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OBJECTIVE: To summarize the surgical experience of totally implantable venous access port in children with malignant tumors, and to explore the coping methods of surgical complications. METHODS: The clinical data of 165 children with malignant tumors implanted in totally implantable venous access port in Department of Pediatric Surgery, Peking University First Hospital from January 2017 to December 2019 were retrospectively analyzed. The operation process, complications and treatment of complications were observed and counted. RESULTS: The children in this group were divided into external ju-gular vein incision group (n=27) and internal jugular vein puncture group (n=138) according to different surgical methods, and the latter was divided into ultrasound guided puncture group (n=95) and blind puncture group (n=43). No puncture complications occurred in the external jugular vein incision group, and the average time for successful catheterization and the number of times for catheter to enter the superior vena cava were more than those in the internal jugular vein puncture group [(9.26±1.85) min vs. (5.76±1.56) min, (1.93±0.87) times vs. 1 time], with statistical significance. The average time of successful catheterization, the success rate of one puncture, the average number of punctures and the incidence of puncture complications in the ultrasound guided right internal jugular vein puncture group were better than those in the blind puncture group [(5.36±1.12) min vs. (6.67±1.99) min, 93.68% (89/95) vs. 74.42% (32/43), (1.06±0.24) times vs. (1.29±0.55) times, 2.11% (2/95) vs. 11.63% (5/43)], with statistically significant differences. The total incidence of complications in this study was 12.12% (20/165). Pneumothorax occurred in 1 case, artery puncture by mistake in 1 case, local hematoma in 5 cases, venous access port related infection in 4 cases (venous access port local infection in 2 cases, catheter related blood flow infection in 2 cases), subcutaneous tissue thinning on the surface of port seat in 2 cases, port seat overturning in 1 case, poor transfusion in 4 cases (catheter discount in 1 case, catheter blockage in 3 cases), and foreign bodies gathered around the subcutaneous pipeline in 2 cases. There were no complications, such as catheter rupture, detachment and catheter clamping syndrome. CONCLUSION: Totally implantable venous access port can provide safe and effective infusion channels for children with malignant tumors. Right external jugular vein incision and ultrasound-guided right internal jugular vein puncture are reliable surgical methods for children's totally implantable venous access port implantation. Surgeons should fully understand the complications of the venous access port, take measures to reduce the occurrence of complications, and properly handle the complications that have occurred.

With the aging of population and the development of social economy, the incidence of chronic wounds is increasing day by day, while the incidence of burns and trauma remains at a high level, making wound repair an increasingly concerned area in clinical practice. Thymosin β4 is a naturally occurring small molecule protein in vivo, which is widely distributed in a variety of body fluids and cells, especially in platelets. Thymosin β4 has biological activities of promoting angiogenesis, anti-inflammation, anti-apoptosis, and anti-fibrosis, and has many important functions in wound repair. Thymosin β4 has been observed to promote the healing of various wounds, such as burns, diabetic ulcers, pressure ulcers. This paper will review the molecular structure, mechanism of wound healing promotion, pharmacokinetics, and clinical application of thymosin β4, aiming to introduce its potential in wound treatment and the shortcomings of current researches.随着人口老龄化和社会经济的发展，慢性创面发病率日益增高，同时烧创伤发病率仍处于较高水平，使得创面修复成为临床日益关注的领域。胸腺素β4是一种体内天然存在的小分子蛋白，其广泛分布于多种体液和细胞内，尤其是血小板中。胸腺素β4具有促进血管生成、抗炎、抗凋亡及抗纤维化的生物活性，在创面修复方面有许多重要的功能。目前已经在烧伤、糖尿病溃疡、压疮等多种创面中观察到胸腺素β4具有促进愈合的作用。该文将从胸腺素β4的分子结构、促创面愈合作用机制、药代动力学及临床应用方面进行综述，旨在介绍该因子在创面治疗中的潜力和当前研究的不足之处。.

