Burst Power Research Articles

Gain Switching of the Microbunching Instability to Produce Giant Bursts of Terahertz Coherent Synchrotron Radiation.

Relativistic electron bunches used to produce synchrotron radiation are systematically subjected to spontaneous appearance of microstructures, when a high number of electrons are used. In storage rings, this usually leads to an intense coherent emission in the terahetz range, with powers that are orders of magnitude higher than standard incoherent emission. However this emission generally displays an erratic behavior, which has strongly limited its domain of application so far. In this Letter-inspired by the process of gain switching in lasers-we present a new method for controlling the electron bunch dynamics during this instability. We show that it is possible to trigger the formation of the microstructures in the bunch, and also to considerably enhance the peak power of the coherent terahertz bursts. The experimental demonstration of this scheme-based on the modulation of a rf-cavity signal-is performed at the SOLEIL facility.

Electroencephalographic Measures of Delirium in the Perioperative Setting: A Systematic Review.

Postoperative delirium (POD) is frequent in older adults and is associated with adverse cognitive and functional outcomes. In the last several decades, there has been an increased interest in exploring tools that easily allow the early recognition of patients at risk of developing POD. The electroencephalogram (EEG) is a widely available tool used to understand delirium pathophysiology, and its use in the perioperative setting has grown exponentially, particularly to predict and detect POD. We performed a systematic review to investigate the use of EEG in the pre-, intra-, and postoperative settings. We identified 371 studies, and 56 met the inclusion criteria. A range of techniques was used to obtain EEG data, from limited 1-4 channel setups to complex 256-channel systems. Power spectra were often measured preoperatively, yet the outcomes were inconsistent. During surgery, the emphasis was primarily on burst suppression (BS) metrics and power spectra, with a link between the frequency and timing of BS, and POD. The EEG patterns observed in POD aligned with those noted in delirium in different contexts, suggesting a reduction in EEG activity. Further research is required to investigate preoperative EEG indicators that may predict susceptibility to delirium.

Novel Electrophysiological Signatures of Learning and Forgetting in Human Rapid Eye Movement Sleep.

Despite the known behavioral benefits of rapid eye movement (REM) sleep, discrete neural oscillatory events in human scalp electroencephalography (EEG) linked with behavior have not been discovered. This knowledge gap hinders mechanistic understanding of the function of sleep, as well as the development of biophysical models and REM-based causal interventions. We designed a detection algorithm to identify bursts of activity in high-density, scalp EEG within theta (4-8 Hz) and alpha (8-13 Hz) bands during REM sleep. Across 38 nights of sleep, we characterized the burst events (i.e., count, duration, density, peak frequency, amplitude) in healthy, young male and female human participants (38; 21F) and investigated burst activity in relation to sleep-dependent memory tasks: hippocampal-dependent episodic verbal memory and nonhippocampal visual perceptual learning. We found greater burst count during the more REM-intensive second half of the night (p < 0.05), longer burst duration during the first half of the night (p < 0.05), but no differences across the night in density or power (p > 0.05). Moreover, increased alpha burst power was associated with increased overnight forgetting for episodic memory (p < 0.05). Furthermore, we show that increased REM theta burst activity in retinotopically specific regions was associated with better visual perceptual performance. Our work provides a critical bridge between discrete REM sleep events in human scalp EEG that support cognitive processes and the identification of similar activity patterns in animal models that allow for further mechanistic characterization.

The contribution of gamma bursting to spontaneous gamma activity in schizophrenia.

