Numerical simulation and testing of laser-MIG hybrid-welding angle-structure sheets.

Numerical simulation and experimental investigation of laser-MIG hybrid angle-welding low-carbon 1.5-mm-thin SPCC steel sheets are presented in this work. The transient simulation analysis provides an access to the thermal-fluid phenomena prediction by employing a hybrid three-dimensional heat source model. Special attention is paid to the melt dynamic behaviors within the triangular molten pool affected by the Marangoni convection. The simulation results show that the temperature and its gradient distribution are symmetrical with respect to the laser beam, which is validated well by the experimental study. The microstructure of the welded joints was analyzed by scanning electron microscopy and transmission electron microscopy. The results show that the cross-section microstructures of welded joint are mainly composed of the weld zone, narrow heat-affected zone, and substrate. The semielliptic-like molten pool shape is consistent with that of the simulated results. The finer microstructure in the weld bead results from the rapid cooling rate of laser welding confirmed by the FEM calculation. The columnar and equiaxed dendrites are formed in the peripheral and central region of the molten pool, which is beneficial for the improvement of the microhardness.

Effects of powder size and preset thickness on the microstructure and properties of Ni35 thin coating prepared by laser cladding.

Ni35 thin coatings were prepared on 40Cr steel by preset powder laser cladding technology. The effects of powder size and preset thickness on the dilution rate, microstructure, and properties of the coating were systematically studied. The results showed that the coating with smaller powder size and larger preset thickness had smaller grain size, denser microstructure, a flatter bottom of the molten pool, and lower dilution rate. The micro-hardness of the coating with large powder size and preset thickness was higher. The friction coefficient of the coating with small powder size and small preset thickness was smaller, but the latter had larger curve fluctuation and wear volume loss. The corrosion rate of the coating was high during the first 24 h, then relatively stable after 68 h, and the corrosion rate and loss of the coating with small powder size and large preset thickness were smaller.

Microstructure evolution and wear behavior of AISI 304 stainless steel after Nd:YAG pulsed laser surface melting.

The microstructure and wear behavior of AISI 304 stainless steel after Nd:YAG pulsed laser surface melting (LSM) were investigated. The microstructural features of the LSM layer were characterized by field emission scanning electron microscope and high-resolution transmission electron microscope. Experimental results showed that the microstructure was obviously refined to the nano- and sub-micrometer scales on the AISI 304 stainless steel surface after LSM treatment. Fine grains with grain size of less than 200 nm were obtained when the applied laser energy densities were in the range of 1.90×107 to 3.52×107J/m2 during LSM. The results indicated that the calculated surface temperature, cooling rate, and measured grain size are closely related to the adopted laser energy densities. The lower the laser energy density is, the lower the surface temperature, and the faster the cooling rate, the finer the grain size. In addition, the microhardness and wear resistance of the stainless steel was significantly improved. Finally, the wear mechanism after LSM process was revealed.

[Layer-specific strain assessment on left ventricular function before and after PCI in patients with ST segment elevation myocardial infarction].

Objective: To evaluate the changes of left ventricular function in patients with ST segment elevation myocardial infarction (STEMI) before PCI and within 24 hours after PCI by layer-specific strain, and to explore the value of this new assessment method for quantitative monitoring on the myocardial function in STEMI patients. Methods: A total of 40 patients with acute anterior wall myocardial infarction, who underwent PCI in Affiliated Hospital of Jiangsu University during July 2017 to July 2018, were included in this prospective cohort study. According to the symptom to balloon time (STB), the patients were divided into STB ≤6 hours group (26 cases) and STB 6-12 hours group (14 cases). Echocardiography was performed before, immediately, 3 hours and 24 hours after PCI. Echocardiographic indexes including endocardial myocardial longitudinal strain (LS-endo), 18-segment full-thickness myocardial longitudinal strain (LS) of left ventricle and left ventricular global longitudinal strain (GLS) were measured. The mean LS-endo and LS values of myocardial segments in infarcted area (IALS-endo, IALS) and the mean LS-endo and LS values of myocardial segments in non-infarcted area (NIALS-endo, NIALS) were calculated. Results: There were 34 males and 6 females in this cohort and age was (62±10) years. In STB≤6 hours group, the IALS-endo value ((13.7±4.9)% vs. (10.0±2.7)%, P<0.05) and NIALS-endo value ((17.0±2.9)% vs. (14.6±2.9)%, P<0.05) were significantly higher at 24 hours after PCI than those before PCI. In the group of STB 6-12 hours, IALS-endo decreased immediately after PCI ((6.7±3.3)% vs. (11.9±6.5)%, P<0.05), and there was a rising trend at 3 hours after PCI (P>0.05). At 24 hours after PCI, the index was higher than that immediately after PCI ((13.6±8.4)% vs. (6.7±3.3)%, P<0.05). The NIALS-endo value was significantly higher at 24 hours after PCI than that before PCI ((17.1±2.1)% vs. (14.5±3.2)%, P<0.05). In the STB 6-12 hours group, the decrease rate of IALS-endo immediately after PCI was higher than that in the STB ≤6 hours group (93% (13/14) vs. 35% (9/26), P<0.001). In STB ≤6 hours group, the NIALS value at 24 hours after PCI was higher than that before PCI (P<0.05), and there was no significant difference in IALS, NIALS and GLS at other time points (P>0.05). Conclusions: Layered LS is superior to full-thickness LS and GLS in evaluating left ventricular function in STEMI patients. LS measured by echocardiography can continuously and quantitatively evaluate the changes of left ventricular myocardial function in STEMI patients before and after PCI.

