Artefacts improvements

The are essentially adjustable parameters and, clearly, unless some of the parameters in A2.4.70 are fixed by physical argument, then calculations using this model will show an improved fit for purely algebraic reasons. In principle, the radii can be fixed by using tables of ionic radii calculations of this type, in which just the A are adjustable, have been carried out by Friedman and co-workers using the HNC approach [12]. Further rermements were also discussed by Friedman [F3], who pointed out that an additional temi is required to account for the fact that each ion is actually m a cavity of low dielectric constant, e, compared to that of the bulk solvent, e. A real difficulty discussed by Friedman is that of making the potential continuous, since the discontinuous potentials above may lead to artefacts. Friedman [F3] addressed this issue and derived... 

In fact, the distinction between two-step and direct dynamics is rather fuzzy. The basic issue is what kind and amount of preliminary work is needed before starting a dynamical calculation. Direct ab initio dynamics [90,97-101] requires a minimum of preparation some tests to choose basis sets and other options may suffice. For large systems, however, fully ab initio calculations are impractical, and one has to resort to QM/MM or PCM approaches but then, a host of empirical parameters are introduced, which may need some readjustement to avoid artefacts and to improve the accuracy before starting the dynamical calculations. The same holds for the semiempirical methods in order to represent at best the excited states, one has to re-parameterize the hamiltonian. In particular, our FOMO-SCF-CI method [56-58] differs considerably from the normal SCF or SCF+CIS procedures, so that the standard parameters need to be modified. However, the parameter sets are fairly transferable, and their optimization can be limited to the atoms belonging to the chromophore. In the two-step strategies one fits the ab... 

Fig. 9). The region of the spectrum between 1900 cm-1 and 2500 cm-1 where diamond absorbs too strongly has shown a higher noise level but no spectral artefact can be observed. A higher number of co-additions can be applied to improve the SNR in that region.

Below is the symmetrized, magnitude, COSY-60 spectrum of camphor with the one-dimensional spectrum plotted to the same scale. This spectrum was collected using the full phase cycling normally applied to suppress artefacts. Each FID consisted of IK data points, and 256 increments were used. The data were multiplied by a sine bell window function in both dimensions to improve the appearance of the contour plot. 

Artefacts that arise from gas in the stomach and adjacent bowel often limit the diagnostic accuracy of abdominal ultrasound. Research to overcome this problem has focused on cellulose-based suspensions. An agent has been developed based on simethicone-coated cellulose— SonoRx (Bracco Diagnostics, Princeton, NJ), which displaces and disperses gas bubbles. In a phase 2 chnical study, 93 patients underwent upper abdominal sonography before and after a randomized dose of the contrast agent (200, 400, 600, 800, or 1000 ml) (15). Anatomical visualization was improved as follows the stomach in 82% of patients, the duodenum in 63%, the pancreatic head and body in 61%, and the pancreatic tail in 67%. There were 14 adverse events in 11 patients and only five were considered to be related to the contrast agent. The main adverse effects were mild diarrhea and nausea. 

The examples discussed above clearly demonstrate that C02-extraction is a more gentle procedure than steam distillation. The smaller processing stress widely avoids the formation of artefacts. Therefore C02-extracts often have a better efficacy or a richer aroma profile reflecting the complete flavour or fragrance spectrum of the herbal raw material. This is also confirmed in the literature where professional fla-vourists have compared the aroma profiles of C02-extracts, essential oils and oleores-ins for a range of different spices [7]. Moreover C02-extraction is carried out under precisely standardised and controlled conditions which allow reproducible results. Since C02-extracts have their own character different from the usual distillates, they are new and powerful means for flavourists and food technologists to modify, improve or boost existing products or to create new premium flavour qualities. 

A treatment for analysing the excitation and fluorescence multiwavelength polarized decay surfaces has been given for the case of a mixture of noninteracting species. An improved model for analysis of fluorescence anisotropy measurements has been presented. Limitations to the use of intense excitation pulses in fluorescence and thermal lens spectrophotometers are discussed in terms of optical saturation. Such artefacts can be eliminated by reference to the fluorescence quantum yield of Rhodamine 6G. A model has been given to describe spectral diffusion in time-resolved hole-burning spectroscopy. ... 

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