2,434 research outputs found
Reclaiming the Night: A Case Study on Reception of #JusticeForRGKar on Selected Social Media Platforms
“Reclaim the Night” or “Night is Ours” is a mass movement sparked by the demand for justice in the rape and murder case of a junior doctor at Radha Gobinda Kar Medical College in Kolkata, West Bengal, India. The movement has underscored the transformative power of social media in mobilizing people from various walks of life, as thousands congregated in the streets to advocate for justice and demand safety for women in the workplace. Employing Goffman’s framing theory, this study examines how social media enabled extensive awareness, solidarity, and collective action among various communities through the analysis of digital activism strategies. Using a qualitative approach, this study investigates the intersection of gender, justice, and digital activism, focusing on how social media posts, news reports, and protest coverage fuelled solidarity and global awareness. This research underscores the significant impact of social media in sustaining grassroots movements, particularly in challenging traditional power structures and ensuring that marginalized voices are heard. Hashtags, such as #JusticeForRGKar; online group; and worldwide solidarity activities highlight the importance of digital activism in the long-term success of social movements. All of the visuals work together to amplify the core messages of defiance, unity, and systematic reform
Outcome analysis in patients with multi vessel coronary artery disease and left ventricular ejection fraction after percutaneous coronary intervention: single center experience
Background: The present study evaluated the changes in baseline left ventricular function and clinical symptoms in multi-vessel coronary artery disease patients after multi-vessel percutaneous coronary intervention.Methods: This was a prospective, observational study conducted at Medical Super-speciality Hospital, Kolkata, India, between August 2017 and August 2019. The study included 48 patients who were diagnosed with ≥2 coronary artery stenosis of ≥50% in native coronary arteries with left ventricular ejection fraction (LVEF) <40%. Echocardiography was performed before and after 3 months of the procedure to observe LVEF. Canadian Cardiovascular Society (CCS) score was calculated before and after 3 months after PCI.Results: Mean age of the patients was 61.89±9.96 years and 89.6% patients were male. Mean LVEF before and after angioplasty was 34.9±4.95% and 42.06±8.78%, respectively (p=0.001). CCS score before and after angioplasty was 2.89 and 1.83, respectively (p=0.001).Conclusions: The results displayed significant improvement in clinical symptoms as well as LVEF after PCI in patients with multi-vessel disease with LVEF <40%. These results will be helpful to conduct larger randomized trials with long term follow-up in order to prove the safety and effectiveness of PCI in such patients over coronary artery bypass grafting
H-2 Evolution with Covalent Organic Framework Photocatalysts
Covalent organic frameworks (COFs) are a new class of crystalline organic polymers that have garnered significant recent attention as highly promising H-2 evolution photocatalysts. This Perspective discusses the advances in this field of energy research while highlighting the underlying peremptory factors for the rational design of readily tunable COF photoabsorber-cocatalyst systems for optimal photo catalytic performance
Single-Site Photocatalytic H-2 Evolution from Covalent Organic Frameworks with Molecular Cobaloxime Co-Catalysts
We demonstrate photocatalytic hydrogen evolution using COF photosensitizers with molecular proton reduction catalysts for the first time. With azine-linked N2-COF photosensitizer, chloro(pyridine)cobaloxime co-catalyst, and TEOA donor, H-2 evolution rate of 782,mu mol h(-1) g(-1) and TON of 54.4 has been obtained in a water/acetonitrile mixture. PXRD, solid-state spectroscopy, EM analysis, and quantum-chemical calculations suggest an outer sphere electron transfer from the COF to the co-catalyst which subsequently follows a monometallic pathway of H-2 generation from the Co-III-hydride and/or Co-II-hydride species
Ionothermal Synthesis of Imide‐Linked Covalent Organic Frameworks
Covalent organic frameworks (COFs) are an extensively studied class of porous materials, which distinguish themselves from other porous polymers in their crystallinity and high degree of modularity, enabling a wide range of applications. COFs are most commonly synthesized solvothermally, which is often a time‐consuming process and restricted to well‐soluble precursor molecules. Synthesis of polyimide‐linked COFs (PI‐COFs) is further complicated by the poor reversibility of the ring‐closing reaction under solvothermal conditions. Herein, we report the ionothermal synthesis of crystalline and porous PI‐COFs in zinc chloride and eutectic salt mixtures. This synthesis does not require soluble precursors and the reaction time is significantly reduced as compared to standard solvothermal synthesis methods. In addition to applying the synthesis to previously reported imide COFs, a new perylene‐based COF was also synthesized, which could not be obtained by the classical solvothermal route. In situ high‐temperature XRPD analysis hints to the formation of precursor–salt adducts as crystalline intermediates, which then react with each other to form the COF
