What is Cycle: Definition and 673 Discussions

The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea (NH2)2CO from ammonia (NH3). This cycle occurs in ureotelic organisms. The urea cycle converts highly toxic ammonia to urea for excretion. This cycle was the first metabolic cycle to be discovered (Hans Krebs and Kurt Henseleit, 1932), five years before the discovery of the TCA cycle. This cycle was described in more detail later on by Ratner and Cohen. The urea cycle takes place primarily in the liver and, to a lesser extent, in the kidneys.

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  1. B

    I have a question if i have a oscillator pushing 7.8 Hz 144 Hz cycle

    I have a question if i have a oscillator pushing 7.8 Hz 144 Hz cycle top (polarity 288 Hz) 432 Hz bottom cycle ... What kind oscillator is this?
  2. R

    What is the significance of cycles and frequency in instrument specifications?

    Hello, I think it is very basic question and i could not able to figure it out anyhow. I have gone through an instrument material which working at 1000Hz. In that manual specifications, they have written about a setting 'cooling time --> 0-100 cycles'. there are also lot more options...
  3. R

    Compute Inversion of (143) Cycle

    Homework Statement Find an inversion of the following cycle (143) Homework Equations (143)^{-1} The Attempt at a Solution Could someone show me how do we compute this?
  4. G

    Understanding Brayton Cycle Temperatures: Finding Outlet Flow Rate"

    This is a general concern with finding temperature values at different processes in the cycle, however i do have an example i am stuck on, and can post that if needs be. anyway, if i was required to find the flow rate at outlet, which temperatures would i need to put in the SFEE as i know...
  5. B

    Show that in this fusion cycle, the energy released is about 30 MeV.

    Homework Statement http://pds24.egloos.com/pds/201201/22/94/f0095594_4f1af1d126bf3.png [Fusion cycle of the SUN] Show that in the fusion cycle, the energy released is about 30 MeV. Homework Equations The Attempt at a Solution Can you do this without any relevant information!? If you have the...
  6. F

    Does the Rankine Cycle really need a liquid phase?

    A question about Thermodynamics, if someone would help with that... I understand a steam engine that follows the Rankine cycle has basically 4 steps: (a) heating in a boiler; (b) expansion on a piston or turbine; (c) condensation; (d) pump back into the boiler. For many years I have been...
  7. M

    Reversible Carnot Cycle and Heat Engine

    Homework Statement A borehole produces 120kg/s of high pressure water at 165°C. A powerplant is to be designed to extract heat from the water, reducing the temp to 147°C. The plant which will initially be assumed to be reversible, will reject heat at 17°C to a river. Take 147°C as the highest...
  8. S

    How Do You Calculate Efficiency in a Carnot Cycle Involving Argon?

    Homework Statement its part VI) of a big problem, where: 0.12 moles of argon (40) undergoes the cycle abca described in the graph. Process ab lies on a 540k isotherm. In the previious 5 sub problems, i figured that: Tc=270k Qbc=670J (lost) Qca=400J (added) Wab=370J Wabca=100J...
  9. G

    Can any one explain Schuler cycle in Inertial Navigation System

    Can anyone please explain schuler cycle, please don not start explaining with same old pendulum with the length of radius of Earth stuff. why is it required ? what is that all about ?
  10. A

    Finding the period of a limit cycle

    Homework Statement We're considering the following special case of the Duffing oscillator, in the limit of small nonlinearity: \ddot x + x + \epsilon x^3 = 0. The problem asks us to find a conserved quantity, and use it to write the period as an integral. Then, to write it as a power...
  11. C

    Why is steam condensed in thermal power cycle?

