Factori fizici din mediu
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Transcript of Factori fizici din mediu
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Factori fizici din mediu
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Energie din mediu
Interactuni specifice
Fotosinteza
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html
6H2O + 6CO2 ----------> C6H12O6+ 6O2
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Interactuni nespecifice
Incalzirea sistemelor
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Cantitati mici de energie absorbite in locuri specifice
Perturbari ale mecanismelor biologice de control
Exemplu: mutatii induse de radiatiile ionizante
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Energia din mediu
informatie“Transportor” de
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Principiul Grottus-Drapper
Energia absorbita este efectiva
Energia total este efectiva
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Mecanisme biologice de amplificare sunt importante
Energia slaba absorbita
In comparatie cu energia termica (kT)
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Exemple: urechea umana (“potectie la zgomotul
termic”) Lantul dublu de ADN (“protectie la radiatiile
ionizante”)
Mecanisme biologice de protectie sunt importante
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Temperatura
Reprezentare Arrhenius:
RT
EAk A
R lnln
Reprezentare Arrhenius:
RT
EAk A
R lnln
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Conductivitatea termica
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dx
dTJ
CQ
Conductivitate termica
(Jm-1s-1K-1)
Directia fluxului termic: de la temperatura ridicata la tempetaratura scazuta
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Convectia
http://www.goalfinder.com/product.asp?productid=59#
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Radiatia termica
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Legea Stefan-Boltzmann
4TJQR
Cantitatea de caldura emisa/absorbita de un corp negru absolut
42-8 10 67,5 KWm
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Evaporarea apei
Evaporarea unui gram de apa
Corpul pierde ~ 2,4 kJ
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Plante
http://www.bbc.co.uk/schools/gcsebitesize/biology/greenplantsasorganisms/1watertransportrev2.shtml
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Animale
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Evaporarea apei depinde de:
Structura suprafetei
Viteza vantului
Diferenta de presiunea vaporilor la suprafata si in mediu
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Presiunea
Importanta la animale acvatice
O crestere a adancimii cu 10 m
Presiunea creste cu 0,1 MPa
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Efecte ale presiunii
Modificari de:
volum ale gazelor din cavitati
solubilitati ale gazelor in sange si apei in tesuturi
structura a apei variatii mari de presiune
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Reducerea solubilitatii oxigenului la altitudini ridicate
Alpinisti si piloti
Cresterea presiunii partiale a oxigenului
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Problema: intoarcere rapida la presiunea normala
Bule de gaz in sange(N2)
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Presiunea poate modifica si echilibrul reactiilor chimice
Important pentru reactii care se produc in gaze
Reactii asociate cu modificari ale structurii apei
Variatii de presiune > 10 MPa