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Perceptual Paradox
A perceptual paradox illustrates the failure of a theoretical prediction. Theories of perception are supposed to help a researcher predict what will be perceived when senses are stimulated. A theory usually comprises a mathematical model (formula), rules for collecting physical measurements for input into the model, and rules for collecting physical measurements to which model outputs should map. When arbitrarily choosing valid input data, the model should reliably generate output data that is indistinguishable from that which is measured in the system being modeled. Although each theory may be useful for some limited predictions, theories of vision, hearing, touch, smell, and taste are not typically reliable for comprehensive modeling of perception based on sensory inputs. A paradox illustrates where a theoretical prediction fails. Sometimes, even in the absence of a predictive theory, the characteristics of perception seem nonsensical. This page lists some paradoxes and seemi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theory
A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may be scientific, belong to a non-scientific discipline, or no discipline at all. Depending on the context, a theory's assertions might, for example, include generalized explanations of how nature works. The word has its roots in ancient Greek, but in modern use it has taken on several related meanings. In modern science, the term "theory" refers to scientific theories, a well-confirmed type of explanation of nature, made in a way consistent with the scientific method, and fulfilling the criteria required by modern science. Such theories are described in such a way that scientific tests should be able to provide empirical support for it, or empirical contradiction (" falsify") of it. Scientific theories are the most reliable, rigorous, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Path
Optical path (OP) is the trajectory that a light ray follows as it propagates through an optical medium. The geometrical optical-path length or simply geometrical path length (GPD) is the length of a segment in a given OP, i.e., the Euclidean distance integrated along a ray between any two points. The mechanical length of an optical device can be reduced to less than the GPD by using folded optics. The ''optical path length'' in a homogeneous medium is the GPD multiplied by the refractive index of the medium. Factors affecting optical path Path of light in medium, or between two media is affected by the following: * Reflection ** Total internal reflection * Refraction * Dispersion of light * Absorption Simple materials used * Lenses * Prisms * Mirrors * Transparent materials (e.g. optical filter An optical filter is a device that selectively transmits light of different wavelengths, usually implemented as a glass plane or plastic device in the optical path, which a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edwin Land
Edwin Herbert Land, ForMemRS, FRPS, Hon.MRI (May 7, 1909 – March 1, 1991) was an Russian-American scientist and inventor, best known as the co-founder of the Polaroid Corporation. He invented inexpensive filters for polarizing light, a practical system of in-camera instant photography, and the retinex theory of color vision, among other things. His Polaroid instant camera went on sale in late 1948 and made it possible for a picture to be taken and developed in 60 seconds or less. Life and career Edwin Land was born to Jewish parents in Bridgeport, Connecticut, to Matie () and Harry Land, a Russian scrap-metal dealer. Growing up, he was known to take apart household appliances, such as a mantel clock and the family's new gramophone, as well as blowing all the house's fuses when he was six years old. He was scolded by his father when taking apart a phonograph and he vowed that "nothing or nobody could stop me from carrying through the execution of an experiment" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Scott Sherrington
Sir Charles Scott Sherrington (27 November 1857 – 4 March 1952) was an eminent English neurophysiologist. His experimental research established many aspects of contemporary neuroscience, including the concept of the spinal reflex as a system involving connected neurons (the " neuron doctrine"), and the ways in which signal transmission between neurons can be potentiated or depotentiated. Sherrington himself coined the word "synapse" to define the connection between two neurons. His book ''The Integrative Action of the Nervous System'' (1906) is a synthesis of this work, in recognition of which he was awarded the Nobel Prize in Physiology or Medicine in 1932 (along with Edgar Adrian). In addition to his work in physiology, Sherrington did research in histology, bacteriology, and pathology. He was president of the Royal Society in the early 1920s. Biography Early years and education Official biographies claim Charles Scott Sherrington was born in Islington, London, Englan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allvar Gullstrand
Allvar Gullstrand (5 June 1862 – 28 July 1930) was a Swedish ophthalmologist and optician. Life Born at Landskrona, Sweden, Gullstrand was professor (1894–1927) successively of eye therapy and of optics at the University of Uppsala. He applied the methods of physical mathematics to the study of optical images and of the refraction of light in the eye. For this work, he received the Nobel Prize in Physiology or Medicine in 1911. Gullstrand is noted also for his research on astigmatism and for improving the ophthalmoscope and corrective lenses for use after removal of a cataract from the eye. He was elected a member of the Royal Swedish Academy of Sciences in 1905, and served on the Academy's Prize Committee for Physics. While serving on the committee, he used his position to block Albert Einstein from receiving a Nobel Prize in Physics for his theory of relativity, which Allvar believed to be wrong. Gullstrand married Signe Breitholtz (1862–1946) in 1885. Due to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation tends to exist within any given population as a result of genetic mutation and recombination. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or more rare within a population. The evolutionary pressures that determine whether a characteristic is common or rare within a population constantly change, resulting in a change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules. The theory of evol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Histology
Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures visible without a microscope. Although one may divide microscopic anatomy into ''organology'', the study of organs, ''histology'', the study of tissues, and '' cytology'', the study of cells, modern usage places all of these topics under the field of histology. In medicine, histopathology is the branch of histology that includes the microscopic identification and study of diseased tissue. In the field of paleontology, the term paleohistology refers to the histology of fossil organisms. Biological tissues Animal tissue classification There are four basic types of animal tissues: muscle tissue, nervous tissue, connective tissue, and epithelial tissue. All animal tissues are considered to be subtypes of these four principal tissue type ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Santiago Ramón Y Cajal
Santiago Ramón y Cajal (; 1 May 1852 – 17 October 1934) was a Spanish neuroscientist, pathologist, and histologist specializing in neuroanatomy and the central nervous system. He and Camillo Golgi received the Nobel Prize in Physiology or Medicine in 1906. Ramón y Cajal was the first person of Spanish origin to win a scientific Nobel Prize. His original investigations of the microscopic structure of the brain made him a pioneer of modern neuroscience. Hundreds of his drawings illustrating the arborizations ("tree growing") of brain cells are still in use, since the mid-20th century, for educational and training purposes. Biography Santiago Ramón y Cajal was born on the 1st of May 1852 in the town of Petilla de Aragón, Navarre, Spain. As a child he was transferred many times from one school to another because of behavior that was declared poor, rebellious, and showing an anti-authoritarian attitude. An extreme example of his precociousness and rebelliousness at the age ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nobel Laureate
The Nobel Prizes ( sv, Nobelpriset, no, Nobelprisen) are awarded annually by the Royal Swedish Academy of Sciences, the Swedish Academy, the Karolinska Institutet, and the Norwegian Nobel Committee to individuals and organizations who make outstanding contributions in the fields of chemistry, physics, literature, peace, and physiology or medicine. They were established by the 1895 will of Alfred Nobel, which dictates that the awards should be administered by the Nobel Foundation. The Nobel Memorial Prize in Economic Sciences was established in 1968 by the Sveriges Riksbank, the central bank of Sweden, for contributions to the field of economics. Each recipient, a Nobelist or ''laureate'', receives a gold medal, a diploma, and a sum of money which is decided annually by the Nobel Foundation. Prize Each prize is awarded by a separate committee; the Royal Swedish Academy of Sciences awards the Prizes in Physics, Chemistry, and Economics; the Karolinska Institute awards the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sense
A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system receives signals from the senses which continuously receive information from the environment, interprets these signals, and causes the body to respond, either chemically or physically.) Although traditionally five human senses were identified as such (namely sight, smell, touch, taste, and hearing), it is now recognized that there are many more. Senses used by non-human organisms are even greater in variety and number. During sensation, sense organs collect various stimuli (such as a sound or smell) for transduction, meaning transformation into a form that can be understood by the brain. Sensation and perception are fundamental to nearly every aspect of an organism's cognition, behavior and thought. In organisms, a sensory organ consists o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43 dioptres. The cornea can be reshaped by surgical procedures such as LASIK. While the cornea contributes most of the eye's focusing power, its focus is fixed. Accommodation (the refocusing of light to better view near objects) is accomplished by changing the geometry of the lens. Medical terms related to the cornea often start with the prefix "'' kerat-''" from the Greek word κέρας, ''horn''. Structure The cornea has unmyelinated nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid. Because transparency is of prime importance, the healthy cornea does not have or need blood vess ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoreceptor Cell
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential. There are currently three known types of photoreceptor cells in mammalian eyes: rods, cones, and intrinsically photosensitive retinal ganglion cells. The two classic photoreceptor cells are rods and cones, each contributing information used by the visual system to form an image of the environment, sight. Rods primarily mediate scotopic vision (dim conditions) whereas cones primarily mediate to photopic vision (bright conditions), but the processes in each that supports phototransduction is similar. A third class of mammalian photoreceptor cell was disc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
