Social Networking Sites, Personalization, and Trust in Government: Empirical Evidence for a Mediation Model

Political communication via social media might well counter the eroding political trust. In particular, social networking sites (SNS) enable direct flows of communication between citizens and the political elite, thereby reducing social and political gaps. Based on the concept of personalization of politics, we argue that interactions with politicians on SNS affect trust in government through a two-step process: First, interactions on SNS make citizens evaluate politicians’ characters more favorably. Second, these evaluations serve as cues for the citizens to develop or withdraw trust in government. We test indirect effects using four character traits as mediators: leadership, benevolence, responsiveness, and likeability. A representative online survey ( n = 1117; in Germany) reveals that interactions with politicians on SNS increase the perceived likeability of candidates, and thus also trust in government. However, they do not affect the evaluation of the other traits: leadership, benevolence, and responsiveness.

Natural Uranium Radioactivity Solution Standard: SRM 4321d

A new natural uranium solution standard has been produced and will be disseminated by the National Institute of Standards and Technology (NIST) as Standard Reference Material 4321d. The standard is certified for the massic activities of 234U, 235U, and 238U in solution, and it is based on isotopic mass data for the metallic Certified Reference Material (CRM) 112-A (originally issued as SRM 960) that was obtained from THE U.S. Department of Energy, New Brunswick Laboratory. The metallic CRM was chemically cleaned, dissolved, and gravimetrically diluted to prepare a master solution, which was quantitatively dispensed into 5 mL aliquots that were contained within flame-sealed glass ampoules for each SRM unit. Homogeneity among SRM units, verifying solution homogeneity, was substantiated by photonic-emission integral counting with a NaI(Tl) well counter. Confirmatory measurements were performed by liquid scintillation counting for the total massic activity, and by isotope dilution α spectrometry for the 234U and 238U massic activities.

Evaluation of PET quantification accuracy in vivo

SummaryQuantitative positron emission tomography (PET) requires accurate scanner calibration, which is commonly performed using phantoms. It is not clear to what extent this procedure ensures quantitatively correct results in vivo, since certain conditions differ between phantom and patient scans. Aim: We, therefore, have evaluated the actual quantification accuracy in vivo of PET under clinical routine conditions. Patients, methods: We determined the activity concentration in the bladder in patients undergoing routine [18F]FDG whole body investigations with three different PET scanners (Siemens ECAT EXACT HR+ PET: n = 21; Siemens Biograph 16 PET/CT: n = 16; Philips Gemini-TF PET/CT: n = 19). Urine samples were collected immediately after scan. Activity concentration in the samples was determined in well counters cross-calibrated against the respective scanner. The PET (bladder) to well counter (urine sample) activity concentration ratio was determined. Results: Activity concentration in the bladder (PET) was systematically lower than in the urine samples (well The patient-averaged PET to well counter ratios for the investigated scanners are (mean ± SEM): 0.881 ± 0.015 (ECAT HR+), 0.898 ± 0.024 (Biograph 16), 0.932 ± 0.024 (Gemini-TF). These values correspond to underestimates by PET of 11.9%, 10.2%, and 6.8%, respectively. Conclusions: The investigated PET systems consistently underestimate activity concentration in the bladder. The comparison of urine samples with PET scans of the bladder is a straightforward means for in vivo evaluation of the expectable quantification accuracy. The method might be interesting for multi-center trials, for additional quality assurance in PET and for investigation of PET/MR systems for which clear proof of sufficient quantitative accuracy in vivo is still missing.