Effect of particle size on the dielectric behaviour of double propionates

Introduction Dicalcium strontium propionate (DCSP) undergoes a ferroelectric phase transition at about 28 1.5 K, with the spontaneous polarization occurring along the tetragonal C-axis.1 Takashige et al.2,3 have recently reported ferroelectricity in annealed samples of dicalcium lead propionate (DCLP) in the range 191 K to 331 K. The removal of the inner biasing field by annealing has been known in the case of DCLP3 and DCSP.4 Because of the possible dependence of the inner biasing field on the particle size, a study of the temperature dependence of the dielectric behaviour of the powdered samples of these compounds was undertaken.

2-[2-(Hydroxymethyl)phenyl]-1-phenylethanol

The title compound, C15H16O2, has a dihedral angle of 19.10 (5)degrees between the mean planes of the two benzene rings. There is an intramolecular O-H center dot center dot center dot O hydrogen bond and the C-C-C-C torsion angle across the bridge between the two rings is 173.13 (14)degrees. The molecules form intermolecular O-H center dot center dot center dot O hydrogen-bonded chains extending along the a axis. C-H center dot center dot center dot pi contacts are also observed between molecules within the chains.

On exact solutions of the unsteady navierstokes equationsâ the vortex with instantaneous curvilinear axis

The unsteady pseudo plane motions have been investigated in which each point of the parallel planes is subjected to non-torsional oscillations in their own plane and at any given instant the streamlines are concentric circles. Exact solutions are obtained and the form of the curve , the locus of the centers of these concentric circles, is discussed. The existence of three infinite sets of exact solutions, for the flow in the geometry of an orthogonal rheometer in which the above non-torsional oscillations are superposed on the disks, is established. Three cases arise according to whether is greater than, equal to or less than , where is angular velocity of the basic rotation and is the frequency of the superposed oscillations. For a symmetric solution of the flow these solutions reduce to a single unique solution. The nature of the curve is illustrated graphically by considering an example of the flow between coaxial rotating disks.

Factors influencing seasonal and monthly changes in the group size of chital or axis deer in southern India

Chital or axis deer (Axis axis) form fluid groups that change in size temporally and in relation to habitat. Predictions of hypotheses relating animal density, rainfall, habitat structure, and breeding seasonality, to changes in chital group size were assessed simultaneously using multiple regression models of monthly data collected over a 2 yr period in Guindy National Park, in southern India. Over 2,700 detections of chital groups were made during four seasons in three habitats (forest, scrubland and grassland). In scrubland and grassland, chital group size was positively related to animal density, which increased with rainfall. This suggests that in these habitats, chital density increases in relation to food availability, and group sizes increase due to higher encounter rate and fusion of groups. The density of chital in forest was inversely related to rainfall, but positively to the number of fruiting tree species and availability of fallen litter, their forage in this habitat. There was little change in mean group size in the forest, although chital density more than doubled during the dry season and summer. Dispersion of food items or the closed nature of the forest may preclude formation of larger groups. At low densities, group sizes in all three habitats were similar. Group sizes increased with chital density in scrubland and grassland, but more rapidly in the latter—leading to a positive relationship between openness and mean group size at higher densities. It is not clear, however, that this relationship is solely because of the influence of habitat structure. The rutting index (monthly percentage of adult males in hard antler) was positively related to mean group size in forest and scrubland, probably reflecting the increase in group size due to solitary males joining with females during the rut. The fission-fusion system of group formation in chital is thus interactively influenced by several factors. Aspects that need further study, such as interannual variability, are highlighted.

1,2,3-Trifluorobenzene

In the title compound, C6H3F3, weak electrostatic and dispersive forces between C(delta+)-F(delta-) and H(delta+)-C(delta-) groups are at the borderline of the hydrogen-bond phenomenon and are poorly directional and further deformed in the presence of pi-pi stacking interactions. The molecule lies on a twofold rotation axis. In the crystal structure, one-dimensional tapes are formed via two antidromic C-H center dot center dot center dot F hydrogen bonds. These tapes are, in turn, connected into corrugated two-dimensional sheets by bifurcated C-H center dot center dot center dot F hydrogen bonds. Packing in the third dimension is furnished by pi-pi stacking interactions with a centroid-centroid distance of 3.6362 (14) angstrom.

