Nano TiO2 as an efficient and reusable heterogeneous catalyst for the synthesis of 5-substituted 1H-tetrazoles

Nano TiO2 is an effective heterogeneous catalyst for the [2+3] cycloaddition of sodium azide with nitriles to afford 5-substituted 1H-tetrazoles in good yields. This method has the advantages of high yields, simple methodology and easy work-up. The catalyst is recovered and reused for several cycles with consistent activity. Keywords: 5-substituted 1H-tetrazole, [2+3] cycloaddition, nano TiO2, heterogeneous catalys

Global age-sex-specific all-cause mortality and life expectancy estimates for 204 countries and territories and 660 subnational locations, 1950–2023: a demographic analysis for the Global Burden of Disease Study 2023

Background: Comprehensive, comparable, and timely estimates of demographic metrics—including life expectancy and age-specific mortality—are essential for evaluating, understanding, and addressing trends in population health. The COVID-19 pandemic highlighted the importance of timely and all-cause mortality estimates for being able to respond to changing trends in health outcomes, showing a strong need for demographic analysis tools that can produce all-cause mortality estimates more rapidly with more readily available all-age vital registration (VR) data. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) is an ongoing research effort that quantifies human health by estimating a range of epidemiological quantities of interest across time, age, sex, location, cause, and risk. This study—part of the latest GBD release, GBD 2023—aims to provide new and updated estimates of all-cause mortality and life expectancy for 1950 to 2023 using a novel statistical model that accounts for complex correlation structures in demographic data across age and time. Methods: We used 24 025 data sources from VR, sample registration, surveys, censuses, and other sources to estimate all-cause mortality for males, females, and all sexes combined across 25 age groups in 204 countries and territories as well as 660 subnational units in 20 countries and territories, for the years 1950–2023. For the first time, we used complete birth history data for ages 5–14 years, age-specific sibling history data for ages 15–49 years, and age-specific mortality data from Health and Demographic Surveillance Systems. We developed a single statistical model that incorporates both parametric and non-parametric methods, referred to as OneMod, to produce estimates of all-cause mortality for each age-sex-location group. OneMod includes two main steps: a detailed regression analysis with a generalised linear modelling tool that accounts for age-specific covariate effects such as the Socio-demographic Index (SDI) and a population attributable fraction (PAF) for all risk factors combined; and a non-parametric analysis of residuals using a multivariate kernel regression model that smooths across age and time to adaptably follow trends in the data without overfitting. We calibrated asymptotic uncertainty estimates using Pearson residuals to produce 95% uncertainty intervals (UIs) and corresponding 1000 draws. Life expectancy was calculated from age-specific mortality rates with standard demographic methods. For each measure, 95% UIs were calculated with the 25th and 975th ordered values from a 1000-draw posterior distribution. Findings: In 2023, 60·1 million (95% UI 59·0–61·1) deaths occurred globally, of which 4·67 million (4·59–4·75) were in children younger than 5 years. Due to considerable population growth and ageing since 1950, the number of annual deaths globally increased by 35·2% (32·2–38·4) over the 1950–2023 study period, during which the global age-standardised all-cause mortality rate declined by 66·6% (65·8–67·3). Trends in age-specific mortality rates between 2011 and 2023 varied by age group and location, with the largest decline in under-5 mortality occurring in east Asia (67·7% decrease); the largest increases in mortality for those aged 5–14 years, 25–29 years, and 30–39 years occurring in high-income North America (11·5%, 31·7%, and 49·9%, respectively); and the largest increases in mortality for those aged 15–19 years and 20–24 years occurring in Eastern Europe (53·9% and 40·1%, respectively). We also identified higher than previously estimated mortality rates in sub-Saharan Africa for all sexes combined aged 5–14 years (87·3% higher in GBD 2023 than GBD 2021 on average across countries and territories over the 1950–2021 period) and for females aged 15–29 years (61·2% higher), as well as lower than previously estimated mortality rates in sub-Saharan Africa for all sexes combined aged 50 years and older (13·2% lower), reflecting advances in our modelling approach. Global life expectancy followed three distinct trends over the study period. First, between 1950 and 2019, there were considerable improvements, from 51·2 (50·6–51·7) years for females and 47·9 (47·4–48·4) years for males in 1950 to 76·3 (76·2–76·4) years for females and 71·4 (71·3–71·5) years for males in 2019. Second, this period was followed by a decrease in life expectancy during the COVID-19 pandemic, to 74·7 (74·6–74·8) years for females and 69·3 (69·2–69·4) years for males in 2021. Finally, the world experienced a period of post-pandemic recovery in 2022 and 2023, wherein life expectancy generally returned to pre-pandemic (2019) levels in 2023 (76·3 [76·0–76·6] years for females and 71·5 [71·2–71·8] years for males). 194 (95·1%) of 204 countries and territories experienced at least partial post-pandemic recovery in age-standardised mortality rates by 2023, with 61·8% (126 of 204) recovering to or falling below pre-pandemic levels. There were several mortality trajectories during and following the pandemic across countries and territories. Long-term mortality trends also varied considerably between age groups and locations, demonstrating the diverse landscape of health outcomes globally. Interpretation: This analysis identified several key differences in mortality trends from previous estimates, including higher rates of adolescent mortality, higher rates of young adult mortality in females, and lower rates of mortality in older age groups in much of sub-Saharan Africa. The findings also highlight stark differences across countries and territories in the timing and scale of changes in all-cause mortality trends during and following the COVID-19 pandemic (2020–23). Our estimates of evolving trends in mortality and life expectancy across locations, ages, sexes, and SDI levels in recent years as well as over the entire 1950–2023 study period provide crucial information for governments, policy makers, and the public to ensure that health-care systems, economies, and societies are prepared to address the world's health needs, particularly in populations with higher rates of mortality than previously known. The estimates from this study provide a robust framework for GBD and a valuable foundation for policy development, implementation, and evaluation around the world