Increased spontaneous gamma (30-100 Hz) activity (SGA) has been reported in the auditory cortex in schizophrenia. This phenomenon has been correlated with psychotic symptoms such as auditory hallucinations and could reflect the dysfunction of NMDA receptors on parvalbumin-expressing inhibitory interneurons. Previous findings are from time-averaged spectra, so it is unknown whether increased spontaneous gamma occurs at a constant level, or rather in bursts. To better understand the dynamical nature of spontaneous gamma activity in schizophrenia, here we examined the contribution of gamma bursting and the slope of the EEG spectrum to this phenomenon. The main results from this data set were previously reported. Participants were 24 healthy control participants (HC) and 24 matched participants with schizophrenia (SZ). The data were from EEG recordings during auditory steady-state stimulation, which were localized to bilateral pairs of dipoles in auditory cortex. Time-frequency analysis was performed using Morlet wavelets. Oscillation bursts in the gamma range were defined as periods during which power exceeded 2 standard deviations above the trial-wide average value for at least one cycle. We extracted the burst parameters power, count, and area, as well as non-burst trial power and spectral slope. Gamma burst power and non-burst trial power were greater in SZ than HC, but burst count and area did not differ. Spectral slope was less negative in SZ than HC. Regression modeling found that gamma burst power alone best predicted SGA for both HC and SZ (> = 90% of variance), while spectral slope made a small contribution and non-burst trial power did not influence SGA. Increased SGA in the auditory cortex in schizophrenia is accounted for by increased power within gamma bursts, rather than a tonic increase in gamma-range activity, or a shift in spectral slope. Further research will be necessary to determine if these measures reflect different network mechanisms. We propose that increased gamma burst power is the main component of increased SGA in SZ and could reflect abnormally increased plasticity in cortical circuits due to enhanced plasticity of synapses on parvalbumin-expressing inhibitory interneurons. Thus, increased gamma burst power may be involved in producing psychotic symptoms and cognitive dysfunction.

Use of External Uterine Electromyography Across Stage I Labor.

Highly sensitive, external uterine electromyography (EMG) measures myometrial electrical activity and is noninvasive compared with the clinical intrauterine pressure catheter. Most experimental studies have measured EMG in 30-minute epochs, limiting the utility of this instrumentation in intrapartum clinical practice. To test proof of concept, surface uterine EMG contraction activity was continuously collected throughout the first stage of labor from healthy women at term gestation with (n = 3) and without (n = 1) epidural or combined spinal-epidural analgesia for a maximal length of 11 hours and 24 minutes. EMG activity was recorded concurrently with tocodynamometer (toco) signals, using a pair of electrodes on the left and right sides of the maternal umbilicus with grounds attached to both hips of the reclining woman in labor. The preamplifier cutoff frequency settings were appropriate to monitor smooth muscle contraction in labor, with the analog high-pass filter set at 0.05 Hz and the low-pass filter at 1.50 Hz. Signals were sampled at 100 Hz, transmitted to a computer, and visualized by Chart 4.2 software. EMG data from epochs at baseline, during the pre-epidural fluid bolus and at the 60-minute post-epidural test dose, and at 3, 5, 6, and 8 cm dilatation were analyzed for burst power spectrum peak frequency (Hz), burst power spectrum amplitude (mV2 ), and burst duration (seconds). Uterine EMG contractile bursts were preceded and followed by a stable baseline and coincided with toco contractions. Movement artifacts were negligible, and large movement artifacts were easily distinguishable. The EMG bursts and toco contractions remained clearly identifiable, even when one woman without epidural analgesia stood beside the bed laboring for approximately 10 minutes. Burst spectral components fell within the expected 0.34-to-1.00 Hz range for term labor. High-quality data demonstrate that EMG instrumentation effectively and accurately measures uterine contraction parameters across the first stage of term labor.

Genetic relatedness and morphology as drivers of interspecific dominance hierarchy in hummingbirds.

