Novel Method for Optimization Cement Slurry Based on the Wellbore Integrity Model in High-Temperature and High-Pressure Conditions.

The integrity of the cement sheath is crucial for ensuring the long-term safe and efficient production of oil and gas wells. The mechanical properties of the cement sheath are improved by optimizing the cement slurry to match the actual operating conditions, further enhancing the wellbore integrity. In high-temperature and high-pressure (HTHP) conditions, a mechanics model of casing-cement sheath-formation was developed based on the thick-walled cylinder theory, considering the coupling effect of temperature and pressure as well as elastic and plastic deformation of the cement sheath. The relationship between the mechanical parameters of the cement sheath, such as elastic modulus, Poisson's ratio, and yield strength, and casing pressure under different temperatures was analyzed based on the simulation results. A control chart of the mechanical properties of the cement sheath under high-temperature and high-pressure environments was subsequently developed. It was concluded that the elastic deformation of the cement sheath occurs first followed by plastic deformation as the casing pressure increases, corresponding to the yielding point of tangential stress on the cement sheath. The cement sheath is more prone to failure in high-temperature conditions due to thermal stress. Sensitivity analysis revealed that a cement sheath with a low elastic modulus and high yield strength contributes to enhancing its integrity. The developed control chart enables a quick and quantitative estimation of whether the cement sheath meets the requirements of downhole conditions. Most importantly, the cement slurry is optimized, based on the theoretical method, to improve the seal integrity of the cement sheath. This study provides a quantitative evaluation of cement slurry optimization and offers practical guidance for managing the wellbore integrity by identifying the mechanical parameters of cement sheaths under operating conditions.

Resonances and antiresonances in heat generation by spin current in a quantum dot.

We study the heat generation in a quantum dot exposed to a rotating magnetic field and coupled to a normal lead. Both electron-phonon interaction and electron-electron interaction are considered in the dot. We show the emergence of resonances and antiresonances in the heat generation, which we attribute to constructive interference and destructive interference between phonon waves emitted from opposite spin channels in the dot.

Study on Rock Mechanical Properties and Wellbore Stability of Fractured Carbonate Formation Based on Fractal Geometry.

To mitigate borehole wall instability in fractured carbonate formations in an oilfield, the main factors affecting borehole wall instability were determined by combining the characteristics of underground cores, logging data, and a series of laboratory mechanics experiments. The geometric morphology characteristics of a carbonate rock fracture surface were studied together with an artificial rock fracture surface formed by triaxial mechanics experiments. A relationship between the geometric morphology characteristics of a fracture surface and rock mechanical properties was established based on fractal geometry. Using the Mohr-Coulomb failure and weak plane failure criteria, a rock strength criterion based on the fractal characteristics of a rock fracture surface was established. Finally, the mechanical rock properties characterized by fractal geometry were imported into the established borehole stability evaluation model. The results show that a collapse formation is mainly limestone with relatively developed microfractures, and some fractures are filled with expansive clay. The anisotropy of mechanical properties of bedrocks and microfractured rocks is obvious, whereas drilling-fluid immersion has little effect on the mechanical properties of a rock. 3D scanning experiments of artificial fracture surfaces formed after a triaxial mechanical test of a bedrock and fracture surfaces of a rock with microfractures show that the geometric characteristics of fracture surfaces after bedrock failure were more complex than those of fractured rocks. The geometric characteristics of rock fracture surfaces were numerically expressed through astatistical analysis and fractal geometry. Function relationships among cohesion, an internal friction angle, and fractal dimensions of bedrocks and microfracture rocks were fitted. A numerical simulation of borehole stability based on the fractal model of a carbonate fracture surface shows that different fracture inclinations and borehole trajectories significantly influence the collapse pressure equivalent density of a borehole wall. On drilling a horizontal well along the inclination of a fracture, the collapse pressure equivalent density of the borehole wall is relatively low when the fracture inclination is along the direction of the minimum horizontal principal stress. Unlike that from a conventional borehole stability model, the collapse pressure equivalent density calculated from the fractal model will increase by 0.1-0.2 g/cm3. The study results provide a theoretical basis for safe and efficient drilling in fractured carbonate formations.

Clinical Results and Aortic Remodeling After Endovascular Treatment for Complicated Type B Aortic Dissection With the "Fabulous" Stent System.

