Low-energy Flux Research Articles

Injection of intense low-energy reactor-based positron beams into a supported magnetic dipole trap

An increased low-energy positron flux is obtained from the reactor based NEPOMUC source when using its primary beam at energies as low as 20 eV. First experiments with this beam in a supported magnetic dipole trap resulted in the maximum current of injected positrons to date. According to single-particle simulations, remaining limitations in the injection efficiency, observed in the experiment, can be attributed to the spatial spread of the beam. In the first trapping measurements with this beam, top-down asymmetries in the electrostatic trapping potential are found to be detrimental to confinement.

Impact of crystallite size on the performance of a beryllium reflector

Beryllium reflectors are used at spallation neutron sources in order to enhance the low-energy flux of neutrons emanating from the surface of a cold and thermal moderator. The design of such a moderator/reflector system is typically carried out using detailed Monte-Carlo simulations, where the beryllium reflector is assumed to behave as a poly-crystalline material. In reality, however, inhomogeneities in the beryllium could lead to discrepancies between the performance of the actual system when compared to the modeled system. The dependence of the total cross-section in particular on crystallite size, in the Bragg scattering region, could influence the reflector performance, and if such an effect is significant, it should be taken into account in the design of the moderator/reflector system. In this paper, we report on the preliminary results of using cross-section libraries, which include corrections for the crystallite size effect, in spallation source neutronics calculations.

Solar Cycle Variation of Coronal Temperature, Emission Measure, and Soft X-Ray Irradiance Observed with Yohkoh Soft X-Ray Telescope

Abstract This paper presents the solar soft X-ray irradiance (0.3–3.0 nm) obtained from the mission-long full-Sun X-ray images observed with the Soft X-ray Telescope (SXT) of the Yohkoh mission (1991–2001). The irradiance was calculated using filter-ratio temperatures and emission measures (EMs) from the full-Sun integrated X-ray signals employing a coronal spectrum synthesized with CHIANTI atomic database version 8.0. Dependence of the results on the assumption of elemental abundances is investigated. The SXT irradiance for a shorter wavelength range was also calculated and compared with the low energy flux (0.1–0.8 nm) of the X-Ray Sensor on board the GOES satellite. To incorporate the spatial information of the observed corona, we tried the alternative method to derive irradiance by applying the filter-ratio method to the images of northern hemispheric corona instead of spatially integrated signals from there. The EM weighted average of the spatially resolved temperatures turned out to be generally 20%–30% lower than those derived from the integrated signals, while the total of spatially resolved EMs are accordingly 1.5–2 times higher. This trend is enhanced when solar activity is the lowest in early 1996. The irradiance obtained from the alternative method does not significantly vary from the result from the integrated signals. This provides some validation for the simpler full-Sun integrated method. The temporal variation of the EMs of cool (<1.5 MK), medium, and hot (>2.5 MK) components indicates that the ratio of the hot component relative to the medium component is higher in the ascending phase (mid 1998–2001) than in the descending phase (1992–1995) of the solar activity cycle.

Increasing Energy Flux to Maintain Diet-Induced Weight Loss.

Long-term maintenance of weight loss requires sustained energy balance at the reduced body weight. This could be attained by coupling low total daily energy intake (TDEI) with low total daily energy expenditure (TDEE; low energy flux), or by pairing high TDEI with high TDEE (high energy flux). Within an environment characterized by high energy dense food and a lack of need for movement, it may be particularly difficult for weight-reduced individuals to maintain energy balance in a low flux state. Most of these individuals will increase body mass due to an inability to sustain the necessary level of food restriction. This increase in TDEI may lead to the re-establishment of high energy flux at or near the original body weight. We propose that following weight loss, increasing physical activity can effectively re-establish a state of high energy flux without significant weight regain. Although the effect of extremely high levels of physical activity on TDEE may be constrained by compensatory reductions in non-activity energy expenditure, moderate increases following weight loss may elevate energy flux and encourage physiological adaptations favorable to weight loss maintenance, including better appetite regulation. It may be time to recognize that few individuals are able to re-establish energy balance at a lower body weight without permanent increases in physical activity. Accordingly, there is an urgent need for more research to better understand the role of energy flux in long-term weight maintenance.

