Nielsen Method Research Articles

Sand ripples generated by regular oscillatory flow

The prediction of ripple geometry is a necessary precursor to the prediction of sand transport under waves for ripple regime conditions. The paper begins with a comparison of four existing methods for predicting the geometry of sand ripples generated by oscillatory flow. The comparison points to substantial differences between ripple dimensions predicted by the methods, especially for field-scale conditions. Ripple geometry experiments carried out in a large oscillatory flow tunnel are then described. The experiments involved a range of sand sizes and sinusoidal and asymmetric flows with periods and velocities typical of field conditions. Comparison of measured and predicted ripple geometries leads to the recommendation that the method of Mogridge, Davies and Willis be used to predict ripple geometry for field-scale oscillatory flows. The Nielsen method yields good predictions of ripple length, but the rapid fall-off in ripple steepness predicted by the Nielsen method at high mobility number is not supported by the measurements. The lengths and heights of symmetric ripples produced by sinusoidal flows are found to be similar to the lengths and heights of asymmetric ripples produced by “equivalent” asymmetric flows. Three-dimensional ripples occur with fine sand in long-period flows typical of field conditions. The dimensions of these ripples cannot be predicted using methods developed for two-dimensional ripples. Previously suggested criteria for predicting the occurrence of three-dimensional ripples fail when tested against a wide range of flow and sand conditions. The occurrence of three-dimensional ripples and the effects of ripple and flow history on ripple geometry require further research.

Crystal growth of (E)-2-butenedioic acid from aqueous solution in batch-cooling crystallization

The Nielsen method [A.E. Nielsen, Crystal Growth, Suppl. J. Phys. Chem. Solids (1967) 419] [1] is applied to the crystal growth mechanism of (E)-2-butenedioic acid (BDA)/water system. Particle sizes are calculated as a function of the supersaturation ratio for various growth mechanisms using solid/liquid interfacial tension of the BDA/water system [A.E. Nielsen and O. Söhnel, J. Crystal Growth 11 (1971) 233] [2] [I. Liszi and M. Hasznos-Nezdei, Hung. J. Ind. Chem., in press] [3]. In this way a set of curves (“map” of crystal growth mechanisms) helps us to select the validity range of the given growth mechanism. The crystallization was carried out by cooling without seed crystals in a batch crystallizer. The average particle size of the final product and the metastable zone width were measured [3]. From this latter datum the maximum value of the initial supersaturation was determined. The logarithm of the particle size and supersaturation ratio were put in the theoretical crystal growth map. According to the map, the crystal growth in this system is controlled by bulk diffusion. The most probable subprocess of layer growth is surface diffusion (BCF model). This last experience is in accordance with the literature [Sh. Sudo et al., Kagaku Kogaku Ronbunshu 15 (1989) 1120] [4].

Predicting ripple roughness and sand resuspension under combined flows in a shoreface environment

Ripple measurements and flow and sediment dynamical data obtained from the shoreface of the Middle Atlantic Bight using instrumented tripods were analyzed to evaluate various predictors of ripple geometry and roughness. Ripple roughness controls on sand resuspension and suspended sediment concentration profiles under combined waves and currents were also evaluated. The limited observation of sand ripples in the field indicates that the Grant and Madsen (1982) method overestimates ripple roughness, while the Nielsen (1981) method tends to under-predict ripple roughness. A modified ripple predictor is thus proposed based on the Grant and Madsen method, and it is shown to give reasonable predictions under the present experiment conditions. This modified ripple prediction along with wave, current and suspended sediment concentration data recorded by the tripods were then brought into the combined-flow bottom boundary layer model of Grant and Madsen (1986) and the modified Rouse equation of Glenn and Grant (1987) to calculate sand resuspension coefficient γ 0 and to predict suspended sediment concentration profiles. It was found that under low-energy fair-weather conditions, sand ripples are in the equilibrium range and ripple roughness increases with the bed shear stress. This causes strong vortex activity close to seabed and thus higher resuspension coefficient. Reference concentrations are moderate due to this high resuspension coefficient, even though bed shear stresses are low. Under moderate storm conditions, ripple break off occurs and ripple roughness will decrease with bed shear stress. This reduces the vortex activity and hence sand resuspension coefficient γ 0. The combination of this moderately high bed shear stress and reduced but still moderate ripple roughness favours sand suspension and produces the highest reference concentration for the encountered experimental conditions. As bed shear stress is further increased, ripples are nearly washed out and sand resuspension coefficient is further decreased approaching the previously-suggested constant value of 1.3 × 10 −4. This corresponds with the lowest reference concentration despite the high bed shear stress. Suspended sediment concentrations predicted by the modified Rouse equation using this time variable resuspension coefficient and properly calculated bottom boundary layer parameters are reasonable compared to the field measured concentration profiles.

