Ligand exchange processes between molybdenum and zinc additives in lubricants: evidence from NMR (1H, 13C, 31P) and HPLC-MS analysis

The tribological performances of engine oils have been shown to be enhanced by the synergistic interactions between Mo dithiocarbamates (Mo(DTC)₂) with other additives, and notably Zn dithiophosphates (Zn(DTP)₂). Being two key components in formulated lubricants, a detailed understanding of the mechanisms involved between these two types of additives is needed to develop engine oils with enhanced friction reduction performances, and improved fuel economy. In this context, we report here the investigation at the molecular level of the interactions between Mo and Zn complexes with DTC and DTP ligands using laboratory experiments. Our analytical approach comprised NMR spectroscopy (¹H, ¹³C, ³¹P) allowing direct investigation of both homoleptic and heteroleptic Mo and Zn complexes as well as a specifically-developed HPLC-MS method for the investigation of the different DTC species formed during lubricant ageing experiments. The results showed that ligand exchange reactions between Mo(DTP)₂ and Zn(DTC)₂ complexes strongly favor the migration of the DTC ligands from Zn to Mo, illustrating the higher affinity of Mo for DTC ligands. In the case of binary mixtures involving Mo(DTC)₂ and Zn(DTP)₂ – a combination of additives frequently used in formulated lubricants – the formation of mixed complexes (Mo(DTC)(DTP)) resulting from ligand exchange reactions could be directly evidenced for the first time by the analytical methods used. These species could account, at least to some extent, for the synergistic effect of Mo(DTC)₂ and Zn(DTP)₂ on the friction reducing properties of engine oils. However, they were formed in significantly lower proportions than those previously reported in the literature using indirect methods.

First direct molecular evidence of ligand exchange between Mo and Zn complexes from lubricants.     

Fully-automated detection of cerebral water content changes: study of age- and gender-related H2O patterns with quantitative MRI

We present a simple and robust method for the automated image analysis of quantitative cerebral water content maps acquired with MRI. The method is based on a new approach for the absolute and quantitative mapping of water content in vivo. Water content maps were automatically segmented into grey and white matter by employing the quantitative T1 information acquired as part of the water content mapping procedure. Based on the segmented maps, twenty-two parameters sensitive to both absolute water content and its spatial organisation are automatically extracted without user interaction. The parameters include, amongst others, absolute water content in grey and white matter and spatial asymmetries of the cerebral water content distribution. Significant age- and gender-related changes in the parameters determined were observed in a study of forty-four healthy subjects. Most notably, the grey matter water content decreases at a rate of 0.034%/year for females between the 3rd and 8th decade of life, whilst a much stronger decrease is observed in males which sets in after the 5th decade of life. In addition, female grey matter water content is, on average, 1.2% higher than the respective male grey matter water content. In contrast to the heterogeneity observed in grey matter, no significant physiological variation was observed for white matter water content. In addition to absolute grey matter water content, characteristic age- and gender-specific variations were also observed in most of the other variables. To check the potential loss of information associated with the large reduction of the dimensionality of the dataset to 22 parameters only, the age and gender of each individual subject were predicted by employing robust linear discriminant analysis based on only the determined twenty-two variables. The median deviation between predicted and real age was 6.3 years resulting in a high correlation coefficient between both values (r = 0.69). Gender is correctly predicted in 68.2% of all cases which improves to 87.5% when age-dependent effects are first corrected, demonstrating the high information content present in the variables even though the dimension of the dataset was significantly reduced. These results form the baseline for future studies of cerebral pathology. The method presented is fully automated, robust and flexible, making it an ideal tool for routine application in both neuroscientific studies and clinical diagnosis based on the quantitative measurement of cerebral water content.     

An indirect analytical approach based on ATR-FTIR spectroscopy for determining the FFA content in vegetable oils

