WikiMili The Free Encyclopedia

**Brendan Kevin Patrick Scaife** FTCD, MRIA, Boyle Laureate ^{ [1] } ( /skeɪf/ ; born 19 May 1928), is an Irish academic engineer and physicist who carried out pioneering work on the theory of dielectrics. Scaife founded the Dielectrics Group in Trinity College Dublin where he is Fellow Emeritus and formerly Professor of Electromagnetism, and previously to that a Professor of Engineering Science. Scaife showed that in a linear system the decay function is directly proportional to the autocorrelation function of the corresponding fluctuating macroscopic variable, and proved how the spectral density of the dipole moment fluctuations of a dielectric body could be calculated from the frequency dependence of the complex permittivity, ε(ω) = ε'(ω) – iε"(ω). It was independent of Ryogo Kubo who in 1957 developed the corresponding theory for magnetic materials. The work was published prior to the work of Robert Cole in 1965 which is often cited.

A **fellow** is a member of a group of learned people which works together in pursuing mutual knowledge or practice. There are many different kinds of fellowships which are awarded for different reasons in academia and industry. These often indicate a different level of scholarship.

The **Royal Irish Academy**, based in Dublin, is an all-Ireland, independent academic body that promotes study and excellence in the sciences, humanities and social sciences. It is one of Ireland's premier learned societies and cultural institutions, and currently has around 501 members including Honorary Members, elected in recognition of their academic achievements. The Academy was established in 1785 and granted a royal charter in 1786.

A **physicist** is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate causes of phenomena, and usually frame their understanding in mathematical terms. Physicists work across a wide range of research fields, spanning all length scales: from sub-atomic and particle physics, through biological physics, to cosmological length scales encompassing the universe as a whole. The field generally includes two types of physicists: experimental physicists who specialize in the observation of physical phenomena and the analysis of experiments, and theoretical physicists who specialize in mathematical modeling of physical systems to rationalize, explain and predict natural phenomena. Physicists can apply their knowledge towards solving practical problems or to developing new technologies.

- Early life
- Career
- Complex permittivity of polar liquids
- Dublin Institute for Advanced Studies; work with Schrödinger and Fröhlich
- Inertial effects
- Polarizability Plot – or "Scaife Plot" – for representing high frequency data
- Casimir effect; high field effects; alkali halides; Garrett Scaife and high pressure studies
- Collaboration with J. H. Calderwood
- Ferrofluids and other interests
- Fellowship of Trinity College Dublin and other recognition
- Bibliography
- Notes
- References

Brendan Scaife was born in London on 19 May 1928 and just after World War II he began his undergraduate studies in the Department of Electrical Engineering at Queen Mary College, University of London; he graduated in 1949. At Queen Mary College there was a high-voltage laboratory run by Professor Hans Tropper, whose lectures on electromagnetic theory inspired Scaife. After graduation, he began research into the properties of insulating materials under Tropper's direction. Scaife's doctoral research broke new ground in the study of dielectrics.

The **University of London** is a federal research university located in London, England. As of October 2018, the university contains 18 member institutions, central academic bodies and research institutes. The university has over 52,000 distance learning external students and 161,270 campus-based internal students, making it the largest university by number of students in the United Kingdom.

**Hans Tropper** (1905–1978) was an Austrian Professor of Electrical Engineering with research interest in breakdown strength of liquid insulation. The ‘Hans Tropper Memorial Lecture’ is held in his honour to open each IEEE International Conference on Dielectric Liquids. He also briefly worked for *Elin Aktiengesellschaft fur Elektrische Industrie*.

Brendan Scaife was the first scientist to successfully measure the complex permittivity of a number of polar liquids such as eugenol, glycerol and water as a function of pressure up to 12 kbar. This is published in a research note in Proc. Phys. Soc. B, 68 (1955) 790. Up to that time, Chan and Danforth working in Bridgman's laboratory in the USA, had measured essentially the equilibrium relative permittivity ε(ω) of a number of liquids. At the time the experimental facilities in this area of research were severely limited. Commercial bridges for measuring complex permittivity were not available. A three terminal transformer coupled ratio arm bridge based on Blumlein's invention prior to the War had been constructed at Queen Mary by an Indian student S. Sharan for his PhD work. This bridge was applied successfully to measurements of samples subjected to high pressures. After completing this work and a brief period of employment with GEC in Wembley, he returned with his Irish parents to Ireland where he remained for the rest of his career in spite of many offers from abroad.

