MW Field Research Articles

The ratio of [Eu/α] differentiates accreted/in-situ Milky Way stars across metallicities, as indicated by both field stars and globular clusters

Abstract We combine stellar orbits with the abundances of the heavy, r-process element europium and the light, α-element, silicon to separate in-situ and accreted populations in the Milky Way across all metallicities. At high orbital energy, the accretion-dominated halo shows elevated values of [Eu/Si], while at lower energies, where many of the stars were born in-situ, the levels of [Eu/Si] are lower. These systematically different levels of [Eu/Si] in the MW and the accreted halo imply that the scatter in [Eu/α] within a single galaxy is smaller than previously thought. At the lowest metallicities, we find that both accreted and in-situ populations trend down in [Eu/Si], consistent with enrichment via neutron star mergers. Through compiling a large dataset of abundances for 54 globular clusters (GCs), we show that differences in [Eu/Si] extend to populations of in-situ/accreted GCs. We interpret this consistency as evidence that in r-process elements GCs trace the star formation history of their hosts, motivating their use as sub-Gyr timers of galactic evolution. Furthermore, fitting the trends in [Eu/Si] using a simple galactic chemical evolution model, we find that differences in [Eu/Si] between accreted and in-situ MW field stars cannot be explained through star formation efficiency alone. Finally, we show that the use of [Eu/Si] as a chemical tag between GCs and their host galaxies extends beyond the Local Group, to the halo of M31 - potentially offering the opportunity to do Galactic Archaeology in an external galaxy.

Microwave assisted efficient non-degenerate four-wave mixing in pulsed regime

We theoretically investigate a N-type 87Rb atomic system for efficient generation and control of a non-degenerate four wave mixing (FWM) signal in pulsed regime. The susceptibility of the atomic medium is customized as a gain profile by a weak probe pulse and two strong continuous wave control fields which allow us to generate the pulsed FWM signal. We study the propagation dynamics of the generated FWM signal inside the nonlinear medium. The FWM signal obtains the exact shape of the probe pulse and travels without changing the shape whereas, the probe pulse is absorbed inside the nonlinear medium. The conversion efficiency of this scheme without a MW field is 5.36%. However, a MW field that couples two metastable ground states enhances the conversion efficiency to 20.6%. The generation and control of such FWM signal in pulsed regime has important applications in signal processing, optical communication and information science.

Microwave optical limiting via an acoustic field in a diamond mechanical resonator.

We investigate the generation and control of the reverse saturable absorption (RSA) and optical limiting (OL) at microwave (mw) range in high-Q single-crystal diamond mechanical resonator (DMR) embedded with many nitrogen-vacancy (NV) centers. The strain-induced acoustic modes enable mechanical manipulation of NV centers. On the basis of strain-coupling mechanism, it is shown that the saturable absorption (SA) switches to the RSA by applying the acoustic field, leading to induce the OL in the diamond through the cross-Kerr effect. We demonstrate that the OL characteristics such as, threshold, efficiency, and dynamic range can be controlled by changing either the intensity or frequency of the acoustic field. Moreover, we show that this optical limiter can amplify noiselessly the low intensity of the mw field input to the sensors and also attenuate any gain-induced noise and increase in the intensity of the mw field if it exceeds the intensity threshold. In addition, it is shown that by increasing either the number of NV centers or length of the diamond, the optical limiter can be more efficient. The physical mechanism of the OL establishment is explained using the analytical expressions, which are in good agreement with the numerical results. Our proposed acoustic-induced optical limiter can be a scheme for protecting different optical and electronic devices in mw range, remote sensing, navigation, communications, microwave heating and thermo/laser therapy.

