Local High Frequency Research Articles

Integrated conjugative plasmid drives high frequency chromosomal gene transfer in Sulfolobus islandicus.

Gene transfer in crenarchaea has been observed within natural and experimental populations of Sulfolobus. However, the molecular factors that govern how gene transfer and recombination manifest themselves in these populations is still unknown. In this study, we examine a plasmid-mediated mechanism of gene transfer in S. islandicus that results in localized high frequency recombination within the chromosome. Through chromosomal marker exchange assays with defined donors and recipients, we find that while bidirectional exchange occurs among all cells, those possessing the integrated conjugative plasmid, pM164, mobilize a nearby locus at a significantly higher frequency when compared to a more distal marker. We establish that traG is essential for this phenotype and that high frequency recombination can be replicated in transconjugants after plasmid transfer. Mapping recombinants through genomic analysis, we establish the distribution of recombinant tracts with decreasing frequency at increasing distance from pM164. We suggest the bias in transfer is a result of an Hfr (high frequency recombination)-like conjugation mechanism in this strain. In addition, we find recombinants containing distal non-selected recombination events, potentially mediated by a different host-encoded marker exchange (ME) mechanism.

Local scale high frequency monitoring of seaweed strandings along an intertidal shore of the English Channel (Luc-sur-Mer, Normandy France) – Effect of biotic and abiotic factors

Seaweed strandings on Luc-sur-Mer beach (Bay of Seine, English Channel, France) were monitored from March 2017 to October 2018 once or twice a week to investigate the wrack deposit dynamics linked to biotic and environmental parameters. The extent of stranded seaweed, algal biomass and composition of algal wrack were monitored through 99 field surveys. Forty-seven macroalgae taxa (14 Phaeophyta, 28 Rhodophyta, and 5 Chlorophyta) were identified in strandings. Almost 83% of the 35 taxa (8 Phaeophyta, 23 Rhodophyta, and 4 Chlorophyta) inventoried on the nearby intertidal rocky shore during the same period were also identified in the wrack deposits, suggesting their local origin. Analysis of wrack composition revealed the dominance of sheet-like species and annual algae mainly represented by Ulva in spring and summer, and by perennial and brown seaweeds in winter. The same stranding dynamics was observed in the two years with largest deposits in spring and summer but strandings occurred earlier in 2017, due to contrasted environmental parameters in the two years. Large wrack deposits (> 4.5 Ha) were mainly observed in spring when the wind speed was greater than 2.6 m.s−1 and the predicted tide height greater than 6.8 m. Most deposits were associated with WSW winds (38%) and SSW winds (26%) winds. These data will help develop a tool to assess the risk of algal bloom in sandy beach ecosystem. The knowledge acquired about the availability and composition of the macroalgae strandings will also help promote the use of this bio-resource which is under-exploited in Normandy.

A new limited-angle CT reconstruction algorithm based on the local anisotropic total variation restoration of continuity

A new limited-angle computed tomography(CT) reconstruction algorithm based on local detail information restoration in the CT image projection domain was proposed in this paper. The lost projection information could be repaired with the new algorithm called local anisotropic total variation repair method of sinogram (LATV). According to the continuity of local gradient in sinogram, local high frequency characteristics can be improved which are blurred by conventional TVM. A series of numerical reconstruction experiments were conducted to validate the new algorithm. The overall quality of images reconstructed by new algorithm was better than conventional TVM algorithm when quantitatively evaluated. Then, a local region with rich details was selected in order to evaluate the reconstruction effect of the internal details. From the perspective of three image quality evaluation parameters, it was shown that the local high frequency details were well repaired. Finally, the reconstruction quality was evaluated by actual CT experimental data. The new method also performed better than conventional method. Therefore, the new LATV algorithm proposed in this paper may be a new method suitable for limited-angle CT reconstruction problems.

