Design and Performance Research of a Precision Micro-Drive Reduction System without Additional Motion.

A micro-drive system is a key part of macro-micro-drive technology and precision positioning technology in which a micro-drive reduction system can provide more precise motion and suitable small space motion. Therefore, it is necessary to study precision micro-drive reduction systems. In this paper, based on the design of a micro-drive reduction mechanism without force and displacement in non-motion direction, a precision micro-drive reduction system driven by a piezoelectric ceramic actuator (PZT) was designed, and the strength, dynamic and motion performance of the system was analyzed. First, based on the principle of a flexure hinge lever and the principle of balanced additional force, a type of precision micro-drive reduction mechanism with an adjustable reduction ratio was designed. Second, the strength performance of the system was analyzed by finite element analysis, and the dynamic performance of the system was analyzed by finite element analysis and experiments. Finally, the kinematic performance of the system was analyzed by theoretical analysis, the finite element method and experiment, and the motion linear equation was calculated based on the linear fitting equations of three methods. The study results showed that the system had good strength and dynamic performances, and the system's motion had the advantages of high precision and good linearity. This research has certain reference value for the design and performance research of micro-drive mechanisms.

Research on Continuous Error Compensation of a Sub-Arc-Second Macro/Micro Dual-Drive Rotary System.

In this paper, a sub-arc-second macro/micro dual-drive rotary system is designed, and the continuous compensation of the system error and its experimental research are completed. First, the macro-drive system is driven by a direct-drive motor, and the micro-drive system uses a piezoelectric ceramic to drive the micro-drive rotary mechanism; the system uses a micro-drive system to compensate the motion error of the macro-drive system, and uses circular grating to feedback the displacement of the macro/micro total output turntable to form a macro/micro dual-drive closed-loop control system. Second, based on the establishment of the system error model, the design of the system's continuous error compensation scheme is completed. Finally, the positioning accuracy testing of the system, direct error compensation of the macro-drive, manual error compensation of the macro-drive, error compensation performance of the micro-drive part and macro/micro compensation of the system are carried out in the study. The results show that the repeated positioning error and the positioning error of the system are reduced by 78.8% and 95.2%, respectively, after macro/micro compensation. The correctness and effectiveness of the designed system design, error compensation and control method are verified through performance tests, and its positioning accuracy is verified to the sub-arc-second (0.1 arcsecond) level. The research in this paper has important reference value for the development of ultra-precision macro/micro dual-drive technology.

Epidemiological and clinical characteristics of bacteremic brucellosis.

OBJECTIVE: To retrospectively investigate the epidemiological features, clinical manifestations and laboratory characteristics of bacteremic brucellosis. METHODS: Brucellosis patients admitted to our clinic from January 2015 to December 2017 were included in the study. Patient electronic medical records were reviewed for epidemiological features, clinical manifestations, and laboratory findings. RESULTS: A total of 132 brucellosis patients were analyzed (64 cases with bacteremic brucellosis and 68 cases with nonbacteremic brucellosis). The median duration from exposure to onset of symptoms was 6.9 weeks (range: 1 day to 32 weeks) and 21.9 weeks (range: 1-76 weeks) in patients with bacteremic and nonbacteremic brucellosis, respectively. More bacteremic than nonbacteremic patients presented with fever and chills. Arthritis was observed in 34 (25.8%) patients, and was more commonly observed in nonbacteremic patients. Using C-reactive protein (CRP) and procalcitonin (PCT) as serological markers, the areas under the receiving operating characteristic curves were 0.64 [95% confidence interval (CI): 0.54-0.73] and 0.61 (95% CI: 0.51-0.70), respectively, for distinguishing bacteremic from non-bacteremic brucellosis. CONCLUSION: Fever and chills were frequently observed in bacteremic brucellosis patients, whereas arthritis was more common in nonbacteremic brucellosis patients. Serum CRP and PCT can be used as potential serological markers for diagnosing bacteremic brucellosis.

Aprepitant Sensitizes Acute Myeloid Leukemia Cells to the Cytotoxic Effects of Cytosine Arabinoside in vitro and in vivo.

