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131.
Serial MR imaging of intracranial metastases after radiosurgery 总被引:1,自引:0,他引:1
Hans Hawighorst Marco Essig Jürgen Debus Michael V. Knopp Rita Engenhart-Cabilic S.O. Schönberg Gunnar Brix Ivan Zuna Gerhard van Kaick 《Magnetic resonance imaging》1997,15(10):1121-1132
Purpose: To evaluate the spatiotemporal evolution of radiosurgical induced changes both in metastases and in normal brain tissue adjacent to the lesions by serial magnetic resonance (MR) imaging. Methods and Materials: Thirty-five intracranial metastases of different primaries were treated in 25 patients by single high-dose radiosurgery. MR images acquired before radiosurgery were available in all patients. Sixty-three follow-up MR studies were performed in these patients including T2- and contrast-enhanced T1-weighted MR images. The average follow-up time was 9 ± 5 months (mean ± standard deviation [SD]). Based on contrast-enhanced T1-weighted MR images, tumor response was radiologically classified in the following four groups: stable disease was assumed if the average tumor diameter after treatment did not show a tumor shrinkage of more than 50% and an increase of more than 25%, partial remission as a shrinkage of tumor size of more than 50%, a disappearance of contrast-enhancing tumor as a complete remission, and an increase of tumor diameter of more than 25% as tumor progress. Moreover, we analysed signal changes on T2-weighted images in brain parenchyma adjacent to the enhancing metastases. Results: The overall mean survival time was 10.5 ± 7 months, with a 1-year actuarial survival rate of 40%. Stable disease, partial or complete remission of the metastatic tumor was observed in 22 patients (88%). Central or homogeneous loss of contrast enhancement appeared to be a good prognostic sign for stable disease or partial remission. This association was statistically significant (p < 0.05). Three patients (12%) suffered from tumor progression. In eight patients (32%) with stable disease or partial remission, signal changes on T2-weighted images were observed in tissue adjacent to the contrast enhancing lesions. A progression of the high signal on T2-weighted images was seen in seven of the eight patients between 3 and 6 months after therapy, followed by a signal regression 6–18 months after irradiation. Conclusion: MR imaging is a sensitive imaging tool to evaluate tumor response as well as the presence or absence of adjacent parenchymal changes following radiosurgery. Loss of homogeneous or central contrast enhancement on Gd-enhanced MR images appeared to be a good prognostic sign for tumor response. Tumor shrinkage seems not to be dependent on time. In addition, most cases of radiation induced changes in normal brain parenchyma observed on T2-weighted images seem to be self limited. 相似文献
132.
Crystal Structure of BaNb6.3(1)Ti3.6(1)O16 containing Nb6O12, fused Ti3O13 Clusters and Ti3O10 Units
A new phase, BaNb6.3(1)Ti3.6(1)O16, has been synthesised. Electron diffraction studies indicate an hexagonal substructure with unit cell parameters a ≈ 8.9 Å and c ≈ 9.5 Å. In some of the ED patterns superstructure reflections are present, indicating a supercell with a = √3 · asub and c = csub. However, X‐ray single‐crystal diffraction studies of a crystallite yielding reflections corresponding to the supercell revealed it to be monoclinic, with the unit cell parameters a = 26.811(2) Å, b = 15.4798(2) Å, c = 9.414(2) Å, β = γ = 90° and α = 90.0(3)°. The average crystal structure was refined, using the subcell with a = 8.937(2) Å, b = 15.479(2) Å, c = 9.414(2) Å, β = γ = 90° and α = 90.0(3)°, space group Cm11, and Z = 4, to RI = 3.24% and RwI = 3.44%. The structure can be described as an hexagonal close packing layers of Nb6 octahedra, Ba, and O atoms (A1, A2) and layers of O atoms (B1, B2), appearing in the packing sequence: A1B1A2B2. The Nb6 octahedra are found in isolated Nb6O12O6 clusters, and the Ti atoms in Ti3O13 and Ti3O10 units in octahedral and tetrahedral voids formed by O atoms, respectively. The Ti positions were found to be only partly occupied. Microanalysis indicates that some Nb atoms are located in the Ti3 triangles. A model is presented that interprets these not fully occupied Ti3 triangles as a result of a superimposing of three different structures. Two of these consist of two fused Ti3O13 units, forming an Ti6O19 unit, and a Ti3O10 unit, while the third consists of alternating Ti3O13 units. 相似文献
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Gunnar Brinkmann 《Journal of Graph Theory》1996,23(2):139-149
In this paper an efficient algorithm to generate regular graphs with small vertex valency is presented. The running times of a program based on this algorithm and designed to generate cubic graphs are below two natural benchmarks: (a) If N(n) denotes the number of pairwise non-isomorphic cubic graphs with n vertices and T(n) the time needed for generating the list of all these graphs, then T(n)/N(n) decreases gradually for the observed values of n. This suggests that T(n)/N(n) might be uniformly bounded for all n, ignoring the time to write the outputs, but we are unable to prove this and in fact are not confident about it. (b) For programs that generate lists of non-isomorphic objects, but cannot a priori make sure to avoid the generation of isomorphic copies, the time needed to check a randomly ordered list of these objects for being non-isomorphic is a natural benchmark. Since for large lists (n ≥ 22, girth 3) existing graph isomorphism programs take longer to canonically label all of the N(n) graphs than our algorithm takes to generate them, our algorithm is probably faster than any method which does one or more isomorphism test for every graph. © 1996 John Wiley & Sons, Inc. 相似文献
137.