Suppression of the zero-order term in off-axis digital holography through nonlinear filtering

We present experimental validation of a new reconstruction method for off-axis digital holographic microscopy (DHM). This method effectively suppresses the object autocorrelation,namely, the zero-order term,from holographic data,thereby improving the reconstruction bandwidth of complex wavefronts. The algorithm is based on nonlinear filtering and can be applied to standard DHM setups with realistic recording conditions.We study the robustness of the technique under different experimental configurations,and quantitatively demonstrate its enhancement capabilities on phase signals.

Geometric Representation of Graphs in Low Dimension Using Axis Parallel Boxes

An axis-parallel k-dimensional box is a Cartesian product R-1 x R-2 x...x R-k where R-i (for 1 <= i <= k) is a closed interval of the form [a(i), b(i)] on the real line. For a graph G, its boxicity box(G) is the minimum dimension k, such that G is representable as the intersection graph of (axis-parallel) boxes in k-dimensional space. The concept of boxicity finds applications in various areas such as ecology, operations research etc. A number of NP-hard problems are either polynomial time solvable or have much better approximation ratio on low boxicity graphs. For example, the max-clique problem is polynomial time solvable on bounded boxicity graphs and the maximum independent set problem for boxicity d graphs, given a box representation, has a left perpendicular1 + 1/c log n right perpendicular(d-1) approximation ratio for any constant c >= 1 when d >= 2. In most cases, the first step usually is computing a low dimensional box representation of the given graph. Deciding whether the boxicity of a graph is at most 2 itself is NP-hard. We give an efficient randomized algorithm to construct a box representation of any graph G on n vertices in left perpendicular(Delta + 2) ln nright perpendicular dimensions, where Delta is the maximum degree of G. This algorithm implies that box(G) <= left perpendicular(Delta + 2) ln nright perpendicular for any graph G. Our bound is tight up to a factor of ln n. We also show that our randomized algorithm can be derandomized to get a polynomial time deterministic algorithm. Though our general upper bound is in terms of maximum degree Delta, we show that for almost all graphs on n vertices, their boxicity is O(d(av) ln n) where d(av) is the average degree.

Diethyl 4-(2,4-dichlorophenyl)-2,6-dimethyl 1,4-dihydropyridine-3,5-dicarboxylate

In the title compound, C19H21Cl2NO4, the dihydropyridine ring adopts a flattened boat conformation. The dichlorophenyl ring is oriented almost perpendicular to the planar part of the dihydropyridine ring [dihedral angle = 89.1 (1)degrees]. An intramolecular C-H center dot center dot center dot O hydrogen bond is observed. In the crystal structure, molecules are linked into chains along the b axis by N-H center dot center dot center dot O hydrogen bonds.

2-[2-(Hydroxymethyl)phenyl]-1-(1-naphthyl)ethanol

The molecular conformation of the title compound, C19H18O2, is stabilized by an intramolecular O-H-O hydrogen bond. In addition, intermolecular O-H-O interactions link the molecules into zigzag chains running along the c axis.

Bond graph model of doubly fed three phase induction motor using the Axis Rotator element for frame transformation

Induction motor is a typical member of a multi-domain, non-linear, high order dynamic system. For speed control a three phase induction motor is modelled as a d–q model where linearity is assumed and non-idealities are ignored. Approximation of the physical characteristic gives a simulated behaviour away from the natural behaviour. This paper proposes a bond graph model of an induction motor that can incorporate the non-linearities and non-idealities thereby resembling the physical system more closely. The model is validated by applying the linearity and idealities constraints which shows that the conventional ‘abc’ model is a special case of the proposed generalised model.

