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Nuclear Astrophysics. == Charged vs. uncharged particles == In the initial collision which begins the reaction, the particles must approach closely enough so that the short-range strong force can affect them. As most common nuclear particles are positively charged, this means they must overcome considerable electrostat... | {
"page_id": 460322,
"source": null,
"title": "Nuclear reaction"
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Spallation – a nucleus is hit by a particle with sufficient energy and momentum to knock out several small fragments or smash it into many fragments. Induced gamma emission belongs to a class in which only photons were involved in creating and destroying states of nuclear excitation. Fission reactions – a very heavy nu... | {
"page_id": 460322,
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"title": "Nuclear reaction"
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These are useful in studying outer shell structure of nuclei. Transfer reactions can occur: from the projectile to the target - stripping reactions from the target to the projectile - pick-up reactions Examples: (α,n) and (α,p) reactions. Some of the earliest nuclear reactions studied involved an alpha particle produce... | {
"page_id": 460322,
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"title": "Nuclear reaction"
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transfers energy to the nucleus, leaving it with too much energy to be fully bound together. On a time scale of about 10−19 seconds, particles, usually neutrons, are "boiled" off. That is, it remains together until enough energy happens to be concentrated in one neutron to escape the mutual attraction. The excited quas... | {
"page_id": 460322,
"source": null,
"title": "Nuclear reaction"
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A diving cylinder or diving gas cylinder is a gas cylinder used to store and transport high pressure gas used in diving operations. This may be breathing gas used with a scuba set, in which case the cylinder may also be referred to as a scuba cylinder, scuba tank or diving tank. When used for an emergency gas supply fo... | {
"page_id": 460321,
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"title": "Diving cylinder"
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"pony" cylinder, carried on the diver's back or clipped onto the harness at the side. Paired cylinders may be manifolded together or independent. In technical diving, more than two scuba cylinders may be needed. When pressurized, the gas is compressed up to several hundred times atmospheric pressure. The selection of a... | {
"page_id": 460321,
"source": null,
"title": "Diving cylinder"
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may also be called aqualungs, a genericized trademark derived from the Aqua-lung equipment made by the Aqua Lung/La Spirotechnique company, although that is more properly applied to an open circuit scuba set or open circuit diving regulator. Diving cylinders may also be specified by their application, as in bailout cyl... | {
"page_id": 460321,
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dive resorts is the "aluminium-S80" which is an aluminum cylinder design with an internal volume of 0.39 cubic feet (11.0 L) rated to hold a nominal volume of 80 cubic feet (2,300 L) of atmospheric pressure gas at its rated working pressure of 3,000 pounds per square inch (207 bar). Aluminum cylinders are also often us... | {
"page_id": 460321,
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"title": "Diving cylinder"
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the periodic hydrostatic, visual and eddy current tests required by regulation and as specified by the manufacturer. The number of cylinders that have failed catastrophically is in the order of 50 out of some 50 million manufactured. A larger number have failed the eddy current test and visual inspection of neck thread... | {
"page_id": 460321,
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"title": "Diving cylinder"
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corrosion, particularly in seawater, and may be galvanized or coated with corrosion barrier paints to resist corrosion damage. It is not difficult to monitor external corrosion, and repair the paint when damaged, and steel cylinders which are well maintained have a long service life, often longer than aluminium cylinde... | {
"page_id": 460321,
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"title": "Diving cylinder"
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provide the best strength and toughness. The cylinders are machined to provide the neck thread and o-ring seat (if applicable), then chemically cleaned or shot-blasted inside and out to remove mill-scale. After inspection and hydrostatic testing they are stamped with the required permanent markings, followed by externa... | {
"page_id": 460321,
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"title": "Diving cylinder"
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and 85 to 100 N⋅m (63 to 74 lbf⋅ft) on aluminum cylinders; 3/4"x14 BSP parallel thread, which has a 55° Whitworth thread form, a pitch diameter of 25.279 millimetres (0.9952 in) and a pitch of 14 threads per inch (1.814 mm); 3/4"x14 NGS (NPSM) parallel thread, sealed by an O-ring, torqued to 40 to 50 N⋅m (30 to 37 lbf⋅... | {
"page_id": 460321,