**Alan Dower Blumlein** was an English electronics engineer, notable for his many inventions in telecommunications, sound recording, stereophonic sound, television and radar. He received 128 patents and was considered as one of the most significant engineers and inventors of his time.

Brendan Scaife joined the Dublin Institute for Advanced Studies in 1954. Here Prof. Erwin Schrödinger was still a Senior Professor as was Cornelius Lanczos. The work of these two leading theoretical Physicists of the 20th century was a source of great inspiration to him and helped in shaping his future work. In 1961 he joined the School of Engineering at Trinity College.

The **Dublin Institute for Advanced Studies** (**DIAS**) was established in 1940 by the then Taoiseach, Éamon de Valera under the *Institute for Advanced Studies Act, 1940* in Dublin, Ireland. As set out in its legislation, 'the functions of the Institute shall be to provide facilities for the furtherance of advanced study and the conduct of research in specialised branches of knowledge and for the publication of results of advanced study and research.'

**Erwin Rudolf Josef Alexander Schrödinger**, sometimes written as **Erwin Schrodinger** or **Erwin Schroedinger**, was a Nobel Prize-winning Austrian physicist who developed a number of fundamental results in the field of quantum theory: the Schrödinger equation provides a way to calculate the wave function of a system and how it changes dynamically in time.

**Cornelius (Cornel) Lanczos** was a Hungarian mathematician and physicist, who was born on February 2, 1893, and died on June 25, 1974. According to György Marx he was one of The Martians.

His interest in the theory of dielectrics led to a collaboration with Professor Herbert Fröhlich at the University of Liverpool, where he was a regular visitor in the 1950s and 1960s. He developed a lifelong friendship with Fröhlich and the members of his research group. Scaife sought to apply the work of Callen and Welton (1951) on the Fluctuation-dissipation theorem to Frohlich's work on dipole moment fluctuations in dielectric bodies. This work on the theory of dielectrics culminated in a long report in 1959 published by the Electrical Research Association (now ERA Technology Ltd ) on "Dispersion and fluctuation in linear systems with particular reference to dielectrics". In this he pointed out that, in a linear system, the decay function was directly proportional to the autocorrelation function of the corresponding fluctuating macroscopic variable. He showed how the spectral density of the dipole moment fluctuations of a dielectric body could be calculated from the frequency dependence of the complex permittivity ε(ω) = ε'(ω) – iε"(ω). This work was later published in *Progress in Dielectrics*, 1963. It was independent of Ryogo Kubo who in 1957 developed the corresponding theory for magnetic materials. The work was published prior to the work of Robert Cole in 1965 which is often cited.

**Herbert Fröhlich** FRS was a German-born British physicist.

The **University of Liverpool** is a public university based in the city of Liverpool, England. Founded as a college in 1881, it gained its royal charter in 1903 with the ability to award degrees and is also known to be one of the six original 'red brick' civic universities. It comprises three faculties organised into 35 departments and schools. It is a founding member of the Russell Group, the N8 Group for research collaboration and the university management school is AACSB accredited.

**Herbert Bernard Callen** was an American physicist specializing in thermodynamics and statistical mechanics. He is considered one of the founders of the modern theory of irreversible thermodynamics, and is the author of the classic textbook *Thermodynamics and An Introduction to Thermostatistics*. During World War II, his services were invoked in the theoretical division of the Manhattan Project.

The theory of the equilibrium relative permittivity, ε(ω) of dipolar substances had been developed by Kirkwood (1939) and Fröhlich (1948), who built on the pioneering work of Debye (1913) and Onsager (1936). It was hoped that the results of his 1959 report could be used to generalise the work of Onsager, Kirkwood and Fröhlich and to obtain a theory for the frequency dependence of the complex permittivity ε(ω) = ε'(ω) – iε"(ω). The first step was to clarify the concept of the reaction field introduced by Onsager. Once this had been done it was possible to see how a generalisation of Onsager's equation for ε(0) to the frequency-dependent case would be obtained. Such an equation was published in a short note in 1964 in the *Proceedings of the Physical Society of London* 84, 616. The justification of this equation had first appeared in an Electrical Research report, which Scaife published in 1965. A more extended version was given in *Complex Permittivity* published in 1971.