OBJECTIVE: To summarize and analyze the clinical characteristics of children with basal ganglia germinoma and to improve the level of early clinical diagnosis. METHODS: The clinical data of children diagnosed with basal ganglia germinoma admitted to the Pediatric Surgery Ward of Peking University First Hospital from January 2013 to December 2020 were retrospectively analyzed, and descriptive statistics were used to analyze the clinical characteristics of children with basal ganglia germinoma. RESULTS: A total of 30 patients were included in the study, 28 were male, 2 were female, the mean age at onset was (9.7±2.2) years, the median disease duration was 7 months, 27 had unilateral disease, and 3 had bilateral disease. The clinical manifestations were decreased limb muscle strength, cognitive function disorders, polydipsia, precocious puberty, intracranial hypertension, dysphonia and swallowing dysfunction. The serum and cerebrospinal fluid tumor marker alpha-fetoprotein (AFP) were normal in the 30 patients, and the serum and cerebrospinal fluid tumor marker β-human chorionic gonadotropin (β-HCG) were normal in 8 patients.The serum β-HCG was normal in 11 patients but the cerebrospinal fluid β-HCG was slightly elevated, and the serum and cerebrospinal fluid β-HCG were slightly elevated in 11 patients. A total of 33 lesions with irregular shapes were found by imaging examination, including 15 (45.5%) patchy lesions, 10 (30.3%) patchy lesions, and 8 (24.2%) round-like high-density lesions. Tumors showed obvious high-density shadows on computed tomography (CT) scan. Magnetic resonance imaging (MRI) scan of the tumors showed low or isointensity on T1WI and isointensity on T2WI, accompanied by mild peritumoral edema, hemispheric atrophy, cerebral peduncle atrophy, calcification, cystic degeneration, ventricular dilatation and wallerian degeneration. On contrast-enhanced scans, the tumor showed no enhancement or heterogeneous enhancement. CONCLUSION: The main age of onset of germ cell tumors in the basal ganglia in children is about 10 years old, and males are absolutely dominant. The clinical features and imaging manifestations have certain characteristics. With both combined, the early diagnosis of germ cell tumors in the basal ganglia can be improved.

For recovering the block-sparse signal with unknown block structures, this paper presents a Block Stage-wise Weak Orthogonal Matching Pursuit (BSWOMP) algorithm. Which partitions the original signal into different groups or segments and conducts the selection for these groups separately using weak selection method to update reconstructing support set. And it proves that the Restricted Isometry Property (RIP) of BSWOMP algorithm is slack than Stage-wise Weak Orthogonal Matching Pursuit (SWOMP) algorithm and Block Orthogonal Matching Pursuit (BOMP) algorithm, this means BSWOMP algorithm generates better convergence than traditional sparse signal recovery algorithm. To further analysis of the performance of BSWOMP, the effectiveness of this algorithm is demonstrated by simulations. Experiments results show that the proposed algorithm effectively selects the nonzero elements of the block-sparse signal by a threshold, and compared with the traditional algorithms, BSWOMP algorithm has higher recovering stability, expedites the approximate conjugate gradient update step and brings an evident performance improvement and application prospect.

