Low-energy Effects Research Articles

Quantum time delay in the gravitational field of a rotating mass

We examine quantum corrections of time delay arising in the gravitational field of a spinning oblate source. Low-energy quantum effects occurring in Kerr geometry are derived within a framework where general relativity is fully seen as an effective field theory. By employing such a pattern, gravitational radiative modifications of Kerr metric are derived from the energy–momentum tensor of the source, which at lowest order in the fields is modelled as a point mass. Therefore, in order to describe a quantum corrected version of time delay in the case in which the source body has a finite extension, we introduce a hybrid scheme where quantum fluctuations affect only the monopole term occurring in the multipole expansion of the Newtonian potential. The predicted quantum deviation from the corresponding classical value turns out to be too small to be detected in the next future, showing that new models should be examined in order to test low-energy quantum gravity within the solar system.

Planck-scale constraints on anisotropic Lorentz and CPT invariance violations from optical polarization measurements

Lorentz invariance is the fundamental symmetry of Einstein's theory of special relativity, and has been tested to great level of detail. However, theories of quantum gravity at the Planck scale indicate that Lorentz symmetry may be broken at that scale motivating further tests. While the Planck energy is currently unreachable by experiment, tiny residual effects at attainable energies can become measurable when photons propagate over sufficiently large distances. The Standard-Model Extension (SME) is an effective field theory approach to describe low-energy effects of quantum gravity theories. Lorentz and CPT symmetry violating effects are introduced by adding additional terms to the Standard Model Lagrangian. These terms can be ordered by the mass dimension of the corresponding operator, and the leading terms of interest have dimension d = 5. Effects of these operators are a linear variation of the speed of light with photon energy, and a rotation of the linear polarization of photons quadratic in photon energy, as well as anisotropy. We analyzed optical polarization data from 72 AGN and GRBs and derived the first set of limits on all 16 coefficients of mass dimension d = 5 of the SME photon sector. Our constraints imply a lower limit on the energy scale of quantum gravity of $10^6$ times the Planck energy, severly limiting the phase space for any theory that predicts a rotation of the photon polarization quadratic in energy.

Thermoelectric Transport in Nanocomposites.

Thermoelectric materials which can convert energies directly between heat and electricity are used for solid state cooling and power generation. There is a big challenge to improve the efficiency of energy conversion which can be characterized by the figure of merit (ZT). In the past two decades, the introduction of nanostructures into bulk materials was believed to possibly enhance ZT. Nanocomposites is one kind of nanostructured material system which includes nanoconstituents in a matrix material or is a mixture of different nanoconstituents. Recently, nanocomposites have been theoretically proposed and experimentally synthesized to be high efficiency thermoelectric materials by reducing the lattice thermal conductivity due to phonon-interface scattering and enhancing the electronic performance due to manipulation of electron scattering and band structures. In this review, we summarize the latest progress in both theoretical and experimental works in the field of nanocomposite thermoelectric materials. In particular, we present various models of both phonon transport and electron transport in various nanocomposites established in the last few years. The phonon-interface scattering, low-energy electrical carrier filtering effect, and miniband formation, etc., in nanocomposites are discussed.

Radiation effects of the laser ablative shockwaves on aluminium under atmospheric conditions

Numerical investigation of laser induced shock wave (SW) propagation into bulk aluminium target with and without the effects of electron thermal radiation (ETR and No-ETR) is demonstrated using MULTI-fs 1D-code over intensity range 1010 – 1011 W/cm2. The radiation emitting from the plasma is observed to show negligible effects on the SW propagating into aluminium target for low energy (25 mJ) and significant effects at high energy (175 mJ) which was found to be dominant up to 50 ns of time. The observations show that two SW have been launched on to the target surface: one during the pulse duration termed as primary SW (PSW) and the other immediately after the laser pulse termination termed as secondary SW (SSW). The effects of ETR were found dominant on SSW compared to that on PSW for 175 mJ. The PSW and SSW found to coalesce at around 30-40 ns and move as a single SW after these time scales. The resultant pressure after coalesce is higher than the individual ones before coalesce for 175 mJ. The PSW pressures at 25 mJ and 175 mJ were found to be ∼1.5 GPa and ∼7 GPa, respectively that were launched at 10 ns and 7 ns.

Adenosine Receptors as a Biological Pathway for the Anti-Inflammatory and Beneficial Effects of Low Frequency Low Energy Pulsed Electromagnetic Fields.

