Separate Channels Research Articles

Symbiotic Backscatter Communication Underlying a Cell-Free Massive MIMO System

In ambient backscatter communications, backscatter devices (BDs) utilize ambient “legacy” radio signals as both a harvested energy source and a carrier on which to modulate data. Symbiotic radio, a subtype in which the legacy system assists both its own users and underlaid BDs, has attracted much research interest recently. Furthermore, cell-free massive multiple-input multiple-output (CF mMIMO) systems are promising for beyond-5G networks from both spectral and energy efficiency perspectives. To reap the benefits of both, we consider a primary CF mMIMO system where the access points (APs) aid an underlaid BD layer to both harvest energy and reflect information toward the primary receivers (which receive data from both layers). To acquire separate channel state information (CSI) of the direct and backscattered channels at the APs, a two-phase uplink pilot training method is proposed, with the effects of pilot contamination and spatial correlation between antennas accounted for. However, the receivers are assumed to only have partial CSI (statistical knowledge plus instantaneous phase information for partially-coherent reception). Assuming uplink/downlink radio channel reciprocity, the CSI is used to design downlink precoding vectors for the APs such that channel hardening is enhanced and both primary receivers and BDs benefit. We derive expressions for the average signal-to-interference-plus-noise ratios of both primary and backscatter signals, accounting for the effects of imperfect CSI, spatial correlation, pilot contamination, and channel hardening. Furthermore, the average power harvested in the BDs is derived. Simulation results demonstrate that the performance of the proposed scheme is much more uniform across all devices with CF mMIMO than with conventional co-located mMIMO. The use of CF mMIMO also largely removes the need for special consideration of the BD layer in the symbiotic system, which is not the case with co-located mMIMO.

Quantifying narrowing partition thickness in a vertical pneumatic separation channel for soybean seed cleaning

The paper highlights that the study of the soybean seed separation processes in a vertical deep aspirating channel contributes to the improvement of technical and economic indicators in grain cleaning equipment. (Research purpose) The research aims to substantiate the thickness of narrowing partitions in the vertical deep aspirating channel. (Materials and methods) A prototype of a vertical deep aspirating channel with three sections of varying height, was used for cleaning soybean seeds. The optimal thickness of the narrowing partitions in the channel has been justified. Impurity extraction completeness and seed separation efficiency within a vertical aspirating channel were assessed for soybean seed cleaning under maximum specific grain load conditions. (Results and discussion) The following parameters have been determined: the optimal thickness for the narrowing partitions is 70 millimeters under a maximum specific grain load of 5 kilograms per square centimeter per hour. Seed losses do not exceed 3 percent in the aspirating channel with narrowing partitions, with impurity extraction completeness of 74 percent for the «Waste» fraction. The efficiency of the separation process stands at 71 percent, and the purity level of the «Seeds» fraction reaches 81 percent in a single pass during the preliminary cleaning stage. (Conclusions) It has been established that the use of narrowing partitions in a vertical aspirating channel during soybean seed cleaning leads to an increase in the specific grain load up to 5 kilograms per square centimeter per hour, compared to 2 kilograms per square centimeter per hour achieved by traditional pneumatic separation channels. The proposed technical solution reduces soybean seed losses to 3 percent (compared to the initial requirements of no more than 10 percent) in a single pass and reduces machine power consumption from 4.5 to 2.25 kilowatt-hours.

On Content-Aware Post-Processing: Adapting Statistically Learned Models to Dynamic Content

