• Felix Guerrero asked a question:
    Can one isolate polysomes without an ultracentrifuge?

    I have a floor centrifuge but it only goes up to 25,000 g. My old protocol requires an ultracentrifuge and 40,000 g, but it is non-functional. I am assuming I can spin at 25,000 g for longer time, but thought I would ask in this forum.

  • Ulrich Sollmann asked a question:
    How do physicians at TCM hospitals face their patients so that they are experienced as more empathetic?

    for example: nonverbal communication, facial expression, time and so on

  • Pradeep Jaswani asked a question:
    How much chemotherapy is essential after surgical resection in a second stage patient of breast cancer?

    if any female of age between 25-30 yrs had a second stage breast cancer since last one year, then how much amount and how many chemotherapy is essential for her, she also had a problem of unbalanced monthly chroming (not in time)

  • Ahmed Dhamad added an answer:
    As a part of preparing TBE buffer, can we keep the EDTA solution after preparing it for a week before autoclaving it?

    Hi every one, I am going to prepare a TBE buffer, and the EDTA preparation takes a long time, so can I keep the EDTA without autoclaving for a long time until I get ready to do so.

    Ahmed Dhamad · University of Arkansas

    Hi Muna, Yes, you can 

  • Leonard Goeirmanto added an answer:
    Do children procrastinate?

    Our study on procrastination is trying to work with vulnerable populations this time. I haven't still come across any finding on procrastination among children population. What will be the best method to study this behaviour among children? 

    Leonard Goeirmanto · Universitas Mercu Buana

    some references maybe can help you:

    Procrastination, academic success and the effectiveness of a remedial Program    DOI:10.1016/j.jebo.2014.12.007

    The Relationship of Procrastination and Self-efficacy with Psychological Vulnerability in Students           DOI:10.1016/j.sbspro.2013.12.797

    Procrastination and Self-efficacy: Tracing vicious and virtuous circles in Self-regulated Learning      DOI:10.1016/j.learninstruc.2013.09.005

    Mediating perceived parenting styles–test anxiety relationships: Academic Procrastination and maladaptive Perfectionism     DOI:10.1016/j.lindif.2014.05.004

  • Israa Albarazanchi added an answer:
    Can i use omnetpp-4.6-src-windows with inet-2.99.0-src.tgz and Castalia-3.3 ?

    if install the versions of all this program together ,, is it ok ?  because some times we must use older version ... i would like make sure no problem will happen .

    Israa Albarazanchi · Technical University of Malaysia Malacca

    depend this page  http://inet.omnetpp.org/index.php?n=Main.Download

    i must choose INET 2.5.0 for OMNeT++ 4.6 , but the manual recommend INET  2.9 ?? wt i choose ?

  • Diego Luis Guarin added an answer:
    How can I use pdf in Matlab to plot a graph?

    I have time period values on the X-axis and the probability of an event occurring at a particular time on the Y-axis.

    Diego Luis Guarin · McGill University

    You need to expand the question, it is not clear what you want to do. Maybe try the function 'hist', I think that is what you are looking for. 

  • Sh. Arshadnejad added an answer:
    Is there an equation relating time and concrete strength?

    Is there an equation relating time and concrete strength?

    Sh. Arshadnejad · Islamic Azad University

    Hi,

    You can find a general model to predict of concrete strength in due time, in a reference book about concrete. It is Concrete properties by Professor Novill.

    Thanks a lot

  • Junfu Bu added an answer:
    How can I determine the parameters to prepare a pellet?

    I wanted to prepare a pellet from a powder using a uniaxial press and a matrix attached to a pump, but with the pressure and the holding time that I have chosen, the pellet obtained breaks up.
    Are there a way to determine the correct pressure and holding time before launching tests?

  • Vijayakumar Narne asked a question:
    What kind of Average for FFR data across subjects should be done?

    When averaging FFR data across all subjects (grand Average). Should time waveform be averaged (Time Domain Averaging) or FFR spectrum be averaged (Spectral Averaging).

    In some of books it is been stated that "time-domain averaging will reduce the noise more compared to Spectral domain averaging". Is this also applicable across subjects or only within subject.

  • Ahmed Dhamad asked a question:
    How many times can we use GE Healthcare GSTrap FF, 1 ml?

