Colossal dielectric constants in transition-metal oxides

Many transition-metal oxides show very large ("colossal") magnitudes of the dielectric constant and thus have immense potential for applications in modern microelectronics and for the development of new capacitance-based energy-storage devices. In the present work, we thoroughly discuss the mechanisms that can lead to colossal values of the dielectric constant, especially emphasising effects generated by external and internal interfaces, including electronic phase separation. In addition, we provide a detailed overview and discussion of the dielectric properties of CaCu3Ti4O12 and related systems, which is today's most investigated material with colossal dielectric constant. Also a variety of further transition-metal oxides with large dielectric constants are treated in detail, among them the system La2-xSrxNiO4 where electronic phase separation may play a role in the generation of a colossal dielectric constant.Comment: 31 pages, 18 figures, submitted to Eur. Phys. J. for publication in the Special Topics volume "Cooperative Phenomena in Solids: Metal-Insulator Transitions and Ordering of Microscopic Degrees of Freedom

A randomized study of intermediate versus conventional-dose cytarabine as intensive induction for acute myelogenous leukaemia

The optimal dose of cytarabine for induction chemotherapy is unknown. Most studies have utilized doses of 100–200 mg/m2/d, although higher doses have been proposed to increase the concentration of the active metabolite ara‐CTP within leukaemia cells. To address this question 101 adults with newly diagnosed acute myeloid leukaemia were randomized to receive treatment with daunorubicin and either conventional‐dose cytarabine (200 mg/m2/d by continuous infusion) or an intermediate‐dose of cytarabine (500 mg/m2 every 12 h). 36/51 (71%) patients assigned to conventional‐dose cytarabine achieved complete remission compared to 37/50 (74%) who achieved remission with intermediate‐dose cytarabine (P = 0.9). Patient age significantly affected remission rate. 8/17 patients age >60 assigned to conventional‐dose cytarabine and 10/17 assigned to intermediate‐dose cytarabine achieved complete remission compared to 27/33 patients under age 60 assigned to the conventional dose and 28/34 patients assigned to the intermediate dose arm (P=0.004). Actuarial 4‐year disease‐free survival for patients assigned to conventional‐dose cytarabine was 20.16% versus 28.17% for patients assigned to intermediate‐dose cytarabine (P=0–9). We conclude that intermediate dose cytarabine did not substantially improve results of induction chemotherapy for acute myeloid leukaemia