Precious metal loaded organically modified silica for organic transformations

PhDPrecious Metal Loaded Organically Modified Silica for Organic Transformations Highly active heterogeneous silica supported palladium ethylthioglycolate, silica-60-G1- Pd(OAc) and silica supported 1,2-bis(ethylthio)ethane palladium, silica-60-C2-Pd(OAc)2 and 1,2-bis(ethylthio)propane palladium, silica-60-C3-Pd(OAc)2 catalysts were prepared and characterised (using elemental analysis, solid state NMR, electron microscopy and nitrogen sorption porosimetry). The catalysts have been shown to be very active, recyclable and resistant to leaching in a representative selection of Suzuki-Miyaura cross-couplings. Two sets of conditions were employed; those regularly reported in the literature, high temperature with xylene, and much milder reaction conditions, room temperature with isopropanol. In both reaction conditions, catalysts silica-60-G1-Pd(OAc), silica-60-C2-Pd(OAc)2 and silica- 60-C3-Pd(OAc)2 gave cross coupled products in high yields. Microwave-assisted cross coupling reactions of more difficult aryl bromides with substituted phenylboronic acid employing catalyst silica-60-C3-Pd(OAc)2 were also investigated. These reactions proceeded smoothly with excellent yields. S S Pd(OAc)2 S O O Pd(OAc) silica-60-G1-Pd(OAc)2 S S Pd(OAc)2 silica-60-C2-Pd(OAc)2 silica-60-C3-Pd(OAc)2 Catalyst silica-60-C3-Pd(OAc)2 was also assessed for the more difficult Mizoroki-Heck cross coupling and displayed slow conversions. Modification of this catalyst with replacement of Pd(OAc)2 with PdCl2 to give silica-60-C3-PdCl2, gave excellent conversions in which aryl halides were combined with styrene. Reactions were carried out in NMP with K2CO3 as a base. Activity was retained in recycles and the catalyst was again found to be resistant to leaching. Microwave assisted reactions of more difficult substrates were also found to give good conversions. Further application of catalyst silica-60-C3-Pd(OAc)2 was explored in the hydrogenation reaction of alkenes, nitriles and imines. High conversions were found as well as effective reVII use of the catalyst several times without loss in activity. Further studies of the pore size effects in the hydrogenation of nitrobenzene revealed catalysts prepared with smaller pores to be more active possibly as a result of the more confined environment. Interesting examples of one-pot tandem hydrogenation and Suzuki-Miyaura cross-coupling reactions catalysed by silica-60-C3-Pd(OAc)2 were also elaborated. Asymmetric hydrogenations were also explored with palladium chiral cysteine derivatised ligands immobilised on silica, silica-60-Nderivatised- L-cysteine-Pd(OAc). Although high conversions were achieved, the selectivity of these catalysts in the hydrogenation of highly substituted imines was very low. Novel active heterogeneous ethylphosphatrioxaadamantane (PAD) ruthenium catalysts, silica- 110-PAD-Ru-DPEN with chiral amine ligands were also prepared for the asymmetric hydrogenation of ketones. These results gave quantitative conversions to the alcohol but low selectivity (18% e.e) was found. So attention was turned to using these immobilised phosphorus ligands, silica-110-PAD, to complex Rhodium compounds and utilising these materials as catalysts in hydroformylation reactions. P RhClPPh3 silica-110-PAD-RhCl(PPh3)2 Hydroformylation reactions of styrene were carried out using CO:H2 in a 1:1 ratio with toluene as a solvent and with silica-110-PAD-RhCl(PPh3)2 as catalyst. Reactions carried out at room temperature were found to favour the formation of branched aldehydes (73:27). At high temperatures, although activity was improved this was coupled with a decrease in the regioselectivity and in some cases some hydrogenated product was also formed. Interestingly, change of the rhodium salt to Rh(CO)2(acac) was found to give better chemoselectivity with no hydrogenated product. Structure activity behaviour of the catalysts was rationalised against their materials characteristics including immobilised ligand, surface area, pore diameters and volumes, metal loading and oxidation state. The work included a study of the relative metal uptake efficiency of the different materials using ICP-OES and a further study of the relative mobility of the immobilised ligands using 13C CP MAS T1 measurements and effects of dipolar dephasing

Aircraft load alleviation by specifying its closed-loop eigenstructure

Reduction of aircraft loads, arising as a result of manoeuvre commands or atmospheric turbulence, by means of active control is an important problem in flight control. A variety of methods of designing appropriate control systems to achieve such reduction are available, but not every method is effective. A feature of this research work is the use of an eigenvalue/eigenvector assignment method using full state variable feedback, to design aircraft load alleviation control systems. [Continues.

