A metamaterial unit-cell based patch radiator for brain-machine interface technology.

This paper presents a novel approach to the design of a brain implantable antenna tailored for brain-machine interface (BMI) technology. The design is based on a U-shaped unit-cell metamaterial (MTM), introducing innovative features to enhance performance and address specific challenges associated with BMI applications. The motivation behind the use of the unit-cell structure is to elongate the electric path within the antenna patch, diverging from a reliance on the electrical properties of the MTM. Consequently, the unit cell is connected to an inset-fed transmission line and shorted to the ground. This configuration serves the dual purpose of reducing the size of the antenna and enabling resonance at the 2.442 GHz band within a seven-layer brain phantom. The antenna is designed using a FR-4 substrate (εr = 4.3 and tan Î´ = 0.025) of 1.5 mm thickness, and it is coated with a biocompatible polyamide material (εr = 4.3 and tan Î´ = 0.004) of 0.05 mm thickness. The proposed antenna achieves a compact dimension of 20 × 20 × 1.6 mm3 (0.338 × 0.338 × 0.027 λg3) and demonstrates a high bandwidth of 974 MHz with its gain of -14.6 dBi in the 2.442 GHz band. It also exhibits a matched impedance of 49.41-j1.32 Ω in the implantable condition, corresponding to a 50 Ω source impedance. In comparison to a selection of relevant research works, the proposed antenna has a low specific absorption rate (SAR) of 218 W/kg and 68 W/kg at 1g and 10g brain tissue standards, respectively. An antenna prototype has been fabricated and measured for return loss in both free space and in-vivo conditions using sheep's brain. The measurement results are found to be in close agreement with the simulation results for both conditions, showing the practical applicability of the proposed antenna for BMI applications.

Dual core photonic crystal fiber based plasmonic refractive index sensor with ultra-wide detection range.

In this study, an ultra-wide range plasmonic refractive index sensor based on dual core photonic crystal fiber is suggested and analyzed numerically. The proposed design achieves fabrication feasibility by employing external sensing mechanism in which silver is deposited onto the flat outer surface of the fiber as plasmonic material. A thin layer of titanium oxide (TiO2) is considered on top of the silver layer for preventing its oxidation problem. The sensor attains identification of a vast array of analytes consisting a wide range of refractive indices of 1.10 - 1.45. It achieves a maximum spectral sensitivity of 24300 nm/RIU along with its corresponding resolution of 4.12 × 10-6 RIU. The maximum figure of merit of the sensor is 120 RIU-1. The sensor also supports amplitude interrogation approach and exhibits a maximum amplitude sensitivity of 172 RIU-1. The impact of the design parameters such as radius of air holes, polishing distance, thickness of silver and titanium oxide layers are investigated thoroughly. An ultra-wide detection range with high sensitivity, fabrication feasibility, and easy application make the sensor a potential candidate for detection of a wide array of bio-originated materials, chemicals, and other analytes.

A convolutional attention mapping deep neural network for classification and localization of cardiomegaly on chest X-rays.

Building a reliable and precise model for disease classification and identifying abnormal sites can provide physicians assistance in their decision-making process. Deep learning based image analysis is a promising technique for enriching the decision making process, and accordingly strengthening patient care. This work presents a convolutional attention mapping deep learning model, Cardio-XAttentionNet, to classify and localize cardiomegaly effectively. We revisit the global average pooling (GAP) system and add a weighting term to develop a light and effective Attention Mapping Mechanism (AMM). The model enables the classification of cardiomegaly from chest X-rays through image-level classification and pixel-level localization only from image-level labels. We leverage some of the advanced ConvNet architectures as a backbone-model of the proposed attention mapping network to build Cardio-XAttentionNet. The proposed model is trained on ChestX-Ray14, which is a publicly accessible chest X-ray dataset. The best single model achieves an overall precision, recall, F-1 measure and area under curve (AUC) scores of 0.87, 0.85, 0.86 and 0.89, respectively, for the classification of the cardiomegaly. The results also demonstrate that the Cardio-XAttentionNet model well captures the cardiomegaly class information at image-level as well as localization at pixel-level on chest x-rays. A comparative analysis between the proposed AMM and existing GAP based models shows that the proposed model achieves a state-of-the-art performance on this dataset for cardiomegaly detection using a single model.

Remediation of Chromium (VI) from Contaminated Agricultural Soil Using Modified Biochars.

