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31.
32.
Tarnishing layers grown on copper exposed to air contaminated by traces of sulfur dioxide and/or hydrogen sulfide were detected by a coulometric and characterized by a chemical method. Depending on the nature of the corrosive gas, or on the use of a gas mixture, it was found that sulfate, sulfide, oxides or a mixed oxide-sulfide compound could be formed in these conditions. The same tarnishing products were found, either in hydrogen sulfide or in a sulfur dioxide + hydrogen sulfide mixture, and the same linear growth law of the copper (I) sulfide was also found, within the limits of the duration of the corrosion test, in the two gaseous environments. 相似文献
33.
Seung Chul Yoon Kurt C. Lawrence John E. Line Gregory R. Siragusa Peggy W. Feldner Bosoon Park William R. Windham 《Sensing and Instrumentation for Food Quality and Safety》2010,4(1):35-49
The presence of Campylobacter in foods of animal origin is the leading cause of bacterially induced human gastroenteritis. Isolation and detection of Campylobacter in foods via direct plating involves lengthy laboratory procedures including enrichments and microaerobic incubations, which
take several days to a week. The incubation time for growing Campylobacter colonies in agar media usually takes 24–48 h. Oftentimes the problem is the difficulty of visually differentiating Campylobacter colonies from non-Campylobacter contaminants that frequently grow together with Campylobacter on many existing agars. In this study, a new screening technique using non-destructive and non-contact hyperspectral imaging
was developed to detect Campylobacter colonies in Petri dishes. A reflectance spectral library of Campylobacter and non-Campylobacter contaminants was constructed for characterization of absorption features in wavelengths from 400 to 900 nm and for developing
classification methods. Blood agar and Campy-Cefex agar were used as culture media. The study found that blood agar was the
better culture medium than Campy-Cefex agar in terms of Campylobacter detection accuracy. Classification algorithms including single-band thresholding, band-ratio thresholding and spectral feature
fitting were developed for detection of Campylobacter colonies as early as 24 h of incubation time. A band ratio algorithm using two bands at 426 and 458 nm chosen from continuum-removed
spectra of the blood agar bacterial cultures achieved 97–99% of detection accuracy. This research has profound implications
for early detection of Campylobacter colonies with high accuracy. Also, the developed hyperspectral reflectance imaging protocol is applicable to other pathogen
detection studies. 相似文献
34.
Line Svennesen Søren S. Nielsen Yasser S. Mahmmod Volker Krömker Karl Pedersen Ilka C. Klaas 《Journal of dairy science》2019,102(1):629-639
The objective of this study was to investigate the association between teat skin colonization and intramammary infection (IMI) with Staphylococcus aureus or Streptococcus agalactiae at the quarter level in herds with automatic milking systems. Milk and teat skin samples from 1,142 quarters were collected from 300 cows with somatic cell count >200,000 cells/mL from 8 herds positive for Strep. agalactiae. All milk and teat skin samples were cultured on calf blood agar and selective media. A subset of samples from 287 quarters was further analyzed using a PCR assay (Mastit4 PCR; DNA Diagnostic A/S, Risskov, Denmark). Bacterial culture detected Staph. aureus in 93 (8.1%) of the milk samples and 75 (6.6%) of the teat skin samples. Of these, 15 (1.3%) quarters were positive in both the teat skin and milk samples. Streptococcus agalactiae was cultured in 84 (7.4%) of the milk samples and 4 (0.35%) of the teat skin samples. Of these, 3 (0.26%) quarters were positive in both the teat skin and milk samples. The PCR detected Staph. aureus in 29 (10%) of the milk samples and 45 (16%) of the teat skin samples. Of these, 2 (0.7%) quarters were positive in both the teat skin and milk samples. Streptococcus agalactiae was detected in 40 (14%) of the milk samples and 51 (18%) of the teat skin samples. Of these, 16 (5.6%) quarters were positive in both the teat skin and milk samples. Logistic regression was used to investigate the association between teat skin colonization and IMI at the quarter level. Based on bacterial culture results, teat skin colonization with Staph. aureus resulted in 7.8 (95% confidence interval: 2.9; 20.6) times higher odds of Staph. aureus IMI, whereas herd was observed as a major confounder. However, results from the PCR analyses did not support this association. Streptococcus agalactiae was isolated from the teat skin with both PCR and bacterial culture, but the number of positive teat skin samples detected by culture was too low to proceed with further analysis. Based on the PCR results, Strep. agalactiae on teat skin resulted in 3.8 (1.4; 10.1) times higher odds of Strep. agalactiae IMI. Our results suggest that Staph. aureus and Strep. agalactiae on teat skin may be a risk factor for IMI with the same pathogens. Focus on proper teat skin hygiene is therefore recommended also in AMS. 相似文献
35.
