The mechanical behaviors of rocks affected by high temperature and stress are generally believed to be significant for the stability of certain projects involving rocks, such as nuclear waste storage and geothermal re...The mechanical behaviors of rocks affected by high temperature and stress are generally believed to be significant for the stability of certain projects involving rocks, such as nuclear waste storage and geothermal resource exploitation. In this paper, veined marble specimens were treated to high temperature treatment and then used in conventional triaxial compression tests to investigate the effect of temperature, confining pressure, and vein angle on strength and deformation behaviors. The results show that the strength and deformation parameters of the veined marble specimens changed with the temperature, presenting a critical temperature of 600 . The triaxial compression strength of a horizontal vein () is obviously larger than that of a vertical vein (). The triaxial compression strength, elasticity modulus, and secant modulus have an approximately linear relation to the confining pressure. Finally, Mohr-Coulomb and Hoek-Brown criteria were respectively used to analyze the effect of confining pressure on triaxial compression strength.展开更多
Patients with locally advanced hepatocellular cancer(HCC)and portal vein tumor thrombosis(PVTT)have a dismal prognosis since limited treatment options are available for them.In recent years,effective systemic therapy,...Patients with locally advanced hepatocellular cancer(HCC)and portal vein tumor thrombosis(PVTT)have a dismal prognosis since limited treatment options are available for them.In recent years,effective systemic therapy,and advances in the understanding of technicalities and effectiveness of ablative therapies especially radiotherapy,have given some hope to prolong survival in them.This review summarized recent evidence in literature regarding the possible role of liver resection(LR)and liver transplantation(LT)in patients with locally advanced HCC and PVTT with no extrahepatic disease.Downstaging therapies have helped make curative resection or LT a reality in selected patients.This review emphasizes on the key points to focus on when considering surgery in these patients,who are usually relegated to palliative systemic therapy alone.Meticulous patient selection based on tumor biology,documented downstaging based on imaging and decrease in tumor marker levels,and an adequate waiting period to demonstrate stable disease,may help obtain satisfactory long-term outcomes post LR or LT in an intention to treat strategy in patients with HCC and PVTT.展开更多
Point-of-care ultrasound(POCUS)of the internal jugular vein(IJV)offers a noninvasive means of estimating right atrial pressure(RAP),especially in cases where the inferior vena cava is inaccessible or unreliable due to...Point-of-care ultrasound(POCUS)of the internal jugular vein(IJV)offers a noninvasive means of estimating right atrial pressure(RAP),especially in cases where the inferior vena cava is inaccessible or unreliable due to conditions such as liver disease or abdominal surgery.While many clinicians are familiar with visually assessing jugular venous pressure through the internal jugular vein,this method lacks sensitivity.The utilization of POCUS significantly enhances the visualization of the vein,leading to a more accurate identification.It has been demonstrated that combining IJV POCUS with physical examination enhances the specificity of RAP estimation.This review aims to provide a comprehensive summary of the various sonographic techniques available for estimating RAP from the internal jugular vein,drawing upon existing data.展开更多
BACKGROUND Hemorrhage associated with varices at the site of choledochojejunostomy is an unusual,difficult to treat,and often fatal manifestation of portal hypertension.So far,no treatment guidelines have been establi...BACKGROUND Hemorrhage associated with varices at the site of choledochojejunostomy is an unusual,difficult to treat,and often fatal manifestation of portal hypertension.So far,no treatment guidelines have been established.CASE SUMMARY We reported three patients with jejunal varices at the site of choledochojejun-ostomy managed by endoscopic sclerotherapy with lauromacrogol/α-butyl cyanoacrylate injection at our institution between June 2021 and August 2023.We reviewed all patient records,clinical presentation,endoscopic findings and treatment,outcomes and follow-up.Three patients who underwent pancre-aticoduodenectomy with a Whipple anastomosis were examined using conven-tional upper gastrointestinal endoscopy for suspected hemorrhage from the afferent jejunal loop.Varices with stigmata of recent hemorrhage or active he-morrhage were observed around the choledochojejunostomy site in all three patients.Endoscopic injection of lauromacrogol/α-butyl cyanoacrylate was carried out at jejunal varices for all three patients.The bleeding ceased and patency was observed for 26 and 2 months in two patients.In one patient with multiorgan failure and internal environment disturbance,rebleeding occurred 1 month after endoscopic sclerotherapy,and despite a second endoscopic sclero-therapy,repeated episodes of bleeding and multiorgan failure resulted in eventual death.CONCLUSION We conclude that endoscopic sclerotherapy with lauromacrogol/α-butyl cyanoac-rylate injection can be an easy,effective,safe and low-cost treatment option for jejunal varicose bleeding at the site of choledochojejunostomy.展开更多
Background: Cavernous transformation of the portal vein(CTPV) due to portal vein obstruction is a rare vascular anomaly defined as the formation of multiple collateral vessels in the hepatic hilum. This study aimed to...Background: Cavernous transformation of the portal vein(CTPV) due to portal vein obstruction is a rare vascular anomaly defined as the formation of multiple collateral vessels in the hepatic hilum. This study aimed to investigate the imaging features of intrahepatic portal vein in adult patients with CTPV and establish the relationship between the manifestations of intrahepatic portal vein and the progression of CTPV. Methods: We retrospectively analyzed 14 CTPV patients in Beijing Tsinghua Changgung Hospital. All patients underwent both direct portal venography(DPV) and computed tomography angiography(CTA) to reveal the manifestations of the portal venous system. The vessels measured included the left portal vein(LPV), right portal vein(RPV), main portal vein(MPV) and the portal vein bifurcation(PVB). Results: Nine males and 5 females, with a median age of 40.5 years, were included in the study. No significant difference was found in the diameters of the LPV or RPV measured by DPV and CTA. The visualization in terms of LPV, RPV and PVB measured by DPV was higher than that by CTA. There was a significant association between LPV/RPV and PVB/MPV in term of visibility revealed with DPV( P = 0.01), while this association was not observed with CTA. According to the imaging features of the portal vein measured by DPV, CTPV was classified into three categories to facilitate the diagnosis and treatment. Conclusions: DPV was more accurate than CTA for revealing the course of the intrahepatic portal vein in patients with CTPV. The classification of CTPV, that originated from the imaging features of the portal vein revealed by DPV, may provide a new perspective for the diagnosis and treatment of CTPV.展开更多
