Carrot-like forms

It can also be seen from Fig. 2.6c-f that the growth of such protrasions produces carrot-like forms, another typical form obtained in copper depositimi under mixed activation-diffusion control. This happens under the condition k 1, when activation control takes place only around the tip of the protrusion, as is illustrated in Fig. 2.6c, d. In this case, Eq. (2.20) can be rewritten in the form ... 

In the case of copper, electrodeposition at low overpotentials produces large grains with relatively well-defined crystal shapes. Further increasing the overpotential leads to the formation of cauliflower-like and carrot-like protrusions, and finally, dendritic deposits are formed in the absence of strong hydrogen co-deposition.13... 

The final form of the carrot-like protrusion is shown in Fig. 2.6e. It can be concluded from the parabolic shape that such protrusions grow as moving paraboloids in accordance with the Barton-Bockris theory [5], the tip radius remaining constant because of the surface energy effect. It can be concluded from Fig. 2.6f that thickening of such a protrusion is under mixed activation-diffusion control because the deposit is seen to be of the same quality as that on the surrounding macroelectrode surface. It can be seen from the Fig. 2.6d that activation control takes place only at the very tip of the protrusion. 

In the body retinol can also be made from the vitamin precursor carotene. Vegetables like carrots, broccoli, spinach and sweet potatoes are rich sources of carotene. Conversion to retinol can take place in the intestine after which retinyl esters are formed by esterifying retinol to long chain fats. These are then absorbed into chylomicrons. Some of the absorbed vitamin A is transported by chylomicrons to extra-hepatic tissues but most goes to the liver where the vitamin is stored as retinyl palmitate in stellate cells. Vitamin A is released from the liver coupled to the retinol-binding protein in plasma. 

One pragmatic approach to the problem is the flavorese concept (i). A crude enzyme preparation from the fresh food or a closely related species is added to the processed food in the hope that the nonvolatile flavor precursors are still present and will yield the full range of fresh flavor components upon enzymatic treatment. This approach has been applied with some success to watercress (1,2), cabbage 1,2, 3, 4), horseradish 2, 3), onions 2, 3), carrots 2, 3, 5), peas, beans 2,3,6), citrus juice (2, 7), raspberries (8), tomato juice (2, 3, 9), bananas (JO), and various flower fragrances 11). This would seem to be a desirable approach since the products of different enzymatic reactions are probably necessary for full flavor. However the flavor-forming activity of the enzyme preparations was variable (5, 6, 7, 9), and the flavors were not always like that of the fresh vegetable (3). The several enzymes and flavor precursors may not have been present in the normal ratios. Also, to be practical, the enzyme preparation must be inexpensive to prepare and store, the substrates must persist in the processed food, and they must be available to enzyme action. One also wonders how processed foods can be enzymatically treated under sterile conditions. 

The bonding orbitals formed from Is-ls and 2s-2s interactions have another important feature in common they are all cylindrically symmetrical. In other words, if you look at the molecular orbital end-on, you can rotate it around the axis between the two atoms by any amount and it looks identical. It has the symmetry of a cigar, a carrot, or a baseball bat. Bonding orbitals with cylindrical symmetry like this are known as c (sigma) orbitals, and the bonds which result from putting two electrons into these orbitals are known as o bonds. The single bond in the H2 molecule is therefore a a bond. 

On a Umited scale, crop covers are used over susceptible crops when there is likely to be damage. These crop covers form veiy effective barriers against pests such as carrot and cabbage root fly and caterpillars. Other than cost the problem with crop covers is that they have to be removed before weeding can be carried out. 

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