[Impact of CD137-CD137L signaling on secretion of mouse vascular smooth muscle cells-derived exosomes: role of Rab7 pathway].

Objective: To investigate whether CD137-CD137L signaling could affect the secretion of mouse vascular smooth muscle cells (VSMCs) -derived exosomes through autophagy mediated Rab7 pathway. Methods: Primary thoracic aorta VSMCs from C57BL/6J mouse were obtained by tissue block adherence method. VSMCs between the third to fifth passages were used and VSMCs were divided into 4 groups: control group, CD137 agonist group, lentivirus control group, Rab7 lentiviral interference group. VSMCs in CD137 agonist group were treated with recombinant protein of CD137L (10 µg/ml), VSMCs in lentivirus control group were treated with lentiviral followed by recombinant protein of CD137L (10 µg/ml), VSMCs in Rab7 lentiviral interference group were treated with Rab7 lentiviral intervention followed by recombinant protein of CD137L (10 µg/ml). Western blot was used to detect the protein expression of LC3Ⅱ, p62, Rab7, CD9, CD81 and Hsc70. Fluorescence microscopy was used to track the changes of autophagy in cells infected with mRFP-GFP-LC3. Transmission electron microscope was used to observe the morphology and size of VSMCs-derived exosomes. The nanoparticle tracking analysis(NTA) was used to detect the concentration and size of exosomes in each group. Results: (1) The expressions of Rab7, LC3Ⅱ and p62 protein in VSMCs of CD137 activation group were significantly higher than those in control group (all P<0.05). The expressions of Rab7, LC3Ⅱ and p62 protein in Rab7 lentivirus interference group was lower than in CD137 activation group (all P<0.05), while the expressions were similar between the lentivirus control group and the CD137 activation group (all P>0.05). (2) The total number of fluorescent spots and yellow fluorescent spots in the VSMCs of the CD137 activation group were higher than those in the control group (all P<0.05), and the number of yellow fluorescent spots was higher than that of the red fluorescent spots in the VSMCs of the CD137 activation group ((50.3±0.9) vs. (10.3±1.5)/cell). The total numbers of fluorescent spots and yellow fluorescent spots in VSMCs of Rab7 lentivirus interference group were lower than those of CD137 activation group (both P<0.05), and the number of red fluorescent spots in VSMCs was higher than that of yellow fluorescent spots ((40.7±4.0) and (10.7±1.2)/cell) in the Rab7 lentiviral interference group. The total numbers of fluorescent spots and yellow fluorescent spots in the VSMCs were similar between the lentivirus control group and the CD137 activation group (all P>0.05). (3) Under transmission electron microscopy, the size of the VSMCs-derived exosomes was about 30-150 nm. The exosome markers (CD9, CD81) could be detected in vesicles by Western blot. NTA results showed that the concentration of VSMCs-derived exosomes was significantly higher in the CD137-activated group than in the control group (P<0.05), which was significantly lower in the Rab7 lentiviral interference group than in the CD137-activation group (P<0.05) and was similar between the lentivirus control group and the CD137 activation group (P>0.05). The expression of Hsc70 protein in exosomes secreted by CD137 activation group was higher than that in the control group (P<0.05). The expression of Hsc70 protein in exosomes was lower in Rab7 lentivirus interference group than in the CD137 activation group (P<0.05), which was similar between the lentivirus control group and the CD137 activation group (P>0.05). The expression of LC3Ⅱ protein in exosome was higher in CD137 activation group than in control group (P<0.05), which was lower in Rab7 lentivirus interference group than in CD137 activation group (P<0.05), which was similar between the lentivirus control group and the CD137 activation group (P>0.05). Conclusion: The CD137-CD137L signaling may affect the secretion of mouse VSMCs-derived exosomes through modulating the Rab7 pathway mediated autophagy.

