Short Separation Research Articles

Coexistence of Power-Controlled Cellular Networks With Rotating Radar

In this paper, we study spectral coexistence between rotating radar and power-controlled cellular networks in radar bands. For two systems to spectrally coexist, they must be able to operate effectively without causing harmful electromagnetic interference to each other. Very short radar-cellular system separation distances are required during 83.3% of time due to the narrow main beam width of the rotational radar antenna. We propose a spatio-temporal analytical approach with adaptive base station (BS) power control for adjacent spectrum sharing between the two systems. We develop a new model for the aggregate interference from power-controlled cellular BSs using log-normal approximation. The cellular system is allowed to transmit at high power when the radar antenna's main beam is pointing elsewhere from it. On the other hand, the cellular system reduces its transmit power only for a short period when the radar directional antenna main beam is pointing toward it. We use the degradation of the radar signal-to-interference plus noise ratio and cellular outage probability as our performance metrics. Numerical results show that power control of cellular BS highly reduces separation distance between the BS and radar, while yielding marginal degradation of outage performance. In addition, the mathematical results given by the log-normal approximation closely follow our simulated results. Detail system level assessments and investigations are presented to comprehensively understand secondary access to this band opportunistically.

Improved Separations of Proteins and Sugar Derivatives Using the Small-Scale Cross-Axis Coil Planet Centrifuge with Locular Multilayer Coiled Columns.

Countercurrent chromatography (CCC) is liquid-liquid partition chromatography without using a solid support matrix. This technique requires further improvement of partition efficiency and shortening theseparation time. The locular multilayer coils modified with and without mixer glass beads were developed for the separation of proteins and 4-methylumbelliferyl (MU) sugar derivatives using the small-scale cross-axis coil planet centrifuge. Proteins were well separated from each other and the separation was improved at a low flow rate of the mobile phase. On the other hand, 4-MU sugar derivatives were sufficiently resolved with short separation time at a highflow rate of the mobile phase under satisfactory stationary phase retention. Effective separations were achieved using the locular multilayer coil for proteins with aqueous-aqueous polymer phase systems and for 4-MU sugar derivatives with organic-aqueous two-phase solvent systems by inserting a glass bead into each locule.

Normal Evoked Response to Rapid Sequences of Tactile Pulses in Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a developmental disorder diagnosed behaviorally, with many documented neurophysiological abnormalities in cortical response properties. While abnormal sensory processing is not considered core to the disorder, most ASD individuals report sensory processing abnormalities. Yet, the neurophysiological correlates of these abnormalities have not been fully mapped. In the auditory domain, studies have shown that cortical responses in the early auditory cortex in ASD are abnormal in multiple ways. In particular, it has been shown that individuals with ASD have abnormal cortical auditory evoked responses to rapid, but not slow, sequences of tones. In parallel, there is substantial evidence of somatosensory processing abnormalities in ASD, including in the temporal domain. Here, we tested the somatosensory domain in ASD for abnormalities in rapid processing of tactile pulses, to determine whether abnormalities there parallel those observed in the auditory domain. Specifically, we tested the somatosensory cortex response to a sequence of two tactile pulses with different (short and long) temporal separation. We analyzed the responses in cortical space, in primary somatosensory cortex. As expected, we found no group difference in the evoked response to pulses with long (700 ms) temporal separation. Contrary to findings in the auditory domain, we also found no group differences in the evoked responses to the sequence with a short (200 ms) temporal separation. These results suggest that rapid temporal processing deficits in ASD are not generalized across multiple sensory domains, and are unlikely to underlie the behavioral somatosensory abnormalities observed in ASD.

On the streamwise and normal vortices forming on plates with spanwise periodic cambering

Three-dimensional measurements of the flow field over rigid plates with periodic cambering in the spanwise direction were performed. Two plates of an aspect ratio of 5 with 5 and 9 periodic cells were used, and measurements were performed at a Reynolds number of 28,000 and three angles of attack. Previous research showed that organized vortices form in the valleys between the periodic cells, and that these vortices contribute to slight enhancement of lift and reduction in drag. In this investigation, the details of these vortices are examined and compared at three different flow fields including: 1) short separation bubble, 2) long separation bubble and 3) fully separated flow. The formation of these primary vortices is observed in all cases. The formation of these vortices is influenced by the interaction between the periodic cambering, and the thickness and strength of the backflow. This interaction becomes strongest when a long separation bubble forms resulting in larger vortices in size and magnitude. The instantaneous flow field shows that the primary vortices form most of the time, while they move in the spanwise direction and breakdown in the streamwise direction at other instances of time. In addition to the primary vortices, smaller vortices also form in the vicinity of the primary vortices. Proper Orthogonal Decomposition results indicate that reconstructing the flow field with different number of modes isolates the primary vortices from the smaller scale vortices.

