Quotations
Thought for us
Penetrating so many secrets, we cease to believe in the unknowable.
But there it sits nevertheless, calmly licking its chops.
H L Mencken
Validity of Molecular Dynamics in Heat Transfer
Molecular Dynamics (MD) is commonly used in computational heat transfer to determine the thermal response of nanostructures. MD is based on classical statistical mechanics with the thermal energy of the atom related to its momentum by the equipartition theorem. Momenta of atoms in an ensemble are determined by solving Newton’s equations with inter-atomic forces derived from Lennard-Jones potentials. Statistical mechanics implicitly assumes the atom has heat capacity as otherwise the temperature of the atom cannot be related to its thermal energy. Moreover, statistical mechanics assumes atoms in nanostructures have the same heat capacity as at the macroscale.
For bulk materials, MD heat transfer based on atoms in submicron computation boxes having macroscopic heat capacity is valid provided periodic boundary conditions are imposed in the MD solution. The statistical mechanics requirement of macroscopic heat capacity is satisfied because the atoms in submicron boxes under periodic boundary conditions are equivalent to atoms in the bulk that do indeed have heat capacity.
In contrast, quantum mechanics (QM) precludes atoms in submicron nanostructures from having the capacity to conserve heat by an increase in temperature. Nevertheless, MD simulations are commonly performed by assuming atoms in discrete or non-periodic nanostructures have heat capacity. Although consistent with statistical mechanics, MD of discrete nanostructures is unequivocally invalid by QM. By QM, atoms in discrete nanostructures lacking heat capacity cannot conserve heat by an increase in temperature, and therefore Fourier’s heat conduction equation that depends on temperature has no meaning. Instead, conservation in discrete nanostructures proceeds by the creation of QED induced non-thermal EM radiation that charges the nanostructure by the photoelectric effect. QED stands for quantum electrodynamics and EM for electrodynamics. Examples of MD simulations that by QM are valid or invalid are presented and recommendations made for how MD heat transfer simulations of discrete nanostructures may be made consistent with QM. See Paper and Press Release
QED Induced Heat Transfer
Over the past century, Fourier’s transient heat conduction equation including the notions of heat capacity of Lavosier and Laplace .have served well in our understanding heat transfer in macroscopic systems. Modern day heat transfer assumes phonons are the heat carriers solids based on theories formulated by Einstein and Debye at the time systems were macroscopic. Today, the heat transfer systems are no longer typically macroscopic, but include the nanoscale. Macroscopic heat capacity in Fourier’s equation is routinely applied in heat transfer simulations at the nanoscale, the consequence of which has led to unphysical results, e.g. standard mixing rules are violated for nanofluids; thermal conductivity of thin films is reduced depending on thickness; the memristor is thought necessary to complete symmetry to the circuit elements of resistor, capacitor, and inductor; molecular polymers in nanoscale electronics have thermal conductivity; unlikely molecular signaling by the lock and key mechanism olfaction, and so forth.
Unphysical observations from application of classical heat transfer to nanostructures may be traced back to Einstein’s and Debye’s theories of heat capacity based on phonons. In contrast, nanoscale heat transfer based on QED by Planck’s photons avoids the unphysical, i.e. thin film conductivity remains at bulk as thickness decreases, nanofluids obey mixing rules, the memristor is a quantum size effect, molecular conductivity is meaningless, olfaction reduces to signaling of the odorant molecule by its unique vibration spectrum, etc. QED stands for quantum electrodynamics. Supporting QED physics is based on quantum mechanics from the Einstein-Hopf relation for the harmonic oscillator in terms of temperature and EM confinement. Both Einstein and Debye phonon theories based on classical statistical mechanics permit the atom at the nanoscale to have the heat capacity necessary to conserve absorbed EM energy by an increase in temperature. But quantum mechanics requires the heat capacity to vanish thereby precluding conservation by a temperature increase at the nanoscale. Instead, conservation proceeds by the creation of non-thermal photons inside the nanostructure by the QED induced frequency up-conversion of absorbed EM energy to the TIR confinement of the nanostructure. TIR stands for total internal reflection. The TIR confinement of the QED photons occurs because the high surface to volume ratio of nanostructures naturally concentrates the absorbed EM energy in the TIR mode, thereby effectively supporting photon confinement. The QED photons may excite phonons, but the absorbed EM energy is primarily conserved by the prompt creation of QED photons that may be converted to electric charge by Einstein‘s photoelectric effect, or lost to the surroundings. Examples of QED physics are presented to illustrate the fact the QED physics extends far beyond nanoscale heat transfer. See Press Release and Presentation
Invalidity of Near-Field Heat Transfer
Over the past decade, extensive research in near-field heat transfer has suggested the EM radiation at submicron distances < 100 nm from a surface is orders of magnitude larger than the limit given by Planck's theory of BB radiation. BB stands for blackbody. But Planck never stated his theory set an upper limit on radiative heat transfer, although he was surely aware bringing BB surfaces close together does not increase their thermal energy.
