What is the Oxygen Isotope Composition of Venus? The Scientific Case for Sample Return from Earth’s “Sister” Planet

Venus is Earth’s closest planetary neighbour and both bodies are of similar size and mass. As a consequence, Venus is often described as Earth’s sister planet. But the two worlds have followed very different evolutionary paths, with Earth having benign surface conditions, whereas Venus has a surface temperature of 464 °C and a surface pressure of 92 bar. These inhospitable surface conditions may partially explain why there has been such a dearth of space missions to Venus in recent years.The oxygen isotope composition of Venus is currently unknown. However, this single measurement (Δ17O) would have first order implications for our understanding of how large terrestrial planets are built. Recent isotopic studies indicate that the Solar System is bimodal in composition, divided into a carbonaceous chondrite (CC) group and a non-carbonaceous (NC) group. The CC group probably originated in the outer Solar System and the NC group in the inner Solar System. Venus comprises 41% by mass of the inner Solar System compared to 50% for Earth and only 5% for Mars. Models for building large terrestrial planets, such as Earth and Venus, would be significantly improved by a determination of the Δ17O composition of a returned sample from Venus. This measurement would help constrain the extent of early inner Solar System isotopic homogenisation and help to identify whether the feeding zones of the terrestrial planets were narrow or wide.Determining the Δ17O composition of Venus would also have significant implications for our understanding of how the Moon formed. Recent lunar formation models invoke a high energy impact between the proto-Earth and an inner Solar System-derived impactor body, Theia. The close isotopic similarity between the Earth and Moon is explained by these models as being a consequence of high-temperature, post-impact mixing. However, if Earth and Venus proved to be isotopic clones with respect to Δ17O, this would favour the classic, lower energy, giant impact scenario.We review the surface geology of Venus with the aim of identifying potential terrains that could be targeted by a robotic sample return mission. While the potentially ancient tessera terrains would be of great scientific interest, the need to minimise the influence of venusian weathering favours the sampling of young basaltic plains. In terms of a nominal sample mass, 10 g would be sufficient to undertake a full range of geochemical, isotopic and dating studies. However, it is important that additional material is collected as a legacy sample. As a consequence, a returned sample mass of at least 100 g should be recovered.Two scenarios for robotic sample return missions from Venus are presented, based on previous mission proposals. The most cost effective approach involves a “Grab and Go” strategy, either using a lander and separate orbiter, or possibly just a stand-alone lander. Sample return could also be achieved as part of a more ambitious, extended mission to study the venusian atmosphere. In both scenarios it is critical to obtain a surface atmospheric sample to define the extent of atmosphere-lithosphere oxygen isotopic disequilibrium. Surface sampling would be carried out by multiple techniques (drill, scoop, “vacuum-cleaner” device) to ensure success. Surface operations would take no longer than one hour.Analysis of returned samples would provide a firm basis for assessing similarities and differences between the evolution of Venus, Earth, Mars and smaller bodies such as Vesta. The Solar System provides an important case study in how two almost identical bodies, Earth and Venus, could have had such a divergent evolution. Finally, Venus, with its runaway greenhouse atmosphere, may provide data relevant to the understanding of similar less extreme processes on Earth. Venus is Earth’s planetary twin and deserves to be better studied and understood. In a wider context, analysis of returned samples from Venus would provide data relevant to the study of exoplanetary systems

Search for jet extinction in the inclusive jet-pT spectrum from proton-proton collisions at s=8 TeV

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.The first search at the LHC for the extinction of QCD jet production is presented, using data collected with the CMS detector corresponding to an integrated luminosity of 10.7  fb−1 of proton-proton collisions at a center-of-mass energy of 8 TeV. The extinction model studied in this analysis is motivated by the search for signatures of strong gravity at the TeV scale (terascale gravity) and assumes the existence of string couplings in the strong-coupling limit. In this limit, the string model predicts the suppression of all high-transverse-momentum standard model processes, including jet production, beyond a certain energy scale. To test this prediction, the measured transverse-momentum spectrum is compared to the theoretical prediction of the standard model. No significant deficit of events is found at high transverse momentum. A 95% confidence level lower limit of 3.3 TeV is set on the extinction mass scale

