853 resultados para bonding agents
Resumo:
In negotiating commercial leases, many landlords and tenants employ property agents (brokers) to act on their behalf; typically these people are chartered surveyors. The aim of this paper is to explore the role that these brokers play in the shaping of commercial leases in the context of the current debate in the UK on upward only rent reviews. This role can be described using agency theory and the theories of professionalism. These provide expectations of behaviour which show inherent tensions between the role of agent and professional, particularly regarding the use of knowledge, autonomy and the obligation to the public interest. The parties to eleven recent lease transactions were interviewed to see if the brokers conformed to the expectations of agency theory or professionalism. Brokers that acted for industrial and office tenants behaved as professionals in using their expertise to determine lease structures. However, those acting for landlords and retail tenants simply followed instructions and behaved as conduits for their clients, a role more usually associated with that of an agent within the principal-agent relationship. None of the landlords’ brokers saw themselves as having responsibilities beyond their clients and so they were not promoting the discussion of alternatives to the UORR. The evidence from these case studies suggests that agents are not professionals; to behave entirely as an agent is to contradict the essential characteristics of a professional. While brokers cannot be held entirely responsible for the lack of movement on the UORR, by adopting predominantly agent roles then they must take some of the blame. However, behind this may be a much larger issue that needs to be explored; the institutional pressures that lead to professionals behaving in this way.
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We report the single-crystal X-ray structure for the complex of the bisacridine bis-(9-aminooctyl(2-(dimethylaminoethyl)acridine-4-carboxamide)) with the oligonucleotide d(CGTACG)2 to a resolution of 2.4 Å. Solution studies with closed circular DNA show this compound to be a bisintercalating threading agent, but so far we have no crystallographic or NMR structural data conforming to the model of contiguous intercalation within the same duplex. Here, with the hexameric duplex d(CGTACG), the DNA is observed to undergo a terminal cytosine base exchange to yield an unusual guanine quadruplex intercalation site through which the bisacridine threads its octamethylene linker to fuse two DNA duplexes. The 4-carboxamide side-chains form anchoring hydrogen-bonding interactions with guanine O6 atoms on each side of the quadruplex. This higher-order DNA structure provides insight into an unexpected property of bisintercalating threading agents, and suggests the idea of targeting such compounds specifically at four-way DNA junctions.
Resumo:
The IR, the ligand field spectra and the crystal structure of the mixed-ligand compound [(aquo)2,2P1 , a = 8.718(5), b = 9.407(5), c = 13.484 (7) Å, = 94.17(4)°, = 105.12(5)°, = 119.75(5)°, Z = 2, R = 0.0332, R W = 0.0869).
Resumo:
The Cannabis sativa herb contains over 100 phytocannabinoid (pCB) compounds and has been used for thousands of years for both recreational and medicinal purposes. In the past two decades, characterisation of the body's endogenous cannabinoid (CB) (endocannabinoid, eCB) system (ECS) has highlighted activation of central CB1 receptors by the major pCB, Δ9-tetrahydrocannabinol (Δ9-THC) as the primary mediator of the psychoactive, hyperphagic and some of the potentially therapeutic properties of ingested cannabis. Whilst Δ9-THC is the most prevalent and widely studied pCB, it is also the predominant psychotropic component of cannabis, a property that likely limits its widespread therapeutic use as an isolated agent. In this regard, research focus has recently widened to include other pCBs including cannabidiol (CBD), cannabigerol (CBG), Δ9tetrahydrocannabivarin (Δ9-THCV) and cannabidivarin (CBDV), some of which show potential as therapeutic agents in preclinical models of CNS disease. Moreover, it is becoming evident that these non-Δ9-THC pCBs act at a wide range of pharmacological targets, not solely limited to CB receptors. Disorders that could be targeted include epilepsy, neurodegenerative diseases, affective disorders and the central modulation of feeding behaviour. Here, we review pCB effects in preclinical models of CNS disease and, where available, clinical trial data that support therapeutic effects. Such developments may soon yield the first non-Δ9-THC pCB-based medicines.
