基态氧（^3O2）氧化硅烯的密度泛函计算研究

采用密度泛函[B3LYP(full)/6-311+G*]方法研究了基态氧(3O2)氧化硅烯(Si2H4)的机理.计算了三重态初始中间体IM1(T1)到单重态中间体IM(S0)反应交叉势能面,报道了各反应中间体、产物和过渡态的构型和能量,用频率分析方法对各过渡态进行了验证,进一步用IRC方法对主要的基元反应进行了考察,确定了历经生成1,2-二氧环氧硅烷中间体的氧化过程的主要反应通道.

大气氧谱带的实验研究

利用流动余辉装置 ,首次报道了金属镍表面催化基态氧原子O(3P)复合从而获得大气氧谱带O2 (b1Σg+ →X3Σg- )的 (0 ,0 )电子跃迁光谱。并且对反应管壁去激活O2 (b1Σg+ )的动力学过程进行了分析 ,间接证实了O2 (b1Σg+ )的浓度在反应管中是非稳态的变化过程。最后对O2 (b1Σg+ )的形成机理进行了简单的讨论。

化学发光演示实验──水溶液中单线态氧的生成

化学发光演示实验──水溶液中单线态氧的生成黄佩丽，崔巍（北京师范大学化学系１００８７５）氧气是生命过程必不可少的，人们每天呼吸的氧气是能量最低的一种基态氧分子。经测定它有顺磁性，证明该氧分于中有自旋平行的两个电子在分开的轨道上。这种具有未成对电子的氧...

有机过氧化物中过氧键的建立(引入)方法

有机过氧化物目前已发展成非常重要的一类抗疟药物.形成/引入过氧键是合成有机过氧化物的关键步骤和难点所在.对合成有机过氧化物时常见的建立或引入过氧键的方法、各方法的适用范围及优劣所在作了简要的综述.

新型飞机燃油抗氧剂膦化物的氧化反应的研究

膦化物为高性能飞机燃油潜在的抗氧剂,能显著地改善飞机燃油的高温稳定性能。实验结果表明,膦化物在燃油介质中的氧化反应有两种反应类型同时进行,即:自由基链反应及膦化物与氧气的直接作用。在相对较低温度时,膦化物与基态氧发生自由基链反应,膦化物很快被氧化为氧化膦;在相对较高的温度,膦化物与激发态氧直接作用,通过三元环状中间体而最终生成氧化膦和次磷酸酯。

新型有机磷光闪烁体材料开发成功

2022年9月26日,从南京工业大学传出消息,中国科学院院士黄维、该校安众福教授团队与厦门大学陈洪敏教授课题组合作,利用纯有机磷光闪烁体材料,实现低X射线剂量下的高效光动力治疗,展现了该类材料在深层肿瘤治疗方面的巨大应用潜力。据介绍,光动力疗法主要通过特定波长的激光照射,使富集于肿瘤部位的光敏剂受到激发,处于激发态的光敏剂会把能量传递给周围的基态氧分子,生成活性氧,其中主要是单线态氧,产生细胞毒性,进而杀灭病变细胞与组织。

CH3CH2＋O（^3P）反应机理的理论研究

利用abinitio方法对CH3CH2+O(3P)反应进行了理论研究,在MP2/6311+G(d,p)水平上优化得到了反应途径上的反应物、中间体、过渡态和产物的几何构型和谐振频率,并在QCISD(T)/6311+G(d,p)水平上进行单点能计算.计算结果表明:CH2O+CH3、CH3CHO+H和CH2CH2+OH是主要反应产物,其中CH2O+CH3主要来自反应通道A1:(R)→IM1→TS3→(A),CH3CHO+H主要来自反应通道B1:(R)→IM1→TS4→(B),CH2CH2+OH主要来自直接抽提反应通道C1和C2:(R)→TS1(TS2)→(C).计算结果同时表明该反应生成CO的通道能垒是非常高的,CO应该不是主要产物.

