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.

View More On Wikipedia.org
Recent contents Top users
  1. L

    Exploring the Saros Cycle: Predicting Eclipses Through Time

    Hey guys. I was wondering, does the period of the Saros cycle stay the same across all time? for example, using the saros cycle could you accurately predict eclipse times thousands of years into the past or future?
  2. B

    Closed cycle rankine cycle engine using alternative fluid.

    I have a solar heat source that will deliver between 80 and 120C temperatures. I want to power a steam engine with this heat but obviously, when the source is below 100C I won't get any power generated. I have considered instead of using water in the steam engine, ethanol. On the output side...
  3. C

    Solving a Rankine Cycle Problem with 45MW Output

    Homework Statement Can anyone help with this particular question Using a steam power plant that operates on a simple rankine cycle and has a net power output of 45MW. Steam enters the turbine at 70 bar and 500 degrees c and is cooled in the condenser at a pressure of 110kPa by running...
  4. C

    Finding Heat and Work in a Three-Step Gas Cycle

    Homework Statement A monatomic ideal gas has pressure p_1 and temperature T_1. It is contained in a cylinder of volume V_1 with a movable piston, so that it can do work on the outside world. Consider the following three-step transformation of the gas: 1. The gas is heated at constant...
  5. P

    Lattice Energy and the Born Haber Cycle

    Ok most questions (that I have come across) when dealing with the Born Haber Cycle give the Sublimation energy, the Dissociation energy, the Electron Affinity, the Ionization Energy, and the Formation Energy. I know that to get the Formation Energy it is: Hf= Hs+Hi.e.+1/2Hd+He.a.+U (Lattice...
  6. P

    Lattice Energy and the Born Haber Cycle

    Ok most questions (that I have come across) when dealing with the Born Haber Cycle give the Sublimation energy, the Dissociation energy, the Electron Affinity, the Ionization Energy, and the Formation Energy. I know that to get the Formation Energy it is: Hf= Hs+Hi.e.+1/2Hd+He.a.+U (Lattice...
  7. A

    Smallest cycle time for electronics

    Hi, I'm just getting properly into electronics. I'm curious as to how fast an analogue circuit can operate. I'm trying to make a circuit which can send an ultrasonic pulse but I need the pulse to operate only for 1/100th of a millisecond. Is it practical or even possible for ordinary...
  8. G

    Thermodynamics Otto Cycle engine

    I'm trying to estimate the temperature of combustion in an Otto Cycle engine, using a formula based on the First Law: T4 = T3 + fQ /cv Where T4 is the combustion temperature, T3 is the air temperature after compression, f is the fuel/air ratio, Q is the heat energy of the fuel, and cv is...
  9. W

    Solar Cycle & Explanation for Recent Changes?

    Is the Sun heading towards a Maunder Minimum? [PLAIN]http://science.nasa.gov/headlines/y2006/10may_longrange.htm[/URL] The following is an excerpt from the above link: The sun's "Great Conveyor Belt" And from the next link, it appears there was a failed solar magnetic field...
  10. M

    Organic Rankine cycle refrigerant expander?

    I am working on a project to design an organic Rankine cycle to convert low temperature thermal energy (waste heat or geothermal) into electrical energy. We are trying to select an expander to extract work from the pressure differential in the refrigerant. The refrigerant (ammonia or R134a)...
  11. radou

    Composing permutations in cycle notation

    I'm currently going through a text about groups, and I'm having problems with composing permutations written in cycle notation, i.e. there are lots of examples and I'm expected to be able to calculate them pretty 'fast', so, is there a way to 'read out' the composition of two permutations direct...
  12. H

    Thermo - Finite Carnot Cycle

    Homework Statement Specify that the finite reservoirs of a Carnot cycle start at initial temperatures T_h and T_c. Acknowledge the consequence of the finiteness of the reservoirs: the hot reservoir will drop in temperature and the cold reservoir will increase in temperature. The two...
  13. G01

    Carnot Cycle: Isothermal Expansion Phase - Work Done?

