Natural and sail-displaced doubly-symmetric Lagrange point orbits for polar coverage

This paper proposes the use of doubly-symmetric, eight-shaped orbits in the circular restricted three-body problem for continuous coverage of the high-latitude regions of the Earth. These orbits, for a range of amplitudes, spend a large fraction of their period above either pole of the Earth. It is shown that they complement Sun-synchronous polar and highly eccentric Molniya orbits, and present a possible alternative to low thrust pole-sitter orbits. Both natural and solar-sail displaced orbits are considered. Continuation methods are described and used to generate families of these orbits. Starting from ballistic orbits, other families are created either by increasing the sail lightness number, varying the period or changing the sail attitude. Some representative orbits are then chosen to demonstrate the visibility of high-latitude regions throughout the year. A stability analysis is also performed, revealing that the orbits are unstable: it is found that for particular orbits, a solar sail can reduce their instability. A preliminary design of a linear quadratic regulator is presented as a solution to stabilize the system by using the solar sail only. Finally, invariant manifolds are exploited to identify orbits that present the opportunity of a ballistic transfer directly from low Earth orbit

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Structural and spectroscopic characterization of methyl isocyanate, methyl cyanate, methyl fulminate, and acetonitrile N-oxide using highly correlated ab initio methods

10 pags.,3 figs., 7 tabs.Various astrophysical relevant molecules obeying the empirical formula CHNO are characterized using explicitly correlated coupled cluster methods (CCSD(T)-F12). Rotational and rovibrational parameters are provided for four isomers: methyl isocyanate (CHNCO), methyl cyanate (CHOCN), methyl fulminate (CHONC), and acetonitrile N-oxide (CHCNO). A CHCON transition state is inspected. A variational procedure is employed to explore the far infrared region because some species present non-rigidity. Second order perturbation theory is used for the determination of anharmonic frequencies, rovibrational constants, and to predict Fermi resonances. Three species, methyl cyanate, methyl fulminate, and CHCON, show a unique methyl torsion hindered by energy barriers. In methyl isocyanate, the methyl group barrier is so low that the internal top can be considered a free rotor. On the other hand, acetonitrile N-oxide presents a linear skeleton, C symmetry, and free internal rotation. Its equilibrium geometry depends strongly on electron correlation. The remaining isomers present a bend skeleton. Divergences between theoretical rotational constants and previous parameters fitted from observed lines for methyl isocyanate are discussed on the basis of the relevant rovibrational interaction and the quasi-linearity of the molecular skeleton. Published by AIP PublishingThis research was supported by a Marie Curie International Research Staff Exchange Scheme Fellowship within the 7th European Community Framework Program under Grant No. PIRSES-GA-2012-31754 and the FIS2013- 40626-P project of the MINECO, Spain. The authors also acknowledge the COST Actions 1401 and 1405. S.D. acknowledges MAEC-ACID (Spain) for the grant.Peer Reviewe

Structural and spectroscopic characterization of various isotopologues of 2-hydroxyacetonitrile using highly correlated ab initio methods

8 pags., 3 figs., 5 tabs.Abstract: Various isotopologues of 2-hydroxyacetonitrile (OHCHCN), a detectable astrophysical molecule, are characterized using explicitly correlated coupled cluster theory (CCSD(T)-F12/AVTZ-F12). Rovibrational parameters and far infrared transitions are computed to help the interpretation of the rotational spectra and radioastronomical observations. OHCHCN displays non-rigid properties. The OH internal rotation intertransforms two conformers, gauche and trans, whose energy separation reaches 1.41 kcal/mol. The process is restricted by energy barriers of V = ~ 645 cm and V = ~ 425 cm. Isotopic effects on the rotational constants and on the torsional energy levels are evaluated for isotopic varieties containing the most abundant cosmological isotopes (C, C, N and D). Effects are relevant for ODCHCN where the ground vibrational state splits in two components separated by 0.51 cm. This gap has been evaluated to be 3.20 cm for the main isotopologue. Graphical abstract: [Figure not available: see fulltext.].This research was supported by the FIS2013-40626-P and FIS2016-76418-P projects of the MINECO, Spain. The authors also acknowledge the COST Actions 1401 and 1405. S.D. acknowledges MAEC-ACID (Spain) for the grant.Peer Reviewe

Theoretical Spectroscopic Characterization at low Temperatures of C2H3NO and its Isomers

MOLEC 2016, Toledo (Spain), 11 - 16 September 2016Relevant astrophysical molecules of empirical formula C2H3NO are characterized using explicitly correlated coupled cluster methods (CCSD(T)-F12/AVTZ-F12). We present results for four species: the most stable methyl isocyanate (CH3NCO), as well as, methyl cyanate (CH3NCO), acetonitrile oxide (CH3CNO) and hydroxyacetonitrile (HOCH2CN). Whereas acetonitrile oxide is a linear C3v structure, the remaining isomers are non-rigid species derived from methyl or OH group torsions. The recently detected methyl isocyanate shows a very low torsional energy barrier (V3=16.2 cm-1). All the torsional energy levels lye over the barrier. Thus, the methyl group can be considered a free rotor. The ground vibrational state rotational constants have been calculated to be A0 =76164.32 MHz, B0 =4411.89 MHz and C0 =4254.58 MHz. Although, the rotational parameters are really dependent of the skeletal motions, our parameters are in a very good agreement with the experimental ones [1]. Methyl cyanate shows a more conventional behavior. In this case, V3= 364.84 cm-1. The rotational constants A0 =39089.80 MHz, B0 = 5314.78 MHz and C0 = 4816.35 MHz were determined in a very agreement with the experimental ones [2]. Hydroxyacetonitrile show two different conformers which energy separation is 1.5 kcal/mol. The hydroxyl group display internal rotation restricted by two energy barriers (Vt=540 cm-1 and Vg¿g=446.4 cm-1. Finally, we provide anharmonic frequencies, predicting possible Fermi interactions, centrifugal distortions constants and torsional transitions. These last were calculated variationally using a CCSD(T)-F12 potential energy surface.Peer Reviewe