Investigating the multiwavelength behaviour of the flat spectrum radio quasar CTA 102 during 2013–2017

ABSTRACT We present a multiwavelength study of the flat-spectrum radio quasar CTA 102 during 2013–2017. We use radio-to-optical data obtained by the Whole Earth Blazar Telescope, 15 GHz data from the Owens Valley Radio Observatory, 91 and 103 GHz data from the Atacama Large Millimeter Array, near-infrared data from the Rapid Eye Monitor telescope, as well as data from the Swift (optical-UV and X-rays) and Fermi (γ-rays) satellites to study flux and spectral variability and the correlation between flux changes at different wavelengths. Unprecedented γ-ray flaring activity was observed during 2016 November–2017 February, with four major outbursts. A peak flux of (2158 ± 63) × 10−8 ph cm−2 s−1, corresponding to a luminosity of (2.2 ± 0.1) × 1050 erg s−1, was reached on 2016 December 28. These four γ-ray outbursts have corresponding events in the near-infrared, optical, and UV bands, with the peaks observed at the same time. A general agreement between X-ray and γ-ray activity is found. The γ-ray flux variations show a general, strong correlation with the optical ones with no time lag between the two bands and a comparable variability amplitude. This γ-ray/optical relationship is in agreement with the geometrical model that has successfully explained the low-energy flux and spectral behaviour, suggesting that the long-term flux variations are mainly due to changes in the Doppler factor produced by variations of the viewing angle of the emitting regions. The difference in behaviour between radio and higher energy emission would be ascribed to different viewing angles of the jet regions producing their emission.

New Model for the Plasma Electrons Fluxes (Part of GREEN Model)

A new specification model of low-energy electrons fluxes, included in the Global Radiation Earth ENvironment (GREEN) model, has been developed at ONERA. This model is based on several data sets, from low altitudes with National Oceanic and Atmospheric Administration-Polar Operational Environmental Satellites measurements to higher altitudes with POLAR, THEMIS, and Los Alamos National Laboratory (LANL) measurements. It provides mean electron fluxes versus $L$ , $B/B _{\mathrm {eq}}$ , magnetic local time (MLT), and energy (for energies between 0.19 keV and few tens of kiloelectron volts). In this paper, the model is compared to AE9/SPM model and Van Allen Probe measurements.

Linking size spectrum, energy flux and trophic multifunctionality in soil food webs of tropical land-use systems.

Many ecosystem functions depend on the structure of food webs, which heavily relies on the body size spectrum of the community. Despite that, little is known on how the size spectrum of soil animals responds to agricultural practices in tropical land-use systems and how these responses affect ecosystem functioning. We studied land-use-induced changes in below-ground communities in tropical lowland ecosystems in Sumatra (Jambi province, Indonesia), a hot spot of tropical rainforest conversion into rubber and oil palm plantations. The study included ca. 30,000 measured individuals from 33 high-order taxa of meso- and macrofauna spanning eight orders of magnitude in body mass. Using individual body masses, we calculated the metabolism of trophic guilds and used food web models to calculate energy fluxes and infer ecosystem functions, such as decomposition, herbivory, primary and intraguild predation. Land-use change was associated with reduced abundance and taxonomic diversity of soil invertebrates, but strong increase in total biomass and moderate changes in total energy flux. These changes were due to increased biomass of large-sized decomposers in soil, in particular earthworms, with their share in community metabolism increasing from 11% in rainforest to 59%-76% in jungle rubber, and rubber and oil palm plantations. Decomposition, that is the energy flux to decomposers, stayed unchanged, but herbivory, primary and intraguild predation decreased by an order of magnitude in plantation systems. Intraguild predation was very important, being responsible for 38% of the energy flux in rainforest according to our model. Conversion of rainforest into monoculture plantations is associated by an uneven loss of size classes and trophic levels of soil invertebrates resulting in sequestration of energy in large-sized primary consumers and restricted flux of energy to higher trophic levels. Pronounced differences between rainforest and jungle rubber reflect sensitivity of rainforest soil animal communities to moderate land-use changes. Soil communities in plantation systems sustained high total energy flux despite reduced biodiversity. The high energy flux into large decomposers but low energy fluxes into other trophic guilds suggests that trophic multifunctionality of below-ground communities is compromised in plantation systems.

