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Using sound velocity and attenuation measurements in high magnetic fields, we identify a new transition in the vortex lattice state of La_{2-x}Sr_{x}CuO_{4}. The transition, observed in magnetic fields exceeding 35 T and temperatures far below zero field T_{c}, is detected in the compression modulus of the vortex lattice, at a doping level of x=p=0.17. Our theoretical analysis based on Eilenberger's theory of the vortex lattice shows that the transition corresponds to the long-sought 45° rotation of the square vortex lattice, predicted to occur in d-wave superconductors near a van Hove singularity.
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BACKGROUND AND AIMS: Whether single nucleotide polymorphisms (SNPs) of homocysteine metabolism enzymes influence the rate of cardiovascular (CV) events in coronary artery disease (CAD) patients remains controversial. METHODS AND RESULTS: In this analysis, 1126 subjects from the AtheroGene study with CAD and 332 control subjects without known CAD were included. The following SNPs were investigated: methylentetrahydrofolate reductase (MTHFR-C667T), methionin synthetase (MS-D919G), and cystathionin beta synthetase (CBS-I278T). The endpoint was the combination of cardiovascular death, stroke, and non-fatal myocardial infarction (N = 286). The median follow-up time was 6.4 years. Kaplan-Meier curve analysis showed an increasing event rate with rising homocysteine levels (p < 0.001) in CAD patients. Further, in Cox-Regression analysis homocysteine was a predictor of the endpoint with a hazard ratio (HR) of 6.5 (95% CI: 2.9-14.6, p < 0.001) in the adjusted model including cardiovascular risk factors. Of the three SNPs, homozygous MTHFR SNP increased homocysteine levels significantly in patients with CAD and individuals without CAD (both p < 0.001). The SNPs in MS and CBS were not related to relevant changes in homocysteine levels in CAD patients or controls. The different SNPs of MTHFR, MS, and CBS were not related to an increased event rate. CONCLUSION: Homocysteine level is a strong predictor of CV events. Subjects with and without CAD and SNPs in the enzyme MTHFR had increased homocysteine levels. This was not observed for MS and CBS SNPs. Although MTHFR SNPs alter homocysteine levels in patients and controls, these polymorphisms had no impact on prognosis in CAD patients.
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5-Metiltetra-Hidrofolato-Homocisteína S-Metiltransferase/genética , Doença da Artéria Coronariana/genética , Cistationina beta-Sintase/genética , Homocisteína/sangue , Metilenotetra-Hidrofolato Redutase (NADPH2)/genética , Polimorfismo de Nucleotídeo Único , Idoso , Área Sob a Curva , Biomarcadores/sangue , Estudos de Casos e Controles , Distribuição de Qui-Quadrado , Doença da Artéria Coronariana/sangue , Doença da Artéria Coronariana/complicações , Doença da Artéria Coronariana/diagnóstico , Doença da Artéria Coronariana/etiologia , Progressão da Doença , Feminino , Frequência do Gene , Estudos de Associação Genética , Predisposição Genética para Doença , Heterozigoto , Homozigoto , Humanos , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Infarto do Miocárdio/etiologia , Infarto do Miocárdio/mortalidade , Fenótipo , Valor Preditivo dos Testes , Modelos de Riscos Proporcionais , Curva ROC , Medição de Risco , Fatores de Risco , Acidente Vascular Cerebral/etiologia , Acidente Vascular Cerebral/mortalidade , Fatores de TempoRESUMO
We report a combined study of the specific heat and de Haas-van Alphen effect in the iron-pnictide superconductor BaFe2(As(1-x)P(x))2. Our data when combined with results for the magnetic penetration depth give compelling evidence for the existence of a quantum critical point close to x=0.30 which affects the majority of the Fermi surface by enhancing the quasiparticle mass. The results show that the sharp peak in the inverse superfluid density seen in this system results from a strong increase in the quasiparticle mass at the quantum critical point.