Effect of Re element on oxidation resistance of Ni_3Al-Mo based alloys at 1150 ℃

The isothermal oxidation behaviors of three kinds of Ni3Al-Mo based alloys at 1150 ℃ were studied.The morphology,structure and element distribution of oxide scales of the alloys were researched by scanning electron microscopy,X-ray diffraction and electron probe microanalysis.The research results show that there are three oxide layers,an outer layer of NiO,an intermediate layer mainly composed of NiO,NiAl2O4 and a small amount of NiMoO4,and an inner layer of NiAl2O4 and Al2O3.Re element was mainly distributed in the intermediate layer,which plays a role as ＂diffusion barrier＂ in the process of oxidation,and effectively reduces the diffusion rate of Al and Mo elements outward and diffusion rate of O element inward.As a result,a Al-rich oxide layer formed in the inner layer inhibits the growth of oxide layer and improves the oxidation resistance of the alloy.

Singlet oxygen synergistic surface-adsorbed hydroxyl radicals for phenol degradation in CoP catalytic photo-Fenton

In recent years,there have been numerous studies on Fenton or Fenton-like reactions mediated by nonfree radicals such as singlet oxygen(1O_(2));however,there are few studies on the synergistic effect of 1O_(2) and free radicals on the degradation of organic molecules,such as phenol in Fenton reaction.In this study,a cocatalyst,CoP,commonly used in photocatalysis was synthesized using a simple two-step method,and a CoP/Fe^(2+)/AM1.5 system was constructed by introducing Fe^(2+)and simulated sunlight(AM1.5)irradiation.The newly constructed CoP/Fe^(2+)/AM1.5 system could effectively degrade various organic pollutants,including dyes,phenols,and antibiotics.Radical quenching experiments and electron paramagnetic resonance detection confirmed that there were three reactive oxygen species(ROS)in the CoP/Fe^(2+)/AM1.5 system,including·OH_(ads),·O_(2)^(-),and 1O_(2).Further,combined with the liquid chromatogram of phenol,its intermediate products,and the fluorescence diagram of o-hydroxybenzoic acid,it can be concluded that a synergistic effect exists between 1O_(2) and the surface-adsorbed·OH_(ads) in the CoP/Fe^(2+)/AM1.5 system.The controllable formation of surface 1O_(2) and·OH_(ads) was achieved through the oxidation(Co^(3+))and reduction(Pδ−)centers exposed on the CoP surface,and the synergistic effect between them results in phenol’s hydroxylation,ring-opening,and degradation.The study of this new mechanism provides a new perspective for revealing the surface interface reaction between ROS and organic pollutants.

Classification of VxOy^q Clusters by △=2y＋q-5x

Vanadium oxide clusters VxOy^q（x≤8, q=0, ±1） are classified according to the oxidation index （△=2y＋q-5x） of each cluster. Density functional calculations indicate that clusters with the same oxidation index tend to have similar bonding characters, electronic structures, and reactivities. This general rule leads to the findings of new possible ground state struc- tures for V206 and V3O6＋ clusters. This successful application of the classification method on vanadium oxide clusters proves that this method is very effective in studying the bonding properties of early transition metal oxide clusters.

Severity of ulcerative colitis is associated with a polymorphism at diamine oxidase gene but not at histamine N-methyltransferase gene

AIM： To analyse the role of two common polymorphisms in genes coding for histamine metabolising enzymes as it relates to the risk to develop ulcerative colitis （UC） and the clinical course of these patients. METHODS： A cohort of 229 unrelated patients with UC recruited from a single centre and 261 healthy volunteers were analysed for the presence of Thr105Ile and His645Asp amino acid substitutions at histamine N-methyltransferase （HNMT） and diamine oxidase （ABP1） enzymes, respectively, by amplification-restriction procedures. All patients were phenotyped and followed up for at least 2 years （mean time 11 years）. RESULTS： There were no significant differences in the distribution of ABP1 alleles between ulcerative colitis patients and healthy individuals [OR （95% CI） for variant alleles = 1.22 （0.91-1.61）]. However, mutated ABP1 alleles were present with higher frequency among the 58 patients that required immunosuppresive drugs [OR （95 % CI） for carriers of mutated alleles 2.41 （1.21-4.83; P=0.006）], with a significant gene-dose effect （P= 0.0038）. In agreement with the predominant role of ABP1 versus HNMT on local histamine metabolism in human bowel, the frequencies for carriers of HNMT genotypes or mutated alleles were similar among patients,regardless clinical evolution, and control individuals. CONCLUSION： The His645Asp polymorphism of the histamine metabolising enzyme ABP1 is related to severity of ulcerative colitis.