In this study, we developed a novel approach for determining a free fatty acid (FFA) in vegetable oils using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. FFA was converted to carboxylate species by a reaction with phthalimide potassium salt, and the linear relationship between FFA content and ATR-FTIR peak areas at 1541–1616 cm⁻¹ (1595 cm⁻¹ as baseline) was established. Results showed that the R² values obtained during calibration and validation were more than 0.99. The calibration method concurred to within ±0.035% over the range of 0.4% to 4.0% (quantitative determination of the percentage of FFA in oils, expressed as the percentage of oleic acid). In the calibration model, the root mean square error of prediction was 0.0104, the relative error was less than 0.246% and the relative average deviation was 0.386%, respectively. These indexes demonstrated that the calibration model has great accuracy, high precision and good stability. The indirect method established using ATR-FTIR has the advantages of excellent reproducibility, high exactitude, independent of oil type, simple operation and easy cleaning of the instrument surface. The slope of the verification equation between FFA prediction values and American Oil Chemists'' Society''s (AOCS) titration method was close to 1, R² value was more than 0.99. These indicators suggested that the proposed method and the AOCS method have a good correlation through AOCS titration and ATR–FTIR spectroscopy to determine validation samples parallel. In addition, for comparison, when the AOCS titration and ATR-FTIR spectroscopy methods were used for sample validation, the results indicated that the latter method is more reproducible, highly sensitive and has strong anti-disturbance. Therefore, the ATR-FTIR technique can be applied as a simple, highly sensitive, convenient and timely method for the analysis of FFAs in oils.

In this study, we developed a novel approach for determining a free fatty acid (FFA) in vegetable oils using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy.     

A method for serum C1q based on its hydroxyproline content

The radial immunodiffusion assay overestimates the C1q in serum. Here we describe a convenient, accurate procedure for measuring C1q in 250 microL of dialyzed serum. This method is based on our previous findings that all C1q in serum precipitates with the euglobulin fraction and that all other serum proteins containing hydroxyproline are excluded from this fraction. Because C1q is 4.3% hydroxyproline, the concentration of C1q in serum can therefore be calculated from the hydroxyproline content of the euglobulin fraction. The procedure, all done in the same tube, consists of precipitating the euglobulin fraction, digesting it with HClO4, and converting hydroxyproline to the corresponding pyrrole, which is extracted with toluene and measured by absorbance at 560 nm.     

Structural changes,thermodynamic properties, 1H magic angle spinning NMR,and 14N NMR of (NH4)2CuCl4·2H2O

The structural changes and thermodynamic properties of (NH₄)₂CuCl₄·2H₂O were studied by differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. In addition, the chemical shift, line width, and spin-lattice relaxation time of the crystals were also investigated by ¹H magic angle spinning nuclear magnetic resonance (MAS NMR), focusing on the role of NH₄ and H₂O near the phase transition temperature. The change at T_C2 (=406 K) and T_C3 (=437 K) seems to be a chemical change caused by thermal decomposition rather than a physical change such as a structural phase transition. The changes in the temperature dependence of these data near T_C2 are related to variations in the environments surrounding NH₄ and H₂O. The ¹⁴N NMR spectrum is also measured in order to investigate local phenomena related to the phase transition.

The structural changes and thermodynamic properties of (NH₄)₂CuCl₄·2H₂O were studied by differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, and nuclear magnetic resonance (NMR).     

Ionic dynamics of the cation in organic–inorganic hybrid compound (CH3NH3)2MCl4 (M = Cu and Zn) by 1H MAS NMR, 13C CP MAS NMR,and 14N NMR

The ionic dynamics of (CH₃NH₃)₂MCl₄ (M = Cu, Zn) by ¹H magic-angle spinning (MAS) nuclear magnetic resonance (NMR), ¹³C cross-polarization (CP) MAS NMR, and ¹⁴N NMR are investigated as a function of temperature with a focus on the role of the CH₃NH₃⁺ cation. The molecular motions in (CH₃NH₃)₂MCl₄ are also discussed based on the ¹H spin–lattice relaxation time in the rotating coordinate frame T_1ρ. From the ¹H T_1ρ results, the activation energies for the tumbling motion of ¹H for CH₃ and NH₃ were similar, and the uniaxial rotations occurred within a large temperature range. The molecular motions for ¹³C and ¹⁴N of the main chain in the CH₃NH₃⁺ cation were rigid, whereas those for ¹H of the side chain in the CH₃NH₃⁺ cation were very free at high temperatures. T_1ρ provides insight into the changes in the cation reorientation rates induced by heating at high temperatures.

The ionic dynamics of (CH₃NH₃)₂MCl₄ (M = Cu, Zn) by ¹H MAS NMR, ¹³C CP MAS NMR, and ¹⁴N NMR are investigated as a function of temperature with a focus on the role of the CH₃NH₃⁺ cation.     