Learning-based post-processing methods generally produce neural models that are statistically optimal on their training datasets. These models, however, neglect intrinsic variations of local video content and may fail to process unseen content. To address this issue, this article proposes a content-aware approach for the post-processing of compressed videos. We develop a backbone network, calledBackboneFormer, where a Fast Transformer using Separable Self-Attention, Spatial Attention, and Channel Attention is devised to support underlying feature embedding and aggregation. Furthermore, we introduce Meta-learning to strengthen BackboneFormer for better performance. Specifically, we propose Meta Post-Processing (Meta-PP) which leverages the Meta-learning framework to drive BackboneFormer to capture and analyze input video variations for spontaneous updating. Since the original frame is unavailable to the decoder, we devise a Compression Degradation Estimation model where a low-complexity neural model and classic operators are used collaboratively to estimate the compression distortion. The estimated distortion is then utilized to guide the BackboneFormer model for dynamic updating of weighting parameters. Experimental results demonstrate that the proposed BackboneFormer itself gains about 3.61% Bjøntegaard delta bit-rate reduction over Versatile Video Coding in the post-processing task and “BackboneFormer + Meta-PP” attains 4.32%, costing only 50K and 61K parameters, respectively. The computational complexity of MACs is 49k/pixel and 50k/pixel, which represents only about 16% of state-of-the-art methods having similar coding gains.

Unexpected dual-functional cyanine fluorophores: NIR multifunctional fluorescent probes for simultaneous monitoring of mitochondrial cysteine /viscosity during kidney ferroptosis in vivo

Cysteine (Cys) level and mitochondrial viscosity are important factors controlling cellular lipid peroxide metabolism and are closely related to ferroptosis. However, simultaneous tracking of these two key target analytes in the context of ferroptosis has not been realized. In this study, we developed a series of novel NIR dual-functional cyanine fluorophores AR-Cy based on a modified Vilsmeier-Haack reaction for simultaneous visualizing of cysteine level and mitochondrial viscosity during kidney ferroptosis in vivo. Intriguingly, this modified Vilsmeier-Haack reaction provides additional electron-withdrawing molecular rotor for improving the sensing performance to Cys and mitochondrial viscosity at two separated fluorescence channels (λem = 650 nm, Cys; λem = 710 nm, viscosity). Notably, by dual-color fluorescent imaging with this excellent probe AR-Cy-3, we found that ferroptosis process (erastin, sorafenib and sulfasalazine as ferroptosis inducers) was accompanied by a slight decrease in Cys channel and a significant increase in mitochondrial viscosity channel for the first time. More importantly, we further revealed that Cys level gradually decreased and mitochondrial viscosity rapidly increased in mouse kidney ferroptosis model in vivo. Therefore, this work provides not only the first dual-functional probe for studying the dynamic changes between the Cys level and mitochondrial viscosity in kidney ferroptosis but also useful cyanine fluorophores for designing powerful probes of relevant analytes to other diseases.

Adenine-based metal–organic framework with 1 D narrow channel for molecular-sieving separation of n-butane and isobutane

Molecular-sieving separation of isomeric C4 paraffins, n-butane (n-C4H10) and isobutane (iso-C4H10), is highly desired but challenging because of their very close molecular sizes and physical properties. However, most of the MOF adsorbents often undergo framework flexibility or ligand rotation or swing, leading to the variation of pore size and the loss of the molecular-sieving effect. In this work, an adenine-based MOF with a suitable window size and rigid narrow 1D channel, namely IPM-101, was selected for n-C4H10/iso-C4H10 separation. Adsorption experiments demonstrate that IPM-101 can sensitively adsorb n-C4H10 in the low-pressure region (0–0.05 bar) and reach a saturation state at 0.1 bar while iso-C4H10 is excluded by the size-exclusion effect. Owing to the high porosity, IPM-101 exhibits a high n-C4H10 adsorption capacity (51.6 cm3 g−1) at 1 bar and 298 K. Density functional theory (DFT) calculations clearly reveal the molecular-sieving mechanism that n-C4H10 molecule can diffuse into the pore channel of IPM-101 easily but the diffusion of iso-C4H10 in IPM-101 is kinetically forbidden for its high diffusion energy barrier. The breakthrough experiments show that n-C4H10 and iso-C4H10 can be efficiently separated and iso-C4H10 with a purity of up to 99.9 % can be directly collected. The regeneration experiments show that IPM-101 has good cycling stability for n-C4H10 adsorption and n-C4H10/iso-C4H10 separation. Therefore, the high separation efficiency, excellent regeneration ability, and low cost indicate that IPM-101 has great application potential for practical n-C4H10/ iso-C4H10 separation in industry.

