Evidence from adiabatic scanning calorimetry for the Halperin-Lubensky-Ma effect at the N-SmA phase transitions in mixtures of 7OCB+heptane with an injected SmA phase

The high-resolution adiabatic scanning calorimetric technique has been used to investigate the nematic-smectic A transition (N-SmA in binary mixtures of the non-smectogenic liquid crystal heptyloxycyanobiphenyl (7OCB) and heptane, exhibiting a so-called injected smectic A phase. With the exception of a mixture with the lowest heptane mole fraction for which only an upper limit of 0.2 ± 0.2 J kg(-1) for a possible latent heat could be obtained, for all other mixtures finite latent heats were obtained. The mole fraction dependence of the latent heat could be well fitted with a crossover function consistent with a mean-field free energy expression with a non-zero cubic term arising from the Halperin-Lubensky-Ma (HLM) coupling between the SmA order parameter and the orientational director fluctuations. The mole fraction dependence of the heat capacity effective critical exponents is similar to that observed in mixtures of the two liquid crystals octyloxycyanobiphenyl (8OCB) and nonylcyanobiphenyl (9OCB). The thermal behavior observed along the N-SmA phase transition line yields further strong evidence for the HLM coupling effect.     

Investigation of annealing effects on the structural, magnetic and transport properties of Co/GaAs(0 0 1) thin films

Present paper deals with the structural, magnetic and transport studies of as-deposited as well as annealed Co/GaAs(0 0 1) thin film at different temperatures. The X-ray diffraction measurements show oriented growth of as-deposited Co film in the hcp (0 0 2) direction. However, the sample annealed at higher temperatures shows formation of ternary Co₂GaAs phase at the interface. Corresponding magnetic and transport measurements show decrement in magnetization and resistivity with annealing temperatures. The observed reductions in magnetization and resistivity values are mainly attributed to the formation of ternary Co₂GaAs phase at the interface.     

Synthesis and structural characterization of a (N,N′-bis[2(S)-pyrrolidylmethyl]-propane-1,3-diamine) nickel (II) complex

The nickel(II) complex [Ni(C₄H₃NCH=N–(CH₂)₃–N=CHC₄H₃N)], (1) containing the symmetrical N₄ tetradentate Schiff base ligand, which is the 2:1 condensation product of pyrrole-2-carboxaldehyde and 1,3-diaminopropane respectively, was prepared. Structural investigation shows that it is monomeric, having space group P2₁/c, a = 7.989(7), b = 17.406(14), c = 9.193(5) Å, = 90, = 100.39(6), = 90, and Z = 4. The coordination geometry around the nickel atom is slightly distorted square planar and the conformation of the six-membered ring containing the metal,azomethine nitrogens and three carbon atoms of the connecting 1,3-diaminopropane is a symmetric boat.     

Velocity-dependent inertial induction—possible explanation for supergravity shift at solar limb

A quantitative model of inertial induction has been earlier proposed by the author which not only results in the exact equivalence of inertial and gravitational masses but also gives rise to an exceedingly small drag dependent on the velocity with respect to the mean rest frame of the universe. This leads to a cosmological redshift in close agreement with the observation. When this velocity drag due to local interaction is considered it is seen that a significant proportion of the secular retardation of the earth’s spin and the moon’s orbital motion can be attributed to this drag. This also resolves the problem of the moon’s close approach to the earth in the past as suggested by a purely tidal friction theory. The observed large secular acceleration of the Phobos is also explained. The present article shows that local interaction also yields a redshift. When applied to the solar radiation it is seen that the observed supergravity shift at the limb can be very satisfactorily explained.     

Angular heterocycles. A convenient synthesis of 6-N-(acetylanilino)-5H-benzo[a]phenothiazin-5-one, 6-N-(acetylanilino)-5H-benzo[a]phenoxazin-5-ones and their derivatives

The reaction of 2-N-(acetylanilino)-3-chloro-1,4-naphthoquinone ( 2 ) with bifunctional aromatic amines afforded angular heterocycles 6 and 7 . Reductive acetylation of 7 provided o-acyl 9 and O,N-diacyl 10 derivatives depending upon the reaction conditions. The ir, uv, pmr and mass spectral data are also presented.     