AIM:To develop an artificial intelligence(AI)diagnosis model based on deep learning(DL)algorithm to diagnose different types of retinal vein occlusion(RVO)by recognizing color fundus photographs(CFPs).METHODS:Totally ...AIM:To develop an artificial intelligence(AI)diagnosis model based on deep learning(DL)algorithm to diagnose different types of retinal vein occlusion(RVO)by recognizing color fundus photographs(CFPs).METHODS:Totally 914 CFPs of healthy people and patients with RVO were collected as experimental data sets,and used to train,verify and test the diagnostic model of RVO.All the images were divided into four categories[normal,central retinal vein occlusion(CRVO),branch retinal vein occlusion(BRVO),and macular retinal vein occlusion(MRVO)]by three fundus disease experts.Swin Transformer was used to build the RVO diagnosis model,and different types of RVO diagnosis experiments were conducted.The model’s performance was compared to that of the experts.RESULTS:The accuracy of the model in the diagnosis of normal,CRVO,BRVO,and MRVO reached 1.000,0.978,0.957,and 0.978;the specificity reached 1.000,0.986,0.982,and 0.976;the sensitivity reached 1.000,0.955,0.917,and 1.000;the F1-Sore reached 1.000,0.9550.943,and 0.887 respectively.In addition,the area under curve of normal,CRVO,BRVO,and MRVO diagnosed by the diagnostic model were 1.000,0.900,0.959 and 0.970,respectively.The diagnostic results were highly consistent with those of fundus disease experts,and the diagnostic performance was superior.CONCLUSION:The diagnostic model developed in this study can well diagnose different types of RVO,effectively relieve the work pressure of clinicians,and provide help for the follow-up clinical diagnosis and treatment of RVO patients.展开更多
BACKGROUND Hepatocellular carcinoma(HCC)patients complicated with portal vein tumor thrombus(PVTT)exhibit poor prognoses and treatment responses.AIM To investigate efficacies and safety of the combination of PD-1 inhi...BACKGROUND Hepatocellular carcinoma(HCC)patients complicated with portal vein tumor thrombus(PVTT)exhibit poor prognoses and treatment responses.AIM To investigate efficacies and safety of the combination of PD-1 inhibitor,transcatheter arterial chemoembolization(TACE)and Lenvatinib in HCC subjects comorbid with PVTT.METHODS From January 2019 to December 2020,HCC patients with PVTT types Ⅰ-Ⅳ were retrospectively enrolled at Beijing Ditan Hospital.They were distributed to either the PTL or TACE/Lenvatinib(TL)group.The median progression-free survival(mPFS)was set as the primary endpoint,while parameters like median overall survival,objective response rate,disease control rate(DCR),and toxicity level served as secondary endpoints.RESULTS Forty-one eligible patients were finally recruited for this study and divided into the PTL(n=18)and TL(n=23)groups.For a median follow-up of 21.8 months,the DCRs were 88.9%and 60.9%in the PTL and TL groups(P=0.046),res-pectively.Moreover,mPFS indicated significant improvement(HR=0.25;P<0.001)in PTL-treated patients(5.4 months)compared to TL-treated(2.7 months)patients.There were no treatment-related deaths or differences in adverse events in either group.CONCLUSION A triplet regimen of PTL was safe and well-tolerated as well as exhibited favorable efficacy over the TL regimen for advanced-stage HCC patients with PVTT types Ⅰ-Ⅳ.展开更多
A consensus meeting of national experts from all major national hepatobiliary centres in the country was held on May 26,2023,at the Pakistan Kidney and Liver Institute&Research Centre(PKLI&RC)after initial con...A consensus meeting of national experts from all major national hepatobiliary centres in the country was held on May 26,2023,at the Pakistan Kidney and Liver Institute&Research Centre(PKLI&RC)after initial consultations with the experts.The Pakistan Society for the Study of Liver Diseases(PSSLD)and PKLI&RC jointly organised this meeting.This effort was based on a comprehensive literature review to establish national practice guidelines for hilar cholangiocarcinoma(hCCA).The consensus was that hCCA is a complex disease and requires a multidisciplinary team approach to best manage these patients.This coordinated effort can minimise delays and give patients a chance for curative treatment and effective palliation.The diagnostic and staging workup includes high-quality computed tomography,magnetic resonance imaging,and magnetic resonance cholangiopancreato-graphy.Brush cytology or biopsy utilizing endoscopic retrograde cholangiopancreatography is a mainstay for diagnosis.However,histopathologic confirmation is not always required before resection.Endoscopic ultrasound with fine needle aspiration of regional lymph nodes and positron emission tomography scan are valuable adjuncts for staging.The only curative treatment is the surgical resection of the biliary tree based on the Bismuth-Corlette classification.Selected patients with unresectable hCCA can be considered for liver transplantation.Adjuvant chemotherapy should be offered to patients with a high risk of recurrence.The use of preoperative biliary drainage and the need for portal vein embolisation should be based on local multidisciplinary discussions.Patients with acute cholangitis can be drained with endoscopic or percutaneous biliary drainage.Palliative chemotherapy with cisplatin and gemcitabine has shown improved survival in patients with irresectable and recurrent hCCA.展开更多
BACKGROUND The prognosis of hepatocellular carcinoma(HCC)combined with portal and hepatic vein cancerous thrombosis is poor,for unresectable patients the combination of targeted therapy and immune therapy was the firs...BACKGROUND The prognosis of hepatocellular carcinoma(HCC)combined with portal and hepatic vein cancerous thrombosis is poor,for unresectable patients the combination of targeted therapy and immune therapy was the first-line recommended treatment for advanced HCC,with a median survival time of only about 2.7-6 months.In this case report,we present the case of a patient with portal and hepatic vein cancerous thrombosis who achieved pathologic complete response after conversion therapy.CASE SUMMARY In our center,a patient with giant HCC combined with portal vein tumor thrombus and hepatic vein tumor thrombus was treated with transcatheter arterial chemoembolization(TACE),radiotherapy,targeted therapy and immunotherapy,and was continuously given icaritin soft capsules for oral regulation.After 7 months of conversion therapy,the patient's tumor shrank and the tumor thrombus subsided significantly.The pathology of surgical resection was in complete remission,and there was no progression in the postoperative follow-up for 7 months,which provided a basis for the future strategy of combined conversion therapy.CONCLUSION In this case,atezolizumab,bevacizumab,icaritin soft capsules combined with radiotherapy and TACE had a good effect.For patients with hepatocellular carcinoma combined with hepatic vein/inferior vena cava tumor thrombus,adopting a high-intensity,multimodal proactive strategy under the guidance of multidisciplinary team(MDT)is an important attempt to break through the current treatment dilemma.展开更多
BACKGROUND It is well-described that the coronavirus disease 2019(COVID-19)infection is associated with an increased risk of thrombotic complications.While there have been many cases of pulmonary emboli and deep vein ...BACKGROUND It is well-described that the coronavirus disease 2019(COVID-19)infection is associated with an increased risk of thrombotic complications.While there have been many cases of pulmonary emboli and deep vein thrombosis in these patients,reports of COVID-19 associated portal vein thrombosis(PVT)have been uncommon.We present a unique case of concomitant PVT and splenic artery thrombosis in a COVID-19 patient.CASE SUMMARY A 77-year-old-male with no history of liver disease presented with three days of left-sided abdominal pain.One week earlier,the patient was diagnosed with mildly symptomatic COVID-19 and was treated with nirmatrelvir/ritonavir.Physical exam revealed mild right and left lower quadrant tenderness,but was otherwise unremarkable.Significant laboratory findings included white blood cell count 12.5 K/μL,total bilirubin 1.6 mg/dL,aminoaspartate transferase 40 U/L,and alanine aminotransferase 61 U/L.Computed tomography of the abdomen and pelvis revealed acute PVT with thrombus extending from the distal portion of the main portal vein into the right and left branches.Also noted was a thrombus within the distal portion of the splenic artery with resulting splenic infarct.Hypercoagulable workup including prothrombin gene analysis,factor V Leiden,cardiolipin antibody,and JAK2 mutation were all negative.Anticoagulation with enoxaparin was initiated,and the patient’s pain improved.He was discharged on apixaban.CONCLUSION It is quite uncommon for PVT to present simultaneously with an arterial thrombotic occlusion,as in the case of our patient.Unusual thrombotic manifestations are classically linked to hypercoagulable states including malignancy and hereditary and autoimmune disorders.Viral infections such as Epstein-Barr virus,cytomegalovirus,viral hepatitis,and COVID-19 have all been found to increase the risk of splanchnic venous occlusions,including PVT.In our patient,prompt abdominal imaging led to early detection of thrombus,early treatment,and an excellent outcome.This case is unique in that it is the second known case within the literature of simultaneous PVT and splenic artery thrombosis in a COVID-19 patient.展开更多
