Paramagnetic oil emulsions as oral magnetic resonance imaging contrast agents

The combination of a paramagnetic agent with an oil emulsion can uniformly enhance the small bowel. We discovered that the entire small bowel becomes homogeneously brighter than its surroundings when imaged with all commonly utilized pulse sequences. We have tried various combinations of ferric ammonium citrate, ferrous sulfate, gadolinium-DPTA and corn oil, olive oil and peanut oil. All paramagnetic oil emulsions tested were uniformly distributed throughout the small bowel, but the enhancement effect is much stronger with the ferric ammonium citrate and gadolinium-DPTA oil emulsions. We have also developed a mixture of Geritol, corn oil, ice cream and milk, which uniformly coats the small bowel wall, has good enhancement effect, tastes good, and is nutritious. With this dietary contrast, retroperitoneal structures including the pancreas can be well delineated. We conclude that the combination of a paramagnetic agent with an oil emulsion can work as a safe and effective magnetic resonance imaging (MRI) oral contrast agent with high patient acceptance.     

Distributed feedback-distributed Bragg reflector coupled cavity laser with a Ti:(Fe:)Er:LiNbO3 waveguide

A thermally fixed photorefractive Bragg grating is written in a single-mode Ti:Fe:Er:LiNbO3 channel waveguide and used to develop a distributed feedback-distributed Bragg reflector coupled cavity laser with a second broadband dielectric cavity mirror. The optically pumped (lambda(p) = 1480 nm, P = 130 mW) laser emits in single-frequency operation as much as 8 mW at lambda = 1557.2 nm with a slope efficiency of approximately 22%. The laser wavelength can be thermo-optically and electro-optically tuned over 100 pm.     

Spins swing like pendulums do: an exact classical model for TOCSY transfer in systems of three isotropically coupled spins 1/2

An exact correspondence is found between the quantum dynamics of three isotropically coupled spins 1/2 and the dynamics of three coupled classical oscillators. This correspondence is demonstrated by experimentally simulating the polarization transfer functions of an isotropic mixing TOCSY experiment with a set of mechanically coupled pendulums. The extend to which the exact correspondence holds is analyzed and it is shown that it breaks down for systems consisting of more than three coupled spins.     

On the class of attainable multidimensional NMR spectra

It is shown that a large class of two‐dimensional NMR spectra is characterized by a matrix algebra and an invariant subspace. Both the matrix algebra and the invariant subspace are determined by the system matrices of the bilinear system which describes the NMR experiments.     

How good are convex hull algorithms?

A convex polytope P can be specified in two ways: as the convex hull of the vertex set V of P, or as the intersection of the set H of its facet-inducing halfspaces. The vertex enumeration problem is to compute V from H>. The facet enumeration problem is to compute H from V. These two problems are essentially equivalent under point/hyperplane duality. They are among the central computational problems in the theory of polytopes. It is open whether they can be solved in time polynomial in |H| + |V| and the dimension. In this paper we consider the main known classes of algorithms for solving these problems. We argue that they all have at least one of two weaknesses: inability to deal well with “degeneracies”, or, inability to control the sizes of intermediate results. We then introduce families of polytopes that exercise those weaknesses. Roughly speaking, fat-lattice or intricate polytopes cause algorithms with bad degeneracy handling to perform badly; dwarfed polytopes cause algorithms with bad intermediate size control to perform badly. We also present computational experience with trying to solve these problem on these hard polytopes, using various implementations of the main algorithms.     

High-pressure Synthesis,Structure, IR Spectroscopy,and Theoretical Calculations of the New Silver Tetraborate Ag2B4O7 with a Unique Crystal Structure

Ag₂B₄O₇ is synthesized at high-pressure/high-temperature conditions of 11 GPa and 1073 K in a multianvil device. It crystallizes in the monoclinic centrosymmetric space group P2₁/c (no. 14) with four formula units per unit cell (Z=4). The cell parameters are a=787.53(3), b=651.63(2), c=943.88(3) pm, β=107.911(2)°, and V=460.90(3) ų. Ag₂B₄O₇ crystallizes in a unique crystal structure that consists of complex anionic borate layers with Ag⁺ ions in between. Additionally, the silver cations show argentophilic interactions. The compound was analysed via single-crystal and powder diffraction as well as infrared spectroscopy. Furthermore, theoretical calculations at HSEsol level were conducted.     

Synthesis and Crystal Structure of the Zinc Borate Zn3B4O9

The new zinc borate Zn₃B₄O₉ was synthesized at high-pressure/high-temperature conditions of 10 GPa and 1173 K in a Walker-type multianvil pressure device. It crystallizes in the space group P (no. 2) with a=5.5028(2) Å, b=6.7150(3) Å, c=7.8887(3) Å, α=83.99(1)°, β=73.38(1)°, γ=74.75(1)°, V=269.35(2) ų, and two formula units (Z=2) per unit cell. The structure was confirmed via single-crystal X-ray diffraction. Zn₃B₄O₉ can be synthesized phase pure, which is shown with a Rietveld refinement. IR-spectroscopic data of a powder sample were collected.