    Why is this done? Wikipedia says that condensing the steam makes the cycle 'more efficient.' How is it more efficient? Why can't the de-energized steam be transferred to the boiler without condensing it?
  12. B

    Proving the Power of a Cycle in Disjoint m-Cycles: A Comprehensive Guide

    let π be a product of disjoint m-cycles. Prove that π is a power of a cycle? So this is like asking show that π = βx for some cycle β and pos. integer x. right? I don't know how to proceed on this except for the fact that the order of π is m. any hints please
  13. A

    Carnot Cycle: Reversibility Under Constant External Pressure

    An ideal, monatomic gas is going through a 4 step Carnot cycle. Step 1 is an adiabatic expansion. Step 2 is an isothermal expansion. Step 3 is an adiabatic compression. Step 4 is an isothermal compression. The whole cycle is reversible. My question is how would the cycle change if step 1 is done...
  14. V

    What is the Efficiency of an Ideal Monatomic Gas Cycle?

    Homework Statement A 1.00 mol sample of an ideal monatomic gas is taken through the cycle shown in the figure. The process A B is a reversible isothermal expansion where PA = 5.0 atm, PB = 3.0 atm, VA = 30.0 L, and VB = 50.0 L. (a) Calculate the net work done by the gas. (b)...
  15. D

    Borne Haber Cycle/ Lattice Enthelpy for KBr

    Homework Statement Draw the Borne Haber cycle for KBr Homework Equations The Attempt at a Solution so the energy required to make the K into gas is +89kJ/mol and it takes +420kJ/mol to take 1 electron from K it takes +112kJ/mol to make Br a gas it takes -342kJ/mol to give...
  16. D

    Calculating Maximum Cycle Temperature in Carnot Cycle | Homework Solution

    Homework Statement An ideal engine operating on the Carnot cycle with a minimum temperature of 25°C develops 20 kW and rejects heat a rate of 12 kW. Calculate the maximum cycle temperature and the required heat supply of the cycle. Homework Equations Qhot/Thot =Qcold/Tcold...
  17. J

    Imaginary Ideal Gas Cycle Proof

    Homework Statement Given an imaginary ideal-gas cycle. Assuming constant heat capacities, show that the thermal efficiency is η = 1 - γ[((V1/V2)-1)/((P3/P2)-1)] Since i can't show you the cycle we are shown that l Qh l = which is absolute value of the heat at high temperature =...
  18. T

    Calculating Energy Efficiency in a Cogeneration Power Plant

    Homework Statement A cogeneration power plant is operating in a thermodynamic cycle at steady state. The plant provides electricity to a community at a rate of 80 MW. The energy discharged from the power plant by heat transfer is denoted by \dot{Q}_{out}. Of this, 70 MW is provided to the...
  19. M

    Magnetic & Electric Fields: A Cycle of Change?

    A changing magnetic field creates a non conservative electric field. If the changing magnetic field is accelerating(2nd derivative in non-zero) the electric field must also be changing. Would this mean that the changing electric field is producing a magnetic field. Depending on the order of...
  20. C

    Medical Can Women Bleed from the Urethra During Their Menstrual Cycle?

    I have a question concerning the menstrual cycle. Is it possible for someone to bleed from the urethra instead of the vagina? And if so what is the cause? A friend claims that she bleeds the urethra when on her cycle but I to find out if it's true or not.
  21. Q

    Physics problem Thermodynamic cycle

    Homework Statement A mole of ideal gas with a temperature T1=300K is expanded isobarically until its volume is tripled .Then the gas gets colder isochorically until we reach the temperature we had in the beginning 300 K.Find the work of the gas. Hint : We have a thermodynamic cycle . Homework...
  22. T

    Understanding the Kreb Cycle and ATP

    Having some trouble understanding if the Kreb cycle is exergonic or endergonic? I know it has to be exergonic because it's releasing ATP?
  23. S

    Thermodynamics Help- Proving Carnot Cycle

    1. Please help with the following question. Given: A Heat engine goes through a Carnot Cycle as the following states: State 2 to 3: air compresses adiabatically (pressure increasing) State 3 to 4: air expanded under isobaric process State 4 to 1: air goes under adiabatic expansion process...
  24. B

    Saros cycle - from Greiner's book

    saros cycle -- from Greiner's book Hi, I'm having some trouble about the calculation of saros cycle in example 13.9 of Greiner's book "classical mechanics: system of particles and hamiltonian dynamics". I am confused about the factor "3" of eqn. (13.35). This equation is derived from (13.27)...
  25. L