Enhancing signal quality in dense wavelength division multiplexed systems by eliminating crosstalk with cascaded optical bandpass filters

Non-orthogonal wavelength division multiplexing (WDM) channels are crucial in achieving significantly higher capacity and spectral efficiency than conventional schemes. Additionally, conventional schemes face challenges in electrical processing of wide-bandwidth signals. To suppress crosstalk in non-orthogonal WDM channels, the use of cascaded bandpass filters with suitable transmissivity and bandwidth is investigated for effective channel separation of large-capacity and multiplexed optical signals. This study employs the bandwidth ratio as a parameter, which is defined as the ratio of the channel spacing to the signal bandwidth, to quantify the extent of signal overlapping, and uses optical bandpass filters to filter non-orthogonal signals with a bandwidth ratio ranging from 1.0 to 0.75. The non-overlapping portion is set as the transmission bandwidth of the filter, and the crosstalk is maximally reduced with two-stage filters using Nyquist, super Gaussian, and Butterworth shaped filters. According to the analysis, the combination of Gaussian N = 1 and Gaussian N = 5 exhibits the lowest error vector magnitude (EVM) performance within a bandwidth ratio of 0.8 to 1.0. Simulations showed that a two-stage OBPF with a combination of Gaussian N = 1 and Gaussian N = 5 provides the best EVM performance at a bandwidth ratio between 0.85 to 1.0 within the combination of filter shapes and their orders we used. Additionally, the study includes an analytical investigation of the impact of amplified-spontaneous-emission noise associated with the Erbium-doped fiber amplifier (EDFA) and frequency resolution tolerance of the LCOS filter. The results demonstrate that cascaded EDFAs can be achieved down to OSNR of 10 dB at a minimum resolution of 4 GHz. Finally, the optimal filter shape is analyzed for different bandwidth ratios. The investigation shows that the optimal filter shape is independent of the function used and remains consistent across all bandwidth ratios. The tolerance of the filter is primarily affected by the −0.5 dB transmittance bandwidth between subchannels, which varies depending on the bandwidth ratio. Furthermore, a high tolerance is observed in the −20 dB transmittance bandwidth.

The Effect of Plasma Activation of Reactive Gas in Reactive Magnetron Sputtering

The effect of plasma activation of reactive gas on the process of reactive magnetron synthesis of oxide coatings was theoretically and experimentally investigated using a radio-frequency inductively coupled plasma source, which creates a flow of activated reactive gas directed towards the surface on which the oxide coating is deposited. The reactive gas passes through a dense inductively coupled plasma located inside the plasma source, while argon is supplied through a separate channel near the magnetron. A theoretical model has been built allowing the calculation of spatial distributions of fluxes of metal atoms and molecules of activated reaction gas, as well as the stoichiometry area of the synthesized coatings. Calculations were performed on the example of aluminum oxide. It was found that the plasma activation of the reactive gas allows to increase the sticking coefficient of oxygen to the surface of the growing coating from values less than 0.1 for non-activated molecular oxygen to 0.9 when 500 W of RF power is introduced into the inductive discharge. In order to verify the developed model, experiments were conducted on depositing an aluminum oxide film on glass substrates located at different distances from the magnetron target, followed by measuring the distribution of film transparency along the substrate length and comparing it with the calculated distribution. A comparison of the calculation results with the experimental data shows a good agreement in the entire studied range of parameters. Based on the generalization of the obtained results, an empirical rule was formulated that the power ratio of the magnetron discharge and the plasma activator should be approximately 8:1.