Several studies explored the biological effects of low frequency low energy pulsed electromagnetic fields (PEMFs) on human body reporting different functional changes. Much research activity has focused on the mechanisms of interaction between PEMFs and membrane receptors such as the involvement of adenosine receptors (ARs). In particular, PEMF exposure mediates a significant upregulation of A2A and A3ARs expressed in various cells or tissues involving a reduction in most of the proinflammatory cytokines. Of particular interest is the observation that PEMFs, acting as modulators of adenosine, are able to increase the functionality of the endogenous agonist. By reviewing the scientific literature on joint cells, a double role for PEMFs could be hypothesized in vitro by stimulating cell proliferation, colonization of the scaffold, and production of tissue matrix. Another effect could be obtained in vivo after surgical implantation of the construct by favoring the anabolic activities of the implanted cells and surrounding tissues and protecting the construct from the catabolic effects of the inflammatory status. Moreover, a protective involvement of PEMFs on hypoxia damage in neuron-like cells and an anti-inflammatory effect in microglial cells have suggested the hypothesis of a positive impact of this noninvasive biophysical stimulus.

Appetite, metabolism and growth regulation in Atlantic salmon ( Salmo salar L.) exposed to hypoxia at elevated seawater temperature

High temperature combined with low dissolved oxygen (DO) is one of the most challenging environmental conditions farmed fish experience; thus, understanding their impact on growth regulation is of relevance to cultured and wild populations. This study examines appetite- and growth-regulating mechanisms in Atlantic salmon postsmolt exposed to either high (HO) or low oxygen (LO) at a suboptimally high temperature (17°C). Additionally, the effects of high (HE) and low (LE) dietary energy (DE) were examined. After a month of treatment, analyses of hormones, regulating appetite (ghrelin) and growth (growth hormone receptor ghr1 and insulin-like growth factor IGF-1), and free amino acids (FAA) were measured pre- and postprandially at −4, −2, 0, 2, 4 and 6 h. No preprandial ghrelin peaks were detected despite a significant reduction in feed intake and growth under hypoxia compared to normoxia. LO treatment also had an overall negative effect on survival compared to HO, while nutrient retention efficiency, FCR and plasma FAA concentrations were unaffected (P > 0.05). Feeding HE diet resulted in increased growth (+17%) and improved FCR (−14%) and energy retention efficiency (+26%) independent of DO. Plasma FAA concentrations were unaffected by LO treatment and DE (P > 0.05). Growth regulatory gene expressions possibly reflect an overall lower growth at a high temperature overriding the impacts of DO and DE. This study also indicates that optimal adaptation time to environmental conditions and feeding regime is crucial for establishing a regular hormonal appetite signalling that reflects real feeding anticipation in salmon.

Left-Right Non-Linear Dynamical Higgs**J. Y. also acknowledges KITPC financial support during the completion of this work

All the possible CP-conserving non-linear operators up to the p4-order in the Lagrangian expansion are analysed here for the left-right symmetric model in the non-linear electroweak chiral context coupled to a light dynamical Higgs. The low energy effects will be triggered by an emerging new physics field content in the nature, more specifically, from spin-1 resonances sourced by the straightforward extension of the SM local gauge symmetry to the larger local group SU(2)L × SU(2)R × U(1)B–L. Low energy phenomenology will be altered by integrating out the resonances from the physical spectrum, being manifested through induced corrections onto the left handed operators. Such modifications are weighted by powers of the scales ratio implied by the symmetries of the model and will determine the size of the effective operator basis to be used. The recently observed diboson excess around the invariant mass 1.8 TeV–2 TeV entails a scale suppression that suggests to encode the low energy effects via a much smaller set of effective operators.

Effects of low dietary energy, with low and normal protein levels, on broiler performance and production characteristics

