Spin Echo, Fidelity, and the Quantum Critical Fan in TmVO_{4}.

Using spin-echo nuclear magnetic resonance in the model transverse field Ising system TmVO_{4}, we show that low frequency quantum fluctuations at the quantum critical point have a very different effect on ^{51}V nuclear spins than classical low-frequency noise or fluctuations that arise at a finite temperature critical point. Spin echoes filter out the low-frequency classical noise but not the quantum fluctuations. This allows us to directly visualize the quantum critical fan and demonstrate the persistence of quantum fluctuations at the critical coupling strength in TmVO_{4} to high temperatures in an experiment that remains transparent to finite temperature classical phase transitions. These results show that while dynamical decoupling schemes can be quite effective in eliminating classical noise in a qubit, a quantum critical environment may lead to rapid entanglement and decoherence.

Antithyroid drugs in Graves' hyperthyroidism: differences between "block and replace" and "titration" regimes in frequency of euthyroidism and Graves' orbitopathy during treatment.

PURPOSE: Whereas antithyroid drugs (ATD) are the preferred treatment modality for Graves' hyperthyroidism (GH), there is still controversy about the optimal regimen for delivering ATD. To evaluate whether 'Block and Replace' (B + R) and 'Titration' (T) regimes are equivalent in terms of frequency of euthyroidism and Graves' Orbitopathy (GO) during ATD therapy. METHODS: A prospective multicentre observational cohort study of 344 patients with GH but no GO at baseline. Patients were treated with ATD for 18 months according to B + R or T regimen in line with their institution's policy. RESULTS: Baseline characteristics were similar in both groups. In the treatment period between 6 and 18 months thyrotropin (TSH) slightly increased in both groups, but TSH was on average 0.59 mU/L (95% CI 0.27-0.85) lower in the B + R group at all time points (p = 0.026). Serum free thyroxine (FT4) remained stable during the same interval, with a tendency to higher values in the B + R group. The point-prevalence of euthyroidism (TSH and FT4 within their reference ranges) increased with longer duration of ATD in both groups; it was always higher in the T group than in the B + R group: 48 and 24%, respectively, at 6 months, 81 and 58% at 12 months, and 87 and 63% at 18 months (p < 0.002). There were no significant differences between the B + R and T regimens with respect to the fall in thyrotropin binding inhibiting immunoglobulins (TBII) or thyroid peroxidase antibodies (TPO-Ab). GO developed in 15.9% of all patients: 9.1 and 17.8% in B + R group and T group, respectively, (p = 0.096). GO was mild in 13% and moderate-to-severe in 2%. CONCLUSION: The prevalence of biochemical euthyroidism during treatment with antithyroid drugs is higher during T compared to B + R regimen. De novo development of GO did not differ significantly between the two regimens, although it tended to be higher in the T group. Whether one regimen is clinically more advantageous than the other remains unclear.

Asymmetry indicates more severe and active disease in Graves' orbitopathy: results from a prospective cross-sectional multicentre study.

PURPOSE: Patients with Graves' orbitopathy can present with asymmetric disease. The aim of this study was to identify clinical characteristics that distinguish asymmetric from unilateral and symmetric Graves' orbitopathy. METHODS: This was a multi-centre study of new referrals to 13 European Group on Graves' Orbitopathy (EUGOGO) tertiary centres. New patients presenting over a 4 month period with a diagnosis of Graves' orbitopathy were included. Patient demographics were collected and a clinical examination was performed based on a previously published protocol. Patients were categorized as having asymmetric, symmetric, and unilateral Graves' orbitopathy. The distribution of clinical characteristics among the three groups was documented. RESULTS: The asymmetric group (n = 83), was older than the symmetric (n = 157) group [mean age 50.9 years (SD 13.9) vs 45.8 (SD 13.5), p = 0.019], had a lower female to male ratio than the symmetric and unilateral (n = 29) groups (1.6 vs 5.0 vs 8.7, p < 0.001), had more active disease than the symmetric and unilateral groups [mean linical Activity Score 3.0 (SD 1.6) vs 1.7 (SD 1.7), p < 0.001 vs 1.3 (SD 1.4), p < 0.001] and significantly more severe disease than the symmetric and unilateral groups, as measured by the Total Eye Score [mean 8.8 (SD 6.6) vs 5.3 (SD 4.4), p < 0.001, vs 2.7 (SD 2.1), p < 0.001]. CONCLUSION: Older age, lower female to male ratio, more severe, and more active disease cluster around asymmetric Graves' orbitopathy. Asymmetry appears to be a marker of more severe and more active disease than other presentations. This simple clinical parameter present at first presentation to tertiary centres may be valuable to clinicians who manage such patients.