Mediators of mechanotransduction between bone cells

Mechanical forces are known to regulate the function of tissues in the body, including bone. Bone adapts to its mechanical environment by altering its shape and increasing its size in response to increases in mechanical load associated with exercise, and by decreasing its size in response to decreases in mechanical load associated with microgravity or prolonged bed rest. Changes in bone size and shape are produced by a cooperative action of two main types of the bone cells - osteoclasts that destroy bone and osteoblasts that build bone. These cell types come from different developmental origins, and vary greatly in their characteristics, such as size, shape, and expression of receptor subtypes, which potentially may affect their responses to mechanical stimuli. The objective of this study is to compare the responses of osteoclasts and osteoblasts to mechanical stimulation. This study has allowed us to conclude the following: 1. A mediator is released from a single source cell. 2. The response to the mediator changes with distance. 3. The value of the apparent diffusion coeficient increases with distance. 4. A plausible proposed mechanism is that ATP is released and degrades to ADP. 5. Future experiments are required to confim that ATP is the mediator as suggested

MicroRNA profiling of tomato leaf curl new delhi virus (tolcndv) infected tomato leaves indicates that deregulation of mir159/319 and mir172 might be linked with leaf curl disease

Background: Tomato leaf curl virus (ToLCV), a constituent of the genus Begomovirus, infects tomato and other plants with a hallmark disease symptom of upward leaf curling. Since microRNAs (miRs) are known to control plants developmental processes, we evaluated the roles of miRNAs in Tomato leaf curl New Delhi virus (ToLCNDV) induced leaf curling. Results: Microarray analyses of miRNAs, isolated from the leaves of both healthy and ToLCNDV agroinfected tomato cv Pusa Ruby, revealed that ToLCNDV infection significantly deregulated various miRNAs representing ~13 different conserved families (e.g., miR319, miR172, etc.). The precursors of these miRNAs showed similar deregulated patterns, indicating that the transcription regulation of respective miRNA genes was perhaps the cause of deregulation. The expression levels of the miRNA-targeted genes were antagonistic with respect to the amount of corresponding miRNA. Such deregulation was tissue-specific in nature as no analogous misexpression was found in flowers. The accumulation of miR159/319 and miR172 was observed to increase with the days post inoculation (dpi) of ToLCNDV agroinfection in tomato cv Pusa Ruby. Similarly, these miRs were also induced in ToLCNDV agroinfected tomato cv JK Asha and chilli plants, both exhibiting leaf curl symptoms. Our results indicate that miR159/319 and miR172 might be associated with leaf curl symptoms. This report raises the possibility of using miRNA(s) as potential signature molecules for ToLCNDV infection. Conclusions: The expression of several host miRNAs is affected in response to viral infection. The levels of the corresponding pre-miRs and the predicted targets were also deregulated. This change in miRNA expression levels was specific to leaf tissues and observed to be associated with disease progression. Thus, certain host miRs are likely indicator of viral infection and could be potentially employed to develop viral resistance strategies

Some iron and manganese complexes of heterocycles

The study describes the various attempts which have been made to synthesize heterocyclic derivatives of transition metals, e.g. iron and manganese, in which the heterocycle is bonded to the metal in an analogous manner to the bonding in pi-cyclopentadienyl-metal compounds. The pi pyrrolyl manganese carbonyl complexes were prepared by one or both or the following methods. In the first the pyrrole or substituted pyrrole was heated with dimanganese decacarbonyl in an inert solvents. In the second method, the potassium salt of the heterocycle was heated with bromomanganese pentacarbonyl. The latter method was found to be more widely applicable and was extended to the preparation of such complexes from pyrroles bearing functional groups, to indoles, pyrazoles and benzotriazole. In some of these cases a-heterocycle manganese pentacarbonyl could be isolated as the first products Similarly the potassium salt of heterocycles containing nitrogen, on reaction with iodo-dicarbonyl cyclopentadienyl iron gave a-complexes, i.e. dicarbonyl-pi-cyclopentadienyl-a-heterocycle iron. These a-bonded complexes by loss of carbon monoxide yielded aza ferrocenes, i.e. pi-cyclopentadienyl-pi-heterocycle iron at higher temperature. Attempts to effect electrophilic substitution of the two parent complexes, i.e. trioarbonyl-pi-pyrrolyl manganese and pi-cyclopentadienyl-pi-pyrrolyl iron were made in order to prepare beterocyclio metal complexes with functional groups. Friedel and Crafts Acylation appeared to give a trace of acylated products, while apiempted aminomethylation resulted in decomposition. The reaction of pyrroyl chloride with sodlomanganese pentacarbonyl resulted in the formation of the a-bonded complex, 2-pyrrolyl manganese pentacarbonyl via pyrroyl manganese pentacarbonyl by loss of carbon monoxide. Allyl iron tricarbonyl iodide on reaction with pyrrolyl potassium gave 2 : 4 Hexadiene tricarbonyl iron. Unsuccessful apiempts have been made to prepare dipyxrolyl analogous of ferrocene, cobaltocene and niokelocene. The reaction between molyledenum hexacarbonyl and pyrrolyl potassium resulted in decomposition