    How many times can we use GE Healthcare GSTrap FF, 1 ml, which is an affinity chromatography column that can capture GST taged-protein ? 

  • Stephen Warren added an answer:
    Is the flow of time an illusion?
    This has been discussed on ResearchGate in a rather ad hoc way in relation to another question about the absolute immutability of some physical laws but it really deserves its own separate discussion. Below I summarise the arguments in favour.
    The philosophers
    The nature of time has been the subject of discussion by philosophers for 2000 years or more. In the last two decades their views have crystallised. If time flows - (1) How do we know? and (2) How do we measure its speed? In other words - what frame of reference can we use to measure time?
    The philosophers' conclusion is that they would have to invent another time dimension for the purpose but this would then need a third time dimension and so on ad infinitum. This would be absurd and so they conclude that the flow of time is an illusion.
    Relativity, Einstein and Godel (A World Without Time - Palle Yourgrau - Penguin Books, 2005)
    According to the theories of relativity two observers can never agree on the simultaneity of two events that both witness and neither has a "preferred" position that makes one of them correct. This implies that all events already exist and that what we perceive as the flow of time is an illusion.
    Godel showed that rotating universes were consistent with relativity and proved that in them it was possible to travel back in time. He immediately realised that this implied that the past must still exist and that what he called "intuitive time" is therefore an illusion. In 1949 he published a formal proof that time (in our intuitive sense) cannot exist in any universe. This uncomfortable discovery was ignored for nearly half a century but was revived by Julian Barbour in "The End of Time" and is now widely discussed and accepted by many physicists.
    The Laws of Physics
    The fundamental laws of physics describing the forces are time-symmetric.
    What can we say about the time dimension?
    Time still exists but only as a chronological map in which events are located;
    Time is not in any way like the spatial dimensions because:
    It is anisotropic and contains an entropy gradient;
    If we exist in more than one location in any of the spatial dimensions then we will also always then be in different locations in the time dimension;
    Separations in 4 dimensions are extensions of Pythagoras's Theorem but have the form:
    separation = √[x2 + y2 + z2 - (ct)2], which means that time measurements are imaginary (ict) where i=√(-1), as Hawking suggests in "A Brief History of Time".
    Consequences
    Free will is also an illusion
    We live all our lives all the time but every instant feels like "now"
    Time travel is impossible because (a) there is no dimension in which travel is possible, (b) we occupy all the spacetime of our lives and cannot take back to an earlier time our memories of a later time.
    Stephen Warren · Marlow

    copy of answer to "Is the speed of light constant?"

    I confess that my interest is in the Nature of Time. I am not an evangelist for block time - or for any other view or theory but, as I have said many times before in other Q&A threads: (1) Relativity has been proved by Godel and EInstein to be incompatible with a flow of time (see below); (2) This is a very uncomfortable result and seems to be ignored by physicists (amongst whom I am not numbered) and, as a humble biochemist, I would like to know why.
    I assumed at first that the whole thing must have been disproved or superseded, but then I read that Stephen Hawking had tried to refute Godel, failed and then tried, and failed, to invoke a new Law to bypass the conclusion; (3) As a scientist, therefore, I provisionally accept the absence of a flow of time as the truth (reality); (4) Next I try to account for what we experience in terms of block time. Our experience is of course not reality but what our brain creates for us* from the electrical signals, which it receives from our senses and our autonomous nervous system, in order to make the universe intelligible to us.
    * This phrase shows how difficult it is because this it implicitly assumes cause and effect, which depends on a flow of time!
    It does, however, produce an interesting result: First we must define block time as τ to distinguish it from our perceived time, t, and also assume that spacetime is quantised at the Planck scale. Since the universe that we perceive is neither static nor random we must infer that the position of an atom or molecule matter can differ from one quantum, at, say, τ to the quantum at τ +1. Furthermore the atom or molecule cannot appear in an entirely different place but must occupy an adjacent spacetime quantum and its "state" cannot change to an extent that a discontinuity appears. Since we know that past still, and the future already, exist the whole mass of the universe must be present in every quantum time interval. But every physical object must “know” the location and state of its predecessor and successor in every quantum adjacent to the one(s) that it currently occupies. For objects moving at terrestrial speeds a detectable change in state or location would occur only about once every1040 Planck units of time. This implies a very extended connection.
    The entropy gradient presumably arises simply because, as the universe gets larger the number quanta, and therefore the number of possible locations, increases as τ increases and decreases as τ decreases.
    We feel that we experience a flow of time because the Universe, including ourselves, just "is". We experience our lives from start to finish all the time but every "now” is defined by our memories and expectations at that moment so that every moment always feels like "now" to us. We cannot go back as we are at time Ƭ + n to time Ƭ taking our (later) memories with us. We don't have to travel in time to experience our past and future, we occupy every quantum of our existence now, but they all feel like "now", although the "nows" are all different. We perceive them as a sequence (a flow of time) because this is the only way they make sense.