Noninvasive Measurement of Humidity Distribution in Polymer Electrolyte Fuel Cells (PEFCs). Part II: Operando Analysis of a Fuel Cell Stack

In the second part of the paper series on a noninvasive method to determine the local high frequency resistance (HFR) distribution in polymer electrolyte fuel cells (PEFC), the method is applied to an operating PEFC stack. While in the first part of this paper series the approach of using multiple surface attached electrodes to locally inject 1 kHz AC currents into a cell and to measure the resulting voltage amplitudes at the flow field’s surface was introduced. Its sensitivity was assessed using a stack fed only by nitrogen at different humidification levels. Here, it is confirmed that the approach works also during electrochemical operation. First, the method’s spatial resolution is further explored and improved by using multiple stimulation patterns after examining the local sensitivity of the different electrode combinations to changes in membrane conductivity by finite element model simulations of the current injection. The method is then applied to a stack operated at different current densities, inlet humidities and gas flow configurations. The HFR distributions are in good agreement with literature data and compare well with the global cell HFR. Finally, the method’s transient capabilities are highlighted by measuring the HFR distribution during a current jump and cell drying.

Non-Invasive Measurement of Humidity Distribution in Polymer Electrolyte Fuel Cells (PEFCs): Part I. In Situ Proof of Concept

A non-invasive method to determine the local relative humidity (RH) and local high frequency resistance (HFR) distribution from inlet to outlet of polymer electrolyte fuel cells (PEFCs) is presented. The method uses a plurality of electrodes attached to the outer flow field surface to inject alternating currents and measure the resulting voltage amplitudes at the flow fields’ surface. Since the measured voltage amplitudes, are highly dependent on the actual electrode positioning on the flow field boundaries, they are interpreted by interpolation between reference measurements at homogeneous relative humidity conditions and known overall cell impedance. The method is implemented experimentally using alternating current injections at a frequency of 1 kHz at well-defined asymmetric in situ N2/N2 conditions on a 200-cm2 cell in a 6-cell short-stack. The comparison between the RH distribution and the outlet RH sensor data yields a very good match. The same can be said when comparing the HFR distribution and the global cell HFR. Finally, the sensitivity of the method is tested by varying the mass flow rate with asymmetrical RH conditions. The results are highly reproducible in all the tested conditions.

Innovative Green Chemistry Approach to Synthesis of Sn2+-Metal Complex and Design of Polymer Composites with Small Optical Band Gaps.

In this work, the green method was used to synthesize Sn2+-metal complex by polyphenols (PPHs) of black tea (BT). The formation of Sn2+-PPHs metal complex was confirmed through UV-Vis and FTIR methods. The FTIR method shows that BT contains NH and OH functional groups, conjugated double bonds, and PPHs which are important to create the Sn2+-metal complexes. The synthesized Sn2+-PPHs metal complex was used successfully to decrease the optical energy band gap of PVA polymer. XRD method showed that the amorphous phase increased with increasing the metal complexes. The FTIR and XRD analysis show the complex formation between Sn2+-PPHs metal complex and PVA polymer. The enhancement in the optical properties of PVA was evidenced via UV-visible spectroscopy method. When Sn2+-PPHs metal complex was loaded to PVA, the refractive index and dielectric constant were improved. In addition, the absorption edge was also decreased to lower photon. The optical energy band gap decreases from 6.4 to 1.8 eV for PVAloaded with 30% (v/v) Sn2+-PPHs metal complex. The variations of dielectric constant versus wavelength of photon are examined to measure localized charge density (N/m*) and high frequency dielectric constant. By increasing Sn2+-PPHs metal complex, the N/m* are improved from 3.65 × 1055 to 13.38 × 1055 m−3 Kg−1. The oscillator dispersion energy (Ed) and average oscillator energy (Eo) are measured. The electronic transition natures in composite films are determined based on the Tauc’s method, whereas close examinations of the dielectric loss parameter are also held to measure the energy band gap.

Faradaic-free electrokinetic nucleic acid amplification (E-NAAMP) using localized on-chip high frequency Joule heating.

