Evidence of polymorphic transformations of Sn under high pressure

The high-pressure polymorphs and structural transformation of Sn were experimentally investigated using angle- dispersive synchrotron x-ray diffraction up to 108.9 GPa. The results show that at least at 12.8 GPa β-Sn→bct structure transformation was completed and no two-phase coexistence was found. By using a long-wavelength x-ray, we resolved the diffraction peaks splitting and discovered the formation of a new distorted orthorhombic structure bco from the bct structure at 31.8 GPa. The variation of the lattice parameters and their ratios with pressure further validate the observation of the bco polymorph. The bcc structure appears at 40.9 GPa and coexists with the bco phase throughout a wide pressure range of 40.9 GPa-73.1 GPa. Above 73.1 GPa, only the bcc polymorph is observed, The systematically experimental investigation confirms the phase transition sequence of Sn asβ-Sn→bct→bco→bco ＋ bcc→bcc upon compression to 108.9 GPa at room temperature.

Monitoring real time polymorphic transformation of sulfanilamide by diffuse reflectance visible spectroscopy

This study investigated the development of a novel approach to surface characterization of drug poly- morphism and the extension of the capabilities of this method to perform ＇real time＇ in situ measure- ments. This was achieved using diffuse reflectance visible （DRV） spectroscopy and dye deposition, using the pH sensitive dye, thymol blue （TB）. Two polymorphs, SFN-β and SFN-γ, of the drug substance sulfanilamide （SFN） were examined. The interaction of adsorbed dye with polymorphs showed different behavior, and thus reported different DRV spectra. Consideration of the acid/base properties of the morphological forms of the drug molecule provided a rationalization of the mechanism of differential coloration by indicator dyes. The kinetics of the polymorphic transformation of SFN polymorphs was monitored using treatment with TB dye and DRV spectroscopy. The thermally-induced transformation fitted a first-order solid-state kinetic model （R2=0.992）, giving a rate constant of 2.43 × 10^- 2 s 1.

Kinetics Estimation and Polymorphic Transformation Modeling of Buspirone Hydrochloride

In this work, solvent-mediated polymorphic transformation of metastable Form II to stable Form I of Buspirone Hy-drochloride (BUS-HCl) was studied. The polymorphic transformation was monitored using in-situ Raman spectroscopy. The solvent-mediated transformation process is governed by the dissolution of Form II and the nucleation and subsequent growth of Form I. The model parameters for each of these sub-processes were determined with the aid of experimental data including polymorphic fraction in solid phase, solute concentration, and the crystal size distribution. In order to estimate the kinetic parameters, independent seeded batch sets of experiments were conducted, first to estimate the growth rate of Form I, and consequently to estimate the secondary nucleation of Form I and dissolution rate of Form II. The experimental data showed that the secondary nucleation of Form I occurred slightly after the dissolution of Form II was initiated. The estimated parameters for growth, nucleation and dissolution rates were successfully implemented in the population model and validated with the experiments.

Tunable Polymorphic Transformation Temperature

Polymorphic transformation temperature of 2,2’:6’,2”-Terpyridine (terpy) has been studied. No transformation was observed for unground terpy (orthrhombic form) crystals, while the ground crystals may be transformed into monoclinic form. The transformation temperature was much lower than reported transformation temperature. In addition the transformation temperature decreased with increase of the grinding time. Factors influencing the transformation temperature of terpy were discussed.

Promoter polymorphism of transforming growth factor-β1 gene and ulcerative colitis

AIM: To elucidate the possible difference in two promoter polymorphisms of the transforming growth factor-β1 (TGF-β1) gene (-800G > A, -509C > T) between ulcerative colitis (UC) patients and normal subjects.METHODS: A total of 155 patients with established ulcerative colitis and 139 normal subjects were selected as controls. Two single nucleotide polymorphisms within the promoter region of TGF-β1 gene (-509C > T and -800G > A) were genotyped using PCR-RFLP. RESULTS: There was a statistically significant difference in genotype and allele frequency distributions between UC patients and controls for the -800G > A polymorphism of the TGF-β1 gene (P < 0.05). The frequency of the TGF-β1 gene polymorphism at position -800 showed that the AA genotype and the allele A frequencies significantly differed between the patients and healthy controls (P < 0.05). At position -509, there was no statically significant difference in genotype and allele frequency between the patients and control subjects.CONCLUSION: The results of our study indicate that there is a significant difference in both allele and genotype frequency at position -800G > A of TGF-β1 gene promoter between Iranian patients with UC and normal subjects.