A fast and simple LC-MS-based characterization of the flavonoid biosynthesis pathway for few seed(ling)s.

Background(Pro)anthocyanidins are synthesized by the flavonoid biosynthesis pathway with multi-layered regulatory control. Methods for the analysis of the flavonoid composition in plants are well established for different purposes. However, they typically compromise either on speed or on depth of analysis.ResultsIn this work we combined and optimized different protocols to enable the analysis of the flavonoid biosynthesis pathway with as little as possible biological material. We chose core substances of this metabolic pathway that serve as a fingerprint to recognize alterations in the main branches of the pathway. We used a simplified sample preparation, two deuterated internal standards, a short and efficient LC separation, highly sensitive detection with tandem MS in multiple reaction monitoring (MRM) mode and hydrolytic release of the core substances to reduce complexity. The method was optimized for Arabidopsis thaliana seeds and seedlings. We demonstrate that one Col-0 seed/seedling is sufficient to obtain a fingerprint of the core substances of the flavonoid biosynthesis pathway. For comparative analysis of different genotypes, we suggest the use of 10 seed(lings). The analysis of Arabidopsis thaliana mutants affecting steps in the pathway revealed foreseen and unexpected alterations of the pathway. For example, HY5 was found to differentially regulate kaempferol in seeds vs. seedlings. Furthermore, our results suggest that COP1 is a master regulator of flavonoid biosynthesis in seedlings but not of flavonoid deposition in seeds.ConclusionsWhen sample numbers are high and the plant material is limited, this method effectively facilitates metabolic fingerprinting with one seed(ling), revealing shifts and differences in the pathway. Moreover the combination of extracted non-hydrolysed, extracted hydrolysed and non-extracted hydrolysed samples proved useful to deduce the class of derivative from which the individual flavonoids have been released.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0880-7) contains supplementary material, which is available to authorized users.

On the interaction of dipolar filaments.

The interactions of dipolar filaments such as magnetic needles and chains in strong homogeneous magnetic/electric field are investigated theoretically. Revisiting the case of uniformly magnetized/polarized parallel needles of finite size L and separated by a distance R , all the relevant regimes of attraction and/or repulsion are properly addressed and discussed. At short inter-needle separation ( R/L ≲ 0.2, the repuive pair potential of two facing needles is governed by R(-1) in strong contrast with R(-3) at long separations (R/L ≳ 2.5). This softening is attributed to an efficient long-range screening owing to the relatively long needle extension in this regime. This whole understanding of dipolar needles effective interaction is then used to grasp that of dipolar chains made up of spherical dipolar beads. When excluded-volume correlations are weak (i.e., the chains are a few beads apart), chains and needles possess virtually the same effective interaction. However, at short separation there is a remarkable hardening upon approaching two chains in registry in qualitative contrast to the needles case.

Mayer waves reduce the accuracy of estimated hemodynamic response functions in functional near-infrared spectroscopy.

Analysis of cerebral hemodynamics reveals a wide spectrum of oscillations ranging from 0.0095 to 2 Hz. While most of these oscillations can be filtered out during analysis of functional near-infrared spectroscopy (fNIRS) signals when estimating stimulus evoked hemodynamic responses, oscillations around 0.1 Hz are an exception. This is due to the fact that they share a common spectral range with typical stimulus evoked hemodynamic responses from the brain. Here we investigate the effect of hemodynamic oscillations around 0.1 Hz on the estimation of hemodynamic response functions from fNIRS data. Our results show that for an expected response of ~1 µM in oxygenated hemoglobin concentration (HbO), Mayer wave oscillations with an amplitude > ~1 µM at 0.1 Hz reduce the accuracy of the estimated response as quantified by a 3 fold increase in the mean squared error and decrease in correlation (R(2) below 0.78) when compared to the true HRF. These results indicate that the amplitude of oscillations at 0.1 Hz can serve as an objective metric of the expected HRF estimation accuracy. In addition, we investigated the effect of short separation regression on the recovered HRF, and found that this improves the recovered HRF when large amplitude 0.1 Hz oscillations are present in fNIRS data. We suspect that the development of other filtering strategies may provide even further improvement.

