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Topics - Alberto Dominguez

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4
General Discussion / University Ranking to obtain job
« on: October 27, 2012, 06:13:27 AM »

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Electromagnetism / Maxwell's Equations
« on: October 07, 2012, 06:13:35 AM »

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Neurobiology / Some numbers...
« on: September 30, 2012, 07:16:51 AM »
From human brain and always approximate:

Number of Neurons: 100.000 millions
Number of Glial Cells: 1.000.000 millions
Neurons size (Soma size): 0,01-0,05 mm
Axon length: 1mm-1m
Axon diameter: 1mm-25mm
Dendrite length: max 2mm

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Classical Mechanics / Resonance phenomena
« on: August 31, 2012, 08:29:21 PM »
Driven Harmonic Oscillators Equation

Periodic force with frecuency of vibration \omega:

F=F_{o}cos(\omega t+\alpha_{o})

Movement equation:

\frac{d^{2}x}{dt^{2}}+2\gamma\frac{dx}{dt}+\omega_{o}^{2}x=\frac{F_{o}cos(\omega t+\alpha_{o})}{m}

\omega_{o}^{2}=\frac{k}{m};\gamma=\frac{b}{2m}

x(t)=x_{h}(t)+x_{p}(t)

Transient solution (depends on initial conditions):

x_{h}(t)=Ce^{-\gamma t}sen(\sqrt{\omega_{o}^{2}-\gamma_{o}^{2}}t+\delta)

Steady State (independent of initial condition):

x_{p}(t)=\frac{F_{o}}{m\sqrt{(\omega_{o}^{2}-\omega^{2})^{2}+4\gamma^{2}\omega^{2}}}sen(\omega t+\alpha_{o}+\beta)

Solution:

x(t)=Ce^{-\gamma t}sen(\sqrt{\omega_{o}^{2}-\gamma_{o}^{2}}t+\delta)+\frac{F_{o}}{m\sqrt{(\omega_{o}^{2}-\omega^{2})^{2}+4\gamma^{2}\omega^{2}}}sen(\omega t+\alpha_{o}+\beta)

When \omega=\omega_{o} the Amplitude is maximum and if b=0 then it is infinite, so a not too great force can collapse an strong structure if this force is applied at this frecuency of vibration.  This is the resonance phenomena.  All materials or structures have several natural frecuencies (\omega_{o}) and they can enter into resonance.  Perhaps the most famous sample is the Tacoma bridge:


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General Discussion / Wheather on Mars
« on: August 25, 2012, 10:26:44 AM »
On this link we can see the atmospheric conditions on MARS:

http://cab.inta-csic.es/rems/marsweather.html



Atmosphere on Mars is very light and its average pressure is between 7 and 9 hPa versus on Earth we have 1013 hPa at sea level.  Also we can see that on the day of the pic, there was winds about 90 Km/h (25m/s).

Also the gravity on Mars is lower than the Earth, the Martian gravity is 38% of Earth's, thus its atmosphere is higher than Earth's.  Its composition consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon and contains traces of oxygen and water.

Martian sunset by Spirit at Gusev crater:



Source of pic: Wikipedia

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General Discussion / Schools and Workshops
« on: August 15, 2012, 10:10:36 PM »
Some links interestings about schools and workshops about Physics:


ETTORE MAJORANA FOUNDATION AND CENTRE FOR SCIENTIFIC CULTURE
Erice, Sicily - Italy

http://www.ccsem.infn.it/

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Biology / Equation of the life
« on: August 12, 2012, 02:26:54 PM »
Equation of the Life:



Diagram with Transcription process:



Diagram with Transcription and Translation process:


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Biology / Animal Cell Structure
« on: August 12, 2012, 02:22:11 PM »

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Biology / Life Cycle
« on: August 12, 2012, 02:13:50 PM »
One picture that I have created on my wife's Ipad that synthesizes the Cycle of the Life in our Universe:



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Astronomy and Astrophysics / Journey to the Starts
« on: June 30, 2012, 10:28:11 AM »

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General Discussion / Einstein Archives Online
« on: March 21, 2012, 08:47:38 PM »

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