We present a novel Faradaic reaction-free nucleic acid amplification (NAA) method for use with microscale liquid samples. Unlike previous Joule heating methods where the electrodes produce electrolysis gaseous by-products and require both the electrodes be isolated from a sample and the venting of produced electrolysis gas, our electrokinetic Nucleic Acid Amplification (E-NAAMP) method alleviates these issues using a radio frequency (RF) alternating current electric field. In this approach, a pair of microscale thin film gold electrodes are placed directly in contact with a nucleic acid reaction mixture. A high frequency (10-40 MHz) RF potential is then applied across the electrode pair to induce a local Ohmic current within the sample and drive the sample temperature to increase by Joule heating. The temperature increase is sustainable in that it can be generated for several hours of constant use without generating any pH change to the buffer or any microscopically observable gaseous electrolysis by-products. Using this RF Joule heating approach, we demonstrate successful direct thermal amplification using two popular NAA biochemical reactions: loop-mediated isothermal amplification and polymerase chain reaction. Our results demonstrate that a simple microscale electrode structure can be used for thermal regulation for NAA reactions without observable electrolytic reactions, minimal enzyme activity loss and sustained (>50 h use per device) continuous operations without electrode delamination. As such, E-NAAMP offers substantial miniaturization of the heating elements for use in microfluidic or miniaturized NAA reaction systems.

Local teratogenic factors and high frequency of Japanese folklore cyclops (yōkai)

Japan is famous for its fabulous creatures ( yōkai ) characterized by their deformities. We wanted to know if local factors were involved in the high frequency of these legendary malformations, and sought to identify local teratogenic elements. Many potential teratogenic elements have been identified, which can be linked to specific malformations (cyclopia, for example). We therefore confirm that local factors would indeed promote the development of cyclops in Japan. This might explain the great frequency of supernatural creatures exhibiting this physical characteristic within Japanese folklore, and who would transmit this empirical knowledge through the generations.

Local and parallel finite element methods based on two‐grid discretizations for unsteady convection–diffusion problem

AbstractIn this article, some local and parallel finite element methods are proposed and investigated for the time‐dependent convection–diffusion problem. With backward Euler scheme for the temporal discretization, the basic idea of the present methods is that for a solution to the considered equations, low frequency components can be approximated well by a relatively coarse grid and high frequency components can be computed on a fine grid by some local and parallel procedure at each time step. The partition of unity is used to collect the local high frequency components to assemble a global continuous approximation. Theoretical results are obtained and numerical tests are reported to support the theoretical findings.

The Effect of Deep Brain Stimulation on High Frequency Oscillations in a Chronic Epilepsy Model

Abstract Temporal lobe epilepsy (TLE) is a severe neurological disease which is often pharmacoresistant. Deep brain stimulation (DBS) is a novel method for treating epilepsy; however, its mechanism of action is not fully understood. We aimed to study the effect of amygdala DBS in the pilocarpine model of TLE. Status epilepticus was induced by pilocarpine in male Wistar rats, and spontaneous seizures occurred after a latency period. A stimulating electrode was inserted into the left basolateral amygdala and two recording electrodes into the left and right hippocampus. A stimulus package consisted of 0.1 ms-long biphasic pulses applied regularly at 4 Hz for 50 seconds. This package was repeated four times a day, with 5-minute pauses, for 10 days. We also used an age-matched healthy control group of stimulated animals and another one of sham-operated rats. From the hippocampal local field potentials high frequency oscillations (HFOs) were analyzed as these are promising epilepsy biomarkers. HFOs are short oscillatory events between 80-600 Hz which were detected offline using an open-source application of MATLAB, the RIPPLELAB system. We found that the HFO rate was significantly higher in pilocarpine-treated rats compared to the control groups (0.41 ± 0.14 HFO/min vs. 0.006 ± 0.003 in the stimulated control group and no HFO in the sham-operated group). In the pilocarpine group an instantaneous decrease in HFO rate was observed while the stimulation was on (0.44 ± 0.15 HFO/min vs 0.07 ± 0.03 HFO/min, p=0.017). The effect was short-lived because the frequency of HFOs did not change significantly in the time windows between stimulus packages or during the ten-day stimulation period. The difference of HFO rates between epileptic and control groups could be used in the electrographic assessment of epilepsy. The decreased frequency of HFOs during stimulation may be useful to study the efficacy of DBS.