Origin of the low-energy gamma ray flux of the long-lasting thunderstorm ground enhancements

To identify the role of the gamma radiation from radon progenies in long-lasting thunderstorm ground enhancement (TGE) flux, the differential energy spectrum is measured with various spectrometers, including precise spectrometer of ORTEC firm built with $3''\ifmmode\times\else\texttimes\fi{}3''$ inches sodium iodide NaI(Tl) crystal; full width at half maximum (FWHM) $\ensuremath{\sim}7.7%$ at 0.6 MeV. The measurements demonstrate that radon progeny radiation significantly contributes to the count rate enhancements measured in the winter of 2018--2019 in the energy range below 3 MeV. However, performed Monte Carlo simulations and observation of long-lasting TGEs with plastic scintillators of various thicknesses and energy thresholds show that TGEs originate in the intracloud electric fields. Radon progenies (mostly $^{214}\mathrm{Bi}$ spectral lines) contribute to count rate in the low-energy domain.

Irradiation hardening induced by blistering in tungsten due to low-energy high flux hydrogen plasma exposure

In this work, the microstructure evolution in the near-surface of tungsten under hydrogen (H) plasma exposure conditions was observed by means of scanning electron microscopy (SEM), plasma focused ion beam (FIB) and transmission electron microscopy (TEM) techniques. Blisters, with existing dislocations distributed around obviously, were observed beneath the tungsten surface when the exposure temperature was 573 K, which was rarely reported in previous studies. However, H bombardment at 1273 K did not lead to the formation of blister-like microstructures. Correspondingly, irradiation hardening occurred after low temperature exposure, but not after high temperature exposure, according to the Berkovich nano-indentation experiments. In order to characterize the indentation size effect and irradiation hardening behavior of plasma-exposed materials, a mechanistic model was proposed for the hardness-depth relationship. A good agreement between the experimental indentation data and theoretical results revealed that plasma-induced dislocations play a dominant role in determining the increase of hardness for H plasma-exposed tungsten.

Thermionic-enhanced near-field thermophotovoltaics

Solid-state heat-to-electrical power converters are thermodynamic engines that use fundamental particles, such as electrons or photons, as working fluids. Virtually all commercially available devices are thermoelectric generators, in which electrons flow through a solid driven by a temperature difference. Thermophotovoltaics and thermionics are highly efficient alternatives relying on the direct emission of photons and electrons. However, the low energy flux carried by the emitted particles significantly limits their generated electrical power density potential. Creating nanoscale vacuum gaps between the emitter and the receiver in thermionic and thermophotovoltaic devices enables a significant enhancement of the electron and photon energy fluxes, respectively, which in turn results in an increase of the generated electrical power density. Here we propose a thermionic-enhanced near-field thermophotovoltaic device that exploits the simultaneous emission of photons and electrons through nanoscale vacuum gaps. We present the theoretical analysis of a device in which photons and electrons travel from a hot LaB6-coated tungsten emitter to a closely spaced BaF2-coated InGaAs photovoltaic cell. Photon tunnelling and space charge removal across the nanoscale vacuum gap produce a drastic increase in flux of electrons and photons, and subsequently, of the generated electrical power density. We show that conversion efficiencies and electrical power densities of ∼ 30% and ∼ 70 W/cm2 are achievable at 2000 K for a practicable gap distance of 100 nm, and thus greatly enhance the performances of stand-alone near-field thermophotovoltaic devices (∼10% and ∼10 W/cm2). A key practical advantage of this nanoscale energy conversion device is the use of grid-less cell designs, eliminating the issue of series resistance and shadowing losses, which are unavoidable in conventional near-field thermophotovoltaic devices.

