There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The Concise Guide to PHARMACOLOGY 2017/18 provides concise overviews of the key properties of nearly 1800 human drug targets with an emphasis on selective pharmacology (where available), plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. Although the Concise Guide represents approximately 400 pages, the material presented is substantially reduced compared to information and links presented on the website. It provides a permanent, citable, point-in-time record that will survive database updates. The full contents of this section can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.13877/full. Enzymes are one of the eight major pharmacological targets into which the Guide is divided, with the others being: G protein-coupled receptors, ligand-gated ion channels, voltage-gated ion channels, other ion channels, nuclear hormone receptors, catalytic receptors and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. The landscape format of the Concise Guide is designed to facilitate comparison of related targets from material contemporary to mid-2017, and supersedes data presented in the 2015/16 and 2013/14 Concise Guides and previous Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature Committee of the Union of Basic and Clinical Pharmacology (NC-IUPHAR), therefore, providing official IUPHAR classification and nomenclature for human drug targets, where appropriate.

/pdf/the-concise-guide-to-pharmacology-2017-18-enzymes-5f548bda69.pdf

THE CONCISE GUIDE TO PHARMACOLOGY 2017/18: Enzymes

Many dynamical systems have an impulsive dynamical behavior due to abrupt changes at certain instants during the evolution process. The mathematical description of these phenomena leads to impulsive differential equations. In this work we present a new approach via variational methods and critical point theory to obtain the existence of solutions to impulsive problems. We consider a linear Dirichlet problem and the solutions are found as critical points of a functional. We also study the nonlinear Dirichlet impulsive problem.

Variational approach to impulsive differential equations

Strong Formulation Finite Element Method Based on Differential Quadrature: A Survey

On the free vibration analysis of laminated composite and sandwich plates: A review of recent literature with some numerical results

The main goal of our work is to study the equatorial orbital dynamics of a spacecraft near the (87) Sylvia sys-tem. Here, we consider a non-homogeneous mass distribution with a dense core inside the primary asteroid. The Mascon gravity framework using the shaped polyhedral source, from lightcurve data, is chosen to cal-culate the gravitational field. The zero-velocity curves show four unstable equilibrium points. In the absence of any solar or other celestial body perturbations, a numerical analysis of the orbital dynamics in the potential field of Sylvia is done to delineate the region of stable and unstable motions.

/pdf/orbital-stability-near-the-87-sylvia-system-4g8yxs6x64.pdf

Orbital stability near the (87) Sylvia system

Mapping orbits with low station keeping costs for constellations of satellites based on the integral over the time of the perturbing forces

The objective of this paper is to study the problem of orbital maneuvers for an artificial satellite moving in a Keplerian Force Field. Analytical equations are derived to solve this problem. Several cases are studied to validate the algorithm developed. The results show that the theory developed here are suitable for real simulations and mission analysis.

/pdf/optimal-space-maneuvers-in-three-dimensions-2ch0xdpgej.pdf

Optimal space maneuvers in three dimensions

https://arc.aiaa.org/doi/pdf/10.2514/6.2014-1639

Optimal Transfer Trajectories to the Haumea System

The gravity-assist manoeuvre is a technique in which a spacecraft changes its orbital energy and angular momentum by a close-approach with a celestial body. The result is a great reduction in the use of fuel and flight time. Several interplanetary missions have applied it for this reason, like the famous Voyagers, Mariner, or Galileo. The astronomers knew the mechanics behind such concept for at least two centuries by noting the change in the orbits of the comets after passing close to Jupiter. The introduction of this phenomenon to spaceflight was a very successful story and motivated many claims that the proposal of the gravity-assist manoeuvres occurred in the early 60s. However, the idea of using such mechanism for interplanetary spaceflight can be traced back to the 20s. The dispute of being the first to have this idea contributed to throw shadow on these early pioneers. In that sense, the present paper has the goal of discussing some aspects related to the history of this manoeuvre in the pre-spaceflight era, trying to show some of the major steps made in its early history. It covers from the first studies found on this topic and goes up to the beginning of the space age, with the launching of the Sputnik satellite. This time period is chosen to bring light to these early works in which the astronomical phenomenon is introduced in the astronautics. Their importance is highlighted by putting these works under their historical context, as it shows how some of them were far ahead of their time. Among these, the work of Tsander, made in mid-20s, is outstanding.

/pdf/a-historical-review-of-the-theory-of-gravity-assists-in-the-3gkc6e9zu5.pdf

Antonio F. B. A. Prado

Papers

Orbital stability near the (87) Sylvia system

Mapping orbits with low station keeping costs for constellations of satellites based on the integral over the time of the perturbing forces

Optimal space maneuvers in three dimensions

Optimal Transfer Trajectories to the Haumea System

A historical review of the theory of gravity-assists in the pre-spaceflight era