Instrumentation, experiments

Secondary ion mass spectra were measured using a Perkin-Elmer+PHI 3500 instrument. Experiments were carried out with 4 kV Ar ions at beam currents of 3 and 300 nanoamps. Spectra were measured to at least 500 daltons (d). Samples were prepared in the manner used for the XPS studies. For measurements on the pure complexes, sample charging occurred, as evidenced by the inability to record secondary ion mass spectra. To reduce charging, a low energy electron beam (50-400 eV) was rastered across the sample during SIMS analysis. Positive and negative ion SIMS spectra were recorded however, only positive ion spectra are of interest for this discussion. In the spectra only unipositive ions were detected, so that the mass numbers detected correspond to combinations of the various isotopes of the elements in the ion. Thus an ion at m/z 17 d is assigned to... 

The composition distribution of the particles produced in a laboratory pulverized coal combustor will be explored in this paper using aerosol classification techniques capable of resolving the composition distribution to 0.03 ym diameter. Unlike previous attempts to measure the composition distribution, the particles were classfied directly, without having to resort to resuspension, using calibrated instruments. Experiments were conducted in a laboratory combustor in which operating parameters can be varied over a wide range. Data are presented which demonstrate that the composition of fine particles varies substantially with combustion conditions and does, under some conditions, differ considerably from that of the bulk ash. 

Materials and instrumentation. Experiments were performed using a special home-made cell coupled to a dual current supply with a maximum output of 10 V/40 mA. A detailed technical description of this system is published elsewhere (10). H NMR spectra were recorded on a Varian Mercury vx300 instrument at 25 °C. GC analysis was performed on an Interscience GC-8000 gas chromatograph with a 100% dimethylpolysiloxane capillary column (DB-1, 30 m x 0.325 mm). GC conditions isotherm at 105 "C (2 min) ramp at 30 °C min to 280 °C isotherm at 280 °C (5 min). Pentadecane was used as internal standard. The ionic liquid [omim] [BF4] was prepared following a published procedure and dried prior to use (8). All other chemicals were purchased from commercial sources (> 98% pure). 

It is very rare that you need to see the individual. However, you do need pointing capabilities, highlighting capabilities, and annotation capabilities. The notion of collaboration around work versus collaboration between individuals strikes me as one of the ways that we will see different tool sets evolve to support those kinds of interactions. Thus, while I accept your premise, I really believe that enterprises are going to focus on things like instrumenting experiments and design representations, as opposed to substituting for this kind of face-to-face interaction. 

Thus, for the determination of the energy potential of a sample, it is essential to use closed pressure resistant cmcibles for these experiments. This is true for DSC, but holds also for other instruments. Experience has shown that gold plated cmcibles with a volume of 50 pi and resistance to pressures up to 200 bar are best suited for safely studies. These crucibles are commercially available. 

C. Meinel, ed., Instrument-Experiment Historische Studien, Verlag fur Geschichte der Naturwissenschaften und Technik, Berlin, 2000. 

The knowledge of the composition of volatile compounds in food has greatly increased during the past decade. Many studies continue to report the identity and the concentration of volatile compounds in food matrices. However concentration alone appears insufScient to explain flavor properties of food. The lack of our knowledge concerning the influence of non-volatile constituents of food on the perception of aroma has to be filled by studies such as those presented in this paper. Data on interactions between aroma and matrix in wine are scarce compared with other food matrices studied. Flavor-matrix interactions in wine have generally been obtained in model systems and with instrumental experiments. However it is possible to develop some hypotheses on the possible sensory contribution of some non-volatile compounds of wine on overall aroma. 

REALITY" Observations Perceptions Instruments Experiments Results... 

In comparative testing the standard run is the complement of the blank run it uses a standard feed and a standard catalyst and indicates any unnoticed departures from standard procedure. Despite the reliability of modern instruments, experience shows that time is saved by frequent checking and calibration. 

Peak broadening effects are, again, difficult to predict from manufacturers documentation. Only one adequate description of these effects has been found. However, the importance of these effects is nevertheless realized by the manufacturers, because they nearly always quote the cell volume, which is 8-10 pi with an optical path length of 10 mm for most instruments. Experience shows, however, that bad peak broadening can sometimes occur with instruments with small cell volumes. This point should be emphasized, as improvement with respect to noise and drift can often be obtained by sacrificing the performance with respect to peak broadening (heat exchangers). 

Aston s two books should indeed be read by those wishing to choose mass spectrometry as their profession. His somewhat personalized description of instruments, experiments, and evaluations of results leaves one with the impression that Aston knew everything that could be known about mass spectrometry, that is, at that time today he might well be considered a (promising) novice. 

Due to the careless handling of cells, pressed discs, plates, films, internal reflection crystals, etc., spurious bands may be observed in spectra due to a person s fingerprints. These bands may be due to moisture, skin oils or even laboratory chemicals. Unfortunately, such carelessness is a common source of error. If an instrument experiences a sudden jolt, a sharp peak may be observed in the spectrum. Similarly, excessive vibration of the spectrometer may result in bands appearing in the spectrum. 

The ability of PLS to develop quantitative models based on the data as they come out of instruments, experiments, and calculations of quantum chemistry and other theories , makes it very useful in the investigation of complicated and interesting systems and processes in all areas of chemistry. 

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