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OBJECTIVE: To provide French guidelines for the management of women with abnormal uterine bleeding (AUB). DESIGN: A consensus committee of 26 experts was formed. A formal conflict-of-interest policy was developed at the beginning of the process and enforced throughout. The entire guidelines process was conducted independently of any industry funding (i.e. pharmaceutical or medical device companies). The authors were advised to follow the rules of the Grading of Recommendations Assessment, Development and Evaluation (GRADE®) system to guide assessment of quality of evidence. The potential drawbacks of making strong recommendations in the presence of low-quality evidence were emphasized. METHODS: The last guidelines from the Collège National des Gynécologues et Obstétriciens Français on the management of women with AUB were published in 2008. The literature seems now sufficient for an update. The committee studied questions within 7 fields (diagnosis; adolescents; idiopathic AUB; endometrial hyperplasia and polyps; type 0-2 fibroids; type 3 or higher fibroids; and adenomyosis). Each question was formulated in a PICO (Patients, Intervention, Comparison, Outcome) format and evidence profiles were compiled. The GRADE® methodology was applied to the literature review and the formulation of recommendations. RESULTS: The experts' synthesis work and the application of the GRADE method resulted in 36 recommendations. Among the formalized recommendations, 19 are strong and 17 weak. No response was found in the literature for 14 questions. We chose to abstain from recommendations rather than providing advice based solely on expert clinical experience. CONCLUSIONS: The 36 recommendations make it possible to specify the diagnostic and therapeutic strategies for various clinical situations practitioners encounter, from the simplest to the most complex.
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Adenomiose , Leiomioma , Adolescente , Feminino , Humanos , Ginecologista , Obstetra , Hemorragia Uterina/diagnóstico , Hemorragia Uterina/terapiaRESUMO
In this Letter, we show that a superconducting two-dimensional electron gas is formed at the LaTiO3/SrTiO3 interface whose transition temperature can be modulated by a back-gate voltage. The gas consists of two types of carriers: a majority of low-mobility carriers always present, and a few high-mobility ones that can be injected by electrostatic doping. The calculation of the electron spatial distribution in the confinement potential shows that the high-mobility electrons responsible for superconductivity set at the edge of the gas whose extension can be tuned by the field effect.
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OBJECTIVES: To date, oral contraceptives remain the most frequently prescribed contraceptive method. New combined oral contraceptive (COC) regimens (continued, extended or flexible) were developed to try and space out or avoid withdrawal bleedings in order to meet women's expectations and improve their quality of life. However, there is no recommendation published regarding the management of the prescription. The purpose of our study was to describe provider's prescription habits when it comes to new COC regimens. METHODS: This is a descriptive observational study. A questionnaire was sent to gynecologists, general practitioners and midwives employed or in training in the Centre Valde Loire region. Prescription habits and knowledge about new oral contraceptive regimens were evaluated. RESULTS: 83% of health professionals frequently prescribed new COC regimens. Most frequent indications were endometriosis, severe menstruation-associated symptoms, patient's desire for amenorrhea or patient's request. The extended regimen (hormone-free interval not every month) was the most frequently used. Provider's knowledge about indications and benefits of those new regimens were satisfactory. However, scientific societies guidelines were poorly acquired. CONCLUSIONS: New COC regimens are frequently proposed by health care professionals with large variability in terms of prescription model. Along with reinforcement of COC prescription guidelines for healthcare professionals, further researches are needed to better understand differences in tolerability and acceptability in terms of quality of life of the several potential regimens.
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Ciclo Menstrual , Qualidade de Vida , Anticoncepcionais Orais Combinados/uso terapêutico , Feminino , Hábitos , Humanos , MenstruaçãoRESUMO
Multilayered cuprates possess not only the highest superconducting temperature transition but also offer a unique platform to study disorder-free CuO2 planes and the interplay between competing orders with superconductivity. Here, we study the underdoped trilayer cuprate HgBa2Ca2Cu3O8+δ and we report quantum oscillation and Hall effect measurements in magnetic field up to 88 T. A careful analysis of the complex spectra of quantum oscillations strongly supports the coexistence of an antiferromagnetic order in the inner plane and a charge order in the outer planes. The presence of an ordered antiferromagnetic metallic state that extends deep in the superconducting phase is a key ingredient that supports magnetically mediated pairing interaction in cuprates.
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OBJECTIVE: To provide French guidelines for the management of women with abnormal uterine bleeding (AUB). DESIGN: A consensus committee of 26 experts was formed. A formal conflict-of-interest (COI) policy was developed at the beginning of the process and enforced throughout. The entire guidelines process was conducted independently of any industrial funding (i.e. pharmaceutical, or medical devices). The authors were advised to follow the rules of the Grading of Recommendations Assessment, Development and Evaluation (GRADE®) system to guide assessment of quality of evidence. The potential drawbacks of making strong recommendations in the presence of low-quality evidence were emphasized. METHODS: The last guidelines from the Collège national des gynécologues et obstétriciens français (CNGOF) on the management of women with AUB was published in 2008. The literature seems now sufficient for an update. The committee studied questions within 7 fields (diagnosis; adolescent; idiopathic AUB; endometrial hyperplasia and polyps; fibroids type 0 to 2; fibroids type 3 and more; adenomyosis). Each question was formulated in a PICO (Patients, Intervention, Comparison, Outcome) format and the evidence profiles were produced. The literature review and recommendations were made according to the GRADE® methodology. RESULTS: The experts' synthesis work and the application of the GRADE method resulted in 36 recommendations. Among the formalized recommendations, 19 present a strong agreement and 17 a weak agreement. Fourteen questions did not find any response in the literature. We preferred to abstain from recommending instead of providing expert advice. CONCLUSIONS: The 36 recommendations made it possible to specify the diagnostic and therapeutic strategies of various clinical situations managed by the practitioner, from the simplest to the most complex.
