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
Visual tilt effects
Due to the effect of a spatial context or temporal context, the perceived orientation of a test line or grating pattern can appear tilted away from its physical orientation. The tilt illusion is the phenomenon that the perceived orientation of a test line or grating is altered by the presence of surrounding lines or grating with a different orientation, and the tilt aftereffect is the phenomenon that the perceived orientation is changed after prolonged inspection of another oriented line or grating. It has been reported that the magnitude and the direction of the perceived orientation shift depends on the relative orientation between test and contextual stimuli. Psychophysics experiments have shown that relative orientations between 0 deg and about 50 deg produce repulsion effects, known as the direct form of the tilt effect, it has been observed that indirect effects are smaller than direct effects. The repulsion peak is about 3 degrees when the relative orientation between the test and contextual stimuli is around 20 degrees.
These effects were first studied by Gibson in 1937. The subject's vision was restricted so that he could see a black line bisecting a white circular field, he could grasp the edges of a disk to rotate the line about its midpoint. An experimenter would sit behind the disk to set the stimuli and to record the subject's adjusted position of the line. During the tilt aftereffect experiment, the subject was required to look at an oriented line for four minutes, to adjust another line to a position which appeared to be vertical. In the simultaneous tilt illusion experiment, a tilted grating was introduced into the circular field of the subject, the subject was supposed to set the adjustable line to vertical before and after the tilted grating had been superposed on it. Both experiments showed that the position which appeared to follow the subject's perceived vertical was off the objective vertical, the perceived orientation shifts depended on the relative orientation between the test line and the adapted line or the induced line.
The tilt effects have been tested with various stimulus parameters, such as spatial frequency, color and contrast differences between the test grating and the contextual grating, disparity depth or temporal separation between them. Dichoptic presentation, "invisible" and natural image contextual stimuli have been studied, it has been shown that both the TAE and the TI are spatial frequency specific, since both effects of the direct form are reduced if the test and the contextual grating differ in spatial frequency. It has been further suggested by Wenderoth and Johnstone that separation between the contextual and test stimuli, with either the spatial gap or the spatial frequency difference, reduces the magnitude of the direct but not the indirect tilt illusion, they showed that reducing the diameter of the contextual stimulus reduces the direct effect but the indirect effects are constant. According to Durant's paper in 2006, in the direct form of tilt effects, the largest illusion occurs when the test stimulus and the context surround are presented simultaneously.
Experiments show that both TI and TAE occur for contextual and test stimuli that differ in color and luminance. When the test line is presented in one eye and the context in the other, the magnitude of the tilt illusion reduces), suggesting that at least part of the effect is due to monocular cells, and a reversed tilt effect was observed recently: a direct form of TI under monocular presentation becomes indirect for dichoptic stimulation, when the vertical test line inclined by a 20 deg line. Another interesting experiment was conducted by Clifford and Harris, in which the contextual surround was followed by a random noise mask covering the surround but not the center, so the contextual surround would not be consciously perceived, it turned out that an oriented contextual grating can affect the perceived orientation of the test grating outside of awareness of this context. Furthermore, the illusion maintains when contextual textures have a broad range of orientations those without a perceivable orientation.
A hypothesis proposed by Blakemore et al. suggested that TAE and TI were both caused by lateral inhibition between cortical orientation detectors. Orientation detectors are evenly in favor of different orientations, but the presence of context could manipulate responses of orientation detectors resulting in detection biases; this hypothesis has been developed. Gibson and Radner suggested that the TAE occurs because prolonged inspection of a tilted contextual stimulus results in the adaptation to the nearest vertical or horizontal axis of space. However, this adaptation theory predicts a symmetrical TAE with relative orientatio
The somatosensory system is a part of the sensory nervous system. The somatosensory system is a complex system of sensory neurons and pathways that responds to changes at the surface or inside the body; the axons of sensory neurons connect with, or respond to, various receptor cells. These sensory receptor cells are activated by different stimuli such as heat and nociception, giving a functional name to the responding sensory neuron, such as a thermoreceptor which carries information about temperature changes. Other types include mechanoreceptors and nociceptors which send signals along a sensory nerve to the spinal cord where they may be processed by other sensory neurons and relayed to the brain for further processing. Sensory receptors are found all over the body including the skin, epithelial tissues, muscles and joints, internal organs, the cardiovascular system. Somatic senses are sometimes referred to as somesthetic senses, with the understanding that somesthesis includes the sense of touch and haptic perception.
