Excess Photon Research Articles

Physiological mechanisms of cross-stress and memory in soybean plants subjected to water deficit and waterlogging

Defense priming is a strategy that enables plants to react faster, minimizing the damage suffered and allowing them to survive stress. Here, we investigated the physiological and morphological changes underpinning stress memory and adaptive capacity in soybean plants subjected to water deficit and/or waterlogging at two developmental stages. Our experiment was carried out in a greenhouse with seven treatments and four replicates: control (non-stressed plants), water deficit at R2; water deficit both at V4 and R2; water deficit in V4 and waterlogging in R2; waterlogging in R2; waterlogging in both V4 and R2; and waterlogging at V4 and water deficit at R2. Samples for biometric analyses, measurements of xylem water potential, leaf gas exchange, chlorophyll a fluorescence, and quantification of photosynthetic pigments were harvested on the last day of stress (R2) and four days after recovery. Primed and cross-primed plants showed improvements in leaf water potential and relative water content due to the greater water use efficiency. Together with the osmotic effects, these plants developed greater protection of the photosynthetic apparatus, showing a superior capacity to transfer energy between photosystems as well as to dissipate photon excess as heat. They also showed a greater ability to recover after periods of stress and maintained carotenoid levels. This study adds another piece of evidence that soybean plants have stress memory, important to maintain high productivity under a global climate change.

The Descartes Code (Spin Orbital Rotation of Photons)–IV. The Harress-Sagnac Color Excess in the Rotation Curves of Galaxies

In 1933, Zwicky formulated the significant bifurcation point in the history of astrophysics. Zwicky postulated an unknown dark matter in order to explain the color excess in the observed Doppler effect in the rotation curves of galaxies. However, until now we have not detected these dark matter particles. In this contribution, we propose to come back to this bifurcation point and to interpret the observed color excess as the Harress-Sagnac effect known in the rotating interferometers. We have described photon properties in those rotating interferometers based on the old color theory of Descartes—rotating light globules (spin-orbital rotation of photons). Therefore, the color excess observed in the rotation curves of galaxies can be interpreted as the additional color excess of photons emitting from distant rotating stars. Formulae for these color excesses are given for different locations of the rotating galaxy inspired by Zwicky’s core-shell model of galaxies. A part of Zwicky’s enigma is an unknown influence of the Solar gravitational field at 1 AU on the distant photon properties. From the forgotten Gerber’s retarded potential formula we have derived an expression for the acceleration of distant photons towards the Sun at 1 AU as ax = 1.171 × 10⁻¹⁰ ms⁻². This is a very surprising coincidence with the Milgrom empirical value a0 = (1.2 ± 0.1) × 10⁻¹⁰ ms⁻². Therefore, we propose to test this new formula at the surface of Mercury and Mars in order to reveal if our gravitational models are universal or “geocentric”, valid for the surroundings of the Earth only.

Constraining the Astrophysical Origin of Intergalactic Magnetic Fields

High-energy photons can produce electron–positron pairs upon interacting with the extragalactic background light. These pairs will in turn be deflected by the intergalactic magnetic field (IGMF), before possibly up-scattering photons of the cosmic microwave background, thereby initiating an electromagnetic cascade. The nonobservation of an excess of GeV photons and an extended halo around individual blazars due to this electromagnetic cascade can be used to constrain the properties of the IGMF. In this work, we use publicly available data of 1ES 0229+200 obtained with the Fermi Large Area Telescope and the High Energy Stereoscopic System to constrain cosmological MHD simulations of various magnetogenesis scenarios, and find that all models without a strong space-filling primordial component or overoptimistic dynamo amplifications can be excluded at the 95% confidence level. In fact, we find that the fraction of space filled by a strong IGMF has to be at least f ≳ 0.67, thus excluding most astrophysical production scenarios. Moreover, we set lower limits of B 0 > 5.1 × 10−15 G (B 0 > 1.0 × 10−14 G) for a space-filling primordial IGMF for a blazar activity time of Δt = 104 yr (Δt = 107 yr).

