Spatial network conduction in carbon nanotube and Ag-Ag₂S-Ag atomic switch network device platforms

<p>Networks of nanomaterials sit at a confluence of desirable features for the fabrication of advanced electronic devices, including facile fabrication, high conducting element density, and novel electrical characteristics. The spatial conduction through carbon nanotube (CNT) and Ag-Ag₂S-Ag atomic switch networks was investigated to determine how better to implement them in novel sensing and computation device platforms. Selective gating of localized regions of CNT networks with varying densities was investigated. To achieve this, lithographically defined FET structures were developed that allowed gating of localised regions of the CNT FET network area. The CNT FET device sensitivity to gating of different regions of the CNT network was measured for devices with network densities close to the percolation threshold. A 10² increase in sensitivity to local gating for CNT FET devices with low network densities was observed compared with high-density CNT networks. Networks densities were all well below a density where metallic shorts could be present, so the trends observed were attributed to m-s junction dominated gating of the network. A better understanding of the dominant conduction in CNT network FETs at low network densities is important for tuning their properties for use as novel biosensing platforms or a tunable connectivity conducting film. A CNT network simulation was developed to test the effects of local gating on networks of bundled CNTs with varying densities. Up to 70,000 bundles on a 60 µm x 60 µm simulated network area were used to generate an electrical network of field sensitive elements where the gate field could be spatially modified to investigate the effect of local gating. Monte Carlo methods were used to simulate large numbers of random networks with m-s junctions as the dominant gate-dependent element. Networks with 13.5% metallic bundles were shown to exhibit trends in local gating similar to the experimental systems. Current density maps showed key conduction paths in low-density devices, which supports a model of m-s junction dominance to explain the local and global gate responses measured in experimental CNT FET systems. Prototype Ag-Ag₂S-Ag atomic switch networks (ASN) device were fabricated using spray-coated silver nanowires which were sulfurised using gas-phase sulfur after deposition. Electrical formation of memristive junctions and hysteretic switching curves were shown under swept voltage bias demonstrating memristive behaviour. ASN devices have been demonstrated to show critical dynamics and memristive characteristics due to the complex connection of atomic switches formed at Ag-Ag₂S-Ag junctions between wires. A fabrication and measurement protocol for ASN based neuromorphic devices on multi-electrode array (MEA) platforms was developed. The electrical measurement system was designed and deployed to facilitate time-resolved measurement across multiple channels simultaneously on those MEA platforms. Under DC bias, MEA-based ASN devices showed switching events with a power-law distribution over two orders of magnitude of conductance changes and time intervals consistent with self-organized criticality within the network. The dynamic response of the critical system was measured across the network area. Changes in the relative voltage across the ASN network area were observed using 16 channel MEA platforms, showing spatiotemporal variation in voltage across the network. Novel application of principal component analysis to ASNswas used to demonstrate reduction of dimension while preserving relative voltage changes. This paves the way for scalable analysis of the complex dynamic signals from critical ASN systems.</p>

Spatial network conduction in carbon nanotube and Ag-Ag₂S-Ag atomic switch network device platforms

