavirus disease (COVID 2019): protocol for a living overview of systematic reviews.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic continues to grow worldwide, and systematic reviews (SRs)/meta-analyses (MAs) on COVID-19 can efficiently guide evidence-based clinical practice. However, SRs/MAs with weaknesses can mislead clinical practice and pose harm to patients, and too many useless SRs/MAs could pose confusion and waste sources. A "living" overview of SRs/MAs aims to provide an open, accessible and frequently updated resource summarizing the highest-level evidence of COVID-19, that can help evidence-users to quickly identify trusted evidence to guide the practice. This study aims to systematically give an overview SRs/MAs of COVID-19, assess their quality, and identify the best synthesis of evidence. METHODS: Databases including Medline, EMBASE, Web of Science, China National Knowledge Infrastructure (CNKI), China Biology Medicine (CBM) and WanFang were systematically searched on May 1, 2020 using relevant terms for identify SRs/MAs related to COVID-19. The study selection, data extraction and quality assessment will be performed by independent reviewers, and results will be crosschecked. The authoritative tools (AMSTAR-2, PRISMA and its extensions) will be used to assess the methodological quality and reporting quality of included SRs/MAs, and potential influence factors will be explored. The consistency of conclusions will be compared among reviews and the best evidence will be summarized. In addition, we will conduct exploratory meta-analyses (MAs) of individual studies when applicable. Data will be reported as number with (or) percentage, risk ratio (RR) or odds ratio (OR), mean difference (MD) or standardized mean difference (SMD) with 95% confidence interval (CI) according to the specific results. R3.6.1 and Microsoft Excel 2016 will be used to analyze and manage data. RESULTS: The results of this overview will be submitted to a peer-reviewed journal for publication. DISCUSSION: In this study, we will present for the first time, an overview of SRs/MAs, which provides a comprehensive, dynamic evidence landscape on prevalence, prevention, diagnosis, treatment, and prognosis of COVID-19.

Molecular-scale origins of wettability at petroleum-brine-carbonate interfaces.

Wettability control of carbonates is a central concept for enhanced petroleum recovery, but a mechanistic understanding of the associated molecular-scale chemical processes remains unclear. We directly probe the interface of calcium carbonate (calcite) with natural petroleum oil, synthetic petroleum analogues, and aqueous brines to understand the molecular scale behavior at this interface. The calcite-petroleum interface structure is similar whether or not calcite was previously exposed to an aqueous brine, and is characterized by an adsorbed interfacial layer, significant structural changes within the calcite surface, and increased surface roughness. No evidence for an often-assumed thin-brine wetting layer at the calcite-petroleum interface is observed. These features differ from those observed at the calcite-brine interface, and for parallel measurements using model synthetic petroleum mixtures (consisting of representative components, including dodecane, toluene, and asphaltene). Changes to the interface after petroleum displacement by aqueous brines are also discussed.

Impact of mineralogy and wettability on pore-scale displacement of NAPLs in heterogeneous porous media.

Subsurface formations often contain multiple minerals with different wettability characteristics upon contact with nonaqueous-phase liquids (NAPLs). Constitutive relationships between microstructure heterogeneity and NAPL fate and transport in these formations are difficult to predict. Several studies have used pore-scale network models with faithful representations of rock pore space topology to predict macroscopic descriptors of two-phase flow, however wettability is usually considered as a spatially random variable. This study attempts to overcome this limitation by considering more realistic representations of rock mineralogy and wettability in these models. This is especially important for heterogeneous rocks where properties vary at the pore-scale. The work was carried out in two phases. First, pore-fluid occupancy maps during waterflooding were obtained by X-ray microtomography to elucidate the impact of pore wall mineralogy and wettability on water preferential flow paths and NAPL trapping within a heterogeneous aquifer sandstone (Arkose). Then, microtomography images of the rock were used to generate a hybrid pore network model (PNM) that incorporated both pore space topology and pore wall mineralogy. In-situ contact angles (CA) measured on the surface of different minerals were assigned to the network on a pore-by-pore basis to describe the exact wettability distribution of the rock (Pore-by-pore model). The equivalent network was used as input in a quasi-static flow model to simulate waterflooding, and the predictions of residual NAPL saturation and relative permeabilities were compared against their experimental counterparts. To examine the sensitivity of the model to the underlying fluid-solid interactions, we also used traditional methods of wettability characterization in the input data and assigned them randomly to the PNM. Wettability in this case was assessed from macroscale CA distribution of oil droplets on the surface of unpolished Arkose substrates released by spontaneous imbibition of water (Arkose model) and from pendant drop measurements on polished quartz (Quartz model). Our results revealed that the Pore-by-pore model predicted waterflooding with the highest accuracy among all three cases. The Arkose model slightly overestimated NAPL removal whereas the Quartz model failed to predict the experiments. More in-depth analysis of the Pore-by-pore and Arkose models showed that macroscopic transport quantities are less dependent to microstructure heterogeneity if minerals are distributed uniformly across the rock. The predictions herein indicate the importance of incorporating mineralogy and wettability maps to improve the prediction capabilities of PNMs especially in systems with high mineral heterogeneity, where minerals are nonuniformly distributed, or selective fluid-mineral interactions are targeted.

