工艺参数对聚乳酸线材熔融沉积尺寸的影响

熔融沉积(FDM)成型中线材直径的变化对打印精度有重要影响。文中利用实验和数值模拟方法研究了单根聚乳酸线材FDM过程中从喷嘴挤出到沉积固化各阶段的直径变化。根据FDM工艺特点及材料性能,量化分析了工艺参数(喷嘴温度、挤出速度、打印速度、层高)对线材喷嘴附近、挤出胀大阶段、拉伸阶段、沉积阶段直径的影响,并推导了打印过程中线材沉积固化时直径的估算公式。研究表明,提高喷嘴温度、增大挤出速度、减少层高可有效改善打印过程中线材的尺寸稳定性,提高打印件的精度。最后,利用沉积固化时的直径公式,完成了线材直径补偿“精度实验”,补偿后打印制品尺寸精度提高了74.1%。

Four-function model analysis of nonsuicidal self-injury-related posts on Sina Weibo

To the editor:Non-suicidal self-injury(NSSI)is defined as direct,repetitive self-injury to bodily tissues without suicidal intent. The estimated prevalence of NsSI among adolescents is 17.2%worldwide with a comparable rate observed in China. As a behavioural addiction, NSSI poses a significant suicide risk,and is emerging as a major mental health problem among adolescents.To unravel this puzzle,the four-function model(FFM)distinguishes between interpersonal and intrapersonal functions,as well as positive and negative reinforcement functions,proving relatively comprehensive among various theoretical models.

三组分反应合成5-(4-甲基苯基)-3-三氟甲基-1H-吡唑的综合实验设计

通过科研反哺教学,本实验将“多组分反应”和“含氟有机化合物”融入到本科实验教学中,通过三组分反应合成了5-(4-甲基苯基)-3-三氟甲基-1H-吡唑。该实验条件温和,操作简单,分离产率高,重现性好,安全性高。该综合实验能帮助学生理解步骤经济性合成的概念,建立绿色化学的理念,是适合引入有机实验教学课程的新课题。

Optimization of Process Parameters for in High-Energy Ball Milling of CNTs/Al2024 Composites Through Response Surface Methodology

The mathematical models are developed to evaluate the ultimate tensile strength( UTS) and hardness of CNTs / Al2024 composites fabricated by high-energy ball milling. The effects of the preparation variables which are milling time,rotational speed,mass fraction of CNTs and ball to powder ratio on UST and hardness of CNTs / Al2024 composites are investigated. Based on the central composite design( CCD),a quadratic model is developed to correlate the fabrication variables to the UST and hardness. From the analysis of variance( ANOVA),the most influential factor on each experimental design response is identified. The optimum conditions for preparing CNTs / Al2024 composites are found as follows: 1. 53 h milling time,900 r / min rotational speed,mass fraction of CNTs 2. 87% and Ball to powder ratio 25 ∶ 1. The predicted maximum UST and hardness are 273.30 MPa and 261.36 HV,respectively. And the experimental values are 283.25 MPa and256.8 HV,respectively. It is indicated that the predicted UST and hardness after process optimization are found to agree satisfactory with the experimental values.

Seed-Assisted Synthesis and Catalytic Performance of Nano-sized ZSM-5 Aggregates in a One-Step Crystallization Process

Hierarchical nano-sized ZSM-5 aggregates were successfully synthesized via a seed-assisted method in the presence of cetyltrimethylammonium bromide(CTAB)through a facile one-step crystallization process.Commercial ZSM-5 zeolites with a SiO2/Al2O3 ratio comparable to that of ZSM-5 products were treated with alkali and used as the seed particles.The influences of crystallization conditions were investigated,and the possible synthesis mechanism was proposed.ZSM-5 zeolites with diff erent amounts of CTAB added were characterized using many techniques and evaluated in toluene alkylation with methanol.The results showed that a trace amount of CTAB signifi cantly promoted the crystallization of ZSM-5 zeolite,with the morphology changing from hexagonal-shape crystals to uniform spherical aggregates.CTAB may act as the structure-directing agent and assemble the primary crystallites to generate hierarchical ZSM-5 aggregates.The ZSM-5 zeolite with the smallest primary particles of 50-80 nm exhibited large specific surface area,abundant mesopores,and the greatest microporosity.The hierarchical nano-sized ZSM-5 aggregate showed higher toluene conversion and a longer lifetime without compromising the selectivity to xylene and p-xylene in toluene alkylation with methanol.

