Simulation study on cuttings transport of the backreaming operation for long horizontal section wells

The backreaming operation plays a significant role in safe drilling for horizontal wellbores, while it may cause severe stuck pipe accidents. To lower the risk of the stuck pipe in backreaming operations, the mechanism of cuttings transport needs to be carefully investigated. In this research, a transient cuttings transport with multiple flow patterns model is developed to predict the evolution of cuttings transported in the annulus while backreaming. The established model can provide predictions of the distribution of cuttings bed along the wellbore considering the bulldozer effect caused by large-size drilling tools(LSDTs). The sensitivity analyses of the size of LSDTs, and backreaming operating parameters are conducted in Section 4. And a new theory is proposed to explain the mechanism of cuttings transport in the backreaming operation, in which both the bit and LSDTs have the “cleaning effect” and “plugging effect”.The results demonstrate that the cuttings bed in annuli is in a state of dynamic equilibrium, but the overall trend and the distribution pattern are obvious. First, larger diameters and longer drilling tools could lead to a higher risk of the stuck pipe. Second, we find that it is not the case that the higher flow rate is always better for hole cleaning, so three flow-rate intervals are discussed separately under the given conditions. When the “dangerous flow rate”(<33 L/s in Case 4) is employed, the cuttings bed completely blocks the borehole near the step surface and causes a stuck pipe directly. If the flow rate increases to the “low flow rate” interval(33-35 L/s in Case 4), a smaller flow rate instead facilitates borehole cleaning. If the flow rate is large enough to be in the “high flow rate” interval(>35 L/s in Case 4),the higher the flow rate, the better the cleaning effect of cuttings beds. Third, an interval of tripping velocity called “dangerous velocity” is proposed, in which the cuttings bed accumulation near the LSDTs is more serious than those of other tripping velocities. As long as the applied tripping velocity is not within the “dangerous velocity”(0.4-0.5 m/s in Case 5) interval in the backreaming operation, the risk of the stuck pipe can be controlled validly. Finally, through the factors analyses of the annular geometry,particle properties, and fluid properties in Section 5, it can be found that the “low flow rate”, “high flow rate” and “dangers flow rate” tend to decrease and the “dangerous velocity” tends to increase with the conditions more favorable for hole cleaning. This study has some guiding significance for risk prediction and parameter setting of the backreaming operation.

Prediction of high-mobility two-dimensional electron gas at KTaO_3-based heterointerfaces

First-principles calculations are performed to explore the possibility of generating the two-dimensional electron gas(2 DEG) at the interface between LaGaO_3/KTaO_3 and NdGaO_3/KTaO_3(001) heterostructures. Two different models —i.e., the superlattice model and the thin film model — are used to conduct a comprehensive investigation of the origin of charge carriers. For the symmetric superlattice model, the LaGaO_3(or NdGaO_3) film is nonpolar. The 2 DEG with carrier density on the order of 1014 cm^(-2) originates from the Ta dxy electrons contributed by both LaGaO_3(or NdGaO_3) and KTaO_3. For the thin film model, large polar distortions occur in the LaGaO_3 and NdGaO_3 layer, which entirely screens the built-in electric field and prevents electrons from transferring to the interface. Electrons of KTaO_3 are accumulated at the interface, contributing to the formation of the 2 DEG. All the heterostructures exhibit conducting properties regardless of the film thickness. Compared with the Ti dxy electrons in SrTiO_3-based heterostructures, the Ta dxy electrons have small effective mass and they are expected to move with higher mobility along the interface. These findings reveal the promising applications of 2 DEG in novel nanoelectronic devices.

Resistance to antibody-drug conjugates in breast cancer:mechanisms and solutions

Antibody-drug conjugates(ADCs)are a rapidly developing therapeutic approach in cancer treatment that has shown remarkable activity in breast cancer.Currently,there are two ADCs approved for the treatment of human epidermal growth factor receptor 2-positive breast cancer,one for triple-negative breast cancer,and multiple investigational ADCs in clinical trials.However,drug resistance has been noticed in clinical use,especially in trastuzumab emtansine.Here,the mechanisms of ADC resistance are summarized into four categories:antibodymediated resistance,impaired drug trafficking,disrupted lysosomal function,and payload-related resistance.To overcome or prevent resistance to ADCs,innovative development strategies and combination therapy options are being investigated.Analyzing predictive biomarkers for optimal therapy selection may also help to prevent drug resistance.

