Protons for Breakfast
Are Mobile Phones Safe?
Week 5
March 2013
In the event of…In the event of a new ice age…
This evening…
0. The Media!
1. How do mobile phones work?
What is the hazard?
2. How do electromagnetic waves interact
wit...
The word ‘radiation’
• The word ‗radiation‘ means
Anything which ‘radiates’ on ray-like paths
• Could be
Sound
Radio
Light...
Media
Media
Sunday, 20 January 2008
It also complements other recent research.
A massive study, following 1,656 Belgian
teenagers for ...
1. How do mobile phones work?
Magic?
Any sufficiently advanced technology
is indistinguishable from magic
Arthur C. Clarke
Not magic
• Mobile Phones are ‗radio‘
phones
• Operating at microwave
frequencies
• Handset power minimised
by having a ne...
Mobile Phones (3)
Recognise the masts?
• Each cell has a transmitter and receiver mast
• Notice the typical three way stru...
3G Masts
Photo Credit Brighton and Hove Green Party
Linking to base stations
• Mast power between
60 watts and 120 watts
• Handset power
less than 1 watt
• Handset sends sign...
Making a mobile-to-mobile call
Its complicated!
Network Control
Knows in which cell
every telephone is
Originating
Telepho...
2G or GSM phone
Hello! How are you?
Sound
217 pulses of encoded sound every second
No sound: No signal
Encoding to Radio S...
2G or GSM phone
Base station
Transmitter
Frequencies
(MHz)
Handset
Transmitter
Frequencies
(MHz)
Peak
Handset
Power
(Watts...
Anatomy of a GSM Signal
2G or GSM phone
217 Pulses per second per telephone call
217 Pulses per second
Each frequency channel can carry 7 calls
Safety
• The safety issues surrounding mobile phones
concern…
• the interactions of the microwaves emitted by
mobile phone...
And its not just mobile phones!
• ‗WiFi‘ Wireless Networking
• Bluetooth devices
• Wireless keyboards and mice
• DECT cord...
2. How do electromagnetic waves
interact with matter?
?
Electromagnetic spectrum
1 101 102 103 104 105 106 107 108 109 1010 1011
1012 1013 1014 1015 1016 1017 1018 1019 1020 1021...
Waves & Matter
• When an electromagnetic wave interacts with matter…
Some absorption
Some reflection
Some transmission
Summary
• Electromagnetic waves interacting with matter can be
Reflected, absorbed or transmitted
• What happens depends o...
1 101 102 103 104 105 106 107 108 109 1010 1011
1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022
Radio & TV
Frequenc...
Absorption demo
Frequency
•Well below the natural frequency
•Not much absorption
•Well above the natural frequency
•Not mu...
Waves & Matter
• When electromagnetic waves are ‘absorbed’ …
• Atoms jiggle faster:
i.e. increase their temperature.
Heat
...
3. How much energy gets absorbed?
S.A.R.
Specific Energy Absorption Rate
Terminology
• Power
watts
• Intensity
watts per square metre
• Specific energy Absorption Rate (SAR)
watts per kilogram
• 1 cm from 20 W source
20 W absorbed in hand
Intensity 8000 watts per square metre
SAR 200 watts per kilogram
• 10 cm fro...
Microwave Hazard
The potential hazard from mobile phones and other
wireless devices arises from
the absorption of microwav...
Microwave Ovens
3a. Microwave ovens
Electromagnetic spectrum
1 101 102 103 104 105 106 107 108 109 1010 1011
1012 1013 1014 1015 1016 1017 1018 1019 1020 1021...
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.01 0.1 1 10 100
Absorbtion
Frequency
Absorption of microwaves by liquid water
• We...
Absorption (1)
Too strong
• If power were absorbed too strongly,
Microwaves would only penetrate a short distance
Surface ...
Absorption (2)
Too weak
• If power were absorbed too weakly,
Microwaves would go right through
No cooking
0
0.05
0.1
0.15
...
Absorption (3)
• If power is absorbed just right,
Microwaves penetrate about 5 cm (2 inches)
Cooks the outer 5 cm of the f...