Transverse Vibrations and Stability of Viscoelastic Axially Moving Rayleigh Beams Under Thermal Fields: an Analytical Approach

In this work, the flexural vibrations and stability of viscoelastic beams under axial motion and thermal fields are investigated using Rayleigh beam theory. The viscoelastic behavior is modeled through the Kelvin-Voigt and Maxwell models, and the governing differential equation is derivative utilizing Hamilton's principle. To create a more realistic model, thermal stresses in the beam are simulated using both linear and non-linear models. An innovative analytical solution method for these equations is presented, employing a power series approach to solve equations. The research provides an explicit mathematical expression for the mixed vibration modes of the beam under axial motion. Various parameters, such as rotational inertia, linear and non-linear thermal stresses, structural damping, and axial movement speed, are analyzed for their effects on the dynamic characteristics and instability of viscoelastic Rayleigh beams under axial motion. The findings indicate that incorporating rotational inertia and Rayleigh beam theory reduces the natural frequencies at low axial speeds but consistently increases the system's critical speed. Furthermore, rotational inertia induces distortions in the vibration mode shapes. Notably, the impact of rotational inertia on the second mode shape is significant, resulting in the loss of the nodal point in the second vibration mode shape of the beam under axial motion.Emerging Sources Citation Inde

Static Stability of Functionally Graded Porous Nanoplates Under Uniform and Non-Uniform In-Plane Loads and Various Boundary Conditions Based on the Nonlocal Strain Gradient Theory

