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This study presents bounds on transient variations of fundamental constants, with typical timescales ranging from minutes to months, using clocks in space. The underlying phenomenology describing such transient variations relies on models for Dark Matter (DM) which suggest possible encounters of macroscopic compact objects with the Earth, due to the motion of the solar system in the galactic halo. If such compact objects possess an effective feeble interaction with the ordinary matter beyond the gravitational one, it may result in effective transient variations of fundamental constants. Such variations leave signatures on clocks onboard GNSS satellites. In this paper, we introduce a phenomenological study dedicated to the search for such DM transient objects using the network of passive hydrogen masers (H-Masers) onboard Galileo satellites. We first model the signature of transient variations of fundamental constants as a frequency modulation in the difference between two satellite clocks, considering the satellite trajectories relative to the transient event. Then, we present first results based on a fast analysis method, the maximum reach analysis. The main result is a significant extension of the discovery range for DM transients, with a sensitivity never achieved before. We investigate indeed the range of transient sizes from 10 5 to 10 9 kilometres, which, apart from indirect and model-dependent non-transient effects, has never been explored previously. [ABSTRACT FROM AUTHOR]

Extragalactic water maser emissions at 22 GHz have been playing vital roles in astrophysics. The limited detection rate of these masers has been motivating researchers to find clues that can help characterise them. The physical environments 22 GHz masers formed in are still ambiguous. Accordingly, statistical studies have been thoroughly used to resolve these favourable environments. This work goes through the essential parameter of Active Galactic Nuclei (AGN), namely, the mass of the central supermassive black hole (M BH) of the maser host galaxy. We study the correlation between maser luminosity (L H 2 O) and M BH in sub-samples of megamasers (MMs), kilomasers (KMs), and disc masers. The regression line of the relation is also calculated for these sub-samples. Unlike the results of previous works, dividing the maser sample into MMs and KMs gives no privilege to MM galaxies. Contrary to expectation, KMs have weak and low significant L H 2 O - M BH correlation, while MMs show no correlation. The positive correlation in KMs can be explained by the role of AGN therein, while the diversity of MMs types, with some of which are not strongly related to AGN, may explain the correlation missing. Surprisingly, the 28 disc maser sample, where tight correlation is expected, shows a very weak and low significant L H 2 O -M BH correlation. Future VLBI studies will eventually lead to a specific classification of a good number of maser galaxies, which is essential to establishing the L H 2 O -M BH relation. [ABSTRACT FROM AUTHOR]

Long-baseline time transfer can nowadays reach rather high frequency stability based on post-processed batch least-squares adjustment using the Precise Point Positioning (PPP) or Integer-PPP (IPPP) methods. For real-time PPP users, time transfer results are degraded due to the filter-based processing mode, and the degraded accuracy of the real-time satellite orbits and clocks compared to the final ones. The Real-Time Kinematic (RTK) time transfer can significantly reduce the satellite-related errors, but has limits on the baseline length similar to the RTK positioning. Also, the delivery of raw observations instead of State-Space Representation (SSR) products could result in pressure on data transfer and difficulties related to latency and prediction. In this study, the PPP-RTK technique, which combines the advantages of the PPP and the RTK methods, is tested for real-time long-baseline time transfer. As an alternative approach to the above two methods, it allows for the time transfer of long baselines, while not relying on external high-sampling and high-precision satellite clocks. By delivering the satellite clocks and satellite phase biases produced within the PPP-RTK regional network, time differences can be estimated between users and the reference network station, with which stable time transfer between users separated by long baselines can be realized. Using dual-frequency GPS and Galileo data, the PPP-RTK time transfer is tested using approximately a thousand-kilometer-scale network in Europe. The time transfer results between two hydrogen masers, i.e., those on the 884 km baseline BRUX-ONSA and the 920 km baseline WTZR-ONSA, are computed. At an averaging time of 10 5 s, Modified Allan Deviation (MDEV) at the level of sub- 10 - 15 to 10 - 15 can be reached when processing the user coordinates in the station fixed, static, or kinematic modes. The median clock residuals can converge to 1 ns and 0.3 ns within 2 min and 15 min, respectively, in the kinematic mode, while in the static and fixed modes the convergence times are shorter. With the augmentation of 150 Low Earth Orbit (LEO) satellites having simulated observations, the clock residuals can converge to 1 ns and 0.3 ns within 30 s and 3.5 min, respectively, for all the three estimation modes. [ABSTRACT FROM AUTHOR]

China plans to establish a lunar orbital VLBI (Very Long Baseline Interferometer) station around 2025, which will carry a space passive hydrogen maser as the time and frequency reference. Since it is the first time to use a space passive hydrogen maser for VLBI observation, its feasibility needs to be studied and verified. Therefore, we carried out VLBI observations using the space passive hydrogen maser as the frequency reference. In the experiment, the active hydrogen atomic clock and space passive hydrogen maser were used as the frequency standard, and the alternate VLBI observations of China's Mars probe TW1 (Tianwen 1) were carried out using the 25 m radio telescope at Sheshan, Shanghai, and other VLBI stations. The results of data processing and analysis show that the standard deviation of VLBI residual group delay based on both active hydrogen atomic clock and space passive hydrogen maser are within 0.5 ns, which indicates that the space passive hydrogen maser can meet the accuracy requirements of VLBI measurement for deep space exploration, and verify its feasibility as the frequency standard of lunar orbital VLBI stations. [ABSTRACT FROM AUTHOR]

Stimulated Brillouin Scattering (SBS) is a nonlinear optical process that can provide significant on-chip gain in various materials and platforms. The utilization of chalcogenide and silicon (Si) waveguides has facilitated the advancement of Brillouin lasers and diverse microwave photonic functionalities. The predominant approach has been centered on interactions between conventional guided modes, specifically TE/TM. This study introduces a novel approach that explores diverse guided-wave configurations capable of sustaining SBS with orbital angular momentum modes (OAM). These configurations include a cross-Si waveguide and a silica/chalcogenide waveguide. The simulations examine the forward and backward SBS utilizing OAM modes up to the 4th order in planar on-chip waveguides. A maximum on-chip SBS gain of up to ∼ 540 W − 1 m − 1 has been observed for pump and Stokes OAM mode numbers satisfying the topological charge conservation law. This OAM multiplexing approach can open new avenues for on-chip integrated nonlinear photonics for various applications, especially where pump and signal beam filtering or separation are critical. [ABSTRACT FROM AUTHOR]

