The cyclic ground state structure of the HF trimer revealed by far infrared jet-cooled Fourier transform spectroscopy.

International audienceThe rovibrationally resolved Fourier transform (FT) far infrared (FIR) spectra of two intermolecular librations of (HF)3, namely the in-plane ν6 and out-of-plane ν4 bending fundamentals centered, respectively, at about 494 cm(-1) and 602 cm(-1), have been recorded for the first time under jet-cooled conditions using the supersonic jet of the Jet-AILES apparatus. The simultaneous rotational analysis of 245 infrared transitions belonging to both bands enabled us to determine the ground state (GS), ν6 and ν4 rotational and centrifugal distortion constants. These results provided definite experimental answers to the structure of such a weakly bound trimer: firstly the vibrationally averaged planarity of cyclic (HF)3, also supported by the very small value of the inertia defect obtained in the GS, secondly the slight weakening of the hydrogen bond in the intermolecular excited states evidenced from the center of mass separations of the HF constituents determined in the ground, ν6 = 1 and ν4 = 1 states of (HF)3 as well as the decrease of the fitted rotational constants upon excitation. Finally, lower bounds of about 2 ns on ν6 and ν4 state lifetimes could be derived from the deconvolution of experimental linewidths. Such long lifetimes highlight the interest in probing low frequency intermolecular motions of molecular complexes to get rid of constraints related to the vibrational dynamics of coupled anharmonic vibrations at higher energy, resulting in loss of rotational information

Superconductivity Induced by Bond Breaking in the Triangular Lattice of IrTe2

IrTe2, a layered compound with a triangular iridium lattice, exhibits a structural phase transition at approximately 250 K. This transition is characterized by the formation of Ir-Ir bonds along the b-axis. We found that the breaking of Ir-Ir bonds that occurs in Ir1-xPtxTe2 results in the appearance of a structural critical point in the T = 0 limit at xc = 0.035. Although both IrTe2 and PtTe2 are paramagnetic metals, superconductivity at Tc = 3.1 K is induced by the bond breaking in a narrow range of x > xc in Ir1-xPtxTe2. This result indicates that structural fluctuations can be involved in the emergence of superconductivity.Comment: 10 pages, 4 figure

Holographic Lithography

This review summarises the work of the Durham-Sheffield, UK team working on Holographic Lithography over the last decade. It collates progress in 3D resolution and overall scale of the substrate wiring patterns designed and considers a range of approaches and applications

Investigating Ramp Wave Propagation inside Silica Glass with Laser Experiments and Molecular Simulations

Under elastic shock compression silica glass exhibits a very specific behaviour. A shock propagating inside a material is usually seen as the propagation of a discontinuity. However in silica glass, shocks are unstable and lead to the propagation of a ramp wave where the shock front becomes gradually larger over time. Ramp waves were already reported in the literature, however their origin remain uncertain. This work presents an original study combining laser shock-induced experiments and molecular dynamics simulation aiming to improve the understanding of the mechanisms involved. Experimental ramp waves were directly observed using shadowgraphy technique allowing for an estimation of the head and tail velocities. Molecular dynamics simulations were carried out in order to reproduce ramp waves and to gain insight into the material properties. Ramp waves were observed for both elastic and plastic shockwaves. In the latter case, the plastic waves were preceded by an elastic ramp precursor. The sound speed, related to the material compressibility, was found to decrease with increasing pressure, as observed experimentally for quasi-static hydrostatic loading, thus providing an explanation for the instabilities that lead to the propagation of ramp waves

High resolution spectroscopy of methyltrioxorhenium: towards the observation of parity violation in chiral molecules

Originating from the weak interaction, parity violation in chiral molecules has been considered as a possible origin of the biohomochirality. It was predicted in 1974 but has never been observed so far. Parity violation should lead to a very tiny frequency difference in the rovibrational spectra of the enantiomers of a chiral molecule. We have proposed to observe this predicted frequency difference using the two photon Ramsey fringes technique on a supersonic beam. Promising candidates for this experiment are chiral oxorhenium complexes, which present a large effect, can be synthesized in large quantity and enantiopure form, and can be seeded in a molecular beam. As a first step towards our objective, a detailed spectroscopic study of methyltrioxorhenium (MTO) has been undertaken. It is an ideal test molecule as the achiral parent molecule of chiral candidates for the parity violation experiment. For the 187Re MTO isotopologue, a combined analysis of Fourier transform microwave and infrared spectra as well as ultra-high resolution CO2 laser absorption spectra enabled the assignment of 28 rotational lines and 71 rovibrational lines, some of them with a resolved hyperfine structure. A set of spectroscopic parameters in the ground and first excited state, including hyperfine structure constants, was obtained for the antisymmetric Re=O stretching mode of this molecule. This result validates the experimental approach to be followed once a chiral derivative of MTO will be synthesized, and shows the benefit of the combination of several spectroscopic techniques in different spectral regions, with different set-ups and resolutions. First high resolution spectra of jet-cooled MTO, obtained on the set-up being developed for the observation of molecular parity violation, are shown, which constitutes a major step towards the targeted objective.Comment: 20 pages, 6 figure