    I don't believe this is really my job and I find it very taxing trying to work out how to match our everyday experience to a world without a flow of time but physicists seem to be obsessed with mathematics and models and have lost touch with concepts. String Theory in all its versions provides a lesson in over-dependence on maths and has become bogged down in its own sophistication. I feel strongly that we need to understand what time is and what it means at a deep conceptual level if we are going to make much progress.
    Can anybody tell me what a 4 dimensional spacetime quantum would look like? .... Please .....
    Einstein- ON THE ELECTRODYNAMICS OF MOVING BODIES.pdf
    Einstein_GRelativity_1916.pdf
    Einstein_Photoelectric.pdf
    planck 1901.pdf
    Time & causation in Godels Universe.pdf
    Einstein, Godel and the Disappearance of time.pdf

  • J. G. Muga added an answer:
    Can someone suggest review literature and mentions about time discretization?
    I would like to get basic knowledge in this topic at least basics. Because I'm new in this field I don't know what is a better way to start. Could anybody suggest any reviews and books on such a topic, or at least where it was mentioned and discussed?
  • Vladimir A. Kulchitsky added an answer:
    Is time in geometrical form ? If yes, how to define the geometric shape? If not, then how is it?

    In the circuit model system, After the rise of the time axis in system of equations and operation we found that the time can be central axis and motion system and can form geometric.

    Vladimir A. Kulchitsky · National Academy of Sciences of Belarus

    To form a geometric shape - it takes time. And vice versa. Time to be measured.

  • Dr. M. C. Hanumantharaju added an answer:
    Can anyone comment on the performance of using FPGA and GPU for image processing ?

    In term of time, latency, throughput,area and slicing

    Dr. M. C. Hanumantharaju · BMS Institute of Technology

    Implementation of image processing algorithms can be classified into several categories based on the architectural approach used; These are General Purpose Processor (GPP), dedicated Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs) and Field Programmable Gate Array (FPGA) implementations. The choice of particular approach is based upon the flexibility, memory requirement, throughput and cost etc. The image processing algorithm implementation on GPP possess a great deal of flexibility compared with other implementations. In the recent years, processing speed of GPP has been increased significantly. However, the technology has approached the upper limit. The GPP are limited in performance, since their instruction sets are not well suited for fast processing of high resolution of image processing algorithms. In addition, the instructions in GPP are executed in sequence, eventually, the throughput of the system decreases. DSPs have been employed for processing of images, provides some improvement over the GPPs. Only marginal improvement has been achieved since parallelism and pipelining incorporated in the design are inadequate. The hardware implementation of image processing techniques have been strongly influenced by the advancement of Very Large Scale Integration (VLSI) technology. The complex computational tasks such as 2D convolution, filtering, smoothing and contrast stretching operations encountered in image processing techniques is well suited for VLSI implementations. In addition, VLSI based hardware implementation exploits pipelining and massive parallel processing operations, resulting in an increased throughput of the image processing system.


    The image processing methods implemented in ASIC increases the performance compared with other realizations. However, ASIC implementations require large time to market and initial investments are high. The ASIC designs are best suited for relatively high volume productions. In the recent years, FPGAs has become an attractive choice of solution for hardware implementation of image processing algorithms, especially when high throughputs are the needs of the hour. In an image processing application, for rapid prototyping of new algorithms developed and to dynamically reconfigure, FPGAs are the right choice. FPGAs provides an optimum blend of flexibility of a GPPs and high speed processing that can be achieved using ASICs. An image processing architecture design for FPGA/ASIC technology can exploit fully the data and I/O parallelism for image processing application. Further, FPGA implementation of image processing techniques is cost effective for low volume productions. 

  • AHMED MAJED AHMED added an answer:
    Do you know how to generate a pulse in Simulink with its rising and falling edges are predefined?

