Birch tarBirch (bark) tar or birch pitch is a substance (liquid when heated) derived from the dry distillation of the bark of the birch tree. Birch tar/pitch is mainly composed of triterpenoid compounds of the lupane and oleanane family, which can be used as biomarkers to identify birch tar in the archaeological record. The most characteristic molecules are betulin and lupeol which are also present in birch bark. Some of these molecules degrade into other lupane and oleanane skeleton triperpenes.
National accountsNational accounts or national account systems (NAS) are the implementation of complete and consistent accounting techniques for measuring the economic activity of a nation. These include detailed underlying measures that rely on double-entry accounting. By design, such accounting makes the totals on both sides of an account equal even though they each measure different characteristics, for example production and the income from it. As a method, the subject is termed national accounting or, more generally, social accounting.
National Income and Product AccountsThe national income and product accounts (NIPA) are part of the national accounts of the United States. They are produced by the Bureau of Economic Analysis of the Department of Commerce. They are one of the main sources of data on general economic activity in the United States. They use double-entry accounting to report the monetary value and sources of output produced in the country and the distribution of incomes that production generates. Data are available at the national and industry levels.
BiocatalysisBiocatalysis refers to the use of living (biological) systems or their parts to speed up (catalyze) chemical reactions. In biocatalytic processes, natural catalysts, such as enzymes, perform chemical transformations on organic compounds. Both enzymes that have been more or less isolated and enzymes still residing inside living cells are employed for this task. Modern biotechnology, specifically directed evolution, has made the production of modified or non-natural enzymes possible.