The mapping of the body surfaces in the brain is called somatotopy. In the cortex, it is referred to as the cortical homunculus; this brain-surface map is not immutable, however. Dramatic shifts can occur in response to injury; the four mechanoreceptors in the skin each respond to different stimuli for long periods. Merkel cell nerve endings are found in hair follicles. Due to having a small receptive field, they are used in areas like fingertips the most. Tactile corpuscles react to moderate light touch, they are located in the dermal papillae. They respond unlike Merkel nerve endings, they are responsible for the ability to feel gentle stimuli. Lamellar corpuscles distinguish rough and soft substances, they react in quick action potentials to vibrations around 250 Hz. They have large receptor fields. Pacinian reacts only to sudden stimuli so pressures like clothes that are always compressing their shape are ignored. Bulbous corpuscles react and respond to sustained skin stretch, they are responsible for the feeling of object slippage and play a major role in the kinesthetic sense and control of finger position and movement.
Merkel and bulbous cells - slow-response - are myelinated. All of these receptors are activated upon pressures that squish their shape causing an action potential. All afferent touch/vibration info ascends the spinal cord via the posterior column-medial lemniscus pathway via gracilis or cuneatus. Cuneatus sends signals to the cochlear nucleus indirectly via spinal grey matter, this info is used in determining if a perceived sound is just villi noise/irritation. All fibers cross in the medulla; the postcentral gyrus includes the primary somatosensory cortex collectively referred to as S1. BA3 receives the densest projections from the thalamus. BA3a is involved with the sense of relative position of neighboring body parts and amount of effort being used during movement. BA3b is responsible for distributing somato info, it projects texture info to BA1 and shape + size info to BA2. Region S2 divides into parietal ventral area. Area S2 is involved with specific touch perception and is thus integrally linked with the amygdala and hippocampus to encode and reinforce memories.
Parietal ventral area is the somatosensory relay to the premotor cortex and somatosensory memory hub, BA5. BA5 is association area. BA1 processes texture info. Area S2 processes light touch, visceral sensation, tactile attention. S1 processes the remaining info. BA7 integrates visual and proprioceptive info to locate objects in space; the insular cortex plays a role in the sense of bodily-ownership, bodily self-awareness, perception. Insula plays a role in conveying info about sensual touch, temperature and local oxygen status. Insula is a connected relay and thus is involved in numerous functions; the somatosensory system is spread through all major parts of the vertebrate body. It consists both of sensory receptors and afferent neurons in the periphery, to deeper neurons within the central nervous system. A somatosensory pathway will have three long neurons: primary and tertiary; the first neuron always has its cell body in the dorsal root ganglion of the spinal nerve. The second neuron has its cell body either in the brainstem.
This neuron's ascending axons will cross to the opposite side either in the spinal cord or in the brainstem. In the case of touch and certain types of pain, the third neuron has its cell body in the VPN of the thalamus and ends in the postcentral gyrus of the parietal lobe. Photoreceptors, similar to those found in the retina of the eye, detect damaging ultraviolet radiation (
A sense is a physiological capacity of organisms that provides data for perception. The senses and their operation and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology, philosophy of perception; the nervous system has a specific sensory nervous system, a sense organ, or sensor, dedicated to each sense. Humans have a multitude of sensors. Sight, taste and touch are the five traditionally recognized senses; the ability to detect other stimuli beyond those governed by these most broadly recognized senses exists, these sensory modalities include temperature, kinesthetic sense, balance and various internal stimuli. However, what constitutes a sense is a matter of some debate, leading to difficulties in defining what a distinct sense is, where the borders lie between responses to related stimuli. Other animals have receptors to sense the world around them, with degrees of capability varying between species. Humans have a comparatively weak sense of smell and a stronger sense of sight relative to many other mammals while some animals may lack one or more of the traditional five senses.