Effect of FASN gene on milk yield and milk composition in the Chinese Holstein dairy population.

Fatty acid synthase (FASN) is a multifunctional protein that catalyzes de novo synthesis of fatty acids in cells. It plays a key role in the lipid biosynthesis as well as in the general metabolism of all living animals. We herein investigated polymorphisms of FASN. As a result, six single nucleotide polymorphisms (SNPs) were found and then genotyped in 752 Chinese Holstein cows. It was found that g.17924A>G was non-synonymous, g.13965 C>T, g.16907 T>C and g.18663T>C were synonymous mutations and two other two SNPs, g.8948 C>T (ss491228481) and g.14439T>C (rs133498277), were in intronic sequences of the gene. All such identified SNPs were found to be associated with milk yield and composition traits (P = 0.0441 to <0.0001). Significant additive and allele substitution effects were observed for three yield traits at all six loci as well (P < 0.05 to <0.01). Complete linkage disequilibrium among the five SNPs, with the exception of g.8948 C>T, was observed.

[Short-term efficacy of empagliflozin in children with glycogen storage disease type â b].

Objective: To analyze the short-time efficacy of empagliflozin in the treatment of glycogen storage disease type Ⅰb (GSD Ⅰb). Methods: In this prospective open-label single-arm study, the data of 4 patients were collected from the pediatric department in Peking Union Medical College Hospital from December 2020 to December 2022. All of them were diagnosed by gene sequencing and had neutropenia. These patients received empagliflozin treatment. Their clinical symptoms such as height and weight increase, abdominal pain, diarrhea, oral ulcer, infection times, and drug applications were recorded at 2 weeks, 1 month, 2 months, 3 months, 6 months, 9 months, 12 months, and 15 months after treatment to assess the therapeutic effect. The liquid chromatography-tandem mass spectrometry method was used to monitor the changes in 1, 5-anhydroglucitol (1, 5AG) concentration in plasma. At the same time, adverse reactions such as hypoglycemia and urinary tract infection were closely followed up and monitored. Results: The 4 patients with GSD Ⅰb were 15, 14, 4 and 14 years old, respectively at the beginning of empagliflozin treatment, and were followed up for 15, 15, 12 and 6 months, respectively. Maintenance dose range of empagliflozin was 0.24-0.39 mg/(kg·d). The frequency of diarrhea and abdominal pain decreased in cases 2, 3, and 4 at 1, 2 and 3 months of treatment, respectively. Their height and weight increased at different degrees.The absolute count of neutrophils increased from 0.84×109, 0.50×109, 0.48×109, 0.48×109/L to 1.48×109, 3.04×109, 1.10×109, 0.73×109/L, respectively. Granulocyte colony-stimulating factor was gradually reduced in 1 patients and stopped in 3 patient. Plasma 1, 5 AG levels in 2 children were significantly decreased after administration of empagliflozin (from 46.3 mg/L to 9.6 mg/L in case 2, and from 56.1 mg/L to 15.0 mg/L in case 3). All 4 patients had no adverse reactions such as hypoglycemia, abnormal liver or kidney function, or urinary system infection. Conclusion: In short-term observation, empagliflozin can improve the symptoms of GSD Ⅰb oral ulcers, abdominal pain, diarrhea, and recurrent infection, also can alleviate neutropenia and decrease 1, 5AG concentration in plasma, with favorable safety.

Low-dose epidural dexmedetomidine improves thoracic epidural anaesthesia for nephrectomy.