Development of a few TW Ti:Sa laser system at 100 Hz for proton acceleration

[EN] We report the development of a table-top high peak power Titanium:Sapphire (Ti:Sa) CPA laser working at 100 Hz capable of delivering 205 mJ, 55 fs pulses. Every amplification stage is pumped by Nd-doped solid-state lasers and fully powered by diodes. Thermal effects in the Ti:Sa amplifiers are compensated passively with optics. This system is intended to be used for proton acceleration experiments at high repetition rates.Centro para el Desarrollo Tecnológico Industrial (CDTI, Spain) within the INNPRONTA program, Grant no. IPT-20111027.Lera, R.; Bellido-Millán, PJ.; Sánchez, I.; Mur, P.; Seimetz, M.; Benlloch Baviera, JM.; Roso, L.... (2019). Development of a few TW Ti:Sa laser system at 100 Hz for proton acceleration. Applied Physics B. 125(1):1-8. https://doi.org/10.1007/s00340-018-7113-8S181251P. Zeitoun, G. Faivre, S. Sebban, T. Mocek, A. Hallou, M. Fajardo, D. Aubert, P. Balcou, F. Burgy, D. Douillet, S. Kazamias, G. de Lachèze-Murel, T. Lefrou, S. le Pape, P. Mercère, H. Merdji, A.S. Morlens, J.P. Rousseau, C. Valentin, Nature 431(7007), 426–429 (2004)V. Malka, S. Fritzler, E. Lefebvre, M.-M. Aleonard, F. Burgy, J.-P. Chambaret, J.-F. Chemin, K. Krushelnick, G. Malka, S.P.D. Mangles, Z. Najmudin, M. Pittman, J.-P. Rousseau, J.-N. Scheurer, B. Walton, A.E. Dangor, Science 298(5598), 1596–1600 (2002)H. Daido, M. Nishiuchi, A.S. Pirozhkov, Rep. Progress Phys. 75(5), 056401 (2012)A. Macchi, M. Borghesi, M. Passoni, Rev. Mod. Phys. 85, 751–793 (2013)T. Tajima, J.M. Dawson, Phys. Rev. Lett. 43, 267–270 (1979)M. Noaman-ul Haq, H. Ahmed, T. Sokollik, L. Yu, Z. Liu, X. Yuan, F. Yuan, M. Mirzaie, X. Ge, L. Chen, J. Zhang, Phys. Rev. Accel. Beams 20, 041301 (2017)D. Strickland, G. Mourou, Opt. Commun. 53(3), 219–221 (1985)G. Cheriaux, B. Walker, L.F. Dimauro, P. Rousseau, F. Salin, J.P. Chambaret, Opt. Lett. 21(6), 414–416 (1996)P. Tournois, Opt. Commun. 140(4), 245–249 (1997)R. Soulard, A. Brignon, S. Raby, E. Durand, R. Moncorgé, Appl. Phys. B 106(2), 295–300 (2012)J. Liu, L. Ge, L. Feng, H. Jiang, H. Su, T. Zhou, J. Wang, Q. Gao, J. Li, Chin. Opt. Lett. 14(5), 051404 (2016)A. Maleki, M.K. Tehrani, H. Saghafifar, M.H.M. Dindarlu, H. Ebadian, Laser Phys. 26(2), 025003 (2016)R. Lera, F. Valle-Brozas, S. Torres-Peiró, A.R. de-la Cruz, M. Galán, P. Bellido, M. Seimetz, J.M. Benlloch, L. Roso, Appl. Opt. 55(33), 9573–9576 (2016)R. Lausten, P. Balling, J. Opt. Soc. Am. B 20(7), 1479–1485 (2003)I. Nam, M. Kim, T.H. Lee, S.W. Lee, H. Suk, Curr. Appl. Phys. 15(4), 468–472 (2015)E. Treacy, IEEE J. Quantum Electron. 5(9), 454–458 (1969)A. Trisorio, S. Grabielle, M. Divall, N. Forget, C.P. Hauri, Opt. Lett. 37(14), 2892–2894 (2012)Y.-H. Cha, Y.-W. Lee, S.M. Nam, J.M. Han, Y.J. Rhee, B.D. Yoo, B.C. Lee, Y.U. Jeong, Appl. Opt. 46(28), 6854–6858 (2007)P. Bellido, R. Lera, M. Seimetz, A.R. de la Cruz, S. Torres-Peiró, M. Galán, P. Mur, I. Sánchez, R. Zaffino, L. Vidal, A. Soriano, S. Sánchez, F. Sánchez, M. Rodríguez-Álvarez, J. Rigla, L. Moliner, A. Iborra, L. Hernández, D. Grau-Ruiz, A. González, J. García-Garrigos, E. Díaz-Caballero, P. Conde, A. Aguilar, L. Roso, J. Benlloch, J. Instrum. 12(05), T05001 (2017

