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DNA supply chain

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DNA supply chain

Published: Tuesday, January 12, 2016 - 14:06 in Biology & Nature

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The regulation of the enzyme ribonucleotide reductase allows for just the right levels of deoxynucleotides, the building blocks of DNA, to be produced in the cell.
Christina Zimanyi, Percival Yang-Ting Chen, and Catherine Drennan

Cell survival depends on having a plentiful and balanced pool of the four chemical building blocks that make up DNA -- the deoxyribonucleosides deoxyadenosine, deoxyguanosine, deoxycytidine, and thymidine, often abbreviated as A, G, C, and T. However, if too many of these components pile up, or if their usual ratio is disrupted, that can be deadly for the cell. A new study from MIT chemists sheds light on a longstanding puzzle: how a single enzyme known as ribonucleotide reductase (RNR) generates all four of these building blocks and maintains the correct balance among them.

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THE BIG BANG:

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Chris LaRocco and Blair Rothstein present: 

THE BIG BANG: 

It sure was BIG!! 

INTRODUCTION 

We certainly know that our universe exists, however, this knowledge alone has not satisfied mankind's quest for further understanding. Our curiosity has led us to question our place in this universe and furthermore, the place of the universe itself. Throughout time we have asked ourselves these questions: How did our universe begin? How old is our universe? How did matter come to exist? Obviously, these are not simple questions and throughout our brief history on this planet much time and effort has been spent looking for some clue. Yet, after all this energy has been expended, much of what we know is still only speculation.

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Design of an Environmental Assessment Model on The Effect of Vehicle Emission in Greater Tehran on Air Pollution With Economic Sensitivity

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Design of an Environmental Assessment Model on The Effect of Vehicle Emission in Greater Tehran on Air Pollution With Economic Sensitivity

Authors : M. Abbaspour; A. Soltaninejad


 

Air pollution is the presence of pollutants in the atmosphere from anthropogenic or   natural substances in quantities  likely to harm human, plant or animal life; to damage human-made materials and structures; to bring about changes     in  weather or climate; or to interfere with enjoyment of life or property (Cooper and Alley 1986; Elson 1987). With regard to  the quality of   air in most of the megacities of the world, vehicular air pollution plays    an    important    role in deteriorating air  quality. Air   pollution in Tehran (Capital of the Islamic Republic of Iran) occurs in  highly   urbanized   areas due  to  mobile anthropogenic sources  which in-turn  is  hastened  by unfavorable topographical   and  meteorological  conditions.  In  general,  the level of economic activities which is highly related to transportation sector is responsible for much of urban air pollution  and  can result in high ambient concentrations that harm people, structures, and environment. This paper examines and estimates the tonnage, concentrations and impacts of air pollutants along with control measures aimed at reducing the effect of pollutants released by transportation navigation, in Tehran.

 

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Environmental fate of pesticides

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ENVIRONMENTAL FATE  OF  PESTICIDES

A.Soltaninejad,  Ph.D

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INTRODUCTION
Pesticides have  become  an  essential input  for  increasing  crop  production. In a pesticide we look for selective activity against a given set of pests or individual species and that too at very low concentrations. Over the past fifty years many pesticides have been developed. They are grouped under insecticides , fungicides , bactericides , herbicides , nematicides , acaricides , etc. With the increased use of pesticides in agriculture and in animal and human health care, the concern for environmental pollution has also been increased. Several studies on the persistence and residues of pesticides in the environment and their harmful effects on man and animal has been made. As a natural consequence, there have also been studies at the fate of the pesticides in nature and their biodegradation.
PESTICIDE USE IN ISLAMIC REPUBLIC OF IRAN:
We grow a large variety of crops under varying agro-climatic conditions in the Islamic Republic of Iran. Our cropping systems and also the climatic conditions favor the occurrence and spread of a large number of pests. The damage caused to our crops, both in the field and in storage, is not clearly known but some estimates indicate its high range.
Over thousands of pesticides are known in the world; about few hundred are registered for use in the Islamic republic of Iran. They are either organic or inorganic substances. A large majority of the organic substances fall under the category of organochlorides and organophosphates, and a limited few such as pyrethrin and natural plant products .While the pesticides act somewhat specifically against a few pests, none of them is active against all the crop pests. We need several pesticides to combat the large number of pests attacking our crop plants. All of them available in the market are considered harmful to human beings when consumed in large doses and hence the governmental regulations for marketing and use of the chemical are of prime importance .

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بقیه مقالات

  1. Environmental Ethics
  2. Human Evolution
  3. Finite Life Span
  4. MARS