Electronics comprises the physics, engineering and applications that deal with the emission and control of electrons in vacuum and matter. The identification of the electron in 1897, along with the invention of the vacuum tube, which could amplify and rectify small electrical signals, inaugurated the field of electronics and the electron age. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes, diodes, integrated circuits and sensors, associated passive electrical components, interconnection technologies. Electronic devices contain circuitry consisting or of active semiconductors supplemented with passive elements; the nonlinear behaviour of active components and their ability to control electron flows makes amplification of weak signals possible. Electronics is used in information processing, telecommunication, signal processing; the ability of electronic devices to act as switches makes digital information-processing possible. Interconnection technologies such as circuit boards, electronics packaging technology, other varied forms of communication infrastructure complete circuit functionality and transform the mixed electronic components into a regular working system, called an electronic system.
An electronic system may be a component of a standalone device. Electrical and electromechanical science and technology deals with the generation, switching and conversion of electrical energy to and from other energy forms; this distinction started around 1906 with the invention by Lee De Forest of the triode, which made electrical amplification of weak radio signals and audio signals possible with a non-mechanical device. Until 1950 this field was called "radio technology" because its principal application was the design and theory of radio transmitters and vacuum tubes; as of 2018 most electronic devices use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of solid-state physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering; this article focuses on engineering aspects of electronics. Digital electronics Analogue electronics Microelectronics Circuit design Integrated circuits Power electronics Optoelectronics Semiconductor devices Embedded systems An electronic component is any physical entity in an electronic system used to affect the electrons or their associated fields in a manner consistent with the intended function of the electronic system.
Components are intended to be connected together by being soldered to a printed circuit board, to create an electronic circuit with a particular function. Components may be packaged singly, or in more complex groups as integrated circuits; some common electronic components are capacitors, resistors, transistors, etc. Components are categorized as active or passive. Vacuum tubes were among the earliest electronic components, they were solely responsible for the electronics revolution of the first half of the twentieth century. They allowed for vastly more complicated systems and gave us radio, phonographs, long-distance telephony and much more, they played a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s. Since that time, solid-state devices have all but taken over. Vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode ray tubes, specialist audio equipment, guitar amplifiers and some microwave devices.
In April 1955, the IBM 608 was the first IBM product to use transistor circuits without any vacuum tubes and is believed to be the first all-transistorized calculator to be manufactured for the commercial market. The 608 contained more than 3,000 germanium transistors. Thomas J. Watson Jr. ordered all future IBM products to use transistors in their design. From that time on transistors were exclusively used for computer logic and peripherals. Circuits and components can be divided into two groups: digital. A particular device may consist of circuitry that has a mix of the two types. Most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage or current as opposed to discrete levels as in digital circuits; the number of different analog circuits so far devised is huge because a'circuit' can be defined as anything from a single component, to systems containing thousands of components.
Analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators. One finds modern circuits that are analog; these days analog circuitry may use digital or microprocessor techniques to improve performance. This type of circuit is called "mixed signal" rather than analog or digital. Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear
Mostafa A. El-Sayed is a cited Egyptian chemical physicist, a leading nanoscience researcher, a member of the National Academy of Sciences and a US National Medal of Science laureate, he is known for the spectroscopy rule named after him, the El-Sayed rule. He earned his B. Sc. from Ain Shams University Faculty of Science, Cairo in 1953. El-Sayed earned his doctoral degree from Florida State University working with Michael Kasha, the last student of the legendary G. N. Lewis, he spent time as a researcher at Harvard University, Yale University and the California Institute of Technology before joining the faculty of the University of California at Los Angeles in 1961. He is the Julius Brown Chair and Regents Professor of Chemistry and Biochemistry at the Georgia Institute of Technology, he heads the Laser Dynamics Lab there. El-Sayed is a former editor-in-chief of the Journal of Physical Chemistry. El-Sayed and his research group have contributed to many important areas of physical and materials chemistry research.
