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From Wikipedia

Homogeneity and heterogeneity

Homogeneity and heterogeneity are concepts relating to the uniformity or lack thereof in a substance. A material that is homogeneous is uniform in composition or character; one that is heterogeneous lacks uniformity in one of these qualities.

The concepts are applicable to combinations at every level of complexity, from atoms to populations of animals or people, to galaxies. Hence, a substance may be homogeneous on a larger scale, compared to being heterogeneous on a smaller scale within the same substance. This is known as an effective medium approach, or effective medium approximations.

Heterogeneity

Heterogeneity is the state of being heterogeneous . It is the nature of opposition, or contrariety of qualities. Pertaining to the sciences, it is a substance that is diverse in kind or nature; composed of diverse parts. In other words, it is composed of dissimilar parts, hence the constituents are of a different kind. The parts (or constituents) are connected, and of a conglomerate mass, and viewed in respect to the parts of which it is made up.

Various disciplines understand heterogeneity, or being heterogeneous, in different ways. For example:

  • In physics it is understood as having more than one phase (solid, liquid, gas) present in a system or process.
  • In chemistry it means visibly consisting of different components.
  • With information technology it means a network comprising different types of computers, potentially with vastly differing memory sizes, processing power and even basic underlying architecture. Alternatively, a data resource with multiple types of formats.
  • Rocks (geology) are inherently heterogeneous, usually occurring at the micro-scale and mini-scale.

Homogeneity

Homogeneity is the state of being homogeneous. Pertaining to the sciences, it is a substance where all the constituents are of the same nature; consisting of similar parts, or of elements of the like nature. For example, homogeneous particles, homogeneous elements, homogeneous principles, or homogeneous bodies; or (algebra) possessing the same number of factors of a given kind, as with a homogeneous polynomial.

Mathematics

In mathematics, homogeneous may refer to:

Chemistry

A heterogeneous mixture is a mixture of two or more compounds. Examples are: mixtures of sand and water or sand and iron filings, a conglomerate rock, water and oil, a salad, trail mix, and concrete (not cement). During the sampling of heterogeneous mixtures of particles, the variance of the sampling error is generally non-zero. Gy's sampling theory quantitatively defines the heterogeneity of a particle as:

h_i = \frac{(c_i - c_\text{batch})m_i}{c_\text{batch} m_\text{aver}} .

where h_i, c_i, c_\text{batch}, m_i, and m_\text{aver} are respectively: the heterogeneity of the ith particle of the population, the mass concentration of the property of interest in the ith particle of the population, the mass concentration of the property of interest in the population, the mass of the ith particle in the population, and the average mass of a particle in the population.

Homogenization is the process of causing a heterogeneous mixture to become homogeneous, as is done with the making of homogenized milk.

Homogeneous and heterogeneous reactions

Homogeneous reactions are chemical reactions in which the reactants are in the same phase, while heterogeneous reactions have reactants in two or more phases. Reactions that take place on the surface of a catalyst of a different phase are also heterogeneous. A reaction between two gases, two liquids or two solids is homogeneous. A reaction between a gas and a liquid, a gas and a solid or a liquid and a solid is heterogeneous.

A mixture can be determined to be homogeneous when everything is settled and equal, and the liquid, gas, object is one color or the same form. Various models have been proposed to model the concentrations in different phases. The phenomena to be considered are mass rates and reaction rates. Surface area affects the reaction rate of heterogeneous reactions but not homogeneous reactions.

Biology

Genetic heterogeneity refers to multiple origins causing the same disorder in different individuals. Heterogeneity of ion channels means diversity of different types of channels serving a specific kind of current, e.g. by channels with different constitutive subunits.



From Yahoo Answers

Question:Does anyone understand how to explain population heterogeneity in terms of ecology? I kind of get what it means but I'm having trouble articulating it properly in order to write an essay. Any help would be greatly appreciated!