Dongmei Jiang Dr. Atsushi Urakawa Dr. Maxim Yulikov Dr. Tamas Mallat Dr. Gunnar Jeschke Prof. Dr. Alfons Baiker Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(45):12255-12262
{Cu(bpy)(H2O)2(BF4)2(bpy)} (Cu‐MOF; MOF=metal–organic framework; bpy=4,4′‐bipyridine), with a 3D‐interpenetrated structure and saturated Cu coordination sites in the framework, possesses unexpectedly high activity in the ring‐opening reaction of epoxides with MeOH, although the reaction rate drops remarkably with more bulky alcohols. This (apparent) size selection and the single Cu2+ sites in an identical environment of the crystalline matrix resemble zeolites. The real nature of active sites was investigated by attenuated total reflection infrared (ATR‐IR), Raman, EPR, and UV/Vis spectroscopies. Cu‐MOF has highly dynamic structural properties that respond to MeOH; its framework dimensions change from 3D to 2D by restructuring to a symmetric coordination of four bpy units to Cu. This interaction is accompanied by the partial dissolution of Cu‐MOF as multi‐Cu clusters, in which Cu2+ ions are connected with bpy ligands. Although both molecular and surface catalysis contribute to the high rate of alcoholysis, the soluble oligomeric species (Cumbpyn) are far more active. Finally, addition of diethyl ether to the reaction mixture induces the reconstruction of dissolved and solid Cu‐MOF to the original framework structure, thereby allowing excellent recyclability of Cu‐MOF as an apparent heterogeneous catalyst. In contrast, the original Cu‐MOF structure is maintained upon contact with larger alcohols, such as iPrOH and tBuOH, thus leading to poor activity in epoxide ring opening. 相似文献
138.
David S. Hart Chithkala Harinarayan Gunnar Malmquist Andreas Axén Mandakini Sharma Robert van Reis 《Journal of chromatography. A》2009,1216(20):4372-4376
Increased recombinant protein expression yields and a large installed base of manufacturing facilities designed for smaller bulk sizes has led to the need for high capacity chromatographic resins. This work explores the impact of three pore sizes (with dextran distribution coefficients of 0.4, 0.53, and 0.64), dextran surface extender concentration (11–20 mg/mL), and ligand density (77–138 μmol H+/mL resin) of cation exchange resins on the dynamic binding capacity of a therapeutic antibody. An intermediate optimal pore size was identified from three pore sizes examined. Increasing ligand density was shown to increase the critical ionic strength, while increasing dextran content increased dynamic binding capacity mainly at the optimal pore size and lower conductivities. Dynamic binding capacity as high as 200 mg/mL was obtained at the optimum pore size and dextran content. 相似文献
139.
For a certain class of extensions of C*-algebras in which B and A belong to classifiable classes of C*-algebras, we show that the functor which sends to its associated six term exact sequence in K-theory and the positive cones of K0(B) and K0(A) is a classification functor. We give two independent applications addressing the classification of a class of C*-algebras arising from substitutional shift spaces on one hand and of graph algebras on the other. The former application leads to the answer of a question of Carlsen and the first named author concerning the completeness of stabilized Matsumoto algebras as an invariant of flow equivalence. The latter leads to the first classification result for nonsimple graph C*-algebras. 相似文献
140.