Epididymis cell atlas in a patient with a sex development disorder and a novel NR5A1 gene mutation

This study aims to characterize the cell atlas of the epididymis derived from a 46,XY disorders of sex development(DSD)patient with a novel heterozygous mutation of the nuclear receptor subfamily 5 group A member 1(NR5A1)gene.Next-generation sequencing found a heterozygous c.124C>G mutation in NR5A1 that resulted in a p.Q42E missense mutation in the conserved DNA-binding domain of NR5A1.The patient demonstrated feminization of external genitalia and Tanner stage 1 breast development.The surgical procedure revealed a morphologically normal epididymis and vas deferens but a dysplastic testis.Microfluidic-based single-cell RNA sequencing(scRNA-seq)analysis found that the fibroblast cells were significantly increased(approximately 46.5%),whereas the number of main epididymal epithelial cells(approximately 9.2%),such as principal cells and basal cells,was dramatically decreased.Bioinformatics analysis of cell–cell communications and gene regulatory networks at the single-cell level inferred that epididymal epithelial cell loss and fibroblast occupation are associated with the epithelial-to-mesenchymal transition(EMT)process.The present study provides a cell atlas of the epididymis of a patient with 46,XY DSD and serves as an important resource for understanding the pathophysiology of DSD.

Effects of slag composition and additive type on desulfurization of rejected electrolytic manganese metal scrap by Na2O-containing electroslag

The recycling rate of rejected electrolytic manganese metal(EMM)scrap can be increased by inhibiting the manganese metal(MM)vaporization during the remelting process with electroslag.However,if the latter is achieved by reducing the remelting temperature,the desulfurization behavior will deteriorate.Therefore,Na_(2)O-containing electroslag and metallic additive were used to increase the rejected EMM scrap recovery ratio.The respective high-temperature experiment was conducted in a MoSi_(2) electrical resistance furnace filled with fluid argon at 1673 K using five different types of electroslag with the Na_(2)O content ranging from 5.81%to 15.71%.High-purity metallic magnesium and magnesium calcium alloy additives were used as deoxidizers.The addition of Na_(2)O and metallic additives effectively promoted the desulfurization and deoxidization of MM.The removal of sulfur and oxygen by the interaction between Na_(2)O-containing electroslag melt and molten MM with metallic additive was analyzed from the thermodynamic and kinetic standpoints.The effect of Na_(2)O-containing electroslag volatilization on desulfurization and deoxidization was considered.With an increase in Na_(2)O content in the slag,the mass loss rates of Na_(2)O and electroslag rose,as well as the final sulfur partition ratio.If the Na_(2)O content volatilized in the slag melt did not exceed 10.44%,the sulfur removal ratio was increased by high sulfide capacity and CaO activity in all slags due to the addition of Na_(2)O.The rejected EMM scrap deoxidization ratio grew with the increased activity of CaO and reduced activity of Al_(2)O_(3) in the molten slag,caused by the increased Na_(2)O content in the molten slag.The addition of metallic Mg and Mg-Ca alloy indirectly promoted desulfurization and deoxidization by reducing the MnO content in the rejected EMM scrap and growing slag oxidability.The Mg-Ca alloy could also react with dissolved sulfur and oxygen,directly promoting desulfurization and deoxidization processes.The Na_(2)O content in slag should not exceed 10.44%to ensure the high desulfurization and deoxidization abilities,fluidity and low volatilization of slag.

Multiple-valley effect on modulation of thermoelectric properties of n-type ZrCuSiAs-structure oxyantimonides LnTSbO(Ln=lanthanides and T=Zn,Mn)

Thermoelectric properties of n-type LnTSbO(Ln=lanthanides and T?Zn,Mn)were firstly investigated by the first-principles method and the semi-classical Boltzmann theory.The results show that a multiplevalley structure appears around the bottom of conduction band.The valley with a high band degeneracy consists of the bands with a weak band dispersion,leading to large magnitudes of the Seebeck coefficient but low electrical conductivity.The valley with a low band degeneracy is made up of the bands with an intense band dispersion,resulting in a high electrical conductivity but small magnitudes of the Seebeck coefficient.The thermoelectric properties are dominated by the energy difference,DE,between the valleys.The DE value of LnZnSbO linearly increases with the ionic radius of Ln.The thermoelectric properties are thus effectively modulated by varying the lanthanides.As a result,LnZnSbO(Ln?Ce-Nd)with the moderate values of DE shows a better thermoelectric performance.The multiple-valley effect is an effective way to modulate the thermoelectric properties of n-type LnTSbO.