复合阻燃剂对聚双环戊二烯复合材料聚合动力学和性能的影响

将固/液复合阻燃剂硼酸锌-磷酸三(2-氯乙基)酯-氢氧化镁-氢氧化铝(ZB-TCEP-MH-ATH)引入双环戊二烯(DCPD)溶液中制备了DCPD稳定分散液,并通过前端开环易位聚合(FROMP)制备了阻燃聚双环戊二烯(PDCPD)复合材料。研究了复合阻燃剂的组分及含量对DCPD的聚合动力学、复合材料的热稳定性、力学性能和阻燃性能的影响。结果表明,复合阻燃剂会影响DCPD的反应活性,降低材料的聚合焓和固化度。随着阻燃剂含量的增加,聚合焓降低程度增大,但在相同阻燃体系中,材料的固化度仅受阻燃剂种类的影响,且材料的储能模量和玻璃化转变温度与材料的固化度线性相关。复合阻燃剂的引入会降低PDCPD复合材料的拉伸强度,但明显提高了材料的热稳定性、断裂伸长率、冲击强度和阻燃性,当ZB-TCEP-MH-ATH的含量为55%时,材料的极限氧指数(LOI)达41%,并通过UL-94 V-0级,材料的热释放速率峰值(pHRR)和燃烧增长速率(FIGRA)值分别仅为PDCPD的8.51%和3%,烟生成速率峰值(pSPR)降幅达80.36%,火灾性能指数(FPI)提高了8倍,具有较好的综合性能。

化学本科生课外阅读的现状与思考——基于湖南省属六所高校的调查

基于2003年和2013年对湖南省6所高校化学本科生开展课外阅读情况的调查,于2021年再次开展了同质性调查和对比分析,发现化学专业在校大一到大三学生中存在课外阅读量下降、不重视期刊阅读、忽视图书馆借阅功能等问题。据此提出新生教育突出引导、课堂教学加强渗透、课外创新养成习惯和社团活动以赛促读等策略和建议。

TET1 knockdown inhibits the odontogenic differentiation potential of human dental pulp cells

Human dental pulp cells （hDPCs） possess the capacity to differentiate into odontoblast-like cells and generate reparative dentin in response to exogenous stimuli or injury. Ten-eleven translocation 1 （TET1） is a novel DNA methyldioxygenase that plays an important role in the promotion of DNA demethylation and transcriptional regulation in several cell lines. However, the role of TET1 in the biological functions of hDPCs is unknown. To investigate the effect of TET1 on the proliferation and odontogenic differentiation potential of hDPCs, a recombinant shRNA lentiviral vector was used to knock down TET1 expression in hDPCs. Following TET1 knockdown, TET1 was significantly downregulated at both the mRNA and protein levels. Proliferation of the hDPCs was suppressed in the TET1 knockdown groups. Alkaline phosphatase activity, the formation of mineralized nodules, and the expression levels of DSPP and DMP1 were all reduced in the TETl-knockdown hDPCs undergoing odontogenic differentiation. Based on these results, we concluded that TET1 knockdown can prevent the proliferation and odontogenic differentiation of hDPCs, which suggests that TET1 may play an important role in dental pulp repair and regeneration.

Microstructure evolution of AZ91 alloy processed by a combination method of equal channel angular pressing and rolling

In the present work,AZ91 alloy was successfully processed by equal channel angular pressing(ECAP)for up to 16 passes and rolling(R)for multiple passes with a total reduction of 75%in addition to a combination method with ECAP plus rolling(ECAP+R).The effects of various processes(ECAP,R and ECAP+R)on microstructure evolution were analyzed and the influence of ECAP process on the rolling performance was examined.The result shows that ECAP contributed to a homogenous grain structure and formed a texture with higher Schmidt factors that was easy for rolling.A plate with smoother surface and reduced edge cracks was observed in the ECAP+R process than in the single R process.Although the microstructure of the alloy was similar after ECAP+R and R process,the sample of ECAP+R was more refined and had stronger second phase precipitation than the sample of R,which resulted in better rolling characteristics,along with the external surfaces.

