Using harmonic beam combining to generate pulse-burst in nonlinear optical laser

The ultrashort lasers working in pulse-burst mode reveal great machining performance in recent years. The number of pulses in bursts effects greatly on the removal rate and roughness. To generate a more equal amplitude of pulses in burst with linear polarization output and time gap adjustable, we propose a new method by the harmonic beam combining(HBC).The beam combining is commonly used in adding pulses into the output beam while maintaining the pulse waveform and beam quality. In the HBC, dichroic mirrors are used to combine laser pulses of fundamental wave(FW) into harmonic wave(HW), and nonlinear crystals are used to convert the FW into HW. Therefore, HBC can add arbitrarily more HW pulses to generate pulse-burst in linear polarization with simple structure. The amplitude of each pulse in bursts can be adjusted the same to increase the stability of the burst, the time gap of each pulse can be adjusted precisely by proper time delay. Because HBC adds pulses sequentially, the peak power density of the burst is the same as each pulse, pulses can be combined without concern of back-conversion which often occurs in high peak power density. In the demonstration, the extendibility of HBC was verified by combining two beams with a third beam. The combined efficiency rates were larger than 99%, and the beam quality of each beam was maintained at M^(2)≈1.4.

Transmission effects of high energy nanosecond lasers in laser-induced air plasma under different pressures

When a high energy nanosecond(ns)laser induces breakdown in the air,the plasma density generated in the rarefied atmosphere is much smaller than that at normal pressure.It is associated with a relatively lower absorption coefficient and reduces energy loss of the laser beam at low pressure.In this paper,the general transmission characterizations of a Joule level 10 ns 1064 nm focused laser beam are investigated both theoretically and experimentally under different pressures.The evolution of the electron density(n_(e)),the changes in electron temperature(T_(e))and the variation of laser intensity(I)are employed for numerical analyses in the simulation model.For experiments,four optical image transfer systems with focal length(f)of 200 mm are placed in a chamber and employed to focus the laser beam and produce plasmas at the focus.The results suggest that the transmittance increases obviously with the decreasing pressure and the plasma channels on the transmission path can be observed by the self-illumination.The simulation results agree well with the experimental data.The numerical model presents that the maximum n_e at the focus can reach 10^(19)cm^(-3),which is far below the critical density(n_(c)).As a result,the laser beam is not completely shielded by the plasmas.

High-precision high-voltage detuning system for HIAF-SRing electron target

The development of a detuning system for the precision control of electron energy is a major challenge when electron targets are used in ion-storage rings.Thus,a high-precision,high-voltage,detuning system was developed for the electron target of a high-intensity heavy-ion accelerator facility-spectrometer ring(HIAF-SRing)to produce accurate electron-ion relative energies during experiments.The system consists of auxiliary,and high-voltage detuning power supplies.The front stage of the auxiliary power supply adopts an LCC resonant converter operating in the soft-switching state and an LC filter for a sinusoidal waveform output in the post-stage.The detuning power supply is a high-voltage pulse amplifier(HVPA)connected with a high-voltage DC(HVDC)module in series.In this paper,the design and development of the detuning system are described in detail,and the test bench is presented.The test results demonstrated that the detuning system conforms to the technical specifications of the dielectronic recombination(DR)experiment.Finally,a Fe15+DR spectrum was measured using the detuning system.The experimental data demonstrated a good experimental resolution and verified the reliability and feasibility of the design.

风化壳淋积型稀土矿的土水特性

风化壳淋积型稀土矿的渗透特性直接影响原地浸矿的浸出效率。土水特征曲线是研究矿体渗透特性的重要基础,与许多因素具有关联性。为了研究不同因素对矿体土水特征曲线的影响,采用压力板仪进行土水特性试验,分析干密度、粒径和溶浸对稀土矿体土水特性的影响及其作用机理。结果表明,随着干密度的减小,孔隙率增大,矿体饱和含水量增加。采用同一基质吸力时,随着粒径的增加,矿体含水率逐渐减小,矿体持水能力降低。在相同体积含水率情况下,基质吸力与粒径大小成反比。采用同一基质吸力时,溶浸后矿体含水量比溶浸前矿体含水量降低,说明溶浸使得矿体持水能力减小。

Antioxidant activity of chito-oligosaccharides on pancreatic islet cells in streptozotocin-induced diabetes in rats

AIM:To investigate the antioxidant activity of chitooligosaccharides(COSs)on pancreatic islet cells in diabetic rats induced by streptozotocin. METHODS:The antioxidant effect of COSs on pancreatic islet cells was detected under optical microscopy and with colorimetric assay and gel electrophoresis.The activities of glutathione peroxidase and superoxide dismutase,total antioxidant capacity,and content of malondialdehyde in serum and tissue slices of pancreas were examined after 60 d to determine the effect of COSs in streptozotocin-induced diabetes in rats. RESULTS:COSs can prohibit the apoptosis of pancreatic islet cells.All concentrations of COSs can improve the capability of total antioxidant capacity and activity of superoxide dismutase and decrease the content of malondialdehyde drastically.Morphological investigation in the pancreas showed that COSs have resulted in the reduction of islets,loss of pancreatic cells,and nuclear pyknosis of pancreatic cells. CONCLUSION:COSs possess various biological activities and can be used in the treatment of diabetes mellitus.