However, experimental support for near-field enhancement is limited to micron and not nanoscale gaps, and therefore support for claims that near-field enhancement in submicron gaps exceeds the Planck limit relies almost entirely on classical EM analysis of evanescent waves by the Maxwell equations.But near-field enhancement based on Maxwell’s equations is refuted because temperature fluctuations in the surfaces of nanoscale gaps as required by the FDT are precluded by QM. FDT stands for the fluctuation-dissipation theorem and QM for quantum mechanics.
The FDT that relates the strength of the oscillations of the dipoles inside a body to the temperature fluctuations cannot be assumed in the solution of Maxwell’s equations because QM precludes atoms in the surfaces of nanoscale gaps to respond to absorption of heat by changes in temperature. Solutions of Maxwell’s equations for by evanescent waves showing Planck theory is exceeded are unphysical because the FDT is no longer valid at the nanoscale.
Given that the thermal energy of a body is not increased by bringing it close to another body, near–field enhancement by tunneling of evanescent waves simply does not exist. Instead, conservation of EM energy proceeds by QED induced heat transfer, and therefore Planck’s theory is indeed an upper bound to near-field radiative heat transfer at the nanoscale. See Press Release, Paper, and Presentation
Johnson-Nyquist Noise
The validity of Maxwell's solutions in near-field heat transfer by tunneling of evanescent waves through nanoscale gaps is of great importance in the hope a breakthrough of a large enhancement in energy harvesting can be realized. However, atoms in the surface of nanoscale gaps are under high EM confinement that by QM are precluded from having the heat capacity necessary to conserve heat flow by a change in temperature, and therefore the temperature fluctuations required by the FDT do not occur in nanoscale gaps suggesting solutions of Maxwell's equations that rely on temperature fluctuations are invalid. See above "Invalidiity of Near-Field Heat Transfer," 2012.
One way of assessing whether the FDT is satisfied is to estimate the effect of EM confinement on the strength of the Johnson-Nyquist (J-N) noise signals from a hypothetical resistor in the surface atoms of nanoscale gaps. See Press Release and Paper.
The J-N signals of V(f) under EM frequencies > 3E+15 Hz ( Gap < 50 nm) show the noise is at least 100 orders of magnitude less than that of a surface free of EM confinement. See above Plot. Since Maxwell solutions require gaps of about 10 nm to achieve enhancements consistent with breakthorughs in energy havesting, the tunneling of evanescent waves through nanoscale gaps is likely to be difficult to achieve in practice.
1/f Noise in Nanowires
he 1/f frequency spectrum is commonly observed in the measurements of power in electronic circuits comprising semiconductors, resistors, vacuum tubes, and transistors. However, no recognized physical explanation of 1/f noise has been proposed. Indeed, the ubiquity of 1/f noise is one of the oldest puzzles of contemporary physics.
In 1925, Johnson and Nyquist discovered electronic or white noise from vacuum tubes. White noise power has a constant frequency f spectrum generated by the thermal agitation of the charges inside a resistor independent of any applied voltage. In contrast, 1/f noise shown above is sometimes called pink noise differs in that under applied voltage the power frequency f spectrum is not constant, but rather shows a slope of -1 on a log-log plot consistent with the frequency f raised to the -1 exponent.