OBJECTIVE: To summarize and analyze the treatment process, long-term efficacy and clinical economics of children's hepatoblastoma (HB) in multi-disciplinary team (MDT) mode, so as to provide basis for the rational choice of diagnosis and treatment. METHODS: From January 2014 to February 2019, 13 cases of hepatoblastoma in children who completed the whole treatment course in the Pediatric Hematology Tumor Ward of Peking University First Hospital were collected and analyzed, and were followed up until June 30, 2020. There were 9 males and 4 females who were diagnosed and treated according to the MDT process in the hospital. The median age was 16 months (2-54 months), 69.23% (9/13) were under 2 years old. The characteristics, diagnosis and treatment process and treatment effect of the cases were summarized, and the cost of clinical treatment was analyzed. RESULTS: According to the pretreatment extent of disease(PRETEXT), there were 1, 9 and 3 children with stages Ⅱ, Ⅲ and Ⅳ. 76.92% (10/13) of the patients had the largest tumor diameter > 10 cm. All the patients received preoperative neoadjuvant chemotherapy (8 patients received 4 cycles of chemotherapy, and 6 patients changed the chemotherapy plan), surgical treatment and postoperative chemotherapy, the tumor volume decreased by more than 50% (64%-95%) in 12 cases, except 1 case with no significant increase of alpha fetal protein and multiple lesions.The median length of stay was 87 days (68-214 days), the median cost of stay was 200 000 yuan (115 000-500 000 yuan), the median length of stay was 7 days (5-17 days), the median cost of stay was 20 000 yuan (15 000-60 000 yuan), and the incidence of postoperative complications was 7.69% (1/13). All the patients were followed up for 16-69 months. All the patients survived. CONCLUSION: Under the MDT mode, the treatment is seamless connection, the long-term prognosis of children with HB is good, and the total hospitalization cost and time are within the acceptable range. Standard preoperative neoadjuvant chemotherapy can significantly reduce the tumor, improve the resection rate, reduce postoperative complications, reduce the total individual expenditure, shorten the total hospital stay, and further improve the long-term disease-free survival rate.

To determine the effect of miR-217 on the apoptosis of atherosclerotic endothelial cells (AECs) through the Toll-like receptor (TLR) 4/PI3K/Akt/NF-κB pathway.Oxidized low-density lipoprotein (ox-LDL) was used to construct an atherosclerotic endothelial cell model, and the expression of miR-217/TLR4/PI3K/Akt/NF-κB in the cells was regulated to explore their effects on the viability, apoptosis, inflammatory factors [tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10)], and endothelial-to-mesenchymal transformation (EndMT) of the endothelial cells.In AECs, miR-217 expression decreased, and the PI3K/Akt/NF-κB pathway was inhibited. The Dual-Luciferase reporter assay revealed that TLR4 was the target of miR-217, and it was up-regulated in AECs, and the further study revealed that up-regulation of miR-217 protected AECs, increased their activity, reduced their apoptosis, and inhibited inflammatory response and EndMT, while TLR4 acted contrary to miR-217. Besides, it was also found that miR-217 inhibited the PI3K/Akt/NF-κB pathway, thus weakening the influence of si-TLR4 on endothelial cells. Furthermore, miR-217 inhibited EndMT by inhibiting TLR4 from activating the PI3K/Akt/NF-κB signal pathway.In AECs, TLR4 expression increased, and miR-217 and the PI3K/Akt/NF-κB signaling pathway are inhibited. Additionally, miR-217 can increase the viability of AECs through the TLR4/PI3K/Akt/ NF-κB signal transduction pathway, and inhibit their apoptosis, inflammatory response, and EndMT.

To assess the expression of LncRNA NKILA and MALAT1 in retinoblastoma and its related mechanisms.Tixty-eight cases of retinoblastoma patients admitted to our hospital from February 2017 to February 2019 were collected as a research group, while 70 healthy people who came to our hospital for checkup at the same time were chosen as a control group. Both retinoblastoma and human colorectal mucosa cells were purchased, expression and clinical value of NKILA and MALAT1 in serum of Rb patients were tested, and sh-NKILA, si-NKILA, NC, sh-MALAT1 and si-MALAT1 were transfected into Weri-Rb1 and Y79 cells. qRT-PCR was adopted to detect the NKILA and MALAT1 levels in samples, and WB was adopted to detect the cle-caspase-3, cle-caspase-9, Bax, Cyclin B1, CDC2 and p-CDC2 protein levels in cells. Cell proliferation was conducted via MTT assay, invasion was carried out through transwell assay, and apoptosis was confirmed by flow cytometry assay.NKILA and MALAT1 were low expressed in retinoblastoma, and AUC of LncRNA NKILA and MALAT1 was over 0.8. LncRNA NKILA and MALAT1 were associated with tumor size, classification and clinical grading in children with retinoblastoma. Over-expression of NKILA and MALAT1 could promote apoptosis, inhibit cell growth and Bcl-2 protein, and promote upregulation of the expression levels of clecaspase-3, clecaspase-9 and Bax.By regulating MALAT1 and NKILA, we controlled the growth and apoptosis of Rb cells, which was expected to be a potential clinical therapeutic target for Rb.

