Charge Density Waves in YBa_{2}Cu_{3}O_{6.67} Probed by Resonant X-Ray Scattering under Uniaxial Compression

We report a comprehensive Cu L_{3}-edge resonant x-ray scattering (RXS) study of two- and three-dimensional (2D and 3D) incommensurate charge correlations in single crystals of the underdoped high-temperature superconductor YBa_{2}Cu_{3}O_{6.67} under uniaxial compression up to 1% along the two inequivalent Cu─O─Cu bond directions (a and b) in the CuO_{2} planes. We confirm the strong in-plane anisotropy of the 2D charge correlations and observe their symmetric response to pressure: pressure along a enhances correlations along b, and vice versa. Our results imply that the underlying order parameter is uniaxial. In contrast, 3D long-range charge order is only observed along b in response to compression along a. Spectroscopic RXS measurements show that the 3D charge order resides exclusively in the CuO_{2} planes and may thus be generic to the cuprates. We discuss implications of these results for models of electronic nematicity and for the interplay between charge order and superconductivity.

Experimental data on the relationship between dyes sensitizers and wavelength during the photocatalytic degradation of diclofenac

Sensitizers are being used to improve the photocatalytic activity of semiconductors in the visible light region of the solar spectrum. Different types of dyes are reported as sensitizer agents, such as ruthenium complex molecules, porphyrins and Pt complexes, which are critically assessed because they are hazardous substance. Therefore, it is necessary to replace these compounds with safer sensitizer like organic dyes. This work evaluated the photocatalytic degradation of diclofenac using two different types of organic dyes (Perinaphtenone and Eosin-Y) as sensitizer agents. The catalyst concentration [0.15; 0.35 g/l], source of light (UVA - Vis) and type of dye were evaluated. The data obtained can be useful to classify organic dyes that could be employees as sensitizers and which is the wavelength more adequate to use as an energy source. The Kapp for the reaction has values between 1*10^-3 to 5*10^-3 min^-1 for UVA, 3*10^-4 to 3*10^-3 min^-1 for Vis and 2*10^-3 to 6*10^-3 min^-1 for UV-Vis.

Uniaxial pressure control of competing orders in a high-temperature superconductor

Cuprates exhibit antiferromagnetic, charge density wave (CDW), and high-temperature superconducting ground states that can be tuned by means of doping and external magnetic fields. However, disorder generated by these tuning methods complicates the interpretation of such experiments. Here, we report a high-resolution inelastic x-ray scattering study of the high-temperature superconductor YBa₂Cu₃O_6.67 under uniaxial stress, and we show that a three-dimensional long-range-ordered CDW state can be induced through pressure along the a axis, in the absence of magnetic fields. A pronounced softening of an optical phonon mode is associated with the CDW transition. The amplitude of the CDW is suppressed below the superconducting transition temperature, indicating competition with superconductivity. The results provide insights into the normal-state properties of cuprates and illustrate the potential of uniaxial-pressure control of competing orders in quantum materials.

Optically induced lattice deformations, electronic structure changes, and enhanced superconductivity in YBa2Cu3O6.48

Resonant optical excitation of apical oxygen vibrational modes in the normal state of underdoped YBa2Cu3O6+x induces a transient state with optical properties similar to those of the equilibrium superconducting state. Amongst these, a divergent imaginary conductivity and a plasma edge are transiently observed in the photo-stimulated state. Femtosecond hard x-ray diffraction experiments have been used in the past to identify the transient crystal structure in this non-equilibrium state. Here, we start from these crystallographic features and theoretically predict the corresponding electronic rearrangements that accompany these structural deformations. Using density functional theory, we predict enhanced hole-doping of the CuO2 planes. The empty chain Cu dy2-z2 orbital is calculated to strongly reduce in energy, which would increase c-axis transport and potentially enhance the interlayer Josephson coupling as observed in the THz-frequency response. From these results, we calculate changes in the soft x-ray absorption spectra at the Cu L-edge. Femtosecond x-ray pulses from a free electron laser are used to probe changes in absorption at two photon energies along this spectrum and provide data consistent with these predictions.