Thoracic epidural anaesthesia alone is an applied technique of anaesthesia for nephrectomy which has both advantages and limitations. Dexmedetomidine is a highly selective alpha2-adrenoreceptor agonist which has both central and peripheral analgesic properties. Forty patients undergoing nephrectomy were enrolled in this clinical trial and allocated randomly to two groups, a control group (C group) and a dexmedetomidine group (D group). The C group received epidural 0.75% levobupivacaine 12 ml with 1 ml of isotonic sodium chloride solution, while the D group received epidural 0.75% levobupivacaine 12 ml with 1 ml (0.5 µg/kg) of dexmedetomidine. Haemodynamic changes, onset time and duration of sensory and motor block, muscle relaxation score, verbal rating score for pain, sedation score and the total postoperative analgesic consumption were evaluated. Sensory blockade duration was longer in the D group than in the C group (P=0.01). The incidence of motor block and the muscle relaxation score were significantly higher in the D group compared with the C group (P=0.01). Compared with the C group, pain scores were significantly lower in the first four postoperative hours in the D group (two hours rest P=0.038; two hours activity P=0.009; four hours rest P=0.044; four hours activity P=0.003). The total amount of flurbiprofen analgesic was significantly lower in the D group compared with the C group (P=0.03). Epidural dexmedetomidine 0.5 µg/kg appears to intensify thoracic epidural anaesthesia with levobupivacaine.

Roll up polymer/oxide/polymer nanomembranes as a hybrid optical microcavity for humidity sensing.

A hybrid optical microcavity from rolled-up polymer/oxide/polymer nanomembranes presents its excellent capability for environmental relative humidity detection. When exposed to a moist surrounding, poly(acrylic acid)/poly(ethylenimine) polymers swell greatly due to the absorption of water molecules, which thus leads to an increased wall thickness of the tubular optical microcavity and therefore presents a profound wavelength redshift of its whispering-gallery mode resonance. These experiments fit well with the calculation based on the Mie-scattering theory. Theoretical calculation also demonstrates that the thin walls of our tubular microcavities contribute to a high detection sensitivity compared to other microcavities. Our work could lead to new designs and applications of optical microcavities.

Large eddy simulation of the unsteady flow-field in an idealized human mouth-throat configuration.

The present study concerns the simulation and analysis of the flow field in the upper human respiratory system in order to gain an improved understanding of the complex flow field with respect to the process affecting drug delivery for medical treatment of the human air system. For this purpose, large eddy simulation (LES) is chosen because of its powerful performance in the transitional range of laminar and turbulent flow fields. The average gas velocity in a constricted tube is compared with experimental data (Ahmed and Giddens, 1983) and numerical data from Reynolds-averaged Navier-Stokes (RANS) equations coupled with low Reynolds number (LRN) κ-ω model (Zhang and Kleinstreuer, 2003) and LRN shear-stress transport κ-ω model (Jayaraju et al., 2007), for model validation. The present study emphasizes on the instantaneous flow field, where the simulations capture different scales of secondary vortices in different flow zones including recirculation zones, the laryngeal jet zone, the mixing zone, and the wall shear layer. It is observed that the laryngeal jet tail breaks up, and the unsteady motion of laryngeal jet is coupled with the unsteady distribution of secondary vortices in the jet boundary. The present results show that it is essential to study the unsteady flow field since it strongly affects the particle flow in the human upper respiratory system associated with drug delivery for medical treatment.

Aerosolized surfactant and dextran for experimental acute respiratory distress syndrome caused by acidified milk in rats.

BACKGROUND: Inhibition of pulmonary surfactant by plasma-derived proteins is an important pathogenetic factor of acute respiratory distress syndrome (ARDS). Inhalation of aerosolized surfactant may be suitable for early treatment of ARDS. However, requirement of a high dose is a drawback. Because dextran reverses surfactant inhibition, we examined whether dextran improves the therapeutic effects of aerosolized surfactant in rats with experimental ARDS. METHODS: Acidified milk (pH 1.8, 1.5 ml kg(-1)) was injected into the trachea of the rats ventilated with pure oxygen using 2.45 kPa peak inspiratory pressure and 0.74 kPa positive end-expiratory pressure. When PaO2 decreased to <13 kPa, the rats were assigned to four groups: control group (n = 8), receiving no material; D-only group (n = 6), receiving aerosolized dextran for 45 min; S-only group (n = 8), receiving aerosolized modified natural surfactant (MNS) for 30 min; and S-plus-D group (n = 9), receiving aerosolized MNS for 30 min followed by aerosolized dextran for 15 min. RESULTS: In the control group and D-only groups, the mean PaO2 remained at <10 kPa for 180 min. In the S-only and S-plus-D groups, the PaO2 increased to 50 kPa (P < 0.01 vs. untreated). The PaO2 of the surfactant-only group gradually decreased to <17 kPa at 180 min, whereas the PaO2 of the S-plus-D group was maintained at >38 kPa for 180 min (P < 0.01 vs. S-only group). CONCLUSION: Inhalation of aerosolized dextran potentiates the effects of aerosolized surfactant by prolonging the therapeutic response.