This work examines the buckling behavior of functionally graded porous nanoplates embedded in elastic media. Size effects are added to the nanoplate constitutive equations using nonlocal strain gradient theory. The fourvariable refined plate theory is employed for nanoplate modeling. This theory assures stress-free conditions on both sides of the nanoplate and has less uncertainty than high-order shear deformation theories. It is postulated that the nanoplate experiences in-plane compressive loads, which may have both linear and nonlinear distributions. Additionally, uniform and non-uniform porosity distributions are considered. The governing partial differential equations are extracted using the notion of the minimal total potential energy. Following this, the Galerkin method is employed to solve these equations utilizing trigonometric shape functions. Simple, clamped, and combined boundary conditions for nanoplate edges are studied. Once the governing algebraic equations were extracted, the critical buckling load of the nanoplate is determined. To conduct a validation study, the obtained data are juxtaposed with the findings of previous studies, revealing a notable level of concurrence. After the critical buckling load has been ascertained, an inquiry is undertaken to assess the influence of various parameters including nonlocal and length scale parameters, boundary conditions, porosity distribution type, inplane loading type, geometric dimensions of the nanoplate, and stiffness of the elastic environment, on the static stability of nanoplates.Emerging Sources Citation Inde

Mechanical performance of aluminum/copper/aluminum nanocomposite at different temperatures using molecular dynamics simulation

With the expansion of science and technology, the application and importance of composites in various industries increased. Aluminum /copper metal layer composites are widely used for their fracture toughness, corrosion resistance, and high electrical conductivity. This research simulated an Aluminum /copper/Aluminum tri-layer nanocomposite to investigate the effects of different temperatures (T = 300, 350, 375, 400, 450, and 500 K) on its mechanical properties. The stress, strain rate, yield strength, and ultimate strength values were recorded. The results indicate that the physical stability of the sample remained unaffected as temperature increased, while the attraction force among different particles was observed. Furthermore, the simulation results suggest that the mechanical strength of aluminum/copper/aluminum tri-layer nanocomposite decreased with rising initial temperature in the computational box. Specifically, the ultimate strength and Young's modulus of nanocomposites reduced to 2.186 GPa and 12.727 GPa, respectively, at 500 K. Aluminum /copper/Aluminum tri-layer nanocomposite showed promising potential for real-world applications, particularly in sectors requiring materials with enhanced mechanical properties. It is expected that these composites will be utilized in advanced engineering fields, such as aerospace and automotive industries, where their high strength-to-weight ratio and thermal stability can significantly improve performance and efficiency

Modeling the Influence of External Heat Flux on Thermal Characteristics of the Silica Aerogel/Paraffin in a Cylindrical Atomic Duct

As the price of fuel rises and the environmental impact of greenhouse gases intensifies, a larger population is opting for alternative sources of sustainable energy. Currently, scientists are facing challenges in discovering an energy-saving method that is effective in diverse scenarios and is user-friendly. Many individuals are interested in using materials that can transition between solid, liquid, and gas states. The objective was to use these materials for heat retention. Silica aerogels exhibit effective thermal regulation, regardless of whether the environment is hot or cold. Phase change materials are substances that store thermal energy effectively and play a crucial role in maintaining temperature stability. This research explored how external heat flux affected the behavior of a tube filled with silica aerogel and phase change materials. Additionally, we incorporated CuO nanoparticles to evaluate their impact on the system. The study utilized LAMMPS software to perform molecular dynamics simulations for this purpose. To achieve our goal, we evaluated various aspects of virtual structure, which can be influenced by factors, such as density, velocity, temperature profile, heat flux, thermal conductivity, and the duration of filling and emptying. The findings indicate that as external heat flux increased, maximum density decreased to 0.1364 atoms/& Aring;3. Conversely, thermal conductivity, maximum velocity, and temperature increase to 1.97 W/m & sdot;K, 0.0138 & Aring;/fs, and 649 K, respectively. Also, with maximum external heat flux, charging time decreases to 5.94 ns, while discharge time is recorded at 8.56 ns. Increased external heat flux resulted in greater thermal energy transfer to the material, causing the atoms to vibrate more vigorously and collide more frequently.Science Citation Index Expande

Examination of the mechanical properties of porous carbon matrix by considering the Nanovoids: A computational study using molecular dynamics simulation