Urea/thiourea derivatives and Zn(II)-DPA complex as receptors for anionic recognition - a brief account
This review covers few examples of anion complexation chemistry, with a special focus on urea/thiourea-based receptors and Zn(II)-dipicolyl amine-based receptors. This article specially focuses on structural aspects of the receptors and the anions for obtaining the desire specificity along with an efficient receptor-anion interaction. Two types of receptors have been described in this brief account; first one being the strong hydrogen bond donor urea/thiourea derivatives, which binds the anionic analytes through hydrogen bonded interactions; while, the second type of receptors are coordination complexes, where the coordination of the anion to the metal centre. In both the cases the anion binding modulate the energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and thereby the spectroscopic response. Appropriate choice of the signalling unit may allow probing the anion binding phenomena through visual detection
US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report
This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in
Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference
Sub-stoichiometric 2D covalent organic frameworks from tri- and tetratopic linkers
Covalent organic frameworks (COFs) are typically designed by breaking down the desired network into feasible building blocks - either simple and highly symmetric, or more convoluted and thus less symmetric. The linkers are chosen complementary to each other such that an extended, fully condensed network structure can form. We show not only an exception, but a design principle that allows breaking free of such design rules. We show that tri- and tetratopic linkers can be combined to form imine-linked [4 + 3] sub-stoichiometric 2D COFs featuring an unexpected bex net topology, and with periodic uncondensed amine functionalities which enhance CO2 adsorption, can be derivatized in a subsequent reaction, and can also act as organocatalysts. We further extend this class of nets by including a ditopic linker to form [4 + 3 + 2] COFs. The results open up possibilities towards a new class of sub-valent COFs with unique structural, topological and compositional complexities for diverse applications
Rational Design of Covalent Cobaloxime–Covalent Organic Framework Hybrids for Enhanced Photocatalytic Hydrogen Evolution
Covalent organic frameworks (COFs) display a unique combination of chemical tunability, structural diversity, high porosity, nanoscale regularity, and thermal stability. Recent efforts are directed at using such frameworks as tunable scaffolds for chemical reactions. In particular, COFs have emerged as viable platforms for mimicking natural photosynthesis. However, there is an indisputable need for efficient, stable, and economical alternatives for the traditional platinum-based cocatalysts for light-driven hydrogen evolution. Here, we present azide-functionalized chloro(pyridine)cobaloxime hydrogen-evolution cocatalysts immobilized on a hydrazone-based COF-42 backbone that show improved and prolonged photocatalytic activity with respect to equivalent physisorbed systems. Advanced solid-state NMR and quantum-chemical methods allow us to elucidate details of the improved photoreactivity and the structural composition of the involved active site. We found that a genuine interaction between the COF backbone and the cobaloxime facilitates recoordination of the cocatalyst during the photoreaction, thereby improving the reactivity and hindering degradation of the catalyst. The excellent stability and prolonged reactivity make the herein reported cobaloxime-tethered COF materials promising hydrogen evolution catalysts for future solar fuel technologies
A flavin-inspired covalent organic framework for photocatalytic alcohol oxidation
Covalent organic frameworks (COFs) offer a number of key properties that predestine them to be used as heterogeneous photocatalysts, including intrinsic porosity, long-range order, and light absorption. Since COFs can be constructed from a practically unlimited library of organic building blocks, these properties can be precisely tuned by choosing suitable linkers. Herein, we report the construction and use of a novel COF (FEAx-COF) photocatalyst, inspired by natural flavin cofactors. We show that the functionality of the alloxazine chromophore incorporated into the COF backbone is retained and study the effects of this heterogenization approach by comparison with similar molecular photocatalysts. We find that the integration of alloxazine chromophores into the framework significantly extends the absorption spectrum into the visible range, allowing for photocatalytic oxidation of benzylic alcohols to aldehydes even with low-energy visible light. In addition, the activity of the heterogeneous COF photocatalyst is less dependent on the chosen solvent, making it more versatile compared to molecular alloxazines. Finally, the use of oxygen as the terminal oxidant renders FEAx-COF a promising and “green” heterogeneous photocatalyst
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