Reconfigurable intelligent surfaces (RISs), with the potential to realize smart radio environments, have emerged as an energy-efficient and a cost-effective technology to support the services and ...demands foreseen for coming decades. By leveraging a large number of low-cost passive reflecting elements, RISs introduce a phase-shift in the impinging signal to create a favorable propagation channel between the transmitter and the receiver. In this article, we provide a tutorial overview of RISs for sixth-generation (6G) wireless networks. Specifically, we present a comprehensive discussion on performance gains that can be achieved by integrating RISs with emerging communication technologies. We address the practical implementation of RIS-assisted networks and expose the crucial challenges, including the RIS reconfiguration, deployment and size optimization, and channel estimation. Furthermore, we explore the integration of RIS and non-orthogonal multiple access (NOMA) under imperfect channel state information (CSI). Our numerical results illustrate the importance of better channel estimation in RIS-assisted networks and indicate the various factors that impact the size of RIS. Finally, we present promising future research directions for realizing RIS-assisted networks in 6G communication.
The study of biologically important Cu
2+
and S
2−
ions has drawn great attention in the recent years since an abnormal level of these ions is an indication for health impairment. Therefore, a ...reliable strategy for effective fluorescence determination of Cu
2+
and S
2−
ions was developed. Simply, the method based on economical plant-dependent thermolysis procedure for efficient green synthesis of water dispersible luminescent polyamine-based carbon dots (PA@C-dots) utilizes
Vitis vinifera
juice as precursor with a high quantum yield (32.1%) and good photo-stability. The fluorescent PA@C-dots were characterized by different spectroscopical, physical, and structural techniques. Furthermore, the synthesized PA@C-dots can be used as an efficient dual functional fluorescent probe for the sensitive and selective estimation of Cu
2+
and S
2−
ions. The incorporation of Cu
2+
ions and their adsorption on the surface of PA@C-dot skeleton leads to the respectable fluorescence quenching of C-dots (turn-off mode). The Cu
2+
-PA@C-dot was found to be sensitive to S
2−
ions. The addition of S
2−
recovers the fluorescence (turn-on mode) of Cu
2+
-PA@C-dots, thanks to its capacity for withdrawing Cu
2+
from the shell of PA@C-dots. Fluorescence quenching in the range of 0.07–60 μM Cu
2+
was obtained with LOD and LOQ of 0.02 and 0.066 μM, respectively. Sulfide detection provides linearity in the range of 0.8 to 95 μM with LOD and LOQ of 0.24 and 0.79 μM, respectively. The optimal excitation and emission wavelengths for all experiments are 435 nm and 498 nm, respectively. Experiment results elucidate that the proposed method is suitable for Cu
2+
and S
2−
ion detection in environmental water samples.
Graphical abstract
Green synthesis of polyamine-functionalized nanoprobe by thermolysis method from plant source as bifunctional sensing platform for determination of Cu
2+
and S
2−
in environmental water samples
•A novel ion pairing between IC and N@C-dots was proposed for the first time.•The interaction resulted in cyan blue color and quenching of N@C-dots fluorescence.•The nanoprobe exhibited good ...sensitivity and selectivity towards IC.•The application of nanoprobe was extended for analysis of IC in beverages.
Indigo carmine (IC) dye is hazardous and allergenic for humans even though it has been excessively used in a wide range of industries. Therefore, the quantitative determination of IC is still challenging. Herein, for the first time, we have developed fluorometric and colorimetric dual-mode nanoprobe derived from the ion-pair association complex between the negatively charged IC and positively charged N@C-dots in pH = 3.0. Consequently, the binding between N@C-dots and IC resulted in cyan blue and quenching of N@C-dots fluorescence. The dependence of the fluorescence response on IC concentrations was linear over the range of 0.73–10.0 µM (R2 = 0.9989) with LOD of 0.24 µM. On the other hand, the linearity of the colorimetric method ranged from 9.97 to 80.0 µM (R2 = 0.9986) with LOD of 3.3 µM. The sensor was applied for estimation of IC in fruit juice and soft drink without the need for exhaustive extraction steps.
