The Process of Activity and the Built Environment

Summary of some of the topics covered by the author under the ACSA-AMAX Research Fellowship, which he won in 1967.     

Book Review

Colloidal silver iodide prepared in several different ways has been examined by electron microscopy. It was found that the particles exhibited well-defined shapes and varied in size from 10-5,000 A according to the method of preparation. Electron microscope observations were supported by the examination of single particles using the microdiffraction technique; this revealed that such particles were normally single crystals. Under the electron optical conditions of the Siemens Elmiskop, two types of phenomenon were observed, namely, highly mobile changes of contrast within the particle and the formation of filaments. The filaments also showed changes of contrast during growth and after formation often exhibited a banded structure. The preparation of thin flat particles of silver iodide enabled some preliminary electron microscope observation of internal structure to be carried out directly. Possible mechanisms for the phenonema observed are discussed.     

A Computational Model for Masked Negative Films

The construction of a computational model representing a masked negative film is described. Model negative tripacks are then used in the context of a complete negative-positive system to demonstrate the changes in colour reproduction which result from increasing the degree of masking of the magenta dye.     

Biotransformation of alkanoylcholines under methanogenic conditions

Ester quaternary ammonium compounds (esterquats), which are mainly used as active ingredients in fabric softeners and personal care products, are beginning to replace traditional quaternary ammonium compounds. As a result of hydrophobicity and increasing use, esterquats reach anaerobic treatment systems. However, little is known about the fate of esterquats under anaerobic conditions. In the present study, the potential inhibitory effect and biotransformation of two alkanoylcholines - acetylcholine chloride (ACh-Cl) and lauroylcholine chloride (LCh-Cl) - which are simple esterquats, under methanogenic conditions were investigated. ACh-Cl up to 300 mg/L was not inhibitory to a mixed methanogenic culture. In contrast, methanogenesis was inhibited by LCh-Cl above 50 mg/L, primarily caused by the accumulation of lauric acid which resulted from the abiotic hydrolysis of LCh. Below inhibitory concentrations, both ACh and LCh were transformed to methane by the mixed methanogenic culture. Mass spectrometric analysis confirmed that both alkanoylcholines were first abiotically hydrolyzed to choline and the corresponding alkanoic acid, which were then biotically transformed to methane, carbon dioxide, and ammonia. Thus, alkanoylcholine-containing waste streams can be bioprocessed to form methane, but hydrolysis products such as long-chain alkanoic acids may adversely impact the anaerobic bioconversion of alkanoylcholines.     

Source characterization of major emission sources in the imperial and Mexicali Valleys along the US/Mexico border

Chemical profiles for particle emissions are needed for source apportionment studies using the chemical mass balance (CMB) receptor model. Source measurements of geological sources, motor vehicle exhaust, vegetative burning (e.g. asparagus, field burning, charbroil cooking), and industrial sources (e.g. oil-fueled glass plant, manure-fueled power plants) were acquired as part of the Imperial/Mexicali Valley Cross Border PM10 Transport Study in 1992. Six different source sampling techniques (i.e. hot- and diluted-exhaust sampling, ground-based source sampling, particle sweeping/grab sampling, vacuum sampling, and laboratory resuspension sampling) were applied to acquire filter samples of PM 2.5 and PM10 (particulate matter with aerodynamic diameters < 2.5 and 10 microm, respectively). Filter samples were analyzed for mass by gravimetry, elements (Na to U) by X-ray fluorescence, anions (Cl(-), NO3(-), SO4(=)) by ion chromatography, ammonium (NH4(+)) by automated colorimetry, soluble sodium (Na+) and potassium (K+) by atomic absorption spectrophotometry, and organic and elemental carbon (OC, EC) by thermal/optical reflectance. Concentration data were acquired for a total of approximately 50 chemical species. Elevated abundances of crustal components (Al, Si, K, Ca, Fe) from geological material, carbon (OC, EC) and trace elements (Br, Pb) from vehicle exhausts, carbon (OC, EC) and ions (K(+), Cl(-)) from vegetative burning, ions (SO4(=), NH4(+), Na(+), K(+), Cl(-)) and elements (Cl, Se) from a manure-fueled power plants, and sulfur and trace elements (Na(+), Pb, Se, Ni, V) from an oil-fueled glass plant were found in the resulting source profiles. Abundances of crustal species (e.g. Al, Si, Ca) in the Imperial/Mexicali Valley geological profiles are more than twice those found in central and southern California. Abundances of lead in motor vehicle exhausts indicate different vehicle fleets in border cities. Emission profiles from field burning and charbroil cooking specific to the border area show that a majority (>60%) of emissions are comprised of carbon, with high organic to total carbon ratios (0.93 to 0.97). Abundances of sulfate and ammonium account for nearly 60% of the manure-fueled power plant's emissions. Elevated levels of metals (Na(+), Pb, Cd, Se) and byproducts of petroleum combustion (S, Ni, V) were found in the oil-fueled glass plant's emissions.     

The eye of the beholder

This article falls into four broad sections.

1. A background to the physical, political, social and cultural attributes of Saudi Arabia.

2. Problems encountered by designers, such as communications, contractors, plant and construction materials, irrigation water.

3. An attempt to establish some design principles, particularly pertinent to working in an arid Islamic environment.

4. Concludes with some recent projects carried out in the Kingdom, which follow some of these principles.