Comparison of Mortality Predictive Models of Sepsis Patients Based on Machine Learning

Objective To compare the performance of five machine learning models and SAPSⅡ score in predicting the 30-day mortality amongst patients with sepsis.Methods The sepsis patient-related data were extracted from the MIMIC-Ⅳ database.Clinical features were generated and selected by mutual information and grid search.Logistic regression,Random forest,LightGBM,XGBoost,and other machine learning models were constructed to predict the mortality probability.Five measurements including accuracy,precision,recall,F1 score,and area under curve(AUC) were acquired for model evaluation.An external validation was implemented to avoid conclusion bias.Results LightGBM outperformed other methods,achieving the highest AUC(0.900),accuracy(0.808),and precision(0.559).All machine learning models performed better than SAPSⅡ score(AUC=0.748).LightGBM achieved 0.883 in AUC in the external data validation.Conclusions The machine learning models are more effective in predicting the 30-day mortality of patients with sepsis than the traditional SAPS Ⅱ score.

A Preliminary Study on Cold Tolerance in Cinnamomum japonicum Sieb. at Different Ages

[ Objective] This study aimed to further expand the production and application of Cirmamomumjaponicum Sieb. and investigate the mechanism of cold resistance in evergreen broad-leaved tree species. [ Method] Using adult Cinnamonum campora as control, during the entire wintering period from October 2011 to March 2012, the wintering adaptability of C. japonicum leaves at different ages was observed; the electrolyte leakage was measured under indoor low-temperature treatment to calculate the semi-lethal temperature （LT50） by fitting Logistic equation, thus conducting dynamic analysis and comprehensive evaluation of the cold re- sistance in C. japonicum. [ Result] The results showed that the chilling injuries in leaves of different materials were aggravated with the decreasing temperature. According to the results of five times of dynamic observation on wintering adaptability, the cold resistance in different materials presented a decreasing order of adult C. japonicum medium-aged C. japonicum 〉 young C. japon/cum 〉 adult C. campora. The relationship between indoor low temperature and leaf injury rate showed an S-shaped curve. The significance test suggested relatively high fitting degree with Logistic equation. The semi-lethal temperature presented a V-shaped curve with the changing temperature and roached the minimum during late December to early February in the following year. The dynamic changes and minimum value of semi-lethal temperature indicated a consistent order of cold resistance in different materials to the results of wintering adaptability observation. Therefore, results of two analysis methods could be combined for cold resistance evaluation. [ Conclusion] This study laid the foundation for the introduction and populariza- tion of C. japonicum in northern gardens along the Yangtze River.

The Research of Urban Rail Transit Sectional Passenger Flow Prediction Method

This paper studies the short-term prediction methods of sectional passenger flow, and selects BP neural network combined with the characteristics of sectional passenger flow itself. With a case study, we design three different schemes. We use Matlab to realize the prediction of the sectional passenger flow of the Beijing subway Line 2 and make comparative analysis. The empirical research shows that combining data characteristics of sectional passenger flow with the BP neural network have good prediction accuracy.

