SUMMARY / RELATED TOPICS

Pasteurization

Pasteurization or pasteurisation is a process in which water and certain packaged and non-packaged foods are treated with mild heat to less than 100 °C, to eliminate pathogens and extend shelf life. The process is intended to destroy or deactivate organisms and enzymes that contribute to spoilage or risk of disease, including vegetative bacteria, but not bacterial spores. Since pasteurization is not sterilization, does not kill spores, a second "double" pasteurization will extend the quality by killing spores that have germinated; the process was named after the French microbiologist, Louis Pasteur, whose research in the 1880s demonstrated that thermal processing would inactivate unwanted microorganisms in wine. Spoilage enzymes are inactivated during pasteurization. Today, pasteurization is used in the dairy industry and other food processing industries to achieve food preservation and food safety. Most liquid products are heat treated in a continuous system where heat can be applied using a plate heat exchanger or the direct or indirect use of hot water and steam.

Due to the mild heat, there are minor changes to the nutritional quality and sensory characteristics of the treated foods. Pascalization or high pressure processing and pulsed electric field are non-thermal processes that are used to pasteurize foods; the process of heating wine for preservation purposes has been known in China since AD 1117, was documented in Japan in the diary Tamonin-nikki, written by a series of monks between 1478 and 1618. Much in 1768, research performed by Italian priest and scientist Lazzaro Spallanzani proved a product could be made "sterile" after thermal processing. Spallanzani boiled meat broth for one hour, sealed the container after boiling, noticed that the broth did not spoil and was free from microorganisms. In 1795, a Parisian chef and confectioner named Nicolas Appert began experimenting with ways to preserve foodstuffs, succeeding with soups, juices, dairy products, jellies and syrups, he placed the food in glass jars, sealed them with cork and sealing wax and placed them in boiling water.

In that same year, the French military offered a cash prize of 12,000 francs for a new method to preserve food. After some 14 or 15 years of experimenting, Appert submitted his invention and won the prize in January 1810; that year, Appert published L'Art de conserver les substances animales et végétales. This was the first cookbook of its kind on modern food preservation methods. La Maison Appert, in the town of Massy, near Paris, became the first food-bottling factory in the world, preserving a variety of foods in sealed bottles. Appert's method was to fill thick, large-mouthed glass bottles with produce of every description, ranging from beef and fowl to eggs and prepared dishes, he left air space at the top of the bottle, the cork would be sealed in the jar by using a vise. The bottle was wrapped in canvas to protect it while it was dunked into boiling water and boiled for as much time as Appert deemed appropriate for cooking the contents thoroughly. Appert patented his method, sometimes called appertisation in his honor.

Appert's method was so simple and workable that it became widespread. In 1810, British inventor and merchant Peter Durand of French origin, patented his own method, but this time in a tin can, so creating the modern-day process of canning foods. In 1812, Englishmen Bryan Donkin and John Hall purchased both patents and began producing preserves. Just a decade Appert's method of canning had made its way to America. Tin can production was not common until the beginning of the 20th century because a hammer and chisel were needed to open cans until the invention of a can opener by Robert Yeates in 1855. A less aggressive method was developed by French chemist Louis Pasteur during an 1864 summer holiday in Arbois. To remedy the frequent acidity of the local aged wines, he found out experimentally that it is sufficient to heat a young wine to only about 50–60 °C for a short time to kill the microbes, that the wine could subsequently be aged without sacrificing the final quality. In honour of Pasteur, this process is known as "pasteurization".

Pasteurization was used as a way of preventing wine and beer from souring, it would be many years before milk was pasteurized. In the United States in the 1870s, before milk was regulated, it was common for milk to contain substances intended to mask spoilage. Milk is an excellent medium for microbial growth, when it is stored at ambient temperature bacteria and other pathogens soon proliferate; the US Centers for Disease Control says improperly handled raw milk is responsible for nearly three times more hospitalizations than any other food-borne disease source, making it one of the world's most dangerous food products. Diseases prevented by pasteurization can include tuberculosis, diphtheria, scarlet fever, Q-fever. Prior to industrialization, dairy cows were kept in urban areas to limit the time between milk production and consumption, hence the risk of disease transmission via raw milk was reduced; as urban densities increased and supply chains lengthened to the distance from country to city, raw milk became recognized as a source of disease.

