High-temperature copper oxide superconductors consist of stacked CuO
planes, with electronic band structures and magnetic excitations that are primarily two-dimensional
, but with superconducting ...coherence that is three-dimensional. This dichotomy highlights the importance of out-of-plane charge dynamics, which has been found to be incoherent in the normal state
within the limited range of momenta accessible by optics. Here we use resonant inelastic X-ray scattering to explore the charge dynamics across all three dimensions of the Brillouin zone. Polarization analysis of recently discovered collective excitations (modes) in electron-doped copper oxides
reveals their charge origin, that is, without mixing with magnetic components
. The excitations disperse along both the in-plane and out-of-plane directions, revealing its three-dimensional nature. The periodicity of the out-of-plane dispersion corresponds to the distance between neighbouring CuO
planes rather than to the crystallographic c-axis lattice constant, suggesting that the interplane Coulomb interaction is responsible for the coherent out-of-plane charge dynamics. The observed properties are hallmarks of the long-sought 'acoustic plasmon', which is a branch of distinct charge collective modes predicted for layered systems
and argued to play a substantial part in mediating high-temperature superconductivity
.
The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon ...coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a “coherent lock-in” measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure.Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.
The coupling between lattice and charge degrees of freedom in condensed matter materials is ubiquitous and can often result in interesting properties and ordered phases, including conventional ...superconductivity, charge-density wave order, and metal-insulator transitions. Angle-resolved photoemission spectroscopy and both neutron and nonresonant x-ray scattering serve as effective probes for determining the behavior of appropriate, individual degrees of freedom—the electronic structure and lattice excitation, or phonon dispersion, respectively. However, each provides less direct information about the mutual coupling between the degrees of freedom, usually through self-energy effects, which tend to renormalize and broaden spectral features precisely where the coupling is strong, impacting one’s ability to quantitatively characterize the coupling. Here, we demonstrate that resonant inelastic x-ray scattering, or RIXS, can be an effective tool to directly determine the relative strength and momentum dependence of the electron-phonon coupling in condensed matter systems. Using a diagrammatic approach for an eight-band model of copper oxides, we study the contributions from the lowest-order diagrams to the full RIXS intensity for a realistic scattering geometry, accounting for matrix element effects in the scattering cross section, as well as the momentum dependence of the electron-phonon coupling vertex. A detailed examination of these maps offers a unique perspective into the characteristics of electron-phonon coupling, which complements both neutron and nonresonant x-ray scattering, as well as Raman and infrared conductivity.
We report the near-full-length genome sequence of a hepatitis C virus (HCV) isolate from a man originating from Democratic Republic of Congo, the genotype of which could not be determined by the ...routinely used sequencing technique. The near-complete genome sequence of this variant BAK1 was obtained by the association of two next-generation sequencing technologies. Evolutionary analysis indicates that this isolate, BAK1, could be the first reported strain belonging to a new HCV-7b subtype. This new subtype has been incorrectly identified as genotype 2 by the Versant HCV Genotype 2.0 assay (LiPA). The requirement of three independent isolates has been filled, and a new subtype can be assigned. More examples of HCV-7 are required to better understand its origin, its pathogenicity and its relationship with genotype 2.
A high incidence of acute hepatitis C virus (HCV) (AHCV) infection has been reported among at-risk HIV-negative MSM. The optimal strategy for early diagnosis of AHCV in this population is not clearly ...defined.
In the ANRS IPERGAY PrEP trial, among high-risk HIV-negative MSM, HCV serology and serum alanine aminotransferase (ALT) were used for screening at enrollment and during follow-up. Behavioral risk factors were compared at baseline between participants who were diagnosed with AHCV during the study compared with those who did not. In participants with a positive HCV serology, we used stored sera to perform the following tests at diagnosis and on previous visits: HCV-antibodies rapid tests, plasma HCV viral load and HCV antigen immunoassay. We evaluated the sensitivity of each test for AHCV diagnosis.
Among 429 enrolled participants, 14 were diagnosed with AHCV infection, with a median follow-up of 2.1 (interquartile range, 1.5-2.8) years. AHCV incidence was 1.40 per 100 person-years (95% confidence interval, 0.74-2.39). Patients with AHCV reported a significantly higher number of sexual acts and/or partners, and more frequent recreational drug use at baseline. At the prior visit before AHCV diagnosis (median of 2 months earlier), sensitivities of HCV RNA and HCV antigen tests were, respectively, 100 and 89%, whereas none of the patients had a positive serology, and only 25% had elevated ALT.
HCV antigen and RNA tests were positive within a median of 2 months before the detection of antibodies and ALT elevation. These tests could be considered for HCV screening in high-risk MSM.