Searches for electroweak neutralino and chargino production in channels with Higgs, Z, and W bosons in pp collisions at 8 TeV

Searches for supersymmetry (SUSY) are presented based on the electroweak pair production of neutralinos and charginos, leading to decay channels with Higgs, Z, and W bosons and undetected lightest SUSY particles (LSPs). The data sample corresponds to an integrated luminosity of about 19.5 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV collected in 2012 with the CMS detector at the LHC. The main emphasis is neutralino pair production in which each neutralino decays either to a Higgs boson (h) and an LSP or to a Z boson and an LSP, leading to hh, hZ, and ZZ states with missing transverse energy (E-T(miss)). A second aspect is chargino-neutralino pair production, leading to hW states with E-T(miss). The decays of a Higgs boson to a bottom-quark pair, to a photon pair, and to final states with leptons are considered in conjunction with hadronic and leptonic decay modes of the Z and W bosons. No evidence is found for supersymmetric particles, and 95% confidence level upper limits are evaluated for the respective pair production cross sections and for neutralino and chargino mass values

SYNTHESIS AND PROPERTIES OF NEMATIC LIQUID CRYSTALS EXHIBITING A POSITIVE DIELECTRIC ANISOTROPY

Des séries de cristaux liquides comportant des groupements benzonitrile et cinnamonitrile en position para ont été préparées. Leurs températures de transition et leurs constantes diélectriques ont été déterminées. L'introduction dans des cristaux liquides d'un groupe nitrile en position para ne change pas de manière significative leurs stabilités thermiques, mais augmente considérablement leurs anisotropies diélectriques. L'adjonction d'une double liaison dans des mésomorphes accroît leurs stabilités thermiques mais joue très peu sur leurs anisotropies diélectriques.A series of liquid crystalline materials comprising 4-substituted benzonitriles and cinnamonitriles were prepared, and their transition temperatures and dielectric constants were investigated. The introduction of a 4-cyano group in a liquid crystal (LC) molecule is not accompanied by significant changes in mesophase thermal stabilities but it leads to materials with a considerable positive dielectric anisotropy. Introduction of an additional double bond in LC molecules increases mesophase thermal stabilities without significant changes in their dielectric anisotropies

Facile Synthesis and Biological Evaluation of New Thieno[2,3-g]indolizine Derivatives

An effective approach to the synthesis of thieno[2,3-g]indolizine derivatives has been developed. A wide variety of reagents such as unsaturated aldehydes, methylvinylketone, esters of acrylic acid, maleic anhydride, methyl propiolate, dimethyl and diethyl acetylenedicarboxylates in the construction of functionally diverse rarely encountered tricyclic system has been used. A high number of structurally various thieno[2,3-g]indolizines has been obtained in domino reactions with medium and high yields, the influence of solvents on the course of transformations has been studied, and the presence of moderate cytotoxic activity for a number of compounds has been established. © 2020 Wiley-VCH Gmb

Synthesis of 1-(para-methoxyphenyl)tetrazolyl-Substituted 1,2,3,4-Tetrahydroisoquinolines and Their Transformations Involving Activated Alkynes

1-(p-Methoxyphenyl)tetrazolyl-substituted 6,7-dimethoxy(6,7-methylenedioxy)-1,2,3,4-tetrahydroisoquinolines formed tetrazolyl-substituted azocines in high yields by using activated alkynes. Unsubstituted at 6,7,8-aromatic fragment 1-tetrazolylisoquinoline interacted in several pathways forming tetrazolyl-substituted azocines, 1-tetrazolyl-1-R-vinylisoquinolines and 3-azaspiro[5.5]undeca-1,7,9-triene