Some animals may intake and interpret sensory stimuli in different ways. Some species of animals are able to sense the world in a way that humans cannot, with some species able to sense electrical and magnetic fields, detect water pressure and currents. A broadly acceptable definition of a sense would be "A system that consists of a group of sensory cell types that responds to a specific physical phenomenon, that corresponds to a particular group of regions within the brain where the signals are received and interpreted." There is no firm agreement as to the number of senses because of differing definitions of what constitutes a sense. The senses are divided into exteroceptive and interoceptive: Exteroceptive senses are senses that perceive the body's own position and state, known as proprioceptive senses. External senses include the traditional five: sight, touch and taste, as well as thermoception and an additional weak magnetoception. Proprioceptive senses include nociception. Interoceptive senses are senses.
Non-human animals may possess senses that are absent in humans, such as electroreception and detection of polarized light. In Buddhist philosophy, Ayatana or "sense-base" includes the mind as a sense organ, in addition to the traditional five; this addition to the acknowledged senses may arise from the psychological orientation involved in Buddhist thought and practice. The mind considered by itself is seen as the principal gateway to a different spectrum of phenomena that differ from the physical sense data; this way of viewing the human sense system indicates the importance of internal sources of sensation and perception that complements our experience of the external world. Sight or vision is the capability of the eye to focus and detect images of visible light on photoreceptors in the retina of each eye that generates electrical nerve impulses for varying colors and brightness. There are two types of photoreceptors: cones. Rods are sensitive to light but do not distinguish colors. Cones are less sensitive to dim light.
There is some disagreement as to whether this constitutes two or three senses. Neuroanatomists regard it as two senses, given that different receptors are responsible for the perception of color and brightness; some argue that stereopsis, the perception of depth using both eyes constitutes a sense, but it is regarded as a cognitive function of the visual cortex of the brain where patterns and objects in images are recognized and interpreted based on learned information. This is called visual memory; the inability to see is called blindness. Blindness may result from damage to the eyeball to the retina, damage to the optic nerve that connects each eye to the brain, and/or from stroke. Temporary or permanent blindness can be caused by medications. People who are blind from degradation or damage to the visual cortex, but still have functional eyes, are capable of some level of vision and reaction to visual stimuli but not a conscious perception. People with blindsight are not aware that they are reacting to visual sources, instead just unconsciously adapt their behavior to the stimulus.
On February 14, 2013 researchers developed a neural implant that gives rats the ability to sense infrared light which for the first time provides living creatures with new abilities, instead of replacing or augmenting existing abilities. Hearing or audition is the sense of sound perception. Hearing is all about vibration. Mechanoreceptors turn motion into electrical nerve pulses. Since sound is vibration, propagating through a medium such as air, the detection of these vibrations, the sense of the hearing, is a mechanical sense because these vibrations are mechanically conducted from the eardrum through a series of tiny bones to hair-like fibers in the inner
An illusion is a distortion of the senses, which can reveal how the human brain organizes and interprets sensory stimulation. Though illusions distort our perception of reality, they are shared by most people. Illusions may occur with any of the human senses, but visual illusions are the best-known and understood; the emphasis on visual illusions occurs because vision dominates the other senses. For example, individuals watching a ventriloquist will perceive the voice is coming from the dummy since they are able to see the dummy mouth the words; some illusions are based on general assumptions the brain makes during perception. These assumptions are made using organizational principles, an individual's capacity for depth perception and motion perception, perceptual constancy. Other illusions occur because of biological sensory structures within the human body or conditions outside the body within one's physical environment; the term illusion refers to a specific form of sensory distortion. Unlike a hallucination, a distortion in the absence of a stimulus, an illusion describes a misinterpretation of a true sensation.