Determination of Aromatic Components of Rosa davurica Pall. by Headspace Solid Phase Microextraction Combined with GC-MS

[Objectives] To determine the aromatic components of Rosa davurica Pall. [Methods] 42 kinds of aromatic components were identified from the flowers of R. davurica by headspace solid phase microextraction( HS-SPME) combined with gas chromatography-mass spectrometry( GC-MS). The main compounds were alcohols( 54. 88%) and aldehydes( 19. 55%). [Results] The top five components with the highest relative content were phenylethyl alcohol( 12. 69%),geraniol( 9. 85%),citronellol( 8. 80%),nerol( 7. 84%) and 2-n-pentylfuran( 7. 45%). [Conclusions] Headspace solid phase microextraction( HS-SPME) combined with gas chromatography-mass spectrometry( GC-MS) can provide basis for further development and utilization of R. davurica.

Selective conversion of biomass-derived furfuryl alcohol into n-butyl levulinate over sulfonic acid functionalized TiO_(2) nanotubes

Sulfonic acid functionalized titanate nanotubes were prepared by the sulphonation reaction of hydrothermally synthesized TiO_(2) nanotubes(TNTs) using chlorosulfonic acid as the sulfating agent.The as-prepared catalysts were characterized by fourier transform infrared(FT-IR)spectroscopy,transmission electron microscopy(TEM),scanning electron microscopy-energy dispersive X-ray spectroscopy(SEM-EDX),Xray diffraction(XRD) analysis,thermogravimetry-differential thermal gravimetry(TG-DTG) and X-ray photoelectron spectroscopy(XPS)techniques.The characterization results revealed that the catalysts retained the tubular structure of the TNTs and possessed a large number of active sulfonic acid sites.The catalytic performance of the catalysts for the synthesis of n-butyl levulinate was investigated via the alcoholysis of biomass-derived furfuryl alcohol under atmospheric pressure.The effects of the reaction factors such as the catalyst dosage,reaction time,and temperature on the alcoholysis of the furfuryl alcohol were systematically studied.Under mild conditions,about 79.9% yield of n-butyl levulinate was achieved.In addition,the catalysts showed a stable catalytic performance after four consecutive cycles.Furthermore,no leaching of the active species was observed during the hot filtration testing,which can be attributed to the covalently linked –SO_(3)H groups on the TNTs surface.In addition,the opened tubular nanostructure of the catalyst and the introduced strong Br?nsted acid sites exhibited synergistic effects,which facilitated the selective conversion of the furfuryl alcohol to butyl levulinate.

Selective oxidation of biomass derived 5-hydroxymethylfurfural to 2,5-diformylfuran using sodium nitrite

A mild and simple process for the effective oxidation of 5-hydroxymethylfurfural（HMF） into 2,5-diformylfuran（DFF） has been developed using Na NO2 as the oxidant. Some important reaction parameters were investigated to optimize the oxidation of HMF into DFF. It was found that the reaction solvent was very crucial for this reaction. Trifluoroacetic acid was the best solvent for the oxidation of HMF into DFF by Na NO2.Under the optimal reaction condition, almost quantitative HMF conversion and high DFF yield of 90.4% were obtained after 1 h at room temperature.

Diagnosis of prostatic neuroendocrine carcinoma: Two cases report and literature review

Two cases of prostatic neuroendocrine carcinoma(PNEC) imaged by computed tomography(CT) and magnetic resonance imaging(MRI), and literature review are presented. Early enhanced CT, MRI, especially diffusionweighted image were emphasized, the complementary roles of ultrasound, CT, MRI, clinical and laboratory characteristic's features in achieving accurate diagnosis were valued in the preoperative diagnosis of PNEC.

