Ooid and Discovery Health Channel

Ooids are small (2 mm in diameter), spheroidal, "coated" (layered) sedimentary grains, usually composed of calcium carbonate, but sometimes made up of iron- or phosphate-based minerals. Ooids usually form on the sea floor, most commonly in shallow tropical seas (around the Bahamas, for example, or in the Persian Gulf). After being buried under additional sediment, these ooid grains can be cemented together to form a sedimentary rock called an oolite. Oolites usually consist of calcium carbonate; these belong to the limestone rock family. Pisoids are similar to ooids, but are larger than 2 mm in diameter, often considerably larger, as with the pisoids in the hot springs at Carlsbad (Karlovy Vary) in the Czech Republic.

Contents 1 Formation 2 Variation 3 Growth mode 4 Growth factors 5 Structural similarity 6 Reference 7 External links

Formation

An ooid forms as a series of concentric layers around a nucleus. The layers contain crystals arranged radially, tangentially or randomly. The nucleus can be a shell fragment, quartz grain or any other small fragment. Most modern ooids are aragonite, a polymorph of calcium carbonate; some are composed of high-magnesium calcite, and some are bimineralic (layers of calcite and aragonite). Ancient ooids can be calcitic, either originally precipitated as calcite (as in calcite seas), or formed by alteration (neomorphic replacement) of aragonitic ooids (or the aragonite layers in originally bimineralic ooids). Moldic ooids (or molds later filled in by calcite cement) occur in both young and ancient rocks, indicating the removal of a soluble polymorph (usually aragonite). Variation

Whether ooids become calcitic or aragonitic can be linked to strontium/calcium substitution within the crystalline structure. This has been shown in some examples to be due to temperature fluctuations in marine environments, which affects salinity levels, which in turn facilitate the substitution. Marine calcitic ooids were typically formed during calcite sea intervals, especially during the Ordovician and the Jurassic Periods. The geochemistry of these seas was a function of seafloor spreading and fluctuating Mg/Ca ratios. Low Mg/Ca ratios favor the precipitation of low-magnesium calcite. Growth mode

Ooids with radial crystals (such as the aragonitic ooids in the Great Salt Lake, Utah, USA) grow by ions extending the lattices of the radial crystals. The mode of growth of ooids with tangential (usually minute needle-like) crystals is less clear. They may be accumulated in a "snowball" fashion from tiny crystals in the sediment or water, or they may crystallize in place on the ooid surface. A hypothesis of growth by accretion (like a snowball) from the polymineralic sediment of fine aragonite, high-magnesium calcite (HMC) and low-magnesium calcite (LMC), must explain how only aragonite needles are added to the ooid cortex. Both in tangential and in radial ooids, the cortex is composed of many very fine increments of growth. Some modern (and ancient) ooids partially or totally lack clear layering and have a micritic (very fine grained) texture. Examination of such micritic ooids by scanning electron microscopy often shows evidence of microbial borings later filled by fine cement. Growth factors

There are several factors that affect ooid growth: supersaturation of the water with respect to calcium carbonate, the availability of nuclei, agitation of the ooids, water depth, and the role of microbes. Structural similarity

Kidney stones are similar to ooids in their layered structure; they are sometimes rich in calcium (calcium oxalate) or phosphate (struvite).

Discovery Health Channel and Ooid

Discovery Health Channel was a U.S. cable television specialty channel dedicated to television programming that highlighted various aspects of health and wellness. Launched on August 2, 1999, the network was a media property of Discovery Communications Inc., the parent company of other popular cable TV networks such as Discovery Channel, TLC, and Animal Planet.

A version of DHC was set up in Canada as well; Discovery Health Canada was a joint venture between Canadian media giant CW Media and Discovery Communications Inc; it evolved into Twist TV on November 2, 2010. Another version of the channel in the United Kingdom has since been renamed Discovery Home & Health.

In the beginning, DHC started out rerunning material from other Discovery Communications entities, most notably the medical-based reality show programming from TLC. As the network matured, it began producing its own programming in the reality show genre, mostly dealing with babies (Babies: Special Delivery, Birth Day), bodies (Plastic Surgery: Before and After, National Body Challenge), and blood (The Critical Hour, Dr. G: Medical Examiner). DHC also shows episodes of the CBS medical drama series Chicago Hope on a semi-regular basis.

DHC won its first Daytime Emmy in 2004 for its original series about adoptive families, Adoption Stories. Most of DHC's fitness-related programming has since been spun off to its sister network FitTV, though some of it remains, such as the annual National Body Challenge series.

In November 2009, it was announced that Discovery Health Channel would become defunct and be replaced with a new network, OWN: Oprah Winfrey Network, at 12:00 am Eastern/Pacific (11:00 pm Central) on January 1, 2011.

Discovery Health returned as a new cable channel on February 1, 2011 as a result of a merger with FitTV to create Discovery Fit & Health.

Contents 1 OWN: Oprah Winfrey Network 2 See also 3 References 4 External links

OWN: Oprah Winfrey Network Main article: Oprah Winfrey Network (U.S. TV channel)

Discovery Health was discontinued at 11:59 pm Eastern/Pacific (10:59 pm Central) on December 31, 2010. A minute later, it was replaced by a new lifestyle network headed by television personality Oprah Winfrey, known as OWN: Oprah Winfrey Network.

On January 1, 2011, most of the programming that had been airing on Discovery Health Channel moved to FitTV. A few Discovery Health Channel shows were picked up by OWN: Oprah Winfrey Network. A month later, FitTV would be rebranded as Discovery Fit & Health. See also Discovery Channel Travel Channel previously owned by Discovery Communications, Inc. Discovery Fit & Health
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