金属标准物质中杂质的辉光放电质谱法溯源分析

标准物质定值分析的溯源性要求比常规分析高很多。在常规分析中,有证标准物质（CRM）可用于校准以及建立可溯源性。尽管与标准物质生产和认定相关的ISO导则并没有十分明确地提到校准,但众多标准物质生产者在定值分析时却不接受基准标准物质用于校准。这些要求制约了标准物质定值方法的使用,因为这些方法可以采用已知高纯度的标准物质、化学计量法及已知高纯度标准物质的混合物进行校准。有效的固体取样技术,例如通常使用的块状标准物质进行校准的辉光放电质谱法（GD MS）或火花源发射光谱法（spark OES）,似乎不太适合定值分析。尤其是固体样品中痕量元素分析测定的有力工具辉光放电质谱法,除金属杂质外,使用特定气体混合物,这种方法也可以分析相关的非金属杂质如硫和磷。我们开发了一种可以使用已知高纯度的标准物质混合物和化学计量法的校准方法,这种校准方法同样可用于辉光放电质谱法。与溶液中基体匹配技术类似,此校准方法基于掺杂的粉末压片。本文还结合铜和钢标准物质的定值分析结果进行了陈述。     

The reliability and validity of the Perceived Stigmatization Questionnaire (PSQ) and the Social Comfort Questionnaire (SCQ) among an adult burn survivor sample.

In this study, 361 adult burn survivors completed the Perceived Stigmatization Questionnaire (PSQ), the Social Comfort Questionnaire (SCQ), and other measures. Both the PSQ and SCQ had good internal consistency indices. Factor analysis of the PSQ yielded 3 factors (absence of friendly behavior, confused/staring behavior, and hostile behavior). The SCQ had 1 factor. Conjoint factor analysis with measures of related constructs (body esteem, body-esteem importance, depression, social support) suggested that PSQ and SCQ measure distinct constructs. Correlations with the related psychosocial constructs and burn characteristics suggested the PSQ and SCQ have good convergent and discriminant validity. Limitations of the study are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quantitative detection of lactic acid bacteria in dried sourdoughs using real-time PCR

A real-time PCR system with 16S rRNA gene-targeted group-specific primers was developed to quantitatively detect lactic acid bacteria (LAB) of the genera Lactobacillus, Leuconostoc, Pediococcus, and Weissella in different types of commercially available dried sourdoughs. Despite a high degree of degradation in the DNA isolated from the doughs, the 341-bp 16S rRNA gene fragment of the sourdough LAB biota could specifically be amplified. For dried sourdoughs, the resulting calculated LAB cell counts were determined to be up to 3.7 × 10⁷ cells/g fresh dough, whereas in non-fermented dough acidifiers, used as a control, the calculated LAB cell counts did not exceed 3.6 × 10⁴ cells/g fresh dough. Moreover, the effect of low pH and/or high lactic acid concentrations prevailing in the doughs on the detectability of LAB cells in spray- and roller-dried sourdoughs by PCR was investigated. Drying of non-acidified sourdoughs still permitted to detect the LAB cells by PCR, whereas drying of acidified doughs reduced the detectable cell counts by approximately 5 (spray dried) and 2 (roller dried) orders of magnitudes. Incubation of acidified doughs for 24 h did not affect the detectability of LAB cells in spray-dried doughs but further reduced the detectable cell counts in roller-dried doughs by additional 2 orders of magnitude.     

Induction time studies of calcium carbonate in ethylene glycol and water

Induction time for precipitation of calcium carbonate precipitated in mono ethylene glycol and water has been studied by conductivity measurements at ethylene glycol concentrations of 0–90 wt% and temperatures from 25 to 80 °C. The supersaturation ratios, S, were in the range of 3–10. The effect of the solvent was separated from the effect of the supersaturation and temperature. Increasing the concentration of ethylene glycol prolongs the induction times for precipitation of CaCO₃ considerably although the supersaturation actually increases, especially at lower temperatures. It was shown that this effect cannot be explained by the change in the interfacial tension. Induction time studies in seeded and unseeded experiments were performed in order to separate changes in the nucleation rate from the impact of the growth time in the varying solvent compositions. The results show that crystal growth is retarded, causing the increased induction time in ethylene glycol containing solutions, and hence that the nucleation rate is actually promoted by ethylene glycol. The nucleation rates determined by measured particle numbers and induction times from unseeded experiments were underestimated for the same reason, thereby illustrating the complexity of nucleation rate investigations in mixed solvents.     

Effects of systematic partial volume errors on the estimation of gray matter cerebral blood flow with arterial spin labeling MRI

Objective

Partial volume (PV) correction is an important step in arterial spin labeling (ASL) MRI that is used to separate perfusion from structural effects when computing the mean gray matter (GM) perfusion. There are three main methods for performing this correction: (1) GM-threshold, which includes only voxels with GM volume above a preset threshold; (2) GM-weighted, which uses voxel-wise GM contribution combined with thresholding; and (3) PVC, which applies a spatial linear regression algorithm to estimate the flow contribution of each tissue at a given voxel. In all cases, GM volume is obtained using PV maps extracted from the segmentation of the T1-weighted (T1w) image. As such, PV maps contain errors due to the difference in readout type and spatial resolution between ASL and T1w images. Here, we estimated these errors and evaluated their effect on the performance of each PV correction method in computing GM cerebral blood flow (CBF).