Identification of wave impacts and separation of responses using EMD

Various marine and off-shore structures experience rare extreme, and frequent substantial wave impacts, and these impacts have significant implications respectively for the ultimate strength and fatigue life of these structures. Likewise, many other structures experience forms of impact among their environmental loads that are critical for their design. One way of exploring these impacts is to study the vibration signal of the structure. However, due to the complexity of the non-stationary signal, the wave impacts on marine and off-shore structures are difficult to analyse. Using signals acquired during trials of a high-speed catamaran as a case study, this paper proposes employing the Empirical Mode Decomposition (EMD) to detect, identify and characterise significant wave impacts (known as ‘slams’), which is shown to be significantly better at classifying events than traditional methods of slam detection. With the application of EMD, the vibration signal is decomposed into many components that may be grouped into three categories: (1) the rigid-body response comprising two parts: the quasi-static response to the underlying wave spectrum (hydrostatic) and rigid-body resonance (hydrodynamic); (2) the elastic structural response (hydroelastic); and (3) local high frequency vibrations and/or noise. It is the second category that responds significantly to wave impact loads. By identifying the gap between the rigid body and structural resonant frequencies, a threshold is established to automate the physically rational separation of this hydroelastic response. Wave impact detection methods are then applied to this separated component, showing 94% true positive classification, compared with 64% for a recently published slam detection method that uses traditional filtering applied to the whole signal. Further, it allows for more targeted subsequent characterisation of the impact response. Thus, this paper concludes that EMD is an effective method to detect and identify wave impacts.

A Comparison between Coastal Altimetry Data and Tidal Gauge Measurements in the Gulf of Genoa (NW Mediterranean Sea)

Satellite altimetry data from X-TRACK products were analyzed for an overall assessment of their capability to detect coastal sea level variability in the Ligurian Sea. Near-coastal altimetry data, collected from 2009 to 2016 along track n.044, were compared with simultaneous high frequency sampled data at the tidal station in Genoa (NW Mediterranean Sea). The two time series show a very good agreement: correlation between total sea level elevation from the altimeter and sea level variation from the tidal gauge is 0.92 and root mean square difference is 4.5 cm. Some relevant mismatches can be ascribed to the local high frequency coastal variability due to shelf and harbor oscillation detected at the tidal station, which might not be observed at the location of the altimetry points of measurement. The analysis evidences discrepancies (root mean square difference of 4.7 cm) between model results for open sea tides and harmonic analysis at the tidal station, mainly occurring at the annual and semiannual period. On the contrary, the important part of dynamic atmospheric correction due to the inverse barometer effect, well agrees with that computed at the tidal station.

Deep brain stimulation induced normalization of the human functional connectome in Parkinson's disease.

Neuroimaging has seen a paradigm shift away from a formal description of local activity patterns towards studying distributed brain networks. The recently defined framework of the 'human connectome' enables global analysis of parts of the brain and their interconnections. Deep brain stimulation (DBS) is an invasive therapy for patients with severe movement disorders aiming to retune abnormal brain network activity by local high frequency stimulation of the basal ganglia. Beyond clinical utility, DBS represents a powerful research platform to study functional connectomics and the modulation of distributed brain networks in the human brain. We acquired resting-state functional MRI in 20 patients with Parkinson's disease with subthalamic DBS switched on and off. An age-matched control cohort of 15 subjects was acquired from an open data repository. DBS lead placement in the subthalamic nucleus was localized using a state-of-the art pipeline that involved brain shift correction, multispectral image registration and use of a precise subcortical atlas. Based on a realistic 3D model of the electrode and surrounding anatomy, the amount of local impact of DBS was estimated using a finite element method approach. On a global level, average connectivity increases and decreases throughout the brain were estimated by contrasting on and off DBS scans on a voxel-wise graph comprising eight thousand nodes. Local impact of DBS on the motor subthalamic nucleus explained half the variance in global connectivity increases within the motor network (R = 0.711, P < 0.001). Moreover, local impact of DBS on the motor subthalamic nucleus could explain the degree to how much voxel-wise average brain connectivity normalized towards healthy controls (R = 0.713, P < 0.001). Finally, a network-based statistics analysis revealed that DBS attenuated specific couplings known to be pathological in Parkinson's disease. Namely, coupling between motor thalamus and motor cortex was increased while striatal coupling with cerebellum, external pallidum and subthalamic nucleus was decreased by DBS. Our results show that resting state functional MRI may be acquired in DBS on and off conditions on clinical MRI hardware and that data are useful to gain additional insight into how DBS modulates the functional connectome of the human brain. We demonstrate that effective DBS increases overall connectivity in the motor network, normalizes the network profile towards healthy controls and specifically strengthens thalamo-cortical connectivity while reducing striatal control over basal ganglia and cerebellar structures.