A Piezoelectrically Driven Microrobot Using a Novel Monolithic Spatial Parallel Mechanism as Its Hip Joint

Inspired by the fast,agile movements of insects,we present a 1.9 g,4.5 cm in length,piezoelectrically driven,quadrupedal microrobot.This microrobot uses a novel spatial parallel mechanism as its hip joint,which consists of two spatially orthogonal slider-crank linkages.This mechanism maps two inputs of two independent actuators to the decoupled swing and lift outputs of a leg,and each leg can produce the closed trajectories in the sagittal plane necessary for robot motion.Moreover,the kinematics of the transmission are analyzed,and the parameters of the flexure hinges are designed based on geometrical constraints and yield conditions.The hip joints,legs and exoskeletons are integrated into a five-layer standard laminate for monolithic fabrication which is composed of two layers of carbon fiber,two layers of acrylic adhesive and a polyimide film.The measured output force(15.97 mN)of each leg is enough to carry half of the robot’s weight,which is necessary for the robot to move successfully.It has been proven that the robot can successfully perform forward and turning motions.Compared to the microrobot fabricated with discrete components,the monolithically fabricated microrobot is more capable of maintaining the original direction of locomotion when driven by a forward signal and has a greater speed,whose maximum speed is 25.05 cm/s.

A customized zeolitic imidazolate framework enabling bionic preconcentration of ultralow CO_(2)

Advancing our understanding of global climate,particularly in polar regions,requires accurate detection of carbon dioxide(CO_(2))in ice cores and deep sea environments.However,detecting trace levels of CO_(2)in these areas presents significant challenges.We introduce a novel preconcentration approach using functionalized zeolitic imidazolate framework,ZIF-8(CN),for the detection of ultra-low CO_(2).ZIF-8(CN)has small pores(4.4■and cyano groups(–CN),enabling highly selective adsorption of CO_(2)(36.2 cm^(3)g^(−1))over N_(2)(1.6 cm^(3)g^(−1))at 298 K.The mechanism involves unique–CN···CO_(2)···–CN interactions within the pore structure.When cast into a film on an aluminum substrate,ZIF-8(CN)demonstrates exceptional CO_(2)preconcentration capability(1 ppm in N_(2))with an extraordinary preconcentration factor of 748,outperforming traditional ZIF and zeolite materials.Additionally,a ZIF-8(CN)preconcentrator is designed and fabricated with bionic gas flow of fractal structure which optimizes the gas-film contact,and thus its performance is further improved by 115%.

Estimation of generalized soil structure index based on differential spectra of different orders by multivariate assessment

Better soil structure promotes extension of plant roots thereby improving plant growth and yield.Differences in soil structure can be determined by changes in the three phases of soil,which in turn affect soil function and fertility levels.To compare the quality of soil structure under different conditions,we used Generalized Soil Structure Index(GSSI)as an indicator to determine the relationship between the“input”of soil three phases and the“output”of soil structure.To achieve optimum monitoring of comprehensive indicators,we used Successive Projections Algorithm(SPA)for differential processing based on 0.0–2.0 fractional orders and 3.0–10.0 integer orders and select important wavelengths to process soil spectral data.In addition,we also applied multivariate regression learning models including Gaussian Process Regression(GPR)and Artificial Neural Network(ANN),exploring potential capabilities of hyperspectral in predicting GSSI.The results showed that spectral reflection,mainly contributed by long-wave near-infrared radiation had an inverse relationship with GSSI values.The wavelengths between 404-418 nm and 2193–2400 nm were important GSSI wavelengths in fractional differential spectroscopy data,while those ranging from 543 to 999 nm were important GSSI wavelengths in integer differential spectroscopy data.Also,non-linear models were more accurate than linear models.In addition,wide neural networks were best suited for establishing fractional-order differentiation and second-order differentiation models,while fine Gaussian support vector machines were best suited for establishing first-order differentiation models.In terms of preprocessing,a differential order of 0.9 was found as the best choice.From the results,we propose that when constructing optimal prediction models,it is necessary to consider indicators,differential orders,and model adaptability.Above all,this study provided a new method for an in-depth analyses of generalized soil structure.This also fills the gap limiting the detection of soil three phases structural characteristics and their dynamic changes and provides a technical references for quantitative and rapid evaluation of soil structure,function,and quality.