Influence of human breathing modes on airborne cross infection risk

CFD simulation is an accurate and reliable method to predict the risk of airborne cross-infection in a room. This paper focuses on the validation of a 3-D transient CFD model used to predict personal exposure to airborne pathogens and infection risk in a displacement ventilated room. The model provides spatial and temporal solutions of the airflow pattern in the room (temperature, velocity and turbulence), as well as contaminant concentration in a room where two thermal manikins simulate two standing people, one of whom exhales a tracer gas N2O simulating airborne contaminants. Numerical results are validated with experimental data and the model shows a high accuracy when predicting the transient cases studied. Once the model is validated, the CFD model is used to simulate different airborne cross-infection risk scenarios. Four different combinations of the manikins’ breathing modes and four different separation distances between the two manikins are studied. The results show that exhaling through the nose or mouth disperses exhaled contaminants in a completely different way and also means that exhaled contaminants are received differently. For short separation distances between breathing sources the interaction between breaths is a key factor in the airborne cross-infection for all the breathing mode combinations studied. However, for long distances the general airflow conditions in the room prove to be more important.

Separation of argon from environmental samples for Ar-37 and Ar-39 analyses

High purity argon is required for ultra-low background measurements of 37Ar and 39Ar. Both short separation times and high argon recovery are required. Here we report the development of an argon separation line from gas samples of 10–120 l volume by a chromatographic desorption from Li-LSX at −120 °C. Gases desorb in the order Ar < O2 < Kr < CH4 ≈ N2 < CO2, in agreement with published heats of adsorption. The optimum temperature of −120 °C for Ar separation from atmospheric air is achieved by a combination of cryogenic cooling with liquid nitrogen and counter-heating. So far, ∼16,500 l of sample gas have been processed on the separation line. The final purity of the argon is >99.99% with a recovery of >94%. The separation process for 80 l atmospheric air requires 3–4.5 h, which allows the purification of 2 samples per working day.

A robust multistage mesoflow reactor for liquid–liquid extraction for the separation of Co/Ni with cyanex 272

Solvent extraction is a key principle for separations of components often requiring relatively large separation times due to large droplet size distributions. A continuous mesoflow reactor setup was evaluated for solvent extraction and phase separation in terms of efficiency of Co/Ni separation with cyanex 272 as extractant in a kerosene mixture. Several mixer types have been evaluated for the solvent extraction capability combined with a thin film coalescer/separator, expediting separation times, resulting in a settling volume that was only 1–2 times the volume of the mixer effectively reducing total residence time compared to classic mixer-settlers, where the ratio is 4–8 times higher. This was mainly attributed to the droplet homogeneity generated in the mixer, resulting is a short separation time. The thin film coalescer partitions in the settler expedited the phase separation further reducing the required settler volume. This paper shows that continuous mesoflow reactor setups can be utilized for small-scale liquid extractions with narrowly defined droplet sizes, enhancing the phase separation time, making it a viable screening utility. It also shows that the useful volume is much higher than those for conventional mixer-settler with a phase-separation-volume-to-equilibrium-volume ratio of 1–2 compared to 4–8 for the conventional mixer-settler expediting parameter screening.

Temporal correlations in neuronal avalanche occurrence

Ongoing cortical activity consists of sequences of synchronized bursts, named neuronal avalanches, whose size and duration are power law distributed. These features have been observed in a variety of systems and conditions, at all spatial scales, supporting scale invariance, universality and therefore criticality. However, the mechanisms leading to burst triggering, as well as the relationship between bursts and quiescence, are still unclear. The analysis of temporal correlations constitutes a major step towards a deeper understanding of burst dynamics. Here, we investigate the relation between avalanche sizes and quiet times, as well as between sizes of consecutive avalanches recorded in cortex slice cultures. We show that quiet times depend on the size of preceding avalanches and, at the same time, influence the size of the following one. Moreover we evidence that sizes of consecutive avalanches are correlated. In particular, we show that an avalanche tends to be larger or smaller than the following one for short or long time separation, respectively. Our analysis represents the first attempt to provide a quantitative estimate of correlations between activity and quiescence in the framework of neuronal avalanches and will help to enlighten the mechanisms underlying spontaneous activity.

Artificial neural networks for retrieving absorption and reduced scattering spectra from frequency-domain diffuse reflectance spectroscopy at short source-detector separation.