BACKGROUND Peripherally inserted central catheters(PICCs)are an essential infusion route for oncology patients receiving intravenous treatments,but lower extremity veni-puncture is the preferred technique for patients...BACKGROUND Peripherally inserted central catheters(PICCs)are an essential infusion route for oncology patients receiving intravenous treatments,but lower extremity veni-puncture is the preferred technique for patients with superior vena cava syndrome(SVCS).We report the case of a patient with a lower extremity PICC ectopic to the ascending lumbar vein,to indicate and verify PICC catheterisation in the lower extremity is safe and feasible.And hope to provide different per-spectives for clinical PICC venipuncture to get the attention of peers.CASE SUMMARY On 24 August 2022,a 58-year-old male was admitted to our department due to an intermittent cough persisting for over a month,which worsened 10 d prior.Imaging and laboratory investigations suggested the patient with pulmonary malignancy and SVCS.Chemotherapy was not an absolute contraindication in this patient.Lower extremity venipuncture is the preferred technique because administering upper extremity venous transfusion to patients with SVCS can exacerbate oedema in the head,neck,and upper extremities.The patient and his family were informed about the procedure,and informed consent was obtained.After successful puncture and prompt treatment,the patient was discharged,experiencing some relief from symptoms.CONCLUSION Inferior vena cava catheterisation is rare and important for cancer patients with SVCS,particularly in complex situations involving ectopic placement.展开更多
Lamprophyres typically appear in hydrothermal gold deposits.The relationship between lamprophyres and gold deposits is investigated widely.Some researchers suggest that the emplacement of lamprophyres triggers gold mi...Lamprophyres typically appear in hydrothermal gold deposits.The relationship between lamprophyres and gold deposits is investigated widely.Some researchers suggest that the emplacement of lamprophyres triggers gold mineralization,whereas others hypothesize that the formation of lamprophyres increases the fertility of mantle sources and ore-forming fluids.K-feldspar veins,with ages between those of lamprophyres and gold deposits,appear in lamprophyres in Zhenyuan.Therefore,K-feldspar veins are ideal for investigating the relationship between lamprophyres and gold deposits.Phlogopite in K-feldspar veins has lower Mg#,Ni,and Cr contents and higher TiO2,Li,Ba,Sr,Sc,Zr,Nb,and Cs contents than phlogopite in lamprophyres.The in-situ Sr isotopic values of apatites(0.7063–0.7066)in K-feldspar veins are within the range for apatites(0.7064–0.7078)from lamprophyres.High large-ion lithophile element concentrations and low Nb and Ta concentrations in phlogopite from lamprophyres,in addition to high(87Sr/86Sr)i values of apatite(0.7064–0.7078),indicate that the magma parental to these phlogopite and apatite crystals is derived from an enriched mantle.Kfeldspar veins are genetically correlated with lamprophyres,whereas sulfide mineral assemblage and trace element compositions of pyrite in K-feldspar veins suggest that K-feldspar veins in lamprophyres are not directly related to gold mineralization of the Zhenyuan deposit.展开更多
Granitic veins(GVs)have a significant influence on the mechanical responses of tunnels excavated in granitic strata.Distinguishing the mechanical properties of host granites(HGs),GVs and vein-granite interfaces(VGIs)i...Granitic veins(GVs)have a significant influence on the mechanical responses of tunnels excavated in granitic strata.Distinguishing the mechanical properties of host granites(HGs),GVs and vein-granite interfaces(VGIs)is critical.For this,this paper analyzed the mechanical behaviors and rupture processes of typical HG,GV,and VGI samples under uniaxial compression condition.For the rocks studied,although the linear axial stress‒strain relation can be identified and the deformation modulus can be determined,the transverse deformation developed nonlinearly with axial stress.As a result,the instantaneous Poisson’s ratio increases continuously and may even exceed 0.5,making it extremely difficult to accurately determine the Poisson’s ratio.In addition,the studied GV samples were found to be significantly brittle,indicating that large-scale GVs cannot be ignored when assessing rockburst hazards in granitic strata with brittle GVs.In terms of the rupture process,the HG and GV samples were gradually damaged by the formation of small-scale cracks and then ruptured by large cracks formed from smallscale cracks,whereas the VGI samples ruptured along large cracks with significant energy release.By examining the characteristic stress thresholds of these three granites,it is noted that the crack closure stress scc exceeds both the crack initiation stress sci and the crack damage stress scd for the HG and VGI samples.The transverse damage to a tested sample appears to be significantly greater than the axial damage,which is essentially related to the rock grain size and grain size distribution.展开更多
Lamellar calcite veins are prevalent in carbonate-rich,lacustrine dark shale.The formation mechanisms of these veins have been extensively debated,focusing on factors such as timing,depth,material source,and driving f...Lamellar calcite veins are prevalent in carbonate-rich,lacustrine dark shale.The formation mechanisms of these veins have been extensively debated,focusing on factors such as timing,depth,material source,and driving forces.This paper examines dark lacustrine shale lamellar calcite veins in the Paleogene strata of Dongying Depression,using various analytical techniques:petrography,isotope geochemistry,cathodoluminescence,inclusion thermometry,and electron probe micro-analysis.Two distinct types of calcite veins have been identified:granular calcite veins and sparry calcite veins.These two types differ significantly in color,grain structure,morphology,and inclusions.Through further investigation,it was observed that vein generation occurred from the shallow burial period to the maturation of organic matter,with a transition from granular calcite veins to sparry calcite veins.The granular calcite veins exhibit characteristics associated with the shallow burial period,including plastically deformed laminae and veins,the development of strawberry pyrite,the absence of oil and gas,weak fractionation in oxygen isotopes,and their contact relationship with sparry calcite veins.These granular calcite veins were likely influenced by the reduction of sulfate bacteria.On the other hand,sparry calcite veins with fibrous grains are antitaxial and closely linked to the evolution and maturation of organic matter.They contain oil and gas inclusions and show a distribution range of homogenization temperature between 90℃ and 120℃ and strong fractionation in oxygen isotopes,indicating formation during the hydrocarbon expulsion period.The carbon isotope analysis of the surrounding rocks and veins suggests that the material for vein formation originates from the shale itself,specifically authigenic micritic calcite modified by the action of methanogens.The opening of horizontal fractures and vein formation is likely driven by fluid overpressure resulting from undercompaction and hydrocarbon expulsion.Veins may form rapidly or through multi-stage composite processes.Early veins are predominantly formed in situ,while late veins are a result of continuous fluid migration and convergence.Furthermore,the veins continue to undergo modification even after formation.This study emphasizes that the formation of lamellar calcite veins in shale is a complex diagenetic process influenced by multiple factors:biology,organic matter,and inorganic processes,all operating at various stages throughout the shale's diagenetic history.展开更多