Transforming growth factor-β and toll-like receptor-4 polymorphisms are not associated with fibrosis in haemochromatosis

AIM:To investigate the role of genetic polymorphisms in the progression of hepatic fibrosis in hereditary haemochromatosis.METHODS:A cohort of 245 well-characterised C282Y homozygous patients with haemochromatosis was studied,with all subjects having liver biopsy data and DNA available for testing.This study assessed the association of eight single nucleotide polymorphisms(SNPs)in a total of six genes including toll-like receptor 4(TLR4),transforming growth factor-beta(TGF-β),oxoguanine DNA glycosylase,monocyte chemoattractant protein 1,chemokine C-C motif receptor 2 and interleukin-10 with liver disease severity.Genotyping was performed using high resolution melt analysis and sequencing.The results were analysed in relation to the stage of hepatic fibrosis in multivariate analysis incorporating other cofactors including alcohol consumption and hepatic iron concentration.RESULTS:There were significant associations between the cofactors of male gender(P=0.0001),increasing age(P=0.006),alcohol consumption(P=0.0001),steatosis(P=0.03),hepatic iron concentration(P<0.0001)and the presence of hepatic fibrosis.Of the candidate gene polymorphisms studied,none showed a significant association with hepatic fibrosis in univariate or multivariate analysis incorporating cofactors.We also specifically studied patients with hepatic iron loading above threshold levels for cirrhosis and compared the genetic polymorphisms between those with no fibrosis vs cirrhosis however there was no significant effect from any of the candidate genes studied.Importantly,in this large,well characterised cohort of patients there was no association between SNPs for TGF-βor TLR4and the presence of fibrosis,cirrhosis or increasing fibrosis stage in multivariate analysis.CONCLUSION:In our large,well characterised group of haemochromatosis subjects we did not demonstrate any relationship between candidate gene polymorphisms and hepatic fibrosis or cirrhosis.

Experimental Evidence of Reversible Crystalline State Transformation of 2,2':6',2"-Terpyridine: Visualization and Seed Effect

We have succeeded in causing reversible polymorphic transformation of 2,2':6',2"-terpyridine (terpy). By contacting a template terpy crystal with the target crystal, reversible orthorhombic-to-monoclinic transformation occurred directly without via melting state. The transformation process is successfully visualized and it is found that the template crystal influences the transition temperature itself.

MTHFR基因多态性对脑梗死患者阿替普酶静脉溶栓后出血性转化的影响

目的分析亚甲基四氢叶酸还原酶(MTHFR)基因多态性对脑梗死患者阿替普酶静脉溶栓后出血性转化(HT)的影响。方法回顾性分析2020年7月—2023年7月在安徽医科大学附属阜阳人民医院接受治疗的120例脑梗死患者的临床资料。依据治疗后24~72 h HT发生情况分为HT组(15例)、无HT组(105例)。比较两组基线资料、MTHFR基因多态性、纤维蛋白原(Fib)、同型半胱氨酸(Hcy)。采用多因素一般Logistic回归模型分析脑梗死患者阿替普酶静脉溶栓后HT发生的危险因素。绘制受试者工作特征(ROC)曲线,分析入院时美国国立卫生院卒中量表(NIHSS)评分、Hcy预测脑梗死患者阿替普酶静脉溶栓后HT发生的价值。结果HT组心房颤动发生率、MTHFR基因型677CT占比、入院时NIHSS评分、Hcy水平均高于无HT组(P<0.05)。多因素一般Logistic回归分析结果显示:心房颤动史[OR=1.478(95%CI:1.126,1.940)]、入院时NIHSS评分升高[OR=1.656(95%CI:1.125,2.438)]、MTHFR基因型为677CT[OR=1.871/2.362(95%CI:1.052,3.328/1.081,4.652)]、Hcy水平升高[OR=2.149(95%CI:1.108,4.168)]均为脑梗死患者阿替普酶静脉溶栓后HT发生的危险因素(P<0.05)。ROC曲线分析结果显示,入院时NIHSS评分、Hcy均可预测脑梗死患者阿替普酶静脉溶栓后HT发生,其敏感性分别为80.0%(95%CI:0.765,0.883)、73.3%(95%CI:0.717,0.834),特异性分别为74.3%(95%CI:0.659,0.817)、74.3%(95%CI:0.824,0.931)。677CT型患者Hcy水平高于677CC、677TT型患者(P<0.05)。结论心房颤动、MTHFR基因型、入院时NIHSS评分、Hcy均为影响脑梗死患者阿替普酶静脉溶栓后HT发生的重要因素,临床应结合以上指标对高危患者进行重点筛查,尽早采取干预措施。

