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21-529: A roller rink is a hard surface usually consisting of hardwood or concrete , used for roller skating or inline skating . This includes roller hockey , speed skating , roller derby , and individual recreational skating. Roller rinks can be located in an indoor or outdoor facility. Most skating center facilities range anywhere from under 14,000 square feet (1,300 m) to more than 21,000 square feet (2,000 m). Massachusetts businessman James Plimpton 's 1863 invention of an improved roller skate led to

42-773: A boom in popularity in the late 19th century, particularly in cities of the American East Coast. At first, people roller skated at home, but within twenty years businesses dedicated to the activity began to spring up. Plimpton himself is credited with opening the first roller skating rink in New York City . Patrons who enjoyed ice skating during the winter months participated in the similar activity, now year-round. Early roller rinks varied greatly in size and type, both indoor and outdoor. Many consisted of simple wooden platforms that sometimes doubled as dance floors or ballrooms. While primarily an activity of eastern cities,

63-561: A few enterprising individuals toured the rural areas of the Midwest and South with wagon-loads of roller skates. These entrepreneurs went from town-to-town, often in conjunction with circuses or carnivals, renting out skates and using whatever locally-available surface as an impromptu rink. The post–World War II baby boom also saw a boom in roller rinks across the United States. Having a roller skating birthday party became something of

84-677: A function, and is still being protected by surrounding living cells. The presence of vessels in xylem has been considered to be one of the key innovations that led to the success of the flowering plants. It was once thought that vessel elements were an evolutionary innovation of flowering plants, but their absence from some basal angiosperms and their presence in some members of the Gnetales suggest that this hypothesis must be re-examined; vessel elements in Gnetales may not be homologous with those of angiosperms, or vessel elements that originated in

105-420: A more complex structure than softwoods and are often much slower growing as a result. The dominant feature separating "hardwoods" from softwoods is the presence of pores, or vessels . The vessels may show considerable variation in size, shape of perforation plates (simple, scalariform, reticulate, foraminate), and structure of cell wall, such as spiral thickenings. As the name suggests, the wood from these trees

126-515: A precursor to the angiosperms may have been subsequently lost in some basal lineages (e.g., Amborellaceae , Trochodendraceae , and Winteraceae ), described by Arthur Cronquist as "primitively vesselless". Cronquist considered the vessels of Gnetum to be convergent with those of angiosperms. Vessel-like cells have also been found in the xylem of Equisetum (horsetails), Selaginella (spike-mosses), Pteridium aquilinum (bracken fern), Marsilea and Regnellidium ( aquatic ferns ), and

147-678: A professional sport of the 1950s and 1960s once considered virtually dead, has seen a DIY , grassroots rebirth in popularity in the early 21st century with amateur and semi-pro teams forming leagues nationwide. Many rink owners support this activity, along with roller hockey, speed skating, and roller figure skating contests. Hardwood Hardwood is wood from angiosperm trees . These are usually found in broad-leaved temperate and tropical forests . In temperate and boreal latitudes they are mostly deciduous , but in tropics and subtropics mostly evergreen . Hardwood (which comes from angiosperm trees) contrasts with softwood (which

168-426: A rite of passage for American children in the 1950s, 1960s, 1970s, and 1980s. Roller rinks in the United States underwent significant changes in the 1970s. New plastics led to improved skate wheels—ones providing a smoother, quieter ride—and easier-to-maintain skate floors. The disco craze from popular 1970s culture led to another increase in the popularity of roller rinks—or roller discos , as some became. Gone were

189-413: A vessel element have pits : more or less circular regions in contact with neighbouring cells. Tracheids also have pits, but only vessel elements have openings at both ends that connect individual vessel elements to form a continuous tubular vessel. These end openings are called perforations or perforation plates. They have a variety of shapes: the most common are the simple perforation (a simple opening) and

210-450: Is due to the variety of characteristics apparent in different timbers, including density, grain, pore size, growth and fibre pattern, flexibility and ability to be steam bent. For example, the interlocked grain of elm wood ( Ulmus spp.) makes it suitable for the making of chair seats where the driving in of legs and other components can cause splitting in other woods. There is a correlation between density and calories/volume. This makes