The continuously developing Global Navigation Satellite Systems (GNSS), in particular with the latest operational BDS and Galileo, provide good opportunities to enhance the performance of precise positioning. This study evaluates the performance of high-rate precise point positioning (PPP) applied for seismogeodesy with very recent BDS and Galileo. The static experiments with 20-Hz GNSS data show that Galileo and BDS-3/BDS-2 achieve comparable performances, with average 3D RMS values of 0.6–1.3 cm and 0.8–1.2 cm, respectively. In the dynamic experiments, we use a single-axis earthquake simulator of Quanser Shake Table II to simulate seismic waveforms of real earthquakes and collect 20-Hz GNSS data to evaluate the PPP performance. Taking the displacements recorded by the embedded encoder of the shake table as the truth, the accuracies of PPP displacements during the seismic events are 4–8 mm for GPS, 6–9 mm for BDS-2, and 3–6 mm for Galileo and BDS-3/BDS-2. By combining BDS-3 with BDS-2, the positioning accuracy of BDS is improved by 50% with respect to BDS-2 only. Galileo and BDS-3/BDS-2 perform slightly better than GPS, which is likely because the two latest operational systems use the more precise passive hydrogen maser clocks and have lower signal-in-space range error. The multi-GNSS solutions with GPS + Galileo + BDS-3/BDS-2 further improve the accuracy reaching 2–5 mm. We also identify a scale factor in the high-rate PPP displacements, which is probably induced by the dynamic stress error and related to the oscillating frequency. The scale factor reaches the maximum of 1.71 at an oscillating frequency around 2.5 Hz and then descends as the frequency increases. The improved performance of high-rate PPP augmented by the recent BDS-3 and Galileo is helpful to improve the practical level of high-rate GNSS in seismogeodesy and expand its applications to many other high-rate and high-accuracy applications. [ABSTRACT FROM AUTHOR]

Graphitic carbon nanocages (GCNCs) are unique graphene-based nanomaterials that can be used for cancer photothermal therapy (PTT). However, low toxicity GCNC-based organic/inorganic hybrid biomaterials for microwave irradiation assisted PTT have not yet been reported. In the present study, chitosan (CS)-coated GCNCs (CS-GCNCs) loaded with 5- fluorouracil (5Fu) were used for cancer therapy when activated by 808-nm laser and microwave co-irradiation. The cytotoxicity of GCNCs was significantly reduced after coating with CS. For example, fewer cell-cycle defects were caused by CS-GCNCs in comparison with non-coated GCNCs. The release rate of 5Fu from CS-GCNCs was significantly slower than that of 5Fu from GCNCs, providing sustained release. The release rate could be accelerated by 808-nm laser and microwave co-irradiation. The 5Fu in CS-GCNCs retained high cancer cell killing bioactivity by enhancing the caspase-3 expression level. The cancer cell killing and tumor inhibition efficiencies of the 5Fu-loaded nanomaterials increased significantly under 808-nm laser and microwave co-irradiation. The strong cell killing and tumor ablation activities were due to the synergy of the enhanced GCNC thermal effect caused by laser and microwave co-irradiation and the chemotherapy of 5Fu. Our research opens a door for the development of drug-loaded GCNC-based nano-biomaterials for chemo-photothermal synergistic therapy with the assistance of microwave irradiation. Graphitic carbon nanocages (GCNCs) are graphene-based nanomaterials that can be used for both drug loading and cancer photothermal therapy (PTT). Herein, we showed that chitosan (CS)-GCNCs hybrid biomaterials had very low cytotoxicity, high ability for loading drug, and exhibited sustained drug release. In particular, although low-power microwaves alone are unable to trigger cancer cell damage by GCNCs, the cell killing and mouse tumor inhibition efficiencies were significantly improved by near-infrared (NIR) laser and microwave co-irradiation compared with laser-triggered PTT alone. This combined use of laser and microwave co-irradiation promises essential therapeutic modality and opens a new avenue for PTT. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Maser emission from water, methanol, silicon monoxide and other molecules can reach brightness temperatures ≫ 10 10 K. Such observations can achieve sub-pc precision for discs around black holes or sub-au scale interactions in protostellar discs and the regions where evolved star winds reach escape velocity. Ultra-high resolution maser observations also provide photon statistics, for fundamental physics experiments. RadioAstron has shown the success – and limitations – of cm-wave maser observations on scales ≪ 1 mas with sparse baseline coverage. ALMA, APEX and earlier single dish searches have found a wealth of mm and sub-mm masers, some of which probably also attain high brightness temperatures. Masers are ideal for high-resolution observations throughout the radio regime and we need to consider the current lessons for the best observational strategies to meet specific science cases. [ABSTRACT FROM AUTHOR]

H 2 O maser emission associated with the massive star formation region W49N were observed with the Space-VLBI mission RadioAstron. The procedure for processing of the maser spectral line data obtained in the RadioAstron observations is described. Ultra-fine spatial structures in the maser emission were detected on space-ground baselines of up to 9.6 Earth diameters. The correlated flux densities of these features range from 0.1% to 0.6% of the total flux density. These low values of correlated flux density are probably due to turbulence either in the maser itself or in the interstellar medium. [ABSTRACT FROM AUTHOR]

We report on our efforts to test the Einstein Equivalence Principle by measuring the gravitational redshift with the VLBI spacecraft RadioAstron, in an eccentric orbit around Earth with geocentric distances as small as ∼ 7000 km and up to 350,000 km. The spacecraft and its ground stations are each equipped with stable hydrogen maser frequency standards, and measurements of the redshifted downlink carrier frequencies were obtained at both 8.4 and 15 GHz between 2012 and 2017. Over the course of the ∼ 9 d orbit, the gravitational redshift between the spacecraft and the ground stations varies between 6.8 × 10 - 10 and 0.6 × 10 - 10 . Since the clock offset between the masers is difficult to estimate independently of the gravitational redshift, only the variation of the gravitational redshift is considered for this analysis. We obtain a preliminary estimate of the fractional deviation of the gravitational redshift from prediction of ∊ = - 0. 016 ± 0. 003 stat ± 0. 030 syst with the systematic uncertainty likely being dominated by unmodelled effects including the error in accounting for the non-relativistic Doppler shift. This result is consistent with zero within the uncertainties. For the first time, the gravitational redshift has been probed over such large distances in the vicinity of Earth. About three orders of magnitude more accurate estimates may be possible with RadioAstron using existing data from dedicated interleaved observations combining uplink and downlink modes of operation. [ABSTRACT FROM AUTHOR]