For example, between 1912 and 1937, some 65,000 people died of tuberculosis contracted from consuming milk in England and Wales alone. Because tuberculosis has a long incubation period in humans, it was difficult

Logical effort

The method of logical effort, a term coined by Ivan Sutherland and Bob Sproull in 1991, is a straightforward technique used to estimate delay in a CMOS circuit. Used properly, it can aid in selection of gates for a given function and sizing gates to achieve the minimum delay possible for a circuit. Delay is expressed in terms of a basic delay unit, τ = 3RC, the delay of an inverter driving an identical inverter with no parasitic capacitance; the absolute delay is simply defined as the product of the normalized delay of the gate, d, τ: d a b s = d ⋅ τ In a typical 600-nm process τ is about 50 ps. For a 250-nm process, τ is about 20 ps. In modern 45 nm processes the delay is 4 to 5 ps; the normalized delay in a logic gate can be expressed as a summation of two primary terms: normalized parasitic delay, p, stage effort, f. D = f + p The stage effort is divided into two components: a logical effort, g, the ratio of the input capacitance of a given gate to that of an inverter capable of delivering the same output current, an electrical effort, h, the ratio of the input capacitance of the load to that of the gate.

Note that "logical effort" does not take the load into account and hence we have the term "electrical effort" which takes the load into account. The stage effort is simply: f = g h Combining these equations yields a basic equation that models the normalized delay through a single logic gate: d = g h + p CMOS inverters along the critical path are designed with a gamma equal to 2. In other words, the pFET of the inverter is designed with twice the width as the nFET of the inverter, in order to get the same pFET resistance as nFET resistance, in order to get equal pull-up current and pull-down current. Choose sizes for all transistors such that the output drive of the gate is equal to the output drive of an inverter built from a size-2 PMOS and a size-1 NMOS; the output drive of a gate is equal to the minimum – over all possible combinations of inputs – of the output drive of the gate for that input. The output drive of a gate for a given input is equal to the drive at its output node; the drive at a node is equal to the sum of the drives of all transistors which are enabled and whose source or drain is in contact with the node in question.

A PMOS transistor is enabled when its gate voltage is 0. An NMOS transistor is enabled when its gate voltage is 1. Once sizes have been chosen, the logical effort of the output of the gate is the sum of the widths of all transistors whose source or drain is in contact with the output node; the logical effort of each input to the gate is the sum of the widths of all transistors whose gate is in contact with that input node. The logical effort of the entire gate is the ratio of its output logical effort to the sum of its input logical efforts. A major advantage of the method of logical effort is that it can be extended to circuits composed of multiple stages; the total normalized path delay D can be expressed in terms of an overall path effort, F, the path parasitic delay P: D = N F 1 / N + P The path effort is expressed in terms of the path logical effort G, the path electrical effort H. For paths where each gate drives only one additional gate, F = G H However, for circuits that branch, an additional branching effort, b, needs to be taken into account.

It can be shown that in multistage logic networks, the minimum possible delay along a particular path can be achieved by designing the circuit such that the stage efforts are equal. For a given combination of gates and a known load, B, G, H are all fixed

Chrysothamnus

Chrysothamnus, known as rabbitbrush and chamisa, are shrubs in the sunflower family. The native distribution is in the arid western United States and northern Mexico, it is known for its bright yellow flowers in late summer. Chrysothamnus may grow up to a 120 cm tall shrub or subshrub with woody stem bases; the leaves are sessile or with short petioles, with entire edges. The flowerheads are singular or in clusters; each composite flower has five to 6 yellow disc florets and no ray florets. Chrysothamnus species are used as food plants by the larvae of some Lepidoptera species including Coleophora linosyridella, Coleophora viscidiflorella and Schinia walsinghami. SpeciesChrysothamnus depressus – dwarf rabbitbrush, longflower rabbitbrush – California Nevada Arizona Utah Colorado New Mexico Chrysothamnus eremobius – pintwater rabbitbrush, remote rabbitbrush – Nevada Chrysothamnus greenei – Greene's rabbitbrush – California Nevada Arizona Utah Colorado New Mexico Wyoming Chrysothamnus humilis – Truckee rabbitbrush – California Nevada Oregon Washington Idaho Chrysothamnus molestus – Arizona rabbitbrush – Arizona Chrysothamnus scopulorum – Arizona Utah Chrysothamnus stylosus – Arizona Utah Chrysothamnus vaseyi – Vasey's rabbitbrush – Arizona Utah New Mexico Colorado Wyoming Chrysothamnus viscidiflorus – yellow rabbitbrushBritish Columbia Washington Oregon California Arizona Nevada Idaho Montana Wyoming Utah Colorado New Mexico South Dakota Nebraska CalFlora Database: Chrysothamnus Jepson Manual Treatment of Chrysothamnus