Earth-abundant insulator hydroxyapatite-based composite for full-spectrum photocatalytic degradation of 2, 4- dichlorophenol

Insulator hydroxyapatite (HAp) was chosen as a candidate to construct full-spectrum photocatalyst. Glucose as a functional precursor was incorporated into HAp by coprecipitated method, and the glucose-modified HAp was then calcined under nitrogen atmosphere. With the loss of OH- group in HAp and the decomposition of glucose during the calcination, oxygen vacancies (OVs) for regulating the band gap, graphitic carbon (GC) as a good electron acceptor, and a channel for rapid carrier separation via the C-O-Ca forming between OV-HAp and GC can be simultaneously achieved. The as-prepared OV-HAp/GC displayed full-spectrum response and rapid separation of carriers. Moreover, it showed high degradation performance for 2, 4-dichlorophenol (2, 4-DCP), phenol, and tetracycline under visible, NIR, and full-spectrum. This strategy is not only facile, but also exhibits a certain universality. This work opens a new window for full-spectrum photocatalysts construction based on insulators, and large-scale production for practical use can be expected.

Double stranded antiferromagnetic helix as an efficient spin filter

We report a large degree of spin filtration in a double stranded (ds) antiferromagnetic helix (AFH) system. Generally spin channel separation is not possible when a magnetic system possesses a vanishing net magnetization. But we show that a highly polarized spin current can be obtained through the ds AFH when it is subjected to a transverse electric field. Describing the physical system within a tight-binding framework, spin-dependent transport phenomena are studied using the well known Green’s function formalism. The effects of chirality (left-handed and right-handed), electric field, electronic hopping (short-range and long-range) in each strand, system temperature, and size of the helix on spin filtration are critically investigated. Two different configurations of magnetic moments in the helix are taken into account, for a more general description. Suitably adjusting the physical parameters, almost cent percent spin polarization can be substantiated and that feature persists even for a broad parameter range. Our analysis may open up a new direction for achieving spin-selective electron transmission and designing of controlled spintronic devices using similar kinds of fascinating helical magnetic systems.

Deep learning denoising by dimension reduction: Application to the ORION-B line cubes

Context. The availability of large bandwidth receivers for millimeter radio telescopes allows for the acquisition of position-position-frequency data cubes over a wide field of view and a broad frequency coverage. These cubes contain a lot of information on the physical, chemical, and kinematical properties of the emitting gas. However, their large size coupled with an inhomogenous signal-to-noise ratio (S/N) are major challenges for consistent analysis and interpretation. Aims. We searched for a denoising method of the low S/N regions of the studied data cubes that would allow the low S/N emission to be recovered without distorting the signals with a high S/N. Methods. We performed an in-depth data analysis of the 13CO and C17O (1–0) data cubes obtained as part of the ORION-B large program performed at the IRAM 30 m telescope. We analyzed the statistical properties of the noise and the evolution of the correlation of the signal in a given frequency channel with that of the adjacent channels. This has allowed us to propose significant improvements of typical autoassociative neural networks, often used to denoise hyperspectral Earth remote sensing data. Applying this method to the 13CO (1–0) cube, we were able to compare the denoised data with those derived with the multiple Gaussian fitting algorithm ROHSA, considered as the state-of-the-art procedure for data line cubes. Results. The nature of astronomical spectral data cubes is distinct from that of the hyperspectral data usually studied in the Earth remote sensing literature because the observed intensities become statistically independent beyond a short channel separation. This lack of redundancy in data has led us to adapt the method, notably by taking into account the sparsity of the signal along the spectral axis. The application of the proposed algorithm leads to an increase in the S/N in voxels with a weak signal, while preserving the spectral shape of the data in high S/N voxels. Conclusions. The proposed algorithm that combines a detailed analysis of the noise statistics with an innovative autoencoder architecture is a promising path to denoise radio-astronomy line data cubes. In the future, exploring whether a better use of the spatial correlations of the noise may further improve the denoising performances seems to be a promising avenue. In addition, dealing with the multiplicative noise associated with the calibration uncertainty at high S/N would also be beneficial for such large data cubes.