A new Cu(II) three-dimensional network with 4,4′-oxybis benzoic acid: structural diversity,EPR, and magnetism

The copper derivative {[Cu₄(oba)₄(H₂O)₄]?H₂O}_n (1) has been hydro(solvo)thermally synthesized by combining flexible 4,4′-oxybis benzoic acid (oba) and divalent copper nitrate. As a result of the potential coordination modes of carboxylate oxygens from the oba ligand, the aforementioned complex leads to the formation of an interesting 3D framework, as evidenced by single-crystal X-ray diffractometry. Concerning the topology in 1, the dimers [Cu₂C₄O₈] are nodes of a 5-fold 4-connected uninodal net of the type lvt, with point symbol {4².8⁴} and vertex symbol [4.4.8₄.8₄.8₈.8₈]. The encapsulation of the copper coordination polymer displays a moderate luminescent property. On temperature-dependent magnetic study, it reveals that the magnetic behaviour of 1 can be associated to a strong antiferromagnetic coupling between the two Cu(II) ions.     

Transition metal catalyzed asymmetric cyclopropanation via diazo decomposition: Ligand architecture defining stereoselectivity

Asymmetric cyclopropanation of alkenes through diazo decomposition mediated by transition metal complexes is a widely investigated catalytic reaction to obtain cyclopropanes where high enantioselectivity is achieved by optimizing metal–ligand combination. Instead of a chronological listing of developments, this review illustrates the existing literature data according to the structural types of ligands in catalytic complexes and attempts to correlate substrate structure and selectivity with ligand design.     

High level ab initio study of the structure and vibrational spectra of HO(2)NO(2)

A high-level ab initio study has been performed on the conformational structure and vibrational spectra of HO(2)NO(2). Calculations carried out with coupled-cluster methods using a series of Pople and Dunning basis sets reveal that there is a significant basis set dependence on the predicted ab initio structure. Higher angular momentum basis sets are shown to be necessary in order to bring the calculated structure into agreement with experimental rotational constants. Harmonic vibrational frequencies of HO(2)NO(2) are computed at the CCSD(T)/aug-cc-pVTZ level of theory while the corresponding vibrational anharmonicities are calculated at the MP2/cc-pVTZ level. In addition, the absorption cross sections of OH stretching overtones in HO(2)NO(2) are calculated using a dipole function computed at the QCISD level of theory and found to be in good agreement with the available experimental data.     

Nicotinamidoxime as an analytical reagent

Summary Cobalt(II) gives a deep blue colour with nicotinamidoxime in alkaline aqueous-ethylalcoholic medium which has been used with advantage for the spectrophotometric determination of this metal. The optimum p_H for the development of colour is 9.8–11.3 in aqueous-alcoholic (40% v./v.) medium in presence of a large excess of the reagent, at 15–40°C. The colour intensity is measured at 580 m,. Sensitivity is 0.01 g cobalt per cm², while visual identification limit is 0.5 g cobalt per ml (12·10⁶). Beer's law is obeyed in the range of 0.2–20 ppm of the metal, with an optimum range of 2–16 ppm. The colour is stable for about half an hour in the p_N range of 9.8–11.3 and at least one hour in the range of 10.5 to 11.0. On account of the high p_N and alcoholic medium used, most of the cations and anions interfere and, hence, must be removed.Part I: See Z. anal. Chem. 168, 326 (1959).     

Chemical and structural effects on the electronic transport in organic single crystals

Effects induced by chemical and structural inhomogeneities on the electronic transport in organic crystals with the focus on highly-ordered polyacenes are discussed in this paper. The material class chosen is of great importance as polyacenes are widely studied with perspectives on applications in thin film devices. As will be shown, the charge carrier mobility in these long-range ordered molecular systems is limited by chemical impurities rather than by structural inhomogeneities. Time-of-flight spectroscopy on polyacenes purified by zone-refinement does not only show coherent carrier movement for holes but also for electrons, which is rarely observed for compounds that can be purified by sublimation only. Finally, we will present a direct comparison between the chemical species and their amount on the surface and in the volume of tetracene crystals. The significantly higher impurity concentration at the surfaces is relevant for the mobility estimated by field-effect transistor (FET) studies on single crystals in planar-geometry.