Electron spin relaxation in organic semiconductors probed through muSR

Muon spin spectroscopy and in particular the avoided level crossing technique is introduced, with the aim of showing it as a very sensitive local probe for electron spin relaxation in organic semiconductors. Avoided level crossing data on TMS-pentacene at different temperatures are presented, and they are analysed to extract the electron spin relaxation rate, that is shown to increase on increasing the temperature from 0.02 MHz to 0.33 MHz at 3 K and 300 K respectively.Comment: International Conference TSN2010 "Trends in spintronics and nanomagnetism

BRAF activating mutations involving the β3-αC loop in V600E-negative anaplastic pleomorphic xanthoastrocytoma

https://deepblue.lib.umich.edu/bitstream/2027.42/142789/1/40478_2018_Article_525.pd

Importance of Spin-Orbit Interaction for the Electron Spin Relaxation in Organic Semiconductors

Despite the great interest organic spintronics has recently attracted, there is only a partial understanding of the fundamental physics behind electron spin relaxation in organic semiconductors. Mechanisms based on hyperfine interaction have been demonstrated, but the role of the spin-orbit interaction remains elusive. Here, we report muon spin spectroscopy and time-resolved photoluminescence measurements on two series of molecular semiconductors in which the strength of the spin-orbit interaction has been systematically modified with a targeted chemical substitution of different atoms at a particular molecular site. We find that the spin-orbit interaction is a significant source of electron spin relaxation in these materials

Muonium avoided level crossing measurement of electron spin relaxation rate in a series of substituted anthradithiophene based molecules

Muon spin spectroscopy and in particular the avoided level crossing technique is introduced, with the aim of showing it as a very sensitive local probe for electron spin relaxation in organic semiconductors. Avoided level crossing data on tert-butyl-ethynyl anthradithiophene, tri-methyl-silyl-ethynyl anthradithiophene and tri-ethygermyl-ethynyl anthradithiophene at different temperatures are presented. This series of molecules have an identical anthradithiophene backbone, but we have performed a targeted substitution on the central atom of the two side groups, of C, Si and Ge. We extracted the electron spin relaxation for the three molecules of this series and discuss them in the context of previously published results

Increased Myocardial Extracellular Volume in Active Idiopathic Systemic Capillary Leak Syndrome

BACKGROUND: The Systemic Capillary Leak Syndrome (SCLS) is a rare disorder of unknown etiology presenting as recurrent episodes of shock and peripheral edema due to leakage of fluid into soft tissues. Insights into SCLS pathogenesis are few due to the scarcity of cases, and the etiology of vascular barrier disruption in SCLS is unknown. Recent advances in cardiovascular magnetic resonance (CMR) allow for the quantitative assessment of the myocardial extracellular volume (ECV), which can be increased in conditions causing myocardial edema. We hypothesized that measurement of myocardial ECV may detect myocardial vascular leak in patients with SCLS. METHODS: Fifty-six subjects underwent a standard CMR examination at the NIH Clinical Center from 2009 until 2014: 20 patients with acute intermittent SCLS, six subjects with chronic SCLS, and 30 unaffected controls. Standard volumetric measurements; late gadolinium enhancement imaging and pre- and post-contrast T1 mapping were performed. ECV was calculated by calibration of pre- and post-contrast T1 values with blood hematocrit. RESULTS: Demographics and cardiac parameters were similar in both groups. There was no significant valvular disorder in either group. Subjects with chronic SCLS had higher pre-contrast myocardial T1 compared to healthy controls (T1: 1027 ± 44 v. 971 ± 41, respectively; p = 0.03) and higher myocardial ECV than patients with acute intermittent SCLS or controls: 33.8 ± 4.6, 26.9 ± 2.6, 26 ± 2.4, respectively; p = 0.007 v. acute intermittent; P = 0.0005 v. controls). When patients with chronic disease were analyzed together with five patients with acute intermittent disease who had just experienced an acute SCLS flare, ECV values were significantly higher than in subjects with acute intermittent SCLS in remission or age-matched controls and (31.2 ± 4.6 %, 26.5 ± 2.7 %, 26 ± 2.4 %, respectively; p = 0.01 v. remission, p = 0.001 v. controls). By contrast, T1 values did not distinguish these three subgroups (1008 ± 40, 978 ± 40, 971 ± 41, respectively, p = 0.2, active v. remission; p = 0.06 active v. controls). Abundant myocardial edema without evidence of acute inflammation was detected in cardiac tissue postmortem in one patient. CONCLUSIONS: Patients with active SCLS have significantly higher myocardial ECV than age-matched controls or SCLS patients in remission, which correlated with histopathological findings in one patient