px; > normal or narrow metabolizable energy to crude protein ratios (ME:CP) on performance,carcass characteristics, body composition and blood parameters in broilers fed from 1 to 42days of age. The chicks were divided into 7 groups. The birds were fed starter & grower diets.Seven experimental diets were formulated in each phase; one control and 6 tested diets. Thecontrol diet was formulated according to the NRC of poultry (1994) and the other six dietsfed three different levels of low energy diets (2900, 2700 & 2500 kcal/kg; one level for each 2groups). The first three tested groups named ''normal calorie-protein ratio” groups in whichthe CP decreased in proportion to the decrease in ME, keeping the normal NRC ratio. In thesecond three tested groups, termed “narrow calorie-protein ratio” groups, the dietaryprotein was kept at the NRC levels leading to ratios narrower than that of the NRC. Resultsshowed that chicks fed low ME diets with normal energy to protein ratio had lower bodyweight and feed utilization efficiency than the chicks fed the control diets. While, birds fedthe low ME diets with normal protein NRC-levels and narrow ratios had nearly equal weightand feed conversion to the control. The body composition and carcass characteristics werenot affected by the dietary treatments. Moreover, the blood parameters had no significantvariations among the groups, except for total protein, ALT and AST which had an increasedresponse to decreased dietary energy density. In conclusion, decreasing the dietary ME levelwithout decreasing the crude protein level was more efficient economically and had no anyadverse effect on the performance. However, decreasing of dietary ME with normal ME:CPratio resulted in decreased performance and low economic efficiency.

The most general form of deformation of the Heisenberg algebra from the generalized uncertainty principle

In this paper, we will propose the most general form of the deformation of Heisenberg algebra motivated by the generalized uncertainty principle. This deformation of the Heisenberg algebra will deform all quantum mechanical systems. The form of the generalized uncertainty principle used to motivate these results will be motivated by space fractional quantum mechanics and non-locality in quantum mechanical systems. We also analyse a specific limit of this generalized deformation for one dimensional system, and in that limit, a nonlocal deformation of the momentum operator generates a local deformation of all one dimensional quantum mechanical systems. We analyse the low energy effects of this deformation on a harmonic oscillator, Landau levels, Lamb shift, and potential barrier. We also demonstrate that this deformation leads to a discretization of space.

Remote Molecular Doping of Colloidal Quantum Dot Photovoltaics

In recent years colloidal quantum dot (CQD) photovoltaics have developed rapidly because of novel device architectures and robust surface passivation schemes. Achieving controlled net doping remains an important unsolved challenge for this field. Herein we present a general molecular doping platform for CQD solids employing a library of metal–organic complexes. Low effective ionization energy and high electron affinity complexes are shown to produce n- and p-doped CQD solids. We demonstrate the obvious advantage in solar cells by p-doping the CQD absorber layer. Employing photoemission spectroscopy, we identify two doping concentration regimes: lower concentrations lead to efficient doping, while higher concentrations also cause large surface dipoles creating energy barriers to carrier flow. Utilizing the lower concentration regime, we remove midgap electrons leading to 25% enhancement in the power conversion efficiency relative to undoped cells. Given the vast number of available metal–organic complexes, this approach opens new and facile routes to tuning the properties of CQDs for various applications without necessarily resorting to new ligand chemistries.

Residual stress in nano-structured stainless steel (AISI 316L) prompted by Xe+ ion bombardment at different impinging angles

The effect of low energy (<1 keV) xenon (Xe+) ion bombardment on the residual stress of polycrystalline iron alloy (AISI 316L steel) is reported. The results take into account the influence of the ion incident angle maintaining constant all other bombarding parameters (i.e., ion energy and current density, temperature, and doses). The bombarded surface topography shows that ions prompt the formation of nanometric regular patterns on the surface crystalline grains and stressing the structure. The paper focalizes on the study of the surface residual stress state stemming from the ion bombardment studied by means of the “sin2 ψ” and “Universal Plot” methods. The analysis shows the absence of shear stress in the affected material region and the presence of compressive in-plane residual biaxial stress (∼200 MPa) expanding up to ∼1 μm depth for all the studied samples. Samples under oblique bombardment present higher compressive stress values in the direction of the projected ion beam on the bombarded surface. The absolute value of the biaxial surface stress difference (σ11-σ22) increases on ion impinging angles, a phenomenon associated with the momentum transfer by the ions. The highest stress level was measured for ion impinging angles of 45° (σ11 = −380 ± 10 MPa and σ22 = −320 ± 10 MPa). The different stresses obtained in the studied samples do not affect significantly the formation of characteristic surface patterns.

Terahertz spectroscopy on Faraday and Kerr rotations in a quantum anomalous Hall state.

Electrodynamic responses from three-dimensional topological insulators are characterized by the universal magnetoelectric term constituent of the Lagrangian formalism. The quantized magnetoelectric coupling, which is generally referred to as topological magnetoelectric effect, has been predicted to induce exotic phenomena including the universal low-energy magneto-optical effects. Here we report the experimental indication of the topological magnetoelectric effect, which is exemplified by magneto-optical Faraday and Kerr rotations in the quantum anomalous Hall states of magnetic topological insulator surfaces by terahertz magneto-optics. The universal relation composed of the observed Faraday and Kerr rotation angles but not of any material parameters (for example, dielectric constant and magnetic susceptibility) well exhibits the trajectory towards the fine structure constant in the quantized limit.