The application of microfluidics in chemistry has gained significant importance in the recent years. Miniaturized chemistry platforms provide controlled fluid transport, rapid chemical reactions, and ...cost-saving advantages over conventional reactors. The advantages of microfluidics have been clearly established in the field of analytical and bioanalytical sciences and in the field of organic synthesis. It is less true in the field of inorganic chemistry and materials science; however in inorganic chemistry it has mostly been used for the separation and selective extraction of metal ions. Microfluidics has been used in materials science mainly for the improvement of nanoparticle synthesis, namely metal, metal oxide, and semiconductor nanoparticles. Microfluidic devices can also be used for the formulation of more advanced and sophisticated inorganic materials or hybrids.
Endodontic infection is a common problem that can result in tooth loss if not effectively treated. This study focused on investigating the use of rutin-gallium (Ga)(III) complex–mediated ...antimicrobial photodynamic therapy (aPDT) for the photoinactivation of Enterococcus faecalis biofilm.
The minimum biofilm eradication concentration of the rutin-Ga(III) complex and the minimum biofilm eradication dose of light-emitting diode against E. faecalis were evaluated. The antimicrobial effect of rutin-Ga(III) complex–mediated aPDT against E. faecalis was assessed. Additionally, the expression of genes associated with E. faecalis virulence, such as ace, gelE, and esp, as well as the production of reactive oxygen species within the cells were evaluated.
The minimum biofilm eradication concentration of the rutin-Ga(III) complex was determined to be 25 μmol/L, whereas the minimum biofilm eradication dose of light-emitting diode irradiation was defined as 5 minutes with an energy density of 300–420 J/cm2. Rutin-Ga(III) complex–mediated aPDT demonstrated a significant dose-dependent reduction in the growth of E. faecalis biofilms. Moreover, aPDT led to increased intracellular reactive oxygen species generation in treated E. faecalis cells. Furthermore, the messenger RNA levels of ace, gelE, and esp genes were significantly down-regulated in E. faecalis treated with rutin-Ga(III) complex–mediated aPDT (P < .05).
Rutin-Ga(III) complex–mediated aPDT effectively reduces E. faecalis biofilm growth by disrupting biofilm structure and down-regulating virulence genes. These findings highlight the potential of aPDT with the rutin-Ga(III) complex as an adjuvant therapeutic approach against E. faecalis biofilms.
Artificial Intelligence (AI) is the revolutionary paradigm to empower sixth generation (6G) edge computing based e-healthcare for everyone. Thus, this research aims to promote an AI-based ...cost-effective and efficient healthcare application. The cyber physical system (CPS) is a key player in the internet world where humans and their personal devices such as cell phones, laptops, wearables, etc., facilitate the healthcare environment. The data extracting, examining and monitoring strategies from sensors and actuators in the entire medical landscape are facilitated by cloud-enabled technologies for absorbing and accepting the entire emerging wave of revolution. The efficient and accurate examination of voluminous data from the sensor devices poses restrictions in terms of bandwidth, delay and energy. Due to the heterogeneous nature of the Internet of Medical Things (IoMT), the driven healthcare system must be smart, interoperable, convergent, and reliable to provide pervasive and cost-effective healthcare platforms. Unfortunately, because of higher power consumption and lesser packet delivery rate, achieving interoperable, convergent, and reliable transmission is challenging in connected healthcare. In such a scenario, this paper has fourfold major contributions. The first contribution is the development of a single chip wearable electrocardiogram (ECG) with the support of an analog front end (AFE) chip model (i.e., ADS1292R) for gathering the ECG data to examine the health status of elderly or chronic patients with the IoT-based cyber physical system (CPS). The second proposes a fuzzy-based sustainable, interoperable, and reliable algorithm (FSIRA), which is an intelligent and self-adaptive decision-making approach to prioritize emergency and critical patients in association with the selected parameters for improving healthcare quality at reasonable costs. The third is the proposal of a specific cloud-based architecture for mobile and connected healthcare. The fourth is the identification of the right balance between reliability, packet loss ratio, convergence, latency, interoperability, and throughput to support an adaptive IoMT driven connected healthcare. It is examined and observed that our proposed approaches outperform the conventional techniques by providing high reliability, high convergence, interoperability, and a better foundation to analyze and interpret the accuracy in systems from a medical health aspect. As for the IoMT, an enabled healthcare cloud is the key ingredient on which to focus, as it also faces the big hurdle of less bandwidth, more delay and energy drain. Thus, we propose the mathematical trade-offs between bandwidth, interoperability, reliability, delay, and energy dissipation for IoMT-oriented smart healthcare over a 6G platform.