In this paper, we study the spin excitation properties of the frustrated triangular-lattice antiferromagnet $\mathrm{Yb}{({\mathrm{BaBO}}_{3})}_{3}$ with nuclear magnetic resonance. From the spectral analysis, neither magnetic ordering nor spin freezing is observed with temperature down to $T=0.26$ K, far below its Curie-Weiss temperature $|{\ensuremath{\theta}}_{w}|\ensuremath{\sim}2.3$ K. From the nuclear relaxation measurement, precise temperature-independent spin-lattice relaxation rates are observed at low temperatures under a weak magnetic field, indicating the gapless spin excitations. Further increasing the field intensity, we observe a spin excitation gap with the gap size proportional to the field intensity. These phenomena suggest a very unusual strongly correlated quantum disordered phase, and the implications for the quantum spin liquid state are further discussed.

Emerging evidence has demonstrated vital regulation of circular RNAs (circRNAs) on tumorigenesis and progression of tumors. Abnormally expressed circRNAs hsa_circ_0005075 (circ_0005075) has been reported in several tumors. In this study, we aimed to explore the expression profiles, prognostic value, and potential function of circ_0005075 in colorectal cancer (CRC) PATIENTS AND METHODS: RT-PCR was used to detect the expression of circ_0005075 in both CRC tissues and cell lines. The associations between circ_0005075 expression and clinicopathological features and clinical prognosis were statistically analyzed. The effects of circ_0005075 on CRC cells were evaluated by Cell Counting Kit-8 (CCK-8), colony formation assays, Flow cytometer, and transwell assays. Western blot was performed to explore whether circ_0005075 modulated the Wnt/β-catenin pathway.We observed that circ_0005075 expression was significantly up-regulated in both CRC tissues and cell lines. Then, clinical assays indicated that high circ_0005075 expression was significantly associated with histology/differentiation, depth of invasion, advanced TNM stage, and shorter overall survival and disease-free survival of CRC patients. Cellular studies indicated that circ_0005075 can enhance the proliferation, migration, and invasion capacities of CRC cells, thereby promoting tumor progression. Further mechanistic investigation showed that circ_0005075 displayed its tumor-promotive roles through activating Wnt/β-catenin pathway.Our present data revealed circ_0005075 as a potential molecular marker and target for the prognosis and treatment of CRC patients.

The existence of a large number of solid wastes has caused great pollution to the environment. In this study, different solid waste such as steel slag, water-quenched manganese slag, red mud and coal gangue was used in cement mortar, and the mechanical properties and hydration products were studied. Results showed that water-quenched manganese slag and high-calcium coal gangue after spontaneous combustion showed higher activity. Coal gangue has the highest activity of 102% and red mud has the lowest activity of 69%. Both steel slag and manganese slag added samples showed higher strength than that of manganese slag and steel slag separately added samples. The composite admixture of steel slag, manganese slag, red mud and coal gangue showed the highest strength at 7%, 8%, 8%, 7% and 7%, 12%, 4%, and 7%, respectively.

In order to enhance the large-scale and high-quality application of limestone powder (LP) and phosphogypsum in the construction industry. Therefore, this paper mainly studies the effect of LP on the physical and mechanical properties of phosphogypsum-based composites, and clear the mechanism of action from the micro level. Based on the results, the conclusions were as follows: LP has the effect of reducing the standard consistency water requirement and shortening the setting time of fresh phosphogypsum-based composites slurry; LP can increase the bulk density and reduce 24-hour water absorption of hardened phosphogypsum-based composites matrix; In addition, the strength of the matrix increases first and then decreases with the increase in the amount of LP and the recommended amount of LP is 5%-10%. Microscopic tests have shown that when the amount of LP is less than 10%, it can effectively reduce the porosity, refine the pore size, and play the role of a dense hardened matrix. In addition, the appropriate amount of LP particles can be adsorbed on the surface of dihydrate crystals, increasing the bonding force between the crystals, which is conducive to increasing the strength of the composite matrix.