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"title": "Diving cylinder"
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by a protective and decorative layer of chrome plating. A metal or plastic dip tube or valve snorkel screwed into the bottom of the valve extends into the cylinder to reduce the risk of liquid or particulate contaminants in the cylinder getting into the gas passages when the cylinder is inverted, and blocking or jammin... | {
"page_id": 460321,
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"title": "Diving cylinder"
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attached to the cylinder valve outlet, and an outlet connection in the middle, to which the regulator is attached. A variation on this pattern includes a reserve valve at the outlet connector. The cylinders are isolated from the manifold when closed, and the manifold can be attached or disconnected while the cylinders ... | {
"page_id": 460321,
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"title": "Diving cylinder"
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on board emergency gas supply of a diving bell is usually manifolded by semi-permanent metal alloy pipes between the cylinder valves. ==== Valve cage ==== Also known as a manifold cage or regulator cage, this is a structure which can be clamped to the neck of the cylinder or manifolded cylinders to protect the valves a... | {
"page_id": 460321,
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"title": "Diving cylinder"
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fresh water after use and storing in a dry place. The added hydrodynamic drag caused by a cylinder boot is trivial in comparison with the overall drag of the diver, but some boot styles may present a slightly increased risk of snagging on the environment. ==== Cylinder net ==== A cylinder net is a tubular net which is ... | {
"page_id": 460321,
"source": null,
"title": "Diving cylinder"
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and proportions of length to diameter and in the same alloy. === Working pressure === Scuba cylinders are technically all high-pressure gas containers, but within the industry in the United States there are three nominal working pressure ratings (WP) in common use; low pressure (2400 to 2640 psi — 165 to 182 bar), stan... | {
"page_id": 460321,
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"title": "Diving cylinder"
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developed pressure when corrected to the reference temperature does not exceed the specified working pressure stamped on the cylinder. This allows cylinders to be safely and legally filled to a pressure that is higher than the specified working pressure when the filling temperature is greater than the reference tempera... | {
"page_id": 460321,
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"title": "Diving cylinder"
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Capacity == There are two commonly used conventions for describing the capacity of a diving cylinder. One is based on the internal volume of the cylinder. The other is based on nominal volume of gas stored. === Internal volume === The internal volume is commonly quoted in most countries using the metric system. This in... | {
"page_id": 460321,
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"title": "Diving cylinder"
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back gas or sidemount 10.2 litres: Available in aluminium, 232 bar, used as single or twins for back gas 10 litres: Available in steel, 200, 232 and 300 bar, used as single or twins for back gas, and for bailout 9.4 litres: Available in aluminium, 232 bar, used for back gas or as slings 8 litres: Available in steel, 20... | {
"page_id": 460321,
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"title": "Diving cylinder"
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pressure is not necessarily the same as the actual working pressure used. Some steel cylinders manufactured to US standards are permitted to exceed the nominal working pressure by 10% and this is indicated by a '+' symbol. This extra pressure allowance is dependent on the cylinder passing the appropriate periodical hyd... | {
"page_id": 460321,
"source": null,
"title": "Diving cylinder"
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nearly neutral buoyancy, which makes it relatively unobtrusive for this mounting style. Internal volume is approximately 5.8 litres (0.20 cu ft) and working pressure 3,000 pounds per square inch (207 bar). Aluminum S63 (9.0 L) 3,000 pounds per square inch (207 bar), and steel HP65 (8.2 L) are smaller and lighter than t... | {
"page_id": 460321,
"source": null,
"title": "Diving cylinder"
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15.0 litres OD = 160mm, 6.0 to 16.0 litres OD = 171mm, 8.0 to 23.0 litres OD = 178mm, 8.0 to 35.0 litres OD = 204mm, 10.0 to 40.0 litres OD = 229mm, 20.0 to 50.0 litres OD = 267mm, 33.0 to 80.0 litres Wall thickness varies depending on location, material, pressure rating and practical considerations. The sides of the c... | {
"page_id": 460321,
"source": null,
"title": "Diving cylinder"
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necessary for strength and corrosion tolerance. Faber steel cylinders to CE standards have slightly decreased in mass for the same cylinder size from 2023. A 200 bar 15 litre cylinder with 203mm outside diameter domed bottom, reduced from 16.2kg to 145kg. The equivalent 232 bar cylinder reduced from 18.2 to 16.7kg. ===... | {
