# What is Retardation: Definition and 20 Discussions

Alpha-thalassemia mental retardation syndrome (ATRX), also called alpha-thalassemia X-linked mental retardation, nondeletion type or ATR-X syndrome, is an X-linked recessive condition associated with a mutation in the ATRX gene. Males with this condition tend to be moderately intellectually disabled and have physical characteristics including coarse facial features, microcephaly (small head size), hypertelorism (widely spaced eyes), a depressed nasal bridge, a tented upper lip and an everted lower lip. Mild or moderate anemia, associated with alpha-thalassemia, is part of the condition. Females with this mutated gene have no specific signs or features, but if they do, they may demonstrate skewed X chromosome inactivation.

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1. ### Constant frictional resistance & retardation

What the question mean by "constant frictional resistance" in terms of formula? I suppose they meant... "resistance force (f)" which is, >> f = m * a. So, here is my try... m = 1.15 ton or 1150 kg vi = 20 m/s vf = 0 d = 800 m v^2 - u^2 = 2ad 0 - 20^2 = 2a* 800 - 400 = 2a* 800 - 400 /...
2. ### B Resistive force that a nail will have to overcome to penetrate a piece of wood

lets say a hammer of 0.5kg strikes a nail at 10m/s. The nail penetrates into the wood by 1cm. The reason why the nail stops is because friction has eventually overcome the nails momentum. The retardation of the nail can be worked out, but Can you calculate the force that stops the nail if you...
3. ### MHB Train Journey: Acceleration, Retardation & Distance Calculations

a train accelerates uniformly from rest to a speed v m/s with uniform acceleration a m/s^2 it then decelerates uniformly to rest with uniform retardation 3a m/s^2. the total distance traveled is s metres. if the average speed for the whole journey is square root (s/2) find the value of a. does...
4. ### Electromagnetic Fields due to Accelerating Charge

Homework Statement What are the electric and magnetic fields due to a charge that is moving with uniform acceleration? (Non relativistic) Homework Equations Retarded solutions for the vector and scalar potentials. The Attempt at a Solution My attempt might be an overkill because I'm using the...
5. ### How Does Quartz Crystal Retardation Change with Thickness?

Homework Statement [/B]Quartz is positive uniaxial crystal with ne (extraordinary axis) = 1.553 and no (ordinary axis) = 1.554. A) determine the retardation per mm at lambda (wavelength) when the crystal is oriented such that retardation is maximized. B) At what thickness(es) does the...
6. ### Partition Coefficient and Retardation Factor

Homework Statement Homework Equations Rd = retardation factor = (1 + (ƥbKd / n)) log(Koc) = -0.55logS + 3.64 Kd = Koc*foc The Attempt at a Solution Part C is the only part I feel sure on. I simply plugged 1480 mg/L into the log(Koc) equation above to solve for Koc. Then I multiplied Koc...
7. ### Solve Retardation Problem: 25m from Traffic Light

Homework Statement A driver applies brakes on seeing a traffic signal 400 m ahead. At the time of applying brakes the vehicle was moving with 15m/s and retarding with 0.3m/s2. The distance of the vehicle after 1 min from the traffic light is? A) 25m B) 375m C) 360m D) 40m Homework...
8. ### Evaluating an integral for an expanding, charged sphere

Homework Statement An expanding sphere, radius ##R(t) = vt## (##t>0##, constant ##v##) carries a charge ##Q##, uniformly distributed over its volume. Evaluate the integral Q_{eff} = \int \rho(\vec{r},t_r) d\tau with respect to the center. (##t_r## is the retarded time and ##d\tau## is an...
9. ### Is there a difference between negative acceleration and retardation

Kindly elaborate on the difference between negative acceleration and retardation...if they are different
10. ### Find the least acceleration and least retardation?

A car is traveling at 10 m/sec. When it is 40 meters from a crosswalk, there is still 3 seconds before the light changes to red. The driver has two choices: the first is to accelerate to reach the crossing before the light changes to red and the second is to try to stop at the light. What is the...
11. ### Cross Polarizers with a wave plate retardation

Homework Statement "Consider a wave plate with a retardation τ=(η_0-n_e)*w*L/c. Show that when it is placed between crossed polarizers with its optical axis at an angle of θ with respect to the polarizer axis, the transmitted intensity is given by: I_out/I_in= (sin^2(2θ)(sin^2(τ/2)) In...
12. ### Experimental proof of retardation in EM fields

In the light that QED suggests the speed of interaction is infinite, are there any experiments which makes it clear that mediating fields are retarded in classical electrodynamics ? Whereas, on the theoretical grounds the causality requires time assymetric interaction, but do we have any...
13. ### Show that the wheel has constant retardation using calculus

Homework Statement I am required to use calculus to show that a flywheel has constant retardation Prior to this I have found the initial angular velocity which is 60rad/s and the angular velocity after 2s which is 58.667rad/s Homework Equations pi=60t-(t^2)/3 dpi/dt = 60 - 2t/3...
14. ### Particle Motion: Retardation & Arithmetic Progression

Homework Statement A particle moves in a straight line away from a fixed point O in the line, such that when its distance from O is x its speed v is given by v=k/x , for some constant k. (a) show that the particle has a retardation which is inversely proportional to x3 The answer is...
15. ### Linear Motion - Minimum Retardation to Avoid Crash?

First post! I would be grateful if anyone could give me any advice on this particular type of problem (i.e min retardation to avoid a crash). I'm not necessarily looking for the answer to this specific question, I would rather if someone could point me in the right direction as to how to go...
16. ### Retardation of a Balloon's Vertical velocity

Because I am working quite a lot with balloons (still theoretically though), I have come across reports of some balloon flights in the 19th century, which gave balloon ascent speeds of up to 15 m/s and descent speeds up to -40 m/s. I agreed to the comment to that text, that normally balloons...
17. ### Relaxation and retardation time for polymeric liquids

Hi all, I am wondering what the typical values of relaxation and retardation time for different real materials? I know these times depend on quite a number of things. But I just want to have a sense of the ratio of the two time scales for different real materials like blood, cervical mucus and...
18. ### Medical What is the I.Q. cutoff forn mental retardation?

I am worried that I could be borderline mentally retarded because when I was 17 years old, I took an I.Q. test that qualified me for special eductation classes after it was discovered that I had a learning disability in math. My overall I.Q. score was 89, which is very low, but is that...
19. ### Are we closer to reversing mental retardation?

http://www.sciam.com/article.cfm?chanId=sa003&articleId=6901F70B-E7F2-99DF-3648F0789D1EC063" With these new findings should we be expecting new drugs out on the market in the near future to reverse mental retardation? Discuss.
20. ### Birth Defects in Biology: Understanding Mental Retardation

We were learning about birth defects in Biology. Stuff about genetics like Down Syndrome, Mobius, that usually lead to an extra/less chromosome causing retardation. Is there a way one can become mentally retarded? I mean, without multiple concussions or whacks/impacts to the head...