El-Sayed's research interests include the use of steady-state and ultra fast laser spectroscopy to understand relaxation and conversion of energy in molecules, in solids, in photosynthetic systems, semiconductor quantum dots and metal nanostructures. The El-Sayed group has been involved in the development of new techniques such as magnetophotonic selection, picosecond Raman spectroscopy and phosphorescence microwave double resonance spectroscopy. A major focus of his lab is on the optical and chemical properties of noble metal nanoparticles and their applications in nanocatalysis and nanomedicine, his lab is known for the development of the gold nanorod technology. Professor El-Sayed has over 500 publications in refereed journals in the areas of spectroscopy, molecular dynamics and nanoscience. Prof. El-Sayed has supervised the research of over 70 PhD students, 35 postdoctoral fellows and 20 visiting professors, several of whom hold key positions in the scientific community. Mostafa El Sayed's son, Ayman El-Sayed, the Professor of Tumour Surgery at the University of California, took part in applying these outcomes on cancerous cells of some animals.
For his work in the area of applying laser spectroscopic techniques to study of properties and behavior on the nanoscale, El-Sayed was elected to the National Academy of Sciences in 1980. In 1989 he received the Tolman Award, in 2002, he won the Irving Langmuir Award in Chemical Physics, he has been the recipient of the 1990 King Faisal International Prize in Sciences, Georgia Tech's highest award, "The Class of 1943 Distinguished Professor", an honorary doctorate of philosophy from the Hebrew University, several other awards including some from the different American Chemical Society local sections. He was a Sherman Fairchild Distinguished Scholar at the California Institute of Technology and an Alexander von Humboldt Senior U. S. Scientist Awardee, he served as editor-in-chief of the Journal of Physical Chemistry from 1980–2004 and has served as the U. S. editor of the International Reviews in Physical Chemistry. He is a Fellow of the American Academy of Arts and Sciences, a member of the American Physical Society, the American Association for the Advancement of Science and the Third World Academy of Science.
Mostafa El-Sayed was awarded the 2007 US National Medal of Science "for his seminal and creative contributions to our understanding of the electronic and optical properties of nanomaterials and to their applications in nanocatalysis and nanomedicine, for his humanitarian efforts of exchange among countries and for his role in developing the scientific leadership of tomorrow." Mostafa was announced to be the recipient of the 2009 Ahmed Zewail prize in molecular sciences. In 2011, he was listed #17 in Thomson-Reuters listing of the Top Chemists of the Past Decade. On June 16, 2015, it was announced that Professor El-Sayed will receive the 2016 Priestley Medal, the American Chemical Society’s highest honor, for his decades-long contributions to chemistry. Intersystem Crossing is a photophysical process involving an isoenergetic radiationless transition between two electronic states having different multiplicities, it results in a vibrationally excited molecular entity in the lower electronic state, which usually decays to its lowest molecular vibrational level.
ISC is forbidden by rules of conservation of angular momentum. As a consequence, ISC occurs on long time scales; however the El-Sayed’s rule states that the rate of intersystem crossing, e.g. from the lowest singlet state to the triplet manifold, is large if the radiationless transition involves a change of molecular orbital type. For example, a singlet could transition to a triplet state, but not to a triplet state and vice versa. Formulated by Prof. Mostafa. A. El-Sayed in the 1960s, this rule found in most photochemistry textbooks is useful in understanding phosphorescence, vibrational relaxation, intersystem crossing, internal conversion and lifetimes of excited states in molecules. El-Sayed, M. A. Acc. Chem. Res. 1968,1,8. Lower, S. K.. A. Chem. Rev. 1966,66,199 Mostafa Amr El-Sayed Biographical References: McMurray, Emily J. Notable Twientieth-Century Scientists, Gale Research, Inc.: New York, 1995. Faculty web page at Georgia Tech Laser Dynamics Lab at Georgia Tech President Bush to laud Georgia Tech’s Mostafa El-Sayed Mostafa El-Sayed praised for, contributions to nanotechnology
Thermodynamics is the branch of physics that deals with heat and temperature, their relation to energy, work and properties of bodies of matter. The behavior of these quantities is governed by the four laws of thermodynamics, irrespective of the specific composition of the material or system in question; the laws of thermodynamics are explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a wide variety of topics in science and engineering physical chemistry, chemical engineering and mechanical engineering. Thermodynamics developed out of a desire to increase the efficiency of early steam engines through the work of French physicist Nicolas Léonard Sadi Carnot who believed that engine efficiency was the key that could help France win the Napoleonic Wars. Scots-Irish physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854 which stated, "Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, the relation of heat to electrical agency."
