Synthesis, Structure, and Magnetic Properties of Amine-Templated Transition-Metal Phosphites

Transition-metal phosphites of cobalt and vanadium, [C4N2H12][Co(HPO3)(2)] (I), [C4N2H14][Co(HPO3)(2)] (II), [Co[C4H8N12)(H2PO3)(2)] (III),[C4N2H14][(VF)-F-III(HPO3)(2)]center dot H2O (IV), and[C3N2H5](2)[V-4(III)(H2O)(3)(HPO3)(4)(HPO4)(3)] (V), have been synthesized and characterized. Organophosphorus esters were employed to stabilize cobalt in tetrahedral coordination and also to prepare the low-dimensional structures, which are otherwise difficult to synthesize. The structures have one- (I, II, IV), two- (III) and three-dimensionally (V) extended networks built up by the linking of metal polyhedra and phosphite units. Another vanadyl phosphite, [C2N2H10][((VO)-O-IV)(3)(H2O) (HPO3)(4)]center dot H2O,([15]) was also prepared and investigated extensively by ESR, magnetic susceptibility, and other studies. All the compounds in the present study exhibit antiferromagnetic interactions. Well-established magnetic models have been used to fit the experimental data. The compounds havealso been characterized in detail by using UV/Vis spectroscopic studies.

On self-interacting oligoribonucleotides. I. Absorption and optical rotatory dispersion of 2′-5′- and 3′-5′-oligoguanylic acids

A series of 2′-5′-oligoguanylic acids are prepared by reacting G(cyclic)p with takadiastase T1 ribonuclease and separating the products chromatographically. The 3′-5′-oligoguanylic acids are obtained by separating the products of alkaline degradation of 3′-5′-poly(G). The optical rotatory dispersion and hypochromism of both 2′-5′- and 3′-5′-oligoguanylic acids are studied at two different pH. The optical rotatory dispersion spectrum of 2′-5′-GpG is significantly different from that of 3′-5′-GpG. The magnitude of rotation of the long-wavelength peak of 2′-5′-GpG is larger than that of 3′-5′-GpG. This finding contradicts the explanation that the extra stability and more intense circular dichroism band of other 3′-5′-dinucleoside monophosphates is due to H-bond formation between 2′-OH and either the base or the phosphate oxygen. The end phosphate group has a marked effect on the spectrum of GpG between 230 and 250 mμ. In addition the optical rotatory dispersion spectra of 2′-5′ exhibit strong pH, temperature, and solvent dependence between 230 and 250 mμ. ΔH and AS for order ⇌ disorder transition is estimated to be 9.7 kcal/mole and 35.2 eu, respectively. The optical rotatory dispersion spectra of guanine-rich oligoribonucleotides, GpGpC, GpGpU, GpGpGpC, and GpGpGpU are compared to the calculated optical rotatory dispersion from the semiempirical expression of Cantor and Tinoco, using measured optical rotatory dispersion of dimers. Contrary to previous studies, agreement is found not at all satisfactory. However, optical rotatory dispersion of 3′-5′-GpGpGpC and GpGpGpU can be estimated from the semiempirical expression, if a next-nearest interaction parameter is introduced empirically. Such interaction parameter can be calculated from the measured properties of trinucleotide sequences like GpGpG, GpGpC, and GpGpU, assuming that only the nearest-neighbor interaction is important. The optical rotatory dispersion of single-stranded poly(G) is also predicted. The importance of syn-anti equilibrium and next-nearest-neighbor interaction in oligoguanylic acids is suggested as a probable explanation.

Transition metal complexes of 3-aryl-2-substituted 1,2-dihydroquinazolin-4(3H)-one derivatives: New class of analgesic and anti-inflammatory agents

Five-coordinate, neutral transition metal complexes of newly designed pyridine-2-ethyl-(3-carboxyhdeneamino)-3-(2-phenyl)-1,2-dihydroquinazoli n-4(3H)-one (L) were synthesized and characterized The structure of ligand is confirmed by single crystal X-ray diffraction studies The compounds were evaluated for the anti-inflammatory activity by carrageenan-induced rat paw edema model while their analgesic activity was determined by acetic acid-induced writhing test in mice wherein the transition metal complexes were found to be more active than the free ligand (C) 2010 Elsevier Masson SAS All rights reserved.