    Just as timer block but  with two inputs for its vectors.

    time (t   0.1-t    0.1+t    0.2-t)

    Magnitude  (1 0 1 0)

    the pulse is continuous... and the block can be used in a close loop.

    AHMED MAJED AHMED · Universiti Teknologi Malaysia

    Dear friends ,,

    thanks a lot for your help and cooperation.

    actually the answer for the problem is achieved by using math functions and  relation &logic operators. 

    regarding repeating sequence builder and pulse generators as mentioned by K. Prakash Kumar and Nooriana Nynza,they can not be used in a close loop system to produce a specific pulse. as my aim is to produce a pulse with specific rising and falling edges at specific sensed angle(converted to time).

    Regarding pulse shaping filter I could not use it to produce the expected pulse,as i did not get the idea of t clearly, Roger Moliner .

    Best Regards for all.

  • Hamouda Assia added an answer:
    How you organize your work and time?
    Do you plan things out in microdetails or you are a spontaneous person?
    Hamouda Assia · Centre de Recherche Scientifique et Technique en Soudage et Contrôle

    to help autistic children to focus in works, some educators, work for 15 minutes and then make a break by playing or giving a candy. i like this method. i change it . i extend working times then i make a break by drinking tea or walking.

    this method really works for me.

  • Andrew Wutke added an answer:
    A question on Time as an emergent property
    Time can be viewed as an emergent property : whenever any change occurs anywhere in the universe - in other words whenever the state space of the universe undergoes any change - then Time itself happens and 'notches up' one tick (at least in the 'neighbourhood' of the change, which is a separate discussion.)

    But isn't this circular reasoning ? For a change in state space to be able to occur in the fist place, isn't the pre-existence of something like time a prerequisite ?

    The only way out of this conundrum is that all elementary state space changes must happen out of time, i.e. instantaneously (with a delta time = 0.) But this would then require the superimposed coexistence of 2 elementary state spaces. Can this happen ? We could probably engineer a situation where the Pauli exclusion principle would then be violated. This would tend to prove that Time as an emergent property cannot be the whole story?

    Any comments?
    Andrew Wutke · Thales Group

    Chris,

    I agree that time as an emergent property is a step in the right direction.

    The next step is that there is no universal emergent tick. Simply there is no time at all.

    Things change interact in one common reality. Some of them are selected as clocks to compare with other states. All I see is a vast number of changing coexisting states of coexisting objects.

    I see some relevance of the concept of traffic. It emerges from the properties of vehicles that move. There is no point you can put your finger and say this is traffic. You finger will always point to a vehicle. Traffic is an abstract concept, like time it "flows" and you can calculate flow rate (number of cars in my street per number of cars in the reference  street both between dawn and dusk) .

    Newton's concept of absolute time has not been abolished as it is claimed, but it has been multiplied and shifted to each inertial frame. We need one more step to abolish it altogether and free ourselves from this entanglement.

    But change as such, and memory of past states is a bit of a mystery so there is plenty of interesting problems yet to be solved by science.

  • Avan Al-Saffar asked a question:
    Why am I getting (Warning:Minimum step size reached near x = 3.14159There may be a singularity, or the tolerances may be too tight) in Matlab?

    My code is :

    function RunlogisticOscilfisher 

    omega=1;

    N0=1;

    k = 10;

    A = 1;

    p0 = .1;

    tspan=(0:0.1:10);

    [t,p] = ode45(@logisticOscilnumerical,tspan,p0,[],omega,k,N0);

     figure (1)

    plot(t,p)

    P = @(T) interp1(t,p,T)

    f = @(t) ( ( A.*( ( N0.* (sin(omega.*t)).^2 .*(1-(2.*P(t)./k))+(omega.*cos(omega.*t) ) ).^2 ) ./( (N0).^2.*(sin(omega.*t)).^4.*((P(t)-(P(t).^2./k)).^2 ) ) ) ) ;

    I1 = integral( f, 1,2,'ArrayValued',true)./2

    I2 = integral( f, 1,4,'ArrayValued',true)./4

    I3 = integral( f, 1,6,'ArrayValued',true)./6

    I4 = integral( f, 1,8,'ArrayValued',true)./8

    I5 = integral( f, 1,10,'ArrayValued',true)./10

    I=[I1,I2,I3,I4,I5]

    T=[2,4,6,8,10]

    figure(2)

    plot(T,I./10.^34)

    title('The Fisher Information with time')

    xlabel('Time')

    ylabel('Fisher Information')

    1;

    % function dpdt = logisticOscilnumerical(t,p,omega,k,N0)

    % dpdt = N0*sin(omega*t)*p*(1-p/k);

    % end

  • Andy Biddulph added an answer:
    How did Schrodinger concluded that adding a complex number to wave function is important? What's the physics behind that?