Effects of Different Seedling Raising Methods on Seedling Growth of Two Kinds of Fritillaria

[Objectives] To reveal the effects of film mulching and open ground seedling raising on the differences between Fritillaria przewalskii Maxim. and Fritillaria pallidiflora Schrenkf., find the optimal seedling raising method, and provide scientific basis for standard seedling raising technique and protecting wild resources of Fritillaria. [Methods] This experiment counted the seedling emergence number and calculated the seedling emergence indicator and the yield. [Results] The results showed that under the condition of film mulching and open ground seedling raising, the changes of Fritillaria seedlings showed an "S" curve, conforming to the Logistic equation, and the rapid growth period appeared 5-13 d after seedling emergence. Compared with the open ground seedling raising, the seedlings of F. przewalskii Maxim. and F. pallidiflora Schrenkf. raised through film mulching emerged 2-4 d earlier, and the yield increased by 56.8% and 21.71%, respectively, and the individual quality was excellent. [Conclusions] The film mulching of F. przewalskii Maxim. and F. pallidiflora Schrenkf. has great significance to protect the wild resources of Fritillaria in Eryin Mountain Area. It is recommended to adopt the film mulching method for Fritillaria seedling raising, to reduce the yield decline due to lodging, and adopt sun-shading net covering after sowing.

Preparation of a Carbon-Based Solid Acid with High Acid Density via a Novel Method

A carbon-based solid acid with high acid density was successfully prepared using camphor tree branches as raw materials through a novel method including dilute sulfuric acid activation, carbonization in refluxing solvent and sulfonation. Physical characterization was detected to show that the carbon-based acid is amorphous with polycyclic aromatic carbon sheets attached plentiful -OH, -COOH, and -SO3H groups. The sulfonic acid density and total acid density of it reached 2.05 mmol·g-1 and 5.63 mmol·g-1, respectively by acid-base titration. As a solid acid catalyst, it showed excellent performance in the ketalization of cyclohexanone with glycol.

形觉剥夺近视早期雏鸡视网膜细胞凋亡相关研究

目的:观察雏鸡形觉剥夺性近视模型视网膜细胞凋亡相关的代谢变化。方法:实验研究。2021年8月将48只8日龄白来航鸡随机分为对照组和形觉剥夺组。雏鸡8日龄时,形觉剥夺组分别予以右眼形觉剥夺1周和3周处理,作为形觉剥夺1周组和3周组,对照组不作形觉剥夺处理,与相应的形觉剥夺组培养相同的时间,作为对照1周组和对照3周组。所有组别均通过检影及A超测量雏鸡形觉剥夺前后屈光度、眼轴等数据,形觉剥夺结束后进行雏鸡视网膜电图、彩色立体眼底照相检查,视网膜切片苏木素-伊红(HE)染色以检测雏鸡眼底结构及功能变化,并使用Western blot方法检测雏鸡视网膜中凋亡相关因子bax、bcl-2、caspase-3、caspase-8的表达水平变化,使用透射电子显微镜观察视网膜细胞超微结构的变化。采用独立样本t检验进行数据分析。结果:①形觉剥夺1周(t=3.53,P=0.002)或3周(t=18.21,P<0.001)组雏鸡眼轴增长量均明显大于相应的对照1周组和对照3周组,且形觉剥夺3周组雏鸡眼轴增长量明显大于形觉剥夺1周组(t=5.28,P=0.030);与各自对照组相比,形觉剥夺1周(t=12.40,P<0.001)或3周(t=12.37,P<0.001)的雏鸡屈光度均向负值方向增大,且形觉剥夺3周雏鸡屈光度明显负于1周雏鸡屈光度(t=2.63,P=0.030)。②在形觉剥夺1周和3周雏鸡中,视网膜电图与对照组相比均未见明显差异(均P>0.05),眼底照相和切片HE染色均未见异常。③形觉剥夺1周和3周后,视网膜bcl-2(t=2.77,P=0.040;t=4.58,P=0.044)表达水平均较相应的对照组下降,bax(t=2.99,P=0.040;t=4.77,P=0.018)、caspase-3(t=3.44,P=0.026;t=3.25,P=0.023)、caspase-8(t=5.82,P=0.028;t=5.38,P=0.013)表达水平均较对照组上升。④对照组和形觉剥夺1周组雏鸡的视网膜细胞中未见明显细胞损伤表现,形觉剥夺3周组视网膜可见细胞质分布不均,染色质固缩,线粒体重度肿胀,嵴消失,空泡变,内质网脱颗粒等现象。结论:形觉剥夺早期雏鸡的眼底尚未出现病理性改变时,凋亡相关因子bax、bcl-2、caspase-3、caspase-8表达量已经发生改变,透射电镜提示视网膜组织发生了细胞凋亡。

