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Differential centrifugation

Differential centrifugation is a common procedure in biochemistry and cell biology used to separate organelles and other sub-cellular particles on the basis of sedimentation rate. Although applied in biological analysis, differential centrifugation is a general technique suitable for crude purification of non-living suspended particles. In a typical case where differential centrifugation is used to analyze cell-biological phenomena, a tissue sample is first lysed to break the cell membranes and release the organelles and cytosol; the lysate is subjected to repeated centrifugations, where particles that sediment sufficiently at a given centrifugation force for a given time form a compact "pellet" at the bottom of the centrifugation tube. After each centrifugation, the supernatant is removed from the tube and re-centrifuged at an increased centrifugal force and/or time. Differential centrifugation is suitable for crude separations on the basis of sedimintation rate, but more fine grained purifications may be done on the basis of density through equilibrium density-gradient centrifugation.

In a viscous fluid, the rate of sedimentation of a given suspended particle is a function of the particle size. Larger particles sediment more and at lower centrifugal forces. If a particle is less dense than the fluid, the particle will not sediment, but rather will float, regardless of strength of the g-force experienced by the particle. In contrast, a more specialized equilibrium density-gradient centrifugation produces a separation profile dependent on particle-density alone, therefore is suitable for more fine-grained separations. High g-force makes sedimentation of small particles much faster than Brownian diffusion for small particles; when a centrifuge is used, Stokes' law must be modified to account for the variation in g-force with distance from the center of rotation. D = 18 η ln ⁡ ω 2 t where D is the minimum diameter of the particles expected to sediment η is the fluid dynamic viscosity Rf is the final radius of rotation Ri is the initial radius of rotation ρp is particle volumetric mass density ρf is the fluid volumetric mass density ω is the angular velocity t is the time required to sediment from Ri to Rf Differential centrifugation can be used with intact particles, or used to separate the component parts of a given particle.

Using the example of a separation of eukaryotic organelles from intact cells, the cell must first be lysed and homogenized. Once the crude organelle extract is obtained, it may be subjected to a varying centrifugation speeds to separate the organelles: The lysed sample is now ready for centrifugation in an ultracentrifuge. An ultracentrifuge consists of a refrigerated, low-pressure chamber containing a rotor, driven by an electrical motor capable of high speed rotation. Samples are attached to the rotor. Rotational speed may reach up to 100,000 rpm for floor model, 150,000 rpm for bench-top model, creating centrifugal speed forces of 800,000g to 1,000,000g; this force causes sedimentation of macromolecules, can cause non-uniform distributions of small molecules. Since different fragments of a cell have different sizes and densities, each fragment will settle into a pellet with different minimum centrifugal forces. Thus, separation of the sample into different layers can be done by first centrifuging the original lysate under weak forces, removing the pellet exposing the subsequent supernatants to sequentially greater centrifugal fields.

Each time a portion of different density is sedimented to the bottom of the container and extracted, repeated application produces a rank of layers which includes different parts of the original sample. Additional steps can be taken to further refine each of the obtained pellets. Sedimentation depends on mass and partial specific volume of a macromolecule, as well as solvent density, rotor size and rate of rotation; the sedimentation velocity can be monitored during the experiment to calculate molecular weight. Values of sedimentation coefficient can be calculated. Large values of S correspond to larger molecular weight. Dense particle sediments more rapidly. Elongated proteins have larger frictional coefficients, sediment more to ensure accuracy. Buoyant density ultracentrifugation Jerome Vinograd Gerald Karp. Cell and Molecular Biology: Concepts and Experiments. John Wiley & Sons. Pp. 28–. ISBN 978-0-470-48337-4. Roger A. Davis and Jean E. Vance, Structure and secretion of lipoproteins, 1996, Elsevier Science B.


Richie Koh

Richie Koh is a Singaporean actor and a contracted artiste under MediaCorp and China’s LongAllStar Entertainment Group. Koh graduated from Ngee Ann Polytechnic's School of InfoComm Technology, with a Diploma in Financial Informatics in 2014, he completed his national service in the Republic of Singapore Air Force. In 2013, Koh was scouted when Channel U’s Hey Gorgeous team went to various campuses in Singapore looking for suitable contestants, he emerged as first runner up. In 2017 after serving National Service, Koh started his career by debuting in Channel 8’s army-themed drama When Duty Calls, a major role that charmed viewers hearts. Fans sang praises of his natural acting and good looks, factors which landed his first nomination for Best Newcomer in Star Awards 2018. October that year saw Koh jetting off to Changzhou, Jiangsu for a month to film China-web movie The Legendary Detective of the Shanghai Bund where he played an assistant to the agency detective; the following year, Koh made cameo appearances in long-running Channel 8 drama, Life Less Ordinary & Toggle series, Die Die Also Must Serve.