Resumo:
One of the important goals of the intelligent buildings especially in commercial applications is not only to minimize the energy consumption but also to enhance the occupant’s comfort. However, most of current development in the intelligent buildings focuses on an implementation of the automatic building control systems that can support energy efficiency approach. The consideration of occupants’ preferences is not adequate. To improve occupant’s wellbeing and energy efficiency in intelligent environments, we develop four types of agent combined together to form a multi-agent system to control the intelligent buildings. Users’ preferential conflicts are discussed. Furthermore, a negotiation mechanism for conflict resolution, has been proposed in order to reach an agreement, and has been represented in syntax directed translation schemes for future implementation and testing. Keywords: conflict resolution, intelligent buildings, multi-agent systems (MAS), negotiation strategy, syntax directed translation schemes (SDTS).
Resumo:
PEGylated organosilica nanoparticles have been synthesized through self-condensation of (3-mercaptopropyl)trimethoxysilane in dimethyl sulfoxide into thiolated nanoparticles with their subsequent reaction with methoxypoly(ethylene glycol) maleimide. The PEGylated nanoparticles showed excellent colloidal stability over a wide range of pH in contrast to the parent thiolated nanoparticles, which have a tendency to aggregate irreversibly under acidic conditions (pH < 3.0). Due to the presence of a poly(ethylene glycol)-based corona, the PEGylated nanoparticles are capable of forming hydrogen-bonded interpolymer complexes with poly(acrylic acid) in aqueous solutions under acidic conditions, resulting in larger aggregates. The use of hydrogen-bonding interactions allows more efficient attachment of the nanoparticles to surfaces. The alternating deposition of PEGylated nanoparticles and poly(acrylic acid) on silicon wafer surfaces in a layer-by-layer fashion leads to multilayered coatings. The self-assembly of PEGylated nanoparticles with poly(acrylic acid) in aqueous solutions and at solid surfaces was compared to the behavior of linear poly(ethylene glycol). The nanoparticle system creates thicker layers than the poly(ethylene glycol), and a thicker layer is obtained on a poly(acrylic acid) surface than on a silica surface, because of the effects of hydrogen bonding. Some implications of these hydrogen-bonding-driven interactions between PEGylated nanoparticles and poly(acrylic acid) for pharmaceutical formulations are discussed.
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The cell catalysts calnexin (CNX) and protein-disulfide isomerase (PDI) cooperate in establishing the disulfide bonding of the HIV envelope (Env) glycoprotein. Following HIV binding to lymphocytes, cell-surface PDI also reduces Env to induce the fusogenic conformation. We sought to define the contact points between Env and these catalysts to illustrate their potential as therapeutic targets. In lysates of Env-expressing cells, 15% of the gp160 precursor, but not gp120, coprecipitated with CNX, whereas only 0.25% of gp160 and gp120 coprecipitated with PDI. Under in vitro conditions, which mimic the Env/PDI interaction during virus/cell contact, PDI readily associated with Env. The domains of Env interacting in cellulo with CNX or in vitro with PDI were then determined using anti-Env antibodies whose binding site was occluded by CNX or PDI. Antibodies against domains V1/V2, C2, and the C terminus of V3 did not bind CNX-associated Env, whereas those against C1, V1/V2, and the CD4-binding domain did not react with PDI-associated Env. In addition, a mixture of the latter antibodies interfered with PDI-mediated Env reduction. Thus, Env interacts with intracellular CNX and extracellular PDI via discrete, largely nonoverlapping, regions. The sites of interaction explain the mode of action of compounds that target these two catalysts and may enable the design of further new competitive agents.
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Polyvinylpyrrolidone is a widely used in tablet formulations with the linear form acting as a wetting agent and disintegrant whereas the cross-linked form is a super-disintegrant. We have previously reported that simply mixing the commercial cross-linked polymer with ibuprofen disrupted drug crystallinity with consequent improvements in drug dissolution behavior. In this study, we have designed and synthesized novel cross-linking agents containing a range of oligoether moieties which have then be polymerized with vinylpyrrolidone to generate a suite of novel excipients with enhanced hydrogen-bonding capabilities. The polymers have a porous surface and swell in most common solvents and in water; properties which suggest their value as disintegrants. The polymers were evaluated in simple physical mixtures with ibuprofen as a model poorly-water soluble drug. The results show that the novel PVPs induce the drug to become “X-ray amorphous”, which increased dissolution to a greater extent than that seen with commercial cross-linked PVP. The polymers stabilize the amorphous drug with no evidence for recrystallization seen after 20 weeks storage.