Water masers are well-known to be variable on a variety of time scales, but only three Galactic H 2 O masers are known to flare to the level of 105–106 Jy ( T B ∼ 10 17 K): Orion KL, W49N, and the recently discovered G25.65+1.05. Recently detected flaring activity of H 2 O maser in the massive star-forming region G25.65+1.05 gave us a unique opportunity to study the fine structure of H 2 O maser emission in the bursting state with extremely high space VLBI angular resolution. Observation of the source was carried out with ∼9 Earth diameter space-ground baseline within the framework of the RadioAstron project. H 2 O maser emission from two spectral features, including the bursting one, was detected in the experiment. Only ∼1% of the bursting H 2 O maser emission was detected on the space-ground baselines: it indicates the presence of a very compact spatial structure with a size of ∼25 μ as, which corresponds to 0.05 AU or ∼5 solar diameters at the distance to the source of 2.08 kpc, and the brightness temperature of ∼3 × 1016 K. Analysis of the flux density as a function of the baseline length for the bursting H 2 O maser feature in the source shows that most of the emission comes from an extended "halo" structure, while the core of emission is very compact and has an extreme brightness temperature. These results are in agreement with the model of interacting maser clouds considered as the likely explanation of the nature of the burst in the source. Under the assumption of such a model, the beam size of maser emission is reduced while the brightness temperatures similar to the highest observed values are produced. [ABSTRACT FROM AUTHOR]

The use of mixed metal oxide anodes in wastewater electrochemical treatment depends on the production of efficient, stable, and economically viable anodes. Thus, Ti/RuO 2 -TiO 2 anodes were prepared by unconventional heating methods using a CO 2 laser and microwave irradiation. The calcination method significantly modified the surface morphology, electronic structure, and electrocatalytic properties of the anodes. Compared with the conventionally-prepared anode, anodes made using laser and microwave display increase by approximately 2 and 3 times the voltammetric charge and decrease by 2.8 and 5.4 times the charge transfer resistance. Moreover, laser and microwave-prepared anodes presented a lifetime of 4.4 and 2.3 times longer than the furnace-prepared anode. High efficiency in generating hypochlorite is achieved in 1 h using a laser-prepared anode (372 mg L−1), which improves the degradation and mineralization of ciprofloxacin by electrolysis. After UVC-irradiation, the anode with the lowest energy consumption (7.14 kWh g–1TOC) was prepared by microwave radiation. [Display omitted] • Microwave heating improved the electroactive area and conductivity of MMO anodes. • Laser heating reduced preparation time by 438-fold and increased anode life by 4.45-fold. • 83% of TOC are removed in just 2 h of PhEC treatment using a microwave-prepared anode. • Unexpectedly, PhEC using the laser-prepared anode did not favor the pollutant removal. [ABSTRACT FROM AUTHOR]

An important aspect of Japanese traditional culture is the design and creation of pots, bowls, and other pottery, an artform that has historically been subject to cultural influences from China and the Korean peninsula. It has been suggested that passing down of hand-crafting techniques to the next generation is quite difficult, as the techniques involve considerable tacit knowledge. Thus, this study aimed to explore the creative processes of a master of the craft using an eye-tracking system. We recorded the eye movements of Hakuga Nakamori, a third-generation artisan, as he created a bowl and a pot. The results showed that, in the process of working toward creating a piece of art, Mr. Nakamori first focused his attention on the whole piece, and then on certain elements thereof. [ABSTRACT FROM AUTHOR]

Active hydrogen maser is the main frequency standard for establishing and maintaining the time scale. It has the characteristics of high short-term stability and low phase noise. At present, it plays an increasingly important role in the international atomic time (TAI) and various local time scales. Firstly, in combination with the internal state parameters of an active hydrogen maser, the correlation between the internal state parameters and the comparison data of a hydrogen maser is analyzed, and a method for the performance monitoring of a hydrogen maser is proposed. Secondly, according to the characteristics of hydrogen maser performance, a method for evaluating the performance of a hydrogen maser is given. The hydrogen maser performance includes mainly two aspects, namely the frequency stability and predictability. The performances of two types of active hydrogen masers (CH1-75 and MHM-2010) are evaluated by this method. The correlation analysis of the atomic clock state parameters and comparison data shows that the state parameter monitoring can effectively predict the variation of the hydrogen maser performance. The evaluation results of atomic clock frequency stability and predictability show that the atomic clock with a higher medium-and-long term frequency stability has a better predictability. There are two methods for the predictability evaluation, one is based on the data published by BIPM (Bureau International des Poids et Measures), and another one is based on the quadratic model. Both methods are consistent with the weights published by BIPM. Therefore, the two methods can be used as a quantitative method to evaluate the predictability of a hydrogen maser. [ABSTRACT FROM AUTHOR]

• Combined analysis of interferometer and reflectometer is developed based on the projection of electron density to equilibrium magnetic surfaces. • The density profile is reconstructed by Gaussian Process (GP) within the Bayesian framework, by which the uncertainty can be quantified via the confidence interval of a posterior probability. • This combined analysis approach is proved to provide a consistent density profile with improved accuracy and reliability. In order to acquire a consistent and accurate electron density profile for HL-2A tokamak, a combined analysis of the laser interferometer and microwave reflectometer based on the mapping of density profiles to a common equilibrium magnetic coordinate has been proposed. In this approach, the edge density profile measured locally by microwave reflectometer is taken as a supplementary boundary condition in the procedure of inverting line-integrated data from interferometer diagnostic. The density profile inside that boundary is reconstructed by a Gaussian Process Tomography (GPT) method [1] within the Bayesian framework, by which the uncertainty of the result can be quantified via the confidence interval of a posterior probability. In the simulation benchmark, two representative cases of density distribution with different profile shapes, e.g. peaked and flat, are tested and the factors that may affect the accuracy of the results are investigated, providing a useful reference for practical applications. The application of this approach to actual data proves its ability to resolve the dynamic evolution of density profiles. Specifically, the effect of Electron Cyclotron Resonance Heating (ECRH) on electron particle transport observed in HL-2A experiments has been confirmed. The combined analysis approach developed is expected to provide a robust means to study the confinement performance and particle transport on HL-2A, with the focus on the core region. [ABSTRACT FROM AUTHOR]

[Display omitted] • Unconventional heating methods produced RuO 2 − Sb 2 O 4 and RuO 2 − TiO 2 anodes. • The preparation method and anode composition were optimized for disinfectant generation. • The electrochemical generation of hypochlorite is related to the anode composition. • RuO 2 − TiO 2 anodes show higher performance for ClO− generation than RuO 2 − Sb 2 O 4. Developing highly selectivity anode materials for hypochlorite generation in low-concentrated sodium chloride (NaCl) solutions is challenging. Here, we describe the synthesis and physical and electrochemical characterization of ruthenium-based binary anodes (Ti/RuO 2 − Sb 2 O 4 and Ti/RuO 2 − TiO 2) prepared by different heating methods (laser, microwave, and furnace). The heating method and chemical composition were crucial in the anode characteristics and catalytic activity. The anodes of Ti/RuO 2 − Sb 2 O 4 composition prepared by laser and microwave show an increase in voltammetric charge by 1.4 and 1.9-folds and a decrease in resistance to charge transfer by approximately 2-folds compared with the corresponding furnace-made anode. The Ti/RuO 2 − TiO 2 anode prepared by unconventional methods (laser and microwave) shows an increased voltammetric charge in approximately 3-folds and reduced resistance to charge transfer at 5.6 and 3.4 times, respectively, compared with the anode prepared in an electric furnace. The composition of MMO and the applied current density are the main factors that influence the production of ClO and chloramine disinfectants. The highest electrocatalytic activity for generating hypochlorite from low-concentrated NaCl solutions was obtained by the Ti/RuO 2 − TiO 2 anode prepared by laser heating using a current density of 60 mA cm−2. Additionally, we evaluated the electrochemical generation of inorganic chloramines. Consequently, this study offers new insights into the preparation of low-cost materials for efficient in situ generation of disinfectants. [ABSTRACT FROM AUTHOR]