PURPOSE: Acute myeloid leukemia (AML) is a complex malignancy characterized by the clonal expansion of immature myeloid precursors. The standard treatment for newly diagnosed AML is chemotherapy consisting of cytosine arabinoside (Ara-C) and anthracyclines with disappointing clinical outcomes and severe adverse effects, such as symptomatic bradycardia, neurotoxicity. Thus, it is promising to treat AML through combination drug therapy to reduce the adverse effects of chemotherapeutics. In our recent published PNAS paper, we reported that NK-1R antagonists, both Aprepitant and SR140333, induce apoptosis of myeloid leukemia cells by inducing oxidative stress through mitochondrial calcium overload. We, therefore, tested the hypothesis of the combination Ara-C with NK-1R antagonist could enhance the efficacy of Ara-C. METHODS: MTT assay was employed to detect the cell proliferation. Flow cytometry was applied to detect the cell cycle and necrosis. PI uptake and LDH release assay were used to detect the disintegration of the plasma membrane. Xenograft model was constructed to explore the effect of combination Ara-C with Aprepitant in vivo. RESULTS: Our results showed that Aprepitant sensitizes HL60 cells to the cytotoxic effects of Ara-C more than 5-fold by enhancing G0/G1 cell cycle arrest and necrosis in vitro. Furthermore, Nec-1, a specific inhibitor of necroptosis, could recover the cell proliferative viability significantly. Attractively, once every 2-days regimen of Ara-C (5 mg/kg) and Aprepitant (10 mg/kg) via in situ injection dramatically reduced the tumor volume from 2175.0 ± 341.9 mm3 in the vehicle group to 828.4 ± 232.4 mm3 in the combination group without obvious toxicity in human myeloid leukemia xenograft mice. CONCLUSION: Taken together, reduced dose of Ara-C combination with moderate Aprepitant provides more effective therapeutical methods for AML treatment in vitro and in vivo with the elimination of the toxicity of Ara-C, which may pay new avenue for the usage of the routine chemotherapy drug Ara-C with low dose to enhance efficacy and reduce toxicity in clinical practice.

Neurokinin-1 receptor is an effective target for treating leukemia by inducing oxidative stress through mitochondrial calcium overload.

Substance P (SP) regulates multiple biological processes through its high-affinity neurokinin-1 receptor (NK-1R). While the SP/NK-1R signaling axis is involved in the pathogenesis of solid cancer, the role of this signaling pathway in hematological malignancy remains unknown. Here, we demonstrate that NK-1R expression is markedly elevated in the white blood cells from acute myeloid leukemia patients and a panel of human leukemia cell lines. Blocking NK-1R induces apoptosis in vitro and in vivo via increase of mitochondrial reactive oxygen species. This oxidative stress was triggered by rapid calcium flux from the endoplasmic reticulum into mitochondria and, consequently, impairment of mitochondrial function, a mechanism underlying the cytotoxicity of NK-1R antagonists. Besides anticancer activity, blocking NK-1R produces a potent antinociceptive effect in myeloid leukemia-induced bone pain by alleviating inflammation and inducing apoptosis. These findings thus raise the exciting possibility that the NK-1R antagonists, drugs currently used in the clinic for preventing chemotherapy-induced nausea and vomiting, may provide a therapeutic option for treating human myeloid leukemia.

Genetic association between mannose-binding lectin polymorphisms and viral hepatitis: a meta-analysis.

Some previous genetic association studies have tried to investigate potential associations between mannose-binding lectin (MBL) polymorphisms and viral hepatitis. However, the results of those studies were not consistent. Therefore, we performed the current meta-analysis to explore associations between MBL polymorphisms and viral hepatitis in a large pooled population. A systematic literature research of PubMed, Web of Science, Embase and CNKI was performed to identify eligible studies for pooled analyses. We used Review Manager version 5.3.3 to conduct statistical analyses. In total, 27 studies were included for analysis (4840 cases and 5729 controls). The pooled analyses showed that MBL promoter (-211C/G, dominant model: P = 0.0002, I2 = 40%; over-dominant model: P = 0.0001, I2 = 22%) and exon 1 (codon 52, 54 and 57, dominant model: P = 0.04, I2 = 49%; allele model: P = 0.01, I2 = 48%) polymorphisms were both significantly associated with viral hepatitis in the overall population. Further subgroup analyses revealed similarly significant findings for MBL promoter polymorphism in HBV and HCV, but no positive results were detected in subgroup analyses for MBL exon 1 polymorphism. These results suggested that MBL promoter and exon 1 polymorphisms could be used to identify individuals at higher susceptibility to HBV and HCV.

Theoretical insight into the mechanism of photoreduction of CO2 to CO by graphitic carbon nitride.

Graphitic carbon nitride (g-C3N4) is a promising photocatalyst for the reduction of CO2 into fuels. However, the reduction mechanism of CO2 using g-C3N4 is not clear in the literature. In the present study, the fixation of CO2 and the formation of carbamate on the nitrogen atom at the edge of g-C3N4 were investigated using first-principles density functional theory. The calculated results shows that two adjacent bare nitrogen atoms at the edge of g-C3N4 could be the activation sites for the proton and CO2 molecule respectively, which are crucial to the formation of carbamate. The calculated energy barrier of carbamate formation is 0.95 eV for a preferential pathway. From studies on these micro processes, we propose a mechanism with proton assistance for the g-C3N4-catalyzed photoreduction of CO2 to CO.

