An hour (symbol: h; also abbreviated hr) is a unit of time conventionally reckoned as 1⁄24 of a day and scientifically reckoned between 3,599 and 3,601 seconds, depending on the speed of Earths rotation. There are 60 minutes in an hour, and 24 hours in a day. The hour was initially established in the ancient Near East as a variable measure of 1⁄12 of the night or daytime. Such seasonal, temporal, or unequal hours varied by season and latitude. Equal or equinoctial hours were taken as 1⁄24 of the day as measured from noon to noon; the minor seasonal variations of this unit were eventually smoothed by making it 1⁄24 of the mean solar day. Since this unit was not constant due to long term variations in the Earths rotation, the hour was finally separated from the Earths rotation and defined in terms of the atomic or physical second. In the modern metric system, hours are an accepted unit of time defined as 3,600 atomic seconds. However, on rare occasions an hour may incorporate a positive or negative leap second, making it last 3,599 or 3,601 seconds, in order to keep it within 0.9 seconds of UT1, which is based on measurements of the mean solar day. Name
Hour is a development of the Anglo-Norman houre and Middle English ure, first attested in the 13th century.It displaced tide tīd, "time" and stound stund, span of time.
It is unknown how many other deaths from Irukandji syndrome have been wrongly attributed to other causes. Pathophysiology
The exact mechanism of action of the venom is unknown, but catecholamine excess may be an underlying mechanism in severe cases. Animal studies appear to confirm a relationship between envenoming and an increase in circulating noradrenaline and adrenaline. Treatment
Similar to other box jellyfish stings, first aid consists of flushing the area with vinegar to neutralize the tentacle stinging apparatus. As no antivenom is available, treatment is largely supportive, with analgesia being the mainstay of management. Nitroglycerin, a common drug used for cardiac conditions, is utilised by medical personnel to minimise the risk of pulmonary edema and to reduce hypertension. Antihistamines may be of benefit for pain relief, but most cases require intravenous opioid analgesia. Fentanyl or morphine are usually chosen. Pethidine (meperidine, brand name Demerol in the US) should be avoided, as large doses are often required for pain relief and in this situation significant adverse effects from the pethidine metabolite norpethidine may occur.Magnesium sulfate (Epsom Salts) has been proposed as a treatment for Irukandji syndrome after being apparently successfully used in one case. Early evidence suggested a benefit; however, according to a later report, a series of three patients failed to show any improvement with magnesium; the author emphasized the experimental status of this treatment.