This study explored the effect of nanovoid size on the mechanical properties of polymer-carbon matrices through detailed molecular dynamics simulations. The investigation focused on spherical nanovoids with radii of 5, 7, 10, 12, and 15 & Aring;, evaluating their effects on critical mechanical properties, such as Young's modulus and ultimate strength. The Tersoff potential was employed to accurately model the atomic and mechanical behavior of the polymer-carbon matrix, considering the presence of these nanovoids. The simulation results indicate that the potential energy and total energy stabilized at-132,279.23 eV and- 131,522.4 eV, respectively, confirming the physical stability of simulated samples. On the other hand, the findings reveal that for a nanovoid radius of 5 & Aring;, the ultimate strength and Young's modulus were 36.41 GPa and 424.93 GPa, respectively. As the radius of nanovoids increased from 5 & Aring; to 15 & Aring;, both ultimate strength and Young's modulus exhibited a decreasing trend, with values dropping from 36.41 GPa and 424.93 GPa to 31.18 GPa and 364.39 GPa, respectively. Moreover, larger nanovoids contributed to increased flexibility and a higher critical strain in the polymer-carbon matrix. This systematic analysis of nanovoid size effects provided a new perspective on void engineering within composites. By enhancing the theoretical understanding of how void dimensions affected material properties, the study offered significant insights for optimizing the mechanical performance of advanced materials and advancing the field of structural engineering.Science Citation Index Expande

Investigating the Effect of Volume Fraction on Brownian Displacement, Thermophoresis, and Thermal Behavior of Graphene/Water Nanofluid by Molecular Dynamics Simulation

Atiah, Younis M./0000-0003-2861-6643Nanotechnology focuses on materials at the nanoscale, including nanoparticles and nanofluids are created by dispersing nanoparticles in a base fluid. This study examined the impact of volume fraction on thermophoresis, thermal conductivity, and Brownian motion in graphene/water nanofluid through molecular dynamics simulations. Simulations were performed at a constant temperature of 300 K, representative of room temperature conditions for thermal applications. This research aimed to understand how the amount of graphene in the water-based nanofluid affected these properties, which were crucial for heat transfer and thermal management systems. The study examined the effects of various nanoparticle volume fractions (1 %, 3 %, 6 %, and 10 %), ranging from dilute to semi-concentrated nanofluids, on thermal conductivity, Brownian motion, and thermophoresis. Results indicate an increase in average Brownian displacement and thermophoresis displacement from 3.06 and 23.88 & Aring; to 4.14 and 26.88 & Aring;, respectively, as the volume fraction increases from 1 % to 6 %. However, as the volume fraction increased from 6 % to 10 %, these values decreased to 3.35 & Aring; and 23.99 & Aring;. This decrease may be attributed to increased interparticle interactions and clustering at higher volume fractions. After 10 ns, increasing the nanoparticle volume fraction to 6 % raised heat flux and thermal conductivity from 39.54 W/m2 and 0.36 W/m & sdot;K to 45.05 W/m2 and 0.46 W/m & sdot;K. However, at a 10 % volume fraction, both parameters decreased to 39.56 W/m2 and 0.37 W/m & sdot;K, respectively. The temperature profile shows that increasing the graphene volume fraction to 6 % raised the maximum temperature from 1415 K to 1879 K; further increasing the volume fraction to 10 % decreased it to 1572 K. These findings indicate that the volume percentage of graphene nanoparticles significantly affected Brownian displacement, thermophoresis displacement, heat flux, thermal conductivity, and maximum temperature in the nanofluid. An optimal volume fraction of approximately 6 % is identified for enhancing thermal performance. Overall, the volume fraction, along with nanoparticle size, shape, and dispersion stability, was crucial in determining the atomic and thermal behavior of nanofluids, highlighting the need to identify the optimal concentration for superior performance.Science Citation Index Expande