Mid‐IR transparent TeO2‐TiO2‐La2O3 glass and its crystallization behavior for photonic applications

In this report, effect of enhanced rare earth (La₂O₃) concentration on substitution of TeO₂ within ternary TeO₂‐TiO₂‐La₂O₃ (TTL) glass system has been studied with respect to its thermal, structural, mechanical, optical, and crystallization properties with an aim to achieve glass and glass‐ceramics having rare‐earth‐rich crystalline phase for nonlinear optical and infrared photonic applications. DSC analysis (10°C/min) demonstrates a progressive increase in glass‐transition temperature (T_g) from 359 to 452°C with the increase in La₂O₃ content. Continuous glass network modification with transformation of [TeO₄] to [TeO₃/TeO₃₊₁] units is evidenced from Raman spectra which is corroborated with XPS studies. While mechanical properties demonstrate enhancement of cross‐linking density in the network. These glasses exhibit optical transmission window extended from 0.4 to 6 μm with calculated zero dispersion wavelength (λ_ZDW) varying from 2.41 to 2.28 μm depending upon La₂O₃ content. Crystallization kinetics of TTL10 (80TeO₂‐10TiO₂‐10La₂O₃ in mol%) glass has been studied via established models. Activation energy (E_a) has been evaluated and dimensionality of crystal growth (m) suggests formation of surface crystals. Glass‐ceramic with crystalline phase of La₂Te₆O₁₅ has been realized in heat‐treated TTL10 glass samples (at 450°C). As predicted from DSC analysis, FESEM study unveils the formation of surface crystallized glass‐ceramics.     

Efficacy of <Emphasis Type="Italic">Bletilla striata</Emphasis> polysaccharide on hydrogen peroxide-induced apoptosis of osteoarthritic chondrocytes

Osteoarthritis (OA) is a degenerative joint disease affecting millions of peoples worldwide. Though the etiology of OA includes joint injury, obesity, aging, and heredity, oxidative stress is majorly considered as the hallmark of OA initiation and clinical progression. Traditional pharmacologic therapies such as acetaminophen, non-steroidal anti-inflammatory drugs, and opioids are effective only against relieving pain and not capable of reverting damaged cartilage. Bletilla striata is a chinese herb majorly reported for its wound healing and anti-inflammatory property. The objective of this study is to demonstrate the potential of Bletilla striata polysaccharide (BSP) as a biomaterial for oxidative stress induced cartilage tissue repair. The polysaccharide extracted and purified from B. striata was characterized by Fourier-Transform Infrared (FT-IR) Spectrometer and ¹H, ¹³C Nuclear Magnetic Resonance (NMR) Spectrometer. Rheological measurements of BSP hydrogel were performed using a rheometer under the frequency sweep model. The BSP also showed antioxidant effects by ABTS antioxidant activity assay. The biocompatibility and cytotoxicity of BSP was demonstrated by WST-1 and LDH assay. H₂O₂ induced oxidative stress was selected to generate osteoarthritic chondrocytes and its detrimental effect was demonstrated by live/dead staining. Finally, the quantitative gene expression of ECM-related genes was studied by RT-PCR in BSP treated and non-treated groups. The outcome of this study has revealed that the down-regulation of catabolic gene expression by BSP treatment may open-up the development of new therapeutic approaches in OA.     

On a Non-linear Electronic Circuit Filtering

The stochastic versions of non-linear dynamic circuits are formalized using non-linear stochastic differential equations. Stochastic differential equations (SDEs) are exploited to analyse dynamical systems in noisy environments. A potential application of the SDEs can be regarded as ‘stochastic processes in electronic circuits’. The noisy sampling mixer, a component of digital wireless communications, is an appealing and standard case from the dynamical systems’ viewpoint. It assumes the structure of a non-linear SDE, and its linearized version becomes time-varying bilinear SDE. This paper derives the filtering equations for the noisy non-linear sampling mixer circuit utilizing the filtering density evolution equation. The filtering model for the stochastic problem of concern here comprises the following: (1) a non-linear SDE describing the noisy sampling mixer and (2) a non-linear noisy observation equation. It is interesting to note that the filtered estimate accounts for observations. On the other hand, the predicted estimate does not account for the observation terms in evolution equations. As a result of this, the filtered estimate confirms the greater accuracy of estimated state trajectory in contrast to the predicted trajectory. The filtering equation of this paper can be further utilized for control of the noisy sampling mixer, where the observations are available.     

