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Ursula Röthlisberger
Ursula Röthlisberger is a professor of computational chemistry at École Polytechnique Fédérale de Lausanne. She works on density functional theory using mixed quantum mechanical/molecular mechanical methods. She is an associate editor of the American Chemical Society Journal of Chemical Theory and Computation and a fellow of the American Association for the Advancement of Science. Early life and education Röthlisberger was born in 1964 in Solothurn. She studied physical chemistry at the University of Bern. She earned her diploma under the supervision of Ernst Schumacher in 1988. She joined IBM Research – Zurich as a doctoral student with Wanda Andreoni. She worked in IBM Zurich as a postdoc until 1992. Röthlisberger moved to the University of Pennsylvania to work with Michael L. Klein. In 1995 she moved to Germany and joined the group of Michele Parrinello at the Max Planck Institute for Solid State Research. Together they used the Car-Parrinello method to study nanosc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biological System
A biological system is a complex network which connects several biologically relevant entities. Biological organization spans several scales and are determined based different structures depending on what the system is. Examples of biological systems at the macro scale are populations of organisms. On the organ and tissue scale in mammals and other animals, examples include the circulatory system, the respiratory system, and the nervous system. On the micro to the nanoscopic scale, examples of biological systems are cells, organelles, macromolecular complexes and regulatory pathways. A biological system is not to be confused with a living system, such as a living organism. Organ and tissue systems These specific systems are widely studied in human anatomy and are also present in many other animals. * Respiratory system: the organs used for breathing, the pharynx, larynx, bronchi, lungs and diaphragm. * Digestive system: digestion and processing food with salivary g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ab Initio Quantum Chemistry Methods
''Ab initio'' quantum chemistry methods are computational chemistry methods based on quantum chemistry. The term was first used in quantum chemistry by Robert Parr and coworkers, including David Craig in a semiempirical study on the excited states of benzene. The background is described by Parr. ''Ab initio'' means "from first principles" or "from the beginning", implying that the only inputs into an ''ab initio'' calculation are physical constants. ''Ab initio'' quantum chemistry methods attempt to solve the electronic Schrödinger equation given the positions of the nuclei and the number of electrons in order to yield useful information such as electron densities, energies and other properties of the system. The ability to run these calculations has enabled theoretical chemists to solve a range of problems and their importance is highlighted by the awarding of the Nobel prize to John Pople and Walter Kohn. Accuracy and scaling ''Ab initio'' electronic structure method ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoinduced Electron Transfer
Photoinduced electron transfer (PET) is an excited state electron transfer process by which an excited electron is transferred from donor to acceptor."Organic and Inorganic Photochemistry" V. Ramamurthy and Kirk S. Schanze 1998 Marcel Dekker Due to PET a charge separation is generated, ''i.e.'', redox reaction takes place in excited state (this phenomenon is not observed in Dexter electron transfer). Breadth Such materials include semiconductors that can be photoactivated like many solar cells, biological systems such as those used in photosynthesis, and small molecules with suitable absorptions and redox states. Process It is common to describe where electrons reside as electron bands in bulk materials and electron orbitals in molecules. For the sake of expedience the following description will be described in molecular terms. When a photon excites a molecule, an electron in a ground state orbital can be excited to a higher energy orbital. This excited state leaves a vac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoinduced Charge Separation
Photoinduced charge separation is the process of an electron in an atom or molecule, being excited to a higher energy level by the absorption of a photon and then leaving the atom or molecule to a nearby electron acceptor. Rutherford model An atom consists of a positively charged nucleus orbited by electrons. The nucleus consists of uncharged neutrons and positively charged protons. Electrons are negatively charged. In the early part of the twentieth century Ernest Rutherford suggested that the electrons orbited the dense central nucleus in a manner analogous to planets orbiting the sun. The centripetal force required to keep the electrons in orbit was provided by the Coulomb force of the protons in the nucleus acting upon the electrons; just like the gravitational force of the sun acting on a planet provides the centripetal force necessary to keep the planet in orbit. This model, although appealing, doesn't hold true in the real world. Synchrotron radiation would cause the orbitin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biomimetics
