Phonon polaritons-light coupled to lattice vibrations-in polar van der Waals crystals are promising candidates for controlling the flow of energy on the nanoscale due to their strong field ...confinement, anisotropic propagation and ultra-long lifetime in the picosecond range
. However, the lack of tunability of their narrow and material-specific spectral range-the Reststrahlen band-severely limits their technological implementation. Here, we demonstrate that intercalation of Na atoms in the van der Waals semiconductor α-V
O
enables a broad spectral shift of Reststrahlen bands, and that the phonon polaritons excited show ultra-low losses (lifetime of 4 ± 1 ps), similar to phonon polaritons in a non-intercalated crystal (lifetime of 6 ± 1 ps). We expect our intercalation method to be applicable to other van der Waals crystals, opening the door for the use of phonon polaritons in broad spectral bands in the mid-infrared domain.
SiC/SiC composites reinforced with 3rd generation SiC fibers (Hi-Nicalon S and Tyranno SA3 fibers) are promising candidates for thermomechanical applications in high technology industries. Both ...composites exhibited a pseudo-ductile mechanical behavior but the HNS/PyC/SiC composite reaches higher failure strains than TSA3/PyC/SiC ones. The mechanical behavior of SiC/SiC composites is linked to the way PyC is bonded to the fiber surface. Analyses have shown that these interactions and the Fiber/Matrix debonding behavior depend strongly on the nature of the carbon on the SiC fiber surface, which is different according to the SiC fiber. In order to understand the mechanism governing the chemical adhesion at the PyC/SiC fiber interface, the formation, the chemistry and the structure of the surface carbon layer were studied. Understanding the origin of this carbon has allowed elucidating the local interaction mechanisms of the studied SiC/SiC composites.
South African artist Irma Stern (1894–1966) is one of the nation's most enigmatic modern figures. Stern held conservative political positions on race even as her subjects openly challenged racism and ...later the apartheid regime. Using paintings, archival research, and new interviews, this book explores how Stern became South Africa's most prolific painter of Black, Jewish, and Colored (mixed-race) life while maintaining controversial positions on race. Through her art, Stern played a crucial role in both the development of modernism in South Africa and in defining modernism as a global movement. Spanning the Boer War to Nazi Germany to apartheid South Africa and into the contemporary #RhodesMustFall movement, Irma Stern's work documents important twentieth-century cultural and political moments. More than fifty years after her death, Stern's legacy challenges assumptions about race, gender roles, and religious identity and how they are represented in art history.
We observed robust coupling between the high- and low-frequency bands of ongoing electrical activity in the human brain. In particular, the phase of the low-frequency theta (4 to 8 hertz) rhythm ...modulates power in the high gamma (80 to 150 hertz) band of the electrocorticogram, with stronger modulation occurring at higher theta amplitudes. Furthermore, different behavioral tasks evoke distinct patterns of theta/high gamma coupling across the cortex. The results indicate that transient coupling between low- and high-frequency brain rhythms coordinates activity in distributed cortical areas, providing a mechanism for effective communication during cognitive processing in humans.
Fever and dyspnea in a 77 year-old man Berger, M; Le Falher, G; Casanova, M-L ...
La revue de medecine interne,
12/2019, Letnik:
40, Številka:
12
Journal Article
Summary Background Paediatric pulmonary hypertension, is an important cause of morbidity and mortality, and is insufficiently characterised in children. The Tracking Outcomes and Practice in ...Pediatric Pulmonary Hypertension (TOPP) registry is a global, prospective study designed to provide information about demographics, treatment, and outcomes in paediatric pulmonary hypertension. Methods Consecutive patients aged 18 years or younger at diagnosis with pulmonary hypertension and increased pulmonary vascular resistance were enrolled in TOPP at 31 centres in 19 countries from Jan 31, 2008, to Feb 15, 2010. Patient and disease characteristics, including age at diagnosis and at enrolment, sex, ethnicity, presenting symptoms, pulmonary hypertension classification, comorbid disorders, medical and family history, haemodynamic indices, and functional class were recorded. Follow-up was decided by the patients' physicians according to the individual's health-care needs. Findings 362 of 456 consecutive patients had confirmed pulmonary hypertension (defined as mean pulmonary artery pressure ≥25 mm Hg, pulmonary capillary wedge pressure ≤12 mm Hg, and pulmonary vascular resistance index ≥3 WU/m−2 ). 317 (88%) patients had pulmonary arterial hypertension (PAH), which was idiopathic IPAH or familial FPAH in 182 (57%), and associated with other disorders in 135 (43%), of which 115 (85%) cases were associated with congenital heart disease. 42 patients (12%) had pulmonary hypertension associated with respiratory disease or hypoxaemia, with bronchopulmonary dysplasia most frequent. Finally, only three patients had either chronic thromboembolic pulmonary hypertension or miscellaneous causes of pulmonary hypertension. Chromosomal anomalies, mainly trisomy 21, were reported in 47 (13%) of patients with confirmed disease. Median age at diagnosis was 7 years (IQR 3–12); 59% (268 of 456) were female. Although dyspnoea and fatigue were the most frequent symptoms, syncope occurred in 31% (57 of 182) of patients with IPAH or FPAH and in 18% (eight of 45) of those with repaired congenital heart disease; no children with unrepaired congenital systemic-to-pulmonary shunts had syncope. Despite severe pulmonary hypertension, functional class was I or II in 230 of 362 (64%) patients, which is consistent with preserved right-heart function. Interpretation TOPP identifies important clinical features specific to the care of paediatric pulmonary hypertension, which draw attention to the need for paediatric data rather than extrapolation from adult studies. Funding Actelion Pharmaceuticals.
Initiation of cellular DNA replication is tightly controlled to sustain genomic integrity. In eukaryotes, the heterohexameric origin recognition complex (ORC) is essential for coordinating ...replication onset. Here we describe the crystal structure of Drosophila ORC at 3.5 Å resolution, showing that the 270 kilodalton initiator core complex comprises a two-layered notched ring in which a collar of winged-helix domains from the Orc1-5 subunits sits atop a layer of AAA+ (ATPases associated with a variety of cellular activities) folds. Although canonical inter-AAA+ domain interactions exist between four of the six ORC subunits, unanticipated features are also evident. These include highly interdigitated domain-swapping interactions between the winged-helix folds and AAA+ modules of neighbouring protomers, and a quasi-spiral arrangement of DNA binding elements that circumnavigate an approximately 20 Å wide channel in the centre of the complex. Comparative analyses indicate that ORC encircles DNA, using its winged-helix domain face to engage the mini-chromosome maintenance 2-7 (MCM2-7) complex during replicative helicase loading; however, an observed out-of-plane rotation of more than 90° for the Orc1 AAA+ domain disrupts interactions with catalytic amino acids in Orc4, narrowing and sealing off entry into the central channel. Prima facie, our data indicate that Drosophila ORC can switch between active and autoinhibited conformations, suggesting a novel means for cell cycle and/or developmental control of ORC functions.
Cellular DNA replication factories depend on ring-shaped hexameric helicases to aid DNA synthesis by processively unzipping the parental DNA helix. Replicative helicases are loaded onto DNA by ...dedicated initiator, loader, and accessory proteins during the initiation of DNA replication in a tightly regulated, multistep process. We discuss here the molecular choreography of DNA replication initiation across the three domains of life, highlighting similarities and differences in the strategies used to deposit replicative helicases onto DNA and to melt the DNA helix in preparation for replisome assembly. Although initiators and loaders are phylogenetically related, the mechanisms they use for accomplishing similar tasks have diverged considerably and in an unpredictable manner.
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