A dominance hierarchy is the set of ranks occupied by species within an assemblage. Species with a high position within the dominance hierarchy tend to dominate subordinate species in contests for access to resources. In hummingbirds, greater weight and wing disc loading have been associated with highest ranks within the dominance hierarchy. Nevertheless, the limit to which the difference between the weight of contending species represents a competitive advantage has not yet been determined. Here, we determined the dominance hierarchy of a hummingbird assemblage exploiting the most abundant floral resource (Palicourea padifolia, Rubiaceae) in a cloud forest of central Veracruz, Mexico. Specifically, we tested whether species weight and wing disc loading influence the dominance hierarchy. Additionally, we tested whether the flowers visited per foraging bout increases with species weight and dominance. We further tested whether weight, wing disc loading, and the genetic relatedness between contenders influenced the dominance relationships in species-pair interactions. Our results indicate that the hierarchy is positively influenced by weight. Hummingbirds visited similar number of flowers regardless their weight or their dominance. Nevertheless, the probability that the heaviest contender won contests was positively associated with the differences of weight and genetic relatedness between contenders. Contrarily, the probability that the contender with greatest wing disc loading won contests was positively associated with differences of weight and negatively associated with the relatedness between contenders. However, these models only explained between 22% and 34% of the variation, respectively. Our results demonstrate that the weight was the major contributor to high dominance values. However, future studies should include (1) the temporal variability of the weight and (2) experimental predictor variables such the burst power of the hummingbirds to evaluate its effects on the dynamics of dominance hierarchies in hummingbird assemblages. All the hummingbird species present in the studied assemblage have developed wide behavioral mechanisms that compensate their morphological differences, which allow them to coexist, even when they compete for the access to the same resource.

Properties of High-redshift Gamma-Ray Bursts

The immense power of gamma-ray bursts (GRBs) makes them ideal probes of the early universe. By using absorption lines in the afterglows of high-redshift GRBs, astronomers can study the evolution of metals in the early universe. With an understanding of the nature of GRB progenitors, the rate and properties of GRBs observed at high redshift can probe the star formation history and the initial mass function of stars at high redshift. This paper presents a detailed study of the dependence on metallicity and mass of the properties of long-duration GRBs under the black hole accretion disk paradigm to predict the evolution of these properties with redshift. These models are calibrated on the current GRB observations and then used to make predictions for new observations and new missions (e.g., the proposed Gamow mission) studying high-redshift GRBs.

Rational La-doped hematite as an anode and hydrous cobalt phosphate as a battery-type electrode for a hybrid supercapacitor.

In recent years, modern appliances require high energy density with a burst power supply. Hybrid supercapacitors show high performance based on high energy density without compromising power density and stability over thousands of charge-discharge cycles. In this work, the optimized hybrid electrodes using lanthanum-doped hematite (lanthanum-doped iron oxide) noted as 7.5%La-HMT as a negative electrode and hydrous cobalt phosphate (CoPO) as a battery-type positive electrode have been successfully fabricated via a simple hydrothermal method and a facile co-precipitation method, respectively. The 7.5%La-HMT showed excellent electrochemical performance due to doping of rare-earth La3+ metal ions, resulting in improvised active sites and reduction in the equivalent resistance. The 7.5%La-HMT operated at a high potential window (0 to -1.2 V) with an ultra-high specific capacitance (Sp) of 1226.7 F g-1 at 1 A g-1 with capacitance retention of 89.3% over 1000 cycles. CoPO could be operated at a high working window (0 to 0.45 V) with a specific capacity of 121.7 mA h g-1 at a current density of 2 A g-1 with capacitance retention of 85.4% over 1000 cycles. The configured CoPO//KOH//10%La-HMT aqueous hybrid capacitor device (Aq-HSC) could be operated at a potential window of 1.6 V and delivered a maximum energy density (E.D) of 83.6 W h kg-1 at a power density (P.D) of 3.2 kW kg-1 with Sp of 235.0 F g-1 at 2 A g-1 and 89.0% Sp retention over 5000 cycles. The simplicity of the synthesis methods for CoPO and 7.5%La-HMT along with their superior super-capacitive properties make them suitable for advanced electrical devices and hybrid vehicles.