This study was carried out explore the mechanism underlying the inhibition of platelet activation by kelp fucoidans in deep venous thrombosis(DVT)mouse.In the control and sham mice,the walls of deep vein were regular ...This study was carried out explore the mechanism underlying the inhibition of platelet activation by kelp fucoidans in deep venous thrombosis(DVT)mouse.In the control and sham mice,the walls of deep vein were regular and smooth with intact intima,myometrium and adventitia.The blood vessel was wrapped with the tissue and there was no thrombosis in the lumen.In the DVT model,the wall was uneven with thicken intima,myometrium and adventitia.After treated with fucoidans LF1 and LF2,the thrombus was dissolved and the blood vessel was recanalized.Compared with the control group,the ROS content,ET-1 and VWF content and the expression of PKC-βand NF-κB in the model were significantly higher(P<0.05);these levels were significantly reduced following treatments with LF2 and LF1.Compared with H_(2)O_(2)treated-HUVECs,combined LF1 and LF2 treatment resulted in significant decrease in the expression of PKC-β,NF-κB,VWF and TM protein(P<0.05).It is clear that LF1 and LF2 reduces DVT-induced ET-1,VWF and TM expressions and production of ROS,thus inhibiting the activation of PKC-β/NF-κB signal pathway and the activation of coagulation system and ultimately reducing the formation of venous thrombus.展开更多
Copper possesses very strong chacophile properties,but under the conditions found in meteorites,its behavior is like that of siderophile elements.The Suizhou meteorite is a highly shocked L6 chondrite.Troilite and tae...Copper possesses very strong chacophile properties,but under the conditions found in meteorites,its behavior is like that of siderophile elements.The Suizhou meteorite is a highly shocked L6 chondrite.Troilite and taenite are considered the main primary carrier of copper in this meteorite,and the post-shock thermal episode is considered the main reason that elemental Cu migrates from its original host phase and forms metallic grains.The Suizhou meteorite contains a few very thin shock melt veins.The occurrence and behavior of metallic copper in this meteorite were studied by optical microscopic examination,electron microprobe analyses,and high-resolution X-ray elemental intensity mapping.Our results show that metallic copper is abundant in the Suizhou chondritic rock.Metallic copper grains adjacent to small troilite grains inside FeNi metal are the most common occurrence,and those at the FeNi metal–troilite interface are the second most common case.The metallic copper grains occurring at the interface of FeNi metal/troililte and silicate are rather rare.Metallic copper grains are not observed within the Suizhou shock veins,Instead,Cu in elemental form is transferred through shock metamorphism into FeNi metal+troilite intergrowths.Four diff erent occurrence types of Cu in the FeNi metal+troilite intergrowths have been identifi ed:the concentrations of Cu in the FeNi+FeS intergrowths for four occurrence types are rather close,we estimate it might be lower than 1 wt%.展开更多
A novel method based on the cross-modality intersecting features of the palm-vein and the palmprint is proposed for identity verification.Capitalising on the unique geometrical relationship between the two biometric m...A novel method based on the cross-modality intersecting features of the palm-vein and the palmprint is proposed for identity verification.Capitalising on the unique geometrical relationship between the two biometric modalities,the cross-modality intersecting points provides a stable set of features for identity verification.To facilitate flexibility in template changes,a template transformation is proposed.While maintaining non-invertibility,the template transformation allows transformation sizes beyond that offered by the con-ventional means.Extensive experiments using three public palm databases are conducted to verify the effectiveness the proposed system for identity recognition.展开更多
Although rock mechanical behaviour has a long record of study,attempts to understand the role of fractures on rock deformation still have unresolved issues.Due to technical and/or economic challenges,natural rock frac...Although rock mechanical behaviour has a long record of study,attempts to understand the role of fractures on rock deformation still have unresolved issues.Due to technical and/or economic challenges,natural rock fractures are often dealt with crudely,without detailed consideration of fracture geometry and heterogeneity in many geoscience applications.Veined rocks that are ubiquitous in the upper Earth crust fall in that category where sustained efforts are needed to offer key information for rock mechanics and geomechanics applications.Following on from a recent study on the rupture of veined rocks(DOI:10.1029/2019JB019052),we further examine stress path constraints on the deformation of veined rocks(i.e.,stress-path-dependent behaviour of veined rocks)under polyaxial conditions.The Discrete Element Method is used to establish a calcite veined model where constant mean stress(σm)and constant least principal stress(σ3)paths that are representative in the subsurface activities are considered.The results reveal the stress-path dependency of brittleness for models under different loading paths.Models tested under constant-σm conditions exhibit no brittleness,compared to cases where constant-σ3 is applied.Sliding along the strike of an inclined vein is evident under constant-σm deformation,irrespective of the level of stress.Shear bands along the dominated(inclined)veins exhibit apparent particle trajectory anisotropy for the constant-σm deformations which is demonstrated by the evident colour contrast of the adjacent rock matrix and the displacement dispersion of the particles forming the shear bands.We envisage that the reactivation of veins is of relevance to Enhanced Geothermal Systems(EGS)development in terms of seismicity mitigation and multiphysics control of fracture and reservoir permeability.展开更多
基金supported by the National Basic Research 973 Program of China (Grant 2013CB036003)the National Natural Science Foundation of China (Grants 51579239, 51323004, and 41572263)the China Postdoctoral Science Foundation (Grant 2016M590518)
文摘The mechanical behaviors of rocks affected by high temperature and stress are generally believed to be significant for the stability of certain projects involving rocks, such as nuclear waste storage and geothermal resource exploitation. In this paper, veined marble specimens were treated to high temperature treatment and then used in conventional triaxial compression tests to investigate the effect of temperature, confining pressure, and vein angle on strength and deformation behaviors. The results show that the strength and deformation parameters of the veined marble specimens changed with the temperature, presenting a critical temperature of 600 . The triaxial compression strength of a horizontal vein () is obviously larger than that of a vertical vein (). The triaxial compression strength, elasticity modulus, and secant modulus have an approximately linear relation to the confining pressure. Finally, Mohr-Coulomb and Hoek-Brown criteria were respectively used to analyze the effect of confining pressure on triaxial compression strength.