Boehmite-supported CuO as a catalyst for catalytic transfer hydrogenation of 5-hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan

2,5-bis(hydroxymethyl)furan(BHMF)is an important monomer of polyester.Its oxygen-containing rigid ring structure and symmetrical diol functional group establish it as an alternative to petroleum-based monomer with unique advantages for the prodution of the degradable bio-based polyester materials.Herein,we prepared a boehmite-supported copper-oxide catalyst for the selective hydrogenation of 5-hydroxymethylfurfural into BHMF via catalytic transfer hydrogenation(CTH).Further,ethanol successfully replaced conventional high-pressure hydrogen as the hydrogen donor,with up to 96.9% BHMF selectivity achieved under suitable conditions.Through characterization and factor investigations,it was noted that CuO is crucial for high BHMF selectivity.Furthermore,kinetic studies revealed a higher by-product activation energy compared to that of BHMF,which explained the influence of reaction temperature on product distribution.To establish the catalyst structure-activity correlation,a possible mechanism was proposed.The copper-oxide catalyst deactivated following CTH because ethanol reduced the CuO,which consequently decreased the active sites.Finally,calcination of the catalyst in air recovered its activity.These results will have a positive impact on hydrogenation processes in the biomass industry.

Recent advances in the catalytic production of bio-based diol 2,5-bis(hydroxymethyl)furan

Biomass-derived 2,5-bis(hydroxymethyl)furan(BHMF)has received great attention and interest due to its broad application prospects in polyesters and medicine.Over the past decades,the catalytic systems including thermocatalytic,biocatalytic,electrocatalytic,and photocatalytic hydrogenation of 5-hydroxymethylfurfural(HMF)into BHMF have been developed to a great extent.To understand the present status and challenges of BHMF production,this review systematically evaluates recent findings and developments of HMF hydrogenation through various reaction systems,with an emphasis on catalyst screening,synthesis processes,and reaction mechanism.Furthermore,a few potential research trends are also proposed,in order to provide innovative ideas for further exploration of BHMF synthesis in a simpler,efficient,and economical way.

通过调整Maltase视标边缘RGB像素模拟图像离焦性质对人眼调节反应和瞳孔直径的影响

目的:探究通过调整Maltase视标边缘RGB像素模拟图像离焦性质对人眼调节和瞳孔直径的影响。方法:横断面研究。随机纳入23例就读于北京大学医学部的健康大学生(男10例,女13例),年龄(21.5±1.3)岁,等效球镜度(-2.53±1.13)D。在1块LCD屏的中央随机呈现14个边缘RGB像素经过调整的Maltase视标。每位受检者分别完成这14个注视任务,每个任务的时长为3 min,使用开放视野红外验光仪连续测量注视过程中的调节反应和瞳孔大小。实际调节反应值与调节需求的差值为调节误差,以实际调节反应值的均方根(RMS)作为调节微波动。采用重复测量方差分析和由Bonferroni校正的事后两两比较来评估Maltase视标的极性、离焦性质和边缘RGB类型对调节误差、RMS值和瞳孔直径的影响。结果:视标边缘RGB像素对调节误差的影响不显著。RMS值在正极性和负极性时分别为(0.22±0.08)D和(0.27±0.11)D,差值为0.05 D(95%置信区间:0.03~0.06)D,差异有统计学意义(P<0.001)。极性、模拟的离焦性质和边缘类型对瞳孔直径的影响均有统计学意义(极性:F=19.41,P<0.001;离焦性质:F=6.42,P=0.019;边缘类型:F=8.89,P=0.005)。极性和离焦性质的交互作用对瞳孔大小有显著影响(F=8.59,P=0.008)。结论:人眼对于视标的极性和其模拟的视网膜正负离焦性质是敏感的,注视正极性视标相较于注视负极性视标表现出更小的RMS值和瞳孔直径。调整Maltase视标边缘RGB像素对瞳孔直径的影响大。

A machine learning-based algorithm used to estimate the physiological elongation of ocular axial length in myopic children