PV-Supercapacitor Cascaded Topology for Primary Frequency Responses and Dynamic Inertia Emulation

Owing to rapid increase in PV penetration without inherent inertia, there has been an unremitting deterioration of the effective inertia of the existing power systems. This may pose a serious threat to the stability of power systems during disturbances if not taken care of. Hence, the problem of how to emulate Synthetic Inertia (SI) in PV Systems (PVS) to retain their frequency stability demands attention. Super Capacitor (SC)-based storage become an attractive option over the other energy storage types because of its high-power density, burst power handling capability, faster response and longer life cycle. Considering this, the authors here propose a novel PV-SC Cascaded Topology (PSCT) as a cost-effective approach to emulate SI by integrating a low voltage SC to a high voltage grid-connected PVS. The proposed PSCT helps in operating the SC as a voltage source rather than a current source. Thus, it eliminates the high gain requirements of the SC interfacing converters. The aim is to target two main frequency response services, i.e., Primary Frequency Response (PFR) and Synthetic Inertial Response (SIR), using a novel common control scheme, but without affecting any other energy intensive services. The authors introduced a Droop-Inspired (DI) method with an adjustable inertia constant to emulate dynamic inertia so that a wider range of Rate of Change of Frequency (RoCoF) values can be serviced with a limited storage. A very streamlined analysis was also carried out for sizing of the SC stage based on a simple Three-Point Linearization (TPL) technique and DI technique with a limited knowledge of the disturbance parameters. The whole system was initially validated in a MATLAB Simulink environment and later confirmed with the OPAL-RT Real-Time Simulator. The investigated response was subject to variation in terms of control parameters, changes in solar irradiance, grid frequency variation, etc.

Differential Effects of Pathological Beta Burst Dynamics Between Parkinson's Disease Phenotypes Across Different Movements.

Background: Resting state beta band (13–30 Hz) oscillations represent pathological neural activity in Parkinson’s disease (PD). It is unknown how the peak frequency or dynamics of beta oscillations may change among fine, limb, and axial movements and different disease phenotypes. This will be critical for the development of personalized closed loop deep brain stimulation (DBS) algorithms during different activity states.Methods: Subthalamic (STN) and local field potentials (LFPs) were recorded from a sensing neurostimulator (Activa® PC + S, Medtronic PLC.) in fourteen PD participants (six tremor-dominant and eight akinetic-rigid) off medication/off STN DBS during 30 s of repetitive alternating finger tapping, wrist-flexion extension, stepping in place, and free walking. Beta power peaks and beta burst dynamics were identified by custom algorithms and were compared among movement tasks and between tremor-dominant and akinetic-rigid groups.Results: Beta power peaks were evident during fine, limb, and axial movements in 98% of movement trials; the peak frequencies were similar during each type of movement. Burst power and duration were significantly larger in the high beta band, but not in the low beta band, in the akinetic-rigid group compared to the tremor-dominant group.Conclusion: The conservation of beta peak frequency during different activity states supports the feasibility of patient-specific closed loop DBS algorithms driven by the dynamics of the same beta band during different activities. Akinetic-rigid participants had greater power and longer burst durations in the high beta band than tremor-dominant participants during movement, which may relate to the difference in underlying pathophysiology between phenotypes.

Prognostic value of neonatal EEG following therapeutic hypothermia in survivors of hypoxic-ischemic encephalopathy

ObjectiveEarly prediction of neurological deficits following neonatal hypoxic-ischemic encephalopathy (HIE) may help to target support. Neonatal animal models suggest that recovery following hypoxia-ischemia depends upon cortical bursting. To test whether this holds in human neonates, we correlated the magnitude of cortical bursting during recovery (≥postnatal day 3) with neurodevelopmental outcomes. MethodsWe identified 41 surviving infants who received therapeutic hypothermia for HIE (classification at hospital discharge: 19 mild, 18 moderate, 4 severe) and had 9-channel electroencephalography (EEG) recordings as part of their routine care. We correlated burst power with Bayley-III cognitive, motor and language scores at median 24 months. To examine whether EEG offered additional prognostic information, we controlled for structural MRI findings. ResultsHigher power of central and occipital cortical bursts predicted worse cognitive and language outcomes, and higher power of central cortical bursts predicted worse motor outcome, all independently of structural MRI findings. ConclusionsClinical EEG after postnatal day 3 may provide additional prognostic information by indexing persistent active mechanisms that either support recovery or exacerbate brain damage, especially in infants with less severe encephalopathy. SignificanceThese findings could allow for the effect of clinical interventions in the neonatal period to be studied instantaneously in the future.