文摘Patients with locally advanced hepatocellular cancer(HCC)and portal vein tumor thrombosis(PVTT)have a dismal prognosis since limited treatment options are available for them.In recent years,effective systemic therapy,and advances in the understanding of technicalities and effectiveness of ablative therapies especially radiotherapy,have given some hope to prolong survival in them.This review summarized recent evidence in literature regarding the possible role of liver resection(LR)and liver transplantation(LT)in patients with locally advanced HCC and PVTT with no extrahepatic disease.Downstaging therapies have helped make curative resection or LT a reality in selected patients.This review emphasizes on the key points to focus on when considering surgery in these patients,who are usually relegated to palliative systemic therapy alone.Meticulous patient selection based on tumor biology,documented downstaging based on imaging and decrease in tumor marker levels,and an adequate waiting period to demonstrate stable disease,may help obtain satisfactory long-term outcomes post LR or LT in an intention to treat strategy in patients with HCC and PVTT.
文摘Point-of-care ultrasound(POCUS)of the internal jugular vein(IJV)offers a noninvasive means of estimating right atrial pressure(RAP),especially in cases where the inferior vena cava is inaccessible or unreliable due to conditions such as liver disease or abdominal surgery.While many clinicians are familiar with visually assessing jugular venous pressure through the internal jugular vein,this method lacks sensitivity.The utilization of POCUS significantly enhances the visualization of the vein,leading to a more accurate identification.It has been demonstrated that combining IJV POCUS with physical examination enhances the specificity of RAP estimation.This review aims to provide a comprehensive summary of the various sonographic techniques available for estimating RAP from the internal jugular vein,drawing upon existing data.
文摘BACKGROUND Hemorrhage associated with varices at the site of choledochojejunostomy is an unusual,difficult to treat,and often fatal manifestation of portal hypertension.So far,no treatment guidelines have been established.CASE SUMMARY We reported three patients with jejunal varices at the site of choledochojejun-ostomy managed by endoscopic sclerotherapy with lauromacrogol/α-butyl cyanoacrylate injection at our institution between June 2021 and August 2023.We reviewed all patient records,clinical presentation,endoscopic findings and treatment,outcomes and follow-up.Three patients who underwent pancre-aticoduodenectomy with a Whipple anastomosis were examined using conven-tional upper gastrointestinal endoscopy for suspected hemorrhage from the afferent jejunal loop.Varices with stigmata of recent hemorrhage or active he-morrhage were observed around the choledochojejunostomy site in all three patients.Endoscopic injection of lauromacrogol/α-butyl cyanoacrylate was carried out at jejunal varices for all three patients.The bleeding ceased and patency was observed for 26 and 2 months in two patients.In one patient with multiorgan failure and internal environment disturbance,rebleeding occurred 1 month after endoscopic sclerotherapy,and despite a second endoscopic sclero-therapy,repeated episodes of bleeding and multiorgan failure resulted in eventual death.CONCLUSION We conclude that endoscopic sclerotherapy with lauromacrogol/α-butyl cyanoac-rylate injection can be an easy,effective,safe and low-cost treatment option for jejunal varicose bleeding at the site of choledochojejunostomy.
文摘Background: Cavernous transformation of the portal vein(CTPV) due to portal vein obstruction is a rare vascular anomaly defined as the formation of multiple collateral vessels in the hepatic hilum. This study aimed to investigate the imaging features of intrahepatic portal vein in adult patients with CTPV and establish the relationship between the manifestations of intrahepatic portal vein and the progression of CTPV. Methods: We retrospectively analyzed 14 CTPV patients in Beijing Tsinghua Changgung Hospital. All patients underwent both direct portal venography(DPV) and computed tomography angiography(CTA) to reveal the manifestations of the portal venous system. The vessels measured included the left portal vein(LPV), right portal vein(RPV), main portal vein(MPV) and the portal vein bifurcation(PVB). Results: Nine males and 5 females, with a median age of 40.5 years, were included in the study. No significant difference was found in the diameters of the LPV or RPV measured by DPV and CTA. The visualization in terms of LPV, RPV and PVB measured by DPV was higher than that by CTA. There was a significant association between LPV/RPV and PVB/MPV in term of visibility revealed with DPV( P = 0.01), while this association was not observed with CTA. According to the imaging features of the portal vein measured by DPV, CTPV was classified into three categories to facilitate the diagnosis and treatment. Conclusions: DPV was more accurate than CTA for revealing the course of the intrahepatic portal vein in patients with CTPV. The classification of CTPV, that originated from the imaging features of the portal vein revealed by DPV, may provide a new perspective for the diagnosis and treatment of CTPV.