    The wave function is complex, Why? Can the time and position for elementary particles have a complex relation (transformation) relative to our time and position?

    All this confusion over i, the square root of minus one comes about because we have been taught to regard it as a relative of the unicorn, a mythical magical beast. In reality it comes about by virtue of the anticommutative property of a certain class of multiplication operations. Let a and b be unit quantities and # be an anticommuting multiplication then a#b=i, i2 = -1. There is no scalar i because scalar multiplication commutes. If we find i in an equation we need to find out what it is rather than inventing unicorns. As David Hestenes says, if we can not identify i then the problem is not well formulated. (New Foundation in Classical Mechanics)
    Waves imply rotations in a plane. Planes are described by unit basis vectors via their outer product. Let x, y be unit basis vectors then the unit directed area bivector is x^y=i because the outer product anticommutes. i is called the pseudoscalar of the plane. Rotors are bivectors, ie scalar multiples of i. Willard Gibbs' description of rotations as the cross product of two vectors giving an axial vector, while having the laudable aim of multiplying vectors to get vectors, obscures the geometrical interpretation of i by describing the duel of a bivector rotor. The cross product is normal to the plane of rotation and has the same magnitude as the bivector rotor. The cross product only has meaning in three dimensions and has difficulties describing rotations that are not orthogonal to the direction of motion. A rotor can be described as some scalar multiple of i but it is more convenient to to use the exponential form R = eiA where A is some angle in radians. Thus the geometrical interpretation of Euler's formula eiPI = -1 is the rotation of a vector by PI radians reverses its orientation.
    In general, a wave is a rotor and a direction of motion not in the i plane. This gives a helical wave. To get a plane wave we could project the rotation onto a plane defined by a fixed vector in the i plane and the direction of motion. Alternatively, we can describe a plane wave as the sum of two helical waves, identical except for their handedness. If we call those going in the same orientation as the i plane R = eiA and those with the opposite handedness R* = e-iA we can simply add, W(a plane wave) = R + R* The handedness convention is quite arbitrary. Thus we get a physically meaningful interpretation of negative frequency. Quantum mechanics do like to throw confusing ideas about.
    There is another way of describing the rotation in a plane by the geometrical product ab = a.b + a^b  Which results in the sum of the sum of a scalar plus the scalar multiple of the unit bivector pseudoscalar i This is a spinor z = a + bi A plane wave is thus W = zz* =(a + bi)(a - bi). The wave function is really spinor but we pretend it is a complex vector and write the dot product <z|z*>.
    All of these ideas may also be expressed as tensors and matrices.
    The use of i comes from the basic geometrical fact that a wave is a combination of a rotation in a plane and a linear motion.  Just to add to the fun combinations of rotational motions involves phasors which are spinors with a different name. Beam me up Scotty.All this confusion over i, the square root of minus one comes about because we have been taught to regard it as a relative of the unicorn, a mythical magical beast. In reality it comes about by virtue of the anticommutative property of a certain class of multiplication operations. Let a and b be unit quantities and # be an anticommuting multiplication then a#b=i, i2 = -1. There is no scalar i because scalar multiplication commutes. If we find i in an equation we need to find out what it is rather than inventing unicorns. As David Hestenes says, if we can not identify i then the problem is not well formulated. (New Foundation in Classical Mechanics)
    Waves imply rotations in a plane. Planes are described by unit basis vectors via their outer product. Let x, y be unit basis vectors then the unit directed area bivector is x^y=i because the outer product anticommutes. i is called the pseudoscalar of the plane. Rotors are bivectors, ie scalar multiples of i. Willard Gibbs' description of rotations as the cross product of two vectors giving an axial vector, while having the laudable aim of multiplying vectors to get vectors, obscures the geometrical interpretation of i by describing the duel of a bivector rotor. The cross product is normal to the plane of rotation and has the same magnitude as the bivector rotor. The cross product only has meaning in three dimensions and has difficulties describing rotations that are not orthogonal to the direction of motion. A rotor can be described as some scalar multiple of i but it is more convenient to to use the exponential form R = eiA where A is some angle in radians. Thus the geometrical interpretation of Euler's formula eiPI = -1 is the rotation of a vector by PI radians reverses its orientation.