"page_id": 460321,
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"title": "Diving cylinder"
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the shallowest decompression stop can lead to incomplete decompression and increased risk of decompression sickness. The change in buoyancy of a diving cylinder during the dive can be more problematic with side-mounted cylinders, and the actual buoyancy at any point during the dive is a consideration with any cylinder ... | {
"page_id": 460321,
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"title": "Diving cylinder"
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one gas source. Diving cylinders may serve different purposes. One or two cylinders may be used as a primary breathing source which is intended to be breathed from for most of the dive. A smaller cylinder carried in addition to a larger cylinder is called a "pony bottle". A cylinder to be used purely as an independent ... | {
"page_id": 460321,
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"title": "Diving cylinder"
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also generically used for any independent open circuit scuba set other than back gas carried by a scuba diver. Commonly divers use aluminium stage cylinders, particularly in fresh water, because they are nearly neutrally buoyant and can be removed underwater with less effect on the diver's overall buoyancy. Suit inflat... | {
"page_id": 460321,
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"title": "Diving cylinder"
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scuba courses. This equipment configuration, although common with entry-level divers and used for most sport diving, is not recommended by training agencies for any dive where decompression stops are needed, or where there is an overhead environment (wreck diving, cave diving, or ice diving) as it provides no functiona... | {
"page_id": 460321,
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"title": "Diving cylinder"
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with about 85 litres (3.0 cu ft) of free air with a diving regulator directly attached, such as the Spare Air. This source provides only a few breaths of gas at depth and is most suitable as a shallow water bailout. ==== Independent twins ==== Independent twin sets or independent doubles consists of two independent cyl... | {
"page_id": 460321,
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"title": "Diving cylinder"
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still in use for large capacity bailout sets for deep commercial diving. ==== Isolation manifolded twins ==== Isolation manifolded twin sets or manifolded doubles with two regulators, consist of two back mounted cylinders with their pillar valves connected by a manifold, with a valve in the manifold that can be closed ... | {
"page_id": 460321,
"source": null,
"title": "Diving cylinder"
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elimination of inert gases. Bailout gas is an emergency supply intended to be used to surface if the main gas supply is lost. ==== Side mount cylinders ==== Side-mount cylinders are cylinders clipped to the harness at the diver's sides which carry bottom gas when the diver does not carry back mount cylinders. They may ... | {
"page_id": 460321,
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"title": "Diving cylinder"
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are intended to be taken off and left at the guideline during the early part of a dive, to be collected on the way back. === Rebreathers === Diving cylinders are used in rebreather diving in two roles: As part of the rebreather itself. The rebreather must have at least one source of fresh gas stored in a cylinder; many... | {
"page_id": 460321,
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"title": "Diving cylinder"
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independent diving cylinders for its gas supply. Using another rebreather as a bail-out is possible but uncommon. Although the long duration of rebreathers seems compelling for bail-out, rebreathers are relatively bulky, complex, vulnerable to damage and require more time to start breathing from, than easy-to-use, inst... | {
"page_id": 460321,
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"title": "Diving cylinder"
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an asphyxiant. === Other uses of compressed gas cylinders in diving operations === Divers also use gas cylinders above water for storage of oxygen for first aid treatment of diving disorders and as part of storage "banks" for diving air compressor stations, gas blending, surface supplied breathing gas and gas supplies ... | {
"page_id": 460321,
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"title": "Diving cylinder"
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hold almost 12 × 232 / 1 = 2,784 litres (98.3 cu ft) of air at atmospheric pressure (also known as free air). In the US the capacity of a diving cylinder is specified directly in cubic feet of free air at the nominal working pressure, as the calculation from internal volume and working pressure is relatively tedious in... | {
"page_id": 460321,
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"title": "Diving cylinder"