Optimum design of hierarchical stiffened shells for low imperfection sensitivity

A concept of hierarchical stiffened shell is proposed in this study,aiming at reducing the imperfection sensitivity without adding additional weight.Hierarchical stiffened shell is composed of major stiffeners and minor stiffeners,and the minor stiffeners are generally distributed between adjacent major stiffeners.For various types of geometric imperfections,e.g.,eigenmode-shape imperfections,hierarchical stiffened shell shows significantly low imperfection sensitivity compared to traditional stiffened shell.Furthermore,a surrogate-based optimization framework is proposed to search for the hierarchical optimum design.Then,two optimum designs based on two different optimization objectives(including the critical buckling load and the weighted sum of collapse loads of geometrically imperfect shells with small-and large-amplitude imperfections)are compared and discussed in detail.The illustrative example demonstrates the inherent superiority of hierarchical stiffened shells in resisting imperfections and the effectiveness of the proposed framework.Moreover,the decrease of imperfection sensitivity can finally be converted into a decrease of structural weight,which is particularly important in the development of large-diameter launch vehicles.

INFLUENCE OF QUERCETIN AND X-RAY ON COLLAGEN SYNTHESIS OF CULTURED HUMAN KELOID-DERIVED FIBROBLASTS

Objective To investigate the effects of quercetin and X-ray on collagen synthesis of cultured human keloid-derived fibroblast and the mechanism.Methods Collagen synthesis of cultured human keloid and normal fibroblasts were detected by hydroxyproline colorimetric analysis. Immunocytochemical staining was used to investigate collagen I and III expression. mRNA expression of collagen I and III, and transforming growth factor (TGF)-β1 were assayed by reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR. Results Quercetin inhibited the collagen synthesis of both keloid and normal fibroblasts in a dose-dependent manner. Immunocytochemical staining indicated that collagen I and III were down-regulated by quercetin and X-ray (P<0.05), particularly collagen I (P<0.05). mRNA expression of both collagen I and III in quercetin groups significantly decreased compared with that in control group (P<0.05), especially in the group treated with both quercetin and X-ray (P<0.01). mRNA level of TGF-β1 gene was down-regulated by quercertin (P<0.05). Conclusions Quercetin will probably be one of the new medicines which could effectively treat keloid. Quercetin combined with X-ray could reduce the dose of radiation.

Influence of coarse tailings on flocculation settlement

The composition of tailings particles in mines plays a key role in the flocculation settlement of slurries.To study the influence of coarse particle tailings(CPTs)on the flocculation settlement of tailings slurries(TSs),static flocculent settling tests,scanning electron microscopy observations,and laser particle size analyses were conducted using the tailings obtained from a copper mine.The results demonstrate that(i)in the accelerated and free settling process,CPTs did not directly settle at the bottom of graduated cylinders;instead,they were netted by the flocculent structures(FSs)and settled together more quickly.The CPTs accelerate the rapid settlement of TSs;the acceleration effect is more obvious when the CPTs content is greater than 50 wt%.(ii)The most appropriate flocculant unit consumption(FUC)is 20 g·t-1,and no substantial increase is observed in the flocculant settling velocity with an increase in the flocculant because the effective FSs did not substantially change and thus did not lead to a notable increase in the settling velocity of the solid–liquid interface(SLI).(iii)In the effective settling space of the thickening facility,free water quickly flowed from the pores of FSs,which is reflected in the period from 0 to 1 min.