Pharmacological inhibition of BAP1 recruits HERC2 to competitively dissociate BRCA1-BARD1, suppresses DNA repair and sensitizes CRC to radiotherapy

Radiotherapy is widely used in the management of advanced colorectal cancer(CRC).However,the clinical efficacy is limited by the safe irradiated dose.Sensitizing tumor cells to radiotherapy via interrupting DNA repair is a promising approach to conquering the limitation.The BRCA1-BARD1 complex has been demonstrated to play a critical role in homologous recombination(HR)DSB repair,and its functions may be affected by HERC2 or BAP1.Accumulated evidence illustrates that the ubiquitination-deubiquitination balance is involved in these processes;however,the precise mechanism for the cross-talk among these proteins in HR repair following radiation hasn’t been defined.Through activity-based profiling,we identified PT33 as an active entity for HR repair suppression.Subsequently,we revealed that BAP1 serves as a novel molecular target of PT33 via a CRISPR-based deubiquitinase screen.Mechanistically,pharmacological covalent inhibition of BAP1 with PT33 recruits HERC2 to compete with BARD1 for BRCA1 interaction,interrupting HR repair.Consequently,PT33 treatment can substantially enhance the sensitivity of CRC cells to radiotherapy in vitro and in vivo.Overall,these findings provide a mechanistic basis for PT33-induced HR suppression and may guide an effective strategy to improve therapeutic gain.

ftr82 is necessary for hair cell morphogenesis and auditory function during zebrafish development

Damages of sensory hair cells(HCs)are mainly responsible for sensorineural hearing loss,while the pathological mechanism remains not fully understood due to the many potential deafness genes unidentified.ftr82,a member of the largely TRIMs family in fish,has been found specifically expressed in the otic vesicle while its function is still unclear.Here,we investigate the roles of ftr82 in HC development and hearing function utilizing the zebrafish model.The results of in situ hybridization illustrate that ftr82 is always restricted to localize in otic vesicles at different stages.The defects of HCs are observed both in ftr82 morphants and mutants,including significantly decreased crista HCs,shortened cilia as well as remarkably reduced functional HCs in neuromasts,which could be successfully rescued by co-injection of exogenous ftr82 mRNA.The behavior assay of startle response indicates that larvae lacking of ftr82 exhibits lower sensitivity to external sound stimuli.Further research reveals that the loss of HCs is mainly caused by cell apoptosis mediated by caspase-3 activation.Our study demonstrates that ftr82 is a crucial hearing-related gene that regulates the HC morphogenesis and auditory function performing,which provides new insight into the rapid identification of the deafness gene.

IOLMaster700与IOLMaster500测量白内障术前眼轴长度的一致性及检出率比较

目的:比较新型扫频源生物测量仪IOLMaster700与传统部分相干光干涉生物测量仪IOLMaster500测量白内障患者眼轴长度(AL)的相关性、一致性及检出率。方法:系列病例研究。选取2017年8-9月于北京同仁医院眼科就诊的年龄相关性白内障患者840例(840眼)纳入研究,分别应用IOLMaster700及IOLMaster500测量AL,2种仪器检出率差异采用χ2检验进行比较,AL的数值差异采用配对t检验进行比较,相关性采用Pearson相关分析,一致性采用Bland-Altman分析。结果:IOLMaster700AL检出率为93.4%,IOLMaster500AL检出率为86.0%,二者差异具有统计学意义(χ2=63.00,P<0.001)。IOLMaster700及IOLMaster500测得的AL结果分别为(23.38±1.02)mm和(23.35±1.01)mm,差值为(0.03±0.04)mm,差异有统计学意义(t=-19.06,P<0.001),2种仪器测得的AL具有高度的相关性(r=1.00,P<0.001),Bland-Altamn分析95%一致性界限范围为0.13(-0.04~0.09)mm,上下限绝对值为0.09mm,一致性较好。结论:新型IOLMaster700与传统IOLMaster500测得的AL相比,具有高度相关性及良好的一致性,其检出率高于IOLMaster500,在白内障患者AL测量中具有一定优势。