Effect of Organic Substrates on the Photocatalytic Reduction of Cr(VI) by Porous Hollow Ga2O3 Nanoparticles.

Porous hollow Ga2O3 nanoparticles were successfully synthesized by a hydrolysis method followed by calcination. The prepared samples were characterized by field emission scanning electron microscope, transmission electron microscope, thermogravimetry and differential scanning calorimetry, UV-vis diffuse reflectance spectra and Raman spectrum. The porous structure of Ga2O3 nanoparticles can enhance the light harvesting efficiency, and provide lots of channels for the diffusion of Cr(VI) and Cr(III). Photocatalytic reduction of Cr(VI), with different initial pH and degradation of several organic substrates by porous hollow Ga2O3 nanoparticles in single system and binary system, were investigated in detail. The reduction rate of Cr(VI) in the binary pollutant system is markedly faster than that in the single Cr(VI) system, because Cr(VI) mainly acts as photogenerated electron acceptor. In addition, the type and concentration of organic substrates have an important role in the photocatalytic reduction of Cr(VI).

Exploring the formation and electronic structure properties of the g-C3N4 nanoribbon with density functional theory.

The optical properties and condensation degree (structure) of polymeric g-C3N4 depend strongly on the process temperature. For polymeric g-C3N4, its structure and condensation degree depend on the structure of molecular strand(s). Here, the formation and electronic structure properties of the g-C3N4 nanoribbon are investigated by studying the polymerization and crystallinity of molecular strand(s) employing first-principle density functional theory. The calculations show that the width of the molecular strand has a significant effect on the electronic structure of polymerized and crystallized g-C3N4 nanoribbons, a conclusion which would be indirect evidence that the electronic structure depends on the structure of g-C3N4. The edge shape also has a distinct effect on the electronic structure of the crystallized g-C3N4 nanoribbon. Furthermore, the conductive band minimum and valence band maximum of the polymeric g-C3N4 nanoribbon show a strong localization, which is in good agreement with the quasi-monomer characters. In addition, molecular strands prefer to grow along the planar direction on graphene. These results provide new insight on the properties of the g-C3N4 nanoribbon and the relationship between the structure and properties of g-C3N4.

Effect of pH on the microstructure of ß-Ga2O3 and its enhanced photocatalytic activity for antibiotic degradation.

Semiconductor photocatalysis has become the focus of recent research on antibiotic treatment because it is a green and efficient technology. In this study, α-GaOOH with several novel microstructures has been synthesized at a low temperature and its subsequent thermal transformation. The influence of pH on the synthesis of α-GaOOH is studied, and the results indicate that pH played an important role in the microstructures of α-GaOOH and ß-Ga2O3. All Ga2O3 samples possess macro-mesoporous network structures and exhibits a remarkable photocatalytic activity for antibiotic degradation. The photoelectron chemical tests show that the separation efficiency of photogenerated charge carriers of Ga2O3-7.0 is higher than that of other Ga2O3. The enhanced photocatalytic activity of Ga2O3-7.0 is mainly ascribed to its morphology and oxygen vacancy. The active species trapping and photoluminescence measurement experiments indicate that OH and O2- are the major active species contributing to the photocatalytic process. This study will bring about the potential application in treatment of the antibiotic pollutants.

Al atom on MoO3(010) surface: adsorption and penetration using density functional theory.

Interfacial issues, such as the interfacial structure and the interdiffusion of atoms at the interface, are fundamental to the understanding of the ignition and reaction mechanisms of nanothermites. This study employs first-principle density functional theory to model Al/MoO3 by placing an Al adatom onto a unit cell of a MoO3(010) slab, and to probe the initiation of interfacial interactions of Al/MoO3 nanothermite by tracking the adsorption and subsurface-penetration of the Al adatom. The calculations show that the Al adatom can spontaneously go through the topmost atomic plane (TAP) of MoO3(010) and reach the 4-fold hollow adsorption-site located below the TAP, with this subsurface adsorption configuration being the most preferred one among all plausible adsorption configurations. Two other plausible configurations place the Al adatom at two bridge sites located above the TAP of MoO3(010) but the Al adatom can easily penetrate below this TAP to a relatively more stable adsorption configuration, with a small energy barrier of merely 0.2 eV. The evidence of subsurface penetration of Al implies that Al/MoO3 likely has an interface with intermixing of Al, Mo and O atoms. These results provide new insights on the interfacial interactions of Al/MoO3 and the ignition/combustion mechanisms of Al/MoO3 nanothermites.

