Contents 1 Overview 2 Detail 3 Advantages over previous methods 4 ReferencesOverviewThe SPA technique is dependent on the energy conversion of radioactive decay, which releases light photons which can be detected via the use of some devices such as the photomultiplier tubes of scintillation counters or CCD imagers. This is a very popular technique in practices that require detecting and quantifying radioactivity.The process of converting radioactivity to light requires a liquid medium of scintillation combination consisting soluble organic scintillators and organic solvents. During the process of radioactive decay, a beta particle will be released. While this particle travels in the medium, the energy it possesses is dissipated as it collides with the surrounding molecules in the solvent, exciting them while doing so. The excited molecules will transfer the energy they now possess to the scintillator molecules, where the energy will be emitted as light. DetailIn more detail, when the radio-labelled molecule is attached or is in proximity to bead, light emission is stimulated. However, if the bead does not become bound to the radio-labelled molecule, the bead will not be stimulated to emit light. This is because the energy released from the unbound molecule is not strong enough to excite the SPA bead which is not then stimulated to produce a signal.The decay of radioactive atom releases electrons as one of the subatomic particles. The energy of these particles influences the distance travelled by the particles itself through a medium such as water. This influence of the energy or the limitation of the water is what this SPA method is dependent upon.For instance, the decay of a Tritium atom releases a beta particle. Tritium is highly recommended as it suits SPA very well. It is due to the 1.5 µm path length through water, which is very short. So, when the ß-particle is within that particular range of 1.5 µm with the scintillant bead, there is sufficient energy to stimulate the bead to emit light. If the distance between them is greater than 1.5 µm, then the ß-particle is incapable of travelling the required distance to stimulate the bead as it has insufficient energy.The beads in SPA are formed from the incorporation of scintillant into small beads known as fluomicrospheres. These are specially designed to bind with specific molecules. When the bead is in close proximity to the radioactive molecule, light is stimulated.The photonmultiplier tube (PMT) can be used to detect the emitted photons. This device converts the emitted photon energy into electrical energy by a photocathode via a series of other electrodes. Another device is known as CCD Imager, which is composed of a set of cooled digital cameras with sensitive charge coupled device detectors and with some refined telecentric lenses to convert the captured photon energy into high quality images.There is also an assortment of bead coatings available that allows this method to be applied to a broad range of applications, such as enzyme assays and radio-immuno assays. Advantages over previous methodsIn comparison to the previous over-coated plate-based methods, SPA has a number of advantages that makes it more popular: Assay flexibility - the concentration of the components in the assay can be adjusted to suit the user due to the higher surface area design of the SPA beads, hence providing the user flexibility in designing assay. Radioactive label reduction - the SPA beads allows a potential reduction in the quantity of radioactive labeling required due to its higher binding capacity, which gives a higher signal. This method also allows the user to optimize the sensitivity of the assay by altering the quantity of SPA beads. Convenient - the key component of the SPA assay, the beads, do not depend on a particular plate type or supplier, hence its wide availability. Bead assortment - there is a diversity of bead types to choose from to suit the need of the user and application. No separation step - allows binding measurement without separation step associated with earlier methods, which reduces errors and allows higher throughput.