**John "Jack" Gamble Kirkwood** was a noted chemist and physicist, holding faculty positions at Cornell University, the University of Chicago, California Institute of Technology, and Yale University.

The **debye** is a CGS unit of electric dipole moment named in honour of the physicist Peter J. W. Debye. It is defined as 1×10^{−18} statcoulomb-centimeters. Historically the debye was defined as the dipole moment resulting from two charges of opposite sign but an equal magnitude of 10^{−10} statcoulomb, which were separated by 1 Ångström. This gave a convenient unit for molecular dipole moments.

**Lars Onsager** was a Norwegian-born American physical chemist and theoretical physicist. He held the Gibbs Professorship of Theoretical Chemistry at Yale University. He was awarded the Nobel Prize in Chemistry in 1968.

In the work published up to 1965, inertial effects had not been fully taken into account. An early attempt to remedy this deficiency was made by Rocard in 1933. A major advance was made by Sack (1953,1957) and Gross (1955). Sack's work was based on the Fokker Planck equation governing the temporal evolution of the orientational distribution for molecules. In an attempt to clarify the physical aspects of the problem, Scaife derived Sack's results by starting from the stochastic Langevin equation (1908) of molecular rotational brownian motion. His work on the plane rotator, and also for the sphere, was published for the first time in 1971; it was published in collaboration with John T. Lewis ^{ [2] } and James Robert McConnell ^{ [3] } (also a Boyle Laureate) in Proceedings of the Royal Irish Academy A, 76 (1976) 43 (It is for this paper that he appears in *Famous Trails to Paul Erdős)*.^{ [4] } In the work on inertial effects it had been usual to neglect dipole-dipole coupling. A correct procedure to remedy this neglect was described in his book published in 1989. Unfortunately an exact, self-consistent solution of the proposed Langevin equation is not possible. Whether an adequate approximate solution can be obtained is still an open question.

In 1963 Scaife suggested^{ [5] } replacing the complex permittivity, ε (ω), Cole-Cole plot (1941), with a polarizability plot, α (ω). In this α"(ω) is plotted against α'(ω), where α'(ω) and α"(ω) are the real and imaginary co-ordinates of the function

- α (ω) = α'(ω) – i α"(ω) = (ε (ω) – 1) / (ε (ω) + 2)

which is directly proportional to the complex polarizability of a macroscopic sphere of unit radius. It has been shown by a number of investigators that the polarizability plot is superior to the Cole-Cole plot for representation of high frequency dielectric data. His book *Principles of Dielectrics* published in 1989 (updated in 1998) contains many results and discussions which had not been previously published.

With his research student T. Ambrose, Scaife applied the theory of dipole moment fluctuations to retardation effects (the Casimir effect) in Van der Waals forces, With another student, W.T.Coffey, he explored the extension of Onsager's theory to take account of high field effects on the polarisation of dipolar materials.

With research students K. Raji, J. C. Fisher, K. V. Kamath and V. J. Rossiter he carried out experimental studies of the equilibrium permittivity of alkali halides when subjected to high pressures. Results were reported in several papers. He was helped by his elder brother, W. Garrett Scaife, whom B. K. P. Scaife had first got interested in dielectrics. Later Garrett Scaife took a keen interest in designing and automating the high pressure equipment and establishing the dielectric measuring techniques, and devoted a good part of his career studying the dielectric properties of liquids and liquid crystals under high pressures.

For several years Brendan Scaife was a visiting Professor at the University of Salford and in collaboration with Professor J. H. Calderwood, he published a number of important papers. In one of the papers published in the *Philosophical Transactions of the Royal Society of London*, 269 (1971) 217, they showed that the complicated transient voltage and current behaviour observed in liquids under irradiation can be explained by a simple model of the motion of space charge in a dielectric medium.