[Diagnosis and treatment of ureteropelvic junction obstruction caused by renal crossing vessels:an analysis of 24 cases].

OBJECTIVE: To investigate the diagnosis, treatment and surgical outcomes of ureteropelvic junction obstruction (UPJO) caused by renal crossing vessels. METHODS: The case records of 24 patients discharged from Peking University Third Hospital between June 2001 and September 2011 with the diagnosis of UPJO caused by renal crossing vessels were reviewed .Of the 24 patients, 17 were male and 7 were female patients. The mean age was 28 years (range, 2-63 years). The mean disease duration was 22.3 months (range, 7 days to 180 months). Of which, 4 patients underwent open surgery, and the other 20 patients were treated with laparoscopic surgery. Surgical approach was decided by operative conditions: adhesion release technique, dismembered pyeloplasty or Y-V anastomosisor, with or without cut off the crossing vessels. The kind of crossing vessels was recorded, and the effect of surgery was evaluated by follow-up. RESULTS: Fifteen cases were caused by oppressed renal crossing artery, 8 cases by renal crossing vein, and 1 case by 2 renal crossing arteries and 1 renal crossing vein. Among them, 11 cases were followed up successfully. Average follow-up time was 48.2 months (range, 13-120 months). Eight cases (8/11) were relieved, and 1 case (1/11) had no obvious improvement, another 2 cases (2/11) were aggravating. Among those 6 cases underwent adhesion release technique, 3 cases were relieved, 1 case had no obvious improvement, and 2 cases were aggravating. Five cases who underwent dismembered pyeloplasty was relieved significantly. CONCLUSIONS: Renal crossing artery is one of the main causes of UPJO, the crossing artery should be retained as far as possible. Crossing vessel oppression is not the only pathological cause of UPJO, so the treatment of UPJ constriction is also very important. Dismembered pyeloplasty seems to be the most efficacies treatment procedure for UPJO caused by repressed vessels, and the remission rate of adhesion release technique seems limited.

The effect of water on the structural, electronic and photocatalytic properties of graphitic carbon nitride.

g-C3N4, as a typical metal-free catalyst for water splitting, has attracted special attention. The structural and electronic properties of water adsorption on g-C3N4 play a key role in understanding the water splitting mechanism at the atomic level. The properties of a single g-C3N4 sheet and the water adsorption on a single g-C3N4 sheet were thoroughly explored based on density functional theory (DFT) calculations. The results show that water adsorption on one side of the single g-C3N4 sheet will lead the initial flat structure to change to a buckle one, while water molecule adsorption on both sides of g-C3N4 will not disturb the flat structure. The flat g-C3N4 is an indirect semiconductor, and interestingly the band structure of g-C3N4 changes from an indirect to a direct one during the flat structure transformation from flat to buckle because of the water adsorption. Water molecules prefer to adsorb around the intrinsic vacancy of the single g-C3N4 sheet at low coverage, and further adsorbed water molecules stay around the intrinsic vacancy. Water adsorption also affects the band edge position of g-C3N4 for water splitting. These results provide a deep insight into the structure and adsorption properties of g-C3N4 in the water environment, which will greatly help to design a new type of metal-free catalyst for water-splitting.

[Analysis of the distribution of VOCs concentration field with oil static breathing loss in internal floating roof tank].

Internal floating roof tank has the advantages of external floating roof tank and fixed roof tank and has its own evaporation loss properties. The influences of volatile organic compounds (VOCs) distribution gradient, molecular diffusion, thermal diffusion and forced convection on the evaporation loss of oil were studied in the space of the homemade platform of an internal floating roof tank. The results showed that thermal diffusion with temperature change was the main cause for the static loss in the internal floating roof tank. On this basis, there were some measures for reduction of the evaporation loss and formulas to calculate the evaporation loss of the internal floating roof tank in this research.

Molecular dynamics study of the response of nanostructured Al/Ni clad particles system under thermal loading.

Molecular dynamics simulations are used to study the exothermic alloying reactions by imposing a thermal loading on a local area of nanostructured Al/Ni clad particles. The combustion parameters, such as particles size, density, and ignition temperature, are characterized. Reducing the size of Al/Ni clad particles makes the propagation velocity of reaction front increase but lowers both the adiabatic combustion temperature and pressure of the system. However, increasing either mass density or ignition temperature makes the propagation velocity of reaction front increase and raises the adiabatic temperature and pressure as well. We estimate the propagation velocity of the chemical reaction front to range from 35.70 to 44.06 m/s.