Grigoriev O.N. Zhunkovski H.L. Vedel D.V. Bega M.D. 《Powder Metallurgy and Metal Ceramics》2020,58(9-10):508-513
Powder Metallurgy and Metal Ceramics - The interaction of hafnium boride and chromium in the HfB2–Cr system is studied. Solid-phase interaction occurs at temperatures up to 1650 ±... 相似文献
36.
Three epiphytic old forest lichens (Usnea longissima, Pseudocyphellaria crocata, and Lobaria pulmonaria) were transplanted along a natural shade–sun gradient comprising three successional stages in boreal spruce forests (dense
young forest, open old forest, and clear-cut) for one summer. After harvest, extractable secondary compounds were analyzed
by high-performance liquid chromatography, and the brown pigmentation in melanic species was quantified by reflectance measurements.
Cortical compounds in all species increased from shady young forests to exposed clear-cuts. Usnic acid, the major cortical,
secondary compound in U. longissima, showed consistently higher concentration in the clear-cut than in the two forested stands. Pseudocyphellaria crocata and L. pulmonaria, lacking extractable secondary compounds in the cortex, significantly increased their amounts of cortical melanins in well-lit
stands. The medullary compounds showed more complex responses. Many were not influenced by environmental conditions during
the transplantation, whereas the majority of those that responded showed the lowest concentration in clear-cut transplants.
Only a few medullary compounds showed the highest concentration in the clear-cut, and at a low level of significance. The
synthesis of UV-B-absorbing usnic acid and melanins seems to be part of an acclimation to increased light exposure. The medullary
compounds in studied species barely function as solar screens despite their strong UV-B absorbance. 相似文献
37.
Brambilla D Verpillot R Taverna M De Kimpe L Le Droumaguet B Nicolas J Canovi M Gobbi M Mantegazza F Salmona M Nicolas V Scheper W Couvreur P Andrieux K 《Analytical chemistry》2010,82(24):10083-10089
A novel application of capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) was proposed to efficiently detect and monitor the interaction between polymeric nanoparticles and the β-Amyloid peptide (Aβ(1-42)), a biomarker for Alzheimer's Disease (AD), at concentrations close to physiological conditions. The CE-LIF method allowed the interaction between PEGylated poly(alkyl cyanoacrylate) nanoparticles (NPs) and the soluble Aβ(1-42) peptide monomers to be highlighted. These results were confirmed by surface plasmon resonance (SPR) and confocal laser scanning microscopy (CLSM). Whereas SPR showed an interaction between the NPs and the Aβ(1-42) peptide, CLSM allowed the formation of large aggregates/assemblies at high NP and peptide concentrations to be visualized. All these results suggested that these nanoparticles could bind the Aβ(1-42) peptide and influence its aggregation kinetics. Interestingly, the non-PEGylated poly(alkyl cyanoacrylate) NPs did not alter the aggregation kinetics of the Aβ(1-42) peptide, thus emphasizing the high level of discrimination of the CE-LIF method with respect to NPs. 相似文献
38.
39.
Larsen EK Nielsen T Wittenborn T Rydtoft LM Lokanathan AR Hansen L Østergaard L Kingshott P Howard KA Besenbacher F Nielsen NC Kjems J 《Nanoscale》2012,4(7):2352-2361
Iron oxide nanoparticles have found widespread applications in different areas including cell separation, drug delivery and as contrast agents. Due to water insolubility and stability issues, nanoparticles utilized for biological applications require coatings such as the commonly employed polyethylene glycol (PEG). Despite its frequent use, the influence of PEG coatings on the physicochemical and biological properties of iron nanoparticles has hitherto not been studied in detail. To address this, we studied the effect of 333-20,000 Da PEG coatings that resulted in larger hydrodynamic size, lower surface charge, longer circulation half-life, and lower uptake in macrophage cells when the particles were coated with high molecular weight (M(w)) PEG molecules. By use of magnetic resonance imaging, we show coating-dependent in vivo uptake in murine tumors with an optimal coating M(w) of 10,000 Da. 相似文献
40.