ICT and environmental sustainability: A global perspective

The positive and negative environmental impacts of information and communication technologies (ICTs) are widely debated. In theory, ICT is among the sources contributing to the increasing levels of CO₂ emissions in terms of production of ICT machinery and devices, energy consumption, and recycling of electronic waste. However, ICT is also expected to reduce CO₂ emissions on a global scale by developing smarter cities, transportation systems, electrical grids, industrial processes, and energy saving gains. These two effects work in opposite direction, creating an inverted-U relationship between ICT and CO₂ emissions. The aim of this study is to investigate this non-linear relationship between ICT and CO₂ emissions on a global scale. Given that global warming is a global issue, it is necessary to look at this relationship in countries at all levels of development. To this end, we use a panel data set consisting of 142 economies, split into 116 developing and 26 developed countries, over the period 1995–2010. The results of our empirical study confirm that the relationship between ICT and CO₂ emissions is an inverted U-shaped relationship. Moreover, while for the sample of developing countries, the ICT turning point is well above the mean value, the opposite is true for the sample of developed countries. This implies that many developed countries have already attained the level of ICT development, at which CO₂ emissions decreases as the level of ICT development improves further.     

Analyzing the capacity of wireless ad hoc networks

In this paper we develop analytical closed form expression for the capacity of a wireless ad hoc network. First, for the general case when nodes can adapt their communication rates to the link quality, a proper formulation for the total network capacity is presented based on the cumulative distribution function (CDF) of the signal to interference power ratio (SIR). Then, a closed form expression for this CDF is analytically derived. This closed form is further studied by fitting it to a normal distribution. Afterwards, the capacity of the network is investigated. By examining the effect of the outage threshold, it is shown that in order to obtain a higher capacity, one may use simple non-adaptive transceivers with higher threshold on the received SIR. These results are obtained by conducting analytical and simulation studies.     

High Surface Area MoS2/Graphene Hybrid Aerogel for Ultrasensitive NO2 Detection

A MoS₂/graphene hybrid aerogel synthesized with two‐dimensional MoS₂ sheets coating a high surface area graphene aerogel scaffold is characterized and used for ultrasensitive NO₂ detection. The combination of graphene and MoS₂ leads to improved sensing properties with the graphene scaffold providing high specific surface area and high electrical and thermal conductivity and the single to few‐layer MoS₂ sheets providing high sensitivity and selectivity to NO₂. The hybrid aerogel is integrated onto a low‐power microheater platform to probe the gas sensing performance. At room temperature, the sensor exhibits an ultralow detection limit of 50 ppb NO₂. By heating the material to 200 °C, the response and recovery times to reach 90% of the final signal decrease to <1 min, while retaining the low detection limit. The MoS₂/graphene hybrid also shows good selectivity for NO₂ against H₂ and CO, especially when compared to bare graphene aerogel. The unique structure of the hybrid aerogel is responsible for the ultrasensitive, selective, and fast NO₂ sensing. The improved sensing performance of this hybrid aerogel also suggests the possibility of other 2D material combinations for further sensing applications.     

Studying Bacillus cereus's ability to biodegrade crude oil in hot areas

In this study, the biodegrading ability of three spices of Bacillus isolated from a soil, which was contaminated by crude oil, was studied. Isolated species are able to biodegrade crude oil carbohydrates by producing biosurfactants and lowering the rate of surface tension at different temperatures and pHs. The decrease of surface tension from 57 mN/m to 31 mN/m at 37°C and to 32.5 mN/m at 20°C by Bacillus cereus B1 in samples with 1% crude oil can be referred to as the results of this research.     

Enhanced compressive strength of carbon aerogels with low density and high specific surface areas

Journal of Porous Materials - Glycidol was firstly used as catalyst to synthesize resorcinol (R) and formaldehyde (F) aerogels and carbon aerogels (CAs). The density, morphology, specific surface...     

Platinum Nanoparticle Loading of Boron Nitride Aerogel and Its Use as a Novel Material for Low‐Power Catalytic Gas Sensing

A high‐surface‐area, highly crystalline boron nitride aerogel synthesized with nonhazardous reactants has been loaded with crystalline platinum nanoparticles to form a novel nanomaterial that exhibits many advantages for use in a catalytic gas sensing application. The platinum nanoparticle‐loaded boron nitride aerogel integrated onto a microheater platform allows for calorimetric propane detection. The boron nitride aerogel exhibits thermal stability up to 900 °C and supports disperse platinum nanoparticles, with no sintering observed after 24 h of high‐temperature testing. The high thermal conductivity and low density of the boron nitride aerogel result in an order of magnitude faster response and recovery times (<2 s) than reported on alumina support and allow for 10% duty cycling of the microheater with no loss in sensitivity. The resulting 1.5 mW sensor power consumption is two orders of magnitude less than commercially available catalytic gas sensors and unlocks the potential for wireless, battery‐powered catalytic gas sensing.     

Disabling of Nanoparticle Effects at Increased Temperature in Nanocomposite Solders

The use of nanoparticles to control grain size and mechanical properties of solder alloys at high homologous temperature is explored. It is found that silica nanoparticles in the 100?nm range coated with 2?nm to 3?nm of gold can be dispersed within solders during the normal reflow soldering process, and that these particles are effective in hardening the solder and restricting dynamic grain growth during compression testing at low homologous temperature. As the homologous temperature increases towards 0.75, the effects of the nanoparticles on both mechanical properties and dynamical grain growth reduce, and by homologous temperatures of 0.86 the effects have completely disappeared. This behavior is explained by introducing the concept of an effective volume fraction of pinning nanoparticles, and the practical implications for using nanoparticles to control solder properties via Zener pinning at high homologous temperatures are discussed.     

Characteristics of secondhand electronic cigarette aerosols from active human use

The electronic cigarette (EC) is a new source of indoor airborne particles. To better understand the impacts of secondhand vaping (SHV) emissions on indoor air quality, real-time measurements of particle size distribution, particle number concentration (PNC), fine particulate matter (PM_2.5), CO₂, CO, and formaldehyde were conducted before, during, and after 10 min EC-use among 13 experienced users in an 80 m³ room. To assess particle transport in the room, multiple sampling locations were set up at 0.8, 1.5, 2.0, and 2.5 m away from the subjects. The arithmetic mean (standard deviation) of background PNC and PM_2.5 concentrations in the room were 6.39 × 10³ (1.58 × 10²) particles/cm³ and 8 (1) μg/m³, respectively. At 0.8 m away from EC users, right after initiation of puffing, the PNC and PM_2.5 concentrations can reach a peak of ～10⁵ particles/cm³ and ～3 × 10³ µg/m³, respectively, and then dropped quickly to background levels within 20 s due to dilution and evaporation. At the 0.8 m sampling location, the mean PNC and PM_2.5 concentrations during puffing were 2.48 × 10⁴ (2.14 × 10⁴) particles/cm³ and 188 (433) µg/m³, respectively. In addition, two modes of SHV particles were observed at about 15 and 85 nm. Moreover, concentrations of SHV particles were negatively correlated with the distances to EC users. At the 1.5 m location, PNC and PM_2.5 levels were 9.91 × 10³ (1.76 × 10³) particles/cm³ and 19 (14) µg/m³, respectively. Large variations of mean PNC levels exhaled per puff were observed both within and between EC users. Data presented in this study can be used for SHV particle exposure assessment.

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