The initial application of thermodynamics to mechanical heat engines was extended early on to the study of chemical compounds and chemical reactions. Chemical thermodynamics studies the nature of the role of entropy in the process of chemical reactions and has provided the bulk of expansion and knowledge of the field. Other formulations of thermodynamics emerged in the following decades. Statistical thermodynamics, or statistical mechanics, concerned itself with statistical predictions of the collective motion of particles from their microscopic behavior. In 1909, Constantin Carathéodory presented a purely mathematical approach to the field in his axiomatic formulation of thermodynamics, a description referred to as geometrical thermodynamics. A description of any thermodynamic system employs the four laws of thermodynamics that form an axiomatic basis; the first law specifies that energy can be exchanged between physical systems as work. The second law defines the existence of a quantity called entropy, that describes the direction, thermodynamically, that a system can evolve and quantifies the state of order of a system and that can be used to quantify the useful work that can be extracted from the system.
In thermodynamics, interactions between large ensembles of objects are categorized. Central to this are the concepts of its surroundings. A system is composed of particles, whose average motions define its properties, those properties are in turn related to one another through equations of state. Properties can be combined to express internal energy and thermodynamic potentials, which are useful for determining conditions for equilibrium and spontaneous processes. With these tools, thermodynamics can be used to describe how systems respond to changes in their environment; this can be applied to a wide variety of topics in science and engineering, such as engines, phase transitions, chemical reactions, transport phenomena, black holes. The results of thermodynamics are essential for other fields of physics and for chemistry, chemical engineering, corrosion engineering, aerospace engineering, mechanical engineering, cell biology, biomedical engineering, materials science, economics, to name a few.
This article is focused on classical thermodynamics which studies systems in thermodynamic equilibrium. Non-equilibrium thermodynamics is treated as an extension of the classical treatment, but statistical mechanics has brought many advances to that field; the history of thermodynamics as a scientific discipline begins with Otto von Guericke who, in 1650, built and designed the world's first vacuum pump and demonstrated a vacuum using his Magdeburg hemispheres. Guericke was driven to make a vacuum in order to disprove Aristotle's long-held supposition that'nature abhors a vacuum'. Shortly after Guericke, the English physicist and chemist Robert Boyle had learned of Guericke's designs and, in 1656, in coordination with English scientist Robert Hooke, built an air pump. Using this pump and Hooke noticed a correlation between pressure and volume. In time, Boyle's Law was formulated, which states that pressure and volume are inversely proportional. In 1679, based on these concepts, an associate of Boyle's named Denis Papin built a steam digester, a closed vessel with a fitting lid that confined steam until a high pressure was generated.
Designs implemented a steam release valve that kept the machine from exploding. By watching the valve rhythmically move up and down, Papin conceived of the idea of a piston and a cylinder engine, he did not, follow through with his design. In 1697, based on Papin's designs, engineer Thomas Savery built the first engine, followed by Thomas Newcomen in 1712. Although these early engines were crude and inefficient, they attracted the attention of the leading scientists of the time; the fundamental concepts of heat capacity and latent heat, which were necessary for the development of thermodynamics, were developed by Professor Joseph Black at the University of Glasgow, where James Watt was employed as an instrument maker. Black and Watt performed experiments together, but it was Watt who conceived the idea of the external condenser which resulted in a large increase in steam engine efficiency. Drawing on all the previous work led Sadi Carnot, the "father of thermodynamics", to publish Reflections on the Motive Power of Fire, a discourse on heat, power and engine efficiency.
The book outlined the basic energetic relations between the Carnot engine, the Carnot cycle, motive power. It marked the start of thermodynamics as a modern scien
Chemistry is the scientific discipline involved with elements and compounds composed of atoms and ions: their composition, properties and the changes they undergo during a reaction with other substances. In the scope of its subject, chemistry occupies an intermediate position between physics and biology, it is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant chemistry, the formation of igneous rocks, how atmospheric ozone is formed and how environmental pollutants are degraded, the properties of the soil on the moon, how medications work, how to collect DNA evidence at a crime scene. Chemistry addresses topics such as how atoms and molecules interact via chemical bonds to form new chemical compounds. There are four types of chemical bonds: covalent bonds, in which compounds share one or more electron; the word chemistry comes from alchemy, which referred to an earlier set of practices that encompassed elements of chemistry, philosophy, astronomy and medicine.