Surface nano structures on W surface exposed to low-energy high flux D plasma

The surface nano structures on W surface exposed to low-energy D plasma was studied by transmission electron microscopy. It was found that the surface nano structures on W surface induced by D plasma were mainly due to two reasons. First, the subsurface nano-sized bubbles will induce nano scale blistering of the surface, resulting in surface nano morphology. The nano scale blistering behaviour is most obvious on [1 1 1] surface at low temperature (500 K). Secondly, during the plasma exposure, oxide layer on W surface will be sputtered by low energy D particles, and the sputtering can also induce nano structures on some surfaces. At low temperature (500 K), the surface nano structures were formed due to the nano scale blistering behaviour and the sputtering of surface oxide layer. At high temperature (1000 K), the surface nano structures were mainly caused by the sputtering of surface oxide layer.

Aggravated blistering and increased deuterium retention in iron-damaged tungsten after exposure to deuterium plasma with various surface temperatures

Effects of iron ion pre-irradiation with energy of 1 MeV on deuterium retention and blistering in tungsten has been investigated after exposure to low-energy (40 eV) and high flux (~1022 D m−2 s−1) deuterium plasma under high fluence of 1 × 1026 D m−2 with various surface temperatures (450 K, 550 K and 750 K). The undamaged and pre-damaged tungsten show a similar temperature dependence of deuterium-induced blistering, as well as deuterium retention in the near surface (within 300 nm). Deuterium concentration in the near surface decreases with increasing the surface temperature in deuterium plasma exposure. For both cases, the most serious blistering is present at the surface temperature of 550 K. Due to the creation of pre-damage the size of surface blister becomes much larger and the near-surface deuterium concentration becomes higher. Analysis of blistering-related cavities in the pre-damaged and undamaged tungsten indicates that in pre-damaged tungsten deuterium aggregates in the place with a much larger depth. Based on the comparison of the pre-damage induced increment of deuterium retention within the near surface region (damage layer) and in the bulk, it reveals that the pre-damage enhances deuterium retention in the bulk more strongly than that in the near-surface region, suggesting that the deuterium flux diffusing into the bulk of pre-damaged tungsten is largely improved.

Diagnosing low earth orbit satellite anomalies using NOAA-15 electron data associated with geomagnetic perturbations

A satellite placed in space is constantly affected by the space environment, resulting in various impacts from temporary faults to permanent failures depending on factors such as satellite orbit, solar and geomagnetic activities, satellite local time, and satellite construction material. Anomaly events commonly occur during periods of high geomagnetic activity that also trigger plasma variation in the low Earth orbit (LEO) environment. In this study, we diagnosed anomalies in LEO satellites using electron data from the Medium Energy Proton and Electron Detector onboard the National Oceanic and Atmospheric Administration (NOAA)-15 satellite. In addition, we analyzed the fluctuation of electron flux in association with geomagnetic disturbances 3 days before and after the anomaly day. We selected 20 LEO anomaly cases registered in the Satellite News Digest database for the years 2000–2008. Satellite local time, an important parameter for anomaly diagnosis, was determined using propagated two-line element data in the SGP4 simplified general perturbation model to calculate the longitude of the ascending node of the satellite through the position and velocity vectors. The results showed that the majority of LEO satellite anomalies are linked to low-energy electron fluxes of 30–100 keV and magnetic perturbations that had a higher correlation coefficient (~ 90%) on the day of the anomaly. The mean local time calculation for the anomaly day with respect to the nighttime migration of energetic electrons revealed that the majority of anomalies (65%) occurred on the night side of Earth during the dusk-to-dawn sector of magnetic local time.