基于压缩感知的3DmDixonQuant对腰椎椎体脂肪含量的定量研究

目的 探讨敏感度编码(sensitivity encoded,SENSE)和压缩感知(compressed SENSE,CS)不同加速因子(acceleration factor,AF)对3D mDixon Quant技术腰椎椎体脂肪定量的影响,并分析腰椎椎体脂肪含量(fat fraction,FF)与年龄、性别和体质...     

Design and simulation of a multilayer Halbach magnet for NMR

Halbach magnet is a type of permanent magnet generating a relatively high and homogeneous magnetic field. It is suitable for Nuclear Magnetic Resonance (NMR) studies of small volume chemical or biological samples. In this article, the model of a Halbach magnet made from an odd number of cylindrical layers is proposed for the first time. Then after the optimization of interlayer distances for odd layers Halbach cylinders, the model is verified by the simulation with a magnet inner radius of 30 mm and an outer radius of 49 mm. Moreover, the disturbance of uniformity in 5 mm DSV (Diameter of Spherical Volume) is presented with errors in magnetic strength and angular variation. As a result, a minimum uniformity of 46 ppm inside a 5 mm DSV is achieved, while it increases practically in the presence of magnetic blocks errors. The good performance of the Halbach magnet with odd layers may find potential applications in NMR. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 45B: 134–141, 2015     

Interaction of beta1H globulin with cell-bound C3b: quantitative analysis of binding and influence of alternative pathway components on binding

Purified beta1H globulin (beta1H) was shown to bind to C3b coated cells by both immunofluorescent and radioactive tracer techniques. With EAC43, the amount of beta1H bound was directly proportional to the amount of C3 used to prepare the cells; EA, EAC14 and EAC14oxy2 bound very small amounts of beta1H. The C3b binding site on beta1H was labile in that not all of the purified 125I-beta1H was capable of binding to C3b, even when an excess of cell-bound C3b was present. Scatchard analysis of binding of beta1H to C3b-coated cells indicated an equilibrium constant of 10(9) L/M. Deviations from linearity were regularly found on Scatchard analyses. This was consistent with the hypothesis that the beta1H binding sites exhibit negative cooperativity in that as more sites become occupied, it becomes more difficult to fill the remaining sites. The stoichiometry of the reaction between C3b and beta1H was examined using EAC14oxy23 prepared with 131I-C3 and beta1H labeled with 125I. Between 0.5--0.8 beta1H molecules were bound per C3b molecule. Other alternative pathway components influenced the binding of 125I-beta1H to cell bound C3b. Both C3b and native C3 inhibited binding of labeled beta1H at an efficiency approximately 1/1,000 that of unlabeled beta1H. Factor B inhibited binding with 1/280 the efficiency of unlabeled beta1H. Properdin caused a dose-dependent increase in the binding of beta1H; this enhancement was abrogated if B was also present in the reaction mixture. Scatchard analysis indicated that the enhancement of beta1H binding by P resulted in an increased number of available binding sites rather than an increase in the affinity of binding.     

基于TaqMan探针的幽门螺杆菌实时荧光定量PCR检测方法的建立

目的探讨基于TaqMan探针的幽门螺杆菌23SrDNA基因片段的实时荧光定量PCR检测的有效方法。方法根据幽门螺杆菌23SrDNA序列设计引物和探针,构建质粒标准品,建立实时荧光定量PCR体系并进行方法学评价,并对2012年5月至10月收集的100份临床样本进行检测同时应用免疫组化及银染方法进行比较分析。结果建立了检测23SrDNA的实时荧光定量PCR方法：107-102copies/ul范围内均有＂S＂型扩增曲线,最低检测浓度为102copies/ul,标准曲线相关系数为1。对临床其它消化道病原体不出现特异性的扩增曲线。对100份样本进行检测,实时荧光定量PCR能检出31份阳性,而免疫组化方法能检出25份阳性,银染方法能检出28份阳性。结论实时荧光定量PCR方法可成功检测幽门螺杆菌,且该方法具有灵敏度和特异性高及重复性好等优点。     

Diagnosis of alkaptonuria by NMR urinalysis: rapid qualitative and quantitative analysis of homogentisic acid

Urinalysis of alkaptonuria using NMR spectroscopy revealed the abnormal amount of homogentisic acid. Qualitative and quantitative determination was performed simultaneously with untreated urine sample and within 15 min.     