Diamond D-Jet and Scintillation proximity assayThe Diamond D-JET is a composite, five-seat, single-engine jet aircraft produced by Diamond Aircraft Industries. The final cost was advertised as US$1.89 million, in March 2009 dollars.By February 2013 the aircraft's development program was suspended pending company reorganization and the D-Jet workforce had been laid off. In May 2014 the company confirmed that the project remained suspended, but not cancelled.Contents 1 Design and development 2 Specifications (D-JET) 3 See also 4 References 5 External linksDesign and developmentDiamond has targeted the aircraft at the owner-pilot market, seeing it as more practical for single-pilot operations than the Eclipse 500 and the Cessna Citation Mustang. By limiting the altitude to 25,000 feet, it will be safer if pressurization fails. Diamond intends the D-JET to have a lower operating cost than other very light jets.On November 9, 2006, at the AOPA Expo in Palm Springs, California, USA, Diamond announced that ATP Flight School (ATP) placed the first fleet order of 20 Diamond D-JETs. ATP will provide factory-approved training to D-JET purchasers beginning in 2008. Toronto-based Chartright Air Group ordered 10 D-JET aircraft with expected delivery beginning 2010.In February, 2008 Diamond announced that the aircraft will be built in a new plant in London, Ontario, Canada. This announcement came after the Government of Canada announced it was giving the company a “Cdn$19.6 million strategic, repayable investment” and the Government of Ontario announced that it had given the company Cdn$11 million. Diamond claims that research and development costs for the D-JET have been Cdn$95.2 million and that the plant to build the aircraft will cost an additional $100 million.In October 2008 Canadian charter operator SwiftJet announced that they had ordered five D-Jets with options for ten more. SwiftJet's intention is to offer air taxi service "anywhere and anytime to destinations around the world." SwiftJet currently operates one Dassault Falcon 20 in the charter role.The Government of Ontario loan was contingent on a matching loan from the federal Canadian government, which was not approved and so the 213 laid off employees have not been rehired.The D-JET was initially to be powered by one Williams FJ33-4A-15 turbofan engine. That 1,564 lbf (6.96 kN) thrust engine was found in early 2008 to produce insufficient bleed air for cabin pressurization and other services. As a result a decision was made to switch to the Williams FJ33-4A-19 turbofan engine, which produces 1,900 lbf (8.5 kN) of thrust instead.The switch in engines delayed the certification schedule and moved the projected first customer deliveries of the aircraft into the spring of 2009.Diamond is also developing a military trainer variant of the D-JET that will likely feature Martin-Baker lightweight ejection seats and is intended to sell for under US$3M.The first flight of the D-JET was made on 18 April 2006 from the London International Airport (ICAO: CYXU) in Ontario, Canada the homebase of Diamond’s North American division. The flight was piloted by test pilot Gérard Guillaumaud and lasted 1:06 hours. The aircraft's public debut was at Oshkosh in July 2006. At that time Diamond expected certification to be complete by the middle of 2009 with deliveries starting at the same time. The Diamond D-JET, partially assembled at the Oakland NBAA, November 8, 2007.On Friday, 20 July 2007 Diamond Aircraft announced the roll out of its second D-JET, serial number 002. Serial number 002 is the first D-JET intended to conform to the expected production configuration in its structural layout and aerodynamic design. D-JET prototype serial number 002 first flew on Friday 14 September 2007. It was joined by D-JET Serial Number 003, which first flew on April 15, 2008.Flight testing and program development was halted in the spring of 2011 as the company lacked funds to proceed. After a failed campaign for federal government support, private investment was found and test flight resumed in September 2011.In July 2012 the company announced that 700 hours of flight testing had been completed, reaching Mach 0.56 (346 kn (641 km/h) true airspeed) along with 30,000 pressurization cycles on a test fuselage. Winglets had been added to the aircraft that improved roll control at all speeds, especially in the stall. With that addition the design was frozen and the company commenced building production tooling for the fourth serial number. At this time certification was forecast for late in 2013 with production deliveries to commence in the third quarter of 2014.In late February 2013, having not located further operational funding after the failed sale to Medrar in 2011, the company laid off the majority of its Canadian staff and suspended work on the D-Jet program, indicating that the company needed to reorganize. By May 2014 work on the D-Jet remained suspended, but the project had not been cancelled. Specifications (D-JET)Data from Diamond AircraftGeneral characteristics Crew: one, pilot Capacity: four passengers Length: 10.7 m (35 ft 1 in) Wingspan: 11.5 m (37 ft 9 in) Height: 3.6 m (11 ft 10 in) Gross weight: 2,320 kg (5,115 lb) Fuel capacity: 789.25 kilograms (1,740 lb) Powerplant: 1 × Williams FJ33-4A-19 turbofan, 8.5 kN (1,900 lbf) thrustPerformance Maximum speed: 583 km/h (362 mph; 315 kn) Cruising speed: 444 km/h (276 mph; 240 kn) Range: 2,500 km (1,553 mi; 1,350 nmi) Service ceiling: 7,600 m (24,934 ft) Rate of climb: 8.467 m/s (1,666.7 ft/min) Time to altitude: 7,620 m (25,000 ft) in 15 minutes See also Very light jet Aircraft of comparable role, configuration and era Piper PA-47 PiperJet
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