Thixotropic gel is an inert (nonreacting) synthetic substance in the bottom of certain tubes. When a specimen in a gel tube is centrifuged the gel undergoes a change in viscosity and moves to a position between the cells and the serum or plasma, forming a physical barrier between them. This separation prevents the cells from continuing to metabolize substances such as glucose in the serum or plasma.
Placement of Citations. 1  Place a citation as close to the quoted or paraphrased material as possible without disrupting the sentence. 2  When material from one source and the same page numbers is used throughout a paragraph, use one citation at the end of the paragraph rather than a citation at the end of each sentence.
EXAMPLES OF REFERENCE CITATIONS IN TEXT--APA STYLE. 1. If author's name occurs in the text, follow it with year of publication in parentheses. Example: Piaget (1970) compared reaction times... 2. If author's name is not in the text, insert last name, comma, year in parenthesis.