Experimental and computational investigation on synergistic enhancement spray cooling using micropillars and capillary-driven wicking hybrid structures

Spray cooling, which has a fast thermal response and low flow rate consumption, is a common and effective thermal management approach for high power electronic systems. Typically, to improve the heat transfer coefficient (HTC) for spray cooling, the target surface wettability is decreased, promoting nucleation boiling by reducing the surface energy barrier for bubble nucleation. However, the merging of bubbles and the formation of a vapor film have limitations in further increasing the critical heat flux (CHF). Hence, maximizing both the HTC and CHF of spray cooling can be mutually exclusive on the same heated surface. This paper presented a novel design for a vapor-liquid separation structure surface. It consisted of lower micropillars that serve as the vapor separation channel. On top of that, there was an upper multi-layer copper micromesh that wicks and spreads the coolant. Additionally, nano-grass attached to the micromesh to enhance capillary force and increase the nucleation sites simultaneously. Subsequently, we calculated the forward velocity and pressure drop of the droplets passing through the copper mesh to study the effects of droplet velocity and capillary force on heat transfer performance. The results show that the forward velocity of the droplets decreases rapidly as the increase of copper mesh layers and it drops to zero when passing through the third mesh. Therefore, the capillary force generated by the copper mesh is another important factor for the atomized droplets to pass through the copper mesh and reach the target surface. We have proven that all the vapor-liquid separation structure surfaces satisfy the condition ΔPcap>ΔPpore+ΔPlocal. Hence, the synergistic effects of the micropillar, copper micromesh, and nano-grass enable a circulation process of wicking-rewetting-vapor evacuation, which improves the onset of nucleate boiling (ONB), enhances the HTC, and increases the maximum heat flux dissipated by the system. Enhanced HTC (7.94 W/cm2/K) and maximum heat flux (817 W/cm2) were achieved at 1.50 ml/s on the vapor-liquid separation structure surfaces (#200 2-layer), representing an enhancement of 79.6% and 80.0% compared with that for the flat surface and the temperature of the heated surface at the ONB maximum decreased by approximately 30.8 °C.

In vivo optical trapping of erythrocytes in mouse liver imaged with oblique back-illumination microscopy

Optical tweezers are ideal tools for cell manipulation in vivo due to their non-contact trapping ability. In the current studies, the optical trapping of cells can only be achieved in light-permeable organs. It is important to expand the application of optical tweezers to opaque tissues and organs, where biological activities are the primary focus of biomedical research. However, the optical manipulation of cells in these opaque organs cannot be imaged using a conventional transillumination microscope due to the opacity of these organs. Here, we use optical tweezers to trap erythrocytes and measure the cell deformability in mouse liver, which are imaged with oblique back-illumination microscopy (OBM). In the microscope system, two fibers are fixed at the same oblique angle on both sides of the microscopic objective, illuminating the trapping target asymmetrically. The dual-wavelength OBM strategy allows for obtaining a differential phase contrast image in a single-shot by color channel separation. The OBM can image the flowing and trapped erythrocytes in vivo in real-time. Furthermore, the erythrocyte deformability in vivo is evaluated with optical tweezers. The spring stiffness in vivo is 8.2 ± 2.1 μN m−1, which is obtained by stretching the trapped cells with blood drag flow. Our works make it possible to utilize optical tweezers to study the live cell dynamics in opaque organs, which will expand the application of optical tweezers in the fields of biomechanical studies.

A robust indium-organic framework with open tubular channels for efficient separation of acetylene

A robust indium-organic framework with open tubular channels for efficient separation of acetylene

Long-Range Charge Separation Enabled by Intramoiety Delocalized Excitations in Copolymer Donors in Organic Photovoltaic Blends.

For over two decades, most high-performance organic photovoltaics (OPVs) have been made with donor:acceptor bulk heterojunctions with domain sizes limited by exciton diffusion, where charge separation mostly takes place through the dissociation of the interfacial charge-transfer (xCT) excitons. Recently, nonfullerene acceptor (NFA)-based OPVs have shown excellent compatibility to device structures with large domains in active layers. However, it remains elusive how the excitations that are distant from the interfaces are converted into free charges. Here, we report the identification of a new charge separation channel in model copolymer/NFA blends mediated by intra-moiety delocalized excitations in both planar heterojunctions and donor-enriched bulk heterojunctions. The delocalized excitations induced by interchromophore electronic interactions in copolymer donors mediate the long-range charge separation and dissociate into free charges without forming the bound xCT states first, releasing the constraints associated with the short exciton diffusion length in organic materials. The long-range charge separation mechanism uncovered in this work, in cooperation with the short-range xCT-mediated pathway, holds the potential to further optimize OPVs with diverse device structures.