Effect of low-energy X-ray radiation on the electrophysical properties of silicon crystals of n- and p-type conductivity

We study the kinetics of the photovoltage decay in silicon crystals, caused by the effect of lowenergy (E = 8 keV) X-ray radiation. A correlation between radiation-induced changes in the short-term and long-term components of the photovoltage decay and the charge state of the surface, determined by measuring the surface distribution of the amplitude and decay time of the photovoltage, is found.

Spin-fermion model with overlapping hot spots and charge modulation in cuprates

We study particle-hole instabilities in the framework of the spin-fermion (SF) model. In contrast to previous studies, we assume that adjacent hot spots can overlap due to a shallow dispersion of the electron spectrum in the antinodal region. In addition, we take into account effects of a remnant low energy and momentum Coulomb interaction. We demonstrate that at sufficiently small values $|\varepsilon (\pi ,0)-E_{F}|\lesssim \Gamma $, where $E_{F}$ is the Fermi energy, $\varepsilon \left( \pi ,0\right) $ is the energy in the middle of the Brillouin zone edge, and $\Gamma $ is a characteristic energy of the fermion-fermion interaction due to the antiferromagnetic fluctuations, the leading particle-hole instability is a d-form factor Fermi surface deformation (Pomeranchuk instability) rather than the charge modulation along the Brillouin zone diagonals predicted within the standard SF model previously. At lower temperatures, we find that the deformed Fermi surface is further unstable to formation of a d-form factor charge density wave (CDW) with a wave vector along the Cu-O-Cu bonds (axes of the Brillouin zone). We show that the remnant Coulomb interaction enhances the d-form factor symmetry of the CDW. These findings can explain the robustness of this order in the cuprates. The approximations made in the paper are justified by a small parameter that allows one an Eliashberg-like treatment. Comparison with experiments suggests that in many cuprate compounds the prerequisites for the proposed scenario are indeed fulfilled and the results obtained may explain important features of the charge modulations observed recently.

Overlapping Hot Spots and Charge Modulation in Cuprates

Particle-hole instabilities are studied within a two dimensional model of fermions interacting with antiferromagnetic spin fluctuations (spin-fermion model). In contrast to previous works, we assume that neighboring hot spots overlap due to a shallow dispersion of the electron spectrum in the antinodal region and include in the consideration effects of a remnant low energy and momentum Coulomb interaction. It turns out that this modification of the model drastically changes the behavior of the system. The leading particle-hole instability at not very weak fermion-fermion interaction is no longer a charge density wave with a modulation along the diagonals of the Brillouin zone predicted previously but a Pomeranchuk-type deformation of the Fermi surface breaking the C$_{4}$ symmetry of the system. This order does not prevent from further phase transitions at lower temperatures. We show that, depending on parameters of the interaction, either d-wave superconductivity or charge density wave with modulations along the bonds of the $CuO$ lattice is possible. The low momentum remnant Coulomb interaction enhances the d-form factor of the charge density wave. Comparison with experimental data allows us to conclude that in many cuprate compounds the conditions for the proposed scenario are indeed fulfilled. Our results may explain important features of the charge modulations observed recently.

A Framework of Photo Acoustic Imaging for Ovarian Cancer Detection by Galvo-mirror System

Ovarian cancer is one of the most common types of cancer among women, which often leads to death. As a result, developing new techniques for diagnosing this disease at early stages, preventing the high rate of death in women with high-risk, and minimizing the large side effects on the economy must be considered seriously by experts. For early diagnosis of this disease, it is necessary to utilize ultrasound integrated with photo acoustic technique in which the minimal amount of cost, energy, and laser are acquired. In addition, the procedure should provide sufficient pulse to make ovaries tissue able to take image. This new clinical diagnosis technique utilizes modest pulse energy and low electrical voltage so that, it could be assumed as a proper alternative for conventional ultrasound in showing the image of abdominal ovary tissue. The researcher aims at presenting a real time photo acoustic-imaging probe for imaging human ovaries tissue; thus, this study seeks to investigate the effect of low electrical voltage and modest laser pulse energy while providing enough pulse for ovarian tissue as well as implementation issue. This model utilizes dual modality imaging approach and describes several researches carried out in order to establish dual-model imaging consisting ultrasound and photo acoustic. The system can accomplish near-simultaneous ultrasound and photo acoustic imaging. The model is capable of reaching thorough diagnostic information based on the tissue where there is only individual imaging model with its limitations.