Microwave Ovens
Summary
• A microwave oven cooks food by heating it
• The heating comes from
• intense waves at 2.45 GHz
•...
Microwave Ovens
Inside a microwave oven
Microwave Power
• Power
– This is a 700 watt oven
– Think of 7 x 100 watt light bulbs
Microwave Electric field
• 700 watts
– Around 140 000 volts per metre
– Look what happens to a CD
Microwave Intensity
– Between 104 to 105 watts per square metre
– (Most intense sunlight around 103 watts per square metre...
Microwave Oven
SAR inside oven
• 700 watts absorbed in 1 kg of water:
– SAR = 700 watts per kg
• Question: After 1 minute,...
Experiment
Microwave Ovens
Comparison with handsets
SAR Watts
per kilogram
Temperature
Rise in 1 kg of
‘Brain Fluid’
Microwave 700 8 ...
Back to Mobile Phones
3b. Mobile Phone SAR
New StyleOld StyleMobile Phones (14)
SAR and Safety
Mobile Phones (8)
Your telephone
• Look in the small print!
Typical SAR with phone near the head
• SAR Averaged over 10 grams
• By law must be less than 2 watts per kilogram
Power In...
Base Station SAR
Base Stations
• Power
6 degrees
50 m to 200 m
Base Station Information
http://www.sitefinder.ofcom.org.uk/
EIRO
Equivalent
isotropic
Radiated
Output
Actual Pattern of
Emitted Radiation
60 W
How this is specified
Mast near my children’s old school
Power
• 30 dBW
• 1000 W
• Equivalent isotropic
Radiated Output
• 60 W to 120 W in
actua...
Comparison of handsets
and base stations
• Base station SAR is extremely low
but you can‘t choose whether you want it or n...
Wireless Networking
• WiFi
802.11(b), 802.11(g), 802.11(n)
• Operates at 2.4 GHz
Power Intensity
(at 1 metre)
SAR
(at 1 me...
Comparison of handsets
and base stations and wi-fi
Power Intensity Maximum
SAR
Watts Watts per
square metre
Watts
per kilo...
4. Are Mobile Phones Safe?
SAR and Safety
Health Protection Agency
• Based on ICNIRP guidelines
http://www.icnirp.de/documents/emfgdl.pdf
Internation...
What are the risks?
• Basic safety assumption is that the main effect of
exposure to microwaves is thermal
• Are there ‘no...
Are mobile phones safe?
Stewart Report
• A group of non-industry related experts
Gave rise to MTHR
Mobile Telecommunicatio...
Stewart Report
Mobile Phones and their
networks are ‘pretty’ safe
There may
be ‘effects’
Precautionary
Approach:
More rese...
Mobile Phones
Suppose we discovered ‘an effect’:
What might it look like?
Nora D. Volkow, Dardo Tomasi, Gene-Jack Wang, Pa...
PET Scan
This device can see you think!
Glucose metabolism in this area appears
to have been affected
What could we do?
What should we do?
In smaller groups
• Please come up with some
questions, and suggestions
• We will gat...
On-line
Resources
• www.protonsforbreakfast.org
This PowerPoint ™ presentation.
Handouts as a pdf file
• blog.protonsforbr...
See you next week to
discuss Nuclear
Power
Goodnight
Mobile Phones
Unused Slides
Perception of risk
Risk is expressed mathematically,
but our judgement of risk is not mathematical
More willing
to take ri...
Electromagnetic
waves
Electricity
Heat
How it all fits together…
Atoms
A Cautionary Tale
Don’t try this at home!
August 14, 2002 I don't want to sound like I know everything in the world or
eve...
Mobile Phones
Suppose we discovered ‘an effect’:
What might it look like?
R Luria, I Eliyahu, R Hareuveny, M Margaliot, N,...
No Match
Click with Left Hand


 
Match
Click with Right Hand
 

Task Completed with
Phone
On LEFT
On RIGHT
OFF
RESULTS
700
750
800
850
900
950
1000
1050
1100
1 2 3 4 5 6 7 8 9 10 11 12
SHAM
LEFT EXPOSURE
RIGHT EXPOSURE
ResponseTime:m...