A new potential specifically marks the sensory thalamus in anaesthetised patients

ObjectiveDuring deep brain stimulation (DBS) surgery, we analysed somatosensory evoked potentials (SSEPs) using microelectrode recordings (MERs) in patients under general anaesthesia. MethodsWe obtained MERs from 5 patients with refractory epilepsy. Off-line analysis isolated local field potentials (LFPs, 2–200 Hz) and high frequency components (HFCs, 0.5–5 kHz). Trajectories were reconstructed off-line. ResultsThe ventral caudate (V.c.) nucleus was most frequently recorded from (171 mm). Very high frequency oscillations (VHFOs) were recorded up to 8 mm in length from all 4 electrodes but were most frequently recorded from the V.c. The properties of VHFOs were similar among all nuclei (frequency >1500 Hz, amplitude ∼3 µV, starting time ∼14 ms, duration 8–9 ms). Consecutive recordings did not show any synchronization or propagation, but a new kind of potential (high frequency oscillation, HFO) appeared abruptly inside the V.c. (frequency = 848 ± 66 Hz, amplitude = 5.2 ± 1.8 µV starting at 17.7 ± 0.5 ms, spanning 3.4 ± 0.3 ms). ConclusionsVHFOs are widely extending and cannot be ascribed to the V.c. HFOs in patients under general anaesthesia can serve as a landmark to identify the V.c. in thalamic DBS surgery. SignificanceThalamic processing involves nuclei other than the V.c, and HFO can be used to improve DBS surgery.

Appearance of Ferromagnetic Property for Si Nanopolycrystalline Body and Vanishing of Electrical Resistances at Local High Frequencies

Reduction in the skin effect for the sintered Si nanopolycrystalline body as an electricity conductor at a high frequency due to its nanostructure was studied. Singular disappearance of electrical resistances near a local high magnetic harmonic frequency of a few MHz was observed. This phenomenon has not been observed for conventional ferromagnetic metals. The measured electrical resistances changed to almost 0 mΩ at room temperature. At the same time, negative resistance of the sintered Si nanopolycrystalline body was observed. It will be applicable to electronic transmittance lines or semiconductors. Numerical calculation was also performed on the electrical resistance with frequency dependency while considering the electric field and magnetic field in the sintered Si nanopolycrystalline body. The experimental and calculated results are compared. The calculation could explain the variation of the relative permittivity of the Si nanopolycrystalline body and the phenomenon for the theoretical disappearance of the resistivity at the MHz frequency. Reduced Si nanoparticles from SiO2powder were synthesized by laser ablation in liquid. A Si nanopolycrystalline body made of the reduced Si nanoparticles was fabricated. It was found by measuring the magnetization property of the body of the sintered Si nanopolycrystalline body which is ferromagnetic. Dangling bonds (unpaired electrons) have long been known to occur due to defects in Si crystals. Perfect Si without defective crystals has no dangling bonds. However, Si nanoparticles have many dangling bonds. High-density dangling bonds cause the sintered Si nanopolycrystalline body to have ferromagnetism. In this study, the density of the unpaired electrons in the sintered Si nanopolycrystalline body was observed using ESR. It has been clarified that the Si nanopowder and the sintered Si nanopolycrystalline body have numerous dangling bonds. Both densities of the dangling bonds were evaluated.

Magnetic Property and Vanishing Resistance in Local High Frequency for Sintered Fe Nanopaste with Fe Nano-polycrystalline

Magnetic Property and Vanishing Resistance in Local High Frequency for Sintered Fe Nanopaste with Fe Nano-polycrystalline

Image Haze Removal via Reference Retrieval and Scene Prior.

