Influence of layer thickness on formation quality,microstructure,mechanical properties,and corrosion resistance of WE43 magnesium alloy fabricated by laser powder bed fusion

Laser powder bed fusion(L-PBF)of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts.Layer thickness(LT)is of great significance to the L-PBF process but has not been studied for Mg alloys.In this study,WE43 Mg alloy bulk cubes,porous scaffolds,and thin walls with layer thicknesses of 10,20,30,and 40μm were fabricated.The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds.Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input.For thin wall parts,a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used,and the porosity disappeared by reducing the layer thickness or laser energy input.A deeper keyhole penetration was found in all occasions with porosity,explaining the influence of layer thickness,geometrical structure,and laser energy input on the porosity.All the samples achieved a high fusion quality with a relative density of over 99.5%using the optimized laser energy input.The increased layer thickness resulted to more precipitation phases,finer grain sizes and decreased grain texture.With the similar high fusion quality,the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41%with the 10μm layer to 287 MPa and 15.12%with the 40μm layer,in accordance with the microstructural change.The effect of layer thickness on the compressive properties of porous scaffolds was limited.However,the corrosion rate of bulk samples accelerated with increasing the layer thickness,mainly attributed to the increased number of precipitation phases.

Improving corrosion resistance of additively manufactured WE43 magnesium alloy by high temperature oxidation for biodegradable applications

Laser powder bed fusion(L-PBF)has been employed to additively manufacture WE43 magnesium(Mg)alloy biodegradable implants,but WE43 L-PBF samples exhibit excessively rapid corrosion.In this work,dense WE43 L-PBF samples were built with the relativity density reaching 99.9%.High temperature oxidation was performed on the L-PBF samples in circulating air via various heating temperatures and holding durations.The oxidation and diffusion at the elevated temperature generated a gradient structure composed of an oxide layer at the surface,a transition layer in the middle and the matrix.The oxide layer consisted of rare earth(RE)oxides,and became dense and thick with increasing the holding duration.The matrix was composed ofα-Mg,RE oxides and Mg_(24)RE_(5) precipitates.The precipitates almost disappeared in the transition layer.Enhanced passivation effect was observed in the samples treated by a suitable high temperature oxidation.The original L-PBF samples lost 40%weight after 3-day immersion in Hank’s solution,and broke into fragments after 7-day immersion.The casted and solution treated samples lost roughly half of the weight after 28-day immersion.The high temperature oxidation samples,which were heated at 525℃ for 8 h,kept the structural integrity,and lost only 6.88%weight after 28-day immersion.The substantially improved corrosion resistance was contributed to the gradient structure at the surface.On one hand,the outmost dense layer of RE oxides isolated the corrosive medium;on the other hand,the transition layer considerably inhibited the corrosion owing to the lack of precipitates.Overall,high temperature oxidation provides an efficient,economic and safe approach to inhibit the corrosion of WE43 L-PBF samples,and has promising prospects for future clinical applications.

Caudate lobe-sparing subtotal hepatectomy as treatment for extensive intrahepatic arterioportal fistula

Intrahepatic arterioportal fistulas(APFs)are abnormal hepatic artery and portal vein(PV)communications that develop as a result of congenital malformation,trauma,ruptured hepatic aneurysm,cirrhosis,tumor-related changes,biopsy,chemotherapy or iatrogenic causes[1,2].The most common symptoms are gastrointestinal bleeding and ascites secondary to portal hypertension;other symptoms include abdominal pain,pyrexia,edema,back pain and jaundice[3].The main goal of therapy is to decrease the portal pressure with variceal bleeding being the absolute indi-cation for surgical management.Transarterial embolization(TAE)should be the first choice to treat APFs,while resection,portocaval shunt and even transplantation may cure APFs in the case of TAE failure[4].In previous reports,caudate lobe-sparing subtotal hep-atectomy(CLSSH)has been applied for the treatment of primary hepatolithiasis and hepatocellular carcinoma[5,6].As far as we know,this is the first report describing CLSSH as treatment for an extensive intrahepatic APF,which involved segments 2 to 8,with corresponding hypertrophy of the caudate lobe.

