Hole size calculations

Obviously, it would be of interest to know what the true ideal metal-ligand bond length is. Some studies, particularly some of those aimed at predicting metal ion se-lectivities based on hole size calculations, require accurate values for r0. The question... 

One problem that has only rarely been appreciated is the fact that with unsym-metrical ligands the metal-ligand distances for each bond have to be varied within specific and different limits. An illustrative example is the hole size calculation of the hexaamine ligand rra/M-diammac which, with many first row transition metal ions, exhibits significantly different metal-ligand distances for the primary and secondary amines [65 182l As shown in Fig. 9.5 there are significant differences in... 

Nevertheless, the experimentally observed trend (Figures 9.1 and 9.2) seems to contradict the expectations of hole size calculations (see below). Based on a simple geometric model, where the hole size is measured and the expected stability related to the hole size versus metal ion size ratio, the order of selectivity of 12- to 16-membered... 

Example 9 Pipe Distrihator A 3-in schedule 40 (inside diameter 7.793 cm) pipe is to be used as a distributor for a flow of 0.010 mVs of water (p = 1,000 kg/m, i= 0.001 Pa s). The pipe is 0.7 m long and is to have 10 holes of uniform diameter and spacing along the length of the pipe. The distributor pipe is submerged. Calculate the required hole size to limit maldistribution to 5 percent, and estimate the pressure drop across the distributor. 

Chemical process plants do not have a large domed containment but rely on vessel integrity and offgas processing. Most nuclear plants have such containment for which the stresses may be calculated if a scenario is defined. However such calculations are uncertain regarding the time of failure, the hole size, and location. 

The hole size used is larger than that necessary to quench a flame in a stagnant flammable gas mixture, i.e., larger than the quenching diameter. Howard recommends that the velocity necessary to prevent flashback be calculated by the following equation ... 

Determine the percent hole area in the active tray portion for pressure drop calculation. Note that hole size does not have to be set at this point (Figure 8-143.)... 

Calculate the optimal hydraulic parameters for the hole depth of 8,555 ft if the available data are as given below Type of pump Continental Emsco F-1600 with 97% pump volumetric efficiency. To prevent rapid pump wear, the pump pressure should not exceed about 80% of the maximum pump pressure at any liner size. The hole size is 12- - in. and the mud weight is 9.7 Ib/gal. 

The first step in the relief sizing calculation for two-phase vents is to determine the mass flux through the relief. This is computed using Equation 4-104, representing choked two-phase flow through a hole ... 

Apart from the different approaches to calculating hole sizes of macrocyclic ligands, there are also considerable differences in the force fields that have been used13,4,45,78,80,84 89]. Unfortunately, no comparative study that systematically analyzes the various methods and force fields is available. It is therefore worth noting that the computation of the cavity size of 12- to 16-membered tetraaza macrocycles with two very different models and force fields led to remarkably similar results (Table 8.2). 

Fig. 9.2. Hole size of the three nondegenerate conformers of [M(/ra s-diammac]n+ (calculated as in Chapter 8, Fig. 8.5 (b)).

A coated, perforated donut-shaped tablet was proposed to deliver a water-soluble drug for 20 hr. A water-soluble polymer was incorporated to carry the drug. The erosion rate constant of 6.6 mg/cm2 hr was measured. The size of a tablet was 1.2 cm. Calculate the central hole size of the tablet to deliver the drug for 20 hr. Drug loading is 300 mg/cm3. 

We now determine the hole sizes of the various conformers of sar. Prepare the files of the six conformers of [Co(sar)]3+ by selecting the six Co-N bonds (Tools/ Build Selections) in each file to set up the constraints for the Energy calculations. Use the. out files but rename them as. hin. As outlined above, the strain energy vs. metal-donor-distance plots for the computation of the hole sizes need to be metal ion independent. Thus, you need to activate the option Without Energy of Selected Terms in the Energy setup window. Also, the donor-metal-donor valence angle term needs to be switched off, since this is also metal ion dependent. You can do that in the Edit/View/Force Field/Atom Type Parameters menu or in the Edit/View/Parameter Array window. Both options have been used before in this tutorial. 

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