    Hi. I have a qualitative question about the work done from state 1 to state 2 of a Carnot cycle. This is the Isothermal Expansion Phase. Is work done by the engine on the environment during THIS PHASE ONLY equal to the energy extracted from the hot reservoir to keep the temperature constant...
  14. F

    Optimizing Motorbike Jump Over Slope: Solving for Minimum Speed

    Homework Statement http://img132.imageshack.us/img132/2847/img1dy7.jpg shows an 11.7 ft wide ditch with approach roads at an angle of 15 degrees.With what minimum speed should a motorbike be moving on a road so that it safely crosses the ditch.Assume the length of the bike to be 5 ft, and it...
  15. 2

    Servo motor duty cycle vs. supply voltage

    I have a servo motor that I'm controlling with a simple PID controller for a constant frequency square wave with varying duty cycle. My supply voltage is 5.17V with ~1V drop across my low side driver. The controller sits right around 50% duty cycle to keep the servo open to position A. A...
  16. M

    What chemicals are in generic 2 cycle motor oil?

    Does anyone have a list of the specific chemicals that are in off the shelf generic 2 cycle oils? Much appriciation if someone can give me an accurate list. Willing to compensate for an accurate list of chemicals and their chemical formulas.
  17. B

    Angular acceleration spin-dry cycle

    Just checking to see fi I did the math right: During the spin-dry cycle of a wash, the motor slows down from 95 rad/s to 30 rad/s while turning the drum through an angle of 402 radians. What is the magnitude of the angular acceleration of the motor? = 1/2(Wo + W)t 402 = 1/2(95 +...
  18. A

    Difference between carnot and rankine cycle

    difference between carnot and rankine cycle. pls give replys
  19. L

    Microchip (PWM) - difference between duty cycle and frequency

    Hey guys. Just trying to program a microchip. Trying to grasp the concept of PWM. I know that varying the duty cycle will vary the speed of my motors...but there are other registers that allow you to set the frequency of the PWM peripheral...NOw I'm getting confused...isn't the duty...
  20. M

    News Why is the US stuck in a Republican-Democrat cycle?

    I recently emigrated to the US, and was doing some research in school when I realized the cycle of Republicans and Democrats. A Republican comes into office and offers tax breaks, which raises his public repuatation, while at the same time affecting the economy effectively. Then a Democrat...
  21. T

    How does the Claude cycle Helium liquifier work?

    I've been working on problem 12-3 in Kittel and Kroemer's "Thermal Physics", and I'm not sure I fully understand what is going on here. As far as I can tell, the system being described is something like this: Gas leaves a compressor at (Tc, Pc) and enters a heat exchanger. The gas leaves...
  22. L

    Ideal Gas Cycle: N2 Undergoing abcd w/ Varying Pressures

    Two moles of N2 gas undergo the cycle abcd. The pressure of the gas in each state is pa = pd = 5500 Pa; pb = pc = 1500 Pa. Note that 5500 Pa > 1500 Pa. The volume of the gas in each state is Va = Vb = 1.80m^3 ; Vc = Vd = 8.70m^3. Note that 8.70 m^3 > 1.80 m^3. The gas may be...
  23. Amith2006

    Ideal gas undergoing cycle change - find temperature

    Sir, One mole of an ideal gas undergoes a cycle change as shown in figure. The process A-B is isothermal. The pressure and volume at A is 1.1 x 10^5 N/m^2 and 22.4 litres respectively. What is the temperature of the gas at C? If the temperature at one point was given the temperature at...
  24. K

    Exploring Advantages & Disadvantages of Superheated Steam Cycle

    does anyone knows what are the advantages and disadvantages of using a superheated steam cycle (i.e. effect of turbine blade)?
  25. M

    Carnot and renkine steam cycle

    Hello to all, this is my first post on this forum. I'm electrical engineer (technical informatics) but in my spare time I'm interested in thermodynamics especially about steam cycle in power plant. I know that condenser is meant to convert steam to water and here we have pure losses of...
  26. C

    The cycle of life? Fractal orbits and spin.

