Aridity definitions

An aridity definition that takes account of the relation precipitation/potential evaporation is the Aridity Index used in the Atlas of Desertification (UNEP, 1993). Four different degrees of aridity can be recognized. These are best defined using the Aridity Index (AI), calculated as the ratio P/PET, where P stands for precipitation and PET for (potential) evapotranspiration. AI values of <1.0 indicate an average annual moisture deficit. According to this criterion, four subzones can be discussed ... 

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Arid and semi-arid zones may be defined in several ways, but the climatic is the one most commonly accepted. According to that definition, aridity represents a lack of moisture in average climatic conditions (UNEP, 1993). This situation may be caused by one of four climatic conditions, which may interact in the case of specific arid/semi-arid zones continentality, topography, anticyclonic subsidence and oceanic cold currents. 

The term acceptable is used widely to describe safe levels of intake and is apphed for chemicals to be used in food production such as, e.g., food additives, pesticides, and veterinary dmgs. The term tolerable is applied for chemicals unavoidably present in a media such as contaminants in, e.g., drinking water and food. The term PTWI (Provisional Tolerable Weekly Intake) is generally used for contaminants that may accumulate in the body, and the weekly designation is used to stress the importance of limiting intake over a period of time for such substances. The tolerable intake is similar in definition and intent to terms such as Reference Dose and Reference Concentration (RfD/RfC), which are widely used by, e.g., the US-EPA. For some substances, notably pesticides, the ARID (Acute Reference Dose), is also established, often from shorter-term studies than those that would support the ADI. The ARfD is defined as the amount of a substance in food that can be consumed in the course of a day or at a single meal with no adverse effects. 

Note that this definition is different in at least two major respects from the conventional definition of an arid as a substance dissociating to give H+ in water. The Lowry-Brnsted definition states that for every acid there be a conjugate base, and vice versa. Thus, in the examples cited above. Cl-. OH-, and NH--are the conjugate bases of HCl, H20. and NH3. 

In presence of appreciable amounts of volatile adds, a separate weighed portion of the substance is mixed with cold water to a definite volume and an ab quot part of the liquid decanted or, if necessary, filtered through glass wool, and titrated as above (total acidity). The fixed acidity is determined by evaporating almost to dryness on a water-bath a known volume of the solution obtained as in 2 (above), the residue being taken up in water and titrated as before volatile acidity = total acidity minus fixed aridity. 

Small dry cooling systems are commonplace today all over the world for various light duties, such as localized air conditioning, while larger systems are used in arid areas, often for electricity generation. Dry cooling systems, by their definition, do not need water they are more flexible in their siting requirements than wet systems and are less expensive to maintain. However, they are not as thermally efficient, and therefore are more expensive to own and operate for a comparable heat load. 

Terms like the northern Great Artesian Basin, surroundings of London, or arid zones of Israel may be suitable for the name or title of a project, but in the report or the paper itself the study area should be precisely defined. The aerial definition may be by coordinates or by names of geographical boundary objects. The study area should always be defined on a clearly readable map, along with a map that shows the study area in a larger geographical frame, for example, a country. 

Briere, P.R. (2000) Playa, playa lake, sabkha Proposed definitions for old terms. Journal of Arid Environments 45, 1-7. 

Most large laboratories will require 12 to 18 months at a minimum, arid frequently more, to progress through the first three phases of definition, acquisition, and implementation. 

The foUovringetmm awve to illustrate this definition of a normal, er as it is sometimes incorrectly celled, a neutral salt, the displaceable stoma of hydrogen in the arid, and the metal by which they have been displaced in the salt, being printed in italics... 

Fluorescence Sensing of Anions, p. 566 Fluorescent Sensors, p. 572 Molecular Logic Gates, p. 893 Molecular Squares, Boxes, and Cubes, p. 909 Molecular Switches, p. 917 Molecular Wires, p. 925 Molecular-Level Machines, p. 931 Photochemical Sensors, p. 1053 Rotaxanes and Pseudorotaxanes, p. 1194 Self-Assembling Catenanes, p. 1240 Self-Assembly Definition and Kinetic arid Thermodynamic Considerations, p. 1248... 

Spatial and temporal distribution of water resources has been a definitive factor in the development of human societies, Although the land was extremely arid, ancient Egypt was able to develop because the source of the Nile... 

Cordinuous design reviews of the virtual arid soft prototypes to achieve Inal aesIheliQ and functional product definition and feasioifity... 

Loess is a special kind of wind-blown deposit under arid-semiarid environment in Quaternary period. Its physical and mechanical properties are related to the forming environment. The stratum and physical properties are general identical under a definite environment, therefore the study for a particular case can provide reference in the area of same deposit unit. 

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