PETROLEUM REFINING PROCESSES

Petroleum

refining processes are the chemical engineering processes and other facilities used

in petroleum refineries to transform crude oil into useful products such as LPG,

gasoline or petrol, kerosene, diesel oil and fuel oils.



Petroleum

refining processes are the chemical engineering processes and other facilities used

in petroleum refineries to transform crude oil into useful products such as LPG,

gasoline or petrol, kerosene, diesel oil and fuel oils.



Many forms

of maize are used for food, sometimes classified each has:






  • Flour corn: Zea mays var. amylacea

  • Popcorn: Zea mays var.

    everta

  • Dent corn : Zea mays var. indentata

  • Flint

    corn: Zea mays var. indurata

  • Sweet corn: Zea mays var. saccharata

    and Zea mays var. rugosa

  • Waxy corn: Zea mays var. ceratina



  • Amylomaize: Zea mays

  • Pod corn: Zea mays var.

    tunicata Larrañaga ex A. St. Hil.

  • Striped maize: Zea mays

    var. japonica



This system has been replaced (though not

entirely displaced) over the last 60 years by multivariable classifications based

on ever more data. Agronomic data were supplemented by botanical traits for a

robust initial classification, then genetic, cytological, protein and DNA evidence

was added. Now, the categories are forms (little used), races, racial complexes,

and recently branches.



Maize is a diploid with 20 chromosomes (n=10).

The combined length of the chromosomes is 1500 cM. Some of the maize chromosomes

have what are known as “chromosomal knobs”: highly repetitive

heterochromatic domains that stain darkly. Individual knobs are polymorphic among

strains of both maize and teosinte.



Barbara McClintock used these

knob markers to validate her transposon theory of “jumping genes”, for

which she won the 1983 Nobel Prize in Physiology or Medicine. Maize is still an

important model organism for genetics and developmental biology today.






The Maize Genetics Cooperation Stock Center, funded by the USDA Agricultural

Research Service and located in the Department of Crop Sciences at the University

of Illinois at Urbana-Champaign, is a stock center of maize mutants. The total

collection has nearly 80,000 samples. The bulk of the collection consists of

several hundred named genes, plus additional gene combinations and other heritable

variants. There are about 1000 chromosomal aberrations (e.g., translocations and

inversions) and stocks with abnormal chromosome numbers (e.g., tetraploids).

Genetic data describing the maize mutant stocks as well as myriad other data about

maize genetics can be accessed at MaizeGDB, the Maize Genetics and Genomics

Database.