排序方式: 共有46条查询结果,搜索用时 109 毫秒
1.
2.
Dev SB Caban JB Nanda GS Bleecher SD Rabussay DP Moerland TS Gibbs SJ Locke BR 《Magnetic resonance imaging》2002,20(5):389-394
Recently, a new type of cancer treatment has been introduced that combines pulsed electric fields (PEF) with anticancer drugs. The proposed mode of action is that PEF create transient pores in the membranes which allow entry of drugs into the cells. This method increases cytotoxicity of some anticancer drugs like bleomycin (BLM) by 2-3 orders of magnitude, which, in turn, reduces systemic drug dosage without decreasing efficacy. In the present study, magnetic resonance imaging (MRI) was used to determine changes in apparent water self-diffusion coefficients (ADC) and spin-lattice (T(1)) and spin-spin (T(2)) relaxation times that occur in an animal laryngeal tumor (HEp-2 cells) model with BLM delivered by PEF. A Bruker 14 Tesla (600 MHz) wide-bore spectrometer with micro-imaging capability was used to generate all the data. Mice carrying approximately 8 mm tumors were treated with several combinations of drug and PEF. All measurements were made on tumor samples excised from mice 24 and 48 hours after treatment with (i) saline, intratumor injection (i.t.), (ii) BLM, i.t., (iii) saline with PEF, and (iv) BLM, i.t., followed by PEF. Although T(1) does not differ between the controls (i, ii, and iii) and full treatment (iv) 6.72 +/- 0.20 s vs. 6.31 +/- 1.7 s, T(2) for (iv) at 24 hours is significantly different from the controls 52.4 +/- 0.91 ms vs. 46.5 +/- 1.54 ms. T(2) differences between treatment and controls disappear at 48 hours. ADC increases significantly from 24 to 48 hours (7.31 +/- 0.16 x 10(-6) to 8.28 +/- 0.28 x 10(-6) cm(2)/sec, p = 0.05). Longer T(2) values may reflect early apoptosis and tumor death when the tumor is structurally less dense. Higher ADC's, associated with the periphery of the tumors and the central region, may indicate loose structural organization and necrosis resulting from the combination treatment. 相似文献
3.
Dibromoacetyl benzene derivatives on condensation with thiourea give 2-amino-4-arylthiazoles instead of the expected 2-amino-4-aryl-5-bromothiazoles. Attempts have been made to find the reaction pathway. 相似文献
4.
5.
Surjeet Kour 《代数通讯》2013,41(11):4100-4110
It is shown that the derivation y r ? x + (xy s + g)? y , where 0 ≤ r < s are integers, is a simple derivation of k[x, y], the polynomial ring in two variables over a field k of characteristic zero. 相似文献
6.
Deepika Geedkar Ashok Kumar Gagandeep Kour Reen Pratibha Sharma 《Journal of heterocyclic chemistry》2020,57(4):1963-1973
Present paper elicits the multicomponent reaction (MCR) strategy assisted by titania nanoparticles hosted on silica (TiO2.SiO2 NPs) as heterogeneous catalyst to synthesize a series of pharmacologically significant 2,3-diaryl-3,4-dihydroimidazo[4,5-b]indole derivatives. To the best of our information, the use of isatin as one of the precursors was hitherto unreported. The decrease in reaction time, low catalyst loading, high product yield (up to 92%), and excellent reusability of the catalyst (up to 7 cycles) put this protocol under the umbrella of green chemistry tenets. Characterization of catalysts was achieved through a number of techniques viz., energy-dispersive X-ray (EDX) spectroscopy, field emission scanning electron microscopy (FESEM), powder X-ray diffraction (XRD), fourier transform infrared (FTIR) spectra of adsorbed pyridine, temperature-programmed desorption of ammonia, and porosity measurements by nitrogen adsorption (Brunauer–Emmett–Teller [BET] method). Also, the structures of synthesized compounds were corroborated on the basis of FTIR, nuclear magnetic resonance (NMR), mass, and elemental analyses data. 相似文献
7.
Summary Ionic chelate complexes of the type, [(5-R)2ML][dtz] [R=cyclopentadienyl (Cp) or indenyl (C9H7); M=TiIV, ZrIV or HfIV; HL=oxine; dtz=phenyldithiocarbazate (PhNHNHCS2)] have been synthesised and characterised. Conductance measurements indicate that the complexes are 11 electrolytes. From i.r. and u.v. spectral studies we conclude that the oxinato-group is chelating. Consequently there is tetrahedral coordination around the metal ion.1H and13C N.m.r. studies are consistent with the stoichiometries. X-ray powder diffraction studies have been made for [(5-Cp)2ZrL][dtz]. For [(5-Cp)2TiL][dtz] and [(5-Cp)2ZrL][dtz] thermal (t.g. and d.t.a.) and mass spectral studies have been carried out. 相似文献
8.
[reaction: see text] Low-temperature 13C NMR spectra of cis-1,4-di-tert-butylcyclohexane (1) showed signals for the twist-boat (1a) and chair (1b) conformations. 13C NMR signals were assigned to specific carbons based on the different populations, different symmetries (time-averaged C(2v) for 1a and time-averaged C(s) for 1b), and calculated chemical shifts (GIAO, HF/6-311+G*). In addition to slow ring inversion and interconversion of the chair and twist-boat conformations, slow rotation of the tert-butyl groups was found. Most of the expected 13C peaks were observed. Free-energy barriers of 6.83 and 6.35 kcal/mol were found for interconversion of 1a (major) and 1b (minor) at -148.1 degrees C. Conformational space was searched with Allinger's MM3 and MM4 programs, and free energies were obtained for several low-energy conformations 1a-c. Calculations were repeated with ab initio methods up to the HF/6-311+G* level. Molecular symmetries, relative free energies, relative enthalpies and entropies, frequencies, and NMR chemical shifts were obtained. A boat conformation (1d; C(2v) symmetry) was generated and optimized as a transition state by ab initio, MM3, and MM4 calculations. 相似文献
9.
Mandeep Kour Sandeep Kumar Savit Andotra Suman Lata Ramanpreet Kaur Gurpreet Singh 《Molecular physics》2020,118(13)
Dimethyl diphenyldithiophosphate complexes of titanium(IV), [(C5H5)2Ti{S2P(OAr)2}nCl2-n] (Ar?= 2,4-(CH3)C6H3, 2,5-(CH3)C6H3, 3,4-(CH3)C6H3, 3,5-(CH3)C6H3, 3-CH3-4-Cl-C6H3O; n?=?1 and 2) have been synthesised and characterised by various physicochemical techniques along with computational analysis of the complexes (2), (9) and (10) using density functional theory (DFT) and time-dependent DFT (TDDFT). Comparison of antimicrobial activity of the free ligands and complexes has shown that the complexes are more effective than the free ligands. The in vitro cytotoxic by using a MTT staining method with RAW 264.7 cells (mouse macrophages) have been investigated. On the basis of analytical and DFT data, a distorted trigonal bipyramidal around titanium(IV) may be assigned to the complexes (1–5) and distorted octahedral geometries for the complexes (6–10). 相似文献
10.
Surjeet Kour 《代数通讯》2013,41(9):4066-4083
If k is a field of characteristic zero, c ∈ k?{0}, s, t ≥ 1, and r ≥ 0 are integers, then it is shown that the k-derivation y r ? x + (y s x t + c)? y of the polynomial algebra k[x, y] is simple. 相似文献