OBJECTIVE: To report the clinical outcomes and aortic remodeling after the implantation of a self-developed, biomechanically optimized, two-stage thoracic stent system named Fabulous. BACKGROUND: Given the efficacy of the PETTICOAT concept, the benefits of Fabulous and the behavior of remodeling in different segments need further investigation. METHODS: This is a prospective and multicenter study. From 2017 to 2019, 145 patients (mean age, 56.6 years; 88.3% male) from 14 centers were included in this cohort. The clinical results and core laboratory results were from a central electronic data capture system. Computed tomographic angiography was performed preoperatively, 1 month, 6 months and yearly thereafter and was used for volumetric analysis by 3mensio (Bilthoven, The Netherlands). After the 1-year follow-up, 97.2 and 87.6% of the clinical and imaging results of the eligible patients were available. RESULTS: Both stent grafts and bare stents were successfully delivered in place in 100% of the patients. The 30-day mortality and 1-year freedom from all-cause mortality were 2.1 and 96.6%, respectively. The incidence of entry flow was 11.7% at 30 days and 6.2% at 365 days. No cases of stent-induced new entry (SINE) or reintervention were observed. After the 1-year follow-up, the true lumen/overall volume ratio reached 88%. The following subdivided segment volume changes were recorded: stent graft segment TL +56%; FL -92%, bare stent segment TL +32%; FL -75%, and there were no significant changes in the visceral segment. CONCLUSIONS: These outcomes indicated that there were favorable clinical benefits of Fabulous stent system. This device achieved a low short-term mortality and a low incidence of reintervention. In addition, patients undergoing Fabulous stent system implantation showed remodeling both on descending aorta and on the distal aorta. The volume changes in the TL and FL varied in the different segments. The long-term follow-up is still ongoing.

Electrically controlled spin reversal and spin polarization of electronic transport in nanoporous graphene nanoribbons.

Based on first-principles calculations, the spin-dependent electronic transport of nanoporous graphene nanoribbons is investigated. A three-terminal configuration is proposed, which can electronically control the spin polarization of transmission, instead of magnetic methods. By modulating the gate voltage, not only could the transmission be switched between completely spin up and spin down polarized states to realize a dual-spin filter, but also the spin polarization could be finely tuned between 100% and -100%. Any ratio of spin up to spin down transport electrons can be realized, providing more possibilities for the design of nanoelectronic devices. Further analysis shows that the transmission spectra, with two distinct transmission peaks with opposite spins around EF, are the key point, which are contributed by p orbitals. And such a phenomenon is robust to the width and length of the nanoporous graphene nanoribbons, suggesting that it is an intrinsic feature of these systems. The electrical control on spin polarization is realized in pure-carbon systems, showing great application potential.

Neurexin and Neuroligins Maintain the Balance of Ghost and Satellite Boutons at the Drosophila Neuromuscular Junction.

Neurexins and neuroligins are common synaptic adhesion molecules that are associated with autism and interact with each other in the synaptic cleft. The Drosophila neuromuscular junction (NMJ) bouton is a well-known model system in neuroscience, and ghost and satellite boutons, respectively, indicate the poor development and overgrowth of the NMJ boutons. However, the Drosophila neurexin (DNrx) and Drosophila neuroligins (DNlgs) are mainly observed in type Ib boutons, indicating the ultrastructural and developmental phenotypes of the Drosophila NMJ. Here, we identified the ultrastructural and developmental features of ghost and satellite boutons by utilizing dneurexin (dnrx) and dneuroligins (dnlgs) fly mutants and other associated fly strains. Ghost boutons contain synaptic vesicles with multiple diameters but very rarely contain T-bar structures and swollen or thin subsynaptic reticulum (SSR) membranes. The muscle cell membrane is invaginated at different sites, stretches to the ghost bouton from different directions, forms several layers that enwrap the ghost bouton, and then branches into the complex SSR. Satellite boutons share a common SSR membrane and present either a typical profile in which a main bouton is encircled by small boutons or two atypical profiles in which the small boutons are grouped together or distributed in beads without a main bouton. Electron and confocal microscopy data showed that dnrx, dnlg1, dnlg2, dnlg3, and dnlg4 mutations led to ghost boutons; the overexpression of dnrx, dnlg1, dnlg2, dnlg3, and dnlg4 led to satellite boutons; and the dnlg2;dnlg3 double mutation also led to satellite boutons. These results suggested that DNrx and DNlgs jointly maintain the development and function of NMJ boutons by regulating the balance of ghost and satellite boutons in Drosophila.

Photogalvanic Effect in Nitrogen-Doped Monolayer MoS2 from First Principles.

We investigate the photogalvanic effect in nitrogen-doped monolayer molybdenum disulfide (MoS2) under the perpendicular irradiation, using first-principles calculations combined with non-equilibrium Green function formalism. We provide a detailed analysis on the behavior of photoresponse based on the band structure and in particular the joint density of states. We thereby identify different mechanisms leading to the existence of zero points, where the photocurrent vanishes. In particular, while the zero point in the linear photovoltaic effect is due to forbidden transition, their appearance in the circular photovoltaic effect results from the identical intensity splitting of the valance band and the conduction band in the presence of Rashba and Dresslhaus spin-orbit coupling. Furthermore, our results reveal a strong circular photogalvanic effect of nitrogen-doped monolayer MoS2, which is two orders of magnitude larger than that induced by the linearly polarized light.

