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Cellulose diacetate film was first created by the German chemists Arthur Eichengrün and Theodore Becker, who patented it under the name Cellit, from a process they devised in 1901 for the direct acetylation of cellulose at a low temperature to prevent its degradation, which permitted the degree of acetylation to be controlled, thereby avoiding total conversion to its triacetate.
Cellulose acetate is also known as "safety" film and started to replace nitrate film in still photography in the 1920s. [1] There are several types of acetate that were produced after 1925, which include diacetate (c. 1923 – c. 1955), acetate propionate (1927 – c. 1949), acetate butyrate (1936–present), and triacetate (c. 1950 – present). [1]
When Bangladesh became independent in 1971, the reserved and proposed reserved forests came under the jurisdiction of the Bangladesh Forest Department. From 1971 to 1989, the Bangladesh Forest Department was under the Ministry of Agriculture. During 1987-89, Forestry was a department of the Ministry of Agriculture, under a Secretary.
Department of Environment (পরিবেশ অধিদপ্তর) is a government department responsible for the protection of the environment in Bangladesh and is located in Dhaka, Bangladesh. [1] [2] The department is headed by a director general. [3] It is under the Ministry of Environment, Forest and Climate Change. [4]
Bangladesh Environment Conservation Act (BECA) is set of laws enacted by the government of Bangladesh in 1995 to conserve the nation's environment. [1] Its main goals were to "provide for conservation of the environment, improvement of environmental standards and control and mitigation of environmental pollution."(Bangladesh Environmental Conservation Act, 1995).
Cellulose acetate film, which was the initial replacement for nitrate, has been found to suffer from "vinegar syndrome". [14] Polyester film base, which replaced acetate, also suffers from fading colors. [5] Storage at carefully controlled low temperatures and low humidity can inhibit both color fading and the onset of vinegar syndrome.
It can happen during a film screening when a frame becomes stuck in the projector's film gate. Acetate films are also subject to degradation over time. With exposure to heat, moisture, or acids, the acetyl groups are broken from their molecular bonds to the cellulose. The now free acetic acid is released into the air. Acetic acid is vinegar ...
Sedimentation in reservoirs effects the turbidity of the reservoir, and erosion patterns along the river. It also presents a cost to the government who has to dredge the rivers of its sediments. In Bangladesh, the government has to remove 0.8 million cubic meters of maintenance dredging and 2 million cubic meters of capital dredging per year.