    Greetings, A thought occurs about a (possibly) fundamental pattern in nature. Why are there several scales of magnitude in which a smaller body spins, while orbitting a larger body? Examples. 1) A galaxy like the Milky Way has an orbital momentum around the core of its Local Cluster...
  27. P

    Calvin Cycle: Understanding Rubisco Structure & Mechanism

    I have been learning about the calvin cycle, and have been told that people think that ribulose bisphosphate is first converted into a 6 carbon sugar as a very short life intermediate, and then is converted to phosphoglyceric acid. Why can't you just synthesise rubisco, work out its structure...
  28. S

    Limit Cycle Analysis: Uncovering the Solutions of DEs

    i want to know that in qualitative analysis of differential equations why we give more importance to a limit cycle on any other trajectories to show the solution of a differential equation
  29. S

    Inertia of the Earth and my biological cycle

    Greetings nerds! Please just read the bold-style basic question at the end of the message if you don't care what my personal problems are. You'll find out soon enough... when I have summoned founds for my 0.27 billion rockets engines. I have this problem: My "biological clock", the part of...
  30. iansmith

    Dendritic cells and mouse cycle

    Lately in our lab, the DC have been growing more rapidly than usual (4 days vs 6 days). Our lab is new to cell culture but according another lab in our department has the same problem. It appears that the problem is seasonal and it start in early in the fall and ends around christmas. Does...
  31. V

    Efficiency of the Stirling Cycle: Examining the Debate

    I've calculated the efficiency of the Stirling cycle like \eta=\frac{R(T_H-T_L)\ln\left(V_2/V_1\right)}{RT_H\ln\left(V_2/V_1\right)+C_{mV}(T_H-T_L)} Where V_2>1. It's also derived http://www.pha.jhu.edu/~broholm/l39/node5.html" . But my ("Highschool", or secondary school) teacher says...
  32. K

    Understanding Otto Cycle: Calculating Cycles, Heat Input, and Efficiency

    Otto Cycle?? Please help ASAP! I have a question that my entire class is confused over. I need help on it for a test, but I have no idea where to go with it. It doesn't seem to fit any of the equations or situations I have been using. The question is: A four-stroke engine runs on the otto...
  33. C

    Otto Cycle - Thermodynamics - Efficiency

    Please help with the following question, completely lost: :yuck: The behavior of a four stroke gasoline engine can be approximated by the so-called Otto cycle. The process is as follows (6 steps): 1) Isobaric Intake (from V=0) at atmospheric pressure up to volume V1 (maximal volume)...
  34. Ivan Seeking

    Breaking the Cycle of Abuse: How to Cope With Emotionally Abusive Women

    I caught a bit on the Today Show that discussed the issue of emotional abuse. Anytime I see something like this it almost always focuses on women who are abused by men. But in my family there was plenty of abuse and it all came from the women - and it still does. Without meaning to start a war...
  35. K

    Thermodynamic Cycle: Calculating Heat Transfer and Work

    Sorry about the double post, I had technical difficulties that I was working on and the title of my orginal post got screwed up. I'm having problems getting started on this one. A gas undergoes a thermodynamic cycle consisting of 3 processes process 1-2 compression with...
  36. K

    Thermodynamic cycle problem

    I'm having problems getting started on this one. A gas undergoes a thermodynamic cycle consisting of 3 processes process 1-2 compression with pressure(p)*volume(V) = constant, from p_{1} = 1 bar V_{1} = 1.6m^3 to p_{2} = ? V_{1} = .2m^3 U_{2}-U_{1}=0 process 2-3 Constant...
  37. S

    Calculating Average Power in Motorcycle Engine at 4000 RPM

    In a motor cycle engine, after combustion occurs in the top of the cylinder, the piston is forced down as the mixture of gaseous products undergo an adiabatic expansion. Find the average power involved in the expansion when the engine is running at 4000 rpm, assuming that the gauge pressure...
  38. T