    In general, a wave is a rotor and a direction of motion not in the i plane. This gives a helical wave. To get a plane wave we could project the rotation onto a plane defined by a fixed vector in the i plane and the direction of motion. Alternatively, we can describe a plane wave as the sum of two helical waves, identical except for their handedness. If we call those going in the same orientation as the i plane R = eiA and those with the opposite handedness R* = e-iA we can simply add, W(a plane wave) = R + R* The handedness convention is quite arbitrary. Thus we get a physically meaningful interpretation of negative frequency. Quantum mechanics do like to throw confusing ideas about.
    There is another way of describing the rotation in a plane by the geometrical product ab = a.b + a^b  Which results in the sum of the sum of a scalar plus the scalar multiple of the unit bivector pseudoscalar i This is a spinor z = a + bi A plane wave is thus W = zz* =(a + bi)(a - bi). The wave function is really spinor but we pretend it is a complex vector and write the dot product <z|z*>.
    All of these ideas may also be expressed as tensors and matrices.
    The use of i comes from the basic geometrical fact that a wave is a combination of a rotation in a plane and a linear motion.  Just to add to the fun combinations of rotational motions involves phasors which are spinors with a different name. Beam me up Scotty.All this confusion over i, the square root of minus one comes about because we have been taught to regard it as a relative of the unicorn, a mythical magical beast. In reality it comes about by virtue of the anticommutative property of a certain class of multiplication operations. Let a and b be unit quantities and # be an anticommuting multiplication then a#b=i, i2 = -1. There is no scalar i because scalar multiplication commutes. If we find i in an equation we need to find out what it is rather than inventing unicorns. As David Hestenes says, if we can not identify i then the problem is not well formulated. (New Foundation in Classical Mechanics)
    Waves imply rotations in a plane. Planes are described by unit basis vectors via their outer product. Let x, y be unit basis vectors then the unit directed area bivector is x^y=i because the outer product anticommutes. i is called the pseudoscalar of the plane. Rotors are bivectors, ie scalar multiples of i. Willard Gibbs' description of rotations as the cross product of two vectors giving an axial vector, while having the laudable aim of multiplying vectors to get vectors, obscures the geometrical interpretation of i by describing the duel of a bivector rotor. The cross product is normal to the plane of rotation and has the same magnitude as the bivector rotor. The cross product only has meaning in three dimensions and has difficulties describing rotations that are not orthogonal to the direction of motion. A rotor can be described as some scalar multiple of i but it is more convenient to to use the exponential form R = eiA where A is some angle in radians. Thus the geometrical interpretation of Euler's formula eiPI = -1 is the rotation of a vector by PI radians reverses its orientation.
    In general, a wave is a rotor and a direction of motion not in the i plane. This gives a helical wave. To get a plane wave we could project the rotation onto a plane defined by a fixed vector in the i plane and the direction of motion. Alternatively, we can describe a plane wave as the sum of two helical waves, identical except for their handedness. If we call those going in the same orientation as the i plane R = eiA and those with the opposite handedness R* = e-iA we can simply add, W(a plane wave) = R + R* The handedness convention is quite arbitrary. Thus we get a physically meaningful interpretation of negative frequency. Quantum mechanics do like to throw confusing ideas about.
    There is another way of describing the rotation in a plane by the geometrical product ab = a.b + a^b  Which results in the sum of the sum of a scalar plus the scalar multiple of the unit bivector pseudoscalar i This is a spinor z = a + bi A plane wave is thus W = zz* =(a + bi)(a - bi). The wave function is really spinor but we pretend it is a complex vector and write the dot product <z|z*>.
    All of these ideas may also be expressed as tensors and matrices.
    The use of i comes from the basic geometrical fact that a wave is a combination of a rotation in a plane and a linear motion.  Just to add to the fun combinations of rotational motions involves phasors which are spinors with a different name. Beam me up Scotty.