Does early response to intravenous glucocorticoids predict the final outcome in patients with moderate-to-severe and active Graves' orbitopathy?

PURPOSE: Intravenous glucocorticoids (ivGCs) given as 12-weekly infusions are the first-line treatment for moderate-to-severe and active Graves' orbitopathy (GO), but they are not always effective. In this study, we evaluated whether response at 6 weeks correlated with outcomes at 12 (end of intervention) and 24 (follow-up) weeks, particularly in patients initially unresponsive. METHODS: Our database (Bartalena et al. J Clin Endocrinol Metab 97:4454-4463, 10), comprising 159 patients given three different cumulative doses of methylprednisolone (2.25, 4.98, 7.47 g) was analyzed, pooling data for analyses. Responses at 6 weeks were compared with those at 12 and 24 weeks using three outcomes: overall ophthalmic involvement [composite index (CI)]; quality of life (QoL); Clinical Activity Score (CAS). Responses were classified as "Improved", "Unchanged", "Deteriorated", compared to baseline. RESULTS: Deteriorated patients at 6 weeks for CI (n = 8) remained in the same category at 12 weeks and 7/8 at 24 weeks. Improved patients at 6 weeks for CI (n = 51) remained in the same category in 63% and 53% of cases at 12 and 24 weeks, respectively. Unchanged patients at 6 weeks (n = 100) eventually improved in 28% of cases (CI), 58% (CAS), 32% (QoL). There was no glucocorticoid dose-dependent difference in the influence of early response on later outcomes. CONCLUSIONS: Patients who deteriorate at 6 weeks after ivGCs are unlikely to benefit from continuing ivGCs. Patients unresponsive at 6 weeks still have a significant possibility of improvement later. Accordingly, they may continue ivGC treatment, or, alternatively, possibly stop ivGCs and be switched to a second-line treatment.

NMR Evidence for Inhomogeneous Nematic Fluctuations in BaFe_{2}(As_{1-x}P_{x})_{2}.

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.

Measurements of nematic susceptibility with phase sensitive nuclear magnetic resonance in pulsed strain fields.

We present nuclear magnetic resonance data in BaFe2As2 in the presence of pulsed strain fields that are interleaved in time with the radio frequency excitation pulses. In this approach, the preceding nuclear magnetization acquires a phase shift that is proportional to the strain and pulse time. The sensitivity of this approach is limited by the homogeneous decoherence time, T2, rather than the inhomogeneous linewidth. We measure the nematic susceptibility as a function of temperature and demonstrate a three orders of magnitude improvement in sensitivity. This approach will enable studies of the strain response in a broad range of materials that previously were inaccessible due to inhomogeneous broadening.

Coexistence of cluster spin glass and superconductivity in Ba(Fe(1-x)Co(x))2As2 for 0.060≤x≤0.071.

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.

Unconventional superconductivity in PuCoGa5.