In addition, he wrapped up filming on 118 Reunion and made a special appearance in local movie Wonderful! Liang Xi Mei directed by Jack Neo, his role as a gangster boss in the movie saw him gain new fans both here and across the Causeway. Koh acted in several Toggle Original productions - Star Crossed aired from April to May and he took the lead role in Divided as well as The Distance Between where he spent six weeks on the road, filming in Australia. In addition, Koh acted in a Gilbert Chan movie 23:59 The Haunting Hour, as a soldier tasked to kill a snake spirit. On 30 August 2018, The Celebrity Agency announced that Koh would be expanding his career to China after it signed a co-management contract with China’s LongAllStar Entertainment Group; the actor will be based in Beijing after filming Toggle Original series Playground but there are plans for him to head back to Singapore when he has a local production to shoot

Sir John Cass Redcoat School

Sir John Cass's Foundation and Redcoat Church of England Secondary School and Sixth Form College is a Church of England voluntary aided school in Stepney, London. The last Ofsted report in October 2015 rated SJCR School as "Outstanding." Sir John Cass was born in the City of London in 1661 and, during his lifetime, served as both Alderman and Sheriff. He was MP for the City and knighted in 1712. In 1710 Cass set up a school for 50 boys and 40 girls and rented buildings in the churchyard of St Botolph-without-Aldgate. Intending to leave the vast majority of his property to the independent school, when he died in 1718 of a brain haemorrhage, Cass had only initialled three pages of his will; the incomplete will was contested, but was upheld by the Court of Chancery thirty years after his death. The charity school was managed by nine independent trustees named in the will, none of whom were ex-officio or nominated by external bodies; the school, which by this time had been forced to close, was re-opened, the foundation established.

It was decided to separate primary and secondary school education, a suitable site was found in Stepney. The Red Coat School, has had various names including Stepney Parish Day Schools, Stepney Church School and the Charity School in the Hamlet of Mile End Old Town, it was established in 1714 by voluntary subscription for the clothing and education of a limited number of boys born within Mile End Old Town. The school-house was built on Stepney Green. Both the Sir John Cass and the Red Coat school merged to become the Sir John Cass's Foundation and Red Coat School, opening doors for the first time on 5 September 1966. In September 2016, SJCR School celebrated fifty years in education. All alumni were invited to join in the celebrations; the school admits pupils aged 11 to 18, with 1400 students in the main school and 720 in the sixth form. Although the school is run by the Church of England, ninety percent of its pupils come from ethnic Bangladeshi Muslim backgrounds. A 2015 inspection by Ofsted declared the school outstanding.