Exposure to radial extracorporeal shock waves modulates viability and gene expression of human skeletal muscle cells: a controlled in vitro study

BackgroundRecent clinical and animal studies have shown that extracorporeal shock wave therapy has a promoting influence on the healing process of musculoskeletal disorders. However, the underlying biological effects of extracorporeal shock wave therapy on human skeletal muscle cells have not yet been investigated.MethodsIn this study, we investigated human skeletal muscle cells after exposure to radial extracorporeal shock waves in a standardized in vitro setup. Cells were isolated from muscle specimens taken from adult patients undergoing spine surgery. Primary muscle cells were exposed once or twice to radial extracorporeal shock waves in vitro with different energy flux densities. Cell viability and gene expression of the paired box protein 7 (Pax7), neural cell adhesion molecule (NCAM), and myogenic factor 5 (Myf5) and MyoD as muscle cell markers were compared to non-treated muscle cells that served as controls.ResultsIsolated muscle cells were positive for the hallmark protein of satellite cells, Pax7, as well as for the muscle cell markers NCAM, MyoD, and Myf5. Exposure to radial extracorporeal shock waves at low energy flux densities enhanced cell viability, whereas higher energy flux densities had no further significant impact. Gene expression analyses of muscle specific genes (Pax7, NCAM, Myf5, and MyoD) demonstrated a significant increase after single exposure to the highest EFD (4 bar, 0.19 mJ/mm2) and after double exposure with the medium EFDs (2 and 3 bar; 0.09 and 0.14 mJ/mm2, respectively). Double exposure of the highest EFD, however, results in a significant down-regulation when compared to single exposure with this EFD.ConclusionsThis is the first study demonstrating that radial extracorporal shock wave therapy has the potential to modulate the biological function of human skeletal muscle cells. Based on our experimental findings, we hypothesize that radial extracorporal shock wave therapy could be a promising therapeutic modality to improve the healing process of sports-related structural muscle injuries.

Particle Acceleration at Structure Formation Shocks

Cosmological hydrodynamic simulations have demonstrated that shock waves could be produced in the intergalactic medium by supersonic flow motions during the course of hierarchical clustering of the large-scale-structure in the Universe. Similar to interplanetary shocks and supernova remnants (SNRs), these structure formation shocks can accelerate cosmic ray (CR) protons and electrons via diffusive shock acceleration. External accretion shocks, which form in the outermost surfaces of nonlinear structures, are as strong as SNR shocks and could be potential accelerations sites for high energy CR protons up to 1018 eV. But it could be difficult to detect their signatures due to extremely low kinetic energy flux associated with those accretion shocks. On the other hand, radiative features of internal shocks in the hot intracluster medium have been identified as temperature and density discontinuities in X-ray observations and diffuse radio emission from accelerated CR electrons. However, the non-detection of gamma-ray emission from galaxy clusters due to π0 decay still remains to be an outstanding problem.

Extracorporeal shock wave therapy with low-energy flux density inhibits hypertrophic scar formation in an animal model.

Hypertrophic scar is characterized by excessive deposits of collagen during skin wound healing, which could become a challenge to clinicians. This study assessed the effects of the extracorporeal shock wave therapy (ESWT) on hyper-trophic scar formation and the underlying gene regulation. A rabbit ear hypertrophic scar model was generated and randomly divided into three groups: L-ESWT group to receive L-ESWT (energy flux density of 0.1 mJ/mm2), H-ESWT (energy flux density of 0.2 mJ/mm2) and sham ESWT group (S-ESWT). Hypertrophic scar tissues were then collected and stained with hematoxylin and eosin (H&E) and Masson's trichrome staining, respectively, to assess scar elevation index (SEI), fibroblast density and collagen fiber arrangement. Expression of cell proliferation marker proliferating cell nuclear antigen (PCNA) and α-smooth muscle actin (α-SMA) were assessed using RT-PCR and immunohistochemistry in hypertrophic scar tissues. H&E staining sections showed significant reduction of SEI and fibroblast density in both ESWT treatment groups compared to S-ESWT, but there was no dramatic difference between L-ESWT and H-ESWT groups. Masson's trichrome staining showed that collagen fibers were more slender and broader and oriented in parallel to skin surface after administration of ESWT compared to control tissues. At the gene level, PCNA-positive fibroblasts and α-SMA-positive myofibroblasts were significantly decreased after L-ESWT or H-ESWT compared to the controls. Furthermore, there was no significant difference in expression of PCNA mRNA between L-ESWT or H-ESWT and S-ESWT, whereas expression of α-SMA mRNA significantly decreased in L-ESWT compared to that of H-ESWT and S-ESWT (P=0.002 and P=0.030, respectively). In conclusion, L-ESWT could be effective on suppression of hypertrophic scar formation by inhibition of scar elevation index and fibroblast density as well as α-SMA expression in hypertrophic scar tissues of the rabbit model.