For example, hearing voices regardless of the environment would be a hallucination, whereas hearing voices in the sound of running water would be an illusion. An optical illusion is characterized by visually perceived images that are misleading. Therefore, the information gathered by the eye is processed by the brain to give, on the face of it, a percept that does not tally with a physical measurement of the stimulus source. A conventional assumption is that there are physiological illusions that occur and cognitive illusions that can be demonstrated by specific visual tricks that say something more basic about how human perceptual systems work; the human brain constructs a world inside our head based on what it samples from the surrounding environment. However, sometimes it tries to organize this information it thinks best while other times it fills in the gaps; this way in which our brain works is the basis of an illusion. An auditory illusion is an illusion of hearing, the auditory equivalent of an optical illusion: the listener hears either sound which are not present in the stimulus, or "impossible" sounds.
In short, audio illusions highlight areas where the human ear and brain, as organic, makeshift tools, differ from perfect audio receptors. One example of an auditory illusion is a Shepard tone. Examples of tactile illusions include phantom limb, the thermal grill illusion, the cutaneous rabbit illusion and a curious illusion that occurs when the crossed index and middle fingers are run along the bridge of the nose with one finger on each side, resulting in the perception of two separate noses; the brain areas activated during illusory tactile perception are similar to those activated during actual tactile stimulation. Tactile illusions can be elicited through haptic technology; these "illusory" tactile objects can be used to create "virtual objects". A temporal illusion is a distortion in the perception of time, which occurs when the time interval between two or more events is narrow. In such cases, a person may momentarily perceive time as slowing down, speeding up, or running backward. Illusions can occur with the other senses including those involved in food perception.
Both sound and touch have been shown to modulate the perceived staleness and crispness of food products. It was discovered that if some portion of the taste receptor on the tongue became damaged that illusory taste could be produced by tactile stimulation. Evidence of olfactory illusions occurred when positive or negative verbal labels were given prior to olfactory stimulation; the McGurk effect shows that what we hear is influenced by what we see as we hear the person speaking. An illusion occurs when the auditory component of one sound is paired with the visual component of another sound, leading to the perception of a third sound; this is a auditory-visual illusion. Some illusions occur as a result of a disorder. While these types of illusions are not shared with everyone, they are typical of each condition. For example, migraine sufferers report fortification illusions. Perception so can be elicited by brain stimulation; the percepts that can be evoked range from simple phosphenes to high-level percepts.
In a single-case study on a patient undergoing presurgical evaluation for epilepsy treatment, electrical stimulation at the left temporo-parietal junction evoked the percept of a nearby person who "closely'shadowed' changes in the patient's body position and posture". Altered state of consciousness Aporia Argument from illusion Augmented reality Cognitive dissonance Delusion Dream argument Holography Illusion costume List of cognitive biases Moon illusion Paradox Pareidolia Simulated reality Universal Veiling Techniques What is an Illusion? by J. R. Block. Optical illusions and visual phenomena by Michael Bach Auditory illusions Haptic Perception of Shape - touch illusions and the geometry of objects, by Gabriel Robles-De-La-Torre. Silencing awareness of visual change by motion
An optical illusion is an illusion caused by the visual system and characterized by a visual percept that appears to differ from reality. Illusions come in a wide variety. According to that, there are three main classes: physical and cognitive illusions, in each class there are four kinds: Ambiguities, distortions and fictions. A classical example for a physical distortion would be the apparent bending of a stick half immerged in water. An example for a physiological fiction is an afterimage. Three typical cognitive distortions are the Ponzo, Müller-Lyer illusion. Physical illusions are caused by e.g. by the optical properties of water. Physiological illusions arise in the eye or the visual pathway, e.g. from the effects of excessive stimulation of a specific receptor type. Cognitive visual illusions are the result of unconscious inferences and are those most known. Pathological visual illusions arise from pathological changes in the physiological visual perception mechanisms causing the aforementioned types of illusions.
