Discharge suppression system for a double focusing, atmospheric pressure ionization mass spectrometer

An electrical discharge suppression system for a medium throughput (∼2 l/s) pumping line has been devised that works up to potentials of ±15 kV. This device permits atmospheric pressure ionization sources to be interfaced to high-resolution, magnetic sector mass spectrometers with source potentials of 6-10 k

Loss of off-site power transient analysis for a sodium-cooled fast reactor equipped with a gas power conversion system and preliminary optimisation of its operation

International audienc

New regime of inverse saturable absorption for self-stabilizing passively mode-locked lasers

The reflectivity of a semiconductor saturable absorber mirror (SESAM) is generally expected to increase with increasing pulse energy. However, for higher pulse energies the reflectivity can decrease again; we call this a ‘roll-over' of the nonlinear reflectivity curve caused by inverse saturable absorption. We show for several SESAMs that the measured roll-over is consistent with two-photon absorption only for short (femtosecond) pulses, while a stronger (yet unidentified) kind of nonlinear absorption is dominant for longer (picosecond) pulses. These inverse saturable absorption effects have important technological consequences, e.g. for the Q-switching dynamics of passively mode-locked lasers. A simple equation using only measurable SESAM parameters and including inverse saturable absorption is derived for the Q-switched mode-locking threshold. We present various data and discuss the sometimes detrimental effects of this roll-over for femtosecond high repetition rate lasers, as well as the potentially very useful consequences for passively mode-locked multi-GHz lasers. We also discuss strategies to enhance or reduce this induced absorption by using different SESAM designs or semiconductor material

Prevalence and Prognostic Value of Mesenteric Artery Stenosis in Patients Undergoing Transcatheter Aortic Valve Implantation.

Data regarding the prevalence of mesenteric artery stenosis in patients undergoing transcatheter aortic valve implantation (TAVI) are scarce. Whether patients with high-risk features for acute mesenteric ischemia (AMesI) have a worse prognosis compared with those without high-risk features is unknown. We aimed to address these questions. We included 361 patients who underwent TAVI between 2015 and 2019. Using pre-TAVI computed tomography exams, the number of stenosed arteries in each patient and the degree of stenosis for the coeliac trunk (CTr), SMA and inferior mesenteric artery (IMA) were analyzed. High-risk features for AMesI were defined as the presence of ≥2 arteries presenting with ≥50% stenosis. Patient demographic and echocardiographic data were collected. Endpoints included 30-day all-cause mortality, mortality and morbidity related to mesenteric ischemia. 22.7% of patients had no arterial stenosis, while 59.3% had 1 or 2 stenosed arteries, and 18.0% presented stenoses in 3 arteries. Prevalence of significant stenosis (≥50%) in CTr, SMA, and IMA were respectively 11.9, 5.5, 10.8%. Twenty patients at high-risk for AMesI were identified: they had significantly higher all-cause mortality (15.0 vs. 1.2%, p < 0.001) and higher mortality related to AMesI (5.0 vs. 0.3%, p = 0.004), compared with non-high-risk patients. Patients at high-risk for AMesI presented with significantly higher 30-day all-cause mortality and mortality related to AMesI following TAVI. Mesenteric revascularization before TAVI interventions may be beneficial in these patients. Prospective studies are needed to clarify these questions

Towards mirror symmetry \`a la SYZ for generalized Calabi-Yau manifolds

Fibrations of flux backgrounds by supersymmetric cycles are investigated. For an internal six-manifold M with static SU(2) structure and mirror \hat{M}, it is argued that the product M x \hat{M} is doubly fibered by supersymmetric three-tori, with both sets of fibers transverse to M and \hat{M}. The mirror map is then realized by T-dualizing the fibers. Mirror-symmetric properties of the fluxes, both geometric and non-geometric, are shown to agree with previous conjectures based on the requirement of mirror symmetry for Killing prepotentials. The fibers are conjectured to be destabilized by fluxes on generic SU(3)xSU(3) backgrounds, though they may survive at type-jumping points. T-dualizing the surviving fibers ensures the exchange of pure spinors under mirror symmetry.Comment: 30 pages, 3 figures, LaTeX; v2: references adde

Supersymmetric D-branes and calibrations on general N=1 backgrounds

We study the conditions to have supersymmetric D-branes on general {\cal N}=1 backgrounds with Ramond-Ramond fluxes. These conditions can be written in terms of the two pure spinors associated to the SU(3)\times SU(3) structure on T_M\oplus T^\star_M, and can be split into two parts each involving a different pure spinor. The first involves the integrable pure spinor and requires the D-brane to wrap a generalised complex submanifold with respect to the generalised complex structure associated to it. The second contains the non-integrable pure spinor and is related to the stability of the brane. The two conditions can be rephrased as a generalised calibration condition for the brane. The results preserve the generalised mirror symmetry relating the type IIA and IIB backgrounds considered, giving further evidence for this duality.Comment: 23 pages. Some improvements and clarifications, typos corrected and references added. v3: Version published in JHE

Pyrvinium pamoate changes alternative splicing of the serotonin receptor 2C by influencing its RNA structure

The serotonin receptor 2C plays a central role in mood and appetite control. It undergoes pre-mRNA editing as well as alternative splicing. The RNA editing suggests that the pre-mRNA forms a stable secondary structure in vivo. To identify substances that promote alternative exons inclusion, we set up a high-throughput screen and identified pyrvinium pamoate as a drug-promoting exon inclusion without editing. Circular dichroism spectroscopy indicates that pyrvinium pamoate binds directly to the pre-mRNA and changes its structure. SHAPE (selective 2\u27-hydroxyl acylation analysed by primer extension) assays show that part of the regulated 5\u27-splice site forms intramolecular base pairs that are removed by this structural change, which likely allows splice site recognition and exon inclusion. Genome-wide analyses show that pyrvinium pamoate regulates \u3e300 alternative exons that form secondary structures enriched in A-U base pairs. Our data demonstrate that alternative splicing of structured pre-mRNAs can be regulated by small molecules that directly bind to the RNA, which is reminiscent to an RNA riboswitch

Atomic-Scale Insights into Semiconductor Heterostructures: From Experimental Three-Dimensional Analysis of the Interface to a Generalized Theory of Interfacial Roughness Scattering

In this manuscript, we develop a generalized theory for the scattering process produced by interface roughness on charge carriers that is suitable for any semiconductor heterostructure. By exploiting our experimental insights into the three-dimensional atomic landscape of Ge/Ge-Si heterointerfaces obtained by atom probe tomography, we are able to define the full set of interface parameters relevant to the scattering potential, including both the in-plane and axial correlation inside real diffuse interfaces. Our experimental findings indicate a partial coherence of the interface roughness along the growth direction within the interfaces. We show that it is necessary to include this feature, previously neglected by theoretical models, when heterointerfaces characterized by finite interface widths are taken into consideration. To show the relevance of our generalized scattering model in the physics of semiconductor devices, we implement it in a nonequilibrium Green's function simulation platform to assess the performance of a Ge/Si-Ge-based terahertz quantum cascade laser