The ultra-high toughness cementitious composites (UHTCC) was modified by different types of epoxy emulsion, the effect of the emulsion on working performance, mechanical properties and impermeability of UHTCC were studied. The result showed that compared with the control without epoxy emulsion, the type I and type II epoxy emulsion improved the working performance of UHTCC with low dosage. However, the type III epoxy emulsion exhibited an improvement effect on working performance of UHTCC only when the dosage was high. The addition of epoxy emulsion to UHTCC caused a decrease in compressive strength and flexural strength, but epoxy emulsion and hydration products formed an excellent energy absorption mechanism in the specimen and enhanced the elastic modulus of UHTCC. Type I and II epoxy emulsion had little effect on the tensile properties of UHTCC. Type III epoxy emulsion greatly increased the ultimate tensile strength of UHTCC, and the strain hardening phenomenon disappeared at low dosage level, however, the effect of strain hardening had been improved by increasing its dosage.

Cytokines produced by various cells are strong local mediators of inflammation. Interleukin-1beta (IL-1β) and C-reactive protein (CRP) play essential roles in the development and progression of diabetes mellitus (DM). Thus periodontal diseases could be related to DM via the same mediators of inflammation. To evaluate plasma and gingival crevicular fluid (GCF) levels of IL-1β and CRP in adolescents with DM to further investigate whether DM has an impact on the levels of inflammation factors at an early stage, and to analyze the risk of developing periodontal diseases in adolescents with DM.A total of 121 adolescents aged from ten to sixteen years were enrolled, 41 adolescents diagnosed with diabetes mellitus were collected in the DM group, and 80 nondiabetic adolescents as the control group. The periodontal indices of each individual were recorded, including plaque index (PLI), modified bleeding index (mBI), probing depth (PD) and attachment loss (AL). GCF and intravenous blood samples were collected, and CRP and IL-1β levels were detected by enzyme-linked immunosorbent assay (ELISA).(1) PLI of DM group and control group were 1.23±0.05 and 0.95±0.04 separately, with significant difference (P=0.001). DM group and control group had mBI of 0.80±0.08 and 0.51±0.06 separately, with significant difference (P=0.003). Attachment loss was found in none of the subjects. PDs of DM group and control group were (2.37±0.51) mm and (2.31±0.05) mm separately, and there was no significant difference. (2) CRP in GCF was only detectable in partial of the individuals, with a detectable rate of 22.9% (11/48) in total. The detectable rate of CRP in GCF was significantly higher in DM group (38.5%) than that in control group (4.5%, P=0.006). The plasma level of CRP in DM group [0.23 (0.15, 1.89) mg/L] was higher than that in control group [0.19 (0.12, 4.18) mg/L], but without significance (P=0.776). (3) The plasma levels of IL-1β in DM group and control group were (14.11±0.57) ng/L and (14.71±0.50) ng/L separately, but there was no significance (P=0.456). GCF levels of IL-1β in DM group and control group were (12.91±1.95) μg/L and (17.68±3.07) μg/L, without significant difference (P=0.185).Periodontitis was not observed in adolescents with DM at an early stage. However, the rising levels of periodontal indices and CRP in GCF, might indicate that adolescents with DM have a higher risk of developing periodontal diseases in the future.

In the Chinese Buddhist Scriptures, there are many stories or topics about the ancient Indian pharmacist, however, they are not the Medicine Buddha as people knows, but real doctors. In the Chinese Buddhist Scriptures, the doctors gave the medical service to the monks and the laymen. Some of them are respected as the "miracle doctor" or the "king of doctor" , influencing the medicine of ancient East Asian.在汉译佛典中，有许多涉及古印度"药师"的典故或论述，这些药师并不是今人所熟悉的"药师佛"，而是实实在在的医生。佛教文献中所记载的这些药师，主要为僧俗提供医疗保健服务。他们中有的人，还被视为"神医"乃至"医王"，其影响已经波及古代东亚地区。.