Chromium (Cr) is a potentially toxic metal occurring in the soil as a result of natural and anthropogenic activities and is mainly found in Cr3+ and Cr6+. The hexavalent chromium has toxic effects on plants, animals, humans and microorganisms depending on exposure level, duration and doses. Biochar is a stable carbon-based material that has been widely documented to immobilize metals in contaminated soils and for soil remediation effectively. The present 90 days incubation study was conducted to investigate the potential use of rice stubble and sawdust-derived modified biochars on Cr6+ remediation and their effects on nutrient availability. Among the treatments, modified rice stubble biochar (RSB-M) contained the highest surface area, pore volume and CEC. The unmodified and modified biochars significantly increased soil pH, EC, CEC, and N, K availability ((p < 0.001)). Statistical analysis showed that modified rice stubble (RSB-M) and sawdust biochars (SDB-M) significantly reduced the Cr6+ with incubation days compared to unmodified biochars, possibly due to the greater porous structure and various functional groups. The submerged incubation condition also greatly impacted Cr6+ reduction since a gradual decrease (up to ~70 mg kg-1 of Cr6+) was observed in control treatments. Therefore, applying modified biochars is imperative to alleviate Cr6+ polluted soils and improve soil fertility.

Spatial distribution and ecological risk assessment of potentially toxic metals in the Sundarbans mangrove soils of Bangladesh.

At present, there are growing concerns over the increasing release of trace metals in the Sundarbans mangrove areas in Bangladesh due to nearby shipbreaking and metallurgical industries, untreated waste discharge, navigation activities, and other natural processes that deposit trace metals into soils. The current study investigated the spatial distribution, contamination level, and ecotoxicity of eight trace metals (Fe, Mn, Cu, Zn, Pb, Cd, Cr, Ni) in Sundarbans soils. Results revealed that all the trace metals except Cr were present in higher concentrations compared to Earth's shale and/or upper continental crust. Principal component analysis and Pearson correlation showed strong positive correlations (p < 0.05) between Fe, Mn, Cu, and Zn; Ni with Mn and Cr. There were significant associations (p < 0.05) of % clay and total organic carbon (TOC) with Pb-Ni-Cr and negative correlations of pH with all the trace metals. The hierarchical cluster analysis grouped Pb, Ni, and Cd into one distinct cluster, suggesting they are derived from the same sources, possibly from anthropogenic activities. Geo accumulation index (I-geo), enrichment factor (EF), contamination factor (CF), and spatial distribution showed moderately polluted soils with Ni, Pb, and Cd (EF = 3-7.4, CF = 1-2.8, I-geo = 0-0.9) and low pollution by Zn, Cu, Fe, and Mn (EF < 3, CF < 1, I-geo < 0). The ecological risk index (RI) revealed that S-4 (RI = 114.02) and S-5 (RI = 100.04) belonged to moderate risk, and other areas posed a low risk (RI < 95). The individual contribution of Cd (25.9-73.7%), Pb (9.2-29.1%), and Ni (9.6-26.4%) to RI emphasized these metals were the foremost concern in the Sundarbans mangroves due to their long persistence time and high toxicity, even if they were present in low concentrations.

Yield improvement of Gracilaria tenuistipitata by optimizing different aspects in coast of cox's bazar, Bangladesh.

This research was designed to find out the effect of different factors such as influence of lunar cycle, harvesting interval, rope type and seeding gap on the production of G. tenuistipitata in coast of Cox's Bazar. Duration of these experiments were sixty days and all the parameters were recorded fortnightly. Monitoring of water quality parameters indicated that salinity, temperature, transparency, pH and DO were suitable for seaweed cultivation. In determining lunar cycle effect, results envisaged that fresh yield was 14.43% increased when seeding and harvesting time was selected considering the moon cycle. Regarding the selection of harvesting interval, it was found that T3 (30 days interval) was the best to harvest the seaweed whereas T4 (40 days interval) showed decreasing trend in production. Our study also found that semi floating single line showed better yield performance compared to semi floating double line system. In case of influence on seeding gap, it has been found that 20 cm gap between two seed showed the highest yields followed by 10 cm, 30 cm and 40 cm, respectively. Overall, it can be concluded that yield of G. tenuistipitata in coast of Cox's Bazar could be improved considering those factors.

Data on heavy metals content and biochar toxicity in a pristine tropical agricultural soil.