Constructing nanoparticle-assembled CdS microspheres on a FeVO4 nanopolyhedrons photoanode for enhanced photoelectrochemical performance

Improving the light energy utilization to augment the charge carrier concentration and modulating the band alignment to facilitate charge carrier transport and separation are essential for semiconductor photoanode to achieve high-efficiently photoelectrochemical (PEC) performance. Herein, a novel FeVO4 nanopolyhedrons photoanode modified by nanoparticle-assembled CdS microspheres is constructed through an in-situ solid-state transformation and a chemical bath deposition, successively, to augment the concentration of carriers by improving light utilization and facilitate efficient transport and separation of carriers by building type-II structure for efficient PEC performance. The constructed nanoparticle-assembled CdS microspheres modified FeVO4 nanopolyhedrons photoanode generates a drastic improvement in photocurrent, which is 29 times higher than that of pristine FeVO4 nanopolyhedrons photoanode at 0.4 V vs. Ag/AgCl under AM 1.5 G simulated solar light irradiation. The experimental measurements of light absorption evidence that the modification of nanoparticle-assembled CdS microspheres substantially improves light harvesting ability of FeVO4 nanopolyhedrons from 300 to 800 nm for substantially generating charge carriers. Spectral measurements of X-ray photoelectron spectroscopy evidence that a band alignment of type-II structure is established at FeVO4/CdS interface, building directional interface charge transport channel for efficient transfer and separation of photoinduced charge carriers. This study offers a referable strategy for designing photoanodes to achieve PEC performance from the perspective of light energy utilization and interface energetics engineering.

International linkages of term structures: US and Korea Treasury bond yields

This study analyzes the international linkages of term structures between the United States (US) and Korea using a Gaussian dynamic term structure model. The empirical analysis shows that the US level factor makes the most important contribution to the Korean term structure fluctuations. When two separate channels (i.e., policy and risk-compensation) are considered for propagating structural shocks into Korean bond yields, the policy channel dominates for the short-term rates, whereas for the long-term yield, the policy channel is dominant for the US level shock, but the risk channel is dominant for other shocks. These results are sensitive to whether or not small-sample bias is corrected. With a help of the bias correction, term premium estimates in the US and Korea exhibit substantial countercyclicality with respect to the US output gap. The US slope factor, which also has a significant impact on Korean long-term yields, is closely related to the global liquidity conditions for Korean bond returns.

Wireless Image Transmission With Semantic and Security Awareness

Semantic communication is an increasingly popular framework for wireless image transmission due to its high communication efficiency. With the aid of the joint-source-and-channel (JSC) encoder implemented by neural network, semantic communication directly maps original images into symbol sequences containing semantic information. Compared with the traditional separate source and channel coding design used in bit-level communication systems, semantic communication systems are known to be more efficient and accurate especially in the low signal-to-the-noise ratio (SNR) regime. This thus prompts a critical while yet to be tackled issue of security in semantic communication: it makes the eavesdropper much easier to crack the semantic information as it can be retrieved even in a highly noisy channel. In this letter, we develop a semantic communication framework that accounts for both semantic meaning decoding efficiency and its risk of privacy leakage. To this end, targeting wireless image transmission, we propose an JSC autoencoder featuring residual structure for efficient semantic meaning extraction and transmission, and the training of which is guided by a well-designed loss function that can flexibly regulate the efficiency-privacy trade-off. Extensive experimental results are provided to show the effectiveness and robustness of the proposed scheme.