1,6-己二酸对聚丁烯-1的结晶行为及晶型转变的影响

本文采用示差扫描量热仪(DSC)和偏光显微镜(POM)等设备研究了聚丁烯-1(PB-1)中加入1,6-己二酸(AA)之后的结晶行为、晶型转变行为及其机理,所获得的复合材料为PB-1/AA。实验结果表明,加入1%质量分数的AA能够显著提升PB-1/AA的结晶温度及晶型转化速度。POM的结果显示,加入AA能够使得PB-1/AA晶体结构松散,这与I型晶体结构相似,疏松的结构有利于II-I相转变。DSC的结果显示,AA能提高PB-1/AA的转化过冷度、结晶温度及结晶度,也能在转化过程中提高PB-1/AA的晶片厚度,使得PB-1/AA非晶区的系带分子和缠结环数量减少。连续自成核退火实验(SSA)结果表明,AA与PB-1的I型晶体存在一定的晶格匹配,从而加速PB-1/AA的相转变。

艾司奥美拉唑镁新晶型的制备

罗列艾司奥美拉唑镁各类晶型(包括艾司奥美拉唑镁的新晶型、二水合物晶型和三水合物晶型),并通过粉末X-射线衍射图表征各晶型之间的差异点。本研究进一步列出艾司奥美拉唑镁各晶型的制备方法,并研究了艾司奥美拉唑镁新晶型向艾司奥美拉唑镁三水合物晶型转换的条件和进一步转变为艾司奥美拉唑镁二水合物晶型的条件,同时建立了艾司奥美拉唑镁三种晶型之间的转换关系。

Differential Polymorphic Transformation Behavior of Polybutene-1 with Multiple Isotactic Sequences

For the solid-solid transformation from form Ⅱ to form Ⅰ of isotactic polybutene-1(iPB),the temperature dependence of form Ⅰ nucleation and growth was deemed to control the transformation process.However,the relationship between formⅠ formation and form Ⅱ disappearance in the transformation process is not clear.In this work,the spontaneous crystal transformation from form Ⅱ to Ⅰ of iPB with 81 mol%mmmm sequence concentration is studied firstly by tracking the two processes,the decay of form Ⅱ and the yielding of form Ⅰ in a wide range of temperature spanning from 0℃ to 50℃ and in a long transformation time ranging from 5 min to 65 days with in situ FTIR and WAXD.Unlike the literature reports,the decay rate of form Ⅱ is firstly found to be lower than the yielding rate of form Ⅰ at all studied temperatures,especially at low transition temperature.This is attributed to the amorphous chains which locate near crystal lamella participating into the nucleation of form Ⅱ.The regular chain folding and growth of i PB form Ⅰ from amorphous chains containing short isotactic sequences also lead to an increase in crystallinity of form Ⅰ compared with that of initial form Ⅱ crystallized at 60℃.An increase in the annealing temperature results in decrease in crystallinity and increase in lamellae thickness of i PB formⅠ.

Association oftransforming growth factor-β1 gene variants with risk of coal workers'pneumoconiosis

Objective： The aim of this case-control study was to explore whether five tagging single nucleotide poly- morphisms （tSNPs） within the transforming growth factor-ill （TGF-fll） gene were involved in manifestation of inflammatory and fibrotic processes associated with coal workers pneumoconiosis （CWP）. Methods： The study included 508 CWP patients and 526 controls who were underground coal miners from Xuzhou Mining Business Group. Five tSNPs were selected from the HapMap and detected by polymerase chain reaction-restriction fragment length polymorphism （PCR-RFLP） method. Results： The single SNP analysis showed that the genotype frequencies of SNP2 （rs1800470, ＋869T/C, extron 1） and SNP5 （rs11466345, intron 5） in CWP cases were significantly different from those in controls. Multivariate logistic regression analysis revealed that SNP2 （rs1800470） CC genotype was associated with decreased risk of CWP （OR = 0.50, 95% CI = 0.32-0.78）, which was evident among subgroups of those never smoke （OR = 0.40, 95%CI = 0.24-0.66）, cases with stage Ⅱ（OR = 0.41, 95%CI = 0.22-0.76） and exposure period （〈 28 y： OR = 0.54, 95%CI = 0.31-0.95; ≥ 28 y： OR = 0.52, 95%CI = 0.32-0.96）. However, the SNP5 （rs11466345） GG genotype was associated with an increased risk of CWP （OR = 2.5, 95%CI = 1.36-4.57）, and further stratification analysis showed that the risk of CWP was increased in both smoking and nonsmoking groups, shorter and longer exposure groups, while the risk of CWP was only increased in patients with stage I and Ⅱ. Conclusion： This study suggests that TGF-β1 polymorphisms may contribute to susceptibility of CWP.

