Iranian Journal of Science and Technology, Transactions A: Science最新文献

In this study, it is aimed to experimentally investigate the transformation and the thermodynamic behaviors of the Ni-rich NiTi Shape Memory Alloy (SMA) at various thermal conditions. Based on XRD and SEM analyses, Ni₄Ti₃ precipitated/un-precipitated structures were identified as function of annealing temperature (450 °C and 650 °C). Through the calorimetric study, by varying the DSC scanning rate, it was proved that transformation temperatures, transformation rate and thermal hysteresis are highly sensitive to the presence of the precipitation phase. Furthermore, thermodynamic properties and kinetic behavior were assessed highlighting the impact of microstructural alteration on changes in enthalpy, entropy, Gibbs free energy and elastic energy. Activation energies of Ni₄Ti₃ precipitated and un-precipitated samples were determined according to Kissinger and Takhor approaches revealing a notable negative activation energy for the un-precipitated sample and considerably high values for the precipitated one. This result implies that, with the presence of Ni₄Ti₃ precipitates, the NiTi SMA requires higher activation energy to conduct the martensitic transformation.

In this paper complex symmetry of slant H-Toeplitz operator is studied. Necessary conditions for complex symmetry of restrictions of slant H-Toeplitz operator, namely slant Toeplitz operator and the slant Hankel operator, with respect to a weighted composition operator are explored along with counterexamples for insufficient conditions. The upper bound for the spectral radius of the slant H-Toeplitz is also obtained.

The action principle is introduced to describe the thermodynamic processes of the state functions from the initial equilibrium state to the final equilibrium state. To capture the path-independent property of the state functions through the thermodynamic processes, one requires an integrability condition called the Lagrangian 1-form closure relation as a direct result of the least action principle with respect to the independent variables.

The main purpose of this work is to investigate of the notions Hopfian (co-Hopfian) acts in which their surjective (injective) endomorphisms are isomorphisms. While we study conditions that are relevant to these classes of acts, their interrelationship with some other concepts for example quasi-injective and Dedekind-finite acts is studied. Using Hopfian and co-Hopfian concepts, we provide several conditions for a quasi-injective act to be Dedekind-finite.

Let G be a simple graph on n vertices. The Estrada index of G, denoted by EE(G), is defined as (EE(G)=sum _{i=1}^ne^{lambda _i}), where (lambda _1,ldots ,lambda _n) are the eigenvalues (the eigenvalues of the adjacency matrix) of G. In this paper we find some sharp bounds on the Estrada index of graphs in terms of the number of vertices, the number of edges and the rank of graphs.

With the rise in applications involving high-radiation exposure, it is imperative to implement measures to minimise the adverse effects of radiation. There is a great need for material development that can be used at high temperatures, especially in the nuclear industry. Superalloys have properties that can serve this purpose. In order to achieve this objective, new Co-based and Ni-based super alloys were produced in the study. Ni, Fe, Mo, Cr, Nb, Ti, Al, Co, Ta and W were selected for developing Co-based alloys, and Ni, Fe, Cr, Nb, Ti, Al, Co and B were selected for Ni-based alloy. The goal of the study is to obtain new materials which have better shielding performances with superior properties. In this regard, the radiation protection parameters; linear attenuation coefficients, mass attenuation coefficients, effective atomic number, half-value layer, mean free path, effective conductivity, effective electron number, exposure and energy absorption buildup factors, atomic and electron cross sections, and fast neutron attenuation cross-sections of the alloys were performed by Phy-X/PSD code. Further, EPR, XRD and EDS-SEM spectroscopic techniques were used and the results were appraised within this context. It can be noted that the content of W, Ta and Mo, due to the features of high density and high atomic number, improves the radiation attenuation efficiency of the alloys. It is also seen that the fast neutron attenuation ability is affected by Ni, Ta, Mn and Mo contents. It was concluded that the newly fabricated super alloys can be evaluated as good radiation shields in high temperature applications such as nuclear reactors.