Synthesis and characterization of liposomes encapsulating silver nanoprisms obtained by millifluidic-based production for drug delivery

Silver nanoprisms (SNPs) have attracted significant attention due to their surface plasmon resonance behaviour, which is strongly dependent on their size and shape. The enhanced light absorption and scattering capacity of SNPs, make them a promising candidate system for non-invasive imaging and drug delivery in nanoparticle-assisted diagnostics and therapy. However, systemic administration of silver nanoparticles (AgNPs) at high concentrations may result in toxic side-effects, arising from non-targeted bio-distribution. These drawbacks could be mitigated by employing liposomes as carriers for AgNPs. However, there is a lack of systematic studies on production and subsequent physico-chemical characterisation of liposomal systems encapsulating SNPs. The present study therefore investigated the synthesis of liposomes encapsulating SNPs (Lipo/SNPs) using a continuous-flow millimetre-scale reactor, whereby liposome formation was governed by a solvent exchange mechanism. An aqueous phase and an ethanolic lipid phase were conveyed through two separate inlet channels, and subsequently travelled through a serpentine-shaped channel where mixing between the two phases took place. The synthesis process was optimised by varying both liposome formulation and the operating fluidic parameters, including the ratio between inlet flow rates (or flow rate ratio) and the total flow rate. The obtained Lipo/SNPs were characterised for their size and electrostatic charge, using a dynamic light scattering apparatus. Liposome morphology and encapsulation efficiency of SNPs within liposomes were determined by transmission electron microscopy (TEM) imaging. The synthesised negatively charged Lipo/SNP samples were found to have an average size of ∼150 nm (size dispersity < 0.3). The AgNPs encapsulation efficiency was equal to 77.48%, with mostly single SNPs encapsulated in liposomes. By using a multiangle TEM imaging approach, quasi-3D images were obtained, further confirming the encapsulation of nanoparticles within liposomes. Overall, the formulation and production technique developed in the present study has potential to contribute towards mitigating challenges associated with AgNP-mediated drug delivery and diagnostics.

High-performance microchip electrophoresis separations of preterm birth biomarkers using 3D printed microfluidic devices

We employed digital light processing-stereolithography 3D printing to create microfluidic devices with different designs for microchip electrophoresis (µCE). Short or long straight channel, and two- or four-turn serpentine channel microfluidic devices with separation channel lengths of 1.3, 3.1, 3.0, and 4.7 cm, respectively, all with a cross injector design, were fabricated. We measured current as a function of time and voltage to determine a separation time window and conditions for the onset of Joule heating in these designs. Separations in these devices were evaluated by performing µCE and measuring theoretical plate counts for electric field strengths near and above the onset of Joule heating, with fluorescently labeled glycine and phenylalanine as model analytes. We further demonstrated µCE of peptides and proteins related to preterm birth risk, showing increased peak capacity and resolution compared to previous results with 3D printed microdevices. These results mark an important step forward in the use of 3D printed microfluidic devices for rapid bioanalysis by µCE.

A kinetic Monte Carlo study of positive streamer interaction with complex dielectric surfaces

We present a computational study of positive streamers in air propagating over dielectric plates with square channels running orthogonal to the propagation direction. The study uses a newly developed non-kinetic Particle-In-Cell model based on Îto diffusion and kinetic Monte Carlo, which does not introduce artificial smoothing of the plasma density or photo-electron distributions. These capabilities permit the computational study to use high-resolution grids with large time steps, and also incorporates geometric shielding for particle and photon transport processes. We perform Cartesian 2D simulations for channel dimensions ranging from 250 µm to 2 mm, and track streamers over a distance of 4 cm and times ranging up to 300 ns, for various voltages ranging from 15 kV to 30 kV. These baseline simulations are supplemented by additional studies on the effects of transparency to ionizing radiation, streamer reignition, dielectric permittivity, and 3D effects. The computer simulations show: 1) Larger channels restrict streamer propagation more efficiently than narrow channels, and can lead to arrested surface streamers. 2) Geometric shielding of ionizing radiation substantially reduces the number of starting electrons in neighboring channels, and thus also reduces the onset point of streamer reignition. 3) Decreasing the streamer channel separation leads to slower streamers. 4) Increasing the dielectric permittivity increases the discharge velocity. The results are of generic value to fields of research involving streamer-dielectric interactions, and in particular for high-voltage technology where streamer termination is desirable.