基于内容分析法的疼痛资源护士岗位胜任力元素分析

目的 对国内外疼痛资源护士相关文献进行内容分析,为构建本土疼痛资源护士岗位胜任力指标体系提供参考.方法 检索国内外疼痛资源护士相关文献,以岗位胜任力理论为指导,采用内容分析法对符合纳排标准的文献进行内容分析.结果 最终纳入文献29篇,提取出专业能力、知识与经验、专业技能、职业态度及个人特质5个主题及26项次级类目.结论...     

Revision of the structure of isochaetoglobosin Db based on NMR analysis and biosynthetic consideration

Isochaetoglobosin D_b is a new chaetoglobosin possessing a unique 3,4-substituted pyrrole ring isolated and named by Qiu et al., and it is different from any one of the 14 sub-types in the macrocyclic ring of chaetoglobosins classified in our previous work. Its chemical shift values, coupling constants and biosynthetic consideration implied that the proposed structure of isochaetoglobosin D_b was incorrect. In this report, based on detailed NMR data analysis together with biosynthetic consideration, the structure of isochaetoglobosin D_b is suggested to be revised to that of penochalasin C. The NMR spectra of penochalasin C measured in the same solvent (DMSO-d₆) as that of isochaetoglobosin D_b supported the above conclusion. The results imply that reasonable biosynthetic consideration could complement spectroscopic structural determination, and also support that the ¹H-NMR rule of chaetoglobosin summarized in our previous work can provide help for dereplication and rectification.

Isochaetoglobosin D_b is a new chaetoglobosin possessing a unique 3,4-substituted pyrrole ring isolated and named by Qiu et al., and it is different from any one of the 14 sub-types in the macrocyclic ring of chaetoglobosins classified in our previous work.     

Effect of pyrolysis temperature on sulfur content,extractable fraction and release of sulfate in corn straw biochar

The contents and release of the nutrient elements N, P and K in biochars have been investigated. Sulfur is an indispensable element for plants, but its content and release in biochar are still unclear. The effect of pyrolysis temperature (300, 500 and 700 °C) on the sulfur content, extractable fraction and release of sulfate in corn straw biochars (CS300, CS500 and CS700) was investigated. The biochars were characterized using element analysis, BET, FTIR, and XRD. It was shown that the contents of sulfur in biochars decreased significantly with increasing pyrolysis temperature. The extraction results indicated that the percentages of water extractable-sulfate (W–SO₄²⁻) and organosulfur in biochars decreased while those of HCl- and NaH₂PO₄-extractable sulfate (HCl–SO₄²⁻, NaH₂PO₄–SO₄²⁻) increased with pyrolysis temperature. Batch release experiments were conducted to test the effect of contact time and addition of Hoagland nutrient solution (HNS) on the release of sulfate from biochars. The release kinetics fitted well with a pseudo-second-order model. Approximately 10.7 mg g⁻¹ of sulfate was released from CS300 during the initial 2 h, whereas 6.32 and 3.93 mg g⁻¹ were released from CS500 and CS700, respectively. Increasing the amounts of HNS led to negative effects on sulfate release. The results indicate that low-temperatures might be optimal for producing biochar from corn straw to improve the sulfur fertilization.

Low pyrolysis temperature is optimal for biochar to release sulfate and the release kinetics fitted well with a pseudo-second-order model.     

Characterization of ovarian tissue based on quantitative analysis of photoacoustic microscopy images

In this paper, human ovarian tissue with malignant and benign features was imaged ex vivo using an optical-resolution photoacoustic microscopy (OR-PAM) system. The feasibility of PAM to differentiate malignant from normal ovarian tissues was explored by comparing the PAM images morphologically. Based on the observed differences between PAM images of normal and malignant ovarian tissues in microvasculature features and distributions, seven features were quantitatively extracted from the PAM images, and a logistic model was used to classify ovaries as normal or malignant. 106 PAM images from 18 ovaries were studied. 57 images were used to train the seven-parameter logistic model, and a specificity of 92.1% and a sensitivity of 89.5% were achieved; 49 images were then tested, and a specificity of 81.3% and a sensitivity of 88.2% were achieved. These preliminary results demonstrate the feasibility of our PAM system in mapping microvasculature networks as well as characterizing the ovarian tissue, and could be extremely valuable in assisting surgeons for in vivo evaluation of ovarian tissue during minimally invasive surgery.OCIS codes: (110.5120) Photoacoustic imaging, (170.3880) Medical and biological imaging     

Human complement C3b inactivator: isolation, characterization, and demonstration of an absolute requirement for the serum protein beta1H for cleavage of C3b and C4b in solution