Effect of cytokine gene polymorphism on histological activity index, viral load and response to treatment in patients with chronic hepatitis C genotype 3

AIM： To investigate the association between cytokine gene polymorphism and disease status in chronic hepatitis C genotype 3 by liver biopsy, ALl, HCV RNA levels and response to treatment. METHODS： Patients with chronic hepatitis C genotype 3 were analyzed for single nucleotide polymorphisms of interleukin （IL）-10, IL-1 beta, interferon-gamma （IFN-y）, tumor necrosis factor-alpha （TNF-y） and transforming growth factor-beta （TGF-β） by polymerase chain reaction using sequence-specific oligonucleotide primers. Liver biopsies were assessed by modified histological activity index （HAI） scoring system using a scale of 0-18 for grading the necro-inflammatory activity and 0-6 for staging the fibrosis. HCV RNA levels were determined by bDNA assay. The patients were treated with interferon alpha and ribavirin for 6 mo. Sustained virological response was assessed 6 mo after the completion of the treatment. RESULTS： Out of the 40 patients analyzed, 26 were males. Mean age was 40.5±12.5 years （range 18- 65 years）. The frequencies of different dimorphic polymorphisms based on single nucleotide substitution were as follows： IL-10-1082 G/A 85%, A/A 12.5%, G/ G 2.5%; IL-10-819 A/C 87.5%, C/C 10%, A/A 2.5%; IL-10-592 C/A 72.5%, C/C 27.5%; IL-1 C 90%, U 10%; IFN-874 T/A 50%, T/T 27.5%, A/A 22.5%; TNF-308 A/G 95%, G/G 5%; TGF-10 T/C 52.5%, C/C 35%, T/T 12.5%. The mean grades of necroinflammatory activity of different genotypes of IL-10 at promoter site -1082 were A/A = 3.6, A/G = 5.0, and G/G = 10.0 and the difference was significant （P = 0.029）. The difference in the stage of disease at a scale of 0-6 was A/A 0.8, A/G 2.3, and G/G 4.0 （P = 0.079）. The difference in the HAI seemed to be related to the presence of allele -1082G.For IL-10 -819 genotypes, mean scores of fibrosis were A/A = 6.0, A/C = 2.2, and C/C = 1.0 （P = 0.020） though the inflammatory activity was not much different. No significant differences in HAI were noted among polymorphisms of other cytokines. Moreover, ALT and HCV RNA levels were not significantly different among different cytokine polymorphisms. There was a significant correlation of HAI and HCV RNA levels with the duration of disease. TGFI3 -10 genotype CC patients had a better end of treatment response than those with other genotypes （P = 0：020）. Sustained virological response to the treatment was not influenced by the cytokine polymorphism. No effect of other factors like viral load, degree of fibrosis, gender, steatosis, was observed on sustained virological response in this population infected with genotype 3. CONCLUSION： There is no significant correlation between cytokine polymorphisms and HAI except for the polymorphisms of anti-inflammatory cytokine IL-10, which may influence hepatic inflammatory activity and fibrosis in patients with chronic hepatitis C genotype 3. Sustained virological response in this genotype does not seem to be influenced by cytokine gene polymorphisms.

High Pressure Response of Rutile Polymorphs and Its Significance for Indicating the Subduction Depth of Continental Crust

α-PbO2-type TiO2 （TiO2-Ⅱ） is an important index mineral for ultrahigh-pressure metamorphism. After the discovery of a natural high-pressure phase of titanium oxide with α-PbO2- structure in omphacite from coesite-bearing eclogite at Shima in the Dabie Mountains, China, a nanoscale （〈2 nm） α-PbO2-type TiO2 has been identified through electron diffraction and high-resolution transmission electron microscopy in coesite-bearing jadeite quartzite at Shuanghe in the Dabie Mountains. The crystal structure is orthorhombic with lattice parameters a = 4.58×10-1 nm, b = 5.42×10-1 nm, c = 4.96×10-1 nm and space group Pbcn. The analysis results reveal that ruffle {011}R twin interface is a basic structural unit of α-PbO2-type TiO2. Nucleation of α-PbO2-type TiO2 lamellae is caused by the displacement of one half of the titanium cations within the {011}R twin slab. This displacement reduces the Ti-O-Ti distance and is favored by high pressure. The identification of α- PbO2-type TiO2 in coesite-bearing jadeite quartzite from Shuanghe, Dabie Mountains, provides a new and powerful evidence of ultrahigh-pressure metamorphism at 4--7 GPa, 850℃-900℃, and implies a burial of continental crustal rocks to 130-200 kilometers depth or deeper. The α-PbO2-type TiO2 may be a useful indicator of the pressure and temperature in the diamond stability field.