基于扫频源相干光断层成像原理与部分相干光干涉原理的生物测量仪在眼轴测量中的比较

目的:比较基于扫频源相干光断层成像原理的OA2000和基于部分相干光干涉原理的AL-Scan在白内障患者眼轴长度测量中的检出率、差异性及一致性。方法:系列病例研究。纳入2017年11月29日至12月15日在首都医科大学附属北京同仁医院眼科门诊就诊,并拟行白内障手术的白内障患者210例(378眼)为研究对象,使用2种生物测量仪OA2000和AL-Scan检测眼轴长度。分别计算2种仪器的眼轴检出率。采用配对t检验比较2种仪器眼轴测量结果间的差异性。采用Pearson相关分析评价2种仪器测量间的相关性。采用组内相关系数(ICC)及Bland-Altman法评价仪器的一致性。并将研究眼分为眼轴<22mm组、眼轴22~26mm组、眼轴>26mm组,使用Bland-Altman法分别评价每组一致性。结果:OA2000和AL-Scan的眼轴检出率分别为98.4%和90.2%,差异有统计学意义(χ2=56.19,P<0.001)。OA2000和AL-Scan检测眼轴长度分别为(24.532±2.678)mm和(24.526±2.679)mm,差异无统计学意义(t=1.847,P=0.066)。2种仪器测量的眼轴长度结果具有密切相关性(r=1.000,P<0.001),ICC为1.000,Bland-Altamn分析95%一致性界限范围为0.23mm(-0.12~0.11mm)。95%一致性界限范围在眼轴<22mm组、眼轴22~26mm组、眼轴>26mm组分别为0.20mm(-0.10~0.10mm)、0.20mm(-0.09~0.11mm)、0.33mm(-0.16~0.17mm),3组的线外点分别为7.7%、4.5%、8.4%。结论:在白内障患者的眼轴测量中,OA2000比AL-Scan具有更高的眼轴检出率。2种仪器眼轴检测结果的相关性及一致性良好,尤其眼轴范围在22~26mm的患者中一致性表现最佳。2者数据可以相互替代使用。

新型扫频生物测量仪OA-2000与IOLMaster 700测量高度近视白内障患者的一致性

目的:比较OA-2000与IOLMaster 700在高度近视白内障患者生物测量中的一致性。方法:系列病例研究。选择2018年1─2月于北京同仁眼科中心拟行白内障手术的高度近视患者119例(119眼)。分别应用OA-2000和IOLMaster 700进行生物测量,获得角膜厚度(CCT)、前房深度(ACD)、晶状体厚度(LT)、眼轴长度(AL)、角膜曲率(Kf和Ks)、散光及轴向、平均角膜曲率(Km)、角膜横径(WTW)等数据,并通过矢量计算公式计算散光矢量J_(0)和J_(45),通过Barrett UniversalⅡ公式计算人工晶状体(IOL)度数。2种仪器测量参数及IOL度数差异比较采用配对t检验,一致性评估采用组内相关系数(ICC)及Bland-Altman法。结果:2种仪器测量Kf、Ks、Km、J_(0)、J_(45)、AL及IOL度数计算结果的差异均无统计学意义,测量CCT、ACD、LT及WTW差异均有统计学意义(t=-29.95、5.00、12.25、-5.56,均P<0.001)。2种仪器各测量参数及IOL度数计算结果的ICC为0.88~1.00。Bland-Altman分析显示2种仪器测量Kf、Ks、Km、J_(0)、J_(45)、CCT、ACD、LT、AL、WTW及IOL度数95%一致性界限(LoA)最大绝对值分别为:0.37 D、0.41 D、0.32 D、0.27 D、0.25 D、32.6μm、0.08 mm、0.18 mm、0.13 mm、0.73 mm及0.53 D。结论:在高度近视白内障患者中,OA-2000和IOLMaster 700测量Kf、Ks、Km、J_(0)、J_(45)、ACD、LT、AL的一致性好。2种仪器测量参数通过Barrett UniversalⅡ公式计算的IOL度数同样具有较好的一致性,可以相互替换使用。