In collaboration with his colleague and former research student, P.C. Fannin, he designed a split toroid technique ("Fannin's (Toroidal) Technique") to measure the magnetic susceptibility of ferrofluids.^{ [6] } He also explored the dispersion of the frequency dependent magnetic susceptibility of these fluids, developing the necessary underlying theoretical understanding. This is published in a number of papers from 1986 to 1991. This work has laid the foundation of yet another important area of research.

Besides his interest in dielectrics and magnetic fluids, he has made contributions to telecommunications, mathematical methods in signal processing and to the history of science and technology. In regard to the latter, while working with his former research student and colleague Sean Swords on a study of the early history of radar, he made contact with many of the pioneers of radar: the information and insights he acquired materially contributed to a new understanding of the international beginnings of radar. Sean Swords' doctoral thesis (under Scaife's supervision) was published as Vol.6 in the IEE History of Technology Series.^{ [7] }

Scaife edited Vol.IV of *The Mathematical Papers of Sir William Rowan Hamilton*^{ [8] } He has also published a biography of James MacCullagh,^{ [9] } another Irish mathematician and theoretical physicist, and contemporary of Hamilton.

Scaife together with another former student, J. K. Vij, developed a new theory of absorbance for the electromagnetic spectrum.^{ [10] } His results contradicted the works published in the literature at the time. This was published in J. Chem. Phys. 122, 174901 (2005) and was verified experimentally through a series of high precision experiments and published [Phys Rev. E 80, 021704 (2009)].

He was elected to Fellowship of Trinity College Dublin (F.T.C.D.) in 1964 and was appointed Reader in 1966. In 1967 he became an Associate Professor. In 1972 he was appointed to a Chair of Engineering Science and in the same year was elected to the Royal Irish Academy. He was awarded a D.Sc.(Eng.) of the University of London for his published work in 1973. In 1986 he was elected to a Personal Chair in Electromagnetism in recognition of his international reputation in the field of Dielectrics. He was awarded the Boyle Medal ^{ [11] } of the Royal Dublin Society in 1992.

Trinity College Dublin awards the B.K.P. Scaife Prize^{ [12] } to undergraduate students in electronic and electrical engineering in his honour.

He has authored (and/or edited) six books:

*Complex permittivity*(1971) English Universities Press;*Studies in Numerical Analysis: Papers in Honour of Cornelius Lanczos*(1974) Academic Press;*Radio Science in Ireland*(1981) Royal Irish Academy, ISBN 0-901714-19-4 (0-901714-19-4)*Principles of Dielectrics*(1989) Clarendon Press;*James MacCullagh, M.R.I.A., F.R.S., 1809–1847*, Proceedings of the Royal Irish Academy 90C (3) (1990), 67–106*The Mathematical Papers of Sir William Rowan Hamilton, Volume IV (Geometry, Analysis, Astronomy, Probability and Finite Differences, Miscellaneous)*, (2000) published by Cambridge University Press.*Scaife, B. K. P.; Vij, J. K.*The Journal of Chemical Physics (2005) 122, 174901.*Scaife, B. K. P.; Sigarev, A. A.; Vij, J. K.; Goodby, J. W.*Physical Review E (2009) 80, 021704.

- ↑ "Archived copy". Archived from the original on 26 July 2011. Retrieved 13 April 2011.CS1 maint: Archived copy as title (link)
- ↑ http://www.stp.dias.ie/people/Lewis/obituary.html
- ↑ "Archived copy". Archived from the original on 26 July 2011. Retrieved 13 April 2011.CS1 maint: Archived copy as title (link)
- ↑ "Math. Intell. references – The Erdös Number Project – Oakland University". Oakland.edu. 20 May 2004. Retrieved 8 April 2011.
- ↑
*New Method of Analysing Dielectric Measurements*Proc. Phys. Soc. 81 124 (1963) doi : 10.1088/0370-1328/81/1/318 - ↑ J. Phys. E: SC. Instrum. 19 (1986) 238
- ↑ Swords, Seán S.,
*Technical History of the Beginnings of Radar*, IEE*History of Technology Series*, Vol. 6, London: Peter Peregrinus, 1986 - ↑
*The Mathematical Papers of Sir William Rowan Hamilton, Volume IV (Geometry, Analysis, Astronomy, Probability and Finite Differences, Miscellaneous)*, published by Cambridge University Press in 2000. - ↑
*James MacCullagh, M.R.I.A., F.R.S., 1809–1847*, Proceedings of the Royal Irish Academy 90C (3) (1990), 67–106 - ↑ Scaife, B. K. P.; Vij, J. K. (May 2005). "Propagation of an electromagnetic wave in an absorbing anisotropic medium and infrared transmission spectroscopy of liquid crystals".
*The Journal of Chemical Physics*.**122**(17): 174901. Bibcode:2005JChPh.122q4901S. doi:10.1063/1.1874833. hdl:2262/29946. PMID 15910063. - ↑ Boyle Medal Laureates Royal Dublin Society
- ↑ Trinity College Dublin: Prizes In The School Of Engineering