RESULTS
With Uncertainty
700
750
800
850
900
950
1000
1050
1100
1 2 3 4 5 6 7 8 9 10 11 12
SHAM
LEFT EXPOSURE
RIGHT EXPOSU...
What could we do?
• Ban mobile phones ?
The ‗Precautionary principle‘
Could there be some harm caused?
How many lives are ...
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Pfb17 week5-presentation

  1. 1. Protons for Breakfast Are Mobile Phones Safe? Week 5 March 2013
  2. 2. In the event of…In the event of a new ice age…
  3. 3. This evening… 0. The Media! 1. How do mobile phones work? What is the hazard? 2. How do electromagnetic waves interact with matter? 3. SAR • Microwave Ovens • Mobile Phone 4. Are mobile phones safe?
  4. 4. The word ‘radiation’ • The word ‗radiation‘ means Anything which ‘radiates’ on ray-like paths • Could be Sound Radio Light Infra-red light Particles or waves emitted from the nuclei of atoms Nuclear Radiation
  5. 5. Media
  6. 6. Media
  7. 7. Sunday, 20 January 2008 It also complements other recent research. A massive study, following 1,656 Belgian teenagers for a year, found most of them used their phones after going to bed. It concluded that those who did this once a week were more than three times – and those who used them more often more than five times – as likely to be "very tired".
  8. 8. 1. How do mobile phones work?
  9. 9. Magic? Any sufficiently advanced technology is indistinguishable from magic Arthur C. Clarke
  10. 10. Not magic • Mobile Phones are ‗radio‘ phones • Operating at microwave frequencies • Handset power minimised by having a network of local transmitters and receivers • 52,500 base stations in UK Roughly hexagonal cells Mast • Each colour represents a base station operating at a slightly different frequency
  11. 11. Mobile Phones (3) Recognise the masts? • Each cell has a transmitter and receiver mast • Notice the typical three way structure
  12. 12. 3G Masts Photo Credit Brighton and Hove Green Party
  13. 13. Linking to base stations • Mast power between 60 watts and 120 watts • Handset power less than 1 watt • Handset sends signals every few minutes to establish which is the nearest mast • A central computer • keeps track of all the telephones that are switched on • remembers which cell they are in
  14. 14. Making a mobile-to-mobile call Its complicated! Network Control Knows in which cell every telephone is Originating Telephone Receiving Telephone
  15. 15. 2G or GSM phone Hello! How are you? Sound 217 pulses of encoded sound every second No sound: No signal Encoding to Radio Signal Hello! How are you? Peak Power 2 W Maximum Average power is 0.25 W Maximum Global System for Mobile Communications
  16. 16. 2G or GSM phone Base station Transmitter Frequencies (MHz) Handset Transmitter Frequencies (MHz) Peak Handset Power (Watts) Originally licensed to GSM900 935 - 960 890-915 2 O2 (Tesco) Vodafone (Asda) GSM1800 1805-1880 1710-1785 1 Orange T Mobile (Virgin)
  17. 17. Anatomy of a GSM Signal
  18. 18. 2G or GSM phone 217 Pulses per second per telephone call 217 Pulses per second Each frequency channel can carry 7 calls
  19. 19. Safety • The safety issues surrounding mobile phones concern… • the interactions of the microwaves emitted by mobile phones base stations with human tissue 6 degrees 50 m to 200 m
  20. 20. And its not just mobile phones! • ‗WiFi‘ Wireless Networking • Bluetooth devices • Wireless keyboards and mice • DECT cordless phones • Baby Monitors • ‗Walkie Talkie‘ • All involve electromagnetic waves in the radio and microwave part of the spectrum
  21. 21. 2. How do electromagnetic waves interact with matter? ?