    Thermodynamics closed cycle entropy cycle

    Homework Statement The figure below shows a plot of temperature T versus entropy S for the closed cycle of a particular heat engine (not necessarily an ideal gas) which consists of 3 processes and which operates between two heater reservoirs, a hot reservoir with temperature T1 and a cold...
  26. R

    What is tha graph of carnot cycle

    what is the graph of carnot cycle in P-V plane using black body radiation? given the internal energy U=aVT^4 where a is the stefan's constant and P=(1/3)aT^4. thank you
  27. Y

    Universe's full cycle: explosion - implosion

    While Universe now continue to expand due to the last BB, there is growing vacuum in the midst of it which with time will reach such tremendous value that the expansion will be stopped and the reverse process will start ?
  28. A

    Does the addition of a new vertex always guarantee a Hamiltonian path or cycle?

    Watching this lecture from nptel about NP completeness: http://www.youtube.com/watch?v=76n4BjlL1cs&feature=player_embedded -We have an algorithm, HC , which given a graph tells us whether or not it has a hamiltonian cycle. -We want to use it in order to create an algorithm that determines...
  29. I

    Thermodynamic cycle related problem

    Homework Statement The problem is as following: Homework Equations \Delta E = \Delta Q-\Delta W The Attempt at a Solution Now I know that if work is done by the system then work sign is negative and that if volume remains unchanged then no work is done. Am I right to say that Internal...
  30. M

    Entropy change in carnot cycle

    Is it true that for a Carnot cycle, the entropy change for the whole system (engine plus the two reservoirs) would add up to zero? I am reasoning that it would, by the Clausius theorem that for a reversible cycle (which a Carnot cycle is), the entropy change is zero. Otherwise it would not be...
  31. K

    Cycle Permutation: Composition of (12345)(12345)

    I feel like I'm doing this correctly but my professor gave us an answer that is different from what I'm getting. Composition of (12345)(12345) Reading right to left I get (13524) but the answer he gives is (135)(24) The odd thing is I'm getting the rest of these correct so I don't feel...
  32. V

    Which thing determine friction in tyres of cycle?

    Hello guys. first question. you must have done cycle ride. It's our common experience that when air pressure inside tires reduced it becomes harder to ride. But as usual my question is why it is so why we need to apply more force(more likely torque ).?? As it is written in highlighted letters...
  33. M

    Finding work done, heat in, and heat out over a reversible thermodynamic cycle

    1. Statement of the Problem One mole of a monatomic ideal gas is taken through the reversible cycle shown. Process bc is an adiabatic expansion, with P_b = 10.0 atm and V_b = 1.00E-3 m^3. Find a) the energy added to the gas as heat, b) the energy leaving the gas as heat, c) the net work done by...
  34. L

    How Does the Proton-Proton Cycle Result in the Formation of Helium?

    Homework Statement Dear members, In proton proton cycle, Two protons fuse together to form a duetron with positron and nuetrino. Then duetron combine with another proton to form 2He3, which then combines with another 2He3 to give 2He4 The final reaction is 41H1+2e---> 2He4 Homework...
  35. S

    Otto cycle with polytropic compression and expansion (thermodynamics)

    Homework Statement attached as pdf (problem 1) (part b)Homework Equations w=p2v2-p1v1 / n-1 w=mR(T2-T1) / 1-nThe Attempt at a Solution I was able to determine the pressure and temperatures at all points, but to find the work i appear to need the volume, I also looked at w=h2-h1 but I am not...
  36. O

    Battery AH and Deep Cycle type & Charger suitability

    I am using this battery for a boat bilge pump. It's all working as expected, but what I am trying to determine is if my battery is suitable for the charger I have and if so, I need assistance decoding the CHARGING TIME chart (picture below) in my charger manual to determine how long I should...
  37. R

    Exploring Work Output of a Carnot Cycle

    Hi From http://en.wikipedia.org/wiki/Carnot_cycle "Reversible isothermal expansion of the gas at the "hot" temperature, TH (isothermal heat addition). During this step the expanding gas makes the piston work on the surroundings. The gas expansion is propelled by absorption of quantity Q1 of...
  38. S

