Preheating-assisted solid-state friction stir repair of Al-Mg-Si alloy plate at different rotational speeds

Additive friction stir deposition(AFSD)is a novel structural repair and manufacturing technology has become a research hotspot at home and abroad in the past five years.In this work,the microstructural evolution and mechanical performance of the Al-Mg-Si alloy plate repaired by the preheating-assisted AFSD process were investigated.To evaluate the tool rotation speed and substrate preheating for repair quality,the AFSD technique was used to additively repair 5 mm depth blind holes on 6061 aluminum alloy substrates.The results showed that preheat-assisted AFSD repair significantly improved joint bonding and joint strength compared to the control non-preheat substrate condition.Moreover,increasing rotation speed was also beneficial to improve the metallurgical bonding of the interface and avoid volume defects.Under preheating conditions,the UTS and elongation were positively correlated with rotation speed.Under the process parameters of preheated substrate and tool rotation speed of 1000 r/min,defect-free specimens could be obtained accompanied by tensile fracture occurring in the substrate rather than the repaired zone.The UTS and elongation reached the maximum values of 164.2MPa and 13.4%,which are equivalent to 99.4%and 140%of the heated substrate,respectively.

Underlying slip/twinning activities of Mg-xGd alloys investigated by modified lattice rotation analysis

The inconsistencies regarding the fundamental correlation between Gd content and slip(twinning)activities of Mg alloys appeal further investigations.However,the traditional slip dislocations analysis by TEM is time-consuming,and that by SEM/EBSD cannot recognize the partial slip modes.These urge a more efficient and comprehensive approach to easily distinguish all potential slip modes occurred concurrently in alloy matrix.Here we report a modified lattice rotation analysis that can distinguish all slip systems and provide statistical results for slip activities in Mg alloy matrix.Using this method,the high ductility of Mg-Gd alloy ascribed to the enhanced non-basal slips,cross-slip,and postponed twinning activities by Gd addition is quantitatively clarified.

Quasi-in-situ study on{10-12}twinning-detwinning behavior of rolled Mg-Li alloy in two-step compression(RD)-compression(ND)process

Twinning-detwinning(TDT)behavior in a strongly basal-textured Mg-Li alloy during two-step compression(RD)-compression(ND)process was investigated using quasi-in-situ EBSD.TDT behavior and TDT variants selection were statistically discussed with the loading path for the first time.Non-Schmid twinning behavior was observed in the first step compression,owing to the local stress fluctuations by neighboring twins;in contrast,Schmid’s law well predicted the detwinning variants selection.This asymmetrical TDT behavior was first investigated to date related with the strong basal texture and loading path.Besides,with the progress of compression,Schmid factors for twinning demonstrated a decreasing tendency;however,those for detwinning during the second step displayed an abnormally increasing trend,fundamentally stemming from prior twinning behavior.

Xin'anjiang Nested Experimental Watershed(XAJ-NEW)for Understanding Multiscale Water Cycle:Scientific Objectives and Experimental Design

This paper presents the background,scientific objectives,experimental design,and preliminary achievements of the Xin’anjiang nested experimental watershed(XAJ-NEW),implemented in 2017 in eastern China,which has a subtropical humid monsoon climate and a total area of 2674 km2.The scientific objectives of the XAJ-NEW include building a comprehensive,multiscale,and nested hydrometeorological monitoring and experimental program,strengthening the observation of the water cycle,discovering the spatiotemporal scaling effects of hydrological processes,and revealing the mechanisms controlling runoff generation and partitioning in a typical humid,hilly area.After two years of operation,preliminary results indicated scale-dependent variability in key hydrometeorological processes and variables such as precipitation,runoff,groundwater,and soil moisture.The effects of canopy interception and runoff partitioning between the surface and subsurface were also identified.Continuous operation of this program can further reveal the mechanisms controlling runoff generation and partitioning,discover the spatiotemporal scaling effects of hydrological processes,and understand the impacts of climate change on hydrological processes.These findings provide new insights into understanding multi scale hydrological processes and their responses to meteorological forcings,improving model parameterization schemes,and enhancing weather and climate forecast skills.

Thrombotic Thrombocytopenic Purpura in a Parturient Leading to Life-Threatening Thrombocytopenia and Neonatal Demise—A Case Report