Aeroelastic model validation with 8 MW field measurements: Influence of constrained turbulence with focus on power performance

Aeroelastic model simulations are essential for the design of wind turbines. Validation of these models is important to have confidence in the results of the models. It is a challenge to ensure that the input for the simulations, that is the wind field, corresponds as closely as possible to the real conditions during the measurement. We present the latest results of a validation campaign at an 8 MW wind turbine. We investigate the appropriateness of TurbSim’s constrained turbulence model TIMESR for model validation and compare the validation results with the Kaimal turbulence model with a focus on power performance. TIMESR wind resulted in a slightly lower power performance in the part-load region than Kaimal wind. In contrast, the rotor speed showed a good agreement with measurements both using TIMESR wind as well as using Kaimal wind. Additionally, the linear regression result implies that the constrained turbulence wind field enables the model to reproduce a specific 10 min measurement. However, up to know the simulations show a consistently lower power in the part load region, which might result from a systematic error in the validation chain.

Microwave-assisted hydrothermal liquefaction for biomass valorization: Insights into the fuel properties of biocrude and its liquefaction mechanism

In contrast to the conventional liquefaction, microwave-assisted hydrothermal liquefaction (MW-HTL) is a recently developed technology for the production of biocrude for energy recovery; however, the exploration on liquefaction process under microwave radiation still presents a gap in understanding. In this study, two samples with typical components were adopted for MW-HTL, and a series of multiple techniques were used to analyze the fuel properties of biocrude as well as the corresponding changes of organic substances. Results found that microwave radiation facilitates the liquefaction process by inhibiting the secondary reactions during heating period and the excessive polymerization during liquefaction processes, resulting in an increase of approximately 39.8–43.9 % of yield, 3.9–4.0 % of higher heating values, and 46.6–59.0 % of energy recovery efficiency than that of biocrude obtained from the conventional liquefaction under similar conditions. The interaction depends on a process termed dipolar polarization was found as the main reason for this improvement, which involves the adsorption of microwave radiation by polar groups in sample within the MW field. Overall, these findings not only provide an efficient process to produce biocrude with superior quality, but also offer a fundamental support on biomass valorization in terms of energy utilization.

Pole analysis of EIT-AT spectrum with Rydberg atoms.

We investigate the electromagnetically induced transparency (EIT) and Autler Townes (AT) splitting spectrum with a four-level Rydberg atom by pole analysis of the probe coherence. A pair of poles corresponding to the two peaks of the spectral splitting is observed. The spectral split or the pole positions are affected by the microwave intensity (MW) and the detuning between the probe and the coupling laser. In the absence of any detuning, the two poles coincide and separate again on the imaginary axis of the complex detuning plane at weak MW field. The two poles do not coincide when the probe (coupling) laser is detuned for scanning the coupling (probe) laser frequency. However, under finite detuning, the two poles approach the nearest distance in the absence of any splitting and are separated again in the direction parallel to the imaginary axis. The spectral analysis of the poles provides an alternate way to establish the relationship between the splitting and the intensity of MW, which may play a role in the application of atomic-based MW measurements.

Quasi-coherent mode evolution in discharges with positive radial electric field at the T-10 tokamak

The effect of the high-power ECRH on the quasi-coherent (QC) mode in the plasma of the T-10 tokamak with the magnetic field Bt = 2.2 T, plasma current Ipl = 230 kA and chord-averaged electron density <ne> ≈ 1⋅1019 m-3 is discussed. The most pronounced changes appear in the core plasma region with r < 0.5a. For the ECRH power PECRH = 2.2 MW causing the appearance of the positive radial electric field (in the OH stage, the occurring field is ), the mean frequency of the QC-mode gradually decreases from (in the OH stage) to , and its frequency spread Δf QC decreases from to . For the ECRH power PECRH = 1.7 MW and weak negative radial electric field (), the mean frequency decreases to , and the frequency spread becomes . After the ECRH-induced drop, the QC-mode mean frequency increases with increasing line-averaged density.