Transport theory for electrical detection of the spin-momentum locking of topological surface states.

We provide a general transport theory for spin-polarized scanning tunneling microscopy (STM) through a doped topological insulator (TI) surface. It is found that different from the conventional magnetic substrate, the tunneling conductance through the tip-TI surface acquires an extra component determined by the in-plane spin texture, exclusively associated with the spin momentum locking. Importantly, this extra conductance unconventionally depends on the spatial azimuthal angle of the magnetized STM tip. By introducing a magnetic impurity to break the symmetry of rotation and local time reversal of the TI surface, we find that the measurement of the spatial resolved conductance can reconstruct the helical structure of spin texture, from which the spin-momentum locking angle can be extracted if the in-plane magnetization is induced purely by the spin-orbit coupling of surface Dirac electrons. Our theory offers an alternative way, differing from existing in-plane-current polarization probed in a multi-terminal setup or angle resolved photoemission spectroscopy, to electrically identify the helical spin texture on TI surfaces.

Bulk RKKY signatures of topological phase transition in silicene.

Silicene offers an ideal platform for exploring the phase transition due to strong spin-orbit interaction and its unique structure with strong tunability. With applied electric field and circularly polarized light, silicone is predicted to exhibit rich phases. We propose that these intricate phase transitions can be detected by measuring the bulk Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. We have in detail analyzed the dependence of RKKY interaction on phase parameters for different impurity configurations along zigzag direction. Importantly, we present an interesting comparison between different terms of RKKY interaction with phase diagram. It is found that the in-plane and out-of-plane terms can exhibit the local extreme value or change of sign at the phase critical point and remarkable difference in magnitude for different phase regions. Consequently, the magnetic measurement provides unambiguous signatures to identify various types of phase transition simultaneously, which can be carried out with present technique.

Effect of impurity resonant states on optical and thermoelectric properties on the surface of a topological insulator.

We investigate the thermoelectric effect on a topological insulator surface with particular interest in impurity-induced resonant states. To clarify the role of the resonant states, we calculate the dc and ac conductivities and the thermoelectric coefficients along the longitudinal direction within the full Born approximation. It is found that at low temperatures, the impurity resonant state with strong energy de-pendence can lead to a zero-energy peak in the dc conductivity, whose height is sensitively dependent on the strength of scattering potential, and even can reverse the sign of the thermopower, implying the switching from n- to p-type carriers. Also, we exhibit the thermoelectric signatures for the filling process of a magnetic band gap by the resonant state. We further study the impurity effect on the dynamic optical conductivity, and find that the resonant state also generates an optical conductivity peak at the absorption edge for the interband transition. These results provide new perspectives for understanding the doping effect on topological insulator materials.

[Karyotype and evolutionary trend analysis of Scutellaria species in Jinyun mountain, Chongqing].

Traditional squash method was used to analyze chromosome number and karyotypes of four Scutellaria species in Chongqing Jinyun Mountain Natural Reserve： Scutellaria tsinyunensis, S.yunnanensis, S.franchetiana and S.indica.The result showed that the chromosome numbers were 26 except for S.franchetiana, which had 24 chromosomes.These species were all diploid with metacentric and submetacentric chromosomes.Their karyotypes were symmetrical and primitive.The karyotype formula of S.tsinyunensis is 2n=2x=26=24m+2sm, 1B type, As.k=55.28%; the karyotype formula of S.yunnanensis var.salicifolia is 2n=2x=26=26m, 1B type, As.k=56.11%; the karyotype formula of S.franchetiana is 2n=2x=24=20m+4sm, 2B type, As.k=58.50%; the karyotype formula of S.indica is 2n=2x=24=20m+4sm, 2B type, As.k=58.41%.The results were compared with the reported data of S.baicalensis and S.alaschanica.S.alaschanica is expected to be the most advanced one whereas S.tsinyunensis, and S.yunnanensis var. salicifolia primitive.These results are expected to provide some references to the origin and differentiation of genus Scutellaria.

[Study on relieving effects of exogenous SNP, Spd on Belamcanda chinensis under salt-alkalline stress].