Despite the importance of the regulatory role of miRNAs, their effect on terpenoids production is still poorly understood. Especially, the regulation of terpenoids biosynthesis by miRNAs in medicinal plants has a proper potential to be investigated. Since many of the known miRNAs are conserved, the prediction of plausible miRNAs is a fast, cheap, and desirable method that can be used as a screening tool to gain initial knowledge of species potential. Here, the transcriptomic data of a number of the Lamiaceae species were explored to identify miRNAs and target genes related to the terpenoids biosynthesis. Based on the results, miR1127, miR1128, miR1133, miR1436 and miR5021 were found in different species, indicating that they are likely specific to the Lamiaceae family. The highest number of predicted miRNAs involved in terpenoids biosynthesis were obtained in Hyssopus officinalis and Lavadula angustifolia. However, H. officinalis showed more diversity in terpenoid biosynthesis pathways, miRNA families, and predicted targets, suggesting that it may have developed a special adaptive strategy to produce diverse terpenoids through miRNA-mediated regulation. Additionally, the phylogenetic trees based on the similarities of the precursor nucleotide sequence of miRNAs manifested that many of the trees reliably recovered the phylogeny of the Lamiaceae family, in turn representing the effectiveness of miRNAs in determining the phylogenetic relationships of the species of the same family. In conclusion, the present research provides a new foundation for investigating the function of miRNAs to enrich the pathways of terpenoids biosynthesis, and their effects on determining the evolutionary relationships of species.

Fluorescent carbon dots (CDs) have attracted great attention for the biomedical applications as a new group of nanoparticles with high biocompatibility and interesting optical properties. In this study, the fluorescent CDs were synthesized by a biogenic hydrothermal method using Taxus baccata extract and ethylene diamine (EDA). The CDs, predominantly semi-spherical and smaller than 20 nm, exhibit high colloidal stability. They have a hydrodynamic size of 43.6 nm, a polydispersity index (PI) of 0.526, and a zeta potential of -56.7 mV. Their surface is rich in hydroxyl and carbonyl groups. They also exhibit fluorescence emission, with a quantum yield (QY) of 11.6% at 490 nm, when excited at 400 nm. The in vitro cytotoxicity assay on the human fibroblast (HFB) and umbilical vein endothelial (HUVEC) cells confirmed the biocompatibility of CDs. These CDs represent significant antibacterial effects on Staphylococcus aureus and Escherichia coli with the minimum inhibitory concentrations (MIC) of 40 and 160 μg mL^− 1, respectively. The rapid and efficient uptake of CDs with E. coli and HFB cells was confirmed by the fluorescence imaging. Based on the results, the biogenic CDs can be a suitable alternative to the antibiotics against pathogenic bacteria and also for the staining and labeling of the microbial cells.

Our study’s primary goal is to accurately predict the equation of state required for calculating the pressure-dependent melting curves of metals. We introduce a unique model for the melting curve, utilizing various equations of state (EOS) such as Murnaghan EOS, Kholiya EOS, Goyal-Gupta EOS, Usual-Tait EOS, Singh and Kao EOS, and Modified Lennard–Jones EOS. This model, rigorously tested and compared with Lindemann’s and available experimental data, establishes the relationship among pressure, bulk modulus, pressure derivative of bulk modulus, and volume compression. Our findings conclusively demonstrate that a significant increase in melting temperature is directly linked to a substantial rise in bulk modulus and a gradual decrease in the first-order pressure derivative of bulk modulus. This study provides unprecedented insights into the fundamental understanding of the effect of pressure on melting temperature. The model we have developed is highly reliable for extrapolating melting temperature to high pressure, instilling confidence in its application. Notably, our study finds that Murnaghan EOS is more suitable for predicting the melting temperature of the metal. Importantly, our results agree with Lindemann’s law and experimental values, validating our approach.

Green synthesis of metal oxide nanoparticles provides an eco-friendly alternative to conventional chemical approaches. This study focuses on synthesizing pure zirconium dioxide (ZrO₂) and europium-doped zirconium dioxide (Eu-ZrO₂) nanoparticles using Jasminum fluminense leaf extract. These materials were evaluated for their effectiveness in photocatalytic degradation of textile dyes and their ability to control bacterial pathogens. Physicochemical analyses, including XRD and EDX, confirmed the crystalline nature and also the purity of the synthesized nanoparticles. ZrO₂ and Eu-ZrO₂ were evaluated for degrading the anionic dye Brilliant Blue G and the cationic dye Nile Blue Sulfate. Eu-ZrO₂ demonstrated over 94% degradation efficiency for both dyes. The antimicrobial activity was assessed through the Agar well diffusion method against different bacterial strains including Enterococcus aeruginosa, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Shigella dysenteriae. Eu-ZrO₂ exhibited a substantial inhibition zone of 48 mm against Salmonella typhi, demonstrating potent antibacterial properties.