Effectiveness and Safety of Computer-controlled Periodontal Ligament Injection System in Endodontic Access to the Mandibular Posterior Teeth

Objective To evaluate the effectiveness and safety of a computer-controlled periodontal ligament(PDL) injection system to the local soft tissues as the primary technique in endodontic access to mandibular posterior teeth in patients with irreversible pulpitis.Methods A total of 162 Chinese patients who had been diagnosed with irreversible pulpitis in their mandibular posterior teeth without acute infection or inflammation in the periodontal tissues were enrolled in this clinical study.The patients were divided into 3 groups according to the position of the involved tooth:the premolar group(PM,n=38),first molar group(FM,n=66),and second molar group(SM,n=58).All the patients received computer-controlled PDL injection with 4% articaine and 1∶100 000 epinephrine.Immediately after the injection,endodontic access was performed,and the degree of pain during the treatment was evaluated by the patients using Visual Analogue Scale for pain.The success rates were compared among the 3 groups.The responses of local soft tissues were evaluated 3-8 days and 3 weeks after the procedure.Results The overall success rate was 76.5%.There was a significant difference in success rates among the PM,FM,and SM groups(92.1%,53.0%,93.1%,respectively;χ2=34.3,P<0.01).Both the PM and SM groups showed higher success rates than that of the FM group(v=1,χ2=16.73,P<0.01;v=1,χ2=24.5,P<0.01).No irreversible adverse effects on the periodontal soft tissues at the injection sites were observed in the follow-up visits in any of the groups.Conclusion The computer-controlled PDL injection system demonstrates both satisfactory anesthetic effects and safety in local soft tissues as primary anesthetic technique in endodontic access to the mandibular posterior teeth in patients with irreversible pulpitis.

Fabrication,microstructure and mechanical properties of Mg matrix composites reinforced by high volume fraction of sphere TC4 particles

A novel liquid settling method was investigated and applied to fabricate TC4 spherical particle reinforced AZ91 alloy matrix composites.This method was called liquid state settling technique in which TC4 particles would settle down under the force of gravity.High volume fraction(50%)particle reinforced AZ91 composites could be easily obtained via this novel method.This is difficult to achieve for other traditional liquid fabrication methods.In addition,there was a good dispersion of TC4 particles in the AZ91 matrix and no clusters were found,which indicate that this method was feasible.Interfacial reaction occurred and the reaction product was confirmed to be Al2Ti.Three kinds of pre-dispersion technologies were used before the settling process and different interfacial microstructures were found.Theoretical calculation and experimental results both indicated that the interfacial product which was embedded in the matrix strengthened the composites and improved the tensile strength.

Non-probabilistic information fusion technique for structural damage identification based on measured dynamic data with uncertainty

Based on measured natural frequencies and acceleration responses,a non-probabilistic information fusion technique is proposed for the structural damage detection by adopting the set-membership identification(SMI) and twostep model updating procedure.Due to the insufficiency and uncertainty of information obtained from measurements,the uncertain problem of damage identification is addressed with interval variables in this paper.Based on the first-order Taylor series expansion,the interval bounds of the elemental stiffness parameters in undamaged and damaged models are estimated,respectively.The possibility of damage existence(PoDE) in elements is proposed as the quantitative measure of structural damage probability,which is more reasonable in the condition of insufficient measurement data.In comparison with the identification method based on a single kind of information,the SMI method will improve the accuracy in damage identification,which reflects the information fusion concept based on the non-probabilistic set.A numerical example is performed to demonstrate the feasibility and effectiveness of the proposed technique.

Expander implantation for correction of high-riding nipple with enlarged nipple-areola complex using revision mastopexy: A case report

BACKGROUND High-riding nipple is one of the common complications after mastopexty and breast reconstruction.However,to date,a limited number of techniques have concentrated on how to lower the high-riding nipple with enlarged areola.CASE SUMMARY This is a case report describing a combination of surgical techniques to decrease high-riding nipple.A 26-year-old woman,who previously underwent several breast operations,sought correction for high-riding nipple with enlarged areola.Expanders were used and multi-stage techniques were performed.After one year of follow-up,lowered nipple,reduced areola size,ensured nipple blood supply,and improved breast ptosis were achieved,and the patient was satisfied with the breast contour.CONCLUSION The proposed technique offers a feasible treatment option for postoperative nipple over-elevation combined with areola dilation.

A 658-W VCSEL-pumped rod laser module with52.6% optical efficiency

A high-efficiency and high-power vertical-cavity surface-emitting laser(VCSEL) side-pumped rod Nd:YAG laser with temperature adaptability are demonstrated. The VCSEL side-pumped laser module is designed and optimized. Five VCSEL arrays are symmetrically located around the laser rod and a large size diffused reflection chamber is designed to ensure a uniform pump distribution. Furthermore, the absorbed pump power distribution of the rod is simulated to verify the uniformity of the pump absorption. Finally, a proof-of-principle experiment is performed in short linear cavity laser with single laser module. A continuous-wave output power of 658 W at 1064 nm is obtained, the corresponding optical-to-optical efficiency is 52.6%, and the power variations are ±0.7% over 400 s and ±3.1% over the temperature range from 16 ℃ to 26 ℃. To the best of our knowledge, this is the highest output power and the highest optical-to-optical efficiency ever reported for VCSEL pumped solid-state lasers. By inserting a telescopic module into the cavity and optimizing the TEM_(00) mode volume, the average beam quality is measured to be M~2= 1.34 under an output power of 102 W. The experimental results reveal that such a high power rod laser module with temperature stability is appropriate for field applications.