    Strange Limit Cycle: Unveiling a 3D Dynamics

    The 3D dynamical system introduced in the following site; http://www.geocities.com/tontokohirorin/mathematics/limitcycle/limitcycle2.htm shows not only chaotic behaviour, but also converges to a strange-shaped limit cycle under a certain parameter setting!
  39. B

    Carnot Cycle and Adiabatic process

    I have a question regarding Carnot Cycles and Adiabatic processs. I have cylinder with n moles of a mono-atomic gas with a specific Volume, Pressure and Temperature. This Cylinder is closed by a piston. This system undergoes the four step Carnot Cycle A-B, B-C, C-D and D-A. A-B: Is...
  40. S

    NIH Factor in American Companies: Why Does It Exist?

    Has an otto cycle engine been developed which gives a non pulsed output?
  41. W

    Einstein Cycle: Analysis of Low Temperature Refrigeration Performance

    I'm sure most of you have heard of the Einstein Referigeration Cycle . For those who have not I've listed the references for further reading.. http://www.me.gatech.edu/energy/pubs/SLA_2.pdf ok 342 K is about 156 F ,for anyone with an attic , it seems to me that this is the perfect solution to...
  42. K

    A different Brayton Cycle concept.

    This is a revisit of a site that we have seen in the past, but there has been some updating and it looks promising. This is definitely not what most have in mind when they talk about the internal combustion (re. Otto/Diesel cycle)engine and list the limitations of it. In fact, it's not even...
  43. S

    Efficiency of Brayton Cycle with Reduced Pressure & Temp

    In brayton cycle, the initial temperature and pressure before compression is less than the final temperature and pressure after work has been done by the hot gases. If the final temperature and pressure is made less than the initial temperature and pressure, would it reduce the efficiency of...
  44. S

    Schematic of the basic rankine cycle

    Thermodynamic -------------------------------------------------------------------------------- A)Draw a schematic of the basic rankine cycle and its equipment B) ddiscuss any three practical improvements to make the basic rankine cycle more efficient, hightlighting the benefit that is...
  45. R

    2 cycle engines (& dyno)

    I have a couple of questions about 2 cycle engines: 1) Can someone further explain “time-area” to me in regard to the 2 cycle engine porting? I do grasp the basic concept of time-area values and I do have a formula to calculate the time-area values for a 2 cycle engine however there is still...
  46. Z

    How Does a Carnot Refrigerator Work Between Different Temperatures?

    hey everyone, I need some help solving the following problem. I am kind of confused on where to start. here is the question from the book. A carnot refrigerator is operated between two heat reservoirs at temperatures of 320K and 270K. a) If in each cycle the refrigerator receives 415J...
  47. J

    Part B: "150W Engine Efficiency - Heat Given off Per Cycle

    An engine with an output of 150W has an efficiency of 25%. It works at 10 cycles/s. A. How much work is done in each cycle? work=power(delta t) = 150 W * 1s = 150 J work =15.0 J per cycle **got part A correct B. How much heat is given off in each cycle? delta...
  48. F

    Having problems with a thermo. cycle

    Having problems with a thermo. cycle! OK, so in the problem A->B is isobaric, B->C is adiabatic, C->D is isothermal, D->A is isochoric. Pa = 2atm, Va = 2 m^3, n = 1mole, Vb = 1/2Va, Pa = 2Pd (That is all the information that is given.) I always end up with the temperatures of B and C...
  49. S

    Finding Heat Flow in a Brayton Cycle for Helium

    The question gives a picture of a brayton cycle with temperature on the x-axis and pressure on the y-axis. It is for the monatomic gas, helium, and we are told that there are two moles. The diagram consists of two adiabatic processes and two isobaris processes. You are given two temparatures...
  50. C

    Solving the Otto Cycle Ideal MEP Query

    Hi everyone. Sorry... I hope I don't bore you all - I fear this thread will be nowhere near as interesting as the most recent one on this forum on why aircraft fly! Anyway, I have a question relating to the Otto cycle - I'm revising my thermodynamics for an exam and on 1 of the past papers it...
Back
Top