Generating large topological charge Laguerre–Gaussian beam based on 4K phase-only spatial light modulator

The resolution of the spatial light modulator(SLM)screen and the encoding algorithm of the computer-generated hologram are the primary limiting factors in the generation of large topological charge vortex beams.This paper attempts to solve these problems by improving both the hardware and the algorithm.Theoretically,to overcome the limitations of beam waist radius,the amplitude profile function of large topological charge Laguerre–Gaussian(LG)beam is properly improved.Then,an experimental system employing a 4K phase-only SLM is set up,and the LG beams with topological charge up to 1200 are successfully generated.Furthermore,we discuss the effect of different beam waist radii on the generation of LG beams.Additionally,the function of the LG beam is further improved to generate an LG beam with a topological charge as high as1400.Our results set a new benchmark for generating large topological charge vortex beams,which can be widely used in precise measurement,sensing,and communication.

关注屈光性白内障手术时代的精准眼球生物测量

近年来,白内障的手术治疗从复明性手术进入屈光性手术时代,对术前精准而全面的眼球生物测量提出了更高的要求。精准眼球生物测量,既包括眼轴长度、角膜曲率、前房深度、晶状体厚度及角膜直径等眼球结构参数的测量,还纳入了Kappa角、Alpha角及波前像差等视光学参数。了解每个参数的测量方法和临床应用,合理的选择检查设备,正确的判读检查结果,是每位屈光性白内障手术医师应掌握的内容。

Encapsulating maytansinoid in pH-sensitive nanocarriers:The importance of using extremely potent cytotoxic agents and fast release for nanomedicine to achieve tumor elimination

The clinical translation of nanomedicine is hindered by the low delivery efficiency, and consequently drug concentration in tumor sites falls short of the therapeutic effective range which leads to poor clinical outcomes. One important lesson learned from the development of antibody-drug-conjugates (ADCs) is that to achieve significant clinical benefits, extremely potent cytotoxic agents and cleavable linkers should be used. By encapsulating maytansinoid, AP3, which is 100-1,000 times more potent than most conventional small molecule anticancer drugs, in pH-sensitive acetalated dextran-polyethylene glycol (PEG)(ADP) nanocarriers, even with only 1% drug loading, we were able to eradicate tumors in 50% of tested animals with negligible side effects, while free AP3 only showed marginal efficacy and severe liver damages. This study suggests that besides improving the low efficiency of nano-delivery systems, the potency of drug to be delivered is also critical to the clinical outcomes of nanomedicine. Our results also showed that ADP nanoparticles (NPs) were able to expand the narrow therapeutic window of maytansinoids in a similar manner to the ADCs.

Free or fixed state of nHAP differentially regulates hBMSC morphology and osteogenesis through the valve role of ITGA7

Nano-hydroxyapatite(nHAP)has been widely used in bone repair as an osteo-inductive and naturally-occurring material.However,the optimal applied form of nHAP and the underlying mechanisms involved remain unclear.Herein,to investigate into these,a range of corresponding models were designed,including three applied forms of nHAP(Free,Coating and 3D)that belong to two states(Free or fixed).The results indicate that when fixed nHAP was applied in the 3D form,optimal osteogenesis was induced in human bone marrow stem cells(hBMSCs)with increased bone volume via integrinα7(ITGA7)-mediated upregulation of the PI3K-AKT signaling pathway,while contrary results were observed with free nHAP.Ectopic osteogenesis experiments in mice subcutaneous transplantation model further confirmed the different tendencies of ITGA7 expression and osteogenesis of hBMSCs in free and fixed states of nHAP.Our results revealed that the two states of nHAP play a different regulatory role in cell morphology and osteogenesis through the valve role of ITGA7,providing cues for better application of nanoparticles and a potential new molecular target in bone tissue engineering.