Photography of hazy scene typically suffers from low-contrast which degrades the visibility of the scene. The performance of single-image dehazing methods is limited by the priors or constraints. In this paper, we present an effective method for haze removal, which utilizes its retrieved correlated haze-free images as external information. The correlated haze-free images are with scene prior offering scene structure and local high frequency information for dehazing, although variations in viewpoints, scales, and illumination conditions exist. To utilize those reference more effectively, global geometric registration and local block matching toward the hazy input are performed to reinforce the spatial correlations. Based on the registration, different kinds of external information are estimated. In addition, we combine that additional external information with internal constraint and regularization for estimating scene transmission map. Experiments demonstrate that our approach can produce dehazing results with better visual quality compared with other state-of-the-art methods.

A two-step FEM-SEM approach for wave propagation analysis in cable structures

Vibration-based methods are among the most widely studied in structural health monitoring (SHM). It is well known, however, that the low-order modes, characterizing the global dynamic behaviour of structures, are relatively insensitive to local damage. Such local damage may be easier to detect by methods based on wave propagation which involve local high frequency behaviour. The present work considers the numerical analysis of wave propagation in cables. A two-step approach is proposed which allows taking into account the cable sag and the distribution of the axial forces in the wave propagation analysis. In the first step, the static deformation and internal forces are obtained by the finite element method (FEM), taking into account geometric nonlinear effects. In the second step, the results from the static analysis are used to define the initial state of the dynamic analysis which is performed by means of the spectral element method (SEM). The use of the SEM in the second step of the analysis allows for a significant reduction in computational costs as compared to a FE analysis. This methodology is first verified by means of a full FE analysis for a single stretched cable. Next, simulations are made to study the effects of damage in a single stretched cable and a cable-supported truss. The results of the simulations show how damage significantly affects the high frequency response, confirming the potential of wave propagation based methods for SHM.

Extreme dissolved oxygen variability in urbanised tropical wetlands: The need for detailed monitoring to protect nursery ground values

Little is known about levels of dissolved oxygen fish are exposed to daily in typical urbanised tropical wetlands found along the Great Barrier Reef coastline. This study investigates diel dissolved oxygen (DO) dynamics in one of these typical urbanised wetlands, in tropical North Queensland, Australia. High frequency data loggers (DO, temperature, depth) were deployed for several days over the summer months in different tidal pools and channels that fish use as temporal or permanent refuges. DO was extremely variable over a 24 h cycle, and across the small-scale wetland. The high spatial and temporal DO variability measured was affected by time of day and tidal factors, namely water depth, tidal range and tidal direction (flood vs ebb). For the duration of the logging time, DO was mainly above the adopted threshold for hypoxia (50% saturation), however, for around 11% of the time, and on almost every logging day, DO values fell below the threshold, including a severe hypoxic event (<5% saturation) that continued for several hours. Fish still use this wetland intensively, so must be able to cope with low DO periods. Despite the ability of fish to tolerate extreme conditions, continuing urban expansion is likely to lead to further water quality degradation and so potential loss of nursery ground value. There is a substantial discontinuity between the recommended DO values in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality and the values observed in this wetland, highlighting the limited value of these guidelines for management purposes. Local and regional high frequency data monitoring programs, in conjunction with local exposure risk studies are needed to underpin the development of the management that will ensure the sustainability of coastal wetlands.

UNDERSTANDING THE PHYSICS OF KAPPA (Κ0): INSIGHTS FROM THE EUROSEISTEST NETWORK

this study we estimate the spectral decay factor κ0 for the EUROSEISTEST array. Site conditions range from soft sediments to hard rock over 14 surface and 6 downhole accelerographs. First, we separate local and regional high frequency attenuation and measure κ0. Second, we use the existing knowledge of the geological profile and material properties to correlate κ0 with different site characterisation parameters (Vs30, resonant frequency, depth-to-bedrock). Third, we use our results to improve our physical understanding of κ0. We propose a conceptual model comprising two new notions. On the one hand, we observe that κ0 stabilises for high Vs values; this may indicate the existence of regional values for hard rock κ0. If so, we propose that borehole measurements may be useful in determining them. On the other hand, we find that material damping may not suffice to account for the total measured attenuation. We propose that, apart from damping, additional site attenuation may be caused by scattering from small-scale profile variability. If this is so, then geotechnical damping measurements may not suffice to infer overall crustal attenuation under a site; but starting with a regional (borehole) value and adding damping, we might define a lower bound for site-specific κ0.