In the Bardeen-Cooper-Schrieffer theory of superconductivity, electrons form (Cooper) pairs through an interaction mediated by vibrations in the underlying crystal structure. Like lattice vibrations, antiferromagnetic fluctuations can also produce an attractive interaction creating Cooper pairs, though with spin and angular momentum properties different from those of conventional superconductors. Such interactions have been implicated for two disparate classes of materials--the copper oxides and a set of Ce- and U-based compounds. But because their transition temperatures differ by nearly two orders of magnitude, this raises the question of whether a common pairing mechanism applies. PuCoGa5 has a transition temperature intermediate between those classes and therefore may bridge these extremes. Here we report measurements of the nuclear spin-lattice relaxation rate and Knight shift in PuCoGa5, which demonstrate that it is an unconventional superconductor with properties as expected for antiferromagnetically mediated superconductivity. Scaling of the relaxation rates among all of these materials (a feature not exhibited by their Knight shifts) establishes antiferromagnetic fluctuations as a likely mechanism for their unconventional superconductivity and suggests that related classes of exotic superconductors may yet be discovered.

Inverse Laplace transformation analysis of stretched exponential relaxation.

We investigate the effectiveness of the Inverse Laplace Transform (ILT) analysis method to extract the distribution of relaxation rates from nuclear magnetic resonance data with stretched exponential relaxation. Stretched-relaxation is a hallmark of a distribution of relaxation rates, and an analytical expression exists for this distribution for the case of a spin-1/2 nucleus. We compare this theoretical distribution with those extracted via the ILT method for several values of the stretching exponent and at different levels of experimental noise. The ILT accurately captures the distributions for ß≲0.7, and for signal to noise ratios greater than ∼40; however the ILT distributions tend to introduce artificial oscillatory components. We further use the ILT approach to analyze stretched relaxation for spin I>1/2 and find that the distributions are accurately captured by the theoretical expression for I=1/2. Our results provide a solid foundation to interpret distributions of relaxation rates for general spin I in terms of stretched exponential fits.

Rituximab treatment in patients with active Graves' orbitopathy: effects on proinflammatory and humoral immune reactions.

In active Graves' orbitopathy (GO), proinflammatory cytokines predominate. Circulating thyroid stimulating hormone (TSH)-receptor antibodies (TRAb) have been correlated with GO clinical activity and severity. In preliminary studies rituximab (RTX), an anti-CD 20 monoclonal antibody, has induced clinical improvement of active GO without a change in serum anti-thyroid antibodies. We have studied whether RTX in GO acts by affecting proinflammatory cytokines and thyroid and orbital-directed antibodies. Ten patients with GO were treated with RTX, administered twice intravenously (i.v.) (1000 mg) at days 1 and 15, and 20 with methylprednisolone, administered weekly i.v. (500 mg), for 16 weeks. Patients were studied before treatment, at B cell depletion and at 4, 8, 16, 20, 30 and 50 weeks. Peripheral lymphocytes, serum interleukin (sIL)-6, sIL-6r, chemokine (C-X-C motif) ligand 10 (CXCL10), TRAb and stimulating antibodies (TSAb) and autoantibodies against orbital calsequestrin, collagen XIII and flavoprotein subunit of succinate dehydrogenase (FP-SDH) were measured at baseline and after treatment. Serum IL-6 and sIL-6R concentrations did not change after RTX [P = not significant (n.s.)]. Serum CXCL10 increased after RTX at B cell depletion and at 30 weeks (P < 0·003). Serum TSAb did not change in relation to TRAb, nor did antibodies against orbital antigens (P = n.s.). In conclusion, this study shows that RTX in GO does not affect humoral reactions. The observed increase of serum CXCL10 concentrations at B cell depletion may result from cell lysis. We suggest that RTX may exert its effect in GO by inhibiting B cell antigen presentation.

Superconductivity in diamond.

Diamond is an electrical insulator well known for its exceptional hardness. It also conducts heat even more effectively than copper, and can withstand very high electric fields. With these physical properties, diamond is attractive for electronic applications, particularly when charge carriers are introduced (by chemical doping) into the system. Boron has one less electron than carbon and, because of its small atomic radius, boron is relatively easily incorporated into diamond; as boron acts as a charge acceptor, the resulting diamond is effectively hole-doped. Here we report the discovery of superconductivity in boron-doped diamond synthesized at high pressure (nearly 100,000 atmospheres) and temperature (2,500-2,800 K). Electrical resistivity, magnetic susceptibility, specific heat and field-dependent resistance measurements show that boron-doped diamond is a bulk, type-II superconductor below the superconducting transition temperature T(c) approximately 4 K; superconductivity survives in a magnetic field up to Hc2(0) > or = 3.5 T. The discovery of superconductivity in diamond-structured carbon suggests that Si and Ge, which also form in the diamond structure, may similarly exhibit superconductivity under the appropriate conditions.

