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Blackboard Places
A blackboard (also known as a chalkboard) is a reusable writing surface on which text or drawings are made with sticks of calcium sulphate or calcium carbonate, known, when used for this purpose, as chalk. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone. Design A blackboard can simply be a board painted with a dark matte paint (usually black, occasionally dark green). Matte black plastic sign material (known as closed-cell PVC foamboard) is also used to create custom chalkboard art. Blackboards on an A-frame are used by restaurants and bars to advertise daily specials. A more modern variation consists of a coiled sheet of plastic drawn across two parallel rollers, which can be scrolled to create additional writing space while saving what has been written. The highest grade blackboards are made of a rougher version porcelain enamelled steel (black, green, blue or sometimes other colours). Porcelain is very hard wearing, and blackboar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laos
Laos (, ''Lāo'' )), officially the Lao People's Democratic Republic ( Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ, French: République démocratique populaire lao), is a socialist state and the only landlocked country in Southeast Asia. At the heart of the Indochinese Peninsula, Laos is bordered by Myanmar and China to the northwest, Vietnam to the east, Cambodia to the southeast, and Thailand to the west and southwest. Its capital and largest city is Vientiane. Present-day Laos traces its historic and cultural identity to Lan Xang, which existed from the 14th century to the 18th century as one of the largest kingdoms in Southeast Asia. Because of its central geographical location in Southeast Asia, the kingdom became a hub for overland trade and became wealthy economically and culturally. After a period of internal conflict, Lan Xang broke into three separate kingdoms: Luang Phrabang, Vientiane and Champasak. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chalkboard Eraser
A chalkboard eraser is a special type of eraser specifically used to erase chalk markings on slating paint (used on chalkboards and slates). It is most commonly made of felt strips attached to a handle. Chalkboard erasers are typically broad and rectangular, intended to clear large areas for new content as part of a lecture or presentation. History Chalkboard erasers were invented around 1863 by John L. Hammett, who owned some stores that sold and created school products in Rhode Island and then later in Boston. Mostly slates were sold there as well as chalk and so on. At the time, rags or old cloths were used to erase and get rid of the chalk markings on slates in schools, offices, and for the most part, everywhere. Hammett created the chalkboard before the invention of the chalkboard eraser by creating ''slating paint''. Hammett then, during a presentation on his chalkboard "discovered" that wool felt strips wiped off the chalk writing better than rags. Following this discovery h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Writing Utensil
A writing implement or writing instrument is an object used to produce writing. Writing consists of different figures, lines, and or forms. Most of these items can be also used for other functions such as painting, drawing and technical drawing, but writing instruments generally have the ordinary requirement to create a smooth, controllable line. Another writing implement employed by a smaller population is the stylus used in conjunction with the slate for punching out the dots in Braille. Autonomous An autonomous writing implement is one that cannot "run out"—the only way to render it useless is to destroy it. Without pigment The oldest known examples were created by incising a flat surface with a rigid tool rather than applying pigment with a secondary object, e.g., Chinese jiaguwen carved into turtle shells. However, this may simply represent the relative durability of such artifacts rather than truly representing the evolution of techniques, as the meaningful applicatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computers
A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These programs enable computers to perform a wide range of tasks. A computer system is a nominally complete computer that includes the hardware, operating system (main software), and peripheral equipment needed and used for full operation. This term may also refer to a group of computers that are linked and function together, such as a computer network or computer cluster. A broad range of industrial and consumer products use computers as control systems. Simple special-purpose devices like microwave ovens and remote controls are included, as are factory devices like industrial robots and computer-aided design, as well as general-purpose devices like personal computers and mobile devices like smartphones. Computers power the Internet, which links bill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WebMD
WebMD is an American corporation known primarily as an online publisher of news and information pertaining to human health and well-being. The site includes information pertaining to drugs. It is one of the top healthcare websites. It was founded in 1998 by internet entrepreneur Jeff Arnold. In early 1999, it was part of a three way merger with Sapient Health Network (SHN) and Direct Medical Knowledge (DMK). SHN began in Portland, Oregon, in 1996 by Jim Kean, Bill Kelly, and Kris Nybakken, who worked together at a CD-ROM publishing firm, Creative Multimedia. Later in 1999, WebMD merged with Healtheon, founded by Netscape Communications founder James H. Clark. Traffic During March 2020, WebMD's network of websites reached more unique visitors each month than any other leading private or government healthcare website, making it the leading health publisher in the United States. In the fourth quarter of 2016, WebMD recorded an average of 179.5 million unique users per month, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Academy Of Allergy, Asthma And Immunology