Nanoelectronics comprise nanostructures that by QM create charge upon dissipating Joule heat. QM stands for quantum mechanics. QM precludes atoms in nanostructures from having the heat capacity necessary to conserve Joule heat by an increase in temperature, and therefore the Joule heat under EM confinement is induced by QED to produce non-thermal radiation that by Einstein’s photoelectric effect creates charge inside the nanostructure. EM stands for electromagnetic and QED for quantum electrodynamics. In this regard, QED induced charge in nanowires finds similarity with memristors including the Ovshinsky Effect in PCRAM devices whereby charge is created in amorphous GST films from excitons (holes and electrons) by the photoelectric effect that locally reduce the film resistance to allow encoding. See this page at Memristors and the Ovshinsky Effect, 2011.
In nanowires, absorption of Joule heat is conserved by the creation of QED photons instead of by an increase in temperature. The QED photons are under the TIR confinement of the diameter d of the nanowire. TIR stands for total internal reflection. The QED photons have Planck energy E = hc/2nd, where h is Planck’s constant, c is the speed of light, and n is the refractive index of the nanowire. Typically, E > 6 eV, and therefore charges in the form of excitons (holes and electrons) are produced by Einstein’s photoelectric effect. What this means is current flow through the nanowire spontaneously creates a step change in charge that reduces the resistance and increased current that eventually dissipated in the otherwise macroscopic electronic circuit. Equivalently, current flow may be considered to produce a steady step change in power, the Fourier transform of which gives the 1/f response in the frequency domain.
Nanowires that naturally produce a steady step change in power may be considered to be a summation of a train of individual steps in the manner of Markov chain. See Press Release and preliminary Paper.
Immunogenicity by QED Radiation
Protein therapeutics is used in the treatment of diabetes and various forms of cancer. A major concern is that repeated administration to patients often leads to immunogenicity by the immune system responding by formation of antidrug antibodies (ADAs) that reject the otherwise beneficial drug in treating the treatment of the disease. Immunogenicity (or an adverse response of the immune system to a drug) is of great interest as the rejection of the drug may be life threatening. Generally, the ADAs are triggered by the tendency of the beneficial monomer form of the protein molecules to aggregate, although why aggregation occurs is not understood. In protein deposition diseases such as Alzheimer and Parkinson, protein aggregates enhance stronger immunogenicity.
Typically, the aggregates known to elicit ADA response are globular proteins having molecular weights from 6 to 100 kDa and diameters from 3 – 10 nm comparable to NPs that based on QM have been linked to DNA damage by the natural emission of low-level QED induced EM radiation at levels beyond the UV. Similarity suggests the toxicity to the immune system by protein aggregation is caused by the UV radiation created as the protein aggregates conserve absorbed EM energy from collisions of water molecules in body fluids. See Press Releases on DNA damage by inanimate and biological NPs.
The UV created in the aggregates dissociates native disulfide bonds causing drastic conformational changes that expose the hydrophobic residues in partially unfolded molecules. Subsequently, the partially unfolded molecules self-assemble into globular protein aggregates by the formation of intermolecular disulfide bonds driven by intermolecular hydrophobic interactions. The combined effects from both the hydrophobic interaction and the formation of intermolecular disulfide bonds dominate this process. See Paper and Press Release
Global Warming and the Second Law of Thermodynamics
Global warming claims that solar radiation absorbed in the Earth’s surface is re-radiated back in the IR and absorbed by CO2 in the atmosphere only to be conserved by the emission of EM radiation as “backradiation” that further warms the Earth. IR stands for infrared and EM for electromagnetic. Global warming argues the Earth therefore warms more by backradiation from CO2 than otherwise, the consequence of which has resulted in the controversy that CO2 emissions need to be regulated to avoid climate change in a warming Earth.