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extreme high work rate, breathing rates can rise to 95 litres per minute. For International Marine Contractors Association (IMCA) commercial diving gas planning purposes, a working breathing rate of 40 litres per minute is used, whilst a figure of 50 litres per minute is used for emergencies. RMV is controlled by blood... | {
"page_id": 460321,
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(4 bar), will consume 20 × 4 × 1 = 80 L/min surface equivalent. A diver with a RMV of 40 L/min at 50 msw (6 bar) for 10 minutes will consume 40 × 6 × 10 = 2400 litres of free air – the full capacity of a 12-litre 200 bar cylinder. Imperial examples: A diver with a SAC of 0.5 cfm (cubic feet per minute) at 100 fsw (4 at... | {
"page_id": 460321,
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"title": "Diving cylinder"
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is calculated as (2) PA = D×g×ρ + atmospheric pressure with D = depth g = Standard gravity ρ = water density in a consistent system of units For metric units, this formula can be approximated by (3) PA = D/10 + 1 with depth in m and pressure in bar Ambient pressure is deducted from cylinder pressure, as the quantity of... | {
"page_id": 460321,
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"title": "Diving cylinder"
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of 18 litres pressurized at 200 bars, can breathe for a period of 72 minutes before the cylinder pressure falls so low as to prevent inhalation. In some open circuit scuba systems this can happen quite suddenly, from a normal breath to the next abnormal breath, a breath which may not be fully drawn. (There is never any... | {
"page_id": 460321,
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"title": "Diving cylinder"
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usable gas of the cylinder be held aside as a safety reserve. The reserve is intended to provide gas for longer than planned decompression stops or to provide time to resolve underwater emergencies. The size of the reserve depends upon the risks involved during the dive. A deep or decompression dive warrants a greater ... | {
"page_id": 460321,
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divers using surface-supplied diving equipment. === Weight of gas consumed === The density of air at sea level and 15 °C is approximately 1.225 kg/m3. Most full-sized diving cylinders used for open circuit scuba hold more than 2 kilograms (4.4 lb) of air when full, and as the air is used, the buoyancy of the cylinder i... | {
"page_id": 460321,
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pressure, both of which are hazardous to the operator, so procedures to control these risks are generally followed. Rate of filling must be limited to avoid excessive heating, the temperature of cylinder and contents must remain below the maximum working temperature specified by the applicable standard. A flexible high... | {
"page_id": 460321,
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the compressed air by water separators. This may be done between stages on the compressor as well as after compression. filtration after compression to remove remaining water, oil, and other contaminants using specialized filter media such as desiccants, molecular sieve or activated carbon. Traces of carbon monoxide ma... | {
"page_id": 460321,
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"title": "Diving cylinder"
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filling: Excess heat can be removed by immersion of the cylinder in a cold water bath while filling. However, immersion for cooling can also increase the risk of water contaminating the valve orifice of a completely depressurized tank and being blown into the cylinder during filling. Dry filling: Cylinders may also be ... | {
"page_id": 460321,
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Gas purity and testing === Diving cylinders should only be filled with suitably filtered air from diving air compressors or with other breathing gases using gas blending or decanting techniques. In some jurisdictions, suppliers of breathing gases are required by legislation to periodically test the quality of compresse... | {
"page_id": 460321,
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depth and may then exceed acceptable or tolerable limits. Common contaminants are: carbon monoxide – a by-product of combustion, carbon dioxide – a product of metabolism, and oil and lubricants from the compressor. Keeping the cylinder slightly pressurized at all times during storage and transportation reduces the poss... | {
"page_id": 460321,
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"title": "Diving cylinder"
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wall thickness or deep pitting due to internal corrosion, neck thread failure due to incompatible valve threads, or cracking due to fatigue, sustained high stresses, or overheating effects in aluminum. Tank bursting due to over-pressure may be prevented by a pressure-relief burst disc fitted to the cylinder valve, whic... | {
"page_id": 460321,
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"title": "Diving cylinder"
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cylinders are failed by the hydrostatic test. Almost all cylinders that fail are failed according to visual inspection criteria. When a cylinder is manufactured, its specification, including manufacturer, working pressure, test pressure, date of manufacture, capacity and weight are stamped on the cylinder. After a cyli... | {