Theoretical Spectroscopic Characterization at low Temperatures of C2H3NO and its Isomers

ICTCM 2017, Kenitra- Morocco, March 15-17, 2017. -- http://www.uit.ac.ma/events/conference-internationale-de-chimie-theorique-modelisation/The astrophysical relevant molecules of empirical formula C2H3NO are characterized using explicitly correlated coupled cluster methods CCSD(T)-F12/AVTZ-F12). Rovibrational parameters and far infrared transitions are provided for five isomers: methyl isocyanate (CH3NCO), methyl cyanate (CH3OCN), methyl fulminate (CH3ONC), acetonitrile N-oxide (CH3CNO). A CH3CON transition state is inspected. The equilibrium rotational constants of acetonitrile N-oxide, Ae =160322.4 MHz, Be = Ce = 3909.39 MHz, correspond to a linear C3v structure. The remaining isomers present a bend skeleton and non-rigidity caused by internal rotation. The recently detected methyl isocyanate, the most stable isomer, contains a rotating methyl group that can be considered a free rotor given the very low torsional energy barrier (V3=16.2 cm-1). The ground vibrational state rotational constants have been calculated to be A0 =76164.32 MHz, B0 =4411.89 MHz and C0 =4254.58 MHz. Divergences between ab initio data and previous parameters fitted from observed lines, are related to the large rovibrational interaction. For methyl cyanate (V3= 364.84 cm-1, A0 =39089.80 MHz, B0 = 5314.78 MHz and C0 = 4816.35 MHz), the ab initio rotational constants are in a very agreement with the experimental ones. Torsional and rotational parameters are computed for methyl fulminate (V3=821.7 cm-1, A0 =37004.74 MHz, B0 =5696.21 MHz, C0 =5083.48 MHz).Peer Reviewe

Structural and Spectroscopic Characterization of Methyl Isocyanate and Various Isomers using highly correlated ab initio methods

Conferencia invitada ; European Conference on Laboratory Astrophysics (2016), Gas on the rocks, CSIC, Madrid, Spain, 21-25 November, 2016 ; http://www.ecla2016.com/BRIEF SUMMARY: The astrophysical relevant molecules of empirical formula C2H3NO are characterized using explicitly correlated coupled cluster methods (CCSD(T)-F12/AVTZ-F12). Rovibrational parameters and far infrared transitions are provided for various isomers: isocyanate (CH3NCO), methyl cyanate (CH3NCO), methyl fulminate (CH3ONC) acetonitrile N-oxide (CH3CNO) and 2-hydroxyacetonitrile (HOCH2CN).Peer Reviewe

Variational evaluation of the HSSH FIR transitions: The anomalous K-doubling

The roto-torsional energy levels of HSSH and DSSD up to J = 20 are evaluated variationally with a Hamiltonian expressed in terms of internal coordinates. The kinetic and potential parameters are derived from ab initio calculations with full optimization of the geometry. The calculated levels are employed for the determination of the centrifugal distortion constants. HSSH is a near-prolate symmetric rotor. The most stable C2 conformer, calculated with MP4(SDQ)/cc-pVQZ, exhibits a 90.55° dihedral angle. For J = 0, the lowest energies of HSSH and DSSD are 413.4876 cm-1 (n = 1), 798.0304 cm-1 (n = 2) and 1151.5773 cm-1 (n = 3), and 304.3185 cm-1 (n = 1), 594.2919 cm-1 (n = 2), and 869.3508 cm-1 (n = 3), respectively. For J = 60, the ab initio calculations allow the reproduction of the anomalous type-K doubling predicted with perturbation theory. © 2000 Academic PressThis work was supported by the “Consejería de Educación y Cultura” de la Comunidad de Castilla y León (BU07/97) and the “Vicerectorado de Investigación y Relaciones Internacionales” of the University of Burgos. Y.G.S. and R.D.G. also acknowledge the financial assistance from the “Comision Interministerial de Ciencias y Tecnologia” of Spain through Grant PB 96-0882.Peer Reviewe

Ab initio determination of the effect of the C-C bond enlargement, the H wagging and the COH bending, on the torsional frequencies of glyoxal

In this paper, the torsional energy levels of glyoxal are determined variationally from fully optimized MP2/cc-pVTZ ab initio calculations using flexible models in one and two dimensions. In the two-dimensional calculations a second internal coordinate is explicitly considered as an independent variable. For this purpose, an internal coordinate (or a linear combination of internal coordinates) that could have an important contribution to the lowest amplitude normal modes, is selected as a second independent variable. This second coordinate will be: the C-C stretching, the symmetric or antisymmetric CCO bending, the symmetric or antisymmetric H wagging coordinate. In the one-dimensional calculations, the second variable is considered as a parameter to be optimized. The effect of the optimization on the torsional levels is compared with the effect of the addition as an independent variable. It can be concluded in the case of the stretching that both ways of considering the coordinate are equivalent. However, the two procedures yield different results for the bending and wagging cases. The main differences between the one- and the two-dimensional model are found for the H wagging coordinates. Finally, the vibrational effects on the rotational constant are also analysed. © 1999 Taylor & Francis Ltd.Peer Reviewe