Prevalence and risk factors for Candida esophagitis among human immunodeficiency virus-negative individuals

BACKGROUND Candida esophagitis(CE) is among the commonest esophageal infections and is known as an opportunistic fungal infection mostly affecting people living with the human immunodeficiency virus(HIV).However,some medical conditions might predispose HIV-negative individuals to esophageal candidiasis.The epidemiology and associated endoscopic findings of CE among people without HIV have rarely been reported.AIM To investigate the prevalence of CE among HIV-negative persons,and determine risk factors predicting CE.METHODS Between January 2015 and December 2018,all consecutive outpatients who underwent routine esophagogastroduodenoscopy as part of health check-ups at their own expense at the Health Check-up Center of the Kaohsiung Veterans General Hospital,Taiwan,were recruited in this study.Those with positive HIV serology results were excluded.Sociodemographic and clinical characteristics including age,gender,economic status,smoking history,alcohol consumption,tea and coffee consumption,underlying diseases,body fat percentage,body mass index,endoscopic findings,and Helicobacter pylori infection status were carefully reviewed.CE was confirmed by endoscopic biopsy and pathological assessment with hematoxylin and eosin and periodic acidSchiff staining.To evaluate independent factors predicting the development of CE,we conducted a univariate analysis of clinical characteristics.The variables found to be significant via univariate analysis were subsequently included in a multivariable analysis of potential risk factors for CE development.RESULTS A total of 11802 participants were included in this study.Forty-seven(0.4%) were confirmed as having CE by pathological examination.Univariate analysis identified older age,the presence of chronic kidney disease,alcohol consumption,and steroid use(P = 0.023,< 0.001,0.033,and 0.004,respectively) as significantly associated with CE.Multivariable analysis revealed older age [adjusted odds ratio(OR) = 1.027;95%CI:1.001-1.053;P = 0.045],chronic kidney disease(adjusted OR = 13.470;95%CI:4.574-39.673;P < 0.001),alcohol consumption(adjusted OR = 2.103;95%CI:1.151-3.844;P = 0.016),and steroid use(adjusted OR = 24.255;95%CI:5.343-110.115;P < 0.001) as independent risk factors for CE development.The presence of dysphagia was associated with severe CE(P = 0.021).CONCLUSION The prevalence of CE among HIV-negative persons was 0.4% in Taiwan.Independent risk factors for CE were older age,chronic kidney disease,alcohol consumption,and steroid use.

Extrahepatic bile duct reconstruction in pigs with heterogenous animal-derived artificial bile ducts:A preliminary experience

BACKGROUND Extrahepatic biliary duct injury(BDI)remains a complicated issue for surgeons.Although several approaches have been explored to address this problem,the high incidence of complications affects postoperative recovery.As a nonimmunogenic scaffold,an animal-derived artificial bile duct(ada-BD)could replace the defect,providing good physiological conditions for the regeneration of autologous bile duct structures without changing the original anatomical and physiologic conditions.AIM To evaluate the long-term feasibility of a novel heterogenous ada-BD for treating extrahepatic BDI in pigs.METHODS Eight pigs were randomly divided into two groups in the study.The animal injury model was developed with an approximately 2 cm segmental defect of various parts of the common bile duct(CBD)for all pigs.A 2 cm long novel heterogenous animal-derived bile duct was used to repair this segmental defect(group A,ada-BD-to-duodenum anastomosis to repair the distal CBD defect;group B,ada-BD-to-CBD anastomosis to repair the intermedial CBD defect).The endpoint for observation was 6 mo(group A)and 12 mo(group B)after the operation.Liver function was regularly tested.Animals were euthanized at the above endpoints.Histological analysis was carried out to assess the efficacy of the repair.RESULTS The median operative time was 2.45 h(2-3 h),with a median anastomosis time of 60.5 min(55-73 min).All experimental animals survived until the endpoints for observation.The liver function was almost regular.Histologic analysis indicated a marked biliary epithelial layer covering the neo-bile duct and regeneration of the submucosal connective tissue and smooth muscle without significant signs of immune rejection.In comparison,the submucosal connective tissue was more regular and thicker in group B than in group A,and there was superior integrity of the regeneration of the biliary epithelial layer.Despite the advantages of the regeneration of the bile duct smooth muscle observed in group A,the effect on the patency of the ada-BD grafts in group B was not confirmed by macroscopic assessment and cholangiography.CONCLUSION This approach appears to be feasible for repairing a CBD defect with an ada-BD.A large sample study is needed to confirm the durability and safety of these preliminary results.

Abdominal drainage systems in modified piggyback orthotopic liver transplantation

To the Editor:Whether orthotopic liver transplantation requires the placement of an abdominal drainage system is a controversial topic.A number of studies have suggested that prophylactic placement of abdominal drainage systems do not improve the diagnostic rate of complications such as bile leakage and hemorrhage after liver transplantation,even increased the risk of infection[1–3].However,there is no uniform standard for the selection of drainage tube and how to place the drainage tube in orthotopic liver transplantation.The types and placement modes of the drainage tubes used in each center are different.If adequate drainage is not possible,it may affect the drainage efficiency,which may lead to the misunderstanding that“it is unnecessary to place the drainage tube”.Herein we aimed to explore the most efficient abdominal drainage in modified piggyback orthotopic liver transplantation,based on the types and placement modes of drainage tubes in our clinical practice.