Senior Leadership TeamMr Paul Woods – Headteacher Ms Leena Hussain – Deputy Headteacher Mr Ben Siaw – Deputy Headteacher Ms Shereka James – Deputy Headteacher Mr Iain Cameron – Assistant Headteacher Mr Neil Jones – Assistant Headteacher Ms Marielle Dow – Assistant Headteacher Ms Shiulee Begum – Assistant Headteacher Ms Claire Dacre-Singh – Assistant Headteacher Ms Nazira Begum Uddin Mr Elliot Green – Assistant Headteacher Ms Gina Katme – Assistant Headteacher Ms Candice Miller Ms Katherine Rowley-Conwy – Assistant Headteacher Ms Nichola Ahmed – School Business ManagerHeads of DepartmentsMs Susan Harewood/ Mr James Knight – Head of English Mr Abdul Alim – Head of Science Mr Shahel Uddin – Head of Mathematics Mr Abdul Jalil – Head of Computer Science/ICT Ms Sam White – Head of Modern Foreign Languages Mr Ciaran Cusack – Head of Geography Mr James Davis – Head of History Mr Mike Coles – Head of RE Mr Matthew Brotherhood – Head of Art and Design Technology Ms Fran Cervi – Head of Drama Mr Craig Holder – Head of Music Mr James Trueman – Head of PE Mr Jahidur Rahman – Head of Business & Economics Ms Shirin Begum – Head of Social Sciences Mr Gordon Perrett – SENDCoHeads of YearMr Uddin Shams– Head of Year 7 Ms Mazada Begum – Head of Year 8 Mr Vicky Jech – Head of Year 9 Mr Jerry Spillane – Head of Year 10 Ms Samantha White – Head of Year 11 GCSE Results 2015141 pupils achieved 5 A*-C grades, including English and Maths 83% of pupils achieved 5+ A*-C grade GCSEs 49% of pupils achieved the English Baccalaureate 87% of pupils made at least expected progress in English 84% of pupils made at least expected progress in Maths 154 pupils achieved an A*-C in English 164 pupils achieved an A*-C in Maths 30 pupils achieved 8 or more A*/A grades including 10 pupils with over 11 A*/A grades 65 pupils achieve 3 or more A*/A grades Key Stage 5 Results - 2015Academic Qualifications Average point score per academic entry 220.3 Average point score per academic student 791.41 Vocational Qualifications Average point score per vocational entry 256.8 Average point score per vocational student 821 All students must wear full and correct uniform for school, school occasions and PE and Drama lessons.

Black shirt / black shirt blouse, tie Mid-grey trousers/ Mid-grey pleated skirt. Blazer. Black low-heeled shoes. Plain V-necked navy pullover. Dark navy cardigan or V-necked pullover. Coats are never permitted within the school building. Any persons seen wearing a coat will be expelled, effective immediately. Years 10 and 11 students may wear the specially designed Cass sweatshirt. Red/white S-Tec Mercury polo shirt, red/white Pulse micro fleece, navy/white S-TecX Cuatro shorts, navy/white S-TecX Cuatro track pants, swimming hat, trainers. Official website Department for Children and Families – EduBase2 – Sir John Cass Foundation and Redcoat Church of England Secondary School Ofsted reports on Sir John Cass Foundation and Redcoat Church of England Secondary School Directgov – School Profile

Love Don't Live Here (Bananarama song)

"Love Don't Live Here" is a song written and recorded by British girl group Bananarama. It was released on 12 April 2010 as the final single from their tenth studio album Viva. "Love Don't Live Here" was released on 11 April 2010 as digital download single and 12 April 2010 on vinyl and CD format. It was written by producer Ian Masterson; the b-side for the CD single is a new version of their 1995 song "Every Shade of Blue", while the b-side tracks for the vinyl editions are remixed versions of "The Runner" and a brand new song "Here Comes The Rain". A music video for "Love Don't Live Here" was shot in London in January 2010; the video features computerized effects and scenes similar to the artwork on the sleeve of the CD single. The video was directed by photographer Tim Walker. Love Don't Live Here was released in several formats including digital. 7 inch vinyl "Love Don't Live Here" "Here Comes The Rain" 12 inch vinyl "Love Don't Live Here" "The Runner" CD Single "Love Don't Live Here" "Every Shade Of Blue 2010" Download iTunes Exclusive Remix Bundle "Love Don't Live Here" "Love Don't Live Here" Remixed by Ian Masterson "The Runner" "The Runner" Remixed by Buzz Junkies

Parascender II

The Parascender II is an American powered parachute, designed and produced by Parascender Technologies of Kissimmee, Florida. Now out of production, when it was available the aircraft was supplied as a kit for amateur construction; the Parascender II was designed to comply with the US FAR 103 Ultralight Vehicles trainer exemption and the US Experimental - Amateur-built aircraft rules. It features a 520.0 sq ft parachute-style wing, two-seats-in-tandem accommodation, tricycle landing gear and a single 50 hp Rotax 503 engine in pusher configuration. The aircraft carriage is built from bolted aluminium tubing, with a unique octagonal dual-tube propeller guard. In flight steering is accomplished via foot pedals that actuate the canopy brakes, creating roll and yaw. On the ground the aircraft has lever-controlled nosewheel steering; the main landing gear incorporates spring rod suspension and was changed to composite suspension in 1993. The aircraft has a typical empty weight of 250 lb and a gross weight of 720 lb, giving a useful load of 470 lb.

