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Exploratory Work in the Quaternary System of Ca?Eu?Cd?Sb: Synthesis, Crystal, and Electronic Structures of New Zintl Solid Solutions.

ABSTRACT: Investigation of the quaternary system, Ca?Eu?Cd?Sb, led to a discovery of the new solid solutions, Ca_1-xEu_xCd?Sb?, with the CaAl?Si? structure type (x ? 0.3?0.9, hP5, P 3 ¯ m1, a = 4.6632(5)?4.6934(3) Å, c = 7.630(1)?7.7062(7) Å), Ca_2-xEu_xCdSb? with the Yb?CdSb? type (x ? 0.6, oS20, Cmc2?, a = 4.646(2) Å, b = 17.733(7) Å, c = 7.283(3) Å), and Eu_11-xCa_xCd?Sb₁₂ with the Sr₁₁Cd?Sb₁₂ type (x ? 1, mS58, C2/m, a = 32.407(4) Å, b = 4.7248(5) Å, c = 12.377(1) Å, ? = 109.96(1)°). Systematic crystallographic studies of the Ca_1-xEu_xCd?Sb? series indicated expansion of the unit cell upon an increase in the Eu content, in accordance with a larger ionic radius of Eu²⁺ vs. Ca²⁺. The Ca_2-xEu_xCdSb? composition with x ? 0.6 adopts the non-centrosymmetric space group, Cmc2?, although the parent ternary phase, Ca?CdSb?, crystallizes in the centrosymmetric space group, Pnma. Two non-equivalent Ca sites in the layered crystal structure of Ca_2-xEu_xCdSb? get unevenly occupied by Eu, with a preference for the interlayer position, which offers a larger available volume. Similar size-driven preferred occupation is observed in the Eu_11-xCa_xCd?Sb₁₂ solid solution with x ? 1.

SUBMITTER: Ovchinnikov A

PROVIDER: S-EPMC6265713 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Exploratory Work in the Quaternary System of Ca⁻Eu⁻Cd⁻Sb: Synthesis, Crystal, and Electronic Structures of New Zintl Solid Solutions.

Ovchinnikov Alexander A Darone Gregory M GM Saparov Bayrammurad B Bobev Svilen S

Materials (Basel, Switzerland) 20181031 11

Investigation of the quaternary system, Ca⁻Eu⁻Cd⁻Sb, led to a discovery of the new solid solutions, Ca1-xEuxCd₂Sb₂, with the CaAl₂Si₂ structure type (x ≈ 0.3⁻0.9, hP5, P 3 ¯ m1, a = 4.6632(5)⁻4.6934(3) Å, c = 7.630(1)⁻7.7062(7) Å), Ca2-xEuxCdSb₂ with the Yb₂CdSb₂ type (x ≈ 0.6, oS20, Cmc2₁, a = 4.646(2) Å, b = 17.733(7) Å, c = 7.283(3) Å), an ...[more]

PMID: 30384471

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Project description:Objectives: To analyze the current situation of cross-border access to clinical trials in the EU with an overview of stakeholders' real-life experience, and to identify the needs, challenges, and potential for facilitation of cross-border access. Methods: We employed a mixed methods design. Semi-structured interviews and an online survey were conducted with a wide range of stakeholders: patient representatives, investigators/physicians, policy and regulatory experts, academic and commercial sponsor representatives, ethics committee members. Interviews underwent a framework analysis. The survey was analyzed descriptively. Results: Three hundred ninety six individuals responded to the survey. The majority were investigators/physicians (46%) and patient representatives (33%). Thirty eight individuals were interviewed. The majority were investigators/physicians (29%) and patient representatives (29%). All European regions were represented in the study. The highest response rate was received from residents of Western European countries (38% of survey respondents, 45% of interviewees), the lowest from Eastern Europe (9% of survey respondents, 5% of interviewees). The study suggested that cross-border participation in clinical trials occurs in practice, however very rarely. Ninety two percentage of survey respondents and the majority of interviewees perceived as needed the possibility to access clinical trials abroad. However, most interviewees also opined that patients ideally should not have to travel in order to access experimental treatment. The lack of access to treatment in the home country of the patient was described as the main motivation to participate in a clinical trial in another country. The logistical and financial burden for patients was perceived as the biggest challenge. Different stakeholders expressed diverging opinions regarding the allocation of financial and organizational responsibility for enabling cross-border access to clinical trials. Participants provided a number of proposals for improving the current system, which were carefully evaluated by the research team and informed future recommendations. Conclusions: Participation in clinical trials abroad is happening rarely but should be facilitated. There was a consensus on the need for reliable and accessible information regarding practical aspects, as well as multi-stakeholder, multi-national recommendations on existing options and best practice on cross-border access to clinical trials. Broader interdisciplinary research is recommended before discussing options in the EU legislative framework to enable clearly defined conditions for cross-border access to clinical trials.

Dataset Information

Exploratory Work in the Quaternary System of Ca?Eu?Cd?Sb: Synthesis, Crystal, and Electronic Structures of New Zintl Solid Solutions.

Publications

Exploratory Work in the Quaternary System of Ca⁻Eu⁻Cd⁻Sb: Synthesis, Crystal, and Electronic Structures of New Zintl Solid Solutions.

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