Persistent Paramagnons Deep in the Metallic Phase of Sr_{2-x}La_{x}IrO_{4}

We have studied the magnetic excitations of electron-doped Sr_{2-x}La_{x}IrO_{4} (0≤x≤0.10) using resonant inelastic x-ray scattering at the Ir L_{3} edge. The long-range magnetic order is rapidly lost with increasing x, but two-dimensional short-range order (SRO) and dispersive magnon excitations with nearly undiminished spectral weight persist well into the metallic part of the phase diagram. The magnons in the SRO phase are heavily damped and exhibit anisotropic softening. Their dispersions are well described by a pseudospin-1/2 Heisenberg model with exchange interactions whose spatial range increases with doping. We also find a doping-independent high-energy magnetic continuum, which is not described by this model. The spin-orbit excitons arising from the pseudospin-3/2 manifold of the Ir ions broaden substantially in the SRO phase, but remain largely separated from the low-energy magnons. Pseudospin-1/2 models are therefore a good starting point for the theoretical description of the low-energy magnetic dynamics of doped iridates.

Collective nature of spin excitations in superconducting cuprates probed by resonant inelastic X-ray scattering

We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor YBa_{2}Cu_{3}O_{6+x} over a wide range of doping levels (0.1≤x≤1). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all x. These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from incoherent particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002 (2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed.

Momentum-dependent charge correlations in YBa2Cu3O6+δ superconductors probed by resonant X-ray scattering: evidence for three competing phases

We use resonant x-ray scattering to determine the momentum-dependent charge correlations in YBa(2)Cu(3) O(6.55) samples with highly ordered chain arrays of oxygen acceptors (ortho-II structure). The results reveal nearly critical, biaxial charge density wave (CDW) correlations at in-plane wave vectors (0.315, 0) and (0, 0.325). The corresponding scattering intensity exhibits a strong uniaxial anisotropy. The CDW amplitude and correlation length are enhanced as superconductivity is weakened by an external magnetic field. Analogous experiments are carried out on a YBa(2)Cu(3)O(6.6) crystal with a dilute concentration of spinless (Zn) impurities, which had earlier been shown to nucleate incommensurate magnetic order. Compared to pristine crystals with the same doping level, the CDW amplitude and correlation length are found to be strongly reduced. These results indicate a three-phase competition between spin-modulated, charge-modulated, and superconducting states in underdoped YBa(2)Cu(3)O(6+δ).

[Eyelid necrosis caused by an hymenopteran insect bite]

We report a case report of extensive eyelid necrosis caused by an insect bite. A 39-year-old man had suffered ocular trauma from a hymenopteran insect in Tunisia. The patient presented with eyelid necrosis. Eyelid necrosis mechanisms following insect bites are discussed and other causes of eyelid necrosis are presented. Eyelid necrosis, often caused by vasoconstrictive medications or animal venoms, notably hymenopteran insect bites, can result in substantial eyelid injury.

[Bilateral elastosis of the limbus]

We report of a case of bilateral limbus involvement by white lesions. A 72-year-old man was referred for bilateral lesions involving the inferior part of the corneal limbus. White excrescences associated with a vascular pannus were observed at biomicroscope examination. Histologic patterns showed degenerative fibroelastosis. Degenerative fibroelastosis can be observed at the inferior corneal limbus.

The pneumonia severity index predicts time to clinical stability in patients with community-acquired pneumonia

SETTING

A total of 33 hospitals in 13 countries in North America, Europe, Africa, Asia and Latin America.

OBJECTIVE

To investigate the relationship between the pneumonia severity index (PSI) and the time to clinical stability from intravenous to oral antibiotic therapy in hospitalized adult patients with community-acquired pneumonia (CAP).

