Scientific matrix

Van der Spoel,D., Berendsen, H.J.C. Determination of proton transfer rate constants using ab initio, molecular dynamics and density matrix evolution calculations. Pacific Symposium on Biocomputing, World Scientific, Singapore (1996) 1-14. 

The degradation and stabilization of polymers are very important problems from the scientific and industrial points of view. A better understanding of their mechanism is necessary to achieve better stabilization. A small amount of compounds, called stabilizers, are added into the polymer matrix to retard degradation and to impart... 

Matrix Components The term matrix component refers to the constituents in the material aside from those being determined, which are denoted as analyte. Clearly, what is a matrix component to one analyst may be an analyte to another. Thus, in one hand for the case of analyses for elemental content, components such as dietary fibre, ash, protein, fat, and carbohydrate are classified as matrix components and are used to define the nature of the material. On the other hand, reference values are required to monitor the quality of determinations of these nutritionally significant matrix components. Hence, there is a challenging immediate need for certified values for dietary fibre, ash, protein, fat, and carbohydrate. Concomitantly, these values must be accompanied by scientifically sound definitions (e.g. total soluble dietary fibre, total sulpha-ted ash, total unsaturated fat, polyunsaturated fat, individual lipids, simple sugars, and complex carbohydrates). 

Some more recent field techniques have focused on the location of the preparation of field fortification samples and have taken some of the responsibility for the preparation of the field fortification samples from the field personnel and placed them with the analytical laboratory. For example, it is becoming more common for the analytical laboratory to prepare air sample field fortifications in the analytical laboratory, freeze them, and ship them to the field for use in a frozen state. Whereas there may be some advantage to this technique in that the air tube fortification samples may possibly be fortified more accurately in the laboratory under controlled conditions than if done in the field, there are some inherent scientific problems with this method. First, one reason for the field fortification is to test the ruggedness of the field techniques of the researcher under extreme field conditions. Second, the act of freezing and thawing the sorbent matrix within the air mbe itself may have an impact on the recovery of the analyte from the air tube after exposing the sorbent to field conditions... 

Fig. 4. Substitution matrix based on disordered protein families. Below the diagonal are the scores for each amino acid substitution. Above the diagonal are the differences between BLOSUM 62 and the disorder matrix. On the diagonal are the scores/differences. (From Radivojac et al., 2002, PSB 2002 7, 589-600, with permission of World Scientific Publishing Co. Pte Ltd.)...

The scientific world was amazed to hear that David Lee, from the laboratory of Reza Ghadiri (Scripps Research Institute, La Jolla, California), had found a self-replicating peptide (Lee et al., 1996) there are analogies to the experiments with oligonucleotides (see Sect. 6.4). Lee was able to show that a certain peptide, containing 32 amino acids, can both function as a matrix and also support its own synthesis autocatalytically. The information transfer is clearly more complex than that involved in nucleic acid replication. In the case of this particular peptide, both the... 

The problem is not simple to address, as some of the methods for scientific investigation provide information on the metal atoms, without directly detecting the protein matrix around them. Other modem techniques reveal details of the protein core, but do not expose the metal centres within. A combination of the various molecular approaches is expected to uncover the fine molecular details of the catalytic action [Kovacs and Bagyinka, 1990, Szilagyi et al., 2002]... 

Figure 8.25 from Brown and Dymott, The use of platform atomisation and matrix modification as methods of interference control in graphite furnace analysis, by permission of Philips Scientific and Analytical Equipment. 

As an integral component of Microsoft Office, the spreadsheet program Excel is installed on many personal computers. Thus, a widespread basic expertise can be assumed. Although initially designed for business calculations and graphics, Excel is also extremely useful for scientific purposes. Its matrix capabilities, as well as the optimisation add-in solver, are not widely known but can often be applied in order to quickly resolve quite complex multivariate problems. We have used Excel 2002 but any other version will do equally well. 

Insulin release from the insuhn-loaded matrix was measured in response to alternating changes of glucose concentration when 150 mg of an insulin-loaded matrix was introduced to 100 mL of PBS at 37°C. The amount of insulin released was measured by taking 1 mL of the release medium at a specific time and immersing the matrix in a fresh medium. Insulin was determined by reverse-phase HPLC, using a Resolvex Cis (Fisher Scientific) and 0.01 N HCl/acetonitrile (80/20-50/50, v/v%) mobile phase over 30 min at a flow rate of 1 mL/min. The eluate was monitored by optical absorption at 210 nm. 

Figure 3.18 Secondary structure of matrix metalloproteinase 12 (MMP12) (A) PDB lYCM (structure determined using solution NMR) and (B) PDB IRMZ (structure determined using X-ray crystallography). Visualized using The PyMOL Molecular Graphics System and ChemDraw Ultra, version 10.0. (Printed with permission of Delano Scientific, LLC and CambridgeSoft Corporation.) (See color plate)...

To state scientific truths or knowledge Present-active PCBs are more strongly retained in the sample matrix as the fat content increases. (From Llompart et ah, 2001)... 

Density Matrix Conference, Kingston, August 28-September 1, 1967. Sponsored by U.S. Air Force, Office of Scientific Research U.S. Office of Naval Research National Research Council of Canada Queen s University. Co-organizers A. J. Coleman and R. M. Erdahl. Proceedings A. J. Coleman and R. M. Erdahl, editors. Reduced Density Matrices with Applications to Physical and Chemical Systems, Queen s Papers in Pure and Applied Mathematics No. 11 (1967), 434 pp. 

Dependencies may be detected using statistical tests and graphical analysis. Scatter plots may be particularly helpful. Some software for statistical graphics will plot scatter plots for all pairs of variables in a data set in the form of a scatter-plot matrix. For tests of independence, nonparametric tests such as Kendall s x are available, as well as tests based on the normal distribution. However, with limited data, there will be low power for tests of independence, so an assumption of independence should be scientifically plausible. 

---