Actions of finite groups on graphs and related automorphisms of free groups

The proof will be completed in Section 6. It is geometrical and the geometrical objects which will be used are graphs on which finite groups act (G-graphs). The following lines are intended to describe the structure of the proof with the main intermediate results. The translation into geometrical language is made possible by the realization theorem of Culler [S] which states that every finite subgroup of Out @ is realized by automorphisms of a graph (see Section 3). Now if G is a finite subgroup of Out Cp and r a graph realizing G then the centralizer of G can be identified with the group Out, n,(T, *) of equivariant conjugacy classes of automorphisms of rc,(f, *). We shall turn to fundamental groupoids and ‘prove with some effort (Sections 4 and 5) that if the G-graph r is suitably chosen (“reduced”) then the natural homomorphism Aut, Z7(r) + Out, z,(& *) is surjective. This way the problem reduces to the more tractable group Aut, n(r) of equivariant automorphisms of the free groupoid n(r). That this group is finitely generated will be proved in Section 6 by an extension of the Nielsen method in free groups. A peculiarity which occurs in the study of Aut, IZ(IJ is that we are forced to consider simultaneously a number of graphs related to r and all isomorphisms between fundamental groupoids of these graphs. In the classical situation of automorphisms of a free group (G trivial, r a wedge of loops) one proves that every automorphism of @ (i.e., of n(r)) can be expressed as a product of Nielsen automorphisms. What we have in the general situation is that (under certain circumstances described in Sec-

Simulation of vancomycin peak and trough concentrations using five dosing methods in 37 patients.

Five methods of dosing vancomycin (Matzke, Moellering, Nielsen, Lake-Peterson, and manufacturer's) were simulated in 37 patients. Ten serum samples were obtained after a 1-hour intravenous infusion of 6.2-20 mg/kg total body weight. A preinfusion serum sample was obtained from patients not studied on the first dose. Initial estimates of pharmacokinetic values were made using nonlinear iterative least squares regression and serum concentration-time data. These data were fitted to a two-compartment, open-infusion model. Simulations of the peak and trough serum concentrations at steady state for each patient were determined by multiple-dose simulated pharmacokinetics and each patient's pharmacokinetic values using the regimen suggested by each of the five methods. Steady-state serum concentrations, predicted systemic clearance by each method (except Lake-Peterson), and the daily dose for each patient recommended by each method were determined. All the methods underpredicted actual drug clearance, with the Nielsen method having the lowest prediction. The Matzke method recommended the largest dosage. Using each of the methods, only 3-16% of patients would have achieved recommended peak and trough serum concentrations. In the simulation model used, no method performed satisfactorily in attaining the desired vancomycin peak and trough concentrations. We suggest that the Lake-Peterson method could be used initially, provided that monitoring is also performed to adjust the dosage regimen further.

A comparison of the bond strength of two ceramometal systems

T he ceramometal restoration has been a major advancement in restorative dentistry. The metal component provides the fit and strength, while the porcelain veneer affords ihe esthetics. The bonding of the two materials is of major importance in the fabrication of the ceramometal restoration. The theory of ceramicto-metal bonding has focused on four possible mechanisms: (1) van der Waals’s forces, (2) compressive forces generated in thermal expansion, (3) mechanical bonding with surface geometry, and (4) chemical bonding with the oxides in the ceramic and the metal. Various test methods have been developed to measure the bond strength at the ceramic-metal interface and to understand the bonding roles of the four mechanisms. The most commonly used test was developed by Shell and Nielsen.’ This was a shear test in which an alloy rod was pulled out of a porcelain block. Anthony et aL2 modified the Shell and Nielsen test using a ring of porcelain instead of a block to reduce the notch effect at the free surface of the bond. With the Shell and Nielsen method or variations, studies have reported bond strengths with 10,000 to 20,000 psi.lv3 The variables include the types of porcelain, the alloy, coating agents, trace elements, degree of roughness, and the type of firing atmosphere. With polished rods of 100% noble alloy, Shell and Nielsen’ measured bond