A familiar phenomenon an example for a physical visual illusion are when mountains appear to be much nearer in clear weather with low humidity than they are. This is; the classical example of a physical illusion is when a stick, half immersed in water appears bent. This phenomenon has been discussed by Ptolemy and was a prototypical example for an illusion. Physiological illusions, such as the afterimages following bright lights, or adapting stimuli of excessively longer alternating patterns, are presumed to be the effects on the eyes or brain of excessive stimulation or interaction with contextual or competing stimuli of a specific type—brightness, position, size, etc; the theory is that a stimulus follows its individual dedicated neural path in the early stages of visual processing and that intense or repetitive activity in that or interaction with active adjoining channels causes a physiological imbalance that alters perception. The Hermann grid illusion and Mach bands are two illusions that are best explained using a biological approach.
Lateral inhibition, where in the receptive field of the retina light and dark receptors compete with one another to become active, has been used to explain why we see bands of increased brightness at the edge of a color difference when viewing Mach bands. Once a receptor is active, it inhibits adjacent receptors; this inhibition creates contrast. In the Hermann grid illusion the gray spots appear at the intersection because of the inhibitory response which occurs as a result of the increased dark surround. Lateral inhibition has been used to explain the Hermann grid illusion, but this has been disproved. More recent empirical approaches to optical illusions have had some success in explaining optical phenomena with which theories based on lateral inhibition have struggled. Cognitive illusions are assumed to arise by interaction with assumptions about the world, leading to "unconscious inferences", an idea first suggested in the 19th century by the German physicist and physician Hermann Helmholtz.
Cognitive illusions are divided into ambiguous illusions, distorting illusions, paradox illusions, or fiction illusions. Ambiguous illusions are pictures or objects that elicit a perceptual "switch" between the alternative interpretations; the Necker cube is a well-known example. Distorting or geometrical-optical illusions are characterized by distortions of size, position or curvature. A striking example is the Café wall illusion. Other examples are the famous Müller-Lyer illusion and Ponzo illusion. Paradox illusions are generated by objects that are paradoxical or impossible, such as the Penrose triangle or impossible staircase seen, for example, in M. C. Escher's Descending and Waterfall; the triangle is an illusion dependent on a cognitive misunderstanding. Fictions are when a figure is perceived though it is not in the stimulus. To make sense of the world it is necessary to organize incoming sensations into information, meaningful. Gestalt psychologists believe one way this is done is by perceiving individual sensory stimuli as a meaningful whole.
Gestalt organization can be used to explain many illusions including the rabbit–duck illusion where the image as a whole switches back and forth from being a duck being a rabbit and why in the figure–ground illusion the figure and ground are reversible. In addition, Gestalt theory can be used to explain the illusory contours in the Kanizsa's Triangle. A floating white triangle, which does not exist, is seen; the brain has a need to see familiar simple objects and has a tendency to create a "whole" image from individual elements. Gestalt means "form" or "shape" in German. However, another explanation of the Kanizsa's Triangle is based in evolutionary psychology and the fact that in order to survive it was important to see form and edges; the use of perceptual organization to create meaning out of stimuli is the principle behind other well-known illusions including impossible objects. Our brain makes sense of shapes and symbols putting them together like a jigsaw puzzle, formulating that which isn't there to that whi
A baseball cap is a type of soft cap with a rounded crown and a stiff peak projecting in front. The front of the cap contains a design or a logo of sports team; the back of the cap may be "fitted" to the wearer's head size or it may have a plastic, Velcro, or elastic and zipper strip, adjuster so that it can be adjusted to fit different wearers. The baseball cap is a part of the traditional baseball uniform worn by players, with the brim pointing forward to shield the eyes from the sun. Since the 1980s varieties of the cap have become a common fashion accessory in the United States. In 1860, the Brooklyn Excelsiors wore the ancestor of the modern rounded-top baseball cap, which featured a long peak and a button on top, by 1900, the "Brooklyn style" cap became popular. During the 1940s, latex rubber became the stiffening material inside the hat and the modern baseball cap was born; the peak known in certain areas as the "bill" or "brim", was designed to protect a player's eyes from the sun. The peak was much shorter in the earlier days of the baseball hat.