Visualizing the microscopic coexistence of spin density wave and superconductivity in underdoped NaFe1-xCoxAs

Although the origin of high temperature superconductivity in the iron pnictides is still under debate, it is widely believed that magnetic interactions or fluctuations play an important role in triggering Cooper pairing. Because of the relevance of magnetism to pairing, the question of whether long range spin magnetic order can coexist with superconductivity microscopically has attracted strong interests. The available experimental methods used to answer this question are either bulk probes or local ones without control of probing position, thus the answers range from mutual exclusion to homogeneous coexistence. To definitively answer this question, here we use scanning tunneling microscopy to investigate the local electronic structure of an underdoped NaFe1-xCoxAs near the spin density wave (SDW) and superconducting (SC) phase boundary. Spatially resolved spectroscopy directly reveal both the SDW and SC gap features at the same atomic location, providing compelling evidence for the microscopic coexistence of the two phases. The strengths of the SDW and SC features are shown to anti correlate with each other, indicating the competition of the two orders. The microscopic coexistence clearly indicates that Cooper pairing occurs when portions of the Fermi surface (FS) are already gapped by the SDW order. The regime TC < T < TSDW thus show a strong resemblance to the pseudogap phase of the cuprates where growing experimental evidences suggest a FS reconstruction due to certain density wave order. In this phase of the pnictides, the residual FS has a favorable topology for magnetically mediated pairing when the ordering moment of the SDW is small.Comment: 18 pages, 4 figure

Consultation and illness behaviour in response to symptoms: a comparison of models from different disciplinary frameworks and suggestions for future research directions

We all get ill and social scientific interest in how we respond – the study of illness behaviour – continues unabated. Existing models are useful, but have been developed and applied within disciplinary silos, resulting in wasted intellectual and empirical effort and an absence of accumulation of knowledge across disciplines. We present a critical review and detailed comparison of three process models of response to symptoms: the Illness Action Model, the Common Sense Model of the Self-Regulation of Health and Illness and the Network Episode Model. We suggest an integrated framework in which symptoms, responses and actions are simultaneously interpreted and evaluated in the light of accumulated knowledge and through interactions. Evaluation may be subconscious and is influenced by the extent to which the symptoms impose themselves, expectations of outcomes, the resources available and understanding of symptoms' salience and possible outcomes. Actions taken are part of a process of problem solving through which both individuals and their immediate social network seek to (re)achieve ‘normality’. Response is also influenced by social structure (directly and indirectly), cultural expectations of health, the meaning of symptoms, and access to and understandings of the legitimate use of services. Changes in knowledge, in embodied state and in emotions can all be directly influential at any point. We do not underestimate the difficulty of operationalising an integrated framework at different levels of analysis. Attempts to do so will require us to move easily between disciplinary understandings to conduct prospective, longitudinal, research that uses novel methodologies to investigate response to symptoms in the context of affective as well as cognitive responses and interactions within social networks. While challenging such an approach would facilitate accumulation of knowledge across disciplines and enable movement beyond description to change in individual and organisational responses

The corticosteroid compounds prednisolone and vamorolone do not alter the nociception phenotype and exacerbate liver injury in sickle cell mice.

Clinicians often hesitate prescribing corticosteroids to treat corticosteroid-responsive conditions in sickle cell disease (SCD) patients because their use can be associated with complications (increased hospital readmission, rebound pain, strokes, avascular necrosis, acute chest syndrome). Consequently, SCD patients may receive suboptimal treatment for corticosteroid-responsive conditions. We conducted a preclinical trial of dissociative (vamorolone) and conventional (prednisolone) corticosteroid compounds to evaluate their effects on nociception phenotype, inflammation, and organ dysfunction in SCD mice. Prednisolone and vamorolone had no significant effects on nociception phenotype or anemia in homozygous mice. Conversely, prednisolone and vamorolone significantly decreased white blood cell counts and hepatic inflammation. Interestingly, the effects of vamorolone were milder than those of prednisolone, as vamorolone yielded less attenuation of hepatic inflammation compared to prednisolone. Compared to controls and heterozygotes, homozygotes had significant liver necrosis, which was significantly exacerbated by prednisolone and vamorolone despite decreased hepatic inflammation. These hepatic histopathologic changes were associated with increases in transaminases and alkaline phosphatase. Together, these results suggest that, even in the setting of decreasing hepatic inflammation, prednisolone and vamorolone were associated with significant hepatic toxicity in SCD mice. These findings raise the possibility that hepatic function deterioration could occur with the use of corticosteroids (conventional and dissociative) in SCD