Founded in 1943, the American Academy of Allergy, Asthma & Immunology (AAAAI) is a professional medical membership organization of nearly 6,800 allergist/ immunologists and related professionals around the world with advanced training and experience in allergy, asthma and other immunologic diseases. The Academy is dedicated to the advancement of the knowledge and practice of allergy, asthma and immunology for optimal patient care. Most members of the AAAAI are board-certified allergist/immunologists. A select group of the membership are elected as Fellows and carry the title FAAAAI. The organization, headquartered in Milwaukee, Wisconsin, hosts a website for patients and healthcare professionals that includes a physician referral directory for patients. Mission The AAAAI is dedicated to the advancement of the knowledge and practice of allergy, asthma, and immunology for optimal patient care. History The American Academy of Allergy, Asthma, and Immunology (AAAAI) dates back to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allergic
Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis. Symptoms may include red eyes, an itchy rash, sneezing, coughing, a runny nose, shortness of breath, or swelling. Note: food intolerances and food poisoning are separate conditions. Common allergens include pollen and certain foods. Metals and other substances may also cause such problems. Food, insect stings, and medications are common causes of severe reactions. Their development is due to both genetic and environmental factors. The underlying mechanism involves immunoglobulin E antibodies (IgE), part of the body's immune system, binding to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine. Diagnosis is t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biodegradable
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradation occurs under a specific set of circumstances. The process of biodegradation is threefold: first an object undergoes biodeterioration, which is the mechanical weakening of its structure; then follows biofragmentation, which is the breakdown of materials by microorganisms; and finally assimilation, which is the incorporation of the old material into new cells. In practice, almost all chemical compounds and materials are subject to biodegradation, the key element being time. Things like vegetables may degrade within days, while glass and some plastics take many millennia to decompose. A standard for biodegradability used by the European Union is that greater than 90% of the original material must be converted into , water and minerals by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Order Of Magnitude
An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic distributions are common in nature and considering the order of magnitude of values sampled from such a distribution can be more intuitive. When the reference value is 10, the order of magnitude can be understood as the number of digits in the base-10 representation of the value. Similarly, if the reference value is one of some powers of 2, since computers store data in a binary format, the magnitude can be understood in terms of the amount of computer memory needed to store that value. Differences in order of magnitude can be measured on a base-10 logarithmic scale in “decades” (i.e., factors of ten). Examples of numbers of different magnitudes can be found at Orders of magnitude (numbers). Definition Generally, the order of magnitude ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whiteboards
A whiteboard (also known by the terms marker board, dry-erase board, dry-wipe board, and pen-board) is a glossy, usually white surface for making non-permanent markings. Whiteboards are analogous to blackboards, but with a smoother surface allowing for rapid marking and erasing of markings on their surface. The popularity of whiteboards increased rapidly in the mid-1990s and they have become a fixture in many offices, meeting rooms, school classrooms, and other work environments. The term ''whiteboard'' is also used metaphorically in reference to features of computer software applications that simulate whiteboards. Such "virtual tech whiteboards" allow one or more people to write or draw images on a simulated canvas. This is a common feature of many virtual meeting, collaboration, and instant messaging applications. The term ''whiteboard'' is also used to refer to interactive whiteboards. History Photographer Martin Heit and Alliance employee Albert Stallion have been cre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on Scratch hardness, scratch hardness comparison. Large calcite crystals are used in optical equipment, and limestone composed mostly of calcite has numerous uses. Other polymorphs of calcium carbonate are the minerals aragonite and vaterite. Aragonite will change to calcite over timescales of days or less at temperatures exceeding 300 °C, and vaterite is even less stable. Etymology Calcite is derived from the German ''Calcit'', a term from the 19th century that came from the Latin word for Lime (material), lime, ''calx'' (genitive calcis) with the suffix "-ite" used to name minerals. It is thus etymologically related to chalk. When applied by archaeology, archaeologists and stone trade pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. Alabaster, a fine-grained white or lightly tinted variety of gypsum, has been used for sculpture by many cultures including Ancient Egypt, Mesopotamia, Ancient Rome, the Byzantine Empire, and the Nottingham alabasters of Medieval England. Gypsum also crystallizes as translucent crystals of selenite. It forms as an evaporite mineral and as a hydration product of anhydrite. The Mohs scale of mineral hardness defines gypsum as hardness value 2 based on scratch hardness comparison. Etymology and history The word ''gypsum'' is derived from the Greek word (), "plaster". Because the quarries of the Montmartre district of Paris have long furnished burnt gypsum (calcined gypsum) used for various purposes, this dehydrated gypsum became known ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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