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In this paper I analyze the general equilibrium in a random Walrasian economy. Dependence among agents is introduced in the form of dependency neighborhoods. Under the uncertainty, an agent may fail to survive due to a meager endowment in a particular state (direct effect), as well as due to unfavorable equilibrium price system at which the value of the endowment falls short of the minimum needed for survival (indirect terms-of-trade effect). To illustrate the main result I compute the stochastic limit of equilibrium price and probability of survival of an agent in a large Cobb-Douglas economy.
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Two pentaaza macrocycles containing pyridine in the backbone, namely 3,6,9,12,18-pentaazabicyclo[12.3.1] octadeca-1(18),14,16-triene ([15]pyN(5)), and 3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca-1(19),15,17-triene ([16]pyN(5)), were synthesized in good yields. The acid-base behaviour of these compounds was studied by potentiometry at 298.2 K in aqueous solution and ionic strength 0.10 M in KNO3. The protonation sequence of [15]pyN(5) was investigated by H-1 NMR titration that also allowed the determination of protonation constants in D2O. Binding studies of the two ligands with Ca2+, Ni2+, Cu2+, Zn2+, Cd2+, and Pb2+ metal ions were performed under the same experimental conditions. The results showed that all the complexes formed with the 15-membered ligand, particularly those of Cu2+ and especially Ni2+, are thermodynamically more stable than with the larger macrocycle. Cyclic voltammetric data showed that the copper(II) complexes of the two macrocycles exhibited analogous behaviour, with a single quasi-reversible one-electron transfer reduction process assigned to the Cu(II)/Cu(I) couple. The UV-visible-near IR spectroscopic and magnetic moment data of the nickel(II) complexes in solution indicated a tetragonal distorted coordination geometry for the metal centre. X-band EPR spectra of the copper(II) complexes are consistent with distorted square pyramidal geometries. The crystal structure of [Cu([15]pyN(5))](2+) determined by X-ray diffraction showed the copper(II) centre coordinated to all five macrocyclic nitrogen donors in a distorted square pyramidal environment.
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Three new phenylmercury(II) and one mercury(II) dithiocarbamate complexes viz. PhHg S2CN(PyCH2) Bz (1), PhHg S2CN(PyCH2)CH3 (2), PhHg S2CN(Bz)CH3 (3), and [Hg (NCS2(PyCH2)Bz)(2)] (4) (Py = pyridine; Bz = benzyl) have been synthesized and characterized by elemental analyses, IR, electronic absorption, H-1 and C-13 NMR spectroscopy. The crystal structures of 1, 2 and 3 showed a linear S-Hg-C core at the centre of the molecule, in which the metal atom is bound to the sulfur atom of the dithiocarbamate ligand and a carbon atom of the aromatic ring. In contrast the crystal structure of 4 showed a linear S-Hg-S core at the Hg(II) centre of the molecule. Weak intermolecular Hg center dot center dot center dot N (Py) interactions link molecules into a linear chain in the case of 1, whereas chains of dimers are formed in 2 through intermolecular Hg center dot center dot center dot N (Py) and Hg center dot center dot center dot S interactions. 3 forms a conventional face-to-edge dimeric structure through intermolecular Hg center dot center dot center dot S secondary bonding and 4 forms a linear chain of dimers through face-to-face Hg center dot center dot center dot S secondary bonding. In order to elucidate the nature of these secondary bonding interactions and the electronic absorption spectra of the complexes, ab initio quantum chemical calculations at the MP2 level and density functional theory calculations were carried out for 1-3. Complexes 1 and 2 exhibited photoluminescent properties in the solid state as well as in the solution phase. Studies indicate that Hg center dot center dot center dot S interactions decrease and Hg center dot center dot center dot N interactions increase the chances of photoluminescence in the solid phase
Resumo:
The structures of 2-hydroxybenzamide(C7H7NO2) and 2-methoxybenzamide (C8H9NO2) have been determined in the gas-phase by electron diffraction using results from quantum chemical calculations to inform restraints used on the structural parameters. Theoretical methods (HF and MP2/6-311+G(d,p)) predict four stable conformers for both 2-hydroxybenzamide and 2-methoxybenzamide. For both compounds, evidence for intramolecular hydrogen bonding is presented. In 2-hydroxybenzamide, the observed hydrogen bonded fragment is between the hydroxyl and carbonyl groups, while in 2-methoxybenzamide, the hydrogen bonded fragment is between one of the hydrogen atoms of the amide group and the methoxy oxygen atom.