<p>Networks of nanomaterials sit at a confluence of desirable features for the fabrication of advanced electronic devices, including facile fabrication, high conducting element density, and novel electrical characteristics. The spatial conduction through carbon nanotube (CNT) and Ag-Ag₂S-Ag atomic switch networks was investigated to determine how better to implement them in novel sensing and computation device platforms. Selective gating of localized regions of CNT networks with varying densities was investigated. To achieve this, lithographically defined FET structures were developed that allowed gating of localised regions of the CNT FET network area. The CNT FET device sensitivity to gating of different regions of the CNT network was measured for devices with network densities close to the percolation threshold. A 10² increase in sensitivity to local gating for CNT FET devices with low network densities was observed compared with high-density CNT networks. Networks densities were all well below a density where metallic shorts could be present, so the trends observed were attributed to m-s junction dominated gating of the network. A better understanding of the dominant conduction in CNT network FETs at low network densities is important for tuning their properties for use as novel biosensing platforms or a tunable connectivity conducting film. A CNT network simulation was developed to test the effects of local gating on networks of bundled CNTs with varying densities. Up to 70,000 bundles on a 60 µm x 60 µm simulated network area were used to generate an electrical network of field sensitive elements where the gate field could be spatially modified to investigate the effect of local gating. Monte Carlo methods were used to simulate large numbers of random networks with m-s junctions as the dominant gate-dependent element. Networks with 13.5% metallic bundles were shown to exhibit trends in local gating similar to the experimental systems. Current density maps showed key conduction paths in low-density devices, which supports a model of m-s junction dominance to explain the local and global gate responses measured in experimental CNT FET systems. Prototype Ag-Ag₂S-Ag atomic switch networks (ASN) device were fabricated using spray-coated silver nanowires which were sulfurised using gas-phase sulfur after deposition. Electrical formation of memristive junctions and hysteretic switching curves were shown under swept voltage bias demonstrating memristive behaviour. ASN devices have been demonstrated to show critical dynamics and memristive characteristics due to the complex connection of atomic switches formed at Ag-Ag₂S-Ag junctions between wires. A fabrication and measurement protocol for ASN based neuromorphic devices on multi-electrode array (MEA) platforms was developed. The electrical measurement system was designed and deployed to facilitate time-resolved measurement across multiple channels simultaneously on those MEA platforms. Under DC bias, MEA-based ASN devices showed switching events with a power-law distribution over two orders of magnitude of conductance changes and time intervals consistent with self-organized criticality within the network. The dynamic response of the critical system was measured across the network area. Changes in the relative voltage across the ASN network area were observed using 16 channel MEA platforms, showing spatiotemporal variation in voltage across the network. Novel application of principal component analysis to ASNswas used to demonstrate reduction of dimension while preserving relative voltage changes. This paves the way for scalable analysis of the complex dynamic signals from critical ASN systems.</p>

Evaluation of River Ecological Status in Plain River Network Area under the Background of Urbanization

21 main streams and tributaries of typical rivers in Jiangsu Province were taken as the research objects to evaluate river ecological status under the background of urbanization in this paper. A system of river ecological evaluation indexes and the evaluation model for plain river network area were constructed, including 4 indexes of aquatic environment, natural ecological system, social service function and water management and protection, and 12 pieces of divided criteria. The ecological status of these rivers in Jiangsu Province was evaluated, of which 71.4% were good. Analyzing the impact of urbanization on the ecological condition of rivers, we came to the conclusion that the level of river ecological status is decreasing with the improvement of urbanization level, and put forward that the reference value of the ISC red line of river ecological condition from good to medium in the urbanization plan of ecological river construction is 28%.

Detection and quantification of SARS-CoV-2 RNA in wastewater influent in relation to reported COVID-19 incidence in Finland

Wastewater-based surveillance is a cost-effective concept for monitoring COVID-19 pandemics at a population level. Here, SARS-CoV-2 RNA was monitored from a total of 693 wastewater (WW) influent samples from 28 wastewater treatment plants (WWTP, N = 21–42 samples per WWTP) in Finland from August 2020 to May 2021, covering WW of ca. 3.3 million inhabitants (∼ 60% of the Finnish population). The relative quantity of SARS-CoV-2 RNA fragments in the 24h-composite samples was determined by using the ultrafiltration method followed by nucleic acid extraction and RT-qPCR assay targeted with N2-assay. SARS-CoV-2 RNA signals at each WWTP were compared over time to the numbers of new and confirmed COVID-19 cases in the sewer network area.Over the 10-month surveillance period, the detection rate of SARS-CoV-2 RNA in WW was 79% (including 6% uncertain results), while only 24% of all samples exhibited gene copy (GC) numbers above the quantification limit. The range of the SARS-CoV-2 detection rate in WW varied from 33% (including 10% uncertain results) in Pietarsaari to 100% in Espoo. Only six out of 693 WW samples were positive with SARS-COV-2 RNA when the reported COVID-19 case number from the preceding 14 days was zero. Overall, the 14-day COVID-19 incidence was 7, 18 and 36 cases within the sewer network area when the probability to detect SARS-CoV-2 RNA in wastewater samples was 50%, 75% and 95%, respectively. The quantification of SARS-CoV-2 GC required significantly more COVID-19 cases: the quantification rate was 50%, 75% and 95% when the 14-day incidence was 110, 152 and 223 COVID-19 cases, respectively, per 100 000 persons. Multiple linear regression confirmed the relationship between the COVID-19 incidence and the SARS-CoV-2 GC quantified in WW at 15 out of 28 WWTPs (overall R2 = 0.36, p < 0.001). At four of the 13 WWTPs where a significant relationship was not found, the GC of SARS-CoV-2 RNA remained below the quantification limit during the whole study period. In the five other WWTPs, the sewer coverage was less than 80% of the total population in the area and thus the COVID-19 cases may have been inhabitants from the areas not covered.Based on the results obtained, WW-based surveillance of SARS-CoV-2 could be used as an indicator for local and national COVID-19 incidence trends. Importantly, the determination of SARS-CoV-2 RNA fragments from WW is a powerful and non-invasive public health surveillance measure, independent of possible changes in the clinical testing strategies or in the willingness of individuals to be tested for COVID-19.