Turbulent natural convection in an enclosure with localized heating from below

This study reports the results of a numerical investigation of turbulent natural convection in a square enclosure with localized heating from below and symmetrical cooling from the vertical side walls. The present study simulates the case of an accidental heat generation due to fire in a typical isolated building of a nuclear reactor or electronic components cabin. The source of fire is considered to be centrally located at the bottom wall with different heated widths, which is assumed to be either isothermal or with isoflux. For the purpose of the analysis, the source length is varied from 20 to 80% of the total width of the bottom wall. The top wall and the unheated portion of the bottom wall are considered to be adiabatic, whereas sidewalls are isothermal. Steady as well as transient forms of two-dimensional Reynolds–Averaged-Navier–Stokes equations and conservation equations of mass and energy, coupled with the Boussinesq approximation, are solved by the control volume based discretisation method employing the SIMPLE algorithm for pressure–velocity coupling. Turbulence is modeled using the standard k–ε model. Rayleigh number, Ra, based on the enclosure height is varied from 10⁸ to 10¹². Stream lines and isotherms are presented for various combinations of Ra and the heated width. A double cell flow pattern is observed with marginal loss in symmetry as Ra increases. The results are reported in the form of local and average Nusselt number on the heated floor. Correlations are developed to predict the heat transfer rates from the enclosure as a function of dimensionless heated width of the bottom wall and Ra, by least square linear regression analysis.     

On the speedup required for combined input- and output-queued switching

Architectures based on a non-blocking fabric, such as a crosspoint switch, are attractive for use in high-speed LAN switches, IP routers, and ATM switches. When operating at the highest speed, memory bandwidth limitations dictate that queues be placed at the input of the switch. But it is well known that input-queueing can lead to low throughput, and does not allow the control of latency through the switch. This is in contrast to output-queueing which maximizes throughput and permits the accurate control of packet latency through scheduling. We ask the question: Can a switch with combined input and output queueing be designed to behave identically to an output-queued switch? In this paper, we prove that if the switch uses virtual output queueing and has an internal speedup of just four, it is possible for it to behave identically to an output-queued switch, regardless of the nature of the arriving traffic. Our proof is based on a novel scheduling algorithm, called Most Urgent Cell First. We find that with a speedup of four the most urgent cell first algorithm (or MUCFA) enables perfect emulation of a FIFO output-queued switch, i.e. one in which packets depart in the same order that they arrived. We extend this result to show that with a small modification, the MUCFA algorithm enables perfect emulation of a variety of output scheduling policies, including strict priorities and weighted fair-queueing. This result makes possible switches that perform as if they were output-queued, yet use memories that run more slowly.     

Evaluation of column studies using Cynodon dactylon plant‐mediated amino‐grouped silica‐layered magnetic nanoadsorbent to remove noxious hexavalent chromium metal ions