Viable microbial aerosol detection remains a grand challenge. Here, we pioneered a new system that integrates laser trapping and microwave irradiation for online discerning of single viable microbial aerosol particle through naked eye. To test the system, three fungal species Aspergillus niger , Aspergillus oryzae , and Trichoderma harzianum and three non-biological particles such as MnO 2 , active carbon, and Fe 3 O 4 were suspended and laser trapped in the air inside a house-made glass cube. When microwave irradiated, some fungal spores were observed to rapidly escape from the trapping and even burst with abrupt morphology changes under a longer irradiation. In contrast, others similar to those non-biological particles were shown to behave differently with little morphology change without the cell burst. For all particles tested, microwave irradiation resulted in particle movement within the trapping region, and a particle trapping was then re-established in a new location. Depending on particle type and irradiation time, light scattering properties also differed between biological and non-biological particles when irradiated. Terminating the microwave irradiation was observed to render the non-biological particles to return where they were being laser trapped. Using the developed system, we have demonstrated the viable microbial aerosol detection using naked eye by simply observing the morphology changes and cell burst upon the laser trapping and microwave irradiation. A portable version of the system was further developed and successfully tested for discerning viable aerosol cells from non-biological ones. Further efforts on this development could lead to a new generation of bioaerosol detection strategy. [Display omitted] • Discerning of single viable aerosol was demonstrated by microwaving particles trapped by laser. • A portable unit was shown successfully in identifying single indoor viable aerosol particle. • Trapped viable and non-biological particles responded very differently to microwave irradiation. We have demonstrated online single bioaerosol particle discerning using naked eye when assisted with laser trapping and microwave irradiation. [ABSTRACT FROM AUTHOR]

For the first time, isothermal equiaxed solidification of a metallic alloy has been observed in situ in space, providing unique benchmark experimental data. The experiment was completed on board the MASER 13 sounding rocket, launched in December 2015, using a newly developed isothermal solidification furnace. A grain-refined Al–20 wt%Cu sample was fully melted and solidified during 360 s of microgravity and the solidification sequence was recorded using time-resolved X-radiography. Equiaxed nucleation, dendritic growth, solutal impingement, and eutectic transformation were thus observed in a gravity-free environment. Equiaxed nucleation was promoted through application of a controlled cooling rate of −0.05 K/s producing a 1D grain density of ~6.5 mm −1 , uniformly distributed throughout the field of view (FOV). Primary growth slowed to a visually imperceptible level at an estimated undercooling of 7 K, after which the cooling rate was increased to −1.0 K/s for the remainder of solidification and eutectic transformation, ensuring the sample was fully solidified inside the microgravity time window. The eutectic transformation commenced at the centre of the FOV proceeding radially outwards covering the entire FOV in ~3 s Microgravity-based solidification is compared to an identical pre-flight ground-based experiment using the same sample and experiment timeline. The ground experiment was designed to minimise gravity effects, by choice of a horizontal orientation for the sample, so that any differences would be subtle. The first equiaxed nucleation occurred at an apparent undercooling of 0.6 K less than the equivalent event during microgravity. During primary equiaxed solidification, as expected, no buoyant grain motion was observed during microgravity, compared to modest grain rotation and reorientation observed during terrestrial-based solidification. However, when the cooling rate was increased from −0.05 K/s to −1.0 K/s during the latter stages of solidification, in both 1 g and micro-g environments, some grain movement was apparent due to liquid feeding and mechanical impingement of neighbouring grains. [ABSTRACT FROM AUTHOR]

In this article, the hydrogen masers in the NTSC (National Time Service Center) timekeeping laboratory are tested. In order to avoid the impact of larger noise of caesium atomic clocks, TA( k) or UTC( k) is not used as reference, instead, the four hydrogen masers are mutually referred and tested. The frequency stability of hydrogen masers is analyzed using the four-cornered hat method, and the Allan standard deviations of each single hydrogen maser in different sample times are estimated. Then, according to the characteristics of hydrogen masers, by removing the trend term, excluding outliers, and smoothing the data with a mathematical method to separate the Gaussian noises of hydrogen masers, and finally by through the Kolmogorov-Smirnov test, the Gaussian noise of each hydrogen maser is estimated. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3 ) gas sensors based on organic field-effect transistor (OFET) using poly(3-hexylthiophene) (P3HT) blended with polystyrene (PS) as a semiconductor layer were fabricated. An optimized composition of 1.6 wt% P3HT in PS matrix exhibited the best performance to various concentrations of NH 3 , which is comparable to that of pure P3HT (8 wt%). The results showed the percentage responses of saturation current were 52% and 16% under 50 ppm and 5 ppm NH 3 , respectively. Also, it showed that there was a remarkable shift in the field-effect mobility after exposed to NH 3 gas. By analyzing the morphologies of blend films and the electrical characteristics of OFET sensors, it was found that the film of P3HT blended with PS has more interface to interact with NH 3 , resulting in more efficient detection to NH 3 even in the range of low concentration. Besides, the PS matrix would prevent the gas from diffusing into the semiconductor/dielectric interface directly, which was beneficial to the selectivity of P3HT/PS blend OFET sensor. Moreover, the sensing property was related to the solvents and molecular weight of PS. In addition, the environmental stability of OFET sensors was measured after storing the sensors under ambient atmosphere for 40 days, and the device with the blend semiconducting layer exhibited the superior stability. [ABSTRACT FROM AUTHOR]