基金Supported by Shenzhen Fund for Guangdong Provincial High-level Clinical Key Specialties(No.SZGSP014)Sanming Project of Medicine in Shenzhen(No.SZSM202011015)Shenzhen Science and Technology Planning Project(No.KCXFZ20211020163813019).
文摘AIM:To develop an artificial intelligence(AI)diagnosis model based on deep learning(DL)algorithm to diagnose different types of retinal vein occlusion(RVO)by recognizing color fundus photographs(CFPs).METHODS:Totally 914 CFPs of healthy people and patients with RVO were collected as experimental data sets,and used to train,verify and test the diagnostic model of RVO.All the images were divided into four categories[normal,central retinal vein occlusion(CRVO),branch retinal vein occlusion(BRVO),and macular retinal vein occlusion(MRVO)]by three fundus disease experts.Swin Transformer was used to build the RVO diagnosis model,and different types of RVO diagnosis experiments were conducted.The model’s performance was compared to that of the experts.RESULTS:The accuracy of the model in the diagnosis of normal,CRVO,BRVO,and MRVO reached 1.000,0.978,0.957,and 0.978;the specificity reached 1.000,0.986,0.982,and 0.976;the sensitivity reached 1.000,0.955,0.917,and 1.000;the F1-Sore reached 1.000,0.9550.943,and 0.887 respectively.In addition,the area under curve of normal,CRVO,BRVO,and MRVO diagnosed by the diagnostic model were 1.000,0.900,0.959 and 0.970,respectively.The diagnostic results were highly consistent with those of fundus disease experts,and the diagnostic performance was superior.CONCLUSION:The diagnostic model developed in this study can well diagnose different types of RVO,effectively relieve the work pressure of clinicians,and provide help for the follow-up clinical diagnosis and treatment of RVO patients.
基金The study was reviewed and approved by the Beijing Ditan Hospital,Capital Medical University Institutional Review Board(Approval No.JDLC 2021-003-02).
文摘BACKGROUND Hepatocellular carcinoma(HCC)patients complicated with portal vein tumor thrombus(PVTT)exhibit poor prognoses and treatment responses.AIM To investigate efficacies and safety of the combination of PD-1 inhibitor,transcatheter arterial chemoembolization(TACE)and Lenvatinib in HCC subjects comorbid with PVTT.METHODS From January 2019 to December 2020,HCC patients with PVTT types Ⅰ-Ⅳ were retrospectively enrolled at Beijing Ditan Hospital.They were distributed to either the PTL or TACE/Lenvatinib(TL)group.The median progression-free survival(mPFS)was set as the primary endpoint,while parameters like median overall survival,objective response rate,disease control rate(DCR),and toxicity level served as secondary endpoints.RESULTS Forty-one eligible patients were finally recruited for this study and divided into the PTL(n=18)and TL(n=23)groups.For a median follow-up of 21.8 months,the DCRs were 88.9%and 60.9%in the PTL and TL groups(P=0.046),res-pectively.Moreover,mPFS indicated significant improvement(HR=0.25;P<0.001)in PTL-treated patients(5.4 months)compared to TL-treated(2.7 months)patients.There were no treatment-related deaths or differences in adverse events in either group.CONCLUSION A triplet regimen of PTL was safe and well-tolerated as well as exhibited favorable efficacy over the TL regimen for advanced-stage HCC patients with PVTT types Ⅰ-Ⅳ.
文摘A consensus meeting of national experts from all major national hepatobiliary centres in the country was held on May 26,2023,at the Pakistan Kidney and Liver Institute&Research Centre(PKLI&RC)after initial consultations with the experts.The Pakistan Society for the Study of Liver Diseases(PSSLD)and PKLI&RC jointly organised this meeting.This effort was based on a comprehensive literature review to establish national practice guidelines for hilar cholangiocarcinoma(hCCA).The consensus was that hCCA is a complex disease and requires a multidisciplinary team approach to best manage these patients.This coordinated effort can minimise delays and give patients a chance for curative treatment and effective palliation.The diagnostic and staging workup includes high-quality computed tomography,magnetic resonance imaging,and magnetic resonance cholangiopancreato-graphy.Brush cytology or biopsy utilizing endoscopic retrograde cholangiopancreatography is a mainstay for diagnosis.However,histopathologic confirmation is not always required before resection.Endoscopic ultrasound with fine needle aspiration of regional lymph nodes and positron emission tomography scan are valuable adjuncts for staging.The only curative treatment is the surgical resection of the biliary tree based on the Bismuth-Corlette classification.Selected patients with unresectable hCCA can be considered for liver transplantation.Adjuvant chemotherapy should be offered to patients with a high risk of recurrence.The use of preoperative biliary drainage and the need for portal vein embolisation should be based on local multidisciplinary discussions.Patients with acute cholangitis can be drained with endoscopic or percutaneous biliary drainage.Palliative chemotherapy with cisplatin and gemcitabine has shown improved survival in patients with irresectable and recurrent hCCA.
文摘BACKGROUND The prognosis of hepatocellular carcinoma(HCC)combined with portal and hepatic vein cancerous thrombosis is poor,for unresectable patients the combination of targeted therapy and immune therapy was the first-line recommended treatment for advanced HCC,with a median survival time of only about 2.7-6 months.In this case report,we present the case of a patient with portal and hepatic vein cancerous thrombosis who achieved pathologic complete response after conversion therapy.CASE SUMMARY In our center,a patient with giant HCC combined with portal vein tumor thrombus and hepatic vein tumor thrombus was treated with transcatheter arterial chemoembolization(TACE),radiotherapy,targeted therapy and immunotherapy,and was continuously given icaritin soft capsules for oral regulation.After 7 months of conversion therapy,the patient's tumor shrank and the tumor thrombus subsided significantly.The pathology of surgical resection was in complete remission,and there was no progression in the postoperative follow-up for 7 months,which provided a basis for the future strategy of combined conversion therapy.CONCLUSION In this case,atezolizumab,bevacizumab,icaritin soft capsules combined with radiotherapy and TACE had a good effect.For patients with hepatocellular carcinoma combined with hepatic vein/inferior vena cava tumor thrombus,adopting a high-intensity,multimodal proactive strategy under the guidance of multidisciplinary team(MDT)is an important attempt to break through the current treatment dilemma.