"page_id": 460321,
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within the jurisdiction of the Occupational Health and Safety Act, 1993. Eddy current testing of neck threads must be done according to the manufacturer's recommendations. === Procedures for periodic inspections and tests === If a cylinder passes the listed procedures, but the condition remains doubtful, further tests ... | {
"page_id": 460321,
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"title": "Diving cylinder"
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valve is off, the threads of cylinder and valve are checked to identify the thread type and condition. The threads of cylinder and valve must be of matching thread specification, clean and full form, undamaged and free of cracks, burrs and other imperfections. Ultrasonic inspection may be substituted for the pressure t... | {
"page_id": 460321,
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are generally used. Removal of coatings by the application of heat may render the cylinder unserviceable by affecting the crystalline microstructure of the metal. This is a particular hazard for aluminium alloy cylinders, which may not be exposed to temperatures above those stipulated by the manufacturer. === Service l... | {
"page_id": 460321,
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"title": "Diving cylinder"
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where they will not be walked on, and stowed under the boat bench or secured to a rack, is the practice of a competent diver. As the scuba set is a life support system, no unauthorised person should touch a diver's assembled scuba gear, even to move it, without their knowledge and approval. Full cylinders should not be... | {
"page_id": 460321,
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"title": "Diving cylinder"
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standards. National standards may refer to other national standards as accepted alternatives. When a standard is superseded, cylinders manufactured to previously accepted standards usually remain legal for continued use provided that they continue to pass inspections and testing as currently required. === Accidents ===... | {
"page_id": 460321,
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"title": "Diving cylinder"
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to close the wound. Cases of lateral epicondylitis have been reported caused by the handling of diving cylinders. === Handling === Cylinders should not be left standing unattended unless secured so that they can not fall in reasonably foreseeable circumstances as an impact could damage the cylinder valve mechanism, and... | {
"page_id": 460321,
"source": null,
"title": "Diving cylinder"
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materials). Selecting the Proper Shipping Name (well known by the abbreviation PSN) is a way to help ensure that the dangerous goods offered for transport accurately represent the hazards. IATA Dangerous Goods Regulations (DGR) 55th Edition defines the Proper Shipping Name as "the name to be used to describe a particul... | {
"page_id": 460321,
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"title": "Diving cylinder"
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for the vehicles and crew. The regulations cover transportation of gas cylinders in a vehicle in a commercial environment. Transportation of pressurised diving gas cylinders with a combined water capacity of less than 1000 litres on a vehicle for personal use is exempt from ADR. Transport of gas cylinders in a vehicle,... | {
"page_id": 460321,
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"title": "Diving cylinder"
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must be closed whilst in transit and checked that there are no leaks. Where applicable, protective valve caps and covers should be fitted to cylinders before transporting. Cylinders should not be transported with equipment attached to the valve outlet (regulators, hoses etc.). A fire extinguisher is required on the veh... | {
"page_id": 460321,
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"title": "Diving cylinder"
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provisions and conditions of the regulations. Cylinders manufactured outside the USA may be transported under a special permit, and these have been issued for solid metal and composite cylinders with working pressures of up to 300 bar (4400 psi) by several manufacturers. Surface transport Commercial transportation of b... | {
"page_id": 460321,
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"title": "Diving cylinder"
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coated to protect against corrosion. The usual finishes include hot-dip galvanisation, zinc-spray, and heavy duty paint systems. Paint may be applied over zinc coatings for cosmetic purposes or color coding. Steel cylinders without anti-corrosion coatings rely on the paint to protect against rusting, and when the paint... | {
"page_id": 460321,
"source": null,
"title": "Diving cylinder"
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cylinder between the parallel section and the pillar valve. For mixed gases, the colours can be either bands or "quarters". Air has either a white (RAL 9010) top and black (RAL 9005) band on the shoulder, or white (RAL 9010) and black (RAL 9005) "quartered" shoulders. Heliox has either a white (RAL 9010) top and brown ... | {