Background and purpose The present study aimed to examine how long-term migration to high-altitude regions affects mentality and cognition, and the correlation with various physiological and biochemical changes. Methods The WHO Neurobehavioral Core Test Battery, Raven's Standard Progressive Matrices (RSPM) and Pittsburgh Sleep Quality Index questionnaire were used to assess 141 young male subjects who lived in plain regions and 217 young male subjects who had migrated to a 4500 m high-altitude region and lived there for 1–5 years. Arterial oxyhemoglobin saturation, cerebral tissue oxygenation indices (TOIs), serum S100B and brain-derived neurotrophic factor (BDNF) were also measured. Results Long-term migrators to a high-altitude region exhibited exacerbated mood disorders, retarded color discrimination ability, decreased visual memory capacity, and impaired perceptual motor skill and motion stability. In addition, the migrators exhibited lower RSPM scores and lower sleep quality. Further analyses revealed significant correlations between sleep quality and cerebral TOIs, mood and sleep quality, mood and certain cognitive functions, mood and serum BDNF levels, and RSPM scores and serum S100B levels. Conclusions Long-term living at high altitudes causes significant impairment of psychological and cognitive function. Cerebral hypoxic extent, sleep quality and biochemical dysfunction are major influencing factors.

In this paper, we studied the effect of earthworm loads on the removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen, and total phosphorus from synthetic domestic sewage and on the bacterial community structure and diversity of substrates in earthworm packing beds. The different vermifiltrations (VFs), including the control, are successful in removing both organic matter (OM) and nutrients. The removal rate of NH3-N at 12.5 g of earthworm/L of soil VF is higher compared with that at 0 and 4.5 earthworm load VFs. The highest Shannon index, in the earthworm packing bed, occurred at 16.5 earthworm load VF. Furthermore, the COD removal rate is significantly correlated with the Shannon index, which reveals that OM removal for synthetic domestic sewage treatment at VF might be more dependent on bacterial diversity at the earthworm packing bed. The band distributions and diversities of the bacterial community for samples from different earthworm loads in VFs suggest that the bacterial community structure was only affected within the earthworm packing bed when the earthworm load reached a certain level. The present study adds to the current understanding of OM and nutrient degradation processes in VF domestic wastewater treatment.

MicroRNAs (miRNAs) are potent regulators of gene transcription and posttranscriptional processes. The majority of miRNAs are localized within intronic regions of protein-coding genes (host genes) and have diverse functions in regulating important cellular processes in animals. To date, few plant intronic miRNAs have been studied functionally. Here we report a comprehensive computational analysis to characterize intronic miRNAs in rice and Arabidopsis. RT-PCR analysis confirmed that the identified intronic miRNAs were derived from the real introns of host genes. Interestingly, 13 intronic miRNAs in rice and two in Arabidopsis were located within seven clusters, of which four polycistronic clusters contain miRNAs derived from different families, suggesting that these clustered intronic miRNAs might be involved in extremely complex regulation in rice. Length analysis of miRNA-carrying introns, promoter prediction and qRT-PCR analysis results indicated that intronic miRNAs are coexpressed with their host genes. Expression pattern analysis demonstrated that host genes had a very broad expression spectrum in different stages of development, suggesting the intronic miRNAs might play an important role in plant development. This comparative genomics analysis of intronic miRNAs in rice and Arabidopsis provides new insight into the functions and regulatory mechanisms of intronic miRNAs in monocots and dicots.

Fatigue life prediction and optimization is becoming a critical issue affecting the structural applications of cast aluminum-silicon alloys in the aerospace and automobile industries. In this study, a range of microstructure and porosity populations in A356 alloy was created by controlling the casting conditions and by applying a subsequent hot isostatic pressing (“hipping”) treatment. The microstructure and defects introduced during the processing were then quantitatively characterized, and their effects on the fatigue performance were examined through both experiment and modeling. The results indicated that whenever a pore is present at or near the surface, it initiates fatigue failure. In the absence of large pores, a microcell consisting of α-Al dendrites and associated Si particles was found to be responsible for crack initiation. Crack initiation life was quantitatively assessed using a local plastic strain accumulation model. Moreover, the subsequent crack growth from either a pore or a microcell was found to follow a small-crack propagation law. Based on experimental observation and finite-element analysis, a unified model incorporating both the initiation and small crack growth stages was developed to quantitatively predict the dependency of fatigue life on the microstructure and porosity. Good agreement was obtained between the model and experiment.