Land Cover Trends Dataset, 1973–2000

The U.S. Geological Survey Land Cover Trends Project is releasing a 1973–2000 time-series land-use/land-cover dataset for the conterminous United States. The dataset contains 5 dates of land-use/land-cover data for 2,688 sample blocks randomly selected within 84 ecological regions. The nominal dates of the land-use/land-cover maps are 1973, 1980, 1986, 1992, and 2000. The land-use/land-cover maps were classified manually from Landsat Multispectral Scanner, Thematic Mapper, and Enhanced Thematic Mapper Plus imagery using a modified Anderson Level I classification scheme. The resulting land-use/land-cover data has a 60-meter resolution and the projection is set to Albers Equal-Area Conic, North American Datum of 1983. The files are labeled using a standard file naming convention that contains the number of the ecoregion, sample block, and Landsat year. The downloadable files are organized by ecoregion, and are available in the ERDAS IMAGINETM (.img) raster file format

Expression of ALS-linked SOD1 mutation in motoneurons or myotubes induces differential effects on neuromuscular function in vitro

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that selectively affects upper and lower motoneurons. Dismantlement of the neuromuscular junction (NMJ) is an early pathological hallmark of the disease whose cellular origin remains still debated. We developed an in vitro NMJ model to investigate the differential contribution of motoneurons and muscle cells expressing ALS-causing mutation in the superoxide dismutase 1 (SOD1) to neuromuscular dysfunction. The primary co-culture system allows the formation of functional NMJs and fosters the expression of the ALS-sensitive fast fatigable type II-b myosin heavy chain (MHC) isoform. Expression of SOD1(G93A) in myotubes does not prevent the formation of a functional NMJ but leads to decreased contraction frequency and lowers the slow type I MHC isoform transcript levels. Expression of SOD1(G93A) in both motoneurons and myotubes or in motoneurons alone however alters the formation of a functional NMJ. Our results strongly suggest that motoneurons are a major factor involved in the process of NMJ dismantlement in an experimental model of ALS

Creation and preclinical evaluation of genetically attenuated malaria parasites arresting growth late in the liver.

Whole-sporozoite (WSp) malaria vaccines induce protective immune responses in animal malaria models and in humans. A recent clinical trial with a WSp vaccine comprising genetically attenuated parasites (GAP) which arrest growth early in the liver (PfSPZ-GA1), showed that GAPs can be safely administered to humans and immunogenicity is comparable to radiation-attenuated PfSPZ Vaccine. GAPs that arrest late in the liver stage (LA-GAP) have potential for increased potency as shown in rodent malaria models. Here we describe the generation of four putative P. falciparum LA-GAPs, generated by CRISPR/Cas9-mediated gene deletion. One out of four gene-deletion mutants produced sporozoites in sufficient numbers for further preclinical evaluation. This mutant, PfΔmei2, lacking the mei2-like RNA gene, showed late liver growth arrest in human liver-chimeric mice with human erythrocytes, absence of unwanted genetic alterations and sensitivity to antimalarial drugs. These features of PfΔmei2 make it a promising vaccine candidate, supporting further clinical evaluation. PfΔmei2 (GA2) has passed regulatory approval for safety and efficacy testing in humans based on the findings reported in this study