"page_id": 460321,
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a white shoulder. == Manufacturers == Cylinder manufacturers identify their products using their registered stamp marking on the cylinder shoulder. Steel cylinders: Avesta Jernverks AB (Sweden) Dalmine (cylinders) (Italy) (historical) Eurocylinder Systems AG (Apolda, Germany) Faber Industrie S.p.A. (Cividale del Friuli... | {
"page_id": 460321,
"source": null,
"title": "Diving cylinder"
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Thiosulfonate esters are organosulfur compounds with the formula R−SO2−S−R'. The parent member S-methyl methanethiosulfonate CH3−SO2−S−CH3 is a colorless liquid. Thiosulfonate esters are usually produced by oxidation of disulfides or the nucleophilic attack of thiolates on organosulfonyl halides. The simplest thiosulfo... | {
"page_id": 43910689,
"source": null,
"title": "Thiosulfonate"
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In statistics and machine learning, lasso (least absolute shrinkage and selection operator; also Lasso, LASSO or L1 regularization) is a regression analysis method that performs both variable selection and regularization in order to enhance the prediction accuracy and interpretability of the resulting statistical model... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
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prediction accuracy in certain cases, such as when only a few covariates have a strong relationship with the outcome. However, in other cases, it can increase prediction error. At the time, ridge regression was the most popular technique for improving prediction accuracy. Ridge regression improves prediction error by s... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
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, β 2 , … , β p ) {\displaystyle \beta :=(\beta _{1},\beta _{2},\ldots ,\beta _{p})} is the coefficient vector, and t {\displaystyle t} is a prespecified free parameter that determines the degree of regularization. Letting X {\displaystyle X} be the covariate matrix, so that X i j = ( x i ) j {\displaystyle X_{ij}=(x_{... | {
"page_id": 22349350,
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"title": "Lasso (statistics)"
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zero-mean. Additionally, the covariates are typically standardized ( ∑ i = 1 N x i 2 = 1 ) {\textstyle {\bigl (}\sum _{i=1}^{N}x_{i}^{2}=1{\bigr )}} so that the solution does not depend on the measurement scale. It can be helpful to rewrite min β ∈ R p { 1 N ‖ y − X β ‖ 2 2 } subject to ‖ β ‖ 1 ≤ t . {\displaystyle \mi... | {
"page_id": 22349350,
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"title": "Lasso (statistics)"
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\quad {\hat {\beta }}{}_{j}^{\!\;{\text{OLS}}}\ =\ (X^{\intercal }X)^{-1}X^{\intercal }y\ =\ X^{\intercal }y~.} S α {\displaystyle \ S_{\alpha }\ } is referred to as the soft thresholding operator, since it translates values towards zero (making them exactly zero in the limit as they themselves approach zero) instead o... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
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\|}\ \beta \ {\Bigr \|}_{0}~\right\}\ } where ‖ ⋅ ‖ 0 {\displaystyle \ \|\cdot \|_{0}\ } is the " ℓ 0 {\displaystyle \ \ell ^{0}\ } norm", which is defined as ‖ z ‖ = m {\displaystyle \ \|z\|=m\ } if exactly m components of z are nonzero. In this case, it can be shown that β ^ j = H N λ ( β ^ j OLS ) = β ^ j OLS ⋅ I ... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
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the lasso objective function are not uniquely determined. In fact, if some β ^ {\displaystyle {\hat {\beta }}} in which β ^ j β ^ k ≥ 0 {\displaystyle {\hat {\beta }}_{j}{\hat {\beta }}_{k}\geq 0} , then if s ∈ [ 0 , 1 ] {\displaystyle s\in [0,1]} replacing β ^ j {\displaystyle {\hat {\beta }}_{j}} by s ( β ^ j + β ^ k... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
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Geometric interpretation === Lasso can set coefficients to zero, while the superficially similar ridge regression cannot. This is due to the difference in the shape of their constraint boundaries. Both lasso and ridge regression can be interpreted as minimizing the same objective function min β 0 , β { 1 N ‖ y − β 0 − ... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
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a given value of λ {\displaystyle \lambda } . It is assumed that X {\displaystyle X} is standardized with z-scores and that y {\displaystyle y} is centered (zero mean). Let β 0 {\displaystyle \beta _{0}} represent the hypothesized regression coefficients and let b OLS {\displaystyle b_{\text{OLS}}} refer to the data-op... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
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= 0 {\displaystyle \lambda =0} , the ordinary least squares solution (OLS) is used. The hypothesized value of β 0 = 0 {\displaystyle \beta _{0}=0} is selected if λ {\displaystyle \lambda } is bigger than R 2 {\displaystyle R^{2}} . Furthermore, if R 2 = 1 {\displaystyle R^{2}=1} , then λ {\displaystyle \lambda } repres... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