Answers:Since you want an essay, you could start as following:- a) Define what is population & / or demographics (study of human population)? b) Classify and define various types of population i.e. heterogenous and homogenous populations. {Hetero = different; Homo = same] c) Talk about the different classes in the animal and plant kingdom. d) Write about species and genus and define them briefly. e) After the brief introduction (points a-d) you can make your next paragraph about your topic namely, population heterogeneity. This is nothing but the world or earth has different classes and species of plants and animals including human race. Homogeneity on the other hand is the presence of a single species from a single class in a given area. f) Now discuss about the disadvantages of homogeneity or homogenous population and the advantages of heterogeneity or heterogenous population. for e.g. It is due to these heterogeneity of the living population that life on earth has sustained. g) Imagine just having only amphibians or reptiles or birds or mammals or just shrubs or bushes or trees or plants or just south indians etc. It would have constituted a homogenous population and there would have been no variety. This would prevent natural selection and there would have been no biodiversity (ecological angle ??) f) Finally talk of biodiversity in the context of population heterogeneity and conclude your essay. Hope this helps you to get some idea initially. Use the internet search and proceed further. Good luck !!!

Question::)

Answers:By definition a solution is a homogeneous mixture.

Question:so i have an essay to do on heterogeneity, but i have no idea what that means. all the definitions i've found don't make it any clearer, so does anyone know what it means?

Answers:the quality of being diverse and not comparable in kind

Question:I have a homework/mini-project in my animal science course, and I have to define a couple of words. I tried looking ofr it myself and combing the definition of "agriculture" and "population," but it doesn't sound right. Can anyone help me? Thanks!

Answers:The agriculture population is the population of people living in a rural area that are engaged in agricultural work. It would exclude people living in a rural area but not engaged in agriculture.

From Youtube

John McKinney Part 3: Phenotypic Heterogeneity and Antibiotic Tolerance :Lecture Overview Human population growth and urbanization have accelerated dramatically in recent centuries, providing unprecedented opportunities for microbes that use our bodies as vehicles for their own propagation and transmission. These conditions have led to the emergence of virulent new pathogens and the increased prevalence of "classic" scourges, such as Mycobacterium tuberculosis. This tenacious microbe is transmitted via infectious aerosols produced by individuals with pulmonary tuberculosis. Infection is lifelong and symptomatic tuberculosis may develop following a period of clinical latency lasting for months, years, or decades. The first part of this lecture provides an overview of the natural history of TB infection and the global impact of TB on human health. Tuberculosis remains one of the most important causes of human disease and death despite the introduction of vaccination in 1921 and chemotherapy in 1952. Although these interventions are inexpensive and widely available their impact is limited. The effectiveness of vaccination is unclear; in clinical trials, the protection conferred by vaccination has been variable and generally poor. Although chemotherapy can be highly effective, multiple drugs must be administered for 6-9 months to provide a reliable cure; the majority of tuberculosis patients are unable or unwilling to complete such a demanding regimen unless closely supervised. The second part of this lecture will discuss the challenges facing ...

ACTIVE Population Density :www.activesol.co.uk - Working out the population density of a ward or Super Output Area is straightforward using ACTIVE Total Solution Mapping. The start-up option we need for this task is 2004 ID SOAs First click on the Areas Tab Select the Generic Definitions Area Group that gives us access to the SOAs Drag and drop the Area Data card to the Card Stack Now click on the Reference Tab In this example we're going to use the Mid-2008 Population Estimates data from ONS Click the heading to access the census table Tick the box for All Ages Drag the Reference Data card to the Card Stack Next click on the Compare Tab Drag and drop the Reference Data card on to Show Data Drag and drop the Area Data card on to Base Data Set the Base Area to Super Output Areas (the bottom option) The Statistics Mode should be set to Show Over Base % Click the Equals Button Click the Compare Stats Button (top right) Click Yes to Continue if there are a lot of Areas represented in the stats The results are shown in table form Next click on the Print Tab Click the Excel button Select the Compare Table option Click OK to export the data to a spreadsheet The Base Count column represents the area in hectares for each SOA The Show Count column represents the estimated population of each SOA The final column contains the population density eg 134 people per hectare in the first SOA Edit the formula to remove the *100 so that it reads E2/B2 Copy the formula down the whole column Right click and format the ...