文摘BACKGROUND It is well-described that the coronavirus disease 2019(COVID-19)infection is associated with an increased risk of thrombotic complications.While there have been many cases of pulmonary emboli and deep vein thrombosis in these patients,reports of COVID-19 associated portal vein thrombosis(PVT)have been uncommon.We present a unique case of concomitant PVT and splenic artery thrombosis in a COVID-19 patient.CASE SUMMARY A 77-year-old-male with no history of liver disease presented with three days of left-sided abdominal pain.One week earlier,the patient was diagnosed with mildly symptomatic COVID-19 and was treated with nirmatrelvir/ritonavir.Physical exam revealed mild right and left lower quadrant tenderness,but was otherwise unremarkable.Significant laboratory findings included white blood cell count 12.5 K/μL,total bilirubin 1.6 mg/dL,aminoaspartate transferase 40 U/L,and alanine aminotransferase 61 U/L.Computed tomography of the abdomen and pelvis revealed acute PVT with thrombus extending from the distal portion of the main portal vein into the right and left branches.Also noted was a thrombus within the distal portion of the splenic artery with resulting splenic infarct.Hypercoagulable workup including prothrombin gene analysis,factor V Leiden,cardiolipin antibody,and JAK2 mutation were all negative.Anticoagulation with enoxaparin was initiated,and the patient’s pain improved.He was discharged on apixaban.CONCLUSION It is quite uncommon for PVT to present simultaneously with an arterial thrombotic occlusion,as in the case of our patient.Unusual thrombotic manifestations are classically linked to hypercoagulable states including malignancy and hereditary and autoimmune disorders.Viral infections such as Epstein-Barr virus,cytomegalovirus,viral hepatitis,and COVID-19 have all been found to increase the risk of splanchnic venous occlusions,including PVT.In our patient,prompt abdominal imaging led to early detection of thrombus,early treatment,and an excellent outcome.This case is unique in that it is the second known case within the literature of simultaneous PVT and splenic artery thrombosis in a COVID-19 patient.
基金the Chongqing Medical Scientific Research Project(a joint project of the Chongqing Health Commission and Science and Technology Bureau),No.2020FYYX046。
文摘BACKGROUND Peripherally inserted central catheters(PICCs)are an essential infusion route for oncology patients receiving intravenous treatments,but lower extremity veni-puncture is the preferred technique for patients with superior vena cava syndrome(SVCS).We report the case of a patient with a lower extremity PICC ectopic to the ascending lumbar vein,to indicate and verify PICC catheterisation in the lower extremity is safe and feasible.And hope to provide different per-spectives for clinical PICC venipuncture to get the attention of peers.CASE SUMMARY On 24 August 2022,a 58-year-old male was admitted to our department due to an intermittent cough persisting for over a month,which worsened 10 d prior.Imaging and laboratory investigations suggested the patient with pulmonary malignancy and SVCS.Chemotherapy was not an absolute contraindication in this patient.Lower extremity venipuncture is the preferred technique because administering upper extremity venous transfusion to patients with SVCS can exacerbate oedema in the head,neck,and upper extremities.The patient and his family were informed about the procedure,and informed consent was obtained.After successful puncture and prompt treatment,the patient was discharged,experiencing some relief from symptoms.CONCLUSION Inferior vena cava catheterisation is rare and important for cancer patients with SVCS,particularly in complex situations involving ectopic placement.
基金supported by the National Natural Science Foundation of China(Grant No.41973045)Basic Science and Technology Research Funding of the CAGS(Grant No.JKYZD202312)+1 种基金the National Key Research and Development Project of China(Grant No.2022YFF0800903)National Natural Science Foundation of China(Grant Nos.41802113,42073053,42273073 and 42261144669).
文摘Lamprophyres typically appear in hydrothermal gold deposits.The relationship between lamprophyres and gold deposits is investigated widely.Some researchers suggest that the emplacement of lamprophyres triggers gold mineralization,whereas others hypothesize that the formation of lamprophyres increases the fertility of mantle sources and ore-forming fluids.K-feldspar veins,with ages between those of lamprophyres and gold deposits,appear in lamprophyres in Zhenyuan.Therefore,K-feldspar veins are ideal for investigating the relationship between lamprophyres and gold deposits.Phlogopite in K-feldspar veins has lower Mg#,Ni,and Cr contents and higher TiO2,Li,Ba,Sr,Sc,Zr,Nb,and Cs contents than phlogopite in lamprophyres.The in-situ Sr isotopic values of apatites(0.7063–0.7066)in K-feldspar veins are within the range for apatites(0.7064–0.7078)from lamprophyres.High large-ion lithophile element concentrations and low Nb and Ta concentrations in phlogopite from lamprophyres,in addition to high(87Sr/86Sr)i values of apatite(0.7064–0.7078),indicate that the magma parental to these phlogopite and apatite crystals is derived from an enriched mantle.Kfeldspar veins are genetically correlated with lamprophyres,whereas sulfide mineral assemblage and trace element compositions of pyrite in K-feldspar veins suggest that K-feldspar veins in lamprophyres are not directly related to gold mineralization of the Zhenyuan deposit.
基金Additionally,the authors appreciate Dr.Zhaopeng Zhang’s assistance in conducting the experiments.This research was funded by the Science and Technology Department of Tibet(Grant No.XZ202201ZY0021G).
文摘Granitic veins(GVs)have a significant influence on the mechanical responses of tunnels excavated in granitic strata.Distinguishing the mechanical properties of host granites(HGs),GVs and vein-granite interfaces(VGIs)is critical.For this,this paper analyzed the mechanical behaviors and rupture processes of typical HG,GV,and VGI samples under uniaxial compression condition.For the rocks studied,although the linear axial stress‒strain relation can be identified and the deformation modulus can be determined,the transverse deformation developed nonlinearly with axial stress.As a result,the instantaneous Poisson’s ratio increases continuously and may even exceed 0.5,making it extremely difficult to accurately determine the Poisson’s ratio.In addition,the studied GV samples were found to be significantly brittle,indicating that large-scale GVs cannot be ignored when assessing rockburst hazards in granitic strata with brittle GVs.In terms of the rupture process,the HG and GV samples were gradually damaged by the formation of small-scale cracks and then ruptured by large cracks formed from smallscale cracks,whereas the VGI samples ruptured along large cracks with significant energy release.By examining the characteristic stress thresholds of these three granites,it is noted that the crack closure stress scc exceeds both the crack initiation stress sci and the crack damage stress scd for the HG and VGI samples.The transverse damage to a tested sample appears to be significantly greater than the axial damage,which is essentially related to the rock grain size and grain size distribution.
