In vivo positive contrast IRON sequence and quantitative T2* measurement confirms inflammatory burden in a patient with asymptomatic carotid atheroma after USPIO-enhanced MR Imaging

The authors report an in vivo human examination of carotid atheroma by using the inversion-recovery ON resonance (IRON) sequence, which is able to produce positive contrast after the infusion of an ultrasmall super paramagnetic iron oxide (USPIO) contrast medium. This technique provides a method of potentially identifying inflammatory burden within carotid atheroma. This may be particularly useful in patients who currently do not meet criteria for intervention (ie, moderate symptomatic stenosis or <70% asymptomatic stenosis) to further risk-stratify this important patient cohort. A 63-year-old man was imaged at 1.5 T before and 36 hours after USPIO infusion by using the IRON sequence. Regions of interest showing profound signal loss at T2*-weighted imaging corresponded well with regions of positive contrast at IRON imaging after the administration of USPIO. These regions also showed a profound decrease in T2* measurements after USPIO infusion, whereas surrounding tissue did not. It has been shown that such strong signal loss on T2*-weighted images after USPIO infusion is indicative of USPIO uptake.

Characterisation of k-Variegated Graphs, k greater-than-or-equal-to 3

A graph is said to be k-variegated if its vertex set can be partitioned into k equal parts such that each vertex is adjacent to exactly one vertex from every other part not containing it. Bednarek and Sanders [1] posed the problem of characterizing k-variegated graphs. V.N. Bhat-Nayak, S.A. Choudum and R.N. Naik [2] gave the characterization of 2-variegated graphs. In this paper we characterize k-variegated graphs for k greater-or-equal, slanted 3.

Conformational transitions in a Pro-Pro peptide on dissolution of single crystals

The peptide t-butyloxycarbonyl-α-aminoisobutyryl-L-prolyl-L-prolyl-N-methylamide has been shown to adopt an extended structure in the solid state. The Pro-Pro segment occurs in the poly-proline II conformation. On dissolution of single crystals at not, vert, similar 233°K, a single species corresponding to the all Image peptide backbone is observed by 270 MHz 1H NMR. On warming, Image to Image isomerization about the Pro-Pro bond is facilitated. Both Image (ψ not, vert, similar−50°) and Image (ψ not, vert, similar 130°) rotamers about the Pro3 Cα---CO bond are detectable in the Pro-Pro Image conformer, at low temperature. These observations demonstrate unambiguously the large differences in the solid state and solution conformations of a Pro-Pro sequence.

Relative Stabilities of Layered Perovskite and Pyrochlore Structures in Transition Metal-Oxides Containing Trivalent Bismuth

In order to investigate the factors determining the relative stabilities of layered perovskite and pyrochlore structures of transition metal oxides containing trivalent bismuth, several ternary and quaternary oxides have been investigated. While d0 cations stabilize the layered perovskite structure, cations containing partially-filled d orbitals (which suppress ferroelectric distortion of MO6 octahedra) seem to favor pyrochlore-related structures. Thus, the vanadium analogue of the layered perovskite Bi4Ti3O12 cannot be prepared; instead the composition consists of a mixture of pyrochlore-type Bi1.33V2O6, Bi2O3, and Bi metal. The distortion of Bi1.33V2O6 to orthorhombic symmetry is probably due to an ordering of anion vacancies in the pyrochlore structure. None of the other pyrochlores investigated, Bi2NbCrO7, Bi2NbFeO7, TlBiM2O7 (M = Nb, Ta), shows evidence for cation ordering in the X-Ray diffraction patterns, as indeed established by structure refinement of TlBiNb2O7.

Theoretical-Studies on the Modes of Binding of Some of the Beta-Glycosidically Linked Glucobioses to Concanavalin-A

The probable modes of binding for methyl-α-d-sophoroside, methyl-β-d-sophoroside, laminariboise and cellobiose to concanavalin A have been determined using theoretical methods. Methyl-d-sophorosides can bind to concanavalin A in two modes, i.e. by placing their reducing as well as non-reducing sugar units in the carbohydrate specific binding site, whereas laminaribiose and cellobiose can reach the binding site only with their non-reducing glucose units. However, the probability for methyl-α-d-sophoroside to bind to concanavalin A with its reducing sugar residue as the occupant of the binding site is much higher than it is with its non-reducing sugar residue as the occupant of the sugar binding site. A few of the probable conformers of methyl-β-d-sophoroside can bind to concanavalin A with either the reducing or non-reducing glucose unit. Higher energy conformers of cellobiose or laminaribiose can reach the binding site with their non-reducing residues alone. The relative differences in the binding affinities of these disaccharides are mainly due to the differences in the availability of proper conformers which can reach the binding site and to non-covalent interactions between the sugar and the protein. This study also suggests that though the sugar binding site of concanavalin A accommodates a single sugar residue, the residue outwards from the binding site also interacts with concanavalin A, indicating the existence of extended concanavalin A carbohydrate interactions.

Stability Of Large Damped Flexible Spacecraft With Stored Angular Momentum

Vibrational stability of large flexible structurally damped spacecraft carrying internal angular momentum and undergoing large rigid body rotations is analysed modeling the systems as elastic continua. Initially, analytical solutions to the motion of rigid gyrostats under torque-free conditions are developed. The solutions to the gyrostats modeled as axisymmetric and triaxial spacecraft carrying three and two constant speed momentum wheels, respectively, with spin axes aligned with body principal axes are shown to be complicated. These represent extensions of solutions for simpler cases existing in the literature. Using these solutions and modal analysis, the vibrational equations are reduced to linear ordinary differential equations. Equations with periodically varying coefficients are analysed applying Floquet theory. Study of a few typical beam- and plate-like spacecraft configurations indicate that the introduction of a single reaction wheel into an axisymmetric satellite does not alter the stability criterion. However, introduction of constant speed rotors deteriorates vibrational stability. Effects of structural damping and vehicle inertia ratio are also studied.