Diagnosis of Circumstellar Matter Structure in Interaction-powered Supernovae with Hydrogen Line Features

Some supernovae (SNe) are powered by the collision of the SN ejecta with dense circumstellar matter (CSM). Their emission spectra show characteristic line shapes of combined broad emission and narrow P Cygni lines, which should closely relate to the CSM structure and the mass-loss mechanism that creates the dense CSM. We quantitatively investigate the relationship between the line shape and the CSM structure by Monte Carlo radiative transfer simulations, considering two representative cases of dense CSM formed by steady and eruptive mass loss. Comparing the Hα emission between the two cases, we find that a narrow P Cygni line appears in the eruptive case but does not appear in the steady case due to the difference in the velocity gradient in the dense CSM. We also reproduce the blueshifted photon excess observed in some Type IIn SNe, which is formed by photon transport across the shock wave, and find the relationship between the velocity of the shocked matter and the amount of blueshift of the photon excess. We conclude that the presence or absence of narrow P Cygni lines can distinguish the mass-loss mechanism and suggest high-resolution spectroscopic observations with λ/Δλ ≳ 104 after the light-curve peak for applying this diagnostic method.

MeV Dark Energy Emission from a De Sitter Universe

The evolution of a de Sitter Universe is the basis for both the accelerated Universe and the late-stationary Universe. So, how do we differentiate between both universes? In this paper, we state that it is not possible to design an experiment using luminous or angular distances to distinguish between the two cases because they are the same during the de Sitter phase. However, this equivalence allows us prediction of the signal of a constant dark energy emission with a signal peak around 29.5 MeV, in which, according to our astrophysical test of survival probability, the radiation must be non-standard photons. Remarkably, experiments by EGRET and COMPTEL have observed an excess of gamma photons in this predicted region, coming from a possible decay process of dark energy emission, which may constitute the smoking gun of a late-stationary Universe with the continuous creation of non-standard radiation, an alternative approach to understanding the current stages of the Universe’s evolution.

Induction of stomatal opening following a night-chilling event alleviates physiological damage in mango trees

Chilling events have become more frequent with climate change and are a significant abiotic factor causing physiological damage to plants and, consequently, reducing crop yield. Like other tropical and subtropical plants, mango (Mangifera indica L.) is particularly sensitive to chilling events, especially if they are followed by bright sunny days. It was previously shown that in mango leaves stomatal opening is restricted in the morning following a night-chilling event. This impairment results in restraint of carbon assimilation and subsequently, photoinhibition and reactive oxygen species production, which leads to chlorosis and in severe cases, cell death. Our detailed physiological analysis showed that foliar application of the guard cell H+-ATPase activator, fusicoccin, in the morning after a cold night, mitigates the physiological damage from ‘cold night–bright day’ abiotic stress. This application restored stomatal opening, thereby enabling gas exchange, releasing the photosynthetic machinery from harmful excess photon energy, and improving the plant’s overall physiological state. The mechanisms by which plants react to this abiotic stress are examined in this work. The foliar application of compounds that cause stomatal opening as a potential method of minimizing physiological damage due to night chilling is discussed.

Tailoring Photon Statistics with an Atom-Based Two-Photon Interferometer.

Controlling the photon statistics of light is paramount for quantum science and technologies. Recently, we demonstrated that transmitting resonant laser light past an ensemble of two-level emitters can result in a stream of single photons or excess photon pairs. This transformation is due to quantum interference between the transmitted laser light and the incoherently scattered photon pairs [Prasad etal., Nat. Photonics 14, 719 (2020)NPAHBY1749-488510.1038/s41566-020-0692-z]. Here, using the dispersion of the atomic medium, we actively control the relative quantum phase between these two components. We thereby realize a tunable two-photon interferometer and observe interference fringes in the normalized photon coincidence rate. When tuning the relative phase, the coincidence rate varies periodically, giving rise to a continuous modification of the photon statistics from antibunching to bunching. Beyond the fundamental insight that there exists a tunable quantum phase between incoherent and coherent light that dictates the photon statistics, our results lend themselves to the development of novel quantum light sources.