Biomimetics or biomimicry is the emulation of the models, systems, and elements of nature for the purpose of solving complex human problems. The terms "biomimetics" and "biomimicry" are derived from grc, βίος (''bios''), life, and μίμησις ('' mīmēsis''), imitation, from μιμεῖσθαι (''mīmeisthai''), to imitate, from μῖμος (''mimos''), actor. A closely related field is bionics. Living organisms have evolved well-adapted structures and materials over geological time through natural selection. Biomimetics has given rise to new technologies inspired by biological solutions at macro and nanoscales. Humans have looked at nature for answers to problems throughout their existence. Nature has solved engineering problems such as self-healing abilities, environmental exposure tolerance and resistance, hydrophobicity, self-assembly, and harnessing solar energy. History One of the early examples of biomimicry was the study of birds to enable human flight. Alth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Car–Parrinello Molecular Dynamics
Car–Parrinello molecular dynamics or CPMD refers to either a method used in molecular dynamics (also known as the Car–Parrinello method) or the computational chemistry software package used to implement this method. The CPMD method is one of the major methods for calculating ab-initio molecular dynamics (ab-inito MD or AIMD). Ab initio molecular dynamics (ab initio MD) is a computational method that uses first principles, or fundamental laws of nature, to simulate the motion of atoms in a system. It is a type of molecular dynamics (MD) simulation that does not rely on empirical potentials or force fields to describe the interactions between atoms, but rather calculates these interactions directly from the electronic structure of the system using quantum mechanics. In an ab initio MD simulation, the total energy of the system is calculated at each time step using density functional theory (DFT) or another method of quantum chemistry. The forces acting on each atom are then de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Mechanics
Molecular mechanics uses classical mechanics to model molecular systems. The Born–Oppenheimer approximation is assumed valid and the potential energy of all systems is calculated as a function of the nuclear coordinates using force fields. Molecular mechanics can be used to study molecule systems ranging in size and complexity from small to large biological systems or material assemblies with many thousands to millions of atoms. All-atomistic molecular mechanics methods have the following properties: * Each atom is simulated as one particle * Each particle is assigned a radius (typically the van der Waals radius), polarizability, and a constant net charge (generally derived from quantum calculations and/or experiment) * Bonded interactions are treated as ''springs'' with an equilibrium distance equal to the experimental or calculated bond length Variants on this theme are possible. For example, many simulations have historically used a ''united-atom'' representation in which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Mechanics
Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, quantum field theory, quantum technology, and quantum information science. Classical physics, the collection of theories that existed before the advent of quantum mechanics, describes many aspects of nature at an ordinary (macroscopic) scale, but is not sufficient for describing them at small (atomic and subatomic) scales. Most theories in classical physics can be derived from quantum mechanics as an approximation valid at large (macroscopic) scale. Quantum mechanics differs from classical physics in that energy, momentum, angular momentum, and other quantities of a bound system are restricted to discrete values ( quantization); objects have characteristics of both particles and waves (wave–particle duality); and there are limits to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dirac Medal
The Dirac Medal is the name of four awards in the field of theoretical physics, computational chemistry, and mathematics, awarded by different organizations, named in honour of Professor Paul Dirac, one of the great theoretical physicists of the 20th century. The Dirac Medal and Lecture (University of New South Wales) The first-established prize is the Dirac Medal for the Advancement of Theoretical Physics, awarded by the University of New South Wales, Sydney, Australia, jointly with the Australian Institute of Physics on the occasion of the public Dirac Lecture. The Lecture and the Medal commemorate the visit to the university in 1975 of Professor Dirac, who gave five lectures there. These lectures were subsequently published as a book: ''Directions of Physics'' (Wiley, 1978 – H. Hora and J. Shepanski, eds.). Professor Dirac donated the royalties from this book to the University for the establishment of the Dirac Lecture series. The prize, first awarded in 1979, includes a sil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World Association Of Theoretical And Computational Chemists
The World Association of Theoretical and Computational Chemists (WATOC) is a scholarly association founded in 1982 "in order to encourage the development and application of theoretical methods" in chemistry, particularly theoretical chemistry and computational chemistry. It was originally called the World Association of Theoretical Organic Chemists, but was later renamed the World Association of Theoretically Oriented Chemists, and in 2005 renamed once more to the World Association of Theoretical and Computational Chemists. Conferences WATOC organizes a triennial world congress with over 1,000 participants in last years. Awards The association awards two yearly medals: the Schrödinger Medal to "outstanding theoretical and computational chemist", and the Dirac Distributed Research using Advanced Computing (DiRAC) is an integrated supercomputing facility used for research in particle physics, astronomy and cosmology in the United Kingdom. DiRAC makes use of multi-core pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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