Periodic gamma-ray emissions from Geminga at or = 10(12) eV

Analysis of data from an atmospheric Cerenkov telescope indicated the periodic emission of gamma rays of energy 10 to the 12th power eV, at 60.25 second period, from 2CG 195+4. The gamma ray flux at 99% confidence level is estimated to be 9.5 x 10 to 12 photons/sq cm/s

An integrated approach of GRA coupled with principal component analysis for multi-optimization of shielded metal arc welding (SMAW) process

Welding distortion is a critical issue as it leads to severe deterioration of structural integrity of welded work piece and dimensional precision. This study aims at studying the e ects of shielded metal arc welding (SMAW) parameters on the evolution of mechanical properties, including tensile strength, impact toughness, and hardness, along with angular distortion on a welded joint from SA 516 grade 70. Such parameters are analyzed and optimized by employing the Taguchi method and Grey relational analysis. SA 516 grade 70 is commercially used for fabrication of storage tanks, boilers and pressure vessels. SMAW is investigated with three levels of root gap, groove angle, electrode diameter, and pre-heat temperature, which were varied on a butt joint in flat (1 G) position to determine their e ects on response variables at room temperature. Nine experiments were designed using a Taguchi L9 orthogonal array, welded according to American Society of Mechanical Engineers (ASME) section IX, and samples were prepared and tested as per ASTM A 370. The Taguchi method and Grey relational analysis were employed to observe the most significant parameters and optimal levels that synergically yield improved responses. Results are validated by conducting confirmatory experiments that show good agreement with optimum results

DDoS Attack Detection Using Cooperative Overlay Networks and Gossip Protocol

DDoS attacks have major impact on the affected networks viz. packet transmission delays, network outage, website sabotage, financial losses, legitimate-user blockage and reputation damage. Existing DDoS detection techniques are either implemented at the victim node (but the damage is already done) or at many intermediate routers which run DDoS detection algorithms, that adds additional delay and more processing. We aim to detect DDoS attacks by using a new technique of cooperative overlay networks which overcomes the above problems by implementing the DDoS detection algorithm at one hop distance nodes (called defense nodes) from the victim. DOI: 10.17762/ijritcc2321-8169.15062

Construction and evaluation of multisite recombinatorial (Gateway) cloning vectors for Gram-positive bacteria

<p>Abstract</p> <p>Background</p> <p>The Gateway recombinatorial cloning system allows easy and rapid joining of DNA fragments. Here we report the construction and evaluation of three different Gram-positive vectors that can be used with the Multisite Gateway cloning system to rapidly produce new gene arrangements in plasmid constructs for use in a variety of Gram-positive bacteria.</p> <p>Results</p> <p>Comparison of patterns of reporter gene expression with conventionally constructed clones show that the presence of residual recombination (att) sites does not have an effect on patterns of gene expression, although overall levels of gene expression may vary. Rapid construction of these new vectors allowed vector/gene combinations to be optimized following evaluation of plasmid constructs in different bacterial cells and demonstrates the benefits of plasmid construction using Gateway cloning.</p> <p>Conclusion</p> <p>The residual <it>att </it>sites present after Gateway cloning did not affect patterns of promoter induction in Gram-positive bacteria and there was no evidence of differences in mRNA stability of transcripts. However overall levels of gene expression may be reduced, possibly due to some post-transcriptional event. The new vectors described here allow faster, more efficient cloning in range of Gram-positive bacteria.</p