Constraining axion-like particles with HAWC observations of TeV blazars

Axion-like particles (ALPs) are a broad class of pseudo-scalar bosons that generically arise from broken symmetries in extensions of the standard model. In many scenarios, ALPs can mix with photons in regions with high magnetic fields. Photons from distant sources can mix with ALPs, which then travel unattenuated through the Universe, before they mix back to photons in the Milky Way galactic magnetic field. Thus, photons can traverse regions where their signals would normally be blocked or attenuated. In this paper, we study TeV γ-ray observations from distant blazars, utilizing the significant γ-ray attenuation expected from such signals to look for excess photon fluxes that may be due to ALP-photon mixing. We find no such excesses among a stacked population of seven blazars andconstrain the ALP-photon coupling constant to fall below ∼4.5×10-11 GeV-1 for ALP masses below 300 neV. These results are competitive with, or better than, leading terrestrial and astrophysical constraints in this mass range.

Antenna Modification in a Fast-Growing Cyanobacterium Synechococcus elongatus UTEX 2973 Leads to Improved Efficiency and Carbon-Neutral Productivity.

Our planet is sustained by sunlight, the primary energy source made accessible to all life forms by photoautotrophs. Photoautotrophs are equipped with light-harvesting complexes (LHCs) that enable efficient capture of solar energy, particularly when light is limiting. However, under high light, LHCs can harvest photons in excess of the utilization capacity of cells, causing photodamage. This damaging effect is most evident when there is a disparity between the amount of light harvested and carbon available. Cells strive to circumvent this problem by dynamically adjusting the antenna structure in response to the changing light signals, a process known to be energetically expensive. Much emphasis has been laid on elucidating the relationship between antenna size and photosynthetic efficiency and identifying strategies to synthetically modify antennae for optimal light capture. Our study is an effort in this direction and investigates the possibility of modifying phycobilisomes, the LHCs present in cyanobacteria, the simplest of photoautotrophs. We systematically truncate the phycobilisomes of Synechococcus elongatus UTEX 2973, a widely studied, fast-growing model cyanobacterium and demonstrate that partial truncation of its antenna can lead to a growth advantage of up to 36% compared to the wild type and an increase in sucrose titer of up to 22%. In contrast, targeted deletion of the linker protein which connects the first phycocyanin rod to the core proved detrimental, indicating that the core alone is not enough, and it is essential to maintain a minimal rod-core structure for efficient light harvest and strain fitness. IMPORTANCE Light energy is essential for the existence of life on this planet, and only photosynthetic organisms, equipped with light-harvesting antenna protein complexes, can capture this energy, making it readily accessible to all other life forms. However, these light-harvesting antennae are not designed to function optimally under extreme high light, a condition which can cause photodamage and significantly reduce photosynthetic productivity. In this study, we attempt to assess the optimal antenna structure for a fast-growing, high-light tolerant photosynthetic microbe with the goal of improving its productivity. Our findings provide concrete evidence that although the antenna complex is essential, antenna modification is a viable strategy to maximize strain performance under controlled growth conditions. This understanding can also be translated into identifying avenues to improve light harvesting efficiency in higher photoautotrophs.

Tracking millisecond pulsars responsible for the Fermi GeV excess

More than 10 years ago, an excess of γ-ray photons coming from the Galactic center was discovered in the Fermi-LAT data. First attributed to dark matter, it has since been shown that it should have at least a partial stellar origin. One hypothesis is the presence of a population of millisecond pulsars (MSPs) confined in the Galactic bulge. We here present our recent progress in the selection of MSP candidates.

