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  • 2020-2022  (2)
  • 1965-1969  (2)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Fresenius' Zeitschrift für analytische Chemie 219 (1966), S. 147-160 
    ISSN: 1618-2650
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird ein empfindliches Verfahren zur Spurenbestimmung in reinem Quecksilber beschrieben, das besonders für routinemäßige Analysen geeignet ist. Die Methode beruht auf der selektiven Abtrennung des Quecksilbers von sämtlichen elektropositiveren Begleitelementen durch Reduktion mit Ameisensäure aus salpetersaurer Lösung. Die für die Reinheitskontrolle von Quecksilber wichtigsten Spurenelemente können bis zu Konzentrationen zwischen 10−6 und 10−7% unter Anwendung amalgamvoltammetrischer (Zn, Cd, Pb, Cu), flammenspektrometrischer (Mg, Tl, Mn, Zn, Cd) sowie photometrischer (Fe) Methoden mit hoher Genauigkeit bestimmt werden. Daneben wird die photometrische Bestimmung der Elemente Zn, Cd, Pb, Cu, Mn, Co, Ni und Bi im unteren ppm-Bereich beschrieben. Die prinzipielle Möglichkeit der Bestimmung einer Reihe weiterer Elemente (Ga, In, Cr, Alkali- und Erdalkalimetalle, Be, Al, Sn, As, Sb, Te, Ti) wird erörtert. Die Vorteile des Verfahrens gegenüber bisher bekannten Methoden zur Reinheitsprüfung des Quecksilbers werden diskutiert. Das Verfahren ist bei entsprechender Modifizierung ebenso auf die Spurenbestimmung in Quecksilbersalzen wie grundsätzlich auch auf die Spurenbestimmung in Silber, Gold und deren Salzen anwendbar.
    Notizen: Summary A sensitive method for the determination of trace amounts of metallic impurities in mercury is described. The procedure is based on a selective separation of mercury from all accompanying trace elements more electropositive than mercury. The mercury is separated by reducing a nitric acid solution of the sample with formic acid. The elements being most important for the purity control of mercury are detectable down to concentrations between 10−7% and 10−6% with high accuracy employing voltammetric (Zn, Cd, Pb, Cu), flame-spectrometric (Mg, Tl, Mn, Zn, Cd) and photometric (Fe) methods. In addition the photometric determination of the elements Zn, Cd, Pb, Cu, Mn, Co, Ni and Bi in the lower ppm-range is described. The possibility to detect a number of further elements, such as Ga, In, Cr, alkali and alkaline-earth metals, Be, Al, Sn, As, Sb, Te and Ti by the same methods is pointed out. The advantages of the mercury separation method by reduction are discussed in comparison with previously known procedures. The method is especially suitable for routine tests. After appropriate modifications the described procedure may also be applied to the determination of trace amounts of impurities in mercurous and mercuric salts and in silver, gold and their salts.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 1966-01-01
    Print ISSN: 0016-1152
    Thema: Chemie und Pharmazie
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2020-09-14
    Beschreibung: The aim of this study was to assess physical activity and sedentary behavior, as well as the usage behavior, usability, acceptance, and motivational impact of an applied activity tracker among nursing home residents. Physical activity and usage behavior were measured among 22 residents (68 to 102 years) by use of a commercial activity tracker worn during waking hours for 77 days on average. Usability, acceptance, and motivational impact of the tracker were examined using an adapted questionnaire. Participants walked, on average, 1007 ± 806 steps per day and spent, on average, more than 9 h (77.2% of their waking time) sedentary. The average steps/day increased significantly within the first five weeks of wearing the activity tracker. The acceptance rate was high (94.4%). The tracker was used for 65.4% of the individual study period, and usage behavior did not significantly change during the first five wearing weeks. Participants with a usage time of ≥50% walked significantly more steps per day than those with a lower usage. Overall, we were able to reveal that the residents were highly inactive and sedentary. The results support the feasibility of a long-term application of activity trackers to assess or even increase physical activity behavior.
    Print ISSN: 1661-7827
    Digitale ISSN: 1660-4601
    Thema: Energietechnik , Medizin
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2020-02-18
    Beschreibung: Intrinsic malignant brain tumors, such as glioblastomas are frequently resistant to immune checkpoint blockade (ICB) with few hypermutated glioblastomas showing response. Modeling patient-individual resistance is challenging due to the lack of predictive biomarkers and limited accessibility of tissue for serial biopsies. Here, we investigate resistance mechanisms to anti-PD-1 and anti-CTLA-4 therapy in syngeneic hypermutated experimental gliomas and show a clear dichotomy and acquired immune heterogeneity in ICB-responder and non-responder tumors. We made use of this dichotomy to establish a radiomic signature predicting tumor regression after pseudoprogression induced by ICB therapy based on serial magnetic resonance imaging. We provide evidence that macrophage-driven ICB resistance is established by CD4 T cell suppression and Treg expansion in the tumor microenvironment via the PD-L1/PD-1/CD80 axis. These findings uncover an unexpected heterogeneity of response to ICB in strictly syngeneic tumors and provide a rationale for targeting PD-L1-expressing tumor-associated macrophages to overcome resistance to ICB.
    Digitale ISSN: 2041-1723
    Thema: Biologie , Chemie und Pharmazie , Allgemeine Naturwissenschaft , Physik
    Publiziert von Springer Nature
    Standort Signatur Erwartet Verfügbarkeit
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