Pore-scale dynamics of nanofluid-enhanced NAPL displacement in carbonate rock.

This study presents a pore-scale investigation of two-phase flow dynamics during nanofluid flooding in subsurface formations containing non-aqueous phase liquids (NAPLs) such as crude oils. The goal was to gain fundamental understanding of the dominant displacement mechanisms of NAPL at different stages of nanofluid injection in a carbonate rock using x-ray microtomography integrated with a miniature core-flooding system. The nanofluid consisted of surfactant-based microemulsions with in-situ synthesized silica nanoparticles. After establishing its initial wettability state, the carbonate core sample was subjected to various pore volumes (PV) of nanofluid flooding (from 0.5 to 10) to examine the impact on NAPL flow dynamics. We found that most NAPL mobilization occurred within the first PV of injection, removing nearly 50% of NAPL from the rock. The nanofluid invaded into larger pores first due to a sharp decrease in NAPL/brine interfacial tension (from 14 to 0.5 mN/m) and contact angle (from 140 to 88°). With higher amount of nanofluid delivered into the pores through advection, over 90% of NAPL droplets were emulsified and their size decreased from 9 to 3 µm. Subsequent nanofluid injection could further remove NAPL from the smaller pores by altering the thickness of NAPL layers adsorbed on the rock. This dynamic solubilization process reached equilibrium after 5 PV of injection, leading to a reduced layer thickness (from 12 to 0.2 µm), a narrower in-situ contact angle distribution around 81°, and an additional 16% of NAPL removal.

Rhenium-Catalyzed Intramolecular Carboalkoxylation and Carboamination of Alkynes for the Synthesis of C3-Substituted Benzofurans and Indoles.

A rhenium-catalyzed carboalkoxylation and carboamination of alkyne is reported. This reaction provides an efficient route to synthesize de novo C3-substituted benzofurans and indoles under mild conditions in moderate to good yields. Mechanistic studies revealed that the rhenium played the role of a π acid catalyst to activate the alkynes, followed by a charge-accelerated [3,3]-sigmatropic rearrangement.

A Fast ML-Based Single-Step Localization Method Using EM Algorithm Based on Time Delay and Doppler Shift for a Far-Field Scenario.

This study discusses the localization problem based on time delay and Doppler shift for a far-field scenario. The conventional location methods employ two steps that first extract intermediate parameters from the received signals and then determine the source position from the measured parameters. As opposed to the traditional two-step methods, the direct position determination (DPD) methods accomplish the localization in a single step without computing intermediate parameters. However, the DPD cost function often remains non-convex, thereby it will cost a high amount of computational resources to find the estimated position through traversal search. Weiss proposed a DPD estimator to mitigate the computational complexity via eigenvalue decomposition. Unfortunately, when the computational resources are rather limited, Weiss's method fails to satisfy the timeliness. To solve this problem, this paper develops a DPD estimator using expectation maximization (EM) algorithm based on time delay and Doppler shift. The proposed method starts from choosing the transmitter-receiver range vector as the hidden variable. Then, the cost function is separated and simplified via the hidden variable, accomplishing the transformation from the high dimensional nonlinear search problem into a few one dimensional search subproblems. Finally, the expressions of EM repetition are obtained through Laplace approximation. In addition, we derive the Cramér⁻Rao bound to evaluate the best localization performance in this paper. Simulation results confirm that, on the basis of guaranteeing high accuracy, the proposed algorithm makes a good compromise in localization performance and computational complexity.

Dual Gold-Catalyzed Formal Tetradehydro-Diels-Alder Reactions for the Synthesis of Carbazoles and Indolines.

This work reports a dual gold-catalyzed tetradehydro-Diels-Alder reaction for the synthesis of nitrogen-containing aromatic heterocycles. Under the catalytic system (IPrAuNTf2 /DIPEA), indolines and carbazoles as well as other N-containing aromatic heterocycles were prepared in high yields with good functional group tolerance. Unlike the traditional thermal tetradehydro-Diels-Alder reactions, diluted reaction concentration and radical prohibitors are not required for this protocol. Experimental data support a mechanism involving gold vinylidene species, which undergoes a 6 π electrocyclization, followed with 1,2-hydrogen shift.

De Novo Synthesis of Phenols and Naphthols through Oxidative Cycloaromatization of Dienynes.

In this work, a rhodium-catalyzed oxidative cycloaromatization of dienynes, which provides a highly straightforward and efficient way to access polysubstituted naphthols and phenols under mild conditions, is described. Challenged electron-withdrawing groups are well tolerated in this protocol, and late-stage phenyl ring formation is demonstrated.