Micro-annulus generation under downhole conditions: Insights from three-dimensional staged finite element analysis of cement hardening and wellbore operations

A micro-annulus(MA)is defined as a high permeability zone or gap initiating/occurring at the casingcement and cement-formation interfaces during the wellbore life span.An MA can significantly compromise wellbore integrity by establishing enhanced fluid flow pathways.This study uses a staged finite element approach to simulate wellbore integrity during various loading steps of wellbore operations under downhole conditions.Particular emphasis is placed on the processes of cement poro-elastic property evolution,volume variation,and pore pressure variation as part of the cement hardening step.The resulting state of stress during the life cycle of a typical injection well(i.e.hardening,completion,and injection)is analyzed to assess the onset and evolution of micro-annuli at various interfaces of the composite wellbore system under downhole conditions.The results show that cement shear failure is observed at the casing-cement interface during pressure testing(excessive wellbore pressure);and tensile debonding failure initiates at the cement-formation interface due to cement shrinkage during hardening and injection-related cooling(thermal cycling).Sensitivity analyses considering several parameters show that:(1)the degree of poro-elastic bulk shrinkage has significant implications for both shear and tensile failure initiation e the less the cement shrinks,the less likely the failure initiation is;(2)cement integrity increases with increasing depth;(3)cement pore pressure evolution has significant implications for tensile failure e if cement pore pressure decreases more,higher temperature differences can be sustained before an MA occurs;and(4)cement temperature fluctuations during hardening promote initiation of debonding failure.In summary,the results presented indicate that establishing downhole conditions to quantitatively analyze MA generation is necessary.The results are different compared to laboratory studies without considering/simulating downhole conditions.The knowledge from this study can raise the awareness of predicting and evaluating MA under downhole conditions and can be used to supplement and improve future laboratory experiments.

Digestive perianastomotic ulcerations after intestinal resection in children

Digestive perianastomotic ulceration(DPAU)is a rare complication after intestinal resection and anastomosis occurring at or near the anastomosis site.The purpose of this review is to summarize the characteristics of DPAU,including the etiology,diagnosis and differential diagnosis,clinical manifestations,treatment,and future research.All recent literature on DPAU was searched in PubMed,Embase,and Cochrane and then reviewed.The clinical manifestations of DPAU are mainly gastrointestinal symptoms such as bloody stool and chronic anemia.The diagnosis of DPAU is difficult.Specific diseases,such as Crohn’s disease,must be ruled out before a diagnosis can be made.In addition,there are no clear treatment guidelines due to the high degree of heterogeneity in response to drugs and surgery.It is recommended to adjust medication in time and combine various treatment methods.In addition,the mechanism that causes DPAU is not well understood;however,several possible mechanisms have been proposed,such as scar tissue ischemia and underlying diseases.Moreover,there is a high risk of relapses,and a long-term follow-up is necessary.Numerous issues remain to be solved in this area;therefore,more randomized controlled trials and studies should be carried out to further understand this disease.

丹江口水库鱼类群落特征及其历史变化

为了解丹江口水库鱼类群落现状及历史变化,作者于2018–2019年采用多网目复合刺网采样和渔民渔获物调查的方式对丹江口水库进行了鱼类群落调查。本次调查共采集鱼类33种,隶属5目11科29属,以鲤科鱼类为主,占总数的63.6%。基于多网目复合刺网采样的鱼类群落多样性指数和单位努力捕捞量(catch per unit effort,CPUE,g·day^(-1)·m^(-2))在各采样点间具有一定的差异。目前丹江口水库以定居性、喜静缓流、杂食性和肉食性鱼类为主。与20世纪50年代和80年代的历史资料相比,丹江口水库鱼类物种丰富度先升高后下降;而生态类型则呈现杂食性鱼类、喜流水性鱼类和洄游性鱼类比例持续下降的趋势。2018–2019年丹江口水库鱼类组成与20世纪80年代的相似性指数为0.35(中等不相似),与20世纪50年代的相似性指数为0.29(中等不相似)。调查结果表明半个世纪以来丹江口水库鱼类群落结构发生了较大变化,目前趋于小型化和简单化。这些变化可能是由大坝建设、渔业放养、不合理捕捞、外来鱼类引入等人类活动所致。

Protective effects of sirtuin 3 on titanium particle-induced osteogenic inhibition by regulating the NLRP3 inflammasome via the GSK-3β/β-catenin signalling pathway

Periprosthetic osteolysis(PPO)remains the key factor in implant failure and subsequent revision surgery and is mainly triggered by wear particles.Previous studies have shown that inhibition of osteoblastic differentiation is the most widespread incident affecting the interface of trabecular and loosening prostheses.Additionally,the NLRP3 inflammasome is activated by prosthetic particles.Sirtuin3,an NAD+-dependent deacetylase of mitochondria,regulates the function of mitochondria in diverse activities.However,whether SIRT3 can mitigate wear debris-induced osteolysis by inhibiting the NLRP3 inflammasome and enhancing osteogenesis has not been previously reported.Therefore,we investigated the role of SIRT3 during the process of titanium(Ti)particle-induced osteolysis.We revealed that upregulated SIRT3 dramatically attenuated Ti particle-induced osteogenic inhibition through suppression of the NLRP3 inflammasome and improvement of osteogenesis in vivo and in vitro.Moreover,we found that SIRT3 interference in the process of Ti particle-induced osteolysis relied on the GSK-3β/β-catenin signalling pathway.Collectively,these findings indicated that SIRT3 may serve as a rational new treatment against debris-induced PPO by deacetylase-dependent inflammasome attenuation.

Dynamic nano-Ag colloids cytotoxicity to and accumulation by Escherichia coli:Effects of Fe^3+,ionic strength and humic acid

Released Ag ions or/and Ag particles are believed to contribute to the cytotoxicity of Ag nanomaterials,and thus,the cytotoxicity and mechanism of Ag nanomaterials should be dynamic in water due to unfixed Ag particle:Ag+ ratios.Our recent research found that the cytotoxicity of PVP-Ag nanoparticles is attributable to Ag particles alone in 3 hr bioassays,and shifts to both Ag particles and released Ag^+ in 48 hr bioassays.Herein,as a continued study,the cytotoxicity and accumulation of 50 and 100 nm Ag colloids in Escherichia coli were determined dynamically.The cytotoxicity and mechanisms of nanoAg colloids are dynamic throughout exposure and are derived from both Ag ions and particles.Ag accumulation by E.coli is derived mainly from extracellular Ag particles during the initial 12 hr of exposure,and thereafter mainly from intracellular Ag ions.Fe^3+ accelerates the oxidative dissolution of nano-Ag colloids,which results In decreasing amounts of Ag particles and particle-related toxicity.Na^+ stabilizes nano-Ag colloids,thereby decreasing the bioavailability of Ag particles and particle-related toxicity.Humic acid(HA) binds Ag^+ to form Ag^+-HA,decreasing ion-related toxicity and binding to the E.coli surface,decreasing particle-related toxicity.HA in complex conditions showed a stronger relative contribution to toxicity and accumulation than Na^+ or Fe^3+.The results highlighted the cytotoxicity and mechanism of nano-Ag colloids are dynamic and affected by environmental factors,and therefore exposure duration and water chemistry should be seriously considered in environmental and health risk assessments.