Field-induced coupled superconductivity and spin density wave order in the heavy fermion compound CeCoIn5.

The high-field superconducting state in CeCoIn(5) has been studied by transverse field muon spin rotation measurements with an applied field parallel to the crystallographic c axis close to the upper critical field mu(0)H(c2) = 4.97 T. At magnetic fields mu(0)H > or = 4.8 T the muon Knight shift is enhanced and the superconducting transition changes from second order towards first order as predicted for Pauli-limited superconductors. The field and temperature dependence of the transverse muon spin relaxation rate sigma reveal paramagnetic spin fluctuations in the field regime from 2 T < or = mu(0)H < 4.8 T. In the normal state close to H(c2) correlated spin fluctuations as described by the self-consistent renormalization theory are observed. The results support the formation of a mode-coupled superconducting and antiferromagnetically ordered phase in CeCoIn(5) for H directed parallel to the c axis.

New immunomodulators in the treatment of Graves' ophthalmopathy.

Steroids have been used in the therapy of the moderate to severe forms of Graves' ophthalmopathy (GO) and other autoimmune diseases as they act only as general immunosuppressants. Previous work has shown that blocking the CD-20 receptor on B lymphocytes has significantly affected the clinical course of GO, by rapidly reducing inflammation and the degree of proptosis. We have studied nine patients with Graves' disease, of whom seven had active GO and two, with newly diagnosed hyperthyroidism, only mild lid signs. We also studied a group of 20 consecutive patients, treated with intravenous glucocorticoids (IVGC) according to a standard protocol. Patients treated with RTX (1000mg i.v. twice at two-week interval) and those treated with IVGC (500mg i.v. for 16 weeks) were studied monthly up to 12 months after the first drug infusion. By ophthalmological examination, GO was assessed by the clinical activity score (CAS) and by the NOSPECS score. Thyroid function and lymphocyte count were measured by standardized methods. RTX was well-tolerated and only minor side-effects were reported in 30% of patients during the first infusion. All patients attained peripheral B-cell depletion with the first RTX infusion. All but one patients showed both CD20+ cells and CD19+ cells depletion, while one had persistent 3-5% CD19+ cells in the periphery, mostly CD19+5+. Thyroid function was not affected by RTX therapy. Titers of antithyroglobulin (TgAb), antithyroperoxidase and anti-TSH receptor antibodies (TRAb) did not change significantly (P=NS) and did not correlate to CD20+ depletion (P=NS). CAS values decreased significantly (P<0.0001). Proptosis decreased significantly after RTX in both patients with active GO (ANOVA; P<0.0001) and in those with Graves' hyperthyroidism and lid signs (ANOVA; P<0.003). The degree of inflammation (NOSPECS class 2) decreased significantly in response to RTX (ANOVA; P<0.001). In patients treated with IVGC, mean CAS value decreased significantly less than in those treated with RTX (P<0.05). Adverse effects were more frequent after IVGC (45% of patients). Seventy-five percent of patients responded to IVGC and 10% showed relapse of active GO six to eight weeks after withdrawal. The results of this study on RTX in GO suggest that the drug is effective in modifying the disease course and that the improvement of the clinical activity of GO after RTX was more significant than after IVGC. We did not observe relapse of active GO, even after B-cell return in peripheral blood. This might be related to the persistence of a significant degree of B-cell depletion after RTX observed in the peripheral blood as late as two years of follow-up. RTX therapy was also effective in improving proptosis and soft tissue inflammation. The mechanism by which RTX affects GO is unknown. It may act as a true immunosuppressor by switching off reactions inducing the active phase of TAO, perhaps by influencing the cytokine production in the orbit or by inducing depletion of antigen presenting B-cells.

