Insights into the Nature of Self‐Extinguishing External Donors for Ziegler-Natta Catalysis: A Combined Experimental and DFT Study

Developing donors for Ziegler‐Natta (ZN) catalysis to control the polymerization reaction and produce polymers with desirable properties has always been challenging due to the multi‐component nature of the catalytic systems. Here, we have developed a new synthetic protocol for making two external donors, D₁ (2,2,2‐trifluoroethyl myristate) and D₂ (2,2,2‐trifluoroethyl palmitate) that show self‐extinguishing properties, followed by a systematic DFT study to understand this peculiar property of these donors. D₁ and D₂ can undergo parallel reactions with aluminum and titanium species present in the system to produce ketones and aldehydes, which are poisons for ZN catalytic systems, thus explaining their self‐extinguishing nature. The non‐covalent interaction between the long alkyl chain of the donors with the surface plays a vital role in determining the donors′ self‐extinguishing nature. There is a significant thermodynamic preference for the binding of the donor with the longer alkyl chain at the titanium center. The current work, therefore, provides interesting insights into how self‐extinguishing donors function in ZN catalytic systems

Speed Prediction Models for Urban Arterials Under Mixed Traffic Conditions

AbstractThe present study extends the basic concept of linear speed-density relation to mixed traffic condition and attempts to develop speed equations for different categories of vehicles generally found on an urban arterial in India. Field data were collected on different sections of urban arterials in New Delhi, Jaipur and Chandigarh by video recording method. All vehicles in the traffic stream were divided into 5 categories and a set of simultaneous equations is developed relating speed of a vehicle type to the densities of all categories of vehicles in their individual terms. These equations are solved for some assumed values of traffic volume and traffic composition and effect on speed of each vehicle type is explained. Accuracy of the equations is checked by comparing the observed values of speed with calculated speeds

Recent Advances in Biodegradable Polymers

Biodegradable polymers are important as an alternative to conventional non-degradable polymers for sustainable eco-system. The recent trends indicate that the new developments in biodegradable polymers focus on novel polymer systems that can cater the need of biomedical and packaging applications in-terms of performance and economics. The new interest is rapidly moving toward reducing carbon footprint through utilization of carbon dioxide and developing new methods of manufacturing such as 3D printing for specific purposes. This review focus on the present state-of-art and recent developments in biodegradable polymers covering their sources, synthetic methodologies, salient properties, degradation patterns, polymer blends and nanocomposites. As well as biodegradable polymers as a 3D printing material and the use of carbon dioxide as a renewable raw material for biomedical and packaging applications

Recent Advances in Biodegradable Polymers

Biodegradable polymers are important as an alternative to conventional non-degradable polymers for sustainable eco-system. The recent trends indicate that the new developments in biodegradable polymers focus on novel polymer systems that can cater the need of biomedical and packaging applications in-terms of performance and economics. The new interest is rapidly moving toward reducing carbon footprint through utilization of carbon dioxide and developing new methods of manufacturing such as 3D printing for specific purposes. This review focus on the present state-of-art and recent developments in biodegradable polymers covering their sources, synthetic methodologies, salient properties, degradation patterns, polymer blends and nanocomposites. As well as biodegradable polymers as a 3D printing material and the use of carbon dioxide as a renewable raw material for biomedical and packaging applications

A conflict-based safety assessment technique for rear-end crash risk at signalized intersections in a lower-middle-income country : A comparison between homogeneous and heterogeneous traffic conditions

Rear-end crashes at signalized intersections are attributed to different traffic behavior and operational characteristics. However, the influences of homogenous traffic conditions in developed countries and heterogeneous traffic conditions in low and middle-income developing countries like India are rarely explored. This study aims to examine the spatial–temporal characteristics of rear-end crash risk at signalized intersections characterized by lane-disciplined homogeneous and non-lane-based heterogeneous traffic conditions. In particular, this study has applied a conflict-based safety assessment framework to compare the rear-end crash risks across these traffic conditions. Vehicular trajectory data of vehicles at four signalized intersections, one in the homogeneous and three in heterogeneous traffic conditions, is analyzed. Rear-end conflicts position and time of occurrence in the upstream and downstream section of the stop-line are identified and modeled by extreme value models. Results show that the vehicles in heterogeneous traffic conditions are more aggressive, resulting in a higher number of conflicts and probable crashes. The presence of smaller-sized vehicles in dominating proportions and disregard of lane discipline with a higher degree of lateral movement are responsible for more traffic conflicts. The estimated extreme value models suggest that the minimum rear-end crash risk probability at signalized intersections with heterogeneous traffic conditions is about three times higher than that at signalized intersections with homogeneous traffic conditions. The observation is similar for crash risks estimated from both surrogate safety measures used in this study. The weak lane discipline and irregular lateral movement of vehicles are responsible for higher crash risks in heterogeneous traffic conditions.</p

Synthesis of N and F co-doped TiO2 nanophotocatalysts for degradation of malathion in water

N and F codoped nanophotocatalysts were synthesized by sol-gel method and their photocatalytic activity were studied for the degradation of insecticide malathion. Photocatalysts were characterised by X-ray diffraction (XRD), scanning electron microscope, transmission electron microscope and micro Raman spectroscopy to determine the structural, morphological properties and phase composition. The particle size calculated by XRD are in agreement with the measured value by TEM. Band gap calculated by absorption spectra shows a shift in the absorption edge towards longer wavelength side. Photoluminescence spectra show emission behaviour of synthesized photocatalysts. In comparison with undoped TiO2, N, F codoped particles exhibits higher photocatalytic activity due to generation of more reactive oxidative species (ROS). Mechanism of ROS generation is graphically discussed

Stabilization of Photoactive γ‑CsPbI₃ Perovskite Phase by Incorporation of Mg

Fully inorganic CsPbI3 perovskite has been widely explored as an alternative light-harvesting material owing to its superior thermal stability over the organic–inorganic halide perovskite and the suitable band gap. However, stabilization of the photoactive CsPbI3 phase at room temperature (RT) remains the biggest challenge. The photoactive α-CsPbI3 which requires high-temperature synthesis (above 320 °C) transforms into the photoactive γ-CsPbI3 at RT and on exposure to ambient rapidly transforms into the non-photoactive δ-CsPbI3. Herein, we investigate the effect of incorporating Mg2+ in the CsPbI3 lattice. It has been found that the photoactive γ-phase of CsPbI3 can be stabilized for more than 167 days at RT in a nitrogen atmosphere by incorporating Mg2+ inside the lattice. Incorporating Mg2+ inside the lattice of CsPbI3 has led to enhanced optoelectronic properties along with enhanced phase and thermal stability