Photoionization-cross-section measurement of the Rb85 5 P3/22 excited state using microwave cavity resonance spectroscopy

We present microwave cavity resonance spectroscopy as a technique to determine excited-state photoionization cross sections of laser-cooled atoms. We demonstrate this technique by measuring the photoionization cross section of the $5^{2}P_{3/2}({F}^{\ensuremath{'}}=4)$ excited state of $^{85}\mathrm{Rb}$ to continuum by creating an ultracold plasma inside a 5-GHz resonant microwave cavity. We find a photoionization cross section of $\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}22}\phantom{\rule{4pt}{0ex}}{\mathrm{m}}^{2}$ for photon excess energies of 50, 100, 200, and 500 K above the ionization threshold. The measurements yield a cross section which is approximately 2 to 3 times smaller than the value provided by existing theory for the $5p$ excited state of $^{85}\mathrm{Rb}$ and two earlier measurements performed with other techniques for similar excess energies.

Photorespiration in eelgrass (Zostera marina L.): A photoprotection mechanism for survival in a CO2-limited world.

Photorespiration, commonly viewed as a loss in photosynthetic productivity of C3 plants, is expected to decline with increasing atmospheric CO2, even though photorespiration plays an important role in the oxidative stress responses. This study aimed to quantify the role of photorespiration and alternative photoprotection mechanisms in Zostera marina L. (eelgrass), a carbon-limited marine C3 plant, in response to ocean acidification. Plants were grown in controlled outdoor aquaria at different [CO2]aq ranging from ~55 (ambient) to ~2121 μM for 13 months and compared for differences in leaf photochemistry by simultaneous measurements of O2 flux and variable fluorescence. At ambient [CO2], photosynthesis was carbon limited and the excess photon absorption was diverted both to photorespiration and non-photochemical quenching (NPQ). The dynamic range of NPQ regulation in ambient grown plants, in response to instantaneous changes in [CO2]aq, suggested considerable tolerance for fluctuating environmental conditions. However, 60 to 80% of maximum photosynthetic capacity of ambient plants was diverted to photorespiration resulting in limited carbon fixation. The photosynthesis to respiration ratio (P E : R D) of ambient grown plants increased 6-fold when measured under high CO2 because photorespiration was virtually suppressed. Plants acclimated to high CO2 maintained 4-fold higher P E : R D than ambient grown plants as a result of a 60% reduction in photorespiration. The O2 production efficiency per unit chlorophyll was not affected by the CO2 environment in which the plants were grown. Yet, CO2 enrichment decreased the light level to initiate NPQ activity and downregulated the biomass specific pigment content by 50% and area specific pigment content by 30%. Thus, phenotypic acclimation to ocean carbonation in eelgrass, indicating the coupling between the regulation of photosynthetic structure and metabolic carbon demands, involved the downregulation of light harvesting by the photosynthetic apparatus, a reduction in the role of photorespiration and an increase in the role of NPQ in photoprotection. The quasi-mechanistic model developed in this study permits integration of photosynthetic and morphological acclimation to ocean carbonation into seagrass productivity models, by adjusting the limits of the photosynthetic parameters based on substrate availability and physiological capacity.

(Invited) Energy Level Alignment at Monolayer MoS2/Electrolyte Interfaces

The fundamental problem that limits the solar energy conversion efficiency of semiconductors such as CdTe and Si is that all excess solar photon energy above the band gap is lost as heat. Avoiding thermalization energy losses is of paramount significance for solar energy conversion because hot-carrier-based systems theoretically achieve 66% efficiency, which breaks the detailed balance limit of 33%.Of all the candidate materials, 2D semiconductors such as monolayer (ML) MoS2 have unique physical and photophysical properties that could make hot-carrier energy conversion possible. The knowledge gap in the field is that the electronic states of 2D materials move with carrier density, due to either light absorption or an applied electrochemical potential. The energy level movements are significant because the real fundamental driving force for charge transfer (ΔG 0´) is unclear for a given reaction and applied potential. In principle, quantifying ΔG 0´ under working conditions opens up the possibility to tune the hot carrier extraction rate relative to the cooling rate. Our research team has employed photocurrent spectroscopy, steady-state absorption spectroscopy, and in situ femtosecond transient absorption spectroscopy as a function of applied potential to characterize underlying steps in a ML MoS2 photoelectrochemical cell. The rich data set informs us on the timescales for hot-carrier generation/cooling and exciton formation/recombination, as well as the magnitudes of changes in exciton energy levels, exciton binding energies, and the electronic band gap. These findings open the possibility of tuning the hot-carrier extraction rate relative to the cooling rate to ultimately utilize hot-carriers for solar energy conversion applications.