Background:Axial myopia is the most common type of myopia.However,due to the high incidence of myopia in Chinese children,few studies estimating the physiological elongation of the ocular axial length(AL),which does not cause myopia progression and differs from the non-physiological elongation of AL,have been conducted.The purpose of our study was to construct a machine learning(ML)-based model for estimating the physiological elongation of AL in a sample of Chinese school-aged myopic children.Methods:In total,1011 myopic children aged 6 to 18 years participated in this study.Cross-sectional datasets were used to optimize the ML algorithms.The input variables included age,sex,central corneal thickness(CCT),spherical equivalent refractive error(SER),mean K reading(K-mean),and white-to-white corneal diameter(WTW).The output variable was AL.A 5-fold cross-validation scheme was used to randomly divide all data into 5 groups,including 4 groups used as training data and one group used as validation data.Six types of ML algorithms were implemented in our models.The best-performing algorithm was applied to predict AL,and estimates of the physiological elongation of AL were obtained as the partial derivatives of AL_(predicted)-age curves based on an unchanged SER value with increasing age.Results:Among the six algorithms,the robust linear regression model was the best model for predicting AL,with a R^(2) value of 0.87 and relatively minimal averaged errors between the predicted AL and true AL.Based on the partial derivatives of the AL_(predicted)-age curves,the estimated physiological AL elongation varied from 0.010 to 0.116 mm/year in male subjects and 0.003 to 0.110 mm/year in female subjects and was influenced by age,SER and K-mean.According to the model,the physiological elongation of AL linearly decreased with increasing age and was negatively correlated with the SER and the K-mean.Conclusions:The physiological elongation of the AL is rarely recorded in clinical data in China.In cases of unavailable clinical dat,an ML algorithm could provide practitioners a reasonable model that can be used to estimate the physiological elongation of AL,which is espedally useful when monitoring myopia progression in orthokeratology lens wearers.

Genomic landscapes of Chinese sporadic autism spectrum disordersrevealed by whole-genome sequencing

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with considerable clinical and genetic heterogeneity.In this study,we identified all classes of genomic variants from whole-genome sequencing (WGS) dataset of 32 Chinese trios with ASD,including de novo mutations,inherited variants,copy number variants (CNVs) and genomic structural variants.A higher mutation rate (Poisson test,P<2.2×10) in exonic (1.37×10) and 3’-UTR regions (1.42×10) was revealed in comparison with that of whole genome (1.05×10).Using an integrated model,we identified 87 potentially risk genes (P<0.01) from 4832 genes harboring various rare deleterious variants,including CHD8 and NRXN2,implying that the disorders may be in favor to multiple-hit.In particular,frequent rare inherited mutations of several microcephaly-associated genes (ASPM,WDR62,and ZNF335)were found in ASD.In chromosomal structure analyses,we found four de novo CNVs and one de novo chromosomal rearrangement event,including a de novo duplication of UBE3A-containing region at 15q11.2-q13.1,which causes Angelman syndrome and microcephaly,and a disrupted TNR due to de novo chromosomal translocation t (1;5) (q25.1;q33.2).Taken together,our results suggest that abnormalities of centrosomal function and chromatin remodeling of the microcephaly-associated genes may be implicated in pathogenesis of ASD.Adoption of WGS as a new yet efficient technique to illustrate the full genetic spectrum in complex disorders,such as ASD,could provide novel insights into pathogenesis,diagnosis and treatment.

A deep learning-based ring artifact correctionmethod for X-ray CT

Purpose In X-ray CT systems,ring artifacts caused by the nonuniform response of detector elements degrades the reconstruction quality and affects the subsequent processing and quantitative analysis of the image.Method In this paper,a novel method is proposed to remove the ring artifacts in CT image by applying deep learning algorithm based on convolutional neural network(CNN)and recurrent neural network(RNN).First,the reconstructed CT images is transformed into polar coordinate system to make rings appear as stripes.Then,a CNN is constructed to detect the stripes,and a RNN is utilized to process the line artifact correction.After that,by retransforming the corrected image from polar coordinate system to Cartesian coordinate system,a ring artifact removal image can be achieved.Results The presented method can successfully reduce the CT ring artifact on simulated and real data.Specifically,in the experiment with real water phantom,the center and peripheral standard deviations reduced 46%and 24%,respectively.Conclusions The proposed method is potential to be widely deployed in industrial and medical CT systems,due to the excellent results on correction and the real-time performance without adjusting parameters manually.