Inducible nitric oxide synthase polymorphism is associated with the increased risk of differentiated gastric cancer in a Japanese population

AIM： To examine the association of inducible nitric oxide synthase （iNOS） C150T polymorphism with gastric cancer, as well as with gastric atrophy and H pylori seropositivity.METHODS： A single nucleotide polymorphism of iNOS CtSOT was examined for 454 Japanese health checkup examinees （126 males and 328 females） aged 35 to 85 years without a history of cancer and 202 gastric cancer patients （134 males and 68 females） aged 33 to 94 years with pathologically confirmed diagnosis of gastric adenocarcinoma.RESULTS： The iNOS C150T polymorphism was not associated with gastric atrophy or with H pylori seropositivity. The odds ratio （OR） of the C/T ＋T/T for gastric cancer was increased without statistical significance （OR=1.19, 95% confidence interval （CI）： 0.68-2.08）. In the differentiated subgroup （n = 113）, however, the OR of the C/T genotvpe for gastric cancer was significant （OR = 2.02, 95% CI： 1.04-3.92） relative to the C/C genotype. In addition, considering the location of gastric cancer （n = 105）, there were significant differences between the controls and non-cardia group with the ORof 2.13 （95% CI： 1.08-4.18） for C/T and 1.94 （95% CI： 1.00-3.78） for C/T ＋ T/T.CONCLUSION： The iNOS C150T polymorphism is associated with the risk of H pylori-related gastric cancer in a Japanese population. This polymorphism may play an important role in increasing the risk of gastric cancer in Asian countires with the highest rates of gastric cancer.

Hidden Relaxation Channels in Aqueous Methylene Blue after Functionalization of Graphene Oxide Probed by Transient Absorption Spectroscopy

The mixture of graphene oxide （GO） and dye molecules may provide some new applications due to unique electronic, optical, and structural properties. Methylene blue （MB）, a typ- ical anionic dye, can attach on GO via π-π stacking and electrostatic interaction, and the molecule removal process on GO has been observed. However, it remains unclear about the ultrafast carrier dynamics and the internal energy transfer pathways of the system which is composed of GO and MB. We have employed ultrafast optical pump-probe spectroscopy to investigate the excited dynamics of the GO-MB system dispersed in water by exciting the samples at 400 nm pump pulse. The pristine MB and GO dynamics are also analyzed in tandem for a direct comparison. Utilizing the global analysis to fit the measured signal via a sequential model, five lifetimes are acquired：（0.61±0.01） ps, （3.52±0.04） ps, （14.1±0.3） ps, （84±2） ps, and （3.66±0.08） ns. The ultrafast dynamics corresponding to these lifetimes was analyzed and the new relaxation processes were found in the GO-MB system, compared with the pristine MB. The results reveal that the functionalization of GO can alter the known decay pathways of MB via the energy transfer from GO to MB in system, the increased intermediate state, and the promoted energy transfer from triplet state MB to ground state oxygen molecules dissolved in aqueous sample.