A new example for the applicability of the relationship between the particle size and the kinetic of the crystal growth

AbstractExperiments have been made with PbCrO4 precipitating system in a batch type tank. In the experiments the speeds of stirring and the residence times were changed. The particle size distribution of precipitates formed has been determined. The rate determining mechanism of the crystal growth were evaluated by two different methods (NIELSEN method and method elaborated in our institute). The two methods used have indicated the same informations about the rate determining processes. It also has been stated that the coagulation does not disturb the selection of the suitable growing mechanism.

On Length Functions and Nielsen Methods in Free Groups

On Length Functions and Nielsen Methods in Free Groups

The Ratio DL/ for Electrons in Helium at 293 K

The Bradbury–Nielsen method has been used to measure the ratio of the longitudinal diffusion coefficient DL to the electron mobility μ in helium at 293 K over the E/N range 0024–0.607 Td. The absolute error is estimated to be less than � 3 %. The present results agree with those of Wagner et al. (1967), to within the combined experimental errors over the common range of E/N values, and are also compatible with the values predicted by Lowke and Parker (1969) from calculations based on the momentum transfer cross section of Crompton et al. (1967).

Pulmonary ventilation and respiratory gas exchange during manual artificial respiration and expired-air resuscitation on apnoeic normal adults. A comparison of the Holger Nielsen method and the mouth-to-mouth method.

SUMMARY Comparative experimental studies on resuscitation by the mouth‐to‐mouth and Holger Nielsen (back‐pressure arm‐lift) methods are reported. The experiments were performed on five normal unconscious apnoeic adults and extended over periods of from 20 to 40 minutes. Tidal air, minute volume and alveolar ventilation/min. were determined pneumographically and/or spirometrically and/or volumetrically. The oxygen saturation and carbon dioxide tension of the arterial blood were determined during the experiments. Sufficient alveolar ventilation with normal arterial oxygen saturation and PCO2 was obtained by the mouth‐to‐mouth method in four out of five cases. In one case, hypoventilation occurred during the performance of the mouth‐to‐mouth method. Sufficient alveolar ventilation with normal arterial oxygen saturation and constant PCO2 was obtained by the Holger Nielsen method in one out of five cases. In four cases, variable degrees of hypoventilation occurred during the performance of the manual manoeuvres with an increase in the PCO2 of the arterial blood. However, an arterial oxygen saturation of more than 80% was maintained throughout the experimental period (30–40 minutes), although resuscitation with atmospheric air was given during the greater part of the period. The advantages and disadvantages of the two methods are discussed. Maintenance of a patent airway during artificial respiration must be considered to constitute a conditio sine qua non. If the Holger Nielsen method is to produce sufficient alveolar ventilation in the field, the respiratory frequency must be 15–16 breaths per minute, and the victim's head should be bent backwards (extension in the atlanto‐occipital joint). The authors are unable to recommend one of the two methods as being superior to the other in adults, but agree with the American investigators in their recommendation of the mouth‐to‐mouth method in infants and small children. The view is expressed that it would be desirable to train the general population as “two‐method” resuscitation operators.

Physiologic principles of resuscitation and oxygen therapy.

For the past 50 years the English-speaking world has employed practically exclusively the prone pressure method of artificial respiration. During the war the method lost favor. There was no conviction that it provided more than minimum lung ventilation and it was realized that no one knew the real efficacy of the procedure. Measurements on fresh cadavers, on unconscious patients unable to breathe, and finally on anesthetized and curarized volunteers confirmed the distrust of prone pressure artificial respiration and led to trial of other procedures. Out of these observations the Danish Holger Nielsen method emerged as tlae best, and is discussed.

THE HOLGER NIELSEN METHOD OF RESUSCITATION

Medical Journal of AustraliaVolume 1, Issue 18 p. 710-711 The Holger Nielsen method of resuscitation THE HOLGER NIELSEN METHOD OF RESUSCITATION First published: 01 May 1939 https://doi.org/10.5694/j.1326-5377.1939.tb114748.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume1, Issue18May 1939Pages 710-711 RelatedInformation

The Nielsen Method of Artificial Respiration

The Nielsen Method of Artificial Respiration