Evaluation of core-wide fuel pin burst during LOCA in APR1400

Core-wide fuel pin burst fractions in a typical APR1400 nuclear power plant during a loss-of-coolant accident (LOCA) are assessed. For the assessment, fuel pin based power distribution at an initial and an equilibrium core of APR1400 is analyzed. Fuel cladding burst probability curves represented as a local peak power are established up to 70 MWd/kgU fuel burnup. Main uncertainty parameters for pin burst related to the fuel and thermal–hydraulic (TH) performance are identified. Monte Carlo method is used for combining uncertainties. FRAPTRAN and MARS-KS integrated code is employed in this study. In the APR1400 core, power ratio of the fuel pin between a target fuel pin and surrounding ones is ranging 0.899–1.131 within ±2 standard deviation. This power ratio has induced about 1.0–2.1 kW/ft burst power change. In the fuel uncertainties, fuel thermal conductivity, fission gas release (FGR), cladding yield stress shows a relatively strong influence on the burst power change. Groeneveld critical heat flux (CHF) and Chen transition boiling correlation shows a strong influence among TH uncertainty parameters. Established cladding burst probability curves reveal that fresh fuel has a relatively low burst power. But, it increases rather steeply until burnup reaches 5–10 MWd/kgU. Then, the burst power is reduced slowly until the lowest power is attained at the fuel burnup of 70 MWd/kgU. Evaluation of fuel pin burst fraction shows that the most susceptible fuel burnup for the core-wide pin burst is fresh one. Beginning-of-cycle (BOC) at the initial core seems to be the most vulnerable during a reactor life time.

Ontogenetic peculiarities of the effect of dantrolene and caffeine on the cardiac, respiratory and motor performance of intact and poisoned by physostigmine of rats

Activities of the somatomotor (MA), cardiovascular and respiratory systems were investigated in conditions of activation and blockade of ryanodine receptors (RyR) impaired cholinergic regulation in rat pups aged 3, 16 and 30 days. It was found that blockage of RyR by dantrolene has a negative chronotropic effect, the severity of which decreases with age, reduces the respiratory rate in rats on P3 and practically does not change in older animals. The amplitude of EMG and the power of motor bursts decreases in rats on P3-P16 and increases on P30. The duration of MA in the activity- rest cycle remains unchanged at P3 and decreases at P16-P30, which indicates a different change in the pattern of MA in rats of different ages after the blockade of RyR. Caffeine-induced activation of RyR is accompanied by an increase in heart rate and respiratory rate in rats on P30 and does not cause significant changes in these parameters on P3-P16. There has been an increase in all MA indices, especially in P3. Certain age-related regularities were revealed in the conditions of acetylcholinesterase inhibition by physostigmine, carried out against the background of RyR inhibition or activation. Maximum sensitivity to such effects was found in rats on P3. It was shown that in early postnatal ontogenesis of rats the sensitivity of RyR, including RyR2, to dantrolene is higher than in adult animals. Changes in RyR activity level do not prevent the development of pathological forms of heart rhythm that developing in rats after the physostigmine injection.

Design, fabrication and characterization of an electrical-explosively actuated MEMS flyer-accelerator inserted with parallel bridge foils