No association between cyclooxygenase-2 and uridine diphosphate glucuronosyltransferase 1A6 genetic polymorphisms and colon cancer risk

AIM：To investigate the association of variations in the cyclooxygenase-2 （COX2） and uridine diphosphate glucuronosyltransferase 1A6 （UGTIA6） genes and non-steroidal anti-inflammatory drugs （NSAIDs） use with risk of colon cancer.METHODS： NSAIDs, which are known to reduce the risk of colon cancer, act directly on COX2 and reduce its activity. Epidemiological studies have associated variations in the COX2 gene with colon cancer risk, but others were unable to replicate this finding. Similarly,enzymes in the UGT1A6 gene have been demonstrated to modify the therapeutic effect of NSAIDs on colon adenomas. Polymorphisms in the UGTIA6 gene have been statistically shown to interact with NSAID intake to influence risk of developing colon adenomas, but not colon cancer. Here we examined the association of tagging single nucleotide polymorphisms （SNPs） in the COX2 and UGTIA6 genes, and their interaction with NSAID consumption, on risk of colon cancer in a population of 422 colon cancer cases and 481 population controls.RESULTS： No SNP in either gene was individually statistically significantly associated with colon cancer, nor did they statistically significantly change the protective effect of NSAID consumption in our sample. Like others, we were unable to replicate the association of variants in the COX2 gene with colon cancer risk （P 〉 0.05）,and we did not observe that these variants modify the protective effect of NSAIDs （P 〉 0.05）. We were able to confirm the lack of association of variants in UGT1A6 with colon cancer risk, although further studies will have to be conducted to confirm the association of these variants with colon adenomas.CONCLUSION： Our study does not support a role of COX2 and UGTIA6 genetic variations in the development of colon cancer.

Association of the myeloperoxidase ^(468)G→K polymorphism with gastric inflammation and duodenal ulcer risk

AIM: To elucidate the relations between the myeloperoxidase ^(-468)G→a polymorphism and the development of duodenal ulcer (DU), and to investigate the impacts of this host genetic polymorphism on the histopathological features of Helicobacter pylori (H py/ori)-related gastritis. METHODS: In a case-control study of 115 consecutive DU patients and 182 controls, the myeloperoxidase ^(-468)G→A polymorphism was genotyped. Additionally, gastric mucosal changes were examined according to the updated Sydney System. RESULTS: The two study groups differed in the distributions of myeloperoxidase genotypes (P=0.008). All six individuals carrying myeloperoxidase A/A genotypes were in the DU group. The carriage of myeloperoxidase allele A and H pylori infection were associated with an increased risk of DU with odds ratios (OR) of 2.3 and 5.8, respectively. The combined risk of the carriage of myeloperoxidase allele A and H pylori infection for DU was 8.7 (95% CI, 3.5-21.8). In the H pylori-infected individuals, allele A carriers displayed higher bacterial density scores (P=0.04) in the antrum than did non-carriers. CONCLUSION: This work verifies for the first time the association of myeloperoxidase ^(-468)G→A polymorphism with antral H pylori density and DU disease. The mechanisms underlying this genetic polymorphism in developing DU disease merit further investigations.

Binding and Transformation of Extracellular DNA in Soil

DNA is the genetic material of various organisms. Extracellular DNA adsorbed or bound on surface-active particles in soils has been shown to persist for long periods against nucleases degradation and still retain the ability to transform competent cells. This paper reviews some recent advances on the binding and transformation of extracellular DNA in soils, which is fundamental to understanding the nature of the soil, regulating biodiversity, and assessing the risk of releasing genetically engineered microo…

Ultrafast Investigation of Excited-State Dynamics in Trans-4-methoxyazobenzene Studied by Femtosecond Transient Absorption Spectroscopy

The ultrafast photoisomerization and excited-state dynamics of trans-4-methoxyazobenzene (trans-4-MAB) in solutions were investigated by femtosecond transient absorption spectroscopy and quantum chemistry calculations. After being excited to the S2 state, the two-dimensional transient absorptions spectra show that cis-4-MAB is produced and witnessed by the permanent positive absorption in 400-480 nm. Three decay components are determined to be 0.11, 1.4 and 2.9 ps in ethanol, and 0.16, 1.5 and 7.5 ps in ethylene glycol, respectively. The fast component is assigned to the internal conversion from the S2 to S1 state. The other relaxation pathways are correlated with the decay of the S1 state via internal conversion and isomerization, and the vibrational cooling of the hot S0 state of the cis-isomer. Comparing of the dynamics in different solvents, it is demonstrated that the photoisomerization pathway undergoes the inversion mechanism rather than the rotation mechanism.