Insulator-metal transition

A theory of the insulator-metal transition in transition-metal compounds is developed in terms of the collapse of the effective energy gap which is a function of the thermally excited electron-hole pairs. This dependence is shown to arise from the hole-lattice interaction. The reaction of the lattice is found to be equivalent to generating an internal positive pressure (strain). Estimates show that the observed typical behaviour of the conductivity jump and the change of volume at the transition temperature can be explained by the present theory.

Charge-order driven multiferroic and magneto-dielectric properties of rare earth manganates

Charge-order driven magnetic ferroelectricity is shown to occur in several rare earth manganates of the general formula, Ln(1-x)A(x)MnO(3) (In = rare earth, A = alkaline earth). Charge-ordered manganates exhibit dielectric constant anomalies around the charge-ordering or the antiferromagnetic transition temperature. Magnetic fields have a marked effect on the dielectric properties of these compounds, indicating the presence of coupling between the magnetic and electrical order parameters. Magneto-dielectric properties are retained in small particles of the manganates. The observation of magneto-ferroelectricity in these manganates is in accordance with theoretical predictions.

Charge-order driven multiferroic and magneto-dielectric properties of rare earth manganates

Charge-order driven magnetic ferroelectricity is shown to occur in several rare earth manganates of the general formula, Ln(1-x)A(x)MnO(3) (In = rare earth, A = alkaline earth). Charge-ordered manganates exhibit dielectric constant anomalies around the charge-ordering or the antiferromagnetic transition temperature. Magnetic fields have a marked effect on the dielectric properties of these compounds, indicating the presence of coupling between the magnetic and electrical order parameters. Magneto-dielectric properties are retained in small particles of the manganates. The observation of magneto-ferroelectricity in these manganates is in accordance with theoretical predictions.

The Finnish Leadership Style in Transition - A Study of Leadership Criteria in the Insurance Business, 1997-2004 (summary section only)

The aim of the study was to explore the importance of evaluating leadership criteria in Finland at leader/subordinate levels of the insurance industry. The overall purpose of the thesis is tackled and analyzed from two different perspectives: - by examining the importance of the leadership criteria and style of Finnish insurance business leaders and their subordinates - by examining the opinions of insurance business leaders regarding leadership criteria in two culturally different countries: the US and Finland. This thesis consists of three published articles that scrutinise the focal phenomena both theoretically and empirically. The main results of the study do not lend support to the existence of a universal model of leadership criteria in the insurance business. As a matter of fact, the possible model seems to be based more on the special organizational and cultural circumstances of the country in question. The leadership criteria seem to be quite stable irrespective of the comparatively short research time period (3–5 years) and hierarchical level (subordinate/leader). Leaders have major difficulties in changing their leadership style. In fact, in order to bring about an efficient organizational change in the company you have to alternate the leader. The cultural dimensions (cooperation and monitoring) identified by Finnish subordinates were mostly in line with those of their managers, whilst emphasizing more the aspect of monitoring employees, which could be seen from their point of view as another element of managers’ optimizing/efficiency requirements. In Finnish surveys the strong emphasis on cooperation and mutual trust become apparent by both subordinates and managers. The basic problem is still how to emphasize and balance them in real life in such a way that both parties are happy to work together on a common basis. The American surveys suggests hypothetically that in a soft market period (buyer’s market) managers employ a more relationship-oriented leadership style and correspondingly adapt their leadership style to a more task-oriented approach in a hard market phase (seller’s market). In making business better Finnish insurance managers could probably concentrate more on task-oriented items such as reviewing, budgeting, monitoring and goal-orientation. The study also suggests that the social safety net of the European welfare state ideology has so far shielded the culture-specific sense of social responsibility of Finnish managers from the hazards of free competition and globalization.

Power and Distribution Network Structure in the People's Republic of China - The Case of an Inland City in Transition

