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21.
Szilvia A. Nagy Mihaly Aradi Gergely Orsi Gabor Perlaki David Olayinka Kamson Andrea Mike Hedvig Komaromy Attila Schwarcz Arpad Kovacs Jozsef Janszky Zoltan Pfund Zsolt Illes Peter Bogner 《Magnetic resonance imaging》2013
Purpose
Our aim was to characterize bi-exponential diffusion signal changes in normal appearing white matter of multiple sclerosis (MS) patients.Methods
Diffusion parameters were measured using mono-exponential (0–1000 s/mm2) and bi-exponential (0–5000 s/mm2) approaches from 14 relapsing-remitting subtype of MS patients and 14 age- and sex-matched controls after acquiring diffusion-weighted images on a 3T MRI system. The results were analyzed using parametric or nonparametric tests and multiple linear regression models.Results
Mono-exponential apparent diffusion coefficient (ADC) slightly increased in controls (P=.09), but decreased significantly in MS as a function of age, nonetheless an elevated ADC was observed with increasing lesion number in patients. Bi-exponential analyses showed that the increased ADC is the result of decreased relative volume fraction of slow diffusing component (fs). However, the fast and slow diffusion components (ADCf, ADCs) did not change as a function of either age in controls or lesion number and age in MS patients.Conclusions
These data demonstrated that the myelin content of the white matter affects diffusion in relapsing-remitting subtype of multiple sclerosis that is possibly a consequence of the shift between different water fractions. 相似文献22.
Linear stability and positivity results for a generalized size-structured Daphnia model with inflow§
We employ semigroup and spectral methods to analyze the linear stability of positive stationary solutions of a generalized size-structured Daphnia model. Using the regularity properties of the governing semigroup, we are able to formulate a general stability condition, which permits an intuitively clear interpretation in a special case of model ingredients. Moreover, we derive a comprehensive instability criterion that reduces to an elegant instability condition for the classical Daphnia population model in terms of the inherent net reproduction rate of Daphnia individuals. 相似文献
23.
Gerbig S Golf O Balog J Denes J Baranyai Z Zarand A Raso E Timar J Takats Z 《Analytical and bioanalytical chemistry》2012,403(8):2315-2325
Negative ion desorption electrospray ionization (DESI) was used for the analysis of an ex vivo tissue sample set comprising primary colorectal adenocarcinoma samples and colorectal adenocarcinoma liver metastasis samples. Frozen sections (12 μm thick) were analyzed by means of DESI imaging mass spectrometry (IMS) with spatial resolution of 100 μm using a computer-controlled DESI imaging stage mounted on a high resolution Orbitrap mass spectrometer. DESI-IMS data were found to predominantly feature complex lipids, including phosphatidyl-inositols, phophatidyl-ethanolamines, phosphatidyl-serines, phosphatidyl-ethanolamine plasmalogens, phosphatidic acids, phosphatidyl-glycerols, ceramides, sphingolipids, and sulfatides among others. Molecular constituents were identified based on their exact mass and MS/MS fragmentation spectra. An identified set of molecules was found to be in good agreement with previously reported DESI imaging data. Different histological tissue types were found to yield characteristic mass spectrometric data in each individual section. Histological features were identified by comparison to hematoxylin-eosin stained neighboring sections. Ions specific to certain histological tissue types (connective tissue, smooth muscle, healthy mucosa, healthy liver parenchyma, and adenocarcinoma) were identified by semi-automated screening of data. While each section featured a number of tissue-specific species, no potential global biomarker was found in the full sample set for any of the tissue types. As an alternative approach, data were analyzed by principal component analysis (PCA) and linear discriminant analysis (LDA) which resulted in efficient separation of data points based on their histological types. A pixel-by-pixel tissue identification method was developed, featuring the PCA/LDA analysis of authentic data set, and localization of unknowns in the resulting 60D, histologically assigned LDA space. Novel approach was found to yield results which are in 95% agreement with the results of classical histology. KRAS mutation status was determined for each sample by standard molecular biology methods and a similar PCA/LDA approach was developed to assess the feasibility of the determination of this important parameter using solely DESI imaging data. Results showed that the mutant and wild-type samples fully separated. DESI-MS and molecular biology results were in agreement in 90% of the cases. 相似文献
24.
We define two closely related notions of degree for permutation patterns of type 2143. These give rise to classes of “m-vexillary elements” in the symmetric group. Using partitions, the Ehresmann–Bruhat partial order, and sets constructed from permutation inversions, we characterize the m-vexillary elements. We relate the maximal bigrassmannian permutations in the (Ehresmann–Bruhat) order ideal generated by any given m-vexillary element w to the maximal rectangles contained in the shape of w. 相似文献
25.