Effects of the myeloperoxidase 463 gene polymorphisms on development of atrophy in H pylori infected or noninfected gastroduodenal disease

AIM： To investigate the relationship between myeloperoxidase polymorphisms as a host-related factor and atrophy caused by H pylori. METHODS： Our study enrolled 77 patients. Biopsy materials obtained during gastrointestinal endoscopies were evaluated for the presence of H pylori. Polymerase chain reaction-restriction fragment length polymorphism assay was used to characterize myeloperoxidase genothpes. RESULTS： Forty four patients （57.1%） were lip （＋） and 33 （42.9%） were Hp （-）. Sixty six （85.7%） had GG genotype, 10 （12.9%） had GA genotype and 1 （1.29%） had AA genotype. The change in atrophy in relation to neutrophil infiltration was significant in Hp （＋） patients （P = 0.0001）. The change in atrophy in relation to neutrophil infiltration in patients with GG genotype was significant （P = 0.002）. However, the change in atrophy in relation to neutrophil infiltration was not significiant in patients with Hp （＋） GG genotype （r = 0.066, P = 0.63）. CONCLUSION： Myeloperoxidase genotype is critical for development of atrophy in relation to the severity of inflammation. However, it is interesting to note that, H pylori does not show any additive effect on development of atrophy.

Cyclooxygenase-2 polymorphisms and the risk of esophageal adeno-or squamous cell carcinoma

AIM： TO determine whether -1195 A→G and/or -765 G→C polymorphisms in Cyclooxygenase-2 CCOX-2） may have a risk modifying effect on the development of esophageal carcinoma in a Dutch Caucasian population. METHODS： Two study groups were recruited, 252 patients with esophageal carcinoma and 240 healthy controls, matched for race, age, gender and recruiting area. DNA was isolated from whole blood and used for genotyping. PCR products were digested with restriction enzymes and products were analyzed by agarose gel electrophoresis. Odds ratios （OR） and 95% confidence intervals （CI） were estimated. RESULTS： The distribution of the -1195A→G polymorphism was significantly different in esophageal cancer patients compared to controls. The -1195 GG genotype resulted in a higher risk of developing esophageal adenocarcinoma （OR = 3.85, 95% CI： 1.45-10.3） compared with the -1195AA genotype as a reference. The -765 G→C genotype distribution was not different between the two groups. The GG/ GG haplotype was present more often in esophageal adenocarcinoma patients than in controls （OR = 3.45, 95% CI： 1.24-9.58; with AG/AG as a reference）. The same trends were observed in patients with squamous cell carcinomas, however, the results did not reach statistical significance. CONCLUSION： Presence of the COX-2 -1195 GG genotype and of the GG/GG haplotype may result in a higher risk of developing esophageal carcinoma.

Reaction Kinetics between Thiobases and Singlet Oxygen Studied by Direct Detection of the 1O2 Luminescence Decay

Thiobase derivatives have received important investigations due to their wide usage as phototherapeutic agents and their potential carcinogenic side effects as immunosuppressants. The substitution of oxygen atom by the sulfur atom makes the ultraviolet absorption of thiobases redshifted and absorbs UVA light (>300 nm), resulting in unusual high quantum yield of triplet state to generate the singlet oxygen (1O2) through photosensitization. As a type of reactive oxygen species, 1O2 is highly reactive toward thiobases. Herein, we report the measurements of reaction rate constants between di erent thiobases and 1O2 in different solvents through the direct detection of 1O2 luminescence decay kinetics at 1270 nm. The rate constants of thiouracils with 1O2 are five times smaller than that of thioguanine with 1O2, which suggests that thiopurines are more reactive than thiopyrimidines and thus less suitable to be a photosensitive drug on the application of photodynamic therapy. Additionally, the rate constants of thiobases and 1O2 were found to be obviously influenced by the solvent polarity. With the increase of solvent polarity, the rate constants of thiobases and 1O2 decrease.