Validation of Computed Tomography-based Attenuation Correction of Deviation between Theoretical and Actual Values in Four Computed Tomography Scanners.

Objective(s):In this study, we aimed to validate the accuracy of computed tomography-based attenuation correction (CTAC), using the bilinear scaling method.Methods:The measured attenuation coefficient (μm) was compared to the theoretical attenuation coefficient (μt), using four different CT scanners and an RMI 467 phantom. The effective energy of CT beam X-rays was calculated, using the aluminum half-value layer method and was used in conjunction with an attenuation coefficient map to convert the CT numbers to μm values for the photon energy of 140 keV. We measured the CT number of RMI 467 phantom for each of the four scanners and compared the μm and μt values for the effective energies of CT beam X-rays, effective atomic numbers, and physical densities.Results:The μm values for CT beam X-rays with low effective energies decreased in high construction elements, compared with CT beam X-rays of high effective energies. As the physical density increased, the μm values elevated linearly. Compared with other scanners, the μm values obtained from the scanner with CT beam X-rays of maximal effective energy increased once the effective atomic number exceeded 10.00. The μm value of soft tissue was equivalent to the μt value. However, the ratios of maximal difference between μm and μt values were 25.4% (lung tissue) and 21.5% (bone tissue), respectively. Additionally, the maximal difference in μm values was 6.0% in the bone tissue for each scanner.Conclusion:The bilinear scaling method could accurately convert CT numbers to μ values in soft tissues.

Superhydrophobic/superoleophilic corn straw fibers as effective oil sorbents for the recovery of spilled oil

AbstractBACKGROUNDIn recent years, superhydrophobic and superoleophilic materials have attracted great interest and have been applied to the removal of oil contaminants from water. The combined effect of hierarchical coarse structure and low surface free energy is essential for the acquisition of superhydrophobicity and superoleophilicity. In the present study, a facile, low‐cost, fluorine‐free and eco‐friendly method is proposed for the development of superhydrophobic/superoleophilic corn straw fibers via conventional impregnation to realize the removal of oil from water.RESULTSThe simultaneous performances of superhydrophobicity and superoleophilicity of the product were attributed to the covalent deposition of hollow spherical zinc oxide (ZnO) particles on the surface of fibers and subsequent hydrophobic modification using hexadecyltrimethoxysilane (HDTMOS). In addition, the superhydrophobic and superoleophilic performances of as‐prepared corn straw remained in complex conditions of corrosive solution and long‐time storage. The absorption capacity of superhydrophobic/superoleophilic corn straw for crude oil was 20.4 g g−1, demonstrating high uptake capacity.CONCLUSIONThe superhydrophobic/superoleophilic corn straw fibers possessed excellent stability and enhanced absorption capacity. The as‐prepared product could be widely used as an oil sorbent for oil/water separation. This study provided evidence for the better utilization of waste corn straw in the field of oil spills cleanup. © 2015 Society of Chemical Industry

Self-encapsulation of organic thin film transistors by means of ion implantation

Long-term stability of devices based on organic materials is still impeding the diffusion of these structures in real applications. In this paper we have investigated the effects of low energy, combined, ion implantation (N and Ne) in the evolution of the electrical performances of pentacene-based Organic Thin Film Transistors (OTFTs) over time by means of current–voltage and photocurrent spectroscopy analyses. We have demonstrated that the selected combination of ions allows reducing the degradation of charge carriers mobility, and also stabilization of the devices threshold voltage over a long time (over 2000h).

Study of non-linear Hall effect in nitrogen-grown ZnO microstructure and the effect of H+-implantation

We report magnetotransport studies on microstructured ZnO film grown by pulsed laser deposition in N2 atmosphere on a-plane Al2O3 substrates and the effect of low energy H+-implantation. Non-linearity has been found in the magnetic field dependent Hall resistance, which decreases with temperature. We explain this effect with a two-band model assuming the conduction through two different parallel channels having different types of charge carriers. Reduced non-linearity after H+-implantation in the grown film is due to the shallow-donor effect of hydrogen giving rise to an increment in the electron density, reducing the effect of the other channel.