The mechanism of microwave-induced mineral transformation and stabilization of arsenic in realgar tailings using ferrous sulfate

Abstract The mechanism of MW irradiation for the enhancement of the long-term stability of arsenic (As) in FeSO4-treated realgar tailings was studied. The efficiency of As stabilization reached 99.5% in the MW-FeSO4-air system, 1.35–fold of that in the FeSO4-air system (71.8%). The increased As stability in realgar tailings was attributed to the enhanced transformation of more stable Fe–As minerals (e.g. symplesite) from unstable Ca/S–As minerals (pharmacolite and realgar). The oxidation of realgar was accelerated by reactive oxygen species (ROS) through the activation of molecular oxygen with FeII of FeSO4 due to the MW athermal effect in the MW-FeSO4-air system. H+ ions from realgar oxidation and FeSO4 hydrolysis facilitated the dissolution of pharmacolite. The released As was captured by the formed ferric oxyhydroxide. “Hot spots” on FeSO4 in MW field initiated the microstructural evolution to Fe–As crystalline minerals due to the MW thermal effect. The introduction of FeSO4 and oxygen promoted the generation of ROS and “hot spots” in MW field, which contributed to the transformation from Ca/S–As minerals to Fe–As crystalline minerals and was of great significance for the long-term stability of As in realgar tailings.

Enhanced microwave electrometry with intracavity anomalous dispersion in Rydberg atoms

Intracavity anomalous dispersion is investigated and proposed to enhance detection sensitivity of weak microwave electric field with Rydberg atoms. When the Rydberg atoms are prepared with Raman gain and the cavity field serves as the probe field driving the metastable-state transition, two cavity modes are amplified due to the gain effect and two gain peaks appear in the cavity transmission, meanwhile, a large anomalous dispersion arises in the gain window. The frequency splitting of two gain peaks shows linear relationship with the MW field strength, which can be used to probe the MW electric-field strength. It is interesting to find that the anomalous dispersion broadens the frequency splitting of two gain peaks dramatically, so the probe sensitivity of MW field could be enhanced by 10 times from simulation, compared with the cavity-less scheme.

Tunable nonlinear measurement of microwave electric fields with a dressed-state analysis

A nonlinear absorption spectrum is proposed for measuring microwave electric fields with tunable sensitivity using electromagnetically induced transparency (EIT) in Rydberg atoms. Interacting dark resonances could enhance the nonlinear absorption, which shows a linear relationship with the microwave field (MW) strength. Compared with the linear case, the nonlinear measurement of MW field improves spectrum resolution by about one order of magnitude, the nonlinearity increases the EIT peak values by about two orders of magnitude, moreover the probe sensitivity could be improved by ten times from simulation. It is found that increasing the ratio of two coupling fields can improve probe sensitivity. The maximum probe sensitivity is predicted and explained. The above results can be well understood with the aid of the dressed-state theory.

Construction of a mathematical model of extraction process in the system "solid body ‒ liquid" in a microwave field

We have analyzed the extraction process in the technology of oilseed processing. This paper describes the original provisions, specificity, modern scientific schools, and the level of representation of the classic extraction process. The specificity of mathematical modeling of the extraction process, given the introduction of an additional driving force that significantly affects the kinetics of extraction in an electromagnetic field of ultra-high frequency, is considered from the classical theory of the process. We have constructed the extraction kinetics calculation formulae, in microwave field, which develop the theory of extraction kinetics in an electromagnetic field. The paper gives an analysis of variants for the representation of a mathematical notation of the extraction process of disperse materials in an electromagnetic field of ultra-high frequency. A complete model of the mass exchange processes during extraction in a microwave field in the differential form will make it possible to generate conditions for conducting comprehensive experimental studies, which would fully define the extraction process of oilseeds. We have theoretically substantiated the process of heat and mass exchange between the all defining objects inside an extraction unit with an electromagnetic field of ultra-high frequency. Based on material balances, we derived equations describing the basic dynamic characteristics of oil extraction mode in an extraction unit. Since the precise analytical solution to the presented mathematical model in the form of a system of differential equations in particular derivatives does not exist, the approximate solution has been proposed. It makes it possible to identify the distribution of an extractant depending on the size of fractions of raw materials, the existence and magnitude of power of the pulsed electromagnetic field of ultra-high frequency, the extractant's hydro-module, temperature, solvents, for any point in time. Based on the experimental research into extraction of oilseed material, it was established that under the action of microwave radiation a value for the mass release coefficient during extraction of oilseed raw materials grows by an order of magnitude (β=1·10 -5 ) compared to extraction without the effect of MW field (β=1·10 -6 ). Oil extraction under the action of a microwave field increases to 30 %, while electricity consumption decreases by 93‒97 %. The application of a microwave field would not only improve production efficiency, but reduce energy costs during process by an order of magnitude