Thrombocytopenia is common (up to 12%) in pregnancy;thrombotic thrombocytopenia is a rare cause of thrombocytopenia;however,it is immediately life-threatening to both mother and fetus and requires immediate intervention.This is compounded by the need to act on a presumptive diagnosis with high level of suspicion given the relatively long laboratory confirmation time.A 31-year-old gravida 3,para 1 parturient at 26 weeks of gestation presented to outside hospital with recent onset of easy bruising and blurry vision.A blood count was drawn and showed a platelet count of 19,000/μL.She was transferred to our institution for management where an initial diagnosis of preeclampsia with severe features was made based on thrombocytopenia and fetal growth restriction (<1%).Platelet count nadired at 14,000/μL and a blood smear showed schistocytes,suggesting microangiopathic hemolysis,prompting discussion of urgent cesarean delivery and anesthesia consult.An urgent hematology consult led to presumptively diagnosing thrombotic thrombocytopenic purpura and cesarean delivery was deferred after discussion with the patient and team.Plasma exchange and steroid therapy were started promptly,and her platelet count improved within 12 hours.Unfortunately,the patient experienced neonatal demise.Undetectable ADAMTS13 levels confirmed diagnosis of thrombotic thrombocytopenia.She was transitioned to rituximab,platelets recovered to baseline,and she continues to do well.Thrombotic thrombocytopenia is a rare,life-threatening cause of thrombocytopenia in pregnancy.Despite grim fetal prognosis,especially in early pregnancy,low threshold of suspicion,early anesthesia involvement,and multi-disciplinary approach can facilitate diagnosis and timely intervention.In our case,it was likely lifesaving.

Cellular Mechanism of Mouse Atrial Development

During the development of mammalian heart, the left and right atria play an important role in cardiovascular circulation. The embryonic atrium is mainly formed by the differentiation of progenitor cells and the proliferation of cardiomyocytes, while the postnatal atrium is primarily shaped by the increase in the volume of cardiomyocytes. Cell proliferation and differentiation of atrial development is the basis for its functions such as “blood reservoir” and “supplementary pump”. Deep understanding the cellular mechanism of atrial development is imperative to explore the causes of common congenital arrhythmia heart diseases such as atrial fibrillation. We used genetically engineered mouse reproduction knowledge, lineage tracing method based on CreloxP system, molecular biology and immunofluorescence technology to track the cardiomyocyte lineage of Nppa-GFP mouse line with stereo fluorescence microscope and ultra-high-speed confocal microscope. Besides the atrium of Nppa-CreER;Rosa26 tdTomato mouse was examined during embryonic (E10.5 - E18.5) and postnatal (P0, P3, P5, P7, P14, P28, P8w) stage. Immunofluorescence results revealed that Nppa-positive cells labeled TNNI3-positive cardiomyocytes and protruded into the atrial cavity at the beginning of E11.5 - E12.0 and during subsequent development to form Nppa-positive myocardial trabeculae. Thick comb-shaped myocardium was observed after birth, and we suspect that this was particularly important for the normal contractile activity and pumping function of the atrium. Additionally, non-single origin of Nppa-positive trabecular myocardiocytes were revealed through Tamoxifen-induced lineage tracing experiment. Our findings reveal proliferation dynamics and non-comprehensive fate decisions of cardiomyocytes that produce the distinct architecture of the atrium chamber.

Multispectral light scattering endoscopic imaging of esophageal precancer

Esophageal adenocarcinoma is the most rapidly growing cancer in America.Although the prognosis after diagnosis is unfavorable,the chance of a successful outcome increases tremendously if detected early while the lesion is still dysplastic.Unfortunately,the present standard-of-care,endoscopic surveillance,has major limitations,since dysplasia is invisible,often focal,and systematic biopsies typically sample less than one percent of the esophageal lining and therefore easily miss malignancies.To solve this problem we developed a multispectral light scattering endoscopic imaging system.It surveys the entire esophageal lining and accurately detects subcellular dysplastic changes.The system combines light scattering spectroscopy,which detects and identifies invisible dysplastic sites by analyzing light scattered from epithelial cells,with rapid scanning of the entire esophageal lining using a collimated broadband light beam delivered by an endoscopically compatible fiber optic probe.Here we report the results of the first comprehensive multispectral imaging study,conducted as part of routine endoscopic procedures performed on patients with suspected dysplasia.In a double-blind study that characterized the system’s ability to serve as a screening tool,55 out of 57 patients were diagnosed correctly.In addition,a smaller double-blind comparison of the multispectral data in 24 patients with subsequent pathology at locations where 411 biopsies were collected yielded an accuracy of 90%in detecting individual locations of dysplasia,demonstrating the capability of this method to serve as a guide for biopsy.

Microstructural evolution and defect formation in a powder metallurgy nickel-based superalloy processed by selective laser melting

In this study,the selective laser melting(SLM)technology has been employed to manufacture a nickelbased superalloy which was conventionally prepared through powder metallurgy(PM)route.The microstructural features and defects were systematically investigated both prior to and after heat treatment and compared with the PM counterpart.Both solidification cracking and liquation cracking were observed in the SLM specimen in which the grain misorientation and low melting point(γ+γ')eutectic played a vital role in their formation mechanism.Columnar grains oriented along building direction were ubiquitous,corresponding to strong<001>fiber texture.Solidification cell structures and melt pools are pervasive and noγ'precipitates were detected at about 10 nm scale before heat treatment.After supersolvus solution and two-step aging treatments,high volume fractionγ'precipitates emerged and their sizes and morphologies were comparable to those in PM alloy.<001>texture is relieved and columnar grains tend to become more equiaxed due to static recrystallization process and grain boundary migration events.Significant annealing twins formed in SLM alloy and are clarified as a consequence of recrystallization.Our results provide fundamental understandings for the SLM PM nickel-based superalloy both before and after heat treatment and demonstrate the potential to fabricate this group of alloys using SLM technology.