  • Saleha Khan asked a question:
    Which is the best solvent to soak Sephadex LH-20 first time?

    Sephadex LH-20

  • Wei Hu added an answer:
    What is the advantage of linear time invariant system (LTI)?

    I need to know the difference between non linear LTI and linear LTI.

    Wei Hu · Xiamen University

    @ Abdulmunem

      Ha-ha ~ It is not a miss ,but a mister.Thanks

  • Zahra Zre added an answer:
    How can I analyse my MMT assay data?

    I'm working on 2 cell lines of colon cancer,treating them with 5FU. i've got the results for 4 time periods but i dont know how to analyse them

    Zahra Zre · Kharazmi University

    thanQ :)

  • Jamal Toutouh added an answer:
    Are there any good tools to measure the performance of VANETs?

    802.11 based VANET Performance measurement tools 

    Jamal Toutouh · University of Malaga

    As Rashed Hussain wrote, you can find different simulators to analyze the performance of a VANET. 

    You can use ns-2 simulator and AWK/Python files or ns-3

    If you follow the link, you will find some ns-2 VANET  simulations and the AWK file to evaluate the PDR, end-to-end delay, normalized routing load, and routing path length

  • Dmitri Martila added an answer:
    How do I do the D/M/1 queue service time calculation?

    I am trying to calculate the value for b0 (probability of backoff time counter reaches zero). Could you please let me know what will be the value of service time (mu) and alpha while starting the experiment? 

    Dmitri Martila · Estonian Physical Society

    Hi! Serious research requires serious reward. Be holy. Bye!

  • Andrew Bell added an answer:
    How do I do a test for endogeneity and time invariant independent variable in panel data?

    I am working with panel data where I am estimating a group fixed effects model as I have some time invariant X variables. I need to test for endogeneity? Can anyone tell me how to do this? GMM does not help.

    Andrew Bell · University of Bristol

    You may want to have a look at this paper:

    https://www.researchgate.net/publication/233756428

    I think the answer to your question depends on what you mean by 'endogeneity'. If you mean correlation between t-variant variables and (time invariant) random effects in a RE model, then this can be thought of as a result of different 'within' and 'between' effects, and can easily be solved using the Mundlak formulation within the RE framework (see above article), allowing the estimation of your t-invariant variables. This is why the Hausman test is a flawed way of deciding between FE and RE models in my opinion.

    However, if by endogeneity you mean correlations between your residuals and t-invariant variables, that would suggest you have omitted t-invariant variables (individual characteristics). These would make any causal interpretation of your t-invariant variable effects rather unwise. This is rather less easy to test for or fix mechanically, unless you happen to have a good instrumental variable.

    Hope that helps,

    Andy

  • Cesar Ortiz Ledon added an answer:
    How can I calculate accuretely the concentration of Pt nanoparticles I synthesized (size is 4 nm)?

    My calculation tells me I supposed to have 1 micromolar but I dont I have try it several times and same problem I get about 40 nM of Pt nanoparticles

    Cesar Ortiz Ledon · New Mexico State University

    Capping agent is citrate they are in water apparently they are not very well disperse becuase the theoretical concentration doesn't match the experimental one, it is about 10 times more diluted. I'm guessing is because they are not very well disperse is there a way to reduce that aggregation and disperse them after the synthesis.

    Thanks

  • Huda A. H. Lubbad added an answer:
    How do you make time synchronization between WSN nodes to send the same signal at the same time in a real time testbed?

    I am working on TI CC2530dk , using Contiki OS. I need two nodes to send the same signal at the same time to the sink. in order that the signals can be added at the receiver. How can I make the time synchronization between the sending nodes in case of applying real time testbed not simulation.

    Huda A. H. Lubbad · University of Science Malaysia

    thanks Anna. I have found this time synchronization  mechanism in Contiki, my problem now how to use the mechanism in my  contiki source code and then program the node

  • Oladele P Kolawole added an answer:
    Before the big bang, did time exist? If it did, is time invented by man or God's creation?
    I believe time is a measure of duration, and man invented clock to measure time. Therefore there should be an empiricism that explains the time that dark matter and dark energy existed before the big bang
    Oladele P Kolawole · Federal University of Technology, Akure

    There was something that can not be described that was later named as time.

About Time

The dimension of the physical universe which, at a given place, orders the sequence of events. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

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