DESIGN

An international, retrospective, observational study of random adult patients meeting the definition of CAP between June 2001 and May 2004.

RESULTS

The risk class (RC) according to the PSI was calculated for all patients. The criteria to define when a patient is clinically stable were evaluated daily during the first 7 days of hospitalization in all patients. The mean time to clinical stability for 254 patients in RC I was 4.2 days, for 233 patients in RC II it was 3.9 days, for 395 patients in RC III it was 4.6 days, for 644 patients in RC IV it was 5.0 days and for 296 patients in RC V it was 6.0 days. Significant positive correlations were observed between RC and time to clinical stability (P < 0.0001).

CONCLUSION

The PSI is a tool that can be used to predict time to clinical stability (i.e., time to antimicrobial switch therapy) in hospitalized patients with CAP.

HIV infection does not influence clinical outcomes in hospitalized patients with bacterial community-acquired pneumonia: results from the CAPO international cohort study

In a case-control study, outcomes for 58 human immunodeficiency virus (HIV)-positive patients with community-acquired pneumonia (CAP) were compared with outcomes for 174 HIV-negative patients with CAP. No differences were found in the time to clinical stability, the length of hospitalization, and mortality. Clinical outcomes for hospitalized patients with CAP may not be influenced by HIV infection.

Infections of the central nervous system of suspected viral origin: a collaborative study from Finland

We studied 3231 patients with acute central nervous system (CNS) symptoms of suspected viral origin to elucidate the current etiologic spectrum. In 46% of the cases, a viral finding was observed. Varicella-zoster virus (VZV) was the main agent associated with encephalitis, as well as meningitis and myelitis. VZV comprised 29% of all confirmed or probable etiologic agents. Herpes simplex virus (HSV) and enteroviruses accounted 11% each, and influenza A virus 7%. VZV seems to have achieved a major role in viral infections of CNS. In encephalitis in our population, VZV is clearly more commonly associated with these neurological diseases than HSV. The increase in VZV findings may in part be a pseudophenomenon due to improved diagnostic methods, however, a true increase may have occurred and the pathogenetic mechanisms behind this should be elucidated.

[Evaluation of the Chromotitre EIA test in the diagnosis of human brucellosis]

BACKGROUND

The aim of the study was to evaluate the diagnostic efficacy of Chromotitre EIA test for the diagnosis of human brucellosis and compare the same with other classical serologic test.

METHODS

A prospective study was performed in 50 patients with active brucellosis. Thirty blood donors, 64 patients with different neoplastic and autoimmune infectious processes, 20 patients with history of brucellosis and 8 subjects with continuous exposure to Brucella at work were analyzed as the control group.

RESULTS

Forty-five patients with brucellosis (90%) presented a positive IgM or IgG ELISA, 32 (62%) only IgM, 34 (68%) only IgG and 22 (44%) both immunoglobulins were positive. The sensitivity and specificity of ELISA test jointly evaluating IgM and IgG was 90 and 68%, respectively with these numbers being 62 and 98% and 68% and 38% for ELISA IgM and ELISA IgG. A moderate correlation was found between ELISA IgM with Bengal's Rose test (r = 0.53, p = 0.003) and sero-agglutination (r = 0.63, p = 0.0001) and ELISA IgG with the Coombs test (r = 0.55, p = 0.003). Only acceptable concordance was observed between ELISA IgM and sero-agglutination (kappa = 0.55, p = 0.0001).

CONCLUSIONS

The ELISA test evaluated was very useful for the detection of IgM antibodies but was found to be insufficient with respect to IgG antibodies. Despite the slight diagnostic efficacy of the ELISA IgG the combined parallel use of both immunoglobulins achieved a performance similar to that achieved with the classical tests.