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2 {\displaystyle R^{2}} of 75% means that in-sample accuracy improves by 75% if the unrestricted OLS solutions are used instead of the hypothesized β 0 {\displaystyle \beta _{0}} values. The individual contribution of deviating from each hypothesis can be computed with the p {\displaystyle p} x p {\displaystyle p} matr... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
≤ R i i ⊗ , 0 if λ > R i i ⊗ . {\displaystyle b_{i}={\begin{cases}(1-\lambda /R_{ii}^{\otimes })b_{{\text{OLS}},i}&{\text{if }}\lambda \leq R_{ii}^{\otimes },\\0&{\text{if }}\lambda >R_{ii}^{\otimes }.\end{cases}}} That is, if regressors are uncorrelated, λ {\displaystyle \lambda } again specifies the minimal influence... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
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{1}{\sqrt {p_{B}}}}p_{B}{\frac {1}{\sqrt {p_{B}}}}={\frac {1}{p}}} . In other words, the inclusion of irrelevant regressors delays the moment that relevant regressors are activated by this rescaled lasso. The adaptive lasso and the lasso are special cases of a '1ASTc' estimator. The latter only groups parameters togeth... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
< 1 {\displaystyle p<1} , so the triangle inequality does not hold). Therefore, since p = 1 is the smallest value for which the " ℓ p {\displaystyle \ell ^{p}} norm" is convex (and therefore actually a norm), lasso is, in some sense, the best convex approximation to the best subset selection problem, since the region d... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
p > n (the number of covariates is greater than the sample size) lasso can select only n covariates (even when more are associated with the outcome) and it tends to select one covariate from any set of highly correlated covariates. Additionally, even when n > p, ridge regression tends to perform better given strongly c... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
1 1 + λ 2 , {\displaystyle y_{(n+p)}^{*}={\binom {y}{0^{p}}},\qquad \lambda ^{*}={\frac {\lambda _{1}}{\sqrt {1+\lambda _{2}}}},} β ∗ = 1 + λ 2 β . {\displaystyle \beta ^{*}={\sqrt {1+\lambda _{2}}}\beta .} Then β ^ = β ^ ∗ 1 + λ 2 {\displaystyle {\hat {\beta }}={\frac {{\hat {\beta }}^{*}}{\sqrt {1+\lambda _{2}}}}} , ... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
the sample correlation matrix because the x {\displaystyle x} 's are normalized. Therefore, highly correlated covariates tend to have similar regression coefficients, with the degree of similarity depending on both ‖ y ‖ 1 {\displaystyle \|y\|_{1}} and λ 2 {\displaystyle \lambda _{2}} , which is different from lasso. T... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
/ 2 {\displaystyle \min _{\beta \in \mathbb {R} ^{p}}{\biggl \{}{\biggl \|}y-\sum _{j=1}^{J}X_{j}\beta _{j}{\biggr \|}_{2}^{2}+\lambda \sum _{j=1}^{J}\|\beta _{j}\|_{K_{j}}{\biggr \}},\qquad \|z\|_{K_{j}}=(z^{\intercal }K_{j}z)^{1/2}} where the design matrix X {\displaystyle X} and covariate vector β {\displaystyle \be... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
phenomenon under study may have important spatial or temporal structure that must be considered during analysis, such as time series or image-based data. In 2005, Tibshirani and colleagues introduced the fused lasso to extend the use of lasso to this type of data. The fused lasso objective function is min β { 1 N ∑ i =... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
^{2}} norms (with weights, if necessary). The bridge regression utilises general ℓ p {\displaystyle \ell ^{p}} norms ( p ≥ 1 {\displaystyle p\geq 1} ) and quasinorms ( 0 < p < 1 {\displaystyle 0<p<1} ). For example, for p=1/2 the analogue of lasso objective in the Lagrangian form is to solve min β ∈ R p { 1 N ‖ y − X β... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
introduced by Zou in 2006 for linear regression and by Zhang and Lu in 2007 for proportional hazards regression. === Prior lasso === The prior lasso was introduced for generalized linear models by Jiang et al. in 2016 to incorporate prior information, such as the importance of certain covariates. In prior lasso, such i... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
=0} , prior lasso is reduced to lasso. If η = ∞ {\displaystyle \eta =\infty } , prior lasso will solely rely on the prior information to fit the model. Furthermore, the balancing parameter η {\displaystyle \eta } has another appealing interpretation: it controls the variance of β {\displaystyle \beta } in its prior dis... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
generally perform well. The "glmnet" package in R, where "glm" is a reference to "generalized linear models" and "net" refers to the "net" from "elastic net" provides an extremely efficient way to implement LASSO and some of its variants. The "celer" package in Python provides a highly efficient solver for the Lasso pr... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
used to count the effective number of parameters. For the lasso, this measure is given by P ^ = ∑ i = 1 p | β i − β 0 , i | 1 p ∑ l | b OLS , l − β 0 , l | , {\displaystyle {\hat {\mathcal {P}}}=\sum _{i=1}^{p}{\frac {|\beta _{i}-\beta _{0,i}|}{{\frac {1}{p}}\sum _{l}|b_{{\text{OLS}},l}-\beta _{0,l}|}},} which monotoni... | {
"page_id": 22349350,
"source": null,
"title": "Lasso (statistics)"
} |