The hepatitis C virus (HCV) epidemic is evolving quickly despite new treatments, and due to behaviour changes increasing at-risk situations. We investigated potential origins and evolution of the ...HCV-4d French emergence among human immunodeficiency virus (HIV)-infected men who have sex with men (MSM), in Paris in 2003.
We analysed all HCV sequences from the initial Paris outbreak with all newly available sequences publicly available, including sampling date and geographical location, resulting in 184, 68, 156, 107, 13 and 2 sequences from France, The Netherlands, other European countries, Africa, the Middle East or Turkey, Americas and Asia, respectively. Phylogenetic reconstruction was performed using maximum likelihood and Bayesian approaches.
HCV-4d sequences from Europe were strongly separated from non-European sequences. Sequences from the initial Paris outbreak were all included into two well-separated and supported clusters with branch support at 100%, mean genetic distance <2.8 substitutions/100 nucleotides and >3.4 substitutions/100 nucleotides between their common ancestor and the previous node. The largest cluster interleaved French (n = 98) and Dutch (n = 28) sequences, suggesting several translocations between these countries. This cluster included 41 French sequences from Lyon sampled after 2014, highlighting its continuous spread within France since the initial outbreak. The smallest cluster included one Paris sequence with UK sequences (n = 9).
A few previous works have shown HCV-4d transmissions occurring between a few countries. In our work, we suggest a new and large connection between France and The Netherlands MSM communities and highlight a well-separated pan-European transmission network. Large collaborative networks are needed to investigate ongoing transmissions across countries and help specific prevention measures.
During 2003–2010, 555 strains isolated from sexually-infected patients at the time of primary HIV-1 infection (PHI) were characterized. Tree topology revealed that 11.7% of PHIs segregated into ...transmission clusters. CXCR4-usage was identified in 27 strains (4.9%) and was significantly associated with subtype B (p 0.003) and low CD4 cell count (p 0.01). In clustered and unique PHIs, the prevalence of CXCR4-tropic strains was 1.5% and 5.3%, respectively (p 0.35). Our results are in line with the hypothesis of a mucosal bottleneck contributing to the high prevalence of CCR5 variants during PHI.
Dye confinement into carbon nanotube significantly affects the electronic charge density distribution of the final hybrid system. Using the electron-phonon coupling sensitivity of the Raman G-band, ...we quantify experimentally how charge transfer from thiophene oligomers to single walled carbon nanotube is modulated by the diameter of the nano-container and its metallic or semiconducting character. This charge transfer is shown to restore the electron-phonon coupling into defected metallic nanotubes. For sub-nanometer diameter tube, an electron transfer optically activated is observed when the excitation energy matches the HOMO-LUMO transition of the confined oligothiophene. This electron doping accounts for an important enhancement of the photoluminescence intensity up to a factor of nearly six for optimal confinement configuration. This electron transfer shifts the Fermi level, acting on the photoluminescence efficiency. Therefore, thiophene oligomer encapsulation allows modulating the electronic structure and then the optical properties of the hybrid system.
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Background. Treatment initiation at the time of primary human immunodeficiency virus (HIV) type 1 (HIV-1) infection has become less frequent in recent years. Methods. In the French prospective PRIMO ...Cohort, in which patients are enrolled at the time of primary HIV-1 infection, 30% of the 552 patients recruited during 1996–2004 did not start receiving antiretroviral treatment during the first 3 months after diagnosis. We analyzed the patients' clinical and immunological outcomes and examined potential predictors of disease progression. Progression was defined as the occurrence of an acquired immunodeficiency syndrome (AIDS)—related clinical event or a CD4 cell count <350 cells/mm3. Results. Fifty-six (34%) of the untreated patients experienced immunological progression during a median duration of follow-up of 24 months, and 1 of these patients had an AIDS-related event. The estimated risks of progression were 25%, 34%, and 42% at 1, 2, and 3 years after enrollment, respectively. Compared with patients who did not have progression, those with progression had significantly lower CD4 cell counts at diagnosis (455 vs. 738 cells/mm3), higher plasma HIV RNA levels (4.9 vs. 4.5 log10 copies/mL), and higher HIV DNA levels (3.3 vs. 3.0 log10 copies/106 peripheral blood mononuclear cells PBMCs). All 3 parameters were significantly associated with progression in univariate analysis. In multivariate analysis, only the CD4 cell count and HIV DNA level were independently predictive of disease progression (relative hazard for CD4 cell count, 1.84 per decrease of 100 cells/mm3; relative hazard for HIV DNA level, 2.73 per increase of 1 log10 copies/106 PBMCs). Conclusions. Both a low initial CD4 cell count and a high HIV DNA level are predictive of rapid progression of untreated primary HIV-1 infection. Affected patients may therefore benefit from close clinical and laboratory monitoring and/or early administration of treatment.
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