• In this work, we proposed to use a Microwave Photonic (MWP) sensing signal to achieve high displacement sensing resolution. The MWP sensing signal is generated by a laser diode (LD) with dual-cavity. In this configuration, the LD serves as both an MWP source and a sensor. The MWP sensing signals are directly generated by laser dynamics without need any external modulator. The information about the measurand is carried by both optical and microwave components of the MWP sensing signals. Hence, rich information about the measurand can be retrieved from the generated MWP sensing signals to greatly improve sensing performance. This work has the following contributions and significances. • We push an optical feedback interferometry (OFI) to operate at a laser state called 'period one' by using a dual-cavity configuration. In such configuration, one cavity is linked with measurand target, the other is used to control the LD dynamic states. Under the optimal system operation condition, a modulated laser intensity in microwave range (we call it as MWP sensing signal) can be generated and it is sensitive to a target movement external the LD and thus is used for displacement sensing. • It is found that the high frequency component contained in an MWP sensing signal can be used to subdivide OFI fringe signals. This is a novel method for subdivision of interference fringe and it is able to achieve super high sensing resolution (in a nano scale in theory) compared to the existing methods. Laser diodes (LDs) experiencing external optical feedback (OF) are known to demonstrate complex nonlinear dynamics and found various applications. Typical sensing configuration using an LD with OF is called optical feedback interferometry (OFI) that can produce an interferometric-like fringe signal (called OFI fringe) with a fringe resolution as half laser wavelength for displacement measurement. This work uses a dual-cavity OFI and operates the LD at Period-One (P1) state. By optimal configuration for such system, a microwave photonic (MWP) signal can be generated in oscillation form at a very high frequency with its amplitude modulated by an OFI fringe signal. The high frequency component contained in the MWP signal is used for subdivision of an OFI fringe to greatly improve sensing resolution. Both simulation and experiment are conducted to confirm the proposed approach for OFI fringe subdivision. [ABSTRACT FROM AUTHOR]

Microwave energy was applied to the laser-induced breakdown spectroscopy (LIBS) of laser-ablated Al plasma using a helical antenna. The process of generating an enhanced laser ablation plasma was visualized with a high-speed camera. The time and space evolution of the plasma were investigated by changing the laser power, microwave energy, and microwave energy duration. The obtained raw images were converted into 8-bit 255 grayscale and binary black and white (BW) images and were analyzed using Matlab. Three major periods of plasma evolution were established based on the key physical process involved. Laser energy was the primary parameter involved in period 1, where laser ablation and initial plasma formation occurred. The microwaves had little significance at the beginning of the ablation process, as suggested by the minimal changes in plasma size and intensity. The microwaves controlled the expansion of the plasma and sustained breakdown in period 2. The post ablation breakdown of the material by microwaves sustained the enlargement of the plasma. The events leading to plasma dissipation comprised period 3, where the nonthermal plasma was sustained for 500 μs after the microwave was turned off. The effects of the laser and microwave parameters in the timeline of these periods were discussed. Complementary emission intensity measurements were also presented. [Display omitted] • The microwave-enhanced plasma demonstrates three periods of evolution. • Period 1 reveals no major effects of microwaves in the laser-induced breakdown. • In Period 2, the plasma expands due to post-ablation breakdown by microwaves. • In Period 3, the plasma drifted away from the target before it abruptly vanished. [ABSTRACT FROM AUTHOR]

• A flexible concentrated solar energy wireless transmission system was developed. • It uses the space sunlight to overcome intermittency of the solar energy application. • Optimal energy transmission modelling and experimental validation was conducted. • Maximum transmitter energy transmission efficiency of 52.0% was obtained experimentally. • Power/weight ratio of the system could be increased by 17.0% by comparing parallels. Solar energy in space is more intensive and continuous compared to that on the Earth, and thus, is encouraged by governments across the world to be utilized for human beings. The continuity of the space sunlight has a great potential to overcome the bottleneck of the variability and intermittency in time and space for ground-based solar energy applications. Space solar power station (SSPS) is known as intermedia that can harvest the space solar energy and transmit it wirelessly to the end-user. However, the current wireless energy transmission via microwave or laser suffers from low energy transmission efficiency because of excessive energy conversion processes. Wireless energy transmission via sunlight without any intermediate energy conversion process was proposed previously theoretically for high energy transmission efficiency, but it also lacks practicability due to heavyweight and inflexibility. Therefore, although promising, practical sunlight-based wireless energy transmission proposals have not ever been presented. Here, through component and structure optimizations in theoretical and experimental approaches, a novel and more practical concentrated solar energy wireless transmission system that transmits the harvested sunlight via lightweight optical fibers is proposed in this paper. It uses a Fresnel lens to collect concentrated solar energy and then, the utilized optical fiber can steer the collected energy to the collimator flexibly. At last, a parallel sunlight beam can be emitted from the collimator to the target end-user. Results show that the transmitter efficiency versus optical fiber length exhibited a linear relationship from both theoretical and experimental approaches. the cloud effect harmed the energy transmission. A maximum transmitter energy transmission efficiency of 52.0% could be attained experimentally. Compared with the performance in the no-cloud condition, the gained voltage could be declined by 37% ∼ 48%. The bending of the optical fiber seemed to not affect much on the energy transmission performance, which guarantees a flexible energy transmission. Besides, the power/weight ratio was increased by 17.0% compared to its counterpart. The innovation of this paper is to reduce the gap between theoretical and practical feasibilities for the proposed system. This paper experimentally demonstrates the feasibility of a wireless concentrated solar energy transmission technology, which promotes the application of SSPS and related aerospace applications. [ABSTRACT FROM AUTHOR]

In this work, we investigated the ability of several poly(9,9-dioctylfluorene) (PFO) derivatives to selectively separate semiconducting single-walled carbon nanotube (sc-SWCNT) from commercial arc discharge SWCNTs. The results illustrated that the separation efficiency of PFO derivatives and the stability of sc-SWCNT inks increased with the sizes of conjugated systems in subunits. The relative height of sc-SWCNTs peaks and the shelf life of sc-SWCNT inks can be up to 0.71 and 5 months when being sorted by poly{(9,9-dioctylfluorene)-2,7-diyl-alt-[3,6-dithiene-2-yl-2,5-di(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione-5,5″-diyl} (PF8-DPP). Electrical properties of thin film transistors (TFTs) and sensors based on PF8-DPP-sorted sc-SWCNTs were also investigated. Printed TFTs showed excellent performance with on/off ratios of 10 6 , effective mobility of 22.6 cm 2 V −1 s −1 , subthreshold swing of 178 mV/dec and small hysteresis at low operating voltage. PF8-DPP-sorted sc-SWCNTs were used as sensing material for selectively detecting ammonia gas at room temperature. Upon exposure to 0.6% NH 3 at room temperature, the ammonia sensors based on sorted sc-SWCNTs exhibited high sensitivity (Δ R / R o ∼ 54.4%), fast response (30 s) and good stability. The desorption rate of NH 3 from carbon nanotube surface can be controlled by tuning the voltage of heating resistor integrated into the platforms, and excellent reversibility can be achieved within 1 min at applied voltage of 1.5 V. [ABSTRACT FROM AUTHOR]

