Video streaming using whitespace spectrum for vehicular applications

We present Scout, a communication system leveraging TV whites-paces to support robust and high–speed streaming services. Scout uses two key techniques to improve video performance. First, it extends network coverage through an asymmetric network archi-tecture where whitespace transceivers are used for the downlink direction while a cellular path is used for the uplink. Scout further leverages some unique opportunities that arise in vehicular systems. In particular, it sends a front radio to lookahead and identify the best channel parameters when the rear radio eventually reaches the forward post. We demonstrate the performance of Scout by using a single base station to stream a high–quality video to a vehicle driving along a 1.3km road stretch

High oxidation state N-heterocyclic carbene molybdenum alkylidene complexes: functional-group tolerant olefin metathesis catalysts

Olefin metathesis reactions belong to the most powerful tools for the formation of carbon-carbon double bonds both in organic synthesis and polymer chemistry. Enormous progress has been made both in terms of activity, selectivity and functional-group tolerance of the catalysts. Nonetheless, turn-over numbers (TONs) are still, with very few exceptions, far below 100,000 in most cases below 5,000. The use of modern, molecularly well-defined olefin metathesis catalysts are mostly restricted to high-end pharmaceutical applications. There, both Schrock and Grubbs catalysts find ample use. Therefore, the synthesis of well-defined catalysts which conquered the weakness of the existing systems has received great attention. Chapter 1 The first chapter of this thesis deals with a history of olefin metathesis as well as a short overview on the synthesis and applications of Schrock catalysts. The context also offers a short description about different olefin metathesis reactions and N-heterocyclic carbenes (NHC). Chapter 2 A single-site catalyst, which is highly active both in terms of turn-over numbers (TONs) and turn-over frequency (TOF), which is tolerant toward water, air and functional- groups with high stereo- and regioselectivity remains a challenge in olefin metathesis. In search for olefin active metathesis catalysts based on cheap metals (Mo/W) and fulfill all the above mentioned criteria, the first N-heterocyclic carbene (NHC) complexes of molybdenum imido alkylidene bis(triflate) complexes have been synthesized. Unlike existing bis(triflate) complexes, the novel 5-fold coordinated 16-electron Mo-complexes contain two carbenes, i.e. a Schrock carbene and an NHC. Single crystal X-ray analysis revealed that the above mentioned complexes are distorted square pyramidal with one triflate (OTf) ligand trans to the NHC. In course of a metathesis reaction, this triflate leaves the complex and generates a trigonal bipyramidal cationic 16-electron Mo-NHC complex (19F-NMR studies). The most important observation is this type of catalysts is active in ring-closing metathesis (RCM), cross-metathesis (CM), the cyclopolymerisation of α,ω-diynes and ring-opening metathesis polymerisation (ROMP). Monomers containing functional-groups, e.g., sec-amine, hydroxy, and carboxylic acid moieties, which are not tolerated by the existing variations of Schrock catalysts, can be used. This novel class of catalysts displays substantial activity even at high temperatures (140 °C), e.g., in RCM. Based on the observation that bis(triflate) complexes show a coalescence temperature for the two triflate groups, an activation mechanism based on a Berry-type pseudorotation, i.e. interconversion between trigonal biyramidal (TBP) configurations through a square pyramidal (SP), is proposed. Activation of the catalysts through the release of one triflate in the SP configuration is in full accordance with the observed reactivity of both neutral and cationic Mo-imido alkylidene NHC complexes and with 19F-NMR. Furthermore, reactions of the Mo-NHC bis(triflate) complexes with one equivalent of a fluorinated alkoxide (e.g., -OCH(CF3)2, -OC6F5, -OCCH3(CF3)2) or with AgB(ArF)4 in dichloroethane afforded the corresponding monoalkoxide and the cationic Mo-imido alkylidene NHC complexes. This particular feature is the presence of the NHC ligand, which delocalizes the cationic charge and stabilizes the molybdenum center. The structures of all compounds have been determined by single-crystal X-ray diffraction and their reactivities in various olefin metathesis reactions have been explored. In selected metathesis reactions, TONs up to 545,000 have been reached. Nonetheless, Mo-imido alkylidene NHC complexes with one electron-withdrawing fluorinated alkoxide and the corresponding cationic complexes in which the remaining triflate replaced by AgB(ArF)4 afforded remarkably active and functional-group tolerant metathesis catalysts. Employing different NHCs such as triazole-2-ylidene, benzimidazolylidene and CAAC (Cyclic Alkyl Amino Carbene) provides access to another novel class of Mo-NHC alkylidene complexes. In fact, Mo-imido alkylidene NHC complexes prepared recently display unprecedented functional-group tolerance. Therefore, these catalysts hold great promise in both organic and polymer chemistry. Chapter 3 In this chapter, the first anionic high oxidation state molybdenum (VI) imido bisalkyl alkylidyne complex [(Mo(N-2,6-Me2-C6H3)(CH2CMe3)2(CCMe2Ph)(Mg.Et2O-μ-Cl)2] (29) is reported. It forms via reaction of [Mo(N-2,6-Me2-C6H3)(CH2CMe2Ph)2(O3SCF3)2(DME)], (DME = 1,2-dimethoxyethane) with an excess of neopentylmagnesium chloride. [Mo(N-2,6-(2-iPr)2-C6H3)(CCMe2Ph)(2,5-Me2-pyrrolide)2(1,3-dimesityl-4,5-dihydro-1H-imidazol-3-ium)] (30) is accessible via reaction of Mo(N-2,6-(2-iPr)2-C6H3)(IMesH2)(CHCMe2Ph)(2,6-Me2-pyrrolide)2 with 1,3-dimesitylimidazolidinium chloride in benzene. X-ray studies of both complexes are also presented. While 29 is inactive in alkyne metathesis and in ring-closing metathesis (RCM), it is active in the ring-opening metathesis polymerization (ROMP) of (substituted) norborn-2-ene(s) and in the 1-alkyne polymerization of 2-ethynyl-trimethylsilylbenzene. The ROMP derived polymers display a high cis-content up to ≥ 96%. Both the proposed mesomerism via dπ-pπ interactions through Mo(IV) between a molybdenum amidatoalkylidyne and a molybdenum amidoalkylidenate and a [1,3-H] shift in course of polymerization that accounts for the unique reactivity of 29 are supported by density functional calculations (DFT)