The study is aimed to provide the theoretical basis for exploiting and utilization of salt-alkaline soil and cultivating Belamcanda chinensis. In this study, we exerted exogenous substances SNP, Spd to relieve the damage of the mixing salt-alkaline stress on B. chinensis seedling which is NaCl, Na2SO4, NaHCO3 and Na2CO3 four kinds of salt molar ratio of 9: 1: 9: 1, salt concentration of 100 mmol x L(-1). The result illustrated that high pH stress is a major factor caused the salt-alkaline stress, the interaction between time and the concentration of each, treatment was observed, what is more, there are synergies between the salt and alkali stress. The content of B. chinensis seedling leaves' membrane peroxidation index (MDA, O2-*) and metabolites (soluble protein, soluble sugars, organic acids) are showing an upward trend in varying degrees under 100 mmol x L(-1) salt-alkaline stress. It is effective to reduce the content of MDA and O2-*. and improve the levels of metabolites, in which the SNP (0.05 mmol x L(-1)) and Spd (0.5 mmol x L(-1)) to alleviate damage effects is the best. Therefore we can hold the conclusion that SNP and Spd can effectively mitigate the damage of B. chinensis seedling on salt-alkaline stress, improve the resistance ability of B. chinensis seedling which can provide the scientific basis for the utilization of salt-alkaline soil, and the cultivation of B. chinensis.

Polyurethanes containing zwitterionic sulfobetaines and their molecular chain rearrangement in water.

Novel polyurethanes with zwitterionic sulfobetaines, termed PUR-APS, were designed and synthesized by chain-extension of biodegradable poly(ε-caprolactone) containing N,N'-bis (2-hydroxyethyl) methylamine ammonium propane sulfonate (PCL-APS) with hexamethylene diisocyanate (HDI). The bulk properties of polymers were characterized by nuclear magnetic resonance spectrum (NMR), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatograph (GPC), and differential scanning calorimetry (DSC). Results showed that the polymers were successfully synthesized. Water contact angles (WCAs) and X-ray photoelectron spectroscopy (XPS) revealed that molecular chains of the polymers rearranged after soaking in water. The amount of protein adsorption, determined by bicinchoninic acid (BCA) assay, was less than 300 ng/cm(2) and decreased after hydration. The blood compatibility of the polymers was evaluated by the degree of hemolytic and activated partial thromboplastic time (APTT) and prothrombin time (PT). Results indicated that PUR-APS polymers had good blood compatibility. Therefore, polyurethanes containing sulfobetaines have a great potential for biomedical application.

[Diameter and length measurement of infrarenal inferior vena cava in Shandong Peninsula adult and its significance].

OBJECTIVE: To measure the diameter and length of infrarenal inferior vena cava (IVC) in Shandong Peninsula adult through digital subtraction angiography (DSA) for better vena cava filter (VCF) choice and placement. METHODS: From April 2008 to June 2010, 83 discontinuous patients (49 males and 34 females, mean age 56.4 years) with deep venous thrombosis (DVT) of lower extremity were placed VCF through DSA according to ACCP-8. During operation, diameter and length of infrarenal IVC were measured. At the same time, the renal vein location and the type of the IVC were identified to help the VCF choice. RESULTS: All the VCFs were placed successfully, no complications occurred. The diameter of infrarenal IVC was 10 to 26 mm with a mean of (19 ± 5) mm. The average length from beginning of IVC to the lower renal vein was (10.6 ± 2.8) cm. The renal vein was located between the first and second lumbar vertebra, the IVC beginning was located between the fourth and fifth lumbar vertebra. CONCLUSIONS: Diameter and length measurement of infrarenal IVC is helpful to the VCF selection and the domestic VCF research. Vena cava angiography is very important to the accurate placement of VCF.

Antitumor-promoting effects of cyclic diarylheptanoids on Epstein-Barr virus activation and two-stage mouse skin carcinogenesis.

Eleven cyclic diarylheptanoids were screened as potential antitumor promoters by examining the ability of the compounds to inhibit Epstein-Barr virus early antigen activation (induced by 12-O-tetradecanoylphorbol-13-acetate) in Raji cells. 13-Oxomyricanol and myricanone showed the highest activity and also exhibited remarkable inhibitory effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. These data suggest that certain diarylheptanoids might be valuable antitumor promoters and/or chemopreventors.

Anti-tumor-promoting effects of isoflavonoids on Epstein-Barr virus activation and two-stage mouse skin carcinogenesis.

As a part of screening studies for anti-tumor promoters, fifteen isoflavonoids isolated from plants of the genus Millettia (Leguminosae) were evaluated by examining their possible inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate in Raji cells. All of the compounds tested in this study showed inhibitory activity against EBV, without showing any cytotoxicity. Auriculasin (11) and millepurone (13), which is an oxidized isoflavone analogue, both having one or more prenyl side-chains and a 3',4'-dihydroxyphenyl group in the molecule, showed more potent activity than any of the other compounds tested. Furthermore, millepurone (13) exhibited a marked inhibitory effect on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. The results of the present investigation indicate that some of these isoflavonoids might be valuable anti-tumor promoters.