Association of Single Nucleotide Polymorphisms in IRF6 and TGFA Genes With Nonsyndromic Cleft Lip With Or Without Cleft Palate in Chinese Patients

Objective： Nonsyndromic cleft lip with or without cleft palate（NSCL/P） is a common birth defect with unclear etiology. Both genetic and environmental factors may contribute to NSCL/P. Many genes have been identified as candidate genes associated with this disease. Interferon regulatory factor 6（IRF6） gene and transforming growth factor-a（TGFA） gene seem to be crucial in the predisposition of NSCL/ P. Here we evaluated some single nucleotide polymorphisms（SNPs） loci of TGFA and IRF6 genes in Chinese nuclear families consisting of fathers, mothers and affected offspring with NSCL/P. Methods：Fifty patients of NSCL/P were confirmed by the plastic surgeons. They and their parents were included in the study, all with the informed consents. SNPs loci of TGFA and IRF6 genes were analyzed by microarray technology. Some PCR products were randomly chosen and sequenced to check microarray results. The distribution of gene type and allele frequency between patient group and parents group were compared. Then a Haplotype Relative Risk（HRR） and Transmission Disequilibrium Test（TDT） were performed. Results：The sequences of randomly selected PCR products were all consistent with the microarray results. All loci were in Hardy-Weinberg equilibrium. There were no significant differences in the distribution of genotypes and alleles between patients and their parents. Using HRR and TDT analyses the V274I of IRF6 was associated with NSCL/P, while another SNP locus oflRF6 was not. Strong evidence of linkage disequilibrium was found between the 2 SNP loci of TGFA and disease with the HRR analysis, but not with the TDT analysis. Conclusion：Our study confirms the contribution of IRF6 in the etiology of NSCL/P in populations of Asian ancestry. The association of TGFA with NSCL/P requires further research.

转化生长因子β1与子痫前期的研究进展

子痫前期是复杂的妊娠特异性疾病,严重者会引起HELLP综合征(溶血、肝酶升高和血小板减少),是孕产妇和婴幼儿死亡的主要原因。转化生长因子β1(TGF-β1)是具有多种生物活性的多肽生长因子,已被证明是胚胎发育和调节滋养层细胞活动所需的多功能细胞因子,在母胎免疫稳态、血管形成及血管张力调控中发挥着重要作用。因此,TGF-β1可能成为子痫前期的生物标记物。

转化生长因子β1基因多态性与左乳腺癌术后放疗发生心脏毒性有关

目的:探讨转化生长因子(TGF)-β1基因的2个位点rs12985162(G>A)和rs10417924(T>C)多态性及表达水平与左乳腺癌术后放疗发生心脏毒性的相关性。方法:纳入接受保乳术或改良根治术后放疗的104例女性左乳腺癌患者和100例右乳腺癌患者为研究对象,应用全自动化学发光免疫分析仪检测患者血清心肌肌钙蛋白I(cTnI)和N末端B型利钠肽前体(NT-proBNP)水平,采用毛细管电泳和片段分析技术对TGF-β基因的2个单核苷酸多态性位点rs12985162、rs10417924进行基因分型。采用实时荧光定量聚合酶链式反应(RT-PCR)测定TGF-β基因mRNA相对表达量。对所有患者定期随访,记录心脏毒性事件发生情况,截止至放疗结束后6个月。结果:左乳腺癌患者的心脏毒性发生比例显著高于右乳腺癌患者(36.5%vs 9.0%,χ^(2)=21.804,P<0.001)。发生心脏毒性的左乳腺癌患者在临床分期和术后行放疗构成比方面与心脏无毒性患者比较,差异有统计学意义(P均<0.05)。左乳腺癌患者心脏毒性组和无毒性组的TGF-β的rs12985162位点GG、GA、AA基因型分布有显著差异(χ^(2)=7.527,P=0.023)。采用Logistic回归校正临床分期和术后是否行化疗后发现,AA或GA基因型左乳腺癌患者发生心脏毒性的风险显著高于GG基因型(P<0.05)。对于rs10417924位点,左乳腺癌患者心脏毒性组和无毒性组的TT、TC、CC基因型分布有显著差异(χ^(2)=6.324,P=0.042)。Logistic回归结果显示,CC或TC基因型左乳腺癌患者发生心脏毒性的风险显著高于TT基因型(P<0.05)。rs12985162和rs10417924位点的等位基因在左乳腺癌患者心脏毒性组和无毒性组中的分布有显著性差异(P均<0.05)。左乳腺癌患者心脏毒性组的TGF-β1基因mRNA相对表达量显著高于无毒性组[(3.44±0.38)vs(1.83±0.15),t=8.643,P<0.001]。左乳腺癌患者心脏毒性患者中rs12985162位点AA+GA基因型患者的TGF-β1mRNA相对表达量显著高于GG基因型(t=4.124,P<0.001)。rs10417924位点CC+TC基因型与TT型比较,TGF-β1基因mRNA相对表达量差异无统计学意义(t=1.864,P=0.284)。结论:TGF-β1基因多态性与左乳腺癌术后放疗发生心脏毒性有关。