Accumulation of heavy metals results in soil degradation and impairs the normal functioning of ecosystems. Thus, monitoring of heavy metals is essential in both pristine and polluted soils. Concentrations of heavy metals were determined in a pristine tropical agricultural soil using acid digestion procedures. The soil samples were also analyzed for physico-chemical parameters and biochar toxicity to earthworms. Data shows that the soil is acidic, with low organic matter content. The level of heavy metals ranged from <0.06±0.0 to 595.8±2.8 µg g-1. However, the concentrations were found to be below the soil regulatory standards of heavy metals in agricultural soils. Furthermore, increased addition of biochar to the soil caused toxic effect on earthworms over a 90 d biochar-soil contact time. The data provides baseline information of heavy metals in pristine agricultural soils from the region, and the effect of biochar amendments on tropical soils.

Invisible transportation infrastructure technology to mitigate energy and environment.

BACKGROUND: Traditional transportation infrastructure built by heat trapping products and the transportation vehiles run by fossil fuel, both causing deadly climate change. Thus, a new technology of invisible Flying Transportation system has been proposed to mitigate energy and environmental crisis caused by traditional infrastructure system. METHODS: Underground Maglev system has been modeled to be constructed for all transportation systems to run the vehicle smoothly just over two feet over the earth surface by propulsive and impulsive force at flying stage. A wind energy modeling has also been added to meet the vehicle's energy demand when it runs on a non-maglev area. Naturally, all maglev infrastructures network to be covered by evergreen herb except pedestrian walkways to absorb CO2, ambient heat, and moisture (vapor) from the surrounding environment to make it cool. RESULTS: The research revealed that the vehicle will not require any energy since it will run by superconducting electromagnetic force while it runs on a maglev infrastructure area and directed by wind energy while it runs on non-maglev area. CONCLUSIONS: The proposed maglev transportation infrastructure technology will indeed be an innovative discovery in modern engineering science which will reduce fossil fuel energy consumption and climate change dramatically.

Efficient design of polarization insensitive polymer optical waveguide devices considering stress-induced effects.

We present an approach for the efficient design of polarization insensitive polymeric optical waveguide devices considering stress-induced effects. In this approach, the stresses induced in the waveguide during the fabrication process are estimated first using a more realistic model in the finite element analysis. Then we determine the perturbations in the material refractive indices caused by the stress-optic effect. It is observed that the stresses cause non-uniform optical anisotropy in the waveguide materials, which is then incorporated in the modal analysis considering a multilayer structure of waveguide. The approach is exploited in the design of a Bragg grating on strip waveguide. Excellent agreement between calculated and published experimental results confirms the feasibility of our approach in the accurate design of polarization insensitive polymer waveguide devices.

Study of optical anisotropies in benzocyclobutene thin films for the efficient design of optical waveguide devices.

We study the in-plane/out-of-plane anisotropies in refractive indices (n) and in thermo-optic coefficients (dn/dT) of benzocyclobutene (BCB) thin film on a substrate. Both nonoxidized and oxidized films are investigated. Aside from the stress-induced effects, oxidation has significant influence on the refractive index anisotropy. The dependence of the anisotropy on each of the thermal stress and the oxidation is determined quantitatively. The anisotropies in the dn/dT values are mainly caused by the thermal stress and are independent of oxidation. However, the original (stress-free) thermo-optic coefficients are obtained as isotropic and significantly different than the measured dn/dT values. Our findings have the potential to optimize the design of polarization insensitive and/or athermal BCB optical waveguide devices.

Simultaneous measurement of thermo-optic and stress-optic coefficients of polymer thin films using prism coupler technique.

We present a simple method for simultaneous measurement of thermo-optic and stress-optic coefficients of polymer thin films by measuring the film refractive indices as a function of temperature (dn/dT). Usually, such dn/dT value is considered as the thermo-optic coefficient. However, in the thin film systems, the measured dn/dT values result from both the thermo-optic and stress-optic effects. To demonstrate the stress-induced effects, the dn/dT values have been investigated for two different polymers: benzocyclobutene (high film stress) and epoxy 3505 (negligible film stress), using a prism coupler technique. The finite element method has been used so as to predict the stresses in the polymer film and, by combining them with the experimental dn/dT values, the individual thermo-optic and stress-optic coefficients have been determined. We found that the obtained thermo-optic coefficient is significantly different than the measured dn/dT values. The method is generic in nature and can thus be applied to a wide range of polymer waveguide materials.