Due to the recent advances in the domain of smart agriculture as a result of integrating traditional agriculture and the latest information technologies including the Internet of Things (IoT), cloud ...computing, and artificial intelligence (AI), there is an urgent need to address the information security-related issues and challenges in this field. In this article, we propose the integration of lightweight cryptography techniques into the IoT ecosystem for smart agriculture to meet the requirements of resource-constrained IoT devices. Moreover, we investigate the adoption of a lightweight encryption protocol, namely, the Expeditious Cipher (X-cipher), to create a secure channel between the sensing layer and the broker in the Message Queue Telemetry Transport (MQTT) protocol as well as a secure channel between the broker and its subscribers. Our case study focuses on smart irrigation systems, and the MQTT protocol is deployed as the application messaging protocol in these systems. Smart irrigation strives to decrease the misuse of natural resources by enhancing the efficiency of agricultural irrigation. This secure channel is utilized to eliminate the main security threat in precision agriculture by protecting sensors' published data from eavesdropping and theft, as well as from unauthorized changes to sensitive data that can negatively impact crops' development. In addition, the secure channel protects the irrigation decisions made by the data analytics (DA) entity regarding the irrigation time and the quantity of water that is returned to actuators from any alteration. Performance evaluation of our chosen lightweight encryption protocol revealed an improvement in terms of power consumption, execution time, and required memory usage when compared with the Advanced Encryption Standard (AES). Moreover, the selected lightweight encryption protocol outperforms the PRESENT lightweight encryption protocol in terms of throughput and memory usage.
The future Internet of Things (IoT) will have a deep economical, commercial and social impact on our lives. The participating nodes in IoT networks are usually resource-constrained, which makes them ...luring targets for cyber attacks. In this regard, extensive efforts have been made to address the security and privacy issues in IoT networks primarily through traditional cryptographic approaches. However, the unique characteristics of IoT nodes render the existing solutions insufficient to encompass the entire security spectrum of the IoT networks. Machine Learning (ML) and Deep Learning (DL) techniques, which are able to provide embedded intelligence in the IoT devices and networks, can be leveraged to cope with different security problems. In this paper, we systematically review the security requirements, attack vectors, and the current security solutions for the IoT networks. We then shed light on the gaps in these security solutions that call for ML and DL approaches. Finally, we discuss in detail the existing ML and DL solutions for addressing different security problems in IoT networks. We also discuss several future research directions for ML- and DL-based IoT security.
Solar thermal systems have low efficiency due to the working fluid's weak thermophysical characteristics. Thermo-physical characteristics of base fluid depend on particle concentration, diameter, and ...shapes. To assess a nanofluid's thermal performance in a solar collector, it is important to first understand the thermophysical changes that occur when nanoparticles are introduced to the base fluid. The aim of this study is, therefore, to analyze the hydrodynamic and heat characteristics of two different water-based hybrid nanofluids (used as a solar energy absorber) with varied particle shapes in a porous medium. As the heat transfer surface is exposed to the surrounding environment, the convective boundary condition is employed. Additionally, the flow of nanoliquid between two plates (in parallel) is observed influenced by velocity slip, non-uniform heat source-sink, linear thermal radiation. To make two targeted hybrid nanofluids, graphene is added as a cylindrical particle to water to make a nanofluid, and then silver is added as a platelet particle to the graphene/water nanofluid. For the second hybrid nanofluid, CuO spherical shape particles are introduced to the graphene/water nanofluid. The entropy of the system is also assessed. The Tiwari-Das nanofluid model is used. The translated mathematical formulations are then solved numerically. The physical and graphical behavior of significant parameters is studied.
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