An **electromagnetic field** is a physical field produced by electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction. It is one of the four fundamental forces of nature.

A **dielectric** is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor but only slightly shift from their average equilibrium positions causing **dielectric polarization**. Because of dielectric polarization, positive charges are displaced in the direction of the field and negative charges shift in the opposite direction. This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, but also reorient so that their symmetry axes align to the field.

The **relative permittivity** of a material is its (absolute) permittivity expressed as a ratio relative to the vacuum permittivity.

In electromagnetism, **absolute permittivity**, often simply called **permittivity**, usually denoted by the Greek letter *ε* (epsilon), is the measure of capacitance that is encountered when forming an electric field in a particular medium. More specifically, permittivity describes the amount of charge needed to generate one unit of electric flux in a given medium. A charge will yield more electric flux in a medium with low permittivity than in a medium with high permittivity. Permittivity is the measure of a material's ability to store an electric field in the polarization of the medium.

**Zero-point energy** (**ZPE**) is the difference between the lowest possible energy that a quantum mechanical system may have, and the classical minimum energy of the system. Unlike in classical mechanics, quantum systems constantly fluctuate in their lowest energy state due to the Heisenberg uncertainty principle. As well as atoms and molecules, the empty space of the vacuum has these properties. According to quantum field theory, the universe can be thought of not as isolated particles but continuous fluctuating fields: matter fields, whose quanta are fermions, and force fields, whose quanta are bosons. All these fields have zero-point energy. These fluctuating zero-point fields lead to a kind of reintroduction of an aether in physics, since some systems can detect the existence of this energy. However this aether cannot be thought of as a physical medium if it is to be Lorentz invariant such that there is no contradiction with Einstein's theory of special relativity.

In classical electromagnetism, **polarization density** is the vector field that expresses the density of permanent or induced electric dipole moments in a dielectric material. When a dielectric is placed in an external electric field, its molecules gain electric dipole moment and the dielectric is said to be polarized. The electric dipole moment induced per unit volume of the dielectric material is called the electric polarization of the dielectric.

In electricity (electromagnetism), the **electric susceptibility** is a dimensionless proportionality constant that indicates the degree of polarization of a dielectric material in response to an applied electric field. The greater the electric susceptibility, the greater the ability of a material to polarize in response to the field, and thereby reduce the total electric field inside the material. It is in this way that the electric susceptibility influences the electric permittivity of the material and thus influences many other phenomena in that medium, from the capacitance of capacitors to the speed of light.

The **Clausius–Mossotti relation** expresses the dielectric constant of a material in terms of the atomic polarizibility, α, of the material's constituent atoms and/or molecules, or a homogeneous mixture thereof. It is named after Ottaviano-Fabrizio Mossotti and Rudolf Clausius. It is equivalent to the Lorentz–Lorenz equation. It may be expressed as:

In physics, the **electric displacement field**, denoted by **D**, is a vector field that appears in Maxwell's equations. It accounts for the effects of free and bound charge within materials. "**D**" stands for "displacement", as in the related concept of displacement current in dielectrics. In free space, the electric displacement field is equivalent to flux density, a concept that lends understanding to Gauss's law. In the International System of Units (SI), it is expressed in units of coulomb per meter square (C⋅m^{−2}).

The **Havriliak–Negami relaxation** is an empirical modification of the Debye relaxation model in electromagnetism. Unlike the Debye model, the Havriliak–Negami relaxation accounts for the asymmetry and broadness of the dielectric dispersion curve. The model was first used to describe the dielectric relaxation of some polymers, by adding two exponential parameters to the Debye equation:

The **Cole–Cole equation** is a relaxation model that is often used to describe dielectric relaxation in polymers.