Optimized liver resection range and perioperative safety in patients with high levels of indocyanine green R15

The indocyanine green(ICG)clearance test is an objective measurement of functional liver reserve(FLR)[1].The liver can preserve normal functions with a 70%−80%functional liver volume resection[2]and the remnant is capable of regeneration.However,liver regenerative properties are affected by hepatitis,fatty liver,cirrhosis and damage caused by chemotherapy[3].ICG combined with the Child-Pugh score are main criteria for evaluating FLR.A safe hepatectomy procedure requires the remnant liver to be 25%−30%of the normal volume.For patients with an indocyanine green retention rate at 15 min(ICG-R15)>20%,segment liver resection,limited hepatectomy or tumor enucleation is recommended,but there has been no clear clarification of the essential remnant liver volume[4].In China,the experts’consensus of preoperative evaluation of liver reserve function incorporates ICGR15 tests.

Injectable mechanical pillows for attenuation of load-induced post-traumatic osteoarthritis

Osteoarthritis(OA)of the knee joint is a degenerative disease initiated by mechanical stress that affects millions of individuals.The disease manifests as joint damage and synovial inflammation.Post-traumatic osteoarthritis(PTOA)is a specific form of OA caused by mechanical trauma to the joint.The progression of PTOA is prevented by immediate post-injury therapeutic intervention.Intra-articular injection of anti-inflammatory therapeutics(e.g.corticosteroids)is a common treatment option for OA before end-stage surgical intervention.However,the efficacy of intra-articular injection is limited due to poor drug retention time in the joint space and the variable efficacy of corticosteroids.Here,we endeavored to characterize a four-arm maleimide-functionalized polyethylene glycol(PEG-4MAL)hydrogel system as a‘mechanical pillow’to cushion the load-bearing joint,withstand repetitive loading and improve the efficacy of intra-articular injections of nanoparticles containing dexamethasone,an anti-inflammatory agent.PEG-4MAL hydrogels maintained their mechanical properties after physiologically relevant cyclic compression and released therapeutic payload in an on-demand manner under in vitro inflammatory conditions.Importantly,the on-demand hydrogels did not release nanoparticles under repetitive mechanical loading as experienced by daily walking.Although dexamethasone had minimal protective effects on OA-like pathology in our studies,the PEG-4MAL hydrogel functioned as a mechanical pillow to protect the knee joint from cartilage degradation and inhibit osteophyte formation in an in vivo load-induced OA mouse model.

Portal vein cavernous transformation at bilioenteric anastomosis

A 30-year-old woman presented with a 3-year history of recurrent melena,without haematemesis,abdominal pain or fever.The lowest hemoglobin was 30 g/L.She had a history of congenital choledochal cyst and underwent extrahepatic bile duct resection with Roux-en-Y cholangiojejunostomy 26 years ago.

Application of Deep Learning on Single-cell RNA Sequencing Data Analysis:A Review

Single-cell RNA sequencing(scRNA-seq)has become a routinely used technique to quantify the gene expression profile of thousands of single cells simultaneously.Analysis of scRNA-seq data plays an important role in the study of cell states and phenotypes,and has helped elucidate biological processes,such as those occurring during the development of complex organisms,and improved our understanding of disease states,such as cancer,diabetes,and coronavirus disease 2019(COVID-19).Deep learning,a recent advance of artificial intelligence that has been used to address many problems involving large datasets,has also emerged as a promising tool for scRNA-seq data analysis,as it has a capacity to extract informative and compact features from noisy,heterogeneous,and high-dimensional scRNA-seq data to improve downstream analysis.The present review aims at surveying recently developed deep learning techniques in scRNA-seq data analysis,identifying key steps within the scRNA-seq data analysis pipeline that have been advanced by deep learning,and explaining the benefits of deep learning over more conventional analytic tools.Finally,we summarize the challenges in current deep learning approaches faced within scRNA-seq data and discuss potential directions for improvements in deep learning algorithms for scRNA-seq data analysis.