The complement regulatory enzyme, C3b inactivator (C3bINA), has been purified from human serum by affinity chromatography on an anti-C3bINA Sepharose column. Subsequent chromatography on DEAE-cellulose and removal of IgG with anti-IgG Sepharose resulted in a product which was found to be homogeneous by polyacrylamide gel electrophoresis at pH 8.9 and by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecule is composed of two disulfide bonded polypeptide chains with mol wt of 50,000 and 38,000 daltons. Human CobINA was found to be a glycoprotein containing at least 10.7% carbohydrate and to have a normal serum concentration of 34 +/- 7 mug/ml (mean +/- 1 SD). Highly purified C3bINA cleaved neither free C3b nor free C4b if trace amounts of contaminating beta1H were removed from these proteins with anti-beta1H Sepharose. However, in the presence of highly purified beta1H and C3bINA, both C3bIna, both C3b and C4b were cleaved. Incubation of native C3 or C4 with C3bINA and beta1H had no effect on their cleaved. Incubation of native C3 or C4 with C3bINA and beta1H had no effect on their structure. The action of C3bINA and beta1H on C3b produced two fragments of the alpha1-chain which did not dissociate without reduction of the molecule. These fragments have mol wt of 67,000 and 40,000 daltons. The action of C3bINA and beta1H on C4b resulted in cleavage of the alpha'-chain giving rise to the 150,000-dalton C4c and the 49,000-dalton C4d fragments which dissociated without reduction. To produce from C3b the immunochemically defined C3c and C3d, fragments, the action of an additional serum enzyme appears to be required, the effect of which can be mimicked by trypsin.     

Development and release characterization of hyaluronan-doxycycline gels based on metal coordination.

A simple mixing with hyaluronan (HA), doxycycline (DC) and divalent metal cation in an aqueous solution enabled a thermoreversible water-soluble gel to form. For the cross-linking, two kinds of interactions were supposed. One was an electrostatic interaction between a positively charged group in DC and a negatively charged carboxyl function of HA, and the other was a chelation at the phenolic diketone moiety in DC. Since the gel was formed physically, the critical polymer concentration for gelation was present, and it was about 0.05% for HA with a molecular weight of 1.6x10(6). The hydrogel would be formed holding water in the HA entanglement network when DCs on HA chains made coordinate bonds through metal chelation. By changing the mixing ratio, two types of gels with different characteristics in drug release could be prepared. One was a gel with zero-order release prepared by mixing the same amount of HA and DC in equivalent. The other was a gel indicating Fickian diffusion-type release by mixing more DC than HA. Further, by controlling the absolute concentration of HA and DC, or the molecular weight of HA, some gels with desired release profiles could be prepared.     

国内全麻患者术前麻醉评估单内容分析

目的分析国内全麻患者术前麻醉评估单的结构层次和文字表达,为改善临床评估效率,实现基于病例信息系统电子化评估提供依据。方法采用方便抽样法,于2017年11月—2018年3月收集了国内三甲医院的成人全麻患者麻醉术前评估单。采用内容分析法对临床评估单进行文献内容分析,应用2013版EXCEL软件对资料进行整合分析。结果共获得22份临床评估单,共析出评估单名称、一般人口学信息、疾病史、体格检查、实验室检查、总体评估六大主题,22份评估单均提及的项目包括姓名、床号、术前诊断、拟施手术、用药史、过敏史、麻醉史、血压、ASA病情估计分级。结论目前各省市临床麻醉术前评估单内容有差异,但部分省市已经实现全省统一。对尚不统一的评估内容今后可根据指南推荐内容结合我国国情进行统一规范。     

基于内容分析法对2型糖尿病患者自我管理现状的研究

目的:了解2型糖尿病患者的自我管理体验,明确2型糖尿病患者自我管理中存在的问题。方法:采用深入访谈法对13例2型糖尿病患者进行访谈,运用Berelson.B(1957)内容分析法进行资料分析。结果:共形成172个自我管理行为分析单元以及饮食、运动、用药、血糖监测4个类目,其中自我管理行为完全按要求进行的分析单元占40.70%,部分按要求进行的分析单元占28.49%,没有按要求进行的分析单元占30.81%。在没有按要求进行的分析单元中饮食和血糖监测占到了20.93%。结论:2型糖尿病患者的自我管理行为有待进一步提高,患者进行的自我管理行为不均衡。