基金the support of the National Natural Science Foundation of China(project number:41572123)。
文摘Lamellar calcite veins are prevalent in carbonate-rich,lacustrine dark shale.The formation mechanisms of these veins have been extensively debated,focusing on factors such as timing,depth,material source,and driving forces.This paper examines dark lacustrine shale lamellar calcite veins in the Paleogene strata of Dongying Depression,using various analytical techniques:petrography,isotope geochemistry,cathodoluminescence,inclusion thermometry,and electron probe micro-analysis.Two distinct types of calcite veins have been identified:granular calcite veins and sparry calcite veins.These two types differ significantly in color,grain structure,morphology,and inclusions.Through further investigation,it was observed that vein generation occurred from the shallow burial period to the maturation of organic matter,with a transition from granular calcite veins to sparry calcite veins.The granular calcite veins exhibit characteristics associated with the shallow burial period,including plastically deformed laminae and veins,the development of strawberry pyrite,the absence of oil and gas,weak fractionation in oxygen isotopes,and their contact relationship with sparry calcite veins.These granular calcite veins were likely influenced by the reduction of sulfate bacteria.On the other hand,sparry calcite veins with fibrous grains are antitaxial and closely linked to the evolution and maturation of organic matter.They contain oil and gas inclusions and show a distribution range of homogenization temperature between 90℃ and 120℃ and strong fractionation in oxygen isotopes,indicating formation during the hydrocarbon expulsion period.The carbon isotope analysis of the surrounding rocks and veins suggests that the material for vein formation originates from the shale itself,specifically authigenic micritic calcite modified by the action of methanogens.The opening of horizontal fractures and vein formation is likely driven by fluid overpressure resulting from undercompaction and hydrocarbon expulsion.Veins may form rapidly or through multi-stage composite processes.Early veins are predominantly formed in situ,while late veins are a result of continuous fluid migration and convergence.Furthermore,the veins continue to undergo modification even after formation.This study emphasizes that the formation of lamellar calcite veins in shale is a complex diagenetic process influenced by multiple factors:biology,organic matter,and inorganic processes,all operating at various stages throughout the shale's diagenetic history.
基金supported by the Special Fund for Clinical Scientific Research of Shandong Medical Association(No.YXH2020ZX058).
文摘This study was carried out explore the mechanism underlying the inhibition of platelet activation by kelp fucoidans in deep venous thrombosis(DVT)mouse.In the control and sham mice,the walls of deep vein were regular and smooth with intact intima,myometrium and adventitia.The blood vessel was wrapped with the tissue and there was no thrombosis in the lumen.In the DVT model,the wall was uneven with thicken intima,myometrium and adventitia.After treated with fucoidans LF1 and LF2,the thrombus was dissolved and the blood vessel was recanalized.Compared with the control group,the ROS content,ET-1 and VWF content and the expression of PKC-βand NF-κB in the model were significantly higher(P<0.05);these levels were significantly reduced following treatments with LF2 and LF1.Compared with H_(2)O_(2)treated-HUVECs,combined LF1 and LF2 treatment resulted in significant decrease in the expression of PKC-β,NF-κB,VWF and TM protein(P<0.05).It is clear that LF1 and LF2 reduces DVT-induced ET-1,VWF and TM expressions and production of ROS,thus inhibiting the activation of PKC-β/NF-κB signal pathway and the activation of coagulation system and ultimately reducing the formation of venous thrombus.
基金supported by Science and Technology Planning Project of Guangdong Province,2023B1212060048.
文摘Copper possesses very strong chacophile properties,but under the conditions found in meteorites,its behavior is like that of siderophile elements.The Suizhou meteorite is a highly shocked L6 chondrite.Troilite and taenite are considered the main primary carrier of copper in this meteorite,and the post-shock thermal episode is considered the main reason that elemental Cu migrates from its original host phase and forms metallic grains.The Suizhou meteorite contains a few very thin shock melt veins.The occurrence and behavior of metallic copper in this meteorite were studied by optical microscopic examination,electron microprobe analyses,and high-resolution X-ray elemental intensity mapping.Our results show that metallic copper is abundant in the Suizhou chondritic rock.Metallic copper grains adjacent to small troilite grains inside FeNi metal are the most common occurrence,and those at the FeNi metal–troilite interface are the second most common case.The metallic copper grains occurring at the interface of FeNi metal/troililte and silicate are rather rare.Metallic copper grains are not observed within the Suizhou shock veins,Instead,Cu in elemental form is transferred through shock metamorphism into FeNi metal+troilite intergrowths.Four diff erent occurrence types of Cu in the FeNi metal+troilite intergrowths have been identifi ed:the concentrations of Cu in the FeNi+FeS intergrowths for four occurrence types are rather close,we estimate it might be lower than 1 wt%.
基金National Research Foundation of Korea funded by the Ministry of Education,Science and Technology,Grant/Award Number:NRF-2021R1A2C1093425。
文摘A novel method based on the cross-modality intersecting features of the palm-vein and the palmprint is proposed for identity verification.Capitalising on the unique geometrical relationship between the two biometric modalities,the cross-modality intersecting points provides a stable set of features for identity verification.To facilitate flexibility in template changes,a template transformation is proposed.While maintaining non-invertibility,the template transformation allows transformation sizes beyond that offered by the con-ventional means.Extensive experiments using three public palm databases are conducted to verify the effectiveness the proposed system for identity recognition.
基金support from the UK Natural Environment Research Council(NERC,NE/W004127/1).
文摘Although rock mechanical behaviour has a long record of study,attempts to understand the role of fractures on rock deformation still have unresolved issues.Due to technical and/or economic challenges,natural rock fractures are often dealt with crudely,without detailed consideration of fracture geometry and heterogeneity in many geoscience applications.Veined rocks that are ubiquitous in the upper Earth crust fall in that category where sustained efforts are needed to offer key information for rock mechanics and geomechanics applications.Following on from a recent study on the rupture of veined rocks(DOI:10.1029/2019JB019052),we further examine stress path constraints on the deformation of veined rocks(i.e.,stress-path-dependent behaviour of veined rocks)under polyaxial conditions.The Discrete Element Method is used to establish a calcite veined model where constant mean stress(σm)and constant least principal stress(σ3)paths that are representative in the subsurface activities are considered.The results reveal the stress-path dependency of brittleness for models under different loading paths.Models tested under constant-σm conditions exhibit no brittleness,compared to cases where constant-σ3 is applied.Sliding along the strike of an inclined vein is evident under constant-σm deformation,irrespective of the level of stress.Shear bands along the dominated(inclined)veins exhibit apparent particle trajectory anisotropy for the constant-σm deformations which is demonstrated by the evident colour contrast of the adjacent rock matrix and the displacement dispersion of the particles forming the shear bands.We envisage that the reactivation of veins is of relevance to Enhanced Geothermal Systems(EGS)development in terms of seismicity mitigation and multiphysics control of fracture and reservoir permeability.