ABSTRACT
We present evidence for nuclear spin-lattice relaxation driven by glassy nematic fluctuations in isovalent P-doped BaFe_{2}As_{2} single crystals. Both the ^{75}As and ^{31}P sites exhibit a stretched-exponential relaxation similar to the electron-doped systems. By comparing the hyperfine fields and the relaxation rates at these sites we find that the As relaxation cannot be explained solely in terms of magnetic spin fluctuations. We demonstrate that nematic fluctuations couple to the As nuclear quadrupolar moment and can explain the excess relaxation. These results suggest that glassy nematic dynamics are a common phenomenon in the iron-based superconductors.
ABSTRACT
We present 75As nuclear magnetic resonance data from measurements of a series of Ba(Fe(1-x)Co(x))2As2 crystals with 0.00≤x≤0.075 that reveals the coexistence of frozen antiferromagnetic domains and superconductivity for 0.060≤x≤0.071. Although bulk probes reveal no long range antiferromagnetic order beyond x=0.06, we find that the local spin dynamics reveal no qualitative change across this transition. The characteristic domain sizes vary by more than an order of magnitude, reaching a maximum variation at x=0.06. This inhomogeneous glassy dynamics may be an intrinsic response to the competition between superconductivity and antiferromagnetism in this system.
ABSTRACT
BACKGROUND: Anti-TNF-alpha agents have been shown to be effective for the induction of remission in Crohn's disease. The role of TNF-alpha blocking agents in ulcerative colitis is, however, unclear and recent studies have yielded conflicting results. OBJECTIVES: To evaluate the efficacy of TNF-alpha antibody for induction of remission in ulcerative colitis, and to determine adverse events associated with TNF-alpha antibody treatment. SEARCH STRATEGY: We searched MEDLINE (1966 to 2005), EMBASE (1984 to 2005), the Cochrane Central Register of Controlled Trials (Issue 3, 2004) and the IBD/FBD Review Group Specialized Trials Register. We hand-searched the articles cited in each publication. SELECTION CRITERIA: Only randomised controlled trials in which patients with active ulcerative colitis (defined by a combination of clinical, radiographic, endoscopic and histologic criteria) were randomly allocated to receive a TNF-alpha blocking agent in the treatment arm, and to receive placebo or another treatment in the comparison arm were included. DATA COLLECTION AND ANALYSIS: Data extraction and assessment of methodological quality of each study were independently performed by two reviewers. Any disagreement among reviewers was resolved by consensus. The main outcome measure was the occurrence of remission as defined by the primary studies. Other endpoints were clinical, histological or endoscopic improvement as defined by the primary studies; improvement in quality of life as measured by a validated quality of life tool and the occurrence of adverse events. MAIN RESULTS: Seven randomised controlled trials were identified that satisfied the inclusion criteria. In patients with moderate to severe ulcerative colitis whose disease was refractory to conventional treatment using corticosteroids and/or immunosuppressive agents, infliximab (three intravenous infusions at 0, 2, and 6 weeks) was more effective than placebo in inducing clinical remission (Relative Risk (RR) 3.22, 95% CI 2.18 to 4.76); inducing endoscopic remission (RR 1.88, 95% CI 1.54 to 2.28); and in inducing clinical response (RR 1.99, 95% CI 1.65 to 2.41) at 8 weeks. A single infusion of infliximab was also more effective than placebo in reducing the need for colectomy within 90 days after infusion (RR 0.44, 95% CI 0.22 to 0.87). AUTHORS' CONCLUSIONS: In patients with moderate to severe ulcerative colitis whose disease is refractory to conventional treatment using corticosteroids and/or immunosuppressive agents, infliximab is effective in inducing clinical remission, inducing clinical response, promoting mucosal healing, and reducing the need for colectomy at least in the short term. Serious adverse events attributable to infliximab were not common in the included studies but physicians should be aware of and be prepared to deal with potential adverse events such as anaphylactic reactions and infections.