Environmental toxicants evaluation in a modern monitoring system - Romanian monitox network area

In this paper a class consisting of 8 environmental toxicants were selected to assess Danube River water quality between Calarasi-Silistra sector until the river flow into the Black Sea, the Romanian Monitox Network Area. A comprehnsive comparison between 2 years of investigations in terms of nutrients contribution, such as different forms of nitrogen (ammonium nitrogen (N-NH4+), nitrite nitrogen (N-NO2-), nitrate nitrogen (N-NO3-), organic nitrogen, total nitrogen (TN)) and phosphorus (orthophosphate phosphorus (P-PO4 -3), total phosphorus (TP)), was made in order to provide information on the spatial and temporal variations of this river water quality. Sampling was performed according to European standards and quantitatively analysed using molecular spectrophotometry using UV VIS spectrophotometer Perkin Elmer Lambda 650S. The obtained results showed differences in nitrite nitrogen loads in surface water samples with higher values in the samples collected from the sampling points situated at the mouths of the Danube River into the Black Sea in 2020. Regarding quality classes, the surface waters were generally framed, in good quality class. The nutrients concentrations, combined in CCME WQI index, give an overview on surface water quality assessement in Romanian Monitox Network Area, with a good quality of Lower Danube (Constanta in 2019 and 2020) and fair quality of Danube Delta in 2020, but very closed to good quality.

Analisis Efesiensi Daya Penerangan Jalan Umum Tenaga Surya di Kecamatan Pulau Ternate

Solar Street Lighting a street lighting solution for areas or areas that are not within the PLN network area or for lighting efficiency using solar power. The use of public street lighting, although it has several advantages, there are still disadvantages in the field conditions, including the improper placement of the lighting so that it is blocked from sunlight, the use of inappropriate materials, unsuitable height of poles and lack of maintenance which results in not optimal utilization of solar energy. In this study, an analysis of the power efficiency of solar street lighting in the District of Ternate Island will be carried out by conducting direct observations and measurements in the field. The results showed that the maximum voltage for street lamps that were not blocked by trees was 23 volts, while those that were blocked by trees were 19 volts. The lighting strength of the street lights that are blocked by trees is 9 lux, while those that are not blocked by trees are 10 lux. The amount of input voltage for the solar panels affects the strength of the lamp lighting

Species-area and network-area relationships in host–helminth interactions

The scaling relationship observed between species richness and the geographical area sampled (i.e. the species-area relationship (SAR)) is a widely recognized macroecological relationship. Recently, this theory has been extended to trophic interactions, suggesting that geographical area may influence the structure of species interaction networks (i.e. network-area relationships (NARs)). Here, we use a global dataset of host–helminth parasite interactions to test existing predictions from macroecological theory. Scaling between single locations to the global host–helminth network by sequentially adding networks together, we find support that geographical area influences species richness and the number of species interactions in host–helminth networks. However, species-area slopes were larger for host species relative to their helminth parasites, counter to theoretical predictions. Lastly, host–helminth network modularity—capturing the tendency of the network to form into separate subcommunities—decreased with increasing area, also counter to theoretical predictions. Reconciling this disconnect between existing theory and observed SAR and NAR will provide insight into the spatial structuring of ecological networks, and help to refine theory to highlight the effects of network type, species distributional overlap, and the specificity of trophic interactions on NARs.