Parallel bridge foils (PBF) with four strip foils, which is derived from traditional single bridge foil (SBF), was designed to study the effect of convergence and collision of plasmas and shock waves on driving flyer. Firstly, Electro-thermal simulation of PBF was performed to analyze temperature distribution before melting, which predicted the synchronous burst characteristic of PBF. Subsequently, a capacitor discharging circuit was designed to initiate bridge foils, results indicated PBF reached higher burst power in shorter time compared with SBF due to better matching between PBF and the test circuit. The flow fields of electrical explosion of bridge foils were photographed by ultra-high-speed camera, which displayed PBF almost burst simultaneously. Moreover, PBF had wider and brighter flow field visualization than SBF owing to convergence and superposition of plasma beams. Most importantly, flyer-accelerators inserted with bridge foils were prepared by MEMS technology, and comparative analysis from PDV revealed MEMS flyer-accelerator inserted with PBF had access to better velocity performances, compared with that inserted with SBF. For instance, PBF flyer-accelerator spent mere 168 ns to 2325 m/s at 900 V/0.22 µF, but SBF flyer-accelerator took 335 ns to 1073 m/s. Finally, we proposed a mathematical model for explaining the enhancement effect of flyer velocity, which to some extent showed good agreement with experimentation.

Silicon wafer etching by pulsed high-power inductively coupled Ar/CF4 plasma with 150 kHz band frequency

A silicon wafer etching using a burst pulse high-power inductively coupled plasma (ICP) is investigated. A 200 μs wide burst of a 157 kHz power supply is employed to generate ICP with a repetition rate of 50 Hz. A rectangular pulsed voltage synchronized with the burst power supply is applied upto 1 kV at the wafer. Mixed gas of argon (Ar) and tetrafluoromethane (CF4) is supplied into the vacuum chamber. The plasma density and electron temperature are 1019 m−3 and 2.8 eV where the wafer is, respectively. In the case of Ar plasma, the silicon etching rate is 0.01 μm min−1 with 1000 V negative bias. The etching rate increases to 0.23 μm min−1 by adding CF4 into Ar and increases linearly with increasing the bias voltage. The target current and emission intensity of Ar+ and F* are depended on bias voltage from −300 to −1000 V. The etching rate sharply increases by increasing CF4 content from 0% to 10%, and it becomes almost constant at 10%. The dependency of emission intensity of F* on CF4 content is similar to the dependency the etching rate.

Coherent phonon dynamics in spatially separated graphene mechanical resonators

Vibrational modes in mechanical resonators provide a promising candidate to interface and manipulate classical and quantum information. The observation of coherent dynamics between distant mechanical resonators can be a key step toward scalable phonon-based applications. Here we report tunable coherent phonon dynamics with an architecture comprising three graphene mechanical resonators coupled in series, where all resonators can be manipulated by electrical signals on control gates. We demonstrate coherent Rabi oscillations between spatially separated resonators indirectly coupled via an intermediate resonator serving as a phonon cavity. The Rabi frequency fits well with the microwave burst power on the control gate. We also observe Ramsey interference, where the oscillation frequency corresponds to the indirect coupling strength between these resonators. Such coherent processes indicate that information encoded in vibrational modes can be transferred and stored between spatially separated resonators, which can open the venue of on-demand phonon-based information processing.

Substance-Specific Differences in Human Electroencephalographic Burst Suppression Patterns.

Different anesthetic agents induce burst suppression in the electroencephalogram (EEG) at very deep levels of general anesthesia. EEG burst suppression has been identified to be a risk factor for postoperative delirium (POD). EEG based automated detection algorithms are used to detect burst suppression patterns during general anesthesia and a burst suppression ratio (BSR) is calculated. Unfortunately, applied algorithms do not give information as precisely as suggested, often resulting in an underestimation of the patients’ burst suppression level. Additional knowledge of substance-specific burst suppression patterns could be of great importance to improve the ability of EEG based monitors to detect burst suppression. In a re-analysis of EEG recordings obtained from a previous study, we analyzed EEG data of 45 patients undergoing elective surgery under general anesthesia. The patients were anesthetized with sevoflurane, isoflurane or propofol (n = 15, for each group). After skin incision, the used agent was titrated to a level when burst suppression occurred. In a visual analysis of the EEG, blinded to the used anesthetic agent, we included the first distinct burst in our analysis. To avoid bias through changing EEG dynamics throughout the burst, we only focused on the first 2 s of the burst. These episodes were analyzed using the power spectral density (PSD) and normalized PSD, the absolute burst amplitude and absolute burst slope, as well as permutation entropy (PeEn). Our results show significant substance-specific differences in the architecture of the burst. Volatile-induced bursts showed higher burst amplitudes and higher burst power. Propofol-induced bursts had significantly higher relative power in the EEG alpha-range. Further, isoflurane-induced bursts had the steepest burst slopes. We can present the first systematic comparison of substance-specific burst characteristics during anesthesia. Previous observations, mostly derived from animal studies, pointing out the substance-specific differences in bursting behavior, concur with our findings. Our findings of substance-specific EEG characteristics can provide information to help improve automated burst suppression detection in monitoring devices. More specific detection of burst suppression may be helpful to reduce excessive EEG effects of anesthesia and therefore the incidence of adverse outcomes such as POD.