Solar neutrino flux at keV energies

We calculate the solar neutrino and antineutrino flux in the keV energy range. The dominant thermal source processes are photo production (γ e→ e νν̄), bremsstrahlung (e+Ze→ Ze+e+νν̄), plasmon decay (γ→νν̄), and νν̄ emission in free-bound and bound-bound transitions of partially ionized elements heavier than hydrogen and helium. These latter processes dominate in the energy range of a few keV and thus carry information about the solar metallicity. To calculate their rate we use libraries of monochromatic photon radiative opacities in analogy to a previous calculation of solar axion emission. Our overall flux spectrum and many details differ significantly from previous works. While this low-energy flux is not measurable with present-day technology, it could become a significant background for future direct searches for keV-mass sterile neutrino dark matter.

Electrokinetic and Biochemical Changes in Erythrocytes under the Action of Terahertz Range Electromagnetic Waves

The effects of electromagnetic radiation of a gyrotron with an operating frequency of 263 GHz on rat erythrocyte electrophoretic mobility, malonic dialdehyde, ATP, and 2,3-diphosphoglycerate concentration have been studied in vitro. The blood was irradiated under continuous and pulsed gyrotron emission modes with the estimated incident energy flux on an object from 0.1 to 20 mW/cm2. It has been established that the studied erythrocyte characteristics changed in different directions depending on the mode and the incident energy flux: the erythrocyte electrophoretic mobility rate and ATP concentration decreased, while the malonic dialdehyde and 2,3-diphosphoglycerate concentration increased at a low incident energy flux and continuous exposure mode; all studied parameters increased under the pulsed exposure mode. An incident energy flux increase caused a reduction of these effects.

The clinical utility of extracorporeal shock wave therapy for burn pruritus: A prospective, randomized, single-blind study

PurposesTo investigate the effect and mechanisms of extracorporeal shock wave therapy (ESWT) on burn scar pruritus. MethodsForty-six patients participated (experimental group, n=23; sham stimulation group, n=23). Patients had complaints of severe pruritus ranging from 5 to 10 on the visual analog scale. The experimental group received 1000–2000 shock waves for each treatment with 100 impulses/cm2, each with low-energy flux density (0.05–0.20mJ/mm2) and a 1-week interval between treatments for 3 weeks. The numerical rating scale (NRS), 5D-Itch Scale, and Leuven Itch Scale were evaluated immediately before ESWT and after the third session. Laser Doppler blood perfusion imaging (LDI) was performed immediately before ESWT and after the first and third sessions. ResultsIn the experimental group, mean NRS scores were 6.30±1.29 before therapy and 3.57±2.09 after the third session, and the difference was significant (p<0.001). NRS scores in the experimental group after the third ESWT were significantly decreased compared to those of the sham stimulation group (p=0.009). The duration, severity, and consequences scores of pruritus on the Leuven Itch Scale after the third ESWT were significantly decreased in the experimental group compared with the sham stimulation group (p=0.033, p=0.007, and p=0.009, respectively). The direction score on the 5-D Itch Scale after the third ESWT was significantly decreased in the experimental group compared to the sham stimulation group (p=0.033). After the first ESWT session and after 3 sessions, the burn area had a significant increase in perfusion according to LDI, compared with the scores before treatment in the experimental group (p=0.023 and p=0.013, respectively). ConclusionESWT is a non-invasive modality that significantly reduced burn-associated pruritus.

Going low: measurement of Solar pp-neutrino flux with liquid scintillator detector

Recently Borexino collaboration announced the first direct measurement of the low-energy neutrino flux from the pp-reaction in the Sun. Together with previous measurements of solar neutrino fluxes from 7Be, 8B and pep reactions the measurement completes the study of the neutrino fluxes from the pp-chain of solar reactions. Technical details of the analysis are presented, and results and implications are discussed.