**Dielectric loss** quantifies a dielectric material's inherent dissipation of electromagnetic energy. It can be parameterized in terms of either the **loss angle***δ* or the corresponding **loss tangent** tan *δ*. Both refer to the phasor in the complex plane whose real and imaginary parts are the resistive (lossy) component of an electromagnetic field and its reactive (lossless) counterpart.

**Kenneth Stewart Cole** was an American biophysicist described by his peers as "a pioneer in the application of physical science to biology". Cole was awarded the National Medal of Science in 1967.

In dielectric spectroscopy, large frequency dependent contributions to the dielectric response, especially at low frequencies, may come from build-ups of charge. This **Maxwell–Wagner–Sillars polarization**, occurs either at inner dielectric boundary layers on a mesoscopic scale, or at the external electrode-sample interface on a macroscopic scale. In both cases this leads to a separation of charges. The charges are often separated over a considerable distance, and the contribution to dielectric loss can therefore be orders of magnitude larger than the dielectric response due to molecular fluctuations.

With increased interest in sea ice and its effects on the global climate, efficient methods are required to monitor both its extent and exchange processes. Satellite-mounted, microwave radiometers, such SSMI, AMSR and AMSU, are an ideal tool for the task because they can see through cloud cover, and they have frequent, global coverage. A passive microwave instrument detects objects through emitted radiation since different substance have different emission spectra. To help us detect sea ice more efficiently, we need to model these emission processes. The interaction of sea ice with electromagnetic radiation in the microwave range is still not well understood. In general is collected information limited because of the large-scale variability due to the emissivity of sea ice.

**Surface plasmon polaritons** (**SPPs**) are infrared or visible-frequency electromagnetic waves that travel along a metal–dielectric or metal–air interface. The term "surface plasmon polariton" explains that the wave involves both charge motion in the metal and electromagnetic waves in the air or dielectric ("polariton").

**Cavity perturbation theory** describes methods for derivation of perturbation formulae for performance changes of a cavity resonator. These performance changes are assumed to be caused by either introduction of a small foreign object into the cavity or a small deformation of its boundary.

A **frequency-selective surface** (**FSS**) is any thin, repetitive surface designed to reflect, transmit or absorb electromagnetic fields based on the frequency of the field. In this sense, an FSS is a type of optical filter or metal-mesh optical filters in which the filtering is accomplished by virtue of the regular, periodic pattern on the surface of the FSS. Though not explicitly mentioned in the name, FSS's also have properties which vary with incidence angle and polarization as well - these are unavoidable consequences of the way in which FSS's are constructed. Frequency-selective surfaces have been most commonly used in the radio frequency region of the electromagnetic spectrum and find use in applications as diverse as the aforementioned microwave oven, antenna radomes and modern metamaterials. Sometimes frequency selective surfaces are referred to simply as periodic surfaces and are a 2-dimensional analog of the new periodic volumes known as photonic crystals.

**Effective permittivity and permeability** are averaged dielectric and magnetic characteristics of a microinhomogeneous medium. They are subject of Effective medium theory. There are two widely used formulae. They both were derived in quasi-static approximation when electric field inside a mixture particle may be considered as homogeneous. So, these formulae can not describe the particle size effect. Many attempts were undertaken to improve these formulae.

- J.K.Vij (1996), Journal of Molecular Liquids (B. K. P. Scaife special issue)| 69 | pages ix–xii
- De Castro, Rodrigo; Grossman, Jerrold W. (1999). "Famous Trails to Paul Erdős".
*The Mathematical Intelligencer*.**21**(3): 51–63. CiteSeerX 10.1.1.33.6972 . doi:10.1007/BF03025416. MR 1709679. Original Spanish version in*Rev. Acad. Colombiana Cienc. Exact. Fís. Natur.***23**(89) 563–582, 1999, MR 1744115.

This page is based on this Wikipedia article

Text is available under the CC BY-SA 4.0 license; additional terms may apply.

Images, videos and audio are available under their respective licenses.

Text is available under the CC BY-SA 4.0 license; additional terms may apply.

Images, videos and audio are available under their respective licenses.