The aim of the current study is to examine the influence of the channel external environment on power, and the effect of power on the distribution network structure within the People’s Republic of China. Throughout the study a dual research process was applied. The theory was constructed by elaborating the main theoretical premises of the study, the channel power theories, the political economy framework and the distribution network structure, but these marketing channel concepts were expanded with other perspectives from other disciplines. The main method applied was a survey conducted among 164 Chinese retailers, complemented by interviews, photographs, observations and census data from the field. This multi-method approach enabled not only to validate and triangulate the quantitative results, but to uncover serendipitous findings as well. The theoretical contribution of the current study to the theory of marketing channels power is the different view it takes on power. First, earlier power studies have taken the producer perspective, whereas the current study also includes a distributor perspective to the discussion. Second, many power studies have dealt with strongly dependent relationships, whereas the current study examines loosely dependent relationships. Power is dependent on unequal distribution of resources rather than based on high dependency. The benefit of this view is in realising that power resources and power strategies are separate concepts. The empirical material of the current study confirmed that at least some resources were significantly related to power strategies. The study showed that the dimension resources composed of technology, know-how and knowledge, managerial freedom and reputation was significantly related to non-coercive power. Third, the notion of different outcomes of power is a contribution of this study to the channels power theory even though not confirmed by the empirical results. Fourth, it was proposed that channel external environment other than the resources would also contribute to the channel power. These propositions were partially supported thus providing only partial contribution to the channel power theory. Finally, power was equally distributed among the different types of actors. The findings from the qualitative data suggest that different types of retailers can be classified according to the meaning the actors put into their business. Some are more business oriented, for others retailing is the only way to earn a living. The findings also suggest that in some actors both retailing and wholesaling functions emerge, and this has implications for the marketing channels structure.

Stability and transition in the flow of polymer solutions

The linear stability analysis of a plane Couette flow of viscoelastic fluid have been studied with the emphasis on two dimensional disturbances with wave number k similar to Re-1/2, where Re is Reynolds number based on maximum velocity and channel width. We employ three models to represent the dilute polymer solution: the classical Oldroyd-B model, the Oldroyd-B model with artificial diffusivity and the non-homogeneous polymer model. The result of the linear stability analysis is found to be sensitive to the polymer model used. While the plane Couette flow is found to be stable to infinitesimal disturbances for the first two models, the last one exhibits a linear instability.

Stress induced phase transition in monomolecular perfluroalkylsilane film self assembled on aluminium surface

We control the stiffnesses of two dual double cantelevers placed in series to control penetration into a perflurooctyltrichlorosilane monolayer self assembled on aluminium and silicon substrates. The top cantilever which carries the probe is displaced with respect to the bottom cantilever which carries the substrate, the difference in displacement recorded using capacitors gives penetration. We further modulate the input displacement sinusoidally to deconvolute the viscoelastic properties of the monolayer. When the intervention is limited to the terminal end of the molecule there is a strong viscous response in consonance with the ability of the molecule to dissipate energy by the generation of gauche defects freely. When the intervention reaches the backbone, at a contact mean pressure of 0.2GPa the damping disappears abruptly and the molecule registers a steep rise in elastic modulus and relaxation time constant, with increasing contact pressure. We offer a physical explanation of the process and describe this change as due to a phase transition from a liquid like to a solid like state.

Electronic phase separation in correlated oxides: The phenomenon, its present status and future prospects

Many transition metal oxide materials of high chemical purity are not necessarily monophasic. Thus, single crystals of chemically pure rare earth manganites and cobaltates of the general formula Ln1-xAxMO3 (Ln=rare earth metal, A=alkaline earth metal, M=Mn, Co) exhibit the phenomenon of electronic phase separation wherein phases of different electronic and magnetic properties coexist. Such phase separation, the length scale of which can vary anywhere between a few nanometers to microns, gives distinct signatures in X-ray and neutron diffraction patterns, electrical and magnetic properties, as well as in NMR and other spectroscopies. While the probe one employs to investigate electronic phase separation depends on the length scale, it is noteworthy that direct imaging of the inhomogeneities has been accomplished. Some understanding of this phenomenon has been possible on the basis of some of the theoretical models, but we are far from unraveling the varied aspects of this new phenomenon. Herein, we present the highlights of experimental techniques and theoretical approaches, and comment on the future outlook for this fascinating phenomenon

Magnetization and magnetoresistive response of LiMn2O4 near the charge ordering transition

We report magnetization and magnetoresistance studies of the geometrically frustrated spinel compound LiMn2O4 near its charge ordering temperature. The effect of a 7 T magnetic field is to very slightly shift the transition in the resistivity to lower temperatures resulting in large negative magnetoresistance with significant hysteresis. This hysteresis is not reflected in the magnetization. These observations are compared with what is found in the colossal magnetoresistance and charge ordering perovskite manganese oxides. The manner in which geometric frustration influences the coupling of charge and spin degrees of freedom is examined.