Complexes of lanthanide perchlorates with the open-chain pentadentate ligand n,n,$n^{'},n^{'}$-tetramethyl-3,6,9-trioxaundecane diamide

Complexes of lanthanide perchlorates with the ligand N,N,N,N-tetra-methyl-3,6,9-trioxaundecane diamide (TUD) of the composition Ln(TUD)2-(ClO4)3 (Ln triple bond; length as m-dash La, Nd, Ho, Er, Y) were isolated. Electrical conductivity values indicate that all the perchlorate groups are ionic. IR and nuclear magnetic resonance (1H and 13C) data prove that the ligand coordinates to the metal via the three ether oxygens and the two carbonyl oxygens. A probable coordination number of ten can be assigned for all the complexes.

MHD Flow of a 2nd Grade Fluid in an Orthogonal Rheometer

The magnetohydrodynamics (MHD) flow of a conducting, homogeneous incompressible Rivlin-Ericksen fluid of second grade contained between two infinite, parallel, insulated disks rotating with the same angular velocity about two noncoincident axes, under the application of a uniform transverse magnetic field, is investigated. This model represents the MHD flow of the fluid in the instrument called an orthogonal rheometer, except for the fact that in the rheometer the rotating plates are necessarily finite. An exact solution of the governing equations of motion is presented. The force components in the x and y directions on the disks are calculated. The effects of magnetic field and the viscoelastic parameter on the forces are discussed in detail.

Crystal structures of 1,4-diaza bicyclo[2.2.2.]octane and N,N-dimethyl formamide adducts of copper acetate

The crystal structures of copper acetate adducts with 1,4-diaza bicyclo [2.2.2.]octane and N,N-dimethyl formamide are shown to be dimeric with Cu---Cu distances of 2.633 Å and 2.616 Å respectively.

DSC studies on the phase transformation of hydrazonium sulfate

The high temperature phase transformation of hydrazonium sulfate, N2H6SO4 has been studied using DSC. The enthalpy of phase transition is found to be 3.63 ± 0.1 kJ mole−1. The phase transition temperature is found to decrease with the increase of particle size. It appears that the strain energy and not surface energy, is responsible for the phase transformation. The molar volume of the salt increases during the transformation as found by the dilatometric experiment involving percentage of linear thermal expansion. On cooling, the transformation from the high temperature modification to orthorhombic form is incomplete and extends over a wide range of temperature.

Compressible boundary-layer flow at a three-dimensional stagnation point with massive blowing

The effect of massive blowing rates on the steady laminar compressible boundary-layer flow with variable gas properties at a 3-dim. stagnation point (which includes both nodal and saddle points of attachment) has been studied. The equations governing the flow have been solved numerically using an implicit finite-difference scheme in combination with the quasilinearization technique for nodal points of attachment but employing a parametric differentiation technique instead of quasilinearization for saddle points of attachment. It is found that the effect of massive blowing rates is to move the viscous layer away from the surface. The effect of the variation of the density- viscosity product across the boundary layer is found to be negligible for massive blowing rates but significant for moderate blowing rates. The velocity profiles in the transverse direction for saddle points of attachment in the presence of massive blowing show both the reverse flow as well as velocity overshoot.

Space and time efficiency of the forest-of-quadtrees representation

A forest of quadtrees is a refinement of a quadtree data structure that is used to represent planar regions. A forest of quadtrees provides space savings over regular quadtrees by concentrating vital information. The paper presents some of the properties of a forest of quadtrees and studies the storage requirements for the case in which a single 2m × 2m region is equally likely to occur in any position within a 2n × 2n image. Space and time efficiency are investigated for the forest-of-quadtrees representation as compared with the quadtree representation for various cases.

Cluster model of the glass transition

A cluster model of the glass transition has been developed, treating the relative size of the cluster as an order parameter. The model accounts for some of the features of the glass transition.

Mechanism of coupling periodate-oxidized nucleosides to proteins

This paper describes a mechanism of coupling periodate-oxidized nucleosides to proteins. Each of the dialdehyde groups of a periodate-oxidized nucleoside is shown to couple to lysine residues on different protein molecules through Schiff bases, thereby cross-linking different protein molecules, forming a polymer. This is in contrast to the previous model in which nucleosides were suggested to couple to proteins through a morpholine structure. The cross-linked structure of the nucleoside-antigen, significantly different when compared to the native protein, may affect the specificity and the efficiency of antibody production.

On the variety of electron diffraction patterns from quasicrystals

A new exciting era in the study of rapidly solidified alloys has been ushered in by the discovery of a quasicrystalline phase in an Al-1O%Mn alloy by Shechtman et al. (l). The fact that a quasicrystal diffracts electrons and X-rays like a single crystal provides a powerful approach for exploring the atomic configuration in these alloys. Shechtman et al deduced the icosahedral point group symmetry exhibited by quasicrystals on the basis of a set of three electron diffraction patterns showing 5-fold, 3-fold and 2-fold axes of symmetry with appropriate angular relationships. The exotic crystallography of quasicrystals has been recently reviewed by Nelson and Halperin (2).