Diffuse reflectance spectroscopy (DRS) based on the frequency-domain (FD) technique has been employed to investigate the optical properties of deep tissues such as breast and brain using source to detector separation up to 40 mm. Due to the modeling and system limitations, efficient and precise determination of turbid sample optical properties from the FD diffuse reflectance acquired at a source-detector separation (SDS) of around 1 mm has not been demonstrated. In this study, we revealed that at SDS of 1 mm, acquiring FD diffuse reflectance at multiple frequencies is necessary for alleviating the influence of inevitable measurement uncertainty on the optical property recovery accuracy. Furthermore, we developed artificial neural networks (ANNs) trained by Monte Carlo simulation generated databases that were capable of efficiently determining FD reflectance at multiple frequencies. The ANNs could work in conjunction with a least-square optimization algorithm to rapidly (within 1 second), accurately (within 10%) quantify the sample optical properties from FD reflectance measured at SDS of 1 mm. In addition, we demonstrated that incorporating the steady-state apparatus into the FD DRS system with 1 mm SDS would enable obtaining broadband absorption and reduced scattering spectra of turbid samples in the wavelength range from 650 to 1000 nm.

FRET from Multiple Pathways in Fluorophore-Labeled DNA

Because of their ease of design and assembly, DNA scaffolds provide a valuable means for organizing fluorophores into complex light harvesting antennae. However, as the size and complexity of the DNA–fluorophore network grows, it can be difficult to fully understand energy transfer properties because of the large number of dipolar interactions between fluorophores. Here, we investigate simple DNA–fluorophore networks that represent elements of the more complex networks and provide insight into the Forster Resonance Energy Transfer (FRET) processes in the presence of multiple pathways. These FRET networks consist of up to two Cy3 donor fluorophores and two Cy3.5 acceptor fluorophores that are linked to a rigid dual-rail DNA scaffold with short interfluorophore separation corresponding to 10 DNA base pairs (∼34 A). This configuration results in five FRET pathways: four hetero-FRET and one homo-FRET pathway. The FRET properties are characterized using a combination of steady-state and time-resolved spectrosc...

Photoinduced Charge Separation in Porphyrin Ion Pairs.

Ion pairs between porphyrin-type compounds have been successfully employed for spectral sensitization of semiconductor surfaces and for the preparation of collective binary ionic materials for photonic and (photo)catalytic applications. The understanding of the photophysical processes occurring within ion-paired porphyrin dimers is thus of remarkable importance for the optimization and improvement of such systems. Herein the ion-pair species formed between ZnTMePyP(4+) (Zn1) or H2TMePyP(4+) (H21) and ZnTPPS(4-) (Zn2) or H2TPPS(4-) (H22) in a variety of solvent mixtures are characterized and their photophysics thoroughly investigated by time-resolved techniques. In all the systems studied, very fast and efficient photoinduced charge separation is observed, with the cationic porphyrin being reduced and the anionic one oxidized. Interestingly, despite the very short charge separation distance, the lifetime for charge recombination, depending on the energy gap, can extend into the nanosecond time domain, showing great potential for the utilization of this molecular design within energy conversion schemes.

Fiber laser-MIG hybrid welding of 5 mm 5083 aluminum alloy

Aluminum and its alloys are difficult to weld due to their specific characteristics. New joining methods such as high power fiber laser-MIG can provide higher overall productivity compared to the arc welding or laser beam welding. There is huge lack of information on how the specific welding parameters in laser-arc hybrid welding affect quality of welds such as torch arrangement, distance between heat sources and shielding gas composition while other parameters were kept at constant. Laser-arc hybrid welds with short separation distance between sources produced severe porosity in one pass 5mm thick aluminum alloy sheets welding due to unstable interactions and keyhole frequent collapses. Higher process stability and lower porosity level can be achieved by applying trailing torch arrangement. Addition of significantly more expensive helium to the shielding gas did not provide any benefits in terms of porosity decrease, process stability and mechanical properties of welds overall as was expected with selected welding parameters.

Energy Transfer between Conjugated Colloidal Ga₂O₃ and CdSe/CdS Core/Shell Nanocrystals for White Light Emitting Applications.

Developing solid state materials capable of generating homogeneous white light in an energy efficient and resource-sustainable way is central to the design of new and improved devices for various lighting applications. Most currently-used phosphors depend on strategically important rare earth elements, and rely on a multicomponent approach, which produces sub-optimal quality white light. Here, we report the design and preparation of a colloidal white-light emitting nanocrystal conjugate. This conjugate is obtained by linking colloidal Ga2O3 and II–VI nanocrystals in the solution phase with a short bifunctional organic molecule (thioglycolic acid). The two types of nanocrystals are electronically coupled by Förster resonance energy transfer owing to the short separation between Ga2O3 (energy donor) and core/shell CdSe/CdS (energy acceptor) nanocrystals, and the spectral overlap between the photoluminescence of the donor and the absorption of the acceptor. Using steady state and time-resolved photoluminescence spectroscopies, we quantified the contribution of the energy transfer to the photoluminescence spectral power distribution and the corresponding chromaticity of this nanocrystal conjugate. Quantitative understanding of this new system allows for tuning of the emission color and the design of quasi-single white light emitting inorganic phosphors without the use of rare-earth elements.