Epoxidation of soybean oil enhanced by microwave radiation

The interest on epoxidized vegetable oils has been increasing in the last years thanks to their use as renewable and sustainable lubricants, plasticisers or as intermediate to produce a wide range of chemicals. The aim of this work is to study the effects of microwave irradiation on the process of epoxidation of soybean oil. A rigorous comparison was performed between the products obtained by conventional and microwave heating, using two batch reactors with the same geometry but different heating sources. The epoxidation of the oil was performed by reaction with peracetic acid generated in situ by reaction between hydrogen peroxide (HP) and acetic acid. Acetic acid and HP 35 wt% were used instead of the commonly used formic acid and HP 60 wt% to reduce the risk of detonation and corrosion. The MW heating showed a strong beneficial effect on the selectivity and especially on the rate of the process, reducing the time required by about 50%. Moreover, MW heating is capable to create a uniform suspension between phases, thanks to the selective heating generated by the MW field. In the MW process, the effect of stirring had negative effects because it promotes coalescence between droplets.

Ultra-Narrow Low-Field Nuclear Spin Resonance in NV Centers in a Bulk Diamond Crystal

Negatively charged nitrogen vacancy (NV) color centers in diamond crystals have been intensively studied in the last few decades with the use of the optically detected magnetic resonance method which usually implies resonance excitation using a DC or pulsed drive field in the gigahertz range (MW field). Various techniques for multi-frequency MW excitation of magnetic resonance in the nuclear structure of 14N atoms in NV centers were developed. Most of them use MW excitation in combination with RF modulation or direct RF excitation of nuclear transition. Here, we report on the possibility to detect ultra-narrow resonances in the nuclear structure of 14N using the ODMR methods with single-frequency DC RF excitation of the nuclear transition at 4.95 MHz. The resonances detected in a bulk sample in weak (0–10 mT) magnetic fields show approximately 7 kHz width HWHM, corresponding to T 2 * = 23 μs, and they seem to be insensitive to the magnetic field direction. These resonances may be of interest for solid-state quantum information processing, as well as for quantum magnetometry, especially in biological and medical applications where a strong MW drive field may be undesirable. We demonstrate that optical pumping can be used to create and detect not only the electron orientation, but also the nuclear one, even in the state with a zero electron spin projection. This allows sensitive non-pulsed detection methods like coherent population trapping to be applied to nuclear spins.

Large‐Amplitude Mountain Waves in the Mesosphere Accompanying Weak Cross‐Mountain Flow During DEEPWAVE Research Flight RF22

AbstractMountain wave (MW) propagation and dynamics extending into the upper mesosphere accompanying weak forcing are examined using in situ and remote‐sensing measurements aboard the National Science Foundation/National Center for Atmospheric Research Gulfstream V (GV) research aircraft and the German Aerospace Center Falcon. The measurements were obtained during Falcon flights FF9 and FF10 and GV Research Flight RF22 of the Deep Propagating Gravity Wave Experiment (DEEPWAVE) performed over Mount Cook, New Zealand, on 12 and 13 July 2014. In situ measurements revealed both trapped lee waves having zonal wavelengths of λx ~ 12 km and less, and larger‐scale, vertically propagating MWs primarily at λx ~ 20–60 km and ~100–300 km extending from west to ~400 km east of Mount Cook. GV Rayleigh lidar measurements from 25‐ to 60‐km altitudes showed that the weak forcing and zonal winds that increased from ~12 m/s at 12 km to ~40 and 130 m/s at 30 and 55 km, respectively, enabled largely linear MW propagation and strong amplitude growth with altitude into the mesosphere. GV Na lidar and airglow imager measurements revealed an extensive MW response from ~70 to 87 km with large amplitudes and vertical displacements at λx ~ 40–300 km but with both decreasing with altitude approaching a critical level near 90 km. These MWs exhibited large‐scale MW breaking and among the largest sustained momentum fluxes observed in the mesosphere. UK Met Office Unified Model simulations of the RF22 MW event captured many aspects of the observed MW field and revealed that despite the dominant large‐scale MW responses in the stratosphere, the major momentum fluxes accompanied smaller‐scale waves.