It is seen as linked to the quest to turn lead or another common starting material into gold, though in ancient times the study encompassed many of the questions of modern chemistry being defined as the study of the composition of waters, growth, disembodying, drawing the spirits from bodies and bonding the spirits within bodies by the early 4th century Greek-Egyptian alchemist Zosimos. An alchemist was called a'chemist' in popular speech, the suffix "-ry" was added to this to describe the art of the chemist as "chemistry"; the modern word alchemy in turn is derived from the Arabic word al-kīmīā. In origin, the term is borrowed from the Greek χημία or χημεία; this may have Egyptian origins since al-kīmīā is derived from the Greek χημία, in turn derived from the word Kemet, the ancient name of Egypt in the Egyptian language. Alternately, al-kīmīā may derive from χημεία, meaning "cast together"; the current model of atomic structure is the quantum mechanical model. Traditional chemistry starts with the study of elementary particles, molecules, metals and other aggregates of matter.
This matter can be studied in isolation or in combination. The interactions and transformations that are studied in chemistry are the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together; such behaviors are studied in a chemistry laboratory. The chemistry laboratory stereotypically uses various forms of laboratory glassware; however glassware is not central to chemistry, a great deal of experimental chemistry is done without it. A chemical reaction is a transformation of some substances into one or more different substances; the basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation, which involves atoms as subjects; the number of atoms on the left and the right in the equation for a chemical transformation is equal. The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.
Energy and entropy considerations are invariably important in all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions, they can be analyzed using the tools of e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists. Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry; the particles that make up matter have rest mass as well – not all particles have rest mass, such as the photon. Matter can be a mixture of substances; the atom is the basic unit of chemistry. It consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud; the nucleus is made up of positively charged protons and uncharged neutrons, while the electron cloud consists of negatively charged electrons which orbit the nucleus. In a neutral atom, the negatively charged electrons balance out the positive charge of the protons.
The nucleus is dense. The atom is the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state, coordination number, preferred types of bonds to form. A chemical element is a pure substance, composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol Z; the mass number is the sum of the number of neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same
A nanostructure is a structure of intermediate size between microscopic and molecular structures. Nanostructural detail is microstructure at nanoscale. In describing nanostructures, it is necessary to differentiate between the number of dimensions in the volume of an object which are on the nanoscale. Nanotextured surfaces have one dimension on the nanoscale, i.e. only the thickness of the surface of an object is between 0.1 and 100 nm. Nanotubes have two dimensions on the nanoscale, i.e. the diameter of the tube is between 0.1 and 100 nm. Spherical nanoparticles have three dimensions on the nanoscale, i.e. the particle is between 0.1 and 100 nm in each spatial dimension. The terms nanoparticles and ultrafine particles are used synonymously although UFP can reach into the micrometre range; the term nanostructure is used when referring to magnetic technology. Nanoscale structure in biology is called ultrastructure. Properties of nanoscale objects and ensembles of these objects are studied in physics.
Nanomaterials Nanotechnology Tube-based nanostructures List of software for nanostructures modeling Nano Flakes May Revolutionize Solar Cells Applications of Nanoparticles
Outline of academic disciplines
An academic discipline or field of study is a branch of knowledge and researched as part of higher education. A scholar's discipline is defined by the university faculties and learned societies to which she or he belongs and the academic journals in which she or he publishes research. Disciplines vary between well-established ones that exist in all universities and have well-defined rosters of journals and conferences and nascent ones supported by only a few universities and publications. A discipline may have branches, these are called sub-disciplines. There is no consensus on how some academic disciplines should be classified, for example whether anthropology and linguistics are disciplines of the social sciences or of the humanities; the following outline is provided as topical guide to academic disciplines. Biblical studies Religious studies Biblical Hebrew, Biblical Greek, Aramaic Buddhist theology Christian theology Anglican theology Baptist theology Catholic theology Eastern Orthodox theology Protestant theology Hindu theology Jewish theology Muslim theology Biological anthropology Linguistic anthropology Cultural anthropology Social anthropology Archaeology Accounting Business management Finance Marketing Operations management Edaphology Environmental chemistry Environmental science Gemology Geochemistry Geodesy Physical geography Atmospheric science / Meteorology Biogeography / Phytogeography Climatology / Paleoclimatology / Palaeogeography Coastal geography / Oceanography Edaphology / Pedology or Soil science Geobiology Geology Geostatistics Glaciology Hydrology / Limnology / Hydrogeology Landscape ecology Quaternary science Geophysics Paleontology Paleobiology Paleoecology Astrobiology Astronomy Observational astronomy Gamma ray astronomy Infrared astronomy Microwave astronomy Optical astronomy Radio astronomy UV astronomy X-ray astronomy Astrophysics Gravitational astronomy Black holes Interstellar medium Numerical simulations Astrophysical plasma Galaxy formation and evolution High-energy astrophysics Hydrodynamics Magnetohydrodynamics Star formation Physical cosmology Stellar astrophysics Helioseismology Stellar evolution Stellar nucleosynthesis Planetary science Also a branch of electrical engineering Pure mathematics Applied mathematics Astrostatistics Biostatistics Academia Academic genealogy Curriculum Multidisciplinary approach Interdisciplinarity Transdisciplinarity Professions Classification of Instructional Programs Joint Academic Coding System List of fields of doctoral studies in the United States List of academic fields Abbott, Andrew.