不同晶体特性CL-20热晶变规律与动力学

六硝基六氮杂异伍兹烷(CL-20)的晶型转变与控制技术是含能材料领域的热点,也是其应用推广时必须解决的关键问题。为了更加深入掌握不同晶体特性ε-CL-20的晶型转变规律与机制,采用原位X射线粉末衍射仪技术,对其热晶变行为及等温晶变动力学进行研究,探讨了晶体表面及内部缺陷对CL-20的ε→γ热晶变行为的影响,计算了不同晶体特性ε-CL-20的等温晶变动力学并获得了相关参数。结果表明,温度是影响ε-CL-20热晶变的主导因素,对于几十到几百微米的ε-CL-20,随着晶体内部及表面缺陷的增多,热晶变起始温度降低、热晶变速率增大。与粒径100μm的ε-CL-20晶体相比,超细ε-CL-20(0.5~1μm)的热晶变起始温度更高,热晶变速率也较快,并从晶体缺陷的两面性解释了超细ε-CL-20的异常热晶变行为。CL-20在热刺激作用下发生ε→γ晶变时,晶体的表面缺陷及内部缺陷作为相变过程的薄弱环节对其有诱导作用,γ晶型在ε-CL-20晶体上成核势垒较低的空位、杂质或位错等缺陷处优先成核,随后在这些位置逐渐长大。

溶剂和结晶温度对尼龙12多晶型的影响

结晶温度和溶剂影响尼龙12晶型。将尼龙12溶于不同溶剂中,将其浇铸成膜并等温结晶,运用广角X射线衍射、差示扫描量热(DSC)法和傅里叶变换红外光谱研究了溶剂和结晶温度对尼龙12多晶型的影响。结果表明,以苯酚/甲酸(v/v=1/1)为溶剂时,室温结晶生成α晶;80℃及以上温度得到γ晶;40~70℃时,α晶与γ晶共存,但α晶含量随着结晶温度的升高而逐渐减少。以甲酸/二氯甲烷(v/v=1/1)为溶剂时,室温结晶得到α晶白色不透明粉末,60℃时却得到γ晶半透明薄膜。DSC结果表明,结晶温度越高,形成的α晶熔点越高,且部分α晶在升温过程中Brill转变为γ晶。尼龙12从甲酸/二氯甲烷溶液结晶所得α晶和γ晶的峰值熔融温度分别高于从苯酚/甲酸溶液所得样品的峰值熔融温度。

基于分子晶体序参数与K-means聚类的TNT晶型转化有限温度弦研究

为揭示炸药转晶稀有事件的分子机制,分别构建了基于键距离(即分子间距离)与键取向和分子取向的两类序参数,借助基于Euclidean距离和密度权重的K-means聚类算法进行了序参数的增强采样。结果表明,基于分子晶体序参数与K-means聚类的增强采样改进了稀有事件常规有限温度弦方法,使自由能快速收敛。将该方法用于TNT晶型转化的研究,避免了分子晶体序参数“维数爆炸”,获得了平均力势面,验证了基于分子晶体序参数与K-means聚类有限温度弦方法在炸药晶型转化研究中的有效性,探明了TNT(O)与TNT(M)之间界面诱导、局部引发、多核非同步生长的晶型转变过程。