Fabrication of segregated poly(arylene sulfide sulfone)/graphene nanoplate composites reinforced by polymer fibers for electromagnetic interference shielding

Poly(arylene sulfide sulfone)/graphene nanoplate(PASS/GNP) composites with segregated structure based on continuous polymer fiber skeletons were fabricated by coating a thin conductive layer on the PASS fibers and then performing compression molding. The formation of a unique segregated conductive network endowed the PASS/GNP composites with high electrical conductivity and excellent electromagnetic interference(EMI) shielding effectiveness(SE), reaching 17.8 S/m and 30.1 d B, respectively, when the content of the GNPs in the conductive layer was 20 wt%. The PASS/GNP composites also exhibited outstanding mechanical properties, which was attributed to the continuous PASS fiber skeletons that could withstand large loads and the strong interfacial interaction between the conductive layers and the PASS fibers that could provide good stress transfer. This approach is suitable for most soluble polymers.

Chinese medical students’interest in COVID-19 pandemic

BACKGROUND The outbreak of coronavirus disease 2019(COVID-19)happened in early December and it has affected China in more ways than one.The societal response to the pandemic restricted medical students to their homes.Although students cannot learn about COVID-19 through clinical practice,they can still pay attention to news of COVID-19 through various channels.Although,as suggested by previous studies,some medical students have already volunteered to serve during the COVID-19 pandemic,the overall willingness of Chinese medical students to volunteer for such has not been systematically examined.AIM To study Chinese medical students’interest in the relevant knowledge on COVID-19 and what roles they want to play in the pandemic.METHODS Medical students at Peking Union Medical College were surveyed via a webbased questionnaire to obtain data on the extent of interest in the relevant knowledge on COVID-19,attitude towards volunteerism in the pandemic,and career preference.Logistic regression modeling was used to investigate possible factors that could encourage volunteerism among this group in a pandemic.RESULTS A total of 552 medical students responded.Most medical students showed a huge interest in COVID-19.The extent of students’interest in COVID-19 varied among different student-classes(P<0.05).Senior students had higher scores than the other two classes.The number of people who were‘glad to volunteer’in COVID-19 represented 85.6%of the respondents.What these students expressed willingness to undertake involved direct,indirect,and administrative job activities.Logistic regression analysis identified two factors that negatively influenced volunteering in the pandemic:Student-class and hazards of the voluntary job.Factors that positively influenced volunteering were time to watch COVID-19 news,predictable impact on China,and moral responsibility.CONCLUSION More innovative methods can be explored to increase Chinese medical students’interest in reading about the relevant knowledge on COVID-19 and doing voluntary jobs during the pandemic.

The Research about the Trans-provincial Centralized Bidding Trading Market of East China Power Grid --I:Empirical Analysis

The clearing price and bidding price in electricity market are two key indicators to measure whether it is reasonable or not. Based on the grey incidence analysis, this paper studies the correlation coefficient between the clearing price and bidding price with the generation cost, the supervision and rules of the market, the supply and demand situation, the behavior of market members over the same period, which is based on the actual data of the trans-provincial centralized trading market of East China Power Grid. The results show that the factors affecting the clearing price and bidding price from largest to smallest are generation cost, supervision and rules of the market, the supply and demand situation, the behavior of market members. The conclusion is that the trans-provincial trading platform of East China Power Grid is a reasonable regional market which can discover the market cost, and regulate the market supply and demand balance, and promote healthy competition.

Perinipple Broken Line Incision: a Novel Approach for Breast Augmentation

Objective To investigate reliability of the infra-nipple broken line incision for breast augmentation. Methods From January 2012 to January 2013, 15 patients underwent primary bilateral retromuscular breast augmentation with round textured silicone-gel implants and a novel infra-nipple broken line incision. Preoperatively, a semicircular incision was marked along the inferior base of the nipple. It was then extended bilaterally using two transverse right-angled geometric broken lines within the pigmented areolar skin. Follow-up was performed to evaluate the sensation of nipple-areolar complex, the scar, and the shape and texture of the breasts. Results The average follow-up was 6.7 months. Most of the patients complained of paresthesia of the nipple or breast skin, but transient decreased sensation improved within 3 months. No patients showed permanent sensory changes of the nipple areolar complex at a minimum follow-up of 4 months. The scars were imperceptible in all patients. Conclusion We believe that for selected patients, the infra-nipple broken line incision is a practical and reliable method to achieve aesthetic result.