[Combined use of rose Bengal and indirect immunofluorescence in the diagnosis of brucellosis]

In the present prospective study we have evaluated the sensitivity, specificity and predictive value of the Bengal rose and indirect immunofluorescence (IIF) in 122 patients with a bacteriological diagnosis of brucellosis. The sensitivity of the Bengal rose was 95.79% and its specificity 98.43%. IIF had a sensitivity of 68.80% and a specificity of 100% when the polyvalent anti-IgS conjugate was used. The combined parallel use of Bengal rose and IIF-IgS resulted in a sensitivity of 89.17% and a specificity of 100%. There was a good correlation between Bengal rose and serum agglutination test (r = 0.72); on the contrary, there were not good correlations between the fluorescent conjugates and Bengal rose, agglutination and Coombs test. In conclusion, the combined use of Bengal rose as a screening test and IIF as a confirmation study is a good diagnostic strategy for human brucellosis.

Placebo-controlled double-blind trial of pirprofen and an ergotamine tartrate compound in migraine attacks

Sixty-one patients, 16 with classic and 45 with common migraine, were treated during three subsequent attacks with pirprofen, a new inhibitor of prostaglandin synthesis; an ergotamine tartrate compound; or placebo, in a randomized, double-blind multicentre study. Pain relief after a single dose and reduction of the attack intensity occurred most often with pirprofen in patients who needed more than one dose. Among them, however, the duration of attack was shortest with ergotamine. Working ability was well preserved with pirprofen, especially among patients with common migraine, and this treatment was ranked highest by the patients. However, no statistically significant differences were found between pirprofen and ergotamine. No serious side effects were observed with pirprofen. This study establishes the usefulness of pirprofen in the treatment of acute migraine.

Localized outbreak of enteroviral meningitis in adults

During a thorough surveillance of viral infections of the central nervous system an outbreak of aseptic meningitis was discovered in the western part of Finland in late 1985. The 21 diseased young adults were carefully studied by different virological methods. A presumed viral etiology, in all cases of enteroviral origin, was found in 16 of 20 (80%) with adequate specimens. Four different enteroviruses were associated with this episode; in 9 cases the presumed etiological agent was echovirus 5, while coxsackie B5, echo 25 and echo 17 viruses appeared to be responsible for 4, 2 and 1 case, respectively. Sensitivity of different diagnostic methods as regards detection of the echovirus 5 infections was in order: increase of type-specific neutralizing serum antibodies, isolation of virus from faeces, isolation from throat and group diagnosis by demonstrating an increase in complement-fixing antibodies to coxsackie B5 virus antigen.

The epidemiology of multiple sclerosis in Finland: increase of prevalence and stability of foci in high-risk areas

Reliable data on the epidemiology of multiple sclerosis (MS) in Finland are available from 1964 and 1972. They show that the whole country is a high-risk area of MS with clustering in the western part. A reassessment of the prevalence data was carried out in the southern province of Uusimaa and in the western province of Vaasa, the prevalence day being January 1, 1979. The age-adjusted prevalence was 52.9 per 100,000 in Uusimaa and 92.9 per 100,000 in Vaasa, figures that were three times higher than those recorded for the same areas in 1964. The communities with the highest prevalence rates in the province of Vaasa were the same as those in the survey of 1972; some rates exceeded 200 per 100,000. The increase in the prevalence rates may be due to a better registration of MS cases, but it may also represent a true increase, a possibility that only can be answered by further incidence studies.

Subacute sclerosing panencephalitis as a cause of chronic dementia and relapsing brain disorder

Two patients with subacute sclerosing panencephalitis (SSPE) are described because of the course of the disease, which is still thought to be unusual but might prove to be rather common. In both cases there was apparent recovery after about two years of illness. One of the patients had a relapse after eight years of remission and seems to have recovered also from this second period of illness, though with a more severe mental defect than after the first one. Thus, SSPE should be kept in mind as a possible aetiological factor in patients with a persisting slight to severe dementia after a brain disorder. Apparent recovery from SSPE does not exclude the possibility of relapse even many years later.