A proctodeum is the back ectodermal part of an alimentary canal. It is created during embryogenesis by a folding of the outer body wall. It will form the lower part of the anal canal, below the pectinate line, which will be lined by stratified squamous non-keratinized (zona hemorrhagica) and stratified squamous keratin... | {
"page_id": 2426407,
"source": null,
"title": "Proctodeum"
} |
Sleep onset is the transition from wakefulness into sleep. Sleep onset usually transits into non-rapid eye movement sleep (NREM sleep) but under certain circumstances (e.g. narcolepsy) it is possible to transit from wakefulness directly into rapid eye movement sleep (REM sleep). == History == During the 1920s an obscur... | {
"page_id": 25429544,
"source": null,
"title": "Sleep onset"
} |
that activates neurons in the lateral part of the hypothalamus and the basal forebrain, and throughout the cerebral cortex. This refers to the ascending reticular activating system (cf reticular formation). The cell group involved in the first pathway is an acetylcholine-producing cell group called pedunculopontine and... | {
"page_id": 25429544,
"source": null,
"title": "Sleep onset"
} |
as histaminergic, serotonergic, orexinergic, noradrenergic, and cholinergic neurons (neurons mentioned above). Levels of acetylcholine, norepinephrine, serotonin, and histamine decrease with the onset of sleep, for they are all wakefulness promoting neurotransmitters. Therefore, it is believed that the activation of sl... | {
"page_id": 25429544,
"source": null,
"title": "Sleep onset"
} |
active and inhibit the wakefulness neurons, or the wakefulness neurons are active and inhibit the sleep neurons, Because these regions are mutually inhibitory, it is impossible for neurons in both sets of regions to be active at the same time. This flip-flop, switching from one state to another quickly, can be unstable... | {
"page_id": 25429544,
"source": null,
"title": "Sleep onset"
} |
Time delay neural network (TDNN) is a multilayer artificial neural network architecture whose purpose is to 1) classify patterns with shift-invariance, and 2) model context at each layer of the network. Shift-invariant classification means that the classifier does not require explicit segmentation prior to classificati... | {
"page_id": 23594537,
"source": null,
"title": "Time delay neural network"
} |
each layer) of a TDNN receive inputs from the outputs of neurons at the layer below but with two differences: Unlike regular Multi-Layer perceptrons, all units in a TDNN, at each layer, obtain inputs from a contextual window of outputs from the layer below. For time varying signals (e.g. speech), each unit has connecti... | {
"page_id": 23594537,
"source": null,
"title": "Time delay neural network"
} |
to right in Fig.1). Backpropagation is then performed from an overall classification target vector (see TDNN diagram, three phoneme class targets (/b/, /d/, /g/) are shown in the output layer), resulting in gradients that will generally vary for each of the time-shifted network copies. Since such time-shifted networks ... | {
"page_id": 23594537,
"source": null,
"title": "Time delay neural network"
} |
problems in speech recognition that were introduced in 1989 and initially focused on shift-invariant phoneme recognition. Speech lends itself nicely to TDNNs as spoken sounds are rarely of uniform length and precise segmentation is difficult or impossible. By scanning a sound over past and future, the TDNN is able to c... | {
"page_id": 23594537,
"source": null,
"title": "Time delay neural network"
} |
effective to recognize speech robustly despite different levels of reverberation. === Lip-reading – audio-visual speech === TDNNs were also successfully used in early demonstrations of audio-visual speech, where the sounds of speech are complemented by visually reading lip movement. Here, TDNN-based recognizers used vi... | {
"page_id": 23594537,
"source": null,
"title": "Time delay neural network"
} |
default training algorithm is a Supervised Learning back-propagation algorithm that updates filter weights based on the Levenberg-Marquardt optimizations. The function is timedelaynet(delays, hidden_layers, train_fnc) and returns a time-delay neural network architecture that a user can train and provide inputs to. The ... | {
"page_id": 23594537,
"source": null,
"title": "Time delay neural network"
} |
Hiemalora is a fossil of the Ediacaran biota, reaching around 3 cm in diameter, which superficially resembles a sea anemone. The genus has a sack-like body with faint radiating lines originally interpreted as tentacles, but discovery of a frond-like structure seemingly attached to some Heimalora has added weight to a c... | {
"page_id": 5244454,
"source": null,
"title": "Hiemalora"
} |
the tentacles on these organisms. Hiemalora has been identified in a wide range of facies and locations globally. == Etymology == The genus was originally named Pinegia, but was renamed two years later when it was realised that a genus of Permian insect already bore the name. The revised name comes from Latin hiemalis ... | {
"page_id": 5244454,
"source": null,
"title": "Hiemalora"
} |
Fertility preservation is the effort to help cancer patients retain their fertility, or ability to procreate. Research into how cancer, ageing and other health conditions effect reproductive health and preservation options are growing. Specifically sparked in part by the increase in the survival rate of cancer patients... | {
"page_id": 12977707,
"source": null,
"title": "Fertility preservation"
} |
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