Nitrogen-doped single-walled carbon nanotubes (N-doped SWCNTs) were synthesized by reacting fluorinated SWCNTs with ammonia gas at reaction temperatures of 300–600 °C. In the N-doped SWCNTs synthesized at 400 °C (N 400°C -doped SWCNTs), nitrogen atoms were introduced into the nanotube framework at a concentration of 3.04 at.%, the concentrations of the pyridinic-, pyrrolic-, graphitic-, and pyridine-N-oxide-type nitrogen species were 1.22, 1.36, 0.34, and 0.08 at.%, respectively, and their percentages with respect to the total nitrogen species were 40.1, 44.7, 11.2, and 2.6%, respectively. The volume resistivity of films of the N 400°C -doped SWCNTs was 2.3 ± 1.1 Ω · cm, indicating that they can be classified as semiconductors. Finally, it was found that the thermopower of the N 400°C -doped SWCNTs was negative at room temperature in air, indicating that they exhibited n-type conduction. [ABSTRACT FROM AUTHOR]

Spin noise emission, absorbed noise, and spontaneous maser emission are distinguished in the hexanol molecule by changing spin noise dynamics along with coupling the spin system to a probe circuit. Inverted magnetization leads to spontaneous maser emission of methyl and methylene resonances permitting separation from broad overlapped peaks. The maser emission resonance shows random intensity the scattering range of which depends on the length of the gradient following magnetization inversion. Combination of thermal noise and spin noise can be altered by varying magnetization orientation. This results in radiation damping which alters how fluctuation signals are coupled with the probe circuit. [ABSTRACT FROM AUTHOR]

Based on microwave plasma torch optical emission spectrometry combined with laser ablation, a direct solid sample detection device was developed for sensitive determination of heavy metals in soil. In the proposed laser ablation microwave plasma torch optical emission spectrometry (LA-MPT-OES) device, a new ablation chamber was designed, which the washout time and the relative standard deviation of this chamber were almost one-third of those of the conventional one, indicating that the proposed chamber had a smaller dead volume to provide efficient and stable transport of ablated sample particles. Meanwhile, to ensure a high signal intensity during a long exposure time, the moving sampling method was used to guarantee a sufficient injection amount. With the optimal experimental parameters, the limits of detection (LODs) of Cu, Pb, Cr and Ag were 0.075, 0.093, 0.068, 0.009 m g · k g − 1 , respectively, which was reduced by one to two orders of magnitude compared with that of laser-induced breakdown spectroscopy and X-ray fluorescence and was similar to the LODs of the digestion-required techniques (e.g., ICP-OES and MP-AES) and other LA-related techniques (e.g., LA-ICP-MS). Furthermore, the LA-MPT-OES was applied to the quantitative analysis of standard samples and actual samples, and the obtained determination results were in agreement with the standard values and that of atomic absorption spectrometry. The practicability and accuracy (relative errors were 0.95%–25.9%) of LA-MPT-OES determination of heavy metal elements were also validated. [Display omitted] • A coupling device was developed with laser ablation and microwave plasma torch optical emission spectrometry. • The fabricated chamber has a small dead volume, good stability and can effectively transport the ablated particles. • The moving sampling method can maintain high signal intensity at a long exposure time. • The limit of detection of Cu, Pb, Cr and Ag were 0.075, 0.093, 0.068 and 0.009 m g · k g − 1 , respectively. • The device has the benefits of direct solid injection, low operating cost and power, high sensitivity and stability. [ABSTRACT FROM AUTHOR]

• Available experimental techniques are reviewed along with basic physical principles description. • Technical requirements are formulated focusing on methods associated with transient combustion. • No universal method exists to measure transient burn rate with required accuracy and time resolution. • Attention is paid to the development of microwave, X-ray radiography and laser recoil techniques. • The work on developing novel experimental approaches must be continued. Various energetic materials, including solid rocket propellants, have found numerous applications in aerospace technology in the past decades. This growing interest initiated an increasing number of experimental and technological studies, leading to a wide range of published experimental data. Due to the intrinsic challenges of data acquisition and processing, assessing the accuracy of the measurement results is important. In this paper, a review of existing experimental techniques for measuring the regression rate of energetic materials is presented along with a description of the fundamental physical principles used for developing the particular methods. Special attention is paid to recent developments in measurements of highly-dynamic processes. Technical requirements for correct determination of regression rate are analyzed focusing on the methods associated with transient combustion. Emphasis is placed on laboratory-scale methods intended to obtain correct and reliable data on regression rate in well-characterized environments that can be used for comparison with theoretical predictions. The measurement methods are divided into direct and indirect ones. It is shown that direct high-speed photography could not be effectively used for recording regression rate oscillations with frequencies higher than 30–50 Hz. The same limitation applies to classical ultrasound techniques and X-ray radiography. However, radiography techniques based on synchrotron and terahertz radiation are promising. Special attention is paid to development of microwave and laser recoil methods that provide high spatial and temporal resolution capable of correctly determining transient regression rate. [ABSTRACT FROM AUTHOR]

Beidou is the regional satellite navigation system in China, consisting of three kinds of orbiting satellites, MEO, GEO and IGSO, with the orbital altitudes of 21500-36000km. For improving the accuracy of satellites orbit determination, calibrating microwave measuring techniques and providing better navigation service, all Beidou satellites are equipped with laser retro-reflector arrays (LRAs) to implement high precision laser ranging. The paper presents the design of LRAs for Beidou navigation satellites and the method of inclined installation of LRAs for GEO satellites to increase the effective reflective areas for the regional ground stations. By using the SLR system, the observations for Beidou satellites demonstrated a precision of centimeters. The performances of these LRAs on Beidou satellites are very excellent. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mesoscopic simulation of in situ X-ray monitored solidification in microgravity. [•] Extent and magnitude of undercooled zone ahead of dendrite front predicted. [•] Dynamic thermal response of new XRMON-GF Bridgman furnace analysed. [Copyright &y& Elsevier]