Chaos of Disciplines. University of Chicago Press. ISBN 978-0-226-00101-2. Oleson, Alexandra; the Organization of knowledge in modern America, 1860-1920. ISBN 0-8018-2108-8. US Department of Education Institute of Education Sciences. Classification of Instructional Programs. National Center for Education Statistics. Classification of Instructional Programs: Developed by the U. S. Department of Education's National Center for Education Statistics to provide a taxonomic scheme that will support the accurate tracking and reporting of fields of study and program completions activity. Complete JACS from Higher Education Statistics Agency in the United Kingdom Australian and New Zealand Standard Research Classification Chapter 3 and Appendix 1: Fields of research classification. Fields of Knowledge, a zoomable map allowing the academic disciplines and sub-disciplines in this article be visualised. Sandoz, R. Interactive Historical Atlas of the Disciplines, University of Geneva
International Standard Serial Number
An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is helpful in distinguishing between serials with the same title. ISSN are used in ordering, interlibrary loans, other practices in connection with serial literature; the ISSN system was first drafted as an International Organization for Standardization international standard in 1971 and published as ISO 3297 in 1975. ISO subcommittee TC 46/SC 9 is responsible for maintaining the standard; when a serial with the same content is published in more than one media type, a different ISSN is assigned to each media type. For example, many serials are published both in electronic media; the ISSN system refers to these types as electronic ISSN, respectively. Conversely, as defined in ISO 3297:2007, every serial in the ISSN system is assigned a linking ISSN the same as the ISSN assigned to the serial in its first published medium, which links together all ISSNs assigned to the serial in every medium.
The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers. As an integer number, it can be represented by the first seven digits; the last code digit, which may be 0-9 or an X, is a check digit. Formally, the general form of the ISSN code can be expressed as follows: NNNN-NNNC where N is in the set, a digit character, C is in; the ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, C=5. To calculate the check digit, the following algorithm may be used: Calculate the sum of the first seven digits of the ISSN multiplied by its position in the number, counting from the right—that is, 8, 7, 6, 5, 4, 3, 2, respectively: 0 ⋅ 8 + 3 ⋅ 7 + 7 ⋅ 6 + 8 ⋅ 5 + 5 ⋅ 4 + 9 ⋅ 3 + 5 ⋅ 2 = 0 + 21 + 42 + 40 + 20 + 27 + 10 = 160 The modulus 11 of this sum is calculated. For calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, counting from the right.
The modulus 11 of the sum must be 0. There is an online ISSN checker. ISSN codes are assigned by a network of ISSN National Centres located at national libraries and coordinated by the ISSN International Centre based in Paris; the International Centre is an intergovernmental organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, the ISDS Register otherwise known as the ISSN Register. At the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept. An ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an anonymous identifier associated with a serial title, containing no information as to the publisher or its location. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change. Since the ISSN applies to an entire serial a new identifier, the Serial Item and Contribution Identifier, was built on top of it to allow references to specific volumes, articles, or other identifiable components.
Separate ISSNs are needed for serials in different media. Thus, the print and electronic media versions of a serial need separate ISSNs. A CD-ROM version and a web version of a serial require different ISSNs since two different media are involved. However, the same ISSN can be used for different file formats of the same online serial; this "media-oriented identification" of serials made sense in the 1970s. In the 1990s and onward, with personal computers, better screens, the Web, it makes sense to consider only content, independent of media; this "content-oriented identification" of serials was a repressed demand during a decade, but no ISSN update or initiative occurred. A natural extension for ISSN, the unique-identification of the articles in the serials, was the main demand application. An alternative serials' contents model arrived with the indecs Content Model and its application, the digital object identifier, as ISSN-independent initiative, consolidated in the 2000s. Only in 2007, ISSN-L was defined in the