The Ability of Different Imputation Methods to Preserve the Significant Genes and Pathways in Cancer

Deciphering important genes and pathways from incomplete gene expression data could facilitate a better understanding of cancer. Different imputation methods can be applied to estimate the missing values. In our study, we evaluated various imputation methods for their performance in preserving significant genes and pathways. In the first step, 5% genes are considered in random for two types of ignorable and non-ignorable missingness mechanisms with various missing rates. Next, 10 well-known imputation methods were applied to the complete datasets. The significance analysis of microarrays （SAM） method was applied to detect the significant genes in rectal and lung cancers to showcase the utility of imputation approaches in preserving significant genes. To determine the impact of different imputation methods on the identification of important genes, the chi-squared test was used to compare the proportions of overlaps between significant genes detected from original data and those detected from the imputed datasets. Additionally, the significant genes are tested for their enrichment in important pathways, using the ConsensusPathDB. Our results showed that almost all the significant genes and pathways of the original dataset can be detected in all imputed datasets, indicating that there is no significant difference in the performance of various imputation methods tested. The source code and selected datasets are available on http：//profiles.bs.ipm.ir/soft- wares/imputationmethods/.

An Optoelectronic thermometer based on microscale infrared-to-visible conversion devices

Thermometric detectors are crucial in evaluating the condition of target objects spanning from environments to the human body.Optical-based thermal sensing tools have received extensive attention,in which the photon upconversion process with low autofluorescence and high tissue penetration depth is considered as a competent method for temperature monitoring,particularly in biomedical fields.Here,we present an optoelectronic thermometer via infrared-to-visible upconversion,accomplished by integrated light receiving and emission devices.Fully fabricated thin-film,microscale devices present temperature-dependent light emission with an intensity change of 1.5%℃^(-1) and a spectral shift of 0.18 nm℃^(-1).The sensing mechanism is systematically characterized and ascribed to temperature dependent optoelectronic properties of the semiconductor band structure and the circuit operation condition.Patterned device arrays showcase the capability for spatially resolved temperature mapping.Finally,in vitro and in vivo experiments implemented with integrated fiber-optic sensors demonstrate real-time thermal detection of dynamic human activity and in the deep brain of animals,respectively.

Tenofovir disoproxil fumarate therapy in patients with chronic hepatitis B and advanced fibrosis or compensated cirrhosis

Background and aims:Tenofovir disoproxil fumarate(TDF)is the first-line therapy for chronic hepatitis B.This interim analysis presents the efficacy and safety data for TDF at Week 144 in patients with chronic hepatitis B and advanced fibrosis or compensated cirrhosis from China.Methods:Patients were assessed for incidence of newly diagnosed hepatocellular carcinoma(HCC)and disease progression,liver stiffness measurement(LSM),virological suppression(serum hepatitis B virus DNA<20 IU/mL),alanine aminotransferase normalization,hepatitis B e antigen(HBeAg)loss and seroconversion,histological liver fibrosis score,and safety at Week 144.Results:Overall,197 patients were enrolled.At Week 144,the incidence of newly diagnosed HCC was observed in 2.1%patients,and the incidence of disease progression was observed in 3.6%patients.The mean(standard deviation)change in LSM from baseline was
5.1(5.85)kPa.Serum hepatitis B virus DNA<20 IU/mL was observed in 94.1%patients,alanine aminotransferase normalization in 33.5%patients,HBeAg loss in 35.6%patients,and HBeAg seroconversion in 14.4%patients.Among patients with stage F3 or F4 fibrosis at baseline by LSM,38.3%patients regressed to stage F0/1,and 22.0%of patients regressed to stage F2 at Week 144.Overall,67.7%patients experienced≥1 adverse events,13.8%patients experienced TDF-related adverse events,and 16.4%patients experienced serious(none were TDF-related).Conclusions:At Week 144 of TDF treatment,low incidence of HCC and disease progression were reported.Virological suppression was observed in 94.1%patients,which was associated with fibrosis regression.No new safety events were identified.

Safety analysis of COVID-19 vaccines in liver transplant recipients:a two-center study

Up to know,product information for COVID-19 mRNA vaccines do not include their use in patients receiving immunosuppressive medication,since they were not included in trials(1).For the BNT162b2 mRNA vaccine,one case of otherwise totally asymptomatic elevations of alanine aminotransferase(ALT),aspartate aminotransferase(AST),alkaline phosphatase(ALP)andγ-glutamyl transpeptidase(GGT)serum concentrations in a liver transplant recipient has been reported after the first injection(2).In the present retrospective study,we present safety outcomes of COVID-19 vaccinations in 56 liver transplant patients from two Chinese centers vaccinated with the domestic PiCoVacc,BBIBP-CorV and ZF2001 vaccines.Thirty vaccinated physicians from the Hepatopancreatobiliary Center of Beijing Tsinghua Changgung Hospital served as control,from which 1 participant received an Ad5-nCoV vaccine.The study deadline was 2021-10-31.The observation period for adverse reactions,such as muscle pain and fatigue was 1 week,while for laboratory examinations such as liver function the follow-up period was 1 month.