A Chandra Study of the Stellar X-Ray Emissivity of Globular Clusters in the M31 Bulge

Abstract The X-ray emissivity (i.e., luminosity per unit stellar mass) of globular clusters (GCs) is an important indicator of their dynamical evolution history. Based on deep archival Chandra observations, we report a stacking analysis of 44 GCs with 0.5–8 keV luminosities L X ≲ 1035 erg s−1 in the M31 bulge, which are supposed to be dominated by cataclysmic variables (CVs) and coronally active binaries (ABs). We obtain a significant detection at the 5σ level in 0.5–8 keV band. The average X-ray luminosity per GC and the average X-ray emissivity are determined to be 5.3 ± 1.6 × 1033 erg s−1 and 13.2 ± 4.3 × 1027 erg s−1 , respectively. Both of these values are consistent with those of Milky Way GCs. Moreover, the measured emissivity of M31 GCs is also consistent with that of the Milky Way field stars. Massive GCs have X-ray luminosities that are marginally higher than those of less massive ones. Massive GCs also show a lower emissivity ( ) than less massive ones ( ), which is consistent with the scenario that the (progenitors of) CVs and ABs were more efficiently destroyed via stellar encounters in the more massive GCs. No dependence of the X-ray emissivity on GC color or on the projected galactocentric distance of GCs is found.

Study into effects of a microwave field on the plant tissue

We report results of experimental research into effects of heat treatment of different plant materials in a microwave field. The effects of seed bio-stimulation are investigated, as well as features of drying and the influence of thermal treatment on the properties of moistened straw. A procedure is proposed for calculating a threshold time of seed exposure to a microwave field, compiled on the basis of hypothesis on the emergence of a bio-stimulation effect. We identified a cascade pressure growth in a container with humid grain when the layer’s temperature exceeds 70 о С. The moisturizing effect of the lower layer of grain was established during its drying in MW field under conditions of a leakproof bottom. It is shown that at an initial moisture content in grain of 20 %, after 14 minutes of drying, the moisture content of the upper layer reached 15.5 %, of the middle layer – 14.5 %, of the lower layer – 21.6 %. It was established that performance efficiency of a microwave chamber substantially depends on the loading volume, material’s type, and moisture content. The chamber’s performance efficiency while heating water can reach 90 %, the chamber’s performance efficiency when loaded with grain does not exceed 67 %. To estimate energy effectiveness of using microwave energy, a dependence is proposed, which includes power output of the magnetron, load volume, and the value of performance efficiency. Dependences for the calculation of performance efficiency when loading a material are proposed to be established experimentally

On the extended stellar structure around NGC 288

We report on observational evidence of an extra-tidal clumpy structure around NGC 288 from an homogeneous coverage of a large area with the Pan-STARRS PS1 database. The extra-tidal star population has been disentangled from that of the Milky Way field by using a cleaning technique that successfully reproduced the stellar density, luminosity function and colour distributions of MW field stars. We have produced the cluster stellar density radial profile and a stellar density map from independent approaches, from which we found results in excellent agreement : the feature extends up to 3.5 times the cluster tidal radius. Previous works based on shallower photometric data sets have speculated on the existence of several long tidal tails, similar to that found in Pal 5. The present outcome shows that NGC 288 could hardly have such tails, but favours the notion that interactions with the MW tidal field has been a relatively inefficient process for stripping stars off the cluster. These results point to the need of a renewed overall study of the external regions of Galactic globular clusters (GGCs) in order to reliably characterise them. Hence, it will be possible to investigate whether there is any connection between detected tidal tails, extra-tidal stellar populations, extent diffuse halo-like structures with the GGCs' dynamical histories in the Galaxy.