Off-axis field approximations for ion traps with apertures

In recent work (Int. J. Mass Spec., vol. 282, pp. 112–122) we have considered the effect of apertures on the fields inside rf traps at points on the trap axis. We now complement and complete that work by considering off-axis fields in axially symmetric (referred to as “3D”) and in two dimensional (“2D”) ion traps whose electrodes have apertures, i.e., holes in 3D and slits in 2D. Our approximation has two parts. The first, EnoAperture, is the field obtained numerically for the trap under study with apertures artificially closed. We have used the boundary element method (BEM) for obtaining this field. The second part, EdueToAperture, is an analytical expression for the field contribution of the aperture. In EdueToAperture, aperture size is a free parameter. A key element in our approximation is the electrostatic field near an infinite thin plate with an aperture, and with different constant-valued far field intensities on either side. Compact expressions for this field can be found using separation of variables, wherein the choice of coordinate system is crucial. This field is, in turn, used four times within our trap-specific approximation. The off-axis field expressions for the 3D geometries were tested on the quadrupole ion trap (QIT) and the cylindrical ion trap (CIT), and the corresponding expressions for the 2D geometries were tested on the linear ion trap (LIT) and the rectilinear ion trap (RIT). For each geometry, we have considered apertures which are 10%, 30%, and 50% of the trap dimension. We have found that our analytical correction term EdueToAperture, though based on a classical small-aperture approximation, gives good results even for relatively large apertures.

1-[(2-Chloro-7-methyl-3-quinolyl)methyl]pyridin-2(1H)-one

In the title compound, C16H13ClN2O, the quinoline ring system is essentially planar, with a maximum deviation of 0.021 (2) angstrom. The pyridone ring is oriented at a dihedral angle of 85.93 (6)degrees with respect to the quinoline ring system. In the crystal structure, intermolecular C-H center dot center dot center dot O hydrogen bonds link the molecules along the b axis. Weak pi-pi stacking interactions [centroid-centroid distances = 3.7218 (9) and 3.6083 (9) angstrom] are also observed.

The oscillation of a spheroid along its axis in a non-Newtonian fluid

The present paper investigates the nature of the fluid flow when a spheroid is suspended in an infinitely extending elastico-viscous fluid defined by the constitutive equations given by Oldroyd or Rivlin and Ericksen, and is made to perform small amplitude oscillations along its axis. The solution of the vector wave equation is expressed in terms of the solution of the corresponding scalar wave equation, without the use of Heine's function or spheroidal wave functions. Two special cases (i) a sphere and (ii) a spheroid of small ellipticity, are studied in detail.

1-[(2-Chloro-3-quinolyl)methyl]indoline-2,3-dione

In the title compound, C18H11ClN2O2, the isatin and 2-chloro-3-methylquinoline units are both almost planar, with r.m.s.deviations of 0.0075 and 0.0086 angstrom, respectively, and the dihedral angle between the mean planes of the two units is 83.13 (7)degrees. In the crystal, a weak intermolecular C-H center dot center dot center dot O interaction links the molecules into chains along the c axis.

5-(4-Chlorophenyl)-3-(2,4-dimethylthiazol-5-yl)-1,2,4-triazolo[3,4-a]isoquinoline

In the title molecule, C21H15ClN4S, the triazoloisoquinoline ring system is approximately planar, with an r.m.s. deviation of 0.054 (2) angstrom and a maximum deviation of 0.098 (2) angstrom from the mean plane for the triazole ring C atom that is bonded to the thiazole ring. The thiazole and benzene rings are twisted by 66.36 (7) and 56.32 (7)degrees respectively, with respect to the mean plane of the triazoloisoquinoline ring system. In the crystal structure, molecules are linked by intermolecular C-H center dot center dot center dot N interactions along the a axis. The molecular conformation is stabilized by a weak intramolecular pi-pi interaction involving the thiazole and benzene rings, with a centroid-centroid distance of 3.6546 (11) angstrom . In addition, two other intermolecular pi-pi stacking interactions are observed, between the triazole and benzene rings and between the dihydropyridine and benzene rings [centroid-centroid distances = 3.6489 (11) and 3.5967 (10) angstrom, respectively].