231-529: Is from gymnosperm trees). Hardwoods are produced by angiosperm trees that reproduce by flowers, and have broad leaves. Many species are deciduous. Those of temperate regions lose their leaves every autumn as temperatures fall and are dormant in the winter, but those of tropical regions may shed their leaves in response to seasonal or sporadic periods of drought. Hardwood from deciduous species, such as oak, normally shows annual growth rings , but these may be absent in some tropical hardwoods . Hardwoods have

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252-554: Is generally harder than that of softwoods, but there are significant exceptions. In both groups there is an enormous variation in actual wood hardness, with the range in density in hardwoods completely including that of softwoods; some hardwoods ( e.g. , balsa ) are softer than most softwoods, while yew is an example of a hard softwood. The structural polymers of hardwoods are cellulose , hemicellulose , and lignin . The constituents of hardwood lignin differs from those included in softwood. Sinapyl alcohol and coniferyl alcohol are

273-453: Is rich in phenolic compounds, such as stilbenes , lignans , norlignans, tannins , flavonoids . Hardwoods are employed in a large range of applications, including fuel , tools , construction , boat building , furniture making, musical instruments , flooring , cooking , barrels , and manufacture of charcoal . Solid hardwood joinery tends to be expensive compared to softwood. In the past, tropical hardwoods were easily available, but

294-451: The denser hardwoods like oak , cherry , and apple more suited for camp fires, cooking fires, and smoking meat, as they tend to burn hotter and longer than softwoods like pine or cedar whose low-density construction and highly-flammable pitch make them burn quickly and without producing quite as much heat. Vessel element Xylem is the tissue in vascular plants that conducts water (and substances dissolved in it) upwards from

315-545: The hardwood significantly differs from the softwood, and mainly consists of triterpenoids , polyprenols and other higher terpenes. Triterpenoids commonly purified from hardwoods include cycloartenol , betulin and squalene . Hardwood polyterpenes are rubber , gutta percha , gutta-balatá and betulaprenols. Although in small quantities, hardwoods also contain mono- , sesqui- and diterpenes , such as α- and β-pinenes , 3-carene , β-myrcene , limonene , hinokitiol , δ-cadinene , α- and δ-cadinols , borneol . Hardwood

336-558: The main monomers of hardwood lignin. Hardwoods contain less amount of non-structural constituents, named extractives , than softwoods. These extractives are usually categorized into three broad groups: aliphatic compounds , terpenes and phenolic compounds . Aliphatic compounds found in hardwoods include fatty acids , fatty alcohols and their esters with glycerol , fatty alcohols (waxes) and sterols (steryl esters), hydrocarbons , such as alkanes , sterols , such as sitosterol , sitostanol and campesterol . The terpene content of

357-443: The plant. In secondary xylem – the xylem that is produced as a stem thickens rather than when it first appears – a vessel element originates from the vascular cambium . A long cell, oriented along the axis of the stem, called a "fusiform initial", divides along its length forming new vessel elements. The cell wall of a vessel element becomes strongly "lignified", i.e. it develops reinforcing material made of lignin . The side walls of

378-406: The roots to the shoots. Two kinds of cell are involved in xylem transport: tracheids and vessel elements. Vessel elements are the building blocks of vessels, the conducting pathways that constitute the major part of the water transporting system in flowering plants. Vessels form an efficient system for transporting water (including necessary minerals) from the root to the leaves and other parts of

399-424: The scalariform perforation (several elongated openings in a ladder-like design). Other types include the foraminate perforation plate (several round openings) and the reticulate perforation plate (a net-like pattern, with many openings). At maturity, the protoplast – the living material of the cell – dies and disappears, but the lignified cell walls persist. A vessel element is then a dead cell, but one that still has

420-483: The staid lighting and old-fashioned organ music as a generally older clientele were replaced by adolescents and twenty-somethings skating under mirror balls and special lights to disco beats. The end of the Disco Era and the advent of inline roller skates hit the roller rink industry hard, with many rinks closing. However, as had happened earlier, most rink owners adapted and survived the economic storm. Roller derby ,

441-550: The supply of some species, such as Burma teak and mahogany , is now becoming scarce due to over-exploitation. Cheaper "hardwood" doors, for instance, now consist of a thin veneer bonded to a core of softwood, plywood or medium-density fibreboard (MDF). Hardwoods may be used in a variety of objects, but are most frequently seen in furniture or musical instruments because of their density which adds to durability, appearance, and performance. Different species of hardwood lend themselves to different end uses or construction processes. This

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