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Leiomioma , Médicos , Doenças Uterinas , Adolescente , Consenso , Escolaridade , Feminino , Humanos , Hemorragia Uterina/etiologia , Hemorragia Uterina/terapiaRESUMO
We report the observation of an apparent parallel magnetic-field-induced metal-insulator transition in a high-mobility two-dimensional electron gas for which spin and localization physics most likely play no major role. The high-mobility metallic phase at low field is consistent with the established Fermi liquid transport theory including phonon scattering, whereas the phase at higher field shows a large insulatinglike negative temperature dependence at resistances much smaller than the quantum of resistance h/e(2). We argue that this observation is a direct manifestation of a quantum-classical crossover arising predominantly from the magneto-orbital coupling between the finite width of the two-dimensional electron gas and the in-plane magnetic field.
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Using the de Haas-van Alphen effect we have measured the evolution of the Fermi surface of BaFe2(As1-xPx){2} as a function of isoelectric substitution (As/P) for 0.41
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In underdoped cuprate superconductors, the Fermi surface undergoes a reconstruction that produces a small electron pocket, but whether there is another, as yet, undetected portion to the Fermi surface is unknown. Establishing the complete topology of the Fermi surface is key to identifying the mechanism responsible for its reconstruction. Here we report evidence for a second Fermi pocket in underdoped YBa2Cu3Oy, detected as a small quantum oscillation frequency in the thermoelectric response and in the c-axis resistance. The field-angle dependence of the frequency shows that it is a distinct Fermi surface, and the normal-state thermopower requires it to be a hole pocket. A Fermi surface consisting of one electron pocket and two hole pockets with the measured areas and masses is consistent with a Fermi-surface reconstruction by the charge-density-wave order observed in YBa2Cu3Oy, provided other parts of the reconstructed Fermi surface are removed by a separate mechanism, possibly the pseudogap.
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The first epidemiological data concerning viruses and asthma were obtained in the 1970s and 1980s by viral isolation and serology. Viral infection can be identified in 24 % to 31.9 % of children, and in 13.3 % of adults. The three most frequent viruses are rhinovirus (RV), respiratory syncytial virus (RSV), and parainfluenza viruses (PIV), detected in 8.8 %, 6.4 % and 6 % of cases, respectively. Due to its amplifying properties, the use of PCR increases the frequency of viral detection, and appears particularly appropriate in asthma where the viral load can be reduced. In a study of bronchiolitis, RSV, PIV3, AdV and RV were identified in 39.3 %, 4.3 %, 1.4 % and 3.9 % of cases, respectively, by IF or culture, and in 62.4 %, 8.3 %, 10.8 % and 12.6 % of cases, respectively, by PCR. Two recent epidemiological surveys used molecular diagnosis in asthma attacks. In a series of 61 adults, 27 (44 %) infections were identified: 16 RV, 4 CV OC43, 3 PIV, 1 RSV, 1 VI, 1 Chlamydia psitacci. In children, viral infection was detected in 226 cases (77 %) : 84 RV, 38 CV, 21 IV, 21 PIV, 12 RSV. We have performed a short retrospective survey for 1997, using molecular biology, on 39 nasal aspirates from children consulting for asthma or wheezing bronchitis. Testing for respiratory viruses by conventional techniques identified 8 (20.5 %) viral infections: 3 RV, 3 RSV, 1 IBV and 1 VPI2. After nucleic acid extraction, PCR-hybridization techniques were applied to these samples to detect RSV, AdV, RV, CV 229E, CV OC43, CP and MP sequences. Twenty six aspirates (54 %) were positive only on molecular biology techniques: 11 RSV, 12 RV, 2 enterovirus, 1 CV OC43. Overall 34 (82 %) viral infections were detected in these children, and a mixed RSV-RV infection was identified in 6 cases. Compared to the studies reported in the literature, we observed the same predominance of RV infections, more RSV infections, probably related to the use of PCR, and a lower incidence of CV infections.