The hat has become more structured, versus the overall "floppy" cap of the 19th and early 20th centuries. The baseball cap still is an important means by which to identify a team; the logo, mascot, or team's initial was placed on the cap. The cap was fashioned in the official colors of a particular team; the basic shape, including curved peak, is similar to some styles of 19th century sun bonnets. Fitted baseball caps — those without an adjuster — are sewn in six sections, may be topped with a matching fabric-covered button on the crown. Metal grommets or fabric eyelets are sewn or attached near the top of each of the six sections of fabric to provide ventilation. In some cases, the rear sections of the crown are made of net-like mesh material for extra ventilation; the peak is stiffened by a sewn-in piece of paperboard or stiff plastic. Baseball caps are made of many types of material and shaped in various styles for different purposes. Major and minor league baseball players wear classic-style caps made of wool with their team's simple logo and colors.
More there are brands that are using uncommon materials for snapback hats as for example wood brims. Baseball caps only came in standard hat sizes. Since the early 70's, they have been available in a one-size-fits-all form, with an adjustment strap in the back; the style called snapback, has become popular as fashion accessories. Advances in textiles have led to the "stretch-fit" hat, which uses Lycra or rubber to allow a hat to have a fitted style while still being "adjustable" within sizes; the front may be stiffened by buckram to display a logo more clearly. Another version of the baseball cap is a plastic mesh cap with a foam front imprinted with a company logo; this style is sometimes called a trucker cap or a "gimme cap" because it is given away for free as a promotional item. Dad hats are unstructured caps with low profile, curved brim, stripe on the back. There are high profile, adjustable. Adjustable hat - unstructured, low profile, curved brim, adjustable. Fitted hat - curved or flat brim, structured cap, high profile, unadjustable.
"Flexfit" hat - curved or flat brim, structured cap, high profile, adjustable by the use of elastic materials. Beginning with the 2014 season, MLB pitchers are permitted to wear a special reinforced cap to protect their heads from line drives. Athletes in other sports wear caps with their team's logo and colors as "sideline" caps. Other caps may have a maker's logo, such as Reebok, Nike or Carhartt. Golfers tend to prefer the sports visor form which does not cover the head but keeps the sun out of their eyes; some armed forces use baseball caps as part of their uniforms, including the United States Navy and United States Coast Guard. Used with the utility uniform and coveralls, the baseball cap has a command logo on the front to denote command affiliation. Baseball caps of a particular color are worn to denote a specific function of a person or particular job. For example, in the United States submarine force, red baseball caps are worn by drill monitors who facilitate and critique members of the boat's crew during drills.
In the United States Army, parachute riggers wear red baseball caps and parachute instructors wear black baseball caps as part of their uniform. In various squadrons of the United States Air Force's civilian auxiliary, squadron-distinctive baseball caps have been issued as headgear for the Battle Dress Uniform displaying squadron colors, squadron number, and/or squadron patch. Although the BDUs have their own cover, a patrol cap in M81 Woodland, some squadrons have opted for more distinctive covers. In many United States police forces, the baseball cap is worn as a more practical alternative to the traditional peaked cap or campaign hat, the latter of, used by Sheriff's departments and state police forces; this is more common on the West Coast, whereas in eastern states the traditional peaked cap is more prominent. A notable exception is the San Francisco Police Department, where peaked caps