In the global warming controversy, skeptics argue backradiation requires heat to be transferred from the CO2 in the cold atmosphere to the warm surface of the Earth, and therefore the Second Law that requires heat to only flow from hot to cold surfaces is violated. Skeptics therefore claim that backradiation is unphysical and does not occur. Hence, the economic costs of avoiding global warning by restricting CO2 emissions are unjustified. See Paper
However, backradiation does not violate the Second law. Indeed, the CO2 molecule does absorb the IR radiation from the Earth, but conservation proceeds by the emission of EM radiation at the vibration frequencies of the CO2 molecule. Since the EM emissions are independent of temperature, backradiation occurs without violating the Second Law. See Press Release
An important issue is whether BB radiation from the Earth is absorbed by the CO2 in the atmoshere. For the Earth at 300K, Wien’s law gives the peak BB emission at about 9.66 microns. Since CO2 absorbs at 14 microns, skeptics say BB radiation at 9.66 microns is not absorbed by CO2, and therefore CO2 cannot cannot undergo backraddiation to the Earth. Hence, CO2 canot contribute to global warming and should not be legislated. However, BB radiation is broadband and has content at 14 microns. How much of the BB radiation content at 300 K is at 14 microns can be determined from Planck’s theory, and is illustrated in Paper1
The Red Rectangle
Astronomers have extensively studied the ERE of the Red Rectangle (RR) Nebula in the Milky Way for nearly a century. ERE stands for extended red emission. Today, controversy surrounds the mechanism by which the ERE is produced. Two competing mechanisms: PL and BB radiation have emerged, both of which rely on the UV emission from a pair of stars in the RR Nebula:. PL stands for photoluminescence and BB for blackbody.
Cosmic dust in the interstellar medium (ISM) comprised of discrete nanoparticles (NPs) separated by large distances. In the ISM, PL may only occur by the absorption of a single UV photon in a NP. Since the PL conversion efficiency < 100%, it may be safely concluded PL from single UV photon absorptions in cosmic dust is not the ERE mechanism.
Since PL in cosmic dust is highly unlikely, PL as the source of ERE was proposed supplemented by thermal BB radiation in Paper1 The stars in the RR Nebula have temperatures of about 7000 K that by Wien’s law limits the BB emission peak to about 0.41 microns or 3 eV, and therefore it can be concluded that BB radiation cannot produce UV photons having Planck energy > 10.5 eV necessary to explain the ERE in the RR.
Because both PL and BB radiation cannot explain ERE, carbon molecules having < 28 atoms were assumed heated to temperatures in excess of 1500 K by absorption of a single UV photon. Ibid. In support of this assumption, laser heating experiments of soot comprising 30-100 nm carbon NPs deposited on the aluminum foil vanes of a Crookes radiometer are presented in Paper2 Laser irradiation of the soot film produces an emission spectrum that resembles that of the RR. Temperatures were estimated and not measured. Fits of BB radiation alone did not appr0oximate the measured spectrum. Mie theory gave a better approximation to the spectra at a temperature of 3800 K.
However, the Mie theory estimate of 3800 K necessary to fit the measured spectrum cannot be correct as the aluminum foil having a melting point of about 960 K would have been exceeded, but foil damage was not reported. Whatever caused the emission spectrum did not require high temperatures as would be expected in Planck’s theory of BB radiation.
Classically, NPs conserve absorbed EM energy of any form by an increase in temperature that in turn is emitted as VIS and IR radiation, but QM differs. QM stands for quantum mechanics. QM requires that UV photon absorption in NPs occurs without a change in NP temperature, i.e., ISM molecules having < 28 carbon atom do not heat to > 1500 K by absorbing UV photons. Further description is given in PressRelease - the conclusions of which are:
1. Both PL and BB radiation including variants thereof may be safely dismissed as mechanisms for the ERE.
2. QED induced radiation asserts the VIS and NIR in the ISM are caused by the absorption of UV radiation in cosmic dust NPs. In the ISM, mid and far IR spectra may also be explained by QED induced redshift, but require larger cosmic dust particles.
3. The redshift measurements of Supernovae explosions have nothing to do with an expanding Universe, but rather cosmic dust. The RR color by QED induced redshift radiation by cosmic dust clearly shows that high Z redshifts need not be limited to distant Supernovae, but are common in the colors we on Earth observe in the Milky Way. See this page http://www.nanoqed.org/, “Cosmology by Cosmic Dust – Update,” 2010
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