The demand for low-cost, high strength-to-weight ratio components continues to drive the development of aluminum alloy castings for new applications. The automotive brake caliper, which has traditionally been made from cast iron, is one such component where aluminum alloys are being considered. The fatigue performance of the brake caliper is an important consideration in evaluating new designs. The use of aluminum alloys in cast components under cyclic loading conditions necessitates a design approach that, in addition to in-service loading, incorporates the impact of microstructural features on fatigue life. In this investigation, a through-process modeling approach has been employed to link a series of mathematical models describing the processing steps of (1) casting, (2) heat treatment, (3) machining, and (4) in-service performance for a preliminary design of a brake caliper made of aluminum alloy A356, Step (1) includes microstructural predictions (secondary dendrite arm spacing and maximum pore size), which are tracked through to the final component. The final lifing of the component combines the effects of these microstructural features with the complex stress state arising from the combined service loading and residual stresses. It was found that all three factors have a strong influence upon the component’s fatigue performance.

Fatigue strength optimization of cast aluminium alloys requires an understanding of the role of micropores resulting from the casting process. High cycle fatigue tests conducted on cast A3 56-T6 show that the pore size and proximity to the specimen surface significantly influence fatigue crack initiation. This is supported by finite element analyses (both elastic and elastic-plastic) which demonstrate that high stress/strain concentration is induced by pores which are both large and near to the specimen surface. A new pore-sensitive model based on a modified stress-life approach has been developed which correlates fatigue life with the size of the failure-dominant pore. The model prediction is in good agreement with experimental data.

Porosity is well known to be a potent initiator of fatigue cracks in cast aluminum alloys. This article addresses the observed scatter in fatigue life of a cast A356-T6 aluminum-silicon alloy due to the presence of porosity. Specimens containing a controlled amount of porosity were prepared by employing a wedge-shaped casting mold and adjusting the degassing process during casting. High-cycle fatigue tests were conducted under fixed stress conditions on a series of specimens with controlled microstructures (especially, the secondary dendrite-arm spacing), and the degree of scatter in the results was assessed. Stochastically, such scatter was found to be adequately characterized by a three-parameter Weibull distribution function. Large pores at or close to the specimen surface were found to be responsible for crack initiation in all fatigue-test specimens, and the resultant fatigue life was related to the initiating pore size through a relationship based on the rate of small-fatigue-crack propagation. With respect to the probabilities for the pores of various sizes and locations to initiate a fatigue crack, a statistical model was developed to establish the relationship between the porosity population and the resultant scatter in fatigue life. The modeling predictions are in agreement with the experimental results. Moreover, Monte-Carlo simulation based on this model demonstrated that the average pore size, pore density, and standard deviation of the pore sizes, together with the specimen size and geometry, are all of consequence regarding scatter in fatigue life.

A micro-scale analytical model for predicting size-dependent microhardness is presented. The indentation size effect is explained by dissipation energy associated with the contact surfaces. Micro-mechanics mechanism of this energy dissipation is studied via a plastic deformation analysis of micro-scale asperities on the contact surface under indentation. The analysis shows that the microhardness depends not only on the properties of the bulk material under test, but also the properties of the contact surface, such as the plastic behavior of the micro-asperities on contact surfaces. The dependence of microhardness on the roughness parameters of the contact surfaces is also revealed from the analysis.

Microscale contact between two solid surfaces induced by the liquid-bridging force is studied in the present article. Attention is focused on the interaction between the size of the contact area and the magnitude of the liquid-bridging force. The liquid-bridging force is related to the contact size and the other parameters, such as the filling angle, the contact angles, and the surface tension of the liquid, by solving the Laplace–Young equation. A singular integral equation for the coupled contact equilibrium problem is established and solved. Two approximate solutions for the same problem are also given and compared with the solution of the singular integral equation. Parametric study reveals the dependence of the semicontact width and the liquid-bridging force on the filling angle and the dimensionless group in the microscale contact.