High Pseduo-Stoke's Shift of a Naphthalene-Bisindolylmaleimide Dye.

An energy transfer cassette was reported with energy donor and acceptor incorporated in one molecular. The two units (naphthalene and bisindolylmaleimide) were connected by covalent single bond. The intramolecular repulsion twisted the molecular conformation, thereby forcing the two units act as independent chromophores. Upon photoexcitation (λ = 280 nm), bright emission peak was observed around 583 nm. The intramolecular cascade energy transfer from the naphthalene moiety to the bisindolylmaleimide framework is efficient and the efficiency is estimated to be 86%, providing large pseudo-Stoke's shift (303 nm). At such a short separation, the orbital overlap interaction was completely isolated between chromophoric units. Computational study was carried out based on DFT. Further analysis of optimized structure and FMOs supports the efficient energy transfer in NBM. Favorable photophysical properties, such as efficient energy transfer, strong emission, and large Stoke's shift make it an attractive functional dye.

Flight-Test Evaluation of Kinematic Precise Point Positioning of Small UAVs

An experimental analysis of Global Positioning System (GPS) flight data collected onboard a Small Unmanned Aerial Vehicle (SUAV) is conducted in order to demonstrate that postprocessed kinematic Precise Point Positioning (PPP) solutions with precisions approximately 6 cm 3D Residual Sum of Squares (RSOS) can be obtained on SUAVs that have short duration flights with limited observational periods (i.e., only ~≤5 minutes of data). This is a significant result for the UAV flight testing community because an important and relevant benefit of the PPP technique over traditional Differential GPS (DGPS) techniques, such as Real-Time Kinematic (RTK), is that there is no requirement for maintaining a short baseline separation to a differential GNSS reference station. Because SUAVs are an attractive platform for applications such as aerial surveying, precision agriculture, and remote sensing, this paper offers an experimental evaluation of kinematic PPP estimation strategies using SUAV platform data. In particular, an analysis is presented in which the position solutions that are obtained from postprocessing recorded UAV flight data with various PPP software and strategies are compared to solutions that were obtained using traditional double-differenced ambiguity fixed carrier-phase Differential GPS (CP-DGPS). This offers valuable insight to assist designers of SUAV navigation systems whose applications require precise positioning.

A Simplified Model Predicting the Kelvin–Helmholtz Instability Frequency for Laminar Separated Flows

A semi-empirical model for the estimation of the Kelvin–Helmholtz (KH) instability frequency, in the case of short laminar separation bubbles over airfoils, has been developed. To this end, the Thwaites's pressure gradient parameter has been adopted to account for the effects induced by the aerodynamic loading distribution as well as by the Reynolds number on the separated shear layer thickness at separation. The most amplified frequency predicted by linear stability theory (LST) for a piecewise linear profile, which can be considered as the KH instability frequency, has been related to the shear layer thickness at separation, hence to the Reynolds number and the aerodynamic loading distribution through the Thwaites's pressure gradient parameter. This procedure allows the formulation of a functional dependency between the Strouhal number of the shedding frequency based on exit conditions and the dimensionless parameters. Experimental results obtained in different test cases, characterized by different Reynolds numbers and aerodynamic loading distributions, have been used to validate the model, as well as to identify the regression curve best fitting the data. The semi-empirical correlation here derived can be useful to set the activation frequency of active flow control devices for the optimization of boundary layer separation control strategies.

Clump formation through colliding stellar winds in the Galactic Centre

The gas cloud G2 is currently being tidally disrupted by the Galactic Centre super-massive black hole, Sgr A*. The region around the black hole is populated by $\sim 30$ Wolf-Rayet stars, which produce strong outflows. We explore the possibility that gas clumps, such as G2, originate from the collision of stellar winds via the non-linear thin shell instability. Following an analytical approach, we study the thermal evolution of slabs formed in the symmetric collision of winds, evaluating whether instabilities occur, and estimating possible clump masses. We find that the collision of relatively slow ($< 750$ km s$^{-1}$) and strong ($\sim 10^{-5}$ Msun yr$^{-1}$) stellar winds from stars at short separations ($<10$ mpc) is a process that indeed could produce clumps of G2's mass and above. Such short separation encounters of single stars along their known orbits are not common in the Galactic Centre, making this process a possible but unlikely origin for G2. We also discuss clump formation in close binaries such as IRS 16SW and in asymmetric encounters as promising alternatives that deserve further numerical study.