  22. 22. Electromagnetic spectrum 1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 Radio & TV Infra Red Microwaves Gamma- Rays X-Rays Ultra Violet Microwaves 0.8 GHz to 1000 GHz Non-ionising Radiation (generally not so bad) Ionising Radiation (generally bad) Frequency (Hertz)
  23. 23. Waves & Matter • When an electromagnetic wave interacts with matter… Some absorption Some reflection Some transmission
  24. 24. Summary • Electromagnetic waves interacting with matter can be Reflected, absorbed or transmitted • What happens depends on the frequency of the electric field the natural frequencies of the atoms and molecules • Microwaves emitted by mobile phone systems Are absorbed by human tissue
  25. 25. 1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 Radio & TV Frequency (Hertz) Microwaves Infra Red Ultra Violet X-rays Gamma Rays Electrons in Atoms Protons in nucleus Atoms in solids or molecules Entire molecules or parts of molecules Lighter particles Stronger forces Waves What vibrates?
  26. 26. Absorption demo Frequency •Well below the natural frequency •Not much absorption •Well above the natural frequency •Not much absorption •Near the natural frequency •Absorption
  27. 27. Waves & Matter • When electromagnetic waves are ‘absorbed’ … • Atoms jiggle faster: i.e. increase their temperature. Heat Electricity Electromagnetic waves Atoms
  28. 28. 3. How much energy gets absorbed? S.A.R. Specific Energy Absorption Rate
  29. 29. Terminology • Power watts • Intensity watts per square metre • Specific energy Absorption Rate (SAR) watts per kilogram
  30. 30. • 1 cm from 20 W source 20 W absorbed in hand Intensity 8000 watts per square metre SAR 200 watts per kilogram • 10 cm from 20 W source 2 W absorbed in hand Intensity 200 watts per square metre SAR 20 watts per kilogram • 1 metre from 20 W source 0.02 W absorbed in hand Intensity 5 watts per square metre SAR 0.2 watts per kilogram SAR: Example using light rather than microwaves
  31. 31. Microwave Hazard The potential hazard from mobile phones and other wireless devices arises from the absorption of microwave radiation Mobile phones • only emit a watt or two • so little power it makes experiments difficult Microwave ovens • emit a few hundred watts • makes experiments easy
  32. 32. Microwave Ovens 3a. Microwave ovens
  33. 33. Electromagnetic spectrum 1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 Radio & TV Infra Red Microwaves Gamma- Rays X-Rays Ultra Violet Microwaves Conventional Oven 200 °C Microwave Oven 2.45 GHz
  34. 34. 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.01 0.1 1 10 100 Absorbtion Frequency Absorption of microwaves by liquid water • Well below the natural frequency • Not much absorption • Well above the natural frequency • Not much absorption • Near the natural frequency • Absorption 2.45 GHz
  35. 35. Absorption (1) Too strong • If power were absorbed too strongly, Microwaves would only penetrate a short distance Surface would be heated Inside would remain uncooked 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.01 0.1 1 10 100 Lossofenergyinwaterat0C Frequency (GHz) Microwave ovens operate at 2.45 GHz
  36. 36. Absorption (2) Too weak • If power were absorbed too weakly, Microwaves would go right through No cooking 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.01 0.1 1 10 100 Lossofenergyinwaterat0C Frequency (GHz) Microwave ovens operate at 2.45 GHz
  37. 37. Absorption (3) • If power is absorbed just right, Microwaves penetrate about 5 cm (2 inches) Cooks the outer 5 cm of the food Good enough for most cases 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.01 0.1 1 10 100 Lossofenergyinwaterat0C Frequency (GHz) Microwave ovens operate at 2.45 GHz
  38. 38. Microwave Ovens Summary • A microwave oven cooks food by heating it • The heating comes from • intense waves at 2.45 GHz • (Instead of a wide spectrum of waves at infra red frequencies) Frequency chosen because of absorption properties of water molecules at that frequency.
  39. 39. Microwave Ovens Inside a microwave oven
  40. 40. Microwave Power • Power – This is a 700 watt oven – Think of 7 x 100 watt light bulbs
  41. 41. Microwave Electric field • 700 watts – Around 140 000 volts per metre – Look what happens to a CD
  42. 42. Microwave Intensity – Between 104 to 105 watts per square metre – (Most intense sunlight around 103 watts per square metre) – Very Dangerous Could I have a stupid volunteer please?