产科麻醉袖珍手册

此袖珍手册的内容系临床经验之总结，来自我们的临床实践，旨在与各位同仁交流经验，并非指南加以推广。手册中的麻醉处方可根据临床实际加以调整应用。特别指出的是所有腰麻和硬膜外麻醉使用药品均不得含防腐剂。

Quantitative analysis of work hardening and dynamic softening behaviors of Cu-6 wt pct Ag binary alloy based on true stress vs strain curves

The work hardening and dynamic softening behaviors of Cu-6 wt pct Ag binary alloy were studied by hot compression tests under temperature range of 700-850℃ at strain rates of 0.01-10s-1.The critical conditions for the onset of dynamic recrystallization （DRX） were determined based on the conventional strain hardening rate curves （dσ/dε versus σ）.The progress of DRX was analyzed by constructing a model of volume fraction of DRX based on flow curves.The strain rate sensitivity （SRS） and activation volume V were calculated.The results show that the DRX almost can happen under all deformation conditions even at high Z deformations where dynamic recovery （DRV） is the main softening mechanism.The DRX fraction curves can well predict the DRX behavior.The strain has significant effects on SRS at the strain rates of 0.01s-1 and 10s-1 which are mainly due to off-equilibrium saturation of dislocation storage and annihilation while the effects of the temperature on the SRS are based on the uniformity of microstructure distribution.The formation of ＂forest＂ of dislocation is contributed to the low activation volume V＊（about 168b3） which is independent of Z values at the initial deformation.The cross-slip due to dislocation piled up beyond the grain boundaries or obstacles is related to the low activation volume under the high Z deformation conditions at high strain （ε=0.6） while the fine DRX grains coarsed is the main reason for the high activation volume at low Z under the same strain conditions.

Superplastic behavior of a powder metallurgy superalloy during isothermal compression

In this work,the flow behaviors and microstructure evolution of a powder metallurgy nickel-based superalloy during superplastic compression is investigated.Based on the strain rate sensitivity m determined by flow data,superplastic region is estimated at relatively low temperature and strain rate domains,specifically around 1000℃/10^-3s^-1.Thereafter,the cylinder specimens are isothermally compressed at 1000℃/10^-3s^-1 and 1025℃/10^-3s^-1 with different strains,to exam the superplasticity and related mechanisms.The experimental results indicate that the accumulated dislocations are mainly annihilated by dynamic recovery and dynamic recrystallization(DRX),and the grain boundary sliding(GBS)contributes to the total strain during superplastic compression as well.In addition,the cavities and cracks at triple junctions or interfaces between matrix and second phase particle have not been detected,which is different from superplastic tensile deformation.

Dioxin induces expression of hsa-mi R-146b-5p in human neuroblastoma cells

Dioxin can cause a series of neural toxicological effects. Micro RNAs（mi Rs） play important roles in regulating nervous system function and mediating cellular responses to environmental pollutants, such as dioxin. Hsa-mi R-146 b-5 p appears to be involved in neurodegenerative diseases and brain tumors. However, little is known about effects of dioxin on the expression of hsa-mi R-146 b-5 p. We found that the hsa-mi R-146 b-5 p expression and its promoter activity were significantly increased in dioxin treated SK-N-SH cells, a human-derived neuroblastoma cell line. Potential roles of hsa-mi R-146 b-5 p in mediating neural toxicological effects of dioxin may be due to the regulation of certain target genes. We further confirmed that hsa-mi R-146 b-5 p significantly suppressed acetylcholinesterase（ACh E） activity and targeted the3′-untranslated region of the ACh E T subunit, which has been down-regulated in dioxin treated SK-N-SH cells. Functional bioinformatic analysis showed that the known and predicted target genes of hsa-mi R-146 b-5 p were involved in some brain functions or cyto-toxicities related to known dioxin effects, including synapse transmission, in which ACh E may serve as a responsive gene for mediating the effect.

Keeping Pregnant Patients Safe During COVID-19 Pandemic

During a crisis such as the coronavirus disease 2019(COVID-19)pandemic,a hospital can suspend all elective surgery to expand capacity for intensive care;1 however,the clinical care on the Labor and Delivery Unit(L&D)cannot be delayed.Pregnant patients must come to the hospital for their obstetric care and delivery,and patients may express concerns and fear regarding the risk of nosocomial infection.The CO VID-19 pandemic poses multiple challenges specifically for L&D Units around the world,such as:(1)caring for CO VID-19 and non COVID-19 pregnant patients simultaneously on the same unit;and(2)the mode of delivery cannot be pre-determined and emergent cesarean delivery is sometimes necessary.Therefore,strategies and guidelines are desperately needed to protect pregnant patients and health care workers(HCWs)from viral transmission while at the same time ensuring safe and swift responses to obstetric emergencies.Throughout the CO VID-19 pandemic,we have learned an enormous amount about how to provide safe obstetric care.Here we report and share our strategies and experience as the CO VID-19 pandemic is accelerating and global peak is still to come.