The nonequilibrium thermodynamics framework is tailored in the present paper to formulate the gas/liquid/solid system. In this system, there are two important issues, namely, the contact line motion and contact angle change, and shear stress singularity, during the dynamic evolution. Traditionally, the fluid mechanics approach has been applied to model these two issues. In the present paper, we applied a thermodynamics formulation to re-examine the first issue, i.e., the dynamic motion of the contact line and angle. It provides a new angle to understand the fundamentals of this classical problem. In order to verify the reliability of the present thermodynamics formulation, the capillary rise problem is revisited by using the formulation. A numerical result obtained based on the thermodynamics formulation is then compared with experimental test data. Excellent agreement between our analytical and experimental results gives us confidence for the future works on this approach.

A thermodynamic formulation is applied to examine the wetting process of a solid surface by a liquid. Attention is focused on the change of the Gibbs free energy of a given gas/liquid/solid system and the moving speed of the contact line on the solid surface. The present study demonstrates that there is a thermodynamic limitation on the wetting speed in a given system. This thermodynamic limitation leads to the verification of the postulate suggested by Blake and Ruschak [Nature (London) 282, 489 (1979)] that there is a maximum speed at which wetting can proceed for the given system.

The LC resonance in the traditional passive quasi resonant soft switched Zero Voltage Switching (ZVS)-SEPIC converter, together with the adoption of pulse frequency modulation leads to the complex control and high electrical stress of its electronic components. In order to resolve this issue, the use of an active clamped topology for the ZVS-SEPIC is proposed. With this technique, the resonant effect on the converter is reduced due to the use of an auxiliary switch and the adoption of pulse width modulation. In addition to this, the converter becomes more efficient as the main and auxiliary switches can be set to ZVS. This paper analyses the principle of this theory and the design of the LC resonant circuit.

The mixtures of mesogen-jacketed liquid crystalline polymers (MJLCP) and epoxy resin (E-51) have been prepared in a certain proportion. The category of the MJLCP is poly{2, 5-bis[(4-butoxyphenyl) oxycarbonyl] styrenes} (PBPCS). Methyl tetrahydro phthalic anhydride (MeTHPA) is served as a curing agent, and N, N-dimethylbenzylamine plays the role of catalyst. Then, based on the curing process, the modified materials have been acquired by casting molding. The effect of PBPCS's improvement has been researched through the mechanical properties test, dynamic thermal mechanical test and scanning electron microscope (SEM). The results indicated that PBPCS could apparently improve the mechanical properties of resin E-51. Compared with unmodified materials, the elongation at break and the tensile strength of PBPCS have been improved remarkably through modification. Both mechanical properties of the 4wt% PBPCS/E-51/MeTHPA were enhanced by 48% and 153% separately, and the characteristics of the 3wt% one were raised by 47% and 19% respectively. Also, the ductile fracture morphology of the resins was exhibited in SEM photograph clearly.

A combination of coagulation and Fenton's process was used for the removal of total oxygen carbon (TOC) from oilfield wastewater. Compared with aluminium sulfate, ferric coagulant had better TOC removal efficiency at the same mass dosage. In Fenton's process, the effect of H2O2 and Fe2+ dose on the removal of TOC was studied. The optimum conditions required for TOC removal were an Fe3+ concentration of 40-50 mg/L, an H2O2 dose of 50 mmol/L and an Fe2+ concentration of 1.0 mmol/L. GC-MS chromatographic analysis indicated that most of the alkyl hydrocarbons of carbon numbers21 were removed in the first minute of Fenton's process mainly through adsorption. Alkyl hydrocarbons and phenols were oxidized almost completely following 120 min of treatment. The pathway of newly formed intermediates in Fenton's process was proposed on the basis of the GC/MS chromatogram.