    Short cycle on off timer plug-in

    I would like to use a timer to turn on and off a 220 Volt appliance. With a "mechanical" plug-in timer you have 20 minute granularity. But I would like to have a 1 minute resolution. For example - 1 minute off and 1 minute on. I bought a cheap 10 euro digital timer. I was mislead by the...
  39. A

    Understanding Carnot's Cycle & Reversible Processes

    Why is it so that along with reversible isothermic processes , reversible adiabatic processes must be taken up to complete carnot's cycle?
  40. PainterGuy

    What is Duty Cycle and How Does it Affect Motors?

    Hi I found these two definitions of duty cycle: 1: The duty cycle of a machine refers to how long it can keep operating before it needs a rest, or what percentage of the time it's designed to be in use. For instance, a machine gun might only be able to fire continuously for 100 rounds...
  41. J

    Ideal Hampson-Linde Cycle: a constant enthelpy device

    Homework Statement consider an ideal hampson-linde cycle in which no heat is lost to the environment. Argue that the combination of the throttling valve and the heat exchanger is a constant enthalpy device, so that the total enthalpy of the fluid coming in this combination is the same as the...
  42. P

    Help finding plans for a simple rankine cycle

    Hello, I am a complete novice and would like to build a simple closed loop rankine cycle that generate electricy, even if it only enough to power a light bulb. I want to learn more about thermal energy conversion in a hands on way, but I am having trouble finding any simple, easy to follow...
  43. T

    Compressed Air Engine for a cycle

    A friend and I are working on this idea which is fairly common, but I'm having trouble starting out. The idea is that of a compressed air engine. Where we take a normal, small capacity engine and modify it such that only compressed air, stored in tanks is sufficient to move the piston. Now...
  44. B

    Explain, briefly, what a hysteresis cycle is

    Homework Statement explain, briefly, what a hysteresis cycle is [2 marks] The Attempt at a Solution I don't think the answer is to draw a graph because that is the next question. The subject is electricity and magnetism but the above question does not refer specifically to electricity...
  45. S

    I have an engine cycle in mind looking for it's name

    This is a simple question I have because I am looking at a particular engine cycle, and I can't seem to think of its name...thus it is very difficult to search for discussions of something you don't know the name of. I'll describe the cycle, if anyone knows the name of the cycle please let me...
  46. A

    Theoretical electrodynamic cycle 2

    Here is a second thought experiment I designed to test if I understand certain concepts concerning electrostatics correctly. Help will be appreciated. There must be an error somewhere in the explanation below; I am giving the explanation as if “factual” only to explain how I understand it at...
  47. A

    Theoretical electrodynamic cycle 1

    I am casually working through Introduction to Electrodynamics, 3rd ed. by David J. Griffiths and created some theoretical situations to test my understanding of the subject matter. I am having difficulty with some, and will appreciate input. Consider the following theoretical cycle (see the...
  48. B

    Can it be easier to cycle uphill?

    I am a lay person trying to solve a bet. I contend that pedalling a bike uphill can easier than pedalling on a level plane at a 1:1 gear ratio, if: [a] The bike is put in a higher gear ratio such as 10:1 [b] The rider accepts travel at a reduced speed and therefore a longer duration ride, if...
  49. M

    T: What is the net work done by an Otto engine?

    Homework Statement Show that the net work done by the otto engine per cycle is Cv(Tc - Tb)(1 - Ta/Tb) PV diagram: [PLAIN]http://www.antonine-education.co.uk/physics_a2/options/module_7/topic_4/Otto_indic.gif Homework Equations Work done by a kmole of gas expanding irreversibly and...
  50. C

    Automotive Automotive application for absorption cycle?

    Hi there, I joined specifically to ask for help in exploring the possibility of harvesting the waste heat from a cars engine and recycling this energy to improve the engines efficiency. I'm assuming most people know about thermo dynamics, internal combustion and volumetric efficiency I:-p...
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