An Ultra-Reliable MMW/FSO A-RoF System Based on Coordinated Mapping and Combining Technique for 5G and Beyond Mobile Fronthaul

We propose and experimentally demonstrate, for the first time, a system which integrates millimeter-wave (MMW) and free-space-optics (FSO) analog radio-over-fiber (A-RoF) channels, and provides enhanced reliability in 5G and beyond mobile fronthaul (MFH) links. The integrated system utilizes a novel coordinated mapping and combining (CMC) technique that senses the signal quality in each data block and apportions the load accordingly. Furthermore, the technique takes advantage of the abundant bandwidth in both MMW and FSO links and is compatible with orthogonal frequency division multiplexing (OFDM). In the CMC design, the data blocks at the transmitter side are interleaved and repeated in both the frequency domain and the time domain, and then the duplicated blocks are combined with adaptive weight coefficients at the receiver side. We demonstrate experimentally that the proposed CMC t echnique improves power margins and enhances the robustness of the adaptive diversity combining technique (ADCT)-based FSO/MMW links by mitigating system impairments caused by frequency/time burst interference and power fading attributable to adverse weather conditions. In experiments, compared with the ADCT-based system, we find a 9 dB gain in received optical power tolerance and a 5.8 dB lower EVM floor under a deliberately injected 20-MHz LTE frequency interference burst.

Design, development and use of the spectrometer for investigating coherent THz radiation produced by micro-bunching instabilities at Diamond Light Source

Schottky barrier diodes (SBDs) are known for their low noise, ultra-fast response and excellent sensitivity. They are often implemented as detectors in the millimetre wavelength regime. Micro-bunch instabilities (MBI) have been detected at many light sources around the world including the Diamond Light Source, UK. These MBI can result in bursts of coherent synchrotron radiation (CSR) with millimetre wavelengths. More research needs to be carried out with regards to the dynamics of MBI in order to confirm the simulations and to eventually harness the power of the CSR bursts. A single shot spectrometer has been designed and is under operation at the Diamond Light Source (DLS). It is composed of eight SBDs ranging from 33-1000 GHz. Unlike previous measurements carried out, each of the SBDs has been individually characterised thus making the results obtained comparable to simulations. In this paper, we present the assessment of each SBD in the spectrometer and the first results of the spectrometer's use in the beam.

Air traffic control: Ocular metrics reflect cognitive complexity

The objective of the study was to evaluate effects of complexity on cognitive workload in a simulated air traffic control conflict detection task by means of eye movements recording. We manipulated two complexity factors, convergence angle and aircrafts minimum distance at closest approach, in a multidimensional workload assessment method based on psychophysiological, performance, and subjective measures. Conflict trials resulted more complex and time-consuming than no conflicts, requiring more frequent fixations and saccades. Moreover, large saccades showed reduced burst power with higher task complexity. A motion-based and a ratio-based strategy were suggested for conflicts and no conflicts on the basis of ocular metrics analysis: aircrafts differential speed and distance to convergence point at trial start were considered determinant for strategy adoption. Relevance to industryEye metrics measurement for online workload assessment enhances better identification of workload-inducing scenarios and adopted strategy for traffic management. System design, as well as air traffic control operators training programs, might benefit from on line workload measurement.