多囊卵巢综合征女性孕期的胎儿生长发育和胎盘特征:基于胎儿和胎盘磁共振成像分析

目的:探讨母亲多囊卵巢综合征(PCOS)对子代胎儿期生长发育和胎盘特征的影响.创新点:首次关注到PCOS女性孕期的胎儿和胎盘磁共振成像(MRI)特征,通过影像学和临床疾病的结合,对胎儿和胎盘MRI图像进行全面分析和测量,评估胎儿生长发育和胎盘特征,并追踪产科和子代随访结局,以期为PCOS对子代的潜在影响提供科学依据.方法:本研究对浙江大学医学院附属妇产科医院2013~2018年行胎儿MRI检查的妊娠女性病例行回顾性分析,根据鹿特丹诊断标准纳入PCOS妊娠女性60例,随机选取与其胎儿MRI检查孕周相匹配的非PCOS妊娠女性120例作为对照,收集胎儿和胎盘MRI图像信息,统计学分析比较PCOS妊娠女性与非PCOS妊娠女性影像学测量指标,包括胎儿的双顶径、头围、腹围、肝脏和肾脏各径线,胎儿肺和肝的信号强度,胎盘异常情况、胎盘厚度、胎盘信号强度和表观扩散系数值(ADC),并比较分析人口学数据、产科和新生儿结局,随访子代儿童期的生长情况.结论:母亲PCOS会造成子代胎儿期生长发育和胎盘特征的改变.因本研究为回顾性研究、样本量偏小及一些潜在的偏差,结论有待进一步证实.

Experimental research of the energy bins for K-edge imaging using a photon counting detector:a phantom and mice study

Purpose K-edge imaging based on the photon counting detectors(PCDs)is an effective enhanced imaging method because the PCDs are conducive to the K-edge imaging due to the adjustable energy thresholds.The energy bins significantly affect the image quality of the K-edge imaging,but the conventional energy bins used for K-edge imaging are continuous which weaken the K-edge signal and decline the image quality.Hence,how to get a better K-edge signal by the optimized energy bins is the key point for the K-edge imaging based on the PCDs.Method This paper experimentally studied the influence of the energy bins used for the K-edge imaging based on the PCDs.The conventional energy bins were determined by the theoretical-attenuation method(TAM),and the optimized energy bins were determined by the threshold-scan method(TSM).For the phantom and mice imaging,we performed both the K-edge subtraction algorithm and the K-edge decomposition algorithm on the projections obtained by the energy bins which were determined by the TAM and TSM.The image quality was compared using the CNR of the objective area.Results The experimental results showed that the energy bins identified by the TSM had a better performance than the TAM in both imaging methods.The TSM improved the CNR by~39%than the TAM in the phantom results and could better highlight the areas where the contrast agents are enriched(such as the kidney).Conclusions The optimized energy bins can better highlight the K-edge signal than the conventional energy bins which can improve the image quality and have the potential to reduce the amount of the contrast agents.

Esterification of levulinic acid into n-butyl levulinate catalyzed by sulfonic acid-functionalized lignin-montmorillonite complex

In this study,sulfonic acid-functionalized lignin-montmorillonite complex(LMT-SO_(3)H)was pre-pared and employed as an efficient heterogeneous catalyst for the esterification of levulinic acid(LA)into n-butyl levulinate(BL).An intermediate pseudo-butyl levulinate(p-BL)was determined by distilled water treatment and nuclear magnetic resonance(NMR)analysis,and a possible mech-anism for the esterification of LA is proposed.The effects of various process parameters were studied and the results showed that the LMT-SO_(3)H catalyst had the excellent catalytic perfor-mance for esterification of the LA.Under optimum reaction conditions,the yield of BL was 99.3%and the conversion of LA was 99.8%.The LMT-SO_(3)H catalyst exhibited strong acidic sites and high stability even after seven cycles of usage.Furthermore,esterification of the LA with various alcohols over the LMT-SO_(3)H was further investigated.