Uniaxial strain control of spin-polarization in multicomponent nematic order of BaFe2As2.

The iron-based high temperature superconductors exhibit a rich phase diagram reflecting a complex interplay between spin, lattice, and orbital degrees of freedom. The nematic state observed in these compounds epitomizes this complexity, by entangling a real-space anisotropy in the spin fluctuation spectrum with ferro-orbital order and an orthorhombic lattice distortion. A subtle and less-explored facet of the interplay between these degrees of freedom arises from the sizable spin-orbit coupling present in these systems, which translates anisotropies in real space into anisotropies in spin space. We present nuclear magnetic resonance studies, which reveal that the magnetic fluctuation spectrum in the paramagnetic phase of BaFe2As2 acquires an anisotropic response in spin-space upon application of a tetragonal symmetry-breaking strain field. Our results unveil an internal spin structure of the nematic order parameter, indicating that electronic nematic materials may offer a route to magneto-mechanical control.

Nuclear magnetic resonance probe head design for precision strain control.

We present the design and construction of an NMR probe to investigate single crystals under strain at cryogenic temperatures. The probe head incorporates a piezoelectric-based apparatus from Razorbill Instruments that enables both compressive and tensile strain tuning up to strain values on the order of 0.3% with a precision of 0.001%. 75As NMR in BaFe2As2 reveals large changes to the electric field gradient and indicates that the strain is homogeneous to within 16% over the volume of the NMR coil.

Graves' orbitopathy as a rare disease in Europe: a European Group on Graves' Orbitopathy (EUGOGO) position statement.

BACKGROUND: Graves' orbitopathy (GO) is an autoimmune condition, which is associated with poor clinical outcomes including impaired quality of life and socio-economic status. Current evidence suggests that the incidence of GO in Europe may be declining, however data on the prevalence of this disease are sparse. Several clinical variants of GO exist, including euthyroid GO, recently listed as a rare disease in Europe (ORPHA466682). The objective was to estimate the prevalence of GO and its clinical variants in Europe, based on available literature, and to consider whether they may potentially qualify as rare. Recent published data on the incidence of GO and Graves' hyperthyroidism in Europe were used to estimate the prevalence of GO. The position statement was developed by a series of reviews of drafts and electronic discussions by members of the European Group on Graves' Orbitopathy. The prevalence of GO in Europe is about 10/10,000 persons. The prevalence of other clinical variants is also low: hypothyroid GO 0.02-1.10/10,000; GO associated with dermopathy 0.15/10,000; GO associated with acropachy 0.03/10,000; asymmetrical GO 1.00-5.00/10,000; unilateral GO 0.50-1.50/10,000. CONCLUSION: GO has a prevalence that is clearly above the threshold for rarity in Europe. However, each of its clinical variants have a low prevalence and could potentially qualify for being considered as a rare condition, providing that future research establishes that they have a distinct pathophysiology. EUGOGO considers this area of academic activity a priority.

Contributions of spin-lattice relaxation to the echo decay of planar Cu in high-temperature superconductors.

Measurement of T2G, the Gaussian component of the spin-echo envelope of planar Cu nuclei in high-temperature superconductors, gives important information about the real part of the Cu electron spin susceptibility. In the traditional picture of the planar Cu echo decay, the internuclear coupling is assumed to remain static with respect to spin-lattice relaxation and mutual exchange fluctuations. In some circumstances, however, this assumption breaks down. We calculate the internuclear corrections arising from spin-lattice relaxation to the conventional theory of T2G and show that T2G can be easily corrected for these effects. We argue that mutual exchanges due to the perpendicular indirect couplings are suppressed in these materials. For YBa2Cu4O8, we find a correction on the order of 10% in T2g and using the corrected values we find that the isotope ration 63T2G/65T2G agrees with theory.

Double resonance probes for close frequencies.

