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A small, but clinically significant proportion of acne patients fail to respond adequately to antibiotic therapy. All non-responding acne patients attending the Leeds General Infirmary between September 1985 and April 1986 (49 out of a total of 610 patients; 8%) were investigated with respect to changes in their acne grade, microbial flora and sebum excretion rate. They were compared with 22 age and sex matched untreated control subjects. It was found that in 65% of non-responding patients there was no microbiological abnormality, in 16% there was evidence of Gram-negative folliculitis and 20% carried predominantly antibiotic resistant propionibacteria compared with only 5% of untreated controls. There was a significant association between erythromycin therapy and the isolation of erythromycin resistant propionibacteria (P less than 0.001). A causal link, however, has yet to be established between carriage of antibiotic resistant propionibacteria and failure to respond to antibiotic therapy. Our results show that for most patients with recalcitrant acne a non-microbiological explanation must be sought for the lack of therapeutic success. The mean sebum excretion rate (SER) of the non-responding patients was significantly higher than that of matched untreated acne patients (P less than 0.001). A majority of non-responders (69%) had an SER above the upper 95% confidence limit of the control mean. The SER may affect treatment efficacy by influencing the antibiotic concentration within the pilosebaceous ducts.

This study presents data on activities for which the Congressional Medal of Honor was presented. We identify two combat orientations among military personnel, which we label war winning and soldier saving. The former is most clearly associated with officers, the latter with low-ranking enlisted men. We suggest that this social-psychological orientation corresponds to a latent role structure within the military based upon a military ethic, and that the Medal of Honor rewards enactment of this latent role structure.

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In the family of double perovskites, colossal magnetoresistance (CMR) has been so far observed only in half-metallic ferrimagnets such as the known case Sr2FeMoO6 where it has been assigned to the tunneling MR at grain boundaries due to the half-metallic nature. Here we report a new material−Tl2NiMnO6, a relatively ordered double perovskite stablized by the high pressure and high temperature synthesis−showing CMR in the vicinity of its Curie temperature. We explain the origin of such effect with neutron diffraction experiment and electronic structure calculations that reveal the material is a ferromagnetic insulator. Hence the ordered Tl2NiMnO6 (~70% of Ni 2+ /Mn 4+ cation ordering) represents the first realization of a ferromagnetic insulating double perovskite, showing CMR. The study of the relationship between structure and magnetic properties allows us to clarify the nature of spin glass behaviour in the disordered Tl2NiMnO6 (~31% of cation ordering), which is related to the clustering of antisite defects and associated with the short-range spin correlations. Our results (L. Ding) † alexei.belik@nims.go.jp (A. A. Belik) highlight the key role of the cation ordering in establishing the long range magnetic ground state and lay out new avenues to exploit advanced magnetic materials in double perovskites. IntroductionPerovskites, a fertile playground for the study of strong interplay between spin, orbital and charge degrees of freedom, can accommodate a large variety of cation species due to their flexible crystal structure, giving rise to diverse and fascinating electronic and magnetic properties [1-7]. In ordered double perovskites, with chemical formula A2BB'O6 (A= rare earth or alkaline, B/B'= transition metal), B and B' cations generally form either rock-salt or layered type superstructure. The former, which leads to alternate stacking of BO6/B'O6 octahedra, is the most common type to minimize the electrostatic energy arising from the different charges of the two cations, and/or the elastic energy due to their different ionic sizes [8-16]. When the radius or the charge of B and B' cations is similar, the probability of antisite (AS) defects (partial occupation of B cations in B' sites and vice versa) increases up to a fully disordered state, effectively tuning the macroscopic properties of the system [11].One of the most intriguing properties of double perovskites is the colossal magnetoresistance (CMR), typically arising from the half-metallic nature of their electronic structures [17][18][19]. For example, half-metallic Sr2FeMoO6 shows a CMR in low magnetic field associated with a ferrimagnetic order above room temperature, providing a promising system for technological applications [17].