Magnetic nanoparticles are desirable adsorbents because of their unique superparamagnetic nature with the enhanced binding specificity and surface material interaction. The above unique features attract researchers to use it for wider applications. Herein, the study focuses on the amino‐induced silica‐layered magnetic nanoparticles amalgamated with plant‐extracted products of Cynodon dactylon in order to turn them into a potent adsorbing material in a continuous column set up for the elimination of noxiously distributed Cr(VI) ionsin the effluents. The selected plant‐mediated magnetite nanoadsorbent, which was used in the fixed column studies, is optimised with the attributes of inlet concentration, adsorbent bed depth, and flow rate. Thomas, Yoon‐Nelson and bed depth model showed the best experimental fit. Breakthrough adsorption time was reported for the various inlet concentrations of 100, 200 and 300 mg/L, adsorbent bed depths 2, 3 and 4 cm and volumetric flow rates of 4, 5 and 6 mL/min. The breakthrough point evaluated for the optimised attribute of inlet concentration of 100 mg/L, packed adsorbent depth 4 cm and flow rate 4 mL/min was 1400 min and the maximum removal efficiency was 60.6%. A better insight of the adsorption of metal ions for large‐scale industrial effluents is provided.     

Recovery of valuable metals from waste printed circuit boards using organic acids synthesised by Aspergillus niveus

Organic acids such as citric acid, itaconic acid and oxalic acid synthesised by Aspergillus niveus were used for the bioleaching of metals from waste printed circuit boards. Bioleaching of valuable metals was performed in one‐step, two‐steps and spent medium approaches using A. niveus. In the absence of waste printed circuit boards (WPCBs), the dry cell weight of A. niveus was higher when compared with the presence of WPCBs. Variations in the dry cell weight were observed for the presence of different particle sizes. The increase in itaconic acid and oxalic acid synthesis was found at a reduced particle size (60–80 mesh) and reached the maximum titre of itaconic acid (22.35 ± 0.87 mM) and oxalic acid (12.75 ± 0.54 mM) in 12 days during the two‐step bioleaching. The maximum recovery of 75.66% Zn, 73.58% Ni and 80.25% Cu from WPCBs was achieved in 15 days in two‐step leaching with particle sizes of the mesh being 60–80.     

Phytosterols in Seaweeds: An Overview on Biosynthesis to Biomedical Applications

Seaweed extracts are considered effective therapeutic alternatives to synthetic anticancer, antioxidant, and antimicrobial agents, owing to their availability, low cost, greater efficacy, eco-friendliness, and non-toxic nature. Since the bioactive constituents of seaweed, in particular, phytosterols, possess plenty of medicinal benefits over other conventional pharmaceutical agents, they have been extensively evaluated for many years. Fortunately, recent advances in phytosterol-based research have begun to unravel the evidence concerning these important processes and to endow the field with the understanding and identification of the potential contributions of seaweed-steroidal molecules that can be used as chemotherapeutic drugs. Despite the myriad of research interests in phytosterols, there is an immense need to fill the void with an up-to-date literature survey elucidating their biosynthesis, pharmacological effects, and other biomedical applications. Hence, in the present review, we summarize studies dealing with several types of seaweed to provide a comprehensive overview of the structural determination of several phytosterol molecules, their properties, biosynthetic pathways, and mechanisms of action, along with their health benefits, which could significantly contribute to the development of novel drugs and functional foods.     

Graphene-nanoplatelet-based photomechanical actuators

This paper reports large light-induced reversible and elastic responses of graphene nanoplatelet (GNP) polymer composites. Homogeneous mixtures of GNP/polydimethylsiloxane (PDMS) composites (0.1-5 wt%) were prepared and their infrared (IR) mechanical responses studied with increasing pre-strains. Using IR illumination, a photomechanically induced change in stress of four orders of magnitude as compared to pristine PDMS polymer was measured. The actuation responses of the graphene polymer composites depended on the applied pre-strains. At low levels of pre-strain (3-9%) the actuators showed reversible expansion while at high levels (15-40%) the actuators exhibited reversible contraction. The GNP/PDMS composites exhibited higher actuation stresses compared to other forms of nanostructured carbon/PDMS composites, including carbon nanotubes (CNTs), for the same fabrication method. An extraordinary optical-to-mechanical energy conversion factor (η(M)) of 7-9 MPa W(-1) for GNP-based polymer composite actuators is reported.