Chaos and complexity in chemical systems

Author(s):  
Raymond Kapral ◽  
Simon J Fraser
Keyword(s):  
Author(s):  
Scott Emerson Wood ◽  
Rubin Battino
Keyword(s):  

2019 ◽  
Author(s):  
Mohammad Mosharraf Hossain ◽  
Joshua Atkinson ◽  
Scott Hartley

Dissipative (nonequilibrium) assembly powered by chemical fuels has great potential for the creation of new adaptive chemical systems. However, while molecular assembly at equilibrium is routinely used to prepare complex architectures from polyfunctional monomers, species formed out of equilibrium have, to this point, been structurally very simple. In most examples the fuel simply effects the formation of a single transient covalent bond. Here, we show that chemical fuels can assemble bifunctional components into macrocycles containing multiple transient bonds. Specifically, dicarboxylic acids give aqueous dianhydride macrocycles on treatment with a carbodiimide. The macrocycle is assembled efficiently as a consequence of both fuel-dependent and -independent mechanisms: it undergoes slower decomposition, building up as the fuel recycles the components, and is a favored product of the dynamic exchange of the anhydride bonds. These results create new possibilities for generating structurally sophisticated out-of-equilibrium species.


2019 ◽  
Author(s):  
Mohammad Mosharraf Hossain ◽  
Joshua Atkinson ◽  
Scott Hartley

Dissipative (nonequilibrium) assembly powered by chemical fuels has great potential for the creation of new adaptive chemical systems. However, while molecular assembly at equilibrium is routinely used to prepare complex architectures from polyfunctional monomers, species formed out of equilibrium have, to this point, been structurally very simple. In most examples the fuel simply effects the formation of a single transient covalent bond. Here, we show that chemical fuels can assemble bifunctional components into macrocycles containing multiple transient bonds. Specifically, dicarboxylic acids give aqueous dianhydride macrocycles on treatment with a carbodiimide. The macrocycle is assembled efficiently as a consequence of both fuel-dependent and -independent mechanisms: it undergoes slower decomposition, building up as the fuel recycles the components, and is a favored product of the dynamic exchange of the anhydride bonds. These results create new possibilities for generating structurally sophisticated out-of-equilibrium species.


Author(s):  
Justyna Żwawiak ◽  
Anna Pawełczyk ◽  
Dorota Olender ◽  
Lucjusz Zaprutko

: Triterpenes are a wide and important group of compounds that have several promising pharmacological properties, such as hepatoprotective, anti-inflammatory, anti-HIV, antioxidant, or anticancer activities. Such potent substances can be successfully incorporated in more complex chemical systems e.g. codrugs or pro-drugs that have better pharmacological profile. The codrug is connected with a drug formation pathway to chemically cohere at least two drug molecules to improve positive therapeutic efficiency or decrease side effects. The codrug can be cleaved in the organism to generate effective compounds previously used as substrates. This article presents an overview of codrugs that consist of pentacyclic triterpene moiety that is chosen as a basic codrug moiety due to their wide range of vital activities and another drug molecule fragment. It was found that triterpenoid codrugs are characterized by a wide range of biological activities. However, most of them have anticancer potency.


Author(s):  
Peter Mann

This chapter discusses the importance of circular motion and rotations, whose applications to chemical systems are plentiful. Circular motion is the book’s first example of a special case of motion using the laws developed in previous chapters. The chapter begins with the basic definitions of circular motion; as uniform rotation around a principle axis is much easier to consider, it is the focus of this chapter and is used to develop some key ideas. The chapter discusses angular displacement, angular velocity, angular momentum, torque, rigid bodies, orbital and spin momenta, inertia tensors and non-inertial frames and explores fictitious forces as well as transformations in rotating frames.


2000 ◽  
Vol 10 (12) ◽  
pp. 2669-2687 ◽  
Author(s):  
JOHN GUCKENHEIMER ◽  
KATHLEEN HOFFMAN ◽  
WARREN WECKESSER

Singularly perturbed systems of ordinary differential equations arise in many biological, physical and chemical systems. We present an example of a singularly perturbed system of ordinary differential equations that arises as a model of the electrical potential across the cell membrane of a neuron. We describe two periodic solutions of this example that were numerically computed using continuation of solutions of boundary value problems. One of these periodic orbits contains canards, trajectory segments that follow unstable portions of a slow manifold. We identify several mechanisms that lead to the formation of these and other canards in this example.


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