Abstract: Astrometry using H2O maser sources in star forming regions is expected to be a powerful tool to study the structures and dynamics of our Galaxy. (hereafter H2007) claimed that the annual parallax of Sharpless 269 is determined within an error of 0.008marcs (mas), concluding that S269 is located at 5.3kpc ±0.2kpc from the sun, and its galactrocetnric distance is R =13.1kpc. From the proper motion, they claimed that the galacto-centric rotational velocity of S269 is equal to that of the sun within a 3% error. This small error, however, is hardly understood when taking into account the results of other observations and theoretical studies of galactic dynamics. We here reanalyzed the VERA archival data using the self calibration method (hybrid mapping), and found that clusters of maser features of S269 are distributed in much wider area than that investigated in H2007. We confirmed that, if we make a narrow region image without considering the presence of multiple maser spots, and only the phase calibration is applied, we can reproduce the same maser structures in a maser feature investigated in H2007. The distribution extent of maser spots in the feature differs 0.2mas from east to west between our results and H2007. Moreover, we found that change of relative positions of maser spots in the cluster reaches 0.1mas or larger between observational epochs. This suggests that if one simply assumes the time-dependent, widely distributed maser sources as a stable single point source, it could cause errors of up to 0.1 mas in the annual parallax of S269. Taking into account the internal motions of maser spot clusters, the proper motion of S269 cannot be determined precisely. We estimated that the peculiar motion of S269 with respect to a Galactic circular rotation is ∼20kms−1. These results imply that the observed kinematics of maser emissions in S269 cannot give a strong constraint on dynamics of the outer part of the Galaxy, in contrast to the claim by H2007. [Copyright &y& Elsevier]

Abstract: I present a simple derivation of the power-broadened linewidth of an optical transition in a two-level atom. The novelty of the approach lies in its flexibility, as the approach described here can be applied to any spectral lineshape, corresponding to either homogeneous or inhomogeneous broadening mechanisms. For a Lorentzian profile, I recover the same dependence of linewidth on laser power that one calculates from the optical Bloch equations. The present treatment makes explicit that power broadening arises because of the saturability of the atomic response to intense lasers, rather than to explicitly quantum mechanical aspects of the laser–atom interaction, all of which are ignored. I discuss the utility of power broadening in resonance ionization mass spectrometry, where it is an important means of mitigating unwanted instrumental isotope fractionation. [Copyright &y& Elsevier]

Abstract: We have been developing a high sensitivity atomic magnetometer for atomic EDM experiments using a lowfrequency nuclear spin maser. In the developed nuclear spin maser of 129Xe, suppression of drift and fluctuation in the magnetic field is one of the important issues. The magnetometer being developed for spin maser EDM experiments utilizes the nonlinear magneto optical rotation (NMOR) e_ect in Rb atomic vapor. The enhancement of the optical rotation in a small magnetic field relies on the long spin-coherence time of Rb atoms in a vapor cell. The NMOR spectrum was measured by using fabricated Rb cells coated with an anti-relaxation material. The NMOR spectrum dependence on laser frequency, cell coating, and laser beam diameter were investigated. The magnetic sensitivity at present is 0:2μG/√Hz from observed NMOR and noise spectra. [Copyright &y& Elsevier]

Abstract: The development of a nuclear spin oscillator system, namely a spin maser with an external feedback, for use in the search for 129Xe atomic EDM is presented. By introducing a new current source for the B0 field solenoid, drifts in the maser frequency were remarkably suppressed. This in turn clearly brought out the correlation between the maser frequency and the environmental field. Correcting for the effect of the environmental field, the frequency precision of 5 nHz in the measurement time of 45,000s was attained. Origins of the remaining drifts in the maser frequency are now under investigation. [Copyright &y& Elsevier]

Abstract: Frequency characteristics of a 129Xe nuclear spin maser was studied, which is under development at Tokyo Institute of Technology for the search for a permanent electric dipole moment in diamagnetic 129Xe atom. Drifts in the solenoid current and cell temperature were found to be the most influential factors on the maser frequency. From correlation coefficient analysis, there seem to exist other origins of frequency fluctuation, such as phase drifts in the maser oscillation. In order to improve the stability of the maser frequency, the intensity of the pumping laser required to fully polarize 129Xe nuclei was evaluated. Construction of a polarization assessment system for 129Xe gas cells and development of a new scheme of current stabilization are also remarked. [ABSTRACT FROM AUTHOR]

Abstract: Recent experiments demonstrated the possibility to realize a single-qubit maser, by coupling an electrical resonator to a superconducting qubit. In the present paper we extend earlier work on single-atom lasers to account for the strong qubit–resonator coupling. We focus in particular on the spectral properties of the lasing radiation and we discuss phase locking induced by an additional ac driving of the resonator. [Copyright &y& Elsevier]

Abstract: We address the growth mechanism of Ge quantum dots (QDs) on C-alloyed strained Si1−x Ge x layers by in situ reflection high-energy electron-diffraction (RHEED). We show that C-induced growth on a Si-rich surface leads to a high density (about 1011 cm−2) of small dome-shaped islands. On surfaces up to ≈65% richer in Ge we observe a decrease of the dot density by two orders of magnitude, which is associated to the increase of the adatom diffusion. Based on quantitative RHEED analysis, the islands are believed to grow in a Volmer–Weber mode even though their spotty electron transmission pattern is not detectable in the initial stages of growth due to the reduced size of the three-dimensional nucleation islands. [Copyright &y& Elsevier]

Abstract: We present preliminary results of an interferometric study of the water megamaser in the merger system Arp 299. This system is composed of two main sources: IC 694 and NGC 3690. There is clear evidence that most of the water maser emission is associated with the nucleus of the latter, confirming the presence of an optically obscured AGN as previously suggested by X-ray observations. Furthermore, emission arises from the inner regions of IC 694, where an OH megamaser is also present. The velocity of the water maser line is blueshifted w.r.t. the optically determined systemic velocity and is consistent with that of the OH megamaser line. This finding might then indicate that both masers are associated with the same (expanding) structure and that, for the first time, strong 22GHz H2O and 1.67GHz OH maser emission has been found to coexist. [Copyright &y& Elsevier]

Abstract: We present a concept for a compact magnetostatic cavity called a “Magic box” that provides a very homogeneous magnetic environment for a polarised 3He neutron spin-filter cell in the presence of moderate magnetic stray fields. Based on this concept different systems have been built and tested. The concept is ideal for the transport or hosting of a spin-filter on a neutron beam-line. [Copyright &y& Elsevier]

Abstract: The multipartite entangled state for the total momentum and relative coordinates of n particles is constructed. The corresponding quantum-mechanical operator with respect to the classical transformation , , , in the state is investigated. [Copyright &y& Elsevier]

Abstract: (Pseudo) radiative pumprate of OH 1612MHz masers is defined for a sample of 44 OH/IR sources (infrared sources with OH 1612MHz maser), irrespective of the real maser pumping mechanisms. The correlation between the (pseudo) maser pumprates and the evolutionary status of the maser sources reveals that the radiative pumprates of stellar OH masers are nearly fixed, which agrees with the theoretical prediction for radiatively pumped OH maser. The (pseudo) radiative pumprates of interstellar OH masers are not only very small but also varying broadly over two orders of magnitude, which is argued to be the manifestation of varying number of quiet absorbing OH cloudlets and/or various OH maser pumping mechanisms and/or competitive gain between mainline and 1612MHz OH masers and/or anisotropy of the maser emission. The radiative pumprates of post-AGB OH masers very possibly decrease with increasing IRAS C32 color indices and distribute in an interim region between the stellar and interstellar OH masers in the pumprate-color diagram. [Copyright &y& Elsevier]