Non-equilibrium photons from the bottom-up thermalization scenario

In this work, I calculate the p⊥ resolved spectra for the three stages of the bottom-up scenario, which are comparable to the thermal contribution, particularly at higher values of the saturation scale Q2. Analytical solutions are obtained by including a parametrization of scaling solutions from far-from-equilibrium classical statistical lattice simulations into a small angle kinetic rate. Furthermore, a theoretically motivated ansatz is used to account for near-collinear enhancement of the low-p⊥ radiation. The system is phenomenologically constrained using the charged hadron multiplicities from LHC and RHIC as in previous parametric estimates and fair agreement with the data available for photons was found. I find that for this realistic set of parameters, the contribution from the pre-equilibrium dominates the excess photons.

BER improvement in SPAD-based photon-counting optical communication system by using automatic attenuation control technique.

In order to overcome the saturation of a single-photon avalanche diode (SPAD)-based receiver and keep the output counts at optimum level automatically, a new, to the best of our knowledge, scheme using the automatic attenuation control (AAC) technique is proposed. In the scheme, an AAC module is applied to attenuate excess incident photons. Furthermore, on the foundation of the bit error rate (BER) model of a photon-counting optical communication system, a reliable and efficient AAC algorithm is developed to compute the optimal attenuation factor. Based on the AAC algorithm, the optimal attenuation factors under different operation conditions are investigated. The results indicate that the incident optical intensity and signal-to-background ratio play an important role in determining the optimal attenuation factor. Moreover, at high incident optical intensity, the system BER utilized AAC module can be improved by 0.5 to 3 orders of magnitude. The AAC technique can effectively expand the dynamic range of the SPAD-based receiver.

Mitochondrial ATP synthesis activated by exciton energy transfer from Müller cell intermediate filaments

• Exciton energy transferred from IFs to mitochondria accelerated ATP production rate. • ATP production rate explored in function of mitochondrial concentration. • ATP production rate explored in function of intensity of light that produced excitons. ATP production by mitochondria isolated from yeast cells ( S. cerevisiae ) was accelerated by exciton energy transfer from intermediate filaments (IFs). The effect was dependent on mitochondrial concentration and the intensity of light used to generate excitons. Presumably, mitochondrial cytochrome C (CC) was activated by IF exciton energy transfer to CC in the inner mitochondrial membrane (IMM), generating electronically excited CC, and the respective excitation energy was then used in the ATP production chain. A qualitative model was proposed describing observations, although more experiments are required before the detailed mechanisms could be deduced. The present results support the earlier proposed hypothesis of ATP production in vertebrate retina by excess photons in daytime, when retina needs extra energy for recovering the used opsins. Additionally, it shows that at early stages of evolution mitochondria could have been using solar radiation to produce ATP.

Vulnerability of Satellite Quantum Key Distribution to Disruption from Ground-Based Lasers.

Satellite-mediated quantum key distribution (QKD) is set to become a critical technology for quantum-secure communication over long distances. While satellite QKD cannot be effectively eavesdropped, we show it can be disrupted (or ‘jammed’) with relatively simple and readily available equipment. We developed an atmospheric attenuation and satellite optical scattering model to estimate the rate of excess noise photons that can be injected into a satellite QKD channel by an off-axis laser, and calculated the effect this added noise has on the quantum bit error rate. We show that a ground-based laser on the order of 1 kW can significantly disrupt modern satellite QKD systems due to photons scattering off the satellite being detected by the QKD receiver on the ground. This class of laser can be purchased commercially, meaning such a method of disruption could be a serious threat to effectively securing high-value communications via satellite QKD in the future. We also discuss these results in relation to likely future developments in satellite-mediated QKD systems, and countermeasures that can be taken against this, and related methods, of disruption.