Constraints on Density Dependent MIT Bag Model Parameters for Quark and Hybrid Stars

We compute the equation of state (EoS) of strange quark stars (SQSs) with the MIT Bag model using density dependent bag pressure, characterized by a Gaussian distribution function. The bag pressure's density dependence is controlled by three key parameters namely the asymptotic value ($B_{as}$), $\Delta B(=B_0 - B_{as})$, and $\beta$. We explore various parameter combinations ($B_{as}$, $\Delta B$, $\beta$) that adhere to the Bodmer-Witten conjecture, a criterion for the stability of SQSs. Our primary aim is to analyze the effects of these parameter variations on the structural properties of SQSs. However we find that none of the combinations can satisfy the NICER data for PSR J0030+0451 and the constraint on tidal deformability from GW170817. So it can be emphasized that this model cannot describe reasonable SQS configurations. We also extend our work to calculate structural properties of hybrid stars (HSs). With the density dependent bag model (DDBM), these astrophysical constraints are fulfilled by the HSs configurations within a very restricted range of the three parameters. The present work is the first to constrain the parameters of DDBM for both SQS and HSs using the recent astrophysical constraints on tidal deformabiity from GW170817 and that on mass-radius relationship from NICER data.Comment: Accepted for publication in Nuclear Physics

Creating Sustainable High-Performance Human Resource Practice through Employees Learning Agility. The Transition Adaptive Approach

Recently, the COVID-19 pandemic posed enormous challenges, compelling organizations to adapt to unforeseen events as a result of direct immediate threats and consequently pushing human resource practitioners to reshape their existing human resources practices. It appears, there is no study so far which has investigated the relationship between employee learning agility (ELA) and high-performance human resources practice (HPHRP) particularly, the mediating effect of the person-organization fit (P-O fit) in reshaping human resource practices through transition adaptive theory.  A self-administered survey among public sector employees in the Fiji Islands yielded a sample of 351 participants. The proposed model was analyzed through structural equation modeling (SEM), to determine the model fit. The findings show that ELA significantly enhances HPHRP. This suggests that learning opportunity provides an opportunity to adopt, modify, and recombine, the current knowledge with new knowledge in creating new knowledge stock. The diffusion of such knowledge can assist significantly in improving human resource practices. Moreover, the mediating effect of P-O fit shows the congruence between ELA and organization, further suggesting that employees perform best in an environment that supports their salient needs and recognizes their knowledge, abilities, and skills in reshaping human resources practices. As such, this study provides a significant contribution to the extant literature on human resource management. Finally, the current research offers theoretical and practical implications, limitations, and further research directions

Advanced Oxidation Processes and Their Application in the Treatment of Different Types of Wastewater Samples

Over the years, urbanization has caused the quality of the water to decline gradually. The production of wastewater has been steadily rising alongside the growth of numerous businesses, including medicines, textiles, processed foods, and many more. Organic molecules from a variety of sources make up the majority of contaminants in wastewater. Some of these chemical molecules are not biodegradable, and it is challenging for anaerobic bacteria to break them down entirely. Because of the molecular structure of them, they can be quite persistent. Several advanced oxidation processes (AOPs) have been studied to remediate wastewater that contains trace organic chemicals (TrOCs). These include ozonation, Fenton oxidation, catalytic wet air oxidation, and photocatalytic oxidation. AOPs have excellent efficiencies, quick oxidation rates, and no secondary pollutants. Each AOP adheres to a particular mechanism in specific circumstances. In this article, we have comprehensively reviewed the underlying mechanism, and factors affecting oxidative pollutant degradation efficiency