A High Conversion Efficiency Q-Switched Intracavity Nd:YVO_4/KTA Optical Parametric Oscillator under Direct Diode Pumping at 880nm

We report a high conversion efficiency Q-switched Nd:YVO_4/KTiOAsO_4(KTA) intracavity optical parametric oscillator(IOPO) operating near 3.5 um based on direct 880 nm laser diode(LD) pumping. A maximum average idler output power of 2.6 W with a pulse width of about 7.9 ns is achieved under an absorbed LD power of 45.4 W at a pulse repetition rate(PRR) of 10 kHz. The maximum optical-optical conversion efficiency from LD power to OPO mid-infrared(MIR) output of 6.74% is achieved. To our knowledge, this is the highest conversion efficiency for a KTA-IOPO by exploiting a Q-switched laser as the parent fundamental pump source. The beam quality factors M^2 of the MIR beam at the full output power with a PRR of 10 kHz are within 2.12 in both the horizontal and vertical directions, indicating a near Gaussian mode.

High-energy picosecond single-pass multi-stage optical parametric generator and amplifier

We demonstrate a new management of multi-stage optical parametric generator(OPG)and amplifier(OPA)to obtain high-energy picosecond sources with high beam quality.The setup of multi-stage OPG-OPA requires mode-matching between the pump beam and the stable mode of the OPG-OPA.In a proof-of-principle experiment,the single-pass multi-stage OPG-OPA consists of three walk-off compensated KTP crystal pairs and two lenses,pumped by an 86 ps,1064 nm 10 kHz picosecond laser.The signal light at~1.77μm has an average output power of 502 mW with record energy up to 50.2μJ.The beam quality factor of the signal light can be improved toM^(2)_(x) ×M^(2)_(y)after filtering out about 40%signal power.To the best of our knowledge,it is the first picosecond single-pass multi-stage OPG-OPA pumped at kHz regime.

Combination of neutrophil gelatinase-associated lipocalin and matrix metalloproteinase-9 are biomarkers for the detection of colon tubular adenocarcinoma

BACKGROUND Tubular adenocarcinoma of the colon,which originates from the epithelium of the glands,is a major health concern worldwide.However,it is difficult to detect at an early stage.The lack of biomarkers is a main barrier to the diagnosis and treatment of tubular adenocarcinoma.Neutrophil gelatinase-associated lipocalin(NGAL)is a secreted protein that induces the expression of matrix metalloproteinase-9(MMP-9)and is involved in various tumors.NGAL and MMP-9 have been reported to be associated with tumorigenesis and development.They may have potential as biomarkers for diagnosis of tubular adenocarcinoma of the colon.AIM To determine whether NGAL and MMP-9 can be used as potential biomarkers to indicate the progression of tubular adenocarcinoma of the colon.METHODS Samples were collected from surgically excised tissue from various patients.The content of pro-gastrin-releasing peptide(pro-GRP)in the serum was measured by an electrochemiluminescence immunoassay.The expression patterns of NGAL and MMP-9 and the relationship between NGAL and MMP-9 were examined by quantitative real-time PCR,Western blotting and immunohistochemical analysis.RESULTS In this study,we found that NGAL and MMP-9 can be used as biomarkers for the detection of tubular adenocarcinoma of the colon and that their combination improved diagnostic accuracy.By analyzing the expression of NGAL in tubular adenocarcinoma at different levels,we found that NGAL expression was significantly upregulated in primary tubular adenocarcinoma tissues compared with normal tissues.The upregulation of NGAL expression was strongly correlated with both the degree of differentiation and the disease stage(I–III),indicating that NGAL could serve as a diagnostic biomarker for tubular adenocarcinoma.When using NGAL as a biomarker for diagnosis,the accuracy was similar to that achieved with the widely used biomarker pro-GRP,suggesting that NGAL is reliable.Moreover,the expression of MMP-9 was also strongly correlated with the differentiation stage,demonstrating that MMP-9 could be used as a biomarker to indicate the progression of tubular adenocarcinoma of the colon.More importantly,the combination of NGAL and MMP-9 produced a more accurate diagnosis of tubular adenocarcinoma,and these results were further confirmed by immunohistochemical analysis of tissue sections.CONCLUSION Our study demonstrated that both NGAL and MMP-9 can be used as biomarkers for the diagnosis of colon tubular adenocarcinoma and that the results could be further improved by combining them.