This is the second paper in a series aiming at searching for infrared pumping lines for galactic 1612 MHz OH masers. Our paper I is devoted to the 34.6 μm absorption lines in ISO SWS spectra towards a large sample of galactic OH/IR sources. This paper analyzes the 53.3 μm line in the ISO LWS spectra towards a similar sample of OH/IR sources. A search with position radius of 1 arcmin in ISO Data Archive (IDA) results in 137 LWS spectra covering 53.3 μm associated with 47 galactic OH/IR sources and 4 ones associated with megamasers and . (These two magamasers are included for comparison purpose only.) Ten of these galactic OH/IR sources are found to show and another 5 ones tentatively show the 53.3 μm absorption while another 7 sources (our group U1 and U2 sources) highly probably do not show this line. The source class is found to be correlated with the type of spectral profile: red supergiants (RSGs) and AGB stars tend to show strong blue-shifted filling emission in their 53.3 μm absorption line profiles while H II regions tend to show a weak red-shifted filling emission in the line profile. GC sources and megamasers mainly show symmetrical profile in the line core while megamasers tend to show an additional absorption tail on the blue side of the line profile. It is argued that the filling emission might be the manifestation of an unresolved half emission half absorption profile of the 53.3 μm doublet which might be produced by the transitions among the two levels: 2Π1/2(J=3/2) and 2Π1/2(J=5/2) and their closely related levels. The 53.3 to 34.6 μm equivalent width (EW) ratio is close to unity for RSGs but much larger than unity for GC sources and megamasers while H II regions only show the 53.3 μm line. The pump rate defined as maser to IR photon flux ratio is approximately 5% for RSGs. The pump rates of GC sources are three order of magnitude smaller. Both the large 53.3 to 34.6 μm EW ratio and the small pump rate of the GC OH masers reflect that the two detected `pumping lines'' in these sources are actually of interstellar origin. The pump rate of is 32% – much larger than that of RSGs, which indicates that the contribution of other pumping mechanisms to this megamaser is important. A handful of non-detections of the 34.6 or 53.3 μm line or both can be explained partly by the genuinely weakness of the OH masers and partly by some other mechanisms weakening the IR pumping lines, such as clumpy OH shell or limb filling emission. [Copyright &y& Elsevier]

Since 2001 an experimental test facility for investigation of lifetime of a copper material, with respect to multiple RF pulse actions, was set up on the basis of the JINR (Dubna) FEM oscillator, in collaboration with IAP RAS (Nizhny Novgorod). A high-Q copper cavity, which simulates the parameters of the accelerating structure of the collider CLIC at an operating frequency of 30 GHz, is used in the investigation. The experimental setup consists of a wavebeam injector—FEM oscillator (power of ∼25 MW, pulse duration up to 200 ns, spectral bandwidth not higher than 0.1%), a quasi-optic two-mirror transmission line, a wave-type converter, and a testing cavity. The frequency and transmission features of the components of the quasi-optic line were analyzed. [Copyright &y& Elsevier]

Two-dimensional (2D) coaxial Bragg structures have been suggested for use in high-power Free Electron Masers (FEM) to synchronize radiation from different parts of an oversized annular electron beam. In this paper, the simulations of field evolution using the three-dimensional code MAGIC are carried out and results are presented. An investigation of 2D Bragg structures obtained by corrugating the inner surface of the outer conductor of a coaxial waveguide or by lining the surface of a smooth waveguide with a dielectric material, which has a bi-periodic permittivity, has been conducted. Experimental studies of 2D Bragg structures were also undertaken and the good agreement between experimental measurements and theoretical predictions is demonstrated. Measurements of a 7 cm diameter annular electron beam produced by a high-current accelerator to be used to drive the FEM are presented and the experimental set-up discussed. [Copyright &y& Elsevier]

We report on experiments which have recently been conducted at the University of Strathclyde investigating rapid amplitude modulations occurring in the microwave output radiation of an electron cyclotron maser (ECM). The experiment used an electron beam injected from a co-axial diode with knife-edged graphite cathode in the fringing field of an adjustable magnet system producing a beam of up to 175 kV and 140 A. The time evolution of the electron beam was measured as the cathode plasma expanded using a Faraday cup in conjunction with upstream beam interceptors as a function of the magnetic compression ratio. The ECM cavity was configured so that its length and the length of the interaction space could be readily adjusted. The microwave output signal was studied using special fast rectifying diode detectors, a high performance deep memory oscilloscope and cut-off filters. Steady-state output was observed at high magnetic compression ratios (16:1) at a frequency of 16 GHz corresponding to cyclotron resonant maser (CRM) coupling between the beam and the radiation in the expected TE1,2 mode. At lower compression ratios modulation was observed after an initial steady-state period and shown by antenna pattern measurements to be associated with transverse mode competition in the microwave cavity. [Copyright &y& Elsevier]

Two methods of efficiency enhancement of free-electron maser (FEM) oscillator with the Bragg resonator having a shift of corrugation phase were studied. The first one is a “starting mode” regime using an additional high-frequency mode located in the vicinity of the main mode. The Bragg resonator having a shift of corrugation phase seems to represent the most attractive oscillator configuration. Another possibility is a special variation of corrugation depth of Bragg reflectors (mirror profiling) providing the possibility of optimizing the longitudinal distribution of the RF field amplitude inside the interaction space and depressing of parasitic side modes of the resonator.Optimization of RF power extraction from FEM, based on Talbot effect, has also been considered. Perspectives of future FEM development are discussed including schemes of pulse power compression and submillimeter wave generation. [Copyright &y& Elsevier]

We have carried out molecular dynamics simulations of non-adiabatic processes with the help of a newly formulated potentially exact quantum-classical approach derived from a method proposed earlier [J. Chem. Phys. 118 (2003) 5302]. In this method, time-dependent Schroedinger equation is solved by representing Ψ on a moving Gauss–Hermite DVR grid, the motion of grid-centre being handled classically, but self consistently with the quantum evolution of the wavefunction. Electronic transitions are allowed anywhere in the configuration space among any number of coupled states. We have tested the method on three model problems proposed by J.C. Tully [J. Chem. Phys. 93 (1990) 1061]. These models are relevant to a wide range of gas-phase and condensed-phase phenomena occurring even at low energies. Excellent agreement of computed transition probabilities with corresponding quantum mechanical (DVR/FFT) results even in the deep quantum regime and its cost-efficiency (computational) are encouraging. [Copyright &y& Elsevier]