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Fluctuations around an antiferromagnetic quantum critical point (QCP) are believed to lead to unconventional superconductivity and in some cases to high-temperature superconductivity. However, the exact mechanism by which this occurs remains poorly understood. The iron-pnictide superconductor BaFe2(As(1-x)P(x))2 is perhaps the clearest example to date of a high-temperature quantum critical superconductor, and so it is a particularly suitable system to study how the quantum critical fluctuations affect the superconducting state. Here we show that the proximity of the QCP yields unexpected anomalies in the superconducting critical fields. We find that both the lower and upper critical fields do not follow the behaviour, predicted by conventional theory, resulting from the observed mass enhancement near the QCP. Our results imply that the energy of superconducting vortices is enhanced, possibly due to a microscopic mixing of antiferromagnetism and superconductivity, suggesting that a highly unusual vortex state is realized in quantum critical superconductors.
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In the quest to increase the critical temperature Tc of cuprate superconductors, it is essential to identify the factors that limit the strength of superconductivity. The upper critical field Hc2 is a fundamental measure of that strength, yet there is no agreement on its magnitude and doping dependence in cuprate superconductors. Here we show that the thermal conductivity can be used to directly detect Hc2 in the cuprates YBa2Cu3Oy, YBa2Cu4O8 and Tl2Ba2CuO6+δ, allowing us to map out Hc2 across the doping phase diagram. It exhibits two peaks, each located at a critical point where the Fermi surface of YBa2Cu3Oy is known to undergo a transformation. Below the higher critical point, the condensation energy, obtained directly from Hc2, suffers a sudden 20-fold collapse. This reveals that phase competition-associated with Fermi-surface reconstruction and charge-density-wave order-is a key limiting factor in the superconductivity of cuprates.
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From analysis of the in-plane resistivity ρ(ab)(T) of La(2-x)Sr(x)CuO(4), we show that normal state transport in overdoped cuprates can be delineated into two regimes in which the electrical resistivity varies approximately linearly with temperature. In the low-temperature limit, the T-linear resistivity extends over a very wide doping range, in marked contrast to expectations from conventional quantum critical scenarios. The coefficient of this T-linear resistivity scales with the superconducting transition temperature T(c), implying that the interaction causing this anomalous scattering is also associated with the superconducting pairing mechanism. At high temperatures, the coefficient of the T-linear resistivity is essentially doping independent beyond a critical doping p(crit)=0.19 at which the ratio of the two coefficients is maximal. Taking our cue from earlier thermodynamic and photoemission measurements, we conclude that the opening of the normal-state pseudogap at p(crit) is driven by the loss of coherence of anti-nodal quasi-particles at low temperatures.
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The origin of pairing in a superconductor resides in the underlying normal state. In the cuprate high-temperature superconductor YBa(2)Cu(3)O(y) (YBCO), application of a magnetic field to suppress superconductivity reveals a ground state that appears to break the translational symmetry of the lattice, pointing to some density-wave order. Here we use a comparative study of thermoelectric transport in the cuprates YBCO and La(1.8-x)Eu(0.2)Sr(x)CuO(4) (Eu-LSCO) to show that the two materials exhibit the same process of Fermi-surface reconstruction as a function of temperature and doping. The fact that in Eu-LSCO this reconstruction coexists with spin and charge modulations that break translational symmetry shows that stripe order is the generic non-superconducting ground state of hole-doped cuprates.
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We report the observation of Shubnikov-de Haas oscillations in the underdoped cuprate superconductor YBa2Cu4O8 (Y124). For fields aligned along the c axis, the frequency of the oscillations is 660+/-30 T, which corresponds to approximately 2.4% of the total area of the first Brillouin zone. The effective mass of the quasiparticles on this orbit is measured to be 2.7+/-0.3 times the free electron mass. Both the frequency and mass are comparable to those recently observed for ortho-II YBa2Cu3O6.5 (Y123-II). We show that although small Fermi surface pockets may be expected from band-structure calculations in Y123-II, no such pockets are predicted for Y124. Our results therefore imply that these small pockets are a generic feature of the copper oxide plane in underdoped cuprates.
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The Nernst coefficient of displays two distinct anomalies in magnetic field. The feature detected at Hk approximately 23 T is similar to what is observed in CeRu2Si2 at Hm = 7.8 T where a metamagnetic transition occurs. In CeCoIn5, new frequencies are observed in de Haas-van Alphen oscillations when the field exceeds 23 T where the Dingle temperature decreases by about 30%. Based on the Nernst coefficient anomalies, the magnetic phase diagram of CeCoIn5 is revised.