This Excel workbook simulates the number of cells N(t) and the increasing logarithmic growth ratio, Log10(N(t)/NInit), of a targeted microorganism during temperature controlled storage in real time. This version of the program simulates the growth of organisms whose isothermal survival curve follows the generalized Verhulst model: dY(t)/dt =k*Y^a*(1-Y/Ya)^b. The temperature dependence of the growth parameters a(Temp), b(Temp) and k(Temp) obey an exponential relationship while Ya(Temp) follows a logistic relationship. For more information on the concept, its various applications in calculating the microbial growth during storage at variable temperatures and its implementation with more complicated growth models, contact Micha Peleg at: http://people.umass.edu/~aew2000/ or Maria Corradini at: firstname.lastname@example.org
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The demonstration workbook is available in a file format for Windows Excel 97 (or newer) and MacOS Excel 98 (or newer). If you have a modern web browser you should be able to download the binary Excel file directly by clicking on the link below.Generates Time, Temperature, N(t) and Log10(N(t)/NInit) values using an internal Temperature Profile equation with user-adjustable parameters.
Note: The first version of the Excel file was dated October 3, 2006. The September 4, 2007 version updated the first reference. The February 4, 2008 version added compatibility with Windows Excel 2007 and made corrections to a few comment notes.
If you have Microsoft Excel installed on your hard disk, you should be able to open the NonIsothermGenLogisticGR.xls file in Excel by double-clicking on its icon. If that doesn't work, open the workbook file by first starting Excel, choosing Open... from the File menu and then selecting the Excel file that was downloaded and saved on your hard disk. If the file does not appear on the list of file names, set the Files of type: pop-up menu to All Files (*.*) then select and open the file. If you were unable to open the file by double-clicking on it, use the alternate method just described to open it and once the file has opened in Excel you should immediately save it by choosing Save from the File menu. This will make it possible to open the file in the future by simply double-clicking on its icon.
When you are shown a dialog box asking about enabling macros, click the Enable Macros button. If you are using a recent version of Excel for Windows, you may need to reduce the security level in Tools>Macro>Security to Medium, then close and reopen the file to enable the macros.
Clicking the Clear button will erase the two charts from Sheet1. Clicking the Solve button erases the charts before the model is solved so it is not necessary to click Clear before clicking Solve. Read the comment notes attached to cells A1 through A5 for instructions on how to run the worksheet models. To view or print all of a workbook's comment notes together click on the link below.
The Excel file NonIsothermGenLogisticGR.xls contains two worksheets. Sheet1 contains instructions, user input cells, two embedded charts, and two buttons labeled 'Clear' and 'Solve'. Sheet2 contains the data for the four parameters of the internal temperature profile model along with four embedded charts showing how each parameter changes with Temperature. Cells that have a red triangle marker in their upper right corner have a comment note attached to them.