  43. 43. Microwave Oven SAR inside oven • 700 watts absorbed in 1 kg of water: – SAR = 700 watts per kg • Question: After 1 minute, how hot would your brain become if subject to an SAR of 700 watts per kg?
  44. 44. Experiment
  45. 45. Microwave Ovens Comparison with handsets SAR Watts per kilogram Temperature Rise in 1 kg of ‘Brain Fluid’ Microwave 700 8 ºC (ish) Mobile Phone 1 Can‘t be measured directly Expect 1/700 of microwave temperature rise The effects of blood flow reduce this further 0.01 °C (ish)
  46. 46. Back to Mobile Phones 3b. Mobile Phone SAR
  47. 47. New StyleOld StyleMobile Phones (14) SAR and Safety
  48. 48. Mobile Phones (8) Your telephone • Look in the small print!
  49. 49. Typical SAR with phone near the head • SAR Averaged over 10 grams • By law must be less than 2 watts per kilogram Power Intensity Maximum SAR Watts Watts per square metre Watts per kilogram 1 200 1 • Typical figures
  50. 50. Base Station SAR
  51. 51. Base Stations • Power 6 degrees 50 m to 200 m
  52. 52. Base Station Information http://www.sitefinder.ofcom.org.uk/
  53. 53. EIRO Equivalent isotropic Radiated Output Actual Pattern of Emitted Radiation 60 W How this is specified
  54. 54. Mast near my children’s old school Power • 30 dBW • 1000 W • Equivalent isotropic Radiated Output • 60 W to 120 W in actual power 1000 W EiRO Actual Pattern of Emitted Radiation 0.3 Watts per square metre 0.01 Watts per square metre SAR 0.001 Watts per kilogram
  55. 55. Comparison of handsets and base stations • Base station SAR is extremely low but you can‘t choose whether you want it or not! Power Intensity Maximum SAR Watts Watts per square metre Watts per kilogram Handset 1 200 About 1 Base Station 60 0.01 About 0.001
  56. 56. Wireless Networking • WiFi 802.11(b), 802.11(g), 802.11(n) • Operates at 2.4 GHz Power Intensity (at 1 metre) SAR (at 1 metre) Watts Watts per square metre Watts per kilogram 0.1 Less than 0.01 About 0.0001
  57. 57. Comparison of handsets and base stations and wi-fi Power Intensity Maximum SAR Watts Watts per square metre Watts per kilogram Handset 1 200 About 1 Base Station 60 0.01 About 0.001 Wi Fi 0.1 < 0.01 About 0.0001
  58. 58. 4. Are Mobile Phones Safe?
  59. 59. SAR and Safety Health Protection Agency • Based on ICNIRP guidelines http://www.icnirp.de/documents/emfgdl.pdf International Commission on Non-Ionising Radiation Protection determines what we believe is safe • How do they do that? • They determine a borderline safe level • Divide by 10 for occupational exposure • Divide by another factor 5 for general public exposure
  60. 60. What are the risks? • Basic safety assumption is that the main effect of exposure to microwaves is thermal • Are there ‘non-thermal’ effects? If so are they harmful? Normal thermal vibrations are much larger than vibrations induced by microwaves emitted by mobile phones. • Question of safety must be resolved by experiment Experiments are very hard
  61. 61. Are mobile phones safe? Stewart Report • A group of non-industry related experts Gave rise to MTHR Mobile Telecommunications and Health Research • ONGOING Research Program • Funded 50:50 government & industry
  62. 62. Stewart Report Mobile Phones and their networks are ‘pretty’ safe There may be ‘effects’ Precautionary Approach: More research please Children Driving
  63. 63. Mobile Phones Suppose we discovered ‘an effect’: What might it look like? Nora D. Volkow, Dardo Tomasi, Gene-Jack Wang, Paul Vaska, Joanna S. Fowler, Frank Telang, Dave Alexoff, Jean Logan, Christopher Wong, Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucose Metabolism Journal of the American Medical Association, February 23, 2011—Vol 305, No. 8
  64. 64. PET Scan This device can see you think! Glucose metabolism in this area appears to have been affected
  65. 65. What could we do? What should we do? In smaller groups • Please come up with some questions, and suggestions • We will gather these together and then ask the experts You decide!