With full fuel of 10 U. S. gallons the payload for the pilot and baggage is 410 lb. The standard day, sea level, no wind, take off with a 50 hp engine is 150 ft and the landing roll is 50 ft; the manufacturer estimated the construction time from the supplied kit as 20 hours. In April 2015 six examples were registered in the United States with the Federal Aviation Administration, although a total of eight had been registered at one time. Data from PurdyGeneral characteristics Crew: one Capacity: one passenger Length: 9 ft 0 in Wingspan: 38 ft 6 in Wing area: 520 sq ft Aspect ratio: 3.0:1 Empty weight: 250 lb Gross weight: 720 lb Fuel capacity: 10 U. S. gallons Powerplant: 1 × Rotax 503 twin cylinder, two-stroke, air-cooled aircraft engine, 50 hp Propellers: w-bladed composite, ground adjustablePerformance Maximum speed: 26 mph Cruise speed: 26 mph Service ceiling: 7,500 ft Rate of climb: 550 ft/min Wing loading: 1.4 lb/sq ft Photo of a Parascender II in flight

Crag Fell

Crag Fell is a hill in the English Lake District. It is part of the Lank Rigg group, standing above Ennerdale Water in the Western Fells; the craggy northern face above the lake gives the fell its name, prominent in views from the car park at Bowness Knott. Ascents are made from the foot of Ennerdale Water; the Western Fells occupy a triangular sector of the Lake District, bordered by the River Cocker to the north east and Wasdale to the south east. Westwards the hills diminish toward the coastal plain of Cumberland. At the central hub of the high country are Great Gable and its satellites, while two principal ridges fan out on either flank of Ennerdale, the western fells in effect being a great horseshoe around this long wild valley. Crag Fell stands near the extremity of the southern arm; the main watershed runs broadly westwards from Great Gable, dividing the headwaters of Ennerdale and Wasdale. The fells in this section are Kirk Fell, Scoat Fell and Caw Fell; the surrounding valleys diverge until other rivers spring up to drain the intervening country.

Worm Gill is one such watercourse, running south westward from Caw Fell, forcing the ridge to detour northwards around the head of its valley. Beyond this stand the fells of the Lank Rigg group, the final high country within the National Park. Crag Fell and Grike complete the westward line of the ridge, whilst Lank Rigg lies to the south across the head of the River Calder; the northern flanks of Crag Fell tumble down to the shore of Ennerdale Water. One tier of crags is directly below the summit, Revelin Crag being a notable feature, whilst a second abuts the lake itself; this is Anglers Crag known as Robin Hood's Chair. By contrast the southern slopes fall to the headstream of the Calder, the lower section being planted with conifers. South eastward from Crag Fell begins the long ridge to Caw Fell, first descending to a col at 1,320 ft and rising over the intermediate top of Iron Crag. To the west a narrower ridge runs along above the plantation to Grike. Crag Fell is bounded by Red Beck in the east.

The remains of a number of iron mines can be found above the shore of the lake. Small trials were driven beneath Revelin Crag, above Anglers Crag and on the upper eastern slopes above Red Beck. Although haematite was found, the quantities were never sufficient and all of the mines had closed by 1896. There are two mounds on the top of the fell; the whole area is grassy. There is a wide panorama to seaward, taking in what Alfred Wainwright described as the "grotesque collection of towers and minarets of the Calder Hall atomic power station"; the head of Ennerdale Water is seen to the east, surrounded by the high cirque of the Western Fells. Distant Fairfield and Ullscarf put in unexpected appearances through the gaps. A narrow road runs east from the village of Ennerdale Bridge, giving access to a pair of car parks near the outflow of the lake. Two principal alternatives are available from here to climb Crag Fell; the first is to loosely follow the course of Ben Gill up beside the plantation, before swinging left toward the summit.

A more interesting route is to use the lakeshore path to reach the top of Anglers Crag, before working up the hillside to turn Revelin Crag to the west. This takes the walker past what Wainwright called the Crag Fell Pinnacles, a fractured spine of rock rising 80 ft above the angle of the slope. Other ascents can be made from the Coldfell Road, south of Ennerdale Bridge. A track the mine road, can be followed to the summit, passing over the flanks of Grike. A circuit of the upper Calder, taking in the whole Lank Rigg group can be started from here