Question: What was the best-known invention of the man that the cryogenic storage dewar was named after?
Context: Cryoconservation of animal genetic resources is a strategy wherein samples of animal genetic materials are preserved cryogenically.  Animal genetic resources, as defined by the Food and Agriculture Organization of the United Nations, are "those animal species that are used, or may be used, for the production of food and agriculture, and the populations within each of them.  These populations within each species can be classified as wild and feral populations, landraces and primary populations, standardised breeds, selected lines, varieties, strains and any conserved genetic material; all of which are currently categorized as Breeds."  Genetic materials that are typically cryogenically preserved include sperm, oocytes, embryos and somatic cells.  Cryogenic facilities are called gene banks and can vary greatly in size usually according to the economic resources available.  They must be able to facilitate germplasm collection, processing, freezing, and long term storage, all in a hygienic and organized manner.  Gene banks must maintain a precise database and make information and genetic resources accessible to properly facilitate cryoconservation.  Cryoconservation is an "ex situ" conservation strategy that often coexists alongside "in situ" conservation to protect and preserve livestock genetics.  Cryoconservation of livestock genetic resources is primarily done in order to preserve the genetics of populations of interest, such as indigenous breeds, also known as local or minor breeds.  Material may be stored because individuals shared specific genes and phenotypes that may be of value or have potential value for researchers or breeders.  Therefore, one of the main goals remains preserving the gene pool of local breeds that may be threatened.  Indigenous livestock genetics are commonly threatened by factors such as globalization, modernization, changes in production systems, inappropriate introduction of major breeds, genetic drift, inbreeding, crossbreeding, climate change, natural disasters, disease, cultural changes, and urbanization.  Indigenous livestock are critical to sustainable agricultural development and food security, due to their: adaptation to environment and endemic diseases, indispensable part in local production systems, social and cultural significance, and importance to local rural economies.  The genetic resources of minor breeds have value to the local farmers, consumers of the products, private companies and investors interested in crossbreeding, breed associations, governments, those conducting research and development, and non-governmental organizations.  Therefore, efforts have been made by national governments and non-governmental organizations, such as the Livestock Conservancy, to encourage conservation of livestock genetics through cryoconservation, as well as through other "ex situ" and "in situ" strategies.  Cryogenic specimens of livestock genetic resources can be preserved and used for extended periods of time.  This advantage makes cryoconservation beneficial particularly for threatened breeds who have low breed populations.  Cryogenically preserved specimens can be used to revive breeds that are endangered or extinct, for breed improvement, crossbreeding, research and development.  However, cryoconservation can be an expensive strategy and requires long term hygienic and economic commitment for germplasms to remain viable.  Cryoconservation can also face unique challenges based on the species, as some species have a reduced survival rate of frozen germplasm. A cryopreservation straw is a small storage device used for the cryogenic storage of liquid samples, often in a biobank or other collection of samples.  Their most common application is for storage of sperm for in-vitro fertilization. A refrigerated transport Dewar is a refrigerated transport vessel with an insulated Dewar flask (vacuum) design to carry cryogenic liquid.  To prevent pressure build-up they are equipped with safety relief valves and/or rupture discs.  The liquid can be withdrawn as a gas by passing liquid through an internal vaporizer or as a liquid under its own vapour pressure. An oxygen tank is an oxygen storage vessel, which is either held under pressure in gas cylinders, or as liquid oxygen in a cryogenic storage tank. Sir James Dewar FRS FRSE (20 September 1842 – 27 March 1923) was a Scottish chemist and physicist.  He is probably best known today for his invention of the vacuum flask, which he used in conjunction with extensive research into the liquefaction of gases.  He was also particularly interested in atomic and molecular spectroscopy, working in these fields for more than 25 years. Georges Jenny (c.1900–1976) was a French musician, poet, and electronic instrument builder.  His best-known invention was an electronic keyboard instrument called the Ondioline (sometimes referred to as the Jenny Ondioline).  It is considered a forerunner of the Synthesizer.  The Ondioline is capable of making an array of sounds, and features a keyboard that produces a natural-sounding vibrato with side-to-side finger movements while depressing keys. Cryogenic fuels are fuels that require storage at extremely low temperatures in order to maintain them in a liquid state.  These fuels are used in machinery that operates in space (e.g. rocket ships and satellites) because ordinary fuel cannot be used there, due to absence of an environment that supports combustion (on earth, oxygen is abundant in the atmosphere, whereas in human-explorable space, oxygen is virtually non-existent).  Cryogenic fuels most often constitute liquefied gases such as liquid hydrogen. Cryogenic energy storage (CES) is the use of low temperature (cryogenic) liquids such as liquid air or liquid nitrogen as energy storage.  Both cryogens have been used to power cars.  The inventor Peter Dearman initially developed a liquid air car, and then used the technology he developed for grid energy storage.  The technology is being piloted at a UK power station. A cryostat (from "cryo" meaning cold and "stat" meaning stable) is a device used to maintain low cryogenic temperatures of samples or devices mounted within the cryostat.  Low temperatures may be maintained within a cryostat by using various refrigeration methods, most commonly using cryogenic fluid bath such as liquid helium.  Hence it is usually assembled into a vessel, similar in construction to a vacuum flask or Dewar.  Cryostats have numerous applications within science, engineering, and medicine. A cryogenic storage dewar (named after James Dewar) is a specialised type of vacuum flask used for storing cryogens (such as liquid nitrogen or liquid helium), whose boiling points are much lower than room temperature.  Cryogenic storage dewars may take several different forms including open buckets, flasks with loose-fitting stoppers and self-pressurising tanks.  All dewars have walls constructed from two or more layers, with a high vacuum maintained between the layers.  This provides very good thermal insulation between the interior and exterior of the dewar, which reduces the rate at which the contents boil away.  Precautions are taken in the design of dewars to safely manage the gas which is released as the liquid slowly boils.  The simplest dewars allow the gas to escape either through an open top or past a loose-fitting stopper to prevent the risk of explosion.  More sophisticated dewars trap the gas above the liquid, and hold it at high pressure.  This increases the boiling point of the liquid, allowing it to be stored for extended periods.  Excessive vapour pressure is released automatically through safety valves.  The method of decanting liquid from a dewar depends upon its design.  Simple dewars may be tilted, to pour liquid from the neck.  Self-pressurising designs use the gas pressure in the top of the dewar to force the liquid upward through a pipe leading to the neck.
Answer: the vacuum flask