Dynamics of ultracold polar molecules in a microwave field

We analyze the temporal evolution of the population of ultracold polar molecules in a microwave (mw) field with a circular polarization. The molecules are in their ground state and treated as rigid rotors with a permanent dipole moment which interact with each other via the dipole–dipole (DD) interaction Vdd. The mw field mixes states with different quantum and photon numbers and the collisional dynamics in the mw field is mostly controlled by the ratios of the mw field frequency versus the rotational constant, and mw field Rabi frequency versus the rotational constant. There exists a special scattering process which is elastic by nature and due to a rotational energy exchange between the ground and the first excited rotational states. To analyze dynamics of polar molecules system in the mw field the equation of motion for the bare and dressed states is solved under different mw field parameters and molecular gas characteristics. Depending on the ratio of the Rabi frequency of a mw field and the magnitude of the DD interaction, beatings and oscillations occur in the bare and dressed states time-development. At a certain relation between the magnitudes of the mw detuning δ and the DD interaction , peak structures appear in the population of the excited bare state. Each peak is associated with an avoided crossing between the dressed states adiabatic curves at the same position of mw detuning.

Dielectric Ceramic EPR Resonators for Low Temperature Spectroscopy at X-band Frequencies

The performance of new dielectric ceramic resonators (DRs) for continuous wave (cw) X-band electron paramagnetic resonance (EPR) spectroscopy is investigated at room temperature and low temperatures (77, 6 K). The DRs with high dielectric constants of about $$\varepsilon _r = 80$$ , featuring low residual paramagnetic impurities, have been developed and produced on the basis of barium lanthanide titanates solid solutions with the general formula Ba $$_{6-x}$$ Ln $$_{8+2x/3}$$ Ti $$_{18}$$ O $$_{54}$$ (Ln = Sm, Nd) that demonstrate at once low dielectric losses in the microwave range ( $$\tan \delta = 7$$ –14 × 10−4 at 10 GHz) and appropriate temperature stability of the dielectric constant ( $$\tau _\varepsilon = \pm$$ 5 ppm/K). They were optimized for samples with small dimensions and can be used in commercial Oxford instruments flow cryostats if the coupling is done via cavity resonators. We found a maximal EPR signal enhancement by a factor up to 74 at 6 K. The increases of quality and filling factors as well as that of the microwave (mw) $$B_1$$ -field in the resonator setup are discussed in dependence on temperature. We show that the absolute sensitivity gain must be related to that increase in the mw field and the remaining relative gain of the SNR is about 18 for small samples. The developed DRs have shown a good potential in EPR application as reliable and easy-to-use components allowing research of thin films and in particular small crystalline structures.

A novel approach to the explanation the effect of microwave heating on isothermal kinetic of crosslinking polymerization of acrylic acid

The effect of microwave heating (MWH) on the isothermal kinetic of crosslinking-polymerization of acrylic acid (CPAA) was investigated. The kinetic curves of CPAA were determined in the temperature range from 303 to 328 K. By applying the model-fitting method it was revealed that the isothermal kinetics of CPAA was described by the first order chemical reaction kinetics model under the MWH and by the second order chemical reaction rate model for the conventionally heated (CH) process. The values of the reaction rate constants of CPAA are about 40 times higher for the microwave heated system than for the conventional heating. The kinetic parameters (activation energy (E a) and pre-exponential factor (lnA)) of the CPAA are significantly lower than the corresponding values for CH process. It was found that the increase in the reaction rate of CPAA for MWH was not a consequence of overheating neither the hot spots in the reaction system. Based on model of selective energy transfer between the reacting molecules and the heating bath a novel explanation of the established effects of MWH on the kinetics of CPAA is given. A quantized nature and value of activation energy was confirmed. The decrease in the value of activation energy of CPAA under microwave heating is explained by the increased value of energy of ground vibration level of resonant oscillator in the AA molecule (v = 1417 cm−1) caused by the absorption of non-thermal energy of MW field.