Jozsef Fetter Maria Kajtar-Peredy Karoly Lempert Helga Vasarhelyi 《Chemistry of Heterocyclic Compounds》1995,31(10):1234-1237
Attempted dephthaloylation 4-methyl-3-phthalimido- of 1-(p-methoxyphenyl)-4-(2-oxo-4thiazolin-4-yl)azetidin-2-one with methylhydrazine resulted in a ring transformation to give a fused thiazolo[3,4-a]pyrazine derivativeDepartment of Organic Chemistry, Technical University Budapest, H-1521 Budapest, Hungary. Central Research Institute for Chemistry of the Hungarian Academy of Sciences, H-1525 Budapest, Hungary. Published in Khimiya Geterotsiklichesicikh Soedinenii, No. 10, pp. 1405–1408, October, 1995. Original article submitted June 15, 1995. 相似文献
26.
Jozsef Bordas-Nagy John L. Holmes Alexander A. Mommers 《Journal of mass spectrometry : JMS》1986,21(10):629-636
The modification of a double-focusing mass spectrometer of BE geometry (VG-Analytical ZAB-2F) to permit the field ionization of fast atoms in high Rydberg states is described. Field ionization was achieved by means of a pair of closely spaced, very fine metal meshes with a (kV) potential difference between them. High Rydberg noble gas atoms were generated from their ions by electron transfer from noble gas targets. Also described is a method, involving a field ionization observation, for measuring the net kinetic energy loss associated with the collision-induced neutralization-reionization of polyatomic ions. 相似文献
27.
Jozsef Garai 《International journal of quantum chemistry》2008,108(4):667-670
Mathematical formulas describing all of the sequences of the chemical elements are derived from double tetrahedron face‐centered cubic lattice model. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
28.
1‐Acetyl‐ and 1‐propionyl‐2‐pyrazolines 11‐27 have been synthesized by the reaction of (3‐coumarinyl)chalcones 1‐10 with hydrazine in hot acetic acid or propionic acid. While 5‐aryl‐3‐(3‐coumarinyl)‐1‐phenyl‐2‐pyrazolines 28‐35 have been prepared by the reaction of (3‐coumarinyl)chalcones 1,3,5‐10 with phenylhydrazine in hot pyridine. Structures of all new compounds have been elucidated by microanalyses, 1H and 13C nmr spectroscopies. 相似文献
29.
A key choice in the development of arbitrary Lagrangian‐Eulerian solution algorithms is how to move the computational mesh. The most common approaches are smoothing and relaxation techniques, or to compute a mesh velocity field that produces smooth mesh displacements. We present a method in which the mesh velocity is specified by the irrotational component of the fluid velocity as computed from a Helmholtz decomposition, and excess compression of mesh cells is treated through a noniterative, local spring‐force model. This approach allows distinct and separate control over rotational and translational modes. The utility of the new mesh motion algorithm is demonstrated on a number of 3D test problems, including problems that involve both shocks and significant amounts of vorticity. 相似文献
30.
The development of antagonists of growth hormone (GH) - releasing hormone (GH-RH) is reviewed. GH-RH antagonists bind with a high affinity to pituitary receptors for GH-RH and inhibit the release of GH in vitro and in vivo. The main applications of GH-RH antagonists would be for tumor therapy. The antitumor effects of GH-RH antagonists are exerted in part indirectly through the inhibition of the secretion of pituitary GH and the reduction in the levels of hepatic insulin like growth factor (IGF-I). However, principal effects of the GH-RH antagonists are exerted directly on tumors. Antagonists of GH-RH inhibit the proliferation of various cancer cell lines in vitro and suppress in vivo the levels and the expression of mRNA for IGF-I and IGF-II in tumors. In many human cancers, the effects of GH-RH antagonists appear to be due to the blockade of the action of tumoral GH-RH. GH-RH ligand is present in various human cancers indicating that it may be an autocrine/paracrine growth factor. Splice variants (SVs) of GH-RH receptors and pituitary type of GH-RH receptors that might mediate effects of tumoral GH-RH and of GH-RH antagonists were demonstrated in many human cancers. This suggests the presence of a stimulatory loop based on GH-RH and SVs or pituitary type of GH-RH receptors in diverse tumors. It was shown that GH-RH antagonists inhibited the growth of various human cancer lines xenografted into nude mice including mammary, ovarian, endometrial and prostate cancers, small cell lung carcinomas (SCLC) and non-SCLC, renal, pancreatic, gastric and colorectal carcinomas, malignant gliomas, osteosarcomas and Non-Hodgkin's lymphomas. Further development of GH-RH antagonists should lead to potential therapeutic agents for various cancers. 相似文献