Genome-Wide Characterization of B-Box Gene Family and Its Roles in Responses to Light Quality and Cold Stress in Tomato.

Perceiving incoming environmental information is critical for optimizing plant growth and development. Multiple B-box proteins (BBXs) play essential roles in light-dependent developmental processes in plants. However, whether BBXs function as a signal integrator between light and temperature in tomato plants remains elusive. In this study, 31 SlBBX genes were identified from the newly released tomato (Solanum lycopersicum) genome sequences and were clustered into five subgroups. Gene structure and protein motif analyses showed relatively high conservation of closely clustered SlBBX genes within each subgroup; however, genome mapping analysis indicated the uneven distribution of the SlBBX genes on tomato chromosomes. Promoter cis-regulatory elements prediction and gene expression indicated that SlBBX genes were highly responsive to light, hormones, and stress conditions. Reverse genetic approaches revealed that disruption of SlBBX7, SlBBX9, and SlBBX20 largely suppressed the cold tolerance of tomato plants. Furthermore, the impairment of SlBBX7, SlBBX9, and SlBBX20 suppressed the photosynthetic response immediately after cold stress. Due to the impairment of non-photochemical quenching (NPQ), the excess photon energy and electron flow excited by low temperature were not consumed in SlBBX7-, SlBBX9-, and SlBBX20- silenced plants, leading to the over reduction of electron carriers and damage of the photosystem. Our study emphasized the positive roles of light signaling transcription factors SlBBXs in cold tolerance in tomato plants, which may improve the current understanding of how plants integrate light and temperature signals to adapt to adverse environments.

The role of light intensity in mediating ascorbic acid content during postharvest tomato ripening: A transcriptomic analysis

Ascorbic acid (ASA) is an essential antioxidant, participating in diverse processes. In this study, tomato fruit at two maturity stages (mature-green, breaker) were first exposed to light at four photosynthetic photon flux density (PPFD) levels [0 (darkness), 50, 300, 600 μmol m-2 s-1], and then to darkness. As PPFD increased, ASA content was enhanced. The light-induced ASA content increase was dependent on the maturity stage, and persisted following darkening. High PPFD up-regulated the expression of key genes of the D-mannose/L-galactose pathway, showing the biosynthesis contributed, while the ASA recycling had a limited contribution. Weighted correlation network analysis showed that high PPFD potentially enhances the photosynthetic photon transduction, especially cyclic electron flow to excess photons. High PPFD up-regulated the expression of genes encoding non-enzymatic antioxidant biosynthesis. We show that photosynthetic photon transduction mediates fruit adaptation to light intensity, and provides new insights into the interactive regulation of fruit ASA accumulation.

후두 기공 협착 예방을 위한 청색광 레이저의 적용

Stomal stenosis is a narrowing of stoma created by surgical incision and one of the most common complications that exist in patients after tracheostomy. Recently, blue laser light (405 nm) has been suggested as a non-surgical and noninvasive tool for preventing stenosis and scar through cell inactivation. However, the excessive photon energy may lead to irreversible damage in biological tissue due to excessive heat generation. Therefore, the purpose of this study is to numerically assess developments of temperature and thermal damage in a multi-layer tissue during 405 nm laser irradiation for the treatment of the stomal stenosis. The proposed simulation evaluates spatio-temporal changes of temperature induced by the 405 nm laser irradiation at 250, 500, and 1000 mW/㎠ for 300 s in the stomal stenosis model. The simulation results show that the irradiation of 250 mW/㎠ for 300 s increases the temperature of the stomal tissue up to 39.6 °C, which can induce a photochemical response with no or minimal thermal damage. Thus, the proposed bio-heat transfer simulation model can predict the extent of the laser-induced heat generation as well as thermal damage in the stomal tissue. Further studies will examine the identified irradiation condition in an animal model to evaluate a therapeutic capacity of the blue laser light for the prevention of the laryngeal stomal tissue.