Materials and methods

Twenty-two volunteers underwent scanning using 2D echo planar imaging (EPI) and 3D spiral ASL. For each PV correction method, GM CBF was computed using PV maps simulated to contain estimated errors due to spatial resolution mismatch and geometric distortions which are caused by the mismatch in readout between ASL and T1w images. Results were analyzed to assess the effect of each error on the estimation of GM CBF from ASL data.

Results

Geometric distortion had the largest effect on the 2D EPI data, whereas the 3D spiral was most affected by the resolution mismatch. The PVC method outperformed the GM-threshold even in the presence of combined errors from resolution mismatch and geometric distortions. The quantitative advantage of PVC was 16% without and 10% with the combined errors for both 2D and 3D ASL. Consistent with theoretical expectations, for error-free PV maps, the PVC method extracted the true GM CBF. In contrast, GM-weighted overestimated GM CBF by 5%, while GM-threshold underestimated it by 16%. The presence of PV map errors decreased the calculated GM CBF for all methods.

Conclusion

The quality of PV maps presents no argument for the preferential use of the GM-threshold method over PVC in the clinical application of ASL.

     

Ultra‐Performance Liquid Chromatography‐Mass Spectrometry Analysis of Free and Esterified Oxygenated Derivatives from Docosahexaenoic Acid in Rat Brain

Docosahexaenoic acid (DHA), a prominent long‐chain fatty acid of the omega‐3 family, is present at high amount in brain tissues, especially in membrane phospholipids. This polyunsaturated fatty acid is the precursor of various oxygenated lipid mediators involved in diverse physiological and pathophysiological processes. Characterization of DHA‐oxygenated metabolites is therefore crucial for better understanding the biological roles of DHA. In this study, we identified and measured, by ultrahigh‐performance liquid chromatography coupled with tandem mass spectrometry, a number of oxygenated products derived from DHA in exsanguinated and nonexsanguinated brains. These metabolites were found both in free form and esterified in phospholipids. Interestingly, both (R)‐ and (S)‐monohydroxylated fatty acid stereoisomers were observed free and esterified in phospholipids. Monohydroxylated metabolites were the main derivatives; however, measurable amounts of dihydroxylated products such as protectin DX were detected. Moreover, exsanguination allowed discriminating brain oxygenated metabolites from those generated in blood. These results obtained in healthy rats allowed an overview on the brain oxygenated metabolism of DHA, which deserves further research in pathophysiological conditions, especially in neurodegenerative diseases.     

NaWuReT-Workshop: Forschung in der Reaktionstechnik für und mit der Gesellschaft

In this article, the results of the NaWuReT (Early Career Reaction Engineers) workshop on the topic “Are we doing relevant science?” are presented. The topics “(In)surmountable hurdles for Citizen Scientists in reaction engineering?” and “Circular Economy in reaction engineering with/for society?” were discussed. Therefrom, a variety of ideas and suggestions were extracted.     

Mass Spectrometry-Based Proteomics Reveal Alcohol Dehydrogenase 1B as a Blood Biomarker Candidate to Monitor Acetaminophen-Induced Liver Injury

Acute liver injury (ALI) is a severe disorder resulting from excessive hepatocyte cell death, and frequently caused by acetaminophen intoxication. Clinical management of ALI progression is hampered by the dearth of blood biomarkers available. In this study, a bioinformatics workflow was developed to screen omics databases and identify potential biomarkers for hepatocyte cell death. Then, discovery proteomics was harnessed to select from among these candidates those that were specifically detected in the blood of acetaminophen-induced ALI patients. Among these candidates, the isoenzyme alcohol dehydrogenase 1B (ADH1B) was massively leaked into the blood. To evaluate ADH1B, we developed a targeted proteomics assay and quantified ADH1B in serum samples collected at different times from 17 patients admitted for acetaminophen-induced ALI. Serum ADH1B concentrations increased markedly during the acute phase of the disease, and dropped to undetectable levels during recovery. In contrast to alanine aminotransferase activity, the rapid drop in circulating ADH1B concentrations was followed by an improvement in the international normalized ratio (INR) within 10–48 h, and was associated with favorable outcomes. In conclusion, the combination of omics data exploration and proteomics revealed ADH1B as a new blood biomarker candidate that could be useful for the monitoring of acetaminophen-induced ALI.     

Hyperhomocysteinemia and Cardiovascular Disease: Is the Adenosinergic System the Missing Link?

The influence of hyperhomocysteinemia (HHCy) on cardiovascular disease (CVD) remains unclear. HHCy is associated with inflammation and atherosclerosis, and it is an independent risk factor for CVD, stroke and myocardial infarction. However, homocysteine (HCy)-lowering therapy does not affect the inflammatory state of CVD patients, and it has little influence on cardiovascular risk. The HCy degradation product hydrogen sulfide (H₂S) is a cardioprotector. Previous research proposed a positive role of H₂S in the cardiovascular system, and we discuss some recent data suggesting that HHCy worsens CVD by increasing the production of H₂S, which decreases the expression of adenosine A_2A receptors on the surface of immune and cardiovascular cells to cause inflammation and ischemia, respectively.