  66. 66. On-line Resources • www.protonsforbreakfast.org This PowerPoint ™ presentation. Handouts as a pdf file • blog.protonsforbreakfast.org Links to other sites & resources Me going on about things
  67. 67. See you next week to discuss Nuclear Power Goodnight
  68. 68. Mobile Phones Unused Slides
  69. 69. Perception of risk Risk is expressed mathematically, but our judgement of risk is not mathematical More willing to take risk Less willing to take risk Example Benefits Direct Indirect Base Stations/ Mobile Phones Technology Familiar Unfamiliar Cars/ Mobile Phones Exposure Voluntary Involuntary Base Stations/ Mobile Phones Exposure Fair Unfair Poverty/ Wealth Exposure Personal Control No Personal Control Driver/ Pedestrian Consequence Not Dreaded Dreaded Cancer/ Broken bone
  70. 70. Electromagnetic waves Electricity Heat How it all fits together… Atoms
  71. 71. A Cautionary Tale Don’t try this at home! August 14, 2002 I don't want to sound like I know everything in the world or even like I know quite a lot. But you had a question regarding ―If a microwave oven door were to open while it was still on, what would happen? Could it hurt you?- JP‖ Well ..Having the thought process that I have, kinda how should I put it? ...Stupid? or inventive or even in-between. Well, my microwave door did happen to come off. Magic Chef 900-watt microwave. Well, I did my best to try to fix it but the hinge on one side did not attach properly, therefore having a gap between the door and the appliance. Being me (stupid) I wondered if it would burn fast or would it gradually warm up. I slid my finger between...You probably dying to hear what happened... But it didn't gradually warm up at all. It was instant heat! It didn't scar me or anything like that, but sure scared the H*** out of me to find out it got so hot so quick. I didn't get any blisters either. But it just burned like touching something hot on the tip of my finger being that is the only thing I put in. Well you know the old adage, "You learn from your mistakes", stands true. lol -
  72. 72. Mobile Phones Suppose we discovered ‘an effect’: What might it look like? R Luria, I Eliyahu, R Hareuveny, M Margaliot, N, Meiran Cognitive Effects of Radiation Emitted by Cellular Phones: The influence of exposure side and time Biolectromagnetics 30: 198-204 (2009) Possibility#1
  73. 73. No Match Click with Left Hand    
  74. 74. Match Click with Right Hand   
  75. 75. Task Completed with Phone On LEFT On RIGHT OFF
  76. 76. RESULTS 700 750 800 850 900 950 1000 1050 1100 1 2 3 4 5 6 7 8 9 10 11 12 SHAM LEFT EXPOSURE RIGHT EXPOSURE ResponseTime:milliseconds Block LEFT HAND RESPONSE 'No Match' RESPONSE 700 750 800 850 900 950 1000 1050 1100 1 2 3 4 5 6 7 8 9 10 11 12 SHAM LEFT EXPOSURE RIGHT EXPOSURE ResponseTime:milliseconds Block RIGHT HAND RESPONSE Match RESPONSE 1 hour 1 hour
  77. 77. RESULTS With Uncertainty 700 750 800 850 900 950 1000 1050 1100 1 2 3 4 5 6 7 8 9 10 11 12 SHAM LEFT EXPOSURE RIGHT EXPOSURE ResponseTime:milliseconds Block LEFT HAND RESPONSE 'No Match' RESPONSE 700 750 800 850 900 950 1000 1050 1100 1 2 3 4 5 6 7 8 9 10 11 12 SHAM LEFT EXPOSURE RIGHT EXPOSURE ResponseTime:milliseconds Block RIGHT HAND RESPONSE 'Match' RESPONSE Only these two points have statistical significance
  78. 78. What could we do? • Ban mobile phones ? The ‗Precautionary principle‘ Could there be some harm caused? How many lives are saved by mobile phones? • Reduce mobile phone power ? Increase the number of mobile phone masts • Reduce mast power ? Increase the mobile phone handset power Increase the number of masts • Ban mobile phone use while driving ? Done: has it been effective? • Nothing ?

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