A new double resonance probe design for NMR experiments for systems with close resonance frequencies is introduced. The design is based on two coupled resonators and was extensively tested on magnetically aligned powders of several high temperature superconductors by performing double resonance experiments between the 65Cu and 63Cu isotopes as well as between transitions of different magnetic quantum number of the same spin. The probe's performance approaches that of a single resonance circuit and it has only 4 variable tuning/matching elements.

Efficacy and safety of three different cumulative doses of intravenous methylprednisolone for moderate to severe and active Graves' orbitopathy.

BACKGROUND: Optimal doses of i.v. glucocorticoids for Graves' orbitopathy (GO) are undefined. METHODS: We carried out a multicenter, randomized, double-blind trial to determine efficacy and safety of three doses of i.v. methylprednisolone in 159 patients with moderate to severe and active GO. Patients were randomized to receive a cumulative dose of 2.25, 4.98, or 7.47 g in 12 weekly infusions. Efficacy was evaluated objectively at 12 wk by blinded ophthalmologists and subjectively by blinded patients (using a GO specific quality of life questionnaire). Adverse events were recorded at each visit. RESULTS: Overall ophthalmic improvement was more common using 7.47 g (52%) than 4.98 g (35%; P = 0.03) or 2.25 g (28%; P = 0.01). Compared with lower doses, the high-dose regimen led to the most improvement in objective measurement of ocular motility and in the Clinical Activity Score. The Clinical Activity Score decreased in all groups and to the least extent with 2.25 g. Quality of life improved most in the 7.47-g group, although not reaching statistical significance. No significant differences occurred in exophthalmos, palpebral aperture, soft tissue changes, and subjective diplopia score. Dysthyroid optic neuropathy developed in several patients in all groups. Because of this, differences among the three groups were no longer apparent at the exploratory 24-wk visit. Major adverse events were slightly more frequent using the highest dose but occurred also using the lowest dose. Among patients whose GO improved at 12 wk, 33% in the 7.47-group, 21% in the 4.98-group, and 40% in the 2.25-group had relapsing orbitopathy after glucocorticoid withdrawal at the exploratory 24-wk visit. CONCLUSIONS: The 7.47-g dose provides short-term advantages over lower doses. However, this benefit is transient and associated with slightly greater toxicity. The use of a cumulative dose of 7.47 g of methylprednisolone provides short-term advantage over lower doses. This may suggest that an intermediate-dose regimen be used in most cases and the high-dose regimen be reserved to most severe cases of GO.

Graves' orbitopathy activation after radioactive iodine therapy with and without steroid prophylaxis.

CONTEXT: The reactivation of Graves' orbitopathy (GO) after radioiodine (RAI) for Graves' disease (GD) is a known effect, and its clinical relevance is controversial. Prevention of RAI-induced GO activation is possible in at-risk patients with oral glucocorticoids (OGC). OBJECTIVES: The aim of the study was to analyze the effects of RAI on GO with or without prophylactic steroids based on known risk factors and to compare the effectiveness of prophylaxis with iv glucocorticoids (IVGC) and OGC. DESIGN: We conducted a retrospective study in which patients were assessed before and 1-12 months after RAI. PATIENTS AND SETTING: A total of 113 patients were included in the study; 83 underwent RAI without prophylactic steroids for the absence of risk of activation, and 30 were treated with either OGC (n = 21) or IVGC (n = 9). MAIN OUTCOME MEASURES: We analyzed the prevalence of GO activation with or without steroid prophylaxis and the difference in the prevalence of GO activation after OGC or IVGC. RESULTS: GO activation was observed in 7.2% of patients without and 33.3% of patients with steroid prophylaxis (P < 0.0001), for an overall prevalence of 14.6%. GO activation occurred in 47.6% of patients treated with OGC but in none of the nine patients treated with IVGC (P = 0.0001). Disease activation was more prevalent in males (P < 0.02) and in older patients (P = 0.04) with a shorter duration of GD (P < 0.01) and time from GO onset (P < 0.01). CONCLUSIONS: GO may occur after RAI in approximately 15% of patients also in the absence of signs of active GO. Prophylactic OGC did not prevent GO activation in a large proportion of patients, compared to IVGC.